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WPI-ADVANCED INSTITUTE FOR MATERIALS RESEARCH NEWS

August 31, 2010

2-1-1 Katahira, Aoba-ku, Sendai 980-8577
Japan
Phone: +81-22-217-5922
FAX: +81-22-217-5129$XJXVW

Volume 10

World Premier International Research Center
Advanced Institute for Materials Research
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Cover: Snapshot of long-lived spatial heterogeneities, projected onto a x-y plane, obtained bynumerically solving the Tokuyama nonlinear stochastic equation for density fluctuations in a
colloidal suspension at a liquid state with volume fraction f=0.466 and a supercooled-liquid state with
f=0.566, where the relaxation time is of order 102 and 6×104, respectively.

(Michio Tokuyama,

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Volume 10

WPI-AIMR NEWS
August 31, 2010

World Premier International Research Center
Advanced Institute for Materials Research
Tohoku University

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Produced by the WPI-AIMR Communication OfficeDirector: Yoshinori Yamamoto
Editor-in-chief: Masaru Tsukada
Executive Editor, writer: Wataru Iwamoto
Associate Editor: Mingwei Chen
Associate Editor: Masashi Kawasaki
Associate Editor: Toshio Nishi
Associate Editor: Terunobu Miyazaki
Associate Editor: Keiichi Hashimoto
Associate Editor: Hiroshi Oikawa
Associate Editor: Sayaka Unoura
We welcome your comments, questions and involvement.
e-mail to: wpi-office@bureau.tohoku.ac.jp, or
tsukada@wpi-aimr.tohoku.ac.jp

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Contents
Preface ....................................................................................................................................................

1

Interviews
Tadafumi ADSCHIRI (PI, WPI-AIMR) ..............................................................................................

5

Kazue KURIHARA (PI, WPI-AIMR).................................................................................................

28

News Update
WPI-AIMR Outreach Activities ..........................................................................................................
st57

The 1 WCU/AMS-WPI/AIMR Joint Workshop at POSTEC ............................................................

59

WCU Project and POSTECH-AMS ....................................................................................................

63

Dr. Inoue’s lecture at reception of Acta Materialia Gold Medal .........................................................

66

Kawasaki Group’s paper was selected for the June issue of the Virtual Journals of Ultrafast Science....

70

Dr. Georgarakis’s paper was selected for ESRF Highlights 2009 .......................................................

72

The 1st WPI-AIMR Awarding Ceremony ............................................................................................

75

Award Information (From April 1, 2010 to August 31, 2010).............................................................

76

Prof. Ikuhara (PI) honored with Humboldt Research Award ..............................................................

77

The third series of WPI-AIMR Joint Seminars FY2010 .....................................................................

78

Research Prospect
Michio TOKUYAMA..........................................................................................................................

89

Proceedings Papers of 2009 WPI-AIMR Annual Workshop ............................................................. 101
New Research Organization ................................................................................................................. 147
Newly Appointed Research Staff .......................................................................................................... 151
Newly Appointed Adjunct Professors .................................................................................................. 157
Announcement
Junior Faculty/Post-Doctoral Positions ............................................................................................... 165
Graduate Student Scholarship in Materials Science/Engineering ....................................................... 166
WPI-AIMR Workshop Guideline ........................................................................................................ 167
Appendix
Snapshots............................................................................................................................................ X-1
Directory ............................................................................................................................................ X-19

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Progress of AIMR during April-August of FY 2010
Yoshinori Yamamoto
Director, WPI-AIMR, Tohoku University
Since volume 9 of WPI-AIMR News was delivered to you in April, four months havepassed. You may be thinking that volume 10 should have already been delivered to
you because four issues per year were published in the past. We have published(1)AIMResearch and (2) WPI-AIMR News through our office. AIMResearch is theprint version of the website “AIMResearch” in which specialists of Macmillan create
abstracts on the top-notch research results that WPI researchers published in top
journals. This print version is published once a year because the website is renewed
every month. In addition to those two publications, (3)Tohoku WPI Tsu-Shin, an
outreach magazine for the public, was launched in June along with MEXT’s request that
we enhance our outreach activities in order to let citizens and students know of theactivities of this WPI research center. Accordingly, it seemed that quarterly
publication of WPI-AIMR News would be too busy for us, and we have decided to
publish WPI-AIMR News three times per year instead. I hope you will understand thischange. Anyway, it is a pleasure for me to now deliver volume 10 to you.
In the middle of July, the third follow-up meeting of the WPI program was held inTokyo. All the follow-up committee members, including foreign members, two Nobel
laureates, the program director, the five program officers, and several MEXT members
gathered at the interview room and listened to the presentation of all five WPI centers.
This is the most important meeting for evaluating the activities of the WPI centers, andthe evaluation report has just appeared on both MEXT and JSPS website. After thereview meeting was over, Professor Kawasaki and Professor Chen gave lectures on theirown research results in front of the committee members. I believe this was a very
good opportunity for us to let them know what kind of top-notch materials research
projects are currently being undertaken at AIMR. At the banquet for this meeting, theMinister of Education, Culture, Sports, Science and Technology, Mr. Tatsuo Kawabata,gave a speech and in it stated that MEXT understands the importance of the WPI
program and, therefore, the 6th WPI center has been decided to be at Kyushu University
even under the present-day financial problems of the Japanese Government. This isvery good news for all of us, and I expect the continuous and strong support of MEXT
for the WPI program.

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We had a joint workshop between WPI-AIMR and POSTECH-AMS in Pohang,
Korea, in the middle of June. This mini-symposium was primarily on the soft materialscience of AIMR. The World Class University (WCU) program was started a few
years ago in Korea and POSTECH-AMS is one of the WCU centers, based on materials
science (primarily soft materials and materials physics). Also, POSTECH is a partner
school of Tohoku University.
The symposium proceeded successfully, andimmediately after the symposium, collaboration between researchers at
POSTECH-AMS and some PIs of AIMR started.
Finally, it is a pleasure for me to announce that Professor Masaru Tsukada has
become the Editor-in-Chief of WPI-AIMR News, since the previous Editor, Professor
Toshio Sakurai, left his position at AIMR. On this occasion I would like to thankProfessor Sakurai very, very much for his tremendous effort on the inauguration of
WPI-AIMR and launching WPI-AIMR News. Now the summer vacation season has
already begun and you may receive volume 10 after the vacation is over.
make a good start to the semester in September.

Let’s all2

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Interviews

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Interview with Professor Tadafumi ADSCHIRI, WPI-AIMR Principal
Investigator“Merry meet, many fusion”

Professor Adschiri (A): I like to ski and I think there are two ways to enjoy skiing.
The first is to ski fast and cool in front of a lot of people. The other is to stumble andplow through freshly fallen snow which no one has yet to set foot in. You don’t knowwhat you will find there, but you may see beautiful scenery in front of you or lookbehind to find that others have followed you creating a ski slope on which everyone canenjoy skiing. To put it simply, it’s either competing to be No.1 or pursuing a path to bea unique “only one.” Both are important, but in my research, I take the “skiing in the
freshly fallen snow” approach.
I was born in Niigata. I moved around a lot because of my father’s job as a banker.
I went to different nursery schools and during elementary school, I transferred school
every year. As a child, I kept thinking “not again!” but I became good at making
friends. How you socialize with people is in part due to your personality based on
DNA, but I believe it mostly relates to how you grew up. Someone pointed this out tome once, and looking back at my life. I agreed.
Professor Komatsu (K): Children are highly adaptable so I suppose they think and act
according to their surroundings.
A: It was hard going from place to place, but I had fun. I actually have an elementary
school reunion next week. All of my classmates are in completely different fields, but
in a sense it is good to meet with people in a different environment because it gives you
the chance to change your way of thinking.
K: That is important. It’s difficult to become friends with people in different fields as
an adult, but for children it’s the opposite. You just have to meet each other and you
become friends. Learning that there are ways of thinking other than your own and that
there are so many kinds of people in the world will be an advantage later on in life.
I’m sure the same is true for your research.

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A: I think so too. Take this room for example. A professor of humanities at a certain
university once told me that holding classes at a café from time to time gives birth tocompletely different ideas than when he holds classes in a classroom. Cafés havemusic playing, greenery, and pictures. I tried to design my office with that in mind. I
have pictures hanging even in the hall. It’s good to have experiment results andnewspaper articles pinned up, but I thought it might be good to have a research
environment in which students and staff can come up with ideas from a different
perspective. It is important to place yourself in an environment where you use a
different part of your brain.
I entered the University of Tokyo and my professor was Dr. Daizo Kunii. When you
blow air into sands from below, the sand-bed enters into a state similar to boiling aliquid. In this state, solid sands behave like a fluid and move from one reactor to thenext. This state is called “fluidization”. This technology led to the current
petrochemical technology for processing large amounts of petroleum with solid
catalysts. This is a technology which makes a new process treating the solid matterlike liquid, and Dr. Kunii was the authority of this field. Originally this technology
was born in U.S., but he made it possible to design the reaction that occurs inside thereactor for the first time.
K: By changing the media, you can modify the specific gravity.
A: That’s right. I said “similar to boiling a liquid”, but we can create the boiled
situation without bubble and the fluid situation where all the sands are blown away.
This determines the performance of whole process.
K: When we apply pressure on solids, it will not spread out equally, but in case of liquid
the pressure works equally by Pascal’s principle, and also we can control the stream of amagnetic or electric field.
A: Creating a magnetic field and controlling it is state-of-the-art research. That isexactly the idea. When we know too much the research surrounding us, we cannot
escape from it. On the contrary, when someone of different field says “Can’t you do it
like this?”, it can be a trigger to change our original idea.
K: What you might call fusion.

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A: Fusion can be achieved even by yourself if you change your surroundings. During
the oil crisis 30 years ago, I was doing my doctoral thesis on gasifying coal in a
fluidized bed in Kunii laboratory. Coal reacts with high temperature steam to fromcarbon monoxide and hydrogen. My research was on the conversion process of theinternal structure of coal slowly changed into gas. By the time I finished my doctoral
course, research on materials became active also in process engineering and I thenstarted research on converting hydro carbon gas into solid carbon through chemical
vapor deposition (CVD). It was very easy as I only had to do the exact opposite ofwhat I had been doing up until then. I had to observe how the structure of carbon, thesolid, changed. Even in this case, we can find a fusion of the totally different
researches.
Unfortunately, close to the end of my research, Dr. Takehiko Furusawa, who was Dr.
Kunii’s protégé, passed away at the young age of 49. I had worked as a researcher at
the Japan Society for the Promotion of Science for a year after earning my doctorate andhad just become an assistant at the lab. So in my second year, he was gone all asudden. Because the professor was gone, the lab was shut down. I had a year’s grace,
but that year passed by quickly as I helped students transfer to other labs.
write a single paper that year.

So I did not

There were many companies who invited me to work for them as I was struggling. I
had almost made up my mind to go into the private sector, but Dr. Kunio Arai and Dr.
Shozaburo Saito invited me to come to Tohoku University. So I decided to do research
there and came to Tohoku University in 1989. I remember thinking to myself that aslong as you do your work diligently, someone will notice and lend a helping hand.
At Tohoku University, I did research on supercritical high-temperature-high-pressuregas, which is the foundation of my current research. In chemical engineering, property
estimation is necessary for developing and designing a process. At high pressure,especially at the supercritical point, where gas no longer condenses at a certain
temperature, a condition where highly pressurized gas remains gas and does not turninto liquid under pressure is created. Under the condition, the properties change
greatly so the property estimation becomes difficult.
Just around this time, Dr. Saito made Tohoku University the center of this research.
I started research along with my boss, Dr. Arai. Changing the density of fluid changes

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the solvent power, so utilizing this property, we did research on material separation.
Since I moved from researching the reaction of coal to fluid properties and equilibrium,
not only my research itself, but my whole mindset changed. I had to specialize inthermodynamics, which I was not very good at during my student days, so it was tough,but I studied hard because the professors gave me the chance to work.
If I had to try something, I thought it would be better to start from scratch rather thanhold on to what I had up until then, so I quit my research on coal and started new
research. At the time, supercritical research was all about research on separation andno one was researching “supercritical-reaction.” You lose sight of the people in thesame field. That was why I was able to achieve fusion on my own. It was“supercritical-reaction-target material.” Coal, heavy oil, biomass, waste disposal,organic synthesis reaction; all of these. Also, the nanoparticles which are what I am
current researching. I started research on all of these simultaneously from 1989.
K: I see.

By discarding your old research you were able to get a fresh look at things.

A: Exactly. If I had continued with my old research, I never would have thought of it.
The moment I made the decision to concentrate on supercritical research, I felt as if I
knew exactly what I had to do.
Dr. Kunii’s research theme was “research on the methodologies for creation.” Hesays that the mindset for creation is calculation. Inventions originating completelyfrom scratch are extremely rare. He says new ideas come from multiplying, adding,
subtracting, and dividing old ideas. They may come from a transposed matrix or atransform matrix. He taught me that I always need to keep this in mind to come up
with new ideas. The idea I brought up earlier was exactly that so it was an easy choice
for me to make.
The other thing is to not think just by yourself. My main research theme right now
is making nanoparticles in supercritical water. This was an idea I came up with
together with my student. In supercritical water, substances are dissolved in highlypressurized, high density steam. Most metal oxides are dissolved. The earth itself ismade in this way. The crust of underwater volcanoes is in a high temperature, highpressure state so subterranean water is always in a supercritical state.

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I’m getting off topic here, but I once had the opportunity to talk to a professor ofgeophysics. I had always thought that magma was molten rock (lava), but it’s actuallyrock which has melted in supercritical water. This makes the water take on
characteristics of rock, creating rock-like water, which keeps dissolving the surroundingrock. Magma is a state in which a lot of rock is dissolved in a small amount of water.
Magma exists and flows even at a temperature lower than the melting point of rock.
When magma rises suddenly, the highly pressured steam returns to a normal
atmospheric pressure all at once and expands. That is a hydrovolcanic explosion.
The Kanto loam layer is actually made up of natural nanoparticles. The melted rockthat erupted from Mount Fuji and Mount Asama was depressurized and stopped melting
and all of it was deposited. The particles deposited are the Kanto loam layer. As it
slowly accumulated, mineral veins emerged. Because deposits occur starting with
substances with lower melting points, you will always find the same type of substancein a single mineral vein.
K: But in the Kanto loam layer, you find small crystals such as pyroxene and olivine
instead of powder. At a stage in which they can still be purified, they erupt along withthe magma and changes in conditions cause them to change as well.
A: Yes.

That’s exactly what naturally synthesized nanoparticles are.

There was a student who just happened to be doing similar research. Apparently hereally did not enjoy his research and came to me for advice. He was making silica andat solubility of 1 wt%, even with a lot of water, all you would be able to make was abouta pinch of silica. He told me he wondered if that would actually benefit anyone. To
be sure, being able to melt a lot is one thing, but it is no fun if you end up with just a
pinch of silica.

We started discussing this and ended up getting drunk together.

When you think of solubility, all you
think of is metal salts. “But wait, if metalsalt can be dissolved into water, maybe thatis all we need,” I said. At these words, thestudent suddenly woke up from his drunken
stupor and went to the library for research.
He came back and said to me “No, that
won’t work. Metal salt will thermally

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decompose in high temperatures and become metal oxides.” Since his aim was tomake metal oxides, I jokingly told him that maybe that was a good thing, but the student
quickly switched to equipment that would allow metal particles to flow and react inhigh temperatures. That was the first original nanoparticle synthesis process at Tohoku
University. I examined it under an electron microscope and thought to myself how
beautiful it was.
He recreated what nature does, not by depressurizing, but by rapidly raising thetemperature. He made the metal salts react by letting it flow while simultaneously
rapidly raising the temperature. This results in creating almost all the same thing.
Using a pressure vessel called an autoclave with extremely thick walls like a cannon,
the temperature rises gradually. By letting it all flow as a fluid like petrochemicals, hemade them react inside and uniform, pretty crystals formed. This is the result thatcame out of a talk with a student. It is not only your own ideas that are important, butalso interaction with others.
K: There are various kinds of interaction; between different generations, those who arelearning and those who are teaching, those who are drunk, etc.
A: At the time I had just started working there so I was able to think from a fresh
perspective without being completely immersed in that research. The free-thinking
must have emerged from there not being a relationship of seniority. That is what
fusion is. I still work with young post doctorates and when we do research on thesame floor in different fields, it is always very refreshing. There is a high potential for
new ideas and technologies to be born. In that sense WPI provides a great place forfusion.
K: Fortunately there are four very different disciplines, so it might be interesting toreally flex the brain muscle to achieve fusion.
A: Seven years ago, I moved to the Institute of Multidisciplinary Research for
Advanced Materials (IMRAM) from the School of Engineering in Aobayama andlaunched a new lab. Fortunately, all the positions were still open and it seemed like it
could be an environment in which I could work together with associate professors,
assistant professors and technical staff. So I decided to try something completely new
again.

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After having researched supercritical fluids for nearly 15 years, I didn’t think I would
be stimulated by people who had been doing similar research. I looked for people who
had what I didn’t have, people in fields such as computer science, biotechnology, andmaterials science. It was a gamble, but I thought I would try to make a place to fuse
new ideas together to create something like “supercritical fluids-bio-materials-computer science,” similar to what I had done when I came to Tohoku University in
1989.
At first, it was as if I was talking to people who used a different language.
Especially for bio research, there are so many abbreviations in that field. For the first
couple of years, we couldn’t understand each other, so we held an educational seminarin our lab where we would give lectures on the very basics: bio, materials, computer andsupercritical. Because it was all things I wanted to learn, things entered my mindsmoothly, unlike when I was a student reluctantly attending classes. We kept throwing
ideas at each other trying to find out if we could do certain things.
Dr. Umetsu, who is now an associate professor at the School of Engineering, built abridge between the nano and bio fields for us. The peptides we use to recognize theparticles we make are formed from a chain of more than ten amino acid molecules.
For example, for zinc oxide we would have to find a peptide that would only stick tozinc oxide, and one that would only bond to the (100) sides of the zinc oxide. Dr.
Umetsu prepared 109 different types of peptides and experimented with them all. That
was something. Viruses infect cells. He injected a little bit of the DNA of each of the
109 different peptides into the viruses. He looked at which peptides would stick on the
Zn O viruses. But it’s is hard to find the ones where only one or two have bonded.
However, we are talking about viruses.

So, you infect this virus to E. coli bacteria.

K: A virus is clump of genes, an aggregate of nucleic acids.
A: Yes, viruses are not alive. They are not living organisms. They have DNA insidethem and work to inject that DNA elsewhere. Cells injected with that DNA are
confused into thinking the alien DNA is their own and thus multiplies the DNA, causing
bacterial or viral infection. For example, even if only one or two virus peptides latch
on to the E. coli, it will help the virus to multiply until the virus grows very large and if
we take a sample of the virus after that and look at its DNA, we can see which peptides

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are attached to it. This method is known as phage display. We have found many
peptide that can recognize inorganic nanoparticles using this method.
At times like this, device people usually come up with completely different ideas.
They usually ask, “Can’t you put the peptides indicated on the foot of the virus on thehead, hands and shoulders of the virus as well?” We can do it. According to the way
device people think, its better to indicate everything here – for example, “here a source,
here metal, here a drain and then on the opposite side, attach a semiconductor particle
and a dielectric around that space there.” They will say, “Can’t we make this circuit
into any design we like?” We have some particles, and when the particles are lined up
in a free-form shape they form a circuit. If you want to line up the particles in aparticular way, it’s better to make living organisms line them up. The idea is that if
you change the necessary blueprints, the DNA of the organisms, you can get theparticles to line up on their own. Living organisms are the only things which cancause particles to go where they want them to go. And while living organisms areconstantly regenerating on their own DNA, things like the positions and shapes of eyes,
noses and mouths hardly ever change.
Last year, a man who participated in WPI as a Junior PI, Dr. Teizer, utilized this idea,
and attempted to find out what would happen if we used this method of using livingorganisms to make particles move. Living organisms move. Muscles move. There
are things called kinesins which move above proteins called micro-tubulins. The
thought was, what if we placed particles in these kinesins? Would they take theparticles with them along the micro-tubulins? We came to this idea thanks tointeraction with people from a different field.
K: That’s interesting. Like one of Aldous Huxley’s mechanisms using livingorganisms to move muscles, but making living organisms do the work. And all of it
can be controlled by people.
A: It would be great if we could put this to practical use by joining our activities
together with others little by little. This was an example of a fusion research with bio,
but also with materials and computer science, we found fusion in our lab. Not only in
our lab, but also with the outside, we found a fusion:More than two years ago, a mathematics professor, Dr. Kotani, and professor at Meiji
University, Dr. Sunada, attempted to try to fuse their work with ours. That was the8
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time I first felt how amazing math really is. The research involved taking clusters
shaped like the Mitsuya Cider logo, made up of three lines separated by 120 degrees
which intersect at a point, and seeing what shape they would form if they wereconnected. On just hearing 120 degrees, chemists, and particularly those of us likemyself who work with carbons, immediately thought that “120 degrees equals sp2
hybrid orbital of carbon.” This is the carbon that graphite and graphene sheets are
made of. I remember thinking that it was obvious that if you connected particles in the
shape of the Mitsuya Cider logo that you would get a pattern made up of a series ofrhombi. However, these mathematicians were thinking in three dimensions. And if
you bend the shapes upward, and then bend them another 120 degrees, it seems you get
a decagon. This was a shock. This was a totally new idea. Mathematics provided
us with a new way of looking at things.
Sometimes when you meet someone from a different field you discover something sosurprising it is like you have been hit on the back of the head. I think that this kind ofshock is extremely important. With both fullerene and carbon nano-chips, we aretalking about things that have been around for a long time. Discovering things thathave been around for a long time and looking for these things are two completely
different processes. Once people think that something exists, they will find it, because
they will go looking for it. If you don’t think to look for something you won’t see it.
What is important is that the new ideas you find be used to synthesize new materials
into your research. This too is a type of fusion.
K: That wasn’t something you were taught, but something that you learned on your own
I think. You didn’t move around for the three years of high school then?
A: I went to Toyonaka High School in Osaka. Luckily I didn’t change schools for
those three years. I was a cocky student even though I almost never studied.
Teachers used to get mad at me because I often
wrote criticisms of their lectures in mynotebook. I enjoyed being made to stand up
and told to leave. But anyway, fortunately I
would enter the University of Tokyo.
We were separated into different courses
according to our sophomore year grades. At

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that time, only those with good grades could enter applied physics, electric engineering
or aerospace courses. On the other hand, my major, chemical engineering, had strange
teachers promising to teach things like “methodologies for creation” so a lot of people
with poor grades came to these courses. Even now, many of the people that I deal withare these kinds of people. However, among them are people who became the CEO oftheir company around age 40. They were different from people who have done
nothing but study I think.
K: Just like in the world of living organisms, diversity is important, isn’t it? Diversity
has helped living organisms to continue on for hundreds of thousands of years. I mean,
if it was just fish, everything would have disappeared long ago.
A: It’s all about diversity which has come about through cross-fertilization though,basically. I think that this is especially why meeting a lot of different people isimportant.
K: During the Meiji Enlightenment, a lot of different people came to Japan from manydifferent countries, and as things jumbled together we really grew, didn’t we?
A: Yes. At the end of the Edo period, those with ambition began trying to do what
they wanted with their lives more and more. They didn’t just interact with those in
their field, but exchanged opinions with many different people, found their ambition,and tried to accomplish something. Things weren’t separated into set groups, but weremore free-flowing. Comparing it to entry into university, we now have the AO(Admission Office) route. I think that such interesting ideas are great.
K: I heard this story from a friend of mine from Stanford University. It seems thatthey purposely form their student body out of those with good grades and those withpoor grades. Apparently this leads to a more effective education in the end.
A: I think that’s absolutely true. In such a situation you are forced to make you own
environment. I have the feeling that for me, happiness is meeting many different
people.
K: Even if you do meet people though, if you can’t absorb anything from them or really
see who they are it doesn’t mean anything. And you as well have something which

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9:32:03will be absorbed.
themes.

The problem for young people today is how to find their own

A: It is just like what I said about ski slopes at the beginning. People should do
research in a field expressly because no one has done much research in that field yet.
If I find out that someone in the laboratory is doing research into something that isalready being researched, I try to convince them to gather their courage and stop that
research. With new snow, it doesn’t matter if you are good at skiing or not. Youmight fall down or fall on your behind, and there might be a lot of holes in the field, but
it doesn’t matter. Because no one is looking at you. You can steadily go where youwant to go.
I spoke about one of our nano-particle synthesis methods earlier, supercriticalhydrothermal synthesis. This method was born out of a discussion with a student.
For students as well, it is important that those with more experience encourage theirclassmates below them to come up with new ideas themselves.
I can’t do anything as grand as teach ambition, but I do think that students are always
watching our actions. When they see someone working really hard on something, they
begin to understand what it’s all about. For this reason, I have called many people tomy new laboratory and had them study organic fusion. I think that their studies andambition will meet up eventually.
In a supercritical high-temperature-high-pressure environment, oil and watercompletely mix together. Oil and water are known as a classic example of two things
that just don’t get along, but in a supercritical environment they completely mix. If
organic and non-organic synthesis reactions occur in the midst of this environment, I
think that we will be able to do some amazing things. Oil and water only mix in thiskind of environment, and that makes me think that in a supercritical environment
especially we will be able to achieve these synthesis reactions. This is anotherchallenge for us. In supercritical environments we have produced materials that are
hybrids between organics and inorganics. Because we were able to create suchmaterials, mixes of organics and inorganics – well, let me show you a polymer. Thismight look like a plastic, but actually its 70% zirconia with nanoparticles added to it.
Although it may not look it because it is clear and flexible, it has a high refractive index.

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When you think of ceramics you think pottery, but this is also a ceramic.
completely mixed with non-organic nanoparticles.

Except it is

K: You might even be able to make a polarized filter I suppose.
A: I think that we will be able to. For instance, I think we might be able to do it
through diffraction grafting. We are talking with the research group of Terunobu
Miyazaki, the expert in magnetism, to see if we can’t make a translucent magnetic film.
Dr. Hitosugi and Dr. Mizukami proposed to explore a Faraday effect on the film. Dr.
Hashizume and his group as well are asking if we can’t incorporate this in their devices– interacting with different people really is interesting, isn’t it?
K: Yes, it’s really interesting.

We really must do it.

A: Currently a 4 billion yen national project “Super Hybrid Materials” is underway at
the IMRAM. By adding boron nitride to thermal conductive materials, we can makepaper-thin films with thermal conductivity 10 times better than what was once possible.
K: This is a fusion of materials. Type II diamonds have several tens of times higher
thermal conductivity than copper does. So adding powdered diamond will raise
thermal conductivity even more. I was actually the one who found that type II
diamonds are mostly found among smaller diamonds. The discovery of type II wasannounced about 100 years ago by three physicists in England. Type II diamonds are
extremely transparent with regard to ultraviolet light and their thermal conductivity is ina class of its own. However, they are extremely rare in nature. Only about one inevery 200 diamonds are type II and therefore, they are expensive. However, whenmining diamonds, sand containing diamonds are run down a grease table and the sand iswashed away, but small diamonds that can become abrasive compounds stick to thegrease. One day I was examining them through ultraviolet absorption, and I
discovered that more than 10% were type II diamonds that are transparent in ultraviolet
light. After I published this in Science, the discovery was put into practical use at the
Bell lab for heat sinks.
A: I will use that idea right away.
K: Later, S and other companies were able to synthetically produce type II diamonds.

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A: I was actually supposed to go to a private company and to make synthetic diamonds.
K: I think you are more suited to the university environment.
your research because you were at a university.

You were able to expand

A: Currently I am challenging to synthesize metallic glass nanoparticles by a chemicalroute. First of all, it’s important to try, especially in fusion research, because
communication will lead to new ideas. Answers may emerge from completely
different fields with someone saying “normally, we do it like this, but we tried it thisway and came up with something interesting.” I am now achieving fusion with many
professors within the WPI.
K: Finally, let me ask you why you decided to go into the sciences.
A: I have a great deal of curiosity for everything. I like things that have a solid logic
behind them. I’ve always liked mathematics and science since elementary school aswell as puzzles and mathematical quizzes. While I was studying in high school, I
realized that what I had thought to be clearly logical up until then, was actually not. I
don’t really know if I am a man of science though.
K: That is fine.

You won’t know by the time you die.

A: I actually also enjoy cultural things such as paintings and music. So, I might beclassified as science-oriented, if I had to choose between science and humanities, but I
think everything is fusion.
K: Indeed.

And you head in the direction for which you are best suited.

Thank you for your interesting interview today.
stories a long time ago.
A: Chit chat is more interesting.

I would have liked to have heard these

I had a fun time.

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K: Thank you.

Interviewer: Prof. H. Komatsu
At Adschiri Lab,
Advanced Materials Processing Building
IMRAM, February 16th, 2010

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9:32:05WPI-AIMR PI 阿尻雅文教授に聞く(Interview with Professor Adschiri－Japanese version)

出会いが生みだすフュージョン研究
阿尻：スキーの話ですが、スキーにも楽しみ方が二種類あると思います。一つは大勢の人の前で格好よく速く滑る。もう一つは、誰も踏み入れたことのない新雪の中を、尻もちをつきながら進んでいく。何があるかはわからないけれど、その先にきれいな景色が見えた
り、振り返ると後ろからいろんな人が来ていて、皆が楽しめるゲレンデになっていたりす
るような楽しみ方です。簡単に言うとナンバーワンを目指してしのぎを削って探求をする
か、オンリーワンを目指すかですね。両方とも重要なことですが、どちらかというと、新雪を滑るような研究が私の目指すところです。
私は新潟で生まれました。銀行マンだった父の都合で、引っ越しが非常に多かったです。
幼稚園も変わりましたし、小学校では毎年引っ越しです。子供心に「またかよ」と思いましたが、友達をつくるのが上手くなりました。人づきあいの仕方はＤＮＡで決まった性格もあるでしょうが、生い立ちによるところも大きいと思います。ある時人からそれを指摘され、自分の生い立ちを振り返ってなるほどと思いました。
小松：子供は非常に柔軟ですから、環境に応じて考えるのでしょうね。
阿尻：各地を渡り歩いて苦労もしましたが、楽しかったです。実は来週も小学校の同窓会があります。同級生は皆全然違う分野ですが、考え方をチェンジする意味でも違う環境の人と会うのはいいですね。
小松：それは大事ですね。大人になってフィールドの違う人とはなかなか仲間になれませんが、子供は逆です。顔合わせていると仲間になる。自分の考えとは別の考え、世の中にはたくさんいろんな人がいるとわかることは、後からプラスになりますね。それが今の研究にも通じているのではないでしょうか。
阿尻：そうですね。例えばこの部屋にしてみてもそうです。ある大学の文系の先生が、ゼミを時々喫茶店でやると、教室でやる時とは全く違う発想が出てくると言っていました。
喫茶店にはＢＧＭが流れていて、緑があり、絵が飾ってある。教授室を作る際、そんな場所を意識しました。廊下にも絵を飾っています。実験結果や新聞記事が掲示されているのもいいですが、学生やスタッフが見て尐し違う発想がパッと出てくる研究環境もいいと思いました。違う頭を使う環境に身を置くことが大切ですね。
高校からは東大に入りました。先生は国井大蔵先生です。流動層といって、砂を下から空気で吹き込むとちょうど液体のように沸騰したような状態になり、一つのリアクターから次のリアクターにその砂を動かすことで、液体と同じように移動させられます。この技術によって、触媒を使って大量の油を処理する今の石油化学技術ができました。固体を液

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体と同じように扱える新しいプロセスをつくり上げる装置工学で、国井先生はその大家です。もともとはアメリカでできた技術ですが、国井先生がその中で起こる反応を初めて設計できる形にしました。
小松：媒体を変えることで比重を変えることもできますね。
阿尻：そのとおりです。先ほど沸騰するような、と言いましたが、沸騰でもバブルができない状態や、全部吹っ飛んでいくような流動など流動状態をつくることができる。それがプロセス全体のパフォーマンスを決めたりします。
小松：固体に圧力をかけても均等にかかりませんが、液体であればパスカルの原理で均等にかかりますし、電場、磁場の流れを制御できますね。
阿尻：磁場をかけて制御することは研究室で最後の方に最先端の研究として行われていました。まさにその発想です。周りの研究を知り過ぎてしまうと、そこから抜けられない。
逆に、全く違う分野の人が「こんなことはできないのか」と言う方が、発想そのものを変えられます。
小松：それこそフュージョンです。
阿尻：自分一人でも環境を変えればフュージョンはできるのです。30年前のオイルクライ
シスの頃、ドクター論文で流動層の中で石炭をガスにする研究をしました。炭素と水蒸気を反応させ、ＣＯと水素に変える。固体が尐しずつガスに変わっていく際の内部構造の課程の研究です。ドクターが終わった頃には材料の研究がアクティブになり、ＣＶＤ（Chemical Vapor Deposition）今度はガスから固体をつくる研究を始めた。今までとは全く逆のことをやればいいので、とても簡単でした。石炭の構造、固体の構造がどう変わるのかを見ればよかった。
ところが研究をしている最後の頃、面倒を見てくださっていた、国井大蔵先生のお弟子さんの古沢健彦先生が、49歳の若さで亡くなりました。私はドクターを卒業して１年間学振の研究員をした後に助手になったのですが、２年目にあっという間に亡くなってしまったのです。そうすると、上の先生がいなくなった研究室はお取りつぶしです。1年間の猶予はありましたが、学生の配属を替える世話で１年間が過ぎてしまいました。ですからそのときの１年間は論文ゼロです。
何にもできず困っていると、「うちに来ないか」と言って下さった企業がたくさんありました。ほとんど企業に行く予定でしたが、東北大学の新井邦夫先生と斎藤正三郎先生方がいらして、東北大学に誘って下さった。それだったらお世話になろうかな、と平成元年に東北大学に来ました。きちんと仕事をしていれば見ていて拾ってくれる人もいるのだと思いましたね。
東北大学に来てからは今の研究の基盤になる、超臨界、高温高圧のガスの状態の研究をしました。化学工学はそのプロセスの開発・設計の学問で物性推算が必要になります。高圧、特に臨界点といって、その温度以上では凝縮しなくなる、圧力をかけても液体にならずに高圧のガスのままでいられる状態ができる。この近辺のところは物性が大きく変化す2
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るので、感度が一番高いわけです。
ちょうどその頃、斎藤正三郎先生がアメリカから研究を輸入し、東北大学を日本の中の出発点にしました。超臨界の物性研究がスタートし、私のボスだった新井邦夫先生とその研究に取り組みました。密度を変えられれば溶かす力を変えられるので、それを使って物の分離に関する研究をしていました。石炭で反応の研究をしていたところから物性、平衡論ですから、研究内容はもちろん、発想そのものが違います。学生の頃にあまり得意ではなかった熱力学を専門にするので大変な思いをしましたが、せっかく拾っていただいたので一生懸命勉強しました。
チャレンジするのであれば、今までのものにしがみついているよりゼロスタートの方がいいと思い、石炭の研究をやめて新しい研究をスタートしました。それまで超臨界を研究している人は、分離の研究ばかりで、「超臨界×反応」の研究はありませんでした。同じ分野にいる人は見えなくなる。だから一人フュージョンができたわけです。「超臨界×反応×対象物質」ですね。石炭や重質油、バイオマス、廃棄物処理、有機合成反応など全てです。それから、現在研究しているナノ粒子合成です。平成元年に同時並行で片っ端から全部やることになりました。
小松：なるほど。古いしがらみをパッと捨てて転換したことで、見る目がフレッシュになったわけですね。
阿尻：そのとおりだと思います。今までの研究をしていたら、この発想は出てきませんでした。全部超臨界でやると決めた瞬間に、自分がやらなければいけない仕事が見えてきた気がします。
国井先生は「創造のための方法論の研究」を研究テーマに掲げていました。創造のための発想とは演算だというのです。真にゼロスタートのオリジナルな発明は非常に稀で、新しい発想は既にあるアイデアの掛け算や足し算、引き算、割り算、転置行列だったり変換行列だったり、そういった演算でからできていることが多いそうです。それを常に頭に入れ、新しい発想を出しなさいと教えられました。先ほどの発想はまさにそれを適応した、
自分にとっては簡単なことでした。
もう一つは、自分だけで考えないことです。今のメインテーマは超臨界の水の中でナノ粒子を作る研究ですが、これは学生と一緒に出てきた発想です。超臨界の水では、高圧高密度の水蒸気の中に物が溶けていきます。金属酸化物は大体溶ける。もともと地球はそうしてできています。海底火山の地殻は高温高圧状態ですから地下水が超臨界です。
脱線してしまいますが、地球物理の先生と話す機会がありました。マグマは岩が溶けたもの（溶岩）だとばかり思っていたのですが、そうではなく超臨界の水の中に岩が溶ける。
そうすると、岩の性質を持った水、岩らしい水ができ、周りの岩をどんどん溶かし込んでいく。尐しの水にたくさんの岩が溶け込んだ状態が溶岩、マグマです。岩の融点よりも低
くてもマグマが存在して流動している。それが突然上に上がってくると、高圧の水蒸気が一気に普通の大気圧の水蒸気に戻りますから、全部膨張する。それが水蒸気爆発、火山爆

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発です。関東ローム層がありますが、あれは「自然のつくったナノ粒子」です。富士山、浅間山の噴火で溶けていた岩が一気に全部減圧されて溶けなくなり、全部析出するしかないのです。それが微粒子として析出したのが関東ローム層です。徐々に上がってくると鉱脈になります。溶解度の低い順番に析出していきますから、同じ鉱脈には必ず同じようなものが析出します。
小松：ただ、関東ローム層の中には、輝石やカンラン石など、パウダーではなく小さな結晶になっていますね。まだ精製できるような条件が、マグマからいきなりドーンと上がって、何かで条件が変わりながら何か変わっていっているのですね。
阿尻：そのとおり。まさに自然が合成したナノ粒子そのものだと思います。
ちょうどそれに近い研究をしていた学生がいました。彼はその研究がとても嫌だったらしく、私に相談に来るのです。作っていたのはシリカですが、溶けるといってもせいぜい１wt％で、大量の水を扱って耳かき１杯程度しかできません。そんなものが本当に役に立つのかと言うわけです。確かに大量に溶けるものならばまだしも、大変なプロセスを動かして耳かき１杯のシリカだったらそれは面白くないと２人で議論し始め、おしまいには飲み会になった。
溶けるといえば金属塩ぐらいしかない。でも待てよ、金属塩が溶けるのだったらそれでもいいんじゃないかと言うと、酔っていたはずの学生がパッと図書館に行って調べてきました。そして「先生、だめです。金属塩は高温にしてしまうと熱分解して金属酸化物に変わります」と言う。目的が金属酸化物をつくる研究だったのだからそれでいいじゃないかと私は半分冗談も含めて投げやりに言ったのですが、その学生はすぐに金属塩が流せる高温場で反応ができるような装置に切り変えました。それが初めての東北大学オリジナルのナノ粒子合成プロセスです。電顕で見たらきれいで、こんなにきれいな粒子ができるのかと思いました。
自然と同じことを、減圧ではなく急速に温度を上げる方法でやったのです。流体を流しながら急速に温度を上げて反応させていました。これによってほとんど全て同じものができる。オートクレーブという非常に分厚い大砲の筒のようなお釜だと、徐々に温度が上がっていきます。それが、石油化学のように全部流体として流し、中で反応させていく方法
を使ったことで、均一できれいな結晶ができました。これも学生との話からです。自分だけの発想でなく、ほかの人とのインタラクションが大事ですね。
小松：ジェネレーションの違う者同士、教育を受けている人間と、教育をする、でき上がった人間とのインタラクションがある。
阿尻：私も入ってきたばかりだったので、その研究に完全に染まり切っていないフレッシ
ュな頭で物を考えられた。上下の関係ではなくて、自由な発想が出たのでしょうね。それがフュージョンです。今も若いポスドクの人と一緒に仕事をしますが、同じフロアで違う分野の研究をやる時は全てフレッシュですね。新しい発想や技術が生まれる可能性を大いに秘めている気がします。ＷＰＩではそういう面でいい融合の場を提供してくれていると

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9:32:07思います。
小松：幸いかなり違うディシプリンが三つあるから、本当に頭を柔軟にして融合したら面
白いかもしれないですね。
阿尻：７年前に青葉山の工学部から多元研に移り、また新しく研究室を作ることになりました。幸いにしてポストが全部空いており、准教授、助手、技官の３名と一緒に仕事をする場ができそうでしたので、その時も全く新しいことしようと思いました。
超臨界で20年近く研究をしてきたので、似たような研究をしていた人が来てもなかなか発想の刺激にはならないと思い、自分にないもの、コンピューターケミストリー、バイオ
テクノロジー、マテリアルサイエンスの人を呼びました。博打でしたが、平成元年に東北大に移ってきた時と同じように「超臨界×バイオ」など、新しい発想の融合の場を作ろうと思ったのです。
ただ、バイオは略語が多く、違う国の人と話しているようでした。初めの１、２年間はお互いに言葉が通じず、基礎の基礎からレクチャーをする教育機関を作りました。自分が知りたいことですから、無理やり授業に出ていた学生の頃と違ってどんどん頭に入っていく。こんなことはできないのかと互いにどんどん投げかけをするのです。
そこでは、現在工学部で准教授として活躍している梅津君が、ナノとバイオの架け橋をしてくれました。我々がつくる粒子を認識するペプチドはアミノ酸が十幾つつながったものです。例えば酸化亜鉛だったら酸化亜鉛しか、しかもその（100）面しかくっつかない、
そういうペプチドを見つけてくるのです。彼は、10の９乗個、10の９乗種類のペプチドを準備して、それを全て実験しました。これはすごいですね。遺伝子操作ができる。ウイル
スは細胞に感染するのですが、そのウイルスのＤＮＡを、10の９乗種類の違うＤＮＡを尐
しずつウイルスの中に入れていきます。入れたウイルスをこの粒子にくっつくかどうかを見るのです。洗い流せばくっついたかどうかわかるので、これは簡単です。しかし、１個や２個しかくっついてないものを見つけるのが大変なのです。ところが、これはウイルスですので例えば大腸菌に感染させてやると…。
小松：ウイルスは遺伝子の固まり、核酸の集合体でしょう。
阿尻：そう、ウイルスは生きていない、生物ではありません。自分の中にＤＮＡを持っていて、そのＤＮＡを注入する機能を持っている。注入された細胞は自分のＤＮＡだと勘違
いし、自分の細胞の中でどんどん増えていき、ウイルスだらけになる。これが細菌感染・
ウイルス感染です。たとえ１個か２個しかついていなくても、ウイルスを大腸菌に感染させると大腸菌がどんどんウイルスを増やしてくれる。その後にウイルスを取り出してＤＮＡを調べれば、どんなペプチドがくっつくのかが見える。この方法がファージディスプレ
イです。この方法を使っていろいろなものを作りました。
こうした時、デバイス屋さんはまた違った発想をします。ウイルスの足に提示させているペプチドを、頭や手、肩にもくっつけられないのかと言うのです。これができるのですね。彼の発想によれば、ここにいろんなものを提示させておけば、ここにソース、金属で

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9:32:08すね、ドレイン、反対側にして、ここのところに半導体の粒子をくっつけて、この間のところには誘電体をつける。こういう回路とかなんかを自分で勝手に並べられるのではないかと。我々は粒子を持っています。ナノ粒子を自由な形に並べられたら回路ができる。自在に並べるには生物に並べさせればいい。必要な設計図であるＤＮＡを書きかえればその粒子を自在に並べられるという発想です。粒子を自在に自分の思いどおりの場所に置くことを唯一できるのが生物です。生物は自分のＤＮＡで常に代謝しているわけですが、目、鼻、口の位置、形はほとんど変わりません。
昨年Junior PIとしてWPIに参加したTeizer先生もそういった発想をつなげて、今これをさらに動かしてみたらどうかとなっています。生物は動いている。筋肉もそうです。キネ
シンとはチューブリンというタンパクですが、その上を走るのです。そこに粒子を入れておけばこの粒子を連れて回ってくれるのではないか。発想が違う分野の人が出てきたときにでき上がってきます。
小松：それは面白い。オルダス・ハクスリーの筋肉を動かすメカニズムをうまく使って、生物にそれをやらせる。それを人間が全部操るということですね。
阿尻：尐しずつ組み上げていって応用ができればいい。現在彼らは、別の場所で活躍していますが、離れていても場所は関係ありません。一度フュージョンを経験した人はまた違う場所でも自分なりのフュージョンをしています。
二年ほど前から数学の小谷先生、明治大学の砂田先生と数学とのフュージョンをしています。数学のすごさを初めて感じました。三ツ矢サイダーのような120度の角度を、つなげていくとどんな形になるのかという研究です。120度と聞いただけで、化学の人、特に私のように炭素を扱っていた人間は、すぐに120度イコール炭素のsp2混成と思い浮かびます。これは炭素でいえばグラファイト構造、グラフェンシートができています。三ツ矢サイダーの構造はつなげていけば六角形が敷き詰められた形になるのが当然だと思っていました。しかし彼女たちはこれを３次元で考えたのです。上に120度で曲がって、さらにまた曲がり、十角形になるらしいです。これはショックでした。我々は装置の設計などで数学には慣れていたつもりですが、発想そのものが全く新しい。数学が新しい視点を与えてくれました。
違う分野の人と出会うことで頭をたたかれたようなショックを受ける、これが大切だと思います。フラーレンやカーボンナノチューブも同じで、昔からあったわけです。あったことと、それが見つかること、探し出すことは違います。あると思った瞬間に皆が探し出すから見つかるのです。見ようと思わないと見えない。大切なのはそういう発想が新しい材料を合成する研究に向かわせてくれたことです。そういう意味でもフュージョンですね。
小松：それは誰からも教わらない、自分自身が学び取った方法論ですね。高校は三年間かわらなかったのですか。
阿尻：高校は大阪の豊中高校で、幸いにして三年間かわりませんでした。ほとんど勉強をしないのに生意気で、先生の講義の講評をノートに書いてよく怒られていました。立たさ

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れたり、「出ていけ」と言われたりしましたが楽しんでいましたね。
大学では２年間の成績で各コースに振り分けがありました。当時は応用物理や電子工学、航空宇宙には成績のいい人しか入れない。私が入った化学工学は、「創造のための方法論を教える」なんてことを教える変な先生がいて、成績の悪い人もたくさん来るわけです。
今でもそういう仲間とのつき合いが多いのですが、四十幾つで社長になった人もいますし、
勉強だけをした人とはちょっと違いますね。
小松：生き物の世界と同じで多様であることが大事ですね。生き物が何百万年も続いているのは多様性があるからで、これが魚だけだったらもうとっくに消えていますね。
阿尻：基本的には交配して変わっていった中での多様性ですよね。だからこそ、いろいろな人たちと出会える場が大切なのではないでしょうか。
小松：明治の文明開化した頃はいろいろな国から人が来て、ごちゃごちゃしながらも伸びていきましたよね。
阿尻：そうですね。幕末の頃から、志を持った人が自分でやりたいことをどんどんチャレ
ンジしていました。同じ分野の中だけでなく様々な人と意見交換をしながら、最後には自分の志を見つけて挑戦していった。輪切り的な採択ではなく、もっとフリーな形です。入試の方法としてＡＯ入試が出てきていますが、そういった面白い考えでやるといいですね。
小松：スタンフォード大学の友人から聞いたのですが、わざわざ成績のいい人と悪い人とを組み合わせているそうです。その方が最終的には効率のいい教育ができるそうです。
阿尻：そのとおりだと思います。そういう場を自分たちの周りでもつくらなければいけないですね。私は幸せにもそういういろんな人たちと出会えていた気がします。
小松：出会っても、ご本人に吸収力や見る目がなければ意味がありません。自分自身が吸収するものを持っていたのですね。今の若い学生の問題は、どのように自分でテーマを発見するかですね。
阿尻：初めにスキーのゲレンデの話をしましたが、同じことだと思います。他の人にほとんど研究されていない分野だからこそやる。研究室では、誰かがしているとわかったら勇気を持ってその研究から撤退しようと言っています。新雪であればどんなに下手でもいいのです。転んでしりもちをついて穴がいっぱいあいても、全然気にすることはない。周りに見ている人はいませんから。着実に自分たちが行きたいところに進めます。
先ほどご紹介した超臨界水熱合成という我々のナノ粒子合成法、これは学生とのディス
カッションから生まれた方法です。学生でも新しいものを自分で生み出せると後輩たちに伝えなければいけませんね。
志を教えるなどという大それたことはできませんが、学生は我々の背中を見て生きていると思います。チャレンジしている姿を見て、「なるほど、こういうものなのか」と学ぶ。
だから、新しい研究室ではいろいろな人を呼んできた他に、有機の合成の研究もしていました。いつかこれを二つ結びつけることができると思っていました。
超臨界の高温高圧の水の中では水と油が完全に混ざるのです。「水と油」は仲の悪い代

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9:32:09名詞ですが、超臨界では完全に混ざり合います。混ざり合った中で有機合成反応も無機合成反応も起きるならば、とてつもないものができると思いました。水と油が混ざるのはこの領域しかありませんから、超臨界でこそできるものがあるはずだと思ったのです。これも一つのチャレンジでした。それでできたのが有機と無機がハイブリッドした材料系です。
これができたことで、有機と無機、例えばポリマーですが、ちょっとお見せしましょう。
これはプラスチックスのように見えますが、これには70％ジルコニアのナノ粒子が入っています。透明でとてもそうは見えないですが、屈折率が高いのです。セラミックスとは陶器ですね、これそのものなので、無機がナノ粒子であってポリマーと完全に混ざり合います。
小松：偏光フィルターもできるかもしれない。
阿尻：できると思います。例えば回折格子をつくるようなこともできるでしょう。それから、磁性の専門の宮崎照宣先生のグループと、フィルムにして透明の磁石はできないかという話になっています。橋詰先生たちはデバイスに加工できないのかとコメントしてくだ
さいますし、やはり違う人たちが出てくると面白いですね。
小松：本当におもしろい。実際やらなきゃいけないな。
阿尻：今、40億のナショナルプロジェクトが多元研の中で動いているのですが、熱伝導材
料、ボロンナイトライドをこの中に入れることで熱伝導が今までの10倍高い紙のようなフィルムを作っています。こういうものもできると思っていませんでした。ただの紙のように見えますが、熱伝導が今までの10倍です。
小松：これは材料のフュージョンですね。タイプⅡダイヤモンドは、熱伝導は銅の十数倍高いので、ダイヤモンドのパウダーを入れたら熱伝導率がさらに上がります。タイプⅡが小さいダイヤモンドに多いことは実は私が発見しました。タイプⅡダイヤは100年ぐらい前にイギリスで３人の物理学者が連名で発表しています。タイプⅡは紫外線にすごく透明
で熱、伝導がずば抜けていい。ところが、自然の中に大へん稀で200個に１個ぐらいしかなく、非常に高いと言われていました。ところで鉱山からダイヤモンドを取ってきてグリーステーブル上にダイヤモンドが入っている砂を流すと、砂は洗い流され、研磨剤になる
小さな砂粒のようなダイヤモンドがグリースにつかまります。ある時それを紫外線吸収で調 べ た ら 、 な ん と 紫 外 線 に 透 明 な タ イ プ Ⅱ が な ん と 10 ％ 以 上 あ っ た 。 こ の こ と を「Science」に発表したら、ベル研究所でヒートシンク（熱吸収板）に使うアイデアが実用化されました。
阿尻：それは早速使わせてもらおう。
小松：タイプⅡは、その後、S社などで人工合成できるようになりました。
阿尻：私は、民間企業に行く予定でそこで人工ダイヤモンドを作ろうと思っていました。
小松：大学の方が先生に合っています。大学だからこそ広げられるのです。
阿尻：今は、メタリックガラスのナノ粒子をつくってそれを分散させる研究をしています。
まずはやってみることが大事です。特にフュージョンリサーチは、やっている間にコミュ

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9:32:10ニケーションができ、発想も生まれてきます。本来こうしてしていたけれどこっちの方がおもしろい結果が出るぞ、というように全然違う分野で解が出る場合もあります。ＷＰＩの中でも現在いろいろな先生方とフュージョンを進めています。
小松：最後に一つ、理系に進んだ理由を教えてください。
阿尻：ロジックのしっかりしたものが好きだったからです。小学校の頃から数学や理科、それからパズルや数学的なクイズも好きでした。特に必ず答えが出るものが好きでした。
実際には、受験勉強をしているうちに、今までシャープさと考えていたことはちょっと間違いだったと気付きました。本当に理系なのかどうかはよくわからないですね。
小松：それがまたいいのです。死ぬまでわからないです。
阿尻：どちらかというと、絵や音楽など文化的なことも好きです。ですから理系、文系という言い方をすると理系になるのかもしれませんが、やっぱりすべてフュージョンなのではないでしょうか。
小松：そうですね。その中で性に合った方に進むわけです。
今日は、本当に楽しいお話でした。もっと前からこんな話をさせてもらったらもっとう
れしかった。
阿尻：本当にこうした話の方がおもしろいですよね。楽しいひとときでした。
小松：ありがとうございました。
２０１０年２月１６日
東北大学多元物質科学研究所素材工学研究棟 PI阿尻雅文教授室にて
小松

ひろし

啓

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9:32:11Interview with Professor Kazue KURIHARA, WPI-AIMR Principal
Investigator“When the “Maybe Girl” Commits herself….”

Administrative Director Iwamoto (I): First, as you were appointed the first female
Principal Investigator of WPI-AIMR back in April, I should have come earlier to havethis interview.

So Professor, I understand that you were not born in Sendai.

Professor Kazue Kurihara (K): I was born in Tokyo.
I: And you also grew up in Tokyo?
K: That’s right. In fact, I lived with my parents in Tokyo right up until I went to theUnited States to be a post doctorate fellow.
I: So you are a true Edo Tokyoite.
K: Well, not strictly speaking an Edo Tokyoite as Shinagawa is considered uptown
Tokyo.
I: And you graduated from the Faculty of Science, Ochanomizu University?
K: Yes, from the Department of Chemistry in Faculty of Science.
I: And I suppose you were interested in science from an early age?
K: Not really. If I would have had to choose when I was young between thehumanities or science I think I would have said the humanities because I enjoyedreading books and writing essays. However, rather than taking a sort of rational
approach to the humanities, I wanted to study in fields that were a little more empirical,
such as history or archeology. That was the basic image I had of myself. But myparents told me I wouldn’t be able to make a living in those fields, and the image they
had for me was to study medicine or pharmacology if I entered a science department orperhaps to study law if I entered a humanities department. As I originally wanted to be28

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9:32:12an archeologist, it was a major concession for me to enter the Department of Chemistryin Faculty of Science.
I: That was certainly a major concession.
K: I did also want to study science a little too. It was at that time that the position ofscience writer was slowly starting to become quite fashionable.
I: Yes, I remember.
K: As I was interested in book publishing, I thought it would be good idea to study
science and then to work at a publishing company. That was how I felt at the time,and so I continued through education in a sense of liberal arts. A lot of my classmatesenjoyed in amateur radio or joined science clubs.
I: But in your case, you wanted to help communicate scientific knowledge to thegeneral public?
K: Not really. I had no so much experience of science outside of studying it at school,
so I wanted to know a little more about the science around me. As for humanities, I
quite often used to go to the library and research and study them.
I: So you had continued from the Faculty of Science on to its Master’s course at
Ochanomizu University. Your specialty had been formed from your Master’s degree
to the School of Engineering, the University of Tokyo.
K: I was actually a member of a humanities circle when I was at university. Quite afew of the other members were studying aesthetics and philosophy, and so whatever wewere discussing they were always on a completely different level to me. So based on
this experience I decided to give more emphasis to the things that I had been studying.
We conducted a student experiment in physical chemistry in my third year which I
found very interesting. Starting from measurement – and this applies just as much
today – we can understand the nature of molecules. Even today, I remember thisexperiment clearly; we measured the dielectric constant to understand the molecules’
dipole moments, and by observing the properties of the solution we were able tounderstand in detail the qualities of the substances dissolved within the solution. I- 1 29

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9:32:12thought that these kinds of measurements were very interesting.
I: So this was your first encounter with measurement.
K: From then on I found the student experiments in physical chemistry extremelyinteresting and so I went to the physical chemistry laboratory. At that time, I still did
not intend to become a researcher in the future and so at graduate school I remained in
the same physical chemistry group and studied interface chemistry in the laboratory for
my Master’s degree. It was during my Master’s degree that I realized I found researchbased on observation to be the most interesting and so carried out the kind of researchthat is based on observation and measurement, and published one paper. So evenwhen I was a student I was able, to a certain extent, to do research that appealed to me.
As a result I found my research interesting, and although originally I thought I wanted
to be an archeologist, I think that perhaps what I really wanted was to be a researcher.
I: So from the start you had a passion for research?
K: My classmate said that it was uninteresting if at least one person in the class did not
go on to do a doctorate and encouraged me to continue on with my studies. At thattime, this classmate talked to an associate professor who was her supervisor that I
should continue onto a doctoral program. The two of them discussed it and suggested
to me that I might enter the University of Tokyo for studying at the group of a professor
who was giving a course at Ochanomizu University.
We knew there had been an example of entering the doctoral program at the Schoolof Engineering in the University of Tokyo from another university. So, I applied forand entered an industrial physical chemistry laboratory because their research was
similar to interface chemistry. It was not really so spontaneous, though I did my
absolute best to pass the tough entrance examination, then study at doctoral program.
I: I thought it interesting when you said that in your case, it was precisely because youwere a member of a humanities club that you decided to do your absolute best and study
science. It seems that what you wanted was to do something based on observation that
could be empirically verified.
K: That’s right.

I have wanted to be an archeologist or a researcher since high school,- 2 30

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9:32:13and I think they are somewhat connected with what I do today, precision measurements.
I: Although archeology is within humanities there is certainly lot of field work required.
K: Science means proof and it can be hard work acquiring this proof. In some ways
the precise measurements required are something like a sport. That is why I enjoyed it.
I: So you continued on to a doctoral course; what was your PhD about?
K: It was on biomimetics, but what has been a common theme throughout my career
has been the self-organization of molecules. My master's thesis was about micelle,
which is the aggregation of surfactants (surface active agents) and is therefore theprincipal ingredient in detergent, and liquid crystals. After that, my doctoral thesis
was about the lipid bilayer membrane. I used a biomembrane model for my research.
I modeled leaf photosynthesis by adding chlorophyll a into the model membrane andthen irradiating light. Various elements of this research were the first of their kind inJapan. My sub-supervisor had researched the lipid bilayer membrane in the UnitedStates, and we were the first in Japan in using the lipid bilayer membrane in chemistry
and conducting researches on reactions within the lipid bilayers.
I: Fundamentally speaking, biomimetics is replicating, which is to say mimicking,living organisms.
K: That’s correct. It is the creation of artificial systems that mimic functions within
living organisms. So an example of biomietics in its purest form is an airplane, as aplane mimics a bird. However, that is not at a molecular-level mimetics; mimicking
leaf photosynthesis would be biomimetics at the molecular level. Photosynthesis
occurs from a reaction between sunlight and the chlorophyll in the chloroplast
membrane in a plant leaf. In the same way, the goal of the research that I was
involved in at that time was to convert light energy into chemical energy and thencollect this energy within a chemical compound. This has recently once again become
an important area of research as it can contribute to achieving a low-carbon society.
The oil shocks were taking place when I was involved in this area of research.
I: That’s right; the first oil shock was in 1973.

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K: This area of research was attracting a lot of attention after the first oil shock as it was
the first into energy conversion systems. It was also about that time when the field of
biomimetics began to emerge. Research into biomembrane models and enzyme
models had just begun, and the materials used in interface chemistry were exactly thesame as those used in areas such as biomembrane modeling in biomimetics. Asinterface chemistry deals with structures made up of aggregations of various molecules,
I was involved in this area of research from the start.
I: Currently, there are various scientists within WPI-AIMR that are researchinginterfaces; it became a globally important field at the end of the 1970s, didn’t it?
K: That’s right. Although the meaning of interface chemistry changes over time, it isa scientific discipline with quite a long history. Aggregate structures of lipids andsurface active agents were used for biomembrane model in the 1970s, as lipids have thesame kind of structure as surface active agents. It was exactly at that time that theideas were emerging about organizing molecules and designing various functional
structures, such as to control the distance of a reaction. This was the first time theseideas had been expressed and they serve as the starting point for the development of thedifferent nanotechnologies of today.
One such starting point was research into molecular self-organization, while anotherwas research into enzymes. The background to this research was that X-rays had
revealed the structures of living organisms, biomembranes, and enzymes. This was
extremely significant for the research occurring at this time as it enabled these newmaterials to be created.
I: So new methods of creating materials, and also methods of observation, were being
realized.
K: Of course today we are at a considerably more advanced stage, but that period oftime was the starting point. Today, nano-level materials are being used in industry andinterfaces have come to be considered extremely important. Although previously
really only a small number of people were involved in this field, today everyone isinvolved and consequently the outermost boundaries are constantly being pushed
further and further back.

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I: Is it related one to your research themes, surface force measurement.
K: I received my doctorate in 1979. My doctoral thesis was based an photoreaction
experiments, and when I then went to America as a post doctorate fellow I entered thelaboratory of the biomimetics specialist Professor Fendler, who was proposed theconcept of membrane mimetic chemistry and researching how to create superiormaterials that mimicked biomembrane functions. Professor Fendler’s laboratory had
many instruments for measuring fast light reactions. Among them was a Laser Flash
Photolysis system, which at that time was the most advanced research instrumentation
available. I wanted access to this equipment so joined Professor Fendler’s laboratory.
Research had commenced into the creation of nanoparticles in special environments.
So next I began creating nanoparticles within organized molecular structures. I
returned to Japan, and spent two years at Department of Synthetic Chemistry, Kyoto
University, in the laboratory of Professor Iwao Tabushi, who was the leading researcher
in the field of biomimetics.
During this part of my career I began to think about the research I wanted to do for
my career. Up until that point, I had created or designed various functional materials.
I was not synthesizing molecules but rather combining component molecules to design
a functionalized system. As I was originally a physical chemist, my research involved
measurments; namely, measuring and identifying characteristics of its advantageous
functions. As I do not synthesize molecules, my approach for improving the functions
could be rather limited when I discover interesting functions. Rather than this type of
research, the research themes that I wanted to pursue are those that would lead me a
special stage after accumulation of experiences, say, for 10 years.
I thought that I might find it in Physical Chemistry. I encountered surface force
measurement when I was trying to find someway of understand molecularnanoarchitectures and self organization. Self
organization
indicates
theproperties
demonstrated by a molecular aggregation, and as
the molecules interact to aggregate, I thought itwould be interesting to use surface force
measurement to try to understand this system.
The laboratory in Sweden that I had moved to- 5 33

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had installed surface force measurement equipment and I was able to conduct a joint
research on this measurement.
I: That was at the Institute for Surface Chemistry in Sweden?
K: Yes, but in Japanese we call it Institute for “Interface” Chemistry.
I: Professor Fendler who directed your research when you were in the United States
was then the Texas A&M professor?
K: Yes, during my stay in the US, he moved to Clarkson University with his group in
exactly the same set up.
I: You stayed in the US for a total of three years, and then went to Sweden, is that right?
K: Yes. More precisely, I returned to Japan for two years, and then two years in
Sweden.
I: Apart from the research results you achieved, what significance do you think yourexperience of researching overseas had in forming you as a person?
K: Professor Fendler frequently said to me that I needed to commit myself.
I: What did he mean by commit yourself?
K: He meant to clearly state my opinion. I was prone to saying “maybe” so much that
I acquired the nickname, the “maybe girl.” So I was told I had to commit myself, thatis, once I had decided what my opinion was I had to clearly state it. In Japan I am
often the only woman in a group of men, but whether male or female, in Japan there are
not many people who clearly speak their mind in front of other people.
I: Yes, you’re right.
K: So, he started to get really anxious about this, about the number of times I was told
to commit myself. So I was made fun of because I did not speak my opinion, they said
that I was the “maybe girl.” But thanks to this experience I think today I am able to- 6 34

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clearly state my opinion if necessary, particularly when I am talking to foreigners.
I: I also spent a long time living overseas, but inevitably Japanese people are prone, likeyou mentioned, to saying “maybe,” or “perhaps.” There are many instances when it
would have been better to have the confidence to speak my mind. Foreigners can say
some very extreme things quite directly, and to some extent this way of speaking would
still be considered unacceptable in Japanese society.
K: Yes, we can’t speak like that in Japan.
I: There are some things we cannot accept, but I think there are attitudes in Japan thatneed to change. This is an extremely important point.
K: For example, when I went to Sweden, it was through Bilateral Programs of the Japan
Society for the Promotion of Science. After the end of stay by this scheme, I remainedin Sweden, but I felt that the salary for my research position was quite low. So I
discussed it with the director of the institute, I said that I felt my salary was rather low.
As Japanese do not generally discuss salaries, if I had still been in Japan I would nothave wanted to have this discussion. But I had heard that overseas, a person’s salaryreflects how much he or she is appreciated by their employer. So I said I would like araise because I wanted to stay there for a long time; as a result, it was doubled.
I: Without question, these kinds of discussions take place overseas.
K: Yes, I spoke after fully considering what I wanted to say. I often remember it as anextremely valuable experience. When overseas, you can get your point across bythinking things through and then stating the main thread of your argument.
I: Yes, I agree. Of course the reason your salary was doubled was because of yourability as a researcher, but you are right that when overseas you have to speak yourmind. If you don’t say anything it is assumed you are happy with the current situation.
If you have even a slightly different opinion, you will be respected if you clearly statethat opinion; I think this a trait that Japan needs to learn.
K: So perhaps one of the most important lessons I learnt from living overseas was not
to be a “maybe girl” but to commit myself. In addition, although this is also the case- 7 35

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in Japan, I have many friends in places throughout the world through conducting
research. I have friends in many universities overseas, and when I am attending an
academic conference and I meet an acquaintance whose appearance has changed and I
am not instantly sure who they are. I am able to work out who they are by mentioningsome peoples’ names and reminisce about them.
I: That is a priceless resource to draw on.
K: Yes it is.
I: So, after you returned from Sweden, you joined Professor Toyoki Kunitake at
Kyushu University and became a group leader of ERATO.
K: To a certain extent, I continued with my research into molecular films that I began
when I was a student. I researched molecular recognition, displaying at the molecular
film on the water surface. Actually, molecular recognition is the specialty of Professor
Tabushi I mentioned earlier. So it was natural for me to research molecular
recognition of monomolecular film when I was in Professor Tabushi’s laboratory thencontinued it at ERATO. At ERATO, the group theme was pursued in a way that I
created a form and it was then developed by other team members who synthesized newmolecules.
I then began carrying out surface force measurements at ERATO. I had heard that
Professor Kunitake was also interested in surface force measurements, so we decided topursue this area when he found out that I was also interested in it. We knew there wasa prototype device for sale in Australia, so we bought it and began our research. Even
though I was a physical chemist, up until that point I had never assembled a large-scalecomplicated instrument. Although we had bought the device, we could purchase only
the main chamber, the main components; we still had to source and assemble all theparts, which was before we even started carrying out the measurements that werethemselves relatively difficult. Although I had had the opportunity to take a look at
the instrument, I had never had one operational. In Japan, I had to assembly it myself
while searching one by one for all the parts, constantly asking questions to lots ofdifferent people. But finally I was able to begin the sub-theme surface force
measurements.

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I: A pretty tough start.
K: We purchased and installed the first upgrade model that was built in the work shopof the Australian National University. I had seen the previous version of the model in
Sweden, and I knew that it was difficult to use and needed upgrading, but you are in fora tough time if you buy equipment that is not up and running. I went to Australia to
see the device in action, as two weeks training period included in the price of themachine. I saw that it worked, thought it would be a good machine, and bought it.
As it was a brand new model, the purchase agreement entitled us to a replacement if it
did not work. I am able to build this device today thanks in large part to how
extensively I was able to study it at that time.
I: Did they show the device so openly there?
K: No, normally I would not have been able to see it. They wanted to show me sometests of the device to confirm that it was a good device in full working order. A person
responsible for developing new instrumentation is a good person who is passionate
about research, and I knew him from my time in Sweden. Perhaps in some part thanks
to him, subsequently I was able to build the instrument myself.
I: So to recap what you have said, of course your research field is interfaces and it waswhile you were accumulating measurement data, as you previously said, you acquired
just the main chamber of this instrumentation and you had to work out by yourself what
you needed to add to it.
K: Yes. It was the first time that I had assembled such a large piece of equipment, andonce it was assembled I then carried out the surface force measurements at ERATO as a
sub-theme. After we had completed them, the quality of the data was such that it
could be quoted in text books. As this was the first time this device had been
operational in Japan, I think that we made some senior researchers very happy, andsome of them traveled all the way to Kyushu to see it. When the ERATO project
ended Nagoya University offered me a position with which I could carry out the samemeasurements in their Biophysics Laboratory, and so I became an associate professor
there.
I: So you moved to Nagoya University?

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K: Yes. I was moving to their Biophysics Laboratory, which had
previously been called the Precision Measurement Laboratory, so I
felt an affinity with it.
Fortunately by coincidence, I was
employed there because the professor of precision measurement wasinterested in my measurements.
Nagoya is a Mecca of physical measurements such as electron microscopes, x-rays,
and moreover the Applied Physics Department had a lot of experiences in building
instruments and had an excellent workshop. So I felt I would be able to build
equipment there.
I: About 10 years ago you moved to Tohoku University.
measurements here?

Are you still carrying out

K: Yes, and thanks to doing these measurements my skill in developing new
instruments and methods is also improving.
I: Could you explain about your development of the shear resonance measurement
method?
K: Conventionally, surface force measurement involves measuring normal forces thatact vertically. This method uses horizontal oscillation to measure shear response. By
adopting the resonance measurement we could further heighten the level of sensitivity
and improve detection levels. It is used to observe friction and liquid flow, by placing
a liquid between two solids, in the scientific disciplines of rheology and tribology.
I started doing these measurements at Nagoya when the atomic force microscope(AFM) was developed. Although, I am a little unsure about the extent to which AFM
can be used to measure surface force, it is quite easy as a measurement method. On
the other hand, surfaces force measurements are extremely precise, but they are quite
time consuming. I thought about what could not be done without using surface force
measurement.
At that time, I thought it would be shear measurements for liquids confined between
two large surfaces, which cannot be measured with an atomic force microscope. I- 10 38

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wanted to build a device to carry out the measurements, and at first I thought that we
could measure shear force in a conventional way. However, something like aresonance vibration effect occurred and accurate measurements were impossible. So
we then monitored the effect in order to check how this resonance vibration was
occurring.
No one else was using the shear resonance measurement method, it was entirely
original. But ultimately we decided to try to use it while monitoring how well it
functioned and we found that it enabled us to achieve some excellent measurements.
Despite the fact that no other researchers were advocating this method, it enabled us toobserve a large signal extremely easily and moreover to measure a range of properties
simultaneously. Therefore, I am actively using this method and I expect it to become
the standard method of measurement in this field.
I: WPI-AIMR has a variety of approaches for materials science, but I think thismeasurement method will play an indispensable role in the creation of new materials.
K: Today, we are especially seeing in many different locations a number of materials
that are more detailed and more precise and there is a demand for confining liquids invery tight spaces. These kinds of composite compounds are important in a wide
variety of fields, particularly when creating materials. To put it very simply, evenwhen discussing wettability, when combining the properties of surfaces with those of
liquids it is extremely important to correctly observe how these properties change innarrow spaces. As a result we get a comparatively large number of applications forjoint research from companies.
I: Changing the subject, congratulations on your selection in 2009 as the President Electof the International Association of Colloid and Interface Scientists. Is this theinternational organization for researches in colloid and interface chemistry?
K: That’s correct, it is the only one.
I: Does it have a lot of members?
K: No, member numbers are not that high, but all the main researchers in the field are
members. There are about 400 members and it is the umbrella organization for other- 11 39

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9:32:17groups around the world. Most of the European colloid scientists belong to theEuropean Colloid and Interface Society, which is a subsidiary organization. The
Division of Colloid and Surface Chemistry, which is part of the Chemical Society ofJapan, and the Division in the American Chemical Society of which the current
President is a member of, are also both subsidiary groups. Also, the Australian groupfalls under its umbrella.
I: I see. And you are the chair person of the Division of Colloid and Surface
Chemistry, the Chemical Society of Japan?
K: Yes. Actually, I have been also a council member of the International Associationof Colloid Scientists for 6 years, and when my term ended I was recommended forpresidency by the German. There was one other candidate, and I was selected byelection. I have been active to find ways of moving the organization forward as anumbrella organization and also as a forum for international exchange, and I think these
efforts have been appreciated. Also, my research field is surface force measurement,
which is one of the most important concepts in colloid-related fields, so I think this wasanother reason I was elected.
I: I heard that in the near future this organization will be holding a major international
conference in Sendai.
K: Yes, it is in 2012.
I: So the year after next; are you busy with preparations?
K: Extremely busy. We are jointly sponsoring the conference with the Science
Council of Japan. We also want to ask to WPI-AIMR to jointly sponsor the event.
I: Yes, thank you for that.
K: As it is two years away, from this summer we must think really carefully about thestructure of the event.
I: By the way, you are so busy at the moment; do you have time for hobbies?

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K: No, at the moment I have no hobbies. I read a little. But I find doing different
work very diverting, and what is most enjoyable for me is being in the laboratory doing
research.
I: So, this is the happiest moment, I guess.
K: Throughout my career, I have moved from position to position so by the time I was
42 years old I had experienced just about everything I could. Also, when I was at
Nagoya I started to build new equipments mostly by myself. So compared to thecareer of a typical university researcher I think I have a lot of diverse experiences on the
research front line. So although these days I am very busy, I am happy because I thinkthat the young researchers value the time we spend together researching and discussing.
I: That is very important. I know, Professor, that you were awarded a prize by The
Society of Japanese Women Scientists. Do you have any advice for female or young
researchers?
K: I have one piece of advice. I think that everyone can achieve a very original
research. First, you should think about what are the most fundamental issues in yourfield. Then, you should what you can do at the leading edge of this field. If you
combine your conclusions in these two areas then I think you should soon be able toconduct new, leading-edge research. You don’t have to be a research genius.
I: Very often, we are prone to feeling that we are not very original, that is not the casewith you?
K: No, I don’t think that is the case with me. But of course observational skills arenecessary. If I look back on myself when I was young, I think I had quite good powersof observation. However, the majority of what I do today is the result of an
accumulation of leading-edge research and the research done daily over a long period.
Also, there is probably a fixed perception of female researchers, and women tend to
think there is a ceiling stopping them rising above a certain point. I think they should
imagine this ceiling to be a little higher than they themselves think it is. Unexpectedthings can happen. When I was a student, it was unthinkable that a woman could
preside over a standard laboratory in a large university. So I thought I would finish my- 13 41

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life as a researcher having always helped someone else. But research is like a game ofcatch. I thought that I should enjoy receiving back from somewhere else the ball that
we ourselves threw even if I would be an assistant. The world of research is changing
and I hope that women can work on a level playing field with men, or even in somecases have the playing field balanced in their favor.
I: Yes, the research world is changing at a dizzying speed. It is not wise to set for
yourself something as a fixed constant, you should try to change it.
K: But it is precisely for that reason that it is vital to strengthen our abilities.
I: Thank you very much for taking time out of your busy schedule to talk with me.

Interviewer: Administrative Director, W. Iwamoto
At Kurihara Lab,
Advanced Materials Processing Building
IMRAM, July 5th, 2010
From April 2010, Wataru Iwamoto, Administrative Director,
replaced Professor Komatsu as the interviewer- 14 42

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9:32:19WPI-AIMR PI 栗原：和枝教授に聞く(Interview with Professor Kurihara－Japanese version)

Ｍａｙｂｅガールがコミットするとき
岩本：本年４月にWPI-AIMRの初の女性主任研究者に就任されたのでもっと早くインタビューに来ようと思っていたのですが、今日になり失礼しました。先生のお生まれは仙台ではないと伺いましたが。
栗原：ええ、東京です。
岩本：東京生まれの東京育ち。
栗原：はい、そうです。私は博士研究員でアメリカに行くまで実はずっと親元から離れたことがなかったのです。
岩本：では、江戸っ子ということで。
栗原：江戸っ子ではないですね。東京っ子ですが、品川なので東京の山の手ですね。
岩本：学部は、お茶の水女子大学の理学部卒業ですね。
栗原：理学部化学科ですね。
岩本：小さいころからやはり理科がずっとお好きだったのですか。
栗原：いいえ、私はどちらかというと本を読む事や、文章を書く事が好きでしたので自分は文系だと思っていました。ただ、文系でも余り理屈でやるようなものよりは、歴史や考古学といった、尐し実証的なものをやりたいと思っていました。どういうわけかそういう具体的なイメージがありました。けれども、両親はそういうものをやっても食べていけないと言い、理学部や理系
でも多分薬学部、医学部とか、あるいは文系だったら法学部などをイメージしていたようです。
私はもともとが考古学なので大分譲って理学部化学にしました。
岩本：大きな譲歩ということですね。
栗原：自分も尐し理系も勉強したかったのです。当時は結構格好のいい職業として理系ライターというのが尐しずつ出てきていた時代なんですよね。
岩本：ああ、そうでしたね。
栗原：ですから、本の出版とか、そういうものには関心があったので、理系のことをやって、将来は、出版社のようなところに勤めて本を作るのもいいかなとか、そういう気持ちがあって、非常に教養的な意味で進学しました。周囲には無線をやっていたり理科クラブに入っていたりと、

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やはりそういう同級生が多かったですね。
岩本：先生の場合にはむしろそういう科学の中身を一般の人に広く知らせたいというお気持ちはあったのですか。
栗原：いや、自分が今まで余り理系の学問は学校の勉強以外はしたことがなかったので、尐しそういうものをきちんと知りたいという気持ちがあったんですね。結構文系のことは図書館に行って調べたり勉強していましたので。
岩本：それから、理学部化学科から修士もお茶の水女子大学に進まれたわけですが、専門性というのはだんだん修士、それから東京大学の工学系研究科の博士課程に行くあたりで決まってきたわけですか。
栗原：私は大学の時、実は文系のサークルに入っていました。けれども、そこでは、美学や哲学とかをやっている人たちが随分いて、何か議論しているとやはり全然議論のレベルが違うので、あるときに、自分で勉強したものを大事にしてみたいなと思ったのと、３年のときに物理化学の学生実験をやったときに、ああおもしろいと思いました。計測から――これは今に通じているけ
れども――計測して、それから分子の性質がわかるというところです。今でも記憶に残っていま
すが、誘電率の測定をやって分子のダイポール、双極子モーメントがわかりますが、それも溶液の性質を見てその中に溶けているもののかなり細かい性質がわかるというようなことから、こういう計測はおもしろいと思ったのです。
岩本：計測との出会いですね。
栗原：それがきっかけで、物理化学の学生実験はとてもおもしろかったので、物理化学の研究室に行きました。そのときは将来研究者になるというつもりはまだなかったので、大学院はそのまま物理化学の研究室という、界面化学分野の研究室の修士に行きました。修士の時には、観察というものに基づく研究というものがおもしろくて、一つ論文になる研究が観察をもとにしてできました。自分らしい研究が学生でも多尐できたわけです。それで研究がおもしろくなったということと、あとはもともと考古学をやりたいというように、そもそも多尐研究者というものになりたかったかもしれないですね。
岩本： もともと研究熱心でいらしたのですね。
栗原：だから、それがたまたま化学だったということと、あとは同級生が、クラスの中で１人ぐらいドクターにいかないとおもしろくないよねと言って、進学を勧めてくれたのです。そのときに、一緒に勉強会をやっていた助教授の先生に彼女は博士課程に進学したら良いと思っているのだけれどと同級生が話して、勝手に彼らが相談して、私に進学したらと言って、そのときに非44

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常勤講師で来ていた先生の研究室に行ったらどうだろうという話になりました。
当時の東大工学系研究科では博士課程からの進学の例があるとのことで、工業化学専攻の工業物
理化学の研究室がで、内容は光電気化学の研究室が界面化学に近いということで、その研究室に行くことになりました。そう具体化してから実は試験も厳しいことが分かり、習っていない科目も多く試験勉強は一生懸命しましたが、もう本当に自主的ではなかったのです。
岩本：伺っていておもしろいと思ったのは、先生の場合、文系のサークルにいらして、だからこそ理科というものをある意味一生懸命やってみたいというようなことがあったということですが、やはり実証的に何か観察に基づいてやろうというお気持ちがあったのですね。
栗原：そうですね。だから、考古学をやりたいと思っていた気分と研究をやりたい気分というのは、高校生のときからあったので、そういうものと今やっている精密測定というのはやはりど
こかもとのところではつながっているのかなと思いますね。
岩本：確かに考古学は人文系にしてはかなり数字も必要ですね。
栗原：サイエンスは実証なので労働としての大変さはあるけれども、きちっと測っていくというのはある意味ではスポーツみたいなところがありますよね。だから、それはよかったなと思いますね。
岩本：それで、博士課程に進まれて、博士論文は、どういう内容ですか。
栗原：バイオミメティックなんですけれども私の場合ずっと共通しているのは、分子の自己組
織性というものです。修士論文はミセルと液晶です。ミセルというのは界面活性剤が集合しているもので洗剤の主成分ですが、それと液晶。それから、博士論文は脂質の二分子膜といって、生体膜のモデルですけれども、それにクロロフィルを入れて光を当てて葉の光合成のモデルのような研究をやりました。これも日本で初という要素がいろいろあって、脂質の二分子膜を米国で習ってきた先生が研究室にいて、日本の化学分野では一番最初に脂質二分子膜での反応の研究をやりました。
岩本：バイオミメティックということは、あたかも生物であるかのような、生物を真似するかのようなものですね。
栗原：そうですね。生物の中で起こっている機能を真似て人工的な系を作ると。だから、バイ
オミメティックの一番単純なのは、例えば飛行機だとも言えます。飛行機は鳥を真似ています。
ただ、それは分子レベルのミメティックではないですが、分子レベルで真似るのなら、例えば葉の光合成の真似があります。植物の葉では葉緑体の膜の中にクロロフィルがあり光がたると、それで反応を起こして光合成が進む訳ですが、それと同じように光を当てて、光のエネルギーを化

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学エネルギーとして、それを化合物に蓄えたいという、そういう研究がそのころからあって、その研究に携わりました。また最近いろいろ、低炭素化社会実現という文脈でそういう研究がまた出てきていますけれども、当時もうオイルショックの後ですから。
岩本：そうですね、第１次オイルショックが１９７３年でしたね。
栗原：オイルショックの後なので非常にそういう研究が注目されていました。エネルギー変換
系の一番最初の研究ですね。それから、バイオミメティックもちょうどそのころに出てきた分野
でして、生体膜のモデルや酵素モデルは、そのころに研究として始まった分野なので、界面化学の分野で扱う材料がちょうどバイオミメティックの生体膜モデルなどに共通するものなのです。
いろいろ分子を集めた集合系みたいなものを界面化学で扱う訳で、最初からそういう分野で研究をやってきました。
岩本：界面というのは今WPI-AIMRでいろいろな研究者の方がやっていらっしゃいます。１９７
０年代の終わりからやはり界面というのは世界的に重要な分野だったのですね。
栗原：そうですね。時代によりそれぞれ意味が違っていると思いますけれども、界面化学というのは結構古い学問ですが、１９７０年代には生体膜のモデルとして、脂質は界面活性剤と同じような構造をしたものなので、脂質や界面活性剤の集合系が使われていました。ちょうどその当時に分子を組織化していろいろな機能系を設計するという考え方、例えば反応する距離をコントロールするだとか、そういうような考え方も出てきて、ちょうどそれらがいろいろな今のナノテ
クにつながる考え方のはしりになっています。
一つは分子の自己組織性ということだと思いますし、もう一つは、酵素は必ずしも自己組織性ではないのですが、酵素も含めたいろいろな生体の機能を真似て良い材料を作ろうという研究のはしりがその頃から出てきました。背景には生体の構造や生体膜の構造、酵素の構造をＸ線で解明したとか、そうした研究がその当時出てきたことが大きいのです。材料も作れるようになってきましたし。
岩本：そういう材料を作る方法も出てきたし、観察する手段も出てきたということですか。
栗原：もちろん今の方がずっと進んでいますけれども、その当時がはしりです。今はナノレベ
ルの材料が工業的にも使われるようになって、界面が大事だと言う風になってきています。それから、多分その当時は本当に一部の人だけがやっていたのが、今はみんながやっている。だから、先端はもっと深くなっていますし。
岩本：今おっしゃったことは、先生の研究テーマの一つの表面力測定と関係するのですか。
栗原：私は１９７９年に博士号をとりましたが、そのときは光反応の実験を博士論文でやって

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いたので、その後アメリカへ博士研究員として行った研究室の先生はやはりバイオミメテイック
をやる、メンブレミメティック・ケミストリーを提唱していたフェンドラー先生といって、生体膜の機能を真似た良い材料を作るという、そういう研究をやっていた方でした。その先生のとこ
ろにはいろいろな光の高速反応を測る装置があって、中でもレーザーフラッシュフォトリシスという当時としては先端の研究手段でした。それをやりたくてそういう装置を持っている先生のところに行きました。当時は、特殊な場でナノ粒子を作るという研究もはじまってきて、今度はナノ粒子も分子組織体の中で作る研究をやって、日本へ戻ってきて、そのころそういうバイオミメ
ティックでやはり当時のトップ研究者と言われた京都大学合成化学科の田伏岩夫先生の研究室に２年ほど行きました。
そのうち、自分らしい研究は何かを考えるようになりました。それまで私は、いろいろな機能
材料を一応作っていました。作っていたというより、系の設計をしていた訳です。材料を合成す
るのではなくて、組み合わせて機能系を設計するということをやっていましたが、自分は元々物理化学なので、何か計測をしてこの特性はこういう性質を持っている、こんなにいい機能があるということを測る研究だったのです。私は合成ではないので、おもしろい機能を見出しても、それをだんだん深めていくというアプローチがとれないので、そういう研究よりは１０年やったら１０年後はもうちょっと違うことができるような研究テーマをやりたいと思いました。それで、分子組織体とか自己組織性がわかる手段として何かないかなと考えていたときに表面力測定に出会いました。自己組織性は分子が集まる性質ということで、相互作用により集まる訳ですから、
そういう系を理解するために表面力測定というのは面白いのではないかということです。その後スウェーデンの研究所に行った時に、その研究所にはその測定装置を導入したところだったので、ちょっと共同研究をさせてもらって、どんな測定法かということがわかってきました。
岩本：スウェーデンの表面化学研究所ですか。
栗原：界面化学研究所と日本では呼ばれています。直訳すると確かに、surface chemistry、表面化学ですけどね。
岩本：先程のお話で、アメリカで研究された時のフェンドラー先生というのはTexas A&Mの恩師ですね。
栗原：そうですね。在米中にはクラークソン大学に先生が移られ、研究室も同じ構成で移りました。
岩本：アメリカには都合３年ぐらい滞在し、その後スウェーデンに行かれたのですか。
栗原：はい。日本に２年戻ってきて、スウェーデンに２年です。

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岩本：外国で研究しという経験は、研究の成果はもちろんのこと、ご自分の人間形成にとってどんな意味があったと思われますか。
栗原：私はフェンドラー先生には頻繁にコミットしろと言われました。
岩本：コミットしろというのは。
栗原：意見をはっきり言え、ということなのです。私はすぐMaybeと言ったらしいんです。
Maybeガールとあだ名をつけられて、だからはっきりとコミットしろ、意見を決めてきちっと言わなければいけないと言われました。日本ですと、特に私は男性の中に入って女性１人というのが多かったこともあるかもしれないけれども、でも、どちらにしても男女を問わずはっきりとした意見を人の前で言うというのは余りないですよね。
岩本：そうですね。
栗原：だから、それがすごく気になったらしく、とても頻繁にコミットと言われましたね。ですから、Maybeガールだ、おまえはMaybeガールだとからかわれていました。
おかげで、もしかすると私は結構はっきりとした意見を、特に外国人に対して言えるようになったような気がするんです。
岩本：私も外国に長い間暮らしましたけれども、どうしても日本人は先程おっしゃったMaybeだ
とかPerhapsだということが多い。もっと自信を持って言えば良いのにというところがあります。
外国人は結構乱暴なことを断定的に言ったりして、その辺はまたある意味日本人としても、日本の社会の中でそれを全部通すということがまだなかなか...
栗原：できないですよね。
岩本：受け入れられないということがあるのですが。むしろ日本の風土を変えていかなくてはいけないと思います。でも、それは非常に重要な点ですね。
栗原：あとは例えばスウェーデンにいたときは、最初は日本学術振興会の二国間交流で行き、それが終了しても引き続き滞在しましたが、先方のお給料が安そうだったのです。それを所長に交渉して、どうもこれは安いのではないかと言いました。日本ではお給料については議論しないということが慣習であるので、私は日本でこういう議論をするつもりはないけれど、どうも外国では給料はその人にいてほしさというものを反映していると聞いている。それだから、このお給料だと私はここにずっといたいという気持ちにはなれないので上げてほしいと言ったら上がったのです。倍ぐらいになりました。
岩本：外国ではそういうところはありますね、確かに。
栗原：そういうことを、非常に考えて言ったのですけれども、そういうことが通ったという部

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分、その後も何か時々外国人と結構交渉事をやることがありますが、そういうことがいい経験になったと思いますし、本当に考えて筋道を通して言えば外国では比較的通ります。
岩本：そうですね。もちろん今のお話は先生の実力があったからですけれども、外国ではやはりはっきり言わないといけませんね。何も言わないとこれに満足していると思われるし。やはりちょっとでも違うのではないかと、こういうことは違うというのはやはりはっきりしていくというのが尊ばれますし、日本も本来は見習わなくてはいけないと思います。
栗原：だから、Maybeでなくコミットしろと言われたのは、それは多分一つの外国にいたときの大きな教訓ですね。
あとは、私は国内もそうですが、随分色々なところで研究させていただいたので友達が大勢います。どこの大学にも友人がいて、外国でも、学会等に出席すると知人に会って風貌が変って誰だ
かわからないでいると、「誰々」と言われて懐かしく話ができるというときが結構ありますよね。
岩本：それは貴重な財産ですね。
栗原：そうですね。
岩本：ところで、先生は、スウェーデンから帰っていらして九州大学の国武豊喜先生のところ
でERATOのグループリーダーになられましたね。
栗原：ここでは単分子膜といって、ある意味で学生のときからの続きです。水の上にやはり界面活性剤に似たような合成の分子を並べて分子認識の研究をしていました。実は分子認識というのは前にお話した田伏先生のお家芸です。私は田伏先生のところにいたときにやはり単分子膜の分子認識の研究を、ちょっと違う形ですけれどもしていました。ＥＲＡＴＯではグループテーマ
で、私が最初に形をつくって、ほかの人たちは新しい分子を合成して展開しました。
表面力測定はERATOで始めました。表面力測定は国武先生も関心を持っていたようなのです。それで、私に関心があるということを知ってやってみようかと、オーストラリアでその装置の原型を売り出していたので、それを買って始めました。私はそれまで物理化学といっても計測器を大きく組む事はやったことはありませんでした。ところが、装置は売っていますが、メインチャン
バー(主容器)というものだけ、メインコンポーネントだけ売っていて、あとは全部自分でそろえて組まなければいけないし、測定も割合難しいものでした。私はたまたま尐し見せてもらったけ
れども、実際は動かしたことはなかったので、国内で組むのに全部部品を一つずつ捜したりいろ
いろな人に聞いたりしながら自分で組んで、サブテーマで表面力測定を始めました。
岩本：大変なスタートだったのですね。
栗原：導入したのは、オーストラリアの国立大学の工作室で作った改良型1号機でした。私は先49

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行モデルをスウェーデンで見ていたましたが、使いにくいということを知っていたので、よくすべきだと思っていたのですが、動かない装置を買ってしまったら後で大変ですよね。どう動くのか見せてほしいと言って装置の価格に含まれていたトレーニング期間２週間を使ってオーストラ
リアに行き、見せてもらい、「ああ、動きそうだから、ではこれ買います」ということで、それで買いました。新しいモデル１号機ですので、もし動かなかったら替えるという契約もしました。
ERATOの運営の人たちと相談しながらでしたが。そのときに向こうが装置をよく見せてくれた。
私が今装置を作れるのはそのときに装置を見せてもらったのがとても大きく役立っています。
岩本：それだけオープンに見せてくれるものなのですか。
栗原：いや、普通は見せないでしょう。だから、それは絶対動くのだということをテストで見せようとしたので。どういうふうにテストするのかを、たまたま新しい装置を開発した人を私はスウェーデンにいるときから知っていたということもあって、それもあったのでしょうが、とても丁寧に見せてくれた。また、その人が人柄のいい研究好きの研究者だったので。だから、以後、装置を作れるようになったのは多分それがすごく大きいです。
岩本：今のお話を伺っていると、やはり先生の分野は界面という研究対象ですが、その測定の積み重ねをされる中で、装置についても、先程のようにメインチャンバーはあるけれども、それにどうやって継ぎ足していくか、それは御自分で考えたのですよね。
栗原：：はい。初めて大きな装置を自分である程度組み立てたことになるのですが、ERATOで表面力測定をサブテーマでやっていて、終わりのころには教科書に引用されるような新しいデータもとれるようになったのです。日本では初めて動いた装置というので随分シニアの先生方が喜んでくださって、中には九州まで見に来てくださった先生もいました。その後、名古屋大学で、そうした測定をやっているなら、生物物理工学研究室で雇ってくださるということで助教授になりました。
岩本：それで、名古屋大学に移られたのですね。
栗原：そうですね。ですから、名古屋では生物物理の研究室に行ったのですが、その研究室の前の名称は精密計測だったときいて縁を感じました。話ができ過ぎていますが、だから精密測定の先生が興味を持っていて雇ってくれたことになります。名古屋は電顕、Ｘ線と非常に物理計測のメッカみたいなところで、応用物理は装置作りがすごく盛んな学科でしたので、学科で立派な工作室を持っていて、だからそこで装置を作るようになったのが装置作りの初めです。
岩本：それで１０年ほど前に東北大学にいらして、今もそういった測定ですか。
栗原：そうです。やっていて、だんだんおかげさまで装置作りも腕が上がってきました。

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岩本：共振ずり測定法も開発されたと伺っていますが。これはどういうことですか。
栗原：普通の表面力測定は垂直に働く力、ノーマルフォースを測るのに対し、それを面を平行にずって、ずることでのレスポンスを測るというので、場合によると垂直力がかかっているとこ
ろをこういうふうにすることでさらに感度よく検出できるという場合もあるのです。もともとは固体の間に液体を挟んで、摩擦とか液体の流れを見るとか、学問分野でいうとレオロジーとかト
ライボロジーとかいう、分野に近いような測定です。
名古屋で測定を始めた時、原子間力顕微鏡が出てきました。これがどの程度の表面力測定に使え
るか尐しわからない部分があったのですが、測定法としてはかなり楽でした。一方、表面力測定の精度はすごくいいのですが、やはり手間のかかる測定なので、その中で表面力測定でないとできない残る部分は何だろうと考えました。
その時、大きな表面に液体をはさみずる測定は残るのだろうと思ったわけです。これは原子間力顕微鏡ではできない。それをやりたいと思って装置を作って、装置ができて、最初は普通に応力を測ろうと思いましたが、何か共振のすそみたいなものがかかってきて、きちっと測れなかったので、ではまず共振がどういうふうに出てくるのかチェックしようということでモニターし出したのがきっかけです。共振法というのはだれもやっていなくて、オリジナルメソッドなのですが、実は結果的に言うとそれをモニターしようと思ってやったら、とてもきれいに測れそうだということになり、できた方法です。ほかの人たちはそういう方法を提案していなかったのですが、大きいシグナルを見るので非常に簡単で、しかもいろいろな性質が同時に測れるというので、私はこれが標準的な方法になるのではないかと期待して一生懸命やっているんです。
岩本：WPI-AIMRでは、材料科学についていろいろなアプローチでやっていくところですから、先生のこういった測定方法は新しい材料を考えていく上で本当に不可欠なものでしょう。
栗原：今は特にどこでもいろいろな材料が微細・精密になっていて、狭い空間に液体を入れなければいけないというような要求もあるようです。そういう複合化というものも色々な分野で大事で、特に材料を作るときにはそうです。非常に単純には濡れ性とかいうことについても、表面の性質と液体の性質との組み合わせとか、狭い空間になったときの性質の変化をきちんと見ていくということがとても大事だということで、割合、企業からの共同研究の申し込みも多いです。
岩本：話は変わりますが、２００９年からは国際コロイド界面化学者連盟 (International
Association of Colloid and Interface Scientists)のプレジデント・エレクトだそうで、おめ
でとうございます。これはそういうコロイドや界面化学の研究者の国際的な団体ですか。
栗原：そうです。これが唯一のものです。

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岩本：かなり会員数も多いのですか。
栗原：いや、会員数は多くないのですが、主な研究者はほとんど入っていて、会員数は４００
名ぐらいです。ヨーロッパのコロイド科学者の大体は、ヨーロピアンコロイドというものに所属していますが、それの上の組織ですし、日本ですと日本化学会の中にコロイド界面化学部会がありますが、それも傘下に入っていますし、アメリカの化学会の部会もそうで、現会長はアメリカ
化学会の部会員がやっていますし、オーストラリアの部会も含め、アンブレラオーガナイゼーシ
ョンです。
岩本：そうですか。先生は日本化学会のコロイド及び界面化学部会の部会長ですよね。
栗原：はい。実は、国際コロイド化学者連盟では理事を６年間させていただいて、任期終了時にどういうわけかプレジデントにドイツから推薦いただいて、他にもう１名、候補がいらしたのですが、選挙で当選させていただきました。私はアンブレラオーガナイゼーションとか国際交流とか、そういう面でうまく進める方法はないかということを一生懸命やってきましたので、そういうところを評価されたのだと思います。また、研究も表面力の測定というのはコロイド関連の分野では最も要になる概念の一つなので、そういう分野の研究をやっているからだと思います。
岩本：この組織は近々仙台で何か大きな国際会議を開催されると聞きましたが。
栗原：２０１２年です。
岩本：再来年ですか。その準備とかお忙しいですね。
栗原：もう大変なんです。日本学術会議と共同主催に採択いただきました。WPI-AIMRにもそのうちに共同主催のお願いに行くつもりなんですけれども。
岩本：はい、それはありがとうございます。
栗原：ちょっとまだ２年後ぐらいなので、今年の夏あたりから１年ぐらい本当にきちっと組織を考えないといけないです。
岩本：話はまた変わりますが、先生はこれだけお忙しい中で趣味は何ですか。
栗原：現在は趣味といえるものは、ありません。本は尐し読んでいますけれど。ただ、違う仕事をさせていただいているのが気分転換ですし、研究室で研究をしているのが一番楽しい。
岩本：それはある意味で一番幸せかもしれませんね。
栗原：私は長く流動ポストという経歴なので４２歳ぐらいまで自分で全部実験していました。
その後も名古屋のときは装置を全部自分で組んでいましたから、そういう意味で普通の大学の一般の研究者に比べると現場が長いので、今は忙しいですけれども、一緒に議論しながら研究をやるということに関して若い人が大事にしてくれるので幸せと思っています。

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岩本：それは重要なことですね。先生は、日本女性科学者の会の賞も受賞されていますけれど
も、女性研究者あるいは若手研究者に対するアドバイスとしたら、どういうことになりますか。
栗原：一つは、私は、だれでも非常にオリジナルな研究はできると思っています。それは自分の分野の非常に基本的な課題で何がわかっていないのかを考えて、それから最先端で何ができるかを考えて、それを組み合わせてちょっと考えればだれでもすぐ先端の新しい研究ができるのではないかと。天才性とかいう話ではない気がします。
岩本：とかく自分はオリジナリティーがないのだと思いがちですが、そんなことはないと。
栗原：そんなことはないと思います。ただ、もちろん観察力は必要です。私は若い時の自分を思うとかなり観察力があったかもしれないですが、例えば今やっているのはやはり先端と毎日の積み重ねでやっているところが多いですね。
あと、女性研究者ですが、従来からの形というのはあるかもしれないですが、女性はこのくらいといった限界などは、世の中は動いているのだから、限界は自分の思うより尐し先にあると思ってやったらいいのではないかと思います。思いもかけないようなことってありますよね。私が学生の頃でしたら大きな大学の普通の研究室を女性が主宰するというのは考えられないことでしたから、私は一生だれかの手伝いをして研究者としては終わるのだろうと思っていました。それでも研究というのはキャッチボールするもので、自分の投げた球はどこかから返ってくるというのは楽しくてそれでいいと思っていました。でも、今はこんなに世の中が変わってきて、女性でも普通にやれるし、あるいは場合によったら普通以上にやることが期待される場合もありますし。
岩本：そうですね。世の中自体がもうどんどんすごい速さで動いていますからね。何かある一定の分みたいなものを自分で設定してしまうと、かえっていけませんね。
栗原：でも、だからこそ、実力を蓄えてというところが大事ではないでしょうか。
岩本：長時間にわたりまして貴重なお話をいただきどうも有り難うございました。

２０１０年７月５日
東北大学多元物質科学研究所材料物性総合研究棟 PI栗原研究室にて
岩本 渉

２０１０年４月１日からインタヴュアーは、小松教授から岩本事務部門長へ交代しました。

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News Update

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WPI-AIMR Outreach Activities
In April 2010, WPI-AIMR decided to further promote outreach activities. Dr. S.
Ikeda was assigned as Outreach Manager, a position responsible for planning andpromoting WPI-AIMR‟s outreach activities. The aim of the outreach is to facilitatecommunication and mutual understanding between WPI-AIMR and the public. On June
19, 2010, the press release regarding “promotion of science and technology
communication with the public” was issued by Tatsuo Kawabata, Minister of State for
Science and Technology Policy (concurrently holds the position of Minister of
Education, Culture, Sports, Science and Technology ) and the Council for Science andTechnology Policy. The press release specifies that the research projects based on
public funds of over 30 million yen will be evaluated not only in their research results
but also in their outreach activities. Now WPI-AIMR has to meet accountability
standards for the public, and show how our research activities are important in society
and what excellent results will be obtained.
The outreach team of WPI-AIMR issued the first volume of our outreach magazine in
June. The magazine was named Tohoku WPI Tsu-Shin. All articles are written in
Japanese for the public distribution. Volume 1 contains greetings from the director, an
explanation of “WPI”, and a brief introduction of ongoing research projects at WPIAIMR. The memorial cover of the first issue was illustrated with a painting drawn by
an elementary school pupil who lives in Miyagi Prefecture. We hope that this painting
acts as a mediator between citizens and WPI-AIMR. The star seems to represent anatom and the stork seems to represent a molecule, and they just seem to be flying out of
the universe (the material world). The column “Communication Square” at the last
page of the magazine invites the questions and comments from the public. Tohoku WPITsu-Shin volume 1 has been mailed to all elementary
schools and junior high schools in Sendai City and all highschools in Miyagi Prefecture. The magazine has beenplaced at Sendai City Information Centers, Sendai Science
Museum, and Sendai Astronomical Observatory. It has also
been distributed to participants in the scientific events
shown on the next page. The magazine will be issued threetimes a year, in June, October and February.
So far, WPI-AIMR opened a booth at the following three
events.

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“Science and Technology Festa in Kyoto” (June 5)
WPI-AIMR made a presentation at the “Science and Technology Festa in Kyoto”
held at Kyoto International Conference Center on June 5, 2010. The five WPI centersgathered to present the WPI program and their research activities. At the same venue,
Prof. Adschiri, PI of WPI-AIMR, was awarded “The Prize of the Minister of Education,
Culture, Sports, Science and Technology in the field of Cooperation among
Government, Industry and Academia” and also opened his booth at the Festa.
“The City of Academia „Sendai-Miyagi‟ Science Day 2010” (July 11)
WPI-AIMR opened a booth at the “City of Academia„Sendai-Miyagi‟ Science Day 2010” held at Kawauchi
North Campus in Tohoku University on July 11, 2010.
About twenty elementary and junior high school
students tried to make transistors using organic
semiconductors and studied a cutting-edge research
topic.
“Tohoku University Open Campus 2010” (July 28 - 29)
Tohoku University Open Campus was held on July 28 and 29, and WPI-AIMR
opened a booth in the Physics A Building, Aobayama Campus to show Tohoku
University‟s activities to high school students. Chemical experiments (reactions andsynthesis) and physical experiments (transistor characteristics) were demonstrated, andan introduction of WPI-AIMR was offered using posters and magazines.
For details of these events, please visit the “News and Information” page of our website.
Profile of Outreach Manager
Susumu Ikeda graduated from the Faculty of Science, Tohoku University in1990. After working at cement companies, he moved to the University of Tokyo in
1995. After obtaining a Ph.D. in 2000, he worked at the University of Tokyo as a
postdoc, research associate and assistant professor. In 2008, he moved to WPIAIMR as an assistant professor. His wide research experiences in mineralogy,
petrology, cement chemistry, surface science (metals, semiconductors andinsulators), organic semiconductors, and electronic devices are helpful in informing the public about
variety of research topics currently in progress at WPI-AIMR.

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The 1st WCU/AMS (POSTECH)-WPI/AIMR (Tohoku University)
Joint Workshop at POSTECH, June 18, 2010
M. Yamaguchi
The 1st WCU/AMS (POSTECH)-WPI/AIMR (Tohoku University) Joint Workshop
was held at POSCO International Center in Pohang University of Science andTechnology (POSTECH) in the Republic of Korea on June 18, 2010. POSTECH,
founded by world-class steel company POSCO at Pohang, is a leading university of the
Republic of Korea in the field of science and technology. The purpose of theworkshop was to promote collaboration and exchange of researchers between
WPI-AIMR and WCU-AMS based on the agreement signed this March at Sendai during
the 2010 WPI-AIMR Annual Workshop. Both programs possess a common purpose in
the development of new frontiers in the materials sciences. Seven PIs visited from
WPI-AIMR with a student who obtained a PhD from POSTECH and is now working
with Professor Adschiri, and six PIs from POSTECH gave talks.
The workshop opened with welcome remarks from Professor Kimoon Kim(POSTECH), WCU-AMS director, explaining the WCU-AMS program in Korea, andannouncing the agreement and future plans. The introduction of WPI-AIMR program
was then provided by WPI-AIMR director Professor Yoshinori Yamamoto.
The first scientific talk in the morning session was given by Professor Kimoon Kim.
He showed a number of cucurbituril derivatives including polymer shells, which canform inclusion complexes with various organic host molecules.
Such novelcompounds can be applied to ion channels embedded in a lipid bilayer, targeted drugdelivery, and immobilizing a protein on a solid surface.
The second talk was given by Professor Kyo Han Ahn at the department of chemistry,
POSTECH. He discussed molecular recognition and sensing of anionic species suchas carboxylates or amines for biochemical study and disease diagnosis. The molecular
probe method was integrated to a gold nanoparticle sensing system and polymerized
liposome sensing systems.
Professor Kingo Itaya of WPI-AIMR presented a new method to study surface
structures. A laser scanning confocal microscope combined with a differential

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interference contrast microscope (LCM-DIM) method allows the observation of a single
atomic step on Si(111) and Si(001) in an NH4F solution. The atomic process of metalelectroplating was revealed by this method, which can be applied to the production ofelectronic devices based on organic semiconductors.
Professor Moon Jeong Park from WCU-AMS was the only female speaker in thisworkshop. She talked about poly (styrenesulfonate-b-methylbutylene) membranes
comprising hydrophilic phases with widths ranging from 2 to 5 nm to control water
retention. Such ion-containing polymer electrolyte membranes (PEMs) can be used infuel cells.
Professor Tadafumi Adschiri of WPI-AIMR described organic-inorganic hybrid
nanoparticles. Organic modified nanoparticles were synthesized in supercritical watertaking advantage of organic molecules and metal salts aqueous solutions being miscible.
The hybrid nanoparticles show high affinity with the organic solvents or polymer matrix,
which facilitates their applications.
After lunch, the afternoon session was started with a lecture by Professor Masatsugu
Shimomura from WPI-AIMR. He discussed novel biomimetic surface materials,
honeycomb-patterned polymer films, which have two-dimensional regular arrays of
micro/nano pores.
Such surfaces show very small light reflectance and asuper-hydrophobic nature.
Professor Danil N. Dybtsev (POSTECH) joined WCU-AMS program from Russia.
He presented enantiopure porous coordination polymers containing zinc metal, which
can be used for chiral separation or fine purification of optically active molecules.
Professor Naoki Asao of WPI-AIMR discussed the use of nanoporous gold in
catalysis particularly in the oxidation reaction of alcohols to aldehydes and ketones in
the presence of molecular oxygen. The monolithic materials consisting of athree-dimensional network of ligaments with diameters on the order of 10 to 50 nm
were shown to be effective for this transformation.
Professor Masahiko Yamaguchi from WPI-AIMR showed a study to integrate smallchiral aromatic molecules to chiral materials. Using helicene as the small molecularunit, substances were integrated to built-up macromolecules and then to gels and60

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nanoparticle aggregates.
Professor Hee Cheul Choi of WCU-AMS showed methods for constructing nano- tomicro-structures using vapor phase reaction (vaporization-condensation-recrystallization)and the solution phase (drop-drying). Using these techniques, hexagonal and helix
structures were constructed.
Professor Toshio Nishi from WPI-AIMR discussed new and practical soft materials
useful for the society in view of the environment, energy, and safety. As examples,development of ultra-low rolling resistance tire compounds and seismic-elastomericisolators was described.
The last talk in this workshop was given by Professor Masaki Kawano, who recently
joined POSTECH as a WCU professor from the University of Tokyo. He developed
the structure determination method of crystalline compounds by powder X-ray analysis,
not by single crystal X-ray diffraction. A porous coordination network was formed bykinetic effect, and the method was applied to analyze the substances.
On the day preceding the workshop, there was a Soccer World Cup Game between
the Republic of Korea and Argentina in South Africa. The game was shown on a large
display in a student hall, and many students enjoyed the game until late at night.
Unfortunately, the Korean team lost the game, although the game itself was very nice.
On the next day, professors and students were discussing the game. Such closeinteractions of professors and students are a merit of POSTECH. I had an opportunity
to work with POSTECH graduate students, and found them to be enjoyable, polite andenthusiastic.
POSTECH is located in the suburbs of Pohang, where most of the students andprofessors live. We stayed at the guest rooms in the POSCO International Center,
which were surprisingly well equipped. We hoped to have such facilities in our
university. It is also notable that the historic city of Gyeongju, the capital of the Silla
Kingdom for almost a thousand years, is located a 30 minute car ride from Pohang.
Professor Kim visited WPI-AIMR this July after the workshop in order to discuss
further interactions and to give talks in Aobayama and Katahira. Several collaboration
programs appear to be starting between Tohoku University and POSTECH. It ishighly likely that WPI-AIMR and WCU-AMS will be excellent partners in the East

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Asian region for the promotion of research in the field of materials sciences.

(Workshop’s Photos)

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WCU Project and POSTECH-AMS
W. Iwamoto
The WCU Project
The Government of the Republic of Korea launched in 2008 the national projectcalled “World Class Universities” in order to meet a critical need to foster research in
key growth-generating fields, and to ensure quality in the development of
next-generation human resources. The project invites global top-level scholars andresearchers to develop world-class academic programs and departments in Korean
universities, which will ultimately lead to the creation of world-leading institutions ofhigher education in. This project was initiated with the purpose of promotion ofquality and excellence, and to increase the competitiveness of higher education
institutions. It also represents the idea of “from brain drain to brain gain”.
The Project focuses on supporting new growth-generating fields that have thepotential to the spearhead national development.
Examples include NBIC
(NanoBioInfoCogno) fusion technology, disruptive technology, breakthroughtechnology, energy science, bio-pharmaceutics, etc. Priority is also given tointer-disciplinary fields that cut across the fields of basic sciences, humanities and social
sciences, which will contribute to national, social and academic development.
The WCU project invites the participation of international scholars and researchers
according to three project types: 1) recruiting scholars to establish new academic
departments or specialized majors in Korean universities, 2) employing foreign scholars
at existing academic programs, and 3) inviting distinguished world-class scholars toteach and research in Korea. The proposals are submitted to panel reviews andinternational peer reviews. In the case of type 1), 32 proposals were selected so far
through the 1st and 2nd round selection processes.
Different from WPI program in Japan, the WCU Project focuses not only on research,
but also education. Moreover, the Project also covers the linkage with humanities andsocial sciences.
POSTECH and AMS
Pohang University of Science and Technology (POSTECH) was established in 1986
as the first research-oriented university in Korea with the strong support of POSCO, a
top global steel production company. With 10 departments and 57 research centers,
the University now has 244 faculty members and 780 researchers together with 3,057

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students (figures are as of 2009). The global partners of POSTECH consist of over 70
universities in 19 countries. It is notable that Tohoku University signed an Academic
Exchange Agreement with POSTECH in September 2000.
POSTECH was selected in all three project types of the WCU Project, the number of
selected proposals totaling 6. The three proposals selected in the first type, i.e. the newacademic department establishment, have progressed to the opening of the Division ofAdvanced Material Sciences, the Division of Integrative Biosciences and Biotechnology,
and the Division of IT Convergence Engineering.
The Division of Advanced Material Sciences (AMS) headed by Professor Kimoon
Kim focuses on fundamental research for the development of new functional materials
and device platforms (Figure 1), based upon four research areas, namely emergent
materials, self-assembled nano hybrid materials, self-assembled soft materials, andemerging device systems. (Figure 2)
Figure1

Figure 2

Figure 3

AMS now has 14 faculty members(PIs) in the areas of physics, chemistry,
and materials science. As the WCU
Project requires 30-40 % of them tocome from abroad, there are 5 foreign
researchers as faculty members (1German, 1 French, 1 Russian, 1Japanese from The University ofTokyo and 1 Korean member who

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just finished 3 years of research activities at UC Berkeley). From last year AMS
receives 15 post-graduate students. The Korean Ministry of Education, Science andTechnology provides about 3 million US dollars to AMS through the WCU Project
annually. This subsidy is used for an annual salary and lab establishment expenses foreach foreign scholar, and research grants for all the faculty members.
While AMS has a great advantage in collaborating with POSTECH Biotech Center,
the National Center for Nanomaterials Technology, and the Pohang Accelerator
Laboratory in POSTECH, it also constitutes global network with the Max Planck
Institutes, the Asia Pacific Center for Theoretical Physics, RIKEN SPring-8 Center and
WPI-AIMR, with which AMS signed an Agreement on Academic Exchange last March.
(Figure 3)
AMS makes great efforts to integrate various disciplines not only in research, but also
in education which is most challenging. On the other hand, AMS involves as much as
possible foreign faculty members who cannot necessarily stay a whole year in Korea.

This article is written based upon the brochuresof the Korean Ministry of Education, Science andTechnology, POSTECH and AMS, together with
precious information provided through interviews
with Professor Kimoon Kim, Director,
WCU-AMS to whom I express my sincere
gratitude for spending his time in spite of the tightschedule of his short visit to WPI-AIMR from 19
to 22 July.

Prof. Kimoon Kim

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Dr. Akihisa Inoue’s lecture
at reception of Acta Materialia Gold Medal
Dr. Akihisa Inoue who is a member of International Advisory Board of WPI-AIMR
and President of Tohoku University was awarded “Acta Materialia Gold Medal”.
The presentation ceremony was held at the WPI-AIMR
Annual Workshop on March 26, 2010 in Sendai. Dr.
Thaddeus B. Massalski, Professor of Carnegie Mellon
University and Executive Secretary ofActa Materialia, Inc, handed over theGold Medal to Dr. Inoue.
Following the ceremony, Dr. Inoue gave a special lecture titled“Development and Applications of Bulk Glassy and Nonequilibrium
Crystalline Alloys”. The summary of the lecture is as follows:

Unlike crystalline solids amorphousalloys do not have a periodic structure
which results in unique properties. Bulk
glassy alloys are produced at coolingrates of 1-100 K/s. The lowest criticalcooling rate for glass formation is 0.067
K/s which is about 15 million times
smaller than that required for ordinary
amorphous alloys.
For example, Pd-Cu-Ni-P glassy alloy
ingots produced in our laboratory are thelargest monolithic metallic glassy objects
obtained up to date owing to
exceptionally high glass-forming abilityof the alloy and application of a special
processing technique.

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For the past two decades weaccumulated a large amount of data on
bulk glassy alloys and we produced large
scale bulk glassy alloys with critical
diameters of over 2 cm in a variety ofalloy systems as shown in the Table.

These alloys consist of three or moreelements, have a significant atomic size
mismatch above 12% and negative heaton mixing. Based on these guiding
rules, we obtained a variety of metallic
bulk-glassy alloys mentioned above.

Initially scientists believed thatmetallic glasses form dense random
packed structures. Later it become clearthat they consist of efficiently packed
atomic clusters. Molecular dynamics
simulation based on plastic crystal model
representing the clusters can explain the
structure of metallic glasses.
Glassy phase transforms to asuper-cooled liquid on heating before
crystallization. In this region the strain
rate sensitivity exponent m~1.0 whichindicates the achievement of the ideal
super plasticity.
Therefore we canobtain a very large elongation of
22,000% in the super-cooled liquid
region (Tx).

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By using the ordinary photo-registercoating process we can produce a nickel
die. By pressing the glassy alloys to thedie in the super-cooled liquid region we
can obtain the diffraction grating ofglassy alloys which has the same shapes
as resistant structures of the grating.

By precise control the incident and therefractive diffraction angles and theintervals, one can obtain red, green andblue colors.
By using these
spectroscopy systems we open up the
new hologram technologies based on
bulk glassy alloys.
Now we arechallenging these hologram technologies.
Some of bulk metallic glasses deform
plastically under compression at room
temperature (RT).
Zr70Ni16Cu6Al8
glassy alloy exhibits RT plastic
elongation of about 3 % upon tensile test.
This is the first example of such abehavior for a monolithic bulk (massive)
metallic glass.
This alloy also shows a very highfracture toughness of 110 MPa*m1/2
which is also maintained after heat
treatment. This alloy shows a very longshear-band length in front regions of thepre-fatigue cracks as well as very large
crack chip opening displacement.

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We also worked on the recording
media and achieved 25 nanometers for
pitch size and 12 nanometers for bit size
corresponding to recording density of one
terabit per square inch. We are now
approaching almost 2 terabit per squareinch and the pitch size is 18 nanometers.

Fe-Cr-based metalloid type soft
magnetic glassy alloys have beencommercialized with the commercialname of Liqualloy by Alps Electrical
Corporation.
The picture shows
Liqualloy consolidated magnetic cores forchoke coils of the power supplies andtheir performance.
Glassy alloy diaphragms for pressure
sensors are produced by net-shaped
casting process.
These glassy alloy
diaphragms have smaller size anddemonstrate higher sensitivities as wellas much higher pressure endurance zones
in comparison with standard steelpressure sensors.
We also obtained Ti-based glassy alloy
pipes with a diameter of 2 mm and wall
thickness of 0.2 mm. These pipes are
suitable for applications for sensing
element to detect the Coriolis force ofliquid or gas flowing inside the Ti-based
glassy alloy pipes subjected to reinforced
oscillations.

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Kawasaki Group’s paper was selected for the June issue of the Virtual
Journals of Ultrafast Science

The paper by Prof. Kawasaki’s group published in the Applied physics Letters 96, 211904(2010),
has been selected for the June issue of the Virtual Journals of Ultrafast Science.
The summary of the paper is as follows:“Exciton properties and ultrafast dynamics in CuScO2 thin films”
F. Liu1,2, T. Makino3, H. Hiraga3, T. Fukumura1, Y. Kong2, M. Kawasaki1,3,4
1

Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
2
School of Physics, Nankai University, Tianjin 300071, China
3
WPI Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
4
Japan Science and Technology Agency, CREST, Tokyo 102-0075, Japan

Cuprous delafossites CuAO2 (e.g., A = Al) are peculiar and promising materials because
the holes (having positive charge) play a role in realizing a high conductivity while
maintaining a good optical transparency [1]. This is significantly different point fromother wide-gap materials because many wide-gap semiconductors, such as ZnO, havenatural tendency to be grown under fairly high residual n type. The crystal structure ofdelafossite CuAO2 consists of an alternating stack of Cu ion layers and AO2 octahedronlayers as shown in the inset of Fig. 1. Replacement of the A site element with Sc has
successfully led to two more intriguing
properties; a direct-transition nature (4.36 eV)and strong excitonic effect (380 meV). These
properties are advantageous from theviewpoint of optoelectronic applications(such as a light-emitting diode). The main
panel of Fig. 1 shows an 80-K opticalabsorption spectrum. It also revealed theoptical characteristics such as wider directband-gap, much larger exciton binding energy,
and much weaker phonon-exciton coupling
than those of ZnO. This can avoid theinstabilization of exciton even at roomFig.
1.
Absorption
temperature. Table 1 compiles the binding
energies of exciton for representative oxide materials. spectrum for CuScO2 thin
We have previously that the binding energies of films. The red [Disc.],[Cont.]
lines
exciton are enhanced from the bulk values with a blue
decreasing in the quantum well layer thickness in represent the results of the
ZnO/MgZnO quantum well heterostructures, as a ground and continuum
result of quantum-confinement effects [4]. The low- states of excitons. Inset
dimensionality inherent to CuScO2 is considered to be shows its crystal structure.
a reason of such a large binding energy of excitons.
Table 1： Bandgap energies (Eg) and binding energies
of exciton (Eexb) for representative oxide materials
CuScO2ZnO
Eg[eV]
Eexb[meV]

4.36
380

3.44
60

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Femtosecond pump-probe experiments were
performed for this exciton system [5] because
none of its dynamical properties is known. The
main dynamical features were shown in Figs. 2(b)and (c) and summarized in the following two
aspects: exceptionally slow thermalization time ina scale of 10 ps and relatively small nonlinearlity
accompanied with the dispersive lineshape aroundthe excitonic resonance. These findings can beconsistently interpreted in terms of remarkably
large binding energy of exciton and of weakphonon interaction. It should be emphasized thatthe observed time-resolved nonlinearlity can be Fig.2 (a) Absorption spectrum andsimply explained only by the screening effect of (b) (c) Inverted experimental andCoulomb potential for the excitons. In other calculateddifferential
words, these dynamical studies on its optical transmission spectra for CuScO2 atnonlinearlity revealed that CuScO2 can manifest delay times of 50 ps and 300 ps.
itself as a model substance for excitonic
nonlinearlity in a naturally low-dimensional structure because the data could be simply
explained in terms of excitonic screening effects.
References:[1] H. Kawazoe et al., Nature 389, 939 (1997).
[2] S. Gilliland et al., Thin Solid Films 516, 1431 (2008)[3] H. Hiraga et al., Appl. Phys. Lett. 95, 211908 (2009)[4] T. Makino et al., Semicond. Sci. Technol. 20, S78 (2005)[5] F. Liu et al., Appl. Phys. Lett. 96, 211904 (2010)71

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Dr. Konstantinos Georgarakis’s paper
was published in “ESRF Highlights 2009”
The paper “Detection of deviation from ideal solution behavior in Zr-Cu metallic
glasses with addition of Al” by Assistant Professor Georgarakis was selected for“ESRF Highlights 2009” issued in February 2010. The Highlights selects to feature
only 76 articles out of about 1500 papers published annually on the works carried out
at the European Synchrotron Radiation Facility (ESRF). The Summary of the paper is
as follows:
Metallic glasses, made by carefully cooling liquid alloys so that they solidify
without crystallization, are metastable materials with unusual structures andremarkable properties. Thanks to an irregular, tightly packed internal arrangement of
atoms, metallic glasses are moldable like plastic when heated to the glass transition
temperature, yet stronger than typical crystalline alloys at room temperature [1,2].
The most accessible method for determining the atomic structure of metallic glasses
is the analysis of their diffraction of X-rays. Whereas conventional X-ray beams arecompletely absorbed near the surface, high energy, high flux radiation fromsynchrotron sources penetrates even thick samples, providing a deeper understandingof the unique internal structure of metallic glasses.
Using real space pair distribution functions (PDFs) derived from high precision xray diffraction data we attempt to probe the internal structure of Zr-Cu metallic glasses
and investigate the effect of a third element (Al) in their atomic structure. The results
indicate that Zr-Cu binary metallic glasses can be satisfactorily approximated as ideal
solid solutions because of the relatively weak interactions between Zr and Cu atoms,
figure 1a. Whereas only very thin glasses can be cast from binary Zr–Cu liquid alloys,
addition of a third strongly interacting component, aluminum (Al), to the liquid alloyleads to easier glass formation such that they can be cast to thicknesses up to several
millimeters without crystallization.
Ternary Zr–Cu–Al metallic glasses deviate markedly from ideal solution behavior,
figure 1b. Zr–Cu–Al glasses are comprised of finite regions of atomic order,
providing the extra support needed to form thicker glasses. This phenomenon isbelieved to be due to strong attractive interactions between the sp-electrons of72

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9:32:39aluminum and the d-electron shell of the larger zirconium atoms. In addition, Al has
an intermediate atomic size between those of Zr and Cu atoms. Thus, addition of Al
promotes chemical short range ordering in the liquid, improves the local packing
efficiency and slows down long range atomic diffusion required for crystallization,
leading to increased glass forming ability (GFA) [3]. The atoms arrange in clusters
resembling icosahedra, which pack together tightly in the glass, figure 1c, as observedin a previous study [4].
In spite of the similar atomic size of Cu and Ni, Zr–Ni binary metallic glasses exhibit
different structural arrangements in the short range order (SRO) and their structure
cannot be approximated by an ideal solution approach, contrary to the case of Zr–Cu.
The highly negative enthalpies of mixing between Zr–Ni atoms, corresponding tostrongly attractive interactions, induce CSRO in Zr–Ni metallic glasses. As in Zr-Cu,
addition of Al in Zr–Ni metallic glasses can increase significantly the stability of thesupercooled liquid state [5].

Figure 1: Gaussian fitting of the first PDF peak for a) Zr50Cu50 and b) Zr50Cu40Al10
metallic glasses. Thick black curves: experimental PDFs, thin red curves: calculatedpartial PDFs derived from the experimental total PDFs, thin blue discontinuous
curves: Gaussian partial PDFs scaled to the weight factors of an ideal solution andthick discontinuous light blue curves: expected total PDFs based on the weight factors[3], c) schematic diagram showing how the atoms in Zr–Cu based metallic glasses
form icosahedral clusters that pack tightly together by sharing faces (right) or edges(left) [4].
References[1] A.R. Yavari, Nature 439 (2006) 405.
[2] A. Inoue, Acta Mater. 48, (2000) 279.

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9:32:39[3] K. Georgarakis, A.R. Yavari, D.V. Louzguine, J. Antonowicz, M. Stoica, M. Satta,
G. Vaughan, A. Inoue, Appl. Phys. Let. 94 (2009) 191912.
[4] Ch.E. Lekka, A. Ibenskas, A.R. Yavari and G.A. Evangelakis, Appl. Phys. Lett. 91(2007) 214103.
[5] K. Georgarakis, A.R. Yavari, M. Aljerf, D.V. Louzguine, M. Stoica, G. Vaughan,
A. Inoue, J. Appl. Phys. 108 (2010) 023514.

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The 1st WPI-AIMR Awarding Ceremony

The 1st WPI-AIMR Awarding Ceremony based on the WPI-AIMR Awarding System*
established in April 2010 was held at the occasion of WPI-AIMR Joint Seminar in
Tohoku University on July 9.
From the applications submitted by theend of June 2010, the four laureates,
Associate Professor Hitosugi, Associate
Professor Nakajima (absent because of his
mission), Assistant Professor Ueno, andResearch Associate Fujinami, were selected
and commended by Director Yamamoto.
* the WPI-AIMR Awarding System
Implementation Guidance for the WPI-AIMR Awarding System
１．Outline
WPI-AIMR Awarding System aims to give a Certificate of Achievement and extra prize for further enhancing
cutting-edge research in their respective fields to the researchers who delivered great performance on their research that
fulfills our purpose and received an award from outside organizations.
２．Applicant Eligibility
WPI-AIMR Award is given to the researchers working in WPI-AIMR at Sendai excluding PIs immediately when they
won the prize from foreign and domestic research organizations, academic societies, academic journals, or
administrative organizations, and Institute Director evaluates their work is worth awarding.
３．Selection Process
In the case a researcher won a prize, he/she shall submit Notification of Award and the photocopy of the notice or
the certificate of the award to Institute Director.

Institute Director evaluates the awarding organization and thesignificance of the award comprehensively, and then Executive Committee conducts screening to make a final decision.
４．Awarding
The praiseworthy researchers are given a Certificate of Achievement and extra prize.

The extra prize is the necessary

expenses for the research activity such as travel expenses and expendable supplies.

It is set to up to 300,000 yen,

however, the amount is subject to change depending on each case.

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76

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Assistant Prof.

PI

Junior PI

Associate Prof.

Masashi Kawasaki

Ali Khademhosseini

Ken Nakajima

FY 2010 the Commedation for Science andTechnology by the Ministry of Education,
Culture, Sports, and Technology "The Young
Scientists Prize"“Prize for Science and Technology(Research
Category)” by the Minister of Education,
Culture, Sports, Science and Technology

Name of Award

Device/System
BMG

Assistant Prof.

PI

Junior PI

Assistant Prof.

Ryo Nouchi

Tadafumi Adschiri

Ali Khademhosseini

Konstantinos Georgarakis

1st BRIDGESTONE Soft Material Frontier
Prize
The Surface Science Society of Japan
Young- Research Lecture Award
The 4th collaborative research topic bestaward

The 42nd Ichimura Prize in Technology－Meritorious Achievement Prize
The 2010 American Chemical Society(ACS) Unilever Award

Soft Materials

Materials Physics

Young Scientist Prize 2010

The 2010 AIChE Colburn Award

The Prize of the Minister of Education, Culture,
Sports, Science and Technology in the field ofCooperation among Government, Industry andAcademia

The 28th JSAP Incentive Award for
Excellent Presentation

Materials Physics The 7th Honda Frontier AwardPI

Yuichi Ikuhara

BMG

Associate Prof.

Soft Materials

Soft Materials

Device/System

Materials Physics

The 2010 Young Investigator Award
The 14th Superconductivity Science
Materials Physics
and Technology Award

Device/System

Koji Nakayama

Research
Associate

Junior PI
PI

Ali Khademhosseini
Masashi Kawasaki
Kazunori Ueno

So Fujinami

Soft Materials

ThrustAssociate Prof. Materials Physics

PI

Tadafumi Adschiri

Taro Hitosugi

Position

NameAwarding
Organization

International Symposium on
Metastable, Amorphous and Nanostructured Materials(ISMANAM)

American Institute for Chemical Engineers (AIChE)MEXT

The Japan Society of Applied Physics (JSAP)The Honda Memorial Foundation

Tohoku University

The Surface Science Society of Japan (SSSJ)The Society of Rubber Industry, Japan

American Chemical Society (ACS)The New Technology Development Foundation

The Society of Non-Traditional Technology

U.S. Office of Naval Research

MEXT

Ministry of Education,
Culture, Sports,
Science and Technology (MEXT)Award Information (From April 1 to August 31)

Professor Ikuhara (PI) honored with Humboldt Research Award
Prof. Ikuhara, PI of WPI-AIMR, wins Humboldt Research Awards, bestowed by theAlexander von Humboldt Foundation in Germany, an organization that promotes
academic co-operation between excellent scientists and scholars from abroad and from
Germany.

The award is granted in recognition of a researcher's entire achievements todate to academics whose fundamental discoveries, new theories, or insights have had asignificant impact on their own discipline and who are expected to continue producing
Prof. Ikuhara becomes the 3rd Japanese

cutting-edge achievements in the future.
winner in the field of materials science.

The award ceremony will be held at Bamberg

in Germany on March, 2011, and the reception will be given by the President of theFederal Republic of Germany on June, 2011.
Prof. Ikuhara is well known internationally recognized scientist in the field ofinterface science and grain boundary engineering in materials.

So far, he has

intensively studied the atomic and electronic structures in various ceramic interface
mainly by transmission electron microscopy (STEM, HREM, EDS, EELS), andquantitatively determined the structures by combining the first principle theoretical
calculations.

Based

on

the

microstructuralcharacterization, he undertook a variety of researchconcerning microstructure control and high temperature
mechanical properties and functional properties of ceramicmaterials, and achieved numerous successful results.

In

particularly, his research concerning grain boundary related
phenomena took a world-leading role in this field of
research.

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The Third Series of WPI-AIMR Joint Seminars FY2010
The third series of the WPI-AIMR Joint Seminars started from April, 2010. The aimof this seminar series is to enhance mutual scientific communications among researchstaffs in WPI-AIMR to promote further fusion researches and the seminars areorganized and managed by younger research staffs in WPI-AIMR. The Sessions are
not constituted only by one way talks based on established research results, but also
lively discussions and exchange of ideas.
Lineup of the third series of WPI-AIMR Joint Seminars (April to July)
1st Seminar, Apr. 9, 2010
Prof. Y. Yamamoto "How can we achieve our mission of WPI?"
2nd Seminar, May 14, 2010
Chen Group
Organizer: T. Fujita, Moderator: K. Akagi
T. Fujita "Introduction"
T. Fujita "Nanoporous Metal and Composite"
A. Hirata "Applications of Super TEM / STEM installed in WPI"D. Pan "Mechanical Behavior of Bulk Metallic Glasses"
3rd Seminar, May 21, 2010
Adschiri Group
Organizer: D. Hojo, Moderator:T. Makino
S. Takami "Overview”
D. Hojo "Dispersibility of Nanocrystals --How do we utilize NCs?"
T. Togashi "Fusion Research Field of Biochemistry and Nanotechnology--Biological application of magnetic nanocrystals"
S. Harton "Directed Assembly of Fe3O4 Nanocrystals using Block Copolymers"
4th Seminar, Jun. 4, 2010
Esashi and Gessner Group
Organizer: Y. Lin, Moderator: A. Lahiri
Y. Lin “Introduction/Overview"
Y. Lin "MEMS bonding technology with MGs and nanostructure"
J. Lee "MG materials for the MEMS structure; The Freestanding PZT Film for MEMS
using Ge sacrificial layer"
N. Kaushik "Application of metallic glass thin films in patterned recording media"
S. Yoshida "MEMS-based data storage system using conductivity-switching polymers"
M. Muroyama "Networked Tactile Sensing Systems for Human Assist and Friendly
Robots"78

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9:32:425th Seminar, Jun. 25, 2010
Hitosugi Group
Organizer: T. Hitosugi, Moderator: T. Fujita
T. Hitosugi "Overview”
T. Ohsawa "Current Issues on Atomic-scale Nature of Functional Metal Oxides"
K. Iwaya "STM for Fusion Research"
S. Shiraki "Magnetism of 1D- and 2D arrays of magnetic atoms and molecules on
surfaces"
6th Seminar, Jul. 9, 2010
Ikuhara Group
Organizer: S. Tsukimoto, Moderator: Y. Lin
S. Tsukimoto "Introduction/Overview"
L. Gu "Zooming into an Atomic World: The Choice of Aberration-CorrectedTransmission Electron Microscopy (TEM)"
M. Saito "Atomic-Scale Characterizations of Functional Materials by TEM/STEM"
Z. Wang "Introducing First-Principles Calculations into the State-of-the-Art
Electron Microscopy:an In-Depth Looking at Materials"
7th Seminar, Jul. 23, 2010
Louzguine Group
Organizer: C. Qin, Moderator: S. Mizukami
C. Qin "Introduction/Overview"
Q. Zhang "Design and fabrication of bulk metallic glasses"
N. Chen "Development of new bulk metallic glasses with unique properties"
A. Caron "1. “Effect of minor composition changes in the Zr-Al-(CuNiCo) bulk metallic
glassy system” 2. “Application of atomic force acoustic microscopy in materials
science”"
S. González "Mechanical properties of Mg-Li-Cu-Y multiphase composites"

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9:32:42The 2nd Seminar (Chen Group)
Nanoporous Metal, Advanced TEM/STEM, and Bulk Metallic Glass
Organizer: T. Fujita (Advanced Functional Materials Lab., BMG)
After brief introduction of Joint Seminar of WPI-AIMR, the three major researchsubjects of Chen lab are introduced. Three subjects are (1) nanoporous metal andcomposite, (2) applications of super TEM/STEM installed in WPI, and (3) mechanicalbehavior of bulk metallic glasses. The summary of three subjects is as follows :(1) Nanoporous metals (NPMs) made by dealloying represent a class of functional
materials with the unique structural properties of mechanical rigidity, electricalconductivity, and high corrosion resistance. They also possess a porous network
structure with feature dimensions tunable within a wide range from a few
nanometers to several microns. Coupled with a rich surface chemistry for further
functionalization, NPMs have great potential for applications in heterogeneous
catalysis, electrocatalysis, fuel cell technologies, biomolecular sensing, surfaceenhanced Raman scattering (SERS).
(2) Basic functions and applications of super TEM/STEM installed in WPI will be
introduced. The super TEM/STEM enables us to see atomic scale structural andchemical information through HAADF, EDS, and EELS techniques. We will show
the preliminary experimental results obtained from nanoparticle, nanoporous metal,
graphene oxide, and bulk amorphous materials.
(3) The widespread enthusiasm for research on bulk metallic glasses is driven by both afundamental interest in die structure and properties of disordered materials and theirunique promise for structural and functional applications. Unlike the case forcrystalline materials, the disordered and nonequilibrium nature of metallic glasses
causes their underlying deformation mechanisms to be poorly known. A definite
correlation between mechanical behavior and the atomic/electronic structures ofmetallic glasses has not been established.
To this presentation, themicromechanisms of mechanical behavior of metallic glasses and present a brief
overview of the current understanding of their strength, ductility, and plasticity at
the microscopic and atomic scales.

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The 3rd Seminar (Adschiri Group)
Utilization of Metal Oxide Nanocrystals ~ Disperssion and Application
Organizer: D. Hojo (Organosoft and Hybrid Materials Lab., Soft Materials)
Dispersibility of nanocrystals (NCs) in solutions is one of the critical issues to utilize
NCs. Due to high surface energy of NCs, NCs are easily aggregated in the solution
preventing from exhibiting true nanometer-size effects of NCs [1]. The mechanism ofdispersion of NCs in a solution was mentioned in terms of the interaction of NCs andthe solution. The method of making NCs accessible to the chemical reaction as a newmolecular system, which consists of organic molecules and inorganic solid surfaces,
was also a topic of the talk [2].
We chose two topics for application of NCs in this seminar. One is related to the
biological application and other is related to polymer technology.
The biological application is one of the promising applications of magnetic NCs. We
introduced why magnetic nanocrystals were focused on the biological field and why theNCs can be used as a drug carrier. In addition, we also showed our research activity on
the nanobio-technology field, such as a topic of biomolecules applying tonanostructured inorganic materials.
Polymer nanocomposites have gained considerable attention in recent years due tothe ability to improve properties such as mechanical strength, electrical conductivity,and permeability/selectivity with relatively low-cost polymers. More recently block
copolymers (BCPs), polymers with chemically different segments in long sequences or“blocks,” have been used as templates to direct assembly of NCs within BCP
nanodomains. We discussed the production of magnetic/paramagnetic thin films (~ 100nm) using magnetite (Fe3O4) NCs within block copolymer templates. By controllingthe interactions between the NC surface, through ligand chemistry, and the two blocksof the BCP, this same technology should be able to simultaneously direct assembly of
the NCs and BCP nanodomains in the presence of a magnetic field as well as allow
reversible “switching” of domain directionality.
References[1] J. Zhang, S. Ohara, M. Umetsu, T. Naka, Y. Hatakeyama, and T. Adschiri; Adv.
Mater. 19, 203 (2007).
[2] D. Hojo, T. Togashi, D. Iwasa, T. Arita, K. Minami, S. Takami, T. Adschiri Chem.
Mater. 22, 1862 (2010).

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The 4th Seminar (Esashi and Gessner Group)
MEMS with Functional Materials
Organizer: Y. Lin (MEMS Materials Lab., Device/System Construction)
Micro/Nano Electro Mechanical Systems (MEMS/NEMS) is the integration of
mechanical elements and electronics on a common silicon substrate through micro/nanofabrication technology. Multitudinous functionalities of components of sensors andactuators could be realized with various materials by using compatible micro/nanomachining processes [1-2]. MEMS was born from semiconductor technologies, andover last tens years many fuctional materials (e.g. piezoelectric materials, CNTs,
polymers, SiC etc.) have been adjected into this field and have opened a new and large
regime for MEMS application [3-4].
MEMS materials laboratory in WPI-AIMR aims at developing practical MEMS
devices and technologies using novel materials as well as nanostructures. Bulk metallic
glasses are well-known with their superior properties, and have been employend to
device structures, patterned recording media, and bonding intermediate. Furthermore, ascientific well-studed random porous nanostructure is used for industrially standrad
MEMS process to enhance conventional bonding functionality. PZT is a famous actuationmaterial utilized for movable MEMS devices. The new process for free-standing films
was developed using Ge sacrificial layer and has realized thick films fabrication.
Conductivity-switching polymers have shown their valuable roles on MEMS-based data
storage system as recording media, which is expected to become the future data storage
system with a recording density beyond 1 Tb in−2. Forward future application of smart

integrated MEMS and LSI, tactile sensor systems of human assist and friendly robots
are developed for safety/smooth interaction between humans and robots.
MEMS is continuously meeting new materials and creating colorful functionalities.
References[1] M. Esashi, H. Komatsu, T. Matsuo, M. Takahashi, T. Takishima, K. Imabayashi and
H. Ozawa, IEEE Trans. on Electron Devices ED-29 , 1, 57 (1982).
[2] D. Scheibner, J. Mehner, D. Reuter, U. Kotarsky, T. Gessner, W. Dötzel, Sensors
and Actuators A 111, 93 (2004).
[3] S. Wang, J. F. Li, K.Wakabayashi, M. Esashi and R. Watanabe, Advanced Materials
10 ,873 (1999).
[4] J. Bonitz, S. E. Schulz, T. Gessner, Microelectronic Eng. 76, 82 (2004).

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The 5th Seminar (Hitosugi Group)
Atomic-scale Characterization of Perovskite Oxide Thin Films
Using Scanning Tunneling Microscopy
Organizer: T. Hitosugi (Interface PhysChem Lab., Materials Physics)
Atomically-controlled thin film growth of transition-metal-oxide heterostructures
has opened up new perspectives for surface and interface physics. For example,
metallic and magnetic interfaces have been discovered between two nonmagnetic
perovskite insulators [1,2]. To further explore unique functionalities at these surfaces
and interfaces, more attention should be paid to the electronic structure of the substratesurfaces at the atomic scale.
Among a wide variety of substrates, strontium titanate SrTiO3 has been mostcommonly used for growing perovskite heterostructures. However, atomic-scale
understanding of the surface structures has been still incomplete.
Scanning tunneling microscopy/spectroscopy (STM/STS) are ideal probes for thispurpose. We have recently constructed a new STM combined with pulsed laser
deposition (PLD), which enables low temperature STM/STS measurements of thinfilms without exposing their surfaces to air.
We have revealed that SrTiO3(001) substrate prepared by a typical annealing
treatment resulted in disordered surface on an atomic scale [3]. To obtain more orderedsurface, homoepitaxial SrTiO3 thin films were grown in different growth mode on thisdisordered substrate, and their surface structures were characterized by STM [3,4]. It
was found that the atomic-scale surface structure including oxygen vacancy strongly
depends on not only the growth condition but also the film thickness. Based on theseresults, we can provide a microscopic picture of the near-surface stoichiometry of thinfilms, which could affect the electronic properties at the SrTiO3-based interfaces.

References[1] A. Ohtomo and H. Y. Hwang, Nature 427, 423 (2004).
[2] A. Brinkman et al., Nat. Mater. 6, 493 (2007).
[3] T. Ohsawa, K. Iwaya, R. Shimizu, T. Hashizume, T. Hitosugi, arXiv: 1004.27.46.
[4] K. Iwaya, T. Ohsawa, R. Shimizu, T. Hashizume, T. Hitosugi, Appl. Phys. Express
3, 075701 (2010).

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9:32:44The 6 th Seminar (Ikuhara Group)
Atomic-Resolution Characterizations of Fuctional Materials
by Advanced Transmission Electron Microscopy
Organizer: S. Tsukimoto (Interface PhysChem Lab., Materials Physics)
Atomic-resolution characterization of structures is requisite for understanding of
the atomistic mechanisms of physical phenomena related to various properties infunctional materials and electronic devices. In recent characterization technologies,
there has been remarkable progress by Scanning Transmission Electron Microscopy(STEM) utilizing the spherical aberration corrector, resulting in enhancement of thespecial resolution (~ 1 Å). In addition, the light elements such as carbon, lithium (Li)and oxygen, which compose Li ion battery and organic compound etc., are possible toobserve directly using the STEM technique, e.g. Super-TEM facility installed in WPIAIMR. The STEM technique enables us not only to observe typical microstructure but
also to identify the locations of atom/dopants, and analyze the local electronic state inmaterials. Thus, TEM/STEM is one of the most powerful characterization techniques.
Accordingly, both fundamentals and applications of the TEM/STEM wereintroduced and our recent (fusion) researches were demonstrated in this seminar. As for
fundamentals, the mechanics, image formation and merit/demerit of the TEM/STEM
were explained minutely by Lin Gu. As for fusion researches, M. Saito introduced thelatest research topics: (i) structure of nano-wiring fabricated in MgO bicrystals [ incollaboration with Schluger group], and (ii) direct evidence of B-site ordering of Fe andTa ions in double-perovskite Sr2FeTaO6 thin films with unique magnetic properties [incollaboration with Kawasaki group] [1]. Z.C. Wang demonstrated the important
advance for merging the state-of-the-art STEM with the high-precision first principle
calculations in the atomic-scale determination of complex structures as well as inrelating that structure to its properties on a quantum level based on our recent researches[2, 3]. As a consequence, the atomic-structure characterization using STEM could play
an important role in rapid progress in the fusion researches in WPI-AIMR.
References[1] S. Chakraverty, A. Ohtomo, M. Saito, S. Tsukimoto, Y. Ikuhara and M. Kawasaki,
to be submitted.
[2] Z.C. Wang, M. Saito, S. Tsukimoto and Y. Ikuahra, Adv. Mater. 21, 4966 (2009).
[3] Z.C. Wang, M. Okude, M. Saito, S. Tsukimoto, A. Ohtomo, T. Kita, M. Tsukada,
Y. Ikuhara and M. Kawasaki, to be submitted.

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9:32:44The 7th Seminar (Louzguine Group)
Development of New Bulk Metallic Glasses with Unique Properties
Organizer: C. Qin (Advanced Functional Materials Lab., BMG )A glass has very slow crystal nucleation and growth kinetics that the liquid can beundercooled far below its melting point before a glass transition is reached, ‘freezing’ asa vitreous solid without crystallizing. The atoms retain an amorphous distribution (i.e.
random packing with no long–range order). The production of a metallic glass by rapid
cooling of the molten Au75Si25 eutectic alloy in 1960 is generally considered to be thebeginning of the era of metallic glasses [1]. Since then, a number of metallic glasses
have been developed in Ni-, Fe-, Pd- and Al-based alloy systems etc. More importantly,
metallic glasses exhibit unique properties that are superior to the conventional
crystalline metals and alloys, such as high strength, high elastic strain limit, highhardness, good soft magnetic properties, and good corrosion resistance [2-4]. However,
the early metallic glasses have mainly been fabricated in the form of thin ribbons, thinfilms and fine wires because of their very high cooling rate requirements of above 105
Ks-1, for glass formation. The limitations of size and shape as well as low thermal
stability have restricted their fields of application.
Currently, with well designed compositions it is possible to cast liquid alloys into theglassy state at low critical cooling rates from 100 Ks-1 to 1 Ks-1 and in large criticalsample sizes up to several centimeters. A recent significant advancement has been
made in developing new types of BMGs and their composites with unique properties inour group, as exemplified for Ni-free Zr-Cu-Fe-Al BMGs with extremely high glassforming ability, ductile Pd-Ni-Si-P BMGs and lighter Mg-Li-Cu-Y glassy composites
etc. In addition, the fusion researches with other groups in WPI aim at using these highperformance materials to manufacture small devices for microelectromechanicalsystems (MEMS), or finding novel properties of metallic glasses as being catalysts,
biomaterials and new energy materials. These progresses greatly raise the hope forpossible applications of metallic glasses as advanced engineering materials.
References[1] W. Klement, R.H. Willens and P. Duwez, Nature 187, 869 (1960).
[2] A. Inoue, Acta Mater. 48, 279 (2000).
[3] W.L. Johnson, MRS Bull. 24(10), 42 (1999).
[4] A.L. Greer and E. Ma, MRS Bull. 32, 611 (2007).

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Research Prospect

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Universality among Diversely Different Glass-Forming Materials
Michio Tokuyama1,3, Yuto Kimura2, Hiroyuki Fujii2, and Yayoi Terada3
1
WPI Research center, Advanced Institute for Materials Research, Tohoku University,
Sendai 980-8577, Japan2
Department of Mechanical Engineering, Tohoku University, Sendai 980-8579, Japan
3
Institute of Fluid Science, Tohoku University, 980-8577, Japan
1. Introduction
Understanding of the glass transition is one of the pioneering problems in a wide
variety of fields [1-3]. It is obviously important in technological applications, such as
how to manufacture window glasses, optical fibers, and bulk metallic glasses (BMG)[4]. As a liquid is cooled from high temperatures, it may crystallize at a melting
temperature Tm , where the first-order phase transition usually occurs. As a liquid isfurther cooled to temperatures below Tm without crystallization, it is called asupercooled liquid. Cooling a supercooled liquid below the glass transition temperature
Tg finally makes a glass. This scenario is essentially the same as that in any viscous
liquids, such as fragile liquids (OTP, Toluene, and etc.), metallic melts (Pd43Ni10Cu27P20,
Zr41.2Ti13.8Cu12.5Ni10Be22.5, and etc), and strong liquids (SiO2, GeO2, and etc). If themechanism of the glass transition is clarified in a simple system, therefore, it may help
us to understand it in more complex systems. Up to now, however, there is nosatisfactory theory to elucidate the glass transition from a first principle. This is mainly
because in a supercooled state the nonlinear fluctuations play an important role andcause long-lived spatial heterogeneities, leading to a non-exponential two-step slow
relaxation, while in a liquid state the linear fluctuations play an important role and cause
short-lived spatial heterogeneities, leading to an exponential decay [5]. In a supercooled
state, therefore, one has to deal with long-time correlations caused by many-bodyinteractions among particles analytically. This is still a hard work to do theoretically,
although such slow relaxation processes in viscous liquids near the glass transition areextensively studied by experiments and computer simulations [6,7] with recent progressin science and technology. Instead of doing such a analytic work, in this paper we
propose an existence of universality near the glass transition among different glassforming materials and thus review two kinds of universalities among different glassforming liquids near the glass transition obtained by analyzing the experimental data
and the simulation results consistently from a unified point of view based on the meanfield theory (MFT) recently proposed by Tokuyama [8]. Thus, we show how these89

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universalities make the dynamics of complex materials such as BMG simple.
One of main purposes in our theoretical group is to find a basic equation to describe
the dynamics of supercooled liquids in different systems. The most famous equation todescribe the dynamics of liquids is a Navier-Stokes equation. The solution depends on aviscosity, time, and length. Hence it is invariant for different liquids if thedimensionless viscosity has the same value. Up to now, the basic equation forsupercooled liquids has not been derived yet. From a unified point of view based on
MFT [9], however, it was shown that the similar situation to the above occurs if thedimensionless long-time self-diffusion coefficient DSL ( O) has the same value. In fact,
the following two types of universalities are proposed. The first is a universality for the
dynamics of self-diffusion in different systems, which is described by a master curve at
a fixed value of DSL ( O) [8-12], where O is a control parameter, such as an inverse
temperature, a volume fraction, a magnetic field, and so on. If DSL ( O) has the samevalue in different systems, the dynamics of a single particle, such as a mean-squaredisplacement M 2 (t) and a mean-fourth displacement M 4 (t) (or a non-Gaussian
parameter D 2 (t)), is completely identical to each other. Thus, one can easily show thatthe dynamics in a fragile glass former coincides with that in a strong glass former. This
enables us to study complex systems by using simple systems. The second isuniversality for the long-time self-diffusion coefficient DSL ( O). For atom or colloid D ,there exists a master curve for DSL ( O), even if D belongs to a complex multi-component
system Ax By Cz   , where D  {A,B,C...} . By using this master curve, therefore, one
can easily predict the whole O dependence of DSL ( O) from a few data points [13].
From these universalities, we conclude that the value of DSL ( O) uniquely determines
the state of the system, such as a liquid state [L], a supercooled state [S], and a glass
state [G]. Hence it is convenient to introduce a universal parameter u by
u log(Vv 0 /DSL ) , where V is a particle diameter and v 0 an average particle velocity.
Once the glass transition point ug is found in one system, then, one can use it for othersystems to determine the glass state [10]. As O is increased from a liquid state [L], asupercooled state [S], and a glassy state [G] appear at OE (or uE ) and Og (or ug ),respectively, where Og ! OE ( ug ! uE ). In fact, detailed analyses of experimental data
for suspensions of colloids [13] suggest that uE | 2.6 and ug | 5.1. Thus, these values
must be universal numbers [9]. In Fig. 1, each state is classified by u . The mean-fieldregion in which MFT is valid depends on the system. For molecular systems it is valid
for 0  u d 3.04 , while 0  u  ug for suspensions. Here we note that the solutions of themode-coupling theory show D 2 (t)  1 for any systems. Hence the mode-coupling theory(MCT) is also valid for the same mean-field region as that of suspensions.

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2. Mean-Field Theory
We briefly summarize the mean-field theory of the glass transition (MFT) recently
proposed by Tokuyama [8-10]. Since we are interested only in selff diffusion of particle
D , the relevant physical quantities to describe the dynamics of particle D are mainly
2

given by the mean-square displacement M 2(D ) (t)  Xi(D ) (t)  Xi(D ) (0) !, and the mean4

fourth displacement M 4(D ) (t)  Xi(D ) (t)  Xi(D ) (0) !, where Xi(D ) (t) denotes the position
vector of ith particle of D at time t . Then, the non-Gaussian parameter is given by
D (2D ) (t) (3/5)M
M 4(D ) (t) / M 2(D ) (t) 2 1 . As shown in the previous paper [8], M 2(D ) (t) is
described by the following two types of mean-field equations:for suspensions of colloids (S)(D )2d (D )
M 2 (t) 6D
DSL ( O)  6>DSS (I )  DSL ( O)@eM 2 (t )/ l ,dt(1)

and for molecular systems (M)(D )2d (D )
M 2 (t) 6D
DSL ( O)  6>v th2 t  DSL ( O)@eM 2 (t )/ l ,dtwhere DSS (I ) is the short-time self-dif
f ffusion coefficient [15] and v th

(2)
(kkB T /mD )1/ 2 , mD

being mass of a particle D . Here the mean-free path l is a length in which a particle can91

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move freely without any interactions between particles. Although it is originally related
to the static structure factor S(q) [9], it is determined by a fitting with data here.
Equations (1) and (2) are easily solved to give formal solutionsª 6t / tºDS6t / tM 2(D ) (t) 6DSL t  l 2 ln«e E  SL 1 e E » for (S),
DS
¬
¼

ª
§t ·2 ­° § 6t · 6t / tE ½
°º
1
6t
/
t
E
2
(D )
L
E
«
 ¨
1 ¨
M 2 (t) 6DS t  l ln e¸¾» for (M) ,¸ ®¨1 t ¸
¸e
«
°
°
t
6 ¨
© f ¹ ¯ © E ¹
¿»
¬
¼


^

`

(3)
(4)

where t E ( l 2 /DSL ) denotes a time for a particle to diffuse over a distance of order lwith the diffusion coefficient DSL and is identical to the so-called E-relaxation time.
Here t f ( l /v th ) is a mean-free time, within which each particle can move freely
without any interactions between particles. As shown in the previous paper Ref. [10],the mean-free path l is uniquely determined by DSL . Hence the solutions (3) and (4)suggest that the dynamics is described by only one parameter DSL .
Next we discuss the long-time self-diffusion coefficient DSL . As discussed in Ref. [11],it can be written in terms of a singular function of O asDSS (I )D ( O)2
DSS (I ) § O ·§ O ·1 N DD¨ ¸¨1 ¸
D0 ©Oc ¹© Oc ¹
L
S

DSL ( O)V DD v 0

for (S) ,(5)for (M),(6)

2

1 §Oc ·§ O ·¨ ¸¨1 ¸
N DD © O ¹© Oc ¹

where Oc is a fictive singular point to be determined and v 0 (HDD /mD )1/ 2 , HDD being anenergy. As shown in the previous paper [11], one can obtain the coefficient N DD
analytically in terms of potential parameters as
rep
V DD § wUDD(r) ·
(7)
N DD
,
¨
¸
HDD ©
wr ¹r V DD
repwhere UDD(r) denotes a repulsive part of the potential UDD (r) . The singular part of Eqs.
(5) and (6) results from the long-time correlation effects due to the many-bodyinteractions between particles and is in general difficult to calculate. In this paper, wetreat it as a fitting parameter. For molecular systems (M), length, time, and temperatureare scaled by V DD , t th , and HDD /k B , respectively.
3. Universality for the dynamics of self-diffusion
We now discuss universality in the dynamics of self-diffusion among different glass-

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Fig. 2. A log-log plot of M 2 (t) versus time for colloïdal suspension and Lennard-Jones binary colloids.
The filled circles indicate the expérimental data for hard-sphere colloids with 6% size polydispersity at[L] I

0.502 and 0.538 from Ref. [14] and the open squares for A colloids at [L] T 1.0 and 0.6 from

Ref. [16]. The solid line indicate the mean-field master curve given by Eq. (3) where u | 1.347 and2.273 from top to bottom. Here t 0

a 2 /D0 , where a is a radius of colloids and D0 a single particle

diffusion constant.

forming systems. As shown in the previous papers [9,12], the dynamics of self-diffusionfin any systems is described by a master curve if the value of u is the same as each other.
We discuss the following three cases: We first discuss universality between selff
diffusion of colloids with 6% size polydispersity [14] and that of A colloids in the
Lennard-Jones binary colloids A80B20 [16]. In Fig. 2, the mean-square displacement
M 2 (t) is compared at two different values of u; in a liquid state [L] u | 1.347 where
I =0.502 for the hard-sphere colloidd and T =1.0 for the binary colloids and a liquid state[L] u | 2.273 where I =0.538 and T =0.6. At each value of u the experimental data andthe simulation results are collapsed on the mean-field master curve given by Eq. (3). We
next discuss universality between selff diffusion of hard spheres in the hard-sphere fluidwith 6% size polydispersity and that of A particles in the Lennard-Jones binary
mixtures A80B20. In Fig. 3, the mean-square displacement M 2 (t) is compared at threedifferent values of u; in a liquid state [L] u | 1.97 where I =0.525 for the hard-sphere
fluid and T =1.0 for the binary mixtures, in a weak supercooled state [S1] u | 2.77 ,where I =0.56 and T =0.625, and in a strong supercooled state [S2] u | 4.44 , where93

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Fig.3. A log-log plot of M 2 (t) versus t /t th for hard-sphere fluids and Lennard-Jones binary mixtures.
The filled circles indicate the simulation results for hard spheres with 6% size polydispersity at [L]

I =0.525, [S1] 0.56, and [S2] 0.581 from Ref. [17] and the open squares for A particles at [L] T =1.0, [S1]0.625, and [S2] 0.455 from Ref. [18]. The solid lines indicate the mean-field master curve given by Eq.
(6), where u | 1.97 [L], 2.77 [S1], and 4.44 [S2].

Fig.4. A log-log plot of M 4 (t) versus t /t th for hard-sphere fluids and Lennard-Jones binary mixtures.
The solid lines are mean-field results. The details are the same as in Fig. 3.

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Fig.5. A log-log plot of M 2 (t) versus t /t th for A in LJ binary mixture, Cu in Cu60Ti20Zr20 melt, and O
in SiO2 melt. The filled circles indicate the simulation results for A in A80B20 at [L] T =1.0 and [S] 0.588
from Ref. [18], the open circles for Cu at [L] T =0.23 from Ref. [20], and the open squares for O at [S]0.2165 =0.2165 from Ref. [22]. The solid lines indicate the mean-field master curve given by Eq. (6),where u | 1.95 [L] and 2.93 [S].

I =0.581 and T =0.455. At each value of u the simulation results are collapsed on themean-field master curve given by Eq. (6), except at a cage stage in [S2], where thesimulation results seem not to reach a final equilibrium state yet. In Fig. 4, the meanfourth displacement M 4 (t) is also shown under the same conditions as those in Fig. 3.
At each value of u, the dynamics of M 4 (t) between different systems coincides witheach other within error.
Finally, we discuss universality among self-diffusion of O in SiO2, that of Cu in
Cu60Ti20Zr20 melt, and that of A particles in the Lennard-Jones binary mixtures A80B20(LJ). In Fig. 5, M 2 (t) is compared at two different values of u; in a liquid state [L]u |1.95, where T 1.0 for LJ and T =0.23 for Cu, and in a supercooled liquid state [S]u |2.93, where T =0.588 for LJ and T =0.2165 for O. At the same value of u all thesimulation results on fragile and strong glass formers are collapsed on the mean-field
master curve given by Eq. (4). As shown above, the dynamics of self-diffusion indifferent systems is identical to each other if u has the same value. Thus, we conclude
that at each value of u there exists a master curve for M 2 (t) and M 4 (t) . We next

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1

0

-2

10

S

L

0

log (D /Vv )

-1

-3

-4

-5

-6
0

0.2

0.4

0.6

0.8

1

1.2

T /T
c

L
S versus

Fig. 6. A log plot of D

Tc /T . The symbols indicate the experimental data for self-diffusion of

Ni in liquids, (Ṽ) Ni [22], (ṳ) Ni80P20 and (ṹ) Pd40Ni40P20 [23], (ṵ) Pd43Ni10Cu27P20 [23], and (ṻ)
Pd40Ni10Cu30P20 [25]. The dotted line indicates the mean-field result given by Eq. (6) for Ni at N NiNi

12

and the solid line a Vogel-Fulcher-Tamman fit from Ref. [13].

discuss a master curve for the long-time self-diffusion coefficient.
4. Universality for long-time self-diffusion coefficient
Finally, we discuss universality for the long-time self-diffusion coefficient. For thesame type of particles, the coefficient N DD is always the same. For example, N AA =48 for
A particles in multi-component Lennard-Jones mixtures Ax By C z    and N CuCu =9 for Cu
in multi-component Cu x Tiy Zrz melt. The difference appears only in the singularpoint Oc , which depends on the details of the systems. This suggests that there exists a
master curve for DSL ( O) of each component if O is scaled by Oc . We first show this byusing the experimental data for self-diffusion of Ni in different liquids, Ni [22], Ni80P20
and Pd40Ni40P20 [23], Pd43Ni10Cu27P20 [24], and Pd40Ni10Cu30P20 [25]. Ni is welldescribed by the Stillinger-Weber potential [26] whose repulsive part is given byrep
2.2183Å, H 1.2879 u1020 J, and mNi(r) H(V NiNi /r)12 , where V NiNi
U NiNi1.0284 u1025 Kg. Hence Eq. (7) leads to N NiNi =12. By using Eq. (3), one can then findthe singular temperature Tc for each liquid, which is listed in Table 1. In Fig. 6, DSL isplotted versus Tc /T for different liquids. All the experimental data are collapsed onto asingle master curve. The data can be described by the mean-field equation (6) with

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1

0

10

L

-2

S

$$ 0

log (D /V v )

-1

-3

-4

-5

-6
0

0.2

0.4

0.6

0.8

1

1.2

T /T
c

L
S versus

Fig. 7. A log plot of D

Tc /T for A particles in different systems, A100, A80B20, and A80B20S. The

circles indicate the simulation results for A particles in A80B20 and the squares for A particles in A100 from
Ref. [18], and the diamonds for A particles in A80B20S from Ref. [27]. The dotted line indicates the meanfield result given by Eq. (6) with N AA

48 and the solid line a Vogel-Fulcher-Tamman fit from Ref. [13].

Table 1. Singular temperatures for different systems [13].
SystemNi
Ni80P20
Pd43Ni10Cu27P20
Pd40Ni40P20
Pd40Ni10Cu30P20
A in A100
A in A80B20S
A in A80B20SO in SiO2

1/Tc
1.05
1.11
1.13
1.15
1.16
3.45
3.41
2.06
5.92

N NiNi 12 up to u | 3.04 well, while for u ! 3.04 they start to deviate from it because
the many-body correlation effects play important role. Since there is no theory in astrong supercooled liquid for u ! 3.04 , one of phenomenological theories, a VogelFulcher-Tamman law, is shown in Fig. 6 for comparison [13]. The second example is
Lennard-Jones liquids, A100 [18], A80B20 [18], and A80B20S [27]. As is shown in Fig. 7,
all simulation results are collapsed onto a single master curve, where N AA 48. Here wenote that the LJ potential was originally used to model Ni. In fact, DSL for A particle
perfectly coincides with that for Ni if it is multiplied by 4.

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5. Summary
In this paper, we have analyzed the simulation results and the experimental data on
different glass-forming materials, including bulk metallic glass-forming Cu60Ti20Zr20
melt and network-forming SiO2 melt, from a unified viewpoint based on the mean-field
theory. We have then shown two types of universalities among those systems. The firstis an existence of a master curve for M 2 (t) and M 4 (t) at a fixed value of u. Hence thedynamics of self-diffusion in any systems is the same as each other at a given value of u(see Figs. 2-5). The second is an existence of a master curve for DSL on a given atom or
colloid. The parameter N DD has the same values for a given particle D , while thesingular point Oc depends on the systems. Hence all the data for the same particle indifferent systems are collapsed on a single curve if DSL is plotted versus O / Oc (see Figs.
6 and 7). Thus, one can predict a whole data for DSL by just measuring only one data fora liquid of interest. Once DSL is given, the dynamics of that liquid is also predicted.
Acknowledgments
The authors are grateful to T. Furubayashi, P. Harrowell, Y.-H. Hwang, H. Löwen, M.
Medina-Noyola, T. Narumi, K. L. Ngai, I. Oppenheim, G. Szamel, A. Takeuchi, and Th.
Voigtmann for fruitful discussions. This work was supported by World PremierInternational Research Center Initiative, MEXT, Japan and also partially supported by
Grants-in-aid for Science Research with No. 18540363 from Ministry of Education,
Culture, Sports, Science and Technology of Japan.
References[1] C. A. Angell, K. L. Ngai, G. B. McKenna, P. F. McMillan, and S. W. Martin, J.
Appl. Phys. 88, 3113 (2000).
[2] P. G. Debenedetti and F. H. Stillinger, Nature 410, 259 (2001).
[3] K. Binder and W. Kob, in Glassy Materials and Disordered Solids (World Scientific,
Singapore, 2005).
[4] A. Inoue, Acta Met. 48, 279 (2000).
[5] M. Tokuyama, Y. Terada, and I. Oppenheim, Eur. Phys. J. E 9, 271 (2002).
M. Tokuyama, Y. Terada, and I. Oppenheim, Physica A 307, 27 (2002).
[6] Proceedings of the 4th Int. Discussion Meeting on Relaxation in fragile Systems,
edited by K. L. Ngai, J. Non-Cryst. Solids 307-310 (2002).
[7] Proceedings of the 3rd Int. Symposium on Slow Dynamics in Complex Systems,
edited by M. Tokuyama and I. Oppenheim (AIP, New York, 2004) , CP 708.
[8] M. Tokuyama, Physica A 364, 23 (2006).

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[9] M. Tokuyama, Phys. Rev. E 80, 031503 (2009).
[10] M. Tokuyama, Physica A 378, 157 (2007).
[11] M. Tokuyama, Physica A 388, 3083 (2009).
[12] M. Tokuyama, T. Narumi, and E. Kohira, Physica A 385, 439 (2007).
[13] M. Tokuyama, to be published in J. Non-Cryst. Solids (2010).
[14] W. van Megen, T. C. Mortensen, S. R. Williams, and J. Müller, Phys. Rev. E 58
(1998) 6073.
[15] M. Tokuyama and I. Oppenheim, Phys. Rev. E 51, R16 (1994).
[16] E. Flenner and G. Szamel, Phys. Rev. E 72, 031508 (2005). Y. Kimura, Master's
Thesis, Tohoku University, 2007.
[17] M. Tokuyama and Y. Terada, Physica A 375, 18 (2007).
[18] T. Narumi and M. Tokuyama, Rep. Inst. Fluid Science 19, 73-78 (2007).
[19] Proceedings of the 5th Int. Workshop on Complex Systems, edited by M.
Tokuyama, I. Oppenheim, and H. Nishiyama (AIP, New York, 2008) , CP 982.
[20] H. Fujii, Master's Thesis, Tohoku University, 2008.
[21] I. Sasaki, Master's Thesis, Tohoku University, 2008.
[22] A. Meyer, S. Stüber, D. Holland-Moritz, O. Heinen, and T. Unruh, Phys. Rev. B 77
(2008) 092201.
[23] S. Mavila Chathoth and A Meyer, Appl. Phys. Lett. 85, 4881 (2004).
[24] A. Meyer, Phys. Rev. B 66, 134205 (2002).
[25] A. Meyer, R. Busch, and H. Schober, Phys. Rev. Lett. 83, 5027 (1999).
[26] T. A. Weber and F. H. Stillinger, Phys. Rev. B 31, 1954 (1985).
[27] P. Gallo, R. Pellarin, and M. Rovere, Phys. Rev. E 67, 041202 (2003).

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Proceedings Papers of2009 WPI-AIMR Annual Workshop

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Proceedings Papers of 2009 WPI-AIMR Annual Workshop
The 2009 WPI-AIMR Annual Workshop was held from March 1, Sunday throughMarch 6, Friday, 2009, at the Miyagi-Zao Royal Hotel in Zao Town of Miyagi
prefecture. One of the main purposes of the workshop was to stimulate immediate
and/or future possible Fusion Researches among WPI-AIMR researchers and withoutside researchers. The Program Committee has set up the plenary sessions, Mini
workshops, and Poster sessions aiming for that task. The total participants of theworkshop counted to 180 and the total presentation at the workshop was 164, which
included 32 invited talks in the eleven plenary sessions and two Special sessions, 50
talks in eight Mini workshops, and 82 Poster presentations.
Here we present several papers of the proceedings of the Workshop whose authors
kindly agreed to be included in the WPI-AIMR NEWS.
(T. Hashizume, program chair)103

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Short-range order of Cu-Zr metallic glasses
N. Mattern and J. Eckert*

IFW Dresden, Institute for Complex Materials, Helmholtzstr. 20, D-01069 Dresden, Germany* also at: TU Dresden, Institute of Materials Science, D-01062 Dresden, Germany
The atomic structure of Cu35Zr65, Cu50Zr50, and Cu65Zr35 metallic glasses was investigated by means ofhigh-energy X-ray diffraction, neutron-diffraction and extended X-ray absorption fine structure
spectroscopy. Three-dimensional structure models were developed by applying the Reverse Monte Carlo
method. Total and partial atomic pair correlation functions were extracted from the model for the different
compositions. The obtained structure models were analyzed in terms of the local atomic arrangements. The
geometric short-range order of Cu-Zr glasses is characterized by a variety of polyhedra. The atomic sitesof the nearest neighbourhood around a Cu or Zr atom are randomly occupied by Cu or Zr atoms. The
composition dependence of the short- and the medium-range order in the Cu-Zr glasses points to a solid
solution-like replacement of Cu and Zr atoms in the whole composition range. No indications wereobserved for the existence of a special atomic arrangement at particular chemical compositions of bulk
glass forming Cu-Zr alloys.

in the Cu-Zr system from electronic arguments stabilizing
the undercooled Cu-Zr liquid [29]. The presence of
icosahedral clusters in bulk glass forming Cu66Zr34 wasalso concluded from Reverse Monte Carlo simulations(RMC) using XRD and EXAFS measurements [30] in
contradiction to results reported on Cu50Zr50 glass [31].
From the analysis of composition dependent structuralparameters no evidence for the existence of a special
atomic arrangement in Cu-Zr glasses was found [16].
The aim of this work was, therefore, to get moreinsight into the atomic structure of Cu-Zr glasses fromthe experimental point of view. Experimental X-ray andneutron diffraction data were determined for different
chemical compositions, which may act as critical tests forstructure models. The partial atomic pair correlations andlocal structure information were extracted by applying
the RMC method [32] which is meanwhile a wellestablished method for modelling the structure of glasses
and disordered materials. Despite the fact, that RMC may
give the most randomized configuration, the method has
been proven to reproduce the general features and local
atomic arrangements of coordination polyhedra present in
the structure e.g. of covalently bonded glasses [33,34].

I. INTRODUCTION

In the last 15 years new bulk metallic glass (BMG)
forming alloys were developed in Zr-, La-, Ti-, Ni-, Pd-,
Mg-, Al-, Fe-, Cu- based systems [1,2]. These multicomponent alloys can be obtained in a glassy state in mm
or cm-dimension by copper mold casting due to highglass forming ability, or low critical cooling rates of 102100 K/s, respectively. This now enables to explore theexceptional mechanical properties of metallic glasses [3].
However, the information content of structuralinvestigations is rather limited for glasses consisting of
two or more different kinds of atoms.
Recently, BMGs could be prepared for some particularcompositions in the binary Cu-Zr system [4-7]. Glassy
samples of 1 - 2 mm thickness were reported for thealloys Cu66Zr34 [4], Cu65.5Zr34.5 [5], Cu50Zr50 [6], andCu46Zr54 [7]. Furthermore, extraordinary plasticity wasobserved for some binary and ternary Cu-based BMGs
[8-12]. These findings renewed the interest in structuralinvestigations of the Cu-Zr system. It is well known fromearlier work that Cu-Zr glasses can be prepared by rapid
quenching from the melt in a wide composition range[13-16]. Partial atomic pair correlation functions ofamorphous Cu-Zr alloys were determined by anomalous
X-ray scattering and extended X-ray absorption finestructure (EXAFS) but the accuracy suffered from theweak energy dependence of the atomic form factors [1719].
Molecular dynamic (MD) simulations of Cu-Zr glasses
were done to correlate the atomic structure withmechanical properties and glass forming ability [20-23].
The atomic structure of metallic liquids and glasses isdiscussed by efficient packing of clusters [24]. For glassy
alloys with low solute concentrations, the medium-rangeorder is determined by packing of one dominantchemically defined polyhedron [25]. For moreconcentrated compositions the situation is much more
complex, due to cluster overlap via solvent-sharing. For
some liquid metals and metallic alloys the presence of an
icosahedral atomic arrangement was concluded [26-28].
Icosahedral Cu8Zr5 clusters are discussed to be dominant

II. EXPERIMENTAL

Pre-alloyed ingots of nominal compositions Cu65Zr35,
Cu50Zr50, and Cu35Zr65, were prepared by arc-melting
elemental Cu and Zr with a purity of 99.9% or better in a
Ti-gettered argon atmosphere. For reaching homogeneity,
the samples were remelted several times. From these prealloys, 3 mm wide and 30 m thick amorphous ribbons
were prepared by means of rapid quenching from themelt using a single-roller melt-spinner under argon
atmosphere. The chemical compositions of the ribbons
were analyzed by the titration technique. The results of
the analysis are in a good agreement with the nominal
values which are used in the following (deviations are <0.2 at%). The amorphous state of the as-quenchedribbons was confirmed for all compositions by thepresence of only diffuse maxima in the XRD pattern, as
well as by analyzing their crystallization behaviour. High1

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corresponding weights wij for the Cu-Zr glasses are given
in table 1. From the structure factor S(q) the total atomic
pair correlation functions g(r) are obtained by the Fouriertransform of S(q) according to [35]:energy X-ray diffraction (XRD) experiments wereconducted at the synchrotron beam-line BW5 at
HASYLAB, Hamburg. Intensities were recorded intransmission geometry by a Ge-point detector using awavelength of  = 0.01250 nm. Neutron scatteringexperiments were carried out at the 7C2 diffractometer at
the Laboratoire Léon Brillouin in Saclay. Samples wereplaced in vanadium containers (diameter 8 mm, wall
thickness 0.1 mm) and measured using a wavelength of
λ= 0.073 nm. The raw data were corrected for empty
instrument background, scattering of the sample holder,absorption, incoherent and multiple scattering using
standard procedures [35]. X-ray absorption spectra at the
Cu- and Zr-K-edges were recorded at the beam-line C at
HASYLAB, Hamburg [36]. From the recorded spectra
the EXAFS-modulations were extracted by means of theusual algorithms implemented in the VIPER-programme[37]. The mass density was determined at room
temperature by the Archimedes principle by weighing
samples in air and in dodecane (C12H26).

4  r   0  ( g (r )  1)


i



(1)

ij

The weights wij(q) are determined by the sample
composition ci and the scattering power of the atoms i. In
the Faber-Ziman formalism [38] they can be expressed as

f i (q) f j (q)wijN  (2   ij )ci c jf (q)bi b j
b

2

,

2

(4)

ij

Figure 1 shows the calculated total pair correlation
functions g(r) of the different Cu-Zr glasses obtained
from the neutron and X-ray structure factors. For all g(r)curves, two components of the first maximum are visible.
The identification of the maxima in the total paircorrelation function can be derived by the comparison
with interatomic distances of crystalline Cu-Zr phases.
However, this is not unambiguous. The first sub-maxima
in the nearest neighbourhood at r = 0.272 nm can be
attributed to the non-resolved superposition of copper-

the corresponding atom pairs i,j [35]:wijX (q)  (2   ij )ci c j  ( S (q)  1)  q  sin(q  r )  dq,

ni nwiij  g ij .
g (r )  For amorphous alloys a single diffraction experimentyields only the total structure factor S(q) (q = 4  sin /
is the absolute value of the scattering vector), which is aweighted sum of the partial structure factors S ij q of

i



(3)

where ρ0 is the mean atomic density (ρ0= σ /NL m, σ:mass density, m: average atomic mass, NL: Avogadro`snumber). The total atomic pair correlation function g(r)describes the weighted probability of finding an atom at agiven distance r from a central atom averaged over all
atoms and normalized to the mean atomic density.
Analogous to the total structure factor, the g(r) curves
represent in the n-component alloy the weighted sum of
the n(n+1)/2 partial atomic pair correlation functions gij,which describe the probability of finding an atom of kindj around atom i :III. RESULTS AND DISCUSSIONni nwi ij (q )  ( S ij (q )  1) .
S (q )  1  


2

1

1

copper ( rCuCu ) and zirconium-copper ( rZrCu ) distances.

The second sub-maxima at r = 0.315 nm corresponds to,1

the nearest zirconium-zirconium ( rZrZr ) distance. This
will be confirmed by the partial atomic pair correlation
functions as shown later. With increasing Cu content thecontributions of Cu-Cu and Cu-Zr pairs to the total
atomic pair correlation functions g(r) becomes more
pronounced whereas the Zr-Zr contribution decreases inaccordance with the composition dependence of theweights wij (table 1). The variation of the weights is also
responsible for the differences of the X-ray and neutron
total atomic pair correlation functions.

(2)

Where  ij is the delta symbol of Kronecker, fi (q) is the
q-dependent atomic form factor in case of X-ray
scattering experiments (index X) and bi is the constantcoherent neutron scattering length (index N). The

X

N

Table 1. Mass density , atomic density 0, weights wij , wij of CuxZr100-x glasses.

2

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Atomic pair correlationg ( r ) =( r ) /0functions, i.e., the structural information, from theexperimental data are obstructed by these modulations of
the EXAFS signals. In the present study feff8.4 was used
to obtain the backscattering factors [41].
Using the RMC method, the atomic partial paircorrelation functions can be separated by simultaneously
modelling X-ray and neutron diffraction measurements
together with EXAFS data [39]. In this method atoms are
moved around at random in a simulation box. Partial paircorrelation functions are calculated from atomic positions
after each move and are transformed to model the X-ray,
neutron diffraction and EXAFS curves. The move isalways accepted if the agreement between experimental
data and model curves improves. To avoid getting
trapped to local minima some moves leading to a worse
agreement are also accepted. For details of the techniquesee [42,43].
Figure 2 shows for the Cu65Zr35 glass the comparisonof the results of the RMC fit with the corresponding
experimental data. For the other two glasses Cu35Zr65 and
Cu50Zr50 similar good agreements between measured andcalculated values were obtained. As a result of the RMC
calculations, models of the three dimensional atomic
structure of the Cu-Zr glasses were obtained. Figure 3
shows the atomic arrangements of the Cu-Zr glasses.
From the model structures the partial pair correlation
functions gij(r) were determined, which are presented in
Figs. 4. The positions of the first maximum represent the8neutron
X-ray

6

Cu65Zr35

4

Cu50Zr50

2

Cu35Zr65

0
0.2

0.3

0.4

0.5

0.6

0.7

0.8

Interatomic distance r ( nm )Fig. 1. Total X-ray and neutron atomic pair correlation
functions g(r) of Cu-Zr glasses.

Each partial structure factor Sij(q) is related to thecorresponding partial pair correlation function gij(r) via
Fourier transformation:

Sij (q)  1 

1partial nearest neighbour distances rij . The integration

40
r sin qr( g ij (r )  1)dr . (5)q over the first maximum gives the nearest neighbour
1

number N ij of j-atoms around an i-atom in the interval
between r1 and r2:

The analysis of the atomic structure of amorphous alloys
requires the determination of the partial structure factors.
For a binary alloy, the linear system of equations eq.(1)can be directly solved if 3 experimental data-sets are athand. The accuracy or stability of this inverse problem
depends on the differences of the weights. For aquantitative definition of the relative information content
of multiple datasets see [39].
Additional information can be extracted from EXAFS
measurements. The interference parts of absorption data
i(q) of the absorber atoms, is a convolution of the partial
pair distribution functions gij(r) of all the different
scatterer atoms j with the EXAFS signal corresponding toa single atom pair ij(q,r) [40] :

j

1

1

The calculated values rij and N ij are given in table 2. The
general behaviour of the corresponding partial paircorrelation function is similar for the Cu-Zr glasses withdifferent compositions. The nearest neighbour distances
do not alter with the composition within the error limitsof  0.002 nm. Differences of the inter-atomic distances
between the different Cu-Zr glasses occur at larger rvalues. The maxima positions of the neighbour shells are
shifted to higher values with increasing Zr-content which
relates to the composition dependence of the atomic
density, or the mean atomic volume respectively. The(6)1

nearest neighbour numbers N ij are proportional to theoconcentration of the corresponding element in the glass.
The monotonic behaviour of the coordination numberswith composition points to a continuous atomic
substitution. This is also in agreement with theconcentration dependences of the mean atomic volume
and the total pair correlation functions of Cu-Zr glasses[16].

The EXAFS signal corresponding to a single atom pair  ij(q,r) is given by ij (q, r )  Aij (q, r ) sin2qr  ij (q, r )

(8)

r1



 i (q)    4r 2 0 ij (q, r ) gij (r )dr .

r2

N   4r 2  ci   0  g ij (r )
1
ij

(7)

with an amplitude Aij(q,r) and phase ij(q,r) modulated
harmonic function. The extraction of the pair distribution

3

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Cu65Zr35

EXAFS at Zr-edge
c= 4nm4

S(q), (q)EXAFS at Cu-edge
neutron diffraction

2
X-ray diffraction0a=measured
RMC fit
2

4

6

8

4n

b=

m

4

nm

Cu65Zr35

a)

10

-1

q(Å )
c = 4 nm

gZrZr
gCuCu
gCuZr

12
Cu65Zr35

a=

4n

m

b=

4n

m

Cu50Zr50b)8
Cu50Zr50c= 4nmPartial pair correlationsgij (r )Fig. 2. Comparison of experimental scattering data and
RMC fit of Cu65Zr35 glass.

4
Cu35Zr65

0
0.2

0.3

0.4

0.5

0.6

0.7

0.8

a=

r ( nm )

4n

m

b=

4

nm

Cu35Zr65c)

Fig: 4. Partial atomic pair correlation functions gij (r) of CuZr glasses.

Fig. 3. Atomic structure of Cu-Zr glasses : a) Cu65Zr35,b) Cu50Zr50 , c) Cu35Zr65 (Cu-atoms: red, Zr-atoms: blue).

1

1

Table 2. Nearest neighbor distances rij , nearest neighbor numbers N ij for CuxZr100-x glasses.

4

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the Cu atoms

Frequency distribution ( %)From the RMC structures models, further information
can be extracted on the local structure in the Cu-Zr
glasses. First, the nearest neighbourhood of Cu and Zr
atoms were analyzed. For this, the kind and the numberof nearest neighbours were counted around all atoms up
to the first minimum of the corresponding atomic paircorrelation functions. Figure 5 shows the frequency
distribution of the numbers of nearest neighbours around1
1
1
1( N Cu = N CuCu + NCuZr ), and around
N Cu
1

1

1

1

the Zr atoms N Zr ( N Zr = N ZrCu + N ZrZr ), respectively.
1

The values N Cu are between 9 and 16 with a maximum
1=12. The coordination number distribution
N Cu

for

around the Cu atoms does not essentially change withcomposition for the different Cu-Zr glasses (Tab. 2, Fig.
5). The number of nearest neighbours around Zr atoms

50

1

Cu35Zr65 : NZr

Cu65Zr35 : NCu

1

Cu65Zr35 : NZr

1

1

Cu50Zr50 : NZr

1

Cu50Zr50 : NCu

40
30
20
10
0

8

10

12

14

16
1

1

Nearest neighbour numbers NCu,NZr

1

ranges from to 10 to 17 with the maximum N Zr =13 for1

the Cu35Zr65 glass, and N Zr =14 for the Cu65Zr35 glass
respectively. This behaviour reflects the effect of thedifferent atomic sizes. The larger Zr atoms can besurrounded by a higher number of the smaller Cu atoms.
With increasing Cu content the number of Cu atoms
around Zr statistically increases resulting in a higher
mean coordination number (Tab. 2, Fig. 5).
The chemical composition of the first neighbourhoodof an Cu (or Zr) atom is given by the ratio of the number
atoms in the first coordination shell (around Cu: cCu/cZr =Fig. 5. Frequency distribution of nearest neighbour
11Frequency distribution ofcCu ( % )numbers N Cu , N Zr of Cu-Zr glasses.

11
11/ NCuZr ; around Zr : cCu/cZr = N ZrCu / N ZrZr ).
NCuCu

Figure 6 shows the frequency distributions cCu around theCu atoms, and the Zr atoms respectively. The obtained
frequency distributions follow probability distributions
with a maximum corresponding to the average chemicalcompositions of the Cu-Zr glasses. There is also no
obvious difference between the composition distributions
around the Cu and the Zr atoms which should be the caseif chemically ordered clusters would be dominant in the
Cu-Zr glasses. The distributions of the kind of the firstneighbour atoms around the Cu and Zr atoms point to asolid solution-like behaviour of the Cu-Zr glasses.
Assuming that a Cu atom has 12 nearest neighbour sites
1

1

Cu35Zr65 : NCu

30: Cu35Zr65: Cu50Zr50: Cu65Zr35a) around Cu

20
10
0
30

0.2
b) around Zr

0.4

0.6

0.4

0.6

0.8

1.0

20
10
0
0.0

0.2

1

0.8
1

1.0
1

Composition cCu= NCu / (NZr+NCu)
Fig. 6. Frequency distribution of chemical composition cCuof the first coordination shell of Cu-Zr glasses: a) around Cu
atoms , b) around Zr atoms. (Distributions for random site
occupations are given by the dashed lines).

1

around ( N CuCu + N CuZr =12), which are randomly

occupied by Cu and Zr atoms, the probability
1
1of Cu atoms
w( N CuCu) of a certain number NCuCu

1( N CuCu = 0,1,..,12) is then given by :1w( NCuCu
)(

12
1
1
)  ( xCu )12 NCuCu  ( xZr ) NCuCu
1
NCuCu

random occupation of 12 nearest neighbours by thedashed lines. The calculations are in a qualitative
agreement with the experimental results. The RMC
results of the Cu-Zr glasses are therefore in accordancewith the random site occupancy of the atoms in the firstneighbourhood of Cu or Zr atoms. The differences
occurring in detail are mainly caused by thesimplification of 12 neighbours only and due to theneglection of the different atomic sizes.
To analyze the topology of the local atomic
arrangements of the Cu-Zr glasses, the Voronoi
tessellation method [44] was applied to the RMC data.

,(9)
with xCu , xZr, as the average element concentrations of the
Cu-Zr glass. Using eq. (9) the frequency distribution
cCu/cZr can be calculated. Figure 6 shows thecorresponding curves of the composition statistics for the

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The Voronoi cell or the Voronoi polyedra of an atom
contains all points in space which are closer to the centreof the atom than to any other atom. The Voronoi
tessellation thus produces convex polyhedral cells(polygons) which have planar faces and completely fill
the space. The different coordination polyhedra
surrounding a central atom can be characterized by theVoronoi index <n3,n4,n5,n6,…> where ni denotes thenumber of i-edged faces of the polyhedron and

Table 4. Frequency distribution of Voronoi polygons of
Cu-Zr glasses.

 n isiithe coordination number. Table 3 summarizes the relative
frequencies of the most prominent polyhedra. A large
amount of different polyhedra (> 1000) were identified
in the structure of the Cu-Zr glasses. The ideal
icosahedron <0,0,12,0> appeared with the highest
frequency
beside many other polyhedra withcoordination number > 12 (Tab.3). With higher Cu
content the fraction of icosahedra in the Cu-Zr glasses
increases. The frequency distribution of the Voronoi
polyhedra is in qualitative agreement with results of MD
calculations [22,30] as well as with RMC analysis
reported for Cu50Zr50 [31] or Ni33.3Zr66.7 [45] glasses.
Several polyhedra having a high number of pentagon
faces can be treated as a kind of distorted icosahedral
arrangements. The frequency distribution of the twodimensional Voronoi polygons is summarized in table 4.
The pentagon is dominant (> 50%) and increases in
number density with the Cu-content. A similar monotonic
behaviour of the polygon distributions is reported for
MD simulations of Cu-Zr glasses for a Cu content
between 30 and 70 at% [22]. The variability of the local
structures is probably the consequence of the substitutionof Zr by Cu atoms with increasing Cu content.

VI. CONCLUSIONS

The atomic structure of Cu-Zr glasses was analyzed bymeans of RMC method using XRD neutron and EXAFS.
The experimental results on the composition dependenceof the atomic structure of Cu-Zr glasses point to a solid
solution-like replacement of Cu and Zr atoms in thewhole composition range. The local structures show alarge variety of polyhedra arrangements. No indications
are observed that would support the existence of adominant special structure or of distinct cluster in theatomic structure. Hence, from the structural point ofview there is no obvious reason that relates to the highglass forming ability or plasticity found for particular CuZr compositions.
ACKNOWLEDGEMENTS

HASYLAB is gratefully acknowledged for the support
during synchrotron beam time. The neutron diffraction
measurements at Saclay (France) were supported by theEuropean Commission under the 6th Framework
Programme through the Key Action: Strengthening theEuropean Research Area, Research Infrastructures.
Contract No: HII3-CT-2003-505925. The authors are
grateful to P. Jovari for RMC calculations, I. Kaban and
S. Gruner for experimental support, and H. Hermann forvaluable discussions.

Table 3. Frequency distribution of Voronoi polyhedronof Cu-Zr glasses.

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Microscopic deformation behavior and microstructural evolution
in Ti-Nb-Ta-M (M=In, Ag, or Cr)  alloys
1

W. Xu 1, M. Calin 2, K. B. Kim 3, J. Das 2,4, K. Xia 1 and J. Eckert 2,5

Department of Mechanical Engineering and ARC Centre of Excellence for Design in Light Metals, University of Melbourne,
Victoria 3010, Australia
2
IFW Dresden, Institute for Complex Materials, Helmholtzstr. 20,
D-01069 Dresden, Germany
3
Department of Advanced Materials Engineering, Sejong University, 98 Gunja-dong,Gwangjin-gu, Seoul 143-747, Korea
4
Indian Institute of Technology, Department of Metallurgical and Materials Engineering, Kharagpur 721302, West Bengal, India
5
TU Dresden, Institute of Materials Science, D-01062 Dresden, Germany
The microstructural evolution upon compressive loading was identified for metastable Ti-Nb-Ta-M(M=In, Ag, or Cr)  alloys with different phase stability against  martensitic transformation. With
increasing degree of deformation, martensitic transformation and deformation twinning are initiallyoperative followed by slip of dislocations for the less stabilized In- and Ag-containing alloys, whereas slip
is initially operative followed by fine deformation twinning for the relatively more stable Cr-containing
alloy. As a result of the cumulative interactions between slip dislocations,  martensite and deformation
twins, a pronounced grain refinement of the  grains to the nanoscale (50~100 nm) occurs in the In- andAg-containing alloys with low stacking fault energy. A plausible mechanism is proposed for the easy
deformation-induced nanostructuring.
1. INTRODUCTION

some -titanium alloys favoring  martensitic
transformation [13, 14], was not observed in Ti-24Nb4Zr-7.9Sn [6] Ti-10Mo-4Nb-2V-3Al [5].
Usually, the differences in macroscopic deformation
behavior can be elucidated by the microscopic
deformation mechanisms that are operative toaccommodate the deformation strain. With decreasingphase stability, the microscopic deformation mechanismof metastable -titanium alloys varies from slip ofdislocations to deformation twinning and/or martensitic
transformation [7, 8, 15, 16]. As a result, the lessstabilized  alloys exhibit a low yield strength as well aslarge strain hardening, whereas the relatively stabilized alloys showed high yield strength and limited strain
hardening [7, 13]. The differences in mechanicalproperties are viewed as a reflection of whether amartensitic transformation happens. However, themicrostructural evolution with increasing degree of
deformation and its correlation with the deformation
behavior are still not well understood and established dueto the complex interaction between slip dislocations,twins and martensite. In the present study, themicrostructural evolution upon compressive loading was
identified for metastable Ti-Nb-Ta-M (M=In, Ag, or Cr) alloys with different  phase stability in order to gain
more insight into the correlation between the microscopic
deformation mechanism, the microstructural evolution
and the overall deformation behavior.

Biocompatible -titanium alloys containing non-toxic
-stabilizing alloying elements have attracted a lot of
attention for biomedical implant applications due to theadvantages of lower Young’s modulus and better
formability over  and + titanium alloys [1-8]. In
terms of mechanical properties, low Young’s modulus
and high yield strength, which strongly depend on alloy
design and materials processing [1, 9], are desirable for-titanium alloys for use as biomedical implants [10, 11].
For example, a solution-treated and aged Ti-29Nb-13Ta4.6Zr (wt.%)  alloy showed a Young’s modulus of 80
GPa as well as a yield strength of 864 MPa [9]. On theother hand, a solution-treated Ti-35Nb-5Ta-7Zr (wt. %) 
alloy exhibited a lower Young’s modulus of 55 GPa anda lower yield strength of 530 MPa [1]. For metastable titanium alloys, phase transformations play a crucial rolein order to control the microstructure and the resulting
mechanical properties. Depending on the stability,
metastable -titanium alloys may undergo martensitic
transformations (, , or ) upon quenching
and/or deformation [12], leading to a distinct deformation
behavior. Many of the metastable -titanium alloys
favoring stress-induced martensitic transformation
exhibit a shape memory effect and pseudoelastic
deformation behavior [5, 6, 13]. In a hot-rolled Ti-24Nb4Zr-7.9Sn (wt. %)  alloy composed of  martensite, arecoverable strain of 3.3% was achieved upon unloadingat an imposed strain of 4% [6]. On the other hand, theorigin of pseudoelastic behavior in Ti-xMo-4Nb-2V-3Al(x>9%, wt. %)  alloys was attributed to the formation ofa new reversible orthorhombic  martensite other than [5]. Upon unloading, a recovery of 80% of theimposed strain was reported for a Ti-10Mo-4Nb-2V-3Al
 alloy [5]. However, the double yielding effect found for

2. EXPERIMENTAL

Ti-Nb-Ta-M (M=In, Ag, or Cr) master alloys with anominal composition of Ti-29Nb-13Ta-5M (wt.%) wereprepared by arc-melting a mixture of pure elements(99.99%) under a Ti-gettered argon atmosphere. The
master alloys were remelted at least four times by
reversing the alloy buttons in order to avoid

1

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9:33:41inhomogeneity. Rods of 4 and 6 mm diameter wereprepared by suction casting the arc-remelted alloys intocylindrical cavities of a water-cooled copper mold.
Structural investigations were carried out by X-ray
diffraction analysis (XRD, Cu-Kα), optical microscopy(OM), scanning electron microscopy (SEM, 30 kV) withan energy dispersive X-ray analyzer (EDX) andtransmission electron microscopy (TEM, 200 kV). Alloy
composition measured by SEM/EDX for the as-cast TiNb-Ta-M alloys is summarized in Table 1. The content ofIn or Ag in the prepared master alloys deviated from thenominal composition to a certain extent due to theevaporation loss during arc melting (the boiling point ofIn or Ag is much lower than Ti, Nb and Ta). The samples
for XRD analysis were prepared by fine polishing inorder to remove the damage layer during cutting andgrinding so as to avoid the formation of stress-induced
martensite due to mechanical processing. Transverse
sections of the resulting samples for the OM and SEM
studies were prepared by conventional mechanicalgrinding, polishing and chemical etching in Kroll’s
reagent. For TEM studies, thin slices were prepared bymechanical grinding and polishing followed by argon ion
milling. The room temperature mechanical properties
were characterized under uniaxial compression loading
using an Instron 8562 testing machine at a strain rate of
1.210-4 s-1. The oxygen content analyzed using a carriergas hot extraction (O/N analyzer TC-436/Leco) was lessthan 600 p.p.m.

Fig. 1. SEM micrographs of the as-cast In-, Ag- and Crcontaining -titanium alloys. (a) Ti-Nb-Ta-In; (b) Ti-Nb-TaAg; (c) Ti-Nb-Ta-Cr. The inset in (b) indicates the formationof tiny domains in the  dendrites of the Ti-Nb-Ta-Ag alloy.
GB: grain boundary.

3. RESULTS

boundaries (marked by black arrows in Fig. 1) wererevealed and the grain size was estimated to be about 80
m. In the as-cast In-containing alloy (Fig. 1 (a)), theFig. 1 shows typical microstructures for the as-cast Tiathermal  martensite [14] was clearly observed to form
Nb-Ta-M  alloys, which are mainly composed ofat the interdendritic zones, as marked by the white arrowdendritic  phase (Microstructures at a lower
in Fig. 1 (a). Similarly,  martensite was also identified
magnification were given in Ref. 7). Large-angle grain
at the interdendritic zones
in the as-cast AgTable 1. Measured alloy composition for Ti-Nb-Ta-M (M=In, Ag, or Cr)  alloys.
containing alloy (Fig. 1(b)). However, the 
martensite plates formedin the as-cast Agcontaining alloy were notclearly visible. Detailed
investigations (inset of
Fig. 1 (b)) indicated that
the

phase
was
composedoftiny
domains of about 100 nm.
Compared with the ascast
Inand
Agcontaining alloys, the ascast Cr-containing alloy
exhibitedamicrostructure consisting onlyof  phase without the3.1. As-cast microstructures of Ti-Nb-Ta-M  alloys

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formation of athermal  martensite (Fig. 1 (c)).
Fig. 2 shows the XRD patterns of the as-cast Ti-NbTa-M  alloys. The bcc  phase was identified as
dominant phase in all alloys, which is in agreement withthe microstructure identification. The formation of theorthorhombic  martensite in the as-cast In- and Agcontaining alloys was also evidenced, especially in the
XRD patterns in the range of 33° ≤ 2θ ≤ 45 at a slow
scan rate (Fig. 2 (b)). Obviously, no  martensite was
detected in the as-cast Cr-containing alloy.
Fig. 3 shows TEM micrographs of the as-cast In- andAg-containing alloys as well as the corresponding
selected-area diffraction (SAD) pattern. Fig. 3 (a) is abright-field image revealing  martensitic plates in theas-cast In-containing alloy. The SAD pattern for Fig.3 (a)indicated the presence of both  and  phases (Fig. 3(b)). The orientation relationship between the  and phases was identified as

3.2. Deformation behavior of Ti-Nb-Ta-M  alloys
It is obvious that the In- and Ag-containing  alloys
have lower stability against  martensitic transformation
upon solidification in comparison with the Cr-containing
alloy. The deformation behavior was found to strongly
depend on the stability of the  phase. Fig. 4 shows theroom-temperature compressive true stress-strain curves
for the Ti-Nb-Ta-M  alloys. All alloys displayed asimilar elastic strain limit of about 0.8~1.0 % (the inset of
Fig. 4). The In- and Ag-containing alloys exhibited asimilar deformation behavior with low yield strength(373 and 414 MPa, respectively) and remarkable strain
hardening. On the other hand, the Cr-containing alloy
showed a different deformation behavior with higher
yield strength of 612 MPa and less pronounced strain
hardening. As a result, the In- and Ag-containing alloys
have lower Young’s moduli of 55 and 60 GPa,

[ 1 15]  [ 1 1 1 ]  . In

addition, although no  phase was detectable from the
XRD patterns, the athermal  phase (ath) can be
identified from the SAD pattern due to the presence of
faint peaks surrounding the peaks of the  phase [14,17-19], as indicated by the white arrows in Fig. 3 (b). For
the as-cast Ag-containing alloy, bright-field images (Fig.
3 (c)) revealed that the  phase was fully composed offine twins with a spacing of 150~200 nm. Ultrafine andstrained  domains of 80~150 nm (marked by the whitearrow in Fig. 3 (c)) were formed in the as-cast Agcontaining alloy, which is probably induced by theinteraction of twins.

Fig. 3. TEM micrographs of the as-cast In- and Agcontaining -titanium alloys with low stability. (a) brightfield image of Ti-Nb-Ta-In; (b) the corresponding selectedarea diffraction pattern of (a); (c) bright-field image of TiNb-Ta-Ag, showing the presence of fine twins.

Fig. 2. X-ray diffraction patterns for the as-cast In-, Agand Cr-containing -titanium alloys. (a) normal scan; (b)slow scan for 33° ≤ 2θ ≤ 45.

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9:33:42Fig. 4. Compressive true stress-strain curves for the ascast In-, Ag- and Cr-containing -titanium alloys (roomtemperature).

Fig. 5. Micrographs showing deformation microstructures
for the In- and Ag-containing -titanium alloys. (a) lessdeformed zone of Ti-Nb-Ta-In (SEM); (b) less deformed zoneof Ti-nb-Ta-Ag, the inset shows the presence of  martensite;(c) partially deformed zone of Ti-Nb-Ta-In (SEM); (d)severely deformed zone of Ti-Nb-Ta-In (OM). SB: shear
bands.

respectively, in comparison with 75 GPa for the Crcontaining alloy.
3.3. Microstructural evolution during deformation

martensite were still visible, shear banding started tooccur and partially contributed to the strain
accommodation, as indicated by the arrow in Fig. 5 (c).
With further increasing degree of deformation at the
sample center, the  dendrites were severely deformed
into filaments (Fig. 5 (d)). At this stage, deformation
twins and  martensite could not be easily identified dueto the filamentary structure. However, remarkable shear
banding was revealed, which mainly contributed to thestrain accommodation.
In order to gain more insight into microstructuralchanges during deformation, detailed TEM investigations
were carried out on the deformed In- and Ag-containing
samples, which are shown in Figs. 6 and 7. Fig. 6 exhibits
bright-field TEM images and the SAD patterns taken at
the less deformed zone of the In-containing alloy. In Fig.
6 (a), the bright plate-like phase with a lamellar spacingof 150 nm was identified as  martensite whereas thedark phase in between was the  parent phase. The SAD

In the uniaxially compressed sample, the degree of
deformation is inhomogeneous and increases from thesample surface towards the center. Depending on degreeof deformation, the microstructure can be classified into
three types occurring in different zones throughout the
specimen, including macroscopically undeformed 
dendrites, partially deformed and elongated  dendrites,and severely deformed  phase in the form of filaments,
which are presented in the following sections in terms ofphase stability of  alloys.
3.3.1.

Deformation microstructures in thestabilized In- and Ag-containing  alloys

lessFig. 5 shows the SEM micrographs illustrating thetypical deformation microstructures corresponding to thethree deformed zones in the less stabilized In- and Agcontaining alloys. Close to the sample surface of thedeformed In-containing alloy, deformation twins formed
and an increase of the volume fraction of  martensite
was observed in comparison with the as-cast sample (Fig.
5 (a)). Some of the  dendrites fully transformed into 
martensite to accommodate the applied strain. Similar to
the In-containing alloy, the Ag-containing alloy also
exhibited deformation twinning at the less-deformed zone
(Fig. 5 (b)). However,  martensite was visible only at ahigher magnification in certain areas (the inset of Fig. 5(b)) and its volume fraction was much lower than in the
In-containing alloy. This indicates that the Ag-containing
alloy has a relatively higher stability than the Incontaining alloy. With increasing degree of deformation,
the equiaxed  dendrites were partially deformed andelongated along the direction perpendicular to the loading
axis (Fig. 5 (c)). Although deformation twins and 

pattern taken along the [ 1 13]  zone axis (the inset of
Fig. 6 (a)) confirmed the presence of both  and phases with [1 13][002]  orientation relationship[7]. In addition, from the SAD pattern a {112}<111>twinned structure was identified within the  phase.
Furthermore, the HRTEM examination on the  phase(Fig. 6 (b) for the dashed-circle region in Fig. 6 (a)) andthe corresponding SAD pattern along the [ 1 12]  zone
axis (inset of Fig. 6 (b)) implied that the athermal phase was present inside the parent  phase, as revealed
from the broadening of the diffraction spots as well as theformation of diffuse streaks. Due to its athermal
characteristics, the  phase has no clear boundary with

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9:33:42Fig. 6. TEM micrographs in the less deformed zone of
the In-containing -titanium alloy. (a) bright-field image,the inset shows the corresponding diffraction pattern; (b)high-resolution TEM image and corresponding selectedarea diffraction pattern in the dashed-circle region of (a),showing the formation of athermal  phase inside the phase.

Fig. 7. TEM micrographs at the severely deformed zoneof the In- and Ag-containing -titanium alloys. (a) brightfield image of Ti-Nb-Ta-In, showing the filamentary
structure composed of nanoscale deformation twins; (b) and(c) bright- and dark-field images of Ti-Nb-Ta-In as well as
corresponding selected-area diffraction pattern, showing theformation of nanoscale  grains; (d) bright-field image of TiNb-Ta-Ag, showing the filamentary structure; (e) and (f)bright- and dark-field images of Ti-Nb-Ta-Ag as well as
corresponding selected-area diffraction pattern, showing thecoexistence of both plate-like and nearly equiaxed  grains.

the  phase [20], but it can be inferred from the stained
contrast in the HRTEM micrograph.
Fig. 7 exhibits bright- and dark-field TEM micrographs and the SAD patterns taken at the severely
deformed zone close to the sample centers of the In- andAg-containing alloys. Fig. 7 (a) shows a bright-field
image of the filamentary structure formed at the severely
deformed zone in the In-containing alloy, in which thefilamentary boundaries are indicated by the arrows. From
the SAD pattern (not shown here), no  martensite andathermal  phase can be identified other than the  phasefor the filamentary structure. Fine deformation twins witha twin boundary spacing of less than 100 nm were foundto form inside some of the  filaments. The deformation
twins formed in each filament were confined by thefilamentary boundary, showing a clear orientation
relationship for twins inside two neighboring filaments.
In addition to the formation of fine deformation twins, apronounced grain refinement was observed in some ofthe  filaments to produce nanostructured  grains in therange of 50~100 nm, as evidenced from the bright- anddark-field images (Figs. 7 (b) and (c), respectively), andthe SAD ring pattern (the right upper inset of Fig. 7 (b)).
The nanostructured  grains exhibited a complicatedmoiré fringe pattern (the lower left inset of Fig. 7 (b)),

which is similar to that of a nanostructured NiTi alloy
processed by severe plastic deformation (SPD) [21]. Fig.
7 (d) shows the filamentary structure formed at theseverely deformed zone in the Ag-containing alloy. In
contrast to the the In-containing alloy (Fig. 7 (a)), no finedeformation twins were visible inside the filaments. In
addition, a remarkable grain refinement (50~100 nm)
also occurred in some of the  filaments at the severely
deformed zone of the Ag-containing alloy, as indicatedfrom the bright- and dark-field images (Figs. 7 (e) and (f),respectively) and the SAD pattern (the inset of Fig. 7 (e)).
Upon severe deformation, the extent of grain refinementin the Ag-containing alloy was less pronounced than for
the In-containing alloy, as evidenced from the SAD
pattern composed of rings and diffraction spots. The
grain refinement in the In-containing alloy led to theformation of nearly equiaxed nanoscale  grains (Fig. 7(c)), whereas insufficient grain refinement in the Agcontaining alloy resulted in the coexistence of both platelike (marked by the white arrow in Fig. 7 (f)) and nearly

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zones, cutting off the filamentary structure in order torelease the increasing strain (Fig. 8 (c)).
Fig. 9 shows bright-field TEM micrographs, and thecorresponding SAD patterns at the severely deformed
zone of the Cr-containing alloy. The filamentary structure
formed in the Cr-containing alloy is illustrated in Fig. 9(a). The SAD pattern (inset of Fig. 9 (a)) indicated thepresence of both  and athermal  phases [14, 17-20], inwhich main diffraction spots and weak diffusing streaks(indicated by the black arrow) correspond to  and 
phases, respectively. No nanostructuring of the  phase
was found for the Cr-containing alloy after severe
deformation. Instead, in some of the filaments both
submicron and nanoscale deformation twins were clearlyvisible, as revealed by the bright-field TEM image shownin Fig. 9 (b). The presence of deformation twins can be
deduced from the higher order diffraction spots (marked
by the white arrows in the inset of Fig. 9 (b)). Fig. 9 (c)shows a high-resolution TEM image of the nanoscale
twins (the dashed-circle region in Fig. 9 (b)). Twin faults

equiaxed  grains, as indicated in Figs. 7 (e) and (f).
Furthermore, it should be noted that the boundaries of therefined  grains were remarkably distorted, especially for
the Ag-containing alloy.
3.3.2. Deformation microstructures in the stabilized
Cr-containing  alloy
Compared with the less stabilized In- and Agcontaining alloys, the relatively stabilized Cr-containing
alloy exhibited different deformation microstructures (Fig.
8). At the less deformed zone, no  martensite anddeformation twins were detectable. Instead, slip bands(marked by the black arrow in Fig. 8 (a)) which could not
be easily identified in the In- and Ag-containing alloys,
formed in some  grains to accommodate the further
imposed strain. With increasing degree of deformation,
the lack of martensitic transformation and deformation
twinning made plastic deformation of the  dendrites
more difficult. Slip is not capable to accommodate theincreasing strain, leading to the occurrence of strain
localization and the apperance of shear bands even in the dendrites without significant shape changes (Fig. 8 (b)).
With further increasing degree of deformation, a large
number of shear bands formed in the severely deformed

Fig. 9. TEM micrographs at the severely deformed zoneof the Cr-containing -titanium alloy. (a) bright-field image
and corresponding selected-area diffraction pattern, showing
the filamentary structure and the presence of the athermal phase; (b) bright-field image and corresponding selected-areadiffraction pattern inside one filament, showing theformation of fine twins in the  phase; (c) high-resolution
TEM image for the fine twins in the dashed-circle region of(b), exhibiting twin faults formed at the twin boundaries.

Fig. 8. Micrographs showing typical deformation microstructures for the Cr-containing -titanium alloy. (a) lessdeformed zone (OM), (b) partially deformed zone (SEM), (c)severely deformed zone (SEM). SB: shear bands.

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9:33:43(marked by white arrows in Fig. 9 (c)) were present at thetwin boundaries. Compared with the stacking faults
formed in the In-containing alloy, the twin faults formedin the Cr-containing alloy exhibited a smaller width [8].

exhibiting an enhanced ductility. The two stages related
to plastic deformation are discussed as follows.
Depending on the phase stability, martensitic
transformation, deformation twinning and slip are viewed
as the main deformation mechanisms for metastable titanium alloys [13, 15, 16]. For the In- and Agcontaining alloys with lower  phase stability, a stressinduced +ath martensitic transformation is easily
triggered after the initial linear elastic deformation rather
than slip [14], leading to low yield strength. Based on thepreexistent martensitic plates formed upon quenching,new  martensite nucleates and freely grows into the dendrites to release the increasing deformation strain. As
reported in a previous study [7], the stability increases
from the interdendritic zone to the center of the dendrites due to solute redistribution. When deformation
proceeds, nucleation of additional  martensitic plates
becomes more difficult towards the central region of thepartially consumed  dendrites. As a result, only some
but not all of the  dendrites can fully transform into 
martensite. In the meantime, deformation twinning{112}<111> is also operative to accommodate theincreasing strain. However, owing to their characteristics,
martensitic transformation and deformation twinningcannot result in a large shape change of the dendrites.
With increasing degree of deformation, it is believed thatslip is activated in the unconsumed dendrites since it isdifficult to further produce more  martensite anddeformation twins. Subsequently, slip dislocations may
interact with  martensite, remaining athermal  phaseand deformation twins, thus influencing the deformation
behavior to a great extent. Especially, the orthorhombic
 martensitic phase with less independent slip systems[22] plays a role as a barrier for slip of dislocations,
resulting in dislocation pile-ups that might be responsible
for the more pronounced strain hardening observed forthe In- and Ag-containing alloys. With further increasing
deformation above a certain strain level, the pronounced
strain hardening proceeds until the occurrence of thereversetransformation.
Thisreversetransformation may happen if the temperature rises

4. DISCUSSION

4.1. Microstructural evolution during deformationand its correlation with the deformation
behavior of -titanium alloys
The control of  phase stability is important for
designing metastable -titanium alloys since it strongly
affects the phases formed upon quenching or deformation.
In metastable -titanium alloys with a large amount of stabilizers, the phase transformations usually involve and/or  martensitic transformations, which toa great extent determine the resultant deformation
behavior. The examination of the microstructural
evolution is, therefore, an effective way to establish acorrelation between phase stability and deformation
behavior. In the present study, the three metastable titanium alloys show different phase stability. Table 2
summarizes the phases formed in both the as-cast anddeformed states for the Ti-Nb-Ta-M  alloys. Amongthese alloys, the In-containing alloy has the lowest
stability, leading to the formation of both  martensite
and athermal  phase upon quenching. On the other hand,
the Cr-containing alloy has the highest stability, resulting
in the formation of only athermal  phase.
As indicated from the compressive true stress-strain
curves (Fig. 4), the -titanium alloys with low stability
exhibit lower yield strength, remarkable strain hardening
and higher ductility in comparison with the stable titanium alloys. For the convenience of establishing thecorrelation between microstructural evolution anddeformation behavior, it is reasonable to divide the truestress-strain curves into three stages corresponding toelastic deformation, strain hardening and easy glide. It isnoted that not only one unique deformation mechanism isoperative to result in such three-stage deformation curves

Table 2. Phases formed in both as-cast and deformed Ti-Nb-Ta-M (M= In, Ag, or Cr)  alloys.

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locally and exceeds the austenitic start temperature As [14]as a result of plastic heat generation upon deformation[23]. This might be the reason that the  martensitic
phase could not be identified at the severely deformed
zones. Most important, the structure change fromorthorhombic to bcc removes the barrier for slip,
rendering some part of the piled-up dislocations tobecome mobile. Subsequently, the stage of easy glide
with little strain hardening occurs, during which thedislocations are able to move over relatively large
distances without encountering barriers (but the motionof dislocations is confined within the  filaments). Thismight be one of the contributions to the ductility
enhancement. In addition, the occurrence ofnanostructuring upon severe plastic deformation might
further contribute to the ductility, which will be discussed
in Section 4.2.
For the Cr-containing alloy with high  phase stability,no  martensitic transformation and deformation
twinning following the initial linear elastic regime could
be identified, indicating that the operative deformation
mechanism is only slip. As a result, the Cr-containing
alloy exhibits high yield strength since the trigger stressfor slip is much higher than that inducing martensitic
transformation [13]. With increasing degree of
deformation, the only barrier encountered by slip ofdislocations is the athermal  phase, which results in alimited strain hardening in comparison with the In- andAg-containing alloys. During this stage of plastic
deformation, dense dislocation walls and dislocation
tangles begin to develop, making further motion of
dislocations difficult. Fine deformation twinning is
becoming the favorable deformation mode for further
strain accommodation. The formation of a large numberof nanoscale twins with a width of less than 10 nm (Fig. 9(b)), is believed to contribute to the ductility to a certain
extent, since the lattice orientation changes by twinning
may enable additional slip to occur [24].

4Zr-7.9Sn (wt.%)  alloy after 90% reduction in
thickness [6]. In addition, a less pronounced grain
refinement was reported for a Ti-24Nb-4Zr-7.6Sn (wt.%)
alloy favoring martensitic transformation [6]. However,
our recent investigation on Ti-Nb-Ta-(In, Cr)  alloys
implied that upon severe plastic deformation
nanostructuring occurrs more easily in the less-stabilized
-titanium alloy with low stacking fault energy,
especially at martensitic transformed zones [8].
According to Wang et al. [29], grain refinement can be
more easily promoted if a complex stress state andcomplicated straining patterns are present. Based on the
deformation behavior (Fig. 4) and the phaseformation/microstructural evolution (Figs. 5-9 and Table2), a plausible grain refinement mechanism can beproposed for the In- and Ag-containing alloys. Easy
nanostructuring might stem from the complex interaction
among slip dislocations, martensite and deformation
twins, which is qualitatively elucidated as follows.
As indicated from Fig. 1 and Table 2, prior to
deformation  martensitic plates are already present at
the interdendritic zones in the as-cast In- and Agcontaining alloys, resulting in an inhomogeneous
microstructure, i.e. martensitic transformed anduntransformed zones. In the martensitic transformed
zones, the martensitic plates have at a spacing of 150 nm,
dividing the  phase into a sandwiched structure with alength-scale as fine as 100 nm. Upon compressive
loading above a trigger stress, stress-assisted athmartensitic transformation [14] and mechnical twinning
are mainly operative to accommodate the deformation
strain at the initial stage of plastic deformation [7]. The
formation of such a fine martensite can be viewed as a
crucial step for the subsequent easy nanostructuring.
With increasing degree of deformation, instead ofmartensitic transformation and mechanical twinning, slip
becomes dominant and mainly contributes toaccommodate the increasing strain. At this stage theinteraction among slip dislocations, pre-existing martensite and twins is quite pronounced [8]. The lowsymmetry orthorhombic  martensite lacks sufficient
independent slip systems [22], making slip dislocationsdifficult to pass through it. Instead, slip dislocations
strongly interact with the partial dislocations of the /interface and pile-up at the interface to subdivide thesandwiched  phase into refined blocks, establishing theprerequisite for subsequent nanostructuring. The
difficulty for the motion of slip dislocations is believed toremarkably contribute to the strain hardening. Withfurther increasing deformation above a certain strain level(severely plastically deformed), the temperature increase
locally exceeds the austenitic start temperature (as low as
166 C for Ti-10V-2Fe-3Al [14]), which might lead tothe reverse  transformation [14] at some localizedzones. The structure change from orthorhombic back to
bcc provides more slip systems, activating part of the
piled-up dislocations at the / interface. These
reactivated dislocations experience an easy glide stage

4.2. Deformation-induced nanostructuring in titanium alloys
Deformation-induced grain refinement to the nanoscale
usually occurs when an externally repeated force is
imposed on bulk polycrystalline metallic materials or
their surfaces such through as ball milling [25], severeplastic deformation [26] and surface mechanical attrition
treatment [27]. The lattice structure and the stacking fault
energy of alloys significantly influence the plastic
deformation in metallic materials, which inherently
govern the deformation-induced grain refinement [27, 28].
Recently,
deformation-induced
grain
refinement
mechanisms were investigated in terms of stacking fault
energy for several typical metallic materials [27]. It was
found that deformation twinning and martensitic
transformation play a crucial role for grain refinement inalloys with low stacking fault energy [27]. For -titanium
alloys, a remarkable grain refinement to the nanoscale(less than 50 nm) was achieved in a cold-rolled Ti-24Nb-

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9:33:44behavior. For the In- and Ag-containing alloys, theorthorhombic  martensitic phase with less independent
slip systems plays a role as a barrier for slip ofdislocations, resulting in dislocation pile-ups that might
be responsible for the more pronounced strain hardening.
In terms of ductility enhancement, the reverse
transformation from orthorhombic  martensite back tothe bcc  phase removes the barrier for slip, making partof the piled-up dislocations become mobile for easy glide
and subsequently contributing to ductility. In addition,
the nanostructuring process and the formation of an
inhomogeneous
deformation
microstructurearebeneficial for ductility enhancement due to the creationof more free volume/defects and the composite-likebimodal microstructure, respectively. On the other hand,for the Cr-containing alloy the lack of interactions amongslip dislocations,  martensite and deformation twins
produces less barriers for slip, leads to limited strain
hardening and makes grain refinement more difficult.

within a  filament and pile-up again at the filamentaryboundary, forming subboundaries and further subdividing
the  filaments into refined blocks. The refining process
will proceed within the filaments with increasing degreeof deformation. Therefore, upon severe deformation easy
nanostructuring occurs rather at the martensitic
transformed zones than at the untransformed zones,
leading to an inhomogeneous microstructure, i.e.
nanoscale  grains (50~100 nm) together with asubmicron  filamentary structure (200~800 nm). It isbelieved that to a great extent the nanostructuring process
and the inhomogeneous microstructure are beneficial tothe enhancement of the ductility. Grain refinement tonanoscale grains creates more free volume/defects (grain
or sub-grain boundaries) that significantly contribute to
the ductility. On the other hand, the inhomogeneous
microstructure consisting of nanoscale equiaxed grains
and submicron  filaments is conceptually similar to thebimodal microstructure observed in a ductile
nanostructured Cu “composite” [29], which is believed togreatly contribute to ductility as deformation proceeds.
In contrary, upon the applied compressive loading easy
nanostructuring was not observed in the Cr-containing
alloy with high stacking fault energy although a very finefilamentary structure was formed at the severely
deformed zone [8]. However, the formation of submicronand nanoscale deformation twins above a certain strainlevel implies that it is feasible to utilize severe plastic
deformation techniques to achieve a grain refinement tonanoscale in -titanium alloys with high stacking fault
energy, which is currently under investigation.

ACKNOWLEDGEMENTS

The authors thank U. Kühn, W. Löser, S. Pauly and B.
Rellinghaus and for valuable discussions, and M. Branzei,
M. Frey and H.-J. Klauß for technical assistance. Funding
from the EU within the framework of the RTN-network
on “Ductile BMG composites” (MRTN-CT-2003504692), the Australian Research Council with the ARC
Centre of Excellence for Design in Light Metals, theAlexander-von-Humboldt Foundation, and the German
Science Foundation is also acknowledged.

5. CONCLUSIONS[1] Long MJ, Rack HJ. Biomaterials 1998; 19: 1621.
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[5] Zhang LC, Zhou T, Alpay SP, Aindow M, Wu MH.
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[6] Hao YL, Li SJ, Sun SY, Zheng CY, Hu QM, Yang
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[12] Collings EW. Physical metallurgy of titanium alloys,
ASM, Metals Park, OH, 1984.

The microscopic deformation behavior and themicrostructural evolution have been identified formetastable Ti-Nb-Ta-M (M=In, Ag, or Cr)  alloys withdifferent phase stability against  martensitic
transformation. Among these alloys, the In-containing
alloy exhibits the lowest stability, leading to theformation of both  martensite and athermal  phaseupon quenching. On the other hand, the Cr-containing
alloy shows the highest stability, resulting in theformation of only athermal  phase. With increasing
degree of deformation, martensitic transformation anddeformation twinning are initially operative followed byslip of dislocations for the In- and Ag-containing alloys,
whereas slip is initially operative followed by finedeformation twinning for the Cr-containing alloy.
Especially, a pronounced grain refinement of  grains to
the nanoscale (50~100 nm) easily occurrs in the In- andAg-containing alloys with low stacking fault energy,
which is attributed to the reversible  martensitic
transformation and the complicated interactions amongslip dislocations,  martensite and deformation twins.
Based on the present results, a preliminary correlation
has been established between microscopic deformation
mechanism, microstructural evolution and deformation

9

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[13] Grosdidier T, Philippe MJ. Mater Sci Eng 2000;
291A: 218.
[14] Duerig TW, Albrecht J, Richter D, Fischer P. Acta
Metall 1982; 30: 2161.
[15] Morinaga M, Kato M, Kamimura T, Fukumoto M,
Harada I, Kubo K. Titanium’92, Science andTechnology, Proc. 7th Int. Conf. on Titanium, San
Diego, USA, 1992. p. 276.
[16] Kuroda D, Niinomi M, Morinaga M, Kato Y,
Yashiro T. Mater Sci Eng 1998; 243A: 244.
[17] Fontaine D De, Paton NE, Williams JC. Acta Metall
1971; 19: 1153.
[18] Fan Z, Miodownik AP. J Mater Sci 1994; 29: 6403.
[19] Ping DH, Mitarai Y, Yin FX. Scripta Mater 2005; 52:
1287.
[20] Sikka SK, Vohra YK, Chidambaram. Prog Mater Sci
1982; 27: 245.

[21] Waitz T, Karnthaler HP. Acta Mater 2004; 52: 5461.
[22] Bowman K. Mechanical behavior of materials, John
Wiley & Sons, USA, 2004. p. 89 and p. 149.
[23] He G, Eckert J, Löser W, Schultz L. Nature Mater
2003; 2: 33.
[24] Smith WF, Hashemi J. Foundations of materials
science and engineering, 4th edition, Mc Graw-Hill,
New York, USA, 2006. p. 240.
[24] Koch CC. Nanostruct Mater 1993; 2: 109.
[25] Valiev R. Nature Mater 2004; 3: 511.
[26] Lu K, Lu J. Mater Sci Eng 2004; 375-377A: 38.
[27] Dieter GE. Mechanical Metallurgy, SI Metric
Edition, McGraw-Hill, London, U.K. 1988. p. 136.
[28] Wang YM, Chen MW, Zhou FH, Ma E. Nature
2002; 419: 912.

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Globally and Locally Strained Si Nanomembranes Fabricated by Elastic Strain Sharing
Francesca Cavallo,* Deborah M. Paskiewicz, and Max G. Lagally
University of Wisconsin-Madison, Madison, Wisconsin 53706, USA

Technology has evolved towards miniaturization ofdevice features with the ultimate goal of integrating many
components onto a compact chip, producing integrated
circuits with low cost and high degrees of functionality.
A recently developed approach is based on the use of nmthick membranes as an alternative to bulk substrates invarious applications. These membranes can be completely freestanding or tethered to a substrate, and they
can be flat or shaped in three-dimensional (3D) structures.

croscopy (AFM), confirms the absence of any mechanism of plastic relaxation, i.e., nucleation of line andplane defects, and roughening. The first step is thegrowth of a compressively strained SiGe layer (below its
kinetic critical thickness for plastic relaxation) on the Si
template layer of a (001) or (110) silicon-on-insulator(SOI) substrate, followed by a top Si capping layer. The
SiGe alloy and top Si layers were pseudomorphicallygrown by chemical vapor deposition (CVD) in a coldwall ultra-high vacuum (UHV) CVD reactor or by solidsource molecular beam epitaxy (MBE). In the as-growntrilayer the SiGe is compressively strained and under
tetragonal distortion, whereas the Si is unstrained, at thesubstrate lattice constant. Membrane formation is thenachieved by removal of the underlying SiO 2, i.e., the buried oxide (BOX). The release of the membrane from the
SiO2 results in its overall lateral expansion driven fromthe elastic strain relaxation of the SiGe layer. During thisprocess the compressive strain in the SiGe membrane
partially transfers to tensile strain in the Si layers. Equalor nearly equal thicknesses of top and bottom Si layers
are mandated to produce flat strain-balanced SiNMs after
the release step.
Membranes were then harvested using a wet-transfer
technique that has so far been used to transfer membranes
in sizes ranging from 5x5 mm2 to 1x1 cm2 to a variety of
substrates. The procedure is scalable to both significantly
larger and smaller dimensions and to almost any hostsubstrate that is not rapidly dissolved in water. A dry
printing technique for transferring the membranes to any
kind of new host has also been used successfully. Similar
methods work for Ge NMs or those of other materials.
Comparison of XRD 2 line scans on as-grown andreleased trilayers with various thicknesses and compositions demonstrate that tensile strain in (110) SiNMs canbe tuned by changing the Ge content in the alloy layer
and the alloy layer thickness relative to the thickness of
the Si layers in the trilayer. A maximum tensile strain of
0.65±0.01% in (110) SiNMs is calculated from XRD
scans and confirmed by continuum elasticity theory.

Nanomembranes (NMs) are distinguished from bulk
materials most significantly by thinness, flexibility, andnearness of two surfaces or interfaces. Excellent structural, electronic, and optical properties have been measured, both for flat and curled films. Furthermore, the ability to transfer released NMs to a large variety of hosts has
been successfully used for the fabrication of hybrid or
highly mismatched single-crystal multilayer stacks, andfor the development of bendable and stretchable electronics.
In recent work we have taken advantage of the mechanical compliance of freestanding NMs to establish a
uniform or spatially varying strain field in the ultra-thinlayer. Elastic strain sharing between a SiGe and a Si film
completely unsupported by a solid allows the fabricationof tensilely strained SiNMs. Similarly, a spatially varying strain field has been established in Si nanoribbons by
growing "local stressors" (e.g., Ge quantum dots (QDs))
rather than a "uniform stressor" (e.g., a SiGe strained
layer). Strain engineering in SiNMs in turn offers thepossibility of tuning materials properties, such as band
gap and carrier mobility, both on a global and a local
scale.
Among the most relevant results achieved in our groupin the field of NM technology are: 1) the fabrication of
dislocation-free (110) Si as thin as 10 nm, isotropicallyand biaxially strained with an in-plane strain as high as
0.6%; 2) the fabrication of hybrid-orientation templates
alternating (110) and (001) Si regions; and 3) the fabrication of a mechano-electronic superlattice in a single material, namely a SiNM. We briefly describe these three
topics.

The transfer of (110) SiNMs (even unstrained) to a(001) oriented Si template and subsequent overgrowthhas been used to fabricate mixed-crystal-orientation templates. This architecture may allow the manufacturing, inclose proximity to each other, of p- and n-channel devices on (110) Si (high hole mobility) and (001) Si (highelectron mobility) regions, respectively, with the benefitof reducing the current drive imbalance between PMOS
and NMOS devices. The ability to transfer the membranes to new hosts opens the possibility for integrating
high-electron mobility (001) regions with dislocation-free

We have used elastic strain sharing in Si/SiGe/Si multilayers to fabricate dislocation-free, tensilely strained(110) oriented SiNMs, which has indeed emerged as an
attractive material because of its higher hole mobility
compared to (001) Si. Good crystal quality of the layers
is revealed by X-ray diffraction (XRD). Surface morphology measurements, performed by atomic force mi-1

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9:33:45strained (110) Si, which promises hole mobility enhancements of up to 75% compared to the (001) universal
mobility. Furthermore, rotating the strained (110) membrane relative to its (001) host during transfer offers a
concrete possibility of optimizing channel direction in nand p-type devices. We have fabricated mixed-crystalorientation material in flexible form using SiNM transfer
and overgrowth. The SiNM fabrication begins with a(110) SOI substrate. The (110) Si template layer is patterned with an array of holes using standard photolithography and RIE, and removed from its handle substrate
via selective etching of the BOX layer. This procedure
creates a temporarily freestanding (110) SiNM, which isthen bonded to a (001) Si substrate. The holes define theregions where the (001) Si crystal planes are exposed
through the membrane. Deposition of Si over the structure using CVD with SiH4 precursor gas, at a substratetemperature of 580°C, fills the holes because the Si
growth rate is about 10 times faster on the (001) orientation than on the (110) orientation at 580°C. Hence fabrication of a flat mesh of (001) Si and (110) Si regions isachieved.

of the band gap for the thinnest ribbons. The calculatedband gap modulation was confirmed qualitatively by
combining photoelectron emission microscopy (PEEM)(as the detection tool) with high-resolution X-ray absorption spectroscopy (XAS). The calculated bandgap modulation in the SiNM due to the growth of nanostressors issimilar to the one observed in a 1D heterostructure withessentially all the band offset occurring in the conduction
band. We solved the variable effective-mass Schrödinger
equation to obtain the miniband structure in a 1D periodic
potential. The results show that minibands with verysmall separations (i.e., minigaps) form within the potential well. However, the widths of minigaps range from 2
up to 8 meV, which is much smaller than the thermal energy kT at 300 K (26 meV). Therefore these minibands
can be essentially considered as continuous states at room
temperature (in the classical limit). The Ge/Si nanoribbon
structure has to be cooled to below 77 K to minimize thethermal smearing sufficiently to make discrete minibands
observable.
We predict that it is possible to observe discrete minibands in the potential well of the 1D strain superlattice atroom temperature if one uses InAs nanostressors QDs,
which form on Si with strain as high as 11.5%. We calculate that the maximum tensile strain beneath a pure-InAs
pyramidal QD with a height of 6 nm and a base width of
11 nm pseudomorphically grown on a Si membrane is~2.7% for a 10 nm thick ribbon. The resulting depressionof the Si band gap is expected to be up to 350 meV, morethan 30% of the bulk value of the band gap for the thinnest ribbons. We predicted the formation of wellseparated minibands in the potential well already for a 25
nm thick membrane (potential well depth 200 meV), withminigaps ranging from 15 to 85 meV, and with only the
first minigap being smaller than the thermal energy of~26 meV at 300 K. It should therefore be possible to observe discrete minibands in the potential near room temperature.

As the third example, strain sharing between Ge
nanostressor islands (quantum dots, QDs) and a compliant SiNM can be used to create very small regions ofhigh local strain in the membrane. As a result the SiNM
undergoes distortion, forming into a slightly wavy sheet.
The local strain provides a feedback for self-organizationof the QDs. We have reported ordered growth ofnanostressors on freestanding ribbons with a 50 to 250
nm width, fabricated from SOI with a 5 to 50 nm-thick Si
templates. Ge or a Ge-rich SiGe alloy is deposited simultaneously on both sides of these free-standing nanoribbons using CVD. Because CVD involves the vapor phasetransport of precursor molecules, deposition is possible at
all locations accessible to the growth gases. The feedback
mechanism leads to a spatially periodic arrangement ofpyramid shaped QDs, alternating on the top and on thebottom surface of the SiNMs. Consequently a periodically varying strain is established along a thin singlecrystal Si ribbon. The strain lattice in the Si membrane inturn produces a modulation in the electronic band structure that extends through the thickness of the membrane,
and thus creates an electronic superlattice without a needfor compositional modulation, the conventional method
for forming electronic heterostructures.
We calculate the periodic change induced in the Siband gap by the strain field as a function of position
along the ribbon. For this purpose the local strain wasmodelled with a 2D finite-element analysis of the elastic
deformation and elastic energy resulting from two opposite-side QDs in one dimension corresponding to the ribbon geometry with one line of dots on each side. Our calculations predict that the maximum tensile strain beneatha Ge QD with a height of 8 nm and a base width of 80 nm,
epitaxially grown on a Si membrane, is ~1.5% for a 10
nm thick ribbon. The resulting reduction of the band gap
can be up to 250 meV, more than 20% of the bulk value* Electronic address: f.cavallo@wisc.edu
Research supported by USDOE, USAFOSR, andUSNSF/MRSEC

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Synthesis of Advanced Materials by Mechanical Alloying
1

C. Suryanarayana,1,* T. Klassen,2 and E. Ivanov3

Department of Mechanical, Materials and Aerospace Engineering, University of Central Florida, Orlando, FL. 32816-2450, USA,
andCurrently, Visiting Professor, Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
2
Institute of Materials Technology, Helmut-Schmidt-University, Holstenhofweg 85, D-22043 Hamburg, Germany
3
Tosoh SMD, Inc., 3600 Ganz Road, Grove City, OH. 43213-1895, USA
Mechanical alloying (MA) is a powder metallurgy processing technique that involves repeated cold
welding, fracturing and rewelding of powder particles in a high-energy ball mill. Started in 1960 toproduce oxide dispersion strengthened (ODS) nickel-based superalloys to obtain high strength both atroom and elevated temperatures, this technique is now widely used to synthesize a variety of nonequilibrium alloys including solid solutions, intermetallics, and glassy alloys. Apart from the ODS alloys,
the products of MA are now finding applications in newer and innovative areas. The present article briefly
summarizes the recent contributions of the author and his colleagues and collaborators in the field of MA
to synthesize commercially useful and advanced materials. Four specific topics have been covered –nanocomposites, Fe-based amorphous alloys, photovoltaic materials, and use of MA powder particles inmetal combustion. The article concludes with an indication of the topics that need special attention in thenear future.

I. INTRODUCTION

II. THE PROCESS OF MECHANICAL ALLOYING

Advanced materials are defined as those where firstconsideration is given to the systematic synthesis andcontrol of the crystal structure and microstructure ofmaterials to provide precisely tailored properties fordemanding applications.1 With the rapid advances taking
place in the technology sectors, there has been a great
demand for materials that are stronger, stiffer, lighter,useful at higher temperatures, and less expensive than theexisting and available materials. Thus, the high-techindustries have given fillip to efforts in developing novel
materials that will perform better for demanding
applications. Some of the advanced materials developed
during the last few decades include metallic glasses2,3(including the relatively recently developed bulk metallic
glasses4), quasicrystals,5,6 high-temperature superconductors, superhard carbo-nitrides, thin-film diamondsynthesis, and nanostructured materials.7-9 A number of
new techniques for processing and characterization ofmaterials have also been developed towards achieving
this goal. But, a common underlying principle inobtaining advanced materials has been to process thematerials under far-from-equilibrium conditions, i.e., thematerials developed are mostly in a metastable condition.
Turnbull10 has coined the phrase “energize and quench”
to describe these processes. It is through such processes
that the constitution and microstructure of the materials
can be drastically altered leading to achieving the desired
properties. Some of these “non-equilibrium processing”
techniques include rapid solidification from the melt,
mechanical alloying, laser processing, plasma processing,spray forming, physical and chemical vapor deposition
techniques, ion mixing, among others. The relativeadvantages and disadvantages of these techniques havebeen discussed in a recent publication.11 In the following
paragraphs, we will describe some of the advanced
materials that have been recently developed using thetechnique of mechanical alloying.

Mechanical Alloying (MA) is a process that wasdeveloped by John Benjamin of INCO International in
the late 1960’s to produce oxide dispersion-strengthenedmaterials.12 The process can be described as a highenergy milling process in which powder particles are
subjected to repeated cold welding, fracturing, andrewelding.13,14 The generally accepted explanation foralloying to occur from blended elemental powders andformation of different types of phases is that a very fineand intimate mixture (often lamellar if the constituent
elements are sufficiently ductile) of the components isformed after milling, if not the final product. The
crystalline defects introduced into the material (grainboundaries, interfaces, dislocations, stacking faults,
vacancies, and others), which act as fast diffusion paths,
and a slight rise in the powder temperature during millingas a result of frictional forces and impact of the grinding
balls against other balls and the surfaces of the container,
were found to facilitate alloy formation. If the final
desired phase had not formed directly by MA, then ashort annealing treatment at an elevated temperature wasfound to promote diffusion and consequently alloy
formation. Accordingly, it was shown that by a properchoice of the process parameters during MA andchoosing an appropriate alloy composition, it is possible
to produce solid solutions (both equilibrium andsupersaturated), intermediate phases (crystalline andquasicrystalline)
andamorphousalloys.
The
thermodynamic criterion that the phase with the lowest
free energy, under the continuous deformation conditions,would be the most stable phase has been found to bevalid. A significant attribute of MA has been the ability
to even alloy metals with positive heats of mixing that are
difficult to alloy otherwise.
The effects of MA could be categorized under twogroups:1
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1. Constitutional changes: Milling of the blended
elemental powders could lead to the formation of solid
solutions (both equilibrium and supersaturated),intermetallic phases (equilibrium, metastable andquasicrystalline), and amorphous phases in alloy systems.
The actual type of phase formed could be different
depending on the alloy system and the milling conditions
employed.
2. Microstructural changes: As a result of MA, theprocessed materials could develop ultrafine-grained andnanostructured phases. In addition, uniform dispersion ofa large volume fraction of very fine oxide or otherceramic particles can be achieved in different matrices;not possible or easy by other processes.
In many cases, chemical reactions have also beenfound to take place leading to the formation of novel
materials and microstructures. Such a process has beenreferred to as mechanochemical processing.15 All theseeffects have been well documented in the literature.13,14,16
As has been frequently pointed out in the literature, thetechnique of MA was developed out of an industrial
necessity in 1966 to produce nickel-based superalloys
that combined the room temperature strength obtained by
precipitation hardening with the high-temperaturestrength achieved through dispersion hardening.12,17 The
historical development of MA during the last 40 years or
so can be divided into three major periods. The first
period, covering from 1966 to 1985, was mostly
concerned with the development and production of oxide
dispersion strengthened (ODS) superalloys forapplications in the aerospace industry. Several alloys,
with improved properties, based on Ni and Fe weredeveloped that found useful applications. These included
the MA754, MA760, MA956, MA957, MA6000, andothers.18 The second period, covering from 1986 up to
about 2000, witnessed lot of advances in the fundamental
understanding of the processes that take place during MA.
Along with this, a large number of dedicated conferenceswere held and there was a burgeoning of publication
activity.16 Comparisons have also been frequently madebetween MA and other non-equilibrium processing
techniques, notably rapid solidification processing (RSP).
It was shown that the metastable effects achieved bythese two non-equilibrium processing techniques are
similar. Revival of the mechanochemical processing(MCP) took place and a variety of novel substances weresynthesized.
Several modeling studies were also
conducted to enable prediction of the phases produced or
microstructures obtained, although with limited success.
The third period, starting from about 2001 saw areemergence of the quest for new applications of the MA
materials, not only as structural materials, but also forchemical applications such as catalysis and hydrogenstorage, with the realization that contamination of themilled powders is the limiting factor in the widespread
applications of the MA materials. Innovative techniques
to consolidate the MA powders to full density while
retaining the metastable phases (including glassy phases
and/or nanostructures) in them were also developed. All

these are continuing with the ongoing investigations toenhance the scientific understanding of the MA process.
As mentioned earlier, in recent years, there has been aresurgence of search for novel applications of MA
products. Apart from this, investigations are also
continuing on developing newer and “better” materials
through MA and also to understand the science behindthe formation of these novel materials. In this paper, we
will summarize our recent activities in the general area of
MA in developing advanced materials. As typicalexamples, we would like to discuss four specific topics:(1)Development of homogeneously-dispersed nanocomposites,(2) Formation of metallic glasses,(3) Synthesis of photo-voltaic materials, and(4) Use of energetic metal particles in combustion.
All the experiments were carried out either in a SPEX
CertiPrep high-energy ball mill or a Fritsch P-5 planetaryball mill or an attritor under controlled conditions.
Loading and unloading of the powders was carried out ina glove box filled with argon gas. Normally a ball-topowder weight ratio of 10:1 was maintained.
Characterization of the milled powders was conducted
through X-ray diffraction, scanning electron microscopy,
and transmission electron microscopy techniques and theresults were analyzed using standard procedures.
III. NANOCOMPOSITES
Achievement of a uniform distribution of thereinforcement in a matrix is essential to achieving goodmechanical properties of the composites. Further, themechanical properties of the composite tend to improvewith increasing volume fraction and decreasing particle
size of the reinforcement.19 Traditionally, a reasonably
large volume fraction of the reinforcement could be
added, if the size of the reinforcement is large (on amicrometer scale). But, if the reinforcement size is veryfine (of nanometer dimensions), then the volume fraction
added is restricted to about 2 to 4 %. This is because thefine powders tend to float to the top of the melt during
processing of the composites through solidification
processing. However, if we are able to introduce a large
volume fraction of nanometer-sized reinforcement, themechanical properties of the composite are likely to be
vastly improved. In our investigations, during the last
few years, we have successfully achieved a very uniform
distribution of the reinforcement phases in different typesof matrices through the solid-state powder processing
technique of MA.20-28 These include homogeneous
dispersion of graphite in an Al-6061 alloy matrix,20 effectof clustering of the reinforcement on the mechanicalproperties of the composites,21 dispersion of a highvolume fraction of Al2O3 in Al,25 and of Ti5Si3 in TiAl,22,28 synthesis of MoSi2+Si3N4 composites for hightemperature applications,23,24,27 and synthesis ofamorphous+intermetallic composites in Al-Mg alloys.26
However, in this chapter, we will describe only two
typical examples.

2
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III. 1. Al-Al2O3 Composites

reinforcements, the volume fraction of the reinforcements
was very small, typically about 2-4% by volume,
indicated by region # 2 in Fig. 1. Thus, as shown by
region # 3 in Fig. 1, there is a gap in understanding thestructure and properties of high volume fraction
composites containing nanometer-sized reinforcements.
Therefore, we have conducted investigations tosynthesize and characterize Al-Al2O3 composites with the
Al2O3 reinforcement varying in size from 50 nm to 5 m,and the volume fraction from 5 to 50% by volume. The
reasons behind the choice of this combination of particle
sizes and volume fractions were to check (i) whether
there is a maximum volume fraction of Al2O3 beyond
which it will be difficult to achieve a uniform distribution
and also (ii) to see if there is a minimum particle size,
below which again it will be difficult to achieve a
uniform distribution of the two components in thecomposite.
Table I lists the powder sizes and volume fractions of
the Al2O3 reinforcements used in this study. Mechanicalalloying of the powder blends containing different
amounts and size fractions of Al2O3 was found to reach astable and uniform distribution of the reinforcement. A
milling time of 20 h was found to be sufficient in all the
combinations of the composites. Figure 2 shows that avery uniform dispersion of the fine 50-nm Al2O3 particles
was achieved even when the volume fraction of thereinforcement was 50%. This corresponds to the finest
particle size and largest volume fraction, the maximum
value achieved so far in any nanocomposite. Similar
uniform distributions were obtained in the larger size andsmaller volume fractions of the reinforcement also. The
uniform distribution of the reinforcement phase was also
confirmed through the X-ray elemental mapping
technique (Fig. 3). An interesting observation madeduring this study was that the stable -Al2O3 transformedto -Al2O3 on milling, when the Al2O3 powder particle
size was small, e.g., 50 and 150 nm.29 However, no suchtransformation occurred when the Al2O3 particle size waslarge, e.g., 5 m.
These composites with a large volume fraction of thereinforcement of the Al2O3 powders were very hard andstrong and consequently it was not easy to consolidatethem to full density by any of the single different
techniques that are presently available. Therefore, todetermine the effect of reinforcement particle size andAluminum-based metal matrix composites are ideal
materials for structural applications in the aircraft andautomotive industries due to their lightweight and highstrength-to-weight ratio. Reinforcement of the ductile
aluminum matrix with stronger and stiffer second-phasereinforcements like oxides, carbides, borides, and nitrides
provides a combination of properties of both the metallic
matrix and the ceramic reinforcement.
Uniform
dispersion of the fine reinforcements and a fine grain sizeof the matrix contribute to improving the mechanicalproperties of the composite.
Most of the work carried out to-date on
discontinuously reinforced aluminum was primarily
concerned with dispersing reinforcements on the
micrometer scale (a few to a couple of hundred
micrometers), as represented by region #1 in Fig. 1. Even
though studies were carried out on nanometer-sized

FIG. 1. Schematic representation of the relationshipbetween interparticle spacing, , particle size, d, and volume
fraction, fv, of the reinforcement phase. Note that at volume
fractions greater than 0.125,  becomes smaller than theparticle size. Regions #1, #2, and #3 correspond to
reinforcements with large particle size and large volume
fractions, small particle size and small volume fractions, andsmall particle size and large volume fractions, respectively.

TABLE I. Powder sizes and volume fractions of the Al2O3 reinforcements used in this study.

3
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FIG. 3. X-ray maps showing the uniform distribution Al(top) and O (bottom) for the Al-Al2O3 (50 nm) powders
milled for 20 h.

FIG. 4. SEM micrograph of Al-10 vol.% Al2O3 composite
powders milled and consolidated to close to 100% density by
a combination of vacuum hot pressing and hot isostaticpressing. (a) Al-5 vol.% Al2O3 (50 nm), (b) Al-10 vol.%Al2O3 (50 nm), (c) Al-5 vol.% Al2O3 (150 nm), and (d) Al10 vol.% Al2O3 (150 nm).

FIG. 2. SEM micrograph of Al-Al2O3 (50 nm) powders
milled to the steady-state condition (20 h) showing a uniform
distribution of Al2O3 in the Al matrix. (a) 20 vol.%, (b) 30
vol.%, and (c) 50 vol.% Al2O3.

iso-strain condition, while composites with the larger
reinforcement size (150 nm) behaved closer to the isostress condition.30,31 This observation clearly suggeststhat it is possible to tailor the modulus (and strength) of
the nanocomposite by choosing the appropriate
reinforcement size and volume fraction.
Such aprocessing methodology should be equally applicable toother systems, even though the details of processing andconsolidation would be different.

volume fraction, nanocomposites with 50 nm and 150 nm
particle sizes and 5 and 10 vol.% were consolidated tofull density. Even at these small volume fractions, full(close to 100%) density was achieved only by a
combination of vacuum hot pressing followed by hot
isostatic pressing (Fig. 4). Compression testing was doneon the fully dense samples, and the strength properties
and modulus values were determined. Table II lists themechanical properties of these composites. Figure 5
shows the variation of the modulus of elasticity as afunction of the Al2O3 content. From this figure, it may be
noted that the strength and modulus increased with (i)increasing volume fraction and (ii) decreasing size of thereinforcement. Comparison of these modulus values withthose calculated using the iso-strain and iso-stressconditions suggested that composites with the smaller
reinforcement particle size (50 nm) behaved closer to theIII. 2. -TiAl-Ti5Si3 Composites
Lightweight intermetallic alloys based on -TiAl arepromising materials for high-temperature structural
applications, e.g., in aircraft engines or stationary
turbines.32,33 Even though they have many desirable
properties such as high specific strength and modulus
both at room and elevated temperatures, and good
corrosion and oxidation resistance, they suffer from4
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TABLE II. Mechanical properties of Al-Al2O3 nanocomposites obtained by milling and subsequent consolidation by vacuum
hot pressing and hot isostatic pressing.

130

Iso-stressIso-strain
50 nm

120

Modulus (GPa)nanostructured materials may not be suitable forachieving the desired creep resistance.
The Ti-Al-Si alloy system was chosen because it is amodel system to study the influence of phase distribution
and microstructure on the high-temperature deformation
behavior of ceramic-intermetallic composites. Earlier
work has demonstrated that favorable deformation
behavior could be obtained in nanostructured/submicronsized TiAl-based intermetallics. Thus, it was decided tocheck whether the microstructure has a similar influenceon the mechanical behavior of ceramic-based ceramicintermetallic composites which could then lead to easy
deformability and eventually the possibility of achieving
superplasticity. It is possible that the creep properties ofthese composites will be poor at low temperatures, but,similar to that in TiAl-based alloys, it could be improved
through grain coarsening after deformation at elevatedtemperatures.
Composites of -TiAl and -Ti5Si3 phase, with thevolume fractions of the -Ti5Si3 phase varying from 0 to
60 vol.%, were produced by MA of the blended
elemental powders.
Fully dense and porosity-freecompacts were produced by hot isostatic pressing, withthe resulting grain size of each of the phases being about
400 nm. Figure 6 shows a scanning electron micrographof the -TiAl + 60 vol.% -Ti5Si3 composite showing thatthe two phases are very uniformly distributed throughout
the microstructure. Such a microstructure is expected tobe conducive to superplastic deformation behavior. To
test this hypothesis, both compression and tensile testingof these composite specimens were conducted at different
temperatures and strain rates. From the tensile stressstrain plots of the -TiAl + 60 vol.% -Ti5Si3 composite
specimen shown in Fig. 7(a), we can draw the following
conclusions.
Firstly, the strength decreased with increasing
temperature and decreasing strain rate, both expectedfrom normal mechanical behavior of metallic materials.
Secondly, the specimens tested at 950 oC and a strain rateof 4x10-5 s-1 and 1000 oC and a strain rate of 4x10-4 s-1
exhibited large ductilities of nearly 150 and 100%,
respectively. Considering that this composite is based ona ceramic material (Ti5Si3) this is a very high amount of

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0.1

0.15

0.2

0.25

Volume Fraction of Al2O3

FIG. 5. Variation of modulus of elasticity with volume
fraction of Al2O3 for two different particle sizes (50 and 150
nm). The solid lines were drawn on the basis of iso-stress or
iso-strain conditions using the rule of mixtures. Note that thevariation is close to the iso-strain condition for 50 nm-size
Al2O3 particles and close to the iso-stress condition for the
150 nm-size Al2O3 particles.

inadequate room temperature ductility and insufficient
creep resistance at elevated temperatures, especiallybetween 800 and 850 oC, an important requirement forelevated temperature applications of these materials.
Therefore, current research programs have beenaddressing the development of high-temperaturematerials with adequate room temperature ductility foreasy formability and ability to increase the hightemperature strength by a suitable heat treatment or
alloying additions to obtain sufficient creep resistance.
It has been shown that the compressive strength ofbinary -TiAl alloys with nanometer-sized grains is about2600 MPa at room temperature and that, at temperatureshigher than about 500 oC, the strength drops very rapidly
to low values.34,35 In fact, the strength was found to
decrease at a faster rate for ultrafine-grained materials
than for the coarse-grained counterparts. That is, thesmaller the grain size of the specimen, the stronger andsharper is the drop in yield strength on increasing thetemperature. This observation suggests that monolithic

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alloy. This should be compared with the coarse-grainedmaterial which shows the superplastic behavior only attemperatures about 300-400 oC higher than thetemperature observed in this investigation.36 Figure 7(b)shows photographs of the actual specimens before andafter tensile testing, showing significant amounts ofelongation in the samples.
IV. GLASS FORMATION IN Fe-BASED SYSTEMS
Metallic glasses have an interesting combination of
mechanical, physical, and chemical properties. They
have been produced in several alloy systems by manydifferent techniques. But, the most commonly usedtechnique has been rapid solidification processing(RSP).37-39 As is well known, the critical cooling rate forglass formation needs to be exceeded so that formation of
the crystalline nuclei could be avoided for the glass toform.
However, since this is an experimentally
determined value (and is time-consuming and alsodifficult to measure), several other empirical criteria havebeen proposed to explain glass formation in alloy systems.
Two most commonly used criteria have been (a) a highreduced glass transition temperature, T rg = Tg/Tl, where
Tg is the glass transition temperature and T l is theliquidus temperature of the alloy, and (b) presence ofdeep eutectics in the phase diagrams. The developmentof bulk metallic glasses in the late 1980’s [Ref. 40] has
attracted the attention of materials scientists all over theworld. Three criteria were proposed for the formation of
bulk metallic glasses, viz., (a) presence of at least threecomponents in the alloy system, (b) atomic radiusdifference of >12% between the elements, and (c)negative heat of mixing among the constituent elements.
A very large number of bulk metallic glasses were
produced using this set of criteria. But, since 2003 anumber of new criteria based on the thermal properties of
the alloys and physical characteristics of the component
atoms were developed. These include the so-called , ,. m, , , etc. parameters. But, it is important toremember that all these criteria have been developed formetallic glasses processed via the solidification route. As
mentioned earlier, mechanical alloying (MA), a
completely solid-state powder processing technique, isanother important technique to produce amorphous alloys.
Therefore, we wished to determine if these same criteria
would be applicable to the solid-state processed
amorphous alloys or other criteria need to be formulated
to predict glass formation in alloy systems processed by
MA. For this purpose, we had undertaken acomprehensive investigation on the glass formation
behavior and stability of several Fe-based glassy alloys
synthesized by MA.

FIG. 6. Scanning electron micrograph of the -TiAl + 60
vol.% Ti5Si3 composite specimen showing that the twophases are very uniformly distributed in the microstructure.
Such a microstructure is conducive to observing superplastic
deformation under appropriate conditions of testing.

(a)

(b)
FIG. 7. (a) Stress-strain curves of -TiAl + 60 vol.%Ti5Si3 composites showing that superplastic deformation
was achieved at 950 oC and a strain rate of 4x10-5 s-1 and1000 oC and a strain rate of 4x10-4 s-1. (b) Photographs of
the actual tensile specimens before and after tensile testing.

deformation, suggestive of superplastic deformation.
Final proof is provided by TEM investigations that
confirm the continued stability of the microstructure after
deformation.
Thirdly, even though the strain rate
employed is relatively low, it is interesting thatsuperplasticity was observed at 950 oC, corresponding toabout 0.5 Tm, where Tm is the melting temperature of theIV.1. Number of Intermetallics in the Phase Diagram
We have chosen the general alloy composition as
Fe42X28Zr10B20 with X = Al, Co, Ge, Mn, Ni, or Sn. The
subscripts represent the composition of the alloy in

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atomic percent. The element X was selected based on thenumber of intermetallics it forms with Zr underequilibrium conditions at room temperature.41 This
number increases from 1 with Mn to 8 with Al, which
provides a basis to analyze the results systematically.
Further, the negative heat of formation of theintermetallics with Zr is much higher than that with either
Thus, the probability of forming an
Fe or B.42
intermetallic with Zr during milling is higher than withFe or B. Blended elemental (BE) powders of thedifferent constituents were weighed out in the correct
proportion and milled in a high-energy SPEX mill fordifferent times.
The sequence of phase formation on milling thepowders was different depending on the alloy system.
An amorphous phase had formed only in some alloy
systems and not in all. The structural evolution in the
Fe42Al28Zr10B20 and Fe42Co28Zr10B20 alloy systems as afunction of milling time is shown in Figure 8. It may be
noted that while an amorphous phase had formed on
milling the Fe42Al28Zr10B20 powder blend for 20 h,
amorphization did not occur in the Fe42Co28Zr10B20
powder blend. The phase formation sequence in all thesix powder blends can be summarized into three groups
as follows:(1) BE powder → Intermetallics → Solid solution
Examples: Mn- and Sn-containing systems,(2) BE powder → Solid solution
Example: Co-containing system,(3) BE powder → Intermetallics → Amorphous phase→ (Mechanical) Crystallization
Examples: Al-, Ge-, and Ni-containing systems.
The time required for amorphization, which can beconsidered a measure of the glass-forming ability (GFA)of the alloy, is also different for different powder blends.
Table III summarizes the results obtained, including theequilibrium number of intermetallic phases present
between X and the constituent elements (Zr, Fe, or B) in
the powder bend.43 A close examination of Table III
clearly reveals that the ease of amorphization (i.e., GFA)
increased with the number of intermetallics present in theconstituent Zr-X binary phase diagrams. This is apparent
from the powder blends containing Al or Ni, which

amorphized in 10 and 20 h, respectively. While thequaternary Fe-Zr-Al-B contains eight intermetallic phasesin the binary system between Zr and Al, the Fe-Zr-Ni-B
system contains seven intermetallic phases in the binary
system between Zr and Ni. Similarly, the Ge-containing
system which also amorphized in 10 h, contains fiveintermetallic phases between Zr and Ge. The Zr-Co, ZrMn, and Zr-Sn systems which did not show

FIG.8. Structural evolution in the blended elemental
powder mix of (a) Fe42Al28Zr10B20 and (b) Fe42Co28Zr10B20 asa function of milling time. Note that the amorphous phase
had started to form on milling for about 10 h and was stable
up to about 40 h in the Fe42Al28Zr10B20 alloy system. An
amorphous phase did not form in the Fe42Co28Zr10B20alloy
system. Instead, a solid solution was the final phase to formin this alloy system.

TABLE III. Time required for glass formation in Fe42X28Zr10B20 alloys and the number of intermetallics in the respective binary
alloy systems.43

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amorphization on milling contain five, one, and threeintermetallic phases, respectively. However, when we
consider the total number of intermetallic phases, it can
be clearly seen that the systems which amorphized on
milling contain ≥ 10 intermetallic phases in all theconstituent binary phase diagrams. If the alloy system
contained <10 intermetallic phases, then amorphization
was not observed.
From an analysis of the phase diagrams of the alloy
systems, it appears that the presence of a large number ofintermetallic phases in the phase diagrams is conducive
to formation of the amorphous phase. Again from thebinary phase diagrams between these elements and Fe, it
is apparent that those alloy systems that formed theamorphous phase contained a number of intermetallic
phases, whereas those that did not form the amorphous
phase easily had phase diagrams which featured a solid
solution at room temperature. Thus, it is clear that thepresence of a large number of intermetallic phases in thesystem helps in promoting the glassy phase formation.
The presence of intermetallics in an alloy system easily
contributes to amorphization. This is due to two
important effects. Firstly, disordering of intermetallics
contributes an energy of about 15 kJ/mole of atoms to thesystem. For example, in strongly ordered intermetallics
such as NiAl and -TiAl that continue to be in theordered state till melting, the disordering energy has been
estimated to be about 17.5 kJ/mol. Secondly, a slightchange in the stoichiometry of the intermetallic increases
the free energy of the system drastically. Additionally,grain size reduction contributes about 5 kJ/mole. Since
MA reduces the grain size to nanometer levels and also
disorders the usually ordered intermetallics, the energy ofthe milled powders is significantly raised. In fact, it israised to a level above that of the hypothetical amorphous
phase. This condition leads to a situation where thepreferential formation of the amorphous phase is favored
over the crystalline phase.
On the other hand, it is noted that in alloy systems
which did not amorphize on milling, a solid solution
phase only had formed. Since the only way a solid
solution could contribute to an increase in the energy ofthe system is by grain size refinement, the total increasein the energy is not sufficiently high to amorphize thesystem. Thus, these observations provide a simple andvisual means of identifying alloy systems which are
likely to become amorphous on subjecting them tomilling. If the equilibrium phase diagrams show thepresence of a room temperature solid solution phase overa wide composition range, then amorphization is not easy.
On the other hand, if the phase diagram contains a large
number of intermetallic phases, then amorphization is apossibility.

amorphous phase led to crystallization, termedmechanical crystallization (Fig. 9).44,45 The main reason
for the mechanical crystallization to occur during
mechanical milling is that the relative stabilities of thedifferent phases change due to the incorporation of avariety of defects. For example, we can discuss therelative stabilities of the competing phases in the
Fe42Ni28Zr10C10B10 system with respect to the free energy
vs. composition diagram shown in Fig. 10.
The different phases that could exist in these alloys are
the blended elemental powder mixture, -Fe phase (thesolid solution of Fe containing the different alloying
elements), intermetallic phases and the amorphous phase.
For our discussion, we have grouped all the possible
intermetallics together and labeled them as“intermetallics” in the diagram.
In alloy systems with negative heat of mixing, theblended elemental powder mixture has obviously a highfree energy (point “1”). Therefore, on MA, the blended
powder mixture is expected to change into a more stableconfiguration to reduce its free energy. Thus, the -Fe″
solid solution phase (point “2”) containing all the solute
elements in Fe is seen to be forming on milling. Since
MA introduces many crystal defects including vacancies,
dislocations, grain boundaries, surfaces, and others, themilled powders will have excess energy. It was clearlyshown by us43 earlier that intermetallics form in the earlystages of milling in many of the Fe-based powder
mixtures. And disordering of such intermetallics can also
substantially increase the free energy of the system.
Hence, on continued milling, the free energy of thecrystalline phase increases to a level above that of the

FIG.
9.
X-ray
diffraction
patterns
ofthe
Fe42Ni28Zr10C10B10 powder blend milled for 8 and 30 h. Notethat the powder milled for 8 h shows the presence of anamorphous phase. On continued milling of this powder
containing the amorphous phase to 30 h, mechanicalcrystallization had occurred resulting in the formation ofseveral crystalline phases.

IV.2. Mechanical Crystallization
We have also noted other interesting observations
during MA of metallic powders. For example, it wasnoted that continued milling of the powder containing the8130

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because of their high conversion efficiency.48 It has beenshown that the band gap of CuInSe2 can be modified
continuously by substituting Ga for In; the band gap
increases with increasing Ga content. For achieving the
maximum efficiency of the cell, a Ga/(Ga+In) ratio of 0.3
and a slight deficiency in the copper content have beenfound to be beneficial.
The CuInSe2-based alloy films are usually obtained
either by multisource thermal evaporation and codeposition or reactive annealing of precursor films.
These processes are very involved, contain a number ofdeposition and annealing steps, pose difficulties inmaintaining the desired film composition, and can be
expensive. Therefore, we decided to perform band gap
engineering through the technique of MA. The two
simple steps involved will be synthesis of stoichiometricpowder of the CuIn0.7Ga0.3Se2 (CIGS) alloy by MA andobtain the bulk target by hot isostatic pressing of themilled powder. Milling of the blended elemental powder
was conducted in a Fritsch Pulverisette P5 mill using acopper container and copper grinding balls at two
different speeds and at two different ball-to-powderweight ratios (BPR).
Milling of the powders even for a short time resulted in
the formation of the desired CuIn0.7Ga0.3Se2 phase. For
example, by milling at a BPR of 20:1 and a speed of 300
rpm, the tetragonal CuIn0.7Ga0.3Se2 phase had formed.
But, small amounts of other phases were also present at
this stage. However, on continued milling of this powderfor 20 min, only the tetragonal CuIn0.7Ga0.3Se2 phase hadformed homogeneously (Fig. 11). This phase could beindexed on the basis of a tetragonal structure with thelattice parameters a = 0.5736 nm, c = 1.1448, and c/a =FIG. 10. Hypothetical free energy vs. composition
diagram to explain the mechanism of mechanicalcrystallization in the Fe42Ni28Zr10C10B10 system. Note thatpoint “1” represents the free energy of the blended elemental
powders. Similarly, point “2” represents formation of the αFe″ solid solution of all the alloying elements in Fe, point“3” formation of the homogeneous amorphous phase, point“4” a mixture of the amorphous phase with a different solutecontent (amorphous′) than at “3” and the solid solution Fe′, and point “5” is for the equilibrium situation when thesolid solution and intermetallics coexist.

amorphous phase which results in the destabilization of
the crystalline phase and the “amorphous” phase (point“3”) begins to be stabilized. But, further milling leads tomechanical crystallization resulting in the formation of asolid solution or intermetallics co-existing with theremaining
amorphous
phase.
Since
primary
crystallization had occurred, the Fe-solid solution will
now have a composition different from the original -Fe″
solid solution; let us call this -Fe′. This solid solution
will now coexist with the amorphous phase which also
has a different composition because of the precipitationof -Fe′ from the original amorphous phase (amorphous′).
Point “4” now represents the free energy of the mixtureof amorphous′ and -Fe′. The lowest free energy for thesystem will, however, correspond to a condition when amixture of the equilibrium solid solution (-Fe) and theintermetallics coexist. This situation is indicated by point“5” in the figure.
The influence of additional alloying elements withdifferent atomic sizes and heats of mixing were also
investigated with useful attributes for consolidating themilled powders to full density.46,47

1.9958 having the space group I 4 2d. Even though thequaternary Cu-In-Ga-Se tetragonal phase exists over a

FIG. 11. X-ray diffraction patterns of the CIGS blended
elemental powder mixture milled at a BPR of 20:1 and a
speed of 300 rpm for 5 and 20 min.. The powder milled for
5 min contained the tetragonal CuIn0.7Ga0.3Se2 phase andsmall amounts of elemental Cu and In. When the powder was
milled for 20 min, it contained only the tetragonal
CuIn0.7Ga0.3Se2 phase.

V. SYNTHESIS OF PHOTOVOLTAIC
MATERIALS
Copper indium diselenide (CuInSe2)-based photovoltaic thin film solar cells continue to receive attention

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wide composition range, the present XRD pattern could
be most satisfactorily indexed on the basis of thetetragonal phase with the stoichiometry CuIn0.7Ga0.3Se2 .
Scherrer analysis of the peak widths49 confirmed that the
crystallite size reached a saturation value of about 8 nm.
The phase identification and crystallite size determination
were confirmed by transmission electron microscopy(TEM) studies.50
The chemical analysis of the milled powder under
different milling conditions is shown in Table IV. From
the results it is clear that the composition of the milled
powder is reasonably close to the targeted composition.
But, because some copper has been picked up from thecontainer and/or the grinding balls during milling, thecopper content appears to be higher than what thestoichiometry requires. But, the powder milled at a BPR
of 10:1 and a speed of 150 rpm for 40 min did not pickup much copper.
Consequently, the chemicalcomposition of the powder milled under these conditions
is quite close to the starting powder mixture. By further
optimizing the powder processing conditions (BPR,
speed of rotation. and time of milling), it is possible tocontrol the composition of the final powder to the exact
desired value.
The milled powder containing the homogeneous
CuIn0.7Ga0.3Se2 phase was consolidated by hot isostaticpressing to full density at 750 oC and 100 MPa for 2 h.
Examination in a scanning electron microscope indicatedthat the compact was fully dense and did not contain any
porosity. Figure 12(a) shows the XRD pattern of the hot
isostatically pressed alloy suggesting that the
CuIn0.7Ga0.3Se2 phase is retained with the exact
stoichiometry and that the peaks are sharper than what
they were in the milled powder.51 This is mainly due tograin growth, as confirmed by TEM investigations, Fig.
12(b). The TEM micrograph shows that the grain size
now is about 50-60 nm.
This investigation clearly proves that it is possible toobtain the CIGS targets of the required stoichiometry
through a combination of MA and hot isostatic pressingor vacuum hot pressing. Further, it is possible to control
the stoichiometry by optimizing the MA processparameters.
Such an approach should be equallyapplicable to synthesize other target materials.

VI. COMBUSTION STUDIES OF METALPARTICLES
One of the potential applications for materials withfine grain sizes is in improving the combustion
characteristics of propellants.52 It is known that Mg canbe easily combusted, but it has a low heat content (14.9
MJ/kg). On the other hand, Al has a higher heat content(32.9 MJ/Kg), but is more difficult to combust. Therefore,
it was decided to see if Al and Mg can be alloyed
together to increase the net heat content and also be able
to combust relatively easily. Accordingly, a series of AlMg powder blends of different compositions weremechanically alloyed in a SPEX mill. Since the milled
powder normally contains a range of particle sizes, the

(a)

(b)
FIG. 12. (a) X-ray diffraction pattern and (b) transmission
electron micrograph of the CIGS powder mechanically milled
and consolidated to full density at 750 oC, 100 MPa and 2 h.
The XRD pattern shows that the CuIn0.7Ga0.3Se2 phase is fullyrecrystallized as revealed from the sharp peaks and the TEM
micrograph confirms this observation. The grain size of therecrystallized material is now about 50 nm.

TABLE IV. Chemical analysis (at.%) of the Cu-In-Ga-Se powder mechanically alloyed under different processing conditions. 50

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milled powder was sieved to well-defined particle sizes
in the ranges of 20-25 m, 45-53 m, and 90-106 m(Fig. 13). These powder particles were then burned in amethane-air premixed flame on a Meeker burner, at atemperature of approximately 1,800 K. Burning of thepowder particles was recorded using chopped images bylong-exposure digital photography. Knowing therotational speed of the chopper and the number of
exposures per revolution, the burning time, b and theignition time, ig could be determined. Figure 14 shows
the plot of variation of ig and b with particle size for two
different alloy compositions (Al-20 at.% Mg and Al-90
at.% Mg).53 It is clear from this plot that both theignition and burning times decrease with (a) a decrease inparticle size and (b) an increase in Mg content. Thus, by
a judicious choice of particle size and alloy composition,
it should be possible to control the ignition and burning
times.

cracks)-free and fully dense materials for obtaining
reproducible results. Further, large-scale applications
require materials that could be produced in tonnage
quantities, and materials that have been wellcharacterized and exhibit reproducible properties. But,
the bane of MA has been the three C′s – Cost,
Consolidation, and Contamination. Powder processing is
expensive and therefore, unless one is able to identify
niche markets for the MA products and the powders
produced in large volumes, cost is likely to continue to behigh. However, in some cases, e.g., hydrogen storage
materials or magnetic alloys, the high cost may be
acceptable in view of the improved properties andenhanced performance.
Consolidation of the milled powder continues to be aserious problem.
There have not been many
investigations to report successful consolidation of MA
powders to achieve full density and simultaneously retain
the metastable effects. Newer and improved methods ormodification/combination of the existing methods may benecessary.54,55
The last point is that contamination of the MA powder
has been a serious issue in many cases.13,14 Somesolutions have also been suggested to minimize/avoid
contamination completely. These include enclosing themills inside chambers that have been evacuated and/or
filled with an inert gas, or using high-purity gaseousatmosphere in which the powders could be milled. Bothoptions could be expensive and/or impractical.
The MA powders could also be used in the asproduced powder condition without consolidation.
Examples for such applications include use as catalysts,
pigments, solder, hydrogen storage materials, materials
for printed electronics, (CIGS powders are already in use
for printed solar cells, Nanosolar ), etc. In that case,some of the above problems mentioned above may not be
relevant. Further, even if a bulk component made of MA
powder needs to be used, then if that material could
tolerate high gaseous impurities, then also there is no
problem. With the intense research activity going on allover the world, there is great potential for MA products
and bright future for research in this area.

VII. CONCLUSIONS
From the above description of the type of activities, it
becomes amply clear that the technique of MA is very
efficient in synthesizing a variety of equilibrium and nonequilibrium advanced materials. Some of the present
issues that need immediate attention are that we needhomogeneous, pure, macro-defect (i.e., porosity and

FIG. 13. Scanning electron micrographs of the sieved AlMg alloy particles after milling. (a) 90-106 m, (b) 45-53
m, and (c) 20-25 m.

ACKNOWLEDGEMENTS
The work reported here is supported by the US
National Science Foundation under grants DMR-0314212
and DMR-0334544 and by the Office of Naval Research.
The authors also acknowledge fruitful collaboration anduseful discussions with Drs. Raj Vaidyanathan, Linan An,
and Ruey-Hung Chen of the University of Central Florida,
Orlando, USA, Professor Rüdiger Bormann of the
Hamburg-Harburg Technical University, Hamburg,
Germany, and Dr. S.J. Hong of Kongju National
University, Kongju, South Korea. C.S. is also thankful tothe experimental input from his graduate students –Pushkar Katiyar, Balaji Prabhu, Satyajeet Sharma, andUma Maheswara Rao Seelam, all from the University ofCentral Florida.

FIG.14. Ignition time, ig and burning time, b as a functionof particle size for two different alloy compositions (Al-20
at.% Mg and Al-90 at.% Mg).

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* Corresponding author. Contact information.
Tel: +407-823-6662; FAX: 407-823-0208; e-mail:csuryana@mail.ucf.edu or surya_orlando@hotmail.com
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T. Klassen, R. Bohn, C. Suryanarayana, G. Fanta, and
R. Bormann, in Processing and Properties ofStructural Nanomaterials, eds. L. Shaw, C.
Suryanarayana, and R.S. Mishra (TMS, Warrendale,PA, 2003), p. 93.
P. Mohan, C. Suryanarayana, and V. Desai, in
Nanomaterials: Synthesis, Characterisation, andApplication, eds. S. Bandyopadhyay et al. (Tata
McGraw-Hill Publ. Co. Ltd., New Delhi, India, 2004),
p. 171.
25 B. Prabhu, C. Suryanarayana, L. An, and R.
Vaidyanathan, Mater. Sci. Eng. A425, 192 (2006).

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52 E.L. Dreizin, Prog. Energy & Combust. Sci. 26, 57(2000).
53 R.H. Chen, C. Suryanarayana, M. Chaos, Adv. Eng.
Mater. 8, 563 (2006).
54 J.R. Groza, in Non-equilibrium Processing ofMaterials, ed. C. Suryanarayana, Pergamon, Oxford,
UK, 1999, pp. 347-372.
55 J.R. Groza, in Nanostructured Materials: Processing,
Properties, and Applications, ed. C.C. Koch, second
edition, William Andrew Publ. Co., New York, 2007,
pp. 173-233.

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Root of tunnel magnetoresistance and its development
Terunobu Miyazaki1, Shigemi Mizukami1, Daisuke Watanabe1, Feng Wu1, Mikihiko Oogane2, and Yasuo Ando2
1

WPI Advanced Institute for Materials Research Tohoku University, Katahira 2-1-1 Aoba-ku, Sendai, 980-8577 Japan2
Department of Applied Physics, Graduate School of Engineering, Tohoku University
Aoba-yama 6-6-05 Aoba-ku, Sendai, 980-8579 Japan
Nowadays usually we use the term, tunnel magnetoresistance, but it required a long time to combine
both words tunnel and magnetoresistance. The study of tunnel junction may originate from p-n junction
studied first around 1950. On the other hand, magnetoresistance effect was reported first in 1857 which
was about 100 years earlier than the start of tunnel junction study. The research of tunnel
magnetoresistance has been mainly developed first for Al-oxide tunnel barrier junctions and made aremarkable progress by the appearance of MgO barrier junctions for both basic research and applications.
Most recently, Heusler electrode tunnel junction exhibits a large TMR ratio up to about 750 %. We will
describe first the history of the study of tunnel junction and magnetoresistance effect. Then, we will focus
on the Heusler electrode junctions and also application of tunnel magnetoresistance junctions.

if the metal or the semiconductor is separated by a thininsulator or a potential barrier. Giaever et al.6) paid
attention to this respect, measured the energy gap of thecharacteristics of various
superconductor for thejunctions, and clarified the density of state ofsuperconductor. On the other hand, Tedrow et al.7, 8)
obtained the various ferromagnetic polarization including
Ni by replacing the other superconductor of the junction
by ferromagnetic material, and analyzing thecharacteristics. These data of spin polarization were fineand very useful in order to investigate a high TMR
junction. Julliere9) (1975) reported on the applied voltage
dependence of conductance of tunnel junction of which
both electrodes consist of ferromagnetic substance.
Moreover, they discussed the change of conductance withthe change of magnetization direction in both magnetic
layersusing
spinpolarization.
The
term“magnetoresistance” is not used, though this paper is thefirst one of the TMR effect. The term magnetoresistance
was not used though the researches using aferromagnetic/insulator/ferromagnetic/ junction by 1990
were often reported. One of double terms, “tunnel” wasoften used in the papers. An interesting respect is a point
to approach to the terms magnetoresistance. The term oftunneling resistance by Maekawa et al. 10) or magnetic
valve by Slonczewski11), was used in each of their papers.
The typical junctions mentioned above are shown in
Table 1, together with the fields of the research. By theway, tunneling junction with the vacuum instead of theinsulator was reported by Binnig et al.12) in 1982. It has
been practically used as STM (Scanning TunnelingMicroscope), which gives much contribution to theresearch on the physics of surface phenomena.

1. Introduction
The discovery of giant magnetorestance effect1,2)(GMR) of a metallic artificial lattice and tunnel
magnetoreistance effect (TMR) 3,4) in the ferromagnetic
tunnel junction became a trigger for the field called“spin-electronics” or “spintronics” in the past about 20
years, which has developed steadily. The point that thisresearch is excellent is that not only the object of a basic
research but also application. It has greatly contributed tothe development of industry, as the magnetoresistive
reading heads and nonvolatile random access memory(MRAM). First of all, the authors want to examine theroot of tunnel magnetoresistance here. Next, thedevelopment of the TMR effect using the Al2O3 barrier is
described. Using the MgO barrier instead of the Al2O3
barrier, the TMR ratio increased rapidly. Also the TMR
ratio increased, when the Heusler alloy is used for theelectrodes. Finally, the situations of spin-RAM
development and a few associated researchare being done
now are introduced.
2. Root of TMR effect(a) Root of tunnel effect
The term TMR consists of the two words of themagnetoresistance and the tunnel. Why does the physics
of the tunnel phenomenon become to be interested in? As
you know, the tunnel effect is a quantum-mechanicalphenomenon which is impossible on basis of classicalmechanics. G. Gamow explained the α particle (Henuclei) - decay on the basis of the tunnel effect in 1928. It
may be said that the term tunnel effect was used, for the
first time, by him. However, it was an electronic tunnel
phenomenon in solid that in around 1960 after about 30
years it was popularly known. Especially, the research of
the diode p-n junction was developed into the device by
Esaki.5) in 1958. Giaever et al.6), early in 1960’s, began
the research of the energy gap of the superconductor,
using the junction consisting of superconductor/
insulator/superconductor. The conduction electron canpass through the insulating layer by the tunnel effect even(b) Root of magnetoresistance effect
The first report of magnetoresistance effect in Ni andFe was published by Thomson13) in 1857. The term of theso-called magnetoresistance was not used at that timeeven though the paper was published on the effect of ananisotropic resistance. By the way, the title is “Effects ofmagnetization on the electric conductivity of Nickel andof Iron.” He was later elevated to Lord Kelvin by his

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Table 1. Historical details of research of junctions.

Table 2. History of research of magnetoresistance effect.

contribution to the fundamental science and engineering.
gradually after 1995 and the term TMR came to be used.
However, the one century is required for the contribution
The author's group used TMR, for the first time in theto engineering in work practically, since at that time it didlatter half of 1990’s. 27) The root in the effect of TMR
effect is summarized as shown in Fig.1. Moreover, thenot attract much practical attention. The term
author's group observed a large TMR ratio of about 18 %magnetoresistance was used in the paper of McKeehan14)
in 1930 though the first paper using magnetoresisetanceat room temperature for the first time with theis not made clear. An overview of anisotropic
corresponding hysteresis curve as shown in Fig. 2 .
magnetoresistance up to about 1975, was given by
Mcguire and Potter.15) Moreover, the review of the
3. Giant tunnel magnetoresistance effectapplied researches that came to be done extensively
around 1960-1970 was given by Thomson.16) The first
3.1 Tunnel junction with MgO barrier
attempt to construct the theory of anisotropic
magnetoresistance was made mainly in Europe in the
During early ten years of the start of TMR research,
1950-1970's. Especially, Smit17) took up this problem atthe effect of TMR with tunnel barrier layer of anearly time. Moreover, both the theory and the experiment
amorphous aluminum oxide (Al-oxide) was a main
have been researched by Fert and Campbell18-20) for acurrent of research. After 2004, however, much morelong time. These theoretical considerations21) were based
attention has been paid to the research of junction of
on the two current model by Mott. Research ofwhich barrier layer is the crystalline magnesium oxide
magnetoresistance is roughly summarized as shown in(MgO). When the electron tunnels through theTable 2. Apparently, the term
“tunnel magnetoresistance” was not
Table 3. Early research of tunnel magnetoresistance effect.
used in the 1980's. Later in 1990's
several reports of magnetoresistanceof the tunnel junction became to be
published besides GMR. It may besaid, from the other point of view,that the research intended for
application could link magnetoresistance with tunnel. The titlesof the papers of tunnel junction
quoted often until 1995 are shownin Table 3. The term tunnel
magnetoresistance (TMR) is not
used, though the two terms of tunnel(tunneling) and magnetoresistancewere used in the title. This kind ofresearch has been increasing

2
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exceeded the maximum of TMR ratio of
the tunnel junction with the Al-oxidebarrier layer at that time is of meaningfuluse, though it was relatively smaller than
the theoretical estimation. Afterwards,
Yuasa et al.(Fig. 3) and Parkin et al.
succeeded in the observation of as large as
200% TMR ratio at room temperature in
2004.31,32) In addition, the researchers at
AIST and Canon-Anelba jointly showedthat the huge TMR ratio can be achieved by
combining the amorphous ferromagnetic
material and the MgO barrier layer named
CoFeB by the sputtering method
appropriate for the productive process.33)
Afterwards, this technology continues
developing, and the TMR ratio up to 600%
Fig. 1. TMR research combined with tunnel and magnetoresistanceat room temperature is observed now. 34)
through GMR.
The MgO barrier tunnel junction is used
now for the read head of the latest hard disk.
amorphous Al-oxide barrier layer, scattering is received
The TMR ratio of typical MgO barrier tunnel junctions is
and information on the wavenumber vector is lostsummarized in Table 4. Moreover, the growth of the(incoherent tunnel). On the other hand, the electron can
TMR ratio at room temperature, using the MgO andtunnel coherently through the tunnel junctions on
Al2O3 barrier for years is plotted in Fig. 4.
epitaxially developed layer such as Fe (001)/MgO(001)/Fe (001) junction. Butler and Mathon29) showedthat it is possible to obtain a giant TMR ratio of as large
as over 1000% by the theoretical calculation for
Fe/MgO/Fe tunnel junction in 2001. In the tunnel
junction with the MgO barrier, Fe/MgO/Fe made by the
MBE method, Yuasa et al.30) observed as large as 88 %TMR ratio experimentally at room temperature. Having

Fig. 3. Magnetoresistance curve of Fe/MgO/Fe junction.
Table 4. TMR ratio of typical MgO barrier tunnel junction.

Fig. 2. (a) magnetoresistance curve of Fe/Al2O3/Fe junction
at RT. (b) the corresponding magnetization curve.

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energy gap, magnetic moment for each unit molecule(theoretical value), crystal structure, and the TMR ratioof the tunnel junction with these electrodes arecollectively shown for typical oxide system half metalreported up to now in Table 5. The band gap of the oxidesystem half metal is as large as 1eV, which isadvantageous for large TMR ratio in the high bias voltage.
On the other hand, the disadvantage is a point that theCurie temperatures of them are rather low. Each of theCurie temperatures of LSMO, LCMO, and CrO2 are levelwith room temperature, therefore it is difficult to observea large TMR ratio at room temperature. As understoodfrom Table 5, TMR ratios at room temperature of tunnel
junction using the oxide system half metal are as small as
10% in the reports of the past, in contrast to the huge
TMR ratios observed at low temperatures. Moreover,another feature of oxide system is for the effect of
inverse-TMR to be observed. In contrast to a usual effectof TMR, inverse-TMR effect has a feature that theparallel resistance is large, but the anti-parallel resistanceis small in respect of orientation of magnetization. It is,physically, a very interesting phenomenon though a huge
effect of inverse-TMR is not observed at present. The
authors explain, here, historical details of the Heusler
alloy that is a half metallic material : it was discovered by
F. Heusler first in 1903, which had been named
commemorating the discoverer.44) It is notable that thematerial exhibits strong ferromagnetism though an alloy
named Cu2MnAl is composed only of the nonmagnetic
metals. Afterwards, it has become attracting the attention
as a half metal material after 1983, though a basic
research on the evaluation of physical properties had
been studied for about 80 years. Groot et al.45) in 1983
carried out the band calculation of the Heusler alloy ofcomposition named NiMnSb and concluded that thismaterial has the half metal electronic state. In 1995
afterwards, the calculated result that the compounds suchas Co2MnSi and Co2MnGe could be the half metal was
reported by Ishida et al.46) It came to be paid attention
again in the Spintronics field, since the high Curie
temperature of the Heusler alloy is very advantageous forapplication. Physical quantities of typical Heusler alloys
such as the Curie temperature, the magnetic moment, andFig. 4. Development of TMR ratio of Ferro/Al2O3/Ferroand Ferro/MgO/Ferro junction (after S. Ikeda).

3.2

Tunnel junction with half metal electrodes

The attempt to improve the TMR ratio by using
ferromagnetic electrode material with the large spinpolarization has been made as an approach besides the
MgO barrier layer tunnel junction.
The so-called half metal is expected for an ideal
ferromagnetic material to improve the effect of TMR. It
is a material that completely polarizes spin on Fermi
surface (only either one type of electronic spin of the two
types of electrons i.e., electron with spin up, or electronwith spin down), of which spin polarization is ideally
100 % (Fig.5). The TMR ratio could be expected to
become infinity theoretically in the tunnel junction using
the half metal for the electrodes, based on the Julliere’s
model9). Half metal material is classified roughly into theoxide system and the metal system. First of all, therelated physical quantities such as Curie temperature,

Table 5. Magnetic properties and TMR ratio of oxide half
metal.

Fig. 5. Electronic state density of half metal material(schematic).

4
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the energy gap are summarized in Table 6. The Heusler
alloys are classified into a half Heusler alloy such as
NiMnSb and a full Heusler alloy such as Co2MnSi. Here,the full Heusler alloy with a large TMR ratio will be
simply described the Heusler alloy, and the authors
explain it a little more in detail. The Heusler alloy
basically has the X2YZ composition, and takes three units
lattice structures according to the rule of the atomicordered arrangement as shown in Fig. 6. The elementsthat enter each of sites are as follows,
X: Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Zn, Ag, Cd,
and Au/chiefly VIII, IB, IIB family
Y: Ti, V, Cr, Mn, Y, Zr, Nb, Hf, Ta, Gd, Tb, Dy, Ho,
Er, Tm, Yb/chiefly III, IV, V, VI, VII family
RE Z: Al, Si, Ga, Ge, As, In, Sn, Sb, Tl, Pb, andBi/chiefly, III B, IVB family.
L21 structure: the atoms are completely andregularly arranged.
B2 structure: the Y-Z atoms are irregularly arranged.
A2 structure: the X-Y-Z atoms are completely
irregularly arranged.
The property as half metal, an electric conduction
characteristic, and magnetic characteristic etc. of Heusler
alloy may be influenced according to the degree of thecalculated the irregularity
order. Miura et.al
dependence of spin polarization and magnetic moment in
the Co2CrAl Heusler alloy. As a result, an ideal state ofhalf metal is achieved in the state of a complete order
structure), but the spin polarization decreases(L
rapidly with an irregularity between Co-Cr (A2 structure).
Therefore, the evaluation of the structure factor isimportant for developing the Heusler alloy.
Theevaluation of the most popular atomic structure factors

can be deduced by the X-ray diffraction experiment.
Briefly, it can be estimated from measuring the strength
ratio of the basic lattice line to the super-lattice line.
The TMR ratios of tunnel junction that combine theHeusler alloy electrode with the amorphous Al-oxidebarrier layer are collectively shown in Tab 7. In apioneering research, the composition NiMnSb of theHeusler alloys was used for an electrode. But the TMR
ratio is as small as about 10% even at low temperature ,which is not enough to prove the characteristics of half
metal. Afterwards, in around 2003 the research using afull Heusler with the structures steadier than the half
Heusler ones was started and the tens % TMR ratio cameto be observed. 55, 57) The breakthrough in the tunnel
junction using Heusler alloy began with making theinterfaces of the epitaxially developed Heusler alloy
between insulators smoothly and cleanly. Sakuraba et al.
obtained the ratio of 159% at low temperature for theCo2MnSi/Al- oxide /CoFe tunnel junction with theCo2MnSi Heusler alloy epitaxially developed on MgO
single crystalline substrate.54) The spin polarization of
Co2MnSi estimated on the basis of Julliere’s model fromthis TMR ratio is as large as 89% (spin polarization of
CoFe is assumed to be 50% ). It was shown for the
first time that the spin polarization of Co2MnSi is veryhigh. Afterwards, 570% TMR ratio was observed injunctionofwhich
Co2MnSi/Al-oxide/Co2MnSi.
composition of both electrodes is Co2MnSi
Table 7. TMR ratio of typical Heusler alloy electrodes andAl-oxide barrier tunnel junctions.

Table 6. Magnetic properties of typical Heusler alloys.

Fig. 7. Temperature dependence of TMR ratio of Heusler
electrode with Al-oxide barrier tunnel junction.

Fig. 6. Crystal structure of Heusler alloy.

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However, the TMR ratio was as small as 100% or less atroom temperature in the junction using the Al-oxidebarrier layer. The analysis of the bias dependence ofconductance shows clearly the band gap of the Co 2MnSielectrodes, but the Fermi level in the gap is very close to
the bottom conduction band (fig.8).This is the reason forthe strong temperature dependence of TMR. Recently,
the development of the tunnel junction that combines the
Heusler alloy with the MgO barrier layer has rapidly
advanced. Table 8 shows typical results. The latticeadjustment of the Heusler alloy and MgO has anadvantage of full possible epitaxial growth up to theabove part of ferromagnetic electrode. In addition, thepossibility to generate a large TMR ratio wastheoretically shown by the synergy effect of the half
metal: the coherent tunneling phenomenon and theHeusler alloy separated by the MgO barrier layer.
Experimentally, a huge TMR ratio of 200% or more wasobtained, at room temperature for the tunnel junction that)High
combines the Heusler alloy with MgO.
expectations have been paid for the progress of a further
research and development in a near future. The growth of
TMR ratio of the tunnel junction with Heusler electrodevs. year is presented in Fig. 9.
4.

Table 8. TMR ratio of typical Heusler alloy electrodes andMgO barrier tunnel junctions.

Spin transfer torques

In the effect of the tunnel magnetoresistance (samewith the effect of GMR), the electric current can becontrolled by the direction of magnetization. In contrast,
the direction of magnetization may be altered, dependingon the current in a spin transfer torque. The current withpolarized spin is altered by a relative angle ofmagnetization for the effect of TMR. Thus the spinpolarized current is needed, to cause the spin transfer
torque.

Fig. 9. Development of TMR ratio of Heusler electrodetunnel junction (after M. Oogane).

For an intuitive image of this physics, it is only
thought that the magnetoresistance effect and spintransfer effect (torque) could analogously correspond to“law of action and reaction” of the Newton mechanics(Fig.10).
We will explain a little more detail ofspin transfer torque: when both ends offerromagnetic(F1)/nonmagnetic(N)/ferromagnetic (F2) junction could
be applied by voltage, current flows
from right to left, and electron, viceversa, as shown in Fig.11. Each of spin
angular momentum of electron inelectrodes is denoted as S1 and S2,
respectively. The (unpolarized) spin of
the conduction electron which enters in
the F1 layer from a left electrode can bechanged to spin-polarized ones parallel
to S . When this polarized spin s passthrough F2 layer, the momentum of scan be altered by interaction of s and S
and the difference of angular momentum
moved to S . As a result, S may receive
torque. The direction of the torquereceived by S is expressed in terms of
Fig. 8. Bias dependence of tunnel conductance of Co MnSi/Al-O/CoFe
S and the unit vector of spin s ofjunction.
conduction electron. It is noted that
depending on the direction of the current,

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cell in switching of themagnetization due to themagnetic field by theconventional wiring current
method. The achievement of
the large capacity MRAM
was considerably difficult
by the cell structure.
Fig. 10. Relation between TMR and spin transfer torque.
However, the reversal ofmagnetization was provento be possible by spintransfer torque as mentioned above, and the developmentof magnetic memory (especially, spin-RAM in distinction
from the conventional type) has come to be paid toattention. The spin memory can be 4 kbit (Sony) 68) in
2005, and 2 Mbit in 2007 (Hitachi-Tohoku University).69)
In addition, using the cell of perpendicular magnetization
to plane than in plane, an excellent spin-RAM technology
has been made in the research of the most recently by
Toshiba . The research for the target has been studied
intensely all over the world. The current trend from
MRAM to spin-RAM is schematically shown in Fig. 12.
Fig. 11. Explanation of spin transfer torque (schematic).
Then, why is the cell geometry of vertical magnetization
advantageous compared with the case in plane? The
Jc0 necessary to reverse thecritical current
this torque movement is attenuated and or the direction ofmagnetization according to the spin transfer torque isspin is made reversed. On the basis of calculation by
given by Slonczewski ,Slonczewski , the reversal spin condition is given by
 I
M VH
 g 
s eff
2 e, where each of the signs α, Ms, V,

J

and Heff is the damping constant that is a measure of the
gyromagnetic precession, the saturation magnetization,
the volume and the effective magnetic field in F2,
respectively. The symbol g is a spin transfer efficiency
coefficient that is a function of the spin polarization.
Each of  / 2 , I and e is the angular momentum, thecurrent and the unit charge of an electron. The research tocontrol the magnetization of the magnetic memory has
been extensively studied by using this physics. In thememory of high density (>Gbits) of which cell size is 100
nm or less, a large current is needed for a conventional
magnetic field reversing method. In contrast, even small
current makes the reversing possible by the flux reversal
technology using this spin transfer torque. This will be
described again by the next section.

c0



2e
dM H
s eff
g 

(1)

Here, d is the film thickness, on the other hand, themeaning of the other signs has been mentioned already inthe foregoing section. The value of 0.5 MA/cm2 is
expected as Jco practicably, though details are skipped
here. On the other hand, the direction of magnetization incell tends to turn around easily by thermal energy kB
with decreasing the size of cell (the signal disappears).
The product of magnetic anisotropy constant and thevolume of magnetic substance should be large to prevent
this loss of signal. The ratio of both of them Δ is given by

5. Development of MRAM using spintransfer torque

K V
u
k T
B

(2)

Magnetic memory MRAM (Magnetoresistive
RandomAccessMemory)development has been increased every year,
i.e., 1 kbit in 2000 (IBM), and 2 Mbit in2004 (Motolola) and 16 Mbit in 2006
(Toshiba-NEC).
However,
power
consumption is as large as about 4 mA per
Fig. 12. Change of TMR cell in research of magnetic memory.

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A necessary condition is Δ>60 for commercial product.
After all, the current density and the heat stability shownby eqs.1 and 2 will mean which to be satisfied easily witha cell of the magnetization in a plane or out of plane. The
effective magnetic fields Heff in eq.(1) are denotedas H k //  2M s and Hk   4M s , respectively,

hysteresis loop of the new perpendicular anisotropy
material Mn2.5Ga which they are studying now (fig.1471)
To be interesting, it has a large perpendicular anisotropyof the order of 107 erg/cm3, even though Ms is as small as1) that J co is
300 emu/cm . Taking account toproportional to α, correspondingly, the study to lower
the damping constant α is also an important subject.
Figure 15 shows thedependence of α. Certainly, αtends to be increased with a decrease of

depending on the magnetization in the plane or out ofplane. Ku in eq.2 is given by Ku=HkMs/2. For various Ms,
both of Jco and Δ may be calculated by eqs. 1 and 2, asshown in Fig. 13. Here, it is assumed that in any case ofin-plane or out of plane, the magnitudes of the quantities
 、 g and d are the same, and 0.01 0.5, and 2 nm,
respectively. The fine lines in the figure are the case of
the magnetization in the plane, while the solid line is theone out of plane. Moreover, Jc0 and Δ are plotted for a
few anisotropic magnetic fields. The out of planemagnetization shown by the solid line can be understoodto take the margin overwhelmingly to satisfy theconditions of both Jco<0.5MA/cm2 and Δ>60 in the rangeof M s between 100 and 400 emu/cm . Therefore, thedevelopment of the thin film material with 400 emu/cm
or less and perpendicular magnetic anisotropy will be
important. For an example, the authors exhibit the

6. Spin transfer resonance and spin torque diodeeffect
The magnetic field exerts a torque on magnetization,
which gives rise to the magnetic moment to precess. The
authors explained that the change in electronic angularmomentum of S was given by the spin polarized electronin Fig.11of the foregoing section. It should be noted that

Fig. 14. Magnetization curve of Mn Ga single crystalline
thin film.

Fig. 13. Critical current density( ) due to spin injection
magnetization reversal and thermal stability (Δ=KuV/k T)
as a function of saturation magnetization of junction
electrode. Solid curves in figure indicate perpendicularmagnetization film, while broken curves magnetization inplane film. Parameters in eq. (1) are, α=0.01, g=0.5, d=2
nm, and junction area φ=100 nm.

Fig. 15. Relation between damping constant α andsaturation magnetization.

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each of an angular momentum or a magnetic moment is
the opposite direction. Fig.16 shows the schematic of theprecession movement when spin (magnetic moment) in
the F2 layer is put on the magnetic field z axially. In thisis a magnetic moment corresponding to .
figure,Moreover, ( ) is the direction shown in figure. Usinga relation led from Newton's law, time derivative ofangular momentum is the torque operating to magnetic
moment, the angular velocity of the precession isexternal magnetic field. This behavior is remarkably
different from that of a conventional semiconductor diode.
As an intuitive understanding why the direct current
voltage is caused, it only has to be thought that theresistance of the element may change by themagnetoresistance effect with the same phase of
frequency of an applied current, since the voltage is a
product of the current and resistance. Refer to details
described in topics 74) and commentary 75) of theMagnetics Japan.

m eL    H  H ,   0 g , where  0 is permeability
2me S2 
of free space, g is g -factor (2 in spin). Underassumption that H = 106 A/m, we have11
L =2.2×10 /sec,or about 35 GHz for frequency f . In

The contents described in secs. 4 and 5 are well-known
among researchers of spintronics field with keen interest
recently. There are many researches such as a basic
research on the magnetic domain wall movement using
spin transfer torques and the application research such as
race-track memory etc. In addition, a similar research on
spintronics of magnetic semiconductor instead of metals
is being advanced. Furthermore for an interesting
phenomenon in spintronics, the coherence length of spin
(several ten Å) , amount of the spin polarization ofmaterial and etc. are important physical quantities. It isnecessary to process the material by the accuracy of thislevel or more to catch the phenomenon adequately if wewould pay attention to the physical quantity of the former.
It came to be able to make an artificial material comparedwith the past, especially the control of the film thickness
by remarkable accuracy with the formation of spintronics.
However, the authors think that there are not a few
studies that should be still done for microfabrication
processing of the magnetic substance.
Are the thin film making technology and themicrofabrication technology that raise the level byanother step indispensable for an ultimate spin control?
Moreover, such a technology might be requested
corresponding to each interesting material. New
development may be opened by its progress.

the figure, ① shows the torque exerted on a magnetic
moment while ② the damping of precession. In
ferromagnetic resonance (FMR), the external highfrequency h  h0 sin L t magnetic field is exerted
vertically on spin, which make the precession to becontinued. The resonance condition depends on both of fand H. In general, f is fixed at constant, and H is swept
for the resonance condition, which is unusually in case of
opposite. Kieselev.et al 72) succeeded the first time in a
spectrum measurement of the high frequency output of
Co/Cu/Co junction. Spin-transfer torque shown in ④ of
figure takes place in this case, and the precession of spin
is continued. On the other hand, the adjustment of both of
the spin polarization current from F1 to F2 and theexternal magnetic field is necessary to look for the
resonance condition in spin-transfer oscillation (STO).
The application of a small radio-frequency alternating
current to a magnetic tunnel junction can give rise to a
direct-current (d.c.) voltage across the device when thefrequency is resonant with the spin oscillations that arise
from the spin-torque effect, which can be tuned by an

Acknowledgements
A part of this work was supported by the IT Programof the Research Revolution 2002(RR2002) by a Grant-in
Aid for Scientific Research from Ministry of Education,
Culture, Sports, Science and Technology of Japan and by
Strategic Information and Communications R&D
Promotion Programme (SCOPE) by Ministry of Internal
Affairs and Communications and NEDO Spintronics
nonvolatile devices project.
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Fig. 16. Spin precession due to external high fieldmagnetic field or spin-transfer torque (Schematic).

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New Research Organization
We modified our research organization as of April 1, 2010 as follows:
Thrust 1: Bulk Metallic Glasses
Advanced Functional Materials Laboratory
Chen group, Louzguine group, Greer group, Yavari group, Hemker group
Theory Laboratory
Tokuyama group
Thrust 2: Materials Physics
Advanced Spectroscopy for Materials Physics Laboratory
Yamada group, Takahashi group, Xue group
Interface PhysChem Laboratory
Kawasaki group, Ikuhara group, Lagally group, Weiss group, Teizer group,
Hitosugi group
Electronic Materials Laboratory
Tanigaki group
Theory Laboratory
Tsukada group, Shluger group
Thrust 3: Soft Materials
Interface PhysChem Laboratory
Itaya group, Kurihara group, Wan group
Organosoft and Hybrid Materials Laboratory
Yamamoto group, Yamaguchi group, Nishi group, Adschiri group, Russell group
Thrust 4: Device/System Construction
Spintronics Materials Laboratory
Miyazaki group
Electronic Materials Laboratory
Ohmi group
MEMS Materials Laboratory
Esashi group, Gessner group
Bio Device Laboratory
Shimomura group, Khademhosseini group, Wu group149

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Newly Appointed Research Staff

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Curriculum Vitae

Hiromitsu TAKABA

Associate Professor
TEL: +81-22-795-7236
E-mail: takaba@aki.che.tohoku.ac.jp
URL: http://www.aki.che.tohoku.ac.jp/index.html

ACADEMIC:
1993 B.S. in Engineering, Tohoku University, Japan
1995 M.S. in Engineering, Tohoku University, Japan
1998 Dr. in Engineering, Tohoku University, Japan

Photo
40mm×30mm

PROFESSIONAL EXPERIENCE:
1996-1998 JSPS Fellow (DC), Department of Chemical Engineering, Tohoku University
1998-2006 Research Associate, Department of Chemical System Engineering, The University of Tokyo(2001-2002 Postdoctoral Fellow, Colorado School of Mines, USA)2006-2008 Associate Professor, Department of Applied Chemistry, Tohoku University
2008-present Associate Professor, Department of Chemical Engineering, Tohoku University
2010-present Associate Professor, WPI Advance Institute for Materials Research, Tohoku University
CURRENT RESEARCH:
Development of an experiment integrated multi-scale modeling technique and its application topractical systems, e.g. fuel cell, water purification, lithium ion battery, and automobile catalyst

Sungdae JI

Assistant Professor
TEL: +81-22-215-2039
E-mail: jsungdae@imr.tohoku.ac.jp

ACADEMIC:
1999 B.S. in Physics, POSTECH, Republic of Korea
2001 M.S. in Physics, POSTECH, Republic of Korea
2007 Ph.D. in Physics, POSTECH, Republic of Korea
PROFESSIONAL EXPERIENCE:
2007
BK21 Post-Doc, Physics, POSTECH, Republic of Korea
2007-2009
Guest Researcher, NIST/University of Virginia, USA
2009-2010
Research Associate, University of Virginia, USA
2010-2010
Guest Researcher, ORNL/University of Virginia, USA
2010-Present Assistant Professor, WPI Advance Institute for Materials Research, Tohoku University
CURRENT RESEARCH:
 Investigation of frustrated magnetism in spinels, kagome and triangular systems including lowdimensional magnetism
 Magneto-elastic coupling in multiferroic materials
 Unconventional superconductivity

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Curriculum Vitae

Jianli KANG

Research Associate
E-mail: kangjianli@wpi-aimr.tohoku.ac.jp

ACADEMIC:
2004 B.S. in Materials Science, Zhengzhou University, China
2006 M.S. in Materials Science, Tianjin University, China
2009 Dr. Eng. in Materials Science, Tianjin University, China.
PROFESSIONAL EXPERIENCE:
2007-2009
Joint Ph. D, Thermal Processing Technology Center, Illinois Institute of Technology,USA
2009-2010
Assistant Professor, School of Mechanical and Electronic Engineering, Tianjin
Polytechnic University, China
2010-present Research Associate, WPI Advance Institute for Materials Research, Tohoku University
CURRENT RESEARCH:
The application of atom probe upon nanostructured materials prepared by electrodeposition andnanocrystallization of metallic glasses

Lei LI

Research Associate
TEL: +81-22-217-6142
E-mail: lilei@wpi-aimr.tohoku.ac.jp
URL: http://www.wpi-aimr.tohoku.ac.jp/

ACADEMIC:
2003 B.S. in Thermal Engineer, Tsinghua University, China
2009 Dr. in Biomedical Engineer, Tsinghua University, China
PROFESSIONAL EXPERIENCE:
2009-present Research Associate, Institute of Semiconductors, Chinese Academy of Sciences
2010-present Research Associate, WPI Advance Institute for Materials Research, Tohoku University
CURRENT RESEARCH:
We use the technologies in MEMS, microfluidics, soft lithography, and surface chemistry to design andprovide new tools for the applications in biological sciences and clinical medicine.

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Curriculum Vitae

Serge OSTROVIDOV
Research Associate
E-mail: ostrovidov@wpi-aimr.tohoku.ac.jp
URL: http://www.wpi-aimr.tohoku.ac.jp/
Specialist in microfluidic and bioMEMS

ACADEMIC:
1997 Doctorate in biology and health Medical school Nancy France
PROFESSIONAL EXPERIENCE:
2003-2005 Post-Doctoral fellow in bioMEMS, the University of Tokyo
2005-2008 Researcher, Pentax Corporation
2008-2009 Researcher Hoya Corporation-Pentax Division
2009-2010 Post-Doctoral fellow in bioMEMS, the University of Tokyo
2010 –currently Research Associate, WPI-Advance Institute for Materials Research, Tohoku University

CURRENT RESEARCH:
Development of bioMEMS for tissue engineering and regenerative medicine

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Newly Appointed
Adjunct Professors

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Curriculum Vitae of Adjunct Professor

Jörg F. Löffler
PRIMARY AFFILIATION:ETH Zurich
Laboratory of Metal Physics and Technology (LMPT)
Department of Materials
Wolfgang-Pauli-Str. 108093 Zurich, Switzerland
Tel: +41 (044) 632 2565
Fax: +41 (044) 633 1421
E-mail: joerg.loeffler@mat.ethz.ch
ACADEMIC:
1994
1997

Diploma in Physics, University of Saarbrucken, Germany
Ph.D. in Physics, ETH Zurich, Switzerland

PROFESSIONAL EXPERIENCE:
1997-1998
Postdoctoral Researcher, Paul Scherrer Institute, Switzerland
1998-2001
Research Fellow (Alexander von Humboldt Foundation), Department of Materials Science,
California Institute of Technology, Pasadena, USA
2001
Senior Research Fellow, California Institute of Technology, Pasadena, USA
2001-2003
Assistant Professor (Tenure-track), Department of Materials Science, University ofCalifornia, Davis, USA
2003-2007
Assistant Professor (Tenure-track), Department of Materials, ETH Zurich, Switzerland
2007-present
Full Professor and Chair of Metal Physics and Technology, Department of Materials, ETH
Zurich, Switzerland
2010-present
Head of Department of Materials, ETH Zurich, Switzerland✦ Various Awards at International Conferences (1996, 1998, 2000)✦ Fellowship of the German National Merit Foundation (1991-1997)✦ ETH Medal and Award for Outstanding Ph.D. Thesis, ETH Zurich, Switzerland (1998)✦ Alexander von Humboldt Fellow (Feodor-Lynen Program), Germany (1998-2001)✦ Visiting Faculty Position, California Institute of Technology, Pasadena, USA (2001)✦ Masing Memorial Prize of the German Society for Materials (2005)

CURRENT RESEARCH:- Bulk Metallic Glasses- Metals for Medical Applications- Magnetism on Mesoscopic Length Scales- Nano-Optics- Microstructure Analysis and Modeling

159

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Curriculum Vitae of Adjunct Professor

Taigang Nieh
PRIMARY AFFILIATION:
Professor
Department of Materials Science & Engineering
422 Dougherty Engineering Building
Knoxville, TN 37996-2200
USA
Tel: +1-865-974-5328
Fax: +1-865-974-4115
E-mail: tnieh@utk.edu

ACADEMIC:
B.S., Physics, National Cheng–Kung University, Taiwan, 1973
M.S., Physics, University of Washington, Seattle, Washington, 1976
Ph.D., Materials Science and Engineering, Stanford University, 1980

PROFESSIONAL EXPERIENCE:
1980-1980

Postdoctoral Fellow, Stanford University

1980-1992

Group Leader, Lockheed Missiles and Space Co., Inc. (now Lockheed-Martin)

1992-2004

Senior Fellow, Lawrence Livermore National Laboratory

2004-present

Professor, University of Tennessee✦Fellow, ASM International, 1992
✦ISI Highly-cited Materials Scientist 2003
✦Fellow, The Minerals, Metals & Materials Society (TMS), 2004

CURRENT RESEARCH:
Bulk metallic glasses, nanocrystalline materials, high temperature alloys, superplasticity and superplastic
forming, lightweight aluminum and magnesium alloys, metal-matrix composites, intermetallics, refractory
metals, bioceramics, and multilayers.

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Curriculum Vitae of Adjunct Associate Professor

Yuzuru TAKAMURA
PRIMARY AFFILIATION:
Associate Professor
School of Materials Science
Japan Advanced Institute of Science and Technology (JAIST)
1-1 Asahidai, Nomi-shi, Ishikawa 923-1292, Japan
Tel: +81-761-51-1661
Fax: +81-761-51-1665
E-mail: takamura@jaist.ac.jp
ACADEMIC:
1990

B.S. in Metallurgy and Materials Science, The University of Tokyo, Japan

1992

M.S. in Metallurgy and Materials Science, The University of Tokyo, Japan1995

Ph.D. in Metallurgy, The University of Tokyo, Japan

PROFESSIONAL EXPERIENCE:
1995-1996
Japan Society for the Promotion of Science Research Fellow, The University of Tokyo
1996-1999
Research Associate, The Institute of Space and Astronautical Science
1999-2003
Research Associate, Department of Materials Engineering, The University of Tokyo
2003-pressent Associate Professor, Department of Materials Science,
Japan Advanced Institute of Science and Technology (JAIST)
2003-2007
PRESTO Researcher of Japan Science and Technology Agency
RECOGNITION:✦ Best Paper Award, International Conference on Solid State Devices and Material (2002)✦ Small and Medium Enterprise Excellent New Technology New Product Award,
Resona Foundation and The Nikkan Kogyo Shinbun (2009)✦ Incentive Award, Society for Chemistry and Micro-Nano Systems (2009)

CURRENT RESEARCH:
Creation of highly integrated functional biochip employing nanofabrication techniqueStudy on high sensitive biosensors using carbon nano tube and nano particles
Development of micro elemental analyzer using liquid electrode plasma in micro channel

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Curriculum Vitae of Adjunct Associate Professor

Mitsuo UMETSUPRIMARY AFFILIATION:
Associate Professor
Tohoku University
6-6-11 Aoba, Aramaki, Aoba-ku, Sendai, 980-8579, Japan
Tel&Fax: +81-22-795-7276
E-mail: mitsuo@kuma.che.tohoku.ac.jp
ACADEMIC:
1995 B.S. in Engineering, Tohoku University
1997 M.S. in Engineering, Tohoku University
2000 Dr. of Engineering, Tohoku University

PROFESSIONAL EXPERIENCE:
2000-2001
JSPS Postdoctoral Fellow for Research Abroad (Leiden University, The Netherlands)
2001-2002
Research associate, Department of Biomolecular Engineering, Tohoku University
2002-2006
Research associate, Institute of Multidisciplinary Research for Advanced Materials,
Tohoku University
2006-present
Associate professor, Department of Biomolecular Engineering, Tohoku University
2008-present
Researcher, Precursory Research for Embryonic Science and Technology (PRESTO),
Japan Science and Technology Corporation (JST)2008-present
Senior Researcher, Bio Electromechanical Autonomous Nano Systems (BEANS)
Laboratory✦ Incentive Award, Aoba Foundation for the Promotion of Engineering (2003)✦YABEC Award, Young Asian Biochemical Engineers’ Community (2004)✦ Incentive Award, Intelligent Cosmos Foundation (2005)✦ Incentive Award (Naito-Masayoshi Prize), Society of Chemical Engineers, Japan (2005)✦ Best Talk Award, Division of Biofunctional Chemistry, The Chemical Society of Japan (2006)✦ Best Poster Award, 2008 MRS Spring Meeting (2008)

CURRENT RESEARCH:✦ Protein engineering design for generating organic-inorganic-biomolecule hybrid nanodevices

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Announcement

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Junior Faculty/Post-doctoral Positions
Tohoku University
WPI-AIMR
Effective October 1, 2007, Tohoku University created a new Research Institute, theAdvanced Institute for Materials Research (AIMR), based on an initiative of theJapanese Department of Education (MEXT) for World Premier International ResearchCenter Initiative (WPI) to bring together scientists involved in research on nano-scienceand technology.
In the 21st century, material science, broadly defined as the study of how complex/novel
properties arise in matters/materials from the interactions of individual components, willcomprise of inter-discipline collaboration.
(http://www.wpi-aimr.tohoku.ac.jp)
Over the next few years, as many as one hundred new appointments at the levels of
post-doctoral fellows and junior faculty will be available. All innovative researchers
are welcome as active promoters of basic/applied sciences in the fields of physicalmetallurgy, physics, chemistry, precision mechanical engineering and electronic /informational engineering.
We are continuously looking for excellent applicants throughout the year.
Please submit
1) a curriculum vitae,
2) research proposal (<3,000 words),
3) summary of previous research accomplishments (<2,000 words),
4) copies of 5 significant publications, and
5) 2 letters of recommendationby email to:
wpi-office@bureau.tohoku.ac.jp
All files must be submitted electronically in pdf or Word format.
Applications from, or nominations of, women and minority candidates are encouraged.
Tohoku University WPI-AIMR is an affirmative action / equal opportunity employer.

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Graduate Student Scholarshipin Materials Science/Engineering
WPI-AIMR
Graduate Student Scholarship
Effective October 1, 2007, Tohoku University created a new Research Institute, theAdvanced Institute for Materials Research (AIMR), based on an initiative of theJapanese Department of Education (MEXT) for World Premier International ResearchCenter Initiative (WPI) to bring together scientists involved in research on nano-scienceand technology.
In the 21st century, material science, broadly defined as the study of how complex/novel
properties arise in matters/materials from the interactions of individual components, will
becomes an essential and most important research topics(http://www.wpi-aimr.tohoku.ac.jp)
TU WPI-AIMR is now looking for young motivated Ph.D. graduate student candidates
in the fields of physical metallurgy, physics, chemistry, mechanical engineering andelectronic / informational technology. All innovative M. S. students are welcome asactive promoters of basic/applied sciences in these fields.
Applications are continuously screened throughout the year.
Please submit
1) a curriculum vitae,
2) research proposal (<1,000 words),
3) 2 letters of recommendation,4) by email to:
wpi-office@bureau.tohoku.ac.jp
All files must be submitted electronically in pdf or Word format.

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Workshop Guideline
Tohoku University’s new Research Institute, the Advanced Institute for Materials
Research (WPI-AIMR) solicits several applications per year for International
Workshops in the field of “broadly defined Materials Science.”
Guidelines:
1) Organizers
Qualified research staff of academic institutions and public or private researchestablishments can submit the application for an international workshop to be held at
WPI-AIMR or its Satellite branches, jointly with the WPI-AIMR principal
investigator(s) whose research interest overlaps with the scope of the workshop.
2) Financial support
Under normal circumstances, WPI-IMR supports up to 2/3 of the workshop budget,
while the organizer is expected to cover the rest.
3) deadline
The application must be received at least four months in advance to:
wpi-office@bureau.tohoku.ac.jp
All files must be submitted electronically in pdf or Word format.

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Appendix

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DIRECTORY
As of September 1, 2010
Name

Phone Number

E-mail Address(+81-(0)22- _____)<Administration>
1. YAMAMOTO, Yoshinori (Institute Director)

217-5130

yoshi@m.tohoku.ac.jp

2. IWAMOTO, Wataru (Administrative Director)

217-5965

iwamoto@wpi-aimr.tohoku.ac.jp

3. ADSCHIRI, Tadafumi (PI, Prof.)

217-5629

ajiri@tagen.tohoku.ac.jp

4. HOJO, Daisuke (Assist. Prof.)

217-5631

dhojo@tagen.tohoku.ac.jp

5. HARTON, Shane (Research Assoc.)

217-5630

shane.harton@wpi-aimr.tohoku.ac.jp

6. ATASHFARAZ, Mehrnoosh (Researcher)217-5630

mehr@mail.tagen.tohoku.ac.jp

7. LU, Jinfeng (Researcher)217-5630

lujf@mail.tagen.tohoku.ac.jp

8. MANABE, Noriyoshi (Researcher)217-5631

manabe@niche.tohoku.ac.jp

9. TOGASHI, Takanari (Researcher)217-5630

togashi@tagen.tohoku.ac.jp

10. WATANABE, Eiichi (Researcher)217-5630

eiwata@mail.tagen.tohoku.ac.jp

11. RANI, Varu (Research Assist.)

217-5630

chauhan@mail.tagen.tohoku.ac.jp

12. CHEN, Mingwei (PI, Prof.)

217-5992

mwchen@wpi-aimr.tohoku.ac.jp

13. FUJITA, Takeshi (Assist. Prof.)

217-5959

tfujita@wpi-aimr.tohoku.ac.jp

14. HIRATA, Akihiko (Assist. Prof.)

217-5959

hirata@wpi-aimr.tohoku.ac.jp

15. CHEN, Luyang (Research Assoc.)

217-5959

chenly@wpi-aimr.tohoku.ac.jp

16. GUAN, Pengfei (Research Assoc.)

217-5959

pf.guan@wpi-aimr.tohoku.ac.jp

17. LANG, Xingyou (Research Assoc.)

217-5959

xylang@wpi-aimr.tohoku.ac.jp

18. KANG, Jianli (Research Assoc.)

217-5959

kangjianli@wpi-aimr.tohoku.ac.jp

19. ESASHI, Masayoshi (PI, Prof.)

795-6934

esashi@mems.mech.tohoku.ac.jp

20. MUROYAMA, Masanori (Assist. Prof.)

795-6937

muroyama@mems.mech.tohoku.ac.jp

21. YOSHIDA, Shinya (Assist. Prof.)

795-6936s-yoshida@mems.mech.tohoku.ac.jp

22. KAUSHIK, Neelam (Research Assoc.)795-6936

neelam@mems.mech.tohoku.ac.jp<Research Staff><Adschiri Group><Chen Group><Esashi Group><Gessner Group>
23. GESSNER, Thomas (PI)+49-37-53124060

thomas.gessner@zfm.tu-chemnitz.de

24. LIN, Yu-Ching (Assist. Prof.)

795-6256

yclin@mems.mech.tohoku.ac.jp

25. LEE, Jae Wung (Research Assoc.)795-6256dlwodnd77@mems.mech.tohoku.ac.jp

X - 19

WPI-03責2.indd

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9:35:04

Name

Phone Number

E-mail Address(+81-(0)22- _____)<Greer Group>
26. GREER, Alan Lindsay (PI)+44-1223-334308

27. MADGE, Shantanu V. (Research Assoc.)

217-5956

alg13@cam.ac.uk
shantanu.madge@wpi-aimr.tohoku.ac.jp< Hemker Group>
28. HEMKER, Kevin (PI)+1-410-5164489

hemker@jhu.edu+81-3-58417688

ikuhara@sigma.t.u-tokyo.ac.jp<Ikuhara Group>
29. IKUHARA, Yuichi (PI)
30. TSUKIMOTO, Susumu (Lecturer)

217-5934

tsukimoto@wpi-aimr.tohoku.ac.jp

31. SAITO, Mitsuhiro (Assist. Prof.)

217-5933

saito@wpi-aimr.tohoku.ac.jp

32. WANG, Zhongchang (Assist. Prof.)

217-5933

zcwang@wpi-aimr.tohoku.ac.jp

33. GU, Lin (Research Assoc.)

217-5933

gu@wpi-aimr.tohoku.ac.jp

34. ITAYA, Kingo (PI, Prof.)

217-5977

itaya@atom.che.tohoku.ac.jp

35. LAHIRI, Abhishek (Research Assoc.)

217-5974

a.lahiri@atom.che.tohoku.ac.jp

36. MUKKANNAN, Azhagurajan (Research Assist.)

217-5974

mazhagurajan@atom.che.tohoku.ac.jp

37. KAWASAKI, Masashi (PI, Prof.)

215-2085

kawasaki@imr.tohoku.ac.jp

38. MAKINO, Takayuki (Lecturer)

215-2088

tmakino@imr.tohoku.ac.jp

39. UENO, Kazunori (Assist. Prof.)

215-2088

uenok@imr.tohoku.ac.jp

40. HIRAGA, Hiroki (Research Assoc.)

215-2088

hiraga.hiroki@imr.tohoku.ac.jp

41. MARYENKO, Denis (Research Assoc.)

215-2088

d.maryenko@imr.tohoku.ac.jp<Itaya Group><Kawasaki Group>< Khademhosseini Group>
42. KHADEMHOSSEINI, Ali (Junior PI)+1-617-768-8395

alik@rics.bwh.harvard.edu

43. RAMALINGAM, Murugan (Assist. Prof.)

217-5997

murugan@wpi-aimr.tohoku.ac.jp

44. SEIDI, Azadeh (Research Assoc.)

217-6142a.seidi@wpi-aimr.tohoku.ac.jp

45. OSTROVIDOV, Serge (Research Assoc.)

217-6142

ostrovidov@wpi-aimr.tohoku.ac.jp

46. KURIHARA, Kazue (PI, Prof.)

217-5673

kurihara@tagen.tohoku.ac.jp

47. HEDIN, Jesper Niels (Researcher)217-5675

jhedin@tagen.tohoku.ac.jp<Kurihara Group><Lagally Group>
48. LAGALLY, Max G. (PI)+1-608-2632078

lagally@engr.wisc.edu

X - 20

WPI-03責2.indd

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9:35:06

Name

Phone Number

E-mail Address(+81-(0)22- _____)<Louzguine Group>
49. LOUZGUINE, Dmitri V. (PI, Prof.)

217-5957

dml@wpi-aimr.tohoku.ac.jp

50. NAKAYAMA, Koji (Assoc. Prof.)

217-5950

kojisn@wpi-aimr.tohoku.ac.jp

51. TAKEUCHI, Akira (Assoc. Prof.)

217-5956

takeuchi@wpi-aimr.tohoku.ac.jp

52. YOKOYAMA, Yoshihiko [Assoc. Prof. (Concurrent)]

215-2199

yy@imr.tohoku.ac.jp

53. QIN, Chunling (Assist. Prof.)

217-5956

clqin@wpi-aimr.tohoku.ac.jp

54. ZHANG, Qingsheng (Assist. Prof.)

217-5956

qszhang@wpi-aimr.tohoku.ac.jp

55. CARON, Arnaud (Research Assoc.)

217-5956

a.caron@wpi-aimr.tohoku.ac.jp

56. CHEN, Na (Research Assoc.)

217-5956

chenn@wpi-aimr.tohoku.ac.jp

57. SANCHEZ, Sergio Gonzalez (Research Assoc.)

217-5956

sergiogs@wpi-aimr.tohoku.ac.jp

58. LI, Song (Researcher)217-5956

lisong@wpi-aimr.tohoku.ac.jp

59. MIYAZAKI, Terunobu (PI, Prof.)

217-6000

miyazaki@wpi-aimr.tohoku.ac.jp

60. MIZUKAMI, Shigemi (Assist. Prof.)

217-6003

mizukami@wpi-aimr.tohoku.ac.jp

61. KUBOTA, Takahide (Research Assoc.)

217-6003

takahide@wpi-aimr.tohoku.ac.jp

62. ZHANG, Xianmin (Research Assoc.)

217-6003

xmzhang@wpi-aimr.tohoku.ac.jp

63. WU, Feng (Research Assoc.)

217-6004

fengwu@wpi-aimr.tohoku.ac.jp

64. NISHI, Toshio (PI, Prof.)

217-5926

nishi.toshio@wpi-aimr.tohoku.ac.jp

65. NAKAJIMA, Ken (Assoc. Prof.)

217-5927

knakaji@wpi-aimr.tohoku.ac.jp

66. FUJINAMI, So (Research Assoc.)

217-5928

fujinami@wpi-aimr.tohoku.ac.jp

67. LIU, Hao (Research Assoc.)

217-5928

liuhao@wpi-aimr.tohoku.ac.jp

68. WANG, Dong (Research Assoc.)

217-5928

wangdthu@wpi-aimr.tohoku.ac.jp795-3952

ohmi@fff.niche.tohoku.ac.jp+1-413-5452680

russell@mail.pse.umass.edu<Miyazaki Group><Nishi Group><Ohmi Group>
69. OHMI, Tadahiro (PI, Prof.)<Russell Group>
70. RUSSELL, Thomas (PI)X - 21

WPI-03責2.indd

21

2010/09/02

9:35:09

Name

Phone Number

E-mail Address(+81-(0)22- _____)<Shimomura Group>
71. SHIMOMURA, Masatsugu (PI, Prof.)

217-5329

shimo@tagen.tohoku.ac.jp

72. ISHII, Daisuke (Assist. Prof.)

217-5824

dishii@tagen.tohoku.ac.jp

73. HIGUCHI, Takeshi (Research Assoc.)

217-5825

higuchi@mail.tagen.tohoku.ac.jp

74. KAWANO, Takahito (Research Assoc.)

217-5825

kawano@poly.tagen.tohoku.ac.jp

75. IWASAKI, Junko (Tech. Staff)+81-11-758-0056

iwasaki@poly.es.hokudai.ac.jp

76. KIMURA, Konomi (Tech. Staff)+81-11-758-0056

kimura@poly.es.hokudai.ac.jp<Shluger Group>
77. SHLUGER, Alexander (PI)217-5942/+44-(0)20 7679 1312

a.shluger@ucl.ac.uk

78. MCKENNA, Keith (Assist. Prof.)

217-5942

k.mckenna@wpi-aimr.tohoku.ac.jp

79. TREVETHAN, Thomas (Assist. Prof.)

217-5942

tomt@wpi-aimr.tohoku.ac.jp

80. TAKAHASHI, Takashi (PI, Prof.)

795-6417

t.takahashi@arpes.phys.tohoku.ac.jp

81. SOUMA, Seigo (Assist. Prof.)

795-6477

s.souma@arpes.phys.tohoku.ac.jp

82. SUGAWARA, Katsuaki (Assist. Prof.)

795-6477

k.sugawara@arpes.phys.tohoku.ac.jp

83. TANIGAKI, Katsumi (PI, Prof.)

795-6469

tanigaki@sspns.phys.tohoku.ac.jp

84. NOUCHI, Ryo (Assist. Prof.)

795-6468

nouchi@sspns.phys.tohoku.ac.jp

85. TANG, Jung (Assist. Prof.)

795-6468

tangjun@sspns.phys.tohoku.ac.jp

86. TANABE, Yoichi (Research Assoc.)795-6468

youichi@sspns.phys.tohoku.ac.jp

87. XU, Jing-Tao (Research Assoc.)795-6468

jtxu@sspns.phys.tohoku.ac.jp

88. MITOMA, Nobuhiko (Research Assist.)795-6468

mitoma@sspns.phys.tohoku.ac.jp<Takahashi Group><Tanigaki Group><Teizer Group>
89. TEIZER, Winfried (Juior PI)

217-5979/+1-979-845-7730

90. OLIVEIRA, Daniel (Research Assoc.)

teizer@physics.tamu.edu

217-5979

oliveira@wpi-aimr.tohoku.ac.jp

91. TOKUYAMA, Michio (PI, Prof.)

217-5953

tokuyama@wpi-aimr.tohoku.ac.jp

92. XU, Limei (Assist. Prof.)

217-5954

limei.xu@wpi-aimr.tohoku.ac.jp

93. CHO, Young Seok (Research Assoc.)

217-5954

jho@wpi-aimr.tohoku.ac.jp

94. CHUTIA, Arunabhiram (Research Assoc.)

217-5954

arun@wpi-aimr.tohoku.ac.jp

95. FUJII, Hiroyuki (Research Assist.)

217-5954

fujii@athena22.wpi-aimr.tohoku.ac.jp<Tokuyama Group>X - 22

WPI-03責2.indd

22

2010/09/02

9:35:14

Name

Phone Number

E-mail Address(+81-(0)22- _____)<Tsukada Group>
96. TSUKADA, Masaru (PI, Prof.)

217-5937

tsukada@wpi-aimr.tohoku.ac.jp

97. AKAGI, Kazuto (Assoc. Prof.)

217-5940

akagi@wpi-aimr.tohoku.ac.jp

98. HAMADA, Ikutaro (Assist. Prof.)

217-5938

ikutaro@wpi-aimr.tohoku.ac.jp

99. TAMURA, Hiroyuki (Assist. Prof.)

217-5938

hiroyuki@wpi-aimr.tohoku.ac.jp

100. MASAGO, Akira (Research Assoc.)

217-5939

masago@wpi-aimr.tohoku.ac.jp

101. ARAIDAI, Masaaki (Researcher)217-5939

araidai@wpi-aimr.tohoku.ac.jp<Wan Group>
102. WAN, Li-Jun (PI)+86-62558934

103. WEN, Rui (Research Assoc.)

795-5869

wanlijun@iccas.ac.cn
ruiwen@atom.che.tohoku.ac.jp<Weiss Group>104. WEISS, Paul S. (PI)+1-310-267-5993

psw@cnsi.ucla.edu

105. WU, Hongkai (Junior PI)+85-223-587-246

chhkwu@ust.hk.

106. LI, Lei (Research Assoc.)

217-6142

lilei@wpi-aimr.tohoku.ac.jp+86-10-62795618

qkxue@mail.tsinghua.edu.cn<Wu Group><Xue Group>
107. XUE, Qikun (PI)108. LIU, Hongwen (Assist. Prof.)

217-5948

liu@wpi-aimr.tohoku.ac.jp109. YAMADA, Kazuyoshi (PI, Prof.)

215-2035

kyamada@imr.tohoku.ac.jp

110. SATO, Toyoto (Assist. Prof.)

215-2039

toyoto@imr.tohoku.ac.jp

111. JI, Sungdae(Assist. Prof.)

215-2039

jsungdae@imr.tohoku.ac.jp

112. HORIGANE, Kazumasa (Research Assoc.)

215-2039

khorigane@imr.tohoku.ac.jp

113. YAMAGUCHI, Masahiko (PI, Prof.)

795-6812

yama@mail.pharm.tohoku.ac.jp

114. YASUI, Yoshizumi (Assist. Prof.)

795-3873

yasui@mail.pharm.tohoku.ac.jp

115. AN, Zengjian (Research Assoc.)795-6815zjan@mail.pharm.tohoku.ac.jp

116. ICHINOSE, Wataru (Research Assist.)795-6813

a9yd1001@s.he.tohoku.ac.jp

117. YAMAMOTO, Koji (Research Assist.)795-6815b0yd1008@s.he.tohoku.ac.jp<Yamada Group><Yamaguchi Group>X - 23

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9:35:17

Name

Phone Number

E-mail Address(+81-(0)22- _____)<Yamamoto Group>
YAMAMOTO, Yoshinori (Institute Director)

217-5130

yoshi@m.tohoku.ac.jp

118. ASAO, Naoki (Prof.)

795-3898

asao@m.tains.tohoku.ac.jp

119. JIN, Tienan [Assoc. Prof. (Concurrent)]

795-3585

tjin@mail.tains.tohoku.ac.jp

120. UZZAMAN, MD. Akhtar (Research Assoc.)795-6582

akhtar@m.tains.tohoku.ac.jp

121. FERRARA, Giovanni (Research Assist.)795-3585<Yavari Group>122. YAVARI, Alain Reza (PI)+33-(0) 4 76 82 65 16

123. GEORGARAKIS, Konstantinos (Assist. Prof.)

yavari@minatec.inpg.fr
georgara@minatec.inpg.fr<Fukuda Group>
124. FUKUDA, Tsuguo (Adjunct Prof.)

217-5983

ts-fukuda@wpi-aimr.tohoku.ac.jp

125. EHRENTRAUT, Dirk (Assoc. Prof.)

217-5983

ehrentraut@wpi-aimr.tohoku.ac.jp

126. BAO, Quanxi (Researcher)217-5983

bao@mail.tagen.tohoku.ac.jp

127. HITOSUGI, Taro (Assoc. Prof.)

217-5944

hitosugi@wpi-aimr.tohoku.ac.jp

128. SHIRAKI, Susumu (Lecturer)

217-5948

shiraki@wpi-aimr.tohoku.ac.jp

129. IWAYA, Katsuya (Assist. Prof.)

217-5948

iwaya@wpi-aimr.tohoku.ac.jp

130. OHSAWA, Takeo (Assist. Prof.)

217-5948

ohsawa@wpi-aimr.tohoku.ac.jp

131. FUKUI, Nobuyuki (Research Assoc.)

217-5948

n-fukui@wpi-aimr.tohoku.ac.jp

132. SHIMIZU, Ryota (Research Assist.)

217-5948

shimizu@chem.s.u-tokyo.ac.jp< Hitosugi Group>X - 24

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9:35:20

Name

Phone Number

E-mail Address(+81-(0)22- _____)<Supporting Staff>
133. HASHIMOTO, Keiichi (Deputy Administrative Director)
217-5980
General Affairs Section

217-5922 or 5972

k-hashi@wpi-aimr.tohoku.ac.jp
wpi-shomu@wpi-aimr.tohoku.ac.jp

134. NAGANUMA, Hiromi (Chief)

naganuma@bureau.tohoku.ac.jp

135. SAITO, Asuka

asuka-s@bureau.tohoku.ac.jp

136. OIKAWA, Hiroshi

hiroshi@bureau.tohoku.ac.jp

137. CHIBA, Yoko

217-5956

ykchiba@wpi-aimr.tohoku.ac.jp

138. ONODERA, Marikom.onodera@wpi-aimr.tohoku.ac.jp

139. UNOURA, Sayaka

unoura-0@wpi-aimr.tohoku.ac.jp

Accounting Section

217-5923 / FAX: 217-5129

wpi-keiri@wpi-aimr.tohoku.ac.jp

140. SATO, Hiroto (Chief)

hiroto-s@bureau.tohoku.ac.jp

141. OKAZAKI, Tomohiro

tokazaki@bureau.tohoku.ac.jp

142. ZENIYA, Ippei

zeniya@bureau.tohoku.ac.jp

143. KOBAYASHI, Yuki

y-kobayashi@bureau.tohoku.ac.jp

Property Management Section

217-5924 / FAX: 217-5129

wpi-yodo@wpi-aimr.tohoku.ac.jp

144. YOSHIDA, Masahiro (Chief)masa-y@bureau.tohoku.ac.jp

145. HIRAYAMA, Hirotaka

h-hiraya@bureau.tohoku.ac.jp

146. YOSHIDA, Hajime

hyoshi@bureau.tohoku.ac.jp

147. ONO, Toshio

toshi-ono@bureau.tohoku.ac.jp

148. DAIGAKU, Norikodaigaku@bureau.tohoku.ac.jp

149. OHTOMO, Yumi

yumi-o@bureau.tohoku.ac.jp

International Academic Affairs Section

217-5971 / FAX: 217-5129

wpi-kenkyo@wpi-aimr.tohoku.ac.jp

150. YANAGAWA, Yasukazu

yanagawa@bureau.tohoku.ac.jp

151. SAITO, Ikuo

s-ikuo@bureau.tohoku.ac.jp

152. HAGITA, Etsuko

217-5978hagita@bureau.tohoku.ac.jp

153. OKAMOTO, Ayumi

217-5978a-okamoto@bureau.tohoku.ac.jp

Safety and Health Management Office217-5970

wpi-safety@wpi-aimr.tohoku.ac.jp

154. KAMOSHIDA, Kazuyoshi (Manager)kamoshida@bureau.tohoku.ac.jp

155. UMEZAWA, Akiko

akiko_umezawa@bureau.tohoku.ac.jp

Outreach Officeoutreach@wpi-aimr.tohoku.ac.jp

156. IKEDA, Susumu (Outreach Manager)

795-6468

sikeda@sspns.phys.tohoku.ac.jp

X - 25

WPI-03責2.indd

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9:35:21WPI-03責2.indd

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2010/09/02

9:35:21

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Cover: Snapshot of long-lived spatial heterogeneities, projected onto a x-y plane, obtained bynumerically solving the Tokuyama nonlinear stochastic equation for density fluctuations in a
colloidal suspension at a liquid state with volume fraction f=0.466 and a supercooled-liquid state with
f=0.566, where the relaxation time is of order 102 and 6×104, respectively.

(Michio Tokuyama,

WPI-AIMR)WPI10表紙.indd

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WPI-ADVANCED INSTITUTE FOR MATERIALS RESEARCH NEWS

August 31, 2010

2-1-1 Katahira, Aoba-ku, Sendai 980-8577
Japan
Phone: +81-22-217-5922
FAX: +81-22-217-5129$XJXVW

Volume 10

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Advanced Institute for Materials Research
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