2016

Issue 1

Science & Technology at the Ames Laboratory

Materials Synthesis

Creating new materials through ... 

• Powder Metallurgy 

• Single Crystals 

• Rapid Solidification

• Solid-state Processing 

• Deposition 

• Inorganic Chemistry 

• Biosynthesis
Adam Schwartz, Director

Copyright 2016 by Ames Laboratory. All rights 

reserved. For additional information about Ames 

Laboratory or topics covered in this publication, 

please contact: 

ENERGY

U.S. DEPARTMENT OF Office of

Science Inquiry Issue 1 | 2016 3

From the Director

Inquiry is published biannually by the Ames 

Laboratory Office of Public Affairs. Iowa 

State University operates Ames Laboratory 

for the U.S. Department of Energy under 

contract DE AC02 07CH11358. 

Editor, Inquiry

Ames Laboratory

111 TASF

2408 Pammel Drive

Ames, Iowa 50011-1015

www.ameslab.gov

Ames Laboratory is a U.S. Department of Energy national laboratory seeking solutions to energy-related problems 

through the exploration of chemical, engineering, materials and mathematical sciences, and physics. Established 

in the 1940s with the successful development of the most efficient process to produce high-purity uranium metal 

for atomic energy, Ames Laboratory now pursues much broader priorities than the materials research that has 

given the Lab international credibility. Responding to issues of national concern, Ames Laboratory scientists are 

actively involved in innovative research, science education programs, the development of applied technologies 

and the quick transfer of such technologies to industry. Uniquely integrated within a university environment, the 

Lab stimulates creative thought and encourages scientific discovery, providing solutions to complex problems and 

educating and training tomorrow’s scientific talent.

Cover photo by Trevor Riedemann, Ames Lab Materials Preparation Center

Steve Karsjen: Public Affairs Director

Kerry Gibson: Editor

Laura Millsaps: Contributing Editor

Grant Luhmann: Art Director

6

P A G E

Perfect Powder

rom its inception, Ames Laboratory has been dedicated to materials synthesis. We 

developed a method for purifying uranium as part of the Manhattan Project and later 

used a similar technique to refine rare-earth metals. It’s even part of our corporate 

tagline—“Creating materials and energy solutions.”

We’re home to the Critical Materials Institute, a U.S. Department of Energy (DOE) energy 

innovation hub that focuses on technologies that make better use of materials and eliminate 

the need for materials that are subject to supply disruptions. We recently were named the 

lead for CaloriCoolTM, a new research consortium for the discovery and development of more 

environmentally friendly and energy-efficient refrigeration technologies, sponsored by DOE’s 

Office of Energy Efficiency and Renewable Energy.

While we are proud of these research efforts and plan to showcase their achievements 

in future issues of Inquiry, we want to focus this time on the variety of methods we employ 

to actually develop new materials. It’s basic science at its best, combining experimental, 

characterization and theoretical work to synthesize materials, measure their various properties and then work 

to develop models that explain a particular material’s structure and how that relates to the properties observed. 

That type of collaboration has also been a hallmark of Ames Laboratory.

A key method is single crystal growth, detailed on pages 8-10. By creating materials with a uniform 

crystalline structure, researchers can probe their properties without having to account for the effects of grain 

boundaries between crystals. It helps provide a clearer picture of what’s taking place within the material.

Conversely, we also create materials by cooling them very quickly so that their normal crystal patterns aren’t 

allowed to form. Rapid-solidification (pages 11-13), which also includes gas atomization (pages 6-7), allows 

for creation of materials not typically possible by other methods. The resulting properties are also out of the 

ordinary in many cases.

We’re also looking at creating materials in solid state (pages 14-15) without the use of solvents or high 

temperatures to drive the reaction to form new compounds. High-energy ball milling and friction are just two 

of the methods being employed to form unique materials not possible by other methods.

Our inorganic chemists are busy developing nanomaterials for possible use in solar cells and catalysis 

(pages 19-21). And others are studying fascinating nanoscale, two-dimensional materials (pages 16-18).

In yet another technique, we are looking at the ways Mother Nature creates beautifully complex structures 

on multiple scales from atomic to macro. Biosynthesis (pages 22-23) is harnessing those natural processes to 

allow creation of man-made materials by following nature’s template.

For any of these techniques to work, it’s vital to start with pure ingredients. Otherwise, you can’t know if 

the resulting properties are intrinsic to the new material or caused by impurities. Fortunately, our Materials 

Preparation Center (detailed on pages 4-5) provides us, and researchers throughout the world, with the perfect 

ingredients we need for materials synthesis.

Materials are everywhere and in everything, and Ames Laboratory is working hard to find new materials 

and new ways to create them.

On a somber note, we marked the passing of senior metallurgist and Iowa State University distinguished 

professor Karl A. Gschneidner, Jr. in April. Karl was an inspiration here and around the world as the foremost 

authority on rare earths. He was a dedicated scientist, colleague and friend and we miss him greatly.

F

4Materials Preparation Center 8

11 Frozen in a Flash

14

Solid-State Processing 16

19 22 Materials

Bioinspired 

Contents
4 Inquiry Issue 1 | 2016 Inquiry Issue 1 | 2016 5

“For example, we had a customer who wanted an alloy of 

tungsten and boron, two metals that are hard to combine, 

but one of our technicians had the expertise to meet the 

customer’s needs,” said Besser. “That comes from his years 

of experience working in this environment.”

Besser said “enabling science” is the MPC’s mantra. 

“Once a satisfied customer said to me ‘No one else in the 

country can do this work for me,’ and he was right.” 

RARE-EARTH MATERIALS PRODUCTION

If you think of the MPC as a pie, one of the largest slices 

would be the production of rare-earth metals.

Rare earths have been part of the Ames Laboratory since 

Frank Spedding, the Laboratory’s first director, got involved 

in metallurgical work for the Manhattan Project. The ionexchange separation process Spedding developed at Ames 

Laboratory to purify rare-earth oxides gave rise to the 

knowledge base the MPC utilizes today for producing highly 

pure rare-earth metals for clients in academia and industry. 

The largest portion of MPC’s rare-earth-using clients is 

generally from research institutes with condensed matter 

physics, materials chemistry, and materials science programs 

involved in fundamental research. 

According to Trevor Riedemann, MPC assistant scientist, 

the MPC also provides rare earths to industrial clients from 

large multinationals to start-up companies that are looking for 

better materials to optimize properties of existing products or 

products under development. 

“What all of our clients have in common is a strong 

research component,” said Riedemann. “And the rare 

earths help them fine-tune whatever materials properties 

they’re studying.” 

Riedemann explained when clients call, they’re usually 

looking for high-purity rare-earth metals because purity is 

critical to the success of today’s materials research. 

“And no one can match the purity of our rare-earths,” 

Riedemann said.

Riedemann added all MPC metals are provided on a costrecovery (non-profit) basis. And because rare-earth metals 

can cost as much or more than gold per ounce, the MPC 

works to meet customer needs in the most efficient manner. 

“Our high-purity-metals are expensive because input 

costs are high and rare-earth production is a labor-intensive 

process,” said Riedemann. “But because the rare earths 

provide scientists a fabulous ‘tool set’ for fine-tuning a 

material’s properties or systematically unraveling the 

mysteries of materials science, they are willing to pay the 

high price. Scientists understand it’s hard to do high-quality 

materials science with low-quality materials.” 

PRECISION-ALLOY PREPARATION

Precision-alloy preparation plays an integral role in the 

MPC success story, according to Besser, who also heads the 

MPC precision-alloy section.

“If a scientist wants an alloy that contains specific amounts 

of iron and carbon, we begin by purchasing the highest purity, 

or clean, metal we can find,” said Besser. “And then we mix it 

to the precise composition asked for, melt it, and serve it up 

in exactly the form the client wants.” 

The MPC also focuses on material size and fabrication. 

Besser said while many commercial providers can only provide 

large quantities of materials, the MPC can accommodate 

much smaller requests. 

“Researchers want only what they need, and we can 

provide anywhere down to a gram, half gram or even smaller 

amounts of metal,” Besser said. 

Once the customer has decided on the amount of material 

needed, the MPC can then fabricate it to their specifications. 

“Sometimes customers want their material in a very 

specific form,” said Besser. “For example, once we started 

with a cast ingot of Galfenol 

about an inch in diameter 

and as long as your forearm.

When we were done 

working with it, we had 

hundreds of feet of wire; 

rolled, swaged and drawn 

until it was the dimension 

the customer needed. The 

wire was used in an energyharvesting project.” 

Customer satisfaction is 

the most essential element 

of the MPC’s success, which 

Besser said requires extensive communication with clients.

“Sometimes customers want one thing, but that might be 

nearly impossible for us to produce. So we’ll talk with them 

about options, plan A and plan B, and almost always we can 

guide the interaction to a realistic conclusion,” said Besser. 

“Response to need is very important to us.”

Arc-cast ingots of high-purity Erbium 

metal, one of the rare-earth metals, are 

prepared for MPC customers. 

Beads of scandium metal are shown 

on a cast on a copper hearth plate. 

Scandium is one of the high-purity 

rare earth metals prepared for 

MPC customers. 

Jacob Fischer, undergraduate research assistant, prepares the 

injection casting system for operation. The injection casting 

system is used to study the solidification behavior of alloys by 

rapidly solidifying ingots with diameters on the order of 1-2mm. 

fter 34 years of producing research and 

developmental quantities of metals for internal Ames 

Laboratory, university, industry, and government 

facilities, the Materials Preparation Center (MPC) 

has developed an international reputation as the go-to 

center for scientists’ materials needs. 

The MPC offers unique capabilities in purification, 

preparation and characterization of high-purity rareearth metals and alloys, intermetallic compounds, and 

single crystals that are not commercially available.

Since inception in 1982, MPC scientists have been 

involved in over 5,000 projects. The largest percentage 

of those projects has been with U.S. industry, followed 

by U.S. universities, foreign institutes and universities, 

and federal laboratories. 

 “Many of our customers over the years have 

been repeat customers,” said Matt Besser, manager 

of the MPC. 

On any typical day, MPC staff produces materials 

for materials scientists, chemists and physicists 

conducting laboratory-scale research experiments. 

But occasionally a scientist will request material for a 

project that’s a bit out of the ordinary. 

Two of the MPC’s more memorable requests 

came from NASA. One was for the production of 

materials for use on the Space Shuttle Endeavor’s 

Brilliant Eyes Ten-Kelvin Sorption Cryocooler 

Experiment (BETSCE). That successful project led 

to more work with NASA’s Jet Propulsion Laboratory 

for the preparation of materials for the instrument 

cooling system on board the European Space Agency’s 

PLANCK space satellite. 

Another key ingredient in the MPC’s success is 

its materials supply chain, which Besser said assures 

customers a quick turnaround on the metal they’re 

requesting. 

“I have a collection of elements in place, and if I 

don’t have the one a customer is looking for on hand, I 

know where to go to find it,” Besser said. 

Once the MPC makes a sought-after alloy, it employs 

its experience with a wide variety of Ames Laboratory 

equipment and techniques to fashion the metal into 

whatever form the customer wants, from wires to ribbons 

and more.

The MPC offers what Besser calls “an incredible 

knowledge base” built up over time from the work done 

by the MPC’s staff. 

Materials Preparation Center

A

BY STEVE KARSJEN
6 Inquiry Issue 1 | 2016 Inquiry Issue 1 | 2016 7

LIKE SAND THROUGH AN HOURGLASS

Iver Anderson and Emma White, metallurgists at Ames 

Laboratory, like to show off samples of metal powders 

encapsulated in custom-made hourglasses to visitors. Dull 

gray, the powders are barely remarkable in and of themselves, 

let alone in comparison to each other. 

Until the hourglasses are flipped and observers can compare 

how the powders flow through the narrow necks of glass. The 

powder created by traditional manufacturing methods doesn’t 

flow, exactly. It starts and trickles and stops. It needs shaking 

and manipulating to get through. The other powder, produced 

at the Laboratory’s high-pressure gas atomization facility, 

pulses smoothly through the hourglass of its own accord. 

It’s all because of the smooth 

spherical particles produced by Ames 

Laboratory’s gas atomization method, 

an improvement over traditionally 

manufactured powders. 

“You can see they’re chunky, 

randomly sized, with rough edges,” 

said White of the traditionally-made 

powder particles, comparing scanning 

electron microscope images of the 

two. “They don’t flow past each 

other, and that’s going to require a pulsing mechanism or an 

agitator in the manufacturing process. That’s going to cost 

the manufacturer more in energy to 

run their production line.” 

It’s only one of the many benefits of 

powders created by the gas atomization 

process, which has garnered the 

Laboratory at least 16 patents over 

the last two decades. It also helped 

create spin-off company Iowa Powder 

Atomization Technologies, which 

was recently acquired by Praxair, and 

exclusively licenses Ames Laboratory’s 

titanium atomization patents to introduce titanium powder 

to an eager marketplace.

SPLITTING LIQUID INTO DROPLETS

Gas atomization is a powder production method that 

uses high-pressure gas flow to distintegrate molten metal 

into particles. In the Metals Development building at Ames 

Laboratory, Anderson, a senior metallurgist, and White, a 

post-doctoral researcher, are able to produce experimental 

quantities of powder with the Laboratory’s experimental 

apparatus, about half of a liter volume per production run. 

Another, larger gas-atomizer at Iowa State University’s 

Applied Sciences Complex can produce around three liters. 

The basic operation is the same in both. Metal is melted 

by an induction furnace and held in a crucible with a 

stoppered opening in the bottom. When the stopper is lifted, 

the metal flows through a specially designed pour tube into 

an atomization nozzle (also unique to Ames Laboratory) 

that focuses a number of round-hole gas jets on the molten 

metal in a tight pattern. The individual jets of gas—argon, 

nitrogen, or helium depending on the run—knit together 

to form a supersonic “curtain” that flows directly across the 

liquid metal flow and forces the melt to couple directly with 

the high kinetic energy of the supersonic gas, creating a 

controlled droplet spray. 

“This energetic coupling happens because the gas curtain 

creates a suction that pulls the melt into the atomization 

zone and simultaneously forces an upward directed gas 

counter-flow to form that splits the liquid as though there 

was an umbrella stuck underneath it and makes it flow 

sideways, across to the outer edge of that round nozzle,” 

said Anderson, who is also an Iowa State University adjunct 

professor of materials science and engineering. “So it gets 

presented to the gas as a thin film that is forced by the gas to 

turn in the gas flow direction so it can shear past the surface 

of that film, and strip off waves of liquid that break at their 

crest to form droplets.

“It’s the same phenomenon you can see on the surface of a 

pond hit with a gust of wind. You see small ripples and a spray 

of water come off that gust.”

Once the droplets form, they solidify rapidly as they fall 

through the spray chamber and are cooled by additional gas 

halos. The resulting powder particles are separated from the 

combined gas flow and settle into two powder collector cans 

that are connected to the end of the spray chamber. The 

cleaned inert process gas exits through two types of final filter 

devices and is exhausted from the lab.

ADVANTAGES

Ames Laboratory’s gas atomization method produces 

powders that are customizable, consistently sized and 

smoothly spherical. The advantages of a perfectly formed 

powder are multiple. Besides the advantage of smooth powder 

flow already mentioned, the individual round particles have 

little internal porosity and pack together optimally in bulk. 

Both qualities reduce dead air space and improve the quality 

of parts produced using these powders. 

Using gas atomization, Ames Laboratory has produced 

powders of iron, aluminum, nickel, copper, tin, magnesium 

and various other metals and alloys, in addition to titanium, 

one of its key research accomplishments.

“The titanium industry is extremely interested in powder 

metallurgy and final-shape consolidation methods,” said White. 

“Titanium is expensive and the large amount of titanium 

waste produced during machining cast parts into final shapes 

significantly increases their costs. They see advances in powder 

metallurgy as an effective cost control strategy by making parts 

into near-final shapes and minimizing waste titanium.” 

The powders produced by this method have also been 

used in the production of stronger alnico (aluminum, nickel, 

cobalt, and iron) permanent magnets, and in the production 

of an experimental power transmission cable fabricated out 

of an aluminum and calcium composite. 

And the possibilities of these metal powders don’t just 

look to the future, but may also redeem materials from the 

past that had been abandoned by researchers and industry as 

impossible to work with.

“You can create an alloy with fantastic properties, but if you 

can’t make something useful out of it, it will never get off the 

lab bench. This method enables us to revisit materials that 

have been around a long time, give them a second chance, 

and find new potential applications for them,” said Anderson. 

IMPOSSIBLE SHAPES OUT OF INCREDIBLE ALLOYS

Ames Laboratory is seeking to expand its powder 

production capabilities beyond research capacity, with the 

goal of being able to produce up to 200 pounds of powder in 

one production run. 

At that scale, new opportunities for research are possible, 

explained Anderson and White. Large batches provide 

sufficient samples amounts for shared research projects 

among multiple national laboratories and industry partners. 

With new 3D printing and additive manufacturing 

capabilities expanding rapidly, Ames Laboratory will be able 

to position itself as a provider of custom metal powders for 

these research areas, continuing to fine-tune the abilities of 

the gas atomization process. 

All of this is a natural progression of the research goals 

Anderson has worked toward for decades. 

“The ability to make impossible shapes out of incredible 

alloys is my mission in life. I want to work on ways to get this 

done,” Anderson said.

BY LAURA MILLSAPS

Perfect Powder:

AMES LABORATORY’S PROCESSES PERFECT METAL POWDERS FOR MANUFACTURING

High-pressure gas atomized metal powders at various levels of magnification showing the perfection of the spherical end product.

Iver Anderson

Emma White

“You can create an alloy with fantastic properties, but if you can’t make something useful out of it, it 

will never get off the lab bench. This method enables us to revisit materials that have been around a long 

time, give them a second chance, and find new potential applications for them.”
“The active component in a laser is a single crystal,” 

said Lograsso, who is also an Iowa State University adjunct 

professor of materials science and engineering, “because the 

crystal grain boundaries would scatter the light.”

From a research viewpoint, especially when creating a 

new material, scientists want to remove as many variables 

as possible to best understand a material’s properties. A 

primary way to do this is to begin with raw materials that 

are as pure as possible and to produce the material as a 

single crystal.

“You don’t want defects in the crystal structure and 

you don’t want impurities, which can be a source of extra 

nucleation,” Lograsso said. “New materials can have new 

physics, and we can determine what those are if we make 

measurements on a clean, pristine sample (i.e. single crystal). 

And if we do that consistently, we can make comparisons to 

other materials and see how it fits into our understanding of 

particular behaviors.”

Ames Laboratory scientists employ a number of 

techniques to grow single crystals, with each suited to 

producing crystals from different types of materials. 

8 Inquiry Issue 1 | 2016 Inquiry Issue 1 | 2016 9

However, the basic premise is the same—oversaturate a 

solution, then precipitate out the crystal.

“As kids, we’re familiar with adding rock salt or sugar to 

hot water until you supersaturate the liquid,” Lograsso said. 

“Then, as the water cools and eventually starts to evaporate, 

crystals of salt or sugar start to form and then grow.”

“You can do the same with about any two materials, using 

one as the solvent and then using heat or high temperatures 

to supersaturate the solvent,” he continued. “The tricky part 

is to get a single crystal to first form and then grow.”

This “practitioner’s art” requires patience and skill, 

though the various techniques described here provide 

some assistance as well. Generally, a high temperature 

gradient also helps promote a stable growth transition from 

liquid to solid.

BRIDGMAN TECHNIQUE

One of the better known methods, the Bridgman 

technique—named for Harvard physicist Percy Williams 

Bridgman—uses a crucible with a pointed, conical end. 

This fine point promotes the growth of a single crystal as 

the crucible exits the heated portion of the furnace. Heat is 

provided through a heating element similar to the one in a 

home oven (resistance) or via a magnetic field (induction).

“Crucibles age over time and become better at producing 

single crystals,” Lograsso said. “Unfortunately, you 

sometimes break the crucible removing the crystal. Because 

they grow inside a crucible, crystals formed in this manner 

may also develop stresses such as cracks or voids.”

Ames Laboratory also has a special Bridgman furnace 

that allows crystal growth at higher pressures—up to 15 

Bar. This allows growth of crystals from alloys that contain 

volatile components. The high pressure prevents these 

components, which have a lower boiling point than alloy’s 

other components, from flashing off as a vapor before the 

crystal can form.

This furnace utilizes induction heating, which provides 

a steeper temperature gradient, allowing faster crystal 

growth rates to further minimize evaporation and reaction 

with the crucible.

CZOCHRALSKI TECHNIQUE

This method also heats the material in a crucible, 

but here, the crystal is actually drawn from the molten 

solution. Lograsso likens it to dipping a candle “except 

you only dip once.”

A seed crystal of the material is attached to the end of a 

rod. The rod is lowered until the seed crystal just touches 

the surface of the molten material in the crucible. The rod 

is then rotated and withdrawn very slowly, pulling the newly 

formed crystal from the liquid.

“Because the crystal is freestanding, it doesn’t have the 

stresses that you sometimes get with the Bridgman method,” 

Lograsso said. “Depending on the material, crystals can also 

be 60 cm in diameter, or larger, and several feet in length. This 

is a very common method for producing large silicon crystals 

which are sliced into wafers for use in semiconductors.”

FLOAT-ZONE TECHNIQUE

Optical float-zone technique uses focused, high-intensity 

light to create single crystals, particularly those containing 

metal oxides. According to associate scientist Yong Liu, the 

technique offers a couple of advantages for growing many 

types of crystals.

“It’s container-free—you don’t need or use a crucible 

to grow the crystal so it eliminates any potential reaction 

between the sample and the container,” Liu said. 

“Because the melt zone is very focused and narrow, we’re 

able to achieve a very large temperature gradient between 

the solid and liquid phases, which results in high-quality 

crystal growth.”

A typical optical float zone furnace consists of four 

high-powered halogen bulbs arranged in a ring around the 

sample. Semi-spherical reflectors around each bulb focus 

the intense light energy in a narrow band around the sample 

hen it comes to creating new materials, 

single crystals play an important role in 

presenting a clearer picture of a material’s 

intrinsic properties. A typical material will be 

comprised of lots of smaller crystals and the grain boundaries 

between these crystals can act as impediments, affecting 

properties such as electrical or thermal resistance.

“Those boundaries can have profound effects, both 

good and bad,” said Ames Laboratory materials scientist 

and deputy director Tom Lograsso. “Generally, a material 

that has smaller and smaller crystals actually has improved 

mechanical properties.”

An exception to this rule is that at high temperature, 

relative to the melting point, small crystals can have a 

tendency to slide past one another, a property called creep. 

It’s for this reason that turbine blades in some jet engines or 

generators are actually formed from single crystals of nickelbased alloy.

A few other everyday applications using single crystals 

are semi-conductors, detectors, such as infrared or radiation 

sensors, and lasers.

W

BY KERRY GIBSON

Single crystals provide clarity

Ames Laboratory scientist Paul Canfield removes a sample from a flux-growth furnace.

Ames Laboratory scientist Deborah Schlagel holds a graphite 

crucible (left) and a Bridgman-grown copper crystal (right).

Four semi-spherical reflectors focus light energy from highpowered halogen bulbs onto the material, which is suspended 

over the port in the center.
10 Inquiry Issue 1 | 2016 Inquiry Issue 1 | 2016 11

To then separate the liquid tin from the Ce-Sb crystal, the 

tube assembly is removed from the furnace and immediately 

placed in a centrifuge, which spins the remaining liquid 

tin off into the catch crucible, leaving the crystal behind. 

The centrifuge delivers up to 100 times the force of simple 

gravitational decanting, resulting in “cleaner” crystals.

“When you develop new materials, you need to have 

some familiarity with the ingredients and the techniques 

at hand,” said Canfield. “With solution growth, we can go 

from looking at superconductors and ferromagnets, to spin 

glasses, to quasicrystals—go from one material to another to 

another—just by changing elements or growth conditions. 

Over the course of 20 years here, we are closing in on 10 

thousand different growths.”

at temperatures up to 2,100 degrees Celsius.

The sample ingot itself starts in two pieces. The shorter 

“seed” side is on the bottom and held in a base. The longer 

“feed” side is suspended closely above the seed side. As the 

two sides begin to melt, a small pool of liquid collects on each 

surface and as they are brought closer together, the surface 

tension of the pools connect to form an hour-glass-shaped 

band of molten material between the seed and feed sides.

By twisting the two sides in opposite directions, the 

liquid sample is effectively “stirred” to ensure a uniform 

distribution of material in the melt zone. The sample is then 

slowly lowered through the focused circle of light, allowing 

the narrow melt zone to progressively melt, mix and solidify 

its way up the feed side of the sample.

“For materials with low vapor pressure, we can grow 

crystals at a rate of one millimeter per hour,” Liu said. “We 

can use the technique on a variety of materials, but we 

always start with the phase diagram (kind of a growth map) 

to determine if it’s possible. We can’t grow crystals with high 

vapor pressure or that may be toxic using this method.”

SOLUTION/FLUX GROWTH

While the other three methods work well for materials 

where the crystalline outcome is known, researchers also 

look to discover and grow single crystals of new binary, 

ternary, quaternary or higher compounds. In many cases, 

the materials in these compounds don’t melt congruently 

meaning they do not melt at a single temperature. 

“Solution growth is extremely versatile, and you can 

often optimize and cycle through it rapidly,” said Ames 

Laboratory physicist and Iowa State University 

Distinguished Professor Paul Canfield. “In general, it 

does not give you as large a crystal, but for basic physical 

measurements, something between a millimeter and a 

centimeter is more than adequate.”

In practice, the compounds for the target crystal are 

combined with a material that will serve as the solution in 

which the crystal compound 

will dissolve. For example, to 

grow a cerium-antimony crystal 

from a tin solution, or flux, you 

may start with four percent each 

of Ce and Sb with the other 92 

percent Sn.

The materials go into a 

“growth” crucible that’s paired 

with a “catch” crucible. These 

are then sealed in a silica tube as shown (top right). The 

tube assembly is placed in a furnace and heated so all the 

elements melt. The temperature is then lowered closer to 

the melting point of the solution element, allowing the target 

crystal to form. In the Ce-Sb in Sn flux example, the initial 

temperature is roughly 1,000 degrees Celsius, then lowered 

to 600 degrees.

A flux-grown ytterbiumsilver-germanium crystal.

Once a crystal has formed in the growth crucible, this assembly is placed in a centrifuge. Excess liquid is captured in the 

catch crucible. The glass wool then traps the liquid, leaving 

the crystal in the growth crucible.

GROWTH

CRUCIBLE

CATCH

CRUCIBLE

SEALED

SILICA

TUBE

Glass wool 

cushions crucibles

during decanting

Glass wool in

catch crucible 

captures excess 

liquid during

decanting

Higher melting 

element (red),

lower melting 

element (green)

f the single crystal growth techniques described 

in the previous article sit at one end of the materials 

synthesis spectrum, then rapid solidification techniques 

fall at the opposite end of the scale. The former promote 

the growth of the material’s equilibrium crystalline structure. 

Rapid solidification techniques promote the opposite effect, 

cooling the material so quickly from liquid to solid, that the 

crystals formed are small, or in some cases non-existent, 

becoming amorphous or glass-like with no discernable 

crystalline pattern to their overall molecular structure.

It’s also a way to form composite materials whose 

constituents have widely varying “freezing” temperatures.

“If you take a molten metal and cool it, what wants to 

form will vary depending on its chemistry,” said Ames 

Laboratory scientist and Division of Materials Sciences and 

Engineering Director Matt Kramer, “because what wants to 

form is not always a homogeneous solid.”

For example, if you freeze a mixture of water and alcohol, 

the water will solidify first—turning to ice—while the 

alcohol remains liquid, leaving a slushy mixture until the 

temperature is lowered to the alcohol’s freezing temperature.

“So when you cast a molten alloy, small crystals will form 

quickly on the surface of the mold, you get segregation of 

the materials and the remaining liquid becomes enriched,” 

said Kramer, who is also an Iowa State University adjunct 

professor of materials science and engineering, “which 

results in a heterogeneous bulk material.”

Rapid solidification allows the material to cool extremely 

quickly so as to suppress or even eliminate the segregation. 

Techniques range from strip casting, which cools materials 

at about 1,000 Kelvins per second to splat quenching which, 

as the name implies, squashes a droplet of liquid material 

between two plates. Splat quenching can cool the material 

as high as 108 Kelvins per second.

“Why is that important? Because there’s an intimate 

relationship between temperature and the time at which 

materials cool,” Kramer said. “We call it TTT—TimeTemperature Transformation.”

It takes a certain finite amount of time for the initial 

crystals to form, a process called nucleation. The molten 

material has to organize itself into crystals only a few 10s of 

atoms across and then those crystals need to grow. 

“There’s a very non-linear relationship between time 

and temperature transformation,” Kramer continued. 

“Solidification occurs over a broad range of temperatures. 

At too high a temperature, it stays molten. At a temperature 

just below the melting temperature, the material solidifies 

slowly, and in cases where constituents have different 

melting temperatures, significant segregation in the casting 

can occur if cooled slowly

Rapid solidification techniques allow researchers to 

bypass the time-temperature transformation so a molten 

metal alloy forms without a crystalline order, creating a 

metallic glass.

“Glassy metals have some very unusual properties,” 

Kramer said. “On average, they tend to have very good 

strength, but not much plasticity, so they are hard to mold 

into shapes.”

However, by first forming a metallic glass, then heating 

the material back up, researchers can achieve metastable 

phases of the material that aren’t attainable by other methods, 

such as casting. And these intermediate phases may have 

desirable properties such as strength, ductility, resistivity, or 

conductivity. 

“Manipulating the phases, their sizes, the degree 

at which we can control their growth, and even their 

morphology, or shapes, are all buried in the details of the 

classical time-temperature transformation,” Kramer said. 

“A lot of the work we’re doing is trying to understand the 

relative balance of cooling rates to phase selection process. 

How can we predict and control those so we can move 

beyond an Edisonian approach.”

Researchers at Ames Laboratory use several techniques 

BY KERRY GIBSON

Frozen in a Flash

Ames Laboratory scientist Brandt Jensen loads a sample into 

the melt spinner. The induction coil melts the sample, which 

is then forced in a stream onto the spinning copper wheel.

I

RAPID SOLIDIFICATION KEEPS MATERIALS ON COOLING FAST TRACK
12 Inquiry Issue 1 | 2016 Inquiry Issue 1 | 2016 13

including melt spinning, injection casting, and high-pressure 

gas atomization (covered separately on pages 6-7) to produce 

small-grained and amorphous materials.

MELT SPINNING

This technique involves shooting a stream of molten 

material onto a spinning copper wheel where it solidifies 

quickly, forming a ribbon of metal. The copper wheel is 

typically water cooled and depending on the speed at which 

it spins, up to 30 meters per second, the molten metal is 

quenched up to 106 Kelvins per second.

“There are limits to the process,” said Ames Laboratory 

scientist and ISU associate professor of materials science 

and engineering Jun Cui. “The copper wheel must be 

perfectly balanced to spin at such high speeds. And 

beyond a certain point, the material no longer flows in a 

ribbon but breaks apart.”

There is also a variation in the process where the copper 

wheel has small grooves cut across its surface. These grooves 

intentionally break the cooled metal into short strips, which 

Cui said are easier to work with in some applications.

INJECTION CASTING

As the name implies, injection casting forces the molten 

material into a copper mold, typically a small cylinder that 

will produce short rods one to four millimeters in diameter. 

The mold is held inside a larger water-cooled copper mold 

providing quench rates fast enough to produce amorphous 

(glassy) samples in some alloys.

“Small samples—usually less than five grams—are 

placed in a graphite or quartz nozzle and rapidly heated by 

induction to several hundred degrees above the melting 

point,” said Matt Besser, Ames Laboratory scientist and 

manager of the Laboratory’s Materials Preparation Center. 

“We then drop it out of the heating zone and pressurize the 

system so the material squirts into the mold.”

By using different shaped molds, material can be cast in 

plates, or wedges. Besser said thermocouples can be placed 

along the length of the wedge to measure the difference in 

cooling rates from the fastest at the thin tip to the slowest at 

the thicker end.

“We’re able to fabricate samples to fit specific needs,” 

Besser said, “and it’s convenient because we can produce 

small samples, especially when the alloy contains 

expensive materials.”

One of the most common and robust ways to create a 

new material, particularly a metallic alloy, is to melt two or 

more constituent materials, mix them in the liquid state, 

then freeze or “solidify” them under certain controlled 

conditions. While seemingly simple, solidification processing 

can produce an incredible variety of material structures 

with important features on scales from nanometers to 

centimeters, giving rise to a host of remarkable properties 

ranging from enhanced strength and stiffness to unusual 

magnetic, thermal, electrical, and photonic properties. 

But the make-up and structure, and therefore the 

properties, of that end result can vary greatly depending on a 

variety of conditions present as the material transitions from 

liquid to solid. Ames Laboratory scientist Ralph Napolitano 

works to explain and predict what takes place at that liquidsolid interface and how those various interactions result in 

certain structures, chemistries and properties.

“When a material goes from a liquid to a solid phase, a lot 

of things must happen as part of that transformation,” said 

Napolitano, who is also an Iowa State University professor of 

materials science and engineering. “Nominally speaking, an 

amorphous or non-crystalline liquid phase has to reconfigure 

itself into some kind of crystalline packing. But many other 

simultaneous events are taking place to make that happen. 

Indeed, it is the way that the different transport processes 

and different structural entities enter into that equation that 

really influences what that final structure may look like.”

If equilibrium yields the normal or expected result, 

there are all kinds of deviations that can shift the result 

from equilibrium. Some of them are very small deviations, 

such as slightly different chemical compositions or 

slightly different concentrations of different kinds of 

crystalline defects. Deviations can also be very large—

completely different crystalline packing or composition 

or even an array of multiple phases that you might never 

see closer to equilibrium.

“What dictates how far away from the final equilibrium 

state you might be is what happens along that pathway 

from the equilibrium liquid to this far-from-equilibrium 

structure,” Napolitano said. “Varying the composition of 

a material and the rate at which we cool it has dramatic 

influence over final phase or assembly.”

“Beyond just the phase—the particular crystalline 

structure—conditions during freezing greatly influence the 

growth morphology,” he continued. “Any given phase will 

grow with a certain morphology that is dynamically optimized 

with respect to all of the different processes—such as the 

redistribution of heat, chemical species, and configuration 

of crystalline defects—making the overall transformation 

more efficient. Composition and cooling rate, along with 

the phase itself and the energies of the crystal defects 

and interfaces, all play a role in this collective dynamical 

optimization, ultimately resulting in the selection of the final 

state, which may look nothing like the equilibrium state. 

“This far-from-equilibrium 

synthesis provides a portal 

or pathway to structures, 

chemistries, and properties 

that aren’t accessible through 

conventional methods,” 

Napolitano said. 

To complicate matters, 

these pathways may include 

several other steps —before 

and after solidification, so 

that the complex freezing 

structure may only serve 

as some intermediate stage, 

along the way to a desired 

structure. 

Cooling rate provides a high level of control in certain 

windows. At the low (slow) end, cooling rate can be 

controlled very carefully, and even cooling rates from 

isothermal treatments to 100 degrees per second can be 

controlled reasonably well.

“We can go to cooling rates of 103 to 104 degrees per 

second with techniques like melt spinning, but within that 

window, process control is challenging and local variations 

exist,” Napolitano said. “We have investigated such 

variations, and our understanding has certainly increased. 

Even so, with relatively few ‘process knobs’ to turn (e.g. melt 

temperature, wheel speed, wheel material, injection rate 

and stream diameter) precise quantitative control remains 

a real challenge.” 

Seeking explanations for 

solidification puzzles

Jacob Fischer, undergraduate research assistant, loads a 

sample into the injection casting system. The melted material is injected into water-cooled copper molds.

As a strategy to reveal a clearer picture of the complex 

behaviors, Napolitano’s group has chosen to focus on a few 

select two-component or “binary” systems. In particular, 

binary systems, such as copper-zirconium and aluminumsamarium, provide great opportunities to investigate farfrom-equilibrium transformation. These systems exhibit 

complex competitive solidification, glass formation, and 

crystallization, forming a host of non-equilibrium phases and 

multi-scale growth structures. At the same time, with only 

two components, analytical and computational treatment of 

the thermodynamics and kinetics become more tractable, 

compared with multi-component systems. 

“With both of these systems, there’s a composition 

range over which the liquid forms a glass rather easily so 

you can cool it at rates that are achievable experimentally,” 

Napolitano said. “Once the alloy is glassy, other treatments 

can be used to crystalize the material at low temperature. 

In this regime, conditions can be controlled carefully, and 

reactions can be slowed substantially, even permitting insitu real-time investigation. Of course, having an accurate 

and comprehensive picture of the system thermodynamics 

is critical. Whether you’re solidifying the material directly 

from a liquid, or first quenching to a glass and then 

heating to crystallize the material, you still have that same 

thermodynamic playing field.”

The aluminum-samarium work is being expanded to a 

larger range of binaries, including other aluminum-rare earth 

alloys. In general, those systems are expected to exhibit 

similar behaviors, though Napolitano warns that very subtle 

effects can dramatically tip the balance between phases 

and growth structures. Very small energetic differences 

exist between the competing phases. Under high driving 

forces, these differences are often negligible and the kinetic 

pathways control the outcome. Even changes in chemical 

composition on the order of a percent or less can dramatically 

change the final state.

“This kind of study is only possible by bringing together 

many different approaches in theoretical condensed matter 

physics, materials science, computational thermodynamics, 

materials synthesis, and state-of-the-art characterization,” 

Napolitano said. “There is no doubt that this work requires 

the full gamut of experimental and computational capability 

and a team of investigators with a broad range of expertise.”

To that end, the new electron microscopy equipment at 

Ames Laboratory’s Sensitive Instrument Facility (SIF) will 

play a vital role. 

“It’s important not only in terms of spatial resolution, 

but some of the in situ capabilities as well,” he said. “Hotstage transmission electron microscopy with atomic scale 

resolution will allow us to look at some of the early stage 

dynamics that really are watershed events that tend to send 

the material down a whole different trajectory. So absolutely, 

the SIF is critical to moving forward in this area.”

Ralph Napolitano
14 Inquiry Issue 1 | 2016 Inquiry Issue 1 | 2016 15

reating materials in their solid state can be

tricky, but offers some advantages over other 

methods. It typically involves subjecting the 

component elements to some type of mechanical 

force—such as stress, shear or strain—to drive a reaction.

“You eliminate the need for solvents, so it removes 

potentially harmful substances from the waste stream,” 

said Ames Laboratory scientist and Iowa State University 

Distinguished Professor Vitalij Pecharsky, “and it offers 

greater selectivity so you can steer it toward a specific 

reaction. Most processing is done at room temperature so 

energy inputs are reduced and the resulting end products 

may be meta-stable as well.”

It also offers a pathway to materials that aren’t 

typically possible by other methods. One example is 

the work Pecharsky has done using ball milling. Using 

this mechano-chemistry technique, you can create a 

homogeneous mixture—a consistent blend throughout 

the entire sample—even though you start with a mixture 

of components that can be 99.9 percent of one component 

and only 0.1 percent of the second component.

“You can get complete dispersion,” Pecharsky said, 

“something that would be very difficult to achieve by 

melting the two components together.”

Because it doesn’t require solvents and often can 

be done without heat and with relatively low energy 

inputs, solid-state processing costs less than other 

methods. In many cases, it’s also scalable to industrial/

commercial applications.

MECHANO-CHEMICAL BALL MILLING

As the name implies, ball milling uses metal balls 

in a closed canister to shake, rattle and roll a chemical 

reaction that turns individual chemical components into 

a compound. Pecharsky said the impact of the balls with 

the container and each other, with the material mixture 

getting smashed between them, transfers the mechanical 

energy of the rattling balls into chemical energy that in 

turns drives the reaction.

The shear, stress and strain fractures the normal 

molecular structure of the component materials, allowing 

them to combine in ways that normally require a solvent 

C

to break the molecular bonds and let the reaction 

take place.

Pecharsky’s group is using the technique to investigate 

creation of metal hydrides to serve as a hydrogen storage 

medium. The group recently added a low temperature 

ball mill that allows processing of materials that are 

plastic or ductile.

“These materials will deform, but don’t fracture at 

room temperature,” Pecharsky said. “By lowering the 

temperature to that of a liquid nitrogen bath, like most 

things, they become brittle and we’re able to process them 

using this technique as well.”

FRICTION CONSOLIDATION

A brand new area for Ames Laboratory, friction 

consolidation uses high pressure and friction to grind, 

tear and press new materials into existence.

“It’s very fundamental,” said 

Ames Laboratory scientist and ISU 

associate professor of materials 

science Jun Cui. “We put material 

in a die and apply pressure with a 

rotating plunger. The friction from 

the rotating plunger creates shear 

stresses within the materials. They eventually heat up, 

soften and flow homogeneously. It’s a violent and chaotic 

process, but there’s also a certain amount of order to it.”

The process typically uses powdered metals which are 

easily consolidated because of the small initial size of the 

particles. Similar to ball milling, friction consolidation allows 

creation of microstructures not possible by other means.

“For example, you can take copper and process it with 

carbon nanotubes and wind up with a nanocomposite 

material that has greater mechanical strength than normal 

copper without any reduction in electrical conductivity, ” 

Cui said, “or may create a magnesium-titanium alloy that 

is corrosion resistant.”

Once the material has been consolidated, it can 

then be extruded or processed by a number of standard 

industrial methods.

GLEEBLE THERMOMECHANICAL SYSTEM

Another new technology for Ames Laboratory is a 

Gleeble system that allows laboratory simulation of any 

number of commercial materials processing techniques. 

The new equipment recently installed in the Laboratory’s 

Metals Development building lets researchers precisely 

control and measure what happens to materials during an 

array of industrial processes from casting and forging to 

sintering and extrusion.

“It allows us to do the precise measuring and monitoring 

of physical simulations of complex processes,” said 

Pete Collins, Ames Laboratory associate scientist and 

Iowa State University associate professor of Materials 

Science and Engineering, “as opposed to computational 

simulations. However, the two really go hand in hand 

—our measurements can validate and inform modeling 

simulations, and modeling can suggest the physical 

simulations we need to run.”

The equipment uses resistive heating to bring samples 

quickly to high temperatures needed to simulate melting, 

casting and welding—thousands of degrees in a few 

seconds. The electrical demands—enough power to 

run two or more average homes—were a primary reason 

for locating the equipment at Ames Laboratory. The 

equipment was part of Collins’ research startup agreement 

when he accepted the faculty position at Iowa State.

“It also made sense from a materials processing 

standpoint to have it located near the (Laboratory’s) 

other additive manufacturing tools, such as the LENSTM 

(laser engineered net shaping) 3D printer,” Collins said. 

“The Gleeble can be an important component of a highthroughput suite of capabilities, so we can rapidly test 

the array of alloy samples that the LENSTM system can 

produce. In addition, we now have the capability to assess 

other powder consolidation techniques. We can also take 

metals powders and simulate how those powders are 

processed under pressure and temperature to optimize 

the conditions for the best results.”

New paths to new materials

An array of ball milling canisters and stainless steel balls Vitalij Pecharsky’s group uses to process materials in their solid state.

Solid-State Processing:

BY KERRY GIBSON

A canister containing elements 

and stainless steel balls is clamped 

in place in a ball mill in 

preparation for shaking. 

Ames Laboratory researcher 

Shalabh Gupta loads material into 

a cryogenic ball mill used to process 

ductile or plastic materials. A liquid 

nitrogen bath cools the materials, 

making them brittle enough to be 

mechano-chemically milled.
16 Inquiry Issue 1 | 2016 Inquiry Issue 1 | 2016 17

wo-dimensional materials are a bit of a 

mind-bending concept. Humans live in a threedimensional world, after all, where everything 

observed in our natural world has height, width, 

and depth. 

And yet when graphene—a carbon material unique 

in its truly flat, one-atom-deep dimension—was first 

produced in 2004, the mind-bending concept became 

reality and an unexplored frontier in materials science.

Ames Laboratory scientists Pat Thiel and Michael 

Tringides are explorers on that frontier, discovering the 

unique properties of two-dimensional (2D) materials and 

metals grown on graphene, graphite, and other carboncoated surfaces. 

“Our work is somewhat of a miracle, if scientists 

can talk about miracles,” said Tringides, who is also a 

professor of physics at Iowa State University. “Only a few 

decades ago, no one would have believed that we could 

see individual atoms, but our capabilities now not only 

allow us to see them, but manipulate them, like a child 

building with Lego® bricks. We’re able to create these 

materials from the bottom up, ones that could never 

happen in nature.”

They’re created in a controlled laboratory setting, in 

an ultra-high vacuum environment, and investigated with 

the aid of scanning tunneling microscopy. After heating 

the substrate to high temperature all impurities and 

defects are removed. The substrate is cooled and atoms of 

interest are deposited one by one from specially designed 

sources. By tuning the temperature and deposition rate, 

the researchers search for the Goldilocks-like condition: 

atoms move not too fast and not too slow so a truly 2D 

material forms. 

While their research groups create a variety of surface 

materials in their work, the fabrications methods all have 

one thing in common: attempting to confine the assembly 

of the atoms to the 2D plane. That’s difficult, because it’s 

counter to what atoms naturally want to do under most 

conditions, to assemble in three dimensions. 

“Atoms are chaotic by nature; we are fighting this 

randomness in everything we do,” said Tringides. “In our 

work, atoms are precisely arranged on a highly reactive 

surface in a vacuum. Every aspect of the environment is 

controlled. Our work is to fabricate very small, very clean, 

and very perfect. Working on materials in the nanoscale 

demands it.”

T

2D MATERIALS REVEAL SURPRISING PROPERTIES BY LAURA MILLSAPS

Ultra-high vacuum equipment provides a clean, stable, and controllable environment for building 2D materials 

and investigating them through scanning tunneling microscopy.

 A scanning tunneling microscopy image of graphene. 

Pat Thiel Michael Tringides
18 Inquiry Issue 1 | 2016 Inquiry Issue 1 | 2016 19

BY STEVE KARSJEN

waste and municipal solid waste. Since these potential 

feedstocks are distributed, modular reactor designs offer the 

potential for economically converting them into useful fuels W and chemicals.

Learning how these materials behave is paramount. 

Because 2D materials are all surface with no bulk, a host 

of unique nanoscale properties—chemical, magnetic, 

electronic, optical, and thermal—can be attributed to them.

“There’s a rule book for the properties of bulk, or threedimensional materials—and it contains big chunks that 

are universally understood and accepted,” said Thiel, a 

physical chemist, materials scientist, and Distinguished 

Professor at Iowa State University. “But the rule book for 

2D materials is largely unwritten. There are lots of things 

we don’t know. We get lots of surprises, and then we must 

explain them.”

Writing the rule book to the behavior of these materials 

is only the first step in a larger goal; creating tunable 

materials that could be potentially useful in a host of 

tech applications, including ultrafast microelectronics, 

catalysis, and spintronics.

It’s the reason that Thiel’s and Tringides’ research has 

focused upon growing metals on 2D substrates over the 

last four years, turning it into a major strength of Ames 

Laboratory’s materials research. 

Graphene has gained a lot of enthusiastic attention in 

both scientific research and the tech industry because 

electrons travel very fast along its surface, explained 

Tringides. But to create functional devices, it necessitates 

patterns of nanoscale-size metal contacts on its surface, 

designed specifically for a desired function. 

“Whatever material we are trying to create, uniformity 

of the surface is the key to a functional device, and that 

is where our ‘perfect’ research comes in. That perfection 

makes us slow, but it’s a trade-off,” said Tringides. “If we 

can gain a thorough understanding of how these contacts 

can be produced under ideal conditions in a controlled 

environment, then these methods can be optimized 

eventually for commercial production and use.” 

Thiel and Tringides’ most recent success is the 

intercalation of dysprosium onto graphite layers. 

Intercalation is the introduction of a material into 

compounds with layered structures. That’s a real challenge 

with graphite, since its purely 2D surface results in “slick” 

layers with no good way to form bonds between them. 

“It’s like a stack of blankets on a bed,” said Thiel. 

“The blankets themselves are structurally sound, but two 

blankets stacked on top of each other slide around, slip off 

the bed, and are easily peeled off in layers.”

But the team has recently discovered the conditions 

under which they can create different types of intercalated 

metal-and-graphite systems, bonding those sliding blankets 

of material together two-dimensionally. It’s a promising 

new way to form a thin coating of a metal protected by 

a carbon skin, and could lead the way to materials with 

unique magnetic or catalytic properties. 

With such a narrowly focused and 

highly controlled experimental focus 

in basic science, it could be tempting 

to assume that their research, like their 

experiments, occurs in a vacuum. But 

Thiel credits the success of surface 

science at Ames Laboratory to the close collaboration of 

varied research groups. 

 “Ames Laboratory is a fertile environment for surface 

science experiments because we have the opportunity to 

collaborate directly with many scientists in diverse areas 

of expertise addressing the same problem from a different 

viewpoint,” said Thiel, including specialists in photonic 

band gap materials, optical physics, theory, and materials 

fabrication. “While that collaboration model has been 

adopted by other institutions and is the norm now, Ames 

Lab’s intimate size and community culture really started 

it all, and our achievements in surface science have 

benefited greatly from it.”

Dysprosium was found to make triangular-shaped crystalline islands on 

graphene. Characterizing the unique structures of materials grown on 

2D surfaces helps researchers better understand their possible electronic, magnetic, or catalytic properties.

“If we can gain a thorough understanding of how these 

contacts can be produced under ideal conditions in a controlled 

environment, then these methods can be optimized eventually 

for commercial production and use.”

hen Cynthia Jenks talks about Ames 

Laboratory’s scientific accomplishments in 

inorganic chemistry, she’s quick to credit any 

successes to the team of specialized scientists 

who are part of the Laboratory’s Chemical and Biological 

Sciences (CBS) program and the Division of Materials 

Science and Engineering.

“Whether designing new nanomaterials, devising new 

homogeneous catalysts, interfacing between homogenous 

and heterogeneous catalysts, or developing ionic liquids, our 

work involves scientists with a diverse skill set in inorganic 

chemistry,” said Jenks, assistant director of Scientific Planning 

and division director for Ames Laboratory’s CBS program.

Jenks said several CBS-based research projects are 

generating interest from the scientific community. For 

example, inorganic chemist Javier Vela is researching 

ways to design more efficient solar cells using a family of 

materials known as perovskites. Chemists Aaron Sadow 

and Igor Slowing are working on a project to design more 

energy-efficient catalysts using earth-abundant materials, 

and solid-state chemist Gordon Miller is using theoretical/

experimental investigation to identify new organic materials 

that show promising chemical and physical properties. 

One project involving teamwork at Ames Laboratory is a 

so-called “Big Idea.” This project, which includes scientists 

and engineers at 12 DOE national laboratories, resulted 

from a Big Idea Summit sponsored by the Department of 

Energy in 2015. Ames Laboratory’s part includes finding new 

catalytic technologies that can efficiently produce biofuels 

from diverse waste streams, including industrial waste, farm 

Cynthia Jenks

“When we all bring our expertise to bear on 

scientific challenges... the result can often be 

the creation of exciting new science.”
20 Inquiry Issue 1 | 2016 Inquiry Issue 1 | 2016 21

“If you want to do something like one of these ‘big ideas’, 

it’s never going to be a single person who will be able to solve 

these problems. It takes a team of scientists, from inorganic 

chemists to engineers to those who understand separations 

and modular design,” said Jenks. “When we all bring our 

expertise to bear on scientific challenges and study the 

foundations of the roadblocks to their success, the result can 

often be the creation of exciting new science.”

MATERIALS SYNTHESIS

Ames Laboratory associate scientist Javier Vela’s research 

focuses on the development of new optical nanomaterials, 

heterostructures, and devices 

for applications in catalysis, 

energy conversion, and 

biological imaging. 

“In my laboratory, we’re 

very good at making things, in 

our case, nano-sized particles of different compounds,” said 

Vela, who likens his work to that of a high end, scientific cook. 

Like any good cook, Vela begins with raw materials, which 

for him include different compounds, either crystalline or 

molecular. Then he consults his toolbox of available reagents 

and mixes in the appropriate amount of ingredients to make 

the appropriate material. It sounds easy, but according to 

Vela there’s little room for error. 

“We have mastered the art of knowing how to combine 

these reagents in the right proportions and under the right 

set of conditions to achieve the desired materials in the 

formulation and with the right properties we’re interested in,” 

said Vela, who is also an associate professor of chemistry at 

Iowa State University. “In the world of synthetic chemistry, 

whatever we make has to be reproducible; nothing can be 

by luck.”

Recently, Vela’s group of synthetic inorganic chemists 

has been cooking with two other Ames Laboratory and 

ISU scientists, Emily Smith, analytical chemist, and Jacob 

Petrich, ultrafast spectroscopist, who, like Vela, study 

organo lead-halide perovskite semiconductors. These tiny 

semiconducting optically active crystals are known to display 

intriguing electronic, light-emitting, and chemical properties. 

“My part of the work is to understand the synthesis issues 

going on inside these perovskites, which has led to several 

interesting phenomena,” said Vela. “With our increased 

knowledge, we are developing a rational, predictable approach 

to modify their structure and to enhance their properties to 

make them better.” 

Ultimately, Vela said, better organo lead-halide perovskites 

could lead to better construction materials for solar cells with 

20 percent solar power-conversion efficiency. 

CATALYSIS

According to Ames Laboratory associate scientist Aaron 

Sadow, much of today’s chemical manufacturing involves 

catalysis—the acceleration of chemical reactions. Many 

of these processes involve mixed-phase heterogeneous 

catalysis, but Sadow said there are also a large number of 

processes that use single-phase homogeneous catalysis, 

most commonly solution-phase catalysts.

Sadow, who is also an ISU associate professor of 

chemistry, has been partnering with computational 

scientists at Ames Laboratory to understand what happens 

at interfaces between liquids and catalytic solids. 

“We’re trying to measure the 

rates of reaction, understand 

mechanisms and then use 

those to guide site synthesis,” 

Sadow said. 

His group is involved in 

cutting-edge research involving 

the design of both homogeneous 

and heterogeneous catalysts 

using earth-abundant materials. 

These materials, like zirconium 

or magnesium, are cheaper and 

more plentiful than commonly 

used catalysts like platinum, 

rhodium and palladium.

“The interesting thing for me 

is these materials provide the 

opportunity to access new mechanisms and new pathways, 

and if we can understand those pathways, we can use these 

earth-abundant metals in interesting processes that could 

one day have an impact on industrial catalysis,” said Sadow. 

INNOVATIVE AND COMPLEX METAL-RICH MATERIALS 

Ames Laboratory associate scientist Gordon Miller is both 

a theorist and experimentalist, two diverse areas of expertise 

he combines to identify new inorganic materials that show 

promising chemical and physical properties. 

“We concentrate on intermetallic compounds because 

they are best suited for combined theoretical/experimental 

investigations,” said Miller, who is also an ISU professor of 

chemistry. “They also offer fundamental opportunities towards 

understanding relationships among chemical composition, 

atomic structure, physical properties and chemical bonding 

in materials due to their elegant complexity.” 

Miller collaborates with scientists throughout the Ames 

Laboratory, using a variety of synthetic approaches to produce 

new materials and then characterizes their atomic structure 

by X-ray diffraction. He also assesses possible chemical 

substitutions that can lead to changes in structure and 

properties. In this way, experiment 

and theory are engaged synergistically 

to yield new metal-rich materials. 

Miller’s approach has led to 

new magnetic refrigerants and 

quasicrystals. His group’s most 

recent work involves researching 

cluster chemistry of intermetallic 

compounds by introducing lithium, 

research that has resulted in the 

discovery of new complex structures 

based on clusters of icosahedra, 

and shows promise of yielding 

unprecedented clusters in solids.

Miller feels his greatest outcome 

has been the students and post 

docs he’s helped teach to approach 

scientific inquiry using both 

experiment and inquiry. “The kind of 

research my group does was not usual when I started 25-30 

years ago,” said Miller. “The field has really developed over 

that time.” 

This is a rendition of a one-dimensional, needle-like nanocrystal, 

such as the one prepared by Javier Vela in collaboration with Emily Smith and Jacob Petrich. Vela’s team has prepared a family of 

highly luminescent perovskite nanocrystals with shape correlated 

emission.

Javier Vela

Aaron Sadow

Gordon Miller

“The interesting thing 

for me is these materials 

provide the opportunity to 

access new mechanisms 

and new pathways, and if 

we can understand those 

pathways, we can use these 

earth-abundant metals 

in interesting processes 

that could one day have 

an impact on industrial 

catalysis.”
22 Inquiry Issue 1 | 2016 Inquiry Issue 1 | 2016 23

ature provides myriad examples of unique

materials and structures developed for specialized 

applications or adaptations. An interdisciplinary 

group of researchers at Ames Laboratory is trying to 

unlock the secrets that organisms use to build such complex 

structures so that power can be used to create materials not 

found in nature and not capable of being synthesized by 

conventional means.

“Nature has lots of examples of these hierarchical structures 

and they’re usually organic-inorganic composite materials,” 

said Surya Mallapragada, Ames Laboratory scientist and 

Iowa State University Carol Vohs Johnson Chair in Chemical 

and Biological Engineering. “A glass sea sponge skeleton is 

a perfect example of these structures that are templated by 

the organic phase. You have inorganic nanocrystals that form 

and it’s a multiscale assembly process, which in most cases 

happens at mild temperatures and conditions, such as pH.”

“So we look to nature for inspiration and as a source of 

bio-molecules to see how we can recreate some of those 

processes that create these wonderful materials with 

hierarchical assemblies or uniform structure,” she said.

So far, Mallapragada’s team has been able to replicate the 

creation of magnetite by studying magnetotactic bacteria. 

These bacteria form magnetic nanocrystals or chains of 

nanocrystals that they use to orient themselves with the 

Earth’s magnetic field. Using self-assembling polymer 

templates and proteins from the bacteria, researchers were 

able to grow magnetite crystals.

“We’ve used this approach successfully to grow magnetite 

nanocrystals,” Mallapragada said, “but we’ve gone beyond 

that, using these techniques to create cobalt ferrite and other 

magnetic nanocrystals that are not found in nature. That’s a 

great example of templated synthesis.”

The group has also worked with calcium phosphate to try 

to mimic the light-weight strength found in bones.

“In some case, we need to come up with synthetic 

analogs which can do the same job, but are more robust,” 

Mallapragada said. “In many cases, the biomolecules aren’t 

as robust. Proteins are fragile molecules so if we can do it 

with synthetic polymers, that gives us a lot more flexibility.”

It’s one thing to create nanocrystals. Getting those 

nanocrystals to then organize and form microstructures and 

then macro-scale structures is something altogether different. 

“They’re not at the level of complexity we see in nature 

—that’s the Holy Grail,” Mallapragada explained, “but 

that’s the inspiration and we’re trying to get there with 

synthetic approaches.”

The latest goal for harnessing this natural building process 

is the creation of metamaterials, so-called left-handed 

materials, that have interesting optical properties that don’t 

occur in nature.

“We’re looking at using organic templates to assemble 

inorganic particles to get the desired properties,” 

Mallapragada. “We have a very strong collaboration with 

Ames Laboratory physicists Costas Soukoulis and Thomas 

Koschny, and they’ve done some wonderful work with 

simulations and predictions of structures and developed 

some lithographic structures, but those are only 2D. So it’s 

really a perfect case for using these bioinspired approaches 

to self-assemble these metamaterials into 3D structures.”

Mallapragada again points to the glass sea sponge for 

the type of multiscale assembly that’s required to build 3D 

metamaterials.

“The sea sponge has order on multiple scales—nanoscale, 

micron-scale, millimeter-scale. It’s a multi-scale assembly— 

it looks like the Eiffel tower—and that’s why it has a very 

great strength to weight ratio,” she said. “So we need a similar 

hierarchy. Define the shapes at nanoscale, but then have an 

ordered arrangement of these nanoscale objects in 2D and 

then 3D to get the desired properties.”

In addition to using self-assembling polymers, which 

provide long-range order, DNA has also been used because 

it allows for specificity in the placement of nanoparticles. 

To create metamaterials, the team is looking at using both 

to control the placement of gold nanoparticles in a specific 

pattern, build up layers and then apply a gold film coating to 

the entire structure to acquire the desired properties.

“It takes a very interdisciplinary approach,” Mallapragada 

said. “We have molecular biologists (Marit Nilsen-Hamilton) 

for the DNA side, materials chemists (Mallapragada) for the 

polymer synthesis, Soukoulis and Koschny for the theoretical 

prediction of the structures and (physicist) Alex Travesset for 

modeling the kinds of structures can we get.”

“We need good characterization so David Vaknin is 

looking at scattering methods and Tanya Prozorov has 

been doing transmission electron microscopy work,” she 

continued. “Andy Hillier (chemical/biological engineer) has 

been involved in metallization, applying the continuous film 

of gold on those nano structured templates. So it’s a multilevel, multi-step, multi-component synthetic process.” N

Mother Nature should be flattered! 

Materials:

Bioinspired 

BY KERRY GIBSON

BORROWING FROM NATURE’S PLAYBOOK

Opposite and top right: A glass sea sponge skeleton showing the complex nature of its structure which provides amazing 

strength. (Photos by Michael Monn, Kesari Lab, Brown University.*) Top left: A micrograph of magnetic nanocrystals grown 

by Surya Mallapragada’s research group. 

*New functional insights into the internal architecture of the laminated anchor spicules of Euplectella aspergillum, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1415502112
Ames Laboratory

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www.ameslab.gov

2016

Issue 1

IN MEMORY

Karl A. Gschneidner, Jr.

“Mr. Rare Earth” - Friend, Mentor, Teacher

November 16, 1930 - April 27, 2016