DOD 

Researchers 

Provide

A Look Inside 

Nanotechnology

Special 

Issue

QUARTERLY

Volume 6, Number 1

A M P T I AC is a DOD Infor ma tion An alys is Center Adm inis te re d by th e De fen se Info rma tion Sys tem s Age n c y, De fen se Te chnical In fo rm ation Cent er and Opera ted by IIT Re s e a rc h Inst i t u te
One of my colleagues from the DOE made the comment a few

months ago over dinner that if his proposals did not have the

term “Nano/Info/Bio-Tech” in the title, there was little chance

of them getting funded. We all laughed and commented on

how sometimes the buzzwords of the moment influence our

re s e a rch efforts more than the warf i g h t e r, defense needs,

national interests, or for that matter, intellectual curiosity. How

many times have you written a proposal and carefully crafted

the title to utilize a word or phrase that at the time was recognized as a buzzword, just to grab a sponsor’s attention?

I am afraid we are all guilty, and in some respects, nanotechnology very effectively fits this category. You see it all over the

national media, from ABC to TLC, from USAToday to the

Wall Street Journal, and from Time Magazine to Scientific

American. And now this special issue of the AMPTIAC

Newsletter has landed on your desk, filled with information on

nanotechnology. Thus, one could say that we too have fallen

prey to the latest pop-culture trend of science.

Now that I have said what many of you may be thinking, let

me explain why we have dedicated significant portions of the

last 12 months to generating the thick, full color document you

hold in your hands, and why we hope that you will come away

from this with a better understanding of nanotechnology and

what it means to the DOD in the 21st century.

People have worked with the nanoscale for centuries, but

until recently lacked the analysis capability to understand its

impact. The 20th century dramatically changed that, first with

ground-breaking tools for investigating the microscale, then

even more astounding tools that enabled investigation of individual atoms. Armies of engineers have driven advances in processing capabilities which have enabled first micro-, then nanotechnology to move from science fiction to engineering fact.

Much like the assembly line revolutionized conventional manufacturing in the early 1900s, batch fabrication and bulk

micromachining have again turned industry on its ear. The

pace of these changes is increasing, with nanoprocessing already

in existence and growing at an exponential rate. Some used to

believe that a handful of computers would be enough to satiate

the world’s needs. Others believed that sequencing the human

genome would take decades, but it was finished in 15 years.

Today many people believe that molecular-level manufacturing

is impractical, but there are materials and structures being produced right now that we don’t even know how to test or analyze yet.

With the help of Dr. James Murday (Superintendent of the

Chemistry Division at the Naval Research Lab, and Director of

the White House initiated National Na n o t e c h n o l o g y

Coordinating Office) we have recruited a stellar team of DOD

researchers to explain how this field is making real contributions now, and what its potential contributions will mean to the

defense of our Nation in the future. In clear, unambiguous

terms, these authors have carefully laid out key aspects of the

science, physics, electronics, chemistry and engineering that are

advancing nanoscience at a blistering pace. From relatively simple coatings with five times the toughness and wear resistance

of conventional materials, to the building blocks of optical and

molecular-based computers that are generations ahead of current silicon-based machines, you will see that nanotechnology

is more than the latest “flavor of the month.”

If you are a regular reader of the Newsletter, then you already

know that AMPTIAC’s primary mission is to be a voice for the

defense materials and processing community. We therefore provide you within these pages a snapshot of what the DOD is

doing to utilize nanotechnology and nanomaterials in practical

terms to improve the readiness of the warfighter. After reading

this issue, you will see that today’s nanoscience is laying the

foundation for the future of nanotechnology, transitioning

many science-level advances to technology applications in the

near and long term. Nanotechnology is more than just a buzzword; it is a natural extension of the history of engineering

innovation that has brought us to this point in time. When the

visions of our researchers and the promise of this field are realized, nanotechnology could very well change the foundations

of engineering, manufacturing and culture.

Wade Babcock

Technical Content Manager

Editorial: Nanotechnology is More

Than the Latest Engineering

Buzzword

Cover Photo Credits: D.W. Brenner, J.D. Schall, and O.A.

Shenderova, Department of Materials Science and Engineering, 

North Carolina State University, Raleigh, NC 27695-7907
Special Issue: 

Nanotechnology

The Coming Revolution: Science and Technology of Nanoscale Structures ... 5

Dr. James S. Murday, Executive Secretary, Nanoscale Science, Engineering and Technology Subcommittee, US National Science and

Technology Council and Superintendent of the Chemistry Division, Naval Research Laboratory

At the most basic level of common understanding, nanoscience involves the study of materials where some critical property is attributable to an internal structure with at least one dimension less than 100 nanometers. This is truly the last frontier for materials science. As "nanotechnology" appears ever more often in the technical and popular media, defense researchers tackle the science and

technology that will transform nanoscience into practical technology. Dr. Murday provides an overview of the efforts of the

President’s National Nanotechnology Initiative, its accompanying work within DOD, and what they mean to the military, our

adversaries, and the future of this exciting field.

Emerging Technologies and the Army ... 11

Col. Kip Nygren, Professor and Head, Civil and Mechanical Engineering, US Military Academy

Technology is changing rapidly and often outpaces humanity’s ability to comprehend its advance. We, as humans, have always

relied on our superior abilities to gather and process information and make proper decisions in a timely manner. This skill spans

the ages from stalking larger mammals in a hunt, to defeating our enemies on the field of battle. Now more than ever, success on

the battlefield is dependent on the rapid access to information and the ability to act on that data. Changing technology presents

some tremendous opportunities as well as pitfalls. Col. Nygren delves into the world of advanced technology and how it is shaping tomorrow’s warfighter.

Polymer Nanocomposites Open a New Dimension for Plastics and Composites ... 17

Dr. Richard Vaia, Materials and Manufacturing Directorate, Air Force Research Laboratory

Humans place great importance on materials when talking about the past, from types of manufacturing to even more fundamental conventions of naming specific epochs after the materials used (i.e. Stone Age, Bronze Age, Iron Age). Today’s frontiers of materials technology are most definitely rooted in the combination of various materials to achieve specific goals with the greatest efficiency of properties. Dr. Vaia shows us how advanced plastics and composites designed for extreme service and environments are

blazing a trail for tomorrow’s incredible advances.

Power from the Structure Within: 

Application of Nanoarchitectures to Batteries and Fuel Cells ... 25

Dr. Richard Carlin, Director of the Mechanics and Energy Conversion Division, Office of Naval Research

Dr. Karen Swider-Lyons, Chemistry Division, Naval Research Laboratory

Probably one of the most established areas of nanotechnology is the use of nanomaterials in power generation and storage. While

highly dispersed nanoscale platinum particles have been used as electrocatalysts in fuel cells for years, the use of nanomaterials in

storage and generation is far from fully exploited. Each year, researchers push the envelope with advances in control and modification of nanoscale properties in electrode structures. Drs. Carlin and Swider-Lyons explain some of the most recent advances in the

state of the art.

MaterialEASE: Materials Engineering with Nature’s Building Blocks ... 31

Richard Lane, Benjamin Craig and Wade Babcock, AMPTIAC Technical Staff

May we suggest that you read this article first? Messrs. Lane, Craig and Babcock provide a comprehensive primer which introduces

the science of the nanoscale. The text is written at a level any reader, from the experienced nanotechnologist to the layperson, will

appreciate. Many basic aspects of the technologies described in the other articles in this issue are also explained in clear, concise

terms. This is definitely a good starting point for the non-“nano-savvy” reader.

The AMPTIAC Newsletter, Spring 2002, Volume 6, Number 1

A M P T I AC is a DO D Inform ation Anal ysis C enter Administe red by the Defense In form ation S ystems Age n c y, Defense Te chnical Inf ormat ion Center and Opera ted by I IT Re s e a rch Inst i t u te
Nanoceramic Coatings Exhibit Much Higher Toughness and Wear Resistance 

than Conventional Coatings ... 37

Dr. Lawrence Kabacoff, Materials Science and Technology Division, Office of Naval Research

Most military and commercial applications re q u i re surface coatings which can resist wear and corrosion. Often taken for granted,

these coatings can dramatically affect the standard service intervals for machinery, useful life of large components, and overall re a d iness of vital systems. While most ceramic coatings do wear ve ry slow l y, they usually fail from a lack of toughness and not a lack of

wear resistance. Dr. Kabacoff describes an innova t i ve processing method which utilizes traditional equipment to deposit films of

i n t e r m i xed nano- and microscale grains which stand up to we a r, but provide significant improvements in toughness and durability.

Nanoenergetics: An Emerging Technology Area of National Importance ... 43

Dr. Andrzej Miziolek, Weapons and Materials Research Directorate, Army Research Laboratory

From the first experiments with gunpowder and fireworks to the latest ammonium nitrate and powdered aluminum high explosives, man has sought to unleash the force of chemical explosives in more powerful and controlled ways. Nanotechnology allows

researchers to bridge the gap between pure chemical evaluation and microstructural analysis, and better understand the phenomena which make energetics work. Dr. Miziolek presents a guided tour of some of the most groundbreaking work going on today in

energetics and how nanoscience is improving our understanding of one of our oldest weapons of war.

The Army Pushes the Boundaries of Sensor Performance Through Nanotechnology ... 49

Drs. Paul Amirtharaj, John Little, Gary Wood, Alma Wickenden and Doran Smith, Sensors and Electron Devices Directorate, 

Army Research Laboratory

The battlefield is a place where too much information is rarely a problem. Our soldiers need every bit of data that can be collected and the field of available sensors and sensing systems is growing every day. An elite team of ARL researchers present some of the

latest thinking in sensor technology and describe how nanotechnology is changing the way sensors are designed, powered, deployed

and utilized in the battlespace.

Fabricating the Next Generation of Electronics from Molecular Structures ... 57

Dr. Christie Marrian, Microsystems Technology Office, Defense Advanced Research Projects Agency

Computers today are fabricated primarily from silicon, its oxides and nitrides, and thin films of metals, all deposited with patterning technologies that are quickly approaching a physical limit of resolution. What if the next paradigm of computing was based

not on the solid, electron conducting paths of silicon and metal compounds, but on molecules and the very atomic structures that

make up our own brains? Dr. Marrian takes us to the limits of molecular-based computing with healthy doses of science-fact and

practical evaluation of components and systems that may very well be the next revolution in computing.

Engineering the Future of Nanophotonics ... 63

Dr. Bob Guenther, Physics Department, Duke University

Dr. Henry Everitt, Associate Director of the Physics Division, Army Research Office

Optical components are already established as the foundation for tomorrow’s telecommunications systems, and are quickly becoming de rigueur in next generation computing technology. In order for this to move from the world of science to technological application, new ways of controlling, transmitting and conveying photonic information will be developed. Drs. Guenther and Everitt

examine the world of nanophotonics and show some of the systems that will transmit, generate, and indeed compute with light.

The AMPTIAC Newsletter is published quarterly by the Advanced Materials and Processes Technology

Information Analysis Center (AMPTIAC). AMPTIAC is a DOD sponsored Information Analysis Center,

operated by IIT Research Institute and administratively managed by the Defense Information Systems Agency

(DISA), Defense Technical Information Center (DTIC). The AMPTIAC Newsletter is distributed to more

than 25,000 materials professionals around the world.

Inquiries about AMPTIAC capabilities, products and services may be addressed to 

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Introduction

The term “Nanoscience” is appearing in the technical literature

at an increasing frequency and each reference offers its own definition, some of which are better than others. At the most basic

level of common understanding, nanoscience involves materials where some critical property is attributable to an internal

structure with at least one dimension limited to between 1 –

100 nanometers. Below that size, the disciplines of chemistry

and atomic/molecular physics have already provided detailed

scientific understanding. Above that size scale, the last 50 years

of condensed matter physics and materials science have provided a detailed scientific understanding of microstructures. So, in

some respects, one might consider the nanoscale to be the last

“size” frontier for materials science.

The interest in nanostructures extends beyond their individual properties. We have learned to exploit the natural selfassembly of atoms/molecules into crystals. The directed selfassembly of nanostructures (one, two and three dimensioned)

into more complex, hierarchical systems is also an important

1980 1985 1990 1995 2000

Year

Figure 3. Nanoscience 

Literature Citation Counts

Dr. James S. Murday

Superintendent, Chemistry Division, Naval Research Laboratory

Executive Secretary, National Science and Technology Council’s Subcommittee on Nanoscale Science, Engineering and Technology

Figure 1. Paleontology 

of Nanostructures

The AMPTIAC Newsletter, Volume 6, Number 1 5

Empiric Epoch Surface Epoch Nano Epoch

1960 1990

Nanolayer

Nanofilaments

Nanodots

Scanning Tunnelling Microscopy/Atomic Force Microscopy

Nanolithography (x10)

Self Assembly (x10)

Nanostructure (x10)

10000

9000

8000

7000

6000

5000

4000

3000

2000

1000

0

Figure 2. Superlattice 

Devices Formed through 

One-Dimensional NanoTechnology Processing

High Electron Mobility

Transistor (HEMT) 

High frequency receiver/

transmitter receiver

Quantum Cascade (QC) 

Laser Gas Sensor

Vertical Cavity Surface

Emitting Laser (VCSEL)

Fiberoptic data communications, optical sensors, encoder, range

finder Honeywell VCSEL

NRL InAs/AlSb HEMT

Lucent Technologies
goal. Without direct self-assembly, manufacturing costs would

severely limit the impact of nanotechnology.

While a scientific understanding of nanostructures is incomplete, their use in technology dates back at least two thousand

years. The Lycurgis cup, a Roman artifact pictured in the lower

left of Figure 1, utilized nanosized gold clusters to provide different colors depending on front or back lighting. The Roman

artisans knew how to achieve the effect, but were unaware of its

nanocluster basis. In the 20th century, nanostructures contributed to many significant technologies. Examples of these include the addition

of nanosized carbon particles to rubber for

improved mechanical properties (tires), the use of

nanosized particles for catalysis in the petrochemical industries, and the nucleation of nanosized silver clusters during photographic film

exposure. As depicted in Figure 1, one might

assign these examples to an empiric epoch in the

continuing evolution of nanotechnology.

Empirically-based technology, without

g reater scientific understanding, is usually difficult to extend or control. The scientific foundation of nanostru c t u res re c e i ved a quantum

a d vance when surface science enjoyed a re n a i ssance, starting in the 1960s. Su rface science constrained one material dimension into the

nanometer size scale. Events catalyzing that re naissance we re the development of new surf a c e -

s e n s i t i ve analytical tools, the ready availability of

ultra-high vacuum (a by - p roduct of the space

race), and the maturity of solid-state physics (surfaces re p resenting a controlled lattice defect – termination of re p e a t i n g

unit cells). The principal economic driving force was the elect ronics industry, but surfaces we re also re c o g n i zed to play an

essential role in many “re l i a b i l i t i e s” – adhesives, corrosion protection, friction, we a r, fracture, etc. From 1960 to the pre s e n t ,

s u rface science has pro g ressed from “clean, flat and cold” into

thin films (two or more nanoscale interfaces) and film pro c e s sTable 2. Characteristic Lengths In Solid State Science Model

Field Property Scale Length

Electronic Electronic Wavelength 10.-- 100nm

Inelastic Mean Free Path 1.-- 100nm

Tunneling 1.-- 10nm

Magnetic Domain Wall 10.-- 100nm

Exchange Energy 0.1 -- 1nm

Spin-Flip Scattering Length 1.-- 100nm

Optic Quantum Well 1.-- 100nm

Evanescent Wave Decay Length 10.-- 100nm

Metallic Skin Depth 10.-- 100nm

Superconductivity Cooper Pair Coherence Length 0.1 -- 100nm

Meisner Penetration Depth 1.-- 100nm

Mechanics Dislocation Interaction 1.--1000nm

Grain Boundaries 1.--10nm

Nucleation/Growth Defect 0.1 --10nm

Surface Corrugation 1.-- 10nm

Catalysis Localized Bonding Orbitals 0.01 --0.1nm

Surface Topology 1.-- 10nm

Supramolocules Primary Structure 0.1 --1nm

Secondary Structure 1.--10nm

Tertiary Structure 10.--1000nm

Immunology Molecular Recognition 1.--10nm

Table 1. Carbon Nanotubes: Prediction and Subsequent Confirmation

Prediction Experimental Confirmation

• Armchair single wall nanotubes (SWNT) metallic • Individual single-wall carbon nanotubes as quantum wires

Mintmire, Dunlap, White, Phys. Rev. Let. 68, 631 (1992) Tans, et al. Nature 386, 474 (1997)

• All metallic SWNTs have a linear dispersion relation e(k) near the • Two-dimensional imaging of electronic wavefunctions in carbon nanotubes

Fermi level with a slope in k vs.e of –1.88 nm-1 eV-1 Lemay, et al. Nature 412, 617 (2001)

Mintmire, Dunlap,White, Phys. Rev. Let. 68, 631 (1992)

• Elastic modulus should be similar to high stiffness in-plane modulus of • Nanobeam Mechanics: Elasticity, Strength, and Toughness of Nanorods

graphite, Robertson, Brenner, Mintmire, Phys. Rev. B. 45, 12592 (1992) and Nanotubes, Wong, Sheehan, and Lieber, Science 277, 1971 (1997)

• Bandgaps of semiconducting SWNTs should obey an analytic • Atomic structure and electronic structure of single-walled carbon nanotubes

relationship inversely proportional to SWNT diameter Odom, Huang, Kim, and Lieber, Nature 391, 62 (1998)

White, Robertson, Mintmire, Phys. Rev. B. 47, 5485 (1993)

• Bandgaps of quasi-metallic SWNTs are inversely proportional to the • Energy gaps in metallic single-walled carbon nanotubes

square of the SWNT diameter, White, Robertson, Mintmire, Ouyang, Huang, Cheung, Lieber, Science 292, 702 (2001)

Clusters and Nanostructured Materials, (Nova, NY 1996) p. 231

• Stability of metallic SWNT conduction channels in presence of • Recent Confirmation: Fabry-Perot interference in a nanotube electron 

disorder, leading to exceptional ballistic transport properties waveguide Liang et al., Nature 411, 665 (2001)

White, Todorov, Nature 393, 240 (1998) 

• Near the Fermi level all semiconducting (metallic) SWNTs with similar • Spatially resolved scanning tunneling spectroscopy of single-walled carbon 

diameters will have similar densities of states with the positions of the nanotubes, Venema et al., Phys. Rev. B. 62, 5238 (2000)

first few peaks obeying a simple analytic relation, White, Mintmire, 

Nature 394, 29 (1998)

6 The AMPTIAC Newsletter, Volume 6, Number 1
ing. Su rface science has provided the scientific underpinning

that enabled a key aspect of “Mo o re’s Law” – the rapid miniaturization of thin film electronics technologies. Su p e r l a t t i c e

devices (see Fi g u re 2) are a manifestation of the rapidly grow i n g

t e c h n o l o g y, where the individual layers are nanometers in thickness and the interfaces are controlled with atomic pre c i s i o n .

So, if nanotechnology has been around so long, why is it only

n ow the current rage? The 1990s nanoscience renaissance has

close parallels to the 1960 surface science renaissance. Fi r s t ,

beginning in 1980, the discove ry and development of prox i m a l

p robes, such as scanning tunneling micro s c o p y / s p e c t ro s c o p y,

atomic force micro s c o p y / s p e c t ro s c o p y, and near-field micros c o p y / s p e c t roscopy have all provided tools for measurement and

manipulation of individual nanosized stru c t u res. It took 10-15

years for reliable commercial instruments to come onto the market which then led to a rapid increase in re f e reed nanoscience

publications beginning in the early 1990s. Fi g u re 3 highlights

these increases for several subject areas. The pro p e rties of individual nanostru c t u res can now be observed, rather than re l y i n g

on ensemble-averaged values. In turn, those pro p e rties can be

defined in terms of composition and/or stru c t u res, and with

such an understanding comes the possibility for contro l .

Second, in addition to the new experimental measurement

capabilities, computer technology is now sufficiently advanced

(speed and memory capacity) such that accurate predictions,

even based on first principles (see AMPTIAC newsletter Vol. 5,

#2, page 1), are enabled for the number of atoms incorporated

in a nanostructure (see Table 1). Analytic predictions, made

years before experimental measurements could confirm their

validity, are now being proven true by direct experimentation.

There is no doubt that modeling and simulation will play a

leading role in the nanotechnology race.

Third, the disciplines of biology, chemistry, materials, and

physics have all reached a point where nanostructures are of

interest – chemistry building up from simpler molecules,

physics/materials working down from microstructures, and

biology sorting out from very complex systems into simpler

subsystems. If one expected to simply extrapolate the properties

of nanostructures from the size scales above or below, then

t h e re would be little reason for the current interest in

nanoscience or nanotechnology.

There are three reasons why nanostructured materials behave

very differently than their adjacent scales. 1) Large surface-tovolume or interface-to-volume ratios, 2) size effects (where

cooperative phenomena like ferromagnetism are compromised

by the limited number of atoms/molecules), and 3) quantum

effects. Many of the models for materials properties at the

micron and larger sizes have characteristic length scales of

nanometers (see Table 2). When the size of the structure is in

the nanometer range, those parameters are no longer adequate

to model/predict the property. As such, one can expect “surprises,” resulting in new materials behavior that may be technologically exploitable.

Finally, there are several economic engines driving the interest in nanotechnology, with information technology (electronics), biotechnology (pharmaceuticals and healthcare), and

materials being the most likely beneficiaries (see Table 3).

With these substantial scientific and economic opportunities, it’s not surprising to find strong global interest in fostering

nanoscience, with the intent of accelerating scientific discovery

into innovative commercial products. Table 4 compares estimated governmental funding in nanosciences around the

globe. From estimates of FY02 budgets, it is anticipated that

over $1.5B will be invested in nanoscale science and technology (S&T) in 2002. Care should be taken when comparing

Table 3. Potential Global Economic Impact 

of Nanotechnology in 15-20 Years [1]

Materials; Materials Processing $340B

Information Technology Devices $300B

Pharmaceuticals/Biotechnology $180B

Chemical Manufacturing, Catalysis $100B

Aerospace $70B

Tools, Automation, Life Cycle Costs $20B

Healthcare - Diagnostics, Prosthetics $30B

Sustainability - Agriculture, Water, Energy $45B

Total ~$1T

Table 4. “Nanotechnology” Research Program Investment ($M)

1997 2000 2001 2002

USA 115 270 420 600

Japan 120 245 500 900

Western Europe 125 200 250 300

Other Countries

(FSU, China, Australia, others) 70 110 200 400

Total 430 825 1,400 >2,200

Table 5. US National Nanotechnology Initiative Program ($M) 

(Funding Breakdown)

Category Lead FY00 FY01 FY02

“Fundamental” Research 87 140 *

Grand Challenges 71 125 *

Nanostructured Materials by Design NSF

Nanoelectronics, Optoelectronics, Magnetics DOD

Advanced Healthcare/Therapeutics NIH

Environmental Improvements EPA

Energy Conversion/Storage DOE

Transportation DOT

Microcraft and Robotics NASA

Instrumentation & Metrology NIST new

Manufacturing Science NSF new

CBRE Protection/Detection DOD new

Centers/Networks 47 66 *

Infrastructure 50 77 *

Ethical/Social Implications 15 21 *

Totals (est.) 270 429 600 

* Figures not available at press

The AMPTIAC Newsletter, Volume 6, Number 1 7
funding levels between different countries. For instance, one

estimate of nanotechnology investment in China is around

$25M/year; however, the manpower costs in China are significantly less than in the US, therefore, their investment is not as

small as it might otherwise seem.

US National Nanotechnology Initiative

The US response to the nanoscale scientific and economic

opportunities is the National Nanotechnology Initiative (NNI)

[2]. The funding categories for the NNI are provided in the

National Nanotechnology In i t i a t i ve supplement to the

President’s FY2001 Budget [3]. The annual investment levels in

nanoscience are presented in Table 5. It would be fair to say

that all of the S&T funded under the NNI is fundamental

research. On the other hand, the S&T activity designated as

“fundamental” in Table 5 corresponds to NSF investment

where the principal motivation is the generic knowledge base

and education.

In the ‘Grand Challenges’ section of Table 5, the fundamental research investments listed are selected with technological

ramifications in mind. The lead agency has the responsibility

for surveying the investment in the designated Gr a n d

Challenge and for identifying investment opportunities/shortfalls. There are three new grand challenges in FY02; the last,

‘C h e m i c a l / Bi o l o g i c a l / R a d i o l o g i c a l / Ex p l o s i ve (CBRE) for

Detection/Protection’, seeks to enable the considerable opportunities for nanostructures to impact homeland defense. As

with any rapidly changing technology, there is some anxiety

over potential economic, environmental and social disruption

by nanotechnology. In response, NSF has sponsored a workshop to address these issues [4]. 

It is expected that nanoscience/nanotechnology will enable

many important advances at the boundaries between traditional disciplines. Interdisciplinary research must be fostered to

accelerate that expectation. Cutting edge research will also

re q u i re expensive instrumentation for measurement and

manipulation of nanostructures. The Centers/Networks and

In f r a s t ru c t u re categories are

meant to address these two

points. Table 6 shows new

Centers initiated under the

NNI. The DOE Centers will 

be user facilities available to all

scientists/engineers in a way

similar to the DOE synchro t ro n

radiation facilities.

The NNI focuses on nanoscience as the enabler of nanot e c h n o l o g y. Experience has

s h own that it takes 10-20 ye a r s

for a scientific discove ry to lead

to a commercial product. However, among the surface sciencestimulated technologies, there

are a number of products now

entering the market. T h e s e

products are mostly the nanodots and nanowires that are the building blocks for systems, but

there are also composite materials. A representative listing of

those products is shown in Table 7.

DOD Contributions to the NNI

The DOD has been investing in fundamental nanoscience

research for over 20 years. One of the early programs dating

back to the 1980s was Ultra-submicron Electronics Research

(USER). In 1997, the DOD identified several S&T topics with

the potential for significant impact on military technology.

Nanoscience was selected as one of several special research area

(SRA) topics. A website [5] and coordinating committee were

established. Its current membership is comprised of Drs.

Gernot Po m renke (Air Fo rce), John Pazik (Navy), Bob

Guenther (Army), and Christie Marrian (DARPA). Further,

each Service has a coordinating group to guide its nanoscience

program (see Table 8). There are many potential areas where

nanoscience/nanotechnology may significantly impact DOD

missions. A selected listing is provided in Table 9.

Each Service has its own laboratory nanoscience programs

(see www.nanosra.nrl.navy.mil). The Army efforts in nanoelectronics, nanooptics, organic light emitting diodes (OLEDs)

and displays, sensors, and NanoElectromechanical Systems

(NEMS) are centered at ARL Adelphi; the work on organic

nanomaterials is largely at ARL Aberdeen. The Air Force nanomaterials program is largely centered at Wright Patterson AFB

in Dayton. This work is focusing on nanocomposites, inorganic nanoclusters, nanophase metals and ceramics, nanotribology,

nanobiomimetics and nanoelectronics. The Navy program is

centered at the Naval Research Laboratory in Washington, DC.

NRL has just created a Nanoscience Institute with the goal of

fostering interdisciplinary research that cuts across the NRL

organizational structures (http://nanoscience.nrl.navy.mil/). A

new Nanoscience Building at NRL has been specially designed

to minimize those noise sources that would limit measurement

and manipulation precision. The new building will open in

2003 (see Table 10). NRL is interested in collaborative projects

Table 6. Nanotechnology Centers

Center Title Investigator Institution

National Science Foundation

Nanoscale Systems in Information Technologies Buhrman Cornell

Center for Nanoscience in Biological & Environmental Engineering Smalley Rice

Nanoscale S&E Center for Integrated Nanopatterning & Detection Mirkin Northwestern

Center for Electronic Transport in Molecular Nanostructures Yardley Columbia

Nanoscale Systems and their Device Applications Westervelt Harvard

Center for Directed Assembly of Nanostructures Siegel RPI

DOE

Integrated NanoSystems Michalske Sandia/Los Alamos

Nanostructured Materials Lowndes Oak Ridge

Molecular Foundry Alivisatos Lawrence Berkeley

NASA

Bio/Nano/Information Technology Fusion TBD in 02

Bio-Nanotechnology Materials and Structures for Aerospace Vehicles TBD in 02

Nanoelectronics Computing and Electronics TBD in 02

DOD

Institute for Soldier Nanotechnologies TBD in 02

8 The AMPTIAC Newsletter, Volume 6, Number 1
with other Services that can exploit

this new building and its speciali zed nanoscience measure m e n t /

manipulation equipment.

Since some of the DOD nanoscience programs are nearly 20

years old, one might expect transition successes. One example fro m

each service is illustrated here .

Under Army funding Dr. Chad

Mirkin, Northwestern University,

invented a way to utilize nanoclusters of gold for the sensitive, selective detection of DNA. This technology has been demonstrated to

work for anthrax. It is now being

c o m m e rc i a l i zed by the start - u p

firm Nanosphere, and is presently

under clinical evaluation.

The Air Force funded Triton

Technologies Inc. under the SBIR

program to insert nanostructured

clay particles into polymers. One

benefit of this composite is reduced

gas permeability. This new material was marketed by Converse in

athletic shoe heels with gre a t e r

elasticity (He gas bubbles trapped

by the low permeability polymer

composite). The reduced permeability is also of interest to the

Army for packages containing

food, beverages and pharmaceuticals. The Navy is interested because

nanoclay particles increase the fire

resistance of organic composite

materials.

Table 7. Examples of Commercially Available Nanotechnology Products

Nanopowders

Altair www.altairtechnologies.com/ TiO2

Argonide Nanomaterials www.argnonide.com aluminum

Bosch www.bosch.de ceramics

BuckyUSA www.flash.net/~buckyusa/ fullerenes

Inframat Corporation www.inframat.com Yttria Stabilized Zirconia (YSZ), FeS,

n-WC/Co, Co/SiO2, Ni-Fe/SiO2

Nanomaterials Research Corp www.nrcorp.com oxides

Nanophase Technologies www.nanophase.com oxides

Nanopowder Enterprises www.nanopowderenterprises.com/ oxides, metals

NanoPowder Industries www.nanopowders.com/ precious/base metals

Nanox www.nanox-online.com/ ZnO

NexTech Materials www.nextechmaterials.com/ oxides

Plasmachem www.plasmachem.de diamond, alumina, SiC, Cu

US Nanocorp, Inc www.usnanocorp.com n-MnO2, n-Ni(OH)2, n-FeS2

Powdermet www.powdermetinc.com/ metals, ceramics

Nanomat Ltd (Ireland) www.nanomatgroup.com/ metal oxides

Nanowires/Nanotubes

Carbon Solutions (Sweden) www.carbonsolutions.se/ carbon nanotubes (CNT)

Carbolex www.carbolex.com single wall nanotube (SWNT)

Carbon Nanotechnology www.cnanotech.com/ SWNT

Hyperion Catalysis www.fibrils.com/ multiwalled nanotubes (MWNT)

Materials & Electrochem. Res. www.mercorp.com/ SWNT, MWNT

NanoLab www.nano-lab.com/ CNT and arrays

Sun Nanotech (China) www.sunnano.com/ MWNT

Piezomax www.piezomax.com/ Carbon Nanotube SPM Tips

eSpin www.nanospin.com/ polymer nanofibers

Nanocomposites

Inframat www.inframat.com/ magnetic nanocomposite

Nanocor www.nanocor.com/ clay in plastics

RTP www.rtpcompany.com/ CNT compounds

Southern Clay Products www.nanoclay.com/ clay in plastics

Triton Systems Inc www.tritonsys.com/ nanoparticles in plastics

Hybrid Plastics www.hybridplastics.com/ organic/inorganic hybrids

Table 8. DOD Points of Contact on Nanotechnology

Navy Nanostructures Working Group

Dr. Larry Cooper Electronics, ONR (larry.cooper@onr.navy.mil)

Dr. Eric Snow Electronics, NRL (snow@bloch.nrl.navy.mil)

Dr. Khershed Cooper Materials, NRL (cooper@anvil.nrl.navy.mil)

Dr. John Pazik Materials, ONR (pazikj@onr.navy.mil)

Dr. Richard Colton Biology, NRL (rcolton@stm2.nrl.navy.mil)

Dr. Keith Ward Biology, ONR (wardk@onr.navy.mil)

Dr. Gary Prinz Nanoscience Institute, NRL (gary.prinz@nrl.navy.mil)

Dr. James Murday Chair (murday@ccf.nrl.navy.mil)

Air Force Nanostructure Working Group

Dr. Gernot Pomrenke AFOSR (gernot.pomrenke@afosr.af.mil)

Dr. Richard Vaia AFRL/ML (Materials/Manufacturing) (richard.vaia@afrl.af.mil)

Dr. David Hardy AFRL/VS (Space Vehicles (david.hardy@kirtland.af.mil)

Mr. Dan Burns AFRL/IF (Information) (burnsd@rl.af.mil)

Mr. Ross Detmer AFRL/SN (Sensors) (ross.dettmer@afrl.af.mil)

Dr. Jim Gord AFRL/PR (Propulsion) (james.gord@afrl.af.mil)

Mr. Bill Baron AFRL/VA (Air Vehicles) (william.baron@afrl.af.mil)

Mr. Rik Warren AFRL/HE (Human Effectiveness) (rik.warren@afrl.af.mil)

Dr. John Corley AFRL/MN (Munitions) (john.corley@elgin.af.mil)

Dr. Don Shiffler AFRL/DE (Directed Energy) (don.shiffler@kirtland.af.mil)

Mr. Joe Orlowski AFRL/XP (Program Management) (joe.orlowski@afrl.af.mil)

Army Nanoscience and Nanotechnology Center

Dr. Andrew Crowson Coordinator, ARO (crowson@aro.arl.army.mil)

Dr. Paul Amirtharaj Sensors and Electron Devices, ARL (pamirtharaj@arl.army.mil)

Dr. Gary Hagnauer Weapons and Materials, ARL (ghagnau@arl.army.mil)

Dr. Raju Namburu Computation and Information, ARL (raju@arl.army.mil)

The AMPTIAC Newsletter, Volume 6, Number 1 9

Table 9. Nanoscale Opportunities with Major 

DOD Impact

Nanoelectronics/Optoelectronics/Magnetics

Network Centric Warfare

Information Warfare

Unmanned Combat Vehicles

Automation/Robotics for Reduced Manning

Effective Training Through Virtual Reality

Digital Signal Processing and Low Probability of Intercept

Nanomaterials “by Design”

High Performance, Affordable Materials

Multifunction Adaptive (Smart) Materials

Nanoengineered Functional Materials (Metamaterials)

Reduced Maintenance (halt nanoscale failure initiation)

BioNanotechnology – Warfighter Protection

Chemical/Biological Agent detection/destruction

Human Performance/Health Monitor/Prophylaxis
10

Under Navy funding, Inframat has developed a thermally

sprayed coating of alumina/titania nanopowders. The properties of this coating are far superior to the micropowder equivalent (see Table 11). This product was one of the R&D

Magazine selections as an R&D 100 product of the year for

2000 and it currently under field evaluation on Naval ships.

Conclusion

DOD programs in nanoscience are major contributors to the

NNI. The other articles in this issue present some of those programs and provide an assessment of the present state-of-the-art

in nanoscience/nanotechnology, with particular emphasis on

DOD needs. T h e re is clearly growing global interest in

nanoscience and nanotechnology, driven by the science opportunities and the expectation of large economic benefits. Since

the US will not dominate the advances in nanoscience and nanotechnology, it is incumbent on the DOD to invest in those

nanoscience/nanotechnology areas important to its interests, to

expeditiously convert nanoscience discovery into innovative

Defense technologies (thereby maintaining technology superiority over opposition forces), and to pay close attention to

developments outside the US.

Cited References

[1] Dr. Mihail Roco, NSF; also NanoBusiness Alliance

[2] http://nano.gov; IWGN Workshop Report with input from academic, private sector and government communities (also Kluwer

Academic Publisher, 1999, ISBN 0-7923-6220-9; Tel:(781) 871-

6600; email: kluwer@wkap.com)

[3] http://nano.gov/nsetrpts.htm

[4] “Societal Implications of Nanoscience and Nanotechnology” NSF

Report, March 2001 (also published by Kluwer Academic Publishing,

2001)

[5] http://www.nanosra.nrl.navy.mil

General References to the data in Table 11

1. Y. Wang, S. Jiang, M. Wang, S. Wang, T.D. Xiao, P.R. Strutt,

“Abrasive Wear Characteristics of Plasma Sprayed Nanostructured

Alumina/Titania Coatings,” Wear 237 (2000) 176-185.

2. R.W. Rigney, Presentation at ONR DUST Nanostructured Coating

Program (ONR contract No. N00014-98-3-0005), Cape Cod, May

17-19, 2000.

3. M. Gell, “Ad vanced Coating Technology De velopment for

Enhanced Durability and Reduced Cost in Naval Application,” ONR

Contract No. N00014-98-C-0010, June 1997-Dec 2001.

4. T.D. Ciao, Y. Wang, S. Jiang, S. Wang, D.M. Wang, & P.R. Strutt,

“Thermal Spray of Nanostructured Alumina/Titania Coatings with

Improved Mechanical Properties,” Procs. 2nd Intl. Conf. Surface

Eng., Wuhan, China, Oct 17-22, 1999, pp12-146. ■

Dr. James S. Murday received a B.S. in Physics from Case Western Reserve in 1964, and a Ph.D. in Solid State Physics from

Cornell in 1970. He joined the Naval Research Laboratory (NRL) in 1970, led the Surface Chemistry effort from 1975-1987, and

has been Superintendent of its Chemistry Division since 1988. From May to August 1997 he served as Acting Director of Research

for the Department of Defense, Research and Engineering. He is a member of the American Physical Society, the American

Chemical Society and the Materials Research Society; and a fellow of the American Vacuum Society (AVS), and the UK Institute

of Physics. For the AVS, he has served as trustee for 1981-1984, director for 1986-1988, representative to the American Institute

of Physics Governing Board 1986-1992, president for 1991-93, and representative to the Federation of Materials Societies 1998-

present. His research interest in nanoscience began in 1983 as an Office of Naval Research program of ficer and continues

through the NRL Nanoscience Institute. He has organized numerous International STM/NANO conferences and their proceedings. Under his direction, both the AVS and the International Union for Vacuum Science, Technology and Applications created a

Nanometer Science/Technology Division. He is Executive Secretary to the US National Science and Technology Council’s

S u b c o m m i t tee on Nanoscale Science Engineering and Te chnology (NSET) and Dire c to r, National Na n ote ch n o l o g y

Coordination Office.

Table 11. Properties of Inframat Nanoalumina/Titania Coating

(www.inframat.com)

Properties Conventional Nanostructured Improvement

Alumina/Titania Alumina/Titania

Toughness Poor Excellent Dramatic

Hardness (VHN) 1,000 VHN 1,000 –

Wear resistance

(N*m/mm3)

7.5 x 10

3 40 x 103

~

5X

Corrosion 

Resistance

Good Exceptional Significant

Grindability Poor Excellent Dramatic

Fatigue Life Failure @ <1 No failure up to

million cycles 10 million cycles >10X

Flex Tolerance Will result in Can be bent to

coating spallation over 180 without Dramatic

any spallation

Bond Strength (psi) 1,900 ~8,000 >4X

Table 10. NRL Nanoscience Building Requirements

Class 100 Cleanroom – 5,000 sq ft, ballroom style

Chemical (hoods, wet processing stations,...)

Dry Processing (dual focused ion beam, chemical vapor deposition,...)

Photolithography (pattern aligner,...)

Nanolithography (e-beam writer, dip-pen lithography,...)

Quiet Laboratories – 8 @ 400 sq ft

EMI <0.3 mG pp 60 Hz

Vibration <3μm/sec rms 10-100 Hz

Acoustic <35dB @ 1kHz

Temperature ±0.5 °C, <0.5 °C/hr

Humidity 45±5%

Ultraquiet Laboratories – 4 @ 400 sq ft

EMI <0.3 mG pp 60 Hz

Vibration <3μm/sec rms 10-100 Hz

Acoustic <25dB @ 1kHz

Temperature ±0.1 °C, <0.1 °C/hr

Humidity 45±5%

The AMPTIAC Newsletter, Volume 6, Number 1
The last decade of the 20th Century provided a glimpse of the

speed and magnitude of the revolutionary changes that will

profoundly transform society and the Army in the early part of

the 21st Century. The emerging technologies that will be the

major contributors to this transformation are biotechnology,

nanotechnology and robotics/artificial intelligence (AI). This

article considers how these technological innovations could

substantially change the nature of warfare and more importantly, highlight the Army’s need to overhaul its processes and

organization to cope with the acceleration of technological

change.

Emerging Technologies

Revolutionary technological change is coming, and two things

will be different about this change than changes in the past –

its magnitude and speed. The magnitude of change is going to

be significantly greater than we can presently envision. There is

broad agreement among experts about the general direction of

technology’s evolution, and that the three emerging technologies of biotechnology, nanotechnology, and robotics/Al are

driving the change. The information technology innovations of

the 1990’s will look tame when compared to the technological

revolution that will occur during the first decade of the 21st

Century, wrought by the synergism of these three technologies. 

BIO-ENGINEERING The sequencing of the human genome

and the genomes of other species have provided access to the

blueprints for the construction of biological entities and we are

at the early stages of learning how to make desired modifications to those entities. This knowledge paves the way for individualized drug therapies, noninvasive surgery, tissue and organ

engineering, neural and sensory implants, biological computing and countless other currently inconceivable possibilities. It

is clear that the quality and length of human life will be significantly increased, and that the promise of improvements

beyond current levels in all areas of human performance is

within reach [1].

NANOENGINEERING In 1986, K. Eric Drexler published a

book called the “Engines of Creation,” [2] which revealed his

vision of a practically utopian future that will be realized by

means of revolutionary machines and structures built on the

molecular scale. The size of these machines is measured in

nanometers (billionths of a meter) and they would theoretically be able to manufacture any physical item, assembling it molecule by molecule from the inside out. The objects produced

would be physically perfect because each and every molecule

would be placed in exactly the right position. The molecular

building materials would be obtained through the actions of

disassemblers, taking apart source materials molecule by molecule for the assemblers to use in construction. No materials

would be wasted and, therefore, pollution would be kept to an

absolute minimum.

The construction of a complex device would require the

assemblers to first replicate themselves to achieve a level of critical mass permitting complete fabrication of any desired part

within a reasonable period of time [3]. Figure 1 is a visualization of a nanoscale robot arm intended to move atoms in the

assembly process. The dream of molecular nanotechnology is to

do for the atom what information technology has done for the

bit [4]. This is the long-term, optimistic vision for nanotechnology, but even today methods of building nanoscale structures and machines are achieving some interesting and useful

results by building from the top down. A crystal is an example

of the natural growth of self-organizing nanoscale atomic structures, and similar properties are being exploited by researchers

to produce a variety of nanostructures including electrical,

Col. Kip Nygren

Professor and Head, Department of Civil & Mechanical Engineering

US Military Academy

Most of the articles in this special issue of the Newsletter address definitions, functions, and applications of nanotechnology and nanoengineered materials. Colonel Nygren takes a broader brushstroke, providing us with a greater perspective on the rapidly changing world

of high technology, and what role nanotechnology will play in the decades to come. An insightful and provocative look into the first half

of the 21st Century! – Editor

Figure 1. Nanoscale Robot Arm

(Drexler, NASA Ames)

The AMPTIAC Newsletter, Volume 6, Number 1 11
mechanical, electromechanical and quantum devices [5].

Potential capabilities include the proliferation of sensors and

actuators which could lead to “. . . clothes that respond to the

weather, interface with information systems, monitor vital

signs, deliver medicines, and automatically protect wounds; 

airfoils that respond to airflow; buildings that adjust to the

weather;” and “bridges and roads that sense and repair 

cracks; . . .” [6].

Microelectromechanical systems or MEMS, measured in

millionths of a meter, are currently used in a variety of applications, including the actuation of automobile airbags, fiber optic

data switching, and the direct integration of analog and digital

circuits on silicon chips used in cellular telephones. As published recently in Physics Today, “. . . the field of micromechanics will change the paradigm of what machines are, how and

where we use them, what they cost, and how we design them.

It may not be an exaggeration to say that we are on the verge of

a new industrial revolution driven by a new and completely different class of machines” [7]. While larger than nanoscale,

MEMS devices are still quite small. A MEMS-scale gear is compared to red blood cells and a grain of pollen in Figure 2.

ROBOTICS/ARTIFICIAL INTELLIGENCE The steady shrinkage of

electronic components will persist into an era of nanoelectronics and permit the processing power of computers to increase

well beyond that of the human brain. Computers already indirectly augment the processing capability of humans today, such

as when a word processing program helps to correct a writer’s

spelling errors. For many years, technology has provided

replacements for bones and joints, augmentation for sight and

hearing, and the support and replacement of damaged organs.

Augmentation of human memory and mental

processing through direct connection to computers will simply be a natural progression of these

existing trends [8]. Extreme miniaturization will

enable people and machines to interact in ways

that are unimaginable except in science fiction

novels. 

SYNERGISTIC COMBINATIONS As these technological advances

combine synergistically, they have the potential to positively

and profoundly transform the world. Nanoscale intelligent

robots could augment and repair living cells leading to the

extension of life and enhanced individual human performance.

Within 25 years, computers with a processing capability millions of times that of today’s computers will be capable of learning on their own [9]. The insights and knowledge they may

learn from reading the entire expanse of human knowledge are

bound to have momentous influences on our connections to

and control of our environment.

Currently, bacteria are being designed by deliberate modification of their DNA to produce protein molecules for computer memory. Laboratories at the University of Connecticut

and Syracuse University have designed and produced three

dimensional, gigabit scale memory modules for the Air Force

consisting of protein molecules suspended within a solid polymer matrix that can store electrons produced by photons of a

particular wavelength and release them on demand [10]. A 

similar three dimensional memory medium has also been 

created using molecular electronics [11]. These memories can

store information in a three dimensional array that is unaffected by electromagnetic impulses and extreme accelerations.

Exponential Change

Why is this great change going to occur at such a rapid rate?

Studies of technological change over the past century lead to

the conclusion that technology is evolving exponentially. This

is not surprising since all evolutionary change is exponential,

but what is surprising is the greater than expected rate of exponential technological change. Figures 3 and 4 show that manufacturing productivity and per capita GDP have increased in

approximately an exponential manner over the past several

years. A study of overall technological change by Raymond

Kurzweil indicates that technology is advancing at approximately a seven percent rate of increase per year, or to put it

another way, the effectiveness of technology doubled every ten

years in the twentieth century [12].

In the first half of the last century, technology evolved over

five doubling periods to become 32 times more advanced (or

more complex, or more important in the life of humans) in

1950 than it was in 1900. Now, continue the doubling of

progress every ten years during the later half of the century and

by the year 2000, technology had become about 1000 times

Figure 2. Micro Gear 

with Pollen and Red 

Blood Cells (Sandia 

National Labs)

12 The AMPTIAC Newsletter, Volume 6, Number 1

50μm

“We will experience an equivalent level of technological 

change in the first decade of the 21st Century to what 

we experienced in all of the 20th Century.”
more advanced, or important in our

lives, than in 1900. Astonishingly, half

of this change occurred in the last

decade of the century and it was certainly the 1990’s that brought the idea

of rapid technological change to the

attention of most observers. It is the

nature of exponential change to materialize faster than we expect it to, because

humans tend to be linear thinkers.

IMPLICATIONS FOR THE FUTURE By

2010, technology will be 2000 times

m o re advanced than in 1900.

Therefore, we will experience an equivalent level of technological change in

the first decade of the 21st Century to

what we experienced in all of the 20th

Century! Extrapolating to the end of

the 21st Century, one finds technology

will have progressed to become a million times more advanced than the

technology that existed in 1900. In

other words, we will experience a thousand times the technological progress

achieved in the 20th Century, during

the 21st Century.

But what about such technologies as

cars, airplanes, bicycles, the can opener,

the mouse trap and many others that

have not appeared to advance much at

all over the last few years, much less

exponentially? The history of technological advance is the story of countless

different technologies erupting exponentially onto the scene and then leveling off in their growth or improvement

in what is classically known as an S

curve of growth. It is the summation of

all technologies that is considered here

and that summation presents a global image of accelerating

change. This aggregate of technological change is probably best

captured by such indices as manufacturing productivity and per

capita GDP. These indicators are effectively exponential in

nature and therefore, provide strong support to the premise

that exponential change is a compelling model for understanding the accelerating advance of technology.

I mplications for the Army

Although the effects of emerging technologies on the future

Army cannot be known, we will speculate about some real possibilities for the future. 

THE DECISION CYCLE Consider the potential to augment the

especially stressful and demanding decision-making process

that is at the heart of winning battles and wars. An effective

model of this process was developed by Colonel John Boyd of

the Air Force from his observations of air to air combat in

Korea. It is known as the Observation – Orientation – Decision

– Act or O-O-D-A cycle. Observe - what is out there? Orient -

what does that mean to me and what are my options? Decide -

select the best course of action. Act - execute the course of

action and begin the process over again [13]. Consider some of

the ways this cycle can be enhanced by the emerging technologies under discussion, and specifically with the AI tool

Commander’s Associate.

Figure 4. US Per Capita GDP Change (US Dept of Commerce)

Figure 3. Manufacturing Productivity (US Dept of Commerce)

The AMPTIAC Newsletter, Volume 6, Number 1 13

Per Capita US GDP Current Year $

40,000

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0

5.2% Growth Rate or14 year Doubling Period

Year

450

400

350

300

250

200

150

100

50

0

2.8% Growth Rate or 25 year Doubling Period

Year

Manufacturing Productivity Index per Year
OBSERVE – Sense. The Army is already using autonomous

robotic vehicles as observers in Afghanistan and these will only

become more reliable and effective as they are employed in the

air, on the ground, and even under the ground. The miniaturization of machines, structures and electronics will make available large masses of sensors of varied types that can be deployed

over the entire battle area to continuously monitor all potential

enemy signatures. Automatic target recognition will relieve

some of the data processing burden and other capabilities may

include the obstruction and confusion of enemy attempts to

observe the telltale signatures of friendly forces.

ORIENT - Process the Information. The principal criticism

heard about information technology in the Army is that commanders and staffs cannot adequately process the vast quantity

of information available in a timely manner, resulting in more

confusion and less clarity. An AI tool known as the

Commander’s Associate will soon be available to alleviate this situation. This artificially intelligent assistant will assess and

assimilate all the incoming data, draw tentative conclusions in

collaboration with the commander and staff, and visually display the important information on a map or in any other

desired format. All this processing is accomplished nearly

instantaneously and will be continuously updated. 

Because the Commander’s Associate also knows all the friendly forces and dispositions, it can just as rapidly offer recommended courses of action. The commander will verbally interact with the AI associate to modify and consider a wide range

of feasible alternatives to accomplish the mission. By means of

sensitivity analysis, the AI associate will be able to assess the

impact of assumptions, advise which operational phases have

the highest risk, and predict probable enemy reactions -- all

accomplished in close collaboration with the commander and

his staff. Once again, these outcomes will be continuously

updated as more data is received.

DECIDE – Select the best Course of Ac t i o n. As the

Commander’s Associate becomes a trusted advisor and sounding

board for the commander’s ideas and judgments, it will be an

invaluable aide in laying out alternative courses of action,

demonstrating the strengths and weaknesses of each, and finally presenting a recommended action with full justification.

Once the decision is made, the AI associate can communicate

the decision and coordinating instructions to appropriate units

either electronically or physically by autonomous air or ground

vehicles. 

ACT – Make it happen. Most importantly, the AI assistant

can monitor all aspects of the action in real time and make recommendations to modify any phases of the plan as it is executed. The entire decision cycle could be completed in minutes or

e ven seconds, as the commander desires, and can 

be continuously iterated by the AI to account for new data.

Boyd demonstrated that the

cycle time is the critical factor in determining success

in combat. T h e

Commander’s Associate will

be instrumental in assuring

the friendly decision cycle

time is less than an opponent’s cycle time, therefore,

driving the opponent to inevitably take action based on an

observation that no longer applies. This will rapidly lead an

enemy commander to realize that he cannot influence the situation in any coherent manner, and with any luck, in total frustration he will lose the resolve to continue the conflict.

Weapon systems needed to create the violence, or the threat

of violence in combat, will change dramatically as a result of

emerging technologies. If we continue with the same basic

weapon types as today, then molecular manufacturing should

be able to produce these weapons, equipment and structures

with minimum weight and maximum strength. Artificially

intelligent and autonomous air, land and subterranean combat

robots in a wide range of sizes from nanometer to meter scales

will be employed individually and in swarms in conjunction

with soldiers to accomplish the mission.

SOLDIER SYSTEMS Soldiers will wear, carry and ride in a formidable new ensemble of weapons, sensors, communications

and protection systems. Each soldier will verbally communicate

with an artificially intelligent personal assistant computer.

Similar to the Commander’s Associate, the personal assistant will

help the soldier make sense of incoming data and offer recommendations for everything from movement routes over terrain

to the call for support fire. The soldier assistant can monitor all

soldier biological functions, begin immediate and comprehensive first aid assistance when wounded, and notify medical personnel when assistance is required. When appropriate, the AI

assistant can enhance human biological performance systems to

ensure the soldier is functioning at optimum capacity in any

situation presented to him. 

Other potential soldier systems include: [14]

• Active chameleon style camouflage systems for a wide

range of the EM spectrum

• Exoskeletons to augment human muscles

• Ballistic protection 5 to 10 times more effective than 

14 The AMPTIAC Newsletter, Volume 6, Number 1

“The Commander’s Associate will be instrumental in assuring cycle time

is less than an opponent’s ... driving the opponent to inevitably take

action based on an observation that no longer applies.”
current systems with correspondingly less weight

• Interactive textile/clothing that provides passive insulation and cooling; chemical and biological agent 

detection, protection, and decontamination; self cleaning;

and electromagnetic and radio frequency shielding

• Clothing and materials that provide energy harvesting,

conversion and storage

• Individual waste disposal, water recovery and recycling

LOGISTICS AND MEDICAL SUPPORT Robotics and artificial

intelligence will permit the continuous monitoring of the supply and maintenance status of all equipment and units. As the

logistics system automatically detects that a unit requires resupply, robotic ground and/or aerial vehicles will be dispatched to

transport the requisite classes of supply directly to the using

unit. With this degree of automation, some current levels of the

logistics system could be eliminated. With advanced biotechnology, the soldier’s health and level of performance can be

continuously monitored and supported in much the same way

as equipment and materiel. Medics using teleoperated surgical

equipment can attend to serious wounds at the lowest echelon.

The entire medical system will know almost instantly the status

of all soldiers and will be prepared to accommodate wounds

and injuries as quickly and proficiently as possible.

TRAINING The foremost benefit for training provided by

emerging technologies will probably be virtual reality simulations that permit the rehearsal of all combat operations at a very

high level of fidelity to include detailed depiction of terrain and

enemy behavior. Individual and unit combat skills can be faithfully honed in highly realistic surroundings against an enemy

designed to authentically respond under any environmental

conditions. Virtual reality training will be similar to the aircraft

simulators currently used to train airline and military pilots in

all aspects of flight.

ACQUISITION The increasing speed of technological change

will compel a complete revision of the current military technology acquisition processes. Technological innovations cannot

be developed in isolation from doctrine, organization, training

and leadership. An integrated and continuous Army transformation process must be established to optimize overall military

effectiveness for a variety of missions performed in all conceivable environments. 

THE DARK SIDE Technology is and always will be a doubleedged sword for society. As technology becomes more advanced

on the positive edge of the blade, so will it possess more potential for perils to society on the negative edge. In the wake of

recent terrorist attacks, the design of new technologies requires

a revision of the public safety design constraint: Public safety

now has gained a higher priority in a new environment where

it can no longer be assumed that individuals will take no deliberate actions that lead directly to their own demise. In some

cases, the public safety will demand a benign abort mode for all

technologies with a potential for harm above a specified energy

or lethality level. In other cases, access to the technology may

be severely restricted and ethical standards for design engineers

strictly adopted and rigidly enforced.

ETHICS AND ARMS CONTROL The importance of ethics and

professional responsibility in engineering design cannot be

overemphasized when weapons of mass destruction can be

inexpensively and straightforwardly created by anyone with

modest specialized knowledge and equipment. Arms control

style agreements offer one option for halting the spread of dangerous technology applications, but these agreements will not

include non-state terrorist and radical militant gro u p s .

However, arms control treaties would still be important tools to

restrain the dark side of emerging technologies, and the Army

could provide the prime forces for verification of compliance

with international treaties and agreements. In the case of nonstate sponsored militant groups, the Army could find itself a

major Homeland Defense Force team member, working closely with intelligence organizations to enforce United Nations

sanctioned ethical standards and controls on research into

unmistakably dangerous technologies; including infectious

biotechnology products, malicious information technology

viruses, and other nefarious weapons.

We are only beginning to come to grips with the new mission of Homeland Defense. It is a far-reaching mission that

involves extensive intelligence operations and sweeping requirements for security and special operations forces. Emerging

technologies can make substantial contributions to the protection, decontamination and neutralization of biologically infectious living organisms and nanoscale mechanisms. Highly sensitive micro and nanotechnology laboratories, constructed on

silicon chips using the same methods as integrated circuits,

could be inexpensively produced and even woven into clothing

to provide detection and decontamination.

The Army Must Meet the Challenge

The accelerating advance and increasing complexity of technology will put enormous strains on the capability of the military

to adapt to an uncertain future and still accomplish its core mission of national security. The Army must embrace change and

continuously transform itself not only technologically, but also

in its organization, doctrine, training, and leadership. Ed u c a t i o n

is the key to continuous transformation. Both individuals and

organizations must become increasingly better at learning and

modifying their behaviors in light of new knowledge and

insights. But this is another subject beyond the scope of this art icle. Howe ve r, the discussion must be joined now because the

u n relenting advance of technology cannot be stopped. 

References

[1] Anton, P.S., R. Silberglitt, et al. (2001). The Global Technology

The AMPTIAC Newsletter, Volume 6, Number 1 15
16 The AMPTIAC Newsletter, Volume 6, Number 1

Re volution: Bi o / Na n o / Materials Trends and their Synergies with

Information Technology by 2015. Santa Monica, CA, RAND.

[2] Drexler, K.E. (1986). Engines of Creation: The Coming Era of

Nanotechnology. New York, Doubleday.

[3] Drexler, K.E. (2001). Machine-Phase Nanotechnology. Scientific

American. 285: 74-75.

[4] Jacobstein, N. (2001). Technical Considerations in the Foresight

Guidelines for Na n o t e c h n o l o gy De ve l o p m e n t. 9th Conference on

Molecular Nanotechnology, Santa Clara, CA, Foresight Institute.

[5] Anton, P.S., R. Silberglitt, et al. (2001). The Global Technology

Re volution: Bi o / Na n o / Materials Trends and their Synergies with

Information Technology by 2015. Santa Monica, CA, RAND.

[6] Ibid.

[7] Bishop, D., P. Gammel, et al. (2001). “The Little Machines That

are Making it Big.” Physics Today 54(10): 38-46.

[8] Ku rz weil, R. (1999). The Age of Spiritual Machines: W h e n

Computers Exceed Human Intelligence. New York, Penguin Books.

[9] On the surface this may seem to be a preposterous claim, but there

is significant technological theory to back it up. For further information compare www. k u rz weilai.net and http://www. t r a n s h u m a n i s t .

com/volume1/moravec.htm for starters.

[10] Birge, R.R. (2001). Pro t e i n - Based Memories & As s o c i a t i ve

Processors. 9th Foresight Conference on Molecular Nanotechnology,

Santa Clara, CA, Foresight Institute.

[11] Marek, J.J. (2001). The Business of Nanotechnology. 2001 ASME

International Mechanical Engineering Congress & Exposition, New

York City, NY, The American Society of Mechanical Engineers.

[12] Kurzweil, R. (2001). The Singularity Is Near: A Book Precis,

Kurzweilai.net. 2001.

[13] Hammond, G.T. (2001). The Mind of War: John Boyd and American Security. Washington and London, Smithsonian Institution Press.

[14] Army Research Office (2001). Nanoscience for the Soldier

Workshop, Army Research Office. 2001. ■

Colonel Kip Nygren is Professor and Head of the Department of Civil & Mechanical Engineering at the US Military Academy,

a position he has held since 1995, having served in other positions on the faculty since 1987. He earned a doctorate in

Aerospace Engineering at Georgia Tech in 1986. Earlier his military career consisted of Armor and Aviation assignments in

Europe, Korea and the US and an acquisition assignment in Aviations Systems Command. His current research interests include

the interaction of technology and society, the history of technology and engineering education.
Introduction: Nanoengineered Materials

Materials and material development are fundamental to our

very culture. We even ascribe major historical periods of our

society to materials such as the stone age, bronze age, iron age,

steel age (industrial revolution), silicon age and silica age (telecom revolution). This reflects how important materials are to

us. We have and always will strive to understand and modify

the world around us and the stuff of which it is made. The next

societal frontiers will be opened not through understanding a

particular material, but rather by understanding and optimizing the relative contributions afforded by material combinations.

The nanoscale, and associated excitement surro u n d i n g

nanoscience and technology (NST), affords unique opportunities to create revolutionary material combinations. These new

materials will enable the circumvention of classic material performance trade-offs by accessing new properties and exploiting

unique synergism between materials that only occur when the

length-scale of morphology and the fundamental physics associated with a property coincide, i.e. on the nanoscale! The confluence of fundamental understanding of materials at this scale

and the realization of fabrication and processing techniques

that provide simultaneous structural control on the nano-, as

well as micro- and macro-, length scales is the core of the exciting area of nanoengineered materials. Examples of such material

technologies are rapidly increasing, impacting many diverse

areas of the commercial and military arena.

One of the ways nanoscience has advanced the state-of-theart has been to enhance and improve the properties of existing

conventional classes of materials. Polymer composites, for

example, have been a mainstay of high-performance aircraft for

over a quarter century, offering a multitude of desirable (and

tailorable) properties, such as high strength and stiffness, and

dimensional and thermal stability. With the advent and application of nanotechnology, polymer composites could become

even more attractive. As surely as polymer composites changed

the face of industry twenty-five years ago, polymer nanocomposites will usher in a new era in materials development.

Polymer Nanocomposites Opportunities

The reinforcement of polymers using fillers, whether

inorganic or organic, is common in the production of

modern plastics. Polymeric nanocomposites, (PNCs) or

the more inclusive term –polymer nanostru c t u re d

materials, represent a radical alternative to these conventional filled polymers or polymer blends. In contrast

to conventional systems where the reinforcement is on

the order of microns, PNCs are exemplified by discrete

constituents on the order of a few nanometers -

~10,000-times finer than a human hair. The relative

s i ze difference between conventional fillers and

nanoscale fillers is illustrated in Figure 1.

Uniform dispersion of these nanoscopically-size d

filler particles (or nanoelements) produces an ultra-large

interfacial area per unit volume between the nanoelement and host polymer. For example, interfacial area

approaching 700 m2/cm3 occur in dispersions of layered

silicates in polymers. This is comparable to a football

field within a raindrop! These dimensions also imply

that the distance between nanoelements is comparable

to their size. For a 1nm-thick plate, the distance

between plates approaches 10 nm at only 7 vol% of

plates. This is a morphology truly dominated by

nanoscale features.

Figure 1. Scanning Electron Micrograph of 

Conventional Graphite Flake Filler In An 

Elastomer Matrix. The Inset Shows a Scanning

Electron Micrograph of a Collection of ~500 

Multi-wall Carbon Nanotubes (MWNT) at the 

Same Magnification

The AMPTIAC Newsletter, Volume 6, Number 1 17

Dr. Richard A. Vaia

Materials and Manufacturing Directorate

Air Force Research Laboratory

10μm
This immense internal interfacial area and the nanoscopic

dimensions between nanoelements fundamentally differentiate

PNCs from traditional composites and filled plastics. These

characteristics imply the overall performance of PNCs can not

be understood by simple scaling arguments that begin with the

behavior of traditional polymer composites. Thus new combinations of properties derived from the nanoscale structure of

PNCs provide opportunities to circumvent traditional performance trade-offs associated with conventional reinforced

plastics, epitomizing the promise of nanoengineered materials.

From both a commercial and military perspective, the value

of PNC technology is not based solely on mechanical enhancements of the neat resin. Rather, its value comes from providing

value-added properties not present in the neat resin, without

sacrificing its inherent processibility and

mechanical properties. Traditionally, blend or

composite attempts at ‘multifunctional’ materials require a trade-off between desired performance, mechanical pro p e rties, cost and

processibility. The literature is full of examples

that suggest PNC technology provides a route

around these traditional limitations [1-6].

For example, consider the rapid advance of

p o l y m e r - l a ye red silicate nanocomposite

(PLSN) technology. Efforts within the last 10

years have demonstrated a doubling of the

tensile modulus and strength without sacrificing impact resistance for numerous thermoplastic (nylon and thermoplastic olefin

{TPO}) and thermoset (urethane, siloxane

and epoxy) resins through the addition of as

little as 2 vol% layered silicate. Recently,

General Motors and partners Basell, Southern

Clay Products and Blackhawk Automotive Plastics

announced external automotive body parts made

f rom thermoplastic olefinlayered silicate nanocomposites. A TPO nanocomposite with as little as

2.5% layered silicate is as

stiff and much lighter

than parts with 10 times

the amount of conventional talc filler. T h e

weight savings can reach

20 percent depending on

the part and the material

that is being replaced by

the TPO nanocomposite. On a volume basis, the nanocomposite parts cost about as much as conventional TPOs because

less material is needed to manufacture them and no new tooling is required to mold the parts. Overall, the weight advantage

could have significant impact on environmental concerns and

material recyclibility. For example, it has been reported that

widespread use of PLSNs by US vehicle manufacturers could

save 1.5 billion liters of gasoline over the life of one year’s production of vehicles and reduce related carbon dioxide emissions

by more than 10 billion pounds [6].

Considering the plurality of potential nanoelements, polymeric resins and applications, the field of PNCs is immense.

De velopment of multi-component materials, whether

microscale or nanoscale, must simultaneously balance four

interdependent areas: constituent-selection, fabrication, processing, and performance. For PNCs, this is still in its infancy,

and ultimately many perspectives will develop, dictated by the

final application of the specific PNC. Two main fabrication

methodologies have been developed for PNCs: in-situ routes

and exfoliation. Currently, exfoliation of layered silicates and

Figure 2. 7nm Ag Nanoparticles in Kapton

Figure 3. Ag-polybenoxazole Fiber

Figure 4. Liquid Crystal Nanodroplets in a Lamella Morphology

18 The AMPTIAC Newsletter, Volume 6, Number 1

200nm

150nm 1500nm

2μm
Figure 6. Nylon 

6-Layered Silicate

Nanocomposite

200nm

The AMPTIAC Newsletter, Volume 6, Number 1 19

carbon nanofibers / nanotubes in commodity and high performance resins are the most heavily investigated PNCs by

industrial, government and academic institutions world-wide

and will be further discussed below. Some examples of precommercial PNCs fabricated via in-situ methodologies are

provided in Figures 2, 3 and 4.

In-situ PNCs

In-situ routes to PNCs are based on the creation of the

nanoelement within the polymer matrix by chemical means or

phase separation. The polymer matrix provides the template

within which the nanoelement is formed. An example of this

route is the decomposition or chemical reaction of a precursor

introduced to the polymer matrix. Figure 2 depicts 7 nm-Ag

nanoparticles formed in the near-surface region of Kapton via

a solution infiltration approach that is amenable to microscale

pattern formation [7].

Figure 3 depicts a Ag-polybenoxazole nanostructured fiber

fabricated via a comparable approach [8]. These fibers are ultratough, electrically conductive, ~200-times stronger and ~50%

lighter than current aerospace signal wire cores. Another example of the in-situ methodology is chemical or processing 

perturbation of an initially homogenous polymer system comprised of a blend of two or more chemically discrete constituents to induce a controllable nanoscale phase separation 

of the constituents.

Figure 7. Comparison of 

Traditional Filled (bottom) 

vs Nanocomposite (top) 

Epoxy Optical Properties

Figure 5. Crystal Structure

of 2:1 Layered Silicates 

(Smectites) [10]

δ −

Exchangeable Cations

(Li+, Na+, K+, Ca+)

Gallery,

Interlayer

Tetrahedral layer

Octahedral layer

Tetrahedral layer

Silicate Layer

0.96 nm

O Al, Mg, Fe

Si OH

δ +
20 The AMPTIAC Newsletter, Volume 6, Number 1

Figure 4 depicts ~70 nm liquid crystal droplets organized within a lamella morphology with ~200nm layer spacing formed via

holographically-induced liquid crystal phase separation from a

photopolymerizable syrup at two magnifications. These structures result in ultrafast (ms) switchable diffractive optics and filters that have military applications. Similar behavior has been

demonstrated for patterning nanoparticles in photopolymerizable syrups [9]. The interested reader is encouraged to examine

the associated references [7-9] and explore related efforts in the

literature to disperse, arrange and/or in-situ form quantum

dots, oxide nanoparticles, metallic nanoparticles, nanowires,

proteins, enzymes, etc. in polymer hosts.

Layered Silicates

Layered silicates (alternatively referred to as 2:1 layered aluminosilicates, phyllosilicates, clay minerals and smectites) are the

most commonly used inorganic nanoelements in PNC research

to-date. Layered silicates possess the same structural characteristics as the well-known minerals talc and mica and are comprised of hydrated aluminosilicate [10]. Their crystal structure

and habit are summarized in Figure 5.

In the figure, the Van der Waals interlayer (or gallery) containing charge-compensating cations (M+

) separates covalently

bonded oxide layers, 0.96 nm thick, formed by fusing two silica tetrahedral sheets with an edge-shared octahedral sheet of

either alumina or magnesia. The charge per unit cell (generally

between 0.5 and 1.3) originates from isomorphous substitution

within the silicate layer (e.g. tetrahedral Si

4+ by Al3+ or octahedral Al3+ by Mg2+). The number of exchangeable interlayer

cations is also referred to as the cation exchange capacity (CEC).

This is generally expressed as milliequivalents/100g, and ranges

between 60 and 120 for relevant smectites. Variation in the

amount, type and crystallographic origin of the excess layer

charge results in a large family of natural (e.g. montmorillonite,

hectorite, saponite) and synthetic (e.g. Laponite, fluorohectorite) layered silicates exhibiting different physical and chemical characteristics, such as layer size, stacking perfection, reactivity and Lewis acidity. For example the lateral dimension of

the layers range from 20 to 1000 nm.

When exfoliated, an individual sheet is 1 nm thick, with

aspect ratios (diameter:thickness) in excess of 100.

Conceptually, the process of layered silicate dispersion in polymers can be likened to removing, and then arranging, millions

of sheets of paper from thousands of tomes on library shelves to

uniformly occupy all the free space in the library. The highly

anisotropic structure of the silicate layer is critical to provide

percolative behavior at low volume fractions, which manifests

in numerous physical property increases at small amounts of

dispersed layers. Figure 6 depicts the morphology of a Nylon 6

-layered silicate nanocomposite [11]. Dark lines are individual

layers of aluminosilicate, 1 nm thick, oriented perpendicular to

the sample surface. This structure results in enhanced mechanical properties at elevated temperatures, opening new opportunities for plastics in the automotive industry [6], as well as

reduced water and CO2 permeability, enabling improved food

and beverage packaging [4].

In general, nanoscale dispersion of the laye red silicate

platelets in resins produces glassy modulus enhancements of

one to two times and rubbery modulus increases of 5-20 fold.

Related increases in heat distortion temperature and enhanced

elevated temperature mechanical properties (strength and modulus) are commonly reported. Additionally, reduced thermal

expansivity (CTE), matrix swellability, gaseous permeability

and flammability upon 1-5 vol% addition of exfoliated layered

silicates will provide new opportunities for various resin systems. An abridged list of polymers investigated with layered silicate includes polystyrene, various polyamides (6, 6-6, 11, 12,

MDX), polyimides, polypropylene, ethylene vinyl acetate

copolymers, poly(styrene-b-butadiene) copolymers (SBS), elastomers (PDMS, EPDM, NBR), polyurethanes, poly(ethylene

oxide), poly(vinyl alcohol), polyaniline, epoxies, and phenolics.

Alexandre et al. [5], Beal and Pinnavaia [2], and Krishnamoorti

and Vaia [3] provide summaries of some of the polymers and

fabrication routes available in the open literature. The bottom

line is that these unique property combinations are observed

Figure 8. Demonstration

of PLSN Self-passivation 

Behavior

Figure 8a

Char Layer

Virgin Material 200μm

Figure 8b
The AMPTIAC Newsletter, Volume 6, Number 1 21

with surprisingly low volume fraction additions of layered silicate (1-5%), thus maintaining polymeric processibility and

reducing weight with respect to micron-scale counterparts

(>20% loading). Note that these comparisons are with regard

to conventional filled polymers and not with regard to continuous fiber re i n f o rced composites. PNCs may prov i d e

enhanced, multi-functional matrix resins, but should not be

construed as a potential replacement for current state-of-the-art

carbon-fiber reinforced composites.

From the military perspective, these enhanced polymer systems provide opportunities in many venues. In addition to a

general desire for higher-performance, higher use-temperature

resins and thermoplastics, PLSNs provide opportunities to

address material limitations in advanced system concepts.

Combinations of reduced impact resistance, CTE control, suppression of microcracking and increased modulus are currently

being examined for next-generation nanoscale rigid-particulate

reinforced resins for advanced fiber reinforced polymeric composites in unmanned aerial vehicles [12]. Thermal stability and

enhanced fire retardancy through char formation have motivated investigation of PLSNs as a component to anti-flammability additives for aircraft interiors [13]. Superior barrier properties against gas and vapor transmission have resulted in applications for food and beverage packaging for military rations

[14] and for barrier liners in storage tanks and fuel lines for

cryogenic fuels in aerospace systems. Also, depending on the

type of polymeric host, PLSNs display interesting ionic conductivity for solid-state electrolytes in batteries [15]. Finally,

along with enhanced scratch resistance and ballistic performance, the nanoscopic phase dimensions and low volume fractions enable maintenance of optical clarity, critical for scratchresistant face shields. Figure 7 compares the optical properties

of traditional filled and nanocomposite epoxy. In the figure the

optical clarity of exfoliated nanoscale morphology (top) is substantially better than the intercalated, conventional filler morphology at comparable loadings (bottom). Recent efforts have

begun to explore use of layered silicates as ceramic precursors

that will react in-situ with aggressive environments to form a

tough ceramic passivation layer on the polymer surf a c e .

Examples of such self-passivation/self healing during exposure

to a solid-rocket motor exhaust (top) and plasma environments

(bottom) [16] are shown in Figure 8. Combinations of the selfpassivation response with CTE control provide unique alternatives to current materials being examined for inflatable membranes for space antennas and solar collectors. Survivability in

real space environments is currently being examined for PLSNs

and other polymer nanocomposites through an exposure experiment on-board the International Space Station [17].

Carbon Nanotubes

In contrast to the 25+ year investigation of layered silicate dispersion in polymers, exploration of carbon nanotubes dispersion is relatively new, hindered until recently by the limited

a vailability of nanotubes. Howe ve r, nanotube-polymer

nanocomposites are garnishing substantial attention today

because carbon nanotubes offer opportunities to impart unique

electrical and thermal properties to the polymer resin as well as

to enhance mechanical and physical response. Figure 9 briefly

summarizes the structural aspects of carbon nanotubes [18].

Tube diameters can range from 1-100 nm with aspect ratios

(length : diameter) in excess of 100 or 1000! As with the layered silicates, the highly anisotropic nature of the tube is critiFigure 9. Images of Singleand Multi-walled Carbon

Nanotubes

Figure 9a Figure 9b

Figure 9c

Figure 9d

TEM cross section view of MWNT.

Tube wall

Tube Axis

Epoxy

3nm

Tube walls

Tube core

100nm
22 The AMPTIAC Newsletter, Volume 6, Number 1

cal to provide percolative behavior at low volume fractions,

resulting in graphite-like electrical and thermal properties at 1-

2 vol% additions.

Overall, carbon nanotubes (i.e. nanoscopically hollow fibers)

are generally considered in two categories: single wall nanotubes (SWNT) and multi-wall nanotubes (MWNT). SWNTs

are comprised of an individual graphene sheet (Figure 9a). The

individual tubes nominally aggregate into ‘ropes’ consisting of

face-center packed individual tubes. Figure 9b shows a transmission electron micrograph (TEM) of a random mat of these

SWNT ropes (Figures 9a and 9b courtesy of R. Smalley,

cnt.rice.edu/pics.html.) Substantial technological excitement

surrounds single-wall carbon nanotubes, based on theoretical

prediction and initial experimental verification of incredible

mechanical properties (E ~1 TPa [19]) and metal-like electrical

conductivity [18] of individual tubes. MWNTs are comprised

of nested single-wall tubes (Figure 9c). The external surface of

a MWNT is a graphene plane and the individual graphene

sheets within the tube interact via van der Waals forces.

Alternative gaseous MWNT fabrication routes also produce a

bamboo-like structure (Figure 9d) comprised of short segments

containing nested tubes with a finite orientation with respect to

the overall MWNT axis (c o u rtesy Applied Sciences, In c .) .

Terminal strained graphene sheets decorate the surface of these

tubes, providing chemical sites for facile surface functionalization and interfacial tailorability.

Challenges associated with the development of low-cost

manufacturing approaches, the processibility of raw SWNT

products and the maintenance of the SWNT properties during

nanotube-polymer fabrication and processing is limiting rapid

success of SWNT as polymer nanofillers. Current prices range

from $500-$1000 per gram for purified SWNTs. Nonetheless,

substantial academic and government investigations are currently addressing these issues.

In contrast, the commercial availability of multiwall nanotubes (MWNT) at $60-$100 per pound is facilitating exciting

successes today. Motivated by similar product considerations as

discussed for the PLSN systems (provide comparable mechanical properties as achieved with microscale fillers, but at lower

loadings, while maintaining processibility and delivering additional functionality), numerous pre-commercial successes have

been reported. For example, MWNTs have been used as direct

replacements to carbon-black in paint powders, providing sufficient electrical conductivity at an order of magnitude lower

filler loading to enable electrostatic powder coating of automotive parts (e.g. Hyperion Catalysis Int.). The ability to chemically tailor the external surface of the tube while maintaining

complete graphene planes within the tube core provides substantial flexibility to independently tailor mechanical, electrical

and interfacial properties. A potential drawback to MWNTs

relative to SWNTs is decreased mechanical reinforcement

because of the weak bonding between the graphene planes

within the tube. However, current applications driving nanotube reinforced plastics appear to be motivated more by addition of electrical and thermal properties than by substantial

(10-100x) mechanical property increases, and thus MWNTs

are expected to make substantial contributions in this arena.

Figure 10 shows homogeneously dispersed carbon MWNTs in

an elastomer matrix, providing a conductive plastic with elastomeric extensibility in excess of 500% [20].

From the military perspective, tailoring electrical or thermal

conductivity of polymer films, fibers or monoliths with very

low loadings provides revolutionary opportunities, spanning

from electro-magnetic shielding to thermally conductive composites to electrostatic discharge layers to smart fabrics for the

future solider. Furthermore, since these nanocomposites can be

tailored to be responsive to applied electrical fields, a range of

adaptive structures is envisioned. Even more revolutionary is

the concept of using the nanoscale percolative network of tubes

to controllably re m ove or transport electrical charge to

nanoscopically structured polymer regions between the tubes,

providing the foundation for technologies ranging from nextgeneration flexible photovoltaics to conformal antennas to

energy storage devices. The potential impact is pervasive, even

greater than that envisioned for PLSNs.

Challenges

Notwithstanding the considerable advances, excitement and

promise of exfoliated PNCs, substantial fundamental research

is still necessary to provide a basic understanding of these materials to enable full exploitation of their nanoengineering potential. Despite the large number of combinations of matrices and

potential reinforcing nanoelements with different chemistry,

size, shape and properties, all PNCs share common features

with regard to fabrication methodologies, processing, morphology characterization and fundamental physics.

The objective of PNC fabrication via exfoliation methodology is to uniformly disperse and distribute the inorganic filler,

initially comprised of aggregates of the nanoparticles, within the

p o l y m e r. The final PNC stru c t u re results from the transformation of the initially microscopic heterogeneous system to a

nanoscopically homogenous system. In general, four appro a c hes have been developed to fabricate PNCs via exfoliation - s o l ution processing, mesophase mediated processing, in-situ polymerizaFigure 10. Scanning Electron Micrograph 

of MWNT Dispersion In Silicone Matrix [20]
The AMPTIAC Newsletter, Volume 6, Number 1 23

tion a n d melt pro c e s s i n g . Each methodology has advantages with

respect to the processing steps necessitated by the desired final

form of the PNC (powd e r, film, paste, fiber, bulk monolith).

Substantial re s e a rch efforts currently endeavor to address the

fundamental challenge of providing general guidelines, including thermodynamic, kinetic and rheological considerations for

morphology control via these fabrication processes. For example, many potential military opportunities depend on successful

incorporation of the nanoelements in thermoset resins. Su rf a c e

functionalization must be carefully chosen to control polymerization rates and initiation points such that separation of the

a g g regate of nanoelements occurs before or during polymerization. This is because the extent of cross-linking reactions determines the gel-point of the matrix, and ultimately the extent of

exfoliation, hence the final PNC morphology [21]. Ad d i t i o n a l

complications arise from pre f e rential partitioning of the va r i o u s

chemical components in these multicomponent resin systems

( re a c t i ve oligomer, pre p o l y m e r, cro s s - l i n k e r, catalyst, etc.,) to the

nanoelement surface modifying reactivities and cre a t i n g

u n k n own gradients in network topology.

The key to any of these fabrication processes is the engineering of the polymer-nanoparticle interface. Surfactants are commonly used to facilitate this process. These range from small

molecules ionically associated with the nanoparticle surface,

such as with layered silicates, to chemically bound small molecules or physi-absorbed polymers for nanotubes. These surface

modifiers mediate interlayer interactions by effectively lowering

the interfacial free energy. Furthermore, they may serve to catalyze interfacial interactions, initiate polymerizations, or serve

as anchoring points for the matrix and thereby improve the

strength of the interface between the polymer and inorganic

filler. However, choice of the optimal modifier to date is at best

empirical. Most efforts currently focus on developing interfacial tailoring that achieves dispersion. This is done without

regard to providing the necessary thermal stability and desired

interfacial response for final form processing, or without a priori determination of the desired interfacial characteristics (e.g.

strong, intermediate or weak bonding) to maximize material

performance. However, these later considerations are paramount to providing components that have a reliable service life.

Developing an understanding of the characteristics of this

interphase region, its dependence on nanoelement surface

chemistry, the relative arrangement of constituents, and ultimately its relationship to the PNC properties is a current

research frontier in nanocomposites. Equally important is the

development of a general understanding of the morphologyproperty relationships for mechanical, barrier and thermal

response of these systems. This necessitates determining the

critical length and temporal scale at which the continuum

description of a physical process gives way to mesoscopic and

atomistic views of these nanoscale systems. This is one of the

current challenges for the burgeoning field of computational

materials science (see AMPTIAC newsletters Vol. 5, #2 and

Vol. 5, #3 for extensive information on the topic of

Computational Materials Science).

Summary

Polymer nanocomposites is a rapidly growing area of nanoengineered materials, providing lighter weight alternatives to

conventional, filled plastics with additional functionality associated with nanoscale specific, value-added properties. If the

promise and excitement surrounding layered silicates and carbon nanotubes are any indication, the future of PNC technology is truly boundless. The opportunities to extend PNC concepts to other nanoelements and polymer hosts are immense,

opening the way to provide tailor-made materials that circumvent current limitations and enable future concepts for the

DOD and the defense community at large.

Acknowledgements

The current article is based on previous collaborations with E.P.

Giannelis and T. Benson-Tolle. M. Alexander (Figures 1,8), E.

Manias (Figure 3) and T Bunning (Figure 2c) contributed to

the Figures. The Air Force Research Laboratory, Materials and

Manufacturing Directorate provided financial support. 

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Kurauchi, O. Kamigaito, J. Mater. Res. 8, 1174-1183 (1993).

Y. Kojima, A. Usuki, M. Kawasumi, A. Okada, T. Kurauchi, O.

Kamigaito, J. Polym. Sci.Part A: Polym. Chem. 31, 983 (1993).

[12] C. Chen, D. Curliss, SAMPE Journal, 37(5), 7-18, 2001.

[13] J.W. Gilman, Applied Clay Sci. 15, 1999, 31-49.

[14] G.W. Beall in Polymer-Clay Composites, T.J. Pinniavaia

and G.W. Beall eds, John Wiley and Sons, New York, 2001, p.

267. Yano, K. Usuki, A.; Okada, A. J. Poly. Sci. A: Polym.

Chem. 35, 1997, 2289-2294.
24 The AMPTIAC Newsletter, Volume 6, Number 1

[15] E. Ruiz-Hitzky, P. Aranda, B. Casal, J.C. Galvan, Adv.

Mater. 7, 1995, 180. Vaia, R.A., Vasudevan, S., Krawiec, W.;

Scanlon, L.G.; Giannelis, E.P. Adv.Mater. 7, 1995, 154-156.

[16] R.A. Vaia, G. Price, P.N. Ruth, H.T. Nguyen, J.

Lichtenhan, App. Clay Sci. 15, 1999, 67-92. H. Fong, R.A.

Vaia, J.H. Sanders, D. Lincoln, Chem. Mater, 2001, 13, 4123-

4129.

[17] Materials International Space Station Ex p e r i m e n t ,

MISSE, FS-2001-07-136-MSFC, ISS Mission 7A.1, STS-105.

[18] R. Saito, G. Dresslhaus, M.S. Dresselhaus, Physical

Pro p e rties of Carbon Nanotubes, Imperial College Pre s s ,

London.

[19] B.T. Kelly, Physics of Graphite (Applied Sci, London,

1987). Yu, Files, Arepalli, Ruoff, Phys. Rev. Lett, 84, 2000.

[20] M. Alexander, C.-S. Wang in Proceeding of 2nd Annual

Na n o s t ru c t rued Materials 2001: Application and

Commercialization, June 2001, Chicago.

[21] T. Lan, P.D. Kaviratna, and T.J. Pinnavaia, Chem. Mater.,

7, 2144 (1995). T. Lan and T.J. Pinnavaia, Chem. Mater., 6,

2216 (1994). ■

Dr. Richard Vaia is currently a senior materials scientist in the Air Force Research Laboratory. Additionally, he is Research

Coordinator for Nanotechnology in the US Air Force’s Materials and Manufacturing Directorate (AFRL/ML) and Direction Leader

for Polymeric Photonics in the Polymer Core Technology Area. Rich is an authority on polymer/inorganic nanocomposites and 

his research group focuses on 1) understanding processing-structure-property relationships of polymer-inorganic nanostructured

system for use in space and propulsion technologies; and 2) fabrication of complex core-shell nanostructures and development

of techniques to achieve three-dimensional control of particle arrangement on meso, micro and millimeter scales for photonic 

systems. 

Dr. Vaia received a Ph.D. from Cornell University (Dr. Emmanuel Giannelis, Materials Science and Engineering) in 1995, 

following a M.S. and B.S. in Materials Science from the Materials and Engineering Department at Cornell. He currently holds 

3 patents, is the editor of one book, and has published over 40 peer-reviewed journal articles in nanomaterials and nanotechnology.
The AMPTIAC Newsletter, Volume 6, Number 1 25

Introduction

The use of nanomaterials for energy storage and conversion in

electrochemical power sources is a rapidly growing field with

tremendous potential. Even though the use of nanomaterials in

power sources is not new, the science at the nanoscale has still

not been fully exploited. A prime example is the use of highly

dispersed nanoscale platinum particles (and more recently

alloys or mixed-metal systems) as effective electrocatalysts in

fuel cells. Although fuel cells have used nanoscale platinum catalysts for decades, their performance improves yearly as scientists learn to control and modify the nanoscale catalysts in the

electrode structures [1]. Due to advances in analytical instrumentation and modeling, the complex electrocatalytic processes in fuel cells, which require concurrent electronic and ionic

t r a n s p o rt with simultaneous catalytic activation at the

nanoscale, are beginning to be addressed in a scientific manner,

as opposed to previous empirical approaches. 

The challenges and opportunities for nanoscience in power

sources lie in the understanding, control, and fabrication of

complex structures and composites at the nanoscale. Only after

engineers and scientists have gained a strong footing in these

areas will it be possible to fully realize and exploit the capabilities of this technology. Certain phenomena are only possible on

the nanoscale due to the dominance of interfacial physics and

chemistry at large surface-to-volume ratios, such as the quantum interactions between nanoscale material phases. By learning to control the physics and chemistry at these small length

scales, one can envision nanoarchitectured materials engineered

to exhibit properties and performance that far exceed the “sum

of the parts.” One such revolutionary approach would be the

implementation of an array of individual electroactive nanoarchitectures performing ultra-fast computations, using singleelectron “bits” shuttled between a nanoscale electron storage

source and driven by nanoscale electrochemical voltage sources.

Figure 1. A Conceptual Nanoarchitectured, Integrated 

Battery-computer with Electro-optic Interfaces to the Macro-world

Dr. Richard T. Carlin

Director of the Mechanics and Energy Conversion Division

Office of Naval Research

Dr. Karen Swider-Lyons

Chemistry Division

Naval Research Laboratory

Cathode “Sink”

Quantum Dot

Anode “Source”

“Gate”

Nanoscale Electro-optic

Interface to Cathode

Nanoarchitectured Array: Anode/Cathode 

and Computational Element

Nanoscale Electro-optic

Interface to Anode

I/O Interface to Macro-World
26

Nanoarchitectured electro-optic devices could be used for

internal interconnects and to connect the array to the

m i c roscale world for data input-output and intermittent

recharging. Such a complex nanoarchitecture would remove the

limitations of electron transport between functioning nanoscale

components. The concept is illustrated in Figure 1.

The potential revolutionary benefits of nanoarchitectured

power-source materials, composites, and eventually multifunctional structures, make them prime strategic research areas. To

exploit these potential benefits, the Office of Naval Research

(ONR) and the Na val Re s e a rch Laboratory (NRL) have

embarked on the challenging path to develop these concepts.

This article provides examples of research directed toward

understanding, controlling, and fabricating complex structures

and composites for battery and fuel cell applications. Such

research is only in its infancy and is likely to undergo dramatic

evolutionary and revolutionary changes as insight into nanoarchitectures becomes clearer through scientific investigations in

all research areas. While the examples presented here come primarily from work supported by ONR, a tremendous amount

of similar and related research is ongoing around the world and

is introduced where appropriate. Recent insightful overviews

on electrochemical applications of nanomaterials have

appeared, including topics on aerogels [2], nanostructured battery materials [3], production of nanostructured electroceramics [4], and nanostructured solid-state electrolytes [5].

Batteries

Battery cells are fundamentally composed of three active components: an anode (negative electrode), a cathode (positive electrode), and an electrolyte. The functions of the anode and cathode are to store, release, and reincorporate electrons and

charge-balancing ions during discharge and charge cycles, thus

the electrodes must possess both high ionic and electronic conductivities. The amount of electrical charge stored by an electrode is referred to as the electrical capacity, typically expressed

either in units of amp-hours per kilogram (Ah/kg) or amphours per liter (Ah/l). Electrical capacity is multiplied by the

electrochemical potential of the battery to obtain its total available energy on a weight or volume basis, typically expressed in

units of Watt-hours per kilogram (Wh/kg) or Watt-hours per

liter (Wh/l) respectively. The electrodes interchange ions in a

cell through an electronically insulating electrolyte (liquid or

solid) that has high ionic conductivity to minimize internal

battery resistance. Cells are used individually or linked in series

or parallel to meet the capacity and energy requirements of an

external load. Additional information on batteries is readily

available from many resources [6-9].

The focus of many current battery research and development

programs is lithium-ion and lithium-metal batteries [9]. The

cathodes for both these cell chemistries typically contain a transition-metal oxide lithium-insertion compound, such as

LiCoO2. The anodes for lithium-ion batteries are usually a

lithium-carbon insertion compound or a lithium-metal alloy,

while metallic lithium is employed as the anode in lithiummetal batteries. Either an organic liquid or a solid-state lithium-ion conductor serves as the electrolyte in both lithium-ion

and lithium-metal batteries. During operation, lithium ions

shuttle between the electrodes through the electrolyte, while

electrons are driven through the external electrical circuit by the

electrochemical potential (typically 3 to 4 V). A Lithium-ion

battery being charged is depected in Figure 2.

Lithium Battery Anodes

Lithium metal offers the highest theoretical specific capacity of

any anode material (3,862 Ah/kg), but dendrite formation durFigure 3. Highresolution TEM

of 1:2 Mole

Ratio Si/TiN

Nanocomposite

Anode

Figure 4. High Licapacity Templated

Anode Consisting of

110-nm Diameter

SnO2 Nanofibers

[15]

Figure 2. Illustration of a Lithium-ion Cell

(Figure Courtesy of D. Sadoway and

A. Mayes, Massachusetts Institute of

Technology)

External Charging

Circuit

Anode Electrolyte Cathode

Li+

Li+

Li+

Li+

e

- e

-

LiMOx Carbon Polymer

Li+

Li+

Li+

Li+

Li-Carbon

Li-Alloys

SnOx/Sn

20nm

The AMPTIAC Newsletter, Volume 6, Number 1
The AMPTIAC Newsletter, Volume 6, Number 1 27

ing cycling has thus far prevented its practical use in rechargeable batteries. Dendrite formation can lead to cell shorting and

to the formation of small particles of metallic lithium that can

undergo detrimental, exothermic reaction with the organic

electrolytes. Lithium alloys are viable options for high-capacity

anodes (LiAl alloy: 993 Ah/kg and 2,681 Ah/l based on the

weight and volume of Al, respectively); however, most of the

desirable alloying metals undergo large dimensional changes

upon lithium alloying that cause fragmentation and rapid

capacity loss during cycling. Most current battery development

therefore focuses on lithium-ion chemistries with graphitic

anodes having theoretical weight and volume electrical capacities of 372 Ah/kg and 837 Ah/l, respectively.

Recently, researchers have discovered that nanoscale tin (Sn)

particles encapsulated in an inert inorganic matrix can undergo

reversible lithium alloying over many cycles with minimal losses in capacity [10]. Some examples of these nanocomposite

anodes include Sn-B0.56P0.4Al0.42O3.6 glass (600 Ah/kg, 2,200

Ah/l) [10], Sn2Fe-SnFe3C (620 Ah/kg, 1,600 Ah/l) [11], and

Sn-Li2O (600 Ah/kg) [12]. The exact role that the nanocomposite structure plays in anode cycle-life and capacity is not well

understand and is an active area of research [3].

With the identification of appropriate nanoscale structures,

new nanocomposite materials are being designed for use as

high-performance lithium-ion anodes. For instance, Professor

Prashant Kumta’s research group at Carnegie Mellon University

is fabricating nanoscale composites of silicon (Si) and titaniumnitride (TiN) with high lithium capacities [13]. The Si phase

reversibly alloys with lithium to form a high capacity storage

medium, while the TiN phase is non-reactive with lithium, but

has high mechanical strength to prevent cracking, and is a good

electrical conductor (2-5x104 -1 cm-1). When mixed together

at the nanoscale, the Si/TiN composite has the electrical and

mechanical pro p e rties needed for a high-capacity lithium

anode. A 1:2 mole ratio Si:TiN nanocomposite obtained after

12 hours of high energy mechanical milling (HEMM) exhibits

a stable capacity of 300 Ah/kg. This is lower than the theoretical value of 776 Ah/kg, calculated assuming complete reaction

of Si with 4.4 molar equivalents of Li; however, the experimental volumetric capacity of 1,100 Ah/l exceeds that of a lithium graphite electrode by 30%. A high-resolution transmission

e l e c t ron micrograph (TEM) of a 1:2 mole ratio Si / Ti N

nanocomposite is shown in Figure 3, in which the dark spots

are electrically conducting TiN nanoparticles of <20 nm diameter embedded in an amorphous Li-ion conducting Si phase.

From TEM and x-ray diffraction studies, it appears that the

nanocomposite consists of nanoscale TiN particles embedded

in an amorphous Si phase. Ongoing work intends to increase

the lithium capacity and overall performance of the Si/TiN

anode using various strategies, including determining and eliminating the sources of interfacial resistances between the Si and

TiN nanoparticles.

Another promising developmental approach to nanoarchitectured lithium-alloy anodes is to use templated nanostructures to fabricate nanoscale materials having the specific sizes

and dimensions needed for optimum performance. This work

was pioneered by Professor Charles Martin (University of

Florida, Gainesville) with support from ONR [14]. One example is a templated anode consisting of 110-nm-diameter SnO2

nanofibers (shown in Figure 4) irreversibly reduced to a Snbased nanocomposite. This anode is capable of 800 reversible

charge-discharge cycles with capacities exceeding 700 Ah/kg

[15]. In addition, discharge rates are an order of magnitude

g reater than those achieved in conventional lithium-ion

anodes, and capacity losses of the nanocomposite anode are

minimal at these rapid discharge rates. The performance of

these nanoarchitectured anodes is attributed to the small size of

the individual nanofibers and to the small domain size of the

Sn grains within the nanofibers.

Lithium Battery Cathodes

Numerous materials have been studied for use as lithium-metal

and lithium-ion battery cathodes, including metal oxides,

metal sulfides, conducting polymers, and polysulfides.

Transition-metal oxides are the most successful materials

because of their chemical and structural stability, high lithiumion capacity, and favorable electrical properties (such as high

conductivity of lithium-ions and electrons). Table 1 summaTable 1. Performance of Selected Transition-metal 

Oxides as Lithium-ion Battery Cathodes

Cathode Theoretical Practical Average

Material Capacity Capacity Cell Voltage

(Ah/kg) (Ah/kg) (V)

LiCoO2 274 142 3.6

LiNiO2 275 145 3.6

LiNi0.8Co0.2O2 274 180 3.6

LiMn2O4 148 120 3.8

Figure 5. (a) TEM of POEM-b-PMMA 

Containing a Precursor 

Gold Salt (LiAuCl4)

(b) A Conceptualization of a Highly

Reversible Self-organizing 

Nanocomposite

Electrode (SONE)

250nm

Figure 5a Figure 5b

POEM Region with

Au Nanoparticles

PMMA Region
28 The AMPTIAC Newsletter, Volume 6, Number 1

rizes the theoretical and practical performance of state-of-theart metal oxide cathode materials. The theoretical capacity is

calculated from the total lithium-ion content of the compound,

whereas the practical capacity corresponds to the actual amount

of lithium that can be reversibly intercalated. (Cell voltages

quoted in Table 1 assume a lithium-graphite anode.) The practical lithium capacity of the oxides is lower than the theoretical

lithium capacity, because the metal-oxide structures allow only

a portion of the lithium ions to be reversibly accessed during

electrochemical cycling.

In addition to the materials listed in Table 1, the lithium-ion

intercalation properties of vanadium oxides have attracted a

great deal of interest. The vanadium oxides display a range of

V:O molar ratios (e.g., V2O5, V3O8, and V6O13) and possess

good lithium capacity; however the voltage of the VOxis lower

(~2-3 V) than the other metal oxides (~3-4V). Recently,

nanophase V2O5 cathode materials have been prepared with

capacities up to 450 Ah/kg and a corresponding specific energy of approximately 1,500 Wh/kg when coupled with a lithium metal anode [2, 9]. Other nanophase cathode materials,

including some in Table 1, show increased capacities compared

to the same compositions having micron-scale particles. This

has been attributed to facile Li+ diffusion into the interior of the

nanoparticles with a concomitant reduction in electrode polarization. 

The nanoscale vanadium oxides discussed above have suffered from capacity loss during cycling, however, ongoing

research support by ONR is helping to resolve this problem.

Recently, Professor Bruce Dunn’s research group at UCLA produced V2O5 nanocomposites, in which carbon nanotubes are

used to electrically “wire” the poorly conducting vanadiumoxide nanoparticles. The benefits are dramatic when this

nanoarchitectured approach is used: the practical capacity of

the wired vanadium-oxide exceeds 400 Ah/kg, which is 2 to 3

times that of current cathode materials, and there are no capacity losses observed over 20 cycles at high discharge rates.

More recently, Professor Dunn has demonstrated a high

reversible capacity for magnesium ions in the V2O5 cathodes

(1.5 Mg 2+ per V2O5). The electrochemical intercalation of the

large Mg2+ ions is not possible with mesoscale vanadium oxides.

This is a key discovery because the double-charge of Mg2+ carries almost twice the energy of Li+

, hence the development of

this concept may lead to magnesium-based rechargeable batteries that offer high capacities and are inherently safer than lithium batteries.

Electrolytes 

Two successful approaches in the development of nanoarchitectured polymer electrolytes for high-capacity lithium-ion batteries are to incorporate inorganic nanoparticles into a conventional polymer electrolyte (e.g. polyethylene oxide with lithium

salt) or to create block copolymers that self-organize into

nanophase regimes that synergistically provide lithium-ion

conductivity and structural stability.

With regard to the former approach,

nanoparticle guests, such as LiAlO2,

Al2O3, TiO2, and SiO2, improve the

performance of polymer electrolytes.

The nanoparticles disrupt the polymer-chain organization and crystallization at the nanoscale and create lithium ion conducting pathways by promoting Lewis acid–base interactions

b e t ween the inorganic nanopart i c l e

and the polymer segments [16]. These

effects result in lithium-ion electrolytes

with increased lithium-ion conductivity and an enhanced lithium-ion transp o rt number, and in addition, the

n a n o p a rticles stabilize the lithiumpolymer interface [16]. 

Professors Anne Ma yes and

Donald Sadoway at MIT have been

Figure 6. Nanoarchitecured Pt/C-SiO2

Electrocatalysts Prepared using Sol-Gel

Techniques (SCF is supercritical fluid)

Figure 7. “Natural” Nanocomposite of Intertwined RuO2

Nanocrystals and Hydrous Proton-Conduction Regions

Vulcan Carbon 9 wt. % Pt/C +

Pt sol

(2nm)

SCF CO2 dry

Silica sol

Pt/C-SiO2

composite

aerogel

RuO2 nanocrystals

hydrous boundaries

2.5 nm
The AMPTIAC Newsletter, Volume 6, Number 1 29

exploiting the elegant nanoarchitectures of block copolymers to

improve the performance of lithium-polymer batteries [17].

They employ poly[oligo(oxy-ethylene) methacrylate]-b-poly-

(methyl methacrylate), or POEM-b-PMMA, with LiCF3SO3

salt as a polymer electrolyte in a Li/polymer/amorphous VOx

cell to achieve cathode capacities of 400 Ah/kg over 200 cycles

and projected cell energy densities of >350 Wh/kg. These block

copolymers are effective lithium-ion electrolytes because the

hydrophilic oxy-ethylene regions transport lithium ions, while

the hydrophobic regimes provide structural stability plus a

“t r a p” to inhibit transport of hyd rophobic anions (i.e.

hydrophobic anions will stay in the hydrophobic regions away

from the hydrophilic regions), and thus increase the lithium

ion transport number.

The Mayes and Sadoway research groups have also prepared

self-organizing nanocomposite electrodes (SONEs) in which

gold nanoparticles are incorporated into the lithium-ion conducting regions to serve as highly reversible lithium-gold alloy

anodes. The segregation at the nanoscale of the gold-precursor

salt into the POEM region of the block copolymer structure is

shown schematically in Figure 5a. The salt becomes segregated

within the relatively hydrophilic POEM regions and becomes

visible as the dark regions in the TEM micrograph. Upon electrochemical reduction, the gold-precursor salt is reduced to

metallic gold nanoparticles, as illustrated in Figure 5b. The gold

nanoparticles then can undergo highly reversible charge-discharge cycling (>700 cycles). The preparation of SONEs that

incorporate other lithium-alloying nanoparticles, such as aluminum, tin, and silicon, may lead to the development of lowcost, practical, high-performance nanoarchitectured anodes for

lithium-ion polymer batteries.

Fuel Cells

As with batteries, fuel cells are composed of an anode, a cathode, and an electrolyte. However, the anode and cathode do

not store charge but rather electrocatalytically activate a fuel

(e.g., hydrogen) at the anode and an oxidizer (e.g., oxygen) at

the cathode. Effective electrocatalysis at the electrodes requires

concurrent ionic and electronic transport [1]. Achieving these

simultaneous dynamic processes requires the intersection of

multiple phases, including the electrocatalyst (e.g., Pt), an ion

conductor (liquid or solid-state), an electronic conductor (e.g.,

carbon powder), and the gas. By controlling the intersection of

these regions at the nanoscale, dramatic improvements in fuelcell performance can be achieved. In addition, the fuel cell electrolyte can be enhanced through nanoscale structural optimization. In fact, the archetypal proton exchange membrane (PEM)

fuel cell electrolyte, NafionTM, is itself a nanostructured material, possessing nanoscale hydrophilic regions that conduct protons and fluorinated hydrophobic regions that provide structural stability [1]. 

ELECTROCATALYSIS Ongoing research at NRL has provided

valuable insight into how the design of nanostructured electrocatalytic architectures can improve fuel cell performance. Dr.

Debra Rolison and co-workers at NRL have prepared nanoarchitectured Pt electrocatalysts in a systematic manner using

sol-gel techniques (illustrated in Figure 6; for additional information, see reference 18). The Vulcan carbon powder provides

a continuous electronic network to the 2-nm carbon-supported colloidal Pt nanoparticles within an architecture defined by

the continuous nanoscale network of the SiO2 aerogel. The

continuous 3-D mesoporous path provides a flux of fuel to the

Pt electrocatalyst, resulting in a >10,000x increase in its catalytic activity for methanol oxidation. This approach emphasizes the advantages of designing a multifunctional nanoarchitectured site to improve the performance of fuel-cell catalysts.

Ad vancements in analytical methods are also leading to

i m p rovements in the development of active nanostru c t u re s .

N R L’s Dr. Karen Sw i d e r - Lyons and co-workers in collaboration

with Professor Takeshi Egami and Dr. Wojtek Dmowski at the

Un i versity of Pe n n s y l vania have used advanced structural analysis methods to demonstrate that the electrochemical pro p e rt i e s

of hyd rous ruthenium oxide are due to its innate nanocomposite nature. Diffraction methods show that this “n a t u r a l”

nanocomposite is composed of nanoscale wires of electro n i c a l l y

conducting Ru O2 n a n o c rystals that are surrounded by hyd ro u s

p roton-conducting regions [19], as shown in Fi g u re 7. The intimate mix of electronic and protonic conduction in this

nanocomposite material explains its high activity as a co-catalyst

for carbon monoxide-tolerant Pt - Ru Oxfuel cell electro c a t a l y s t s

[1] and is key to understanding the performance of hyd ro u s

ruthenium oxide as a pseudocapacitor [2]. Understanding the

relationship between the nanoscale stru c t u re and electro c h e m ical pro p e rties in materials will also lead to the design of other

a c t i ve materials for electrochemical power sources. 

ELECTROLYTE As mentioned earlier, PEM fuel cells already

employ the nanocomposite electrolyte NafionTM. Perhaps even

more interesting, however, is the potential for nanoarchitectured structures to dramatically enhance the performance of the

ceramic electrolytes used for high-temperature solid oxide fuel

cells. Recent studies on nanocomposites of alternating layers of

CaF2 and BaF2 show a linear increase in ionic conductivity (fluoride ion) parallel to the interface when the layers are 50 and

430 nm thick [20]. Space-charge calculations indicate that the

increase is proportional to the interface density. However, a disproportionate increase in conductivity is observed when the

alternating layers are narrower (16 to 50 nm thick). Under such

conditions, the interfacial space-charge regions overlap, and the

nanoscale layers lose their individual behaviors, taking on the

p ro p e rties of a super-ionic-conducting material possessing

anomalous transport properties [20]. Similar enhancements in

ionic transport (and electronic transport) may be possible with

other ceramics, opening up exciting opportunities for nanoarchitecturing of future fuel-cell electrolytes.

Opinions, interpretations, conclusions, and recommendations are

those of the authors and are not necessarily endorsed by the Office

of Naval Research or the Naval Research Laboratory.
30

References

[1] Gottesfeld, S. Advances in Electrochemical Science and

Engineering, R.C. Alkire, H. Gerischer, D.M. Kolb, and C.W.

Tobia, Editors, Vol. 5, P. 195 (1997).

[2] Rolison, D.R. and Dunn, B. J. Mater.Chem. 11, 963

(2000).

[3] Nazar, L.F., Goward, G., Leroux, F., Duncan, M., Huang,

H., Kerr, T., and Gaubicher, J. Int. J. Inorg. Mater, 3, 191–200

(2001).

[4] Schoonman, J. Solid State Ionics 135, 5 (2000).

[5] Tuller, H. J. Electroceramics 1, 211 (1997).

[6] Tuck, C.D.S. Modern Battery Technology, Ellis Howard,

Chichester (1991).

[7] Scrosati, B. and Vincent, C.A. Modern Batteries, Second

edition, Arnold, London (1997).

[8] Pistoia, G. Lithium Batteries Elsevier, Amsterdam (1994);

Tarascon, J.M. and Armand, M. Nature 414 359 (2001).

[9] Winter, M., Besenhard, J.O., Spahr, M.E., and Novák, P.

Adv. Mater. 10, 725 (1998).

[10] Idota, Y., Kubota, T., Matsufuji, Maekawa, and Miyasaka

(1997) Science 276, 1395.

[11] Mao, O. and Dahn, J.R. (1999) J. Electrochem. Soc. 146,

423.

[12] Foster, D.L., Wolfenstine, Read, J.R., and Behl, W.K.

(2000) J. Electrochem. Soc. 3, 203.

[13] Kim, I., Kumta, P.M., and Blomgren, G.E. Electrochem.

Solid-State Letters, 3, 493 (2000).

[14] Hulteen, J.C. and Martin, C.R. J. Mater. Chem. 7, 1075

(1997).

[15] Li, N., Martin, C.R. Martin, Scrosati, B. J. Power Sources

97-98, 240 (2001).

[16] Croce, F., Persi, L., Ronci, F., and Scrosati, B. Solid State

Ionics 135, 47 (2000).

[17] Huang, B., Cook, C.C., Simon, M., Soo, P.P., Staelin,

D.H., Mayes, A.M., and Sadoway, D.R., J. Power Sources 97-

98, 674 (2001).

[18] Anderson, M.L, Stroud, R.M., Rolison, D.R. Nano Lett. 2

(2001), in the press.

[19] Swider-Lyons, K.E., Bussmann, K.M., Griscom, D.L.,

Love, C.T., Rolison, D.R., Dmowski, W., and Egami, T. in

Solid State Ionic Devices II - Ceramic Sensors, edited by E. D.

Wachsman, et.al, Electrochemical Society Proceedings 2000-32

(2000), p 148; Dmowski, W., and Egami, T., Swider-Lyons,

K.E., Love, C.T., Rolison, D.R., submitted to J. Phys. Chem.

[20] Sata, N., Eberman, K., Maier, E. Nature 408 946 (2000).

■

Dr. Richard T. Carlin is currently the Director of the Mechanics and Energy Conversion Division at the Office of Naval Research

(ONR). Previously he served as an ONR Program Officer for the Undersea Propulsion and Electrochemistry S&T Programs. Other

past positions have included Research Chemist, Air Products & Chemicals, Inc.; Assistant Professor of Inorganic/Analytical

Chemistry, University of Alabama; and Chief of the Electrochemistry Division, Frank J. Seiler Research Laboratories, USAF

Academy. Dr. Carlin holds a Ph.D. in Inorganic Chemistry from Iowa State University and has published over 100 scientific papers

and been awarded 7 US patents. 

Dr. Karen Swider-Lyons is a staff scientist in the Chemistry Division at the Naval Research Laboratory in Washington DC. She studied Chemistry as an undergraduate at Haverford College and earned her Ph.D. in Materials Science and Engineering from the

University of Pennsylvania in 1992. Her research is dedicated to power sources, with a focus on the study of transport mechanisms in solid state ionic materials. She currently does research and development of microbattery systems and in new oxide-based

catalysts for use in polymer exchange membrane fuel cells. She also serves as a technical consultant on two DARPA fuel cell programs. Dr. Swider-Lyons is a member of the Materials Research Society, the Electrochemical Society, and the International Society

for Solid State Ionics.

The AMPTIAC Newsletter, Volume 6, Number 1
AMPTIAC

M a t e r i a l 15

E A S E

A M P T I AC is a DOD In fo rmation Anal ysis Ce nter Ad m i n i ste red by the D efense In fo rmation Systems Ag e n c y, Defens e Te chnical In fo rma ti on C en ter and Opera ted by IIT Re s e a rc h Inst i t u te

This article provides a brief overview of the major events, science, tools and processes in nanotechnology. Part One highlights the history of nanotechnology,

Part Two discusses the tools used to study such small-scale materials and the underlying mechanisms responsible for the novel properties observed, and Part Three

covers the major processing methods of nanomaterials.

MATERIALS ENGINEERING WITH NATURE’S BUILDING BLOCKS

Richard Lane, Benjamin Craig and Wade Babcock

AMPTIAC, Rome, NY

17 AMPTIAC

Part One: His tory of Nano Materials Engineering

Nanotechnology is definitely one of the most talked about “new” areas of

study today. The idea that nanostructured materials would exhibit unique properties is accredited to Gleiter and Turnbull for the work they did independently in the early 1980s [1]. Since then the field of nanotechnology has expanded dramatically due to the realization of its potential technological benefits.

Nanotechnology basically is the process of manipulating matter at the

atomic scale. There are many interpretations of what this includes, but for our

purposes and our inherent focus on materials engineering, we will include the

purposeful creation, manipulation and machining of engineered materials at

the nanoscale. Typically, nanomaterials have some critical dimension more

than 1 and less than 100 nanometers, where a nanometer is one billionth of

a meter, or one thousandth of a micron. The typical “yardstick” at small scales

- a human hair - is about 200,000 nanometers in diameter. (A more thorough

description of nanoscale is included in Part Two.)

Humans have been utilizing nanomaterials for centuries, dating back to

Roman potters and possibly before. Ancient craftspeople utilized nanoscale

particles in glazes to create unique colors that changed with incident lighting.

In the 19th century, the use of metals in new and astounding structural applications drove the importance of microstructure to the front of engineers’ minds.

With this focus, empirical methodologies for processing metals yielded massive improvements in strength, toughness, ductility and hardness. Much of this

work was microtechnology, even before the field existed, and one could argue

that it bordered on the nano regime with the empirical manipulation of

microstructure, precipitates and crystallographic grains.

Eventually, innovations such as the automobile demanded more durable

consumables like rubber, glass, and ultimately, plastics. Rubber may have been

the first modern example of nanotechnology, with the addition of carbon black

and sulfur to improve durability. Even though the ability of engineers to study

the exact mechanisms at work did not exist, carbon black’s nanoscale particles served to modify the behavior of rubbers, thus assisting the growth of one

of the most important manufacturing booms of the late 19th and early 20th

centuries. While nanotechnology claims its roots in chemistry, the fields of

physics and engineering have joined the fray and are pushing the boundaries

of the possible.

Many trace the roots of modern nanotechnology and nanomaterials to a

1959 talk given by Dr. Richard Feynman at a meeting of the American Physical

Society.* It was in this now-famous lecture that Feynman proposed the all-toosimple hypothesis that there was “plenty of room at the bottom.” He speculated that future scientists and engineers would build complex structures from

atoms and molecules.

It wasn’t until 1974 that the field was given the name “nanotechnology”

however, and that is widely attributed to University of Tokyo researcher Norio

Taniguchi. He made the distinction between engineering at the micrometer

scale (the basis for modern microelectronics that was just starting to hit its stride

in the 70s) and the new field of sub-micrometer engineering that was beginning to emerge†[2]. Nascent nanotechnology began to “grow up” and enter

the mainstream consciousness in the mid-1980s with work by Richard Smalley

at Rice University on what would be called Buckminster Fullerenes (now

famously known as “Buckyballs”) and MIT researcher K. Eric Drexler’s publication of “The Engines of Creation.”

While Smalley tantalized chemists and physicists with the discovery of a

“new” form of one of the building blocks of nature, Drexler outlined a future

dominated by a new form of manufacturing done at the molecular, and even

atomic level. The study of Buckyballs has led to the discovery of tube-like structures of carbon atoms which are basically sheets of graphite rolled up with

their edges connected to form a cylinder. They can be thousands of times

longer than they are in diameter. It is these carbon nanotubes (CNTs) which

have piqued the interest of so many engineers as they may hold the promise

of extremely high tensile strength inclusions for nanocomposites, structural

beams for nanomachines, and possibly even conductors (wires) for nanoelectronics. CNTs and other molecular-level structures form the bases of what

Drexler describes as a coming revolution in molecular manufacturing.

What is most amazing about the development of micro- and then nanotechnology is the pace at which it has advanced. Taniguchi predicted in

1974 that within 15 years there would be machining methods capable of sub100 nm dimensional precision. This prediction was largely proven correct. By

the early 1990s, nanotechnology’s capabilities could not only image and

probe atomic structures, but move individual atoms, one at a time, around on

a substrate. The “quantum stadium” image generated by IBM researchers provides a poignant example of this in Figure 1. The image consists of 76 iron

atoms on a copper substrate. Wave patterns in the interior are from the densi -

ty distribution of trapped electrons.

Since 1990, significant advancements have been made, both in actual

materials fabrication and in computational simulation. The manufacturing of

CNTs and many other nanomaterials has been improved and scaled up, 
making affordable materials available for test and

evaluation which did not

ex i st just 5 ye a rs ago.

C o mp u ter power has

i mp roved dra m a t i c a l ly

over the past 10 to 15

years, enabling atom-level

simulation of many new

nanomaterials before sign i ficant re s o u rces are

i nve sted in pro d u c i n g

them. Researchers are now

able to theorize, simulate,

manufacture, test, and evaluate new materials in much shorter times, further

expanding the field and reducing wasted effort. While many of the ideas surrounding engineering at the atomic and molecular level are still in a highly

speculative stage, experts agree that there seem to be no physical laws barring further advances.

Many of the advancements in nanotechnology were made possible by

concurrent advancements in analysis tools capable of resolving atomic, molecular and crystallographic structures. Just in the last 20 years, various forms of

scanning probe microscopy (SPM) and transmission electron microscopy

(TEM) have become available to researchers on a reliable basis. These tools,

described more fully in Part Two, have provided views into the inner workings

of atomic bonding, molecular assembly, and the structure of materials at the

smallest scales in history. It is these tools that have taken atomic manipulation

out of the chemistry beaker and into the realm of engineering.

Part Two: The How and Why of Nanotechnology

A Sense of Scale

To grasp what nanotechnology encompasses, it is critical to have a mental

concept of what “nano” really means. Roger Whatmore of Cranfield University

in the UK provides an excellent example in which he proposes that one imagine a human hair is roughly the size of a large tree trunk, one meter across.

Now a typical bacterium (1 micrometer) would be about as big as a caterpillar on that tree and a typical virus (which is about 100 nanometers long)

would be the size of an ant. And that is where nanotechnology is just g etting

started. Figure 2 presents an overview of items from the macro to the

nanoscale. One can see that multiple technical disciplines of chemistry,

physics, engineering, biology and others converge as we approach the lower

reaches of size.

Analysis and Tools

In order to study materials on the nanoscale, instruments capable of very fine

resolution must be utilized. Many of the microscopy tools used for characterizing nanostructures can easily fit inside a shoebox. Advances in microscope

probe tip technologies have come about from the study of nanostructured

materials, creating even better tools for characterization. Figure 3 compares

some microscopy techniques and illustrates the incredible recent growth of

tools with micro- and then nanoscale resolution.

Scanning Probe Microscopy One of the first tools used for nanomaterials

investigation was the scanning tunneling microscope, or STM, developed by

Gerd Binnig and Heinrich Röhrer at IBM in 1981. (They would win a Nobel

Prize in 1986 for this work.) The STM formed the basis for what would later

become a family of scanning probe tools, or scanning probe microscopy

(SPM), the key features of which are depicted in Figure 4.

Scanning probe microscopes use an atomically “sharp” tip (typically pyramidal in shape and coming to a point that is literally one or two atoms across)

which is moved over a sample’s surface a few Angstroms from making contact.

The tip is then scanned across the surface in a regular pattern (much as one

would mow a lawn) and the electrical current, which traverses the gap

between the tip and the sample, is monitored. By keeping the height of the tip

constant and measuring the changing electrical current (more when close to

the sample, less when farther away), or by keeping the current constant and

measuring the deflection of the tip, a topographical map can be generated of

the sample’s surface. The device relies upon the small amount of electric current which crosses the gap between the tip and the sample (“tunneling”).

The other most widely used member of the SPM family is the atomic force

microscope or AFM. Similar to the STM, it uses an atomically sharp tip, but

instead of carefully moving it just Angstroms from the sample, the AFM actually drags its tip along the sample’s surface. (This exaggerates the interaction at

this scale - the atomic forces actually prevent atoms from “dragging,” they

simply are pushed into very close proximity.) The tip is mounted on a cantilever

M a t e r i a l

E A S E

Figure 1. Quantum Stadium 

(Courtesy: IBM, Almaden 

Research Center. All rights reserved)

Figure 2. Scale of Common Natural and Manmade Items

(Reprinted with permission of the Office of Basic Energy Sciences, 

Office of Science, US Department of Energy)
which flexes as the tip moves up and down the surface topography. Its deflections can be tracked by bouncing a laser beam off the cantilever into a split

photodiode or by other techniques.

M a g n etic Fo rce Micro s c o py (MFM) is another te ch n i que of SPM, but

uses a magnetic probe to sense the magnetic field above the surface of a

m a te rial. The probe is sta n d a rd silicon- or silicon nitri d e - c o a ted with a th i n

m a g n etic film, such as cobalt, capable of mapping the magnetic domain of

a specimen with a resolution up to 20 nm. Two passes are re qu i red to dist i nguish the to p o gra p hy of the sample. The fi rst pass is in contact or semiconta c t

w i th the sample and the second pass is at a specific constant height above

the fi rst pass.

Electron microscopes have been instrumental in the study and characterization of materials since the invention of the first electron microscope in the

1930s. High resolution transmission electron microscopy can now provide

structural characterization at better than 0.2 nm spatial resolution. In its simplest

form, a TEM consists of an electron beam that is projected through a thin sample, generating a diffraction pattern onto a receiving device, such as a phosphorescent screen or CCD camera. At low resolution, amplitude contrast

images are used to map material structures in the 0.5 nm to 1 mm range.

Specimens must be < 10 nm thick to provide the highest resolution 

Nanoscience

The promise of nanotechnology is based upon the ability to create nanostruc -

tured materials that will produce novel properties on the macroscale. That ability now exists, however in many cases the mechanisms behind these observed

properties are not yet clearly understood. Despite this incomplete understanding, it is still possible to attribute, by inference, the novel qualities of these nanomaterials to the following changes in internal structure.

1. The increased total surface area of grains, as grain size is decreased, will

alter the physical properties of nanomaterials.

2. The increased volume of grain boundaries relative to unit structure, as grain

size is decreased, will alter the physical properties of nanomaterials.

3. Discrete electronic levels (quantum behavior) will alter the electrical and

optical properties of nanomaterials as grain sizes approach the molecular

scale. The discrete energies associated with electron orbits become more

evident as grain size nears the molecular scale (approximately < 5 nm),

creating non-linear property effects.

Mechanical Properties The most widely accepted hypothesis to explain the

mechanical properties in polycrystalline nanomaterials is that the strength and

hardness follow the Hall-Petch relationship, increasing with smaller grain size,

down to a critical grain size, dc 10 nm, where a decrease in strength and

hardness results thereafter, as depicted in Figure 5 [3].

The increase in strength is based upon the piling up of dislocations at grain

boundaries; i.e. by increasing the total surface area of grains, the dislocation

density increases and in turn increases strength. However, pileups cannot

occur when the grain size is less than the dislocation spacing in the pileup [4];

and so the Hall-Petch relationship will no longer be valid on this scale. The

strength of nanoscale-thickness, multi-layered materials also follows the HallPetch relationship, replacing grain size with layer thickness.

By decreasing grain size, the grain boundary volume relative to the unit volume will increase. At roughly 5 nm, 50% of the volume will be grain boundaries [5], which may then dominate the properties observed in the material.

The decrease in strength at this small end of the nanoscale may be attributed

to grain boundary sliding due to the high defect density allowing fast diffusion

of atoms and vacancies in the stress field [6]. Superplasticity [+] has been

observed in nanostructured metals and ceramics at about 200°C lower than

microstructured materials. This creates improved formability of nanostructured

materials, which is especially important for ceramics.

Thermal Properties The enhanced diffusivity observed in the grain boundary

structure of nanostructured materials is the mechanism thought responsible for

the changes in thermal properties. In metals, thermal conductivity and melting

point have been observed to decrease (such as a 27°C lower melting point

for gold) while thermal expansion coefficients have been observed to

increase. The decrease in thermal conductivity of nanostructured ceramic materials such as yttria stabilized zirconia may broaden their use as thermal barrier coatings.

Chemical Reactivity An increased chemical activity can be obtained by the

large number of atoms on the surface of nanocrystallites providing active sites

for reactions. For instance, nonstoichiometric CeO2-x has a high chemical reactivity resulting from an unusually high oxygen vacancy concentration [7].

Nanostructured CeO2-x has been demonstrated to offer catalytic activation for

SO2 reduction and CO oxidation at significantly lower temperatures as well

as enhanced poisoning resistance (resistance to the loss of catalytic reactivity).

A second class of reactive materials are nanostructured porous materials.

Conventional porous materials such as aluminosilicates and phosphates are

Figure 4: Graphical Depiction of the Key Features of an SPM

1800 1850 1900 1950 2000

Year

106

105

104

103

102

10

1

ROSS

AMICI

ABBE RUSKA

ASH

REASON

YOUNG

BETZIG

BINNIG

DIETRICH

BINNIG & ROHRER

Fine probe positioning and

deflection measurement

Course positioning structure

Stage

Measure electrical

current between

probe and sample

Probe tip

Atomic surface

Figure 3: History of Lateral Resolution in Microscopy

(Courtesy of J. Murday, Naval Research Laboratory)

AMPTIAC A D VA N C E D M A T E R I A L S A N D P R O C E S S E S T E C H N O L O G Y

MARTON
used for catalytic reactions and gas absorption applications, but they are limited due to their small pore sizes of less than 15 Å [8]. Nanostructured aluminosilicates with optimized pore sizes in the range of 20–100 Å have been

developed which extend their use in these markets. Similar research is being

applied to the use of transition metal oxides in petrochemical production, pollution control, and pharmaceutical and fine chemical synthesis. Extending the

pore sizes beyond the 20–100 Å range could provide benefits for enzyme

catalysis, bioseparation and biosensing.

Optical Properties The size of dispersion materials in a composite can alter

the wavelength of light that is absorbed by the particulates. The quantum effect

is responsible here where the discrete electron energies in the particulates

determine the wavelength of light absorbed. Altering the size of a particle can

change the associated energy and wavelength of light absorbed. Cadmium

selenide is one material extensively studied where crystallites of ~ 1.5 nm will

appear yellow, 4 nm will appear red, and larger particles will appear black

[9]. This discovery is now being applied to sunscreen lotions using zinc oxide

and titania to filter ultraviolet radiation.

Electrical Properties Quantum ef fects in nanomaterials have been shown to

produce a non-linear dependence of electrical conductivity on electric field

and can produce electron tunneling characteristics. Quantum mechanical interference between separate paths an electron may take through a material can

strongly enhance or suppress electrical conductivity. Most of the research to

date in nanostructured electronic devices comes from fabrication via lithography, but inroads are being made into molecular-level structures fabricated from

chemical reactions or self assembly. For instance, quantum dots are pyramidor faceted dome-shaped clusters of atoms, typically between a few nanometers and hundreds of nanometers in diameter. They self-assemble from the deposition of a large lattice constant material onto a substrate with a small lattice

constant, whereby the compressive strain in the deposited material relieves

itself by causing the material to spontaneously coalesce or clump into islands

on the substrate. They may be utilized as three-dimensional potential wells if

they are overgrown by a material with a larger bandgap and have application potential in nanoelectronics. (See the article in this issue by Dr. Amirtharaj

et al for further information and application of quantum dots.)

CNTs (the tubes formed from rolled up sheets made of carbon atoms joined

in hexagonal arrays) have shown some interesting electrical properties as well.

The way in which the two ends of the sheet wrap and meet can modify the longitudinal conductivity of the tube. In fact, they can be made to conduct freely

like metals or behave like semiconductors. And further advancements have

shown that various-sized tubes can be nested inside one another for structural

or electrical performance modifications.

Magnetic Properties Magnetic nanoparticles exhibit unusual behaviors resulting from the size effects and charge transfer characteristics. Changes seen in

these materials include Giant Magneto-Resistance (GMR) in some layered

composite materials and granular solids, spin valves, and spin injection in ferromagnet/insulator/ferromagnet sandwich materials.

Part Three: Processing of Nanomaterials

Bulk Methods 

A number of processes are used for producing nanomaterials in bulk powders,

coatings, thin films, laminates, and composites. However, there are two fundamental approaches to fabricating nanomaterials. The “bottom-up” approach

represents the concept of constructing a nanomaterial from basic building

blocks, such as atoms or molecules. This approach illustrates the possibility of

creating exact materials – materials that are designed to have exactly the

properties desired. The second approach, the “top-down” method, involves

restructuring a bulk material in order to create a nanostructure.

INERT GAS CONDENSATION C o n s i d e red a “bot tom-up” method, inert ga s

condensation (IGC) was the fi rst method used to inte n t i o n a l ly produce a nanost ru c t u red mate rial, and has become widespread. It can be used to pro d u c e

n a n o st ru c t u red metals, alloys, inte rm etallics, ceramic oxides, and comp o s i te s .

The process begins by energizing a source mate rial, which ge n e ra tes a va p o r

of atoms. This eva p o ration process can be perfo rmed th rough electron beam

heating, laser ablation, sputte ring, or plasma methods, but is most often done

th rough Joule-heating. Due to condensation, the va p o rized atoms aggl o m e ra te

and fo rm ve ry small cluste rs when th ey are introduced to the inert gas. These

c l u ste rs are carried by a conve ction current, induced by th e rm o p h o resis, to a tube cooled by

l i quid nitro gen where th ey accum u l a te .

Adjusting certain parameters,

such as the gas used (i.e. He, Ar,

Kr, Xe), the gas pressure, the precursor evaporation rate, and the

residence time, allows some control over the particle size and dist ribution. The smallest part i c l e

sizes produced using this method

are about 5–25 nm using a precursor with a low evaporation rate

Figure 5: Strength/Hardness of Nanostructured Materials [3]

H, y d

-1/2

amorphous

dc Grain Size, d

Hall-Petch Equations

y = o + Kd -1/2 H = Ho + Kd -1/2

y

: yield strength H : hardness

o: lattice yield stress Ho: single crystal

(minimum stress hardness

required to move

a dislocation)

K: constant

d: average grain size

M a t e r i a l E A S E
AMPTIAC A D VA N C E D M A T E R I A L S A N D P R O C E S S E S T E C H N O L O G Y

and a light inert gas at low pressure [10]. Since the process takes place in

ultra-high vacuum systems (UHV), there is very little contamination of the material, and therefore, it remains highly pure.

MECHANICAL ALLOYING Another process commonly used to produce

nanos tructured materials is mechanical alloying, which is an example of a

“top-down” method. There are two basic versions of this process. The first, more

specifically called mechanical attrition, is a process where high-energy ball

milling is used to grind and refine the structure to produce highly mixed, ultrafine powders. Grain sizes of the material are partially dependent on time,

where extended milling times result in more uniform grain sizes. The second

version, reaction milling, involves in-situ solid-state chemical reactions between

precursor materials while they are mixed and milled.

Producing large quantities of nanostructured material is one advantage of

the mechanical alloying process. Moreover, various types of nanomaterials,

such as metals, ceramics, intermetallics and composites, can be produced

using these straightforward processes. However, contamination from the milling

hardware and environment, non-uniform particle sizes due to short milling

times, and non-homogeneous chemical composition due to incomplete milling

reactions are problems for mechanical alloying processes. One way to lessen

the effects of environmental contamination is to perform the process in the presence of liquid nitrogen, which is also referred to as cryogenic milling.

SEVERE PLASTIC DEFORMATION Severe plastic deformation (SPD) is used to

fabricate nanocrystalline metals and intermetallics. There are several different

types of SPD processes, but the three most common processes are equal-channel-angular extrusion (ECAE), torsional straining and accumulative roll-bonding

(ARB) [10]. Nanosized grains are created when the material is subjected to a

very large deformation causing a modification of its structure by fragmenting

the existing phases. Recrystallization of these broken phases results in structures

with significantly reduced sizes. The materials formed by SPD generally have

average grain sizes of about 100 nm, although grain sizes down to 20 nm

have been obtained for metals [11]. The grain size controlling parameters in

this process include temperature, strain, strain rate, and applied pressure.

Severe plastic deformation is capable of forming nanostructured materials with

little contamination and little or no porosity. A further advantage is that SPD is

a scalable process, meaning that it could be used for industrial applications.

However, since there is significant straining of the material, high residual stresses may be present in the end product.

SOL-GEL The sol-gel method is a solution phase processing technique that

is used more of ten to fabricate nanostructured materials than any other liquid

phase process. This is a process capable of producing nanostructured ceramics and nanocomposites. There are essentially two phases present during this

technique, where one is a homogeneous solution phase and the other is an

elastic, gel-like, solid phase. The homogeneous solution is dried, thereby transforming it into a gel, while maintaining a constant volume. Subsequent drying

causes a phase transformation of the gel along with a corresponding reduction in volume, ultimately resulting in the desired phase. The key to obtaining 

a nanostructured material using this process is to control the processing parameters. One advantage to solution phase processing is the excellent control it

provides over the chemical composition, which leads to a more homogeneous

composition [10]. A disadvantage to this process is that the starting materials

can be expensive.

Coating and Laminate Methods

Nanostructure coatings have been primarily deposited via thermal spraying.

Processes used to fabricate laminates include: Radio Frequency sputtering, DC

magnetron sputtering, chemical vapor deposition, electroplating, and physical

vapor deposition methods including electron beam, cathodic arc, and jet

vapor deposition [12]. 

THERMAL SPRAYING Thermal spraying is a process capable of producing

nanostructured materials and nanostructured coatings. Control over the composition and structure of the final material is very important when producing

nanostructured materials, and for this reason powders are typically used as the

starting materials. The powders are carried by a gas (i.e. air, N2) and heated

such that they are at least partially melted. Deposition onto a substrate results

in the deformation and solidification of the particles.

ELECTRODEPOSITION Electrodeposition has traditionally been used as a

coating process, although recently it has also been used to form bulk nanocrystalline materials. This process is capable of producing a nanocrystalline material with grain sizes down to 5 nm. The factors affecting the resulting grain sizes

include pH, temperature, current density, and type of current among others

[10]. The process can be carried out at room temperature and the time of fabrication is of course dependent on the size of the material to be produced. For

example, as one would expect, larger materials take longer, but compared to

other deposition processes, electrodeposition is capable of rapid deposition.

Moreover, electrodeposition is a less expensive process that can be used for

large-scale production [10]. 

JET VAPOR DEPOSITION Jet vapor deposition is a relatively cost-effective

technique capable of rapidly depositing multilayered films with alternating

material layers to produce a nanostructured composite [13]. Nanostructured

multilayered films consist of layers with nanoscale thickness. Sonic or nearly

sonic gas jets, typically helium, carry an atomized material and deposit it as a

film on a substrate. Uniform deposition occurs with a rotating or oscillating substrate which is mounted on a carousel. Alloys and multilayered composites are

formed by employing two or more jets simultaneously or in sequence, respectively. An optimum deposition temperature needs to be maintained to ensure

minimal interdiffusion between the layers and a continuous nature of the layers

without impurities forming in between.

SPUTTERING Sputtering is a well-known and widely used technique for producing thin films. It is a vacuum method capable of producing nanostructured

materials. In this technique, plasma, which is generated by energizing a lowpressure gas such as argon, strikes a target transferring its momentum which

causes the target material to be ejected and subsequently deposited onto a

substrate. The main disadvantage to the sputtering method is that it is difficult

to control. DC-magnetron sputtering and RF-diode sputtering have been used

to prepare nanolaminate materials. These methods are capable of depositing

layers of a material with a thickness below 100 nm.

CHEMICAL VAPOR DEPOSITION The process of chemical vapor deposition

(CVD) involves a gas-phase chemical reaction which forms a solid material on

a substrate. Nanostructured ceramics and composites are the most common

types of nanomaterials produced by CVD (Carbon nanotubes are also fabricated using CVD). Vapors of the precursor materials are transported by a carrier gas to a heated substrate where they are deposited and subsequently

react with the substrate to form a solid material. Although it is a relatively slow

process, chemical vapor deposition offers good control over the chemical
M a t e r i a l

E A S E

composition and is capable of deposition over a large area. There are several variations of the CVD process, such as plasma assisted CVD and laser

assisted CVD.

CHEMICAL VAPOR INFILTRATION Chemical vapor infiltration (CVI) is a tec hnique that is used to form nanostructured fiber-reinforced composite materials.

A very similar process to CVD, CVI uses a transporting gas to carry vaporous

precursors to a porous fiber preform, while diffusion takes the precursors inside

where they react and form the nanostructured matrix. An important issue with

CVI is ensuring that the outer parts of the fiber preform are not sealed off prior

to the interior being fully deposited. To prevent premature surface densification,

the chemical vapor infiltration process is slowed by adjusting the process

p a ra m ete rs, such as te mp e ra t u re, pre s s u re, and re a c tant concentra t i o n .

Another factor to CVI being a slow process is that it is limited by the diffusion

mechanism of the gaseous precursors. The advantage to CVI is that it is capable of producing a fiber-reinforced composite without damaging the fibers,

which is often a problem in other composite processes.

CHEMICAL VAPOR CONDENSATION Another chemical vapor process used to

produce nanomaterials is chemical vapor condensation (CVC). A precursor

vapor carried by a gas stream is sent through a heated (hot-wall) reactor tube,

where the pyrolysis of the precursor occurs to form nanoparticles. The

nanoparticles are then collected on a liquid-nitrogen cooled tube. The CVC

process is a low-pressure technique that requires a low concentration of the

precursor in the carrier gas stream. Process parameters such as temperature,

pressure, and residence time can be adjusted to determine the size of the

nanoparticles. A variation of this process is the combustion flame version which

replaces the hot-wall reactor with a combustion flame reactor. The combustion

flame reactor supplies a significantly higher temperature which increases the

reaction rate.

For further coverage of the subject matter, the interested reader can find

more information on nanostructured materials in “Nanomaterials: Synthesis,

Properties and Applications” [14].

References and Endnotes

[1] R. Birri n ge r, “St ru c t u re of Na n o st ru c t u red Mate ri a l s ,” Na n o p h a s e

Materials: Synthesis – Properties – Applications, Proceedings of the NATO

Advanced Study Institute on Nanophase Materials: Synthesis – Properties –

Applications, Kluwer Academic Publishers, 1994, pp. 157-180.

[2] “The Development of Achievable Machining Accuracy”, from Current

Status in, and Future Trends of, Ultraprecision Machining and Ultrafine

Materials Processing, by Norio Taniguchi, Tokyo Science University, Annals of

the CIRP Vol. 32/2/1983 page 573. 

[3] T.G. Nieh and J. Wadsworth, Scripta Met., Vol. 25, 1991, pp. 955-958.

[4] V.G. Gryazanov, V.A. Solo’ev and L.I. Trusov, Scripta Met. Mater., Vol 24,

1990, pp. 1529-1534

[5] C. Suryanarayana and F.H. Froes, “The Structure and Mechanical

Properties of Metallic Nanocrystals”, Metall. Trans,, Vol 23A, 1992, pp.

1071-1081.

[6] S. Veprek, “Ultra Hard Nanocomposite Coatings with Hardness of 80 to

105 GPa”, Int. Conf. on Trends and Applications of Thin Films, TAFT 2000,

Nancy, France, March 2000.

[7] A.S. Tschöpe and J.Y. Ying, Nanostr. Mater., Vol.4, 1994, p. 617.

[8] J.Y. Ying, “Nanostructure Processing of Advanced Catalytic Materials”,

WTEC Study on Na n o p a rticles, Na n o st ru c t u red Mate rials, and

Nanodevices. Part 1. Proceedings of the 1997 US Review Workshop,

A rl i n g ton, VA, May 19 97, National Te chnical Info rmation Service, US

Department of Commerce.

[9] R.W. Whatmore, “Nanotechnology”, Ingenia, February 2001.

[10] L.L. Shaw, “Processing Nanostructured Materials: An Overview”, JOM,

Vol. 52, No. 12, The Minerals, Metals & Materials Society, December 2000,

pp 41-45.

[11] R.Z. Valiev, I.V. Alexandrov, R.K. Islamgaliev, “Processing and Properties of

Nanostructured Materials Prepared by Severe Plastic Deformation”, NATO

Ad vanced Study Inst i t u te on Na n o st ru c t u red Mate rials: Science &

Technology, Kluwer Academic Publishers, July 1999, pp. 121-142.

[12] M. Gell, “Applying Nanostructured Materials to Future Gas Turbine

Engines”, JOM, Vol. 46, No. 10, The Minerals, Metals & Materials Society,

October 1994, pp. 30-34.

[13] H.N.G. Wadley, L.M. Hsiung, and R.L. Lankey, “Artificially Layered

Na n o c o mp o s i tes Fa b ri c a ted by Jet Vapor Deposition,” Comp o s i te s

Engineering, Elsevier Science Ltd, Vol. 5, No. 7, 1995, pp. 935-950.

[14] A.S. Edelstein, R.C. Cammarata, Nanomaterials: Synthesis, Properties

and Appications, Inst. of Physics, October 1998.

* First published in the February 1960 issue of Caltech’s Engineering and

Science, which owns the copyright. It has been made available on the web at

http://www.zyvex.com/nanotech/feynman.html with their kind permission.

† Norio Taniguchi shows the trend in ultraprecision machining from 1900 and

projects that it will reach “Atomic lattice distance” (0.3 nanometers) around

2017.

+ Superplasticity is the ability of a material to exhibit large ductility, usually >

200%.
The AMPTIAC Newsletter, Volume 6, Number 1 37

Introduction

Modifying material surfaces to enhance wear and corrosion

resistance is a common practice for both military and commercial applications. Electrodeposited hard chrome is one of the

most widely used protective coatings. Ceramic coatings, both

single phase and composite types, are also common and they

are frequently applied using plasma spray. In this process, the

coating material (usually in the form of a powder) is injected

into a plasma stream where it is heated and accelerated toward

the substrate surface. After impacting the surface the ceramic

rapidly cools thus forming a coating layer.

Both hard chrome and ceramic coatings have serious deficiencies that can

limit their use. Chrome electroplating

uses closely regulated hazardous materials. Compliance with the various environmental safety regulations has made hard

c h rome increasingly expensive to use.

Pl a s m a - s p r a yed ceramic coatings are

somewhat less expensive than chrome

(when clean up costs are included), but

are generally brittle and have limited success adhering to substrates, which is also a

problem for hard chrome. The need for

better coating materials has been recognized and considerable effort has recently

gone into finding replacements.

Over the last five years, a consortium of

companies, universities and Navy personnel have been developing a new generation of wear resistant “nanostructured”

ceramic coatings. The consortium is lead

by Inframat, Inc. and the University of

Connecticut, and team members include

the A&A Company, Rutgers University,

St e vens Institute of Te c h n o l o g y, the

Naval Surface Warfare Center (Carderock

Division) and Puget Sound Na va l

Shipyard. It is funded by the Office of

Naval Research and its objective has been

to achieve mechanical and wear properties unobtainable from more conventional materials (i.e. materials with structural

aspects at the micron scale or larger). 

Nanostructured materials are characterized by an ultra-fine

m i c ro s t ru c t u re with some physical aspect less than 100

nanometers in size. This feature can be grain size, particle or

fiber diameter, or layer thickness (Figure 1). There are two reasons why reducing the scale of a material’s microstructure can

significantly alter its properties. First, as grain size gets smaller,

the proportion of atoms at grain boundaries or on surfaces

increases rapidly. In a polycrystalline material with a grain size

of 10nm, as many as 50% of its atoms are at grain boundaries,

resulting in a material with properties far different than norFigure 1. Nanostructured Materials are Characterized by the Inclusion 

of One or More Types of Features with Dimension Below 100 Nanometers

Dr. Lawrence T. Kabacoff

Materials Science and Technology Division

Office of Naval Research

Particle Diameter Layer Thickness

Fiber Diameter Grain Size
mally seen. The other reason is related to the fact that many

physical phenomena (such as dislocation generation, ferromagnetism, or quantum confinement effects) are governed

by a characteristic length. As the physical scale of the material falls below this length, properties change radically. Until

recently, these changes in deformation behavior and modes

of failure have not been well understood due to the inability to consistently fabricate high quality materials. This situation is changing rapidly, with considerable progress now

being made in the fabrication of nanomaterials, as well as

and the understanding of the interrelations betwe e n

nanoscale processing, structure, and macroscale properties.

Fabrication of Nanoceramic Coatings

The strategy employed to develop nanostructured coatings

concentrated on compositions similar to currently available

conventional coatings and to use existing deposition equipment to fabricate them. As only the microstructure of the coatings was changed, it greatly simplified the process of implementing the new technology in both military and commercial

applications. One of the coatings under development, a plasma

sprayed nanoceramic composite with a composition of Al2O3 -

13 TiO2, has exhibited wear resistance, bond strength, and

toughness unprecedented in a ceramic, and is now in use

aboard Navy surface ships and submarines, reducing maintenance costs due to wear and corrosion. 

Plasma spray, the process used to fabricate ceramic coatings,

is very simple in concept, but very complex in practice. An

inert gas is passed through a region of electrical discharge,

where it is heated to very high temperature (typically 10,000 to

20,000 K). The rapidly expanding plasma is forced out through

a nozzle at velocities between 1,200 and 1,500 m/sec and

directed toward a substrate. Particles are injected into the plasma, where they are heated and accelerated. Although the plasma and particle temperatures are high, substrate surface heating

is minimal. A schematic of a typical plasma spray gun is shown

in Figure 2. The complexity arises from the large number of

parameters that must be selected and which can affect the

structure and properties of the coating. The temperature and

velocity of the plasma depend on the power applied to the gun

and the type and flow rate of the gas used. Usually, two gasses

are used, an inert gas such as helium or argon, and a secondary

gas, such as hydrogen. Other factors include the morphology of

the powder particles, distance from the gun to the substrate,

position and orientation of the powder injection ports, and surface preparation of the substrate. Taken all together, these

38 The AMPTIAC Newsletter, Volume 6, Number 1

Figure 2. Schematic Diagram 

of Typical Plasma Torch

(Courtesy of R.W. Rigney)

Figure 3. Indentation Crack Growth

Resistance vs. Critical Plasma Spray

Parameter (proportional to plasma

temperature) [3]

Figure 4. Effect of Nanoparticle

Agglomerate Melting on

Coating Microstructure [3]

Tungsten

Cathode

Nozzle

Copper

Anode

Plasma

Spray Deposit

Spray Stream

Prepared

Substrate

Electric

Arc

Powder and

carrier gas

Electrical (+)

Connection

and Water In

Arc gas

Electrical (-)

Connection

and Water Out

290 320 350 380 410 440

CPSP

(A Parameter which is proportional to Temperature

CPSP=Applied Power/Primary Gas Flow Rate)

14

12

10

8

6

4

2

0

Not Melted

Partially Melted

All Melted

Starting

Microstructure

Coating

Microstructure

● -Al2O3 (0.5 ~2.0 μm)

● -Al2O3 with dissolved Ti

4+ (20-100 nm)

● Oxide solution of TiO2 and/or oxide additives (20-100 nm)

2-1/2 in. - 6 in.

(64 to 152 mm)

nanostructured

conventional
parameters determine the thermal history of the injected particles, velocity of impact, and flow and solidification characteristics after impact, thus dictating the resultant microstructure.

As compared to traditional plasma spray processes, plasma

spraying nanostructured materials introduces a number of

complications. The first is that nanoparticles cannot be sprayed

by particle injection into the plasma. Very small particles lack

the momentum necessary to penetrate into the plasma, or to

impact the surface while the plasma sweeps to the side near the

substrate. To be sprayed, the particles must be formed into

agglomerates approximately 30-100 microns in diameter. For

an Al 2O3 - TiO2 nanocomposite, this is usually accomplished

by dispersing alumina and titania nanoparticles in a fluid with

a binder and spray drying [1]. If necessary, the agglomerates are

partially sintered to improve structural integrity.

The next problem is forming a nanostructured coating on

the substrate. This is not trivial since the agglomerates are greatly heated (promoting rapid grain growth) and are at least partially melted. There are three mechanisms for creating or retaining a nanoscale microstructure: avoiding melting or grain

growth of the feedstock (very difficult), inclusion of nanoscale

particles with very high melting temperature that remain solid

while the rest of the material melts, or formation of a nanostructure during solidification of the sprayed material upon

impact. The last mechanism occurs in composites consisting of

two or more immiscible phases (as is the case for Al2O3 and

TiO2) and results from solid state decomposition of a single,

metastable phase formed by rapid solidification during impact.

The metastable phase formed by Al2O3 and TiO2 is a highly

defected Spinel [2]. 

The microstructure and properties of nanostructured Al2O3

- 13TiO2 coatings depend strongly on the temperature of the

plasma [3]. This is in sharp contrast to the conventional coating, as illustrated in Figure 3, which shows a plot of indentation crack resistance as a function of a parameter (applied

power divided by primary gas flow rate) which is proportional

to the plasma temperature. Data is shown for both the nanostructured and conventional coatings. One can see that the

crack growth resistance for the conventional material is virtually independent of plasma temperature while the nanostructured coating exhibits a strong dependence.

The reason can be found by following the thermal history of

the injected particles. In the plasma spraying of conventional

Al2O3 - 13TiO2, the feedstock consists of large fused and

crushed particles that are fully melted prior to impact. Full

melting is achieved over a wide range of temperature because of

the high thermal conductivity of fused and crushed particles

(relative to nanoparticle agglomerates). The coatings typically

have grain sizes greater than one micron. When the nanoparticle agglomerates are sprayed at relatively high temperature

(under conditions that result in full melting), the “nano” structure consists entirely of grains formed from the decomposition

of the metastable Spinel phase.

The difference between the micro-grained material formed

f rom fused and crushed feedstock and the nanostru c t u re formed

f rom the agglomerates arises from the degree of homogeneity in

the melted particles. Because of the short residence time, the liqThe AMPTIAC Newsletter, Volume 6, Number 1 39

Figure 5. Cup Test Performed on Conventional (Left)

and Nanostructured (Right) Al2O3 -13TiO2 Coatings

(Courtesy of R.W. Rigney)

Figure 6. CrossSectional Views of

Crack Propagating

in Conventional

Al2O3-13TiO2

Coating [3]

50μm

15μm
40

uid formed from melting the fused and crushed particles will

contain alumina and titania rich regions. When this liquid solidifies rapidly, the grains formed will be larger than would be

obtained from a homogeneous liquid. When plasma spray is

carried out at a re l a t i vely low temperature, little melting occurs

and the stru c t u re consists of incompletely sintered particles that

h a ve undergone some degree of grain growth. The middle temp e r a t u re range gives partial melting of the agglomerates and

results in regions of micron sized grains (from unmelted part icles that have experienced grain growth) surrounded by

nanoscale grains from the fully melted material and is illustrated in Fi g u re 4. It is this “d u p l e x” stru c t u re that gives the best

p ro p e rties, not a homogeneous nanoscale stru c t u re. 

Properties of Nanostructured Al2O3 - 13TiO2 Coatings

The obvious parameter by which to judge a “wear resistant coati n g” is wear rate. Wear can be termed as either sliding or abras i ve. Both are measured by running a “we a r i n g” medium ove r

the surface and measuring weight loss. For many coatings, and

p a rticularly for brittle materials such as ceramics, this parameter

can be misleading. The wear resistance of coatings in use today

is outstanding, with wear rates orders of magnitude less than the

uncoated surface. Brittle coatings usually do not fail by “we a r i n g

o u t”, but rather suffer from cracking, delamination and spallation. At least as important as wear resistance is bond stre n g t h

(adhesion to the substrate) and toughness (the ability to withstand an impact or applied strain). It is in these pro p e rties that

the nanoceramic coatings excel to a re m a rkable degre e .

The bond strength of the nanostructured coatings, as measured by tensile pull tests on coatings applied without a bond

coat, is about double that of a conventional coating. The

toughness of the nanostructured Al2O3 - 13TiO2 coatings is

extraordinary, as is dramatically illustrated in Figure 5. This

shows a “cup test” in which a coated coupon is forced down

onto a one-inch diameter steel ball (coated side away from the

ball), causing it to deform. The deformation is greatest in the

center decreasing to zero at the edges. The conventional coating shows the typical cracking and spalling observed in a

ceramic. The nanostructured coating actually deforms along

with the substrate and no macroscopic cracking is observed. A

blow from a hammer severe enough to deform a steel substrate

would not be sufficient to cause failure in the coating. This

toughness translates into greater wear resistance, which is two

to four times greater than that of the conventional coating [4].

Another important benefit of enhanced coating toughness is

improved grindability as almost all ceramic coatings must be

ground and polished after spray deposition. Nanostructured

ceramic coatings can be ground and polished in about half the

time required for conventional ceramic coatings. Since grinding and polishing operations represent about forty percent of

the total cost of the coating (compared to about five percent for

the cost of the feedstock powder), nanostructured coatings are

actually less expensive to apply.

The performance of the conventional and nanostructured

coatings can be better understood by examining how cracks

propagate in these materials. In the conventional coating,

cracks follow the “splat boundaries” which mark the borders

between the materials deposited from each droplet (Figure 6).

The arrows in this figure point towards a splat boundary. A

crack can be seen following another splat boundary [3]. In the

nanoceramic composite, the cracks do not follow the splat

boundaries, but instead propagate through the nanostructured

material that formed during solidification until they encounter

a region of larger grains formed from partially melted feedstock. Here, the cracks are either deflected or stop inside the

“coarse grained” region. This can be clearly seen in Figure 7,

which illustrates that cracks terminate inside regions (see

arrows) of large grains formed from unmelted feedstock [3].

Any strain imposed upon a nanostructured coating is accommodated by the creation of microcracks in the normal way, but

these cracks are blunted before they can propagate very far or

link up with other cracks. The result is a ceramic material that

can deform to a degree much greater than in a more conventional, brittle ceramic.

Figure 7. CrossSectional Views of

Crack Propagating in

Nanostructured Al2O3 -

13TiO2 Coating With

“Duplex Structure” [3]

The AMPTIAC Newsletter, Volume 6, Number 1

10μm 50μm
Applications

The applications for nanostructured Al2O3 - 13TiO2 coatings

can be grouped according to the properties to be exploited. The

simplest applications are those in which the nanostructured

coatings replace existing conventional ceramic coatings. In such

cases, the advantage is greater longevity and reliability. The second case is as a replacement for hard chrome coatings. Here,

the advantages are lower cost, elimination of toxic hazardous

materials and in some cases, improved performance. The

improved performance comes from the non-metallic nature of

ceramics. Metallic surfaces in contact with seawater for long

periods of time experience buildup of calcareous deposits.

Actuator rods with such buildups can severely damage seal areas

when the rods are retracted. Electrically non-conducting coatings experience no such buildup. Also ceramics do not promote

galvanic corrosion, which occurs when two dissimilar metals

are in contact with an electrical conductor such as seawater. In

spite of these advantages, conventional ceramic coatings frequently cannot be used over metallic coatings because they lack

sufficient bond strength and toughness. Nanostructured ceramics overcome this limitation. In fact, nanostructured Al2O3 -

13TiO2 coatings are now being used to coat titanium components on seawater-exposed portions of submarines specifically

to eliminate galvanic corrosion on nearby steel structures. The

most unique applications are in circumstances where no coatings could previously be employed. For example, many shafts

used aboard ships, such as propulsion shafts, undergo sufficient

torsional strain to cause failure in a conventional coating.

Nanostructured Al2O3 - 13TiO2 coatings exhibit sufficient

strain tolerance to be a viable candidate for coating of severe

wear areas on certain types of shafts.

The qualification of a new material for military applications

can be a fairly invo l ved process. This process has been gre a t l y

simplified for nanostru c t u red Al2O3 - 13Ti O2 coatings because

the coatings are similar in composition to existing approved coatings and are applied using the same equipment and pro c e d u re s .

They have now been approved under MIL STD 1687A, which

g overns use of thermal spray coatings on shipboard machinery.

The number of applications in use aboard surface ships and submarines is rapidly expanding. T h e re are literally thousands of

potential applications and the impact on the cost of maintaining

ships, aircraft, and ground vehicles can be ve ry large. This can be

demonstrated by examining a typical example.

The component illustrated in Figure 8 is a reduction gear set

from an 80-ton air conditioning unit used on surface ships.

The coated areas of these gears are indicated by the arrows.

Currently gears are replaced on average at six year intervals.

Eventually, abrasives form on the shaft, excess heat is generated

and it welds to the aluminum sleeve in which it rotates, thus

causing it to seize up. With application of the new coatings,

these gears can be repaired instead of replaced. The damaged

surface is ground down and replaced with a nanostructured

Al2O3 -13TiO2. The savings fleet-wide from this one application is about $500,000 per year, or about $13,000,000 over the

projected thirty-year life of these ships. When one considers the

large number of other applications, such as pumps, valves, electric motors, diesel engines, bearings, journals and actuators, the

magnitude of the cost savings becomes apparent. Moreover,

most of these components are not military-specific. Coatings

are now being applied to commercial hardware as well.

While nanostructured ceramic particles and thin films have

been available for some time, nanostructured Al2O3 -13TiO2

represents the first bulk ceramic material to be commercialized.

Other nanostructured coating materials are under development

and are expected to become available in the near future. These

include cemented carbides, such as Tungsten Carbide-Cobalt

(WC-Co) and other ceramics, such as chrome oxide and yttriastabilized zirconia. All of these coatings are expected to find a

wide range of application and should greatly benefit both military and commercial operating and maintenance costs.

The AMPTIAC Newsletter, Volume 6, Number 1 41

Figure 8. High Speed

Reduction Gear Set

From 80 Ton Air

Conditioning Unit.

Coated Areas are

Marked with an

Arrow (Courtesy of

R.W. Rigney)
42 The AMPTIAC Newsletter, Volume 6, Number 1

References

[1] L. Shaw, D. Goberman, R. Ren et al., Surf. Coat. Technol.

Vol. 130 (2000) 1.

[2] B.H. Kear, Z. Kalman, R.K. Sadangi, G. Skandan, J.

Colaizzi, W.E. Mayo, J. Thermal Spray Technol. Vol. 9 (2000)

483.

[3] M. Gell, E.H. Jordan, Y.H. Sohn, D. Goberman, L. Shaw,

T. D. Xiao, Surf. Coat. Technol., In Press.

[4] K. Jia, T.E. Fischer, Wear Vol. 200 (1997) 310. ■

Dr. Lawrence T. Kabacoff is a Program Officer in the Materials Science and Technology Division, at the Office of Naval Research,

where he directs programs in synthesis and processing of nanostructured materials, electronic packaging, and IR transparent materials. He obtained a Ph.D. in Solid State Physics from the University of Connecticut in 1978. He then served as a Post Doctoral

Research Fellow at Northeastern University until 1979, where he conducted research into the origins of glass formation and stability in metallic glasses. Subsequently, he joined the Naval Surface Warfare Center, White Oak, as a research Physicist in the

Materials Division, where he conducted research on magnetoelastic metallic glasses and shape memory alloys. Since 1991, he

has served as a program officer in the Materials Division of the Office of Naval Research. He has managed programs in the

areas of acoustical damping in structural materials, fabrication of optical quality diamond, multi-chip module packaging, improvement of high temperature mechanical properties of sapphire (for IR domes), and synthesis and processing of nanostructured alloys

and ceramics.
Introduction

Energetic materials are a major component of weapons systems

used by all branches of the US military. Their primary use is in

explosives, as well as in gun and missile propulsion. Over the

last century new chemicals have been discovered or designed

for rapid release of energy in either relatively simple compositions, like that used in certain warheads, or in more complex

formulations like the advanced composites used as propellants.

Currently, a class of energetic materials known as nitramines are

actually used for both explosives and propulsion applications in

various weapons systems. Some major considerations for successful weaponization of energetic materials include performance (e.g. energy density, rate of energy release), long-term storage stability, and sensitivity to unwanted initiation.

As demands on munitions increase with regards to improved

performance (i.e. increased lethality and survivability as well as

the development of emerging high precision weapons concepts), the challenge on the R&D community is ever increasing. Additional drivers and concerns for the US military come

from the continuing development of new munitions (including

new types of energetics) by foreign nations. Munitions development is also fundamentally impacted by the approaching

limit of the amount of improvement that is possible for the traditional and now rather mature C, H, N,

and O energetic chemistries.

In recent years researchers have found

that energetic materials/ingredients that are

produced on the nanoscale have the promise of increased performance in a variety of

ways including sensitivity, stability, energy

release, and mechanical pro p e rties. As

such, they represent a completely new frontier for energetic material research and

development with the potential for major

payoffs in weapons systems. Very simply,

nanoenergetics can store higher amounts of

energy than conventional energetic materials and one can use them in unprecedented

ways to tailor the release of this energy so as

to maximize the lethality of the weapons.

The field of nanoenergetics R&D is quite

young, but is already undergoing rapid

growth. The goal of this article is to give

the reader a sense for the physical and

chemical characteristics and properties that

make these materials so promising. This

will be accomplished through a discussion of a few selected

examples of current research.

Background

The 221st National Meeting of the American Chemical Society

held during April 2001 in San Diego featured a symposium on

Defense Applications of Nanomaterials. One of the 4 sessions was

titled Nanoenergetics. This session featured speakers from government labs (DOD and DOE) and academia (for further

information about this symposium, please contact the author).

This session provided a good representation of the breadth of

work ongoing in this field, which is roughly 10 years old. A

number of topics were covered, including a few that will be discussed in detail below, namely Metastable In t e r m o l e c u l a r

Composites (MICs), sol-gels, and structural nanomaterials.

The presentations given at this symposium largely form the

basis for this report.

At this point in time, all of the military services and some

DOE and academic laboratories have active R&D programs

aimed at exploiting the unique properties of nanomaterials that

h a ve potential to be used in energetic formulations for

advanced explosives and propellant applications. Figure 1 represents some concepts of how nanomaterials, especially

The AMPTIAC Newsletter, Volume 6, Number 1 43

Figure 1. Weaponization of

Advanced Energetic Technologies

Dr. Andrzej W. Miziolek

Weapons and Materials Research Directorate

US Army Research Laboratory

ETC Plasma Injectors: Functionalized Polymer 

Nanocomposite, Radiation Tunable 

(ETC=Electro Thermal Chemical)

Novel Energetics/Nanostructured Propellant 

Formulations (High Energy, Insensitive, Plasma

Specific, Low Erosivity Gradient: Nanoengineered

Progressivity, No Residue)

Novel Energetics/Nanostructured Energetics for

Warhead Explosives Formulations (High Explosive

Power, Structured Nanocomposite Matrix,

Insensitive, Environmentally Degradable)

Fuses/Initiators

(Metastable 

Nanointermetallics 

& Composites)

Nanocomposite Materials for Cartridge Cases

(Energetic, Consumable, Structurally Strong)

KE Munition

Thermobaric Warhead

Shaped Charge
44 The AMPTIAC Newsletter, Volume 6, Number 1

nanoenergetics could be used for improving components of

munitions. The figure shows that nanoenergetic composites

and ingredients can be used in the ignition, propulsion, as well

as the warhead part of the weapon. With regards to the latter

application, nanoenergetics hold promise as useful ingredients

for the thermobaric (TBX) and TBX-like weapons, particularly due to their high degree of tailorability with regards to energy release and impulse management.

Metastable Intermolecular Composites (MICs)

Metastable Intermolecular Composites (MICs) are one of the

first examples of a category of nanoscale energetic materials

which have been studied and evaluated to a considerable

degree. MIC formulations are mixtures of nanoscale powders of

reactants that exhibit thermite (high exothermicity) behavior.

As such, they differ fundamentally from more traditional energetics where the reactivity is based on intramolecular (not intermolecular) properties. The MIC formulations are based on

intimate mixing of the reactants on the nanometer length scale,

with typical particle sizes in the tens of nanometers range (e.g.

30 nm). One important characteristic of MICs is the fact that

the rate of energy release can be tailored by varying the size of

the components. T h ree specific MIC formulations have

received considerable attention to date; Al/MoO3, Al/Teflon,

and Al/CuO.

Research and development on MIC formulations is being

performed in laboratories within all military services, as well as

at Los Alamos National Laboratory (LANL). LANL researchers

Drs. Wayne Danen and Steve Son, along with their colleagues,

have not only pioneered the dynamic gas condensation method

for the production of nanoscale aluminum powders (also

known as Ultra Fine Grain [UFG]), but they have also conducted numerous studies on physical and chemical properties.

As an example, Figure 2 shows a scanning electron microscope

(SEM) image of a nanoscale MIC (Al/MoO3 mixture) produced by the dynamic gas condensation process at LANL. One

critical aspect of producing successful MIC formulations is the

ability to produce nanoscale aluminum particles of small particle sizes in the tens of nanometer range, as well as with reasonably narrow size distribution. And, of course, the production

process needs to be reproducible batch to batch. The current

state of UFG aluminum production is that this is an area that

still requires considerable effort. Even though there are commercial sources for UFG aluminum (such as the ALEX process

originated in Russia, or commercial sources in other nations

such as Japan), the need for reliable non-government sources of

ingredient materials for uses in MIC applications is still there.

Progress in this area is being made by companies such as

Technanogy and Nanotechnology.

Another example of a significant effort at producing MIC

compounds is found at the Indian Head Division of the Naval

Surface Warfare Center (NSWC/IH). This work is being performed by Dr. Magdy Bichay, Pam Carpenter, and Tom

Devendorf along with other co-workers. The Indian Head

process for producing UFG aluminum is also based on the

dynamic gas condensation process with some changes, such as

the use of resistance heating instead of RF coils. Figure 3 shows

Figure 2. SEM of MIC (Al/MoO3 Mixture)

Figure 3. The Process Schematic for the Production of Nanoscale Al for MIC 

Applications at NSWC/Indian Head

Figure 4. Al Nanoparticles with a Passivation Layer of Al2O3

Al Wire

Feed

100nm 20nm

Cooling

Water

Mass

Flow

Meter

Helium

Cylinder

Pyrometer Electric 

Motor

Power Supply

Collection Unit

Display

Container

Vacuum

Pump

Mass Flow Meter

Oxygen

Cylinder

Power Supply

440 V, 3 

SCR Thyristor

Control Unit

Vaporization

Chamber

20nm

TEM EFTEM

Al

O
The AMPTIAC Newsletter, Volume 6, Number 1 45

the process schematic as developed by Professor Jan Puszynski

of the South Dakota School of Mines, working in concert with

Indian Head. Design goals included the use of continuous aluminum wire feed, a continuous collection system, as well as a

production rate of approximately 10 grams/hour. It was found

that one major limitation of the process was the 12 hour life of

the titanium diboride/boron nitride ceramic resistance boat

used for heating the material. 

Figure 4 shows an example of the typical UFG aluminum

that is produced by the Indian Head process. A transmission

electron microscope (TEM) image of the Al nanoparticles is

shown on the left while an EFTEM (energy filtered TEM) is

shown on the right, clearly indicating a thin passivation layer of

A l2O3. These images we re taken at Lawrence Live r m o re

National Laboratory (LLNL). In summary, much more

research and development needs to be done in the production

and characterization of these and new types of MIC formulations. Issues of MIC ignition and safety characteristics (such as

impact, friction, and electrostatic initiation) are promising, but

need to be fully explored. Overall though, certain key MIC

characteristics are very attractive and quite promising for practical applications. These include energy output that is 2x that

of typical high explosives, the ability to tune the reactive power

(10 KW/cc to 10 GW/cc), tunable reaction front velocities of

0.1-1500 meters/sec, and reaction zone temperature exceeding

3000K. Specific areas of possible applications include use in

environmentally clean primers and detonators, chem/bio agent

neutralization, improved rocket propellants, IR flares/decoys,

thermal batteries, and others.

Sol-Gels

Researchers at LLNL, Drs. Randall Simpson, Alexander Gash,

et al., have pioneered the use of the sol-gel method as a new

way of making nanostructured composite energetic materials.

The advantages of making energetics on the nanoscale are

shown in Figure 5 which provides a comparison between conventional energetic compounds (micron scale) and those which

are composed of nanoscale ingredients. The sol-gel chemistry

involves the reactions of chemicals in solution to produce primary nanoparticles, called “sols”, which can be linked in a 3-

dimensional solid network, called a “gel”, with the open pores

being occupied by the remaining solution. There are typically

two types of sol-gels. “Xerogels” are the result of a controlled

evaporation of the remaining solution/liquid phase, yielding a

dense, porous solid. On the other hand, “aerogels” can be

formed by supercritical extraction (SCE), which eliminates the

liquid surface tension and thus alters the capillary forces of the

egressing liquid that normally would lead to pore collapse.

Since the pores have been largely kept intact through the use of

the SCE method, the resulting solid is highly porous and lightweight, with excellent uniformity given that the particles and

the pores are both in the nanometer range. Figure 6 illustrates

the sol-gel methodology.

The sol-gel approach is fundamentally different than most

approaches to energetic material production in that it is a relatively simple methodology (e.g. chemistry in a beaker) performed at low temperatures. It can also be relatively inexpensive

and has the promise of creating entirely new energetic materials with desirable properties. 

One current promising nanocomposite being pursued by the

researchers at LLNL involves the use of Fe2O3 which is generated using the sol-gel method. The reason that Fe2O3 is chosen

is because its thermite reaction with UFG aluminum is very

exothermic (with only CuO and MoO3 yielding greater energy

of reaction). An example of the high degree of mixing and uniFigure 5. Composite Energetic Materials: Conventional vs Nanosized

Figure 6. The Sol-Gel Methodology

Figure 7. Sol-Gel Fe2O3/Al Nanocomposite

1. Conventional (μm-sized particles): • mass transport an issue

• lower power

• energy lower

(incomplete reaction)

2. Energetic nanocomposite (nm-sized particles): • mass transport minimized

• higher power 

(faster reaction)

• higher total energy

• Inexpensive

• Safe

• Cast complex shapes

• Low temperature processing

Non-supercritical 

extraction of 

liquid phase

Condense Super-critical

extraction

Aerogel: low or high density

Xerogel: low or high density

Sol: a colloid Gel:

a 3D structure

25nm

TEM

EFTEM

Al

O
46

formity between two nanophases is found in Figure 7, which

indicates the excellent dispersion of Al and Fe on the nanoscale

domain. The Fe2O3 was prepared by the use of an organic

epoxide which was added to an Fe(III) salt solution resulting in

the formation of nanoscale crystalline and amorphous Fe2O3.

The reaction to produce Fe2O3 was done in solution which

already contained the UFG aluminum. In this case, the

nanoparticle aluminum was sonnicated (suspended in isopropanol and placed in an ultrasonic bath to break up any aluminum aggregates) before mixing with the Fe(III) salt solution.

For this work, the UFG aluminum was supplied by the NSWC

researchers at Indian Head using the dynamic gas-phase condensation method (discussed above), which yielded an average

aluminum particle size of approximately 35 nanometers.

As sol-gel materials and methodology advances, there are a

number of possible application areas that are envisioned. These

include: (1) high temperature stable, non-detonable gas generators, (2) adaptable flares, (3) primers, and (4) high-power,

high-energy composite explosives. In addition, the sol-gel

chemistry may have advantages of being more environmentally

acceptable compared to some other methods of producing

energetics.

Functionalized Carbon Nanotubes for Energetic Applications

Dr. Lalitha Ramaswamy and her colleagues at the University of

Maryland, along with Army Research Laboratory scientists

(Drs. Matt Bratcher, Pamela Kaste, and Sam Trevino) are

exploring the use of carbon nanotube structures (Figure 8) as

starting material for various possible energetics applications.

One concept involves the functionalization of carbon nanotubes with the notion of incorporating or binding this material into propellant matrices. The hope is that by doing so there

will be significant performance enhancement in the areas of initiation, overall propellant performance, safety, as well as in

mechanical properties. One specific goal that is being pursued

is the assessment of carbon nanotube-based ingredients for the

improvement of propellant initiation for either an advanced

plasma-based initiator (which is under development), or for use

with more conventional electrical initiators. Here the optical as

well as electrical properties of nanotubes may be important in

generating an improved propellant formulation. In particular,

the high electron density that characterizes the nanotube structure as well as the high conductance along the tube wall may

lead to more robust and reliable ignition behavior.

Long-term storage stability is one of the key elements of a

successful propellant formulation. In this regard, there is hope

that carbon nanotubes could be used to encapsulate nanoscale

energetic ingredients, perhaps even the nitro-organic energetic

compounds themselves (e.g. HMX, RDX), to yield a propellant that not only has the same (or better) performance for

energy release, but also much improved performance for handling and long-term storage. An example of progress in the

effort to functionalize carbon nanotubes is given in Figure 9

which shows a micrograph of some amine-terminated carbon

nanotubes. In addition to the synthesis of functionalized carbon nanotubes this effort also involves chemical analyses of the

products as well as the use of characterization techniques such

as Prompt Gamma Activation Analysis for elemental ratio

analyses.

Center for NanoEnergetics Research at the University of

Minnesota

One of the major challenges that will be faced by the

Department of Defense sometime in the near future (with

regards to the utilization and implementation of nanoenergetic

materials and ingredients) will be the ability to produce such

materials in not only large quantities, but also in controlled

sizes, size distributions, and chemical compositions. To address

this eventuality, the DOD has recently funded a universitybased research program in a competitive process through the

Defense University Research Initiative on NanoTechnology

(DURINT) program. This research program is headed by the

University of Minnesota, which established the Center for

Na n o Energetics Re s e a rch (CNER) (see www. m e . u m n . e d u /

~mrz/cner.html). The primary goal of the CNER is to conduct

a comprehensive and multidisciplinary study of the high rate

production and behavior of nanoenergetics. Professor Michael

Zachariah is the Director of the CNER and he has expertise in

the synthesis and in-situ characterization of nanoparticles, as

well as molecular dynamics simulations of particle growth and

Figure 8. The Coiled

Graphitic Structure of

Carbon Nanotubes

Figure 9. Micrograph

of Amine-Terminated

Carbon Nanotubes

The AMPTIAC Newsletter, Volume 6, Number 1
The AMPTIAC Newsletter, Volume 6, Number 1 47

production. A significant aspect of

this DURINT-funded program is

the close scientific collaboration

with a DOD research organization, namely the Army Research

Laboratory. ARL researchers Dr.

Barrie Homan and the author of

this article are working closely

with Professors Zachariah and

Steven Girshick and their research

g roups in developing virt u a l l y

identical nanoenergetics production and characterization facilities.

Figure 10 shows a schematic of

this research facility which represents the centerpiece of the

CNER. It is based primarily on

the use of a thermal plasma arc

reactor for processing of a large

number of possible precursors in

the solid, liquid and vapor phases.

In addition to the plasma, provisions have been made for the use

of a furnace, as well as a diffusion flame apparatus, to serve as

alternate techniques for producing nanoscale ingredients. In

addition to the production of single or multicomponent (e.g.

metals or multimetals) nanoscale particles, this facility allows

for the in-situ coating of the particles using a number of different approaches (e.g. condensation or uv curing). This coating

could be chosen to be an inert shield to keep the core nanoingredient from further reacting with air (oxygen or moisture), or

it could be chosen to be energetic to dramatically increase the

energy density of the final energetic formulation.

Characterizing the nanoenergetic particles produced in this

facility is accomplished by two major diagnostic approaches.

The first involves the use of a single particle mass spectrometer

(SPMS, inset photo in Figure 10). Here the SPMS is used to

provide size and elemental composition of the particles as they

are sampled from the reactive flow. As such, this tool tracks the

growth as well as the coating of the targeted nanoenergetic

ingredients/composites. Nanoscale particles of different sizes

are selected for analysis using aerodynamic focusing. These

selected particles can also be analyzed in-situ using spectroscopy. Two techniques in particular are powerful tools for

analyzing small particles; Laser Induced Bre a k d ow n

Spectroscopy (LIBS) and Laser Induced Incandescence (LII).

LII has been developed primarily by the combustion research

community as a major tool for understanding the formation of

combustion-generated particulate matter. This technique utilizes a pulsed laser to rapidly heat the small particles. By monitoring the rate of decay of the resulting incandescent radiation,

one can extract particle size information, as the rate is related to

the size of the particle. In order to get information on the

chemical composition of the particles through the use of spectroscopy, it is necessary to use a different technique. LIBS is an

emerging major new tool for the analysis of chemical composition (see http://www.arl.army.mil/wmrd/LIBS).

In LIBS, a pulsed laser is tightly focused on the sample to

induce a breakdown (microspark) of the sample material. The

spark process leads to the breakup of the sample into its elemental components and simultaneous excitation of the resulting atoms and ions, which subsequently emit light. Thus, by

monitoring the emission from this plasma, one can determine

the nature of the element by its characteristic emission wavelength and the relative abundance by the intensity of the emitted light at a given wavelength. The LIBS sensor technology is

a d vancing so rapidly that instrumentation has curre n t l y

become available for the capture of light between 200-940 nm,

a region where all elements emit. Thus, researchers are now in

a position to simultaneously detect all of the constituent elements of nanoparticles, including the metals, carbides, and

organic and/or oxide coatings. Since the LIBS data is generated in real-time (response time 1 second or less), one can keep

track of rapid changes in the composition of the particles during the actual production run. Recently Professor David W.

Hahn of the University of Florida has demonstrated LIBS

analysis of nanoscale particles and has found that the LIBS

technique can be very sensitive, having a resolution in the femtogram range (10-15 gm), and it is capable of detecting as few as

100 particles per cubic centimeter.

There are a number of other researchers and topics under the

CNER umbrella. Professors Steven Girshick and Sean Garrick

at the University of Minnesota are working on nucleation theory, aerosol dynamics, and the simulation of reactive flows

while their colleague Pro f. Alon McCormick, as well as

Professor Tom Brill of the University of Delaware, are working

on various aspects of sol-gel science. Other principal investigators include Professor Jan Puszynski of the South Dakota

School of Mines who is working on solid-state chemistry and

kinetics. On the theoretical side, Professors Don Thompson of

Oklahoma State University and Don Truhlar of University of

Figure 10. Schematic of Instrument to Produce Nanoscale Energetic Ingredients (Photo inset

is the single particle mass spectrometer at the CNER- University of Minnesota)

Advanced Nanoenergetic Ingredients for Explosives & Propellants

Nanometals, Nanoorganics, Coatings; Production, Characterization, Processing

Energetic 

Organics 

and Solvent 

or Sol-Gel

Agile research facility for the production & properties optimization of nanoenergetic materials.

Coating Flow

Counter Flow

Thermal Plasma Reactor 

Flame Furnace Particle 

Collector

Pump

Flow

“Spray-Freeze”

Coating Reactor

UVSource
48

Minnesota are working in the area of fundamental computations aimed tow a rds the simulation of the behavior of

nanocomposites. All in all, the CNER represents a major

national resource for understanding the science and engineering as they relate to the generation and behavior of nanoenergetic compounds and ingredients. It should be mentioned that

the Army Research Office (Drs. David Mann and Robert

Shaw) had a major role in the selection of the DURINT topic

on nanoenergetics and in the continued administration of the

CNER contract which started in 2001 and could run through

2005.

Acknowledgements

The author would like to thank Drs. Alex Gash, Jan Puszynski,

Lalitha Ramaswamy, Steven Son, and Michael Zachariah for

furnishing information and for their assistance in producing

this article. Also, I would like to thank my ARL colleagues Drs.

Brad Forch, Barrie Homan, Pamela Kaste, and Rose PesceRodriguez for their editorial assistance.

Selected References

Aumann, C.E.; Skofronick, G.L.; and Martin, J.A., “Oxidation

Behavior of Aluminum Nanopowders,” Journal of Vacuum

Science & Technology B, Vol. 13(2): pp. 1178-1183 (1995).

Bratcher, M.; Pesce-Rodriguez, R.; Kaste, P.; Ramaswamy, A.L.,

“Nanotube Modification of Energetic Materials”, Proceedings of

the 38th Meeting of the JANNAF Combustion Subcommittee,

Destin, FL, April (2002).

Cliff, M.; Tepper, F.; Lisetsky, V., “Ageing Characteristics of

Alex Nanosize Aluminum,” AIAA-2001, p. 3287 (2001).

Gash, A.E.; Simpson, R.L.; Tillotson, T.M.; Satcher, J.H., and

Hrubesh, L.W., “Making Nanostructured Pyrotechnics In A

Be a k e r,” Proceedings of the 27th In t e rnational Py ro t e c h n i c s

Seminar, pp. 41-53, Grand Junction, Colorado (2000).

Gash, A.E., Tillotson, T.M.; Satcher, J.H., Jr.; Hrubesh, L.W.;

Simpson, R.L., “Use of Epoxides in the Sol-Gel Synthesis of

Porous Fe2O3 Monoliths from Fe(III) Salts”, Chem. Mater.

2001, Vol. 13, p. 999, (2001).

Gash, A.E., Tillotson, T.M.; Poco, J.F.; Satcher, J.H., Jr.;

Hrubesh, L.W.; Simpson, R.L., “New Sol-Gel Synthetic Route

to Transition and Main-Group Metal Oxide Aerogels Using

Inorganic Salt Precursors”, J. Non-Cryst. Solids, Vol. 285, pp.

22-28, (2001).

Hahn, D.W. and Lunden, M.M., “Detection and Analysis of

Aerosol Particles by Laser-Induced Breakdown Spectroscopy”,

Aerosol Science and Technology, Vol. 33, p. 30-48 (2000).

Ma rtin, J.A.; Mu r r a y, A.S.; and Busse, J.R., “Me t a s t a b l e

Intermolecular Composites”, Warhead Technology, pp. 179-191

(1998).

Miziolek, A.W.; McNesby, K.L.; and Russell, R.S., “Military

Applications of Laser Induced Bre a k d own Sp e c t ro s c o p y

(LIBS)”, Abstract Book for Pittcon 2002, New Orleans, LA,

March (2002).

Puszynski, J.A., “Advances in the Formation of Metallic and

Ceramic Nanopowders”, Powder Materials: Current Research

and Industrial Practices, pp 89-105, F.D.S. Marquis ed., The

Minerals, Metals, and Materials Society (2001).

Puszynski, J.A.; Jayaraman, S.; Bichay, M.; Carpenter, G., and

C a r p e n t e r, P., “Formation and Reactivity of Na n o s i ze d

Aluminum Powders”, Proceedings of the World Congress on

Particle Technology, Sydney, Australia, July (2002).

R a m a s w a m y, A.L. and Kaste, P., “Nanoscale Studies for

Environmentally Benign Explosives & Propellants”, Proceedings

of the Meeting on Advances in Rocket Propellant Performance,

Denmark, September (2002).

Simpson, R.L.; Tillotson, T.M.; Satcher, J.H., Jr.; Hrubesh,

L . W.; Gash, A.E., “Na n o s t ru c t u red Energetic Ma t e r i a l s

Derived from Sol-Gel Chemistry”, Int. Annu. Conf. ICT (31st

Energetic Materials), Karlsruhe, Germany, June, (2000).

Son, S.F.; Asay, B.W.; Busse, J.R.; Jorgensen, B.S.; Bockmon,

B., and Pa n t oya, M., “Reaction Propagation Physics of

Al/MoO3 Nanocomposite Thermites”, Proceedings of the 28th

In t e rnational Py rotechnics Se m i n a r, pp. 833-843, Ad e l a i d e ,

Australia, November (2001).

Tillotson, T.M.; Gash A.E.; Simpson, R.L.; Hrubesh, L.W.;

Thomas, I.M.; Poco, J.F., “Nanostructured Energetic Materials

Using Sol-Gel Methods” J. Non-Cryst. Solids, Vol. 285, pp.338-

345, (2001).

Zachariah, M.R.; Mehadevan, R.; Lee, D.; and Sakurai, H.,

“Measurement of Solid State Reaction Kinetics in the Aerosol

Phase Using Single Pa rticle Mass Sp e c t ro m e t ry”, De f e n s e

Applications of Na n o m a t e r i a l s, Miziolek, A.W.; Karna, S.;

Mauro, M.; Vaia, R., eds., ACS Symposium Series Book,

American Chemical Society, Washington, DC (in preparation -

to be published in 2002). ■

Dr. Andrzej W. Miziolek is a Research Physicist at the US Army Research Laboratory/Weapons and Materials Research

Directorate, Aberdeen Proving Ground, MD. He is recognized for his expertise in combustion (particularly flame suppression) and

plasma research; multiphoton spectroscopy and collisional dynamics; and for his work in applying laser spectroscopy to problems

in chemical analysis and combustion diagnostics. Recently he has focussed his attention to research on nanoscale materials, in

particular on nanoenergetics, as well as on developing technology for force protection and anti-terrorism applications. Dr.

Miziolek has co-authored over 45 refereed journal papers, three book chapters, and 80 government technical reports and 

publications. He has published a book on Halon Replacements: Technology and Science (A.W. Miziolek and W. Tsang, eds.,

ACS Symposium Series 611, 1995) and is currently working as lead editor on two books: (1) Laser Induced Breakdown

Spectroscopy (LIBS): Fundamentals and Applications to be published by Cambridge University Press, and (2) Defense

Applications of Nanomaterials to be published by ACS Books. 

The AMPTIAC Newsletter, Volume 6, Number 1
The AMPTIAC Newsletter, Volume 6, Number 1 49

Sensors are not the first things that come to mind when considering the panorama of potential applications anticipated

from the burgeoning field of nanoscience and nanotechnology.

However, sensors are ubiquitous and play critical roles in the

function of a wide range of electrical and electronic systems,

from tiny electronic circuits to large and complex systems. For

instance, electronic and optoelectronic circuits need voltage,

current, temperature, light, and other sensors to operate.

Jumbo jets need mechanical sensors and actuators to function.

Nanotechnolgy offers hitherto unheard of possibilities in revolutionizing the sensors in use today and opening new frontiers

in functionalities. To paraphrase Richard Feynman (please see

this issue’s MaterialEASE), there is indeed still much room at the

bottom [1].

The Sensors and Electron Devices Directorate of the US

Army Re s e a rch Laboratory (ARL/SEDD), located in the

Maryland suburbs of Washington, DC, is dedicated to the

development of state-of-the-art sensors for our warfighters. We

are actively pursuing avenues that take advantage of the exciting potential of nanosystems to improve on the current

approaches, as well as look ahead to new sensor modalities. For

example, we are harnessing the properties of semiconductor

quantum-dots (QD) to improve infrared detection and are pursuing nanosize gold (Au) colloidal particles to enhance detection of biological threats. The advantages of nanoengineered

materials are realized by harnessing the quantum properties

observable in the nanoscale regime. Nanoscaled objects comprise the building blocks of the mesoscale world as we know it.

However, our technology has only recently allowed us to design

structures at this scale by having fundamental control over

physical and chemical processes and molecular attributes.

ARL/SEDD has taken an integrated approach to developing

sensors and advancing the underlying technology. For example,

nanophase materials are grown and fabricated through techniques such as molecular beam epitaxy (MBE), yielding semiconductor quantum dots for infrared (IR) detectors. These

materials are fabricated to produce functional devices which are

then packaged and integrated into subsystems to produce fully

functional prototype sensors. Substantial facilities, equipment

and investments have been dedicated to the emerging field of

nanosensors.

The Army has developed specialized tools to fabricate and

analyze these tiny structures. One example is the magnetic resonance force microscope (MRFM), which is a scanning-probetype instrument capable in some instances, of measuring the

nuclear magnetic resonance (NMR) response of a single proton. Instead of detecting small electrical signals as conventional magnetic resonance imaging (MRI) does, MRFM detects

atomic and subatomic forces mechanically. The instrument

uses tiny magnets mounted on cantilevers fabricated using

MEMS techniques. MRFM is several orders of magnitude

more sensitive than conventional MRI for objects smaller than

one-thousand cubic micrometers. Until recently, conventional

electrically-detected MRI has lacked the sensitivity to make

solids MRI useful, but MRFM will make force detected solids

MRI a reality. (Note: Solids MRI differs significantly from

medical MRI, which is a form of liquids MRI. This is because

the human body is primarily composed of water, which provides an excellent NMR response to traditional magnetic resonance technology.) When perfected, MRFM should be able to

image a single atom in a three dimensional (3-D), non-homogenous object. Such a breakthrough would find broad applications in biology, medicine, materials science, semiconductors,

polymers, and many other areas.

Self-Assembled Quantum Dots for IR Detector Application

Molecular beam epitaxy (MBE) is a specialized, ultrahigh vacuum evaporation technique normally used to grow multilayer

semiconductor films with interfaces that are essentially flat,

even at the atomic level. However, if a material with a relatively large lattice constant were grown on top of a material with a

smaller lattice constant, the large compressive strain energy

could be relieved by spontaneous coalescence of the larger lattice constant material into 3-D ‘islands’ on the surface. These

islands would take the form of crystallographic pyramids or

multifaceted domes and could range in size from a few

nanometers to several hundred nanometers. Because of their

extremely small size and the manner in which they are formed,

they are referred to as self-assembled quantum dots.

Figure 1 shows an atomic force micrograph of a set of InAs

quantum dots grown on a GaAs substrate. The lateral dimensions are exaggerated because the radius of curvature of the

Dr. Paul M. Amirtharaj, Dr. John Little, Dr. Gary L. Wood, Dr. Alma Wickenden, and Dr. Doran D. Smith

Sensors and Electron Devices Directorate

US Army Research Laboratory

Adelphi, MD
probe tip is comparable to the size of the dots. If the islands are

embedded in a host material with a larger bandgap (e.g., by

crystal overgrowth of GaAs), they form isolated 3-D potential

wells that have been shown to bind several discrete energy levels much like isolated atoms [2]. This is the 3-D analog to the

one-dimensional (1-D) semiconductor quantum well that is

formed when a very thin layer of a low-bandgap material is

sandwiched between two higher-bandgap layers. 

One of the results of carrier confinement in quantum wells is

a strong infrared absorption that occurs when electrons in the

ground state of the well (due to doping with electron donor

impurities) are excited to a higher energy subband (allowed

energy level within the conduction and valence “bands” of the

quantum well). This effect has been used to make quantum

well infrared photodetectors (QWIPs), which are the fundamental element of high-performance thermal imaging systems.

Polarization selection rules for these intersubband transitions

dictate that only light that is polarized in the direction of quantization (i.e., perpendicular to the quantum well layer) can be

absorbed. Unfortunately, the typical geometry of a 2-D imaging array of QWIPs is such that light incident on the array has

no polarization component perpendicular to the quantum well

layers. This requires that each pixel of the array have a polarization rotating structure (typically a diffraction grating) etched

into its surface, which limits the efficiency and producibility of

QWIP detector arrays.

Since quantum dots confine carriers in all three dimensions,

intersubband transitions can be excited by all polarizations of

infrared light. Also, due to the discrete nature of the energy levels, the peak oscillator strength for normal-incidence infrared

absorption should be very large in doped quantum dots. This

suggests that quantum dots could be used to replace integrated

optical coupling structures used in quantum well infrared

detectors.

Figure 2 shows the polarization-dependent infrared photocurrent spectra of a quantum dot infrared photodetector

(QDIP), consisting of a stack of InAs quantum dot layers separated by GaAs barrier layers. The QDIP responds to both

polarizations of light in the wavelength range of interest for

thermal imaging. However, infrared detectors based on quantum dots are in their earliest stages of development. The dark

currents are high, and it is difficult to predict the operating

wavelength a priori because of the complexity of the structures.

Researchers at ARL are currently conducting a systematic study

of the interactions between the electronic levels of the quantum

dots and the quasi-continuum of electronic states in the host

(barrier) material surrounding them. Because of the wide range

of semiconductor materials that are available for use in quantum dot systems and the flexibility and control of growth

parameters offered by MBE techniques, rapid advances in the

performance of infrared detectors based on self-assembled

quantum dots will occur in the near future.

Nanotechnology for Displays and Biodetection

The Army has extensively investigated nanoscale structures to

enhance the performance of a number of engineered material

systems for a variety of sensor applications. Dendrimers have

been examined as a means to encapsulate or capture chromophores and augment their physical and chemical properties.

In other work, nanoscale structures and particles have been

investigated for luminescent research that could have applications for future Army displays. Finally, nanostructures are being

i n vestigated for surface-enhanced Raman scattering in an

attempt to detect and identify harmful biological agents in the

environment.

Re s e a rch and development of electronic materials form the

foundation of the modern information re volution. As the

dimensions of bulk solid-state devices rapidly approach the

limits of pro c e s s a b l i t y, molecular-based devices that inherently take advantage of quantum physics will play incre a singly important roles in electronic evolution. Organic semiconductors have demonstrated their potential as a new class

of electronic materials for commercial applications including

50

Figure 2. Photocurrent Spectra for a InAs/GaAs

Quantum Dot Detector Structure (grown, fabricated,

and tested at ARL) for Light Polarized Parallel and

Perpendicular to the Quantum-dot Layers

9

8

7

6

5

4

3

2

1

0

2 4 6 8 10 12 14

E vector parallel to dot layers

E vector perpendicular to dot layers

Wavelength (μm)

Figure 1. Atomic Force Micrograph of InAs

Quantum Dots on a GaAs Substrate

0.0 0.25 0.50 0.75 1.00

micrometers

The AMPTIAC Newsletter, Volume 6, Number 1

1.00

0.75

050

0.25

0.00 
e l e c t ro p h o t o g r a p h y, light-emitting

diodes (LEDs) [3], transistors [4],

and sensors [5]. The pioneering

w o rk by Tang and Van Slyke [3]

demonstrated that organic lightemitting devices (OLEDs) indeed

h a ve the necessary attributes and

c o m p e t i t i ve advantages to be cons i d e red seriously for display applic a t i o n s .

An important distinction must be

made between inorganic semiconductors and organic-based semiconductors. Inorganic semiconductors

h a ve occupied and unoccupied

energy bands, valence, and conduction bands, respectively, that can

extend over many unit cells. For

typical Si-based semiconductors,

these energy bands are determined

by a tetrahedral bonding structure

formed by sp3 hybridization. For

organic semiconductors, the occupied and unoccupied energy levels

are formed from planar structures of

sp2 bonds as well as -bonds. The

combination of bonds form the

highest occupied molecular orbitals (HOMO) and lowest

unoccupied molecular orbitals (LUMO), where the benzene

ring is the typical bonding structure for most organic semiconductors.

For OLED applications, the organic films are typically not

crystalline, which leads to a high degree of localization of the

molecular orbitals on a single molecule. Thus, molecular-based

electro-optical devices such as OLEDs rely on nanotechnologyengineered materials that take advantage of quantum confinement at a molecular level. In OLEDs, the transport and light

emission properties are limited by the injection and subsequent

diffusion of hole and electron carriers from the anode and cathode, respectively, to the light emission region. The drift diffusion of holes and electrons is determined by a field-dependent

hopping from a molecular orbital state that is energetically

lower than the molecular state in a neighboring molecule.

Cross-section of layered thin-film structure

LUMO 

Energy 

Levels

Photon

NPB Alq

–

+

+

+

–

–

HOMO

Energy 

Levels

Electron migration

Electron-Hole pair forms

Excition, produces photon

Hole migration

The AMPTIAC Newsletter, Volume 6, Number 1 51

Figure 3. Energy Diagram for a Typical Small Molecule OLED

Individual Fit Results

Experimental Data

NPB

Temperature (K)

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Fit Results

Experimental Data

Alq

Temperature (K)

NPB

Alq

Figure 4. Thermally Stimulated Luminescence (TSL) Spectra for NPB and Alq. Results Show that the Energy Disorder (corresponding to

temperature in the graphs) in Alq is Twice as Large as NPB. (The TSL for Alq occurs at a higher temperature than it does for NPB, thus

the greater energy disorder.)

0 100 200 300 0 50 100 150 200 250 300
52

Then, an electron-hole pair combines on a single molecule,

forming an exciton that ultimately decays with the emission of

a photon.

Figure 3 displays an energy diagram for a typical small molecule OLED. The energetic disorder in molecular glassy films

has been measured by the Army using thermally stimulated

luminescence (TSL) [6]. These results show that the energy disorder is inherently larger in the electron-transporting tris-8

hydroxyquinoline aluminum (Alq) layer as compared to the

hole-transporting N,N'-bis-(1-naphthyl)-N,N'-diphenyl1-1,1-

biphenyl1-4,4'-diamine (NPB) layer. This is in good agreement

with the lower electron mobility in Alq as compared to NPB

and can lead to an unbalanced carrier pair in the emissive

region and device instabilities [7]. Figure 4 compares the TSL

for NPB and Alq. In addition to organic-based displays, we are

investigating inorganic nanoparticle-based emitters for display

applications. As with organics, the quantum confinement in

nanophosphors improves the recombination cross-section and

light output efficiency.

Raman spectroscopy is an optical technique that provides

information about the structure of molecules. It can be used in

aqueous systems due to the weak Raman signal from water,

making it ideal for analysis of biological organisms. Raman

spectroscopy is inherently weak, but methods to enhance the

signals have been known for over 25 years. Surface-enhanced

Raman spectroscopy (SERS) requires nanometer-scale metal

features to enhance the signals by up to 16 orders of magnitude. Army researchers are investigating several methods for

preparing substrates with such nanoscopic features for the

detection and identification of bacteria [8]. They include Au

colloidal particles immobilized on surfaces, electrochemically

roughened Au surfaces, and periodic particle arrays from Prof.

Richard van Duyne at Northwestern University [9]. In each of

these substrates, the feature size is in the 10 nm to 150 nm

range. The degree of enhancement is strongly related to the size

of the nanoscopic features and the excitation wavelength used.

The first critical step in collecting SERS spectra of bacteria is

to develop an SERS substrate that the bacteria can approach

within 10-100 nm. This distance requirement is established by

the short range of the SERS enhancement. Since both a metal

surface or particle and the bacterium have a negative surface

charge, it is necessary to either modify the particle or surface

with a small molecule to neutralize its charge or hold the surface at a neutral or slightly positive charge. The size of the

enhancing features can then be optimized for the chosen excitation wavelength. Once the bacteria move within the SERS

enhancement range, the spectra can be collected using laser

excitation at 647.1 nm. Once a library of spectra is collected,

advanced statistical analysis methods such as chemometrics or

a neural network can be trained for the identification of the

genus and species of the bacterium.

Nanoscale Electromechanical Systems (NEMS) 

for Radio frequency (RF) Filter Applications

ARL has a strong effort in piezoelectric microelectromechanical

systems (MEMS) device fabrication, with specific expertise in

lead zirconate titanate (PZT) based piezoelectric devices. These

include thin film resonators, magnetometers, vacuum pumps

for chip-scale mass spectrometers, and power generation

devices. PZT resonators with resonant frequencies from 0.2 to

9 MHz have been fabricated at ARL, and their response has

been studied intensively [10]. Resonator arrays for RF filter

devices operating in the GHz frequency range are of interest to

the Army for lightweight, low-power, high-precision frequency

selection applications, including wireless communication,

tracking and surveillance, and weapons guidance and fusing. A

high quality factor, or Q, is required in the resonator device to

reduce phase noise and ensure stability against frequency-shifting phenomena [11].

Electromechanical resonator devices offer potential advantages in size, weight, and power consumption over surface

acoustic wave (SAW) or bulk acoustic resonators currently used

for frequency filtering applications. Pi ezoelectric electromechanical resonator devices should demonstrate advantages

over equivalent electrostatic devices for high-frequency applications, since they are less sensitive to degraded coupling strength

as the device dimensions are reduced [12]. Equation 1 displays

the Euler-Bernoulli beam equation for the natural resonance

frequency of a doubly clamped mechanical resonating beam,

where L is the length of the beam, t is the beam thickness, E is

the elastic modulus, and ρ is the density [13]. 

0(L) E t ——— = 1.027 — — Eq. 1

2 ρ L

2

For resonance frequencies in the GHz range of interest,

electromechanical resonator devices typically require lengths in

the range of 1 to 10 mm, with thickness and width dimensions

on the order of hundreds of nanometers. Material properties

factor prominently in the frequency response. The roles of

grain boundaries, defects, and other nonbulk materials characteristics of thin films are unknown at present and must be

investigated to effectively model device response and to ensure

predicted device operation and reliability.

Research on NEMS for high-Q resonator filter array fabrication has recently begun at ARL, in collaboration with research

groups at the University of Maryland. While PZT is an attractive material for piezoelectric filters (due to its high piezoelectric coupling coefficient [14]), the operating frequency of PZT

resonators is limited to the MHz range, due to the large

acoustic time constant of the material. For this reason, piezoelectric materials such as aluminum nitride (AlN), zinc oxide

(ZnO), and related compounds are being investigated. The fast

acoustic response times of these wide bandgap semiconductor

materials translate to theoretical maximum frequencies of more

than 100 GHz [15]. Additionally, AlN and ZnO may be grown

as thin films (100 nm thick or less) by a variety of techniques,

on either silicon substrates (for cost advantages) or a wide

bandgap substrate such as silicon carbide (SiC). AlN in particular is chemically inert, radiation hard, and can withstand high

temperatures, and chemically harsh environments, making it

an excellent candidate for integration of NEMS resonator filters into SiC integrated circuits.

The AMPTIAC Newsletter, Volume 6, Number 1

√
The AMPTIAC Newsletter, Volume 6, Number 1 53

Detailed device models are required to ultimately enhance filter performance and sensor output quality. The investigation of

nonlinear behavior and nanoscale surface effects is planned

using ARL’s characterization capabilities described elsewhere in

this article. In addition, the formation of thin film microstructure is being investigated in collaboration with the California

Institute of Technology (Caltech.) Predictive theory, validated

by targeted experiments, is being developed to guide materials

development, materials selection, and device design. In particular, the piezoelectric materials used as the active components

of the NEMS resonator devices are typically composed of

domains due either to the deposition technique or to the

requirement of unmatched materials systems in the device

design. The effects of domain structure in the thin films, where

the film thickness may be less than or of the same approximate

scale of the domains themselves, is considerably different from

that of bulk polycrystalline or textured materials. The resultant

device properties may be strongly influenced by the ability to

manipulate the domain structure. In the ideal case, a resonator

beam formed on a single grain would be expected to exhibit

single crystal properties that would result in maximum Q for

the device.

The fabrication of MEMS and NEMS devices is performed

in ARL’s new state-of-the-art 10,000 square foot class 100

Cleanroom. An expansion of this facility is currently being

planned to include additional Class 100 and Class 10 fabrication areas. A compliment of pattern transfer techniques are

available for MEMS/NEMS device fabrication, as listed in

Table 1. Electron beam direct-write

lithography is used to generate device

f e a t u res on the scale of tens of

nanometers. Figure 5 illustrates 50

nm scale quantum dot patterns with

100 nm spacing exposed in polym e t h y l m e t h a c rylate (PMMA) elect ron beam resist, and gold finger

structures with widths of less than 40

nm, which have been patterned in

A R L’s fabrication facility. Si m i l a r

metal patterns are used as masking

l a yers for subsequent re a c t i ve ion

etching or ion milling techniques,

which enable pattern transfer into

thin films that form the active device

s t ru c t u re. Both anisotropic and

isotropic dry etching techniques are

employed in the fabrication of freestanding MEMS/NEMS resonators.

In addition to developing prototype

devices, test structures are specially

fabricated to investigate the physical

p ro p e rties of thin film materials.

These structures provide feedback to

the fundamental materials investigations on grain formation and also

facilitate direct measurement of physical properties such as tensile strength

of thin films formed under varying deposition or growth conditions. Such fundamental information will subsequently be

used to allow more accurate and sophisticated modeling of

devices, enabling the improvements in device operation and

design through investigation of materials and device properties

at the nanoscale.

Force Detected Magnetic Resonance of GaAs

Force detected magnetic resonance is a recent technique for the

detection of magnetic resonance, where the signal is detected

mechanically instead of electrically. Magnetic Re s o n a n c e

Imaging (MRI) is the most recognizable nuclear magnetic resonance (NMR) application, as its primary use is for medical

purposes. Conventional MRI employs electrical detection,

effectively for most objects greater than 10 mm in size.

Electrically detecting NMR is very insensitive at smaller scales

while mechanical detection on the other hand, is much more

sensitive at the nano and low-micron scales. The first proposal

and demonstration of a technique for mechanically detecting

magnetic resonance was done by A. Gozzini in 1963 [16]. At

the time the approach was not practical but research continued.

In 1991, John Sidles [17, 18] suggested attaching a small magnetic particle to a cantilever and using the magnetic field gradient from the particle to perform nanometer imaging. Sidles

called his approach magnetic resonance force micro s c o p y

(MRFM).

MRFM entails measuring the force between the magnetic

moment of nuclei (or electrons) in a sample and the magnetic

Figure 5. Scanning

Electron Microscopy

(SEM) Images of 

Patterns Written at ARL

using Electron-Beam

Direct-Write Lithography:

a) 50nm Quantum Dot

Patterns on 100 nm

Centers, and b)

Nanoscale Gold Finger

Structure, with Metal

Deposited using 

a Liftoff Technique 

after Lithographic 

Patterning

(a)

(b)

206nm

37nm
54

moment of a nearby magnetic particle (Figure 6). A magnetic

particle is attached to a microcantilever, and the sample is

placed nearby. The sample contains nuclei that have an associated magnetic moment. The magnet mounted on the cantilever

feels a force from the sample, thus displacing the cantilever.

The two magnets either attract or repel each other depending

on their relative orientation. 

By using a combination of amplitude and frequency-modulated RF radiation the sample magnetic moments are cyclically

‘flipped’. Cyclical flipping of the magnetic moments, or magnetic resonance, occurs when the energy of an individual RF

photon (energy = Planck constant times frequency, or E=hf)

equals the energy difference between the nuclei’s energy levels.

Each nuclei has energy levels that are due to the relative orientation of its magnetic moment with respect to a background

magnetic field (parallel or antiparallel). For example, magnetic

resonance for 75As (Arsenic-75 isotope) at 1 T (Tesla) occurs at

a frequency of 7.2919 MHz and is 51.56 MHz at 7.07 T. The

difference between the energy levels is a linear function of the

magnetic field stre n g t h .

When the RF is in resonance

with the energy differe n c e ,

the nuclei either absorb energy or are stimulated to emit

e n e r g y, there by oscillating

between the two energy levels. The nuclei’s oscillation

between energy levels oscillates the nuclei’s magnetic

moment between parallel and

antiparallel to the magnetic

field.

As the two magnets cyclically attract and repel each

o t h e r, the cantilever will

begin to oscillate. This oscillation is detected by a fiberbased interferometer. If Q is

the mechanical quality factor

of the cantilever, applying an

oscillating force at the

mechanical resonance frequency of the cantilever results in a Q

enhancement of the cantilever’s amplitude. Thus, the signal is

mechanically amplified at least 10,000 times, making detection

with the fiber interferometer easier.

A number of groups have reported force-detected NMR in

solids. Rugar was the first to report an NMR signal using

MRFM techniques [19], exhibiting an orders-of-magnitude

improvement over conventional NMR. The magnetic particle

creates a changing magnetic field across the sample that assures

that only nuclei within a narrow slice experience the correct

value of magnetic field to be in resonance with the RF. Nuclei

outside of the resonant slice are at the wrong magnetic field to

be in resonance with the RF. The slice-selective character of

MRFM allows a 3-D image of the sample to be obtained by

scanning the magnetic particle with respect to the sample in

3-D [20].

The proximate goal of our research is force detection and

imaging of nuclear magnetization in as-grown material and in

as-fabricated Group III-V (of the periodic table) semiconducThe AMPTIAC Newsletter, Volume 6, Number 1

Figure 6. Typical MRFM Apparatus

Cantilever

Magnetic Particle

RF Coil

Resonant Slice

Sample

Optical Fiber

E-beam lithography

Contact lithography

Photolithography cluster tool

UV photostabilization

Downstream plasma ashing

Mask making

Silicon deep reactive ion etching 

(DRIE)

Isotropic silicon etching 

Deep dielectric etching

Refractory metal etching

Dielectric (oxide/nitride) dry etching

Ion milling

PZT reactive ion etching

Laser Doppler vibrometry

Metal sputtering

Metal/compound e-beam evaporation

Plasma Enhanced Chemical Vapor

Deposition (PECVD) oxide/nitride

Low Pressure CVD oxide/nitride

Sol-gel PZT

Wet and dry thermal oxidation

Wafer-to-wafer alignment

Anodic and fusion wafer bonding

Variable angle spectroscopic 

ellipsometry

Wafer bow stress measurement

Nanospec film thickness analysis

Four point probe analysis

Profilometery

Table 1. Partial List of Capabilities for MEMS/NEMS Device Processing in ARL’s Class 100 Cleanroom Facility
The AMPTIAC Newsletter, Volume 6, Number 1 55

tor devices. As a step toward this goal, we have constructed an

MRFM apparatus suitable for force detecting NMR at 4 K. We

applied the technique to observe 69Ga, 71Ga, and 75As in GaAs,

increasing the number of isotopes observed with force detection from four (1H, 19F, 59Co, and 23Na) to seven [21]. The sample we examined was a 3-μm epilayer of GaAs, doped at 0.6 x

1018 cm-3 Si and 2.0 x 1018 cm-3 Be. A hand-cleaved rectangle of

this material (~210 μm x ~150 μm) was then attached to the

cantilever (k ~0.05 N/m) using silver-filled epoxy. This cantilever was coated with 0.2 μm of Au on each side to enhance

thermal conductivity, and when loaded it had a resonance frequency of 1.034 KHz, and Q = 154 at 5 K in the presence of

He exchange gas. Q is the quality factor of the cantilever resonance. The magnetic gradient source was a 250 μm diameter Fe

cylinder positioned ~35 μm from the sample. Because of

Newton’s third law of motion – for every force there is an equal

and opposite force - it does not matter if the sample or magnetic particle is attached to the cantilever. A 1 1/2 turn, 710-

μm diameter coil generates the 4-gauss RF magnetic field. The

motion of the cantilever was detected by a wavelength-tuned

fiber optic interferometer.

Figure 7 displays a force-detected NMR spectrum of our

sample observed by sweeping the applied magnetic field at a

fixed RF center frequency of 51.56 MHz. All three isotopes are

clearly resolved, with cantilever displacements of ~1.3 picometers. The large width of the NMR peaks represents the spatial

extent of the sample.

As shown, Army researchers have applied force-detected

NMR techniques to GaAs and imaged its nuclear isotopes with

1-μm resolution. MRFM technology promises countless applications to material science, medicine, biology, and device fabrication. The ultimate goal for the MRFM community is 3-D

imaging of proteins, where the location of every proton in the

protein is measured with 0.1-nm accuracy (protein structure).

For Group III-V device work, ARL expects to be able to measure such properties as the local value of the electric field; the

shape of electron wavefunctions in quantum wells; and 3D

strain, internally and nondestructively in as-grown material and

as-fabricated devices.

Conclusion

The potential of nanostructures seems limitless in providing

detailed information on the cellular, molecular and even atomic level processes. Substantial advantages have already been realized in radiation detection as well as electronic displays.

Revolutionary detection modalities, such as real-time biological

threat detection, are on the horizon. The future undoubtedly

will bring more exciting developments which will advance the

state-of-the-art and in the process, provide our military services an additional edge over our adversaries.

Acknowledgements

The authors wish to acknowledge the contributions made by the following persons to this article: Eric Forsythe, Nicholas F. Fell, Jr., Brett

Piekerski, and Kent R. Thurber.

References

[1] R.P. Feynman, There’s Plenty of Room at the Bottom, Reprinted in

JMEMS 1, 60 (1992).

[2] M. Grunmann, O. Stier, and D. Bimberg, Phys. Rev. B15, 52 (16),

11969 (1995).

[3] C.W. Tang and S.A. VanSlyke, Appl. Phys. Lett. 51, 913 (1987).

[4] D.J. Gundlach, Y.Y. Lin, T.N.

Jackson, S.F. Nelson, and D.G.

Schlom, IEEE Elec. Dev. Lett., 18,

87 (1997).

[5] Q. Zhou and T.M. Swager, J.

Amer. Chem. Soc. 117, 7017 (1995).

[6] E.W. Forsythe, D.C. Mo rt o n ,

C.W. Tang, and Y. Gao, Appl. Phys.

Lett. 73, 1457 (1998).

[7] H. Aziz, Z.D. Popovic, N.X. Hu,

A.M. Hor, and G. Xu, Science 283,

1900 (1999).

[8] N.F. Fell, Jr., A.G.B. Smith, M.

Vellone, A.W. Fountain III, SPIE Vol

4577 Bellingham, WA, in pre s s

(2001).

[9] C.L. Haynes and R.P. van Duyne,

J. Phys. Chem. B 105, 5599-5611

(2001).

[10] B. Piekarski, D. De Voe, M.

Du b e y, R. Kaul, and J. Conrad,

Sensors and Actuators A 91, 313-320

(2001).

[11] C.T.-C. Nguyen, L.P.B. Katehi,

and G.M. Rebeiz, Proc. IEEE, Vol.

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0

Applied Magnetic Field (Tesla)

71Ga 69Ga 75As

Figure 7. Typical Plot Output for an MRFM
56

Dr. Paul M. Amirtharaj is a Physicist at ARL with expertise in the interaction of light with semiconductors. His current research interests include the physics of nanoscale structures and devices, in particular their optical behavior. He has held staff positions at the

Night Vision Lab (1984-1989), National Institute of Standards and Technology (1990 to 1999) and joined the Sensors and

Electron Devices Directorate at ARL in 1999. He has coauthored more than 60 publications which include three book chapters.

Dr. Amirtharaj received his Ph.D. from Emory University in 1981.

Dr. John W. Little received his Ph.D. in physics from the University of Tennessee in 1982. His thesis work involved theoretical and

experimental studies of the optical properties of metallic nanoparticles. He currently leads a research team in the Infrared

Materials Branch at the Army Research Laboratory in Adelphi, Maryland. His work includes studies of III-V semiconductor structures such as strained-layer superlattices, quantum wells, and quantum dots for application in high-performance thermal imaging

systems.

Dr. Doran D. Smith, received his Ph.D. in physics from the University of Michigan in 1985. He joined the Army Research Laboratory

(then LABCOM) in 1985 where he worked on mesoscopic devices, magneto-transport and magneto-optical properties of III-V

semiconductors, and high-speed devices. In 1995 he initiated ARL’s force detected magnetic resonance program. Dr. Doran holds

two patents and is the author of 35 publications and one book chapter on single electron devices.

Dr. Alma E. Wickenden conducts research in MEMS/NEMS devices and process development in the Sensors and Electronics

Devices Directorate at ARL. Her research interests focus on the relationship between the microstructure of materials and resultant

electronic and mechanical properties, and she has published over 60 papers in the field. She is currently pursuing electron beam

lithography of nanoscale electromechanical devices and novel sensor concepts. From 1993-2001, she conducted research on

III-nitride semiconductor thin film growth by MOCVD at the Naval Research Laboratory. She had previously worked as an engi -

neer in industry in GaAs VPE growth and SAW device process development. Dr. Wickenden received her Ph.D. (1993) and M.S.

(1989) degrees in Materials Science and Engineering from Johns Hopkins University, Baltimore, MD.

Dr. Gary Wood received his B.S. in Physics from Drexel University in 1980, his M.S. in Physics in 1982, and his Ph.D. in Physics

from Catholic University In 1992. Dr. Wood has been a US Army Civilian Employee from 1982 to the present. He has worked

at both the Night Vision Lab and the Army Research Laboratory over that period. Dr. Wood’s research has included basic and

applied research in the areas of nonlinear transmission and light induced gratings. Dr. Wood is currently the Branch Chief of the

Optics branch in the Sensors and Electron Devices Directorate of ARL. Dr. Wood has authored chapters in three textbooks and is

the author or coauthor of more than 100 publications in refereed journals and conference proceedings. His work includes many

patents and he is a recipient of two Army R&D Achievement Awards.

86, No. 8, 1756 (1998), and references therein.

[12] D.L. DeVoe, Sensors and Actuators A 88, 263-272 (2001).

[13] A.N. Cleland, M. Pophristic, and I. Ferguson, Appl. Phys. Lett.

79, 2070-2 (2001).

[14] P. Muralt, Integrated Ferroelectrics 17, 297-307 (1997), and 

references therein.

[15] A. Ballato, “Mi c ro - e l e c t ro-acoustic Devices for Wi re l e s s

Communication,” IEEE Sarnoff Symposium on Advances in Wired

and Wireless Communications (March, 1999).

[16] A. Gozzini, Proceedings of the XIIth Colloque Ampere, Bordeaux

17-21 Sept. 1963, Ed.: R. Servant and A. Charru, Electronic Magnetic

Resonance and Solid Dielectrics.

[17] J.A. Sidles, J.L. Garbini, K.J. Bruland, D. Rugar, O. Zuger, S.

Hoen, and C.S. Yannoni, Appl. Phys. Lett., 58, 2854 (1991).

[18] J.A. Sidles, et al., Rev. Mod. Phys. 67, 249 (1995).

[19] D. Rugar, O. Zuger, S. Hoen, C.S. Yannoni, H.-M. Vieth, and

R.D. Kendrick, Science 264, 1560 (1994).

[20] O. Zuger, S.T. Hoen, C.S. Yannoni, and D. Rugar, J. Appl. Phys.

79, 1881 (1996).

[21] K.R. Thurber, L.E. Harrell, R. Fainchtein, D.D. Smith, Appl.

Phys. Lett. in press (to appear, March 11, 2002). ■

The AMPTIAC Newsletter, Volume 6, Number 1
Introduction

Miniaturization of electronics brings a multitude of benefits,

particularly when a number of disparate functions are integrated onto the same substrate. In the case of the ubiquitous microprocessor chip, the substrate itself is the chip. Its functions are

logic, memory, and control circuitry, which deal with the

information flow both on and off the chip. Tremendous gains

in reliability were obtained by integrating these functions within the same device. These initial gains were mostly due to eliminating connections between individual chips of first generation integrated circuits, as well as reducing the total number of

parts. Since that time, miniaturization has driven up the number of individual transistors on chips to well over 10 million. It

has also resulted in a multibillion dollar industry which represents a significant fraction of the US Gross Domestic Product.

Integrated chips are now in most modern conveniences, such as

alarm clocks, coffee makers, and most forms of public and private transportation.

The microelectronics industry is driven by two purposes: the

development of new applications and the miniaturization of

existing ones. This is why most consumers find buying a new

computer every few years irresistible, realizing upwards of a sixfold increase in the performance for the same number of dollars they spent three years before. The process of miniaturization is characterized by ‘Moore’s law’, named after Gordon

Moore, the founder of Intel, who first noticed that the number

of transistors on a chip doubled every eighteen months.

However, this is not a law of physics, but rather a law of economic survival. Companies that can’t keep up with this frenetic pace soon find they are uncompetitive, and then fail.

Compounding this challenge is the fact that as the integration

level increases, the cost of manufacture per unit area of chip

must remain the same.

A version of Moore’s law is represented in Figure 1, plotting

the characteristic dimension of manufactured integrated circuits (ICs) over the last forty years. Many predicted ‘ends’ to

Moore’s law have come and gone. For example, at one time it

was thought impossible to manufacture a chip with feature sizes

much below a micron. New approaches are actively being

developed to allow manufacture of chip features down to 20

nm (2/100 of a micron) in size.

Now we are faced with the end of Moore’s law being determined by the physics of the transistors and circuits themselves,

presently projected to be around 20-30 nm. Below this size, it

becomes increasingly difficult (i.e. expensive) to get these small

transistors to turn off, leading to unacceptable power dissipation. While this problem may be solved by innovative devices

and circuit design, the transistor size is rapidly approaching the

point when there are so few atoms in the critical regions of the

transistor that the underlying solid state (i.e. bulk material)

physics begins to break down.

So is there a different paradigm for the manufacture and

integration of switches and memory elements? Given that we

are looking for devices that have dimensions around 10 nm and

lower, it is natural to turn to the chemist who after all is

extremely skilled at working in this size regime. The question

then becomes, can we design individual molecules that have a

specific electronic functionality? Anticipating success, two further questions come to mind. First, can we look for additional

help in assembling these molecular components into a useful

circuit? Wiring up our molecular memory element to our

molecular switch by direct manipulation looks hopelessly

impractical apart from heroic onesies and twosies demonstrations. Second, what kind of circuits should we aim for, or more

specifically what will the architecture of our memory and logic

blocks look like?

These issues also represent the three thrusts of the DARPA

Molecular Electronics program and the remainder of this 

Figure 1. Recent IC Developments 

Have Followed Moore’s Law

Dr. Christie R. K. Marrian

Microsystems Technology Office

DARPA

100

10

1

0.1

0.01

0.001

1960 1970 1980 1990 2000 2010 2020 2030

Year

Single

First Integrated

256K

64M

16G

MOSFET (Metal Oxide Semiconductor 

Field Effect Transistor) Scaling

The AMPTIAC Newsletter, Volume 6, Number 1 57
article is framed accordingly. The last section will briefly discuss

the prospects for molecular electronics and where we might see

these first commercial products emerge.

Devices

To date, chemists’ ingenuity in designing and synthesizing electronically advantageous molecules has rather outpaced engineers’ ability to reliably test their properties at the single molecule level. However, this trend has begun to change as a number of ways of studying electronic transport of single (or small

numbers of) molecules have been reported. As a result, the pace

of molecular design optimization is accelerating.

One of the landmark papers on conduction through single

molecules was published by Aviram and Ratner [1]. They

pointed out that if one could couple a readily oxidizing group

(D) to a readily reducing group (A), the alignment of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO)

would be such that electron hopping

(the main mode of electronic conduction in single molecules) would be easier in one direction than the other

( Fi g u re 2). This would result in a

molecular diode. While straight forward in principle, this has been difficult to demonstrate. Not so much

because of the difficulty in synthesizing

the molecules, but because of the difficulty in testing them.

An example from the work of Jim

Heath and Fraser Stoddard at UCLA

[2] is somewhat more complicated and

a full mechanistic study continues. The molecule, an example

of which is shown in Figure 3, is a member of the rotaxane family. The groups at either end of the molecule are designed to

bond to the electrode surfaces. The area of interest is the center

of the molecule, which is comprised of two electron-donating

(oxidizing) groups connected by a short spacer. They are surrounded by a ring which has a positive charge. This ring can

move up and down the backbone of the molecule and has a 

sufficiently positive charge to change a donor group to a net

acceptor (reducing group). This motion can be induced by

oxidizing/reducing the molecule. The net result is an I/V characteristic akin to a diode which reverses polarity! The oxidation/reduction is caused by raising the voltage across the ends

of the molecule above a threshold (of a few volts). This is a 

particularly fascinating characteristic, as there is no equivalent

two-terminal device in the solid-state world. The applications

to memory are obvious, but Heath and his collaborators in 

Stan Williams’ group at Hewlett-Packard (HP) Labs are also

looking at logic applications and are continuing to refine the

molecular design.

A second example, which works on a slightly different principle, comes from the collaboration of Jim Tour (a chemist at

Rice Un i versity) and Ma rk Reed (an engineer at Ya l e

University) [3]. The I/V characteristics, presented in Figure 4,

show a negative differential resistance (NDR) and is reminiscent of a resonant tunneling diode, although it is believed to be

governed by a different mechanism. For example, it has been

proposed that the discontinuities in the characteristic are due to

successive oxidations of the molecule (included on the I/V

characteristic). This changes the conductivity of the molecule

dramatically as each extra electron is taken on. The inset shows

the electron orbital calculations of Jorge Seminario at the

University of South Carolina [4]. He has correlated the oxidation states with an overlap of the electron orbitals which favor

conduction in the “on” states of the molecule. In the “off” state,

there is no such pronounced overlap. Interestingly, his results

suggest a conformal change (a twisting of the central ringed

group) associated with this conductivity change. Some experimental findings supporting the importance of this conformational change were recently published by Paul Weiss’s group at

Pennsylvania State Univeristy [5]. They measured the switching

rates of Tour-Reed NDR molecules through careful Scanning

58

Figure 2. A Schematic of 

a Molecular Rectifier

Figure 3. Molecular Diode

which can Reverse Polarity

Reverse

D

A

Low probability of hopping

Forward

A

D

High probability of hopping

This ring structure

may “slide” along 

the molecule’s backbone

No Gradient

D

A

Metal contacts

The AMPTIAC Newsletter, Volume 6, Number 1

Lumo

Homo

EF
The AMPTIAC Newsletter, Volume 6, Number 1 59

Tunnelling Mi c roscopy (STM)

measurements of individual molecules in a background of an inert

alkane SAM (self-assembling molecule). One of Weiss’ main conclusions was that the local order (i.e.

packing) was extremely important

and that NDR molecules could

effectively be locked into one of its

conduction states if it were not

given “room to move” [6].

While progress in single molecular devices has been impressive,

they have yet to be optimized.

Molecular devices developed to

date have limited operating wind ows. For example, the re s u l t s

re p o rted above we re tested and

evaluated at a temperature of 60K.

However, this class of molecules is

currently being re-engineered to

work at higher temperatures. Another issue key to the performance of molecular devices is that of the end groups (often

referred to as alligator clips) which bind the molecules to electrode metals. In fact, it turns out that the current that can flow

through an individual molecule is often dominated by conduction through/across the alligator clips. To date, thiol end groups

have been mostly used as their chemistry is reasonably well

understood and they form stable, covalent bonds with a gold

surface. However, they by no means provide the best ‘ohmic’

contacts.

Assembly

Now that chemists are enjoying a degree of success in designing

molecules with electronic functionality, the key challenge turns

to the assembly of these components into viable circuits. One

problem is that the molecules are so small (nanometer scale)

that none of our existing tools can manipulate them at anything remotely close to a viable rate. Some interesting results

have been published using proximal probes to manipulate

atoms and molecules. But even the most ardent devotees of this

work admit that it is far too slow for fabricating circuits of any

complexity or number. Similarly, even the most advanced lithographic tools cannot match the resolution of molecular

devices. Instead, we must look to other ways to put molecular

circuits together. One approach would be simply to ‘synthesize’

the entire circuit as a single (very large) molecule. At the present time, this is not a feasible concept, although we will probably see the synthesis of increasingly large functional molecules

in the years to come.

Carbon nanotubes provide a possible framework for building

such large molecules. To date, some novel devices have been

reported using the nanotubes as the conduction channel for

m i n i a t u r i zed transistors [7]. Charlie Lieber at Ha rva rd

University has also used crossed nanotubes to produce devices

with very small active areas (<10 nm2) [8]. However, the actual

device sizes are dominated by the contacts to the nanotubes

being many orders of magnitude larger than the active areas.

One reason for this is the difficulty in manipulating nanotubes.

To fully exploit the scaling possible with this device configuration, the nanotubes must be positioned with nanometer precision. While impressive advances in directed nanotube growth

and fluidic manipulation have been made, we are still some way

from being able to fully exploit the benefits of these nanoscale

components.

We again look to the chemist for additional help in putting circuits together from molecular devices. Ord e red films can be

formed from disord e red solutions of monomers, designed so that

one end has an affinity for a particular substrate material. W h e n

this affinity results in a covalent bond (as in the case of a

monomer with a thiol end group and a gold substrate), the

p rocess is described as self-assembly. Langmuir-Blodgett films are

s i m i l a r, but the monomer-substrate bond is we a k e r. In both

cases, the monomers are designed such that the densely packed

film on the substrate is a lower energy configuration than the diso rd e red solution. He re, the energy is related to the bond formed

b e t ween monomer and substrate. But there are other possible

energy drivers such as surface energy, electrical energy, etc. 

The challenge then becomes to design a configuration where

the minimum energy state corresponds to something resembling a functional circuit. While something of the complexity

of a conventional microprocessor would appear to be out of

reach, simpler building block circuits such as a memory block

or logic gate(s) could be put together in this way. Even so, it

appears a series of assembly processes will be needed operating

at successively larger length scales. At this point, the research is

not as advanced as with molecular devices. Nonetheless, some

first steps have been taken.

Under DARPA sponsorship, the Penn State Group headed

by Theresa Mayer and Tom Mallouk has demonstrated at least

two levels of hierarchical assembly. They have been working

with metallic nanowires fabricated by a process of templated

electroplating. Porous membranes can be obtained with a large

Figure 4. Nitroamine 

Molecule and Its Behavior

1200

1000

800

600

400

200

0

0.0 0.5 1.0 1.5 2.0 2.5

V (V)

Au

O2N

NH2

S

Au

Ipeak=1.03 nA

q = -1

Ivalley=1 pA

q = -2

T = 60K
60

number of essentially identical diameter tracks. This provides

the template for the plating. Functionality can be built into the

nanowires. For example, some of the functional molecules

described above can be included by interrupting the plating

and self-assembling the molecules in the middle of the metallic

nanowire. The plating can then be continued. The resulting

functional nanowire can be manipulated in a number of ways.

One way is to use DNA as a ‘glue’ to adhere the nanowires

selectively to a substrate (or to each other). The Penn State

team has also designed a novel circuit where the metallic

nanowires will ‘assemble’ between two landing pads, driven by

a minimization of the electrical (capacitive) energy of the system [9]. Furthermore once one nanowire has bridged the gap,

the process self-limits so one, and only one, nanowire will be

positioned across the landing pads. The group is continuing to

refine these assembly methods and is also looking at other techniques operating at larger length scales.

So a series of hierarchical assembly steps seem possible and

are beginning to forge a path which could fabricate a circuit

with a degree of complexity and computational functionality

per unit area greater than extensions of Si-based microelectronics. However, these assembly processes are energy driven, so it

seems inevitable that there will be defects such as incorrectly

positioned structures and/or molecules. Thus to be useful, the

circuit architecture must be tolerant of a significant defect level.

Architecture

Molecular memory based on molecular devices (of the type

described in Section 2) appears feasible. However, to fully

exploit the miniaturization benefits of molecular electronics,

defect-tolerant circuits are needed. In contrast, today’s volumeproduced microelectronic chips are extraordinarily intolerant of

defects. All of the tens of millions of transistors in a microprocessor must be functional, or the chip is no more useful

than the pile of sand from which the silicon was made. An

example of a functional computation machine containing

defective components is the HP Teramac [10]. The key to the

Teramac’s operation is the inclusion of significant redundancy

of components and interconnections. Further, a period of ‘self

evaluation’ is necessary to identify and route around the defective components. In other words, the machine was first put

together and then examined to find out what was functioning

usefully.

More recently, these ideas have been extended to the circuit

level. The same group at HP that developed the Teramac

recently patented a design for a multiplexer, where the connections between the address lines and the data lines are random.

In a normal multiplexer, N data wires are addressed by logN

address lines, that is, each address line can be thought of as representing a power of 2 in the address of the data line. The group

pointed out that by providing extra address lines, there is a vanishingly small probability that all the N data lines will not be

addressable even if the connections between the address and

data lines are random [11]. As the required number of address

lines scales with the logarithm of the number of data lines, for

a large array, the added area taken by the extra address lines is

insignificant. A discovery phase is needed for such a circuit as

there will be address duplication (some data lines will not have

unique addresses). Thus, by providing redundancy and allowing for the discovery phase, it is hoped to fabricate a functioning circuit with a non-deterministic (random) critical patterning step. Many believe that fabrication of this type of random

structure may be amenable to chemical-based assembly.

Other researchers are pursuing similar techniques to assemble circuits with a degree of randomness that can, nonetheless,

perform a useful information processing function. The key

issue becomes the time required for the discovery phase along

with any modifications that must be made to the structure of

the circuit. These ideas are completely contrary to present day

functional circuit design. Molecular electronics offers the

potential of miniaturization and reduced manufacturing cost,

with the caveat that circuit architecture will not be completely

understood at the outset. This is the most radical part of current molecular electronics research.

Summary: What’s Next

For a disruptive technology such as molecular electronics to

move from the research lab to commercial products, an overwhelming economic-based case needs to be made. At present,

the microelectronics industry can look forward to at least a

decade of continued prosperity based on miniaturization.

Thus, early introduction of molecular-based technology will

probably be in a niche product that marries the advantages of

molecular electronics with the existing Si-dominated infrastructure. An example might be non-volatile (or limited volatility) memory for digital cameras and other storage-intensive

applications. These applications require dense memories with

volatilities measured in weeks, which can be manufactured efficiently and economically.

The field is moving rapidly and there is considerable optimism as to what will be possible in the not too distant future

[12]. Whether this optimism can be turned into a viable technology remains to be seen. Now that there have been convincing demonstrations of molecular devices with useful electronic

functionality, the key challenges will be the assembly of these

molecular components into functional circuits.

The AMPTIAC Newsletter, Volume 6, Number 1
Acknowledgements

I would like to thank the participants in the DARPA

Molecular Electronics programs who have performed the vast

majority of the research summarized here. I am also deeply

indebted to William Warren, Kwan Kwok and John Pazik with

whom I have managed these programs over the last 3 years.

References

[1] Aviram, A., and Ratner, M.A., “Molecular Rectifiers,” Chemical

Physics Letters, 15 November 1974, pp. 277-283.

[2] C.P. Collier, E.W. Wong, M. Belohradsky, F.J. Raymo, J.F.

Stoddart, P.J. Kuekes, R.S. Williams and J.R. Heath, “Electronically

Configurable Molecular-Based Logic Gates,” Science, (5/1999).

[3] Chen, J.; Reed, M.A.; Rawlett, A.M.; Tour, J.M. “Large On-Off

Ratios and Negative Differential Resistance in a Molecular Electronic

Device,” Science 1999, 286, 1550-1552.

[4] Seminario, J.M.; Zacarias, A.G.; Tour, J.M. “Theoretical Study

of a Molecular Resonant Tunneling Diode,” J. Am. Chem. Soc. 2000,

122, 3015-3020.

[5] Conductance Switching in Single Molecules thro u g h

Conformational Changes, Z.J. Donhauser, B.A. Mantooth, K.F.

Kelly, L.A. Bumm, J.D. Monnell, J.J. Stapleton, D.W. Price Jr., D. 

L. Allara, J.M. Tour, and P. S. Weiss, Science 292, 2303 (2001).

[6] The title of a favorite John Mayall song.

[7] V. Derycke, R. Martel, J. Appenzeller, and Ph. Avouris, “Carbon

Nanotube Inter- and Intramolecular Logic Gates,” Nano Letters (26

August 2001). And http://pubs.acs.org/cgi-bin/jtextd?nalefd/

a s a p / h t m l / n l 0 1 5 6 0 6 f.html and Adrian Bachtold, Peter Ha d l e y,

Takeshi Nakanishi, and Cees Dekker, “Logic Circuits With Carbon

Nanotube Transistors,” Science 294, 1317 (2001).

[8] Yu Huang, Xiangfeng Duan, Qingqiao Wei, and Charles M.

Lieber, “Directed Assembly of One-Dimensional Nanostructures

Into Functional Networks,” Science 291, 630 (2001).

[9] P.A. Smith, C.D. Nordquist, T.N. Jackson, T.S. Mayer, B.R.

Martin, J. Mbindyo, T.E. Mallouk, Applied Physics Letters, 77, #9,

1399 (2000).

[10] James R. Heath, Philip J. Kuekes, Greg Snider, and R. Stanley

Williams, “A Defect Tolerant Computer Architecture: Opportunities

for Nanotechnology,” Science, 280,1717 (1998). P. Kuekes, Teramac.

[11] P. Kuekes and R.S. Williams, “Demultiplexer for a Molecular

Wi re Crossbar Ne t w o rk (MWCN DEMUX),” US Patent #

6,256,767.

[12] Science magazine December 21, 2001 issue – Breakthrough of

the Year – “Molecules Get Wired.” ■

The AMPTIAC Newsletter, Volume 6, Number 1 61

Christie R.K. Marrian is currently on detail from the Naval Research Laboratory to the Microsystems Technology Office at the

Defense Advanced Research Projects Agency (DARPA) in Arlington VA. He is currently Program Manager for the Molecular

Electronics (Moletronics), Nanoimprinting (MLP) and Heterogeneous Integration (HGI) programs.

Christie obtained his B.A. and Ph. D. Degrees from the Electrical Engineering Department of Cambridge University in 1973

and 1978 respectively. He then spent three years as a postdoctoral fellow at the European High Energy Physics Center (CERN)

in Geneva, Switzerland. There he worked on the design and fabrication of a large (~2m3) detector for free quarks. In 1980, he

crossed the Atlantic to join the Surface Physics Branch at the Naval Research Laboratory (NRL) in Washington DC. Christie initiated a program on Nanoelectronics in 1985. This research started with research into material modification mechanisms possible

with the scanning tunneling microscope (STM). In 1993, he was appointed Head of the Nanoelectronics Processing Facility at

the NRL where he led a group performing nano- and micro-fabrication in a wide variety of materials for electronics, optoelectronics, materials science and plasma processing. His personal research interests revolved around nanofabrication and the properties of nanometer scale structures and devices.

Christie has authored over 105 technical publications and holds 13 patents. He is a Fellow of the American Vacuum Society

(AVS) and also a Senior Member of the IEEE. He has served as Secretary of the Nanometer Science and Technology Division

of the AVS since its inception in 1992 and was elected to the AVS Board of Directors in 1997. Christie was vice chair of the 38th

AVS National Symposium in 1991 and chair of the International Program Committee of NANO 3 which was held in conjunction

with the AVS National Symposium in 1994. In 1996, he edited a special issue of the Proceedings of the IEEE on Nanometerscale Science and Technology. He was the Program Chair in 1998 of the 42nd International Conference on Electron, Ion and

Photon Beam Technology and Nanofabrication. In 2000, he was co-chair of NANO 6 and chair of the Gordon Research

Conference on Nanostructure Fabrication. 
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Just as electronic devices continue to shrink in size and provide

greater computing power and storage, photonic devices will follow the same trend, providing greater efficiency and functionality. However, increasingly smaller photon emitters, detectors,

waveguides, filters, and other optical components face limitations of scale. As the size of these devices approaches the wavelength of light (< 1 micron), it grows increasingly difficult for

them to confine photons in the dielectric structure. A promising solution to this photon leakage problem is provided by the

concept of photonic band engineering, which allows the control of photon dispersion, transmission, and reflection through

the creation of periodic or quasi-periodic dielectric structures.

Photonic Crystals

Photonic crystals (also called photonic bandgap materials) are

micro-structured materials in which the dielectric constant

(equal to the square of the index of refraction at optical wavelengths) is periodically modulated on a length scale comparable

to the desired wavelength of the electromagnetic radiation.

Multiple interference between optical waves scattered from

each unit cell results in a range of frequencies that do not propagate in the structure. At these frequencies, the light is strongly reflected from the surface, while at other frequencies light is

transmitted.

For example, highly reflective surfaces are routinely constructed from simple layered dielectric structures with alternating layers of high and low refractive indices. One-dimensional

photonic crystals have long been used as anti-reflection coatings or as wavelength-selective mirrors which do not reflect

heat, (such as the ones used in dentists’ work lights). In two

dimensions, one can construct a periodic variation in index of

refraction by assembling an array of cylinders, such as the array

shown in Figure 1a. A two-dimensional photonic crystal may

be either a lattice of air columns in a dielectric material or a lattice of dielectric columns in air. Measuring transmission

through the cylinders shows a broad band where the transmission drops to zero (Figure 1b).

A band gap that prohibits propagation in any direction can

be created by fabricating a structure that has the proper threedimensional periodicity in the index, as seen in Figure 2. This

bandgap in photon energies is analogous to electron bandgaps

in semiconductors. The gemstone opal is a naturally-occurring,

three-dimensional photonic crystal. The distinctive color of

opal is due to reflected light, the reflection being caused by the

partial photonic band gap of the crystal. Therefore, two- and

three-dimensional photonic crystals act as novel two- and

three-dimensional mirrors. Defects may be created inside photonic crystals by removing or adding dielectric material, thereby allowing the light propagation to be modified.

Photonic crystals with and

without defects have been

demonstrated at microwave

frequencies, but fabricating

s i m i l a r, visible-wave l e n g t h

photonic crystals would

re q u i re state-of-the-art

nanofabrication techniques.

Waveguides

Photonic crystals are interesting for optoelectro n i c

devices because they make

possible the control and

confinement of photons in

small volumes (on the scale

of one wavelength cubed).

The use of defects in photonic stru c t u res has the

The AMPTIAC Newsletter, Volume 6, Number 1 63

Figure 1. Two-Dimensional Photonic Crystal and Its Calculated Transmissivity [1]

Figure 2. Three-Dimensional 

Photonic Crystal [2]

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

0.0 0.1 0.2 0.3 0.4 

Normalized Frequency

2 layers

4 layers

8 layers

(a) (b)

Dr. Bob D. Guenther

Department of Physics

Duke University

Dr. Henry O. Everitt

Associate Director, Physics Division

Army Research Office
64

potential for guiding light through sharp bends in integrated

optical systems. The tighter the bends that can be made, the

more compact the integrated photonic system can be. Photonic

crystals therefore provide a revolutionary capability to shrink

integrated photonic systems dramatically.

On the other hand, photonic crystals can be drawn into optical fibers for low loss, long range communication and routing

of information. Two types of photonic crystal fiber have been

demonstrated. The first consists of a two-dimensional photonic crystal with a defect in the center (Figure 3a). The photonic

crystal is replicated in the third (non-periodic) dimension

many meters. Light is guided down the defect and confined by

the two-dimensional photonic crystal surrounding it. The second consists of a one-dimensional photonic crystal wrapped

into a long cylindrical tube (Figure 3b). Again, light is guided

down the center and confined by the highly reflective photonic crystal. In both cases, light is guided down an air core, in

contrast with current optical fiber which confines light in a

glass core. As a result, low loss light guiding can be accomplished at any wavelength, not just the wavelengths of lowest

absorption in glass fiber (1.3 and 1.55 microns). Reduced optical nonlinearities promise much larger transmission bandwidths than are currently achievable, and operation at visible

w a velengths promise much higher

detection efficiency using state of the

art avalanche photodiodes.

Resonators and Lasers

The use of periodic structures to form

resonators and lasers is not new. Onedimensional photonic crystals are simply dielectric mirrors, and two such

reflectors facing each other form a

Fabry-Perot resonator. Vertical cavity

s u rface-emitting lasers (VCSELs) are

formed by placing a quantum we l l

a c t i ve region in the “d e f e c t” space

between such a Fabry-Perot resonator.

Increased lateral confinement of the

photons is achieved through total internal reflection by etching the VCSELs into narrow posts such as

shown in Figure 4a.

Using the same principle of total internal reflection, a circular “whispering gallery mode” resonator can also be used as a

laser cavity (Figure 4b). Such lasers have greater confinement

and higher cavity energy density (Q) than conve n t i o n a l

VCSELs, yielding lower lasing thresholds but weaker, omnidirectional emission. Slight deformations of the microdisk have

permitted more directional emission.

To gain even more control over the emission and threshold,

higher dimension photonic crystal resonators may be used.

Two-dimensional photonic crystals with defects have been fabricated in Si, GaAs and InGaAsP materials to couple filters and

switches with low loss. Point defects can be used to form laser

cavities, such as a missing hole in a hexagonal array of holes, as

depicted in Figure 5. Micro-cavities with a mode volume of

0.03 cubic microns have been fabricated in InGaAsP and lasing

was observed at a wavelength of 1.5 microns with optical

pumping.

These defects could potentially increase the spontaneous

emission rate of photons in the visible or near-infrared region.

Larger defects provide higher output powers because of the

greater active material volume. The large cavity shown in

Figure 3a Figure 3b

Figure 3. Photonic Crystal Optical Fiber [3] and Integrated Photonic Waveguide [4]

Figure 4. Vertical Cavity Sur face Emitting Laser [5] and Microdisk Laser [6]

The AMPTIAC Newsletter, Volume 6, Number 1

Figure 4a Figure 4b
The AMPTIAC Newsletter, Volume 6, Number 1 65

Figure 5 has modes similar to the whispering gallery modes of

the microdisk laser (Figure 4b).

Quantum Information Science

One of the most exciting potential applications for nanophotonic devices may be the demonstration of the first quantum

information processing units. Unlike classical bits of information which must be either in the “0” or “1” state, quantum

information is based on the laws of quantum mechanics which

permit a “quantum bit” or “Qbit” to be in a superposition of

both states simultaneously. Recently, an all-optical scheme for

performing quantum computing was proposed using linear

optical components and the nonlinear measurement process. A

version of this quantum computer may someday be constructed using photonic crystal-based nanophotonic components.

Another goal of quantum information processing is to transport quantum bits and teleport quantum information over optical fiber. To

do this, two new nanophotonic devices

are needed: single photon sources and

low loss optical fiber. Recently, groups

at St a n f o rd Un i versity and the

University of California, Santa Barbara

demonstrated the first semiconductor

single photon sources based on

VCSELs and microdisk re s o n a t o r s ,

respectively. Likewise, sources of entangled photon pairs and atomic or solid

state systems for quantum logic and

quantum memory may work more efficiently at wavelengths other than 1.3 or

1.55 microns. Low loss photonic crystal

fiber may prove to be ideal means for transporting and preserving these fragile photonic quantum states in the visible wavelength region.

References

[1] Pictures taken with the kind permission from the web site

of A.L. Reynolds (www.areynolds.com) Copyright © 2000

Photonic Band Gap Materials Research Group, University of

Glasgow.

[2] Courtesy of Axel Scherer, Cal Tech.

[3] Courtesy of Crystal Fibre and A. Gaeta, Cornell University.

[4] Courtesy of John Joannopoulos, MIT.

[5] Courtesy of Axel Scherer, Cal Tech.

[6] Courtesy of Atac Imamoglu, University of California, Santa

Barbara.

[7] Courtesy of Axel Scherer, Cal Tech. ■

Figure 5a 

Figure 5b

Figure 5. Single Defect and Large Defect Cavities In 2D Photonic Crystals [7]

Dr. Henry Everitt serves as associate director for the Physics Division of the Army Research Office. He is a program manager for

the Army’s extramural 6.1 basic research program in experimental condensed matter physics. His program specializes in research

involving quantum information science, nanophysics, and nanooptics. He serves as chairman of the US quantum information 

science coordinating group and has recently served as spokesman for the Army’s nanoscience program.

Dr. Everitt is also an adjunct professor of physics at Duke University. There he directs a research laboratory in which the ultrafast optical properties of wide bandgap semiconductors are investigated. His students also study photonic cr ystals, molecular 

collision dynamics, far infrared lasers, ultrafast optical techniques, astronomical interferometric imaging, and variable stars in 

globular clusters.

Dr. Bob D. Guenther received his undergraduate degree from Baylor University and his graduate degrees in Physics from the

University of Missouri. He has had research experience in Condensed Matter and Optical Physics. For nine years he was active

in Research Management as a Senior Executive in the Army, responsible for the Physics Research sponsored by the Army. In that

role he managed a program of about $20M/year involving about 100 individual projects. He also served as a senior advisor

to the Army on a variety of issues such as electric gun technology, high energy lasers, and automatic target recognition. From June

1997 through May 1999, he held the position of Interim Director of the Duke Free Electron Laser Laboratory.
66 The AMPTIAC Newsletter, Volume 6, Number 1

23rd International Conference 

on Microelectronics

5/12/02 – 5/15/02

Nis, Yugoslavia

Mr. Vojkan Davidovic, MIEL 2002

Treasurer

Faculty of Electronic Engineering

University of Nis

Beogradska 14

18000 Nis, Yugoslavia

Magnetic Nanostructures

5/12/02 - 5/17/02

Barga, Italy

R. Celotta

National Institute of Standards 

&Technology

100 Bureau Drive, MS 8412

Gaithersburg, MD 20899-8412

Email: robert.celotta@nist.gov

Web Link: www.grc.ur.edu

First International Conference on Nanoscale/Molecular Mechanics (N/MM-I)

05/12/02 - 05/18/02

Maui, HI

M. Roukes

Caltech

MC 114-36

Pasadena, CA 91125

Fax: (626) 683-9060

Email: roukes@caltech.edu

NanoBusiness Spring 2002

5/19/02 – 5/21/01

New York, NY

NanoBusiness Alliance

244 Madison Avenue, Suite 485

New York, NY 10016

Phone: (845) 247-8920

Email: info@nanobusiness.org

Web Link: www.nanobusiness.org

Nanocrystals 18th Conf. 

on Crystal Growth & Epitaxy

06/02/02 - 06/05/02

Fallen Leaf Lake, CA

J. DeYoreo

Fax: (925) 423-4240

Email: deyoreo@llnl.gov

Web Link: www.crystalgrowth.org

SEM Annual Conference and Exposition:

MEMS: Mechanics and Measurements

6/10/02 – 6/12/02

Milwaukee, WI

Society for Experimental Mechanics, Inc.

7 School Street

Bethel, CT 06801-1405

Phone: (203) 790-6373

Fax: (203) 790-4472 

Email: sem@sem1.com 

Web Link: www.sem.org

NANO 2002, 6th International

Conference on Nanostructured Materials

06/16/02 - 06/21/02

Orlando, FL

L. Kabacoff

Office of Naval Research

Materials Division #332

800 North Quincy Street

Arlington, VA 22217-5660

Email: kabacol@onr.navy.mil

Web Link: www.nano2002.com

2nd Annual MEMS Technology Seminar

6/17/02 – 16/19/02

Boston, MA

Jennifer Burns

ASME

Three Park Avenue

New York, NY 10016

Phone: (212) 591-7423

Fax: (212) 591-7143

Email: burnsj@asme.org

Web Link: www.asme.org

7th International Nanotechnology

Conference

6/24/02 – 6/28/02

Malmo, Sweden

Lennart Hakansson

Malmo Congress Bureau

Ostergatan 3

S- 211 25 MALMO

Sweden

Email: lennart@malmo-congress.com

Web Link: www.malmo-congress.com

SPIE 47th Annual Meeting, 

"Materials and Nanotechnologies"

07/07/02 - 07/11/02

Seattle, WA

SPIE

P.O. Box 10

Bellingham, WA 98227-0010

Fax: (360) 647-1445

Email: spie@spie.org

Web Link: www.spie.org

Faraday Discussion 125: 

Nanoparticle Assemblies

7/14/03 – 7/16/03

University of Liverpool, UK

Christine Hall

Conference and Awards

Royal Society of Chemistry

Burlington House

Piccadilly, London W1J OBA

Phone: +44 (0) 20 7437 8656

Fax: +44 (0) 20 7734 1227 

Email: hallc@rsc.org

Web Link:

www.rsc.org/lap/confs/fara125.htm

SmallTalk 2002: The Microfluidics,

Microarrays & bioMEMs Conference

& Exhibition

7/28/02 – 7/31/02

San Diego, CA

smallTalk 2002

1201 Don Diego Avenue

Sante Fe, NM 97505

Phone: (505) 988-5326

Fax: (505) 989-1073

Email: ala_office@labautomation.org

Web Link:

labautomation.org/smallTalk/ST02

Workshop on Nanostructures for

Electronics & Optics – NEOP

8/18/02 – 8/21/02

Dresden, Germany

Inst. of Ion Beam Physics 

& Materials Research

P.O. Box 51 01 19

01314 Dresden, Germany

Fax: +49 351 260 3285

Email: info@neop.de

Web Link: www.neop.de

2nd IEEE Workshop on Technology

(IEEE-NANO 2002)

08/26/02 - 08/28/02

Arlington, VA

C. Lau

Office of Naval Research

800 N. Quincy St.

Arlington, VA 22217 USA 

Fax: (703) 588-1013

Email: lauc@onr.navy.mil

Web Link: ewh.ieee.org/tc/nanotech/

nano2002/title.html

Aerospace Materials, Processes, and

Environmental Technology

(AMPET Conference)

9/16/02 – 9/18/02

Von Braun Center

P.O. Box 928

Huntsville, Alabama 35804-0928

Phone: (256) 533-5923

Email: jweiner@aol.com

Web Link: http://ampet.msfc.nasa.gov/

IMAPS 2002

9/4/02 – 9/6/02

Denver, CO

International Microelectronics 

& Packaging Soc

611 2nd Street, N.E.

Washington, DC 20002

Phone: (202) 548-4001

Fax: (202) 548-6115

Web Link: www.imaps.org/imap2002

Mark Your Calendar
The AMPTIAC Newsletter, Volume 6, Number 1 67

AMPTIAC Directory

G ove rnment Pe rs o n n e l IITRI Pe rs o n n e l

TE CH N I CA L MA NAG E R/ COT R

Dr. Lewis E. Sloter II

Staff Specialist, Materials & Structures

ODUSD(S&T)/Weapons Systems

1777 North Kent St., Suite 9030

Arlington, VA 22209-2110

(703) 588-7418, Fax: (703) 588-7560

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AS S O C I AT E COT RS

CERAMICS, CERAMIC COMPOSITES

Dr. S. Carlos Sanday

Naval Research Laboratory

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AFRL/MLS

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Email: roger.griswold@wpafb.af.mil

METALS, METAL MATRIX COMPOSITES

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Army Research Laboratory

Weapons & Materials Research Directorate

AMSRL-WM-MC

APG, MD 21005-5069

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Email: jwells@arl.army.mil

ELECTRONICS, ELECTRO-OPTICS, PHOTONICS

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Email: robert.denison@wpafb.af.mil

ENVIRONMENTAL PROTECTION

& SPECIAL FUNCTION MATERIALS

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Naval Research Laboratory

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Washington, DC 20375-5320

(202) 767-3026, Fax: (202) 404-7139

Email: murday@ccsalpha3.nrl.navy.mil

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DI R E C TO R, AMPTIAC

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DE P U TY DI R E C TO R, AMPTIAC

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TE CH N I CA L DI R E C TO R S

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CERAMICS, CERAMIC COMPOSITES

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ORGANIC STRUCTURAL MATERIALS &

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Jeffrey Guthrie

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ELECTRONICS, ELECTRO-OPTICS,

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ENVIRONMENTAL PROTECTION

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IIT Research Institute

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Email: bschulte@iitri.org

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