NANO-MATERIALS FOR AEROSPACE AND SECURITY
APPLICATIONS
L. Boehm
Israel Aircraft Industries
Nanotechnology is "the next big thing". As this phrase becomes
common in business and scientific circles throughout the world, the very
perception causes concern about the implications and issues surrounding
the entire emergence of nanotechnology as well as its impact on so many
things affecting our daily lives, and it will affect virtually all aspects of
human experience.
Nanotechnology, is more than just a new buzzword;. In fact this
phenomenon is best realized in the National Science and Technology
Council's recently published "National Nanotechnology Initiative:
Research and Development Supporting the Next Industrial Revolution".
In this initiative several areas are identified as having the potential to
realize significant economic, governmental and societal impact. The
areas which are drawing the most attention are the closer to the market:
1. Nano-Crystalline Materials – Nano-Structured materials by
design
2. Manufacturing at the Nanoscale – Carbon-nano-tubes (CNT)
3. Chemical-Biological-Radiological-Explosive Detection and
Protection
4. Nano-Electronics, -Photonics, and -Magnetics
5. Healthcare, Therapeutics, and Diagnostics
6. Efficient Energy Conversion and Storage – Fuel cells
7. Microcraft and Robotics
Nano-crystalline materials are materials possessing grain sizes on
the order of a billionth of a meter. They manifest extremely fascinating
and useful properties, which can be exploited for a variety of structural
and non-structural applications.
All materials are composed of grains, which in turn comprise
many atoms. These grains are usually invisible to the naked eye,
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depending on their size. Conventional materials have grains varying in
size anywhere from 100’s of microns (µm) to millimeters (mm). A
micron (µm) is a micrometer or a millionth (10-6) of a meter. An average
human hair is about 100 µm in diameter. A nanometer (nm) is even
smaller a dimension than a µm, and is a billionth (10-9) of a meter. A
nano-crystalline material has grains on the order of 1-100 nm. The
average size of an atom is on the order of 1 to 2 angstroms (Å) in
radius. 1 nanometer comprises 10 Å, and hence in one nm, there may be
3-5 atoms, depending on the atomic radii. Nano-crystalline materials are
exceptionally strong, hard, ductile at high temperatures, wear-resistant,
erosion-resistant, corrosion-resistant, and chemically very active. Nanocrystalline materials, or nano-materials, are also much more formable
than their conventional, commercially available counterparts.
There are five widely known methods to produce nano-materials,
and they are as follows:





Sol-gel synthesis,
Inert gas condensation,
Mechanical alloying or high-energy ball milling,
Plasma synthesis, and
Electrodeposition.
All these processes synthesize nano-materials to varying degrees
of commercially-viable quantities.
Since nano-materials possess unique, beneficial chemical,
physical, and mechanical properties, they can be used for a wide
spectrum of aerospace, defense and security technologies and
applications.
Aerospace components with enhanced performance
characteristics
Drivers for the aerospace industry for exploiting new technologies
include:
 Increased safety
 Reduced emissions
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 Reduced noise
 Increased capacity
 Increased mobility
Due to the risks involved in flying, aircraft manufacturers strive
to make the aerospace components stronger, tougher, and last longer.
One of the key properties required of the aircraft components is the
fatigue strength, which decreases with the component’s age. By making
the components out of stronger materials, the life of the aircraft is
greatly increased. The fatigue strength increases with a reduction in the
grain size of the material. Nano-materials provide such a significant
reduction in the grain size over conventional materials so that the fatigue
life is increased by an average of 200-300%. Composite materials with
improved fatigue life, damping properties and higher damage tolerance
properties due to CNT inclusions, is vastly investigated in the last years.
Nanotubes. Are described as ‘the most important material in
nanotechnology today’, These materials have a remarkable tensile
strength. Indeed, taking current technical barriers into account,
nanotube-based material is anticipated to become 50–100 times stronger
than steel at one-sixth of the weight. This development would dwarf the
improvements that carbon fibres brought to composites.
A lot of effort is also invested in developing functionalizedcarbon-nanotubes (FCNT), as it will provide materials that can enable
new technologies in aircraft platforms performance, ballistic protection
and conductive fibres.
Also high performance nano-composite materials which are
combination of polymers, metals and ceramics, can be used for
tribological coatings of aircraft platforms operated at higher
temperatures.
Furthermore, components made of nano-structured materials that
are perhaps 100x lighter than conventional materials of equivalent
strength are possible, so an aircrafts can fly faster and more efficiently
(for the same amount of aviation fuel).
Fig. 1 shows the possibility of reducing the weight of aircraft
components using composite materials reinforced with carbon-nanotubes (CNT).
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Fig 1. Nanotube-Reinforced Polymer (CNTFRP) and NanotubeReinforced Aluminum (CNT/Al) Composites compared to an advanced carbon
fiber reinforced polymer (IM7 CFRP) composite:
Longer-lasting satellites
Satellites are being used for both defense and civilian
applications. These satellites utilize thruster rockets to remain in or
change their orbits due to a variety of factors including the influence of
gravitational forces exerted by the earth. Hence, these satellites are
repositioned using these thrusters. The life of these satellites, to a large
extent, is determined by the amount of fuel they can carry on board. In
fact, more than 1/3 of the fuel carried aboard by the satellites is wasted
by these repositioning thrusters due to incomplete and inefficient
combustion of the fuel, such as hydrazine. The reason for the
incomplete and inefficient combustion is that the onboard ignitors wear
out quickly and cease to perform effectively. Nano-materials, such as
nano-crsytalline tungsten-titanium diboride-copper composite, are
potential candidates for enhancing these ignitors’ life and performance
characteristics.
In spacecrafts, elevated-temperature strength of the material, is
crucial for components such as rocket engines, thrusters, and vectoring
nozzles. High performance nano-materials can be used for these
components as well as for special coatings.
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Also, embedding nanoscale electromechanical system components
into earth-orbiting satellites, planetary probes, and piloted vehicles
potentially could reduce the cost of future space programs. The
miniaturised sensing and robotic systems would enhance exploration
capabilities at significantly reduced cost.
The vision of NASA for the use on nano-materials for different
platforms in presented in Fig. 2
Materials
-Singlewalled
nanotube
fibers
-Nanotube
composites
- Integral
thermal/shape
control
-Smart
“skin”
materials
-Biomimetric
material
systems
Electronics/
computing
-Low-Power
CNT
electronic
components
-Molecular
computing/data
storage
-Fault/radiation
tolerant
electronics
-Nano
electronic
“brain” for
space
Exploration
-Biological
computing
Sensors, s/c
components
-In-space
nanoprobes
-Nano flight
system
components
-Quantum
navigation
sensors
-Integrated
nanosensor
systems
-NIEMS flight
systems @ 1W
Nano-material impact on Security - High-sensitivity sensors
The advance of civil technologies, particularly in the area of IT,
electronics and communications, has particular relevance to the design
of defence and security systems. In particular, nano-materials will
impact on all critical aspects of maintaining a technologically superior
capability in these areas . The key drivers of which are:
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 Biological and chemical threat detection - nanoBio sensors
 High performance information technology/remote control
 Military uniforms with enhanced features including protection
and self-healing
 New vaccines and medical treatments
 Minimising civilian casualties through the use of smart sensors
Sensors employ their sensitivity to the changes in various
parameters they are designed to measure. The measured parameters
include electrical resistivity, chemical activity, magnetic permeability,
thermal conductivity, and capacitance. All of these parameters depend
greatly on the microstructure (grain size) of the materials employed in
the sensors. A change in the sensor’s environment is manifested by the
sensor material’s chemical, physical, or mechanical characteristics,
which is exploited for detection. For instance, a carbon monoxide sensor
made of zirconium oxide (zirconia) uses its chemical stability to detect
the presence of carbon monoxide. In the event of carbon monoxide’s
presence, the oxygen atoms in zirconium oxide react with the carbon in
carbon monoxide to partially reduce zirconium oxide. This reaction
triggers a change in the sensor’s characteristics, such as conductivity (or
resistivity) and capacitance. The rate and the extent of this reaction are
greatly increased by a decrease in the grain size. Hence, sensors made
nano-crystalline materials are extremely sensitive to the change in their
environment. Typical applications for sensors made out of nanocrystalline materials are smoke detectors, engine performance sensor,
etc.
Another family of nano-materials for security applications are the
structural multifunctional nano-materials. The requirements from such
materials are: lightweight; mechanically durable; sensing/actuation;
radiation protection; electrical conductivity; thermal conductivity. A
multifunctional material based on single wall nano-tube (SWNT)
combined with polymer nano-composite, was developed at NASA for
sensing temperature and pressure. Also a CNT-FET material was
developed for sensing gases, such as HCl, NO2 , benzene, acetone and
other hazard gasses for environmental monitoring and biothreat
detection.
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Recently, it was published that Fraunhofer Institutes in Germany
developed an Electro-Chemical sensor based on nano-wires (nano-grass)
of Au/Sn. This material and its characteristic performance, is shown in
Fig. 3
”Nano-grass” for electrochemical Sensors
Nano-wires lead to strongly
enlarged surface
To a strongly increased
current
Improved Signal/NoiseRatio
 increased Sensitivity
 shortened response time
Fig 3. Electro-Chemical sensor, Michael Krausa, Fraunhofer IZT (2005).
Summary
Nanotechnology is primarily about making things. For this reason,
most of the activity of R&D is focused on ‘nano-materials’: novel
materials whose molecular structure has been engineered at the
nanometre scale. It was stated by several people that material science
and technology is fundamental to a majority of the applications of
nanotechnology.
The materials that follow involve either bulk
production of conventional compounds that are much smaller (and hence
exhibit different properties) or new nano-materials, such as fullerenes
and nano-tubes.
The market’s range of nano-materials are considerable.Indeed, it
has been estimated that, aided by nanotechnology, novel materials and
processes can be expected to have a market impact of over US$340
billion within a decade.
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The major nano-materials currently in research and development
for Aerospace and Security
 Carbon nano-tubes (CNT): two types of nano-tubes, the single
wall carbon nano-tube (SWNT) and the multilayer nano-tubes.
The main applications are for space and aircraft manufacture.
 Nano-composite: composite materials are combination of
polymers, metals and ceramics. These
materials with
multifunctional behaviour, might be used for special coatings
and high-temperature applications.
 Nano-wires: wires of various metals used as gas sensors,
environmental monitoring and nano-actuators.
 Quantum wells: ultra thin layers, a few nanometers thick of
semiconductor materials. The main applications are for quantum
well lasers for telecommunication and optics.
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