By Will Soutter
Topics Covered
Introduction
Nanostructured Metals
Polymer Nanocomposites
Tribological Coatings
Conclusion
References and Further Reading
Introduction
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Figure 1. The
aerospace industry is under pressure to improve it's
environmental footprint, primarily by making aircraft more efficient.
Image credit: Bureau of
Labor Statistics.
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There are few industries where the applications of nanotechnology
are so clearly beneficial as in the aerospace industry. The primary
development goals match almost exactly with the advantages offered by
using various nanomaterials in the place of traditional bulk metals
like steel.
The aerospace industry is one of the most important heavy industries
in the world. Countless companies rely on the ability to ship products
and people around the world with the speed that can only by achieved by
air. The aircraft manufacturing market was worth xxx billion in 20xx,
and the bulk of this was accounted for by military spending.
Along with this huge economic value, however, comes huge
consumption, and one of the largest carbon footprints on the planet
relative to the size of the market. For this reason, the major drivers
in current aerospace R&D are towards lighter construction materials
and more efficient engines - the overall goal being to reduce fuel
consumption and carbon emissions associated with air travel and air
freight. The significant interest in nanotechnology for the aerospace
industry is justified by the potential of nanomaterials and
nanoengineering to help the industry achieve this goal.
This article will review some of the nanomaterials which are already
being applied in aerospace manufacturing, and the benefits they can
provide.
Nanostructured Metals
Bulk metals with some nanoscale structure are already widely used in
aircraft manufacturing. It is now well known that nanostructured metals
- exhibit considerably improved properties compared to their
counterparts with microscale or larger grain structure.
This is particularly noticeable for properties which are crucial for
materials used in aircraft - primarily yield strength, tensile strength
and corrosion resistance, coupled with low density which helps keep the
total weight of the aircraft down.
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Figure 2. Bulk
nanostructured metals exhibit much better mechanical properties and
corrosion resistance than their counterparts with larger crystal
structures. Image credit: Los
Alamos National Laboratory.
Polymer Nanocomposites
Various nanomaterials have been used as filler materials to enhance
the properties of structural and non-structural polymers used in
aircraft construction. The most commonly used nanomaterials include
nanoclays, carbon nanotubes, nanofibres, and graphene.
Carbon nanotubes in particular have been shown to give excellent
advantages when used as fillers in various polymers, due to their
exceptional stiffness, toughness, and unique electrical properties.
Nanocomposites typically have superb weight-to-strength ratios, and
enhanced resilience to vibration and fire, making them ideal for use in
the aviation industry. The properties of the nanofillers, like the
conductivity of nanotubes, for example, can create interesting
opportunities for multifunctional materials.
The properties of polymers enhanced by nanomaterial fillers are so
well-tuned to the requirements of aircraft manufacturers, that they are
actually being used to replace some of the metals used in the
airframes. This obviously brings along huge weight savings, and often
cost savings as well.
Tribological and Anti-Corrosion
Coatings
Another major trend in the materials used in aircraft is towards
nanocoatings to enhance the durability of metals. In particular,
magnesium alloys, which are far lighter than steel or aluminium, are
prone to corrosion, due to the high chemical reactivity of magnesium.
Coatings can help prevent corrosion, but the type typically used
contain chromium complexes which are a highly toxic pollutant.
Materials used for these novel anti-corrosion nanocoatings include
silicon and boron oxides, and cobalt-phosphorous nanocrystals.
Nanocoatings are also now being used on turbine blades and other
mechanical components which have to withstand high temperatures and
friction wear.
Tribological coatings can drastically lower the friction coefficient
and improve resistance to wear - this greatly improves the efficiency
of the engines.
Many nanostructured and nanoscale coating materials have been
suggested as possible friction modifying agents, such as carbides,
nitrides, metals, and various ceramics.
.jpg)
Figure 3. The defense
sector drives a lot of the innovation in many industries, and aerospace
is no exception. High-performance military aircraft require exceptional
materials, which will eventually find their way into commercial
vehicles. Image credit: Penn State University.
Conclusion
This is just a brief overview of some of the nanomaterials being
used in aerospace. The drive for lighter and more efficient air
vehicles has led to the rapid adoption of nanotechnology in aerospace
manufacturing.
The
main roadblock, as with many industries looking to adopt
nanotechnology,
is caused by uncertainty over the environmental and health and safety
implications of these materials. Whilst nanomaterials can often be less
toxic than the current materials used, the effects of long-term
exposure to these novel materials are still uncertain.
The potential of nanotechnology in the aerospace industry cannot be
denied, however. Outside of airframe and component materials,
nanotechnology applications have been found in lubricants, fuel,
adhesives and many other areas.
Nanotechnology is also helping engineers to create vehicles with the
necessary properties to endure the harsh conditions of space.
References and Further
Reading