Nanotechnology can play a vital role in defence and space systems by minimising size, weight and power consumption that are important for long-range coverage. Also, embedded nanosensors enabled with wireless networks can enhance the intelligence of future warfare systems. There are several possible applications of nanotechnology for defence and space applications, as shown below:
• Light-weight vehicles to enhance fuel economy; longer distances can be covered for the same fuel capacity
• Smart components with built-in condition and load-monitoring sensors, such as fibre Bragg
• Adaptive structures, like adaptive skin, for better thermal control • High energetic propellants such as nano-dispersed aluminum • Lightweight protective clothes
• Anti-ballistic and shatterproof armour
• Advanced sensors, such as, high-resolution vision systems, RF, infrared, acoustic arrays, terahertz and through-the-wall radar vision
• Physical identification tags (RFID) for goods, digital ID tags for documents and information
• Biometric sensing for personal identification characteristics, such as, fingerprint, face, DNA
• Ambient intelligence for surveillance by means of distributed wireless sensor networks • Tracking and tracing with position and motion sensors
Intelligent textiles with embedded sensors in the soldiers’ attire is another important potential
area for application of nanotechnology. The clothes soldiers wear can be modified to provide better protection against heat and cold and integrated nanosensors can be used for remote monitoring of heartbeat and blood pressure. In addition, clothing can have built-in protection against bullets.
Nanotechnology is needed for improved detector sensitivities (signal-to-noise ratios), to miniaturise sensor arrays for selectivity, to tailor-make high surface area materials for detection/absorption/deactivation and to create selective catalysts. Microsystems technology and nanotechnology will therefore enable small portable sensor systems capable of identifying chemical, bio, nuclear, radiation or energy threats. This will enhance the flexibility of deployment and operations, increase the safety of soldiers and civilians and enhance environmental security. Onboard intelligence will continuously increase, facilitating automated control and maintenance. Naval vessels have additional requirements with respect to detection and surveillance sensor systems.
Other technologies which can be integrated in future weapons are RF ID-tags in guns, cartridges, target positioning/recognition (via micro IR camera on guns or PDAs, microradar, RF-array, through-the wall THz radar), and smart helmets to pull the trigger from a distance (teleweapon), various ammotypes (shaped ceramic materials, softer bullets, high-penetration bullets, sensor modes/smart dust and insensitive tailored explosives to limit collateral damage).
Closely connected to the concept of the smart helmet is that of anti-ballistic protection via a light-weight helmet consisting of a combination of polymers, fibres and nanomaterials. This new nanocomposite should have higher impact resistance than present fibre composite systems and should have a significantly reduced weight. The application of nanofibres and buckypaper in combination with present high-strength fibres and polymer materials to create new composite materials seems to be most promising. For the next generation of helmets, the use of fibres such as Kevlar, Dyneema or M5 is most realistic in combination with nanomaterials which can enlarge the strength of the composite and keep the fibres closely packed in the composite structure at impact. M5 is the newest type of fibre in this category and product applications of this fibre are expected in the next few years. Nanoclay in a silliputty-type of polymer matrix combined with fibres is a possible alternative. These high-strength fibres can, in theory, bring significant improvement. The same applies to metal nanoparticles coated with a multiple-layered ceramic nanocoating. These coatings were originally developed for turbine blade protection but the extreme hardness is also of use for anti-ballistic nanofillers in composites. In the long term (10–15 years), a more dominant use of electrospun nanofibres to create basic fibre strength in the composite can be expected. These CNT fibres and other nanofibres have a theoretical strength of 130–180 GPa. Thanks to the technological advances in high strength polymer fibres such as carbon, aramide and Dyneema, the performance of antiballistic suits has improved considerably over the last 20 years, with subsequent reduction in weight (30%). These suits with integrated or inserted
composite fibre structures are quite effective and are being successfully applied for ballistic protection of the body. However, the composite structures are not sufficiently flexible to be used for protection of extremities such as the arms, legs and neck. At present, injuries of these extremities have become the dominant factor in casualties, especially from bombings and subsequent shatter, resulting in loss of military power and high cost of medical treatment. In view of this, several concepts for flexible armour have been proposed and are now in development.
Magneto-restrictive fluid—a nanoparticle-filled flexible medium that can be electrically
activated to become rigid
Shear-thickening fluid—a nanoparticle-filled binder for high-strength textiles that
is flexible under low shear rate and that becomes rigid under high shear rate impact (passive system, ARL). This nanoparticle-filled system inhibits deformation and sliding of high strength fibres at high shear rate.
Silliputty-type of elastomers in combination with ceramic armour—an elastomer system
which is deformable and elastic at low shear rate and stiff at high shear rate. It is similar to shear thickening fluids, but has so far been less effective in antiballistics (passive system, for example, D3O material).
The ultimate goal will be to create nanorobots or nanobots for activities on land and NUAV (nano-unmanned aerial vehicles) for reconnaissance and sensory activities in the air (flying artificial insects). Uninhabited combat vehicles (fighter, submarine, and vehicle) with higher performance and lower casualty risk can also be expected. Ideally, all microvehicles and robots should be less visible for enemy troops (biomimetic structures), should last long enough to gather essential information, and should be low in cost and therefore redundant.
Wounds can be dressed with intelligent bandaids which monitor the moisture level and bacterial activity, and release antimicrobials on nanoparticles to kill the bacteria. Part of this health monitoring system can be a portable sample preparation and lab-on-chip analysis kit enabling the soldier to test his own body fluids when he needs more specific data and water and food. Ideally, this analysis system will be built into his smart suit and will be able to detect bioagents and apply antidotes to the soldier. Biosensors for body-function monitoring can be expected to be integrated subcutaneously in the body of future combat soldiers. Core temperature measurement with a swallowable passive RF-sensor is one of the solutions for accurate and low-cost core temperature measurement of soldiers in combat.
Smaller satellites are now becoming feasible, owing to the miniaturization enabled by nanotechnology. Besides reducing their size, weight and power consumption, the use of micromachined devices could give better component integration in areas such as propulsion, communication, data processing, power generation and navigation. With a distributed network of small satellites instead of one big one, both functionality (multi-aperture synthesis for better accuracy, formation flying) as well as redundancy is gained. The ultimate goal is to develop
a complete satellite-on-chip, the so-called picosatellites. Microsatellites (~ 10–30 cm) are in development in many countries: USA/NASA, UK, France, Germany, Sweden and Spain, both for civil and defence applications.
4.15 STRUCTURAL APPLICATIONS
The increased rate of forming or the lower temperature related to the superplastic deformation of nanocrystalline materials would make superplasticity more industrially accessible, extending its possible limits of use. With nanocrystalline metals, superplastic deformation can extend rapid and large-scale forming processes. It is speculated that nanocrystalline superplasticity will have an advantage over traditional superplastic materials when materials chemistry may not be changed because of the nature of the application (for example, in electronics applications), or high strength is demanded after forming. Another area is that of diffusion bonding. It has been shown that the use of a superplastic intermediate layer in
diffusion bonding of non-superplastic stainless steel dramatically improves the properties of
the joint, especially if the mating surfaces are rough. Superplasticity may also be utilised in the processing of nanocrystalline ceramics themselves. Nanocrystalline ceramics are difficult to produce by the pressureless sintering routes typically used for conventional ceramics, but they may be produced by sinter forging which uses the superplasticity of the materials itself by closing pores with the aid of plastic flow.
The higher strength of nanocrystalline materials may be utilised in several potential applications, when processing of the materials is adequately developed. The development of nanocrystalline M50 steel as the main shaft bearing material has improved the performance of engines in gas turbine industries. Development of WC–Co nanocomposites has been driven by the expectation of obtaining cutting tools and hard metal coatings with superior properties compared to their traditional counterparts. These materials are already starting to have commercial impact and are used in the manufacture of machine tools, drill bits and wear parts. Tools made of cemented carbide nanocomposites have enhanced hardness, fracture toughness and wear resistance compared to their conventional counterparts.
Currently, nanocrystalline titanium is considered to be a potential material for medical implants. In order to obtain adequate strength, titanium alloys (mainly Ti–6Al–4V) are used, for example, for hip prostheses. Development of nanocrystalline pure titanium for such an application would allow the alloying content to be decreased for increased biocompatibility. Both the static and the fatigue strength of commercially pure titanium fasteners and threaded articles could be substantially increased by ECA processing, producing a nanocrystalline grain structure. Nanocrystalline ceramics have also been considered for orthopedic and dental implants of the future. Nanomaterials with improved mechanical properties could then replace some of the conventional biomaterials and could be tailored to meet clinical requirements associated with anatomical differences or patient age.
Incorporation of nanotubes instead of carbon fibres as reinforcing elements into plastic, ceramic and metallic matrixes can potentially provide structural materials with dramatically improved modulus and strength. Many improvements have taken place in the use of
nanoparticles as filler materials in polymers. These include fillers in dental polymers to improve their performance, for example, wear resistance or stiffness as in polymer-layered silicate nanocomposites.
Applications of nanocrystalline metallic materials have been limited because of low ductility in tension. However, cold rolling of nanocrystalline copper has opened up interesting vistas for developing novel processing of some metallic materials utilizing the nanocrystalline structure. The traditional deformation–annealing technique routinely used may be much simplified by using nanocrystalline metals as starting materials. With proper post–heat treatments, microstructure may be easily controlled so that the desired properties in the final product can be achieved.
SUMMARY
Nanomaterials and technology are making their impact in almost all areas of life.
• Development of novel devices based on nano-opto-electronic materials, molecular devices and quantum structures are creating new directions for miniaturization with increased efficiency of nano-electronic systems.
• MEMS and NEMS find extensive use both as sensors and actuators in a wide spectrum of engineering application.
• An entire gamut of nanosensors for biomonitoring, health parameter surveillance, safety logics, environmental control, process control, etc., have been developed. • In the field of medicine, nanotechnology finds application for both diagnostic tools as
well as for advanced therapy.
• Nanomaterials have a promising future in enhancing efficiencies of green energy technologies, like solar cells, hydrogen cells, etc.
• Development of smart textiles with in-built sensors and functional nanoparticles are set to be introduced on a wide scale both for defense as well as for domestic use.
Gordon Earle Moore is the co-founder of Intel Corporation, USA. Born in 1929 at San Francisco, California, he obtained his doctoral degree in Physics and Chemistry from CalTech in 1954. Intel Corporation was co-founded by Moore in 1968, where he served as Executive Vice President until 1975, after which he became President and Chief Executive Officer. Dr Moore became Chairman of the Board and Chief Executive Officer in 1979. He became Chairman Emeritus of Intel Corporation in 1997.