Materials scientists and engineers have made significant developments in the improvement of methods of synthesis of nanomaterial solids. A brief review of future trends in nanotechnology developments is given in this article.
Unprecedented opportunities are arising for re-engineering existing products. For example, cluster of atoms (nanodots, macromolecules), nanocrystalline structured materials (grain size less than 100 nm), fibres less than 100 nm in diameter (nanorods and nanotubes), films less than 100 nm in thickness provide a good base to develop further new nanocomponents and materials.
The buckyball (C60) has opened up a excellent field of chemistry and material science with many exciting applications because of its ability to accept electrons. Carbon nanotubes have shown a promising potential in the safe, effective and risk free storage of hydrogen gas in fuel cells, increasing the prospects of wide uses of fuel cells and replacement of internal combustion engine. The potential of nanotubes can be further exploited in oil and gas industry. The nanotube market is likely to hit 1.35 billion dollars in 2005. Nanotechnology offers a myriad of applications for production of new gas sensors, optical sensors, chemical sensors, and other energy conversion devices to bio implants.
Nanoporous oxide films such as TiO2 are being used to enhance photo voltaic cell technology. Nanoparticles are perfect to absorb solar energy and they can be used in very thin layers on conventional metals to absorb incident solar energy. New solar cells are based on nanoparticles of semi conductors, nanofilms and nanotubes by embedding in a charge transfer medium. Films formed by sintering of nanometric particles of TiO2 (diameter 10-20 nm) combine high surface area, transparency, excellent stability and good electrical conductivity and are ideal for photovoltaic applications. Non porous oxide films are highly promising material for photovoltaic applications. Nanotechnology opens the opportunity to produce cheaper and friendlier solar cells.
In China and U.K., nanocarbon fibres have been produced. The production of nanofibres offers the potential of using the woven reinforcement as body armor. The future soldier’s uniform would incorporate soft woven ultra strong fabric with capabilities to become rigid when a soldier breaks his legs and would protect him against pollution, poisoning and enemy hazards.
Nanotechnology offers unlimited opportunities to produce new generation pressure, chemical, magneto resistive and anti-collision automobile sensors. Many of the novel applications such as new sensors, better photovoltaic cells, lighter and strong materials for defense, aerospace and automotives are already in use, and applications such as anti-corrosion coating, tougher and harder cutting tools, and medical implants and chips with 1 nm features may be developed in another 5-15 years. Nanostructured materials for nanoelectronic components, ultra fast processors, nanorobots for body parts are still in the state of infancy.
Spending and Investment
Despite the hype surrounding nanotechnology, the progress achieved in the last five years is remarkable as shown by dramatic public spending in recent years. The total global investment in nanotechnology is currently around 5 billion euros, two billion of which comes from the private sector.
Ultra Light Materials
Nanotechnology is viewed as a key technology for the development of ultra light materials which would result in energy, fuel and materials savings and development of spectacular materials with complete control over structure and properties at a subatomic level not hitherto known to scientists and engineers. With the future development of nanocatalyst, diesel oxidant using nanoscale layers of Pt, Pd, the major environmental killers smog, pollution and toxic pesticide would be eliminated and humans will be able to breathe in healthy air. Improvement in nanofilters would enable bacteria less than 30 nm to be filtered and achieve water purity of 99.999997. The future avalanche of nano-age involves replacement of existing chips by super chips, plastic semiconductors, stronger and lighter jet fighters, amazingly invisible clothing for soldiers, super fuel cells and super batteries. The next twenty years would unleash a new era of nanotechnology when a fullerene molecule (C6) would be described in a high school chemistry book and all materials science textbooks would contain chapters on nanomaterials.
Corrosion and Corrosion Prevention
Despite the progress in understanding the structure of nanomaterials, there is no evidence to show that nanomaterials are more resistant to corrosion than their conventional counterparts. A typical feature of nanomaterials is the defect core structure, which is caused by incorporation of vacancies, dislocations, grains or interphase boundaries, which alter the density and conduction in defect core regions where 50% of the atoms are located. All misfits are concentrated in the grain boundary. The grain boundary is associated with high diffusivity and higher electrical resistivity. Solute atoms with little solubility also segregate into the boundary regions. Summing up, the grain boundary region is highly active in nanomaterials. Nanograin size, enhanced diffusivity and concentration of defects would make grain boundary sensitive to attack by corrosion. Increased electrical resistivity due to electron scattering would enhance corrosion resistance. Increased number of grain boundaries would also lead to development of more anodic sites for nucleation of corrosion. Theoretically, the structural evidence does not present an optimistic picture of corrosion resistance. There is no clear evidence to prove that nanomaterials are more resistant to corrosion than conventional materials. This is in contrast to the corrosion prevention of nanostructured materials as the studies on coatings have proved. Nanoparticles incorporated in coatings have shown a dramatic resistance to corrosion of the substrate due to their hydrophilic, anti-wear, anti-friction and self-cleaning properties. Engine components are subjected to severe environmental stimulus for corrosion. Diesel engines produce sulfuric acid and formic acid as combustion products. Nano Zirconia powder has been used to coat engine components by plasma spray with success. Nanocoatings create a lotus effect and properties, which keeps corrosion away.