This article was updated on the 29th April 2019.
Materials scientists and engineers have made significant improvements to the 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, clusters of atoms (nanodots, macromolecules), nanocrystalline structured materials (grain size less than 100 nm), fibers less than 100 nm in diameter (nanorods and nanotubes) and films less than 100 nm in thickness provide a good base to develop new nanocomponents and materials.
The buckyball (C60) has opened up an excellent field of chemistry and material science with many exciting applications due to 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 for its wider use and the replacement of the internal combustion engine. The potential of nanotubes can be further exploited in the oil and gas industries and the nanotube market is likely to hit 1.35 billion dollars in 2005. Nanotechnology offers a myriad of applications including new gas, optical and chemical sensors, energy conversion devices and bio implants.
Nanoporous oxide films such as TiO2 are being used to enhance photovoltaic cell technology. Nanoparticles can be used in very thin layers on conventional metals to absorb incident solar energy. Films formed by sintering nanometric particles of TiO2 (diameter 10-20 nm) combine high surface area, transparency, excellent stability and good electrical conductivity making them ideal for photovoltaic applications. Nonporous oxide films are also highly promising materials for photovoltaic applications. Nanotechnology opens the opportunity to produce cheaper and more efficient solar cells.
Nano carbon fibers have been produced in China and the UK. 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 them against pollution, poisoning and enemy hazards.
Nanotechnology offers unlimited opportunities to produce next generation pressure, chemical, magneto resistive and anti-collision automobile sensors. Many aerospace and automotive applications are already in use, and further applications such as anti-corrosion coating, tougher and harder cutting tools, and medical implants and chips are expected to be developed in the next 5-15 years. Nanostructured materials for nanoelectronic components, ultra-fast processors, nanorobots for body parts are all still in the state of infancy.
Spending and Investment
The remarkable progress achieved in the last five years has fuelled the hype surrounding nanotechnology, which is reflected 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.
Nanotechnology is viewed as a key technology for the development of ultra-light materials which would result in energy, fuel and materials savings and give engineers unprecedented control over structure and properties at a subatomic level.
With the future development of nanocatalyst diesel oxidants using nanoscale layers of Pt and Pd, the major environmental killers (smog, pollution and toxic pesticide) would be eliminated allowing humans to breathe in healthy air. Improvements in nanofilters would enable bacteria less than 30 nm to be filtered, achieving a water purity of 99.999997%.
The future avalanche of the nano-age involves replacement of existing chips by super chips, plastic semiconductors, stronger and lighter jet fighters, invisible clothing for soldiers, super fuel cells and super batteries.
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, altering the density and conduction in defect core regions where 50% of the atoms are located. All misfits are concentrated in the grain boundary which 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.
Reviewed by Clare Kiernan
Dr. Zaki Ahmad
Mechanical Engineering Department, King Fahd University of Petroleum & Minerals