Centre for Material and Fibre Innovation
ITRI
Nanomaterials are materials that possess structured components in the nanoscale region. (http://www.nanotec.org.uk/report/chapter3.pdf) They are manufactured by 'bottom-up' or 'top-down' processes. The properties of nanomaterials differ significantly from those of other materials because of their increased surface area and quantum effects.
Two-dimensional nanomaterials, such as thin films and engineered surfaces, have been used for many years in fields such as electronic device manufacture, chemistry and engineering. In the silicon-integrated circuit industry, for example, many devices rely on thin films for their operation, and control of film thickness approaching the atomic level is routine. (http://www.nanotec.org.uk/report/chapter3.pdf)
For example, organic light-emitting diode (OLED) displays look set to take over from LCD and plasma displays in monitors and TV sets. (http://www.siliconchip.com.au/cms/A_30650/article.html) An RGB OLED cell is manufactured by depositing a conductive, transparent anode material onto a transparent substrate. Organic layers are added next and a reflective metal cathode completes the structure. The organic compounds used are luminescent and act as hole/electron transporters. The thickness of the structure - not including the substrate - is only about 300 nm. OLED displays have high brightness and contrast, ultra-wide viewing angle, no need for a backlight, fast response time and low power consumption.
One dimensional nanomaterials such as nanotubes and nanowires, have a nanoscale thickness and are the subject of considerable research. For example, carbon nanotubes are extended tubes of rolled graphene sheets, and may be multi-walled (several concentric tubes) or single-walled (one tube). (http://www.nanotec.org.uk/report/chapter3.pdf) Single-walled carbon nanotubes can be considered to be formed by the rolling of a single layer of graphite into a seamless cylinder. A multi-walled carbon nanotube can be considered to be a coaxial assembly of cylinders of single-walled nanotubes, the separation between the tubes being about equal to that between the layers in natural graphite. (http://www.nanotech-now.com/nanotube-buckyball-sites.htm)
Zero-dimensional nanomaterials, such as nanoparticles, have a nanoscale diameter of less than about 100 nm. The ability to fabricate and control the structure of nanoparticles allows the scientist and engineer to influence the resulting properties and, ultimately, design materials to give the desired properties. The current and potential applications for nanoparticles are growing and cover an extremely broad range of areas including biomedical & cancer treatment, renewable energy, environmental protection, pharmaceuticals, personal care, surface coatings, plastics, textiles, food, building materials, electronics, automotives, etc.
Nanoparticles exist widely in the natural world, for example, as the products of photochemical and volcanic activity. Manufactured nanoparticles are typically not products in their own right, but generally serve as raw materials, ingredients or additives in existing products. (http://www.nanotec.org.uk/report/chapter3.pdf)
Nanoporous materials are 3-dimensional (bluk) materials that possesses nanoscale pores. Due to their large interior surfaces and in the nanometer sized pore space, nanoporous materials interact with atoms, ions and molecules in a significantly efficient manner, which opens up many applications in various fields such as ion exchange, separation, catalysis, sensor, biological molecular isolation and water purifications. The nanoporous structures can be used for inclusion chemistry and as templates for synthesising nanowires and nanoparticles.
Nanocrystalline bulk materials are 3-dimensional materials that consist of nanoscale grains. Their unique properties derive from not only the nanocrystals but also the grain boundaries between the nanocrystals. Nanocrystalline bulk materials are of particular importance in the fields of metallurgy and engineering ceramics. For example, cutting tools made of nanomaterials, such as tungsten carbide, tantalum carbide, and titanium carbide, are much harder, much more wear-resistant, erosion-resistant, and last longer than conventional large-grained counterparts. Unique combinations of grains and grain-boundary materials enables ductile ceramics that show super-plasticity. Rare-earth based permanent magnets can have significantly improved properties by balancing between the grain size, magnetic domain size and grain boundary materials.
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