Nanomaterials (nanocrystalline materials) are materials possessing grain sizes on the order of a billionth of a meter. They manifest extremely fascinating and useful properties, which can be exploited for a variety of structural and non-structural applications.
Putting Nanomaterials into Perspective
All materials are composed of grains, which in turn comprise many atoms. These grains are usually invisible to the naked eye, depending on their size. Conventional materials have grains varying in size anywhere from 100’s of microns (µm) to millimeters (mm). A micron (µm) is a micrometer or a millionth (10-6) of a meter. An average human hair is about 100 µm in diameter. A nanometer (nm) is even smaller a dimension than a µm, and is a billionth (10-9) of a meter. A nanocrystalline material has grains on the order of 1-100 nm. The average size of an atom is on the order of 1 to 2 angstroms (Å) in radius. 1 nanometer comprises 10 Å, and hence in one nm, there may be 3-5 atoms, depending on the atomic radii. Nanocrystalline materials are exceptionally strong, hard, ductile at high temperatures, wear-resistant, erosion-resistant, corrosion-resistant, and chemically very active. Nanocrystalline materials, or nanomaterials, are also much more formable than their conventional, commercially available counterparts. Nanomaterials research literally exploded in mid-1980’s in the U. S.
Production of Nanomaterials
There are five widely known methods to produce nanomaterials, and they are as follows:
• Sol-gel synthesis,
• Inert gas condensation,
• Mechanical alloying or high-energy ball milling,
• Plasma synthesis, and
All these processes synthesise nanomaterials to varying degrees of commercially-viable quantities. To date, of all the above process, only sol-gel synthesis can
• Produce materials (both metals and ceramics) at ultra-low temperatures (around 150-600 °F vis-à-vis 2500-6500 °F for conventional techniques),
• Large quantities (to be commercially viable) relatively cheaply,
• Synthesize almost any material,
• Co-synthesize two or more materials simultaneously,
• Coat one or more materials onto other materials (metal or ceramic particulates, and three-dimensional objects),
• Produce extremely homogeneous alloys and composites,
• Synthesise ultra-high purity (99.9999%) materials,
• Tailor the composition very accurately even in the early stages of the process, because the synthesis is actually performed on an atomic level,
• Precisely control the microstructure of the final products, and
• Precisely control the physical, mechanical, and chemical properties of the final products.