What are Nanomaterials?
Just a man
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.
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 ( m) to millimeters (mm). A
micron ( m) is a micrometer or a millionth (10-6) of a meter. An
average human hair is about 100 m in diameter. A nanometer (nm) is
even smaller a dimension than a m, 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
( ) in radius. 1 nanometer comprises 10 , 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.
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
Electrodeposition.
All these processes synthesize 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,
synthesize 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.