We live in a
macro world. Objects have a distinct position (the computer
is on the desk, the desk is on the floor, etc.) and
momentum (speed and direction). Matter behaves as massive
particles, and nothing moves too fast. However, an entirely
different world is abstracted from our view. On the
order of billionths of a meter, life is much different.
The physical laws of Newton with which we intuitively
approach life are replaced by those of Einstein, Plank,
Bohr, Heisenberg and many more. This is the world of
quantum mechanics and to most of us, this world is a
highly unintuitive and complex place. Matter behaves
as both particles and waves, position and momentum are
mere probability, and mass, length, and time are all
dynamic quantities. Nanomaterials exist in these scales
and possess amazing properties and are the subject of
much research and application. In the future, practically
every field will apply the benefits of these materials.
Nanotubes can
be made from several materials, but as the first to
be discovered, carbon nanotubes are by far the most
widely studied. Carbon nanotubes are long cylindrical
arrangements of carbon atoms much like a sheet of graphite
rolled into a cylinder and capped by half bucky ball
structures. (A sheet of graphite is a 2 dimensional
hexagonal arrangement of carbon atoms. Imagine a sheet
of paper on a desk. It has a depth (y dimension) and
a width (x dimension) but negligible height (z direction).
Further, imagine covering the paper with a mosaic of
hexagons (hexagons because of chemical bonding) where
each bend in the line represents the location of a carbon
atom much like the left side of the navigation bar above.
If we folded this sheet upon itself to create a cylinder,
we would have the majority portion of a carbon nanotube.
We just need to cap the ends. If you cut a soccer ball
in half and imagine covering it with the same mosaic
of carbon hexagons, you create a half bucky ball structure
(named for Buckminister Fuller). Place the half bucky
balls on both ends, and we have created an imaginary
carbon nanotube. In our mind, the carbon nanotube is
too large by magnitudes of order. In reality, the cylinders
are nanometers in diameter (billionths of a meter) and
up to millimeters (thousandths of a meter) in length.
Carbon nanotubes
were discovered in 1991 by S. Iijima, and since that
time have been subject to ever increasing research.
Because of their unique and incredible structural, electrical,
and thermal properties there seems no end to the possible
applications of nanotubes. For example, based on weight
alone, carbon nanotubes are 400x stronger than steel.
They have the highest known current density of any material
(109 A/cm^2), and have variable electronic properties
depending upon their length, diameter, and chirality
(twisting of the tube).
From the hard work
of researchers around the world, the materials science
community at large gathers an ever increasing database
of knowledge concerning the properties and characteristics
of nanomaterials. The possible applications and material
modifications grow everyday. From nanoscale medical devices
to superthin superstrong fibers, from electrical applications
to thermal applications, nanomaterials are the material
of the future. |
