What are Carbon Nanotubes?
A significant nanoparticle discovery that came to light in 1991 was
carbon nanotubes. Where buckyballs are round, nanotubes are cylinders
that haven’t folded around to create a sphere. Carbon nanotubes are
composed of carbon atoms linked in hexagonal shapes, with each carbon
atom covalently bonded to three other carbon atoms. Carbon nanotubes
have diameters as small as 1 nm and lengths up to several centimeters.
Although, like buckyballs, carbon nanotubes are strong, they are not
brittle. They can be bent, and when released, they will spring back to
their original shape.
One type of carbon nanotube has a cylindrical shape with open ends,
as shown in the following figure.
A carbon nanotube.
Another type of nanotube has closed ends, formed by some of the
carbon atoms combining into pentagons on the end of the nanotube, as
shown in the following figure.
A carbon nanotube with closed ends.
The properties of nanotubes have caused researchers and companies to
consider using them in several fields. For example, because carbon
nanotubes have the highest strength-to-weight ratio of any known
material, researchers at NASA are combining carbon nanotubes with other
materials into composites that can be used to build lightweight
Carbon nanotubes can occur as multiple concentric cylinders of carbon
atoms, called multi-walled carbon nanotubes (MWCTs) and shown in the
following figure. Logically enough, carbon nanotubes that have only one
cylinder are called single-walled carbon nanotubes (SWCTs). Both MWCT
and SWCT are used to strengthen composite materials.
A multi-walled carbon nanotube.
Excerpted from Nanotechnology For Dummies (2nd edition), from Wiley Publishing