Special Topics
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Carbon Nanotubes |
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In 1985, a
team led by Dr. Richard Smalley at Rice University
discovered a new form of carbon, buckyministerfullerene
C60, a geometric cage-like structure of carbon
atoms that is composed of hexagonal and pentagonal
faces. Smalley’s work resulted in the discovery
of carbon nanotubes by Iijima in 1991 and
his receiving the 1997 Nobel Prize in chemistry.
Since the discovery of carbon nanotubes, significant
research is underway to study the unique structural,
mechanical, electrical, thermal, and chemical
properties of carbon nanotubes and explore
their potential applications.
The fullerene
structure of carbon nanotubes, derived from
the honeycomb lattice representing
a single atomic layer of crystalline graphite
and held together by strong and high conductive
sp2 bonds, is vastly different from conventional
graphite or carbon structures.
Theoretical modeling and
experimental measurements have showed that
carbon nanotubes possess extraordinary mechanical
properties. Specifically, the strength of
carbon nanotubes is predicted to be 30 to
120 times stronger than steel, yet only 1/6
the weight of steel. Further, they also can
sustain large elastic deformation without
breaking. For example, their fracture strains
are estimated to be 10-30%, a factor of 10-100
times better than those of carbon fibers,
such as IM7, a fiber commonly used in military
and aerospace applications.
These evaluations
of carbon nanotubes indicate that they possess
amazing mechanical properties greater than
those of graphite fiber. Besides their extraordinary
mechanical properties, carbon nanotubes offer
either metallic or semiconducting characteristics
based on the chiral structure of fullerene.
They also possess superior thermal and electrical
properties: thermal stability up to 2800᾿
in a vacuum and 750_C in air, thermal conductivity
about twice as high as diamond, with electric
current transfer capacity 1000 times greater
than copper wires.
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