Carbon Nanotubes


     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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