ABSTRACT
Carbon nanotubes are cylindrical carbon structures of few nanometers in diameter and several micrometers in length. Depending on the rolled up unit cell of the graphite sheet we speak about zig-zag, arm-chair or chiral nanotubes. Generally, we say that carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. Depending on the material of the rolled up unit cell we can construct other nanotubes as well as the silicone nanotube and the boron nitride nanotube. Carbon nanotubes can be produced by arc discharge, laser ablation, plasma torch or chemical vapor deposition using various metallic catalysts. Other nanotubes are semiconductors that have band-gap of about 1 eV. Carbon nanotubes are the strongest and stiffest materials yet discovered. The present application of nanotubes is mostly limited as a composite material in order to improve mechanical, electrical or thermal properties of a bulk material.
