Carbon Nanotubes

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Carbon Nanotubes

In 1991 lijimaSumio of NEC Corporations Fundamental Research Laboratory, Tsukuba Science City, Japan has investigated the material which is extracted from the solids that are growing on the tips of carbon electrodes after being discharged under C60 formation conditions. Iijima found that these solids consist of tiny tubes made up of numerous concentric graphene cylinders. Each cylinder wall is consisting of a sheet of carbon atoms that are arranged in hexagonal rings. The cylinders are usually had the closed offends and is ranging from 2 to 10 micrometers in length and 5 to 40 nanometers in diameter. High-resolution of transmission electron microscopy is later revealed that these multiwall molecules of carbon nanotubes MWNTs are seamless and that the spacing between the adjacent layers is about 0.34 nanometer, which is the close spacing observed between the sheets of graphite. The number of concentric cylinders in the given tube ranged from 3 to 50 and the ends were generally capped by domes of fullerene that includes the pentagonal rings which are necessary for the closure of tubes. It was soon shown that the single-walled nanotubes SWNTs could also produce by this method. It was soon than shown that the single-walled nanotubes are also produced by this method when the catalyst of cobalt-nickel was used. In 1996 the group which is led by Smalley produced SWNTs in very high purity by vaporization of carbon by a laser which is impregnated with nickel and cobalt. These nanotubes are essentially elongated fullerenes.


Individual carbon nanotubes may be semiconducting or metallic, depending on the helical orientation of the rows of hexagonal rings present in the walls of the tubes. Rather than conducting electricity via transport of electron, a diffusive process that resulting the scattering of electron and conductive heating, SWNTs is exhibiting the ballistic transport, the fast conduction process and highly efficient electrons is prevented from diffusing through the wall of the tube or around its circumference by the regular hexagonal array of the carbon atoms which is propagating rapidly along the axis of the tube. Open-ended SWNTs are emitting the electrons at currents that are attaining approximate 100 nanoamperes. Owing to such remarkable properties, electrical conductors are made of bundles of nanotubes should exhibit zero energy loss. Aligned MWNTs show promise as field emission devices with potential applications in electronic flat panel displays. Nanotubes can also be used as highly resilient probe tips for scanning tunnelling microscopes and the atomic force microscopes.

Carbon nanotubes are exhibiting faster phonon transport than diamond which is previously recognized as the best thermal conductor and the electric current carrying capacity of nanotubes is approximately four orders of magnitude which are higher than copper.

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