CARBON NANO-TUBES: DESCRIPTION, PROPERTIES AND APPLICATIONS

Carbon nano-tubes (CNTs) are hollow cylinders of graphite carbon atoms. These tubes are on the nanoscale (10-9 m), which is so small that 10,000 of them could fit within the diameter of one human hair. Carbon nano-tubes are a new form of carbon with unique electrical and mechanical properties. They can be considered as the result of folding graphite layers into carbon cylinders. These cylinders may be composed of a single shell single wall carbon nano-tubes (SWCNTs), or of several shells multi-wall carbon nano-tubes (MWCNTs). SWCNTs tend to be stronger and more flexible than MWCNTs. Their interesting electronic structure makes CNTs ideal candidates for making novel molecular devices. Metallic Nano-tubes for example, were utilized as Coulomb islands in single-electron transistors. SWCNTs are nanometer-diameter cylinders consisting of a single graphite sheet wrapped up to form a tube. They have emerged as a very promising new class of electronic materials. Both metallic and semi-conducting SWNTs are found to possess electrical characteristics that are comparable favorably to the best electronic materials available. Field emission cathodes based on CNTs are potential candidates for lowcost replacement of thermionic cathodes used in microwave tubes. The combination of Poly-methyl-methacrylate (PMMA) known as a bone cement and hydroxyl-apatite with MWCNTs has revolutionized orthopedic surgery. Due to their small dimensions and high aspect ratio, they exhibit exceptional physical and chemical properties. This paper presents a brief account of their description, properties and applications of CNTs.