Carbon nanotube (CNT) is the name of ultrathin carbon fibre with nanometer￾size diameter and micrometer-size length and was accidentally discovered by a
Japanese scientist, Sumio Iijima, in the carbon cathode used for the arc￾discharging process preparing small carbon clusters named by fullerenes. The
structure of CNT consists of enrolled graphitic sheet, in a word, and can be
classified into either multi-walled or single-walled CNT (MWCNT or SWCNT)
depending on its preparation method. It is understood that CNT is the material
lying in-between fullerenes and graphite as a quite new member of carbon
allotropes.