FULLERENES, NANOTUBES, ONIONS AND RELATED CARBON STRUCTURES

Fullerenes, containing five- and six-membered carbon rings, of which C -60 and C-70 are the prominent members, exhibit phase transitions asso ciated with orientational ordering. When C-60 is suitably doped with e lectrons, it shows novel superconducting and magnetic properties. We r eview these and other properties of fullerenes in bulk or in film form along with the preparative and structural aspects. Carbon nanotubes a nd onions (hyperfullerenes) are the other forms of carbon whose materi al properties have aroused considerable interest. Besides discussing t hese new forms of carbon, we briefly introduce other possible forms, s uch as those involving five-, six- and seven-membered rings and hybrid s between diamond and graphite.