A structure model and growth mechanism for novel carbon nanotubes

The growth of carbon nanotubes from catalytic thermal decomposition of acetylene on fine iron particles has been studied. Electron microscopic images of the carbon nanotubes “as formed” and after annealing treatment are presented. Besides the ordinary carbon nanotubes which have been reported (S. Iijima, Nature, 354 (1991) 56), we have found, at first time, two other new kinds of carbon nanotubes: one is straight or curved nanotube with many irregular multi-layered diaphragms in the hollow core, in particular, the fringes of the wall of the tubes are not parallel to the axis of the tube; another one has many regular diaphragms (bamboo-like) which keep almost constant distance with each other. A model that postulates two steps growth of nanotubes from catalyst particles is proposed to explain the microstructure of the novel carbon nanotubes.