A structure model and growth mechanism for novel carbon nanotubes

The growth of carbon nanotubes from catalytic thermal decomposition of acet ylene on fine iron particles has been studied. Electron microscopic images of the carbon nanotubes "as formed" and after annealing treatment are prese nted. Besides the ordinary carbon nanotubes which have been reported (S. Ii jima, Nature, 354 (1991) 56), we have found, at first time, two other new k inds of carbon nanotubes: one is straight or curved nanotube with many irre gular multi-layered diaphragms in the hollow core, in particular, the fring es of the wa II of the tu bes a re not parallel to the axis of the tu be; a nother one has ma ny regular diaphragms (bamboo-like) which keep almost con stant distance with each other. A model that postulates two steps growth of nanotubes from catalyst particles is proposed to explain the microstructur e of the novel carbon nanotubes. (C) 1999 Kluwer Academic Publishers.