Synthesis of multiwalled carbon nanotubes from bamboo charcoal and the roles of minerals on their growth

Multiwalled carbon nanotubes (MWCNTs) were synthesized. from bamboo charcoals by chemical vapor deposition in the presence of ethanol vapor. Fresh bamboo culms were first heat treated at 1000-1500 degrees C to form charcoals. The elemental composition and structure of mineral phases in the bamboo charcoal treated at different temperatures were analyzed. The results showed that Mg2SiO4 and particularly calcium silicate were responsible for the nucleation and growth of MWCNTs at 1200-1400 degrees C. Transmission electron microscope and energy dispersive X-ray spectrometer observations indicated that the tips of nanotubes synthesized at 1200-1400 degrees C consist mainly of calcium silicate. Such silicate tips acted as effective catalysts for nanotubes. The growth of MWCNTs followed the vapor-liquid-solid model including an initial decomposition of ethanol vapor into carbon, dissolution of carbon inside molten silicate and final nucleation of nanotubes. (C) 2011 Elsevier Ltd. All rights reserved.