Growth mechanism of carbon nanocoils

Carbon nanocoils were prepared by catalytic pyrolysis of acetylene using iron-coated indium tin oxide as the catalyst. The effects of the constitution of catalyst, the growth temperature and time, the flow rate of acetylene gas on the growth of carbon nanocoils were investigated. It is found that the coils grow mainly from the interface of iron and indium tin oxide films. The coils generally consist of two or more nanotubes. Each coil has its own external diameter and pitch, which is determined by the structure of the catalyst at its tip. The growth of the carbon nanocoil is considered to be due to the nonuniformity of the carbon extrusion speed at different parts of the catalyst particle containing iron, tin, indium and/or oxygen. It is confirmed that iron is crucial in the formation of a nanotubule and indium tin oxide induces the helical growth of the nanotubule. (C) 2002 American Institute of Physics.