CVD growth of carbon nanotube films on nickel substrates

Carbon nanotubes were grown on nickel substrates by thermal chemical vapor deposition (CVD) with polyethylene as precursor. Various preparation methods for samples of nickel substrates were used: abrasive grinding, mechanical and chemical polishing. It was established by X-ray diffraction that mechanical treatment produces the nanostructured metal in the near-surface layer of nickel. The assumption was made that such treatment increases substantially the surface catalytic activity and carbon diffusion in the subsurface layer and provides formation of relatively uniform carbon nanotube films. The dependence of outer diameter distribution on the surface treatment was found for carbon nanotubes grown at 700 degreesC. Such dependence is absent for nanotubes grown at 800 degreesC. It was concluded, that solid and liquid particles are responsible for the nanotube growth at 700 and 800 degreesC, respectively. Correlation between the catalytic activity and grain size of nanocrystalline nickel was established. This was interpreted as evidence that intergrain boundaries are active sites for the catalytic carbon deposition. It was proposed, that fast carbon intergrain diffusion can in some cases initiate fragmentation of nanostructured nickel surface along grain boundaries. (C) 2003 Elsevier Science B.V. All rights reserved.