Effect of catalyst on the growth of carbon nanotubes using a detonation approach

Carbon nanotubes were prepared by the heat-induced detonation of an explosive-catalyst precursor-hydrocarbon system in a sealed stainless steel pressure vessel. TEM, HRTEM, XRD and TG techniques were employed to investigate the effect of the catalyst precursors of ferrocene, nickel formate and cobalt acetate on the growth of the nanotubes. The morphologies, structure and crystallinity of carbon nanotubes are largely dependent on the kind of catalyst. Cobalt acetate acting as catalyst precursor can yield high-purity (about 80%-90%) carbon nanotubes with good microstructures and hollow channels. Ferrocene can give low-purity (10%-20%) nanotubes with most of them having a bamboo-like appearance. Nickel formate precursor generates 10%-20% nanotubes with substantial structural defects. Many ends of the Ni-catalyzed nanotubes are blown into a bulb with diameters up to ～160nm. XRD characterization indicates that these metal compounds are subjected to decomposition and a reduction reaction after the detonation and are converted into metallic nanoparticles, which show important catalytic activity for the nucleation and growth of carbon nanotubes under the experimental conditions. Based on the differences in the quality and purity of the nanotubes, the activity of the catalysts follows the order: CoFeNi. The diverse activities exhibited by different catalysts in the specific high carbon concentration environment generated by detonation are discussed briefly.