Aligned carbon nanotubes by catalytic decomposition Of C2H2 over Ni-Cr alloy

High density, well-aligned carbon nanotubes (CNTs) were prepared by thermally decomposing acetylene at 700 degrees C with the help of Ni Cr alloy as catalyst in a thermal chemical vapor deposition system. The density and alignment of CNTs were characterized by scanning electron microscope (SEM). It was found that the density of the CNTs could be remarkably increased and the alignment could be improved with the decrease of the thickness ratio of Ni:Cr. Also found in our experiment was that the catalyst encapsulated in CNT was single crystal Ni, which was confirmed by high-resolution transmission electron microscopy (HRTEM) and electron dispersion X-ray spectrum (EDX). Finally, the growth mode of CNTs was discussed based on the Ni-Cr alloy catalysts under our experimental conditions. The results are helpful in providing a better understanding of the acting of catalyst and the controlling of the desirable density and alignment of CNTs for various applications. (C) 2005 Elsevier Ltd. All rights reserved.