Influence of the inherent metal species on the graphitization of methane-based carbon nanofibers

Carbon nanofibers (CNFs) containing different proportions of Ni and Si were produced from methane decomposition in a fluidized bed reactor with a nickel-copper based catalyst. They were subjected to heat treatment in the temperature interval 1800-2800 degrees C for the purpose of studying the influence of the inherent metal species on their ability to graphitize. The participation of Ni and Si species on the graphitization of the methane-based CNFs through the formation of a nickel silicide phase as an intermediate state which further promotes the production of silicon carbide was inferred. Moreover, since silicon carbide was observed by X-ray diffraction after the heat treatment of the CNFs at temperatures >= 2400 degrees C, the formation of graphite at the expense of the carbide decomposition seems to be a plausible mechanism to explain the catalytic graphitization of these CNFs. Because of this effect, carbon materials with crystalline parameters in the range of synthetic graphites which are currently employed in energy applications were prepared in this work. A progressive improvement of the degree of the structural order of the materials prepared with increasing Si/Ni weight ratio in the CNFs was observed. (C) 2012 Elsevier Ltd. All rights reserved.