Differences between carbon nanofibers produced using Fe and Ni catalysts in a floating catalyst reactor

Carbon nanofibers were produced by the catalytic CVD process by the floating catalyst method, in semi-industrial systems at temperatures above 1350 K. Iron-derived carbon nanofibers Were produced from natural gas and xylene, using ferrocene as catalyst source, yielding a thickened submicron vapor grown carbon fibers with a core of multi-wall nanotubes. For the production of Ni derived nanofibers, natural gas was used as the carbon feedstock, and the Ni was added in a nickel compound solution. When no sulfur is used, only soot was obtained, but when sulfur is added to the reactive feedstock, a highly graphitic and very nice stacked-cup-type nanofibers with no free-CVD thickened layer were produced. TEM-EDS analysis confirms that this type of stacked-cup carbon nanofiber is produced only with a partially molten catalyst and methane as hydrocarbon source. In fact, very few fibers have either a particle tip at the end or trapped metal particle inside the wide hollow core of this type of produced carbon material. (C) 2006 Elsevier Ltd. All rights reserved.