Structural characterization of carbon nanofibers formed from different carbon-containing gases

Catalytically grown carbon nanofibers, a novel mesoporous carbon material for catalysis, were synthesized by the decomposition of carbon-containing gases (CH4, C2H4 or CO) over supported nickel-iron alloy and unsupported iron. It was shown that the structures of as-synthesized and modified CNFs, including the arrangement of the graphenes in CNF, and the crystallinity and texture of CNF depended on the catalyst composition and the type of carbon-containing gas. Three types of CNFs with different microstructures were obtained: platelet CNF (Fe-CO), fishbone CNF (supported Ni-Fe alloy-CH4, C2H4 or CO) and tubular CNF (supported Ni-CO). All the CNFs were mesoporous carbon materials possessing relatively high surface areas (86.6-204.7 m(2)/g) and were highly graphitic. Purification with acid-base treatments or high temperature treatment removed the catalyst residue without changing the basic structures of the CNFs. However, annealing significantly decreased their surface areas through the formation of loop-shaped ends on the CNF surfaces. Oxidative modification in the gas and liquid phases changed the structures only slightly, except for oxidation in air at 700 degrees C. The structures and textures were studied using SEM, TEM, XRD, BET and TGA. (c) 2006 Elsevier Ltd. All rights reserved.