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

• Published in: Carbon (New York) 2006-12, Vol.44 (15), p.3255-3262
• Main Authors: Zhou, Jing-Hong, Sui, Zhi-Jun, Li, Ping, Chen, De, Dai, Ying-Chun, Yuan, Wei-Kang
• Format: Article
• Language: English
• Subjects: Carbon nanofibers; Chemical vapor deposition; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Materials science; Microstructure; Physics; Specific materials; Surface modification; Texture
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2006.06.028

Catalytically grown carbon nanofibers, a novel mesoporous carbon material for catalysis, were synthesized by the decomposition of carbon-containing gases (CH 4, C 2H 4 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-CH 4, C 2H 4 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 °C. The structures and textures were studied using SEM, TEM, XRD, BET and TGA.