Formation of vapor grown carbon fibers with sulfuric catalyst precursors and nitrogen as carrier gas

Vapor grown carbon fibers (VGCFs) with a maximum length of 2 cm and a diameter of a few micrometres have been fabricated by a conventional thermal deposition method at 1000 degreesC using ferric sulfate or ferrous sulfate as catalyst precursors, nitrogen as carrier gas, benzene as the source of carbon and a ceramic tube as substrate. Experiments employed a feeding gas of 27 wt.% benzene vapor and 73 wt.% nitrogen with a flow rate of 13.9 ml/min for a deposition time of 5 to 90 min on a ceramic substrate coated catalyst precursor from a 0.5 M aqueous solution. It was found that the combination of the sulfuric catalyst and nitrogen is capable of producing VGCFs satisfactorily. Observation about the nucleation phenomenon of catalyst, the lengthening and thickening of the VGCFs, reveals that catalyst particles with a mean diameter of 78 nm were generated at 1000 degreesC while carbon filaments were firstly found after 10 min carbon deposition. In addition, the lengthening and thickening of the VGCFs were confirmed to occur simultaneously in the growth process. (C) 2000 Elsevier Science Ltd. All rights reserved.