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 diame ter of a few micrometres have been fabricated by a conventional thermal dep osition method at 1000 degreesC using ferric sulfate or ferrous sulfate as catalyst precursors, nitrogen as carrier gas, benzene as the source of carb on and a ceramic tube as substrate. Experiments employed a feeding gas of 2 7 wt.% benzene vapor and 73 wt.% nitrogen with a flow rate of 13.9 ml/min f or 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 satisfa ctorily. Observation about the nucleation phenomenon of catalyst, the lengt hening and thickening of the VGCFs, reveals that catalyst particles with a mean diameter of 78 nm were generated at 1000 degreesC while carbon filamen ts were firstly found after 10 min carbon deposition. In addition, the leng thening and thickening of the VGCFs were confirmed to occur simultaneously in the growth process. (C) 2000 Elsevier Science Ltd. All rights reserved.