Growth of Carbon Nanotubes and Vapor-Grown Carbon Fibers Using Chemical Vapor Deposition of Methane

Abstract

Carbon nanotubes and vapor-grown carbon fibers (VGCFs) were fabricated by means of chemical vapor deposition (CVD) of methane at 1100°C. The experiments were conducted by introducing a mixture of 20% methane and 80% nitrogen at a total flow rate of 500 ml/min into a tubular quartz reactor containing a ceramic substrate coated with iron oxide particles as catalysts for the growth of nanotubes. Iron oxide particles were formed by drying/dehydration of 0.5 M ferric sulfate aqueous solution, followed by nucleation of ferric sulfate. After a deposition time of 10 to 40 minutes, carbon nanotubes, with diameters of about 10 to 100 nm, and VGCFs, with diameters of a few to 10βm, formed. Many types of nanotubes and VGCFs, including cylindrical, spiral, ring-like and sheet-like types, were found in our study. In addition, the direction of the gas flow was reversed about halfway through the deposition process. It was discovered that the VGCFs bent 180 degrees, suggesting that the orientation of the growing nanotubes and VGCFs followed the direction of the gas flow.