Chemical vapour deposition in hot-wall reactors:: the role of the ratio of substrate surface area to reactor volume

The deposition of pyrolytic carbon from methane has been used to investigate the influence of the ratio of substrate surface area to reactor volume, A(S)/V-R, on deposition chemistry and kinetics. Deposition studies were performed at a pressure of about 100 kPa (ambient pressure), a methane partial pressure of 10 kPa, and a temperature of 1100 degreesC. The A(S)/V-R ratio was varied from 0.18 to 8.2 mm(-1). Carbon deposition rates and corresponding compositions of the gas phase were determined as a function of residence time. The experimental results show volume-related carbon formation rates increasing with increasing surface area or increasing A(S)/V-R ratio, but surface-related carbon deposition rates decreasing with increasing surface area or increasing ratio. The latter result implies that any kinetics of chemical vapour deposition determined in the past are only valid for the reaction system used.