Chemical vapor deposition of carbon from methane at various pressures, partial pressures and substrate surface area/reactor volume ratios

Carbon deposition from methane was studied as a function of substrate length at a temperature of 1100 degreesC, total pressures ranging from 90 to 10 kPa at a constant methane partial pressure of 10 kPa, methane pressures ranging from 5 to 20 kPa, and residence times of 0.55 s and 1.1 s using substrates with surface area/volume ratios of 0.78, 1.65 and 3.55 mm(-1). Various total pressures at constant methane pressure have significant influences on the deposition profile of carbon, but they are mainly caused by different boundary conditions. The methane pressure reference suggests saturation adsorption (Langmuir - Hinshelwood kinetics) upto a pressures of about 15 kPa. Increasing surface area/volume ratios leads to decreasing surface related deposition rates, because the deposition chemistry is changed. (C) 2001 Kluwer Academic Publishers.