Chemistry and kinetics of chemical vapor deposition of pyrocarbon - IV - Pyrocarbon deposition from methane in the low temperature regime

Pyrocarbon deposition from methane was studied at ambient pressure and 1100 degrees C using a vertical hot-wall deposition reactor; the methane initial partial pressure was varied up to 75 kPa and the residence time up to 1 second. The influence of hydrogen partial pressure was studied at constant methane partial pressure. Steady-state pyrocarbon deposition rates and corresponding compositions of the gas-phase were determined. Reaction models of homogeneous gas-phase and heterogeneous pyrocarbon deposition reactions were derived and used for simulation of pyrocarbon deposition kinetics influenced by residence time, initial partial pressures of methane and hydrogen, and concentrations of active sites. The importance of active sites and their blocking by hydrogen is discussed with special emphasis. (C) 1998 Elsevier Science Ltd. All rights reserved.