Chemistry and kinetics of chemical vapor deposition of pyrolytic carbon from ethanol

Synthesis of pyrolytic carbon as a matrix for carbon fiber reinforced carbon composites by chemical vapor infiltration (CVI) is studied experimentally and numerically using the oxygen-containing precursor ethanol. The effects of residence time on microstructure and deposition rate of pyrolytic carbon are investigated. A short residence time is found to favor the formation of high-textured pyrolytic carbon. The evolutions of microstructure and deposition rate of pyrolytic carbon are compared with those of carbon deposited from methane. Compared to methane, ethanol exhibits a much higher deposition rate of pyrolytic carbon with similar microstructures. Pyrolysis of ethanol is modeled using a two-dimensional flow model coupled with a detailed gas-phase reaction mechanism involving 261 species taking part in 1177 reversible reactions. Reaction rate analysis reveals that C-3-hydrocarbons are the most important intermediate species contributing to the maturation of gas-phase composition. A comparison of the kinetic predictions with equilibrium calculations demonstrates that the CVD reactor applied is operated far away from equilibrium. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.