Modeling of carbon deposition from propane in chemical vapor infiltration

A reaction model including global reactions and 1 074 elementary reactions of 285 species in both the gas phase and the solid surface was used to numerically simulate the gas phase composition and the deposition kinetics of pyrocarbon on carbon fibers in chemical vapor infiltration using propane. The global reactions were simplified to be the direct dehydrogenation reactions from the hydrocarbon species in the gas phase while the elementary reactions included 66 surface species and 250 elementary steps. Simulated results were compared with experiments performed in a perfectly stirred reactor at 2.6 kPa from 1 173 to 1 323 K for 0.5 to 4 s, using propane as the carbon precursor and nitrogen as the diluting gas. Excellent agreement between the simulated and the experimental results are found for both the gas phase compositions and deposition kinetics at various conditions. The simulation indicates that the pyrocarbon precursors are mostly small unsaturated species (acetylene and ethylene) and methyl radicals, and the deposition kinetics could be quantitatively described by the deposition of these species.