MODELING OF CHEMICAL VAPOR INFILTRATION OF CARBON IN POROUS CARBON SUBSTRATES

A model has been developed to account for reaction, diffusion, and deposition during chemical vapor infiltration (CVI) of carbon in porous substrates. The model was applied to the case of isothermal CVI of carbon-carbon composite substrates during propylene pyrolysis, and experimental results were predicted successfully. A kinetic scheme based on experimental observations, which consists of initiation, nucleation, growth, and deposition of a carbon precursor, was incorporated into the model. The initial Thiele modulus for deposition, which provides the intrinsic rate of deposition relative to the rate of diffusion, was found to control the uniformity of densification.