MATHEMATICAL-MODEL FOR CHEMICAL-VAPOR INFILTRATION IN A MICROWAVE-HEATED PREFORM

A mathematical model, in which mass fluxes are expressed according to the ''dusty gas'' model, is proposed to describe densification of a ce ramic preform by chemical vapor infiltration (CVI). Local temperatures previously computed for a preform subjected to microwaves are input t o the mass transport model. The model is solved numerically for deposi tion of SiC from trichloromethylsilane in a porous SiC preform. The co mputed results clearly demonstrate an advantage in employing microwave heating in CVI. Also, greater infiltration is achieved in a preform o f greater pore size and at lower temperature. However, for successful infiltration, diffusion/chemical-reaction-controlled CVI is shown to i mpose limits on the preform size.