Phase-Field Model for the Chemical Vapor Infiltration of Silicon Carbide

A phase-field model, which is based on the description of the gas-solid interface as a diffuse region, is applied for determining the evolution of the deposit surface during chemical vapor infiltration of silicon carbide. The heterogeneous chemical reaction (transformation of a gaseous reactant into a solid product) is expressed in terms of a phase-field parameter through an equation of the Ginzburg-Landau type, which is coupled with the equation of mass balance of the species. The crucial point of the research is the way the equation of mass balance is modified using process intensities. This is realized by multiplying the terms contributing to mass transport in the gas phase and the substrate surface with the intensities of the corresponding processes. The corresponding evolution of the interface is coupled through the use of an extra variable, interpreted as a concentration of silicon carbide (SiC). The process of depositing SiC, which is initially considered isothermal and isobaric, is modeled with a single decomposition reaction from methyltrichlorosilane. Numerical results using a finite element method are presented to predict the evolution of the substrate surface and the concentration profiles.