Pearson random walk algorithms for fiber-scale modeling of Chemical Vapor Infiltration

Chemical Vapor Infiltration (CVI) is a popular processing route for the preparation of high-quality Ceramic-Matrix Composites which involves rarefied gas transfer in a disordered fibrous array and heterogeneous deposition reactions. The fiber-scale modeling of CVI in large 3D images of actual porous media (e.g. tomographic images) is a challenging task. We address it with a numerical method based on Pearson random walks for transport/reaction of gases, on a Simplified Marching Cubes technique for the surface discretization, and on a pseudo-VOF technique for surface growth. Two different chemical situations are considered, depending on whether the gas precursor is synthesized inside the pores or not. Numerical validations of the code with respect to analytical estimates are presented; finally, in applications to large 3D images of fibrous media, we discuss the consequences of the competition between diffusion and reaction on the deposit morphology.