(369a) Pore Network Modeling of the CVD Processes in the Preparation of Nanoporous SiC Membranes

A Pore network model is developed in order to describe the preparation of nanoporous silicon carbide membranes by the chemical vapor deposition (CVD) technique. The membrane's pore space is represented by a three-dimensional network of interconnected pores, in which the effective size of the pores is distributed according to a pore size distribution (PSD). The chemical reaction, the various transport processes, and the evolution of the pore sizes during the deposition during the CVD process are included in the model. The Maxwell-Stefan equations are used for describing the pore-level transport processes, which include the Knudsen and hindered diffusion, as well as viscous flow. The effect of pore blockage is taken into account. The simulator monitors the PSD as the membrane's structure evolves. Also computed is the carrier gas' permeance during the CVD. Good agreement is found between the simulation results and our experimental data for the single gas permeance. The results also indicate the fundamental significance of the pore blockage to the evolution of the membrane's structure, i.e., the percolation effect.