KINETIC-STUDY OF THE MODIFIED CHEMICAL-VAPOR-DEPOSITION PROCESS IN POROUS-MEDIA

A kinetic study of the modified CVD process in porous ceramic substrat es is reported by both theoretical analysis and an experimental approa ch. The theoretical analysis indicates that with a heterogeneous react ion the decrease in the pore size is proportional to the deposition ti me and the pore closure time is proportional to the original pore size . With a homogeneous reaction the pore size decreases exponentially wi th the deposition time and it is very difficult to achieve pore closur e. The deposition width should decrease with increasing deposition tem perature in a homogeneous reaction, while in a heterogeneous reaction the deposition width could either increase or decrease with increasing deposition temperature. The experimental results indicate that the de position of yttria-stabilized zirconia inside pores of porous ceramic membranes is a heterogeneous reaction.