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

A kinetic study of the modified CVD process in porous ceramic substrates is reported by both theoretical analysis and an experimental approach. The theoretical analysis indicates that with a heterogeneous reaction the decrease in the pore size is proportional to the deposition time and the pore closure time is proportional to the original pore size. With a homogeneous reaction the pore size decreases exponentially with the deposition time and it is very difficult to achieve pore closure. The deposition width should decrease with increasing deposition temperature 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 deposition of yttria-stabilized zirconia inside pores of porous ceramic membranes is a heterogeneous reaction.