Karel Jan de Vries

Kinetic study of the modified chemical vapour 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.

Growth of thin dense gas-tight (Tb,Y)-ZrO2 films by electrochemical vapour deposition

Electrochemical vapour deposition has been applied to depositing thin, dense, gas-tight terbia- and yttria-stabilized zirconia films on porous ceramics using metal chlorides as precursors. (Tb,Y)-ZrO2 solid solutions have a fluorite-type structure and have a high mixed conductivity and oxygen semipermeability.