Thick-film coating of hexaaluminate catalyst on ceramic substrates for high-temperature combustion

Structural and chemical stabilities of substituted hexaaluminate catalyst films coated on some ceramic substrates were investigated for high-temperature combustion applications. The thermal stability of the hexaaluminate catalyst films on alpha-SiC substrate was greatly enhanced by the insertion of both, a neat hexaaluminate and mullite intermediate layer. Pure alumina substrate was preferable in depositing the substituted hexaaluminate catalyst film to pure mullite, mullite-zirconia composite, or partially stabilized zirconia substrates. The thermal stability of the hexaaluminate catalyst films, coated on these oxide ceramic substrates, greatly depended on the extent of diffusion of components between the film and substrate at high temperatures. The substituted hexaaluminate microparticles in the film rearranged during the sintering process above 1400 degrees C, and their (001) plane oriented parallel to the surface of the substrate. Manganese introduced in the substituted hexaaluminate films or disks gradually decreased with an increase in the heat-treatment temperature because of its volatilization. (C) 1999 Elsevier Science B.V. All rights reserved.