Sol-gel -aluminum titanate thin film coating

摘要

-Al.sub.2 TiO.sub.5 protective coatings have been developed for both dense and porous ceramics such as SiC and Si.sub.3 N. sub.4 using a chemical solution processing method involving the hydrolysis and condensation of aluminum tri-sec butoxide and titanium butoxide. The solution viscosities, pH values, H.sub.2 O/alkoxide molar ratios, and dip coating withdrawal rates required for crack-free -Al. sub.2 TiO.sub. 5 are 1.0 to 6.2 cP, pH 1-4.5, molar ratio 1.5-10, and withdrawal rate of 2.2-8.0 cm/min, respectively. Conversion of the amorphous coating to crystalline -Al.sub.2 TiO.sub.5 is achieved by a succession of calcination below 450 C. and a final heat-treatment at 1300. degree. C. for ten hours with controlled heating and cooling rates.