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GeO 2 thick (410 lm) ceramic films were fabricated by facile liquid-phase deposition. The solubility of hexagonal GeO 2 in water was increased ten times on adding aqueous ammonia at 701C because of the formation of soluble Ge 5 O 11 2-. With the addition of sulfuric acid, the alkaline GeO 2 -aqueous ammonia was neutralized, leading to the transformation of Ge 5 O 11 2À into GeO 2 precipitates. When the H 2 SO 4 /NH 4 OH molar ratio was higher than 11.7, immediate precipitation of GeO 2 particles took place in the solution with no GeO 2 particles deposited on the substrate. When the H 2 SO 4 /NH 4 OH molar ratio was decreased from 5.85 to 0.29, the precipitation process was retarded, leading to the gradual growth of uniform hexagonal GeO 2 thick films on the substrates. The compactness of the film increased with a decrease in the H 2 SO 4 /NH 4 OH molar ratio. The growth of the GeO 2 crystal film followed the Bravais-Freidel-Donnay-Harker and Hartman-Perdok models, and the cubic GeO 2 particles with a size of about 10 lm were finally formed on the film. No GeO 2 precipitate was produced on the substrate when the GeO 2 -aqueous ammonia had an excessively low H 2 SO 4 / NH 4 OH molar ratio (r0.15) because the GeO 2 solute did not reach the saturation level and the nucleation process could not take place on the substrate. The particles on the film surface deposited from the solution with an H 2 SO 4 /NH 4 OH molar ratio of 0.29 exhibited a nanopore structure. An initial study using this film as a support for KNO 3 catalyst was carried out and the result revealed that the catalyst showed good catalytic activity of diesel soot oxidation.

With the addition of polyvinylpyrrolidone (PVP), alumina sol with an aluminum sec-butoxide/water molar ratio of 1 : 45 was synthesized. The surface tension of this alumina sol was found to be lower by 35% than the sol without PVP. Alumina/PVP hybrid film with a critical thickness up to 2 mm was fabricated by dip-coating method. The heat treatment between 200 and 3008C could produce a film with perfect hybrid nanocomposite structures. Alumina particles with a size of about 20 nm were uniformly distributed in this material. The hardness of the film samples increased with the increment of heat treatment temperature, and hardness values higher than the original metal were detected after heat treated above 4008C. The film-coated metals that were heat treated below 1508C or above 4008C exhibited relatively weak adhesion, but strong adhesion was obtained when heat treated between 200 and 3008C for 30 min. The corrosion rate of the film-coated metal that was heat treated between 2008C and 3008C for 30 min was lower by 95% than the uncoated metal.