Preparation of thick silica films by the electrophoretic sol-gel deposition using a cationic polymer surfactant

Thick silica films were prepared on the cathode by the electrophoretic sol-gel deposition using a cationic polymer surfactant, polyethylenimine (PEI). The weight of the silica particles deposited on the cathode was maximized when the content of PEI added was 0.01 mass% and pH of the coating sols was 5. As the amount of PEI added increased over the optimum content (0.01 mass%), the weight of the silica particles deposited decreased with an increase in PEI content because of H-2 generation at the cathode and the aggregation and precipitation of silica particles in the coating sols, Thick silica films obtained had no cracks and the thickness was ca. 20 mu m.