ABSTRACT
Abstract Alumina thin films, with roughness of 20-50 nm and pseudoboehmite nanocrystals precipitated on the surface, were formed through immersion of porous alumina gel films in hot water. By coating hydrolyzed fluoroalkylsilane on such a thin film with slight roughness, a superhydrophobic surface with high transparency was obtained. Additives such as hydrochloric acid, sodium hydroxide, sodium chloride, manganese chloride, ethanol and ethylene glycol were dissolved in the hot water, and the effects of these additives on pseudoboehmite nanocrystal formation during hot water treatment were examined. Pseudoboehmite nanocrystals were formed at pH = 5.5-8.0 when an acid or a base was added to water. The addition of inorganic salts and alcohol diminished the boehmite nanocrystal formation. These results suggest that the boehmite nanocrystals were formed through a dissolution and re-precipitation process.
