Formation mechanism of titania nanosheet cryatallites on silica–titania gel films by vibration hot-water treatment

The control of the nanostructures of the titania-based coatings further offers an exciting opportunity to enhance their unique physical and chemical properties. By immersing silica–titania gel film coatings in hot-water concurrently with applying a vibration, nanosheet crystallites of hydrated titania were precipitated at the surface of the gel films. The main objective of this study is to design the functionality of titania-based coatings through the control of their surface morphology and crystallinity at low processing temperatures. Two types of vibration treatments, i.e. perpendicular and parallel directions against the gel films, were used. On 87.5SiO2·12.5TiO2 composition, parallel vibration direction enhances the nanosheet structure formation to 180 nm thickness after 5 h, whereas the perpendicular vibration provides 150 nm thickness, which is about 18% lower than that of nanosheet structure formed by the parallel vibration. The attachment of the precipitates from dissolved titania species should be an important driving force for the formation of the sheet-like structure.