Surface properties of sol-gel processed TiO2-SiO2 amorphous composite films

TiO2-SiO2 amorphous composite films were synthesized via a sol-gel chemical method. Their properties, including wetting behavior, transmittance and hardness, were investigated depending on the content of SiO2 in the films. The pure TiO2 film revealed the typical surface properties that have normally been observed in sol-gel processed TiO2 films. The addition of SiO2 facilitated the hydrophilic state of the composite films, probably due to an increase of the surface hydroxyl groups. Under ultraviolet exposure, the water contact angle decreased more slowly and its recovery was retarded by increasing the content of SiO2. Meanwhile, the addition of SiO2 improved the transmittance in the ultraviolet-visible light region, resulting in a deterioration of the hardness.