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.