Preparation And Tribological Properties Of Nano Tio₂ Thin Films By Sol-gel Process

Nano-TiO₂ can be widely used in chemical, optical, biological, mechanical and electrical fields for its excellent physical and chemical properties. At present, TiO₂ thin films has recognized as catalytic material because of the higher photocatalytic activity. In the same time, TiO₂ thin films have implemented in large scale as self-cleaning glass because of the photo-induced hydrophilic properties. In this paper, the homogeneous, dense TiO₂ nano thin films were prepared on the glass substrates by sol-gel process and their tribological properties were studied. We also prepared the composite nano-TiO₂ films on glass substrate by using metal doping and molecular self-assembly technology. In addition, the effect of UV irradiation on the tribological properties of TiO₂ thin films was investigated. The main results are showed as follows:(1) The TiO₂ nano thin films prepared by sol-gel process are dense and uniform, and have super-hydrophilic properties. The wear life of the thin films is 150s at load of 0.5N.(2) Compared to undoped TiO₂ nano thin films, the Cu-doped and Ni-doped TiO₂ nano thin films are still dense and homogeneous, having much smaller the surface roughness. The tribological properties of the doped films have improved significantly, and when the doping content of the Cu and Ni is 5% (molar concentration), the tribological properties are the best.(3) With using the molecular self-assembly technology, (Heptadecafluoro-1,1,2,2- tetradecyl) trimethoxysilane (FAS) monolayer was deposited on the surface of TiO₂ nano thin film. It was found that their tribological performance was significantly improved, and the wear life is as long as 550s.at the load of 0.5N.(4) After UV irradiation treatment, the tribological properties of TiO₂ thin films deteriorated significantly. UV irradiation restored the ultra-hydrophilic properties of the thin films and thus increased the adhesion wear of the film surface. On the other hand, the surface morphology of the films was destroyed after the UV irradiation. Among them, the latter was the main reason that leading to the deterioration of the tribological properties.In fact, the tribological properties of nano-TiO₂ thin films affect their persistence in the practical application. In this paper, the tribological properties of the TiO₂ films have been significantly improved through metal doping and self-assembly techniques. Then the factors that affect the tribological properties of the films after the UV irradiation have been studied. The results here can play great role in real application of TiO₂ thin films.