Study On Preparation, Structure And Photo-catalytic Activity Of TiO₂ Thin Films

Photo-catalytic TiO2 thin films have promising application in the environmental protection, such as air purification, waste water treatment ,bacillus resistance, pollution elimination, mist prevention and self-cleanness. In this study, a new technology for synthesis of nano-TiO2 thin films on slide glass substrates from industrial meta-titanic acid was developed via sol-gel method and dip-coating techniques. Using of industrial meta-titanic acid as raw material will decrease the cost for industrial production, and at the same time will inaugurate a new way for the comprehensive utilization of Ti resource in our country.TiO2 thin films prepared from meta-titanic acid are difficult to bond on the surface of ceramic glaze. TiO2 sol precursor was calcined in temperature range from room temperature to 1000. XRD was used to examine the microstructure character and phase change mechanism during calcination process. The results of experiment and calculation indicated that the transformation from anatase to rutile TiO2 occurred in a high temperature range of 950-1000 .Above result indicated that TiO2 calcined at high temperature will improve the bonding strength between TiO2 thin films and ceramic glaze and supply the elemental data for photo catalytic ceramic glaze which calcined TiO2 sol and glaze raw material.Fixed titanium oxide films on ceramic glaze were improved by adding acetylaceton in sol in case of using Ti(OC4H9)4 as raw material.Because of the requirement of too high temperature in traditional heat treatment process, the application of substrates endured low temperature is limited. In present study, microwave and ultraviolet radiation were used to prepare the photo-catalytic nano-TiO2 thin films at temperature about 100. Low temperature heat treatment makes it possible for wide selection of substrates for TiO2 thin films.Methyl orange solution was used as the model substance to examine the photo-catalytic activity of nano-TiO2 thin films. In present study, water solution of Cu(CH3COO)2 was smeared on substrates before TiO2 thin films, its improvement of photo catalytic activity of nano-TiO2 thin films up to 53%, and a SiO2 sol prepared in room temperature and atmospheric pressure smeared on substrates before T1O2 thin films, which improved the photo-catalytic activity of nano-TiO2 thin films up to 71.75%. The two doping technologies are simple and have effective results.The present study investigated the effects of microstructure parameters and morphology of TiO2 thin films prepared by different technique routes on TiO2 photo-catalystic activity.XRD quantitative phase analysis indicated that TiO2 thin films doped with Cu2+ or SiO2 would induced the formation of rutile. In this paper has proposed the transformation mechanism of anatase to rutile TiO2 doped foreign ions. When foreign ions came into crystal lattice, it will disfigure the crystal lattice and the accrete the disfigurement density of rutile, in the same time which cause the crystal lattice of anatase unstable, therefore induce the formation of rutile.The analysis of the microstructure of TiO2 thin films doped with Cu2+ and SiO2 indicated that the lattice stress changed disciplinarily. That has more lattice stress and it will possess more photo-catalytic activity. TiO2 thin films with complex crystal phase of rutile/ anatase suitable ratio have good photo-catalytic activity too.XPS analysis indicated that content of Ti3+ with better photo catalytic activity and surface hydroxyl with higher hydrophile increased apparently when TiO2 thin films doped with Cu2+ and SiO2.TiO2 thin films prepared with sol-gel method belonged to nano-particles, whichpresented spherical size of 10-50nm and the particles distributed on the surface of substrates uniformly. The brittle interface surface presented obvious compact sandwich structure. The thin films were closely combined with substrates and the brittle interface had no obvious crack.