Effect Of Substrates On Properties Of TiO₂ Thin Film & Correlation Between Environment Of Surface Of TiO₂ Thin Film And Its Properties

In several decades, studies on photocatalysis have attracted considerable attention. Titanium dioxide (TiO₂) has emerged as an excellent photocatalyst material for environmental purification. As a kind of excellent photocatalyst material, titania is able to decompose almost all kinds of organic contaminants into CO₂, H₂O etc., some of which can not be decomposed by other ways such as chemical, biological way. And it is cheap and has no secondary contamination. All of these proved that titania is a kind of material which is very promising in environment preservation field.Photocatalysis reaction just occured at interfaces between crystallized nanoparticles,or at the surface of the photocatalyst. So, environment and structure of the surface of the photocatalyst played an important role in photocatalysis activity.In present thesis, effect of substrates on properties of TiO₂ films was studied, and also correlation between the environment of the surface of TiO₂ films and its performance in photodegradation and superhydrophilicity. The growing mechanism of titania nanorods was studied, too.It was found that orientation of crystallized nanoparticles of TiO₂ film prepared in our experiment was independent of the substrates. However, the substrates had great effect on the microstructure of surface of TiO₂ film and its properties. The size of crystallized nanoparticles of TiO₂ films is smaller than that on stainless plates. Photo-decomposed efficiency of the former is high as twice as the later, and the later have better hydrophilicity. Water contact angles of The TiO₂ films prepared on stainless plates decreased linearly with increasing annealing temperature from 400℃ to 550℃ while oleophilicity of the films hardly changed. Photo-decomposed performance of the film annealed at 400℃ was better than the rest of samples. And its photo-degradation efficiency is high as 1.85 times as the TiO₂ film annealed at 500℃.TiO₂ film prefabricated was dipped into TiO_2P25 aqueous suspension at 90 ℃ for half an hour. Rod-like crystallized nanoparticles were found on the surface of the TiO₂ film prefabricated. The rest of the samples was prepared in the same way, only dipping time changed. When the dipping time was an hour, there few rod-likecrystallized nanoparticles existed on the sample. The best hydrophilicity without UV radiation was obtained when dipping time was half an hour. Water contact angle was 2.38° in ambient atmosphere. The best hydrophilicity under UV radiation was obtained when dipping time was two hours. The worst hydrophilicity was led when dipping time was ten hours whether under UV radiation or not.The mechanism of how TiO₂ nanorods grow was also studied. Another anatase TiO₂ layer grew successfully on the titania film prefabricated by putting the film into H₂O₂ solution where metallic Ti was placed at the same time. Although the TiO₂ nanorod did not formed , it showed that dissolution precipitation mechanism played an important part in the forming of the TiO₂ layer.