Study On The Preparation Technology Of Nano-sized TiO₂ By Sol-Gel Process

The special structure characteristic, function, the unique photocatalysis activity and super-hydrophile of TiO₂, as well as it's present and future prospect in various fields are introduced in this paper. All kinds of methods for producing nanocrystalline TiO₂ are classified and synthesized. Principles and procedures of several common methods are briefly introduced.The experimental principle, technological process and experimental condition of Sol-Gel method to prepare nanocrystalline TiO₂ using Ti(OBu)₄ as main raw material have been studied. The amount of water and alcohol, the PH value and the temperature have important effect on the distribution, stability, transparency of the products. From that, the best technological process and experience data are obtained. Experimental results show that the powder and film can be obtained respectively as the ratios of alcohol to Ti(OBu)4 are 16 and 28 under acid condition and are 9 and 18 under alkaline condition, the ratio of H₂O: Ti(OBu)₄ is 10 : 2 and the control solvent to Ti(OBu)₄ are 0.7 and 1.5 respectively. When making dropping solution and host solution, the continuity in material choosing is very important, and the best hydrolysis temperature is controlled at 20-30℃.The TiO₂ dried-gel was produced at different procedures and temperatures. On the basis of XRD and SEM, the annealing temperature of the nanocrystalline TiO₂ powders obtained under acid conditions has a smaller crystallite-size and a lower annealing temperature than that under alkaline condition. According to x-ray diffraction and the Scherrer formula, (1) with increasing of the annealing temperature, the average crystallite-size increases. (2) At the annealing temperature of 450℃, the sample average crystallite-size was 9-19.3nm with Anatase structure. (3) As the annealing temperature higher than 500℃to 900℃, the average crystallite-size was 48.6nm. (4) At the temperature 500-600℃, the TiO₂ is mainly of Rutile type. As the temperature was higher than 600℃, all the samples transformed into the Rutile type.27 kinds of films with different amount of layers were prepared on the Si, Glass and ceramics pieces. It was found from the surface observation that the more the amount of the layer increased, the lower the dropping frequency, the thicker the film was. Analysis of XRD shows the structure of film was Anatase type by the 500℃annealing and the average grain size was estimated approximately 30nm.