Low-temperature Preparation, Structure And Property Of Anatase Sol Excited By Broad-range Spectra

The environment and resource drew many attentions of governments and people when the industry and modern life make so much pollution. Titanium dioxide, as a excellent semi-conductor which can absorb sunlight and be excited to decompose organic pollutions, become very popular in science research in recent years.The scientists now can prepare TiO₂ powders and films through several ways and dope them to get better properties of absorbing light and decomposing organics. Researchers always use technical ways to limit hydrolyzing of the precursors in wet chemical method to prepare titanic dioxide, which makes the high temperature heat treatment (to make anatase crystals grow out) during the preparation or afterwards a must. But high temperature heat treatment localized the application area of titanic dioxide. On the other hand, doping method just extended the spetra to part of visible light, which is still not enough to use full solar energy. Also the photocatalytic property is influenced.This dissertation describes a titanic dioxide sol containing anatase crystals and able to be excited by broad-range spectra, which is prepared through sol-gel method under low temperature. The main parts are as following:1. Study on Low-temperature Preparation of Anatase SolA new reaction system and the according technical route were explored, and TiO₂ sol containing anatase crystals was prepared at low temperature. Anatase TiO₂ sol was prepared under 30-70℃, using Ti(OC₄H₉)₄, H₂0, C₂H₅OH and HCl system with mol ratio of 1:185-200:10-16:0.1-0.3, by dropping the solution of Ti(OC₄H₉)₄ and C₂H₅0H slowly into stirring solution of H₂0 and HCl to ensure the precursor hydrolyzes thoroughly. The sol possessesdirect photocatalytic property without the traditional high-temperature heat-treatment in the powder and film research.2. Study On the Factors of Sol PreparationThe effects of system compositions and technical routes were studied and the author found out the self-growing rule of anatase crystals as "gathering-integrating" model. The crystals get a similar, but not standard, [TiO6] structure. The tests revealed that the water amount and its dropping turn determine both the hydrolyzing degree of the precursor and the creation of anatase crystals. The acidic amount influences the electrical environment and the stability of the sol. The preparing temperature affects the crystallization and defects of the anatase crystals in the sol, so accordingly affects the range of light using of the sol. The aging time influences the structural parameters and shape of the anatase crystals in the sol.3. Study On the Property of Being Excited by Broad-range Spectra Through the analysis of broad-range excitation property, a new theorywas made up to broaden the light use of titanic dioxide and enhance the photon efficiency of it out of the traditional doping method. The energy band split makes out new meso-stable energy band, and there are many defects when the crystals grow up in the liquid. Both meso-stable energy band and the crystalline defects can let the excited electrons stay temporarily, which gives the sol the ability of broad-range spectra excitation. Thus the sol can use more light of solar energy, also can it possess a better photocatalytic performance.4.Study On the Photocatalytic Reaction CourseThe influences of concentration and solution volume were analyzed in the paper and reaction kinetics of the sol on Rhodamine B were studied in detail. The author made up a new reaction theory of sol photocatalyst, far different from those of powder and film photocatalyst. It was foundthat the reaction of photocatalysis can be devided into two steps: firstly slow first-order reaction of breaking up the congeries of Rhodamine B molecules, and the following fast complex reaction of breaking up the bonds inside Rhodamine B molecules. The quantum effect, huge surface and the Brown activities of the anatase crystals in the sol make the photocatalytic reaction much more complex than those of powder' s and film' s. There are lots of sub-reaction and their following ones occurring at the same time. All of them together make the whole reaction course can be simulated not by the traditional zero-order or first-order simulation, but by Boltzmann simulation. Also the film photocatalysis performance of the sol was test, and just like the common research, it' s a first-order reaction.5. Study On the Application of the SolThe author also studied the filming course and made up the temporary theory of sol filming and crystal transformation. Through the studies of different filming methods, base materials and diluting degrees, the author found out ways to affect the crystals shape in the final film. Also the photocatalytic property of the film was analyzed. Finally the anatase crystalline sol was compared with some outside sol products. We can see that the anatase crystalline sol can substitute the import products on kinds of properties.