Study On Novel Methods For Preparation Of Nano-Sized TiO₂ Crystals And Self-Cleaning Super-Hydrophilic Films

In the treatment technology of environmental pollutions with TiO₂ photo-catalytic reaction, the organic pollutants have been degraded thoroughly and unselectively with solar energy as drive force of the reaction, moreover there aren't any secondary pollutions in the process. So the corresponding studies on the theory and exploitation of products have enormous social and economic benefit.The paper reports a novel original method, pyrolysis of titanyl organic compounds, for preparation of nano-sized TiO2 crystals with high photo-catalytic activity. The reaction of synthesizing titanyl organic compounds from titanium tetrabutoxy and acetic anhydride has been studied with FTIR, NMR and TGA. The pyrolysis process of titanyl organic compounds has been inspected with TGA-FTIR couple. XRD, TEM, DTA, TGA, BET, and DSC characterized the TiO₂ powders, moreover, surface Ti³+ and OH of the crystals have been determined quantitatively with XPS, and then the relation of surface Ti³+/OH ratio and photo-catalytic activity has been discussed. The research results show that single crystallite got from pyrolysis of titanyl organic compounds is sphere particle that is 17-31nm in size. The particle size of crystals is mainly influenced by calcination temperature, and but the crystal phase is equally influenced by calcinations temperature and time. When the ratio of surface Ti³+ and OH formed in pyrolysis reached 1, the TiO₂ crystals showed high photo-catalytic activity. The ratio of the sample obtained at 600 ℃ 3 h is 0.95. Results of photo-catalytic activity evaluation indicate the sample has the highest photo-catalytic activity and the rate constants of degradation reaction of rhodamine and aniline are 3-4 times of the sample from Sol-Gel and the sample STT-65C-S from Japan.The liquid method is important one of methods for synthesis TiO₂ crystals, especially rutile. A novel liquid method is reported in the paper, that is synthesis of nano-sized TiO₂ crystals from titanyl organic compounds in water and nitric acidic solution at normal pressure and low temperature. The researches of XRD and TEM reveal that the crystals got in water are antase that are 5-8nm in size and the ones innitric acidic solution are rutile that are particle or needle shape, which secondary agglomerates are spindle shape. The specific area of the rutile sample obtained in 0.3 mol.L"1 for 3 h is 149.3 m2.g"1,and it's 37.5 rn^g"1 after calcinating for 3 h at 700°C.Silica is often added into the film solution for preparation self-cleaning super-hydrophilic film that is an important application product of nano-sized TiC>2 for increasing hydrophilicity and improving the physic characters. Three methods for preparing SiC>2 are reported in the paper. Single dispersion acidic SiC>2 particles that are 110-550nm in size were synthesized in W/O micro-emulsion system with Span80-Tween60 complex surfactant (HLB=13) as emulsifying agent. The particle sizes decrease along with increasing of R (nWater/nSurfacyant), reache minimum and then increase. As to H (nwater/nTEos), tne particle sizes increase along with increasing of the ratio. It was discovered that the acidic SiC>2 particles that are 20-400nm in size can be formed with heating the mixture of acetic acid and alcohol in cyclohexane. The particle sizes of the SiC>2 obtained using CH3OH are smaller than ones using C2H5OH and the size contribution of front one is narrower. The basic SiC>2 particles were synthesized from hydrolysis of TEOS with NH3 as catalyst. The morphology of particles was observed and the average sizes were measured with TEM. The experiment results reveal that particle size changes bigger along with increase of H, and changes littler along with rise of temperature but bigger as the concentration of NH3 is increased.Base on the studies on synthesis of TiO2 and TiC>2 as well as the mechanism of photo-catalytic activity, self-cleaning super-hydrophilic TiO2-SiO2 complex films were studied, and a new original method of manufacturing films with non-aqueous film solution is reported. The SEM image shows that the complex film is make up of sphere shape and bar shape particles and the results of XPS display the ratio of surface Ti3+/OH of TiO2 film is 1.06 that approaches 1, which testifies the surface states of the film obtained from non-aqueous film solution is in favor of photo-catalytic reaction. The dope of Fe(NC>3)3 accelerated the photo-catalytic reaction, but the FeCb and CrCb prohibited the reaction.