The Preparation And Properties Of TiO₂ Super-Hydrophilic Membrane

Titanium dioxide(TiO2) is one of semiconductor material,with low-cost, pollution-free, non-toxic to the human body and good thermal stability,etc.. TiO2 membrane has good electrical properties, chemical stability, excellent photocatalytic property and super-hydrophilic properties, which led to the promising applications in many fields(i.e. biological materials and optical materials, et al.). In this paper, mechanism of superhydropilic, the principle of self-cleaning and anti-fogging, the preparation methods of TiO2 membrane including chemical methods and physical methods are investigated. The advantages and disadvantages of different methods are briefly described. Progress in modification of TiO2 films are discussed at home and abroad.The TiO2 super-hydrophilic membrane was prepared by sol-gel method. The best scheme of several materials(i.e. Precursor,solvent and water) was gained by ratios adjustment. Through the doping and modification of TiO2 membrane, effect of visible light inducing the super-hydrophilcity and persistence of super-hydrophilcity of TiO2 membrane in dark were studied. By non-metallic elements(i.e. F and N) doped, the effects of chemical modification on visible light induced super-hydrophilcity of TiO2 membrane was investigated. Organic high polymer material was added in the sol as template, and geometric morphology was changed and surface roughness was improved. In this method, TiO2 membrane super hydrophilicity was extended in the absence of irradiation.The results indicated that: When the weight ratios of precursor,inhibitor and solvent was 1:1:15 in A solution,and the weight ratios of precursor with solvent and water in B solution was 1:3:3, the best sol was gained. After heat treatment at 500℃ for an hour,particle size of the prepared TiO2 was 15 ~30nm. The particle was uniform and dense. Fluorine doping can promote light response range to visible light wavelength. The red shift of fluorine,nitrogen co-doping films were similar to PEG200 modified fluorine, nitrogen co-doping films.It’s worse than nitrogen doping, but better than fluorine doping. After heat treatment, nano TiO2 membrane was super-hydrophilic. Contact Angle was less than 10°. Persistence of super-hydrophilicity in darkness were studied. The super-hydrophilicity of pure TiO2 membrane can only be kept 24 h. N doping, F doping and F, N co-doping can be kept around 24 h. Super-hydrophilic of PEG200 modified F, N co-doping TiO2 membrane can be kept 120 h,because the pores of the membrane was occurred, and the roughness was increased. The recovery to super-hydrophilic under light was tested. The results indicated that all samples under UV irradiation for 20 minutes were returned to super-hydrophilic. Pure Ti O2 membrane did not returned to super hydrophilicity after 2h sun light. TiO2 membrane of F doped was recovered to hydrophilic. All samples of N doped were returned to super-hydrophilic.