Preparation And Characterization Of Self-Cleaning TiO₂ Thin Film On External Ceramic Tile

Titanium dioxide（TiO₂） is the most widely used photocatalytic material at present stage, which has advantages such as high activity, low cost and good chemical stability. Photocatalytic ceramic with function of self-cleaning, air purification, antibacterial and antivirus can be prepared by loading titanium dioxide on tiles to make a film, but the film has photocatalytic effect only under UV irradiation. In order to improve the photocatalytic performance and broaden the light absorption wavelength range of the film, we prepared film of Si, Ni and N doped titanium dioxide on tiles by sol-gel method. XRD, SEM, DSC, FT-IR and XPS were used to analyze the phase compositions, microstructure and valence state of element of the samples. The photocatalytic efficiency, hydrophilicity, chromaticity and durability of the thin TiO₂ film on tiles were characterized by different methods. In the result, the self-cleaning external tile has excellent photocatalytic efficiency and hydropilicity..The anatase to rutile phase transformation temperature of TiO₂ doped with SiO₂ increases from 800℃ to 1200℃ compared with undoped TiO₂. Athough having better stability, the incorporation of Si into TiO₂ reduces photocatalytic ability of titanium dioxide. When Si/Ti=0.2,calcined at 800℃ for 2h, TiO₂ has best photocatalytic ability up to 70%. The temperature of phase transformation reduces greatly by doping TiO₂ with 0.2wt% MC and CTAB. Doping TiO₂ ammonium citrate、Urea and H₃BO₃ has little effect on the phase transformation temperature of TiO₂. The phase transformation temperature of TiO₂ doped with phosphruse rises from 800℃ to 1000℃ compared with undoped TiO₂.Added with Ni（NO₃）₂·6H₂O in the precursor sol, the thin film of Ni doped TiO₂ was prepared by dip-coating method. The result shows that the thin film of Ni doped titanium dioxide has better visible light catalytic efficiency, but pooer ultraviolet catalytic efficiency. When Ni/Ti=0.3, calcined at 600℃ for 2h, NiTiO₃ was detected and the crystallinity of Ni doped TiO₂ is the best. But the incorporation of Ni into TiO₂ reduces the crystal growth rate of titanium dioxide, furthermore, the thin film of Ni doped titanium dioxide makes the surface of tiles show metallic luster.The thin film of N doped TiO₂ was prepared by adding PVP in the precursor sol. It was studied that the mechanism of titanium dioxide doped with N. N atoms replace part of O atoms in the lattice of TiO₂, and produce defects,as a result, waiden the absorption range of light wavelength of TiO₂. Irradiated under visible light for 12 h, the film of N doped TiO₂ has degradation rate of methyl blue solution up to 68%, contact angle down from 50°to 19°. The thin film of TiO₂/2wt%PVP on the unglazed tiles has a good adhesion of rank 5B,a pencil hardness higher than 6H and a chromaticity which is basically identical to that of unglazed tiles without film.