Key Engineering Materials Vols. 336-338

Abstract: The dispersion of titania particles in different solvents and doping of dispersants at different levels were studied. Results showed butanol is a good solvent and triethanolamine(TEA) is a good dispersant at 3wt% level for TiO2. Based on the dispersion results, titania coatings were prepared by electrophoretic deposition in organic solvents with addition of PEG and without. The deposition amount and the photocatalytic activity of titania coatings were investigated.

Abstract: The uniform and transparent nano-crystalline thin films of pure and co-doped with Fe3+/Sn4+ titanium dioxide photo-catalysts were prepared via sol-gel dip-coating process, and were loaded firmly on the surface of glass substrates. The structure and surface morphology of films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). In particular, the photo-catalytic activity of films was measured by ultraviolet-visible (UV-VIS) spectrophotometer. Methyl orange was used as a model compound to study the photo-catalytic activity of films. The effects of the concentrations of doping ions and the number of layers on photo-catalytic degradation of methyl orange solutions were investigated. Experimental results showed clearly that the co-doping of iron and tin ions exhibited a synergistic effect, which increased significantly the photo-catalytic activity of titanium dioxide. Especially, the photo-catalytic activity of nano-crystalline titanium dioxide thin films co-doped with 0.1 mol%Fe3+ and 11.41mol%Sn4+ was 2.0 times higher than that of those un-doped for photo-degradation of methyl orange solutions under the 125W self-ballasted fluorescent high-pressure mercury lamp irradiation.

Abstract: A new functional photocatalytic paint was prepared by adding N-doped nanocrystalline anatase TiO2 powders into self-engineered oxidation resistance latex paint system. The property of the UV-Vis light absorbance of the paint was characterized. The effects of the amount, types, and the introducing methods of the TiO2 in the paints on the behavior of the UV absorption, photocatalytic properties of the paint were systematically investigated. UV-Vis absorption spectra reveal that the ultraviolet light can strongly be absorbed by the paints. The absorption edge of the N-doped nanocrystalline anatase powders modified paint has red-shifted to visible light region. The colony counting method is used to study its sterilization performance under visible light irradiation. The sterilization experiments show that the rate of sterilizing staphylococcal bacteria by the N-doped TiO2 modified paint can exceed more than 99% after the paint has been irradiated by the visible light for 2 to 4 hours.

Abstract: The photocatalytic efficiencies of three commercially available TiO2 samples were evaluated and compared for TiO2 powder dispersed system with respect to pH and the water to be used for the perpetration of TiO2 slurry. All the TiO2 samples of P-25, NT-C, NT-20 showed a significant dependence of the photocatalytic efficiency on pH and exhibited higher photocatalytic efficiency in the pH between 5 and 7. The water used for the preparation of the TiO2 slurry also affected the photocatalytic efficiency of the TiO2 samples presumably due to a few cation ions existing in the water. The photocatalytic properties of TiO2 samples varied significantly depending on the key experimental conditions applied to the TiO2 slurry.

Abstract: N-doped TiO2 powders with high photocatalytic activity under visible-light irradiation have been prepared by calcining anatase nanocrystalline TiO2 powders and guanidine hydrochloride at 350 °C, 450 °C, 550 °C and 650 °C with the holding time ranged from 1.5 h to 3 h, respectively. The guanidine hydrochloride content was varied from 1 to 6 M for the experiments. XRD patterns indicate that all the powders are anatase crystalline phase. The specific surface area is 25~45 m2/g measured by BET method. XPS results show that N atoms were incorporated into the lattice of TiO2 and the amount of N doped in TiO2 is reached up to 8.26 at%. UV-Vis absorption spectra show that the absorption edge of the synthesized N-doped TiO2 powders, calcined at 350 °C for 2.5 h, has red-shifted well into visible region up to 700 nm. Degradation of methylene blue (MB) aqueous solution has been investigated by UV-Vis light spectrophotometer. The 400-mL 10 mg/L aqueous solution of methylene blue could be degraded completely with 4 g N-doped TiO2 within 4.5 h of visible light irradiation.

Abstract: MOCVD was applied to deposit TiO2 thin films on glass substrates. Effects of the deposition conditions (source temperature and substrate temperature) were studied. The phase and micro- structure of the TiO2 thin films were examined by X-ray diffraction and electron microscopy, respectively. The results indicate that substrate temperature affects both the morphology and the phase of the TiO2 film, while source temperature only affects the surface morphology of TiO2 film. Highly oriented anatase film on glass substrate was obtained at a source temperature of 140 oC and a substrate temperature of 350 oC. XRD pattern shows that only the (200) peak of anatase appears under the conditions. The crystallines in the highly oriented anatase were rectangular in top view.

Abstract: Nanocrystalline tungsten oxide doped titanium dioxide (WOx-TiO2) powders were prepared by TiCl4 hydrolysis and characterized by XRD, XPS, UV–Vis absorption spectra and TEM. Results showed that WOx not only hindered the growth of TiO2 particles but also greatly increased the transformation temperature (>800 oC) from anatase to rutile during sintering; the dominant fraction of tungsten oxides was non-stoichiometric tungsten oxide (WxOy) with Wn+ (4

1979