Tungsten

About: Tungsten is a research topic. Over the lifetime, 35225 publications have been published within this topic receiving 456213 citations. The topic is also known as: W & element 74.

Tungsten Carbides: Structure, Properties and Application in Hardmetals

Abstract: Introduction.- Phases and Equilibria in the W - C and W - Co - C Systems.- Ordering of Tungsten Carbides.- Nanocrystalline Tungsten Carbide.- Hardmetals WC - Co Based on Nanocrystalline Powders of Tungsten Carbide WC.

Tungsten Doped TiO2 with Enhanced Photocatalytic and Optoelectrical Properties via Aerosol Assisted Chemical Vapor Deposition

Abstract: Tungsten doped titanium dioxide films with both transparent conducting oxide (TCO) and photocatalytic properties were produced via aerosol-assisted chemical vapor deposition of titanium ethoxide and dopant concentrations of tungsten ethoxide at 500 °C from a toluene solution. The films were anatase TiO2, with good n-type electrical conductivities as determined via Hall effect measurements. The film doped with 2.25 at.% W showed the lowest resistivity at 0.034 Ω.cm and respectable charge carrier mobility (14.9 cm3/V.s) and concentration (×1019 cm−3). XPS indicated the presence of both W6+ and W4+ in the TiO2 matrix, with the substitutional doping of W4+ inducing an expansion of the anatase unit cell as determined by XRD. The films also showed good photocatalytic activity under UV-light illumination, with degradation of resazurin redox dye at a higher rate than with undoped TiO2.

Effect of promoters including WO3 and BaO on the activity and durability of V2O5/sulfated TiO2 catalyst for NO reduction by NH3

Abstract: The effect of tungsten and barium oxides on the activity and durability of V2O5/TiO2 catalyst for NO reduction by NH3 was examined. Tungsten enhanced the NO removal activity of V2O5 catalyst supported on sulfur-free TiO2, while no effect of tungsten was observed for the V2O5 catalyst supported on sulfated TiO2. The tungsten oxide promotes the formation of polymeric vanadate that is a strong active reaction site for NO reduction by NH3. When both tungsten and sulfur simultaneously exist on the surface of V2O5/TiO2, the sulfur species seems to play a more important role for NO removal activity than tungsten. The tungsten oxide on the V2O5/TiO2 catalyst also enhances the activity for SO2 oxidation by promoting the adsorption of SO2, regardless of the presence of sulfur species on the catalyst surface. The NO removal activity of V2O5 catalyst supported on sulfur-free TiO2 has been significantly reduced by barium oxide, mainly due to the formation of inactive VOBa compound through the strong interaction of vanadia with barium oxide. No change of NO removal activity over V2O5-BaO/sulfated TiO2, however, was examined by the addition of barium oxide, since the structure of vanadium oxide was not altered on the surface of the sulfated TiO2. The SO2 oxidation reaction over V2O5-BaO/TiO2 catalysts was significantly suppressed by the addition of barium oxide to the catalyst. The barium oxide seems to reduce the redox ability of vanadium oxide on the catalyst surface as well as the adsorption capacity of SO2. Based on the temperature programmed reduction (TPR), Raman and XPS observations, the surface structure of vanadium and its interaction with tungsten and barium oxides has been illustrated when sulfur exists on the surface of TiO2.