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Violet Tungsten Oxide

Details: Category: Tungsten Information; Published on Thursday, 05 February 2015 11:13; Written by cq; Hits: 1716

Violet tungsten oxide (VTO) is a kind of tungsten oxide. Violet tungsten oxide is a finely divided violet crystalline powder. It is produced by rotary calcining ammonium paratungstate at closely controlled temperatures in a reducing atmosphere. Violet tungsten oxide is used primarily for the production of tungsten metal powder and tungsten carbide.

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Tungsten Blue Oxide Uses

Details: Category: Tungsten Information; Published on Thursday, 05 February 2015 11:10; Written by cq; Hits: 1746

Blue tungsten oxide (BTO) is also called tungsten blue oxide (TBO). Tungsten blue oxide is one of the most important, highly pure intermediates for the production of other tungsten compounds including tungsten metal powder.

Tungsten blue oxides are finely divided blue-violet powders.They are produced by heating ammonium paratungstate at closely controlled temperatures in a reducing atmosphere. GTP produces two standard grades differing mainly in oxygen content. Tungsten blue oxide is used primarily for the production of tungsten metal powder and fine tungsten carbide as well as wire products.

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Tungsten Oxide Nanowires

Details: Category: Tungsten Information; Published on Thursday, 05 February 2015 11:03; Written by cq; Hits: 1759

Tungsten oxide nanowires were prepared by a vapor transport method using yellow tungsten oxide powder as a raw material. The crystal structure and morphology of WO3 nanowires were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The obtained nanowires were hexagonal WO3.

The major factors that influenced the morphology were the furnace temperature and the substrate position. The diameter of the nanowires decreased as the distance of the substrate from the raw material increased. Sensors were fabricated by pouring a few drops of nanowire-suspended ethanol onto oxidized Silicon substrates equipped with a pair of interdigitated Pt electrodes. The sensor made of the nanowires as thin as 50 nm showed the highest response to NO2 at a low operating temperature of 100 °C. The temperature dependence of the response was discussed in relation to the formation of NO2− and NO3− ions on the surface of WO3. The response slightly increased with decreasing diameter if the nanowires are regional depleted in NO2, while it largely increased if the nanowires are in volume depletion. A theoretical calculations based on assumptions were proposed in order to clarify the correlation between the nanowire response and their diameter.

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Partial Thermal Reduction of Ammonium Paratungstate Tetrahydrate

Details: Category: Tungsten Information; Published on Thursday, 05 February 2015 11:05; Written by zsq; Hits: 563

Thermal decomposition of ammonium paratungstate tetrahydrate, (NH₄)₁₀[H₂W₁₂O₄₂]·4H₂O has been followed by simultaneous TG/DTA and online evolved gas analysis (TG/DTA-MS) in flowing 10% H₂/Ar directly up to 900°C. Solid intermediate products have been structurally evaluated by FTIR spectroscopy and powder X-ray diffraction (XRD). A previously unexplained exothermic heat effect has been detected at 700–750°C. On the basis of TG/DTA as well as H₂O and NH₃ evolution curves and XRD patterns, it has been assigned to the formation and crystallization heat of γ-tungsten-oxide (WO_2.72/W₁₈O₄₉) from β-tungsten-oxide (WO_2.9/W₂₀O₅₈) and residual ammonium tungsten bronze.

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A Re-investigation of Thermal Decomposition of Ammonium Paratungstate

Details: Category: Tungsten Information; Published on Thursday, 05 February 2015 11:02; Written by zsq; Hits: 540

The thermal decomposition of monoclinic ammonium paratungstate (APT) and amorphous ammonium metatungstate (AMT) has been studied over the temperature range 20 to 500° C using thermogravimetry, evolved gas analysis, X-ray diffraction analysis, differential thermal analysis and scanning electron microscopy. A mechanism of decomposition which postulates the formation and subsequent decomposition of various lower ratio tungstates is proposed and substantiated by the experimental data.

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