Tungsten Suboxide Research Articles

Investigations of Nonstoichiometric Tungsten Oxide Nanoparticles

Recently, pure phases of hollow multi-walled WS2 nanotubes were prepared from a surface reaction with reduced tungsten oxide nanowhiskers. During the process, which starts with WO3−x nanoparticles and finishes with WS2 nanotubes, particular care has been devoted to the evolution of the tungsten oxide cores once the first encapsulating WS2 layer has been formed. The reduced tungsten oxide phases were previously studied by a combination of techniques, including high-resolution transmission electron microscopy and X-ray diffraction. In the present study, Raman spectroscopy combined with the previous two techniques is used to give further detail concerning the structure of the reduced oxide phases. This study sheds some further light on the reduction process of the tungsten suboxide phases and the growth mechanism of oxide nanowhiskers and subsequently WS2 nanotubes from quasi-isotropic tungsten oxide nanoparticles.

Quantitative Phase Analysis of Mixtures Containing α‐, β‐Tungsten and WO2

AbstractFor incandescent lamp wire fabrication various powder metallurgical steps are necessary. The stepwise reduction of WO3 to the tungsten metal powder is one of these. During reduction chemical reactions take place under participation of doping elements (K, Si and Al) causing the structure of non‐sag wires. The origin of secondary β‐W like an indicator for the activity of dopings has been attributed importance. Therefore it has been developed a method for quantitative phase analysis of α‐W, β‐W, WO2 mixtures consisting of oxidation value determination to establish the WO2 content and X‐ray phase analysis for a quantitative separation of the α‐W and β‐W content. The influence of extinction effects caused by particle size has been investigated and it is proposed a correction method of the measured integral intensities as a function of half‐width of the (110) α‐W reflex. In regard of the obtained results the formation of the tungsten suboxide W3O has been excluded.

Comportement electrochimique d'electrodes monocristallines de tungstene (plan 110)

The anodic oxidation of tungsten single crystal electrodes ({110}) has been studied in a H 2SO 4 1 M medium, by the voltage sweep method. A technique to regenerate the electrode surface after each anodic polarisation cycle is proposed. This regeneration implies the formation of a tungsten sub-oxide base from which successive oxidation stages are revealed as in thermal oxidation in the gas phase. Kinetic parameters of such electrochemical stages have been classed. For a fast enough voltage sweep, these reactions are sufficiently slow to give only monolayers of stochiometric oxides. Inhibiting properties and the chemical dissolution of the tungsten trioxide has been demonstrated. It has been possible to take into account the valve effect of this oxide.