There are many forms of tungsten oxides, mainly contains tungsten dioxide, tungsten trioxide, blue tungsten oxide, violet tungsten oxide ect.. Tungsten oxides are mainly used for producing metal tungsten and other subsequent products in tungsten smelting industry.
Tungsten oxide belongs to tungsten anhydride, is the tungstate products, including tungsten oxide and tungsten trioxide dioxide, and mainly used for the production of pure tungsten and tungsten carbide. Tungsten oxide also has a gas-sensitive detection, and being used to detect nitrogen dioxide, ammonia and other toxic gases. At presently, film of tungsten oxide and nanoparticle tungsten oxide gas sensors have been prepared, the found of nanosensors has greatly improving the detection of low concentration toxic gases.
Tungsten dioxide is a brown monoclinic crystal powder, also known as brown tungsten oxide, is mainly used in preparing tungsten powder and tungsten trioxide. Tungsten dioxide is easily being oxidized which shows it’s unstable, and usually can not be sold directly.Tungsten dioxide insoluble in water, alkali, hydrochloric and sulfuric acid, also it is easily oxidized into high tungsten oxide by nitric.
Tungsten trioxide (chemical formula: WO3), the important intermediate substance in tungsten industry. The structure of tungsten trioxide depends on the temperature: when the temperature is higher than 740 °C , it shows in tetragonal, orthorhombic at 330-740 °C , monoclinic at 17-330 °C , and three monoclinic system at -50~17 °C. Monoclinic is the most common structure, its space group is P21/n.
Yellow tungsten oxide is a tungsten oxide powder with yellow appearance, often used for producing tungsten powder or metal compound and ceramic pigment. Tungsten oxide comes from ammonium paratungstate by calcination in a controlled temperature. To a large extent, the exact time and temperature determines the physical property of tungsten oxide.
Blue tungsten oxide is fine powder with blue-violet, also known as tungsten blue oxide (TBO), and coming from ammonium paratungstate by calcining and reduction with temperature strict controlled. We can offer two kinds of tungsten oxide powders with different oxygen content. Tungsten blue oxide is mainly used for manufacturing metal tungsten powder and tungsten carbide.
Violet tungsten oxide is a form of tungsten oxide, has a unique crystal structure and property compared with other tungsten oxide (such as blue tungsten oxide). It is soon used in production, due to its unique crystal structure when it is used for producing fine tungsten powder and tungsten carbide fine powder.
A variety of known tungstic acids are tungsten trioxide combined with each other and different ratios of water to form polymeric compounds. Tungstic acids will loss one molecule of water and become tungsten anhydride when heated to 100℃. It is slightly soluble in water, and soluble in alkali, hydrofluoric acid and ammonia, almost insoluble in acid.
White powder, tetragonal structure, the relative density of 6.062. Slightly soluble in water, ammonium chloride solution, and decomposed in the thermal hydrochloric acid. Calcium tungstate is self-activated phosphors, the very efficient light-emitting material in X-rays, electron beams and ultraviolet excitation.
Sodium tungstate is flaky crystal or crystalline powder with a white gloss, appearing in slightly alkaline (pH value of 8.5-9) when dissolved in water, it can not dissolve in ethanol, and slightly dissolve in ammonia. Sodium tungstate will loss water to become anhydrous when heated to 100 ℃.
Ammonium metatungstate, the white or slightly yellow crystalline powder, is used in the manufacturing catalyst and other petrochemical tungsten compound in petrochemical industry, and being the main raw material of tungsten-based catalyst. Ammonium metatungstate can be produced ammonium tungstate by solvent extraction and ion exchange method, and then obtain evaporation and crystallization.
Ammonium paratungstate, white powder, is the salt composed with ammonium and tungsten , and being the most important pioneers of majority tungsten products; also it is used for preparing high purity tungstic acid, tungsten metal powder, and tungsten carbide. When heated to 600℃, ammonium paratungstate will decomposite into tungsten trioxide and other tungsten oxide.