Blue tungsten oxide refers to a class of tungsten (VI) and tungsten (V) mixed valence state typically formed in the solution. As usual, heat tungsten oxide under the temperature between 1300℃and 1500℃ in vacuum, and reduced by hydrogen. Blue tungsten oxide is also called as the product of reductant and the tungsten compound. The wet tungsten oxide will turn into tungsten blue when it exposed under UV radiation or white gum tungstate in sunlight. Tungsten blue is different with blue tungsten oxide. Blue tungsten oxide is an important raw material for producing tungsten powder rather than yellow tungsten powder.
Preparation description:
The preparation method of blue tungsten oxide mainly uses ammonium paratungstate, tungsten trioxide and sodium tungstate as raw materials. Blue tungsten oxide commonly refers to compound of WO2.72、WO2.90、W20O58 and (NH4)х·WO3.(NH4)х·WO3 is called as ammonium tungsten bronze. Blue tungsten oxide is a good raw material to produce excellent tungsten products.
The preparation method of blue tungsten oxide can be divided into two categories: pyrogenic method and wet method.
1. Pyrogenic method
Pyrogenic method is commonly used in the industry. Usually use ammonium paratungstate tungsten as (APT) as raw material to generate blue tungsten oxide through reduction or thermal decomposition. And also can reduce WO3 in the condition of slight hydrogen, but the result is not better than the form method using APT as raw material. In the process of production blue tungsten oxide in industrial usually uses four or eleven tube to reduce APT by using hydrogen. The chemical composition of blue tungsten oxide is WO2.88 ~WO2.92 including NH30.3%~0.8%.
2. Wet method
Wet method is a new method developed in recent years. Blue tungsten oxide（3.5(NH4)2O·5WO2·13WO3·4.5H2O）can be prepared by hydrogen reduction. Blue tungsten oxide with the ratio O/W=2.82 is prepared by reducing tungsten solvent Xin under slight hydrogen condition. And also can use internal reducing method to produce blue tungsten oxide with main phase of WO2.90.
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