Blue Tungsten Oxide History

Blue tungsten oxide (BTO) is a kind of dark blue compound containing tungsten (VI) and tungsten (V) mixed valence state. It is the product of the action of reducing agent and tungsten compound. It is usually called blue tungsten, which is usually formed in solution. Blue tungsten oxide is one of the important raw materials for the manufacture of tungsten powder. The blue tungsten oxide in industry mainly refers to WO_2.90, and the tungsten W_2.72 is also classified as blue tungsten in the early stage.

The composition of blue tungsten oxide is very complicated, among them still exists WO₂ and other intermediate oxides. Blue tungsten, calculated as its composition WO_2.9, has a tungsten content of 82.13% and a tungsten content of 79.30% in WO₃, meaning that the content of tungsten in blue tungsten oxide is greater than tungsten trioxide. According to the requirements of the blue tungsten oxide product standard, the purity of the product is 99.95%, and the tungsten content should be 80.00%~80.80%.

There are three main methods for the preparation of blue tungsten oxide: APT closed calcination, APT hydrogen reduction and internal reduction. The essence of ATP closed calcination is to keep the furnace system in a positive pressure during the heating decomposition process, so that air can not enter the furnace. The ammonia produced by APT decomposition can produce hydrogen and nitrogen, so that the furnace can maintain a weak reducing atmosphere, and the final product is blue tungsten. APT mild hydrogen reduction is carried out in a multi tube furnace. After APT is loaded, it is decomposed into the furnace tube to decompose and feed hydrogen into the furnace tube, so that the reducing atmosphere can be maintained in the furnace tube, and the decomposed gas products and exhaust gas can be drained away to the outside of the furnace. The phase composition of the resulting blue tungsten oxide can be adjusted by controlling the hydrogen flow rate, the reduction temperature and the pinch speed. The internal reduction method is to dissolve tungstic acid into ammonia water, add the right amount of urea, and use the oxalic acid to adjust the acidity to get the intermediate IRT. After that, IRT decomposes in nitrogen and decomposes to produce blue tungsten oxide by the ammonium decomposition inside the molecule. At present, the first two kinds of industry are widely used in China.

Blue tungsten first appeared in the 70s of last century. In the United States, France, Britain and other countries, blue tungsten oxide was used as raw material instead of yellow tungsten oxide to produce tungsten powder. At the beginning of 80s, many mines in China began to produce blue tungsten oxide at the request of foreign businessmen. Because blue tungsten oxide has more excellent characteristics than yellow tungsten oxide, blue tungsten almost replaced yellow tungsten in the early 90s.

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