Tungsten Oxide

Blue tungsten oxide is one of the most important raw materials for the manufacture of tungsten powder. Compared with yellow tungsten oxide, blue tungsten oxide with its high activity, large surface area, easy doping, original crystalline shape is seen as an upgraded version of the Yellow tungsten oxide and used. There are three main methods for preparation of the blue tungsten oxide: APT closed calcination method, APT mild hydric reduction method and intrinsic reduction method. And the APT closed calcination method is the most used method. In APT closed calcinations, ammonia escaping by thermal decomposition or a small amount of introduced ammonia gas is used as reducing agent. Characteristics of this method: thermal decomposition temperature fluctuates between 550℃-700℃, high yield and stable quality. Phase composition of blue tungsten oxide is 70% W 20 O 58  and 30%WO 3 . APT closed calcination method always keeps the furnace system with positive pressure in the heating pro...