Blue nano tungsten oxide, which is applied to produce infrared ultraviolet shielding material for applying in heat insulation filed, may be prepared by reduction method using ammonium paratungstate (5(NH4)2O?12WO3?5H2O) as a raw material.
In a container with good sealing properties, ammonium paratungstate is fed, and the container is heated. The heating temperature is set to 400°C~600°C to thermally decompose the 5(NH4)2O?12WO3?5H2O into tungsten trioxide, ammonia gas and water vapor. In the container, by using the characteristic of tungsten oxide --- a good catalyst of ammonia gas decomposition, the above-mentioned thermally decomposed ammonia gas is further decomposed into nitrogen gas and hydrogen gas. The tungsten trioxide is reduced to blue tungsten oxide by hydrogen in a vessel by controlling a certain reaction temperature (550°C~800°C) and an appropriate furnace gas pressure (0 to 2 mbar). A blue tungsten oxide powder can be obtained by cooling the blue tungsten oxide at the discharge port.
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http://www.tungsten-powder.com/Blue-Tungsten-Oxide.html
