Nano violet tungsten oxide powder may be used to prepare ceramic microsphere for applying in the production of heat insulating materials such as thermal insulation films. Violet tungsten oxide can also be used to prepare submicron tungsten powder.
The violet tungsten oxide is continuously reduced three times. The reduction process is as follows: a temperature of 640°C, a temperature of 760°C, a temperature of 860°C. Keep warm for 20min when the temperature reaches 860°C. Twice oxidation. The oxidation process is: tungsten powder in air is slowly heating to 500°C. When the temperature reaches 500°C, keep warm for 10min, then submicron tungsten powder with particle size distribution between 0.11 and 0.95μm (accounting for 93.68%), and BET of 1.082m2 ? g-1 can be obtained.
According to the mechanism of oxidation-reduction deposition growth, although violet tungsten oxide is also a mixture, its phase composition is relatively simple. During the reduction process, most of the reduction process of tungsten oxide is basically carried out simultaneously, except that a small amount of tungsten oxide exists. Some of the tungsten oxide is first reduced, and some of the tungsten oxide is reduced latter, so that the tungsten powder of the post-reduced tungsten oxide is deposited on the tungsten powder which first reduced, resulting in the growth of the tungsten powder particles. Therefore, the particle size distribution of the obtained powder is relatively concentrated and uniform. However, in the process of preparing submicron tungsten powder, the oxidation of tungsten powder into tungsten trioxide in the air has a relatively serious agglomeration phenomenon.
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