Blue tungsten oxide not only may be applied to produce heat-insulating glass window film for applying in buildings and automotives, but also can be used for the preparation of tungsten powder. Some researchers have focused on the four major phase transitions of blue tungsten oxide powder during the reduction process when the reduction temperature is 770°C~900°C: β-tungsten oxide (WO2.9) → γ-tungsten oxide (WO2.72) → tungsten dioxide (WO2)→tungsten powder. The following mainly discusses the reduction process from WO2.72 to WO2.
From the results, as the reduction proceeds further, the oxygen atoms in the γ-tungsten oxide are further reduced and the vacancies are further increased. At the same time, γ-tungsten oxide develops into a small short rod shape, which becomes looser. And it is more conducive to the formation of moisture and hydrogen into the interior of the particles, such γ-tungsten oxide is suitable for the preparation of ultrafine tungsten powder.
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