Violet Tungsten Oxide Main Phase Of Reduction Reaction

Understanding the main phase of violet tungsten oxide (VTO) has great impact on producing good properties tungsten powder. Because violet tungsten oxide main phase will influence tungsten particle grains morphology. Violet tungsten oxide in hydrogen reduction process undergone two major phase transition, γ-tungsten oxide→tungsten oxide (WO_2.72) → tungsten dioxide (WO₂) → tungsten powder.
After study found during the restore reaction the first phase transition is violet tungsten oxide to tungsten dioxide. At this stage with the reduction development the oxygen atoms decrease and oxygen vacancy increase of violet tungsten oxide, tungsten dioxide particles become denser than γ- tungsten oxide. But this is not easy to make hydrogen gas into the interior of the particles, the reduction process of the water molecules are also difficult to discharge, which is not conducive to the produce ultrafine or nano tungsten powder.
In the second stage of phase transition is tungsten dioxide restore to tungsten powder. According to the phase data, with the degree of reduction depth, tungsten dioxide’s oxygen atoms decrease and vacancies increased, resulting denser particles of tungsten powder, but little different with tungsten dioxide. Obviously, the morphology change of tungsten powder happen before produce tungsten dioxide.



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