With the development of research, the ultra-fine particles as a new material have been widely used in modern industry and science. Violet tungsten oxide (VTO) has special properties and structure so get a lot of favor in the producing ultrafine tungsten powder. During producing tungsten powder not only process conditions is important but the raw marital particle size is also an important factors. Therefore, to study the factors which influence violet tungsten particle size is very important.

Producing violet tungsten oxide is through boatload an amount of ammonium paratungstate and pushes it into the reduction furnace hot zone. At the same time add a certain proportion of hydrogen and steam mixture to heat at a certain temperature, after a period heat preserving then cooling to obtain.

During the reaction, the factors that influence the violet tungsten oxide grain size are the raw material (APT) particle size and production process conditions. Production process conditions include reducing temperature, heating rate, water vapor and hydrogen pressure ratio, material thickness and reaction time. The study showed that, the relationship between violet tungsten oxide and raw material particle size is raw materials get smaller the particle size is smaller.



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After many observed violet tungsten oxide the researchers found violet tungsten oxide has special structure which is good for producing fine or submicron tungsten powder.
After detailed studies of these three powders found loose structure violet tungsten oxide is conducive to speed up the reaction proceeds, and powder particle size is small than using other tungsten oxide to produce.
Using violet tungsten oxide as raw material to produce tungsten powder and the tungsten powder particle shape is kind of short rod or a chain particles which form by many particles, uniform size, particle size between 0.1 ~ 1um. Tungsten carbide powder particles shape is mainly equiaxed particle, uniform size, particle size is also between 0.1 ~ 1um. But the size is larger than the tungsten powder. This is mainly due to when carbonization the tungsten atoms does not occur large migration.
So using violet tungsten oxide to produce submicron tungsten oxide and tungsten carbide powder the particle shape are complicate and also has little single particle exist.



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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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Violet tungsten oxide (VTO) has a special structure and properties, is one of the most suitable materials for producing fine tungsten powder. Using violet tungsten as raw material by hydrogen reduction to obtain tungsten powder, tungsten powder and carbon mixture obtained submicron tungsten carbide powder, and then mixed with carbide powder to form submicron tungsten powder which has great significance for producing outstanding performance superfine alloy. Through the study of tungsten powder and tungsten carbide powder properties so that they can be more widely used in the different fields.

Through data analysis, violet tungsten oxide has special structure which is different form other tungsten oxide. Violet tungsten oxide is combined with rod-like and needle-like crystal, there are non-uniform of thickness, but it has big length-diameter ratio. So the kind of this structure has a lower bulk density which is good for hydrogen reduction reaction. So that the tungsten powder and tungsten carbide powder which produce by violet tungsten oxide can obtain submicron level particle size. 



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