Ultrafine Tungsten Powder Preparation from ART Self Reduced Tungstate

At present, in the production of tungsten powder, most of the tungstate thermal decomposition of blue tungsten oxide, blue tungsten oxide hydrogen reduction process to tungsten powder. The conventional process generally uses ammonium paratungstate as the initial raw material, but it is difficult to obtain ultrafine tungsten powder with average particle size of less than 1 micron by hydrogen reduction.

At the end of last century, a group of organic amine tungstates, called self-reducing tungstates, were prepared in laboratory by domestic scholars. Ultrafine tungsten powder can be prepared by hydrogen reduction using ART. Although ART was prepared in laboratory with satisfactory results, when this method was applied to industrial production experiments, the precipitation rate was not high, ART products were difficult to filter and dry, and the consumption of hydrazine was high.

Recently, some scholars have made breakthroughs in the research of ART, including: 1. ammonium tungstate solution tank; 2. evaporator; 3. hydrazine tank; 4. reactor; 5. solid-liquid separation equipment; 6. dryer; 7. tail liquid tank; 8. tube oven or rotary kiln; 9. tube oven or rotary kiln; 10. superfine tungsten powder products.

Ammonium tungstate solution in ammonium tungstate solution tank [1], containing tungstate ion 0.5-1.5 mol/l, which can also contain a certain amount of free ammonia or ammonium chloride (or ammonium nitrate and other strong acid ammonium salt), added to the evaporator [2] to evaporate ammonia, so that the solution pH value is reduced to 7-9, added to the reactor [4], at this time, the tank [3] hydration diamine is also added. In the reactor [4], the molar ratio of N₂H₄/WO₂ is 0.8-1.5/l, the reaction time is 4-5 hours at the temperature above 40 ℃, the solid is diamine paratungstate filter cake is obtained by solid-liquid separation equipment [5], and the white powder ART is obtained by drying at 110 C for about 4 hours. The pure blue tungsten can be obtained by thermal decomposition at 420-470 ℃ for 20-30 minutes, and the protective atmosphere can be hydrogen or nitrogen or other inert gases. Ultrafine tungsten powders of different sizes can be obtained with a loading capacity of 150-200 g/boat, and the precipitation tail liquid from the solid-liquid separation equipment [5] enters the tank [7], thereby being recovered or discharged.

Compared with the existing APT process for producing ultrafine tungsten powder, this process has the characteristics of low energy consumption, high production efficiency and fine particle size of tungsten powder.

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