One Step Reduction of Tungsten Powder

To produce tungsten powder from ammonium paratungstate, it is usually necessary to first burn tungsten oxide in a weak reducing atmosphere, and then carry out hydrogen reduction to produce tungsten powder. Most of the tungsten powders prepared by this process are very regular polycrystalline, which are the main raw materials for the preparation of tungsten alloy and tungsten carbide.

However, some scholars think that the traditional process is long, easy to bring impurities, and the production cost is relatively high. Therefore, he proposed a one step reduction method to directly produce tungsten powder from ammonium paratungstate across the tungsten oxide process.

The main process of one step reduction method is as follows: 1. In the first step of controlling the formation of blue tungsten like intermediates, a certain proportion of hydrogen and nitrogen mixed gas is introduced into the reduction furnace to replace ammonia gas. 2. Load 50g, hydrogen flow 32 / h, heating rate 10 ℃ / min, 500 ℃ for 200Min, 900 ℃ for 1.5h, air-cooled to 100 ℃.

In the process of hydrogen reduction, it can be found that the morphology of the particles from ammonium paratungstate to blue tungsten has no obvious change, but there are obvious cracks on the surface of the particles. In the reduction process, a large amount of water gas is produced, which mainly comes from two aspects: first, crystallization water removed by apt, which accounts for the majority; second, due to the existence of weak reduction atmosphere, a small amount of tungsten trioxide is reduced to blue tungsten or violet tungsten in the reduction process.

The results show that the one step reduction of tungsten powder by ammonium paratungstate is feasible, and the yield of tungsten powder under the optimum conditions is more than 98.5%. Moreover, the reduction temperature can be controlled to control the particle size of tungsten powder. Prolonging the reduction time will make the tungsten powder grains grow up and become more complete polygons. The lower the initial hydrogen reduction temperature, the better the formation of fine tungsten powder; the larger the boat load, the worse the uniformity of tungsten powder. Therefore, although the one step reduction method has operability, it is not perfect. First of all, its process requirements are very strict, and it requires a high purity of ammonium paratungstate.

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