Nano Tungsten Powder Preparation by High Purity Ammonium Paratungstate

Nanocrystalline cemented carbide has excellent properties such as high strength, high toughness, high hardness, good wear resistance and heat resistance, which is difficult to be produced by conventional materials. Nano tungsten powder is the key raw material to prepare nano carbide carbide.

In the current technology, tungsten powder is mainly prepared by reduction of tungsten oxide (WO₃). The preparation method of tungsten oxide (WO₃) is mainly calcined and pyrolysis. However, the tungsten oxide (WO₃) obtained by the above pyrolysis method is coarser. This makes the tungsten oxide (WO₃) prepared by the traditional pyrolysis process more and more difficult to meet the grain size demand. People began to turn the research into other methods of preparing WO₃, for example, the gas phase method. However, the gas phase method can obtain more detailed and fine WO₃ powder, but its preparation cost is much higher than that of pyrolysis method, and the scale of industrialization is also difficult to meet the requirements. Therefore, the improvement of the pyrolysis process can be more beneficial to the preparation of nano tungsten powder.

First of all, the size of about 5 m, the purity of more than 99.9% high pure ammonium paratungstate (APT) as raw materials, adding distilled water in the reaction vessel, and the use of electromagnetic stirring for mixing, stirring speed 180-200r/min, stirring while adding citric acid solution; The molar ratio of ammonium paratungstate (APT) to citric acid was calculated to be 1-3.

Second, wait for the citric acid solution to be completely dissolved and mixed uniformly, and add the high-purity ammonium paratungstate (APT) to the reaction vessel while stirring;

Third, ammonium parotungstate (APT) is added and ammonia water is added, the concentration of ammonia water is 30%, and the reaction solution is obtained by mixing.

Fourth, the reaction solution is placed in an evaporation container for concentration, and the concentrated concentrate obtained is dried in a drying apparatus at 150-160 ° C to obtain a precursor;

Fifth, the precursor is pulverized in a grinding apparatus, and then placed in a crucible with oxygen for heat treatment to finally obtain a tungsten oxide (WO₃) nanopowder;

Sixth, the tungsten oxide (WO₃) nanopowder is reduced in hydrogen atmosphere, the flow rate of oxygen is calculated as 50-60ml / min per g precursor, the temperature is 500-520 ° C, the time is 1.2-1.5h; the temperature of reduction 600 ℃, the reduction time of 1.5h, resulting in tungsten nano powder;

After optimizing the raw material composition and the corresponding ratio and optimization of preparation parameters associated with the system, the uniform distribution of particle size of tungsten oxide (WO₃) nano powder, and then restore the excellent performance of the prepared nano tungsten powder, this method can not only meet the needs of large-scale production, but also save the cost.

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