Self-propagating High Temperature Synthetic Tungsten Powder

Tungsten has many advantages, such as high melting point, high density, high strength, high hardness, high wear resistance, low thermal expansion coefficient, good corrosion resistance, oxidation resistance and excellent thermal conductivity. It has been widely used in cutting-edge scientific fields, national defense industry and civil industry.

Self-propagating high-temperature synthesis (SHS) is a new technology which uses the exothermic heat of chemical reaction to prepare materials. The most remarkable feature of SHS is to make full use of the high heat generated by the reaction. In addition to the small amount of energy required to start the reaction, the whole reaction process is mainly maintained by its own exothermic heat. Some researchers believe that if tungstate is used to synthesize tungsten powder from propagating high temperature, the production cost will be greatly reduced.

In order to reduce the combustion temperature of tungsten synthesis by tungstate combustion, tungsten powder is added to the reaction product as a diluent. The main processes include:

A.Tungstate and magnesium powder are mixed in proportion of molar ratio tungstate to magnesium powder=1-6:3-25, then compacted into a vertical circular cylinder or disc container made of carbon felt, and then loaded into a high pressure vessel for self-propagating high temperature synthesis, and then cooled naturally.

B.Take out the synthesized product and crush it, soak it in 1-10 mol/L hydrochloric acid solution for 1-5 hours, dissolve the MgO impurities in the product completely in hydrochloric acid, drain, wash with deionized water, repeat many times, until there is no Cl in the filtrate detected by AgNO₃, and finally dry it for 1-5 hours in the oven at 100-110 C to obtain the final product tungsten powder.

The use of high pressure vessels and general self-propagating high-temperature synthesis (SHS) requires no special requirements. With relatively cheap tungstate as raw material, the operation process from mineral raw material to product production process is reduced. The overall process is simple, the output is large, the purity is good, and the efficiency is high, which is conducive to reducing the production cost of tungsten powder.

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