The main methods for producing submicron tungsten powder are high-energy ball milling, dry atmosphere reduction, violet tungsten oxide reduction, tungsten halide hydrogen reduction, spray drying-fluidized bed method, tungstate reduction, molten salt electrolysis, and plasma technology. These methods have disadvantages like time-consuming, energy-consuming, low production efficiency, high production costs, or difficult to achieve industrial production.
Use high purity ammonium paratungstate circulatory oxidation reduction producing submicron spherical tungsten powder has advantages of less pollution, narrow particle size distribution, simple and easy process line, easy to control process parameters, simple equipment and suitable for industrial mass production. The obtained product is spherical, it is benefits to the shrinkage and uniformity during calcination process, so as to better control the grain size.
(1)Firstly, ammonium paratungstate is heated to 800 ° C in argon at a slow heating rate and retained for 10 min at 800 ° C, violet tungsten oxide is obtained.
(2)Use VTO obtained in (1) to reduce and produce tungsten powder.
(3)Oxidize tungsten powder from (2) by heating to 500℃, when temperature reaches 500℃, keep it warm for 10 min, tungsten trioxide is obtained.
(4)Reduce tungsten trioxide in hydrogen for the second time, produce tungsten powder.
(5)Use tungsten powder in (4) and repeat the process in (3), making a second oxidation, obtain tungsten trioxide.
(6)Use tungsten trioxide from step (5) to repeat process in (2), making the third reduction and obtain tungsten powder.