Preparation of coarse and spherical tungsten powders by ammonium paratungstate

Coarse and spherical tungsten powders were prepared by wet hydrogen reduction.Ammonium tungstate solutions with the additives of Li,Na and K alkali metal salts were used as raw materials.The effects of the type and content of the alkali metal salts as well as reduction time on the microstructure,chemical composition,phase composition, and particle size of ammonium paratungstate(APT) and coarse tungsten powders were investigated by scanning electronic microscopy,energy dispersive spectroscopy,X-ray diffraction,and test sieves.It is shown that ideal tungsten powders with good fluidity,sphericity,integrity and even distribution can be obtained by using the ammonium tungstate solution with 3 g·L^-1 NaCl,KCl and Li₂CO₃ and reducing at 1000℃for 180 min in wet hydrogen atmosphere.The average particle size of the obtained tungsten powders is 67μm,the maximum particle size is 150μm,the biggest loose density is 13.41 g·cm^-3,and the best powder flowability is 9 s for 50 g tungsten powders.