Formation Mechanism of Tungsten Powder with Irregular Morphology

Tungsten powder was prepared by direct hydrogen-reducing of ammonium metatungstate.Phase transformation and morphology evolution process of tungsten powder were researched using XRD and SEM respectively to interpret the formation mechanism of tungsten powder with irregular morphology.The results show that the reduction of the tungsten oxides goes through a series of complicated phase transformation,which could be divided into three stages: WO3→WO2.90→WO2→W.During the reduction of powder at 750 ℃,the mechanism of partial reaction is in dominance,and the tungsten powder with irregular morphology and incompact particle is obtained.With the increasing of reduction temperature,the volatilization-aggradation mechanism is in dominance,the tungsten powder with regular morphology is obtained.