不规则形貌钨粉的形成机理

Formation Mechanism of Tungsten Powder with Irregular Morphology

采用偏钨酸铵(Ammonium Metatungstate,or AMT)为原料直接氢还原制备钨粉。研究了偏钨酸铵在还原过程中的相转变和颗粒形貌的演变过程,解释了不规则形状钨颗粒形成的机理。采用XRD研究了还原过程中粉末的相变化过程,扫描电镜对钨粉的形貌进行了表征。实验结果表明:在还原的过程中,钨经历了WO3→WO2.90→WO2→W的相转变过程。由于"局部反应"机理的主导作用,偏钨酸铵在750℃直接氢还原,制备出的钨粉颗粒形状不规则,粉末颗粒存在松散的聚集。当还原温度升高时",挥发-沉积"作用显著,还原的钨粉颗粒形状逐渐规则化。

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→WO250→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.