中文摘要：

针对氧化钨氢还原过程中因＂挥发-沉积＂作用而导致W粉晶粒快速长大和异常长大现象,利用添加碳的方法抑制氧化钨挥发,制备了平均粒径56.4 nm的球形W粉,并研究了添加碳对还原机制的影响。结果表明,W粉的粒度和纯度与前驱体配碳比有关,最佳配碳比为2.6。W粉粒径随还原时间延长不断增加,长大趋势与还原温度密切相关。随着还原温度由680℃升高至760℃,W粉晶粒长大速率变慢,粒径和残余碳含量显著降低,分散性变好;继续升高温度,W粉粒径略有增加。在710℃以上,还原产生的水蒸气与碳反应生成CO和H2,显著降低体系中水蒸气的分压,抑制挥发性水合物WO2（OH）2的产生,W粉的主导长大方式也由挥发-沉积转变为原子扩散机制。

英文摘要：

Spherical tungsten powders with the average grain size of 56.4 nm were prepared by hydrogen reduction assisted by carbon, because the volatilization of tungsten oxide, which is the fundamental reason of the rapid and abnormal grain growth of tungsten powder during hydrogen reduction, was inhibited by carbon addition. The effect of carbon on the reduction mechanism of tungsten oxide was investigated. Results show that the C：W molar ratio of precursors has a great influence on the grain size and residual carbon content of tungsten powders, and the optimum molar ratio is 2.6. The grain size increases with the prolongation of reduction time, and the grain growth rate is closely related to the reduction temperature. With the reduction temperature increasing from 680 ℃ to 760 ℃, the growth rate of W powder decreases, the grain size and residual carbon of tungsten powders decreases and the dispersion is improved, and then the grain size increases slightly when the reduction temperature increase to 800 ℃. The reaction between carbon and H2O steam occurs when the reduction temperature exceeds 710 ℃, which can reduce the partial pressure of H2O steam. Therefore, the volatilization of tungsten oxides is inhibited, and the dominant growth mechanism of tungsten powders transforms from volatilization-sedimentation to atomic diffusion.