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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H_2,显著降低体系中水蒸气的分压,抑制挥发性水合物WO_2(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。
Aiming at the rapid growth and abnormal growth of W grains due to the “Volatile-deposition” effect during the hydrogen reduction of tungsten oxide, spherical carbon W with an average particle size of 56.4 nm was prepared by adding carbon to suppress the volatilization of tungsten oxide Powder, and studied the effect of adding carbon on the reduction mechanism. The results showed that the particle size and purity of W powder were related to the carbon ratio of the precursor, and the optimum carbon ratio was 2.6. The particle size of W powder increases with the extension of the reduction time, and the growth tendency is closely related to the reduction temperature. As the reduction temperature increased from 680 ℃ to 760 ℃, the grain growth rate of W powder became slower, the particle size and residual carbon content decreased significantly, and the dispersibility became better. The particle size of W powder increased slightly with increasing temperature. Above 710 ℃, the water vapor produced by the reduction reacts with carbon to form CO and H 2, which significantly reduces the partial pressure of water vapor in the system and restrain the production of volatile hydrate WO_2 (OH) _2. Volatile - sedimentation into atom diffusion mechanism.