直流脉冲辉光冷等离子体氢还原金属氧化物的特性研究

CHARACTERISTICS OF METAL OXIDE REDUCTION WITH HYDROGEN COLD PLASMA IN A DC GLOW DISCHARGE

利用直流脉冲电场下产生的非平衡等离子态的氢对CuO进行了强化还原实验,考察等离子体的固有化学特性对还原过程的影响。在体系压力450Pa、温度200℃的条件下,分子态的氢不能还原CuO,而等离子态的氢可还原CuO得到金属Cu。随着还原时间的增加,等离子态的氢还原CuO得到金属Cu层厚度的变化随着试样放置方式的不同呈现不同的规律,等离子体鞘层的变化对还原速率有很重要的影响。还原层厚度随时间的变化可以分为三个阶段,前两个阶段的反应速率主要受制于到达氧化物表面氢活性粒子流的通量,活泼的等离子体氢在反应产物层向反应界面的扩散是第三阶段的速率限制性环节。

Experiments were carried out to investigate the enhancement of oxide reduction with hydrogen cold plasma generated by a DC pulsed glow discharge and the effect of the inherent chemical characteristics of cold plasma on the reduction. The reduction of metal oxide CuO to metallic Cu with nonequilibrium hydrogen plasma produced by a DC pulsed glow discharge was investigated at 200 ℃ under a pressure of 450Pa, but the same reduction were not completed when using molecular hydrogen. With the increasing of reduction time, the thickness variation of the reduced layer presented a different trend according to the sample placement on the cathode with different way. The sheath of plasma played an im- portant role in the reduction rate of plasma hydrogen. The change of the reduced layer as a function of reduction time included three stages. For two fore stages, the rate limiting step was the flux of active plasma hydrogen species arriving at the sample surface. Diffusion of hydrogen species through the product layer to reaction interface was the rate limiting step for the final stage.