W-ThO_2 阴极材料蒸发的热力学分析

Thermodynamics Analyses for Evaporation Processes of WThO2 Cathode Material

依据热力学原理计算了Ｗ－ＴｈＯ２阴极材料的蒸发速率，并分析了其蒸发规律．结果表明：随温度升高，各成分的蒸发速率按指数方式增大，其中ＴｈＯ２的蒸发速率最大，其次是Ｗ、Ｔｈ及ＷＯ２．在工作一定时间后，阴极表层会出现缺ＴｈＯ２区，Ｔｈ的蒸发受ＴｈＯ２还原反应的控制．通过与实验方法对比，认为采用热力学原理计算蒸发速率是一种简便可靠的方法．

Thermodynamics analyses for evaporation processes and calculations for evaporation rates of WThO2 cathode were made systematically. The results show that evaporation strongly depends on the temperature. The evaporation rate is controlled by ThO2 reacting with W. The further calculations demonstrate that ThO2 shows the fastest evaporation rate, followed by W、Th、WO2 in that order. An area lacking ThO2 under the surface of the cathode could be formed after a certain time. Compared with experimental and numerical results, the data of thermodynamics calculation are reasonable.