稀土镧钼热阴极材料稳定发射机理——碳化及发射寿命  

Stable emission mechanism of Mo-La_2O_3 cathode—Carbonization and emission lifetime

作　　者：周文元[1] 张久兴[1] 刘燕琴[1] 万小峰[1] 周美玲[1] 左铁镛[1] 

机构地区：[1]北京工业大学新型功能材料教育部重点实验室,北京100022

出　　处：《中国有色金属学报》2004年第6期985-989,共5页The Chinese Journal of Nonferrous Metals

基　　金：国家重点基础研究发展规划资助项目(G1998061316)

摘　　要：探讨了碳化Mo La2O3热阴极的寿命机理,分析了阴极工作温度和碳化度(碳化层厚度)对碳化Mo La2O3阴极电子管寿命的影响。研究结果表明:碳化Mo La2O3热阴极的发射寿命是由碳化层中Mo2C的损耗决定的,阴极表面Mo2C消耗殆尽,阴极发射寿命即终结。阴极表面Mo2C一方面作为还原剂与La2O3作用被消耗,另一方面它在高温下会发生分解,阴极中Mo2C的损耗包括上述两个方面。在相同温度时,碳化Mo La2O3阴极中与La2O3还原反应损耗的Mo2C和Mo2C在高温下分解损耗的相当。通过理论分析与计算建立了各因素影响寿命的数学模型,并通过高温分解实验得到了Mo2C在不同温度下的分解速率。在1673K,Mo2C的分解速率为1.21×10-7g/(cm2·s),碳化度δ≥15%,Mo La2O3热阴极可稳定发射1000h以上。The lifetime mechanism of Mo-La_2O_3 cathode was discussed, and the effect of the operating temperature of cathode and the carbonized ratio (thickness of carbonized layer) on lifetime of tubes equipped with carbonized Mo-La_2O_3 cathode was analyzed respectively. The emission can keep stable only when the operating temperature is in range of 1 600 K to 1 700 K and the carbonized layer must be composed of Mo_2C. The results show that the lifetime of carbonized Mo-La_2O_3 cathode is decided by the consuming velocity of Mo_2C of the carbonized layer of cathodes. The Mo_2C is consumed as reducer for La_2O_3 and vaporized after decomposition during the working time. At 1 673 K, The consuming velocity is 1.21×10^(-7) g/(cm^(2)·s). The stable emission lifetime of tubes equipped with carbonized Mo-La_2O_3 cathodes can exceed 1000h if the carbonized ratio is above 15%.

关 键 词：Mo-La2O3 阴极 碳化 发射寿命 数学模型 

分 类 号：TG146.4[一般工业技术—材料科学与工程] O462.1[金属学及工艺—金属材料]