——碳化及发射寿命
( 北京工业大学 新型功能材料教育部重点实验室，
北京 100022)
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1.21×10-7 g/(cm2·s)， 碳化度δ≥15%， Mo-La2O3热阴极可稳定发射1000h以上。
关键字: Mo-La2O3阴极；碳化； 发射寿命； 数学模型
—Carbonization and emission lifetime
（ Key Laboratory of Advanced Functional Materials, Ministry of Education, Beijing University of Technology, Beijing 100022, China）
Abstract: The lifetime mechanism of Mo-La2O3 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-La2O3 cathode was analyzed respectively. The emission can keep stable only when the operating temperature is in range of 1600K to 1700K and the carbonized layer must be composed of Mo2C. The results show that the lifetime of carbonized Mo-La2O3 cathode is decided by the consuming velocity of Mo2C of the carbonized layer of cathodes. The Mo2C is consumed as reducer for La2O3 and vaporized after decomposition during the working time. At 1673K, The consuming velocity is 1.21×10-7 g/(cm2·s). The stable emission lifetime of tubes equipped with carbonized Mo-La2O3 cathodes can exceed 1000h if the carbonized ratio is above 15%.
Key words: Mo-La2O3 thermoinic cathode; carbonization; emission lifetime; mathematical mode
