——碳化及發(fā)射壽命
萬小峰， 周美玲， 左鐵鏞
( 北京工業(yè)大學 新型功能材料教育部重點實驗室，
北京 100022)
摘 要: 探討了碳化Mo-La2O3熱陰極的壽命機理，分析了陰極工作溫度和碳化度(碳化層厚度)對碳化Mo-La2O3陰極電子管壽命的影響。研究結(jié)果表明： 碳化Mo-La2O3熱陰極的發(fā)射壽命是由碳化層中Mo2C的損耗決定的， 陰極表面Mo2C消耗殆盡， 陰極發(fā)射壽命即終結(jié)。陰極表面Mo2C一方面作為還原劑與La2O3作用被消耗，另一方面它在高溫下會發(fā)生分解， 陰極中Mo2C的損耗包括上述兩個方面。在相同溫度時， 碳化Mo-La2O3陰極中與La2O3還原反應損耗的Mo2C和Mo2C在高溫下分解損耗的相當。通過理論分析與計算建立了各因素影響壽命的數(shù)學模型， 并通過高溫分解實驗得到了Mo2C在不同溫度下的分解速率。在1673K， Mo2C的分解速率為1.21×10-7 g/(cm2·s)， 碳化度δ≥15%， Mo-La2O3熱陰極可穩(wěn)定發(fā)射1000h以上。
關(guān)鍵字: Mo-La2O3陰極；碳化； 發(fā)射壽命； 數(shù)學模型
—Carbonization and emission lifetime
WAN Xiao-feng, ZHOU Mei-ling, ZUO Tie-yong
（ 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
