【作者】 李娜；

【导师】 周美玲；

【作者基本信息】 北京工业大学 ， 材料学， 2005， 硕士

【摘要】 本论文以研制有效实用的次级电子发射材料为目的,对稀土钼阴极材料的工艺及成分进行了系统的研究。从不同的粉末制备方法(固固掺杂、液固掺杂和Sol-gel)和不同的烧结温度(1300℃、1400℃和1500℃)的角度对相同成分的La2O3-Y2O3-Mo 次级电子发射材料的制备工艺进行了分析比较,研究了活化处理工艺对于材料的影响。采用Sol-gel法制备了不同成分的La2O3-Y2O3-Mo(LaYMo)系和CeO2-Y2O3-Mo(CeYMo)系混合粉末,结合放电等离子快速烧结(SPS)制成烧结体样品,进行分析与研究。应用XRD、SEM、EDS、激光粒度分析仪等实验手段研究了样品的成分、微观形貌、粒度分布与元素分布等。不同的粉末制备方法结合SPS 烧结制备的稀土钼次级电子发射材料的研究表明,Sol-gel 制粉SPS 烧结体的次级电子发射性能最好,固固掺杂样品的最差,1500℃为理想的烧结温度,对次级电子发射材料的活化处理明显提高了次级电子发射系数δm。对LaYMo 系及CeYMo 系次级电子发射材料的研究显示,Y2O3的掺入对于材料的组织细化作用明显优于La2O3及CeO2。伴随样品中Y2O3含量的升高,材料的微观组织更为细小,元素分布的均匀性更好,显微硬度值逐渐升高。在LaYMo4(La2O3 与Y2O3 的质量比为1:3,WMo=70%)和LaYMo5(La2O3 与Y2O3 的质量比为1:6,WMo=70%)样品的粉末和烧结体中,观察不到La2O3的衍射峰。研究表明,样品中存在La3+代替Y2O3晶格中的Y3+的置换固溶现象。在LaYMo 系中,LaYMo4 样品的次级电子发射性能最优。而CeYMo 样品具备较优的次级电子发射性能,在最佳激活温度激活后,δm 均在3.50 以上。其中CeYMo4 样品(CeO2 与Y2O3 的质量比为1:2,WMo=70%),在1200℃激活后,δm 达到11.11 的最高值。文中,对本类次级电子发射材料的热发射性能也进行了初步研究。更多还原

【Abstract】 In order to obtain the secondary emission material which could meet the reqirement for practical application, the studies on the preparation technique and the composition of the rare earth molybdenum materials have been carried out in this paper. The doping methods (including solid-solid method, liquid-solid method and Sol-gel method) and the sintering temperature (including 1300℃, 1400℃and 1500℃) were researched. The effect of activation treatment on the property of La2O3-Y2O3-Mo was investigated. La2O3-Y2O3-Mo (LaYMo) and CeO2-Y2O3-Mo (CeYMo) samples were prepared by Sol-gel powder method followed by Spark Plasma Sintering method. The composition, microstructure, particle size distribution, surface analysis and the element analysis of these materials were studied by XRD, SEM, EDS and Laser particle analyzer etc. The studies on doping methods results showed that the grain size of the Sol-gel sample had the best property of secondary emission, the performance of the solid-solid sample was worst. The sample sintered at 1500℃exhibited better and stable secondary emission property, indicating that 1500℃was the suitable sintering temperature. Activation treatment can improve the secondary emission properties of the rare earth molybdenum cathode. The studies on LaYMo and CeYMo secondary emission materials indicated that the more the content of Y2O3, the finer the microstructure, the more uniform the elements distribution and the higher the micro-rigidity. Studied on the LaYMo samples displayed that due to the substitution of La3+ to Y3+ in Y2O3 lattice, La2O3 could not be found in the XRD pattern of the LaYMo4 and LaYMo5 samples. The lattice constant of Y2O3 in LaYMo4 was test. The result showed that the lattice constant of Y2O3 in LaYMo4 was bigger than the standard value. Emission results showed that the weight ratio of La2O3 /Y2O3 =1:3 will be beneficial to the emission properties. The CeYMo samples also showed the better performance in the secondary emission.δm of the CeYMo samples were higher than 3.50, and the CeYMo4 sample (the weight ratio of CeO2 and Y2O3 is 1:2) had the highest secondary emission coefficient among all the CeYMo samples. After activating in 1200℃, which δm can be as high as 11.11. Primary investigation on the thermionic emission properties of secondary emission materials was carried out.更多还原