Chemical States of Lanthanum in Carbonized La2O3-Mo Thermionic Cathode Materials

The chemical reaction between lanthanum oxide and molybdenum carbide was studied by thermodynamic calcu-lation, thermal analysis and in-situ X-ray Photoelectron Spectroscopy. The theoretical results show that at the environment allowing for the evaporation of lanthanum, such as in high vacuum, La2O3 in the La2O3-Mo materials can be reduced to metallic lanthanum by molybdenum carbide (Mo2C). To confirm the conclusion, many analysis methods such as XRD, SPS, and TG-DTA were taken. The experimental results show that the chemical state of lanthanum changes during heat-ing. It was proved, for the first time, that reacted metallic lanthanum appears at the surface of this kind of material at high temperature.     

钪系阴极基体的研究

采用氧化钪与钨机械混合、氧化钨与钪盐水溶液固液掺杂法制备了氧化钪-钨基体，采用扫描电镜及原位俄歇电子能谱方法研究了基体中钪的分布及阴极基体的抗离子轰击性能。结果表明，采用液固法制备的烧结体，氧化钪分布均匀，这样的结构有利于钪的扩散和补充，原位俄歇轰击实验结果表明，阴极基体具有良好的耐高温和耐离子轰击性。     

长寿命高稳定度液态金属离子源

本文介绍一种用多孔W筒作料池的同轴针型液态金属Ga和Au离子源。料池内Ga和Au的贮量分别为200mg和150mg,具有低蒸发、长寿命的优点。由于液态金属与W针尖及多孔W料池内壁都能良好浸润,因而流阻低,电流稳定性好。在总离子发射电流10μA时Ga的离子流稳定度和5μA时Au源的稳定度都可达到±1.5%/h,连续寿命试验分别超过500h和150h,故已具有实用价值。本文还讨论了影响稳定性的诸因素。     

氧化物阴极激活过程的俄歇能谱分析

本文介绍了一种实验室用的俄歇电子能谱分析装置。利用该装置对氧化物阴极及其活性镍基金属进行了分析研究,观察到激活前后Ba、Sr原子浓度比有明显变化,这种变化与活性Ni中激活剂向表面富集有关。激活好的氧化物阴极表面BaO多于SrO,而且有盈余Ba存在。     

用俄歇电子能谱仪研究钡钨阴极的表面状况

在实验室条件下,AES研究阴极表面,应用小束流以减少表面损伤。利用自制AES系统地分析了钡钨阴极在分解、激活、老炼过程中表面组分和状态的变化。对于铝酸钡钙扩散型阴极表面,当温度高于1100℃时,钡的覆盖度明显下降。经较长时间老炼后钡在钨上平均只有不到一个单原子层的覆盖量。激活良好的处于正常工作状态时,阴极表面上主要是钨、氧、钡,而且钡可能以金属钡和氧化钡共存。阴极中的主要杂质碳和阴极材料、处理工艺、贮放条件和历史以及工作条件有密切关系。激活后的阴极表面含碳量和发射性能有一定的关系。较大量的硫可能来自组成多孔钨体的钨粒内部,高温时有可能消除掉。     

Preparation and emission property of scandia pressed cathode

Scandia pressed cathodes were prepared by powder metallurgy method using mixed powder of scandia doped tungsten and barium-calcium aluminates obtained by different mixing methods.The element distribution uniformity greatly affected the emission property.The powder prepared by ball-milling had small particle size and uniform distribution of different elements.This kind of powder was favorable for the chemical reaction among Ba,Ca aluminates,scandia and tungsten to take place sufficiently to form active substance which can improve the emission property.The emission current density of the cathode prepared with ball-milling powder was about 8 times higher than that prepared by manually mixing method,4 times higher than Os coated M-type cathode.The higher content of the active substance on the cathode surface prepared by ball-milling led to the better emission performance of the cathode.     

High Temperature XPS/AES Investigation of Mo-La_2O_3 Cathode-Ⅰ. Species and Properties of Oxygen on Surface

Mo-Laz0aisaperspectivecathodematerialandcanbesubstitutedfortheW-Th02filamentwidelyusedinmiddle0rhigh-powertubeswhichhasradioactivity,drasticbritilenessandhigheroperatingtemPerature(19O()~2000K).InsituemissionmechanismoftheM0-La203canbede-terndned0nthematerialschceandtheoxygenspeciescanbecharacterized0ntheoperatingcath0de.Itisverydifficultt0analyzethosema-terialsinsituontheh0tcath0de.Therewirenoexperimentalreportsonthisth0ughs0metheoriesorhypotheseshavebeenputf0rw.d[lJ.Inthe.jprior..rk[z],w…     

混合基含钪扩散阴极微观结构与性能研究

为了获得发射性能优异,均匀性良好的热电子发射阴极,本文采用液-液掺杂结合两步氢还原法制备出氧化钪掺杂钨粉,并在此基础上通过压制、烧结和浸渍工艺制备出浸渍型扩散阴极.采用SEM、电子发射测量装置和AES对阴极微观结构、发射性能和激活期间阴极表面活性元素的变化进行了研究.研究结果显示阴极孔度合适,孔结构良好,孔分布均匀,颗粒达到亚微米级.该阴极的发射测试结果显示在850℃b时Jdiv为51A·cm-2.分析认为阴极的亚微米结构有利于激活和工作过程中活性物质的扩散和在表面的均匀分布,对阴极的发射起促进作用.     

钡钨阴极与钪系阴极的表面研究

利用表面分析技术对 Ba-W 阴极和钪系阴极激活前、后和遭受离子轰击后表面元素及其化学态的变化以及它们与发射性能的相互关系进行了分析研究。分析结果有助于对阴极性能、它们对不同器件的适用性以及工作机理的进一步认识。     

太赫兹史密斯-珀塞尔辐射源带状电子注阴极的研究

为适应太赫兹史密斯-珀塞尔辐射源的迫切需求,研究从阴极表面直接产生微米尺度带状电子注的技术和检测方法,获得电流密度50 A/cm2,600μm×100μm的矩形层流电子注。