Mo-La2O3阴极丝的AES深度剖析

激活后发射良好的Mo La2 O3 阴极表层含有大量镧 ,原子浓度比约为 (稍大于 )10 % ;发射衰减的阴极表层中镧含量减少 ,未激活的原始阴极丝表层中镧更少。对不同状态阴极中氧含量及其变化的比较 ,以及碳、钼峰分析认为 :发射良好阴极中镧的活性程度较大 ,即超额镧的存在是影响阴极工作性能的主要因素 ;衰减后阴极中镧的总量虽不小 ,但镧的活性显著降低是阴极发射不好的主要原因     

A Study on La2O3－Y2O3－Mo Secondary Emission Material

The substrate molybdenum doped with La2O3, Y2O3 cathode material was made by the powder metallurgy method. The secondary emission coefficients of the materials were tested. The experimental results show that Mo cathodes doped with La2O3, Y2O3 have good secondary emission properties. When the cathodes are activated, the maximal secondary emission coefficients of these cathodes are higher than 2.0 and can meet the practical requirement. The distribution of the rare earth in the interior and at surface of this kind of cathode material before and after emission was studied using Scanning Electronic Microscopic (SEM) and X-Ray Photoelectron Spectrum(XPS). The analysis results show that the rare earth is easy to gather at grain boundaries and the relevant concentration of rare earth on the surface after emission is obviously greater than that before emission.     

Function of Oxygen in Mo-La2O3 Cathode

Different atomic ratio La/O film cathodes were prepared by pulsed laser deposition under various vacuum conditions. The emission properties were measured and their surface composition was investigated with in situ AES analyses. The function of oxygen in thermoionic emission of Mo-La2O3 cathode was investigated. Excess oxygen is negative to electron emission because lanthanum is easy to become stable La2O3, but proper proportion oxygen can weaken the evaporation of lanthanum and conduce to cathodes＇ stable work. The formation of oxygen vacancies enhances semiconductor property of La-O compound and improves greatly the performance of cathodes.     

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In order to accurately control the rare earth content in liquid steel in electroslag remelting (ESR) process, according to the ion and molecule coexistence theory (IMCT) of slag structure and corresponding phase diagrams, a thermodynamic calculating model for the evaluation of mass action concentrations (designated by Ni for structure unit i) for La2O3-Al2O3-CaF2 slag system was formulated. The results show that the calculated values of NLa2O3 are in good agreement with the reported measured values, indicating that this calculating model can wholly embody the characteristics of the slag system. The activity of La2O3 decreases with the increasing of the Al2O3 and CaF2 content, and Al2O3 is stronger than CaF2 in decreasing the activity of La2O3. But the activity of La2O3 increase with the increasing in temperature at the composition range of 30% La2O3, 20% Al2O3, 50% CaF2. Above all, the activity of La2O3 in La2O3-Al2O3-CaF2 slag system can be quantitatively analyzed by this thermodynamic model, and this model can provide a theoretical basis for precisely controlling the lanthanum content in molten steel in ESR process.     

High Temperature Oxidation Behavior of La2O3-MosSi3/MoSi2 Composites

The oxidation behavior of 0. 8% La2O3- Mo5Si3/MoSi2 composites at 1200℃ in air was investigated. The results reveal that the oxidation resistance of the material with 0. 8% La2O3 and Mo5Si3 is impaired. The oxidation resistance is decreased with increasing Mo5Si3 content. The mass loss follows a linear law in the initial oxidation. With oxidation time prolonging, a continuous and dense oxidation scale prevents oxygen from diffusing increasing when and leads to mass change a Mo5Si3 content is less than 30%. However, the composite shows ＂PEST＂ with the addition of 40% Mo5Si3. With increasing Mo5Si3 content, the oxidation resistance of 0.8% La2O3- Mo5Si3/MoSi2 decreases. This attributes to the poor oxidation resistance of M05Si3 and the relative density decreasing of 0. 8% La2O3-Mo5Si3/MoSi2 composite.     

Mo-La2O3烧结坯的韧化机制研究

通过扫描电镜，定点探针分析，X射线衍射分析及俄歇电子能谱分析研究了Mo-La2O3烧结坯的韧化机制，结果表明：La2O3的加入提高了烧结钼坯的横向断裂强度和韧性，Mo-La2O3O烧结坯的韧化机制源于间隙杂质在La2O3粒子表面的吸附作用。     

Mo—La—Ce稀土钼合金丝材及其制备方法

本发明涉及一种Mo—La—Ce稀土钼合金丝材及其制备方法。其特征在于该钼合金丝材中含有重量百分比为0．4％～1．0％La2O3和CeO2,且La2O3：CeO2的重量比为4：1。制备方法与传统的粉末冶金生产工艺不同,是将二氧化钼、La（NO3）3、Ce（NO3）4溶液进行真空干燥液-固掺杂,而后进行二次还原制取二元稀土掺杂钼粉,再经压制、烧结、压力加工等工序,制备出规格为Ф0．5～0．8mm Mo—La—Ce稀土掺杂钼丝。本发明的原料廉价、易得,所制备的钼丝抗拉强度高、耐磨性能强、工艺简单、不易弯曲脆断、成品率高、一致性好、使用寿命长。     

La2O3-Mo阴极材料中La2O3稳定性研究

本文采用高温光电子能谱方法对La2O3-Mo阴极及碳化La2O3-Mo阴极材料表面La2O3的化学稳定性进行了研究.实验结果表明,La2O6并不具备文献报道的极好的化学稳定性.材料中的La2O3在高温、真空条件下,其部分晶格氧发生分离.La2O3可以被Mo2C还原成单质La.单质La的结合能高于La2O3的结合能.实验证实单质La3d5/2的结合能为835.96eV,并首次给出La3d3/2的结合能实验数值为852.23eV.     

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.     

La2O3在空气中稳定性的研究

通过对 L a2 O3 粉末在空气中吸水的增重测定及增重前后的 X射线衍射结构分析 ,发现 L a2 O3 吸水之后转变成 L a(OH) 3 。因此 ,L a2 O3 是一种化学性质不稳定的化合物 ,从前文献中关于“L a2 O3 是一种化学性质稳定的氧化物”的观点值得商榷。     

ICP—AES法测定SYP烧结增效剂中B2O3、MnO2

研究用等离子发射光谱测定SYP烧结增效剂中主元素BO23、MnO2的方法。建立了最佳工作条件,讨论了试样溶解的方法,分析谱线的选择,干扰及其校正,并建立了分析方法。同时对回收率和精密度等进行试验。试验结果表明本方法简便、快速、准确,分析结果令人满意,该方法现已应用于工作中。     

La2O3对MnO2碳热还原的催化

研究了稀土氧化物Ｌａ２Ｏ３作为添加剂对ＭｎＯ２碳热还原的作用，通过不还原实验，发现Ｌａ２Ｏ３对ＭｎＯ２碳热还原具有催化作用，对还原后试样进行ＳＥＭ分析，认为其催化作用是通过催化试样中碳的气化反应面实现的。     

La2O3纳米晶的制备及表征

以硝酸镧、酒石酸铵为原料,采用络合沉淀法制备了前驱物.前驱物经80℃烘干,用红外光谱,TG-DTA进行了测定,结果表明,前驱物为酒石酸镧络合物La2L3·12H2O.然后置于马弗炉中于650℃、750℃和850℃分别煅烧2h,得到不同粒径的La2O3样品,用XRD、TEM和SEM等测试方法进行了表征,样品的平均粒径分别约为20.67nm、28.14nm和39.55nm.     

ICP－AES法测定高纯La_2O_3中Ni、Co、Mn、FeP、Cr、Mg、

采用优级纯ＨＣＩ加二次水为介质，连续测定９９．９９％Ｌａ＿２Ｏ＿３中１０个非稀土杂质，采用正交设计实验Ｌ＿９（３￣４）￣［１］，同时考虑稀土杂质的测定，对ＩＣＰ－ＡＥＳ进行工作参数的最佳选择，并考察了基体镧的影响，指出了连续测定的最佳基体浓度和酸度，在最佳条件下，测出杂质的回收率在８８．０％～１０７．６％之间，相对标准偏差（ＲＳＤ）在３．４４％～１４．０３％之间，检出限在０．０６～３．４５μｇ／ｇ范围内，本方法快速、简便、准确，能满足９９．９９％Ｌａ＿２Ｏ＿３产品中非稀土杂质的测定。     

Si和La元素对Mo丝显微组织与力学性能的影响

系统研究了La、Si单元掺杂和复合掺杂对钼丝的显微组织和力学性能的影响及其作用机制,优化出具有优异力学性能的Mo-Si-La合金丝的成分为Mo-0.15Si-(0.5～0.8)La.MoSi2与Mo原位反应生成Mo5Si3和Mo3 Si硬质相,起到良好的晶粒细化作用和弥散强化作用.La2O3颗粒通过延迟微裂纹的形成和扩...     

Mo-Y_2O_3阴极发射机理研究

采用热重分析、X射线衍射、扫描电镜及光电子能谱等方法对Mo Y2 O3阴极中钇的价态进行了研究 ,探讨了该阴极的发射机理。Y2 O3与Mo2 C在 1173K以上发生化学反应。Y2 O3与Mo2 C混合物经 1873K高温处理后 ,产物中含有两种价态的Y :Y0 和化合态的Y3 。Mo Y2 O3阴极的发射可用原子膜机理解释 ;在阴极工作过程中 ,Mo2 C将Y2 O3还原成单质钇 ,钇覆盖在钼基体表面 ,降低了基体钼的逸出功 ,促进了阴极的发射。     

Fe—Mo—Cl—H2O混合体系中铁和钼的价态分析

用FeCl_3浸取辉钼矿时,溶液中可能存在着Fe-Mo氧化-还原平衡体系。为准确测定该体系中各价态离子的含量,必须保证已有的平衡不被破坏。因此,传统的分析方法显然不适合这样的体系。文献曾提出一种将直接电位法与容量法相结合用以测定复杂体系的方法,该法可以不破坏已有的平衡而获得较可靠的结果。本文在此基础上提出了用电位法测铁电对式量电位及体系平衡电位,以EDTA容量法分别测定高价离子的合量及铁、钼各自总量,从而建立方程     

Thermionic Electron Emission Stability of Mo-La2O3 Cathode

TheMo La2 O3cathode ,whichpossessesthead vantagesofhighstrengthandgoodambientductility ,excellentelectronemissionability ,lowoperatingtem peratureandradioactive freepollution ,isapromisingcathodeforreplacingW ThO2 cathodeinavarietyofvacuumelectrondevices[1～4 ] .However ,itisfoundthattheemissioncurrentofMo La2 O3cathodeelectrontubesattenuatedwithlifetimerapidly .Inordertoob tainstableemissionofMo La2 O3tubes ,muchefforthasbeendoneonthematerialcomposition ,thecar bonizingprocessandemissionm…     

CeO2和La2O3对高炉喷吹煤粉燃烧过程的影响

在模拟高炉喷吹的条件下,对添加CeO2 和La2O3的混合煤粉进行了燃烧试验,考察了稀土氧化物对高炉喷吹煤粉燃烧过程的影响,并探讨了其助燃作用机理.     

阴极气膜微弧放电沉积ZrO2-Y2O3陶瓷涂层

采用阴极气膜微弧放电沉积制备ZrO2-Y2O3陶瓷涂层，利用水溶液中阴极气膜放电产生的等离子体的能量，使在阴极表面形成的沉积物直接烧结为陶瓷涂层。研究了沉积涂层的影响因素和涂层形貌及结构。SEM，EDS和XRD分析结果表明，获得的ZrO2-Y2O3陶瓷涂层表面光滑、与基体结合致密、成分和相结构均匀，是一种由Y2O3部分稳定的ZrO2陶瓷涂层。通过测试阴极气膜放电过程中电流随时间的变化以及电位在两电极间分布，分析了阴极气膜放电沉积陶瓷涂层的机制。