Effect of scandia on tungsten oxide powder reduction process

Scandia doped tungsten powders were prepared by spray drying combined with two-step hydrogen reduction.The particle size of doped tungsten powder,powder morphology and doped tungsten matrix were characterized by scanning electron microscope,X-ray diffrac-tion and laser diffraction particle size analyzer,respectively.The reduction behavior of Sc2O3 doped tungsten oxide and the effect of Sc2O3 on the property of tungsten powder were studied by the temperature programmed reduction.The experimental results showed that the pre-cursor powders prepared by spray drying had spherical shape.The addition of Sc2O3 could decrease the reduction temperature of tungsten oxide.The scandia doped tungsten powder had sub-micrometer size in the range of 0.1 to1 μm and scandium distributed evenly in the powder.By using this kind powder,sub-microstructure cathode matrices with semispherical grains and homogenous distribution of scan-dium were obtained.     

Effect of scandia on tungsten oxide powder reduction process

Scandia doped tungsten powders were prepared by spray drying combined with two-step hydrogen reduction. The particle size of doped tungsten powder, powder morphology and doped tungsten matrix were characterized by scanning electron microscope, X-ray diffraction and laser diffraction particle size analyzer, respectively. The reduction behavior of Sc₂O₃ doped tungsten oxide and the effect of Sc₂O₃ on the property of tungsten powder were studied by the temperature programmed reduction. The experimental results showed that the precursor powders prepared by spray drying had spherical shape. The addition of Sc₂O₃ could decrease the reduction temperature of tungsten oxide. The scandia doped tungsten powder had sub-micrometer size in the range of 0.1 to1 μm and scandium distributed evenly in the powder. By using this kind powder, sub-microstructure cathode matrices with semispherical grains and homogenous distribution of scandium were obtained.     

纳米钨粉制备浸渍阴极基体的研究

采用常规钨粉、纳米钨粉和掺杂氧化钪纳米钨粉制备了浸渍阴极。利用扫描电镜、压汞仪等测试手段分析了阴极基体的微观结构,用水冷阳极二极管检测了阴极的发射性能。研究表明,采用纳米钨粉制备的阴极基体具有比常规阴极基体更细微的显微结构,阴极的直流发射电流密度为4.6 A/cm2,而常规阴极为4.13 A/cm2。掺杂氧化钪后,阴极的发射性能明显提高,其直流发射电流密度为5.31 A/cm2。     

难熔金属阴极及涂层研究进展

介绍了稀土钼金属陶瓷阴极、钪钨基扩散阴极及化学气相沉积法制备钨涂层。为了满足大功率磁控管的发展要求,研究了新型稀土钼金属陶瓷阴极。经过高温激活处理后,材料的最大次级发射系数达5.24,实用管型测试结果表明,稀土钼金属陶瓷阴极的性能优于钡钨阴极,显示了良好的应用前景。亚微米结构的钪钨基扩散阴极具有优异的热发射性能,850℃下阴极的发射电流密度可达42A/cm2,激活后Ba,Sc,O等元素形成的活性多层,均匀覆盖在阴极表面,促进了阴极的发射。采用热壁开管气流CVD法,以WF6和H2为反应源气体,可以方便地制备成难熔金属钨沉积层。所获得钨沉积层具有高纯度(>99%)和高致密度(>19g/cm3)。     

A Study of Scandia Doped Tungsten Nano-Powders

Scandia and rhenium doped tungsten powders were prepared by solid-liquid doping combined with two-step reduction method. The particle size of doped tungsten and distribution of scandia and rhenium were studied by SEM, EDS, XRD and granularity analysis. Experimental results showed that scandia distributed evenly on the surface of tungsten particles. Addition of scandia and rhenium decreased the particle size of doped tungsten, and the more the content of scandia and rhenium, the smaller the doped tungsten particles. Tungsten powders doped with 3 % Sc2O3 and 3 % Re （mass fraction） had an average size of about 80 nm in diameter. The mechanism of the decrease in the tungsten particle size was discussed.     

从硬质合金微观结构和性能对湿磨工艺的敏感性评价WC粉末的内在质量

以XLWC25型WC粉末为原料,采用滚动湿磨和搅拌湿磨工艺经过不同的湿磨时间制备5组WC-6Co硬质合金。从合金微观组织结构参数(平均晶粒度、邻接度、晶粒分布)和力学性能对湿磨工艺的敏感度方面,探讨了硬质合金关键原材料WC粉末内在质量的评定方法。结果表明,合金微观组织结构和力学性能对湿磨工艺变化的敏感度较低,在一定程度上反映了XLWC25型WC粉末具有较好的内在质量。采用搅拌湿磨工艺,湿磨6¹0 h,WC-6Co合金的微观组织结构均匀性和综合性能可达到最佳状态,优于滚动湿磨58 h制备的参比合金的综合性能。     

Effect of microstructure on the mechanism of emission for tungsten-barium dispenser cathodes

The effect of tungsten powder fineness and microstructure parameters of the tungsten skeleton on the emission of dispenser cathodes (DC) in the stages of degassing and high-temperature activation are studied. Quantitative analysis of the cathode surface microstructure is investigated. It is established that the work function of the DC after high-temperature activation does not depend upon the size of tungsten powder particles in the test range of fineness (average particle size 1.4–20 μm) and porosity of the tungsten skeleton (22 and 35%). The time for reaching the maximum DC activity increases with an increase in particle size and skeleton porosity. The highest emission uniformity is exhibited by cathodes with a uniform microstructure prepared from tungsten powder with an average size of 1 and 4 μm. It is shown that the DC emission capacity is connected with the marked three-dimensional structure of BaO-CaO at the cathode surface, and also monatomic films (Ba-O and Ba) and excess oxygen at the surface of the tungsten phase.     

高性能等离子喷枪用多元复合稀土钨电极研制

本论文以"多元复合稀土钨电极及其制备技术"2008年国家技术发明二等奖为基础,采用喷雾干燥法并结合两段氢气还原成功制备出多元复合稀土掺杂钨粉。经过冷等静压压制、中频感应烧结后制备出等离子喷枪电极。实验结果表明,多元复合稀土的掺杂,降低了钨粉的粒度,进而提高了稀土在电极中元素的分布均匀性,稀土元素分布均匀性的提高降低了钨电极的烧损量,同时采用中频感应烧结制备的电极密度要大于垂熔烧结制备的电极。与目前使用的等离子喷枪电极相比,采用中频感应烧结制备的多元复合稀土钨电极抗烧损性能更好,电极寿命更长。     

活化烧结对金刚石增强型硬质合金复合齿性能的影响

在金刚石增强型硬质合金复合齿基体中球磨添加不同量红磷，比较相应的金刚石增强型硬质合金基体的性能，确定添加(质量分数)0．3％P的复合齿基体性能最好；同时采用化学镀Ni-P合金添加P结合球磨添加0．1％P的方式，其超硬复合齿基体力学性能及复合齿的磨耗比、抗冲击功远远优于单纯球磨添加0．3％P方式超硬复合齿的性能。说明为了实现金刚石增强型硬质合金复合齿的活化烧结方式，磷元素最优的添加方式是化学镀结合球磨的添加方式。     

Enhancement of secondary emission property of molybdenum cathode co-doped with La_2O_3 and Y_2O_3

La2O3 and Y2O3 co-doped Mo secondary emitters were prepared by three kinds of doping method combined with high temperature plasma sintering.The secondary electron emission property and microstructure of the cathodes were studied.It showed that the cathode prepared by liquid-liquid doping method exhibited the best emission property among all the samples prepared by liquid-solid doping,solid-solid doping and liquid-liquid doping methods due to a uniform distribution of different substances.RE2O3 existed unifo...     

钡钨阴极钨粉某些物理特性的研究

应用JCXA-733型电子探针扫描电镜和SKC-2000型光透射粒度测定仪对钡钨阴极钨粉的某些物理特性作了较详细的分析;并对钡钨阴极压坯断口形貌、钡钨阴极表面状态与阴极发紂电流密度性能的关系进行了对比试验;运用颗粒表面物理理论论述了钡钨阴极钨粉某些物理特性的内在规律,对粉末分级方法和材料研究具有实际意义。     

高性能阴极基体用超细钨粉的制备

采用反向滴加沉淀法、微乳法和溶胶-凝胶法3种液相方法合成超细WO3，然后将超细WO3在高纯氢气氛中还原成超细钨粉。XRD，SEM和数学统计分布软件结果分析表明，溶胶-凝胶法得到立方相钨粉，颗粒大小均匀且具有良好的球形度，平均粒径约为200nm，满足高性能阴极基体的要求。微乳法制备的钨粉形貌为片状，不适合作阴极基体的原始粉料。     

掺杂方式对钨电子发射材料性能和结构的影响

分析了电子发射材料制备中通用的掺杂工艺，研究了新的掺杂工艺，并对几种不同掺杂工艺：固一固、液一固、液一液进行了对比研究。在自行设计的发射测量设备上，研究了液一液掺杂材料的电子发射性能，着重阐述了掺杂方式对材料发射性能和结构的影响；并通过XRD，SME等检测方法，研究了掺杂方式对稀土在电子发射材料中分布均匀性的影响，揭示了液一液掺杂在混合机制上的特殊性，证明了液．液掺杂的高效性、均匀性及优越性。     

稀土元素对掺杂钨粉还原过程及性能的影响

利用中止还原的方法,研究了稀土元素对掺杂钨粉还原过程及其性能的影响。结果表明,在同样的还原工艺条件下,稀土元素能使掺杂钨粉的还原速率减小,分裂时间更晚,但最终的钨粉粒度更细小,可获得几百纳米的超细钨粉。还原后,粉末的形貌由准球形转变为规则的立方体形。稀土元素还促进钨粉中钾含量的提高。     

不同形态炭黑对粗颗粒钨粉配碳的影响

研究以同批粗颗粒钨粉为原料,考察炭黑形态和配碳方式对所制得的粗颗粒WC粉末性能的影响。实验结果表明:不管是采用经典的球磨配碳还是采用较为新型的混合配碳,使用粉状炭黑配碳制备出的粗颗粒WC粉末质量更优良。     

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.     

A Study on La_2O_3-Y_2O_3-Mo Secondary Emission Material

Thephenomena ,mechanismandtheapplicationofsecondaryemissionofmanykindsofmaterialshavebeenstudiedsincethesecondaryemissionphenomenawasdiscoveredbyCompellin 1899.Withthedevel opmentofelectronictechnologythephenomenaofsec ondaryemissionhavebeenincreasinglyappliedinmanyfields[1,2 ] ,especiallyinhighpowermagnetrontube .Nowadays ,thecathodesofhighpowermag netrontubeusedinthefieldsofbroadcast,correspon denceandnationaldefensearemainlyBa Wcath odes[3] andsomeTh Wcathodes .However ,Ba Wcathodeishard…     

钨渗铜材料室温力学性能与组织研究

分别从不同原料钨粉粒度和不同钨骨架密度的角度,对材料的室温拉伸性能进行研究,并结合SEM断口形貌观察,分析材料在室温状态的断裂形式及其变化规律。研究表明:(1)无论是用中颗粒还是细颗粒钨粉制备的钨渗铜材料,在83%的骨架相对密度下,材料的室温强度呈现出一个峰值;(2)在相近骨架相对密度的情况下,细颗粒钨粉制备的试样,其室温拉伸强度均明显高于相应中颗粒钨粉制备的试样;(3)对于钨渗铜材料,室温下的断裂形式为穿晶和沿晶断裂两种形式并存,并且随着骨架密度的提高,穿晶断裂的比例逐渐上升。对于相近骨架相对密度的两种试样,中颗粒试样比细颗粒试样具有更多的解理面。     

多元复合稀土钨电极的制备及其焊接特性研究

本论文采用机械混合法结合二段氢气还原成功制备出稀土掺杂钨粉。还原后的稀土钨粉冷等静压压制成钨棒后,采用中频感应烧结法制备出稀土钨电极。实验结果表明,制备的稀土钨粉,由于稀土元素的存在,降低了钨粉的粒度。稀土元素以稀土氧化物的形式存在。与垂熔法相比,采用中频感应烧结后的钨棒机械加工性能优异。电极成品率提高了5%,能耗则降低了60%以上。并且制成电极后的焊接性能得到了进一步提高。     

H2O2氧化水热晶化法制备超细钨粉

通过H2O2氧化工业级钨粉颗粒制备出纳米级WO3粉体,采用两段还原法对所得的产物进行氢还原后得到超细钨粉。用XRD、SEM、BET等对所得产物进行了一系列的表征。结果表明:工业级钨粉经氧化水热晶化处理后所得产物为单斜相WO3,平均粒径约为60 nm;将制得的WO3在氢气氛下还原,800℃下保温45 min后得到颗粒分布较窄、平均粒径约150 nm的立方相钨粉。当还原温度升高至900℃时,所得的钨粉颗粒明显长大,部分粒径长大至2~3μm,但颗粒的球形度更好。