激光镀锆/钪钡铝酸盐复合薄膜钪型阴极的研究

钪型阴极具有优异的电子发射潜力,但同时也存在着发射均匀性和重复性差等共性问题。本文提出采用脉冲激光镀膜技术在浸渍钪型阴极表面沉积锆/高活性钪钡铝酸盐复合叠层薄膜,以实现对其性能的改进。实验完成了阴极表面膜层的制备,阴极二极管电子发射性能测试,阴极表面光/热发射电子显微镜观察,以及激活阴极表面成分及其深度方向分布的俄歇电子显微镜分析。研究结果表明,覆膜钪型阴极激活后,其表面Ba、Sc含量提升,获得了约110 ~ 130 nm厚的活性层,阴极展现出良好的发射性能;同时,阴极的表面发射均匀性获得明显提升。     

熔盐电解法制备铝钪合金的研究

本文采用了熔盐电解法研究铝钪合金的制备。以氧化钪为原料，LiF—ScF3-ScCl3为电解质体系，铝液为阴极，石墨为阳极，生产过程中析出的主要产物为CO和CO2。随着电解时间的延长，电流效率逐渐增加。最高可达到73％，后又适渐减小，且合金中钪的含量也逐渐增加，最高可达5．88％。随着电解时间的延长，反电动势有升高的趋势。但温度从780℃升高到850℃时，反电动势可以由2．4V降低到1．73V。通过扫描电镜观察发现合金比较均匀。以氧化钪为原料，在电解槽中直接以熔盐电解法生产铝钪合金不仅可以降低合金的生产成本，而且可以减少环境污染。     

氧化钪混合钨基扩散型阴极表面结构的研究

采用XRD、SEM和AES等分析方法对氧化钪混合钨基及浸渍后的阴极微观结构及表面活性元素的行为进行研究.结果表明:基体内Sc_2O_3弥散均匀分布.在阴极激活过程中,Ba和Sc从内部向表面扩散,在阴极表面形成含Ba、Sc、O的表面活性层,其厚度为M型阴极活性层厚度的10倍以上.对自由钪的产生机制进行了探讨.     

微波烧结法制备含钪扩散阴极及其发射性能研究

采用溶胶凝胶结合氢还原法制备出Sc均匀掺杂的钨粉,随后采用微波烧结法成功制备出浸渍型含钪扩散阴极。对Sc掺杂钨粉特性、Sc掺杂钨海绵基体微观结构、阴极发射性能和阴极表面活性物质分布进行了分析,结果显示:Sc以Sc2O3的形态均匀分布于平均粒径1μm的钨粉中,海绵体骨架主要由大小均匀的亚微米级准球形颗粒构成,表面孔结构良好,孔分布均匀,平均孔径在0.46μm左右,Sc_2O_3均匀分布于基体之中。电子发射测试结果表明,该阴极950℃b时脉冲偏离点电流密度Jdiv为137.59 A/cm~2,发射斜率1.431。激活后的阴极表面Ba:Sc:O的原子比例为1.8:1:2.2,同时阴极表面存在大量的纳米粒子,对阴极发射有促进作用。     

Al-Mg-Sc中间合金的制备

在非真空条件下用氟化物熔盐体系镁 (铝 )热还原法制备了Al Mg Sc中间合金 ,讨论了金属还原剂的选择及还原温度、时间等工艺条件对钪收率的影响 ,并研究制定了氧化钪固相氟化制备氟化钪熔盐工艺。采用Al Mg合金熔体为还原剂经二次还原后钪收率 >80 %,制备的Al Mg Sc中间合金铸锭中钪含量 >1.9%,最佳的还原反应温度为 110 0K ,还原时间 40min .。氟化钪还原产生的初生态钪与铝作用形成稳定的Al3 Sc化合物 ,促进了还原的进行 ,使钪收率得到了大幅度提高。     

铸态下钪在铝基体中的存在状态

采用X射线物相分析的方法,研究了铸态下钪在铝中的存在状态,结果表明,铸态下试样中的钪元素部分固溶于铝基体中,部分与铁生成Fe2Sc相。     

氟盐体系中Sc^3＋在Ag电极上的阴极还原过程

采用循环伏安法和计时电位法研究了钪离子在１０４３Ｋ下、ＬｉＦＮａＦ体系中银电极上的阴极还原过程。结果表明，Ｓｃ３＋在Ａｇ电极上的还原过程是可逆的简单电荷传递的三电子反应，阴极过程受扩散控制。     

钪对镁-铝-锌合金显微组织与力学性能的影响

通过铸锭冶金及形变热处理工艺,制备了含0.3%Sc的Mg-llAl-1.2Zn(质量分数)合金.采用X射线衍射、金相及扫描电镜观察与拉伸性能测试,研究微量钪在基体合金中的作用与存在形式.结果表明,基体合金中添加0.3%Sc后,合金的晶粒明显得到细化,Mg17Al12相的形态与分布得到有效改善.合金的相组成主要由a-Mg基体相、Mg17Al12相及MgAlSc相组成.同时,0.3%Sc的添加也提高了挤压态合金在室温与高温下抗拉强度,室温时的抗拉强度达到340MPa,而伸长率超过了10%.     

掺杂方式对Mo-La2O3合金组织和力学性能的影响

分别采用液．固和液．液掺杂方式向钼粉中引入氧化镧，烧结出Mo-La2O3合金，通过扫描电镜和透射电镜观察，研究了不同掺杂方式制备的Mo-La2O3合金中第二相粒子的粒度分布和形貌，分析了第二相粒子在钼基体中的分布规律，检测了钼丝的拉伸性能，通过位错塞积理论讨论了La2O3颗粒形貌和分布对Mo-La2O3拉伸性能的影响机制。结果表明：液．液掺杂方法能够使钼基体中的La2O3粒子均匀分散，细化La2O3粒径；直径0．6mm、液．液掺杂钼丝的拉伸性能优于液-固掺杂钼丝。     

熔盐电解法制备铝-钪合金电解质体系电化学性质研究

熔盐体系的电化学性质对熔盐电解过程有很大影响,通过选用铝电解工业通用的冰晶石-氧化铝体系作为熔盐电解制取铝钪合金的基本电解质体系,采用循环伏安法、线性伏安法和稳态极化法对Sc3+在冰晶石熔盐体系中铝电极上的电化学还原过程及氧化钪在石墨电极上的分解电压进行研究.结果表明,Sc3+在熔盐中电解还原过程为一步获得三个电子的简单电荷传递过程.     

Scandia doped tungsten matrix for impregnated cathode

As a matrix for Sc-type impregnated cathode,scandia doped tungsten with a uniform ldistribution of SC2O3 was obtained by powder metallurgy combined with the liquid-solid doping method.The microstructure and composition of the powder and the anti-ion bombardment behavior of scandium in the matrix were studied by means of SEM,EDS,XRD,and in-situ AES methods.Tungsten powder covered with scandium oxide,an ideal scandium oxide-doped tungsten powder for the preparation of Sc-type impregnated cathode,was obtained using the liquid-solid doping method.Compared with the matrix prepared with the mechanically mixed powder of tungsten and scandium oxide,SC2O3-W matrix prepared with this kind of powder had smaller grain size and uniform distribution of scandium.Sc on the surface of Sc2O3 doped tungsten mauix had good high temperature stability and good anti-ion bombardment capability.     

A novel approach to synthesis of scandia-doped tungsten nano-particles for high-current-density cathode applications

A novel synthesis approach for scandia-doped tungsten nano-powder using a sol–gel method is developed. It involves dissolving tungsten oxide at 300 °C in the presence of a mixture of nitric acid, citric acid and ammonia. The dissolved tungsten oxide reacts with an aqueous solution of scandium nitrate in the liquid–liquid phase, which results in the homogeneous mixing of tungsten and scandium particles. A spherical shape particle was obtained due to the dissolving of tungsten oxide in the solution. Citric acid enhances the mixing of ions at the atomic scale, which affects the hydrolysis reactions and leads to the formation of the phase pure nano-particle. The synthesized nano-powder was characterized by SEM (Scanning Electron Microscopy), EDS (Energy-dispersive X-ray spectroscopy), TEM (Transmission Electron Microscopy), and XRD (X-ray Diffraction) analyses. The spherical morphology was observed via a SEM analysis and a narrow particle size distribution was noted by means of a TEM analysis. The XRD analysis of the powder showed the complete formation of the phase pure nano-particle with an average diameter of 50 nm without any contamination by other materials.     

蓝钨与紫钨氢还原法生产超细钨粉的比较

在相同的工艺条件下,比较了蓝钨与紫钨氢还原法生产的钨粉的性能差别.结果表明:与蓝钨相比,紫钨生产的钨粉粒度更细更均匀,并且钨粉粒度受装舟量和氢气流量的影响较小.并从原料的微观结构和氢还原机理两方面分析了造成不同原料生产的钨粉粒度和均匀性差别的原因.     

Anodic oxide growth on tungsten studied by EQCM, EIS and AES

Anodic oxide growth on tungsten in 0.1 M H₂SO₄ + 0.4 M Na₂SO₄ has been studied on stationary and rotating electrodes using the electrochemical quartz crystal microbalance (EQCM), Auger electron spectroscopy (AES) depth profiling, electrochemical impedance spectroscopy (EIS) and the rotating ring disc electrode (RRDE). The sputter rate of tungsten oxide was calibrated with respect to a tantalum oxide reference film using Rutherford backscattering spectroscopy (RBS). Long time polarisation experiments at constant potential showed that at a stationary electrode the oxide thickness determined by AES increased with time, whereas a steady state was reached after a few seconds under rotating conditions. On the other hand, EIS indicated a time independent oxide thickness on both stationary and rotating electrodes. Both methods yielded a higher absolute thickness for stationary electrodes. The oxide growth behaviour at short times was studied with the EQCM by monitoring the current and the mass change resulting from a potential step. From these data the film growth fraction and the oxide thickness change were calculated. After an initial period of a few seconds dominated by film growth, the rotating electrodes exhibited a significant mass loss contrary to stationary electrodes. RRDE experiments confirmed dissolution during anodic polarisation of a rotating electrode. The results of this study demonstrate the necessity to combine several experimental methods when studying anodic film growth and they illustrate the usefulness of the EQCM which can monitor directly and with sub-second time resolution the mass change of the electrode together with the current density. They show the decisive effect of convection conditions on anodic oxide growth on tungsten.     

Effect of surface state properties of modified TiO2 powders on their photo—catalytic activity

With an attempt to investigate the effect of impurity and tungstem oxide on the recombination and separation of electron-hole pairs,and disclose the effect of surface state on the photo-catalytic activity of TiO2,an innovative photo-catalyst 3%WO3/0.5%Au^3 /AiO3 was prepared by means of sol-el method.The photo-oxidation efficiency of photo-catalyst was evaluated by conducting a set of experiments to photo-degraeds methylene blut(MB)in aqueous solution.The surface state properties were examined by means of surface photovoltage spectra(SPS)and electron-field-induced SPS(EFISPS).The experiments demonstrate that the strongest peak is attributed to electron excited from valence band to conduction band and the second strongest peak is attributed to electron excited from valence band to oxygen molecular for all samples,Electron is trapped by O2 absorbed on the surface of TiO2.And the surface state of O2^- forms.For(1%,3%)Au^3 /TiO2 sample,two new peaks that significantly present at 414nm and 400nm respectively should be attributable to gold impurity energy level.And for tungsten oxides doping samples,4 peaks that significantly present in the region of 500-800nm should be attributable to tungstem impurity energy level.The intensity of EFISPS decreases with increasing the content of gold ion or tungsten oxide when its content is no more than their optimal dosage.However,when the content of gold ion or tungsten oxide is more than their optimal dosage,impurity energy level becomes recombination center from separation center and the intensity of all peaks increases for them.     

以蓝钨为原料制取的粗颗粒W粉、WC粉特性的研究

本文从粉末粒度分布、微观结构以及对合金性能的影响等三方面探讨了以蓝钨为原料制取用颗粒W粉、WC粉的特性。结果表明，从W粉、WC粉的粒度分布曲线来看，蓝钨原料与黄钨原料没有什么本质区别，要制取粒度分布比较平坦、没有尖峰的粗颗粒W粉和粒度分布曲线不出现双峰的粗颗粒WC粉不能靠选择原料种类来解决；用扫描电镜观察W粉、WC粉的微观形貌时发现，用黄钨为原料制的W粉、WC粉颗粒表面存在明显微孔，而这一现象在以蓝钨为原料制得的W粉、WC粉中没有发现；与黄钨相比，以蓝钨为原料制得的WC－Co、WC－Co－Ni硬质合金具有较好的综合性能。     

离子束合成表面微合金及其抗蚀性研究

用Ar~-离子束溅时沉积制膜与高能Xe~-离子轰击相结合的离子束动态混合技术,直接在轴承钢GCr15基体上制备出富Ta微合金。经TEM、XPS、AES与EDAX分析确定在特定工艺条件下可获得一定组分的非晶态合金膜。分别在H_2SO_4、NaCl和FeCls_3溶液中检验膜的抗均匀腐蚀与抗局部腐蚀的能力,证明所形成的非晶态微合金具有优良的抗腐蚀性。     

氧化钨相成分对超细钨粉均匀性的影响

研究了通过传统氢还原工艺制备超细钨粉末过程中氧化钨原料相组成对超细钨粉均匀性的影响。结果表明：单一相组成的氧化钨能制得超细而均匀的钨粉,多种相组成的氧化钨,由于其在还原过程中存在不同的还原路径和还原速度,制得的钨粉虽细但不均匀。     

Influence of Yttrium Addition on the Reduction Property of Tungsten Oxide Prepared via Wet Chemical Method

W-Y_2O_3 composite nanopowders prepared via wet chemical method exhibit unique morphologies and micro structures.The yttrium addition during chemical reaction process affects not only the composition of tungsten acid hydrate precursors,but also the reduction property of tungsten oxide transformed from precursors.In this study,the morphology evolution of the samples with and without yttrium during reduction process has been studied,and it is found that the addition of yttrium can exert a strong influence on the reduction route of tungsten oxide and the final morphology of tungsten particles.The cause of the difference of reduction route and tungsten particle morphology is also analyzed.It is suggested that the composition of the samples with yttrium at the beginning of reduction is pure cubic system WO_3(c-WO_3),and the c-WO_3 particles have c-WO_3 whiskers attached to the surface.This kind of whiskers is essential for c-WO_3 to be reduced directly to tungsten and also helpful to obtain W-Y_2O_3 powders with small size and good uniformity.