复合稀土氧化物-钼-铼金属陶瓷阴极的次级发射性能

研究了复合稀土氧化物-钼-铼金属陶瓷阴极的二次电子发射系数和抗暴露大气性能,对发射后的表面进行了表面分析,并与单元、复合稀土-钼金属陶瓷阴极进行了对比.研究结果表明:加入微量铼的复合稀土氧化物-钼金属陶瓷阴极的二次电子发射系数可提高8%,其最大次级发射系数δm为2.65,且具有较好的抗暴露大气性能.     

稀土-钼阴极二次电子发射性能研究

采用固固掺杂、液固掺杂和液液掺杂方法制备了稀土氧化物掺杂钼粉,随后利用等离子体快速烧结(spark plasma sinterin,SPS)和传统的压制与高温烧结分别制备稀土-钼金属陶瓷材料,利用金相显微镜、发射性能测试方法对样品的微观结构和二次电子发射性能进行了研究。结果表明:稀土氧化物均匀掺杂和组织的细化有利于材料发射性能提高。经过高温氢气处理,使得样品激活温度大幅降低,发射系数大幅提高。     

折叠波导行波管铪栅极退火温度及其性能

在充分考虑电子枪栅极的工作环境后,对铪(Hf)栅极进行了800、900和1000℃的真空退火处理,对其组织、织构特点进行了分析,并利用离子束辅助沉积技术在Ba-W阴极表面分别沉积金属钼膜和铪膜,以模拟栅控行波管中钼栅极和铪栅极表面吸附阴极蒸发物质时的表面状态,测试了这两种栅极表面“热电子发射”能力和“二次电子发射”系数.结果表明,随着退火温度的升高,铪(Hf)栅极的结晶度、晶粒尺寸增加,织构减少,铪的最佳退火温度为900℃,铪栅极表面吸附的阴极发射物质要远少于钼栅极,用金属铪作栅极材料能有效抑制栅电子发射.     

折叠波导行波管铪栅极退火温度及其性能（英文）

在充分考虑电子枪栅极的工作环境后,对铪(Hf)栅极进行了800、900和1000℃的真空退火处理,对其组织、织构特点进行了分析,并利用离子束辅助沉积技术在Ba-W阴极表面分别沉积金属钼膜和铪膜,以模拟栅控行波管中钼栅极和铪栅极表面吸附阴极蒸发物质时的表面状态,测试了这两种栅极表面"热电子发射"能力和"二次电子发射"系数。结果表明,随着退火温度的升高,铪(Hf)栅极的结晶度、晶粒尺寸增加,织构减少,铪的最佳退火温度为900℃,铪栅极表面吸附的阴极发射物质要远少于钼栅极,用金属铪作栅极材料能有效抑制栅电子发射。     

一种细晶稀土氧化物掺杂钼合金及其制备方法

本发明提供一种细晶稀土氧化物掺杂钼合金及其制备方法，以二氧化钼为原料，采用雾化法掺杂稀土氧化物，掺杂后的钼合金粉经过球磨、过筛处理后，在800℃-100℃的多段马弗炉中使用氢气进行还原处理，再将还原后的粉体在150MPa～200MPa下冷等静压压制成型，成型后的坯料在中频感应烧结炉中分段烧结，时间为16小时-24小时。烧结后的材料经过75％-97％的变形加工采用常规机加工方法制备钼合金棒材或板材等材料。本发明的钼合金，具有细小的晶粒组织，平均晶粒宽度为0．5μm～1．2μm，平均尺寸小于300n。的细小稀土氧化物均匀弥散分布在钼合金基体上，与普通粗晶钼合金相比，具有更高的强度、延展性和韧性，具有更广泛的用途。     

放电等离子烧结钼的组织和性能

研究了放电等离子烧结（SPS）钼的致密化,组织和硬度,与其它烧结方法相比,SPS是一种时间短,温度低的先进快速烧结法。利用SPS在比CIP－S和热压烧结（HP）低180－500℃下进行烧结,保温3min,得到钼的相对密度是95．2％－97．9％,硬度比其它方法烧结的高出HV20－HV75。SPS烧结钼的密度呈现随烧结温度的升高而增加的趋势。但是其硬度有所下降,SPS在较低温度下烧结的钼的硬度较高,原因是其晶粒较细,SPS烧结钼的断口呈沿晶断裂,属于脆性断裂。     

复合稀土钼材料次级发射性能

利用溶胶-凝胶法制备稀土氧化物掺杂钼粉,随后利用放电等离子体烧结法将该粉末制备成稀土钼金属陶瓷材料,利用SEM、DTA、电子发射性能测试等方法对样品次级电子发射性能进行研究.结果表明:稀土氧化物均匀掺杂和组织的细化有利于材料发射性能提高,但不能降低其激活温度;经过高温氢气处理,样品的真空激活温度大幅降低,发射系数提高;稀土氧化物易吸收水分和气体的特性导致后续真空激活过程中阴极表层钼氧化,而高温氢气处理消除了样品中多余的水分和气体,保持了样品中金属与氧化物的相间分布状态,这是样品在活化前后发射性能发生变化的主要原因.     

SPS制备难熔钼及钼钽溅射靶材的组织和性能

采用放电等离子体烧结(SPS)技术,在烧结温度1400～1600℃、保温时间5 min及压力30 MPa下制备纯钼和两种不同成分(Mo-3％Ta、Mo-5％Ta,质量分数)的钼钽靶材.研究了烧结样品的物相、显微形貌、致密度、硬度及热导率,并与商业纯钼靶材的性能进行对比.结果 表明:SPS烧结的钼靶材晶粒尺寸远小于商业纯...     

CoSb3纳米晶块体热电材料的制备研究

采用机械合金化．放电等离子烧结工艺(MA-SPS)，在200℃～600℃之间制备了纳米晶CoSb3合金块体材料。采用XRD和TEM对材料的相组成和微观组织进行了测试分析。实验结果表明，烧结前粉末为高能球磨得到的平均晶粒尺寸为20nm～35nm的纳米晶CoSb3粉末，SPS烧结后CoSb3合金块体的平均晶粒尺寸小于100nm，其致密度达到了91．3％～99．6％。CoSb3块体的晶粒尺寸随着烧结温度的降低而减小，而密度却随着烧结温度的升高而增加。CoSb3纳米晶块体热电材料的制备机理是MA使粉末晶粒细化到纳米级，放电等离子烧结的快速、短时、低温和特殊烧结机理显著抑制了烧结时的晶粒长大。     

放电等离子技术快速烧结纳米WC-10％Co-0．8％VC硬质合金

研究了放电等离子烧结(SPS)纳米WC-10%Co-0.8%VC硬质合金的致密化机理,并与真空烧结的制品显微组织及性能进行对比。SPS特殊的直流脉冲电压使烧结中蒸发-凝固、塑性流动、表面扩散等过程得到加强,使制品在低温下快速致密,有效抑制了晶粒的长大,如在1200℃烧结5min的制品平均晶粒尺寸<100nm。与真空烧结相比,SPS可以使制品在低温、短时间内获得高密度、高硬度,如1300℃烧结3min,制品相对密度达97.7%,HV30比相同烧结温度下真空烧结30min的相对密度92.8%的制品高近16.4%。SPS烧结温度降低至1200℃,虽然密度有所降低,但HV30和KIC分别提高了15.4%和12.2%。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。