浸渍型钡钨阴极用高性能铝酸盐研究

采用固相反应法和化学液相共沉淀法合成钡钨阴极电子发射材料铝酸盐.XRD,TG-DSC分析表明:液相共沉淀法最佳合成温度为1100℃,比高温固相反应法的合成温度降低了150℃;产物主晶相为Ba5CaAl4O12合成的盐制备成阴极,化学液相共沉淀法的脉冲发射电流密度25.3865 A/cm2,是固相反应法的2倍;平均蒸散速率为Vevap=5.04×10-8(g·cm-2)·s-1.液相法合成的铝酸盐满足了钡钨阴极的使用要求.     

溶胶-凝胶法制备稀土钼超细粉末

采用溶胶-凝胶(Sol-Gel)法成功制备了(La,Y)2O3-Mo超细粉末,利用XRD、TEM对还原后粉末相结构、形貌、粒度等进行了分析.结果表明:900℃二次还原后,钼以单质形式存在,稀土以氧化物形式存在.TEM观察表明,还原后稀土钼粉末粒径在70 nm左右,粒度分析表明粉末D(n,50)=80 nm.红外光谱(FT-IR)分析表明,镧和钇通过氧与钼键合,削弱Mo=O键,使稀土钼复合氧化物可还原性增强.能谱分析显示烧结体中稀土元素分布均匀.     

热处理温度对YAG粉体及其多孔陶瓷合成的影响

采用共沉淀法合成的钇铝石榴石(YAG)粉体真空烧结制备多孔陶瓷,通过分析讨论表明,YAG前驱体中绝大部分吸附水蒸发以及绝大部分Al(OH)3和Y(OH)3的分解分别转变成Al2O3和Y2O3失去离子水而产生的失重出现在600℃以下完成。YAG前驱体在1100℃下煅烧后,大量YAG晶相已经形成,而且具有完整的晶型。升高煅烧温度对晶粒尺寸和晶粒形貌的影响显著,也说明YAG粉体颗粒粒径和形貌对最终煅烧温度非常敏感。采用真空烧结技术,成功制备了孔结构均匀规整,大部分微孔径处于5μm左右,且外形保持良好的YAG多孔陶瓷,综合考虑性价比,确定YAG多孔陶瓷的烧结温度为1500℃较为适宜。     

Bi-2212前驱粉末的制备

采用共沉淀法制备了不同化学计量比的Bi-2212前驱粉末,系统地研究了空气、纯氧和氩氧混合气氛对粉末相组成、粒度和碳含量的影响.通过对成相烧结过程相变规律的研究提出了对最终装管前粉末中特征相(如Bi-2212,2201,14∶24AEC等)的控制方法,得到了主相纯度高、各相分布均匀、粒度适宜和碳含量较低的前驱粉末.     

压力对热压烧结制备Mo-20Cu复合材料的影响

以仲钼酸铵(NH_4)_6Mo_7O_(24)·4H_2O、硝酸铜Cu(NO_3)_2·3H_2O、甘氨酸和乙二胺为原料采用甘氨酸硝酸盐(GNP)法制备前驱体粉末,再经过700℃氢气还原得到Mo-20Cu复合粉末,经压制后在1150℃于不同压力下进行热压烧结,研究不同压力对钼铜合金烧结体性能的影响。结果表明:GNP-H_2还原法可以制备出平均晶粒尺寸为70~80 nm且大小均匀、分散性优异的球形Mo-Cu纳米复合粉末,经加压烧结致密度达到99.7%,各相组织分布均匀,且在一定的范围内压力增大可以使烧结体硬度、电导率和热导率有所增大。     

溶胶-凝胶法制备纳米复合Mo-La2O3阴极

采用溶胶-凝胶法制备出平均粒径小于60nm的Mo-La2O3粉末。将所制备出的纳米复合Mo-La2O3粉末经冷压、热压工艺后烧结成纳米复合Mo-La2O3阴极。发现用溶胶-凝胶法制备的Mo-La2O3阴极组织均匀，晶粒细小，La2O3粒子晶粒大多在100nm以下，且弥散分布在晶内及晶界上。在燃弧实验中发现用溶胶．凝胶法制备的纳米复合Mo-La2O3阴极击穿点分布存阴极表面的大部分面积上，烧蚀坑浅，且击穿优先发生在La2O3相上。     

Y2O3对SPS烧结纳米AlN粉末的影响

利用低温燃烧法合成出了平均粒度为100 nm的AlN粉末,将合成的粉末采用放电等离子(SPS)技术进行低温强化烧结,研究Y2O3对烧结过程以及烧结试样特性的影响.XRD进行物相分析,SEM观察断口形貌,排水法测烧结试样的密度,激光闪光法测烧结试样的热导率.实验表明采用低温燃烧法合成出的AlN粉末具有非常好的烧结性能,采用SPS烧结技术,40 MPa压力下,在1600℃保温4 min,就能得到非常致密的AlN陶瓷;Y2O3对纳米AlN粉末在SPS低温强化烧结过程仍有促进作用,使试样在更低的温度下烧结致密,并且晶粒更细小,从而热导率也较低;加入Y2O3的烧结试样晶界强度增加,断口中有较多的穿晶断裂形式,而不加入Y2O3的烧结试样主要以沿晶形式断裂.     

共沉淀法制备Sr4Al14O25:Eu2+,Dy3+长余辉发光材料

首先利用共沉淀法制备了发光材料前驱体,然后以石墨为还原剂、1280℃保温2 h烧结合成Sr4Al14O25Eu2+,Dy3+长余辉发光材料.通过XRD、荧光光谱分析方法,研究了助熔剂、稀土离子、烧结制度等对发光材料物相结构和发光性能的影响.结果表明发光粉体的主晶相为Sr4Al14O25,属斜方晶系,晶胞参数为a=2.480 nm,b=0.850nm,c=0.489nm;其激发光谱为一主峰波长在398 nm和356 nm的连续谱,包括紫外线和可见光;发射光谱为一主峰波长为491 nm的宽带谱,经自然光、紫外光照射后可发出明亮的蓝绿色光.     

粉末粒度对二硅酸锂玻璃陶瓷烧结行为、微观结构和弯曲强度的影响(英文)

采用热压烧结技术成功制备了SiO2-Li2O-P2O5-ZrO2-Al2O3-K2O-CeO系二硅酸锂玻璃陶瓷。研究了不同粉体粒度对其烧结行为、相组成、微观结构和弯曲强度的影响。结果表明,不同粉体粒度制备的玻璃陶瓷晶相组成类似,主晶相均为Li2Si2O5晶体;微观形貌均为互锁的Li2Si2O5棒状晶粒,但Li2Si2O5晶体的晶粒尺寸及分布随粉末粒度变化有所不同。当玻璃粉末粒度为14μm时,烧结出的二硅酸锂玻璃陶瓷晶粒尺寸合适,密度较高,三点弯曲强度最高,可达354±17 MPa;且透光性能良好,与医用EMAX材料接近。     

微波烧结制备Y_(1.8)La_(0.2)O_3透明陶瓷

以Y2O3(4N)和La2O3(3N)为原料,采用化学共沉淀方法制备Y1.8La0.2O3粉体,粉体压制后氢气氛下分别采用常规烧结和微波烧结制备Y1.8La0.2O3透明陶瓷。结果表明:900℃煅烧2 h制备的粉体近似球形,粒径约40~60 nm,采用氢气氛下1450℃微波烧结30 min下,可以获得致密性较高、晶粒细小、韧性好、透光率较高的Y1.8La0.2O3透明陶瓷。与常规气氛烧结相比,微波气氛烧结温度明显降低,时间显著减少,且晶粒更细小,其断裂形式由常规烧结时的沿晶断裂逐步过渡到穿晶断裂。     

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).     

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.     

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.     

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。