Co-Ni-xNiFe2O4惰性阳极的电导率及耐腐蚀性能

采用冷等静压-烧结的方法制备了铝电解用Co-Ni-xNiFe2O4(x=5%,10%,15%,20%,质量分数,下同)金属基惰性阳极,并对试样的导电性和抗腐蚀性进行了研究.结果表明阳极试样的电导率随NiFe2O4含量的增加和温度的升高而降低,在900℃时惰性阳极47.5Co 47.5Ni 5.0NiFe2O4和42.5Co 42.5Ni 15.0NiFe2O4的电导率分别为550 S·cm-1和300 S·cm-1.SEM照片表明试样的抗腐蚀性随着NiFe2O4含量的增加而增强.由于氧化作用和铝热反应,电解极化腐蚀速率要比静态腐蚀速率大.     

铝电解用NiFe2O4-10NiO基金属陶瓷惰性阳极的耐腐蚀性能

制备铝电解用NiFe2O4-10NiO基金属陶瓷惰性阳极,并在实验室电解槽中考察其电解腐蚀性能。结果表明,电解过程中虽然惰性阳极在960°C熔盐电解质中表现出优异的耐腐蚀性能,但采用XRD、SEM/EDX和金相分析其物相组成和微观结构后发现,电解后阳极中的金属相发生了优先腐蚀,在阳极表面产生大量孔洞。NiFe2O4相中的 Fe 元素的优先溶解可能导致 NiFe2O4晶粒的不均匀腐蚀。溶解在电解液中的 Al2O3与阳极中的 NiO 或FeO 发生反应生成的 NiFe2O4-NiAl2O4-FeAl2O4相对 NiO 相的吞并以及体积膨胀,阳极表面形成致密的NiFe2O4-NiAl2O4-FeAl2O4保护层。因此,致密的NiFe2O4-NiAl2O4-FeAl2O4保护层可以阻挡阳极表面金属相的损失和陶瓷相的腐蚀。     

Yb_2O_3掺杂对15(20Ni-Cu)/(NiFe_2O_4-10NiO)金属陶瓷性能的影响

采用冷压-烧结技术制备NiFe2O4-10NiO基金属陶瓷材料;通过对烧结体的显微结构和物相组成、电导率、电解试样的表层形貌、电解质和阴极铝的杂质增量等的分析检测,研究Yb2O3掺杂对15(20Ni-Cu)/NiFe2O4-10NiO金属陶瓷致密度、导电率和耐腐蚀性能的影响。结果表明:1 300℃烧结的0.5%Yb2O3-15(20Ni-Cu)/(NiFe2O4-10NiO)金属陶瓷具有较好的性能,相对密度为98.53%,960℃时的电导率为53.06 S/cm,电解腐蚀后金属腐蚀层厚度为20~30μm,总杂质增量为0.079 g。     

氧化银对惰性阳极耐熔盐腐蚀性能的影响

以Fe2O3、NiO和Ag2O为主要原料,采用固相烧结工艺制备了NiFe2O4/Ag惰性阳极,用X射线衍射和扫描电子显微镜对材料的组成和微观结构进行了研究,采用水冷法测量了样品的抗热震性,并测量了其在冰晶石熔盐中的电解腐蚀速率。结果表明:Ag2O的加入提高了样品的抗热震性,降低了惰性阳极试样在冰晶石熔盐中的电解腐蚀速率,当Ag2O含量为6%时,试样的电解腐蚀速率最低。     

氧化铝、硝酸铝复合YSZ的烧结性能、电性能及力学性能研究

分别以Al2O3、Al(NO3)3为铝源与氧化钇稳定氧化锆（YSZ）机械混合,经干压技术和高温烧结制得YSZ/Al2O3复合材料。通过扫描电子显微镜、电化学交流阻抗谱和三点弯曲测试等方法对样品进行分析,研究了不同铝源和添加量对YSZ电解质烧结性能、电导率及力学性能的影响。结果表明：适量的Al2O3或Al(NO3)3复合均能够促进YSZ的烧结,提高其电导率和弯曲强度;Al2O3作铝源的复合样品的烧结性能和电导率优于Al(NO3)3铝源的,但其强度低于同比例Al(NO3)3铝源。其中,加入0.5 wt.%Al2O3时,所制备的复合电解质经1350 ℃烧结10 h后的相对密度为98.8%;800 ℃时的电导率达0.0703 S·cm-1。基于该材料制备的电解质支撑型单元电池在800 ℃时以氢气为燃料的最大功率密度为308 mW·cm-2,高于纯YSZ电解质电池的,并表现出良好的稳定性。     

基于GA-BP的NiFe2O4基金属陶瓷阳极优化设计

采用BP神经网络对铝电解NiFe2O4基金属陶瓷惰性阳极的电解腐蚀过程进行了系统辨识。建立了以Al2O3质量浓度、电解温度、分子比、面积比和电流密度为输入,腐蚀率为输出的网络模型。在材料的设计中,采用了GA-BP优化方法,BP网络参与GA迭代计算时对个体的评价。应用结果表明,NiFe2O4基金属陶瓷惰性阳极的电解腐蚀率预测结果与实测值吻合;优化设计的结果与实验值很接近。     

[emim]OTf离子液体中镀铌不锈钢双极板在PEMFC环境中的电化学行为

以对水和空气稳定的离子液体1-乙基-3-甲基咪唑三氟甲磺酸盐([emim]OTf)为电解质,在不锈钢双极板表面电沉积铌,并在模拟质子交换膜燃料电池(PEMFC)环境中研究了镀铌改性的双极板的电化学行为。结果表明,铌镀层以孤岛的形式均匀分布在不锈钢表面,其高度在100nm以内。XPS、XRD测试结果表明,镀铌不锈钢表面生成化学惰性良好的NbO、Nb2O5。在模拟阳极环境中,镀铌不锈钢的腐蚀电位比不锈钢的腐蚀电位提高530mV;恒电位-0.1V时电流密度从4.5315μA·cm-2降低到2.7554μA·cm-2;在模拟阴极环境中,镀铌不锈钢的腐蚀电位比不锈钢提高430mV,恒定电位0.6V时电流密度从4.4008μA·cm-2降低到0.0028μA·cm-2。电化学测试结果表明,镀铌不锈钢的电化学极化性能得到改善,反应电阻增大,提高了耐蚀性能。     

小型金属陶瓷惰性阳极的低温铝电解实验

本实验采用自行研制的小型镍铁尖晶石基惰性阳极 (直径 43mm)与冰晶石 -氧化铝系低温电解质 ,在 85 0℃下进行电解实验 ,保持阳极电流密度lA/cm2 ,实验共进行 11小时 ,得到了少量的金属铝。实验结果表明 ,在此电解温度下 ,构成惰性阳极的金属陶瓷材料抗电解质腐蚀的能力较强 ;阳极在实验后出现的裂纹说明材料的抗热震性有待进一步提高 ,而且本实验中惰性阳极与金属导杆的连接方式也需更深入研究。     

ZnFe2O4基材料在NaF-AlF3-Al2O3熔盐中的腐蚀

采用锌铁尖晶石材料作为铝电解惰性阳极,考察了这种阳极在 熔盐中的腐蚀 行为,阳极电流密度为0～2.5A/cm2．实验结果表明,锌铁尖晶石材料在阳极极化条件下的NaF-AlF3-Al2O3熔盐中具有很好的耐腐蚀性能．在低电流密度下,阳极材料的腐蚀速度随电流密度的增大而增大,最高的腐蚀速度出现于0.5～0.75A/cm2．此后,腐蚀速度随电流密度的增大而降低．实验证明,高阳极电流密度(＞1.5A/cm2)、熔盐电解质中保持高Al2O3含量和低NaF/AlF3摩尔比,对降低阳极材料的腐蚀速度有利,这也将是惰性阳极应用的重要条件．     

交流阻抗谱在炉渣电导率测定中的应用

利用电化学交流阻抗谱法对CaO SiO2 Al2 O3 FeOx 渣系的电导进行了研究。结果表明 ,随着渣相中氧化亚铁浓度的增大 ,温度系数逐渐减小 ;三价铁离子对电导率的影响随渣相中铁氧化物浓度的增大而显著 ,但当铁氧化物浓度小于 2 0 % (摩尔分数 )时 ,三价铁离子对电导率的影响较小 ;CaO SiO2 Al2 O3 Fe2 O3 渣系中存在电子导电 ,电子电导率约为 10 -3 ～ 10 -2 S·cm-1。     

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。