粉末-凝胶法制备铌酸锶钡/钛酸锶钡陶瓷及其表征(英文)

钛酸锶钡(SrxBa1-xTiO3, BST)和铌酸锶钡(SrxBa1-xNb2O6, 0.25≤x≤0.75, SBN)是重要的铁电材料,具有优良的热电、介电和红外快速响应性能。使用廉价的 Nb2O5粉末,应用粉末-溶胶工艺合成铌酸锶钡/钛酸锶钡复相陶瓷(SBN/SBT)。XRD 结果表明:钨青铜相和钙钛矿相共存于体系之中。复相陶瓷形成过程中形成了 TiO2、BaNb2O6(BN)、SrNb2O6(SN)等中间相。干凝胶在800°C下预烧3h,X射线光电子能谱(XPS)分析表明,随着体系组分的变化,Ti元素只存在+4价的化合态,而Nb元素的价态和体系的组分有关。     

钡硅铝合金中硅、钡、铝含量分析测定

钡硅铝合金是近年来开发使用的一种新型冶炼脱氧剂、脱磷剂,其价格低廉,使用效果好,被广泛用于冶炼工业中,本文介绍一种分析测定钡硅铝合金中硅、钡、铝含量的方法。     

硅钡孕育剂中钙、钡的测定

硅钡合金是一种新的炼钢脱氧剂和铸造用孕育剂,并且还具有很好地脱硫、脱磷能力,能改变钢铁中非金属夹杂物的性能,可球化和细化钢铁中的夹杂物,降低非金属夹杂物的有害作用.对硅钡合金孕育剂和含钡球化剂中钙钡含量的准确测定,无论对生产工艺和产品质量都十分重要.     

球化剂中钡的测定

用硝酸、氢氟酸在塑料杯中溶样,以硫酸钡沉淀法快速测定球化剂中的钡量。     

低钙钡的硅钡孕育剂

介绍一种低钙钡的硅钡孕育剂，其Si、Ba、Ca、Al组元配比合理，既具有强的石墨化作用，又具有良好的脱氧性能，因此能延缓孕育衰退时间，防止铸件局部白口，使铸件硬度均匀。用于铸态球铁，可以获得足量的铁素体；用于灰铸铁，可以稳定获得A型石墨，石墨长度达4～6级，力学性能提高。     

硅钡合金与75硅铁孕育效果比较

用硅钡合金与７５硅铁比较，研究了两种孕育剂对灰铸铁白口趋向，断面敏感性以及强度性能等的影响。结果表明：硅钡合金较７５硅铁具有失效、白口趋向小、易获得Ａ型石墨、断面敏感性小等优点，适合处理高牌号薄壁灰铸铁件。     

钛表面原位生长钛酸锶钡陶瓷膜

用微等离子体氧化法在钛金属基体上制备钛酸锶钡(BST)陶瓷膜。讨论了Ba／Sr的摩尔比对陶瓷膜相组成的影响，并利用X射线衍射(XRD)、扫描电镜(SEM)和电子探针(EPMA)等测试手段对陶瓷膜的相组成、形貌特征和元素分布进行了分析。结果表明，在所选定的工艺参数条件下可得到钛酸锶钡陶瓷膜，膜层由接近于纯相的钛酸锶钡构成，表面相对较为平整，各元素在陶瓷膜层中分布均匀，无梯度变化。     

硅钡合金孕育处理KTH350—10的试验研究

用硅钡合金作孕育剂，并与相同条件下用铝孕育处理可锻铸铁进行比较，研究了钡对第一和第二阶段石墨化的影响。组织观察和性能测试结果表明：钡可促进第一和第二阶段石墨化过程，有利于获得铁素体基体；经硅钡孕育处理后铸铁组织中絮状石墨的外形趋于团球化，石墨的尺寸也有所减小，强度和塑性都有不同程度的提高。     

溶胶-凝胶法制备纳米钡铁氧体磁性能

以柠檬酸为络合剂络合硝酸盐中的Fe3+和Ba2+离子,在铁钡摩尔比分别为10～13条件下利用溶胶-凝胶自蔓延燃烧法制备了M型纳米钡铁氧体粉末样品,利用X射线衍射及场发射扫描电子显微镜对所制钡铁氧体样品的结构与形貌进行表征。结果显示:钡铁氧体的物相组成与铁钡摩尔比关系密切。当Fe/Ba=12时,在800℃煅烧180min条件下制备的钡铁氧体样品的磁性能得到优化,磁学参数如下:饱和磁化强度Ms(2T)=61.555(A·m2)·kg-1、剩余磁化强度Mr=32.216(A·m2)·kg-1和高的矫顽力Hc=5822.2×79.6A/m。同时利用Kelly-Hankel(δM)曲线揭示出钡铁氧体纳米颗粒之间的相互作用。     

放电等离子烧结制备钛酸锶钡陶瓷

以BaCO3,SrCO3,TiO2为原料,采用传统的固相反应方法制备BST粉体,采用传统烧结方法和放电等离子烧结(SPS)方法制备了钛酸锶钡(Ba0.5Sr0.5TiO3)陶瓷.并对两种方法制备的钛酸锶钡陶瓷的做了比较.研究了SPS烧结对BST陶瓷的微观结构以及介电性能的影响.结果表明SPS方法使钛酸锶钡陶瓷的晶粒尺寸降低,介电常数降低,居里温度略有降低,由于SPS烧结速度快、时间短,烧结体内部微区成分起伏较高,立方-四方相变弥散性增加.     

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。