溶胶-凝胶法制备锶铁氧体纳米粉体的研究

掺杂锶铁氧体(SrFe12O19)作为磁性材料和微波材料具有广泛应用.采用以柠檬酸作金属离子络合剂的溶胶-凝胶法合成组份分别为SrTixCoxFe(12-2x)O19,SrNixCoxFe(12-2x)O19,和SrZnxCoxFe(12-2x)O19(x=0～1.5 mol%)的溶胶-凝胶,加热浓缩至自燃,制得铁氧体纳米粉体的先驱粉体,再经900～1100℃烧结制备出铁氧体粉体产物.用XRD研究产物的晶相及其晶粒的平均大小;用TEM和SEM观察粉体形貌.研究结果表明:当Ti/Co共掺时,锶铁氧体的晶相没有变化,相粒平均大小30～50 nm;当Ni/Co或Zn/Co共掺时,锶铁氧体晶相的含量随掺杂量x的增大而减小,并出现Fe3O4晶相和α-Fe2O3晶相杂质;当共掺量为1.5 mol%时,所得粉体均为Fe3O4晶相、晶粒平均尺寸约40 nm的纳米粉体.     

Gd~(3+)/Ga~(3+)共掺杂石榴石型Yb_3Al_5O_(12)材料的制备及热物理性能

采用柠檬酸溶胶-凝胶法制备了Gd~(3+)/Ga~(3+)双掺杂的石榴石型Yb_(3-x)Gd_xAl_(5-x)Ga_xO_(12)固溶体陶瓷材料(x=0,0.1,0.2,0.3,0.4,0.5;YGAGO)。结果表明:Gd~(3+)/Ga~(3+)共掺杂的YGAGO保持了石榴石相结构;随着Gd~(3+)/Ga~(3+)掺杂量的增加,固溶体样品的衍射峰位整体向低角度偏移;SEM形貌表明Yb_3Al_5O_(12)材料的微观形貌由纳米级晶粒和高密度晶界构成;大离子Gd~(3+)与Ga~(3+)分别对Yb_3Al_5O_(12)晶体结构中Yb~(3+)与Al~(3+)晶格位的取代,不仅因引入的点缺陷明显降低了材料的热导率,同时还造成石榴石型Yb_3Al_5O_(12)晶体结构的松弛,利于热膨胀系数的提高。随着Gd~(3+)/Ga~(3+)掺杂量的增加,晶体中点缺陷浓度不断升高,声子平均自由程不断减小,使得YGAGO的热导率在x=0.5时达到最低值(λ=1.67W/(m·K),T=1273 K),热膨胀系数达到最高值(α_1=11.71×10~(-6)K~(-1),T=1273 K)。     

Gd~(3+)掺杂La_2Mo_2O_9的相稳定性及热导率

La_2Mo_2O_9具有极低的热导率,但其在580℃左右会发生α-β相变,严重影响其性能和应用。本实验以Gd_203掺杂La_2Mo_2O_9制备了一系列La_(2-x)Gd_xMo_2O_9 (x=0.0～0.5)固溶体,研究了掺杂Gd~(3+)对La_2Mo_2O_9相稳定性和热导率的影响。结果表明,随着Gd~(3+)掺杂量的增加,相变得到有效抑制,当x≥0.2时样品以β相存在。样品的热导率随Gd~(3+)掺杂量的增加先减小后增加,室温下在x=0.2时达到最低,此后缓慢上升,但所有样品的热导率均小于1 W/(m·K)。     

强磁场下共沉淀-相转化法制备纳米鈷铁氧体颗粒

在强磁场下采用共沉淀-相转化法制备出了纳米级的钴铁氧体颗粒;通过SEM,XRD和VSM等分析手段,考察了磁感应强度对纳米钴铁氧体形貌及性能的影响规律.结果表明:无磁场及磁感应强度小于2T时,纳米钴铁氧体颗粒为球形;当磁感应强度大于、等于4 T时,棒状纳米钴铁氧体开始形成.随着磁感应强度的增大,棒状纳米颗粒数量增加,纳米钴铁氧体的晶化程度提高,磁性能(Mr,Ms,Mr/Ms)也大幅度提高.与无磁场相比, 10 T时制备的纳米钴铁氧体颗粒的剩余磁化强度Mr增加近15倍,饱和磁化强度Ms提高约1.44倍.从磁聚合定向生长和临界磁畴角度分析了强磁场影响共沉淀-相转化法制备的纳米钴铁氧体的形貌、晶化程度及磁性变化的机理.     

Pr掺杂量对Ce1-xPrxO2晶体结构的影响

通过改变Pr掺杂量,即Ce1-xPrxO2中的x值(0.01≤x≤0.50),以Ce(NO3)3·6H2O,Pr6O11为主要原料,用低温燃烧合成法在247℃～291℃点火,合成了具有纳米晶粒的粉体,其晶粒尺寸在12nm～41nm之间.采用DSC,XRD,SEM测试分析手段,研究了Pr掺杂量对其结构的影响.结果表明所合成粉体为萤石型Ce1-xPrxO2固溶体,不同的x值对反应物着火温度、产物晶型结构及形貌和晶粒尺寸均有影响.改变x值对反应物点火温度影响不大,产物晶型结构均未发生变化,为均一的萤石型结构.掺杂后Ce1-xPrxO2粉体的晶胞参数与未掺杂的CeO2相比有不同程度的减小,说明Pr进入CeO2晶格形成Ce1-xPrxO2置换固溶体.改变Pr掺杂量,颜料晶粒粒度随x值的增大而减小.     

溶胶-凝胶法制备SmZn掺杂纳米钡铁氧体磁性能

以柠檬酸为络合剂,利用溶胶-凝胶自蔓延燃烧法制备Sm及SmZn掺杂的M型纳米钡铁氧体(Ba1-xSmxFe12O19及Ba1-xSmxFe12-xZnxO19,x=0～0.6)粉末样品,进而利用X射线衍射仪对所制钡铁氧体样品的结构进行表征、分析。结果显示,钡铁氧体的物相组成与掺杂含量关系密切:当掺杂量x超过0.2时,在制备的样品中会出现α-Fe2O3及SmFeO3等杂相,对样品的磁性能产生不利的影响。由于受到超精细场、磁稀释及自旋倾斜的影响,掺杂Sm3+后,钡铁氧体的饱和磁化强度(Ms)先增大后减小,而矫顽力(Hc)则随着掺杂含量的增加而增大。掺杂Zn2+后,磁性能的研究结论显示Zn2+替代4f2晶位的Fe3+,使制备的钡铁氧体的Ms有所升高,而Hc下降。     

Sm~(3+)掺杂Co_2Z型铁氧体的组织结构和吸波性能

采用普通陶瓷工艺制备了Sm~(3+)掺杂的Co_2Z型平面六角铁氧体,研究了Sm~(3+)掺杂Co_2Z型铁氧体材料的组织结构和吸波性能。结果表明,掺杂一定量Sm~(3+)的铁氧体相结构仍以Co_2Z型六角晶系相为主相,但出现了呈颗粒状弥散分布的富Sm相。掺杂Sm~(3+)样品的吸波性能明显优于未掺杂Sm~(3+)样品,在频率为6.3 GHz时,其最大反射损耗可达到-20 d B,耗损大于10 d B的频带带宽为5 GHz,具有较宽的吸收频带。吸波涂层的附着强度均大于10 MPa,具有良好的力学性能。     

微量Al3+掺杂对钴铁氧体磁和电性能的影响

采用固相反应法,制备了Al3+掺杂的钴铁氧体CoFe2xAlxO4(x=0.000,0.012,0.023,0.035,0.069,0.092)系列样品。从XRD的结果分析,钴铁氧体磁性离子间跃迁距离随x的增加而降低,表明Al3+掺杂进入了尖晶石晶格,拉曼光谱的结果验证了这一结论。当x≤0.069,随着x的增大,钴铁氧体直流电阻率增加约2个数量级;当x>0.069,直流电阻率开始下降。微量Al3+掺杂后钴铁氧体的矫顽力略有降低,但饱和磁化强度增加。最大磁致伸缩量比未掺杂Al3+的低,但磁致伸缩系数增加。     

锌-铜混合纳米铁氧体催化活性对草酸镧分解动力学的影响（英文）

采用溶胶-凝胶法合成纳米结构锌-铜混合铁氧体。XRD分析表明,不同组分Zn_((1-x))Cu_xFe_2O_4(x=0.0,0.25,0.50,0.75)铁氧体为单相反尖晶石结构。随着铜含量的增加,晶粒尺寸增大。采用SEM表征样品的表面形貌,结果表明粒子为多孔结构。采用FT-IR和TEM分析所制备的样品。当x=0.75及催化剂为5%(摩尔分数)时,速率常数k值最高,这归因于高铜含量以及除Cu~(2+)-Cu~+和Fe~(3+)-Fe~(2+)外,由于电荷相互作用而产生的混合位Cu~(2+)-Fe~+和/或Cu~+-Fe~(2+)离子对。混合氧化物活性增加归因于通过新离子产生而增大的活性位置浓度。随着锌含量的增加,颗粒尺寸增大。铁氧体粉末催化活性的变化是因为催化活性组分价态的变化,这能氧化从草酸镧中释放的一氧化碳。     

纳米晶La1-xSrxMnO3的溶胶-凝胶法合成及表征

采用溶胶-凝胶法制备了纳米晶La1-xSrxMnOa,运用场发射扫描电镜(FESEM)、X射线衍射分析仪(XRD)和红外光谱分析仪(FTIR)等手段对掺杂样品的微结构、形貌等进行了分析.结果表明:当掺杂浓度x为0～0.5时,所制备的粉体为单一钙钛矿相;不同的掺杂浓度和热处理温度会使样品的晶格参数发生显著变化;La1-xSrxMnO3纳米晶粒子尺寸为10～80 nm;掺杂浓度和热处理条件对样品粒子尺寸产生很大的影响,在相同的热处理条件下,掺杂浓度高的样品晶粒尺寸较小,且掺杂浓度的增大会引起晶粒特征红外振动的红移和宽化现象.     

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。