化学还原-球磨法制备Sn-Co-C锂离子电池负极材料的性能

采用化学还原法得到纳米级Sn-Co粉末,再经过与硬碳粉混合球磨得到Sn-Co-C复合粉体.能谱测试表明,样品Sn、Co、C原子分数分别为3.89%、1.47%、94.64%.SEM观察显示,50～100 nm锡钴微粒附着在片状的硬碳颗粒上.复合粉体与锂片组成模拟电池,首次放电比容量为558.4 mAh/g,首次充电比容量为338.5 mAh/g.30次循环后,放电比容量保持在348.2 mAh/g,保持率为62.4%;充电比容量保持在335.4 mAh/g,保持率为99.1%.充放电比容量较硬碳提高3倍左右.由分析放电曲线可知,第一次放电后在电极表面形成了固体电解质界面膜(SEI)膜,循环一次后该膜消失.     

共沉积Co3O4-石墨负极材料及其在锂离子电池中的循环性能

在0.5 mol/L Co(NO3)2溶液中添加石墨粉,在铜箔集流体的表面电化学共沉积前驱体薄膜,然后在245℃真空热处理使之形成Co3O4-石墨粉复合负极材料.研究了共沉积Co3O4-石墨负极材料在锂离子电池中的循环性能.XRD分析和SEM观察表明,该电极材料结构由蜂窝状的Co3O4包覆石墨粉复合而成,Co3O4晶粒尺寸为0.7～2.2 nm.0.5C充放电倍率测试表明,在0.5 mol/L Co(NO3)2电解液中添加5%石墨粉形成的Co3O4-石墨复合材料负极的性能最好,该电极的初始充电比容量为872.7 mA·h/g,第20周循环的充电比容量为732.7mA·h/g,第50周循环的充电比容量为545.2 mA·h/g,比容量保持率分别为83.96%和62.47%;而纯Co3O4电极的初始充电比容量为665.3 mA·h/g,经过20次循环后充电比容量为407.9 mA·h/g,第50周循环的充电比容量为124.5mA·h/g,保持率仅分别为61.31%和18.31%.     

模板-电沉积法制备锡钴碳锂离子电池负极材料

以柠檬酸、EDTA为络合剂,CoCl2、SnCl4为主盐的基础电解液,首先在基础电解液中加入硬碳制备Sn-Co-C复合电极材料.SEM观察表明获得的Sn-Co-C复合电极表面为镶嵌C小颗粒的菜花状结构,C物理夹杂在Sn-Co合金中,硬碳的引入使得电极材料的循环性能得到提高,首次充放电比容量分别为563.8和763.2 mA·h/g,而经过50次循环后充放电比容量分别为400.3和416.2 mA·h/g.然后,在基础电解液中加入甲酸,在聚苯乙烯微球(PS)为模板的辅助下制备孔状结构Sn-Co-C复合材料.获得的材料中Sn、Co、C的原子比分别为36.87%,2.82%,20.61%.充放电测试结果表明,孔状结构的Sn-Co-C电极表现出更好的循环性能,首次充放电比容量分别为821.1和946.6 mA·h/g,循环第50次后充放电比容量为401和457.6 mA·h/g,循环第60次后充放电比容量为349.7和401.5 mA·h/g,放电比容量达到400 mA·h/g以上.     

Synthesis and Electrochemical Performance of Li2MnSiO4/C as Cathode Materials with High Capacity for Lithium ion Batteries

在三元液相体系中合成了球形Li2MnSiO4/C 复合正极材料,XRD、SEM和电化学性能测试对材料进行了表征。XRD测试表明Li2MnSiO4 具有正交结构,对应Pmn21空间群。SEM显示所得样品为小于1 μm的球形颗粒。将Li2MnSiO4/C 组装成扣式电池进行电化学测试的结果表明,在1.5~4.6 V,该样品的初始充电容量达310 mAh/g,放电容量高至 286 mAh/g,为理论比容量的85.9%;循环30 次后放电比容量为142 mAh/g。     

高容量锂离子电池Li_2MnSiO_4/C正极材料的合成和电化学性能研究（英文）

在三元液相体系中合成了球形Li_2MnSiO_4/C复合正极材料,XRD、SEM和电化学性能测试对材料进行了表征。XRD测试表明Li_2MnSiO_4具有正交结构,对应Pmn21空间群。SEM显示所得样品为小于1μm的球形颗粒。将Li_2MnSiO_4/C组装成扣式电池进行电化学测试的结果表明,在1.5~4.6 V,该样品的初始充电容量达310 mAh/g,放电容量高至286 mAh/g,为理论比容量的85.9%;循环30次后放电比容量为142 mAh/g。     

锂离子电池Sn薄膜电极厚度对其电化学性能的影响

用电沉积方法在铜集流体上分别制备出不同厚度(2,0.5,0.25,0.12μm)的锡薄膜电极。用扫描电镜观察其表面形貌、以充放电实验比较其性能。结果表明,减小Sn薄膜厚度可改善电极的循环性能,但首次容量损失也增大。0.5μm厚的Sn薄膜具有最高的放电容量和较好的循环稳定性;其首次放电比容量为749mAh/g,40次循环时放电比容量仍保持578mAh/g。     

电沉积法制备Sn-Co-C锂离子电池负极材料

分别采用柠檬酸和乙二胺四乙酸(EDTA)作为络合剂在CoCl2、SnCl4溶液中用电沉积方法制备Sn-Co合金电极,然后在相同条件下在镀液中加入硬碳制备Sn-Co-C复合电极.充放电测试结果显示,EDTA作为络合剂时镀层循环性能明显好于柠檬酸,且比容量也较高.Sn-Co合金电极循环30次比容量保持率达91.6%,加入硬碳的Sn-Co-C复合电极比容量及循环性能较之Sn-Co合金电极都有了较大提高.电子探针结果表明,EDTA作为络合剂的Sn-Co-C镀层中Sn、Co、C原子分数分别为61.8401%,22.3788%,12.5409%.SEM观察Sn-Co-C镀层表面为稳定的球状结构.     

热处理对Sn-Co/石墨复合材料结构和电化学性能的影响

采用球磨法将Sn-Co合金与石墨复合制备了Sn-Co/石墨复合材料,并对其进行热处理,研究了热处理温度对复合材料结构和电化学性能的影响。结果表明,Sn-Co/石墨复合材料由Co Sn相和石墨组成,Sn-Co合金一部分嵌入石墨颗粒内部,一部分吸附在石墨颗粒表面。电化学测试表明,Sn-Co/石墨复合材料兼具高容量和长循环寿命的优点,首次放电容量和库伦效率分别为349 m A·h/g和81.3%,经过25次循环后的容量保持率为88.3%。热处理导致Sn-Co合金的晶粒长大和Co3Sn2新相的出现,同时降低了复合材料的比表面积。当热处理温度为500℃时,首次放电容量和库伦效率分别为362 m A·h/g和83.6%,经过25次循环后的容量保持率达92.8%,表现出良好的结构稳定性。     

Electrochemical Behavior of Fe—Based Coatings Containing Amorphous Phase Prepared by Electric Arc Spraying

采用倒相法在Cu箔上制得与Cu箔结合牢固的PAN与石墨多孔复合膜,以其作阴极、纯Sn作阳极进行脉冲电沉积, Sn通过多孔复合膜的微孔沉积在铜箔上,然后在氩气气氛中热处理,得到具有复合结构的Sn基合金电极(碳膜隔离的Cu-Sn合金),用作Li离子电池的负极. SEM和EDS能谱分析以及模拟电池的电化学性能测试结果表明:与通常的在裸Cu箔上直接电沉积Sn并热处理的Sn电极相比,这种具有复合结构的Sn电极热处理后具有更好的循环性能和更高的循环容量,首次放电容量达到538.3 mA·h/g,50次循环后充电(Li离子的脱出)循环容量保持率仍有85.5%.     

复合金属掺杂的LiFePO4/C复合材料的制备与电化学性能研究

以超声波辅助沉淀法合成的纳米级球形FePO4·2H2O为原料,采用碳热还原法制备了复合金属掺杂的LiFePO4/C复合材料。通过X射线衍射(XRD),扫描电镜(SEM),恒电流充放电测试,循环伏安和交流阻抗测试表征了FePO4·2H2O和LiFePO4/C的物相、结构和电化学性能。结果表明,溶液浓度为0.1 mol/L时制备的FePO4·2H2O为分布均匀的纳米级球形颗粒。复合金属掺杂显著提高了LiFePO4的放电比容量,Ni和Nb复合掺杂的LiFePO4/C复合材料表现出了最佳的电化学性能,0.1 C倍率条件下首次放电容量158.8 mAh/g,1 C倍率下首次放电容量150.2 mAh/g,100次循环后容量保持率分别为98.30%和97.8%。Ni和Nb复合掺杂后提高了LiFePO4的锂离子扩散速率和电导率。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.