锂掺杂对石墨电化学性能的影响

研究了掺杂锂元素对用作锂离子电池负极的石墨材料的结构与性能的影响. XRD及元素分析结果表明 锂以化合物的形式存在于石墨材料中, 由于缺陷结构的增加, 掺杂后石墨材料的BET比表面积略有增大. 电化学测试结果表明 预先掺锂能够有效减少首次充放电过程中的不可逆容量, 使石墨电极的可逆容量增加. 与未掺杂的热处理石墨比较, 可逆嵌锂容量由304.5 mA*h/g增加到312.2 mA*h/g, 首次充放电不可逆容量由66.4 mA*h/g减少到52.9 mA*h/g. 以掺锂改性石墨为负极制作成063448型锂离子电池后, 电池的容量和循环稳定性均得到改善, 以1C倍率充放电时, 放电容量可达845 mA*h, 循环200次后的容量保持率为91.65%.     

电沉积制备的两种形貌Sn薄膜锂离子嵌入电极性能的比较

用电沉积方法在Cu集流体上分别制备出用于锂离子电池负极材料的密集细粒状(＜0.5 μm)和分散粗粒状(≈3 μm)两种Sn薄膜电极.用X射线衍射、扫描电镜、循环伏安及充、放电实验研究比较了两电极的组织与性能.结果表明,在氟硼酸盐溶液中使用以醛类为主的复合添加剂,在静止条件下可制得细粒Sn薄膜电极,在搅拌条件下可制得粗粒Sn薄膜电极;细粒Sn薄膜电极比粗粒Sn薄膜电极具有较优的初始嵌锂容量和循环稳定性:细粒Sn薄膜电极首次放电比容量达到787 mA·h/g,40次循环时放电比容量仍保持在630 mA·h/g;而粗粒Sn薄膜电极首次放电比容量只有576 mA·h/g,至20次循环放电比容量降至150 mA·h/g.     

碳化钙骨架碳负极材料的制备及电化学性能

以碳化钙为原料、新鲜氯气为刻蚀剂,在400～700℃范围内制备碳化钙骨架碳作为锂离子电池新型负极材料.用X射线衍射(XRD)、扫描电镜(SEM)、氮气吸附实验、恒流充放电、交流阻抗(EIS)等对碳化钙骨架负极材料进行表征及电化学性能测试,并探讨制备温度对碳化钙骨架碳结构和电化学性能的影响.结果表明:所有温度下制备的碳化钙骨架碳均为无定形碳材料,但随着制备温度的升高,材料出现部分石墨化倾向;600℃制备的碳化钙骨架碳具有良好的电化学性能,在0.1 C充放电时,首次放电比容量为890.9 mA·h/g,可逆容量为335.4mA·h/g,循环30次后的可逆容量为266.8 mA·h/g.     

Li4Ti5O12/石墨复合材料的湿法制备与表征

以醋酸锂、钛酸丁酯和石墨为原料,无水乙醇为溶剂,采用湿法制备Li4Ti5O12/石墨复合材料.采用X射线衍射、红外光谱、扫描电镜和电化学测试对合成产物进行表征.结果表明:600 ℃氩气气氛中煅烧6 h可制得含碳量5%左右的Li4Ti5O12/石墨复合材料,其可逆容量达到167.1 mA·h/g;经80次循环后,0.1C放电时容量保持率为99.0%,2.0C放电时容量保持率达到105.1%.与纯Li4Ti5O12相比,Li4Ti5O12/石墨复合材料具有更好的循环性能和倍率性能,是一种优良的锂离子电池负极材料.     

LiNi_(0.87)Co_(0.10)Mg_(0.03)O_2正极材料的合成和电化学性能（英文）

采用共沉淀法制备钴镁共掺的LiNi0.87Co0.10Mg0.03O2正极材料。结果表明,所制备的LiNi0.87Co0.10Mg0.03O2正极材料具备良好的电化学性能,在3.0~4.3 V(Li+/Li)的条件下,该电极0.2C和1C的首次放电容量分别为202.6mA·h/g和190.5 mA·h/g;经过50次循环后,该电极0.2C和1C的容量保持率分别为96.1%和93.4%。而且,将该材料制作成型号为053048的全电池,在1C充放500次后,电池的容量保持率为81.7%,性能接近工业用钴酸锂电池的水平。因此,采用该方法制备的正极材料能够用于高能量密度的移动数码产品。     

电沉积制备锡钴碳复合负极材料的结构与性能

采用电沉积法把Sn、Co原子沉积在硬碳颗粒上得到Sn-Co-C复合负极材料,然后球磨。XRD分析表明复合粉体由Sn、Co2C、CoSn2和C组成。电子探针测试表明试样中Sn、Co、C原子分数分别为2.9145%,0.6921%,95.3879%。SEM观察显示,锡钴粒子尺寸为50～100nm,沉积在片状的硬碳颗粒上。试样与锂片组成模拟电池,首次放电比容量为551.5mAh/g,充电比容量为309.4mAh/g。循环50次后放电比容量仍保持在319.6mAh/g,充电比容量保持在281.6mAh/g。交流阻抗测试表明,在第一次放电后形成了固体电解质层膜,但循环一次后消失。     

多孔泡沫铜支撑锡薄膜阳极材料的制备及性能

以三维多孔泡沫铜为基底,采用化学镀的方法制备锂离子电池薄膜Sn负极材料.利用扫描电镜、X射线衍射分析以及恒电流充放电测试等手段研究不同厚度薄膜Sn电极的形态、结构和电化学行为.结果表明:化学镀工艺制备的Sn电极表面的大量微孔和岛状突起不仅增大电极的表面积,而且显著缓解电极在充放电过程中体积的变化;其中镀层较薄的样品C薄膜Sn电极的初始充电(脱锂)容量为660.6 mA·h/g,经100次循环后,容量保持在299.5 mA·h/g,具有较好的循环性能.     

Al掺杂对Li_4Ti_5O_(12)结构及性能的影响

以金红石型TiO2、Li2CO3和Al2O3为原料,采用高温固相法制备锂离子电池负极材料Li4Ti5O12和Li4AlxTi5-xO12(x=0,0.025,0.05,0.1,0.2,0.4)。利用X射线衍射仪、扫描电镜、半电池充放电测试和交流阻抗测试研究材料的物相、结构、形貌以及电化学性能。结果表明:Al掺杂不会改变Li4AlxTi5-xO12的尖晶石结构,但会导致材料颗粒尺寸增大;适当Al掺杂后,材料的循环稳定性和极化性能得到改善,充放电比容量和可逆比容量不同程度降低;Li4Al0.025Ti4.975O12具有最优的电化学性能,0.1C倍率下首次充电比容量达到156.7 mA.h/g。     

Fe3+掺杂Li4Ti5O12的结构及电化学性能

采用高温固相法合成Li4FexTi5-xO12(x=0.025,0.1,0.2)负极材料。通过X射线衍射、扫描电镜、充放电性能测试等对掺杂Fe3+的Li4Ti5O12材料的组成、结构、形貌进行表征,并对其电化学性能进行研究。结果表明,所合成的材料具有良好的尖晶石结构,无杂相。适当Fe3+掺杂能细化材料,提高材料的电子导电性,使材料的循环性能得到改善。Li4Fe0.025Ti4.975O12的充电容量最佳,0.1C倍率下首次充电比容量达到162.5 mA.h/g,循环性能较好。     

Co掺杂LiFePO4/C的共沉淀——微波合成及电化学性能

采用共沉淀-微波法制备了Co掺杂的锂离子电池正极材料LiFe1-xCoxPO4/C(x=0.00、0.01、0.03、0.05、0.07、0.09).研究了微波时间、柠檬酸量、掺Co量等因素对材料结构、形貌和电性能的影响.XRD、SEM和电化学测试表明:该方法制备的样品为橄榄石型非晶结构,粒径尺寸为0.5～5 μm,颗粒分布比较均匀.微波15 min、柠檬酸量为20wt％时,LiFePO4/C电化学性能最优,0.1C倍率放电可达124 mA·h/g,第20次循环的比容量为117mA·h/g.掺杂Co在很大程度上可以提高LiFePO4/C的电化学性能,当Co含量为5wt％时,LiFe0.95Co0.05PO4/C的比容量为最大值,0.1C倍率放电可达136 mA·h/g,第20次循环的比容量为125 mA· h/g,容量保持率为91.9％.     

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。