共沉淀法制备球形LiCr_(0.1)Ni_(0.45)Mn_(1.45)O_4正极材料及性能表征

采用共沉淀和固相烧结工艺制备LiNi0.5Mn1.5O4和LiCr0.1Ni0.45Mn1.45O4正极材料,对其比表面积、振实密度、倍率性能、高低温循环性能等性能指标进行测试,并利用SEM、XRD对所制材料进行形貌观察及物相分析。结果表明:添加微量Cr元素可稳定材料结构,降低比表面积,改善LiNi0.5Mn1.5O4材料电化学性能;LiCr0.1Ni0.45Mn1.45O4正极材料振实密度可达到2.32 g/cm3,比表面积可达到0.51 m2/g,25℃下1.5C充放电,最高容量达到127.2 m A·h/g,300次循环后容量保持率为94.9%;50℃下1.5C充放电,初始容量达到128.5 m A·h/g,200次循环后容量保持率为88.7%。经XRD分析,循环完成后材料尖晶石的结构没有变化。     

碳酸盐共沉淀法合成LiNi1/3Co1/3Mn1/3O2及其电化学性能

以碳酸盐共沉淀法合成了Ni1/3Co1/3Mn1/3CO3前驱体,然后以Ni1/3Co1/3Mn1/3CO3和LiOH·H2O为原料,合成出了层状锂离子电池正极材料Li Ni1/3Co1/3Mn1/3O2.通过XRD,SEM和电化学测试对Li Ni1/3Co1/3Mn1/3O2材料的结构、形貌及电化学性能进行了测试和表征.结果表明,800℃烧结12 h所合成的样品粒度大小分布比较均匀,以0.2 C充放电,其首次放电容量为153 mAh·g-1,循环30次后容量为140 mAh·g-1.     

LiNi0.6Co0.1Mn0.3O2正极材料的合成与性能

采用共沉淀-高温固相法制备LiNi0.6Co0.1Mn0.3O2锂离子正极材料,并使用X 射线衍射仪（XRD）和扫描电镜（SEM）技术分别表征其结构和形貌.然后将所得LiNi0.6Co0.1Mn0.3O2正极材料组装成扣式电池,并表征其电化学性能,探讨烧结温度和锂配量对其电化学性能的影响.结果表明：所得LiNi0.6Co0.1Mn0.3O2正极材料的放电比容量随烧结温度的升高而增大,且在900℃时表现出最佳的电化学性能.室温下,1C倍率下,锂配量(n(Li)/n(Ni+ Co+ Mn)=1.09)时,正极材料的首次放电容量为143.7 mAh/g,50次循环后,正极材料的放电比容量仍有141.3 mAh/g,容量保持率为98.3%.     

AlF_3包覆LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2正极材料及其电化学性能

采用喷雾干燥法制备Li Ni1/3Co1/3Mn1/3O2正极材料,溶胶—凝胶法制备Al F3包覆Li Ni1/3Co1/3Mn1/3O2正极材料。通过XRD、SEM、电化学测试等对Al F3包覆Li Ni1/3Co1/3Mn1/3O2正极材料的结构、形貌和电化学性能进行研究。结果表明:Al F3包覆Li Ni1/3Co1/3Mn1/3O2正极材料为α-Na Fe O2型结构,属空间群。样品为类球形,颗粒大小均匀。包覆后的样品首次放电容量略有降低,但是显著提高了其循环性能,其首次充放电容量为148 m A·h/g,25次充放电循环后容量保持率为93.9%。     

包覆型锂离子正极材料LiNi0.9Mn0.03Co0.07O2的合成与性能

采用复合包覆法合成了锂离子正极材料LiNi0.9Mn0.03Co0.07O2,前驱体的合成过程条件与最终包覆的材料性能有关。讨论了包覆沉淀反应过程中沉淀剂、pH值、搅拌速度和氨水浓度对电化学性能的影响。同时还考察了煅烧制度对材料电化学性能的影响。结果表明：在优化条件下Co,Mn均匀包覆在β-Ni（OH）2表面上;合成的正极材料LiNi0.9Mn0.03Co0.07O2在电压范围3～4.3V,电流密度30mA·g^-1下,第二次放电容量为194mAh·g^-1,50次循环后容量仍保持为189mAh·g^-1,材料循环性能稳定。     

碳酸盐前驱体Ni1/3Co1/3Mn1/3CO3合成条件的研究

以碳酸盐为沉淀剂,采用共沉淀法合成Ni1/3Co1/3Mn1/3CO3前驱体,再按照一定的锂配比将其烧结合成层状Li（Ni1/3Co1/3Mn1/3）O2。通过SEM及电性能测试仪等方法,研究了碳酸盐前驱体的合成条件,考察了碳酸盐前驱体的振实密度与合成时pH值、溶液浓度以及反应时间的关系。经过实验分析,在pH=8、溶液浓度C=2mol.L^-1、反应时间t=12-13h时,合成的碳酸盐前驱体Ni1/3Co1/3Mn1/3CO3振实密度达到最高值0.98g.cm^-3。     

富锂锰基层状正极材料的发展现状

介绍了富锂锰基层状系列正极材料x Li2Mn O3·(1-x)Li MO2的结构及机理、合成及改性进展,与Li Co O2、Li[Ni1/3Mn1/3Co1/3]O2等常见材料相比,价格更低、安全性更好、对环境更为友好。但仍存在首次充放电效率低、倍率性能较差、低温性能差、振实密度低等不足之处。在揭示该材料的研究现状和亟待解决的问题基础上,更明确了今后的发展方向。     

LiMn1.8Co0.2O3.95F0.05的络合燃烧法合成及其性质研究

以醋酸锂、醋酸锰、醋酸钴、氟化锂、柠檬酸及乙二醇为原料，采用燃烧辅助有机酸络合法合成LiMn1．8Co0．2O3．95F0．05，用X射线衍射检测和分析产物的物相及晶格常数，用循环伏安、交流阻抗技术研究产物的氧化-还原及界面过程，用恒流充放电测试产物的容量及循环性能。研究表明，各条件下合成的LiMn1．8Co0．2O3．95F0．05粉末的X射线衍射峰强度大、峰尖锐，粉末具有良好的结晶性LiMn1．8Co0．2O3．95F0．05容量随热处理温度的升高而增大，即由750℃热处理4h的92mAh／g升高到850℃热处理4h的105mAh／g。相对LiMn2O4而言，LiMn1．8Co0．2O3．95F0．05的初始容量虽略有下降，但双掺杂后的循环性能得到了显著提高。     

碳酸盐共沉淀法合成Li1＋xNi0.6Co0.2Mn0.2O2Fx正极材料及其电化学性能

采用碳酸盐共沉淀法合成Li1＋xNi0.6Co0.2Mn0.2O2Fx正极材料,研究了不同含量的Li、F复合掺杂对LiNi0.6Co0.2Mn0.2O2样品的晶型结构、形貌以及电化学性能的影响.研究结果表明：Li、F复合掺杂未改变LiNi0.6Co0.2Mn0.2O2样品的层状结构;掺杂后的样品颗粒细化;电化学循环性能和电极过程的可逆性明显得到提高.掺杂量x=0.06时,Li1＋xNi0.6Co0.2Mn0.2O2Fx样品的首次充放电容量分别为168,160 mA·h/g,循环50次后容量为153 mA·h/g.     

非均匀沉淀法包覆合成LiNi0.9 Co0.07 Mn0.03O2锂离子正极材料

采用非均匀沉淀法包覆合成了LiNi0.9Co0.07Mn0.03O2锂离子正极材料.前驱体合成中各工艺条件与包覆材料的比表面积和电化学性能息息相关.试验研究了沉淀剂、搅拌速度、pH值和氨水浓度对包覆沉淀的影响及煅烧过程对材料电化学性能的影响.结果表明:在优化实验条件下Co/Mn复合包覆在β-Ni(OH)2表面上;正极LiNi0.9Co0.07Mn0.03O2首次放电容量为195mAh·g-1,50次循环后容量仍保持为188.6mAh·g-1.循环伏安研究表明:与LiNiO2相比,Co/Mn复合包覆合成正极材料LiNi0.9Co0.07Mn0.03O2的相变得到很好的抑制,材料显示出良好的循环性能.     

溶胶-凝胶自燃烧法合成镍铜锌纳米晶铁氧体及其吸波性能的研究

利用溶胶-凝胶自燃烧法合成了Ni0.25Cu0.25Zn0.5Fe2-xCexO4纳米晶铁氧体.借助DTA和XRD技术,对干凝胶的热分解过程、合成纳米晶的成分及其吸波性能进行了研究.结果表明,由金属硝酸盐和柠檬酸形成的干凝胶具有自燃烧的特性.通过自燃烧反应可以直接获得镍锌铜铁氧体粉末,经900℃热处理后可以转变成单一的尖晶石相,吸波性能测试发现,Ni0.25Cu0.25Zn0.5Fe2-xCexO4的吸波性能在8.2GHz～12.5GHz范围内随x的变化而不同,当x=0.07时,吸波性能最好,最高吸收峰值达到29.634dB.     

Tempering Behavior of 4.5Cr-2W-0.25V Steel

The tempering behavior of a Cr-W-V steel was investigated in this research.This new alloy with the composition of Fe-4.5Cr-2W-0.25V-0.1C was austenitized at 1000 ℃ for 30 min and tempered at 600 and 700 ℃ for different time up to 100 h.An OM analysis of the microstructure of air cooled and water quenched specimens before tempering showed that although under both conditions fully martensitic matrix formed,finer structure had formed in the water quenched specimens.The XRD and TEM results showed that the most stable carbides formed during tempering of the steel were M23C6 and M7C3,respectively.Other carbides such as M3C and M2C,formed in the first stages of tempering,and stable MC were also observed.The results showed that when the tempering time,temperature and cooling rate were increased,mass percent of extracted precipitates was increased.In addition,the formation rate of the stable carbides such as M23C6 and dissolution rate of the metastable carbides such as M3C and M2C were increased.     

0.25C-1.1Cr-0.7Mn-0.25Mo-0.05V高速动车车轴用钢的热塑性、组织和力学性能

0.25C-1.1Cr-0.7Mn-0.25Mo-0.05V钢经60 t EBT电弧炉-LF-VD-8.4 t铸锭流程冶炼。热模拟试样取自250 m/m×250 mm轧坯。通过Gleeble-3800热模拟试验机测试了温度(室温~1 200℃)对钢力学性能的影响,并得出0.1~35℃/s冷却速度下该钢的连续冷却转变曲线。并通过箱式电阻丝炉和盐浴炉测试了200 mm×200 mm坯经920℃正火,880~900℃油淬,630~680℃回火的力学性能。结果表明,该钢在900~1 200℃具有良好的热加工性能;当冷却速度大于15℃/s时可获得贝氏体+马氏体组织;采用920℃正火,880℃油淬,650~680℃回火后,该钢屈服强度R_(p0.2)为525~570 MPa,抗拉强度R_m为710~745 MPa,伸长率A为22%~23%,纵向冲击功(U-5mm)68~82 J,横向冲击功(U-5 mm)65~76 J,均符合标准要求。     

La~(3+) doped LiCo_(0.25)Zn_(0.25)Fe_2O_4 spinel ferrite nanocrystals:Insights on structural,optical and magnetic properties

This paper addresses the manipulation of structural,morphology,optical and magnetic properties of LiCo_(0.25)Zn_(0.25)Fe_2 O_4 ferrite via incorporation of different proportions of La~(3+) at the expense of iron ions using a sol-gel method.The samples were characterized using the X-ray diffraction technique(XRD),Fourier transform infrared(FT-IR) spectroscopy,the energy dispersive X-ray spectra(EDX),inductively coupled plasma optical emission spectroscopy(ICP-OES),high resolution scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET) surface area analysis,ultraviolet-diffuse reflectance spectroscopy(UV-DRS),and vibrating sample magnetometer(VSM) technique.The Rietveld refinements of the samples indicate that at higher concentrations of La3+,nanostructures with dual phase,i.e.cubic spinel and orthorhombic LaFeO_3 perovskite with space group(Pbnm) appear.Optical studies show that the energy band gap(E_g) of the bare LiCo_(0.25)Zn_(0.25)Fe_2 O_4 ferrite sample(2.18 eV) reaches up to 2.47 eV at x=0.06 and above this concentration,it drops sharply to 2.00 eV.Although the saturation magnetization and the coercivity of LiCo_(0.25)Zn_(0.25)La_xFe_(2-x)O_4 are lower than that of LiCo_(0.25)Zn_(0.25)Fe_2 O_4 NPs.Overall,the superparamagnetic nature and low values of saturation magnetization and coercivity of LiCo_(0.25)Zn_(0.25)La_xFe_(2-x)O_4 NPs are suitable to be applied in transformers core.     

Silicide Precipitation in Alloy Ti-6AI-5Zr-0.5Mo-0.25Si

Silicide precipitation in the titanium alloy containing by wt pct 6Al-5Zr-0.5Mo-0.25Si (Alloy 685) has been investigated using electron diffraction. The solutionizing temperature for this alloy is 1323 K. It is observed that no resolvable silicide precipitates are present in the alloy as received, furnace cooled from 1323 K and aged at 823 K, or oil quenched from 1323 K and aged at 823 K. Specimen solutionized at 1323 K for 30 minutes followed by water quenching and aging at 923 K for 24 hours shows fine precipitates at boundaries of α′ platelets. Diffraction analysis shows that the fine precipitates belong to two different types of identifiable hexagonal silicides similar to those observed by Floweret al in the ternary Ti-5Zr-0.5Si alloy to be (TiZr)₅Si₃ and another of unknown stoichiometry. However, aging of the water quenched specimens for 24 hours at higher temperatures, 973 K and 1073 K, results in the precipitation of a silicide similar to the latter one. It is analyzed that this silicide has lattice parameters a = 0.70₂ nm and c = 0.36₈ nm. Since aging at 973 K and 1073 K gives rise to precipitation of the same silicide, it is concluded that this is the stable silicide in Alloy 685 in the temperature range investigated.