AlF_3包覆锂离子电池正极材料Li_(1.2)(Mn_(0.54)Ni_(0.16)Co_(0.08))O_2的制备、表征及电化学性能(英文)

采用溶胶-凝胶法合成锂离子电池正极材料Li1.2(Mn0.54Ni0.16Co0.08)O2,并用Al F3对这种材料进行表面包覆改性。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨率透射电子显微镜(HRTEM)等表征材料的结构和形貌。结果表明,合成的Li1.2(Mn0.54Ni0.16Co0.08)O2具有典型的层状α-Na Fe O2结构,AlF3均匀包覆在Li1.2(Mn0.54Ni0.16Co0.08)O2材料表面,包覆层厚度为5~7 nm。电化学测试表明,包覆Al F3后材料的电化学性能得到提高,在1C倍率下,包覆的AlF3材料的首次放电容量为208.2 m A·h/g,50次循环后容量保持率为72.4%,而未包覆AlF3的材料的首次放电容量和容量保持率分别为191.7 m A·h/g和51.6%。     

AlF3包覆锂离子电池正极材料Li1.2(Mn0.54Ni0.16Co0.08)O2的制备、表征及电化学性能（英文）

采用溶胶-凝胶法合成锂离子电池正极材料Li1.2(Mn0.54Ni0.16Co0.08)O2,并用Al F3对这种材料进行表面包覆改性。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨率透射电子显微镜(HRTEM)等表征材料的结构和形貌。结果表明,合成的Li1.2(Mn0.54Ni0.16Co0.08)O2具有典型的层状α-Na Fe O2结构,AlF3均匀包覆在Li1.2(Mn0.54Ni0.16Co0.08)O2材料表面,包覆层厚度为5~7 nm。电化学测试表明,包覆Al F3后材料的电化学性能得到提高,在1C倍率下,包覆的AlF3材料的首次放电容量为208.2 m A·h/g,50次循环后容量保持率为72.4%,而未包覆AlF3的材料的首次放电容量和容量保持率分别为191.7 m A·h/g和51.6%。     

LiNi0．85Co0．10Al0．05O2正极材料合成及表征

以LiOH·H2O,Ni2O3,Co2O3和Al(OH)3为原料,采用固相反应法合成Co-Al共掺入LiNiO2的化合物LiNi0.85Co0.10Al0.05O2,由TG-DTA,XRD,SEM,DSC和电化学测试表征材料.结果表明,该材料首次放电容量达186.2mAh/g(3.0 V～4.3 V,18 mA/g),10次循环之后,容量还有180.1 mAh/g,容量保持率为96.7%;与未掺杂的LiNiO2相比,该材料显示出良好的循环性能,且热稳定性也有所提高,是一种很有应用前景的锂离子电池正极材料.     

表面掺杂Al的球形尖晶石LiMn2O4的高温循环性能

采用控制结晶工艺合成了球形Mn3O4，通过在球形Mn3O4的表面包覆Al（OH）3，然后与LiOH一起混合焙烧制备了表面掺杂Al的尖晶石LiMn2O4。采用SEM，XRD，EDS以及电池系统测试等方法，研究了所制备材料的结构和性能。SEM分析表明：表面掺杂后，Al（OH）3均匀地包覆在颗粒表面。XRD和EDS分析表明：焙烧后，Al元素占据了Mn的位置，且颗粒表面的Al含量高于其总体的平均含量，说明Al只是在表面富集，即表面掺杂。电池测试表明：表面掺杂后，尖晶石LiMn2O4的初始充放电容量有所下降，但在高温55℃下的循环性能有显著的提高，表面掺杂6％Al的尖晶石LiMn2O4 50次循环的容量保持率从68．3％提高到79．0％。说明以Al^3＋作为掺杂离子通过表面掺杂来改善LiMn2O4的高温循环性能是有效的。     

碳纤维表面改性对Cf/Mg复合材料微观组织和界面的影响

研究在碳纤维表面分别用化学法镀Ni和溶胶-凝胶法涂SiO2两种涂层,用真空压力浸渗法制备Cf/Mg复合材料.用SEM、EDS和TEM对Cf/Mg复合材料微观组织和界面特征进行分析.结果表明:无涂层的碳纤维与Mg基体浸润性较差,碳纤维在Cf/Mg复合材料微观组织巾分布不均匀,界面结合强度较弱.碳纤维表面包覆Ni或SiO2涂层改善了碳纤维与Mg基体的润湿性;包覆Ni涂层的碳纤维在Mg基体中分布均匀,并在其界面处生成金属间化合物Mg2Ni,界面为强结合;碳纤维表面的SiO2涂层与Mg进行少量的反应生成MgO和Si,界面结合好.能很好地传递载荷.     

MoS2颗粒表面包覆Al2O3及其在镀层中的应用

采用非均匀形核法将Al2O3包覆到MoS2颗粒表面,提高颗粒的亲水性能。研究了溶液pH值、Al(NO3)3的摩尔浓度和预处理工艺对包覆率的影响;采用SEM及EDS分析了包覆前后MoS2颗粒的微观形貌和表面成分;通过测量接触角研究了颗粒表面的亲水性。结果表明,颗粒表面均匀包覆了一层Al(OH)3;溶液pH值对包覆率的影响最大,Al(NO3)3的摩尔浓度次之。最佳工艺为:溶液pH值为5.5,Al(NO3)3浓度为0.15mol/L,预处理过程不添加表面活性剂。随着包覆率的提高,MoS2颗粒的亲水性提高。利用包覆Al2O3的MoS2制得了Ni-P-MoS2化学复合镀层,提高了镀层中沉积粒子的均匀致密性。     

有机溶剂醇热法对LiCoO2正极表面修饰

采用有机溶剂醇热法,以异丙醇铝为原材料对LiCoO2进行表面处理.通过XRD、SEM对包覆前后正极材料的微观结构进行表征,对包覆前后正极材料的电化学性能进行测试.结果表明:包覆后正极材料的充放电效率明显提高,循环30次后容量保持率由包覆前的84.1%提高到包覆后的93.2%.这归因于包覆后LiCoO2表面形成的Al2O3或LiAlxCo1-xO2层,该层起到阻挡层的作用,有效地抑制Co4 与电解液反应,稳定了LiCoO2结构,提高了电化学循环性能.     

LiMg_(0.03)(Ni_(0.77)Co_(0.1)Mn_(0.1))O_2·B_2O_3球形高镍材料的制备与性能

采用液相共沉淀法制备球形掺镁高镍三元材料前驱体,结合高温固相法制备了氧化硼包覆高镍三元材料LiMg0.03(Ni0.77Co0.1 Mn0.1)O2·B2O3,对样品物理性能、电化学性能及安全稳定性进行分析测定,并对性能改善的机理进行分析。结果表明:通过Mg元素体相掺杂和B2O3表面包覆制备的球形高镍三元材料LiMg0.03(Ni0.77Co0.1Mn0.1)O2·B2O3具有良好的电化学性能和物理性能,对锂负极初始放电容量达到181 m A·h/g,对碳负极300次循环后,放电容量保持率达到92%,压实密度达到3.9 g/cm3。同时,LiMg0.03(Ni0.77Co0.1 Mn0.1)O2·B2O3具有良好的热稳定性和抗过充电的能力,在充电态下热分解温度比未掺杂和未包覆的样品提升12℃。     

Al2O3包覆LiNi0.03Co0.05Mn1.92O4正极材料的制备及其电化学性能

以Al(NO3)3?9H2O为包覆原料，通过燃烧法制备得到LiNi0.03Co0.05Mn1.92O4@Al2O3正极材料。通过X射线衍射(XRD)，场发射扫描电子显微镜(FESEM)和透射电镜(TEM)等表征手段对材料的结构和形貌进行分析，并通过恒电流充放电、循环伏安(CV)、交流阻抗(EIS)等测试分析材料的电化学性能。结果表明，Al2O3包覆没有改变LiNi0.03Co0.05Mn1.92O4的尖晶石型结构，包覆层厚度约10.6nm。LiNi0.03Co0.05Mn1.92O4@Al2O3正极材料电化学性能得到了明显改善，1 C和10 C倍率下初始放电比容量分别为119.9 mAh?g-1和106.3 mAh?g-1，充放电循环500次后容量保持率分别为88.4%和78.2%，而未包覆的LiNi0.03Co0.05Mn1.92O4在1 C和10 C倍率下初始放电比容量分别为121.2 mAh?g-1和104.0 mAh?g-1，500次循环后容量保持率分别为84.1%和67.6%。LiNi0.03Co0.05Mn1.92O4@Al2O3活化能为32.92 kJ?mol-1，而未包覆材料的活化能为36.24 kJ?mol-1，包覆有效降低了材料Li+扩散所需克服的能垒，提高了材料的电化学性能。     

V_2O_5包覆对Li_(1.6)(Fe_(0.2)Ni_(0.2)Mn_(0.6))O_(2.6)材料的表面改性（英文）

在采用低温共沉淀-水热-煅烧法合成锂离子电池Fe-Ni-Mn体系正极材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的基础上,对合成的材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6进行V2O5的包覆改性研究,以提高材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的首次放电比容量和循环性能。用XRD、SEM、TEM、ICP光谱和恒流充放电测试研究包覆材料的结构和电化学性能。结果表明,V2O5包覆并没有改变材料的晶体结构,只存在于材料的表面,与未包覆的材料相比,V2O5包覆后的材料具有更好的首次放电容量和容量保持率。50周循环后,添加质量分数3%V2O5样品Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的放电比容量可以维持在200.3 mAh/g,大于未添加V2O5样品Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的194.0 mAh/g。CV测试表明,包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应。     

Synthesis and characterization of LiNi0.95-xCoxAl0.05O2 for lithium-ion batteries

Samples of LiNi0.95-xCoxAl0.05O2 （x = 0.10 and 0.15） and LiNiO2, synthesized by the solid-state reaction at 725℃ for 24 h from LiOH-H2O, Ni2O3, Co2O3, and AI（OH）3 under an oxygen stream, were characterized by TG-DTA, XRD, SEM, and electrochemical tests. Simultaneous doping of cobalt and aluminum at the Ni-site in LiNiO2 was tried to improve the cathode performance for lithium-ion batteries. The results showed that co-doping （especially, 5 at.% A1 and 10 at.% Co） definitely had a large beneficial effect in increasing the capacity （186.2 mA.h/g of the first discharge capacity for LiNio.s.42OoaoAlo.0502） and cycling behavior （180.1 mA-h/g after 10 cycles for LiNio.85CooaoAlo.osO2） compared with 180.7 mA.h/g of the first discharge capacity and 157.7 mA.h/g of the tenth discharge capacity for LiNiO2, respectively. Differen- tial capacity versus voltage curves showed that the co-doped LiNio.95_xCoxmlo.osO2 had less intensity of the phase transitions than the pristine LiNiO2.     

微米金刚石负载纳米银的电化学性能

微米金刚石拥有优异的物理化学性能。为拓展其应用领域,通过葡萄糖还原银氨溶液中的络合Ag+,在微米金刚石表面负载纳米银颗粒。通过SEM、TEM、EDS和XRD等分析手段表征复合材料的形貌、组成和结构。使用旋转圆盘电极进行实验,研究不同银负载量的微米金刚石的氧还原和析氧特性。结果显示:微米金刚石表面负载质量分数为10%的银时,氧还原反应极限电流密度是4.1mA/cm2,析氧反应的极限电流密度是27.5mA/cm2。      

Uniform AlF3 thin layer to improve rate capability of LiNi1/3Co1/3 Mn1/3O2 material for Li-ion batteries

LiNi1/3Co1/3Mn1/3O2 was coated with uniform nano-sized AlF3 layer by chemical precipitation method to improve its rate capability. The samples were characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), charge-discharge cycling, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Uniform coated layer with a thickness of about 3 nm was observed on the surface of LiNi1/3Co1/3Mn1/3O2 particle by TEM. At 0.5C and 2C rates, 1.5% (mass fraction) AlF3-coated LiNi1/3Co1/3Mn1/3O2/Li in 2.8-4.3 V versus Li/Li+ after 80 cycles showed less than 3% of capacity fading, while those of the bare one were 16.5% and 45.9%, respectively. At 5C rate, the capacity retention of the coated sample after 50 cycles maintained 91.4% of the initial discharge capacity, while that of the bare one decreased to 52.6%. EIS result showed that a little change of charge transfer resistance of the coated sample resulting from uniform thin AlF3 layer was proposed as the main reason why its rate capability was improved obviously. CV result further indicated a greater reversibility for the electrode processes and better electrochemical performance of AlF3-coated layer.     

Microstructure and anti-oxidation property of Si-W-Cr coating for SiC coated carbon-carbon composites

To protect carbon/carbon (C/C) composites from oxidation at high temperature, a Si-W-Cr coating was prepared on the surface of SiC coated C/C composites by a simple pack cementation technique. The microstructure and phase composition of the as-received multi-coating were examined by SEM, XRD and EDS. The coating obtained by first step pack cementation was porous α-SiC structure. New phases of WSi₂ and CrSi₂ together with α-SiC deposited on the porous SiC inner layer. Oxidation test shows that the weight loss of single SiC coated C/C is up to 8.21% after 9 h in air at 1773 K, while the weight loss of Si-W-Cr/SiC coated C/C composites is only 2.26% after 51 h. After thermal cycling between 1773 K and room temperature for 40 times, the weight loss is only 3.36%. The weight loss of coated C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks in the coating.     

纳米SiC颗粒表面改性研究

根据置换反应的原理将Cu2+还原为Cu原子,在纳米SiC颗粒表面形核,实现了Cu包覆纳米SiC颗粒。SEM分析表明:复合粉体包覆完全,分散均匀,无明显团聚,大部分呈球形。EDS和XRD分析表明:复合粉体在空气中会部分氧化,生成一定量的Cu2O,应用时可根据需要进行适当处理。纳米SiC颗粒表面改性后,可以改善在Cu基合金中的分散性和相容性,满足了表面改性的要求。     

U71Mn钢轨铣削用PVD-TiAlN涂层刀片失效分析

目的分析研究PVD-TiAlN涂层刀片铣削钢轨(U71Mn)后的失效行为,确定涂层刀片铣削U71Mn的磨损机制及失效机理,为进一步改进铣削U71Mn用涂层刀片的使用性能提供指导。方法采用多弧离子镀技术在硬质合金基体刀片上制备了厚度约2.13μm的TiAlN涂层,通过扫描电子显微镜、能谱仪、金相检测仪等仪器,检测了刀片基体和涂层的显微组织和金相结构。采用立式铣床对U71Mn进行铣削,通过扫描电子显微镜观察失效刀片前刀面、刃口和后刀面的微观形貌,结合能谱仪微区成分分析,确定涂层刀片的磨损机制和失效机理。结果通过金相检测仪和扫描电子显微镜检测,YG10细晶粒硬质合金基体无明显组织缺陷。采用多弧离子镀制备的涂层膜基结合力等级为HF1,具有较好的膜基结合强度。失效刀片的刃口处存在贯穿前刀面、刃口和后刀面的裂纹,并且刃口区域的裂纹内部有被加工材料的填充物。后刀面裂纹尖端有涂层的微崩裂,前刀面的磨损带边界较后刀面磨损带边界平齐。刃口附近的涂层表面上出现了相互交联的裂纹。失效刃口多出现锯齿形缺口,缺口内部有大量的碎屑填充物,缺口对应的后刀面处分布着深浅不同的沟槽。磨损的刃口上粘接有大量的被加工材料。结论刀片的磨损机制有磨粒磨损、粘接磨损和氧化磨损。另外,刃口的崩裂在刀片失效过程中也扮演着重要角色,崩裂的缺口会为硬质颗粒提供存储空间,从而加剧磨料磨损,在多种磨损机制共同作用下,刀片刃口最终被磨耗而失效。可通过提高基体的强韧性、合理的刃口设计、改善涂层的韧性和结合力、提高涂层的抗氧化性等方面,提高涂层刀片铣削U71Mn的性能。     

Effects of hot rolling on microstructure and properties of a 20 vol. % SiCp／Al composite

A 20 vol.% SiCp/Al composite was fabricated by squeeze casting, of which a new process for fabricating the preform was used by blending Al powder and SiC particulates with average diameters of 10 and 3.5μtm, respectively. The microstructure of the as-cast and the hot-rolled composite was investigated by using TEM, EDS, and SEM, and their tensile properties were measured at room temperature. The results show that the ultimate tensile strength and ultimate elongation of the hot-rolled composite are 80% and 140% higher than those of the as-cast one. The TEM observation result indicates that there are high density of dislocations and dislocation tangles in the hot-rolled composite. Al2O3 layers in the composite resuiting from the surface oxidation of the aluminum powders were damaged to spherical particles during hot rolling. All the results indicate that hot-rolling can improve the mechanical properties of the composite and, therefore, engineering components of the 20 vol.% SiCp/Al composite can be produced by squeeze casting followed by hot-rolling.     

聚合-热解法制备Co0.2Zn0.2Mn0.6Fe2O4纳米颗粒及其表征

采用聚合-热解法制备了Co0．2Zn0．2Mn0．6Fe2O4磁性纳米颗粒，借助热重分析法（TG）、X射线衍射（XRD）、透射电镜（TEM）和振动样品磁强计（VSM）对产物进行了表征．结果表明，产物具有尖晶石结构，无杂相，粒径分布范围在8-15nm之间．常温下该材料的剩磁强度和矫顽力分别为0．516和2．388kA／m．     

Preparation of LiNi_(1-y)Co_yO_2 in certain oxygen pressure

1　INTRODUCTIONLi ionbatteryisthenewlydevelopedrecharge ablebatterysubsequenttoCd/NiandMH/Nibat tery .Itshighenergypropertyisnotonlyfitforthepowersupplyofsmallscaleelectricproductdevelop ingattopspeed ,butalsofitforthepowersupplyofthelargescalemotivepowertooltoavoid pollutingtheenvironment .Thepreparationofcathodematerialisthekeylinksforthedevelopmentoflithiumionbattery .Atpresent ,thecathodematerialsusedinlithiumionbatteryareLiCoO2 ,LiNiO2 ,LiMn2 O4 andtheirderivatives .Amongthem ,…     

Tribological performance of surface engineered tool steel at elevated temperatures

Tribological components operating at elevated temperatures can experience high wear, oxidation, thermal fatigue and changes in mechanical properties. In this work, the friction and wear characteristics of plasma nitrided and surface coated (CrN and TiAlN) tool steel during sliding against AISI52100 bearing steel have been studied at room temperature and 400 °C respectively using a ball on disc machine. Surface profiler and SEM/EDS techniques were used to characterise the surface topography and resulting surface damage of the test specimens. The results show that the friction of plasma nitrided tool steel during sliding against bearing steel ball is very high at room temperature and it drastically drops at 400 °C. The wear is mainly abrasive at room temperature and adhesive at elevated temperatures. In case of CrN coated tool steel the friction is high but its wear is negligible at room temperature. At 400 °C, the friction decreases marginally and transfer of bearing steel to the coated CrN coated disc has been observed. The TiAlN coating has shown relatively lower friction, compared to CrN and negligible wear at room temperature. At 400 °C, the friction is very high and unstable and transfer of TiAlN coating to the mating ball occurs.