层状LiNi1/2-xC02xMn1/2-xO2正极材料的合成与电化学性能研究

采用共沉淀-喷雾造粒法制备前驱体,于700℃在空气中煅烧20h合成出层状LiNi1/2-xC02xMn1/2-xO2正极材料,研究了不同掺钴量对材料的结构和电化学性能的影响,并用XRD、SEM及电性能测试考察了所得材料的结构、形貌与电化学性能.XRD分析表明,LiNi1/2-xCo2xMn1/2-xO2是具有α-NaFeO2层状结构的纯相物质,C03 的掺入可促进层状结构的生成,有效减少阳离子混排.电性能测试结果显,LiNi1/2-x,Co2xMn1/2-x,02随着掺钴量的增大,放电容量提高,循环性能变好.样品Li(Ni1/3 Co1/3 Mn1/3)O2表现出最好的电化学性能,其首次放电效率充放电效率达90%,首次放电容量为172.8mAh/g,40次循环容量无衰减.     

球形LiNi0.5-xCo2xMn0.5-xO2的合成及其电化学性能

以化学共沉淀法制备的球形Ni0.5-xCo2cMn0.5-xCO3（x=0.075,0.1,1/6）为前驱体合成了球形锂离子电池正极材料LiNi0.5-xCo2xMn0.5-xO2（x=0.075,0.1,1/6）,研究了钴含量对LiNi0.5-xCo2xMn0.5-xO2的物理性能和电化学性能的影响.SEM研究表明,球形LiNi0.5-xCo2xMn0.5-xO2由许多一次颗粒构成,随着钴含量的增加,产物中一次颗粒增大.XRD分析表明,LiNi0.5-xCo2xMn0.5-xO2均为具有层状结构的纯相物质.电化学性能测试结果显示,LiNi0.5-xCo2xMn0.5-xO2随着钴含量的增加,材料的充放电容量提高,且循环性能变好：0.2C倍率下、2.7～4.3V的电压范围内,LiNi0.425CO0.15Mn0.425O2的放电比容量为145mAh·g^-1、LiNi0.4CO0.2Mn（0.4）O2为150mAh·g^-1、LiNi1/3Co1/3Mn1/3O2为158mAh·g^-1,循环50周期后LiNi0.425CO0.15Mn0.425O2和LiNi0.4Co0.2Mn0.4O2的容量衰减率在3%以内,LiNi1/3Co1/3Mn1/3O2容量无衰减.交流阻抗测试结果表明,随着钴含量的增加,材料阻抗值减小.     

氢氧化物共沉淀法合成LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2及其性能研究

以氢氧化物共沉淀法合成了Ni0.4Co0.2Mn0.4(OH)2前驱体,然后以Ni0.4Co0.2Mn0.4(OH)2和LiOH为原料,合成出了层状结构的锂离子电池正极材料LiNi0.4Co0.2Mn0.4O2.通过XRD、SEM和电化学测试对LiNi0.4Co0.2Mn0.4O2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12h合成的样品粒度大小分布比较均匀,以0.2C充放电,其首次放电容量为148mAh·g-1,循环30次后容量为136mAh·g-1.     

以Ni-Mn水滑石为前驱体制备LiNi_(0.5)Mn_(0.5)O_2及锂过量对其性能的影响

以共沉淀法制得的前驱体与LiOH混合,在空气中800℃烧结12h得层状结构正极材料LiNi0.5Mn0.5O2X射线衍射结果表明,前驱体为层状镍锰水滑石结构;各LiNi0.5Mn0.5O2样品结晶完整但均有少量Li2MnO3杂质,且锂过量25%还有不明杂质生成.扫描电镜分析表明:前驱体为多孔隙的蜂窝结构;随着掺锂量的增加,LiNi0.5Mn0.5O2样品团聚加剧.电化学测试结果表明:在2.5～4.5V范围内,锂过量10%所合成样品首次放电容量最高,达181.2mAh/g;锂过量20%所合成样品循环性能最好,首次放电容量为172.8mAh/g,循环30次容量保持率为97.7%.     

富锂型锂离子电池正极材料的合成及性能研究

以LiAc·2H2O、Mn(Ac)2·4H2O、Ni(Ac)2·4H2O为原料,采用水溶液法合成锂离子电池正极材料LiNi0.5Mn0.5O2和Li1.2Ni0.3Mn0.5O2。通过X射线衍射(XRD)、扫描电子显微镜(SEM)对所得样品的结构和形貌进行表征,并测试了该材料的电化学性能。结果表明,样品LiNi0.5Mn0.5O2首次放电比容量能达到125.6mAh/g,经过30周循环以后,放电比容量为111.2mAh/g,容量保持率为96.2%;而富锂样品Li1.2Ni0.3Mn0.5O2首次放电比容量能达到187.2mAh/g,经过30周循环以后放电比容量为184.5mAh/g,容量保持率为98.6%,远高于富锂前样品。另外,富锂后的样品Li1.2Ni0.3Mn0.5O2倍率性能优于富锂前。     

锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2的合成及性能

采用氢氧化物共沉淀法合成了LiNi1/3Co1/3Mn1/3(OH)2前驱体,然后以Ni1/3Co1/3Mn1/3(OH)2和LiOH·H2O为原料,合成出了层状锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2.通过XRD、SEM和电化学测试对LiNi1/3-Co1/3Mn1/3O2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12h所合成的样品粒度大小分布比较均匀,该材料以0.2C充放电,其首次放电容量为150mAh·g-1,循环30次后容量为137mAh·g-1.     

锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2的合成及性能研究

以氢氧化钠为沉淀剂,采用共沉淀法合成了Ni1/3Co1/3Mn1/3(OH)2前驱体,前驱体和LiOH·H2O充分混合高温烧结制备了锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2.采用X射线衍射(XRD)、扫描电子显微镜(SEM)和电化学性能测试对LiNi1/3Co1/3Mn1/3O2正极材料的结构、微观形貌及电化学性能进行了表征.XRD结果表明,所合成的LiNi1/3Co1/3Mn1/3O2物相单一无杂相,具有标准的α-NaFeO2型层状结构.SEM测试显示,颗粒粒度均一,粒径大约在0.5μm,粒径分布窄.以20mA/g电流密度放电,充放电电压在2.8～4.4 V之间,首次放电比容量达到181mAh/g,80次循环之后放电比容量仍然保持在172mAh/g;循环伏安测试显示,LiNi1/3Co1/3Mn1/3O2反应中主要是Ni2 /Ni4 、Co3 /Co4 2个电对在起作用,锰的价态保持不变,起到支撑结构的作用.     

LiNi0.8-x Znx Co0.2 O2的合成及电化学性能研究

掺杂改性和表面修饰的LiNi0.8Co0.2O2是锂电池正极换代候选材料.采用共沉淀法制备了系列LiNi0.8-xZnxCo0.2O2材料,并对其进行X射线衍射(XRD)、扫描电镜(SEM)、循环伏安(CV)、电化学阻抗(EIS)和充放电循环性能(CP)测试分析.恒流循环(0.2C、3.0～4.2V)测试结果显示,Zn的掺入使材料的初始放电比容量有大幅增加,循环性能有所改善.其中LiNi0.78Zn0.02Co0.2O2的首次放电比容量达到206.37 mAh·g-1.第30循环时,放电比容量仍为204.03 mAh·g-1,不可逆容量损失仅为2.34 mAh·g-1,显示了很好的初期循环性能.     

钴含量对锂离子电池正极材料LiCo_xMn_(2-x)O_4的性能影响

采用流变相法合成了LiCoxMn2-xO4(x=0.00,0.05,0.10,0.15),并结合XRD、SEM和电化学性能测试等手段,研究了掺钴量对锂离子电池正极材料LiCoxMn2-xO4的晶体结构、外观形貌和电化学性能的影响。研究结果表明:钴的掺入能提高合成材料的结构稳定性;当x=0.05时,材料LiCoxMn2-xO4具有较高的放电比容量和较好的循环性能,可作为锂离子电池的正极材料。     

草酸盐共沉淀法合成锂离子电池LiNixMn0.8-xCo0.2O2（x=0.4,0.5）正极材料及电化学性能

采用草酸盐共沉淀法,结合高温固相反应法,合成了LiNix Mn0.8-x Co0.2O2(x=0.4,0.5)粉末材料,考察了焙烧时间和镍含量对LiNix Mn0.8-x Co0.2O2(x=0.4,0.5)结构与性能的影响。采用XRD、SEM和电池充放电测试方法等表征了材料的结构与性能。结果表明,800℃焙烧20h制备的LiNi0.5Mn0.3Co0.2O2具有良好的层状结构和综合电化学性能,阳离子混排程度小、六角晶格有序性好。0.2C倍率首次入放电容量为151mAh/g,循环20次后放电容量为148.4mAh/g。SEM结果表明LiNi0.5Mn0.3Co0.2O2是由0.5μm的一次颗粒组成,LiNi0.4Mn0.4Co0.2O2材料由0.5μm的一次颗粒团聚而成约8μm的二次颗粒组成。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.