表面活性剂tween60对正极材料LiFePO_4/C的制备及其电化学性能影响

采用高温固相法合成锂离子正极材料LiFePO4/C,在合成过程中分别采用高能球磨和引入表面活性剂。用扫描电镜(SEM),粒度分布仪和X-ray粉末衍射仪(XRD)对材料微观形貌、晶体结构进行表征,并进行电化学性能测试。结果表明:所制备LiFePO4/C材料晶型完美,二次颗粒分布范围1~30μm,一次颗粒分布范围100~200nm,具有较高的振实密度1.3g/cm3和良好的电化学性能。在25℃时,0.1C和5C倍率下放电容分别达到161.5和120mAh/g。在-20℃,0.1C下放电容仍然能达到123.5mAh/g。在25℃,高倍率5C下,LiFePO4/C显示优异的循环性能,经过300次循环后容量保持率还能达到97%。研究结果表明所制备LiFePO4/C正极材料能够满足混合动力汽车应用。     

Ru-Cr下底层成分对Co-W磁性薄膜结构和磁性能的影响

用直流磁控溅射在300℃不同Ru-x%Cr(x=0,20,40)下底层沉积制备了Co-15%W(原子分数)磁性薄膜。用XRD表征了薄膜的精细晶体结构,分析了Co-W和Ru-Cr层的取向关系,估算了薄膜层的晶格常数、c轴分散角、fcc/hcp体积百分比和堆垛层错密度值。结果表明,随着Ru-Cr下底层Cr成分的增加Co-W磁性层和Ru-Cr下底层间的晶格错配度降低,hcp-Co的晶格常数比c/a随之减小。磁性能测试结果证实,由于Co-W磁性层中晶格常数比c/a的减小磁性层的磁各向异性能显著提高。     

球形LiFePO4材料碳包覆的研究

主要研究了采用不同碳源和掺碳量包覆对液相共沉淀-碳热还原法制备的球形LiFePO4材料性能的影响.结果表明,采用过量5%葡萄糖作碳源制备的材料在0.1C下,首次放电比容量达到了154.6mAh/g,并且循环性能良好.     

水热合成LiFePO_4/C材料电化学性能的颗粒尺度敏感性

通过控制水热法过程中的水热反应加热速度,制备了3种不同颗粒尺度的LiFePO4/C锂离子电池正极材料。结果表明,加热速度越快,LiFePO4/C平均粒径越小,分布越集中。当加热速率从5℃/min升至15℃/min时,材料颗粒半径从336nm减小到200nm,0.1 C放电容量从154 mAh/g增至162mAh/g,而20C放电容量则从75mAh/g显著增大至127mAh/g。LiFePO4/C材料的电化学性能表现出明显的尺度敏感性,特别是在高倍率充放电条件下。     

球形纳米晶LiFePO4和Li4Ti5O12的制备及电池研究

分别通过"控制结晶"和"外凝胶"工艺合成了球形纳米晶LiFePO4/C和Li4Ti5O12/C材料.通过XRD、SEM、比表面及电化学性能测试等分析手段表明,合成的LiFePO4/C和Li4Ti5O12/C材料均为纳米一次粒子(晶粒)组成的球形二次粒子(颗粒),具有较大的比表面积,振实密度分别达到1.25和1.71g/cm3;1C倍率下的首次放电比容量分别达到144.0和144.2mAh/g,并表现出优良的循环性能.以LiFePO4/C和Li4Ti5O12/C为正负极材料组成的1.8V锂离子电池具有平稳的充放电电压平台和优异的循环性能.     

控制结晶-碳热还原制备LiFePO_4正极材料

通过"控制结晶"-碳热还原工艺合成出了球形LiFePO4/C材料。通过XRD、SEM、比表面及电化学性能测试等分析手段表明,通过调整控制结晶工艺参数,可以对产品颗粒粒径进行有效调控;合成出的LiFePO4/C材料呈类球形,具有较好的流动性和较高的堆积密度。比较了不同粒径材料的性能,发现平均粒径在5μm时材料具有相对最好的综合性能。将该材料与目前市场上的几个优质产品进行了横向测评,以该材料制作出的电池具有更优异的电化学性能,特别是在高倍率下的电化学性能。     

表面多孔球形LiFePO4/C的制备及其电化学性能

采用一步溶剂热法合成球形LiFePO4,并进一步在饱和葡萄糖溶液中浸泡包碳形成表面多孔球形LiFePO4/C.利用XRD、SEM、HRTEM、FTIR和BET对样品的纯度、成分、晶型、形貌和孔结构进行了表征.实验结果表明:表面多孔结构使表面多孔球形LiFePO4/C拥有更大的比表面积以及更多的活性位点,并极大缩短了锂离子在充放电过程中的迁移距离,降低锂离子在材料中扩散及脱嵌阻力;在保持较高振实密度(1.36 g·cm-3)的前提下进一步提高材料的利用率以及较大倍率下的充放电性能,使表面多孔球形LiFePO4/C拥有优良的电化学性能.     

柠檬酸包覆合成LiFePO4/C工艺的优化

以柠檬酸为碳源,采用机械液相球磨与高温固相烧结相结合制备了LiFePO4/C复合材料,考察了烧结温度、烧结时间、柠檬酸用量、球磨时间等工艺条件对LiFePO4/C材料性能的影响.采用XRD、SEM和恒电流充放电等手段对该材料进行结构表征和电化学性能测试.结果表明,合成LiFePO4/C复合正极材料的适宜工艺为,球磨时间10h,烧结温度600℃,烧结时间18h,柠檬酸用量10%,气体流量0.6L/min.在优化工艺条件下制备的LiFePO4/C复合正极材料首次放电容量可达到146.2mAh/g.     

聚乙二醇对磷酸铁锂形貌及电化学性能的影响

采用溶胶-凝胶法制备了LiFePO4。研究了聚乙二醇对LiFePO4材料形貌和电化学性能的影响。结果表明,添加聚乙二醇制备的材料具有更小的粒径,更大的比表面积;该材料以0.2C、1C、5C、10C的倍率放电,首次放电比容量分别达到143.9mAh/g、133.4mAh/g、124.2mAh/g、112.7mAh/g,比没添加聚乙二醇制备的材料具有更好的倍率性能。     

用两种碳源制备高性能LiFePO4/C正极材料

为了提高LiFePO4材料的电化学性能,以碳溶胶和葡萄糖两种物质为碳源、采用高温固相法制备了LiFePO4/C复合正极材料.通过XRD、TEM、恒电流充放电等方法研究了材料的结构与电化学性能.XRD结果表明,两种碳源的添加对LiFePO4的晶体结构没有影响.从TEM图上可观测到颗粒外部明显的碳包覆层.电化学性能测试表明,在同样倍率下,以两种碳源制备的LiFePO4/C材料放电比容量高于以单一碳源制备的LiFePO4/C,且表现出优良倍率性能和循环稳定性:在0.1C下的放电比容量达162mAh/g,1C下放电比容量为157mAh/g,循环20次后容量没有任何衰减.     

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.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

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.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

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.……     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.