非对称电化学电容器负极材料Li4Ti5O12的研究进展

Li4Ti5O12是一种尖晶石结构的可嵌锂材料,具有比能量高、循环性能稳定等特点,是电化学储能器件理想的电极材料.综述了Li4Ti5O12用作非对称电化学电容器电极材料的结构特点、储能原理、合成方法、电化学性能以及改性研究.针对Li4Ti5O12作为非对称电化学电容器负极材料大电流充放电时性能不佳的问题,提出了改进Li4Ti5O12电极材料电化学性能的研究思路.     

负极活性材料Li4Ti5O12的研究进展

介绍了负极材料Li4Ti5O12的物理特性和电化学性能，详细介绍并评述了Li4Ti5O12在锂离子电池和不对称型超级电容器中的应用情况，总结了Li4Ti5O12的不同合成方法及材料的电化学改性研究进展．     

尖晶石Li4Ti5O12-xFx的制备与电化学计量性能研究

为了改善尖晶石型Li4Ti5O12材料的电子电导率和离子导电性,许多研究者认为阳离子掺杂改性是较有效的途径之一。主要通过金属阳离子V5+,Mn4+,Fe3+,Al3+,Ga3+Co3+,Cr3+,Ni2+,Mg2+等取代锂位或者钛位来提高导电性,改善电化学特性。本文主要是通过高温固相法合成F-掺杂的尖晶石化合物Li4Ti5O12-xFx及对其电化学性能的影响。     

己二酸辅助溶胶-凝胶法合成Li_4Ti_5O_(12)及其电化学性能

以己二酸为络合剂,通过溶胶-凝胶法合成了具有优良电化学性能的电极材料Li4Ti5O12。采用XRD、SEM、恒流充放电测试对材料的结构、形貌和电化学性能进行了表征。结果表明:通过该法制备的样品为颗粒细小均匀的立方尖晶石Li4Ti5O12纯相,并显示出优良的电化学性能;0.1C倍率下首次放电比容量为169.59mAh/g,经过30充放电循环后仍然保持在158.17mAh/g。在2.0C倍率下,其可逆容量仍可达到124mAh/g,表现出良好的倍率性能。     

精细化砂磨制备纳米Li_4Ti_5O_(12)电极材料及其电化学性能研究

在固相法合成纳米Li4Ti5O12电极材料的过程中采用精细化砂磨技术,研究发现砂磨处理时间是影响纳米Li4Ti5O12微观结构和电化学性能的关键因素,XRD表明砂磨处理后Li4Ti5O12仍为尖晶石结构,粒度分布和SEM照片显示经过精细化砂磨处理后,Li4Ti5O12颗粒平均粒径由500 nm减小为370 nm,粒径分布也更加均匀;电化学性能评价结果显示,砂磨处理可使Li4Ti5O12电极材料倍率比容量增大约10~20 mAh/g,高倍率下增幅较低倍率更大,100次循环容量基本无衰减,稳定性很好。     

Li4Ti5O12-聚苯胺复合材料的制备与电化学性能

以醋酸锂和钛酸四丁酯为原料，以乙醇为溶剂，采用溶胶．凝胶法制备Li4Ti5O12；以苯胺、过硫酸铵为原料，以盐酸为溶剂，采用原位聚合法合成Li4Ti5O12-聚苯胺复合材料。采用x射线衍射、红外光谱和电化学测试等对复合材料进行了表征。结果表明，聚苯胺的加入明显提高了Li4Ti5O12的电子导电性能，Li4rri5O12-PAn复合材料具有比Li4Ti5O12更好的高倍率性能和循环稳定性。0.1C和2.0C放电时Li4Ti5O12-PAn的放电容量达到了191．3和148．9mAh．g^-1，经80次循环后二者平均每次循环容量衰减率分别为0．13％和0．61％。     

尖晶石钛酸锂的三乙醇胺辅助溶胶-凝胶法合成及其性能

以三乙醇胺为配位剂,Ti(OC4H9)4和LiAc·2H2O为原料,通过溶胶-凝胶法制备锂离子电池负极材料尖晶石Li4Ti5O12。通过X射线衍射、扫描电子显微镜、循环伏安、电化学阻抗和恒流充放电分析检测产物的结构、形貌及电化学性能。结果表明:配位剂的用量对Li4Ti5O12结构及电化学性能有显著影响,其中三乙醇胺与Ti摩尔比为0.8时,Li4Ti5O12具有良好的的电化学性能。1.0C下,其首次放电容量为153.0mAh·g-1,35次循环后放电容量仍为139.9mAh·g-1,容量保持率为91.5%。     

锂离子电池Li_4Ti_5O_(12)负极材料的尿素掺杂氮化修饰

Li4Ti5O12是最具前景的混合电动汽车用锂离子动力电池负极材料之一.为了提高其倍率性能,以尿素为氮源对Li4Ti5O12进行掺杂热处理,以在Li4Ti5O12颗粒表面自生长一层高电导TiN修饰膜,利用X射线衍射仪、扫描电镜、透射电镜、X射线能谱仪、Raman光谱仪和半电池充放电测试仪研究了材料的物相、结构、形貌、成分以及电化学性能.结果表明:氮化修饰Li4Ti5O12样品与未修饰样品具有相同的尖晶石Li4Ti5O12的衍射峰,氮化修饰后Li4Ti5O12颗粒表面自生长了一层均匀的薄膜,该薄膜不仅含有N元素,而且还具有TiN的Raman光谱特征振动峰;氮化修饰Li4Ti5O12样品的0.1C首次放电比容量比未修饰Li4Ti5O12样品有所降低,但是却展示了优异的电化学倍率性能和循环性能,3C倍率充放电比容量是未修饰Li4Ti5O12样品的2.6倍,0.1C充放电循环100次后其容量损失仅3%.     

尖晶石型 Li4Ti5O12电极材料的合成与电化学性能研究

分别采用三种方法合成了尖晶石型Li4Ti5O12电极材料.考察了不同的工艺条件对目标材料性能的影响.应用XRD、SEM、LSD、CV、AC impedance以及恒流充放电测试等手段对目标材料进行了结构表征和性能测试.结果表明,利用溶剂分散湿磨可以在较短的时间内得到纯相的Li4Ti5O12.葡萄糖的加入能够提高Li4Ti5O12导电性,使材料具有良好的嵌锂性能.在0.2C倍率下进行充放电测试,其可逆比容量超过160mAh·g-1,44次循环后,容量没有明显衰减.Li4Ti5O12/LiFePO4实验电池测试表明Li4Ti5O12是可选的锂离子负极材料.     

Li4Ti4.95Al0.05O12/C复合负极材料的制备及电性能研究

Li4Ti5O12是具有良好应用前景的锂离子电池负极材料之一.本研究以聚丙烯酰胺(PAM)为模板剂和碳源,采用改进的固相合成法制备锂离子电池负极材料Li4Ti4.95Al0.05O12和Li4Ti4.95Al0.05O12/C.利用X射线衍射仪、场发射扫描电镜等测试手段表征材料的物相结构和形貌.结果表明:Al掺杂未改变Li4Ti5O12的尖晶石结构,合成过程中PAM模板剂的引入能够有效调控材料微观形貌并降低颗粒团聚程度.采用恒流充放电和交流阻抗测试材料的电化学性能,Li4Ti4.95Al0.05O12/C复合材料的比容量和循环性能得到明显改善,0.2C倍率下首次充放电比容量分别达到159.2和160.8 mAh/g,5C倍率时仍有较好的循环性能.     

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.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

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.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

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 ...