TiO_2改性PVDF锂离子电池隔膜的研究

静电纺丝制备聚偏氟乙烯(PVDF)锂离子电池隔膜电化学性能一般,可采用混纺增强其电化学性能。采用二氧化钛(TiO_2)与PVDF混纺,制得TiO_2/PVDF锂离子电池隔膜,研究不同TiO_2的添加量对TiO_2/PVDF锂离子电池隔膜性能的影响,考察其力学性质、离子电导率、放电比容量和循环性能。结果表明:在添加1.5%(wt,质量分数)TiO_2条件下,制得的TiO_2/PVDF锂离子电池隔膜的孔隙率高达52.54%,吸液率403.70%,离子电导率4.2×10~(-4)S/cm;在0.5C条件下放电比容量为134.0mAh/g,循环25次条件下,TiO_2/PVDF锂离子电池隔膜的放电比容量仍有130.0mAh/g,放电比容量的波动小,循环稳定性好。     

PVDF/PMMA/TiO_2型聚合物隔膜的制备

为提高锂离子电池聚偏氟乙烯(PVDF)基聚合物隔膜的导电性和降低PVDF基聚合物隔膜的结晶度,引入聚甲基丙烯酸甲酯(PMMA)与聚偏氟乙烯(PVDF)进行共混,掺杂无机纳米材料TiO_2,采用相转化方法制备PVDF/PMMA/TiO_2型聚合物隔膜。通过对制备的PVDF/PMMA/TiO2型多孔膜吸液率、微观形貌和电化学性能的分析研究,确定制膜的最佳工艺条件为聚合物浓度为5%,PVDF∶PMMA为72∶28,纳米TiO_2添加量为5%,非溶剂添加量为3%,水浴温度为55℃。该方案下制备的多孔膜结晶度较纯PVDF薄膜结晶度降低,吸液率达到109.76%,离子电导率为2.64mS/cm,电化学稳定窗口为4.86V,高于4.5V,能够满足锂离子电池正常工作需要。     

直接挥发法制备无纺布增强型聚合物电解质

以N,N-二甲基-甲酰胺(DMF)为溶剂, 采用直接挥发法制备无纺布增强型聚偏氟乙烯-六氟丙烯(PVDF-HFP)聚合物电解质, 并以锂为负极制备了聚合物电池.用扫描电子显微镜、交流阻抗和循环伏安对所制聚合物膜性能进行了表征,用充放电实验对所制聚合物电池电化学性能进行了测试.实验结果表明,直接挥发法制得的聚合物膜孔穴丰富,微孔呈蜂窝状,吸液率为280%,电化学稳定窗口为4.5V,浸取电解液后室温离子电导率为1.5mS/cm;以LiCoO2为正极制得的聚合物电池0.1C充放电, 放电平台为3.9V左右, 首次放电容量为137.5mAh/g,20次循环后容量保持在134mAh/g以上,充放电库仑效率高于95%,0.5C放电时放电平台为3.7V,0.5和1C放电分别能保持0.1C放电容量的96%和93%.     

LiCoO2正极材料的络合法合成及其电化学性能研究

采用络合法制备了锂离子电池的活性正极材料LiCoO2纳米粉体,实验表明:合成的LiCoO2粉体结晶良好,层状结构发育完善,平均粒径为60nm而且粒径分布窄,比表面积大.电池充放电测试表明,正极的电化学性能与LiCoO2粉体的合成温度有关,其中700°C合成得到的LiCoO2正极材料具有最优的电化学性能:首次放电比容量高达167mAh/g,30次循环后其可逆比容量仍高达144mAh/g,容量损失13.8%.     

LiCoO2正极材料的络合法合成及其电化学性能研究

采用络合法制备了锂离子电池的活性正极材料iCoO2纳米粉体，实验表明：合成的LiCoO2粉体结晶良好，层奖结构发育完善，平均粒径为60nm而且粒径分布窄，比表面积大、电池充放电测试表明，正极的电化学性能与LiCoO2粉体的合成温度有关，其中700℃合成得到的LiCoO2正极材料具有最优的电化学性能：首次放电比容量高达167mAh/g,30次循环后其可逆比容量仍高达144mAh/g，容量损失13．8％。     

低温固相法制备Li离子电池正极材料FeSO_4F_yOH_(1-y)

采用低温固相法制备羟化氟硫酸铁正极材料。通过对煅烧温度和煅烧时间等因素进行摸索,得到最优化的实验条件,并用XRD、SEM和电化学测试系统对样品进行表征测试。研究发现,经300℃煅烧并保温10h,得到的样品颗粒尺寸均匀,尺寸保持在500nm左右,颗粒晶型完成,显示出最优的电化学性能。在0.1C倍率下首次放电比容量为60mAh/g,50次充放电循环后比容量的保持率为95.8%。     

电池级四氟硼酸锂制备工艺的优化及电化学性能研究

以氢氟酸、硼酸和碳酸锂为原料,溶液法新工艺制备电池级四氟硼酸锂。采用正交试验对工艺参数进行优化,通过电池测试系统及电化学工作站测试产物的电化学性能。确定最佳工艺参数为:反应温度7.5℃,原料摩尔比n(氢氟酸)∶n(硼酸)∶n(碳酸锂)=4.05∶1.00∶0.55,乙醇蒸发量为溶剂质量的65%,重结晶温度15℃。在此条件下获得的四氟硼酸锂纯度为99.59%,收率为90.08%。电化学性能测定结果:配制的电解液电导率为10.1ms/cm,组装的纽扣电池首次放电容量为152.9mAh/g,放电容量为139.9mAh/g,在1.0C的倍率下循环30次后其容量保持率达84.74%,循环效率维持在98.00%。     

添加有NiOOH的混合晶型Ni(OH)_2的电化学性能研究

采用络合沉淀法制备了具有特殊表面纳米片状结构的微米级混合晶型氢氧化镍,并研究了添加化学氧化NiOOH纳米颗粒对上述材料电化学性能的影响.采用SEM、XRD等手段表征了样品的形貌及物相特征,并考察了其作为镍氢电池正极活性材料的电化学性能.结果表明:添加的纳米片状β-NiOOH随机分布在氢氧化镍表面.以制备的样品为正极材料组装成镍氢模拟电池,在0.2C充放电条件下,制备材料的放电比容量可达306mAh/g;添加NiOOH能有效地改善镍电极的电化学性能,添加量为7wt%时,0.2C充放电条件下样品放电比容量为326mAh/g,在2C充放电条件下放电比容量可达311mAh/g.     

PVDF/PMMA/PEG型聚合物隔膜的制备

为提高锂离子电池聚偏氟乙烯(PVDF)基聚合物隔膜对电解液体系的亲和性和导电性,引入聚甲基丙烯酸甲酯(PMMA)与聚偏氟乙烯(PVDF)进行共混,并添加有机增塑剂聚乙二醇PEG-400对PVDF基聚合物隔膜进行改性研究。采用先干法后湿法的相转化方法制备PVDF/PMMA/PEG型聚合物隔膜。通过对制备的聚合物隔膜的孔隙率、吸液率、微观形貌和电化学性能的分析研究,确定制膜的最佳工艺条件为聚合物占溶剂质量百分比为8%,PVDF∶PMMA=7∶3,增塑剂含量为30%,非溶剂含量为3%,反应温度为45℃,在此最佳工艺条件下制备的PVDF/PMMA/PEG隔膜的离子电导率可达2.848 m S/cm,对电解液体系的亲和性和导电性得到显著提高。     

LiFePO4/C制备工艺的优化及其性能

用共沉淀法制备了球形NH4FePO4·H2O前驱体,再与Li2CO3和葡萄糖混合用固相焙烧法制备了LiFePO4/C正极材料.利用正交实验考察了焙烧温度、焙烧时间、球磨时间、x(Li):x(Fe)和葡萄糖用量等对材料首次放电比容量的影响,得到了最佳工艺条件.通过XRD、SEM、FTIR和恒流充放电测试仪等测试了材料的结构和电化学性能.所得材料在室温下电流密度为0.1、0.5和1C时首次放电比容量分别为147.6、136.7和122.3mAh/g,循环50次后容量分别为142.8、127.3和106.7mAh/g;在60℃下电流密度为0.5C时,其首次放电比容量为163.8mAh/g,循环性能良好.     

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.……     

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.     

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 ...