Magnetic properties of isomeric N,N′-di-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl)xylyl imine

Three novel isomeric N,N′-di-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl)xylyl imine (compounds 1, 2 and 3) were prepared and their structures were determined by X-ray single-crystal diffraction (except compound 1). ESR spectra were measured at room temperature. Temperature dependences of magnetic susceptibility down to 5 K for the organic biradicals 2 and 3 are described. The Weiss constants for compounds 2 and 3 are 0.2 and −0.03 K, respectively. The small differences in the magnetic properties of compounds 2 and 3 might arise from the isomeric difference in the molecular structure.     

Nano-structured LSM-YSZ refined with PdO/ZrO2 oxygen electrode for intermediate temperature reversible solid oxide cells

To promote the application of traditional (La_0.8Sr_0.2)_0.95MnO_3-δ-YSZ (LSM-YSZ) oxygen electrodes to both solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) modes at intermediate temperatures, we select PdO as the catalyst and ZrO₂ as the PdO stabilizer to decorate the LSM-YSZ. The high active PdO particles enhance the electrocatalytic activity, and stable ZrO₂ can hinder the growth and agglomeration of the PdO particles. PdO and ZrO₂ are co-impregnated into the LSM-YSZ to form a nano-structured PdO/ZrO₂ -LSM-YSZ composite electrode. At 750 °C, the obtained cell attains a power density peak of 1.114 W cm⁻² in SOFC mode and shows significant improvement of the cell with LSM-YSZ composite oxygen electrode. As a SOEC, when the water content is 90 vol%AH (absolute humidity) at the hydrogen electrode, the cell exhibits an extraordinary current density of 2.322 A cm⁻² under applied voltage of 2.0 V at 750 °C. Moreover, the cell shows notable long-term stability during water electrolysis. Therefore, this study demonstrates that the nano-structured PdO/ZrO₂ -LSM-YSZ based material as a high active and stable oxygen electrode can greatly promote the application of LSM-YSZ electrode in reversible solid oxide electrolysis cell (RSOCs) field.     

考虑晶粒尺寸影响的硬度预测模型

目的研究了晶粒尺寸对冷成形过程中材料硬度变化的影响。方法通过不同的退火处理,获得了具有不同晶粒尺寸的材料。采用压缩试验、压痕试验和有限元模拟相结合的方法,研究了不同初始晶粒尺寸条件下材料硬度与等效应变的关系。结果初始晶粒尺寸d对材料初始硬度HV0、硬化系数K、硬化指数n有较大影响,随着晶粒尺寸的增大,它们呈减小趋势。同时提出了一个考虑晶粒尺寸影响的硬度预测模型,并进行了实验验证,硬度的预测值与测量值吻合较好。结论该模型能准确预测具有不同初始晶粒尺寸的材料在冷成形过程中的硬度分布。     

智能锻造系统的研究现状及发展趋势

锻件在装备制造行业领域属于重要的承力基础零部件。随着我国由制造大国向制造强国转变,锻造行业迫切需要向智能制造方向发展。从智能锻造系统的4个模块阐述了智能锻造技术的发展:第一个模块为机器人自动化生产线及集成控制系统,是自动化产线的核心,用于执行端命令的下达;第二个模块是多机器人协作优化系统,用于调节机器人及设备运动以保证产线高效运作;第三个模块是锻造产线实时数据存储及分析系统,用于判断实时产线运行状况以触发新事件;第四个模块为新锻件工艺快速开发系统,用于新锻件工艺的设计与开发。还分析了目前智能锻造领域存在的问题,认为只有建立企业、高校和研究所等的紧密联系,以问题为导向进行攻关,在此基础上培养交叉复合型人才,才能促进智能锻造的进一步发展。     

固体氧化物燃料电池力学性能和形变行为研究

通过流延成型、丝网印刷和共烧结法成功制备了阳极支撑的平板式固体氧化物燃料电池(SOFCs)。采用陶瓷样品同轴环施力方式和双扭法测试单电池的抗弯强度和断裂韧性分别为156.69 MPa与2.51 MPa•m^1/2。当阳极支撑体由陶瓷(NiO/YSZ)还原为金属陶瓷(Ni/YSZ), 其抗弯强度和断裂韧性分别为104.48 MPa与3.95 MPa•m^1/2。同时电池的弯曲变形测试表明: 单电池经过阳极还原后弯曲变形程度变大, 平整化压力从电池阳极还原前的108 N增加至184 N, 而电池抵抗破裂能力增强。本研究显示, 随着阳极支撑体还原后单电池的断裂韧性显著提高, 将有效减缓其弯曲变形所引起的不利影响, 改善单电池的综合力学性能。     

纳米SiC晶须增强Ti(C,N)基金属陶瓷的显微组织与力学性能

采用真空烧结法制备了纳米SiC晶须增强Ti(C,N)基金属陶瓷复合材料,用XRD、FESEM、EDS、万能试验机及维氏硬度仪等手段研究了纳米SiC晶须对复合材料显微组织和抗弯强度及断裂韧度的影响。结果表明:复合材料的显微组织具有典型的芯-壳结构,主要由黑色的硬质核心相,灰色的环形相,灰白色的粘结相以及部分分布于外环形相/粘结相界面、部分弥散分布于粘结相中的白色增强相组成;随着纳米SiC晶须添加量的增加,粘结相的体积分数减小,增强相的体积分数增大;与未添加晶须的金属陶瓷相比,复合材料的抗弯强度和断裂韧度均有显著提高,当纳米SiC晶须的体积分数为7.5%时,复合材料的力学性能最佳,抗弯强度为2 346 MPa,断裂韧度为16.82 MPa·m~(1/2)。     

基于SOA的业务流程管理在模具协同设计任务管理中的应用

为了实现模具设计任务的自动管理,结合模具设计任务的特点,提出了基于活动树的任务分解模型.该模型能最大程度地避免任务间冲突的发生,并且能够保证模具设计人员之间模型信息的一致.在此模型的基础上,结合业务流程管理技术开发出了一套模具协同设计任务管理原型系统.该系统提高了模具协同设计的自动化程度,实现了模具设计任务的自动管理.     

电磁平板自由胀形3D数值模拟(英文)

电磁成形是一种高速率成形方法,它能够有效提高金属板材的成形极限。但是电磁成形过程复杂,涉及到磁场?结构场之间的耦合分析。数值模拟提供一种手段去解决耦合问题。然而,大多数的数值模拟都限于2D。建立3D有限元模型去分析电磁平板胀形。成形过程中考虑了板料与底模的接触和板料变形对磁场的影响。板料中心节点和半径20mm处节点的位移随着时间的变化与实验结果一致。分析了塑性应变能和塑性应变。     

Microstructure,tensile properties and fractography of A356 alloy under as-cast and T6 obtained with expendable pattern shell casting process

The microstructure, tensile properties and fractography of A356 alloy were studied under as-cast and T6 conditions obtained with expendable pattern shell casting, and the results were compared with lost foam casting (LFC). The results indicate that a(Al) primary, eutectic silicon and Mg₂Si are the main phases in the microstructure of A356 alloy obtained with this casting process. The eutectic silicon particles are spheroidized and uniformly distributed at the grain boundaries after T6 treatment. The average length, average width and aspect ratio of eutectic silicon particles after T6 condition decrease. The sizes of a(Al) primary phase and eutectic silicon of this casting process are smaller than those of LFC. The tensile strength, elongation and hardness of A356 alloy after T6 obviously increase, they reach 260.53 MPa, 6.15% and 86.0, respectively and have a significant improvement compared to LFC. The fracture surfaces of expendable pattern shell casting show a mixed quasi-cleavage and dimple fracture morphology as a transgranular fracture nature. However, the fracture surfaces of LFC display a brittle fracture.     

Development of novel glass-based composite seals for planar intermediate temperature solid oxide fuel cells

Novel glass-based composite seals prepared by tape casting are evaluated as sealing materials in solid oxide fuel cell. The leakage rates are measured at the inlet pressure of 1, 2 and 3 psi under different compressive stresses and temperatures respectively. The results show that all of measured leakage rates are lower than 0.01 sccm cm⁻¹ and increase with higher inlet pressure and lower test temperatures. The leakage rates during thermal cycling are conducted under a compressive stress of 20 psi at 750 °C, which indicate excellent thermal cycle stability of the seals. Good compatibility between seals and the adjacent components provide well interface contact which could avoid the formation of leakage paths. When the seal is applied for single cell testing, the open circuit voltage of 1.13 V and undetectable degradation clearly demonstrate the applicable performance of glass-based composite seal in solid oxide fuel cell.