YBCO高温超导磁体线圈的设计与优化

基于YBCO涂层导体的临界电流特性,采用有限元数值计算法设计了一个螺管型结构的混合带材高温超导磁体线圈。根据磁场分布、并考虑到带材的临界电流随磁场大小和方向的变化关系,给出了影响磁体工作电流特性的磁场分量在线圈中的位置分布。为了进一步提高磁体的工作电流和储能量大小,在考虑到磁场分量最不利点位置分布的情况下,对涂层导体磁体的结构和形状进行了优化,其结果对涂层导体超导电力装置的设计和构造具有一定的指导意义。     

新型高温超导直线感应电机的设计及有限元分析

结合直线感应电机设计原理,对高温超导直线感应电机的结构进行设计和对电磁场进行研究,最后利用大型有限元软件ANSYS对电机的电磁场、电磁力等进行仿真,同时进行了数据对比,仿真结果和理论分析取得较好的一致性。     

乳胶+PVA体系水基流延成型99氧化铝陶瓷材料

研究了乳胶+PVA复合粘结剂体系水基流延浆料制备99氧化铝陶瓷基片.通过研究浆料pH值、分散剂、粘结剂的比例等因素对水基流延浆料流变学性能的影响,得到了水基流延浆料的最佳配比范围.当pH值为9.0时,分散剂PAA含量为粉料的0.8%(质量分数)时能获得固含量为55vol%、稳定分散的氧化铝浆料.研究表明PVA与乳胶的化学相容性好,采用两种粘结剂复合,可以互补不足.加入复合粘结剂4.5%(质量分数) (乳胶:PVA=7:3),制备出的99氧化铝素坯片其厚度可在50～1000 μm之间进行调控,素坯相对密度可以达到56%左右.制备的流延片在烧结温度1650 ℃、保温2 h的条件下获得了相对密度为98.5%、平整、半透明的99氧化铝陶瓷基片.     

Fabrication of a working Bi-2223 superconducting magnet cooled by liquid nitrogen

A practical Bi-2223 superconducting magnet, working in liquid nitrogen (L.N₂), was designed and fabricated. Bi-2223 tape with a critical current of 147 A was prepared by a controlled overpressure (CT-OP) process at 77.3 K in self-field. Ten double-pancake coils were resistively connected by copper terminals. The bore diameter was 54 mm?, the magnet outer diameter was 122 mm?, the height of the magnet was 124 mm, and the weight of the magnet was about 3 kg. The maximum magnetic field at the center of the bore was 0.48 T with an operating current of 50 A. The experimental results agree well with design predictions calculated by finite element method. AC operation was also performed, and no distortion of the voltage waveform was observed. Therefore, this Bi-2223 superconducting magnet is a suitable replacement for copper magnets designed for applications in science and technology.     

Experimental study on the double-evaporator thermosiphon for cooling HTS (high temperature superconductor) system

A cryogenic thermosiphons is an efficient heat transfer device between a cryocooler and a thermal load that is to be cooled. This paper presents an idea of thermosiphon which contains two vertically-separated evaporators. This unique configuration of the thermosiphon is suitable for the purpose of cooling simultaneously two superconducting bearings of the HTS (high temperature superconducting) flywheel system at the same temperature. A so-called double-evaporator thermosiphon was designed, fabricated and tested using nitrogen as the working fluid under sub-atmospheric pressure condition. The interior thermal condition of the double-evaporator thermosiphon was examined in detail during its cool-down process according to the internal thermal states. The double-evaporator thermosiphon has operated successfully at steady-state operation under sub-atmospheric pressure. At the heat flow of 10.6 W, the total temperature difference of the thermosiphon was only 1.59 K and the temperature difference between the evaporators was 0.64 K. The temperature difference of two evaporators is attributed to the conductive thermal resistance of the adiabatic section between the evaporators. The method to reduce this temperature difference has been investigated and presented in this paper. The proper area selection of condenser, evaporator 1, and evaporator 2 was studied by using thermal resistance model to optimize the performance of a thermosiphon. The superior heat transfer characteristic of the double-evaporator thermosiphon without involving any cryogenic pump can be a great potential advantage for cooling HTS bulk modules that are separated vertically.     

流延法制备SOFC阳极支撑体基片

系统地研究了流延法制备SOFC阳极支撑体基片过程中影响流延浆料粘度和素坯质量的主要因素, 分析了球磨时间、有机混合溶剂类型、分散剂添加量、增塑剂/粘结剂比例(R)等参数以及除泡工艺对浆料流变性能的影响. 研究发现: 混合溶剂乙醇/二甲苯(体积比1:1)对粉料的湿润性能最好, 粉体的悬浮性能和浆料流变性能最佳; 分散剂添加量为1.8wt%时, 浆料的粘度最低; 研磨时间为24h制备的浆料流变性接近最佳状态; 浆料的粘度随R值的增大而急剧减小, 当R为1时粘度达到最佳值, 流变性能得到明显改善; 少量的除泡剂和真空搅拌对消除浆料制备过程中所产生的气泡极为有效.     

直流牵引电动机电枢后端钢丝绑扎可靠性分析

直流牵引电动机电枢后端有钢丝绑扎和无纬带绑扎两种结构形式,通过分析其利弊,结合试验对比及国内电机的实践运用,阐明钢丝绑扎在牵引电机上运用的必要性和运用安全可靠性.     

Investigations of nano- and macro-wear of magnetic tape head materials

The nano- and macro-wear characteristics of calcium titanate, single crystal ferrite and polycrystalline ferrite were investigated using nano-scratch testing and wear bar testing. Nano- and micro-indentations were made to determine nano- and micro-hardness, and nano-scratch testing was used to evaluate relative wear rates on the nano-scale. The macro-wear characteristics of the various head materials against metal particle tapes was investigated as a function of tape speed using wear bars mounted in a DLT tape drive. The micro-indentation method was used to investigate wear of the head/tape interface in a linear tape drive. The results from nano- and macro-wear tests were analysed and correlated with the microstructure of the materials.     

Some experiments on the micro-indentation of digital audio tape

The durability of digital audio tape is a function of the elastic and plastic properties of the magnetic layer and substrate. In this work a micro-indentation method has been used to estimate these properties. The loading part of the compliance curve (load against indentor penetration) is analysed to obtain magnetic layer hardness. The unloading part is used to determine the reduced elastic modulus. Indentations at various depths have been recorded and an extrapolation technique used to predict layer properties. Rate dependence of the magnetic layer has been studied through constant loading rate tests. Results are presented isochronally, to indicate any viscous elastic–plastic non-linearities.     

High density packaging technology ultra thin package & new tab package

As electronic devices become more highly integrated, the demand for small, high pin count packages has been increasing. We have developed two new types of IC packages in response to this demand. One is an ultra thin small outline package (TSOP) which has been reduced in size from the standard SOP and the other, which uses Tape Automated Bonding (TAB) technology, is a super thin, high pin count TAB in cap (T.I.C.) package. In this paper, we present these packages and their features along with the technologies used to improve package reliability and TAB. Thin packages are vulnerable to high humidity exposure, especially after heat shock.1 The following items were therefore investigated in order to improve humidity resistance: (1) The molding compound thermal stress, (2) Water absorption into the molding compound and its effect on package cracking during solder dipping, (3) Chip attach pad area and its affect on package cracking, (4) Adhesion between molding resin and chip attach pad and its affect on humidity resistance. With the improvements made as a result of these investigations, the reliability of the new thin packages is similar to that of the standard thicker plastic packages.