极低温—力—电—磁多场环境场下高温超导材料性能测试仪器研制及其应用研究

发布时间：2018-03-16 08:37

本文选题：高温超导带材　切入点：YBCO　出处：《兰州大学》2017年博士论文　论文类型：学位论文

【摘要】：高温超导材料具有高的临界转变温度、高的上临界磁场及在高磁场环境下优越的载流性能,在电力运输、强磁场科学、交通领域等展现出广阔的应用前景。在以上应用中,超导材料均处在低温、强磁场及大电流复杂多场环境中,其热应力、电磁力会导致超导材料发生变形,进而降低其临界电流,给超导器件带来巨大的安全隐患,因此研究高温超导材料在极低温-力-电-磁多场环境下的临界电流特性成为优化材料制备工艺、进一步推动其工程实用化的关键科学问题。另外,受目前高温超导材料可制备长度限制,接头成为其应用中关键组成部件,开展接头制备工艺及其在多场复杂环境下的力学、电学特性研究具有重要的科学意义和工程应用价值。本论文针对这两类问题开展研究,取得的主要成果如下:首先,研制了一套液氮直接冷却、力-电-磁多场环境超导材料临界电流测试系统(第一代)。该系统可实现超导材料临界电流的多环境场、及其载流稳定性的测试,具有较高的测试精度。在此基础上对YBCO涂层导体(YBCO CC)和Bi系第一代带材(Bi-2223)开展了多场环境下临界电流测试,得到了77K自场环境下的临界电流、力-电-磁特性、不可逆应变、稳定性等重要参数。接着,在第一代仪器基础上设计了一套研究横向压缩引起超导材料临界电流变化的测试夹具。对YBCO CC开展了横向压缩特性测试,并通过n值揭示了临界电流衰减的原因。同时,研制了一套液氮环境、电、磁多环境场超导材料层间剥离强度的测试设备。对YBCO CC开展了常温、液氮温度机械剥离强度测试及77K环境下力-磁、力-电等特征测试,并借助三维有限元的方法分析揭示了YBCO CC的剥离位置及剥离机制。然后,提出一种的新的超导接头焊接工艺,当焊接长度为8cm时,接触电阻为8.35n?,成为目前文献报道中的最小值。实验发现,采用该种新的焊接工艺所获得的焊接接头具有较优越的力-电性能,与完整带材基本相当。接着对制备工艺过程参数如焊接预压力、焊接长度等关键参数对接头性能的影响开展了系统研究,获得了最优的工艺流程参数。最后对横向压缩和剥离过程中接头端部效应引起临界电流的衰减进行了研究,揭示出这两个过程中临界电流衰减的本质原因为端部的应力集中导致YBCO超导层损坏。最后,提出了相应的接头强化方案,并给予了实验证实。最后,设计一种新的高温超导二流引线,成功解决了密闭空间大电流引入及传输焦耳热等技术难题,自主研制了一套采用G-M制冷机直接冷却的力-热-电-磁多场环境、且具有可视化功能的测试装置(第二代)。该设备在超高真空、极小空间内可实现6.59K至300K连续变温控制,最大测试电流可达600A,最大拉伸应变20%,外加垂直磁场0~5T,具备多场环境下的超导材料力学、电磁学性能测试的功能。另外,结合磁光系统实现了超导材料内部损伤的原位、实时观测,这使得对超导材料在变形过程中内部损伤机制及其对临界电流的影响研究成为可能。最后,利用该设备对YBCO CC和Bi-2223展开了变温环境下的多场性能测试,并根据测试数据对已有的理论预测模型的合理性进行了分析。
[Abstract]:High temperature superconducting materials with high critical temperature, high critical magnetic field in high magnetic field environment and superior carrier performance, strong magnetic field in the power transportation, science, transportation and other fields show a broad application prospects. In the above applications, superconducting materials are in low temperature, strong magnetic field and high current complex multi field in the environment, the thermal stress, the electromagnetic force will cause deformation of superconducting materials, thereby reducing the critical current, bring great hidden troubles in superconducting devices, so the research of high temperature superconducting materials at extremely low temperature force electric critical current characteristics of magnetic field environment into the preparation process optimization of materials, to further promote the the key scientific problems in practical engineering. In addition, the high temperature superconducting material can be prepared by the length limit, joint has become the key components in the application, to carry out joint preparation process and mechanics in a multi field under complex environment Study on electrical properties, it has important scientific significance and engineering application value. This thesis focuses on the two types of research, the main results are as follows: firstly, we developed a set of direct liquid nitrogen cooling, magneto electro field critical current superconducting material environment test system (first generation). The system can realize multi field critical current of superconducting materials, and the current carrying stability test, with high precision. On the basis of YBCO coated conductor (YBCO CC) and Bi is the first generation of strip (Bi-2223) to carry out critical current field test, obtained the 77K critical current self field environment. Electro - magnetic properties, irreversible strain, stability and other important parameters. Then, in the first generation of instrument is designed based on the transverse compression test fixture caused by changes in the critical current of superconducting materials. A research on YBCO CC carried out a transverse compression characteristic measurement Try, and through the n value revealed the critical current attenuation. At the same time, developed a set of liquid nitrogen environment, electrical test equipment, peel strength magnetic environment field superconducting material layer. The YBCO CC was carried out at room temperature and liquid nitrogen temperature mechanical peeling strength test and 77K environment stress magnetic force electric, etc. characteristics of the test, and with the analysis of three-dimensional finite element method to reveal the position and YBCO CC stripping stripping mechanism. Then, put forward a kind of new superconducting joint welding process, when the welding length is 8cm, the contact resistance is 8.35n?, has become the minimum value reported in the literature. The experimental results showed that, by using welding joints the new welding process has superior mechanical electrical properties, and the complete strip is quite basic. Then the preparation process parameters such as welding pressure, welding length of key parameters on joint properties studied, obtained The optimal process parameters. At the end of the end of the joint effect caused by attenuation of critical current of transverse compression and stripping process, reveals the essential reason of the two critical current attenuation in the process of concentrating stress caused YBCO superconducting layer damage. Finally, put forward the corresponding joint strengthening scheme, and given the experimental results. Finally, the design of a new high temperature superconducting second lead, successfully solved the technical problem of large current into the confined space and transmission of Joule heat, developed by a G-M cryocooler directly cooled by a thermo electric magnetic field environment, the test device and with the visualization function (the second generation). The equipment in ultra high vacuum, small space can be realized within 6.59K to 300K continuous temperature control, the maximum test current is 600A, the maximum tensile strain 20%, perpendicular magnetic field 0~5T with multi field environment super Guide the material mechanics, electromagnetism performance test function. In addition, combined with the magnetic optical system in situ, internal damage of superconducting materials and real-time observation, which makes the superconducting material in the deformation process of internal damage mechanism and its influence on the critical current as possible. Finally, the multi field performance test under varying temperature of YBCO CC and Bi-2223 with the equipment, and according to the test data prediction model has analyzed the rationality of the existing theory.

【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM26

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