国外BSCCO HTS带材研究进展

评述了国外BSCCO高温超导（HTS）带材的最新进展。目前，工业轧制的Bi（Ph）－2223多芯带材短样的Jc（77K，0T）高达58000A·cm－2,千米以上长带的Jc（77K，自场）在1×104A·cm-2以上。用BSCCOHTS带村绕制的大线圈在20K产生了高达7T的磁场。在提高带材性能的同时，人们还研究成功许多制取BSCCO带材的改进工艺，其中，带材连续制取工艺可使BSCCO带的成本降低到一般产品的水平。

Characteristics of Bi-2223 HTS Tapes Under Short-Circuit Current Impacts in Hybrid Energy Transmission Pipelines

A hybrid energy transmission pipeline is proposed with the aim of long-distance cooperative transmission of electricity and chemical fuels, which is composed of an inner high-temperature superconducting (HTS) power cable and outer liquefied natural gas (LNG) pipeline. The flowing LNG could maintain the operating temperature of the inner HTS power cable within the range of 85 K-90 K, thus the Bi-2223 superconductors in the HTS power cable produce little Joule loss with the transmission current below the critical current. Owing to the advantages of high power density, low transmission losses and economical manufacturing costs, the hybrid energy transmission pipeline is expected to be widely utilized in the near future. In order to ensure the safety of the HTS power cable and explosive LNG in case of short-circuit faults, this paper tests and analyzes the characteristics of Bi-2223 HTS tapes of the Type HT-CA, Type HT-SS and Type H models under short-circuit current impacts at the LNG cooling temperature (85 K-90 K). An experimental platform is designed and established for the ampacity tests of HTS tapes above LN2 cooling temperature (77 K). The AC over-current impact tests at 85 K-90 K are carried out on each sample of Bi-2223 tapes respectively, and the experimental results are analyzed and compared to evaluate their performances under different operating conditions. The results indicate that the Type HT-CA tape can withstand 50 Hz short-circuit current impact with the amplitude of 1108 A (10 times of critical current Ic ) for 100 ms at 90 K, and its resistance is the smallest of the three tested samples under similar current impacts. Therefore, the Type HT-CA Bi-2223 tape is the optimal superconductor of the HTS power cable in the hybrid energy transmission pipeline.

Numerical simulation of the mechanical behavior of superconducting tape in conductor on round core cable using the cohesive zone model

Cables composed of rare-earth barium copper oxide(REBCO)tapes have been extensively used in various superconducting devices.In recent years,conductor on round core(CORC)cable has drawn the attention of researchers with its outstanding current-carrying capacity and mechanical properties.The REBCO tapes are wound spirally on the surface of CORC cable.Under extreme loadings,the REBCO tapes with layered composite structures are vulnerable,which can lead to degradation of critical current and even quenching of superconducting devices.In this paper,we simulate the deformation of CORC cable under external loads,and analyze the damage inside the tape with the cohesive zone model(CZM).Firstly,the fabrication and cabling of CORC are simulated,and the stresses and strains generated in the tape are extracted as the initial condition of the next step.Then,the tension and bending loads are applied to CORC cable,and the damage distribution inside the tape is presented.In addition,the effects of some parameters on the damage are discussed during the bending simulations.

Effects of Deformation and Heat－treatment Process on Texture of Bi－2223／Ag Su perconducting Tapes

The effects of deformation and heat-treatment on texture of BSCCO-2223/Ag tapes were investigatedby using single orientation quantitative texture analytical methods. The results show that when tapes weresintered at 835℃ for 24～48 h, the texture developed quickly, and further prolonging sintering tirne hadno significant influence on it. With the increase of deformation rate, the volume fraction of c-axis texturewas improved in linear form at first and then changed slowly. The highest volume fraction of c-axis texture(vol%)in these experiments is 33 . 49 % .

连接参数对Bi系(BSCCO)超导带材扩散连接接头性能的影响

采用高温直接加压退火工艺扩散连接61芯B i系高温超导带材。研究了835℃连接温度下接头搭接长度、搭接区窗口的台阶数、保温时间对接头结合界面特征及其超导电性的影响。结果表明,连接参数对接头超导电性Ic影响明显,超导电性低的接头其超导芯结合界面处有未焊合迹象,母材经过835℃扩散连接热循环后超导电性显著降低。

Elaboration of a Promising Design of the HTS Conductor for the Central Solenoid of a Compact Thermonuclear Reactor TRT

The results of the preliminary development of the HTS conductor based on the VS-type design and parallel stacks for the central solenoid of the compact thermonuclear reactor TRT are presented. One of the main problems that need to be solved for the successful implementation of such projects is the creation of high-current high-temperature superconducting (HTS) conductors for Toroidal Field coils (TF) and Central Solenoid (CS) sections. The conductor must have a high engineering current density of at least 90 A/mm2. The induction of the magnetic field in the central solenoid reaches 14 T, which leads to the occurrence of large mechanical stresses due to the influence of Lorentz forces. Like many large magnets, CS has a lot of stored energy. For the safe withdrawal of stored energy from the magnet, it requires the inclusion of elements in the conductor that provide an acceptable level of electrical voltage and heating of the conductor insulation. Thus, a sufficient amount of stabilizing and reinforcing materials should be placed in the conductor. In addition, the “cable-in-conduit” type of conductor must have channels for pumping the refrigerant. Two fundamentally different versions of the conductor based on radially arranged REBCO tapes and on the basis of pre-assembled tape packages are considered. Based on the analysis of the magnetic field distribution in the conductor by finite element method, the design characteristics of the proposed conductors under various operating modes of the electromagnetic system (EMS) of the tokamak TRT was evaluated. The results of the evaluation of the current carrying capacity of the conductor and the estimation of energy losses in a changing magnetic field in comparison with known methods are also presented.

基于BSCCO-CC的准各项同性超导股线电流特性研究

设计了一种基于铋锶钙铜氧化物高温超导带材(BSCCO-CC)的方形四分准各向同性超导股线结构,研究其电流特性的主要参数,包括自场临界电流、n值和外场临界电流及它们随外加磁场的变化关系。随后利用电磁仿真软件Ansoft Maxwell建模仿真,得到超导股线自场下的磁场分布,并结合Matlab软件进行计算,得到超导股线自场临界电流值、n值和外场临界电流值,并对外场电流值与外加磁场的变化关系进行分析得到相关结论。仿真验证本文所设计的BSCCO-CC方形四分准各向同性超导股线结构的合理性,证明该结构具备优良的电流特性。

Progress in inhomogeneity of critical current and index n value measurements on HTS tapes using contact-free method

The development of high temperature superconducting(HTS)tapes has recently made great progress,and Bi-based tapes(1 G) and YBCO coated conductor(2 G)are commercially fabricated with practical length.Application of HTS in electric power apparatuses made important achievement,various superconducting devices were demonstrated in grid,laying solid foundation for their commercialization.However,since their intrinsic microscopic defects such as weak-link,granularity,small second phase likely exist,critical current and index n value of the HTS tapes in practical length are impossible homogeneous,which have significant influences on safety,stability and efficiency of the HTS apparatuses.Therefore,critical current and index n value are two important parameters describing inhomogeneity of HTS tapes,thus two important indices for evaluating quality of practical long HTS tapes.This paper focuses on main progresses in inhomogeneity of critical current and index n value measurements on HTS tapes using contact-free methods.The statistical analytical methods evaluating the inhomogeneity of critical current and index n value are suggested.They can provide essential references for design and operation of HTS apparatuses.

BSCCO超导带材的工艺要点与应用

高温超导材料的发现,推进了超导技术的实用化。作为典型的高温超导材料,铋系(BSCCO)超导带材目前已在超导电缆、超导限流器和超导储能等领域实现商用。粉末套管法是制备BSCCO超导带材最常用的方法,主要工艺步骤包括装粉、拉拔、轧制和热处理等。本文介绍了粉末套管法的工艺,重点介绍了各工艺步骤中的关键点,阐述了超导带材在超导限流器和超导储能系统中的应用,提出了BSCCO超导带材未来的发展方向。

Experimental investigation on frequency-dependent critical current of HTS tapes

Based on characteristics of alternating current （AC） critical current of high temperature superconducting （HTS） tapes on the frequency, this paper focuses on AC voltage-current （U-I） behaviors of two kinds of high temperature superconducting tapes, by which BSCCO and YBCO carrying different frequency AC currents are tested in liquid nitrogen temperature of 77 K. It is shown that the AC U-I characteristic curves of different tapes consist of two parts, that is, the resistive part and the hysteresis part. Additionally, the n values of the two parts and the relationship between AC critical current and frequency are obtained through experiments. The experimental results agree with calculated ones well, which is useful for the application of HTS tapes to power technology.

接头电阻对CORC电缆交流损耗的影响分析

采用第二代高温超导(HTS)带材绕制的CORC电缆具有载流能力高、力学性能好等优点,是制造核聚变磁体的理想电缆之一。然而,当由CORC电缆制造的核聚变磁体闭环运行时,现有的工艺很难保证每根CORC电缆的超导带材的接头电阻完全相同,这会对CORC电缆的交流损耗等电气特性产生重要影响。因此,该文搭建了含接头电阻的CORC电缆的三维有限元模型,分析了接头电阻对CORC电缆交流损耗的影响。结果表明,当CORC电缆传输交流电流时,不均匀的接头电阻将导致CORC电缆三根超导带的电流分布不均匀,进而增加了电缆的总体交流损耗。此外,得到了CORC电缆的交流损耗总是随着接头电阻不均匀程度的增加而增大的分析结果。

Bi2223/Ag带HTS双饼线圈中的接头焊接

降低双饼线圈间的搭接电阻 ,可有效提高 HTS磁体的稳定性并降低制冷费用。文中在分析影响搭接电阻因素的基础上 ,对双饼线圈间的焊接工艺和接头性能进行了实验研究 。

HTS磁体性能实验研究

系统介绍 HTS实验磁体的液氮、液氦实验和固氮浸渍实验 ,获得 78.6～ 4 .2 K不同温度下磁体的伏～安特性曲线和 Ic～ T曲线 ,在很宽的范围内研究了 HTS实验磁体性能。

HTS电流引线中接头电阻的研究和焊接工艺

针对Bi-2223/Ag-Au高温超导带材制造的二元HTS电流引线设计中不同材料之间连接的技术要求,设计了减小接头电阻的焊接工艺实验,包括焊接温度、焊料、搭接长度和焊锡层厚度对接头电阻的影响。着重分析了HTS电流引线中应用的三种接头的焊接工艺对焊接电阻的影响,并总结出在HTS电流引线中接头电阻的焊接工艺参数。

实用Bi系高温超导带材

介绍了(Bi,Pb)2Sr2Ca2Cu3Ox(BSCCO)带材产业化生产技术,并就几个关键环节如前驱粉制备与预处理、导线的机械加工以及带材的形变热处理等作了详尽的阐述,比较了世界各国的发展现状。针对特定的高温超导应用方向如超导电缆、超导磁体和电流引线等,研究了提高长导线均匀性的关键技术,进行BSCCO导线的多样化设计以降低导线的交流损耗、热导率和临界弯曲半径,并对导线进行表面改性处理如涂镀绝缘漆和镀锡等。结合已有的研究基础,从提高BSCCO带材的性能和降低生产成本出发,指出了BSCCO带材产业化技术今后的发展方向。

应用高温超导线(带)的研制现状与进展

提供了当前高温超导线的最新发展 ,第一代高温超导材料的机电性能参数和热物性参数 ,以及 4种美国超导公司的商业产品和中国超导带材的基本参数。论述了第二代高温超导线的研究进展。从高温超导电力应用的观点 ,展望高温超导电力技术应用前景 ,文中的工程与实验数据对高温超导线 (带 )材的应用可供参考。

高温超导线(带)材的研究进展

综述了高温超导线(带)材的最新研究进展。主要介绍了第一代铋系高温超导线材,第二代钇系高温超导涂层带材以及新型MgB2超导线材的研究现状,并探讨了其发展方向和研究重点。

扭绞和宽厚比对Bi-2223超导带交流损耗的影响

在77K及在外磁场下,对具有不同扭矩的多芯Bi-2223超导带的交流损耗进行测量。该研究中所使用的样品(扭矩6～12mm)具有扭绞芯线和非扭绞芯线。在频率范围为3.33～2430Hz的正弦变化的外磁场下,对交流磁场损耗进行了测量。研究了扭绞对Bi-2223超导带的临界电流和交流损耗影响。研究发现,临界电流随扭矩的减小而减小。另外,可以观察到,在平行场下,由于扭绞带芯线的退耦,造成扭绞带中平行磁场损耗也随之减小。在垂直场下,芯线的扭绞对垂直磁场损耗的减小是不明显的,通过运用小的扭矩和选择小的宽厚比的带材,能够明显减小交流损耗。

铋系银包套高温超导多芯带材的显微组织结构

采用粉末装管法制备了Ｍ２７ （２７ 芯）， Ｍ１９ （１９ 芯） 六种铋系银包套高温超导多芯带材， 利用标准四引线法测量其电学性能临界温度（Ｔｃ） 和临界电流密度（Ｊｃ）， 利用高分辨电子显微镜， 配有能谱仪的透射电子显微镜和扫描电子显微镜研究其显微组织结构。超导多芯带材的相组成以２２２３ 相为主， 可以观察到少量的２２１２ 相， 且与２２２３ 相共生。在超导相晶粒之间和三叉晶界存在非晶层。超导相界面、超导相和银包套界面较为平直， 超导相和银包套界面夹角为５°。超导相的晶粒具有一定的织构， 晶粒的ａｂ 面大致平行于带材的带长方向，ｃ 轴大致垂直于轧面。扫描电子显微镜观察表明国外超导带材的晶粒较国内大而明显。在样品中存在ＣｕＯ、ＳｒＯ和ＣａＯ杂相。一些杂相在超导相的周围沿晶界分布， 一些杂相独立存在。

高温超导材料的研发、产业化与经济性能提高

20世纪80年代末发现的氧化物超导体超导转变温度达到了90K以上,可以工作在液氮环境中。由于氮气资源的极为丰富以及相对于4.2K制冷成本的大大降低,使得超导技术的大规模应用变为可能。通过20多年来对高温超导实用成材技术的研发,基于铋锶钙铜氧体系的第一代高温超导带材已经实现了产业化。基于钇钡铜氧体系的第二代高温超导带材也已制备出了单根长度达千米的带材,标志着制约产业化的长度瓶颈已经解决。由于第二代高温超导带材性能更为优越,不需要贵金属,因而具有成本进一步下降的潜力。因此,第二代高温超导带材的产业化有可能在不远的将来就会实现,它将会极大地推动超导技术的大规模应用。