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Your search keyword '"Liu, Shifa"' showing total 27 results
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27 results on '"Liu, Shifa"'

2. High-performance Ba1-xKxFe2As2 superconducting tapes with grain texture engineered via a scalable and cost-effective fabrication

Author

Liu, Shifa, Yao, Chao, Huang, He, Dong, Chiheng, Guo, Wenwen, Cheng, Zhe, Zhu, Yanchang, Awaji, Satoshi, and Ma, Yanwei

Subjects
Condensed Matter - Superconductivity
Abstract

Nowadays the development of high-field magnets strongly relies on the performance of superconducting materials. Iron-based superconductors exhibit high upper critical fields and low electromagnetic anisotropy, making them particularly attractive for high-field applications, especially in particle accelerator magnets, nuclear magnetic resonance spectrometers, medical magnetic resonance imaging systems and nuclear fusion reactors. Herein, through an industrially scalable and cost-effective manufacturing strategy, a practical level critical current density up to 1.1x10^5 A/cm2 at 4.2 K in an external magnetic field of 10 T was achieved in Cu/Ag composite sheathed Ba0.6K0.4Fe2As2 superconducting tapes. The preparation strategy combines flat rolling to induce grain texture and a subsequent hot-isostatic-pressing densification. By varying the parameters of rolling, the degree of grain texture was engineered. It is found that the transport properties of the Ba1-xKxFe2As2 tapes can be enhanced by applying a large amount of deformation during rolling, which can be attributed to the improved degree of c-axis texture. Microstructure characterizations on the highest-performance tape demonstrate that the Ba1-xKxFe2As2 phase has a uniform element distribution and small grains with good connectivity. Grain boundary pinning is consequently enhanced as proved by large currents circulating through the sample even at 25 K. Our work proves that Cu/Ag composite sheathed Ba1-xKxFe2As2 superconducting tapes can be a promising competitor for practical high-field applications in terms of the viable, scalable and cost-effective fabrication strategy applied and the high transport properties achieved in this work., Comment: 30 pages, 7 figures, accepted to SCIENCE CHINA Materials

Published
2021
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3. Chemical stability and superconductivity in Ag-sheathed CaKFe4As4 superconducting tapes

Author

Cheng, Zhe, Dong, Chiheng, Huang, He, Liu, Shifa, Zhu, Yanchang, Wang, Dongliang, Vlasko-Vlasov, Vitalii, Welp, Ulrich, Kwok, Wai-Kwong, and Ma, Yanwei

Subjects
Condensed Matter - Superconductivity
Abstract

Ag-sheathed CaKFe4As4 superconducting tapes have been fabricated via the ex-situ powder-in-tube method. Thermal and X-ray diffraction analyses suggest that the CaKFe4As4 phase is unstable at high temperatures. It decomposes into the CaAgAs phase which reacts strongly with the silver sheath. We therefore sintered the tape at 500C and obtain a transport critical current density Jc(4.2 K, 0 T)~ 2.7x10^4 A/cm2. The pinning potential derived from magnetoresistance measurements is one order of magnitude lower than that of the (Ba/Sr)1-xKxFe2As2 tapes. Combining with the scanning electron microscopy and magneto-optical imaging results, we suggest that bad connectivity between superconducting grains caused by the low sintering temperature is the main factor responsible for the low Jc. However, this system is still a promising candidate for superconducting wires and tapes if we further optimize the post-annealing process to achieve better grain connectivity., Comment: 17 pages, 6 figures

Published
2018
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4. Superconducting joint between iron-based superconductor tapes

Author

Zhu, Yanchang, Wang, Dongliang, Zhu, Chundong, Huang, He, Xu, Zhongtang, Liu, Shifa, Cheng, Zhe, and Ma, Yanwei

Subjects
Condensed Matter - Superconductivity
Abstract

Superconducting joints are essential for iron-based superconductor's applications in future. In this study, a process for fabricating superconducting joints between Sr1-xKxFe2As2 (Sr-122) tapes is developed for the first time. The Ag sheath was peeled off from one side of each sample. The exposed superconducting parts of the two tapes were joined and wrapped again with Ag foil. The diffusion bonding of the iron-based superconducting joint was achieved by hot-pressing process in Argon atmosphere. The superconducting properties, microstructures and the elements distribution of the joint regions had been investigated. The pressure and pressing times were optimized in order to enhance the transport current of the joints. At 4.2 K and 10 T, a transport critical current Ic of 57 A for the joint was obtained, which is approximately 63.3% of the current capacity of the tapes themselves. Furthermore, the joint resistances dV/dI were estimated from the V-I curve of the joints and the calculated joint resistances values are below 10^-9 Ohm. These results demonstrate that the hot pressing was useful for fabricating the superconducting joint samples., Comment: 26 pages, 9 figures, main results were published in SuST

Published
2018

8. Mechanical properties and densification mechanism of powder-in-tube Ba x K1−x Fe2As2 superconductors

Author

Han, Meng, primary, Yao, Chao, additional, Zhang, Xianping, additional, Wang, Dongliang, additional, Dong, Chiheng, additional, Liu, Cong, additional, Huang, He, additional, Yang, Peng, additional, Guo, Wenwen, additional, Tu, Chang, additional, Liu, Shifa, additional, Liu, Xinyuan, additional, Zhang, Qianjun, additional, Zhang, Zhihao, additional, Xie, Jianxin, additional, and Ma, Yanwei, additional

Published
2022
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14. Enhancement of transport Jc in (Ba, K)Fe2As2 HIP processed round wires.

Author

Guo, Wenwen, Yao, Chao, Huang, He, Dong, Chiheng, Liu, Shifa, Wang, Chengduo, and Ma, Yanwei

Subjects
ISOSTATIC pressing, HOT pressing, TRANSITION temperature, SUPERCONDUCTORS, IRON-based superconductors, ANISOTROPY
Abstract

Iron-based superconductors have become a promising candidate for high-field applications due to their high transition temperature, ultra-high upper critical field, and low anisotropy. For practical applications, it is important to improve the transport Jc and lower the cost of superconductors. In this paper, with groove rolling and hot isostatic pressing (HIP) process, the transport Jc of the Cu/Ag composite sheathed (Ba, K)Fe2As2 powder-in-tube round wires was increased to 4.7 × 104 A cm−2 at 10 T and 4.2 K. The utilization of HIP and groove rolling process improved the mass density of the wire. Moreover, a certain axial texture was introduced through groove rolling. It is suggested that the combination of groove rolling and HIP processes are of great help to improve the microstructure of the wires, thereby obtaining a higher transport Jc. [ABSTRACT FROM AUTHOR]

Published
2021
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22. High-performance Ba1−xKxFe2As2superconducting tapes with grain texture engineered viaa scalable fabrication

Author

Liu, Shifa, Yao, Chao, Huang, He, Dong, Chiheng, Guo, Wenwen, Cheng, Zhe, Zhu, Yanchang, Awaji, Satoshi, and Ma, Yanwei

Abstract

Nowadays the development of high-field magnets strongly relies on the performance of superconducting materials. Iron-based superconductors (IBSs) exhibit high upper critical fields and low electromagnetic anisotropy, making them particularly attractive for high-field applications, especially in particle accelerator magnets, nuclear magnetic resonance spectrometers, medical magnetic resonance imaging systems and nuclear fusion reactors. Herein, through an industrially scalable manufacturing strategy, a practical-level critical current density up to 1.1×105A cm−2at 4.2 K in an external magnetic field of 10 T was achieved in Cu/ Ag composite-sheathed Ba1−xKxFe2As2(Ba122) superconducting tapes. The preparation strategy combines flat rolling to induce grain texture and subsequent hot-isostatic-pressing densification. By varying the parameters of rolling, the degree of grain texture was engineered. It is found that the transport properties of the Ba122 tapes can be enhanced by applying a large amount of deformation during rolling, which can be attributed to the improved degree of c-axis texture. Microstructure characterizations on the highest-performance tape demonstrate that the Ba122 phase has a uniform element distribution and small grains with good connectivity. Grain boundary pinning is consequently enhanced as proved by large currents circulating through the sample even at 25 K. Our work proves that Cu/Ag composite-sheathed Ba122 superconducting tapes can be a promising competitor for practical high-field applications in terms of the viable, scalable and cost-effective fabrication strategy applied and the high transport properties achieved in this work.

Published
2021
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