• Title/Summary/Keyword: bi-2212/Ag

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Influence of Ag Precoating of $Bi_{2212}$ Superconductor-In Base Solder Soldering ($Bi_{2212}$ 초전도체와 In 계열 solder의 soldering에서 Ag precoating의 영향)

  • Jang Ji-Hoon;Kim Sang-Hyun;Shin Seung-Yong;Lee Yong-Chul;Kim Chan-Joong;Hyun Ok-Bae;Park Hae-Woong
    • Journal of the Korean institute of surface engineering
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    • v.39 no.2
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    • pp.57-63
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    • 2006
  • In this study, In-base solder was applied to the interface between $Bi_2Sr_2Ca_1Cu_2O_x(Bi_{2212})$ superconductor and Cu-Ni shunt metal at the temperature lower than $150^{\circ}C$. Most of the cases, $Bi_{2212}$ superconductor was precoated with Ag by electroplating in order to improve the contact properties of the solder layer. When the superconductor was directly soldered on to the superconductor, the solder was easily separated without external force. The shear strength of the contact between superconductor and shunt metal increased from 69.2 kgf to 74.4 kgf and 80.1 kgf, as the current density of the Ag electroplating was changed from 63 mA to 96 mA and 126 mA, respectively. The contact strength also increased to 49.9 kgf and 69.2 kgf when thickness of the electroplated Ag layer increased to $5{\mu}m$ and $10{\mu}m$, reapectively.

Effect of pre-annealing conditions on mechanical and superconducting properties of Bi-2223/Ag tapes (초전도 선재의 전 열처리에 따른 기계적 및 초전도 특성에 미치는 효과)

  • 양주생;하동우;이동훈;최정규;황선역;하홍수;오상수;권영길;김명호
    • Progress in Superconductivity
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    • v.5 no.2
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    • pp.124-127
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    • 2004
  • Many of research efforts have been focused on the improvement of critical current density (Jc) of silver-sheathed Bi-2223 tapes far practical applications. In this study, the transformation of Bi-2212 phase was investigated, which was transformed to orthorhombic from tetragonal through pre-annealing during powder packing and drawing process. The relationship between hardness of Bi-2212 orthorhombic phase and workability of Bi-2223/Ag tape was investigated. Bi-2223 superconducting wires with 55 filaments were fabricated by stacking and drawing process with different heat-treatment histories. Before rolling process, round wires were pre-annealing at 76$0^{\circ}C$ and in a low oxygen partial pressure. We confirmed that pre-annealing step was to transform to Bi-2212 orthorhombic structure from Bi-2212 tetragonal structure and to reduce the formation of second phases. However the breakages were created at Ag-alloy clad during rolling for pre-annealed Bi-22231Ag tapes. Several pre-annealing scenarios were introduced to reduce the breakages during rolling process. Microstructure and critical current density of pre-annealed Bi-2223 superconducting tapes were investigated. We could achieve proper pre-annealing conditions for Ag-alloy clad Bi-2223 superconducting tapes.

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Study on fabrication process of long length of Bi-2223/Ag MTS wires for high critical current (Bi-2223/Ag HTS 장선재의 Ic 특성 향상 공정 연구)

  • 하동우;양주생;황선역;이동훈;최정규;하홍수;오상수;권영길
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2003.02a
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    • pp.105-108
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    • 2003
  • Long length of Bi-2223 superconducting wires were fabricated by stacking, drawing process with different precursor owders and different heat-treatment histories. The precursor powders were 2 kinds of Pb content. And a part of the tapes were experienced pre-annealing process which caused tetragonal structure of Bi-2212 phase to orthorhombic structure of it was during drawing process. We confirmed the transformation of Bi-2212 phase from tetragonal structure to orthorhombic structure and reduction of second phases. We designed and made a continuous Ic measurement system for Bi-2223/Ag HTS tape. We could achieve best Ic of 65 A at the Bi-2223/Ag tape using low Pb content of precursor powder and experienced pre-annealing process.

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Properties of Bi-2223/Ag HTS tapes using different content of precursors (조성이 다른 전구체 분말에 따른 Bi-2223/Ag 초전도 테이프의 특성 변화)

  • Ha, Dong-Woo;Yang, Joo-Saeng;Ha, Hong-Soo;Oh, Sang-Soo;Hwang, Sun-Yuk;Lee, Dong-Hoon;Choi, Jung-Kyu;Lee, En-Yong;Kwon, Young-Kil
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.05a
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    • pp.69-72
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    • 2003
  • Bi-2223 superconducting wires were fabricated by stacking, drawing process with different precursor powders and different heat-treatment histories. The precursor powders were 2 kinds of Pb content. And a part of the tapes were experienced pre-annealing process which caused tetragonal structure of Bi-2212 phase to orthorhombic structure of it was during drawing process. We confirmed the transformation of Bi-2212 phase from tetragonal structure to orthorhombic structure and reduction of second phases. XRD and DC magnetization analysis were performed in order to investigate the fraction of Bi-2223 phase in Bi-2223/Ag HTS tape. We could achieve best Ic of 70 A class at the Bi-2223/Ag tape using low Pb content of precursor powder and experienced pre-annealing process. DC magnetization analysis was useful to investigate the fraction of Bi-2223 phase in the Bi-2223/Ag tape.

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Effect of External Reinforcement on Stress/Strain Characteristics of Critical Current in Ag Alloy Sheathed Bi-2212 Superconducting Tapes. (Bi-2212 초전도 테이프에서 임계전류의 응력/변형률 특성에 미치는 외부강화의 영향)

  • ;;K. Katagiri
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2001.02a
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    • pp.17-20
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    • 2001
  • Stress/strain dependencies of the critical current I$_{c}$ in AgMgNi sheathed multifilamentary Bi(2212) superconducting tapes were evaluated at 77K. The external reinforcement was accomplished by soldering Ag-Mg tapes to single side or both sides of the sample. With the external reinforcement, the strength of tapes increased but I$_{c}$ decreased. The I$_{c}$ degradation characteristic according to the external reinforcement was improved markedly in terms of the stress although it appeared less remarkable on the basis of the strain. Effects of external reinforcement were discussed in a viewpoint of monitoring sensitivity of cracking in superconducting filaments by considering n-value representing the transport behavior of the current, which is closely associated with the location of them relative to the voltage-monitoring region in the tape. tape.

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Fabrication and fault test of 12 kVA class BSCCO SFCL element (12 kVA급 BSCCO 한류소자 제작 및 특성 실험)

  • Oh, S.Y.;Yim, S.W.;Kim, H.R.;Hyun, O.B.;Jang, G.E.
    • Progress in Superconductivity and Cryogenics
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    • v.10 no.1
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    • pp.24-27
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    • 2008
  • For the development of superconducting fault current limiters(SFCLs) having large current capacity, we fabricated an SFCL element that consists of Bi-2212 superconductor and Cu-Ni alloy tubes. First, Ag was plated on the surface of the Bi-2212 for the enhancement of soldering process. On the Ag-plated Bi-2212 tube, a Cu-Ni alloy tube was soldered using optimized solders and soldering conditions. The BSCCO/Cu-Ni composite was processed mechanically to have a helical shape for the improvement of the SFCL characteristics. The total current path of the SFCL element was 1330 mm long with 12 turns, and had critical current of 340 A at 77 K. Finally, we carried out the fault test using the fabricated SFCL element. It showed successful current limiting performance under the fault condition of 50 $V_{rms}$ and 5.5 kA. From the results, the rated voltage of the SFCL element was decided to be 0.4 V/cm, and the power capacity was 12 kVA at 77 K. The fabrication process of the SFCL and the fault test results will be presented.