• Title/Summary/Keyword: critical current density

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Influence of Corrosion Potential and Current Density on Polarization Curve Variations using Polycarbonate[III]

  • Park, Chil-Nam;Yang, Hyo-Kyung;Kim, Sun-Kyu;Kim, Myung-Sun;Cheong, Kyung-Hoon
    • Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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    • v.4 no.1
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    • pp.43-50
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    • 2000
  • In this study, experiments were carried out to measure the variations in the corrosion potential and current density of polarization curves using polycarbonate. The results were particularly examined to identify the influences affecting the corrosion potential including various conditions such as temperature, pH, catalytic enzyme, and salt. The lines representing the active anodic dissolution were only slightly shifted in the potential direction by temperature, pH, enzyme, and salt. The tafel slope for the anodic dissolution was determined based on the polarization effect with various conditions. The slope of the polarization curves describing the active-to-passive transition region were noticeably shifted in direction. Also, from the variation in the conditions, the optimum conditions were established for the most rapid transformation, including temperature, pH, corrosion rate, and resistance of corrosion potential. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity(Ir/If). The value of Ir/If was then used in measuring the extent of the critical corrosion sensitivity of the polycarbonate. The potentiodynamic parameters of the corrosion were obtained using a Tafel plot.

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Transport current loss of YBCO Coated Conductor and Bi-2223 tape (Bi-2223 선재와 YBCO Coated Conductor 선재의 전송전류 손실 비교)

  • Lim Hyoungwoo;Lee Kwangyoun;Cha Gueesoo;Lee Jikwang;Park Chan
    • Proceedings of the KIEE Conference
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    • summer
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    • pp.1010-1012
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    • 2004
  • AC loss is an important factor in the development of superconducting tapes and superconducting power applications. In this paper we measured and compared characteristics of BSCCO tape and YBCO Coated Conductor(YBCO CC). BSCCO tape was fabricated by PIT method. We measured critical current density and transport current loss of it. Also, YBCO CC tape consist of substrate. buffer, YBCO and metal layers. We measured critical current density on variations of external magnetic field and transport current loss of these cases. The results of measurement show that normalized critical current of YBCO CC is smaller then that of BSCCO tape in the external magnet field. According to the results. measured loss and calculated of the YBCO CC show the same tendency.

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Development of the Fabrication Technology of High Tc Superconductor for Electrical Energy Storage (전기 에너지 저장을 위한 초전도 나노 합성 기술)

  • Lee, Sang-Heon
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.9
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    • pp.442-445
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    • 2006
  • In order to realize the commercial application of HTSC materials, it is necessary to develop the fabrication process of high Tc oxide superconductor materials with desired shape and for practical application and high critical current density as well as good mechanical strength which can withstand high lorenz force generated at high magnetic field. Much studies have been concentrated to develop the fabrication technique for high critical current density but still there are a lot of gap which should be overcome for large scale application of HTSC materials at liquid nitrogen temperature. Recently some new fabrication techniques have been developed for YBaCuO bulk superconductor with high mechanical strength and critical current density. In this project, the establishment of fabrication condition and additive effects of second elements were examined so as to improve the related properties to the practical use of YBaCuO superconductor, and we reported the production of the YBaCuO high Tc superconductor by the pyrolysis method.

A study on the improvements of Critical Current Density of Bi2223 Superconducting Tapes in PIT process (PIT법에 의한 Bi-2223 고온 초전도 테이프의 임계전류밀도 향상에 관한 연구)

  • 장현만;오상수;하동우;류강식;김상현
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1996.05a
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    • pp.198-201
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    • 1996
  • In order to investigate control factors to critical current density, Ag sheathed Bi2223 superconducting tapes were fabricated using PIT process. Optimizing the reduction ratio of rolling, critical current density 7f rolled Bi2223 tape could be improved with the value of 15,000 A/$\textrm{cm}^2$(77 K, zero field). The correlation between J$\_$c/ and work inhomogeneity was revealed as a dependence of COV of measured oxide layer thickness.

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Fabrication Technology of high Tc Superconductor for Electrical Equipment (전력기기 초전도 합성기술)

  • Lee, Sang-Heon
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.7
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    • pp.364-366
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    • 2006
  • In order to realize the commercial application of HTSC materials, it is necessary to develop the fabrication process of high Tc oxide superconductor materials with desired shape and for practical application and high critical current density as well as good mechanical strength which can withstand high lorenz force generated at high magnetic field. Much studies have been concentrated to develop the fabrication technique for high critical current density but still there are a lot of gap which should be overcome for large scale application of HTSC materials at liquid nitrogen temperature. Recently some new fabrication techniques have been developed for YBaCuO bulk superconductor with high mechanical strength and critical current density. In this project, the establishment of fabrication condition and additive effects of second elements were examined so as to improve the related properties to the practical use of YBaCuO superconductor, and we reported the production of the YBaCuO high Tc superconductor by the pyrolysis method.

The effect of cryogenic rolling on critical current density of Bi-2223/Ag HTS tapes (Bi-2223/Ag 고온초전도선재의 Jc와 미세조직에 미는 저온압연의 영향)

  • 최정규;황선역;하동우;오상수;권영길;이세종
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2003.10a
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    • pp.142-145
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    • 2003
  • In order to investigate the effect of cryogenic rolling on the critical current density (Jc), 54 and 55-multi-filament Bi-2223/hg tapes have been fabricated using a PIT process including two different types of cooling methods. The densification of oxide filament was found to occur due to the cryogenic rolling, and this enhanced the critical current density. However, when the wire was fully immersed in liquid nitrogen used as the coolant in cryogenic rolling, Jc degradation appeared caused by the nitrogen penetration into the filament. The cryogenically rolled tape with an improved type of cooling showed approximately 10% Jc's increase.

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$100 A/mm^2$ Class Bi-2223 Tapes in Electromechanical Devices (전력기기에서 $100 A/mm^2$급 Bi-2223테이프)

  • 류경우;최경주;성기철;류강식
    • Progress in Superconductivity and Cryogenics
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    • v.4 no.1
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    • pp.55-60
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    • 2002
  • $100 A/mm^2$ class Bi-2223 tapes have recently become commercially available. Some important characteristics of the tapes, e .g. critical current, ac loss, characteristics at joint, fault current characteristics, are required for an application such as a power cable or a power transformer. In this paper they have been investigated experimentally. The results indicate that the self-field loss of the high current density tapes is not negligible, compared to resistive loss in a copper wire for the same currents. In a cable, the self-field loss for relatively large currents is much larger than the magnetization loss due to an external field. But in a transformer, the magnetization loss is dominant, compared to the self-field loss. Finally the fault current characteristics show that the high current density tapes are never safe from burn-out even for fault currents with a few cycles.

Effects of a compaction method for powder compacts on the critical current density of MgB2 bulk superconductors

  • Kang, M.O.;Joo, J.;Jun, B.H.;Choo, K.N.;Kim, C.J.
    • Progress in Superconductivity and Cryogenics
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    • v.21 no.2
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    • pp.40-44
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    • 2019
  • In this study, the effects of the compaction method for (Mg+2B) powders on the apparent density and superconducting properties of $MgB_2$ bulk superconductor were investigated. The raw powders used in this study were nano-sized boron (B) and spherical magnesium (Mg). A batch of a powder mixture of (Mg+2B) was put in a steel mold and uniaxially pressed at 1 ton or 3 tons into pellets. Another batch of the powder mixture was uniaxially pressed at 1 ton and then pressed isostatically at $1800kg/cm^2$ in the water chamber. All pellets were heat-treated at $650^{\circ}C$ for 1 h in flowing argon gas for the formation of $MgB_2$. The apparent density of powder compacts pressed at 3 ton was higher than that at 1 ton. The cold isostatic pressing (CIP) in a water chamber allowed further increase of the apparent density of powder compacts, which influenced the pellet density of the final products ($MgB_2$). The compaction methods (uniaxial pressing and CIP) did not affect the formation of $MgB_2$ and superconducting critical temperature ($T_c$) of $MgB_2$, but affected the critical current density ($J_c$) of $MgB_2$ significantly. The sample with the high apparent density showed high $J_c$ at 5 K and 20 K at applied magnetic fields (0-5 T).

Electrical Characteristics of $Nb/Al-AlO_x/Nb$ Tunnel Junction fabricated with $I_c$ Values in the Range of $28 A/cm^2~ 940 A/cm^2$ ($28 A/cm^2~ 940 A/cm^2$의 임계전류밀도 범위로 제작된 $Nb/Al-AlO_x/Nb$ 터널접합의 전기적 특성)

  • 홍현권;김규태;박세일;김구현;남두우
    • Progress in Superconductivity and Cryogenics
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    • v.4 no.1
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    • pp.4-7
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    • 2002
  • Samples of $Nb/Al-AlO_x/Nb$ tunnel junction with the size of $50 ${\mu}{\textrm}{m}$ {\times} 50 ${\mu}{\textrm}{m}$$ were fabricated by using self-aligning and reactive ion etching technique In the high quality samples, the $V_m$ value (the product of the critical current and subgap resistance measured at 2 mV) was 34 mV at the critical current density of $J_c: 500 A/cm^2 and the V_g$ value (the gap voltage) was 2.8 mV. For the higher $J_c$ sample, voltage fluctuation at the gap voltage was observed. The $V_m and J_c$ values for this sample were 8 mV and 900 A/cm$^2$, respectively. Also, the relationship between critical current density $J_c$ and specific normal conductance $G_s$ of the junctions with $J_c$ in the range of 28 A/cm$^2$~940 A/cm$^2$was investigated.

Effect of Heat Treatment on Superconducting Properties on Bi2212/Ag Wire (Bi2212/Ag 선재의 초전도 특성에 대한 열처리의 영향)

  • Kim, S.C.;Ha, D.W.;Song, K.J.;Oh, S.S.;Lee, N.J.;Han, I.Y.;Oh, J.G.;Sohn, H.S.
    • Progress in Superconductivity
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    • v.8 no.1
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    • pp.54-58
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    • 2006
  • We have fabricated double stacked 385 filamentary Bi2212/Ag round wires which have different Ag ratios. The wires have been heat-treated at the maximum temperature($T_{max}$) of $882{\sim}896^{\circ}C$ for 0.5 h. Effect of heat treatment on critical current density and critical temperature on Bi2212/Ag round wires has been studied. Critical current density of the wire heat -treated at $890^{\circ}C$ showed 206,250 $A/cm^2$ at 4.2 K, 0 T and critical temperature of the wire was 83 K. Microstructure of the wires also has been studied via optical microscopy and SEM.

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