• 제목/요약/키워드: flux pinning center

검색결과 37건 처리시간 0.022초

산화은을 첨가한 초전도체의 자기 속박효과 (Magnetic Pinning Effect of High Tc Superconductor)

  • 이상헌
    • 대한전기학회논문지:전기물성ㆍ응용부문C
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    • 제55권4호
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    • pp.209-212
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    • 2006
  • The electromagnetic effect observed in a BiSrCaCuO superconductor was studied. The electromagnetic properties of a $Ag_2O$ doped BiSrCaCuO superconductor and an undoped superconductor were evaluated to investigate the contribution of the pinning effect. It was confirmed experimentally that a large amount of magnetic flux was trapped in the $Ag_2O$ doped BiSrCaCuO than that in the undoped one, indicating that the pinning centers of magnetic flux are related closely to the occurrence mechanism of magnetic phenomena. It was considered that by adding $Ag_2O$, the area where normal conduction takes place increases and the magnetic flux penetrating through the sample increases. It also was considered that $Ag_2O$ acts to increase pinning centers of magnetic flux.

BiPbSrCaCuO 초전도 벌크의 Magnetic Suspension (Magnetic Suspension Effect of BiPbSrCaCuO Superconducting Bulk)

  • 이상헌
    • 한국전기전자재료학회논문지
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    • 제17권5호
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    • pp.545-551
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    • 2004
  • Magnetic suspension effect has been studied by using superconductor of BiPbSrCaCuO ceramics containing Ag$_2$O. Magnetic flux measurements of a toroidal magnet revealed a concave shaped field distribution with a null field along the axis of the torus at the point where the field reversed. The suspension effect was observed only for the Ag$_2$O doped and field cooled sample which is attributed to the enhanced flux pinning due to the field cooled condition. It has been cleared that Ag$_2$O acts as pinning center which plays an important role to the magnetic suspension effect. Magnetic repulsive force which affects a superconductor located in magnetic flux from toroidal magnet has been investigated. It has been concluded that the magnetic suspension effect arises from the interaction between the pinning effect and the diamagnetic effect.

The application of hydrated fine MgO particles for flux pinning center in the HTS-BSCCO system

  • 김성환;김철진;정준기;박성창;유재무
    • Progress in Superconductivity
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    • 제3권2호
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    • pp.188-192
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    • 2002
  • To introduce flux pinning center in HTS-BSCCO system, nano-size MgO particles were uniformly distributed within the Bi-2223 grain by partial hydration of MgO. The existing method MgO doped Bi-2223 used nato-size MgO powders, which resulted in agglomeration during mixing or grain growth during heat-treatment due to the high surface energy of the fine particles. By hydration of the MgO surface, the agglomeration of the MgO powders was avoided and the size of remaining MgO core was controlled by changing hydration medium and time. The thin film obtained by spin coating of (Bi_$1.8/Pb_{0.4}$)$Sr_2$$_{Ca}$$2.2/Cu_3$ $O_{y}$ nitrate solution mixed with hydrated MgO showed the even distribution of nano-size MgO particles in the Bi-2212 grains.s.s.

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TiO2 Nano-doping Effect on Flux Pinning and Critical Current Density in an MgB2 Superconductor

  • Kang, J.H.;Park, J.S.;Lee, Y.P.;Prokhorov, V.G.
    • Journal of Magnetics
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    • 제16권1호
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    • pp.15-18
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    • 2011
  • We have studied the $TiO_2$ doping effects on the flux pinning behavior of an $MgB_2$ superconductor synthesized by the in-situ solid-state reaction. From the field-cooled and zero-field-cooled temperature dependences of magnetization, the reversible-irreversible transition of $TiO_2$-doped $MgB_2$ was determined in the H-T diagram (the temperature dependence of upper critical magnetic field and irreversibility line). For comparison, the similar measurements are also obtained from SiC-doped $MgB_2$. The critical current density was estimated from the width of hysteresis loops in the framework of Bean's model at different temperatures. The obtained results manifest that nano-scale $TiO_2$ inclusions served as effective pinning centers and lead to the enhanced upper critical field and critical current density. It was concluded that the grain boundary pinning mechanism was realized in a $TiO_2$-doped $MgB_2$ superconductor.

BSCCO계 초전도체에서 서냉 열처리에 의한 2차상 석출 (The Precipitation of Second Phases by Annealing Heat Treatment in the $(Bi,Pb)_2$${Sr_2}{Ca_2}{Cu_3}{O_{10}}$ Superconductor System)

  • 이상희;김철진;유재무
    • 한국세라믹학회지
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    • 제37권12호
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    • pp.1212-1220
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    • 2000
  • Bi-2223 초전도체계에서 석출물을 flux-pinning center로 이용할 수 있는지 가능성을 타진하기 위하여 $Bi_{1.8}$P $b_{0.4}$S $r_{2}$C $a_{2.2}$C $u_3$ $O_{8}$ 조성을 가진 Bi-2223/Ag 선재를 반응온도, 산소분압, 시간 등을 변화시키면서 열처리를 행하였다. 열처리 후 석출물들은 XRD, SEM, TEM, EDS로 분석하였다. Bi-2223 모상내의 (Ca, Sr)$_2$(Pb,Bi) $O_4$, B $i_{0.5}$ P $b_3$S $r_2$C $a_2$Cu $O_{12+}$$\delta$/ (3221)와 같은 2차상들의 크기와 분포는 2223 입자들의 연결성을 파괴하지 않고 열처리 조건에 의해서 조절할 수 있었다. 서냉 열처리가 된 시편은 임계전류밀도( $J_{c}$)값이 증가하였는데, 이는 2223 입자내 나노미터 크기로 형성된 석출물들이 flux-pinning sites로 작용한 것으로 추정된다.다.

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Magnetic Pinning Properties and Flux Jumps in Superconducting $MgB_2$

  • Yoon, W.S.;Lee, Eui-Wan;Kim, C.J.;Kim, B.G.;Ri, H.C.
    • Progress in Superconductivity
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    • 제9권1호
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    • pp.11-17
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    • 2007
  • Magnetization studies have been carried out on $MgB_2$ polycrystalline samples in the temperature range of 5 - 44 K and in the magnetic field up to 7 Tesla. The critical current density was calculated from hysteresis loops using the Bean's critical state model, and the highest value of $J_c$ at 20 K was $2.7{\times}10^5\;A/cm^2$ at 2 Tesla. The hysteresis loops were carefully examined to determine the temperature and magnetic field range where flux jumps appeared. The first jump occurred typically at 1 Tesla. Due to the strong pinning, we observed the presence of flux jump below H = 1 Tesla at temperature below 30 K.

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YBCO 다층박막에 첨가된 $Y_2O_3$와 ZnO 나노입자의 자속꽂음 중심 특성 비교 (Comparison of $Y_2O_3$ and ZnO Nanoparticles Introduced in YBCO Multilayered Films as Artificial Pinning Centers)

  • 위창환;;;강병원;김이정;오상준;이남훈;강원남
    • Progress in Superconductivity
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    • 제13권2호
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    • pp.90-96
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    • 2011
  • We investigated the properties of artificial pinning centers of YBCO multilayer films in which $Y_2O_3$ and ZnO nanoparticles are uniformly introduced by using the pulsed laser deposition (PLD) technique. $Y_2O_3$ and ZnO nanoparticles were deposited on top of YBCO buffer layer and the density of nanoparticles was controlled by varying the number of nanoparticle layers. YBCO superconducting layers with total thickness of 250 nm were deposited on top of $Y_2O_3$ and ZnO nanoparticles. Based on analyses of the surface morphology, the transition temperature $T_c$, and the critical current density $J_c$, we discussed the difference between the two kinds of nanoparticles as flux pinning centers.