• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1994년도 추계학술대회강연 및 발표대회 강연및 발표논문 초록집
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• pp.24-24
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• 1994

• 한국전기전자재료학회논문지
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• 제13권9호
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• pp.801-804
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• 2000

High-temperature superconductor of Bi-2212 system was fabricated by CFP(Centrifugal Forming Process). To make a uniform specimen slurry was prepared in the ratio of 7:3(powder : binder) and ball milled for 24 hours. Milled slurry was charged into a rotating mold with 450 rpm and dried at room temperature. Then the specimen was performed binder burn-out at 35$0^{\circ}C$ and heated for partial melting to 86$0^{\circ}C$. XRD analysis of most specimens were shown 2212 phase and observed a local plate shped microstructure with a well aligned c-axis direction from SEM images. Measured T$_{c}$(Critical temperature) was about 64 K.K.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.189-192
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• 2000

High-temperature superconductor of Bi-2212 system was fabricated by CFP(centrifugal forming process). To make a uniform specimen slurry was prepared in the ratio of 7:3(powder:binder) and ball milled for 24 hours. Milled slurry was charged into a rotating mold with 450 rpm and dried at room temperature. Then the specimen was performed binder burn-out at 35$0^{\circ}C$ and heated for partial melting to 86$0^{\circ}C$. XRD analysis of most specimens were shown 2212 phase and observed a local plate shaped microstructure with a well aligned c-axis direction from SEM images. T$_{c}$(Critical temperature) of Bi-2212 was 64K.K.

• Bulletin of the Korean Chemical Society
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• 제12권6호
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• pp.606-612
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• 1991

We have carried out an extended Huckel calculation to rationalize the role of $CuO_3$ chains and the size effect of the charged model clusters for the following charged model culsters : ${{Cu_6}{O_{21}}^{28-},\;{{Cu_6}{O_{22}}^{30-}\;,{{Cu_9}{O_{30}}^{39-}\;,{{Cu_9}{O_{32}}^{43-}\;,{{Cu_{12}{O_{38}}^{48-}\;,{{Cu_{15}{O_{50}}^{65-}\;,{{Cu_{18}{O_{54}}^{66-}\;,{{Cu_{18}{O_{55}}^{68-}\;,{{Cu_{24}{O_{70}}^{84-}\;and\;{{Cu_{27}{O_{78}}^{93-}$ for high-$T_c$ superconductor $YBa_2Cu_3O_7$: ${{Cu_6}{O_{18}}^{22-}\;,{{Cu_9}{O_{26}}^{31-}}\;,{{Cu_{12}{O_{32}}^{36-}\;,{{Cu_{15}{O_{42}}^{49-}\;,{{Cu_{18}{O_{46}}^{50-}\;,{{Cu_{24}{O_{60}}^{64-}\;and\;{{Cu_{27}{O_{66}}^{69-}$ for insulator $YBa_2Cu_3O_6$. The results show that the electronic structures and properties of the charged model clusters relating to high-$T_c$ superconductor are very sensitive to the size change of the clusters with various environmental effects, wherease those of the charged model clusters for insulator $YBa_2Cu_3O_6$ are monotonous to the size change. The $CuO_3$ chains along the b-direction may yield cooperative electronic coupling with the $CuO_2$ layers in determining both conducting and superconducting properties of $YBa_2Cu_3O_{7-x}$ system.

• 한국초전도ㆍ저온공학회논문지
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• 제24권4호
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• pp.55-58
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• 2022

Carbon-based doping to MgB₂ superconductor is the simplest approach to enhance the critical current densities under magnetic fields. Carbon quantum dots is synthesized in this work as a carbon provider to MgB₂ superconductors. Polyvinyl Pyrrolidone is pyrolyzed and dispersed in dimethylfomamide solvent as a dopant to the mixture of Mg and B powders. Doped MgB₂ bulk samples clearly show the decrease of a-axis lattice constant, grain refinements, and broadening of FWHM of diffraction peaks compared to un-doped MgB₂ possibly due to the carbon substitution and/or boron vacancy at the boron site in MgB₂ lattice. Also, high-field J_c for the doped MgB₂ is enhanced significantly with the crossover about 3 T at 5 & 20 K when increasing the doping of carbon quantum dots.

• 한국세라믹학회지
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• 제38권12호
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• pp.1104-1109
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• 2001

110K상의 산화물 고온초전도체를 B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+}$$\delta$/의 출발조성비로 고상반응법(solid-state reaction)에 의해 합성하였다. 이렇게 합성된 Bi계 110K상의 산화물 고온초전도 물질을 다시 분말 상태로 만든 후, Ag 금속분말을 10wt%, 30wt%, 50wt%의 각 비율로 혼합하였다. Ag 금속분말이 혼합된 시편들을 86$0^{\circ}C$~875$^{\circ}C$로 24시간 동안 최종 소결시켰다. 그후, 각 시편들에 대하여 x-선, $T_{c}$, SEM 등을 측정하여 Ag 혼합량에 대한 초전도특성 및 표면의 grain 크기변화 등에 대한 조사를 진행하였다. Ag 혼합량이 증가됨에 따라 Ag peak의 강도는 증가되었고, 시편 내 2223 상의 비율은 감소하고 2212상의 비율은 증가되었다.비율은 증가되었다.

• 한국세라믹학회지
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• 제40권6호
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• pp.530-538
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• 2003

110 K 상의 산화물 고온초전도체를 B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+}$$\delta$의 출발조성비로 고상반응법에 의해 합성하였다. 합성된 Bi계 110 K 상의 산화물 고온초전도 물질을 다시 분말 상태로 만든 후, MgO 금속산화물 분말을 5~50 wt%의 각 비율로 혼합하였다. MgO 금속산화물 분말이 혼합된 시편들을 820~86$0^{\circ}C$로 24시간동안 최종 소결시켰다. 그 후, 각 시편들에 대하여 x-선, $T_{c}$, SEM 등을 측정하여 MgO 금속산화물 혼합량에 대한 초전도특성 및 표면의 입자 크기 변화 등에 대한 조사를 진행하였다. MgO 금속산화물의 혼합량이 증가됨에 따라 MgO 관련 피크들의 강도 및 2212 상들의 피크들의 비율은 증가되었고, 시편 내 2223 상의 비율은 감소하고 2212상의 비율은 증가되었다.다.은 증가되었다.다.

• 한국전기전자재료학회논문지
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• 제16권6호
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• pp.522-531
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• 2003

Samples with the nominal composition, B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+{\delta}}$ high- $T_{c}$ superconductors containing MgO as an additive were fabricated by a solid-state reaction method. Samples with MgO of 5~30 wt% each were sintered at 820~86$0^{\circ}C$ for 24 hours. The structural characteristics, critical temperature, grain size and image of mapping with respect to MgO contents were analyzed by XRD(X-Ray Diffraction), SEM(Scanning Electron Microscope) and EDS(Energy dispersive X-ray spectrometer) respectively. As MgO contents increased, intensity of MgO Peaks and ratio of Bi-2212 phase in superconductors intensified and the proportion of the phase transition from Bi-2223 to Bi-2212 was increased.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.211-215
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• 2000

Bi-2212 HTS tube was fabricated by CFP(Centrifugal Forming Process). Slury was prepared in the mixing ratio of 8:2 between powder and binder and ball-milled for 24 hrs. Slurry was initially charged into the rotating mold with 300${\sim}$450 rpm and heated at the temperature ranges of 840${\sim}$860$^{\circ}$C for partial melting to finally obtain a uniformly textured tube shape. It was observed the plate-like grains with more than 20 ${\mu}$m were well oriented along the rotating axis and the measured T$_c$ was around 67K. In this paper we will discuss and analyze the tube characteristics depending on many different processing parameters such as, powder composition, binder mixing ratio between powder and binder, motor speed, heating temperature and etc.

• 한국초전도ㆍ저온공학회논문지
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• 제16권1호
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• pp.9-13
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• 2014

Effects of neutron irradiation on the superconducting properties of the undoped $MgB_2$ and the carbon(C)-doped $MgB_2$ bulk superconductors, prepared by an in situ reaction process using Mg and B powder, were investigated. The prepared $MgB_2$ samples were neutron-irradiated at the neutron fluence of $10^{16}-10^{18}n/cm^2$ in a Hanaro nuclear reactor of KAERI involving both fast and thermal neutron. The magnetic moment-temperature (M-T) and magnetization-magnetic field (M-H) curves before/after irradiation were obtained using magnetic property measurement system (MPMS). The superconducting critical temperature ($T_c$) and transition width were estimated from the M-T curves and critical current density ($J_c$) was estimated from the M-H curves using a Bean's critical model. The $T_cs$ of the undoped $MgB_2$ and C-doped $MgB_2$ before irradiation were 36.9-37.0 K and 36.6-36.8 K, respectively. The $T_cs$ decreased to 33.2 K and 31.6 K, respectively after irradiation at neutron fluence of $7.16{\times}10^{17}n/cm^2$, and decreased to 22.6 K and 24.0 K, respectively, at $3.13{\times}10^{18}n/cm^2$. The $J_c$ cross-over was observed at the high magnetic field of 5.2 T for the undoped $MgB_2$ irradiated at $7.16{\times}10^{17}n/cm^2$. The $T_c$ and $J_c$ variation after the neutron irradiation at various neutron fluences were explained in terms of the defect formation in the superconducting matrix by neutron irradiation.