• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 초전도 자성체 연구회
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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.

• Progress in Superconductivity
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• 제3권1호
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• pp.91-94
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• 2001

By varying fabricating process, precursor powders with different initial conditions were prepared. Subsequently, Bi-2223/Ag tapes were made through these powders. The effects of precursor powders on the phase evolution and Jr properties of Bi-2223/Ag tapes were studied along with several thermomechanical cycles. Our results showed that the initial conditions of precursor powders could strongly influence the phase formation rate and $J_{c}$ value in final tapes. The factors of precursor powders that influence the phase formation and $J_{c}$ of Bi-2223/Ag tapes must be studied and optimized in combination.ion.

• 한국재료학회지
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• 제7권2호
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• pp.140-144
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• 1997

은 튜브에 장입되기 전의 초기 분말의 입자 크기가 Ag/Bi-2223초전도 선재의 미세구조와 상전이, 임계 전류 밀도등에 미치는 영향에 대해 고찰하였다. 분말의 입자 크기는 하소 분말을 볼밀을 이용하여 0-48 시간 동안 분쇄하여 조절하였다. 열처리 후 최종 초전도 선재의 전기적 성질은 초기 분말의 입자 크기에 영향을 받는 것으로 나타났으며 분말의 분쇄에 의한 반응성의 증가에 의해 열처리시 2223 상으로의 상전이가 빠르게 일어났고 이차상의 크기와 분율이 감소된 미세구조를 얻을 수 있었다. 그러나 과다한 분쇄에 의한 반응성의 증가에 의해 열처리시 2223상으로의 상전이가 빠르게 일어났고 이차상의 크기와 분율이 감소된 미세구조를 얻을 수 있었다. 그러나 과다한 분쇄는 분말의 비정질화를 유발하여 2223 상으로의 전이를 방해함으로써 선재의 임계 전류 밀도를 감소시키는 결과를 나타내었다.

• Progress in Superconductivity
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• 제4권2호
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• pp.162-167
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• 2003

The critical current value of Bi-2223/Ag tape can be influenced by various factors. In particular, it was known that properties of precursor powders could affect the formation of Bi -2223 and grain growth rate of the same. Since, moistures and organic matters can easily contaminate the precursor powders of Bi-2223 tapes and degrade properties of superconductors, the precursor powders should be kept in optimal conditions to minimize contamination. In this study, the effect of moisture and organic matters has been investigated. A Bi-2223/Ag tape contaminated with a large amount of moisture and organic matter has been characterized by low critical current values and bubbling. It has been found that as the quantity of moisture increases, the Bi-2223 phases are formed at lower temperature and the amount of non-superconducting phase increases.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.585-588
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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. AC magnetization analysis were performed in order to investigate the fraction of Bi-2223 phase in Bi-2223/Ag HTS tape. The cross sections of 55 filaments and 61 filaments were investigated after rolled in order to understand deformation mechanism of superconducting cores. 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. AC magnetization analysis was useful to investigate the fraction of Bi-2223 phase in the Bi-2223/Ag tape.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1997년도 한국재료학회 춘계학술발표회
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• pp.44-44
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• 1997

• Progress in Superconductivity
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• 제6권2호
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• pp.124-128
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• 2005

Homogeneous and fine powders for Bi-2223 tape were prepared by ultrasonic spray pyrolysis (SP) method from an aqueous solution of metal nitrates. Bi-2223 precursor powders were synthesized with various solutes concentration and pyrolysis temperature. The synthesized precursor powders had a narrow particle size distribution and an average particle size was $\~{\cal}um$. The reactivity of precursor powder by SP method is very high, attributed to the fine and narrow particle size distribution. Bi-2223/Ag tape was prepared using PIT method and followed by various sintering conditions. The precursor powder by SP method promoted a very quick formation of the Bi-2223 phase for short sintering time while the secondary phase such as large AEC phase and $Ca_2PbO_4$ were minimized for SP tapes.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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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.

• Progress in Superconductivity
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• 제4권1호
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• pp.94-98
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• 2002

Two kinds of multifilament Bi-2223／Ag tapes, which are different in the precursor calcination temperatures, were heat treated for different time (12, 20, 30, 50, 70, or 100 h) firstly to obtain varied B2223 contents, and then followed by the same pressing and sintering cycles. The relation of the 2223 phase contents after the first sintering and the transport property of the fully processed tapes was studied. The results show that 75-80% 2223 phase formed in tapes before the first cold pressing is beneficial to get a high $I_{c}$ in the final tapes. Compensating the total heat treatment time of the tapes first sintered for 20 h to the same length as that first sintered for 50 h in the subsequent sintering stages, different $I_{c}$ enhancements were observed in these two tapes. No improvement on $I_{c}$ was found in the tape made from the powder calcined at higher temperature, whereas for the tape prepared with the lower temperature calcined powder, the $I_{c}$ was increased to the same level as that first sintered for 50 h. The 2223 contents before the intermediate mechanical work is related to the residual reactants, especially to the liquid phase, which is of vital importance to the phase conversion and healing microcracks, meanwhile, to the size and distribution of the non-superconducting secondary phases. The lower temperature calcined powder resulted in slow formation of 2223 phase, but also provided more reactants and liquid phase for the further phase conversion, as a consequence, for the Improvement of $I_{c}$. c/.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.343-345
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• 2002

The influence of starting precursor powders on the phase formation and transport properties of Bi-2223/Ag tapes has been studied. The experimental results show that the average particle size of precursors as fine as 1.64 ${\mu}{\textrm}{m}$ and 1.51 ${\mu}{\textrm}{m}$ can still increase the transport properties. The J$_{c}$-B behavior is also enhanced in tapes fabricated with powders in finer particle sizes. However, at higher magnetic fields, J$_{c}$ of tape started from the powder with the finest particles drops rapidly at the direction of H//c, which is possibly attributed to the small grain sizes and weak flux pinning ability that due to the short induction period at the initial stage of phase formation as the result of fine particles in precursor powder.der.