• 한국초전도ㆍ저온공학회논문지
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• 제8권1호
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• pp.1-4
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• 2006

The $MgB_2$ tapes with several metal powder addition were fabricated by PIT method with or without heat treatment. The $J_c$ value of $5.600A/cm^2$ and $16.000A/cm^2$ at 4.2 K and 5 T were obtained for the $MgB_2$ tape and 10 vol % of Cu added $MgB_2$ tape without heat treatment respectively. The $J_c$ value of $8.000A/cm^2$ and $35,000A/cm^2$ at 4.2 K and 5 T were obtained for the $MgB_2$ tape and 10 vol. % of Al added $MgB_2$ tape with heat treatment, respectively. The $J_c-B$ curve shows enhancement in $J_c$ under magnetic field. which suggests enhancement in workability and grain connectivity with several metal powder addition.

• Progress in Superconductivity
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• 제5권2호
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• pp.109-113
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• 2004

MgB$_2$ and FeTi composites was prepared to study the effect of FeTi particles on superconductivity of MgB$_2$. The sample, which had contained magnesium, boron and FeTi particles, was synthesized by the Commercial Stainless Steel Tube Enveloping Technique(COSSET) at 92$0^{\circ}C$ for 2 hours. The structure and properties of the sample was investigated by XRD, SEM, and SQUID magnetometer. It was found that there was a little change of T$_{c}$ compared with pure MgB$_2$ superconductor in spite of high percentage of FeTi particles, and there was no proof of structure change of MgB$_2$ superconductor due to FeTi particles. But the high porosity which was appeared in the pure MgB$_2$ was disappeared in the composites. We conclude that FeTi particles do not influence the superconductivity of MgB$_2$ and it is expected that fe-Ti material system will be a good material for a tube of the PIT process and for a substrate of the film.m.

• 한국초전도ㆍ저온공학회논문지
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• 제21권2호
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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).

• 한국초전도ㆍ저온공학회논문지
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• 제22권2호
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• pp.26-31
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• 2020

Since 2014, Sam Dong Co., Ltd. has successfully developed high-performance MgB₂ superconducting wires with a kilometer-scale. Herein, we studied performances of various MgB₂ wires fabricated by the Sam Dong with different Cu fractions and diameters for practical applications. Critical current densities of our commercial wire, 18+'1'Cu multifilamentary MgB₂ wire, are estimated to be 270,000 A/㎠ at 3 T and 4.2 K and 100,000 A/㎠ at 2 T and 20 K, respectively. We further discuss research progress of various MgB₂ superconducting wires at Sam Dong Co., Ltd and make an effort to align with customers' requirements.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.32.1-32.1
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• 2011

39 K의 임계온도를 갖는 $MgB_2$ 초전도체를 이용한 전력에너지와 MRI 의료 기기로의 응용 가능성이 높아지고 있다. $MgB_2$ 초전도체 제조에 있어서 마그네슘과 반응성이 좋은 비정질의 붕소 원료 분말 가격이 비싼 반면 상대적으로 경제적인 결정질 분말의 기계적 밀링 공정을 이용하여 비정질화와 나노 입자로의 크기 감소 효과를 얻을 수 있다. 또한 탄소를 이용한 붕소 치환으로부터 고 자기장하에서 초전도 임계 성질을 향상시키고자 유, 무기물 형태의 여러 가지 탄소 소스를 개발하는 연구가 진행되어 왔다. 본 연구에서는 저가의 95~97% 순도, 약 1 ${\mu}m$ 이하 크기를 갖는 준결정상의 붕소 분말을 이용하여 기계적 밀링에 따른 붕소 분말의 비정질화 및 입자 나노화, $MgB_2$ 반응성 향상, $MgB_2$ 결정립 크기 감소 및 결정립계 피닝 증가에 의한 초전도 임계 물성 향상에 대하여 알아보았다. 또한 여러 시간 동안 밀링된 각 붕소 분말에 액체 글리세린을 이용한 탄소 도핑 전처리를 통하여 밀링 시간의 최적화를 알아보았고 이로부터 제조된 $MgB_2$ 초전도 벌크의 경우 적절한 임계온도 감소, 격자 왜곡 결함과 높은 결정립계 밀도 등에 의한 플럭스 피닝 향상으로 $MgB_2$ 초전도체의 임계전류밀도 및 비가역자기장이 증가함을 알 수 있었다. 즉, 경제성 있는 저급의 준결정상을 갖는 붕소 원료 분말의 입자 비정질 나노화 및 탄소 도핑 전처리를 통하여 $MgB_2$ 초전도 임계 물성을 향상시킬 수 있었다.

• 한국초전도ㆍ저온공학회논문지
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• 제9권2호
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• pp.15-18
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• 2007

The sub micron sized spherical $MgB_2$ powders were synthesized by spray reaction method. $MgB_2$ tapes with Al addition were fabricated by Powder in Tube (PIT) method. The superconducting property and microstructure of Al doped $MgB_2$ tapes were characterized by X-ray diffraction, optical microscopy and transport measurement under magnetic field. The $J_c$ value of $MgB_2$ tapes was increased with 10 vol. % Al addition. The $J_c$ value of 5,500 A/$cm^2$ and 11,000 A/$cm^2$ at 4.2 K and 5 T were obtained for the $MgB_2$ tape and 10 vol. % of Al added $MgB_2$ tape without heat treatment, respectively. The $J_c$ value of 8,000 A/$cm^2$ and 33,000 A/$cm^2$ at 4.2 K and 5 T were obtained for the $MgB_2$ tape and 10 vol. % of Al added $MgB_2$ tape with heat treatment, respectively. The $J_c$-B curves show enhancement in $J_c$ (B), which suggests that the microstructure and transport properties of $MgB_2$ tapes have been improved with Al addition.

• Progress in Superconductivity
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• 제12권2호
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• pp.88-92
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• 2011

특수합금 등 금속분말을 이용하는 분말압연 공정을 적용하여 $MgB_2$ 판재를 제조하고 공정변수에 대한 특성을 조사하였다. 압연롤 간격 0.7 mm와 회전속도 0.7 rpm(~120 cm/min) 조건에서 두께 ~1 mm, 폭 ~100 mm, 그리고 길이 수 cm 크기의 $MgB_2$ 판재를 성공적으로 제조하였으며, 측정된 최고 밀도는 2.05 g/$cm^3$이고 이론 값 대비 약 78 %로 계산되었다. 분말압연 공정을 통해 최종 선재의 크기(특히 두께 측면에서)에 가깝게 공정을 시작할 수 있고 높은 충진 밀도를 유지할 수 있으므로 초전도 선재의 특성 향상과 더불어 생산 비용, 생산속도 측면에서도 매우 유리한 방법이 될 것이다. 또한 자기장하 $MgB_2$ 초전도 특성 향상을 위해 자속 고정점 역할을 할 다양한 도핑 물질(분말 형태 또는 액체 형태 등)을 첨가하는 공정에 있어서 도 본 분말압연 공정을 쉽게 적용될 수 있다.

• Progress in Superconductivity
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• 제9권1호
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• pp.1-4
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• 2007

The most common technique to fabricate $MgB_2$ superconducting wire is by powder-in-tube (PIT) technique. Therefore, the starting powder for the processing of $MgB_2$ superconductors is an important factor influencing the superconducting properties and performance of the conductors. In this study, the influence of magnesium precursor powders and annealing temperatures on the transition temperatures ($T_c$) and critical current densities ($J_c$) of $MgB_2/Fe$ wires was investigated. All the $MgB_2/Fe$ wires were fabricated by in situ PIT process. It was found that higher $J_c$ was obtained for $MgB_2$ wires with smaller particle size of magnesium precursor powders. The $J_c$ also increases with decreasing annealing temperatures.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2008년도 High Temperature Superconductivity Vol.XVIII
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• pp.61-61
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• 2008

• Progress in Superconductivity
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• 제9권1호
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• pp.80-84
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• 2007

Charcoal was used as a carbon source for improving the critical current density of $MgB_2$ and the effect of annealing temperature on the $J_c$ of $MgB_2$ was investigated. The charcoal powder used in this study was $1{\sim}2$ microns in size and was prepared by wet attrition milling. $MgB_2$ bulk samples with a nominal composition of $Mg(B_{0.95}C_{0.05})_2$ were prepared by in situ process of Mg and B powders. The powder mixture was uniaxially compacted into pellets and heat treated at temperatures of $650^{\circ}C\;-\;1000^{\circ}C$ for 30 minutes in flowing Ar gas. It was found that superconducting transition temperature of $Mg(B_{0.95}C_{0.05})_2$ decreased by charcoal additions which indicates the carbon substitution for boron site. $J_c$ of $Mg(B_{0.95}C_{0.05})_2$ was lower than that of the undoped $MgB_2$ at the magnetic fields smaller than 4 Tesla, while it was higher than that of the undoped sample especially at the magnetic field higher than 4 T. High temperature annealing seems to be effective in increasing $J_c$ due to the enhanced carbon diffusion into boron sites.