• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2000년도 KIASC Conference 2000 / 2000년도 학술대회 논문집
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• pp.3-5
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• 2000

Among the various processing techniques used in HTS wire fabrication, the PIP(Powder In Tube) method is currently one of the most promising for applications on an industrial scale. In this study, we have fabricated Bi-2223/Ag superconducting tapes using the modified PIT process, where several process factors were changed and improved, ie., powder packing, drawing, rolling and heat treatment. We obtained Bi-2223 tape that have high critical current, 46 a at 77.3 K, have high critical current, 46A at 77.3 K, self field although the tape was not pressed but only rolled. The critical current of 100m class long length tape was measured 21.6A at the same criterion. Besides, the critical current of Bi-2223/Ag tape was measured applying magnetic fields with different directions at various temperatures.

• Progress in Superconductivity
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• 제3권2호
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• pp.247-251
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• 2002

In general, the bubbling, generated during the fabrication of the tapes, breaks the superconducting filament, and critical current of the tapes will be decreased. Heat-treatment schemes of Bi-2223/Ag HTS tapes were modified, such as pre-annealing of multi-stacked billet, 2-step main sintering and ramp rate etc. The generation of bubbling was drastically decreased from 20 bubbles/m to 0 ~ 1 bubble/m by the modified heat-treatment. Therefore, the value of critical current of the tapes without bubbling was increased almost twice higher than that of already existing tapes. Critical current up to 42 A in 40 m length Bi-22231Ag tapes have been measured at 77K, self-field, 1$mutextrm{V}$/cm criterion. It could be confirmed that elimination of bubbling is effective to maintain the superconducting property along the tape length.

• Progress in Superconductivity
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• 제13권1호
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• pp.28-33
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• 2011

Distribution of the local critical temperature and current density in YBCO coated conductors were analyzed using Low-temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). We prepared YBCO coated conductors of various bridge types to study the spatial distribution of the critical temperature and the current density in single and multi bridges. LTSLHPM system was modified for detailed linescan or two-dimensional scan both scanning laser and scanning Hall probe method simultaneously. We analyzed the local critical temperature of single and multi bridges from series of several linescans of scanning laser microscopy. We also investigated local current density and hysteresis curve of single bridge from experimental results of scanning Hall probe microscopy.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1251-1252
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• 2006

In order to investigate 95% retained critical current of Bi-2223/Ag tapes under various stress-strain conditions, load cell attached tension and bending apparatus was used. The critical current of stress-strained tape was degraded below 95% retained critical current when tension and bending was simultaneously applied together. But only one of this tension or bending did not degrade the tape below 95% retained critical current. Deformation temperature was important to maintain the 95% retained Ic of Bi-2223/Ag tapes after bending or tension deformation because mechanical strength of tapes can be changed drastically between room temperature and 77 K.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1243-1244
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• 2006

Five kinds of double stacked 385 (55 x7) filamentary Bi2212/Ag round wires and 55 filamentary tapes with different Ag ratios (silver area/superconductor area) have been fabricated via PIT method, and the effects of Ag ratio and processing factors on critical current density were studied. The effects of the maximum temperature and average filament diameter on critical current density were also studied. The wire of 0.74 mm diameter having Ag ratio 3.7 showed critical current density of $2,218\;A/mm^2$ at 4.2 K, 0 T.

• 소성∙가공
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• 제29권1호
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• pp.37-43
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• 2020

Increasing the critical current density of superconducting wire is one of the difficult challenges in the field of superconductivity. It is well known that the higher volume fraction of uniformly dispersed α-Ti is able to enhance the critical current density of superconducting material NbTi because α-Ti serves as a flux pinning center. The volume fraction of α-Ti highly depends on the grain size of NbTi because α-Ti precipitates at the grain boundaries or triple points. For this purpose, we investigated the effect of initial microstructures of NbTi obtained from hot rolling in various temperature conditions on the critical current density. In addition, subsequent heat treatment was assigned to precipitate α-Ti and groove rolling/cold drawing was adopted to produce a wire with a diameter of about 1.0 mm. It was observed that the band structure was formed after hot rolling at 500~600℃. It was also found that the volume fraction of α-Ti after hot rolling at 500~600℃ was higher and it led to the highest critical current density.

• 한국초전도ㆍ저온공학회논문지
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• 제17권3호
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• pp.47-50
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• 2015

The high temperature superconducting (HTS) magnet has been developed for the high magnetic field applications such as NMR, MRI and other industrial machinery. In designing process of these HTS magnets, the accurate estimation on the critical current (Ic) is essential to predict and secure the electromagnetic performance. The critical current of 2G HTS tape has anisotropic Ic degradation characteristics with the application of magnetic field - angular dependency of critical current. It is known that the perpendicular magnetic field to the face of HTS tape makes dominant degradation on the critical current for conventional 2G HTS tape. However, recently developed 2G HTS tape has more complex characteristics due to the artificial pinning center. Therefore, the method for Ic estimation reflecting such characteristics of 2G HTS tape needs to be devised. The method considering the angular dependency is introduced in this paper. And the result of newly devised method is compared with that of previous method.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.249-252
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• 2002

The change of critical current with a crack formation in a Bi-2223/Ag tape was studied by experimental and numerical analyses. Critical current of Bi-2223/Ag tape was measured with a continuous DC-power supply. The current-voltage relation of a Bi-2223/Ag tape is measured by the four point method. Numerical method is used to solve two dimensional heat conduction equation. By comparing the experimental and numerical results, the validity of numerical method is verified.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.189-1-190-1
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• 2008

A high temperature superconducting(HTS) power cable is available for high capacity current in normal condition. But resistance was appeared to operate unbalance load by thermal current characteristic. This characteristic of HTS power cable used to design for unstated condition. And than, It used to understand and analyze characteristic of power cable thermal and critical current. This study appeared that quench resistance reason from shield and former current rise to superconductor(SC) current. The resistance of SC occurred that the cable temperature rise to fault current after decreased critical current. The quench resistance of SC increased in temperature or decreased in critical current. So the quench resistance of SC correlated with resistance of both shield and former current. It need to sufficiently influenced the parameters of HTS cable design.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.363-364
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• 2009

본 연구는 IEC/TC 90 규격을 참조하여 Cu stabilizer/Ag/$LaMnO_3$/IBAD-MgO/$Y_2O_3$/$Al_2O_3$/Hastelloy C276/Cu stabilizer의 구조를 가지는 coated conductor의 DC 임계 전류의 결정에 대한 사전 연구를 위해 (1) 시편의 냉각시간, (2) 전류 선의 용량을 변화하여 임계 전류의 변화를 관찰하여 다음과 같은 결과를 얻었다. (1) 5분 이상의 시편 냉각시간은 COV가 약 0.4% 정도로 거의 임계 전류 결정에 영향을 주지 않았으며, 냉각 시간이 길면 길수록 임께 전류 이하에서 전압의 기저면이 낮아지는 경향을 보였다. (2) 전류 선의 용량이 클수록 임계 전류 이하에 전압의 기저면이 낮아지는 경향을 보였다.