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Twisted Multifilamentary BSCCO 2223 Tapes by Using High Resistive Sheath
Yoo, Jai-Moo,Ko, Jae-Woong,Kim, Hai-Doo,Chung, Hyung-Sik The Korean Superconductivity Society 2000 Progress in superconductivity Vol.1 No.2
Different twist pitches of multi filamentary BSCCO 2223 tapes using high resistivity sheath were fabricated to investigate the effect of twist pitches on the microstructure and critical current property. A conductor with a high resitstivity matrix is possible to allow larger twist pitch for reducing ac losses and reduce eddy current losses simultaneously. The $J_{ct}$ values of 10 mm and 5 mm twisted tapes drop faster than that of untwisted and 20 mm twisted tapes under increasing magneticfield, especially in low field regime (0 $\sim$ 0.03 T). It suggests that weak links in the former are more serious than in the latter, which is in accordance with the microstructure analysis.
MOD 공정에 의해 제조된 YBCO 박막의 압력 의존성
Yoo, Jai-Moo,Chung, Kook-Chae,Ko, Jae-Woong,Kim, Young-Kuk,Wang, Xiao Lin,Dou, Shi Xue 한국초전도저온학회 2006 한국초전도저온공학회논문지 Vol.8 No.1
The growth properties of MOD-YBCO films were investigated. To enhance the growth rate of YBCO layer and inhibit the build-up of HF gas during the annealing process in TFA-MOD for YBCO coated conductors the method of low pressure annealing was employed. Total pressure was changed from 700Torr to 1Torr and its effect on growth of YBCO films was compared with atmospheric one. The lower Pressure was effective to control of the pore size in MOD method . Surface morphology of YBCO films processed at low total pres sure was rough and composed of random YBCO (103) grains. But large pores, usually observed at atmospheric process in MOD disappeared and also the number of pores was reduced at low pressure annealing. Also discussed ate the effects of Fluorine-free Y and Cu precursor solution on the development of microstructure. Dense surface me phology and with less and small pores can be provided through controlling Fluorine content.
이종무 ( Chong Moo Lee ),박세근 ( Se Geun Park ),유재영 ( Jai Young Yoo ),김춘추 ( Choon Choo Kim ),강성구 ( Sung Koo Kang ),김예회 ( Re Hwe Kim ),김주현 ( Joo Hwen Kim ) 대한내과학회 1973 대한내과학회지 Vol.16 No.12
1n 1942 Klinefelter, Reifenstein and Albright described a syndrome which was consisted of gynecomastia, eunuchoidism, small atrophic testes and increased excretion of gonadotropine. The atrophic testes was characterized dy hyalization and as ermatogenesis.
Ko, Jae-Woong,Yoo, Jai-Moo,Kim, Hai-Doo,Chung, Hyung-Sik The Korean Superconductivity Society 1999 Progress in superconductivity Vol.1 No.1
Ultra fine MgO particles added BSCCO tapes were fabricated by tape casting using Doctor Blade Method and enclosed by silver foil for different starting compositions (that is, 2223 major, 2212 major). In order to obtain optimum microstructure, thermomechanical treatment was done. Microstructure and phase were analyzed by XRD, SEM and DTA. The critical current density was measured under magnetic field at 77K. The tapes fabricated from the precursor powder with BSCCO-2223 phase (>90%) result in a microstructure with a larger grain size and higher transport critical current density value under magnetic field at given thermomechanical treatment conditions.
Fabrication of $MgB_2$ tape with metal powder addition
Ko, Jae-Woong,Yoo, Jai-Moo,Kim, Young-Kuk,Chung, Kook-Chae,Yoo, Sang-Im,Wang, Xio Lin,Dou, Shi Xue The Korean Society of Superconductivity and Cryoge 2006 한국초전도저온공학회논문지 Vol.8 No.1
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.
Oxide precursor-based MOD processing of YBCO thin films
Kim, Young-Kuk,Yoo, Jai-Moo,Ko, Jae-Woong,Chung, Kook-Chae,Heo, Soon-Young The Korea Institute of Applied Superconductivity a 2004 한국초전도저온공학회논문지 Vol.6 No.4
A low cost MOD processing using YBCO oxide powder as a starting precursor was employed for fabrication of YBCO thin films. YBCO oxide is advantageous over metal acetates or TFA salts which are popular starting precursors for conventional MOD-TFA process. YBCO thin films were prepared by oxide-precursor-based MOD process and annealing condition was optimized. The YBCO thin film annealed at 78$0^{\circ}C$ shows no transport $I_c$ and poor microstructure. However, the YBCO thin film annealed at higher temperature shows improvement in microstructure and current transport property. In order to improve critical current, YBCO thin film was prepared by double coating method. YBCO thin film prepared with double coating approach shows enhanced superconducting performance ($I_c$>100A/cm-w).
F-free Y & Cu 전구용액을 이용한 YBCO 박막 제조
Kim, Young-Kuk,Yoo, Jai-Moo,Ko, Jae-Woong,Chung, Kook-Chae,Kim, Young-Jun,Han, Bong-Soo,Wang, X.L.,Dou, S.X. 한국초전도저온학회 2006 한국초전도저온공학회논문지 Vol.8 No.1
A new precursor solution wilt low fluorine content was synthesized for MOD processing of coated conductors. In this study, the precursor solution for MOD processing was synthesized using F-free yttrium and copper precursor. It was shown that crack-free and uniform precursor films were formed after calcination in humidified oxygen atmosphere. Less than 2 hours were required to finish the calcination process. The relatively gradual weight loss during the calcination process is attributed to the feasibility of fast calcination profile. The calcined precursor film was converted to a YBCO film without any secondary phases after annealing in wet $Ar/O_2$ atmosphere. Fully converted film shows uniform microstructure and high critical current density. $(Jc=2.7MA/cm^2) $.
Chung, Kook-Chae,Yoo, Jai-Moo,Ko, Jae-Woong,Kim, Young-Kuk,Wang, X.L.,Dou, S.X. 한국초전도저온학회 2006 한국초전도저온공학회논문지 Vol.8 No.1
Optimization of process variables, including oxygen and water partial pressure and also an nesting temperature, was performed in batch-type process to fabricate YBCO films on LaAlO3 single crystal. In this work, YBCO oxide powder was used as a starting precursor for metal-organic deposition(MOD)method. The precursor films were fabricated in batch furnace and they were converted to the epitaxial YBCO films at the same furnace with varying the process variables. The oxygen partial pressure was varied from 100ppm to 2000ppm and the water partial pressure from 1.2% to 12.2%. The window for optimal P(O2) was narrow about 700ppm for batch-type process. YBCO films in bathc-thype MOD process were optimized at 740-770oC and P(H2O) of 2.3%-7.3%.