• Progress in Superconductivity
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• v.3 no.1
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• pp.125-129
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• 2001

NiO buffer layers were deposited on texture Ni tapes fur YBCO coated conductors by MOCVD(metal organic chemical vapor deposition) method, using a single solution source. Variables were deposition temperature and flow rate of $0_2$carrier gas. At higher temperatures, The NiO(111) texture was well developed, but the NiO(200) texture was developed at low temperatures. The best result was obtained at the deposition temperature of$ 470^{\circ}C$ and the gas flow rate of 200 sccm. FWHM value of $\omega$-scan fur NiO(200) of the film and $\Phi$-scan for NiO(111) of the film was $4.2^{\circ}$ and $7^{\circ}$, respectively.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.7
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• pp.315-319
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• 2003

We improved quench properties of a superconducting fault current limiter (SFCL) based on YBCO thin films by their serial and parallel combinations. The SFCL consisted of 6 switching elements fabricated of 4 inch-diameter YBCO thin films. The quench currents of the switching elements were distributed between 33.9 A and 35.6 A. Simple serial connection resulted in imbalanced power dissipation between switching elements even at the quench current difference of 0.6 A. On the other hand, $2{\times}2$ and $3{\times}2$ stack combinations produced simultaneous quenches. The $3{\times}2$ stack combination showed better simultaneous quench behavior than the $2{\times}2$ stacks. This is suggested to be because the currents between switching elements in parallel connection of the $3{\times}2$ stacks were more effectively redistributed than the $2{\times}2$ stacks.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04a
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• pp.29-33
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• 2002

종자결정성장법은 단결정형 YBCO 초전도체를 제조하기에 매우 유용한 방법이다. 이 방법은 YBCO 성형체 위에 Sm123나 Nd123 종자를 올려놓고 용융 열처리하여 초전도 결정을 특정한 방위로 성장하게 하는 방법이다. 그러나 이 공정의 단점은 초전도체의 결정성장속도가 매우 느리기 때문에 전체공정시간이 길다는 것이다. 이를 개선하고자 본 연구에서는 성형체 위에 같은 결정방위를 갖는 여러 개의 종자들을 동시에 올려 놓고 열처리하여 단결정형 초전도체의 제조시간을 단축하고자 하였다. 이 공정을 다중종자결정성법이라 명명하였으며, 이 공정의 적용으로 공정시간을 상당히 단축할 수 있음을 증명하였다. 본 연구에서는 초전도체의 결정 성장과정, 종자의 갯수와 공정시간의 관계, 종자에서 생성, 성장된 결정들이 만드는 결정입계특성 동에 대해 논의하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04a
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• pp.21-24
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• 2002

In this paper, for the study on the fabrication of YBCO superconductor wire, a double layered YBCO superconductor wire was fabricated by electrophoretic method on metal Ag wire(${\Psi}$0.8 mm). On the basis of previous researches for the fabrication of superconductor wire, the acetone suspension solution with 8 vol.% of 1% PEG(1000) was used and high molecular adhesive was experimentally performed for an improvement of the critical current density of superconductor wire. It was found that the Ag inter-layer deposited on the superconductor wire affect to the state of second YBCO film and its critical current density.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.16-19
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• 2003

YBCO film을 이용하여 2 stripe-meander 형태의 초전도 한류기를 제작하고 시험하였다. 초전도 film의 hot spot에 의해 발생하는 열을 분산시키기 위해 gold shunt layer를 입혔다. 사고각 $0^{\circ}$에서 사고발생 후 최초 quench 전류값은 $9.56A_{peak}$이었고 약 0.63 msec동안 fast quench 가 진행되고 이후에는 gold층의 열발생에 의한 저항증가가 약 3주기동안 진행된 후 안정되었다. 사고각 $45^{\circ}$와 $90^{\circ}$ 에서는 전류가 상승하는 도중 혹은 최고지점에서 사고가 발생했기 때문에 fast quench time이 각각 0.56 msec와 0.26msec를 보였다. 초전도 한류기를 적용하였을 때 사고전류는 사고직후 약 5배, 3주기후에는 약 8.5배까지 효과적으로 제한함을 알 수 있었다.

• Journal of the Speleological Society of Korea
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• no.76
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• pp.1-13
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• 2006

Electrophoretic deposition (EPD) of alcohol YBCO suspensions on the Ag wire electrode is studied. Poly(ethylene glycol) was coordinated to a structure formed by the EPD process with YBCO particles. The suspension is characterized in terms of zeta potential and conductivity. The d.c electric fields of 200-300 V/cm are applied for 1-10 min. The optimal condition for the EPD allows modifying the properties and microstructure of the deposited films. Superconducting coatings with nanometer-sized pores and a preferred orientation along the c-axis were prepared from the result with chemically modified precursor solution. In contrast, YBCO coatings of submicrometer-sized pores and randomly orientated grains were prepared from the solution without PEG.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.371-373
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• 1998

The SmBa$_2$Cu$_3$O$\sub$x/ single crystals were used as seeds to induced YBCO growth in MTG process. As the result, the large bulk oriented YBCO superconductors were prepared with dimension of plane 21mm and 32mm in diameter and 10mm in height. The typical Jc value of the sample is 6.5${\times}$10$^4$A/$\textrm{cm}^2$ and its flux float force is 4.6N/$\textrm{cm}^2$. The oxygen absorption in large bulk textured YBCO samples in pure oxygen was studied at several constant temperatures. It can be divided into two steps: a chemical reaction step and a diffusion step.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.491-493
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• 1998

The SmBa$_2$Cu$_3$O$\sub$x/ single crystals were used as seeds to induced YBCO growth in MTG process. As the result, the large bulk oriented YBCO superconductors were prepared with dimension of plane 21mm and 32mm in diameter and 10mm in height. The typical Jc value of the sample is 6.5${\times}$10$^4$A/$\textrm{cm}^2$ and its flux float force is 4.6N/$\textrm{cm}^2$. The oxygen absorption in large bulk textured YBCO samples in pure oxygen was studied at several constant temperatures. It can be divided into two steps: a chemical reaction step and a diffusion step.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.24-26
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• 2003

We fabricated Ni and Ni alloy substrates for YBCO coated conductors. The Ni and Ni alloy substrate was fabricated by powder metallurgy technique and cold rolling. The texture of substrates had a strong 4-fold symmetry and ［111］∥ND texture after annealing temperature of 100$0^{\circ}C$. The measured full-width half-maximum (FWHM) of in-plane and out-of-plane was in the range of 6$^{\circ}$-10$^{\circ}$. The powder metallurgy technique is fabrication of the substrates for considered to be suitable for the application of YBCO coated conductors.

• Journal of Magnetics
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• v.6 no.3
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• pp.83-85
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• 2001

The magnetoresistance properties of NiO/NiFe/Cu/NiFe spin valve film deposited on MgO(100) substrate with YBa$_2$$Cu_3O_7$(YBCO) film were investigated at room temperature and at 77 K. The magnetoresistance (MR) curves of the hybrid superconductor-magnetoresistor film structure showed an exchange coupling field of 300 Oe and an inverse magnetoresistance ratio of -6.5%. The magnetization configurations of the two magnetic layers in the NiO spin valve were antiparallel due to an increment in the conduction electron flow to superconductor YBCO film. This sample showed an inverse MR ratio.