http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
TFA-MOD법으로 제조된 YBCO 박막의 습도분압 효과
장석헌,임준형,윤경민,이승이,김규태,이창민,주진호,나완수,이희균,홍계원,Jang, Seok-Hern,Lim, Jun-Hyung,Yoon, Kyung-Min,Lee, Seung-Yi,Kim, Kyu-Tae,Lee, Chang-Min,Joo, Jin-Ho,Nah, Wan-Soo,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1
We fabricated $YBa_2Cu_33O_{7-x}$(YBCO) films on(00l) $LaAlO_3$ substrates prepared by metal organic deposition(MOD) method using trifluoroacetate(TFA) solution and evaluated the effects of the humidity on the microstructure, phase purity, and critical properties. The films calcined at $430^{\circ}C$ were fired at $775^{\circ}C$ at 0%, 4.2%, 12.1%, and 20.0% humidified As gas mixed with 0.1% $O_2$. We observed that the amount of $BaF_2$ phase was effectively reduced and that a sharp and strong biaxial texture formed under a humidified atmosphere, leading to increased critical properties. For the films fired at 0% humidity, the $T_c\;and\;I_c$ were undetectably small. When the humidity was increased to 4.2%, the corresponding $T_c$(onset) and $I_c$ were increased to 90.5 K and 8 A/cm-width, respectively. For the films at the humidity range of 12.1-20.0%, the $I_c$ was found to be 35 A/cm-width. According to the results of the XRD, pole-figure, and SEM, these improved critical properties are probably attributed to the formation of a purer YBCO phase, larger grain size, and stronger c-axis orientation.
TFA-MOD법에 의한 YBCO 박막의 열처리변수 효과
장석헌,임준형,김규태,이진성,윤경민,주진호,이희균,홍계원,Jang, Seok-Hern,Lim, Jun-Hyung,Kim, Kyu-Tae,Lee, Jin-Sung,Yoon, Kyung-Min,Joo, Jin-Ho,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2006 Progress in superconductivity Vol.7 No.2
We fabricated YBCO coated conductors (CCs) by TFA-MOD process and evaluated microstructure, texture formation, and critical temperature ($T_c$) and current ($I_c$). YBCO precursor solution was synthesized using metal-trifluoroacetates and dip coated on $LaAlO_3$(LAO) substrate. The phase formation and microstructure was characterized by X-ray diffraction and scanning electron microscopy (SEM) and the degree of texture was evaluated by pole-figure analysis. The CC was heat-treated in various calcining temperatures ($370^{\circ}C-460^{\circ}C$) and firing temperatures ($750^{\circ}C-800^{\circ}C$). As fired at $775^{\circ}C$ for 4h, the CC had the highest $T_c$ of 89.5 K and $I_c$ of 40 A/cm-width ($J_c=2.0\;MA/cm^2$). Microstructural observation indicated that the YBCO film was dense and homogeneous and had a strong cube texture without formation of second phase and its in-plane full-width at half-maxima; $5.2^{\circ}$ under optimum condition.
TFA-MOD법을 이용한 YBCO 박막의 열처리 온도와 두께의 영향
장석헌,임준형,이진성,윤경민,김규태,주진호,김찬중,나완수,Jang Seok-Hern,Lim Jun-Hyung,Lee Jin-Sung,Yoon Kyung-Min,Kim Kyu-Tae,Joo Jin-Ho,Kim Chan-Joong,Nah Wan-Soo 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.5
We fabricated the YBCO films on LAO substrate using the TFA-MOD method and evaluated the effects of heat treatment temperature and film thickness on the microstructure, degree of texture, and critical properties. The calcining and firing were peformed at the temperature range of $370^{\circ}C-460^{\circ}C\;and\;750^{\circ}C-800^{\circ}C$, respectively. For the films fired at $775^{\circ}C$ after calcining at $400^{\circ}C-430^{\circ}C$showed highest critical temperature (Tc-onset) of 89.5 K and critical current (Ic) of 40A/cm-width which corresponds to critical current density (Jc) of $1.8MA/cm^2$. The highest critical properties are probably attributed to the formation of purer YBCO phase, stronger biaxial texture, and higher oxygen content, according to the XRD, pole-figure, SEM, Raman analysis. From the multi-coated films, the Ic increased from 39 to 169 A/cm-width as the coating repeated to four times, while the corresponding Jc was measured from once to be in the range of $0.8-1.2MA/cm^2$. Both Ic and Jc degraded as the coating repeated further, indicating that the optimum thickness is in the range of $1.0{\mu}m-1.7{\mu}m$.
TFA-MOD법으로 제조된 다층 YBCO 박막의 미세구조 관찰
장석헌,임준형,이창민,황수민,최준혁,심종현,주진호,김찬중,Jang, Seok-Hern,Lim, Jun-Hyung,Lee, Chang-Min,Hwang, Soo-Min,Choi, Jun-Hyuk,Shim, Jong-Hyun,Joo, Jin-Ho,Kim, Chan-Joong 한국초전도학회 2008 Progress in superconductivity Vol.9 No.2
We fabricated $YBa_2Cu_3O_{7-x}$(YBCO) films on (00l) $LaAlO_3$ substrates prepared by metal organic deposition(MOD) method using trifluoroacetate(TFA) solution. The films with various thicknesses were prepared by repeating the dip-coating and calcining processes. The effects of film thickness on phase formation, microstructures, and critical properties were evaluated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The microstructure and resultant critical current($I_C$) and critical current density($J_C$) varied remarkably with film thickness: The ($I_C$) value increased from 39 to 160 A/cm-width as the number of coatings increased from one to four, while the corresponding $J_C$ was measured to be in the range of $0.84-1.21\;MA/cm^2$. Both the $I_C$ and $J_C$ decreased when an additional coating was applied due to microstructural degradation, indicating that the optimum thickness is in the range of $1.1-1.8\;{\mu}m$. The possible cause for the decrease in the $I_C$ and $J_C$ value for film thicker than $1.8\;{\mu}m$ include non-uniform thickness, increased surface roughness, and the poor formability of the YBCO phase and texture arising from the insufficient heat treatment time with respect to the increased thickness.
BSCCO-2212/$SrSO_4$ 벌크 초전도체의 제작 및 특성평가
김규태,장석헌,박의철,황수민,주진호,홍계원,김찬중,김혜림,현옥배,Kim, Kyu-Tae,Jang, Seok-Hern,Park, Eui-Cheol,Hwang, Su-Min,Joo, Jin-Ho,Hong, Gye-Won,Kim, Chan-Joong,Kim, He-Lim,Hyun, Ok-Bae 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1
We fabricated Bi-2212/$SrSO_4$ bulk superconductors by the casting process and evaluated the effects of the powder mixing method and annealing temperature on the texture, microstructure, and critical current. In the process, the Bi-2212 powders were mixed with $SrSO_4$ by hand-mixing(HM) and planetary ball milling(PBM) method and then the powder mixtures were melted at $1100^{\circ}C{\sim}1200^{\circ}C$, solidified, and annealed. We observed that the rod made by the PBM had a more homogeneous microstructure and smaller $SrSO_4$ and second phases than that of the rod made by the HM, resulting in increased $I_c$. The $I_c$ of the rod also depended on the annealing temperature and the highest $I_c$ was obtained to be 200 A when prepared by HM at $1200^{\circ}C$ and annealed at $810^{\circ}C$ which is probably due to the moderate density and 2212 texture and the smaller and less second phase compared to that at higher temperature. The possible causes of the variations of $I_c$ with the powder mixing method and annealing temperature were related to the microstructural evolution based on the SEM, EPMA, and DTA analyses.
Electroforming을 이용하여 제조한 Ni 기판의 기계적 특성 및 내마모 거동 분석
이승이,장석헌,이창민,최준혁,주진호,임준형,정승부,송건,Lee, Seung-Yi,Jang, Seok-Hern,Lee, Chang-Min,Choi, Jun-Hyuk,Joo, Jin-Ho,Lim, Jun-Hyung,Jung, Seung-Boo,Song, Keun 한국재료학회 2007 한국재료학회지 Vol.17 No.10
We fabricated the Ni plate by electroforming process and evaluated the microstructure, mechanical properties and wear behavior of the Ni plate. Specifically, the effects of addition of wetting agents, SF 1 and SF 2 solutions, on the microstructure and properties were investigated. The microstructure and surface morphology were characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM), respectively, and friction coefficient was measured by the ball-on-disk method. We found that the microstructure and mechanical properties of Ni plate were changed with kind and amount of wetting agents used. The hardness and tensile strength of Ni plate formed without wetting agents was 228 Hv and 660.7 MPa, respectively, whiled when wetting agent was added, those were improved to be 739 Hv and 1286.3 MPa. These improvements were probably due to the finer grain size and less crystallization of Ni. In addition, when both wetting agents were added, the friction coefficient was reduced from 0.73 to 0.67 which is partially caused by the improved hardness and smooth surface.
211 공정을 이용한 새로운 TFA-MOD YBCO 박막 선재 제조
임준형,장석헌,김규태,이진성,윤경민,박의철,주진호,Lim, Jun-Hyung,Jang, Seok-Hern,Kim, Kyu-Tae,Lee, Jin-Sung,Yoon, Kyung-Min,Park, Eui-Cheol,Joo, Jin-Ho 한국초전도학회 2006 Progress in superconductivity Vol.7 No.2
We fabricated the YBCO films on single crystal $LaAlO_3$ substrates via a metal organic deposition (MOD) process. In the process, $Y_2Ba_1Cu_1O_x$ and $Ba_3Cu_5O_8$ powders were dissolved in trifluoroacetic acid (TFA) followed by calcining and firing heat treatments. To evaluate the effects of the firing temperature on YBCO phase formation and critical properties, the films were fired at $750^{\circ}C,\;775^{\circ}C\;and\;800^{\circ}C$ after calcining at $430^{\cric}C$. Microstructure observation indicated that a crack-free surface formed and a strong biaxial texture was developed. The FWHM of out-of-plane texture was measured to be in the range of $4.3^{\cric}-7.0^{\circ}$ for all the films. When the YBCO film was fired at $775^{\cric}C$, it had the highest critical properties: 88.5 K of critical temperature and 16 A/cm-width of critical current ($1MA/cm^2$ as critical current density). On the other hand, those properties were degraded as firing at $750^{\circ}C\;and\;800^{\circ}C$. It is considered that the improved critical values are partly owing to dense and homogeneous microstructure, strong texture, and high oxygen content.
Y<sub>2</sub>Ba<sub>1</sub>Cu<sub>1</sub>O<sub>x</sub>공정을 이용한 TFA-MOC YBCO 박막 공정 개발
임준형,장석헌,김규태,이진성,윤경민,하홍수,주진호,나완수,Lim, Jun-Hyung,Jang, Seok-Hern,Kim, Kyu-Tae,Lee, Jin-Sung,Yoon, Kyung-Min,Ha, Hong-Soo,Joo, Jinho,Nah, Wansoo 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.2
YBCO film was synthesized by using a new approach to the TFA-MOD method. In the fabrication process, $Y_2Ba_1Cu_1O_x\;and\;Ba_3Cu_5O_8$ powders were used as precursors (the so called '211 process'), instead of Y-, Ba-, and Cu-based acetates, and dissolved in trifluoroacetic acid followed by calcining and firing heat treatment. Consequently, we successfully fabricated YBCO film and evaluated the phase formation, texture evolution, and critical properties as a function of the calcining and firing temperature and humidity, in order to explore its possible application in coated conductor fabrication. The films were calcined at $430-460^{\circ}C$ and then fired at $750-800^{\circ}C\;in\;a\;0-20\%$ humidified $Ar-O_2$ atmosphere. We observed that $BaF_2$ phase was effectively reduced and that a sharp and strong biaxial texture formed under humidified atmosphere leading to increased critical properties. In addition, we found that the microstructure varied significantly with the firing temperature: the grain grew further, the film became denser, and the degree of texture and phase purity varied as the firing temperature increased. For the film fired at $775^{\circ}C$ after calcining at $460^{\circ}C$, the critical current was obtained to be 39 A/cm-width (corresponding critical current density is $2.0\;MA/cm^2$ which was probably attributed to such factors as the enhanced phase purity and out-of-plane texture, the moderate film density and grain size, and crack-free surface.
용융주조법으로 제조한 BSCCO-2212 초전도체의 공정변수 연구
김규태,장석헌,임준형,주진호,김찬중,홍계원,김혜림,현옥배,Kim, Kyu-Tne,Jang, Seok-Hern,Lim, Jun-Hyung,Joo, Jinho,Kim, Chan-Joong,Bong, Gye-Won,Kim, Rye-Lim,Hyun, Ok-Bae 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.6
We fabricated BSCCO-2212 (2212) bulk superconductor by melt casting process, and evaluated the dependence of the critical properties on the temperature and cooling .ate of mold and the pouring methods of melt. It was observed that the critical current (Ic) of 2212 was significantly dependent on the pre-heating temperature of the mold. At the pre-heating temperature of $500^{\circ}C$ followed by air cooling condition, Ic of 48 A at 77 K was obtained which was higher than others processed at different temperatures. In addition, the Ic improved to 132 A when tilt casting method was applied. The improved Ic is probably due to the fact that the tilt casting reduced a turbulent flow of the melt during casting causing less porosity and more homogeneous microsructure. Critical temperature was measured to be 87-89 K after the first heat treatment and it improved to 90-91 K when subsequently heat treated at $650^{\circ}C$ in a nitrogen atmosphere. This improvement was considered to be due to an optimization of the oxygen content in the range of 8.16-8.2.
BSCCO(2212) 벌크 초전도체의 주조조건 및 SrSO<sub>4</sub> 최적함량에 대한 연구
김규태,박의철,장석헌,임준형,주진호,김찬중,김혜림,현옥배,Kim Kyu-Tae,Park Eui-Cheol,Jang Seok-Hern,Lim Jun-Hyung,Joo Jin-Ho,Kim Chan-Joong,Kim Hye-Rim,Hyun Ok-Bae 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.6
We fabricated BSCCO-2212 (2212) rod by the melt casting process (MCP) and evaluated the effect of the melt flowing on the critical current ($I_c$) by using vertical and tilt casting. It was observed that the $2212-SrSO_4$ rod processed by the tilt casting method with homogeneous pre-heating temperature of the mold had a higher $I_c$ than that processed by the vertical casting method. We also evaluated the influence of the strontium sulfates ($SrSO_4$) addition on the texture, microstructure, critical current and temperature, and mechanical hardness of the $2212-SrSO_4$ rods. It was observed that the addition of $SrSO_4$ improved the critical current ($I_c$) and mechanical hardness of the 2212. The $I_c$ of the 2212 increased as the $SrSO_4$ content increased and reached a peak value (260 A at 77 K) at an $SrSO_4$ content of 6 wt.%. In addition, the addition of $SrSO_4$ had a beneficial effect on the mechanical hardness of the 2212. We studied the possible cause of the variation in the $I_c$ with the melt flowing and the $SrSO_4$ content based on the XRD, EPMA analysis and the microstructural observation.