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DCA-MOD 법에 의한 High $J_c$ YBCO 박막의 제조
김병주,김혜진,이금영,이종범,김호진,이희균,홍계원,Kim, Byeong-Joo,Kim, Hye-Jin,Yi, Keum-Young,Lee, Jong-Beum,Kim, Ho-Jin,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1
High $J_c\;YBa_2Cu_3O_x$ superconducting films were fabricated by MOD method using fluorine-free dichloroacetic acid(DCA) as chelating solvent for preparing precursor solution. Coating solutions were prepared by dissolving Y-, Ba- and Cu-acetates in DCA solvent followed by drying in rota vapor to obtain the blue gel that is diluted in methanol and 2-methoxyethanol for adjusting the cation concentration. DCA-MOD precursor solution was coated on a single crystal(001) $LaAlO_3(LAO)$ substrate by a dip coating method with a speed of 25 mm/min. Coated films were calcined at lower temperature up to $500^{\circ}C$ in flowing oxygen atmosphere with a 7.2% humidity. Conversion heat treatment was performed at various temperatures of $780{\sim}810^{\circ}C$ for 2 h in flowing Ar gas containing 1000 ppm oxygen with a humidity of 9.45%. SEM observations showed that films have very dense microstructures for the films prepared at the temperature higher than $800^{\circ}C$ regardless of diluting solvent; methanol or 2-methoxyethanol. X-ray diffraction analysis showed that YBCO grains grew with a (001) preferred orientation. A High critical current density($J_c$) of 1.28 $MA/cm^2$(@77 K and self-field) was obtained id. the YBCO film prepared using 2-methoxyethanol as a solvent.
DCA-MOD 방법으로 제조된 YBCO 박막의 미세조직에 미치는 열처리 효과
김병주,김혜진,조한우,유석구,유정희,이희균,홍계원,Kim, Byeong-Joo,Kim, Hye-Jin,Cho, Han-Woo,Yu, Seok-Koo,Ryu, Jung-Hee,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2007 Progress in superconductivity Vol.9 No.1
[ $YBa_2Cu_3O_{7-{\delta}}$ ] films have been prepared on $LaAlO_3$ (100) single-crystal substrates by a metalorganic deposition using dichloroacetate precursors (DCA-MOD). Calcination conditions were varied in order to optimize the microstructure and the superconducting properties of YBCO film. Coated films were calcined at various temperatures ranging from $400{\sim}700^{\circ}C$ in flowing humid oxygen atmosphere. Ramping rate to calcination tempertures was $2.22^{\circ}C/min$. Conversion heat treatment was performed at $800^{\circ}C$ for 2 h in flowing Ar gas containing 1000 ppm oxygen with a humidity of 9.45%. Observations of surface and cross sectional SEM microstructure showed that the particle size in the calcined film increased in the range of 100-200 nm with heating rate and the calcination temperature. SEM EDS analysis showed that 13 a/o of chlorine was contained in the calcined film. It was also observed that the porosity increased with the heating rate and temperature. Porous microstructure was developed when YBCO films were prepared using porous calcined film. Dense microstructure and high $J_c$ over $1\;MA/cm^2$ was obtained when calcination was carried out at the temperature of $500^{\circ}C$ with a heating rate of $2.22^{\circ}C/min$.
DCA-MOD 법으로 YBCO 박막 제조시 하소열처리의 승온속도 효과
김병주,김혜진,조한우,권연경,유정희,이희균,홍계원,Kim, Byeong-Joo,Kim, Hye-Jin,Cho, Han-Woo,Kwon, Youn-Kyung,Ryu, Jung-Hee,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2007 Progress in superconductivity Vol.8 No.2
High $J_c\;YBa_2Cu_3O_{7-x}$ superconducting films have been fabricated $LaAlO_3(100)$ substrate by MOD method using dichloroacetic acid(DCA) as chelating solvent for preparing precursor solution. Heating rate was varied in order to optimize the calcination heat treatment condition in DCA-MOD method. Coated films were calcined at lower temperature up to $500^{\circ}C$ in flowing humid oxygen atmosphere. The heating rate was calcined from $13.3^{\circ}C/min\;to\;0.28^{\circ}C/min$. Conversion heat treatment was performed $800^{\circ}C$ for 2 h in flowing Ar gas containing 1000 ppm oxygen with a humidity of 9.45%. Surface and cross sectional SEM microstructures showed that particle sizes were increased with heating rate at a calcination step. The amount of pores was increased with heating rate in the calcined films. Dense microstructure and sharp texture were developed in an YBCO films after conversion heat treatment. A high critical current density (Jc) of $1.26MA/cm^2$ (@77 K and self-field) was obtained for the YBCO film which was prepared with a heating rate of $0.28^{\circ}C/min$.
질산염 전구체 원료로 분무 열분해 방법에 의한 YBCO 박막 증착
김병주,홍석관,김재근,이종범,이희균,홍계원,Kim, Byeong-Joo,Hong, Seok-Kwan,Kim, Jae-Geun,Lee, Jong-Beom,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2010 Progress in superconductivity Vol.12 No.1
Y123 films have been deposited on $LaAlO_3$ (100) single-crystal and IBAD substrates by spray pyrolysis method using nitrate precursors. Ultrasonic atomization was adopted to decrease the droplet size, spraying angle and its moving velocity toward substrate for introducing the preheating tube furnace in appropriate location. A small preheating tube furnace was installed between spraying nozzle and substrate for fast drying and enhanced decomposition of precursors. C-axis oriented films were obtained on both LAO and IBAD substrates at deposition temperature of around $710{\sim}750^{\circ}C$ and working pressures of 10~15 torr. Thick c-axis epitaxial film with the thickness of $0.3{\sim}0.6\;{\mu}m$ was obtained on LAO single-crystal by 10 min deposition. But the XRD results of the film deposited on IBAD template at same deposition condition showed that the buffer layers of the IBAD metal substrate was affected by long residence of metal substrate at high temperature for YBCO deposition.
질산염 전구체 원료로 Ex-situ 공정에 의한 GdBCO 박막 제조
김병주,이철선,이종범,이재훈,문승현,이희균,홍계원,Kim, Byeong-Joo,Lee, Chul-Sun,Lee, Jong-Beom,Lee, Jae-Hun,Moon, Seung-Hyun,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2011 Progress in superconductivity Vol.13 No.2
Many research groups have been manufacturing coated conductor by various processes such as PLD, MOD, and MOCVD, but the methods with production cost suitable for wide and massive application of coated conductor did not develop yet. Spray pyrolysis method adopting ultrasonic atomization was tried as one of the possible option. GdBCO precursor films have been deposited on IBAD substrate by spray pyrolysis method at low temperature and converted to GdBCO by post heat treatment. Ultrasonic atomization was used to generate fine droplets from precursor solution of Gd, Ba, and Cu nitrate dissolved in water. Primary GdBCO films were deposited at $500^{\circ}C$ and oxygen partial pressure of 1 torr. After that, the films were converted at various temperatures and low oxygen partial pressures. C-Axis oriented films were obtained IBAD substrates at conversion temperature of around $870^{\circ}C$ and oxygen partial pressures of 500 mtorr ~ 1 torr in a vacuum. Thick c-axis epitaxial film with the thickness of 0.4 ~ 0.5 ${\mu}m$ was obtained on IBAD substrate. C-axis epitaxial GdBCO films were successfully prepared by ex-situ methods using nitrate precursors on IBAD metal substrate. Converted GdBCO films have very dense microstructures with good grain connectivity. EDS composition analysis of the film showed a number of Cu-rich phase in surface. The precursor solution having high copper concent with the composition of Gd : Ba : Cu = 1 : 2 : 4 showed the better grain connectivity and electrical conductivity.
REBCO 초전도 박막제조를 위한 Fluorine-free MOD 전구체 용액 개발
김병주,임선원,김호진,홍계원,이희균,Kim, Byeong-Joo,Lim, Sun-Weon,Kim, Ho-Jin,Hong, Gye-Won,Lee, Hee-Gyoun 한국초전도학회 2006 Progress in superconductivity Vol.7 No.2
New precursor solution with dichloroacetic acid (DCA) was developed for fabricating high $J_c$ REBCO film. DCA based-precursor solution was coated on $LaAlO_3$(001) substrate by dip coating method. Processing parameters such as oxygen partial pressure, water vapor, ramping rate and pyrolysis temperature were controlled in order to obtain a good epitaxial film. The film with thickness of 0.5 micrometer was obtained by single coating and no crack was observed at calcined films. Oxygen partial pressure was controlled in the range of $100{\sim}1,000$ ppm and conversion heat treatment was carried out at the temperature range of $705-765^{\circ}C$. A critical transition temperature ($T_c$) of 90 K and a critical transport current density ($J_c$) of $>0.5\;MA/cm^2$ (77 K and self-field) were obtained for the GdBCO film. It is thought that fluorine-free MOD solution using DCA is promising precursor solution for fabricating high quality REBCO films.
사관생도의 무도수업 교수행동인식에 따른 학습몰입과 수업만족도가 재참여의사에 미치는 영향
김병주(Kim, Byeong-Joo),전상윤(Jeon, Sang-Yun),최진(Choi, Jean) 한국체육과학회 2013 한국체육과학회지 Vol.22 No.2
This study aims to investigate effect of studying immersion and class satisfaction on aviation cadets’ re-taking the class according to teacher’s teaching behaviors of the martial arts class. The number of the subjects in the study is a total of 374 cadets including who are attending Air Force Academy as of 2012. The resulting data were processed by reliability analysis, factor analysis, frequency analysis, correlation analysis, multiple regression analysis and path analysis through multiple regression analysis by applying SPSS WIN 17.0 program as a statistical treatment. The study has concluded as follows: Firstly, the subcomponents of teacher’s teaching behaviors such as intimacy, clarity and enthusiasm have affected learning tasks of studying immersion and only intimacy and clarity have influenced on learning integration, learning behavior and thinking integration. Secondly, the subcomponents of teacher’s teaching behaviors such as intimacy, clarity and enthusiasm have affected a classroom environment satisfaction. Clarity and enthusiasm have influenced on teacher’s behaviors satisfaction while intimacy has affected individual ability satisfaction. Thirdly, clarity and enthusiasm except intimacy have affected students’ re-taking the class. Fourthly, the subcomponents of studying immersion such as learning tasks immersion, learning integration, learning behaviors and thinking integration have influenced on classroom environment satisfaction. Only learning tasks immersion and learning integration have affected teacher’s behavior satisfaction and individual ability satisfaction. Fifthly, all of the subcomponents of studying immersion such as learning tasks immersion, learning integration, learning behaviors and thinking integration have influenced on students’ re-taking the class. Sixthly, all of the subcomponents of class satisfaction such as teacher’s behavior satisfaction, classroom environment satisfaction and individual ability satisfaction have affected students’ re-taking the class. Seventhly, teacher’s teaching behaviors have influenced on students’ re-taking the class through studying immersion and class satisfaction and they are major factors hidden between independent and dependent variables.
탄소나노튜브 및 그래핀 나노플레이트 폴리프로필렌 복합재 필름 압출 및 물성 평가
김병주 ( Byeong Joo Kim ),( Biplab K Deka ),강구혁 ( Gu Hyuk Kang ),황상하 ( Sang Ha Hwang ),박영빈 ( Young Bin Park ),정인찬 ( In Chan Jeong ),최동혁 ( Dong Hyuk Choi ),손동일 ( Dong Il Son ) 한국복합재료학회 2013 Composites research Vol.26 No.4
본 연구에서는 폴리프로필렌과 다양한 탄소나노소재를 사용하여 제조한 복합재의 압출방향 및 권취속도에 따른 기계적 물성과 결정화도에 대한 연구를 수행하였다. 폴리프로필렌에 탄소나노소재를 균일하게 분산시키기 위해 미분쇄기에 폴리프로필렌 분말(<700 μm)과 탄소나노소재를 혼합한 후 나노복합재 필름 제조를 위해 압출기를 사용하였다. 나노복합재 필름의 결정화도를 분석하기 위해 differential scanning calorimetry를 이용하였다. 기계적 물성을 인장시험을 통해서 측정한 후 순수 폴리프로필렌 물성과 비교하였고, 압출 시 필름 권취속도에 대한 나노복합재 결정화도의 차이를 확인하였다. 탄소나노소재를 첨가함으로써 고분자 필름의 기계적 물성이 향상됨을 확인하였고, 그에 따른 결정화도 역시 증가하는 것을 확인하였다. 반면, 권취속도가 증가 할수록 압출물의 냉각속도도 역시 증가함으로써 결정화도가 오히려 감소함을 확인하였다. Polypropylene films reinforced with multi-walled carbon nanotubes and exfoliated graphite nanoplatelets were fabricated by extrusion, and the effects of filler type and take-up speed on the mechanical properties and microstructure of composite films were investigated. Differential scanning calorimetry revealed that the addition of carbon nanomaterials resulted in increased degree of crystallinity. However, increasing the take-up speed reduced the degree of crystallinity, which indicates that tension-induced orientations of polymer chains and carbon nanomaterials and the loss of degree of crystallinity due to rapid cooling at high take-up speeds act as competing mechanisms. These observations were in good agreement with tensile properties, which are governed by the degree of crystallinity, where the C-grade exfoliated graphite nanoplatelet with a surface area of 750 m2/g showed the greatest reinforcing effect among all types of carbon nanomaterials used. Scanning electron microscopy was employed to observe the carbon nanomaterial dispersion and orientation, respectively.