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김지민,정혁,김도진,Kim, Jimin,Jung, Hyuck,Kim, Dojin 한국재료학회 2013 한국재료학회지 Vol.23 No.1
A simple thermal oxidation of Cu thin films deposited on planar substrates established a growth of vertically aligned copper oxide (CuO) nanorods. DC sputter-deposited Cu thin films with various thicknesses were oxidized in environments of various oxygen partial pressures to control the kinetics of oxidation. This is a method to synthesize vertically aligned CuO nanorods in a relatively shorter time and at a lower cost than those of other methods such as the popular hydrothermal synthesis. Also, this is a method that does not require a catalyst to synthesize CuO nanorods. The grown CuO nanorods had diameters of ~100 nm and lengths of $1{\sim}25{\mu}m$. We examined the morphology of the synthesized CuO nanorods as a function of the thickness of the Cu films, the gas environment, the oxidation time, the oxidation temperature, the oxygen gas flow rate, etc. The parameters all influence the kinetics of the oxidation, and consequently, the volume expansion in the films. Patterned growth was also carried out to confirm the hypothesis of the CuO nanorod protrusion and growth mechanism. It was found that the compressive stress built up in the Cu film while oxygen molecules incorporated into the film drove CuO nanorods out of the film.
전기방사와 수열합성법으로 제작한 광전화학셀 전극용 나노 계층형 아연산화물 구조 연구
이환표,정혁,김옥길,김효진,김도진,Yi, Hwanpyo,Jung, Hyuck,Kim, Okkil,Kim, Hyojin,Kim, Dojin 한국재료학회 2013 한국재료학회지 Vol.23 No.11
Photoelectrochemical cells have been used in photolysis of water to generate hydrogen as a clean energy source. A high efficiency electrode for photoelectrochemical cell systems was realized using a ZnO hierarchical nanostructure. A ZnO nanofiber mat structure was fabricated by electrospinning of Zn solution on the substrate, followed by oxidation; on this substrate, hydrothermal synthesis of ZnO nanorods on the ZnO nanofibers was carried out to form a ZnO hierarchical structure. The thickness of the nanofiber mat and the thermal annealing temperature were determined as the parameters for optimization. The morphology of the structures was examined by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The performance of the ZnO nanofiber mat and the potential of the ZnO hierarchical structures as photoelectrochemical cell electrodes were evaluated by measurement of the photoelectron conversion efficiencies under UV light. The highest photoconversion efficiency observed was 63 % with a ZnO hierarchical structure annealed at $400^{\circ}C$ in air. The morphology and the crystalline quality of the electrode materials greatly influenced the electrode performance. Therefore, the combination of the two fabrication methods, electrospinning and hydrothermal synthesis, was successfully applied to fabricate a high performance photoelectrochemical cell electrode.
산화아연-단일벽탄소나노튜브복합체의 일산화질소 감지 특성
장동미,안세용,정혁,김도진,Jang, Dong-Mi,Ahn, Se-Yong,Jung, Hyuck,Kim, Do-Jin 한국재료학회 2010 한국재료학회지 Vol.20 No.11
Semiconducting metal oxides have been frequently used as gas sensing materials. While zinc oxide is a popular material for such applications, structures such as nanowires, nanorods and nanotubes, due to their large surface area, are natural candidates for use as gas sensors of higher sensitivity. The compound ZnO has been studied, due to its chemical and thermal stability, for use as an n-type semiconducting gas sensor. ZnO has a large exciton binding energy and a large bandgap energy at room temperature. Also, ZnO is sensitive to toxic and combustible gases. The NO gas properties of zinc oxide-single wall carbon nanotube (ZnO-SWCNT) composites were investigated. Fabrication includes the deposition of porous SWCNTs on thermally oxidized $SiO_2$ substrates followed by sputter deposition of Zn and thermal oxidation at $400^{\circ}C$ in oxygen. The Zn films were controlled to 50 nm thicknesses. The effects of microstructure and gas sensing properties were studied for process optimization through comparison of ZnO-SWCNT composites with ZnO film. The basic sensor response behavior to 10 ppm NO gas were checked at different operation temperatures in the range of $150-300^{\circ}C$. The highest sensor responses were observed at $300^{\circ}C$ in ZnO film and $250^{\circ}C$ in ZnO-SWCNT composites. The ZnO-SWCNT composite sensor showed a sensor response (~1300%) five times higher than that of pure ZnO thin film sensors at an operation temperature of $250^{\circ}C$.
오동훈,강영진,정혁,송혜진,조유석,김도진,Oh, Dong-Hoon,Kang, Young-Jin,Jung, Hyuck,Song, Hye-Jin,Cho, You-Suk,Kim, Do-Jin 한국재료학회 2009 한국재료학회지 Vol.19 No.9
Thin films of single-wall carbon nanotubes (SWNT) with various thicknesses were fabricated, and their optical and electrical properties were investigated. The SWNTs of various thicknesses were directly coated in the arc-discharge chamber during the synthesis and then thermally and chemically purified. The crystalline quality of the SWNTs was improved by the purification processes as determined by Raman spectroscopy measurements. The resistance of the film is the lowest for the chemically purified SWNTs. The resistance vs. thickness measurements reveal the percolation thickness of the SWNT film to be $\sim$50 nm. Optical absorption coefficient due to Beer-Lambert is estimated to be $7.1{\times}10^{-2}nm^{-1}$. The film thickness for 80% transparency is about 32 nm, and the sheet resistance is 242$\Omega$/sq. The authors also confirmed the relation between electrical conductance and optical conductance with very good reliability by measuring the resistance and transparency measurements.
PAD법으로 제작된 산화코발트-산화주석 복합체의 가스 감응 특성
안세용,이위,장동미,정혁,김도진,An, Sea-Yong,Li, Wei,Jang, Dong-Mi,Jung, Hyuck,Kim, Do-Jin 한국재료학회 2010 한국재료학회지 Vol.20 No.11
A cobalt oxide - tin oxide nanocomposite based gas sensor on an $SiO_2$ substrate was fabricated. Granular thin film of tin oxide was formed by a rheotaxial growth and thermal oxidation method using dc magnetron sputtering of Sn. Nano particles of cobalt oxide were spin-coated on the tin oxide. The cobalt oxide nanoparticles were synthesized by polymer-assisted deposition method, which is a simple cost-effective versatile synthesis method for various metal oxides. The thickness of the film can be controlled over a wide range of thicknesses. The composite structures thus formed were characterized in terms of morphology and gas sensing properties for reduction gas of $H_2$. The composites showed a highest response of 240% at $250^{\circ}C$ upon exposure to 4% $H_2$. This response is higher than those observed in pure $SnO_2$ (90%) and $Co_3O_4$ (70%) thin films. The improved response with the composite structure may be related to the additional formation of electrically active defects at the interfaces. The composite sensor shows a very fast response and good reproducibility.
김경삼(Kyeongsam Kim),차지훈(Jihun Cha),정혁(Hyuck Jung),이광범(Kwangbum Lee),배중호(Joongho Bae),권해붕(Haeboung Kwon) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
The traction battery that is one of the key parts of EV. Became a element is affecting significantly regard to performance and costs for EV. Thus, the guarantee of traction battery reliability is becoming big issue. Recently, To reduce the loss of time and costs about developing period. It has been determined to make a short evaluation period and secure a reliability as a methods of Accelerated life test. So It was performed the method of lithium battery"s accelerated life test using the temperature element as a factor of acceleration at 45.9℃
전기자동차용 납산, 리튬이온 구동축전지팩 성능특성 비교
차지훈(Jihun Cha),박용성(Yongsung Park),배중호(Joongho Bae),이광범(Kwangbum Lee),정혁(Hyuck Jung) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
Successful commercialization of electric vehicle is depended on research and development level of traction battery being main component of Electric vehicle. Standard test procedure for Li-ion traction battery for performance, reliability and safety is under discussion in the standard of ISO-12405. This paper evaluated Energy-Capacity, Power and Energy efficiency at fast charging of Lead-acid and Li-ion battery pack in the view of ISO/DIS 12405-2. By the tests, This paper confirms the certain performance gap between commercialized Pb-acid and Li-ion traction battery pack. This performance gap would be caused by different material characteristic including chemical potential and internal resistance. The result of this paper could be applied to basic data when designing Battery Management System of traction battery pack. Also this paper evaluated the validity of test procedures of ISO/DIS 12405-2 by actual test.
自然膣式 分娩한 滿朔兒의 臍帶血 酸一鹽基値 平衡 및 가스 分壓의 正常 役値 設定
김영미,홍관표,정혁 朝鮮大學校 附設 醫學硏究所 1991 The Medical Journal of Chosun University Vol.16 No.1
The increasing interest in the use of umbilical cord acid-base determinations to assess intraparturn events makes it important to define more precisely the normal values of these parameters. Therefore this study was performed to obtain normal values of pH, PCO_(2), PO_(2), and bicarbonate in umbilical artery and vein. Cord blood acid-base values were determined from normal infants born after uncomplicated labor and vaginal deliveries at 38 to 41 weeks' gestation and infants had normal base fetal heart rate and Apgar score≥7 at 1 minute. The results were summarized as follow, 1) Mean umbilical arterial values ± SD for the parameters studied were : pH 7.25±0.09, PCO_(2) 52.5±9.7 mmHg, PO_(2) 17.0±5.1 mmHg and bicarbonate 22.9±2.8mmol/L, 2) Mean umbilical venous values were : pH 7.29±0.08, PCO_(2) 46.0±8.9mmHg, PO_(2) 22.6±6.7mmHg and bicarbonate 22.1±2.6 mmol/L. We anticipate that increasing attention will be focused on the acid-base status of the newbom infant. This biochemical status will then be retrospectively correlated with obstetric management and anterospectively correlated with short-and long-term neonatal outcome. Normal mean values and standard deviations for umbilical artery and vein pH, PCO_(2), PO_(2) and bicarbonate have been provided 39 selected vaginal deliveries.