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열 산화법을 이용한 Cu<sub>2</sub>O 나노선의 대면적 합성
이근형,Lee, Geun-Hyoung 한국재료학회 2014 한국재료학회지 Vol.24 No.7
$Cu_2O$ nanowires were synthesized at large scale on copper plate by thermal oxidation in air. The effect of oxidation time and temperature on the morphology of the nanowires was examined. The oxidation time had no effect on the diameter of the nanowires, while it had a great effect on the density and the length of the nanowires. The density and the length of the nanowires increased, and then decreased, with increasing oxidation time. The oxidation temperature had a tremendous effect on the size-distribution as well as the density of the nanowires. When the oxidation temperature was $700^{\circ}C$, uniform size-distribution and high density of the nanowires was achieved. At lower and higher temperatures, the density of the nanowires was lower, and they displayed a broader size-distribution. It is suggested that the $Cu_2O$ nanowires were grown via a vapor-solid mechanism because no catalyst particles were observed at the tips of the nanowires.
유연생산시스템의 투입우선순서결정을 위한 Simulated Anneaing의 적용
이근형,황승국,이강우 한국산업경영시스템학회 2000 한국산업경영시스템학회지 Vol.23 No.54
One form of job shop scheduling problem in contemporary automated manufacturing such as flexible manufacturing systems (FMS's) is presented which we call the FMS dispatching priority problem. The FMS dispatching priority problem seeks the best dispatching priority of parts and operations, and is essentially a combinatorial optimization problem. Because of the complicated mechanism of the system, the performance of a given dispatching priority must be evaluated via simulation. Simulated annealing have been applied to the problem, and it is found that appropriate parameter setting will be desirable to get good, if not the optimal, solutions within a limited amount of time under the presence of heavy computational burden due to simulation. More specifically, experiments reveal that initial temperature is the single most important factor among other parameters and factors, and that the appropriate initial temperature depends on the allowable computer time in such a way that the less time one can afford to spend, the lower the appropriate initial temperature should be.
ZnS와 C의 혼합 분말을 열증발시켜 생성된 ZnO 나노/마이크로구조의 형상 과 발광 특성에 미치는 ZnS/C 질량비의 영향
이근형 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.4
ZnO nano/microstructures were grown via a simple thermal evaporation process in air at atmospheric pressure. Mixtures of ZnS and carbon powders were used as the sources. The effects of growth temperature and mass ratio of carbon powder to ZnS on the morphologies and luminescence properties of the ZnO nano/microstructures were investigated in this study. When the growth temperature was 1000 oC, ZnO nanowires with a hexagonal wurtzite crystal structure started to be formed and were preferentially grown along the [0001] direction. As the temperature increased to 1200 oC, the crystal growth in the lateral direction perpendicular to the [0001] direction was enhanced, which resulted in a decreasing aspect ratio of the onedimensional ZnO nanowires. When source powders with different mass ratios of ZnS:C=2:1, 1:1 and 1:2 were used to grow ZnO nano/microstructures at 1200 oC, ZnO microrods with wurtzite crystal structure were formed in all the samples. As the mass ratio of carbon powder to ZnS increased, the aspect ratio of ZnO microrods was reduced, which suggests that the carbon powder enhanced the growth of ZnO microrods in the lateral directions. A strong ultraviolet emission band centered at 380 nm was observed in the ZnO nano/ microstructures synthesized using the source powders with the mass ratios of ZnS:C=1:1 and 1:2, indicating that the ZnO nano/microstructures had a high crystalline quality.
이근형,김민성 대한금속·재료학회 2010 ELECTRONIC MATERIALS LETTERS Vol.6 No.2
This study investigated the dependence of crystal structure on growth temperature in the TiO₂ thin films deposited on c-, a-, and r-plane sapphire substrates by reactive RF magnetron sputtering. Deposition of the films was carried out at temperatures ranging from 400°C to 700°C. X-ray diffraction patterns revealed that TiO₂with a rutile structure was epitaxially grown on substrates independent of substrate orientations. TiO₂thin films were grown with a dominant peak of (200) on c-plane sapphire, and their crystallization and crystal quality were improved with growth temperature. For the films formed on a-plane and r-plane sapphires, the preferential orientation was [101]. However, the intensities of the (101) peak were very weak and were not dependent on growth temperature. The TiO₂ thin films formed on the sapphire had a band gap of about 3.7 eV, which was larger than that of bulk (3.03 eV).
Al과 SnO2 혼합 분말을 사용한 일차원 Al과 Al2O3 나노/마이크로구조의 저온 성장
이근형 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.9
One-dimensional Al and Al2O3 nano/microstructures were fabricated via thermal oxidation of Al and SnO2 powder mixtures at temperatures below the melting point of Al (660 oC). Furthermore, the synthesis process was carried out in air at atmospheric pressure, which made the process very simple and easy. Sn metal particles with spherical shape were observed on the tips of the Al and Al2O3 nano/microstructures, suggesting that the nano/microstructures were grown via a catalyst-assisted growth mechanism. The Sn acted as a catalyst for growing the Al and Al2O3 nano/microstructures. The Sn with low melting point (232 oC) was produced via the reduction of SnO2 by Al, and formed catalyst droplets at the growth temperatures. Al atoms diffused and dissolved into the Sn liquid droplets, leading to the nucleation and then the growth of the Al and Al2O3 nano/microstructures. At 400 oC, the diffusion of Al atoms into the Sn liquid droplets was associated with high stress generated at the Al2O3/Al interface. At 600 oC close to the melting point of Al, Al atoms were diffused from the thin Al liquid layer, which was formed on the surface of the Al powder, to the Sn liquid droplets. Simultaneously, the Al atoms reacted with oxygen in air and formed solid Al2O3 nuclei. A relatively strong ultraviolet emission band centered at 330 nm was observed in the sample prepared at 600 oC.