• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.175-175
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• 2010

Transparent conducting oxide (TCO) films are widely used as transparent conducting thin film material for application in various fields such as solar cells, optoelectronic devices, heat mirrors and gas sensors, etc. Recently the increased utilization of many transparent electrodes has accelerated the development of inexpensive TCO materials. Indium tin oxide (ITO) film is well-known for TCO materials because of its low resistivity, but there is disadvantage that it is too expensive. ZnO film is cheaper than ITO but it shows thermally poor stability. On the contrary, antimony-doped tin oxide films (ATO) are more stable than TCO films such as Al-doped zinc oxide (AZO) and ITO. Moreover, SnO2 film shows the best thermal and chemical stability, low cost and mechanical durability except the poor conductivity. However, annealing is proved to improve the conductivity of ATO film. Therefore, in this work, antimony (6 wt%) doped tin oxide films to improve the conductivity were deposited on 7059 corning glass by RF magnetron sputtering method for the application to transparent electrodes. In general, of all TCO films, glass is the most commonly selected substrate. However, for future development in flexible devices, glass is limited by its intrinsic inflexibility. In this study, we report the growth and properties of antimony doped tin oxide (ATO) films deposited on PES flexible substrate by using RF magnetron sputtering. The optimization process was performed varying the sputtering parameters, such as RF power and working pressure, and parameter effect on the structural, electrical and optical properties of the ATO films were investigated.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.212-212
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• 2011

In addition to the catalysts' activity and selectivity, the deactivation of catalysts during use is of practical importance. It is crucial to understand the phenomena of the deactivation to predict the loss of activity during catalyst usage so that the high operational costs associated with catalyst replacement can be reduced. In this study, the activity of Ru catalysts, such as nanoparticles (3~6 nm) and polycrystalline thin film (50 nm), have been investigated under CO oxidation and oxidative/reductive reaction conditions at various temperatures with the ambient pressure X-Ray photoelectron spectroscopy (APXPS). With APXPS, the surface oxides on the catalyst are measured and monitored in-situ. It was found that the Ru film exhibited faster oxidation-and-reduction compared to that of nanoparticles showing mild oxidative-and-reductive characteristics. Additionally, the larger Ru nanoparticles showed a higher degree of oxide formation at all temperatures, suggesting a higher stability of the oxide. These observations are in agreement with the catalytic activity of Ru catalysts. The loss of activity of Ru films is correlated with bulk oxide formation, which is inactive in CO oxidation. The Ru nanoparticle, however, does not exhibit deactivation under similar conditions, suggesting that its surface is covered with a highly active ultrathin surface oxide. Since the active oxide is more stable as nanoparticles than as a film, the nanoparticles showed mild oxidative/reductive behavior, as confirmed by APXPS results. We believe these simultaneous observations of both the surface oxide of Ru catalysts and the reactivity in real time enable us to pinpoint the deactivation phenomena more precisely and help in designing more efficient and stable catalytic systems.

• 한국태양에너지학회 논문집
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• 제33권2호
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• pp.93-100
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• 2013

Two-step thermochemical cycle using ferrite-oxide($Fe_2O_4$) device was investigated. The $H_2O$(g) was converted into $H_2$ in the first experiment which was performed using a dish type solar thermal system. However the experiment was lasted only for 2 cycles because the metal oxide device was sintered and broken down. Another problem was that the reaction was taken place mainly on a side of the metal oxide device. The m-$ZrO_2$, which was widely known as a material preventing sintering, was applied on the metal oxide device. The ferrite loading rate and the thickness of the metal oxide device were increased from 10.67wt% to 20wt% and from 10mm to 15mm, respectively. The chemical reactor having two inlets was designed in order to supply the reactants uniformly to the metal oxide device. The second-experiment was lasted for 5 cycles, which was for 6 hours. The total amount of the $H_2$ production was 861.30ml. And cerium oxide($CeO_2$) device was used for increasing $H_2$ production rate. $CeO_2$ device had low thermal resistance, however, more $H_2$ production rate than $Fe_2O_4$ device.

• 한국재료학회지
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• 제26권3호
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• pp.109-116
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• 2016

To achieve the fabrication of high-quality Ag-coated Cu particles through a wet chemical process, we reported herein pretreatment conditions using an ammonium-based mixed solvent for the removal of a $Cu_2O$ layer on Cu particles that were oxidized in air for 1 hr at $200^{\circ}C$ or for 3 days at room temperature. Furthermore, we discussed the results of post-Ag plating with respect to removal level of the oxide layer. X-ray diffraction results revealed that the removal rate of the oxide layer is directly proportional to the concentration of the pretreatment solvent. With the results of Auger electron spectroscopy using oxidized Cu plates, the concentrations required to completely remove 50-nm-thick and 2-nm-thick oxides within 5 min were determined to be X2.5 and X0.13. However, the optimal concentrations in an actual Ag plating process using Cu powder increased to X0.4 and X0.5, respectively, because the oxidation in powder may be accelerated and the complete removal of oxide should be tuned to the thickest oxide layer among all the particles. Back-scattered electron images showed the formation of pure fine Ag particles instead of a uniform and smooth Ag coating in the Ag plating performed after incomplete removal of the oxide layer, indicating that the remaining oxide layer obstructs heterogeneous nucleation and plating by reduced Ag atoms.

• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.117-123
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• 2018

Recently, aqueous method has attracted lots of attention because it enables the solution-processed metal oxide thin film with high electrical properties in low temperature fabrication condition to various flexible devices. Focusing the development of aqueous route, many researchers are only focused on metal oxide materials. However, for expansive application of the aqueous-based metal oxide films, the systematic study of performance change with process variables for the development of aqueous-based metal oxide insulator film is urgently required. Here, we propose importance of process variables to achieve high electrical-performance metal oxide insulator based on the aqueous method. We found that the significant process variables including precursor solution temperature and humidity during the spincoating process strongly affect chemical, physical, and electrical properties of $AlO_x$ insulators. Through the optimization of significant variables in process, an $AlO_x$ insulator with a leakage current value approximately $10^5$ times smaller and a breakdown voltage value approximately 2-3 times greater than un-optimized $AlO_x$ was realized. Finally, by introducing the optimized $AlO_x$ insulators to solutionprocessed $InO_x$ TFTs, we successfully achieved $InO_x/AlO_x$ TFTs with remarkably high average field-effect mobility of ${\sim}52cm^2V^{-1}\;s^{-1}$ and on/off current ratio of 106 at fabrication temperature of $250^{\circ}C$.

• 문화기술의 융합
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• 제9권3호
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• pp.593-599
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• 2023

질산니켈육수화물염(nickel(II) nitrate hexahydrate) 수용액을 공업용 펄프에 함침시킨 전구체를 이용하여 세라믹스 분말을 제조하는 간단한 액상 합성법으로 산화니켈(NiO) 나노입자를 성공적으로 합성하였다. 질산니켈육수화물염 수용액이 함침된 전구체의 미세구조를 주사전자현미경(SEM)으로 확인하였고, 전구체의 열처리온도 증가에 따라 생성되는 산화니켈(NiO) 입자의 결정구조 및 입자크기를 X선회절분석(XRD) 및 SEM으로 분석하였다. 그 결과 전구체의 유기물질이 완전하게 열분해 되는 온도는 495-500℃이며, 열처리 온도의 증가에 따라 생성되는 산화니켈 입자의 크기 및 결정성이 증가하는 것을 XRD, SEM 분석을 통하여 확인하였다. 500-800℃에서 각각 1시간 동안 열처리하여 얻어진 산화니켈 입자의 크기는 50-200nm였다. 열처리 온도 380℃에서 NiO 결정상이 형성되고, 800℃까지는 NiO 단일상만 존재하며, 열처리 온도가 높아짐에 따라 생성되는 입자의 크기가 커지고 있음을 XRD 및 SEM 분석으로 확인하였다.

• 문화기술의 융합
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• 제9권6호
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• pp.855-859
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• 2023

질산구리삼수화물염(copper(II) nitrate trihydrate) 수용액을 공업용 전분(starch)에 함침 시킨 전구체를 이용하여 산화구리(CuO) 나노 입자를 합성하였다. 주사전자현미경(SEM)을 통하여 질산구리삼수화물염 수용액이 함침된 전구체에 대한 구조를 분석하였고, 전구체에 대한 열처리 온도를 증가 시킴에 따라 생성되는 산화구리 입자의 입자 크기와 결정 구조를 X선회절분석법(XRD)과 주사전자현미경(SEM)으로 분석하였다. 분석 결과에 따르면, 전구체에서 유기물질이 완전히 열분해 되어지는 온도는 450-490℃이며, 열처리하는 온도가 증가함에 따라 생성되는 산화구리 입자의 크기와 결정성이 증가하는 것을 확인할 수 있었고, 또한 500-800℃에서 1시간씩 열처리하여 얻은 산화구리 입자의 크기는 100nm-2㎛인 것으로 나타났다. 하소 온도 400℃에서 산화구리 결정상이 형성되고, 800℃까지는 산화구리 단일상만 존재하며, 하소 온도의 증가에 따라 생성되는 입자의 크기가 커지는 것을 확인하였다.

• 한국전기전자재료학회논문지
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• 제37권4호
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• pp.400-406
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• 2024

Next-generation wide-bandgap semiconductors such as SiC, GaN, and Ga2O3 are being considered as potential replacements for current silicon-based power devices due to their high mobility, larger size, and production of high-quality wafers at a moderate cost. In this study, we investigate the gradual modulation of chemical composition in multi-stacked metal oxide semiconductor thin films to enhance the performance and bias stability of thin-film transistors (TFTs). It demonstrates that adjusting the Ga ratio in the indium gallium oxide (IGO) semiconductor allows for precise control over the threshold voltage and enhances device stability. Moreover, employing multiple deposition techniques addresses the inherent limitations of solution-processed amorphous oxide semiconductor TFTs by mitigating porosity induced by solvent evaporation. It is anticipated that solution-processed indium gallium oxide (IGO) semiconductors, with a Ga ratio exceeding 50%, can be utilized in the production of oxide semiconductors with wide band gaps. These materials hold promise for power electronic applications necessitating high voltage and current capabilities.

• Journal of Microbiology and Biotechnology
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• 제34권6호
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• pp.1229-1238
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• 2024

This study aimed to develop and assess a chitosan biomedical antibacterial gel ZincOxide-GrapheneOxide/Chitosan/β-Glycerophosphate (ZnO-GO/CS/β-GP) loaded with nano-zinc oxide (ZnO) and graphene oxide (GO), known for its potent antibacterial properties, biocompatibility, and sustained drug release. ZnO nanoparticles (ZnO-NPs) were modified and integrated with GO sheets to create 1% and 3% ZnO-GO/CS/β-GP thermo-sensitive hydrogels based on ZnO-GO to Chitosan (CS) mass ratio. Gelation time, pH, structural changes, and microscopic morphology were evaluated. The hydrogel's antibacterial efficacy against Porphyromonas gingivalis, biofilm biomass, and metabolic activity was examined alongside its impact (MC3T3-e1). The findings of this study revealed that both hydrogel formulations exhibited temperature sensitivity, maintaining a neutral pH. The ZnO-GO/CS/β-GP formulation effectively inhibited P. gingivalis bacterial activity and biofilm formation, with a 3% ZnO-GO/CS/β-GP antibacterial rate approaching 100%. MC3T3-e1 cells displayed good biocompatibility when cultured in the hydrogel extract.The ZnO-GO/CS/β-GP thermo-sensitive hydrogel demonstrates favorable physical and chemical properties, effectively preventing P. gingivalis biofilm formation. It exhibits promising biocompatibility, suggesting its potential as an adjuvant therapy for managing and preventing peri-implantitis, subject to further clinical investigations.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.295-295
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• 2006

In present study, poly(acrylic acid) (PAA) and hydrophobically modified poly(ethylene oxide) (HM-PEO) multilayers based on the hydrogen bonding between the component polymer pair have been prepared by the LbL deposition method. Dip assembled HM-PEO/PAA multilayers yield unique film morphologies in comparison with PEO/PAA multilayers due to the micellar formation of HM-PEO owing to the hydrophobic attraction between alkyl chains end-capped with the PEO chains. Individual HM-PEO micelles were connected through the bridging PEO chains to form temporary networks on multilayer surface and induced peculiar surface morphology on HM-PEO/PAA multilayers above the critical number of bilayers.