• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.173-173
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• 2003

Nanowire와 nanorod 같은 1차원의 반도체 재료는 디멘젼과 크기와 물리적 특성과의 관계 등을 연구하는데 중요한 역할을 하며 laser ablation, arc discharge, chemical vapor depostion, vapor phase transport Process와 solution등의 방법으로 성공적으로 합성되었다. ZnO 는 3.37eV의 넓은 밴드갭과 다른 넓은 밴드갭 재료에 비해 높은 exciton bindng energy (60meV)를 가지며 UV LED, laser diode에 적용하기 유리하고 최근 디스플레나 나노 광전소자로서의 가능성 이 대두되면서 최근 이에 관한 연구가 증가하고 있다. 본 연구에서는 열적탄소환원법(carbothermal reduction process)으로 ZnO와 graphite 분말을 1:1 중량비로 혼합한 분말을 90$0^{\circ}C$, 100$0^{\circ}C$에서 air 분위기에서 20분간 반응 후 로 내에서 냉각 하였다. 직경 이 50nm-1000nm, 길이가 수 미크론인 내부 결함이 전혀 없는 육각형 단결정의 nanowire가 합성되었고 XRD, FE-SEM과 TEM으로 조성 및 형상, 내부구조를 분석하였다. 합성된 ZnO nanowire는 직경 이 변하는 부분에서 성장방향으로의 계단을 형성하였고 이는 layer by layer 방법으로 nanowire가 성장한다는 것을 나타낸다.

• Analytical Science and Technology
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• v.11 no.6
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• pp.460-468
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• 1998

Schiff base ligands such as $SOPDH_2$, $SNDH_2$, $EBNH_2$, and $PBNH_2$ and their Co(II) complexes such as [$Co(II)(SND)(H_2O)_2$], [$Co(II)(SOPD)(H_2O)_2$], [$Co(II)(EBN)(H_2O)$], and [$Co(II)(PBN)(H_2O)$] have been synthesized. The mole ratio of Shiff base ligand to cobalt(II) for the Co(II) complexes was found to be 1:1. Also these complexes have been configurated with hexa-coordination. Reduction of dioxygen was investigated by cyclic voltammetry at glassy carbon electrodes modified with Schiff base Co(II) complexes in 1 M KOH aqueous solution. At modified glassy carbon electrode with Schiff base Co(II) complexes, reduction peak current of oxygen was increased and peak potential was shifted to more positive direction compared to bare glassy carbon electrode. The electrokinetic parameters such as number of electron and exchange rate constant were calculated from the results of cyclic voltammogrms. The reduction of dioxygen at glassy carbon electrode has been $2e^-$ reaction pathway. Exchange rate constant at glassy carbon electrode modified with Co(II) complexes was increased 2~10 times compared to bare electrode.

• Journal of the Korean Chemical Society
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• v.37 no.9
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• pp.806-812
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• 1993

Complexes of $Cu(I)(hfac)PR_3$(P: phosphine and R: Me, Et and Bu) as Cu(I)(${\beta}$-diketonate) compounds have been synthesized and their electrochemical properties have been investigated using glassy carbon and carbon microelectrode in aprotic solvent. Reduction process of $Cu(I)(hfac)PR_3$ compounds carried out one electron pathway to Cu(0) by cyclic voltammetry in acetonitrile solution. Chronoamperometric curve using carbon microelectrode shows that these complexes are one electron process and diffusion coefficients are $4.5{\sim}6.7{\times}10^{-6}cm^2$/sec.

• Journal of the Korean Institute of Gas
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• v.18 no.2
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• pp.62-68
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• 2014

Composite repair methods besides welding methods such as surfacing and sleeve welding have been used as repair of damaged gas pipelines in foreign countries. Importance of safety management of city gas pipelines have been emphasized recently and our own repair manuals and codes for repair of city gas pipelines are required. It is right time to conduct research on the composite repair methods since the composite repair was introduced rather recently compared to the welding repair methods which have been investigated for long time. In this study, as a starting point of safety assessment of gas pipeline repaird by composite materials, structural analysis of gas pipeline repaired by carbon fiber composite materials was conducted using finite element analysis(FEA) method and the results was discussed.

• Journal of Energy Engineering
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• v.8 no.4
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• pp.560-566
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• 1999

PDTF (Pressurized drop tube furnace) experiments using variations of temperature, oxygen/coal ratio, steam/coal and pressure with Roto coal (Sub A) were performed in order to investigate the effects of these experimental parameters on global gasification characteristics at elevated pressure. The results shows that the gasification at elevated pressure is more profitable than that at atmospheric pressure considering the carbon conversion and cold gas efficiency. The oxygen/coal ratio at which maximum cold gas efficiency was appeared ranged from 0.5 to 0.7 g/g. only when the temperature is sufficiently high enough, the raise of steam/coal ratio brings improvement of cold gas efficiency. As the pressure increased, the volume of carbon conversion by heterogeneous reaction increased but the volume of carbon conversion by pyrolysis decreased relatively.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.05a
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• pp.23-31
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• 1999

PDTF(Pressurized drop tube furnace) experiments using varied temperature, oxygen/coal ratio, steam/coal ratio and pressure with Roto coal(Sub A) were performed in order to investigate the effects of these experimental parameters on global gasification characteristics at elevated pressure. The results shows that the gasification at elevated pressure is more profitable than that at atmospheric pressure considering the carbon conversion and cold gas efficiency. The oxygen/coal ratio at which maximum cold gas efficiency was appeared ranged from 0.5 to 0.7g/g. Only when the temperature is sufficiently high enough, the raise of steam/coal ratio brings improvement of cold gas efficiency. As the pressure increased, the volume of carbon conversion by heterogeneous reaction increased but the volume of carbon conversion by pyrolysis decreased relatively.

• Applied Chemistry for Engineering
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• v.32 no.1
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• pp.49-54
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• 2021

Plasma-polymerized methyl methacrylate (MMA) thin films were synthesized by remote plasma, and effects of plasma power, reaction pressure and direct-indirect plasma on the growth rate and chemical bonding were investigated with alpha-step, FT-IR, XPS and Langmüir probe method. As the plasma power and pressure increased, the tendency of growth rate showed maximum value at a certain range. FT-IR and XPS analyses revealed that composition ratio of C/O and hydrocarbon (C-C) % in the deposited films increased with plasma power, but ester (COO) C % decreased with it. Direct plasma method was effective for fast growth rate, but indirect plasma method was favorable for maintaining the chemical structure of MMA.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.04a
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• pp.181-187
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• 1997

고강도 알루미늄 합금 링롤재의 급냉, 링 팽창(expansion) 및 링 압축(compression) 응력제거처리후 잔류응력을 예측하기 위하여 2차원 축대칭 열해석 및 탄소성 해석을 수행하였다. 급냉 및 응력제거처리 후 2단 과시효 처리(T73)된 링롤재에 대하여 3단계 절단법(Three step sectioning method)을 적용하여 링롤재의 두께에 따른 잔류응력 분포를 측정하였으며, 측정결과를 급냉 및 응력제거처리후 잔류응력 해석결과와 비교분석하였다. 링의 급냉후 원주 및 축방향의 잔류응력 해석값은 T73후 측정값과 비슷한 경향을 보였으며, 링의 내면과 외면에서 압축응력을 나타내었고 중심에서 인장응력을 나타내었다. 잔류응력은 링 팽창(T7351) 및 링 압축(T7352) 적용후 T73에 비해 현저히 감소하였으며, 축방향의 제거 효과가 원주방향보다 우수하게 나타났다. 또한 링 압축에 의한 제거효과가 링 팽창보다 크게 나타났다. 링롤재의 응력제거처리는 제거 효과 및 실용성 측면에서 링 압축 공정이 유리하며, 치수제어 및 장비용량 측면에서 링 팽창 공정이 유리하다는 결론을 얻었다.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.187-192
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• 1998

탄소피막된 UCO 핵연료를 가압경수로의 핵연료로서 적용하는 방안에 대해 경제성 평가를 하였다 성형가공비용이 3675$/kgU이고, 성형가공 선행기간이 8개월이라고 가정하여 계산한 결과, 할인을 5%의 경우 UCO 핵연료는 $UO_2$ 핵연료에 비해 0.04mills/kwhre만큼 유리하였고, 할인을 10%의 경우 0.llmills/kwhre만큼 경제성면에서 유리하게 나왔다. 그러나 성형가공비용이 550$/kgU, 성형가공 선행기간이 12개월일 때는 할인을 5%, 10%경우 각각 0.41mills/kwhre, 0.47mills/kwhre 만큼 경제성측면에서 불리하게 나왔다. 따라서 UCO 핵연료의 가압경수로 적용은 $UO_2$ 핵연료와 비교할 때 할인을 5%의 경우 성형가공의 비용 및 선행기간의 1.37배까지, 할인을 10%의 경우 1.45배까지는 경제성을 갖는다고 할 수 있다.

• Composites Research
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• v.20 no.6
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• pp.1-7
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• 2007

Expanded graphite/carbon fiber hybrid conductive polymer composites were fabricated by the preform molding technique. The conductive fillers were mechanically mixed with a phenol resin to provide an electrical property to composites. The conductive filler loading was fixed at 60wt.% to accomplish a high electrical conductivity. Expanded graphites were excellent in forming a conductive networking by direct contacts between them while it was hard to get the high flexural strength over 40MPa with using only expanded graphite and phenol resin. In this study, carbon fibers were added in composites to compensate the weakened flexural strength. The effect of carbon fibers on the mechanical and electrical properties was examined according to the weight ratio of carbon fiber. As the carbon fiber ratio increased, the flexural strength increased until the carbon fiber ratio of 24wt.%, and then decreased afterward. The electrical conductivity gradually decreased as the increase of the carbon fiber ratio. This was attributed to the non-conducting regions generated among the carbon fibers and the reduction of the direct contact areas between expanded graphites.