• Korean Chemical Engineering Research
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• 제59권1호
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• pp.49-53
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• 2021

고분자 연료전지(PEMFC) 고분자막의 화학적 내구성을 평가하는데 Fenton 반응이 자주 사용된다. 그러나 과산화수소와 철 이온의 격렬한 반응 때문에 재현성이 낮아 실험 데이터를 비교하기가 어려운 문제점이 있다. 본 연구에서는 Fenton 반응에 의한 고분자막 내구성 실험의 재현성을 향상시키기 위한 반응조건을 찾고자 하였다. 과산화수소 농도는 30%로 고정시키고 철이온 농도와 온도, 교반속도, 시료크기를 변화시키며 라디칼에 열화된 Nafion 고분자막의 불소이온 농도를 측정했다. 철이온 농도를 높게하거나 고분자막 시료 크기를 크게하고, Fenton 반응 온도를 80 ℃로 높게하면 실험편차가 커져서 철이온 농도 10 ppm, 온도 70 ℃와 시료크기 0.5 ㎠가 적합하였다.

• 한국세라믹학회지
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• 제55권6호
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• pp.581-589
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• 2018

This work concentrated on the effect of different laser beams on the microstructure and dielectric properties of $BaTiO_3$ nanoparticles at different calcinations times during the gelling preparation step. The nanoparticles were prepared by the sol-gel method. A green (1000 mW, 532 nm) and red laser beam (500 mW, 808 nm), were applied vertically at the center of stirring raw materials. The samples were sintered at $1000^{\circ}C$ for 2, 4, and 6 h. X-ray diffraction (XRD) analysis showed that samples prepared under the green laser have the highest purity. The FT-IR spectra showed that the stretching and bending vibrations of TiO bond without any other bonds, which are compatible to the X-ray diffraction (XRD) results. Samples were characterized by transmission electron microscopy (TEM), Scan electron microscopy (SEM), and UV-Visible spectrophotometer. Characterization showed the samples prepared under the green laser to have the highest particle size (~ 50 nm) and transparency for all sintering durations. Laser beam effects on electrical characterization were studied. BT nanoparticles prepared under the green laser show the higher dielectric constant, which was found to increase with sintering temperature.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.146-148
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• 2012

In our study, we have focused on optimizing good quality of ZnS buffer layer by chemical bath deposition (CBD) from a bath containing $ZnSO_4$, Thiourea and Ammonia in aqueous solution onto CIGS solar cells. The influence of deposition parameter such as pH, deposition temperature, stirring speed played a very important role on transmission, homogeneity, crystalline of ZnS buffer layer. The transmission spectrum showed a good transmission characteristic above 80% invisible spectral region. CIGS thin flim solar cell with ZnS buffer layer has been realized with the efficiency of 14.2%.

• Korean Chemical Engineering Research
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• 제45권5호
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• pp.424-432
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• 2007

바이오디젤은 식물유지 및 동물유지와 같은 재생 가능한 자원으로부터 얻어지는 친환경 대체에너지로서 주목받고 있다. 바이오디젤은 식물유지 또는 동물성 지방으로부터 얻어지는 긴사슬 지방산의 모노알킬에스터이다. 본 총설에서는 (1) 바이오디젤을 얻기위한 전이에스테로화 반응에 대한 촉매의 타입, 자유지방산 및 수분, 알콜과 유지의 반응비, 알콜타입, 반응온도 및 시간과 교반강도의 영향, (2) 전이에스테르화 이후의 바이오디젤에 대한 분리공정, 그리고 (3) 대체에너지로서 바이오디젤의 내연기관 적합성을 바이오디젤의 물성에 기초하여 소개한다.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.109-113
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• 2003

Low pressure or vacuum carburizing(LPC) has undergone major further developments since 1980 and now it has achieved industrial maturity. The advantage of low pressure vacuum carburizing over gas carburizing is not only the creation of surface entirely free of oxide and environmentally friendly but also a reduction in batch times, lower gas and energy consumption and the prevention of soot. In this study the experiment was carried out to investigate the effects of vacuum atmosphere in the heating furnace. Heat transfer rate and uniformity of temperatures of test samples in the pressure range of a few 0.1torr was examined on a test charge of 100kg. It is found that the fuel saving rate due to decreasing heating time reach to 20% in the vacuum heating mode as compared with atmospheric heating mode. Also the uniformity of temperatures in the samples was improved significantly in the vacuum heating mode. Also the effects of the RC fan for stirring atmosphere inside furnace was examined. Results shows RC fan appears to provide a reasonable tool for improving uniformity of temperature in the atmospheric heating mode.

• 한국분말재료학회지
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• 제19권4호
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• pp.278-284
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• 2012

$Al_2O_3$ foam is an important engineering material because of its exceptional high-temperature stability, low thermal conductivity, good wear resistance, and stability in hostile chemical environment. In this work, $Al_2O_3$ foams were designed to control the microstructure, porosity, and cell size by varying different parameters such as the amount of amphiphile, solid loading, and stirring speed. Particle stabilized direct foaming technique was used and the $Al_2O_3$ particles were partially hydrophobized upon the adsorption of valeric acid on particles surface. The foam stability was drastically improved when these particles were irreversibly adsorbed at the air/water interface. However, there is still considerable ambiguity with regard to the effect of process parameters on the microstructure of particle-stabilized foam. In this study, the $Al_2O_3$ foam with open and closed-cell structure, cell size ranging from $20{\mu}m$ to $300{\mu}m$ having single strut wall and porosity from 75% to 93% were successfully fabricated by sintering at $1600^{\circ}C$ for 2 h in air.

• 한국표면공학회지
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• 제50권1호
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• pp.24-28
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• 2017

The electrodeposition of Ni-Co alloy from a sulfamate bath was investigated. The cobalt content in the Ni-Co deposits is more influenced by the temperature or stirring effect than the current density in the process parameters. As cobalt contents in the Ni-Co deposited layer increased from 0 wt.% up to 43 wt.%, hardness value of the layer rised from 400 Hv up to 700 Hv and crystal orientation (111) increased. However, (200) and crystal size significantly reduced. The tensile and yield strength also increased, while the modulus of elasticity showed the maximum value of $10.4N/mm^2$ at 29 wt.%.

• Bulletin of the Korean Chemical Society
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• 제24권3호
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• pp.345-349
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• 2003

The quantity, process and kinetics of di-(2-ethylhexyl)phthalate (DEHP) migration in the 30/70 and 40/60 poly(vinylchloride) (PVC)/DEHP blends were investigated using gas chromatograph. A thin and flexible PVC sheet was soaked in surrounding medium (SM) of water/ethanol mixture and acetonitrile with constant stirring to release DEHP. By observed concentration of DEHP in the SM, it is found that acetonitrile is more intense in DEHP migration than water/ethanol mixture. In addition the amount of extracted DEHP is proportional to the leaching temperature and added ratio of DEHP. The behavior of DEHP migration from flexible PVC sheets was described by the Ficks's law with $2.72-10.1\;{times}\;10^{-10}$ cm²/s of the diffusion coefficients.

• Fibers and Polymers
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• 제3권4호
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• pp.159-168
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• 2002

Polyurethane foams were produced by using a homogenizer as a mixing equipment. Effects of stirring speed on the foam structure were investigated with SEM observations. Variation of the bubble size, density of the foam, compressive strength, and thermal conductivity were studied. A hybrid foam consisting of polyurethane foam and commercial polystyrene foam is produced. Mechanical and thermal properties of the hybrid foam were compared with those of pure polyurethane foam. Advancement of flow front during mold filling was observed by using a digital camcorder. Four types of mold geometry were used for mold filling experiments. Flow during mold filling was analyzed by using a two-dimensional control volume finite element method. Variation of foam density with respect to time was experimentally measured. Creeping flow, uniform density, uniform conversion, and uniform temperature were assumed for the numerical simulation. It was assumed for the numerical analysis that the cavity has thin planar geometry and the viscosity is constant. The theoretical predictions were compared with the experimental results and showed good agreement.

• 대한화학회지
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• 제55권4호
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• pp.656-661
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• 2011

5-(3,4,5-Triethoxyphenyl)-1,3,4-oxadiazole-2-thiol 6을 3-(bromomethyl)-2-chloroquinoline or 2-(p-tolyloxy)-3-(bromomethyl) quinoline 4a-j 화합물과 반응시켜서 3-((5-(3,4,5-triethoxyphenyl)-1,3,4-oxadiazol-2-ylthio)methyl)-2-chloroquinoline 또는 3-((5-(3,4,5-triethoxyphenyl)-1,3,4-oxadiazol-2-ylthio)methyl)-2-(p-tolyloxy)quinoline 7a-j를 합성하였다. 합성한 화합물들에 대한 항균활성을 측정하였으며, 화합물 7d, 7i 및 7j 은 우수한 활성을 나타내었다.