• Applied Chemistry for Engineering
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• v.8 no.1
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• pp.29-38
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• 1997

In the w/o concentrated emulsion, the volume fraction of the dispersed is greater than 0.74 and the hydrophilic liquid is dispersed in the hydrophobic liquid of the continuous phase. The emulsion has the same appearance and behaviour as a gel. The polarity of the hydrophilic liquids and hydrophobic liquids, the pH and the ionic strength of the hydrophilic liquid are found to be important factors in the stability at the polymerization temperature such as $50^{\circ}C$. The lower the polarity of the hydrophobic liquid and the higher the polarity of the hydrophilic liquid, the more stable the emulsion. Electron microscopy studies of the hydrophilic-hydrophobic polymer composites show that the particles of polyacrylamide, the dispersed phase, are separated by he network of the thin film of polystyrene, the continuous phase. This hydrophilic-hydrophobic polymer composites show higher permselectivity to water in the mixture of water-ethanol. The pervaporation experiment shows that the selectivity of the membrane ranges between 4-40 and increases with increasing enthanol concentration in the feed. The rate of permeation decreases with increasing ethanol concentration in the feed.

• Clean Technology
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• v.12 no.1
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• pp.45-51
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• 2006

Colloidal Liquid Aphrons(CLAs) were prepared from different solvents such as nonpolar hydrocarbons, alcohols, and amines. Water-soluble surfactant and oil-soluble surfactant were used in this study. The effect of PVR (phase volume ratio) and concentration of extractant on the stability of CLA was investigated. The stability of CLA was affected by PVR. As PVR was increased, the stability of CLA was decreased.

• Korean Journal of Materials Research
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• v.7 no.5
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• pp.444-450
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• 1997

기계적합금화 한 AI-Ti합금의 상온 및 고온 인장강도는 25at.% Ti을 Ce으로 치환함에 따라 증가하였다. 그러나 25at.% 이상의 Ce첨가는 합금의 인장강도를 감소시켰다. 이는 Ce이 적은 고용도 효과에 의해 금속간화합물의 초대화를 억제하여 합금의 강도를 증가시키지만 다량 첨가시에는 Ti에 비해 무거운 원자량으로 인해 분산상의 부피분율을 감소시켜 합금의 강도가 오히려 저하시킨 것으로 생각된다. Ce의 첨가는 40$0^{\circ}C$와 51$0^{\circ}C$에서 합금의 열저안정성을 향상시키는 것으로 나타났다. 300-51$0^{\circ}C$ 온도범위에서 측정된 AI-8wt.%(Ti+Ce)합금의 변형에 필요한 활성화에너지는 AI의 자기확산에 필요한 에너지 (142kJ/mode)의 1.3-1.9배로 나타났다. 이로부터 AI-Ti-Ce 합금의 고온 변형은 Orowan기구에 의한 것을 생각된다.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.315-319
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• 1997

In this study, the optimum analytical conditions for determination of distribution of propylene oxide in a nonionic surfactant and separation of fatty alcohols were investigated by Reversed Phase High Performance Liquid Chromatography. To analyse the distribution of propylene oxide (PO) and carbon chain length of a fatty alcohol, we derivatized samples for the purpose of using a UV detector. Also, we studied the influences of columns and mobile phase composition to obtain the optimum separation conditions. In our experiment, Waters Symmetry $C_8(3.9{\times}150mm)$ column was used. And the optimum condition were obtained by gradient elution with methanol and water as the mobile phase. In the plot of log k' vs composition of water in the binary phase, the linerality was very good. We ploted the calibration curve to conform the quality of fatty alcohol, a good linerality was obtained.

• Journal of the Korean Chemical Society
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• v.37 no.12
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• pp.1035-1046
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• 1993

Some iron(III)porphyrin complexes were prepared, and identified by the spectroscopic methods. Elution behavior of iron(III)porphyrin complexes was investigated by reversed-phase HPLC. The optimum conditions for the separation of iron(III)porphyrin complexes were examined with respect to flow rate and mobile phase strength. These complexes were successfully separated on NOVA-PAK $C_{18}$ column using methanol / water(95/5) for $[T_pCF_3PP)Fe(R)]$ and methanol / water (98/2) for $[(P)Fe(C_6F_5)]$ as a mobile phase. It was found that these complexes were largely eluted in an acceptable range of capacity factor value ($0{\leq}logk'{\leq}1$). The dependence of the capacity factor (k') on the volume fraction of water in the binary mobile phase as well as the dependence of k' on the liquid-liquid extraction distribution ratio$(D_c)$ in methanol-water / n-pentadecane extraction system showed a good linearity. It means that the retention of iron(III)porphyrin complexes on NOVA-PAK $C_{18}$ column is largely due to the solvophobic effect. Also, there was a good linear dependence of the capacity factor(k') on the column temperature and enthalpy calculated by van't Hoff plot. From these results, it was confirmed that the retention mechanism of iron(III)porphyrin complexes in reversed-phase liquid chromatography was invariant under the condition of various temperature, and the solvophobic binding process exhibited isoequilibrium behavior.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.49-55
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• 2018

Under the era of energy crisis, hydrogen energy is considered as one of the most potential alternative energies. Liquid hydrogen has much higher energy density per unit volume than gas hydrogen and is counted as the excellent energy storage method. In this study, Navier-Stokes equations based on 2-phase model were solved by using a computational fluid dynamics program and the liquefaction process of gaseous hydrogen passing through a cryogenic cooling tube was analyzed. The copper with high thermal conductivity was assumed as the material for cryogenic cooling tube. For different inlet velocities of 5 m/s, 10 m/s and 20 m/s for hydrogen gas, the distributions of fluid temperature, axial and radial velocities, and volume fractions of gas and liquid hydrogens were compared. These research results are expected to be used as basic data for the future design and fabrication of cryogenic cooling tube to transform the hydrogen gas into liquid hydrogen.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.201-213
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• 2017

Water is removed from crude oil containing water by using oil separator. This study aims to develop a three-dimensional (3D) Eulerian computational fluid dynamics (CFD) model to predict the separation efficiency of air-water-oil separator. In the incompressible, isothermal and unsteady-state CFD model, air is defined as continuous phase, and water and oil are given as dispersed phase. The momentum equation includes the drag force, lift force and resistance force of porous media. The standard k-${\varepsilon}$ model is used for turbulence flow. The exit pressures of water and oil play an important role in determining the liquid level of the oil separator. The exit pressures were identified to be 6.3 kPa and 5.1 kPa for water and oil, respectively, to keep a liquid level of 25 cm at a normal operating condition. The time evolution of volume fractions of air, water and oil was investigated. The settling velocities of water and oil along the longitudinal separator distance were analyzed, when the oil separator reached a steady-state. The oil separation efficiency obtained from the CFD model was 99.85%, which agreed well with experimental data. The relatively simple CFD model can be used for the modification of oil separator structure and finding optimal operating conditions.

• Clean Technology
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• v.7 no.3
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• pp.169-178
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• 2001

Textile printing prints around twenty bilion linear meters of textile each year. Rotary and flat bed screen printing requires pre and post treatments, leading to the loss of dyes and the environmental problems due to effluents. Digital ink jet printing can offer a solution to the existing problems, especially the environmental problems, in addition to its flexibility. Pigments are used as a dispersion inks in the digital inkjet textile printing. Molecular dynamic simulation like Stokesian dynamic simulation was employed to simulate the behavior of pigments and velocity distribution under the pressure driven flow in the printer nozzle. The simulation shows that the particle distribution in the flow are uniform if particle volume fraction is low, the ratio of nozzle and particle diameter is large, and the dimensionless average suspension velocity is low.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.386-391
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• 1996

SiC particles (average size is 270 nm) of 0, 10, 20, 30, 40 vol% were dispersed in $Si_{3}N_{4}$, and $Si_{3}N_{4}/SiC$ nanocomposites were fabricated by hot press. After sintering, matrix phase, ${\alpha}-Si_{3}N_{4}$ was transformed to ${\beta}-Si_{3}N_{4}$, and second phase, ${\beta}-SiC$ was not changed. No grain boundary crystalline phase by adding of sintering additives was detected. Grain growth of $Si_{3}N_{4}$ was supressed with increasing of SiC contents, and then fine grain was occurred. The highest fracture strength was obtained at 10 vol% SiC, and fracture toughness was decreased, but hardness was linearly increased with SiC content.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.73-73
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• 2011

Zn-Sn-O (ZTO) 다성분계 산화물 박막은 일반적인 rf 스퍼터법으로 성막할 경우 비정질상으로 성장하여 결정질 산화물 박막에 비해 우수한 표면평탄도와 식각 단면을 제공한다. 비정질임에도 불구하고 넓은 자유전하 농도 범위에서 높은 Hall 이동도를 제공할 수 있는 것으로 보고되어 있어 비정질 산화물의 투명도전성 박막에 대한 관심이 높아지고 있다. 투명 TFT에 적용되는 또 다른 비정질계 산화물 박막인 In-Zn-O (IZO) 박막에 비해 ZTO 박막은 상대적으로 제한된 연구가 이루어졌으나, In의 함유되지 않아 경제적으로 유리하고, 특히 SnO2의 우수한 기계적 및 화학적 특성과 ZnO의 내환원성 특성을 잠재하고 있는 유망한 투명도전성 박막재료이다. 본 연구에서는 Zn-Sn-O계 박막을 통상의 rf 스퍼터법으로 성막하여 조성, 증착 온도, 그리고 열처리 온도에 따른 ZTO 박막의 구조적인 특성 변화와 이에 따른 전기적 및 광학적 특성 변화에 대하여 고찰하였다. ZnO 타겟과 SnO2 타겟을 사용하여 co-sputtering하여 ZnO의 부피 분률을 13~59 mol%까지 변화되도록 조절하여 증착하였다. 증착 온도는 상온, 150 및 $300^{\circ}C$로, 그리고 성막가스 중의 산소분률은 0%, 0.5% 및 1% 로 변화시켰다. 40 mol% 이상의 ZnO를 함유한 ZTO 박막은 가시광 영역에서의 평균 광투과도는 좋으나 전기적인 특성이 열악하였으며, ZnO 분율이 낮은 ZTO 박막은 10-2~10-3 ohm-cm 정도의 비교적 낮은 비저항을 나타내었으나 광투과도 면에서 떨어지는 단점을 보였다. 평균 광투과도는 증착 온도가 증가할수록, 그리고 산소의 양이 증가할수록 향상 되었다. 자유전하농도가 1017~1020 cm-3 정도의 넓은 범위에서 10 cm2/Vs 을 넘는 홀 이동도를 가지는 ZTO 박막의 증착이 가능함을 확인하였으며, 이로부터 투명 TFT 소자로 적용이 가능성이 있음을 보였다. EPMA를 이용한 정량분석 및 XRD를 이용한 구조분석과 연계한 ZTO 박막의 물성 및 최적 조건에 대한 논의가 이루어질 것이다.