• Polymer(Korea)
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• v.38 no.6
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• pp.791-800
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• 2014

4-Chlorobenzoyl (CB) group-attached multi-walled carbon nanotube (c-MWNT) was prepared via a direct Friedel-Crafts acylation of MWNT with 4-chlorobenzoic acid (CBA) in a $P_2O_5$/poly(phosphoric acid) medium. c-MWNT with a maximum chlorine content of 5.3 wt% (CB group content of 20.9 wt%) was obtained by controlling the amount of CBA during the reaction. Using a self-condensation polymerization of 4-chlorobenzenethiol (CBT) to poly(phenylene sulfide) (PPS), MWNT-g-PPS was prepared by adding c-MWNT of chlorine content of 5.3 wt% during the self-polymerization of CBT and removing homo PPS after polymerization in order to increase the interfacial interaction between PPS and MWNT. Thermal and surface properties of the MWNT-g-PPS were characterized. The results showed that PPS was formed on the surface of c-MWNT by the condensation of c-MWNT and CBT.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.380-380
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• 2010

Currently, organic light-emitting diodes (OLEDs) have been proven of their readiness for commercialization in terms of lifetime and efficiency. In accordance with emerging new technologies, enhancement of light efficiency and extension of application fields are required. Particularly inverted structures, in which electron injection occurs at bottom and hole injection on top, show crucial advantages due to their easy integration with Si-based driving circuits for active matrix OLED as well as large open area for brighter illumination. In order to get better performance and process reliability, usually a proper buffer layer for carrier injection is needed. In inverted top emission OLED, the buffer layer should protect underlying organic materials against destructive particles during the electrode deposition, in addition to increasing their efficiency by reducing carrier injection barrier. For hole injection layers, there are several requirements for the buffer layer, such as high transparency, high work function, and reasonable electrical conductivity. As a buffer material, a few kinds of transition metal oxides for inverted OLED applications have been successfully utilized aiming at efficient hole injection properties. Among them, we chose 2 nm of $WO_3$ between NPB [N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine] and Au (or Al) films. The interfacial energy-level alignment and chemical reaction as a function of film coverage have been measured by using in-situ ultraviolet and X-ray photoelectron spectroscopy. It turned out that the $WO_3$ interlayer substantially reduces the hole injection barrier irrespective of the kind of electrode metals. It also avoids direct chemical interaction between NPB and metal atoms. This observation clearly validates the use of $WO_3$ interlayer as hole injection for inverted OLED applications.

• Advances in materials Research
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• v.8 no.1
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• pp.47-73
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• 2019

Joining of Mg/Ti hybrid structures by welding for automotive and aerospace applications has attracted great attention in recent years due mainly to its potential benefit of energy saving and emission reduction. However, joining them has been hampered with many difficulties due to their physical and metallurgical incompatibilities. Different joining processes have been employed to join Mg/Ti, and in most cases in order to get a metallurgical bonding between them was the use of an intermediate element at the interface or mutual diffusion of alloying elements from the base materials. The formation of a reaction product (in the form of solid solution or intermetallic compound) along the interface between the Mg and Ti is responsible for formation of a metallurgical bond. However, the interfacial bonding achieved and the joints performance depend significantly on the newly formed reaction product(s). Thus, a thorough understanding of the interaction between the selected intermediate elements with the base metals along with the influence of the associated welding parameters are essential. This review is timely as it presents on the current paradigm and progress in welding and joining of Mg/Ti alloys. The factors governing the welding of several important techniques are deliberated along with their joining mechanisms. Some opportunities to improve the welding of Mg/Ti for different welding techniques are also identified.

• Journal of Electrochemical Science and Technology
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• v.13 no.2
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• pp.269-278
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• 2022

Utilization of high-voltage electrolyte additive(s) at a small fraction is a cost-effective strategy for a good solid electrolyte interphase (SEI) formation and performance improvement of a lithium-rich layered oxide-based high-energy lithium-ion cell by avoiding the occurrence of metal-dissolution that is one of the failure modes. To mitigate metal-dissolution, we explored fluorinated dual-additives of fluoroethylene carbonate (FEC) and di(2,2,2-trifluoroethyl)carbonate (DFDEC) for building-up of a good SEI in a 4.7 V full-cell that consists of high-capacity silicon-graphite composite (15 wt% Si/C/CF/C-graphite) anode and Li_1.13Mn_0.463Ni_0.203Co_0.203O₂ (LMNC) cathode. The full-cell including optimum fractions of dual-additives shows increased capacity to 228 mAhg^-1 at 0.2C and improved performance from the one in the base electrolyte. Surface analysis results find that the SEI stabilization of LMNC cathode induced by dual-additives leads to a suppression of soluble Mn²⁺-O formation at cathode surface, mitigating metal-dissolution event and crack formation as well as structural degradation. The SEI and structure of Si/C/CF/C-graphite anode is also stabilized by the effects of dual-additives, contributing to performance improvement. The data give insight into a basic understanding of cathode-electrolyte and anode-electrolyte interfacial processes and cathode-anode interaction that are critical factors affecting full-cell performance.

• Applied Chemistry for Engineering
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• v.35 no.3
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• pp.230-238
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• 2024

In the present work, the interaction of lipid-based zwitterionic surfactant CDP-W with the vesicle membrane of phospholipids was investigated. For this purpose, interfacial properties such as critical micelle concentration (CMC) and surface tension were measured for the zwitterionic surfactant CDP-W and lecithin S100-3. The zeta potential of 1 wt% aqueous surfactant solutions was also measured as a function of pH to determine the iso-electric point of CDP-W surfactant, where the characteristic of CDP-W surfactant changes from a cationic surfactant to an anionic surfactant. Based on the iso-electric point measurement of CDP-W surfactant, the effects of pH change and CDP-W addition on the stability of S100-3 liposome systems were studied, such as average particle size, polydispersity index (PDI), and zeta potential. The effect of CDP-W on the fluidity characteristics of liposome membranes such as fluorescence anisotropy ratio, deformability, and melting point was investigated at pH 6 where the most stable liposomes were prepared to understand the effect of the fluidity of the liposome membrane on the encapsulation efficiency of active materials and the stability of liposome systems.

• Journal of Soil and Groundwater Environment
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• v.12 no.2
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• pp.9-19
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• 2007

This study investigated the interaction between groundwater and stream water systems, which is caused by the artificial weir on streambed, enforcing external stresses on the groundwater system. The study area is in Nami Natural Recreation Woods located in Chungcheongnam-do Geumsan-gun Nami-myeon Geoncheon-ri. In this study both of hydrophysical methods (hydraulic head) and hyrdochemical investigations (pH, EC, major ion analysis) were applied. In order to identify the relationship between each of study results, cross-correlation analysis is performed. From results of hydrophysical methods, water level fluctuation at BH-14, installed by the weir, shows the double-recession pattern much more frequently and much higher amplitudes than the fluctuation at each of other monitoring wells. Using the results by hydrochemical investigations, hydrochemical properties at BH-14 is similar to the hydrochemical characteristics in stream water. To analyze the interrelationships between the results from each of applied methods, cross-correlation analysis was applied. Results from the correlation analyses, water levels at BH-14 and stream weir showed the highest cross-correlation in hydrophysical aspects. On the other hand, the correlation between stream weir and bridge was the highest in hydrochemical aspects. The difference between the results from each of methods is due that the hydrophysical response at BH-14, such as water level, is induced by the pressure propagation-not with mass transfer, but the hydrochemical interaction, caused by mass transport, takes much more times. In conclusion impermeable artificial weir on streambed changes the interfacial condition between the stream and surrounding aquifers. The induced water flux into the groundwater system during flood period make water level at BH-14 increase instantly and groundwater quality higly similar to the quality of stream water. Referred similarities in both of water level and water quality at BH-14 become much higher when water level at weir grow higher.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.560-567
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• 1997

A new approach to obtain stable $W_1/O/W_2$ multiple emulsions has been studied ; The basis of the interfacial interaction between a PCL-PEO-PCL triblock copolymer and a lipophilic emulsifier in the dispersed oil phase was examined. $W_1/O/W_2$ multiple emulsions were prepared by the two-step method. Arlacel P-l35 was used as a liphophilic emulsifier and Synperonic PE/F 127 as a hydrophilic one. Eutanol-G was used as an oil phase. NaCl was encapsulated within the multiple emulsion droplets as the internal marker and its release rate studies were carried out. The suability of the multiple emulsions have been assessed by measuring Separation Ratios(%) and microscopic observations. The release of NaCl was significantly reduced in $W_1/O/W_2$ multiple emulsions containing PCL-PEO-PCL triblock copolymer(2k-4k-2k or 6k-4k-6k) in the oil phase. It may be concluded that the copolymer and the emulsifier form effective interfacial complex to enhance stability and to control the release rate. The effective diffusion coefficients of the NaCl were estimated as $2.64{\times}10^{-15}s$and $3.23{\times}10^{-16}gcm^2/s$ for the $W_1/O/W_2$ multiple emulsion containing 1.2 wt % of PCL-PEO-PCL triblock copolymers with compositions of 2k-4k-2k and 6k-4k-2k, respectively. The rate of release decreased with the increase of the initial concentration of NaCl. The results were examined in view of Higuchi mechanism. A kinetic model which is similar to the model for release of dispersed drugs from a polymeric matrix was found to be suitable for the release of NaCl from $W_1/O/W_2$ multiple emulsions.

• Economic and Environmental Geology
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• v.54 no.1
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• pp.105-115
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• 2021

The geological CO2 sequestration in underground geological formation such as deep saline aquifers and depleted hydrocarbon reservoirs is one of the most promising options for reducing the atmospheric CO2 emissions. The process in geological CO2 sequestration involves injection of supercritical CO2 (scCO2) into porous media saturated with pore water and initiates CO2 flooding with immiscible displacement. The CO2 migration and distribution, and, consequently, the displacement efficiency is governed by the interaction of fluids. Especially, the viscous force and capillary force are controlled by geological formation conditions and injection conditions. This study aimed to estimate the effects of surfactant on interfacial tension between the immiscible fluids, scCO2 and porewater, under high pressure and high temperature conditions by using a pair of proxy fluids under standard conditions through pendant drop method. It also aimed to observe migration and distribution patterns of the immiscible fluids and estimate the effects of surfactant concentrations on the displacement efficiency of scCO2. Micromodel experiments were conducted by applying n-hexane and deionized water as proxy fluids for scCO2 and porewater. In order to quantitatively analyze the immiscible displacement phenomena by n-hexane injection in pore network, the images of migration and distribution pattern of the two fluids are acquired through a imaging system. The experimental results revealed that the addition of surfactants sharply reduces the interfacial tension between hexane and deionized water at low concentrations and approaches a constant value as the concentration increases. Also it was found that, by directly affecting the flow path of the flooding fluid at the pore scale in the porous medium, the surfactant showed the identical effect on the displacement efficiency of n-hexane at equilibrium state. The experimental observation results could provide important fundamental information on immiscible displacement of fluids in porous media and suggest the potential to improve the displacement efficiency of scCO2 by using surfactants.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.23-28
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• 2015

Lacquer sap extracted from lacquer trees exhibits good thermal stabilities and antimicrobial properties. To apply these superior properties to functional packaging, polyurushiol (YPUOH) powders were prepared and blended into LDPE (low density polyethylene) to prepare three different LDPE/YPUOH composite films via a twin screw extruder system. Their morphology, thermal and antimicrobial properties as well as barrier properties of the LDPE/YPUOH composite films were thoroughly investigated to find out applicablities of the films as functional packaging materials. Although the interfacial interaction between LDPE and YPUOH was relatively weak, LDPE/YPUOH composite films exhibited good dispersion of YPUOH in LDPE, resulting in the enhanced thermal stability with YPUOH loading. Due to the good antibacterial property of as-prepared YPUOH, LDPE/YUOH composite films also showed an excellent antibacterial activity (R) of 99.9% against E. coli. Furthermore, the moisture barrier property of LDPE/YPUOH composite films increased with increasing YPUOH contents. Incorporating the relatively low amount of YPUOH in LDPE resulted in the apparent enhancement in thermal stabilities, antibacterial and moisture barrier properties, which made them promising candidates as a functional filler for packaging materials.

• Membrane Journal
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• v.28 no.1
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• pp.55-61
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• 2018

With vigorous development of petroleum and chemical industry, emission of carbon dioxide has attracted tremendous attention globally due to global warming problem and abnormal climate change. To address these problems, in this study, a PEGBEM-g-POEM graft copolymer with high $CO_2$ affinity was synthesized and $CaCO_3$ was incorporated to form mixed matrix membranes (MMMs) for enhancement of $CO_2$ permeance. By varying the addition weight of $CaCO_3$ in MMMs, high separation performance of $CO_2$ over $N_2$ was obtained. At 50 wt% loading of $CaCO_3$, the greatest separation performance was obtained with an enhanced $CO_2$ permeance from 22.5 to 28.16 GPU and slightly increased $CO_2/N_2$ selectivity from 44.7 to 45.42. It resulted from the increased $CO_2$ solubility of MMMs due to specific interaction between $CaCO_3$ and $CO_2$ molecules. Upon excess loading of $CaCO_3$, MMMs exhibited loss of $CO_2$ separation performance due to the formation of interfacial defects. Based on this result, it is considered that the proper addition of $CaCO_3$ is crucial for improvement of $CO_2$ separation performance.