• Composites Research
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• v.33 no.5
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• pp.235-240
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• 2020

In this study, in order to improve the impact resistance of the B₄C tile-inserted B₄C_p/Al7075 hybrid composite, a control method of the B₄C/Al7075 interface was developed and the characteristics of the controlled interface were analyzed. B₂O₃, Ni, and Si were coated on the B₄C tile surface using additional thermal oxidation, electroless plating, and plasma spraying. The coated B₄C tile is inserted into the B₄C_p/Al7075 composite material using the liquid pressurization method. Interfacial energy, bonding strength, and impact resistance were measured to analyze the effect of the coating. All coatings enhanced interfacial energy, bonding strength, and impact resistance, and in particular, it was confirmed that the impact resistance increased by 86.8% when B₂O₃ coating was used. This study is significant in developing and analyzing a core surface treatment method that improves the performance of B₄C/Al series composites, which are attracting attention as next-generation lightweight amour and bulletproof materials.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.155-161
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• 2013

In this study, a metal-plated polycarbonate was adopted as a material for bipolar plates in a polymer electrolyte membrane fuel cell (PEMFC). The coated layers included 40-${\mu}m$-thick copper, 10-${\mu}m$-thick nickel, and 0.3-${\mu}m$-thick gold that respectively played the roles of current conduction, adhesion between copper and gold, and minimization of surface corrosion. The maximum power of the air-breathing PEMFC with polycarbonate bipolar plates was $120mW/cm^2$, which was similar to that of graphite bipolar plates. Finally, the maximum power of a 12-cell stack of polycarbonate bipolar plates was $132.7mW/cm^2$, and it had an operating time of 12 h. Therefore, this was considered a suitable material for bipolar plates in PEMFCs.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.06a
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• pp.135-153
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• 1998

Nanofiltration (NF) is a recently introduced term in membrane separation. In 1988, Eriksson was one of the first authors using the word 'nanofiltration' explicitly. Some years before, FilmTech started to use this term for their NF50 membrane which was supposed to be a very loose reverse osmosis membrane or a very tight ultrafiltration membrane. Since then, this term has been introduced to indicate a specific boundary of membrane technology in between ultrafiltration and reverse osmosis. The application fields of the NF membranes are very broad as follows: Demeneralizing water, Cleaning up contaminated groundwater, Ultrapure water production, Treatment of effleunts containing heavy metals, Offshore oil platforms, Yeast production, Pulp and paper mills, Textile production, Electroless copper plating, Cheese whey production, Cyclodextrin production, Lactose production. The earliest NF membrane was made by Cadotte et al, using piperazine and trimesoyl chloride as monomers for the formation of polyamide active layer of the composite type membrane. They coated very thin interfacially potymerized polyamide on the surface of the microporous polysulfone supports. The NF membrane exhibited low rejections for monovalent anions (chloride) and high rejections for bivalent anions (sulphate). This membrane was called NS300. Some of the earliest NF membranes, like the NF40 membrane of FilmTech, the NTR7250 of Nitto-Denko and the UTC20 and UTC60 of Toray, are formed by a comparable synthesis route as the NS300 membrane. Commercially available NF membranes nowadays are as follows: ASP35 (Advanced Membrane Technology), MPF21; MPF32 (Kiryat Weizmann), UTC20; UTC60; UTC70; UTC90 (Toray), CTA-LP; TFCS (Fluid Systems), NF45; NF70 (FilmTec), BQ01; MX07; HG01; HG19; SX01; SX10 (Osmonics), 8040-LSY-PVDI (Hydranautics), NF CA30; NF PES 10 (Hoechst), WFN0505 (Stork Friesland). The typical ones among the commercially available NF membranes are polyamide composite membrane consisting of interfacially polymerized polyamide active layer and microporous support. While showing high water fluxes and high rejections of multivalent ions and small organic molecules, these membranes have relatively low chemical stability. These membranes have low chlorine tolerance and are unstable in acid or base solution. This chemical instability is appearing to be a big obstacle for their applications. To improve the chemical stability, we have tried, in this study, to prepare chemically stable NF membranes from PVA. The ionomers and interfacially polymerized polyamide were used for the modification of'the PVA membranes. For the detail study of the active layer, homogeneous NF membranes made only from active layer materials were prepared and for the high performance, composite type NF membranes were prepared by coating the active layer materials on microporous polysulfone supports.

• Composites Research
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• v.25 no.4
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• pp.93-97
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• 2012

Carbon nano fibers (CNFs) reinforced magnesium alloy (AZ91) matrix composites have been fabricated by liquid pressing process. In order to improve the dispersibility of CNFs and the wettability with magnesium alloy melt, CNFs were mixed with submicron sized SiC particles ($SiC_p$). Also, the mixture of CNFs and $SiC_p$ were coated with Ni by electroless plating. In liquid pressing process, AZ91 melts have been pressed hydrostatically and infiltrated into three reinforcement preforms of only CNFs, the mixture of CNFs and $SiC_p$ (CNF+$SiC_p$), and Ni coated CNFs and $SiC_p$ ((CNF+$SiC_p$)/Ni). Some CNFs agglomerates were observed in only CNFs reinforced composite. In cases of the composites reinforce with CNF+$SiC_p$ and (CNF+$SiC_p$)/Ni, CNFs were dispersed homogeneously in the matrix, which resulted in the improvement of mechanical properties. The compressive strengths of CNF+$SiC_p$ and (CNF+$SiC_p$)/Ni reinforced composites were 38% and 28% higher than that of only CNFs composite.

• Journal of Korea Foundry Society
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• v.22 no.1
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• pp.42-48
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• 2002

Effects of coating treatment of metallic Cu, Ni-P film on $SiC_p$, for $SiC_p$/iron aluminide composites were studied. Porous hybrid preforms were fabricated by reactive sintering after mixing the coated $SiC_p$, Fe and Al powders. Then the final composites were manufactured by squeeze casting after pouring AC4C Al alloy melts in preforms. The change of reactive temperature, density, microstructure of the preforms and microstructure of the composites were investigated. The exprimental results were summarized as follows. The thickness of Cu and Ni-P metallic layer formed on $SiC_p$ by electroless plating method were about $0.5{\mu}m$ and coated uniformly. There was no remakable change in the ignition temperature with variation of the mixing ratio of Fe and Al powder while in the case of coated $SiC_p$ it was lower about $20^{\circ}C$ than in the non-coated $SiC_p$. The maximum reaction temperature increased with increasing Al contents, but decreased with increasing $SiC_p$ contents. Expansion ratio of preform after reactive sintering increased with amount of Cu coated $SiC_p$. In the case of Fe-70at.%Al, the expansion ratio was about 7% up to 8wt.% of $SiC_p$, addition but further addition of $SiC_p$, increased the ratio significantly. And in the case of Fe-50 and 60at.%Al, it was about 20% up to 16wt.% of $SiC_p$ addition and about 28% in 24wt.% of $SiC_p$, addition. The microstructures of compounds showed that the grains became finer as amount of $SiC_p$, and mixing ratio of iron powder increased and the shape of compounds was changed gradually from irregular to spheroidal.

• Polymer(Korea)
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• v.36 no.2
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• pp.169-176
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• 2012

Based on our experience in developing resistive humidity sensor, interdigital gold electrodes with different fingers and gaps have been fabricated on a glass epoxy (GE) substrate using screen printing techniques. The basic structure of the electrode consisted of a 3-, 4- and 5-fingers with gaps of 310 and 460 ${\mu}m$. Gold electrode/GE was prepared by first printing silver nanopaste, followed by consecutive electroless plating of Cu, Ni and then Au. Copolymer of [2-(methacryloyloxy)ethyl] dimethyl benzyl ammonium chloride (MDBAC) and methyl methacrylate (MMA) was used as a humidity-sensing polyelectrolyte, which was fabricated by a screen printing method on the Au electrode/GE substrate. The flexible humidity sensor showed acceptable linearity between logarithmic impedance and relative humidity in the range of 20-95%RH, low hysteresis of 1.5%RH, good response and recovery time of 75 sec at 1 V, 1 kHz, and $25^{\circ}C$. Electrode construction had a significant influence on the humidity-sensing characteristics of polymeric humidity sensors. The activation energy between electrode and ion conducting polyelectrolyte plays an important role in explaining the differences of humidity sensing characteristics such as temperature dependence, sensitivity, linearity and hysteresis.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.774-780
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• 2019

An efficient Pd-coated $La_{0.1}Sr_{0.9}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ (LSCF-1928) catalyst for total oxidation of methane under landfill gas at low tmeperature has been developed. Synergism was observed between Pd coating and LSCF-1928 substrate. When Pd coating on LSCF-1928, we used electroless plating method and conformed characteristic of catalyst through TPR(Temperature Programmed Reduction) analysis, XRD(X-ray Diffraction) analysis, SEM(Scanning Electron Microscope). The results demonstrated that the Pd coated LSCF-1928 catalysts showed higher performance than non-Pd LSCF-1928. Pd coated LSCF-1928 had low total oxidation temperature of methane (< $475^{\circ}C$) which is lower than total oxidation temperature of methane about non-Pd LSCF-1928 catalysts (= $475^{\circ}C$). Also, $O_2$ conversion rate was higher than non-Pd LSCF-1928 at same temperature.

• Resources Recycling
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• v.30 no.3
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• pp.47-54
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• 2021

Palladium present in colloidal-type plated spent catalyst solution that is used in electroless plating process has not been recovered but discharged as wastewater so far. Recyclig of paladium in colloidal-type plated spent catalyst solution is achieved with this study. This study presents the estimation of resource consumption and GHG emissions during the recycling and disposal of palladium in the plated spent catalyst solution using life cycle assessment. The reduction of resources and GHG are also estimated. Based on the palladium amount of 1 kg during disposal, the GHG emission amount was estimated to be 9.67E+03 kgCO₂eq., and the amount of resource consumption was 3.94E+01 kgSb-eq. However, GHG emission was 1.96E+03 kgCO₂eq., and the amount of resource consumption was 1.54E+01 kgSb-eq. during recycling. Considering the major substances affecting GHG emissions and amount of resource consumption, CO₂ was found to significantly affect GHG emissions, accounting for 91.42% in disposal and 98.37% in recycling. The major substance affecting the amount of resource consumption was hard coal, which accounted for 40.63% in disposal and 60.73% in recycling. Upon recycling 1 kg palladium, 8,967.17 kgCO₂eq. of greenhouse gas emission was reduced, while the resource consumption was reduced to 10.10 kg Sb-eq. In addition, the direct palladium resource reduction rate due to palladium recycling was 50%.