• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.475-480
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• 2003

Nanocomposite of Au doped ZrO$_2$ films was prepared, which could be used as non-linear optic materials, selective absorption and transmission films. After heat treatment of prepared thin film by dip-coating method, the characteristics were investigated by X-ray diffraction, UV-VIS Spectrometer, Atomic Force Microscopy (AFM) and Scanning Electron Microscope (SEM). Film thickness was about 150 nm, the Au particle size was 15~35 nm. The thin film had a smooth surface roughness about 1.06 nm. Nonlinearity optics was found that films showed absorption peak at 600~650 nm visible region by plasma resonance of Au metal particles.

• Clean Technology
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• v.29 no.1
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• pp.71-75
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• 2023

In general, the presence of non-selective intercrystalline (grain boundary) defects in polycrystalline metal-organic framework (MOF) or zeolite membranes, which are known to be ca. 1 nm in size, causes lower membrane performance (selectivity) than the intrinsically expected. In this study we show that applying a thin polymeric coating of polydimethylsiloxane (PDMS) on a polycrystalline MOF membrane is effective to cap the non-selective intercrystalline defects and therefore improve membrane performance. To demonstrate the concept, first, polycrystalline UiO-66, one of Zr-based MOFs, membranes were prepared by an in-situ solvothermal growth. By controlling membrane growth condition with respect to growth temperature, we were able to obtain polycrystalline UiO-66 membranes at 150 ℃ with intercrystalline defects of which the quantity is not significant, so it can be plugged by the suggested PDMS deposition. Second, their performances were compared before and after the PDMS deposition. As expected, the PDMS deposition ended up with a noticeable increase in CO₂/N₂ ideal selectivity from 6 to 14, indicating successful intercrystalline defect plugging. However, the enhancement in CO₂/N₂ selectivity was accompanied by a significant reduction in CO₂ permeance from 5700 to 33 GPU because the PDMS deposition not only plugs defects but also forms a continuous coating on membrane surface, adding an additional transport resistance.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.5
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• pp.267-271
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• 2006

A polymeric waveguide-type wavelength filter based on a Bragg grating has been proposed and fabricated using the simple nanoimpring technique, for the first time to our knowledge. An ultraviolet transparent stamp with the single-mode waveguide pattern incorporating a surface-relief-type Bragg grating was specially designed selective dry-etching process. Using this stamp, the device fabrication was substantially involving just a single-step process of imprint followed by polymer spin-coating. The achieved maximum reflection was higher than 25 dB at the center wavelength of 1569 nm. And the 3-dB bandwidth was 0.8 nm for the device length of 1.5 cm.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.99-100
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• 2006

Orthogonally protected block copolymers of based on p-hydroxystyrene were prepared with high control via nitroxy mediated radical polymerization using an alkoxyamine as an unimolecular initiator. Thin films of partially protected block copolymer were prepared by spin or dip coating. A well defined nanostructure could be observed as a result of phase separation e.g. cylinders in a matrix oriented perpendicular or parallel to the substrate. The nanostructure of the polymeric films can be defined by the block copolymer composition and it determines surface properties and allows further, selective functionalization, e.g. via click chemistry. The thin films can be designed in a way to allow a patterning based on a thermal or photochemical stimulus.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.451-456
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• 2024

Organic photovoltaic (OPV) devices have attracted attention due to their high efficiency and simple manufacturing process. Applying an overlayer to OPV devices is one way to improve their performance because it can improve charge extraction and suppress vertical phase separation. In addition, dichloromethane (DCM) was used as an orthogonal solvent to minimize the effect on other layers. However, an coating problems due to the use of DCM were found, which affects surface morphology as rough or peeling. Additional research efforts are needed to solve these problems, and optimal results are expected to be obtained by utilizing various buffer layers or selective organic solvents.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05a
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• pp.94-97
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• 2004

Micro/nano-sized L $a_{0.6}$S $r_{0.4}$Co $O_{3-}$$\delta$/ particles are considered to improve oxygen permeability in highly selective inorganic oxygen separation membrane. A L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/ membrane with perovskite structure is fabricated by a conventional solid-state reaction. As the oxygen permeation flux of the L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/ membrane was lower than commercial gas separation membranes, we coated the L $a_{0.6}$S $r_{0.4}$Co $O_{3-}$$\delta$/ particles to enhance the oxygen permeation flux. It has been demonstrated that the effective area of reactive free surface is an important factor in determining the effectiveness of the introduction of coating layer for oxygen permeation. The introduction of micro/nano L $a_{0.6}$S $r_{0.4}$Co $O_{3-}$$\delta$/ particles was very effective for increasing oxygen flux, as the flux was as much as 2 to 6 times higher than that of an uncoated L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/ membrane.\delta$/ membrane.>/ membrane.brane.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.3
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• pp.218-224
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• 2005

Surface modification of glutaraldehyde fixed bovine pericardium (GFBP) was success­fully carried out with hyaluronic acid (HA) derivatives. At first, HA was chemically modified with adipic dihydrazide (ADH) to introduce hydrazide functional group into the carboxyl group of HA backbone. Then, GFBP was surface modified by grafting HA-ADH to the free aldehyde groups on the tissue and the subsequent HA-ADH hydrogel coating. HA-ADH hydrogels could be prepared through selective crosslinking at low pH between hydrazide groups of HA-ADH and crosslinkers containing succinimmidyl moieties with minimized protein denaturation. When HA­ADH hydrogels were prepared at low pH of 4.8 in the presence of erythropoietin (EPO) as a model protein, EPO release was continued up to $85\%$ of total amount of loaded EPO for 4 days. To the contrary, only $30\%$ of EPO was released from HA-ADH hydrogels prepared at pH=7.4, which might be due to the denaturation of EPO during the crosslinking reaction. Because the carboxyl groups on the glucuronic acid residues are recognition sites for HA degradation by hyaluronidase, the HA-ADH hydrogels degraded more slowly than HA hydrogels prepared by the crosslinking reaction of divinyl sulfone with hydroxyl groups of HA. Following a two-week subcutaneous implantation in osteopontin-null mice, clinically significant levels of calcification were observed for the positive controls without any surface modification. However, the calcification of surface modified GFBP with HA-ADH and HA-ADH hydrogels was drastically reduced by more than $85\%$ of the positive controls. The anti-calcification effect of HA surface modification was also confirmed by microscopic analysis of explanted tissue after staining with Alizarin Red S for calcium, which followed the trend as observed with calcium quantification.

• Clean Technology
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• v.27 no.4
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• pp.332-340
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• 2021

With the recent reinforcement of emission standards, it is necessary to make efforts to reduce NOx from air pollutant-emitting workplaces. The NOx reduction method mainly used in industrial facilities is selective catalytic reduction (SCR), and the most commercial SCR catalyst is the ceramic honeycomb catalyst. This study was carried out to reduce the NOx emitted from steel plants by applying De-NOx catalyst coated on metallic monolith. The De-NOx catalyst was synthesized through the optimized coating technique, and the coated catalyst was uniformly and strongly adhered onto the surface of the metallic monolith according to the air jet erosion and bending test. Due to the good thermal conductivity of metallic monolith, the De-NOx catalyst coated on metallic monolith showed good De-NOx efficiency at low temperatures (200 ~ 250 ℃). In addition, the optimal amount of catalyst coating on the metallic monolith surface was confirmed for the design of an economical catalyst. Based on these results, the De-NOx catalyst of commercial grade size was tested in a semi-pilot De-NOx performance facility under a simulated gas similar to the exhaust gas emitted from a steel plant. Even at a low temperature (200 ℃), it showed excellent performance satisfying the emission standard (less than 60 ppm). Therefore, the De-NOx catalyst coated metallic monolith has good physical and chemical properties and showed a good De-NOx efficiency even with the minimum amount of catalyst. Additionally, it was possible to compact and downsize the SCR reactor through the application of a high-density cell. Therefore, we suggest that the proposed De-NOx catalyst coated metallic monolith may be a good alternative De-NOx catalyst for industrial uses such as steel plants, thermal power plants, incineration plants ships, and construction machinery.

• Membrane Journal
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• v.27 no.2
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• pp.167-181
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• 2017

Graphene-based materials have been considered as a promising membrane material, due to its easy processability and atomic thickness. In this study, we studied on gas permeation behavior in few-layered GO membranes prepared by spin-coating method. The GO membrane structures were varied by using different GO flake sizes and GO solutions at various pH levels. The GO membranes prepared small flake size show more permeable and selective gas separation properties than large one due to shortening tortuosity. Also gas transport behaviors of the GO membranes are sensitive to slit width for gas diffusion because the pore size of GO membranes ranged from molecular sieving to Knudsen diffusion area. In particular, due to the narrow pore size of GO membranes and highly $CO_2$-philic properties of GO nanosheets, few-layered GO membranes exhibit ultrafast and $CO_2$ selective character in comparison with other gas molecules, which lead to outstanding $CO_2$ capture properties such as $CO_2/H_2$, $CO_2/CH_4$, and $CO_2/N_2$. This unusual gas transport through multi-layered GO nanosheets can explain a unique transport mechanism followed by an adsorption-facilitated diffusion behavior (i.e., surface diffusion mechanism). These findings provide the great insights for designing $CO_2$-selective membrane materials and the practical guidelines for gas transports through slit-like pores and lamellar structures.

• Journal of the Korean Chemical Society
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• v.35 no.1
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• pp.90-95
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• 1991

A method for the selective syntheses of alkyl (alkoxymethyl)benzoates from halobenzyl halides by two steps in one pot process is described. In the first step, benzyl halide moiety is etherified with alkoxide anion in alcohol by Williamson ether process. In the second step, aryl halide moiety is carbonylated to give alkyl (alkoxymethyl)benzoate with alcohol, Na$_2$CO$_3$, CH$_3$I, and carbon monoxide (1 atm) in the presence of a catalytic amount of Co$_2$(CO)$_8$ in excellent yield.