• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.118-124
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• 2005

In this study, a novel deposition method of Pt catalysts onto Nafion membranes modified with polypyrrole (PPy) has been proposed for PEMFC application. The PPy/Nafion composite membranes were fabricated by chemical polymerization of pyrrole using $FeCl_3$ and $Na_2S_2O_8$ as initiator. The proton conductivity and water uptake of the chemically prepared PPy/Nafion composites were investigated. The ionic conductivity and water uptake of PPy/Nafion composite membrane prepared with $Na_2S_2O_8$ were decreased with polymerization time of pyrrole. In the case of $FeCl_3$, the ionic conductivity was almost retained and the water uptake was decreased with polymerization time of pyrrole. When the Pt particle was deposited on PPy/Nafion composites membrane by chemical reduction of $H_2PtCl_6$, the Pt loading on Nafion membrane was enhanced by polypyrrole due to electronic conduction property. The performance evaluation with membrane electrode assembly composed of Pt/PPy/Nafion composite and diffusion electrode was carried out using a single cell. As a result of fuel cell test, current density of $569mA/cm^2$ at 0.3 V has been obtained for MEA contained with Pt/PPy/Nafion composite. This study shows that direct deposition of Pt catalysts on Nafion impregnated polypyrrole is a promising method to prepare thin catalyst layer for the PEMFC.

• Journal of the Korean Wood Science and Technology
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• v.27 no.3
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• pp.73-81
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• 1999

This paper was intended to evaluate the effect of the blending condition of pigments on the packing structure of coating color and the interaction between pigments and latices on the optical and interior properties of coated paper. It has been studied many ways to modify the coating structure to induce the interaction among coating components as followings ; 1) to use dispersant for pigment, 2) to control the charge density and the type of surface charge of latex, 3) to support the water retention by adding water retention agent or flow modifier. This paper was performed through the introduction of interaction between pigments which were two kinds of clays and one precipitated calcium carbonate(PCC) and ionic latices of which anionic and amphoteric respectively under the certain blending condition of pigments where their blending ratio of clays to calcium carbonate was 70pph to 30pph. The reason is that packing volume of pigments was highest in that region and thixotropical behavior appears in measuring rheology of coating color. We measured the properties of coating color, interaction with pigments and latex, and properties of coated paper and its printability. As a results, we could find out that amphoteric latex had a great influence on the interaction with pigments, especially clays, no matter what grade and also affected the coating structure significantly in case that this blending condition was 70(clays) to 30(PCC). It produced a powerful effect on the forming of bulky and smooth coating structure and in turn improved the printability of coated paper.

• Membrane Journal
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• v.22 no.3
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• pp.224-233
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• 2012

To improve permeation performance of gas separation membrane, polysulfone hollow fiber membrane was prepared by wet-dry phase inversion method using Triton X-100 as non-ionic additive. And variation of gas permeation behavior by additive was investigated. Various spinning conditions such as air gap, concentration of polymer, dope tank temperature were controlled and these effects were studied. The morphology and gas permeation property of hollow fiber membranes were investigated using scanning electron microscope (SEM) and bubble flow meter respectively. We confirmed that the membranes added with Triton X-100 had a smooth external skin at various air gap length conditions. The macrovoids of these hollow fiber membranes were more developed with increase of air-gap from 4 to 90 cm and that induced higher permeance. The permeance of polysulfone membranes has the higher value at comparatively lower concentration polymer (30 wt% polysulfone) and lower concentration of additive (15 wt% Triton X-100). When temperature in dope tank was controlled, the membranes prepared at $100^{\circ}C$ showed low permeance because of volatilization of additive and solvent.

• Journal of Adhesion and Interface
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• v.17 no.2
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• pp.49-55
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• 2016

In this study, we designed an environment friendly, water-based adhesive using the acrylic emulsion method as a replacement for solvent-based adhesives, which are most commonly used in layered laminates for flexible food packaging. We designed adhesives with different combinations of anionic, non-ionic, and phosphoric ester surfactants, and with different concentrations of chain transfer agent (CTA). We also examined the effect of the degree of cross-linking by synthesizing and comparing 8 test group adhesives with different types of functional monomers. Additionally, we synthesized 2 other test group pressure-sensitive adhesives (PSA) using styrene/alpha-methyl styrene/acrylic acid (SAA) semipolymer dispersing agents (with molecular weights of 13,000 g/mol and 8,600 g/mol, respectively) to replace the conventional surfactants. We evaluated whether the 10 test group pressure-sensitive adhesives met the basic physical property criteria required for flexible food packaging by carrying out a physical analysis of their glass transition temperature (Tg), particle size, adhesion, and molecular weight. In our test, 2 test group adhesives manufactured with the combination of anionic and non-ionic surfactants, CTA concentration of 0.2%, and functional monomers of hydroxyethyl acrylate (HEA) and glycidyl methacrylate (GMA) demonstrated molecular weight and flexibility suitable for flexible packaging, with low adhesiveness and small particle size.

• Restorative Dentistry and Endodontics
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• v.25 no.2
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• pp.272-288
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• 2000

Calcium hydroxide is used as a root canal medicament with its several pharmacological effects. However, it has been known that the usage of calcium hydroxide in the root canal system before canal filling with gutta-percha and zinc oxide eugenol-based cement induced change in the properties of root canal cement which might adversely affect sealing ability of the canal filling. The purpose of this study was to identify the reactivity of calcium hydroxide-eugenol compound made from chemical interaction of between calcium hydroxide and zinc oxide eugenol. Chemical properties of calcium hydroxide, eugenol, zinc oxide eugenol, calcium hydroxide-eugenol and calcium hydroxide-zinc oxide eugenol compound were analyzed using XRD. FT-IR Spectrophotometer and FT-NMR Spectrometer. The results were as follows: 1. The compound made from interaction between calcium hydroxide and zinc oxide eugenol was as follows : 2. Calcium hydroxide was shown to make chemical bond (ionic bond) with eugenol. 3. Since bonding between $Ca^{2+}$ and eugenol is simple ionic nature, under water existence, calcium hydroxide-eugenol compound may be ionized easily and its physical property be deteriorated.

• Macromolecular Research
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• v.17 no.10
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• pp.776-784
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• 2009

N,N-dimethyldodecylamine (tertiary amine)-modified MMT (DDA-MMT) was prepared as an organically modified layered silicate (OLS), after which styrene-butadiene rubber (SBR) nanocomposites reinforced with the OLS were manufactured via the latex method. The layer distance of the OLS and the morphology of the nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). By increasing the amount of N,N-dimethyldodecylamine (DDA) up to 2.5 g, the maximum values of torque, tensile strength and wear resistance of the SBR nanocomposites were increased due to the increased dispersion of the silicate layers in the rubber matrix and the increased crosslinking of the SBR nanocomposites by DDA itself. When SBR nanocomposites were manufactured by using the ternary filler system (carbon black/silica/OLS) to improve their dynamic properties as a tire tread compound, the tan $\delta$(at $0^{\circ}C$ and $60^{\circ}C$) property of the compounds was improved by using metal stearates instead of stearic acid. The mechanical properties and wear resistance were increased by direct substitution of calcium stearate for stearic acid because the filler-rubber interaction was increased by the strong ionic effect between the calcium cation and silicates with anionic surface. However, as the amount of calcium stearate was further increased above 0.5 phr, the mechanical properties and wear resistance were degraded due to the lubrication effect of the excessive amount of calcium stearate. Consequently, the SBR/organoclay nanocomposites that used carbon black, silica, and organoclay as their ternary filler system showed excellent dynamic properties, mechanical properties and wear resistance as a tire tread compound for passenger cars when 0.5 phr of calcium stearate was substituted for the conventionally used stearic acid.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.139-139
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• 2010

LSM is widely used as a cathode material in SOFC, because of its high electrochemical activity, good stability and compatibility with YSZ electrolyte at high temperature. However, LSM in traditional cathode materials will not generate a satisfactory performance at intermediate temperature. In order to reduce the polarization resistance of cell with the operating temperature of SOFC system, the cathode material of LSCF is one of the most suitable electrode materials because of its high mixed ionic and electronic conductivity. In this report, cathode material, $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ powder for intermediate temperature SOFC was synthesized by Pechini method using the starting materials such as nitrate of La, Sr, Co and Fe including ethylene glycol, etc. As a result, the synthesized powder that calcined above $700^{\circ}C$ exhibits successfully perovskite structure, indicating phase-pure of LSCF. Moreover, the particle size, surface area, crystal structure and morphology of the synthesized oxide powders were characterized by SEM, XRD, and BET, etc. In order to evaluate the electrochemical performance for the synthesized powder, slury mixture using the synthesized cathode material was coated by screen-printing process on the anode-supported electrolyte which was prepared by a tape casting method and co-sintering. Finally, electrochemical studies of the SOFC unit cell, including measurements such as power density and impedance, were performed.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.8-12
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• 1999

$\textrm{WO}_3$ semiconductive film, which is known to have a sensitivity on $\textrm{NO}_X$ gas was prepared on 8YSZ (8% Yttria stabilized $\textrm{ZrO}_2$) ionic conductor substrate that has oxygen ion pumping effect. Microstructure and electrical properity, especially $\textrm{NO}_X$ sensitivity as a function of DC voltage applied to 8YSZ substrate was examined. When the $\textrm{WO}_3$ film was annealed, it showed amorphous structure, while crystallization was occurred at $600^{\circ}$C revealing orthorhombic phase of $\textrm{WO}_3$. As the annealing temperature increases, (111) and (001) peaks of $\textrm{WO}_3$ film was enhanced. At $400^{\circ}C$ when DC voltage was applied, comparing with no DC bias, more stable and large response characteristics was showed, and the best sensitivity was observed at 2V. Recovery characteristics of NO gas was much better that that of $\textrm{NO}_2$ gas.

• Journal of the Korean Electrochemical Society
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• v.19 no.4
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• pp.123-128
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• 2016

In this study, poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP)-based gel polymer electrolyte incorporating nano-size $Al_2O_3$ ceramic particle was prepared by electrospinning. The gel polymer electrolyte (GPE) incorporated with $Al_2O_3$ ceramic particle showed higher ionic conductivity of $9.5{\times}10^{-2}Scm^{-1}$ than pure PVdF-HFP GPE without ceramic particle and improved the electrochemical stability up to 5.2 V. The GPEs were assembled with $LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ (NMC) cathode for electrochemical test. The GPE batteries at 0.1 C-rate delivered $168.2mAh\;g^{-1}$ for pure GPE and $189.6mAh\;g^{-1}$ for hybrid GPE, respectively. Therefore, the incorporation of high dielectric constant ceramic particle will be good strategy to enhance the stability and electrochemical properties of lithium ion gel polymer batteries.

• Advances in environmental research
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• v.7 no.2
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• pp.139-159
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• 2018

Green Leaf Volatiles (GLVs) is a class of biogenically emitted oxygenated hydrocarbons that have been identified as a potential source of Secondary Organic Aerosols (SOA) via aqueous oxidation. The physico-chemical properties of GLVs are vital to understanding their fate and transport in the atmosphere via fog processing, but few experimental data are available. We studied the aqueous solubility, 1-octanol/water partition coefficient, and Henry's law constant ($K_H$) of five GLVs at $25^{\circ}C$: methyl jasmonate, methyl salicylate, 2-methyl-3-buten-2-ol, cis-3-hexen-1-ol, and cis-3-hexenyl acetate. Henry's law constant was also measured at temperatures and ionic strengths typical of fog. Experimental values are compared to scarcely-available literature values, as well as estimations using group and bond contribution methods, property-specific correlations and molecular dynamics simulations. From these values, the partition coefficients to the air-water interface were also calculated. The large Henry's law constant of methyl jasmonate ($8091{\pm}1121M{\cdot}atm^{-1}$) made it the most significant GLV for aqueous phase photochemistry. The HENRYWIN program's bond contribution method from the Estimation Programs Interface Suite (EPI Suite) produced the best estimate of the Henry's constant for GLVs. Estimations of 1-octanol/water partition coefficient and solubility are best when correlating an experimental value of one to find the other. Finally, the scavenging efficiency was calculated for each GLV indicating aqueous phase processing will be most important for methyl jasmonate.