• Korean Membrane Journal
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• v.11 no.1
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• pp.1-7
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• 2009

This work reports the preparation of proton conductive crosslinked polymer electrolyte membranes by blending poly(vinyl chloride)-g-poly(hydroxyl ethyl acrylate) (PVC-g-PHEA) and poly(vinyl alcohol) (PVA). The PHEA chains of the graft copolymer were crosslinked with PVA using sulfosuccinic acid (SA) via the esterification reaction between -OH of polymer matrix and -COOH of SA. The PVC-g-PHEA graft copolymer was synthesized via atom transfer radical polymerization (ATRP) using direct initiation of the secondary chlorines of PVC backbones. Ion exchange capacity (IEC) continuously increased with increasing concentrations of SA, due to the increasing portion of charged groups in the membrane. However, the water uptake increased up to 20.0 wt% of SA concentration above which it decreased monotonically. The membrane exhibited a maximum proton conductivity of 0.026 S/cm at 20.0 wt% of SA concentration, which is presumably due to competitive effect between the increase of ionic sites and the crosslinking reaction.

• Journal of Electrochemical Science and Technology
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• v.14 no.2
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• pp.194-204
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• 2023

Models based on diffusion-limited aggregation (DLA) have been extensively used to explore the mechanisms of dendritic particle aggregation phenomena. The physical and chemical properties of systems in which DLA aggregates emerge are given in their fractal. In this paper, we present a comprehensive study of the growth of electrodeposited copper dendrites in flat plate electrochemical cells from a fractal perspective. The effects of growth time, applied voltage, copper ion concentration, and electrolyte acidity on the morphology and fractal dimension of deposited copper were examined. 'Phase diagram' set out the variety of electrodeposited copper fractal morphology analysed by metallographic microscopy. The box counting method confirms that the electrodeposited dendritic structures manifestly exhibit fractal character. It was found that with the increase of the voltage and copper ion concentration. The fractal copper size becomes larger and its morphology shifts towards a dendritic structure, with the fractal dimension fluctuating around 1.60-1.70. In addition, the morphology of the deposited copper is significantly affected by the acidity of the electrolyte. The increase in acidity from 0.01 to 1.00 mol/L intensifies the hydrogen precipitation side reactions and the overflow path of hydrogen bubbles affects the fractal growth of copper dendrites.

• Corrosion Science and Technology
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• v.23 no.3
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• pp.215-220
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• 2024

Recently, the demand for Zn-Ni electrogalvanized steel sheets for home appliances and automobiles is increasing. Products should have a thick plating (30 to 40 g/m²) on both side with a thin thickness (≤ 0.8 mm) and the highest surface quality. By a high current density operation, current is concentrated in the edge part of the steel sheet, resulting in large surface dent defects due to dendritic plating. This can lead to a low productivity due to low line speed operation. To solve this problem, this study aimed to identify factors influencing dendritic plating. A cylindrical electroplating device was manufactured. Effects of cut edge shape and thickness of steel plate, current density, temperature, flow rate, electrolyte concentration, and pH on dendrite generation of Zn-Ni electroplating were examined. To investigate effect of edge shape of the steel sheet, the steel sheet was manufactured using three processing methods: shearing, polishing after shearing, and laser. Relative effects thickness and cut edge processing methods of the steel plate, current density, temperature, flow rate, electrolyte concentration, and pH of plating solution on dendrite plating were investigated. To prevent dendrite plating, an edge mask was manufactured and its application effect was investigated.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.36-43
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• 2016

Hydrosilylation reactions of 2.4.6.8-tetrahydro-2.4.6.8-tetramethylcyclotetrasiloxane with allyl butyrate catalyzed by Karstedt's, $H_2PtCl_6$ and Pt/C catalyst were studied and 2.4.6.8-tetra (propyl butyrate)-2.4.6.8-tetramethylcyclotetrasiloxane was obtained. The reaction order, activation energies and rate constants were determined. Ringopening polymerization of 2.4.6.8-tetra (propyl butyrate)-2.4.6.8-tetramethylcyclotetrasiloxane in the presence of $CaF_2$, LiF, KF and anhydrous potassium hydroxide in $60-70^{\circ}C$ temperature range was carried out and methylsiloxane oligomers with regular arrangement of propyl butyrate pendant groups were obtained. The synthesized products were studied by FTIR and NMR spectroscopy. The polysiloxanes were characterized by wide-angle X-ray, gel-permeation chromatography and DSC analyses. Via sol-gel processes of oligomers doped with lithium trifluoromethylsulfonate or lithium bis (trifluoromethylsulfonyl)imide, solid polymer electrolyte membranes were obtained. The dependences of ionic conductivity of obtained polyelectrolytes on temperature and salt concentration were investigated, and it was shown that electric conductivity of the polymer electrolyte membranes at room temperature changed in the range $3.5{\times}10^{-4}{\sim}6.4{\times}10^{-7}S/cm$.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2949-2954
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• 2012

Nano ZnO with an average size of 8 nm was prepared by thermal decomposition of zinc oxalate at $450^{\circ}C$. A series of based composite polymer electrolyte PEO-$LiClO_4$ and nano ZnO as a filler have been synthesized using solution cast technique, with varying the filler ratio systematically. XRD, DSC and FTIR studies have been conducted to investigate the structure and interaction of different groups in the composite polymer electrolyte. Effect of nano ZnO ceramic filler concentration on the structure of composites and their electrical properties (DC-conductivity, AC-conductivity, dielectric constant, dielectric loss and impedance) at different frequencies and temperatures was studied. Melting temperature ($T_m$) of PEO decreased with the addition of both $LiClO_4$ salt and nano ZnO filler due to increasing the amorphous state of polymer. All composite samples showed an ionic conductivity. The maximum room temperature ionic conductivity is found for $(ZnO)_{0.5}(PEO)_{12}(LiClO_4)$ composite sample. All the results are correlated and discussed.

• Journal of the Korean Society of Safety
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• v.14 no.4
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• pp.114-119
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• 1999

When NaOCl was generated and put into sea-water cooling machine in order to overcome the biological hindrances against sea-water cooling machine, it was converted into metallic ion, particularly Ca and Mg, as a hydrate in sea-water and is to stick to electrolyte as a side reaction. This phenomena make the distance between the electrolytes narrow to decrease the flow rate, which induces the local vortex flow which erodes the pole plate. Moreover, this increases the resistance of the electrolyte as well as voltage to decrease the electrolytic efficiency, which has curtailed a chlorine yield and caused a pole plate cut. We are able to overcome these problems by chemical cleaning and intend to extend the life-time of electrolyte and to increase output of the sea-water electrolysis facilities by studying optimal policy regarding chemical cleaning of electrolytic cell. Cleaning time of electrolytic facilities is determined when both increase in electrolytic efficiency and decrease in pole-plate voltage are 10%. At this time as operating current of electrolytic facilities is high, operating time is diminished. Whereas, parameter of end point determination according to cleaning is Mg ionic concentration in solution. When we use Cleaner as a 7wt% HCl, cleaning time is about 80min proper. We are able to maintain pole plate performance by protecting against pole plate cut by means of electrolytic by-product, improve operating rate of facilities, and cut down on maintenance expenditure after acidic cleaning.

• Journal of the Korean Applied Science and Technology
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• v.22 no.2
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• pp.151-156
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• 2005

Many researchers have been focused on polymer electrolyte membrane (PEM) to improve performance of a fuel cell. Sulfonpolyimide with hydrocarbon was synthesized from ODA (4,4-diaminodiphenyl ether), ODADS (4,4-diaminodiphenyl ether-2,2-disulfonic acid), NTDA (1,4,5,8-naphthalenetetracarboxylicdianhydride) and CSA (chlorosulfonic acid). In order to estimate the feasibility as a fuel cell, the performance of sulfonpolyimide was analyzed through a swelling degree, IEC (ion exchange capacity), ion conductivity and TEM (transmission electron microscope). As the results of this performance test, swelling degree, IEC and ion conductivity were 37%, 0.06 meq/g and 0.08 S/cm respectively, when the CSA concentration was 0.4 M. It was thought that sulfonpolyimide could be used as a fuel cell through improvement of electrolyte membrane.

• Journal of the Korean Ceramic Society
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• v.42 no.12 s.283
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• pp.854-859
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• 2005

Performance of micro scale intermediate temperature solid oxide fuel cell system has been successfully evaluated by computer simulation based on macro modeling. Two systems were studied in this work. The one is designed that the ceria-based electrolyte placed between composite electrodes and the other is designed that electrodes alternately placed on the electrolyte. The injected gas was composed of hydrogen and air. The polarization curve was obtained through a series of calculations for ohmic loss, activation loss and concentration loss. The calculation of each loss was based on the solving of mathematical model of multi physical-phenomena such as ion conduction, fluid dynamics and diffusion and convection by Finite Element Method (FEM). The performance characteristics of SOFC were quantitatively investigated for various structural parameters such as distance between electrodes and thickness of electrolyte.

• Journal of Korean Society on Water Environment
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• v.31 no.4
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• pp.360-366
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• 2015

In this study $TiO_2$ nanotube was grown on Ti by anodic oxidation to be used as a photocatalyst. The growth and formation of $TiO_2$ nanotube was monitored during anodization in ethylene glycol electrolyte by changing voltage and composition of electrolyte. Commercially available titanium plate (purity>99.8%, thickness:1mm) Applied voltage and concentration of $NH_4F$ and $H_2O$ were varied to find the optimum condition. Applied voltage is important to make $TiO_2$ nanotube and the electrolyte containing ethylene glycol, 0.2 wt% $NH_4F$ and 2 vol% $H_2O$ was confirmed to be the optimum conditions for the formation and growth of $TiO_2$ nanotubes.

• Proceedings of the Safety Management and Science Conference
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• 2004.05a
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• pp.247-257
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• 2004

Electrodes were fabricated based on activated carbon powder BP-20, conducting agent such as Super P, vapor grown carbon fiber (VGCF) and acetylene black (AB), and the mixed binders of flexible poly(vinylidenefluoridehexafluoropropylene) [P(VdF-co-HFP)] and cross linking dispersion agent of polyvinylpyrrolidone (PVP) to increase mechanical strength. According to impedance measurement of the electrode with the addition of conducting agent, we found that it was possible to charge rapidly by the fast steady-state current convergence due to low equivalent series resistance (AC-ESR, fast charge transfer rate at interface between electrode and electrolyte and low RC time constant. The self-discharge of unit cell showed that diffusion process was controlled by the ion concentration difference of initial electrolyte due to the characteristics of Electric Double Layer Capacitor (EDLC) charged by ion adsorption in the beginning, but this by current leakage through the double-layer at the electrode/electrolyte interface had a minor effect and voltages of curves were remained constant regardless of electrode material. We found that the 2.3V/230F grade EDLC would be applied to industrial safety usage such as uninterrupted power supply (UPS) because of the constant DC-ESR by IR drop regardless of discharge current.