• Membrane Journal
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• v.32 no.1
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• pp.43-49
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• 2022

Solid-state supercapacitors with high safety and robust mechanical properties are attracting global attention as next-generation energy storage devices. As an electrode of a supercapacitor, an economical carbon-based electrode is widely used. However, when an aqueous electrolyte is introduced, the charge transfer resistance increases because the interfacial contact between the hydrophobic electrode surface and aqueous electrolyte is not good. In this regard, we propose a method to obtain higher electrochemical performance based on improved interfacial properties by treating the electrode surface with oxygen plasma. The surface hydrophilization induced by the enriched oxygen functionalities was confirmed by the contact angle measurement. As a result, the degree of hydrophilization was easily adjusted by controlling the power and duration of the oxygen plasma treatment. As the electrolyte of the supercapacitor, PVA/H₃PO₄, which is a typical solid-state aqueous electrolyte, was used. Free-standing membranes of PVA/H₃PO₄ electrolyte were prepared and then pressed onto the electrode. The optimal condition was to perform oxygen plasma treatment for 5 seconds with a low power of 15 W, and the energy density of the supercapacitor increased by about 8%.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1153-1159
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• 2013

A novel solid-contact indium(III)-selective sensor based on bis-(1H-benzimidazole-5-methoxy-2-[(4-methoxy-3, 5-dimethyl-1-pyridinyl) 2-methyl]) thiosulfinate, known as an omeprazole dimer (OD) and a neutral ionophore, was constructed, and its performance characteristics were evaluated. The sensor was prepared by applying a membrane cocktail containing the ionophore to a graphite rod pre-coated with polyethylene dioxythiophene (PEDOT) conducting polymer as the ion-to-electron transducer. The membrane contained 3.6% OD, 2.3% oleic acid (OA) and 62% dioctyl phthalate (DOP) as the solvent mediator in PVC and produced a good potentiometric response to indium(III) ions with a Nernstian slope of 19.09 mV/decade. The constructed sensor possessed a linear concentration range from $3{\times}10^{-7}$ to $1{\times}10^{-2}$ M and a lower detection limit (LDL) of $1{\times}10^{-7}$ M indium(III) over a pH range of 4.0-7.0. It also displayed a fast response time and good selectivity for indium(III) over several other ions. The sensor can be used for longer than three months without any considerable divergence in potential. The sensor was utilized for direct and flow injection potentiometric (FIP) determination of indium(III) in alloys. The parameters that control the flow injection method were optimized. Indium(III) was quantitatively recovered, and the results agreed with those obtained using atomic absorption spectrophotometry, as confirmed by the f and t values. The sensor was also utilized as an indicator electrode for the potentiometric titration of fluoride in the presence of chloride, bromide, iodide and thiocyanate ions using indium(III) nitrate as the titrant.

• Journal of the Korean Ceramic Society
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• v.36 no.9
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• pp.982-990
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• 1999

YSZ/LSM composite cathode was fabricated by dip-coating of YSZ sol on the internal pore surface of a LSM cathode followed by sintering at low temperature (800-100$0^{\circ}C$) The YSZ coating significantly increased the TPB(Triple Phase Boundary) where the gas the electrode and the electrolyte were in contact with each other. Sinter the formation of resistive materials such as La2Zr2O7 or SrZrO3 was prevented due to the low processing temperature and TPB was increased due to the YSZ film coating the electrode resistance (Rel) was reduced about 100 times compared to non-modified cathode. From the analysis of a.c impedance it was shown that microstructural change of the cathode caused by YSZ film coating affected the oxygen reduction reaction. In the case of non-modified cathode the RDS (rate determining step) was electrode reactions rather than mass transfer or the oxygen gas diffusion in the experimental conditions employed in this study ($600^{\circ}C$-100$0^{\circ}C$ and 0,01-1 atm of Po2) for the YSZ film coated cathode however the RDS involved the oxygen diffusion through micropores of YSZ film at high temperature of 950-100$0^{\circ}C$ and low oxygen partial pressure of 0.01-0.03 atm.

• Korean Journal of Materials Research
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• v.13 no.3
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• pp.160-168
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• 2003

The co-firing processes for the supported type planar solid oxide fuel cell were investigated. A flat cell of $7.7${\times}$10.8\textrm{cm}^2$ was fabricated successfully by the co-firing process, in which green films were co-sintered in the forms of two layers of anode/electrolyte or of three layers of anode/electrolyte/cathode with gas distributor. A co-fired cell of two layers yielded a power of 200 ㎽/$\textrm{cm}^2$ at 608 ㎷. Its performance loss was mainly due to iR drop in the anodic gas distributor, which was attributed to poor contact between anodic gas distributor and current collector. The performance in the co-fired cell of three layers was much lower than that of two layers, which resulted from the large iR drop and activation overvoltage at the cathodic side. In the co-fired cell of two layers, the impedance analysis indicated that the performance decay during cell operation is due to both anode overvoltage and iR drop at anode side. Also the electrode reaction of the co-fired two layers' cell is considered to be controlled by activation overvoltage within the low current of 50 ㎃.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.568-573
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• 2016

We investigated the charging characteristics of a conducting solid sphere (glassy carbon sphere) comparing with that of a water droplet and check the applicability of the perfect conductor theory. For the systematic research, sphere size, applied voltages, viscosity of the medium were changed and the results were compared with that of corresponding water droplets and the perfect conductor theory. Basically, a glassy carbon sphere follows the perfect conductor theory but the charging amount was lower as much as 70~80% of theoretical prediction value due to oil film formed between electrode and a carbon sphere. We hope this result provides basic understandings on the solid sphere contact charging phenomenon and related applications.

• Bulletin of the Korean Chemical Society
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• v.29 no.9
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• pp.1774-1780
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• 2008

New PVC based polymeric membrane electrodes (PME) and coated glassy carbon electrodes (CGCE) based on synthesized Schiff base complexes of Co(III); [Co(Salen)$(PBu_3)_2$]$ClO_4$, [Co($Me_2$Salen)$(PBu_3)_2$]$ClO_4$, [Co(Salen)$(PBu_3)H_2O$]$ClO_4$; as anion carriers for potentiometric determination of $ClO_4\;^-$were studied. The PME and also CGCE electrodes prepared with [Co(Me2Salen)$(PBu_3)_2$]$ClO_4$ showed excellent response characteristics to perchlorate ions. The electrodes exhibited Nernstian responses to $ClO_4\;^-$ ions over a wide concentration range with low detection limits ($1.0 {\times} 10^{-6}\;mol\;L^{-1}$ for PME and $9.0 {\times} 10^{-7}\;mol\;L^{-1}$ for CGCE). The electrodes possess fast response time, satisfactory reproducibility, appropriate lifetime and, most importantly, good selectivity toward $ClO_4\;^-$ relative to a variety of other common inorganic anions. The potentiometric response of the electrodes is independent of the pH in the pH range 2.5-8.5. The proposed sensors were used in potentiometric determination of perchlorate ions in mineral water and urine samples. The interaction of the ionophore with perchlorate ions was shown by UV/Vis spectroscopy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.1
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• pp.98-101
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• 2022

Liquid-based Triboelectric nanogenerator (L-TENG) is one of the alternatives to solid-based Triboelectric nanogenerator (S-TENG) because of the absence of surface damage which can decrease the durability of the generator. However, the L-TENG also has an obvious drawback of significantly lower output than that of S-TENG. This article produces water-sloshing-based electricity generating device (W-ED) with a new design of L-TENG that improves electrical output in portable form. The dual-electrode system, consisting of closed-loop circuit and inner electrode which enables water to contact directly in the bottle, can generate the open-circuit voltage and the short-circuit current of up to 348 V and 5.1 mA, respectively. By investigating the motion of water for each frequency, we propose that W-ED is suitable device for a variety of human motions. We expect that W-ED can be applied in small electrical devices or sensors in daily-use items.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.312-312
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• 2013

GaN based light emitting diodes (LEDs) are important devices that are being used extensively in our daily life. For example, these devices are used in traffic light lamps, outdoor full-color displays and backlight of liquid crystal display panels. To realize high-brightness GaN based LEDs for solid-state lighting applications, the development of p-type ohmic electrodes that have low contact resistivity, high optical transmittance and high refractive index is essential. To this effect, indiumtin oxide (ITO) have been investigated for LEDs. Among the transparent electrodes for LEDs, ITO has been one of the promising electrodes on p-GaN layers owing to its excellent properties in optical, electrical conductivity, substrate adhesion, hardness, and chemical inertness. Sputtering and e-beam evaporation techniques are the most commonly used deposition methods. Commonly, ITO films on p-GaN by sputtering have better transmittance and resistivity than ITO films on p-GaN by e-bam evaporation. However, ITO films on p-GaN by sputtering have higher specific contact resistance, it has been demonstrated that this is due to possible plasma damage on the p-GaN in the sputtering process. In this paper, we have investigated the advanced sputtering using plasma damage-free p-electrode. Prepared the ITO films on the GaN based LEDs by e-beam evaporation, normal sputtering and advanced sputtering. The ITO films on GaN based LEDs by sputtering showed better transmittance and sheets resistance than ITO films on the GaN based LEDs by e-beam evaporation. Finally, fabricated of GaN based LEDs by using advanced sputtering. And compared the electrical properties (measurement by using C-TLM) and structural properties (HR-TEM and FE-SEM) of ITO films on GaN based LEDs produced by e-beam evaporation, normal sputtering and advanced sputtering. As a result, It is expected to form plasma damage free-electrode, and better light output power and break down voltage than LEDs by e-beam evaporation and normal sputter.

• Composites Research
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• v.36 no.3
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• pp.224-229
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• 2023

Due to the increasing demand for wearable devices and miniaturization of various electronic devices, the trend of nanofabrication in IT devices is underway. In order to overcome the limitations of battery size and capacity, there has been a lot of research interest in energy harvesting technology, also known as triboelectric nanogenerator. AAO(Anodic Aluminum oxide) coated with fluoride is a structure that includes an anode layer with high properties in the triboelectric series, an dielectric layer that helps transfer the triboelectrically generated charges to the electrode without loss, and the electrode. For these reasons, AAO has been a lot of research on its application to frictional energy harvesting nanogenerators. In this work, we analyzed the correlation of AAO between the surface morphology and thickness of the insulating layer by utilizing aluminum oxide, which is advantageous for the application of triboelectric nanogenerators, and adjusting the thickness of the insulating layer.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.916-917
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• 2006

Solid Oxide Fuel Cell technology uses powder processes to produce electrodes with residual porosity by partially sintering a mixture of electronically and ionically conducting particles. We model porous fuel cell electrodes with 3D packings of monosized spherical particles. These packings are created by numerical sintering. Each particle-particle contact is characteristic for an ionic, electronic or electrochemical resistance. The numerical packing is then discretized into a resistor network which is solved by using Kirchhoff's current law to evaluate the electrode's electrochemical performance. We investigate in particular percolation effects in functionally graded electrodes as compared to other types of electrodes.