• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.5
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• pp.206-206
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• 2003

It is hard to expect excellent electrical, mechanical and chemical properties from most of the composite materials presently used as insulators due to insufficient wettability property caused by the difference of interfacial properties between the matrix material and the reinforcer. Therefore, various interfacial coupling agents have been developed to improve the interfacial properties of composite materials. But if the wettable coupling agents are used outdoor for a long time, change in quality takes place in the coupling agents themselves, bringing about deterioration of the properties of the composite materials. In this study, glass surface was treated by plasma to examine the effect of dry interface treatment without coupling agent. It was identified that the optimum parameters for the best wettability of the samples at the time of generation of plasma were oxygen atmosphere, 0.1 torr of system pressure, 100 W of discharge power, and 3 minutes of discharge time. Also, the surface resistance rate and dielectric property were improved.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.5
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• pp.206-212
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• 2003

It is hard to expect excellent electrical, mechanical and chemical properties from most of the composite materials presently used as insulators due to insufficient wettability property caused by the difference of interfacial properties between the matrix material and the reinforcer. Therefore, various interfacial coupling agents have been developed to improve the interfacial properties of composite materials. But if the wettable coupling agents are used outdoor for a long time, change in quality takes place in the coupling agents themselves, bringing about deterioration of the properties of the composite materials. In this study, glass surface was treated by plasma to examine the effect of dry interface treatment without coupling agent. It was identified that the optimum parameters for the best wettability of the samples at the time of generation of plasma were oxygen atmosphere, 0.1 torr of system pressure, 100 W of discharge power, and 3 minutes of discharge time. Also, the surface resistance rate and dielectric property were improved.

• Journal of Hydrogen and New Energy
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• v.24 no.2
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• pp.179-185
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• 2013

The behavior of surface film formation was greatly dependent on the speed of potential cycling. In $LiClO_4$ / EC + DEC, cyclic voltammetry results showed that the peaks originated from surface film formation on graphite electrode at the high charge-discharge rate was shifted to the lower potentials as the charge-discharge rate decrease. This indicates that surface films with different morphology and thickness were formed by different charge-discharge rate. Transmission electron microscopy (TEM) results indicated that the properties such as thickness and morphology of the surface film were greatly affected by the charge-discharge rate. Electrochemical impedance spectroscopy (EIS) showed that the resistance of surface film was affected by the speed of potential cycling. In addition, the charge transfer resistance was also dependent on the charge-discharge rate indicating that the charge transfer reaction was affected by the nature of surface film. TEM and EIS results suggested that the chemical property as well as the physical property of the surface film was affected by the charge-discharge rate.

• Korean Journal of Materials Research
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• v.25 no.2
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• pp.100-106
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• 2015

Plasma properties of dielectric barrier discharges (DBDs) at atmospheric pressure were measured and characterized using optical emission spectroscopy. Optical emissions were measured from argon, nitrogen, or air discharges generated at 5-9 kV using 20 kHz power supply. Emissions from nitrogen molecules were markedly measured, irrespective of discharge gases. The intensity of emission peaks was increased with applied voltage and electrode gap. The short wavelength peaks (315.9 nm and 337.1 nm) measured at the middle of DBDs were significantly increased with applied voltage. The optical emission from DBDs decreased with the addition of oxygen gas, which was especially significant in argon discharge. Emission from oxygen molecules cannot be measured from air discharge and argon discharge with 4.8% oxygen. The emission intensity at 337.1 nm and 357.7 nm related with nitrogen molecule was sensitively changed with electrode types and discharge voltages. However, the pattern of argon emission spectrum was nearly the same, irrespective of electrode type, oxygen content, and discharge voltage.

• Journal of Hydrogen and New Energy
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• v.10 no.1
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• pp.49-57
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• 1999

In order to study the effect of high energy ball milling on the $Mg_2Ni+Ni$, $Mg_2Ni+0.5Ni+0.5Al$ powders, we have investigated on the discharge properties, microstructures. The powder size of samples decreased as ball milling time. From the XRD results, the crystal structure of $Mg_2Ni+Ni$ mixed powders were changed to amorphous or nano-structure after 60hr ball milling. The discharge capacities of both $Mg_2Ni+Ni$ and $Mg_2Ni+0.5Ni+0.5Al$ powders increased, with increasing ballmilling time, the maximum capacity(342mAh/g) was shown for the 60 hrs ballmilled $Mg_2Ni+Ni$ sample. The capacity decreased drastically after a few charge-discharge cycles.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.157-159
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• 2000

Vanadate glass in the $Li_2O-P_2O_5-V_2O_5$ system with 60mol% $V_2O_5$ was prepared by melting the bath in pt. crucible followed by quenching on the copper plate. We found that $Li_2O-P_2O_5-V_2O_5$ glass ceramics obtained from nucleation of $Li_2O-P_2O_5-V_2O_5$ glass showed significantly higher capacity and longer cycle life than conventionally made crystalline $LiV_3O_8$. In the present paper, We describe the charge/discharge properties during crystallization process and find the best crystallization condition of $Li_2O-P_2O_5-V_2O_5$ glass as cathode material. The Charge and discharge capacity of $Li_2O-P_2O_5-V_2O_5$ glass was about 220mAh/g for the cell heat-treated at $250^{\circ}C$ for 2.5hr.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05a
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• pp.185-188
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• 2004

A diode structure of field emission lamps based upon carbon-nanotube is studied. The single-walled carbon nanotubes(SWNTs) were produced by arc discharge method. We made the 1-inch diode type flat lamp using CNTs. We applied anode voltage gradually to refine the field emission behavior of emitter in dynamic vacuum system to study the emission current. the brightness and efficiency, etc. The field emission properties was estimated by varying gaps between the cathode and anode, contents of the glass frit. The good luminous efficiency is showed in the gap $900{\mu}m$, $1200{\mu}m$ and contents of the proper glass frit. For the upper conditions, the luminous efficiencies were respectively 23.30, 11.12 1m/W.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.69-75
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• 2008

Discharge capacity of $LiCoO_2$ in preparation by mechanochemical process decreased remarkably over 4.3V. However, Zr coating of $LiCoO_2$ showed very stable electrochemical properties up to 4.5V. Zr coating of $LiCoO_2$ in this experiment showed the discharge capacity of 197 mAh/g at 3.0-4.5V, and it maintained 96% of the initial discharge capacity after 50 cycle of charge/discharge.

• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3682-3686
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• 2011

The electrochemical properties of lithium-sulfur batteries with binary electrolytes based on DME and DOL, TEGDME and DOL mixed solvent containing $LiClO_4$, LiTFSI, and LiTF salts were investigated. The ionic conductivity of 1M LiTFSI and $LiClO_4$ electrolytes based on TEGDME and DOL increased as the volume ratio of DOL solvent increased, because DOL effectively reduces the viscosity of the above electrolytes medium under the same salts concentration. The first discharge capacity of lithium-sulfur batteries in the DME and DOL-based electrolyte followed this order: LiTFSI (1,000 mAh/g) > LiTF (850 mAh/g) > $LiClO_4$ (750 mAh/g). In case of the electrolyte based on TEGDME and DOL, the first discharge capacity of batteries followed this order: $LiClO_4$ (1,030 mAh/g) > LiTF (770 mAh/g) > LiTFSI (750 mAh/g). The cyclic efficiency of lithium-sulfur batteries at 1M $LiClO_4$ electrolytes is higher than that of batteries at other lithium salts-based electrolytes. Lithium-sulfur battery showed discharge capacity of 550 mAh/g until 20 cycles at all electrolytes based on DME and DOL solvent. By contrast, the discharge capacity of batteries was about 450 mAh/g at 1M LiTFSI and LiTF electrolytes based on TEGDME and DOL solvent after 20 cycles.

• Transactions on Electrical and Electronic Materials
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• v.9 no.5
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• pp.186-192
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• 2008

Cross linked polyethylene (XLPE) insulators are used as insulation in ultra-high voltage electric power cables. This study investigated the electrical properties of XLPE at different temperatures. The electrical properties of the changing tree phenomenon was examined as a function of temperature applied to the electrical conductors by measuring the partial discharge at $25^{\circ}C$ to $80^{\circ}C$ and applied voltages to the electrodes ranging from 1 kV to 40 kV. The activity of the partial discharge was examined at various temperatures using the K-means distribution. The results revealed the specimen at $80^{\circ}C$ to have the lowest inception voltage and breakdown voltage. In addition, the core of clusters was moved $0^{\circ}$ and $180^{\circ}$ at the positive region and $180^{\circ}$ and $360^{\circ}$ in the negative region in the K-means. The distribution of clusters was concentrated on the inception condition and spread out widely at the breakdown voltage.