• Clean Technology
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• v.14 no.3
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• pp.171-175
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• 2008

The effect of the addition of $Al^{3+}$ dopant on the electrochemical characteristics of $Li_{4}Ti_{5}O_{12}$ was investigated. $Li_{4}Ti_{5}O_{12}$ is known as a 2ero-strain material, and $Li_{3.95}Al_{0.15}Ti_{4.9}O_{12}$ has been manufactured by solid-state reaction with high energy ball milling (HEBM). The samples were heated at 800, 900 and $1000^{\circ}C$ in electric furnace. The structural and surface structures were measured by XRD (X-ray diffraction) and SEM (scanning electron microscopy). Cut-off voltage of charge/discharge cycles was $1.0{\sim}3.0 V$ to investigate reversible capacity, cycle stability and plateau voltage. The reversible capacity of $Li_{3.95}Al_{0.15}Ti_{4.9}O_{12}$ was 138 mAh/g.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.1
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• pp.1-8
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• 1999

In recent years, concern has been raised about the technique of controlling electrical breakdown by using laser in many fields. Especially, laser has attracted much attention in the Electro-Discharge Machining(EDM) because of its many rrents. 1berefore, this research has been perfonred to obtain fundarrental data for the discharge guide technology by a pulsed Nd:YAG laser which can be awJied to discharge processing machining. 1be experilnnts of laser-guided de discharge have been carried out at low air pressure ranging from 0.2 to 20 torr. The minimum laser-guided de discharge voltage $V_{G.min}$ at the given pressures P and distances d between an anode and a cathode was rreasured It is found that $V_{G.min}$ is much lower than the natural discharge voltage $V_{ND}$, and the values of VGrrin and $V_{ND}$ as a function of P.d has a similar tendency. The laser output energy $E_{out}$ decreases with input pulse duration $t_p$ increasing, and the rrore the value of $t_p$ increases, the higher that of V$V_{G.min}$ is obtained because the number of photons N decreases with $t_p$ increasing. In addition, the laser-guided de discharge range and the discharge guide characteristics as laser outpIt $E_{out}$ was investigated.igated.

• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.69-79
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• 2016

Lithium ion battery with high energy density is expanding its application area to electric automobile and electricity storage field beyond existing portable electric devices. Such expansion of an application field is demanding higher characteristic and stable long life characteristic of an anode material, the natural graphite that became commercialized in lithium ion battery. This thesis produced cathode by using natural graphite anode material, analyzed creation of the cathode SEI film created due to initial reaction by using electrolyte additives, VC (vinylene carbonate), VEC (vinyl ethylene carbonate), and FEC (fluoroethylene carbonate), and considered correlation with the accompanying electrochemical transformation. This study compared and analyzed the SEI film variation of natural graphite cathode according to the electrolyte additive with SEI that is formed at the time of initial filling and cathode of $60^{\circ}C$ life characteristic. At the time of initial filling, the profile showed changes due to the SEI formation, and SEI was formed in No-Additive in approximately 0.9 V through EVS, but for VC, VEC, and FEC, the formation reaction was created above 1 V. In $60^{\circ}C$ lifespan characteristic evaluation, the initial efficiency was highest in No-Additive and showed high contents percentage, but when cycle was progressed, the capacity maintenance rate decreased more than VC and FEC as the capacity and efficiency at the time of filling decreased, and VEC showed lowest performance in efficiency and capacity maintenance rate. Changes of SEI could not be verified through SEM, but it was identified that as the cycle of SEI ingredients was progressed through FT-IR, ingredients of Alkyl carbonate ($RCO_2Li$) affiliation of the $2850-2900cm^{-1}$ was maintained more solidly and the resistance increased as cycle was progressed through EIS, and specially, it was identified that the resistance due to No-Additive and SEI of VEC became very significant. Continuous loss of additives was verified through GC-MS, and the loss of additives from partial decomposition and remodeling of SEI formed the non-uniform surface of SEI and is judged to be the increase of resistance.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.3
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• pp.209-213
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• 2019

Recently, demand for high energy density and long cycling stability of energy storage system has increased for application using with frequency regulation (F/R) in power grid. Supercapacitor have long lifetime and high charge and discharge rate, it is very adaptable to apply a frequency regulation in power grid. Supercapacitor can complement batteries to reduce the size and installation of batteries. Because their utilization in a system can potentially eliminate the need for short-term frequent replacement as required by batteries, hence, saving the resources invested in the upkeep of the whole system or extension of lifecycle of batteries in the long run of power grid. However, low energy density in supercapacitor is critical weakness to utilization for huge energy storage system of power grid. So, it is still far from being able to replace batteries and struggle in meeting the demand for a high energy density. But, today, LIC (Lithium Ion Capacitor) considered as an attractive structure to improve energy density much more than EDLC (Electric double layer capacitor) because LIC has high voltage range up to 3.8 V. But, many aspects of the electrochemical performance of LIC still need to be examined closely in order to apply for commercial use. In this study, in order to improve the capacitance of LIC related with energy density, we designed new method of pre-doping in anode electrode. The electrode in cathode were fabricated in dry room which has a relative humidity under 0.1% and constant electrode thickness over $100{\mu}m$ was manufactured for stable mechanical strength and anode doping. To minimize of contact resistance, fabricated electrode was conducted hot compression process from room temperature to $65^{\circ}C$. We designed various pre-doping method for LIC structure and analyzing the doping mechanism issues. Finally, we suggest new pre-doping method to improve the capacitance and electrochemical stability for LIC.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.183-187
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• 2006

The choice of solvents for electrolytes solutions is very important to improve the characteristics of charge/discharge in the Li-ion battery system. Such solvent systems have been widely investigated as electrolytes for Li-ion batteries. In this paper, the electrochemical properties of the solid electrolyte interphase film formed on carbon anode surface and the solvent decomposition voltage in 1 M LiPF6/EC:MA(x:y) electrolyte solutions prepared from the various mixing volume ratios are investigated by chronopotentiometry, cyclic voltammetry, and impedance spectroscopy. As a result, the solvent decomposition voltages are varied with the ionic conductivity of the electrolyte. Electrochemical properties of the passivation film were different, which are dependent on the mixture ratio of the solvents. Therefore, the most appropriate mixing ratio of EC and MA as a solvent in 1 M $LiPF_6/(EC+MA)$ system for Li-ion battery is approximately 1:3 (EC:MA, volume ratio).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.33-35
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• 2008

We have fabricated and evaluated new high efficiency green light emitting phosphorescent devices with an emission layer of $[TCTA_{1/3}TAZ_{2/3}/TAZ]:Ir(ppy)_3$. The whole experimental devices have the basic structure of $2-TNATA(500 {\AA})/NPB(300{\AA})/EML(300{\AA})/BCP(50{\AA})/SFC137(500{\AA})$ between anode and cathode. We have also fabricated conventional phosphorescent devices with emission layers of $(TCTA_{1/3}TAZ_{2/3}):Ir(ppy)_3$ and $(TCTA/TAZ):Ir(ppy)_3$ and compared their electroluminescence characteristics with those of the device with an emission layer of $(TCTA/TCTA_{1/3}TAZ_{2/3}/TAZ):Ir(ppy)_3$. The current density(J), luminance(L), and current efficiency($\eta$) of the device with an emission layer of $(80{\AA}-TCTA/90{\AA}-TCTA_{1/3}TAZ_{2/3}/130{\AA}-TAZ):10%-Ir(ppy)_3$ were 95 $mA/cm^2$, 25000 $cd/m^2$, and 27 cd/A at an applied voltage of 10V, respectively. The maximum current efficiency was 52 cd/A under the luminance of 400 $cd/m^2$. The peak wavelength and FWHM(full width at half maximum) in the electroluminescence spectral were 513nm and 65nm, respectively. The color coordinate was (0.30, 0.62) on the CIE (Commission Internationale de l'Eclairage) chart. Under the luminance of 15000 $cd/m^2$, the current efficiency of the device with an emission layer of $(80{\AA}-TCTA/90{\AA}-TCTA_{1/3}TAZ_{2/3}/130{\AA}-TAZ):10%-Ir(ppy)_3$ was 34 cd/A, which has been improved 1.7 times and 1.4 limes compared to those of the devices with emission layers of $(300{\AA}-TCTA_{1/3}TAZ_{2/3}): 10%-Ir(ppy)_3$ and $(100{\AA}-TCTA/200{\AA}-TAZ):10%-Ir(ppy)_3$, respectively.

• Analytical Science and Technology
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• v.9 no.3
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• pp.262-269
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• 1996

The muiltiwire proportional counter for the measurement of low-level and environmental $\alpha$ particles emitting nuclides was developed. External dimension of the devloped multiwire proportional counter is $350{\times}290{\times}30mm$ and the sensitivity area is $250{\times}200mm$. The wall material of the detector was selected the stainless steel to prevent the deformation by external impact and to obtain minimum background. The anode and cathode wires were used the stainless steel material of diameter $50{\mu}m$. The spacing of each wires are 10.0mm, 5.0mm and the numbers of total wire are 21, 42 lines, respectively. The multiwire proportional counter was designed that the measurement source is placed within the detector to prevent the wall absorption effect and the efficiency variation by various source heights. The characteristics of the developed detector have been investigated to obtain the plateau, operating voltage, background, counting efficiency, position sensitivity and energy resolution etc. For the $^{241}Am$ nuclide, the calculated LLD(Lower Limit of Detection) is 5.0mBq/L which is lower than 40mBq/L of recommended LLD value by ISO(International Organization for Standardization).

• Journal of Radiation Protection and Research
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• v.8 no.2
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• pp.15-35
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• 1983

High voltage paper-electrophoresis of fission products from 24 hour neutron-irradiated and 150 days-decayed 90% highly enriched uranyl nitrate solution has been carried out by using the specially designed migration apparatus. The separation of Zr-95 and Nb-95 from the other fission products is possible under the migration condition of 0.1 $M-HClO_4$ (pH=0.85), 0.05 M-HCl+0.09M-KCl (pH=0.9), 0.1M-HCl (pH=1.1) and 0.01 M-HCl (pH=2.0). Zr-95 and Nb-95 are separated out at+1cm from the fiducial point. The separation of Zr-95 and Nb-95 from each other is possible under the migration condition of 0.1 $M-HClO_4$, 0.05 M-HCl+0.09 M-KCl, 0.1 M-HCl and 0.1 M-HAc+0.1 M-NaAc (pH=4.68) together with 2% ammonium oxalate. Nb-95 is separated out at $-6{\sim}-7cm$ from the fiducial point and Zr-95 at $+1{\sim}-lcm$. The separation of Ru-103 from the other fission products is possible under the migration condition of 0.025 $M-Na_2CO_3+0.025\;M-NaHCO_3$ (pH=10.0), 0.01M-$Na_3PO_4$ (pH=11.7) and 0.1 M-NaOH (pH=13.2). Ru-103 migrates towards the anode -6cm, -4cm and -3cm, respectively.

• Journal of the Korean Electrochemical Society
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• v.15 no.1
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• pp.27-34
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• 2012

$Li_3V_2(PO_4)_3$/carbon composite materials are synthesized from a sucrose-containing precursor. Amorphous $Li_3V_2(PO_4)_3/C$ (a-LVP/C) and crystalline $Li_3V_2(PO_4)_3/C$ (c-LVP/C) are obtained by calcining at $600^{\circ}C$ and $800^{\circ}C$, respectrively, and electrochemical performance as the negative electrode for lithium secondary batteries is compared for two samples. The a-LVP electrode shows much larger reversible capacity than c-LVP, which is ascribed to the spatial $Li^+$ channels and flexible structure of amorphous material. In addition, this electrode shows an excellent rate capability, which can be accounted for by the facilitated $Li^+$ diffusion through the defect sites. The sloping voltage profile is another advantageous feature for easy SOC (state of charge) estimation.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.59-64
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• 2008

In this paper, white polymer light emitting diodes(WPLEDs) were fabricated and investigated the electrical and optical properties for the prepared devices. ITO(indium tin oxide) and PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(styrene sulfolnate)] as anode and hole injection materials, PFO [poly(9,9-dioctylfluorene)] and MEH-PPV [poly(2-methoxy-5(2-ethylhe xoxy)-1,4-phenylenevinyle)] were used as the light emitting host and guest materials, respectively. The LiF(lithium flouride) and Al(aluminum) were used electron injection materials and cathode materials. Finally, the WPLED with structure of ITO/PEDOT:PSS/PFO:MEH-PPV/LiF/Al was fabricated. The prepared WPLED showed white emission with CIE coordinates of (x=0.36, y=0.35) at the applied voltage of 9V. The maximum current density and luminance were about $740mA/cm^2\;and\;900cd/m^2$ at 13V, respectively. And the maximum current efficiency was 0.37 cd/A at $200cd/m^2$ in luminance.