• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1060-1062
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• 1999

Pulsed Nd:YAG laser is used widely for materials processing and instrumentation. It is very important to control the laser energy density in materials processing by a pulsed Nd:YAG laser. A pulse repetition rate and a pulse width are regarded as the most dominant factors to control the energy density of laser beam. In this study, the alternating charge-discharge system was designed to adjust a pulse repetition rate. And the parallel mesh is added to increase laser output power. This system is controlled by one chip microprocessor and allows to replace an expensive condenser for high frequency to a cheap condenser for low frequency. In addition, we have investigated the current pulse shape of flashlamp and the operating characteristics of a pulsed Nd:YAG laser. As a result, it is found that the laser output of the power supply using the parallel mesh and the alternating charge-discharge system is not less than that of typical power supply. As the pulse repetition rate rises from 10pps to 110pps by the step of 20pps at 1000V and 1200V, it is found that the laser efficiency decreases but the laser output power increases about 5W at each step.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2204-2206
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• 1999

Pulsed Nd:YAC laser is used widely for materials processing and instrumentation. It is very important to control the laser energy density in materials processing by a pulsed Nd:YAG laser. A pulse repetition rate and a pulse width are regarded as the most dominant factors to control the energy density of laser beam. In this study, the alternating charge-discharge system was designed to adjust a pulse repetition rate. This system is controlled by one chip microprocessor and allows to replace an expensive condenser for high frequency to a cheap condenser for low frequency. In addition. we have investigated the current pulse shape of flashlamp and the operating characteristics of a pulsed Nd:YAG laser. As a result, it is found that the laser output of the power supply using the alternating charge-discharge system is not less than that of typical power supply. As the pulse repetition rate rises from 30pps to 120pps by the step of 30pps at 1200V, it is found that the laser efficiency decreases but the laser output power increases about 6W at each step.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1462-1464
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• 1997

The spinel $LiMn_2O_4$ has been synthesized by solid-state reaction. $LiMn_2O_4$ which includes 3 mix $Li_2CO_3$ or $LiNO_3$ and $MnO_2$ prepared by Prelim heating at $350^{\circ}C$ for 24hr. $LiMn_2O_4$ fired at temp range from $600^{\circ}C$ to $800^{\circ}C$ for 48hr. The structure a electrochemical characteristics of spinel $LiMn_2O_2$ wh fabricated by changing sintering condition from st materials are investigated. The spinel $LiMn_2O_4$ prepared by the mixture of L CMD at $800^{\circ}C$ for 48hr showed an initial charge ca of 146mAh/g. The spinel $LiMn_2O_4$ prepared by the m of $LiNO_3$/CMD at $600{\sim}800^{\circ}C$ for 48hr stabilized ch discharge capacity after 50th cycles.

• Journal of Sensor Science and Technology
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• v.5 no.6
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• pp.35-42
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• 1996

In this paper, a development of model based battery SOC indicator is described. The proposed method is independent upon initial SOC, is reliable on the sudden change of load, and could estimate the available driving distance. The mathematical model of battery which has relation of the current, voltage and SOC estimates the SOC by least square estimation to minimize the error between measured voltage and estimated voltage. For experiment, the charging and discharging system using computer was designed to acquire the current and voltage data for model. The feasibility in electric vehicle was confirmed by variable load testing using the developed SOC indicator by stand-alone type microcontroller.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.275-275
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• 2007

Two sorts of electrode composed of Sulpur/CNT/PVDF and Silver/CNT/PVDF were prepared by in situ chemical method and their electrochemical performance were evaluated by using cyclic voltammetry, impedance measurement and constant-current charge/discharge cycling technique. Also, composite electrodes were characterized by FE-SEM and BET. Raw materials such as CNT/Silver and CNT/Sulfur were mixed in ethanol, dried. These mixed materials were heated at 900 and $320^{\circ}C$ for 2hr, respectively in order to enhance contact among CNT electrodes. Electric double layer capacitor cells were fabricated using these mixed powder with polymer of PVDF. For the charging and discharging characteristics measured at scan rate of 1 mA/s, Supercapacitor of Sulphur-CNT-PVDF electrode showed a better performance than that of Ag-CNT-PVDF, which seems to be related with lower contact resistance of Sulphur-CNT-PVDF electrode.

• Polymer(Korea)
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• v.35 no.6
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• pp.586-592
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• 2011

In this study, we synthesized vinylbenzyl chloride-co-styrene-co hydroxyethyl acrylate (VBC-co-St-co-HEA) copolymer that can be applied to redox the flow battery process. The anion exchange membrane was prepared by the amination and crosslinking of VBC-co-St-co-HEA copolymer. The chemical structure and thermal properties of VBC-co-St-co-HEA copolymer and aminated VBC-co-St-co-HEA(AVSH) membrane were characterized by FTIR, $^1H$ NMR, TGA, and GPC analysis. The membrane properties such as ion exchange capacity(IEC), electrical resistance, ion conductivity and efficiency of all-vanadium redox flow battery were measured. The IEC value, electrical resistance, and ion conductivity were 1.17 meq/g, $1.9{\Omega}{\cdot}cm^2$, 0.009 S/cm, respectively. The charge-discharge efficiency, voltage efficiency and energy efficiency from all-vanadium redox flow battery test were 99.5, 72.6 and 72.1%, respectively.

• Composites Research
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• v.37 no.3
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• pp.190-196
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• 2024

The bipolar plate is a crucial element of the vanadium redox flow battery (VRFB) as it serves as both the electrical conduit and the structural support for the cell within the VRFB stack. Although, the graphite material is primarily used for the bipolar plate due to its excellent electrical conductivity, a significant limitation of performance of the VRFB is present due to high interfacial contact resistance (ICR) arises between the electrode and bipolar plate in the cell stack. This study aims to develop an integrated electrode-bipolar plate assembly that will address the limitations of the ICR. The integrated assembly was constructed using a single carbon felt with thermoplastic and thermoset polymers utilizing hot press method. Experimental results verify that the bipolar plate assembly exhibits reduced area specific resistance (ASR) due to the continuous electrical path. Additionally, from the charge/discharge cell test results, the integrated assembly shows improved cell performance. Therefore, the developed integrated electrode-bipolar plate assembly can serve as a substitute for the conventional bipolar plate and electrode assembly.

• Korean Chemical Engineering Research
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• v.45 no.2
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• pp.178-182
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• 2007

Non-aqueous supercapacitors by using activated C and $LiMn_2O_4$ as an active material in a positive electrode were prepared and characterized. From the cyclic voltammetry and AC impedance analysis, the capacitive effect by electric double layer of activated carbon and the faradic effect by intercalation/deintercalation of $Li^+$ ion were observed. Increasing the ratio of $LiMn_2O_4$, specific capacitances and energy densities of supercapacitor were increased. At the ratio of 0.86:0.14 ($LiMn_2O_4:C$), the maximum specific capacitance of 17.51 Wh/L and energy density of 23.83 F/cc were obtained, which were more than twice of those for a conventional electric double layer capacitor. Even after 1,000 charge/discharge cycle, the supercapacitor by using the electrode containing 14% of activated carbon and 86% of $LiMn_2O_4$ showed 60% better specific capacitance and energy density than that by using the electrode containing 100% activated carbon.

• Journal of the Korean Electrochemical Society
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• v.17 no.2
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• pp.86-93
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• 2014

Mesoporous tin oxide (meso-$SnO_2$) with 5 nm mesopore and well-aligned $SnO_2$ nanowire-bundles with 5~7 nm diameters were prepared by template synthesis method. In addition to meso-$SnO_2$, meso-$SnO_2$/$SiO_2$, which has almost the same structure as meso-$SnO_2$ including $SiO_2$ used as the template were prepared by the modification of template synthesis. X-ray diffraction, N2 adsorption-desorption isotherms, transmission electron microscopy observed structures of meso-$SnO_2$ and meso-$SnO_2$/$SiO_2$. Although the meso-$SnO_2$/$SiO_2$ showed some positive evidences to suppress the volume change of meso-$SnO_2$ through cyclic voltammogram, electrochemical impedance spectroscopy, and voltage profiles during cycling, its cycle life was not improved highly to address modified structural effects. Thus, further study might be done to control the nanostructure of meso-$SnO_2$/$SiO_2$ for enhanced cycle performance.

• Journal of the Korean Electrochemical Society
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• v.4 no.4
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• pp.139-145
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• 2001

Various compositions of iron oxide based materials as a cathode of lithium secondary battery have been fabricated and tested with electrochemical method. A layered form of $LiFeO_2$ was synthesized by mixing and heating the initial materials of $FeCl_3\;6H_2O,\;LiOH$ and NaOH at low temperature. The effect of changing the precursors composition was investigated. As a result, when increasing the additive amount of NaOH, the capacity of the electrode is decreased but the performance and declining rate of capacity became smaller. $LiFeO_2$ synthesized with the weight ratio of $NaOH/FeCl_3/LiOH,\;2/1/7$ showed the largest capacity, but the discharging efficiency was sharply decreased after 30 cycles. Charge-discharge tests of lithium cells with $LiFeO_2$ cathode having the layer structure were performed. This cell showed the reversibility in the range of 1.5-4.5V of cell voltage. By using CPR method, chemical diffusion coefficients were measured in 1M $LiPF_6/EC/DEC$ solution. The value of chemical diffusion coefficient decreased with increasing the lithium content x, In 0.5$10^{-11}^cm^2/s$.