• Journal of Powder Materials
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• v.26 no.4
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• pp.340-344
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• 2019

Due to the rapid development of electricity, electronics, information communication, and biotechnology in recent years, studies are actively being conducted on nanopowders as it is required not only for high strengthening but also for high-function powder with electric, magnetic, and optical properties. Nonetheless, studies on nickel nanopowders are rare. In this study of the synthesis of nickel nanoparticles from $LiNiO_2$ (LNO), which is a cathode active material, we have synthesized the nanosized nickel powder by the liquid reduction process of $NiSO_4$ obtained through the leaching and purification of LNO. Moreover, we have studied the reduction reaction rate according to the temperature change of liquid phase reduction and the change of particle size as a function of NaOH addition amount using hydrazine monohydrate ($N_2H_4{\cdot}H_2O$) and NaOH.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.149-151
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• 2008

This paper presents an architecture for driving multiple parallel cold cathode fluorescent lamps (CCFLs) for back lighting applications. The key to the architecture is a proposed capacitive coupling approach for lamp ignition. This system is consist of a flyback converter, a single inverter to drive multiple lamps and conductive floating reflector. The topology is capable of driving a number of parallel lamps with independent accurate lamp, current regulation and improving cost effectiveness with significant reduction in size and weight, compared to typical high frequency ac ballast. Experimental demonstration results for ten of parallel CCFLs with simultaneous ignition.

• 전기의세계
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• v.30 no.3
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• pp.172-176
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• 1981

The reduction in the breakdown field strength due to electrode surface roughness was calculated by applying the streamer breakdown criterion and the surface roughness factor, and measurements of static breakdown voltage for a gap with an artificial protrusion were made under the uniform field at pressures up to 4 bar in pressurized $SF_{6}$. The effect of polarity of highly stressed electrode on the breakdown field strength was also investigated. The measurements have shown that the measured breakdown levels for a protrusion located on the cathode agree with those calculated and the values measured with an identical anode protrusion are substantially higher and more scattered. This may be explained if it assumed that a high rate of production of initiatory electrons is maintained at the tip of a cathode protrusion by field emission. In practical point of view, the breakdown levels in pressurized $SF_{6}$ can be bereliably estimated from the values calculated.

• Journal of KSNVE
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• v.6 no.4
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• pp.493-497
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• 1996

TVs or computer monitors with speakers often have a phenomenon called microphonic which shows fringe-like dark pattern on their screens. The major source of this phenomenon is vibration of the shadow mask inside of the Cathode RAY Tube(CRT) which is caused by the sound generated from the speakers. Reducing phenomenon microphonic by modifying the structure of the shadow mask frame in CRT has been examined in this study. A 15" for computer monitor were chosen. Using finite element analysis for vibration and impact, shape of the shadow mask frame was found to reduce microphonic phenomeon. Improved 15" monitors showed good results.d results.

• Journal of the Korean institute of surface engineering
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• v.26 no.2
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• pp.82-86
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• 1993

An attempt was made to reduce directly Nd2O3 in a cryolited based fluoride bath. Neodymium metal was electrodeposited on the iron cathode to produce the Fe-Nd eutectic alloy in a liquid state at 90$0^{\circ}C$. Graphite was adopted for the anode and pure iron for the cathode. Electrolyte was composed of Na3AlF6 50wt.%. AlF3 34wt.% and Nd2O3 16wt.%. Analysis of typical alloy product showed Al 63.4wt.% Fe 26.9wt.% and Nd 7.0 wt.% The enrichment of neodymium in the alloy couldn't be obtained because aluminum codeposited with ne-odydmium. Experimental results proved that the cryolited based electrolyte was unstable for the electrolysis of rare earth oxides even though their prominent solubilities.

• Journal of the Korean Institute of Gas
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• v.4 no.1 s.9
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• pp.40-48
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• 2000

A fuel cell is an electrochemical device continuously converting the chemical energy in a fuel and an oxidant to electrical energy by going through an essentially invariant electrode-electrolyte system. Phosphoric acid fuel cell employs concentrated phosphoric acid as an electrolyte. The cell stack in the fuel cell, which is the most important part of the fuel cell system, is made up of anode where oxidation of the fuel occurs cathode where reduction of the oxidant occurs; and electrolyte, to separate the anode and cathode and to conduct the ions between them. Fuel cell performance is associated with many parameters such as operating and design parameters associated with the system configuration. In order to understand the design concepts of the phosphoric fuel cell and predict it's performance, we have here introduced the simulation of the fuel-cell stack which is core component and modeled in a 3-dimensional grid space. The concentration of reactants and products, and the temperature distributions according to the flow rates of an oxidant are computed by the help of a computational fluid dynamic code, i.e., FLUENT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.136-140
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• 1992

The purpose of this research is to develop the lithium secondary battery. This paper describes the preparation, electrochemical properties of nontstoichiometric(NS)-$V_6O_{13}$ and characteristics of Li/$V_6O_{13}$ secondary battery. NS-$V_6O_{13}$ was prepared by thermal decomposition of $NH_4VO_3$ under Ar stream of 140ml/min~180ml/min flow rate. And then, this NS-$V_6O_{13}$ was used for cathode active material. Cathode sheet was prepared by compressing the composite of NS-$V_6O_{13}$, acetylene black(A.B) and teflon emulsion (T.E). Characteristics of the test cell are summarised as follows. Oxidation capacity of NS-$V_6O_{13}$ was about 20% less than its reduction capacity. A part of NS-$V_6O_{13}$ cathode active material showed irreversible reaction in early charge-discharge cycle. This phenomena seems to be caused by irreversible incoporation/discoporation of lithium cation to/from NS-$V_6O_{13}$ host. Discharge characteristics curve of Li/$V_6O_{13}$ cell showed 4 potential plateaus. Charge-discharge capacity was declined in the beginning of cycling and slowly increased in company with increasing of coulombic efficiency. Energy density per weight of $V_6O_{13}$ cathode material was as high as 522Wh/kg~765Wh/kg.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.251-257
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• 2001

A present semiconductor cleaning technology is based upon RCA cleaning, high temperature process which consumes vast chemicals and ultra Pure water(UPW). This technology gives rise to the many environmental issues, therefore some alternatives have been studied. In this study, intentionally contaminated Si wafers were cleaned using the electrolyzed water(EW). The EW was generated by an electrolysis equipment which was composed of anode. cathode, and toddle chambers. Oxidative water and reductive water were obtained in anode and cathode chambers, respectively. In case $NH_4$Cl electrolyte, the oxidation-reduction potential(ORP) and pH for anode water(AW) and cathode water(CW) were measured to be +1050mV and 4.7, and -750mV and 9.8, respectively. For cleaning metallic impurities, AW was confirmed to be more effective than that of CW, and the particle distribution after various particle removal processes was shown to be same distribution.

• Journal of Korean Society on Water Environment
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• v.28 no.6
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• pp.917-922
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• 2012

In order to improve applicability of a microbial fuel cell the laboratory-scaled study has been performed by adopting an air-cathode MFC system with high concentrated anaerobic slugies in this study. The concentrations of microbes are grouped into three types, Type A (TS 1.7%), Type B (TS 1.1%) and Type C (TS 0.51%). The open circuit voltage $(V_{oc})$ characteristics showed that the medium microbes concentration of 1.10% (Type B) kept a constant voltage of 1.0 V for 150 hours, which showed the longest time among three types (Type A and Type C). The discharge charge curves for a closed circuit with $500 \Omega$ also showed that Type B generated a stable discharge voltage of 0.8 V for a longer time as in the open circuit voltage case. This could be explained by the relatively large amount of the attached microbes. Under the $V_{oc}$condition the COD removal efficiency of Type B was found to be low for a long time, but those of Type A and C were found to be high for a short period of time. Therefore, the suspended microbes could decrease the coulombic efficiency. It was concluded that the high $V_{oc}$ was caused by low COD and the $V_{oc}$ became low after the COD removal. The COD reduction resulted in an unstable and low working voltage. From the polarization characteristics Type A was found to show the highest power density of $193\;mW/m^2$ with a fill factor of 0.127 due to the relatively high remaining COD even after the MFC reaction.

• Journal of the Korean Ceramic Society
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• v.56 no.5
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• pp.497-505
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• 2019

Lanthanum-based transition metal cations containing perovskites have emerged as potential catalysts for the intermediate-temperature (600-800℃) oxygen reduction reaction (ORR). Here, we report a facile acetylacetone-assisted combustion route for the synthesis of nanostructured La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF6428) cathodes for intermediate-temperature solid-oxide fuel cells (IT-SOFCs). The as-prepared powder was analyzed by thermogravimetry analysis-differential scanning calorimetry. The powder calcined at 800℃ was characterized by X-ray diffraction, scanning electrode microscopy, energy dispersive X-ray spectroscopy, and Brunauer-Emmett-Teller surface area measurements. It was found that the porosity of the air electrode significantly increased by utilizing the nanostructured LSCF6428 instead of commercial powder. The performance of a single cell fabricated with the nanostructured LSCF6428 cathode increased by 112%, from 0.4 to 0.85 W cm^-2, at 700℃. Electrochemical impedance spectroscopy showed a considerable reduction in the area-specific resistance and activation energy from 133.5 to 61.5 kJ/mol, resulting in enhanced electrocatalytic activity toward ORR and overall cell performance.