• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.8
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• pp.96-101
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• 2007

Gas Discharge Tubes (GDTs) are widely used as surge protectors for communication applications due to their small internal capacitance. In these days, however, they are mostly used in combined configurations, because the sparkover voltage required to initiate the discharge process in the GDTs and the time taken for arc formation process can be large enough to damage to sensitive circuits. For GDTs with a considerably high initial residual voltage, we should limit the peak voltage using a TVS or filter. We made a hybrid SPD circuits of common-mode type and differential-mode type with the filter using common-mode choke. Also, we applied lightning impulse voltage and ring wave voltage which frequency bandwidth are different each other and verified the characteristics of hybrid SPD circuits according to waveshapes. We describe how the applied SPDs operate in protection process steps with the actual data obtained from the residual voltage measurement at each step. The experiment results show that the surge voltage reduction with the choke coil is more effective in differential-mode circuit than in common-mode circuit.

• Journal of the Korean Electrochemical Society
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• v.12 no.3
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• pp.239-244
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• 2009

This paper aims to report the effect of surface treatment on graphite and its effect on the improvement of $Al_2O_3$ and $nano-Li_4Ti_5O_{12}$. The structure and property of surface treatment on graphite were determined by scanning electron microscopy, transmission electron microscopy and electrochemical property and safety were determined by charge/discharge cycler, accelerating rate calorimeter. The composite with different metallic oxide exhibited the first efficiency of 82.5% and specific capacity of 350 mAh/g. Although the composite showed same efficiency and specific capacity at first cycle, surface treatment on graphite by $nano-Li_4Ti_5O_{12}$ exhibited a higher charge/discharge rate, cycle life and thermal stability.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.553-553
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• 2013

상압 플라즈마 기술은 표면처리, 온존 발생장치, VOC (Volatile Organic compound) 제거등 다양한 산업분야에서 응용되고 있다. 상압플라즈마 기술 또한 DBD (Dielectric barrier discharge), Griding Arc, SDIP (Surface Discharge Induced Plasma) 등 다양한 기술들이 개발되어져 왔다. VOC를 제거하기 위한 다양한 플라즈마 기술중 특히 BDB 방법과 SDIP 기술들은 플라즈마에 의한 VOC 분해 뿐만 아니라 오존 발생을 통하여 VOC성분을 분해하는 것으로 알려져 있으며 효율이 매우 뛰어난 것으로 보고 되고 있다. 그러나 BDB 방전의 경우 방전이 발생하는 간격이 매우 작아 공기를 정화시키기 위해 좁은 유로를 통하여 일정넓이를 이동하여하 하기 때문에 압력감소가 심하며 이를 개선하기위해 다단으로 설계할 경우 구조가 복잡하고 가격이 고가인 단점이 있다. 본 연구에서는 두 개의 면 전극이 마주보는 형태로 된 DBD 구조의 단점을 보완하기 위하여 빗살무늬 모양의 다층구조의 선형전극으로 구조를 변화시켜 전극에 의한 압력감소를 방지하고 효율적으로 플라즈마 및 오존을 발생시킬 수 있는 VOC제거용 상압 플라즈마 발생장치를 개발하였다. 또한 플라즈마 발생 및 오존발생량이 우수한 것으로 알려져 있는 SDIP 장치 또한 제작하여 비교 평가를 하였다. 제작된 플라즈마 발생장치는 60 Hz와 20kHz의 교류 고압파워 서플라이를 이용하여 플라즈마 발생실험을 진행하였다. 선행 연구에서는 60 Hz의 고압 파워 서플라이를 이용하여도 플라즈마 방전이 잘 된다고 보고되었는데 본 실험에서 60 Hz 파워 서플라이를 사용할 경우 15 kV 이상이 인가될 때 아주 약하게 오존이 발생하는 현상이 관찰되었으나 육안으로 구분이 될 만큼의 플라즈마 방전은 발생하지 않았다. 20kHz의 고압파워 서플라이를 사용한 경우에는 비교적 낮은 전압인 7 kV에서 방전이 관찰되었으며 분당 22 mg의 오존이 발생하였다. SDIP를 이용한 경우 플라즈마가 발생하는 조건은 SDIP의 기하학적 형상에 많이 의존하게 된다. 본 실험에 SDIP 장치는 매우 낮은 전압에서 방전을 시작하였다. 기존의 DBD와는 다르게 1.7 kV에서 플라즈마 발생하였으며 1.8 kV에서 정상적인 플라즈마 방전이 발생하였다. 이때 분당 3.1 mg의 오존이 발생하였다. 오존 발생양은 앞에 빗살형 플라즈마 방전장치에 비하여 낮은데 인가되는 전력을 고려하면 입력된 전기 에너지당 오존발생양은 비슷한 수준이였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.552-552
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• 2013

In our study we consider Al2O3 ceramic substrates for Plasma Surface Treatments in order to improve deposited diamond surface and increase diamond deposition rate by applying DBD (Dielectric Barrier Dischrge) system. Because Plasma Surface Treatments was used as a modification method of material surface properties like surface free energy, wettability, and adhesion. By applying Plasma Surface Treatments diamond films are deposited on the Al2O3 ceramic substrates. DC Arc Plasmatron with mathane and hydrogen gases is used. Deposited diamond films are investigated by SEM (Scanning Electron Microscopy), AFM (Atomic Force Microscopy) and XRD (X-ray Diffractometer). Then the C-H stretching of synthetic diamond films by FTIR (Fourier Transform Infrared Spectroscopy) is studied. As a result, nanocrystalline diamond films were identified by using SEM and diamond properties in XRD peaks at (111, $43.8{\Box}$, (220, $75.3{\Box}$ and (311, $90.4{\Box}$ were shown. Absorption peaks in FTIR spectrum, caused by CHx sp3 bond stretching of CVD diamond films, were identified as well. Finally, we improved such parameters as depostion rate ($2.3{\mu}m$/h), diamond surface uniformity, and impurities level by applying Plasma Surface Treatments. These experimental results show the importance of Plasma Surface Treatments for diamond deposition by a plasma source.

• Journal of Hydrogen and New Energy
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• v.10 no.2
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• pp.141-149
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• 1999

Recently the Ni/MH secondary battery has been studied extensively to achieve higher energy density, longer cycle life and faster charging-discharging rate etc. In this work, the electrode properties of $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$ alloy and $Ti_{0.6}Zr_{0.4}V_{0.6}Ni_{1.4}$ alloy with addition of Pd were investigated. These alloys did not show any change in XRD pattern by Pd addition. As Pd was added as alloy element, the activation behavior was not affected significantly in both $AB_2$ type and $AB_5$ type electrodes and, On charging and discharging in high current density, Discharge capacity with increasing of Pd content was more decreased. But cycle life was showed increasing. Especially the electrode of $Ti_{0.6}Zr_{0.4}V_{0.6}Ni_{1.4}+0.5wt%$ Pd alloy was not almost decreased discharge capacity for 400cycles.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2038-2040
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• 2000

The main objective of this paper is to design and test a new type of polymer ZnO surge arrester for AC power system of railroad vehicles. Metal oxide surge arrester for most electric power system applications, electric train and subway are now being used extensively to protect overvoltage due to lightning. Surge arresters with porcelain housing must not have explosive breakage of the housing to minimize damage to other equipment when subjected to internal high short circuit current. When breakdown of ZnO elements in a surge arrester occurs due to flashover, fault short current flows through the arrestor and internal pressure of the arrester rises. The pressure rise can usually be limited by fitting a pressure relief diaphragm and transferring the arc from the inside to the outside of the housing. However, there is possibility of porcelain fragmentation caused by the thermal shock, pressure rise. etc. Non-fragmenting of the housing is the most desired way to prevent damage to other equipment. The pressure change which is occurred by flashover become discharge energy. This discharge energy raises to damage arrester housing and arrester housing is dispersed as small fragment. Therefore, the pressure relief design is requested to obstruct housing dispersion. The main research works are focused on the structure design by finite element method, pressure relief of module, and studies of performance of surge arrester for electric railway vehicle.

• Journal of Surface Science and Engineering
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• v.36 no.1
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• pp.27-33
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• 2003

Pulsed magnetron sputtering of graphite target was employed for deposition of diamond-like carbon (DLC) films. Time-resolved probe measurements of magnetron discharge plasma have been performed. It was shown that the pulsed magnetron discharge plasma density ($∼10^{17}$ $m^{-3}$ ) is close to that of vacuum arc cathode sputtering of graphite. Raman spectroscopy was sed to examine DLC films produced at low ( $U_{sub}$ / < 1 kV) pulsed bias voltages applied to the substrate. It has been shown that maximum content of diamond-like carbon in the coating (50-60%) is achieved at energy per deposited carbon atom of $E_{c}$ =100 eV. In spite of rather high percentage of $sp^3$-bonded carbon atoms and good scratch-resistance, the films showed poor adhesion because of absence of ion mixing between the film and the substrates. Electric breakdowns occurring during the deposition of the insulating DLC film also thought to decrease its adhesion.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05a
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• pp.74-77
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• 2000

The main objective of this paper is to design and test a new type of polymer ZnO surge arrester for AC power system of railroad vehicles. Metal oxide surge arrester for most electric power system applications, electric train and must not have explosive breakage of the housing to minimize damage to other equipment when subjected to internal high short circuit current. When breakdown of ZnO elements in a surge arrester occurs due to flashover, fault short current flows through the arrester and internal pressure of the arrester rises. The pressure rise can usually be limited by fitting a pressure relief diaphragm and transferring the arc from the inside to the outside of the housing. However, there is possibility of porcelain fragmentation caused by the thermal shock. pressure rise, etc. Non-fragmenting of the housing is the most desired way to prevent damage to other equipment. The pressure change which is occurred by flashover become discharge energy. This discharge energy raises to damage arrester housing and arrester housing is dispersed as small fragment. Therefore, the pressure relief design is requested to obstruct housing dispersion. The main research works are focused on the structure design by finite element method, pressure relief of module, and studies of performance of surge arrester for electric railway vehicle.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.417-417
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• 2009

Although a transparent conductive film (TCF) belongs to essential supporting materials for many device applications such as touch screens, flat panel displays, and sensors, a conventional transparent conductive material, indium-tin oxide (ITO), suffers from considerable drawback because the price of indium has soared since 2001. Despite a recent falloff, a demand of ITO is expected to increase sharply in the future due to the trend of flat panel display technologies toward flexible, paper-like features. There have been recently extensive studies to replace ITO with new materials, in particular, carbon nanotubes (CNTs) since CNTs possess excellent properties such as flexibility, electrical conductivity, optical transparency, mechanical strength, etc., which are prerequisite to TCFs. This study fabricated TCFs with single-walled carbon nanotubes (SWCNTs) produced by arc discharge. The SWCNTs were dispersed in water with a surfactant of sodium dodecyl benzene sulfonate (NaDDBS) under sonication. Carbon black and fullerene nanoparticles were added to the SWCNT-dispersed solution to enhance contact resistance between CNTs. TCFs were manufactured by a filtration and transfer method. TCFs added with carbon black and fullerene nanoparticles were characterized by scanning electron microscopy (SEM), UV-vis spectroscopy (optical transmittance), and four-point probe measurement (sheet resistance).

• Korean Journal of Materials Research
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• v.19 no.9
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• pp.488-493
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• 2009

Thin films of single-wall carbon nanotubes (SWNT) with various thicknesses were fabricated, and their optical and electrical properties were investigated. The SWNTs of various thicknesses were directly coated in the arc-discharge chamber during the synthesis and then thermally and chemically purified. The crystalline quality of the SWNTs was improved by the purification processes as determined by Raman spectroscopy measurements. The resistance of the film is the lowest for the chemically purified SWNTs. The resistance vs. thickness measurements reveal the percolation thickness of the SWNT film to be $\sim$50 nm. Optical absorption coefficient due to Beer-Lambert is estimated to be $7.1{\times}10^{-2}nm^{-1}$. The film thickness for 80% transparency is about 32 nm, and the sheet resistance is 242$\Omega$/sq. The authors also confirmed the relation between electrical conductance and optical conductance with very good reliability by measuring the resistance and transparency measurements.