• Title, Summary, Keyword: Cathode pressure

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Atmospheric Pressure Micro Plasma Sources

  • Brown, Ian
    • Journal of the Korean institute of surface engineering
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    • v.34 no.5
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    • pp.384-390
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    • 2001
  • The hollow cathode discharge is a kind of plasma formation scheme in which plasma is formed inside a hollow structure, the cathode, with current to a nearby anode of arbitrary shape. In this scheme, electrons reflex radially within the hollow cathode, establishing an efficient ionization mechanism for gas within the cavity. An existence condition for the hollow cathode effect is that the electron mean-free-path for ionization is of the order of the cavity radius. Thus the size of this kind of plasma source must decrease as the gas pressure is increased. In fact, the hollow cathode effect can occur even at atmospheric pressure for cathode diameters of order 10-100 $\mu\textrm{m}$. That is, the "natural" operating pressure regime for a "micro hollow cathode discharge" is atmospheric pressure. This kind of plasma source has been the subject of increasing research activity in recent years. A number of geometric variants have been explored, and operational requirements and typical plasma parameters have been determined. Large arrays of individual tiny sources can be used to form large-area, atmospheric-pressure plasma sources. The simplicity of the method and the capability of operation without the need for the usual vacuum system and its associated limitations, provide a highly attractive option for new approaches to many different kinds of plasma applications, including plasma surface modification technologies. Here we review the background work that has been carried out in this new research field.

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Experimental Analysis for Variation of Pressure Difference on Flooding in PEM Fuel Cell at Cathode Channel Outlet (Cathode 출구 압력 변화에 따른 PEM Fuel Cell 내에서의 플러딩에 관한 실험적 연구)

  • Ahn, Deuk-Keun;Han, Seong-Ho;Kim, Kyoung-Rock;Choi, Young-Don
    • Transactions of the Korean hydrogen and new energy society
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    • v.20 no.5
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    • pp.390-396
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    • 2009
  • The flooding, especially in channel, is one of the critical issue to put proton exchange membrane fuel cell (PEMFC) to practical use. In this paper, channel flooding was investigated the pressure difference at cathode channel outlet. A ratio of pressure difference changes to 25, 50% as its variation rate. The pressure variable rate is reflected in dimensionless number FN. As a result, modified dimensionless number $FN^*$ correctly predicted the channel flooding. This study analyzes that a variety of pressure difference is how to affect flooding at the cathode of the PEMFC.

Fundamental Studies of the Electrical Characteristics of the Glow Discharge for the Development of HPLC Detector (글로우방전을 이용한 액체크로마토그라피 검출기 개발을 위한 기초특성연구)

  • 이현주;김효진
    • YAKHAK HOEJI
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    • v.39 no.4
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    • pp.427-432
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    • 1995
  • The plasma oscillation has been observed in an argon pressure between a tungsten anode and cathode consisting of an aqueous conducting solution. The effects of experimental parameters on the electrical characteristics of the glow discharge have been studied. The experimental parameters include the anode-cathode distance, pressure, methanol flow rate, and cathode materials. The glow discharge with liquid cathode and solid anode showed the potential sensitive detector for HPLC

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A study of the hollow cathode discharge (HOLLOW CATHODE DISCHARGE의 방전 특성 연구)

  • Cho, S.M.;Seo, Y.W.;Kim, M.J.;Whang, K.W.
    • Proceedings of the KIEE Conference
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    • pp.139-141
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    • 1989
  • The characteristics of the hollow cathode discharge were investigated. Temperature distribution of the hollow cathode was investigated and I-V curves of the hollow cathode discharge were obtained. In this paper variables are chamber pressure, Ar gas flow rate injected through the cathode tube and the gap distance between cathode and anode. The inter electrode electron temperature and density were measured by Langmuir probe.

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A Study on The Fabrication and Electrochemical Characterization of Amorphous Vanadium Oxide Thin Films for Thin Film Micro-Battery (마이크로 박막 전지용 비정질 산화바나듐 박막의 제작 및 전기화학적 특성에 관한 연구)

  • 전은정;신영화;남상철;조원일;윤영수
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.634-637
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    • 1999
  • The amorphous vanadium oxide as a cathode material is very preferable for fabricating high performance micro-battery. The amorphous vanadium oxide cathode is preferred over the crystalline form because three times more lithium ions can be inserted into the amorphous cathode, thus making a battery that has a higher capacity. The electrochemical properties of sputtered films are strongly dependent on the oxygen partial pressure in the sputtering gas. The effect of different oxygen partial pressure on the electrochemical properties of vanadium oxide thin films formed by r.f. reactive sputtering deposition were investigated. The stoichiometry of the as-deposited films were investigated by Auger electro spectroscopy. X-ray diffraction and atomic force microscopy measurements were carried out to investigate structural properties and surface morphology, respectively. For high oxygen partial pressure(>30% ), the films were polycrystalline V$_2$O$_{5}$ while an amorphous vanadium oxide was obtained at the lower oxygen partial pressure(< 15%). Half-cell tests were conducted to investigate the electrochemical properties of the vanadium oxide film cathode. The cell capacity was about 60 $\mu$ Ah/$\textrm{cm}^2$ m after 200 cycle when oxygen partial pressure was 20%. These results suggested that the capacity of the thin film battery based on vanadium oxide cathode was strongly depends on crystallinity.y.

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Observer Based Nonlinear State Feedback Control of PEM Fuel Cell Systems

  • Kim, Eung-Seok
    • Journal of Electrical Engineering and Technology
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    • v.7 no.6
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    • pp.891-897
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    • 2012
  • In this paper, the observer based nonlinear state feedback controller has been developed to control the pressures of the oxygen and the hydrogen in the PEM(Proton Exchange Membrane) fuel cell system. Nonlinear model of the PEM fuel cell system was introduced to study the design problems of the state observer and model based controller. A cascade observer using the filtering technique was used to estimate the pressure derivatives of the cathode and the anode in the system. In order to estimate the pressures of the cathode and the anode, the sliding mode observer was designed by using these pressure derivatives. To estimate the oxygen pressure and the hydrogen pressure in the system, the nonlinear state observer was designed by using the cathode pressure estimates and the anode it. These results will be very useful to design the state feedback controller. The validity of the proposed observers and the controller has been investigated by using the Lyapunov's stability analysis strategy.

Characteristics of the closed microhollow cathode discharge for DC Plasma Display Panels

  • Park, Hae-Il;Noh, Joo-Hyon;Ryu, Byung-Gil;Baik, Hong-Koo
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.105-106
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    • 2000
  • The positive slope of the current-voltage characteristic at pressure up to 850 torr was obtained using the closed microhollow cathode without the individual and/or distributed ballast. This indicates that the stable parallel operation of the discharge was also achieved using the closed microhollow cathode. The parallel operation makes it possible to manufacture de plasma displays with high pressure, small discharge current, and long lifetime.

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A Study on the Nitriding of Sintered Metallic Components by Hollow Cathode Discharge (할로우 캐소드 방전에 의한 금속소결부품의 질화처리에 관한 연구)

  • Kim, Y.C.;Han, C.S.
    • Journal of the Korean Society for Heat Treatment
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    • v.25 no.2
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    • pp.80-84
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    • 2012
  • An apparatus was constructed to nitrify small metallic sintered components by using a hollow-cathode discharge plasma method. A stainless steel basket, which contains a sintered part to be nitrified, is potentially grounded and serves as hollow-cathode electrode. Hollow-cathode plasma was produced by supplying the positive voltage to the anode. In this study sintered carbon iron and stainless steel were used as testing specimens. It was shown that an effective nitrifying took place by controlling the total pressure of nitrogen and hydrogen gas and applied voltage.

Unsteady Internal Flow Analysis of a Cathode Air Blower Used for Fuel Cell System (연료전지용 캐소드 공기블로어의 비정상 내부유동장 연구)

  • Jang, Choon-Man;Lee, Jong-Sung
    • New & Renewable Energy
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    • v.8 no.3
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    • pp.6-13
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    • 2012
  • This paper describes unsteady internal flow characteristics of a cathode air blower, used for the 1 kW fuel cell system. The cathode air blower considered in the present study is a diaphragm type blower. To analyze the flow field inside the diaphragm cavity, compressible unsteady numerical simulation is performed. Moving mesh system is applied to the numerical analysis for describing the volume change of the diaphragm cavity in time. Throughout a numerical simulation by modeling the inlet and outlet valves in a diaphragm cavity, unsteady nature of an internal flow is successfully analyzed. Variations of mass flow rate, force and pressure on the lower moving plate of a diaphragm cavity are evaluated in time. The computed mass flow rate at the same pressure and rotating frequency of a motor has a maximum of 5 percent error with the experimental data. It is found that flow pattern at the suction process is more complex compared to that at the discharge process. Unsteady nature of internal flow in the cathode air blower is analyzed in detail.

Effect of Fabrication Method of Cathode on OCV in Enzyme Fuel Cells (효소연료전지의 Cathode 제조조건이 OCV에 미치는 영향)

  • Lee, Se-Hoon;Kim, Young-Sook;Chu, Cheun-Ho;Na, Il-Chai;Lee, Jung-Hoon;Park, Kwon-Pil
    • Korean Chemical Engineering Research
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    • v.54 no.2
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    • pp.171-174
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    • 2016
  • Enzyme fuel cells were composed of enzyme cathode and PEMFC anode. Enzyme cathode was fabricated by compression of a mixture of graphite particle, laccase as a enzyme and ABTS as a redox mediator, and then coated with Nafion ionomer. Open circuit voltage (OCV) were measured with variation of cathode manufacture factors, to find optimum condition of enzyme cathode. Optimum pressure was 4.0 bar for enzyme cathode pressing process. Highest OCV was obtained at 95% graphite composition in enzyme cathodee. Optimum glucose concentration was 0.4 mol/l in cathode substrate solution.