• Title/Summary/Keyword: Mixture Electrode

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Electrochemical Reduction of SiO2 Granules to One-Dimensional Si Rods Using Ag-Si Eutectic Alloy

  • Lee, Han Ju;Seo, Won-Chul;Lim, Taeho
    • Journal of Electrochemical Science and Technology
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    • v.11 no.4
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    • pp.392-398
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    • 2020
  • Producing solar grade silicon using an inexpensive method is a key factor in lowering silicon solar cell costs; the direct electrochemical reduction of SiO2 in molten salt is one of the more promising candidates for manufacturing this silicon. In this study, SiO2 granules were electrochemically reduced in molten CaCl2 (850℃) using Ag-Si eutectic droplets that catalyze electrochemical reduction and purify the Si product. When Ag is used as the working electrode, the Ag-Si eutectic mixture is formed naturally during SiO2 reduction. However, since the Ag-Si eutectic droplets are liquid at 850℃, they are easily lost during the reduction process. To minimize the loss of liquid Ag-Si eutectic droplets, a cylindrical graphite container working electrode was introduced and Ag was added separately to the working electrode along with the SiO2 granules. The graphite container working electrode successfully prevented the loss of the Ag-Si eutectic droplets during reduction. As a result, the Ag-Si eutectic droplets acted as stable catalysts for the electrochemical reduction of SiO2, thereby producing one-dimensional Si rods through a mechanism similar to that of vapor-liquid-solid growth.

AC Impedance Study of Hydrogen Oxidation and Reduction at Pd/Nafion Interface

  • Song, Seong-Min;Koo, Il-Gyo;Lee, Woong-Moo
    • Transactions of the Korean hydrogen and new energy society
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    • v.12 no.3
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    • pp.231-238
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    • 2001
  • Electrocatalytic activity of palladium for hydrogen oxidation and reduction was studied using AC impedance method. The system under study was arranged in electrolytic mode consisting of Pd electrode under study, Pt counter electrode and Nafion electrolyte between them. Two types of Pd electrodes were used - carbon-supported Pd (Pd/C) and Pd foil electrode. Pd/C anode contacting pure hydrogen showed a steady decrease of charge transfer resistance with the increase of anodic overpotential, which is an opposite trend to that found with Pd foil anode. But Pd foil cathode also exhibited a decrease of the resistance with the increase of cathodic overpotential. The relationship between imposition of overpotential and subsequent change of the charge transfer resistance is determined by the ratio of the rate of faradaic process to the rate of mass transportation; if mass transfer limitation holds, increase of overpotential accompanies the increase of charge transfer resistance. Regardless of the physical type of Pd electrode, the anode contacting hydrogen/oxygen gas mixture did not reveal any independent arc originated from local anodic oxygen reduction.

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Fabrication and Electro-photolysis Property of Carbon Nanotubes/Titanium Composite Photocatalysts for Methylene Blue

  • Zhang, Feng-Jun;Chen, Ming-Liang;Oh, Won-Chun
    • Bulletin of the Korean Chemical Society
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    • v.30 no.8
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    • pp.1798-1804
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    • 2009
  • In this study, we have studied on improved performance of carbon nanotubes/titanium (CNT/TiO2) structure electrode for methylene blue (MB). The composite electrodes consisting of CNTs and a titanium oxide matrix with phenol resin binder was fabricated with a mixture method. The chemical and morphological structure of CNT/Ti$O_2$ composites were characterized by means of BET surface area, X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis absorption technique, Raman spectroscopy and energy dispersive X-ray (EDX). The electrode showed a remarkably enhanced performance for MB oxidation under UV illumination with or without electro-chemical reaction (ECR). Such a remarkably improved performance of the CNT/Ti$O_2$ structure electrode might be due to the enhanced MB oxidation by electro- and photo-generated electrons and holes in the CNTs and Ti$O_2$ under UV illumination with or without ECR.

Micro Emulsion Synthesis of LaCoO3 Nanoparticles and their Electrochemical Catalytic Activity

  • Islam, Mobinul;Jeong, Min-Gi;Ghani, Faizan;Jung, Hun-Gi
    • Journal of Electrochemical Science and Technology
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    • v.6 no.4
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    • pp.121-130
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    • 2015
  • The micro emulsion method has been successfully used for preparing perovskite LaCoO3 with uniform, fine-shaped nanoparticles showing high activity as electro catalysts in oxygen reduction reactions (ORRs). They are, therefore, promising candidates for the air-cathode in metal-air rechargeable batteries. Since the activity of a catalyst is highly dependent on its specific surface area, nanoparticles of the perovskite catalyst are desirable for catalyzing both oxygen reduction and evolution reactions. Herein, LaCoO3 powder was also prepared by sol-gel method for comparison, with a broad particle distribution and high agglomeration. The electro catalytic properties of LaCoO3 and LaCoO3-carbon Super P mixture layers toward the ORR were studied comparatively using the rotating disk electrode technique in 0.1 M KOH electrolyte to elucidate the effect of carbon Super P. Koutecky-Levich theory was applied to acquire the overall electron transfer number (n) during the ORR, calculated to be ~3.74 for the LaCoO3-Super P mixture, quite close to the theoretical value (4.0), and ~2.7 for carbon-free LaCoO3. A synergistic effect toward the ORR is observed when carbon is present in the LaCoO3 layer. Carbon is assumed to be more than an additive, enhancing the electronic conductivity of the oxide catalyst. It is suggested that ORRs, catalyzed by the LaCoO3-Super P mixture, are dominated by a 2+2-electron transfer pathway to form the final, hydroxyl ion product.

The influence of Ne-Xe gas mixture ratio on vacuum Ultraviolet and infrared line in AC-PDP

  • Oh, Phil-Y.;Cho, I.R.;Jung, Y.;Park, K.D.;Ahn, J.C.;Choi, E.H.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2003.07a
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    • pp.743-747
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    • 2003
  • The improvement of luminance and luminous efficiency is the one of the most important part in AC-PDPs. To achieve high luminance and luminous efficiency, high VUV emission efficiency is needed. We measured the emission spectra of vacuum ultraviolet(VUV) and infrared(IR) rays in surface discharge AC-PDP with Ne-Xe mixture gas. The influence of Ne-Xe gas-mixture ratio on resonance state $Xe^{\ast}(3P_{1})$ and exited state $Xe^{\ast}(3P_{2})$ has been investigated. It is found that the intensity of VUV 147nm emission is proportional to that of the IR 828 nm emission, and the VUV 173nm emission is roughly proportional to that of the IR 823nm emission. The electron temperature and plasma density have been experimentally measured from the center of sustaining electrode gap by a micro Langmuir probe in AC-PDPs. The plasma density from the center of sustaining electrode gap are shown to be maximum value of $9{\times}10^{11}cm^{-3}$, where the electron temperature is about 1.6 eV in this experiment

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Voltammetric Determination of Copper(II) at Chemically Modified Carbon Paste Electrodes Containing Alga

  • Bae, Zun-Ung;Kim, Young-Lark;Chang, Hye-Young
    • Analytical Science and Technology
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    • v.8 no.4
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    • pp.611-615
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    • 1995
  • The design of appropriate chemically modified electrodes should allow development of new voltammetric measurement schemes with enhanced selectivity and sensitivity. Microorganism like algae has high ability to trap toxic and heavy metal ions and different affinities for metal ions. A copper(II) ion-selective carbon paste electrode was constructed by incorporating alga Anabaena into a conventional carbon paste mixture, and then the film of 10% Nafion was coated to avoid the swelling of the electrode surface. Copper ion could be deposited at the 25% algamodified electrode for 15 min without the applied potential while stirring the solution by only immersing the electrode in a buffer (pH 4.0) cot1taining copper(II). Temperature was controlled at $35^{\circ}C$. After preconcentration was carried out the electrode was transferred to a 0.1 M potassium chloride solution and was reduced at -0.6 volt at $25^{\circ}C$. The differential pulse anodic stripping voltammetry was employed. A well-defined oxidation peak could be obtained at -0.1 volt (vs SCE). In five deposition / measurement / regeneration cycles, the responses were reproducible and relative standard deviations were 3.3% for $8.0{\times}10^{-4}M$ copper(II). Calibration curve for copper was linear over the range from $2.0{\times}10^{-4}M$ to $1.0{\times}10^{-3}M$. The detection limit was $7.5{\times}10^{-5}M$. Studies of the effect of diverse ions showed that the coexisting metal ions had little or no effect for the determination of copper. But anions such as cyanide. oxalate and EDTA seriously interfered.

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Dielectric Strength of $SF_6/CF_4$ Mixture Under Standard Lightning Impulse Voltages in Non-Uniform Field (불평등 전계에서 표준 뇌 임펄스 전압의 $SF_6/CF_4$ 혼합 가스의 절연 내력)

  • Huh, Chang-Su;Sung, Heo-Gyung;Park, Shin-Woo;Hwang, Cheong-Ho;Kim, Nam-Ryul
    • Proceedings of the KIEE Conference
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    • 2007.11a
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    • pp.165-166
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    • 2007
  • In these days $SF_6$ mixtures and alternative gas have been studied because of global warming and liquefying at low temperature and high pressure. At present work the breakdown characteristics of $SF_6/CF_4$ mixture in non-uniform field was performed. The experiments were carried out under positive and negative standard lightning impulse (SLT) voltages. The point-plane electrode was used with 3 mm gap distance in the test chamber. The $SF_6/CF_4$ mixture which contain 20% of $SF_6$ was compared with pure $SF_6$ and $CF_4$ gas. Experimental gas pressure ranged from 0.1 to 0.4 MPa. The breakdown voltage under negative SLI is higher than the breakdown voltage under positive voltage. And the breakdown voltage of $SF_6$ 20%, $CF_4$ 80% mixture is similar to that of pure $SF_6$.

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A Study on Welding Performance Improvement of $CO_2$ Inverter Arc Welding Machine by Arc Reignition Detection (아크 재생 검출에 의한 $CO_2$ 인버터 아크 용접기의 용접성능향상에 관한연구)

  • 이정락
    • Proceedings of the KIPE Conference
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    • 2000.07a
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    • pp.581-586
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    • 2000
  • Gas metal arc welding(GMAW) uses a continuously fed electrode as a filler metal. The arc is shielded from atmospheric contamination by an inert gas active or inert/active gas mixture delivered through the welding gun and cable assembly. The recent research topics on $CO_2$ are welding machines are focused mainly on the reduction method of generated spatter by using new type consumable electrode metal or inverter control method. The various current waveform control methods have been researched for welding performance improvement. Until now current waveform control methods reduce to spatter occurred by instantaneous short circuiting,. but these methods is drawback that no reduce spatter occurred by arc reignition. In this paper the previous arc reignition current control method for welding performance improvement of inverter arc welding machine is studied and compared the various current control methods with the previous arc reignition current control method.

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Determination of Higenamine in the Commercial Aconiti Tuber and Its Pharmaceutical Preparations

  • Hahn, Young-Hee;Cheong, Kyo-Soon;Paik, Seung-Whan;YunChoi, Hye-Sook
    • Korean Journal of Pharmacognosy
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    • v.17 no.1
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    • pp.1-6
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    • 1986
  • A cardiac principle of Aconiti tuber, higenamine was analyzed with a differential pluse voltammetry employing a glassy carbon electrode. The peak potentials for the oxidation of higenamine were varied depending on the pH of the media. Higenamine at the concentration of $5.4{\times}10^{-7}M$ (0.146ppm) was easily determined using a pH 7.0 phosphate buffer. The amounts of higenamine in the crude Aconiti tuber and tablets containing A. tuber were determined by a standard addition method after extracting with methanol, partitioning with a mixture of $H_2O$ and $CHCl_3$, and freeze-drying the aqueous layer.

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The Optimization of AC-PDP Cell by 2D Simulations

  • Kim, Woong;Y.K. Shin;C.H. Shon;J.H. Kang;Park, J.S.;Lee, J.K.
    • Proceedings of the Korean Vacuum Society Conference
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    • 1999.07a
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    • pp.227-227
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    • 1999
  • Plasma display panel(PDP) is a leading technology for large-area flat panel displays. A current issue in operating the PDP cell is that the efficiency of the PDP cell is very low. To increase the efficiency of the PDP cell, the visible light needs to be maximized and the power consumption minimized. Since the excited xenons are related to the production of the visible light, it is important to optimize the cell geometry and the gas composition that produce the excited xenons more efficiently. A 2D-fluid code (FL2P) is developed and used to simulate the plasma dynamics and the radiation transport in the PDP cell. The cell is optimized with the code for various operating conditions and cell dimensions such as the voltage pulse, electrode length, electrode spacing, gap size, dielectric constant, gas mixture ratio, pressure, and pulse duration.

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