Molecular, ionic and electronic transport in solid oxide membranes and fuel cells.
Item
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Title
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Molecular, ionic and electronic transport in solid oxide membranes and fuel cells.
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Identifier
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AAI9605589
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identifier
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9605589
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Creator
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Deng, Huiming.
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Contributor
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Adviser: Benjamin Abeles
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Date
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1995
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Condensed Matter | Engineering, Chemical
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Abstract
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We solve the transport equations for diffusion-reaction in solid oxide membranes and fuel cells which have a basic structure that consists of a mixed ionic electronic conductor (MIEC) porous anode and cathode separated by a thin dense layer. The large surface area of the porous electrodes enhances the chemical reaction and correspondingly gives rise to an enhanced ionic current. The purpose of the dense layer is to block the direct passage of gas molecules between the electrodes. In the case of a fuel cell this dense layer is an ionic conductor which allows only the passage of oxygen ions while in the case of a membrane the dense layer is a mixed ionic electronic conductor (MIEC) which allows the passage of electrons as well as ions. In an oxygen membrane with electrodes having surface area 100 {dollar}\rm m\sp2/gm,{dollar} an ion current of over two orders of magnitude over that of membrane without porous electrodes, is theoretically achievable. In the case of the fuel cell the corresponding increase in the short circuit current is a factor of 30.;We synthesize thin dense blocking layers, in the range 0.05-1 {dollar}\mu\rm m,{dollar} and nano-scale particles 50-100 A for the porous electrodes, by pulsed laser deposition of the ionic conductor yttrium stabilized zirconia and the MIEC {dollar}\rm SrCo\sb{lcub}0.8{rcub}Fe\sb{lcub}0.2{rcub}O\sb{lcub}3-\delta{rcub}.{dollar} X-ray, SEM and TEM microscopy, electrical conductivity and optical transmission measurements were used to characterize the materials. The YSZ electrode interfacial impedance has the constant phase angle form. The conductivity of {dollar}\rm SrCo\sb{lcub}0.8{rcub}Fe\sb{lcub}0.2{rcub}O\sb{lcub}3-\delta{rcub},{dollar} is interpreted by a charge transfer conduction process and it has an activation energy of 0.17 eV. The optical absorption spectrum of {dollar}\rm SrCo\sb{lcub}0.8{rcub}Fe\sb{lcub}0.2{rcub}O\sb{lcub}3-\delta{rcub}{dollar} is interpreted in terms of an effective one-electron band structure diagram.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
