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Title: The influence of constrictivity on the effective transport properties of porous layers in electrolysis and fuel cells
Authors : Holzer, Lorenz
Wiedenmann, Daniel
Münch, Beat
Keller, Lukas
Prestat, Michel
Gasser, Philippe
Robertson, Iain
Grobéty, Bernard
Published in : Journal of Materials Science
Volume(Issue) : 48
Issue : 7
Pages : 2934
Pages to: 2952
Publisher / Ed. Institution : Springer New York LLC
Issue Date: 2013
License (according to publishing contract) : Licence according to publishing contract
Type of review: Peer review (Publication)
Language : English
Subjects : Map
Subject (DDC) : 621.3: Electrical engineering and electronics
Abstract: The aim of the present investigation is to define microstructure parameters, which control the effective transport properties in porous materials for energy technology. Recent improvements in 3D-imaging (FIB-nanotomography, synchrotron X-ray tomography) and image analysis (skeletonization and graph analysis, transport simulations) open new possibilities for the study of microstructure effects. In this study, we describe novel procedures for a quantitative analysis of constrictivity, which characterizes the so-called bottleneck effect. In a first experimental part, methodological tests are performed using a porous (La,Sr)CoO3 material (SOFC cathode). The tests indicate that the proposed procedure for quantitative analysis of constrictivity gives reproducible results even for samples with inhomogeneous microstructures (cracks, gradient of porosity). In the second part, 3D analyses are combined with measurements of ionic conductivity by impedance spectroscopy. The investigations are preformed on membranes of electrolysis cells with porosities between 0.27 and 0.8. Surprisingly, the tortuosities remain nearly constant (1.6) for the entire range of porosity. In contrast, the constrictivities vary strongly and correlate well with the measured transport resistances. Hence, constrictivity represents the dominant microstructure parameter, which controls the effective transport properties in the analysed membrane materials. An empirical relationship is then derived for the calculation of effective transport properties based on phase volume fraction, tortuosity, and constrictivity.
Departement: School of Engineering
Organisational Unit: Institute of Computational Physics (ICP)
Publication type: Article in scientific Journal
DOI : 10.1007/s10853-012-6968-z
ISSN: 0022-2461
Restricted until : 2019-01-01
Appears in Collections:Publikationen School of Engineering

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