Mechanical properties of NiO/Ni-YSZ composites depending on temperature, porosity and redox cycling

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    Abstract

    The Impulse Excitation Technique (IET) was used to determine the elastic modulus and specific damping of different Ni/NiO-YSZ composites suitable for use in solid oxide fuel cells (SOFC). The porosity of the as-sintered samples varied from 9 to 38% and that of the reduced ones from 31 to 52%. For all samples a linear relation between Young's modulus and porosity was found. The temperature dependency of the mechanical properties of both as-sintered and reduced composites was investigated by IET up to 1200 degrees C. In the as-sintered state, first an increase and peak of stiffness coinciding with the Neel temperature, 250 degrees C, of NiO was observed. Above this temperature, a linear decrease occurred. Specific damping showed a peak at 170-180 degrees C and increased above ca. 1000 degrees C in NiO-YSZ. In the reduced state the elastic modulus decreased linearly with temperature; specific damping increased above ca. 600 degrees C and was found to be very dependent on microstructure. Damage caused by redox cycling degraded the elastic properties of the composites. Degradation started linearly from 0.5 to 0.6% redox strain leading to macroscopic sample failures at about 2.5% dL/L-o. A simple continuum elastic damage model was fitted to the degradation data. (C) 2008 Elsevier Ltd. All rights reserved.
    Original languageEnglish
    JournalJournal of the European Ceramic Society
    Volume29
    Issue number9
    Pages (from-to)1657-1664
    ISSN0955-2219
    DOIs
    Publication statusPublished - 2009

    Keywords

    • Fuel Cells and hydrogen
    • Ceramic Membranes

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