Mechanical characterization of meso-porous alumina by micro- and nano-indentation
Résumé
Meso-porous γ-alumina ceramics used as catalyst supports are characterized by high porosity fraction (>70%) and specific surface area (>200 m²/g) targeted to ensure high catalytic performances, but at the expense of the mechanical strength. The aim of this work is to link the mechanical properties of three different catalyst supports with their microstructure. Instrumented indentation tests were performed at two different length scales to assess mechanical properties at both macroscopic scale (support) and at constituents scale (grains and matrices). The distribution of porosity fraction in grains and matrices is estimated with image processing on Scanning Electron Microscopy (SEM) pictures. The mechanical behavior of catalyst supports are strongly influenced by their microstructure. In spite of a larger porosity fraction, macro-and meso-porous grains exhibit higher mechanical properties than the matrices. Matrix of the three alumina supports have almost similar volume fraction of porosity but different mechanical properties. Finally, Focused Ion Beam (FIB) cross-sections of residual indents indicate a damageable behavior under contact loading, with densification of larger pores.
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