Biaxial strength and slow crack growth in porous alumina with silica sintering aid |
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Authors: | Astrid Bakken Susanne Wagner Michael J Hoffmann Bernt Thorstensen Mari-Ann Einarsrud Tor Grande |
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Affiliation: | 1. Department of Materials Science and Engineering, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway;2. Institute for Applied Materials-Ceramics in Mechanical Engineering, Karlsruhe Institute for Technology (KIT), D-76131 Karlsruhe, Germany;3. KeraNor AS, Brobekkveien 104 A, NO-0582 Oslo, Norway |
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Abstract: | Biaxial strength, fracture toughness and subcritical crack growth are reported for coarse grained porous alumina ceramics. The materials were prepared with a varying amount of a silica sintering aid, which resulted in the formation of a glassy secondary phase at the grain boundaries. Crystalline mullite was additionally found in the material with the highest silica content. The biaxial strength, measured by Ball-on-Ring and Ball-on-3-Balls, was highest for the material without mullite at the grain boundaries, and the biaxial strength decreased with increasing porosity. The fracture toughness of the materials was in the range of 1.7–1.9 MPa m0.5. Measurements of subcritical crack growth by a modified lifetime method in air and aqueous environments demonstrated a higher crack growth rate in water and acid relative to in air. The effect of porosity and grain boundary phase were discussed in relation to subcritical crack growth and fracture mode in the coarse grained alumina ceramics. |
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Keywords: | Porous alumina Biaxial strength Fracture toughness Subcritical crack growth |
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