In Situ Platelet Reinforcement of Alumina and Zirconia Matrix Nanocomposites – One Concept, Different Reinforcement Mechanisms

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Abstract
Zirconia-alumina composites are structural ceramics which due to their high strength and toughness are interesting in biomedical and engineering applications. Reinforcement of such materials with in situ formed platelets can improve fracture toughness and reliability, the mechanisms are however not yet fully understood. In this study alumina and zirconia based composites (ZTA and ATZ) reinforced with various hexaaluminates were investigated. In ZTA materials the main effect of platelets is the improvement of toughness as the the grain size distribution of the microstructure is broadened and transformability of the zirconia dispersion is improved. Crack deflection by platelets is unimportant, toughening is commonly achieved at the expense of strength and hardness. In case of zirconia based composites results are strongly depending on the type of stabilizer (Y-TZP or Ce-TZP) used and the type of hexaaluminates formed in situ. Here platelets can cause crack deflection and crack bridging. By variation of the composite recipes a multitude of compositions can be produced which have mechanical properties tailored for individual applications.

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