Self-healing Al₂O₃ ceramics: Selection and testing of novel healing particles

Alumina (Al2O3) is an attractive ceramic for engineering applications operating at elevated or high temperatures because of its good thermal and chemical resistance. It also maintains high strength and hardness at high temperatures. These desirable properties are due to the strong covalent and ionic bonds existing between its atoms.
However, these same strong and directional bonds are the origins of its inherent brittleness. Over the last decade, material scientists have adopted self-healing as a means of restoring the load bearing capability of such materials after damage from micro-sized surface cracks. In this methodology, the material is restored to a status comparable to the original one by the ‘healing’ of such surface cracks at high temperatures. Healing is achieved by the addition of ‘healing agents’ to the base ceramic material which upon the occurrence of a crack oxidise into a healing oxide which fills and seals of the crack. There are some gaps in the build-up of the knowledge ladder of self-healing ceramics to an application ready level. This thesis addresses some design questions and tests the capability of newly identified healing particles under laboratory and application conditions.