Thesis defence L. Boatemaa: self healing
07 May 2018 10:00 - Location: Aula, TU Delft - By: webredactie
Self-Healing of Al203 ceramics: Selection and testing of novel healing particles. Promotor 1: Prof.dr.ir. S. van der Zwaag (LR); Promotor 2: Dr.ir. W.G. Sloof (3mE).
Alumina (Al2O3) is an attractive ceramic for engineering applications operating at high temperatures because of its good thermal and chemical stability. 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. This thesis addresses some design questions and tests under laboratory and application conditions the capability of newly identified healing particles.
On the design, particles of Ti, Cr, Zr, Nb, Hf, TiC, TiN, Cr3C2, Cr2N, ZrN, NbC and NbN were identified as promising materials for autonomous healing of alumina at high temperatures. In another study, the effect of particle size on healing was investigated. It is interesting to know that self-healing can be tailored to a specific service temperature by tuning the size of the healing particle.
On testing of novel particles, Ti and TiC were confirmed as effective healing agents for components made of Al2O3. The Ti2AlC MAX phase, which undergoes intrinsic self-healing, was also confirmed as a viable option for crack-healing in alumina.
Finally, a study of self-healing in a combustion chamber showed that healing was not affected by the low oxygen partial pressure levels or the vibrations in the combusting chamber as the results were similar to those of the samples studied under static laboratory conditions.
For access to theses by the PhD students you can have a look in TU Delft Repository, the digital storage of publications of TU Delft. Theses will be available within a few weeks after the actual thesis defence.