Qinqin Xu
Sujet de thèse: Dislocations and nanomechanics in Al2O3 using atomistic simulations.
Ph.D Advisors: Dr. Jonathan Amodeo, Pr. Jérôme Chevalier.
Micro- and nano-objects as pillars, wires, thin films and particles have recently drawn intensive scientific attention due to their outstanding mechanical properties. They generally show very high yield strengths compared to their massive counterpart, as well as an increased ductility and a lack of failure under extreme compressive stresses. While these size effects have been widely studied in metals, few recent studies show that these original properties could apply to other material families as e.g., ceramics, intermetallics or semi- conductors opening routes toward new super-hard nanocrystalline materials. In the case of nano-ceramics, this would imply a real technological push forward, in terms of processing and mechanical properties during use. We have shown for example that ceramic nano- powders could be plastically deformed without breaking, opening new doors for their process by plastic forming or for their use, with a significant amount of plasticity before failure1-3. This would apply in the field of modern surgery where the use of ceramics as biocompatible alternatives to metallic alloys continuously increases even if they are known for their lack of ductility so far. In this context, Qinqin Xu uses atomistic simulations to investigate the mechanical properties of various alumina polymorphs at the nano-scale.