Investigation of the stress field in nanostructured oxide materials during phase transformation by combining full-field modelling and X-ray diffraction

Recruitment of a Post Doc fellow (f/m), 18 months

Investigation of the stress field in nanostructured oxide materials during phase transformation

Responsibilities

The objective of this postdoctoral position is to estimate the stress field that accumulates in an oxide material sub- mitted to thermal loading. We will in particular study zirconium oxide (zirconia), which is extensively employed at an industrial scale as a refractory material in the glass industry, for dental implants, among other applications. Zirconia undergoes a tetragonal → monoclinic phase transition during cooling, starting around 1170°C. Modelling results will be compared with quantitative in situ high-temperature X-ray diffraction measurements performed at the European Synchrotron Radiation Source (ESRF). Stress levels in the GPa range are expected at the grain (nanometric) scale [1] in this material. Such significant levels of stress lead to the formation of a nanocrack network. Moreover, the process of phase transition may be influenced by such stresses, for example by enabling the formation of a high-pressure orthorhombic phase. The relatively uncomplicated microstructure of the specimens (featuring 24 crystal orienta- tions/variants) has been key to multi-year experiments at the ESRF from our group, enabling 3D scanning of the crys- tallographic reciprocal space [2] and surface imaging at 300 nm spatial resolution [3]. The responsibilities of the post- doctoral researcher will be twofold:

• The modelling of the stress field in monoclinic zirconia by employing a spectral (FFT) full-field method [4] during thermal loading is the subject of this study. In order to achieve this objective, random monoclinic polycrystalline microstructures will be constructed on the basis of established crystallographic rules for variant selection, in continuation of our previous work [5].
• The subsequent step will involve the extraction of synthetic X-ray diffraction diagrams from the model results, which will then be compared to the experimental ones. This comparison will be based on the experience of the team in this field [6]. Therefore, this position will also require analysis of experimental datasets to derive quan- titative values suitable for comparison with the model results.

Fiche de poste

Contacts

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