Description du sujet de thèse

Refractory ceramics are specialized materials used for linings in industrial reactors that process molten substances, such as steel, aluminum, copper, glass, and mineral solids like cement clinker, at high temperatures. This PhD focuses on multiphase composite refractory materials for use in cement rotary kilns, which consist of a magnesium matrix with spinel (MgAl2O4) and/or hercynite (FeAl2O4) inclusions.
These composites have a complex microstructure characterized by multi-scale microcracking, caused by the heterogeneous interdiffusion of elements (like iron and aluminum) and abnormal aggregate growth during heat treatments. This microcracking enhances thermal shock resistance, which is the primary objective of this research. To understand how microstructure can optimize thermal shock resistance, we will utilize various characterization techniques:
- **High-Resolution Transmission Electron Microscopy (HRTEM)** will monitor structural changes.
- **Electron Backscattered Diffraction (EBSD)** will measure crystallographic orientations, providing insights into the microstructure of refractory aggregates and revealing structural defects. We will also perform crystal orientation mapping to link microstructural evolution with mechanical behavior and quantify phases and microcracks.
Micromechanical tests using wedge-splitting under scanning electron microscopy (SEM) will help identify the micro-mechanisms behind microcracking through localized strain field measurements. A specialized labeling system will be developed to improve correlation techniques for accurate strain measurements.
Additionally, we will conduct a metrological study on displacement and strain measurements to address low strain levels, assess image defects from beam instability, and propose correction strategies.

The main challenge of this PhD is to adapt and optimize these techniques for refractory materials, allowing us to study mechanical cracking behaviors at the microstructural level, with careful attention to sample surface preparation for accurate characterization.

Contexte de travail

This PhD is in the frame of the "THEFRAMIC" project, which focuses on the thermal shock resistance of refractory ceramics, the characterization of microstructure, and micromechanical analysis. It has been submitted as part of the AAP region Nouvelle Aquitaine 2025.

Additionally, this project aligns well with the Franco-Austrian ANR PRCI project NanOX-ML, which examines the evolution of nanostructures in oxide materials at high temperatures using advanced X-ray scattering and machine learning data analysis. This project began in spring 2024 and involves a joint thesis with the University of Leoben in Austria. It focuses on the characterization of materials with similar microstructures and utilizes common experimental equipment.
Finally, the PPrime laboratory's expertise in developing image correlation strategies is expected to enhance the precision of deformation field measurements for samples tested under stress.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.