Description of the thesis topic

The MAX phases are compounds with the formula Mn+1AXn, where M is an early transition metal, A belongs to groups 12 to 16, and X is carbon or nitrogen. These phases are promising for various nuclear applications, including core structures and fuel cladding in Generation IV nuclear reactors, as well as Zircaloy coatings to enhance accident-tolerant fuel (EATF) in pressurized water reactors. However, their microstructure tends to change under irradiation, leading to a decline in mechanical properties. Therefore, enhancing the radiation resistance of MAX phases is crucial for the long-term operation of nuclear reactors.

High Entropy MAX phases (HE-MAX phases) typically incorporate 3 to 5 elements in their M or A sites. These phases generally exhibit superior properties and potentially greater stability under irradiation compared to conventional MAX phases. The ANR HEIRMAX project (Development of High Entropy, Irradiation Resistant MAX Phases) aims to design and assess the radiation tolerance of medium to high entropy MAX phases. The tolerance will be evaluated through ion irradiation, focusing on the stability of their microstructure from nano- to meso-scale and mechanical properties (hardness, toughness, and compression behavior).

This project (ANR HEIRMAX) involves four French laboratories. Institut P' (Poitiers) is responsible for synthesizing the MAX and HE-MAX phases and characterizing their meso-scale microstructures. IJC-Lab (Orsay) will conduct ion irradiations and in situ transmission electron microscopy. GPM-Rouen and LEM3 (Metz) will study microstructure evolution under irradiation from nano- to micro-scales and correlate this with changes in mechanical properties. Three PhD students will be recruited to collaborate on this project.

At GPM, the PhD student will focus on nanoscale characterization to understand how ion irradiation affects the microstructure of a reference MAX phase (Ti3SiC2) and the new HE-MAX phases. He/she will participate in irradiation experiments and in situ observations at IJC Lab and will lead experimental investigations at GPM using transmission electron microscopy (TEM) and atom probe tomography (APT). Collaboration with LEM3 modellers will be crucial for improving and calibrating models using experimental data and for interpreting results mechanistically. Comparing his/her findings with mechanical data from another PhD supervised at LEM3 will provide deeper insights into the relationship between microstructure and properties. Their tasks of the PhD student at GPM will include:
- Literature review
- Sample preparation (focused ion beam machining)
- Microstructure characterization (APT, TEM)
- Data analysis and interpretation
- Participation in ANR progress meetings
- Dissemination of results (conferences, scientific papers)

Work Context

The Material Physics Group (GPM, UMR 6634) is a laboratory from the University of Rouen Normandie (URN), the National Center for Scientific Research (CNRS) and INSA Rouen Normandie. It is located on the Sciences and Engineering Rouen Normandie Campus in Saint-Etienne du Rouvray. The GPM is structured into 5 departments:
 Scientific Instrumentation,
 Metallurgy, Microstructure, Mechanics
 Functional materials and nanostructures
 Disordered systems and polymers
 Thematic openings and Innovations
It brings together 140 staff including 60 Associate professors, professors and Researchers, 30 Technical and Administrative staff and 50 PhD students, postdocs and internship students.
The recruited researcher will be attached to the "Metallurgy, Microstructure, Mechanics" department which includes 4 thematic teams:
 Nuclear materials
 Phase transformations Microstructures
 Multi-scale modeling of phase transformations
 Mechanics of materials
He will work in the "Nuclear Materials" team. This team is working on understanding the aging mechanisms (thermal or irradiation aging) of materials used in current reactors (generation II), on the development of new materials for next reactor generations (Generation IV, fusion) and on the relationships between microstructures and mechanical properties. It now brings together 4 Associate professors / professors, 3 PhD students and is supported by 8 research engineers, study engineers and technicians.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.

Constraints and risks

Work in controlled area (Radioprotection)

Additional Information

The ideal candidate should have a Master's degree or equivalent in materials science (microstructure, phase transformation, mechanical properties, diffusion). Knowledge of irradiation effects in materials is an advantage. Strong experimental skills, report-writing ability, and teamwork are essential, as collaboration with other PhD students in the project is vital.