Description du sujet de thèse

Ceria-stabilized zirconia-based composites: influence of microstructure, composition and manufacturing process on phase transformation-induced plasticity and shape memory effect.
Context. This PhD thesis will be carried out within the framework of the bilateral collaborative project “ImPatienCe” (ANR-25-CE08-1872-01 Ductile ceramics for patient-specific implants; between BAM-Berlin and MATEIS-Insa Lyon) aimed at optimizing ceria-stabilized zirconia-based "ductile" composites (Ce-TZP composites) for ceramic additive manufacturing (AM) using stereolithography (SLA). Although ceramic SLA technologies show an excellent degree of maturity, they still generate processing defects that can be critical for “brittle” ceramics. “ImPatienCe” has its origins in our results showing that the use of SLA enhances transformation induced plasticity (TRIP) in tri-phasic Ce-TZP composites. In addition, we have also shown that the use of "ductile" ceramics tolerates the presence of typical AM processing defects, without compromising their mechanical performances. In the longer-term, this PhD work will contribute to the development of 3D printed patient-specific ceramic medical implants (e.g. jaw, mandibular joint, etc.) with improved osseointegration, mechanical properties and durability.
Objective and research activities. Within this context, the objective of this thesis is to better understand the mechanisms governing the microstructure evolution of “conventionally” and SLA-processed Ce-TZP composites after the shaping step (i.e. during thermal post-treatments of debinding and/or sintering) and the impact of microstructural features on the degree/characteristics of TRIP and the resulting shape-memory effect. These aspects will be examined in a multi-scale experimental approach, studying phenomena occurring at the macro scale (mechanical test samples), in the range where tetragonal (t) to monoclinic (m) phase transformation bands are formed under stress (mesoscale) and at the grain scale (micron scale). Thus, the project will focus on studying different compositions (triphasic or biphasic Ce-TZP composites) and/or post-thermal treatments characteristics (heating rate, temperature, time) to optimize both microstructures as well as the mechanical behaviour. Scientific questions addressed will include: 1) the TRIP-microstructure relationships, 2) SLA-paste scraping and/or LASER-UV curing effects, 3) the role of zirconia grains crystallographic orientation and/or of residual stresses on their transformability, 4) the reversibility of the mechanically induced t-m transformation by heating, 5) the cyclability or number of loading-unloading-heating cycles without a decrease in the mechanical strength.
Responsibilities include: working on the work packages of the ANR project “ImPatienCe” with the aim of obtaining a Doctorate Degree, processing ceramics from powders/pastes (by pressing/CIP/SLA) and performing thermal treatments and characterization on green/final ceramics (dilatometry, XRD, density, thermal analyses, Vickers hardness), performing electron microscopy measurements (SEM, TEM, SEM-EBSD, FIB-tomography), developing and carrying out mechanical tests to evaluate the mechanical behaviour (ex situ and in situ) in relation to “t-m” zirconia phase transformation (and to the inverse “m-t” transformation by heating), quantitative evaluation and modeling of data and results, collaborating with national and international partners, writing scientific papers, giving national and international scientific oral communications, writing the PhD manuscript and preparing the dissertation, supervising master students, participating in scientific vulgarization activities.

Contexte de travail

MATEIS is a Materials Science laboratory at the intersection of disciplinary fields, mainly in chemistry, physics and mechanics. The MATEIS laboratory studies the three classes of materials (metals, ceramics, polymers) and their composites by integrating volume, surface and interface characteristics. The laboratory is committed to describing the relationships between elaboration, microstructure and properties, with an experimental and modelling approach. MATEIS is involved in the fields of advanced development processes, characterization of the microstructure (often in-situ and/or in 3D), modelling at different scales, characterization of use properties and their evolution.
MATEIS is currently one of the largest French laboratories in terms of staff in the field of "Materials Science and Engineering" (particularly for so-called "structural" materials). The laboratory has about 170 people, organized into 6 research teams. It is a Joint Research Unit (UMR5510), under the supervision of: INSA Lyon (main supervision), Claude Bernard Lyon 1 University and CNRS. The unit is mainly located on the Lyon-Tech Campus of La Doua at INSA Lyon, but some members interested in the study of materials-cells interactions work on the Lyon-Est faculty of health.
The MATEIS lab consists of 6 research teams. The METAL, PVMH and CERA teams are each interested in a class of materials (metals and alloys; polymers and semi-crystalline amorphous materials; ceramics and composites, respectively). The CORRIS, SNSM and I2B teams present a more generic activity applicable to the three classes of materials. The SNMS team develops new techniques for observing microstructures and their evolution, in connection with their applications. The CORRIS group is interested in surface properties and the study of corrosion and corrosion resistance. Finally, the I2B team develops and characterizes all types of materials for medical purposes, with a particular interest in the in-depth study of biological interactions.
MATEIS is a member of the Ingélyse Federation and the Carnot Institute I@L, it is associated with the Institute of Chemistry of Lyon and participates in the Axelera, Plastipolis, Viameca and Techtera competitiveness clusters. The laboratory was a founding member of the GIS "Multimatériaux architecturés" (Grenoble INP and INSA de Lyon) and is involved in laboratories of excellence (iMust, Manutech). The laboratory actively participates in national projects (ANR, Region, etc.), European projects and projects in relation to industry.
The project proposed in the framework of this PhD thesis will be carried out within the "Ceramics and Composites" group of the MATEIS laboratory (CERA team). The CERA group works on the different aspects of the Science and Technology of Ceramic Materials, balancing fundamental and applied research. The group is made up of 50 members (15 researchers and teacher-researchers, including 10 HDRs), working on 4 themes: 1) nanostructured/multifunctional ceramics and composites; 2) thermostructural composites for aeronautical and space applications; 3) ceramics and composites for biomedical applications; and 4) mineral and organo-mineral materials for construction. The CERA group develops research themes ranging from the development of ceramics, through the study of the evolution of the microstructure (during shaping, consolidation and/or service) to the characterization of the properties of use.
We are therefore looking for a candidate for this thesis with a background in materials science and an interest in ceramics materials and/or electron microscopy techniques. Knowledge or previous internship in mechanical testing and/or additive manufacturing would be appreciated as well as basic knowledge of programing and software skills. Finally, good communication, initiative/commitment and ability to work in a team, willingness to cooperate and willingness to learn will be appreciated.