New Reliable Strategies for Optimizing Predictive Thermodynamics Models
Predictive thermodynamic models, developed by the Calphad method, are essential for designing new materials by anticipating their behavior without resorting to costly and time-consuming experiments. These models allow for the extrapolation of the properties of complex materials, predicting their behavior in extreme environments, and linking energy properties to in-service performance. However, current methods for developing these models are complex, and uncertainties are not quantified in existing software. Scientists still rely on their expertise to adjust and validate these models, which is time-consuming and poorly suited to the era of automation.
To address this, it is proposed to develop a reliable, autonomous, and fast digital tool capable of optimizing thermodynamic models based solely on experimental data provided by users. The goal is to provide simple, reliable, validated, and modular models, enabling users to make strategic decisions with confidence, such as evaluating new process conditions or optimizing manufacturing without risking uncertain extrapolations. This project aims to bridge the gap between specific experimental data and modern nonlinear programming methods, using advanced optimization approaches.
Investigation of Very High Cycle Fatigue Behavior of 13-4 Martensitic Stainless Steel Manufactured by Laser Metal Deposition: Influence of Microstructure, Post-treatments and Temperature Project
Recent research on 13-4 martensitic stainless steel manufactured by metal additive manufacturing, particularly using the Laser Metal Deposition (LMD) process, has made it possible to obtain materials with good mechanical properties. Following this optimization phase, current work is now focused on studying their Very High Cycle Fatigue (VHCF) behavior, which is a critical criterion for components subjected to repeated loading under severe operating conditions.
Fatigue is one of the main causes of failure in metallic components during service. This thesis therefore aims to understand and model the fatigue behavior of LMD-produced 13-4 steel. The work will investigate the influence of microstructure, thermomechanical treatments, and testing conditions on crack initiation and propagation during mechanical loading.
Experimental investigations will be carried out using ultrasonic fatigue testing devices. Failure mechanisms will be analyzed through multi-scale characterization techniques such as EBSD, SEM, and TEM. The final objective is to develop a predictive model capable of estimating the service life of components under operating conditions.
Characterization and Understanding of Degradation Mechanisms in Encapsulation Materials Used in New-Generation Silicon Photovoltaic (PV) Modules under Humidity and UV Stress
New-generation photovoltaic technologies (TOPCon, SHJ, tandems) are particularly sensitive to environmental stressors, including humidity (Damp Heat, DH), UV radiation, and thermal cycling. These stresses accelerate the degradation of encapsulation materials (EVA, POE, TPO), leading to performance losses in modules—such as reduced transparency, delamination, metal contact corrosion, and Potential-Induced Degradation (PID). Despite their increasing adoption, these novel encapsulants lack long-term durability data, while widely used EVA exhibits premature aging (degradation after 10–15 years of exposure). The combined degradation mechanisms (DH + UV + temperature) remain understudied, yet they reflect real-world exposure conditions
This thesis aims to identify and understand the physicochemical degradation mechanisms of polymer encapsulants under coupled stressors, focusing on:
- Multi-scale analysis (chemical structure, optical properties, microstructure) of materials during accelerated aging
- Development of an experimental protocol replicating real-world conditions (coupled DH/UV stress) to assess material resilience
- Study of additive roles in encapsulant degradation, including UV absorbers, peroxides etc.
Understanding microstructural changes during heat treatment of iron-rich SmCo magnets
The magnetic properties of SmCo magnets (remanence and coercivity) are linked to their microstructure. The final microstructure develops after sintering during homogenization and ageing heat treatments. The optimum temperature and/or duration of these treatments depend on the magnet’s composition. One of the major areas of development for commercial Sm2Co17 magnets is to achieve both high magnetic performance and a reduction in critical materials (notably cobalt). This is achieved by substituting part of the Co with Fe, which also helps to reduce raw material costs. However, the literature shows that when the Fe content exceeds 20% by weight, the coercivity of the magnets is diminished.
The aim of the thesis will be to understand the role and sensitivity of the process parameters that govern the evolution of the microstructure within Fe-rich Sm2Co17 magnets and the resulting properties. These developments will be monitored through various characterization techniques (chemical analyses, magnetic measurements, SEM and TEM observations, etc.) carried out on samples taken at different stages of the process. The aim is to systematically monitor (for the first time for this type of magnet) the structural transformations (chemical segregation, changes in Sm content, presence of defects, oxygen contamination, etc.) that occur from the synthesis of the alloy through to the final magnet. These characterizations should lead to a description of the mechanisms underlying the formation of the expected microstructure. These mechanisms are activated during the various heat treatments, but the influence of the metallurgical and chemical state (for example, defect density and chemical inhomogeneity) inherited from previous stages of the process is still poorly understood and will need to be clarified.
Growth of FAPbBr3 by CSS for X-ray detection
Lead halide perovskites, and particularly hybrid organic-inorganic materials based on formamidinium, possess exceptional optoelectronic properties that have been intensively exploited for photovoltaic (PV) applications. Within this family of materials, FAPbBr3 is also particularly promising for X-ray detection in medical applications. However, this technology requires the ability to deposit thick layers (>100 µm) over large areas. CEA-LITEN has developed an innovative approach for depositing inorganic perovskites using close-space sublimation (CSS), which meets these criteria. Very recently, it has been shown that it is possible to deposit FAPbBr3 using this method, marking a world first.
However, the growth mechanisms of FAPbBr3 and hybrid perovskites via CSS are largely misunderstood, and the possibilities offered by this deposition method are yet to be fully explored. Furthermore, these results are also extremely promising for PV applications, as similar growth is expected by substituting Br to form FAPbI3.
This thesis aims to (i) determine and optimize the growth conditions via CSS for FAPbBr3 layers, (ii) understand the growth mechanisms of FAPbBr3 through advanced characterizations (in-situ and ex-situ), and (iii) optimize devices for X-ray detection. The extension of this work to FAPbI3 for PV applications is also anticipated. The novelty of this approach and the potential to address multiple applications offer prospects for publications and patents.
Toward Robust Earthquake Location and Uncertainty Quantification in Dense Seismic Networks: Methodological Developments and Application to Cephalonia Island (Western Greece) and the Middle Durance region (France)
This PhD project aims to develop a robust methodological framework for earthquake location and realistic uncertainty quantification in the context of dense seismic networks. Despite recent advances in automatic detection, deep-learning-based phase picking, and earthquake relocation techniques, uncertainties related to velocity models and network geometry remain a major limitation and are often underestimated by conventional approaches. The project will compare and benchmark different detection, picking, and location methodologies in order to assess their respective strengths and limitations. Particular emphasis will be placed on identifying, quantifying, and disentangling the main sources of uncertainty, including phase picking errors, network configuration, and velocity model assumptions. The research will primarily rely on data from Cephalonia Island (Greece). In a second phase, the developed methodologies will be transferred to the Middle Durance region near Cadarache (France), allowing their applicability to lower-seismicity environments to be assessed. The expected outcomes include improved seismic catalogs, a better understanding of active tectonic processes.
Development of durable and flexible KNN piezoelectric materials: toward an alternative to lead-based ceramics and fluorinated polymers
The project aims to develop lead-free and PFAS-free (perfluoroalkyl and polyfluoroalkyl substances) piezoelectric thin films based on potassium sodium niobate (KNN) that are compatible with flexible substrates, in direct response to the growing regulatory and environmental constraints affecting conventional piezoelectric materials. PZT ceramics (lead titanate-zirconate) and PVDF polymers (polyvinylidene fluoride), which currently dominate the market, have significant limitations related to lead toxicity and the environmental persistence of PFAS, respectively. In this context, identifying sustainable and integrable alternative materials is a strategic priority for the CEA, particularly for flexible electronics applied to medical, embedded, and sustainable devices.
KNNs are among the most promising alternatives due to their high piezoelectric properties and high Curie temperature. However, their integration in the form of thin films remains severely limited by crystallization temperatures exceeding 600 °C, which are incompatible with polymer substrates. The project’s objective is to overcome this barrier by developing an innovative sol-gel combustion deposition process, enabling localized or global crystallization at low temperatures (<350 °C), compatible with flexible substrates. Beyond the KNN system, this approach could constitute
Characterisation of the physico-chemical properties of solid residues from biomass hydrothermal carbonisation
Hydrothermal carbonisation (HTC) is a thermochemical conversion process performed in pressurized water (2-6 MPa) between 180 and 260°C. The main product is a carbonaceous solid residue (hydrochar). Various applications are foreseen for hydrochar: combustion, gasification, adsorption, catalysis, soils amendment, hard carbon for Na-ion batteries, …, each of them requiring specific properties.
The objective of the thesis is to characterise and better understand the origin of several physico-chemical properties of biomass hydrochars. A special attention will be paid to hydrophobicity and drying capacity, to physical and textural characteristics of the particles (porosity, granulometry, specific surface), as well as to chemical characteristics (composition). The influence of biomass type and HTC conditions on these properties will be investigated.
The approach will consist in: experimentations in batch reactors on pre-selected biomass resources, together with use of different characterisation techniques for hydrochars; analysis of results aiming at determining links between the characteristics, elucidating the links between the resource and its hydrochar properties as a function of operational conditions.
Dual Active Bridge Topology Based on SiC Synthetic Switches for Ultra-Fast Active Stabilization of a Low-Inertia Converter-Dominated DC Grid.
With the massive deployment of direct current (DC) technologies on the grid, particularly photovoltaics and grid-connected battery energy storage systems (BESS), a growing share of electrical energy now flows through static power converters. Unlike classical grids dominated by rotating machines, which benefit from high natural inertia, power-electronics-dominated networks exhibit very limited inertia and may therefore experience highly dynamic voltage spikes, voltage drops, or even complete collapse. Some research focuses on synthetic inertia, emulated through specific control strategies implemented in static converters, but these approaches depend on equipment manufacturers and do not rely on established standardization. Another approach consists in designing dedicated equipment specifically intended for the active stabilization of low-inertia power systems, which is the direction explored in this PhD project.
A particularly demanding case concerns MVDC grids, which by construction rely entirely on static power converters, therefore exhibiting extremely low natural inertia, and requiring the use of converters based on specific technologies. Within the framework of this PhD, we propose the study and proof of concept of a converter connected to an MVDC electrical network operating between 6 and 12 kV, capable of injecting or absorbing very high levels of power in a transient manner, on the order of ten megawatts for durations ranging from 10 µs to 100 ms. The system will rely on an isolated Dual Active Bridge (DAB) topology, with a medium voltage capacitive DC bus at its primary.
This power electronics topic presents several technological bottlenecks. Synthetic switches (series-connected SiC devices, as investigated in a previous PhD in the laboratory) will have to be implemented in a real DAB converter. A highly isolated power supply for the gate drivers of these synthetic switches will need to be designed. The medium-frequency DAB transformer must be designed to transfer very high transient power while minimizing volume. Particular attention will therefore be paid to transient-oriented design, with the objective of identifying the key parameters that maximize, within a complex structure, the ratio between the converter rated power and its peak power.
Potential extensions toward other pulsed-power applications that could benefit from such a converter will be explored, taking into account their specific constraints.
Integrated waste treatment: design and optimisation of a multi-waste treatment scheme for a multi-purpose energy production
At the city scale, multiple waste streams such as household waste, compost, sewage sludge, yard waste, non-recyclable plastics, used oils, metals, glass, and others. All of these feedstocks exhibit variable seasonality and carbon content. Nowadays, the aforementioned streams are managed through recycling, and in some cases incineration or landfilling. Alternative treatment technologies, such as gasification, hydrothermal gasification, and anaerobic digestion, are being explored as potential pathways to improve the overall sustainability of waste management.
Existing scientific studies have largely focused on the conversion of individual waste types or on the application of a single technology to a specific waste stream, without accounting for regional integration, resource variability or systemic assessment. A city-scale analysis of waste streams could enable the identification of synergies between different waste types and the identification of optimal conversion pathways.
In this context, a key scientific challenge lies in the development of an integrated, multi-waste treatment framework capable of modelling, optimizing, and assessing a multi-waste, multi-product energy system at the city scale. The objective of this PhD project is to investigate waste treatment at the city scale, accounting for the seasonality of waste generation, waste stream composition, and local energy demand (heat, electricity, and gas). The work will consider local and European regulations (Waste Framework Directive, AGEC law, and RED III directive) as well as techno-economic and environmental aspects. The study will focus on one to three representative geographic areas and will establish a methodology that can be further applied to a broad range of territorial contexts.