Recycling of Alkaline Silicate Solutions from the Photovoltaic Industry for the Synthesis of Functional Nanoparticles.
The PhD project focuses on the valorization of alkaline silicate solutions generated from the cleaning, etching, and texturing of silicon wafers during photovoltaic cell manufacturing. These waste solutions, produced in large quantities (around 5000 m³ per GW of cells), are being studied as a potential source for synthesizing advanced materials such as nanoparticles (zeolites, MOFs) or activated materials used for pollutant capture.
The aim of this thesis work is to combine atomistic simulations (metadynamics) with experiments (small-angle scattering, NMR spectroscopy) to understand both the structure of these basic solutions and the mechanisms of crystallization or formation of mesoporous solids at different scales.
In addition to the synthesis of functional nanoparticles, a detailed understanding of these colloidal systems would provide deeper insight into the surfactant properties of silicates, potential interactions with polymer stability in solution, coating properties after drying, and the dissolution behavior of magnesium oxide, with the goal of developing new low-carbon hydraulic binders.
Effectiveness and robustness of the market design of low carbon electricity markets: the case of investment in new nuclear
The subject deals with the role of nuclear power in a low-carbon energy system, helping to lower the costs of the electricity system in the face of the penetration of timed renewable energies (wind, solar). Despite its systemic benefits, nuclear power is struggling to generate sufficient revenues in today's electricity markets, due to price volatility and declining load factors. Models show that very high prices during periods of load shedding could compensate for these losses, but such hypotheses remain to be proven. What's more, any construction contingencies (delays, extra costs) accentuate the risks for investors. To deal with this, suitable economic instruments are proposed: contracts for difference (CfD), capacity mechanisms, and regulated asset bases (RAB). The thesis aims to assess the effectiveness of these instruments through several steps: (1) long-term modeling of a low-carbon interconnected power system, (2) evaluation of the profitability of nuclear power in an “Energy only” market, and (3) modeling integrating these regulatory mechanisms to test their ability to cover construction and operating risks. Finally, tools such as real options or futures markets will be explored to address the uncertainties associated with the mass deployment of new nuclear reactors, from a national energy policy perspective.
Modeling and Characterization of Glass-Based Positive Electrodes for Li-Ion and Na-Ion Batteries
Amorphous cathode materials for Li-ion batteries have regained interest thanks to their practical capacities, which can exceed those of conventional commercial oxide cathode materials. Despite somewhat lower cell voltages, it could lead to significant enhancements in energy density. Nevertheless, the known amorphous cathode materials still face serious challenges prevent them from practical application: i) High irreversible capacity, ii) Low electronic conductivity, iii) Limited cyclability, iv) Lack of understanding of the involved phenomena due to their amorphous state, v) Most of the glassy cathode compositions explored so far are based on toxic vanadium.
In order to gain a deeper understanding of the influence of transition metals, glass formers, and synthesis conditions on the electrochemical performance of the cathode material, a PhD thesis is proposed in collaboration with CEA (Marcoule and Grenoble) and the National University of Singapore. The study will aim to combine various simulation approaches and experimental techniques, such as machine learning to design even more efficient cathode materials, computational modeling coupled with advanced in situ/operando characterization methods, and finally the development and performance evaluation of the synthesized materials.
Study of degradation mechanisms in silicon/perovskite tandem devices and correlation with operational behavior
Organic-inorganic hybrid perovskites have become one of the most promising photovoltaic technologies of the last decade, paving the way for the development of even more efficient solar panels at an affordable cost. A perovskite cell can be combined with a silicon cell to form a tandem cell with optimized light absorption. Today, this technology has achieved a record efficiency of 34.9%.
The CEA Tandem Solar Cells Laboratory (LCT) at the INES Institute is developing silicon/perovskite tandem solar cells. One of the main stumbling blocks to the spread of this technology is its stability over time. Indeed, the ionic nature of the perovskite absorber and various problems at the interfaces lead to degradation mechanisms that may or may not be reversible. These problems are closely linked to illumination, temperature and their variations (day/night and thermal cycles).
The LCT implements accelerated tests (continuous or cyclic illumination, thermal cycling, electrical bias) to understand degradation mechanisms according to cell architecture, and to predict behavior in real-life rooftop situations. This last aspect is crucial to guarantee the reliability of future commercial tandem panels, with lifetimes equivalent to those of today's silicon panels.
The candidate will produce his/her own devices according to the laboratory's state of the art. These cells may be encapsulated using the laboratory's reference process. Accelerated stability tests will be carried out with different climatic chambers at the LCT, including one capable of alternating day/night cycles at different temperatures. This latter chamber will be used to apply accelerated aging modes which, in recent studies, have demonstrated their ability to reproduce real outdoor behavior. In addition, the candidate will be able to modify the cell to integrate so-called “passivating” layers to improve stability, adapt the current of each sub-cell of the tandem structure, or analyze spectral effects on cell performance. Finally, the candidate will benefit from the LCT's expertise in terms of characterization (electrical measurements, photoluminescence, electron microscopy, XRD, etc.) as well as from the contribution of Grenoble's nanocharacterization platform with advanced characterization tools (XPS, cAFM, TOF-SIMS, etc.).
Study of the corrosion behaviour of complex multi-element materials/coatings in H2SO4 and HNO3 environments
This thesis is part of the CROCUS (miCro laboRatory fOr antiCorrosion solUtion design) project. The aim of this project is to develop a micro-laboratory for in situ corrosion analysis that can be brought into line with processes for synthesising anti-corrosion materials or coatings
By testing a wide range of alloy compositions using AESEC (a technique providing access to elementally resolved electrochemistry), the project will provide a real opportunity to build up a corrosion database in different corrosive environments, whether natural or industrial, with varying compositions, concentrations, pH and temperatures.
The aim of the thesis will be to study the corrosion behaviour of promising multi-element complex materials/coatings using electrochemical techniques coupled with AESEC.
The first part of this work concerns the determination of the limits of use of these promising alloys as a function of the proton concentration in H2SO4 and HNO3 media for temperatures ranging from room temperature to 80°C. The passivity of these alloys as a function of acid concentration will be studied using electrochemical techniques (voltammetry, impedance, AESEC).
The presence of certain minor elements in the composition of these alloys, such as molybdenum, may have a beneficial effect on corrosion behaviour. To this end, the passivation mechanisms involved will be studied using model materials (Ni-Cr-Mo), electrochemical techniques (cyclic and/or linear voltammetry, impedance spectroscopy and AESEC) and surface analysis.
The second part deals with the transition between passivity and transpassivity, and in particular the occurrence or non-occurrence of intergranular corrosion (IGC) as a function of oxidising conditions (presence of oxidising ions). The aim will be to determine the different kinetics (comparison between grain and grain boundary corrosion rates), as well as to validate the models set up to study IGC in steels.
Finally, the student will participate in the development of a materials database for corrosion in aggressive environments, whether natural or industrial, with different compositions, concentrations, pH and temperatures, enabling the development of new generations of corrosion-resistant materials or coatings through the use of digital design and artificial intelligence optimisation tools.
Modeling and prediction of electromagnetic emissions from power converters using deep learning
In recent years, electromagnetic compatibility (EMC) in power converters based on wide bandgap (WBG) semiconductors has attracted growing interest, due to the high switching speeds and increased frequencies they enable. While these devices improve power density and system efficiency, they also generate more complex conducted and radiated emissions that are challenging to control. In this context, this thesis focuses on the prediction, modeling, and characterization of electromagnetic interference (EMI) (> 30 MHz), both conducted and radiated, in high-frequency power electronic systems. The work is based on a multi-subsystem partitioning method and an iterative co-simulation approach, combined with in situ characterization to capture non-ideal and nonlinear phenomena. In addition, deep learning techniques are employed to model EMI behavior using both measured and simulated data. Generative artificial intelligence (Generative AI) is also leveraged to automatically generate representative and diverse configurations commonly encountered in power electronics, thereby enabling efficient exploration of a wide range of EMI scenarios. This hybrid approach aims to enhance analysis accuracy while accelerating simulation and design phases.
Integrating social interactions between chiropterans and variations in prey abundance to understand the distribution of chiropterans
The feeding behaviour of animals is of vital importance for the physical condition of individuals and is strongly influenced by the transfer of inter-individual information and competition. The study of these cause-effect relationships is particularly difficult for elusive taxa such as bats, whose extremely diverse hunting behaviour and strategies introduce a new degree of complexity. Bats increase the efficiency of their foraging by being attentive to the information-carrying behaviour of other individuals; they then adapt their own behaviour either to avoid competition or to increase it. Previous studies on this phenomenon of listening among bats have produced very different and partly contradictory results, probably because they generally focused on a single species, differed considerably in the rate of eavesdropping and generally did not take account of the activity of conspecifics. Taking these social interactions into account now seems essential both to advance our ‘global’ understanding of how chiropterans integrate social information into their decision-making, to explain species distribution patterns and to elucidate the mechanisms by which species coexist. This understanding will help to provide answers in the field of conservation in relation to the increase in anthropogenic pressures, such as lighting and the fragmentation of environments. The aim of this thesis is to identify the pairs of species that are most subject to competition, in order to understand the causes and perceive the consequences at the scale of the landscape and anthropogenic pressures (light pollution). A second objective will be to characterise the feeding areas and to study the spatio-temporal rearrangement of the food resource - measured directly - over time, and its consequences for chiropterans and their interactions. A third objective will be to apply these concepts to a practical case of anthropogenic modification of natural balances and to model the effects (causal model). The case will be that of the effect of light pollution, and will enable clear hypotheses to be put forward on the effect of light pollution (most of the arthropod prey of chiropterans being attracted and concentrated under light sources) and its consequences on the competitive equilibrium in chiropterans.
Reducing the complexity of France's building stock to better anticipate anticipate energy demand flexibility and the integration of solar solar resources
The aim of this work is to respond to the current challenges of energy transition in the building sector, France's leading energy consumer. French public policies are currently proposing far-reaching solutions, such as support for energy-efficient home renovation and incentives for the installation of renewable energy production systems. On a large scale, this is leading to structural changes for both building managers and energy network operators. As a result, players in the sector need to review their energy consumption and carbon impact forecasts, integrating flexibility solutions adapted to the French standard. Some flexibility levers are already in place to meet the challenges of energy and greenhouse gas emission reduction, but others need to be anticipated, taking into account long-term scenarios for energy renovation and the deployment of renewable energy sources, particularly photovoltaic energy, across the whole of France. The issue of massification is therefore an underlying one. That's why this thesis proposes to implement a methodology for reducing the size of the French installed base based on previously defined criteria. In particular, the aim will be to define a limited number of reference buildings that are statistically representative of the behavior resulting from the application of flexibility strategies that meet the challenges of energy efficiency and limiting greenhouse gas emissions. To this end, the CSTB (Centre Scientifique et Technique du Bâtiment) is developing and making available a database of French buildings (BDNB: Base de Données Nationale des Bâtiments), containing information on morphology, uses, construction principles and energy consumption and performance.
Optimising the durability of high-temperature metal alloys: exploring new oxidation conditions
The aim of the OPTIMIST exploratory project is to increase the service life of metal alloys (alumina and chromia forming alloys) by forming a protective oxide layer, as is almost always the case to protect alloys from corrosion. The great originality of OPTIMIST will consist in forming an oxide layer with a minimum of 0D (point defects) and 2D (grain boundaries) structural defects. This objective will be based on two distinct strategies: the first will consist of forming a so-called endogenous oxide layer, i.e. by pre-oxidising the substrate by carefully choosing the pre-oxidation conditions (temperature, oxidising medium, oxygen partial pressure) in two types of Rhines Pack specifically developed at CEA/DES and IJL; the second will consist of forming a so-called exogenous oxide layer, i.e. created by a deposition technique: the HiPIMS recently commissioned at the CEA/INSTN. Different pre-oxidation conditions (for the endogenous layer) and process conditions (for the exogenous layer) will be investigated, then their 0D and 2D defects will be characterised at SIMaP using a novel combination of cutting-edge structural (TEM-ASTAR), chemical (atom probe, SIMS, nano-SIMS) and electronic (PEC PhotoelEctroChemistry) techniques. Finally, these characterised samples will be corroded in two environments (in air and in molten salts) at high temperatures to assess the effectiveness of the protection compared with conventional pre-oxidation. The stages of oxide growth, its stoichiometry and its microstructure (grain size and shape, nature of the grain boundaries) will thus be identified as a function of the endo and exogenous growth conditions so as to control them in order to achieve an oxide layer containing as few defects as possible.
Simplified Model for Rotary Tube Calcination
Since the vitrification lines at La Hague began operation in 1989, ORANO (formerly AREVA) has faced difficulties in controlling the calciner. Actions taken to significantly reduce these problems have considerably eased them, but without completely eliminating them. Most of the recommended actions are based on expert opinions, which themselves are based on inactive test results that don't cover all situations encountered by ORANO. To definitively resolve these control difficulties, it was decided to launch a more theoretical modeling study, while simultaneously investigating new calciner control instrumentation.