High yield strength austenitic stainless steels for nuclear applications: numerical design and experimental study
The PhD thesis is part of a project that aims at designing new austenitic stainless steels grades for nuclear applications, which are specifically suitable to in-service conditions encountered by the components and to the manufacturing process. More precisely, the subject deals with bolt steels achieved by controlled nitriding of powders which are then densified by hot isostatic pressing. Indeed, current bolt steel grades may suffer from stress corrosion cracking, while nitriding allows to increase the chromium content, which is beneficial from that point of view.
The study will start by the definition of specifications and associated criteria, then CALPHAD calculations in the Fe-Cr-Ni-Mo-X-N-C system will be done to define promising compositions. Then, selected compositions will be supplied as powders. The behaviour of powders during nitriding will be studied and modelled. Samples will be nitrided, densified and heat treated. One grade will be then selected and fully characterised: mechanical properties and deformation mechanisms, corrosion behaviour. One important objective is to demonstrate the advantages of the new grade compared to the industrial solution.
Brines for metal recycling
Critical metals are essential for a range of technologies that are vital to reduce our carbon dioxide emissions. However, the global recycling rate for metals contained in electronic waste is below 20%, indicating that electronic waste is a relatively untapped source of metals. Additionally, it is increasingly urgent to develop effective processes for recycling waste from products like solar panels, as the volume of waste solar pannels generated is set to rise significantly in the coming years. Currently, conventional hydrometallurgical methods often rely on toxic aqueous solutions to dissolve metals, which presents substantial environmental challenges.
This project proposes an innovative alternative by using concentrated brines (aqueous salt solutions) to oxidize and dissolve metals. This thesis will investigate the fundamental properties of brines and their ability to dissolve metals through various techniques, particularly electrochemical methods. Artificial intelligence methods developed within the lab will be employed to screen a wide range of brines that would allow metal dissolution. Subsequently, brine-based recycling processes will be developed to recover metals from printed circuit boards and solar panels. Finally, metal separation and the treatment of used brines will be explored using membrane and electrochemical processes.
Understanding the mechanisms of direct CO2 hydrogenation using (Na,K)FeOx catalysts via theoretical-experimental coupling
In the context of climate change, we need to reduce our CO2 emissions by using less energy. Another approach is to capture, store and use CO2, with the aim of moving towards a circular carbon economy and, ultimately, defossilization. With this in mind, the direct hydrogenation of CO2 enables it to be transformed into molecules of interest such as hydrocarbons, via the coupling of the reverse water gas shift (RWGS) reaction and Fischer-Tropsch synthesis (FTS).
Computational operando catalysis has recently emerged as a reasoned alternative to the development of new catalysts, thanks to a multi-scale approach from the atom down to the active particle, to model catalyst selectivity and activity. New tools combining ab initio simulations (DFT) and molecular dynamics (MD) via machine learning algorithms bridge the gap between the precision of DFT calculations and the power of atomistic simulations. Current bifunctional catalysts (active for RWGS, and FTS) for direct CO2 hydrogenation are based on doped iron oxides (metal promoters).
The aim of this project is the theoretical study of Na-FeOx and K-FeOx catalysts doped with Cu, Mn, Zn and Co, in 4 stages: DFT simulations (adsorption energies, density of states, energy barriers, transition states), microkinetic modeling (reaction constants, TOF), construction of interatomic potentials by DFT/machine learning coupling, simulation of whole particles (selectivity, activity, microscopic quantities).
This theoretical study will go hand in hand with the synthesis and experimental measurements of the studied catalysts, and optimized catalysts emerging from the computational results. All the accumulated data (DFT, MD, catalytic properties) will be fed into a database, which can eventually be exploited to identify descriptors of interest for CO2 hydrogenation.
study of lithium isotopes separation by laser
This thesis concerns the study of different ways of separating lithium isotopes by laser. The work will be conducted both theoretically and experimentally. The objective is to determine an optimal way as well as its performances.
Flotation for Li-ion active materials recycling : limitations and influence of hydrodynamics and interfacial physico-chemistry on their selective separation
Battery recycling is now a major geopolitical, economic and environmental issue for the EU. Graphite, which makes up the anode of Li-ion batteries, is very rarely recycled. It is concentrated in a fraction called blackmass, where it is mixed with metal oxides of high commercial value. This graphite is then considered as an impurity and causes oversizing of hydrometallurgical operations. Since natural graphite is considered critical by EU and in order to reduce the operating and investment costs of hydrometallurgical processes, it is proposed to carry out a pre-treatment step on the blackmass in order to valorize the graphite directly. This stage is carried out by flotation. This process for separating solids suspended in water uses gas in the form of air bubbles to separate the particles according to their difference in wettability and therefore their attachment to the air bubbles. The complexity of the flotation process, linked to the dependence on both the nature of the interfaces and the hydrodynamic conditions, requires in-depth understanding of the mechanisms involved.
The aim of the proposed project, which follows on from two internal projects, is to identify the mechanisms at work during flotation, using methods of interfaces characterization, stability and rheology of foam fraction, imaging, etc., with a view to improving the performance of the flotation stage and extending it to other recycling challenges.
The PhD thesis work will be carried out at the Laboratoire des technologies de Valorisation des procédés et des Matériaux pour les ENR (LVME) at CEA Grenoble and in close collaboration with the Laboratoire de Caractérisations Avancées pour l'Energie (LCAE) at CEA Grenoble, the Laboratoire des Procédés Supercritiques et décontamination (LPSD) and the Laboratoire de développement des procédés de recyclage et valorisation pour les systèmes énergétiques décarbonnés (LRVE) at CEA Marcoule (30). In parallel with the experimental work, the models and mechanisms involved and the associated technical solutions will have to be proposed.
The scientific and industrial interest of the subject guarantees that the work will be promoted through international communications. After the PhD, you can join one of the best academic or applied research teams, or pursue an R&D career directly in industry.
Biogas upgrading with an advanced Biorefinery for CO2 conversion
The use of renewable energy sources is a major challenge for the coming decades. One way of meeting the growing demand for energy is to valorize waste. Among the various strategies currently developed, the recovery of biogas from anaerobic digestion plants appears to be a promising approach. Biogas is composed mainly of methane, but also of unused CO2 (around 40%). The project proposed here is to reform biogas using a renewable biohydrogen source to convert the remaining CO2 into pure CH4. We propose to set up a stand-alone advanced biorefinery that will combine photoproduction of hydrogen from waste (e.g.: lactoserum) by the bacterium Rhodobacter capsulatus combined with the CO2 present in the biogas in a biomethanation unit containing a culture of Methanococcus maripaludis, a methanogenic archaea able to produce CH4 from CO2 and H2 only (according to the Sabatier reaction). The aim is to produce CH4 in an energy-efficient and environmentally-friendly way.
Study of of the thermodynamic of K2CO3-CO2-H2O for the development of NET and SAF technologies
.Bioenergy with Carbon Capture and Storage (BECCS) uses biomass energy while capturing the carbon dioxide released by the process, resulting in negative emissions into the atmosphere. The reference process in Europe uses potassium carbonate but at atmospheric pressure [1], whereas its sequestration or hydrogenation into sustainable molecules requires high pressures.
The thesis consists in acquiring new thermodynamic and thermo-chemical data at high temperature/pressure [2] required for the energy optimization of such a process, and integrating them into a thermodynamic model.
The overall process will then be reassembled in order to quantify the expected energy gain.
The thesis will be carried out at the Thermodynamic Modeling and Thermochemistry Laboratory (LM2T), in collaboration with LC2R (DRMP/SPC) for the experimental part.
References :
[1]K. Gustafsson, R. Sadegh-Vaziri, S. Grönkvist, F. Levihn et C. Sundberg, «BECCS with combined heat and power: assessing the energy penalty,» Int. J. Greenhouse Gas Control, vol. 110, p. 103434, 2021.
[2] S. Zhang, X. Ye et Y. Lu, «Development of a Potassium Carbonate-based Absorption Process with Crystallization-enabled High-pressure Stripping for CO2 Capture: Vapor–liquid Equilibrium Behavior and CO2 Stripping Performance of Carbonate/Bicarbonate,» Energy Procedia, 2014