CIFRE thesis in the field of non-destructive testing using magnetic sensors in collaboration with 3 partners:
Laboratoire de Nanomagnétisme et Oxyde (SPEC/LNO) du CEA Paris-Saclay
Laboratoire de Génie Electrique et Ferroélectricité (LGEF) de l’INSA Lyon
Entreprise CmPhy
Ferritic steels are being considered as structural materials in future fission and fusion nuclear reactors. These alloys have highly original properties, due to the coupling between chemical, magnetic and elastic interactions that affect their thermodynamic properties, the diffusion of chemical species and the diffusion of point defects in the crystal. The aim of the thesis will be to model all of these effects at the atomic scale and to integrate them into Monte Carlo simulations in order to model the segregation and precipitation kinetics under irradiation, phenomena that can degrade their properties in use. The atomic approach is essential for these materials, which are subjected to permanent irradiation and for which the laws of equilibrium thermodynamics no longer apply.
The candidate should have a good background in statistical physics or materials science, and be interested in numerical simulations and computer programming. The thesis will be carried out at CEA Saclay's physical metallurgy laboratory (SRMP), in a research environment with recognised experience in multi-scale modelling of materials, with around fifteen theses and post-doctoral contracts in progress on these topics.
A Master 2 internship on the same subject is proposed for spring 2025 and is highly recommended.
To assess the safety of nuclear power plants, the CEA develops and uses multi-scale thermohydraulic simulation tools. The application of CFD to two-phase flows is limited because it requires many models that are difficult to determine. Among our other tools, direct numerical simulations (DNS) with resolved interfaces provide reference data inaccessible by experimental means. This is for example the case of bubble swarms, where heat and mass transfers are influenced by complex collective effects.
In order to reduce the cost of these DNS simulations, we recently developed an approach [1] which shows promising results: it consists of coupling a fine resolution of thermal transfers at the liquid-vapor interfaces to a far field calculated on a less resolved mesh. To broaden the application of this method to more industrial cases, it is necessary to take into account collisions between bubbles and to adapt the model to the phase change.
During this thesis, we propose to start with this physical modeling work and its implementation in C++ in our open-source simulation code TRUST/TrioCFD [2]. Next, we will use this new capacity to carry out a parametric study and an in-depth physical analysis of the phenomena which would ultimately lead to an improvement in heat transfer models in industrial codes.
[1] M. Grosso, G. Bois, A. Toutant, Thermal boundary layer modelling for heat flux prediction of bubbles at saturation: A priori analysis based on fully-resolved simulations, International Journal of Heat and Mass Transfer, Vol 222, 2024, https://doi.org/10.1016/j.ijheatmasstransfer.2023.124980
[2] Trio_CFD webpage : http://triocfd.cea.fr/recherche/modelisation-physique/two-phase-flows
In the field of industry and particularly energy, liquid water circuits are omnipresent. Fluids, by interacting with pipes made from metal alloys, inevitably lead to the formation of corrosion products.
Predicting the behavior of small particles (order of magnitude of µm) is therefore of particular interest. Indeed, due to their size, the behavior of the latter is governed by forces of electrical origin responsible for their adhesion to the surfaces. The electrokinetic properties and in particular the surface potential thus control the fate of the particle and can be defined using the zeta potential. This quantity characterizes a solid/solution couple and takes into consideration both the particle and its surface chemical properties as well as the solution where the particle is located.
If the characterization of the zeta potential at room temperature is quite widespread, its determination at high temperature is today confined to a few examples (theses by C. Cherpin 2022 [1] and M. Barale 2006 [2], studies of VTT [3] and EDF with the University of Besançon 2002 [4] and the EPRI patent 1994 [5]). The CEA (LC2R) has developed an innovative measurement method currently being patented to explore poorly developed experimental techniques based on theoretical hypotheses to be confirmed.
Through multi-physics (flow, temperature, chemistry, electrochemistry, etc.) and multi-scale (microscopic particles influencing a macroscopic state) approaches, the objective of the thesis is therefore to carry out measurements of the surface properties of particles in water at high temperature depending on the physicochemical conditions (pH, RedOx and temperature), to adapt existing models or propose new ones then validate them with experimental data.
The data thus obtained is intended to feed the simulation codes in order to better understand and control the aging of the circuits.
[1] C. Cherpin, PhD, 2022, Modelling the behaviour of colloidal corrosion products in the primary circuit of Pressurized Water Reactors
[2] M. Barale, PhD, 2006, Etude du comportement des particules colloïdales dans les conditions physico-chimiques du circuit primaire des réacteurs à eau sous pression
[3] E. Velin, Master’s Thesis, 2013, The effect of Temperature on the Zeta Potential of Magnetite Particles in Ammonia, Morpholine and Ethanolamine Solutions
The widespread use of MOX fuels (based on (U,Pu)O2 mixed oxides) in nuclear reactors is an option currently being studied in France. Such a strategy could help to stabilise the plutonium inventory while conserving natural uranium resources. Such scenario involves the multi-recycling of plutonium, which requires an upgrade of the existing infrastructures to enable the reprocessing of spent MOX fuel at industrial scale. Consequently, the development of innovative processes and related basic research is then imperative.
The oxidation of MOX spent fuel by ad hoc thermal treatment could overcome a major technological barrier identified, i.e. how to separate the fuel from its cladding prior to the dissolution step. However, there is limited data available on the oxidation of (U,Pu)O2 and even less has investigated the impact of fission products and the fuel microstructure properties. The aim of this PhD thesis is to help fill this gap. The selected student will study (U,Pu)O2 samples with a microstructure identical to that of industrial MOX fuels, as well as (U,Pu)O2 doped with inactive fission products, thus simulating irradiated fuels, as shown in a thesis defended in the laboratory. The experimental work will focus on oxidation experiments coupled with in-situ and multi-scale analyses using laboratory technics and synchrotron radiation-based characterizations. These results will lead to the proposal of a phenomenological description linking the kinetics of (U,Pu)O2 oxidation with the fission products chemistry, the O2 partial pressure and the temperature and duration of the thermal treatment.
By the end of this PhD, the graduate student with a background in physical chemistry of materials will have developed expertise in a broad range of experimental techniques. These skills will open up many career opportunities in academic research or industrial R&D, both within and beyond the nuclear sector.
High throughput screening, which has been used for many years in the pharmaceutical field, is emerging as an effective method for accelerating materials discovery and as a new tool for elucidating composition-structure-functional property relationships. It is based on the rapid combinatorial synthesis of a large number of samples of different compositions, combined with rapid and automated physico-chemical characterisation using a variety of techniques. It is usefully complemented by appropriate data processing.
Such a methodology, adapted to lithium battery materials, has recently been developed at CEA Tech. It is based, on the one hand, on the combinatorial synthesis of materials synthesised in the form of thin films by magnetron cathode co-sputtering and, on the other hand, on the mapping of the thickness (profilometry), elemental composition (EDS, LIBS), structure (µ-DRX, Raman) and electr(ochim)ical properties of libraries of materials (~100) deposited on a wafer. In the first phase, the main tools were established through the study of Li(Si,P)ON amorphous solid electrolytes for solid state batteries.
The aim of this thesis is to further develop the method so as to enable the study of new classes of battery materials: crystalline electrolytes or glass-ceramics for Li or Na, oxide, sulphides or metal alloys electrode materials. In particular, this will involve taking advantage of our new equipment for mapping physical-chemical properties (X-ray µ-diffraction, Laser-Induced Breakdown Spectroscopy) and establishing a methodology for manufacturing and characterising libraries of thin-film all-solid-state batteries. This tool will be used to establish correlations between process parameters, composition, structure, and electrochemical properties of systems of interest. Part of this work may also involve data processing and programming the characterisation tools.
This work will be carried out in collaboration with researchers from the ICMCB and the CENBG
N-doped oxides and/or oxinitrides constitute a booming class of compounds with a broad spectrum of useable properties and in particular for novel technologies of carbon-free energy production, surface coatings for improving the mechanical strength of steels or protection against corrosion and multifunctional sensors. In this research field the search for new materials is particularly desirable because of unsatisfactory properties of current materials. The insertion of nitrogen in the crystal lattice of an oxide semiconductor allows in principle to modulate its electronic structure and transport properties enabling new functionalities. A detailed understanding of these aspects requires materials that are as perfect as possible. The production of corresponding single crystalline thin films is however highly challenging. In this thesis work, single crystalline oxynitride heterostructures will be grown by atomic plasma-assisted molecular beam epitaxy. The heterostructure will combine two N doped layers: a N doped BaTiO3 will provide ferroelectricity and a heavily doped ferrimagnetic ferrite whose magnetic properties can be modulated using N doping to obtain new artificial multiferroic materials better suited to applications. The resulting structures will be investigated with respect to their ferroelectric and magnetic characteristics as well as their magnetoelectric coupling, as a function of the N doping. These observations will be correlated with a detailed understanding of crystalline and electronic structures. The later will be modelled thanks to electronic structure calculation to reach a comprehensive description of this new class of materials.
The student will acquire skills in ultra-high vacuum techniques, molecular beam epitaxy, ferroelectric and magnetic characterizations as well as in state-of-the-art synchrotron radiation techniques. X-ray magnetic dichroism is particularly suited to this study and the project will give rise to close collaboration and/or co-supervision with the DEIMOS beamline of SOLEIL synchrotron.
Spinel-type transition metal oxides (AB2O4) appear spontaneously during the generalized corrosion of steels or alloys in aqueous or gaseous environments at high temperatures. This spinel phase forms a continuous corrosion layer and thus regulates corrosion processes by controlling conductivity and material transport between the material and the oxidizing medium. They are also applied voluntarily as protective coatings against degradation phenomena. In particular, the Mn-Co-O spinel system is very promising as protective conductive layers on ferritic stainless steel used to fabricate interconnects in solid oxide fuel cells for green hydrogen production. The composition of the spinel phase determines the protective performance of the coatings. This feature is particularly delicate for materials used in high-temperature electrolyzers, as electronic transport must be optimal (high electrolysis), but must not be accompanied by material transport (low cation diffusion).
In contrast, electronic transport properties of spinel-type transition metal oxides are generally not well understood. Measurements are made on complex corrosion layers (or coatings) of variable composition, low crystallinity, complex microstructure and low thickness. Furthermore, spinel oxides exhibit magnetic properties and composition-dependent cationic disorder that are usually ignored, even though they have a strong impact on electronic transport. The properties highlighted here are the ones that also hold significant importance within the field of spintronics. Thus, tuning the chemical composition of these spinel-structured oxides (normal, inverse or mixed) offers a wide range of magnetic (ferrimagnetic, antiferromagnetic) and electronic (semimetallic, semiconductor, insulator) properties. In particular, CoMn2O4 is expected to exhibit a complex magnetic configuration [1], mainly related to the arrangement of Co2+ and Mn3+ cations in interstitial sites, which needs to be analyzed in detail. Unlike corrosion layers, these physical studies require the synthesis of thin films of well-controlled composition and high crystallinity.
The aim of the thesis is to build up knowledge of physicochemical and structural properties of (Mn,Co)3O4 in order to contribute to the elaboration of Mn-Co-O phase diagrams and electronic transport models based on the relationship between order/disorder, magnetic properties and resistivity of (Mn,Co)3O4. Eventually, the whole (Fe,Cr,Mn,Co)3O4 system will be also considered. The study will be carried out on thin films of perfectly controlled composition and high crystallinity, and will be enhanced by numerical simulations. The experimental and theoretical work will be based on the results of previous studies on (Ni,Fe,Cr)3O4 epitaxial thin films [2,3].
The thesis will be divided as follows:
- Growth of thin films and multilayers by MBE (Molecular Beam Epitaxy) (J.-B. Moussy)
- Spectroscopic characterization using XPS (X-ray photoemission spectroscopy) (F. Miserque)
- Fine structure characterization by DRX and X-ray absorption (XMCD) (P. Vasconcelos)
- Modeling of core-level spectra (XPS, XAS and XMCD) and atomistic modeling (A. Chartier)
- Magnetic characterization by SQUID/VSM magnetometry and electric transport characterization (J.-B. Moussy)
[1] Systematic analysis of structural and magnetic properties of spinel CoB2O4 (B= Cr, Mn and Fe) compounds from their electronic structures, Debashish Das, Rajkumar Biswas and Subhradip Ghosh, Journal of Physics: Condensed Matter 28 (2016) 446001.
[2] Stoichiometry driven tuning of physical properties in epitaxial Fe3-xCrxO4 thin films, Pâmella Vasconcelos Borges Pinho, Alain Chartier, Denis Menut, Antoine Barbier, Myrtille O.J.Y. Hunault, Philippe Ohresser, Cécile Marcelot, Bénédicte Warot-Fonrose, Frédéric Miserque, Jean-Baptiste Moussy, Applied Surface Science 615 (2023) 156354.
[3] Elaboration, caractérisation et modélisation de films minces et multicouches à base d’oxydes (Ni,Fe,Cr)3O4 appliquées à la corrosion et à la spintronique, A. Simonnot, thèse en cours.
Context : Understanding the behavior of metals at high deformation rate [4] (between 104 and 108 s-1) is a huge scientific and technologic challenge. This irreversible (plastic) deformation is caused by linear defects in the crystal lattice : these are called dislocations, which interact via a long-range elastic field and contacts.
Nowadays, the behavior of metals at high deformation rate can only be studied experimentally by laser shocks. Thus, simulation is of paramount importance. Two approaches can be used : molecular dynamics and elastodynamics simulations. This thesis follows the second approache, based on our recent works [1, 2], thanks to which the first complete numerical simulations of the Peierls-Nabarro Equation (PND) [5] was performed. The latter equation describes phenomena at the scale of the dislocation.
PND is a nonlinear integrodifferential equation, with two main difficulties : the non-locality in time and space of the involved operators. We simulated it thanks to an efficient numerical strategy [1] based on [6]. Nevertheless, the current implementation is limited to one CPU –thus forbidding thorough investigations on large-scale systems and on long-term behaviors.
Thesis subject : There are two main objectives :
- Numerics. Based on the algorithmic method of [1], implement a HPC solver (High Performance Computing) for the PND equation, parallel in time and space, with distributed memory.
- Physics. Using the solver developped, investigate crucial points regarding the phenomenology of dislocations in dynamic regime. For exploiting the numerical results, advanced data-processing techniques will be employed, potentially enhanced by resorting to AI techniques.
Depending on the time remaining, the solver might be employed for investigating dynamic fractures [3].
Candidate profile : The proposed subject is multidisciplinary, between scientific computing, mechanics, and data-processing. The candidate shall have a solid background in scientific computing applied to Partial Differential Equations. Mastering C++ with OpenMP and MPI is recommended. Moreover, interest and knowledge in physics –especially continuum mechanics- will be a plus.
The PhD will take place at the CEA/DES/IRESNE/DEC in Cadarache (France), with regular journeys to Paris, for collaboration with CEA/DAM and CEA/DRF.
[1] Pellegrini, Josien, Shock-driven motion and self-organization of dislocations in the dynamical Peierls model, submitted.
[2] Josien, Etude mathématique et numérique de quelques modèles multi-échelles issus de la mécanique des matériaux. Thèse. (2018).
[3] Geubelle, Rice. J. of the Mech. and Phys. of Sol., 43(11), 1791-1824. (1995).
[4] Remington et coll., Metall. Mat. Trans. A 35, 2587 (2004).
[5] Pellegrini, Phys. Rev. B, 81, 2, 024101, (2010).
[6] Lubich & Schädle. SIAM J. on Sci. Comp. 24(1), 161-182. (2002).
Controlling the behavior of fission gases in nuclear fuel (uranium oxide) is an important industrial issue, as fission gas release or precipitation limit the use of fuels at extended burn-ups. The gas behavior is strongly influenced by the material’s microstructure evolution due to the aggregation of irradiation-induced defects (gas bubbles, dislocation loops and lines). Cluster dynamics (CD) (a kind of rate theory model) is relevant for modelling the nucleation/growth of the defect clusters, there gas content and the gas release. The current model has been parameterized following a multiscale approach, based on atomistic calculations (ab initio or empirical potentials). This model has been successfully applied to annealing experiments of UO2 samples implanted with rare gas atoms and has emphasized the impact of the irradiation damage on gas release. The aim of this PhD thesis is now to improve the model, particularly the damage parameterization, and to extend its validation domain through in depth comparison of simulation with a large set of recently obtained experimental results, such as gas release measurement by annealing of sample implanted in ion beam accelerator, bubble and loop observation by transmission electrons microscopy, and positron annihilation spectroscopy. This global analysis will finally yield an improved parameterization of the CD model.
The research subject combines a “theoretical” dimension (improving the model) with an “experimental” one (interpreting existing experiments or designing some new ones). The variety of techniques will introduce the candidate into the experimental world and thus broaden his scientific skills. The candidate will also have to manage collaborations for the experiments analysis, for the model development and for the specification of additional atomistic calculations. He will be at the interface of atomistic techniques, large-scale simulation and various experimental techniques. Therefore, he will develop a broad view of irradiation effects in materials and of multi-scale modelling in solids in general.
This project is an opportunity to contribute to the overall development of numerical physics applied to multi-scale modeling of materials, occupying a pivotal position and adopting a global viewpoint. This will allow experiencing oneself the way computed fundamental microscopic data finally helps solving complex practical issues.
Further readings:
Skorek et al. (2012). Modelling Fission Gas Bubble Distribution in UO2. Defect and Diffusion Forum, 323–325, 209.
Bertolus et al. (2015). Linking atomic and mesoscopic scales for the modelling of the transport properties of uranium dioxide under irradiation. Journal of Nuclear Materials, 462, 475–495.