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.
Study of the laser-driven ion acceleration in the relativistically induced transparency regime using ultra-thin foils and cryogenic targets
Laser-driven ion acceleration (LDIA) presents a compact and cost-effective alternative to traditional particle accelerators. Recent developments have enabled proton energies up to 160 MeV using ultra-thin foil targets irradiated by ultra-intense laser pulses, exploiting relativistic transparency regimes. This regime occurs when the laser pulse penetrates a near-critical plasma, generated by tailoring target thickness to the laser parameters, enabling multi-stage acceleration and enhancing proton energies without the need for contrast-enhancing techniques like plasma mirrors. This PhD project aims to further optimize proton acceleration in the transparency regime, with the goal of achieving 200 MeV energies using high-repetition-rate laser systems.
The first phase involves 3D Particle-In-Cell (PIC) simulations with Smilei, focusing on the sensitivity of laser-target interaction to temporal laser profiles for robust acceleration. The second phase investigates cryogenic hydrogen ribbon targets, developed by CEA, as an alternative to solid foils. These targets are near-critical in density, tunable in thickness, and compatible with high-repetition-rate operation, while providing mono-species proton beams. Experimental work will be conducted in collaboration with LULI and CEA, with preparations for experiments at the Apollon facility.
Plasma Mirrors Towards Extreme Intensity Light Sources and High-Quality Compact Electron Accelerators
The research programs conducted at the Lasers Interactions and Dynamics Laboratory of the French Atomic Energy Commission (CEA) aim to understand the fundamental processes involved in light-matter interactions and their applications. As part of the CEA-LIDYL, the Physics at High Intensity (PHI) group conducts studies of laser-matter interactions at extreme intensities, for which matter turns into an ultra-relativistic plasma. Using theory, simulations and experiments, researchers develop and test new concepts to control the laser-plasma interaction with the aim to produce novel relativistic electron and X-UV attosecond light sources, with potential applications to fundamental research, medicine and industry.
In collaboration with the Lawrence Berkeley National Laboratory, the group is a core developer of the exascale Particle-In-Cell (PIC) codes WarpX/PICSAR for the high-fidelity modelling of laser-matter interactions. It also pioneered the study and control of remarkable optical components called ‘plasma mirrors’, which can be obtained upon focusing a high-power laser with high-contrast on an initially solid target. In the past five years, the PHI group has developed two concepts exploiting plasma mirrors to manipulate extreme light for pushing the frontiers of high-field science. The first concept uses relativistic plasma mirrors to amplify the intensity of existing lasers by orders of magnitude and probe novel regimes of Strong-Field Quantum Electrodynamics (SF-QED). The second uses plasma mirrors as high-charge injectors to level up the charge produced in laser-plasma accelerators (LPAs) to enable their use for medical studies, industrial applications and fundamental research (collider design, electron-laser collisions for SF-QED studies).
In this context, the PhD candidate will first improve our simulation tool WarpX to speed-up plasma mirror simulations. They will then use WarpX to optimize the use of plasma mirrors as intensity boosters for the study of SF-QED. In collaboration with Brigitte Cros's team at CNRS and within the framework of novel collider designs based on Laser-Plasma Accelerators (LPAs), the PhD candidate will finally investigate and optimize the use of plasma mirrors as optical components for the coupling of multiple LPA stages. This will be crucial for developing compact acceleration schemes that can be scaled to produce high-energy, high-quality electron beams.
VHEE Radiotherapy with Electron Beams from a Laser-Plasma Accelerator
The research programs conducted at the Lasers Interations and Dynamics Laboratory of the French Atomic Energy Commission (CEA) aim to understand the fundamental processes involved in light-matter interactions and their applications. As part of the CEA-LIDYL, the Physics at High Intensity (PHI) group conducts studies of laser-matter interactions at extreme intensities, for which matter turns into an ultra-relativistic plasma. Using theory, simulations and experiments, researchers develop and test new concepts to control the laser-plasma interaction with the aim of producing novel relativistic electron and X-UV attosecond light sources, with potential applications to fundamental research, medicine and industry.
In collaboration with the Lawrence Berkeley National Laboratory, the group strongly contributes to the development of the code WarpX used for the high-fidelity modelling of laser-maIer interactuons. It also pioneered the study and control of remarkable optical components called ‘plasma mirrors’, which can be obtained by focusing a high-power laser with high contrast on an initially solid target. In the past five years, the PHI group has developed core concepts exploiting plasma mirrors to manipulate extreme light for pushing the frontiers of high-field Science. One of these concepts uses plasma mirrors as high-charge injectors to level up the charge produced in laser-plasma accelerators (LPAs) to enable their use for medical studies such very high energy electrons (VHEE) radiotherapy. This concept is being implemented at CEA on the UHI100 100 TW laser facility in 2025 to deliver 100 MeV - 200 MeV electron beams with 100 pC charge/bunch for the study of high-dose rate deposition of VHEE electrons on biological samples.
In this context, the PhD candidate will use our simulation tool WarpX to optimize the properties of the electron beam produced by LPAs for VHEE studies (electron beam quality and final energy). He/She will then study how the LPA electron beam deposits its energy in water samples (as biological medium) using Geant4. This will help assessing dose deposition at ultra-high dose rate and develop novel dosimetry techniques for VHEE LPA electron beams. Finally, the Reactive Oxygen Species (ROS) production and fate in water will be studied using the Geant4-DNA toolkit. This module has mainly data tabulated at electron energies below 10 MeV and will therefore require measures cross-section of water-ionization processes from experiments at 100 MeV. This will be performed on the UHI100 100 TW laser by the DICO group of the CEA-LIDYL, in collaboration with the PHI group.
Towards strong coupling between a single spin and a superconducting resonator via magnetic mode hyper-focusing
Magnetic resonance is a non-invasive tool that plays a central role in a wide range of fi elds, from medical imaging (MRI) to analyticalchemistry, and more recently in quantum computing, where it is used to control and read spin-based qubits. However, this techniquesuff ers from low sensitivity, requiring the collective response of a large number of spins to produce a detectable signal. Recent advancesin superconducting quantum technologies have dramatically improved this sensitivity—by more than ten orders of magnitude—bycombining the Purcell eff ect with novel detectors such as microwave photon counters.
This project builds on these breakthroughs by developing an innovative superconducting platform for the fast and effi cient readout of
Mots clés - Keywords
single electron spins, based on enhancing the spin-resonator coupling through magnetic mode hyper-focusing.
Using a specially designed parallel-plate capacitor geometry, featuring a central nanowire, the magnetic fi eld of the microwave mode canbe concentrated within a region of just a few hundred nanometers. This signifi cantly increases the local interaction between the fi eld andthe electron spin located just beneath the nanowire. The central objective of the project is to boost the Purcell factor by two orders ofmagnitude, from 10¹³ to 10¹5, in order to drastically reduce spin detection time and potentially reach the strong coupling regime at thelevel of a single spin.
In a first phase, the project will focus on Er³? ions implanted in crystals such as CaWO4, Y2SiO5, or directly in silicon, with the aim ofintegrating them into hybrid quantum computing architectures combining superconducting circuits and spin-based quantum memories.In a second phase, the platform will be extended to more realistic paramagnetic systems, such as organic radicals or metallic centers inproteins, paving the way for quantum spectroscopy of complex molecular compounds, well beyond the scope of current model systems.
Building on the expertise of the Quantronics group at CEA Saclay in superconducting circuits, nanofabrication, cryogenics, andmicrowave single-photon detection, the project will provide the PhD student with comprehensive training at the intersection ofexperimental physics, nanoscience, and quantum information, within a world-class research environment.
Evaluation of nanoscale surface coatings on high energy density positive electrodes for lithium-ion batteries.
Nickel-rich layered oxides LiNi1-x-yMnxCoyO2 (NMC) and LiNi1-x-yCoyAlzO2 (NCA) are exceptional materials for the positive electrode of lithium batteries due to their high reversible storage capacity. However, under real conditions, undesired reactions can lead to the dissolution of transition metals and electrodes cracking, thus affecting their electrochemical properties. This phenomenon is linked to the presence of hydrofluoric acid (HF) in the electrolyte, mainly due to the degradation of the LiPF6 salt. To address this problem, surface treatments are needed to protect the active material and improve performance. The EVEREST project proposes an innovative, flexible, and affordable method for creating inorganic coatings at the nanoscale. This method is based on a recent technique, coaxial electrospinning, which allows the production of nanofibers with a well-defined core-sheath structure. For this project, we propose to evaluate the impact of nanofiber shaping parameters on morphology, electrochemical performance and the underlying mechanism. The electrochemical performances of the coated and the pristine positive electrodes will be compared in a half-cell with Li metal as a counter electrode. Redox processes, charge transfer mechanisms and structural modifications will be studied in the operando mode using the synchrotron radiation beam.
Ultrafast spin currents and ferroic oxides
This PhD thesis lies at the intersection of ultrafast spintronics and the physics of spin currents on sub-picosecond timescales. Pure spin currents are currently attracting considerable attention due to their central role in the development of next-generation spintronic devices. As data consumption continues to grow exponentially, information and communication technologies must process increasingly large volumes at higher speeds, all while minimizing energy consumption. In this context, ultrafast information processing has become a major challenge.
Pure spin currents offer several decisive advantages: in addition to their dissipationless propagation, they can now be generated, transmitted, and detected on timescales of just a few hundred femtoseconds. This progress paves the way for the emergence of ultrafast spintronic components and devices operating in the terahertz range.
The aim of this thesis project is to investigate the fundamental mechanisms governing the generation and propagation of pure spin currents on picosecond and sub-picosecond timescales, with a particular focus on ferroic oxides. These materials exhibit a wide range of remarkable and tunable properties, making them ideal candidates for enabling ultrafast spin current functionalities and addressing the societal challenges of tomorrow.
The core of this thesis work will involve the implementation of time-resolved optical and magneto-optical techniques to probe the ultrafast magnetic dynamics in epitaxial thin films of ferromagnetic and antiferromagnetic oxides. The main expected outcomes include overcoming key bottlenecks: on one hand, the tunability of ultrafast spin current generation through the half-metallicity of selected ferromagnetic oxides; and on the other hand, the control of spin information propagation at terahertz frequencies in antiferromagnetic oxides.
Custom synthesis of diamond nanoparticles for photocatalytic hydrogen production
Diamond nanoparticles (nanodiamonds) are used in nanomedicine, quantum technologies, lubricants and advanced composites [1-2]. Our recent results show that nanodiamond can also act as a photocatalyst, enabling the production of hydrogen under solar illumination [3]. Despite its wide band gap, its band structure is adaptable according to its nature and surface chemistry [4]. Moreover, the controlled incorporation of dopants or sp2 carbon leads to the generation of additional bandgap states that enhance the absorption of visible light, as shown in a recent study involving our group [5]. The photocatalytic performance of nanodiamonds is therefore highly dependent on their size, shape and concentration of chemical impurities. It is therefore essential to develop a "tailor-made" nanodiamond synthesis method, in which these different parameters can be finely controlled, in order to provide a supply of "controlled" nanodiamonds, which is currently lacking.
This PhD aims to develop a bottom-up approach to grow nanodiamond using a sacrificial template (silica beads) to which diamond seeds < 10 nm are attached by electrostatic interaction. The growth of diamond nanoparticles from these seeds will be achieved by microwave-enhanced chemical vapor deposition (MPCVD) using a homemade rotating reactor available at CEA NIMBE. After growth, the CVD-NDs will be collected after dissolution of the sacrificial pattern. Preliminary experiments have demonstrated the feasibility of this approach with the synthesis of faceted <100 nm nanodiamonds (so called CVD-ND), as shown in the scanning electron microscopy image.
During the PhD work, the nature of the diamond seeds (ultra-small NDs [size ˜ 5 nm] synthesized by detonation or HPHT, or molecular derivatives of adamantane) as well as CVD growth parameters will be studied to achieve better controlled CVD-NDs in terms of crystallinity and morphology. Nanodiamonds doped with boron or nitrogen will be also considered, playing on the gas phase composition. The crystalline structure, morphology and surface chemistry will be studied at CEA NIMBE using SEM, X-ray diffraction and Raman, infrared and photoelectron spectroscopies. A detailed analysis of the crystallographic structure and structural defects will be carried out by high-resolution transmission electron microscopy (collaboration). CVD FNDs will then be exposed to gas-phase treatments (air, hydrogen) to modulate their surface chemistry and stabilize them in water. The photocatalytic performance for hydrogen production under visible light of these different CVD-NDs will be evaluated and compared using the photocatalytic reactor recently installed at CEA NIMBE.
References
[1] Nunn et al., Current Opinion in Solid State and Materials Science, 21 (2017) 1.
[2] Wu et al., Angew. Chem. Int. Ed. 55 (2016) 6586.
[3] Marchal et al., Adv. Energy Sustainability Res., 2300260 (2023) 1-8.
[4] Miliaieva et al., Nanoscale Adv. 5 (2023) 4402.
[5] Buchner et al., Nanoscale 14 (2022) 17188.
In situ study of the impact of the electric field on the properties of chalcogenide materials
Chalcogenide materials (PCM, OTS, NL, TE, FESO, etc.) are the basis of the most innovative concepts in microelectronics, from PCM memories to the new neuromorphic and spinorbitronic devices (FESO, SOT-RAM, etc.). Part of their operation relies on out-of-equilibrium physics induced by the electronic excitation resulting from the application of an intense electric field. The aim of this thesis is to measure experimentally on chalcogenide thin films the effects induced by the intense electric field on the atomic structure and electronic properties of the material with femtosecond (fs) time resolution. The 'in-operando' conditions of the devices will be reproduced using a THz fs pulse to generate electric fields of the order of a few MV/cm. The induced changes will then be probed using various in situ diagnostic methods (optical spectroscopy or x-ray diffraction and/or ARPES). The results will be compared with ab initio simulations using a state-of-the-art method developed with the University of Liège. Ultimately, the ability to predict the response of different chalcogenide alloys on time scales fs under extreme field conditions will make it possible to optimise the composition and performance of the materials (e- switch effect, electromigration of species under field conditions, etc.), while providing an understanding of the underlying fundamental mechanisms linking electronic excitation, evolution and the properties of the chalcogenide alloys.
Silver nanowires synthesized from end-of-life solar panels for CO2 reduction and transparent electrodes
Silver nanowires (AgNW) networks are remarkable materials with both the highest electrical and thermal conductivity at ambient temperature, and a good chemical stability. They are used in transparent electrodes, for instance in organic solar cells, heating films or electrochromic devices. Their synthesis has been upscaled at the industrial level with high yield and reproducibility. More recently, they also found promising applications in low-emissivity layers on windows, and in catalysis of CO2 reduction at ambient temperature as a selective electrocatalyst.
In this PhD project, we will turn to recycled sources of silver from dismantled end-of-life silicon solar panels for the synthesis of AgNWs, in a “green chemistry” approach. The quality of the nanomaterial will be checked directly in two relevant devices, namely IR-low-emissivity films for reduction of heat loss, and electroreduction of CO2 for the production of e-fuels. The project will focus on understanding the fundamental basis of the impact of impurities on the synthesis of AgNWs, the physical properties of the AgNW networks, their stability under electrical stress or chemical wear, and their performance as active material in the devices.
The work will take place in Grenoble, the second scientific hub in France. The PhD student will be hired by CEA, a major French research institution with a high focus on alternative energies. He/she will join the fundamental research lab SyMMES, expert in nanomaterial design and energy devices such as solar cells, batteries and electrolyzers. She/he will work in co-supervision in the partner lab LMGP expert in materials science, synthesis and implementation at Grenoble INP. SYMMES and LMGP belong to University Grenoble Alpes and host widely international teams. The project will be actively supported by a local industrial recycling company.
Applicants should hold a Master 2 degree in chemistry, physics or materials science with skills in nanomaterials, electrochemistry or physical chemistry and in basic science for energy. Good English proficiency and a strong interest for innovation and collaborative work are expected.