Solvothermal synthesis of carbon dots for optoelectronic applications
Carbon dots (C-dots) are nano-sized particles of carbon that exhibit unique electronic, optical and chemical properties due to their exceptional physico-chemical properties. These small, high surface-to-volume ratio materials are semiconductors that glow under irradiation, making them ideal for detecting ionizing radiation. Conventional plastic scintillators rely on energy transfer from the ultraviolet to visible light via organic fluorophores. The ability of CDs to absorb photons in the ultraviolet range and emit them in the visible range means that they could potentially replace organic fluorophores in their role as a bridge between ultraviolet and visible light. With low production costs, they can be synthesized either by conventional stepwise organic synthesis or, more rapidly, by top-down or bottom-up single-step approaches using a variety of chemicals. In this context, we have recently developed an interesting synthesis route enabling the preparation of C-dots emitting at different wavelengths, thus covering the entire visible range.
Secure Implementations of Code-Based Post-Quantum Cryptography: Software-Hardware Co-Design and Side-Channel Resistance
Quantum computing threatens traditional cryptographic schemes like RSA and ECC, prompting the need for post-quantum cryptography (PQC). NIST’s standardization process selected algorithms like HQC, a code-based Key Encapsulation Mechanism. Efficient and secure implementation of these algorithms, especially in resource-constrained environments such as IoT and embedded systems, remains a challenge. Physical attacks, particularly side-channel and fault injection attacks, require robust countermeasures like masking, shuffling, and hiding. These protections, however, introduce performance overhead, making hardware/software co-design essential. The project focuses on the secure software implementation of HQC with strong resistance to physical attacks. Target platforms include RISC-V embedded systems. The research involves designing and evaluating side-channel countermeasures on these platforms. Later phases will extend the work to FPGA prototypes for validating security in hardware. ASIC design may follow to optimize area, power, and performance while maintaining security. The candidate will also develop algorithmic and architectural techniques for attack mitigation. Contributions will include open-source tools and benchmarking. The work will support secure deployment of PQC in real-world applications.
AI : modelisation and scaling in laborator astrophysics
In astrophysics, accreting systems produce X-ray sources commonly observed by satellites and ground
based telescopes. Spectral signatures allow us to deduce the mass, magnetic field, accretion rate, and
chemical composition of the star and structures. However, these structures are found in very small spatial
areas and are not resolved by observational tools. Laboratory astrophysics allows us to miniaturize these
processes and study them through experiments using high-power lasers. These experiments allow for the
characterization of the plasma and its spatial structuring.
The postdoctoral fellow will exploit the possibilities of using physically informed neural networks to study the possibility of extrapolating radiative hydrodynamic simulation results. He will develop a tool to simply determine the relevant materials and regimes for sizing laboratory experiments. Finally, he will use AI to try to find scaling law relationships between two systems.
PV module designed for repair and recycle using ultrasonic delamination
PV panels, crucial for producing decarbonized electricity, have a limited lifespan due to performance degradation, failures, or economic factors. In the next decade, millions of tons of PV panels will become waste, posing significant environmental and societal challenges. Europe has recognized this problem through the WEEE directive (Waste Electrical and Electronic Equipment) to manage electronic waste, including PV.
PV modules are complex devices containing critical materials such as silver and long-life pollutants like fluorinated polymers. On top of that, the glass sheet and the silicon solar cells show a high carbon footprint, making the reuse essential to mitigate environmental impact. Various dismantling techniques have been explored in R&D labs to obtain pure fractions of metals, polymers and glass, but these methods require further improvement. Key objectives include selectivity and purity, material yield and control of residual pollution. To boost the sustainability of photovoltaic energy, managing module lifespans in a circular economy vision is essential.
The LITEN institute is leading research into delamination and separation methods to enhance the quality of recycled materials. In this postdoc opportunity, we will explore the implementation of ultrasonic waves for dismantling or repairing PV modules. The development of a numerical model to understand vibration phenomena in PV panels will support the design of a tool for efficient wave coupling. Beside modelling ant tool set-up, we will explore new PV architectures based on "design to recycle" and "design to repair" principles, focusing on composite layers sensitive to ultrasound. Evaluating various phenomena induced by these layers, such as optical transmission and thermo-mechanical behaviour, will be a key aspect of the study. The research will leverage a high-level scientific environment, with expertise in thermo-mechanical numerical modelling, PV module design and prototype’s fabrication.
PeRovskItes based SpectroMetric imagers (PRISM)
For many years, CEA has been involved in the development of semiconductor-based X-ray and gamma-ray spectrometric imagers (20keV-1MeV). The main applications targeted are medical imaging, nuclear, security and astronomical observations. State of the art detectors based on Cadmium Telluride single crystals (Cd(Zn)Te) are efficient but costly and their detection area is limited. In recent years, halide perovskites have proven to be promising alternatives. The energy resolution of single pixel detectors made with these crystals proved to be in line with that of CdTe based detectors. However, to this day, the performances of perovskite single crystals as application specific spectroscopic imagers have never been established. The objective of this 18-months project (PRISM) is to benchmark halide perovskite single crystals from different suppliers for X and gamma-ray spectro-imaging in key areas for CEA: astrophysics
Multi-Agent Negotiation for Collaborative Resource Placement in Distributed Cloud Networks
This research project aims to design a decentralized and autonomous resource management system for heterogeneous cloud networks. Building on the shift toward distributed architectures driven by concerns over data sovereignty and performance, the project seeks to move beyond the traditional centralized control plane model used in Kubernetes. Each organization involved in a federation of clusters would be represented by an intelligent agent, capable of negotiating resource placement according to its own objectives while preserving data confidentiality. The interaction among these agents is modeled as a multi-agent game, where incentive mechanisms are designed to reach a mutually beneficial equilibrium. The project plans to formalize the problem, adapt multi-agent reinforcement learning methods to the challenges of distributed settings (such as fault tolerance and asynchronous communication), and develop a functional implementation in Rust. In doing so, it lays the groundwork for a new paradigm of collaboration among cloud service providers.
Study of the Velocity-Vorticity-Pression formulation for discretising the Navier-Stokes equations.
The incompressible Navier-Stokes equations are among the most widely used models to describe the flow of a Newtonian fluid (i.e. a fluid whose viscosity is independent of the external forces applied to the fluid). These equations model the fluid's velocity field and pressure field. The first of the two equations is none other than Newton's law, while the second derives from the conservation of mass in the case of an incompressible fluid (the divergence of velocity vanishes). The numerical approximation of these equations is a real challenge because of their three-dimensional and unsteady nature, the vanishing divergence constraint and the non-linearity of the convection term. Various discretisation methods exist, but for most of them, the mass conservation equation is not satisfied exactly. An alternative is to introduce the vorticity of the fluid as an additional unknown, equal to the curl of the velocity. The Navier-Stokes equations are then rewritten with three equations. The post-doc involves studying this formulation from a theoretical and numerical point of view and proposing an efficient algorithm for solving it, in the TrioCFD code.
Modeling and integrating Local-First Data Types
Existing modeling frameworks have limited collaboration capabilities. Collaboration at model level is one of the top desired features as identified in the literature. However, most port of solutions primarily rely on cloud-based and centralized databases as their technological solution. While these solutions ease collaboration among connected partners by employing concurrency control techniques or adopting a "last writer wins" policy, they do not support disconnected collaboration scenarios, which is an important feature for designing local-first sofware. This situation presents a significant compromise: utilizing cloud-based solutions and sacrificing data ownership control versus adopting separate instances and without collaborative capabilities. The objective of this postdoctoral project is to contribute and extend an existing local-first Model-Based Systems Engineering (MBSE) framework, related to this work [5], built upon specialized Conflict-free Replicated Data Types (CRDTs). The goal is to enable real-time collaboration through modeling-specific CRDTs. The proposed approach involves extending a middleware layer utilizing CRDTs to seamlessly synchronize distributed, offline-capable engineering models.
TREATMENT OF RADIOACTIVE ORGANIC EFFLUENTS
The ECCLOR project (Project labelled 'Investment for the Future') aims to find a management route for challenging radioactive organic effluents. A strategy under investigation is to make the effluents compatible with existing outlets by decontaminating them of radioelements by column filtration. This involves developing ion-selective extractants in a form suitable for use in columns.
Studies are being carried out at CEA to improve the treatment of radioactive aqueous effluents by developing processes capable of achieving "zero discharge" while producing a minimum of waste. The challenge of the ECCLOR project will be to transpose this work to contaminated organic solvents with various radiological compositions and rheological properties. A first post-doctoral contract was dedicated to the development of materials for this application. A number of inorganic supports (silicas, geopolymers, aluminas, etc.) were considered for decontaminating these organic effluents.
The performance of the various materials developed in previous work can be optimised in terms of actinide capacity and selectivity with respect to competitor ions. In particular, the performance of existing materials needs to be studied further on more complex simulated LORs, with the necessary adaptations to the analytical method.
This project is intended for a post-doctoral fellow wishing to develop skills in extraction mechanism comprehension and analytical methods, with an interest in advancing the field of radioactive waste management. It will be will build upon the expertise of two laboratories at CEA Marcoule: the Design and Characterization of Mineral Materials Laboratory for materials elaboration and characterization, and the Supercritical and Decontamination Processes Laboratory for materials grafting and decontamination experiments.
Development of a new generation of reversible polymer adhesives
Polymeric adhesives are generally cross-linked systems used to bond two substrates throughout the lifetime of an assembly, which may be multi-material, for a wide range of applications. At their end of life, the presence of adhesives makes it difficult to separate materials and recycle them. Moreover, it is difficult to destroy the cross-linking of the adhesives without chemical or thermal treatment that is also aggressive for the bonded substrates.
In this context, the CEA is developing adhesives with enhanced recyclability, by integrating recyclability into the chemical structures right from the synthesis of the polymer networks. The first approach involves incorporating dynamic covalent bonds into polymer networks, which can be exchanged under generally thermal stimulus (e.g. vitrimers). A second approach involves synthesising polymers that can be depolymerised under a specific stimulus (self-immolating polymers) and have the ability to cross-link.
The post-doc will develop 2 networks that can be used as adhesives with enhanced recyclability. A first network will be based on a depolymerizable chemistry under stimulus already developed on linear polymer chains, to be transposed to a network. A second vitrimer network will be synthesised on the basis of previous work at the CEA. Activation of the bond exchange in this network will take place via a so-called photolatent catalyst, which can be activated by UV and will make it possible to obtain a UV- and heat-stimulated adhesive. The choice and synthesis of these catalysts and their impact on the adhesive will be the focus of the study. The catalysts obtained could also be used to trigger depolymerisation of the first depolymerisable system under stimulus.