Development and application of TERS/TEPL technique for advanced characterization of materials
TERS/TEPL (Tip-Enhanced Raman Spectroscopy and Tip-Enhanced Photoluminescence) are powerful analytical techniques developed for nanoscale material characterization. The recent acquisition of a unique and versatile TERS/TEPL equipment at PFNC (Nano-characterization Platform) of CEA LETI opens up new horizons for materials characterization. This tool combines Raman spectroscopy, photoluminescence, and scanning probe microscopy. It features multi-wavelength capabilities (from UV to NIR), allowing a wide range of applications and providing unparalleled insights into the composition, structure, and mechanical/electrical properties of materials at nanoscale resolution. The current project aims to develop and accelerate the implementation of the TERS/TEPL techniques at PFNC to fully exploit its potential in diverse ongoing projects at CEA-Grenoble (LETI/LITEN/IRIG) and with its partners.
Conditioning of waste from a NaCl-MgCl2 molten salt reactor
In recent years, interest in molten salt nuclear reactors (MSR) has been revived in France and abroad, and the use of chlorinated salts is now being considered. Irrespective of the technological issues to their development, the credibility of this approach depends on the controlled management of the final waste produced during the operation of such reactors. This involves a conditioning stage, which needs to be developed in line with the nature of the waste in question.
The conditioning of two types of waste, resulting from the treatment of spent fuel from a NaCl-MgCl2 molten salt reactor according to different scenarios, is the subject of this post-doctorate, which will be structured in two distinct directions.
The first part of the post-doctorate is dedicated to the vitrification of solutions with complex compositions and enriched in magnesium compared to the usual vitrified fluxes. For this purpose, an aluminoborosilicate matrix is being considered. In order to validate the feasibility of such vitrification, it is essential to assess the microstructure, structure and chemical durability of the resulting glasses, with regard to the expected magnesium contents. Thus, a series of aluminoborosilicate glasses with variable magnesium content will be developed and characterized. The study of these glasses alteration in aqueous solution will be coupled with their structural characterization (Raman, RMN).
The second line of the post-doctorate is dedicated to the conditioning of chlorinated waste, in particular alkaline and alkaline-earth chlorides. In this case, the conditioning method currently favored is ceramization, and will be the subject of a bibliographic study. The chosen route(s) will be tested and characterized, and its containment performance determined.
Skills required: materials science, glass, ceramics, taste for experimentation. Knowledge of Raman will be appreciated.
Manufacturing of analytical microsystems by thermoplastics micro-milling
Micro-fabrication techniques and especially micro-milling can be used to manufacture microsystem prototypes with a timescale of days, as close as possible to the application. Polymethylmethacrylate (PMMA - Commercial name Plexiglas) is a commonly used material for microsystems fabrication, limited however by its chemical incompatibility with acids and solvents.
The goal of this post-doctoral project is to study the feasibility of machining thermoplastic materials other than PMMA and to optimise the associated manufacturing parameters. The post-doctoral project will start with the selection of materials in line with the aimed applications (optical and physico-chemical properties). The materials will be selected among the thermoplastics family (PC, POM, PS, HDPE, PEEK, PVC, PP, PTFE, ULTEM, etc).
The optimisation of the micro-milling step will be realized by varying parameters such as the tool rotation speed, the feed rates, the depth of cut, etc. The surfaces and channels will be characterized by optical or mechanical profilometry, optical microscopy and/or scanning electron microscopy.
Crystal plasticity in classical molecular dynamics and mesoscopic upscaling
Thanks to new supercomputer architectures, classical molecular dynamics simulations will soon enter the realm of a thousand billion atoms, never before achieved, thus becoming capable of representing the plasticity of metals at the micron scale. However, such simulations generate a considerable amount of data, and the difficulty now lies in their exploitation in order to extract the statistical ingredients relevant to the scale of "mesoscopic" plasticity (the scale of continuous models).
The evolution of a material is complex, as it depends on lines of crystalline defects (dislocations) whose evolution is governed by numerous mechanisms. In order to feed models at higher scales, the quantities to be extracted are the velocities and lengths of dislocations, as well as their evolution over time. These data can be extracted using specific analysis techniques based on characterization of the local environment ('distortion score', 'local deformation'), a posteriori or in situ during simulation. Finally, machine learning tools can be used to analyze the statistics obtained and extract and synthesize (by model reduction) a minimal description of plasticity for models at higher scales.
Postdoc in Catalytic Supercritical Water Gasification process (Grenoble, 2 years contract)
You are a motivated young researcher, and you are looking for new challenges in the Circular Carbon Economy field. We offer a postdoc contract at CEA-Liten for studying the interactions between innovative catalysts and inorganic compounds from biomasses and wastes in supercritical water conditions.
Development of innovative metal contacts for 2D-material field-effect-transistors
Further scaling of Si-based devices below 10nm gate length is becoming challenging due to the control of thin channel thickness. For gate length smaller than 10nm, sub-5nm thick Si channel is required. However, the process-induced Si consumption and the reduction of carrier mobility in ultrathin Si layer can limit the channel thickness scaling. Today, the main contenders that allow the extension of the roadmap to ultra-scaled devices are 2D materials, particularly the semiconducting transition metal dichalcogenides (TMD). Due to their unique atomically layered structure, they offer improved immunity to short-channel-effects in comparison to usual Si-based field-effect-transistors (FETs). This makes them very attractive for the application of more-Moore electronics.
However, the scalability of MOSFET device and the introduction of new material make source and drain contact a major issue. If many efforts have been made, in the past years, to reduce Fermi level pinning and Schottky barrier height, for many, these approaches are not industrially scalable. The main objective of this work is then to propose an in-depth understanding of electrical contact characteristics (based on different material) to identify the lowest contact resistance. The processes involved, offering an optimal contact resistance, must be compatible with wafer-scale processing for an integration in our 200/300mm advanced CMOS platform. The post-doc will in-depth study mechanisms enabling the formation of small contact resistances (between MoS2 and metal). It will have to identify the most promising contact material and to develop the associated deposition processes (ALD/PVD). Finally, electrical characterization of contact will be performed to qualify both material and interfaces enabling optimal operation of future 2D FETs
New Sustainable Carbon Catalysts for PEMFC
The aim of the project is to develop and test for ORR, a mesoporous and graphitised graphene aerogel based material, presenting a hierarchical structuring allowing a better material transfer and graphitic domains increasing the durability and conductivity of the final material, and functionalised by Pt-NPs.
These graphene-based structures developed at IRIG/SyMMES possess surface chemistries and micro/meso/macro porosities that depend on the synthesis, functionalisation and drying methods used. The aim will be to increase their degree of graphitisation, and then to deposit Pt-NPs by chemical means. The electrocatalytic properties of these materials will then be tested.
Advanced meso-structural characterisation of these materials by scattering (X-ray or neutrons) methods will enable to investigate the structural properties of these new electro-catalysts. These properties will thenbe correlated to their electrocatalytic properties, and performances in fuel cell systems. This knowledge will be gained through ex-situ and operando analyses.
HPC simulation of electrode mechanical properties in Li-ion batteries
Li-ion batteries are complex multi-physics systems in which chemical reactions, transport phenomena, and mechanical deformation are strongly coupled. The battery electrodes are composed of micrometric granular materials (the microstructure) where the lithium can insert and disinsert, a process that creates internal mechanical stress and strain in the materials and subsequent volumic changes. While it is currently observed that the coupling between electrochemical reactions and mechanical deformation at the microstructure level strongly impacts the battery performances, lifespan and safety, the origin of this impact is poorly understood. The global objective of this position is to better understand the coupling between mechanical deformations of the microstructure and the local conditions of lithium transport in the electrode. The study should lead to practical applications such as recommendation on the electrode design to increase life capability of Li-ion batteries.
Design of new microfluidic tools for liquid-liquid extraction chemical processes
This 12-month post-doc proposal is part of the PIA MiRAGe: Future Investment Plan “Microfluidic Tools for Accelerated R&D on Recycling Processes”.
The MIRAGE project aims to provide a set of micro and millifluidic tools, platforms and methods to accelerate, intensify and make more flexible R&D on new recycling processes for strategic metals, nuclear or non-nuclear, while minimizing quantities of materials used.
To do this, new microfluidic tools have been designed at CEA ISEC to perform counter-current liquid-liquid extraction operations. These tools make it possible to redefine the orders of magnitude in the importance of the physico-chemical phenomena involved.
The interest of this invention is twofold and will be the core work of this post-doc:
- Carry out extraction operations over very low times and liquid volumes.
- Transpose this invention to larger volumes.
Thus, initially this post-doc work will seek to study in more detail the capabilities of this new microfluidic device, then to transpose this new technique to larger contactors.
The work will be carried out in the ISEC facilities at the CEA, on the Marcoule site in partnership with the CNRS, Universities and the INP of Toulouse.
Direct electrification of innovative reactors for reverse water gas shift (RWGS)
Technologies such as direct electrification and use of clean hydrogen could play a role in defossilizing energy sector and chemical industries. Anyway, for some specific areas, like maritime or aviation transport or carbon based chemical intermediates production, it will be necessary to replace fossil molecules by renewable ones. Reverse water gas shift (RWGS), consisting in a catalytic hydrogenation of highly stable CO2 molecule into a more common CO rich syngas , is a key for a retrofit of various fossil based infrastructure. Indeed, such syngas is used in chemical industry for about a century to synthesize chemicals and fuels.
Anyway, RWGS being an endothermal equilibrated reaction favoured at high temperature, the thermal management of the reaction is still an issue, particularly the heat input to the reactor, which in this context should be efficient and from a decarbonized source.