Couplings between the distributions of water and current density in operating Proton Exchange Membrane Fuel Cell (PEMFC)
The post-doc work will be focused on the measurement of the current density and of the water distributions in an operating fuel cell with a real design, in order to give a better understanding of PEMFC operation as a function of the operating parameters (Temperature, Gas hydration, Pressure, Gas composition). The measurement of the distribution of the current density will be performed using a reliable commercial setup on a full size cell. CEA developed a technique based on Small Angle Neutron Scattering (SANS) as a non-intrusive tool in order to quantify the water distribution during fuel cell operation within and without the membrane. CEA benefits for international recognition on this topic. These measurements will be conducted in high flux neutron reactors, such Institut Laue Langevin (ILL). Some specific high and low resolution neutron imaging experiments could be also be conducting additionally in order to have a complete 3D view of water repartition.
Minimizing modifications at III-V pattern sidewalls after plasma etching for heterointegrated optoelectronics and nonlinear photonics
This project will focus on understanding plasma-induced damage at the sidewalls of micro-nano-patterned III-V semiconductors to find relevant technological solutions capable to minimize this damage. There is a clear need of knowledge on by which mechanisms and to what extent the plasma etching process modifies the III-V pattern sidewalls and the consequences it has on the device optical performances. The selected III-V semiconductor will be aluminium gallium arsenide which exhibits excellent optoelectronic properties and strong nonlinear parametric gain.
The student will be mainly focused on understanding how the key plasma process parameters influence the structural and chemical changes at the III-V sidewalls, as well as changes of optical properties. This will require the development of a methodology for a 3D quantitative characterization of the sidewalls at the nanoscale, based on Auger microscopy and cathololuminescence. The main objective will be to correlate plasma-induced structural defects and modifications of the optoelectronics properties. The second step will consist in developing optimized plasma etching processes for III-V semiconductors, exploring alternative plasma technologies. You will also be involved in the development of processes for restoring and passivating the AlGaAs sidewalls.
DEM’N’MELT Process : Optimisation of operating conditions by modelling
Within the framework of the PROVIDENCE project (Plan Relance, France), the DEM'N'MELT process was developed with the aim of marketing a solution for the treatment and conditioning of high and medium level waste to sites operators undergoing dismantling or remediation, in France and abroad. In this context, studies have been undertaken to optimise the operating conditions of the process.
The candidate will have to take in charge the software used in our Laboratory (Fluent, Workbench, SpaceClaim, Meshing), to appropriate the existing models. These models will have to evolve to :
o take into account additional measurements to calibrate the model
o study the sensitivity of the system to the physical properties of the glass
o optimise furnace operation and manage the feed capacity according to the filling level
o add agitation to the glass bath.
The candidate will be able to rely on the skills of the LDPV Laboratory, both experimentally and in modelling.
Researcher in Artificial Intelligence applied to self-driven microfluidic
This postdoctoral position is part of the 2FAST project (Federation of Fluidic Autonomous labs to Speed-up material Tailoring), which is a part of the PEPR DIADEM initiative. The project aims to fully automate the synthesis and online characterization of materials using microfluidic chips. These chips provide precise control and leverage digital advancements to enhance materials chemistry outcomes. However, characterising nano/micro-materials at this scale remains challenging due to its cost and complexity. The 2FAST project aims to utilise recent advances in the automation and instrumentation of microfluidic platforms to develop interoperable and automatically controlled microfluidic chips that enable the controlled synthesis of nanomaterials. The aim of this project is to create a proof of concept for a microfluidic/millifluidic reactor platform that can produce noble metal nanoparticles continuously and at high throughput. To achieve this, feedback loops will be managed by artificial intelligence tools, which will monitor the reaction progress using online-acquired information from spectrometric techniques such as UV-Vis, SAXS, and Raman. The postdoctoral position proposed focuses on AI-related work associated with the development of feedback loop design, creation of a signal database tailored for machine learning, and implementation of machine learning methods to connect various data and/or control autonomous microfluidic devices.
Modelling and evaluation of the future e-CO2 refinery
In the context of achieving carbon neutrality by 2050, the CEA has initiated a project in 2021 to assess the relevance of coupling a nuclear power system with a direct atmospheric carbon capture device (DAC) thanks to the use of the system's waste heat.
As a member of a team of about twenty experts(energy system evaluation, techno-economic engineering, energy system modeling, optimization and computer programming), you will participate in a research project on the modeling and evaluation of a CO2 refinery dedicated to the production of Jet Fuel fed by a nuclear reactor and coupled with an atmospheric CO2 capture process.
Agglomerate breakage model and homogenisation by DEM simulations: Calibration with tomographic micro-compressions in X ray beam line Soleil
Context:
The reference ceramic fabrication process involves three main stages: grinding, pressing, and sintering. Pellet compaction during pressing relies on three main densification steps rearrangements by motion, compaction by strain, and agglomerate fractures by compression. This research project aims to explore the influence of the pressing step on the microstructure behavior during the sintering process. The study focuses on a powder composed of agglomerates with a microstructure based on a homogeneous mix of TiO2-Y2O3, TiO2 for surrogate UO2 and Y2O3 for surrogate PuO2. Each agglomerate consists of unbreakable elementary particles included in breakable aggregates, synthesized using the Cryogenic Granulation Synthesis Process (CGSP) [1].
Recent investigations at the Anatomix X-ray beam line in the synchrotron Soleil [2] have validated the results of tomographic micro-compressions, aligning with Kendall's theory, Fig 1. The experiments involved one-way cyclic micro-compression tests on agglomerates subjected to a simple load and unload cycle until breakage. Tomographic post-treatments provided insights into porosities, crack initiation, and propagation. Several DEM simulation studies have also been used to explore agglomerate behavior under dynamic or quasi-static loading with and without breakage, however without fully calibrating the breakage model [3], [4], [5].
Detection of traces of narcotics in saliva by electrochemiluminescence on diamond electrodes
The consumption of narcotics is becoming a problem for road safety because 23% of road deaths in France occur in an accident involving at least one driver who tested positive. Thus, one objective of road safety in consultation with the concerned ministries (Ministry of Transport, Ministry of Interior, Ministry of Health and Ministry of Economy) is to improve the fight against road insecurity linked to narcotics consumption. In particular, this involves increasing and facilitating roadside checks using a portable device dedicated to controlling the use of narcotics on the roadside, similar to what is already done for breathalyzer tests. Such a device is not commercially available today. The main prerequisites of this device will be to provide reliable, immediate confirmation results with evidentiary value for the courts as well as a purchase cost compatible with large-scale deployment on French road networks. In this context, the subject of study proposed aims to study the possible detection of traces of narcotics in saliva using electroluminescence on a boron-doped diamond electrode. This method is considered promising for such an application because it potentially allows extremely low detection thresholds to be reached and, in accordance with legislative requirements, offers multiple possibilities aimed at achieving high selectivity towards chemical targets, with a high detection capacity. miniaturization of equipment and a relatively low cost of apparatus compared to analytical tools such as mass spectrometer, IMS, etc.
Large-scale depletion calculations with Monte Carlo neutron transport code
One of the main goals of modern reactor physics is to perform accurate multi-physics simulations of the behaviour of a nuclear reactor core, with a detailed description of the geometry at the fuel pin level. Multi-physics calculations in nominal conditions imply a coupling between a transport equation solver for the neutron and precursor populations, thermal and thermal-hydraulics solvers for heat transfer, and a Bateman solver for computing the isotopic depletion of the nuclear fuel during a reactor cycle. The purpose of this post-doc is to carry out such a fully-coupled calculation using the PATMOS Monte Carlo neutron-transport mini-app and the C3PO coupling platform, both developed at CEA. The target system is core of the size of a commercial reactor.
Simulation of reactive gas-liquid multi-phase flows
The objective of this postdoctoral position is to develop and implement a simulation method for the simulation of a
sodium spray fire. Two key points need to be adressed. First, one needs to propose a proper representation of the sodium
droplets (dispersed phase) from their generation by a jet (separate phase) fragmentation to their behavior (motion,
oxidation, combustion) in the air atmosphere. This requires to derive a flow model that accounts for multiple components
with multiple interface topology regimes (dispersed and separate). Second, one needs to develop a robust discretization
strategy for this complex flow model.
The numerical work will be implemented in a new numerical tool to perform simulations of sodium spray fires developed at CEA. This tool is based on the canoP. Canop is a library designed for solving computational fluid dynamics problems using a cell-based
Adaptive Mesh Refinement (AMR) approach and parallel calculation.