This project aims to establish a new research and development on purification devices for fuel reformers for hydrogen fuel cells. This work is of prime importance for fuel cell systems fed by different sources of hydrogen. Used in "power full" or "range extender" modes, the reformer and gas purification system are elements of the chain that have to be optimized.
Objective is to develop an electrochemical device for purifying the gas from a reformer whose basic principle is similar to that of a PEM electrolyzer. The gases from the reformer undergo a selective electrocatalytic oxidation to separate hydrogen and conventional pollutants directly power a fuel cell.
The project will focus on selection and characterization of catalysts electrocatalytic performance and the achievement of functional prototypes. These developments will assess the economic relevance of the device vis-à-vis other systems and identify areas of research to develop thereafter.
SiCf/SiC ceramic matrix composites are foreseen candidates for structure materials and claddings in fast neutron reactor of 4th generation. However, their use may be limited because of their too low thermal conductivity in the operating conditions (< 10 W/mK).
SiCf/SiC ceramic matrix composites are now elaborated by chemical vapour infiltration (CVI). In order to improve their thermal conductivity (reduced porosity), it is planned to develop a hybrid elaboration process combining CVI and liquid routes.
The objective of this study is to determine the conditions of elaboration of a SiC matrix by liquid routes and then to characterize the thermo-mechanical behaviour of the hybrid composites, particularly in relation to CVI references.
CEA LETI develops innovative highly flexible strain sensors which exploit the piezoelectric properties of self-organized gallium nitride nanowires. The fabrication steps are basically: i) nanowire growth, ii) nanowire assembly, iii) encapsulation, iv) contacting. First demonstrators with small active area (1.5 cm²) have already been achieved using the Langmuir Blodgett (LB) technique for the assembly of nanowires. The present project is concerned with the scaling-up of the assembly process over large surface areas, as well as controlled patterning of nanowire assemblies in 1D and 2D by using an innovative CEA LITEN roll-to-roll technology called Boostream® which has the same functionalities as LB in its basic function.
The aim of the post doc is to develop a new building block for the Boostream® equipment enabling a controlled assembly of wires with a pre-defined design. The candidate will carry out studies to optimize the wire assembly, develop the process of film patterning and fabricate, integrate and characterize GaN nanowire piezoelectric transducers with dimensions of 15x15 cm².
More generally, this post doc will also provide the opportunity to develop a generic knowledge to manipulate micro or nano wires or fibers giving new solutions in various fields such as surface structuration, electronic skin, energy...
The proposed research project aims at developing an in situ analytical device based on the LIBS technique for the characterization of hard environment liquid media such as high temperature melting materials or highly volatile liquid metals used for development of low carbon energy production. The project involves two CEA teams specialized in LIBS instrumentation, analytical developments and high temperature environments.
At high temperature, the molten metals have a high surface reactivity leading to processes of oxidation, slagging … Non-intrusive analysis of this surface by traditional LIBS tools leads to a non-representative results of the molten metal chemical composition. In this project, a new-patented concept based on a mechanical stirring coupled to the LIBS device is developed in order to have a renewable and stable surface of the liquid metal. The aim is to have an on-line representative composition of the metal during the treatment process. The developed demonstrator will be validated for the analysis of impurities (at ppmw ranges) in liquid silicon (T> 1450 °C) during the purification process and the crystallization one for photovoltaic applications. At the end of the project, recommendations for in-situ analysis of liquid sodium (used as cooling fluid in nuclear reactors) will be given.
This subject takes place in the frame of the development of proton exchange membrane fuel cells (PEMFC) and the main objective is to increase their performance and durability for operation above 100°C at low relative humidity.
The current standard membranes for use in PEMFC applications remain perfluorosulfonated ionomers such as Nafion® due their good proton conductivity and chemical stability. Nevertheless, their proton conductivity decreases for relative humidity below 70% especially at high temperature because of a too low density of proton conducting groups. This characteristic is a limitation for their use in the working conditions of the requirements for the automotive application. With these polymers, an increase of the proton conducting group density leads to a decrease of mechanical and dimensional stability. Yet, this stability is already quite low and decreases the PEMFC durability. The goal of this subject is to develop new membrane structures based on interpenetrating polymer networks that do not present this antagonism between good mechanical stability and proton conductivity. This strategy which has recently been patented by CEA (patent application number 08 06890) is based on the association of two entangled polymer networks, one sulfonated for proton conductivity and one fluorinated for mechanical and chemical stability.
The applicant will make the membranes and then will characterize their mechanical properties, proton conductivity as well as gas permeability. He will also quantify their performance and durability in a running fuel cell.
This subject aims to develop specific nanoimprint processes for various materials and to apply them to the realization of various components on plastic film. Several themes will be addressed through different materials, on the substrate itself or on a more or less thin layer deposited on a flexible plastic film. An incomplete list of these materials is presented below. They correspond to various potential applications. In the field of electronics, printing processes of dielectric materials will be studied. Particular substrates are also pressed for the creation of OTFT. In the field of optics, the structuring of several conducting polymers with special optical properties is considered for various applications. Some of these polymers belong to the family of PEDOT used also in the field of photovoltaics. The multilayer structure of polymers will be explored for the realization of 3D structures.
Finally, the ability to print polymer films loaded nanoparticles will also analyzed.
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.
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].
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.