The aim is to develop surface acoustic wave sensors (SAW) with high sensitivity and high selectivity to gaseous compounds (< 100 ppb). The development strategy involves the use of diamond nanoparticles based guiding layers deposited on the piezoelectric substrate and chemically modified to tune the specificity of the sensors. In order to increase further the selectivity, the sensors will be coupled to specific filters placed before the sensors and based on probe molecules trapped in porous sol-gel based materials and able to react non-reversibly with interferent molecules. The topic includes 4 mains sections: 1) synthesis and functionalisation of diamond nanoparticles, 2) study of probe molecules and immobilisation in porous matrices, 3) study of the filtering capacity of the filters toward relevant interferent species, 4) metrology and calibration of the sensors. This work will be carried out in the "Diamond Sensors Laboratory" as well as laboratoire Francis Perrin both located in CEA Saclay.
The development of new and more effective extractants than those currently used is therefore an important issue for the mining of uranium. In particular, access to specific chelating systems with high affinity for uranium with selective properties in regards to competitor’s ions and less susceptible to hydrolysis remains a challenge.
Recently, new bifunctional molecules amio-phosphine oxide type has shown their potential for the extraction of uranyl in sulfuric media with excellent properties in terms of affinity and selectivity for the metal.
The objective of this postdoctoral fellowship will be to optimize this family of ligands, with the development of concise and efficient routes for their chemical and suitable for the preparation of large quantities of extractant for further study the optimization of the process.
The fabrication of solar cells with high performances at a reduced cost is a key challenge addressed by many research institutions and industrials worldwide. Many technological solutions are being investigated. Among them, a promising approach consists in forming narrower metal lines to limit shadowing of active areas of the cells. This work aims at replacing serigraphy by new fabrication processes able to reduce line width. For this purpose, the conducting substrate is coated by an insulating mask in which the lines are defined. The metal is then directly plated selectively onto the weakly conducting portions of the substrate, i.e. the lines, using electrolytic or electroless reactions. The process conditions will be adapted with regard to the nature of the initial conducting surfaces.
A post-doctoral position is available for one year at CEA-Marcoule
The study will be the modeling of concentrated aqueous phases of heavy metal salts using both microscopic and mesoscopic modeling.
Separation processes for heavy metals recycling usually use liquid-liquid extraction with the transfer of ionic species from a concentrated aqueous phase to an organized organic phase.
This post-doctoral research subject relates to the chemical properties of these processes, and especially to the characterization of the aqueous phase using as accurate as possible models. The goal is to understand the various effects (solvation, electrostatic and van der waals forces, entropy…) influencing the structural and energetic properties of these solutions. A multi-scale approach will be used to study some systems of interest for both fundamental and industrial point of view, the aim being the characterization of these solutions from their molecular structure to their thermodynamic properties. The tools and the approach used here have to be be valid for separative chemistry overall.
Under irradiation, structural materials inside nuclear reactors undergo changes in mechanical properties, which result from the formation of point defect clusters, such as cavities (clusters of vacancies) and interstitial dislocation loops (clusters of self-interstitial atoms). Understanding the formation processes of such clusters is thus of prime importance. Recently, three-dimensional interstitial clusters, known as C15 clusters, have been shown theoretically to be highly stable in iron. In order to detect such clusters experimentally, an idea is to make them grow, as shown for dislocation loops after helium implantation. This approach will be carried out experimentally in various bcc metals in the framework of the ANR project EPigRAPH, in collaboration with Chimie ParisTech, GEMaC and LPS.
In this project, the following modelling tasks will be performed by the postdoc:
- Electronic structure calculations will be done to obtain the energetic properties of point defects and point defect clusters in the bcc metals envisaged in the project.
- These data will then be used to parameterize a kinetic model based on cluster dynamics. This formalism is particularly well adapted to simulate the evolution of point defect clusters over long physical times.
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...
Le palladium est un métal rare dont la demande mondiale est en forte augmentation. Or, il est présent en tant que produit de fission dans les combustibles nucléaires usés qui sont retraités en France. Il serait donc intéressant de recycler ce métal. Pour cela, il est nécessaire de procéder à une épuration isotopique, afin de supprimer un des isotopes du palladium, le 107, qui est un radionucléide artificiel à vie longue émetteur béta. Dans le cadre d'un nouveau projet sur 4 ans construit en réponse à l'appel d'offre du Plan d'Investissement et d'Avenir de l’État, le Service d’Etude des Procédés d’Enrichissement propose un contrat post-doctoral ayant pour objectif la compréhension des interactions gaz/laser dans le procédé de séparation isotopique du palladium par Lasers actuellement en cours de développement. L’objectif principal du projet est la démonstration finale de la faisabilité de séparation de palladium naturel (et non radioactif) pour la phase suivante de développement d’un premier pilote.
Le post-doctorant devra en particulier assurer l’étude du mode de production de la vapeur atomique près du point de fusion du métal pur, des mesures de spectroscopie par laser dans l’UV afin d’affiner les séquences sélectives de photoionisation des isotopes désirés. Pour ce faire, il participera à la définition, au montage et au développement de l'évaporateur, et au couplage des lasers du procédé avec l’enceinte à vide. Des échanges seront mis en place sur ce sujet spécifique avec des spécialistes reconnus au sein de la Direction de la Recherche Fondamentale du CEA. Les mesures de diagnostics des lasers mais aussi les mesures provenant des interactions gaz/laser sont à développer. La programmation (en Python et/ou sous Labview) de ces outils est un point essentiel du poste proposé. Une attention particulière sera portée sur les publications à réaliser essentiellement dans le cadre des interactions gaz/laser (photoionisation sélective des atomes d’intérêt et extraction).
This study aims at the chemical synthesis of infrared emitting nanocrystals for integration in LEDs.
These nanocrystals will be characterized by TEM, XRD, EDX, UV-vis, PL, NMR, FTIR. Formulation of colloidal solutions suitable for deposition via inkjet printing.
The candidate will work in the partner lab INAC/LEMOH