PhD : selection by topics
Mathematics - Numerical analysis - Simulation
Biochemistry
Optics - Laser optics - Applied optics
Solid state physics, surfaces and interfaces
Biotechnologies,nanobiology
Biotechnology, biophotonics
Analytic chemistry
Electronics and microelectronics - Optoelectronics
Materials and applications
Thermal energy, combustion, flows
Mechanics, energetics, process engineering
Physical chemistry and electrochemistry
Medical imaging
Instrumentation
Electromagnetism - Electrical engineering
Radiation-matter interactions
Chemistry
Automatics, Remote handling
Nuclear physics
Ultra-divided matter, Physical sciences for materials
Neutronics
Biotechnologies,nanobiology
Biotechnology, biophotonics
Biochemistry
Materials and applications
Solid state physics, surfaces and interfaces
Electronics and microelectronics - Optoelectronics
Theoretical Physics
Ultra-divided matter, Physical sciences for materials
Chemistry
Sciences pour l\'ingénieur >> Chimie physique et électrochimie
8 propositions.
Influence of surface modification on Li distribution and SEI formation in Li-ion silicon-based negative electrodes by combining ToF-SIMS/Auger/XPS characterization
A Li-ion battery is typically composed of a positive electrode and a negative electrode. The latter is generally based on graphite material for its reliable behaviour though a limited specific capacity of 372 mA.h/g. For that reason, silicon appears to be a promising alternative material thanks to a high specific capacity of 3580 mA.h/g. However, the biggest issue - a high volumic expension of more than 300% during Li insertion - favours particle grinding and Solid Electrolyte Interphase (SEI) instability, leading to electrode degradation and electrochemical performance loss with time. In order to get rid of these problems, it is proposed to nanostructure the surface of the electrode material, thus avoiding any contact with the electrolyte. Among the objectives of the PhD research, the influence of surface modification, electrode formulation or test conditions on Li distribution and SEI formation will be evaluated. This will be allowed with preparation tools which are implemented on the Nanocharacterization Platform in Minatec, in particular an in situ FIB implemented on a new ToF-SIMS. Li distribution in a single particle, or throughout the entire electrode, will be easier to determine, by using ToF-SIMS spectroscopy, and also Auger spectroscopy with the help of an UHV transfer suitcase. The results will help in understanding the electrode behaviour, opening ways for improvements relative to negative electrode durability and cycling performance. The research work will consist, in a first step, in developing skills for the use of in situ FIB with ToF-SIMS, in particular for the specific topic described above, and also for UHV transfer based studies between ToF-SIMS/Auger/XPS. In a second step, Li distribution and SEI evolution of reference materials and cycled electrodes will be characterized and correlated with the applied surface modifications. This study will be achieved in collaboration with an industrial partner that will provide the material and the necessary surface modifications.
See the summary of the offerAging analysis of a battery module under vibration constraints
The objective is to understand the process leading to battery module aging under vibration constraints. The final goal is to have a clear understanding of the test plan needed for battery modules in electric vehicles. The idea is to validate: - the impact of mechanical vibrations on the aging of the module assembly of electrochemical accumulators (electrical connexion loss, increase of internal resistance, electronic board functionality, mechanical integrity...) - the impact of mechanical vibrations on the aging of electrochemical accumulators into a module assembly. The research process will associate experimentation and numerical modelling.
See the summary of the offerDiamond microelectrode arrays for analytical and electrophysiological applications
Boron doped diamond microelectrode systems have been developped for several years by the research team at the Diamond Sensors Laboratory of CEA-LIST for various applications including biosensors and implants. This work involves the optimization of the material synthesized in the laboratory by Chemical Vapor Deposition (CVD) processes along with its electrochemical properties. Considerable efforts have also been put into the development of micro-patterning methods and more generally the fabrication processes. Furthermore, an ultrafast activation process was developed that can be applied directly in complex analytical media. This development offers wide opportunities for on-line monitoring for various applications ranging from biomedical diagnostic to environmental monitoring. The topic of the PhD studentship lies in the continuity of these research activities. The student will focus in particular on the immobilization of functional receptors, either in the form of organic receptors of metal catalysts, toward the development of multisensor systems including biochips or electronic tongues.
See the summary of the offerReal-time diagnosis of PEMFC performance and durability using impedance spectroscopy
PEMFC are very promising converters of chemical energy into electrical energy for stationary and transport applications. For many years, LITEN works on the development of MEA, stacks and PEMFC systems. This work led to the development of fuel cells based on bipolar plates stamped in perfect adequation with the market for this technology. At the same time, the development and testing of prototypes in actual operating conditions have allowed acquire, for LITEN, an important feedback on these systems and to highlight the impact of fuel cells operating conditions on their performances and their lifetime. It seems to be interesting to monitor in real time, the evolution of different operating parameters to quickly control the command-control and avoid degradations linked with extreme operation conditions. The PhD thesis deals with development of a diagnostic tool in real time based on fuel cell electrochemical impedance. In this work, the development of an electric model based on physical phenomena will be made. This model will then be streamlined in in order to online diagnosis system implementation. In a second step, electrochemical impedance spectroscopy measurements will be performed in nominal operating conditions and in degraded conditions (humidity, pressure and stoichiometry defects). The correlation between model and impedance measurements will be analysed. Finally, the impedancemeter will be implemented on a fuel cell system in order to validate the relevance of laboratory measurements and to evaluate the advantages of the embedded real-time diagnosis hardware for the command-control of fuel cell system.
See the summary of the offerHigh temperature steam electrolysis: analysis of the cell degradation by a multi-scale and multi-physic approach
Because of its great potential, hydrogen production by high temperature steam electrolysis has received an increasing national and international interest in recent years. The hydrogen produced by water electrolysis if taking advantage of sustainable energy sources would constitute an energy carriers with low carbon footprint and would allow limit greenhouse gas emission. However, this scheme will be relevant only if the durability and the reliability of the electrolyser is improved in order to reduce the cost of the produced hydrogen. In the thesis, it is proposed to analyse the mechanisms responsible of the electrolyser cells' degradation. Firstly, some durability tests will be carried out on elementary cells to measure their efficiency decrease over time. The degradation mechanisms will be then analysed by coupling a multi-physic modelling approach associated to a fine characterisation of the electrodes material properties. A special attention will be given to investigate the morphological and physical destabilisation of the electrodes by using X-ray adsorption methods at the European synchrotron Radiation Facility in Grenoble (ESRF). This work aims at proposing solutions in terms of microstructure optimisation and strategy of the electrolyser operation to limit the degradation.
See the summary of the offerCharacterization and Quantification of Membrane/Electrode Assembly Degradation in Proton Exchange Membrane Fuel Cell
The proton exchange membrane fuel cell (PEMFC) is one of the most promising candidates as zero emission alternative power sources for transport and stationary applications. While their performance has been greatly improved in recent years, their cost and lifetime remain the two major issues for a wide commercialization. To achieve this objective, it is necessary to optimize the membrane-electrode assembly (MEA) that constitutes the core of the fuel cell and consequently to study in details their degradation mechanisms. The MEA consists of a diffusion layers and a membrane coating with two active layers where the electrocatalyst reactions take place. These active layers exhibit a multiscale structure of aggregated carbon particles supporting platinum nanoparticles, the catalyst, and covered by ionomer. During the fuel cell operation, these components are degradated. The aim of this PhD work is to analyze, understand and quantify the MEA degradation. To carry out this study, the PhD student will mainly use the state-of-the-art electron microscopes available on the Nano-characterization platform at CEA-Grenoble (PFNC) as well as electrochemical characterization techniques.
See the summary of the offerNew high capacity electrode materials for all-solid-state lithium microbatteries
The recent technological development of the stand-alone microsystems is limited by the miniaturized source able to power such systems. All-solid-state thin film batteries are attractive systems to power such devices. Their thickness do not exceed 10 microns, and they are built of several layers including a glassy lithium ion conductor as electrolyte, deposited by PVD or CVD techniques. Nevertheless, their surface capacity is generally less than 100 µAh.cm-2.µm-1. The aim of this PhD thesis is to study new positive electrode materials, called conversion materials in order to greatly improve this surface capacity. Hence, transition metal sulfides will be prepared in a thin film form by sputtering. The influence of sputterring parameters on both the composition and the structure of the films will be studied. Electrochemical performances and lithium insertion/deinsertion mechanisms in these materials will be comprehensively studied. A wide panel of characterization techniques will be used to study these materials and all-solid-state cells including them: ICP, RBS, EPMA, XPS, Auger spectroscopy for determination of the chemical composition; XRD, Raman and Mössbauer spectroscopies,HRTEM to determine the structure; SEM to study the morphology and electrochemical methods (EIS, Galvanostatic cycling, cyclic voltammetry).
See the summary of the offerDevelopment of nanocatalyst for PEM Fuel Cell
PEM fuel cell is a promise technology in the context of new energy development. Indeed, it allows feeding an electrical device for transport application (automotive) or stationary application (back-up) without any greenhouse gas emission. However, to reach the objectives of power requested by the utilisation, the use of catalyst made of platinum is required. Platinum is a noble and expensive metal which is a brake of the widespread dissemination of the technology. To support the dissemination of this technology, new synthesis of nanostructured catalyst has to be developed. This thesis is focused on the synthesis, characterisation and performance tests of new catalysts which contain less platinum than thus currently used. These catalysts based on nanostructured alloy will be supported on carbon nanotubes (or other nanostrutured carbon). The nanostructuration allows a better catalyst use and thus decrease the platinum loading of the active layer. Characterisation by electron microscopy (SEM, TEM) will allow validating the nanostructuration.
See the summary of the offer