La corrosion et la dégradation des matériaux sont des problèmes majeurs qui impactent économiquement de nombreux domaines d’activités. Cette dégradation dépend de nombreux paramètres environnementaux. Dans ce cadre, le suivi de la dégradation des matériaux est primordial. L’objectif de cette thèse est donc d’élaborer des capteurs de dégradation de matériaux, sans fils et passifs énergétiquement. Pour cela, notre travail sera basé sur la technologie RFID (Radio Frequency Identification) passive. Nous présentons alors, des résonateurs sensibles à la dégradation et à la corrosion des matériaux. Celles-ci étant souvent liées à la présence d’eau dans le milieu environnant, une partie de la thèse concerne le suivi de l’absorption dans les revêtements organiques et les bétons. Afin de corréler la présence d’eau avec une dégradation du métal présent dans le diélectrique, un résonateur sensible au potentiel de corrosion est ensuite proposé. Pour finir, une étude sur la détection des sels dissouts dans le milieu est réalisée par ce type de technique. Suite à la présentation de ces résultats, une partie plus courte consacrée à la réalisation d’un démonstrateur sur la bande ISM autorisée à 2.45 GHz est présentée. Elle permet une discussion sur l’utilisation de ce type de capteur dans des situations réelles. / Corrosion and material degradation are major problems that economically impact many areas of activity. This degradation depends on many environmental parameters. In this context, monitoring the degradation of materials is crucial. The objective of this thesis is to develop materials degradation sensors that are chipless and wireless. For that purpose, this work will be based on passive RFID (Radio Frequency Identification). We present different resonators sensitive to the degradation and corrosion of materials. These are often linked to the presence of water in the environment; part of the thesis concerns the monitoring of the absorption in organic coatings and concrete. In order to correlate the presence of water with a degradation of the metal present in the dielectric, a resonator sensitive to the corrosion potential is then proposed. Finally, a study on the detection of dissolved salts in the medium is performed by this type of technique. Following these results, a shorter part of the realization of a demonstrator in the authorized ISM band at 2.45 GHz is presented. It provides a discussion about the use of this type of sensor in real situations.

The molten salt reactor (MSR) is one of the advanced nuclear reactors expected to be alternatives to the conventional water-cooled nuclear reactor systems. Despite many advantages of MSRs, properties of molten salts have not been sufficiently measured in previous studies. In addition, the corrosion of structural alloys by molten salt is the biggest challenge for the operation of MSRs. This study focuses on measurements of thermophysical and thermodynamic properties of fluoride salt fuels, salt purification, and the degradation of structural materials in static and flowing molten-salt fuels. For the measurements of properties, phase transition, specific heat capacity, vapor pressure, contact angle on nuclear-grade graphite, and density were measured. The methodologies for the property measurements used in this study were validated by measuring the properties of metals or salts that have been well studied. For the flow-induced corrosion tests, the salt flow with different velocities was simulated by rotating the stainless steel 316H (SS316H) specimens in molten NaF-KF-UF4 (FUNaK) contained in glassy carbon crucibles at 1073 K. Salt samples were intermittently collected to monitor concentration changes of corrosion products in the salt, and surfaces and cross-sections of post-test SS316H specimens were analyzed to study their corrosion behaviors. Different batches of FUNaK were synthesized using different methods of purification, such as thermal purification, U-metal purification, and hydrofluorination with electrochemical purification (chemical purification) to study impacts of salt purification on the corrosion of SS316H. The corrosion test of SS316H by thermally purified FUNaK showed that the Fe concentration increased at the beginning and then decreased while the Cr concentration continued increasing while the rate decreased. In addition, (Cr, Fe)7C3 layers, Cr-metal particles, and dendritic structures concentrated with Cr and Fe were observed on the glassy carbon crucible after the 2 m/s test. The U-metal purification and hydrofluorination with electrochemical purification reduced concentrations of oxygen and hydrogen in FUNaK and mitigated the corrosion of SS316H significantly. The infiltration of the fluoride fuel salts into graphite and the fluorination of graphite by the salts at different pressures and temperatures were also studied. The salt infiltration into graphite at pressures above its threshold pressure was observed, and the formation of carbon fluorides on the surface of post-test graphite specimens was identified. / Doctor of Philosophy / As conventional water-cooled nuclear power systems showed safety issues, the Generation IV International Forum was established to expedite the development of next-generation nuclear reactor systems. Among the six advanced nuclear reactors, the molten salt reactor (MSR) stands out for its remarkable technical advantages, including low operating pressures and increased efficiency resulting from higher operating temperatures compared to water-cooled nuclear systems. Despite their advantages, further studies need to be conducted to develop and operate MSRs, as properties of molten salts have not been comprehensively measured in previous studies, and the corrosion of structural materials by molten salt is a significant challenge to their operation. The corrosion of alloys by molten salt can be attributed to many different factors, and the level of impurities in salt is an important factor directly linked to corrosion. Thus, the purification of salt is imperative to mitigate the corrosion of MSRs and needs to be well studied. In this study, methodologies for measuring thermophysical and thermodynamic properties of fluoride fuel salts were developed and validated using reference data. In addition, the corrosion of stainless steel 316H (SS316H) in a flowing fuel salt was also studied. Although various corrosion tests with static molten salts have been conducted, studies on corrosion of alloys in flowing molten salt fuels containing uranium fluorides are still limited. This study addresses this gap by developing a test apparatus equipped with a rotating disk to simulate the flow of molten salt on the surface of alloy specimens. Different batches of fuel salts with varying impurity levels, especially oxygen and hydrogen, were prepared using different purification methods. These salts were then used for corrosion tests under the same conditions, such as temperature and time duration, to explore the impacts of the non-metallic impurities on the corrosion of SS316H. The findings revealed that the salts with lower levels of oxygen and hydrogen caused less corrosion of SS316H, underscoring that the purification of salt is indispensable to the mitigation of corrosion in MSRs. This study also explored interactions of molten-salt fuels with graphite which is a promising candidate for a moderator or reflector of MSRs for enhancing neutron economy for thermal nuclear reactors. A high-pressure graphite-infiltration test apparatus was developed to investigate infiltration of fluoride fuel salts into graphite and the fluorination of graphite.

The diploma thesis introduces the reader to the problems of chemical sensors and the basics of degradation processes in materials of animal origin. It describes some types of sensors and their principles. Atmel ATmega328 microprocessor, its parameters and programming are described. In the next part of the thesis there is a proposal and production of equipment for monitoring of degradation processes in materials of animal origin. Sample sof chicken and milk were mesuared. From these measurements, the gas concentration values were determined, where samples can be considered suitable for consumation.

Dans le cadre de l’évolution du plus grand accélérateur circulaire de particules « LHC », un important programme de mise à niveau sur l’ensemble des détecteurs qui le constitue a été lancé. Parmi eux, on retrouve la mise à niveau du détecteur LHCb qui comprend le remplacement complet de plusieurs sous-détecteurs. La fréquence de lecture élevée de 40MHz, sans précédent dans une expérience de physique des particules, et l’environnement de rayonnement sévère lié à l’augmentation de l’intensité du LHC, sont les principaux défis à relever par les nouveaux sous-détecteurs. Le travail présenté dans ce manuscrit, décrit une petite partie de l’évolution du détecteur LHCb. Le développement et la construction d’un nouveau trajectographe à grande échelle, basé sur une nouvelle technologie à fibres scintillantes «SciFi», lues avec des photomultiplicateurs au silicium «SiPM», est l’un des projets clés du programme de mise à niveau de LHCb. La première partie, consiste à étudier les échanges thermiques et à concevoir un système de refroidissement pour chaque Read-Out Box « ROB » qui contient deux cartes électroniques frontales « FE », et qui permettent de lire les données du détecteur. Ces dernières possèdent une dissipation thermique d’environ 110W.Pour assurer le bon fonctionnement des composants électroniques, il est obligatoire de mettre en place un refroidisseur. Des contraintes importantes sont prisent en compte dans cette étude, la première représente l’espace limité en regard du besoin du système de refroidissement, des interfaces électroniques et mécanique, la seconde concerne les SiPM. Reliés à l’électronique par des câbles flexibles, elles sont situées à proximité de l’électronique « FE » et leur température de fonctionnement doit être parfaitement réglée autour des -40°C. Des travaux de simulations numériques sur les logiciels FloTHERM et ANSYS ont été menés sur le banc expérimental réalisé au sein du laboratoire, et qui nous ont permis de déterminer la solution de refroidissement la mieux adaptée. Cette étude nous a aussi montré qu’il est plus que nécessaire d’intégrer des interfaces thermiques « IT» telles que des pâtes thermiques afin d’assurer un meilleur transfert de chaleur entre les composants électroniques et le refroidisseur. La deuxième partie, représente une étude approfondie sur les interfaces thermiques qui sont un point délicat de transfert de chaleur, car elles peuvent avoir plusieurs dizaines de pour cent de la résistance thermique globale. Pour garantir une utilisation adéquate et durable de ces matériaux, plusieurs paramètres ont été vérifiés, en particulier la dureté, la consistance (pas de production de graisse ou d’huile) et la conductivité thermique, grâce à un banc de mesures adapté d’après la méthode normalisé ASTM D5470, grâce auquel on a pu mesurer le flux de chaleur qui traverse l’échantillon d’interface thermique testé et qui est généré par une source chaude et un source froide qui sont montées aux extrémités de notre banc.Grâce à l’installation CHARME (CERN) et à la plate-forme PAVIRMA (Campus des Cézeaux), une série de mesure d’irradiations aux neutrons et aux rayons X sont également effectuées, correspondant à l’environnement dans lequel elles seront exposées dans l’expérience, d’un côté pour identifier les dégradations et changements possibles sur les résistances thermiques par l’analyse de l’impédance thermique, de l’autre pour identifier l’interface thermique qui convient le mieux à notre application et qui permet d’assurer un excellent échange thermique et donc un bon refroidissement de l’électronique frontale au sein du trajectographe du détecteur LHCb. / In the context of the evolution of the biggest circular accelerator of particles «LHC», an important program of upgrade on all the detectors which establishes itself was thrown. Among them, we find the upgrade of the detector LHCb which includes the complete replacement of several sub-detectors. The frequency of high reading of 40MHz, an unprecedented in an experiment of physical appearance of particles, and the environment of severe radiation bound to the increase of the intensity of the LHC, are the main challenges by the new sub-detectors. The work presented in this manuscript, described as a small part of the evolution of the LHCb detector. The development and the construction of a new wide-scale tracker, based on a new technology with scintillating fiber «SciFi», read with photomultipliers to the silicon «SiPM», is one of the key projects of the LHCb upgrade program. The first part, consists in studying the thermal exchanges and designing a cooling system for every Read-Out Box «ROB» which contains two electronic front-end « FE », and which allow to read the data of the detector. The latter has a thermal dissipation about 110W. To ensure the smooth running of electronic components, it is compulsory to set up a cooler. Important constraints are taken into account in this study, the first one represents the space limited compared to the need for the cooling system, the electronic interfaces and mechanical, the second concerns the SiPM. Connected with the electronics by flexible cables, they are located near the electronics «FE» and their temperature of operation is perfectly settled around -40 ° C. Works of digital simulations on the software FloTHERM and ANSYS were led on the experimental bench realized within the laboratory, and which allowed us to determine the best adapted solution of cooling. This study also showed to us that he is more than necessity to integrate thermal interfaces «IT» such as thermal pastas to assure a better transfer of heat between electronic components and cooler. The second part, represents an in-depth study on the thermal interfaces which are a delicate point of transfer of heat, because they can have dozens percent of the global thermal resistance. To guarantee an adequate and sustainable use of these materials, several parameters were verified, in particular hardness, consistency (no production of fat or oil) and the thermal conductivity, thanks to a bench of measures adapted according to the method normalized ASTM D5470, with this bench we could measure the flow of heat through the tested thermal interface sample and which is generated by a hot source and a cold source that are mounted at the ends of our bench.With the installation CHARME (CERN) and PAVIRMA (Cézeaux), a series of measure of irradiations at the neutrons and the X-rays are also made, correspond-ing to the environment in which they will be exposed in the experience, on one side to identify the damages and the possible changes on the thermal resistances by the analysis of the thermal impedance, the other one to identify the thermal interface which suits best our application and which allows to assure an excellent thermal exchange and thus a good cooling of the frontal electronics within the trajectographe of the detector LHCb.

In recent years, Polymer Electrolyte Membrane Fuel Cells (PEMFC) have attracted much attention due to their potential as a clean power source for many applications, including automotive, portable and stationary devices. This resulted in a tremendous technological progress, such as the development of new membranes and electro-catalysts or the improvement of electrode structures. However, in order to compete within the most attractive markets, the PEMFC technologies did not reach all the required characteristics yet, in particular in terms of cost and durability.Because of the strong coupling between different physicochemical phenomena, the interpretation of experimental observations is difficult, and analysis through modeling becomes crucial to elucidate the degradation and failure mechanisms, andto help improving both PEMFC electrochemical performance and durability.The development of a theoretical tool is essential for industrials and the scientific community to evaluate the PEMFC degradation and to predict itsperformance and durability in function of the materials properties and in a diversity of operating conditions. This manuscript summarizes my scientific research efforts in this exciting topic during the last 9 years in France, including my invention of the MEMEPhys multiscale simulation package,developed on the basis of my childhood passion for the New Technologies for Energyin Argentina. My perspectives of adapting this approach to other electrochemical systems such as water electrolyzers and batteries are also discussed.