A new barometric technique measuring stored stress in quartz inclusions via laser Raman microspectrometry was employed in an attempt to elucidate the extent of highpressure (HP) metamorphism in the Llano Uplift of central Texas. Rare lithologies within the Llano Uplift contain mineralogical evidence of HP metamorphism (pressures from 1.4 to 2.4 GPa at temperatures from 650 to 775°C), but much of the uplift is composed of felsic gneisses lacking any HP signature; these felsic gneisses may never have transformed to HP assemblages, or they may have been thoroughly overprinted by later low-pressure events. Barometry via laser Raman microspectrometry computes entrapment pressure for a quartz inclusion in garnet from measurement of the displacements of its Raman peak positions from those of a quartz standard at atmospheric pressure. Quartz inclusions in garnets that grew in felsic gneisses under HP conditions should retain HP signatures, despite later overprinting. Application of the Raman microspectrometry technique should therefore allow barometry of previously uncharacterizable rocks. For two localities in the Llano Uplift, entrapment pressures from Raman barometry (0.6-0.7 GPa and 0.2-0.3 GPa) were substantially lower than pressures expected based on conventional barometers (1.4 GPa and 1.6-2.4 GPa). This absence of any HP signatures in the Llano rocks contrasts with more successful applications of the Raman technique by previous workers in high P/T blueschist-facies rocks. A key difference in the Llano rocks is that they reached peak temperatures at which intracrystalline diffusion in garnet, driven by compositional gradients produced during growth, had noticeable effects: complete homogenization of growth zoning had occurred in the locality that produced the greatest discrepancies between Raman and conventional pressures, and modest relaxation of zoning occurred in the locality with the smaller discrepancies. The failure of the Raman technique to recover pressures consistent with conventional barometry in the Llano Uplift is therefore attributed to relaxation of stress on the quartz inclusions as the result of intracrystalline diffusion within the garnet. This conclusion suggests that use of the Raman barometric technique must be restricted to rocks whose time-temperature histories produce only very limited intracrystalline diffusion in garnet, typically those rocks whose peak metamorphic temperatures fall at or below upper amphibolite-facies conditions. / text

Many geologic processes occur in association with hydrothermal fluids and some of these fluids are eventually trapped as fluid inclusions in minerals formed during the process. Fluid inclusions provide valuable information on the pressure, temperature and fluid composition (PTX) of the environment of formation, hence understanding PTX properties of the fluid inclusions is required. The most important step of a fluid inclusion study is the identification of Fluid Inclusion Assemblages (FIA) that represent the finest (shortest time duration) geologic event that can be constrained using fluid inclusions. Homogenization temperature data obtained from fluid inclusions is often used to reconstruct temperature history of a geologic event. The precision with which fluid inclusions constrain the temperatures of geologic events depends on the precision with which the temperature of a fluid inclusion assemblage can be determined. Synthetic fluid inclusions trapped in the one-fluid-phase field are formed at a known and relatively constant temperature. However, microthermometry of synthetic fluid inclusions often reveals Th variations of about ± 1- 4 degrees Centigrade, or one order of magnitude larger than the precision of the measurement for an individual inclusion. The same range in Th was observed in well-constrained natural FIAs where the inclusions are assumed to have been trapped at the same time. The observed small variations are the result of the effect of the fluid inclusion size on the bubble collapsing temperature. As inclusions are heated the vapor bubble is getting smaller until the pressure difference between the pressure of the vapor and the confining pressure reaches a critical value and the bubble collapses. It was observed that smaller inclusions reach critical bubble radius and critical pressure differences at lower temperatures than larger inclusions within the same FIA. Homogenization temperature (Th) variations depend on many factors that vary within different geological environments. In order to determine minimum and acceptable Th ranges fro FIAs formed in different environments we investigated several geologic environments including sedimentary, metamorphic, and magmatic hydrothermal environments. The observed minimum Th ranges range from 1-4 degrees Centigrade and acceptable Th range from 5-25 degrees Centigrade. The variations are mostly caused by the fluid inclusion size, natural temperature and pressure fluctuations during the formation of an FIA and reequilibration after trapping. Fluid inclusions containing H₂O-CO₂-NaCl are common in many geologic environments and knowing the salinity of these inclusions is important to interpret PVTX properties of the fluids. A technique that combines Raman spectroscopy and microthermometry of individual inclusions was developed to determine the salinity of these inclusions. In order to determine the salinity, the pressure and temperature within the inclusion must be known. The pressure within the inclusions is determined using the splitting in the Fermi diad of the Raman spectra of the CO₂ at the clathrate melting temperature. Applying the technique with to synthetic fluid inclusions with known salinity suggests that the technique is valid and useable to determine salinity of H₂O-CO₂-NaCl fluid inclusions with unknown salinity. / Ph. D.

Cette étude prend place dans le cadre du projet ANR Inxilicium visant à la réalisation de cellules solaires en couches minces de silicium par jet d’encre. Les nanoparticules de silicium sont des matériaux à fort potentiel pour la levée de verrous technologiques grâce à leurs propriétés spécifiques. Des encres de nanoparticules de Si issues de diverses méthodes de synthèse ont été imprimées par jet d’encre sur différents substrats : quartz, électrodes métalliques (aluminium, molybdène) et transparente conductrice (ZnO:Al). L’optimisation du procédé d’impression, de l’interaction encre/substrat (via la modulation de l’énergie de surface des substrats) et de l’étape de séchage a permis l’obtention de couches minces homogènes et continues (plusieurs centaines de nm à quelques µm d’épaisseur)A posteriori, une étape de recuit est nécessaire pour recouvrer des propriétés fonctionnelles. L’utilisation de nanoparticules à la physico-chimie de surface contrôlée fait décroître les températures de frittage de 1100 °C à environ 600 °C. En complément, des recuits sélectifs (micro-ondes et photonique) ont été évalués pour leur application sur des substrats flexibles et bas coûts.Les propriétés optiques et les interfaces électrode/silicium ont été examinées afin d’intégrer ces couches dans des dispositifs (cellule solaire…). La formation de transitions métallurgiques Al-Si et Mo-Si a été étudiées par DRX-in situ. L’ensemble de ces travaux a permis la réalisation d’une jonction PN montrant un comportement photovoltaïque à fort champ grâce aussi à la mise au point d’une méthode innovante de collage ouvrant la voie à une réduction du bilan thermique des procédés de fabrication. / This study takes place in the frame of the Inxilicium project from the National Research Agency, which targets the fabrication of silicon thin film solar cells by inkjet-printing. Thanks to their specific properties, silicon nanoparticles are materials with strong potential for technological breakthroughs. Silicon nanoparticle-based inks made by different synthesis routes have been inkjet-printed on different substrates: quartz, metallic electrodes (aluminum, molybdenum) and transparent electrodes (ZnO:Al). Homogeneous and continuous thin films (from several hundreds of nm to some µm thick) have been obtained through optimization of the printing process, the ink/substrate interaction (via substrates surface energy tuning) and the drying step.A posteriori, an annealing step is mandatory for recovering of functional properties. By using nanoparticles with tailored surface physical chemistry, the sintering temperature decreases from 1100 °C to 600 °C. In order to allow the use of this material on flexible and low cost substrates, selective sintering (microwave and photonics) have been also evaluated.Thin film optical properties and electrode/silicon interfaces have been investigated with the purpose to integrate those layers into devices (solar cells…). Metallurgical evolution of Al-Si and Mo-Si physical interfaces has been studied by in situ XRD.This work allowed the fabrication of a PN junction with a photovoltaic behaviour under strong polarization voltage thanks to the development of an innovative thermal pasting process, which opens the way to the reduction of process thermal budget.

Le démantèlement des réacteurs nucléaires de première génération UNGG (Uranium Naturel Graphite Gaz) génèrera en France environ 23 000 tonnes de déchets de graphites irradiés. Les principaux radionucléides présents dans ces déchets sont des produits d’activation tels que le 14C, le 36Cl et le 3H. Les deux premiers sont dimensionnants pour le stockage, le 14C (T =5730 ans) essentiellement en raison de son inventaire initial important et le 36Cl du fait de sa longue période (302 000 ans). Le scénario de référence envisagé pour la gestion de ces déchets de faible activité à vie longue est le stockage mais une décontamination préalable plus ou moins poussée a également été envisagée. De ce fait, la connaissance de la localisation et la spéciation de ces radionucléides dans le graphite irradié est un prérequis indispensable pour l’optimisation d’un procédé de traitement et l’évaluation de la sûreté du stockage. L’objectif de cette thèse CIFRE, réalisée en partenariat avec EDF, est de mettre en oeuvre des études expérimentales permettant, dans une première partie, de simuler et d’évaluer l’impact de la température, de l’irradiation et de la corrosion radiolytique du graphite sur le comportement migratoire du 14C en réacteur et sur les modifications structurales qui en découlent. Les données ainsi acquises servent d’appui à la deuxième partie de ce travail consacrée à l’étude d’un procédé de décontamination thermique du graphite en présence de vapeur d’eau. Ce travail est mené par implantation de l’isotope stable 13C permettant de simuler la présence de l’isotope radioactif 14C. L’utilisation de différentes natures de graphite de référence tels qu’un graphite vierge de qualité nucléaire, un graphite modèle HOPG bien ordonné de structure lamellaire et un graphite de structure nanoporeuse de type SLX 50 broyé permet de simuler les différents états de structure rencontrés dans un graphite irradié par des neutrons. L’étude d’échantillons inactifs permet ainsi de s’affranchir des contraintes liées à l’étude d’échantillons radioactifs et de réaliser des études paramétriques du comportement migratoire de l’espèce implantée, difficiles à mettre en oeuvre sur du graphite irradié. La première partie de ce travail consiste en l’étude des effets couplés et découplés de la température et de l’irradiation ionique (simulant l’irradiation neutronique) sur le comportement migratoire du 13C. Les résultats obtenus montrent que, dans la gamme de températures du graphite en réacteur (200 - 500 °C), le 13C est stable quel que soit l’état de l’endommagement de la structure du graphite. D’une manière générale, l’irradiation et la température ont des effets antagonistes. L’irradiation induit une déstructuration du graphite compensée par les effets de recuit conduisant à la réorganisation de la structure dont le degré dépend de l’état initial. Ainsi, en fonction de la localisation du graphite au sein du modérateur, son état de structure sera contrasté selon qu’il aura été irradié dans les zones chaudes à haut flux neutronique ou dans les zones à bas flux et plus froides. Cependant, dans tous les cas, le 14C aura été stabilisé. La deuxième partie concerne l’étude du procédé de décontamination thermique en présence de vapeur d’eau qui a été réalisée sur un dispositif de thermogravimétrie couplé à un générateur de vapeur d’eau. L’influence de la température (700 °C et 900 °C) et de l’humidité relative (50 % HR et 90 % HR) a été testée à un débit de gaz humide fixe de 50 mL/min sur les différents échantillons de référence. L’utilisation d’eau marquée avec de l’18O a permis de tracer la migration des espèces oxydantes dans le graphite. Ainsi, l’efficacité du procédé a été mise en évidence permettant une élimination préférentielle par gazéification des zones les plus nanoporeuses qui sont à priori également les plus concentrées en 14C / The decommissioning of French gas cooled nuclear reactors (UNGG) will generate around 23000 tons of irradiated graphite waste containing radionuclides such as 14C, 36Cl. Both might be dose determining at the outlet, 14C as major contributor to the radioactive dose and 36Cl due to its mobility in the clay repository. The reference management for this Low-Level Long-Lived Waste (LLW-LL) is disposal but its partial decontamination has also been foreseen. Therefore, information on inventory, location and speciation of the radionuclides in the irradiated graphite are mandatory for optimizing the decontamination process and to get reliable insights on the behavior of the radionuclides in the repository. This thesis supported by EDF aims in a first part at studying the impact of temperature, graphite irradiation and radiolytic corrosion on the behavior of 14C and following structure modification. Then, the acquired data are used to support the second part devoted to study 14C decontamination by steam reforming. 13C implantation is used to simulate the presence of 14C. The experiments are carried out on different reference samples such as virgin nuclear graphite, a model and ordered lamellar HOPG graphite and a nanoporous graphite SLX 50 that allow simulating the different structural states of a neutron irradiated graphite. The first part investigates the coupled and decoupled effects of ion irradiation (used to simulate neutron irradiation) on 13C migration. The results show that, at reactor temperatures of 200 - 500 °C, 13C remains stable whatever the graphite structural disorder level. Irradiation and temperature have antagonist effects: irradiation disorders graphite whereas temperature has an annealing effect leading to a reordering of the graphite structure at a level depending on its initial one. Thus, according to graphite position in the moderator this will lead to structure contrasts depending on whether it has been irradiated at high neutron flux and high temperature or low neutron flux and colder temperature. However, 14C is stabilized in the graphite structure in all cases. The second part is devoted the study of 14C steam reforming using a thermogravimetric analyzer coupled to a steam generator. The reference samples were analyzed at temperatures of 700 °C and 900 °C and relative humidities of 50 % and 90 % at a constant humid gas rate of 50 mL/min. 18O labelled water was used to follow the migration of the oxidizing species into graphite. Accordingly, the tests put in evidence the preferential gasification of nanoporous graphite that should also be the richest in 14C. Moreover, the addition of Ni to graphite before steam reforming proved to be very efficient but the gasification was very important and needs adjusting Ni impregnation

The thesis comprehensively investigates 2 pcs of ferrous and 14 pcs of bronze Celtic artefacts from a region of Zdejciny by Beroun. The study by means of ore microscopy, x-ray fluorescent microspectrometry, chemical microanalysis, Raman microspectrometry and x-ray powder diffractive analysis has showed that the bronze artefacts are made mainly of bronze. The phases present in the studied items correspond to fields and + of the Cu-Sn phase diagram. Content of Sn in bronze ranges between 4 and 33 wt.%. For the bronze selected items there was also Vickers microhardness measured. There were two artefacts where areas with a significant lead enrichment were found. Corrosive products were also deeply analysed and identified.