Rechargeable batteries have already conquered the market of portable electronics (i.e., mobile phones and laptops) and are set to further enable the large-scale deployment of electric vehicles and hybrid electric vehicles in a not too distant future. In this context, a deeper understanding of the fundamental processes governing the electrochemical behavior of electrode materials for batteries is required for further development of these applications. The aims of the work described in this thesis have been to investigate how electrochemical properties and structural properties of novel electrode materials relate to each other. In this sense, electrochemical characterization, structural analysis using XRD and their combined simultaneous use via in operando XRD experiments have played a crucial part. The investigations showed that: Two oxohalides, Ni3Sb4O6F6 and Mn2Sb3O6Cl, react with Li-ions in a complex manner involving different types of reaction mechanisms at low voltages in Li half cells. In operando XRD show that both of these materials are reduced in a conversion reaction via an in situ formation of nanocomposites, which proceed to react reversibly with Li-ions in a combination of alloying and conversion reactions. Carbon-coated Na2Mn2Si2O7 was synthesized and characterized as a possible positive electrode material for non-aqueous Na-ion batteries. DFT calculations point to a structural origin of the modest electrochemical behavior of this material. It is suggested that structural rearrangements upon desodiation are associated with large overpotentials. It is demonstrated via an in operando synchrotron XRD study that Fe(CN)6 vacancies in copper hexacyanoferrate (CuHCF) play an important role in the electrochemical behavior toward Zn2+ in an aqueous CuHCF/Zn cell. Furthermore, manganese hexacyanomanganate (MnHCM) is shown to react reversibly with Li+, Na+ and K+ in non-aqueous alkali metal half cells. In contrast to CuHCF, which is a zero-strain material, MnHCM undergoes a series of structural transitions (from monoclinic to cubic) during electrochemical cycling.

With the emerging interest in nanoscale materials, the fascinating field of surface science is rapidly growing and presenting challenges to the design of both experimental and theoretical studies. The primary aim of this dissertation is to shed some light on the physical and chemical properties of selected nanoscale materials at the interface. Furthermore, we will discuss the effective application of cutting edge theoretical and experimental techniques that are invaluable tools for understanding the systems at hand. To this effect, we use density functional theory (DFT) with the inclusion of van der Waals (vdW) interactions to study the effect of long-range interactions on the adsorption characteristics of various organic molecules (i.e. benzene, olympicene radical, and sexithiophene) on transition metal surfaces. Secondly, the detailed analysis of x-ray absorption spectroscopy (XAS), scanning transmission electron microscopy (STEM), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements will be presented. These investigations will be dedicated to the study of (i) the effect of pre-treatment on the coarsening behavior of Pt nanoparticles (NPs) supported on ?-Al2O3 and (ii) deconvoluting the intrinsic (size effects) and extrinsic (ligand effects) physical and electronic properties of Au NPs encapsulated by polystyrene 2-vinylpiridine ligands.

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Catalysts consisting of silver on α-Al₂O₃, α-SiC, and β-SiC supports were synthesized and tested for catalytic performance in the gas-phase direct oxidation of ethylene to ethylene oxide. For this study, which used no promoters, ethylene oxidation selectivity of SiC-supported catalysts ranged from 10 to 60% and conversion from 0-4.5%. Silicon carbide supported catalysts exhibited poor performance except for a surface-modified β-SiC-supported catalyst, which demonstrated conversion and selectivity similar to that of an α-Al₂O₃-supported catalyst. This Ag/β-SiC catalyst was further investigated with a kinetic study, and the reaction orders were found to be 0.18 with respect to ethylene and 0.34 with respect to oxygen. The kinetic results were consistent with Langmuir-Hinshelwood rate expressions developed from single-site and dual-site reaction mechanisms. Gold nanoparticles on titanium oxide and titania-silica supports are active for the formation of propylene oxide by the oxidation of propylene with hydrogen and oxygen mixtures. This study investigates the effect of cyanide treatment on gold supported on titanosilicate zeolite supports (Au/TS-1). Catalysts treated with weak solutions of sodium cyanide resulted in preferential removal of small gold particles, while catalysts treated with strong solutions resulted in dissolution of the gold and re-precipitation as gold (+1) cyanide. X-ray absorption spectroscopy demonstrated that catalysts which produce propylene oxide in the presence of hydrogen and oxygen mixtures had supported gold (+3) oxide nanoparticles of 3 nm size after synthesis, which were reduced to gold metal at reaction conditions. Samples treated with strong solutions of sodium cyanide resulted in supported gold (+1) cyanide particles of large size, 9-11 nm. These particles did not produce propylene oxide but, surprisingly, showed high selectivity toward propylene hydrogenation. Increasing gold (+1) cyanide particle size resulted in a decrease in hydrogenation activity. TS-1 and Au/TS-1 surfaces were studied with laser Raman spectroscopy. Surface fluorescence was substantially reduced with a low-temperature ozone treatment, allowing observation of titanosilicate framework bands. Hydrocarbon vibrations are observed for TS-1 and Au/TS-1 under propylene. Density functional theory models indicated that propylene adsorbed to a metal site along the Ï bond would show a Raman spectrum very similar to gas-phase propylene except for out-of-plane C-H vibrations, which would be moved to higher energy. This adsorption spectrum, with out-of-plane vibrations shifted to higher energy, was observed for both TS-1 and Au/TS-1. Langmuir adsorption isotherms were generated for both TS-1 and Au/TS-1, and a scaling factor derived from propylene uptake experiments allowed these isotherms to be scaled to propylene coverage of titanium. / Ph. D.

No / The potential of Mg in Arctica islandica as a climate proxy is explored through analysis of live-collected shells from Irvine Bay, NW Scotland. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis of the right hand valve from two specimens indicates that seasonal Mg/Ca variations do not correlate with seawater temperature. The highest Mg/Ca typically occurs at the annual growth checks in ~ November¿February. Mg/Ca variations between growth checks are significant in one specimen but usually not significant in the other. Mg/Ca measurements taken laterally across the band (i.e. perpendicular to direction of the growth) to determine heterogeneity of the aragonite deposited at the same time indicates that Mg/Ca concentration decreases with increasing distance from the periostracum in both shells. X-ray Absorption Near Edge Spectroscopy (XANES) indicates that Mg is not substituted into aragonite but is hosted by a disordered phase e.g. organic components or nanoparticles of an inorganic phase. Shell Mg/Ca variations may reflect changes in the concentration or composition of the disorded phase, as well as changes in the composition of the extrapallial fluid used for calcification. Such changes could reflect the relative transportation rates of Mg and Ca to the calcification site.

Orientador: Luis Vicente de Andrade Scalvi / Resumo: A proposta deste trabalho é a investigação e compreensão de propriedades ópticas e eletrônicas da heteroestrutura formada pelo semicondutor III-V GaAs e o semicondutor óxido SnO2. A deposição de filmes finos de GaAs é feita por evaporação resistiva, e a de filmes finos de SnO2 dopados com o íon terra-rara Eu3+ pelo processo sol-gel-dip-coating, combinando um material semicondutor com alta mobilidade eletrônica e transição direta (GaAs), com semicondutor de bandgap largo (SnO2) e condutividade naturalmente do tipo-n, onde a emissão de Eu3+ é bastante eficiente. Amostras desses dois materiais foram investigadas preliminarmente de forma separada, como filmes finos, ou pós de SnO2:Eu prensados na forma de pastilhas. Fotoluminescência foi medida em heteroestruturas GaAs/SnO2:2%Eu com tratamentos térmicos em baixa temperatura (200 e 400°C), enquanto filmes de SnO2:2%Eu isolados apenas apresentaram picos de emissão do Eu3+ quando tratados com temperatura elevada (1000°C), porém com baixa intensidade. A hipótese para esse fenômeno foi associada com aglomerados de Eu3+ na superfície das amostras. Medidas de XAFS têm possibilitado o estudo da incorporação do dopante Eu na matriz SnO2, e na compreensão do mecanismo da luminescência encontrada. Análises de XANES mostraram que o átomo de európio permanece no estado de oxidação trivalente após a síntese da solução e tratamentos térmicos feitos, e que a heteroestrutura apresenta menos distorção na rede e estrutura mais ordenada quando compa... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The purpose of this work is the investigation and comprehension of optical and electronic properties of the heterostructure, formed by the III-V semiconductor GaAs and the oxide semiconductor SnO2. The deposition of GaAs thin films is accomplished by the resistive evaporation technique, and thin films of SnO2, doped with the rare earth ion Eu3+, by the sol-gel-dip-coating process, combining a semiconductor material with high electronic mobility (GaAs), with a wide bandgap semiconductor (SnO2) which is naturally n-type, where Eu3+ emission is quite efficient. Samples of these two materials were initially investigated separately, as thin films, or SnO2:Eu powders pressed into pellets. Photoluminescence was measured in GaAs/SnO2:2%Eu heterostructures with thermal annealing at low temperature (200 and 400°C), while SnO2:2%Eu films showed Eu3+ emission peaks only when treated with higher temperature (1000°C), but with low intensity. The hypothesis for this phenomenon was associated with Eu3+ agglomerates on the sample surfaces. XAFS measurements have allowed the study of the incorporation of the Eu doping in the SnO2 matrix, and in the understanding of the mechanism of luminescence found. Analysis of XANES showed that the europium atom remains in the trivalent oxidation state after the synthesis of the solution and thermal annealing done, and that the GaAs/SnO2:2%Eu heterostructure presents less distortion in the lattice and more ordered structure when compared to films of SnO2:2%... (Complete abstract click electronic access below) / Doutor

L’étude des plasmas denses et tièdes est un domaine qui suscite aujourd’hui l’intérêt de nombreux groupes de recherche de part son large spectre d’applications. Ce régime de la matière, qui recouvre une densité proche de celle du solide et une température allant de 0.1 à une dizaine d’eV, est encore mal connu et présente une grande complexité de part son caractère partiellement dégénéré (électrons) et partiellement corrélé (ions). Afin d’explorer ce régime, nous proposons de le sonder par spectroscopie d’absorption X près des seuils grâce à une source X ultra-rapide (ps), intense, produite par laser. La spectroscopie d’absorption X près des seuils (XANES, EXAFS) est un diagnostic qui permet l’étude de la structure atomique locale de milieux éventuellement non-cristallins (solides, liquides, plasmas denses et tièdes). Elle nécessite l’utilisation de sources X de large bande spectrale ajustée au seuil d’absorption de l’élément étudié (...) / The possibility of producing, in a controlled way, matter at solid density (1-10 g/cm3) while maintaining it at temperatures ranging from 0.1 to 100 eV has been for a long time a desired goal. At the boundary between condensed matter and plasma physics, the study of matter in the Warm Dense Matter (WDM) regime involves, nowadays, many laboratories worldwide. This state is still poorly understood and presents a very complex character, being partly degenerated (electrons) and partly correlated (ions). To explore this regime, we proposed to probe WDM by X-ray absorption fine spectroscopy with an ultra-fast X-ray source (ps), produced by ultra intense lasers. X-ray absorption fine spectroscopy, specifically XANES and EXAFS spectroscopy, is a diagnostic tool that allows the study of local atomic structures, even in non-crystalline states (solid, liquid, WDM, plasmas). It requires the use of broadband X-ray sources adjusted on the x-ray absorption edge of studied element (...)

Les artefacts en céramique ont une longue histoire et ont été récupérés dans presque toutes les régions du monde. La conservation n’est que rarement impactée par le milieu d’enfouissement. Donc, ils sont des matériaux idéaux pour comprendre l'histoire et la culture de homme. Les principales études archéologiques sur les céramiques anciennes concernent la provenance (datation, atelier, commerce), les matières premières (identification, origine), le processus de fabrication et l'utilisation (analyse des résidus de contenu). Mon travail porte plus précisément sur le processus de fabrication. Les principales étapes du processus de fabrication sont: la sélection des matières premières, la préparation, le façonnage, salle de bains, sur deux possibilités. Soit le vase est cuit avant l'étape de décoration, soit la décoration est appliquée sur le vase cru. Pour finir, l'ensemble est cuit. Mon objectif est d'obtenir des informations sur le procédé de fabrication en analysant la structure des céramiques anciennes, et en particulier, la structure des couches décoratives. La structure des céramiques anciennes est une structure complexe en couches avec des hétérogénéités à différentes échelles (mm à nm). Une céramique décorée est généralement composée d'une pâte et d'un revêtement, y compris de la décoration. Le revêtement peut contenir des natures différentes. L'épaisseur peut être variable de mm à nm. La couche décorative peut être une partie ou du tout la revêtement. La couche décorative peut être constitutive d'une phase vitrifiée amorphe et divers cristaux, tels que cristaux colorants, feldspath, quartz, etc., dont la taille varie de plusieurs microns à nanomètre. La description de cette structure nécessite l'analyse à haute résolution (nm) avec grande zone représentative (souvent plusieurs mm3). C’est difficile à réaliser. Dans mon travail, j'ai proposé une autre approche. L'approche est basée sur trois étapes. Premièrement, les analyses rapides (principalement microscopie optique) à faibles résolutions sont effectuées pour analyser et sélectionner la zone nécessitant une analyse à haute résolution. Ensuite, la zone sélectionnée est analysée à haute résolution par des techniques appropriées en tenant compte des informations recherchées. Troisièmement, on essaie de construire la structure de l'objet sur la base des données partielles, et d’en déduire le processus de fabrication. Je vais illustrer cette approche par trois exemples. La première concerne le pigment jaune de la terre sigillée marbrée romaine (chapitre III). Le second concerne le processus de cuisson des poteries attiques (chapitre III). Le troisième concerne les variations de couleur de la décoration bleue des porcelaines Qinghua (chapitre IV). / Ceramic artifacts have a long history and have been discovered worldwide. Their conservations are rarely impacted by the burial sites. Thus, they are ideal materials for understanding the human history and culture. The main archaeological studies concerning ancient ceramics contains provenance (dating, workshop, trade), raw materials (identification, origin), manufacturing process and utilization (analysis of content residues). For my work, I focused on the investigation of the manufacturing process. The main steps of fabrication process of ancient ceramics is composed of selection of raw materials, preparation (leaching, purification, body, glaze or slip, pigments), shaping (the plastic paste is shaped to the lathe or using the molds). Then, there are two possibilities: either the vase is fired before the decoration stage, or the decoration is applied to the raw vase. To finish, the whole is fired. My objective is to obtain information on the manufacturing process by analyzing the structure of ancient ceramics, and in particular the structure of decorative layers. The structure of ancient ceramics is complex with heterogeneities at different scales (mm to nm). A decorated ceramic generally is composed of a body and a coating, which including of the decoration. The coating could contain different natures. The thickness can be variable from mm to nm. The decorative layer can be a part of the coating or the whole coating. The decorative layer can be constituent of an amorphous vitrified phase and diverse crystals, such as colorant crystals, feldspar, quartz, etc., of which the size varies from several microns to nanometer. The description of such structure requires the analysis at high resolution (nm) with large representative zone (often, several mm3). It is difficult to realize. In my work, I proposed an alternative approach. The approach is based on three stages. Firstly, the rapid investigations (principally, optical microscopy) at low resolutions are effected to analyze and select the zone requiring analysis at high resolution. Secondly, the selected zone is analyzed at high resolution by appropriate techniques according to the information sought. Thirdly, I try to construct the structure of the object based on the partially data, and therefore deduce the manufacturing process. I will illustrate this approach through three examples. The first one concerns the yellow pigment of the Roman marbled terra sigillata (Chapter III). The second one is about the firing process of Attic potteries (Chapter III). The third one concerns the color variations of blue decoration of Qinghua porcelains (Chapter IV).

La vernadite est un phyllomanganate nanocristallin présentant un empilement de feuillets turbostratique, c'est à dire des fautes d'empilement aléatoire systématiques entre deux feuillets successifs. La présence de lacunes foliaires et/ou de manganèse hétérovalent dans le feuillet induit un déficit de charge compensé par la présence de cations interfoliaires hydratés. Ces caractéristiques confèrent à la vernadite des propriétés d'adsorption et/ou un potentiel redox à l'origine de sa réactivité dans l'Environnement, où, en tant que phase ubiquiste, elle joue un rôle majeur pour le devenir de nombreux polluants organiques et métalliques. Malgré ce rôle, sa structure et celle de son analogue delta-MnO2 sont encore mal connues car leur désordre structural ne permet pas d'utiliser les techniques classiques d'affinement. Nous avons donc appliqué une approche spécifique, couplée à des méthodes chimiques et des mesures spectroscopiques (EXAFS et XANES), pour déterminer la structure d'échantillons de delta-MnO2 et de vernadites produites par des champignons ainsi que l'origine de leur réactivité. Nous avons également montré que la structure de delta-MnO2 évolue en fonction des conditions de pH et avec le temps, avec un impact fort sur sa réactivité. Nous avons enfin déterminé les mécanismes d'adsorption de métaux modèles (Ni et Zn) sur delta-MnO2. L'adsorption se fait majoritairement à l'aplomb de lacunes foliaires, les mécanismes d'asorption dépendant de la structure initiale de delat-MnO2 et du métal.