<p>Lithium ion insertion into electrode materials is commonly used in rechargeable battery technology. The insertion implies changes in both the crystal structure and the electronic structure of the electrode material. Side-reactions may occur on the surface of the electrode, which is exposed to the electrolyte and form a solid electrolyte interface (SEI). The understanding of these processes is of great importance for improving battery performance. The chemical and physical properties of water and alcohols are complicated by the presence of strong hydrogen bonding. Various experimental techniques have been used to study geometrical structures and different models have been proposed to view the details of how these liquids are geometrically organized by hydrogen bonding. However, very little is known about the electronic structure of these liquids, mainly due to the lack of suitable experimental tools.</p><p>This thesis addresses the electronic structure of liquids and lithium battery materials using resonant inelastic X-ray scattering (RIXS) at high brightness synchrotron radiation sources. The electronic structure of battery electrodes has been probed, before and after lithiation, studying the doping of electrons into the host material. The chemical composition of the SEI on cycled graphite electrodes was determined. The local electronic structure of water, methanol and mixtures of the two have been examined using a special liquid cell. Results from the study of liquid water showed a strong influence on the 3a₁ molecular orbital and orbital mixing between molecules upon hydrogen bonding. The study of methanol showed the existence of ring and chain formations in the liquid phase and the dominating structures are formed of 6 and 8 molecules. Upon mixing of the two liquids, a segregation at the molecular level was found and the formation of new structures, which could explain the unexpected low increase of the entropy.</p>

This thesis addresses the electronic structure of vanadium and copper oxides using soft X-ray absorption (SXA) spectroscopy and resonant inelastic X-ray scattering (RIXS) at high brightness synchrotron radiation sources. In RIXS incident photons, tuned to the energy of specific absorption resonances, are inelastically scattered leaving behind a low energy valence excitation in the system studied. Effects of electron localization are reflected by the occurrence of low-energy excitations in form of dd- and charge-transfer excitations that are modelled by cluster calculations. Band-like states are dominating when the intermediate core excited state is delocalized. RIXS at V 2p and O 1s resonances has been used to study the electronic structure of the monovalent vanadium oxides VO2 and V2O3, and of the mixed valence compounds, NaV2O5 and V6O13. For NaV2O5 and V6O13 significant contributions from localized low-energy excitations reflect the partly localized character of their valence band electronic structure, whereas VO2 and V2O3 appear mostly as band-like. Effects of carrier doping are addressed for the case of Mo doping into VO2 and reveal a quasi-rigid band behavior. In the cases of VO2 and V6O13 the temperature dependent metal-insulator transition could be monitored by following the spectral evolution of bands originating from V 3d and V 3d - O2p hybridized states. For Na2V3O7 nanotubes it was possible to selectively probe states from the apical and the basal oxygen sites of VO5 pyramids that constitute these nanotubes. Furthermore, the RIXS technique has been demonstrated to be highly valuable in characterizing the charge transfer processes that accompany lithium insertion into vanadium oxide battery cathodes. Finally, for insulating cuprates RIXS at O 1s, Cu 3p and Cu 3s resonances has been recorded at high-resolution for the detailed investigation of crystal field excitations.

Lithium ion insertion into electrode materials is commonly used in rechargeable battery technology. The insertion implies changes in both the crystal structure and the electronic structure of the electrode material. Side-reactions may occur on the surface of the electrode, which is exposed to the electrolyte and form a solid electrolyte interface (SEI). The understanding of these processes is of great importance for improving battery performance. The chemical and physical properties of water and alcohols are complicated by the presence of strong hydrogen bonding. Various experimental techniques have been used to study geometrical structures and different models have been proposed to view the details of how these liquids are geometrically organized by hydrogen bonding. However, very little is known about the electronic structure of these liquids, mainly due to the lack of suitable experimental tools. This thesis addresses the electronic structure of liquids and lithium battery materials using resonant inelastic X-ray scattering (RIXS) at high brightness synchrotron radiation sources. The electronic structure of battery electrodes has been probed, before and after lithiation, studying the doping of electrons into the host material. The chemical composition of the SEI on cycled graphite electrodes was determined. The local electronic structure of water, methanol and mixtures of the two have been examined using a special liquid cell. Results from the study of liquid water showed a strong influence on the 3a1 molecular orbital and orbital mixing between molecules upon hydrogen bonding. The study of methanol showed the existence of ring and chain formations in the liquid phase and the dominating structures are formed of 6 and 8 molecules. Upon mixing of the two liquids, a segregation at the molecular level was found and the formation of new structures, which could explain the unexpected low increase of the entropy.

L’étoile Wolf-Rayet WR 46 est connue pour sa variabilité complexe sur des échelles de temps relativement courtes de quelques heures et sur des échelles de temps plus longues de plusieurs mois. Des décalages périodiques mais intermittents en vitesse radiale ont déjà été observés dans ses raies d’émission optiques. Plusieurs périodes photométriques ont aussi été mesurées dans le passé. Des pulsations non-radiales, une modulation liée à la rotation rapide, ou encore la présence d’un compagnon de faible masse dont la présence reste à confirmer ont été proposées pour expliquer le comportement de l’étoile sur des échelles de temps de quelques heures. Dans un effort pour dévoiler sa vraie nature, nous avons observé WR 46 avec le satellite FUSE sur plusieurs cycles de variabilité à court terme. Nous avons trouvé des variations sur une échelle de temps d’environ 7,5 heures dans le continu ultraviolet lointain, dans l’aile bleue de la composante d’absorption du profil P Cygni du doublet de O vi 1032, 1038, ainsi que dans la composante d’absorption du profil P Cygni de S vi 933, 944. Nous avons également récupéré des données archivées de cette étoile obtenues avec le satellite XMM-Newton. La courbe de lumière en rayons X montre des variations sur une échelle de temps similaire aux courbes de lumière du continu ultraviolet et ultraviolet lointain, et le spectre rayons X de WR 46 est très mou avec un pic d’émission à des énergies plus faibles que 1 keV. Nous discutons des différentes contraintes sur la nature de la variabilité de cette étoile que ces nouvelles observations aident à poser. Parmi les scénarios suggérés, nous concluons que celui des pulsations non-radiales est le plus probable, bien que nous soyons encore loin d’une compréhension détaillée de WR 46. / The Wolf-Rayet star WR 46 is known to exhibit a very complex variability pattern on relatively short timescales of a few hours and also on longer timescales of months. Periodic but intermittent radial velocity shifts of optical lines as well as multiple photometric periods have been found in the past. Nonradial pulsations, rapid rotational modulation or the presence of a yet-to-be-confirmed low-mass companion have been proposed to explain the short-term behaviour. In an effort to unveil its true nature, we observed WR 46 with FUSE over several short-term variability cycles. We found significant variations on a timescale of about 7.5 hours in the FUV continuum, in the blue edge of the absorption trough of the O vi 1032, 1038 doublet P Cygni profile, and in the S vi 933, 944 P Cygni absorption profile. We also retrieved archival XMM-Newton data of this star. We found the X-ray light-curve to show variations on a timescale similar to the UV and FUV continuum light-curves, and the X-ray spectrum of WR 46 to be very soft with a peak below 1 keV. We discuss the different constraints on the nature of the variability that these new observations help to establish. Among the suggested scenarios, we conclude that non-radial pulsations is the most likely, although we are far from a complete picture.

Ce rapport de thèse présente une étude de la dynamique transitoire de molécules de taille réduite en solution induite par photoexcitation. Celle-ci est réalisée au travers d'une expérience de mesure de diffusion de rayons X aux grands angles (TR-WAXS). La partie principale de ce rapport s'articule autour de la dertermination des structures transitoires avec l'utilisation de plusieurs schémas structurelles d'optimisation. Certains résultats obtenus par TR-WAXS sont complétés avec ceux obtenus par spectroscopie optique résolue dans le temps (TOAS) ainsi que par spectroscopie d'émission de rayons X de ces molécules (TR-XES) permettant une plus complète description de ces systèmes.Ce travail est composé de 4 differents projets lesquelles peuvent être regroupé en 2 groupes selon le type de réaction declenchées par photoexcitation: dissociation et transfert d'électron. Le premier groupe comprends la molécule triatomique de mercure, halogénure métallique et le triiodide où nous étudions la dynamique de recombinaison des photofragments libres. Cette partie démontre la possibilité de développer de nouvelles connaissances concernant la dynamique de ces modèles, comme par exemple, la découverte de la recombinaison par canaux ou bien par l'apparition de réactions intermédiaires en moins de 100 ps, correspondant à la longueur de l'impulsion de rayons X générée par le synchrotron, mise en évidence en utilisant la technique de découpage temporelle. Le deuxième groupe de systèmes est composé de complexes de métaux de transition, très pertinents pour les applications liées à la récolte de lumière, [Fe(NHC)2]2+ et Ru=Co, où le spin et les structures dynamiques sont étudiées. Ces projets prolongent de précedents travaux à une famille de systèmes plus complexes avec un numéro atomique bas (première colonne de transition metallique) et fait la lumière sur de nouveaux composés en photochimie. / This thesis investigates photoinduced transient dynamics of small molecules in solution with the use of time-resolved wide angle x-ray scattering (TR-WAXS). The core of the thesis is the precise determination of transient structures with the use of various structural optimization schemes. Some of the TR-WAXS results are supplemented with transient absorption optical spectroscopy (TOAS) and time-resolved x-ray emission spectroscopy (TR-XES) measurements allowing for a more complete description of the systems.par The work includes four different projects which can be grouped into two classes according to the type of reaction appearing upon photoexcitation: dissociation and electron transfer. The first class includes the simple triatomic molecules mercury halides and triiodide where we study the recombination dynamics of the free photofragments. This part of the thesis demonstrates the possibility to gain new knowledge about the dynamics of these model systems such as new recombination channels and reaction intermediates appearing in less than 100 ps, the xray pulse length from the synchrotron, by the use of time-slicing technique. The second class of systems includes transition metal complexes that are highly relevant for light harvesting applications, [Fe(NHC)2]2+ and Ru=Co, where the spin and structural dynamics are investigated. These projects extend previous work to a family of more complex systems constituted of relatively low-Z atoms (first row transition metals) and bring new insights into the photochemistry of the compounds.

Made available in DSpace on 2014-06-11T19:24:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-03-24Bitstream added on 2014-06-13T18:51:41Z : No. of bitstreams: 1 lima_jpm_me_arafo.pdf: 3908479 bytes, checksum: 1c7f63e885d8dafaeb577071612f7aa7 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Atualmente, vários novos materiais estéticos são lançados no mercado odontológico destinados especificamente à confecção de restaurações diretas. Embora tais compósitos apresentem bons resultados clínicos, o que garantem ser indicados nas regiões anterior e posterior, ha a necessidade de comprovações adicionais para que se possam ser utilizados com segurança. As informações disponíveis de cada material recém introduzido ainda trazem duvidas sobre sua real composição e sobre suas propriedades físicas e mecânicas, gerando confusão para o clinico, que pode estar ciente ou não de qual resina melhor atende as necessidades de cada paciente. O conhecimento dimensional do conteúdo inorgânico dos sistemas de resinas compostas ainda e o responsável pela classificação dos mesmos e parecem estimar sobre suas propriedades mecânicas. Assim, nos propusemos a (1) estudar através de ampla e profunda revisão sistemática da literatura, a influencia das partículas inorgânicas nas propriedades físicas, químicas e mecânicas de resinas compostas e; (2) descrever a morfologia e a composição química das partículas inorgânica das resinas compostas atuais, como forma de dotar o clinico de um parâmetro de comparação entre os materiais restauradores resinosos, e de auxiliá-lo na indicação deste material mediante situação clínica. Na primeira etapa de nosso estudo, foram determinados os critérios de inclusão e exclusão, e estabelecida a estratégia de busca – palavras-chave e limites de assuntos, em varias combinações – dos estudos laboratoriais nas principais bases de dados eletrônicas (ISI – Web of Science, Medline, Biblioteca Cochrane, SciELo, Lilacs e Biblioteca Digital de Teses – Portal Capes), e outras fontes de informação. / Currently, dozens of new aesthetic materials are launched on the dentistry market designed specifically to the confection of direct restorations. Although such composite show good clinical results, which guarantees be given in anterior and posterior regions, there is a need for additional evidence so that it can be used safely. The information available of each newly introduced material also brings questions about their real composition and on its physical and mechanical properties, creating confusion for the clinician, which may be or not aware of resin which best meets the necessities of each patient. The dimensional knowledge of the inorganic content of the composed resin systems also is responsible for the classification of the same ones and seems estimate on its mechanical properties. Thus, we proposed (1) to study through extensive and meticulous systematic review of literature, the influence of inorganic particles in the physical, chemical and mechanical properties of composite resins and; (2) to describe the morphology and chemical composition of the inorganic particles of current composite resins, as a way of giving the clinician with a parameter of comparison among the resinous restorative materials, and of assisting it in the indication of this material through of clinical situation. In the first stage of our study, the criteria of inclusion and exclusion had been determined, and established the strategy of search – keywords and limits of subjects, in some combinations – of the laboratory studies in the main electronic databases ((ISI – Web of Science, Medline, Biblioteca Cochrane, SciELo, Lilacs and Digital Library of Theses – Portal Capes), and others sources of information. Of the 138 abstracts located, only 59 were selected (most located on Pubmed) being in accordance with the pre-established criteria.

In this work silver atoms were deposited by ion sputtering on the surface of two types of diglycidyl ether of bisphenol A (DGEBA) epoxy resin. The films of DGEBA and its precursors were characterized by Raman and infrared spectroscopy to identify the main functional groups and their relationship with the deposited silver atoms. Thermogravimetric (TG) and differential themogravimetric (DTG) analysis, and Raman spectroscopy was performed to study the thermal effects in the resin. Silver thin films of 5, 10, 15 and 20 nm were deposited on the epoxy resin at room temperature. Both the initial film of DGEBA and the subsequent silver thin film were analyzed by Atomic Force Microscopy (AFM) in non-contact mode. Silver thin films were also analyzed by x-ray diffraction (XRD) at room temperature. The AFM results showed the formation of silver crystallites on the surface of DGEBA at very low coverage whereas XRD indicated that most of them had their main axis aligned to the normal of the surface. Increase in the coverage led to an increase in the grain size as indicated by AFM. XRD results however indicated that the crystallite size remained almost constant while the appearance of peaks corresponding to other crystalline orientati ons suggests the coalescence of the original crystallites and an increase in size of the more dense planes, namely [111]. / Neste trabalho átomos de prata foram depositados por ion sputtering na superfície de dois tipos de resina epóxi diglicidil éter de bisfenol A (DGEBA). Os filmes de DGEBA e seus precursores foram caracterizados por espectroscopia Raman e infravermelha para identificas os principais grupos funcionais e suas relações com os átomos de prata depositados. Análises termogravimétrica (TG), termogravimétrica diferencial (DTG), e espectroscopia Raman foram realizadas para estudar os efeitos térmicos na resina. Filmes finos de prata de 5, 10, 15 e 20 nm foram depositados na resina epóxi a temperatura ambiente. Ambos filmes iniciais de DGEBA e o subsequente filme fino de prata foram analisados por Microscopia de Força Atômica (AFM) no modo de não contato. Os filmes finos de prata também foram analisados por difratometria de raios X (DRX) a temperatura ambiente. Os resultados de AFM mostram a formação de cristalitos de prata sobre a superfície da DGEBA para pequenas espessuras de recobrimento, enquanto DRX indica que a maioria dos cristalitos tem seu eixo principal alinhado normal à superfície. Um aumento na espessura de recobrimento leva a um aumento no tamanho do grão como indicado por AFM. Resultados de DRX porém, mostram que o tamanho de cristalito permaneceu quase constante, enquanto o aparecimento de picos correspondentes a outras orientações cristalinas sugere a coalescência dos cristalitos originais e um aumento no tamanho dos planos mais densos, principalmente [111].

O presente estudo foi desenvolvido para caracterizar a área de influência dos corredores de tráfego, através do monitoramento da concentração de elementos-traço em cascas de árvores. Amostras (n = 98) de cascas de árvores de diversas espécies foram coletadas em cinco parques urbanos da cidade de São Paulo. Para controle, foram coletadas cascas de árvores numa zona rural de Embu-Guaçu, longe de tráfego ou de indústrias. As concentrações de Ba, Co, Cr, Cu, Fe, Ca, Pb, S e Zn foram determinadas nas amostras de cascas de árvores por espectrometria de fluorescência de raios-X. Amostras coletadas nos parques urbanos apresentaram níveis mais elevados de elementos-traço em comparação com as da região controle. Elementos relacionados a atividades antropogênicas exibiram maiores concentrações nas amostras coletads na periferia dos parques, diminuindo gradativamente para os seus centros. Áreas próximas a grandes avenidas ou próximas a semáforos e cruzamentos apresentaram maiores concentrações de elementos nas cascas. Em conclusão, o estudo mostrou que medidas de acúmulo de elementos traço em cascas de árvore, associadas a métodos geoestatísticos, podem auxiliar a determinação das zonas de maior influência da poluição veicular no cenário urbano / The present study was designed to characterize the area of influence of high traffic corridors by monitoring trace element concentrations on tree barks. Samples (n=98) of tree barks were collected from several tree species in five urban parks of the city of São Paulo. For controlling purposes, we collected tree barks in a rural area of Embu-Guaçu which is far from traffic or industries. Concentrations of Ba, Co, Cr, Cu, Fe, Ca, Pb, S and Zn were determined in these barks by X-ray fluorescence spectrometry. Samples from urban parks exhibited higher levels of trace elements in comparison with those from control region. Elements related to anthropogenic activities exhibited higher concentrations in tree barks at the periphery of the parks, decreasing when moving towards their centers. Areas facing the busy streets or those close to traffic lights or traffic junctions presented higher concentrations of elements in barks. In conclusion, the present study showed that measures of trace elements accumulation in tree barks within geostatistical methods can indicate areas of strong influence of vehicular pollution in the urban scene

Orientador: Roger William Fernandes Moreira / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-24T03:19:50Z (GMT). No. of bitstreams: 1 Mendes_MarceloBrenoMeneses_D.pdf: 3820602 bytes, checksum: 7c13797c10676481e3ebfd0492c570a9 (MD5) Previous issue date: 2014 / Resumo: O objetivo deste estudo foi avaliar, através da análise de rugosidade superficial, microscopia eletrônica de varredura (MEV), análise de composição através de espectroscopia de raios-X e análise de resistência mecânica, dois diferentes sistemas de fixação interna usados em fixação de osteotomia sagital do ramo mandibular. Foram selecionadas cinco placas retas do sistema 2,0 mm com quatro furos e 20 parafusos de 6 mm de comprimento de dois sistemas de fixação interna, grupo I: Tóride (Tóride Indústria e Comércio Ltda. -Mogi Mirim, São Paulo -Brasil) e grupo II: Medartis (Medartis AG -Basel, Suíça). Para os testes mecânicos, foram selecionadas dez hemimandíbulas de poliuretano, dividindo-as igualmente entre os grupos I e II. Inicialmente, foi realizada análise de rugosidade superficial em todas as placas dos dois sistemas, e os dados foram submetidos à análise de variância e teste de Tukey (p>0,05) para a comparação entre as médias. Em seguida, as mesmas placas foram avaliadas no espectrômetro por meio de difração de raios-X e logo após foram analisadas no MEV. Por último, foi realizado o teste mecânico, no qual as hemimandíbulas de poliuretano foram fixadas e submetidas ao teste de carregamento (1mm/min). Os dados foram analisados quanto à carga de pico (em Newtons) e o deslocamento de pico (em mm) para todos os grupos estudados, e posteriormente submetidos ao teste t. Os grupos testados apresentaram vestígios superficiais dos processos de usinagem, principalmente nas margens dos elos. O grupo II apresentou revestimento com uma camada de nitreto de titânio. A análise da rugosidade revelou diferença entre as regiões de centro e margem da placa para o grupo I; diferente do grupo II, o qual apresentou valor de rugosidade menor e mais uniforme. O teste mecânico revelou que o grupo II apresentou maior carga de pico. Os dados demonstraram que há diferença microestrutural e mecânica entre os grupos testados. / Abstract: The aim of this study was to evaluate, through surface roughness analysis, scanning electron microscopy (SEM), composition analysis by X-ray spectroscopy and analysis of mechanical strength, two different systems used in internal fixation of mandibular sagittal split osteotomy fixation. Five straight 2.0 mm system plates with four holes and 20 screws 6 mm length of two internal fixation systems were selected, group I: Toride (Toride Indústria e Comércio Ltda -Mogi Mirim, São Paulo -Brazil.) and group II: Medartis (Medartis AG -Basel, Switzerland). For mechanical testing, ten polyurethane hemimandibles were used, distributing them equally into groups I and II. Initially, surface roughness analysis was performed on all plates of the two systems, and the data were subjected to analysis of variance and Tukey's test (p> 0.05) for comparison between means. Then, the same plates were evaluated in the spectrometer by means of X-ray diffraction and after this evaluation, they were subjected to SEM. Finally, mechanical testing was performed, in which the polyurethane mandibles were fixed and subjected to the load (1mm/min) test on an Instron testing machine, Model 4411 (Instron Corp., Norwood, MA). Data were analyzed for peak load (in Newtons) and peak displacement (in mm) for all groups, and then subjected to t test. The groups tested showed superficial traces of machining processes, especially on links periphery. Group II had coated with a layer of titanium nitride. The roughness analysis revealed differences among the regions of the center and edge of the plate for group I; group II showed roughness value smaller and more uniform, than group I.The mechanical test showed that group II had higher peak load. The data demonstrated that there are microstructural and mechanical differences between the tested groups. / Doutorado / Cirurgia e Traumatologia Buco-Maxilo-Faciais / Doutor em Clínica Odontológica

Transition-metal oxides (TMOs) display numerous fascinating and complex properties, such as mixed-valency, low dimensionality, lattice distortion, and phase transition, etc. These properties arise from the partially filled d- or f-electron shells of TM cations and are often accompanied by the intriguing interplay between degrees of freedom. To understand the complexity of d-electron TMOs, this thesis is primarily focused on studying their underlying electronic structure using X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES), X-ray photoemission spectroscopy (XPS), and resonant inelastic X-ray scattering (RIXS). The measurements at the O K- and TM L-edges are achieved by taking advantage of high-flux and high-resolution synchrotron radiation light with tunable monochromatic photon energy. Four electronically and structurally distinctive oxides are selected as representative TMOs for investigation in this thesis. To begin with, through a comparative study of WO3 and Na0.67WO3 crystals, the narrowing of the conduction band is observed with Na doping and the core-hole energy shift in the O K-edge XAS process is experimentally determined. Indirect and direct band gaps of photoanode WO3 are measured from the resonant XES with polarization-dependent experimental geometry. The other sodium bronze studied is quasi-one-dimensional β-Na0.33V2O5 polycrystalline film. The film stoichiometry, preferential orientation, and orbital anisotropy are well characterized by a variety of photon and electron techniques and compared to density-functional theory (DFT) calculation. The V 3d orbital splitting of β-Na0.33V2O5 is surveyed by the V L-edge RIXS and compared with isoelectronic β-Sr0.17V2O5 regarding distortions to VO6 octahedra. Furthermore, the complex electronic structure of Mott insulators La1-xLuxVO3 is investigated to understand their spin-orbital phase diagram. The effects of rare-earth size on the O 2p hybridization states and the local crystal field of VO6 octahedron are found to agree with the prediction of DFT calculation and the evolution of crystal structure. The changes of experimental spectra with temperature are associated with Jahn-Teller distortion and orbital ordering due to structural phase transition. Lastly, the band structure and low-energy excitations of spinel MnV2O4 are explored using soft x-ray spectroscopies and theoretical calculations. The presence of Hubbard bands and the mixing between V and Mn 3d states are suggested both experimentally and theoretically.