Argilominerais são componentes abundantes nas frações < 2 &mu;m solos, com grande papel no controle de processos geoquímicos e de formação de solos. Nos manguezais brasileiros, apesar das caracterizações gerais já realizadas, há ausência de estudos cristaloquímicos detalhados que possam evidenciar mecanismos de formação/transformação envolvendo essas fases. Este trabalho se propõe, através de dois estudos comparativos, aprofundar a caracterização cristaloqímica das frações 2-0,2 &mu;m e < 0,2 &mu;m, sugerir processos de transformação envolvendo os argilominerais dos manguezais e entender quais atributos ambientais estão associados a essas transformações. Esta caracterização se baseia nas técnicas de modelagem de DRX, decomposição de picos 060 de padrões não-orientados de DRX, FTIR, espectroscopia Mössbauer, análises térmicas, análise química da água intersticial e modelagem geoquímica dos componentes químicos em solução. Os resultados, que serão detalhados nos capítulos 2 e 3, sugerem uma série de transformações minerais, via fases interestratificadas, que devem ter importantes implicações para a compreensão dos processos pedogenéticos envolvendo argilominerais, do seu papel no ciclo biogeoquímico dos elementos associados à sua gênese e relação indireta ou direta com componentes bióticos do ecossistema, que podem influenciar nas transformações que envolvem os minerais. / Clay minerals are ubiquitous components in < 2 &mu;m size fraction of soils, having an important role in the control of geochemical processes and soil genesis. Despite of the general characterizations performed in Brazilian mangroves soils there is a lack of a detailed crystal chemical study able to evidence mechanisms of formation/transformation of such minerals. This study aims (by two different comparative works) to enhance the crystal chemical characterization of mineral phases in the 2-0,2 &mu;m and < 0,2 &mu;m size fractions of mangrove soils, suggesting the existence of mineral transformation involving clay phases and comprehending what environmental settings are related to these transformations. This characterization is based on XRD modelling of oriented patterns, peak fitting of 060 peaks in randomly XRD patterns, Mössbauer spectroscopy, thermal analysis, chemical analysis of soil pore water and geochemical modelling of inorganic soluble compounds. The results, which are described in chapters 2 and 3 indicate a sequence of mineral transformations, via mixed-layered clays, which may have important consequences for the comprehension of soil genesis processes involving clay minerals, their role in the biogeochemical cycles of structural elements of clays and a straight relationship with biotic components of mangrove ecosystem.

O presente trabalho tem por objetivo investigar e propor uma metodologia rápida e eficaz de avaliação da reatividade do cimento Portland frente ao ataque por sulfatos. O método consiste na utilização de amostras de pasta de cimento hidratada em pó, colocadas em contato direto com soluções concentradas de Na2SO4 e MgSO4, em temperatura elevada (65ºC), para acelerar o ataque. Apesar dos cimentos estudados possuírem composição química parecida, os resultados de SO3 combinado mostraram que o cimento Classe G foi pouco menos suscetível ao ataque por sulfatos em função do maior teor de Fe2O3 presente. Da TG e DRX observou-se a formação de etringita no ataque por ambos os sais de sulfato; e formação de gipsita no ataque por MgSO4. Enquanto havia disponibilidade de portlandita na pasta hidratada, o cimento com adição mineral incorporada apresentou mesma taxa de ataque que os demais (sem adição), entretanto a partir do momento que toda a portlandita foi consumida, iniciou-se um processo de descalcificação do C-S-H, observado pela DRX. / The main point of this research is to propose a fast and effective method of evaluation of the cement reactivity to sulfate attack. Resistance to sulfate attack was measured by determining the combined sulfate in cement paste samples with exposure to Na2SO4 and MgSO4 solution, at high temperature (65°C). The samples of cement paste was triturated (powdered) in the proposed method. The results of combined SO3 showed that the Class G cement was little less susceptible to the sulfate attack because it has larger amount of Fe2O3. The ettringite formation was observed in the attack for both sulfate salts; and gypsum formation in the attack for MgSO4 (results of TG and XRD). The blended cement presented same results that the others, however when the Ca(OH)2 was totally consumed, it observed the decalcification of the C-S-H, by XRD.

La2Mo2O9, premier composé de la famille LAMOX, est intéressant pour des applications comme électrolyte dans des piles à combustible car il présente une conductivité ionique élevée. Il a été découvert durant l'investigation du diagramme de phases de La2O3 -MoO3. Cela montre bien le rôle important de l'étude de diagrammes de phase dans la découverte de nouveaux matériaux qui est devenue un objectif majeur de nombreux chimistes du solide. Selon ce concept, les deux diagrammes de phases ternaires La2O3-Nb2O5-WO3 et La2O3-Nb2O5-MoO3 ont été explorés et analysés pour la première fois en utilisant la synthèse par voie solide. Les structures des échantillons obtenus ont été caractérisées par diffraction des rayons X et des neutrons sur poudre et par microscopie électronique en transmission tandis que leurs propriétés électriques ont été testées par spectroscopie d'impédance complexe sur des pastilles frittées.La majorité des zones mono-, bi- et tri-phasées de ces deux diagrammes ont été définies. Plus particulièrement, les structures de deux nouvelles phases La3NbWO10 et La5NbMo2O16 ont été résolues ab-initio. La connaissance des structures des 2 nouveaux composés a permis une meilleure approche du diagramme de phase ternaire. D'une part, la mailleLa3NbWO10 est une sur structure de la maille fluorine(2aF*2aF*2aF) avec un axe c allongé. En considérant la formulation La18Nb6W62O604 (Z = 6), on constate aisément que la structure présente 2 types de défauts:des lacunes anioniques et cationiques sur les sites des atomes d'oxygène et de lanthane. D'autre part, la phaseLa5NbMo2O16 est un isotype du composé Pr5Mo3O16. Sa maille correspond aussi à une surstructure fluorine. Elle cristallise dans un système cubique (a = 11.22 Å) avec le groupe d'espace rare Pn n. Ce composé est prometteur puisqu'il présente une conductivité par les ions oxyde proche de celle de La2Mo2O9 à basse température. / La2Mo2O9, the first compound in the LAMOX family, is interesting for its applications as electrolytes in fuel cells because it presents a high ionic conductivity. It was discovered during the investigation of La2O3 - MoO3phase diagram. That shows the important role of phase diagram study in the discovery of new materials which has become a major objective of many solid chemists.In this concept, two ternary phase diagrams of La2O3-Nb2O5-WO3 and La2O3-Nb2O5-MoO3 were explored and analyzed for the first time using the solid-state synthesis. The structures of the obtained samples were characterized by the powder X-ray and neutron diffraction and by the transmission electronic microscopy. Besides, their electric properties were tested by the complex impedance spectroscopy onsintered pellets.As results, most of the mono-, bi-, tri-phase zones in the title phase diagrams have been defined. Particularly, during the phase-diagram investigation, the structures of two new phases La3NbWO10 and La5NbMo2O16 were ab-initio resolved. Firstly, the La3NbWO10 cell is asuperstructure of a fluorine (2aF*2aF*2aF) with the lengthened c axis. Considering the La18Nb6W62O604(Z = 6) formulation, we can easily note that the structure presents 2 types of defaults: cationic and anionic vacancies. Secondly, the La5NbMo2O16 phase is isotype of Pr5Mo3O16 compound. Its cell is also a fluorine superstruture. It crystallized in a cubic system (a = 11.22Å) with the space group Pn n. The compound is promising because it presents an oxygen conductivity comparable to that of La2Mo2O9 at low temperature.

Dyes for inkjet printing are typically of the chromonic type. Chromonic mesophases have gained considerable attention as a well-defined group of lyotropic mesogens with different properties from conventional amphiphiles. While extensive research has been dedicated to the field of surfactant liquid crystals, structural and aggregation studies of chromonics have only emerged as a topic of interest within the last few years. The liquid crystalline structures in aqueous solutions of commercial Cu - phthalocyanine and black dyes have been examined using a combination of optical microscopy, UV-vis spectroscopy, nuclear magnetic resonance, wide- and small-angle X-ray diffraction and electronic paramagnetic resonance with a view to examining the phase behaviour of the chromonic mesophases formed over a broad range of concentrations and temperatures. These studies were performed in order to resolve outstanding problems concerning structural properties of these systems. Optical microscopy allowed us to identify the liquid crystalline phases and to construct the phase diagram. The observations show that both of these dyes form nematic mesophase above 15% wt / wt% dye. The small-angle diffraction data confirmed that the nematic phase for the black dye is maintained throughout the 16-25% composition range. A further increase in concentration leads to the formation of the hexagonal phase. The Cu – phthalocyanine dye also formed a nematic phase at low concentrations, with the aggregates undergoing a phase transition to an orientationally ordered chromonic liquid crystal phase at high dye concentration. These studies showed that this ordered phase possessed hexagonal symmetry. The wide-angle X-ray results demonstrated that aggregation involved π-π stacking of the molecules into columns. An additional reflection at ca. 6.8Å was observed for the black dye, which is believed to arise from “head – to – tail” packing of the molecules within the aggregates (a similar phenomenon observed in other azo dyes, e.g. Edicol Sunset Yellow).The densities of both dyes were measured over the studied range of concentrations. This enabled us to calculate the parameters of the aggregates within the hexagonal mesophase. A comparison between the area of the molecule and the cross-section of the aggregates showed that the aggregates of both dyes were the unimolecular stacks.

Les composés de la famille LAMOX, dérivés de La2Mo2O9, présentent une conductivité ionique élevée mais peuvent être conducteurs mixtes s'ils sont réduits sous atmosphère pauvre en oxygène. Dans ce travail, de nouvelles méthodes de synthèse de La2Mo2O9 par chimie douce (la voie sol gel et le procédé polyol) sont optimisées pour faciliter la mise en forme selon l’application souhaitée.Concernant les synthèses réalisées par voie sol gel, le composé La2Mo2O9 pur a été obtenu à partir de l’acétate de lanthane et du molybdate d’ammonium ou du chlorure de molybdène. L’influence de plusieurs paramètres de synthèse a été déterminée. L’ajout de deux tensioactifs a été testé : le bromure de diméthyldioctadécyl-ammonium (DDAB) et le F127. Les poudres finales sont quasi-pures après un traitement thermique à 950°C pendant 2 heures, ce qui ne permet pas d’avoir des surfaces spécifiques élevées.Dans le cas du procédé polyol, nous avons obtenu La2Mo2O9 pur sous forme de roses des sables par agglomération de plaquettes polycrystallines très fines constituées de cristallites de quelques dizaines de nanomètres, après un traitement thermique à plus basse température de l’ordre de 550°C. L’effet de plusieurs paramètres sur la morphologie et la pureté des poudres a été testé. En particulier, des particules sphériques agglomérées ont été obtenues en utilisant l’éthylèneglycol comme solvant en présence d’urée. L’ajout du tensioactif bromure de diméthyl-dioctadécyl-ammonium (DDAB) permet de doubler la surface spécifique par rapport aux échantillons sans tensioactif, celle ci passant de 16 à 30 m2.g-1. Finalement, de tous premiers essais ont été réalisés pour tenter d’obtenir des films minces par centrifugation.Les mesures de conductivité ont été enregistrées sur des pastilles à porosité fermée (densité relative supérieure à 92%) sans avoir recours à une étape de broyage. Les mesures de conductivité montrent que, selon les paramètres de synthèse, la conductivité de grain peut être légèrement accrue.L’étude de la réductibilité, sous H2 dilué, des poudres issues de la synthèse par voie polyol, montre que les pertes en oxygène sont plus rapides et plus importantes que pour des poudres synthétisées par voie solide. La ré-oxydation des poudres amorphes est également plus rapide et se produit à bien plus basse température dans le cas des poudres obtenues par la voie polyol. / La2Mo2O9 based oxides (LAMOX) exhibit high ionic conductivity but can be mixed conductors if they are reduced under low-oxygen atmosphere. In this work, new synthesis methods of La2Mo2O9 by soft chemistry (sol gel route and polyol process) are optimized to facilitate the sample shaping depending on the desired application.Concerning the sol gel syntheses, pure La2Mo2O9 compound was obtained from lanthanum acetate and ammonium molybdate or molybdenum chloride. The influence of several synthesis parameters was determined. The addition of two surfactants was tested: dimethyl dioctadecyl ammonium bromide (DDAB) and F127. The final powders are almost pure after heat treatment at 950 °C for 2 hours, which prevents from high specific surface areas.In the case of the polyol process, pure La2Mo2O9 was obtained as desert roses by agglomeration of very fine polycrystalline platelets built from crystallites of a few tens of nanometers size, after a heat treatment at a lower temperature of about 550°C. The effect of various parameters on the morphology and purity of the powder was tested. In particular, agglomerated spherical particles have been obtained using ethylene glycol as solvent in the presence of urea. The addition of DDAB surfactant enables a doubling the specific surface area comparatively to samples without surfactant, from 16 to 30 m2.g-1. Finally, first tests were carried out as attempts to obtain thin films by centrifugation.Conductivity measurements were recorded on pellets presenting closed porosity (relative density greater than 92%), obtained without the help of a milling step. Conductivity measurements showed that, depending on the synthesis parameters, the grain conductivity can be slightly increased.The study of the reducibility, under diluted H2, of powders resulting from the synthesis by the polyol process, shows that the oxygen losses are faster and larger than with powders synthesized by solid state reaction. Reoxidation of amorphous powders is also faster and occurs at much lower temperature in the case of powders obtained by the polyol pathway.

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.

Summary Serpentinites from the northern Vermont were examined for the distribution and abundance of As. XRD and electron microprobe showed the samples are composed of antigorite, chromite, magnetite, and carbonate minerals (magnesite, dolomite, calcite). The concentration in As when the samples were dissolved in H3PO4 was 10% of the concentration in As when the samples were dissolved in concentrated HF/HNO3, suggesting that As is mainly incorporated in the structure of antigorite. X-ray absorption near-edge structure spectra showed that the As is As(III) in the samples. Extended X-ray absorption fine structure spectra suggested that the As has a tetrahedral coordination and is located in the Si-site in serpentine.

L’objet de cette thèse consiste en des développements de méthodes en spectroscopie et imagerie Raman. Après une revue des outils statistiques permettant de traiter de gros volumes de données (analyse multivariée, classification), l’étude est appliquée à deux familles de matériaux déjà bien connus, utilisés comme modèles pour tester les limites des développements mis en oeuvre. La première famille est une série de matériaux carbonés, traités à différentes températures, avec des inhomogénéités à l’échelle du nm, dont la taille est déduite d’une approche conjointe Raman-diffraction des rayons X. Un autre résultat concerne l’effet du polissage, qui induit des artefacts Raman conduisant à surestimer le désordre structural local, et une méthode basée sur la largeur de la bande G est proposée. L’autre classe de matériaux présente cette fois des inhomogénéités à des échelles supérieures au micromètre, il s’agit de céramiques d’oxyde d’uranium appauvri. L’imagerie Raman, particulièrement bien adaptée en termes d’échelle spatiale, est utilisée pour sonder les surfaces obtenues, Le traitement des données est effectué par un approche mêlant analyse multivariée (analyse en composantes principales), et ajustement classique par Lorentziennes. L’interprétation des données obtenues est soutenue par une analyse par electron backscattering diffraction (EBSD), permettant de séparer l’effet d’orientation des grains de céramiques, d’autres effets sous-jacents. Ceux-ci, principalement localisés aux joints de grains, avec l’existence d’un mode Raman caractéristique, paraissent liés à des variations de stoechiométrie en oxygène ou d’impuretés, ou à des inhomogénéités de contrainte. Les perspectives de ce travail portent notamment sur la mise en oeuvre d’autres méthodes mathématiques, et pour l’aspect matériaux, sur l’analyse fine d’endommagements par irradiation des UO2, (effets d’anisotropie, rôle des joints de grains. / This thesis is aimed at developing methodologies in Raman spectroscopy and imaging. After reviewing the statistical instruments which allow treating giant amount of data (multivariate analysis and classification), the study is applied to two families of well-known materials which are used as models for testing the limits of the implemented developments. The first family is a series of carbon materials pyrolyzed at various temperatures and exhibiting inhomogeneities at a nm scale which is suitable for Raman--X-ray diffraction combination. Another results concern the polishing effect on carbon structure. Since it is found to induce Raman artifacts leading to the overestimation of the local structural disorder, a method based on the use of the G band width is therefore proposed in order to evaluate the crystallite size in both unpolished and polished nanographites. The second class of materials presents inhomogeneities at higher (micrometric) scales by the example of uranium dioxide ceramics. Being well adapted in terms of spatial scale, Raman imaging is thus used for probing their surfaces. Data processing is implemented via an approach combining the multivariate (principal component) analysis and the classical fitting procedure with Lorentzian profiles. The interpretation of results is supported via electron backscattering diffraction (EBSD) analysis which enables us to distinguish the orientation effects of ceramic grains from other underlying contributions. The last ones are mainly localized at the grain boundaries, that is testified by the appearance of a specific Raman mode. Their origin seems to be caused by stoichiometric oxygen variations or impurities, as well as strain inhomogeneities. The perspectives of this work include both the implementation of other mathematical methods and in-depth analysis of UO2 structure damaged by irradiation (anisotropic effects, role of grain boundaries).

Uma série de amostras do sistema catalítico V2O5/TiO2 foi preparada pelo método sol-gel com diferentes teores da fase ativa (de 0 a 9% em massa de V2O5) e calcinada em diferentes temperaturas (de 250 a 6000C). Sistema similar foi obtido pelo método de impregnação para a comparação. Os catalisadores foram caracterizados quanto suas propriedades texturais e estruturais pelas técnicas de Adsorção de N2 a 77K, Difratometria de Raios-X (DRX), Espectroscopia Raman, Ressonância Paramagnética Eletrônica (EPR), Espectroscopia de Fotoelétrons Excitados por Raios-X (XPS) e Espectroscopia de Absorção de Raios-X (XAS). Testes catalíticos para a verificação da atividade e seletividade foram realizados frente à reação de conversão do metanol. O sistema obtido pelo método sol-gel apresentou elevada área superficial e porosidade, as quais foram ampliadas com o aumento do teor de vanádio e reduzidos com o aumento da temperatura de calcinação. O sistema preparado por impregnação apresentou as mesmas propriedades texturais do suporte comercial. A análise de DRX identificou a existência de TiO2 nas formas cristalográficas anatásio e rutilo, não foi identificada a presença de V2O5 na forma cristalina. No sistema preparado por impregnação a estrutura cristalográfica do suporte se mantém, independente do teor de vanádio, porém a partir de 6% de V2O5 foi identificado à presença de V2O5 cristalino. Os espectros de Raman mostraram a presença de dois grupos superficiais de vanádio, os vanadilos monoméricos e os vanadatos poliméricos mesmo em elevados teores de vanádio, nos sistemas preparados pelo processo sol-gel. Nos catalisadores obtidos por impregnação foram identificados modos vibracionais referentes ao V2O5 cristalino.Os resultados obtidos por XAS confirmaram os obtidos por DRX e indicaram a presença de vanádio V4+ e V5+, porém com simetria diferente da forma cristalina V2O5. A determinação da razão entre os átomos V/Ti superficiais feita por XPS mostrou ser crescente com o aumento do teor de vanádio. Os espectros de EPR indicaram a presença de pelo menos três famílias de íons V4+ em diferentes simetrias, duas delas inseridas na matriz da titânia na fase rutilo e a outra dispersa na superfície. O sistema obtido por impregnação apresentou poucos íons V4+. Os testes catalíticos revelaram que a atividade e seletividade catalítica foram praticamente as mesmas para os sistemas preparados pelos dois métodos. Entretanto, a estabilidade catalítica do sistema obtido via sol-gel foi superior ao sistema preparado por impregnação. / A series of samples of the catalytic system V2O5/TiO2 was prepared by the sol-gel method with different proportions of the active phase (from 0 to 9% in mass of V2O5) and calcined in different temperatures (from 250 to 6000C). A similar system was obtained by the impregnation method for comparison. The catalyst were characterized by their textural and structural properties by Adsorption of N2 at 77K, X-Ray Diffraction (XRD), Raman Spectroscopy, Electronic Paramagnetic Resonance (EPR), X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Absorption Spectroscopy (XAS). Catalytic tests for the verification of the activity and selectivity were performed by the conversion reaction of the methanol. The system obtained by the sol-gel method presented a high superficial area and porosity, which were enlarged by the increase of vanadium proportion and reduced with increase of the calcinations temperature. The system prepared by impregnation presented the same textural proprieties of the commercial support. XRD analysis identified the existence of TiO2 in two crystallographic forms, anatase and rutile. It was not identified the presence of V2O5 in the crystalline form. In the system prepared by impregnation the crystallographic structure of the support keeps, independent of the vanadium content, however starting from 6% of the vanadia was identified crystalline V2O5. Raman spectra showed the presence of two superficial groups of vanadium, the monomeric vanadyls and the polymeric vanadates even for elevated contents of vanadium, in the system prepared by the impregnation method vibrational modes were identified referring to V2O5 crystalline. The results obtained by XAS confirmed the obtained by XRD and indicated the presence of V4+ and V5+, however with different symmetry from the V2O5 in a crystalline form. The determination of the proportion between the surface V/Ti atoms determined by XPS showed to be increased with the increase of the vanadium content. EPR spectra indicated the presence of at least three V4+ion families in different symmetries; two of them inserted in the matrix of titania in the rutile phase and to other dispersed on the surface. The system obtained by impregnation presented few V4+ ions. The catalytic tests reveled that the catalytic activity and selectivity were practically the same for the systems prepared by both methods. However, the catalytic stability of the system obtained via sol-gel was superior to the system prepared by impregnation.

The diploma thesis deals with surface integrity evaluation for different types of steels after case hardening and machining. This thesis compares Barkhausen noise analyses with residual stress depth profile set by X-Ray diffraction method with consideration of different penetration depth of both method. General purpouse of this thesis is verify the concept of the Sum Of Effective Residual Stresses as the index of part quality evaluation during manufacturing process.