Orientador: Heloise de Oliveira Pastore / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-21T15:14:46Z (GMT). No. of bitstreams: 1 Ramos_FranciscaSolaneadeOliveira_M.pdf: 5550553 bytes, checksum: c97e45758df14cd712ea691a6174a574 (MD5) Previous issue date: 2012 / Resumo: A aplicação dos silicatos lamelares como catalisadores apresenta como limitações as baixas área superficial e acidez, porém, esses sólidos têm como principais propriedades a reatividade dos grupos Si-OH e Si-ONa da superfície de suas lamelas e sua capacidade de troca iônica. Em função disso, esses sólidos podem sofrer uma variedade de modificações em sua superfície e em seu espaço lamelar e até passar de uma estrutura 2D para uma estrutura 3D. As lamelas do silicato lamelar Na-RUB-18, além de serem recobertas por Si-OH e Si-O, são constituídas de cavidades de quatro anéis de cinco membros [5], presentes tanto no RUB-24 quanto na MOR, assim como em outros zeólitos, indicando que tal lamelar seja potencial precursor de estruturas zeolíticas. Por tais motivos, o presente trabalho teve como objetivo estudar e descrever como o Na-RUB-18 se transforma nas estruturas zeolíticas MOR e RUB-24, por processos hidrotérmico e topotático, respectivamente, e como essas estruturas 2D e 3D se relacionam. A gradual aproximação das lamelas do Na-RUB-18 e conseqüente condensação dos grupos Si-OH, ou seja, unidades Q ([O4Si]3Si-OH), ocasiona a formação de ligações Si-O-Si, unidades Q ([O4Si]4-Si), gerando a estrutura 3D. No caso do zeólito MOR, esse processo é induzido pela adição de uma fonte de alumínio, Al[OCH(CH3)2]3 ou Na2Al2O4. O presente trabalho também investiga a etapa de aproximação das lamelas do Na-RUB-18, ocasionando na sua condensação em RUB-24. A condensação das lamelas do precursor lamelar no RUB-24 via processo topotático é conduzida por um agente direcionador de estrutura, o íon trietilenotetramônio, comprovando que tal processo, como a transformação hidrotérmica, não acontece aleatoriamente / Abstract: The application of the layered silicates in heterogeneous catalysis has limitations such as low surface area and acidity. However, these solids also have ion exchange capacity and their surfaces can be covalently modified with silylation reagents. As a result, they can undergo a variety of surface changes yielding modifications in interlayer space and in the structure lamellar that may even cause collapse of a 2D structure to a 3D. The framework of layered silicate Na-RUB-18 is composed of four five-membered rings, [5] and its surface made of Si-OH and Si-ONa. The [5] cage is a building unit also found in zeolitic structures, as RUB-24 and MOR, indicating that the structure of Na-RUB-18 contains important elements of microporous materials structures and should be regarded as a potential precursor structure to the three-dimensional four-connected microporous framework silicates. This work aimed of studying and describing the transformations of the Na-RUB-18 into MOR and RUB-24 by hydrothermal and topotactic process, respectively. The gradual reduction of interlayer distance of the Na-RUB-18 led to the condensation of the Si-OH groups, Q units ([O4Si]3Si-OH), forming Si-O-Si bonds, Q units ([O4Si]4-Si), i.e., a 3D structure. In the preparation of MOR zeolite by hydrothermal transformation, the process is conducted through addition of a aluminum source, Al[OCH(CH3)2]3 or Na2Al2O4. This work also investigated the formation of RUB-24 through Na-RUB-18 collapsing. The topotactic reaction between Si-OH groups of the lamellar precursor was conducted by a structure-directing agent, triethylenetetrammonium ion, proving that this process, as the hydrothermal transformation, does not occur randomly / Mestrado / Quimica Inorganica / Mestra em Química

Les microbialites sont des roches organo-sédimentaires dont les processus de formation restent mal compris. L'objectif central de cette thèse est de mieux comprendre les conditions environnementales permettant le développement de microbialites actuels provenant de 10 lacs volcaniques mexicains. Une grande diversité de compositions minéralogiques des microbialites a été observée, comprenant divers carbonates et la quasi omniprésence de silicates de magnésium authigènes. A partir de cette étude nous proposons une valeur minimale d'alcalinité permettant le développement des microbialites. De plus, une corrélation positive entre l'alcalinité et la teneur en sodium des lacs est apparue. Cette corrélation pourrait s'expliquer par des niveaux différents d'évaporation des lacs et/ou des degrés différents d'altération des silicates alentours. L'étude plus particulière des silicates de magnésium a révélé que ces phases sont faiblement cristallisées, semblables à la kérolite et ont un fort potentiel de fossilisation des microorganismes et de la matière organique. Ces silicates de magnésium sont parfois associés à du fer dont l'origine pose question dans ces environnements alcalins et oxygénés. Nous avons mis en évidence la présence de différents types de phases porteuses du fer : des hydroxydes doubles lamellaires (hydrotalcites), des oxy(hydroxy)des, des silicates de magnésium et des sulfures. Nous proposons plus spécifiquement que l'hydrotalcite pourrait être issue de l'altération des basaltes par la circulation de fluides souterrains et plus généralement que cette phase pourrait être un précurseur des silicates de magnésium abondamment observés dans les microbialites actuels. / The processes leading to the formation of microbialites, which are organo-sedimentary rocks, are not well understood. The main goal of this thesis is to better understand the environmental conditions allowing the development of modern microbialites. Here we performed geochemical analyses of water solutions and mineralogical analyses of microbialites in 10 Mexican volcanic lakes. We found a large diversity of microbialites in terms of mineralogical composition, with occurrence of diverse carbonate phases as well as the frequent presence of authigenic magnesium silicate phases. From this study, we infer a minimum alkalinity value for the formation of lacustrine microbialites. Moreover, we observe a positive correlation between the alkalinity and the sodium content of the lakes. This may relate to variations in evaporation intensity and/or various degrees of weathering of the surrounding silicates. The study of Mg-silicates revealed that this phase is similar to kerolite, a poorly crystalline hydrated talc phase, and has a strong potential for the fossilization of microorganisms and organic matter. These silicates are sometimes associated with iron, the origin of which remains uncertain in these alkaline and oxidized environments. By the mineralogical study of several microbialites, we found several phases bearing iron: layered double hydroxides (hydrotalcites), Mg-silicates, oxy(hydroxi)des and sulfides. We propose more specifically that hydrotalcite could be the by-product of basalts weathering by groundwater. We propose more generally that hydrotalcite could be a precursor phase of Mg-silicates abundantly observed in modern microbialites.

Ces travaux traitent de phénomènes diffusifs pouvant se dérouler à la surface de verres fonctionnalisés avec des couches minces de silicates lors de traitements thermiques. La gamme de température considérée s’étend de 550°C à 1050°C. Les échanges diffusifs entre le verre et l’empilement de couches minces conduisent souvent à une diminution des propriétés des couches actives. Les échanges entre un verre plat silico-sodocalcique et des couches minces de silice (pouvant être dopées alumine) se déroulent avec deux cinétiques distinctes. Une diffusion rapide des alcalins du verre vers la silice est observée dans un premier temps, conduisant ensuite à une homogénéisation plus lente entre le substrat et la couche, déclenchée par la diminution de la viscosité de la silice. Le paramètre clé contrôlant ces deux étapes est la quantité d’alumine présente dans la silice. En effet, la couche incorpore des alcalins sous forme de compensateur de charge et modificateur de réseau en quantités proportionnelles à la teneur en alumine. Plutôt que de les limiter, ces phénomènes diffusifs peuvent également être contrôlés pour obtenir par exemple de la séparation de phases dans ces géométries « couche mince ». Dans les couches de compositions SiO2-BaO-B2O3 étudiées, la morphologie après démixtion et la croissance des domaines sont pilotées d’une part par des paramètres similaires à ceux dans les verres massifs (température, composition, durée recuit, …) mais également par des énergies de surface qui deviennent non négligeables. La nucléation des phases dans ces systèmes confinés se fait alors préférentiellement en surface et l’épaisseur des couches à un impact direct sur la taille des domaines. / This work studies diffusive phenomena on glass surface functionalized with silicate thin films during thermal treatments. The temperature range extends from 550°C to 1050°C. In most cases diffusive phenomena between glass substrate and thin films stack can lead to a decrease of the properties of the active layers. Diffusive exchanges between a soda-lime flat glass and silica thin films (which can be doped with alumina), take place with two distinct kinetics. A fast migration of alkali ions from glass to silica is first observed, followed by a slow homogenization at the interface between the silica layer and the glass substrate due to the silica viscosity decrease. The key parameter which controls these two steps is the amount of aluminum in the silica layer. Indeed, the layer incorporates alkali ions in the form of charge compensator and network modifier in quantities depending linearly to the alumina content. Rather than limiting them systematically, these diffusive phenomena can also be controlled in order to obtain for example phase separation in these “thin film” geometries. For the silicate layers with SiO2-BaO-B2O3 compositions studied in this work, the morphology after phase separation and the kinetics of domains growth are influenced by similar parameters than in bulk glasses (such as temperature, composition, annealing duration, …) but also by surface energies which become non-negligible. In these confined systems, nucleation of phase separated domains occurs then preferentially at the interface with air and the thin film thickness influences directly the domains size.

Kyoto University (京都大学) / 0048 / 新制・論文博士 / 博士(工学) / 乙第12335号 / 論工博第4013号 / 新制||工||1466(附属図書館) / 27190 / UT51-2009-D550 / (主査)教授 森山 裕丈, 教授 伊藤 秋男, 教授 高木 郁二 / 学位規則第4条第2項該当

L'interprétation des expériences de relaxométrie RMN nécessite une modélisation précise des interactions entre le noyau étudié et son environnement. Pour un noyau quadrupolaire, l'interaction entre le gradient du champ électrique (EFG) émis par l'environnement avec le quadruple électrostatique du noyau est prépondérante. Notre travail a porté sur le développement du calcul des temps de relaxation RMN pour ces noyaux par simulation moléculaire. Nous nous sommes intéressés à la relaxation d'ions mono-atomiques en phase condensée à travers deux systèmes simples et réalistes : des solutions aqueuses d'électrolytes et des verres de silicate de sodium. L'EFG dé aux électrons de l'ion est obtenu en calculant la réponse du nuage électronique grâce à des calculs quantiques combinés à une récente méthode pour reconstruire la contribution des électrons de cœur. L'EFG dû à l'environnement est obtenu à partir d'une simulation moléculaire où les interactions sont décrites par un champ de force polarisable nouvellement développé. Les temps de relaxation obtenus en combinant ces deux contributions reproduisent correctement les résultats expérimentaux. Les simulations moléculaires nous permettent aussi d'extraire les mécanismes microscopiques. Pour les ions dans l'eau à dilution infinie, nous avons étudié les propriétés statistiques et dynamiques des fluctuations de l'EFG. Nous avons montré en particulier le rôle fondamental des fluctuations de densité de l'eau dans la première sphère de solvatation de l'ion. Cette thèse ouvre la voie à une meilleur compréhension des processus de relaxation RMN des ions mono-atomiques quadrupolaires dans des systèmes simples ou complexes. / Interpreting NMR relaxometry experiments requires an accurate modeling of interactions between the nucleus under study and its environment. For a quadrupolar nucleus, the interaction between the electric field gradient (EFG) arising from the environment and the electrostatic quadrupole of the nucleus is preponderant. The present work deals with a new method to compute NMR relaxation times for such nuclei with molecular simulations. We consider the relaxation of monoatomic ions in condensed matter through two simple and realistic systems: aqueous electrolytes and sodosilicate glasses. The EFG due to electrons around the ion is obtained by computing the electronic response with quantum calculation combined with a new method to obtain the contribution of core electrons. The EFG due to the environment is obtained from a molecular simulation where interactions are described using a recently developed polarisable force field. NMR relaxation times obtained by combining both these contributions compare well with experimental data. Molecular simulations allow us to highlight the microscopic mechanisms. For ions in water at infinite dilution, we studied the statistical and dynamical properties of EFG fluctuations. We notably demonstrated the primary role of water density fluctuations in the first solvation shell around the ion. This thesis opens the way for a better understanding of the mechanism behind the NMR relaxation of monoatomic and quadrupolar ions in simple and complex systems.

La théorie de la rigidité permet de prédire les comportements de nombreuses propriétés de verres, que ce soit avec la composition, la température ou la pression, tout en réduisant la structure de ceux-ci à un simple critère mécanique : flexible, isostatique ou rigide sur-contraint. Des travaux récents ont mis en évidence l'utilité d'une telle analyse, tant de manière expérimentale que théorique. Dans cette thèse, nous appliquons une méthode d'établissement de contraintes à partir de simulations par dynamique moléculaire, afin d'explorer la rigidité dans différentes conditions de température, pression ou composition pour des verres ayant des potentiels d'application. Cet algorithme de dénombrement de contraintes, radiales ou angulaires, nous a permis de définir des zones de compositions particulières dans les verres d'oxydes, avec une compréhension différente de la structure et des contraintes entourant les ions dans la silice. Par la suite, nous avons aussi pu montrer des effets topologiques faibles des gaz nobles dans la silice, et relier les anomalies dynamiques observées dans la silice sous pression à des conditions de rigidité du réseau. / Rigidity theory allows to predict the behavior of many properties of glasses with respect to composition, while considering the underlying network as simple mechanical trusses that can be flexible, isostatic or stressed-rigid. Some recent works showed how useful such an analysis can be, either theoretically or experimentally. In the thesis we will use a method to analyse topological constraints from molecular dynamics simulations in order to establish the rigidity of silica systems of interest under various conditions of composition, pressure and temperature. Applying this constraints counting algorithm to radial and angular constraints in soda-lime systems allowed us to establish composition intervals of isostatic properties while giving a novel comprehension of the constraints and the structure surrounding the ions. We later highlight the faint influence of noble gases atoms upon silica when melted in the bulk. That study also allowed us to link dynamical anomalies of silica under pressure to rigidity changes of the network.

No description available.

Refractory mastics are used for making compact brickworks or for sealing up the joints. This thesis deals with lenghthening of best before date of Regnaterm mastic, modification of recipe and suggestion of suitable method for evaluating reologic characteristics.

PhDENV (Geology) / Department of Mining and Environmental Geology / The Cretaceous period marked the breaking up of Gondwana, giving rise to the separation of the African and South American continents with the subsequent emergence of the South Atlantic Ocean. Most correlation studies between the two continents with respect to paleoenvironmental conditions and tectonic settings during the Cretaceous- Tertiary periods have been concentrated more on the use of flora and fauna as indicators with less application of kaolinite as paleoenviromental proxies, hence, this study. The research involved the evaluation of paleoenvironmental conditions and tectonic settings of four (4) selected Cretaceous-Tertiary kaolin deposits with two (2) each from the Eastern Dahomey (Eruku and Lakiri) and Niger Delta (Awo-Omama and Ubulu-Uku) Basins in Nigeria. Representative kaolin samples collected from the selected deposits were analysed for physico-chemical, mineralogical, geochemical, isotopic, and geochronological data. The geochemical data obtained by x-ray fluorescence (XRF) spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LAICPMS) were used in unraveling the provenance and tectonic settings of the kaolins. The kaolinite stable isotopic data for oxygen and hydrogen determined using a Finnigan Delta XP Mass Spectrometer were used to assess the paleoenvironmental and paleoclimatic conditions under which the kaolins were formed. The detrital zircon geochronological data acquired by laser ablation – single collector – magnetic sectorfield – inductively coupled plasma – mass spectrometry (LA-SFICP-MS) as well as kaolinite stable isotopic data were employed in constraining the probable timing of kaolinisation. The industrial applications of the kaolins were assessed based on the physico-chemical (Colour, particle size distribution (PSD), pH, electrical conductivity, and Atterberg limits), mineralogical, and geochemical data. The mineralogical data were obtained through x-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, Thermogravimetric analysis and differential scanning calorimetry, and scanning electron microscopy (SEM). Correlative studies between selected Cretaceous African and South American kaolins were conducted. The results showed that the dominant colour in the studied kaolins was pale red (39 %) followed by pinkish and light grey (35 %) as well as reddish yellow, light pink, light brown, vii reddish brown, and pinkish white. The pH and EC values generally ranged from 4.27 to 5.29 and 0.2 to 13.1 μS/cm, respectively. The kaolins predominantly have clay to sandy clay textures with plasticity indices between 10 and 22 wt %. Bulk mineralogical quantitative results indicated that the Cretaceous kaolins have kaolinite, quartz, and muscovite present in that decreasing order with anatase, goethite, and hematite in traces whereas Tertiary kaolins have kaolinite and quartz present in that decreasing order with anatase and goethite in traces. In the silt fractions, kaolinite and quartz were the dominant mineral constituents, whereas in the clay fractions, the dominant clay mineral was kaolinite accounting for 69 to 99 wt % with the non-clay minerals like quartz, anatase, hematite and goethite accounting for percentages between 1 to 28 wt % in the Cretaceous – Tertiary kaolins. Morphologically, the studied kaolins were characterised by pseudohexagonal stacks to books and thin platy kaolinite particles with moderate structural order. The chemical compositions of the Cretaceous-Tertiary kaolin deposits were identical to hydrated alumino-silicates based on the dominance of SiO2, Al2O3 and LOI. The chemical index of alteration (CIA) and chemical index of weathering (CIW) values varied between 96.98 to 99.39 % and 98.95 to 99.89 %, respectively. The clay fractions were enriched in Cr, Nb, Sc, Th, U, V, Zr, and LREE and depleted in Ba, Co, Rb, Sr, and HREE, respectively, relative to the average Upper Continental Crust (UCC). The Th/Sc, La/Sc, Th/Cr, and Eu/Eu* ratios were within the range of sediments derived from felsic rocks. The TiO2 versus Al2O3 and La-Th-Sc plots indicated source rocks with granitic – granodioritic - gabbroic compositions. Geochemical discrimination plots showed that the Cretaceous and Tertiary kaolins were deposited in passive margin tectonic settings. The stable isotopic results indicated that the values of the Cretaceous kaolins ranged from – 47 to – 57 ‰ and 19.1 to 19.8 ‰, respectively, with paleotemperatures between 29.0 and 32.2 ˚C, whereas the δD and δ18O corresponding values for the Tertiary kaolins ranged from – 54 to – 66 ‰ and 20 to 21.5 ‰, respectively, with paleotemperatures between 17.0 and 23.9 ˚C. viii The U-Pb dating of the detrital zircons showed that the Cretaceous - Tertiary kaolins have inputs from rocks of Eburnean (2500 – 2000 Ma) and Pan African (750 – 450 Ma) ages. The age of maximum deposition determined from the least to statistically robust approach corresponds to the Ediacaran Period (645 – 541 Ma) of the Neoproterozoic Era (1000 – 541 Ma). The Cretaceous – Tertiary kaolins were formed under intense anoxic chemical paleoweathering conditions of predominantly felsic rocks in addition to contributions from intermediate and mafic rocks in passive margin tectonic settings. The Cretaceous kaolins were formed under warmer conditions relative to the Tertiary kaolins. The West African Massif rocks were the main sediment sources for the Cretaceous kaolins, whereas both the West African and Northern Nigerian Massif rocks were the major sediment sources for the Tertiary kaolins. The most probable timing of kaolinisation for the Cretaceous – Tertiary kaolins occurred between the Ediacaran (645 – 541 Ma) and Early Cretaceous Periods for the Cretaceous kaolins and between the Ediacaran Period (645 – 541 Ma) and Oligo – Miocene age for the Tertiary kaolins. The Nigerian and Brazilian Cretaceous kaolins formed under similar warm tropical paleoclimate. The study corroborated the occurrence of the Eburnean (Transamazonian) and Pan African (Brasiliano) orogenic events across the African and South American continents. Beneficiation of the Cretaceous – Tertiary kaolins will allow large scale industrial applications in paper coating, ceramics, pharmaceutical, and cosmetics industries. The major contributions from this study have been: the better understanding of the past environmental conditions and tectonic settings, the dating of the possible timing of kaolinisation, and improvement on the potential industrial applications of the Cretaceous – Tertiary kaolins. / NRF

No description available.