Nous avons développé une méthode pour analyse isotopique de Yb et Er, deux terres rares aux propriétés chimiques identiques et aux températures de condensation différentes, avec comme objectifs (1) de déterminer la variabilité isotopique de ces éléments dans les processus pétrologiques terrestres, et (2) de comparer leurs compositions isotopiques dans les chondrites, la Terre et la Lune afin de déterminer le rôle potentiel de la condensation à haute température à partir de vapeurs qui a suivi l’impact géant à l’origine de la formation de la Lune. Les résultats obtenus montrent une plus grande variabilité des fractionnements isotopiques de Yb par rapport à ceux d’Er. Deux effets contribuent à cette différence : un effet oxydo-réducteur et un effet de température. La corrélation positive obtenue entre la composition isotopique en Yb, et le rapport La/Yb dans les échantillons terrestres, peut être interprétée par la présence d’une faible fraction d’ Yb(2+), Yb étant majoritairement présent sous la forme Yb(3+). La kimberlite (liquide magmatique formé par un faible taux de fusion partielle) est enrichie en isotopes lourds et les grenats, résidus de fusion partielle, sont isotopiquement légers, tandis que les basaltes de ride ou d’îles ont des compositions isotopiques intermédiaires.La composition isotopique en Yb de la Lune est enrichie en isotopes légers par rapport à celle de la Terre et des chondrites. Dans le disque proto-lunaire, les frictions entre les phases fondues et gazeuses favorisent la migration des premiers condensats très réfractaires et enrichis en isotopes lourds vers la Terre, et celle de la vapeur enrichie en isotopes légers, vers l’extérieur, au-delà de la limite de Roche à partir de laquelle la Lune s’accrète. Ceci est un nouvel argument en faveur de la condensation de la Lune à partir de vapeur générée par un impact géant. La mesure de la composition isotopique d’Er dans les échantillons lunaires reflète pour la première fois la capture par 167Er des neutrons produits par interaction du rayonnement cosmique galactique avec la surface lunaire. L’apport de Er aux systèmes communément utilisés pour déterminer le spectre d’énergie des neutrons d’un matériau peut permettre de couvrir une gamme énergétique plus large et de disposer ainsi d’un proxy plus complet pour l’étude des histoires des irradiations des matériaux planétaires. / Er and Yb are two refractory rare-earth elements that have overall similar crystallochemical properties but differ in their temperatures of condensation from the nebular gas. We developed an analytical protocol for the measurement of Er and Yb isotope compositions 1) to establish their isotopic variability in terrestrial magmatic processes 2) to compare their isotopic composition in chondrites, Earth and Moon in order to study fractionation during the high temperature condensation of vapor formed by the giant impact that generated the Moon. The range of mass-dependent isotope fractionation obtained is larger for Yb than Er isotopes. Two effects contribute to the difference between Er and Yb : a redox effect and a temperature effect.First, for terrestrial rocks, the presence of a small fraction of Yb(2+) together with the most common Yb(3+) is inferred from the positive corre- lation between δYb and the La/Yb ratio. Yb(3+) fractionates favorably into tighter bonds and, at the same time, is much more compatible than Yb(2+). Small-degree melts (kimberlite) tend to be enriched in the heavy Yb isotopes, whereas the opposite is true for residual garnets. Second, the stronger volatility of Yb with respect to Er is demonstrated by the apparent deficit of heavy Yb isotopes in the Moon with respect to the Earth, chondrites, and eucrites. Separation of vapor from melt and of heavy from light isotopes is first expected during the adiabatic expansion of the initial vapor plume. Subsequently, friction between melt and gas tends to further enrich the Moon feeding zone in silicate vapor to compensate the inward migration of melt out of the pre-lunar disk. The lighter isotope composition of Yb in lunar samples provides new evidence that the Moon formed by condensation of silicate vapor in the aftermath of the giant lunar impact.Erbium isotope ratios in lunar samples reflect for the first time the capture by 167Er of secondary neutrons produced by interactions of galactic cosmic rays with the lunar surface. The cross section of 167Er for neutron capture being particularly strong and its first resonance standing out at energies poorly covered by other nuclides, 167Er anomalies may help refine the knowledge of the neutron energy spectrum on the Moon and other planetary bodies.

Desde a descoberta das ligas amorfas em 1960, os motivos pelos quais algumas ligas podem ser facilmente amorfizadas enquanto outras não podem, não é claramente conhecido, assim não há teoria universal para predizer a habilidade de formação vítrea em sistemas metálicos. No presente trabalho, um critério de seleção foi aplicado ao sistema Ni-Nb-Zr com o objetivo de predizer as melhores estequiometrias com as mais altas tendências de formação vítrea. As habilidades de formação vítrea das ligas foram avaliadas pelo parâmetro térmico γm e os resultados mostraram uma pobre correlação com as predições. Este critério preditivo correlaciona as taxas de resfriamento para a formação vítrea com a instabilidade topológica de estruturas cristalinas, as diferenças médias de função trabalho e densidade eletrônica entre os elementos constituintes da liga. O parâmetro térmico depende de temperaturas características de transformações de fases que podem ser facilmente determinadas a partir de curvas de calorimetria exploratória diferencial dos vidros metálicos. As hipóteses iniciais para explicar a pobre correlação entre os resultados e as predições foram atribuídas às influências de fatores não considerados nos cálculos como os compostos intermetálicos desconhecidos e contaminação por oxigênio. Assim, algumas ligas solidificadas rapidamente foram investigadas com mais rigor com o objetivo de entender a formação das fases cristalinas que competem contra a formação vítrea. As fases cristalinas foram caracterizadas e comparadas com estruturas cristalinas encontradas na literatura como também alguns diagramas de fases. Os diagramas de fases foram utilizados como guias para o melhor entendimento do comportamento de cristalização. Em adição, o critério de seleção também foi utilizado para predizer o melhoramento da tendência de formação vítrea de uma liga do sistema Ni-Nb-Zr com pequenas adições dos elementos terras-raras Y ou Er. É bem conhecido que uma pequena adição de um elemento terra-rara apropriado pode aumentar significativamente a habilidade de formação vítrea de algumas ligas. As tendências de formação vítrea da liga base e das ligas dopadas com terras-raras também foram avaliadas pelo parâmetro térmico &#947m e os resultados concordaram muito bem com a tendência predita pelo cálculo. As amostras amorfas volumosas foram produzidas por injeção em molde de cobre. A natureza amorfa foi analisada por difração de raios-X e calorimetria exploratória diferencial. As fases cristalinas foram analisadas por microscopia eletrônica de transmissão, microscopia eletrônica de varredura, espectroscopia de raios-X por dispersão em energia e difração de raios-X. A contaminação por oxigênio foi quantificada pelo método de fusão em gás inerte. / Since the discovering of amorphous alloys in 1960, the actual causes of why some alloys can be easily formed into glasses while others cannot, are not clearly known, thus there is no universal theory to predict the glass forming ability in metallic systems. In the present work, a selection criterion was applied in the Ni-Nb-Zr system in order to predict the best stoichiometries with high glass forming ability. The actual glass forming ability of alloys were evaluated by the thermal parameter γm and the results have shown a poor correlation with the predictions. This criterion correlates critical cooling rate for glass formation with topological instability of stable crystalline structures; average work function difference and average electron density difference among the constituent elements of the alloy. The thermal parameter depends on the characteristic temperatures of phase transformations which can be easily measured from differential scanning calorimetry curves of metallic glasses. The initial hypotheses to explain the poor correlation between the experimental results and the predictions concerned with the influence of factors not considered in the calculation, such as unknown intermetallic compounds and oxygen contamination. Thus some rapidly quenched alloys were investigated with more accuracy in order to understand the formation of crystalline phases which compete against the glass formation. We characterized the crystalline phases and compared them to crystalline structures found in literature as well as some phase diagrams. The phase diagrams were used as guides in order to understand the crystallization behavior. In addition, the selection criterion also was used to predict the glass forming ability improvement of a Ni-Nb-Zr alloy with minor additions of rare-earth elements Y or Er. It is well known that the minor amount addition of proper rare-earth elements can greatly enhance the glass forming ability of some glass-forming alloys. The actual glass forming ability of the base alloy and rare-earth doped alloys also were evaluated by the thermal parameter &#947m and the results agree very well with the tendency predicted by the calculation. Bulk amorphous specimens were produced by injection casting. The amorphous nature was analyzed by X-ray diffraction and differential scanning calorimetry. The crystalline phases were analyzed by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and x-ray diffraction. Oxygen contamination was quantified by the inert gas fusion method.

Submitted by Rosimeri Vergara (rosimerivergara@unipampa.edu.br) on 2018-12-11T20:02:55Z No. of bitstreams: 1 Giovani Nunes Parisi 2018 Dissertação.pdf: 4002594 bytes, checksum: 976b398edffec278577b6c3d951dfc9c (MD5) / Approved for entry into archive by Dayse Pestana (dayse.pestana@unipampa.edu.br) on 2018-12-12T12:09:44Z (GMT) No. of bitstreams: 1 Giovani Nunes Parisi 2018 Dissertação.pdf: 4002594 bytes, checksum: 976b398edffec278577b6c3d951dfc9c (MD5) / Made available in DSpace on 2018-12-12T12:09:45Z (GMT). No. of bitstreams: 1 Giovani Nunes Parisi 2018 Dissertação.pdf: 4002594 bytes, checksum: 976b398edffec278577b6c3d951dfc9c (MD5) Previous issue date: 2018 / A presente dissertação apresenta resultados petrográficos e litoquímicos de mármores calcíticos e dolomíticos coletados em quatro áreas distintas do Bloco São Gabriel, que seguem: (i) área Batovi, (ii) Área Palma; (iii) Área Passo Feio; e (iv) Área Porongos. O conjunto de mármores que afloram nessas áreas compõe um grupo mineralogicamente homogêneo. O carbonato predomina largamente sobre os outros minerais na composição modal destas rochas. Entretanto em algumas áreas, onde há minerais magnesianos como a serpentina e o talco, pode haver uma tendência a dolomitização. Após a análise e tabulação de dados das amostras de mármores calcíticos e dolomíticos, ficou estabelecido um critério prospectivo para os mármores do Bloco São Gabriel, onde foi possível separar duas populações de mármores. A primeira composta pelas áreas (i) Batovi e (ii) Palma com mármores de composição predominante Calcítica e uma segunda população de mármores predominantemente Dolomíticos, composta pelas áreas (iii) Passo Feio e (iv) Porongos. Já o estudo geoquímico, através dos Elementos Terras Raras na sequência Metassedimentar de origem carbonática, constatou que amostras apresentaram anomalias negativas de Cério e positiva de Eu. No que se refere à anomalia negativa de Ce, que ocorre devido à baixa concentração de Elementos Terras Raras da água do mar. Esta anomalia de Ce é em consequência do Ce+4e o Ce+3, terem um grande campo de estabilidade Eh-Ph. A anomalia negativa de Ce em rochas sedimentares, particularmente em rochas carbonáticas, tem sido utilizada comumente como um argumento de origem marinha, enquanto a sua inexistência é atribuída à influência de águas continentais, particularmente para rochas carbonáticas. Quanto à anomalia positiva de Eu nos sedimentos marinhos ou na água do mar, esta tem sido atribuída a um fluxo hidrotermal. / The present dissertation presents petrographic and litoquímicos results of calcitic and dolomitic marbles collected in four distinct areas of the São Gabriel Block, which follow: (i) Batovi area, (ii) Palma Area; (iii) Passo Feio Area; and (iv) Porongos Area. The set of marbles that appear in these areas make up a mineralogically homogeneous group. The carbonate predominates largely of the modal composition of these rocks. However in some areas where there are magnesian minerals such as serpentine and talc, there may be a tendency to dolomite. After analyzing and tabulating data of the samples of calcitic and dolomitic marbles, a prospective criterion was established for the marbles of the São Gabriel Block, where it was possible to separate two populations of marbles. The first one consists of the areas (i) Batovi and (ii) Palma with marbles of predominantly Calcitic composition and a second population of predominantly dolomite marbles, composed of (iii) Feio and (iv) Porongos areas. On the other hand, the geochemical study, through the Rare Earth Elements in the Metassedimentary sequence of carbonate origin, found that samples presented negative anomalies of Cerium and positive of Eu. Regarding the negative anomaly of Ce, this occurs due to the low concentration of Rare Earth Elements of sea water. This Ce anomaly is a consequence of Ce + 4e and Ce + 3, having a large Eh-Ph stability field. The negative anomaly of Ce in sedimentary rocks, particularly in carbonate rocks, has been commonly used as an argument of marine origin, while its absence is attributed to the influence of continental waters, particularly for carbonate rocks. As for the positive anomaly of Eu in marine sediments and in sea water, this has been attributed to a hydrothermal flow.

Desde a descoberta das ligas amorfas em 1960, os motivos pelos quais algumas ligas podem ser facilmente amorfizadas enquanto outras não podem, não é claramente conhecido, assim não há teoria universal para predizer a habilidade de formação vítrea em sistemas metálicos. No presente trabalho, um critério de seleção foi aplicado ao sistema Ni-Nb-Zr com o objetivo de predizer as melhores estequiometrias com as mais altas tendências de formação vítrea. As habilidades de formação vítrea das ligas foram avaliadas pelo parâmetro térmico γm e os resultados mostraram uma pobre correlação com as predições. Este critério preditivo correlaciona as taxas de resfriamento para a formação vítrea com a instabilidade topológica de estruturas cristalinas, as diferenças médias de função trabalho e densidade eletrônica entre os elementos constituintes da liga. O parâmetro térmico depende de temperaturas características de transformações de fases que podem ser facilmente determinadas a partir de curvas de calorimetria exploratória diferencial dos vidros metálicos. As hipóteses iniciais para explicar a pobre correlação entre os resultados e as predições foram atribuídas às influências de fatores não considerados nos cálculos como os compostos intermetálicos desconhecidos e contaminação por oxigênio. Assim, algumas ligas solidificadas rapidamente foram investigadas com mais rigor com o objetivo de entender a formação das fases cristalinas que competem contra a formação vítrea. As fases cristalinas foram caracterizadas e comparadas com estruturas cristalinas encontradas na literatura como também alguns diagramas de fases. Os diagramas de fases foram utilizados como guias para o melhor entendimento do comportamento de cristalização. Em adição, o critério de seleção também foi utilizado para predizer o melhoramento da tendência de formação vítrea de uma liga do sistema Ni-Nb-Zr com pequenas adições dos elementos terras-raras Y ou Er. É bem conhecido que uma pequena adição de um elemento terra-rara apropriado pode aumentar significativamente a habilidade de formação vítrea de algumas ligas. As tendências de formação vítrea da liga base e das ligas dopadas com terras-raras também foram avaliadas pelo parâmetro térmico &#947m e os resultados concordaram muito bem com a tendência predita pelo cálculo. As amostras amorfas volumosas foram produzidas por injeção em molde de cobre. A natureza amorfa foi analisada por difração de raios-X e calorimetria exploratória diferencial. As fases cristalinas foram analisadas por microscopia eletrônica de transmissão, microscopia eletrônica de varredura, espectroscopia de raios-X por dispersão em energia e difração de raios-X. A contaminação por oxigênio foi quantificada pelo método de fusão em gás inerte. / Since the discovering of amorphous alloys in 1960, the actual causes of why some alloys can be easily formed into glasses while others cannot, are not clearly known, thus there is no universal theory to predict the glass forming ability in metallic systems. In the present work, a selection criterion was applied in the Ni-Nb-Zr system in order to predict the best stoichiometries with high glass forming ability. The actual glass forming ability of alloys were evaluated by the thermal parameter γm and the results have shown a poor correlation with the predictions. This criterion correlates critical cooling rate for glass formation with topological instability of stable crystalline structures; average work function difference and average electron density difference among the constituent elements of the alloy. The thermal parameter depends on the characteristic temperatures of phase transformations which can be easily measured from differential scanning calorimetry curves of metallic glasses. The initial hypotheses to explain the poor correlation between the experimental results and the predictions concerned with the influence of factors not considered in the calculation, such as unknown intermetallic compounds and oxygen contamination. Thus some rapidly quenched alloys were investigated with more accuracy in order to understand the formation of crystalline phases which compete against the glass formation. We characterized the crystalline phases and compared them to crystalline structures found in literature as well as some phase diagrams. The phase diagrams were used as guides in order to understand the crystallization behavior. In addition, the selection criterion also was used to predict the glass forming ability improvement of a Ni-Nb-Zr alloy with minor additions of rare-earth elements Y or Er. It is well known that the minor amount addition of proper rare-earth elements can greatly enhance the glass forming ability of some glass-forming alloys. The actual glass forming ability of the base alloy and rare-earth doped alloys also were evaluated by the thermal parameter &#947m and the results agree very well with the tendency predicted by the calculation. Bulk amorphous specimens were produced by injection casting. The amorphous nature was analyzed by X-ray diffraction and differential scanning calorimetry. The crystalline phases were analyzed by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and x-ray diffraction. Oxygen contamination was quantified by the inert gas fusion method.

Obsidian has been a center of interest both for geologists and archaeologists. Geologists have studied on physical and chemical properties of obsidian where archaeologists have worked on this material as a common artifact found in excavations. In this study, obsidian samples from &Ccedil / atalh&ouml / y&uuml / k excavations are examined using their rare earth element (REE) concentrations. Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) have been used for this purpose. A mixture (4:1) of lithium metaborate and lithium tetraborate was used for fusion of samples. Because of the low concentrations of REEs, a preconcentration step is needed. Successful recovery results have been achieved with Amberlite IR-120. The developed method is tested using the standard reference material SARM-1.

Lead-free solders such as SnAg and SnAgCu are used extensively as replacements of SnPb solders in microelectronics packaging. But these alloys have several drawbacks, such as poor wetting ability and formation of intermetallic compounds (IMC). Doping of rare earth element (RE) on SnAg alloys has been found to improve the wetting property, reduce IMCs and their growth, and refine the microstructure which results in improved mechanical properties of the solder. This study focuses on establishing the quantitative effects of RE doping on the microstructure and mechanical behavior of 96.5Sn3.5Ag alloy. SnAg alloys with different amounts of Lanthanum were made. Specimens were cast under typical reflow conditions, and then aged at different temperatures for three different aging times. Quantitative microscopy was conducted on samples with different amounts of La doping. It was found that doping greatly reduces the grain size, as well as the size of the intermetallic particles Ag3Sn. However, the inter-particle spacing remains relatively unaffected by the La doping amount. Creep tests at various temperatures and strain rates were conducted. The results show that La doping increases creep resistance of the SnAg alloy by ~15%. The creep test result can be fit into a modified microstructure dependent Anand model. A new constitutive law was also proposed to account for the hierarchal microstructure over multiple length scales. Specifically, at the sub micrometer scale, the SnAg eutectic region is treated as a particulate-reinforced composite with the Ag3Sn being the particle and Sn being the matrix. At the micrometer length scale, the solder alloys is treated as a two-phase composite with the Sn dendrite as the particle and the SnAg eutectic region as the matrix. Good agreement was found between the model predictions and the creep test results. Fatigue test was performed on bulk samples. It was found that RE doping increases the fatigue life of SnAg alloy by a factor of 5.

Bentonite clays are exposed in Paleogene strata stretching over 650 km parallel to the Texas coastline. This study focuses on a white and blue and a yellow and brown commercial Ca-montmorillonite bentonite near the city of Gonzales, Gonzales county, Texas. The deposits have stratigraphic ages of Late Eocene (~36.7 - 32.7 Ma). The bentonites in these deposits have varying colors, purities and brightness affording them diverse industrial uses. The distribution and geologic character of the high purity white and blue bentonite suggests that the deposit represents an accumulation of volcanic ash in a secondary tidal channel during the ash-fall event. A low rate of terrigenous clastic sedimentation and rapid accumulation of fresh ash were critical to the formation of high purity clay. The lower purity yellow and brown bentonites appear to have a fluvial origin marked by higher rates of detrital sedimentation and episodic accumulation of clay and ash. The bentonite and associated strata were studied using optical microscopy, SEM, XRD and REE analyses to constrain their textural, mineralogic, and chemical character. vii Eocene pyroclastic volcanism is well documented from sources in southwestern North America, specifically in the Sierra Madre Occidental (Mexico), Trans-Pecos (Texas) and Mogollan-Datil (New Mexico) volcanic fields. Projected Eocene wind patterns support this region as a potential source for the Gonzales bentonites. A comparison of the trace and REE fingerprints of the white and blue bentonites and the yellow and brown bentonites with data available for Late Eocene volcanics in the North American Volcanic Database provides a couple of potential matches. The strongest potential match for the Late Eocene bentonite protolith is described as a sample of silicic tuff with an age range of 32.2 – 30.6 Ma, located in the southern Mexican state of Oaxaca. While the trace and REE match is strong, the tuff is somewhat young compared to the Jackson Group sediments. In addition, the sample location is due almost directly south of the Gonzales deposits, rather than the western location expected for a Gonzales bentonite source. The other potential matches are located in New Mexico, and the Mexican state of Chihuahua. These potential matches only have 6 REE available for comparison, and require further investigation. Many Paleogene volcanic units in southern North America are undocumented with regard to REE data or precise absolute ages. As additional geochemical analyses become available for a more extensive suite of Paleogene volcanic units, stronger matches with Gulf of Mexico Basin bentonites are expected to emerge. / text

Submitted by Haroudo Xavier Filho (haroudo.xavierfo@ufpe.br) on 2016-04-01T18:23:34Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese Juliana Carvalho da Silva UFPE.pdf: 7095359 bytes, checksum: d445a956305aec4d1e8bc5f1753f949b (MD5) / Made available in DSpace on 2016-04-01T18:23:34Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese Juliana Carvalho da Silva UFPE.pdf: 7095359 bytes, checksum: d445a956305aec4d1e8bc5f1753f949b (MD5) Previous issue date: 2015-07-31 / CAPES / O petróleo, por sua relevância na economia global, demanda um volume crescente de pesquisas no setor e com isso a necessidade do uso de materiais resistentes à ambientes agressivos como é o caso do petróleo cru, gerando procedimentos eficazes e seguros que minimizem impactos ao meio ambiente. Revestimento termicamente aspergido tem sido intensamente utilizado na indústria de petróleo, aeroespacial, elétrica entre outros. Os revestimentos podem ser feitos de metal, cerâmica, vidros e a maioria dos plásticos, e o uso de um compósito adequado pode melhorar a resistência à corrosão em altas temperaturas. As cerâmicas apresentam alto ponto de fusão e são bons isolantes térmicos, porém apresentam baixa tenacidade e fragilidade. Estudos mostram que o uso de óxidos como ZrO2, TiO2 como reforços e de aditivos como óxidos de elementos de terras raras Y2O3, La2O3 podem melhorar a tenacidade da cerâmica à base de alumina. A primeira etapa desta pesquisa teve como objetivo a produção de compósitos cerâmicos à base de alumina, reforçados com 5%, 10%, 15%, 20% e 30% em peso de zircônia estabilizada com óxidos de terras raras La2O3 e Y2O3 variando entre 1 e 7%. A metodologia experimental utilizada consistiu da preparação do compósito cerâmico através da moagem em moinho de bolas, confecção de pastilhas por prensagem uniaxial em prensa hidráulica, e sinterização das amostras que foi realizada nas temperaturas de 13000C, 1350 0C e 14000C por 48h, com posteriores análises de absorção, dureza vickers, microscopia ótica, DRX e MEV. De posse dos resultados, numa segunda etapa a pesquisa foi direcionada à aplicação do compósito cerâmico Al2O3 – ZrO2 reforçado com óxido de ítrio em revestimento de chapas metálicas usadas na fabricação de tanques de armazenamento e transporte de petróleo depositado pelo processo de aspersão térmica a plasma – Atmospheric Plasma Spray, com e sem Bond coat (método de aspersão HVOF – High Velocity Oxi-Fuel), seguidos de ensaios para caracterização e pré-qualificação dos revestimentos como ensaios de adesão, riscamento e MEV. De um modo geral, os valores obtidos nos ensaios de adesão e as imagens de MEV indicam que o compósito estudado é adequado para revestimentos tipo barreira térmica para aplicação em ambientes corrosivos ao petróleo cru. / Oil, for its relevance in the global economy requires a growing body of research in the industry as well as need for the use of materials resistant to harsh environments such as crude oil, generating effective and safe procedures that minimize impacts on the environment . Thermally sprayed coating has been intensively used in the oil industry, aerospace, electrical and more. The coatings may be made of metal, ceramic, glass and most plastics, and the use of an appropriate composite can improve the corrosion resistance at high temperatures. Ceramics have a high melting point and are good insulators, but have low toughness and fragility. Studies show that the use of oxides such as ZrO2, TiO2 as fillers and additives such as oxides of rare earth elements Y2O3, La2O3 can improve the toughness of alumina based ceramic. The first step of this research was aimed at the production of ceramic composites based on alumina reinforced with 5%, 10%, 15%, 20% and 30% zirconia weight stabilized with rare earth La2O3 and Y2O3 oxides ranging from 1 and 7%. The used experimental methodology consisted of the preparation of ceramic composite by grinding in ball mill, preparation of pellets by uniaxial pressing in a hydraulic press, and sintering of the samples was performed at temperatures of 13000C, 13500C and 14000C for 48 hours with subsequent analysis absorption, Vickers hardness, optical microscopy, XRD and SEM. With the results in a second step the research was directed to the application of the ceramic composite Al2O3 - ZrO2 reinforced with yttrium oxide coating of sheet metal used in the manufacture of storage tanks and transport of oil deposited by thermal spray process the plasma - Atmospheric Plasma Spray, with and without bond coat (HVOF spraying method - High Velocity Oxy-Fuel), followed by assays for characterization and classification of pre-testing coatings such as adhesion, scratching and SEM. In general, the values obtained in the adhesion tests and SEM images indicate that the composite studied is suitable for thermal barrier-type coatings in corrosive environments for application to the crude oil.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2018-02-27T16:02:43Z No. of bitstreams: 1 Roeser.pdf: 28201874 bytes, checksum: 73be7d16511d8f5aa3fb6e4876b12a51 (MD5) / Made available in DSpace on 2018-02-27T16:02:43Z (GMT). No. of bitstreams: 1 Roeser.pdf: 28201874 bytes, checksum: 73be7d16511d8f5aa3fb6e4876b12a51 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Fundação de Amparo a Pesquisa do Estado do Rio de Janeiro / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / Foram estudados testemunhos sedimentares em duas regiões da Plataforma Continental Brasileira (Sudeste e Sul): Cabo Frio – RJ e Depressão do Albardão – RS; com o objetivo de avaliar temporalmente o aporte terrígeno nestas áreas e associar as mudanças das características sedimentares ao longo do tempo com suas possíveis causas. Deu-se ênfase ao estudo da sedimentação inorgânica, sendo os principais proxies estudados os elementos terras raras (ETR) e os argilominerais. Os ETR possuem uso tradicional em estudos de proveniência sedimentar. A composição mineralógica da fração fina sedimentar também é utilizada neste tipo de estudos e os argilominerais podem ainda, sob determinadas condições, oferecer registros de condições climáticas passadas. Os testemunhos foram subamostrados em resolução de dois centímetros. As amostras foram submetidas à análise multielementar, por ativação neutrônica; mineralogia, por difração de raios-X e espectroscopia de infravermelho; granulometria, em granulômetro a laser. Densidade aparente, teor em água, matéria orgânica total e teor em carbonatos foram obtidos por gravimetria. As duas áreas estudadas representam ambientes de sedimentação distintos. Cabo Frio é uma área sujeita à ressurgência de massa de águas frias, aumentando a produtividade local. Isso se reflete diretamente na qualidade dos sedimentos, ricos em carbonatos. Depressão do Albardão por sua vez possui aporte de alto caráter detrítico, e reflete a entrada terrígena de sedimentos do Rio da Prata. Os ETR se mostraram proxie importante para estudos de origem sedimentar em ambas as áreas de estudo. Em Cabo Frio eles ressaltam a mistura de fontes sedimentares e para a Depressão do Albardão confirmam a origem platina. Os argilominerais devem ser utilizados com cautela no que tange interpretações de climas passados, considerando-se principalmente as escalas temporais envolvidas. Eles se mostraram proxie interessante para estudos paleoclimáticos relacionados à bacia do Rio da Prata, dadas as características dos sedimentos da Depressão do Albardão. / Sediment Bohrkerne wurden aus zwei Regionen der Brasilianischen Plattform (Südwesten und Süden) untersucht: Cabo Frio – RJ und Depressão do Albardão – RS, mit dem Ziel an diesen Stellen den Kontinentalen Beitrag der Sedimentation zu bestimmen und die Ursachen der zeitlichen Veränderungen der sedimentären Eigenschaften zu ermitteln. Der Schwerpunkt der Arbeit liegt auf der Anorganischen Sedimentation. Die hauptsächlich untersuchten proxies sind die Seltene Erden Elemente (SEE) und Tonminerale. SEE werden traditionell in Studien über Sedimentäre Herkunft angewendet. Die Tonmineralogie wird auch zu solchen Studien herangezogen, außerdem können Tonminerale unter bestimmten Bedingungen auch Aussagen über das Klima der Vergangenheit geben. Aus den Bohrkernen wurden jede zwei Zentimeter Proben genommen und analysiert. Die Haupt und Spuren Elemente wurden mittels Neutronen Aktivierungs Analyse; die Mineralogie, via Röntgen-Diffraktometrie und Infrarot-Spektrometrie; die Granulometrie, via Laser-Granulometer bestimmt. Dichte, Wassergehalt, organischer und karbonatischer Anteil wurden mit gravimetrischen Methoden ermittelt. Die untersuchten Gebiete haben unterschiedliche Sedimentations- Bedingungen. Cabo Frio ist ein Gebiet wo Kaltwasser von upwelling an die Oberfläche gebracht wird und die lokale Produktivität erhöht. Dies hat direkten Einfluss auf die Sediments Qualität, Sedimente haben hier hohen Anteil an Karbonaten. Depressão do Albardão auf der anderen Seite zeigt hauptsächlich Kontinentalen Einfluss vom Prata Fluss. Die SEE haben sich als nützliche proxies gezeigt zur Klärung der Sedimentären Herkunft beider Gebiete. In Cabo Frio zeigen sich verschiedene Quellen und in Depressão do Albardão zeigt sich die Signatur der Sedimente vom Prata Fluss. Tonminerale sollten aber vorsichtig gebraucht werden wenn man sie für Paläoklimatische Interpretationen benutzt, da die untersuchte Zeitspanne zu beachten ist. Trotzdem sind sie interessante proxies für Paläoklimatischte Fragen im Falle des Prata Beckens, da man in Depressão do Albardão hauptsächlich detritische Sedimente vorfindet

Rare earth elements (REEs) and their isotopes (such as Nd isotopes) can be potentially used to trace a wide range of oceanic processes in both modern and ancient oceans, but their successful application as tracers requires a comprehensive understanding of REE cycling in the modern ocean. Previous studies of REEs in seawater were largely constrained by analytical difficulties in generating accurate and precise REE data from seawater, which typically contain REE concentrations at a sub-ppt to ppt level. A new, and relatively simple, analytical method for precise and accurate determination of all dissolved REE concentrations in reasonably small (∼100 ml) seawater samples is presented in this thesis. With the application of the new method, this thesis reports the first full-depth, zonal ocean section of all dissolved REE concentrations, collected during the CoFeMUG cruise along ∼12°S in the South Atlantic. The section approach of this study places the distribution of dissolved REE concentrations in a well-constrained hydrographic context, allowing the first quantitative assessment (by an inverse model) of the relative importance of hydrographic controls resulting from advection/mixing of ocean circulation, together with non-conservative controls resulting from local particle scavenging and remineralization, in controlling the distribution of dissolved REEs in this region. A noteworthy decoupling of Ce and Mn with respect to their cycling in the water column was also observed in this study. The application of Nd isotopes as a tracer to reconstruct changes in ocean circulation in the NW European chalk shelf sea during rapid climatic events, including the mid-Cenomanian Event and oceanic anoxic event 2 (OAE 2), suggests a tight coupling between ocean circulation and transient climatic cooling during the general warm Late Cretaceous. An advected volcanic signal during OAE 2 was registered in the seawater Nd-isotope record from the English Chalk, probably suggesting a period of enhanced ocean ventilation/mixing at this time.