In this study ferroboron (Fe - 14 at %B) was synthesized in crystalline form (Fe + Fe2B) via electrodeoxidation. For this purpose, Fe2O3 and H3BO3 were mixed in suitable proportions via spex mill. The powder was cold pressed and sintered at 900 &deg / C yielding a two phase structure Fe3BO6 and Fe2O3. The sintered pellets were electro-deoxidized in CaCl2 by applying 3.1 Volts at 850&deg / C for 12 hours. This yielded Fe and Fe2B in proportions slightly deviating from the target composition. The chemical pathway of reduction is inspected by the help of the available thermodynamic data and the x-ray characterization of partially reduced samples. CaO and the formation of Ca3B2O6 were found to be effective in the mid-steps of this electrodeoxidation process.

Este trabalho teve como objetivo a síntese e a caracterização de pós e filmes finos da fase ß-BaB2O4 (ß-BBO) a partir do sistema temário BaO-B2O3-TiO2. A preparação destas amostras foi baseada na utilização de dois métodos de síntese: o método dos precursores poliméricos e o método de deposição por evaporação utilizando um feixe de elétrons. O estudo das amostras na forma de pós mostrou que a adição de TiO2 ao sistema BaO-B2O3 acelera o processo de decomposição térmica e reduz a temperatura de cristalização e de fusão da fase ß-BBO. No que concerne a obtenção da fase ß-BBO, a composição mais adequada é a que contém 4% de TiO2 e cristalizada a 700°C durante 2 horas. As propriedades estruturais, microestruturais e ópticas dos filmes também foram influenciadas pela quantidade de TiO2. Os filmes finos contendo 4% de TiO2 e cristalizados a 650°C apresentam somente a fase ß-BBO com um alto grau de orientação preferencial quando depositados sobre substratos de quartzo amorfo, silício e quartzo monocristalinos. Filmes finos cristalinos depositados pelo método de evaporação por feixe de elétrons contendo a fase ß-BBO somente foram obtidos \"in-situ\" quando os substratos foram aquecidos a 650°C. Os filmes cristalinos obtidos por ambos os métodos apresentaram o efeito de geração de segundo harmônico (\"SHG\"). / The main objective of this work was the synthesis and the characterization of the ß-BaB2O4 (ß-BBO) phase in a powder and thin film form from the BaO-B2O3-TiO2 ternary system. The powder and thin film samples were obtained using two different methods, the polymeric precursor method and the electron beam evaporation method. The study of the powder samples showed that the addition of titanium oxide to the BaO-B2O3 system accelerate the decomposition process, reduces the crystallization temperature and the ß-BBO melting point. The ß-BBO phase was obtained as the main phase for the sample containing 4% of titanium and heat-treated at 700°C for 2h. Structural, microstructural and optical properties of the thin films were also influenced by addition of TiO2. Thin films with 4% of TiO2 and crystallized at 650°C shown only ß-BBO phase with a higher degree of preferred orientation when coated on fused silica, silicon and quartz substrates. The microstructural and the optical properties of these thin films were affected by the type of the substrate and by crystallization temperature and by the heating rate. For the thin film deposited by electron beam evaporation the crystallization of ß-BBO phase \"in-situ\" was only possible when the substrates was heated at 650°C during the deposition. Thin films prepared by both methods presents the effect of Second Harmonic Generation (SHG).

Este trabalho teve como principal objetivo o estudo sistemático da obtenção da fase beta-BaB204 (beta-BBO) a partir de uma fase vítrea do sistema BaO-B2O3-TiO2. Foram estudadas amostras contendo entre 4 e 16% de TiO2. A avaliação das propriedades térmicas, estruturais e microestruturais das amostras foi realizada empregando as técnicas de Analise Térmica Diferencial (DTA), Difração de Raios-X (DRX), Microscopia óptica (MO), Microscopia Eletrônica de Varredura (MEV), Espectroscopia Raman, Absorção e Transmissão óptica no Infravermelho, Espectroscopia de Absorção de Raios-X (XAS) e Ressonância Magnética Nuclear (RMN). O coeficiente de Geração de Segundo Harmônico (GSH) foi obtido através das medidas do loci de casamento de fase e da Franja de Maker. O estudo do processo de cristalização revelou que em todas as amostras prevaleceu o mecanismo de cristalização superficial. Nas amostras contendo 4 e 8% de TiO2 foi observada a cristalização da fase beta-BBO enquanto que nas amostras contendo 15 e 16% de TiO2, foi observado que o processo de cristalização se inicia pela fase BaTi(BO3)2 e que somente após longos tempos de tratamento, a fase beta-BBO se toma a fase predominante. A identificação da fase BaTi(BO3) somente foi possível com a utilização da técnica de Espectroscopia Raman. O estudo da estrutura local através das técnicas de XAS e RMN mostrou que a estrutura local ao redor dos átomos de titânio, bário e boro nas amostras cristalizadas é pouco afetada quando a quantidade de TiO2 passa de 4 para 16%. A análise dos resultados da medida de geração de segundo harmônico mostrou que nas amostras contendo uma camada da superfície cristalizada, o valor do coeficiente de geração de segundo harmônico (deff) é equivalente ao do quartzo monocristalino e na amostra contendo 16% de TiO2, corresponde a 70% do valor observado na fase beta-BBO em sua forma monocristalina / This work consists of a systematic study of the beta-BaB2O4 (beta-BBO) crystalline phase obtained from the BaO-B2O3-TiO2 glass system containing amounts of titanium varying from 4 to 16 mol%. The thermal, structural and microstructural properties of the samples were evaluated by the following techniques: Differential Thermal Analysis (DTA), X-Ray Diffraction (XRD), Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Raman Spectroscopy, Infrared Optical Absorption Spectroscopy, X-Ray Absorption Spectroscopy (XAS) and Nuclear Magnetic Resonance (NMR). The Second Harmonic Generation (SHG) coefficient (def) was obtained from the phase matching Loci and Maker fringe curves. A study of the crystallization process revealed that the surface crystallization mechanism predominated in each of the samples. Only the beta-BBO phase was observed in the samples containing 4 and 8 mol% of TiO2. However, in the samples containing 15 and 16 mol% of TiO2, crystallization of the BaTi(BO3)2 occurred first and was followed by crystallization of the P-BBO phase, which subsequently became the main phase as the period of heat treatment increased. The identification of the BaTi(BO3)2 phase in the early stage of the crystallization process was only possible by using the Raman spectroscopy technique. Based on the results obtained from the XAS and NMR techniques, it was found that the increasing the titanium concentration does not affect significantly the short-range order around Ti, Ba and B atoms. An analysis of the SHG data obtained from the crystallized surface of the glassy samples indicated that the SHG coefficient, def, was comparable to that of the z-quartz monocrystalline sample and, in the sample containing 16 mol% of TiO2, it corresponded to 70% of the value observed for the monocrystalline beta-BBO sample

Este trabalho teve como principal objetivo o estudo sistemático da obtenção da fase beta-BaB204 (beta-BBO) a partir de uma fase vítrea do sistema BaO-B2O3-TiO2. Foram estudadas amostras contendo entre 4 e 16% de TiO2. A avaliação das propriedades térmicas, estruturais e microestruturais das amostras foi realizada empregando as técnicas de Analise Térmica Diferencial (DTA), Difração de Raios-X (DRX), Microscopia óptica (MO), Microscopia Eletrônica de Varredura (MEV), Espectroscopia Raman, Absorção e Transmissão óptica no Infravermelho, Espectroscopia de Absorção de Raios-X (XAS) e Ressonância Magnética Nuclear (RMN). O coeficiente de Geração de Segundo Harmônico (GSH) foi obtido através das medidas do loci de casamento de fase e da Franja de Maker. O estudo do processo de cristalização revelou que em todas as amostras prevaleceu o mecanismo de cristalização superficial. Nas amostras contendo 4 e 8% de TiO2 foi observada a cristalização da fase beta-BBO enquanto que nas amostras contendo 15 e 16% de TiO2, foi observado que o processo de cristalização se inicia pela fase BaTi(BO3)2 e que somente após longos tempos de tratamento, a fase beta-BBO se toma a fase predominante. A identificação da fase BaTi(BO3) somente foi possível com a utilização da técnica de Espectroscopia Raman. O estudo da estrutura local através das técnicas de XAS e RMN mostrou que a estrutura local ao redor dos átomos de titânio, bário e boro nas amostras cristalizadas é pouco afetada quando a quantidade de TiO2 passa de 4 para 16%. A análise dos resultados da medida de geração de segundo harmônico mostrou que nas amostras contendo uma camada da superfície cristalizada, o valor do coeficiente de geração de segundo harmônico (deff) é equivalente ao do quartzo monocristalino e na amostra contendo 16% de TiO2, corresponde a 70% do valor observado na fase beta-BBO em sua forma monocristalina / This work consists of a systematic study of the beta-BaB2O4 (beta-BBO) crystalline phase obtained from the BaO-B2O3-TiO2 glass system containing amounts of titanium varying from 4 to 16 mol%. The thermal, structural and microstructural properties of the samples were evaluated by the following techniques: Differential Thermal Analysis (DTA), X-Ray Diffraction (XRD), Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Raman Spectroscopy, Infrared Optical Absorption Spectroscopy, X-Ray Absorption Spectroscopy (XAS) and Nuclear Magnetic Resonance (NMR). The Second Harmonic Generation (SHG) coefficient (def) was obtained from the phase matching Loci and Maker fringe curves. A study of the crystallization process revealed that the surface crystallization mechanism predominated in each of the samples. Only the beta-BBO phase was observed in the samples containing 4 and 8 mol% of TiO2. However, in the samples containing 15 and 16 mol% of TiO2, crystallization of the BaTi(BO3)2 occurred first and was followed by crystallization of the P-BBO phase, which subsequently became the main phase as the period of heat treatment increased. The identification of the BaTi(BO3)2 phase in the early stage of the crystallization process was only possible by using the Raman spectroscopy technique. Based on the results obtained from the XAS and NMR techniques, it was found that the increasing the titanium concentration does not affect significantly the short-range order around Ti, Ba and B atoms. An analysis of the SHG data obtained from the crystallized surface of the glassy samples indicated that the SHG coefficient, def, was comparable to that of the z-quartz monocrystalline sample and, in the sample containing 16 mol% of TiO2, it corresponded to 70% of the value observed for the monocrystalline beta-BBO sample

Este trabalho teve como objetivo a síntese e a caracterização de pós e filmes finos da fase ß-BaB2O4 (ß-BBO) a partir do sistema temário BaO-B2O3-TiO2. A preparação destas amostras foi baseada na utilização de dois métodos de síntese: o método dos precursores poliméricos e o método de deposição por evaporação utilizando um feixe de elétrons. O estudo das amostras na forma de pós mostrou que a adição de TiO2 ao sistema BaO-B2O3 acelera o processo de decomposição térmica e reduz a temperatura de cristalização e de fusão da fase ß-BBO. No que concerne a obtenção da fase ß-BBO, a composição mais adequada é a que contém 4% de TiO2 e cristalizada a 700°C durante 2 horas. As propriedades estruturais, microestruturais e ópticas dos filmes também foram influenciadas pela quantidade de TiO2. Os filmes finos contendo 4% de TiO2 e cristalizados a 650°C apresentam somente a fase ß-BBO com um alto grau de orientação preferencial quando depositados sobre substratos de quartzo amorfo, silício e quartzo monocristalinos. Filmes finos cristalinos depositados pelo método de evaporação por feixe de elétrons contendo a fase ß-BBO somente foram obtidos \"in-situ\" quando os substratos foram aquecidos a 650°C. Os filmes cristalinos obtidos por ambos os métodos apresentaram o efeito de geração de segundo harmônico (\"SHG\"). / The main objective of this work was the synthesis and the characterization of the ß-BaB2O4 (ß-BBO) phase in a powder and thin film form from the BaO-B2O3-TiO2 ternary system. The powder and thin film samples were obtained using two different methods, the polymeric precursor method and the electron beam evaporation method. The study of the powder samples showed that the addition of titanium oxide to the BaO-B2O3 system accelerate the decomposition process, reduces the crystallization temperature and the ß-BBO melting point. The ß-BBO phase was obtained as the main phase for the sample containing 4% of titanium and heat-treated at 700°C for 2h. Structural, microstructural and optical properties of the thin films were also influenced by addition of TiO2. Thin films with 4% of TiO2 and crystallized at 650°C shown only ß-BBO phase with a higher degree of preferred orientation when coated on fused silica, silicon and quartz substrates. The microstructural and the optical properties of these thin films were affected by the type of the substrate and by crystallization temperature and by the heating rate. For the thin film deposited by electron beam evaporation the crystallization of ß-BBO phase \"in-situ\" was only possible when the substrates was heated at 650°C during the deposition. Thin films prepared by both methods presents the effect of Second Harmonic Generation (SHG).

Mica based glass - ceramics have been produced by subjecting the glasses in the SiO2 , Al2O3 , CaO , MgO, K2O , and F system to a controlled heat treatment called crystallization. TiO2 was added into the batch in the amount of 1 wt% of the glass as nucleating agent. B2O3 additions in the amounts of 1, 2, 4 and 8 wt% of the glass have been made in the batch to see and evaluate the effects of B2O3 additions on the texture of the mica glass ceramics. Crystallization was accomplished in two steps, nucleation and crystal growth. Nucleation temperature was 650 &amp / #61616 / C. Crystal growth temperatures were 850 and 1000 &amp / #61616 / C. The time for holding the specimens at the temperatures was 8 hours. The X-Ray diffraction analysis revealed that resultant glass ceramics possessed not only synthetic fluormica crystals called phlogopite which provide machinability, but also wollastonite crystals which provide biocompatibility. The scanning electron microscopy examinations have indicated that the amount and distribution of the crystalline phases varied as a function of B2O3 content and heat treatment schedule applied.

Transparent glass-ceramics have been of industrial interest because of their multifarious applications. These are becoming increasingly important because of the flexibility that is associated with this route of fabricating intricate sizes and shapes as per the requirement. A number of glass-ceramics, based on well known ferroelectric crystalline phases (LiNbO3, LaBGeO5, SrBi2Nb2O9, Bi2WO6 etc.) were fabricated and their polar and electro-optic properties were reported. Keeping the potential applications of transparent glass-nano/microcrystal composites in view, attempts were made to fabricate SrBi2B2O7 and CaBi2B2O7 glasses and glass-nano/microcrystal composites. An attempt has been made to employ strontium bismuth borate SrBi2B2O7 (SBBO) as a reactive host glass matrix for growing the nanocrystals of ferroelectric oxides belonging to the Aurivillius family. The in situ nucleation and growth of SrBi2Nb2O9 (SBN) nanocrystals in a reactive SrBi2B2O7-Nb2O5 system and its influence on various physical (dielectric, pyroelectric and optical) properties were investigated. The strategy has been to visualize the formation of nanocrystalline SrBi2Nb2O9 as a result of the simple chemical reaction between glassy SrBi2B2O7 and Nb2O5. Indeed at lower concentrations of Nb2O5 transparent glasses were obtained which upon heat-treatment at appropriate temperatures yielded nanocrystalline SrBi2Nb2O9 phase in a transparent glass matrix. Textured SrBi2Nb2O9 ceramics were obtained by quenching the melts of SrBi2B2O7-Nb2O5 in equimolar ratio and their physical properties were studied. A strong anisotropy in physical properties (which are akin to single crystals) were demonstrated in the textured ceramics.

Widespread use of solid oxide fuel cells is hindered by a lack of long-term durability of seals between metallic and ceramic components caused by thermal expansion mismatch induced cracking. A novel gas seal design incorporating an engineered thermal expansion gradient in a SrO-La₂O₃-A₂O₃-B₂O₃-SiO₂ glass matrix with a TiNiHf shape memory alloy mesh for active stress relief and crack healing is being developed. Coefficient of thermal expansion (CTE) measurements of the seal and fuel cell components shows the possibility for a thermal expansion gradient. Differential scanning calorimetry and microscopy have shown that the TiNiHf alloy has a shape memory transition in the desired range of 200-250ºC. The oxide glass partially crystallizes during thermal cycling which has been observed through X-ray diffraction and dilatometry. The CTE decreases from 9.3Ã 10-6/°C to 6.6Ã 10-6/°C after thermal cycling. Neutron diffraction data from TiNiHf /glass composite samples reveals that the TiNiHf alloy has the ability of absorbing residual stresses from a glass matrix during martensitic phase transition. There is evidence from microscopy that the glass composition is important in determining if reaction will occur with the TiNiHf alloy. The TiNiHf alloy mesh structures can be created using the 3D printing process. This process has been adapted to allow for printing of very thin wire mesh structures of Ni and NiTi powders with a more suitable binder solution. A bi-layer test fixture has been developed which will be useful for assessing leak rate through seal materials. / Master of Science

Ce travail de thèse porte sur la synthèse et la caractérisation de matériaux amorphes et cristallin sous forme de poudres et de couche minces du systhème Er2O3-Y2O3-Al2O3-B2O3. L'objectif principal du travail a été de préparer des couches minces amorphes dopées erbium dont la composition est proche de YAl3(BO3)4 (YAB), en vue de la réalisation d'amplificateurs pour l'optique guidée. Pour la synthèse des échantillons, les méthodes des précurseurs polymériques et sol-gel ont été utilisées. Les caractérisations thermiques, structurales et optiques des échantillons, sous forme de poudre et de couches minces, ont été réalisées par l'analyse thermogravimétrique, microcalorimétrie différentielle, diffraction des rayons X, spectroscopie infrarouge à transformé de Fourier, spectroscopie Raman, microscopie électronique à balayage, microscopie à force atomique, spectroscopie “m-line”, et de luminescence. L'ensemble de ces résultats nous a permis de parfaitement contrôler l'élaboration de couches minces vitreuses de compositions Y1-xErxAl3(BO3)4 (x = 0,02; 0,05; 0,1; 0,3 et 0,5) qui présentent une très bonne homogénéité chimiques et de bonnes propriétés optiques. Les couches minces recuites à des températures comprises entre Tg et Tc, présentent les meilleures conditions pour obtenir des dépôts très denses et homogènes, conduisant à de bonnes efficacité de guidage, d'émission de luminescente et de durées de vie. Les couches vitreuses de composition Y0,9Er0,1Al3(BO3)4 et d'épaisseurs comprises entre 500 et 800 nm sont des guides d'onde monomodes qui présentent durées de vie comparables à d'autres systèmes borates amorphes. Ces résultats confirment la possibilité d'utilisation de ces couches amorphes comme amplificateurs pour l'optique guidée.

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