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Este trabalho teve como principal objetivo a síntese e o estudo do processo de cristalização dos sistemas vítreos B2O3-BaO-SiO2, e B2O3-BaO-SiO2-Al2O3, assim como do sistema B2O3-BaO-SiO2 dopado com cério e prata. Amostras do sistema B2O3-BaO-SiO2 contendo 8 e 15% de SiO2, amostras do sistema B2O3-BaO-SiO2-Al2O3 contendo 2, 4 e 8 mol% de Al2O3 e amostras do sistema B2O3-BaO-SiO2 contendo 15% de SiO2 dopada com cério e prata foram caracterizadas através da técnica de analise térmica diferencial (DTA), difração de raios X (DRX), microscopia óptica (MO), espectroscopia Raman, medidas de transmissão na região do ultra-violeta/visível e medidas de luminescência. O estudo do processo de cristalização revelou que em todas as amostras prevaleceu o mecanismo de cristalização superficial. O tratamento térmico em temperaturas acima de Tg e abaixo de Tc levou a formação de uma única fase cristalina, a fase beta -BaB2O4 (beta-BBO). A morfologia dos cristais da fase beta -BBO presentes na superfície das amostras vítreas depende da quantidade de SiO2 e Al2O3. A amostra dopada com cério e prata quando submetida a radiação proveniente de um laser de HeCd e a um posterior tratamento térmico a 400 ºC apresentou somente um efeito de fotosensibilidade superficial devido a alta absorção dos átomos de cério presentes na amostra. / The main purpose of this work was the synthesis and study of the crystallization process of B2O3-BaO-SiO2 and B2O3-BaO-SiO2-Al2O3 as well cerium and silver co-doped B2O3-BaO-SiO2 glassy systems. Samples of 8 and 15 mol% SiO2-containing B2O3-BaO-SiO2 system, 2, 4 and 8 mol% Al2O3-containing B2O3-BaO-SiO2-Al2O3 system and samples 15% mol % SiO2-containing B2O3-BaO-SiO2 system doped with cerium and silver were characterized by different techniques as differential thermal analysis (DTA), X-ray diffraction (XRD), optical microscopy (OM) and Raman spectroscopy. The study of the crystallization process showed that, in all the prepared samples, surface crystallization was the predominant mechanism. The heat treatment at temperatures above Tg and below Tc led to the formation of a single crystalline phase: beta-BaB2O4 (abbreviated as beta-BBO). The morphology of the crystals that appear at the glass surface depends on the amount of SiO2 and Al2O3 in the systems. When subjected to radiation from a HeCd laser and a subsequent heat treatment at 400 ºC, the glass system doped with cerium and silver, showed a photosensitivity effect on the surface due to high absorption of cerium atoms present on the glass sample.

Este trabalho teve como principal objetivo a síntese e o estudo do processo de cristalização dos sistemas vítreos B2O3-BaO-SiO2, e B2O3-BaO-SiO2-Al2O3, assim como do sistema B2O3-BaO-SiO2 dopado com cério e prata. Amostras do sistema B2O3-BaO-SiO2 contendo 8 e 15% de SiO2, amostras do sistema B2O3-BaO-SiO2-Al2O3 contendo 2, 4 e 8 mol% de Al2O3 e amostras do sistema B2O3-BaO-SiO2 contendo 15% de SiO2 dopada com cério e prata foram caracterizadas através da técnica de analise térmica diferencial (DTA), difração de raios X (DRX), microscopia óptica (MO), espectroscopia Raman, medidas de transmissão na região do ultra-violeta/visível e medidas de luminescência. O estudo do processo de cristalização revelou que em todas as amostras prevaleceu o mecanismo de cristalização superficial. O tratamento térmico em temperaturas acima de Tg e abaixo de Tc levou a formação de uma única fase cristalina, a fase beta -BaB2O4 (beta-BBO). A morfologia dos cristais da fase beta -BBO presentes na superfície das amostras vítreas depende da quantidade de SiO2 e Al2O3. A amostra dopada com cério e prata quando submetida a radiação proveniente de um laser de HeCd e a um posterior tratamento térmico a 400 ºC apresentou somente um efeito de fotosensibilidade superficial devido a alta absorção dos átomos de cério presentes na amostra. / The main purpose of this work was the synthesis and study of the crystallization process of B2O3-BaO-SiO2 and B2O3-BaO-SiO2-Al2O3 as well cerium and silver co-doped B2O3-BaO-SiO2 glassy systems. Samples of 8 and 15 mol% SiO2-containing B2O3-BaO-SiO2 system, 2, 4 and 8 mol% Al2O3-containing B2O3-BaO-SiO2-Al2O3 system and samples 15% mol % SiO2-containing B2O3-BaO-SiO2 system doped with cerium and silver were characterized by different techniques as differential thermal analysis (DTA), X-ray diffraction (XRD), optical microscopy (OM) and Raman spectroscopy. The study of the crystallization process showed that, in all the prepared samples, surface crystallization was the predominant mechanism. The heat treatment at temperatures above Tg and below Tc led to the formation of a single crystalline phase: beta-BaB2O4 (abbreviated as beta-BBO). The morphology of the crystals that appear at the glass surface depends on the amount of SiO2 and Al2O3 in the systems. When subjected to radiation from a HeCd laser and a subsequent heat treatment at 400 ºC, the glass system doped with cerium and silver, showed a photosensitivity effect on the surface due to high absorption of cerium atoms present on the glass sample.

Le changement local de l'indice de réfraction (CLIR) est l’élément constitutif des fonctions optiques créées par laser dans des matériaux transparents. Selon le régime de l'interaction et en particulier en fonction de la dose d’énergie déposée, de la durée de l'impulsion laser et des conditions de focalisation on peut induire un CLIR isotrope et positif ou produire à l’échelle nanométrique des structures auto-arrangées présentant une biréfringence. Ce changement est essentiel pour les applications photoniques intégrées utilisant des matériaux comme la silice, ce qui été démontré dans la thèse par réalisation des composants optiques allant du simple guide canal enterré à des dispositifs sensibles à la polarisation. En parallèle au développement d’applications photoniques nous avons étudiés les mécanismes microscopiques à l’origine de la modification des propriétés optiques des diélectriques utilisés. Nous avons appliqué les techniques de micro photoluminescence et microspectroscopie Raman pour étudier la formation des défauts ponctuels et des chemins de réorganisation de la structure du verre. Ces modifications de structure de verres jouent un rôle important dans le changement des propriétés électroniques de la silice fondue et, par conséquent, de ses constantes optiques. L’ensemble de ces résultats spectroscopiques nous a permis de revisiter les schémas de densification dans la silice et de proposer un scénario de densification assistée par les défauts générés suite à la relaxation des excitons auto-piégés / Local refractive index changes (RIC) are the building blocks of laser-induced optical functions in bulk transparent materials, where the use of a fused silica as a target material plays a paramount role. Depending on the regime of laser interaction ultra-short pulses can induce positive isotropic refractive index changes (usually denoted as type I) or produce self-arranged nano-scale layered structures resulting in form birefringence (type II). In this thesis we have studied two objectives related to these material transformations. From the one side, we qualitatively determined the effects of the focused ultra-short laser pulses on the fused silica and borosilicate glasses. With the independent control of the energetic dose, pulse duration and focusing conditions, the isotropic type I and birefringent type II traces could be performed with the certain optical properties. Finally, complex polarization sensitive devices were designed and fabricated. From the other side, as these types of RIC have consequences in the functionality and the performances of 3D embedded optical devices, an investigation of the laser-induced structures is particularly useful. We applied photoluminescence and Raman microscopy (RM) to investigate defect formation and glass network reorganization paths. The proposed spectroscopy study distinguishes type I and type II regions by presence and distribution of silicon clusters and non-bridging oxygen hole centers (NBOHC). RM reveals signs of compaction of the glass network in the RIC regions. At the same time, zones with high concentration of NBOHC where no visible RIC and densification signs were detected. Assuming that these zones are precursors of permanent visible modification, we propose a scenario of cold defect-assisted densification realized in type I irradiation regime. This, thereby, revises the densification paths in fused silica

Ce travail porte sur le fractionnement des produits de fission et les actinides mineurs (simulées par des terres rares) dans une vitrocéramique borosilicate riche en molybdène contenant des cristallites de powellite (CaMoO4) étudié par techniques d'analyse élémentaire (LIBS, LA-ICP-MS, et l'EMPA). Il a été montré que des terres rares et Sr (émetteur bêta) sont incorporés préférentiellement dans la phase powellite, tandis que Al, Fe, Zr, Zn et Cs (sources bêta-decay) restent dans le verre. Le comportement de monocristaux orientés de powellite dopé en terres rares (simulants des actinides mineurs) sous irradiations est décrit et commenté afin de comprendre son comportement à long terme dans des conditions de stockage, en utilisant l'interférométrie optique, la spectroscopie Raman, TEM, et la spectroscopie de photoluminescence. On observe que l'irradiation induit un gonflement dans powellite augmentant avec la dose d'irradiation (de 0,012 à 1,2 dpa). La saturation est atteinte à 1,2 dpa. Une contrainte anisotrope associée à un changement du volume de la maille dans le monocristal de powellite a été mis en évidence et analysée par suivi de la position des raies v1 (Ag) et v3 (Eg) des modes Raman. Le désordre induit dans la structure de powellite irradiée est signé par l'augmentation de la largeur des raies Raman. La caractérisation fine par TEM indique que les dommages structuraux induits dans la powellite irradiée suivent l'évolution suivante de la structure cristalline : défauts ponctuels, dislocations, mosaïcité. Il a été confirmé à la fois par Raman et par TEM que la structure powellite résiste fortement à l'irradiation et n'atteint jamais l'état d'amorphisation dans la gamme dpa étudiée (0,012 à 5,0) / The fractionation of fission products and minor actinides (simulated by rare-earth elements) is studied in a Morich borosilicate glass-ceramic containing powellite (CaMoO4) crystallites, using elemental analysis techniques (LIBS, LA-ICPMS, and EMPA). For Mo-rich borosilicate glass-ceramic containing powellite crystallites, it was suggested that rare earth elements and Sr (beta-decay source) are prone to incorporate into the powellite phase, while Al, Fe, Zr et Cs (beta-decay source) and Zn remain in the glass matrix. The behavior of rare-earth (surrogates of radioactive minor actinides) doped powellite single crystal under irradiations figure out its longterm behavior in storage conditions, using optical interferometry, Raman spectroscopy, TEM, and luminescent spectroscopy. It is observed that the irradiation-induced swelling in powellite first increased with irradiation dose (0.012 to 1.2 dpa), then reached saturation after 1.2 dpa Anisotropic stress and lattice volume change induced by irradiation in powellite single crystal were found and analyzed by determining the peak position of V1 (Ag) et V3 (Eg) Raman modes. Structure disorder of irradiated powellite in medium-range order was represented by the Raman linewidth broadening. According to the TEM characterization, the structural damages of irradiated powellite followed an evolution of crystalline structure, point defects, dislocations, mosaicity. It was confirmed by both Raman and TEM that powellite resisted strongly and never reached amorphization within the studied dpa range (0.012 to 5.0)

Dans cette thèse, nous décrirons les effets structuraux (structure moyenne et à l’ordre local) engendrés par la substitution de l’aluminium par du bore dans la gehlénite (Ca2Al2-xBxSiO7). Les modifications des environnements atomiques à courtes et moyennes distances ont pu être déterminées grâce à une analyse poussée par diffraction sur poudre et à l’utilisation des dernières techniques de RMN haute résolution en phase solide. La première partie du manuscrit donne une description complète de la structure du minéral non substitué Ca2Al2SiO7. L’ensemble des 7 environnements de l’aluminium a été décrit par une simulation combinée de spectres RMN MAS et MQMAS 27Al acquis à différents champs et attribué à l’aide d’expériences d’édition spectrale. L’existence de liaisons Al-O-Al a été démontrée. Par ailleurs, la détermination de la proportion des unités Q3(2Al) nous a permis d’accéder à l’enthalpie de mise en ordre Al/Si dans ce système. Le mécanisme de substitution Al/B et l’évolution structurale de la solution solide Ca2Al2-xBxSiO7 (0 x 2), synthétisée par cristallisation de verres de même composition, ont été caractérisés par affinements Rietveld de données collectées par diffraction des rayons X et des neutrons. Des observations effectuées par RMN MAS sur les trois noyaux du système (27Al, 29Si et 11B) nous ont permis de compléter ces résultats. Un nouveau borosilicate de calcium de formule CaSi1/3B2/3O8/3, appartenant au diagramme de phase Ca2Al2SiO7-Ca2B2SiO7, a pu être identifié et synthétisé. Sa structure a été déterminée in situ et ab initio en combinant des techniques de diffraction, de microscopie électronique en transmission et de résonance magnétique nucléaire. / This work describes the structural modifications (average structure and local order) due to the substitution of boron for aluminum in gehlenite (Ca2Al2-xBxSiO7). The modifications of the short and medium range in the structure order have been determined using neutron and X-ray powder diffraction and recent advanced high resolution solid-state NMR techniques. The first part of this manuscript provides a full description of the structure of the non substituted mineral (Ca2Al2SiO7). All the 7 aluminum sites are identified and quantified by 27Al MAS, MQMAS and spectral editing NMR experiments performed at 9.4 and 17.6T. The existence of Al-O-Al linkage is demonstrated. The quantification of the Q3(2Al) species by 29Si MAS NMR allows the determination of the enthalpy related to the Al/Si ordering in the system. The Al/B substitution mechanism and the structural evolutions of the Ca2Al2-xBxSiO7 (0 x 2) solid solution, synthesised by crystallisation from glass, have been characterised by Rietveld refinements from Xray and neutron powder diffraction data. These results have been completed by solid-state NMR experiments (11B, 27Al and 29Si). A new calcium borosilicate phase (CaSi1/3B2/3O8/3), observed in the Ca2Al2SiO7-Ca2B2SiO7 phase diagram, has been identified and synthesised. The in situ and ab initio structure determination of this phase has been performed using the charge flipping method by combining powder diffraction, transmission electron microscopy and solid-state NMR analyses.

Ce travail contribue à la compréhension des réactions et mécanismes d'oxydoréduction du fer dans les silicates fondus. Il a été réalisé à partir de compositions appartenant aux systèmes Na2O-B2O3-SiO2-FeO et Na2O-Al2O3-SiO2-FeO. L'influence des substitutions bore-sodium et aluminium-sodium et du taux de fer sur les propriétés et la structure des verres ainsi que sur les cinétiques d'oxydoréduction a été étudiée par spectroscopie Raman, Mössbauer et XANES aux seuils K du bore et du fer. Dans les borosilicates, une augmentation du taux de fer ou de l'état rédox Fe3+/ΣFe entraîne un réarrangement structural des espèces BO4 au sein du verre alors que les proportions relatives de BO3 et BO4 sont très peu affectées. Dans tous les verres et silicates fondus étudiés, Fe3+ est un formateur de réseau en coordinence 4, sauf pour les aluminosilicates de rapport Al/Na>1 où il joue un rôle de modificateur de réseau en coordinence 5. Les cinétiques d'oxydoréduction sont contrôlées près de Tg par la diffusion des cations modificateurs de réseau, accompagnée d'un contreflux de trous électroniques. Aux températures proches du liquidus, la diffusion de l'oxygène est considérée comme le mécanisme gérant les processus d'oxydoréduction. Cette étude met en évidence le rôle joué par la polymérisation du réseau sur les cinétiques rédox. Dans les borosilicates fondus, les cinétiques rédox sont dépendantes de la spéciation du bore entre BO3 et BO4 qui elle-même dépend du taux de sodium. Par ailleurs, plus le rapport formateurs/modificateurs de réseau est important, plus la diffusivité de l'oxygène diminue et plus les vitesses de cinétiques rédox sont réduites. Les résultats obtenus ont permis de décrire les cinétiques rédox pour des compositions plus complexes de laves naturelles ou s'approchant de celles de verre de confinement de déchets nucléaires.

Today, ceramic, polymer, and composite nanofibers are among the most charming materials for nanotechnology. Because of their small characteristic dimension, high surface area, and microstructural features, they provide unique mechanical, optical, electronic, magnetic, and chemical properties for an extensive variety of materials applications. Electrospinning provides an effective way of the nanofiber production in a nanometer scale. This technique utilizes a high voltage DC to create a strong electric field and a certain charge density in a viscous solution contained in a pipette. As a result, fibers with diameters ranging from the micrometer to nanometer are formed from this charged solution. This study deals with, the fabrication of alumina borosilicate ceramic nanofibers using electrospinning technique. Alumina borosilicates contain important components having intriguing characteristics for many applications and have been widely studied with different compositions. In this study, alumina borosilicate/PVA solution was prepared using the conventional sol-gel method. Polyvinyl alcohol (PVA) was added into this solution to increase the viscosity for electrospinning. After the alumina borosilicate/PVA solution was electrospun into fibers, high temperature sintering was carried to obtain ceramic alumina borosilicate fibers. The products were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), Fourier transform-infrared spectroscopy (FT-IR), and thermogravimetric/differential thermal analysis (TG-DTA) techniques.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-12-08T17:00:54Z No. of bitstreams: 1 felixsoaresdelimaneto.pdf: 3304649 bytes, checksum: 1cb4641ba963788c0c4b2143b23a8c5d (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-12-22T11:34:06Z (GMT) No. of bitstreams: 1 felixsoaresdelimaneto.pdf: 3304649 bytes, checksum: 1cb4641ba963788c0c4b2143b23a8c5d (MD5) / Made available in DSpace on 2017-12-22T11:34:06Z (GMT). No. of bitstreams: 1 felixsoaresdelimaneto.pdf: 3304649 bytes, checksum: 1cb4641ba963788c0c4b2143b23a8c5d (MD5) Previous issue date: 2011-11-28 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho foram estudados vidros borossilicatos dopados com nanopartículas de enxofre e íons de Er+3 com o objetivo de determinar a difusividade térmica do sistema vítreo (SNABP), através da técnica de Espectroscopia de Lente Térmica. As propriedades espectroscópicas de tais amostras foram investigadas por meio das medidas de absorção _óptica na região espectral de 400 a 2000 nm. A caracterização das propriedades termo- _ópticas foram realizadas por meio da espectroscopia de Lente Térmica de feixe duplo no modo descasado com excitação em 50mW a 3W. Verificou-se que a difusividade térmica diminuiu quando a matriz SNABP foi dopada com nanocristais de PbS e íons Er3+. Com o tratamento térmico, a amostra SNABP Er manteve a menor difusividade praticamente em todos os tempos. Os resultados foram discutidos em termos de transporte de calor por fônons, onde a redução da difusividade térmica observada foi analisada considerando a diminuição do livre caminho médio dos fônons devido aos efeitos de espalhamento. / In this work we studied borosilicate glasses doped with nanoparticles of sulfur and Er3+ ions in order to determine the thermal diffusivity of the glassy system (SNABP), using the thermal lens technique. The spectroscopic properties of these samples were investigated by measuring absorption in the optical spectral region from 400 to 2000nm. The characterization of the thermo-optic properties was performed by thermal lens tecniqueby with excitation at 50mW to 3W. It was found that the thermal difusivity decreased when the SNABP matrix was doped with PbS nanocrystals and Er3+ ions. Thermal treatment of the SNABP samples reduced the thermal difusivity. The results were discussed in terms of heat transport by phonons, where the observed reduction in thermal diffusivity was analyzed considering the decrease in the mean free path of phonons due to the scattering effects.

Glasses and ceramics offer several unique characteristics over polymers or metals. However, they suffer from a shortcoming due to their brittle nature, falling short in terms of fracture toughness and mechanical strength. The aim of this work is to reinforce borosilicate glass matrix with reinforcements to increase the fracture toughness and strength of the glass. Boron nitride nanomaterials, i.e. nanotubes and nanosheets have been used as possible reinforcements for the borosilicate glass matrix. The tasks of the thesis are many fold which include: 1. Reinforcement of commercially derived and morphologically different (bamboo like and cylinder like) boron nitride nanotubes in borosilicate glass with the concentration of 0 wt%, 2.5 wt% and 5 wt% by ball milling process. Same process was repeated with reinforcing cleaned boron nitride nanotubes (after acid purification) into the borosilicate glass with similar concentrations. 2. Production of boron nitride nanosheets using liquid exfoliation technique to produce high quality and high aspect ratio nanosheets. These boron nitride nanosheets were reinforced in the borosilicate glass matrix with concentrations of 0 wt%, 2.5 wt% and 5 wt% by ball milling process. The samples were consolidated using spark plasma sintering. These composites were studied in details in terms of material analysis like thermo-gravimetric analysis, detailed scanning electron microscopy and transmission electron microscopy for the quality of reinforcements etc.; microstructure analysis which include the detailed study of the composite powder samples, the densities of bulk composite samples etc; mechanical properties which include fracture toughness, flexural strength, micro-hardness, Young’s modulus etc. and; tribological properties like scratch resistance and wear resistance. Cleaning process of boron nitride nanotubes lead to reduction in the Fe content (present in boron nitride nanotubes during their production as a catalyst) by ~54%. This leads to an improvement of ~30% of fracture toughness measured by chevron notch technique for 5 wt% boron nitride nanotubes reinforced borosilicate glass. It also contributed to the improvement of scratch resistance by ~26% for the 5 wt% boron nitride nanotubes reinforced borosilicate glass matrix. On the other hand, boron nitride nanosheets were successfully produced using liquid exfoliation technique with average length was ~0.5 µm and thickness of the nanosheets was between 4-30 layers. It accounted to an improvement of ~45% for both fracture toughness and flexural strength by reinforcing 5 wt% of boron nitride nanosheets. The wear rates reduced by ~3 times while the coefficient of friction was reduced by ~23% for 5 wt% boron nitride nanosheets reinforcements. Resulting improvements in fracture toughness and flexural strength in the composite materials were observed due to high interfacial bonding between the boron nitride nanomaterials and borosilicate glass matrix resulting in efficient load transfer. Several toughening and strengthening mechanisms like crack bridging, crack deflection and significant pull-out were observed in the matrix. It was also observed that the 2D reinforcement served as more promising candidate for reinforcements compared to 1D reinforcements. It was due to several geometrical advantages like high surface area, rougher surface morphology, and better hindrance in two dimensions rather than just one dimension in nanotubes.