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.

A laboratory scale study was carried out on a set of 6 borosilicate waste glasses made from simulated high-level nuclear waste. The test matrix was designed to explore the composition region suitable for the long-term geologic disposal of high-temperature-and high-waste-containing glasses. The glass compositions were selected to achieve maximum waste loading without a sacrifice in glass durability. The relationship between glass composition and chemical durability was examined. The qualitative effect of increasing B2O3 content on the overall waste glass leaching behavior has also been addressed. The glass composition matrix was designed by systematically varying the factors: %waste loading and (SiO2+Frit):B2O3 ratio, with (SiO2:Frit) ratio being held constant. In order to assess the chemical durability, the Product Consistency Test (ASTM C-1285) was performed. Under PCT protocol, crushed glass was allowed to react with ASTM type I water under static conditions. All leachate solutions were analyzed by the technique; Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). A statistical regression technique was utilized to model the normalized release of the major soluble elements, Na, Si, and B, as a function of the individual as well as interactive chemical effects (B2O3, Al2O3, Fe2O3, MnO, SiO2, SrO, Na2O, B2O3*SiO2, B2O3*Al2O3, Fe2O3*Na2O, Al2O3*Na2O, and MnO*SiO2). Geochemical modeling was performed using the computer code EQ3/6 to: (1) determine the saturation states of the possible silicate minerals, a-cristobalite and chalcedony; and (2) predict the most stable mineral phase based on the mineral thermodynamic data. Mineral/water interactions were analyzed by representing the resultant glass data on a Na-Al-Si-O-H stability diagram.

No description available.

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

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)

La dissolution de verres borosilicatés en présence de minéraux magnésiens a été étudiée. Ces minéraux (dolomite, illite, smectite…) appartiennent à la couche géologique (Callovo-Oxfordien) destinée à accueillir le stockage des déchets nucléaires vitrifiés en France. Ils contiennent du magnésium, élément capable d'entretenir l'altération du verre lorsqu'il est disponible en solution. Dans les milieux confinés du stockage, la réactivité des solides contrôle la composition de la solution et peut être la force motrice de l'altération des verres nucléaires. Les expériences montrent que les carbonates magnésiens (hydromagnésite, dolomite) entretiennent l'altération du verre : la précipitation de silicates de magnésium empêche la recondensation du silicium dans la couche passivante en surface du verre. Plus le minéral magnésien est soluble, plus l'altération du verre est importante. Les phases argileuses purifiées (illite, smectite…) du Callovo-Oxfordien (COx) augmentent également l'altération du verre. La moitié du magnésium échangeable de ces phases a été remplacée par du sodium lors du protocole de purification. Dans ces conditions, l'effet des phases argileuses sur l'altération du verre est en partie dû au pH acide qu'elles imposent. Le modèle d'altération des verres GRAAL implémenté dans le code de transport réactif HYTEC a permis de confirmer et de quantifier les mécanismes identifiés à partir des expériences en système fermé. Des expériences en cellule de diffusion, deux compartiments séparés par une barrière diffusive inerte, ont permis de valider une modélisation du transport réactif. Ces expériences, plus représentatives des conditions de stockage, où le bloc de verre sera séparé du COx par les produits de corrosion des aciers, illustrent le ralentissement des cinétiques attendu compte tenu de l'éloignement du verre et des minéraux réactifs. / Borosilicate glasses dissolution has been studied in presence of magnesium minerals. Those minerals (dolomite, illite, smectite…) belong to the Callovo-Oxfordian (COx) claystone layer, studied in France as a potential site for nuclear waste disposal. Such minerals contain magnesium, an element able to sustain glass alteration when it is available in solution. In the confined media of the wastes disposal, thesolids reactivity controls the solution composition and can be the driving force of nuclear glass alteration. Experiments show that magnesium carbonates (hydromagnesite and dolomite) increase in the glass alteration: the precipitation of magnesium silicates consumes silicon which slows down the formation of the glass passivating layer. The lower the magnesium mineral solubility, the lower the glass alteration.The purified clay phases (illite, smectite…) from the COx layer increase the glass alteration. Half the magnesium was remplaced by sodium during the purification process. In such conditions, the effect of clay phases on glass alteration is in part due to the acidic pH-buffering effect of the clay fraction. The GRAAL model implemented in the geochemical transport code HYTEC has confirmed and quantified the mechanisms put in evidence in the experiments. Cells diffusion experiments where the two solids were separated by an inert diffusion barrier allow to valid reactive transport modelling. Such experiments are more representative of the glass package which will be separated from the COx by corrosion products. They show that glass alteration rate is reduced when solids are not close.

La vitrification des déchets nucléaires de hautes activités est une étape importante à maîtriser afin d’assurer leur confinement. Depuis 2010, un procédé de vitrification en creuset froid présentant de nombreux avantages est exploité à cet effet dans l’usine de La Hague. Cette technologie est basée sur la circulation de courants électromagnétiques directement dans la charge du creuset dont les parois sont refroidies. Grâce au gradient thermique créé entre ces parois refroidies et le bain de verre en fusion, une couche de verre solide appelée autocreuset est formée jouant le rôle de barrière anticorrosive et électriquement isolante. Du fait de leur composition et de leur microstructure complexes, l’étude des propriétés électriques et diélectriques des verres d’intérêt nucléaire et la compréhension des phénomènes mis en jeu sont nécessaires afin de maîtriser convenablement le fonctionnement du procédé en creuset froid ainsi que les simulations thermo-hydrauliques qui lui sont associées.L’étude présentée ici porte sur la description des phénomènes de mouvements de charges électriques à l’origine des propriétés électriques et diélectriques ayant lieu au sein de verres borosilicatés d’intérêt nucléaire. Des relations entre ces propriétés et la composition ainsi que la microstructure de ces verres sont également établies. Ces problématiques sont tout d’abord abordées dans le cas de deux verres technologiques inactifs de compositions complexes grâce à des caractérisations microstructurales et des mesures d’impédance complexe à l’état solide. Une description plus détaillée des phénomènes mis en jeu est réalisée grâce à la caractérisation de verres simplifiés à 5 oxydes (SiO2-B2O3-Na2O-CaO -RuO2 ou -MoO3) permettant ainsi une meilleure compréhension des mouvements de charges selon la fréquence du champ électrique, la température ainsi que la composition et la microstructure du matériau. / The vitrification of high-level nuclear waste is an important step to master in order to ensure their immobilization. Since 2010, a cold crucible induction melter is used in the La Hague plant due to its advantages. This process is based on electromagnetic currents directly induced on the load of the crucible whose walls are water-cooled. Thanks to the thermal gradient established between these cooled walls and the molten glass, a solid glass layer called self-crucible is created which protects the crucible from corrosion effects and acts as an electrical insulator. Due to their complex composition and microstructure, the study of electrical and dielectric properties of nuclear glasses and the understanding of the related phenomena are necessary in order to efficiently master the cold crucible process and the associated thermo-hydraulic simulations.This study is dealing with the description of the electric charge motion phenomena involving the electrical and dielectric properties of the nuclear borosilicate glasses. Relationships between these properties, the composition and the microstructure are also given. These issues are firstly broached through the investigation of two industrial inactive glasses of complex composition thanks to microstructure characterizations and complex impedance measurements in the solid-state. A more detailed description of the phenomena is performed thanks to the characterization of simplified glasses containing 5 oxides (SiO2-B2O3-Na2O-CaO -RuO2 or -MoO3) allowing a better understanding of the charge motion according to the electrical field frequency, the temperature, the composition and the microstructure of the material.

On étudie le comportement thermomécanique de colis de déchets vitrifiés par modélisation multi- physiques. Les colis sont réalisés avec un conteneur en acier inoxydable dans lequel est coulé un verre borosilicaté. Pour le verre, la méthode des éléments finis est employée pour les calculs thermiques, la relaxation structurale du volume massique, le comportement viscoélastique et l’endommagement. Ces lois consécutives modélisent l’influence de la sollicitation thermique initiale. La relaxation structurale du verre, issue du modèle TNM-KAHR, permet la prise en compte d’effets fondamentaux quant à la transition vitreuse, en fonction des traitements thermiques expérimentaux et simulés. Lorsque le verre dépasse localement une criticité du champ de contrainte, on procède au couplage du calcul de structure viscoélastique, pour le verre solide en relaxation,avec la mécanique de l’endommagement qui réactualise la rigidité et les contraintes en mode I et en mode II. On applique cette méthodologie complète de simulation à l’issue des adaptations nécessaires au cas de blocs de verre massifs en solidification. Ces modèles permettent alors l’obtention de surfaces de fracturation quantifiées, dans le verre, à partir de l’énergie dissipée par le modèle d’endommagement. / We study the thermomechanical behavior of vitrified waste packages by multiphysics modeling. The packages are manufactured by the cast of borosilicate glass into stainless steel canisters. The finite element method is used for the thermal computations.In the glass, the finite element analysis is also used to compute the specific volume evolution and the viscoelastic behavior, due to the structural relaxation of glass, as well as the simulation of the damage behavior. These consecutive behavior laws model theinfluence of the initial thermal response. Glass structural relaxation is computed using the TNM-KAHRmodel, which allows us to take into account fundamental phenomena of the glass transition, depending on the results of experimental and simulated thermal treatments. For the solid glass within this relaxation process, the stress may locally increase beyond critical values. The viscoelastic structure simulation is then coupled with continuum damage mechanics where stresses and stiffness are updated in mode I and mode II. We apply this simulation protocol after adopting conditions relative to the case of these manufactured bulky solidifying glass casts. The models then allow us to quantify the cracking surfaces inside the glass fromthe energy dissipated within the damagemodel.