A otimização de combustíveis nucleares para uso em reatores a água pressurizada pode ser obtida pelo aumento da taxa de queima do combustível. Para isso, no entanto, é necessário levar em conta o aumento na reatividade inicial no reator, causada pelo maior enriquecimento do combustível. Esse problema, por sua vez, pode ser contornado por meio da introdução dos chamados venenos queimáveis diretamente nas pastilhas combustível de UO2. Alguns elementos do grupo das terras-raras possuem propriedades físicas e químicas que os tornam apropriados para esse uso dentro de reatores. Para caracterizar a microestrutura do combustível UO2 utilizado em reatores a água pressurizada dopado de érbio, pastilhas de UO2-Er2O3 foram preparadas, com teor de Er2O3 variando de 1,0 a 9,8 wt%, e analisadas por difração de raios X (DRX) para determinar se houve a formação de solução sólida pelo composto e determinar a variação do parâmetro de rede da solução em função da concentração de érbia. Apesar da análise por DRX ter mostrado que todo o érbio se incorporou à rede de UO2, ela também evidenciou a emergência de uma segunda fase, de estrutura do tipo fluorita, e cuja fração mássica aumenta em função do teor de érbia, enquanto seu parâmetro de rede diminui. Esses resultados são compatíveis com o fenômeno de segregação de defeitos, que consiste na formação de microdomínios segregados da rede principal nos quais há uma concentração maior dos defeitos i.e. são regiões mais ricas em érbio. Assim, a análise por DRX mostrou que houve formação de solução sólida de (U,Er)O2, mas que são necessários ajustes nos parâmetros de sinterização para que seja obtida uma solução monofásica. / Optimization of nuclear fuel for use in pressurized water reactors can be achieved by obtaining higher burnups. This, however, requires the excess reactivity caused by increasing the fuels enrichment to be taken into account, which can be done by introducing burnable absorbers into the UO2 fuel pellets themselves. Some of the rare earth elements have thermal and mechanical properties that make them appropriate for use inside the reactor. In order to characterize the microstructure of erbium-doped UO2 fuel, sintered UO2-Er2O3 pellets were prepared, with Er2O3 content ranging from 1.0 to 9.8wt%, and analyzed by X-ray diffraction to determine whether the composite formed solid solutions and, if so, evaluate the lattice parameter as a function of erbia concentration. While XRD analysis showed the Er2O3 completely dissolved in the UO2 powder, it also evidenced the emergence of a second fluorite-type phase, whose phase fraction increases and lattice parameter decreases with increasing erbia concentration. Analysis of the diffraction patterns showed this emerging phase has the same crystalline structure as the host lattice, but with a smaller lattice parameter. These results are compatible with the phenomenon of defect segregation, which consists in the formation of microdomains with a higher concentration of defects i.e. rare-earth richer regions. Thus, XRD analysis showed the formation of (U,Er)O2 solid solution, but such that there are still adjustments in the sintering parameters that need to be made in order to achieve a single-phase solid solution.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-07-21T11:52:53Z No. of bitstreams: 1 carlagrijofonseca.pdf: 2158196 bytes, checksum: 37ce85a4e86118ec5feb00909a92bb90 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-09T13:13:20Z (GMT) No. of bitstreams: 1 carlagrijofonseca.pdf: 2158196 bytes, checksum: 37ce85a4e86118ec5feb00909a92bb90 (MD5) / Made available in DSpace on 2017-08-09T13:13:20Z (GMT). No. of bitstreams: 1 carlagrijofonseca.pdf: 2158196 bytes, checksum: 37ce85a4e86118ec5feb00909a92bb90 (MD5) Previous issue date: 2013-07-26 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Compostos tipo hidrotalcita têm sido amplamente utilizados em catálise heterogênea, como catalisadores, suporte para catalisadores ou como precursor de catalisadores. A principal razão para isso é a capacidade desses materiais para gerar, por decomposição térmica, óxidos mistos de composição Mg1-x Alx □x/2 O(1+x/2) , com área superficial elevada (>200 m2 g-1). Embora se reconheça a importância desse óxido, a estrutura destes materiais não é bem conhecida. Eles são obtidos na forma de pó e em geral apresentam baixa cristalinidade, o que dificulta a análise via difração de raios X por policristais. Dados de RMN de 27Al e EXAFS mostraram que alguns cátions de Al migram de sítios octaédricos para sítios tetraédricos durante o processo de decomposição térmica. Com isso, algumas propostas de estrutura têm sido sugeridas por alguns autores: a princípio estruturas com cátions em sítios octaédricos somente, e a partir dos resultados de RMN, estruturas com átomos de Al localizados em sítios octaédricos e tetraédricos. Como não há informações conclusivas sobre a estrutura, a utilização de cálculos teóricos para propor modelos estruturais que podem descrever este composto, se torna uma abordagem promissora. Este trabalho tem por objetivo a utilização de um algoritmo genético (AG), de modo a obter modelos estruturais com diferentes composições que possam simular as características estruturais do Mg(Al)O. Nestes modelos, somente sítios octaédricos foram ocupados por cátions e vacâncias e a estabilidade relativa entre as diferentes propostas foi avaliada pela energia total, que foi inicialmente calculada com o GULP, por meio de potenciais interatômicos, e em uma segunda etapa por cálculos ab initio baseados na Teoria do Funcional da Densidade. AG's são robustos, genéricos e facilmente adaptáveis. Basicamente, o que um AG faz é criar uma população de possíveis respostas para o problema a ser tratado para depois submetê-la ao processo de evolução em busca das melhores soluções. O AG foi previamente testado e mostra resultados satisfatórios, pois converge em 100% dos casos para a estrutura teste previamente conhecida, sendo possível a sua utilização em problemas onde a estrutura não é completamente resolvida, como é o caso do Mg(Al)O. Este estudo também demonstrou a vantagem do uso de potenciais interatômicos, devido ao grande número de candidatos produzidos pelo AG. As características das estruturas mais estáveis do óxido misto Mg(Al)O foram confrontadas com propriedades disponíveis na literatura, tais como, DRX por policristais, parâmetros geométricos e dados termodinâmicos. Os resultados sugerem que os modelos investigados são a princípio representativos da estrutura do óxido misto obtido por algumas rotas da calcinação da hidrotalcita. / Hydrotalcite-type compounds have been widely used in heterogeneous catalysis, as catalysts as supports for catalysts or as catalyst precursor. The main reason for this is the ability of these materials to generate, by thermal decomposition, mixed oxides of composition Mg1-x Alx □x/2 O(1+x/2) , with a relatively high surface area (> 200 m2 g-1). In spite of the importance of the mixed oxides being recognized, the structure of these materials is not wellknown. They are obtained in powder form and usually have low crystallinity degree, making it difficult to analyze in detail the structure of the mixed oxide by X-ray diffraction . 27Al MAS-NMR and EXAFS data showed that some Al cations migrate from octahedral to tetrahedral sites during thermal decomposition. Thus, some models have been suggested by some authors: first, structures with cations in octahedral sites only, and due to the results of NMR, structures with Al atoms located in tetrahedral and octahedral sites. Since there is no conclusive information about the structure, the use of theoretical calculations to propose structural models which can describe the structure, can be a promising approach. This work aims to the use of a genetic algorithm (GA), in order to obtain structural models with different compositions that can simulate the structural characteristics of the Mg(Al)O. In these models only octahedral sites were occupied by cations and vacancies. The relative stability between the various proposals was evaluated by the total energy, that was first calculated with the GULP program, through interatomic potential, and in a second step by ab initio calculations based on Density Functional Theory. GA's are robust, generic and easily adaptable. Basically, what makes a GA is create a population of possible answers to the problem being treated and then submit it to the process of evolution in search of the best solutions. GA was previously tested and showed satisfactory results because converges in 100% of cases for the test structure previously described, being possible its use in problems where the structure is not completely solved, as is the case of the Mg(Al)O oxide. This study also demonstrated the advantage of using interatomic potential due to the large number of candidates produced by the GA. The characteristics of the more stable Mg(Al)O mixed oxide structures were compared with the properties available in the literature, such as XRD, geometrical parameters and thermodynamic data, The results suggest that the models investigated are representative of the mixeds oxides structure obtained by some routes of the thermal decomposition of the MgAl hydrotalcite.

Les batteries lithium ions sont la technologie de référence pour le stockage électrochimique de l’énergie. Cependant, les matériaux cathodiques de ces batteries comme LiCoO2, LiMn2O4 ou LiFePO4 présentent une capacité spécifique limitée (<160 mAh/g). De nombreux composés sont à l’étude pour améliorer cette performance dont le fluorure de fer (III) en raison de sa capacité théorique de 711 mAh.g-1. Ce travail présentera la synthèse de FeF3 par différentes méthodes de fluoration. Les matériaux obtenus seront comparés en termes de structures et de liaison (DRX, Mössbauer, spectroscopies IR et Raman) mais aussi de texture (isothermes d’adsorption à l’azote à 77K). Les propriétés électrochimiques des matériaux obtenus seront également comparées et testées. Enfin, l’étude du mécanisme électrochimique de cette famille de composés sera menée via une méthode de caractérisation « in operando » : la spectroscopie d’absorption des rayons X (XAS). / The lithium-ion batteries are the current solution for electrochemical energy storage. However, their performances are limited by the cathode materials, such as LiCoO2, LiMn2O4 or LiFePO4 of specific capacity lower than 160 mAh/g. Many materials are good candidates to improve this capacity such as iron trifluoride of theoretical capacity of 711 mAh.g-1. This work will present the synthesis of FeF3 through different fluorination ways. The resulting materials will be characterized owing to their structure by XRD, Mössbauer, Raman and IR spectroscopies and their texture by nitrogen adsorption isotherms at 77K and SEM. After that, the electrochemical properties will be evaluated and compared. Finally, the study of the electrochemical mechanism of this family of compounds will be led with a method of characterization “in operando” : the X-rays absorption spectroscopy (XAS).

Although the austenitic stainless steels 304 and 321 are often treated nominally as equivalents in their hot rolling characteristics, the question remains whether any subtle differences between the two allow further optimisation of their respective hot rolling schedules. The hot workability of these two types of austenitic stainless steels was compared through single-hit Gleeble simulated thermomechanical processing between 800℃ and 􀀄􀀅00℃ while the strain rate was varied between 0.00􀀄s􀀈􀀉 and 5s􀀈􀀉. It was found that the constants for the hyperbolic sinh equation for hot working of AISI 321 steel are Q = 465 kJ/mol, 􀀖􀀗 = 􀀘.􀀙6 􀀚 􀀄0􀀉􀀛 􀀜􀀝􀀞􀀈􀀉􀀟􀀈􀀉, 􀀠 = 0.00􀀘 􀀜􀀝􀀞􀀈􀀉 and 􀀡 = 6.􀀄 while for 304 steel the constants are Q = 446 kJ/mol, 􀀖􀀗 = 􀀅.􀀄4 􀀚 􀀄0􀀉􀀛 􀀜􀀝􀀞􀀈􀀉􀀟􀀈􀀉, 􀀠 = 0.008 􀀜􀀝􀀞􀀈􀀉and 􀀡 = 6.􀀄. It is shown that the occurrence of dynamic recrystallisation starts when the Zener-Hollomon parameter 􀀢 􀀣 6.4 􀀚 􀀄0􀀉􀀛s􀀈􀀉 for both steels but that the differences in the values of Q and A3 (the structure factor) between the two steels does lead to consistently lower steady state stresses for the steel 321 than is found in the steel 304 at the same Z values. This may, therefore, offer some scope for further optimisation of the hot rolling schedules and in particular in the mill loads of these two respective steels. A modelled constitutive equation derived from hot working tests to predict hot rolling mill loads is proposed and validated against industrial hot rolling data for AISI 321 stainless steel. Good correlation is found between the predicted Mean Flow Stress, the Zener-Hollomon Z parameter and actual industrial mill load values from mill logs if allowances are made for differences in Von Mises plane strain conversion, friction and front or back end tension. The multipass hot working behaviour of this steel was simulated through Gleeble thermomechanical compression testing with the deformation temperature varying between 1200℃ down to 800℃ and the strain rate between 0.001s-1 and 5s-1. At strain rates greater than 0.05s-1, dynamic recovery as a softening mechanism was dominant, increasing the dynamic recrystallisation to dynamic recovery transition temperature DRTT to higher temperatures. This implies that through extrapolation to typical industrial strain rates of about 60s-1,most likely no dynamic recrystallisation in plant hot rolling occurs in this steel but only dynamic recovery. Grain refinement by DRX is, therefore, unlikely in this steel under plant hot rolling conditions. Finally, mill load modelling using the hot working constitutive constants of the near-equivalent 304 instead of those specifically determined for 321, introduces measurable differences in the predicted mill loads. The use of alloy-specific hot working constants even for near-equivalent steels is, therefore, recommended. / Thesis (PhD)--University of Pretoria, 2014. / lk2014 / Materials Science and Metallurgical Engineering / PhD / unrestricted

L’acier inoxydable martensitique à l’azote XD15NW (Fe–15,5%Cr–0,4%C–0,2%N–1,7%Mo–0,3%V) est un candidat attractif pour les bagues de roulement des moteurs spatiaux. Il possède de bonnes propriétés mécaniques et une bonne résistance à la corrosion grâce à l’azote qui contribue à la formation de précipités de petite taille dans une matrice à grains fins. Nous avons étudié les évolutions microstructurales de cet acier au cours d’une succession de traitements thermiques: austénitisation et trempe, revenu, traitement de surface par induction. Outre les techniques usuelles d’analyse microstructurale (MEB, MET, dilatométrie), nous avons utilisé la diffraction des rayons X de haute énergie in situ (rayonnement synchrotron). Cette technique nous a permis d’obtenir les cinétiques d’évolution des phases en fonction de la température et du temps, les gradients de microstructure au sein de pièces traitées par induction en surface et les évolutions de paramètres de maille des phases / The nitrogen martensitic stainless steel XD15NW (Fe–15,5%Cr–0,4%C–0,2%N–1,7%Mo–0,3%V) is an attractive candidate for the bearing rings of the space engines turbopumps. It owns good mechanical properties and a good corrosion resistance thanks to the nitrogen which contributes to the formation of little size precipitates in a fine grains matrix. The microstructural evolutions of this steel during a succession of thermal treatments were studied: austenitisation and quenching, tempering, induction surface heat treatment. In addition to the usual techniques of microstructural analysis (SEM, TEM, dilatometry), the in situ high energy synchrotron X-ray diffraction was used. It allowed to obtain the evolution kinetics of the phases as a function of temperature and time, the microstructural gradients in induction treated samples and the lattice parameters evolutions which are linked to the chemical composition or the internal stresses evolutions of the phases

Les piles au lithium tiennent une place importante dans de nombreuses applications, notamment dans le secteur industriel à forte valeur ajoutée. Les oxyfluorures de graphites et graphènes, ainsi que leurs précurseurs oxydes, ont été identifiés comme des matériaux de cathode pouvant permettre d’augmenter la densité d'énergie de ces piles. Durant cette thèse, afin d’obtenir des nouveaux oxyfluorures de graphite, deux voies de synthèse ont été prospectées. Lors de la synthèse enchainant oxydation de Hummers puis fluoration gaz-solide, le paramètre température d’oxydation a été modulé et a donné lieu à des composés contenant des proportions différentes de fonctions oxygénées de type OH, COOH, COC. Lors de la synthèse débutant par la fluoration, différentes méthodes de fluoration ont été mise en oeuvre faisant agir soit le fluor moléculaire soit le fluor radicalaire à deux échelles de synthèse (laboratoire et micropilote). Une caractérisation minutieuse des matériaux issus de chaque voie, croisant les analyses structurales (DRX, ATG, diffusion Raman...) et analyses chimiques (IR, RMN, XPS...) a permis de cerner les modularités sur les effets de structure et de distribution de fonctions à l'échelle locale. Ce panel de composés a été testé en décharge galvanostatique en pile au lithium afin de corréler activité électrochimique des fonctions et gain en performances. / Primary Lithium Batteries are substantial in many applications, particularly in industrial niche sectors. Graphite oxifluorides and their precursors, graphite oxides, are promising materials for the cathodes. We explored two-step synthesis combining Hummers' oxidation and solid-gas fluorination. Temperature of oxidation was key parameter to control OH, COC and COOH ratio. Direct fluorination and controlled fluorination were processed at laboratory and scaled-up. Because of complexity of the materials and specificity at each scale, we cross-checked the data from several techniques for structure (XRD, TGA, Raman spectroscopy...) and chemistry (IR, MAS NMR, XPS...) for an accurate picture. We tested the broad set of materials. Galvanostatic discharges enabled us to understand the electrochemical activity of functions at stake and key factors of design for better performances.

Plusieurs structures hiérarchisées des fluorures de fer et de nickel avec des matrices carbonées ou métalliques ont été obtenues par deux voies de fluoration : fluoration gaz-solide de nanoparticules par le fluor moléculaire pur ou par fluoration en milieu liquide via l’agent fluorant NH 4 F. Les différentes nanostructures des matériaux ainsi préparées ont été caractérisées par les techniques classiques de microscopies électroniques, de spectroscopies vibrationnelles (infrarouge et Raman) ou encore d’analyse thermogravimétrique. En complément, la diffraction des rayons X a permis d’étudier les matériaux tant à l’ordre global, qu’à l’ordre local par affinement et analyse PDF sous rayonnement synchrotron. Ainsi, les conditions de synthèse et les mécanismes de formation de différents assemblages de type 0D avec des structures core-shell nickel/fluorure de nickel ; mais aussi 1D avec des nanotubes de carbone double parois remplis par du fluorure de fer, ou encore 3D (« flower-like ») avec le greffage de nanoparticules de fluorures de nickel en surface de nanotubes de carbone simple ou multi parois ont pu être appréhendés. Finalement, les nanostructures les plus adaptées à la diffusion des ions lithium (particules core-shell et flower-like) ont finalement été testées comme matériaux de cathode. / Some hierarchized structures made of iron or nickel fluorides together with carbonaceous or metallic matrix were obtained owing to two fluorination ways : solid-gas fluorination proceeding by pure molecular fluorine gas or fluorination in liquid media using NH 4 F in solution. The different nanostructures have been characterized thanks to classical technics such as electronic microscopies, vibrational spectroscopies (infrared and Raman) or thermogravimetric analysis. Many attentions have been paid to determine the global and local structures by using X-ray diffraction, refinement of the diffraction pattern by Rietveld analysis or Pair Distribution Function analysis on pattern registered on synchrotron. So, the synthesis conditions and the formation mechanism of various assemblies have been carried out on 0D core-shell nickel/ nickel fluoride, 1D double-walled carbon nanotubes filled with iron fluoride or 3D single and multi-walled carbon nanotubes decorated with flower-like nickel fluoride. Finally, the nanostructures the most favorable to lithium-ion diffusion (core-shell and flower like nanostructures) have been used as electrode in secondary lithium batteries.

Le kétoprofène est un anti-inflammatoire non stéroïdien connu par ses propriétés analgésiques et antipyrétiques. Cependant, il présente une très faible solubilité dans l'eau, ce qui limite sa biodisponibilité. Afin de résoudre ce problème, le principe actif est administré sous forme de sels solubles dans l’eau avec le sodium, la lysine, l’arginine, la N-méthylglucamine et le trométamol. L’objectif de cette thèse était d’apporter pour la première fois la caractérisation structurale des sels de kétoprofène racémique et du S-kétoprofène avec la L-lysine et le trométamol, et de chercher à obtenir la structure cristalline de nouveaux co-cristaux ou sels de kétoprofène, pour analyser la relation structure-propriétés de ces formes solides. Nous avons réussi à faire la croissance cristalline des sels de kétoprofène racémique et de S-kétoprofène avec le trométamol et la L-lysine, ainsi qu’avec l’amine 2-amino-2-méthylpropanol. L’analyse des structures de ces sels a montré qu’ils sont tous formés par des couches anioniques de kétoprofènates entre les quelles s’insèrent les cations grâces aux liaisons hydrogène fortes de type N-H…O et O-H…O. Les cations forment des couches dans les sels avec le trométamol et la L-lysine. Cependant, ils ne sont connectés que par des interactions de Van der Waals dans les sels de 2-amino-2-méthylpropanol. La cohésion des couches anioniques est assurée par des interactions faibles de type C-H…O, C-H…π ou C-H…N. L’étude de l’épaisseur des couches anionique, ainsi que la surface et le volume occupé par un anion kétoprofènate dans une couche montre des variations significatives dans les différents sels. Ces variations peuvent être expliquées par des différences des conformations des anions kétoprofènates. L’étude des paramètres géométriques des anions kétoprofènates dans les sels et ceux des molécules de kétoprofène dans les principes actifs montre que les variations les plus importantes touchent les angles de torsions engageant le groupement carboxylate/acide carboxylique qui interagit avec les molécules/anions voisines par des liaisons hydrogène intermoléculaires courtes et fortement directionnelles. Les interactions dans lesquelles les cycles aromatiques sont engagés sont plutôt faibles, par conséquent les angles de torsions mettant en jeu ces cycles varient peu dans les différentes structures cristallines. Différentes techniques ont été également utilisées pour caractériser les sels : diffraction des rayons X sur poudre, calorimétrie différentielle à balayage (DSC), spectroscopie infrarouge (IR), analyse thermogravimétrique (ATG) et résonance magnétique nucléaire à l’état solide (RMN). Les résultats obtenus ont été corrélés aux structures cristallines. Les mesures de solubilité du sel de kétoprofène racémique-trométamol et des deux polymorphes des sels de S-kétoprofène avec le trométamol confirment que ces derniers ont des solubilités très améliorées par rapport aux principes actifs purs / Ketoprofen is a non-steroidal anti-inflammatory drug known by its analgesic and antipyretic properties. However, it has a very low water solubility, which limits its bioavailability. To solve this problem, the active pharmaceutical ingredient is administered as a water soluble salt with sodium, lysine, arginine, N-methylglucamine or trometamol. The scope of this thesis is to study, for the first time, the crystal structures of salts of both racemic and S-ketoprofen with L-lysine and trometamol, and to obtain the crystal structure of new ketoprofen co-crystals or salts, in order to analyze the relationship between the structure and the properties of these solid forms. We succeeded to control the crystal growth of the salts of racemic and S-ketoprofen with trometamol and L-lysine, and with 2-amino-2-methyl propanol. The analysis of these salt structures has shown that they are formed by anionic layers of ketoprofenates which are inserted between the cations thanks to strong N-H...O and O-H...O hydrogen bonds. The cations form layers in trometamol and L-lysine salts. However, they are only connected by van der Waals interactions in the salts of 2-amino-2-methylpropanol. The cohesion of the anionic layers is ensured by weak C-H...O, C-H...π or C-H...N interactions. The study of the thickness of anionic layers, as well as that of the surface and the volume occupied by a ketoprofenate anion in each anionic layer, shows significant differences in the salts. These variations may be explained by differences in the conformations of ketoprofenates anions. The study of geometrical parameters of ketoprofenate anions in the salts and those of the ketoprofen molecules in the pure active ingredients shows that the most important changes affect the twisting angles engaging the carboxylate/carboxylic acid that interacts with neighboring molecules/anions by short and highly directional intermolecular hydrogen bonds. The interactions in which the aromatic rings are incurred are rather weak, therefore the twisting angles involving these cycles slightly vary in the different crystal structures. Various techniques have also been used to characterize the salt, such as powder X-ray diffraction, differential scanning calorimetry (DSC), infrared (IR) spectroscopy, thermogravimetric analysis (TGA) and solid state nuclear magnetic resonance (NMR). The results were correlated with the crystal structures. The solubility measurements of the racemic ketoprofen-trometamol salt and the two polymorphs of S-ketoprofen-trometamol salts confirm that they have greatly improved solubility compared to the pure active ingredients

La famille des matériaux semiconducteurs III-N présente des propriétés adéquates pour diversesapplications que ce soit dans le domaine de l’optique ou de l’électronique. Certaines de ces applicationsconsistent à intégrer ces matériaux dans des environnements hostiles et notamment soumis à l’actiond’ions lourds à différentes énergies. Lors de cette thèse, le travail consistait tout d’abord à comprendrel’évolution microstructurale sous irradiation du substrat alpha-Al2O3, puis du film mince GaN, afin d’établirun profil de l’évolution de l’endommagement en fonction de la profondeur. Un comportement assezsimilaire concernant l’évolution des paramètres de maille a été observé pour les deux matériaux. Dansla direction parallèle à la trajectoire du faisceau d’ions, une importante augmentation du paramètre demaille a été mise en évidence tandis que peu de variations ont été relevées perpendiculairement à latrajectoire du faisceau d’ions. Les formations de couche amorphe pour l’alpha-Al2O3 et de couche fortementendommagée pour le GaN ont été observées en surface. Les épaisseurs de ces couches augmentent enfonction de la fluence, associé à l’augmentation des contraintes résiduelles au sein du matériau. Al’aide d’hypothèses et des différents résultats obtenus, deux profils d’endommagement en profondeuront été proposés. D’autre part, la nanoindentation a montré que les paramètres de dureté et de moduled’élasticité évoluent fortement sous irradiation en fonction de la fluence. / Nitride semiconductors are attractive materials for the development of optical and electronic devices.Some of these applications can expose materials to extreme environments and especially radiation ofheavy ions at different energies. In this thesis, the study focused first on behaviour evolution underirradiation of alpha-Al2O3 and then of GaN thin film, in order to establish a profile of damage evolution asfunction of the depth. Concerning lattice parameter, a similar behaviour was observed for both materials.An important increase of lattice parameter parallel to ion beam was highlighted while few variations wasnoted for the lattice parameter perpendicular to ion beam. Formation of amorphous layer for alpha-Al2O3and highly disordered layer for GaN were observed in surface. Layers thicknesses increase as functionof the fluence with an increase of residual stresses in material. Using different results and assumptions,two damage profiles as function of the depth have been proposed. In addition, nanoindentation hasshown hardness and modulus of elasticity parameter evolve highly under irradiation as function of thefluence.

El principal problema que afecta a la vida útil de las estructuras de hormigón armado es la corrosión de las armaduras. Los riesgos más importantes para dicha corrosión son la carbonatación del recubrimiento de hormigón y el ingreso de iones cloruro. Por estas razones, la investigación en nuevos conglomerantes que favorezcan la resistencia a la corrosión de las armaduras es un campo de interés para la ingeniería civil. El catalizador de craqueo catalítico (FCC) es un material de base solicoaluminosa y estructura zeolítica que se usa en las refinerías de petróleo. Cuando el FCC pierde sus propiedades catalíticas, se debe reemplazar por nuevo catalizador. En estudios previos se ha comprobado que el FCC mejora las propiedades emcánicas de los morteros y hormigones debido a una densificación de la matriz cementicia causada por la reacción puzolánica. No obstante, existe una carencia en el conocimiento de cómo la incorporación de este residuo puede afectar a la corrosión de las armaduras de hormigón frente a los clásicos ataques por dióxido de carbono y cloruros. Este trabajo se ha llevado a cabo para estudiar el papel del FCC en el proceso de corrosión de las armaduras de hormigón, cuando se emplea como sustitución parcial del cemento, sometiendo probetas de mortero con FCC a ambientes agresivos (Co2 y Cl-). Se realizaron ensayos de carbonetación acelerada de morteros con distintos niveles de sustitución de cemento por FCC y varias relaciones agua/material cementante (a/mc). En los mismos se puedo comprobar que el consumo de parte de la reserva alcallina de los morterios debido a la reacción puzolánico del FCC, puede ser un factor que acelere el proceso de carbonatación de los recubrimientos de hormigón. No obstante, este fenómeno sólo se puso de manifiesto para relaciones a/mc elevadas. Para relaciones a/mc inferiores a 0,5, la incorporación de FCC en cantidades de hasta el 15% con respecto al peso de cemento, no ofrecía diferencias significativas en cuento a la vel / Zornoza Gómez, EM. (2007). El papel del catalizador usado de craqueo catalítico (fcc) como material puzolánico en el proceso de corrosión de armaduras de hormigón [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/1843