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Thermal barrier coatings (TBCs) are advanced material systems used in the hot sections of gas turbines. The TBCs are designed to provide insulation against hot gases by a ceramic top coat and to provide oxidation and corrosion resistance by a metallic bond coat. As the operating environment is harsh and complex, the TBC often requires stricter material properties. Failure of TBCs can limit the longevity of the turbine severely. In this study, failure caused by erosion has been the main focus. The erosion behaviour of TBCs processed by atmospheric plasma spay (APS), electron beam physical vapour deposition (EB-PVD), and plasma spray physical vapour deposition (PS-PVD) has been studied by an experimental investigation and a literature study. The erosion performance of different TBCs was studied by conducting erosion tests under 90° and 15° alumina particle impact (50 μm) and measuring the weight loss and thickness loss of the ceramic top coat. Variables affecting the erosion behaviour were studied by means of scanning electron microscopy (SEM), investigating the microstructure, the erosion damage, porosity content, and column density. Hardness tests were also conducted to investigate a potential correlation between hardness and erosion performance. It was evident that the 8YSZ top coat processed by EB-PVD had higher erosion resistance than APS, which in turn had higher erosion resistance than PS-PVD. Their microstructures are significantly different, resulting in different erosion failure mechanisms. APS TBCs have a splat-on-splat lamellar microstructure, and the failure mechanismsare ploughing of furrows, splat boundary failure, and tunneling via pores. In contrast, EB-PVD TBCs have columnar microstructure and fail by near-surface cracking. The investigated PS-PVD TBC had a feathery columnar microstructure, containing many large grain boundaries and flaws, making grain boundary failure the governing mechanism. The APS and EB-PVD TBCs impacted at a 90° angle had significantly higher erosion rates than those eroded at 15°, which also was reported in literature. However, the opposite was observed for the PS-PVD TBCs. The level of porosity and hardness of the TBC top coat was found to affect the erosion rate, even though no evident correlations could be observed in this study. No factor alone was found to dictate the erosion behaviour of the investigated TBCs. Based on the literature study and findings in the experimental study, a TBC with good erosion performance has, in general, low porosity, few defects, high hardness and high fracture toughness. Specifically for APS TBCs, good splat bonding is favourable and for EB-PVD and PS-PVD it recommended to have high column density, columns orthogonal to the substrate, and low gap width between the columns.

En las últimas décadas, el interés por los sistemas poliméricos, en particular por los copolímeros bloque, ha ido incrementándose, no solo desde el punto de vista académico sino también desde el tecnológico, porque permiten obtener materiales con propiedades especificas debido a la presencia de sus dos o más fases. Además, los copolímeros bloque presentan procesos de separación en microfases o formación de estructuras auto-ensambladas que los convierte en excelentes candidatos para aplicaciones en nanotecnología y electrónica. En esta Tesis se desarrollan técnicas para la obtención de membranas nanoporosas a partir del auto-ordenamiento de copolímeros bloque de Poli(estireno)-bloque-Poli(metil metacrilato), PS-b-PMMA. Los copolímeros fueron sintetizados, empleando polimerización aniónica en alto vacío, y caracterizados química y térmicamente mediante numerosas técnicas analíticas, tales como Cromatografía por exclusión de tamaños (SEC), Resonancia Magnética Nuclear de protón (1H-NMR), Espectroscopia Infrarroja con Transformada de Fourier (FTIR), Calorimetría Diferencial de Barrido (DSC), Análisis Termogravimétrico (TGA). Todos los copolímeros mostraron tener un control adecuado de las masas molares, presentando bajos índices de polidispersión para un amplio rango de masas molares y composiciones, además los resultados permitieron corroborar la formación de nanoestructuras. Se prepararon películas de los copolímeros sobre sustratos de silicio (Si), en los cuales se implementaron técnicas para la orientación de los dominios de PMMA en la matriz de PS. La metodología con mejores resultados fue la aplicación de una película de un copolímero al azar de PS-r-PMMA, de composición similar a los copolímeros bloque, que actúe como neutralizante del sustrato de modo que ambos bloques del copolímero sean afines a la superficie. Posteriormente, se degradó el bloque de PMMA, de manera de obtener una membrana nanoporosa. Estas membranas se caracterizaron morfológicamente mediante Microscopía de Fuerza atómica (AFM), y Microscopía electrónica de barrido (SEM). Las membranas nanoporosas presentaron poros de los tamaños esperados de modo de poder convertirse en prototipos para la preparación de membranas de filtración en aplicaciones industriales, como por ejemplo, filtros de virus. Los resultados informados en esta Tesis constituyen un aporte de interés respecto a las técnicas de preparación de membranas ya existentes. En tal sentido, se ha desarrollado una metodología de separación de las películas del sustrato, de modo de poder desarrollar una tecnología que permita soportarlas en sustratos porosos con el objeto de obtener membranas de filtración de virus u otras sustancias de tamaños similares. / In recent decades, interest in polymeric systems, in particular block copolymers, has been increasing, not only from the academic but also from the technological point of view. This allows obtaining materials with specific properties due to the presence of the two or more phases. In addition, block copolymers exhibit microphase separation and the formation of self-assembled structures, which makes them excellent materials for applications in nanotechnology and electronics. In this thesis, techniques were developed for obtaining nanoporous membranes from the self-ordering of polymer blocks in Poly(styrene) -block-Poly (methyl methacrylate), PS-b-PMMA. The copolymers were synthesized using high vacuum anionic polymerization and characterized chemically and thermally using analytical techniques such as Size Exclusion Chromatography (SEC), Proton Nuclear Magnetic Resonance (1H-NMR), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA). All the copolymers showed adequate control of the molar masses, presenting low polydispersity rates on a wide range of molar masses and compositions, besides the results allowed to corroborate the formation of nanostructures. Films of the copolymers were prepared on silicon (Si) substrates, in which several technics were implemented for the orientation of the PMMA domains in the PS matrix. The methodology with the best results was the application of a film of a random PS-r-PMMA copolymer, of similar composition to the block copolymers, which acts as a neutralizer of the substrate so that both blocks of the copolymers are surface related. Subsequently, the PMMA block was degraded in order to obtain a nanoporous membrane. These membranes were characterized morphologically by Atomic Force Microscopy (AFM), and Scanning Electron Microscopy (SEM). Nanoporous membranes presented pores of the expected sizes for converting in prototypes for the preparation of filtration membranes in industrial applications, such as virus filters. The results reported in this thesis constitute a contribution of interest regarding the techniques of preparation of already existing membranes. In this sense, a methodology has been developed for separating the films from the substrate, in order to develop a technology that allows them to be supported on porous substrates with the object of obtaining filtration membranes for virus or similar sized substances.

No / The paper presents a 2-D large eddy simulation (LES) modelling approach to investigate the properties of the plunging waves. The numerical model is based on the smoothed particle hydrodynamics (SPH) method. SPH is a mesh-free Lagrangian particle approach which is capable of tracking the free surfaces of large deformation in an easy and accurate way. The Smagorinsky model is used as the turbulence model due to its simplicity and effectiveness. The proposed 2-D SPH-LES model is applied to a cnoidal wave breaking and plunging over a mild slope. The computations are in good agreement with the documented data. Especially the computed turbulence quantities under the breaking waves agree better with the experiments as compared with the numerical results obtained by using the k- model. The sensitivity analyses of the SPH-LES computations indicate that both the turbulence model and the spatial resolution play an important role in the model predictions and the contributions from the sub-particle scale (SPS) turbulence decrease with the particle size refinement.

Partie créative : À un pas. Nous sommes tous à un pas de la mort. Ou presque. Comment vivre avec cette menace qui plane toujours au-dessus de nos têtes ? Comment vivre avec la perte d'êtres chers ? Dix nouvelles qui décortiquent la mort sous plusieurs angles, qui se font écho entre elles dans une structure architecturale particulière, qui sont intrinsèquement liées, comme la mort et la vie. De ce thème macabre jaillit, paradoxalement, surtout une passion pour la vie, un désir de vivre. La vie est parfois plus forte que tout. Quand la mort ne s'en mêle pas. Partie réflexive : Écrire pour l'éternité. Pourquoi écrire ? Tous les humains sont voués à mourir un jour, à disparaître. Mais les écrits, eux, restent. L'écriture ne meurt pas. Elle existe pour toujours. Écrire pour laisser une trace, pour défier la mort un mot à la fois. Écrire pour fuir la mort en s'inscrivant dans la pérennité, en déjouant le temps. Écrire pour ne pas mourir. Écrire pour vivre. Encore. Mieux. Écrire, c'est une passion, une façon de vivre, un souffle, une exaltation. Écrire encore et encore. Toujours. À jamais. Pour l'éternité. L'obsession de la mort peut donc être un thème inspirant pour des nouvelles, mais aussi la raison inconsciente qui pousse à écrire ces mêmes nouvelles. La mort omniprésente s'impose partout. Après tout, elle fait partie de la vie.