Les technologies d'empilement vertical de circuits intégrés, plus connues sous le terme « intégration 3D », ont connu un développement important durant les six dernières années, dans l'optique de proposer une alternative aux approches bidimensionnelles traditionnelles comme les Systems on Chip (SoC). Cette nouvelle architecture a été adaptée au domaine du packaging des circuits intégrés à travers le packaging en 3D réalisé à l'échelle de la plaque ou 3D-WLP pour 3D-Wafer Level Packaging. L'intégration 3D-WLP permet une diminution des tailles des dispositifs finaux, une augmentation de la densité des interconnexions ainsi qu'une réduction des coûts de fabrication. La maîtrise de la réalisation des via traversant, ou TSV pour Through Silicon Via, est une étape clé qui permet d'assurer une connexion électrique entre les différents niveaux empilés. On s'intéresse dans ces travaux de thèse au TSV dans son approche via-last, c'est-à-dire fabriqué en face arrière du dispositif, après les transistors et les niveaux de métallisation de la face avant, et plus particulièrement à l'étape de passivation organique des TSV. En effet, ce via traversant est d'un diamètre trop important pour être complètement rempli avec sa métallisation en cuivre. L'étude concerne donc une solution incluant un remplissage en polymère afin d'améliorer la solution existante en termes de fiabilité et de compatibilité avec des empilements verticaux supplémentaires. / 3D integration technologies for integrated circuits have been widely developed during the six last years in order to propose an alternative to bi-dimensional approaches such as the Systems on Chip (SoC). This new architecture is also used for integrated circuits packaging through 3D-Wafer Level Packaging (3D-WLP). Thus, vertical stacking allows smaller package footprint, higher interconnection density and lower fabrication costs. Through silicon via (TSV) is a key technology that insures vertical electrical interconnection between the stacked levels. This thesis deals with the via-last approach which consists in realizing the TSV at the back-side of the wafer, after the Front End Of the Line (FEOL) and the Back End Of the Line (BEOL), both located at the front-side. During the metallization steps, only a copper liner is electroplated in the TSV since its diameter is too large to achieve a complete metal filling. This study focuses on the TSV polymer insulation step and more specifically, a solution including a TSV polymer filling in order to improve the existing configuration in terms of reliability and compatibility with further 3D stacking.

Dans un contexte général de réduction de la pollution atmosphérique, l’industrie automobile cherche à augmenter le rendement des moteurs thermiques pour en limiter la consommation et les émissions. Pour satisfaire cet objectif, les températures de combustion sont en constante augmentation, ce qui entraîne une augmentation de la sollicitation thermique de la face d’échappement de ces moteurs. Ces pièces n’étant pas refroidies, elles sont exposées à des températures toujours plus élevées, ce qui nécessite une durabilité à haute température accrue des matériaux. Cette thèse a pour objectif d’évaluer la durabilité des pièces de fonderie de la face échappement telles que les collecteurs, corps de turbine ou turbo collecteurs réalisées en fonte GSSiMo+ et en acier inoxydable moulé 1.4826Nb à des températures supérieures à leur température maximale actuelle d’utilisation. Une première étape a porté sur l’effet de la vapeur d’eau sur l’oxydation de la surface pendant des traitements thermiques continus et cycliques et sur l’évolution associée de la microstructure. La seconde étape a porté sur l’effet de ces traitements thermiques sur les propriétés mécaniques à température ambiante. Enfin, un montage de fatigue thermomécanique par dilatation différentielle entre un support en carbure de silicium et une éprouvette métallique en V a été conçu pour être utilisé sur un banc d’oxydation cyclique sous atmosphère contrôlée afin d’étudier les mécanismes de fissuration et d’endommagement en fatigue thermomécanique ainsi que l’effet de l’environnement sur l’initiation de fissures dans ces conditions. L’augmentation de la température maximale des cycles thermiques appliqués de 700 à 800°C pour la fonte GS SiMo+ et de 850 à 950°C pour l’acier 1.4826Nb a pour principale conséquence une accélération de la perte de section par oxydation et une diminution des propriétés mécaniques du fait de l’évolution de la microstructure. Cette perte de section paroxydation est fortement accélérée en présence de vapeur d’eau. Les essais préliminaires réalisés avec le montage de fatigue thermomécanique ont permis de valider son dimensionnement et de mettre en avant les cycles thermomécaniques pour lesquels l’initiation et la propagation de fissures étaient les plus rapides sur des cycles 300-800°C pour la fonte et 300-950°C pour l’acier.Une plus ample campagne d’essai reste à réaliser pour évaluer les mécanismes de fissuration et l’effet de l’environnement en fonction de la température maximale / Due to tightening environmental standards, the automotive industry is constantly trying to improvethe efficiency of the internal combustion engines in order to increase their fuel economy andreduce their carbon emissions. The main way to meet this goal on a turbocharged engine is toincrease the combustion temperature. This leads to increasing exhaust gas temperature andincreasing thermal loads on exhaust manifolds and turbine housings. These components beinguncooled, their maximum temperature is increasing and require better durability at hightemperature. The main objective of this thesis is to evaluate the durability of SiMo spheroidalgraphite iron (SGI) and 1.4826Nb cast stainless steel (CSS) at higher temperature than the actualmaximum operating temperature in order to evaluate their use on engines with higher power. Thefirst part of the study focuses on the effect of water vapor on high temperature oxidation duringcontinuous and cyclic heat treatments and on the underlying microstructure evolution. The secondpart focuses on the effect of these heat treatments on the tensile properties at room temperature.At last, a thermomechanical fatigue test setup has been designed to study the effect ofenvironment on crack initiation during thermomechanical fatigue (TMF). This setup uses thedifference in thermal expansion between silicon carbide and metallic materials to generatemechanical strain and stress in a V-shaped specimen during thermal cycling in a controlledatmosphere cyclic oxidation test bench. Increasing maximum temperature during thermal cyclingfrom 700 to 800°C for SiMo SGI and from 850 to 950°C for 1.4826Nb CSS leads to acceleratedwall thickness loss due to increased oxidation and to a drop in mechanical properties duemicrostructure evolution. The wall thickness loss is further accelerated in humid atmosphere.Preliminary tests performed with the TMF setup demonstrated the design is valid and enabled toidentify the thermomechanical loads leading to faster crack initiation and propagation for 300-800°C thermal cycling of SiMo SGI and 300-950°C thermal cycling of 1.4826Nb CSS. More testsare necessary to identify the crack initiation mechanisms according to the maximum temperatureof the thermal cycle and the atmosphere

Lors du fonctionnement des packages électroniques, ceux ci sont exposés à diverses sollicitations d'ordres thermiques et mécaniques. De même, la combinaison de ces sources de contraintes constitue l'origine de la quasi majorité des défaillances des packages électroniques. Pour s'assurer de la bonne résistance des packages électroniques, les fabricants pratiquent des tests de fiabilité et des analyses de défaillance avant toute commercialisation. Toutefois, les essais expérimentaux, lors de la phase de conception et de l'élaboration des prototypes, s'avèrent contraignants en termes de temps et de ressources matérielles. En revanche, la simulation numérique à l'aide de la méthode des éléments finis constitue une option alternative en termes de temps et de ressources. Les objectifs dévolus aux travaux de recherche visent à élaborer quatre modèles éléments finis en 3D, validés/calibrés par des essais expérimentaux, intégrant les recommandations JEDEC (1) en vue de : - Procéder à la caractérisation thermique et thermomécanique des packages électroniques ; - Et prédire la durée de vie en fatigue thermique des joints de brasures et ce, en lieu et place de la caractérisation expérimentale normalisée. Or, la mise en œuvre des modèles éléments finis présente certains inconvénients liés aux incertitudes au niveau de la géométrie, des propriétés matériaux, les conditions aux limites ou les charges. Ceux ci ont une influence sur le comportement thermique et thermomécanique des systèmes électroniques. D'où la nécessité de formuler le problème en termes probabilistes et ce, dans le but de mener une étude de fiabilité et d’optimisation des packages électroniques. Pour remédier au temps de calcul énorme généré par les méthodes d’analyse de fiabilité classiques, nous avons développé des méthodologies spécifiques à cette problématique, via des méthodes d’approximation basées sur le krigeage avancé,qui nous ont permis de bâtir un modèle de substitution, qui rallie efficacité et précision. Par conséquent, une analyse de fiabilité a été menée avec exactitude et dans un temps extrêmement court, via les méthodes de simulation Monte Carlo et FORM/SORM, couplées avec le modèle de krigeage avancé. Ensuite, l’analyse de fiabilité a été associée dans le processus d’optimisation, en vue d’améliorer la performance et la fiabilité de la conception structurelle des packages électroniques. A la fin, nous avons procédé à l’applicabilité des dites méthodologies d’analyse de fiabilité aux quatre modèles éléments finis ainsi développés. Il résulte que les analyses de fiabilité menées se sont avérées très utiles pour prédire les effets des incertitudes liées aux propriétés matériaux. De même, l’analyse d’optimisation de fiabilité ainsi réalisée nous a permis d’améliorer la performance et la fiabilité de la conception structurelle des packages électroniques. (1) JEDEC (Joint Electron Device Engineering Council) est un organisme de normalisation des semi-conducteurs. / During operation, electronic packages are exposed to various thermal and mechanical solicitations. These solicitations combined are the source for most of electronic package failures. To ensure electronic packages robustness, manufacturers perform reliability testing and failure analysis prior to any commercialization. However, experimental tests, during design phase and prototypes development, are known to be constraining in terms of time and material resources. This research aims to develop four finite element models in 3D, validated/calibrated by experimental tests, integrating JEDEC recommendations to : - Perform electronic packages thermal and thermomechanical characterization ; - Predict the thermal fatigue life of solder joints in place of the standardized experimental characterization.However, implementation of the finite element model has some disadvantages related to uncertainties at the geometry, material properties, boundary conditions or loads. These uncertainties influence thermal and electronic systems thermomechanical behavior. Hence the need to formulate the problem in probabilistic terms, in order to conduct a reliability study and a electronic packages reliability based design optimization.To remedy the enormous computation time generated by classical reliability analysis methods, we developed methodologies specific to this problem, using approximation methods based on advanced kriging, which allowed us to build a substitution model, combining efficiency and precision. Therefore reliability analysis can be performed accurately and in a very short time with Monte Carlo simulation (MCS) and FORM / SORM methods coupled with the advanced model of kriging. Reliability analysis was associated in the optimization process, to improve the performance and electronic packages structural design reliability. In the end, we applied the reliability analysis methodologies to the four finite element models developed. As a result, reliability analysis proved to be very useful in predicting uncertainties effects related to material properties. Similarly, reliability optimization analysis performed out has enabled us to improve the electronic packages structural design performance and reliability. In the end, we applied the reliability analysis methodologies to the four finite element models developed. As a result, reliability analysis proved to be very useful in predicting uncertainties effects related to material properties. Similarly, reliability optimization analysis performed out has enabled us to improve the electronic packages structural design performance and reliability.

Carcaças de transmissão estão geralmente sujeitas a tensões cíclicas geradas durante o funcionamento do motor, e estas tensões são mais críticas a temperaturas elevadas e em tempos prolongados. Os gradientes térmicos induzidos no interior de componentes sujeitos a variações de temperatura durante o período de funcionamento podem levar a tensões e deformações internas e a repetição destes ciclos térmicos pode causar a nucleação e a propagação de trincas por um processo denominado de fadiga termomecânica. Este trabalho apresenta um estudo sobre as diferenças das propriedades mecânicas de duas ligas de Al-Si fundidas sobre pressão em molde permanente (injetadas), uma identificada como sendo a Liga A, que contém o elemento de liga Mg, e a Liga B que não contém o Mg, para uso em carcaças de transmissão de veículos automotivos. Neste estudo foram realizados ensaios mecânicos de dureza, de tração e de fadiga isotérmica e anisotérmica e análises fratográficas e microestruturais por microscopia ótica e eletrônica de varredura. A Liga A apresentou resistência mecânica superior à Liga B em toda a faixa de temperatura analisada, apesar da maior quantidade de defeitos de fundição existentes nesta liga. Foi utilizada a metodologia S-N, cujos dados foram inferidos a partir dos ensaios de fadiga termomecânica. A Liga A apresenta desempenho ligeiramente superior à Liga B, especialmente para baixos níveis de tensão aplicados. Entretanto, para ensaios executados sob controle de deformação, não houve diferença significativa na resistência à fadiga entre as duas ligas. / Gear Box housings are usually subjected to cyclic stresses generated during engine operation. Such stresses are more critical at high temperatures and long times. Thermal gradients induced within the components submitted to variation of temperature during working may result in internal stresses and strains. Thermal cycling can result in crack nucleation and propagation by the process of thermomechanical fatigue (TMF). The main aim of this work was to evaluate the effects of Mg content on the mechanical properties of permanent mold cast Al-Si alloys. Two alloys, one containing Mg addition (\"A\" alloy) and another without Mg (\"B\" alloy) were tested under strain temperature TMF controlled conditions. In this study were performed mechanical tests of hardness, tensile strength, and anisotropic / isothermal fatigue and microstrutural / photographic analysis by scanning electronic microscopy (SEM). Using the S-N approach inferred from the TMF results, \"A\" alloy (Mg-added) presented a slightly better performance then \"B\" alloy especially at low stress amplitude levels. However, in the TMF testing conditions was not observed any significant difference in fatigue resistance for both alloys.

O Cu e suas ligas têm diferentes aplicações na sociedade moderna devido as excelentes propriedades elétricas, condutividade térmica, resistência à corrosão dentre outras propriedades. Estas aplicações podem ser em válvulas, tubulações, panelas para absorção de energia solar, radiadores para automóveis, condutores de corrente e eletrônico, elementos de termostatos e partes estruturais de reatores nucleares, como, por exemplo, bobinas para campo toroidal para um reator de fusão nuclear. Dentre as ligas utilizadas em reatores nucleares, podemos destacar Cu-Be, Cu-Sn e Cu-Pt. O Ni e o Co, freqüentemente são adicionados às ligas de Cu para que a solubilidade seja deslocada para temperaturas mais elevadas com relação aos sistemas binários de Cu-Sn e Cu-Pt. A adição de Ni-Pt ou Ni-Sn ao Cu em porcentagens iguais ou inferiores a 1,5 % aliado a tratamentos termos-mecânico alteram as propriedades do Cu. Estudamos neste trabalho sete diferentes ligas: três ligas de Cu-Ni-Pt 1 (97,99 % Cu - 1,55 % Ni - 0,46 % Pt), 2 (99,33 % Cu - 0,23 % Ni -0,43 % Pt) 3 (98,01 % Cu - 0,48 % Ni - 1,51 % Pt); três ligas de Cu-Ni-Sn 4 (98,31% Cu - 1,12 % Ni - 0,58 % Sn), 5 (98,79 % Cu – 0,57 % Ni - 0,65 % Sn), 6 (98,39% Cu – 0,46 % Ni – 1,16 % Sn) e Cu eletrolítico 0 (0,0058 % Pb - 0,0007 % Fe - 0,0036 % Ni - 0,0024 % Ag). As referentes ligas foram desenvolvidas a partir de um forno a arco voltaico e passaram por tratamentos termo-mecânicos pré-determinados. As microestruturas foram analisadas diretamente por microscopia óptica e microscopia eletrônica de varredura / EDS e indiretamente por medidas de dureza Vickers e condutividade elétrica. O objetivo deste trabalho, portanto, foi observar e constatar os efeitos da mudança da microestrutura em relação às propriedades dureza e condutividade elétrica. / The Cu and its alloys have different applications in the owed modern society the excellent electric properties, thermal conductivity, resistance to the corrosion and other properties. These applications can be in valves, pipes, pots for absorption of solar energy, radiators for automobiles, current driver, electronic driver, thermostats elements and structural parts of nuclear reactors, as, for example, reels for field toroidal for a reactor of nuclear coalition. The alloys used in nuclear reactors, we can highlight Cu-Be, Cu-Sn and Cu-Pt. Ni and Co frequently are added to the Cu alloys so that the solubility is moved for temperatures more elevated with relationship to the binary systems of Cu-Sn and Cu-Pt. The addition of Ni-Pt or Ni-Sn to the Cu in the same or inferior percentages to 1,5% plus thermomechanical treatments changes the properties of the copper. We studied the electric conductivity and hardness Vickers of the Cu-Ni-Pt and Cu-Ni-Sn and compared with the electrolytic Cu. In the proposed flowcharts, breaking of the obtaining of the ingot, we proceeded with thermo mechanical treatments.

Esta Dissertação de Mestrado tem como Objetivo estudar a influência da tangente delta, envelhecimento termomecânico e força no comportamento de uma borracha de polibutadieno baixo cis perante o desgaste abrasivo através de experimentos em roda de borracha, utilizando planejamento fatorial completo em dois níveis (DOE 2k). A literatura possui muitas informações em relação à força indicando uma relação exponencial com a taxa de desgaste, todavia em relação à tangente delta e ao envelhecimento termomecânico quase não há dados. Ao final do trabalho foi possível verificar que todos os fatores estudados são significativos com relação ao desgaste da borracha, sendo a força a variável com maior influência, seguida pelo envelhecimento. A histerese medida pela tangente delta, apesar de ser um fator importante, só exerce influência no desgaste quando a borracha se encontra no estado envelhecido. Além disto, este trabalho também apresenta informações complementares sobre propriedades que são características da borracha e pouco difundidos, como o smearing, características de ondas de abrasão (abrasion pattern), comprimento de onda (Schallamach wavelength) e ondas de destacamento (waves of detachment). / This goal of this Master thesis is the study the influence of loss factor, thermomechanical aging and applied load to the abrasion behavior of low cis polibutadiene rubber through rubber wheel testing machine experiments using 2k factorial experiment design in two levels (DOE 2k). The literature has many information involving action of force showing exponential relationship between wear rate with applied load, almost no data related to the influence of loss factor and the thermomechanical aging. It was observed that all the studied factors are significant to the wear of rubber, the force being the variable with the greatest influence, followed by aging. The loss factor, despite being an important factor, only influences the wear behavior of aged rubber. In addition, this work presents some information regarding to the typical properties only for rubber and rubber products, such as smearing, abrasion pattern and Schallamach wavelength.

Depuis des décennies, le rôle joué par les joints de grains dans le comportement plastique des matériaux cristallins interroge mécaniciens, métallurgistes, spécialistes des matériaux. Après les avancées décisives de la plasticité individuelle des cristaux et de leur comportement collectif au sein d’agrégats, les effets complexes des interfaces sur le comportement effectif constituent l’enjeu restant à maîtriser. Car si les joints peuvent aussi bien être sites d’endommagement que réseau de consolidation dans une structure polycristalline, ils contribuent toujours fortement aux propriétés macroscopiques de cette dernière. Le travail réalisé est une contribution à l’étude du comportement des joints lors de traitements thermomécaniques induisant leur mobilité. On parle de migration.Nous avons étudié les caractéristiques essentielles de la migration de joints de grains à partir du mécanisme de SIBM (croissance de grains sans germination après faible déformation plastique). La migration des joints de grains sous recuit après déformation a été suivie in situ en MEB. Les évolutions microstructurales sont analysées en MEB et en AFM. Les principales forces et caractéristiques contribuant à la migration des joints sont étudiées. Pour les forces, un diagramme de migration reliant le déplacement des joints à l’énergie de courbure et à l’énergie stockée par déformation plastique a permis d’évaluer la pertinence de l’expression usuelle de la force motrice de migration et d’en discuter de possibles ajustements. Pour les caractéristiques, nous avons confirmé l’effet de surface de la gravure thermique et celui plus intrinsèque des jonctions triples sur la mobilité des joints de grains. / For many decades, the role of grain boundaries in the plastic behavior of crystalline materials questions engineers, metallurgists, materials scientists. After the decisive progress in plasticity of individual crystals and for their collective behavior in aggregates, the complex effects of boundaries on the actual behavior are the remaining challenge to master. If boundaries can as well be considered as damage sites as strengthening network in a poly-crystalline structure, they always contribute greatly to the macroscopic properties of the latter. This work is a contribution to the study of the behavior of boundaries during thermomechanical treatments inducing mobility. We talk about migration.We studied the essential characteristics of the migration of grain boundaries from SIBM mechanism (Strain Induced Boundary Migration). The migration of grain boundaries under annealing after deformation was monitored in situ SEM. Microstructural changes are analyzed by SEM and AFM. The main strengths and characteristics contributing to the boundary migration are studied. For strengths, a migration diagram linking the displacements of grain boundaries to the curvature energy and the stored energy from plastic deformation allowed to assessing of the relevance of the usual expression for the migration driving force and to discussing possible adjustments. For characteristics, we confirmed the surface effect of the thermal grooving and the more intrinsic one of triple junctions on the mobility of grain boundaries.

<div>The objective of this dissertation is to develop new methods in the areas of multiscale topology optimization, thermomechanical topology optimization including heat convection, and thermal-fluid topology optimization. The dissertation mainly focuses on developing five innovative topology optimization algorithms with respect to structure and multistructure coupling fluid, thermal and mechanical analysis, in order to solve customary design requirements. Most of algorithms are coded as in-house code in MATLAB.</div><div><br></div><div><div>In Chapter One, a brief introduction of topology optimization, a brief literature review and the objective is presented. Five innovative algorithms are illustrated in Chapter Two</div><div>to Six. From Chapter Two to Four, the methods with respect to multiscale approach are presneted. and Chapter Five and Six aims to contribute further research associated with</div><div>topology optimization considering heat convection. In Chapter Two, a multiphse topology optimization of thermomechanical structures is presented, in which the optimized structure is composed of several phases of prescribed lattice unit cells. Chapter Three presents a</div><div>Multiscale, thermomechanical topology optimization of self-supporting cellular structures. Each lattice unit cell have a optimised porousity and diamond shape that benefit additive</div><div>manufacturing. In Chapter Four, the multiscale approach is extended to topology optimization involved with fluid mechanics problem to design optimized micropillar arrays in</div><div>microfludics devices. The optimised micropillars minimize the energy loss caused by local fluid drag force. In Chapter Five, a novel thermomechanical topology optimization is developed, in order to generate optimized multifunctional lattice heat transfer structure. The algorithm approximate convective heat transfer by design-dependent heat source and natural convection. In Chapter Six, an improved thermal-fluid topology optimization method is created to flexibly handle the changing of thermal-fluid parameters such as external heat source, Reynolds number, Prandtl number and thermal diffusivity. The results show the</div><div>changing of these parameters lead versatile optimized topologies. Finally, the summary and recommendations are presented in Chapter Seven.</div></div><div><br></div>

Polymer nanocomposites (PNCs), mixtures of nanometer-sized particles and polymeric matrices, have attracted continuing interest over the past few decades, primarily because they offer the promise of significant property improvements relative to the pure polymer. It is now commonly accepted in the community that the spatial organization of nanoparticles (NPs) in the polymer host plays a critical role in determining the macroscopic properties of the resulting PNCs. However, till date there is still dearth of cost-effective methods for controlling the dispersion of NPs in polymeric hosts. In this dissertation, we are dedicated to developing practically simple and thus commercially relevant strategies to controllably disperse NPs into synthetic polymer matrices (both amorphous and semicrystalline). We first investigate the influence of casting solvent on the NP spatial organization and the thermomechanical properties in a strongly attractive PNC consisting of bare silica NPs and poly(2-vinylpyridine) (P2VP) hosts cast from two different solvents - methylethylketone (MEK) or pyridine. In MEK, we show that P2VP strongly adsorbs onto the silica surface, creating a stable bound polymer layer and thus helping sterically stabilize the NPs against agglomeration. On the contrary, in pyridine, P2VP does not adsorb on the silica NPs, and the phase behavior in such case is a subtle balance among electrostatic repulsion, polymer-induced depletion attraction, and the kinetic slowdown of diffusion-limited NP aggregation. Using Brillouin light scattering, we further show that in pyridine-cast films, there is a single acoustic phonon, implying a homogeneous mixture of silica and P2VP on the mesoscopic scales. However, in MEK-cast samples, two longitudinal and two transverse acoustic phonons are probed at high particle content, reminiscent of two metastable microscopic phases. These solvent-induced differences in the elastic mechanical behavior disappear upon thermal annealing, suggesting that these nanocomposite interfacial structures in the as-cast state locally approach equilibrium upon annealing. Next, to disperse silica NPs into an energetically unfavorable polystyrene (PS) matrix in a controllable fashion, we have proposed a simple and robust strategy of adsorbing a monolayer of PS-b-P2VP block copolymer onto the silica surface, where the short P2VP block is densely coated around the silica particles and thus helps to reduce the inter-core attraction while the long PS block provides a miscible interface with the matrix chains. As a result, we have found that the silica particles can be uniformly dispersed in the PS matrices at a low grafting density of 0.01 chains/nm2. Even more interestingly, we have shown that the BCP coated NPs are remarkably better dispersed than the ones tethered with bimodal PS-P2VP brushes at comparable PS grafting characteristics. This finding can be reconciled by the fact that in the case of BCP adsorption, each NP is more uniformly coated by a P2VP monolayer driven by the strongly favorable silica-P2VP interactions. Since each P2VP block is connected to a PS chain we conjecture that these adsorbed systems are closer to the limit of spatially uniform sparse brush coverage than the chemically grafted case. Finally, we have examined the interplay between NP organization and polymer crystallization in a melt-miscible model semicrystalline nanocomposite comprised of poly(methyl methacrylate) or poly(methyl acrylate) grafted silica NPs in poly(ethyleneoxide) matrices. Here we have achieved active NP organization at a length scale of 10-100 nm by isothermal polymer crystallization. We have shown that the melt-miscible spherical NPs are engulfed by the polymer crystals and remain spatially well-dispersed for crystallization faster than a critical growth rate (G > Gc ~ 0.1 um/s). However, anisotropic sheet-like NP ordering results for slower G - the NPs are preferentially segregated into the interlamellar zone of the multiscale, hierarchical polymer crystal structure spanning lamellae (10-50 nm), fibrils (um) and spherulites (mm). This NP ordering is found to favorably impact the elastic modulus while leaving fracture toughness unaffected. We thus conclude that polymer crystal growth kinetics coupled to the unusual morphology of semicrystalline polymers represent a novel handle for in-situ fabricating hierarchical, anisotropic NP structures in a synthetic semicrystalline polymer, which could inspire significant applications.

Os aÃos inoxidÃveis austenÃticos (AIAs) sÃo largamente aplicados nas indÃstrias de alimentos, transportes nuclear, petroquÃmica devido à adequada combinaÃÃo de resistÃncia mecÃnica, conformabilidade e resistÃncia à corrosÃo. Dentre estes tipos de aÃo, destaca-se o AISI 301 por sua resistÃncia mecÃnica superior. Entretanto, este tipo de aÃo apresenta um dos piores desempenhos em termos de corrosÃo. Toda a resistÃncia à corrosÃo dos AIAs se baseia em sua camada de filme passivo contendo Cr203 que pode facilmente ser destruÃda em ambientes contendo cloreto. Neste trabalho, estabeleceu-se a meta de estudar os aÃos AISI 301 LN e 316L em respeito Ãs mudanÃas na microestrutura por imposiÃÃo de deformaÃÃo e seu efeito na corrosÃo por pites, visto que o AISI 301LN foi escolhido como material base dos vagÃes que servirÃo o sistema de transporte metropolitano de Fortaleza. Empregou-se difraÃÃo de raios âX, metalografia quantitativa, microscopias Ãtica, eletrÃnica de varredura e de forÃa atÃmica para caracterizar a microestrutura, textura cristalogrÃfica, caracterizaÃÃo magnÃtica, microdureza e ensaio de imersÃo em FeCl3 6H2O para caracterizar o comportamento dos dois aÃos em corrosÃo por pites. A deformaÃÃo provocou a formaÃÃo de martensita &#61537;â no aÃo 301LN e encruamento da austenita. Isto provocou o mais baixo desempenho em corrosÃo por pites. A textura cristalogrÃfica forneceu indÃcios para inferir que a transformaÃÃo austenita-ferrita se deu obedecendo a relaÃÃo de KURDJUMOV-SACHS.