Dissertations / Theses: 'Aluminyl'

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Ergin, Guvenc. "Étude de la mouillabilité des particules granulaires par les alliages d'aluminium durant la filtration d'aluminium /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2006. http://theses.uqac.ca.

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Thèse (D.Eng.) -- Université du Québec à Chicoutimi, 2006.
La p. de t. porte en outre: Thèse présentée à l'Université du Québec à Chicoutimi pour l'obtention du doctorat en ingénierie. CaQCU Bibliogr.: f. 130-147. Document électronique également accessible en format PDF. CaQCU

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Roselló, Serra Maite. "Estrategias de resistencia a aluminio en dos variedades de Oryza Sativa: exclusión vs detoxificación." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/399682.

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El arroz (Oryza sativa) es un cultivo altamente tolerante a Al. Entre otros mecanismos, una mayor expresión de los genes STAR1 / STAR2 como también de Nrat1 y ALS1 puede al menos en parte ser responsable de la tolerancia inducible por Al en esta especie. Se analizaron las distintas respuestas a Al en dos variedades de arroz Nipponbare y Modan. Todos los marcadores de toxicidad / tolerancia analizados (crecimiento de la raíz, azul de Evans, tinciones con hematoxilina y morin) indicaron una tolerancia a Al superior en la variedad Nipponbare que en Modan. Nipponbare acumuló mucho menos Al en las raíces que Modan. El suministro de aluminio provocó la expresión más fuerte de STAR1 en Nipponbare que en Modan. En las raíces de Nipponbare se encontró un aumento claramente mayor de la acumulación de ácido abscísico (ABA) inducido por Al que en las raíces de Modan. Se observaron altos niveles de ABA y JA en Nipponbare después de 48 h de exposición a Al. Estos picos coincidieron en el tiempo con el nivel de expresión más alto de STAR1. Se propone que ABA y JA puede ser necesario para la remodulación de la pared celular facilitado por el mayor transporte de UDP-glucosa a las paredes a través del complejo STAR1 / Star2. En contraste, en las raíces de Modan la expresión tanto de NRAT1, que codifica para una membrana plasmática transportadora de Al, como de ALS1, que codifica para un transportador de Al localizado el tonoplasto, mejoraron considerablemente en presencia de Al. Por otra parte, Modan tenía una mayor expresión de ASR1 inducido por Al, un gen que se ha propuesto para codificar una proteína que actúa como secuestrador de oxígeno reactivo. En conclusión, la estrategia de exclusión de Al de Nipponbare, mediada al menos en parte por STAR1 y probablemente regulada por ABA, produjo una mejor protección contra la toxicidad de Al que la estrategia de acumulación y desintoxicación interna de Modan mediada por NRAT1, ALS1 y ARS1.

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Lebeau, Thomas. "Wetting of alumina-based ceramics by aluminum alloys." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68039.

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During the last 20 years, ceramic fiber reinforced metal matrix composites, referred to as MMCs, have provided a relatively new way of strengthening metals. High specific modulus and a good fatigue resistance in dynamic loading conditions or for high temperature applications make these composites very attractive for replacing classic alloys. The first requirement for the fabrication of MMCs, especially by processes involving liquid metals, is a certain degree of wetting of fibers by the liquid metal which will permit a good bonding between the two phases.
The conventional experimental approach to wettability consists of measuring the contact angle of a drop of the liquid metal resting on flat substrate of the ceramic reinforcement materials.
This work deals with the fabrication of eutectic $ rm ZrO sb2/Al sb2O sb3 (ZA), ZrO sb2/Al sb2O sb3/TiO sb2$ (ZAT), and $ rm ZrO sb2/Al sb2O sb3/SiO sb2$ (ZAS) ceramic substrates and the study of their wetting behavior by different classes of Al alloys. Wetting experiments were performed under high vacuum or under ultra high purity Ar atmosphere. Four major variables were tested to study the wetting behavior of the different ceramic/metal systems. Variables include holding time, melt temperature, alloy and ceramic compositions.
Ceramic materials were sintered under vacuum at temperatures ranging from 1500$ sp circ$C to 1790$ sp circ$C for 2.5 hours, and achieved over 96% of the theoretical density. An experimental set-up was designed to measure in-situ contact angles using the sessile drop method. For any ceramic substrate, a temperature over 950$ sp circ$C was necessary to observe an equilibrium wetting angle less than 90$ sp circ$ with pure Al; by alloying the aluminum, wetting could be observed at lower temperatures ($ theta$ = 76-86$ sp circ$ at 900$ sp circ$C for Al-10wt%Si, $ theta sim72 sp circ$ at 850$ sp circ$C for Al-2.4wt%Mg). Finally, ZAS specimens reacted with molten Al alloys over 900$ sp circ$C to produce Zr-Al based intermetallics at the metal/ceramic interface.

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Mearini, Gerald Thaddeus. "Mechanical properties of thin aluminum/alumina multilayer films." Case Western Reserve University School of Graduate Studies / OhioLINK, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1056049755.

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Pereira, Marinalda Claudete [UNESP]. "Estudo morfológico e cinético da corrosão por pites em liga de alumínio 1050." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/103764.

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O objetivo deste trabalho foi estudar as características morfológicas da corrosão localizada na liga de alumínio 1050 e a cinética de crescimento em tamanho dos pites induzidos por ensaios de imersão estática em solução de NaCl, pH 6,0, aerada naturalmente à temperatura ambiente. As amostras foram examinadas antes e após o ensaio de corrosão por microscopia ótica e microscopia eletrônica de varredura e, posteriormente foram analisadas através de um método de captura, processamento digital e análise de imagens, recentemente desenvolvido pelo grupo de Corrosão e Eletroquímica da FEG/UNESP. Exames na superfície da liga após 168h de imersão em NaCl 0,0043 mol/L indicaram um ataque localizado na matriz adjacente às partículas Al:Fe:Si e Al:Fe as quais revelaram um caráter catódico. Mediante análise da variação temporal dos parâmetros obtidos concluiu-se que a área dos pites não muda significativamente enquanto a densidade e a fração de área corroída aumentam com o tempo. A variação temporal indicou que velocidade de corrosão, em termos de propagação superficial, diminui com o tempo de imersão. As características morfológicas e os tamanhos dos pites nos perfis da superfície corroída foram estudados. Os pites induzidos não podem ser representados por uma única geometria, senão pela distribuição morfológica seguinte: i) sem exclusão das cavidades: hemisférico > transição A > transição B > irregular > cônico > cilíndrico; ii) com exclusão das cavidades: hemisférico > transição A > transição B > irregular ~cônico, sem evidências dos pites cilíndricos. Os pites mais profundos foram encontrados especialmente na classe de transição B. A velocidade de crescimento em profundidade (P) ou em largura (L) dos pites foi melhor representada, após a exclusão das cavidades, mediante a lei cinética seguinte:...
This work aim has beem to study the morphologic characteristics of localized corrosion on aluminum alloy 1050 and the growth kinetics in size of pits induced by static immersion tests in NaCl solution, pH 6.0, naturally aerated at room temperature. The samples have been examined before and after the corrosion test by optical microscopy and scanning electron microscopy and subsequently analyzed by a capturing method, digital processing and image analysis, recently developed by the Corrosion and Electrochemistry group of FEG / UNESP. Investigations on the alloy surface after 168h immersion in NaCl 0.0043 mol / L has showed a localized attack on the matrix adjacent to the particles Al: Fe: Si and Al: Fe which have disclosed a cathodic character. By analyzing the temporal variation of obtained parameters it has been concluded that pits area does not change significantly while density and corroded area fraction increase with the time. Temporal variation has indicated that corrosion rate in terms of propagating surface, decreases with immersion time. The morphological characteristics and pits sizes in the corroded surface profiles have been studied. The induced pits may not be represented by a unique geometry, but by the following morphologic distribution: i) without cavities exclusion: hemispheric > transition A > transition B > irregular > conical > cylindrical ii) excluding cavities: hemispheric > transition A > transition B > irregular ~ conical, without cylindrical pits evidence. The deepest pits have been found particularly in transition B class. The pits growth rate in depth (P) or in width (L) has been better represented, after cavities exclusion, by the following kinetics law: P or L = ktm, with k and m empirical values that depend on a combination of different factors

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Mattos, João Jose Ifarraguirre de. "Propriedades de fadiga e micromecanismos de fratura da liga de aluminio-silicio AlSi7Mg0,6 utilizada em cabeçote de motor diesel." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265248.

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Orientador: Itamar Ferreira
Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica, Faculdade de Engenharia Eletrica e de Computação e Instituição de Quimica
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Resumo: O crescente uso das ligas alumínio-silício fundido na indústria automotiva deve-se principalmente a redução de peso, consumo de combustível e níveis de emissões. Isto inclui a liga de alumínio-silício EN AlSi7Mg0,6, equivalente a liga ASTM A357.0, que é empregada em cabeçotes de motores Diesel. É importante conhecer o impacto na integridade e confiabilidade deste componente na presença de defeitos intrínsecos dos processos de fundição convencional como a de molde permanente. Tais defeitos, como porosidades e filmes de óxidos, quando localizados na superfície, ou próxima a esta, são nucleadores de trincas de fadiga. Neste estudo é analisado o impacto na resistência à fadiga e nos micromecanismos de fratura pelo ensaio de corpos-de-prova fresados com dimensões de 7x14x60mm, retirados do cabeçote da linha de produção e submetidos a ensaio de flexão em três pontos. As superfícies de fratura dos espécimes foram analisadas em microscópio eletrônico de varredura (MEV) a fim de caracterizar os micromecanismos de fratura e o local de iniciação da trinca de fadiga. A resistência à fadiga média, para 1 milhão de ciclos, foi determinada como sendo ao redor de 140MPa. Foi observado na superfície de fratura dos espécimes testados, um claro contraste entre o micromecanismo da zona de fadiga (estrias) e zona final de fratura (alvéolos), sendo que o fator predominante para nuclear trincas de fadiga foram poros próximos da superfície.
Abstract: The increase usage of casting aluminum-silicon alloys in the automotive industry is due to reduce weight, fuel consumption, and emissions level. This includes the aluminum-silicon cast alloy EN AlSiMg0.6 (ASTM A357.0) which is used to make Diesel engine cylinder head. It is important to know the impact on the integrity and reliability of this component in the presence of intrinsical defects of conventional casting parts produced on permanent mold process. Such defects, as porosity and oxide film, when locate on the surface or subsurface of casting parts, could be a fatigue crack initiators. In this paper is analyzed the impact on the fatigue strength and micromechanisms of fracture, by using 7x14x60mm specimens machined from cylinder head drew from production assembly line, and submitted to three point bending tests. Fracture surface of the specimens were observed by SEM to characterize the micromechanisms and the initiation fracture local. The average fatigue strength, based on 1 million of cycles, is about 140MPa. It was observed on the fracture surface of fatigue test specimens, a clear contrast between the micromechanisms of fatigue zone (striations) and the final fracture zone (dimples) and fatigue crack initiation occurs at the porosities near the surface.
Mestrado
Materiais
Mestre em Engenharia Automobilistica

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Panchula, Martin Lawrence. "Synthesis and sintering of nanocrystalline alumina and aluminum nitride." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85366.

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Silva, Beethoven Max Alves da. "Influencia da microestrutura inicial e material de molde na tixoconformação da liga A356." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263687.

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Orientador: Maria Helena Robert
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Neste trabalho investiga-se a influência da microestrutura inicial e do material do molde na tixoconformação da liga A356. São produzidas e testadas em operações de tixoforjamento pastas obtidas por três distintos processos: fusão parcial controlada de estrutlJ'aS dendríticas grosseiras, fusão parcial controlada de estruturas ultra-refinadas e pastas obtidas por agitação mecânica do líquido durante solidificação. É produzido ainda um compósito A356 + Ab03 obtido por compofundição. Os tixoforjados foram submetidos à análise metalográfica para caracterização microestrutural, medindo-se a fração da fase primária e o tamanho médio de glóbulo ou roseta da fase sólida. Os resultados obtidos mostram a viabilidade da utilização de moldes não metálicos e operações de tixoconformação com produtos de bom acabamento superficial e dimensional. As forças de tixoforjamento são dependentes da condição inicial da matéria-prima, de forma que forças maiores são requeridas com o aumento do parâmetro microestrutural básico (espaçamento interdendrítico, tamanho de glóbulo e tamanho de roseta) da matéria-prima
Abstract: This research aims the influence of initial microstructure and die material on thixofonning of A356 alloy. Obtained slurries are produced and tested in thixoforging operation by three distinct processes: controlled partial melting of coarse dendritic structures, controlled partial melting of ultra-refined structures and obtained slurries by liquid mechanical stirring during solidification. It is still produced a composite A356 + AbO:i obtained by compocasting. Thixoforged samples were submitted to metalographic analysis for microstructural characterisation, measuring the primary phase fraction and globule average size or 50lid phase rosette. Obtained results showed the viability of non-metallic dies in thixoforming operations with good superficial and dimensional finishing produds. Thixoforging forces are dependent on initial condition of raw material, 50 that higher forces are required with the increasing of basic microstructural parameter Onterdentritic spacing, globule size and rosette size) of raw material
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

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Di, Paolo Pereyra Celeste Gisela. "Evaluación de los efectos de la exposición crónica a aluminio a través de la dieta en ratones Tg2576. Papel protector de la melatonina." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/461611.

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La Malaltia d'Alzheimer (AD) és una malaltia neurodegenerativa progressiva, irreversible i d'origen fins ara desconegut. La hipòtesi de la interacció dels metalls (i en els últims añys, en concret l'alumini) amb altres factors per causar l'AD ha anat guanyant importància gràcies a estudis en els quals s'ha trobat nivells de tres a cinc vegades més grans d'alguns metalls (Cu, Fe, Zn, al ...) acumulats al cervell de pacients de l'AD. La hipòtesi d'aquest treball ha estat: La melatonina és capaç de protegir el cervell contra els danys bioquímics i cognitius ocasionats per l'exposició crònica a alumini en un model de ratolí transgènic per a la Malaltia d'Alzheimer. Per a això s'ha avaluat l'aprenentatge i la memòria, s'han mesurat les concentracions de metalls en diferents teixits i també s'ha quantificat la concentració de caspasa-3 i SOD2 present en còrtex i hipocamp. Finalment, la sobreexpressió del gen APP sembla generar un augment en l'activitat. El tractament amb AlCit provoca dèficits d'aprenentatge i impedeix la retenció de la memòria a llarg termini en els ratolins Tg2576. La melatonina no sembla tenir cap efecte sobre la concentració dels metalls estudiats. Tampoc es va apreciar un efecte significatiu del tractament amb melatonina sobre la quantitat de Aß en el còrtex i hipocamp. Els grups tractats amb alumini i citrat van mostrar els majors nivells de caspasa-3 i SOD2 tant en els grups wild-type com en els Tg2576 i la melatonina no va produir un efecte protector estadísticament significatiu.
La Enfermedad de Alzheimer (AD) es una enfermedad neurodegenerativa progresiva, irreversible y de origen hasta ahora desconocido. La hipótesis de la interacción de los metales (y en los últimos, en concreto el aluminio) con otros factores para causar la AD ha ido ganando importancia gracias a estudios en los que se ha encontrado niveles de tres a cinco veces mayores de algunos metales (Cu, Fe, Zn, Al…) acumulados en el cerebro de pacientes de la AD. La hipótesis de este trabajo ha sido: La melatonina es capaz de proteger al cerebro contra los daños bioquímicos y cognitivos ocasionados por la exposición crónica a aluminio en un modelo de ratón transgénico para la Enfermedad de Alzheimer. Para ello se ha evaluado el aprendizaje y la memoria, se han medido las concentraciones de metales en diferentes tejidos y también se ha cuantificado la concentración de caspasa-3 y SOD2 presente en córtex e hipocampo. Finalmente, la sobreexpresión del gen APP parece generar un aumento en la actividad. El tratamiento con AlCit provoca déficits de aprendizaje e impide la retención de la memoria a largo plazo en los ratones Tg2576. La melatonina no parece tener ningún efecto sobre la concentración de los metales estudiados. Tampoco se apreció un efecto significativo del tratamiento con melatonina sobre la cantidad de Aβ en el córtex e hipocampo. Los grupos tratados con aluminio y citrato mostraron los mayores niveles de caspasa-3 y SOD2 tanto en los grupos wild-type como en Tg2576 y la melatonina no produjo un efecto protector estadísticamente significativo.
Alzheimer's disease (AD) is a progressive, irreversible neurodegenerative disease with an unknowning origin. The hypothesis of the interaction of metals (and nowadays, in particular aluminum) with other factors to cause AD has been gaining importance through studies in which levels of different metals accumulated in the brains of AD patients (Cu, Fe, Zn, Al ...) were three to five times higher. The hypothesis of this study was: Melatonin is able to protect the brain from the biochemical and cognitive damages caused by chronic exposure to aluminum in a transgenic mouse model for Alzheimer's disease. For this purpose, learning and the memory have been evaluated, the concentrations of metals in different tissues have been measured and the concentration of caspase-3 and SOD2 present in cortex and hippocampus had been quantified. Finally, overexpression of the APP gene appears to generate an increase in activity. Treatment with AlCit causes learning deficits and inhibits long-term memory retention in Tg2576 mice. Melatonin does not appear to have any effect on the concentration of the metals studied. Also, there was no significant effect of melatonin treatment on the amount of Aβ in the cortex and hippocampus. The aluminum and citrate treated groups showed the highest levels of caspase-3 and SOD2 in both wild-type and Tg2576 groups and melatonin did not have a statistically significant protective effect.

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Suarez, Jimmy. "Modélisation de la combustion diphasique de l’aluminium et application sur la post-combustion d'une charge explosive condensée dans l'air." Thesis, Toulouse, INPT, 2020. http://www.theses.fr/2020INPT0099.

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La combustion de l'aluminium est un phénomène présent dans de nombreux domaines, tels que le domaine du spatial, de la défense et de l'automobile. Une fois allumée, une particule d'aluminium représente un excellent vecteur d'énergie pour l'écoulement environnant grâce à sa grande densité énergétique. Sa combustion avec l'air, ou avec d'autres oxydants, a fait l'objet de quelques études expérimentale et numérique, ce qui a mis en avant l'une des particularités de cette combustion diphasique. Lors de la combustion de l'aluminium, elle produit une espèce appelée alumine qui existe uniquement en phase liquide dans ses gaz brûlés. Cette particularité rend la modélisation de la combustion diphasique de l'aluminium complexe à modéliser. L'objectif de cette thèse est divisé en deux parties. La première partie est de développer un modèle de combustion diphasique de l'aluminium avec l'air. Cette modélisation est une simulation Euler- Lagrange réalisée avec AVBP, qui est un code de simulation mis en place par le CERFACS. Elle prend en compte la combustion rapide de l'aluminium en phase gazeuse et les changements de phase qui interviennent comme la fusion et l'évaporation de l'aluminium, mais aussi la condensation et la solidification de l'alumine. Une méthode de germination est développée pour permettre la condensation de l'alumine dans les gaz brûlés et suivre de façon lagrangienne sa croissance derrière la flamme aluminium-air. Cette modélisation nous a permis de simuler des flammes aluminium-air 1D et 2D pour les comparer aux données expérimentales trouvées dans la littérature. La seconde partie de cette thèse est l'analyse de la dispersion et de la participation énergétique de l'aluminium dans la post-combustion d'une charge explosive. Le phénomène de post-combustion est très lumineux et rapide, ce qui empêche expérimentalement de connaître l'évolution de l'état des particules d'aluminium contenues initialement dans la charge explosive. Ces simulations permettent de suivre la dispersion des particules et leurs interactions avec les différentes phases qui composent la post-combustion. Un modèle de combustion de particule isolée est repris de la littérature et adapté à notre cas d'étude. Ainsi l'influence de la présence physique des particules et de la chaleur dégagée par leur combustion a pu être évaluée sur l'évolution de la boule de feu et la propagation du choc secondaire. L'ensemble de ces travaux de thèse, que ce soit pour la modélisation de la flamme aluminium-air et l'analyse de l'impact de l'aluminium sur la post-combustion, a montré des résultats convaincants par rapport aux données de la littérature. Les modèles numériques utilisés et développés sont prometteurs pour des futures études sur la combustion de l’aluminium
The combustion of aluminum is a phenomenon present in many fields, such as the space, defense and automotive fields. Once ignited, an aluminum particle represents an excellent energy carrier for the surrounding flow with its high energy density. Its combustion with air, or with other oxidants, has been the subject of some experimental and numerical studies, which has highlighted one of the particularities of this two-phase combustion. During the aluminum combustion, it produces a species called alumina which exists only in the liquid phase in its burning gases. This particularity makes the modeling of the two-phase combustion of aluminum complex to model. The objective of this thesis is divided into two parts. The first part is to develop a model of two-phase combustion of aluminum with air. This modeling is an Euler-Lagrange simulation created with AVBP, which is a simulation code implemented by CERFACS. It takes into account the rapid combustion of aluminum in the gaseous phase and the phase changes that occur such as the melting and evaporation of aluminum, but also the condensation and solidification of alumina. A germination method is developed to allow the condensation of alumina in the burning gases and to follow its growth in a Lagrangian way behind the aluminum-air flame. This modeling allowed us to simulate 1D and 2D aluminum-air flames to compare them to the experimental data found in the literature. The second part of this thesis is the analysis of the dispersion and the energetic participation of aluminum in the post-combustion of an explosive charge. The phenomenon of post-combustion is very bright and rapid, which experimentally prevents knowing the evolution of the state of the aluminum particles initially contained in the explosive charge. These simulations make it possible to follow the dispersion of the particles and their interactions with the different phases that make up the post-combustion. An isolated particle combustion model is taken from the literature and adapted to our case study. Thus the influence of the physical presence of particles and of the heat released by their combustion could be evaluated on the evolution of the fireball and the propagation of the secondary shock. All of this thesis work, whether for the modeling of the aluminum-air flame and the analysis of the impact of aluminum on the post-combustion, showed convincing results compared to the data of the literature. The numerical models used and developed are promising for future studies on the combustion of aluminum

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Burtin, Pierre. "Transformation des alumines de transition en alumine alpha. Influence d'éléments étrangers sur la stabilité des alumines." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 1985. http://tel.archives-ouvertes.fr/tel-00845793.

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Les oxydes et hydroxydes d'aluminium sont des produits chimiques très répandus industriellement. La principale utilisation des alumines est la production de l'aluminium, mais elles sont également très employées dans l'industrie des abrasifs, des céramiques et des matériaux réfractaires. De même parmi les oxydes métalliques utilisés dans les processus catalytiques, l'alumine est l'un des plus employés. Elle peut être utilisée comme catalyseur intrinsèque, ou comme l'un des éléments d'un catalyseur multicomposant ou encore comme support d'un catalyseur métallique. En tant que support de catalyseur, une des applications de l'alumine est l'épuration des gaz d'échappement des véhicules automobiles rendue obligatoire depuis quelques années dans certains pays (1974 pour les U.S.A. et le Japon), et qui le deviendra également dans certains pays de la Communauté Européenne au cours des prochaines années (vers 1989 en Allemagne) Les normes ainsi imposées pour la composition des effluents gazeux rejetés par les moteurs et leur teneur en composés nocifs nécessitent de la part du catalyseur une bonne efficacité. D'autre part le support du catalyseur est caractérisé par la nature du produit, sa résistance mécanique, sa texture et sa stabilité. Toutes ces propriétés doivent être conservées dans les conditions d'utilisation. L'épuration des gaz d'échappement demande donc un système catalytique très performant, notamment pour les propriétés mécaniques et surtout pour la résistance à l'attrition. Et ces propriétés ne doivent pas être affectées aux hautes températures (1000 à 1100°C). A ces températures le support doit également rester neutre vis-à-vis des espèces catalytiques (métal ou oxyde) déposées à sa surface.

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Silva, Cássia Cavalcanti da [UNESP]. "Utilização da curva de resfriamento na análise do refino de grão da liga AA 356." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/94396.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
A liga AA 356 é uma liga de alumínio de grande importância porque é amplamente utilizada na indústria automobilistica e aeronáutica. Para melhorar as propriedades mecânicas dessa liga, são usados inoculantes para o refino de grãos; essas propriedades, apresentadas pelo produto final, dependem também das condições em que o metal foi fundido e solidificado. Os componentes solidificados em molde de metal, com uma taxa de extração de calor maior, têm propriedades mecânicas superiores àqueles solidificados em moldes de areia, que têm uma taxa de extração de calor mais baixa. A curva de resfriamento é usada como uma ferramenta para avaliar a eficácia de refino de grão e, é influenciada por fatores como o material do molde, a taxa de resfriamento e adições de inoculantes para refino de grão. Com o uso da curva de resfriamento, algumas propriedades da liga podem ser obtidas, tais como: o calor latente de solidificação, a fração sólida, as temperaturas liquidus e solidus, o tempo local de solidificação, além de identificar a presença de inoculantes para o refino de grão. A primeira derivada da curva melhora a precisão das informações apresentadas na curva de resfriamento. Essa derivada representa a taxa de resfriamento. Para o desenvolvimento desse trabalho alguns lingotes foram refundidos variando-se o material do molde e, consequentemente, a taxa de resfriamento; adicionando-se ou não inoculante para o refino de grão na forma de liga mãe Al-5Ti-1B, na proporção de 0,05%. As curvas de resfriamento para as solidificações foram plotadas e analisadas. Confirmou-se que a curva de resfriamento com sua primeira derivada fornecem, além das temperaturas solidus e liquidus, as temperaturas de transformações de fases e informações sobre a eficácia do refino de grão. Variando-se o material...
The AA 356 alloy is an aluminum alloy of great importance because it is widely used in the automobile and aeronautic industries. To improve the mechanical properties of this alloy, inoculants are used for grain refinement; these properties, presented by the final product, also depend on conditions, under which the metal was melted and solidified. The components solidified in a metal mold, with a higher heat extraction rate, have mechanical properties superior to the ones solidified in sand molds that have a lower heat extraction rate. The cooling curve is used as a tool to evaluate the effectiveness of grain refinement and it is influenced by factors as: mold material, cooling rate and of inoculants additions for grain refinement. With the use of the cooling curve analysis can be obtained some properties of the alloy, such as: the latent heat of solidification, the solid fraction, the solidus and liquidus temperatures, the local time of solidification. In addition, to evaluate the presence of inoculants for grain refinement. The first curve derivative improves the accuracy of the information given in the cooling curve. That derivative represents the cooling rate. For this work development, some ingots were remelted varying the mold material and, consequently, the cooling rate; also added or not the grain refinement inoculants in the form of master alloy Al-5Ti-1B, at the rate of 0.05%. Cooling curves for solidifications were plotted and analyzed. It was confirmed that the cooling curve with its first derivative provides, in addition to the liquidus and solidus temperatures, the phase transformation temperatures and information about the effectiveness of grain refinement. Varying the material of molds and through optical microscopy techniques... (Complete abstract click eletronic access below)

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Rodrigues, Ana Carolina Oliveira da Palma [UNESP]. "Efeito no processo ECAP (EQUAL CHANNEL ANGULAR) na microestrutura e nas propriedades mecânicas de uma liga comercial de alumínio AA3104." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/94461.

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A Engenharia tem buscado a fabricação de materiais com elevados valores de resistência mecânica e tenacidade. Uma das formas de obter tais propriedades é promover a redução do tamanho de grão do material. A fim de reduzir o tamanho de grãos e obter tais propriedades neste trabalho foi aplicado o processo ECAP (Equal Channel Angular Pressing) em amostras da Liga de Alumínio AA3104, liga de Al-Mn não Tratável Termicamente. As amostras de alumínio foram deformadas plasticamente por cisalhamento simples na região de interseção dos canais. A repetição deste processo resulta no encruamento do material. Os resultados mostram que após o processamento a microestrutura esta com grãos alongados devido ao encruamento do material e por meio de ensaios de dureza Vickers verifica-se um aumento de dureza após 3 passes de ECAP aplicados
A constant search in Engineering is the manufacturing of materials with high values of strength and tenacity. One way to obtain such properties is to promote the reduction of grain size of the material. In order to reduce the size of grains and obtain such properties in this work was applied the ECAP (Equal Channel Angular Pressing) process in samples of Aluminum Alloy AA3104, Al-Mn alloy is non-heat treatable. A sample of aluminum was deformed by simple shear in the intersection of the channels that leads to a severe plastic deformation. The repetition of the process results in a material with a cold work hardening. The results show that after the processing ECAP microstructure with elongated grains and by Vickers hardness testing the hardness increase after the three pass of ECAP applied

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14

Rodrigues, Ana Carolina Oliveira da Palma. "Efeito no processo ECAP (EQUAL CHANNEL ANGULAR) na microestrutura e nas propriedades mecânicas de uma liga comercial de alumínio AA3104 /." Guaratinguetá, 2013. http://hdl.handle.net/11449/94461.

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Orientador: Angelo Caporalli Filho
Banca: Valdir Alves Guimarães
Banca: Wyser José Yamakami
Resumo: A Engenharia tem buscado a fabricação de materiais com elevados valores de resistência mecânica e tenacidade. Uma das formas de obter tais propriedades é promover a redução do tamanho de grão do material. A fim de reduzir o tamanho de grãos e obter tais propriedades neste trabalho foi aplicado o processo ECAP (Equal Channel Angular Pressing) em amostras da Liga de Alumínio AA3104, liga de Al-Mn não Tratável Termicamente. As amostras de alumínio foram deformadas plasticamente por cisalhamento simples na região de interseção dos canais. A repetição deste processo resulta no encruamento do material. Os resultados mostram que após o processamento a microestrutura esta com grãos alongados devido ao encruamento do material e por meio de ensaios de dureza Vickers verifica-se um aumento de dureza após 3 passes de ECAP aplicados
Abstract: A constant search in Engineering is the manufacturing of materials with high values of strength and tenacity. One way to obtain such properties is to promote the reduction of grain size of the material. In order to reduce the size of grains and obtain such properties in this work was applied the ECAP (Equal Channel Angular Pressing) process in samples of Aluminum Alloy AA3104, Al-Mn alloy is non-heat treatable. A sample of aluminum was deformed by simple shear in the intersection of the channels that leads to a severe plastic deformation. The repetition of the process results in a material with a cold work hardening. The results show that after the processing ECAP microstructure with elongated grains and by Vickers hardness testing the hardness increase after the three pass of ECAP applied
Mestre

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15

Oguocha, Ikechukwuka N. A. "Characterization of aluminum alloy 2618 and its composites containing alumina particles." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0021/NQ37903.pdf.

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Nielsen, Guilherme Fernandes [UNESP]. "Filmes orgânicos contendo óxido de alumínio depositados a plasma." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/99661.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Filmes finos de alumina vêm sendo amplamente estudados em função de suas propriedades físicas e químicas. Em aplicações industriais, filmes de alumina são utilizados, por exemplo, em ferramentas de corte e em circuitos microeletrônicos. Neste trabalho empregou-se o processo de PECVD (do inglês, Plasma Enhanced Chemical Vapor Deposition) para sintetizar fimes contendo óxido de alumínio. Os filmes foram depositados a partir de plasmas excitados por radiofrequencia (13,56 MHz) em misturas de acetilacetonato de alumínio e argônio. Uma configuração experimental inédita foi empregada para permitir a incorporação de alumínio nos filmes: o pó do organometálico foi colocado diretamente no eletrodo por onde um plasma de argônio foi excitado. A pulverização catódica aliada a sublimação do organometálico faz com que haja, em determinadas condições, a deposição de filmes contendo alumina. Foram avaliados os efeitos da pressão do plasma e da potência do sinal de excitação nas propriedades dos filmes resultantes. A técnica de perfilometria foi utilizada para determinar a espessura da camada depositada. Difração de raios X (DRX), com a incidência de ângulos rasantes, foi empregada para investigar a estrutura do material. As técnicas de espectroscopia de absorção no infravermelho por transformada de Fourier (FTIR) e espectroscopia de energia dispersiva (EDS) foram respectivamente utilizadas para analisar a estrutura e a composição química dos filmes. A morfologia das amostras preparadas sobre aço-inoxidável foi analisada por microscopia eletrônica de varredura (MEV) enquanto a dureza foi avaliada por nanoindentação. Foram obtidos filmes amorfos com espessuras de até 7 μm que contêm carbono, alumínio, oxigênio e hidrogênio. Observou-se que as proporções de alumínio e carbono são altamente dependentes da energia cinética dos íons presentes no plasma...
Recently aluminium oxide thin films have been widely studied due to their important physical and chemical properties. Depositions in cutting tools and in microelectronic circuits are examples of industrial applications of industrial applications of aluminum oxide films. In this work, alumina-containing films were prepared by PECVD (Plasma Enhanced Chemical Vapor Deposition) using a new configuration of the plasma system; the metalorganic powder was placed directly on the powered electrode while the substrates were mounted on the grounded topmost electrode. The plasma was excited by applying radiofrequency (13.56 MHz) power to the lower electrode in an argon atmosphere. The sputtering combined with the sublimation of organometallic compound enabled the growth of an alumina-containing organic layer. The effect of the plasma excitation parameters on the properties of the resulting films was studied. Film thickness was measured using profilometry. Grazing angle incidence X-ray diffractometry (GAXRD) was used to determine the structure of the films. Fourier trasnform Infrared Spectroscopy (FTIR) and energy dispersive spectroscopy (EDS) techniques were used to analyze chemical structure and coposition, respectively. The surface morphology was analyzed by scanning electron microscopy (SEM) while film hardness was evaluated by nanoindentation Amorphous organic films were deposited with thicknesses of up to 7 μm. The films were composed of aluminum, carbon, oxygen and hydrogen, the proportions of carbon and aluminum being strongly dependent on the kinetic energy of the ions. The film surface was uniform but presented particulares and, in some cases, wrinkles. The proportion of such defects depends on the plasma excitation parameters

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Gianelli, Bruno Fernando [UNESP]. "Avaliação de ciclo de vida comparativa dos processos de anodização e oxidação eletrolítica com plasma de liga de alumínio." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/110888.

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Este projeto se propôs a realizar o tratamento superficial de ligas de alumínio por meio de método de oxidação eletrolítica com plasma (PEO) e elaborar uma avaliação de ciclo de vida (ACV) comparativa entre este processo e o de anodização convencional. Com tal intuito definiu-se como unidade funcional, uma amostra de alumínio AA5052-H34, com 11,1 cm2, sendo que para o processo de PEO empregou-se uma solução de 20 gramas de Na2SiO3 por litro de água deionizada, mantendo a densidade de corrente em i=0,01 a/cm2 e utlizando a mesma solução em 06 séries consecutivas de tratamento. Os resultados de caracterização dos filmes indicaram que as propriedades dos revestimentos começam a divergir após a terceira reutilização da solução. Assim, a quantidade de insumos foi alterada para 6.67 g (Na2SiO3)/333mL (H2O), influenciando a ACV desse tratamento superficial. As resistências à corroção e abrasão foram avaliadas para determinar a vida útil das amostras revestidas por ambos os processos. Com isso verificou-se que a correta relação entre a unidade funcional de ambos os tratamentos é de 26 amostras anodizadas por amostra tratada via PEO. Baseado nos dados expostos realizou-se a ACV dos processos, constatando cinco categorias de impacto relevantes: Combustíveis Fósseis, Respiráveis Inorgânicos, Carcinogêneos, Mudança Climática e Minerais, todas elas com um impacto maior para a anodização. Sendo assim, é possível constatar o menor impacto ambiental do processo de oxidação por plasma eletrolítico em comparação à anodização convencional
The ain of the present was to perform a surface treatment of aluminum alloys through the plasma electrolytic oxidation (PEO) method and implement a life cycle assessment (LCA) comparison between this process and the conventional anodizing. Within this context it was defined a functional unit an aluminum AA5052-H34 sample with 11.1 cm2, whit the PEO process performed using a solution of 20 grams of Na2SiO3 per liter of deionized water and a current density kept at i=0,01 A/cm2. The same solution has been reused for 6 consecutive treatments. The results of film characterization revealed the diverge of the coating properties after the third reutilization of the solution, changing the amount of inputs used to 6.67 g (Na2SiO3) / 333 mL (H2O), affecting the LCA for this surface treatment. Corrosion and wear resistances have been adopted as indicative of the lifetime of samples coated by both methods. According to the results, the corrent relationship between the functional unit of both treatments was defined as 26 anodized as 26 anodized samples to each PEO sample. Based on the above data a LCA was performed for both processes, finding out five relevant impact categories: Fossil Fuels, Inorganic Resp., Carcinogens , Climate Change and Minerals, all them with greater impact on the amodizing. According to the results, it is possible to note a lower environmental impact of PEO surface treatment as compared to conventional anodizing

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Gianelli, Bruno Fernando. "Avaliação de ciclo de vida comparativa dos processos de anodização e oxidação eletrolítica com plasma de liga de alumínio /." Bauru, 2014. http://hdl.handle.net/11449/110888.

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Orientador: Nilson Cristino Cruz
Banca: Maria Zanin
Banca: Sandro Donnini Mancini
Banca: Antonio Riul Júnior
Banca: Rogério Pinto Mota
Resumo: Este projeto se propôs a realizar o tratamento superficial de ligas de alumínio por meio de método de oxidação eletrolítica com plasma (PEO) e elaborar uma avaliação de ciclo de vida (ACV) comparativa entre este processo e o de anodização convencional. Com tal intuito definiu-se como unidade funcional, uma amostra de alumínio AA5052-H34, com 11,1 cm2, sendo que para o processo de PEO empregou-se uma solução de 20 gramas de Na2SiO3 por litro de água deionizada, mantendo a densidade de corrente em i=0,01 a/cm2 e utlizando a mesma solução em 06 séries consecutivas de tratamento. Os resultados de caracterização dos filmes indicaram que as propriedades dos revestimentos começam a divergir após a terceira reutilização da solução. Assim, a quantidade de insumos foi alterada para 6.67 g (Na2SiO3)/333mL (H2O), influenciando a ACV desse tratamento superficial. As resistências à corroção e abrasão foram avaliadas para determinar a vida útil das amostras revestidas por ambos os processos. Com isso verificou-se que a correta relação entre a unidade funcional de ambos os tratamentos é de 26 amostras anodizadas por amostra tratada via PEO. Baseado nos dados expostos realizou-se a ACV dos processos, constatando cinco categorias de impacto relevantes: "Combustíveis Fósseis", "Respiráveis Inorgânicos", "Carcinogêneos", "Mudança Climática" e "Minerais", todas elas com um impacto maior para a anodização. Sendo assim, é possível constatar o menor impacto ambiental do processo de oxidação por plasma eletrolítico em comparação à anodização convencional
Abstract: The ain of the present was to perform a surface treatment of aluminum alloys through the plasma electrolytic oxidation (PEO) method and implement a life cycle assessment (LCA) comparison between this process and the conventional anodizing. Within this context it was defined a functional unit an aluminum AA5052-H34 sample with 11.1 cm2, whit the PEO process performed using a solution of 20 grams of Na2SiO3 per liter of deionized water and a current density kept at i=0,01 A/cm2. The same solution has been reused for 6 consecutive treatments. The results of film characterization revealed the diverge of the coating properties after the third reutilization of the solution, changing the amount of inputs used to 6.67 g (Na2SiO3) / 333 mL (H2O), affecting the LCA for this surface treatment. Corrosion and wear resistances have been adopted as indicative of the lifetime of samples coated by both methods. According to the results, the corrent relationship between the functional unit of both treatments was defined as 26 anodized as 26 anodized samples to each PEO sample. Based on the above data a LCA was performed for both processes, finding out five relevant impact categories: "Fossil Fuels", "Inorganic Resp.", "Carcinogens ", "Climate Change" and "Minerals", all them with greater impact on the amodizing. According to the results, it is possible to note a lower environmental impact of PEO surface treatment as compared to conventional anodizing
Doutor

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19

Hafley, Johanna L. "A comparison of the aging kinetics of a cast alumina-6061 aluminum composite and a monolithic 6061 aluminum alloy." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26927.

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Electrical resistivity and hardness measurements were conducted during isothermal aging treatments of an alumina particulate reinforced 6061 aluminum metal matrix composite and a monolithic 6061 aluminum control material. Transmission electron microscopy was utilized to examine the microstructural changes accompanying the changes in the resistivity of the monolithic during aging. In addition, differential scanning calorimetry was used to investigate the growth kinetics and thermal stability of the metastable phases in the control sample. From DSC experiments, the heats of formation of the metastable phases were determined as functions of aging time and temperature. These results were used to characterize the aging behavior of the matrix material. Keywords: Aluminum composite, Conductivity, Aluminum alloys. (jes)

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Moreira, Lucas Tadeu Silva [UNESP]. "A influência da aplicação de fluído de corte no torneamento da liga de aluminio AA 7075." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/94423.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Atualmente, dentre os tipos de metais utilizados na indústria metal-mecânica, as ligas de alumínio têm sido largamente utilizadas, principalmente na indústria aeroespacial, devido suas propriedades físicas e mecânicas. As ligas de alumínio mais utilizadas são as da série 7000, as quais apresentam ótimas propriedades após o tratamento térmico, sendo o Zn o seu principal elemento de liga seguido de Mg, Cu e Cr. Nas operações de usinagem existentes, o torneamento permanece como a operação mais importante no trabalho destas ligas, onde o aumento da produtividade e a redução dos custos de fabricação são a chave para o sucesso dos negócios. Testes de laboratório realizados anteriormente mostraram que a redução da temperatura de corte se apresenta como um fator importante para o aumento da vida da ferramenta. Em contrapartida, na última década, algumas pesquisas tiveram como meta restringir ao máximo o uso de fluidos refrigerante e/ou lubrificante na indústria metal-mecânica. Dentre os fatores que justificaram esse procedimento estão os custos operacionais da produção, as questões ecológicas acompanhadas das exigências legais de conservação do meio ambiente e a preservação da saúde do ser humano. Desta maneira, a técnica da mínima quantidade de fluido (MQF) ganhou espaço, baseada também na necessidade do uso de lubrificantes ecologicamente corretos e com altíssima taxa de redução de calor. O trabalho proposto visa estudar a influência da aplicação das técnicas de lubrirefrigeração abundante e de mínima quantidade de fluido (MQF) no processo de torneamento da liga de alumínio AA 7075, estabelecendo uma relação entre o comportamento da rugosidade, forma do cavaco e o desgaste da ferramenta de corte. Através dos resultados deste trabalho foi possível...
Currently, among the types of metals used in metalworking industry, aluminum alloys have been widely used, especially in the aerospace industry because of their physical and mechanical properties. Aluminum alloys are the most commonly used 7000 series, which have excellent properties after heat treatment, the Zn being the main alloying element followed by Mg, Cu and Cr. In existing machining operations, turning remains the most important operation in the work of these alloys, where increasing productivity and reducing manufacturing costs are the way to business success. Laboratory tests have shown previously that reducing the cutting temperature is presented as an important factor for increasing the tool life. In contrast, in the last decade, some research had the goal much to restrict the use of refrigerant fluids and / or lubricant in metalworking industry. Among the factors that justified this procedure are operational costs of production, ecological issues accompanied by the legal requirements of environmental conservation and preservation of the health of human beings. Thus, the technique of the minimum quantity of fluid (MQF) gained space, also based on the need to use environmentally friendly lubricants and with high reduction ratio of heat. The proposed work aims to study the effect of applying the techniques of lubrication and cooling wet and minimal quantity of fluid (MQF) in the process of turning aluminum alloy AA 7075, establishing a relationship between the behavior of the roughness, chip and wear of the cutting tool. Through the results of this study has shown the potential use of the technique of minimal quantity of fluid (MQF) in machining of aluminum alloy AA 7075, considering his behavior was not below in relation to tool wear, the roughness of surfaces and the chip formed when compared... (Complete abstract click electronic access below)

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21

Moreira, Lucas Tadeu Silva. "A influência da aplicação de fluído de corte no torneamento da liga de aluminio AA 7075 /." Guaratinguetá : [s.n.], 2012. http://hdl.handle.net/11449/94423.

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Orientador: Marcos Valerio Ribeiro
Banca: Marcelino Pereira do Nascimento
Banca: Amauri Hassui
Resumo: Atualmente, dentre os tipos de metais utilizados na indústria metal-mecânica, as ligas de alumínio têm sido largamente utilizadas, principalmente na indústria aeroespacial, devido suas propriedades físicas e mecânicas. As ligas de alumínio mais utilizadas são as da série 7000, as quais apresentam ótimas propriedades após o tratamento térmico, sendo o Zn o seu principal elemento de liga seguido de Mg, Cu e Cr. Nas operações de usinagem existentes, o torneamento permanece como a operação mais importante no trabalho destas ligas, onde o aumento da produtividade e a redução dos custos de fabricação são a chave para o sucesso dos negócios. Testes de laboratório realizados anteriormente mostraram que a redução da temperatura de corte se apresenta como um fator importante para o aumento da vida da ferramenta. Em contrapartida, na última década, algumas pesquisas tiveram como meta restringir ao máximo o uso de fluidos refrigerante e/ou lubrificante na indústria metal-mecânica. Dentre os fatores que justificaram esse procedimento estão os custos operacionais da produção, as questões ecológicas acompanhadas das exigências legais de conservação do meio ambiente e a preservação da saúde do ser humano. Desta maneira, a técnica da mínima quantidade de fluido (MQF) ganhou espaço, baseada também na necessidade do uso de lubrificantes ecologicamente corretos e com altíssima taxa de redução de calor. O trabalho proposto visa estudar a influência da aplicação das técnicas de lubrirefrigeração abundante e de mínima quantidade de fluido (MQF) no processo de torneamento da liga de alumínio AA 7075, estabelecendo uma relação entre o comportamento da rugosidade, forma do cavaco e o desgaste da ferramenta de corte. Através dos resultados deste trabalho foi possível... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Currently, among the types of metals used in metalworking industry, aluminum alloys have been widely used, especially in the aerospace industry because of their physical and mechanical properties. Aluminum alloys are the most commonly used 7000 series, which have excellent properties after heat treatment, the Zn being the main alloying element followed by Mg, Cu and Cr. In existing machining operations, turning remains the most important operation in the work of these alloys, where increasing productivity and reducing manufacturing costs are the way to business success. Laboratory tests have shown previously that reducing the cutting temperature is presented as an important factor for increasing the tool life. In contrast, in the last decade, some research had the goal much to restrict the use of refrigerant fluids and / or lubricant in metalworking industry. Among the factors that justified this procedure are operational costs of production, ecological issues accompanied by the legal requirements of environmental conservation and preservation of the health of human beings. Thus, the technique of the minimum quantity of fluid (MQF) gained space, also based on the need to use environmentally friendly lubricants and with high reduction ratio of heat. The proposed work aims to study the effect of applying the techniques of lubrication and cooling wet and minimal quantity of fluid (MQF) in the process of turning aluminum alloy AA 7075, establishing a relationship between the behavior of the roughness, chip and wear of the cutting tool. Through the results of this study has shown the potential use of the technique of minimal quantity of fluid (MQF) in machining of aluminum alloy AA 7075, considering his behavior was not below in relation to tool wear, the roughness of surfaces and the chip formed when compared... (Complete abstract click electronic access below)
Mestre

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Silva, Cássia Cavalcanti da. "Utilização da curva de resfriamento na análise do refino de grão da liga AA 356 /." Guaratinguetá [s.n.], 2012. http://hdl.handle.net/11449/94396.

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Orientador: Carlos Kiyan
Coorientador: Kratus Ranieri
Banca: Ana Paula Rosifini Alves Claro
Banca: Mirian de Lourdes Noronha Motta Melo
Resumo: A liga AA 356 é uma liga de alumínio de grande importância porque é amplamente utilizada na indústria automobilistica e aeronáutica. Para melhorar as propriedades mecânicas dessa liga, são usados inoculantes para o refino de grãos; essas propriedades, apresentadas pelo produto final, dependem também das condições em que o metal foi fundido e solidificado. Os componentes solidificados em molde de metal, com uma taxa de extração de calor maior, têm propriedades mecânicas superiores àqueles solidificados em moldes de areia, que têm uma taxa de extração de calor mais baixa. A curva de resfriamento é usada como uma ferramenta para avaliar a eficácia de refino de grão e, é influenciada por fatores como o material do molde, a taxa de resfriamento e adições de inoculantes para refino de grão. Com o uso da curva de resfriamento, algumas propriedades da liga podem ser obtidas, tais como: o calor latente de solidificação, a fração sólida, as temperaturas liquidus e solidus, o tempo local de solidificação, além de identificar a presença de inoculantes para o refino de grão. A primeira derivada da curva melhora a precisão das informações apresentadas na curva de resfriamento. Essa derivada representa a taxa de resfriamento. Para o desenvolvimento desse trabalho alguns lingotes foram refundidos variando-se o material do molde e, consequentemente, a taxa de resfriamento; adicionando-se ou não inoculante para o refino de grão na forma de liga mãe Al-5Ti-1B, na proporção de 0,05%. As curvas de resfriamento para as solidificações foram plotadas e analisadas. Confirmou-se que a curva de resfriamento com sua primeira derivada fornecem, além das temperaturas solidus e liquidus, as temperaturas de transformações de fases e informações sobre a eficácia do refino de grão. Variando-se o material... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The AA 356 alloy is an aluminum alloy of great importance because it is widely used in the automobile and aeronautic industries. To improve the mechanical properties of this alloy, inoculants are used for grain refinement; these properties, presented by the final product, also depend on conditions, under which the metal was melted and solidified. The components solidified in a metal mold, with a higher heat extraction rate, have mechanical properties superior to the ones solidified in sand molds that have a lower heat extraction rate. The cooling curve is used as a tool to evaluate the effectiveness of grain refinement and it is influenced by factors as: mold material, cooling rate and of inoculants additions for grain refinement. With the use of the cooling curve analysis can be obtained some properties of the alloy, such as: the latent heat of solidification, the solid fraction, the solidus and liquidus temperatures, the local time of solidification. In addition, to evaluate the presence of inoculants for grain refinement. The first curve derivative improves the accuracy of the information given in the cooling curve. That derivative represents the cooling rate. For this work development, some ingots were remelted varying the mold material and, consequently, the cooling rate; also added or not the grain refinement inoculants in the form of master alloy Al-5Ti-1B, at the rate of 0.05%. Cooling curves for solidifications were plotted and analyzed. It was confirmed that the cooling curve with its first derivative provides, in addition to the liquidus and solidus temperatures, the phase transformation temperatures and information about the effectiveness of grain refinement. Varying the material of molds and through optical microscopy techniques... (Complete abstract click eletronic access below)
Mestre

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23

Dehurtevent, Marion. "Élaboration d'une céramique dentaire par stéréolithographie." Thesis, Valenciennes, 2017. http://www.theses.fr/2017VALE0036.

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La stéréolithographie, technique additive de mise en forme couche par couche, permet de limiter les contraintes de l’usinage mais doit répondre aux exigences des normes dentaires en vigueur pour son utilisation clinique. L’effet de la formulation de différentes céramiques alumineuses mises en barbotines et de l’orientation des modèles lors de la mise en forme ont été évalués. Ces travaux ont permis de développer et d’optimiser les différentes étapes de stéréolithographie à masque dynamique sans racleur et les propriétés physiques et mécaniques des céramiques densifiées adaptées à une application dentaire. Pour cette application, la mise en forme des barbotines était assurée lorsque la viscosité est inférieure ou égale à 138 mPa.s. Lorsque la viscosité était supérieure ou égale à 151 mPa.s, la mise en forme est impossible. L’augmentation du taux de matière sèche des barbotines d’alumine a augmenté la viscosité et la durée minimale nécessaire à la mise en repos avant photo-polymérisation. La diminution de la proportion de la phase organique a permis de limiter l’apparition de défauts et d’augmenter les propriétés mécaniques des céramiques. Le compromis entre un taux de matière sèche élevé et une viscosité maximale à ne pas dépasser a permis de sélectionner la barbotine avec un taux matière sèche de 80% et une grande granulométrie, comme meilleure formulation pour une utilisation dentaire. Lors de la mise en forme, l’augmentation de la surface des couches polymérisées a augmenté la durée de mise en repos des barbotines mais également le risque d’apparition de défauts dans les pièces. Ceci est à l’origine d’une diminution des propriétés mécaniques des céramiques. La surface maximale des couches pour ce type de procédé doit donc être limitée. Parallèlement, l’analyse microstructurale de l’alumine pure densifiée a montré une texturation. En effet, l’axe principal des grands grains suit l’orientation des couches, ce qui peut induire des propriétés mécaniques anisotropes. Plus précisément, lorsque ces grains étaient orientés perpendiculairement à la charge, la ténacité (par flexion) des céramiques a augmenté par rapport à celles des céramiques dont l’axe principal des grains était orienté parallèlement à la charge. Enfin, la répartition du stress dans une infrastructure de bridge, analysée par la méthode des éléments finis, était comparable entre les céramiques mises en forme par stéréolithographie et les céramiques usinées commercialisées. En vue d’une utilisation clinique, les céramiques mises en forme par stéréolithographie sans racleur doivent donc être orientées afin de présenter la plus faible surface de couche. Si l’axe principal des grands grains dans la céramique suit l’axe de la mise en forme, ces particules doivent être orientées perpendiculairement à la charge occlusale. Enfin, des études complémentaires sont nécessaires pour étudier la précision d’adaptation d’une infrastructure sur la préparation dentaire afin d’optimiser son ajustage
Stereolithography is a layer-by layer additive manufacturing method. It allows to reduce the strains that occur with milling methods. Its use for clinical purposes needs to follow dental material standards. The impact of slurry composition and the influence of layer orientation on mechanical and physical properties have been studied. This work permitted to develop and optimize a stereolithographic manufacturing process with digital light processing with no blade in order to obtain suitable physical and mechanical properties of alumina ceramics for dental applications. The slurries could be processed by stereolithography when their viscosity was below 138 mPa.s. Viscosity values beyond 151 mPa.s caused deformations in the printed layers. High dry matter content increased the viscosity and the minimal time needed to relax the slurries before photopolymerization. Reduction of the organic phase reduced the formation of defects and thus increased mechanical strength of the ceramics. The compromise between a high dry matter content and low viscosity that is compatible with stereolithography manufacturing was found for 80% dry matter content slurries having large particle size. The great layer surfaces increased the period needed to relax the slurries between two polymerizations, and the risk of defects to appear. This can reduce mechanical strength of the ceramics. To avoid this drawback, the maximal surface of the printed layers should be limited. In addition, microstructural analysis showed a texturation of pure densified alumina. In fact, the main axis of large particles followed the orientation of the printed layers. This led to anisotropic mechanical properties. Moreover, an orientation of these particles perpendicular to the load increased fracture toughness (measured by flexural strength) of the ceramics compared to those of ceramics presenting particles oriented parallel to the load. Finally, compared finite element analysis of a bridge framework showed similar strain repartition between stereolithographic and subtractive methods. In conclusion, stereolithography with no blade of dental ceramics need to orientate the models in order to present the smallest layer surfaces. If the axis of the large particles is the same as the printing axis, these particles must be oriented in order to be perpendicular to masticatory forces. More studies are required to evaluate the marginal gap between prosthetic frameworks and dental crown preparations to allow clinical use

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Hentour, Karim. "Nouveaux revêtements nanocomposites chargés en espèces carbonées pour applications tribologiques." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30229.

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Les aciers inoxydables austénitiques sont très utilisés dans l’industrie. Reconnus pour leur résistance à la corrosion, ils le sont également pour leur forte susceptibilité à l’usure adhésive (grippage). Cela a pour conséquence une dégradation accélérée des matériaux, ce qui conduit à des pannes brutales, à des pertes de performances et à une augmentation des coûts d’exploitation. Le CETIM et le CIRIMAT explorent des solutions basées sur des revêtements protecteurs afin de diminuer le coefficient de frottement et le volume d’usure. Des sols chargés en carbone sont élaborés et déposés par trempage-retrait sur des substrats en acier inoxydable 304L. Après gélification et traitement thermique en atmosphère inerte, des revêtements carbone-céramique d’une épaisseur d’environ 2 à 7 μm sont obtenus. Deux matrices (alumine et alumine-silice) sont étudiées, ainsi que différentes charges carbonées: du graphite commercial et des nanotubes de carbone (NTC) dont le nombre de parois moyen est égal à 2, 8 ou 20. Des essais tribologiques rotatifs bille-plan réalisés selon la norme ASTM G99 (bille en acier, charge normale 2N, vitesse 10 cm/s, 250 m de glissement) ont montré que les revêtements graphite-alumine présentent un plus faible coefficient de frottement et une plus faible usure que les revêtements alumine et NTC-alumine. Nous montrons que la surface totale de carbone disponible dans l’échantillon est le paramètre pertinent et que l’exfoliation progressive du graphite en graphène oligocouche (2-5) pendant l’essai permet de générer in situ de nouvelles surfaces, tandis que les NTC ne subissent pas d’endommagement majeur. Nous mettons en évidence la formation d’un tribofilm lubrifiant au contact bille/revêtements composites. Nous nous sommes donc orientés vers la pré-exfoliation du graphite dans le sol par différentes méthodes. Nous mettons en évidence qu’une méthode impliquant de grandes contraintes de cisaillement permet la pré-exfoliation efficace du graphite, la surface de carbone étant alors 1300 fois plus grande qu’avec la dispersion par sonde à ultrasons. Nous montrons que ce sont les échantillons GBC-alumine qui présentent les plus faibles volumes d’usure (0,0023 mm3) et coefficient de frottement (0,14) de ce travail. Le dernier chapitre est consacré à l’étude de l’adhérence du revêtement au substrat et du comportement tribologique des revêtements lors d’un essai industriel sévère (ASTM G133). Il est notamment mis en évidence que les revêtements à matrice alumine-silice présentent une meilleure adhérence que ceux à matrice alumine
Austenitic stainless steels are widely used in industry. Recognized for their resistance to corrosion, they are also known for their high susceptibility to adhesive wear (seizure). This results in accelerated material degradation leading to sudden failures, loss of performance and increased operating costs. CETIM and CIRIMAT are actively exploring solutions based on protective coatings in order to reduce the friction coefficient and the wear volume. Carbon-loaded sols are prepared and deposited by dip-coating on 304L stainless steel substrates. After gelation and heat-treatment in an inert atmosphere, carbon-ceramic coatings about 2 to 7 μm thick are obtained. Two matrices (alumina and alumina-silica) are studied, as well as different carbonaceous fillers: commercial graphite and carbon nanotubes (CNT) with an average number of walls equal to 2, 8 or 20. Rotative friction tests performed according to the ASTM G99 standard (steel ball, normal load 2N, velocity 10 cm/s, distance 250 m) have shown that the graphite-alumina coatings show a lower friction coefficient and a lower wear than the alumina- and CNT-alumina coatings. We show that the total available carbon surface area in the sample is the relevant parameter and that the progressive exfoliation of graphite to flew-layered-graphene (2-5) during the test generates new surfaces in situ whereas the CNT do not sustain any major damage. We bring to light the formation of a lubricating tribofilm in the contact between the friction ball and the composite coating. Therefore, we have focused on the pre-exfoliation of graphite in the sol by different methods. We show that a method involving high shear stresses allows an efficient pre-exfoliation of graphite, the carbon surface area being 1300 times higher than when performing the dispersion using an ultrasonic probe. We show that the BLG-alumina samples have the lowest wear volumes (0.0023 mm3) and friction coefficient (0.14) reported in this work. The last chapter is devoted to the study of the adhesion of the coating to the substrate and to the tribological behavior of the coatings in a severe industrial test (ASTM G133). It is notably demonstrated that the alumina-silica matrix coatings show a better adhesion than the alumina-matrix ones

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25

Keles, Ozgur. "Production And Characterization Of Alumina Fiber Reinforced Squeeze Cast Aluminum Alloy Matrix Composites." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609726/index.pdf.

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The aim of the present study was to investigate the effects of different levels of Saffil alumina fiber addition, magnesium content in aluminum alloy matrix and casting temperature on the mechanical behavior, microstructure and physical properties of short fiber reinforced aluminum matrix composites. The main alloying element silicon was kept constant at 10 wt%. Magnesium contents were selected as 0.3 wt% and 1 wt%. Saffil alumina fiber preforms varied from 10 to 30 vol%. The casting temperatures were fixed at 750 °
C and 800 °
C. Micro porosity was present at the fiber-fiber interactions. Closed porosity of the composites increased when fiber vol% increased, however, variation in casting temperature and magnesium content in matrix did not have influence on porosity. Hardness of the composites was enhanced with increasing fiber vol%, magnesium content in matrix and decreasing casting temperature. Alignment of fibers within the composite had an influence on hardness
when fibers were aligned perpendicular to the surface, composites exhibited higher hardness. The highest hardness values obtained from surfaces parallel and vertical to fiber orientation were 155.6 Brinell hardness and 180.2 Brinell hardness for AlSi10Mg1 matrix 30 vol% alumina fiber reinforced composite cast at 800 °
C and at 750 °
C, respectively. 30 vol% Saffil alumina fiber reinforced AlSi10Mg0.3 matrix composite cast at 750 °
C showed the highest flexural strength which is 548 MPa. Critical fiber content was found as 20 vol% for all composites.

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26

Almeida, Filho Claudio de. "Sintese de materiais via sol-gel : casos : titanato de aluminio e alumina ativada." reponame:Repositório Institucional da UFSC, 1998. http://repositorio.ufsc.br/xmlui/handle/123456789/77956.

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Dissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro Tecnologico
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As matérias-primas cerâmicas alumina ativada e titanato de alumínio (ba-AI2TiO5) foram preparados pelo método sol-gel. A alumina ativada na forma de microesferas foi produzida por geleificação externa utilizando nitrato de alumínio como precursor. Obteve-se microesferas não densas de pseudoboemita, com poros de até 50 mm de diâmetro, que apresentaram área superficial específica de aproximadamente 250 m2/ g. Quando estas microesferas foram calvinadas a 500°C a área superficial específica aumentou para 300 m2/ g. Os testes de calcinação desse material mostrou a g-alumina já formada a 350 °C e a a-alumina bem cristalizada a 1100 °C. Para produzir pó de titanato de alumínio utilizou-se alcóxidos de alumínio e de titânio como precursores com adição de ácido clorídrico. O gel mais translúcido preparado promoveu sob tratamento térmico uma evolução estrutural atípica: a cristalização direta da fase titanato de alumínio a 900 °C. Nesta temperatura a fase titanato de alumínio foi detectado após 3 horas de tratamento. Com 5 horas de tratamento a 900 °C a fase apresentou-se bem cristalizada e permaneceu assim com 10 horas de tratamento. A 1400 °C ocorreu a formação de titanato de alumínio em todas as amostras preparadas.

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27

Silva, José Wilson de Jesus [UNESP]. "Efeito dos oxi-ânions do grupo VIB sobre a corrosão aquosa das ligas Al(2024) e Al(7050) utilizadas na indústria aeronaútica." Universidade Estadual Paulista (UNESP), 2003. http://hdl.handle.net/11449/97122.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Foram caracterizados os comportamentos eletroquímicos e avaliadas as resistências à corrosão das ligas aeronáuticas 2024-T351 e 7050-T7451 em soluções aquosas de cloreto contendo cromato, molibdato e tungstato. Foram realizados ensaios de corrosão não-eletroquímicos de imersão prolongada acompanhados de análise metalográfica de superfície por microscopia óptica e identificação dos produtos de corrosão por difratometria de raios-X. A análise quantitativa de superfícies das ligas após a imersão, indica que os pites formados têm áreas médias similares. Os pites são mais largos do que profundos e de geometria, predominantemente, cônica ou quase-cônica e irregular. Em todos os produtos de corrosão de cada liga foi encontrado hidróxido de alumínio, em suas diferentes formas cristalinas. Medidas de perda de dureza, como uma conseqüência da deterioração superficial, também foram determinadas. Além disso, ensaios eletroquímicos como medidas de potencial em circuito aberto, curvas de polarização e voltametria cíclica complementaram este estudo. Em meio aerado os resultados obtidos mediante medidas eletroquímicas são consistentes com aqueles obtidos nos ensaios de imersão, em particular o efeito do CrO42- e do MoO42-. O WO42- mostrou-se agressivo em períodos prolongados de imersão. Apesar dos ensaios revelarem uma redução parcial de MoO42- em ambas as ligas, o efeito desse oxi-ânion parece ser diferente sobre cada liga. Em meio desaerado as ligas apresentam passivação em todos os eletrólitos. A adição dos oxi-ânions não modificou significativamente o potencial de pite para a liga 7050, enquanto que para a liga 2024 ele foi deslocado levemente para valores mais positivos.
It has been characterized the electrochemical behavior and evaluated the 2024-T351 and 7050-T7451 aircraft alloys corrosion resistance in chloride aqueous solutions containing chromate, molybdate and tungstate. It has been carried out non-electrochemical long immersion corrosion testings accompanied by surface metalography analysis achieved by light microscopy and corrosion products identification by X-ray difratometry. Surfaces quantitative analysis upon the alloys after immersion, indicates that formed pits have similar average area. Pits are widther than deeper and own predominantly a conical or quasi-conical and irregular geometry. In all corrosion products of each alloy it has been found aluminum hydroxide in its different crystalline ways. Hardness loss measurements have also been determined. In addition, electrochemical testings such as open circuit potential measures, polarization curves and cyclical voltammetry have completed this study. In aerated means the obtained results before electrochemical mesurements are similar to those obtained in the immersion tests, in particular CrO42- and MoO42- effects. WO42- has been found to be aggressive in very long immersion period. Though tests display a MoO42- partial reduction in both alloys, this oxi-anion effect seems to be different upon each alloy. In de-aerated means alloys present passivation in all eletrolytes. Oxi-anion addition has not changed significantly pit potential for 7050 alloy, while for 2024 alloy it has been dislocated, slightly, for more positive values.

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Costa, Regis Silva da. "Estudo da corrosão entre a caixa de distribuição e o bloco de cilindros de um motor ciclo Diesel." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265572.

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Orientador: Rodnei Bertazzoli
Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica, Faculdade de Engenharia Eletrica e de Computação e Instituto de Quimica
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Resumo: A presente dissertação de mestrado tem por objetivo o estudo do fenômeno de corrosão entre dois componentes do motor de combustão interna, ciclo Diesel, caixa de distribuição (liga de alumínio AA A380.0) e bloco de cilindros (ferro fundido cinzento), bem como o estudo de alternativas para minimização desta corrosão. Foram utilizados métodos de medição de diferença de potencial galvânico, caracterização de materiais e medições de perda de massa. A liga de alumínio que atualmente é utilizada na caixa de distribuição apresenta maior diferença de potencial com o bloco de cilindros quando comparada às demais ligas de Al que foram ensaiadas com o bloco de cilindros, com a diferença de potencial em torno de 200 mV. Possui maior susceptibilidade à corrosão galvânica com o bloco de cilindros, agindo como anodo no par galvânico. A liga AA 413 possui menor diferença de potencial (150 mV) no par galvânico com o bloco de cilindros de ferro fundido cinzento, em comparação com a liga AA A380.0, possuindo semelhante resistência mecânica. As ligas AA 410, 5052 e 1100, foram as ligas que apresentaram menor diferença de potencial com o bloco de cilindros, em torno de 45 mV. Com a passivação da liga AA A380.0 em solução polimérica, a diferença de potencial diminuiu para 165 mV. Pelo ensaio de perda de massa da liga A380.0, sem par galvânico, obteve-se a densidade de corrente e taxa de corrosão, e por consequência a perda de massa da caixa de distribuição estimada para 300.000 km que foi de 7 g. O ensaio de perda de massa da liga AA A380.0 com formação de par galvânico com o bloco de cilindros, possibilitou estimar a perda de massa por corrosão para a caixa de distribuição com 300.000 km que ficou em torno de 100 g, evidenciando a severidade da corrosão galvânica na caixa de distribuição no par galvânico com o bloco de cilindros. Para a liga AA A380.0 passivada em solução polimérica a perda de massa estimada para a caixa de distribuição com 300.000 km ficou em torno de 36 g e para a liga AA 413 ficou em torno de 57 g. Para ambas ligas uma melhora significativa na resistência à corrosão, quando comparado à liga AA A380.0
Abstract: The present investigation has for purpose the study of the corrosion phenomenon between two components of Diesel engine, timing case (aluminum alloy AA A380.0) and crankcase (grey iron casting), and the study of alternatives for the decreasing of this corrosion. Measurement methods of potential galvanic difference, materials characterization and mass loss measurements had been used. The aluminum alloy that is currently used in the timing case presents greater potential difference with the crankcase when compared with the other Al alloys that was tested with the crankcase, with the potential difference around 200 mV. It has greater feasibility to the galvanic corrosion with the crankcase, acting as anode in the galvanic couple. AA 413 alloy presents lower potential difference (150 mV) in the galvanic couple with the crankcase, in comparison with AA A380.0 alloy. AA 410, 5052 and 1100 alloys, had been the alloys that had presented minor potential difference with the crankcase, around 45 mV. With the AA A380.0 protection in polymeric solution, the potential difference decreased to 165 mV. By the mass loss measurements AA A380.0 alloy, without galvanic couple, it was gotten chain density and corrosion rate, and consequently the mass loss of timing case appraised for 300.000 km that was around 7 g. Through the mass loss measurements AA A380.0 alloy, with formation of galvanic couple with crankcase, made possible appraise the corrosion mass loss for the timing case with 300,000 km that was around 100 g, evidencing the severity of the galvanic corrosion in the timing case in the galvanic couple with crankcase. For AA A380.0 alloy passivated in polymeric solution the mass loss appraised for timing case with 300,000 km was around 36 g and for AA 413 alloy it was around 57 g. For both alloys a significant improvement in the corrosion resistance, when compared with AA A380.0 alloy
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Automobilistica

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29

Zimmer, Andre. "Influência da aspersão térmica por plasma e suas altas taxas de resfriamento na cristalinidade de fases do sistema Al2O3-TiO2-Al2TiO5." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/18584.

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Esta tese investigou o efeito da taxa de resfriamento em partículas de Al2O3, Al2O3 - TiO2, e Al2TiO5 aspergidas por pistola a plasma e submetidas a diferentes taxas de resfriamento (alta: aspersão contra um substrato metálico a 100 mm de distância da pistola de plasma, e baixa: contra uma superfície de água, a 300 mm de distância). Os resultados foram avaliados por microscopia eletrônica de varredura (com EDX) e por difração de raio X para a caracterização de fases e cálculo de tamanho de cristalito por Single Line. O óxido Al2TiO5 na forma de pó quase amorfo com composição estequiométrica de tialita (tialita*) aspergido foi obtido por coprecipitação, a partir dos precursores TiCl4 e Al(NO4)3, tratado termicamente a 400, 600, 800, 900, 1000, 1200, 1300 e 1400 °C, com 6 h de patamar. Nos tratamentos térmicos com 6 horas de patamar a 800 °C e mais nitidamente a 900 °C, é identificada a formação parcial da fase tialita; desta forma, foram realizados tratamentos térmicos a 900, 1000 e 1100 °C, porém com 30 minutos de patamar. A Al2O3-a com tamanho de cristalito micrométrico foi obtida para menores taxas de resfriamento. Com o aumento da taxa de resfriamento, predominaram nanocristalitos de alumina Al2O3-g, coexistindo com fase amorfa. Já para a titânia, a fase rutilo pode ser obtida mesmo com altas taxas de resfriamento. Quando a tialita* foi submetida à alta taxa de resfriamento, levou exclusivamente à formação da fase metaestável tialita b como estrutura cristalina. No entanto, o mesmo pó, a taxas de resfriamento não tão altas, resultou na obtenção de tialita b, Al2O3-a e rutilo. Tratamentos térmicos da tialita* propiciaram a formação de tialita b, e incipientemente anatásio, com tamanho de cristalito muito pequeno (abaixo de 30 nm). À medida que a temperatura de tratamento térmico aumentou, surgiram simultaneamente as fases Al2O3-a, rutilo e tialita b. A obtenção de fases metaestáveis só foi possível quando o tamanho de cristalito era pequeno – abaixo de 100 nm, o que evidenciou a importância do número de átomos na superfície, como fator de estabilização (ou metaestabilização) de fases obtidas foras do equilíbrio.
This thesis investigated the effect of cooling rate of Al2O3, Al2O3 - TiO2 and Al2TiO5 particles plasma sprayed and subjected to different cooling rates (high: to spray against a metal substrate to 100 mm away from the plasma gun, and low: against a surface of water, 300 milimeters away). The results were evaluated by scanning electron microscope (with EDX) and X ray diffraction to characterize phases and crystallite size through Single Line. The sprayed Al2TiO5 oxide was a quasi-amorphous powder with stoichiometric composition of tialite (tialita*) obtained by co-precipitation from precursors TiCl4 and Al(NO4)3, heat treated at 400, 600, 800, 900, 1000, 1200, 1300 and 1400 °C with 6 hours of dwell. In the heat treatments with 6 hour of dwell at 800 ° C and more explicitly at 900 °C, is identified partial formation of tialite phase; then, heat treatments were performed at 900, 1000 and 1100 ° C, but with 30 minutes of dwell. Basically, a-Al2O3 with micrometer crystallite size was obtained for smaller cooling rates. By increasing the cooling rate, there were predominantly g-Al2O3 nanocrystallites coexisting with amorphous phase. However, for the titania, the rutile phase could be obtained even with high cooling rates. When tialita* was subjected to high cooling rate, exclusively, metastable b tialite was observed as crystalline phase. However, the same powder, with cooling rates not so high, resulted in b tialite, a-Al2O3 and rutile. Heat treatments of tialita* provided the formation of b tialite, and incipiently anatase with crystallite size very small (below 30 nm). As the heating treatment temperature was increased, there were simultaneously a-Al2O3, rutile and b tialite phases. Metastable phases were obtained only when the crystallite size was small - less than 100 nm. This highlighted the importance of the number of atoms on the surface as a stabilizing factor (or metastabilization) to produce phases out of equilibrium.

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30

Harper, Christopher Paul. "Effect of alumina particle additions on the aging kinetics of 2014-aluminum matrix composites." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/26510.

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Differential Scanning Calorimetry (DSC) was conducted on 2014 aluminum, 2014 aluminum reinforced with 10 and 15 percent by volume of alumina particles, 2024 aluminum, and a A1/4%Cu alloy. Electrical resistivity and matrix micro-hardness measurements were conducted on the 2014 aluminum alloy and the metal matrix composites (MMC) during isothermal aging. Transmission Electron Microscopy (TEM) and DSC were used to identify the metastable phases formed in the 2014 aluminum alloy. The effect of alumina particle addition on the precipitation, growth and thermal stability of the metastability phases in the 2014 aluminum alloy and MMC were studied. Results were used to characterize the effect of the alumina reinforcement on the aging kinetics of the 2014 aluminum alloy matrix

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31

Allen, Susan Marie. "Effect of alumina particle additions of the aging kinetics of 6061 aluminum matrix composites." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA238052.

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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 1990.
Thesis Advisor(s): Dutta, I. "June 1990." Description based on title screeen viewed on October 15, 2009. DTIC Descriptor(s): Scanning, aging(materials), composite materials, growth(general), thermal stability, phase, particles, aluminum oxides, electrical resistance, kinetics, hardness, metastable state, isotherms, calorimetry, protective treatments, addition, measurement DTIC Indicator(s): Aluminum matrix composites. Author(s) subject terms: Aluminum matrix composites. Includes bibliographical references (p. 54-56). Also available in print.

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32

Angélico, Cristiano [UNESP]. "Soldagem TIG-AC onda retangular: efeitos da velocidade de soldagem sobre as propriedades mecânicas da Liga AA 6063-T6." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/96488.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Neste trabalho foram investigados os efeitos da velocidade de soldagem no comportamento mecânico em juntas da liga AA 6063-T6, soldadas pelo processo TIG-CA com onda retangular desbalanceada. Foram analisadas as características macroestruturais (diluição do metal de base e coeficiente de forma). O planejamento experimental contemplou a utilização de metal de adição (AWS ER 4043), chanfro em v (60º), e variações nos parâmetros de ajuste de onda retangular nominalmente: amplitude de corrente negativa e tempo de polaridade negativa do eletrodo. A análise microestrutural utilizou microscopia ótica e microscopia eletrônica de varredura em observações no metais de solda obtidos e correspondentes ZTA. A avaliação mecânica foi realizada por meio de ensaios de tração nas juntas soldadas e medidas de microdureza Vickers. Adicionalmente, foram medidas as temperaturas máximas alcançadas nas juntas durante a soldagem. Os resultados mostram alterações nos valores das diluições do metal de base e na configuração geométrica dos cordões, em função da variação na velocidade de soldagem. As microestruturas desenvolvidas nos meios de solda e ZTA não se diferenciaram significativamente e, por consequencia, o comportamento mecânico detectado foi similar em todas as condições de soldagem aplicadas
In this study were investigated the welding speed effects in the mechanical behavior in welded joints of AA 6063-T6 alloy, welded by TIG-CA process with retangular wave. Were analyzed characteristics macrostructural (base material dillution, width and depth) of the weld bead. The experimental planning used and addition metal (AA 4043 alloy), bevel type v (60º) and variations in the setting parameter of retangular wave called negative current amplitude and duration of negative electrode polarity. The microstructural analysis used optical microscopy and scanning electron microcopy observation in the weld metals and HAZ obtained. The mechanical evaluation was performed by a tensile test on welded joints and Vickers microhardness measurements. In addition, it was measure the maximum temperature reached in during welding. The results show market changes in the values of the dillutions tested and the geometric configuration of the weld beads, mainly due to the variation in the welding speed. The microstuctures developed in the weld meal and HAZ did not differ significantly and, consequently, the mechanical behavior detected was similar in all welding conditions applied

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Lunardi, Nadia 1976. "Analise in vitro da resistencia ao cisalhamento de braquetes metalicos submetidos a reciclagem repetida : fixados com diferentes materiais." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289328.

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Orientadores: João Sarmento Pereira Neto, Simonides Consani
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: O objetivo desta pesquisa foi avaliar in vitro a resistência ao cisalhamento de braquetes ortodônticos metálicos submetidos a duas reciclagens consecutivas com jato de óxido de alumínio, em função de quatro tipos diferentes de materiais fixadores. A amostra consistiu de 40 incisivos bovinos para confecção dos corpos-de-prova. Quarenta braquetes metálicos edgewise, de incisivo central Ultraminitrim (Dentaurum), foram colados nos dentes bovinos com os seguintes materiais fixadores: Transbond XT, Concise, Smartbond e Fuji Orto, seguindo as instruções do fabricante. Após a colagem os corpos-de-prova foram armazenados em água destilada numa estufa a 37ºC por 24 horas e submetidos à 500 ciclos térmicos com 30 segundos em cada balho (5ºC e 55ºC). O ensaio de resistência ao cisalhamento foi realizado numa máquina Instron com velocidade de 0,5mm/min. Os braquetes removidos foram reciclados com jateamento de óxido de alumínio (50 micrômetro) e colados novamente no mesmo corpo-de-prova, utilizando os mesmos materiais fixadores. Após o segundo ensaio de resistência ao cisalhamento, os procedimentos de reciclagem, recolagem e ensaio de força foram repetidos. Os dados foram submetidos à análise de variância e ao teste de Tukey (p=0.05), aplicado para cada sistema adesivo nos diferentes tratamentos dos braquetes metálicos. Foi comprovado que reciclagens repetidas, utilizando o jateamento de óxido de alumínio, não interferem na resistência adesiva, independente do sistema adesivo empregado. Dentre os adesivos utilizados, o Transbond XT apresentou os maiores valores de resistência ao cisalhamento, independente do tratamento do braquete. Assim, concluímos que o efeito cumulativo das reciclagens não afetou a resistência ao cisalhamento de braquetes metálicos e que o efeito adesivo do material utilizado para fixação do braquete não foi alterado pelas reciclagens repetidas
Abstract: The aim of this research was to evaluate in vitro shear bond strength of metallic orthodontic brackets submitted to two consecutive recyclings with aluminium oxide air abrasion, making use of four different bond materials. The sample consisted of 40 bovine incisives. Forty metallic orthodontic edgewise brackets of central incisor Ultraminitrim (Dentaurum), were fixed in the bovine teeth with the following bonded material: Transbond XT, Concise, Smartbond and Fuji Orto, following the manufacturer's instructions. After bonding, they were stored in distilled water in incubators at 37ºC for 24 hours and submitted to 500 thermal cycles with 30 seconds in each bath (5ºC and 55ºC). The shear bond strength was determined with an Instron universal machine with 0,5mm/min speed. The removed brackets were recycled with aluminium oxide air abrasion (50 micrometer) and bonded again in the same bovine incisive, using the same bond material. After the second shear bond strength test the recycling procedures, the rebonding and shear bond strength test were repeated. The data were submitted to Analysis of Variance and Tukey's test (p=0.05), applied for each adhesive system in different treatments of metallic brackets. It was demonstrated that repeated recyclings, using the aluminium oxide air abrasion, don't interfere in the adhesive resistance, independent of the employed bond material. Among the used bond materials, Transbond XT presented the largest resistance values of shear bond strength, independent of the treatment of the bracket. Thus, we concluded that the recycling cumulative effects didn't affect the shear bond strength of metallic orthodontic brackets and that the effect bond material used for fixation of the bracket was not altered by the repeated recyclings
Mestrado
Ortodontia
Mestre em Ortodontia

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34

Angélico, Cristiano. "Soldagem TIG-AC onda retangular : efeitos da velocidade de soldagem sobre as propriedades mecânicas da Liga AA 6063-T6 /." Bauru : [s.n.], 2012. http://hdl.handle.net/11449/96488.

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Orientador: Gilberto de Magalhães Bento Gonçalves
Banca: Sérgio Rodrigues Barra
Banca: Yukio Kobayashi
Resumo: Neste trabalho foram investigados os efeitos da velocidade de soldagem no comportamento mecânico em juntas da liga AA 6063-T6, soldadas pelo processo TIG-CA com onda retangular desbalanceada. Foram analisadas as características macroestruturais (diluição do metal de base e coeficiente de forma). O planejamento experimental contemplou a utilização de metal de adição (AWS ER 4043), chanfro em "v" (60º), e variações nos parâmetros de ajuste de onda retangular nominalmente: amplitude de corrente negativa e tempo de polaridade negativa do eletrodo. A análise microestrutural utilizou microscopia ótica e microscopia eletrônica de varredura em observações no metais de solda obtidos e correspondentes ZTA. A avaliação mecânica foi realizada por meio de ensaios de tração nas juntas soldadas e medidas de microdureza Vickers. Adicionalmente, foram medidas as temperaturas máximas alcançadas nas juntas durante a soldagem. Os resultados mostram alterações nos valores das diluições do metal de base e na configuração geométrica dos cordões, em função da variação na velocidade de soldagem. As microestruturas desenvolvidas nos meios de solda e ZTA não se diferenciaram significativamente e, por consequencia, o comportamento mecânico detectado foi similar em todas as condições de soldagem aplicadas
Abstract: In this study were investigated the welding speed effects in the mechanical behavior in welded joints of AA 6063-T6 alloy, welded by TIG-CA process with retangular wave. Were analyzed characteristics macrostructural (base material dillution, width and depth) of the weld bead. The experimental planning used and addition metal (AA 4043 alloy), bevel type "v" (60º) and variations in the setting parameter of retangular wave called "negative current amplitude and duration of negative electrode polarity". The microstructural analysis used optical microscopy and scanning electron microcopy observation in the weld metals and HAZ obtained. The mechanical evaluation was performed by a tensile test on welded joints and Vickers microhardness measurements. In addition, it was measure the maximum temperature reached in during welding. The results show market changes in the values of the dillutions tested and the geometric configuration of the weld beads, mainly due to the variation in the welding speed. The microstuctures developed in the weld meal and HAZ did not differ significantly and, consequently, the mechanical behavior detected was similar in all welding conditions applied
Mestre

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35

Belenguer, Rizo Marc. "Funcionalització de superfícies d'alumini anoditzat." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/396301.

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Utilitzant una tecnologia implementada prèviament en el grup, en aquesta Tesi s'ha optimitzat el procés de formació de plantilles d'Alumini / Alúmina mitjançant anoditzat d'aliatges AA 1050 i 1080. L'estructura i geometria de les plantilles s'ha optimitzat mitjançant tècniques de reducció de la capa barrera (procés BLT) i d'obertura de porus (procés OBL i atac amb àcid fosfòric). Amb aquestes plantilles s'han obtingut electroquímicament nanoestructures 1D de Ni, Au i Co. En tots els casos s'ha comprovat que les úniques tècniques que permeten obtenir nanodipòsits de qualitat són les polsants, amb polsos complexos que combinen polsos de reducció, d'oxidació i a circuit obert. Amb tots els metalls s'ha estudiat el procés de creixement i s'ha constatat que hi ha importants diferències entre el creixement del níquel i el dels altres dos metalls: mentre el creixement dels nanofils de Ni es produeix uniformement en tots els porus de la plantilla, els de Au i Co es produeixen en feixos distribuïts aleatòriament per tota la superfície. En un estudi paral•lel de les primeres etapes de l'anoditzat, s'ha caracteritzat l'estructura i composició de les protuberàncies que apareixen en l'anomenat procés de cremat (burning) de l’alumini; s'ha comprovat que en tots els casos en què apareixen aquestes protuberàncies l'EDX detecta Fe en el vèrtex. Es tracta, doncs, de les restes d'una partícula inter-metàl•lica AI Fe Si , dissolta en el pretractament de I 'alumini .
Using a technology previously implemented in the group, in this PhD thesis the process of obtaining aluminium/alumina templates has been optimized by anodizing AA1050 and 1080 aluminium alloys. The structure and geometry of the template has been optimized using techniques such as barrier layer reduction (BLT process) and opening of pores (OBL process and attack with phosphoric acid). With these templates 1D nanostructures of Ni, Au and Co have been obtained electrochemically. Pulse techniques have demonstrated to be the most suitable to obtain the nanowires. The growth process has been studied for all metals and it has been verified that, while the growth of Ni nanowires occurs uniformly in all the pores of the template, those of Au and Co do occur randomly distributed across the surface. In a parallel study of the early stages of anodization, the structure and composition of the bumps that appear in the process called burning of aluminium have been characterized. In all cases Fe has been detected at the apex of the bumps. It is, therefore, the remains of an intermetallic particle of A1FeSi dissolved in the pretreatment of aluminium.

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36

Somani, Vikas. "ALUMINA-ALUMINUM TITANATE-TITANIA NANOCOMPOSITE: SYNTHESIS, SINTERING STUDIES, ASSESSMENT OF BIOACTIVITY AND ITS MECHANICAL AND." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2489.

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This thesis reports the development, synthesis and characterization of a ceramic-ceramic nanocomposite system for its possible application as structural and electronic biomaterial in the biomedical industry. The study selected and synthesized alumina-aluminum titanate-titania (Al2O3-Al2TiO5-TiO2) nanoceramic composite using a simple Sol-Gel technique, which can be easily reproduced. Aluminum propoxide and titanium propoxide were used as precursor chemicals. Propanol and 2- methoxy ethanol were used as solvent and stabilizer, respectively. Thermal analyses were performed for a systematic understanding of phase evolution from the synthesized gel. X-Ray diffraction technique was used to confirm the phase evolution, phase purity, crystallite size and crystal structure(s) of the phase(s). Calcination of the powder at low temperatures (700°C) leads to formation of Al2O3-TiO2 nanocomposite and at higher temperatures into Al2O3-Al2TiO5-TiO2 nanocomposite confirmed by XRD analysis. Electron microscopic techniques were used to investigate powder morphology, crystallite size and inter-planner spacing. High Resolution Transmission Electron Microscopy images of the calcined powder showed agglomerates of powder particles with particle size in 15-20 nm range. As-synthesized powder was uniaxially pressed into cylindrical pellets and sintered at elevated temperatures (1000-1400oC) to study the sintering behavior, densification characteristics, and measurement of mechanical and electrical properties and assessment of bioactivity. Phase transformation induced by the sintering process was analyzed by X-ray powder diffraction technique. The effects of nanosize of powder particles and multi-phases on densification, and mechanical and electrical properties were investigated. Vickers hardness and biaxial flexural strength tests were used to determine mechanical properties. Bioactivity of the nanocomposite was assessed in Simulated Body Fluid (SBF), which has the same ionic concentration as that of human plasma. Effects of biodegradation and change in mechanical properties of the composite when kept in SBF and maintained in a static condition were studied in terms of weight loss, change in the pH of the acellular solution and change in mechanical properties (hardness and biaxial strength). Scanning Electron Microscopy was used to observe the formation of apatite crystals on the surface of the nanocomposite specimens soaked in SBF. The results obtained throw light on biocompatibility and bioactivity of Al2TiO5 phase, which has not been reported so far in the literature to the best of our knowledge. Dielectric constant and dissipation factor of the sintered nanocomposite pellets were measured using HP 4284A impedance-capacitance-resistance meter and 16451 B dielectric test fixture at 1 MHz frequency. The effects of sintering time, temperature and phases present on the electrical properties were studied and are reported in the thesis.
M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering

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37

Xu, Liang. "The deformation and fracture of co-continuous alumina-aluminum composites under monotonic and cyclic loading /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487858417982165.

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38

Etchepare, Pierre-Luc. "Revêtements barrière d'alumine amorphe appliqués à l’intérieur de flacons pharmaceutiques en verre, par le procédé de dépôt chimique en phase vapeur." Thesis, Toulouse, INPT, 2015. http://www.theses.fr/2015INPT0062.

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Les matériaux utilisés dans le domaine de l’emballage sont parfois revêtus d’une couche barrière afin de réduire les interactions entre le contenant et son contenu. Sur les flacons en verre, le dépôt de ces couches permet de limiter la dégradation de leur surface interne, de réduire le lessivage des cations du verre et d’améliorer la stabilité des propriétés du produit au contact. Dans ce contexte, un procédé de dépôt chimique en phase vapeur (CVD) à partir de tri-isopropoxyde d’aluminium (TIA) par injection liquide directe est mis en œuvre pour appliquer des revêtements d’alumine amorphe sur les parois internes de flacons en verre. Etant donné le nombre important de paramètres expérimentaux et la complexité de la géométrie à revêtir (une cavité avec un seul orifice étroit), le procédé de dépôt est modélisé avec le code de Mécanique des Fluides Numériques Fluent. Le modèle représente les profils locaux de vitesse d’écoulement, de température et de concentration des espèces gazeuses dans l’enceinte réactionnelle, ainsi que les vitesses locales de croissance, s’appuyant sur une loi cinétique hétérogène apparente de décomposition du TIA en alumine. Il permet une meilleure compréhension des phénomènes physico-chimiques se produisant à l’intérieur du corps creux et conduit ainsi à l’amélioration de la configuration du réacteur pour obtenir une couche mince transparente et d’épaisseur relativement uniforme. Le modèle est ensuite utilisé comme guide dans le choix des conditions opératoires pour revêtir la surface interne du flacon à pressions élevées, se rapprochant des conditions de fonctionnement à pression atmosphérique sur les lignes de production industrielle. Une interaction entre expériences et simulations est nécessaire pour adapter la configuration du réacteur aux dépôts à hautes pressions. Des films submicroniques sont déposés à différentes pressions de 666 Pa àt 97,3 kPa, pour un profil prédéterminé de températures le long des parois du flacon comprises entre 480 et 650 °C. Les films obtenus sont amorphes, stœchiométriques, sans traces de carbone et présentent une microstructure dense et légèrement rugueuse. Les flacons revêtus sont soumis à un essai de vieillissement hydrothermal lors d’un cycle de stérilisation pendant une heure à 121 °C et 200 kPa en contact avec de l’eau ultra-pure. La résistance hydrolytique, qui correspond à la résistance du verre à la cession de substances minérales solubles au contact de l’eau est évaluée pour des revêtements de différentes épaisseurs comprises entre 45 et 650 nm en moyenne. Les mécanismes de diffusion et d’extraction des cations sont analysés par spectroscopie de photoélectrons induits par rayons X et spectrométrie par torche plasma. Les effets du vieillissement sur l’adhérence, la nature et la microstructure en surface de la couche d’alumine amorphe sont étudiés. Une synthèse évaluant entre autre la robustesse du procédé, les vitesses de dépôt, les performances barrières et la résistance au vieillissement hydrothermal des couches minces d’alumine, en vis-à-vis des solutions de traitements de surface sur flacon déjà existantes, permet de conclure sur la maturité industrielle et la valeur ajoutée de ce procédé
Materials for packaging applications are sometimes coated with a barrier film in order to decrease the interactions between the content and the container. Deposition of such coatings on glass bottles allows limiting the deterioration of the internal surface, decreasing the leaching of cations from the glass and improving the stability of the properties of the liquid content. In this context, a chemical vapor deposition (CVD) process has been designed for the deposition of amorphous alumina thin films on the inner walls of a glass container. The process involves aluminum tri-isopropoxide (ATI), which is fed to the deposition volume by a direct liquid injection (DLI) technology. Given the number of experimental parameters and the complexity of the substrate (a hollow body with a unique narrow entrance), a model of the process has been developed with the Computational Fluid Dynamics code Fluent. The model displays the local profiles of mass flow, temperature and gas species concentrations in the reactor, and the local growth rates based on the kinetic law of the apparent heterogeneous reaction of ATI decomposition to alumina. A good agreement has been found between the experimental and the calculated growth rates. The model allowed gaining a better insight into the physic-chemical phenomena occurring inside the hollow body and thus improving the reactor configuration to obtain transparent and relatively uniform thin films. Following, the model was used as a guide for the choice of the operating conditions of the depositions at higher pressure. An interplay between experimental and simulated results was used to adapt the reactor configuration for depositions at atmospheric pressure. Submicronic films were performed for several pressures between 666 Pa and 97.3 kPa, for thermal profiles along the bottle walls ranging from 753K to 923K. The deposited films are amorphous, stoichiometric without carbon residues, dense and slightly rough. The coated bottles underwent a test of hydrothermal ageing with a cycle of sterilization filled with ultra-pure water during one hour at 121°C and 200 kPa. The hydrolytic resistance, which is the resistance of the glass to the release of soluble mineral substances into water, is measured for films with several thicknesses ranging from 45 to 650 nm on average. The mechanisms of diffusion and extraction for the alkali ions have been analyzed by X-ray photoelectron spectroscopy and inductively coupled plasma spectrometry. The impacts of ageing on the adhesion, the nature and the surface microstructure of the amorphous alumina films have been studied. The robustness of the process, the growth rate, barrier performances and resistance to the hydrothermal ageing of thin films, and the comparison of the above with the scarce existing solutions of surface treatments on glass bottles, allows concluding on the industrial viability and the added value of the process

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Dibelka, Jessica Anne. "Mechanics of Hybrid Metal Matrix Composites." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50579.

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The appeal of hybrid composites is the ability to create materials with properties which normally do not coexist such as high specific strength, stiffness, and toughness. One possible application for hybrid composites is as backplate materials in layered armor. Fiber reinforced composites have been used as backplate materials due to their potential to absorb more energy than monolithic materials at similar to lower weights through microfragmentation of the fiber, matrix, and fiber-matrix interface. Composite backplates are traditionally constructed from graphite or glass fiber reinforced epoxy composites. However, continuous alumina fiber-reinforced aluminum metal matrix composites (MMCs) have superior specific transverse and specific shear properties than epoxy composites. Unlike the epoxy composites, MMCs have the ability to absorb additional energy through plastic deformation of the metal matrix. Although, these enhanced properties may make continuous alumina reinforced MMCs advantageous for use as backplate materials, they still exhibit a low failure strain and therefore have low toughness. One possible solution to improve their energy absorption capabilities while maintaining the high specific stiffness and strength properties of continuous reinforced MMCs is through hybridization. To increase the strain to failure and energy absorption capability of a continuous alumina reinforced Nextel" MMC, it is laminated with a high failure strain Saffil® discontinuous alumina fiber layer. Uniaxial tensile testing of hybrid composites with varying Nextel" to Saffil® reinforcement ratios resulted in composites with non-catastrophic tensile failures and an increased strain to failure than the single reinforcement Nextel" MMC. The tensile behavior of six hybrid continuous and discontinuous alumina fiber reinforced MMCs are reported, as well as a description of the mechanics behind their unique behavior. Additionally, a study on the effects of fiber damage induced during processing is performed to obtain accurate as-processed fiber properties and improve single reinforced laminate strength predictions. A stochastic damage evolution model is used to predict failure of the continuous Nextel" fabric composite which is then applied to a finite element model to predict the progressive failure of two of the hybrid laminates.
Ph. D.

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Abi, Aad Jane. "Dégradation chimique et mécanique de l'alumine en phase aqueuse : mécanisme et inhibition en conditions ambiantes et hydrothermales." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066642/document.

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L'alumine, utilisée comme support de catalyseurs pour la réaction de Fischer-Tropsch ou pour la conversion de la biomasse, se transforme partiellement en présence d'eau en phases (oxy)hydroxydes à l'origine de fines qui posent problème dans la mise en ¿uvre de procédés en réacteurs de type slurry. Afin de concevoir des catalyseurs plus stables et plus résistants, ce travail de thèse visait à identifier le mécanisme d'hydratation et de dégradation des alumines de transition en phase aqueuse, et à étudier la façon dont des additifs organiques (alcools, polyols) ou inorganiques (Mg, Zr, Ni et Si) permettent de limiter cette dégradation. La conduite d'une étude systématique sur l'hydratation des alumines à 70°C à pression atmosphérique, ou à 150°C en conditions hydrothermales, a permis de définir un mécanisme général en deux étapes: une dissolution de la surface de l'alumine, suivie d'une précipitation, respectivement, d'hydroxydes d'aluminium Al(OH)3 ou de boehmite AlOOH sur les grains d'alumine. Par ailleurs, la dégradation chimique tend à favoriser la dégradation sous contraintes mécaniques. La présence de polyols en phase aqueuse, principalement des molécules à 5 ou 6 atomes de carbone, ralentit la dissolution de l'alumine et inhibe la précipitation de la boehmite. Les ions métalliques utilisés comme dopants de l'alumine ont tous un effet similaire sur la diminution de l'hydratation. Une inhibition totale de l'hydratation est obtenue par greffage de silicium à partir de TEOS. Une étude DRIFT dans la région des vibrations OH suggère que les additifs inorganiques inhibent la dissolution de l'alumine en bloquant des sites Al-OH localisés sur les faces latérales des particules
Alumina, used as a catalyst support for the Fischer-Tropsch reaction or for the conversion of biomass, partially transforms in presence of water into (oxy)hydroxides phases. The formation of the latter leads to the production of fine particles that may cause plugging problems in the implementation of processes based on slurry bubble column reactors. In order to design more stable and more resistant catalysts, this PhD work aimed at identifying the mechanism of hydration and degradation of transition aluminas in aqueous phase, and to study how organic (alcohols, polyols) or inorganic (Mg, Zr, Ni and Si) additives can limit this degradation. The conduct of a systematic study on the hydration of alumina at 70°C under atmospheric pressure, or at 150°C in hydrothermal conditions, allowed defining a general two-step mechanism: a dissolution of the surface of alumina, followed by a precipitation of, respectively, aluminum hydroxides (Al(OH)3) or boehmite (AlOOH) on alumina grains. Furthermore, the chemical degradation tends to promote the degradation under mechanical stress. The presence of polyols in aqueous phase, mainly molecules with 5 or 6 carbon atoms, slows down the dissolution of alumina and inhibit the precipitation of boehmite. Metal ions used as dopants of alumina all have a similar effect on the decrease of hydration. A total inhibition of hydration is obtained by grafting silicon using TEOS. A DRIFTS study in the OH vibration region suggests that inorganic additives inhibit the dissolution of alumina by blocking Al-OH sites located on the lateral facets of the particles

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Silva, José Wilson de Jesus. "Efeito dos oxi-ânions do grupo VIB sobre a corrosão aquosa das ligas Al(2024) e Al(7050) utilizadas na indústria aeronaútica /." Guaratinguetá : [s.n.], 2003. http://hdl.handle.net/11449/97122.

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Resumo: Foram caracterizados os comportamentos eletroquímicos e avaliadas as resistências à corrosão das ligas aeronáuticas 2024-T351 e 7050-T7451 em soluções aquosas de cloreto contendo cromato, molibdato e tungstato. Foram realizados ensaios de corrosão não-eletroquímicos de imersão prolongada acompanhados de análise metalográfica de superfície por microscopia óptica e identificação dos produtos de corrosão por difratometria de raios-X. A análise quantitativa de superfícies das ligas após a imersão, indica que os pites formados têm áreas médias similares. Os pites são mais largos do que profundos e de geometria, predominantemente, cônica ou quase-cônica e irregular. Em todos os produtos de corrosão de cada liga foi encontrado hidróxido de alumínio, em suas diferentes formas cristalinas. Medidas de perda de dureza, como uma conseqüência da deterioração superficial, também foram determinadas. Além disso, ensaios eletroquímicos como medidas de potencial em circuito aberto, curvas de polarização e voltametria cíclica complementaram este estudo. Em meio aerado os resultados obtidos mediante medidas eletroquímicas são consistentes com aqueles obtidos nos ensaios de imersão, em particular o efeito do CrO42- e do MoO42-. O WO42- mostrou-se agressivo em períodos prolongados de imersão. Apesar dos ensaios revelarem uma redução parcial de MoO42- em ambas as ligas, o efeito desse oxi-ânion parece ser diferente sobre cada liga. Em meio desaerado as ligas apresentam passivação em todos os eletrólitos. A adição dos oxi-ânions não modificou significativamente o potencial de pite para a liga 7050, enquanto que para a liga 2024 ele foi deslocado levemente para valores mais positivos.
Abstract: It has been characterized the electrochemical behavior and evaluated the 2024-T351 and 7050-T7451 aircraft alloys corrosion resistance in chloride aqueous solutions containing chromate, molybdate and tungstate. It has been carried out non-electrochemical long immersion corrosion testings accompanied by surface metalography analysis achieved by light microscopy and corrosion products identification by X-ray difratometry. Surfaces quantitative analysis upon the alloys after immersion, indicates that formed pits have similar average area. Pits are widther than deeper and own predominantly a conical or quasi-conical and irregular geometry. In all corrosion products of each alloy it has been found aluminum hydroxide in its different crystalline ways. Hardness loss measurements have also been determined. In addition, electrochemical testings such as open circuit potential measures, polarization curves and cyclical voltammetry have completed this study. In aerated means the obtained results before electrochemical mesurements are similar to those obtained in the immersion tests, in particular CrO42- and MoO42- effects. WO42- has been found to be aggressive in very long immersion period. Though tests display a MoO42- partial reduction in both alloys, this oxi-anion effect seems to be different upon each alloy. In de-aerated means alloys present passivation in all eletrolytes. Oxi-anion addition has not changed significantly pit potential for 7050 alloy, while for 2024 alloy it has been dislocated, slightly, for more positive values.
Orientador: Eduardo Norberto Codaro
Coorientador: Roberto Zenhei Nakazato
Banca: Luis Rogerio de Oliveira Hein
Banca: Gilberto Luis Jardim Pinto da Silva
Mestre

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42

Vilela, Ruan Larisson Toninatto. "Avaliação do desempenho de coagulantes recuperados de lodo de ETA por extração via alcalina-ácida /." Ilha Solteira, 2020. http://hdl.handle.net/11449/192280.

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Orientador: Rosane Freire Boina
Resumo: No processo de tratamento de água visando sua potabilidade é gerado um resíduo (lodo) cujo manejo e disposição são problemas de caráter urgente, principalmente, devido à escassez de soluções eficazes. Um desafio extra a esses problemas é que esse lodo pode possuir em sua composição uma concentração acentuada de alumínio (elemento com efeitos nocivos aos organismos e ao meio ambiente) devido ao coagulante utilizado no processo de tratamento. Recuperar e reutilizar os componentes coagulantes do lodo pode ser uma alternativa para a sua destinação. Assim, com esse propósito, será possível economizar no custo de dosagem com a reciclagem do produto obtido, além de possibilitar a diminuição do volume final do lodo devido à remoção de água durante o processo. O método consistiu na recuperação, via alcalina-ácida, do coagulante do lodo (desaguado) de duas ETAs distintas. Inicialmente, os lodos foram submetidos a extração em pH 12, com hidróxido de sódio (NaOH – 20%) e, posteriormente, extração em pH 2, testando o ácido sulfúrico (H2SO4 – 20%) e o ácido clorídrico (HCl – 20%). A proporção utilizada foi 1:10 (m:v). A reutilização dos coagulantes recuperados foi realizada em Jar Test utilizando água bruta de um dos pontos de captação do município de Presidente Prudente – SP. O efeito coagulante foi validado fazendo comparativo com o coagulante comercial PAC, por meio dos parâmetros turbidez (NTU) e cor (PCU), além da análise frente aos valores máximos permitidos (VMP) pelo Ministério da ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In water treatment process, aiming at its potability, a residue (sludge) is generated, which management and disposal are urgent problems, mainly due to the lack of effective solutions. An extra challenge to these problems is that the sludge may have a high aluminum concentration in its composition (an element with harmful effects to organisms and the environment) due to the coagulant used in the treatment process. Recovering and reusing coagulant components of the sludge can be an alternative for its destination, since for this purpose it is possible to save the dosage cost by recycling the obtained product, in addition to reducing the final sludge volume due to the water removal during the process. The method consisted of recovering, through an alkaline-acid, coagulant from two different WTPs sludge. Initially, the sludge was subjected to extraction at pH 12, with sodium hydroxide (NaOH - 20%) and, later, extraction at pH 2, testing sulfuric acid (H2SO4 - 20%) and hydrochloric acid (HCl - 20%). The proportion used was 1:10 (m: v). The reuse of the recovered coagulants was carried out in Jar Test using raw water from one of the collection points in the city of Presidente Prudente - SP. The coagulant effect was validated by comparing it with the commercial coagulant PAC, using the parameters turbidity (NTU) and color (PCU), besides to the analysis compared with the maximum allowed values (MAV) by the Ministry of Health for the same parameters. The results showed that three of ... (Complete abstract click electronic access below)
Mestre

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43

Costa, Douglas Henrique da Silva [UNESP]. "Estudo do efeito do processo de shot peening na taxa de propagação de trinca por fadiga na liga aeronáutica 2024 - T3." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/123234.

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Este trabalho tem por finalidade avaliar o efeito do processo de shot peening na taxa de propagação de uma trinca por fadiga já existente. O shot peening é um processo de trabalho a frio, que consiste no jateamento repetitivo com microesferas de aço, cerâmica ou vidro, na superfície de uma peça, produzindo encruamento e induzindo tensões residuais compressivas nas superfícies tratadas. Devido a isso, o shot peening tem-se mostrado um método bastante eficiente para dificultar o início e a propagação de uma trinca por fadiga a partir da superfície do material, melhorando a sua resistência à fadiga. Contudo, estudos de seu efeito sobre uma trinca já existente são pouco conhecidos. Corpos de prova do tipo CT, para a liga aeronáutica de alumínio 2024 - T3, foram inicialmente trincados por fadiga e, em seguida, submetidos ao processo de shot peening em ambos os lados. Após o tratamento, os ensaios foram reiniciados nas mesmas condições. Os ensaios foram realizados com amplitude constante em duas espessuras de corpos de prova e duas razões de carga, R, para analisar possíveis efeitos do estado de tensão na ponta da trinca nos resultados. Duas intensidades de shot peening foram utilizadas para cada valor de R ou espessura analisada. Também foram estudadas duas regiões de aplicação do processo de shot peening (atrás e em volta da ponta da trinca) em dois tamanhos de trincas. Curvas comparativas do comportamento da taxa de propagação de trincas por fadiga, mostrando a influência de cada um dos parâmetros descritos, são apresentadas, e suas diferenças, discutidas. Os resultados encontrados mostram que o processo de shot peening, quando realizado em um tamanho de trinca em pleno estágio II de propagação, apresenta maior influência quando aplicado atrás da ponta da trinca, com menor intensidade, em corpos de prova em estado ... (Resumo Completo, clicar acesso eletrônico abaixo)
This work focuses to evaluate the effect of the shot peening process in the propagation rate of a fatigue crack already existing. The shot peening is a cold working process, which consists of repetitive blasting with steel shot, ceramic or glass, the surface of a workpiece, producing hardening and inducing compressive residual stresses on the treated surfaces. Because of this, shot peening has proved a very efficient method for hindering the initiation and propagation of a fatigue crack from the surface of the material, improving its fatigue strength. However, studies of its effect on an already existing crack are little known. Specimens of type CT to the aeronautics aluminum alloy 2024 - T3, were initially cracked by fatigue and then subjected to shot peening process on both sides. After treatment, the tests were resumed under the same conditions. Tests were carried out with constant amplitude in two thicknesses of specimens and two load ratios, R, to analyze possible effects of stress state on the crack tip results. Two shot peening intensities were used for each R value or thicknesses analyzed, and were also studied two application regions of shot peening process (behind and around the crack tip) in two sizes of cracks. Comparative curves of the fatigue crack propagation rate, showing the influence of each of the parameters described are shown, and their differences discussed. The results show that the shot peening process, when performed in a crack size in full stage II propagation, has greater influence when applied behind the crack tip, with lower intensity, in the specimens in plane stress state and lower load ratio. For crack lower (close to the stage I of propagation), the shot peening process applied behind the crack tip induced delay in their propagation rate in all conditions studied. The delay effect on fatigue crack propagation rate ... (Complete abstract click electronic access below)

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Campo, Kaio Niitsu 1988. "Uso da extrusão em canal angular na produção da liga A356 para tixoconformação." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265929.

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Orientador: Eugênio José Zoqui
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este trabalho investigou o uso da extrusão em canal angular (ECA) na produção de matéria-prima para tixoconformação visando à obtenção de uma rota simples e eficiente na formação de microestruturas globulares. Para tanto, uma liga de alumínio A356 foi submetida a um único passe ECA e, em seguida, reaquecida ao estado semissólido a 580°C. Dessa forma, pôde-se determinar a evolução morfológica e os mecanismos envolvidos na formação da pasta metálica, a influência do tratamento isotérmico na evolução microestrutural no estado semissólido, o comportamento de deformação durante a compressão a quente e o comportamento mecânico em tração do material tixoconformado. Os resultados indicaram que apenas um passe ECA foi suficiente para gerar uma pasta metálica refinada e globular apenas com o reaquecimento da matéria-prima. O engrossamento da microestrutura durante o tratamento isotérmico foi controlado principalmente pelo mecanismo de Ostwald ripening, fato comprovado pelo baixo valor da constante taxa de engrossamento K, o que mostrou a estabilidade dessa pasta no estado semissólido. As amostras exibiram comportamento tixotrópico típico com baixos valores de viscosidade aparente, na faixa de 10^2 a 10^3 Pa.s para as taxas de cisalhamento testadas. Por fim, as amostras tixoconformadas apresentaram valores de ductilidade e resistência à tração superiores aos das amostras fundidas e deformadas por um passe ECA
Abstract: This work investigated the use of equal channel angular pressing (ECAP) for the production of raw materials for thixoforming in order to obtain a simple and efficient processing route to generate globular microstructures. Therefore, an A356 aluminum alloy was processed by one ECAP pass, and then reheated to the semisolid state up to 580°C. Thus, it was possible to determine the morphological evolution and mechanisms involved in the formation of the semisolid slurry, the influence of isothermal treatment on microstructural evolution in the semisolid state, the deformation behavior during hot compression tests and the tensile properties of the thixoformed material. The results indicated that a single ECAP pass was sufficient to promote a refined and globular semisolid slurry. Microstructure coarsening during the isothermal treatment was mainly controlled by Ostwald ripening, which was verified by the low rate constant K, showing the stability of the reheated material in the semisolid state. The samples exhibited typical thixotropic behavior with low apparent viscosity ranging from 10^2 to 10^3 Pa.s over the applied shear rates. Finally, the thixoformed samples exhibited values of ductility and tensile strength superior to the as-cast and ECAPed samples
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

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Minto, Thiago Alexandre. "Influência do tratamento superficial 3IP na vida em fadiga da liga de alumínio AA7050-T7451 para aplicação aeronáutica /." Guaratinguetá, 2016. http://hdl.handle.net/11449/144331.

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Orientador: Herman Jacobus Cornelis Voorwald
Coorientadora: Midori Yoshikawa Pitanga
Banca: Verônica Mara de Oliveira Velloso
Banca: Marcelino Pereira do Nascimento
Banca: Luiz Fábio dos Santos Vieira
Banca: Miguel Justino Ribeiro Barboza
Resumo: O estudo do comportamento em fadiga e corrosão dos materiais é de extrema importância para a indústria aeronáutica, considerando componentes estruturais que estão submetidos a carregamentos cíclicos constantemente. As ligas de alumínio desempenham papel fundamental nesse ramo, principalmente as ligas da série 7xxx de alta resistência. Como esses componentes também operam em ambientes marítimos, os revestimentos anticorrosivos são utilizados como proteção. Dos processos de revestimentos disponíveis atualmente, a substituição dos processos de anodização é considerado como urgente no meio acadêmico e nos setores industriais, devido à liberação de resíduos prejudiciais à saúde e ao meio ambiente gerados na aplicação dos revestimentos. O objetivo deste trabalho é estudar a influência do tratamento de implantação iônica por imersão a plasma (3IP) na vida em fadiga e corrosão da liga AA7050-T7451. Os ensaios de fadiga e corrosão com diferentes condições de tratamento 3IP permitiram uma análise comparativa, estabelecendo uma relação entre os parâmetros de tratamento como: voltagem x frequência x tempo. Observou-se uma grande interferência nas taxas de aquecimento, temperatura máxima, microdurezas e nanodureza superficiais, rugosidade, potenciais de corrosão, análises de EDS, DRX e fadiga principalmente quando há uma variação da frequência do processo 3IP. Os melhores resultados obtidos de resistência à fadiga e à corrosão dentre todas as combinações voltagem x frequência estudadas ne... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The fatigue and corrosion behavior study of high strength materials are very important for the aeronautical industry, considering that structural components are constantly loaded to variable amplitude loading. Aluminum alloys play an important role in this subject, especially 7xxx alloys. These components also operate in marina environments, and then coatings are used as protection. The replacement of anodizing processes is considered urgent in the academic and industrial sectors, due to the release of waste and harmful conditions to health and the environment generated from the application of the coatings. The objective of this work is to study the influence of plasma immersion ion implantation (IIIP) on the fatigue life of AA7050-T7451 aluminum alloy. Fatigue and corrosion tests with different PIII treatments, established a relationship between treatment parameters such as voltage x frequency x time. It was observed a large interference on heating rate, maximum temperature, surface microhardness, nanohardness, roughness, corrosion potential, EDS, XRD and fatigue resistance especially with the frequency variation on the PIII process. The best results of fatigue resistance and corrosion with all combinations in this work, were obtained by procedures with lower temperature as a consequence the low impact frequency
Doutor

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Sousa, Lucíola Lucena de. "Desenvolvimento e caracterização de cerâmicas porosas moldáveis à base de alumina-mulita para uso como isolamento térmico em altas temperaturas." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-16112015-161700/.

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Com o objetivo de reduzir o consumo energético, tem crescido o uso de cerâmicas porosas refratárias como isolantes térmicos para altas temperaturas. Entre as técnicas comumente empregadas na produção desses materiais, destaca-se aquela baseada na geração de poros por meio de transformação de fases. Esse método, que não libera voláteis tóxicos, apresenta uma importante limitação em relação ao uso prolongado em altas temperaturas: os compostos de transição formados após a desidroxilação tendem a acelerar a sinterização, reduzindo a porosidade. É bastante conhecido o fenômeno de que, durante a sinterização em temperaturas elevadas, peças de alumina com alta porosidade, sofrem a eliminação progressiva dos poros presentes. Por essa razão, compostos que dificultam a densificação das peças porosas têm sido adicionados para manter a porosidade originada pela decomposição do hidróxido de alumínio. O objetivo desse trabalho foi obter cerâmicas porosas moldáveis a partir de alumina, hidróxido de alumínio e diversas fontes de sílica (mulita eletrofundida, quartzo e microssílica), utilizando a técnica de decomposição de hidróxidos com o intuito de se formar mulita, composto capaz de diminuir a taxa de densificação em altas temperaturas e com aplicações na indústria petroquímica e do alumínio. As amostras foram sinterizadas entre 1100ºC e 1500ºC e os resultados mostraram que houve aumento da resistência mecânica com a elevação do teor de mulita eletrofundida, quartzo e microssílica incorporada ao sistema. Além disso, o sistema mulita eletrofundida para a composição 0,4-SMT apresentou uma PT = 53,58%, módulo elástico e resistência a compressão (E = 13,03 GPa e σR = 16,83 MPa). O sistema com a adição de quartzo, a amostra 0,2-SQZ, teve pequenas mudanças nos níveis de porosidade (PTG = 59,50%) e não apresentou um elevado aumento do módulo elástico e da resistência a compressão (E = 6,51 GPa e σR = 13,91 MPa) e o sistema contendo microssílica a composição 0,2-SMS apresentou os melhores resultados, tendo um ganho de propriedades mecânicas em temperaturas a 1100ºC e a 1500ºC manteve a porosidade (PTG = 56,23%), reduziu o tamanho médio de poros e apresentou também ótimas propriedades mecânicas (E= 15,39 GPa e σR = 36,79 MPa) proporcionando sua atuação como isolante térmico.
Refractory porous ceramics have largely been used as thermal insulators for high temperatures aiming to reduce energy consumption. The generation of pores through phase transformation (such as Al(OH)3 dehydroxilation) is one of the most interesting techniques employed to produce such materials. This method, which does not release toxic volatile, imposes an important limitation on the prolonged use at high temperatures. The transition compounds formed after the dehydroxylation tend to accelerate sintering and reduce porosity. It is well known that during sintering at high temperatures (above 1100ºC), parts of alumina with high porosity amounts undergo gradual pores\' elimination. Therefore, compounds that hinder densification of porous pieces have been added to these compositions in order to maintain the porosity generated by the decomposition of aluminum hydroxide. This thesis addresses the production of castables porous ceramics from alumina, aluminum hydroxide and different sources of silica (electrofuse mullite, quartz and microsilica), employed for the in situ formation of mullite, a compound that reduces the rate of densification at high temperatures. The applications include petrochemical and aluminum industries. Samples were sintered between 1100ºC and 1500ºC and the results of the systems which contained electrofused mullite, quartz and microsilica showed less intense porosity levels reduction. The system with addition of electrofused mullite showed PTG = 53,58%,E = 13,03 GPa and σR = 16,83 MPa. The system containing quartz, presented a lower change of porosity (PTG = 59,50%) and the system containing microsilica provided the best results and an increment in the mechanical properties at temperatures between 1100°C and 1500°C. This last system also kept porosity (PTG = 56,23%), and reduced the average pore size. Its good mechanical properties (E = 15,39 GPa and σR = 36,79 MPa) proved it can be used as a thermal insulator.

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Jansen, Ann Marie. "The mechanical properties and microstructures of aluminum containing 25 vol.% of 0.3[mu]m alumina particles." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/42809.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996.
In title on t.p., "[mu]" is the lower-case Greek letter.
Includes bibliographical references (leaves 175-183).
by Ann Marie Jansen.
Ph.D.

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Salles, Nicolas. "Etude des différents polymorphes de l'alumine et des phases transitoires apparaissant lors des premiers stades d'oxydation de l'aluminium : simulation à l'échelle atomique par un modèle à charges variables en liaisons fortes." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOS034/document.

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L’objectif de ce travail consiste à développer un nouveau potentiel SMTB-Q, puis à l’incorporer dans un code de dynamique moléculaire (DM) afin d’étudier les premiers stades de l’oxydation de l’aluminium. Le potentiel peut modéliser les différents polymorphes de l’alumine ainsi qu’une transition de la phase amorphe vers une phase cristalline. Notre approche couple un terme covalent avec la charge. Il utilise le schéma de Rappé et Goddard pour la partie électrostatique et le modèle du réseau alterné de C. Noguera pour la partie covalente. Le potentiel SMTB-Q obtenu est validé par une approche Monte Carlo. Nous y présentons les outils utilisés pour l’optimisation du potentiel ou analyser les résultats obtenus pour les situations hétérogènes. Cette étude permet de montrer que le potentiel SMTB-Q donne une description satisfaisante de la liaison Al-O dans différentes configurations atomiques. Cette liaison résulte de la compétition entre trois contributions énergétiques : électrostatique, covalente et répulsion de Pauli entre les oxygènes. Après son incorporation dans le logiciel LAMMPS, le potentiel SMTB-Q est utilisé en DM pour l'étude d'oxydes à stœchiométrie constante. Les transitions de phases de l’alumine sont étudiées sous haute pression et en température. Le problème du changement de stœchiométrie de l’oxyde est traité à partir de l'étude de diverses structures de différentes stœchiométries. Nous introduirons la liaison métallique dans le potentiel. La superposition des liaisons iono-covalentes et métalliques sera étudiée pour des systèmes métal/oxyde. Enfin, nous discuterons du formalisme du potentiel SMTB-Q face au changement de stœchiométrie dans l’oxyde
The goal of this work is to develop a new SMTB-Q potential in order to study the early stages of the oxidation of aluminium by molecular dynamics (MD).Our potential is able to model different alumina polymorphs as well as transitions from the amorphous state to a crystalline phase. Our approach couples a covalent term with the charge. It uses Rapp_ and Goddard scheme for the electrostatic part and the model of alternating network developed by C. Noguera for the covalent part.The SMTB-Q potential was validated with a Monte Carlo approach. This study shows that the potential SMTB-Q gives satisfactory results for the Al-O bonding in different atomic configurations. The bonding results from the competition between three energy contributions: electrostatic, covalent and Pauli repulsion between the oxygens.After implementation in the LAMMPS software, the potential SMTB-Q is used to study by DM constant stoichiometry oxides. Alumina phase transitions are observed under high pressure and temperature. We also introduce the metallic bonding in the potential. The superposition of the iono-covalent and metallic bonds was investigated for metal / oxide systems. Finally, we discuss the formalism of the SMTB-Q potential to take into account the change of stoichiometry in the oxide

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Nehari, Abdeldjelil. "Étude et caractérisation de la synthèse de milli-billes d’alumine alpha et de la cristallogenèse du saphir pur et dopé titane (Ti3+)." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10334.

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Ce travail est consacré à l’étude de la croissance cristalline du saphir non dopé et dopé titane (Ti3+). Pour faire croître des cristaux ayant des performances optimisées, il est indispensable de maitriser l’alumine (Al2O3) de départ. Toute contamination de la charge initiale à fondre, dégrade l’état stationnaire de croissance, entraîne la propagation de défauts cristallins, provoque la corrosion des creusets, en particulier en molybdène, et affecte les propriétés physico-chimiques, optiques et laser du cristal. Dans la première partie de ce travail, un nouveau procédé industriel de synthèse de millibilles d’alumine alpha (Al2O3-α) de géométrie sphérique, de haute pureté, a été mis au point. Le procédé est basé sur l’écoulement goutte à goutte de l’alumine fondue à travers des filières situées sous le creuset. Le procédé est particulièrement complexe, les études menées ont néanmoins visé à des descriptions qualitatives et quantitatives des phénomènes. La simulation et la modélisation de la thermique autour du creuset en iridium ont permis de maitriser le système et le contrôle continu du procédé. Dans le but de valider la qualité des millibilles d’alumine obtenues, des cristaux de saphir ont été tirés en utilisant des installations de croissance du LPCML (Czochralski, micro-pulling down) et de la société RSA le Rubis (EFG) qui ont des paramètres de fonctionnement différents (chauffage, atmosphère, creuset). La deuxième partie de la thèse, concerne la croissance cristalline du saphir dopé titane (Ti3+) qui est un matériau de très haute technologie. La demande actuelle porte sur des cristaux de 200 mm de diamètre, leur contrôle et caractérisation, le contrôle de la matière première, la mise en œuvre de différents procédés de croissance, le développement de mesures spécifiques des propriétés structurales, optiques et laser des cristaux. L’incorporation de l’ion Ti3+ dans la matrice du saphir se fait par substitution de l’ion Al3+. La différence de rayons ioniques rend difficile l’incorporation du Ti3+, conduisant à une concentration réelle en titane inférieure à celle souhaitée. Il s’ensuit une ségrégation du titane entre le bain fondu et le cristal lors de la croissance cristalline, ce qui provoque des hétérogénéités qui dégradent la qualité des cristaux. Dans cette partie de thèse, nous avons travaillé sur :1-La croissance stable en bain fondu de cristaux de Ti: saphir de 100 mm. 2-L’amélioration des procédés de croissance pour produire de manière reproductible des cristaux plus homogènes (concentration constante en ions titane), de bonne qualité optique (exempt de défauts) et offrant de bonnes performances laser. 3-La caractérisation des propriétés structurales
This PhD thesis is established to study undoped and titanium (Ti3+) doped sapphire single crystal growth. To grow crystals with optimized performances, it is necessary to control starting Alumina (Al2O3). Any contamination of initial charge to be melted, will affect the stationary crystal growth, causes defects propagation in the crystal, crucibles corrosion, particularly Molybdenum and affect the physical-chemistry, optics and laser properties of the crystal. In the first part of this work, a new industrial process to synthesize (Al2O3-) alpha alumina millibilles of spherical geometry, high purity has been developed. The process is based on drop flow from shaped crucible. The process is complex, the study involve description of qualitative and quantitative phenomena during the synthesis stage. The thermal modeling and simulation around iridium crucible have allowed controlling the system and continued process. In order to validate the quality of the obtained Alumina (millibilles), sapphire crystals have been pulled by crystal growth equipments (Czochralski, micro—pulling down) available in LPCML laboratory and (EFG) in RSA Le Rubis company which have different operating parameters. The second part concern titanium (Ti3+) doped sapphire single crystal growth, which is material for high technology. Current demand is for controlled 200 mm diameter crystals, characterization, starting material control, adjustment of crystal growth process, development of specific measurement of structure properties, optics and lasers of the crystals. The incorporation of Ti3+ in sapphire host, is realised by the substitution of Al3+ ion. Because of the difference of the ionic radii, the incorporation of Ti3+ is difficult and the real titanium concentration will be lower than the wishes one. Segregation of titanium during crystal growth causes heterogeneities which damage the crystal quality. In this PhD part we have worked on: 1-Stable melt crystal growth of Ti-sapphire of 100 mm in diameter. 2- Improvement of crystal growth process to produce reproducible homogeneous crystals ( constant ions titanium concentration), good optical quality ( defects free) and good laser performances. 3- Characterisation of structural, optics and laser crystals properties

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Coraini, Rafael [UNESP]. "Soldagem GMAW-P robotizada de alumínio: influência do tipo de chanfro, tecimento e sentido de laminação na distorção." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/96483.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A utilização do alumínio em escala industrial vem crescendo cada vez mais nos últimos anos e um dos principais motivos é o espaço que esse material vem conquistando em substituição ao aço. O interesse da indústria em ter um maior controle das distorções provocadas pela soldagem de alumínio se deve ao fato das tolerâncias dimensionais e geométricas estarem cada vez mais precisas nas especificações de projeto, motivando a engenharia de fabricação a desenvolver processos estáveis e que garantam a rotina de produção. O elevado coeficiente de expansão linear desse metal, se comparado ao aço, é uma das suas principais características que geram dificuldades nesse cenário. Visando isso, o presente trabalho tem como principal objetivo analisar o quanto situações rotineiras utilizadas na soldagem robotizada de alumínio podem influenciar nas distorções angulares deste material, sem comprometer a integridade mecânica da junta soldada e com confiabilidade estatística. Utilizando a liga AA 5052 H34, e a soldagem robotizada no processo GMAW pulsado, foram aplicados três tipos de tecimento ao longo do comprimento da solda, em juntas de topo montadas sem chanfro e com chanfro de 60º, dispostas tanto transversais quanto longitudinais ao sentido de conformação da chapa. A medição das distorções foi realizada por um braço tridimensional, antes e após a soldagem, em três regiões distintas nos corpos de prova. O perfil do cordão de solda foi o fator determinante para as diferentes formas das distorções encontradas, assim como revelado pelas análises macrográficas. A junta com chanfro de 60º apresentou maiores amplitudes das distorções que a junta sem chanfro. O tecimento não foi uma variável de influência estatística significativa nessas amplitudes. Ensaios de tração foram realizados para se avaliar o comportamento mecânico das juntas soldadas
The use of aluminum by industry has been recently growing more and more each time and one of the main reasons is the position that this material is gaining as a replacement for steel. The industry's interest in having a greater control of the distorcions caused by aluminum welding is due to the geometric and dimensional tolerances been more and more precise in the project specifications, motivating the manufacturing engineering to develop stable processes and to ensure routine production. The high coefficient of linear expansion of this metal, which is one of its main features, can create a difficult scenario when compared to the steel. Aiming at it, the main goal of this present work is to analyze how much routine situations used int the robotic aluminum welding can influence in the angular distortions of this material, without affecting the mechanical integrity of the welded joint and with statistical reliability. Using the alloy AA 5052 H34, and the robotic welding in pulsed GMAW process, it was applied three types of weaving throughout the length of the weld, in butt joints assembled without groove and with 60º single-V-groove, arranged transversely as well as longitudinally to the rolling direction of the plate. The measurement of the distortions was made by a three-dimensional equipment, before and after the welding, in three distinct regions in the speciments. The profile of the weld bead was the main factor for the different types of distortions found, as revealed by macrographical analysis. The 60º single-V-groove had higher amplitudes of distortions as the joint without groove. The weaving wasn't a variable of statistically significant influence in this amplitudes. Tensile tests were made to evaluate the mechanical properties of the welded joints

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