Dissertations / Theses: 'Aluminum fins'

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Farjam, Aslan. "Influence of Alumina Addition to Aluminum Fins for Compact Heat Exchangers Produced by Cold Spray Additive Manufacturing." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/33383.

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Aluminum and aluminum-alumina powder mixtures were used to produce pyramidal fin arrays on aluminum substrates using cold spray as an additive manufacturing process. Using aluminum-alumina mixtures instead of pure aluminum powder could be seen as a cost-effective measure, preventing nozzle clogging. The fin geometries that were produced were observed using a 3D digital microscope to determine the flow passages width and fins geometric details. Heat transfer and pressure tests were carried out using different ranges of appropriate Reynolds numbers for the sought commercial application to compare each fin array and determine the effect of alumina content. It was found that the presence of alumina reduces the fins’ performance when compared to pure aluminum but that they still outperform traditional fins. Numerical simulations were performed and were used to explain the obtained experimental results. The numerical model opens up new avenues in predicting different parameters such as pressure and substrate temperature.

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Malan, Daniel Johannes. "Latent heat thermal energy storage for solar water heating using flat heat pipes and aluminum fins as heat transfer enhancers." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/96140.

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Thesis (MEng) -- Stellenbosch University, 2014.
ENGLISH ABSTRACT: Solar energy is a time dependent, high-temperature radiant energy resource. The utility of a solar thermal energy system increases if the hot temperature source is available when it is needed most. This is realized by the thermal storage of the solar energy. Thermal storage gives greater versatility to a solar energy system by decoupling the heat source from the heat sink. A large quantity of energy may be stored during the melting process in a phase change material (PCM) within a small temperature range. This molten PCM can then deliver its absorbed heat at a constant temperature in a heating application. In this study a phase change storage system (PCS) is developed and proposed for a solar water heating application. This PCS system stores more heat per unit mass than would be possible with water across the same temperature range. The heat transfer rate in and out of many PCMs is slow because of the low thermal conductivity of the PCM. However, heat transfer enhancers (HTE), such as heat pipes and fins may be added to enhance heat absorption and heat removal rates. Heat pipes have the inherent capability to transfer heat at high rates across large distances, even where the temperature difference is small. In this thesis a description is given of a PCS system consisting of paraffin wax as the PCM and which uses rectangular heat pipes in conjunction with aluminium fins to enhance heat transfer. The storage design is modular and each module has the characteristic that enhanced heat transfer in and out of the PCM is possible when the module is heated or cooled. It also has the capability to quickly absorb or alternatively to supply heat at a nearly constant temperature during the phase change of the module. A rectangular module was designed and built. The module was then analysed under controlled heat absorption and heat removal cycles. The heat up experiment involved an electrical kettle as the hot temperature source. The heat sink was a mains water heat exchanger. The experimental results were compared to those of a transient numerical model, which calculates theoretically how the module will perform thermally under the given test conditions. The numerical model of the experimental set-up was validated when it was found that the numerical model results resemble the experimental results. The numerical model was then adapted to simulate a novel solar water heater (SWH) with an additional PCS container. The improvement over previous designs is that the additional storage container can be heated to a higher temperature than the allowable geyser temperature. The system also heats up and cools down at a faster rate than would be possible without the HTEs. From the numerical simulation the size and performance of such a system is determined. This numerical analysis indicated that a phase change storage system in a SWH application will increase the hot water delivered by a given solar collector and geyser by increasing the storage capacity and by heating up the geyser overnight for early morning hot water use.
AFRIKKANSE OPSOMMING: Son energie is ‘n tyd afhanklike, hoë temperatuur radiasie energiebron. Die bruikbaarheid van ‘n sontermiese energie sisteem verhoog indien die hoë temperatuur bron beskikbaar is wanneer dit die meeste benodig word. Dit kan verwesenlik word deur die sonenergie termies te stoor. Termiese storing bied groter veelsydigheid aan ‘n sontermiese stelsel deur effektief die hittebron te ontkoppel van die hitte sink. ‘n Groot hoeveelheid energie kan, gedurende die smeltingsproses in ‘n faseveranderingsmateriaal binne ‘n nou temperatuurband gestoor word. Hierdie gesmelte materiaal kan weer op sy beurt in die waterverhittingstoepassing, die geabsorbeerde hitte teen ‘n konstante temperatuur oordra. In hierdie studie word ‘n sonwaterverwarmer stelsel wat aangepas is deur ‘n addisionele latente hittestoor daaraan te heg, voorgestel. Hierdie faseverandering hittestoor kan meer hitte stoor as wat water in dieselfde temperatuur band sou kon. Die hitteoordrag tempo na en van baie van die faseveranderingsmateriale (FVM) is egter as gevolg van die lae termiese geleidingskoëfisient, stadig. Hierdie eienskap kan gelukkig verbeter word deur hittepype en hitteoordrag verhogings materiaal soos vinne by te voeg. Hittepype het die inherente eienskap om hitte teen ‘n hoë tempo oor groot afstande, oor te dra, selfs oor ‘n klein temperatuurverskil. In hierdie tesis word ‘n ondersoek rakende ‘n faseverandering storingsisteem wat bestaan uit paraffien was as die FVM en reghoekige hittepype wat te same met met aluminium finne gebruik word om die hitteoordragtempo te verhoog, beskryf. Die stoorontwerp is modulêr en elke module het die kenmerk van hoë hitteoordrag na en van die FVM. Die module het verder ook die eienskap om vining hitte te absorbeer of hitte af te gee. Dit gebeur teen ‘n konstante temperatuur gedurende die faseverandering van die FVM. Presies so ‘n reghoekige module is ontwerp en gebou en onder beheerde hitte absorbering- en hitte verwyderingsiklusse analiseer. Tydens die verhittings eksperiment is ‘n elektriese ketel van gebruik gemaak wat gedien het as die hoë temperatuur bron. Die hitte sink was ‘n hitteruiler wat kraanwater van ‘n konstante hoogte tenk ontvang het. Die resultate van die volledige toets is met die resultate van tydafhanklike numeriese model vergelyk. Hierdie numeriese model bereken teoreties wat die module se storing verrigting onder gegewe toets omstandighede sal wees. Die numeriese model se resultate het goed vergelyk met die resultate van die eksperimente. Die numeriese model van die module is toe aangepas om ‘n sonwaterverwarmer met addisionele stoortenk wat fase verandering materiaal gebruik, te simuleer. Hierdie ontwerp is anders as vorige ontwerpe in die sin dat hoër temperature as wat die warmwatertoestel kan hanteer, in die faseverandering storingstenk, bereik kan word. Die sisteem kan ook as gevolg van die hitteoordrag verhoging materiaal, vinniger verhit of afkoel en teen ‘n vinniger tempo. Die simulasie van die sonwaterverwarmer met FVM word gebruik om die grootte en verrigting van die sisteem te bepaal. Hierdie numeriese model toon aan dat wanneer ‘n addisionele faseverandering storingstelsel in ‘n sonwaterverwarmer toepassing gebruik word, die warm water wat die verbruiker uit die sisteem kan verkry, kan verhoog. Die rede hiervoor is dat meer hitte gestoor kan word, wat beskikbaar gemaak word aan die warm water tenk.

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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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Silva, Marcelo Marques da [UNESP]. "Formação de filmes finos de Al2O3 por anodização e seu uso em dispositivos com filmes de Poli(3-Hexiltiofeno)." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/99672.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Neste trabalho é apresentada a preparação de filmes finos de Al2O3 usando a técnica eletroquímica de anodização em solução aquosa de etileno glicol e ácido tartárico. Os filmes de Al2O3 foram crescidos sobre camadas de alumínio as quais foram depositadas por evaporação em vácuo sobre lâminas de vidro. No processo de anodização se utilizou a densidade de corrente constante de 0,48 mA/cm2, seguido da aplicação de diferença de potencial constante durante 2 minutos. Filmes com espessuras entre 10 e 60 nm foram crescidos sendo a espessura determinada pela tensão final aplicada na célula. Os filmes de Al2O3 foram caracterizados através de medidas de capacitância e perda dielétrica em função da frequência e das curvas características da corrente elétrica versus a tensão elétrica. Os resultados mostraram que a perda dielétrica é da ordem de 10-3 indicando que os filmes de Al2O3 possuem muito boa qualidade como isolante elétrico. As medidas de corrente versus tensão mostraram que a resistividade elétrica dos filmes é da ordem de 10(13)m. Na parte final do trabalho foi mostrado que os filmes de Al2O3 podem ser usados para a construção do capacitador metal-isolante-semicondutor (MIS) para operar entre no intervalo de tensão de +3V. Além disso, o capacitador MIS apresentou o fenômeno do chaveamento da condução elétrica quando foram aplicadas tensões elétricas elevadas, e, portanto, são candidatos para a fabricação de memórias
This work presents the preparation of Al2O3 films using the electrochemical anodisation tehcnique in aqueous solution of ethylene glycol and tartaric acid. The Al2O3 films were grown from aluminum layers deposited by evaporation in vacuum onto glass slides. The anodisation process was performed using a constant current density of 0.48 mA/cm2 followed by application of a constant voltage during 2 minutes. Films with thicknesses ranging from 10 to 60 nm were grown and the thickness was determined by the final voltage applied to the cell. Films were characterized through measurements of capacitance and dielectric loss versus frequency curves and characteristics of electric current versus voltage. The results showed that the dielectric loss is of the order of 10-3 showing that Al2O3 film is a very good electrical insulator. Current versus voltage measurments showed that the electrical resistivity of the Al2O3 films is of the order of 10(13)m. Finally, it is shown that Al2O3 films can be used to fabricate metal-insulator-semiconductor (MIS) capacitor that can be operated in the voltage range of +3V. The MIS capacitor also presented the electrical conduction switching when the applied voltage was increased, therefore, it can be a candidate to be used as memory

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Ivanova, Nadezda. "Dobudování VUT - Fakulta výtvarných umění." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-227142.

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The object consists of 3 volumes: two 6-storey academic buildings, interconnected with public space. Simple geometry of complex is formed by the existing urban development. Repeating street directions and continuing visual contact with the housing of the Law Faculty, the building in terms of shape represents letter V and forms enclosed courtyards. In the lower part of the building of the Faculty of Fine Arts there are workrooms, library and repository that are loaded from the north facade. The first three floors are connected by a corridor with a recreational area of public space created for a comfortable communicating and solitary classes. On the other floors there are workshops, studios and studio offices of ceramics, sculpture, metal, photography, printing and 3D-graphics, cabinets of deanery and classrooms. On the top floor, that is 6 m height, there are art studios, additionaly lightened by lanterns on the roof. The housing is designed in that way that it has the open airy atrium, which, along with half-transparent facades, provides natural light in most interiors. Facade structure is highlighted with the shell of the vertical and horizontal aluminum fins and shelves, which gives to a compex an interesting and constantly changing pattern. Unified composition is also highlighted with shades of warm and cold colors of the spectrum. Four underground floors are used for car parking, and the ground flloor of them is given for the operation of the university. In the future, the project also envisages planting of greenery of building facades and of the surrounding area.

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Leger, Pierre-Emmanuel. "Rôle de la microstructure sur les mécanismes de corrosion marine d’un dépôt à base d’aluminium élaboré par projection dynamique par gaz froid (« cold spray »)." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM005.

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Le principe de la projection dynamique par gaz froid ou « cold spray » repose sur la projection de particules de poudres convoyées par un gaz à des vitesses supersoniques vers un substrat. La déformation des particules à l’impact avec ce dernier permet la construction d’un dépôt. Ce procédé permet de conserver la microstructure des particules de poudre et de produire des dépôts peu poreux. Cette dernière caractéristique est essentielle dans le cadre d’applications anticorrosion. L’ambition de la thèse est de comprendre le rôle de la microstructure sur les mécanismes de corrosion marine d’un dépôt à base d’aluminium élaboré par cold spray. Pour atteindre cet objectif sont projetées des poudres à base d’aluminium (aluminium pur, alliages d’aluminium et mélanges avec ajout d’alumine) sur un substrat en acier. Les microstructures des dépôts sont étudiées jusqu’à l’échelle nanométrique (MET). L’adhérence des dépôts est mesurée par l’essai de plot collé. A partir des microstructures sont proposés plusieurs mécanismes de formation de la porosité dans un dépôt cold spray à différentes échelles. Une étude numérique par éléments finis complète cette analyse microstructurale. Grâce aux mesures de la vitesse (DPV-2000) et de la température (caméra thermique) d’impact des particules, les paramètres de nouveaux modèles matériau sont optimisés pour simuler le comportement de l’aluminium et de l’alumine à l’impact. De plus, plusieurs essais de corrosion marine (immersion et brouillard salin) sont conduits. L’étude des microstructures corrodées permettent d’établir différents mécanismes de corrosion du dépôt cold spray. Un lien entre la porosité du dépôt et son comportement en corrosion est notamment montré. Enfin, une première approche du transfert de technologie du procédé à l’échelle industrielle est décrite
Cold spray process is based on spraying particles carried by a gas at a supersonic speed onto a substrate. Particle deformation during impact with the substrate creates a coating. This spraying process can retain particle microstructure and produce very dense coating. This property is crucial for anticorrosion applications. The aim of this work is to understand the effect of cold spray aluminum coating microstructure on marine corrosion mechanisms. To achieve this goal, several aluminum powders (including pure aluminum, aluminum alloys and mixtures with alumina) are sprayed onto a steel substrate. Coating microstructure is studied down to a nanoscale (TEM). The coating-substrate bond strength is determined using pull-off testing. From a thorough microstructure study, various mechanisms are proposed to explain multiscale porosity formation in coatings. A numerical study using finite elements modeling complements this microstructure analysis. From particle speed (DPV-2000) and temperature (thermal camera) measurements during impact, new material models are optimized to model aluminum and alumina behavior at particle impact. Moreover, corrosion tests are conducted (including immersion and salt spray tests). The study of corroded coating microstructures is used to identify corrosion mechanisms which occur in the coating. A relationship between coating porosity and its corrosion behavior is particularly brought into light. Finally, a first approach to a technological transfer of this process to an industrial application is proposed

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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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10

Lunas, Fabrícia Roberta [UNESP]. "Caracterização de filmes finos de ZnO dopados com Al e Mn depositados em substrato vítreo pelo método de Spray Pirólise." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/91987.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Neste trabalho foram depositados em substrato vítreo, filmes finos de Óxido de Zinco puro (ZnO) e dopados com alumínio (ZnO:Al) e manganês (ZnO:Mn), utilizando a técnica spray-pirólise. Foram investigadas as propriedades estruturais, ópticas e elétricas dos filmes, assim como, a dependência com a temperatura de deposição e concentração. As temperaturas utilizadas para deposição dos filmes finos foram 400 ºC e 450 ºC, e a concentração de dopantes variaram de 1 a 5 átomo por cento (at%). As técnicas de difração de raios-X e espectroscopia por refletância no infravermelho foram utilizadas para avaliar as características estruturais dos filmes. A Espectroscopia de transmitância na região do UV-Vis foi utilizada como uma das técnicas no estudo das propriedades ópticas, fornecendo valores da banda proibida. A técnica do ângulo de Brewster, foi utilizada com o intuito de avaliar o índice de refração e a espessura dos filmes finos. A avaliação da resistividade foi realizada com a finalidade de estudar a propriedade elétrica, e medidas do efeito Hall para investigar a densidade dos portadores de carga e mobilidade dos filmes semicondutores. A análise dos difratogramas de raio-X, revela picos de difração típicos de uma estrutura policristalina tipo wurtzita. As medidas de refletância especular por FTIR identificam ligações de estiramento do Zn-O na região de 450 cm-1. A técnica do ângulo de Brewster fornece resultados das espessuras dos filmes finos na faixa de 150 a 240 nm. As medidas de espectroscopia de transmitância na região UV-vis é avaliada em torno de 85%. Com os resultados da espessura dos filmes pelo ângulo de Brewster e medidas de transmitância foi calculado na região de forte absorção o coeficiente de absorção destes filmes. O valor do coeficiente de absorção é um parâmetro fundamental para determinação da banda de energia proibida...
In this work were deposited in glass substrate, thin films of pure zinc oxide (ZnO) and doped with aluminum (ZnO: Al) and manganese (ZnO: Mn) used the spray-pyrolysis technique. The structural, electrical and optical properties of thin films were investigated in dependence the concentration and temperatures deposition. The thin films temperatures deposition were 400 °C and 450 º C, and the doping concentration were from 1 at% to 5 at% range. The deposition technique used aims to obtain good adhesion to the substrate and uniformity of the films. The X-ray diffraction spectroscopy and infrared reflectance were used to evaluate the structural characteristics of the films. The UV-Vis transmittance spectroscopy was used in the study of optical properties, providing values of band gap. The other technique for this purpose is the Brewster angle technique in order to evaluate the refractive index and thickness of thin films deposited on a glass substrate. The resistivity and Hall Effect measurements were used for to investigate the charge carriers density and mobility in semiconductor films. The analysis of the X-ray diffraction shows typical peaks of polycrystalline wurtzite structure. Measurements the FTIR specular reflectances identify bond stretching of Zn-O in the region of 450 cm-1. The Brewster angle technique provides results the thin films thickness in the 150 to 240 nm range. The thin films UV/VIS transmittance measurements are valued around 85%. With the results of the thin film thickness by Brewster angle and measures transmittance were calculated the absorption coefficient data values in strong absorption region. The absorption coefficient is an important parameter for determination the band gap energy. These values, for the ZnO semiconductor is in 3.2 eV range. The resistivity’s measurements by Van der Pauw method showed the resistivity of ZnO thin films doped with... (Complete abstract click electronic access below)

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11

Brandstadt, Katrina L. "Thermal oxidation of fine aluminum powders in carbon dioxide gas." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81530.

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The thermal oxidation of fine aluminum (Al) powders in carbon dioxide (CO2) gas was investigated for the purpose of metal-based propulsion fuel development. The thermal behavior and reaction energy was studied using simultaneous thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). The reactivities of Al powders with nanometer and micrometer-scale average particle sizes were compared. The particle morphology was examined at different stages of the process using field emission gun scanning electron microscopy (FEG-SEM) and transmission electron microscopy (TEM). The corresponding chemical changes were analyzed by X-ray diffraction spectrometry (XRD) and energy dispersion X-ray spectrometry (EDS).
Nano- and micrometer-scale Al powders exhibited different calorimetric behaviour. The primary oxidation occurred at around 533°C for the nanopowders and at 1045°C for the micropowders. The mechanism of the oxide growth, particle deformations, and hollow oxide shells are discussed. A low-temperature transformation of the amorphous Al2O3 coating to crystalline gamma-Al 2O3 is identified as a trigger to the exothermic reaction in the case of the Al nanopowders. Carbon was also shown to be involved in the reaction.

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12

Boratto, Miguel Henrique [UNESP]. "Investigação de propriedades de filmes finos de Al2O3 para aplicação em dispositivos eletrônicos." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/88357.

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O escopo deste trabalho é a obtenção de filmes finos de óxido de alumínio (alumina) através da evaporação resitiva de alumínio, seguido da oxidação térmica em atmosfera adequada (ar ou rica em O2), com varaiação do tempo e da temperatura do tratamento térmico. A investigação deste material tem por finalidade sua utilização como camada isolante em transistores de efeito de campo, mais especificamente do tipo metal-óxido-semicondutor (MOSTFET), visando a diminuição da corrente de fuga no gate e aumento do controle de corrente no canal de condução. Além de se tratar de dipositivo transparente, que permite a interação com luz. A análise das propriedades ópticas e estruturais dos filmes investigados mostra que na temperatura de 550ºC ocorre uma completa oxidação do material, a qual é acelerada em atmosfera de oxigênio. Valores de resistividade elétrica concordam com a tendência de oxidação revelada pelos dados de Difração de Raios X (DRX). Além disso, resultados de espectroscopia no infravermelho (FTIR) e Raman, em bom acordo com resultados de DRX, apresentam-se estrutura y-Al2O3. Amostras de alumina depositadas sobre substrato de vidro sodalime apresentam silício cristalino na interface com o Al2O3 advindo do substrato, enquanto amostras de Al2O3 sobre SnO2 não apresentaram esse material. A heterojunção entre SnO2:4at%Sb e Al2O3 foi caracterizada por DRX, Microscopia eletrônica de varredura (MEV) e Microscopia Confocal, que mostraram alta rugosidade do filme isolante sobre o semicondutor, e um provável processo de difusão entre as camadas isolante e semicondutora, em concordância com resultados de corrente x voltage (IxV), obtidos a partir da construção de um dispositivo simples, com contatos de Sn, ao qual foram submetidos dispositivos com diferentes números de camadas isolantes...
The goal of this work is is to obtain aluminum oxide (alumina) thin films deposited by resistive evaporation of Al, followed by thermal oxidation in proper atmosphere (air or O2-rich), with varying time and temperature of thermal annealing. The investigation of this material of this material aims using this material for application as insulating layer in field effect transistors, specifically metal-oxide-semiconductor (MOSFET), seeking for low leakage current and efficient current control in the conduction channel. Besides, it is a transparent device, which allows interaction with light. Analysis of optical and structural properties of investigated films reveals that temperature of 550ºC is responsable for fair oxidation, which is accelerated in oxygen-rich atmosphere. Results of electrical resistivity agree with the oxidation, which is accelerated in oxygen-rich atmosphere. Results of electrical resistivity agree with the oxidation tendency found in the X-ray diffraction data (XRD). Moreover, results of infrared spectroscopy (FTIR) and Raman show the presence of y-Al2O3, also found in XRD data. Alumina samples deposited on soda-line glass substrates leads to the presence of crystalline Si, coming from the substrate leads to the presence of crystalline Si, coming from the substrate, whereas... (Complete abstract click electronic access below)

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13

Lunas, Fabrícia Roberta. "Caracterização de filmes finos de ZnO dopados com Al e Mn depositados em substrato vítreo pelo método de Spray Pirólise /." Ilha Solteira : [s.n.], 2009. http://hdl.handle.net/11449/91987.

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Orientador: Victor Ciro Solano Reynoso
Banca: Cláudio Luiz Carvalho
Banca: Celso Xavier Cardoso
Resumo: Neste trabalho foram depositados em substrato vítreo, filmes finos de Óxido de Zinco puro (ZnO) e dopados com alumínio (ZnO:Al) e manganês (ZnO:Mn), utilizando a técnica spray-pirólise. Foram investigadas as propriedades estruturais, ópticas e elétricas dos filmes, assim como, a dependência com a temperatura de deposição e concentração. As temperaturas utilizadas para deposição dos filmes finos foram 400 ºC e 450 ºC, e a concentração de dopantes variaram de 1 a 5 átomo por cento (at%). As técnicas de difração de raios-X e espectroscopia por refletância no infravermelho foram utilizadas para avaliar as características estruturais dos filmes. A Espectroscopia de transmitância na região do UV-Vis foi utilizada como uma das técnicas no estudo das propriedades ópticas, fornecendo valores da banda proibida. A técnica do ângulo de Brewster, foi utilizada com o intuito de avaliar o índice de refração e a espessura dos filmes finos. A avaliação da resistividade foi realizada com a finalidade de estudar a propriedade elétrica, e medidas do efeito Hall para investigar a densidade dos portadores de carga e mobilidade dos filmes semicondutores. A análise dos difratogramas de raio-X, revela picos de difração típicos de uma estrutura policristalina tipo wurtzita. As medidas de refletância especular por FTIR identificam ligações de estiramento do Zn-O na região de 450 cm-1. A técnica do ângulo de Brewster fornece resultados das espessuras dos filmes finos na faixa de 150 a 240 nm. As medidas de espectroscopia de transmitância na região UV-vis é avaliada em torno de 85%. Com os resultados da espessura dos filmes pelo ângulo de Brewster e medidas de transmitância foi calculado na região de forte absorção o coeficiente de absorção destes filmes. O valor do coeficiente de absorção é um parâmetro fundamental para determinação da banda de energia proibida... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In this work were deposited in glass substrate, thin films of pure zinc oxide (ZnO) and doped with aluminum (ZnO: Al) and manganese (ZnO: Mn) used the spray-pyrolysis technique. The structural, electrical and optical properties of thin films were investigated in dependence the concentration and temperatures deposition. The thin films temperatures deposition were 400 °C and 450 º C, and the doping concentration were from 1 at% to 5 at% range. The deposition technique used aims to obtain good adhesion to the substrate and uniformity of the films. The X-ray diffraction spectroscopy and infrared reflectance were used to evaluate the structural characteristics of the films. The UV-Vis transmittance spectroscopy was used in the study of optical properties, providing values of band gap. The other technique for this purpose is the Brewster angle technique in order to evaluate the refractive index and thickness of thin films deposited on a glass substrate. The resistivity and Hall Effect measurements were used for to investigate the charge carriers density and mobility in semiconductor films. The analysis of the X-ray diffraction shows typical peaks of polycrystalline wurtzite structure. Measurements the FTIR specular reflectances identify bond stretching of Zn-O in the region of 450 cm-1. The Brewster angle technique provides results the thin films thickness in the 150 to 240 nm range. The thin films UV/VIS transmittance measurements are valued around 85%. With the results of the thin film thickness by Brewster angle and measures transmittance were calculated the absorption coefficient data values in strong absorption region. The absorption coefficient is an important parameter for determination the band gap energy. These values, for the ZnO semiconductor is in 3.2 eV range. The resistivity's measurements by Van der Pauw method showed the resistivity of ZnO thin films doped with... (Complete abstract click electronic access below)
Mestre

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14

Breakey, J. W. Matthew. "Co-deformation of an aluminum zinc alloy." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/399.

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In some systems, including copper niobium, it has been found that as the scale of the two phases decreases, there is an anomalous increase in strength. Mechanisms of this strengthening have been postulated, but a general theory has yet to be developed. A model system to study the co-deformation of fine scale materials was developed and characterized. An aluminum 18.5at.% zinc alloy was selected and discontinuously precipitated to produce 100% transformation and an interlamellar spacing of 240nm.The material was tested using strain rate jump tests to determine the temperature sensitivity, tensile tested to determine work hardening and the temperature sensitivity, wire drawn to study the effect of large plastic deformation and finally tension compression tested to determine internal stresses. The bulk properties of the two phases are well known allowing for a detailed analysis of the composite properties when combined with the mechanical results. The material showed increased strength above the rule of mixture prediction from bulk properties due to a fine scale microstructure . Although the lamellar material had a much higher strength than the rule of mixtures would predict, the overall strength of the alloy did not approach that of more conventional high strength aluminum alloys. The material was found to be temperature and rate dependent, with an increased work hardening rate as the temperature was decreased. Temperature was found to play a key role in the stress partitioning between the two phases. Temperature dependent relaxation processes lowered the stress partitioning between the hard and soft phases as the temperature was increased. Therefore, stress relaxation must be minimized to maximize the strengthening found in fine scale materials.

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15

Spurr, G. J. "Fretting wear of a fine particulate reinforced aluminium alloy." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260524.

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16

Bowen, J. R. "The formation of ultra-fine grained model aluminium and steel alloys." Thesis, University of Manchester, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508036.

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17

Santos, Thales Borrely dos. "Controle de propriedades de filmes finos de óxido de alumínio através da assistência de feixe iônico." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-03062017-212721/.

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Este trabalho tem por objetivo a caracterização de filmes finos de óxido de alumínio produzidos por deposição assistida por feixe de íons Ar+. Tal caracterização consiste em estabelecer a relação entre os parâmetros de produção (energia do feixe e uxo relativo de Ar), a composição e a estrutura dos lmes. Para tanto, utiliza-se técnicas de microscopia de força atômica, difração de raios-x, reetividade de raios-x e análise por feixe iônico. Resultados mostram que amostras produzidas à temperatura ambiente e à 450 oC são amorfas independentemente da energia do feixe iônico. Filmes formados com assistência de feixe possuem qualidade superior àqueles formados por deposição física de vapor. O bombardeamento de íons Ar+ mostra-se capaz de controlar a concentração de hidrogênio, a estequiometria, a rugosidade, o tamanho dos grãos e a densidade dos lmes nos. Amostras com excelente qualidade baixa rugosidade, estequiometria próxima da ideal e boa densidade foram produzidas utilizando íons com energia dentre 300 eV e 600 eV.
The scope of this work is the characterization of aluminum oxide thin films produced by Ar+ ion beam assisted deposition. This characterization consists in establishing the relationship between production parameters (ion beam energy and argon relative ux), structure and composition of these lms. In order to undertake this task, the following techniques were used: atomic force microscopy, x-ray diraction, x-ray reectivity and ion beam analysis. Results show that samples produced at room temperature and at 450 oC are amorphous regardless the ion beam energy. Films grown under ion assistance have better characteristics than the ones deposited by physical vapor deposition. The ion beam bombardment is capable of controlling hydrogen concentration, stoichiometry, roughness, grain size and density of alumina samples. High quality lms at surface and increased density lms with near ideal stoichiometry were produced with 300 eV and 600 eV ion beam energy.

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Mukunthan, Kannappar. "Properties of ultra fine grain [beta]-CuAlNi strain memory alloys." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26724.

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A method has been developed to produce grain sizes as low as 5µm in β-CuAlNi alloys and the effect of grain size on mechanical and strain-memory properties was studied. The thermomechanical treatment procedure involved two. sequential warm working and recrystallization steps at 600° C and 800° C respectively on eutectoid alloys. Three different eutectoid alloys, two with Ms temperature of around 0°C and one with Ms = 220° C were used for the present studies. Even at fine grain sizes, the specimens produced were of single β- phase type without any second phases. Two-stage characteristic stress-strain curves were obtained for most of the specimens in both the strain memory and pseudoelastic states. It was found that the ultimate tensile strength and strain to failure increased with decreasing grain size according to a Hall-Petch relationship down to a grain size of 5µm with the exception of one alloy. Fracture strengths of 1,200 MPa and fracture strains of 10% could be obtained. It was found that the major recovery mode, whether pseudoelastic or strain memory, did not have any significant effect on the total recovery obtained. Recovery properties were not affected significantly by decreasing grain size. Approximately 86% recovery could be obtained for an initial applied strain of 5% at a grain size of around 10µm. Grain refinement increased the fatigue life considerably, possibly due to high ultimate fracture strength and ductile fracture mode. Fatigue life of 275,000 cycles could be obtained for an applied stress of 330 MPa and a steady state strain of 0.6%. Most of the fractures are due to intergranular-type brittle fracture. At fine grain sizes, transgranular-type brittle fracture and microvoid coalescence-type ductile fracture dominated the fracture mode. Oxygen segregation at grain boundaries is the possible explanation for the different mechanical properties shown by different alloys in the present work by being a major factor in causing intergranular-type fracture.
Applied Science, Faculty of
Materials Engineering, Department of
Graduate

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Santos, Júlio César dos [UNESP]. "Deposição e caracterização de filmes finos de GaAs e 'Al IND. 2''O IND. 3' para potencial utilizado em transistores." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/88451.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Neste trabalho foi realizada a deposição através da técnica de evaporação resistiva, de filmes finos de GaAs (arseneto de gálio) e de Al (alumínio) com posterior oxidação deste último, formando 'Al IND. 2''O IND. 3' (óxido de alumínio ou alumina) e a caracterização dos filmes de GaAs e da heteroestrutura formada por 'Al IND. 2''O IND. 3' e GaAs. A confecção do dispositivo combinando estes compostos serviu para a investigação das características relevantes do sistema para potencial aplicação em transistores. O trabalho compreendeu investigação sobre as condições de deposição, e foram avaliadas principalmente as características elétricas dos filmes produzidos individualmente. Os resultados apresentados incluem: resistividade em função da temperatura, corrente-voltagem em função da temperatura, difração de raios-X e transmitância na região do infravermelho. Para caracterização do desempenho do sistema 'Al IND. 2''O IND. 3'/GaAs, um transistor simples foi construído sob um substrato de vidro borossilicato com uma camada de GaAs e outra de 'Al IND. 2''O IND. 3'. Os contatos de fonte, dreno e gate foram feitos de In. Essa estrutura permite a medida da corrente de fuga e a avaliação de outras características do sistema. Neste dispositivo foram avaliadas as características corrente-voltagem em função da temperatura, e também a interação com luz, já que GaAs, por apresentar gap direto, torna-se atraente para aplicações opto-eletrônicas. Assim medidas de elétricas foto-induzidas foram realizadas com excitação com fontes de luz branca. Com o intuito de se avaliar a qualidade dos filmes de GaAs obtidos pela evaporação resistiva, tanto a caracterização estrutural quando elétrica também foram feitas em filmes finos de GaAs depositados por sputtering, de modo a se ter um padrão de comparação.
In this work, the deposition of GaAs (gallium arsenide) and Al (aluminum) thin films is carried out by the resistive evaporation technique. In the latter case, an oxidation of the film is accomplished, leading to 'Al IND. 2''O IND. 3' (alumina) formation. The characterization of GaAs thin films and the heterostructure formed by 'Al IND. 2''O IND. 3' and GaAs is also carried out. The elaboration of the device combining these compounds allows investigating the relevant characteristics of this system to potential application in transistors. The work evolved investigation on the deposition conditions, and the electrical characteristics of the films were also evaluated separately. Results includes: resistivity as function of temperature, X-ray diffraction and near infrared transmittance. For characterization of the performance of the 'Al IND. 2''O IND. 3'/GaAs system, a simple transistor was built on a borosilicate glass substrate, with a 'Al IND. 2''O IND. 3' layer on top of a GaAs layer. The contacts of source, drain and gate were done using In. This structure allows evaluating the leak current and other characteristics of this system. In this device, it was evaluated the current - voltage characteristics and the interaction with light, because GaAs, due to its direct bandgap, become very attractive for opto-electronic applications. The, the photo-induced electrical measurements were done under excitation with white light. Aiming the evaluation of the quality of films deposited by the resistive evaporation technique, electrical as well as structural characterization were also carried out for GaAs thin films deposited by sputtering, in order to have a comparing parameter.

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Oliveira, Isaias de. "Desenvolvimento de suporte catalítico monolítico para fins aeroespaciais empregando a manufatura aditiva." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/97/97134/tde-04122018-143447/.

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No presente trabalho foi desenvolvido um suporte catalítico monolítico para fins aeroespaciais empregando a manufatura aditiva. Para tanto, foi proposta uma geometria que proporcione um escoamento turbulento, permitindo um maior contato entre o reagente e a superfície do catalisador, proporcionando menor perda de carga ao sistema. Esta nova estrutura foi obtida via manufatura aditiva, através da técnica de Sinterização Seletiva a Laser (SLS) indireta. Para utilizar a técnica SLS e material cerâmico, foi necessário desenvolver um revestimento sobre as partículas de alumina para promover a aderência entre as mesmas durante o processo de manufatura aditiva. Em seguida foram definidos, experimentalmente, os parâmetros de aplicação da técnica SLS para o compósito alumina/poliamida. Por fim, foi fabricado, via SLS, o suporte catalítico na forma monolítica. Após a confecção do suporte monolítico, foi desenvolvido um revestimento composto de pseudo-boemita e nitrato de alumínio e aplicado na superfície do monólito, a fim de expandir a área superficial específica do material. Este aumento da área específica favorece a dispersão da fase ativa, composta de óxidos de cobalto e manganês, na superfície do suporte. A caracterização do catalisador monolítico foi realizada a partir das técnicas de Adsorção de Nitrogênio, Análise Termogravimétrica, Microscopia Eletrônica de Varredura e Espectrometria de Emissão Ótica com Fonte de Plasma (ICP-OES). O desempenho do catalisador monolítico na decomposição do H2O2 concentrado foi analisado via teste de gota, monitorado por câmera de alta velocidade. Os bons resultados obtidos nesta reação apontam esta técnica de obtenção de suporte catalítico monolítico através da manufatura aditiva como uma metodologia promissora a ser empregada em sistemas catalíticos com elevada difusão de massa e calor, mas principalmente em sistemas propulsivos a monopropelente.
This work was developed by the additive manufacture monolithic catalytic support to apply aerospace applications. A geometry was proposed to implement a turbulent flow allowing a better contact with catalytic surface and reagent with a low pressure drop in the system. This new structure was obtained by additive manufacture through indirect Selective Laser Sintering (SLS) technique. Firstly, in order to use the SLS for the ceramic material was developed a coating on the alumina particles to promote a melting between them during addictive manufacturing process. Secondly, the printer parameters SLS was configurated into the alumina/polyamide particle. Finally, the monolithic catalytic support was built via SLS. After the monolithic support building, the pseudo-boehmite and aluminum nitrate coating was developed and applied on the monolithic surface to increase the specific superficial area of the material. This increasing of the specific surface area helps the spread of the active phase to made up of cobalt and manganese oxide in the support surface. The characterization of the monolithic catalyst was carried out using the nitrogen adsorption technique, thermogravimetric analysis, scanning electron microscopy and inductive coupled plasma with optical emission spectrometry. The monolithic catalytic performance in the H2O2 concentrated decomposition was analyzed via drop test monitored by the high-speed camera. The good results of this reaction and such a technique of monolithic catalytic support obtainment through the additive manufacture show that a promising methodology can be used in the catalytic system with high diffusion of mass and heat but mainly, in monopropellant propulsive system.

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Anderson, Jonathan D. "Impacts of amending bauxite residue sands with residue fines for the establishment of vegetation on residue disposal areas /." Murdoch University Digital Theses Program, 2009. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20090831.155453.

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Arbab, Chirani Shabnam. "Méthodologie pour la prise en compte des contraintes résiduelles dans un calcul prévisionnel de durée de vie en fatigue de pièces en aluminium." Troyes, 1998. http://www.theses.fr/1998TROY0002.

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Les travaux qui font l'objet de cette thèse concernent la réalisation d'une démarche complète de prise en compte des contraintes résiduelles dans un calcul prévisionnel de durée de vie en fatigue. La mise au point de cette démarche nécessite trois phases principales. La première consiste à modéliser la trempe par la méthode des éléments finis. Afin de vérifier la validité du modèle, les résultats numériques sont comparés aux résultats expérimentaux obtenus par les méthodes du perçage pas à pas et de diffraction des neutrons. La deuxième étape consiste à étudier la relaxation des contraintes résiduelles dues à la trempe. Pour ce faire, nous utilisons une méthode simplifiée basée sur la nature du matériau ; dans ce cas il est nécessaire de tenir compte du changement des caractéristiques du matériau, survenu à la suite du traitement. La validité de la méthode est vérifiée en étudiant la relaxation des contraintes résiduelles dues au grenaillage. Le niveau des contraintes est déterminé de façon expérimentale. Ensuite, ces contraintes sont introduites dans la structure par des méthodes numériques. Dans le cas d'un matériau à durcissement cyclique, en utilisant les caractéristiques mécaniques monotones et la loi d'écrouissage isotrope linéaire, la relaxation des contraintes est estimée. La troisième phase consiste à mettre au point une méthode inverse pour définir les conditions de traitement thermique, à partir d'une durée de vie en fatigue fixée. Dans un premier temps, le champ de contraintes résiduelles admissible est déterminé en utilisant les criètres de fatigue multiaxiale et à partir de la durée de vie en fatigue désirée. Une fois ce champ admissible calculé, les conditions de traitement THERMIQUE SONT DEFINIES DE FACON A CE QUE L'ON OBTIENNE UN CHAMP DE CONTRAINTES RESIDUELLES PROCHE DU CELUI ADMISSIBLE. LA COMPARAISON ENTRE CES CHAMPS DE CONTRAINTES EST EFFECTUEE AU NIVEAU DES PRESSIONS HYDROSTATIQUES. CET ENSEMBLE DE METHODES D'ANALYSE ET DE SIMULATION PERMET DE FAIRE UNE VERITABLE APPROCHE D'INGENIERIE SIMULTANEE.

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Souto, K?sia Karina de Oliveira. "Desenvolvimento de membranas porosas de alumina para fins de tratamento de efluente industrial t?xtil." Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12837.

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Textile production has been considered as an activity of high environmental impact due to the generation of large volumes of waste water with high load of organic compounds and strongly colored effluents, toxic and difficult biodegradability. This thesis deals with obtaining porous alumina ceramic membranes for filtration of textile effluent in the removal of contaminants, mainly color and turbidity. Two types of alumina with different particle sizes as a basis for the preparation of formulation for mass production of ceramic samples and membranes. The technological properties of the samples were evaluated after using sintering conditions: 1,350?C-2H, 1,450?C-30M, 1,450?C-2H, 1,475?C-30M and 1,475?C-2H. The sintered samples were characterized by XRD, XRF, AG, TG, DSC, DL, AA, MEA, RL, MRF-3P, SEM and Intrusion Porosimetry by Mercury. After the characterization, a standard membrane was selected with their respective sintering condition for the filterability tests. The effluent was provided by a local Textile Industry and characterized at the entry and exit of the treatment plant. A statistical analysis was used to study the effluent using the following parameters: pH, temperature, EC, SS, SD, oil and grease, turbidity, COD, DO, total phosphorus, chlorides, phenols, metals and fecal coliform. The filtered effluent was evaluated by using the same parameters. These results demonstrate that the feasibility of the use of porous alumina ceramic membranes for removing contaminants from textile effluent with improved average pore size of 0.4 micrometre (distribution range varying from 0,025 to 2.0 micrometre), with total porosity of 29.66%, and average percentages of color removal efficiency of 89.02%, 92.49% of SS, turbidity of 94.55%, metals 2.70% (manganese) to 71.52% (iron) according to each metal and COD removal of 72.80%
A produ??o t?xtil tem sido considerada uma atividade de alto impacto ambiental, devido ? gera??o de grandes volumes de rejeitos com alta carga de compostos org?nicos e efluente fortemente colorido, t?xico e dif?cil biodegradabilidade. O presente trabalho trata da obten??o de membranas cer?micas porosas de alumina para filtra??o de efluente industrial t?xtil na remo??o de contaminantes, em especial, cor e turbidez. Utilizou-se dois tipos de alumina com granulometrias diferentes como base para o preparo de formula??es de massas cer?micas para a produ??o dos corpos de prova e membranas. As propriedades tecnol?gicas dos corpos de prova foram avaliadas ap?s suas sinteriza??es nas condi??es de: 1.350?C 2H, 1.450?C 30M, 1.450?C 2H, 1.475?C 30 M e 1.475?C 2H. Foram caracterizadas por DRX, FRX, AG, TG, DSC, DL, AA, MEA, RL, MRF-3P, MEV e Porosimetria por Intrus?o de Merc?rio. Ap?s essa caracteriza??o definiu-se uma membrana padr?o, com a sua respectiva condi??o de sinteriza??o, para os ensaios de filtrabilidade. O efluente foi fornecido por uma Ind?stria t?xtil do RN, e caracterizado nos pontos de entrada e sa?da da ETE. Utilizou-se um tratamento estat?stico dos resultados analisados no efluente atrav?s dos seguintes par?metros: pH, temperatura, CE, SS, SD, ?leos e graxas, turbidez, DQO, OD, f?sforo total, cloretos, fen?is, metais e coliformes termotolerantes. O permeado (EF) foi avaliado pelos mesmos par?metros. Os resultados obtidos demonstram a viabilidade no uso de membranas cer?micas porosas de alumina na remo??o de contaminantes de efluente industrial t?xtil, com melhor tamanho m?dio de poro de 0,4?m (faixa de distribui??o de tamanhos de poros variando de 0,025 a 2 ?m), com porosidade total de 29,66%, com percentuais m?dios de efici?ncia na remo??o de cor de 89,02%, SS de 92,49%, turbidez de 94,55%, metais variando de 2,70% (mangan?s) at? 71,52% (ferro) de acordo com cada metal e remo??o de DQO de 72,80%
2020-01-01

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Lakki, Angeliki. "Mechanical spectroscopy of fine-grained zirconia, alumina and silicon nitride /." [S.l.] : [s.n.], 1994. http://library.epfl.ch/theses/?nr=1266.

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Souza, Ana Maria de. "Sinterização em duas etapas de Pós Ultra Finos de Alumina." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2011. http://tede2.uepg.br/jspui/handle/prefix/1406.

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Alumina ceramic is one of the most widely used in industry due to its properties. However, some properties, such as low fracture toughness, limit its range of structural applications. In order to improve this property has been studied several ways to control the microstructure of these ceramics, seeking a refined and homogeneous microstructure. The firing curve control to manipulate the microstructure during sintering is a way that has been studied and has advantages such as simplicity and economy. This work studied the two-step sintering of alumina ultrafine powders using steps at a low temperature sintering and the two-steps sintering proposed by Chen and Wang. With the help of statistical analysis was determined the variables that most influence in sintering processes studied. After sintering, the samples were characterized by apparent density and grain size. It was observed that the use of two-step sintering is effective in controlling the final microstructure of alumina, altering both the densification and grain growth.
A alumina é uma das cerâmicas mais utilizadas na indústria, devido a suas propriedades. Entretanto, algumas propriedades, tal como a baixa tenacidade à fratura, limita sua gama de aplicações estruturais. Com o intuito melhorar essa propriedade vem sendo estudadas várias maneiras de se controlar a microestrutura dessas cerâmicas, buscando uma microestrutura homogênea e refinada. O controle da curva de queima para manipular a microestrutura durante a sinterização é uma maneira que vem sendo estudada e apresenta vantagens como simplicidade e economia. Neste trabalho foi estudada a sinterização em duas etapas de pós ultrafinos de alumina utilizando tanto patamares a baixa temperatura quanto a sinterização em duas etapas proposta por Chen e Wang. Com o auxílio da análise estatística de Planejamento de Experimentos determinou-se as variáveis que exercem maior influência nesses processos de sinterização, sempre visando atingir microestruturas com altas densidades e mínino crescimento de grãos. Após sinterização, as amostras foram caracterizadas por medidas de densidade aparente e de tamanho de grão. Observou-se que a utilização da sinterização em duas-etapas é eficiente em controlar a microestrutura final da alumina, alterando tanto a densificação quanto o crescimento de grão.

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Su, Veronica Mei Tiing. "Architecture and performance of ultra-fine scale alumina fibre membranes." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648640.

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Nielsen, Guilherme Fernandes. "Filmes orgânicos contendo óxido de alumínio depositados a plasma /." Bauru : [s.n.], 2011. http://hdl.handle.net/11449/99661.

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Orientador: Elidiane Cipriano Rangel
Banca: Rogerio Valentim Gelamo
Banca: Sandro Doninini Mancini
O programa de Pós graduação em Ciência e Tecnologia de Materiais, PosMat, tem carater institucional e integra as atividades de pesquisa em materiais de diversos campi da UNESP
Resumo: 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... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: 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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Prado, Eduardo Silva. "Técnica híbrida de plasma para a deposição de filmes de alumina /." Bauru, 2015. http://hdl.handle.net/11449/132495.

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Orientador: Elidiane Cipriano Rangel
Banca: Francisco Trivinho Strixino
Banca: Steven Frederick Durrant
O Programa de Pós Graduação em Ciência e Tecnologia dos Materiais, PosMat, tem caráter institucional e integra as atividads de pesquisa em materiais de diversos campi
Resumo: Neste trabalho é proposta uma nova tecnologia de plasma para a deposição de filmes de alumina a partir do acetilacetonato de alumínio, AAA. A possibilidade de se depositar filmes a partir da pulverização catódicado AAA em plasmas de argônio foi demonstrada em trabalho prévio do grupo. No presente trabalho, foi realizada uma mudança nesta metodologia de forma a associar bombardeamento iônico do substrato ao processo de deposição. Para tal, o plasma foi gerado pela aplicação de sinal de radiofrequência (13,56 MHz) ao eletrodo inferior de um sistema de plasma capacitivamente acoplado, onde o pó do AAA foi espalhado. O eletrodo superior, também usado como porta-amostras, foi polarizado com pulsos retangulares negativos de amplitude, frequência e ciclo de trabalho controlados. A pulverização católica de fragmentos do AAA pelo plasma fornece precursores para a deposição do filme enquanto a polarização do porta-amostras acelera íons em direção aos substratos promovendo bombardeamento iônico da camada em crescimento. Os parâmetros de excitação do plasma (11 Pa, 13,56 MHz, 150 W, 3600 s) foram mantidos iguais aos otimizados em trabalho anterior do grupo. Variou-se a amplitude dos pulsos de popularização, entre 0 e 2800 V, de modo a modificar a energia fornecida pelo bombardeamento iônico à estrutura. A frequencia e foi fixada em 300 Hz e os pulsos de trabalho variaram entre (0, e 100%). Investigou-se o efeito da intensidade dos pulsos nas propriedades da camda resultante. A taxa de deposição foi determinada a partir do tempo de deposição e da espessura dos filmes, medida por perfilometria. A estrutura molecular das camadas foi analisada por espectroscopia no infravermelho no modo IRRAS (Infrared Reflectante Absorbance Spectroscopy). Difração de raios X foi empregada para avaliar se houve precipitação de fases cristalinas da alumina. A morfologia do material depositado foi inspecionada por microscopia...
Abstract: A new plasma methodology for deposition of alumina from aluminum acetylacetonate, AAA, is proposed. In a previous study by his this group, the possibility of depositing films from the AAA, by sputtering in argon atmosphere. In the present work, this methodology was modified by coupling a bombardment to the deposition process. For this, the plasma was generated by the application of radifrequency signal (13.56 MHz) to the lowermost electrode of a capacitively coupled plasma system with the AAA powder was spread. The topmost electrode, also used as the sample holder, was biased with retangular negative pulses of controlled amplitude, frequency and duty cycle. Sputtering of AAA fragments by the argon plasma provides precursors for film deposition while the polarization of the holder accelerates ions toward the substrates, promoting ion bombardment of the growing layer. The plasma excitation parameters (11 Pa, 13.56 MHz, 150 W, 3600 s) were the same as those optimized in the previous work of the group. The magnitude of the pulses was varied from 0 to 2800 V. To change the energy delivered by ion bombardment to the structure. A fixed pulse frequency and duty cycle were fixed of 300 Hz and duty cicle changed between (0 and 100%). The effect of P on the film properties was investigated. Deposition rates were determined from the deposition time and film thinckness, measured by profilometry. Infrared spectroscopy in the IRRAS mode (InfraRed Reflectante Absorbance Spectroscopy) was used to investigate the molecular structure of the layers. X-ray diffractometry was employed to verify if there was precipitation of crystalline alumina phases. The material microstructure was investigated by scanning electron and atomic force microscopies. Elemental composition analyses were performed by Energy Dispersive Spectroscopy while data obtained by nanoindentation tests allowed the calculation of hardness. The structures present (C-H, C=O, C=C e (C-H)3 organic...
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Gomide, Viviane Silva. "Desenvolvimento e caracterização mecanica de compositos hidroxiapatita-zirconia, hidroxiapatita-alumina e hidroxiapatita-titania para fins biomedicos." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263377.

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Orientador: Cecilia Amelia de Carvalho Zavaglia
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia mecanica
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Resumo: Existe uma crescente demanda de materiais que possibilitam a remodelação e reconstrução de partes ósseas. A indicação de biomateriais para reconstrução dos defeitos cranianos depois do trauma, tumor ou infecção, ocorre devido a razões estéticas e proteção de estruturas intracraniais. Várias técnicas cirúrgicas vários materiais já foram utilizados na confecção dessas próteses crâniomaxilofaciais, mas é importante avaliar o comportamento desse material quanto à estabilidade fisiológica e resistência mecânica. O objetivo principal deste trabalho é desenvolver biomateriais para uso em preenchimento de defeitos ósseos. A hidroxiapatita, cerâmica bioativa semelhante à parte mineral do tecido ósseo, é um material que poderia ser utilizado para essa finalidade. Porém, essa cerâmica possui baixas tenacidade à fratura e resistência mecânica à compressão. Com a finalidade de obter materiais mais adequados para restaurações ósseas e implantes crâniomaxilofaciais, foram associadas a hidroxiapatita obtida no laboratório de materiais cerâmicos do DEMA-FEM-UNICAMP, partículas de reforço de três cerâmicas: zircônia, alumina e titânia, nas proporções de 30,40 e 50% em peso para cada composição. Os compósitos obtidos e sinterizados foram caracterizados por medida de tamanho de partículas, Microscopia Eletrônica de Varredura, Difração de Raios X e Espectroscopia de Fluorescência de Raios X e tiveram suas densidades aparentes, densidades teóricas, absorção de água, volumes aparentes e porosidades aparentes determinadas pelo ensaio de Archimedes. Algumas propriedades mecânicas como resistência à compressão, dureza e tenacidade à fratura foram determinadas. Os compósitos que tiveram melhor comportamento geral foram escolhidos para continuidade do trabalho (ensaios ¿ in vitro" e ¿Hin vivo ")
Abstract: There is a growing demand of materiaIs that make the remodeling and reconstruction of bone parts possible. Reconstruction of defects of the skulI after trauma, tumor or infection is indicated for aesthetic reasons and for protection of internal structures. Different materiaIs have been used for this purpose and alI of them must be evaluated as for their stability in physiological environments and mechanical strength. The main objective of this work is to develop biomaterials for use in fulfilIing of bone defects. The hydroxyapatite, similar bioactive ceramics to the mineral part of the tissue bone, is a material that could be used for this purpose. However, this ceramics possess decreases tenacity to the breaking and resistance mechanics the compression. With the purpose to get more adequate materiaIs for bone restorations and craniomaxilofacials implantations associates had been hydroxyapatite gotten in the laboratory of ceramic materiaIs of the DEMA-FEM-UNICAMP, particles of three ceramics bioinert, zirconia, alumina and titania, in the ratios of 30%, 40% and 50% in weight for each composition. The composites obtained and sintered were characterized by particles size measure, Scanning Electronic Microscopy, X Rays Difratometry and Spectroscopy of Fluorescence of X Rays and had its apparent densities and apparent porosity determined by the assay of Archimedes. Some mechanical properties as compressive strength, hardness and tenacity to the breaking had been performanced. The composites that had general behavior had been better chosen for continuity ofthe work (assays "in vitro" and "in vivo")
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

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Pille, Annika. "Development of optically transparent alumina and spinel ceramics with fine microstructure." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCD026/document.

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Ce travail de thèse porte sur l’élaboration et l’étude des propriétés physiques de céramiques à base d’alumine optiquement transparentes et luminescentes pour lesquelles des applications sont envisagées dans le domaine des matériaux résistants aux rayonnements ionisants. L’enjeu de ce travail a consisté à obtenir un matériau qui présente simultanément une densité élevée et des tailles de grains à l’échelle nanométrique afin de conférer respectivement à la céramique des propriétés de transparence et une résistance aux radiations ionisantes par la capture et la recombinaison des charges induites au niveau des joints de grains.Des céramiques de composition Al2O3 et MgAl2O4 ont été consolidées par Spark Plasma Sintering (SPS) à partir d’alumines ultra-poreuses (UPA) d’une part, et par frittage réactif d’un mélange de précurseur Al2O3 : MgO dans un ratio 1 : 1 d’autre part. Les UPA ont été élaborés par un procédé original mis en place au LSPM. Elles ont ensuite été imprégnées par une solution de nitrate de magnésium puis calcinée à basse température afin d’obtenir le « Précurseur Nanostructuré » (PN) pour la phase spinelle MgAl2O4. Les PNs synthétisés, tout comme les UPA, ont ensuite été consolidées par SPS. Les paramètres de frittage ont été optimisés de manière à obtenir des céramiques possédant les propriétés microstructurales et physiques visées. L’effet de Ta2O5 comme inhibiteur de croissance des grains a été éprouvé sur la microstructure des céramiques élaborées. Les propriétés de transmittance ainsi que de luminescence, avant et après irradiation, des matériaux les plus prometteurs ont été mesurées et corrélées à leurs caractéristiques structurales
This thesis deals with the elaboration and study of the physical properties of optically transparent and luminescent alumina-based ceramics for which applications are foreseen in the field of ionizing radiation resistant materials. The challenge of this work was to obtain a material that simultaneously has a high density and grain size at the nanoscale in order to give the ceramic transparency properties and resistance to ionizing radiation by capturing and recombination of induced charges at the grain boundaries. Ceramics of composition Al2O3 and MgAl2O4 were consolidated by Spark Plasma Sintering (SPS) from ultra-porous aluminas (UPA) on the one hand, and by reactive sintering of a mixture of Al2O3: MgO precursor in a ratio of 1 : 1 on the other hand. The UPAs were developed using an original process implemented at the LSPM. They were then impregnated with a solution of magnesium nitrate and then calcined at low temperature to obtain the "Nanostructured Precursor" (NP) for the spinel phase MgAl2O4. The synthesized NPs, like the UPAs, were then consolidated by SPS. The sintering parameters have been optimized to obtain ceramics with the desired microstructural and physical properties. The effect of Ta2O5 as a grain growth inhibitor has been tested on the microstructure of elaborated ceramics. The transmittance and luminescence properties, before and after irradiation, of the most promising materials were measured and correlated with their structural characteristics

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Rambaud, Pierrick. "Modélisation numérique des distorsions post usinage pour les pièces aéronautiques en alliage d’aluminium : application aux parois minces." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEM025/document.

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La fabrication de grandes pièces structurelles aéronautiques en alliage d’aluminium nécessite la réalisation de multiples étapes de mise en forme (laminage, matriçage, forgeage…), de traitements thermiques et usinage. Pendant ces étapes de fabrication, les différents chargements thermomécaniques subis par la pièce avant son usinage induisent des déformations plastiques ainsi que des modifications de la microstructure qui sont sources de contraintes résiduelles. A ces contraintes résiduelles issues de l’histoire thermomécanique de la pièce, viennent s’ajouter celles issues directement de l'étape d'usinage. En effet lors de cette étape jusqu’à 90% de la matière initiale d'une pièce peut être retirée en utilisant des conditions de coupe parfois sévères. Les pièces aéronautiques présentent parfois des géométries complexes avec des parois minces. Ainsi, pendant et à l’issue de l’usinage, la géométrie de la pièce usinée se trouve fortement modifiée et une redistribution des contraintes résiduelle est alors à l’œuvre. Ces contraintes résiduelles qu’elles soient héritées ou induites par le procédé, influencent fortement la géométrie finale obtenue et sont une des causes principales de non-conformité des pièces avec les tolérances dimensionnelles du produit fini. Engendrant une perte conséquente pour les industries manufacturières. Au cours de ce travail de thèse, nous nous sommes concentrés sur la prise en compte de ces deux types de contraintes résiduelles dans un modèle numérique de prédiction des distorsions. Nous nous sommes uniquement focalisés sur les pièces en aluminium issues de l’aéronautique. Nous avons ainsi couplé des modèles numériques avancés d’immersion et de remaillage avec un logiciel industriel existant afin de proposer une nouvelle solution numérique, rapide et robuste. En se basant sur les hypothèses de la littérature nous avons décidé de simuler l’usinage comme un enlèvement de matière massif où la trajectoire de l’outil et les machine seront négligées. L’objectif numérique est donc de proposer une méthode qui puisse rendre compte de la redistribution des contraintes résiduelles au sein de la pièce. Chaque étape de la gamme d’usinage est ainsi représentée par une étape de remaillage où le « volume usiné » sera supprimé du maillage pour céder ensuite sa place à un calcul mécanique permettant de rendre compte de la réorganisation des contraintes et les déformations qu’elle induisent. Ce processus itératif, réalisé dans un environnement parallèle a nécessité de nombreux développements numériques. Ainsi une nouvelle stratégie de remaillage et de repartitionnement a été proposée pour pouvoir obtenir un maillage à même de capturer les contraintes résiduelles issues de l’usinage en proche surface ainsi que pour réduire de manière significative les temps de calcul liés aux modifications de la géométrie par la découpe. Un modèle d’élasticité linéaire simplifié a aussi été ajouté au programme pour réduire le coût numérique des calculs mécaniques et permettre de traiter des problèmes de taille plus conséquente sur des ordinateurs de puissance raisonnable. Afin de confirmer les résultats obtenus par ces calculs, les simulations ont été comparées à des résultats expérimentaux tirés de la littérature et réalisés spécifiquement pour ce travail de thèse
The manufacture of large aeronautical structural parts made of aluminium alloys requires multiple forming steps (rolling, die forging, forging, etc.), heat treatment and machining. During these manufacturing steps, the various thermomechanical loads suffered by the part before its machining induce plastic deformations as well as modifications of the microstructure which are sources of residual stresses. In addition to these residual stresses resulting from the thermomechanical history of the part, others result directly from the machining step. Indeed, during this step, up to 90% of the raw material of a part can be removed using sometimes severe cutting conditions. Aeronautical parts sometimes have complex geometries with thin walls. Thus, during and after machining, the geometry of the machined part is significantly modified by the redistribution of residual stresses at work. These residual stresses, whether inherited or induced by the process, strongly influence the final geometry obtained and are one of the main causes of non-conformity of the parts with the dimensional tolerances of the finished product. This results in a significant loss for manufacturing industries. In this thesis work, we focused on considering these two types of residual stresses in a numerical model predicting distortions. We focused only on aluminium parts from the aeronautics industry. We have thus coupled advanced numerical fitting and remeshing models with existing industrial software to provide a new numerical solution, fast and efficient. Based on the assumptions in the literature, we decided to model machining as a massive material removal where tool path and interaction with the machine will be neglected. The numerical objective is therefore to propose a method that can account for the redistribution of residual stresses within the part. Each step of the machining plan is thus represented by a remeshing step where the "machined volume" will be removed from the mesh followed by a mechanical computation to account for the reorganization of stresses and the deformations they induce. This iterative process, carried out in a parallel environment, required many numerical developments. Thus, a new remeshing and repartitioning strategy has been proposed to obtain a mesh capable of capturing the residual stresses resulting from near-surface machining and to significantly reduce the calculation times associated with changes in geometry through cutting. A simplified linear elasticity model has also been added to the approach to reduce the numerical cost of mechanical computation and allow for larger problems to be addressed on computers of reasonable power. In order to confirm the results obtained by these computations, the simulations were compared with experimental results from the literature and carried out specifically for this thesis work

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Goyal, Anchal. "Comportement mécanique d'un alliage d'aluminium à grains ultrafins. Analyse et modélisation du rôle exacerbé des joints de grains." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX091/document.

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Les alliages à grains ultrafins semblent prometteurs, au vu de leur forte résistance en traction et de la possibilité d'une mise en forme superplastique à basse température. Toutefois, leurs mécanismes de déformation, qui comportent une part plus ou moins forte de glissement aux joints de grains restent mal connus, et leurs performances en fatigue ont été peu étudiées. Ce travail vise à comparer et analyser le comportement viscoplastique et les mécanismes de déformation et d'endommagement en traction et en fatigue d’un alliage d’aluminium-magnésium "classique" et à grains ultrafins (600nm en moyenne) obtenu par déformation plastique sévère, selon le procédé ECAP.Des essais de relaxation, fluage et traction à diverses vitesses et températures ont permis de mesurer les évolutions des sensibilités à la vitesse en fonction de ces deux paramètres et de montrer: 1) que le raffinement microstructural accroît sensiblement la sensibilité à la vitesse 2) que ce paramètre augmente avec la vitesse de déformation 3) qu'il contrôle la ductilité du matériau à grains ultrafins, qui s'accroît donc à faible vitesse 4) que cette ductilité devient supérieure à celle du matériau classique lorsque la température s'élève. Les domaines de vitesse et température dans lesquels le raffinement microstructural accroît ou diminue la résistance en traction ont été délimités.Les mécanismes de déformation et d'endommagement des deux matériaux ont été étudiés au moyen d'essais de traction sous MEB accompagnés de mesures des champs de déformation par corrélation d'images à plusieurs échelles: méso et microscopique, grâce à des microgrilles d'or et sub-micrométrique, grâce à un mouchetis très fin obtenu par démouillage d'un film d'or. Le glissement aux joints est d'autant plus actif, dans les deux matériaux, que la température augmente et que la vitesse de déformation diminue. Dans l'alliage à grains ultrafins, il a un caractère coopératif et survient préférentiellement aux joints de forte désorientation. Les champs de déformation sont plus hétérogènes dans le matériau à grains ultrafins, où le taux de déformation dépasse 100% dans des bandes localisées.Un modèle éléments finis 2D intégrant, outre la viscoplasticité au sein des grains, un glissement visqueux des joints, a été identifié dans toute la gamme de température explorée et rend assez bien compte du comportement viscoplastique des deux matériaux et de la contribution beaucoup plus forte du glissement aux joints dans l'alliage à grains ultrafins. Il permet également de préciser comment évolue cette contribution au cours de l'écrouissage.Des essais de traction-compression à déformation plastique imposée ont permis d'étudier la plasticité cyclique et les mécanismes d'endommagement en fatigue oligocyclique et des essais à contrainte imposée, d'explorer la fatigue à grand nombre de cycles. Les essais ont été suivis d'observations des surfaces de rupture et d'une analyse statistique de l'endommagement en surface, ainsi que d'observations au MET des arrangements de dislocations. Les deux matériaux manifestent un durcissement cyclique, plus modeste dans l'alliage à grains ultrafins, qui présente, à forte amplitude, une croissance de ses grains. L'écrouissage isotrope prédomine dans l'alliage classique, où la densité de dislocations augmente fortement avec la plasticité cyclique, alors que l'écrouissage cinématique prédomine dans l'alliage à grains ultrafins, en raison de sa moindre aptitude à stocker des dislocations et de la plus grande hétérogénéité de sa déformation plastique. A même amplitude plastique, ce dernier a une durée de vie plus faible, en raison d'un amorçage bien plus rapide des fissures, à partir de particules intermétalliques. A contrainte imposée, le matériau a grain ultrafins a une durée de vie légèrement supérieure, grâce à une propagation plus lente des microfissures, dont le trajet est transgranulaire dans les plus gros grains et intergranulaire dans les plus petits
Ultrafine grained (UFG) alloys seem promising, based on their high tensile properties and the possibility of superplastic forming at relatively low temperature. However, their deformation mechanisms are not fully understood, and their performance in fatigue has not been thoroughly investigated. This work compares the viscoplastic behavior, and the deformation and damage mechanisms in tension and fatigue of a UFG Al-Mg alloy (600 nm mean grain size) obtained by severe plastic deformation (ECAP process) with that of its coarse-grained (CG) counterpart.The strain rate sensitivity (SRS) of both materials has been measured during creep, relaxation and tensile tests run at various strain rates and temperature. Microstructural refinement is shown to increase the SRS, which rises as the strain rate decreases, and controls the ductility. The UFG material becomes softer and more ductile than the CG material at high temperature. The temperature and strain rate domain for which the UFG alloy is stronger or softer has been determined.Tensile tests run in a SEM, with DIC measurements of strain fields at meso/ micro scales (using gold microgrids printed by electron beam lithography) and at sub-micron scale (using a superfine speckle obtained by film remodelling) have shown that grain boundary sliding is more and more active in both materials as the temperature rises and as the strain rate decreases. Grain boundary sliding is cooperative and occurs mostly at high-angle grain boundaries in the UFG alloy, where the strain field is more heterogeneous, and where very high strain levels (> 100%) are often observed in localized bands.A 2D finite element model taking into account the viscoplastic behaviour inside the grains, and viscous sliding at the grain boundaries has been identified other the whole temperature range investigated. It captures well the observed behaviours and the much larger contribution of grain boundary sliding in the UFG alloy. It also provides the evolution of this contribution during strain hardening.Plastic strain-controlled push-pull tests and stress-controlled push-pull tests were run to investigate the cyclic behaviour and damage mechanisms of the two materials in low and high-cycle fatigue. The tests were followed by fractographic observations, statistical analysis of surface damage, as well as TEM observations of dislocations arrangements. Both materials exhibit cyclic hardening, although it is more modest in the UFG alloy, in which grain growth occurs at high amplitude. While isotropic hardening predominates in the CG alloy where the density of dislocation strongly increases during cyclic tests, kinematic hardening predominates in the UFG alloy, because of its limited capacity to store dislocations and its more heterogeneous plastic deformation. For a given plastic strain range, the UFG alloy has a shorter fatigue life than its CG counterpart, because of a much easier crack initiation, mostly from intermetallic particles. For a given stress range, it has a slightly higher life, due to a slower development of microcracks, which have a transgranular path in the largest grains, with some intergranular growth within the smallest grains

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Mercier, David. "Lois de comportement des matériaux utilisés dans les contacts électriques pour application " flip chip "." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI083/document.

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Dans le cadre de l'intégration « 3D », une technologie d'assemblage par report de puces sur tranche de silicium (« flip chip ») reposant sur un procédé de microinsertion a été développée ces dernières années. Cette technologie est basée principalement sur la mise en contact par thermocompression, de réseaux de (micro)inserts en Nickel ECD, avec des plots de connexions métalliques en Al(Cu). Au cours de ce travail, un scénario de formation du contact entre un unique microinsert de Nickel rugueux et un film mince d'Aluminium lisse, prenant en compte la présence d'Alumine native à l'interface de contact, est proposé pour une gamme de pressions allant du MPa au GPa. L'analyse du contact métal-oxyde-métal se base essentiellement sur la fissuration de l'oxyde natif suivie de l'extrusion du métal au travers des fissures, et nécessite d'établir au préalable les lois de comportement des matériaux mis en jeu à partir d'essais de nanoindentation instrumentée couplés à des simulations numériques. Enfin, la mesure de l'évolution de la résistance électrique de contact en fonction de la force appliquée à l'aide de dispositifs expérimentaux originaux, permet de mettre en évidence les différents mécanismes de formation du contact métallique lors du procédé de microinsertion
In the field of « 3D » microelectronic integration, a wafer level technology using flip chip stacking and based on a microinsertion process has been developed recently. This technology is mainly based on the contact realized by thermocompression between a network of microinserts made of Nickel ECD, with connections pads in Al(Cu). In this work, a scenario describing the contact establishment between a unique rough microinsert of Nickel and a smooth thin Aluminum film taking into account the presence of native Alumina at the contact interface, is developed for a range of pressures from MPa to GPa. The analysis of the metal-oxide-metal contact is essentially based on the fracture of the native oxide followd by the metal extrusion through cracks, and requires the knowledge of the behaviour laws of materials, obtained from instrumented nanoindentation tests coupled with numerical modeling. Finally, the measure of the electrical contact resistance evolution in function of applied load, with specific pioneering experimental setup, showcases the mechanisms driving the formation of metallic contact during the microinsertion process

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Silva, Marcelo Marques da. "Formação de filmes finos de Al2O3 por anodização e seu uso em dispositivos com filmes de Poli(3-Hexiltiofeno) /." Presidente Prudente, 2012. http://hdl.handle.net/11449/99672.

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Orientador: José Alberto Giacometti
Coorientador: Neri Alves
Banca: Clarissa de Almeida Olivati
Banca: José Leonil Duarte
O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp
Resumo: Neste trabalho é apresentada a preparação de filmes finos de Al2O3 usando a técnica eletroquímica de anodização em solução aquosa de etileno glicol e ácido tartárico. Os filmes de Al2O3 foram crescidos sobre camadas de alumínio as quais foram depositadas por evaporação em vácuo sobre lâminas de vidro. No processo de anodização se utilizou a densidade de corrente constante de 0,48 mA/cm2, seguido da aplicação de diferença de potencial constante durante 2 minutos. Filmes com espessuras entre 10 e 60 nm foram crescidos sendo a espessura determinada pela tensão final aplicada na célula. Os filmes de Al2O3 foram caracterizados através de medidas de capacitância e perda dielétrica em função da frequência e das curvas características da corrente elétrica versus a tensão elétrica. Os resultados mostraram que a perda dielétrica é da ordem de 10-3 indicando que os filmes de Al2O3 possuem muito boa qualidade como isolante elétrico. As medidas de corrente versus tensão mostraram que a resistividade elétrica dos filmes é da ordem de 10(13)m. Na parte final do trabalho foi mostrado que os filmes de Al2O3 podem ser usados para a construção do capacitador metal-isolante-semicondutor (MIS) para operar entre no intervalo de tensão de +3V. Além disso, o capacitador MIS apresentou o fenômeno do chaveamento da condução elétrica quando foram aplicadas tensões elétricas elevadas, e, portanto, são candidatos para a fabricação de memórias
Abstract: This work presents the preparation of Al2O3 films using the electrochemical anodisation tehcnique in aqueous solution of ethylene glycol and tartaric acid. The Al2O3 films were grown from aluminum layers deposited by evaporation in vacuum onto glass slides. The anodisation process was performed using a constant current density of 0.48 mA/cm2 followed by application of a constant voltage during 2 minutes. Films with thicknesses ranging from 10 to 60 nm were grown and the thickness was determined by the final voltage applied to the cell. Films were characterized through measurements of capacitance and dielectric loss versus frequency curves and characteristics of electric current versus voltage. The results showed that the dielectric loss is of the order of 10-3 showing that Al2O3 film is a very good electrical insulator. Current versus voltage measurments showed that the electrical resistivity of the Al2O3 films is of the order of 10(13)m. Finally, it is shown that Al2O3 films can be used to fabricate metal-insulator-semiconductor (MIS) capacitor that can be operated in the voltage range of +3V. The MIS capacitor also presented the electrical conduction switching when the applied voltage was increased, therefore, it can be a candidate to be used as memory
Mestre

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Mechri, Oussama, and Oussama Mechri. "Modélisation par éléments finis de l'usinage des piéces en alliages d'aluminium AA 7175-T74." Master's thesis, Université Laval, 2016. http://hdl.handle.net/20.500.11794/27490.

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Ce mémoire introduit une approche globale de modélisation de l’usinage des alliages d’aluminium à haute résistance (grade aéronautique). Un modèle Éléments Finis 2D de coupe orthogonale d’un alliage d’aluminium en formulation Lagrangienne permettant la formation d’un copeau, le calcul des efforts de coupe ainsi que la prédiction de la surface générée est présenté. Ce modèle a été obtenue en utilisant le logiciel commercial, ABAQUS / Explicit V6.13. La loi de comportement de Johnson-Cook (JC) avec endommagement a été utilisée pour décrire le comportement du matériau de la pièce à usiner. L’équation d’endommagement de JC a été utilisée pour tenir compte de la localisation de cisaillement lors de la formation du copeau segmenté. Les coefficients de la loi de comportement de JC sont identifiés par des tests mécaniques et des essais d'usinage spécifiques. Le modèle de frottement de Coulomb-Orowan a été utilisé pour caractériser les effets collant/glissant au niveau de l'interface outil-copeau, le coefficient de frottement et les flux de cisaillement ont été déterminés par des essais d'étalonnage et d’usinage, respectivement. Une étude de sensibilité a montré une précision raisonnable dans la géométrie du copeau et dans les efforts de coupe prédites en utilisant les propriétés des matériaux déterminées expérimentalement et le modèle de friction proposé. Mots-clés : usinage, alliages d’aluminium, élément Finis, formulation Lagrangienne, coupe orthogonale, loi de comportement de Johnson-Cook (JC), loi d’endommagement de JC, modèle de frottement de Coulomb-Orowan, copeau segmenté, efforts de coupe.
Ce mémoire introduit une approche globale de modélisation de l’usinage des alliages d’aluminium à haute résistance (grade aéronautique). Un modèle Éléments Finis 2D de coupe orthogonale d’un alliage d’aluminium en formulation Lagrangienne permettant la formation d’un copeau, le calcul des efforts de coupe ainsi que la prédiction de la surface générée est présenté. Ce modèle a été obtenue en utilisant le logiciel commercial, ABAQUS / Explicit V6.13. La loi de comportement de Johnson-Cook (JC) avec endommagement a été utilisée pour décrire le comportement du matériau de la pièce à usiner. L’équation d’endommagement de JC a été utilisée pour tenir compte de la localisation de cisaillement lors de la formation du copeau segmenté. Les coefficients de la loi de comportement de JC sont identifiés par des tests mécaniques et des essais d'usinage spécifiques. Le modèle de frottement de Coulomb-Orowan a été utilisé pour caractériser les effets collant/glissant au niveau de l'interface outil-copeau, le coefficient de frottement et les flux de cisaillement ont été déterminés par des essais d'étalonnage et d’usinage, respectivement. Une étude de sensibilité a montré une précision raisonnable dans la géométrie du copeau et dans les efforts de coupe prédites en utilisant les propriétés des matériaux déterminées expérimentalement et le modèle de friction proposé. Mots-clés : usinage, alliages d’aluminium, élément Finis, formulation Lagrangienne, coupe orthogonale, loi de comportement de Johnson-Cook (JC), loi d’endommagement de JC, modèle de frottement de Coulomb-Orowan, copeau segmenté, efforts de coupe.
This study introduces a global solution for modelling machining process of high-strength‎ aluminium alloy (aeronautical grade). A 2D finite element model, based on a Lagrangian approach, for orthogonal cutting of an aluminum alloy allowing the formation of a chip, the calculation of the cutting forces as well as generated surface is presented. The solution was achieved using a commercial software package, ABAQUS/Explicit V6.13. The Johnson-Cook (JC) equation with damage evolution is used to describe the workpiece material behavior. The JC damage equation was used to take into account for the shear localization during the segmented chip formation. The JC coefficients are identified by material tests and machining data. The JC coefficients are identified by material tests and machining data. Coulomb-Orowan friction model has been used to characterize the sliding/sticking effects on the tool-chip interface with the friction coefficient and shear flow stress determined by force calibration and machining data, respectively. A sensitivity analysis has shown a reasonable accuracy for predicted chip geometry and cutting forces using the experimentally determined material properties and the proposed friction model. Keywords: machining, aluminum alloy, finit element, Lagrangian approach, orthogonal cutting, Johnson-Cook (JC) equation, JC damage equation, Coulomb-Orowan friction model, segmented chip, cutting forces.
This study introduces a global solution for modelling machining process of high-strength‎ aluminium alloy (aeronautical grade). A 2D finite element model, based on a Lagrangian approach, for orthogonal cutting of an aluminum alloy allowing the formation of a chip, the calculation of the cutting forces as well as generated surface is presented. The solution was achieved using a commercial software package, ABAQUS/Explicit V6.13. The Johnson-Cook (JC) equation with damage evolution is used to describe the workpiece material behavior. The JC damage equation was used to take into account for the shear localization during the segmented chip formation. The JC coefficients are identified by material tests and machining data. The JC coefficients are identified by material tests and machining data. Coulomb-Orowan friction model has been used to characterize the sliding/sticking effects on the tool-chip interface with the friction coefficient and shear flow stress determined by force calibration and machining data, respectively. A sensitivity analysis has shown a reasonable accuracy for predicted chip geometry and cutting forces using the experimentally determined material properties and the proposed friction model. Keywords: machining, aluminum alloy, finit element, Lagrangian approach, orthogonal cutting, Johnson-Cook (JC) equation, JC damage equation, Coulomb-Orowan friction model, segmented chip, cutting forces.

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Ying, Jia. "Water Droplet Behavior on an Anisotropic Aluminum Fin— A Case Study in Surface Wettability Modification and Control." Miami University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=miami1281310217.

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Lenhard, Sébastien Wagner Thierry. "Texture, microstructure et propriétés d'un alliage Fe-40AI à grains fins obtenus par métallurgie des poudres et extrusion : influence des paramètres du procédé et de traitements thermiques." [S.l.] : [s.n.], 2001. ftp://ftp.scd.univ-metz.fr/pub/Theses/2001/Lenhard.Sebastien.SMZ0128.pdf.

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Lenhard, Sébastien. "Texture, microstructure et propriétés d'un alliage Fe-40AI à grains fins obtenus par métallurgie des poudres et extrusion : influence des paramètres du procédé et de traitements thermiques." Metz, 2001. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/2001/Lenhard.Sebastien.SMZ0128.pdf.

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L'élaboration par mécanosynthèse des intermétalliques Fe40%at. Al, de structure B2, renforcés par une dispersion fine d'oxyde d'yttrium, a ouvert une voie pour remédier aux problèmes liés à leur fragilité et à leur faible ductilité. Cette étude s'attache à caractériser l'influence de paramètres du procédé d'élaboration sur l'évolution des microstructures, des textures et des propriétés mécaniques de barres extrudées. Pour cela, la température et le rapport d'extrusion ont été modifiés. Des poudres de natures différentes, ont été employées et l'effet de traitements thermiques a été caractérisé. La microstructure a été caractérisée en MET, les textures ont été mesurées par diffraction des RX, EBSP et par MOI. Les propriétés mécaniques ont été déterminées par essais de traction. L'analyse de la formation des textures a été complétée par des simulations à l'aide du modèle Taylor et le modèle de Young a été calculé en utilisant les modèles de Reuss, Voigt et Hill. L'élévation de la température d'extrusion renforce d'abord la texture de déformation caractérisée par une fibre <110>. En revanche, à 1250°C, la texture de la fibre <110> est partiellement remplacée par une fibre <111> associée à l'apparition de la recristallisation. La conservation de la texture de déformation jusqu'à 1200°C est due à la fine dispersion d'oxyde qui inhibe la recristallisation. En terme de rigidité, l'app de la fibre <111>, est compensée, par l'affaiblissement de la composante <110>. L'influence de la microstructure sur la limite de l'élasticité a été rationalisée en tenant compte des durcissements associés à la taille de grain et de particules et à la présence de défauts dans la matrice. Les traitements thermiques ont montré qu'au delà d'une température, correspondant à la transition de phase B2 → A2 (vers 1270°C), une croissance anormale de grains d'orientation <111> intervient sans recristallisation primaire. En dessous de cette température critique la microstructure est très stable
The elaboration of B2 structured Fe 40 %at. Al intermettalics by mechanical alloying, reinforced by a fine dispersion of yttrium oxides, have blast a way to overcome the problems due to their brittleness and poor ductility. This study deals with the characterization of the influence of parameters of the elaboration process on the evolution of the microstructures, the textures and the mechanical properties of extruded bars. In order to analyse this evolutions, the extrusion ratio and temperature were modified. Powders of different nature were also used and the effect of heat treatments were investigated as well. The microstructure have been characterized by TEM, the textures have been measured by X ray diffraction, by EBSP and by OIM. Tensile tests were carried out to determine the mechanical properties. The analysis of the formation of textures have been completed by simulations with the help of the Taylor model and the anisotropy have been characterized by using models of Reuss, Voigt and Hill. The increase of the extrusion temperature reinforces first the deformation texture characterized by a <110> fibre. At 1250°C, the <110> fibre texture is partly replaced by a <111> fibre related with recrystallization. The fact that deformation texture is retained up to 1200°C is due to the fine oxide dispersion inhibiting the recrystallization. In terms of stiffness, the appearance of the <111> fibre is counterbalanced by the weakening of the <110> component. The influence of the microstructure on the yield strength could be rationalized by considering the hardening due to the grain and the oxide particles sizes as well as the hardening due to the presence of matrix defects. The heat treatments showed that above a temperature, identified to be B2 → A2 phase transition temperature (near 1270°C), abnormal growth of <111> oriented grains takes place without primary recystallization. Bellow this critical temperature the microstructure remains very stable

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Swisher, Douglas Lee. "Production of ultra-fine grains and evolution of grain boundaries during severe plastic deformation of aluminum and its alloys." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA386708.

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Thesis (Degrees of Mechanical Engineer and M.S. in Materials Science and Engineering) Naval Postgraduate School, Dec. 2000.
Thesis advisor(s): McNelley, Terry R. "December 2000." Includes bibliographical references (p. 67-69). Also available in print.

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Ahmed, Mohamed Mohamed Zaky. "The development of Thick Section Welds and Ultra-Fine Grain Aluminium Using Friction Stir Welding and Processing." Thesis, University of Sheffield, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515422.

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Veronica, Berggren, and Gunnarsson Malin. "En analys av vilka utmaningar som finns för kompositmaterial inom flygindustrin." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-35567.

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Sammanfattning Inom flygindustrin blir komposit allt vanligare, framförallt på primära strukturdelar. Syftet med arbetet har varit att få en bild av de problem och utmaningar som finns för kompositer inom flygindustrin idag. Denna rapport har ett underhållsperspektiv och en analys har gjorts för att ta reda på vilka utmaningar och problem som användandet av kompositer kan medföra. Även för- och nackdelar har undersökts samt en jämförelse mellan komposit och aluminium har genomförts. För att ta reda på vilka utmaningar och problem som kan kopplas till komposit har intervjuer med kunniga personer inom flygbranschen gjorts. Dessa intervjuer har varit kvalitativa med öppna frågor för att på detta sätt ge intervjudeltagarna större chans till egna reflektioner och synvinklar inom ämnet. För att komplettera och få fördjupade kunskaper inom främst komposit samt aluminium har artiklar, handböcker och internethemsidor använts. Som ett resultat av intervjuerna samt inhämtning av fakta har problemformuleringen besvarats. Där fördelar med komposit visats vara viktbesparing, mindre korrosion samt mindre underhållskrävande. Däremot finns nackdelar som svårare att inspektera, dyrare material och det kräver andra kunskaper än vad aluminium gör. Samtidigt finns utmaningar som reparation av skada, mer resurskrävande vid reparation samt planeringsutmaningar. Framtida utmaningar för komposit är bland annat att identifiera skador, något som redan idag är ett problem. Samtidigt ser den tekniska utvecklingen ut att gå framåt för att kunna möta de problem som finns med kompositer. Arbetet har enbart beaktat det civila flygperspektivet i frågan, därmed har varken militära eller privata perspektiv tagits upp. De personer som har intervjuats är ingenjörer eller tekniker, inga tillverkare eller beslutfattare högre upp i flygbolagen har kontaktats. I framtiden kommer kanske kombinationer av nya aluminiumlegeringar samt komposit användas för att optimera flygplanet.
Abstract Within the aircraft industry composite becomes more common, especially on primary structures. The purpose of this thesis has been to get a picture of the problems and challenges that exist today related to composite. This report has a maintenance perspective and an analyse have been done to find problems and challenges that the use of composite can result in. Advantages and disadvantages between aluminium alloys and composite have been investigated as well as a general comparison. Interviews have been performed with people of knowledge within the airline industry to find out the challenges and problems connected to particularly composite. Qualitative and open questions have been used in the interviews, the people who were interviewed had an opportunity to tell their own perspective. In addition to interviews a collection of information about aluminium alloys and composite have been done in articles, handbooks and web pages. As a result of the interviews and the gathering of facts, the problem formulation has been answered. The benefits with composite are shown to be a saving in weight, less corrosion and less demanding maintenance. On the other hand, there are disadvantages like harder to inspect, more expensive material and it require different skills compared to aluminium. At the same time, there are challenges like the repair of damage, more demanding of resources when repairing and difficulties with planning. Future challenges for composite is among other things to identify damages, this is something that is already a problem today. At the same time, it looks like the technical development is going forward to meet the problems that are with composite. This thesis has only observed the perspective of the civil aircraft, the perspective of the military and the private sector have not been investigated. The people who have been interviewed are engineers and technicians, aircraft manufacturers or people high up in the airline who makes decisions have not been contacted. I the future there may be a combination of new aluminium alloys and composite on the aircraft to optimize the construction.

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Campos, Karina Felisbino. "Desenvolvimento de sistema de fixação de fachada ventilada com porcelanato de fina espessura." reponame:Repositório Institucional da UFSC, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/95496.

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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Civil, Florianópolis, 2011
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Atualmente verifica-se um grande crescimento das inovações tecnológicas, possibilitando a realização de projetos com sistemas construtivos inovadores. A fachada é de fundamental importância para a apresentação do imóvel e há uma tendência das fachadas de edifícios serem revestidas com revestimentos cerâmicos, proporcionando maior proteção da edificação. As especificações estão voltadas para novos materiais e técnicas construtivas, com a finalidade de valorizar a estética dos empreendimentos, obter aumento de produtividade nas obras, aumentar o desempenho, especificar materiais e serviços de qualidade. A tecnologia de fachadas ventiladas apresenta várias vantagens, como: maior agilidade no prazo de execução da obra, maior segurança referente ao destacamento das placas, melhor desempenho do conforto térmico, redução dos problemas de infiltrações de água, quando comparado com o sistema tradicional. O objetivo do trabalho é o dimensionamento de uma fachada ventilada utilizando como revestimento o porcelanato de fina espessura e fixação do revestimento por meio de uma subestrutura auxiliar em alumínio, sendo essa técnica de execução utilizada para as fachadas cortinas de vidro. O dimensionamento é baseado na determinação dos esforços devido ao vento, sendo que o vento é o carregamento que incide diretamente na subestrutura auxiliar em alumínio e porcelanato de fina espessura. Para o comportamento estrutural da subestrutura auxiliar em alumínio realizam-se os cálculos para a flecha máxima admissível, momento de inércia mínimo, momento resistente mínimo, dilatação térmica linear e tensão atuante. Para o porcelanato de fina espessura é calculada a resistência à flexão e então se determina a quantidade de apoios necessários à estrutura. A ligação da subestrutura auxiliar em alumínio e porcelanato de fina espessura é realizada por meio de um selante estrutural. Para a fachada em estudo verifica-se também o dimensionamento do selante estrutural mediante determinação da resistência à tração e ao cisalhamento. Descreve-se o sistema construtivo da fachada ventilada com o porcelanato de fina espessura. Verifica-se a compatibilidade entres os materiais e dimensionamentos de acordo com as especificações.
Currently, there is a large growth of technological innovation, enabling the execution of projects with innovative building systems. The façades has a fundamental importance for the presentation of the building and there is a trend of covering the façades with ceramic tiles, providing a greater protection of the building. Specifications are focused on new materials and construction techniques in order to have a greater aesthetic value of the projects, to achieve productivity growth in the construction works, to increase the performance and to specify materials and services with quality. The technology of ventilated façades has several advantages such as: greater agility in the lead time of the construction work, more security regarding to the fixing of the pieces, improved performance of the thermal comfort, reducing the problems of water infiltration when compared with the traditional system. The purpose of this dissertation is the dimensioning of a ventilated façade using as the coating the low thickness porcelain tile and fixing of the tile by an auxiliary substructure in aluminum, this executive technique is used for glass curtain walls. The dimensioning is based on the determination of loads due to wind and the wind is the loading applied on the auxiliary substructure in aluminum and low thickness porcelain tile. For the structural behavior of the auxiliary substructure in aluminum, the values for maximum allowable deflection, minimum moment of inertia, minimum resistant moment, linear thermal expansion and active tension are calculated. For the low thickness porcelain tile, the bending resistance is calculated and then the necessary quantity of supports to the structure is determined. The connection of the auxiliary substructure in aluminum and low thickness porcelain tile is made by means of a structural sealant. It is also verified the dimensioning of the structural sealant by determination of tensile and shear strength for the façade which has been studied here. The building system of ventilated façade with low thickness porcelain tile is described. The compatibility between materials and dimensions according to specifications is checked.

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43

Alaaeddine, Ali. "Complexes organométalliques des groupes 3 et 13 : applications en chimie fine et catalyse de polymérisation." Rennes 1, 2008. http://www.theses.fr/2008REN1S014.

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Dans un premier temps, nous avons étudié des systèmes organométalliques formés in situ à partir de différents précurseurs d’aluminium AlX₃ et de pro-ligands {salen}H₂. Les études à l’état solide et en solution indiquent, dans certains cas, la formation, outre des complexes attendus AlX{Salen}, de complexes secondaires de type bimétalliques [AlX₂]₂{Salen}. Les différentes espèces qui résultent de ces combinaisons in situ ont été isolées, caractérisées et testées individuellement en cyanosilylation asymétrique de l’acétophénone. Plusieurs fois, une amélioration de l’activité et de l’énantiosélectivité par rapport aux systèmes catalytiques générés in situ a été constatée. L’influence des ligands chiraux (Salen) et achiraux (X) sur l’activité et la sélectivité de la réaction a pu être mise en évidence. Notamment, le système hexafluoro-2-propylate d’aluminium-Salen présente une activité sans précédent pour un catalyseur aluminique. Dans un second temps, des familles de complexes bis(oxazoline) (Box) de métaux du groupe 3 ont été synthétisés. Ces complexes ont démontré une activité et une productivité sans précédent pour la polymérisation du rac-lactide. Cependant, quelle que soit la nature achirale ou chirale du ligand BOX, tous les PLA(s) obtenus présentent une microstructure atactique. Des familles de nouveaux complexes diimino-dialcoxy fluorés d’aluminium et d’yttrium ont également été synthétisés. Les études structurales par RMN et par diffraction des rayons X montrent clairement que ces complexes adoptent des structures comparables à leurs homologues dérivés de ligands Salen. Un complexe d’aluminium a démontré un bon contrôle et une haute sélectivité pour la production de PLA isotactique (80%)
For the first time, we have studied the organometallic outcome of the catalyst systems generated in situ from an aluminum precursor AlX₃ and a diprotio {Salen}H₂ pro-ligand. The different species that result from these binary combinations have been isolated, characterized and individually evaluated in the asymmetric cyanosilylation of acetophenone. It is shown that, in some cases, those discrete catalysts display dramatically different performances than the binary systems which are assumed to generate them. The influence of the achiral ligand on both the enantioselectivity and activity of the reaction has been investigated, resulting in the definition of a highly active hexafluoro-2-propoxide-based catalyst. For the second time, the family of bis[bis(oxazolinato)]lanthanide complexes have been synthesized. These complexes show a high activity and productivity for the rac-lactide polymerization. However, such complexes based on well-known chiral Box ligands appear unable to control the microstructure of the polymer: only atactic PLAs. New families of diimines-dialcooxy fluorinated aluminium and yttrium complexes have been synthesized. These complexes were caracterized by NMR-spectroscopy and X-ray diffraction analysis and it was shown that they are the familiar structure Salen-complexes. Alumnium complexes show high control and selectivity for production of isotactic PLA (80%)

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Ouellet, Réjean. "Étude du problème d'ablation à deux dimensions par la méthode des éléments finis de frontière /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1987. http://theses.uqac.ca.

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45

Anghelus, Adrian. "Élaboration de matériaux multicouches par « laminage cumulé contrôlé »." Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10116/document.

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Cette étude porte sur la faisabilité de l’élaboration de matériaux multicouches à grains ultrafins par un procédé original de métallurgie douce : le laminage cumulé contrôlé. Les multicouches à base d’aluminium sont renforcés par des alliages de compositions Al-Ni-Sm pris dans des états amorphe ou cristallisés. Cette combinaison à ce jour inédite est originale compte tenu de la différence marquée de comportement mécanique et de mécanisme de déformation des constituants. Les paramètres du procédé sont d’abord définis à partir de la caractérisation de la stabilité microstructurale des constituants et de leur comportement mécanique. Plusieurs types de traitement thermique et mécanique, ainsi que différents nombres de couches ont été testés afin d’optimiser la microstructure et par tant l’aptitude à la mise en forme. Les transformations de phases (recristallisation dynamique ou non de l’aluminium, changements de phases au sein des alliages Al-Ni-Sm…) ont été analysées par diffractométrie X, microscopies et calorimétrie différentielle. Parmi les principaux résultats, la cristallisation du verre métallique induite par déformation est démontrée. En relation avec la modification de propriétés mécaniques induite par le changement de microstructure des renforts, les multicouches élaborées à partir de renforts à l’état cristallin sont plus malléables que celles obtenues au moyen d’alliages à l’état amorphe. La différence est reliée à la fois à la morphologie des débris et à l’accommodation des déformations au niveau des interfaces matrice/renfort. Au stade actuel du travail, un multimatériau a été synthétisé à partir de 216 couches d’aluminium et de 180 feuilles de renfort à l’état cristallin. Ce matériau à grains ultrafins présente encore une distribution non uniforme de fragments de renforts
This study of feasibility deals with the development of ultrafine grained (UFG) multilayers by an original process i.e. controlled accumulative roll bonding. Aluminium based multilayers are reinforced by Al-Ni-Sm alloys taken either in the amorphous or crystallized state. This association of materials is particularly interesting according to the significant difference of mechanical behavior and mechanism of deformation of both constituents. The definition of the process parameters arises from the study of both the stability and the mechanical behaviour of the constituents. Numerous thermal and mechanical treatments as well as various numbers of stacked layers have been considered in order to optimize the microstructure and therefore workability of the multilayers. The phase transformations (dynamical or static recrystallization of Al, crystallization of amorphous alloys…) have been investigated by X-ray diffractometry, various kinds of microscopy and differential scanning calorimetry. Among the main results, the crystallization of the metallic glass due to deformation has been proved. Due to the modification of the mechanical properties induced by the change of microstructure of the reinforcements, the multilayers bearing crystalline reinforcements are more deformable than those containing amorphous alloys. The difference is explained by the morphology of the fragments of reinforcements as well as by the accommodation of deformation at their interfaces. Finally, a multimaterial has been prepared from 216 Al layers and 180 layers of crystalline reinforcements. This UFG material presents a heterogeneous distribution of reinforcements

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Prado, Eduardo Silva [UNESP]. "Técnica híbrida de plasma para a deposição de filmes de alumina." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/132495.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Neste trabalho é proposta uma nova tecnologia de plasma para a deposição de filmes de alumina a partir do acetilacetonato de alumínio, AAA. A possibilidade de se depositar filmes a partir da pulverização catódicado AAA em plasmas de argônio foi demonstrada em trabalho prévio do grupo. No presente trabalho, foi realizada uma mudança nesta metodologia de forma a associar bombardeamento iônico do substrato ao processo de deposição. Para tal, o plasma foi gerado pela aplicação de sinal de radiofrequência (13,56 MHz) ao eletrodo inferior de um sistema de plasma capacitivamente acoplado, onde o pó do AAA foi espalhado. O eletrodo superior, também usado como porta-amostras, foi polarizado com pulsos retangulares negativos de amplitude, frequência e ciclo de trabalho controlados. A pulverização católica de fragmentos do AAA pelo plasma fornece precursores para a deposição do filme enquanto a polarização do porta-amostras acelera íons em direção aos substratos promovendo bombardeamento iônico da camada em crescimento. Os parâmetros de excitação do plasma (11 Pa, 13,56 MHz, 150 W, 3600 s) foram mantidos iguais aos otimizados em trabalho anterior do grupo. Variou-se a amplitude dos pulsos de popularização, entre 0 e 2800 V, de modo a modificar a energia fornecida pelo bombardeamento iônico à estrutura. A frequencia e foi fixada em 300 Hz e os pulsos de trabalho variaram entre (0, e 100%). Investigou-se o efeito da intensidade dos pulsos nas propriedades da camda resultante. A taxa de deposição foi determinada a partir do tempo de deposição e da espessura dos filmes, medida por perfilometria. A estrutura molecular das camadas foi analisada por espectroscopia no infravermelho no modo IRRAS (Infrared Reflectante Absorbance Spectroscopy). Difração de raios X foi empregada para avaliar se houve precipitação de fases cristalinas da alumina. A morfologia do material depositado foi inspecionada por microscopia...
A new plasma methodology for deposition of alumina from aluminum acetylacetonate, AAA, is proposed. In a previous study by his this group, the possibility of depositing films from the AAA, by sputtering in argon atmosphere. In the present work, this methodology was modified by coupling a bombardment to the deposition process. For this, the plasma was generated by the application of radifrequency signal (13.56 MHz) to the lowermost electrode of a capacitively coupled plasma system with the AAA powder was spread. The topmost electrode, also used as the sample holder, was biased with retangular negative pulses of controlled amplitude, frequency and duty cycle. Sputtering of AAA fragments by the argon plasma provides precursors for film deposition while the polarization of the holder accelerates ions toward the substrates, promoting ion bombardment of the growing layer. The plasma excitation parameters (11 Pa, 13.56 MHz, 150 W, 3600 s) were the same as those optimized in the previous work of the group. The magnitude of the pulses was varied from 0 to 2800 V. To change the energy delivered by ion bombardment to the structure. A fixed pulse frequency and duty cycle were fixed of 300 Hz and duty cicle changed between (0 and 100%). The effect of P on the film properties was investigated. Deposition rates were determined from the deposition time and film thinckness, measured by profilometry. Infrared spectroscopy in the IRRAS mode (InfraRed Reflectante Absorbance Spectroscopy) was used to investigate the molecular structure of the layers. X-ray diffractometry was employed to verify if there was precipitation of crystalline alumina phases. The material microstructure was investigated by scanning electron and atomic force microscopies. Elemental composition analyses were performed by Energy Dispersive Spectroscopy while data obtained by nanoindentation tests allowed the calculation of hardness. The structures present (C-H, C=O, C=C e (C-H)3 organic...

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47

Gueydan, Antoine. "Vieillissement et fiabilité métallurgique de microfils copper-clad aluminium employés comme substitut au cuivre polycristallin dans l'industrie électrique et électronique." Caen, 2014. http://www.theses.fr/2014CAEN2049.

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Du fait de la hausse des prix des matières premières et notamment du cuivre, beaucoup d’entreprises s’intéressent aux solutions alternatives au cuivre. Dans la communauté du câble, des fils et microfils, une solution semble émerger : le copper-clad aluminium (ou CCA). Ce bimétal combine l’excellente conductivité électrique du cuivre avec la légèreté de l’aluminium pour un coût bien inférieur à celui du cuivre. Cependant, lors de la mise en œuvre du produit composite, des problèmes tels que la formation d'intermétalliques, influençant fortement les propriétés mécaniques et électriques du bimétal. L’objectif de ce travail fut donc de comprendre les mécanismes de diffusion d’interface dans ce microsystème cuivre-aluminium sous forme de microfils électriques (300 µm) afin de mieux appréhender les problèmes d’élaboration et de vieillissement métallurgique de ces structures. Tout d’abord, cette étude à débuté par un état de l’art concernant les couples Cu-Al rencontrés dans la littérature, pour en dégager les principaux phénomènes observés. La partie suivante expose les résultats en fluage obtenus sur les fils CCA. L'analyse des différents états métallurgiques des fils avant et après traitement thermique a permis de montrer le rôle joué par la microstructure sur leur comportement en température au cours du fluage. Ensuite, les observations microstructurales à la fois par microscopie optique et diffraction électronique, mais aussi par analyse de composition à l’interface ont permis de déterminer les mécanismes de croissances interfaciales au sein des fils. Une comparaison a été établie avec des couples Cu-Al modèles. Enfin, une synthèse des résultats a été réalisée, suivie d'un complément sur l'étude thermocinétique, basé à la fois sur un modèle et des essais expérimentaux. Ceux-ci ont pu alimenter la discussion autour des mécanismes de vieillissement des fils CCA
Due to the rising prices of raw materials especially copper, many companies are interested in alternatives to copper. In the community of cables, wires and microwires, a solution seems to emerge: the copper-clad aluminum (CCA). This bimetal combines the excellent conductivity of copper with the lightness of aluminum for a lower cost than copper. However, during the implementation of the composite product, problems such as intermetallics formation strongly influence the mechanical and electrical properties of the bimetal. The aim of this study was therefore to understand the diffusion mechanisms of the interface in this copper-aluminum microsystem as electrical microwires (300 µm) to better understand the manufacturing problems and metallurgical aging of these structures. First, this study began with a state of the art for Cu-Al couples encountered in literature to identify key phenomena. The next section presents the results obtained on creep CCA wires. Analysis of the various metallurgical state of wires before and after heat treatment showed the role of microstructure on the temperature behavior during creep. Then microstructural observations by both light microscopy and electron diffraction, but also by compositional analysis at the interface were used to determine the mechanisms of interfacial growth in the wires. A comparison was made with Cu-Al couples models. Finally, a summary of the results was performed, followed by an addition on the thermo-kinetic study, based on a model and experimental testing

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48

Aristizabal, Felipe. "Modelling of the generation of ultra fine aluminum particles from the quench of superheated vapour in turbulent flow by Felipe Aristizabal." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33954.

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This work reports on a Low Reynolds Number (LRN) turbulent model to simulate such systems for the production of pure metal powders. Aluminium has been chosen as an example.
The fluid flow in the turbulent regime was simulated using the LRN model by Jones and Launder (1973); while the dynamic behaviour of the particulate system was modeled in terms of the leading moments of the particle size distribution. The shape of the aerosol size distribution was approximated by a unimodal lognormal function.
The set of governing equations were solved numerically using the Finite Volume formulation, while the SIMPLER algorithm (Patankar 1980) was used to solve the momentum equations coupled with the continuity equation. The effect of different process parameters on the characteristics of the product was investigated. The model presented can be used to assist the understanding and scale up of such ultra fine particle generators. (Abstract shortened by UMI.)

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Leduc, Bruno, and Bruno Leduc. "Méthode d'évaluation d'assemblages industriels en aluminium liés par adhésifs structuraux." Master's thesis, Université Laval, 2014. http://hdl.handle.net/20.500.11794/25341.

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Ce mémoire entame le développement d’une méthode d’évaluation d’assemblages en aluminium liée par adhésifs structuraux dans un contexte d’ingénierie du secteur industriel. Les travaux ont pour but de fournir à l’entreprise Services Précicad inc. des outils de conception applicables sur le véhicule électrique Kargo. Plus spécifiquement, des séries d’essais expérimentaux sont réalisées sur des échantillons ASTM au moyen de plans d’expériences employant la méthode Taguchi pour étudier l’incidence des conditions de préparation manufacturière sur la résistance mécanique et pour faire un dépistage de produits commerciaux. La famille des méthacrylates est alors privilégiée pour répondre aux besoins de flexibilité d’utilisation et de préparation de surface. Ensuite, différents modèles de calculs analytiques sont étudiés et une analyse paramétrique est réalisée sur le joint en cisaillement à simple recouvrement (SLS). Le modèle du joint sandwich simplifié de Bigwood et Crocombe est choisi comme outil de calculs de prédimensionnement de joints génériques, cependant une bonne connaissance des conditions limites est nécessaire. L’approche de simulation par la méthode des éléments finis en mécanique des milieux continus est alors recommandée. D’importantes difficultés de convergence des résultats des contraintes sont identifiées avec cette théorie, entre autres par la présence de singularités numériques aux interfaces du volume de l’adhésif. Des techniques de modélisation simplifiées, utilisant les outils du logiciel NX Nastran, sont ensuite testées et l’outil Surface-Gluing est alors proposé pour permettre la simulation de joints qui reflètent les caractéristiques de modélisation « industrielles » de Précicad. Finalement, une méthode de mesure des propriétés élastiques in situ pour adhésifs flexibles, compensée au moyen d’analyses par éléments finis, est développée afin de pouvoir réaliser une caractérisation avec un extensomètre conventionnel, tout en préservant la précision souhaitée. Ainsi, il a été possible d’isoler les modules de cisaillement et de tension de l’adhésif H8000.
Ce mémoire entame le développement d’une méthode d’évaluation d’assemblages en aluminium liée par adhésifs structuraux dans un contexte d’ingénierie du secteur industriel. Les travaux ont pour but de fournir à l’entreprise Services Précicad inc. des outils de conception applicables sur le véhicule électrique Kargo. Plus spécifiquement, des séries d’essais expérimentaux sont réalisées sur des échantillons ASTM au moyen de plans d’expériences employant la méthode Taguchi pour étudier l’incidence des conditions de préparation manufacturière sur la résistance mécanique et pour faire un dépistage de produits commerciaux. La famille des méthacrylates est alors privilégiée pour répondre aux besoins de flexibilité d’utilisation et de préparation de surface. Ensuite, différents modèles de calculs analytiques sont étudiés et une analyse paramétrique est réalisée sur le joint en cisaillement à simple recouvrement (SLS). Le modèle du joint sandwich simplifié de Bigwood et Crocombe est choisi comme outil de calculs de prédimensionnement de joints génériques, cependant une bonne connaissance des conditions limites est nécessaire. L’approche de simulation par la méthode des éléments finis en mécanique des milieux continus est alors recommandée. D’importantes difficultés de convergence des résultats des contraintes sont identifiées avec cette théorie, entre autres par la présence de singularités numériques aux interfaces du volume de l’adhésif. Des techniques de modélisation simplifiées, utilisant les outils du logiciel NX Nastran, sont ensuite testées et l’outil Surface-Gluing est alors proposé pour permettre la simulation de joints qui reflètent les caractéristiques de modélisation « industrielles » de Précicad. Finalement, une méthode de mesure des propriétés élastiques in situ pour adhésifs flexibles, compensée au moyen d’analyses par éléments finis, est développée afin de pouvoir réaliser une caractérisation avec un extensomètre conventionnel, tout en préservant la précision souhaitée. Ainsi, il a été possible d’isoler les modules de cisaillement et de tension de l’adhésif H8000.
This thesis initiates the development of a structural assessment method for aluminium adhesively bonded joints, intended for the industrial engineering businesses sector. The present work is devoted to the company Services Précicad inc, who needs design tools that can be used for its Kargo electric vehicle assemblies. In particular, the Taguchi design of experiment method is used to study the effects of joint conditioning on the static strength of different ASTM samples configurations. Commercially available products are screened out during the process. Thus, methacrylates is found to be the best adhesive chemical category for Précicad design and manufacturing needs. Subsequently, a review of different analytical models is carried and the Bigwood & Crocombe sandwich model is selected to perform a parametric analysis on the Single Lap Shear joint (SLS). The simplified version of the sandwich model was found to be the best suited for pre-sizing generic forms of adhesive joints, although a good knowledge of the boundary conditions is mandatory to make a realistic assessment. Consequently, the standard continuum mechanics finite element method is recommended for most joints analysis. However, major convergence difficulties can be found when using this theory, partly due to the presence of numerical singularities in the adhesive domain. Several simplefied modelling techniques using NX Nastran are tested on the SLS joint and the Surface-Gluing tool is proposed for evaluating complex “industrial” meshes such as the ones used by Precicad. Finally, a method for measuring in situ elastic properties of flexible adhesives with finite element analysis compensation is developed for achieving a complete characterization with a conventional clip gauge. Thus, it has been possible to measure the shear and tensile modulus of the H8000 adhesive.
This thesis initiates the development of a structural assessment method for aluminium adhesively bonded joints, intended for the industrial engineering businesses sector. The present work is devoted to the company Services Précicad inc, who needs design tools that can be used for its Kargo electric vehicle assemblies. In particular, the Taguchi design of experiment method is used to study the effects of joint conditioning on the static strength of different ASTM samples configurations. Commercially available products are screened out during the process. Thus, methacrylates is found to be the best adhesive chemical category for Précicad design and manufacturing needs. Subsequently, a review of different analytical models is carried and the Bigwood & Crocombe sandwich model is selected to perform a parametric analysis on the Single Lap Shear joint (SLS). The simplified version of the sandwich model was found to be the best suited for pre-sizing generic forms of adhesive joints, although a good knowledge of the boundary conditions is mandatory to make a realistic assessment. Consequently, the standard continuum mechanics finite element method is recommended for most joints analysis. However, major convergence difficulties can be found when using this theory, partly due to the presence of numerical singularities in the adhesive domain. Several simplefied modelling techniques using NX Nastran are tested on the SLS joint and the Surface-Gluing tool is proposed for evaluating complex “industrial” meshes such as the ones used by Precicad. Finally, a method for measuring in situ elastic properties of flexible adhesives with finite element analysis compensation is developed for achieving a complete characterization with a conventional clip gauge. Thus, it has been possible to measure the shear and tensile modulus of the H8000 adhesive.

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Battaglin, Felipe Augusto Darriba. "Abordagem inovadora com plasma de baixa temperatura para a deposição de filmes a partir do acetilacetonato de alumínio /." Sorocaba, 2016. http://hdl.handle.net/11449/143092.

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Orientador: Elidiane Cipriano Rangel
Banca: José Humberto Dias da Silva
Banca: Adriana de Oliveira Delgado Silva
Resumo: Filmes de alumina foram depositados a partir de um nova metodologia de deposição a plasma, utilizando o pó de acetilacetonato de alumínio (AAA) como precursor. Em trabalho prévio do grupo, foi demonstrada a viabilidade do sputterring do AAA em plasma de argônio para deposição de filmes finos. Os bons resultados obtidos estimularam o desenvolvimento do presente trabalho, visando a aperfeiçoamento da metodologia de deposição. Para isso, primeiramente foram investigados os efeitos da alteração da composição química da atmosfera do plasma, por meio da incorporação de diferentes proporções de oxigênio (02%) ao argônio, tornando o processo em sputtering reativo. As deposições foram realizadas espalhando-se o pó do AAA no eletrodo inferior de uma sistema de plasma acoplado capacitivamente. Argônio, oxigênio ou mistura de ambos foram admitidos até a pressão de 11,0 Pa. O plasma foi gerado pela aplicação de sinal de radiofrequêcia (13,56 MHz, 150 W) ao eletrodo contendo o pó, mantendo-se o eletrodo superior, também utilizando como porta-amostras, aterrado. O tempo de deposição foi de 90 minutos. Investigou-se o efeito da O2%, variada de 0 a 100% nas propriedades dos filmes. Na etapa subsequente, filmes foram depositada por sputtering reativo utilizando-se a condição considerada ótima na última etapa do trabalho (02% = 25%) e mantendo-se as condições de pressão, potência e tempo de tratamento constantes. Todavia, ao invés de aterrar o porta-amostras, pulsos retangulares negativos (600 V, 2 kHz, 1-100% de ciclo dos trabalho) foram aplicados, promovendo bombardeamento iônico durante a deposição por sputtering reativo. O efeito de ciclo de trabalho dos pulsos nas propriedades dos filmes foi avaliado. Na última etapa do trabalho, filmes foram depositadas pelo sputtering reativo a partir de atmosferas contendo 25% de O2 e 75% de Ar e em condições mais... (Resumo completo, clicar acesso eletrônio abaixo)
Abstract: Alumina films were deposited by a new plasma deposition method using aluminum acetylacetonate (AAA) powder as precursor. In a previous study by our group, the feasibility of AAA sputtering in argon plasmas for thin films deposition was demonstrated. The good results stimulated the development of this work, aiming at the improvement of the deposition methodology. For this, the effects of modification in the chemical composition of the plasma atmosphere were first investigated, through the use of different oxygen to argon proportions (O2%), making the process a reactive sputtering. The deposition were performed by spreading the AAA powder on the lower electrode of a capacitively coupled plasma system. Argon, oxygen or a mixture of both were admitted up to a pressure of 11.0 Pa. Application of radiofrequency power (13.56 MHz, 150 W) to the powder covered electrode generated the plasma, keeping the upper electrode, also used as a sample holder, grounded. Deposition times of 90 minutes were used. The effects of varying the oxygen proportion from 0 to 100% on the film properties were studied. In the subsequent stage, films were deposited by reactive sputtering using the condition considered best in the stage of the work (O2%=25%) and keeping the pressures, power and treatment time constant. Instead of grounding the sample holder, however, negative rectangular pulses (600 V, 2 KHz, 1-100% duty cycle) were appliedm promoting ion bombardment during the deposition by reactive sputerring. The influence of the pulse duty cycle on the properties of the films was evaluated. In the last study stage, films were deposited by reactive sputtering from atmspheres containing 25% O2 and 75% Ar and with more energetic conditions than those used in previous cycles. For such, a first samples set was prepared by resistive heating of the sample holder (410ºC) in a lower plasma pressure (4,0 Pa) than that previously used... (Complete abstract electronic access below)
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