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Tarragó, Diego Pereira. "Processo de combustão de solução aspergida (CSA) para a obtenção de eletrodos para SOFC." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/169811.
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A diminuição nos custos de fabricação das SOFC e também a flexibilização do combustível utilizado em seu abastecimento são obstáculos que, uma vez transpostos, podem possibilitar a utilização em larga escala das SOFC. A melhoria no desempenho dos componentes das SOFC pode fazer esse dispositivo trabalhar em temperaturas mais baixas, facilitando a operação do dispositivo e aumentando sua vida útil. Nesse sentido, é útil o desenvolvimento de métodos de fabricação simples e de baixo custo de componentes de SOFC, que atualmente são obtidos na forma de filmes finos cerâmicos. Assim, é proposto o desenvolvimento de uma nova técnica baseada na reação de combustão para síntese de pós e a aerografia, no intuito de, por via úmida, obter filmes finos porosos de composições cerâmicas. Foram realizadas deposições de manganitas de lantânio dopadas com estrôncio e cromo (LSM e LSCM) e óxido de cério dopado com lantânio (LCO) sobre substratos de zircônia estabilizada com ítria (YSZ) e de aço AISI 430, com o propósito de verificar a viabilidade do método de combustão de solução aspergida (CSA) proposto neste trabalho. Embora vários dos filmes fabricados tenham ficado descontínuos ou com uma quantidade excessiva de trincas, alguns resultados foram satisfatórios. Alguns filmes de LSM depositados sobre YSZ apresentaram tamanho de grão reduzido, da ordem de algumas dezenas de nanômetros, e uma porosidade fina e interconectada que levou o material a apresentar um bom desempenho eletroquímico, visando sua aplicação como cátodo de SOFC. A partir das suas propriedades eletroquímicas e, principalmente, pela energia de ativação dos processos do eletrodo, verificou-se que a microestrutura conferida pelo método de CSA proporcionou uma melhoria no desempenho da LSM. Os filmes de LSM obtidos nesse trabalho apresentaram energias de ativação inferiores a 1,26 eV, enquanto na literatura são encontrados valores mais altos para meia-células semelhantes.Lowering fabrication costs of SOFC’s and also their fuel flexibility are obstacles that, once transposed, can make possible the mass utilization of such devices. The improvement on the performance of SOFC’s components can allow these devices to work in lower temperatures, facilitating their operation and increasing their lifespan. In this sense, is very useful the development of simple and cheap fabrication techniques of SOFC’s components, which are nowadays obtained in the form of thin ceramic films. Thus, the development of a new fabrication method is proposed, based on the solution combustion synthesis reaction and airbrush painting, in order to obtain, by a wet chemical route, thin and porous ceramic films. Depositions of strontium and cobalt doped lanthanum manganites (LSM and LSCM) and lanthanum doped cerium oxide (LCO) were carried out over yttria-stabilized zirconia (YSZ) and AISI 430 steel with the intent of verifying the viability of the Airbrushed Solution Combustion (ASC) method, proposed in this work. Although several films fabricated by ASC were discontinuous or excessively cracked, some results were satisfactory. Some LSM films deposited over YSZ showed reduced grain size, in the order of tens of nanometers, and a fine interconnected porosity, which led the material to present good electrochemical performance, aiming its application as a SOFC’s cathode. From their electrochemical properties and, mainly, through activation energy of the electrode processes, it was seeing that the microstructure acquired with the ASC method enhanced the overall performance of LSM. The LSM films obtained in this work showed activation energies below 1,26 eV, while in the literature the values are higher than this for similar half-cells.
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Xu, Lei. "Plasma arc welding fabrication using thin titanium sheet." Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.605800.
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This work was motivated by the industrial and academic needs for process development of automated keyhole plasma arc welding (K-PA W) in thin Ti- 6AI-4V sheet and the control required for the process to be suitable for aerospace components. K-PAW, is a high energy density precision welding process which is a lowcost alternative to laser and electron beam welding. It is potentially capable of fabricating high integrity titanium alloy welds in aero-engine thin panel structures. However, the process has always represented a challenge owing to the complexity of welding torch configurations and the associated large number of process parameters to take into consideration. Three types of weld joint, which represent the welding fabrications in a simplified aero-engine casing component, were manufactured in the work: flat bead-on-plate, flat Tjoint and curved T -joint. A new welding procedure was developed to produce thin sheet T-joints by K-PAW, which has overcome the difficulty of operating the structurally complicated welding torch in limited space. An analytical model was experimentally validated and was employed to identify the process parametric envelopes for valid keyhole welding modes from the numerous possible parameter combinations. Weld joints were characterised in tenns of thermal history, micro-hardness and metallurgical microstructure. Distortion and residual stresses are maJor concerns associated with fusion welding fabrication. While distortions can lead to geometrical inaccuracy, paIticularly in the thin panel stl11ctures, residual stresses can combine with applied stresses to reduce the life of components. In this thesis, the out-of-plane l distortions of welded thin Ti-6AI-4V bead-on-plate and T-joint welds were measured using contact and non-contact coordinate-measuring techniques, from which the effects of welding sequence on the distortions can also be identified. Residual stress distributions in the welded sheet were detennined by synchrotron X-ray and neutron diffraction techniques. The use of synchrotron X-ray methods is relatively newly developed as titanium alloys respond weakly to neutron beams. These not only have provided improved understanding of residual stresses in thin sheet welds but also have greatly contributed to validation of finite element (FE) modelling work undertaken by other researchers.
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Cadiou, Stephen. "Modélisation magnéto-thermohydraulique de procédés de fabrication additive arc-fil (WAAM)." Thesis, Lorient, 2019. http://www.theses.fr/2019LORIS544.
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Un des freins au développement des procédés de fabrication additive réside dans la qualité des pièces ainsi fabriquées. Certains défauts, tels que des porosités ou des déformations peuvent apparaître. Ces défauts sont étroitement liés au choix des paramètres opératoires et à l’histoire thermique subit lors de la fabrication. La modélisation numérique peut donc aider à comprendre comment ces paramètres opératoires influent sur la géométrie du dépôt, et sur les cinétiques thermiques qui conditionneront la microstructure et les déformations de la pièce finale. Dans cette thèse, plusieurs modèles numériques de complexité croissante ont été développés afin de mieux appréhender l’état final de la pièce. La première étape a consisté à développer un modèle d’arc représentant un tir statique TIG en 2D axisymétrique. Les équations électromagnétiques, thermiques, et hydrodynamiques sont résolues dans le plasma et le bain de fusion. Ce cas de référence a permis de valider les choix faits pour la description mathématique et numérique. Ensuite, le modèle est complexifié en ajoutant une méthode level set pour le suivi des interfaces mobiles permettant la description du procédé MIG pulsé dans une configuration axisymétrique. Après avoir été validé grâce à des expériences, le modèle est transposé en 3D pour décrire la fabrication d’un mur à l’échelle du bain de fusion avec le procédé CMT. Enfin, le modèle est simplifié en ne résolvant que le transfert de chaleur afin de décrire les transferts thermiques à l’échelle d’une pièce complèteOne of the obstacles to the development of additive manufacturing processes is the quality of the built parts. Some defects, such as porosity, deformations or cracks, may appear. These defects depend strongly on the choice of operating parameters. Numerical modelling can therefore help to understand how these operating parameters control the final geometry, and the thermal cycles experienced by the material, which impact the microstructure, the deformations and residual stresses of the final part. In this thesis, several numerical models have been developped in order to better understand the final characteristics of the part. The first one concerns a 2D axial-symmetric model of arc to deal with a static TIG process. The Maxwell equations coupled with the mass, momentum, energy equations are solved in the plasma and the melt pool. Using this reference case, the arc model has been validated. This model has been made more complex by adding a level set method to track the gas-liquid interface present in pulsed MIG process in 2D axial-symmetric geometry. This model has been validated through experimental data and then extended to a 3D geometry to simulate the build-up of a wall using a CMT process. This multiphysics model was limited to the scale of the melt pool. A second 3D model was then proposed at the scale of the wall using a purely thermal model to simulate the multi-layer process with geometry prediction
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Aubouin, Pascal. "Etude expérimentale et modélisation d'un arc stabilise par ablation dans un lanceur électrothermique." Lyon, INSA, 1993. http://www.theses.fr/1993ISAL0033.
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Le principe du lanceur électrothermique consiste à convertir de l'énergie stockée en énergie thermique par l'intermédiaire d'un arc électrique stabilisé par ablation (plasma), puis thermique en cinétique par détente des gaz produits. Le but de cette étude est de développer un outil global de simulation de l'arc électrique, simple d'utilisation, rapide ; afin d'optimiser l'installation. A partir de l'étude bibliographique, un tronc commun d'hypothèses et dégagé : état quasi stationnaire, plasma isotherme, ablation radiative, couche vapeur entre la plasma et les parois. Le modèle de LOEB et KAPLAN qui sert de base à notre travail, est présenté et critiqué. Parallèlement, les résultats expérimentaux mettent en évidence deux mécanisme supplémentaires : l'ablation des électrons et du tube du lanceur. Un méthode originale de dépouillement de la mesure continue de vitesse balistique du lanceur et la température moyenne des gaz de propulsion. L'analyse de l'ensemble de ces informations, les équations de notre modèle ont été établies et résolues par la méthode de NEWTON. La comparaison à l'expérience a montré que dès que le régime de décharge est établi, le calcul restitue parfaitement le comportement de l'arc. Trois enseignements majeurs sont tirésThe aperation principle of electrothermal launcher consist in converting electrical energy in thermal energy through an ablation-stabilised arc (plasma), and then in kinetic energy through the expansion of the generated gases. The goal of this study is to develop a simple model for simulating electrical arc in order to optimize the facilities. From a bibliographical analysis, a common set of hypothesis is defined: quasi stationary state, isothermal plasma, radiative ablation, vapour shield between the plasma and the walls. The model of LOEB & KAPLAN, which is our work basis is described and criticized. Concurrent experimental results show up two other mechanisms: ablations of both electrodes and gun barrel. An original method to analyse the projectile velocity measurement by L. D. I. Is used to characterize the ballistic expansion and to estimate the temperature in the barrel. Data processing gives some qualitative relations which characterize the arc resistance, the ablated masses and the launcher efficiency. The equations of our model are established according to these considerations and solved by the NEWTON method. Numerical results are in good agreement with experiments when the discharge is established. Three important teachings are brought out
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Delaportas, Dimitrios. "Fabrication and characterization of metal oxide nanoparticles by arc-discharge in water." Thesis, University of Liverpool, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578046.
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The aim of this project was to establish the arc discharge in water method as a valid method of producing metal oxide nanoparticles (NPs) with dielectric properties. A vertical arc discharge system was designed and fabricated and several diagnostic tools were attached to the system in order to monitor in situ the propagation of the plasma. Electrical measurements, high speed imaging, optical emission spectroscopy and electrode mass reduction measurements were employed to three different anode materials; aluminum and tantalum rods as well as a mixture of copper-tantalum compressed powder grains. The cathode of the DC arc was in all cases was a carbon rod. The product of the discharge was collected in powder form and examined by means of electron microscopy, x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and broadband dielectric spectroscopy (BDS). The experiments showed that, during discharge, the physical processes occurring between the electrodes, force the anode material to evaporate in the atomic level. While atomization takes place, the water molecules surrounding the plasma region gets vaporized due to the localized high temperature resulting in the division of oxygen and hydrogen atoms. Metal and oxygen atoms bond, becoming the seeds for nanoparticle formation. The particle growth stops when quenching occurs due to the continuous condensation and expansion of the plasma. High-Resolution Transmission Electron Microscopy (HR-TEM) examination revealed that spherical crystalline nanoparticles are formed, with an average size of 40 nm when using either aluminum or tantalum rod. XRD and XPS analyses concluded that high purity Ah03 and Ta20s NPs are produced by using the arc discharge method respectively. HR-TEM was also employed to the nano-product of the composite anode showing a peculiar core-shell NP structure (mean size 20 nm). Scanning Transmission Electron Microscopy (STEM) was used in High Angle Annular Dark Field (HAADF) imaging and Energy Dispersive X-ray Spectroscopy (EDX) modes to identify the atomic arrangement resulting in the formation of an oxidized copper core with an oxidized tantalum shell. The nano-powder was tested via BDS showing a capacitive behavior. Throughout this work it was been proven that arc discharge in water is a cost- effective and easy to implement method of preparing dielectric NPs. A methodology for studying both the process as well as the product has been described. High purity Ah03 and Ta20s have been successfully produced. CuO- Ta20s core-shell NPs were synthesized for the first time and were characterized structurally and electrically. Adjustments in order to improve the efficiency of the system were proposed and new ideas for the formation of composite metal oxides have emerged.
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Ly, Michel. "Etude des fils électrodes pour l'usinage par étincelage érosif." Paris, ENMP, 2005. http://pastel.archives-ouvertes.fr/pastel-00705214.
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Il s'agit de relier l’avantage en termes de vitesse d’usinage, que procurent des revetements complexes de phases du systeme cuivre zinc oxygene sur les fils-electrodes de laiton, a la thermodynamique de l’arc electrique. Il apparait que les fils revetus usinent plus vite que les fils nus, pour la meme intensite, et ce malgre une tension d’arc plus faible. Les tensions d’arc moyennes de differents fils, employes en polarite negative, ont ete mesurees, comparees aux donnees bibliographiques, et modelisees. La tension d'arc d'une cathode est d’autant plus faible que la pression de vapeurs metalliques qu’elle genere est elevee. Une faible chute de potentiel a la cathode limite son echauffement, donc son erosion. Une pression elevee pendant l’arc permet d’ejecter une plus grande proportion de la matiere en fusion presente a la surface des electrodes a la fin de l'arc d’usinage. Des mesures de pertes de masse sur differents fils electrodes et sur differentes pieces confirment notre theseZinc coated electrical discharge machining wires have a cutting speed advantage over plain brass wires. This advantage has been related to the thermodynamics of the arcs. For the same discharge current, and despite a lower arc voltage, coated wires cut faster than bare ones. Average arc voltages of different wires have been measured, and compared to published values. A thermodynamic model of the cathode has been made. Arc tension decreases as the metallic vapour pressure released by the cathode increases. Lower cathodic arc tensions release less heat, and lead to lower mass loss at said electrode. Higher arc pressures lead to higher molten electrode material ejection at the end of the arc discharges. Mass loss measurements on different wire electrodes and pieces confirm our point of view
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Querard, Vincent. "Réalisation de pièces aéronautiques de grandes dimensions par fabrication additive WAAM." Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0001/document.
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Dans le domaine de la fabrication additive plusieurs technologies cohabitent et présentent des maturités et des applications différentes : le lit de poudre, la projection de poudre et le dépôt de fil pour ne citer que les principales. Nous avons étudié, dans le cadre de cette thèse, la réalisation de pièces de grandes dimensions du domaine aéronautique en alliage d’aluminium, par technologie WAAM (Wire Arc Additive Manufacturing) robotisée. Cette technologie repose sur l’utilisation un générateur de soudure à l'arc, d’un système de protection gazeuse et d’un système d'alimentation en métal d'apport sous forme de fil. Pour répondre à cette problématique, plusieurs voies de recherche ont été investiguées. La première traitait principalement de la génération de trajectoires : Plusieurs expérimentations ont permis de montrer l’intérêt et l’importance de la génération de trajectoires et notamment la maitrise de l’orientation outil pour la fabrication additive de pièces complexes en étudiant le respect de la géométrie souhaitée. La seconde concernait l’étude de la santé matière des pièces fabriquées. Des observations au niveau de la microstructure, mais aussi des caractéristiques mécaniques ont permis de mettre en évidence l’influence des paramètres opératoires sur la qualité de la matière déposée. Enfin, la réalisation de pièces fonctionnelles dans le cadre d’un projet financé par la DGA/DGAC et dont les partenaires étaient : STELIA, CONSTELLIUM, CT INGENIERIE et l’Ecole Centrale de Nantes, a permis de mettre en avant l’intérêt du procédé pour la fabrication de pièces aéronautiques. Un élément de structure aéronautique composé de raidisseurs a été fabriqué avec le procédé WAAM sur un substrat double courbure en alliage aluminium. Les difficultés accrues de réalisation ont pu être levées par l'emploi de la méthodologie développée dans le cadre de la thèseIn the field of additive manufacturing (AM), several processes are present and have different applications and levels of development: the main technologies are powder-bed based AM, powder projection and Wire Additive Manufacturing (WAM). We have studied, in this PhD work, the manufacturing of large scale components in aluminum alloy for aircraft industry with Wire Arc Additive Manufacturing (WAAM). This technology is based on a welding generator, a shielding gas protection and a feedstock (wire in this case). To solve this issue, several ways of research were investigated. The first one dealt with toolpath generation: several experiments have highlighted the importance of tool path generation and the tool orientation to manufacture complex parts and improve the part accuracy. The second one was about the validation of the material quality after deposit. Microstructural observations and mechanical tests have demonstrated the effect of process parameters on the deposit quality. Finally, in the context of a DGA/DGAC funded research project, whose partners were STELIA, CT INGENIERIE, CONSTELLIUM and l’Ecole Centrale de Nantes, the manufacturing of functional part in aluminum alloy has shown the interest of the process for aircraft industry. A structural component based on a double curvature geometry has been manufactured with WAAM. The methodologies developed in this PhD work have enabled us to solve the issues to manufacture that type of component
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Ly, Michel. "Étude des fils électrodes pour l'usinage par étincelage érosif." Phd thesis, École Nationale Supérieure des Mines de Paris, 2005. http://pastel.archives-ouvertes.fr/pastel-00705214.
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Il s'agit de relier l'avantage en termes de vitesse d'usinage, que procurent des revêtements complexes de phases du système cuivre zinc oxygène sur les fils-électrodes de laiton, a la thermodynamique de l'arc électrique.Il apparait que les fils revêtus usinent plus vite que les fils nus, pour la même intensité, et ce malgré une tension d'arc plus faible. Les tensions d'arc moyennes de différents fils, employés en polarité négative, ont été mesurées, comparées aux données bibliographiques, et modélisées.La tension d'arc d'une cathode est d'autant plus faible que la pression de vapeurs métalliques qu'elle généré est élevée. Une faible chute de potentiel a la cathode limite son échauffement, donc son érosion. Une pression élevée pendant l'arc permet éjecter une plus grande proportion de la matière en fusion présente a la surface des électrodes a la fin de l'arc d'usinage.Des mesures de pertes de masse sur différents fils électrodes et sur différentes pièces confirment notre thèse.
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Ravary, Benjamin. "Modélisation thermique et hydrodynamique d'un réacteur plasma triphasé : contribution à la mise au point d'un procédé industriel pour la fabrication de noir de carbone." ENSMP, 1998. https://pastel.archives-ouvertes.fr/tel-01138155.
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Le noir de carbone dont la production mondiale s’élève à 6 millions de tonnes par an est aujourd'hui presque exclusivement produit par un procédé de combustion incomplète particulièrement polluant. Le craquage d'hydrocarbures par plasma constitue une alternative écologique et flexible, qui a fait l'objet de plusieurs travaux de recherche. Le projet initié par l’École des Mines de Paris, a permis de réaliser un réacteur pilote à plasma d'arcs triphasés de 100 kW et de démontrer la faisabilité du procédé. La modélisation hydrodynamique du pilote s'inscrit dans le cadre de la caractérisation et de l’amélioration du procédé en cours de développement. L'analyse de l’écoulement a montré que les arcs triphasés constituent le principal moteur de l’écoulement. Ils transmettent l’énergie électrique et leurs interactions électromagnétiques conduisent à un mouvement d'ensemble centrifuge observé à la caméra rapide. Les forces de Lorentz ont été évaluées, en supposant des petites déformations des arcs. Elles ont été moyennées et introduites sous forme d'un terme source de quantité de mouvement, dans une zone spécifique du modelé hydrodynamique. Ce modèle est construit à l'aide du code de dynamique des fluides numériques fluent. Il inclut le rayonnement entre les parois et différents modèles de turbulence ont été testés. L'influence des paramètres de réglage du réacteur (nature du gaz plasma, débit et puissance électrique) a été étudiée numériquement. Le principal paramétre libre du modèle est la conductivité des parois. Le modèle a été validé par des mesures de pertes calorimétriques et de températures de parois, obtenues grâce à l'instrumentation du pilote qui est présentée. Il a été utilisé pour identifier les meilleures conditions, en termes de mélange et d'isolation, lors de l'injection radiale depuis la paroi, d'un gaz froid de même nature que le plasma.
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Ledoux, Martial. "Acide rumenique : presence dans le beurre et influence des procedes de fabrication ; incidence sur l'atherosclerose experimentale chez le hamster." Phd thesis, INAPG (AgroParisTech), 2005. http://pastel.archives-ouvertes.fr/pastel-00003476.
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Les acides linoléiques conjugués (ALC) sont des isomères positionnels et géométriques de l'acide linoléique 18:2 9c,12c, représentés par deux isomères principaux : l'acide ruménique ou 9c,11t, et l'isomère 10t,12c. L'acide ruménique est naturellement retrouvé dans les produits laitiers ; mais les tables de composition des aliments souffrent actuellement d'un manque de données concernant cet acide gras particulier. Les ALC, et notamment l'acide ruménique, semblent présenter des propriétés biologiques intéressantes pour la santé humaine, notamment lors de l'athérogenèse. Cependant, ces études utilisent des mélanges d'ALC. Le rôle respectif de chaque isomère est encore mal connu. Le premier volet de notre travail constituait déterminer les teneurs en acide ruménique de matières grasses laitières de plusieurs régions de France, sur plusieurs saisons, et d'étudier les variations de ces teneurs lors du passage du lait, à la crème, puis au beurre. Nos résultats montrent que les taux d'acide ruménique dans la matière grasse laitière varie avec la région et la saison étudiées. Ces différences pourraient être principalement imputables aux teneurs en acides gras poly-insaturés, et notamment en acide linoléique, de l'alimentation des bovins. Aucune variation n'est remarquée lors de la fabrication du beurre ; l'écrémage du lait, la maturation de la crème et le barattage ne semblent pas modifier les taux d'acide ruménique de la matière grasse laitière. Le deuxième volet de notre étude avait pour but de différencier le rôle de chacun des deux principaux isomères, et de focaliser sur les propriétés propres de l'acide ruménique, chez le hamster nourri avec un régime athérogène. Il ressort de nos travaux que l'acide ruménique exercerait un effet bénéfique supérieur à celui de l'isomère 10t,12c, sur une souche de hamster lors d'athérogenèse très précoce. Cependant cet effet bénéfique ne se fait plus sentir chez une autre espèce plus sensible à cette maladie, lors de stade plus avancé. En conclusion, l'exploration des propriétés biologiques de l'acide ruménique en regard de l'athérogenèse demande des travaux supplémentaires sur un modèle animal mieux adapté.
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Alam, Muhammad Faisal. "Squeeze Casting as Alternative Fabrication Process for Carbon Fiber Reinforced Aluminium Matrix Composites." Thesis, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24361.
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Aluminium matrix composites are among the most promising candidate materials for light weight and high strength applications such as transportation and armour. In a previous study 6061 aluminum matrix composites reinforced with plain weave carbon fiber preform (AS4 Hexcel) were successfully fabricated by squeeze casting using the laminate fabrication technique. This research aims at optimizing the fabrication process in order to achieve improved strength and mechanical properties. It focuses on the liquid infiltration squeeze casting method. Good mechanical bonding between fiber and aluminium is achieved thanks to improved infiltration and impregnation of the fabric by liquid aluminium. Oxidation products at fiber/aluminium interface and porosity are reduced. As a result, composites are produced with overall improved mechanical properties. The flexural strength is increased by up to 19.9% and 15.4% compared to the laminate approach and the reference 6061 aluminium alloy squeeze cast under identical conditions, respectively. Similarly, overall hardness is improved. However, the impact strength is reduced by 7.76% and 25.78% when compared to casts fabricated by the laminate method and the reference aluminium alloy, respectively. The thesis constitutes a good basis for further research on fiber and particle reinforced aluminium matrix composites with the goal of further improving fracture toughness, particularly for gradient materials used in armour applications.
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Singh, Jagat. "Commissioning of an Arc-Melting/Vacuum Quench Furnace Facility for Fabrication of Ni-Ti-Fe Shape Memory Alloys, and the Characterization." Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2104.
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Shape memory alloys when deformed can produce strains as high as 8%. Heating results in a phase transformation and associated recovery of all the accumulated strain, a phenomenon known as shape memory. This strain recovery can occur against large forces, resulting in their use as actuators. The goal of this project is to lower the operating temperature range of shape memory alloys in order for them to be used in cryogenic switches, seals, valves, fluid-line repair and self-healing gaskets for space related technologies. The Ni-Ti-Fe alloy system, previously used in Grumman F-14 aircrafts and activated at 120 K, is further developed through arc-melting a range of compositions and subsequent thermo-mechanical processing. A controlled atmosphere arc-melting facility and vertical vacuum quench furnace facility was commissioned to fabricate these alloys. The facility can create a vacuum of 10-7 Torr and heat treat samples up to 977 °C. High purity powders of Ni, Ti and Fe in varying ratios were mixed and arc-melted into small buttons weighing 0.010 kg to 0.025 kg. The alloys were subjected to solutionizing and aging treatments. A combination of rolling, electro-discharge machining and low-speed cutting techniques were used to produce strips. Successful rolling experiments highlighted the workability of these alloys. The shape memory effect was successfully demonstrated at liquid nitrogen temperatures through a constrained recovery experiment that generated stresses of over 40 MPa. Differential scanning calorimetry (DSC) and a dilatometry setup was used to characterize the fabricated materials and determine relationships between composition, thermo-mechanical processing parameters and transformation temperatures.M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
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Das, Mainak. "TISSUE ENGINEERING THE MOTONEURON TO MUSCLE SEGMENT OF THE STRETCH REFLEX ARC CIRCUIT UTILIZING MICRO-FABRICATION, INTERFACE DESIGN AND DEFINED MEDIUM FORMULATION." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4491.
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The stretch reflex circuit is one of the most primitive circuits of mammalian system and serves mainly to control the length of the muscle. It consists of four elements: the stretch sensor (muscle spindle/ intrafusal fiber lie parallel between extrafusal, contractile musculature), extrafusal muscle fiber, sensory neuron and motoneuron. The basic principle of the stretch reflex arc circuit is as follows: whenever there is a sudden stretch in a muscle, it needs to compensate back to its original length so as to prevent any kind of injury. It performs this compensation process using a simple negative feed back circuit called the stretch reflex arc. Any form of stretch in a muscle activates the stretch sensors (muscle spindle/ intrafusal fiber) lying deep in each muscle. After the stretch sensors get activated, it sends a train of signals to the spinal cord through the sensory neurons. The sensory neurons relay this information to the motoneuron. The motoneuron performs the necessary information processing and sends the message to the extrafusal fibers so as to compensate for the sudden stretch action. The motoneuron conveys this message to the extrafusal fibers by communicating through the special synaptic junctions called neuromuscular junctions. Based on this information, the extrafusal fibers act accordingly so as to counter the effect of sudden stretch. This is also called the monosynaptic stretch reflex that involves a single synapse between a sensory neuron and a motoneuron. To date studying these stretch reflex circuits is only feasible in animal models. Almost no effort has been made to tissue engineer such circuits for a better understanding of the complex development and repair processes of the stretch reflex circuit formation. The long-term goal of this research is to tissue engineer a cellular prototype of the entire stretch reflex circuit. The specific theme of this dissertation research was to tissue engineer the motoneuron to muscle segment of the stretch reflex arc circuit utilizing micro-fabrication, interface design and defined medium formulations. In order to address this central theme, the following hypothesis has been proposed. The first part of the hypothesis is that microfabrication technology, interface design and defined medium formulations can be effectively combined to tissue engineer the motoneuron to muscle segment of the stretch reflex arc. The second part of the hypothesis is that different growth factors, hormones, nanoparticles, neurotransmitters and synthetic substrate can be optimally utilized to regenerate the adult mammalian spinal cord neurons so as to replace the embryonic motoneurons in the stretch reflex tissue engineered construct with adult motoneurons. In this body of work, the different tissue engineering strategies and technologies have been addressed to enable the recreation of a in vitro cellular prototype of the stretch reflex circuit with special emphasis on building the motoneuron to muscle segment of the circuit. In order to recreate the motoneuron to muscle segment of the stretch reflex arc, a successful methodology to tissue engineer skeletal muscle and motoneuron was essential. Hence the recreation of the motoneuron to muscle segment of the stretch reflex circuit was achieved in two parts. In the part 1 (Chapters 2-5), the challenges in skeletal muscle tissue engineering were examined. In part 2 (Chapters 6-7), apart from tissue engineering the motoneuron to muscle segment, the real time synaptic activity between motoneuron and muscle segment were studied using extensive video recordings. In part 3 (Chapters 8-10), an innovative attempt had been made to tissue engineer the adult mammalian spinal cord neurons so that in future this technology could utilized to replace the embryonic neurons used in the stretch reflex circuit with adult neurons. The advantage of using adult neurons is that it provides a powerful tool to study older neurons since these neurons are more prone to age related changes, neurodegenerative disorders and injuries. This study has successfully demonstrated the recreation of the motoneuron to muscle segment of the stretch reflex arc and further demonstrated the successful tissue engineering strategies to grow adult mammalian spinal cord neurons. The different cell culture technologies developed in these studies could be used as powerful tools in nerve-muscle tissue engineering, neuro-prosthetic devices and in regenerative medicine.Ph.D.
Burnett School of Biomedical Sciences
Medicine
Biomedical Sciences
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Kuchan, Abigail. "The integration of active flow control devices into composite wing flaps." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44758.
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Delaying stall is always an attractive option in the aerospace industry. The major benefit of delaying stall is increased lift during takeoff and landings as well as during high angle of attack situations. Devices, such as fluidic oscillators, can be integrated into wing flaps to help delay the occurrence of stall by adding energized air to the airflow on the upper surface of the wing flap. The energized air from the oscillator allows the airflow to remain attached to the upper surface of the wing flap. The fluidic oscillator being integrated in this thesis is an active flow control device (AFC). One common method for integrating any device into a wing flap is to remove a section of the flap and mechanically secure the device. A current trend in the aerospace industry is the increased use of fiber-reinforced composites to replace traditional metal components on aircraft. The traditional methods of device integration cause additional complications when applied to composite components as compared to metal components. This thesis proposes an alternative method for integration of the AFC devices, which occurs before the fabrication of wing flaps is completed and they are attached to the aircraft wing.
Seven design concepts are created to reduce the complications from using current methods of integration on composite wing flaps. The concepts are based on four design requirements: aerodynamics, manufacturing, maintenance, and structure. Four of the design concepts created are external designs, which place the AFC on the exterior surface of the wing flap in two types of grooved channels. The other three designs place the AFC inside the wing flap skin and are categorized as internal designs. In order for the air exiting the AFC to reach the upper surface of the wing flap, slots are created in the wing flap skin for the internal designs. Within each of the seven design concepts two design variants are created based on foam or ribbed core types.
Prototypes were created for all of the external design AFC devices and the side inserted AFC and retaining pieces. Wing flap prototypes were created for the rounded groove straight AFC design, the semi-circular groove with straight AFC, and the side inserted AFC designs. The wing flaps were created using the VARTM process with a vertical layup for the external designs. The rounded groove and semi-circular groove prototypes each went through three generations of prototypes until an acceptable wing flap was created. The side inserted design utilized the lessons learned through each generation of the external design prototypes eliminating the need for multiple generations. The lessons learned through the prototyping process helped refine the designs and determine the ease of manufacturing to be used in the design evaluation.
The evaluation of the designs is based on the four design requirements stated above. The assessment of the designs uses two levels of evaluation matrices to determine the most fitting design concept. As a result of the evaluation, all four of the external designs and one of the internal designs are eliminated. The two remaining internal designs' foam core and ribbed variants are compared to establish the final design selection. The vertically inserted AFC foam core design is the most fitting design concept for the integration of an AFC device into a composite wing flap.
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Ibrahim, Hamdy Ibrahim. "Bioresorbable Magnesium-Based Bone Fixation Hardware: Alloy Design, Post-Fabrication Heat Treatment, Coating, and Modeling." University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1503678544356525.
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Gomez, Ortega Arturo. "Prototypage rapide de pièces en alliage d’aluminium : étude du dépôt de matière et d’énergie lors de la fusion à l’arc d’un fil par le procédé MIG-CMT." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS067/document.
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Un nouveau procédé de fabrication additive de pièces métalliques, basé sur le procédé de soudage à l’arc appelé CMT (Cold Metal Transfert), est étudié dans l’objectif de réaliser des pièces en alliage d’aluminium Al-5Si. Un banc de fabrication additive basé sur le principe des imprimantes 3D open source, sur lequel a été intégré le procédé CMT, a été spécialement développé. Le procédé CMT permet de contrôler la fusion d’un fil d’aluminium et son dépôt sous la forme de gouttelettes sur la surface de construction, formant après solidification des « cordons » qui peuvent être superposés pour fabriquer des pièces. L’influence des paramètres du procédé sur les phénomènes de transfert de matière et de chaleur lors de la fusion du métal et de son dépôt sur la surface de construction, ainsi que sur les caractéristiques géométriques des cordons déposés, dans le cas de dépôts mono-cordon, puis dans le cas de murs formés par la superposition d’un grand nombre de cordons, est étudiée. Plusieurs défauts géométriques ont été observés, et les conditions de leur apparition analysées, grâce notamment à l’utilisation d’une caméra rapide. La compréhension des relations entre paramètres procédé, mécanismes de transfert de chaleur et de matière, et géométrie des cordons, a permis de corriger ces défauts en identifiant puis modifiant les paramètres procédé responsables de leur apparition. Enfin, une méthode de contrôle en ligne du procédé, basée sur l’analyse des signaux de tension et d’intensité produits par le générateur de soudage au cours du phénomène de dépôt, qui permet de détecter précocement l’apparition de défauts, et ainsi de modifier les paramètres procédé avant qu’ils ne s’amplifient, a été proposéeA new additive manufacturing process for metallic parts, based on the arc welding process known as CMT (Cold Metal Transfer), is studied with the objective of building parts with the aluminium alloy Al5Si. A workbench for additive manufacturing based on the 3D printers open-source principle, on which the CMT generator was integrated, was specially developed. The CMT process allows to control the aluminium wire melting and its deposition under the form of droplets on the building surface, forming, after solidification, beads that can be superposed for the parts construction. The process parameters influence on the material transfer and heat transfer during the metal melting and deposition on the build surface, as well as on the geometric characteristics of the deposed beads, in the case of mono-layer deposits, and in the case of multi-layer walls, is studied. Many geometric defects were observed, and their apparition conditions analysed, thanks in particular to the use of a high-speed camera. The understanding of the relations between the process parameters, the melting and heat transfer mechanisms, and the beads geometry, allowed the defects correction by identifying and modifying the process parameters responsible of their apparition. Finally, an on-line control method for the process, based on the analysis of the voltage and current signals produced by the welding generator during the deposition phenomena, making possible the early detection of defects, and then the modification of the process parameters before they are amplified, has been proposed
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Bourlet, Clément. "Développement de la fabrication additive par procédé arc-fil pour les aciers : caractérisation microstructurale et mécanique des dépôts en nuances ER100 et 316L pour la validation des propriétés d'emploi de pièces industrielles." Thesis, Paris, ENSAM, 2019. http://www.theses.fr/2019ENAM0058.
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L'arc-fil est un nouveau procédé de fabrication additive utilisant une cellule desoudage robotisée pour la fabrication, couche par couche, de pièces de grandes dimensions. Ilpermet de réaliser des ébauches de pièces unitaires ou de petites séries avec des coûts et desdélais de fabrication réduits. Les premiers développements se sont principalement orientés sur laréalisation de pièces à forte valeur ajoutée en alliage de titane et d’aluminium pour le secteuraéronautique et aérospatial, et intéressent maintenant d’autres secteurs tels que les industriesnavales, pétrolières, ferroviaires et mécaniques utilisant des aciers. Ce travail propose uneméthodologie de sélection des paramètres et des stratégies de dépôts, avec le contrôle final despièces fabriquées. Il porte sur deux matériaux : un acier C-Mn à haute limite d’élasticité(ER100) et un acier inoxydable austénitique (316LSi). Le résultat des caractérisations permetd’établir le lien entre les conditions de fabrication, les dimensions géométriques et les propriétésmicrostructurales et mécaniques des pièces obtenues, ce qui conduit au final à une démarchepermettant de faire évoluer le procédé vers l’industrialisationWire-arc additive manufacturing is a new process using a common weldingrobotic cell to build large parts layer by layer. It allows building rough single pieces orsmall series parts with a low cost and a short delay. First developments were done ontitanium and aluminum parts for aeronautic and space applications, but more industriessuch as maritime, oil and gas, railway…are now interested into it. In this work, amethodology is proposed to define suitable process parameters and deposit’s strategies,with the final control of the elaborated parts. Developments are done on both highstrength steel ER100 and austenitic stainless steel 316LSi. The results of theexperimental characterisation enable to show the relations between the manufacturingconditions, the dimensions, the microstructure and the mechanicals properties of theparts, and finally lead to guidelines to evolve the wire-arc additive manufacturingtowards industrialisation
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Kottman, Michael Andrew. "Additive Manufacturing of Maraging 250 Steels for the Rejuvenation and Repurposing of Die Casting Tooling." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1416854466.
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楊世權. "Research of Fabrication Copper Nanofluid by Plasma Arc System." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/13634383109450458847.
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碩士國立臺灣師範大學
機電科技研究所
99
The purpose of experiment is aim to a methods of nanofluid produce by arc plasma. Refer to previous research data and correction. Consist with several stages: preparation, modification, system installation, tested; use “Evaporation synthesi- zed condensation system” to implement copper/water nanofluid by selected high energy plasma arc that can vaporize any kind of metal as a heating source, collect vaporized nanoparticle into nanofluid collector. To avoid condensed bigger size of particle due to high temperature or cluster, take paramenter in consideration during the period of experiment; such as working current, collector function, trying to obtain process minimum and average nanoparticle. By mean of two stage experiment, base on different current parameter (50A, 60A, 70A, 80A) collector to gain the proper nanoparticle by target meterial melting situation. Preliminary analyze to determine what type of current maybe optimum parameter. Marcoscopic results show current 60A and 70A are optimum parameter for particle collect on stage one. In the second stage, base on fixed current used three different working current plasma arc torch pulse. Then stimulate with ultrasonic after that, analyze by SEM, EDS, particle size analyzer to define which process can produce perfect nanoparticle. As a result, working current 60A/25Hz average particle is 548nm, 70A/25Hz average particle is 3500nm, process copper/water nanofluid heating resistance test, found that heating resistance reach to -30% under water temperature 50℃, paramenter 70A/25Hz.
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Lin, Ke-Cheng, and 林科呈. "Fabrication of Titanium Dioxide Photocatalytic Film by Micro-Arc Oxidation." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/97958685656391679323.
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碩士龍華科技大學
工程技術研究所
98
Titanium dioxide had appropriate band gap (3.2eV), good photocatalytic effect and heat and chemical stability; therefore, it is widely used for photocatalysts. The study make use of the Micro-arc oxidation(MAO) technique to fabricate titanium dioxide film in the titanium surface; then used UV to irradiate the methylene blue solution to analyze the photocatalytic effect. The surface characters of titanium dioxide coating were analyzed using coating thickness meter, contact angle meter, SEM and XRD. The MAO operating variables include the current density and micro-arc reaction time. The result indicate that the photocatalytic effect and the TiO2 content of the coating increase with the current density and micro-arc reaction time; furthermore, the photocatalytic effect may reach 10% under current density 10 A/dm2 and micro-arc reaction time 60 min.
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Chen, Jeng-shiung, and 陳正雄. "Fabrication of Carbon Nanotubes Using Arc-Discharge System with Samarium-Cobalt Catalyst." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/90844260200173744141.
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碩士大同大學
光電工程研究所
94
In this thesis, the carbon nanotubes (CNTs) was fabricated by arc-discharge method with the samarium-cobalt (Sm-Co) chloride as the catalyst. The experimental apparatus was designed and assembled by ourselves. The Sm-Co chloride was first applied as catalyst for CNT formation. The optimized recipes were also determined by a series experiments. By the TEM observations, we observed the main products are multi-walled carbon nanotubes (MWCNTs). We also used the commercial MWCNTs to serve as carbon sources and fabricated the MWCNT with less tube walls. With the assistance of the Sm-Co chloride catalyst, the radial breathing modes (RBMs) of the Raman spectra were measured. Generally, the RBM only belongs to the characteristic Raman signals of single-walled carbon nanotubes (SWCNTs) or induced by the thin MWCNTs with large outer diameter. The tunneling electron microscopy (TEM) observations revealed our nanotubes are mainly multi-walled. These tubes have good graphitic structures and less bamboo defects which agree with their Raman measurements with high IG/ID ratio (~88). The IG and ID are the intensity of the tangential modes (TMs) of the Raman spectra. These tubes were unlikely to generate RBMs due to the observation from TEM which the thick MWCNT were mainly found. We believe that the product from our arc-discharge system contain few SWCNTs which give RBMs. However, the quantity of these SWCNTs may be too low to be observed by TEM. In our experiments, the CNTs fabricated using Sm-Co chloride catalyst exhibited good quality in structure. Our CNTs have no catalyst particles encapsulated inside the tube which is the advantage using such catalyst to fabricate CNTs. Compare to the MWCNTs fabricated from chemical vapor deposition (CVD) which usually have bamboo defects and catalyst encapsulations. The results of our experiments show that it is an unique approach to grow high quality CNTs.
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Chang, Yu-Chun, and 張宇淳. "Plasma Arc System Applied In Fabricating Aluminum Oxide Nanofluid." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/3tj5m5.
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碩士國立臺北科技大學
製造科技研究所
93
This article describes a novel nanofluids manufacturing and collecting system .Different to other preparing methods, the development method cools the vaporized metal aerosol by mixing the noanparticles with pre-cooling deionized water when the aerosol flows through the designed tunnel. This experimental equipment mainly contains a plasma arc system, water cooling circulatory system, the gas inducting system and coolant collection system. The bulk metal is melt by the generated plasma arc with a high temperature up to 12000K. The gas inducting system extracts and cools the mixture fluid into the collection tank. The Al2O3 nanofluid were prepared in different experimental parameters, such as discharge circuit、collection temperature、collection method. The dimensional and material properties of nanofluid were examined by using Field Emission Gun Scanning Electron Microscope(FEG-SEM) , Transsimision Electron Microscope (TEM), Particle Size Analizer(PSA), X-RAY, EDAX. Results show that the smallest Al2O3 particle diameter 10 nm. Meanwhile the prepared nanoparticles were mixed with gasoline for combustion test in determing the effects of burning performance enhancement.
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CHEN, CHIEN-CHANG, and 陳建彰. "A Study on the Fabrication and Properties of PET/ Ag-ACC Composite Materials." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/79986400663200497290.
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Chen, Kuan-Chih, and 陳冠志. "Quantification of Arc Discharge Processing on Silver Nanofluid Fabrication and Suspension Stability Analysis." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/9632b8.
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碩士國立臺北科技大學
電機工程系所
97
The principal of arc discharge fabricating theorem is using the concentrated arc energy to melt the electrodes surface, then spraying, quenched, and suspended immersed into the dielectric solution (pure water). In this research, the main purpose is to quantificate the particle and ionic silver concentration arising rate, finally, the silver nanofluid suspension stability been analized. Therefore, this research could be separated into two issues. The 1st issue is “quantificating the arc discharge processing on silver nanofluid fabrication.” By using the precision scale and titrator, under different on-off duration setting, the silver particle and ionic silver had been quantification. For the arcing energy quantification issue, once, take arcing rate and central-limit-theorem into consideration could successfully realize arcing energy calculation technique. The 2nd issue is “nanofluid suspension stability analysis.” By using UV-Visible-spectrum-meter and Zeta-sizer, the result shows, the saturated concentration of silver nanoparticle, but not the ionic silver, surely reduces the suspension stability. In this study, without adding any dispersant, only adjust the total arc discharge processing time. Thus the Zeta-potential vs. pH experimental result shows, the suspension stability of shorter processing time is still slightly worse than adding 2 ppm citric acid.
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Cheng, Guo-Wei, and 程國威. "Fabrication of graphene by solid carbon sources using a vacuum arc discharge system." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/93023625108871679431.
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碩士國立臺灣海洋大學
電機工程學系
102
In this study, graphene was fabricated on copper foils using an vacuum arc-discharge method assisted with high temperature furnace. The optimal fabrication condition was determined through a series of experiments on various ambient conditions such as process pressure、process time、arc current and electrode distance. Observations by scanning electron microscopy, Raman spectroscopy and optical microscopy. The main products were single and multi-layered graphene which were estimated the layer numbers from 1 to 10. Embedded carbon atoms obtained by thermal disintegrated graphite by vacuum arc, high temperatures furnace driving carbon atoms into the copper substrate surface. When carbon contains saturated in cu then we rapidly cooled to room temperature to precipitate the formation of bonding and generate graphene. Our experiment present a promising route to fabricate graphene by solid carbon sources, unlike conventional method, our experiment provide low-cost, non-toxic process to fabricate single and multi-layer graphene.
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CHEN, JUN-YOU, and 陳俊佑. "Simuulation and Fabrication of Steps- and Graded-type ARC Structure for Solar Cell Application." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/61740663982468514429.
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碩士國立雲林科技大學
電子工程系
104
Global 195 signing countries agreed to comply with the limits of fossil resources to reduce pollution, and signed the Paris agreement in order to prevent the temperature of the Earth from rising up and be able to drop in global warming temperature in 2020. Recently, with the electrodes of the high-efficiency solar cell are moved into cell back to reduce shade effect, so the design of ARC(antireflection coating) becomes more important. In this study, we will use simulation method to disguss the effect of various refractive indexs to ARC first and then we operate the rf sputter to deposite the films. With thin film matrix theory and the data of various materials to simulate the best average reflection and the best central wavelenth of single layer、double layer、triple layer and graded layer. In this study we simulate the standard samples V-coating D3-F with average reflectivity of 7.19%, and then we simulate the other structure of SRO(Silicon-rich SiOx) and SRN(Silicon-rich SiNx) in comparison with the standard sample to find the best struture. Single layer for optimal S3 (SiOx:78nm/n:1.959) structure shows low average reflectivity of 7.59% and current desity of 31.777 mA/cm2. it is shown more terrible compared to the standard samples S1. SRO double layer for optimal D1-G(SiO2:66 nm/SiOx:111 nm) structure shows low average reflectivity of 1.21% and it is shown about 83.23% improvement compared to the standard samples S1, and further have 5.30% improvement in current desity. SRN double layer for optimal D4-F (SiO2:100nm /SiNy:49nm) structure shows low average reflectivity of 1.73% and it is shown about 75.98% improvement compared to the standard samples S1, and further have 5.02% improvement in current desity. Triple layer for optimal T4-G(SiO2:78nm/Si3N4:11nm/ SiNy:87nm) structure which is the best SRN structure shows low average reflectivity of 1.52% and it is shown about 78.8% improvement compared to the standard samples S1, and further have 5.04% improvement in current desity. In operation, we can prove that it is feasible by controlling the rate of the gas to deposite the step SRN film.
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Lin, Tsung-ying, and 林宗穎. "Fabrication of Nano-crystalline Silicon Thin Film on Flexible Substrate by Vacuum Arc Discharge." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/57707674210668756004.
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碩士大同大學
光電工程研究所
97
Nano-crystalline silicon has been deposited on glass and plastic substrates by direct vacuum arc system at room to cryogenic temperature(77 K). Solid silicon wafer source were amount on both anode and cathode to be the electrodes which were highly doped single crystal silicon wafer(0.005 Ω/cm). It is suitable for deposited thin films on flexible substrate due to low deposition temperature. Silicon films were characterized by Raman spectroscopy、x-ray diffraction (XRD)、tunneling electron microscope (TEM) and scanning electron microscope (SEM). The result revealed that the crystalline structure embedded in amorphous matrix. High-resolution transmission electron microscopy (HRTEM) was used for direct analyzing the particle where the fully crystallized structure were inert the particles and these particles were random distributed over the substrate. The crystalline volume fraction were calculated from Raman spectrum and it showed the values between 0~92 ％. The impurity concentration was measured by SIMS, that the P-type and N-type impurity was permeated simultaneously into the film during the deposition without additional doping process, thus P-N junction could be achieved. Nano-crystalline silicon has higher electron mobility and more stability against prolong light exposure than amorphous silicon. According to our research, the opto-electronic effect were not obviously, we assume that a large number of defects existed in the films. Compared to CVD process, arc discharge system has the advantages of low cost, less environment pollution and non-dangerous of processing. Such research has not yet been observed. Low temperature deposited nano-crystalline silicon thin film has attracted much attention due to applicable on low-cost substrates, like glass and flexible plastic substrate. Key words: Direct vacuum arc, Flexible substrate, crystalline volume fraction.
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Rego, Gaspar Mendes do. "Arc-induced long-period fibre gratings : fabrication and their applications in optical communications and sensing." Tese, 2006. http://hdl.handle.net/10216/12213.
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Chen, Yu-Jen, and 陳宥任. "Fabrication and Characterization of Micro Arc Oxidation Coatings on Hot-dip Aluminized Medium Carbon Steel." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/49992064220950379322.
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碩士國立臺灣科技大學
機械工程系
103
In this study, the characteristics of the coating on the hot-dip aluminized middle carbon steel using Micro-Arc oxidation are discussed in silicate system electrolyte. The microstructures, hardness, phase structures, and corrosion resistances are discussed by adjusting duty ratio under constant frequency (1000Hz), working voltage (400V) and working time (20 minutes). Then, compared with coatings on pure aluminum in the same parameters. With duty ratio increasing, the pores on the surface will become larger and non-homogeneous. And the thickness of the coatings also increase. But the coating of duty ratio 70% is thinner than 30% and 50%. There are some cracks on the surface on the coating of 70% . Because duty ratio 70% provide higher energy, the coating not only cracks but also flaking. The main phase structure of the coatings are -Al2O3. Al6Si2O13 phase are observed in the coatings of duty ratio 30% and 50%. From the formation of Al6Si2O13 phase revealed that dense and thick coatings could get stable phase easily. Duty ratio 10% and 70% can be observed Al substrate diffraction peak because the coatings are thinner than the other two duty ratio and there are some cracks on the surface of the coating in duty ratio 70%. The thickness of the coatings and the cracks have a great influence for the mechanical properties and corrosion behavior. Duty ratio 50% provide the highest thickness (16.93m), the optimum mechanical properties (406 HV) and the most anti-corrosive behavior (3.18•104 Ω‧cm2) Comparing the coatings of hot-dip Aluminized steel with the coatings of pure aluminum using MDO showed that pure aluminum’s coatings in every duty ratio are better the HDA steel’s coatings. From the Line scan analysis, it can be observe that the coating of HDA steel contain iron. Then, iron probably is present in the form of a solid solution of the coating by using XRD analysis and phase diagram of comparison. If the iron more than the maximum amount of more than will be deposited on the oxide film when the maximum amount of solute boundary layer resulting in a layer of iron oxide and aluminum layer, so that the micro-arc oxidation eventually unable to continue, the iron in the coating which not only affects the micro-arc oxidation, also reduce the hardness, corrosion resistance and resistance to phase.
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Jao, Kun Liang, and 饒?樑. "The study on the fabrication of phase shift fiber bragg grating using arc discharge technique." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/376ym9.
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碩士國立虎尾科技大學
光電與材料科技研究所
98
Fiber Bragg grating (FBG) is widely used in fiber communications system and fiber sensors system. Recently, fiber Bragg grating quickly developed as the optical filter. Fiber Bragg grating have several advantages over conventional electrical devices such as compact in size, robust, chemically inert, low loss, low cost, nonconductive and are immune to electromagnetic interference (EMI). In this thesis, we proposed a simple method to manufacture phase shifted FBG or super-structure FBG. The electric arc discharge technology is used to achieve localized defect in the FBG structure. The appropriate parameters such as arc discharge intensity, duration and arc discharge location were chosen to change the effective refractive index of FBG by using simple electrical arc discharge method. The relationship between phase shift fiber Bragg grating (PS-FBG) and these parameters was also investigated in this article. Finally, we provide several experimental results of PS-FBG and compare to the numerical simulation results by using transfer matrix method. These results demonstrate that the arc discharge method can be manufacture PS-FBG and superstructure FBGs.
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Jao, Kun Liang, and 饒堃樑. "The study on the fabrication of phase shift fiber bragg grating using arc discharge technique." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/hy5ct5.
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碩士國立虎尾科技大學
光電與材料科技研究所
98
Fiber Bragg grating (FBG) is widely used in fiber communications system and fiber sensors system. Recently, fiber Bragg grating quickly developed as the optical filter. Fiber Bragg grating have several advantages over conventional electrical devices such as compact in size, robust, chemically inert, low loss, low cost, nonconductive and are immune to electromagnetic interference (EMI). In this thesis, we proposed a simple method to manufacture phase shifted FBG or super-structure FBG. The electric arc discharge technology is used to achieve localized defect in the FBG structure. The appropriate parameters such as arc discharge intensity, duration and arc discharge location were chosen to change the effective refractive index of FBG by using simple electrical arc discharge method. The relationship between phase shift fiber Bragg grating (PS-FBG) and these parameters was also investigated in this article. Finally, we provide several experimental results of PS-FBG and compare to the numerical simulation results by using transfer matrix method. These results demonstrate that the arc discharge method can be manufacture PS-FBG and superstructure FBGs.
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Rego, Gaspar Mendes do. "Arc-induced long-period fibre gratings : fabrication and their applications in optical communications and sensing." Doctoral thesis, 2006. http://hdl.handle.net/10216/12213.
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Chih-Hung, Lo. "Fabrication and Analysis of Cu-Based Nanofluids Prepared by a Continuously Controlled Submerged Arc Nano Synthesis System." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0006-2406200616291500.
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Lo, Chih-Hung, and 羅志宏. "Fabrication and Analysis of Cu-Based Nanofluids Prepared by a Continuously Controlled Submerged Arc Nano Synthesis System." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/n4zv33.
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博士國立臺北科技大學
機電科技研究所
94
Preparation of nano-materials is one of the most significant matters for the development of nano-technology. In this dissertation, a continuously controlled submerged arc nano synthesis system was proposed and developed, using the principle of pressure difference of the operating condition maintaining, a constant pressure and an isothermal environment. The synthesis system device mainly comprises an arc generator and servo control unit, a parameter control unit, a constant pressure control unit, an isothermal control unit, a manufacture data feedback unit, an on-line conductivity measurement unit, an automatic liquid refilling unit and a sampling unit. In order to increase the production amount of nanofluids, the synthesis system was designed to operate continuously to synthesize nanofluids with a small particle size and uniformly dispersed distribution. The specific electric resistance of dielectric liquid is the key factor for the proposed continuous preparation. In addition, experiments based on Taguchi method were conducted to investigate the key parameters, such as electric voltage, electric current, pulse-duration frequency, dielectric liquid temperature and specific electric resistance of the dielectric liquid. Furthermore, Taguchi method was used to investigate the optimum process parameters to prove try- and- error process. Experimental results show a close relationship between the electric resistance of dielectric liquid and the nanoparticle size. The electric resistances of sampling and refilling liquid were set at 1255 and 2600 , respectively. Using the robust design method and the optimized process parameters, the size of the prepared needle-like shape CuO nanoparticle was found nm in length and nm in width. In addition, the 1.2 L/hr nanofluids with a concentration of 0.8 w. t. % can be prepared using the developed technique. According to the different thermal conductivity, mixing solution of de-ionized water and ethylene glycol can be used to prepare different shapes of Cu-based nanopaericles. The growing faces theory of the relationship between the type of dielectric liquid and the morphology of the prepared Cu-based nanoparticles was carefully studied and analyzed. Furthermore, we control the temperature of dielectric liquid to prepare CuO nanorods. A length of 1-2 with a width of 30-50 nm of CuO nanorods can be prepared under a low temperature condition at -5℃. The pH of the as-prepared CuO nanofluids is 6, which is greatly different to that of isoelectric point (IEP) about pH9.5 0.4. These nanofluids can be well suspensed in the liquid for longer than one year. Furthermore, this study also employs an ambient temperature controller to maintain a low temperature of the working environment and to record data on the motion behavior of suspended nanoparticle for analysis of its stability. Results show that the most stable working condition for preparation of the as-prepared CuO nanofluids is at 20℃. It was identified that the stability of nanofluids will deteriate when the temperature drops lower than 20℃. This dissertation also examined the thermal conductivity of nanofluids containing copper oxide of different volume fractions and at different specimen temperatures. The experimental results showed that both volume fraction and specimen temperature of nanofluids are linearly related to thermal conductivity. When specimen temperature was set at 40
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Wu, Ming-Feng, and 吳明峰. "The Study of the Fabrication Parameters of Micro-arc Oxidation on Hydroxyapatite Coating on Pure Titanium Plate." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/25393134650693236155.
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碩士大同大學
材料工程學系(所)
98
TiO2-based coatings were prepared on pure titanium by micro-arc oxidation (MAO) in an electrolytic solution containing Ca(CH3COO)2．H2O, Ca(H2PO4)2．H2O, EDTA–2Na and NaOH. SEM/EDS and XRD were adopted to investigate the microstructure, elements distribution and phase composition of the coatings prepared in the above electrolytes. Macro-porous titania-based coatings were formed on the titanium substrates at various voltages, charging times, duty ratios, Ca/P ratios, and concentrations of NaOH. The phase, Ca and P content, morphology, and thicknesss of the coatings were strongly dependent on the applied voltage, Ca/P ratio and concentration of NaOH. In particular, HA- and CaTiO3-containing coatings were produced at higher Ca/P ratio and concentration of NaOH. With increasing applied voltage from 260V to 320V, the thickness, roughness of the coatings and the crystallinity of HA and CaTiO3 increased; the rutile phase was formed in the coatings with anatase phase. EDX analysis shows that Ca and P elements tend to present primarily in the region of the coatings.
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Kao, Chi-Yuan, and 高啟原. "Fabrication of ion-implanted ZnO thin film with transparent conductive properties using metal vapor vacuum arc technique." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/90868514621338947735.
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碩士國立成功大學
微機電系統工程研究所
94
Transparent conductive thin film is capable to absorb ultraviolet, transmit visible light and reflect infrared. Usually Tin-doped indium oxide (ITO) is primarily used, whereas the cost for the preparation the thin-film ITO is still too high. Novel coating materials or techniques are developing to replace the thin-film ITO such as Al-doped ZnO (AZO). In this study, we utilize metal vapor vacuum arc (MeVVA) technique that forward the vaporized aluminum ions implanted into zinc oxide (ZnO) as a thin solid film. By applying different ion-implanted doses and manipulating the operational parameters, the conductivity and optical property of the ZnO thin film can be improved. In the experiment, a glass substrate was used as the base, then a thin-film ZnO or ZnO:Al (2%, as a reference) was coated using RF reactive magnetron sputtering deposition (RF-MSD) system. The thin-film ZnO was then treated by MEVVA, with which the forward aluminum ions can penetrate the thin-film ZnO into a diffused layer of several hundreds nanometers depth. The film thickness, deposition rate, transparency, conductivity and surface morphology of the treated ZnO surface were significantly influenced by the employment of RF-MSD or MeVVA treatment. From the above-mentioned parameters, an optimized adjustment was chosen, while the RF-MSD-treated ZnO:Al (2%) film was referenced. Experimental result demonstrated that under the condition of non-thermal effect and the deposited ZnO coating of 261 nm, the conductivity of ZnO thin film was originally poor (3.02×107Ω). However after the vaporized aluminum ions implantation, the resistance of the ion-implanted ZnO decreased from 3.02×107 to 3.03×104 Ω. At the same time the transparency of the aluminum ions-implanted ZnO was mostly preserved (91.5% at the wavelength of 550 nm). Potentially it provides a method with highly promising applications.
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Ku, Chih-Yang, and 古智陽. "Fabrication of an Electrode Insulation Layer of Electrochemical Machining by Using Hot Dip Aluminizing and Micro-Arc Oxidation Method." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/84703450504114698779.
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碩士逢甲大學
機械與電腦輔助工程學系
104
In this research, electrode insulation of the electrochemical machining tool has been produced by hot dip aluminized micro arc oxidation techniques. In order to form an effective insolation layer on the tungsten carbide tool and achieve higher precision, the tool will then be micro-arc oxidizing, convert the aluminum-rich into aluminum oxide insolating layer. Withstanding Voltage of the tool is being tested afterward by sodium chloride electrolysis method, and the surface and the cross section is being observed. Eventually the tools were examined and discussed for their machining performance by ECM drilling through stainless steel plate. We were expecting to produce a precise and better insulation. By reducing ECM stray effect, the precision can be achieved. The experimental result shows the optimum parameters are aluminum dipping for 4 minutes, 450 V of micro-arc voltage for 20 minutes and 40 minutes of boiling water sealing, reaching 10.2V of withstanding voltage. A further electrochemical drilling has been done to explore the effect of insolation. Two electrodes, with and without insolation had been compared. The difference between the entrance and the exit diameter of the hole of insolated tool reaches 17um, compare to the one without insolation, we have successfully reduce 81um. The result shows that the insolation has massively reduce the stray effect, and achieve high precision machining.
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LIU, YI-REN, and 劉譯仁. "Fabrication of an electrode insulation layer of electrochemical machining by using hot-dip aluminizing and micro-arc oxidation method on stainless steel substrate." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/526n8w.
Full textAbstract:
碩士逢甲大學
機械與電腦輔助工程學系
106
In this research, electrode insulation of the electrochemical machining tool has been produced by hot dip aluminized micro arc oxidation techniques. In order to form an effective insolation layer on the stainless steel tube and achieve higher precision, the tool will then be micro-arc oxidizing, convert the aluminum-rich into the aluminum oxide insulating layer. Withstanding Voltage of the tool is being tested afterward by sodium chloride electrolysis method, and the surface and the cross-section is being observed. Eventually, the tools were examined and discussed for their machining performance by ECM drilling through stainless steel plate. We were expecting to produce a precise and better insulation. By reducing ECM stray effect, the precision can be achieved. The experimental result shows the optimum parameters are aluminum dipping for 4 minutes, 475 V of micro-arc voltage for 10 minutes and Electrophoretic deposition sealing reaching 12.2V of withstanding voltage. By using electrochemical drilling to discuss the electrode with the insulation layer and the electrode without insulation. the difference between the results of drilling the entrance of the product showed that without the insulating layer electrode the insulating layer electrode drilling hole diameter value is 4.23 mm, the exit diameter of 3.75 mm, the insulating layer drilling hole diameter value is 3.52 mm, the exit diameter of 3.35mm.Through observation, the difference between the entrance and exit values indicates that the electrochemical insulating layer successfully reduces a large amount of stray current and improves the drilling accuracy.