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Measuring and understanding grain boundary properties of engineering ceramicsNorton, Andrew David January 2013 (has links)
This thesis aims to measure the mechanical properties of ceramics on the microscale using microcantilever beams. Focussed Ion Beam milled triangular cross-sectional beams (approximately 3 x 5 x 20µm) were fractured using a nanoindenter to measure the Young’s modulus, fracture strength, and fracture toughness. By developing the technique with a sapphire bicrystal, it was found that the mechanical properties could be successfully ascertained if correction factors were used. Experiments and theoretical work showed that sapphire and polycrystalline alumina beams undergo moisture assisted sub-critical crack growth when tested in air. Whilst corrections for the Young’s modulus have been previously reported, this is the first reported attempt to correct for the notch tip residual stress and the first to consider sub-critical crack growth. Once these factors were characterised using the sapphire bicrystal, the technique was applied to a range of different ceramics, such as polycrystalline α-alumina and silicon nitride. These are the first reported direct measurements the grain boundary toughness of these ceramics using microcantilever beams. The grain boundary toughness was correlated with the macroscopic fracture properties and the characteristics of the ceramic (grain boundary composition, impurities, and fracture mode). Two grades of α-alumina were used and the macro- and micro-scale properties extensively compared. The damage evolution during uniaxial compression of alumina was investigated in depth, and compared to a previous reported microcrack evolution model using the measured grain boundary toughness. Investigation of whether deformation twins formed during loading was undertaken and the phenomenon was shown to not occur.
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X-ray and neutron diffraction analysis and fem modelling of stress and texture evolution in cubic polycrystalsXie, Mengyin January 2014 (has links)
The thesis reports improvements in the characterization techniques for stress and texture in crystalline materials by x-ray and neutron powder diffraction. Furthermore, advances are made in texture evolution modelling and validation against experimental observations. In the beginning, the fundamental assumption of diffraction strain analysis is numerically examined and verified, namely, that the lattice parameter value determined from fitting the diffraction pattern is equal to the average lattice parameter within the gauge volume. Next, the task of shear strain determination from powder diffraction measurements is addressed. A method is developed and implemented for the complete 2D strain tensor determination from the multi-directional energy-dispersive x-ray diffraction patterns. The method not only offers a way to evaluate the shear strain, but also provides a better overall strain averaging approach. Rotation and translation of sample and/or detectors in powder diffraction mode can effectively increase the pole figure coverage and thus the accuracy of texture determination. However, the movements also introduce uncertainties and aberrations into data analysis due to the changes in the diffraction volume and transmitted intensity. In order to overcome these problems, accurate <strong>single exposure</strong> texture characterization techniques are proposed based on several different powder diffraction setups. Numerical analyses are carried out to prove that any simple texture in cubic polycrystals can be effectively determined using single exposure Debye-Scherrer diffraction pattern analysis. Several experiments are reported on collecting Debye-Scherrer diffraction patterns, multi-directional energy-dispersive x-ray diffraction patterns and multi-directional TOF neutron setup. Efficient data processing procedures of the diffraction patterns for ODF determination are presented. Crystal plasticity finite element models are developed to model the texture evolution in polycrystalline engineering samples during manufacturing. In the present thesis, quantitative measures extracted from orientation distribution function are employed to make precise comparison between the model and experiment. Unlike the simple uni-axial compression and tension considered in the literature, in the present thesis the complex texture evolution during linear friction welding is modelled as a sequence of different shear deformations.
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High energy white beam X-ray diffraction studies of strains in engineering materials and componentsZhang, Shu Yan January 2008 (has links)
The primary aim of this research was to develop and improve the experimental method and data interpretation for strain measurements using diffraction methods to gain a better understanding of micromechanical deformation and anisotropy of lattice strain response. Substantial part of the research was devoted to the development of the laboratory high energy X-ray diffractometer (HEXameter) for bulk residual strain evaluation. White beam energy dispersive X-ray diffraction was chosen as the principal diffraction mode due to its extreme efficiency in utilising X-ray flux and its ability to capture large segments of diffraction patterns. The specimens that have been examined were real engineering components, mechanically deformed specimens and thermally treated specimens, ranging from dynamic in-situ measurements to ex-situ materials engineering. For the real engineering components, a wedge coupon from the trailing edge of a Ti64 wide fan blade and a turbine combustion casing were examined. Among the mechanically deformed specimens that have been measured were shot-peened steel plates, elasto-plastically bent bars of Mg alloy and cold expanded Al disks. Amongst the thermally deformed specimens, laser-formed steel plates, thermal spray coatings, a manual inert gas weld of Al plates, a friction stir weld of Al plates and Ni tubes and a quenched Ni superalloy cylinder used for strain tomography were studied. In-situ loading experiments have also been carried out, such as experiments on pointwise mapping of grain orientation and strain using the 3DXRD microscope at the ESRF and in-situ loading experiments on titanium alloy, rheo-diecast and high pressure diecast Mg alloy, IN718 Ni-base superalloy and Al2024 aluminium alloy. Experimental results from X-Ray diffraction and strain tomography were used to achieve a better understanding of the material properties. Some results were compared with polycrystal Finite Element model predictions. Amongst the most prominent research achievements are the development on the HEXameter laboratory instrument, including: (i) the development of special collimation systems for the detectors and the source tube; (ii) the development of a twin-detector setup (that allows for simultaneous determination of strain in two mutually orthogonal directions); (iii) improved alignment procedures for better performance; and (iv) the adaptation of instrumentation for efficient scanning of both large and small components, that included choosing and adapting translation devices, programming of the translation system and designing sample mounting procedures. In this research several approaches to data treatment were investigated. Quantitative phase analysis, single peak fitting (using custom Matlab routines and GSAS) and full pattern fitting (with individual pattern data refined by GSAS and batch refinement done by invoking GSAS via a Matlab routine) were applied. Different Matlab routines were written for specific experimental setups; and various analysis methods were selected and used for refinement depending on the requirements of the measurement results interpretation. 16 papers were published, ensuring that the results of this thesis are readily available to other researchers in the field.
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Etude et modélisation de l'effet du revenu sur les évolutions des microstructures, du comportement thermomécanique et des contraintes résiduelles de trempe / Study and modelling of the influence of the tempering process on the evolutions of the microstructure, thermomechanical behaviour and quenching residual stressWang, Yunning 10 October 2006 (has links)
La relaxation des contraintes résiduelles de trempe au cours du revenu dépend fortement des évolutions des microstructures et du comportement thermomécanique. Ainsi, la prévision de l’évolution des contraintes résiduelles nécessite le couplage entre les calculs des champs de température, des transformations de phases, des contraintes et des déformations au cours du traitement. Dans ce travail, nous avons développé un modèle métallurgique pour décrire les cinétiques de précipitation au cour du revenu : la germination, la croissance et la coalescence (ou dissolution) du carbure epsilon et de la cémentite. Ce modèle permet de calculer les évolutions de la composition chimique de la matrice, du type, des distributions de taille des précipités lors du revenu de la martensite d’aciers faiblement alliés. Dans une deuxième étape, nous avons développé un modèle thermomécanique permettant de prédire l’évolution de la contrainte d’écoulement de la martensite revenue, basé sur les évolutions des paramètres microstructuraux obtenus par le modèle métallurgique. Le modèle thermomécanique prend en compte les différents mécanismes de durcissement (durcissement par solution solide, durcissement par les précipités et durcissement par dislocations), et l’effet de la température de déformation. Une validation expérimentale de ces modèles a été menée dans le cas de l’acier 80MnCr5 en s’appuyant sur des résultas obtenus par microscopie électronique à transmission et dilatométrie thermomécanique. Les modèles métallurgique et thermomécanique ont finalement été introduits dans le logiciel de calcul par éléments finis ZeBuLoN pour simuler l’évolution des contraintes internes lors de la trempe et du revenu. Une première analyse de la relaxation des contraintes au cours du revenu a été effectuée. / The relaxation of the residual stress during the tempering process is strongly related to the evolutions of the microstructure and thermomechanical properties. Thus, the simulation of the evolution of residual stresses requests the coupling of the temperature field, the phase transformations and the stress and strain evolutions all along the process. In this work, firstly, a metallurgical model has been developed to describe the tempering kinetics: nucleation, growth (or dissolution) and coarsening of the epsilon carbide and the cementite. This model allows to predict the evolutions of the matrix composition, the type, size and distribution of the precipitates during the tempering of martensite for low and middle alloyed steels. Secondly, based on the microstructure parameters calculated by the metallurgical model, a thermomechanical model has been also developed to predict the evolution of the flow stress of tempered martensite. The thermomechanical model not only takes into account the different hardening mechanisms (solution hardening, precipitate hardening and the dislocation hardening), but also the effect of deformation temperature. An experimental validation of the two models has been performed for a 80MnCr5 steel using the results obtained by electron transmission microscopy and thermomechanical dilatometry. Finally, the metallurgical model and the thermomechanical model have been implemented into the finite element calculation software ZeBuLoN to simulate the evolution of internal stress during the quenching and tempering process. A first analysis of the stress relaxation during tempering has been performed.
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Influence des propriétés morphologiques et mécaniques des barrières thermiques sur la fissuration interfaciale induite par perçage laser impulsionnel / Influence of morphological and mechanical properties of thermal barrier coating on interfacial delamination induced by impulsionnal laser drillingGuinard, Caroline 15 December 2016 (has links)
De nombreuses pièces aéronautiques telles que les chambres de combustion sont percées d'une multitudes de trous de refroidissement. Ce perçage, généralement effectué par un laser de puissance peut induire des endommagements dans la matière percée. Sur les systèmes barrières thermiques, une fissuration pouvant conduire à l'écaillage de la barrière thermique se produit à l'interface céramique/sous-couche lors du perçage laser. Cette thèse présente des éléments de compréhension des phénomènes de formation et de propagation de la fissure interfaciale. Pour cela, un protocole spécifique a été utilisé, consistant en la réalisation de perçage interrompus. De plus, afin de comprendre l'influence de la sous-couche et de l'interface sous-couche / céramique sur cette fissuration, une large gamme d'échantillons aux propriétés morphologiques et mécaniques bien distincts ont été sélectionnés. Pour cela, la sous-couche a été modifiée par la variation des paramètres de projection, du procédé de projection ainsi que par des post traitements sur la sous-couche. Le lien entre ces interfaces et les endommagements liés au perçage laser sont présentés au travers d'observations 2D et 3D, destructives et non destructives ainsi que par l'étude des modifications des contraintes résiduelles avant et après perçage laser pour différentes barrières thermiques. De manière a réduire encore la fissure interfaciale, plusieurs stratégies de perçage sont étudiées via la variation de la puissance laser entre les différentes impulsions laser nécessaires pour percer le matériau multicouches. Les résultats obtenus offrent des perspectives intéressantes pour améliorer la résistance à la fissuration des pièces aéronautiques. / Many aircraft engines parts such as combustion chambers are drilled with numerous cooling holes. These holes, generally performed by a high power laser machine can induce damages in the part materials. On thermal barrier coatings systems, cracking can lead to spalling of the coating occurs at the ceramic / bond-coat layer interface during laser drilling. This thesis presents elements of understanding of the interfacial crack formation end propagation phenomena. In this purpose, a specific protocol was used, consisting of interrupted drilling process. Moreover, in order to understand the influence of the bond coat and the ceramic / bond coat interface on cracking, a wide range of samples with specific morphological and mechanical properties were selected. With this in mind, the bond coat was modified by varying spraying parameters, spraying process and also by post treatments on the bond coat. The link between these interfaces and the associated damages due to laser drilling are presented through 2D and 3D observations, destructive and non-destructive, as well as the study of residual stress modification before and after laser drilling for several thermal barrier coatings systems. For further reducing the interfacial crack, several drilling strategies are considered through the laser peak power variation between the different laser pulses needed to drill through the multi-layer material. The results offer interesting perspectives for improving crack resistance of aeronautical engines parts.
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Développement et amélioration de structures mobiles embarquées dans les interconnexions des puces microélectroniques : Etude du contact mécanique et électrique / Development and improvement of embedded structures in microelectronic chips : Study of mechanical and electrical contactOrellana, Sebastian 11 October 2016 (has links)
Ces dernières années la miniaturisation des microsystèmes atteint la limite physique de leur développement. Ainsi une de voie d’innovation dans l’industrie des semiconducteurs est l’intégration des fonctionnalités supplémentaires au sein des composants déjà existants.Le projet consiste à intégrer, dans une même couche métallique d’interconnexion CMOS, un MEMS capable, par sa rotation, d’établir un contact électrique.Les verrous se situent dans la libération des parties mobiles par dissolution de l’oxyde environnant (déformation hors plan sous l’effet des contraintes résiduelles, stiction, présence de résidus qui empêchent le contact), dans l’actionnement (densité de courant, répétabilité, durabilité, fiabilité) ainsi que, la capacité d’établir un vrai contact électrique à faible résistance (aire réelle / apparente du contact des surfaces rugueuses, pollution du contact).Le travail réalisé a porté sur la conception, le design et la simulation des microsystèmes afin de surmonter ces difficultés et / ou d’étudier le comportement et mesurer les effets. / In recent years the miniaturization of microsystems is reaching the physical limit of its development. Thus, a path of innovation in the semiconductor industry is additional functionalities in existing components.The project consists to integrate a MEMS, within the same metal interconnect of CMOS layer which, by rotating, can establish an electrical contact.The obstacles are in the release of the moving parts by dissolution of the surrounding oxide (out of plane deformation under the effect of residual stress, stiction, residues which prevent contact), in the actuation (current density repeatability, durability, reliability) and, for ohmic switches, the ability to establish a real electrical contact with low resistance (real / apparent area of contact with rough surfaces, contact pollution).The work carried out has focused on conception (design) and simulation of microsystems to overcome these difficulties and / or to study the behavior and measure the effects.
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Comportamento de fadiga e perfis de tensões residuais de cerâmicas odontológicas / Fatigue behavior and residual stress profiles of dental ceramicsFukushima, Karen Akemi 02 March 2015 (has links)
Capítulo 1. Objetivos: Medir e comparar o perfil de tensão residual da cerâmica de recobrimento aplicada sobre infraestruturas em zircônia tetragonal policristalina estabilizada por ítria (Y-TZP), em um compósito de alumina/zircônia (ZTA) e em uma alumina policristalina (AL). Material e Métodos: Os perfis de tensão residual de cada um dos materiais foi medido por meio do método \"hole-drilling\" em discos de 19 mm de diâmetro e 2,2 mm de espessura (0,7 mm de infraestrutura + 1,5 mm de porcelana de cobertura) .Resultados: Os espécimes de AL exibiram tensões de compressão que aumentaram numericamente com a profundidade, enquanto que as tensões compressivas mudaram para tensões de tração no interior das amostras de Y-TZP. As amostras de ZTA exibiram tensões de compressão na superfície, decrescendo com a profundidade até 0,6 mm, tornando-se compressivas novamente próximo à infraestrutura. Conclusão: O ZTA não apresentou tensões de tração em nenhum ponto ao longo da espessura da cerâmica de recobrimento. A AL apresentou um perfil de tensão residual mais favorável, gerado pelas tensões compressivas. A Y-TZP apresentou o perfil mais desfavorável, por apresentar tensões de tração próximo à infraestrutura. Capítulo 2. Objetivos: 1) Comparar os coeficientes de susceptibilidade ao crescimento subcrítico (n), de uma zircônia tetragonal policristalina estabilizada por ítria, obtidos por meio de dois ensaios de fadiga: cíclica e dinâmica. 2) Verificar o efeito da frequência usada no ensaio de fadiga cíclica no tempo de vida característico. Material e Métodos: Espécimes em forma de barras (25 mm x 4 mm x 3 mm) foram confeccionadas de acordo com as recomendações do fabricante. Os ensaios de fadiga dinâmica (n=70) e de fadiga cíclica (n=75) foram realizados por meio de resistência à flexão em quatro pontos para a obtenção dos parâmetros de crescimento de trincas subcrítico (SCG). O ensaio de fadiga cíclica também foi realizado em duas frequências (2 e 10 Hz), utilizando valores de tensão máxima entre 350 e 600 MPa. Todos os espécimes fraturados foram inspecionados em microscópio eletrônico de varredura para que fosse identificada a origem da fratura. Os dados de fadiga dinâmica foram analisados por meio das fórmulas apresentadas na ASTM C 1368-00. Os dados de fadiga cíclica foram analisados por meio da estatística de Weibull e por meio de análise tipo \"General Log Linear Model\". Resultados: A Y-TZP apresentou valores dos parâmetros de SCG obtidos no ensaio de fadiga dinâmica de ?fo = 667 MPa e n = 54. Os parâmetros de Weibull obtidos a partir dos resultados do mesmo ensaio foram de m = 7,9, ?0 = 968,9 MPa e ?5% = 767 MPa. Os parâmetros de Weibull obtidos no ensaio de fadiga cíclica foram estatisticamente semelhantes para as duas frequências utilizadas, o m* foi de 0,17 para 2Hz e de 0,21 10Hz; os tempos de vida característicos (?, em número de ciclos) foram de 1,93 x 106 e 40.768, respectivamente para 2 e 10 Hz. O valor de n obtido na fadiga cíclica foi de 48 e 40, nas frequências de 2 e 10 Hz, respectivamente. Não foi observado o efeito da frequência da aplicação da tensão, do nível de tensão, nem da interação dos dois no tempo de vida da Y-TZP, quando analisados pelo General Log Linear Model. Conclusão: Os coeficientes de susceptibilidade ao crescimento subcrítico (n) obtidos por meio de fadiga cíclica e dinâmica foram semelhantes para a Y-TZP testada. Os extensos intervalos de confiança obtidos nos ensaios de fadiga cíclica indicaram não haver efeito da frequência usado nesse método de fadiga nos tempos de vida característicos da Y-TZP testada. / Chapter 1. Objective: was: to measure and compare the residual stress profile in the veneering ceramic layered on three different polycrystalline ceramic frame-work materials: Y-TZP, alumina polycrystalline (AL) and zirconia toughened alumina (ZTA).Materials and Methods. The stress profile was measured with the hole-drilling method in bilayered disk samples of 19 mm diameter with a 0.7 mm thick Y-TZP, AL or ZTA framework and a 1.5 mm thick layer of the corresponding veneering ceramic. Results: The AL samples exhibited increasing compressive stresses with depth, while compressive stresses switching into interior tensile stresses were measured in Y-TZP samples. ZTA samples exhibited compressive stress at the ceramic surface, decreasing with depth up to 0.6 mm from the surface, and then becoming compressive again near the framework. Conclusions: Y-TZP samples exhibited a less favorable stress profile than those of AL and ZTA samples. Chapter 2. Objectives: 1) To compare the stress corrosion coefficient (n) of a Y-TZP, obtained by two fatigue tests: cyclic and dynamic and 2) Evaluate the effect of frequency used in the cyclic fatigue test in the characteristic lifetime. Methods: Bar shaped specimens (4 mm x 25 mm x 3 mm) were prepared according to the manufacturer\'s recommendations. The dynamic fatigue test (n = 70) and cyclic fatigue (n = 75) were performed by four-point bending to obtain the slow crack growth parameters (n) .The cyclic fatigue test was also conducted in two frequencies (2 and 10Hz), using stress levels between 350 and 600 MPa. All fractured specimens were inspected by SEM so that the origin of the fracture were identified. The dynamic fatigue data were analyzed using the formulas given in ASTM C 1368-00. Cyclic fatigue data were analyzed using Weibull statistics and by the Log General Linear Model. Results: The material showed values of parameters obtained in the SCG assay dynamic fatigue ?fo = 667 and n = 54. The Weibull parameters obtained from the same test results were m = 7.9, ?0 = 968, 9 and ?5% = 767. The Weibull parameters obtained by cyclic fatigue were statistically similar for the two frequencies used, the m* was 0.17 (2 Hz) and 0.21 (10 Hz); characteristic lifetimes (?) were 1.93 x 106 and 40768, respectively. The n value obtained by cyclic fatigue was 48 and 40 at frequencies of 2 and 10 Hz, respectively. There was no effect of the frequency, the stress level or the interaction of the two in the Y-TZP lifetime, when analyzed by General Log Linear Model. Conclusion: The n values obtained by cyclic and dynamic fatigue tests were similar to Y-TZP tested. The extensive confidence intervals obtained in cyclic fatigue tests showed no effect of frequency used this method in fatigue characteristic lifetimes of the Y-TZP tested.
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Simulação, fabricação e caracterização de MEMS para extração de propriedades mecânicas de filmes finos. / Simulation, fabrication and characterization of MEMS for extraction of mechanical properties of thin films.Érick Araujo dos Santos 24 October 2017 (has links)
A concepção deste trabalho está ligada ao desenvolvimento de sistemas microeletromecânicos (MEMS) para RF na faixa de frequências de ondas milimétricas. Dentro deste contexto, o Grupo de Novos Materiais e Dispositivos (GNMD) do Laboratório de Microeletrônica (LME) da Escola Politécnica da Universidade de São Paulo (EPUSP) já fabricou RF MEMS que tiveram resultados bastante promissores. No entanto, para obtenção de melhores resultados, é necessária a otimização eletromecânica destes dispositivos e para isso é necessária a extração de suas propriedades mecânicas. Assim, este trabalho teve como objetivo o desenvolvimento de uma metodologia para extração do módulo de elasticidade e tensão residual em MEMS, através da simulação e fabricação de microestruturas específicas para este fim. As técnicas de nanoindentação, frequência de ressonância, raio de curvatura e M-TEST foram estudadas. As microestruturas fabricadas foram cantileveres e pontes feitas de alumínio e cobre. Foram realizadas simulações no software ANSYS para prever as frequências de ressonância e as tensões de pull-in das estruturas antes de serem fabricadas. O módulo de elasticidade do alumínio extraído através da nanoindentação foi de 75,6 ± 4,1 GPa, e o do cobre extraída através da técnica de frequência de ressonância foi de 123 ± 12 GPa. A tensão residual do cobre foi extraída através da técnica de medição do raio de curvatura e foi de -199±105 MPa. O trabalho está vinculado ao projeto Jovem Pesquisador FAPESP (2011/18167-3). / The approach of this work is linked to the development of microelectromechanical systems (MEMS) for RF in the frequency range of millimeter waves. Within this context, the Group of New Materials and Devices (GNMD) of the Laboratory of Microelectronics (LME) of the Polytechnic School of the University of São Paulo (EPUSP) has already manufactured RF MEMS which have had very promising results. However, to obtain better results, it is necessary the electromechanical optimization of these devices through the extraction of their mechanical properties. Thus, this work has the objective of developing a methodology for the extraction of the Young\'s modulus and residual stress in MEMS, through the simulation and fabrication of specific microstructures for this purpose. The techniques of nanoindentation, resonance frequency, radius of curvature and M-TEST were studied. The fabricated microstructures were cantilevers and bridges in aluminum and copper materials. Simulations were performed in the ANSYS software to predict the resonance frequencies and the pull-in voltages of the structures before they were fabricated. The Young\'s modulus of aluminum extracted through nanoindentation was 75,6 ± 4,1 GPa, the resonance frequency of copper extracted by the technique of the same name was 123 ± 12 GPa and the residual stress of copper was extracted through the technique of measuring the radius of curvature and was -199±105 MPa. The work is linked to the project Jovem Pesquisador from FAPESP (2011/18167-3).
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Medição de tensões residuais em filmes finos durante o processo de deposição. / Thin films residual stress measurement during deposition process.Lagatta, Cristiano Fernandes 28 July 2011 (has links)
Neste trabalho foram realizadas algumas deposições de filmes de Nitreto de Titânio sobre substrato de aço inoxidável. Foi utilizado o processo conhecido como triodo magnetron sputtering. Os parâmetros de deposição foram mantidos entre as deposições, exceto pela voltagem de bias no substrato, que foi variada de uma deposição para outra. Medições in-situ das tensões residuais no filme depositado foram realizadas. As medições foram feitas através do método da curvatura do substrato, utilizando-se um sensor capacitivo posicionado dentro da câmara de deposição. Embora o dispositivo não tenha sido capaz de quantificar os valores de tensão, foi possível identificar a natureza das mesmas, indicando se elas são de caráter trativo ou compressivo. Comprovou-se a possibilidade do uso de sistemas capacitivos para medições em sputtering. Observou-se que os filmes depositados apresentaram tensões de caráter trativo durante as deposições. / In this work, a series of depositions of titanium nitride thin films was conducted in a triode unbalanced magnetron sputtering chamber. Similar parameters were selected during each deposition, except for the substrate bias voltage, which was different for every deposition. An in-situ measurement of film residual stresses was carried out as the depositions proceeded. This measurement was based on substrate curvature, which was assessed by a home-built capacitive sensor positioned inside the sputtering chamber. Although the measurement device was not able to quantify the stress values, it was possible to identify if they were tensile or compressive. It was proved the possibility of using capacitive measurement devices in sputtering processes. It was possible to observe that the films underwent tensile stresses during the deposition.
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Simulação, fabricação e caracterização de MEMS para extração de propriedades mecânicas de filmes finos. / Simulation, fabrication and characterization of MEMS for extraction of mechanical properties of thin films.Santos, Érick Araujo dos 24 October 2017 (has links)
A concepção deste trabalho está ligada ao desenvolvimento de sistemas microeletromecânicos (MEMS) para RF na faixa de frequências de ondas milimétricas. Dentro deste contexto, o Grupo de Novos Materiais e Dispositivos (GNMD) do Laboratório de Microeletrônica (LME) da Escola Politécnica da Universidade de São Paulo (EPUSP) já fabricou RF MEMS que tiveram resultados bastante promissores. No entanto, para obtenção de melhores resultados, é necessária a otimização eletromecânica destes dispositivos e para isso é necessária a extração de suas propriedades mecânicas. Assim, este trabalho teve como objetivo o desenvolvimento de uma metodologia para extração do módulo de elasticidade e tensão residual em MEMS, através da simulação e fabricação de microestruturas específicas para este fim. As técnicas de nanoindentação, frequência de ressonância, raio de curvatura e M-TEST foram estudadas. As microestruturas fabricadas foram cantileveres e pontes feitas de alumínio e cobre. Foram realizadas simulações no software ANSYS para prever as frequências de ressonância e as tensões de pull-in das estruturas antes de serem fabricadas. O módulo de elasticidade do alumínio extraído através da nanoindentação foi de 75,6 ± 4,1 GPa, e o do cobre extraída através da técnica de frequência de ressonância foi de 123 ± 12 GPa. A tensão residual do cobre foi extraída através da técnica de medição do raio de curvatura e foi de -199±105 MPa. O trabalho está vinculado ao projeto Jovem Pesquisador FAPESP (2011/18167-3). / The approach of this work is linked to the development of microelectromechanical systems (MEMS) for RF in the frequency range of millimeter waves. Within this context, the Group of New Materials and Devices (GNMD) of the Laboratory of Microelectronics (LME) of the Polytechnic School of the University of São Paulo (EPUSP) has already manufactured RF MEMS which have had very promising results. However, to obtain better results, it is necessary the electromechanical optimization of these devices through the extraction of their mechanical properties. Thus, this work has the objective of developing a methodology for the extraction of the Young\'s modulus and residual stress in MEMS, through the simulation and fabrication of specific microstructures for this purpose. The techniques of nanoindentation, resonance frequency, radius of curvature and M-TEST were studied. The fabricated microstructures were cantilevers and bridges in aluminum and copper materials. Simulations were performed in the ANSYS software to predict the resonance frequencies and the pull-in voltages of the structures before they were fabricated. The Young\'s modulus of aluminum extracted through nanoindentation was 75,6 ± 4,1 GPa, the resonance frequency of copper extracted by the technique of the same name was 123 ± 12 GPa and the residual stress of copper was extracted through the technique of measuring the radius of curvature and was -199±105 MPa. The work is linked to the project Jovem Pesquisador from FAPESP (2011/18167-3).
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