Lactec / O presente trabalho tem por objetivo principal estudar o comportamento à erosão a quente de revestimentos cerâmicos YSZ (Yttria Stabilized Zirconia) depositados por aspersão térmica a plasma. Os revestimentos YSZ, cuja função é diminuir a transferência de calor em componentes submetidos à elevadas temperaturas, são depositados sobre uma camada de revestimento metálico de NiCrAlY (níquel, cromo, alumínio e ítria), com a função de proteger contra a oxidação. A união destes revestimentos formam o revestimento do tipo TBC (Thermal Barrier Coating), normalmente aplicado para a proteção de componentes de turbinas a gás contra a ação da elevada temperatura e oxidação do ambiente. Além das altas temperaturas esses revestimentos também podem ser submetidos ao impacto de partículas sólidas, oriundas da poeira, que passam pelos filtros, ou dos estágios de compressão ou câmara de combustão, vinda da queima do combustível, ocasionando o desgaste do revestimento. Para entender o fenômeno e suas implicações nos revestimentos YSZ, avaliou-se a resistência destes revestimentos frente ao desgaste erosivo à altas temperaturas, avaliando-se a influência de sua composição química, ângulo de incidência e temperatura. Os ensaios de erosão foram realizados entre 700 e 900ºC, sob diferentes ângulos de incidência entre 30º e 90º. Em todos os testes, a velocidade de impacto, fluxo de partículas e o abrasivo foram mantidos constantes, sendo que o teste teve embasamento na norma ASTM G 76. A superfície desgastada dos revestimentos foram avaliadas por meio de perfilometria ótica e microscopia eletrônica de varredura. Com as diferentes ligas comerciais, constatou-se que o revestimento YSZ 7Y 1,7Hf, menos poroso e mais aderente obteve uma maior resistência ao desgaste. O mecanismo de desgaste observado foi a partir da quebra e destacamento individual das lamelas do revestimento devido a intersecção de trincas. De forma geral, observou-se uma redução da perda de massa dos revestimentos com o aumento da temperatura, dentro das temperaturas utilizadas no trabalho. A taxa de erosão demonstrou ser diretamente proporcional aos perfis de rugosidade, dessa maneira uma diminuição da taxa de erosão acarreta uma diminuição da rugosidade do revestimento. Quanto ao efeito do ângulo de impacto, observou-se que o aumento do ângulo de incidência das partículas propiciou uma maior taxa de erosão. / The present work has the main objective to study the behavior of YSZ (Yttria Stabilized Zirconia) deposited by thermal spraying exposed to solid particle hot erosion. The YSZ coatings, whose function is to decrease the heat transfer, are deposited over a metal coating layer of NiCrAlY (nickel, chromium, aluminum and yttrium), which has the function to protect against oxidation. The union of these layers form the coating of the type TBC (Thermal Barrier Coating), generally used for protection of gas turbine components against the action of elevated temperature and oxidizing environment. In addition to the high temperatures, these coatings can also be subjected to the impact of solid particles, that comes with the dust that pass through the filters, or that comes from the compression stages or combustion chamber and that comes from the fuel burns, leading to the wear of the coating. In order to understand the phenomenon and the implications of this for the application of coatings, it was evaluated the resistance of these coatings facing the erosive wear at high temperatures, evaluating the influence of the chemical composition, impingement angles and the temperature used. The tests were performed from 700 to 900 ºC, under different impingement angles of 30 º and 90 º. In all tests, the impact velocity, the flow and the abrasive particles were maintained constant, and the test was based in the ASTM G 76. The worn surfaces of the coatings were studied by optical profilometry and scanning electron microscopy. With the different commercial alloys, it was found that the YSZ 7Y 1,7Hf coating with lower porosity and more adherent coating obtained a higher wear resistance. The mechanism of mass loss observed was by individual rupture and detachment of the lamellae from the coating by the intersection of cracks. A reduction in the mass loss of the coatings was observed with the increasing of the temperature, within the temperatures used in the work. For the roughness of the coatings, the erosion rate was shown to be directly proportional, wherein with the decrease in erosion rate there was a reduction in the roughness of the coatings. As for the effect of the angle of impingement, it was observed that with the increase of the angle of impingement higher was the erosion rate.

Lactec / O presente trabalho tem por objetivo principal estudar o comportamento à erosão a quente de revestimentos cerâmicos YSZ (Yttria Stabilized Zirconia) depositados por aspersão térmica a plasma. Os revestimentos YSZ, cuja função é diminuir a transferência de calor em componentes submetidos à elevadas temperaturas, são depositados sobre uma camada de revestimento metálico de NiCrAlY (níquel, cromo, alumínio e ítria), com a função de proteger contra a oxidação. A união destes revestimentos formam o revestimento do tipo TBC (Thermal Barrier Coating), normalmente aplicado para a proteção de componentes de turbinas a gás contra a ação da elevada temperatura e oxidação do ambiente. Além das altas temperaturas esses revestimentos também podem ser submetidos ao impacto de partículas sólidas, oriundas da poeira, que passam pelos filtros, ou dos estágios de compressão ou câmara de combustão, vinda da queima do combustível, ocasionando o desgaste do revestimento. Para entender o fenômeno e suas implicações nos revestimentos YSZ, avaliou-se a resistência destes revestimentos frente ao desgaste erosivo à altas temperaturas, avaliando-se a influência de sua composição química, ângulo de incidência e temperatura. Os ensaios de erosão foram realizados entre 700 e 900ºC, sob diferentes ângulos de incidência entre 30º e 90º. Em todos os testes, a velocidade de impacto, fluxo de partículas e o abrasivo foram mantidos constantes, sendo que o teste teve embasamento na norma ASTM G 76. A superfície desgastada dos revestimentos foram avaliadas por meio de perfilometria ótica e microscopia eletrônica de varredura. Com as diferentes ligas comerciais, constatou-se que o revestimento YSZ 7Y 1,7Hf, menos poroso e mais aderente obteve uma maior resistência ao desgaste. O mecanismo de desgaste observado foi a partir da quebra e destacamento individual das lamelas do revestimento devido a intersecção de trincas. De forma geral, observou-se uma redução da perda de massa dos revestimentos com o aumento da temperatura, dentro das temperaturas utilizadas no trabalho. A taxa de erosão demonstrou ser diretamente proporcional aos perfis de rugosidade, dessa maneira uma diminuição da taxa de erosão acarreta uma diminuição da rugosidade do revestimento. Quanto ao efeito do ângulo de impacto, observou-se que o aumento do ângulo de incidência das partículas propiciou uma maior taxa de erosão. / The present work has the main objective to study the behavior of YSZ (Yttria Stabilized Zirconia) deposited by thermal spraying exposed to solid particle hot erosion. The YSZ coatings, whose function is to decrease the heat transfer, are deposited over a metal coating layer of NiCrAlY (nickel, chromium, aluminum and yttrium), which has the function to protect against oxidation. The union of these layers form the coating of the type TBC (Thermal Barrier Coating), generally used for protection of gas turbine components against the action of elevated temperature and oxidizing environment. In addition to the high temperatures, these coatings can also be subjected to the impact of solid particles, that comes with the dust that pass through the filters, or that comes from the compression stages or combustion chamber and that comes from the fuel burns, leading to the wear of the coating. In order to understand the phenomenon and the implications of this for the application of coatings, it was evaluated the resistance of these coatings facing the erosive wear at high temperatures, evaluating the influence of the chemical composition, impingement angles and the temperature used. The tests were performed from 700 to 900 ºC, under different impingement angles of 30 º and 90 º. In all tests, the impact velocity, the flow and the abrasive particles were maintained constant, and the test was based in the ASTM G 76. The worn surfaces of the coatings were studied by optical profilometry and scanning electron microscopy. With the different commercial alloys, it was found that the YSZ 7Y 1,7Hf coating with lower porosity and more adherent coating obtained a higher wear resistance. The mechanism of mass loss observed was by individual rupture and detachment of the lamellae from the coating by the intersection of cracks. A reduction in the mass loss of the coatings was observed with the increasing of the temperature, within the temperatures used in the work. For the roughness of the coatings, the erosion rate was shown to be directly proportional, wherein with the decrease in erosion rate there was a reduction in the roughness of the coatings. As for the effect of the angle of impingement, it was observed that with the increase of the angle of impingement higher was the erosion rate.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-08-04T12:41:31Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação de Mestrado - Natasha Lopes Gomes.pdf: 9410241 bytes, checksum: 569cb64525645737ca47e38f379de72c (MD5) / Made available in DSpace on 2016-08-04T12:41:31Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação de Mestrado - Natasha Lopes Gomes.pdf: 9410241 bytes, checksum: 569cb64525645737ca47e38f379de72c (MD5) Previous issue date: 2016-02-26 / FACEPE / A indústria aeroespacial é um setor que contribui significativamente para o desenvolvimento econômico e social de alguns países. A confiabilidade e a disponibilidade de seus equipamentos são uma preocupação constante, uma vez que estes operam a temperaturas elevadas. Dentre os equipamentos que mais falham prematuramente devido à temperatura, destacam-se os bocais de exaustão das turbinas a gás, compostos por um conjunto de ligas à base de níquel ou à base de cobalto. No entanto, os fabricantes de turbinas tem demonstrado um maior interesse no uso de compósitos cerâmicos para revestimento nas seções quentes, devido sua maior capacidade de suportar altas temperaturas e exigência de menor refrigeração do ar. Mas a fragilidade intrínseca das cerâmicas é ainda um fator limitante para o uso destes materiais em estruturas mecânicas e aplicações industriais. Para reduzir fragilidade e aumentar resistência mecânica e tenacidade, normalmente as cerâmicas são reforçadas com incorporação de aditivos. Estudos vêm sendo realizados acerca da utilização da zircônia incorporada com outros óxidos, pois em comparação com outros cerâmicos, a zircônia tem propriedades mecânicas superiores, tais como alta resistência mecânica, estabilidade química e boa tenacidade à fratura. Neste trabalho foram produzidos compósitos cerâmicos zircônia-titânia (ZrO2-TiO2) reforçados com um óxido de terra rara, lantânio (La2O3), variando o teor de TiO2 em 5%, 10%, 15% e 20% e o teor de La2O3 em 5%, 7% e 10%. Os compósitos foram produzidos por processo termomecânico e sinterizados à 1385°C. Posteriormente, foram caracterizados quanto à estrutura, microestrutura e propriedades mecânicas através de difração de raios X, densidade relativa, microscopia óptica, microscopia eletrônica de varredura, espectroscopia de energia dispersiva e microdureza Vickers. A microestrutura do material sinterizado revelou uma boa homogeneidade em distribuição e tamanho de partículas, e a microdureza Vickers mostrou que o compósito com 15% de TiO2 e 10% de La2O3 obteve um melhor resultado, indicando que este possui boas propriedades físicas que apontam para uma possível aplicabilidade. No entanto, é necessário avaliar outras propriedades mecânicas a fim de garantir sua utilização como revestimento cerâmico de exaustores de turbinas a gás aeroespaciais. / The aerospace industry is a sector that contributes significantly to the economic and social development of some countries. The reliability and availability of your equipment is a constant concern, since they operate at high temperatures. Among the equipment more fail prematurely due to temperature, we highlight the exhaust nozzles of gas turbines, comprising a set of nickel based alloys or cobalt-based. However, turbine manufacturers have shown an increased interest in the use of ceramic composite coating on hot sections due to their greater ability to withstand high temperatures and requiring less cooling air. But the intrinsic brittleness of ceramics is still a limiting factor for the use of these materials in mechanical and industrial applications structures. To reduce brittleness and increase strength and toughness, typically ceramics are reinforced by incorporation of additives. Studies have been conducted on the use of zirconia incorporated with other oxides, as compared to other ceramic, zirconia has superior mechanical properties such as high mechanical strength, chemical stability and good fracture toughness. In this work we were produced composite ceramic zirconia-titania (ZrO2-TiO2) reinforced with a rare earth oxide, lanthanum (La2O3), varying the TiO2 content of 5%, 10%, 15% and 20%, and the La2O3 content 5%, 7% and 10%. The composites were produced by thermomechanical process and sintered at 1385 ° C. Later, they were characterized as to structure, microstructure and mechanical properties through X-ray diffraction, relative density, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and microhardness. The microstructure of the sintered material showed a good homogeneous distribution and particle size, and Vickers microhardness showed that the composite with 15% TiO2 and 10% La2O3 obtained best results, indicating that it has good physical properties which indicate a possible applicability. However, it is necessary to assess other mechanical properties to ensure their use as ceramic coating aerospace gas turbine exhaust.

Novel inorganic-organic hybrid materials made previously in the laboratory have utilized acids catalysts such as HCI, acetic acid, toluene sulfonic acid and polystyrene sulfonic acid to catalyze the sol-gel reaction. The sol-gel reaction can also be catalyzed under near neutral (i.e. 5 < pH < 7) and basic conditions. The effects of synthesizing hybrid materials under near basic and basic conditions has not been studied. Attempts to synthesize hybrid materials from polytetramethylene oxide (PTMO) end functionalized with triethoxy silyl groups and, tetraethylorthosilicate (TEOS) under basic conditions met with only partial success. The films obtained had low mechanical stability. This was attributed to the low reactivity of the triethoxy species under neutral and basic conditions. In contrast, films with good mechanical stability were obtained when the TEOS was replaced with titanium tetraisopropoxide (TIOPR). The microstructure of the TIOPRlPTMO hybrid synthesized under near neutral conditions was generally similar to the acid catalyzed PTMOffIOPR hybrids. / Ph. D.

Les travaux présentés dans ce manuscrit visent à étudier la propagation d'un défaut interfacial de géométrie connue soumis à un cisaillement macroscopique à partir d'une méthodologie expérimentale développée durant la thèse qui consiste à i) élaborer un système revêtu céramique/métal dont la morphologie d'interface est contrôlée, ii) introduire un défaut d'interface par la technique de choc laser, iii) soumettre le système revêtu pré-fissuré à un cisaillement macroscopique grâce à une machine de fatigue biaxiale coplanaire et iv) mesurer in situ l'évolution de ce défaut. Le système revêtu subit donc une sollicitation dynamique par la technique de choc laser et quasi-statique par les essais biaxiaux. La morphologie d'interface, paramètre influant sur la fissuration, est également étudiée. Un dépôt d'alumine pure est directement projeté par plasma sur un substrat métallique, un superalliage base cobalt Haynes 188 et un acier inoxydable 304L, sans sous-couche.Un premier travail d'analyse du défaut introduit par choc laser en fonction des paramètres laser et de la morphologie d'interface a tout d'abord été réalisé. Le défaut d'interface résultant se caractérise par une zone délaminée circulaire de quelques millimètres de diamètre et d'une cloque formée par la couche de céramique de quelques dizaines de micromètres de hauteur. Ces dimensions caractéristiques ont été mesurées à partir de techniques d'observation non destructives : profilométrie 3D, observation optique et thermographie infrarouge. La fissuration par choc laser a été étudiée par éléments finis grâce à un modèle de type contact cohésif pour l'interface.La propagation du défaut soumis à un cisaillement macroscopique a été caractérisée expérimentalement grâce aux observations optiques et à la technique de stéréo-corrélation d'images. L'analyse par élément finis du problème a permis d'accéder aux modes de sollicitation le long du front de fissure et de donner une première explication quant aux formes délaminées obtenues expérimentalement. Cette analyse s'appuie sur un modèle de zone cohésive dont les conditions aux limites imposées sont déterminées à l'aide des mesures de déplacement obtenues par corrélation d'images. En particulier, il a été mis en évidence que l’ouverture du front de fissure (mode I), induit par le flambage de la couche et par le chargement macroscopique, favorise la propagation du délaminage qui reste pilotée essentiellement par le cisaillement local (mode II et III). L'influence du cisaillement macroscopique dans le plan de la couche déposée sur la propagation du délaminage interfacial a ensuite été étudiée à partir de trois cas de chargement. Une analyse par éléments finis basée sur la mécanique linéaire de la rupture dans un matériau homogène a permis de déterminer l'influence du cisaillement macroscopique sur le chargement local le long du front de fissure. / The work presented in this manuscript aims to investigate the growth of an interfacial flaw, whose geometry is known, under macroscopic shear loading. An experimental methodology is thus developed in which i) a ceramic/metal coated system with controlled interface roughness is processed, ii) an interfacial flaw is introduced using the laser shock technique, iii) a macroscopic shear loading is applied on the coated system using a biaxial in-plane testing device and iv) interfacial crack growth and buckling are measured in situ. Hence, both dynamic and quasi-static loadings are applied on the coated system by respectively the laser shock technique and biaxial testing. The interface roughness, which affects the crack growth, is also considered in the study. A pure alumina coating is deposited by air plasma spraying on a metallic substrate, polycrystalline cobalt base superalloy Haynes 188 and stainless steel 304L substrates, with no bond coat.First, the flaw resulting from the propagation of a laser shock wave has been analyzed according to the laser parameters and the interface roughness. An interfacial flaw is characterized by a circular delamination with a diameter of a few millimeters and a circular blister with a height of a few tens of micrometers. These characteristic dimensions have been measured thanks to non destructive techniques: 3D profilometry and image analysis based on optical observations and infrared thermography. A finite element analysis has been carried out to investigate the crack behavior under laser shock wave propagation using a cohesive contact to account for the interface behavior.The interfacial flaw growth under macroscopic shear loading has been characterized with optical observations and the digital image stereo-correlation technique. The related finite element analysis enabled to identify the local loading along the crack front and gave a first explanation about the shapes of the delaminated area observed experimentally. This analysis relies on a cohesive zone model whose applied boundary conditions are established from the displacements measured by digital image correlation technique. By this way, the delamination growth was revealed to be mostly driven by local shear (mode II and III) and the crack opening (mode I), induced by the buckling of the deposited layer and the macroscopic shear, makes the delamination growth easier. Finally, the influence of the macroscopic shear loading on the interfacial delamination has been studied from three different macroscopic shear loadings. The finite element analysis based on linear elastic fracture mechanics in a homogenous material has allowed to study the influence of the macroscopic shear loading on the local loading along the crack front.

Made available in DSpace on 2016-12-08T17:19:26Z (GMT). No. of bitstreams: 1 Franciele Cunico.pdf: 3433679 bytes, checksum: d1b2f4bdf3c2cb1319aec0d878accf90 (MD5) Previous issue date: 2015-08-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The search for different alternatives for using solid waste contributes to effective sustainable development of industries and the generation of new consumer goods. Under this scenario this paper proposes an alternative to the use of exhaust dust generated in the in the green sand molding and demolding process in the foundry industry, bringing alternative uses for this by-product in more noble applications such as ceramic coating. The ceramic industry has assumed the role of consumer-products generated by industries, especially the existence of some similarity between the composition of by-products and raw materials used in the industry. This study aimed to show the effect of exhaust dust addition in a ceramic matrix for development of ceramic coatings. A preliminary study was performed which determined the parameters for use in a Design of Experiments model. The raw materials used were characterized by Scanning Electron Microscopy, X-ray diffraction, X-Ray Fluorescence, grain size, pycnometry density, Loss Fire, Differential Scanning Calorimetry and thermal gravimetric analysis. In addition, the variables used in the statistical model and its respective upper and lower limits have been defined in the preliminary study too. In order to obtain better efficiency of the data, a factorial project with 3³ Statistic software for the analysis of the results was performed. Three factors have been selected for the project, and for each factor three levels were chosen, with residue content (0%, 20% and 40%), compacting pressure (10MPa, 30MPa and 50MPa) and sintering temperature (1000°C, 1100°C and 1200°C ). Cylindrical specimens were made to determine the technological and mechanical properties and rectangular specimens for the three-point bending test. In order to achieve reliability of the experimental data using the average values, a replica of the experiment was carried out. The results confirmed the feasibility of using the residue in the ceramic body and it show effectively in the interaction between the variables and the importance of controlling the fire temperature, the amount of waste used, and the compaction pressure. / A busca por alternativas para o uso de resíduos sólidos contribui para o efetivo desenvolvimento sustentável das indústrias e a geração de novos bens de consumo. Dentro deste cenário este trabalho propõe uma alternativa para uso do pó de exaustão gerado no processo de moldagem e desmoldagem em areia a verde na indústria de fundição, trazendo alternativas de uso deste subproduto em aplicações mais nobres como o revestimento cerâmico. A indústria cerâmica já assumiu o papel de consumidor de subprodutos gerados pelas indústrias, principalmente pela existência de alguma similaridade entre a composição dos subprodutos e das matérias-primas empregada no setor. Este estudo procurou mostrar o efeito da adição deste pó de exaustão em uma matriz cerâmica para desenvolvimento de revestimentos cerâmicos. Foi realizado um estudo preliminar que determinou parâmetros para a utilização em um modelo de Planejamento de Experimentos. As matérias-primas empregadas foram caracterizadas por Microscopia Eletrônica de Varredura, Difratometria de Raios X, Fluorescência de Raios X, Granulometria, Densidade picnométrica, Perda ao Fogo, Análise Térmica Diferencial e Termogravimétrica. As variáveis utilizadas no modelo estatístico e seus respectivos limites inferiores e superiores, foram definidos no estudo preliminar. Para obter uma melhor eficiência dos dados obtidos foi realizado o projeto fatorial 33 com software Statistic, para a análise dos resultados. Foram selecionados três fatores para o projeto, e para cada fator três níveis, sendo teor de resíduo (0%, 20% e 40%), pressão de compactação (10MPa, 30MPa e 50MPa) e temperatura de sinterização (1000ºC, 1100ºC e 1200ºC). Foram confeccionados corpos de prova cilíndricos para determinar as propriedades tecnológicas e retangulares para ensaio mecânico de resistência a flexão em três pontos. Para atender com confiabilidade os dados experimentais com o uso dos valores médios, foi realizado uma réplica do experimento. Os resultados confirmaram a viabilidade do uso do resíduo na formulação da massa cerâmica e mostraram efetivamente a interação entre as variáveis e a importância do controle da temperatura de queima, a quantidade de resíduo utilizada e a pressão de compactação.

Submitted by Haroudo Xavier Filho (haroudo.xavierfo@ufpe.br) on 2016-04-01T18:23:34Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese Juliana Carvalho da Silva UFPE.pdf: 7095359 bytes, checksum: d445a956305aec4d1e8bc5f1753f949b (MD5) / Made available in DSpace on 2016-04-01T18:23:34Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese Juliana Carvalho da Silva UFPE.pdf: 7095359 bytes, checksum: d445a956305aec4d1e8bc5f1753f949b (MD5) Previous issue date: 2015-07-31 / CAPES / O petróleo, por sua relevância na economia global, demanda um volume crescente de pesquisas no setor e com isso a necessidade do uso de materiais resistentes à ambientes agressivos como é o caso do petróleo cru, gerando procedimentos eficazes e seguros que minimizem impactos ao meio ambiente. Revestimento termicamente aspergido tem sido intensamente utilizado na indústria de petróleo, aeroespacial, elétrica entre outros. Os revestimentos podem ser feitos de metal, cerâmica, vidros e a maioria dos plásticos, e o uso de um compósito adequado pode melhorar a resistência à corrosão em altas temperaturas. As cerâmicas apresentam alto ponto de fusão e são bons isolantes térmicos, porém apresentam baixa tenacidade e fragilidade. Estudos mostram que o uso de óxidos como ZrO2, TiO2 como reforços e de aditivos como óxidos de elementos de terras raras Y2O3, La2O3 podem melhorar a tenacidade da cerâmica à base de alumina. A primeira etapa desta pesquisa teve como objetivo a produção de compósitos cerâmicos à base de alumina, reforçados com 5%, 10%, 15%, 20% e 30% em peso de zircônia estabilizada com óxidos de terras raras La2O3 e Y2O3 variando entre 1 e 7%. A metodologia experimental utilizada consistiu da preparação do compósito cerâmico através da moagem em moinho de bolas, confecção de pastilhas por prensagem uniaxial em prensa hidráulica, e sinterização das amostras que foi realizada nas temperaturas de 13000C, 1350 0C e 14000C por 48h, com posteriores análises de absorção, dureza vickers, microscopia ótica, DRX e MEV. De posse dos resultados, numa segunda etapa a pesquisa foi direcionada à aplicação do compósito cerâmico Al2O3 – ZrO2 reforçado com óxido de ítrio em revestimento de chapas metálicas usadas na fabricação de tanques de armazenamento e transporte de petróleo depositado pelo processo de aspersão térmica a plasma – Atmospheric Plasma Spray, com e sem Bond coat (método de aspersão HVOF – High Velocity Oxi-Fuel), seguidos de ensaios para caracterização e pré-qualificação dos revestimentos como ensaios de adesão, riscamento e MEV. De um modo geral, os valores obtidos nos ensaios de adesão e as imagens de MEV indicam que o compósito estudado é adequado para revestimentos tipo barreira térmica para aplicação em ambientes corrosivos ao petróleo cru. / Oil, for its relevance in the global economy requires a growing body of research in the industry as well as need for the use of materials resistant to harsh environments such as crude oil, generating effective and safe procedures that minimize impacts on the environment . Thermally sprayed coating has been intensively used in the oil industry, aerospace, electrical and more. The coatings may be made of metal, ceramic, glass and most plastics, and the use of an appropriate composite can improve the corrosion resistance at high temperatures. Ceramics have a high melting point and are good insulators, but have low toughness and fragility. Studies show that the use of oxides such as ZrO2, TiO2 as fillers and additives such as oxides of rare earth elements Y2O3, La2O3 can improve the toughness of alumina based ceramic. The first step of this research was aimed at the production of ceramic composites based on alumina reinforced with 5%, 10%, 15%, 20% and 30% zirconia weight stabilized with rare earth La2O3 and Y2O3 oxides ranging from 1 and 7%. The used experimental methodology consisted of the preparation of ceramic composite by grinding in ball mill, preparation of pellets by uniaxial pressing in a hydraulic press, and sintering of the samples was performed at temperatures of 13000C, 13500C and 14000C for 48 hours with subsequent analysis absorption, Vickers hardness, optical microscopy, XRD and SEM. With the results in a second step the research was directed to the application of the ceramic composite Al2O3 - ZrO2 reinforced with yttrium oxide coating of sheet metal used in the manufacture of storage tanks and transport of oil deposited by thermal spray process the plasma - Atmospheric Plasma Spray, with and without bond coat (HVOF spraying method - High Velocity Oxy-Fuel), followed by assays for characterization and classification of pre-testing coatings such as adhesion, scratching and SEM. In general, the values obtained in the adhesion tests and SEM images indicate that the composite studied is suitable for thermal barrier-type coatings in corrosive environments for application to the crude oil.

There is a consistent need in many industries, especially oil and gas, to develop coatings which have higher corrosion resistance and better hardness to extend the lifetime of equipment when it is exposed to hostile environments. Electrodeposition has been a favorable method in the synthesis of metal coatings because of its low cost, convenience, ability to work at low temperatures, and ability to control surface morphology and structure. The inclusion of ceramic nanoparticles in metal matrix composites has previously been investigated as a technique to not only increase the corrosion resistance of the native metal but also to improve the hardness and mechanical properties. Cerium oxide nanoparticles were modified through the grafting of organic groups with increasing hydrophobicity for use in nickel coatings on stainless steel to further improve the corrosion properties while maintaining the hardness of the nanocomposite coatings. The process of modifying the cerium oxide nanoparticles involved the use of aryl diazonium salts and resulted in multilayers forming on the surface of the nanoparticles. Praseodymium oxide nanoparticles were also investigated as additives to nickel coatings, since praseodymium oxide has not yet been studied as a possible corrosion protection enhancement in coatings. These coatings were evaluated for composition and corrosion using many different types of instrumental and electrochemical techniques. With the addition of both the modified cerium oxide nanoparticles and the praseodymium oxide nanoparticles into nickel coatings, an increase in coating hardness and corrosion resistance was observed over pure nickel, resulting in an improvement of the lifetime of these coatings.

The demand for high-performance Radio Frequency (RF) passive devices has been steadily increasing due to the growing complexity and sophistication of wireless communication systems. The Quality factor (Q-factor) is a key parameter for describing the signal losses and the energy efficiency of resonators. Previous studies have been done on the spin coating technique of intermediate coating, which presented some limitations in terms of 3D resonators. In this master thesis, we investigate the development of a intermediate layer using dip coating to enhance the Q-factor, i.e., the performance of RF passive devices. The dip coating method is applied to add a nano ceramic coating to the 3D structure as the intermediate layer between the resonator ceramic substrate and the conductive silver coating. After the fabrication process, the samples are observed under Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) and tested with Vector Network Analysis (VNA). Analysis and calculations are mainly conducted with the software Matlab and Gwyddion. The proposed technique improves the smoothness of the samples by 78.95%, and the Q-factor is tested to have a 20.87% enhancement using VNA. The results demonstrate that the intermediate layer with the dip coating technique significantly improves the performance of RF passive devices by reducing the roughness of the resonator surface. These findings open up new opportunities for the design and development of high-performance RF passive devices in various applications, including wireless communication systems, radar systems, and satellite communication. Further studies can be carried out to reduce defects during fabrication and to stabilize the performance of the silver coating. / Efterfrågan på högpresterande passiva RF-enheter har stadigt ökat på grund av den växande komplexiteten och sofistikeringen hos trådlösa kommunikationssystem. Q-faktorn är en viktig parameter för att beskriva signalförluster och energieffektivitet hos resonatorer. Tidigare studier har gjorts på spin coating-tekniken för intermediära beläggningar, vilket presenterade vissa begränsningar för 3D-resonatorer. I denna masteruppsats undersöker vi utvecklingen av ett intermediärt lager med hjälp av doppbeläggning för att förbättra Q-faktorn, det vill säga prestandan hos passiva RF-enheter. Doppbeläggningstekniken tillämpas för att lägga till en nanokeramisk beläggning på 3D-strukturen som intermediärt lager mellan resonatorns keramiska substrat och den ledande silverbeläggningen. Efter tillverkningsprocessen observeras proverna med SEM och AFM och testas med VNA. Analys och beräkningar utförs främst med programvaran Matlab och Gwyddion. Den föreslagna tekniken förbättrar provernas släthet med 78.95%, och Q-faktorn testas och visar en förbättring med 20.87% med hjälp av VNA. Resultaten visar att det intermediära lagret med doppbeläggningstekniken signifikant förbättrar prestandan hos passiva RF-enheter genom att minska ojämnheten på resonatorns yta. Dessa resultat öppnar upp nya möjligheter för design och utveckling av högpresterande passiva RF-enheter inom olika tillämpningsområden, inklusive trådlösa kommunikationssystem, radarssystem och satellitkommunikation. Ytterligare studier kan genomföras för att minska defekter under tillverkningen och stabilisera prestandan hos silverbeläggningen.

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