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1
Dobedoe, Richard Simon. « Glass-ceramics for ceramic/ceramic and ceramic/metal joining applications ». Thesis, University of Warwick, 1997. http://wrap.warwick.ac.uk/4217/.
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The use of sintered cordierite/enstatite glass-ceramics as interlayers for joining silicon nitride to itself and to metals has been investigated. The role of the additives B203 and P205, which control the dynamics of sintering and crystallisation, has been studied using SEM, XRD and non-isothermal DTA-based measurements of activation energy. The measured activation energies for the crystallisation of μ-cordierite, for compositions with no additives, with B203 only, and with P205 only, did not differ significantly and were in the range 415-460 kJ mol-1. When both B203 and P205 were present this was increased to 503-524 kJ mol-1. The activation energy for α-cordierite formation when no additives were present was 952 ± 57 kJ mol-1. This was substantially reduced by the presence of B203 (540 ± 27 kJ mol-1), P205 (668 ± 41 kJ mol-1) and when both were present (352 ± 26 kJ mol-1). Cordierite/enstatite glass-ceramics have been successfully used to join silicon nitride to itself. Joining at 1050-1100'C in N2 with an applied load of ~ 2.5 MPa, resulted in joint strengths, measured in 4-pt bending, of 110-170 MPa. This is comparable to the intrinsic strength of the glass-ceramic and sufficient for practical applications. These strengths were obtained using an interlayer with a TCE (5.7 MK-1) greater than that of the silicon nitride (3.0 MK-1). Suggestions for further improvements to the joint strength are discussed. The use of a glass-ceramic joint with graded thermal expansion to bridge a TCE mismatch is discussed, and the geometrical restrictions on the joint, which limit possible practical applications, are outlined. The concept of a ceramic/metal compression joint with a glass-ceramic interlayer has been demonstrated for joining silicon nitride to both Nimonic alloy 80A and Ti. The requirements for continuity of electronic structure at the Nimonic 80A/glass-ceramic and the Ti/glass-ceramic interfaces are satisfied by reaction between the glass/glass-ceramic and, the pre-oxidised surface of the Nimonic alloy to form a MgTi205-Al2TiO5 solid solution phase, and the Ti to form Ti5Si3. For the lower WE mismatch (Ti-silicon nitride) the residual joining stresses generated on cooling were marginally too high and need to be further reduced, either by a slight alteration to the joint geometry and/or a smaller WE mismatch.
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Wade, James. « Contact damage of ceramics and ceramic nanocomposites ». Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/24932.
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Herein, we study the contact damage performance of two armour ceramics, alumina and silicon carbide, with varying microstructures and one particle-reinforced ceramic nanocomposite, alumina/silicon carbide, in an attempt to understand the microstructural mechanisms that affect plasticity and cracking under quasi-static and dynamic conditions. Quasi-static contact damage was imitated using Vickers indentation over a varying load regime. Numerical analysis of the indentation size effect, performed using the proportional specimen resistance model, allowed the contributions of plastic deformation and cracking to be separated into two individual values. In all three samples, higher levels of surface energy were found to correlate with increased amounts of cracking per unit area of indentation impression. Analytical modelling of crack initiation during Vickers indentation together with quantitative measurements of surface flaw populations revealed that such an increase in cracking damage was the result of higher densities of larger flaws. The hardness of the monolithic ceramics was found vary based on grain size and porosity levels, a smaller average grain size and lower porosity levels resulting in higher hardness values. In the nanocomposite materials, hardening was found to occur with further additions of silicon carbide nanoparticles. Such an effect has been attributed to the increased dislocation densities, as measured using Cr3+/Al2O3 fluorescence spectroscopy, and the impedance of dislocation movement within the lattice due to the presence of silicon carbide nanoparticles. In order to simulate dynamic contact damage, a low velocity, scaled-down drop-weight test was designed and developed. The dynamic contact damage resistance was determined based on the depth of penetration of a blunt indenter. In the monolithic ceramics, the indenter penetration was found to be shallower in materials of higher hardness. However, the nanocomposite materials displayed an opposing trend, the indenter penetration becoming deeper in the samples of higher hardness. The macro-scale fracture patterns produced during drop-weight impacts were seen to vary based on flaw populations and indenter penetration. In certain microstructures, extensive micro-cracking was also observed.
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Minatti, José Luiz [UNESP]. « Desenvolvimento de cerâmicas de mulita a partir de alumina, ácido silícico e aerosil ». Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/103747.
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Neste trabalho, apresenta-se uma rota alternativa para produção de cerâmicas de mulita (3Al2O3.2SiO2), a partir da mistura de pós de alumina (Al2O3) e sílica (SiO2), para uma possível aplicação em um dispositivo de perfuração de rochas por jato supersônico quente (thermal spallation). Os pós precursores foram utilizados de dois modos diferentes: no primeiro com tamanho micrométrico, tal como fornecido pelos fabricantes; no segundo, a alumina foi moída e misturada separadamente com ácido silícico e aerosil nanométricos, ambos usados como fontes de sílica. O processo consistiu basicamente na mistura a úmido dos pós, secagem, prensagem e sinterização. Além do tamanho das partículas dos pós, foi avaliada a influência da pressão de prensagem (40 a 300 MPa), dos aditivos de sinterização (MgO, CaO e Y2O3), do meio de dispersão (água e álcool), da calcinação dos pós, da temperatura (1600 e 1650 ºC) e do tempo (1 e 3h) de sinterização. As cerâmicas obtidas foram caracterizadas de acordo com a contração, perda de massa, porosidade e densidade aparente e resistência à flexão. A microestrutura foi caracterizada por meio da microscopia óptica e microscopia eletrônica de varredura (MEV), e complementada com difração de raios X. Os resultados obtidos mostram que cerâmicas de mulita para aplicações comerciais, que requerem resistência mecânica até aproximadamente 207 MPa, podem ser obtidas utilizando pós de alumina moída e aerosil 380, com 1 % de CaO, homogeneizadas com álcool, calcinadas a 600 ºC, prensadas com 160 MPa (ou mais), pré-sinterizadas a 1000 ºC por 1h e sinterizadas a 1650 ºC por 1h. Estas cerâmicas demonstram também, grande potencial para uso em queimadores para fornos e tubeiras para thermal spallation.
The present study was made in order to obtain an alternative process to produce mullite ceramic (3Al2O3.2SiO2), from powder mixture of alumina (Al2O3) and silica (SiO2), for a possible use in a device for rock drilling hot supersonic jet (thermal spallation). The precursors powders were employed in two different ways: the first powder, in micrometric size, was used as supplied by the manufacturer; the second, milled alumina was alternated with silicic acid and nanometric aerosil®, both used as silica sources. The ceramic processing consisted basically of four steps: mixture of humid powders, drying, pressing and sintering. Besides the powder particle size, it was also evaluated the influence of the pressing (40 to 300 MPa), the sintering additives (MgO, CaO and Y2O3), the middle of dispersion (water and alcohol), the powder calcination and the time (1 and 3h) and sintering temperature (1600 and 1650 ºC). The obtained ceramics were characterized according to the contraction, mass loss, porosity, densification and resistance to flexing. The microstructure was analyzed by light microscopy, scanning electron microscopy (SEM) besides X-ray diffraction. The obtained results show that mullite ceramic for commercial applications requiring mechanical resistance up to about approximately 207 MPa, it can be obtained using milled alumina powder and aerosil 380® with 1 % CaO, homogenized with alcohol, calcined in 600 ºC, pressed with 160 MPa (or more), pre-sintered to 1000 ºC for 1h and sintered to 1650 ºC for 1h. These ceramic also show, great potential to be used in burners for ovens and nozzles for thermal spallation.
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Mussi, Toschi Vitoria. « Lead-free ferroelectric ceramics for multilayer ceramic capacitors ». Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC089.
Texte intégralRésumé :
De nos jours, la consommation des condensateurs céramiques multicouches (MLCCs) augmente en raison de leur efficacité et leur fiabilité. La miniaturisation résultant dans une plus grande dissipation volumique de chaleur et les nouvelles applications demandent des MLCCs qui peuvent travailler de 300 à 350°C, au-delà des limites actuelles de 200 – 250°C. De plus, les exigences environnementales augmentent également avec les réglementations REACH et RoHS qui interdisent l'utilisation du plomb en Europe. Il est donc impératif de créer des nouveaux matériaux sans plomb capables de répondre aux nouvelles attentes des MLCC.Cependant, la compatibilité avec les méthodes de production industrielle, ainsi que les prix du marché sont des limites importantes. Trois familles de matériaux sans plomb ont été examinées : celle du BaTiO3 (BT), du K0.5Na0.5NbO3 et du Na0.5Bi0.5TiO3 (NBT). Le NBT-BT à la MPB (6 % BT) a été choisi comme matériau diélectrique de base. Plusieurs méthodes et paramètres de synthèse ont ensuite été étudiés pour déterminer les meilleures conditions de synthèse. La synthèse à l'état solide et le frittage traditionnel ont été choisis pour les échantillons en massif et le coulage en bande a été choisi pour les couches. Pour éviter l'évaporation des espèces volatiles, le frittage a été effectué en couvrant le NBT-BT par une poudre de ZrO2. Tous les échantillons présentaient des phases secondaires contenant du Ba (Ba2TiO4 et Ba2Ti9O20) en raison de l'évaporation du Na pendant le frittage. Un effet de peau créé par la coexistence des phases tétragonale, rhomboédrique et cubique a également été observé, lié à la concentration locale de Ba dans le réseau cristallin du NBT. Les effets des paramètres de synthèse et la stœchiométrie des réactifs sur les propriétés diélectriques, la résistance d'isolement et la séparation des phases ont été analysés. La stœchiométrie nominale Na0.44Bi0.48Ba0.06TiO3 était la plus appropriée pour les MLCC en raison de sa résistance d'isolement élevée, de ses faibles pertes diélectriques et de sa stabilité de la permittivité en température. La présence de phases secondaires est initialement bénéfique en raison de l'élimination des lacunes d'oxygène. Au-delà d'une fraction volumique critique (2.5 à 3.0 %) et d'une taille de grain moyenne critique (0.9 à 3.0 m2), la tendance s'inverse en raison de la nature conductrice des phases secondaires.Pour atteindre la fraction volumique et la taille de grain critiques, un agent dispersant a été utilisé lors du broyage dans la jarre de YSZ, avec du MEK et de l'éthanol comme solvants, et sans sécher les réactifs avant la pesée. Enfin, la relaxation des contraintes a été réalisée à 400°C pendant 3 heures. Trois modèles ont été utilisés pour expliquer la dispersion des propriétés diélectriques en fréquence : le modèle de Maxwell-Wagner, le modèle de Nyquist et la loi de Curie-Weiss modifiée. Les incompatibilités entre les propriétés diélectriques du NBT-BT rapportées dans la littérature ont ensuite été analysées soulignant l'importance d'avoir des méthodes de synthèse et de mesure strictes. Les trois principaux facteurs affectant les propriétés diélectriques induisant ces incompatibilités étaient la stœchiométrie, la méthode de métallisation et la fixation des fils électriques à l'aide de la laque d'argent. Des pertes diélectriques croissantes à haute température a aussi été observée après chaque cycle thermique dépassant les 300°C, indiquant une dégradation thermique des échantillons.Enfin, les monocouches céramiques ont montré une faible densité (62%) après frittage, limitant la plage de température correspondant aux spécifications d'Exxelia. Cependant, en utilisant un pressage des couches avant frittage, l'échantillon multicouche fritté présentait une densité élevée (89%). Une mesure des propriétés diélectriques doit être effectuée sur cet échantillon multicouche synthétisé, afin de déterminer sa compatibilité avec les spécifications d’ExxeliaMLCC consumption is today increasing due to their high efficiency, reliability and frequency characteristics. MLCCs that can work from 300 to 350°C are required both for miniaturization, resulting in greater volume heat dissipation and for new applications. Moreover, environmental requirements are also increasing, the REACH and RoHS regulations prohibiting the use of lead in Europe. It is imperative to create new lead-free materials that are able to meet those requirements.However, the compatibility with the production methods, price, and market are important industrial limitations that need to be considered.Three families of lead-free materials were examined: BaTiO3-based, K0.5Na0.5NbO3-based and Na0.5Bi0.5TiO3-based materials. NBT-BT at the morphotropic phase boundary (6% BT) was chosen as the base dielectric material.Several synthesis methods and parameters were studied to determine the best synthesis conditions. Solid-state synthesis and traditional sintering were chosen for the bulk samples and tape casting was chosen for the layer samples preparation. Sintering was done under ZrO2 powder to prevent the evaporation of volatile species.All samples had secondary Ba-containing phases (Ba2TiO4 and Ba2Ti9O20) formed because of the evaporation of Na during sintering. A skin-effect was observed due to a phase coexistence (tetragonal, rhombohedral, and cubic) due to the local concentration of Ba in the NBT lattice.The effects of the synthesis parameters and the stoichiometry of the reactants on dielectric properties, insulation resistance, and phase separation were analysed.The Na0.44Bi0.48Ba0.06TiO3 nominal stoichiometry was the most suitable for the MLCCs due to its high insulation resistance, low dielectric losses, and stability of permittivity in temperature.The phase separation was initially beneficial, due to the resulting elimination of oxygen vacancies. Above a critical volume fraction (2.5 to 3.0%) and a critical mean surface area (0.9 to 3.0 m2), the trend was reversed due to the conductive nature of the secondary phases.To achieve the critical volume fraction and surface area of the secondary phases, a dispersing agent was used during ball-milling in YSZ jar, with MEK and ethanol as solvents, and without drying the reactants prior to weighing. Finally, a strain relaxation was done at 400°C for 3 hours.Three models explained the frequency dispersion of the dielectric properties: the Maxwell-Wagner model, the Nyquist plot and the modified Curie-Weiss law.Incompatibilities between the dielectric properties of NBT-BT reported in the literature were then analysed, showing the importance of maintaining strict synthesis and measurement methods. The three main factors affected the dielectric properties, creating these incompatibilities in the bulk samples. There were the stoichiometry, the metallization method, and the fixing of the electrical leads using silver paste.An increase of the high-temperature dielectric losses after each thermal cycle reaching more than 300°C was observed, indicating a thermal degradation of the material.Finally, the sintered ceramic monolayers showed a low density (62%), limiting the temperature range corresponding to Exxelia’s specifications. However, after pressing the layers together before sintering, the sintered multilayer sample showed a high density (89%). Dielectric property measurement should be carried out for these synthesized multilayers
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Hill, Arnold Hill. « PRODUCTION OF BULK CERAMIC SHAPES FROM POLYMER DERIVED CERAMICS ». Master's thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4248.
Texte intégralRésumé :
A method has been developed to produce bulk ceramic components from a class of ceramics known as polymer derived ceramics. In the past polymer derived ceramics have been limited to thin film applications or in the fabrication of MEMS devices. The reason being that when the polymer is into a ceramic, large quantities of gas are generated which produce internal pressure that fractures the ceramic components. The method developed here solves that issue by casting into the polymer a 3 dimensional network of polymer fibers in the form of a foam which, during pyrolysis, burns out and leaves a network of open channels that allows decomposition gases to escape thus preventing pressure from building up. The inclusion of the polymer foam allows for the formation of strong plastic like green bodies which can be machined into any shape. The green bodies are then pyrolized into ceramic components. This process allows for the simple and inexpensive fabrication of complex ceramic components that have the potential to replace current components that are made with traditional methods.M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science & Engr MSMSE
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Feilden, Ezra. « Additive manufacturing of ceramics and ceramic composites via robocasting ». Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/55940.
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In the last two decades additive manufacturing (AM) has emerged as a highly important and influential technology. A large range of approaches to AM have been developed which give rise to hundreds of distinct techniques. Many of these are specific to one material system, and only a handful have been successful at producing ceramic parts. Robocasting is one such technique, having been used to produce complex ceramic parts with reasonable mechanical properties. In this thesis robocasting is investigated further, firstly by characterising the rheology of the robocasting paste, and then by measuring the strength and reliability of ceramic parts produced by robocasting. The critical defects associated with the process are identified, and efforts have been made to eliminate them. Furthermore, it was possible to produce a new class of ceramic composites consisting of alumina platelets aligned by the shear forces that arise during printing. These platelets themselves and the composites were extensively characterised. A new in-situ double cantilever test was developed in order to study the fracture behaviour of the composites. Lastly, the principle of using the printing process to align platelets was applied to fibres in order to create printed fibre reinforced ceramic matrix composites, and printed carbon fibre reinforced epoxy.
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Sütçü, Mücahit Akkurt Sedat. « Development of Dense Ceramic Tiles From Mixtures of Alumina Powders With Different Psd/ ». [s.l.] : [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/malzemebilimivemuh/T000462.pdf.
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Santana, Jerusa Góes Aragão [UNESP]. « Desenvolvimento de cerâmicas multicamadas de carbeto de silício destinadas a aplicações térmicas ». Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/103760.
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Companhia Siderurgica de Tubarao
Cerâmicas multicamadas de carbeto de silício foram obtidas por conformação por consolidação ou prensagem e utilizando diferentes técnicas de adesão das camadas. Produzidas com duas ou três camadas e apresentando gradientes de porosidades, a sistemática para obtenção destas cerâmicas teve início com o estudo individual das amostras. Para atender a níveis de porosidades previamente estabelecidos (15, 30 e 50%), foram conformadas amostras com diferentes composições e percentuais de sólidos. Na prensagem uniaxial utilizou-se um aditivo de sinterização (YAG) para controle do nível de porosidade das amostras. Por meio da realização de ensaios físicos, mecânicos, microscópicos e termomecânicos, foi possível conhecer as particularidades e características inerentes ao método de conformação empregado. As cerâmicas conformadas por prensagem apresentaram melhores acabamentos superficiais, poros pequenos, menores incidências de defeitos, porosidade e resistência mecânica influenciada pelo teor de aditivo empregado. Nas cerâmicas conformadas por consolidação, a existência de uma elevada porosidade associada a defeitos como trincas e fissuras, deterioraram a resistência mecânica das amostras. Baseando-se nos resultados obtidos, partiu-se então, para confecção das cerâmicas multicamadas. Na conformação por consolidação foram produzidas cerâmicas com duas ou três camadas, utilizando-se dois métodos: sobreposição direta e sobreposição por meio de sulcos. Na sobreposição direta a constituição das camadas ocorreu por entorno da dispersão sobre uma camada anteriormente processada. Entretanto, as tensões originadas durante as etapas de secagem conduziram a formação de abaulamento no ponto de adesão das camadas, comprometendo a sua resistência. A utilização de um defloculante polietilenimina...
Multilayer ceramics of silicon carbide were obtained by consolidation or pressing by using different techniques for layers adhesion. Produced with two or three layers and showing porosity gradients, the method for obtaining these ceramics began with the individual study of the samples. In order to achieve the porosity levels previously established (15, 30 and 50%), the samples were conformed with different compositions and percentages of solids. A sintering additive (YAG) was used in the uniaxial pressing in order to control the porosity of the samples. Through physical, mechanical, microscopic and thermomechanical tests, it was possible to know the peculiarities and characteristics related to the conforming method that was used. The obtained ceramics by pressing showed better superficial finish, small pores, lower incidence of defects, porosity and mechanical strength, influenced by the percentage of additive employed in the samples. The ceramic samples by consolidation had their mechanical strength damaged due to the high porosity associated with defects such as cracks and fissures. Multilayer ceramics were produced from the obtained results. Ceramic samples were produced by consolidation with two or three layers, by using two methods: direct overlap and overlap through grooves. In the direct overlap, the layer forming was performed by pouring the dispersion over another layer previously processed. However, the arisen tensions during the drying steps, made the interface between the layers become convex, compromising their strength. The use of the dispersant polyethylenimine (Lupasol SK), with high molecular weight, formed a thick film on the sample surface, allowing the production of grooves between the layers. The reduction of tensions on sample layers enabled the ceramic forming without defects on the interface. Samples produced... (Complete abstract click electronic access below)
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Gasparotto, Gisele [UNESP]. « Síntese e caracterização da cerâmica PZT dopada com estrôncio e com nióbio e estrôncio ». Universidade Estadual Paulista (UNESP), 2002. http://hdl.handle.net/11449/92039.
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gasparotto_g_me_araiq.pdf: 3340587 bytes, checksum: bbf8cb1346b8377c9399b7fc2540fdc4 (MD5)A cerâmica Titanato Zirconato de Chumbo, PZT, se destaca por suas notáveis características piezoelétricas, sendo candidata a várias aplicações tecnológicas como transdutores, dispositivos ressonantes, entre outras, devido também a seu baixo custo e facilidade na fabricação (DESHPANDE, 1994). A adição de íons modificadores pode melhorar as propriedades da cerâmica, tornando-a mais eficiente. Inúmeros íons como nióbio (Nb+5) e estrôncio (Sr+2) podem ser usados para alterar parâmetros estruturais ad estrutura perovskita A(B’B”)O3 . O método Pechini é um dos mais empregados para síntese de pós cerâmicos com homogeneidade adequada ao estudo da dopagem. Neste trabalho, este método foi utilizado para síntese de pós de PZTS e PZTSN seguindo a composição Pb(1-x)Srx(Zr0,5Ti0,5)O3 e Pb(1-x)Srx[(Zr0,5Ti0,5)Nb0,04]O3, respectivamente, onde 0,01
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Adicks, Michael Kent. « Strength characterization of thin-wall hollow ceramic spheres from slurries ». Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/9318.
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Katti, Kalpana Shastri. « Microstructure and local dielectric function in barium titanate based electroceramics / ». Thesis, Connect to this title online ; UW restricted, 1996. http://hdl.handle.net/1773/10590.
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Martinez, Tais Cruz [UNESP]. « Avaliação da resistência á flexão de cerâmicas dentais Y-TZP : efeito de material e espessura ». Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/89675.
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martinez_tc_me_arafo.pdf: 873272 bytes, checksum: 438b65835375d34883a0dfb0195b8ae2 (MD5)O objetivo deste trabalho foi avaliar a resistência à flexão de cerâmicas de zircônia estabilizada por ítrio em função de marca comercial e espessura. A resistência à flexão (MPa) foi testada pelo método uniaxial de 3 pontos, conforme Norma ISO 6872/2005 em Máquina de Ensaios Universal EMIC DL 2000, usando célula de carga de 5kN, velocidade de 0,5 mm/min. e suporte com 20 mm de distância entre os apoios. Foram testados 2 sistemas cerâmicos de zircônia parcialmente estabilizada por ítrio (Y-TZP) ZirCAD© - Ivoclar Vivadente e LavaTM Framework - 3MESPE e 2 espessuras (norma ISO: 2,00 mm e uso clinico: 0,7 mm): ZC_2; ZC_0,7; LV_2 e LV_0,7. ANOVA one way e post Hoc de Bonferroni foram utilizados com significância para p<0,05. Não houve diferença estatisticamente significativa entre as médias de resistência a flexão entre ZC_2 (Média = 673,62 e dp = 129,95), ZC_0,7 (Média = 533,63 e dp = 129,84), LV_2 (Média = 593,56 e dp = 122,78) e LV_0,7 (Média = 673,02 e dp = 81,36). Conclusão: Os sistemas cerâmicos Y=TZP ZirCAD e Lava apresentam resistência a flexão (MPa) semelhantes independente da espessura. Espessuras de 0,7 mm podem ser utilizadas nos testes de resistência a flexão para melhor simular as situações de uso clinico dos sistemas cerâmicos Y-TZP
The objective of this study was to evaluate the flexural strength of ceramics by Yttrium stabilized zirconia as a function of thickness and trademark. Flexural strength (MPa) was tested by the method of three uniaxial points, in accordance with ISO 6872/2005. The Universal Testing Machine EMIC DL 2000, using a 5 kN load cell, crosshead speed of 0.5 mm / min. and holder with 20 mm distance between supports was used. We tested 2 systems ceramic zirconia partially stabilized by yttrium (Y-TZP) ZirCAD © - Ivoclar Vivadente and LavaTM Framework - 3MESPE and 2 thicknesses (ISO: 2.00 mm and clinical use: 0.7 mm): ZC_2; ZC_0 7; LV_2 and LV_0, 7. One-way ANOVA and post hoc Bonferroni was used with significance for p <0.05. There was no statistically significant difference between the mean flexural strength between ZC_2 (Mean = 673.62 and SD = 129.95), ZC_0, 7 (mean = 533.63 and SD = 129.84), LV_2 (Average = 593 , 56 and SD = 122.78) and LV_0, 7 (mean = 673.02 and SD = 81.36). Conclusion: Y-TZP ceramic systems ZirCAD and Lava have flexural strength (MPa) similar independent of the thickness. Thickness of 0.7 mm can be used in tests of flexural strength for better simulate the clinical conditions of use of Y-TZP ceramic systems
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Paula, Amauri Jardim de [UNESP]. « Síntese de templates para aplicação em piezocerâmicas livre de chumbo ». Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/92080.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
As piezocerâmicas de chumbo a base de Pb(Zr1-xTix)O3 (PZT) sempre tiveram destaque devido às suas excelentes propriedades piezoelétricas. Suas aplicações como sensores, atuadores e capacitores tornaram essas cerâmicas um alvo de incessantes estudos. Entretanto, cresce a necessidade de substituí-las devido ao impacto ambiental causado pelo chumbo. Com este objetivo, pesquisas em busca de materiais alternativos vêm ganhando destaque na comunidade científica internacional. Nesse contexto, os únicos materiais que apresentaram características equiparáveis ao PZT foram os niobatos alcalinos texturizados. Entretanto, para a obtenção dessas cerâmicas texturizadas foi necessária a produção de templates de niobato de sódio (NaNbO3) por complexos processos de síntese, uma vez que estes não estão disponíveis comercialmente. Nessa linha de estudo, o presente projeto de pesquisa buscou a síntese de moldes (templates) de niobato de sódio e de potássio para texturização de cerâmicas livres de chumbo a base de niobatos alcalinos (NaKLiNbO3) por método “Templated Grain Growth” (TGG) e “Reactive Templated Grain Growth” (RTGG). Os templates foram produzidos por síntese hidrotérmica assistida por microondas (H-M), a 200ºC, e com variações de tempo, tipo de precursor de nióbio e concentração de reagentes. Os templates de NaNbO3 e KNbO3 foram produzidos através da reação entre um precursor de nióbio (Nb2O5 ou NH4.NbO.(C2O4)2.(H2O)2.(H2O)n) e o hidróxido do respectivo metal alcalino (NaOH ou KOH). O NaNbO3 foi produzido com ambos os precursores de nióbio, embora o oxalato amoniacal favoreça a cristalização de partículas cúbicas de maior tamanho (>4μm). Durante a síntese do NaNbO3, as análises de difratometria de raios X (DRX) e de microscopia eletrônica de varredura (MEV) mostraram que as microfibras de Na2Nb2O6.nH2O formadas são uma fase intermediária...
PZT-based materials [Pb(Zr1-xTix)O3] are the most used piezoceramics around the world due to their excellent piezoelectric properties. Their applications as sensors, actuators and capacitors made these ceramics the center of unceasing studies. However, the necessity of substituting these materials has been increased mainly because of the environment impact caused by the lead element. With this objective, new researches aiming the discovery of alternative materials have been growth in the scientific community. In this context, the only materials which presented properties at the level of PZT were the texturized alkalines niobates. Nevertheless, to produce such texturized ceramics, the use of complexes methods of synthesis was necessary to create templates of sodium niobate (NaNbO3), once they are not commercially available. Therefore, this project attempted to produce templates of sodium and potassium niobates intending the texturization of alkaline niobate-based ceramics (NaKLiNbO3) by Templated Grain Growth (TGG) and Reactive Templated Grain Growth (RTGG) methods. The templates were produced by means of a microwave assisted hydrothermal synthesis (M-H), at 200ºC, by varying the time, type of niobium precursor and reactants concentrations. The templates of NaNbO3 e KNbO3 were produced through the reaction between a niobium precursor (Nb2O5 or NH4.NbO.(C2O4)2.(H2O)2.(H2O)n) and the hydroxide of the respective alkaline metal (NaOH or KOH). The NaNbO3 was synthesized by both niobium precursors, though the niobium ammoniacal oxalate promoted the formation of cubic particles of NaNbO3 with greater sizes (>4μm). During the synthesis of the NaNbO3, the analysis of X-ray diffratometry (XRD) and scanning electronic microscopy (SEM) indicated that the microfibers of Na2Nb2O6.nH2O are formed as an intermediary phase towards the NaNbO3 crystallization... (Complete abstract click electronic access below)
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Santana, Jerusa Góes Aragão [UNESP]. « Estudo e desenvolvimento de cerâmicas porosas de dióxido de titânio aditivadas com proteínas de soja ». Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/97080.
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Universidade Estadual Paulista (UNESP)
Este trabalho foi realizado com o objetivo de verificar a possível conformação de cerâmicas de dióxido de titânio (TiO2) utilizando proteína vegetal (soja) como agente ligante e elemento formador de poros. Para tanto, foram confeccionados corpos cerâmicos com diferentes composições de sólidos e variações nos percentuais de proteínas (extrato e proteína texturizada de soja). Como auxiliar de defloculação, com o intuito de reduzir as viscosidades das dispersões estudadas, utilizou-se a sacarose. A escolha destes materiais, além da já conhecida propriedade bactericida do dióxido de titânio, deveu-se a características tais como: baixo custo, não toxicidade, facilidade de obtenção e, principalmente, propriedades inertes, que conferiram ao produto final condição de uso, sem prováveis danos a saúde. Para melhor entendimento do comportamento das proteínas de soja, foram estudadas algumas propriedades reológicas destes materiais, puros ou em presença da sacarose. A caracterização das peças cerâmicas constou de medidas de rugosidade superficial e densidade aparente, além da verificação por meio de microscopia óptica. Os resultados obtidos permitiram conhecer as peculiaridades e comportamento das proteínas de soja, mostrando suas capacidades de conformação, além das características distintas que concedem aos materiais utilizados diferentes possibilidades de usos; enquanto as proteínas texturizadas são mais apropriadas para filtros domésticos ou membranas, o extrato de soja apresenta características mais adequadas para o desenvolvimento de cerâmicas utilizadas como isolantes térmicos.
The main purpose of this work was to verify the possible formation of titanium dioxide (TiO2) ceramics by using vegetable protein (soya bean) as a binder and pore forming element. Accordingly, ceramic specimens were made from different compositions of solids as well as variations in the percentage of proteins (soya essence and texturized soya). Saccharose was used as a dispersion agent in order to reduce the viscosities. Titanium dioxide and soya protein were particularly chosen. The former was for its bactericide property; the latter was due to its low cost, no toxicity, besides being easily acquired. However, the utmost feature is its inert property responsible for the perfect condition of use, probably without any health risks. In order to understand the function of soya proteins, some of their reological behavior were studied, either pure or when in presence of saccharose. The specimens studied were characterized by superficial roughness measurements, apparent density and the verification using optical microscopy. The results obtained showed the peculiarities, as well as the behavior of soya proteins, indicating their formation capacity. Besides this, it was also verified distinct properties that allow the use of soya proteins in different ways. Whereas the texturized soya is more appropriate for residencial filters or membranes, the soya essence presents better performance to the development of ceramics used as thermal insulating.
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Sujirot, Kuljira. « Silicate glass-ceramics containing fluoride for application in ceramic-matrix-composites ». Thesis, Imperial College London, 1995. http://hdl.handle.net/10044/1/7435.
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Gopnik, Hilary. « The ceramics of Godin II, ceramic variability in the archaeological record ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0019/NQ53817.pdf.
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Matthews, Stephen John. « Cavitation erosion of aluminium alloys, aluminium alloy/ceramic composites and ceramics ». Thesis, Coventry University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317927.
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Fu, Yu. « Residual Strength of Metal Particulate Reinforced Ceramic Matrix Composites with Multiple Cracks ». Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/FuY2008.pdf.
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Gonzalez, Sandra C. « Preparation and characterization of new porous ceramic filters for hot gas clean-up ». Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-12052009-020046/.
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Ranieri, Maria Gabriela Araújo [UNESP]. « Caracterização tecnológica das argilas da cidade de Cunha para fins de cerâmica artística ». Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/97084.
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A cidade de Cunha, no interior de São Paulo, é hoje reconhecida como um dos principais centros de cerâmica artística de alta temperatura. Nessa cidade, há a maior concentração de fornos noborigama da América do Sul, que é um forno de tradição milenar oriental. As peças produzidas nesse tipo de forno são reconhecidas como sendo cerâmica artística com alto valor agregado. Os ceramistas não possuem nenhum tipo de apoio técnico em relação à matéria-prima utilizada, que é a argila. Então, foi realizada neste trabalho a caracterização tecnológica de duas argilas da região, uma de coloração escura e outra de coloração clara, que são misturadas em três proporções diferentes, com o intuito de obter uma massa com boa trabalhabilidade para o processo de conformação. Foram utilizadas algumas técnicas para a caracterização mineralógica como análise térmica diferencial, análise termogravimétrica e difração de raios X. Para a caracterização física pré-queima realizou-se ensaios de análise granulométrica, massa específica dos grãos de solo e limites de Atterberg. Também, foram avaliadas as propriedades tecnológicas pós-queima em três temperaturas diferentes a 950°C, 1.150°C e 1.350°C, as propriedades avaliadas foram porosidade aparente, absorção de água, massa específica aparente, retração linear, rugosidade e resistência mecânica por flexão (3 pontos). A argila de cor clara apresentou melhores resultados na maioria dos ensaios quando comparados com os resultados obtidos com a argila de coloração escura e as respectivas misturas. Em relação a essas misturas, não houve variações significativas nas propriedades avaliadas. Observou-se que a temperatura de queima teve forte influência nas propriedades finais, principalmente a 1.350°C.
Cunha, a small Town located in São Paulo State, Brazil, is known today as one of the major centers of high temperature artistic ceramics. It is the place with the largest concentration of “noborigamas”, which are secular traditional oriental ovens. The items, made in this kind of ovens are recognized as being artistic ceramics with a high aggregated value. The ceramists do not have any kind of technical support regarding the clay, the raw material used by them. In this work the technical characterization was performed in two types of clay from Cunha: a dark colored one and a light colored one, both mixed in three different proportions in order to obtain a paste of good workability for the shaping process. Some techniques were used to get the mineralogical characteristics such as differential thermal analysis (DTA), thermogravimetric analysis (TGA) and X-ray diffraction technique. Experiments of particle size analysis, grain specific mass and Atterberg’s limit were done for the preburning physical characterization. The technological properties were also estimated before and after burning the clay in three different temperatures: 950° C, 1.150° C and 1.350° C. The properties estimated were: apparent porosity, water absorption, bulk density, linear shrinkage, roughness and flexural strength (3 points) The light colored clay reached better results in most of the experiences compared to the results obtained from the dark one and the respective mixtures. There were not expressive variations regarding these mixtures. It was observed that the burning temperature had a strong influence over the final properties, especially at 1.350°C. Both types of clay and their respective mixtures get through a “cure” process or “soting” in the ceramists workshop. The samples of clay analyzed in this experience were obtained from the mine without the previous treatment used by the ceramists. The “cure” process can alter the clay properties.
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Chung, Jae Hoon. « Compressive mechanical behavior of hollow ceramic spheres and bonded-sphere forms ». Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/9984.
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Laurie, Joyce. « Freeze casting : a modified sol-gel process ». Thesis, University of Bath, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260248.
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Senapati, Rajeev. « Discrete element modelling of silicon nitride ceramics crack formation and propagation in indentation test and four point bending test / ». To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Day, Jenna. « Coumarinyl-Caged Ceramides, a New Tool for Assessing the Biological Effects of Ceramide In Cells ». Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32336.
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Ceramide, a sphingolipid, is an important lipid second messenger that is involved in regulating a number of cellular processes, including programmed cell death, cell growth and differentiation, as well as cellular responses to stress stimuli. Many of the biological effects of ceramide are linked to its ability to modulate the biophysical properties of membranes and cause clustering of signalling molecules in ceramide-rich domains, which allows for more efficient signal transmission in the cell. However, the specific roles of different ceramide species in these signaling pathways have yet to be clearly established. Assessing the effects of long N-acyl chain ceramides in cells involves some limitations due to their poor solubility and their low membrane permeability. Caging these molecules with photolabile protecting groups allows for their delivery into cells where photochemical uncaging of the biologically active compound can be achieved with spatial and temporal control.
A series of coumarinyl-caged ceramides has been prepared in order to probe the biological effects of ceramide in cells. This unique series of compounds was used to investigate the dependence of these cellular effects on N-acyl chain length. Hereafter, I describe the photophysical and photochemical characterization of these novel caged ceramides, assess their uptake and measure the biological effects of the different ceramides which are generated photochemically in HeLa cells. The caged ceramides were shown to be taken up by the cells and to cause a decrease in viability, with UV irradiation, that can be detected after 24 hours of treatment. An investigation of the mechanism of cell death induced by coumarinyl-caged ceramides in HeLa cells revealed that cell death proceeds in a caspase-independent manner and involves the mitochondria. The role of the mitochondria in this cell death pathway, however, remains to be studied further. RIP1 kinase activity, which was also probed in the cells, was determined to not be implicated in cell death caused by photochemically generated ceramide. Intracellular ROS generation, however, was shown to occur in this system, but results primarily from UV irradiation of the free coumarin. Overall, the results from this study have provided insight into the signalling pathways triggered by treatment of HeLa cells with the bioactive lipid ceramide using coumarin photocages.
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Herath, Herath Mudiyanselage Thushari Uthpala. « Novel ceramics and ceramic structures : an 'in-vitro' study of osteoblast response ». Thesis, Queen Mary, University of London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429185.
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Bleay, S. M. « Microstructure and micromechanics in glass and glass-ceramics reinforced with ceramic fibres ». Thesis, University of Bath, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293064.
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Stevenson, Greg. « Ceramic design for modern living : an archaeology of British ceramics 1927-37 ». Thesis, University of Wales Trinity Saint David, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.683311.
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Marins, Eleasar Martins [UNESP]. « Otimização e caracterização microestrutural de cerâmicas de carbeto de silício obtidas com material nacional para uso em blindagem balística ». Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/103735.
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Armas de fogo têm sido usadas em periódo dificeis da história, nos quais conflitos entre países têm ocorrido, ou no cotidiano cada vez amis violento das grandes cidades. Neste sentido, a blindagem de veículos, aeronaves e de pessoas é uma necessidade cada vez maior. Das cerâmicas utilizadas para esse fim, o carbeto de silício tem um excelente desempenho devido à alta dureza e baixa densidade. O objetivo desse trabalho é otimizar a manufatura de cerâmicas de carbeto de silício feitas de matéria prima nacional, caracterizá-las tanto quanto comparar suas características com aquelas de material importado, visando sua aplicação em blindagem balística pessoal ou de veículos leves. a fim de proporcionar independência tecnológica nessa área. Foram confeccionadas cerâmicas de carbeto de dilício de dois tipos de pós: um nacional Microservice e importado - H. C. Starck. As cerâmicas foram conformadas por prensagem uniaxial, seguida de prensagem isostática e sinterização com fase líquida, utilzando YAG como aditivo de sinterização. A caracterização das cerâmicas foir formada por: ensaios de flexão por quatro pontos, medidas de densidade, testes de dureza e ceramografia. As cerâmicas confeccionadas com o SiC H. C, Starck apresentaram maior densidade e maior resistência mecânica do que as demais. Enquanto que, as amostras nas quais o SIC da Microservice associado a 10% de YAG como aditivo foi usado, demostraram a mais alta homogeneidade e valores de resistência mecânica e dureza os mais próximos aos valores daquelas feitas com matéria-prima importada. Esses resultados mostram que é possível usar cerâmicas feitas com o SIC nacional para propósitos de blindagem balística.
Firearms have beem used either in hard periods of history, in which conflicts between countries have occurred, or in the everyday life of the large cities, wich are more and more violent. Thus, the protection of vehicles, aircraft and people is an increasing need. Among ceramics used for this purpose, silicon carbide has an excellent performane due to its high hardness and low density. The goal of this work is to optimize the manufacture of the silicon carbide ceramics made from Brazilian raw-materials, characteriza them as well as to compares their characteristics with those form imported raw-material, aiming their application in personnel or in light vehicles armor to provide technological independence in this field. Silicon carbide ceramics were made of two kinds of powders: Brazilian - Microservice and importe - H. C. Starck. The ceramics were shaped by uniaxial pressing, followed by isostatic pressing, and liquid phase sintering using YAG as an sintering additive. The characterization of the ceramics was consisted of the four-point flexural tests, measurements of density, hardness testsm and ceramography. The ceramics made of SIC H.C. Starck presentes higher density and higher mechanical resistance than the others. While the samples of ceramicsm in wich the SIC of Microservice and a 10-percent of YAG as an additive was used, presented the highest homogeneity and mechanical resistance and hardness values closets to the values from those made of importes raw-materials. These results show it is possible to use ceramics, made of Brazilian sources for ballistica armor purposes.
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Boismenu, Nicholas. « Indirect Measure ». Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etd/3351.
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This paper is in support of my thesis exhibition “Indirect Measure” May 5th – June 3rd 2017, at the Reece Museum, located on the campus of East Tennessee State University. This document is an account of my examination into what constitutes art and the change in my perception of the utilitarian ceramic vessel during my research into the perceived difference between craft and art. Using broad definitions, I define what I believe art to be and how it is different from, and the same as craft.
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Rosa, Marinalva Aparecida Alves [UNESP]. « Espumas cerâmicas produzidas pela conjugação dos processos sol-gel, aeração e emulsificação ». Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/102563.
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Espumas cerâmicas de zircônia sulfatada foram produzidas com sucesso empregando moldes de espumas líquidas e emulsões associadas ao processo solgel. Os parâmetros de preparação dos moldes a partir da suspensão coloidal aquosa de sulfato básico de zircônio empregando diferentes tensoativos, misturas de tensoativos e diferentes quantidades de fase apolar nas emulsões foram analisados visando estabelecer correlações entre esses parâmetros de processo e as características estruturais da espuma cerâmica final. Os tensoativos iônicos dodecilsulfato de sódio (SDS) e brometo de octadeciltrimetilamônio (OTAB) apresentaram melhores propriedades estabilizantes da interface ar-líquido nas espumas líquidas, produzindo materiais com elevada porosidade e poros esferoidais com paredes texturizadas. Os tensoativos não-iônicos (IGEPAL e PLURONIC) favoreceram a estabilização das emulsões como moldes dos poros, gerando macro e mesoporos dipostos em uma estrutura hierárquica com elevada área de superfície. A mistura dos tensoativos SDS e PLURONIC em moldes de espumas líquidas permitiu associar as propriedades macroporosas obtidas com o SDS às mesoporosas do PLURONIC. A memória das mesofases lamelares observadas por espalhamento de raios X a baixo ângulo (SAXS) nos géis contendo maiores concentrações dos tensoativos manifesta-se na estrutura das espumas cerâmicas. Esta memória é revelada pela análise das histereses das isotermas de adsorçãodessorção de N2 que indicam a presença de mesoporos com formato de fendas e pelas imagens obtidas por microscopia eletrônica de varredura, que evidenciaram a estrutura de lâminas encaixadas características do precursor de zircônia. As espumas de zircônia sulfatada apresentaram elevada atividade catalítica na reação modelo de desidratação do etanol, com conversão total...
Sulfated zirconia ceramic foams were successfully produced using liquid foams and emulsion templates associated to the sol-gel process. The preparation parameters of the templates, from an aqueous colloidal suspension of basic sulfate zirconium containing different surfactants, surfactants mixtures and different amounts of non-polar phase in the emulsion were analyzed in order to establish correlations between these process parameters and the structural characteristics of final ceramic foam. The sodium dodecilsulfate (SDS) and octadecyltrimethylammonium bromide (OTAB) ionic surfactants have shown the best stabilizing properties of the air-liquid interface for the liquid foams, producing materials that present high porosity and spheroidal pores with textured walls. The non-ionic surfactants (IGEPAL and PLURONIC) favored the stabilization of the emulsions as pores templates, generating macro and mesopores organized in a hierarchical structure that shows high surface area. The mixtures of SDS and PLURONIC surfactant in the liquid foams templates allowed to associate the macroporous properties obtained from the SDS to the mesoporous ones from PLURONIC. The memory of lamellar mesophases observed by small angle X ray scattering (SAXS) for gels containing the larger surfactants concentrations manifests in the ceramic foams structures. This memory is revealed from the analysis of the in the nitrogen adsorption-desorption isotherms hysteresis that indicate the presence of slit-like mesopores, and from the scanning electron microscopy images, which have shown the stacked plates structure characteristic of the zirconia precursor. The sulfated zirconia foams presented high catalytic activity for the ethanol dehydration model reaction, showing total conversion to ethene at 300ºC for the foams prepared from the liquid foams... (Complete abstract click electronic access below)
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Papageorge, Marc Vasilios. « Characterization of metal/ceramic interfaces on aluminum nitride ». Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/9352.
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Shin, Hyunho. « Interface reactions and their influence on properties of SiC fiber-reinforced ceramic matrix composites ». Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/19122.
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Villalobos, Guillermo Roberts. « Strength enhancement of nicalon reinforced lithium aluminosilicate containing a Ta₂O₅ second phase ». Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/19969.
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Lima, Camila da Costa. « Francisco Brennand : aspectos da construção de uma obra em escultura cerâmica / ». São Paulo : [s.n.], 2009. http://hdl.handle.net/11449/86972.
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Orientador: Geralda Mendes Ferreira Silva DalglishBanca: José Leonardo do Nascimento
Banca: Solange Maria Leão Gonçalves
Resumo: Esta pesquisa tem como tema a obra de Francisco Brennand, com enfoque em sua escultura cerâmica - seu processo de concepção e realização, bem como a relação da escultura com as demais linguagens e técnicas trabalhadas pelo artista. Para tanto, iniciou-se esta investigação com um levantamento de aspectos biográficos relevantes para o entendimento da produção de Brennand: a relação da família Brennand com a indústria cerâmica, a formação artística e a construção da Oficina Brennand. Na sequência, empreendeu-se um estudo sobre o trabalho do artista em diversas técnicas e linguagens - desenho, pintura, murais e escultura cerâmica - trazendo à tona características e temas que permeiam toda a sua obra, conferindo a esta uma unidade que pode ser descrita como um "estilo brennandiano". Ao final foram analisadas as técnicas e os processos criativos envolvidos na realização da escultura cerâmica de Brennand, revelando como as características únicas da matéria fornecem o suporte ideal para os temas retratados pelo artista e resultam em obras de caráter ímpar, capazes de se destacar mesmo em meio à vasta produção de Brennand em outras técnicas.
Abstract: This research has as its theme the work of Francisco Brennand, focusing on his ceramic sculpture - his process of conception and performing, as well the relationship among the sculpture with the other languages and techniques used by the artist. Therefore, this research was started with a gathering of data about relevant biographical aspects for the understanding of Brennand's work: the relationship of the Brennand family with the ceramic industry, the artistic formation and the construction of Oficina Brennand. After that, a study about the artistic craft in several technique and languages was performed - drawing, painting, murals and ceramic sculpture - bringing to the surface characteristics and themes that permeate all his work, giving it a unity which can be described as a "brennandian style". In the end the techniques and creative processes involved in the producing of Brennand's ceramic sculpture were analyzed, revealing how the unique characteristics of the material offer the ideal support for the themes portrayed by the artist and result in pieces of work with a unique character, able to highlight themselves even among the vast production of Brennand in other techniques.
Mestre
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Lee, Shin Steven. « Damage analysis and mechanical response of as-received and heat-treated Nicalon/CAS-II glass-ceramic matrix composites ». Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-10032007-171633/.
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Ramsey, Melissa. « Manufacturing Ceramics : Ceramic Ecology and Technological Choice in the Upper Cumberland River Valley ». UKnowledge, 2013. http://uknowledge.uky.edu/anthro_etds/10.
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Ceramic material culture recovered from archaeological sites has more to offer the researcher than placing the site or strata into a cultural historic timeline. By examining the characteristics of ceramics manufactured during the Woodland Period in southern Kentucky, this thesis answers questions related to the behavior of the potters who lived and worked there. Using the theoretical basis of ceramic ecology and technological choice, this thesis examines the choices made by the potters of two sites, the Long (15Ru17) and Rowena (15Ru10) sites, located along the Cumberland River in Russell County, Kentucky. The two sites are also compared to one another and similar assemblages in the Upper Cumberland River Valley, in terms of temporal occupation and utilization of tempering resources. Ultimately, the potters who occupied the Long and Rowena sites during the Woodland Period used locally available materials to temper their clay, even as they emulated other ceramic types. In terms of the two sites themselves, it appears that while they were not occupied by the same population of potters, they did employ similar tempering agents and stylistic types. Examining the behavior of potters who occupied these two sites informs the researcher about the behavior of the larger region of the Upper Cumberland Valley.
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Hays, Kelley Ann. « Anasazi ceramics as text and tool : Toward a theory of ceramic design "messaging" ». Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185829.
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This study illustrates the importance of finding out whether painted ceramics represent the total repertoire of decorated artifacts that are expected to carry social information. Painted designs on pottery are the focus of study because (1) painted decoration has had great importance in Southwest archaeology for studying social interaction, cultural affiliation, and fine-grained chronology based on stylistic change, and (2) painted decoration is less constrained by technology and intended vessel function than other attributes, and is most free to vary for social or ideological reasons. Two assumptions underlying previous work on ceramic design "messaging" are examined. First, are ceramics the most important medium for carrying social information? Second, is ethnicity the kind of information they are most likely to carry? These questions are addressed in a case study from the American Southwest. Decorated pottery, baskets, textiles, figurines, and rock art from the seventh century Basketmaker III period occupation of rock shelters in the Prayer Rock District, northeastern Arizona are examined. Comparison of design structure and content across these different media reveals two decorative styles, one for the portable household artifacts and one for rock art. In this case, pottery does not carry the full range of potential social information signalled by applied designs. The contexts of these two decorative styles are suggested by considering aspects of artifact function, design visibility, spatial distribution of artifacts, rock art, and architecture, together with hypotheses about gender differentiation and community organization. It is concluded that for the Prayer Rock Basketmakers, pottery decoration may have carried messages that had more to do with gender than ethnicity.
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Texier, Anne. « The fabrication of carbon-fiber composites by aqueous suspension prepregging with larc-tpi and peek ». Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-03172010-020638/.
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Passos, Aline Ribeiro [UNESP]. « Preparação de aluminas porosas hierarquicamente estruturadas ». Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/92061.
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Cerâmicas porosas possuem resistência a altas temperaturas e a ambientes corrosivos, permitindo sua utilização em uma variedade de aplicações. A distribuição de tamanho, forma e volume dos poros é determinante na definição do desempenho da função desejada. Estruturas hierárquicas de poros vêm atraindo o interesse de pesquisadores que procuram desenvolver materiais com elevadas taxas de transferência de massa e calor bem como elevada área superficial específica. A combinação das propriedades texturais das aluminas, suas intrínsecas características ácido-base e a estrutura hierárquica de poros, pode ser de grande interesse para o desenvolvimento de novos materiais. Neste trabalho aluminas com meso e macroporos foram produzidas pela conjugação do processo sol-gel e direcionadores de estrutura porosa baseados em tensoativos e emulsões. Foi realizado um estudo sistemático das condições de preparação das aluminas e estabelecidos alguns parâmetros determinantes na formação e estabilidade destes materiais. Além disso estabeleceram-se as correlações entre a composição da emulsão, os tratamentos após a gelatinização e a estrutura porosa do material cerâmico final. Alterando a quantidade de tensoativo na síntese, a área superficial específica, o volume e diâmetro dos mesoporos podem ser ajustados, sem grandes alterações na estrutura macroporosa. A adição de cotensoativo altera a estrutura de meso ou macroporos dependendo do tamanho da cadeia do álcool utilizado. Durante a etapa de secagem dos materiais ocorre retração e formação de fraturas, no entanto quando as amostras são secas a 50 °C esses efeitos são menos pronunciados. Os materiais obtidos apresentam elevada estabilidade térmica, a estrutura bimodal e estreita distribuição de tamanho de poros foi mantida...
Porous ceramics are resistant to high temperatures and corrosive environments, enabling their use in a variety of applications. The distribution of size, shape and pore volume are very important in definition of the performance function. Hierarchical structures of pores are attracting interest from researchers seeking to develop materials with high rates of mass transfer and heat as well as high surface area. The combination of the textural properties of alumina, its intrinsic acid-base characteristics and the hierarchical structure of pores, can be of great interest for the development of new materials. In this context alumina with meso and macropores were produced through the conjugation of the sol-gel route as well as dual soft template technique that consists of surfactants and emulsion. In this work a systematic study was conducted about the preparation conditions of alumina and some parameters determining the formation and stability of these materials were set. The correlation between the compositions of the emulsion, the gel aging, drying conditions and porous structure of the final ceramic material was studied. Changing the amount of surfactant in the synthesis, the specific surface area, volume and diameter of the mesopores can be adjusted without major changes in the macroporous structure. The addition of a co-surfactant changes the structure of meso- or macropores depending on the chain size of the used alcohol. During the drying step the material shrinkages and the formation of crack occurs, however when the samples are dried at 50 °C these effects are less pronounced. The obtained materials exhibit high thermal stability, structure and narrow bimodal size distribution of pores which are retained after calcination between 500 °C and 1000 °C. At 1100 °C occurs sintering of... (Complete abstract click electronic access below)
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Gonçalves, Júnior Marcos [UNESP]. « Efeitos dos parâmetros de usinagem no acabamento superficial de materiais cerâmicos a verde ». Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/122227.
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A usinagem de cerâmica verde tem sido investigada como um método para fabricação de formas complexas. Tal método fornece uma alternativa possível para a fabricação de cerâmica de geometria complexa com dimensões próximas as finais, devido à baixa resistência mecânica, apresentando vantagens em termos de custo benefício e melhoria no acabamento superficial, em comparação com a usinagem realizada somente após a sinterização. Neste trabalho foram medidas as forças de usinagem de corpos cerâmicos a verde, e analisado a sua correlação com os parâmetros de corte e com o acabamento superficial. A correlação entre a potência de corte e a taxa de remoção são parâmetros inadequados podem produzir danos superficiais excessivos na peça. O presente trabalho objetivou a elaboração e a concepção de um sistema de aquisição de dados das forças de usinagem, utilizando um dinamômetro de três coordenadas, para monitorar as forças de corte, avanço e profundidade. Para isso, corpos de prova cilíndricos de alumina de 99,8% de pureza foram conformados em prensa isostática a 200 MPa, sendo torneados com diferentes parâmetros de corte por três tipos de ferramenta de cermet sob condições constantes de usinagem. Foram confrontados com os esforços variáveis como acabamento e rugosidade superficial, raio de ponta e desgaste da ferramenta de corte e a temperatura durante a usinagem, registrada através de um microtermopar inserido próximo da ponta da ferramenta de corte. Os resultados mostraram forte influência do desgaste da ferramenta de corte no incremento dos esforços e no acabamento superficial, como também, o raio de ponta da ferramenta teve influência no acabamento superficial e na vida útil da ferramenta. Foi verificado que a profundidade de corte não teve efeito considerável sobre a qualidade da superfície, sendo a velocidade de corte e de avanço as variáveis que apresentaram maior efeito no acabamento...
The machining of green ceramic has benn investigated as a method for manufacturing of complex shapes. Such method provides a possible alternative for manufacturing of ceramic of complex geometry with dimensions close to the final, due to low mechanical strength, presenting advantages in terms of cost-benefit and improvement surface finishing compared to machining performed only after the sintering. In this work, the forces of machining of green ceramic workpiece and analyzed its correlation with the cutting parameters and surface finishing were measured. The correlation between the cutting power and removal rate are important parameters in order to define the project in ceramic products, in which inadequate parameters can produce excessive damage to the work piece surface. The present paper aimed the elaboration and conception of data acquisition system of the machining forces, using a dynamometer three coordinates for monitoring the cutting forces, feed and depth. For this purpose, cylindrical speciments of alumina 99.8% purity were conformed into isostatic press at 200 MPa, being turned with different cutting parameters by three types of cermet tool under machining constant conditions. Efforts were confronted with variables such as finishing and surface roughness, tip radius and wear of the cutting tool and temperature during the machining, registered through a microtermopar inserted next to tip of the cutting tool. The results showed a strong influence of the wear of the cutting tool in increased efforts and surface finish, as well as the radius of the tool tip had influence on surface finishing and in the tool life. If was verified that the depth of cut had no significant effect on the surface quality, being the cutting speed and feed the variables that had greater effect on the finishing. The feed force showed major increase efforts and the force of depth minor increments during the machining. The recorded temperature did not...
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Mussolin, Simone Monte-Mor. « Caracterização e controle do defeito ocasionado pelo uso do fonolito em massas ceramicas gres ». reponame:Repositório Institucional da UFSC, 1996. http://repositorio.ufsc.br/xmlui/handle/123456789/76390.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro TecnologicoMade available in DSpace on 2012-10-16T09:53:58Z (GMT). No. of bitstreams: 0Bitstream added on 2016-01-08T21:11:04Z : No. of bitstreams: 1 106496.pdf: 6058997 bytes, checksum: 2e837f9da21107c4397e3133e801c68e (MD5)
Estudo e caracterização de um defeito identificado em produtos cerâmicos de pavimento esmaltado tipo grês, estando a sua ocorrência relacionada com a utilização do fonolito na formulação da massa cerâmica. A etapa de peneiramento da barbotina foi selecionada como meio de controle desse defeito, tendo sido utilizada para análise uma metodologia baseada em FMEA - Failure Mode and Effects Analysis.
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ANNUNZIATA, ESTER MARIA. « “Archeologia e Archeometria della ceramica medievale : un approccio multidisciplinare per la diagnostica dei manufatti ceramici della Basilicata” ». Doctoral thesis, Università degli studi della Basilicata, 2022. http://hdl.handle.net/11563/158626.
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Bhatt, Hemanshu D. « Effect of interfacial thermal conductance and fiber orientation on the thermal diffusivity/conductivity of unidirectional fiber-reinforced ceramic matrix composites ». Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07282008-135034/.
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Tan, Chin Wah John. « Determination of dynamic response of ceramics and ceramic-metals under shock compression and spall ». Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/4972.
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Approved for public release; distribution is unlimitedng responses of the material studied were determined through planar impact experiment conducted on a single stage light-gas gun at NPS Impact Physic Lab. Impact velocities ranged from 0.2 to 0.35 km/s. The impactor material for asymmetric experiments was z-cut single crystal sapphire. Diagnostics used included a VISAR system, to measure particle velocities, PZT pins to measure onset of impact, and contact pins to measure impactor velocities and tilt angles. Through this study, dynamic loading response of ceramic Corbit-98 and ceramet tungsten carbide were determined. The Hugoniot Elastic Limit (HEL) of GC-915 was found to be 0.935 GPa and spall strength of approximately 2 GPa was also measured.
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Pemberton, Sonya Rachel. « Toughening ceramics : optimising the fracture behaviour of metallic fibre reinforced ceramic matrix composites (MFCs) ». Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607820.
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Sahlen, E. Daniel. « Ceramic technology and technological traditions : the manufacture of metalworking ceramics in late prehistoric Scotland ». Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2707/.
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The goal of this thesis is to investigate the manufacture of metalworking ceramics in late prehistoric Scotland (ca 1000BC – AD800) from the perspective of ceramic technology and with the aim to reconstruct social and material trajectories. This has been implemented through the use of an integrated analytical methodology, interpreted by developing current theories on technology. Previous studies of metalworking ceramics in Scotland have rarely paid full attention to ceramic technology; research has instead focused on metallurgical issues such as metal identification and material morphology. This is central for answering questions regarding metallurgical processes, but fails to answer important questions regarding the technology and manufacture of the ceramic material. The successful production of moulds and crucibles requires that a craft specialist has expert skills in the preparation and firing of clay as well as understanding of the process and design of metal casting. This makes metalworking ceramics an important resource for investigating variation in individual skill and experience, cultural traditions, and scale of production. The main focus is on moulds and crucibles, but parallels, both in terms of method and theory, are made to other types of metalworking ceramics and pottery. The technological relationship between pottery and metalworking ceramics is therefore a vital link in the assessment of production and technological traditions. In addition, clays from a number of sites have been sampled, with the goal to monitor the utilization of clays for the production of different ceramic materials. Materials from nine primary sites, from Traprain Law (East Lothian) in the south to Mine Howe (Orkney) in the north, are central to the discussion of ceramic technologies. The context of casting and crafts from further sites in Scotland and beyond has been essential in the reconstruction of casting production in the late prehistoric period. Developing from ideas of technology as an active process, this study has investigated the collection and preparation of clays to make different ceramic materials. This investigation has employed a range of analytical techniques frequently applied to the study of archaeological ceramics, including ceramic petrography, Scanning Electron Microscopy, X-Ray Spectrometry and X-Ray Diffraction. The focus has been on technology; studies of provenance are auxiliary to the broader questions. It is a central conclusion of this work that the production of metalworking ceramics saw a development towards a more specialised function and technology during the late prehistoric period, and that this development was closely related to material traditions, to some extent transcending wider social trajectories. This research, highlighting particular and general technologies, has showed that the study of ceramic technology of moulds and crucibles can be a valuable resource for the study metallurgical production and technology.
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Nociti, Denyse Meirelles [UNESP]. « Aproveitamento de rejeitos oriundos da extração de minério de ferro na fabricação de cerâmicas vermelhas ». Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/94442.
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O objetivo deste trabalho é a avaliação da viabilidade de adicionar uma quantidade específica de rejeito proveniente da mineração de ferro na massa cerâmica, mantendo sua trabalhabilidade e minimizando um problema ambiental. Dois rejeitos foram escolhidos para esta avaliação. Estes foram fornecidos por uma mineradora que produz aproximadamente 640.000 toneladas/mês de rejeito arenoso e 450.000 toneladas/mês de rejeito lama. Na pesquisa foram usados argila e carvão provenientes da região de Guaratinguetá, que são matérias-primas normalmente utilizadas na fabricação de blocos cerâmicos. As caracterizações da argila e dos rejeitos foram realizadas por meio de análises de fluorescência de raios-X, difração de raios-X, análise granulométrica, análise térmica diferencial (ATD) e análise termogravimétrica (ATG). Para determinação da proporção do rejeito (arenoso ou lama) que deveria ser adicionada à massa cerâmica foram realizados ensaios de limite de liquidez e de plasticidade. Estes ensaios consideraram amostras sem adição, e, separadamente, amostras contendo diferentes porcentagens de rejeito misturado à argila. Após os testes, as proporções de 7,5% e de 5,0%, respectivamente, dos rejeitos arenoso e lama se mostraram as mais adequadas, pois mantêm a trabalhabilidade do material próxima àquela da massa cerâmica original. Após a determinação da quantidade ideal, todas as amostras foram conformadas por prensagem uniaxial e sinterizadas à 900ºC, temperatura esta comparável à utilizada pela indústria cerâmica para fabricação dos blocos. Para a caracterização dos corpos cerâmicos sinterizados utilizou-se técnicas de rugosimetria, determinação de porosidade e de densidade aparentes e resistência à flexão por três pontos. Os resultados, após trabalho estatístico...
The aim of this experience is to evaluate the viability of the addiction of a specific amount of iron mining residue into the red ceramic blend, keeping its workability and minimizing environmental problems. Two sorts of residues were chosen to be tested. Both residues were supplied by a mining company, which produces approximately 640,000 tons of sand like waste and 450,000 tons of mud waste per month. In this research we used the red ceramic blend mass and the coal from the region of Guaratinguetá; these materials are commonly used to produce clay block brick. Analyses by X-Ray Fluorescence, X-ray diffraction, granulometry, differential thermal (DTA) and thermogravimetric (TGA) were carried out in order to characterize the raw material (clay and the mining wastes). Liquid and plastic tests were done in order to determine the waste ratio that should be added to the ceramic mass. We produced samples of ceramic with and without the waste addiction, tested for different ratios. After the tests, the amounts of 7.5% for the sand like residue or 5.0% for the mud residue were considered to be the most appropriate ones. All the samples were formed by uniaxial pressing and sintering to 900ºC, like the temperature used to produce ceramic blocks. The three points flexural, perfilometry, porosity and apparent density tests were used to characterize the ceramics. The results, after the statistic work by Weibull method, pointed to a positive use of waste mixture into the ceramic mass. Adding the correct amount of residues in the red ceramic mass, it is possible to produce red brick for sealing purposes, in other words, with no structure function
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Gimenes, Rossano [UNESP]. « Preparação e caracterização de compósitos polímero/cerâmica com potencial de aplicações médicas ». Universidade Estadual Paulista (UNESP), 2001. http://hdl.handle.net/11449/97750.
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O projeto desenvolvido buscou o estudo sistemáticos de compósitos com potencial de aplicação médica. Pós cerâmicos de Titanato Zirconato de Chumbo dopado com 0,4 mol% de nióbio (PZTN) e Titanato de Bário (BT) foram preparados pelo método Pechini. Utilizou-se também pó de hidroxiapatita de origem comercial (OSTEOSYNTH) Os pós de PZT+0,4mol%Nb e BT foram compactados e sinterizados a 1100ºC/4h. Os compactos sinterizados foram moídos para garantir pós de alta cristalinidade. Foram obtidos filmes compósitos polímero/cerâmica com cerca de 40μm de espessura, pela homogeneização da solução de fluoreto de polivinilideno (PVDF)/dimetil formamida (DMA) com os pós cerâmicos. Os filmes foram depositados pelo espalhamento de solução sobre placa de vidro e também pela técnica spin coating. Também foram obtidos filmes de PVDF puro e do copolímero P(VDF-TrFE) 60/40 mol%. Os filmes foram cristalizados em temperaturas de 70 a 100ºC. As estruturas cristalinas dos filmes foram verificadas por IV e DRX. Resultados de DRX demostraram que filmes de PVDF obtidos por solução cristalizam preferencialmente na fase α. Os filmes de copolímero apresentaram somente uma fase polar. As microestruturas dos compósitos observada por MEV revelaram que o aumento da concentração de cerâmica favorece a formação de aglomerados. Os filmes foram submetidos a polarização pelo método de Rampas de tensão. A polarização ferroelétrica observada para os filmes de P(VDFTrFE)/ BT foi atribuída a otientação dos dipolos na fase ferroelétrica do polímero. Testes de citotoxidade revelaram que o P(VDF-TrFE)/BT 90/10% é um material atoxico. Experimentos in vivo indicaram que o compósito pode induzir o reparo do osso lesado.
The developed project seeks the systematic studies of composites with medical application. Niobiun dopped Lead Titanate Ziconate (PZTN) and Barium Titanate (BT) powders were prepared by Pechini method. Commercial hidroxiapatite powder was used in this project. The PZTN and BT powders were compacted and sintered at 1100 ºC for 4 hours. Sintered compacts were moiled to obtaining powders with high crystallinity. Composites films polymer/ceramic of 40 μm thick were obtained by mixture of poly(nivylidene fluoride)/dimethylacetamide (DMA) solution with ceramic powders. The films were manufactured by spreading of solution onto a glass sheet and also it was obtained by spin coating method. PVDF pure and P(VDF-TrFE) 60/40 %mol copolymer were obtained. The films were crystallized at temperatures ranges from 70ºC at 100ºC. Films structures were verified by IR and XRD analysis. XRD results demonstrated that PVDF films obtained by solution cast it crystallized in the phase α preferably. Only one polar phase was observed for copolymer films. The microstructure of the composites obtained by MEV revealed that an increase in the ceramic concentration favours the formation of agglomerates. The films were poled by ramp voltage method. Electrical polarization was observed to P(VDF-TrFE)/BT films and it was attributed to dipolar alignment in polymer ferroelectric phase. A Citotoxic testis shows that P(VDF-TrFE)/BT 90/10 mol% is an atoxic material. In vivo composite implanted shows that this material can induce bone repair.
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Vanderlei, Aleska Dias. « Resistência de união e discrepância marginal absoluta de infraestruturas feitas em cerâmica Y-TZP : influência de novos métodos de tratamento de superfície / ». São José dos Campos : [s.n.], 2011. http://hdl.handle.net/11449/105539.
Texte intégralRésumé :
Resumo: O objetivo deste trabalho foi avaliar o efeito de diferentes tratamentos de superfície da cerâmica Y-TZP na resistência de união, durabilidade e discrepância marginal. Para os testes de resistência adesiva, foram obtidos 144 corpos de prova (cp) da cerâmica VITA In-Ceram YZ for InLab (5,25 x 3,75 x 4,5 mm), que foram divididos em 6 grupos (G) (n=24), conforme o tratamento de superfície: G1: sem tratamento (controle); G2: jateamento com partículas de alumínio revestidas por sílica (CoJet®-Sand, 3M ESPE AG) (silicatização); G3: vitrificação 1 (Glaze Spray VITA AKZENT), condicionamento com ácido fluorídrico (HF) (1 min); G4: vitrificação 1 (Glaze Spray VITA AKZENT), silicatização; G5: vitrificação 2 (Glaze VITA AKZENT), condicionamento com HF (1 min); G6: vitrificação 2 (Glaze VITA AKZENT), silicatização. Após todos os tratamentos, as superfícies foram silanizadas por 5 min (ESPE-SIL) e a cimentação com Panavia F (Kuraray) foi realizada. Metade dos espécimes de cada tratamento foi ensaiada 24h após cimentação (SECO), a outra metade foi submetida à armazenagem (150 dias) e termociclagem (12.000x) (TC), e então realizado o ensaio de cisalhamento (1 mm/min). G7: G1+TC; G8: G2+TC; G9: G3+TC; G10: G4+TC; G11: G5+TC; G12: G6+TC. Superfícies tratadas foram analisadas por perfilometria óptica 3D para obtenção dos dados de rugosidade (Ra) e microscopia eletrônica de varredura (MEV) (1000x). Análise por energia dispersiva de raio-X (EDS) foi realizada para determinar os elementos químicos presentes na superfície de cada grupo. Para a análise de adaptação marginal foram confeccionadas 60 infraestruturas (adaptadas em um troquel metálico) nas quais foram realizados os mesmos tratamentos de superfícieAbstract: The aim of this study was to evaluate the effect of different surface treatments of Y-TZP ceramic on bond durability and marginal fit. 144 specimens of VITA In-Ceram YZ for InLab ceramic (5.25 x 3.75 x 4.5 mm) were obtained and divided into 6 groups (n=24) according to the surface treatment: G1: no treatment (control); G2: chairside tribochemical silica coating system (CoJet®-Sand, 3M ESPE AG) (Cojet); G3: vitrification 1 (Glaze Spray VITA AKZENT), conditioning with hydrofluoric acid (HF) (1 minute); G4: vitrification 1 (Glaze Spray VITA AKZENT), Cojet; G5: vitrification 2 (Glaze VITA AKZENT), conditioning with HF (1 minute); G6: vitification 2 (Glaze VITA AKZENT), Cojet. Then, the ceramic surfaces were silanized and the cementPanavia F (Kuraray) was applied. Half of the specimens from each treatment was tested 24 hours after cementation (DRY), the remaining specimens were stored in distilled water for150 days,thermocycled(12,000x) (AGING) and then the shear test was performed (1mm/minute). Conditioned surfaces were evaluated by 3D optical profilometry in order to obtain roughness data (Ra) and analysed by scan electronic microscopy (SEM) (1000x). Analysis by energy x-ray dispersive (EDS) was performed to determine the chemical elements present in each surface group. For analysis of marginal adaptation 60 crowns were produced (adapted into a metal die) and the same surface treatments were carried out on the internal surface of the crowns. The data were analysed using. The results suggest the vitrification 1 and vitrification 2 groups showed the highest bond strength compared to the control group. The highest marginal discrepancies were observed in the vitrification groups (117.36±29.61 to 105.78±12.23) comparing with the other groups (55.29±8.71 and 55.04±8.55).
Orientador: Luiz Felipe Valandro
Coorientador: Fernando Eidi Takahashi
Banca: Marco Antonio Bottino
Banca: Renata Marques Melo
Banca: Paulo Francisco Cesar
Banca: Marcelo Giannini
Doutor
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Wijesinghe, Dayanjan. « Ceramide Kinase and Ceramide-1-Phosphate ». VCU Scholars Compass, 2008. http://scholarscompass.vcu.edu/etd/1621.
Texte intégralRésumé :
Ceramide-1-phosphate (C1P) is a bioactive lipid that has been implicated in many biological processes. Our laboratory has conclusively demonstrated its role in inflammation via activation of cPLA2α. The only known enzyme to date responsible for direct synthesis of C1P is ceramide kinase. Very little was known about this enzyme in terms of its enzyme kinetics and substrate specificity. As CERK is an enzyme that acts on membrane lipids, its kinetics cannot be studied using standard bulk dilutions methods. Thus we developed a surface dilution approach using Triton X 100 mixed micelles for studying the kinetics of CERK. We discovered that ceramide kinase has an affinity for naturally occurring long chain ceramides while ceramides containing shorter than 8 carbons are very poor substrates for the enzyme. Also of note is the discovery that there is no discrimination between the naturally occurring long chain ceramides leading to the conclusion that the preponderance of D-e-C16 C1P in cells are due to an availability effect. We also investigated the chain length specificity of interaction between C1P and cPLA2α. Our data indicate that cPLA2α is activated by C1P’s containing acyl chains longer than two carbons. The study showed C2 C1P as being unable to activate cPLA2α thus establishing a tool for the investigation of cPLA2α dependent and independent effects of C1P. In the course of the study we investigated the ethanol/dodecane delivery system as a means of safely delivering lipids to cells. Our data conclusively demonstrate that this delivery system successfully delivers lipids to the internal membranes where their biological action takes place and that at low lipid concentration (<1µM), is non toxic to cells. A significant technical hurdle in the study of C1P was the lack of accurate and reproducible method of quantitatively and qualitatively analyzing the lipid. Using a mass spectrometric approach we developed an accurate technique that now allows us to quantify the lipids in cells. Using this and radiolabeling studies we discovered evidence for production of C1P from S1P via an acyl transferase pathway. Further studies are currently being carried out to identify the enzyme/s responsible for this pathway.