OBJECTIVES: Evaluate the effect of different veneering techniques, Y-TZP core thicknesses, and firing cycles with different heat rates and holding times on the mechanical properties of veneering porcelain. MATERIALS AND METHODS: Biaxial flexural strength and Thermal shock resistance tests were conducted to evaluate the mechanical properties of veneer porcelain. Core material, Y-TZP and two porcelain veneers, IPS e.max Ceram and VITA VM9, were used in this study. Vita YZ zirconia blocks were sectioned and sintered to provide slabs of 1.65, 3.25, and 6.50mm in thickness. Two techniques were used to fabricate VITA VM9 and e.max Ceram porcelain veneer porcelain discs, Hand Layered, mixing powder with manufacturer’s molding liquid, condensed in a mold, and Pressed, pressing powder uniaxially in a mold. A layer of carbon paint was applied to the zirconia to allow removal of the porcelain discs. For thermal shock test the veneering porcelain fired on the Y-TZP core with a wash layer. After the veneer discs were fabricated, they were sintered: (1) According to the manufacturer’s instructions; (2) Two different cycles with slower heat rate and longer holding than the recommended value. Biaxial flexural strength was determined using a universal mechanical tester. Thermal shock tests were performed using a Pober thermal shock device. Statistical analysis was conducted for all tests using ANOVA and Tukey post hoc test at p= 0.05. RESULTS: There was significant effect from changes of YZ Core thickness, firing cycle, and veneer technique on the mechanical properties of porcelain veneer. The veneering technique had the largest impact on the mechanical properties of veneer porcelain followed by firing cycle, followed by YZ core thickness. In using different firing cycles with different heat rates and holding times, slowing the heating rate had more influence on the mechanical properties of veneer porcelain. In measuring the surface temperature of the Y-TZP/VITA VM9 assembly, the specimen surface temperature was coincidental with the furnace programmed firing cycle using a slower heating rate firing cycle. CONCLUSIONS Veneering technique, slower heat rate firing cycle, and Y-TZP core thickness have significant impact on veneering porcelain mechanical properties. / 2018-09-28T00:00:00Z

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-09-19T12:59:11Z No. of bitstreams: 1 BARTOLOMEU JORGE DA SILVA - TESE (PPGEP) 2012.pdf: 6329226 bytes, checksum: ee082ac88e7b97ca751012c45cc0fe2e (MD5) / Made available in DSpace on 2018-09-19T12:59:11Z (GMT). No. of bitstreams: 1 BARTOLOMEU JORGE DA SILVA - TESE (PPGEP) 2012.pdf: 6329226 bytes, checksum: ee082ac88e7b97ca751012c45cc0fe2e (MD5) Previous issue date: 2012-06-22 / Atualmente o setor produtivo de cerâmica vermelha utiliza dois ciclos de queima, lento e rápido. No entanto, o ciclo lento, o mais utilizado pelos ceramistas brasileiros, chega muitas vezes a períodos de 24 a 48 horas de duração, acarretando demora na produção e, consequentemente, maior consumo de energia térmica, mais demanda de combustíveis e a geração de resíduos e poluentes. Este trabalho teve como objetivo avaliar a influencia da taxa de aquecimento sobre a microestrutura e propriedades de peças obtidas a partir de massas empregadas na obtenção de produtos da cerâmica vermelha. Para tanto, foram utilizadas matérias-primas provenientes de olarias dos Estados da Paraíba e do Rio Grande do Norte. As massas foram beneficiadas e posteriormente submetidas às seguintes caracterizações: físicas, químicas, mineralógica, granulométrica e térmica. Os corpos de prova foram conformados por extrusão, em seguida submetidos a queima em temperaturas de 800, 900 e 1000 ºC e taxas de aquecimento de 1, 2, 5, 10, 15, 20 e 30ºC/min, permanecendo na temperatura máxima durante 1 hora. Por fim foram avaliadas as seguintes propriedades: densidade aparente, retração linear, absorção de água e resistência à flexão, também foi avaliada a cor de queima. As massas cerâmicas apresentaram teores de óxidos e plasticidade de acordo com as utilizadas para a produção de produtos da cerâmica vermelha. As peças obtidas com a massa contendo menores teores de óxido de ferro e óxidos alcalinos, quando submetidas às taxas de aquecimento mais rápidas apresentaram melhor estabilidade e propriedades tecnológicas. Através da analise mineralógica dos pós, após a etapa de queima pode-se observar picos característicos das fases quartzo, mulita, anortita, hematita e mica. As superfícies de fratura das peças queimadas apresentaram morfologias caracterizadas por texturas rugosas, presença de poros interconectados e isolados, trincas e partículas de quartzo. Para as maiores taxas de aquecimento foi possível observar a presença de poros maiores e regiões com aspecto esponjoso, característico da presença do defeito denominado “coração negro”. / Currently the production of red ceramic industry uses two firing cycles, slow and fast. However, the low rate is more used in traditional ceramic, periods often reached 24-48 hours, causing delay in the production and therefore increased consumption of thermal energy. This work aimed to evaluate the influence of heating rate on the microstructure and properties of parts obtained from masses used to obtain products of red ceramic. For this purpose, it was used clay masses provided by two red ceramics industries from the state of Paraíba and one from the state of Rio Grande do Norte. The masses were humidified, until reaching the adequate plasticity, remained in rest for 24 hours, and then were submitted to the process of extrusion. Then they were sintered in a laboratory electrical oven, at temperatures of 800, 900 and 1000oC, with different heating rates: 1, 2, 5, 10, 15, 20 and 30oC/min. After the sintering stage it was determined the following properties: water absorption, linear shrinkage, apparent porosity and mechanical bending resistance in three points. The color after firing also was evaluated. The oxide contents and plasticity presented in the ceramic masses are consistent with the ones used for the production of red ceramics. Parts obtained from the mass containing smaller amounts of iron oxide and alkali oxides, when subjected to heating rates faster showed better stability and technological properties. It can be observed for the three temperatures, the presence of characteristic peaks for quartz, mica anorthite, illite, hematite and mullite. The fracture surfaces of the parts were characterized by rough textures, presence of isolated and interconnected pores, cracks and quartz particles. For higher heating rates was possible to observe the presence of larger pores and regions with spongy characteristic.

Made available in DSpace on 2014-12-17T14:07:09Z (GMT). No. of bitstreams: 1 JoseCCSJ_TESE.pdf: 3857511 bytes, checksum: 1d384b3892d7aeac8dab23519e4bb09a (MD5) Previous issue date: 2012-05-31 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Over recent years the structural ceramics industry in Brazil has found a very favorable market for growth. However, difficulties related to productivity and product quality are partially inhibiting this possible growth. An alternative for trying to solve these problems and, thus, provide the pottery industry the feasibility of full development, is the substitution of firewood used in the burning process by natural gas. In order to contribute to this process of technological innovation, this paper studies the effect of co-use of ceramic phyllite and kaolin waste on the properties of a clay matrix, verifying the possible benefits that these raw materials can give to the final product, as well as the possibility of such materials to reduce the heat load necessary to obtain products with equal or superior quality. The study was divided into two steps: characterization of materials and study of formulations. Two clays, a phyllite and a residue of kaolin were characterized by the following techniques: laser granulometry, plasticity index by Atterberg limits, X-ray fluorescence, X-ray diffraction, mineralogical composition by Rietveld, thermogravimetric and differential thermal analysis. To study the formulations, specifically for evaluation of technological properties of the parts, was performed an experimental model that combined planning involving a mixture of three components (standard mass x phyllite x kaolin waste) and a 23 factorial design with central point associated with thermal processing parameters. The experiment was performed with restricted strip-plot randomization. In total, 13 compositional points were investigated within the following constraints: phyllite ≤ 20% by weight, kaolin waste ≤ 40% by weight, and standard mass ≥ 60% by weight. The thermal parameters were used at the following levels: 750 and 950 ?C to the firing temperature, 5 and 15 ?C/min at the heating rate, 15 and 45min to the baseline. The results showed that the introduction of phyllite and/or kaolin waste in ceramic body produced a number of benefits in properties of the final product, such as: decreased absorption of water, apparent porosity and linear retraction at burn; besides the increase in apparent specific mass and mechanical properties of parts. The best results were obtained in the compositional points where the sum of the levels of kaolin waste and phyllite was maximal (40% by weight), as well as conditions which were used in firing temperatures of 950 ?C. Regarding the prospect of savings in heat energy required to form the desired microstructure, the phyllite and the residue of kaolin, for having small particle sizes and constitutions mineralogical phases with the presence of fluxes, contributed to the optimization of the firing cycle. / Ao longo dos ?ltimos anos a ind?stria de cer?mica estrutural no Brasil vem encontrando um mercado bastante favor?vel para o crescimento. Entretanto dificuldades relacionadas ? produtividade e qualidade dos produtos est?o inibindo parcialmente esse poss?vel crescimento. Uma das alternativas para tentar solucionar esses problemas e, consequentemente, proporcionar ao setor oleiro a viabilidade do pleno desenvolvimento, ? a substitui??o da lenha utilizada no processo de queima pelo g?s natural. Com o intuito de contribuir nesse processo de inova??o tecnol?gica, o presente trabalho trata-se de um estudo do efeito da co-utiliza??o de filito cer?mico e res?duo de caulim sobre as propriedades de uma matriz argilosa, verificando os poss?veis benef?cios que esses materiais podem atribuir ao produto final, bem como, a possibilidade dessas mat?rias-primas reduzirem a carga t?rmica necess?ria para obten??o de produtos de igual ou superior qualidade. O trabalho foi divido em duas etapas: caracteriza??o dos materiais e estudo das formula??es. Duas argilas, um filito e um res?duo de caulim foram caracterizados atrav?s das seguintes t?cnicas: granulometria ? laser, ?ndice de plasticidade pelos limites Atterberg, fluoresc?ncia de raios X, difra??o de raios X, composi??o mineral?gica por Rietveld, an?lise termogravim?trica e an?lise t?rmica diferencial. Para o estudo das formula??es, mais especificamente para avalia??o das propriedades tecnol?gicas das pe?as, foi executado um modelo experimental que combinou um planejamento envolvendo mistura de tr?s componentes (massa padr?o x filito x res?duo de caulim) e um planejamento fatorial 23 com ponto central associado aos par?metros t?rmicos de processamento. A experimenta??o foi realizada com restri??o na aleatoriza??o por strip-plot. No total foram investigados 13 pontos composicionais dentro das seguintes restri??es: filito ≤ 20% em peso; res?duo de caulim ≤ 40% em peso; e massa padr?o ≥ 60% em peso. Os par?metros t?rmicos foram utilizados nos seguintes n?veis: 750 e 950 ?C para temperatura de queima; 5 e 15 ?C/min para a taxa de aquecimento; 15 e 45 min para o patamar. Os resultados obtidos demostraram que a introdu??o do filito e/ou res?duo de caulim na massa cer?mica produz uma s?rie de benef?cios nas propriedades do produto final, tais como: redu??o na absor??o de ?gua, porosidade aparente e retra??o linear de queima; al?m do aumento na massa espec?fica aparente e na resist?ncia mec?nica das pe?as. Os melhores resultados foram obtidos nos pontos composicionais em que a soma dos teores de filito e res?duo de caulim foi m?xima (40 % em peso), assim como, nas condi??es de queima em que foram utilizadas temperaturas de 950 ?C. Em rela??o ? perspectiva de economia na energia t?rmica necess?ria para forma??o da microestrutura desej?vel, o filito e o res?duo de caulim por apresentarem pequenos tamanhos de part?culas e constitui??es mineral?gicas com presen?a de fases fundentes, contribu?ram para a otimiza??o do ciclo de queima.