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Abstract(s)
Este trabalho enquadra-se na necessidade dos fabricantes de aeronaves em produzirem novos componentes, capazes de contribuir para a diminuição da emissão de gases poluentes e do consumo de combustível, melhorando a performance da aeronave. Sendo os compósitos de matriz cerâmica o principal sucessor das superligas de níquel utilizadas atualmente.
Com este trabalho pretendeu-se propor, desenvolver e caracterizar CMC’s contendo na sua matriz zirconato de cálcio (CaZrO3). Selecionaram-se dois materiais de reforço, o óxido de magnésio (MgO) e o dióxido de titânio (TiO2), e analisou-se a influência da sua adição à matriz de zirconato de cálcio. Obtiveram-se materiais de 3 composições diferentes (CaZrO3, CaZrO3+MgO e CaZrO3+MgO+TiO2) após homogeneização e moagem das composições, prensagem unidirecional a frio e sinterização otimizada em atmosfera oxidante.
Os materiais foram caracterizados fisicamente (porosidade e densidade), mecanicamente (flexão em 3 pontos, compressão, dureza e tenacidade à fratura), microestruturalmente (microestrutura e superfície de fratura) e eletricamente (resistividade). Concluiu-se que tanto a adição do MgO como do TiO2 melhoram as propriedades mecânicas do zirconato de cálcio, sendo que a adição do TiO2 foi a mais significativa. Para a composição CaZrO3+MgO+TiO2 obteve-se uma densidade teórica de 99%, sendo também aquela onde se obteve melhores valores de resistência mecânica (126 MPa para a resistência à flexão e 220 MPa para a resistência à compressão). Da observação microestrutural observou-se diferentes modos preferenciais de fratura – grãos de MgO têm fratura preferencial transgranular e os de TiO2 intergranular. Para a caracterização elétrica não foi possível obter os valores desejados, uma vez que as 3 composições apresentaram elevados valores de resistividade superficial em área.
This work is in line with the need for aircraft manufacturers to produce new components, which can contribute to the reduction of the emission of pollutant gases and the consumption of fuel, improving the performance of the aircraft. Being the ceramic matrix composites the main successor of the nickel super alloys currently used. With this work is intended to propose, develop and characterize CMC's containing calcium zirconate (CaZrO3) in its matrix. Two reinforcing materials, magnesium oxide (MgO) and titanium dioxide (TiO2), were selected, and the influence of their addition on the calcium zirconate matrix was analyzed. Materials of 3 different compositions (CaZrO3, CaZrO3+MgO and CaZrO3+MgO+TiO2) were obtained after homogenization and milling of the compositions, cold unidirectional pressing and optimized sintering in an oxidizing atmosphere. The materials were physically characterized (porosity and density), mechanically (3-point bending, compression, hardness and fracture toughness), microstructurally (microstructure and fracture surface) and also an electrical characterization (resistivity). It was concluded that both the addition of MgO and TiO2 improved the mechanical properties of calcium zirconate, with the addition of TiO2 being the most significant. For the composition CaZrO3+MgO+TiO2, a theoretical density of 99% was obtained, also it is the one where the best values of mechanical strength were obtained (126 MPa for the flexural strength and 220 MPa for the compressive strength). From the microstructural observation, different preferred modes of fracture were observed - MgO grains had preferential transgranular fracture and TiO2 intergranular. For the electrical characterization it was not possible to obtain the desired values, since the 3 compositions showed high values of surface resistivity in the area.
This work is in line with the need for aircraft manufacturers to produce new components, which can contribute to the reduction of the emission of pollutant gases and the consumption of fuel, improving the performance of the aircraft. Being the ceramic matrix composites the main successor of the nickel super alloys currently used. With this work is intended to propose, develop and characterize CMC's containing calcium zirconate (CaZrO3) in its matrix. Two reinforcing materials, magnesium oxide (MgO) and titanium dioxide (TiO2), were selected, and the influence of their addition on the calcium zirconate matrix was analyzed. Materials of 3 different compositions (CaZrO3, CaZrO3+MgO and CaZrO3+MgO+TiO2) were obtained after homogenization and milling of the compositions, cold unidirectional pressing and optimized sintering in an oxidizing atmosphere. The materials were physically characterized (porosity and density), mechanically (3-point bending, compression, hardness and fracture toughness), microstructurally (microstructure and fracture surface) and also an electrical characterization (resistivity). It was concluded that both the addition of MgO and TiO2 improved the mechanical properties of calcium zirconate, with the addition of TiO2 being the most significant. For the composition CaZrO3+MgO+TiO2, a theoretical density of 99% was obtained, also it is the one where the best values of mechanical strength were obtained (126 MPa for the flexural strength and 220 MPa for the compressive strength). From the microstructural observation, different preferred modes of fracture were observed - MgO grains had preferential transgranular fracture and TiO2 intergranular. For the electrical characterization it was not possible to obtain the desired values, since the 3 compositions showed high values of surface resistivity in the area.
Description
Keywords
Cerâmica Estrutural Compósitos de Matriz Cerâmica (Cmc) Dióxido de Titânio. Óxido de Magnésio Zirconato de Cálcio