Sinterização ultrarrápida por micro-ondas do compósito mulita-cordierita

Abstract

ResumoA sinterização ultrarrápida por micro-ondas é uma técnica que oferece enorme potencial para a fabricação de diversos materiais cerâmicos com microestruturas cerâmicas diferenciadas. Assim, este trabalho teve por objetivo sinterizar compósitos cerâmicos do tipo mulita-cordierita em forno de micro-ondas. Para realizar essa pesquisa, foi utilizado um compósito 60%mulita-40%cordierita, originário da empresa Scimarec Co. Amostras desse compósito foram sinterizadas em forno convencional e por sinterização ultrarrápida em forno de micro-ondas. A caracterização foi feita por difratometria de raios X, microscopia eletrônica de varredura e determinação de densidade aparente. A sinterização ultrarápida do compósito por micro-ondas foi realizada em menos de 10% do tempo gasto para realizar a sinterização convencional e apresentou mesmos mecanismos de sinterização com potencia e tempo controlados. Palavras-chave: sinterização, mulita, mulita-cordierita, cordierita, micro-ondas. Abstract Microwave fast sintering is a technique with a huge potential for the manufacture of a variety of ceramic materials with controlled ceramic microstructures. The objective of the present work was the microwave fast sintering of mullite-cordierite type ceramic composites in a microwave oven and to examine the infl uence of power and sintering time on the material. In this research, we usedan industrial 60%mullite-40%cordierite composite. Samples of the composite were sintered by the conventional and microwave routes, after which they were characterized by X-ray diffraction and scanning electron microscopy, and their density determined. The microwave fast sintering process took less than 10% of the time required for conventional sintering and showed the same sintering mechanisms with power and time controlled.

Effect of MgO addition on the sinterability and mechanical properties of mullite ceramics

“…Mullite is a refractory ceramic of great industrial importance because of its variety of applications since it can be used in traditional applications such as dishes and refractory products as well as in advanced ones, including structural and functional applications [1][2][3][4][5]. Such versatility is because of its properties, namely: low thermal conductivity, low thermal expansion coefficient, hightemperature resistance, good chemical stability, low density (3.18 g/cm 3 ), excellent creep and thermal shock resistance, high melting point, and excellent electrical resistance [1,2,[5][6][7][8][9][10]. In the Al 2 O 3 -SiO 2 phase diagram, mullite is the only stable crystalline phase up to around 1800 ºC under atmospheric pressure [8][9][10][11].…”

“…In the Al 2 O 3 -SiO 2 phase diagram, mullite is the only stable crystalline phase up to around 1800 ºC under atmospheric pressure [8][9][10][11]. However, due to its high covalent bond degree, and slow diffusion of the Al 3+ and Si 4+ ions in the mullite network and grain boundaries, its production requires high temperatures, above 1600 ºC, and long sintering times to achieve good densification [2,3,6,7,9]. Atisivan et al [12] reported that mullite densification was observed at high temperatures, around 1650 ºC.…”

“…Sintering additives help to reduce the glassy phase viscosity, making easier silicon and aluminum ions diffusion through the mullite network [3,4,13,14]. The reduction in the activation energy for diffusion improves mullite densification and reduces mullitization temperature [2,3,6,7,9,14,15]. This enables the production of high-density mullite at relatively low temperatures which is important for the refractory industry.…”