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 ultr… Show more
“…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].…”
Section: Introductionmentioning
confidence: 99%
“…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.…”
Section: Introductionmentioning
confidence: 99%
“…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.…”
Mullite is a refractory material with singular properties, although high temperatures and long sintering times are required to obtain this material with good densification. In this study, aluminum hydroxide and colloidal silica were used to produce mullite through reactive sintering and MgO was employed as a sintering additive. The compositions were prepared with different amounts of MgO and sintered at 1350, 1450, and 1550 °C, and then analyzed using X-ray diffraction, scanning electron microscopy, and measurements of apparent porosity (AP) and flexural strength. The results showed that the raw materials used allowed the mullite formation at relatively low temperatures (1350 °C), regardless of the amount of MgO added but with the increase in MgO content, a spinel phase appeared, resulting in a fraction of residual α-alumina. The MgO addition lowered the densification temperature at around 50 °C. Furthermore, the higher the sintering temperature and the MgO content, the larger and more anisotropic the mullite grains were. At sintering temperatures above 1450 °C, AP was reduced to approximately 10%. The MgO addition and increase in sintering temperature improved the flexural strength of mullite materials.
“…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].…”
Section: Introductionmentioning
confidence: 99%
“…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.…”
Section: Introductionmentioning
confidence: 99%
“…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.…”
Mullite is a refractory material with singular properties, although high temperatures and long sintering times are required to obtain this material with good densification. In this study, aluminum hydroxide and colloidal silica were used to produce mullite through reactive sintering and MgO was employed as a sintering additive. The compositions were prepared with different amounts of MgO and sintered at 1350, 1450, and 1550 °C, and then analyzed using X-ray diffraction, scanning electron microscopy, and measurements of apparent porosity (AP) and flexural strength. The results showed that the raw materials used allowed the mullite formation at relatively low temperatures (1350 °C), regardless of the amount of MgO added but with the increase in MgO content, a spinel phase appeared, resulting in a fraction of residual α-alumina. The MgO addition lowered the densification temperature at around 50 °C. Furthermore, the higher the sintering temperature and the MgO content, the larger and more anisotropic the mullite grains were. At sintering temperatures above 1450 °C, AP was reduced to approximately 10%. The MgO addition and increase in sintering temperature improved the flexural strength of mullite materials.
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