Effect of Al2O3 + 4SiO2 Additives on Sintering Behavior and Thermal Shock Resistance of MgO-Based Ceramics

Abstract

In order to improve the sinterability and thermal shock resistance of ceramic based on MgO magnesium oxide of micron grain size composition is used as the main starting raw material with additions of nano-Al₂O₃ and nano-SiO₂. Ceramic based on MgO is prepared by adding different amounts of Al₂O₃ and SiO₂ to MgO in a molar ratio 1:4. The mixture is molded and sintered in an air atmosphere. Ceramic phase composition and microstructure are studied in an x-ray diffractometer and a scanning electron microscope. The effect of adding different amounts of Al₂O₃ + 4SiO₂ on sinterability and thermal shock resistance of MgO base ceramic is studied. Addition of Al₂O₃ + 4SiO₂ has a favorable effect on test ceramic sinterability and thermal shock resistance. During reaction of solid substances there is formation of magnesia-alumina-spinel and forsterite that leads to retardation of periclase phase grain migration. The degree of specimen compaction is improved and this has a favorable effect on sinterability of ceramic based on MgO. The degree of compaction increases as there is an increase in sintering temperature in the range 1400 to 1500°C. In addition, specimen thermal shock resistance is improved due to connection between microcracks. As a result of adding Al₂O₃ in an amount up to 30 wt.% + SiO₂ in an amount up to 45 wt.% MgO sinterability and thermal shock resistance are improved.