Effects of doping Al2O3/2SiO2 on the structure and properties of magnesium matrix ceramic

Abstract

To improve the sintering properties and the thermal shock resistance of magnesium matrix ceramic, this work used micron-sized MgO as the main raw material and nano-Al 2 O 3 and SiO 2 as additives. Magnesium matrix ceramic was doped with different amounts of Al 2 O 3 and SiO 2 (Al 2 O 3 and SiO 2 at a molar ratio of 1:2) and sintered under standard atmospheric conditions. The effect of Al 2 O 3 /2SiO 2 doping amounts on sintering properties, thermal shock resistance, phase composition, and microstructure of composite ceramic materials were investivigated. The results suggested that introducing Al 2 O 3 /2SiO 2 could improve the sintering properties of magnesium matrix ceramic. The grain boundary migration of its periclase phase could be hindered by the magnesium aluminate spinel and forsterite formed by solid reaction including Al 2 O 3 , SiO 2 addition, and the MgO itself. Furthermore, according to the mechanism of thermal expansion mismatching, with increasing Al 2 O 3 /2SiO 2 addition, thermal shock times increased significantly, the number of ceramic internal micro-cracks increased after the thermal shock and the material fracture surface energy was improved. It is found that the way of transgranular combining intergranular fractures can decrease the stress concentration at the crack tips and hinder crack propagation. The secondary phase particles deflected matrix internal micro-cracks and the crack propagation path length thus increased, residual stress field were subjected to interference and energy dissipation mechanisms improved. Meanwhile, thermal shock times for the material were enhanced and the degree of densification increased with increasing sintering temperature.

Preparation and characterization of microporous magnesia‐based refractory

“…With the development of metallurgical industry, the lightweight heat‐insulation materials for high temperature vessel including ladle, tundish and others have played an increasingly important role in the iron and steel‐making industry, especially the basic lightweight refractories with good thermal insulation properties 1 . Magnesia is a main raw material of basic refractories, which are widely applied in steel making industry due to good corrosion resistance and high refractoriness under load 2 . Thus, the development and application of lightweight microporous magnesia‐based refractories is extremely important.…”