Effect of polymorphism of Al2O3 on the synthesis of magnesium aluminate spinel

Abstract MgAl 2 O 4 spinel was prepared by reaction sintering and the effect of polymorphism of Al 2 O 3 on the synthesis and densification of the spinel studied. γ-Al 2 O 3 , ρ-Al 2 O 3 and α-Al 2 O 3 were mixed with analytical reagent of MgO according to the stoichiometric spinel ratio, respectively, and pressed into billets with diameter of 20 mm and height of 15 mm. The green-body billets then were sintered at temperature from 800 °C to 1600 °C in an air atmosphere. Bulk density, porosity, linear expansion changes, phase composition, microstructure and grain size of final sintered products were analyzed. The results indicated that γ-Al 2 O 3 is beneficial for synthesize of spinel because it has a crystal structure similar to that of spinel. Among materials sintered at 1600 °C for 3 h, samples using γ-Al 2 O 3 as raw material had the highest density, up to 91% of the theoretical density of MgAl 2 O 4 , and had the largest grain size of spinel.

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