Impact of Precursor Granulometry on the Synthesis of Calcium-Aluminate Phases

Abstract

Calcium aluminate phases were synthesized in the range 950–1450°C from available raw materials: carbonate rock and metallurgical alumina, predominantly in the γ form with different grain sizes. The calculations of the amount of raw materials were based on the requirement to ensure the chemical composition of the product: Al2O3 71–72 and CaO 27–28 wt %. The designed phase composition of the samples is 65 wt % CaAl2O4 and 35 wt % CaAl4O7. When alumina with a grain size of 90 μm and a spherulitic microstructure is introduced into the reaction, the formation of the CaAl2O4 and CaAl4O7 phases mainly occurs in the range of 1250–1350°C, and phase equilibrium is established at 1450°C. Reducing the size of γ-alumina grains to 10 μm and destroying their spherulitic microstructure shifts the formation of calcium aluminates to the temperature range below 1250°C, and also significantly increases the rate of synthesis of target products.