Mullite Synthesis Kinetics from Polydispersed Vibration-Milled Wastes of Commercial Corundum in the Presence of High-Silica Melt: Experimental and Modelling Results

Abstract

The experimental kinetic data of mullite synthesis using commercial regular corundum vibration-milled wastes and silica by isothermal heat treatment were studied. The principle of diffusion flux symmetry to a convex surface was applied to perform theoretical analysis of partially and fully immersed quasispherical polydispersed particle interaction with a liquid phase (PAFIQPP method) to further derive the kinetic equations of mullite synthesis in the range of conversion degrees 0< a< 0.75-0.85 assuming corundum dissolution as a limiting stage in the molten silicate. The rate constants and activation energy of the process were calculated and adequately approximated by the PAFIQPP method experimental data: the rate constant growth from 3.3 9 10 -8 cm s À1 to 9.2 9 10 À8 cm s À1 was observed in the temperature range 1350-1500°C; the activation energy was 160 kJ/mol.