Simulation and experimental investigation of preferred β-Sialon growth and its effects on thermo-mechanical properties of Al2O3–C refractories

Abstract

Abstract β-Sialon bonded Al2O3–C refractories possess high strength and superior thermal shock performance. In this study, the growth of preferred β-Sialon (Si3Al3O3N5) and its effects on thermo-mechanical properties of Al2O3–C refractories were investigated via simulations and experiments. The results indicate that the additive Fe2O3 contributed to the formation of β-Sialon and helped its column structure become plate-like. Transmission electron microscopy confirmed that the (101) crystal plane was a growth plane of plate-like β-Sialon. The growth mechanism of β-Sialon was suggested by density functional theory; calculation results revealed that the key step for the formation and growth of β-Sialon was the adsorption of the gaseous molecule Al2O on the Si3N4 (101) crystal plane. It was found that the existence of Fe atoms could significantly reduce the adsorption energy. Additionally, Al2O3–C refractories containing plate-like β-Sialon possessed a high cold modulus of rupture and crushing strength, which increased by 40% and 15%, respectively, compared with the specimens containing column β-Sialon. It was also found that the formation of plate-like β-Sialon resulted in significantly better thermal shock resistance for the Al2O3–C refractory specimens, and the residual strength loss ratio of the sintered specimens was only 4% after five thermal shock cycles.