First-principles simulation of the growth of in situ synthesised β-Sialon and its effects on the thermo-mechanical properties of Al2O3-C refractory composites

Columnar beta-Sialon bonding phases were in situ synthesised in Al2O3-C refractory composites and their growth mechanism was simulated based on first-principles calculations. The experimental results indicated that the addition of Fe2O3 as a catalyst accelerated the transformation of Si3N4 to beta-Sialon, resulting in a well-developed columnar structure. The (100) facet was the primary surface for crystal growth during the transformation process of Si3N4 into beta-Sialon. According to first-principles calculations, the surface energy of the (100) facet decreased greatly due to the substitution of (Si, N) pairs with (Al, O). The catalyst could promote the adsorption of gaseous phases on the (100) facet of Si3N4 and decreased the gas adsorption energy of both SiO and Al2O. Owing to the presence of in situ synthesised columnar beta-Sialon bonding phases, the residual crushing strength of Al2O3-C refractory composites after 5 thermal shock cycles increased by 25.1%.