SYSTEM SI-AL-MG-O - THERMODYNAMIC ASPECTS OF ITS INFLUENCE ON THE OXIDATION RESISTANCE OF SILICON-CARBIDE AT HIGH-TEMPERATURE

With the aim to protect silicon carbide based materials against oxidat ion at high temperature, the influence of silica-based refractory glas ses is examined through thermodynamic equilibrium calculations. The sy stems Si-Al-Mg-O and Si-Al-Mg-O-C are considered The thermodynamic dat a for the ternary liquid phase are obtained through a 'cells' model. T he vaporization behaviour of different slag compositions (2000-2250 K) are deduced from heterogeneous calculations and from comparison with pure silica. Trends of lowering the vaporization and the reactivity ag ainst silicon carbide are strongly related with the amount of alumina and magnesia in the liquid phase.