The microstructure and some properties of magnesia-alumina spinel materials with sialon matrix.

In the pseudo ternary MgO-Si₃N₄-Al₂O₃ system at 1800 °C the occurrence of liquid phase is limited to areas near the MgO-Si₃N₄ line, close to Si₃N₄. The area near the MgO-Al₂O₃ line is interesting from the point of view of refractory materials. The results of investigations into the properties and microstructure of magnesia-spine! materials with oxynitride and nitride matrix obtained bysintering are presented. The materials with a matrix composed of AIN polytypoids were characterized by very high refractoriness under load (RUL) in reducing conditions (T_0.6>1700°C) and relatively high RUL in air (mm T_0.5> 1620°C). The TG curves showed that the oxidation course was similar to and depended on the composition and mixture of samples. A very good correlation was found between the calculated values of R coefficient and resistance to thermal shocks sustained by the cylinders subjected to sudden heating up to 950 °C and cooling. [ABSTRACT FROM AUTHOR]