The morphological evolution of the oxide products of Si₃N₄/Al₂O₃ composite refractory under different oxidizing conditions

Abstract

The reaction behavior of Si 3 N 4 /Al 2 O 3 composite at 9001500°C in dry O 2 and Ar containing 20 vol.% H 2 O for 50 h was investigated using thermogravimetric method. The phase, microstructure and macroscopic cross sections of the products were characterized by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy as well as optical microscopy, respectively. Especially the morphological evolution of mullite, the main oxide product, was investigated. The results show that both the reaction atmosphere and temperature have significant influence on the morphology of the oxide product. Based on experimental results, the reaction kinetics of Si 3 N 4 /Al 2 O 3 composite was discussed using the real physical picture model.