Preparation of AlN–SiC bonded Al2O3–C refractory and its properties evolution after oxidation

Abstract

The low carbon Al2O3–C refractory was prepared using tabular alumina aggregates and fines, Al2O3 micro-powder, Al powder, and Si powder as starting materials. The physical properties, hot modulus of rupture (HMOR), and thermal shock resistance (TSR) as well as oxidation behavior of samples before and after oxidation at 1500 °C for 3–9 h were investigated. Furthermore, the relationship between properties degradation due to oxidation and microstructure evolution was discussed. The results showed that the in-situ AlN and SiC whiskers forming network structure in Al2O3–C materials conferred good thermo-mechanical properties of the obtained composites. However, the materials were seriously oxidized at 1500 °C for 3–9 h, which resulted in a significant decrease in both physical properties and HMOR. The oxidation percent reached 86% after oxidation for 9 h, and HMOR decreased from 25.8 MPa to 10.5 MPa with increasing oxidation time from 0 to 9 h. However, the oxidized samples have excellent TSR and the residual strength ratio exceeds 90%, which is attributed to the formation of microcracks, mullite, and glass phase in the oxidized layer, and the residual non-oxide whiskers in the unoxidized layer.