Preparation and Properties of Low-Carbon Al2O3-ZrO2-SiC-C Composite Refractories Containing LaAl11O18 Ceramic Phase

Low-carbon alumina-zirconia-silicon carbide-graphite (Al2O3-ZrO2-SiC-C, AZSC) composite refractories containing a lanthanum hexaaluminate (LaAl11O18) ceramic phase were prepared by the in-situ reaction sintering. The effects of raw materials ratio, sintering temperature, and La2O3 addition on the phase composition, microstructure, shrinkage ratio, apparent porosity, bulk density, and cold crushing strength of the AZSC refractories were investigated. AZSC refractories with good properties can be prepared at 1723 and 1773 K for 3 h. During the sintering process, t-ZrO2, c-ZrO2, and beta-SiC formed due to an in-situ reaction between ZrSiO4 and C. La2O3 reacted with Al2O3 to produce LaAl11O18, which was platelike and formed on the Al2O3 matrix. The enhancement of properties was attributed to the formation of t-ZrO2, c-ZrO2, beta-SiC, and LaAl11O18 in the AZSC refractories.