Optimized Mechanical Properties and Oxidation Resistance of Al2O3-B4C-C Refractory Ceramics

The effect of B4C addition (0, 3 wt%, 6 wt%, 9 wt%) on the mechanical properties and oxidation resistance of Al2O3-C refractory ceramics was studies in the paper. The results indicated that the addition of B4C could reduce the apparent porosity, increase the mechanical strengths and improve the oxidation resistance. After fired at 1100 °C, the specimen with 6 wt% B4C achieved lowest porosity and permanent linear change. The cold crushing strength was improved from 14.65 MPa to 47.18 MPa. The cold modulus of rupture was significantly improved from 12.1 MPa to 36.29 MPa. When the fired temperature rose to 1450 °C, the lowest porosity and permanent linear change were obtained when B4C additive was 3 wt%. CCS was significantly improved from 12.40 MPa to 57.32 MPa. CMOR was also increased from 7.16 MPa to 28.71 MPa correspondingly. Meanwhile, the oxidation index could be also reduced from 47.6% to 3.9% when B4C content was 6 wt%. These improved properties were due to the formation of liquid phase B2O3 by the reaction between B4C and O2/CO. The compact structure was constructed by volumetric expansion of B2O3.