Effect of Al and ZrO2 on Sinterability and Mechanical Properties of B4C
Ceramics composites of B4C matrix with 5 wt% Al and various amount of ZrO2 additives were pressureless sintered under vacuum at 2250 °C for 60 min. Density, hardness, flexural strength and microstructure of the specimens were measured and characterized. Densities above 97% theoretical density (TD) were determined in the samples prepared with the addition of 8 wt% ZrO2 and 5 wt% Al, compared to 86% TD for single-phase B4C. X-ray diffraction analysis showed that B2O3 (impurity in B4C) was eliminated and new phases (ZrB2 and B4C1-x) were formed in the sintered samples, suggesting that in situ reactions between B4C/B2O3 and Al/ZrO2 happened during sintering process. It was showed that the elimination of B2O3 and the forming of boron rich solution of B4C1-x significantly improved the sinterability of B4C matrix ceramics, and consequently enhanced the densification rate greatly. The flexural strength and Vickers hardness of the sintered samples with addition of 8 wt% ZrO2 and 5 wt% Aluminum reached the value of 560 MPa and 30.2 GPa respectively, much higher than those of single-phase B4C ceramics.
Guojun Zhang and Jessica Xu
W. S. Lin and L. He, "Effect of Al and ZrO2 on Sinterability and Mechanical Properties of B4C", Advanced Materials Research, Vols. 160-162, pp. 1494-1497, 2011