▎ 摘　　要

A kind of B4C/SiC composite ceramic toughened by graphene platelets and Al was fabricated by spark plasma sintering. The effects of graphene platelets and Al on densification, microstructure and mechanical properties were studied. The sintering temperature was decreased about 125-300 degrees C with the addition of 3-10 wt% Al. Al can also improve fracture toughness but decrease hardness. The B 4 C/SiC composite ceramic with 3 wt%Al and 1.5 wt% graphene platelets sintered at 1825 degrees C for 5 min had the optimal performances. It was fully densified, and the Vickers hardness and fracture toughness were 30.09 +/- 0.39 GPa and 5.88 +/- 0.49 MPa m(1/2), respectively. The fracture toughness was 25.6% higher than that of the composite without graphene platelets. The toughening mechanism of graphene platelets was also studied. Pulling-out of graphene platelets, crack deflection, bridging and branching contributed to the toughness enhancement of the B4C-based ceramic.