Microstructure and properties of a graphene platelets toughened boron carbide composite ceramic by spark plasma sintering

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 °C with the addition of 3-10 wt% Al. Al can also improve fracture toughness but decrease hardness. The B4C/SiC composite ceramic with 3 wt%Al and 1.5 wt% graphene platelets sintered at 1825 °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 m1/2, 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.