Combined effects of graphene nanoplatelet and zirconium diboride additions on spark plasma sintered boron carbide composites with square geometry

In the present work, graphene nanoplatelets (GNPs) in varying amounts (1, 2, and 3 vol%) were incorporated into B4C composite powders containing 5 and 15 vol% ZrB2. The square-shaped composites were produced by spark plasma sintering (SPS) at 1540 degrees C under 50 MPa with a 7 min holding time. The effects of GNP addition on the densification behavior, homogeneity, mechanical properties, and microstructure of the composites were evaluated. The results showed that adding GNPs into the B4C-ZrB2 matrix enhanced the relative density and improved the homogeneity across different sections (center, edge, corner) of the square-shaped composites. Composites containing 15 vol% ZrB2 and 1 vol% GNP demonstrated optimal performance with relative density, hardness, and fracture toughness of similar to 99.5 %, 34.76 GPa, and 4.15 MPa.m(1/2), respectively. Moreover, crack deflection, branching, and bridging were identified as primary toughening mechanisms.