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°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 ∼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.