B4C–Graphene Nanoplatelet Composite Fabricated by Hot Pressing of Heterogeneously Co-Precipitated Powder Mixtures

Boron carbide (B4C) ceramics suffer from poor sinterability and inherent brittleness, which severely limit their engineering applications. In this work, B4C–graphene nanoplatelet (GNP) composites were fabricated by hot pressing using heterogeneously co-precipitated powder mixtures, with cetyltrimethyl ammonium bromide (CTAB) as a surfactant for achieving uniform dispersion of GNPs within the B4C matrix. The formation mechanisms of B4C–GNP hybrids were systematically elucidated. The results show that CTAB endows GNPs with positive charges, enabling electrostatic co-precipitation with negatively charged B4C particles to construct layered hybrid architectures. The GNP content has a significant modulation effect on the microstructure and mechanical properties of B4C composites. A maximum relative density of 99.65%, Vickers hardness of 33.5 GPa, and flexural strength of 488 MPa were obtained at 1 wt% GNPs, while the fracture toughness reached a peak value of 4.89 MPa·m1/2 at 2 wt% GNPs, representing a 63.5% improvement over monolithic B4C. The enhanced fracture toughness is attributed to multiple toughening mechanisms, including crack deflection, crack bridging, GNP pull-out, step-like fracture, and zigzag crack propagation. This study provides a feasible strategy for preparing uniformly dispersed ceramic–graphene composites with balanced mechanical properties.