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·m^1/2 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.