Fabrication and mechanical properties of graphene nanoplatelets-reinforced β/α-SiC composite ceramics

The inherent brittleness and limited fracture toughness of silicon carbide (SiC) ceramics pose significant challenges to their structural reliability in advanced applications. This study proposes a phase-interface engineering strategy to overcome these limitations by synergistically incorporating graphene nanoplatelets (GNPs) and a β-SiC phase into an α-SiC matrix. GNPs/β/α-SiC composite ceramics were fabricated via pressureless sintering at 2120°C, with systematic variation of GNPs content (1–3 wt.%) against a fixed 10 wt.% β-SiC addition. The effects of GNPs on the phase evolution, densification behavior, and mechanical properties were comprehensively investigated. Results indicate that GNPs incorporation reduced bulk density and increased open porosity. Notably, all key mechanical properties—flexural strength, Vickers hardness, and fracture toughness—exhibited a distinct maximum at an optimal GNPs content of 1 wt.%. The composite with 1 wt.% GNPs demonstrated a superior combination of properties: a fracture toughness of 5.34 MPa·m 1 / 2 , a flexural strength of 451 MPa, and a hardness of 23.5 GPa. Microstructural analysis revealed that the remarkable enhancement originates from a synergistic toughening mechanism, where GNPs interact with the elongated β-SiC grains to promote multi-scale energy dissipation through crack deflection, bridging, and interface debonding. This work not only presents a high-performance composite but also elucidates a microstructural design principle for developing damage-tolerant ceramic materials.