Tailoring the material properties of graphene-reinforced silicon nitride composites fabricated via spark plasma sintering

The present study explores the development and optimisation of graphene nanoplatelets (GNPs)-reinforced silicon nitride (Si 3 N 4 )-based composites to enhance material performance. The composites were synthesised utilising magnesium oxide and yttrium oxide as sintering additives via spark plasma sintering (SPS). The present study has the novelty that such combination of sintering additives has never been utilised to sinter GNPs-reinforced Si 3 N 4 ceramics. Varying concentrations of GNPs were introduced into the Si 3 N 4 matrix, and the resulting materials were extensively characterised using X-ray diffraction for phase analysis, Raman spectroscopy for carbon structure evaluation, and field-emission scanning electron microscopy for microstructural assessment. The results demonstrate that a low GNP content (0.5 wt%) leads to a simultaneous improvement in mechanical (peak hardness of 16.5 GPa), fracture toughness (6.7 MPa m 1/2 ), tribological performance (wear volume = 0.027 mm 3 , wear rate = 4.3 × 10 −8 mm 3 .N −1 .m −1 , and a μ m e a n ≈ 0.11 ), and thermal conductivity (64.8 W.m −1 K −1 ) under identical SPS conditions. The study further elucidates the relationship between graphene dispersion, phase evolution, and property degradation at higher GNPs contents, providing a comprehensive assessment of the reinforcement efficiency of GNPs in Si 3 N 4 ceramics.