Influence of graphene addition and sintering temperature on physical properties of Si 3 N 4 matrix composites

Abstract The Si 3 N 4 -graphene composites (1 wt% addition of graphene) were manufactured using powder metallurgy and consolidated using the Spark Plasma Sintering (SPS) method. In order to achieve composites with high mechanical properties, optimisation of a Si 3 N 4 and Si 3 N 4 -graphene sintering temperatures were carried on for five and four different sintering temperatures respectively. Obtained samples were characterised by measurements of their density, hardness, fracture toughness and Young's modulus. Qualitative and quantitative phase composition was analysed by XRD diffraction. Microstructure analysis of sinters was also performed using Scanning Electron Microscopy (SEM). The highest relative density (99.31% and 99.32%) and fracture toughness (K IC = 6.0 MPa ∗ m 0.5 ) was measured for samples sintered at 1650 °C and 1700 °C respectively, for Si 3 N 4 and Si 3 N 4 –Gn composite. That shows no increase of fracture toughness between pure silicon nitride sinter and composite with 1% wt of graphene. Furthermore, XRD results showing 33% less of β grains in Si 3 N 4 –Gn composite compared to pure Si 3 N 4 sample, proving that graphene stabilise the α phase in silicon nitride.