Enhanced thermal conductivity and mechanical properties of a GNP reinforced Si₃N₄ composite

Graphene nanocomposites can significantly enhance the thermal conductivity and mechanical properties of ceramics at relatively low nano-filler addition. Herein, graphene nano-platelet reinforced Si₃N₄ (GNP/Si₃N₄) composites were prepared by hot press (HP) sintering using fluoride (AlF₃, MgF₂) sintering-additives. The microstructural properties revealed the enhanced crystallization degree and density of the GNP/Si₃N₄ composites with different concentrations of graphene nano-platelets (GNPs). These properties help to achieve a significantly improved thermal conductivity (from 82.42 to 137.47 W m^-1 K^-1) of the GNP/Si₃N₄ composites. The morphology of the composites shows a uniform distribution of GNP, whereas overlapping of GNPs (2 to 4 platelets) at the grain boundaries of Si₃N₄ was observed. The fracture toughness and Vickers hardness of the composites also increased with the increasing content of GNP. The toughening mechanism was similar in all composites with GNP addition in respect of pull out, crack deflection, crack branching and crack bridging.