Spark plasma sintering and toughening of graphene platelets reinforced SiBCN nanocomposites

The possibility of incorporating graphene platelets (GPL) as nanofillers in SiBCN nanocomposites was studied to evaluate the potential improvement on mechanical properties. GPL-SiBCN mixed powders prepared by ball milling of graphene platelets and SiBCN amorphous powders with Al₂O₃ balls was consolidated by spark plasma sintering technique to form bulk samples with different contents of graphene platelets. The effect of added graphene platelets on the improvement of fracture toughness is particularly significant and the fracture toughness increases rapidly with increasing GPL content in the composites. Nearly 650% increase in fracture toughness of GPL/SiBCN ceramic with 5 vol% GPL content, reaching a maximum of 5.40±0.63 MPa·m^1/2. Results show that the nanofillers in ceramic nanocomposites remained uniformly and survived at high temperature. Main toughening mechanisms in graphene platelets reinforced SiBCN ceramic are pull-out, bridging, crack penetration graphene and crack deflection.