Graphene and carbon nanotube (GNT)-reinforced alumina nanocomposites

Alumina nanocomposites reinforced with hybrid GNTs (graphene nanoplatelets, GNPs, and carbon nanotubes, CNTs) were fabricated by hot-pressing. The effects of varied GNT contents on the microstructural features and mechanical properties of the nanocomposites were investigated. The well-dispersed GNT fillers resulted in higher sintered densities (>99%) in the composites, whilst the fracture mode alteration, grain refinement and improved strength and flexibility of the composites are associated with the CNTs and GNPs. The average fracture toughness of the nanocomposites reached up to 5.7 MPa m1/2, against 3.5 MPa m1/2 of the plain alumina, and the flexural strength improved from 360 MPa to 424 MPa, at a hybrid addition of 0.5 wt% GNPs and 1 wt% CNTs. Toughening mechanisms attributed with the unique morphologies and structures of the GNT fillers were also discussed based on analyses on the morphology, grain sizes and fracture mode.