Improved Fracture Toughness and Crack Arrest Ability of Graphene-Alumina Nanocomposite

In this work, high fracture toughness graphene-alumina composite was developed through a novel chemical method using boehmite and graphene, which is followed by extrusion and consolidation. The mixed precursors were consolidated by sintering at 1550 degrees C in a nitrogen atmosphere. The plate-like structures of boehmite form alpha-alumina; meanwhile, graphene particles at the grain boundaries hinder the growth of alumina grains. The graphene reinforcement was bonded to alpha-alumina matrix by van der Waals forces. The XRD pattern reveals the presence of graphene with a plane (002) along with alpha-alumina. Properties such as fracture toughness (5.6 +/- 0.01 MPa m(0.5)), Vickers hardness (1872 +/- 25 kgf/mm(2)) and true density (3.8 g/cm(3)) were achieved in 0.5 wt.% graphene-alumina composite when compared to alpha-alumina with fracture toughness (5.3 +/- 0.1 MPa m(0.5)), Vickers hardness (1984 +/- 28 kgf/mm(2)) and true density (3.91 g/cm(3)). The bridging and deviation of cracks in 0.5 wt.% graphene-alumina composite are attributed to the anchoring and dissipation of energy during crack growth, which enhances the fracture toughness, whereas alpha-alumina exhibits failure caused by linear crack propagation. Meanwhile, the slight decrease in Vickers hardness and true density of 0.5 wt.% graphene-alumina composite is due to the tribological and low-density properties of graphene. The obtained properties of composite could be suitable in high-temperature, wear-resistant applications such as crucibles, bearings, etc.