Influence of graphene-based nanostructures processing routes and aspect ratio in flexural strength and fracture mechanisms of 3Y-TZP-matrix composites

Abstract

In this work, the influence of the aspect ratio of graphene-based nanostructures (GBNs) and content on the mechanical properties of 3 mol% yttria tetragonal zirconia polycrystalline 3Y-TZP matrix composites was analysed. The influence of the dispersion method and sintering parameters on the flexural strength and elastic modulus of the composites was studied, and the fracture surfaces were characterized to determine the fracture mechanisms that occur. The results showed that small amounts of exfoliated graphene nanoplatelets, with reduced lateral size, and few layer graphene, up to 1.0 and 2.5 vol%, respectively, slightly increase the 3Y-TZP flexural strength. This has been attributed to the tortuosity of the crack propagation pathways and strengthening mechanisms. Higher contents cause a decrease in flexural strength and stiffness because of overlapped GBNs, which can promote the crack propagation. The pull-out of GBN was more significant in composites with non-exfoliated graphene nanoplatelets, where no increase on the flexural or biaxial strength was measured.