Title: Effect of nano-scale graphene and carbon nanotubes on mechanical properties of alumina- zirconia nanocomposites

Abstract

The brittle nature of alumina and other technical ceramics limits their mechanical performance under various operating conditions. Through microstructural tailoring, the fracture toughness and other mechanical attributes of alumina can be improved adding nanoscale materials such as graphene, carbon nanotubes and zirconia to form a nanocomposite. For the current studies, alumina-zirconia nanocomposites reinforced with both graphene and carbon nanotubes have been fabricated via colloidal mixing and followed by hot-pressing sintering process. The effect of 0.5wt% graphene and 2wt% carbon nanotubes on the alumina-zirconia microstructure and mechanical properties were characterized using the single edge notched beam (SENB) test and conventional indentation fracture toughness (IFT) test. Typically, there is a relatively high degree of grain refinement of the nanocomposites due to the synergistic effect of carbon nanotubes and graphene. This directly influenced the physical and mechanical properties of the hybrid nanocomposites such as density, hardness and fracture toughness. Fractography studies after the SENB tests also demonstrate the toughening mechanisms of the individual carbon additives as well as their synergistic role in improving the fracture toughness of monolithic alumina. Both intergranular and transgranular fracture modes were depicted by the hybrid nanocomposites during the bending tests are were prevalent in the fractography of the fabricated samples.