Design and Mechanical Properties of ZTA–Niobium Composites with Reduced Graphene Oxide

Niobium–graphene oxide–zirconia-toughened alumina (ZTA) composites were produced by wet mixing and spark plasma sintering. The microstructure and mechanical properties of this novel composite have been studied. The results show that niobium particles are homogeneously dispersed in the ZTA matrix. Raman spectroscopy confirmed the thermal reduction in graphene oxide during sintering. The presence of ductile metal and graphene flakes leads to an increase in the crack resistance value of the ZTA matrix. The developed composites demonstrate a fracture toughness of 16 MPa∙m1/2, which is three times higher than ZTA ceramic composites. The high toughness values found in this new composite are a consequence of the strong interaction between the simultaneous action of several toughening mechanisms, specifically involving crack trapping, crack blunting, crack renucleation, and the bridging mechanisms of the metallic and graphene particles. Moreover, this increase has also occurred due to the enhancement of the transformability of zirconia in ceramic–metal composites.