Effect of TaC and graphene nanoplatelets on the microstructure and mechanical properties of ZrB₂

In this experiment, in order to investigate the effect of TaC addition on the microstructure, densification and mechanical properties of ZrB₂ composites reinforced with graphene nanoplatelets (GNP), three composites were fabricated via spark plasma sintering (SPS) at 1900 °C. Relative density was determined by Archimedes method. The XRD and EDS analyses were used to explore the phase composition and elemental distribution. Also, Field emission scanning electron microscopy (FE-SEM) was employed to characterize the microstructure (grain size and porosity). Flexural strength, fracture toughness and hardness were determined by three-point bending test, single-edge notched beam (SENB) and macro and micro Vickers methods, respectively. The results showed that the presence of the GNP, alone and combined with TaC, increases the relative density sharply to 99.6 %. In addition, full densification occurred by the addition of 10 and 20 vol% TaC compared to the monolithic ZrB₂ ceramic with 83 % relative density. Maximum flexural strength and fracture toughness of 580 MPa and 4.5 MPa.m^0.5 were obtained, respectively, for ZrB₂- GNP and ZrB₂- GNP doped with 10 vol% TaC.