Influence of graphite platelets with and without SiC on the densification and fracture toughness of ZrB2 ceramic sintered by SPS

Few studies have been performed on ZrB2-graphite platelet composite made by spark plasma sintering (SPS) technique. In this research, the influence of adding graphite platelets (Gp) with and without SiC on the fracture toughness of ZrB2 ceramic was studied. The ZrB2-10Gp, ZrB2-15Gp, ZrB2-30SiC-10Gp, and ZrB2-30SiC-15Gp specimens were sintered by the SPS method at the temperature of 1850 °C for 8 min. The fracture toughness and work of fracture (WOF) were evaluated using the Single-Edge Notched Beam (SENB) technique. It was found that the fracture toughness and WOF were improved by the alone and combined addition of Gp and SiC to the monolithic ZrB2. The maximum fracture toughness of 4.8 ± 0.1 MPa m1/2 was obtained for the ZrB2-15Gp specimen. It seems that adding Gp alone was more effective in enhancing the fracture toughness of ZrB2 than the combined addition of Gp and SiC. While the addition of Gp and SiC simultaneously modified the densification behavior to reach full-densified samples.