Densification behavior and mechanical properties of spark plasma sintered ZrC-SiC and ZrC-SiC-CNT composites

ZrC-SiC and ZrC-SiC-CNT composites containing 0-30 vol% SiC and 0.25-1 wt% CNT were prepared by spark plasma sintering at 1750-1850°C for 300 s under a pressure of 40 MPa. Fully dense ZrC based composites with a relative density of approximately 99% were obtained. The hardness of ZrC-SiC composites increased from 18.2 GPa to 20.6 GPa when the content of SiC increased from 10 to 30 vol% and the fracture toughness of ZrC increased from 3.3 to 5.5 MPa·m^1/2 with the addition of 30 vol% SiC. Additionally, mechanical properties of ZrC-SiC composites having 30 vol% SiC increased with 0.25 wt% CNT. However, further addition of CNT resulted in lower hardness values and there was not any considerable difference in fracture toughness values for ZrC-SiC-CNT composites. The highest values of hardness and fracture toughness were 21.6 GPa and 5.8 MPa·m^1/2 which was about 75% better compared to monolithic ZrC, and achieved with the addition of 30 vol% SiC and 0.25 wt% CNT.