Microstructure and mechanical properties of hot-pressed ZrC–Ti–CNTs composites

ZrC-based ceramic composites doped with 20   vol.% titanium (Ti) and 3   vol.% carbon nanotubes (CNTs) were prepared by hot pressing. The densification behavior, microstructural evolution and mechanical properties of the composites were studied. The results indicated that the sinterability of the composites was significantly improved, resulting in highly dense matrix (98.27%) at reduced sintering temperature (1600   °C). In addition to the main phase of (Zr, Ti)C, the composites also contained a certain amount of TiC, which was shown to be beneficial for the improvement of mechanical properties. As a result, the flexural strength of the composites was measured to be 415   MPa at room temperature and 647   MPa at 800   °C, respectively. Moreover, the composites showed a high fracture toughness of 5.27   MPa   m 1/2 , which increased by 32% compared with the monolithic ZrC (4   MPa   m 1/2 ). The improved fracture toughness was attributed to crack deflection, crack bridging and crack branching.