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

• ZrC–20Ti–3CNTs (vol. %) composite was prepared by hot pressing at 1600 °C.
• Highly dense matrix with a relative density of 98.27% was obtained.
• The fracture toughness of the composite was measured to be 5.27 MPa·m1/2.

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 m1/2, which increased by 32% compared with the monolithic ZrC (4 MPa m1/2). The improved fracture toughness was attributed to crack deflection, crack bridging and crack branching.

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