Densification and characterization of hot-pressed ZrC-based composite doped with Nb and CNT

• ZrC-based ultra-high temperature ceramic composite (ZNC) was prepared in this paper, which is composed of ZrC + 20Nb + 3CNTs (vol.%).
• Highly dense ZNC with a relative density of 99.28% was obtained at 1600 °C by hot pressing.
• The ZNC showed a fracture toughness of 7.23 MPa·m1/2, which increased by 80% compared with the monolithic ZrC ceramic.

ZrC-based composite doped with 20 vol.% niobium (Nb) and 3 vol.% carbon nanotubes (CNT) was prepared by hot pressing. Due to the addition of Nb and CNT, the sinterability of ZrC was significantly improved, resulting in highly dense matrix (99.28%) at reduced sintering temperature (1600 °C). The flexural strength was 590 MPa at room temperature and 563 MPa at 800 °C, respectively. The fracture toughness was 7.23 MPa·m1/2, which increased by 80% compared with the monolithic ZrC (4 MPa·m1/2). In addition, the work of fracture was calculated to be 267 J/m2. Based on the microstructure characterizations, the improved fracture properties could be attributed to crack deflection, crack bridging and crack branching, which consumed more fracture energy during the fracture process.

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