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

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. Keywords: ZrC, Nb, CNT, Microstructure, Mechanical properties