Synthesis and characterization of in-situ CNTs reinforced TiB2-based composite by CVD using Ni catalysts

In-situ synthesized Carbon nanotubes-(Ni)-TiB2 (CNTs(Ni)-TiB2) composite powders were produced by chemical vapor deposition. The effect of the synthesis temperature (700–1100°C) on the growth of the CNTs was investigated. The bulk CNTs(Ni)-TiB2 composites were consolidated from the as-prepared powders by spark plasma sintering at 1500–1700°C. The results showed that the highest flexural strength and fracture toughness of the CNTs(Ni)-TiB2 composite were obtained when it was synthesized at 1000°C and then sintered at 1600°C, which were determined to be 1182 ± 53MPa and 15.8 ± 0.4MPam1/2, respectively. These superior properties were attributed to the dense microstructures, well-dispersed CNTs and the strong interfacial strength between the CNTs and the TiB2 powders. The fracture mode was a mixed mode, including transgranular and intergranular modes. The CNTs debonding and pull-out were thought to be effective strengthening mechanisms to exhaust the fracture energy.