Synthesis of cBN-hBN-SiC w Nanocomposite with Superior Hardness, Strength, and Toughness.

Nanocomposites with one-dimensional (1D) and two-dimensional (2D) phases can demonstrate superior hardness, fracture toughness, and flexural strength. Cubic boron nitride-hexagonal boron nitride-silicon carbide whiskers (cBN-hBN-SiC w ) nanocomposites with the simultaneous containing 1D SiC w and 2D hBN phases were successfully fabricated via the high-pressure sintering of a mixture of SiC w and cBN nanopowders. The hBN was generated in situ via the limited phase transition from cBN to hBN. Nanocomposites with 25 wt.% SiC w exhibited optimal comprehensive mechanical properties with Vickers hardness of 36.5 GPa, fracture toughness of 6.2 MPa·m 1/2 , and flexural strength of 687.4 MPa. Higher SiC w contents did not significantly affect the flexural strength but clearly decreased the hardness and toughness. The main toughening mechanism is believed to be a combination of hBN inter-layer sliding, SiC w pull-out, crack deflection, and crack bridging.