Microstructure and mechanical properties of h-BN-SiC ceramic composites prepared by in situ combustion synthesis

摘要

h-BN-SiC ceramic composites were prepared by in situ combustion synthesis of B_4C and Si powder compacts under high nitrogen pressure. The high reaction nitrogen pressure was beneficial to the improvement of the relative density and mechanical properties of the products, but higher nitrogen pressure of 120MPa was favorable to the formation of Si_3N_4, which was consistent with the theoretical thermodynamic calculation. The h-BN-SiC ceramic composites have good mechanical properties over those of conventionally processed ones because of the in situ formed h-BN and SiC phases fabricated under high temperature and pressure. The bending strength and fracture toughness of the h-BN-SiC ceramic composites prepared under 100 MPa nitrogen pressure were 82 MPa and 1.9 MPa m~(1/2), respectively.