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

Abstract

► h-BN–SiC ceramic composites were fabricated by one-step SHS under high nitrogen pressure. ► Si 3 N 4 is the preferential formation phase under high nitrogen pressure of 120 MPa. ► h-BN–SiC ceramic composites have good bond strength and mechanical properties. h-BN–SiC ceramic composites were prepared by in situ combustion synthesis of B 4 C 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 120 MPa was favorable to the formation of Si 3 N 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.