A novel strategy to prepare BN interface and its effects on microstructure and properties of SiC_w/BN/SiC composites

Based on the microstructure and composition design idea of continuous fiber toughened ceramic matrix composites (CFCCs), a BN interface layer was prepared on the surface of silicon carbide whiskers (SiC_w) for the first time. And SiC_w toughened SiC ceramic matrix composites with BN interface (SiC_w/BN/SiC composites) were prepared by precursor infiltration and pyrolysis (PIP) combined with reactive melt infiltration (RMI). The as-prepared SiC_w/BN/SiC composites possess high strength and high density, as well as the isotropic characteristics. By adjusting the thickness of the BN interface, the residual stress inside the composites is reduced and the bonding strength between the whisker and the matrix is optimized, thereby improving the toughness of the SiC_w/BN/SiC composites. When the thickness of BN interface is about 3 nm, the flexural strength and the fracture toughness of the composites attain 425 MPa and 6.6 MPa m1/2, respectively. The bulk density of the SiC_w/BN/SiC composites is about 2.87 g cm⁻³ and the open porosity is less than 4%, indicating the high densification and excellent gas tightness. The toughening mechanisms of SiC_w/BN/SiC composites contain SiC_w toughening and micron-sized SiC particles (produced by RMI process) toughening, which ensure a good toughness for the dense composites together with the positive effect of BN interface.