Influence of interfacial microstructure on the mechanical properties of SiC/SiBCN composites

Abstract

SiC/SiBCN composites were prepared via polymer infiltration and pyrolysis technique (PIP) and the influence of the interfacial microstructure on the mechanical properties of the composites was investigated. In this paper, an amorphous SiOC layer was observed at the fiber-matrix interface for the first time. Formation of the SiOC layer stems from SiO gas formed inside the ceramic matrix may diffused towards the interface and reacted with the carbon-rich layer of SiC fibers to form Si atom. Si atom dissolved in the O–C molecular network to form a 100 nm chemical bonding SiOC layer, which caused the SiC fibers to pull out in a whole bundle and the pull-out length was short, leading to a composite flexural strength of only 143 ± 30 MPa. By introducing SiC coating, SiC fibers were effectively protected from chemical reactions, and the coating acted as a barrier to the diffusion and migration of the matrix elements to the interface and weakened the interfacial bonding strength (IFBs), in which IFBs decreased from 266 ± 19 MPa to 170 ± 10 MPa. Hence, the flexural strength of composites increased up from 143 ± 30 MPa to 388 ± 16 MPa.

Keywords

• SiC/SiBCN composite
• Interfacial microstructure
• Flexural strength
• Interface bonding mechanism