SiCN-based composite ceramics fabricated by chemical vapor infiltration with excellent mechanical and electromagnetic properties

Abstract

A novel SiCN ternary phase was introduced into porous Si3N4 preform by chemical vapor infiltration from SiCl4–C3H6–NH3–H2–Ar, which was used to fabricate Si3N4–SiCN composite ceramics. SiCN was composed of amorphous Si3N4 matrix and crystalline SiC nano-particles (with a homogeneous size of ~5nm) uniformly distributed in amorphous matrix. This distinctive microstructure made the Si3N4–SiCN ceramics not only maintain a high flexural strength of 227MPa but realize a low dielectric constant and a high dielectric loss, which led to a minimal electromagnetic wave reflection coefficient of −42.6dB, ranking the best level in the already-reported structural and wave-absorbing ceramic materials for high-temperature applications.