Preparation and properties of SiCN/Sialon nanocomposites

Aiming at obtaining high quality RAM (radar-wave absorbing materials), we used nanometer SiCN powder as radar-wave absorber and Sialon as matrix to prepare SiCN/Sialon composite by pressureless sintering process. The SiCN powder were synthesized by laser induction of HMDS and ammonia. The effect of addition of SiCN powder into Sialon on strength and permittivity of the SiCN/Sialon composite was studied. XRD, SEM and strength analyses were performed on the samples. XRD results indicate that the composite is composed of β-Sialon, β-SiC and SiO₂, and β-Sialon is its main phase. SEM and strength analyses show that the content and size of β-Sialon and strength of the composite decrease with increasing content of SiCN powder in the samples. The addition of SiCN powder into Sialon increases the glutinosity of glass formed during sintering process by additives and SiO₂ film on the surface of Si₃N₄, and lowers the sintering densities of the samples. The higher glutinosity of the formed glass hinders dissolution of α-Si₃N₄ into it, reduces the concentration of Si₃N₄ in the glass, and decreases the nuclear formation of β-Sialon in the glass, and prevents the growth of formed β-Sialon.