Mechanical and electromagnetic wave absorption properties of Cf-Si3N4 ceramics with PyC/SiC interphases

Abstract

Aiming to obtain microwave absorbing materials with excellent mechanical and microwave absorption properties, carbon fiber reinforced Si3N4 ceramics (Cf-Si3N4) with pyrolytic carbon (PyC)/SiC interphases were fabricated by gel casting. The influences of carbon fibers content on mechanical and microwave absorption properties of as-prepared Si3N4 based ceramics were investigated. Results show that chemical compatibility between carbon fibers and Si3N4 matrix in high temperature environment can be significantly improved after introduction of PyC/SiC interphases. As carbon fibers content increases from 0 to 4 wt%, flexural strength of Si3N4 based ceramics decreases slightly while fracture toughness obviously increases. Moreover, both the real and imaginary parts of complex permittivity increase with the rising of carbon fibers content within the frequency range of 8.2–12.4 GHz. Investigation of microwave absorption shows that the microwave attenuation ability of Cf-Si3N4 ceramics with PyC/SiC interphases is remarkably enhanced compared with pure Si3N4 ceramics. Effective absorption bandwidth (<−10 dB) of 10.17–12.4 GHz and the minimum reflection less of −19.6 dB are obtained for Si3N4 ceramics with 4 wt% carbon fibers in 2.0 mm thickness. Cf-Si3N4 ceramics with PyC/SiC interphases are promising candidates for microwave absorbing materials with favorable mechanical property.