Improved mechanical and microwave absorption properties of SiC_f/SiC composites with SiO₂ filler

SLF and KD-S SiC fibers were used to fabricate SiC_f/SiC composites by precursor impregnation and pyrolysis (PIP) method. To simultaneously improve both the mechanical and electromagnetic wave absorption properties of SiC_f/SiC composites, the SiO₂ fillers were mixed into the PSC/xylene precursor solution as inert filler. In this research, the effects of SiO₂ filler on the micro morphologies, XRD patterns, mechanical and dielectric property were investigated. The results exhibit that the flexural strength of the SLF and KD-S SiC_f/SiC composites was improved from 167.69 MPa to 241.95 MPa and 248.16 MPa–324.87 MPa with SiO₂ filler, respectively. The lower complex permittivity and better impedance matching are attributed to a broken conductive network in the SiC matrix, which is caused by SiO₂ filler. Therefore, the reflection loss values of SLF SiC_f/SiC composites with SiO₂ filler were approach at −40 dB, and the KD-S SiC_f/SiC composites with SiO₂ filler of that over −12 dB. The effective absorption bandwidths of SLF and KD-S SiC_f/SiC composites with SiO₂ filler are 3.44 GHz and 2.75 GHz, respectively.