Effects of ceramic matrix composition on microwave absorbing performance and mechanical properties in SiC_f/mullite composites

Ceramic matrix composition is crucial for enhancing flexural strength, fracture toughness, and microwave absorbing properties. This work prepared the SiC_f/mullite composites with different Al₂O₃ contents via a precursor infiltration-pyrolysis process (PIP). The phase composition and structure were investigated according to the XRD patterns and Fourier Transform Infrared (FT-IR) of composites. In addition, the effects of Al₂O₃ contents on flexural strength, toughness, and microwave absorbing performance were also investigated. With the increase of the Al₂O₃ contents from 50 wt% (50AC) to 72 wt% (72AC), the flexural strength improved from 210.77 ± 8.15 to 331.02 ± 2.12 MPa, and the fracture modulus from 63.61 ± 3.57 (GPa) to 77.70 ± 1.06 (GPa). In addition, the effective absorption bandwidth (EAB, RL ≤ −10 dB) of 50AC at the thickness of 3.0 mm was 3.89 GHz which covered 93% of the X-band, showing excellent microwave absorption performance.