Effect of interface structure on microwave absorbing performance and oxidation behavior of SiC_f/mullite composites

Interface structure of ceramic matrix composite is crucial for flexural strength, fracture toughness, electromagnetic wave (EMW) absorbing properties, and oxidation resistance. This work prepared the multi-layer C-SiC interfaces in SiC_f/mullite composites via a precursor infiltration-pyrolysis process (PIP) combining ball-milling dispersion. The effects of the interface thickness on the flexural strength, toughness, and EMW absorbing performance were investigated. The result shows that the SiC_f/mullite with a thickness (t) of 0.32 μm C-SiC interface exhibits excellent flexural strength (154.66 MPa) and strong absorbing performance with a broad effective absorption bandwidth (EAB, RL ≤ -10 dB) covering the whole X-band. The composite with a 1.35 μm C-SiC interface significantly improves up to 32.01 MPa m^1/2 in fracture toughness. The oxidation behaviors of SiC_f/C-SiC/mullite under 1000 °C were also investigated by analyzing the cross-section morphology and fracture models. The C-SiC interface isolated the SiO₂ generated on the fiber from the Al₂O₃ in the matrix. The flexural strength retention rate of the oxidized composite is 82 % when the thickness of C-SiC interface is 0.32 μm.