Simultaneous enhancement of mechanical and microwave absorption properties with a novel in-situ synthesis α-Al2O3 fillers for SiCf/SiC composites

The Al and H 3 BO 3 mixed powder was introduced into the PCS/Xylene precursor solution as in-situ synthesis α-Al 2 O 3 filler by precursor infiltration and pyrolysis (PIP) method. The in-situ synthesis filler can effectively decrease the open porosity of SiC f /SiC composites and give rise to multiple scattering of microwave and dipolar polarization. Therefore, the mechanical and microwave absorption properties of SiC f /SiC composites can be simultaneously enhanced. The effects of in-situ synthesis filler on the morphologies, flexure strength and reflection loss values of SiC f /SiC composites were investigated. With 2 wt% in-situ synthesis filler, the flexure strength of SiC f /SiC composite was 305 MPa and the maximum reflection loss ( RL m ) can reach − 54.68 dB with the effective absorption band (EAB) of 3.51 GHz in the X band. With 5 wt% in-situ synthesis filler, the flexure strength of SiC f /SiC composite was 207 MPa and the RL m was − 30.91 dB. Due to the inefficient infiltration process, the RL m of SiC f /SiC composites with 10 wt% in-situ synthesis filler was only − 27.36 dB. Nevertheless, the flexure strength of that composite was 259 MPa, owing to the dense matrix. Additionally, the flexure strength of SiC f /SiC composite without filler was 148 MPa and the RL m was − 26.40 dB.