Construction of compound interface in SiCf/mullite ceramic-matrix composites for enhanced mechanical and microwave absorbing performance

SiC fiber-reinforced mullite ceramic-matrix (SiCf/mullite) composite is a promising load-bearing and microwave absorption material. However, the strong interfacial bonding strength and low permittivity cause poor mechanical and absorption performance. Herein, we report SiCf/C-SiC/mullite composite containing a carbon nanosphere network (CNSN) in the SiC interface prepared by precursor infiltration and pyrolysis (PIP). Due to the contribution of CNSN towards interface debonding, fiber slipping, and individual fiber pull-out, the composite shows significant improvement in the flexural strength (by 187%, from 56.23 +/- 4.89 MPa to 161.69 +/- 13.43 MPa) and the failure displacements (by 238%, from 0.080 +/- 0.006 mm to 0.271 +/- 0.015 mm). Moreover, the real and imaginary parts of complex permittivity (epsilon ', epsilon '') are enhanced from 5.57 to 5.98-6.36-7.11 and from 1.27 to 1.95-2.97-4.69, respectively. Under the synergistic effect of appropriate impedance matching in company with effective conductive loss and multiple polarization loss, the effective absorption bandwidth (EAB) increases from 0.98 GHz to the entire X band, and the minimum reflection loss (RLmin) enhanced from - 14.31 dB to - 41.51 dB.