Morphology regulation of SiC functional phases in alumina-mullite fiber reinforced Al2O3-based composites: Electromagnetic wave absorption and flexural performance

This work explores SiC morphology regulation for structure-function integration in porous oxide/oxide ceramic matrix composites (CMCs). Alumina-mullite fiber reinforced Al 2 O 3 -based composites containing SiC particles were heat-treated at 1150 °C and modified by subsequent chemical vapor infiltration (CVI) at 1100 °C to introduce SiC nanowires (SiCnws) or spheroidal SiC deposits. The composite with a moderate nanowire content combined a flexural strength of 208.9 ± 6.3 MPa with the widest effective absorption bandwidth (EAB) of 6.19 GHz at 2.0 mm, while retaining non-brittle fracture behavior. The increased flexural strength is associated with SiCnw reinforcement and further matrix consolidation during CVI, and the wide EAB is attributed to a favorable balance between dielectric attenuation and impedance matching. Further SiCnw growth yielded a minimum reflection loss of −55.9 dB at 1.6 mm but was accompanied by lower flexural strength and a narrower EAB. By comparison, the particulate reference exhibited insufficient attenuation, whereas the composite containing compact aggregates of spheroidal deposits showed stronger attenuation but poorer impedance matching, limiting its bandwidth. Tailoring SiC morphology and content therefore offers a route to integrating broadband electromagnetic wave absorption with load-bearing performance in porous CMCs.