Fabrication and characterization of Al₂O₃-3YSZ@SiOC core–shell structure for Al₂O_3f/Oxide composites with tunable electromagnetic protection

Continuous alumina fiber-reinforced oxide composites (Al₂O_3f/Oxide) are considered highly promising electromagnetic protection carrier materials for aerospace applications due to their excellent thermal stability, high strength, thermal insulation capability, and porous loadable structure. In this work, Al₂O₃-3YSZ@SiOC- n C ceramic spheres with a core–shell structure were prepared via a polymer-derived ceramic route. Subsequently, a continuous aluminosilicate fiber (AF18)/Al₂O₃-3YSZ@SiOC- n C composites were successfully fabricated by integrating the ceramic spheres with AF18 fibers through a hot-pressing process. Their microstructure, phase composition, thermal properties, and electromagnetic protection performance and mechanisms were systematically investigated. Benefiting from the synergistic effects of multiple components, the AF18/Al₂O₃-3YSZ@SiOC-1C composites exhibit excellent electromagnetic wave absorption (EWA) performance, with a minimum reflection loss of −43.07 dB at 9.5 GHz and a thickness of 2.6 mm, accompanied by an effective absorption bandwidth of 3.5 GHz. By adjusting the carbon content, the composites successfully surpassed the percolation threshold, enabling the functional transition from EWA to electromagnetic interference shielding. Therefore, this work provides an effective strategy for the design and fabrication of Al₂O_3f/Oxide-based composites with tunable electromagnetic protection functions.