3D in situ heterogeneous SiC/mullite hollow constructs for broadband electromagnetic absorption

Silicon carbide (SiC) is a promising electromagnetic-absorbing material applied in harsh conditions, but it is challenging to coordinate its impedance matching and attenuation characteristics. Herein, we propose a simple three-step strategy to create three-dimensional (3D) in situ heterogeneous SiC/mullite hollow constructs with efficient electromagnetic absorption property using phenolic-resin-coated fly ash as feedstock. Numerous heterointerfaces exist in the synthesized SiC/mullite composite that provide favorable conditions for significant interfacial polarization. Meanwhile, abundant hierarchical pores resulting from the interior hollow construct of SiC/mullite, interspaces between stacking SiC/mullite, and the gaps among crosslinking SiC/mullite related to 3D printing contribute to improve impedance matching and the multiple-reflection effect. As a result, the SiC/mullite composite shows a minimum reflection loss of −60.89 dB at 17.74 GHz and a maximum effective absorption bandwidth (< −10 dB) of 12.06 GHz (5.94–18.00 GHz). This work provides a novel approach for fabricating broadband SiC composite absorbers in an eco-friendly way.