Lightweight yolk-shell EW@Void@ZrO₂ composites for electromagnetic wave absorption and multifunctional integration

Lightweight electromagnetic wave (EMW) absorbers with integrated multifunctionality are essential for the development of next-generation electromagnetic functional materials. Here, we report a yolk-shell structured composite, carbonyl iron powder (CIP, EW grade) @Void@ZrO₂, synthesized via sol-gel coating and selective etching. Introducing an internal void reduces the density by 20.89 % compared to the initial EW. Meanwhile, the composite achieves ultrabroadband EMW absorption, superior thermal protection, and enhanced infrared reflectance simultaneously. First, the composite exhibits a maximum effective absorption bandwidth (EAB_max) of 8.6 GHz (8.64–17.24 GHz) and a minimum reflection loss (RL_min) of −60.64 dB, attributable to improved impedance matching from the synergistic interaction between dielectric and magnetic losses. Secondly, the engineered hollow architecture, coupled with a ceramic shell, elevates the oxidation onset temperature to 300°C and reduces the surface temperature by 30.41 % under heating at 215°C, owing to phonon scattering, thermal buffering, and radiative suppression. Finally, the hierarchical refractive index and interfacial scattering enhance near-infrared reflectance up to 56.4 % at 1070 nm. This work offers a viable strategy for constructing lightweight, multifunctional materials, thereby advancing the practical application of traditional EMW absorbers toward broader utilization.