Liquid metal assisted dual hydroxide heterostructures of carbonyl iron powder for multifunctional electromagnetic wave absorption

Electromagnetic wave (EMW) absorbers for complex environments require appropriate impedance matching, strong absorption, and rapid heat dissipation. Although carbonyl iron powder (CIP) exhibits high magnetic loss, its practical application is hindered by intrinsic oxidation, as well as severe impedance mismatch and low thermal conductivity at low filler loadings. Herein, by applying an ultrasonic cavitation-driven Ga-based liquid metal (LM) encapsulation process, we constructed a core-shell heterostructure (CIP@C@LM), in which an intermediate C shell was introduced to protect the CIP core from severe oxidation and to improve impedance matching. During this process, an oxygen-vacancy rich αGaOOH outer shell and a small amount of interfacial α-FeOOH form in situ, enabling dielectric-loss dominated attenuation through enhanced polarization relaxation and a secondary magnetic-loss contribution. Consequently, at a filler loading of 60 wt.%, the composite achieves a minimum reflection loss (RL_min) of-52.6 dB at a thickness of 2.31 mm and a maximum effective absorption bandwidth (EAB_max) of 7.56 GHz (10.44-18 GHz) at a thickness of 2.08 mm. The excellent performance significantly outperforms that of the pristine CIP (RL_min =-16.29 dB; EAB_max = 4.17 GHz). Furthermore, the C and dualhydroxide shells act as a physical barrier and a heat-conducting network, providing strong corrosion resistance and rapid cooling ability (from 96.7 °C to 37.7 °C in 40 s). This work provides new insights into interfacial engineering, offering a viable route toward next-generation multifunctional EMW absorbers.