Fabrication of porous X-shaped Fe3O4@C core-shell structures for tunable microwave absorption

Designing porous materials with low density and high specific surface area is one of the strategies to obtain excellent wave absorbing properties. In this study, the carbon-coated porous X-shaped Fe3O4 composites used as microwave absorption materials were prepared by heat treatment of FeOOH@Polydopamine (PDA) core-shell precursors. It revealed that the X-shaped Fe3O4 core showed improved magnetic loss in GHz band due to its special shape anisotropy and large specific surface area. In addition, the modification of carbon enabled the Fe3O4 absorbers to have stronger polarization and higher electrical conductivity. The composites exhibited great freedom in performance tunability, allowing for strong absorption (RL<-40 dB) at different frequencies. For composites with thick carbon shell, the reflection loss reached the optimal value of - 64.92 dB at 15.04 GHz at the thickness of 1.75 mm, and the effective bandwidth was up to 4.64 GHz (13.04-17.68 GHz). The impressive performance of the as-prepared Fe3O4 @C core-shell composites was mainly attributed to the complementary behaviors of strong dielectric loss and magnetic loss.