Architectured Graphene/Iron Microsphere Meta-Composites for Effective Microwave Dissipation

Spherical Fe/graphene composite microwave-absorbing materials are synthesized with liquid-phase atomization and redox composite ball-milling process. The effects of graphene content on the microstructure, electromagnetic parameters, and wave absorption properties are investigated. Results demonstrate that Fe particles maintain a nearly spherical morphology with an average diameter of approximately 2 µm, while graphene is uniformly dispersed in a sheet-like form. The crystallographic structures of both Fe and graphene are preserved after the composite formation. As the graphene content increases, both the real and imaginary components of the dielectric constant of the composite gradually increase. The dielectric loss mechanisms transitioned from polarization relaxation dominance at low graphene content to conductivity loss dominance at higher concentrations. In terms of magnetic losses, magnetic resonance primarily governs the low-frequency range, while eddy current losses dominate at medium to high frequencies. The sample with 25% graphene content exhibits the strongest electromagnetic wave attenuation capability, while the 10% sample demonstrates optimal impedance matching characteristics. When the graphene content is 15%, and the matching thickness is 1.7 mm, the material achieves a minimum reflection loss of −19.87 dB, with an effective absorption bandwidth of 4.4 GHz at a thickness of 1.2 mm.