Constructing core-shell biomass carbon@Fe3O4 composites for enhanced mid-to-low frequency electromagnetic wave absorption

Presently, the escalating issue of electromagnetic pollution, propelled by the rapid advancement in electronic information technology, is attracting heightened attention. This problem is particularly pronounced within the 2-10 GHz frequency range, where electronic devices make a substantial contribution to electromagnetic pollution. Research suggests that carbon-based magnetic composites are a viable solution for mitigating this pollution. In our study, we synthesized magnetic composites composed of Fe3O4 particles and biomass carbon (C) derived from corn silk, using a hydrothermal method. The low conductivity of Fe3O4 particles plays a key role in hindering microcurrent transmission, thus reducing the excessive dielectric properties of the carbon material. Additionally, the formation of multiple heterogeneous interfaces between Fe3O4 particles and biomass carbon significantly enhances interfacial polarization. Importantly, adjusting the Fe3O4 particle content in these composites enables modulation of their dielectric and magnetic properties, thus improving impedance matching and signal attenuation. Notably, at a C to Fe3O4 mass ratio of 1:1, the C@Fe3O4 composites exhibit outstanding wave-absorbing efficiency, characterized by an effective bandwidth of 3.3 GHz at a thickness of 2.13 mm. Most significantly, they achieve a reflection loss of -57.86 dB at 7.36 GHz, representing a considerable breakthrough in high-efficiency microwave absorption.