Microwave absorption properties of reduced expanded graphite oxide with Fe3O4

Expanded graphite (EG) is distinguished as a superior material for the absorption of electromagnetic energy, attributable to its significant surface area, low density, and porous architecture. However, research elucidating the impact of surface functional groups, defects, electrical conductivity, and oxidation–reduction processes on the absorption performance of electromagnetic waves remains relatively scant. In this study, various degrees of oxidized expanded graphite oxide (EGO) were initially synthesized using an optimized Hummer’s method, which, upon the introduction of oxygen-containing functional groups, exhibited enhanced polarization and dielectric relaxation effects. Subsequently, reduced expanded graphite oxide (REGO) with varying degrees of reduction was prepared using L-ascorbic acid, wherein the removal of oxygen-containing functional groups led to the formation of vacancy defects, thereby enhancing the dielectric relaxation behavior of REGO. Ultimately, Fe₃O₄/REGO (FR) composites were synthesized via hydrothermal and freeze-drying methods. The synergistic interaction between Fe₃O₄ and REGO led to improve magnetic and diel ectric loss characteristics, as well as enhanced impedance matching. The findings reveal that the FR-3 specimen exhibited a minimum reflection loss of −50.78 dB at a frequency of 16.10 GHz, coupled with an effective absorption bandwidth (EAB) of 5.26 GHz at a thickness of 2.3 mm. This study provides robust support for future applications of electromagnetic wave absorbing materials.