Fe3O4–Graphite Composites as a Microwave Absorber with Bimodal Microwave Absorption

Microwave absorption in the low-frequency region is a major challenge in the development of carbon-based absorbers. Fe3O4–graphite composites with both low-frequency region and high-frequency region absorption were prepared through a facile solvothermal method. The electromagnetic properties and impedance matching characteristics of the samples were regulated by changing the dosage of graphite. Interestingly, an excellent bimodal microwave absorption (MA) performance was obtained when the molar ratio of iron and graphite was 3:10 (Fe3O4–2PG). With the optimal matching thickness of 4 mm, the Fe3O4–2PG sample shows good performances with respect to the effective absorption bandwidth of 3.3 GHz; the minimum reflection loss (RLmin) in C-band (4–8 GHz) is −40.6 dB, and its RLmin in Ku-band (12–18 GHz) is −29.82 dB. The good bimodal MA performance of Fe3O4–2PG could be attributed to the synergistic effects and interfacial polarization between Fe3O4 nanoparticles and graphite. Furthermore, Fe3O4–2PG and Fe3O4–1PG have electromagnetic absorption peaks in both the C-band and Ku-band, which broaden the absorption band of electromagnetic waves, which is beneficial to solve the problem of 5 G electromagnetic radiation. Therefore, the research results have special significance for the radiation interference of 5 G technology and the shielding absorption of C-band radar waves.