Improvement of co-frequency synergy between dielectric and magnetic losses of core–shell Fe3O4@C composites for enhancing their microwave absorption properties

Core–shell Fe3O4@C composite with nano and submicron Fe3O4 core structures was prepared by vacuum heat treatment of Fe2O3@phenolic resin (Fe2O3@PR) precursor. The multi-scale core structures confer the composite with improved electromagnetic synergy. As a result, the composite exhibits optimized impedance matching, strong attenuation capability, and excellent microwave absorption properties. In the high-frequency (10–18 GHz) band, its minimum reflection loss (RL, RL value below − 10 dB represents above 90% microwave absorption) is − 54.45 dB and effective absorption bandwidth (EAB, frequency range of RL < − 10 dB) is 6.34 GHz. In the low-frequency (2–10 GHz) band, the obtained minimum RL and EAB are − 53.57 dB and 3.38 GHz, respectively. These results suggest that the multi-scale core structures can effectively enhance the microwave absorption properties of core–shell Fe3O4@C composites and it may be an effective idea for the design of high-performance microwave absorption materials.