Porous Fe/FeO/Fe₂O₃ nanorod/RGO composites with high-efficiency electromagnetic wave absorption property

Electromagnetic wave absorbers composed of reduced graphene oxide (RGO) and magnetic nanoparticles integrates dielectric and magnetic loss features, which is extremely desirable for enhancing electromagnetic wave absorption ability. Here, porous Fe/FeO/Fe₂O₃ nanorods/RGO composites (FFORGO) are synthesized via anchoring FeO(OH) nanorods on graphene oxide (GO) through dopamine polymerization followed by thermal reduction treatment. The porous Fe/FeO/Fe₂O₃ nanorods are anchored on RGO, and crosslinked structure formed in FFORGO composites when the GO addition is higher than 5 mg‧ml⁻¹. The abundant active sites (e.g., functional groups, dangling bonds, and lattice defects), the numerous heterointerfaces (among Fe, FeO, Fe₂O₃ and RGO) and crosslinked structure trigger multiple dipole polarization, interface polarization and enhanced conductive loss. The EM wave absorption property is optimized by tuning the GO addition. FORGO4 with filler loading of 30 wt% achieves the maximal reflection loss of −24.1 dB at a thickness of 1.9 mm and the effective bandwidth below −10 dB of 3.01 GHz with a thickness of 2.2 mm, owing to the proper ratio of Fe/FeO/Fe₂O₃ nanorods/RGO and synergistic effect between dielectric loss (dipole polarization, interface polarization, conductive loss) and magnetic loss (eddy current loss and exchange resonance). With the filler loading of 35 wt%, the maximal reflection loss of FFORGO4 is −50.7 dB at a thickness of 1.7 mm and the effective bandwidth reaches to 3.74 GHz at a thickness of 1.8 mm.