Modulation of the composition and surface morphology of expanded graphite/Fe/Fe3O4 composites for plasmon resonance-enhanced microwave absorption

Abstract

Expanded graphite (EG)/Fe/Fe3O4 composites were prepared through chemical vapor deposition. The composition and surface morphology of the composites were controlled by changing Fe(CO)5 vol (δ). With increasing δ from 1 mL to 4 mL, the contents of Fe and Fe3O4 increased from 0 to 6.64% and 81.84%, respectively. Fe/Fe3O4 nanoparticles anchored on the EG surface formed a strawberry-like structure at δ = 1–3 mL and a compact particle film at δ = 4 mL. In this case, the Ms values gradually increased with increasing Fe3O4 and Fe contents. The Hc values gradually decreased due to the synergistic effect of the coupling and spatial confinement effect, shape anisotropy, and crystal size. EG/Fe/Fe3O4 composites with strawberry-like surface (S1−S3) exhibited higher permeability, permittivity, and microwave absorption properties than pure EG and composites with compact particle film. Composites with strawberry-like surface (S3) displayed optimal microwave absorption property, with a minimum RL value of −41.6 dB at 7.84 GHz and frequency range (RL ≤ −20 dB, 99% absorption) of 15.7 GHz. The excellent properties could be attributed to the enhanced permittivity, permeability, and multiple resonances caused by the localized surface plasmon resonance (LSPR). This work provides a significant guide for design and synthesis of microwave absorbers with broad bandwidth and light weight.