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

Abstract Expanded graphite (EG)/Fe/Fe 3 O 4 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 Fe 3 O 4 increased from 0 to 6.64% and 81.84%, respectively. Fe/Fe 3 O 4 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 M s values gradually increased with increasing Fe 3 O 4 and Fe contents. The H c values gradually decreased due to the synergistic effect of the coupling and spatial confinement effect, shape anisotropy, and crystal size. EG/Fe/Fe 3 O 4 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 R L value of −41.6 dB at 7.84 GHz and frequency range ( R L  ≤ −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.