Sandwich-like graphene nanosheets decorated with superparamagnetic CoFe2O4 nanocrystals and their application as an enhanced electromagnetic wave absorber

Abstract

Sandwich-structured CoFe₂O₄/graphene hybrids are fabricated through a facile one-pot polyol route, and the electromagnetic wave absorption properties are investigated. TEM images and elemental mapping indicate that the graphene nanosheets are decorated with numerous tiny CoFe₂O₄ nanocrystals with a relatively uniform size of 7.8 nm, forming sandwich-like nanostructures. Magnetization measurement reveals that the CoFe₂O₄/graphene hybrids possess superparamagnetism at room temperature with zero coercivity. Investigations of the electromagnetic properties indicate that the complex permittivity of CoFe₂O₄/graphene hybrids is significantly improved in comparison with that of pure CoFe₂O₄ nanocrystals, leading to enhanced electromagnetic wave absorption properties of the CoFe₂O₄/graphene hybrids. The maximum reflection loss of the CoFe₂O₄/graphene hybrids is up to −36.4 dB at 12.9 GHz with the matching thickness of 2.5 mm, and the absorption bandwidth with reflection loss values below −10 dB is in the range of 5.4–18 GHz when the matching thicknesses are only 1.5–4.0 mm. These results suggest that the sandwich-like CoFe₂O₄/graphene hybrids with enhanced electromagnetic wave absorption properties and wide absorption bandwidth are an ideal candidate for electromagnetic wave absorption applications in the future.