Fe₃O₄/carbon chain-like core/shell composites: Synthesis and microwave absorption properties

Abstract

Fe3O4/carbon core/shell composites were fabricated via a two-step process. Fe3O4/phenol formaldehyde resin (PFR) core/shell composites were first obtained by hydrothermal method, and the Fe3O4/carbon core/shell composites were produced by annealing Fe3O4/PFR core/shell composites under nitrogen flow. The phase structures and morphologies of the composites had been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM). The microwave absorption properties of the Fe3O4/carbon core/shell composites were measured by vector network analysis (VNA). When the ratio of Fe3O4 and carbon is 1:2 and the sample thickness is 2.4 mm, the Fe3O4/carbon core/shell composites have an optimal absorption peak value of about −45.3 dB at 9.7 GHz and its effective absorption bandwidth lower than −10 dB reaches 2.3 GHz (from 7.8 to 11.1 GHz). The reflection loss results indicate that the Fe3O4/carbon core/shell composites possess higher microwave absorption. The excellent electromagnetic wave absorption properties of the Fe3O4/carbon core/shell composites were attributed to effective complementarities between the dielectric loss and the magnetic loss.