Microwave absorbing properties of flake-shaped carbonyl iron/reduced graphene oxide/epoxy composites

Abstract Microwave absorbers are used in a wide range of fields such as radar-cross section (RCS) reduction for stealth aircrafts, electromagnetic interference (EMI) reduction for electronic products and health protection for human. In this study, the flake-shaped carbonyl iron (FCI) powder was obtained from raw spherical carbonyl iron (SCI) powder by ball milling for 60 h. The SCI powder was mixed with reduced graphene oxide (rGO) and then ball-milled for 60 h to obtain rGO/FCI composite particles. Flake-shaped rGO/FCI particles have length of 1–20 μm, thickness of 0.3–1 μm, and aspect ratio of 1–60. The electromagnetic properties ( e ′ , e ′′ , μ ′ , μ ′′) of rGO/FCI/epoxy composite absorbers were measured by the transmission/reflection method in the frequency range of 2–18 GHz for three samples with 50 wt% of SCI, FCI and rGO/FCI particles, respectively. The results show that the values of permittivity and permeability both increase after ball-milling treatment. Compared with FCI/epoxy composite, the rGO/FCI/epoxy composite absorber exhibits higher dielectric loss and lower reflection loss. For absorbers with the same thickness, the rGO/FCI/epoxy composite shows better reflection loss with the target frequency shifting to the lower frequency region. For 50 wt% of rGO/FCI/epoxy absorber with a thickness of 2 mm, the minimum reflection loss reaches −32.3 dB at matching frequency of 11.0 GHz.