Characteristics of Oxidized Fe Topcoat and Its Effects on the Absorbing Property of Carbonyl Iron Coating

The hybrid particle (oxidized-Fe/carbonyl iron/resin powder) was fabricated via the corrosion process of carbonyl iron particles (CIPs) coating. Morphologic properties of the oxidized-Fe particles were measured using the scanning electron microscopy and x-ray diffraction patterns. The saturation magnetization was obtained in the vibrating sample magnetometer and x-ray photoelectron spectroscopy measurements were done to get the magnetic oxidizing composition. The permittivity and permeability were tested using a vector network analyzer in 8–18 GHz as the hybrid particle was added into the paraffin. Then the intrinsic parameters of the hybrid particles could be calculated using a fitting process based on the effective medium rule. Our results showed that oxidized Fe was present in the hybrid particles with a complex crystal structure; there were still a few CIPs in the powder core. Based on the effective medium theory, from the permittivity and permeability of the composite added the variable oxidized powder could be derived. The fitted permittivity and permeability were reliable because the fitting errors were less than 0.3 + j0.2 and 0.2 + j0.1, respectively. Since the oxidized powder was added in the topcoat, the reflection coefficient (RC) of the two-layer coating was lower than that of the single coating, the absorbing bandwidth with RC < − 5 dB was 9–18 GHz as the bottom layer thickness was 0.5 mm.