Enhanced Microwave Absorption and Corrosion Properties of Carbonyl Iron by Blackening Treatment

In this work, the corrosion properties of carbonyl iron (CI) were studied by surface modification with blackening treatment. The structure and morphology of the materials were determined by scanning electron microscopy, x-ray diffraction, and Raman scattering spectroscopy. The complex permittivity of CI powders (CIP) was reduced after blackening treatment, thereby achieving the desired impedance matching. For blackened CIP, the minimum reflection loss (RLmin) was -12.6 dB at 7.5 GHz and the effective absorption bandwidth was 3.2 GHz (RL<-10 dB) at a thickness of 1.5 mm. The absorption properties of the blackened CIP were slightly altered after corrosion treatment with NaCl solution. Moreover, the polarization curve indicated that significant improvement in corrosion resistance could be achieved for blackened CIP. Thus, blackening treatment can be applied to enhance the corrosion resistance of CIP, which can greatly expand its application prospects.