Composite coatings reinforced with carbonyl iron nanoparticles: preparation and microwave absorbing properties

The composite microwave absorbing coatings reinforced with carbonyl iron nanoparticles were systematically studied. The morphologies of Fe-Si-Al powders (FSA), carbonyl iron nanoparticles (nmCIP) and the corresponding composite coating sections were characterised by scanning electron microscope (SEM) and transmission electron microscope (TEM). The electromagnetic performances of the microwave absorbents mentioned above were measured by vector network analyser and vibrating sample magnetometer, and the corresponding attenuation mechanisms of the absorbents were discussed. The composite coatings with polyurethane as matrix were fabricated by employing carbon black, FSA and nmCIP as absorbents. Moreover, the microwave absorption properties of these composite coatings with different absorbents were measured by the arch method. Results showed that nmCIP was an efficient magnetic loss absorbent with low density. The microwave absorption properties of the coatings were significantly enhanced: the peak value of reflection loss (RL) reached -25.8 dB, and bandwidth (RL<- 10 dB) was expanded to 3.6 GHz. While it was composited with FSA, which had the same loss mechanism with nmCIP, the location of effective absorption band could be modified with reduced areal density.