Effect of surface modified SiO2 powders on microwave absorbing properties of flaky FeSiAl coatings

Flake FeSiAl (FFSA) powders were used as absorbent in absorption coatings with a thickness of 1 mm. Two types of SiO2 powders (DNS-2, RNS-A) were added to the coatings in order to improve the impedance matching and the absorption properties. The electromagnetic parameters of FFSA and two types of SiO2 powders were measured by transmission/reflection technology, and the reflection loss of coatings was measured by the arch method in the frequency range of 2-18 GHz. The effect of FFSA content on the microwave absorbing properties was analyzed. And as the content increases, the effective absorption bandwidth (RL <= - 10 dB) firstly increases and then decreases and the absorbing peak shifts to lower frequency ranges. Then the absorbing properties of the FFSA/SiO2 coatings were investigated. The results show that the microwave absorption performance was improved significantly when the appropriate amount of SiO2 powder was added to the coating. The minimum reflection loss decreased by 10 dB (DNS-2) and 24.3 dB (RNS-A), respectively. The effective absorption bandwidth (RL <= - 10 dB) increased by 2 GHz and 1.8 GHz. The interface polarization and SiO2-channel models were built to analyse the enhanced microwave absorption mechanism of the coatings.