Double-layer microwave absorber based on CoFe2O4 ferrite and carbonyl iron composites

Abstract

Abstract The microwave absorption properties of carbonyl iron (CI) and CoFe 2 O 4 ferrite with single-layer and double-layer composite absorbers were investigated based on the electromagnetic transmission line theory and the impedance matching principle in the frequency range from 2 GHz to 18 GHz. XRD and SEM were used to characterize the structure of the powdered composites. Coaxial method was used to measure the electromagnetic parameters of CI and CoFe 2 O 4 . The reflectances of the matching and absorbing layers of different thicknesses and orders were also calculated. The results show that using CoFe 2 O 4 as matching layer and CI as absorbing layer can greatly expand the coating absorption bandwidth and decrease the reflectance peak. Double-layer absorbers have much better microwave absorption properties than single-layer absorbers. The microwave absorption properties of the double-layer structure are influenced by the coupling interactions between the absorbing and matching layers. The double-layer microwave absorbers with reflection loss less than −10 dB over the range from 8.6 GHz to 18 GHz (the absorption bandwidth is 9.4 GHz), which almost covers the X-band (8.2 –12.4 GHz) and the whole Ku-band (12.4–18 GHz) were achieved when the thicknesses of CoFe 2 O 4 and CI were 2.4 and 0.5 mm, respectively.