Preparation, characterization and microwave absorbing properties of Fe₈₅Si_9.6Al_5.4 alloys in the low frequency range

The Fe₈₅Si_9.6Al_5.4 alloys were prepared by mechanical alloying (MA) method. The phase structure, morphology, soft magnetic properties of the Fe₈₅Si_9.6Al_5.4 alloys, the electromagnetic and absorbing properties of the FeSiAl/paraffin absorbers were investigated with XRD, SEM, VSM and VNA. The results show that the crystalline structures of the FeSiAl alloys prepared by both one-step MA process and two-step MA process are disordered bcc-Fe(Si, Al) solid solutions. The shape of FeSiAl alloy prepared by the one-step MA process is irregular, while the FeSiAl alloy prepared by the two-step MA process is flake-shaped. The specific saturation magnetization and coercivity are similar to the FsSiAl alloys prepared by two methods. Compared with the irregular FeSiAl/paraffin absorber, the absorber filled with flaky FeSiAl alloys possesses the higher complex permittivity and permeability and presents lower reflectivity in the range of 0.5-5 GHz. For the 2-5 mm absorber filled with flaky FeSiAl alloys, the minimum reflectivity decreases and the matching frequency moves towards the lower frequency with the increase of the thickness. The absorption bandwidth of the 2mm absorber (RL≤-10 dB) is 1.07 GHz.