Enhanced microwave absorption properties of the milled flake-shaped FeSiAl/graphite composites

FeSiAl alloy powders in an irregular shape mixed with graphite were ball-milled for 24 h to achieve flake-shaped FeSiAl/graphite composites. The size of the milled composite particles is in the range of 5–40 μm with the average thickness less than 1 μm. The complex permittivity (ε′ − jε″) and permeability (μ′ − jμ″) are measured by using the transmission/reflection method in the frequency range of 2–18 GHz. Compared to the raw irregular-shaped FeSiAl, the complex permittivity (ε′ and ε″) of the milled composites are greatly enhanced as the weight ratio of graphite in the composite samples increases. For milled FeSiAl/graphite (weight ratio of 8:2) composites absorber with a coating layer thickness of 3 mm, the reflection loss reaches a minimum of −21.0 dB at 6.7 GHz with −10 dB bandwidth of 2.0 GHz. The microwave absorption is significantly enhanced as the weight ratio of graphite in the FeSiAl/graphite composite increases from 10% (9:1) to 20% (8:2). Moreover, the absorption bandwidth with reflection loss exceeding −10 dB can reach up to 2.4 GHz with the coating thickness only of 1.5 mm, and the absorption frequency range can be tuned easily by varying the coating thickness. The results indicate that the milled flake-shaped FeSiAl/graphite composites can be potential microwave absorbers in the higher GHz range compared with those of raw FeSiAl and milled FeSiAl absorbers.

► Flake-shaped FeSiAl/graphite composites were prepared by the ball milling method.
► The simulated RL data were compared to those from the experimental one-port technique.
► Microwave absorption properties have been greatly enhanced in higher GHz frequency.
► The band width of 2.4 GHz (RL > −10 dB) was obtained with the thickness only of 1.5 mm.
► The absorption frequency range can be tuned easily by varying the thickness.