Microwave Absorption Properties of Flaky Carbonyl Iron @ Fe₃O₄ Produced by Plasma-Assisted Ball Milling

In this work, large-diameter flaky carbonyl iron (FCI) and FCI@Fe₃O₄ composite materials were prepared by employing a simple plasma-assisted ball milling and heat treatment process. Large FCI was obtained, with 30-70 μm diameters and a thickness of 300 nm. The results show that, compared with the original polycrystalline carbonyl iron fiber, FCI exhibited higher wave-absorbing performance. When the matching thickness was 2 mm, FCI showed strong absorption of electromagnetic waves, and the minimum reflection loss reached − 33.5 dB at 11 GHz. When the matching thickness was 1.6 mm, the effective absorbing bandwidth reached 5.3 GHz at a reflection loss of <  − 10 dB. The absorption properties were enhanced further by producing the FCI@Fe₃O₄ composites, for which the maximum reflection loss reached − 52 dB at 3.8 GHz, with a matching thickness of 4.6 mm. This study demonstrated an effective way to improve the microwave absorbing performance of polycrystalline carbonyl iron at low frequencies while supporting industrial mass production.