Study on low-frequency and broadband response microwave absorption properties of arrayed flake carbonyl iron/PDMS flexible films

To address the evolving challenges of low-frequency radar detection technology, this study fabricated array-like flaky carbonyl iron (FCI)/polydimethylsiloxane (PDMS) flexible composite films with low-frequency/broadband response via a magnetic field-induced strategy. A uniform magnetic field (50 mT), generated by a computer-controlled coil system, was employed to induce a vertical array structure of FCI within the PDMS matrix – designated as sample S50. Its performance was compared with samples induced by square magnets (F30, F50, F70) and a non-oriented sample (F0). Results indicate that the uniform magnetic field significantly enhanced the orientation degree of FCI, leading to the formation of a well-aligned longitudinal array. Sample S50 achieved a reflection loss (RL) ≤ −5 dB over 2.4–18.0 GHz at a thickness of 3.1 mm, a minimum reflection loss (RL_min) of −51.47 dB at 5.0 GHz for a 2.5 mm thickness, and an effective absorption bandwidth (EAB, RL < −10 dB) of 6.0 GHz at 1.3 mm. The excellent performance is attributed to synergistic multiple loss mechanisms: the vertically oriented structure enhances magnetic coupling effects, interfacial polarization losses, and an antenna-like effect that prolongs the electromagnetic wave propagation path. Furthermore, S50 exhibited significantly exhibited significantly improved hydrophobicity (water contact angle of 114°) compared to the non-oriented sample (water contact angle of 97.5°), which is ascribed to the film's array structure. This study demonstrates the simultaneous achievement of broad low-frequency absorption, flexibility, and surface hydrophobicity through structural regulation, providing insights for the further multifunctional application of organic polymer-based absorbing materials and their magnetically induced controllable fabrication in the field of wave-absorbing materials.