Excellent microwave absorption performances of high length-diameter ratio iron nanowires with low filling ratio

Reducing the filling content of high-density ferromagnetic particles is a key prerequisite for obtaining lightweight absorbers. To this end, large iron nanowires (Fe NWs) with high length-diameters, uniform length of approximately 21 μm and diameters of approximately 60 nm were synthesized through a facile magnetic field-induced in situ reduction method without templates and surfactants. The phase structures, and micromorphology of the high-aspect-ratio Fe NWs were analyzed, and the electromagnetic properties of Fe NWs-paraffin composites were measured with a vector network analyzer at 2-18 GHz. The Fe NWs-paraffin composite with a low filler loading also exhibited satisfactory microwave absorption performance, and the composites filled with 20 wt.% of as-prepared Fe NWs shows a minimum reflection loss (RLmin) of -44.67 dB at 2.72 GHz and effective absorption bandwidth (EAB) with reflection loss below -10 dB reached 8.56 GHz at a layer thickness of 1.42 mm. At a thickness of 3 mm, the RLmin value and EAB (RL ⩽ -10 dB) reached -29.74 dB and 3.28 GHz (3.84-7.12 GHz), respectively. This study suggests that Fe NWs with high-aspect-ratios have promising microwave absorbing applications, and provides a good reference for the preparation of ferromagnetic metal-based lightweight electromagnetic wave-absorbing materials.