Impedance-Matched Iron-Added Polymeric Composite Film Incorporated with Iron Nanowire for Electromagnetic Absorption Application

Salisbury screen-type radar absorption structures (RASs) consisting of a resistance sheet, a spacer, and a conductive base provide an efficient method for microwave absorption. An impedance-matched resistance sheet allows microwaves to enter, whereas superior microwave absorbers enhance their performance further. In the present work, an impedance matching composite film was prepared by using polymer/iron/iron nanowires. By varying the polymer, poly (methyl methacrylate) (PMMA), poly (vinylidene fluoride) (PVDF), and poly (vinyl alcohol) (PVA), to iron powder ratios (1:1, 2:1, and 4:1), composite films were synthesized and examined by scanning electron microscopy, X-ray diffraction, and the four-point probe method to determine the materials' characteristics. An impedance-matched composite film was prepared based on the selected composition with 1-10 wt.% iron nanowire additions. Experimental results showed that the polymeric composite film prepared by a ratio of iron-PVA of 4:1 exhibited a sheet resistance of 49 ± 9.7 Ω/sq due to well dispersion of iron powder in PVA. With 1 wt.% Fe nanowire addition, the optimal composite sheet resistance was 329.7 ± 45.3 Ω/sq, which corresponded to an impedance matching degree (i.e., |Z_in/Z₀| value) of 0.88 ± 0.12 and can be used as a resistance sheet for a Salisbury screen-type absorber in RAS applications.