Preparation of graphene/flaky carbonyl iron/polyurethane foam composites and research on their microwave absorption properties

In this study, the polyurethane (PU) foam-based microwave absorbing materials filled with graphene (GP) and flaky carbonyl iron (FCI) particles were fabricated, and the effects of GP content and morphology structure on the microwave absorption (MA) properties were investigated. Scanning electron microscopy (SEM) and vector network analyzer (VNA) were used to elucidate the morphology structure and electromagnetic properties of the composite samples. The results showed that the absorption bandwidth of the materials could be improved by increasing the cell density. In particular, for a composite with 1.5 wt.% of GP and 70 wt.% of FCI, the minimum reflection loss (RL) of −53.8 dB was achieved at 9.4 GHz with the thickness of 2.2 mm, and the effective absorbing bandwidth (RL < -10 dB) of 8.1 GHz (9.9–18 GHz) was achieved with the thickness of 1.7 mm. The excellent MA properties of these materials were ascribed to the synergistic effect between the GP and FCI particles and the improved impedance matching resulting from the porous structure.