Graphene's role in enhancing Fe3O4 nanofibers: a comparative exploration of room temperature impedance characteristics and EMI shielding performance

In this work, an electrospinning technique was used for the fabrication of nanofibers to examine the structural, electrical, and EMI shielding characteristics of pure Fe₃O₄ and Fe₃O₄-graphene (Fe₃O₄-Gr) nanofibers, exploring the potential contribution of graphene to the overall performance of Fe₃O₄. A consistent fibrous morphology with an average diameter of 62 nm was shown in field emission scanning electron microscopy (FE-SEM) analysis of the Fe₃O₄ nanofibers. However, the addition of graphene resulted in few aggregated fibers with an average diameter of 68 nm, which was slightly larger than that of pure Fe₃O₄ nanofibers. X-ray diffraction (XRD) pattern confirms that the spinel structure of pure Fe₃O₄ was retained in pure Fe₃O₄ and Fe₃O₄-Gr nanofibers. For both these nanofibers, impedance spectroscopy results showed a single semicircular response, indicating bulk relaxation processes. Fe₃O₄-Gr nanofibers exhibited greater bulk resistance at room temperature owing to the increased polarization effects introduced by graphene's conductive pathways. This effect was observed in the modulus plane plots, where Fe₃O₄-Gr stored more energy as graphene enabled charge movement and changes in dielectric relaxation. Compared with Fe₃O₄, Fe₃O₄-Gr nanofibers showed stronger polarization and higher dielectric constants, with two distinct relaxation peaks in the dielectric constant and tangent loss graphs. As per EMI shielding studies, Fe₃O₄-Gr nanofibers were better than pure Fe₃O₄ in terms of total shielding effectiveness (SE_T), mainly because graphene's conductive network helped increase the absorption component (SE_A).