Reduction of electromagnetic signature by the epoxy-based nanocomposite with ferrite@ferrite nanostructure

The highly efficient electromagnetic interference (EMI) shielding materials that can be applied for signature reduction are the subject of numerous studies due to their applicability potential in the military and aerospace fields. A novel approach to characterize epoxy-based nanocomposites with complex ferrite nanostructures was used and applied in order to determine the possibility of using an epoxy-based nanocomposite with ferrite@ferrite nanostructure as a signature reduction material. Two nanostructures, i.e. Fe₃O₄@CoFe₂O₄ and Fe₃O₄@NiZnFe₂O_4, were developed, and their magnetic and dielectric properties were compared with the pure core – Fe₃O₄. Analysis of magnetodielectric properties allowed us to choose the bi-magnetic Fe₃O₄@CoFe₂O₄ nanostructure as the most adequate one for preparing the nanocomposite with high EMI shielding performance. An epoxy-based nanocomposite with these nanoparticles and an organic filler (amorphous yellow dextrin and rice starch mixture) was prepared. The shielding efficiency analysis in the transmission and reflection modes confirmed that the composite with 50 wt% of Fe₃O₄@CoFe₂O₄ can enhance the absorption of electromagnetic radiation. A reduction of the reflectivity from 0.97 to 0.45 and the increase in absorptivity from 0.03 to 0.55 at 8 GHz compared to pure polymer matrix backed by a metallic plate, was observed. Also, shielding efficiency related to the reflection of the electromagnetic wave decreased from 14.74 dB to 2.61 dB, confirming a change of the EMI shielding mechanism from reflection (for metallic components) to absorption (for metallic surface covered by a nanocomposite).