Comparative study of electromagnetic functional epoxy composites filled with Fe-based materials

Considering that epoxy composites filled with Fe-based materials can be an alternative for the processing of microwave absorbing materials (MAMs) and electromagnetic shielding materials, this work presents a comparative study with three different Fe-based materials, two with magnetic characteristics: manganese zinc ferrite–MZ and carbonyl iron–CI and a non-magnetic one: ferric oxide–FO. This study compares the main structural and morphological characteristics of fillers with the electromagnetic interference shielding effectiveness (EMI SE) and the reflection loss (RL) behaviors of epoxy composites, prepared with 30, 50, and 70 wt% of fillers by mechanical mixing. The results show that the intrinsic magnetic properties of MZ and CI had a significant influence on the EM properties, as expected, and also on the electrical conductivity. Notably, a higher content of magnetic particles (MZ and CI) increased the EMI SE. Epoxy/MZ-70 achieved 30 dB of EMI SE, with a predominant shielding mechanism by absorption. The 2.1 mm thick epoxy/CI-70 presented the most effective RL result (− 20 dB at 10.4 GHz). The epoxy/FO composite showed less significant results because this filler does not have magnetic and electrical characteristics. The experimental and simulated RL curves were close, with a slight shift in frequency. Simulated curves allowed exploring the behavior of MAMs at different thicknesses. This work clearly shows the influence of the different magnetic natures of Fe-based fillers on the EMI SE and RL behaviors of epoxy composites, emphasizing the EM behavior of materials processed with magnetic and non-magnetic Fe-based fillers.