Abstract:
Microwave absorbing materials (MAM) are in great demand for various applications in both defense and commercial sectors. Polymer composites with tailorable properties have great potential for use as MAM owing to their low density, ease of processing, and low cost. In this work, the microwave absorption by epoxy composites containing, Fe3O4 nanoparticles deposited on the copper nanowires (i.e., Fe3O4@CuNW hybrid), copper nanowires (CuNW), and/or Fe3O4 nanoparticles were investigated for the first time. A set of epoxy composites with different filler loadings were prepared using a solvent-free resin blending method and were characterized for their morphological, surface composition, electrical, dielectric, magnetic, and microwave absorbing properties. The electrical conductivity values of the samples were measured, and the non-hybrid composites demonstrated percolated behavior, whereas hybrid samples exhibited non-percolated behavior. The non-hybrid composite containing 12 wt. % CuNW and 8 wt. % Fe3O4 exhibited the highest electrical conductivity value of 9.8 × 10−5 s/m compared to all other composites. The dielectric and magnetic losses obtained in the hybrid composites are higher than in non-hybrid composites. Furthermore, the hybrid composites containing 12 wt. % CuNW and 8 wt. % Fe3O4 exhibited the highest dielectric loss of 0.9 and magnetic loss of 1.4 as compared to other composites. The hybrid epoxy composites exhibited significantly large absorption with minimal reflections of microwaves as compared to non-hybrid composites containing equal loadings of CuNW or Fe3O4. The hybrid composites containing 12 wt. % CuNW and 2 wt. % Fe3O4 exhibited low reflection power of 26 % and high absorption power of 64 % of the incident microwave as compared to all other composites. The one-millimeter thick hybrid composite filled with 12:8 (wt. %/wt. %) CuNW: Fe3O4 sample demonstrated EMI shielding effectiveness of 19.3 dB and absorbed 60 % of the microwave power over the X-band frequency range of 8–12.4 GHz.