Electromagnetic wave absorption properties of Fe/MgO composites synthesized by a simple ultrasonic spray pyrolysis method

Abstract

Electromagnetic (EM) wave absorbing materials consisting of iron (Fe) nanoparticles supported by magnesium oxide (MgO) matrix were synthesized by ultrasonic spray pyrolysis (USP) and subsequent hydrogen reduction. The Fe nanoparticles were formed by the selective reduction of iron oxide in the as-pyrolyzed powder, itself acting as a microreactor, and were successfully embedded in or at the MgO surface, allowing for magneto-dielectric structures without aggregation. Fe content in the composite particles was controlled only by the molar ratio of the precursor solution ([Fe3+]:[Mg2+]). The remarkable shielding effectiveness reached −65.6 dB at 12 GHz with a corresponding thickness of 1.5 mm and an absorption bandwidth for reflection loss (RL) of less than −20 dB is about 7.8 GHz. This design approach can be extended to realize magneto-dielectric materials with tailored absorption frequencies of high bandwidth due to the combination of the well-dispersed decoration of magnetic particles with controlled content and effective insulation. This type of material would be well suited for use in the research community and industry alike due to the reduction in energy required for synthesis and attendant oxidation losses.