Surface structural engineering of carbonyl iron powder for enhancing microwave absorption and anti-oxidation performance

Abstract

Surface structural engineering is desirable in modifying the surface performance of carbonyl iron powder (CIP) to enhance microwave absorption (MA) and anti-oxidation performance. Herein, the surface shape-dependent CIP absorbers are designed via surface coating with zinc oxide (ZnO) nanoparticles and then a thermal annealing treatment. The morphology of ZnO nanoparticles which can be easily regulated by controlling the annealing temperature ultimately affects the MA performance of CIP coating with ZnO nanoparticles (CIP@ZnO). The core-shell CIP@ZnO particles with cubic cone ZnO nanoparticles exhibit excellent MA performance and thermal stability in comparison to the original CIP. Specifically, the CIP@ZnO annealed at 350 °C (CIP@ZnO-350) samples which have the cubic cone ZnO nanoparticles exhibit a minimum reflection loss (RLmin) of –55.35 dB at a thickness of 2.1 mm and a maximum effective absorption bandwidth (EAB) of 7.09 GHz at a thickness of 2.0 mm. In addition, the antioxidant property of the CIP@ZnO composite particles is abruptly enhanced, which breaks the restriction of the application of CIP at high temperatures. The superior MA performance of CIP@ZnO particles with cubic cone ZnO nanoparticles comes from the enhancement in surface shape-dependent multiple microwave scattering, interfacial polarization, and electromagnetic-dielectric synergism between ZnO and CIP.