Synthesis, Multi-Nonlinear Dielectric Resonance, and Excellent Electromagnetic Absorption Characteristics of Fe₃O₄/ZnO Core/Shell Nanorods

Abstract

Fe3O4/ZnO core/shell nanorods are successfully fabricated by combing an inorganic-phase reaction with a hydrogen annealing process. The transmission electron microscopy analysis indicates that the diameter and the length of the core/shell nanorods are 25−80 and 0.35−1.2 μm, respectively. Electromagnetic properties of the core/shell nanorod−wax composites are investigated. The permittivity of the composites shows four dielectric resonant peaks in 2−18 GHz, which can be explained by the transmission line theory. The resonant behavior mainly results from interface polarization induced by the special core/shell structures, dipole polarization of both Fe3O4 and ZnO, and electron transfer between Fe2+ and Fe3+ ions in Fe3O4. The maximum reflection loss is about −30 dB at 10.4 GHz for the composites with a thickness of 1.5 mm, and the absorption bandwidth with the reflection loss below −20 dB is up to 11 GHz for an absorber with the thickness in 2−4 mm. Thus, our results demonstrate that the Fe3O4/ZnO core/shell nanorods are attractive candidates for a new kind of the electromagnetic wave absorptive materials.