Double dielectric modification of nickel foam-based microwave absorbers with improved impedance matching and absorption performances

Abstract Proper physical property and well-designed microscopic structures are significant in determining the electromagnetic energy conversion. In this work, nickel foam (NiF)-based rod-like absorbers with double dielectric regulation were achieved via continuous hydrothermal reaction and subsequent heating treatment. The NiF-based uniform integration of binary metal oxides not only maintain the inherent excellent dielectric property of NiF, but also introduce extra dipolar polarizations (caused by multiple covered dielectrics) and Maxwell-Wagner-Sillars effect (induced by large dielectric property differences at the interfaces), which all contribute to the excellent microwave absorption performance. In addition, derived from the high/low dielectric synergetic effect, a balance between the introduction and dissipation of the electromagnetic energy can be realized. Based on that, the maximum bandwidth of NiF-based binary absorber reaches 7.28 GHz at 2.4 mm. This work not only provides a facile and versatile strategy to fabricate NiF-based ternary microwave absorbers, but also demonstrates the significant role of dielectric synergetic effect in optimizing microwave absorption performance.