Uniformly coating MnOx nanoflakes onto carbon nanofibers as lightweight and wideband microwave absorbers with frequency-selective absorption

Abstract

Microwave absorption materials have drawn significant attention due to their potential application in information safety and military stealth. In this work, we report a facile strategy to synthesize carbon nanofiber/MnOx core-shell composites (CNF@MnOx) in order to collaborate their advantage for high-performance microwave absorption application. Through a simple ozone pretreatment process, ultrathin MnOx nanoflakes can be uniformly coated onto CNFs by a hydrothermal method. The mixture of several MnOx forms coexists in CNF@MnOx composites because of the readily available crystalline phase transformation from different manganese oxides. The investigation of microwave absorption properties shows that the absorbing capabilities CNF@MnOx composites have significant improvement compared to the pure CNFs and most of single-phase manganese oxides. The minimum reflection loss for CNF@MnOx can arrive at −47.2 dB at 9.4 GHz with a thickness of 2.8 mm, and the widest effective absorption bandwidth was measured to be 5.0 GHz. Furthermore, polymorphic MnOx endows CNF@MnOx with selective-frequency microwave absorption. The dramatic enhancement of microwave absorption is ascribed to dielectric loss, magnetic loss, impedance matching and geometrical effect. Hence, the present CNF@MnOx may be a capable candidate for strong-absorption, broadband and lightweight microwave absorber.