Enhanced microwave absorption properties of MnO₂ hollow microspheres consisted of MnO₂ nanoribbons synthesized by a facile hydrothermal method

MnO₂ hollow microspheres consisted of nanoribbons were successfully fabricated via a facile hydrothermal method with SiO₂ sphere templates. The crystal structure, morphology and microwave absorption properties in X and Ku band of the as-synthesized samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and a vector network analyzer. The results show that the three-dimensional (3D) hollow microspheres are assembled by ultra thin and narrow one-dimensional (1D) nanoribbons. A rational process for the formation of hollow microspheres is proposed. The 3D MnO₂ hollow microspheres possess improved dielectric and magnetic properties than the 1D nanoribbons prepared by the same procedures with the absence of SiO₂ hard templates, which are closely related to their special nanostructures. The MnO₂ microspheres also show much better microwave absorption properties in X (8–12 GHz) and Ku (12–18 GHz) microwave band compared with 1D MnO₂ nanoribbons. The minimum reflection loss of −40 dB for hollow microsphere can be observed at 14.2 GHz and reflection loss below −10 dB is 3.5 GHz with a thickness of only 4 mm. The possible mechanism for the enhanced microwave absorption properties is also discussed. - Graphical abstract: MnO₂ hollow microspheres composed of nanoribbons show the excellent microwave absorption properties in X and Ku band. - Highlights: • MnO₂ hollow microspheres consisted of MnO₂ nanoribbons were successfully prepared. • MnO₂ hollow microspheres possess good microwave absorption performances. • The excellent microwave absorption properties are in X and Ku microwave band. • Electromagnetic impedance matching is great contribution to absorption properties.