Carbon-Coated Mn₄N Nanowires with Abundant Internal Voids for Microwave Absorption

Combining carbon-coated architecture with inner voids/cavities is charming for the application of a one-dimensional (1D) nanocomposite. Herein, the carbon-coated Mn4N nanowires (Mn4N@C NWs) with abundant internal voids were synthesized by thermal nitridation of polydopamine-coated MnO2 nanowires (MnO2@PDA NWs). The as-synthesized composite exhibited outstanding microwave absorption properties: the minimum reflection loss (RLmin) of the Mn4N@C NW/paraffin was −58.0 dB at 12.6 GHz, and a wide effective absorption bandwidth (EAB, RL < 10 dB) reached 6.1 GHz (11.3–17.4 GHz) at the thickness of 2.4 mm. The loss mechanism of the as-prepared sample was in-depth discussed in view of the internal void microstructure, complex conductive network, multiple polarization relaxations, and synergetic effect between the Mn4N and C coating. This work not only provides an attractive absorber but also opens up an avenue to the rational design and fabrication of 1D transition metal nitrides decorated by carbon coating for microwave absorption.