Manipulation of nitrogen doping levels in SiC nanowires and their negatively correlated microwave absorption properties

Silicon carbide nanowires (SiCnws) are promising microwave absorbers, yet their performance is limited by a low dielectric constant and a lack of magnetic loss. While doping offers a potential solution, controlling doping levels in SiCnws remains challenging, and its effect on absorption performance is unclear. In this study, we developed a simple chemical vapor deposition (CVD) method to prepare nitrogen-doped SiCnws with tunable nitrogen content on carbon fiber cloth. By adjusting the nitrogen amount, the microstructure and electromagnetic parameters of SiCnws could be regulated, and their effect on the electromagnetic wave absorption ability was further investigated. Surprisingly, the absorption capacity of SiCnws decreased with increasing nitrogen content. Compared to nitrogen-doped SiCnws, undoped SiCnws exhibited the best absorption performance, achieving an effective absorption bandwidth of 4.17 GHz (13.83–18 GHz, 1.30 mm thickness) and a minimum reflection loss of −37.15 dB (1.40 mm thickness). This unexpected trend is attributed to the imbalance between dielectric constant and magnetic permeability caused by small atom doping. This study not only provides a simple method for regulating the nitrogen doping levels in SiCnws but also offers insights for the development of SiCnws-based microwave absorbers.