Synthesis of setaria viridis-like TiN fibers for efficient broadband electromagnetic wave absorption in the whole X and Ku bands

The setaria viridis-like TiN fibers with efficient electromagnetic wave absorption in the whole X and Ku bands were prepared by electrospinning and hydrothermal methods. The results of XRD, Raman, and XPS suggested the presence of cubic TiN phase with TiOxNy solid solution form in fibers. The nanoneedles uniformly grew on the fibers' surfaces along the (200) plane of cubic TiN crystal and formed a setaria viridis-like morphology. The bionic hierarchical structure gave rise to a large number of interfaces and pores, which would provide the suitable impedance matching, multiple reflections and scatterings, conductivity loss, and Debye relaxation through the synergistic effect. Hence, the superior absorption properties were achieved in the whole X and Ku bands by adjusting the fibers' filler loading. The optimal reflection loss could reach -45.8 dB (X-band) at a thickness of 1.38 mm and -47.8 dB (Ku-band) at the thickness of 1.11 mm as the fibers absorbent contents were 20 wt% and 15 wt%, respectively. Furthermore, the effective absorption bandwidth covered the entire X and Ku bands with a thin thickness of 1.0-2.0 mm.