Interface engineering in honeybee-leg-like TiO2@NiCo2O4 nanocomposites: A novel platform for high-performance microwave absorbers

This study reports fabrication of novel TiO2@NiCo2O4 nanocomposites featuring a honeybee-leg-inspired hierarchical architecture, in which radially aligned NiCo2O4 nanoneedles grow on TiO2 fibers to mimic the branched morphology of honeybee legs. This unique architecture generates abundant heterointerfaces and multi-level scattering centers, which directly contribute to enhanced interfacial polarization, impedance matching, and microwave attenuation. The nanocomposites were constructed by electrospinning dual-phase TiO2 nanofibers, followed by the hydrothermal growth of radially aligned NiCo2O4 nanoneedles. Structural and morphological characterization via XRD, SEM, and TEM revealed the formation of a heterostructure with well-defined interfaces. Microwave absorption properties were examined between 2-12 GHz considering reflection loss (RL), impedance matching, complex permittivity and permeability, Cole-Cole plots, Eddy current loss, and attenuation constant. Results demonstrated that the TiO2@NiCo2O4 nanocomposite achieved a minimum reflection loss (RLmin) of-21.30 dB at 9.35 GHz with a 4 mm thickness, and an effective absorption bandwidth (EAB) of 4.27 GHz (7.50-11.77 GHz), covering 94.3 % of the X-band. Additionally, with 5 mm thickness, it reached an RLminof-20.51 dB at 7.31 GHz and an EAB of 3.93 GHz (5.38-9.31 GHz), corresponding to 65.5 % C-band and 32.8 % Xband coverage. These superior absorption capabilities are derived from the bio-inspired hierarchical design, which synergistically integrates dielectric and magnetic losses with morphology-assisted multiple-scattering. The findings demonstrate the significance of bio-inspired design and interface engineering in the development of next-generation high-performance microwave absorbing materials.