Interface Engineering in Honeybee-Leg TiO2@NiCo2O4 Nanocomposites: A Novel Platform for High-Performance Microwave Absorbers

Abstract

This study reports fabrication of novel TiO<inf>2</inf>@NiCo<inf>2</inf>O<inf>4</inf> nanocomposites featuring a honeybee-leg-inspired hierarchical architecture, in which radially aligned NiCo<inf>2</inf>O<inf>4</inf> 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 TiO<inf>2</inf> nanofibers, followed by the hydrothermal growth of radially aligned NiCo<inf>2</inf>O<inf>4</inf> 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 TiO<inf>2</inf>@NiCo<inf>2</inf>O<inf>4</inf> nanocomposite achieved a minimum reflection loss (RL<inf>min</inf>) 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 RL<inf>min</inf> of -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 % X-band 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. © 2025 Elsevier B.V.