Biomimetic hierarchical TiO2@NiCo2O4 heterostructures for enhanced microwave absorption by the synergy of multiple loss mechanisms

Abstract In this study, TiO 2 @NiCo 2 O 4 hierarchical heterostructures were fabricated by integrating dual-phase electrospun TiO 2 nanofibers with rose-petal-like NiCo 2 O 4 nanostructures through a controlled hydrothermal process. The NiCo 2 O 4 ratio in the heterostructure was tuned from 25 to 100 wt% to investigate its influence on structural, magnetic, and electromagnetic properties. Structural and morphological analyses confirmed the formation of densely packed, petal-like NiCo 2 O 4 architecture uniformly attached to the TiO 2 backbone promoting abundant heterogeneous interfaces. Electromagnetic characterization revealed that these interfaces significantly enhanced microwave absorption performance in the 2–18 GHz range. Among all, the TiO 2 @NiCo 2 O 4 (50 wt%) sample exhibited the most remarkable performance, achieving a minimum reflection loss of -24.10 dB at 12.67 GHz with a broad effective absorption bandwidth of 5.96 GHz at a 3 mm thickness. This superior response is attributed to the synergistic contributions of conduction loss, interfacial and dipolar polarization, multiple reflections enabled by the hierarchical morphology, and magnetic loss mechanisms including natural and exchange resonances. The optimal balance between impedance matching and attenuation capability further enhances overall efficiency. These findings demonstrate that the rational design of hierarchical heterostructures through interface engineering and compositional tuning provides an effective strategy for developing lightweight, high-performance, and broadband microwave absorbing materials suitable for stealth technologies.