Reflection‐Phase Coordination in Low‐Interface, High‐Gradient Electromagnetic Absorbers

ABSTRACT Designing advanced electromagnetic wave (EMW) absorbers remains challenging because improved attenuation is often accompanied by deteriorated impedance matching. Although multilayer and gradient architectures can mitigate this conflict, increasing structural complexity does not necessarily guarantee enhanced absorption, as additional interfaces may alter local reflection behavior and overall electromagnetic response. Here, ultralight carbon nanotube/Ni nanowire aerogels (∼34 mg cm − 3 ) were employed as a model platform to compare a low‐interface, high‐gradient L–H bilayer with a more finely graded L–M–H trilayer. The L–H bilayer achieved a minimum reflection loss of −58.3 dB at 4.7 mm with full X‐band coverage (8.2–12.4 GHz), outperforming L–M–H despite lower attenuation capability and less favorable point‐value impedance matching. This architecture‐dependent absorption hierarchy is associated with concentrated electromagnetic contrast at the L/H interface, together with a relatively large local interfacial reflection coefficient (| Γ L/H | ≈ 0.17), a surface‐reflection phase close to the nominal antiphase condition ( ΔΦ = ‐177°), and an appropriate impedance‐attenuation balance. A similar absorption hierarchy was reproduced in pristine CNT controls and full‐wave simulations, while RCS simulations confirmed scattering suppression. These findings highlight interfacial topology and reflection‐phase characteristics as complementary considerations beyond conventional impedance‐attenuation optimization for lightweight layered EMW absorbers.