Supercritical CO2-driven interfacial engineering of hierarchical CNT/PANI/Ni heterostructures for efficient low-frequency microwave absorption

Developing high-efficiency electromagnetic wave (EMW) absorbers for the low frequency (1–8 GHz) remains a formidable challenge, primarily due to the inherent conflict between thickness reduction and impedance matching at longer wavelengths. Herein, we propose a supercritical CO 2 (SC CO 2 ) fluid-assisted interfacial engineering strategy to construct a hierarchical “core-shell-satellite” carbon nanotube/polyaniline/nickel (CNT/PANI/Ni) ternary composite. Unlike conventional liquid-phase methods that suffer from phase agglomeration, the gas-like diffusivity and negligible surface tension of SC CO 2 facilitate the uniform encapsulation of PANI on CNTs and the atomic-scale anchoring of Ni nanoparticles via robust Ni-N coordination bonds. This unique architecture effectively moderates the conductivity of the CNT network to optimize impedance matching, while the abundant heterogeneous interfaces (CNT/PANI and PANI/Ni) induce significant Maxwell-Wagner-Sillars (MWS) polarization and dipole relaxation losses. Consequently, the optimized CNT/PANI/Ni composite exhibits exceptional low-frequency absorption performance, achieving a minimum reflection loss (RL min ) of −57.11 dB at 6.47 GHz with a matching thickness of only 3.5 mm, overcoming the “thickness bottleneck” of low-frequency absorbers. This work not only provides a scalable route for fabricating heterogeneous composites but also unravels the mechanism of SC CO 2 -induced interfacial synergy, offering a robust solution for anti-interference in 5G and satellite communications.