In-situ synthesis of SmFeO3/Fe@CNTs nanocomposites with optimized impedance matching for strong and broadband microwave absorption

SmFeO₃/Fe@carbon nanotubes (CNTs) nanocomposites are synthesized in-situ using SmFeO₃ as catalysts and C₂H₂ as carbon sources with CVD method. CNTs are grown from Fe nanoparticles on SmFeO₃ surface by tip-growth mechanism, and CNTs content increases with the increasing CVD time. In-situ synthesized Fe and CNTs greatly enhances magnetic and dielectric properties, leading to the excellent microwave absorption performance of SmFeO₃/Fe@CNTs nanocomposites. Among them, SmFeO₃–4 (CVD for 4 min) exhibits the best microwave absorption capacities with a minimum reflection loss of −50.16 dB at 11.84 GHz and a broad effective absorption bandwidth of 3.92 GHz at a thin thickness of 2.0 mm. The optimized impedance matching ensures SmFeO₃/Fe@CNTs nanocomposites capture almost incident microwaves, and then attenuates microwaves through dielectric losses and magnetic losses. The conductive CNTs and higher specific surface area leads to higher dipole polarization, interfacial polarization, and conduction loss, while magnetic Fe nanoparticles result in the natural resonance, exchange resonance, and eddy current loss. Finally, the incident microwaves travelled through the different components of SmFeO₃/Fe@CNTs nanocomposites leads to the microwaves attenuation through multiple reflections and scattering.