Morphology engineering of YNi-MOFs derivatives for broadband electromagnetic wave absorption

Abstract

Morphology control strategy is a critical factor in optimizing permittivity and impedance matching. Nevertheless, developing materials with tunable morphology enabling broadband electromagnetic wave (EMW) absorption is a challenging task. In this work, Y2O3/Ni@N-doped carbon (YNC) composites were prepared by solvothermal method and high-temperature carbonization using metal-organic frameworks (MOFs) as raw materials. By regulating the molar ratio of Y3+/Ni2+, the morphology evolved from microsphere to spiky microspheres, and eventually formed dumbbell-like structures. This controllable morphological transformation provides an effective approach for modulating the permittivity. Especially, the spiky microspheres exhibited stronger EMW absorption performance than other morphologies. When the molar ratio of Y3+/Ni2+ was 3:7, the minimum reflection loss of YNC reached −64.74 dB at a 25 wt% filling ratio. At a thickness of 2.02 mm, the effective absorption bandwidth value reached 6.56 GHz (11.44–18.00 GHz), covering the entire Ku band. Notably, the composites with the controllable matching thickness and porous structure achieved effective absorption in multiple bands (C, X, and Ku). The exceptional absorption capability was linked to the tunable morphology of the composites, achieving a balance of impedance matching and attenuation capacity. Furthermore, the presence of magnetic Ni nanoparticles provided magnetic loss capability for the composites. Density functional theory indicated that the formation of heterostructures boosted the carrier mobility, facilitating effective electron transfer across interfaces, and thus increasing interfacial polarization. Therefore, this study offered a new idea for designing rare-earth based MOFs derived absorbers with broadband absorption capability.