Liquid Metal-Derived Two-Dimensional Layered Double Oxide Nanoplatelet-Based Coatings for Electromagnetic Wave Absorption

Room-temperature liquid metals offer intriguing chemistry for obtaining atomic nanomaterials with unique composition and morphologies. However, the use of liquid metals for the synthesis of layered double oxide (LDO) materials has rarely been reported. When surrounded with water, liquid metal alloys produce low-dimensional hydroxides on their interfacial regions. In this work, highly electrostatically polarized two-dimensional (2D) aluminum hydroxides, featuring OH bonds, are devised as adsorption sites for divalent cations including Ni2+, Co2+, Mg2+, Mn2+, Zn2+, and Fe2+ ions. For Ni2+ and Co2+ ions, remarkably, through changing synthesis conditions, different orientations of 2D Al/NiCo-LDO nanoplatelets can be synthesized. The change in the orientation of the surface platelets, that is, parallel or vertical, to the plane of aluminum oxide resulted in excellent electromagnetic wave (EW) absorption performance. The effective absorption bandwidth reaches 5.61 GHz at a composite thickness of only 1.7 mm. The different nanomorphology and annealing temperature of Al/NiCo-LDO resulted in fundamentally different electromagnetic losses. Results indicating the developed framework have tunable and excellent EW absorption capabilities. 2D Al/NiCo-LDOs prepared by the developed liquid metal synthesis method shows a great promise for applications in the fields of EW absorption and electromagnetic protection. Due to their lightweight, high-surface-area, and mechanically strong material features, aluminum oxide compounds are suitable for the synthesis of other LDO compounds including Mg2+, Mn2+, Zn2+, and Fe2+. The incorporation of a variety of divalent cations into the nanostructure and facet engineering are promising pathways for the production of reinforced lightweight nanomaterials for utilization in various applications. This work fundamentally explores the effect of achieved materials' polarization through fully characterizing the absorption.