Layered Aluminum for Electromagnetic Wave Absorber with Near-Zero Reflection

Abstract

Ideal electromagnetic (EM) wave absorbers can absorb all incident EM waves, regardless of the incident direction, polarization, and frequency. Absorptance and reflectance are intrinsic material properties strongly correlated with electrical conductivity; hence, achieving perfect absorptance with zero reflectance is challenging. Herein, we present a design strategy for preparing a nearly ideal EM absorber based on a layered metal that maximizes absorption by utilizing multiple internal reflections and minimizes reflection using a monotonic gradient of intrinsic impedance. This approach was experimentally verified using aluminum nanoflakes prepared via topochemical etching of lithium from Li9Al4, and the impedance-graded structure was obtained through the size-based sorting behavior of aluminum nanoflakes sinking in dispersion. Unlike in traditional shielding materials, strong absorption (26.76 dB) and negligible reflectivity (0.04 dB) with a ratio of >103 can be achieved in a 120 μm thick film. Overall, our findings exhibit potential for developing a novel class of antireflective shielding materials.

Influence of Graphene Nanoplatelet Lateral Size on the Electrical Conductivity and Electromagnetic Interference Shielding Performance of Polyester Nanocomposites

“…The incident microwave energy dissipates within the material through the interactions of the EM field with the material’s molecular and electronic structure, which can convert the EM wave into thermal energy. In recent years, researchers have adopted two strategies to improve the microwave absorption performance of polymer composites: Using a combination of magnetic loss materials (such as ferrites) [ 40 ], magnetic metals (e.g., Fe, Co, Ni) [ 7 ], and dielectric loss carbon materials (such as graphene, CNT) [ 6 ]; Using new complex architectures such as multi-layered gradient structures [ 41 ] and foam-based materials [ 42 ]. …”

“…Using new complex architectures such as multi-layered gradient structures [ 41 ] and foam-based materials [ 42 ].…”

Hierarchical Engineering of Double‐Shelled Nanotubes toward Hetero‐Interfaces Induced Polarization and Microscale Magnetic Interaction

“…Multicomponents manipulation and ingenious structure design are two crucially employed strategies in pursuing high‐performance for microwave absorbers, [ 1,2 ] in which mismatched impedance and lacking of magnetic loss ability for carbon materials, [ 3,4 ] high density and easy oxidation capability for magnetic metal/alloys, [ 5 ] and narrow absorption bandwidth issue for traditional solid absorbers, [ 6 ] can be simultaneously addressed by balancing the obvious advantages of two aforementioned strategies. Accordingly, a variety of hierarchical architectures with multiple magnetic‐dielectric components, such as core/yolk–shell or 3D microspheres, [ 7,8 ] hierarchically tubular structure, [ 9 ] hybrid aerogels, [ 10,11 ] et al., have been intensely investigated.…”

A Competitive Reaction Strategy toward Binary Metal Sulfides for Tailoring Electromagnetic Wave Absorption

“…Conventional single-component dielectric materials have difficulties achieving perfect impedance matching and strong electromagnetic wave (EMW) attenuation. [1][2][3][4] In principle, the rational design of multicomponent composites can endow materials with adequate complex permittivities and permeabilities, facilitating an improvement in the impedance matching. Simultaneously, during component modulation, some interfaces and defects will accordingly change, and thus, the corresponding interfacial/defect-induced polarizations are highly adjustable, which is beneficial to the EMW attenuation.…”