Tailoring Self‐Polarization of Bimetallic Organic Frameworks with Multiple Polar Units Toward High‐Performance Consecutive Multi‐Band Electromagnetic Wave Absorption at Gigahertz

Abstract

Multiple relaxation behaviors are promising for broad frequency band and strong electromagnetic wave (EMW) absorption based on polarization‐controlled electromagnetic (EM) attenuation. However, rational selection of materials and structure manipulation through tunable substitution or phase control are challenging toward optimization of EMW absorption. Herein, bi‐metallic organic frameworks (B‐MOFs) with various morphologies are employed as EMW absorbers. Remarkably, the polar units can be enhanced by introducing Ni‐metal nodes into the Cu‐coordinated MOFs, rendering the B‐MOFs with self‐polarized properties and consecutive multifrequency EMW absorption behaviors. The maximum reflection loss of acetylene black (ACET) filled NiCu‐MOFs can reach –40.54 dB together with a wide bandwidth (<‐10 dB) of 5.87 GHz at a thickness of 2.5 mm. As a counterpart of the Ni/Cu/C derivatives, significantly increased broad band absorption (6.93 GHz) and multifrequency absorbing and polarization characteristics are also maintained in bimetal coexisting carbonized architectures as prepared by calcination of CuNi‐MOFs. This work demonstrates that the performance of effective absorbing frequency band can be enhanced in multi‐metallic organic frameworks‐based architectures, and paves a novel avenue for developing broadband and strong EMW absorbers.

1D CNT-Expanded 3D Carbon Foam/Si3N4 Sandwich Heterostructure: Utilizing the Polarization Compensation Effect for Keeping Stable Electromagnetic Absorption Performance at Elevated Temperature

“…50 As we know, the nanoscale contact area could boost interfacial coupling effects to the gigahertz band range we are concerned about. 45 In this work, the addition of Ni and CNTs can lead to the generation of abundant nano-interfaces between the CF/Si 3 N 4 skeleton and a high specific area as shown in Figures 3b,c and S10.…”

“…The defects and doping atoms generated between the heterointerfaces and in the CF could also act as dipolar centers to promote the dipolar polarization loss mechanism. , In addition to dipolar polarization, the interfacial effect between multiple hetero-interfaces is also affected by the contact area . As we know, the nanoscale contact area could boost interfacial coupling effects to the gigahertz band range we are concerned about . In this work, the addition of Ni and CNTs can lead to the generation of abundant nano-interfaces between the CF/Si 3 N 4 skeleton and a high specific area as shown in Figures b,c and S10.…”

“…Generally, two main polarization mechanisms can occur in the gigahertz range: (1) dipolar and (2) interfacial polarization. 45 In our work, the introduction of CNTs and Si 3 N 4 will lead to multiple edge-induced dipolar centers owing to the construction of multiple interfaces and their different electrophilicities. 2,46,47 The edges in our work could appear in the edges of CNTs/CF, Ni/CNTs, Ni/CF, and CF/CNTs/Si 3 N 4 .…”

Multifunctional Epoxy‐Based Electronic Packaging Material MDCF@LDH/EP for Electromagnetic Wave Absorption, Thermal Management, and Flame Retardancy

“…[ 21 ] It is well known that the multi‐interface structure can not only adjust the specific surface area of the material to increase the transmission path of the EMW inside the EMW absorber but also increase the content of the polarized interface per unit volume to achieve multiple reflections, thereby achieving high EMW loss. [ 22 ] Herein, the specific surface area and pore size distribution (inset) of MDCF@LDH were determined by nitrogen adsorption–desorption measurements, and the displayed typical IV isotherms are shown in Figure 1g, indicating their mesoporous structures. The specific surface areas of MDCF@LDH‐1, MDCF@LDH‐2, and MDCF@LDH‐3 are 111.2, 92.8, and 81.6 m 2 g −1 , and their pore size distribution are ≈4, ≈3.1, and ≈2.8 nm, respectively.…”

Marine polysaccharide-based electromagnetic absorbing/shielding materials: design principles, structure, and properties

“…1–3 The competition for EM spatial information advantages applied in military has prompted researchers to focus on the development of efficient EMW absorbing materials for national defense security. 4–6 Nevertheless, fossil energy scarcity and environmental pollution have restrained the design and development of various EM response materials, which has forced researchers to divert their attention to green and renewable energy sources. The abundant biomass materials in nature with diverse microstructures have been considered by researchers as natural templates to design multifunctional components.…”