Controllable fiberization engineering of cobalt anchored mesoporous hollow carbon spheres for positive feedback to electromagnetic wave absorption

The excellent performance of electromagnetic wave absorbers primarily depends on the coordination among components and the rational design of the structure. In this study, a series of porous fibers with carbon nanotubes uniformly distributed in the shape of pine leaves are prepared through electrospinning technique, one‐pot hydrothermal synthesis, and high‐temperature catalysis method. The impedance matching of the nanofibers with a porous structure is optimized by incorporating melamine into the spinning solution, as it undergoes gas decomposition during high‐temperature calcination. Moreover, the electronic structure can be modulated by controlling the NH4F content in the hydrothermal synthesis process. Ultimately, the Ni/Co/CrN/CNTs‐CF specimen (P3C NiCrN12) exhibited superior performance, while achieving a minimum reflection loss (RLmin) of −56.18 dB at a thickness of 2.2 mm and a maximum absorption bandwidth (EABmax) of 5.76 GHz at a thickness of 2.1 mm. This study presents an innovative approach to fabricating lightweight, thin materials with exceptional absorption properties and wide bandwidth by optimizing the three key factors influencing electromagnetic wave absorption performance.

Porous Structure Fibers Based on Multi‐Element Heterogeneous Components for Optimized Electromagnetic Wave Absorption and Self‐Anticorrosion Performance

Zhu,

Lan,

Liu

et al. 2024

Microporous Cobalt Ferrite with Bio‐Carbon Loosely Decorated to Construct Multi‐Functional Composite for Dye Adsorption, Anti‐Bacteria and Electromagnetic Protection

Ma,

Lan,

Zhang

et al. 2024

Currently, facing electromagnetic protection requirement under complex aqueous environments, the bacterial reproduction and organic dye corrosion may affect the composition and micro‐structures of absorbers to weaken their electromagnetic properties. To address such problems, herein, a series of CoFe2O4@BCNPs (cobalt ferrite @ bio‐carbon nanoparticles) composites are synthesized via co‐hydrothermal and calcining process. The coupling of magnetic cobalt ferrite and dielectric bio‐carbon derived from Apium can endow the composite multiple absorption mechanisms and matched impedance for effective microwave absorption, attaining a bandwidth of 8.12 GHz at 2.36 mm and an intensity of −49.85 dB at 3.0 mm. Due to the ROS (reactive oxygen species) stimulation ability and heavy metal ions of cobalt ferrite, the composite realizes an excellent antibacterial efficiency of 99% against Gram negative bacteria of Escherichia coli. Moreover, the loose porous layer of surface stacked bio‐carbon can promote the adsorption of methylene blue for subsequent eliminating, a high removal rate of 90.37% for organic dye can be also achieved. This paper offers a new insight for rational design of composite's component and micro‐structure to construct multi‐functional microwave absorber for satisfying the electromagnetic protection demand in complicated environments.

Kirkendall Effect‐Induced Ternary Heterointerfaces Engineering for High Polarization Loss MOF‐LDH‐MXene Absorbers

Sun,

Lan,

Jia

et al. 2024

Heterogeneous interfacial engineering has garnered widespread attention for optimizing polarization loss and enhancing the performance of electromagnetic wave absorption. A novel Kirkendall effect‐assisted electrostatic self‐assembly method is employed to construct a metal–organic framework (MOF, MIL‐88A) decorated with Ni‐Fe layered double hydroxide (LDH), forming a multilayer nano‐cage coated with Ti3C2Tx. By modulating the surface adsorption of Ti3C2Tx on LDH, the heterointerfaces in MOF‐LDH‐MXene ternary composites exhibit excellent interfacial polarization loss. Additionally, the Ni‐Fe LDH@Ti3C2Tx nano‐cage exhibits a large specific surface area, abundant defects, and a large number of heterojunction structures, resulting in excellent electromagnetic wave absorption performance. The MIL‐88A@Ni‐Fe LDH@Ti3C2Tx‐1.0 nano‐cage achieves a reflection loss value of −46.7 dB at a thickness of 1.4 mm and an effective absorption bandwidth of 5.12 GHz at a thickness of 1.8 mm. The heterojunction interface composed of Ni‐Fe LDH and Ti3C2Tx helps to enhance polarization loss. Additionally, Ti3C2Tx forms a conductive network on the surface, while the cavity between the MIL‐88A core and the Ni‐Fe LDH shell facilitates multiple attenuations by increasing the transmission path of internal incident waves. This work may reveal a new structural design of multi‐component composites by heterointerfaces engineering for electromagnetic wave absorption.