Hierarchical Fe-Co@TiO₂ with Incoherent Heterointerfaces and Gradient Magnetic Domains for Electromagnetic Wave Absorption

Abstract

Induced polarization response and integrated magnetic resonance show prosperous advantages in boosting electromagnetic wave absorption but still face huge challenges in revealing the intrinsic mechanism. In this work, we propose a self-confined strategy to construct hierarchical Fe-Co@TiO 2 microrods with numerous incoherent heterointerfaces and gradient magnetic domains. The results demonstrate that the use of polyvinylpyrrolidone (PVP) coating is crucial for the subsequent deposition of Co-zeolitic imidazolate frameworks (ZIF-67), the distance of ordered arranged metal ions manipulates the size of magnetic domains, and the pyrolysis of PVP layers restricts the eutectic process of Fe-Co alloys to some extent. As a result, these introduced lattice defects, oxygen vacancies, and incoherent heterointerfaces inevitably generate a strong polarization response, and the regulated gradient magnetic domains realize integrated magnetic resonance, including macroscopic magnetic coupling, long-range magnetic diffraction, and nanoscale magnetic bridge connection, and both of the intrinsic mechanisms in dissipating electromagnetic energy are quantitatively clarified by Lorentz off-axis electron holography. Owing to the cooperative merits, the Fe-Co@TiO 2 absorbents exhibit enhanced absorption intensity and strong absorption bandwidth. This study inspires us to develop a generalized strategy for manipulating the size of magnetic domains, and the integrated magnetic resonance theory provides a versatile methodology in clarifying magnetic loss mechanism.

Robust and flexible composite aerogel films with porous multilayered structures toward broadband electromagnetic wave absorption

“…At the same time, numerous self-generated lattice defects and oxygen vacancies existed in the magnetic Ni nanochains and MXene nanosheets, respectively, leading to strong dipole polarization with the electron density deviating from the original center under the effect of an applied alternating electromagnetic field. 55 While the magnetic Ni nanochains generated magnetic losses through natural/exchange resonance, magnetic coupling effects, and eddy current losses. 56 In addition, the layered structure built a continuous and conductive network, which provided enough paths for transferring electrons and improved the dielectric loss, which was the most important loss mechanism for EMW absorption.…”

Ti3C2Tx MXene Nanosheet/Cellulose Nanofiber/Poly(ethylene glycol) Porous Composites for Absorption-Dominated Electromagnetic Interference Shielding

“…Only the dielectric constants of PEG porous polymers are tested to explain the electromagnetic shielding mechanism since they are nonmagnetic materials. The real part (ε′), the imaginary part (ε″), and the loss angle tangent (tan δ ε = ε″/ε′) of the complex dielectric constant are shown in Figure S2. Porous polymers have a lower dielectric constant than conductive materials. − However, as they are not electrically conductive, there is no significant reflection of incoming electromagnetic waves, and the porous polymer has a certain thickness of the porous structure, which ensures that the sample has a certain electromagnetic wave absorption ability.…”

Heterostructured MXene/Ni Composites for Tunable Electromagnetic Wave Absorption

“…Additionally, the electrostatic adsorption of magnetic Ni nanoparticles with MXene reduced the agglomeration of magnetic particles and self-stacking of MXene, ensuring the magnetic coupling of the material and enhancing the magnetic loss . Third, the interface polarization and dipole polarization both generated dielectric loss, accompanied by corresponding relaxation processes, contributing significantly to the attenuation of EMWs. On the one hand, the irregular distribution of magnetic Ni nanoparticles on the conductive surfaces, interlayers, and edges of MXene created a multitude of “microcapacitor” configurations, leading to various heterogeneous interfaces for charge buildup and consequent interface polarization loss .…”