Confinedly tailoring Fe3O4 clusters-NG to tune electromagnetic parameters and microwave absorption with broadened bandwidth

An ideal electromagnetic interference shielding and microwave absorber material should have dielectric and magnetic loss capabilities including good impedance matching, which can induce attenuation and absorption of incident electromagnetic waves. In this article, we have systematically reviewed recent advances on spinel ferrite and MXene-based innovative novel nanocomposites for electromagnetic interference shielding and microwave absorption application. The article covers MXene–spinel ferrite composite, MXene–spinel ferrite–carbon/graphene ternary composite, and MXene–spinel ferrite–polymer composite including a brief discussion on the basics of electromagnetic interference shielding and microwave absorption. Development strategies of nanocomposites with various components are also discussed. The challenges and future prospects of MXene and spinel ferrite-based nanocomposites are also proposed, which will pave the way to design an innovative next-generation outstanding electromagnetic wave absorber.

Recent prospects and trends on zeolitic imidazolate frameworks for microwave absorption and EMI shielding applications

We synthesized Fe and Co‐based (Fe48Co41Si3B8) alloy nanopowders by a mechanochemical technique and investigated their structure, magnetic and electromagnetic properties. The nanopowders have a bcc (A2) phase and demonstrate high magnetization with low coercivity. The analysis reveals that their magnetization process may be described by a two‐phase model. The microwave measurements performed by the coaxial method over a broad band up to 18 GHz show that the nanocomposites comprising the nanopowders possess high, broadband magnetic permeability, promising applications in electromagnetic shielding and microwave absorption. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Negative permittivity materials show promising applications in electromagnetic shielding and microwave absorption. SnO2-based composite ceramics with 5wt%, 10wt%, and 15wt% conductive carbon black (CBs) were prepared via solid-phase reaction under an argon atmosphere. Results indicate that CBs inhibit SnO2 grain growth and form conductive pathways along grain boundaries. At room temperature, the 5wt% and 10wt% CBs samples exhibit positive permittivity, whereas the 15wt% CBs composite shows negative permittivity due to exceeding the percolation threshold. As temperature increases, higher carrier concentrations lead to negative permittivity in all samples. The Drude analysis verifies that free electron plasma oscillations within the CBs-generated conductive pathways induce negative permittivity.

Perfect microwave absorbers, which absorb electromagnetic waves completely, play pivotal roles in electromagnetic shielding, and stealth technologies. Existing microwave absorber technologies rely on either electromagnetic properties of absorptive materials, the resonance behavior of meta-atoms, or a combination of both. So far, achieving simultaneous broadband absorption, high efficiency, and compact sizes remains a great challenge. Inspired by atomic doping techniques employed in conventional optical materials to broaden spectral bandwidths, a single-layer microfluidic metasurface microwave absorber is proposed with the assembly of two distinct types of water meta-atoms. By manipulating electromagnetic resonances of these water meta-atoms, the metasurface maintains impedance matching over a broad working range. A microwave absorber design with a thickness equivalent to 0.2 times the central wavelength is showcased, measuring over 93% absorption across both K and Ka bands (17.5-40.0GHz). The results highlight unprecedented superiorities of microwave absorbers based on a 2D doped water meta-atom lattice when compared to previously reported metasurface absorbers utilizing identical meta-atoms. This absorber has advantages including small thickness, broad bandwidth, and cost-effectiveness, making it promising for applications in electromagnetic shielding, camouflage, and multi-spectral stealth.

Several carbon nanotubes and spinel ferrite-based nanocomposites have been created in recent years and are considered to be viable options for an effective electromagnetic interference (EMI) shielding and microwave absorber material. The current development of carbon nanotube and spinel ferrite-based nanocomposites for EMI shielding and microwave absorption is the topic of this study. The fundamental mechanism of EMI shielding and microwave absorption is described. The EMI shielding and microwave absorption properties of carbon nanotubes and spinel ferrite, as well as their numerous components such as graphene, MXene, semiconductor nanoparticles, polymer, rubber, and so on, are thoroughly examined. This paper also discusses potential problems and solutions for creating new nanocomposites for the next generation of shielding applications.

Chapter 29 - Functionalized nanofibers for EMI shielding and microwave absorption applications

In this study, we employed a microwave plasma assisted reduction (MPAR) method to prepare metallic nanoparticles with desirable morphology. Compared with the hydrogen thermal reduction technique, the MPAR technique could greatly maintain the original morphology of self-sacrificing precursors, as well as proving to be highly efficient, energy-saving and pollution-free. Taking ferromagnetic metallic Co as a forerunner, Co nanosheets with inerratic hexagonal morphology were successfully synthesized on a large scale uniformly. The lateral dimension of the achieved Co nanosheets is in the range of 3∼5 μm with tens of nanometers in thickness. The intact hexagonal flaky shape of Co nanosheets is beneficial for improving dielectric loss by increasing electric channels and interfacial polarization. Consequently, the minimum reflection loss could reach up to −71 dB at a thin thickness of 1.2 mm. Furthermore, the effective bandwidth (RL < −10 dB) could be achieved in a wide range of 2.8∼18 GHz by integrating the thickness from 5.0∼1.0 mm, which provides the possibility for applications in electromagnetic shielding and radar stealth fields. It is believed that the MPAR technique is suitable for designing and preparing novel microwave absorbers on the basis of appropriate precursors, providing new opportunities to acquire high-performance microwave absorbers in the future.

Porous carbon materials based on MOFs in microwave absorbing

Composites based on layered materials for absorption of microwaves and electromagnetic shielding

Vermicular Ni@RL-CS: Preparation, characterization and its applications in electromagnetic shielding

Developing lightweight multifunctional materials with both strong electromagnetic microwave (EMW) absorption and robust flame retardancy is essential for addressing electromagnetic interference and fire risks in modern electronics. In this work, ZIF‐67@NH 2 ‐MIL‐88B(Fe)/MXene‐modified melamine foam (ZIF@MIL/MXene/MF) composite aerogels were constructed to achieve synergistic dielectric loss and magnetic loss mechanisms. The optimized ZIF@MIL/MXene/MF‐5 exhibited outstanding EMW absorption, with a minimum reflection loss (RL min ) of −55.82 dB and an effective absorption bandwidth of 4.52 GHz, along with a radar cross‐section reduction of 15.27 dB·m 2 . The superior absorption originates from conductive network pathways, abundant heterogeneous interfaces for polarization loss, dipole relaxation, and magnetic loss from CoFe alloy nanoparticles, combined with excellent impedance matching. Additionally, the composite demonstrated excellent fire safety, with peak heat release rate, total heat release, and total smoke production reduced by 34.0%, 64.6%, and 87.9%, respectively, owing to catalytic graphitization and the formation of a compact char barrier. These results demonstrate an effective strategy for designing lightweight multifunctional aerogels for next‐generation electromagnetic protection and fire‐safe engineering applications.

Design and microwave absorption properties of thistle-like CoNi enveloped in dielectric Ag decorated graphene composites

Industrially sole-phase magnetic powders for microwave absorption (MA) purposes rely mainly on magnetic loss, restricting better impedance matching. Concurrently, the massive disposal of single-use industrial products, such as medical diagnostics, presents a pressing environmental challenge. Herein, we introduce a cross-industrial strategy to transform waste nitrocellulose (NC) membranes from medical lateral flow assay (LFA) strips into functional MA materials via dimethyl sulfoxide (DMSO)-induced structural reconstruction. The dissolved NC transforms from a porous network into a condensed binding matrix, enabling the fabrication of two distinct product forms: (1) flexible, transparent, and magnetic Fe3O4/NC hybrid films, and (2) Fe3O4 aggregates bonded by NC. DMSO concentration was revealed as a factor regulating the microstructure and MA behavior of the NC-treated Fe3O4 aggregates. With improved impedance matching, the NC-treated Fe3O4 aggregates show good MA properties, e.g., a minimum reflection loss (RL) of −38.94 dB at 11.57 GHz (70 wt % filler/paraffin), −42.31 dB at 15.55 GHz (60 wt % filler/paraffin), and −47.02 dB at 6.54 GHz (50 wt % filler/paraffin). This work establishes a scalable strategy for designing MA materials from discarded medical resources.

Morphology dependent EMI shielding performance of Ag-Ni core-shell nanowires