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[Display omitted] Nowadays, ferrites/carbon fibers have attracted considerable attention as microwave absorption materials (MA) due to the synergistic effect between dielectric and magnetic loss. Herein, the ZnFe 2 O 4 /C fibers were fabricated via electrospinning and calcination methods, and then polypyrrole (PPy) successfully coated on the fibers via oxidative polymerization. The ZnFe 2 O 4 /C@PPy composites exhibit enhanced EM wave absorption performance with the loading of 25 wt%. The optimal reflection loss (RL) value is up to −66.34 dB (13.80 GHz) and effective absorption bandwidth (EAB) is 5.74 GHz (11.78–17.52 GHz) with a matching thickness of 1.93 mm. Besides, high-efficient absorption performance of the ZnFe 2 O 4 /C@PPy composites is mainly attributed to the dielectric loss and ideal impedance matching. This study reveals a novel approach to development of ferrites/carbon fibers coated with PPy, and the ZnFe 2 O 4 /C@PPy composites exhibit great potential application as the materials with high-efficient absorption properties. [ABSTRACT FROM AUTHOR]

Various wireless devices have been widely used in every aspect of life and further lead to the severe electromagnetic waves pollution. Fortunately, researchers have developed microwave absorbing materials which are able to transfer the harmful electromagnetic waves into other energy, such as thermal energy. In recent years, numerous studies on preparing microwave absorbing materials with various components, morphologies and structures have been reported. Metal oxide-related composites are widely used as microwave absorbers due to their excellent electromagnetic properties. The morphology and nanostructure would play a key role on the microwave absorbing performances, which can cause "structural effect". The ideal microwave absorbing materials should meet following demands: widely effective absorption frequency (fE), thinner thickness (d), light-weight, and strong absorption. In this review, we summarized various common morphologies and structures of metal oxide/metal oxide-based composites, and categorized them from a dimensional perspective. The different microwave absorbing properties and mechanisms are given much attention in detail. [ABSTRACT FROM AUTHOR]

[Display omitted] In recent years, electromagnetic pollution has become more and more serious, and there is an urgent need for microwave absorbing materials with superior performance. Prussian blue analogue (PBA) is a metal organic framework material with the advantages of diverse morphology and tunable composition. Therefore, PBA has attracted a lot of attention in the field of microwave absorption. In this work, PBA was coated on the surface of carbon composites by hydrothermal method, and then PPy was compounded on its surface after carbonization treatment to construct hierarchical core–shell CoC@CoFe/C@PPy fibers. The fibers have Co-doped C composites as the core and CoFe/C decorated with PPy as the shell. This unique hierarchical structure and various microwave absorption mechanisms are described in detail. The microwave absorption performance is optimized by adjusting the filling of the sample. The best microwave absorption performances are achieved at 25 wt% filling of CoC@CoFe/C@PPy. At a thickness of just 1.69 mm, CoC@CoFe/C@PPy fiebrs have a minimum reflection loss (RL min) of −64.32 dB. When the thickness is 1.88 mm, CoC@CoFe/C@PPy achieves a maximum effective absorption bandwidth (EAB max) of 5.38 GHz. The results indicate that the CoC@CoFe/C@PPy composite fibers have a great potential in the field of microwave absorption. [ABSTRACT FROM AUTHOR]

With the advancement of wireless communication and electronic equipment, microwave absorption materials (MAMs) have more and more broad applications in related fields. Ti 3 C 2 T x -MXene with unique two-dimensional structure and excellent dielectric properties is often used as a precursor of nano-TiO 2 , which is a potential MAMs. Carbon nanofibers, as a one-dimensional material, have great electrical conductivity and can form interconnected three-dimensional conductive networks. In this study, Ti 3 C 2 T x -MXene was prepared by in-situ HF etching method, and further combined with the benefits of Co, Ce metals, and carbon nanofibers. Co/CeO 2 /TiO 2 /CNFs were prepared via a facile technique for electromagnetic microwave (EM) absorption, exhibiting excellent EM absorption performance due to the synergistic effects of dielectric and magnetic properties. The minimum reflection loss (RL min) and effective absorption bandwidth (EAB) reache −63.35 dB (11.2 GHz) and 3.6 GHz (9.5–13.1 GHz), with a thickness of only 2.35 mm and a filling rate of 30 wt%, while the maximum EAB reaches 5.4 GHz (12.4–17.8 GHz) with a thickness of 1.82 mm, covering nearly the entire Ku band. By offering a novel strategy to the creation of brand-new, high-performance MAMs based on 1D carbon nanofibers with dielectric/magnetic synergy, this work is believed to support the development of upcoming MAMs. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) microwave absorbing materials (MAMs) can induce self-assembly of graphene into aerogels, which provides ideas for the preparation of new MAMs. In here, 3D flower-like Fe 3 O 4 @SiO 2 @MnO 2 @reduced graphene oxide (RGO) (FSMG) composite aerogels have been fabricated via hydrothermal method, in which 1D Fe 3 O 4 @SiO 2 (FS) nanochains and two-dimensional (2D) MnO 2 sheets form a nano-scale core-shell structure on the surface of the RGO nanosheets. The unique microstructure of aerogels greatly enhances the microwave absorption capability. Particularly, the addition of RGO regulates the complex permittivity and improves the impedance matching of 1D Fe 3 O 4 @SiO 2 @MnO 2 (FSM) nanochains. Results demonstrate that the well-designed 3D conductive networks with significant oxygen vacancy defects powerfully favor the electromagnetic wave (EMW) absorption. The as-prepared FSMG composite aerogels show efficient microwave absorption (MA) properties with the maximum effective absorption bandwidth (EAB) of 4.26 GHz (7.13–11.39 GHz) at the corresponding coating thickness of 3.2 mm, accompanied by the minimum reflection loss (RL min) of about −55.01 dB. This work indicates that the FSMG composite aerogels are excellent absorbers with wide bandwidth, strong absorption, thin thickness and light weight, which can become a hopeful candidate in the field of MA. Unlabelled Image • The novel lightweight composite aerogels of Fe 3 O 4 @SiO 2 @MnO 2 @RGO were fabricated successfully. • One-dimensional flower-like Fe 3 O 4 @SiO 2 @MnO 2 nanochains were uniformly anchored onto the surface of the RGO nanosheets. • The microwave absorption mechanism of Fe 3 O 4 @SiO 2 @MnO 2 @RGO composite aerogels was elucidated in depth. • The composite aerogels exhibit strong absorption (RL min = −55.01 dB at 7.78 GHz) and broad bandwidth (7.13–11.39 GHz). [ABSTRACT FROM AUTHOR]

[Display omitted] Nowadays, facing the inevitable electromagnetic (EM) pollution caused by many electronic products, it is urgent to develop high-performance microwave absorbing materials. In particular, the bimetallic carbon-based composites derived from MOFs exhibit excellent microwave absorption potential due to their simple preparation, low cost, adjustable morphology and magnetoelectric synergy mechanism. In this work, we successfully prepared plum-like NiCo@C composite by simple solvothermal method and carbonization treatment, which displays strong absorption (-55.4 dB) and wide effective absorption band (EAB, 7.2 GHz) when the loading is 20 wt%. The plum-like structure greatly enriches the non-uniform interface and the structural anisotropy contributes to the dissipation of electromagnetic waves. At the same time, the band hybridization and magnetic coupling of NiCo@C contribute to the coordination of EM characteristics. Overall, this work proves the feasibility of NiCo@C hierarchical composite in the field of microwave absorbing, and provides insight for the development of high-performance absorbers. [ABSTRACT FROM AUTHOR]

The appearance and development of two-dimensional titanium carbide materials provide a new idea for our research on microwave absorption materials. Its excellent electrical conductivity and surface functional groups allow it to be used as a microwave absorber. In this study, Ti 3 C 2 T x @NiCo 2 O 4 composites were prepared by simple hydrothermal method and subsequent annealing process. With the change of annealing temperature, the state of composites is changed, so the structure and properties of samples are further adjusted. When the annealing temperature is 350 °C, an optimal reflection loss value of −50.96 dB can be obtained at 2.18 mm. The excellent microwave absorption performance is not only caused by polarization behavior, but also related to multiple reflections and multiple scattering produced by unique structures. Therefore, the prepared Ti 3 C 2 T x @NiCo 2 O 4 is expected to be a promising microwave absorber with thin thickness and high absorption intensity. Image 1 • The layer of Ti 3 C 2 T x sheets was prepared by a simple method. • The microwave absorption mechanism of the composite material is explained. • The higher reflection loss value was -50.96db with the thinner thickness of 2.18mm. [ABSTRACT FROM AUTHOR]

Making effective usage of quantum size effect is a foregrounded strategy to design and fabricate excellent electromagnetic microwave absorption materials. In this research, ZnFe 2 O 4 quantum dots were coated by hybrid amorphous carbon to form a sea islands structure by a facile electrostatic self-assembly synthetic technology. Simultaneously, the rejection of heterogeneous charges leads to the formation of quantum dots, by which the quantum size effects on dielectric and magnetic characteristic were investigated. Consequently, multiple hetero-interface and interfacial polarization was originated from polycrystalline feature of ZnFe 2 O 4 with spinel and inverse spinel structures. In particular, the electromagnetic microwave absorption properties of ZnFe 2 O 4 were greatly optimized, as the minimized reflection loss reached −40.68 dB at the frequency 11.44 GHz and thickness 2.5 mm, while the effective bandwidth corresponding was 3.66 GHz (from 9.87 to 13.52 GHz). The largest effective bandwidth was 4.16 GHz (from 8.08 to 12.24 GHz) with a thickness of 3 mm. It is suggested that high performance of microwave absorption of ZnFe 2 O 4 quantum dots was well guided by the optimized impedance matching and attenuation constants. Image 1 [ABSTRACT FROM AUTHOR]

Nowadays, electronic equipment has brought great convenience to people. However, the electromagnetic microwave it generates also brings adverse effects. It is generally hoped to prepare electromagnetic microwave absorption materials with the characteristics of light and thin, wide absorption band and strong absorption performance. Recently, the metal organic framework (MOF) has been regarded as an ideal material. Usually, the combination of magnetic metal and MOF can improve the magnetic loss performance of the material and make the material have a wider application. This paper analyzes and summarizes the latest development of magnetic MOF microwave absorption materials thoroughly, including the classification of magnetic MOF microwave absorption materials, microwave absorption mechanism, design principle and preparation methods. Finally, the development of magnetic MOF microwave absorption materials and the challenges faced in the development process are reasonably prospected, which provides a reference for the development of magnetic MOF microwave absorption materials. [Display omitted] • In this review, the representative magnetic MOF microwave absorption materials are introduced based on the classification of characteristic magnetic metals, and the microwave absorption properties of similar materials are summarized and compared. • The absorption principle, development process, opportunities and challenges of magnetic MOF absorption materials are briefly discussed. • Some ideas for the synthesis of magnetic MOF microwave absorption material and the practical application are provided. [ABSTRACT FROM AUTHOR]

CoNi alloys are well known as excellent magnetic microwave absorption materials, but their various structures greatly influence electromagnetic properties, especially chains versus particles. Hierarchical CoNi chains were prepared using the solvothermal method in conjunction with an external magnetic field, and hierarchical CoNi particles were obtained in the absence of the magnetic field. Changing the reaction time from 6 to 12 h can change the surface structures of hierarchical CoNi alloys, as seen in the SEM images. The lattice parameters of samples are determined by XRD results, which include crystalline structures, lattice constants, mean crystallite sizes, and internal strain. The investigation of magnetic properties indicates that CoNi chains possess a stronger saturation magnetization and higher coercivity than CoNi particles as a result of their higher aspect ratios and larger crystalline sizes. Furthermore, CoNi chains have a higher microwave absorption capacity than CoNi particles, with a minimum reflection loss value of −42.113 dB (16.5 GHz) and an effective absorption bandwidth of 3.5 GHz (13–16.5 GHz). Conductive loss, defect-induced polarization relaxation, eddy current effect, exchange resonance, N é el relaxations, multiple reflections, and scatterings all contribute to the excellent microwave absorption performance of the CoNi chains. This research establishes that a chain-like structure outperforms a particle-like structure for hierarchical CoNi alloys as microwave absorbers, and it will provide clear guidance for designing high-performance magnetic microwave absorption materials. [Display omitted] • Hierarchical CoNi chains were first prepared via a magnetic-field-induced solvothermal method. • CoNi chains exhibit better microwave absorption capacity than particles. • CoNi chains possess the RL min value of − 42.113 dB and EAB of 3.5 GHz in the Ku band. • High aspect ratios and hierarchical surfaces result in excellent microwave energy dissipation. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS 2) is a transition metal sulfide that is widely used as a microwave absorption material (MAM) due to its excellent structural and physicochemical properties. MoS 2 has semiconductor properties, a large specific surface area and a large number of defects that allow it to exhibit excellent microwave loss characteristics. The lamellar MoS 2 can effectively increase the scattering and absorption of microwaves within the absorber by building a variety of different structures. The MoS 2 -based synthetic strategy, structure and properties are presented in this review. The current knowledge on the performance of MoS 2 -based MAMs is comprehensively concluded and analyzed. Moreover, the recent progress of MoS 2 -based MAMs is objectively evaluated and overviewed while the main issues and development difficulties are dissected. Therefore, MoS 2 -based composites are expected to be promising candidates as ultrathin and lightweight MAMs. • The 2D MoS 2 has special electromagnetic properties and promising applications in the field of microwave absorption. • The achievements and challenges of MoS 2 and composites are reviewed, and the preparation methods, structures and microwave absorption properties are analyzed. • The review shows the way to prepare new 2D MoS 2 -based MA materials. [ABSTRACT FROM AUTHOR]