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• NiCo/Co 4 S 3 @C hybrid materials were prepared by a simple two-step process. • The complete carbon shell cladding and Co 4 S 3 doping can be observed. • The minimum RL value of −56.96 dB at 10.32 GHz with the matching thickness is only 2.71 mm. • The effective absorption bandwidth can be covered 13.36 GHz with the thickness is 1.8–5.0 mm. Producing electromagnetic wave absorbers with high absorption capacity and wide absorption bandwidth is still a challenge task, which limits its application in human life. In this study, a novel carbon-coated NiCo alloy/Co 4 S 3 hybrid material was fabricated by a simple strategy. By adjusting the annealing temperature, the electromagnetic wave absorption property of NiCo/Co 4 S 3 @C hybrid material can be further improved. Herein, the NiCo/Co 4 S 3 @C hybrid material obtained at 750 °C exhibits satisfactory electromagnetic wave absorption performance. The minimum reflection loss value of −56.96 dB is obtained at 10.32 GHz, and the matching thickness is only 2.71 mm. When the thickness of the absorber is in the range of 1.8–5.0 mm, the effective absorption bandwidth is controlled between 4.64 and 18 GHz. The satisfactory properties of the hybrid materials are attributed to the space charge polarization caused by heterogeneous NiCo alloys, interfacial polarization between components and good impedance matching characteristics. The results show that NiCo/Co 4 S 3 @C hybrid material is a potential electromagnetic wave absorber. [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] • 3D MXene-supported magnetic carbon nanotube composites are prepared. • Composite materials combine the advantages of dielectric and magnetic losses. • NiCo/TiC/TiO/CNTs exhibit the RL min of −51.98 dB (1.9 mm) and the EAB of 7.76 GHz (2.1 mm). • Detailed revelation of possible EMW absorption mechanisms. The widespread use of communication equipment has exacerbated the deterioration of the electromagnetic environment, urgently requiring the development of more efficient electromagnetic wave (EMW) absorption materials. Two-dimensional metal carbides are highly regarded for their characteristic structure and excellent electrical conductivity. Here, to break the single way of designing Ti 3 C 2 T x MXene composites and to compensate for their lack of magnetic loss capability, an attempt was made to prepare composites with magnetic NiCo/Carbon nanotubes (CNTs) modification to achieve EMW absorption. Such CNTs-encapsulated Ni and Co metal particles anchored in the matrix, coupled with a multilayer laminate structure, enable the composite to have enhanced EMW absorption. Remarkably, the NiCo/TiC/TiO/CNTs composites exhibit excellent EMW absorption performance at a filling level of only 14.2 wt%. The minimum reflection loss (RL) of −51.98 dB and the maximum effective absorption bandwidth of 7.76 GHz were obtained at thicknesses of 1.9 mm and 2.1 mm, respectively. In addition to this, the possible mechanisms involved in EMW absorption have been elucidated in detail. These results demonstrate an environmentally friendly and simple strategy for the preparation of EMW absorbers based on Ti 3 C 2 T x MXene substrate. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel accordion-like structure was synthesized by ZIF-67 derivation strategy. • Their morphological evolution in various stages is clarified. • Revealing the contribution of dielectric property modulation to absorption performance. • The EAB reached 5.68 GHz at a thickness of 2.6 mm for NiSe 2 -CoSe 2 @C/Ti 3 C 2 T x composite. Two-dimensional metal carbide or nitride materials are considered as a new class of electromagnetic wave absorbing materials due to their unique multilayer structure and metal-like properties. The NiSe 2 -CoSe 2 @C/Ti 3 C 2 T x composites were prepared through a facile hydrothermal treatment and selenization reaction. Distinctly, the maximum reflection loss (RL) is −60.46 dB with the mass fraction of NiSe 2 -CoSe 2 @C/Ti 3 C 2 T x of 40 wt% at 2.6 mm. The bandwidth of RL < −10 dB reaches up to 5.68 GHz (10.32–16 GHz). The synergistic mechanism of the multiple scattering and multi-interface polarization effects of NiSe 2 -CoSe 2 @C compounded with Ti 3 C 2 T x is reviewed to interpret the significant improvement of electromagnetic wave absorption performance. The results indicate that NiSe 2 -CoSe 2 @C/Ti 3 C 2 T x composites have potential applications as realistic electromagnetic wave absorbing materials. [ABSTRACT FROM AUTHOR]

In order to provide electronics and aerospace equipment with effective immunity to electromagnetic interference and to improve their adaptability to very harsh electromagnetic environments, high-performance electromagnetic wave-absorbing materials are urgently needed for civil and military applications. Unfortunately, their effective absorption bandwidth width is still unsatisfactory (<10 GHz) due to the insufficient regulation of their component mixing and microstructure. By employing nanocage-structured UiO-66 as a doping phase, MXene/ZrO 2 /tungsten-doped carbon (MXene/ZrO 2 /W-C) interpenetrating fiber networks were prepared by the electrostatic spinning method. According to the experimental results, the introduction of the dopant phase and the formation of the interpenetrating network significantly improves impedance matching, resulting in a wide absorption bandwidth of 11.12 GHz for the composites, completing the coverage of the X and Ku bands. The radar scattering cross section of MXene/ZrO 2 /W-C has been simulated using three-dimensional electromagnetic field simulation, and as a result of its excellent stealth performance, it is able to generate corresponding electromagnetic responses in radar detection environments that exhibit different far-field emission bands. Further, MXene/ZrO 2 /W-C exhibits outstanding hydrophobicity, corrosion resistance, and temperature resistance. These characteristics allow it to be used for the preparation of electromagnetic wave (EMW) absorbing devices for complex environmental applications. It is important to note that the results of this study will be extremely useful in the development of composites based on MXene with ultra-wide absorption bands as well as in the analysis of EMW absorption mechanisms. In this paper, MXene/ZrO 2 /tungsten doped carbon (MXene/ZrO 2 /W-C) interpenetrating fiber network was prepared by electrospinning with a nanocage structure UiO-66 as the doping phase. According to the experimental results, the introduction of the doped phase and the formation of an interpenetrating network significantly improve impedance matching, resulting in an effective absorption bandwidth of 11.12 GHz in the composite material, as well as full coverage of the X and Ku bands. In particular, the radar cross section of MXene/ZrO 2 /W-C is simulated by three-dimensional electromagnetic field simulation. It is found that the corresponding electromagnetic response can be made in different radar detection environments. It has guiding significance for the development of MXene-based composites with ultra-wide absorption bands and for the study of electromagnetic wave absorption mechanisms. [Display omitted] • Using electrospinning technology, multi-phase doped fiber interpenetrating network improves impedance matching. • The MXene/ZrO2/W-C nanofibers have an ultra-wide absorption bandwidth of 11.12 GHz, covering the X and Ku bands. • The synergistic effect of composition and structure is responsible for the excellent electromagnetic wave absorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • The 2D MXene-based accordion-like hybrid structure was obtained. • Controlling the addition of Ti 3 C 2 T x can effectively control the dielectric parameters. • The effective bandwidth is up to 4.24 GHz with a matched thickness of 1.5 mm. Owing to their unique structure and high dielectric loss, two-dimensional transition metal carbides and nitrides (MXenes) are widely used in electromagnetic wave absorption. The novel Co 9 S 8 /C/Ti 3 C 2 T x hybrid material with a multilayer structure was successfully fabricated by hydrothermal and annealing processes. The unique multilayered hybrid material is assembled from Ti 3 C 2 T x film layers, Co 9 S 8 particles, and carbon flakes. The Co 9 S 8 particles were uniformly anchored on Ti 3 C 2 T x and carbon flakes. The Co 9 S 8 /C/Ti 3 C 2 T x -100 hybrid material has demonstrated impressive electromagnetic absorption performance after the multi-component introduction and interface design were optimized. Besides, the hybrid material exhibits the maximum reflection loss of −50.07 dB at 7.6 GHz under a matched thickness of 2.51 mm, and the effective absorption bandwidth (RL ≤ -10 dB) is covered 4.24 GHz. The synergistic effect of dielectric and magnetic loss, interfacial polarization, and multilayer structure was beneficial to the improvement of electromagnetic wave absorption performance. This research provides a simple demonstration of the design and synthesis of high-performance MXenes-based absorbing materials. [ABSTRACT FROM AUTHOR]