Preparation and characterization of branch-like heteroatoms-doped Ni@C nanofibers for high-performance microwave absorption with thin thickness
TL;DR: In this article, a branch-like multi-wall carbon nanotubes (MWCNTs) were used to extend the transmission path of microwave and reduce the thickness effectively, achieving an optimal reflection loss value of −53.2 dB at 14.3 GHz and effective absorption bandwidth of 5.6 GHz.
Abstract: Magnetic Ni@C nanofibers with branch-like multiwall carbon nanotubes (MWCNTs) were prepared through a two-step strategy of electrospinning and following in situ pyrolysis to explore the electromagnetic microwave absorption (MA) performance. The morphology and chemical composition were controlled by mass ratio of nickel (II) acetylacetone (Ni(acac)2) and poly (phthalazinone ether nitrile ketone) (PPENK) resin. 3D structure with branch-like morphology extends the transmission path of microwave and reduces the thickness effectively. The heteroatoms-doped Ni@C nanofibers reach the optimal reflection loss value of −53.2 dB at 14.3 GHz and effective absorption bandwidth of 5.6 GHz from 12.4 to 18.0 GHz with rather thin thickness of 1.5 mm. The MA mechanisms are discussed in detail and the multi-component nanofibers of magnetic Ni particles and nonmagnetic carbon have achieved synergistic effect of dielectric and magnetic loss. This work explores the relevancy of morphology and composition on microwave absorption performance, revealing a potential application for excellent microwave absorber with low filler ratio and thinner matching thickness.
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TL;DR: In this article , a type of nickel/manganese oxide (Ni/MnO)/carbon nanocomposite fibers were prepared via a facile and scalable electrospinning and carbonization approach.
Abstract: A type of nickel/manganese oxide (Ni/MnO)/carbon nanocomposite fibers were prepared via a facile and scalable electrospinning and carbonization approach. In comparison to the pure carbon showing a severe agglomeration, the uniformly embedded MnO and Ni nanoparticles promoted the formation of the fibrous carbon-based nanocomposites with an average diameter of 250 nm and a rough surface. The synergistic coactions of the MnO nanoparticles acting as impedance modulating mediator, the magnetic Ni nanoparticles, and the conductive, fibrous carbon with large aspect ratio and rough surface contributed to the excellent electromagnetic wave (EMW) absorbing performance of the nanocomposites. The nanocomposites with a MnO/Ni ratio of 1:1 exhibited an effective absorption bandwidth of 6.5 GHz at a thickness of 2.9 mm and a minimum reflection loss of −53.23 dB at a thickness of 2.3 mm. The EMW absorption mechanisms of the nanocomposite fibers were discussed at length, which showed the importance of the multi-component building units and microstructure for achieving high EMW absorbing performance. This work thus suggested a convenient, facile, and scalable manufacturing approach for constructing high-performance multi-component nanocomposite fiber based EMW absorbing materials.
46 citations
TL;DR: In this paper , a rod-like Fe/Fe3O4/FeN/N-doped carbon (FON/NC) composite was synthesized via dual-ligand strategy and following calcination.
37 citations
TL;DR: In this paper, a rod-like Fe/Fe3O4/FeN/N-doped carbon (FON/NC) composite was synthesized via dual-ligand strategy and following calcination.
37 citations
TL;DR: In this article , a superalloy/graphite (FeNi 3 @C) nanocapsules were synthesized and exhibited effective absorbing bandwidth 7.04 GHz with absorber thickness 3 mm.
Abstract: The magnetic nanocapsules composed of soft-magnetic core and dielectric graphite shell in nanoscale are of great significance for electromagnetic wave (EMW) absorbing materials. As an ideal model system, novel nanocomposite superalloy/graphite FeNi 3 @C nanocapsules were synthesized that showed two significant advantages including extremely stable magnetic behavior from 5 K to 300 K and strong anti-oxidation ability up to 719 K, simultaneously. The tuning regularity of enhanced EMW absorption, including magnetic core, filling ratio, dielectric shell, was systemically investigated. A reflection loss (RL) - 47.26 dB at 13 GHz and an absorption bandwidth 7.04 GHz (RL < −10 dB) with absorber thicknesses 3 mm were obtained while the effective absorbing bandwidth remained at top level in magnetic nanocapsules system. This work not only extends EMW absorption application of magnetic nanocapsules in wide temperature range, but also provides a clear optimal sequence to support the material design strategy to achieve best EMW absorption in nanocomposite systems. • The superalloy/graphite (FeNi 3 @C) nanocapsules were synthesized and exhibited effective absorbing bandwidth 7.04 GHz. • The FeNi 3 @C nanocapsules exhibit stable magnetic stability from 5 K to 300 K. • The strong resistance to high temperature oxidation until to 719 K was found in FeNi 3 @C nanocapsules. • Based on above two advantages, FeNi 3 @C nanocapsules can be applied in wide temperature range EMW absorption. • The optimal tuning regularity of enhanced EMW absorption was found with FeNi 3 @C nanocapsules as the model system.
30 citations
TL;DR: In this article , a step-by-step synthesis of polyaniline (PANI)/FeCo@C composite microspheres by hydrothermal, calcination and in-situ polymerization was reported.
Abstract: Composite microwave absorbers with multiple loss mechanism have attracted more and more attention. Herein, we report a strategy of step-by-step synthesis of polyaniline (PANI)/FeCo@C composite microspheres by hydrothermal, calcination and in-situ polymerization. The multilayer heterogeneous interfaces of microspheres and the multi dipole center of polyaniline molecular chain significantly improve the polarization relaxation loss. Polyaniline on the surface connects the microspheres to form a conductive network, which effectively enhances the conduction loss. FeCo alloy particles also provide a certain magnetic loss. Their synergistic effect makes the composite microspheres exhibit good microwave absorption performance. When the thickness of P2 is only 1.7 mm, it could exhibit an effective absorption bandwidth (EAB) of 5.31 GHz and maximum reflection loss (RL) of −33.86 dB. Moreover, we optimized the macro structure of the absorber through gradient design, and successfully extended the effective absorption bandwidth to 11.81 GHz by introducing multiple interference. This work provides a useful reference for the comprehensive optimization of micro regulation and macro design of composite microwave absorbers.
29 citations
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TL;DR: The broadband and tunable high-performance microwave absorption properties of an ultralight and highly compressible graphene foam (GF) are investigated and it is shown that via physical compression, the microwave absorption performance can be tuned.
Abstract: The broadband and tunable high-performance microwave absorption properties of an ultralight and highly compressible graphene foam (GF) are investigated. Simply via physical compression, the microwave absorption performance can be tuned. The qualified bandwidth coverage of 93.8% (60.5 GHz/64.5 GHz) is achieved for the GF under 90% compressive strain (1.0 mm thickness). This mainly because of the 3D conductive network.
1,533 citations
TL;DR: In this article, the phase transformation from dendritic α-Fe2O3 to Fe3O4, Fe by partial and full reduction, and Fe 2O3 by reduction−oxidation process.
Abstract: Iron-based microstructured or nanostructured materials, including Fe, γ-Fe2O3, and Fe3O4, are highly desirable for magnetic applications because of their high magnetization and a wide range of magnetic anisotropy. An important application of these materials is use as an electromagnetic wave absorber to absorb radar waves in the centimeter wave (2−18 GHz). Dendrite-like microstructures were achieved with the phase transformation from dendritic α-Fe2O3 to Fe3O4, Fe by partial and full reduction, and γ-Fe2O3 by a reduction−oxidation process, while still preserving the dendritic morphology. The investigation of the magnetic properties and microwave absorbability reveals that the three hierarchical microstructures are typical ferromagnets and exhibit excellent microwave absorbability. In addition, this also confirms that the microwave absorption properties are ascribed to the dielectric loss for Fe and the combination of dielectric loss and magnetic loss for Fe3O4 and γ-Fe2O3.
866 citations
TL;DR: By considering good chemical homogeneity and microwave absorption, it is believed the as-fabricated Fe3O4@C composites can be promising candidates as highly effective microwave absorbers.
Abstract: Core–shell composites, Fe3O4@C, with 500 nm Fe3O4 microspheres as cores have been successfully prepared through in situ polymerization of phenolic resin on the Fe3O4 surface and subsequent high-temperature carbonization. The thickness of carbon shell, from 20 to 70 nm, can be well controlled by modulating the weight ratio of resorcinol and Fe3O4 microspheres. Carbothermic reduction has not been triggered at present conditions, thus the crystalline phase and magnetic property of Fe3O4 micropsheres can be well preserved during the carbonization process. Although carbon shells display amorphous nature, Raman spectra reveal that the presence of Fe3O4 micropsheres can promote their graphitization degree to a certain extent. Coating Fe3O4 microspheres with carbon shells will not only increase the complex permittivity but also improve characteristic impedance, leading to multiple relaxation processes in these composites, thus the microwave absorption properties of these composites are greatly enhanced. Very inte...
817 citations
TL;DR: In this paper, a carbon nanocage was synthesized by direct pyrolysis of a core-shell ZIF-8@ZIF-67 polyhedron.
419 citations
TL;DR: In this paper, metal-organic frameworks derived nanoporous Fe3O4@ carbon (Fe3O 4@NPC) composites were successfully obtained by a simple method, in which the electromagnetic wave absorbing performances were significantly enhanced due to the optimal impedance matching and strong attenuation via the synergy between the dielectric loss and the magnetic loss.
331 citations