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Journal ArticleDOI: 10.1039/D0TA10942H

Rationally designed hierarchical N-doped carbon nanotubes wrapping waxberry-like Ni@C microspheres for efficient microwave absorption

02 Mar 2021-Journal of Materials Chemistry (The Royal Society of Chemistry)-Vol. 9, Iss: 8, pp 5086-5096
Abstract: Hierarchical microstructures are playing important roles in the design and fabrication of high-performance microwave absorbing materials (MAMs) owing to their unique advantages. In this work, a series of special “double-hierarchical” N-doped carbon nanotubes wrapping waxberry-like Ni@C microspheres (NC@NCNTs) have been rationally designed and successfully fabricated by two-step pyrolysis processes, where the loading amount of NCNTs on the waxberry-like Ni@C microspheres can be easily modulated by changing the dosage of melamine. Benefiting from sufficient attenuation ability and good impedance matching, NC@NCNTs-2, whose relative carbon content is 51.1 wt%, exhibits the best reflection loss (RL) characteristics among this series of composites, including the minimum RL intensity of −41.5 dB and an effective absorption bandwidth of 5.2 GHz with an absorber thickness of only 1.7 mm. This performance is superior to that of many homologous Ni/C composites reported previously. The investigation on EM properties indicates that the unique “double-hierarchical” architecture of NC@NCNTs can not only create stronger dipole orientation and interfacial polarization relaxation, but can also result in higher conductive loss as well as extra multiple reflection effects for incident electromagnetic waves. We believe that these results will provide some inspirations and pathways for the production of high-performance MAMs with senior microstructures in the future.

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Topics: Reflection loss (53%), Carbon nanotube (52%)
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28 results found


Open accessJournal ArticleDOI: 10.1007/S40820-021-00658-8
Xue Zhang1, Jing Qiao1, Yanyan Jiang1, Fenglong Wang1  +5 moreInstitutions (1)
06 Jun 2021-Nano-micro Letters
Abstract: To tackle the aggravating electromagnetic wave (EMW) pollution issues, high-efficiency EMW absorption materials are urgently explored. Metal–organic framework (MOF) derivatives have been intensively investigated for EMW absorption due to the distinctive components and structures, which is expected to satisfy diverse application requirements. The extensive developments on MOF derivatives demonstrate its significantly important role in this research area. Particularly, MOF derivatives deliver huge performance superiorities in light weight, broad bandwidth, and robust loss capacity, which are attributed to the outstanding impedance matching, multiple attenuation mechanisms, and destructive interference effect. Herein, we summarized the relevant theories and evaluation methods, and categorized the state-of-the-art research progresses on MOF derivatives in EMW absorption field. In spite of lots of challenges to face, MOF derivatives have illuminated infinite potentials for further development as EMW absorption materials. Highlights: 1 In terms of components and structures, this review summarizes progresses and highlights strategies of MOF derivatives for efficient electromagnetic wave absorption.2 We also systematically delineate relevant theories and points out the prospects and current challenges.

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18 Citations


Journal ArticleDOI: 10.1016/J.JCIS.2021.04.107
Weibo Huang1, Zhouyu Tong1, Yuxin Bi1, Mingliang Ma1  +6 moreInstitutions (2)
Abstract: Herein, coralloid core-shell structure NiS/Ni3S4@PPy@MoS2 nanowires were elaborately designed and successfully synthesized through a three-step route to obtain exceptional microwave absorption (MA) properties. Ni nanowires were first fabricated, and then used as the substrate to be coated with a layer of PPy. Ni chalcogenides were obtained by using Ni nanowire as sacrificial templates while growing MoS2 nanorods by hydrothermal method. Both the one-dimensional (1D) core-shell structure and the coralloid surface generated by MoS2 nanorods were beneficial for the attenuation of microwaves. After investigating the electromagnetic properties of different loading content absorbers (30 wt.%, 40 wt.% and 50 wt.%), it is found that the 50 wt.% loading absorber has the optimal MA performance. The minimum reflection loss (RLmin) value can reach −51.29 dB at 10.1 GHz with a thickness of 2.29 mm, and the corresponding effective absorption bandwidth (EAB, RL

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Topics: Nanowire (54%), Nanorod (52%), Absorption (electromagnetic radiation) (51%) ... read more

11 Citations


Journal ArticleDOI: 10.1021/ACSAMI.1C04962
Yu Wang1, Qingbin Qi1, Guang Yin1, Wei Wang1  +1 moreInstitutions (1)
Abstract: Flexible, ultralight, and mechanically robust electromagnetic interference (EMI) shielding materials are urgently demanded to manage the increasing electromagnetic radiation pollution, but it remains a great challenge to simultaneously achieve ultralight yet mechanically robust properties while retaining high-efficiency EMI shielding performance. Herein, we fabricate a novel waterborne polyurethane/Ti3C2Tx MXene/nickel ferrite (WPU/MXene/NiFe2O4) hybrid aerogel by constructing a strong chemical bonding interaction between an NCO-terminated WPU prepolymer and hydroxyl functionalized MXene nanosheets. The resultant aerogels exhibit remarkable lightweight and mechanical properties, particularly high compressive stress far exceeding that of other MXene-based and WPU-based porous materials. Furthermore, synergistic effects of the oriented porous architecture and the multiphase skeleton endow the hybrid aerogels with a high X-band EMI shielding effectiveness (SE) of 64.7 dB at a low density of ∼38.2 mg/cm3. The corresponding specific SE value achieves 1694-3124 dB·cm3/g, and the SSE/d is up to 15,620 dB·cm2/g, surpassing that of most reported EMI shielding materials. Importantly, this aerogel, with excellent electromagnetic radiation protection effects and shielding reliability, is highly promising for long-term and effective EMI shielding service in various application environments.

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7 Citations


Journal ArticleDOI: 10.1016/J.COMPOSITESB.2021.109114
Chenghao Wang1, Lishuai Zong1, Yunxing Pan1, Nan Li1  +3 moreInstitutions (1)
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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Topics: Nanofiber (53%), Reflection loss (52%), Microwave (52%) ... read more

5 Citations


Journal ArticleDOI: 10.1016/J.JMST.2021.03.048
Fengyuan Wang1, Ping Xu1, Ning Shi1, Liru Cui1  +5 moreInstitutions (1)
Abstract: Constructing three-dimensional (3D) foam-like structure in magnetic metal/carbon composites is regarded as a promising pathway to reinforce their electromagnetic (EM) functions. Herein, a nitrate-assisted polymer-bubbling strategy is reported for the synthesis of Co/carbon foams, which is simply accomplished by direct pyrolyzing the mixture of polyvinylpyrrolidone (PVP) and cobalt nitrate hexahydrate (Co(NO3)2∙6H2O). Co(NO3)2∙6H2O not only plays as the source of Co nanoparticles, but also accounts for the formation of 3D microstructure through releasing gas. By manipulating the weight ratio of Co(NO3)2∙6H2O to PVP, the chemical composition, microstructure, and EM properties of these composites can be easily regulated. When the weight ratio reaches 1.5, the resultant composite displays good microwave absorption performance, whose reflection loss intensity and effective absorption bandwidth are superior to those of many common Co/C composites. EM analysis reveals that such architecture is greatly helpful to establish cross-linked conductive networks in the wax matrix, resulting in powerful dielectric loss under low absorber loading. Meanwhile, 3D microstructure is also beneficial for multiple reflections that equal to extend the transmission path of incident EM waves. Simple synthesis strategy and desirable properties of these magnetic carbon foams may render them as the low-cost substitute of 3D graphene for the application against EM pollution.

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Topics: Microstructure (52%), Reflection loss (51%), Absorption (electromagnetic radiation) (50%) ... read more

4 Citations


References
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57 results found


Journal ArticleDOI: 10.1103/PHYSREVB.61.14095
Andrea C. Ferrari1, John Robertson1Institutions (1)
15 May 2000-Physical Review B
Abstract: The model and theoretical understanding of the Raman spectra in disordered and amorphous carbon are given. The nature of the G and D vibration modes in graphite is analyzed in terms of the resonant excitation of \ensuremath{\pi} states and the long-range polarizability of \ensuremath{\pi} bonding. Visible Raman data on disordered, amorphous, and diamondlike carbon are classified in a three-stage model to show the factors that control the position, intensity, and widths of the G and D peaks. It is shown that the visible Raman spectra depend formally on the configuration of the ${\mathrm{sp}}^{2}$ sites in ${\mathrm{sp}}^{2}$-bonded clusters. In cases where the ${\mathrm{sp}}^{2}$ clustering is controlled by the ${\mathrm{sp}}^{3}$ fraction, such as in as-deposited tetrahedral amorphous carbon (ta-C) or hydrogenated amorphous carbon (a-C:H) films, the visible Raman parameters can be used to derive the ${\mathrm{sp}}^{3}$ fraction.

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Topics: Amorphous carbon (52%), Raman spectroscopy (50%)

11,122 Citations


Journal ArticleDOI: 10.1103/PHYSREVB.20.392
Robert J. Nemanich1, Stuart A. Solin2Institutions (2)
15 Jul 1979-Physical Review B
Abstract: First- and second-order Raman scattering from graphite has been studied. The second-order spectra of single crystals and of highly oriented pyrolytic graphite are continuous and exhibit several well-defined bands which can be attributed to features in the density of vibrational states as determined from current lattice-dynamics models. The density of states deduced from the lattice-dynamics model of Nicklow, Wakabayashi, and Smith provides the best replication of the second-order Raman spectrum, but is nevertheless somewhat deficient in this regard, and in need of improvement. The dependence of the first- and second-order graphite Raman spectra on crystallite size has also been studied for a series of samples with typical dimensions ${L}_{c}$ and ${L}_{a}$ as small as 30 \AA{}. With decreasing crystal size the features in the second-order spectrum broaden noticeably and additional broad features appear in both the first- and second-order spectra. The additional first- and second-order features are also attributed to structure in the vibrational density of states and arise from the wave-vector selection-rule relaxation that results from finite-crystal-size effects. Evidence is presented to demonstrate that the above described spectral features are intrinsic and not associated with impurity excitations.

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Topics: Highly oriented pyrolytic graphite (58%), Raman spectroscopy (56%), Raman scattering (55%) ... read more

1,795 Citations


Journal ArticleDOI: 10.1002/ADMA.200306460
Renchao Che1, Lian-Mao Peng, Xiaofeng Duan2, Qing Chen1  +1 moreInstitutions (2)
05 Mar 2004-Advanced Materials
Abstract: CNT/crystalline Fe nanocomposites (see Figure) have excellent microwave-absorption characteristics. This absorption property is shown to result from the confinement of crystalline Fe in carbon nanoshells, deriving mainly from magnetic rather than electric effects-the complex permittivity and permeability depend both on the shape and phase of the CNT/Fe nanocapsulates.

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Topics: Permittivity (58%), Carbon nanotube (53%)

1,428 Citations


Journal ArticleDOI: 10.1002/ADMA.201503149
Qinghe Liu1, Qi Cao1, Han Bi1, Chongyun Liang1  +4 moreInstitutions (2)
01 Jan 2016-Advanced Materials
Abstract: The synthesis of CoNi@SiO2 @TiO2 core-shell and CoNi@Air@TiO2 yolk-shell microspheres is reported for the first time. Owing to the magnetic-dielectric synergistic effect, the obtained CoNi@SiO2 @TiO2 microspheres exhibit outstanding microwave absorption performance with a maximum reflection loss of -58.2 dB and wide bandwidth of 8.1 GHz (8.0-16.1 GHz, < -10 dB).

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Topics: Reflection loss (51%)

907 Citations


Journal ArticleDOI: 10.1021/CM103441U
Genban Sun1, Bingxiang Dong1, Minhua Cao2, Bingqing Wei3  +1 moreInstitutions (3)
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.

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Topics: Magnetic anisotropy (58%), Magnetization (57%), Microwave (54%) ... read more

735 Citations