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
TL;DR: In this paper, a 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.
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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TL;DR: In this paper , the advances in low-dimensional core-shell EM wave absorption materials are outlined and a selection of the most remarkable examples is discussed, and the derived key information regarding dimensional design, structural engineering, performance, and structure-function relationship are comprehensively summarized.
Abstract: Electromagnetic (EM) wave absorption materials possess exceptionally high EM energy loss efficiency. With vigorous developments in nanotechnology, such materials have exhibited numerous advanced EM functions, including radiation prevention and antiradar stealth. To achieve improved EM performance and multifunctionality, the elaborate control of microstructures has become an attractive research direction. By designing them as core-shell structures with different dimensions, the combined effects, such as interfacial polarization, conduction networks, magnetic coupling, and magnetic-dielectric synergy, can significantly enhance the EM wave absorption performance. Herein, the advances in low-dimensional core-shell EM wave absorption materials are outlined and a selection of the most remarkable examples is discussed. The derived key information regarding dimensional design, structural engineering, performance, and structure-function relationship are comprehensively summarized. Moreover, the investigation of the cutting-edge mechanisms is given particular attention. Additional applications, such as oxidation resistance and self-cleaning functions, are also introduced. Finally, insight into what may be expected from this rapidly expanding field and future challenges are presented.
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TL;DR: This review summarizes progresses and highlights strategies of MOF derivatives for efficient electromagnetic wave absorption, and summarizes the relevant theories and evaluation methods, and categorized the state-of-the-art research progresses in EMW absorption field.
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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TL;DR: In this paper, the absorption properties of CNT/crystalline Fe nanocomposites have been investigated and it was shown that the absorption property is due to the confinement of crystalline Fe in carbon nanoshells, deriving mainly from magnetic rather than electric effects.
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TL;DR: 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.
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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