In-situ synthesis of hierarchically porous and polycrystalline carbon nanowires with excellent microwave absorption performance

Pan, Hongxing; Yin, Xiaowei; Xue, Jimei; Cheng, Laifei; Zhang, Litong

doi:10.1016/j.carbon.2016.05.045

Cited by 159 publications

(69 citation statements)

References 61 publications

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“…Generally, σ is constant for a certain material. Meanwhile, the value of μ is usually constant (μ ≈ 1) at high frequency due to the existence of Snoek's limit [64]. Theoretically, the skin depth will decrease with higher frequency, leading to the decrease of ac conductivity σ ac .…”

Section: Resultsmentioning

confidence: 99%

Improved dielectric permittivity and retained low loss in layer-structured films via controlling interfaces

Mao

Shi

Wang

et al. 2018

Adv Compos Hybrid Mater

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The search for high-performance dielectric materials has long been driven by the urgent needs for various modern electronics. However, enhanced permittivity is always accompanied by elevated loss, which seriously hinders the development and applications of dielectric materials. Herein, negative-k layers were introduced into layer-structured films, forming a new class of multilayer composites consisting of alternately stacked positive-k and negative-k layers. Compared with traditional multilayer composites without negative-k layers, the layered composites containing extra positive-k/negative-k interfaces exhibit superior ability in balancing the contradict parameters: permittivity and loss, yielding substantially enhanced permittivity without sacrificing the low loss. It is indicated that the permittivity was enhanced by the charge accumulations and reinforced polarizations on the interfaces between positive-k and negative-k layers. Meanwhile, the loss induced by the leakage current was suppressed by the blocked transport of carriers between adjacent layers. The trilayered 60-3.5-60 composite exhibits an enhanced dielectric constant (ε′ ≈ 33 @10 kHz) and retained low loss (tanδ ≈ 0.12 @10 kHz) compared with the single-layer BT/PVA composite containing 60 wt% BT fillers (ε′ ≈ 9.5 @10 kHz, tanδ ≈ 0.075 @10 kHz). This research offers an effective way to design and fabricate novel high-performance dielectric materials.

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Section: Resultsmentioning

confidence: 99%

Improved dielectric permittivity and retained low loss in layer-structured films via controlling interfaces

Mao

Shi

Wang

et al. 2018

Adv Compos Hybrid Mater

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“…Many EM wave absorption materials show good EM wave absorption ability because of destructive interference, which is based on the quarter wavelength cancellation model. When the EM wave absorption layer thickness equals a quarter of a wavelength, the interference of the reflected EM wave from the upper and lower surfaces occurs, corresponding to RL min . This can be expressed by the following equation:

n = \frac{4 d f \sqrt{|ε_{r}| |μ_{r}|}}{c} false(n = 1, 3, 5, \dots false)

where d is the sample thickness; f is the frequency; ε r and μ r are the complex permittivity and permeability, respectively; and c is the velocity of light in vacuum .…”

Section: Resultsmentioning

confidence: 99%

“…When the EM wave absorption layer thickness equals a quarter of a wavelength, the interference of the reflected EM wave from the upper and lower surfaces occurs, corresponding to RL min . 38 This can be expressed by the following equation:…”

Section: Dielectric and Em Wave Absorption Propertiesmentioning

confidence: 99%

Interface evolution of a C/ZnO absorption agent annealed at elevated temperature for tunable electromagnetic properties

Yin

et al. 2019

J Am Ceram Soc

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Excellent electromagnetic (EM) wave absorption agents that attenuate EM waves by mechanisms based on impedance matching, conductive loss and polarization loss instead of destructive interference are urgently needed but remain challenging. Here, an EM wave absorption agent with a tailorable heterogeneous interface is designed and prepared by the in situ growth of ZnO nanoparticles on the surface of mesoporous carbon hollow microspheres (PCHMs@ZnO) via hydrothermal synthesis followed by annealing. A controlled interface evolution associated with abundant heterogeneous interfaces plays a crucial role in optimized impedance matching and enhanced interfacial polarization loss. With this method, targeted EM wave absorption agents with an excellent absorption ability that is derived mainly from polarization loss and conductive loss rather than destructive interference are successfully obtained. When the PCHMs@ZnO annealed at 700°C were combined with paraffin, the effective absorption bandwidth of the resultant composites covers the whole X band, and the mean value of reflection loss (RL) reaches −12 dB, exceeding those of other reported ZnO‐based materials. When the thickness of the composites varies from 3.3 to 4.3 mm, the value of the RL is lower than −8 dB in the whole X band. This work provides a promising model for preparing high‐performance EM wave absorption agents.

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“…[1][2][3][4] Therefore, the researches on microwave absorbing materials have attracted considerable interests in recent years. [1][2][3][4] Therefore, the researches on microwave absorbing materials have attracted considerable interests in recent years.…”

Section: Introductionmentioning

confidence: 99%

“…Electromagnetic radiation has detrimental effects on device performance and the surrounding environment with the rapid development of electronic instruments and telecommunication technologies. [1][2][3][4] Therefore, the researches on microwave absorbing materials have attracted considerable interests in recent years. The most widely used high-temperature electromagnetic wave (EMW) absorbers are nanocarbon materials, [5][6][7] SiC grains or fibers 8,9 and SiCN-based ceramics, [10][11][12] which have low density, high environmental stability, and excellent electromagnetic wave attenuation characteristics.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and EMW absorption properties of CVI Si₃N₄–SiCN ceramics with BN interface annealed in N₂ atmosphere

Xue

Yin

et al. 2017

J Am Ceram Soc

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A kind of chemical vapor infiltration (CVI) Si3N4–BN–SiCN composite ceramic with excellent electromagnetic wave (EMW) absorbing properties is obtained by CVI BN interface and SiCN matrix on porous Si3N4 ceramics, and then annealed at high temperatures (1200°C‐1500°C) in N2 atmosphere. The crystallization behavior, EMW absorbing mechanism and mechanical properties of the composite ceramics have been investigated. Results showed CVI SiCN ceramics with BN interface were crystallized in the form of nanograins, and the crystallization temperature was lower. Moreover, both EMW absorbing properties and mechanical properties of CVI Si3N4–BN–SiCN composite ceramics firstly increased and then decreased with the increase in annealing temperature due to the influence of BN interface on the microstructure and phase composition of the composite ceramics. The minimum reflection coefficient (RC) and maximum effective absorption bandwidth (EAB) of the composite ceramics annealed at 1300°C were −47.05 dB at the thickness of 4.05 mm and 3.70 GHz at the thickness of 3.65 mm, respectively. The flexural strength and fracture toughness of the composite ceramics annealed at 1300°C were 94 MPa and 1.78 MPa/m1/2, respectively.

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In-situ synthesis of hierarchically porous and polycrystalline carbon nanowires with excellent microwave absorption performance

Cited by 159 publications

References 61 publications

Improved dielectric permittivity and retained low loss in layer-structured films via controlling interfaces

Improved dielectric permittivity and retained low loss in layer-structured films via controlling interfaces

Interface evolution of a C/ZnO absorption agent annealed at elevated temperature for tunable electromagnetic properties

Microstructure and EMW absorption properties of CVI Si₃N₄–SiCN ceramics with BN interface annealed in N₂ atmosphere

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In-situ synthesis of hierarchically porous and polycrystalline carbon nanowires with excellent microwave absorption performance

Cited by 159 publications

References 61 publications

Improved dielectric permittivity and retained low loss in layer-structured films via controlling interfaces

Improved dielectric permittivity and retained low loss in layer-structured films via controlling interfaces

Interface evolution of a C/ZnO absorption agent annealed at elevated temperature for tunable electromagnetic properties

Microstructure and EMW absorption properties of CVI Si3N4–SiCN ceramics with BN interface annealed in N2 atmosphere

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Microstructure and EMW absorption properties of CVI Si₃N₄–SiCN ceramics with BN interface annealed in N₂ atmosphere