Significantly improved dielectric performances of sandwich-structured polymer composites induced by alternating positive-k and negative-k layers

Shi, Zhicheng; Wang, Jing; Mao, Fan; Yang, Chaoqiang; Zhang, Chao; Fan, Runhua

doi:10.1039/c7ta03403b

Cited by 124 publications

(48 citation statements)

References 58 publications

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“…As shown in the schematic diagram in Figure 5(b), the interstices among the SiO 2 microspheres are filled with silver, and the current loops can be induced around the SiO 2 microspheres when the composites are put under an alternating current magnetic field. The direction of the induced magnetic field from these current loops is opposite to the external magnetic Research 7 field, which would cancel part of external magnetic field and thus leads to negative susceptibility [5]. When the induced magnetic field is even dominant, negative permeability will be achieved [7,31].…”

Section: Researchmentioning

confidence: 99%

“…Metamaterials, with unique negative electromagnetic parameters (e.g., negative refraction, permeability and permittivity), have gained extensive research attention due to their original applications in cloaking, waveguide, wireless power transfer, electromagnetic shielding and high-permittivity capacitor, etc. [1][2][3][4][5]. Metamaterials typically consist of artificially periodic array structure with different geometrical configuration (split-ring resonators, wires, fishnet, or cut-wire pairs) [1].…”

Section: Introductionmentioning

confidence: 99%

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Targeted Double Negative Properties in Silver/Silica Random Metamaterials by Precise Control of Microstructures

et al. 2019

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Creative Commons Attribution License (CC BY 4.0).The mechanism of negative permittivity/permeability is still unclear in the random metamaterials, where the precise control of microstructure and electromagnetic properties is also a challenge due to its random characteristic. Here silver was introduced into porous SiO 2 microsphere matrix by a self-assemble and template method to construct the random metamaterials. The distribution of silver was restricted among the interstices of SiO 2 microspheres, which lead to the precise regulation of electrical percolation (from hoping to Drude-type conductivity) with increasing silver content. Negative permittivity came from the plasma-like behavior of silver network, and its value and frequency dispersion were further adjusted by Lorentz-type dielectric response. During this process, the frequency of epsilon-near-zero (ENZ) could be adjusted accordingly. Negative permeability was well explained by the magnetic response of eddy current in silver micronetwork. The calculation results indicated that negative permeability has a linear relation with 0.5 , showing a relaxation-type spectrum, different from the "magnetic plasma" of periodic metamaterials. Electromagnetic simulations demonstrated that negative permittivity materials and ENZ materials, with the advantage of enhanced absorption (40dB) and intelligent frequency selection even in a thin thickness (0.1 mm), could have potentials for electromagnetic attenuation and shielding. This work provides a clear physical image for the theoretical explanation of negative permittivity and negative permeability in random metamaterials, as well as a novel strategy to precisely control the microstructure of random metamaterials.

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Section: Researchmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Targeted Double Negative Properties in Silver/Silica Random Metamaterials by Precise Control of Microstructures

et al. 2019

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“…However, the dielectric permittivities of polymer dielectrics are usually very low (below 10 @1 kHz), which greatly hindered their wide applications. Toward this end, two strategies have been developed to improve the dielectric constants of polymer composites: (1) ceramic-polymer composites composed of high-k ceramic fillers (e.g., BaTiO 3 [23][24][25][26][27], TiO 2 [28,29], SrTiO 3 [30]) dispersed in polymer matrix and (2) conductor-polymer composites consisting of conductors (e.g., metals, [31,32], graphite [33,34], carbon nanotube [35][36][37], graphene [38,39], carbon black [40], and conductive polymer [41,42]) dispersed in polymer matrix. For ceramic-polymer composites, the enhancement of permittivity is limited (below 50 @10 kHz) even when the ceramic loading excesses 50 vol%, leading to deteriorated mechanical properties, high loss, and low breakdown strength [43].…”

Section: Introductionmentioning

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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“…It is interesting that the magnitude of negative ε′ in the composites is less than that of metal/ceramic composites, which should be attributed to the low free carrier density and the two‐dimension structure of GR. The composites with small negative values of ε′ can used for constructing bilayer or multilayer composites with high permittivity and low loss, which can well be applied in energy‐storage capacitors . The small |ɛ′| also benefit their applications in the microwave absorbers and antenna .…”

Section: Resultsmentioning

confidence: 99%

Radio‐frequency negative permittivity in the graphene/silicon nitride composites prepared by spark plasma sintering

et al. 2017

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Graphene/silicon nitride (GR/Si 3 N 4 ) ceramic composites with uniformly dispersed GR sheets were prepared using spark plasma sintering. The effects of GR content on the microstructure and electrical properties of the composites were investigated in detail. With the GR content rising, the conductive GR network was formed in the composites, leading to the appearance of a percolation phenomenon, and the conductive mechanism also changed from hopping conductivity to metal-like conductivity. When the GR content reached the percolation threshold, the composites showed a negative permittivity behavior, which resulted from the low frequency plasmonic state generated by the formative conducting GR networks. The increasing GR content resulted in a higher plasma frequency and larger magnitude of negative permittivity, which was consistent with the analysis of Drude model. A relatively high dielectric loss was observed in the composites and mainly induced by the high leakage current among GR sheets. Our work is beneficial to expound the regulation mechanism of negative permittivity, and the obtained ceramic composites present some potential applications in microwave absorption, shielding and capacitors. K E Y W O R D Sdielectric materials/properties, percolation, silicon nitride, spark plasma sintering

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Significantly improved dielectric performances of sandwich-structured polymer composites induced by alternating positive-k and negative-k layers

Abstract: A significantly enhanced dielectric constant and suppressed loss were simultaneously achieved in sandwich-structured composites consisting of alternating positive-k and negative-k layers.

Cited by 124 publications

References 58 publications

Targeted Double Negative Properties in Silver/Silica Random Metamaterials by Precise Control of Microstructures

Targeted Double Negative Properties in Silver/Silica Random Metamaterials by Precise Control of Microstructures

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

Radio‐frequency negative permittivity in the graphene/silicon nitride composites prepared by spark plasma sintering

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