Rational design of core-shell Co@C microspheres for high-performance microwave absorption

Ding, Ding; Wang, Ying; Li, Xuandong; Qiang, Rong; Xu, Ping; Chu, Wei; Han, Xijiang; Du, Yunchen

doi:10.1016/j.carbon.2016.10.059

Cited by 680 publications

(243 citation statements)

References 74 publications

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“…Natural resonance can also be excluded due to nonmagnetism of Ag/SiO 2 composites. Therefore, the eddy current loss is the only source of magnetic loss, and the eddy current loss can be expressed by [36]…”

Section: Researchmentioning

confidence: 99%

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%

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

et al. 2019

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“…As inferred from XRD figure 1(g), crystalline Fe 3 O 4 is a contaminant in the obtained spinel Mn ferrite nanoparticles. As explained earlier, this contaminant was not eliminated from the final product as this may help in enhancing the saturation magnetization; one of the key requirements of shielding materials is high permeability which also leads to higher saturation magnetization …”

Section: Resultsmentioning

confidence: 99%

Rational Design of Multilayer Ultrathin Nano‐Architecture by Coupling of Soft Conducting Nanocomposite with Ferrites and Porous Structures for Screening Electromagnetic Radiation

et al. 2017

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Fabrication of multilayered thin polymer films by rational arrangement of tailor‐made nanocomposites was designed to absorb electromagnetic (EM) radiation. Mn (manganese) ferrite nanoparticles were incorporated in polyvinylidene fluoride (PVDF) matrix, along with conductive MWCNTs, treated as outer layers of the multilayer assembly. The higher permittivity, permeability and attenuation constant ensure the higher absorption ability of these resulting outer layers. Selectively etching of one of the phases of the inner layers, which consist of immiscible blends of polycarbonate (PC) and PVDF with conductive MWCNTs, porous structure can be designed to maximize the penetration of incoming EM radiation from outer layers. Further scattering of the penetrated EM wave between the interfacial walls of conducting nano fillers inside the porous matrix enhance the shielding efficiency. The resulting ultrathin (0.60 mm) multilayered architecture was able to block >99.999 % (ca. −50dB) of the incoming EM radiation. This new‐age EM radiation absorbing material, powered by multi‐functionality henceforth, offers amendable, cost‐effective replacement to the existing solutions.

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“…According to quarter-wavelength theory, with the thickness increasing, the maximum absorption peaks shift towards a lower frequency. Tuning the thickness from 1 to 5 mm, the range of effective absorption bandwidth of Co@NC@RGO-1 and Co@NC@RGO-2 could reach up to as wide as 13.9 GHz (from 4.1 to 18 GHz), while the Co@NC@RGO-3 could cover 14.3 GHz (from 3.7 to 18 GHz), covering 89.4% of the whole microwave band (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) (Figure 6a-c). Figure 6d gives the effective bandwidth of more than 3 GHz with optimized respective thickness (from 2.0 to 3.0 nm).…”

Section: Full Papermentioning

confidence: 99%

“…In fact, many researchers have proved that the absorbents with single composition and structure were unable to meet the application demand. Recently, dielectric and magnetic nanohybrids, such as, Co/C composites, [4][5][6][7][8] Fe 3 O 4 / C coreÀ shell nanosheets, [9][10] CoÀ C/MWCNTs composites, [11] RGO-MnFe 2 O 4 nanocomposites [12] and NiO/RGO [13] have been applied in electromagnetic wave loss field.…”

Section: Introductionmentioning

confidence: 99%

High‐Performance Microwave Absorption of MOF‐Derived Core‐Shell Co@N‐doped Carbon Anchored on Reduced Graphene Oxide

Liu

Wang

et al. 2019

ChemNanoMat

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Nanocomposites of MOF-derived N-doped-carbonwrapped cobalt anchored on reduced graphene oxide (Co@NC@RGO) have been successfully fabricated for use as microwave absorption materials. A unique core-shell nanostructure with cobalt nanoparticles as core and N-doped graphitized carbon as shell was grown on the surface of laminated reduced graphene oxide (RGO). An enhanced synergistic effect between magnetic and dielectric components can be readily achieved by changing the dispersion of Co@NC nanoparticles on RGO. The as-synthesized microspheres are composed of numerous nanoscale core-shell Co@NC units, which combined magnetic Co cores with intrinsically contributing magnetic loss and N-doped graphitized carbon providing a pathway for electron transfer as well as transition between magnetic Co cores and high electrical conductivity of RGO. The resulting Co@NC@RGO composites exhibit excellent reflection loss (RL) values and effective absorption bandwidths. The optimized Co@NC@RGO-3 minimum RL (RLmin) value could reach À 46.5 dB at 9.4 GHz with a thickness of 3.5 mm. Tuning the thickness from 1.5-5 mm, the effectivity absorption frequency range could achieve up to 14.3 GHz (from 3.7 to 18 GHz). The excellent microwave absorption performance may be attributed to the magnetic loss, dielectric loss and interfacial polarization.[a] L.

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Rational design of core-shell Co@C microspheres for high-performance microwave absorption

Cited by 680 publications

References 74 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

Rational Design of Multilayer Ultrathin Nano‐Architecture by Coupling of Soft Conducting Nanocomposite with Ferrites and Porous Structures for Screening Electromagnetic Radiation

High‐Performance Microwave Absorption of MOF‐Derived Core‐Shell Co@N‐doped Carbon Anchored on Reduced Graphene Oxide

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