Modeling for the electromagnetic properties and EMI shielding of Cf/mullite composites in the gigahertz range

Xia, Xiaodong; Yang, Li; Long, Lan; Luo, Hang; Pang, Ling; Xiao, Xiazi; Zhou, Wei

doi:10.1016/j.jeurceramsoc.2020.03.031

Cited by 20 publications

(3 citation statements)

References 40 publications

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“…The effect of EMI shielding in the nanocomposite can be classified by the reflection loss ( R ), absorption loss ( A ), and multiple-reflection loss ( M ) of electromagnetic waves. Therefore, the EMI shielding effectiveness of the overall nanocomposite, SE , is calculated with the consideration of wave impedance in the near field based on the solutions to Maxwell’s equations [33]…”

Section: The Two-scale Homogenization Scheme Of Progressively Agglomerated Cnt/polymer Nanocomposites Under the Perfect Interface Conditimentioning

confidence: 99%

Dual percolations of electrical conductivity and electromagnetic interference shielding in progressively agglomerated CNT/polymer nanocomposites

Xia

Weng

2021

Mathematics and Mechanics of Solids

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Recent experiments have revealed two distinct percolation phenomena in carbon nanotube (CNT)/polymer nanocomposites: one is associated with the electrical conductivity and the other is with the electromagnetic interference (EMI) shielding. At present, however, no theories seem to exist that can simultaneously predict their percolation thresholds and the associated conductivity and EMI curves. In this work, we present an effective-medium theory with electrical and magnetic interface effects to calculate the overall conductivity of a generally agglomerated nanocomposite and invoke a solution to Maxwell’s equations to calculate the EMI shielding effectiveness. In this process, two complex quantities, the complex electrical conductivity and complex magnetic permeability, are adopted as the homogenization parameters, and a two-scale model with CNT-rich and CNT-poor regions is utilized to depict the progressive formation of CNT agglomeration. We demonstrated that there is indeed a clear existence of two separate percolative behaviors and showed that, consistent with the experimental data of poly-L-lactic acid (PLLA)/multi-walled carbon nanotube (MWCNT) nanocomposites, the electrical percolation threshold is lower than the EMI shielding percolation threshold. The predicted conductivity and EMI shielding curves are also in close agreement with experimental data. We further disclosed that the percolative behavior of EMI shielding in the overall CNT/polymer nanocomposite can be illustrated by the establishment of connective filler networks in the CNT-poor region. It is believed that the present research can provide directions for the design of CNT/polymer nanocomposites in the EMI shielding components.

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Section: The Two-scale Homogenization Scheme Of Progressively Agglomerated Cnt/polymer Nanocomposites Under the Perfect Interface Conditimentioning

confidence: 99%

Dual percolations of electrical conductivity and electromagnetic interference shielding in progressively agglomerated CNT/polymer nanocomposites

Xia

Weng

2021

Mathematics and Mechanics of Solids

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“…[20]. Many polymer-based composites [21,22] have been recently developed to obtain materials and understand their EMI shielding behavior [23,24].…”

Section: Introductionmentioning

confidence: 99%

Epoxy Coatings Containing Modified Graphene for Electromagnetic Shielding

et al. 2022

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This study presents the functionalization and characterization of graphene and electromagnetic interference (EMI) attenuation capacity in epoxy-nanocomposites. The modification of graphene involved both small molecules and polymers for compatibilization with epoxy resin components to provide EMI shielding. The TGA and RAMAN analyses confirmed the synthesis of graphene with a different layer thickness of the graphene sheets. Graphene samples with different layer thicknesses (monolayer, few layers, and multilayer) were selected and further employed for epoxy coating formulation. The obtained nanocomposites were characterized in terms of EMI shielding effectiveness, SEM, micro-CT, magnetic properties, and stress-strain resistance. The EMI shielding effectiveness results indicated that the unmodified graphene and hexamethylene diamine (HMDA) modified graphene displayed the best EMI shielding properties at 11 GHz. However, the epoxy nanocomposites based on HMDA modified graphene displayed better flexibility with an identical EMI shielding effectiveness compared to the unmodified graphene despite the formation of aggregates. The improved flexibility of the epoxy nanocomposites and EMI shielding characteristics of HMDA functionalized graphene offers a practical solution for textile coatings with microwave absorbing (MA) capacity.

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“…[1][2][3] Typical examples include electromagnetic interference shielding component, 4,5 energy storage equipment, 6,7 microwave absorption device, 8 etc. Generally, ordinary composites can be classified into the polymer-based, 9,10 metal-based, 11 and ceramic-based composites 12,13 according to the matrix material. Polymerbased and metal-based composites are easily damaged in the complex high-temperature environment, for example, rocket engines in the aerospace.…”

Section: Introductionmentioning

confidence: 99%

Multi‐scale modeling for frequency‐dependent dielectric responses of non‐uniform porous carbon fiber/mullite composites

Xia

Zhao

Long

et al. 2021

Int J Applied Ceramic Tech

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The frequency-dependent dielectric responses of non-uniformly dispersed porous carbon fiber/mullite composites fabricated by gel-casting are intensively investigated in the X-band range. Experimental data have shown the frequency dependence of dielectric permittivity and electrical conductivity of the overall composite. The dielectric responses of non-uniformly dispersed porous carbon fiber/mullite composites in X-band are quantitatively modeled through a multi-scale homogenization method based on the effective-medium approximation. The non-uniform dispersion of carbon fibers and micro-pores in the mullite ceramic has been included via a corresponding multi-scale geometric setting. The effective dielectric permittivity and electrical conductivity of the composite both enhance with the fiber volume concentration. It is demonstrated that the decreasing dielectric permittivity and increasing electrical conductivity with respect to the AC frequency can be attributed to frequency-dependent dielectric relaxation and electron hopping effects at the interface. Furthermore, improving the uniform dispersion of carbon fibers in the mullite is essential to achieve the enhanced dielectric response of porous carbon fiber/mullite composites. The present paper can provide the directions to design the porous carbon fiber/mullite composites for micro-electronic devices in the high-temperature environment. K E Y W O R D Sdielectric response, multi-scale, non-uniform dispersion, porous carbon fiber/mullite composite, X-band How to cite this article: Xia X, Zhao S, Long L, Li Y, Zhou W. Multi-scale modeling for frequency-dependent dielectric responses of non-uniform porous carbon fiber/ mullite composites.

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Modeling for the electromagnetic properties and EMI shielding of Cf/mullite composites in the gigahertz range

Cited by 20 publications

References 40 publications

Dual percolations of electrical conductivity and electromagnetic interference shielding in progressively agglomerated CNT/polymer nanocomposites

Dual percolations of electrical conductivity and electromagnetic interference shielding in progressively agglomerated CNT/polymer nanocomposites

Epoxy Coatings Containing Modified Graphene for Electromagnetic Shielding

Multi‐scale modeling for frequency‐dependent dielectric responses of non‐uniform porous carbon fiber/mullite composites

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