Light-weight epoxy/nickel coated carbon fibers conductive foams for electromagnetic interference shielding

Yang, Jianming; Yang, Yaqi; Duan, Hongji; Zhao, Guizhe; Liu, Yaqing

doi:10.1007/s10854-016-6266-7

Cited by 29 publications

(13 citation statements)

References 26 publications

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“…Otherwise, multi-reflections and backscattering occur in a porous matrix, between the air/matrix [9,44]; these losses are negligible compared to the measured losses of our composites. Multi-reflections occur also between the matrix and the fibers [35] and the attenuation of the waves (by trapping) in fiber agglomerates is expected [45].…”

Section: Effect Of Carbon Fiber Lengths On Dielectric Properties Of Cf-loaded Compositesmentioning

confidence: 62%

Long Carbon Fibers for Microwave Absorption: Effect of Fiber Length on Absorption Frequency Band

et al. 2020

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This work presents lightweight epoxy foams loaded with very low weight percentages (≤0.5 wt.%) of carbon fibers (CFs) with different lengths (3 mm, 6 mm, and 12 mm) as broadband microwave absorbing materials for anechoic chamber application. The effect of CF length on microwave absorption, especially on the absorption frequency band, is investigated for frequencies between 1 and 15 GHz. For the elaboration of composites, three different methods—spatula, shear mixing, and ultrasounds—are used for the dispersion of CFs. The observation of these CFs, after the dispersion step, shows a high fiber breakage rate when shear mixing is used, unlike when spatula or ultrasounds methods are used. On the other hand, the characterization of the elaborated composites highlights a correlation between the mixing methods, hence the fiber brakeage, and the measured reflection coefficient (reflection loss) of the composites. As a result, the minimum value of the reflection coefficient is shifted toward the high frequencies when the fiber breakage is observed, suggesting that short CFs absorb at high frequencies while long CFs absorb at low frequencies. Dielectric properties, extracted from the measurement in free space, of composites elaborated with different fiber lengths (3 mm, 6 mm, and 12 mm) confirm that short CFs (3 mm) show maximum losses at high frequencies (around 15 GHz) while long CFs (12 mm) show maximum dielectric losses at low frequencies (below 4 GHz). However, no significant variation is observed on the real part of the relative permittivity, as a function of fiber length, for these porous composites loaded with very low CF rates. A hybrid composite, with a mix of different CF lengths, is prepared and characterized. The simulation of the absorption performance of a pyramidal absorber, based on this hybrid composite, is compared to the one of pyramidal absorber based on composites loaded with a single length of carbon fibers. The pyramidal absorber-based hybrid composite predicts the best absorption performance, especially at the low frequency band. The simulated reflection coefficient of this absorber is less than −12 dB in all the studied frequency range, and less than −40 dB for frequencies higher than 3 GHz. This result confirms the interest of using a mix of carbon fiber lengths to achieve a broadband microwave absorber.

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Section: Effect Of Carbon Fiber Lengths On Dielectric Properties Of Cf-loaded Compositesmentioning

confidence: 62%

Long Carbon Fibers for Microwave Absorption: Effect of Fiber Length on Absorption Frequency Band

et al. 2020

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“…The microstructures of the composites obtained using the chemical foaming method are shown in Figure 8b. [90] Yang et al [91] added nickel-plated carbon fibers (NCCFs) as conductive fillers to EP, and EP/NCCF conductive foam was prepared via chemical foaming. The foam structure improved the efficiency of the conductive path; when the filler content was 5.03 vol%, the conductivity was as high as 21.27 S m −1 , and the specific electromagnetic shielding was 77 dB cm 3 g -1 .…”

Section: Foam Structurementioning

confidence: 99%

Review on Shielding Mechanism and Structural Design of Electromagnetic Interference Shielding Composites

Wang

Liu

et al. 2021

Macro Materials & Eng

134

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Conductive polymer composites (CPCs) for electromagnetic interference shielding have received significant attention and shown rapid development. According to the electromagnetic wave interface conduction theory of Schelkunoff, excellent conductive performance and perfect conductive network structure are prerequisites for high shielding efficiency of electromagnetic interference shielding composites. Effective multiple interface reflection absorption, dielectric loss, and hysteresis loss characteristics of the materials are crucial for realizing the regulation of the electromagnetic interference shielding performance of CPCs. Therefore, the structural design of conductive and magnetic network for CPCs is crucial for achieving high shielding performance. In this study, it is established that an electromagnetic shielding composite with a uniform structure is widely used because of its simple preparation process, but its inefficient conductive network causes a high percolation threshold. The inefficiency can be solved by designing a composite structure and improving the efficiency of the conductive network. Currently, common structural designs include segregated structural, layered structural, and foam structural designs. These structural designs effectively solve the problem of high percolation threshold of CPCs and coordinate the contradiction between the performance of electromagnetic interference shielding and other advantages.

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“…As one of the lightweight materials, epoxy foams have attracted considerable attention because of their broad range of applications in the automotive, electronic, aerospace, and marine industries . Epoxy foams can be easily fabricated by foaming epoxy compounds with a chemical foaming agent (CFA) at the decomposition temperature of the CFA and then further curing under a high postcuring temperature .…”

Section: Dsc Thermogram Data Of Lim‐foam and Fre‐foam Postcured At DImentioning

confidence: 99%

Preparation of Microcellular Epoxy Foams through a Limited‐Foaming Process: A Contradiction with the Time–Temperature–Transformation Cure Diagram

Wang¹,

Zhang²,

Gong³

et al. 2017

Advanced Materials

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3D cross-linking networks are generated through chemical reactions between thermosetting epoxy resin and hardener during curing. The curing degree of epoxy material can be increased by increasing curing temperature and/or time. The epoxy material must then be fully cured through a postcuring process to optimize its material characteristics. Here, a limited-foaming method is introduced for the preparation of microcellular epoxy foams (Lim-foams) with improved cell morphology, high thermal expansion coefficient, and good compressive properties. Lim-foams exhibit a lower glass transition temperature (T ) and curing degree than epoxy foams fabricated through free-foaming process (Fre-foams). Surprisingly, however, the T of Lim-foams is unaffected by postcuring temperature and time. This phenomenon, which is related to high gas pressure in the bubbles, contradicts that indicated by the time-temperature-transformation cure diagram. High bubble pressure promotes the movement of molecular chains under heating at low temperature and simultaneously suppresses the etherification cross-linking reaction during post-curing.

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Light-weight epoxy/nickel coated carbon fibers conductive foams for electromagnetic interference shielding

Cited by 29 publications

References 26 publications

Long Carbon Fibers for Microwave Absorption: Effect of Fiber Length on Absorption Frequency Band

Long Carbon Fibers for Microwave Absorption: Effect of Fiber Length on Absorption Frequency Band

Review on Shielding Mechanism and Structural Design of Electromagnetic Interference Shielding Composites

Preparation of Microcellular Epoxy Foams through a Limited‐Foaming Process: A Contradiction with the Time–Temperature–Transformation Cure Diagram

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