Carbon Composite Networks with Ultrathin Skin Layers of Graphene Film for Exceptional Electromagnetic Interference Shielding

Abstract

Natural cotton was selected as a cheap and renewable carbon source to fabricate novel carbon networks with porous three-dimensional conductive frameworks composed of numerous unique hollow carbon fibers by pyrolysis, and outstanding electromagnetic interference (EMI) shielding effectiveness (SE) of ∼26.9–46.9 dB was observed for the samples (∼0.3 mm in thickness) with density of ∼0.14–0.06 g/cm3. Moreover, the combination of cotton-derived carbon networks with graphene through the construction of a sandwich configuration, where graphene sheets were dispersed inhomogeneously on both sides of carbon networks, was further developed and the resultant carbon composite networks with ultrathin skin layers of graphene film in thickness of only ∼2 μm possessed higher EMI SE of ∼48.5–87.0 dB than that (∼33.7–55.6 dB) of pure carbon networks in thickness of ∼0.3–0.7 mm, possibly due to the enhanced EM reflection and absorption of EM waves penetrating the material. The SE increment of ∼26–41% was also observed in the sandwiched samples in comparison with the counterparts with homogeneous graphene dispersion, demonstrating a very promising configuration for the significant SE enhancement.

High-Performance Carbonized Waste Corrugated Boards Reinforced with Epoxy Coating as Lightweight Structured Electromagnetic Shields

“…36,37,45,46 Moreover, the effect of different CCB type on ultimate shielding performance was also investigated (Figure 3B), and interestingly, the SE total decreased from ∼82.0 dB for 1500-A to ∼65.3 and ∼55.3 dB for 1500-B and 1500-E composites owing to the slight weakening of EM-reflection and strengthening of EM-absorption (R↓ and A↑, Figure 3C). It may be because that, though the first microwave-reflection at the input interface is similar on account of their similar electrical properties, the microwave penetrating the inner sawtooth with longer side (A > B > E-type) can be dissipated more effectively based on our previous study, 36 which may lead to less microwave to interact with the first-reflected microwaves by constructive interference between two parallel surfaces, 37,38,45 and thus, stronger total EM-reflection could be detected for the A-type CCB sample. The weaker EMabsorption can also be observed if the energy-dissipation caused by the inner sawtooth structure is weaker than that induced by constructive interference.…”

“…The 800-A composite had a SE total of ∼46.0 dB, and this value is improved to ∼60.7 dB for 1000-A composite and further to ∼82.0 dB for 1500-A composite, which is in accordance with the reported results of biomass-derived MCAs presenting a continuous increment with the elevated carbonization temperature by reason for the enhancement of electrical properties (the very similar results could be obtained for XXX-B and XXX-E composites in Figure S4 as well). 14,38 To the best knowledge, the EMI SE of ∼46.0−82.0 dB signified the effective attenuation of ∼99.997−99.9999993% incident microwaves, far surpassing the SE requirements for civilian applications and close to military standards. Their R-A coefficients of ∼0.701− 0.904 and ∼0.298−0.095 (Figure 3C) suggested that such prominent EMI-shielding capability should ascribe to the strong microwave-reflection originating from the large impedance mismatch at the interface, 23,44 as well as the weak microwave-absorption relating to the conduction loss together with the special construction capable of internal multiple reflections (scattering) and constructive interference (the constructive interference would happen when multiple reflections are aligned between two parallel carbon sheets in the CCB samples).…”

“…SEM observation clearly revealed that macroscopic construction of sawtooth pattern sandwiched between two parallel surfaces for the original corrugated boards could be well-maintained in the CCB (Figures 1C,D and S1) accompanying by the occurring of large volume shrinkage (VS) and weight loss (WL), and the inner closely stacked wood-fibers have been converted into more closely stacked carbon-fibers with decreased diameters (Figure 1G−I), benefiting the rapid transport of electrons. 38 The hopping or tunneling phenomena is mainly responsible for close packed electrical transportation here. The calculation showed that the elevated carbonization temperature from 800 to 1500 °C brought about a slightly increased VS and WL value of ∼39−43% and ∼72−76% (Figure 2A), and these data were very similar for different sample types.…”

Structure Engineering of Graphene Nanocages toward High‐Performance Microwave Absorption Applications

“…Actually, the fact that 3DIGC-750 presents the highest electrical conductivity (the average value is as high as ≈1265.8 S m −1 ) among 3DIGCs has been demonstrated by the experimental measurement, as shown in Figure 5c. This impressive conductivity is even much higher than those of most graphene electromagnetic shielding materials and graphene electrode materials, [56,57] which can undoubtably be ascribed to the elaborate interconnected scaffold of samples. An interesting phenomenon noticed is that 3DIGC-800 shows a relatively moderate electrical conductivity (average ≈833.3 S m −1 ), despite having the highest graphitization degree.…”

Strong breathable membrane with excellent self‐cleaning, wave‐transparent, and heat dissipation performances

“…For ceramic‐based heat dissipation materials, the complex processing technology and high processing temperature lead to their high cost. For metal‐based heat dissipation materials, they generally show poor chemical resistance 4,5 . Meanwhile, metal‐based components possess high electrical conductivity, which significantly attenuate electromagnetic waves and interfere with signals during the use of electronic equipment.…”