Graphene aerogel films with expansion enhancement effect of high-performance electromagnetic interference shielding Jiabin Xi a, 1 , Youliang Li a, c, 1 , Erzhen Zhou a, b, 1 , Yingjun Liu a , Weiwei Gao a , Yan Guo a , Ji Ying b, *** , Zichen Chen b, ** , Guogui Chen c , Chao Gao a, * a MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027, PR China b Department of Mechanical Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027, PR China c Zhejiang WeiXing New Building Materials CO. LTD., Economic Development Zone of Linhai, BaiYe road, Zhejiang Province, PR China article info Article history: Received 8 March 2018 Received in revised form 4 April 2018 Accepted 16 April 2018 Available online 17 April 2018 abstract Lightweight and flexible materials with high electromagnetic interference (EMI) shielding performance are highly desirable in numerous occasions to prevent interference between electronic devices. Here, we designed graphene aerogel films (GAF) with multilayer structure, which showed low density (0.02 g cm 3 ), high flexibility and excellent shielding effectiveness (SE). SE reaches ~135dB in 0.1 e3 GHz at thickness of 1.4 mm, and shows an uptrend from 65 to 105 dB in 2e18 GHz at thickness of 120 mm. In depth study reveal the excellent shielding performance is attributed to expansion enhance- ment effect, that shielding effectiveness can be significantly improved by expansion in an individual identical substance. The design of GAFs and the discovery of EEE open the avenue to lightweight ma- terials with high EMI shielding performance. © 2018 Elsevier Ltd. All rights reserved. 1. Introduction Electromagnetic interference (EMI) shielding is the isolation of electromagnetic fields between two spatial regions, to control their harmful effects on communication systems, sensitive electronic equipment, and living organisms [1e4]. According to the electro- magnetic theory, the foremost mechanism of EMI shielding is reflecting the radiation by impedance mismatching and attenu- ating the wave energy by dielectric or magnetic loss [5]. As a result, materials with higher electrical conductivity usually show a better shielding performance, and metals, carbon [6,7], and conductive polymers have long been researched as EMI shielding materials [8]. However, except for designing materials with high electrical con- ductivity and high permeability, there is no effective way to further improve the shielding effectiveness (SE). As a result, integrating series of high performances into one shielding material is still a challenge. For example, highly conductive metals suffer from heavy weight and poor chemical instability. The lightweight and chemi- cally stable carbon and conductive polymer are not as good as metals considering the shielding performances. Therefore, the best way to solve the problem is enhancing the EMI shielding perfor- mance by structural design without damaging other merits including lightweight, flexibility, etc. Here, we designed graphene aerogel films (GAF) with multilayer structure by free expansion of graphene oxide (rGO) films. GAFs show low density (0.02 g cm 3 ), high flexibility and excellent shielding effectiveness (SE). SE reaches ~135dB in 0.1e3 GHz at thickness of 1.4mm, and shows an uptrend from 65 to 105 dB in 2e18 GHz at thickness of 120 mm. Considering the thickness- averaged specific shielding effectiveness (TASSE), GAFs reach the value of 100,000 dB cm 2 g 1 that is among the best in former re- ports. According to the theoretical analysis and experimental re- sults, the expanded multilayer structure is the key reason for the high EMI SE of GAFs. We propose an “expansion enhancement ef- fect (EEE)” that expanding the interlayer spacing in a multilayer structure can intensively enhance SE. The increment of SE (DSE) owning to EEE is further estimated by a modified Simon formula, which signifies the DSE is positively correlated to the expansion ratio, intrinsic electrical conductivity (electrical conductivity of the conductive units) and wave frequency in the multilayer structure. * Corresponding author. ** Corresponding author. *** Corresponding author. E-mail address: [email protected] (C. Gao). 1 The authors contributed equally to this paper. Contents lists available at ScienceDirect Carbon journal homepage: www.elsevier.com/locate/carbon https://doi.org/10.1016/j.carbon.2018.04.041 0008-6223/© 2018 Elsevier Ltd. All rights reserved. Carbon 135 (2018) 44e51
Graphene aerogel films with expansion enhancement effect of high-performance electromagnetic interference shielding
Jun 17, 2023
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