Directional Electromagnetic Interference Shielding Based on Step-Wise Asymmetric Conductive Networks

Abstract

Some precision electronics such as signal transmitters need to not only emit effective signal but also be protected from the external electromagnetic (EM) waves. Thus, directional electromagnetic interference (EMI) shielding materials (i.e., when the EM wave is incident from different sides of the sample, the EMI shielding effectiveness (SE) is rather different) are strongly required; unfortunately, no comprehensive literature report is available on this research field. Herein, Ni-coated melamine foams (Ni@MF) were obtained by a facile electroless plating process, and multiwalled carbon nanotube (CNT) papers were prepared via a simple vacuum-assisted self-assembly approach. Then, step-wise asymmetric poly(butylene adipate-co-terephthalate) (PBAT) composites consisting of loose Ni@MF layer and compact CNT layer were successfully fabricated via a facile solution encapsulation approach. The step-wise asymmetric structures and electrical conductivity endow the Ni@MF/CNT/PBAT composites with unprecedented directional EMI shielding performances. When the EM wave is incident from Ni@MF layer or CNT layer, Ni@MF-5/CNT-75/PBAT exhibits the total EMI SE (SET) of 38.3 and 29.5 dB, respectively, which illustrates the ΔSET of 8.8 dB. This work opens a new research window for directional EMI shielding composites with step-wise asymmetric structures, which has promising applications in portable electronics and next-generation communication technologies.

Interconnected MXene/Graphene Network Constructed by Soft Template for Multi-Performance Improvement of Polymer Composites

“…Table 1 compares the MGPP100-3 composite with other polymeric composites reported in the literature [ 20 , 36 , 41 – 52 ]. Conductive metallic materials were initially widely used for electromagnetic protection, but their poor corrosion resistance and inflexibility limit their applications.…”

“…A PNA-N5244A vector network analyzer from Agilent (Cary, NC) was employed to receive the EMI SE over the X band. From the scattering coefficients S 11 and S 21 , reflection parameter ( R ), transmission parameter ( T ), absorption parameter ( A ), total EMI SE ( SE T ), reflection loss ( SE R ), absorption loss ( SE A ), and multiple internal reflection loss ( SE M ) of electromagnetic waves can be obtained by the following formula [ 20 , 24 , 31 ]: …”

“…Long-range continuous electrical [ 10 – 12 ] and thermal network [ 13 – 15 ] is an essential structural feature for the formation of multifunctional polymer composites with high performance. The 3D soft templates represented by polyurethane (PU) sponge [ 11 , 16 – 19 ], melamine foam [ 10 , 20 – 22 ], and polyimide foam [ 23 , 24 ], combined with functional fillers, can easily obtain the continuous interconnected structure. Compared with the aerogel formed by the hydrogen bonding interaction [ 25 , 26 ], the network is more supportive in the polymer matrix [ 16 , 27 ].…”

“…After covering with MXene suspension of 4 mg mL −1 for 4 dip-coating cycles, the MXene@MS composite sponge exhibited excellent electromagnetic interference (EMI) shielding effectiveness (SE) of 53.16 dB. Xue et al [ 20 ] fabricated Ni@MF/CNT/PBAT composites with a stepped asymmetric structure by a simple solution encapsulation method. The composites exhibited directional electromagnetic shielding efficiency.…”

Graphene Oxide Nanosheets and Ni Nanoparticles Coated on Glass Fabrics Modified with Bovine Serum Albumin for Electromagnetic Shielding

“…The characteristic diffraction peak for RGO at around 2θ = 26° in XRD patterns of BGGs, RNGs, and BRNGs is invisible, resulting from the overlap with the diffraction peaks of GFs and the low amount of RGO nanosheets . The obvious characteristic diffraction peak for Ni-GFs, BNGs, RNGs, and BRNGs at 44.5° corresponds to the (111) plane of face-centered cubic phase Ni, indicating that relatively well crystallized FCC Ni nanoparticles are formed on the fabrics after the plating of Ni …”