Ultralightweight Silver Nanowires Hybrid Polyimide Composite Foams for High-Performance Electromagnetic Interference Shielding

Abstract

Ultralightweight silver nanowires (AgNWs) hybrid polyimide (PI) composite foams with microcellular structure and low density of 0.014-0.022 g/cm(3) have been fabricated by a facile and effective one-pot liquid foaming process. The tension flow generated during the cell growth induced the uniform dispersion of AgNWs throughout the cell walls. The interconnected AgNWs network in the cell walls combined with the large 3D AgNWs network caused by 3D structure of foams provided fast electron transport channels inside foams. The electromagnetic interference (EMI) shielding effectiveness (SE) of these foams increased with increasing AgNWs loading as well as the nanowire aspect ratio due to the increasing connections of the conduction AgNWs network. Appropriate surface treatment like etching or spraying facilitated the construction of the seamlessly interconnected 2D AgNWs network on the surface, which could effectively reflect electromagnetic waves. Maximum specific EMI SE of values of 1210 dB·g(-1)·cm(3) at 200 MHz, 957 dB·g(-1)·cm(3) at 600 MHz, and 772 dB·g(-1)·cm(3) at 800-1500 MHz were achieved in sprayed composite foams containing <0.044 vol % AgNWs loading, which far surpasses the best values of other composite materials. The reflections of interconnected AgNWs networks on the surface and inside foams combined with the multiple reflections at interfaces contributed to the shielding effect.