Electromagnetic\nInterference Shielding Performance\nof Anisotropic Polyimide/Graphene Composite Aerogels

Abstract

Anisotropic\npolyimide (PI)/graphene composite aerogels were fabricated\nby unidirectional freezing. A poly­(amic acid) (PAA) ammonium salt/graphene\ndispersion was first synthesized by mixing together PAA, H₂O, triethylamine (TEA), and graphene and then was successively subjected\nto one-way freezing, freeze-drying, and thermal imidization. The one-way\ngrowth of ice crystals endowed the composite aerogels with highly\narranged tubular pores. The PI/graphene composite aerogels possessed\nanisotropic conductivity, electromagnetic interference (EMI) shielding,\nheat transfer, and compression performance. Moreover, the composite\naerogels with low density (0.076 g·cm^–3) exhibited\nhigh EMI shielding effectiveness (SE) of 26.1–28.8 dB, and\nits specific EMI SE value achieved 1373–1518 dB·cm²·g^–1 when the graphene content was\n13 wt %. The main electromagnetic interference shielding mechanism\nof these composite aerogels was microwave absorption. The composite\naerogels had excellent thermal stability, and their 5% weight loss\ntemperature was higher than 546 °C in nitrogen. This research\nprovided an easy and environmentally friendly approach to prepare\nlightweight and anisotropic PI-based composite aerogels.