ACS Applied Materials & Interfaces · 2020 · 320 citations · 39 references
Natural SciencesMaterials EngineeringMaterials SciencePolymer ChemistryPolymer EngineeringPolymer MaterialsComposite MaterialsGraphene NanomaterialsHigh-performance PolymersNanocompositesShielding MaterialsAerogelsAnisotropic ConductivityElectromagnetic InterferenceElectromagnetic ShieldingGraphene CompositesHeat Transfer MechanismsMicrowave AbsorptionThermal Stability
The study presents an easy, environmentally friendly method to fabricate lightweight, anisotropic PI/graphene composite aerogels. The aerogels were produced by unidirectional freezing of a PAA/graphene dispersion followed by freeze‑drying and thermal imidization, yielding a structure whose microwave absorption provides the primary EMI shielding mechanism. The resulting aerogels exhibit highly arranged tubular pores, anisotropic conductivity, and excellent EMI shielding (26.1–28.8 dB, specific SE 1373–1518 dB·cm²·g⁻¹ at 13 wt % graphene), along with high thermal stability (5 % weight loss > 546 °C).
Anisotropic polyimide (PI)/graphene composite aerogels were fabricated by unidirectional freezing. A poly(amic acid) (PAA) ammonium salt/graphene dispersion was first synthesized by mixing together PAA, H2O, triethylamine (TEA), and graphene and then was successively subjected to one-way freezing, freeze-drying, and thermal imidization. The one-way growth of ice crystals endowed the composite aerogels with highly arranged tubular pores. The PI/graphene composite aerogels possessed anisotropic conductivity, electromagnetic interference (EMI) shielding, heat transfer, and compression performance. Moreover, the composite aerogels with low density (0.076 g·cm-3) exhibited high EMI shielding effectiveness (SE) of 26.1-28.8 dB, and its specific EMI SE value achieved 1373-1518 dB·cm2·g-1 when the graphene content was 13 wt %. The main electromagnetic interference shielding mechanism of these composite aerogels was microwave absorption. The composite aerogels had excellent thermal stability, and their 5% weight loss temperature was higher than 546 °C in nitrogen. This research provided an easy and environmentally friendly approach to prepare lightweight and anisotropic PI-based composite aerogels.
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