Multifunctional electromagnetic interference (EMI) shielding materials would solve electromagnetic radiation and pollution problems from electronic devices. Herein, the directional freeze-drying technology is utilized to prepare the aramid nanofiber/polyvinyl alcohol aerogel with a directionally porous structure (D-ANF/PVA), and the Ti₃C₂T x dispersion is fully immersed into the D-ANF/PVA aerogel via ultrasonication and vacuum-assisted impregnation. Ti₃C₂T x /(ANF/PVA) EMI shielding composite films with directionally ordered structure (D-Ti₃C₂T x /(ANF/PVA)) are then prepared by freeze-drying and hot pressing. Constructing a directionally porous structure enables the highly conductive Ti₃C₂T x nanosheets to be wrapped on the directionally porous D-ANF/PVA framework in order arrangement and overlapped with each other. And the hot pressing process effectively reduces the layer spacing between the stacked wavy D-ANF/PVA, to form a large number of Ti₃C₂T x -Ti₃C₂T x continuous conductive paths, which significantly improves the conductivity of the D-Ti₃C₂T x /(ANF/PVA) EMI shielding composite film. When the amount of Ti₃C₂T x is 80 wt%, the EMI shielding effectiveness (EMI SE) and specific SE (SSE/t) of D-Ti₃C₂T x /(ANF/PVA) EMI shielding composite film achieve 70 dB and 13790 dB·cm²·g⁻¹ (thickness and density of 120 μm and 0.423 g·cm⁻³), far superior to random-structured Ti₃C₂T x /(ANF/PVA) (R-Ti₃C₂T x /(ANF/PVA)) composite film (46 dB and 9062 dB·cm²·g⁻¹, respectively) via blending-freeze-drying followed by hot pressing technology. Meanwhile, the D-Ti₃C₂T x /(ANF/PVA) EMI shielding composite film possesses excellent flexibility and foldability.
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Zhang et al. (2022) studied this question.
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