Yali Zhang, Zhonglei Ma, Kunpeng Ruan and Junwei Gu*. Flexible Ti3C2Tx/(Aramid Nanofiber/PVA) Composite Films for Superior Electromagnetic Interference Shielding. Research, 2022, 2022: 9780290.（1区综合类Top期刊，2021中国最具国际影响力学术期刊，《Science》自1880年创建以来第一本合作期刊）

https://doi.org/10.34133/2022/9780290

Abstract

Multifunctional electromagnetic interference (EMI) shielding materials would solve electromagnetic radiation & pollution problems from electronic devices. Herein, the directional freeze-drying technology is utilized to prepare the aramid nanofiber/polyvinyl alcohol aerogel with directionally porous structure (D-ANF/PVA), and the Ti3C2Tx dispersion is fully immersed into the D-ANF/PVA aerogel via ultrasonication & vacuum-assisted impregnation. Ti3C2Tx/(ANF/PVA) EMI shielding composite films with directionally ordered structure (D-Ti3C2Tx) are then prepared by freeze-drying and hot-pressing. Constructing directionally porous structure enables the highly conductive Ti3C2Tx 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 Ti3C2Tx-Ti3C2Tx continuous conductive paths, which significantly improves the conductivity of the D-Ti3C2Tx/(ANF/PVA) EMI shielding composite film. When the amount of Ti3C2Tx is 80 wt%, the EMI shielding effectiveness (EMI SE) and specific SE (SSE/t) of D-Ti3C2Tx/(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 Ti3C2Tx/(ANF/PVA) (R-Ti3C2Tx/(ANF/PVA)) composite film (46 dB and 9062 dB·cm2·g-1, respectively) via blending-freeze drying followed by hot pressing technology. Meantime, the D-Ti3C2Tx/(ANF/PVA) EMI shielding composite film possesses excellent flexibility and foldability.

随着柔性可穿戴电子设备和5G通信技术的迅猛发展和广泛使用，迫切需要柔性多功能电磁干扰（EMI）屏蔽材料来解决其电磁辐射和电磁污染问题。本文采用定向冷冻干燥工艺制备具有定向孔结构的芳纶纳米纤维/聚乙烯醇（D-ANF/PVA）气凝胶，借助超声振荡和真空辅助浸渍工艺将Ti3C2Tx分散液充分、均匀浸渍在D-ANF/PVA气凝胶中，再经冷冻干燥和热压成膜工艺制备具有定向有序结构的Ti3C2Tx/(ANF/PVA)（D-Ti3C2Tx/(ANF/PVA)）电磁屏蔽复合膜。定向多孔结构的构建使高导电Ti3C2Tx纳米片包裹在定向有序D-ANF/PVA骨架上整齐有序排列且相互搭接，在同等Ti3C2Tx用量下实现更高效、更完整的导电网络。热压成膜工艺有效减小了堆叠的波浪状D-ANF/PVA间的层间距，使附着于D-ANF/PVA骨架上的大量Ti3C2Tx纳米片高效接触，形成大量连续的导电通道，显著提高了D-Ti3C2Tx/(ANF/PVA)复合膜的电导率（σ）。当Ti3C2Tx用量为80 wt%时，120 μm厚D-Ti3C2Tx/(ANF/PVA)复合膜（密度为0.423 g·cm-3）的EMI屏蔽效能（EMI SE）和比屏蔽效能（SSE/t）高达70 dB和13790 dB·cm2·g-1，远优于由共混-冷冻干燥-热压成膜工艺制备的无序Ti3C2Tx/(ANF/PVA)（R-Ti3C2Tx/(ANF/PVA)）复合膜（EMI SE和SSE/t分别为46 dB和9062 dB·cm2·g-1）。D-Ti3C2Tx/(ANF/PVA)复合膜的力学性能呈现各向异性，当Ti3C2Tx用量为80 wt%时，平行于定向冷冻方向的拉伸强度和断裂伸长率分别为13.1 MPa和4.2%，明显优于R-Ti3C2Tx/(ANF/PVA)复合膜的拉伸强度（8.4 MPa）和断裂伸长率（2.7%）。同时，D-Ti3C2Tx/(ANF/PVA)复合膜具有出色的柔性和可折叠性。

论文创新点

1、定向多孔结构的构建使高导电Ti3C2Tx纳米片包裹在定向有序D-ANF/PVA骨架上整齐有序排列且相互搭接，实现同等Ti3C2Tx用量下复合膜更高效、更完整的导电网络。

2、热压成膜工艺减小了堆叠波浪状D-ANF/PVA间的层间距，使D-ANF/PVA骨架上的Ti3C2Tx纳米片高效接触，形成大量连续的导电通道，显著提高D-Ti3C2Tx/(ANF/PVA)复合膜的σ。

3、当Ti3C2Tx用量为80 wt%时，120 μm厚D-Ti3C2Tx/(ANF/PVA)复合膜（密度为0.423 g·cm-3）的EMI SE和SSE/t高达70 dB和13790 dB·cm2·g-1，远优于由共混-冷冻干燥-热压成膜工艺制备的R-Ti3C2Tx/(ANF/PVA)复合膜（EMI SE和SSE/t 分别为46 dB和9062 dB·cm2·g-1）。

4、当Ti3C2Tx用量为80 wt%时，平行于定向冷冻方向的拉伸强度和断裂伸长率分别为13.1 MPa和4.2%，明显优于R-Ti3C2Tx/(ANF/PVA)）复合膜的拉伸强度（8.4 MPa）和断裂伸长率（2.7%）。