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區綜合類Top期刊，2021中國最具國際影響力學術期刊，《Science》自1880年創建以來第一本合作期刊）
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.
隨著柔性可穿戴電子設備和5G通信技術的迅猛發展和廣泛使用，迫切需要柔性多功能電磁干擾（EMI）屏蔽材料來解決其電磁輻射和電磁污染問題。本文采用定向冷凍干燥工藝制備具有定向孔結構的芳綸納米纖維/聚乙烯醇（D-ANF/PVA）氣凝膠，借助超聲振蕩和真空輔助浸漬工藝將Ti3C2Tx分散液充分、均勻浸漬在D-ANF/PVA氣凝膠中，再經冷凍干燥和熱壓成膜工藝制備具有定向有序結構的Ti3C2Tx/(ANF/PVA)（D-Ti3C2Tx/(ANF/PVA)）電磁屏蔽復合膜。定向多孔結構的構建使高導電Ti3C2Tx納米片包裹在定向有序D-ANF/PVA骨架上整齊有序排列且相互搭接，在同等Ti3C2Tx用量下實現更高效、更完整的導電網絡。熱壓成膜工藝有效減小了堆疊的波浪狀D-ANF/PVA間的層間距，使附著于D-ANF/PVA骨架上的大量Ti3C2Tx納米片高效接觸，形成大量連續的導電通道，顯著提高了D-Ti3C2Tx/(ANF/PVA)復合膜的電導率（σ）。當Ti3C2Tx用量為80 wt%時，120 μm厚D-Ti3C2Tx/(ANF/PVA)復合膜（密度為0.423 g·cm-3）的EMI屏蔽效能（EMI SE）和比屏蔽效能（SSE/t）高達70 dB和13790 dB·cm2·g-1，遠優于由共混-冷凍干燥-熱壓成膜工藝制備的無序Ti3C2Tx/(ANF/PVA)（R-Ti3C2Tx/(ANF/PVA)）復合膜（EMI SE和SSE/t分別為46 dB和9062 dB·cm2·g-1）。D-Ti3C2Tx/(ANF/PVA)復合膜的力學性能呈現各向異性，當Ti3C2Tx用量為80 wt%時，平行于定向冷凍方向的拉伸強度和斷裂伸長率分別為13.1 MPa和4.2%，明顯優于R-Ti3C2Tx/(ANF/PVA)復合膜的拉伸強度（8.4 MPa）和斷裂伸長率（2.7%）。同時，D-Ti3C2Tx/(ANF/PVA)復合膜具有出色的柔性和可折疊性。
論文創新點
1、定向多孔結構的構建使高導電Ti3C2Tx納米片包裹在定向有序D-ANF/PVA骨架上整齊有序排列且相互搭接，實現同等Ti3C2Tx用量下復合膜更高效、更完整的導電網絡。
2、熱壓成膜工藝減小了堆疊波浪狀D-ANF/PVA間的層間距，使D-ANF/PVA骨架上的Ti3C2Tx納米片高效接觸，形成大量連續的導電通道，顯著提高D-Ti3C2Tx/(ANF/PVA)復合膜的σ。
3、當Ti3C2Tx用量為80 wt%時，120 μm厚D-Ti3C2Tx/(ANF/PVA)復合膜（密度為0.423 g·cm-3）的EMI SE和SSE/t高達70 dB和13790 dB·cm2·g-1，遠優于由共混-冷凍干燥-熱壓成膜工藝制備的R-Ti3C2Tx/(ANF/PVA)復合膜（EMI SE和SSE/t 分別為46 dB和9062 dB·cm2·g-1）。
4、當Ti3C2Tx用量為80 wt%時，平行于定向冷凍方向的拉伸強度和斷裂伸長率分別為13.1 MPa和4.2%，明顯優于R-Ti3C2Tx/(ANF/PVA)）復合膜的拉伸強度（8.4 MPa）和斷裂伸長率（2.7%）。