超弹性石墨烯基复合气凝胶，用于极端温度环境下的热和电磁保护

摘要：由于其多孔特性，与纳米材料堆叠的气凝胶材料通常具有良好的隔热和电磁波（EMW）吸收性能。然而，在极端温度环境下的连续机械载荷循环会导致不可逆的结构和机械损伤。此外，多重界面的特性与其抗疲劳性能之间存在内在矛盾。本文，天津大学秦盟盟教授、封伟教授等在《A

1成果简介

由于其多孔特性，与纳米材料堆叠的气凝胶材料通常具有良好的隔热和电磁波（EMW）吸收性能。然而，在极端温度环境下的连续机械载荷循环会导致不可逆的结构和机械损伤。此外，多重界面的特性与其抗疲劳性能之间存在内在矛盾。本文，天津大学秦盟盟教授、封伟教授等在《ADVANCED FUNCTIONAL MATERIALS》期刊发表名为“Superelastic Graphene-Based Composite Aerogel for Thermal and Electromagnetic Protection in Extreme Temperature Environments”的论文，研究将聚酰亚胺（PI）纤维分散在石墨烯气凝胶中，通过原位焊接形成复合气凝胶（G-PI@F20/CNTx）。多级多孔结构赋予气凝胶优异的超弹性、隔热和 EMW 吸收性能。

该气凝胶在-196至160 °C的温度范围内可承受 90% 的应变压缩循环，变形损失保持在5%以下。这种多级多孔结构阻碍了声子传导，导致热导率低（0.0313 W m−1K−1).厚度为4.1mm 的气凝胶实现了12.48GHz 的有效吸收带宽（EAB）。通过将厚度增加到20.3mm，实现了15.24GHz 的超宽带吸收和最佳反射损耗（RLmin）达到−43.49dB。这些发现为多功能EMW吸收材料的设计提供了重要的见解，并为合成超弹性气凝胶提供了通用策略。

2图文导读

图1、a) SEM image of the cross-section of G-PI@F20/CNT4 and the “weld points” in cross-linked PI fiber networks. b) Schematic diagram of the resilience enhancement mechanism of cross-linked PI fiber network. c) Intermolecular and intramolecular thermal imidization reactions and other cross-linking reactions of PI fibers.

图2、XPS spectra of PI fiber aerogel a–c) before and d–f) after thermal treatment at 500 °C. Compression cycle curves of G-PI@F20/CNT4 at g) ultralow temperature, h) room temperature, and i) high temperature. j) Compression cycling process of the aerogel in liquid nitrogen. k) Vacuum compression cycling process of the aerogel.

图3、EMW absorption performance analysis of G-PI@F20/CNTx (x = 2, 4, 6). Samples thermally treated at 400 °C (A1–A3): a–c) RL curves, d) RLmin and corresponding EAB, e,f) Trends in the real and imaginary parts of complex permittivity and complex permeability. Samples thermally treated at 600 °C (D1–D3): g–i) RL curves, j) RLmin and corresponding EAB, k,l) Trends in the real and imaginary parts of complex permittivity and complex permeability.

图4、a) Schematic representation of the solar sail panel folding process with the aerogel layer. Samples thermally treated at 500 °C without compression (B1–B3): b–d) 3D RL value plots, e) EAB of B2 within the 2.6–4.6 mm range, f) RLmin values and corresponding EAB, g) ε′ and ε″ values, h) µ′ and µ″ values. Samples subjected to 1000 compression cycles (C1–C3): i) 3D RL value plots, j) EAB of C2 within the 2.6–4.6 mm range, k) RLmin values and corresponding EAB, l) ε′ and ε″ values, m) µ′ and µ″ values.

图5、a) Schematic diagram of a satellite being detected by radar. b) Satellite micro-model covered with a B2 skin layer (4 mm, 4.35 mg cm−3). c) 3D scattering signal and d) absorption-related energy flow distributions of non-stealth and stealth satellites. e) Monostatic RCS simulation of non-stealth and stealth satellites across different PW angles (−90° to 90°) at a monitoring wavelength of 14.74 GHz. f) RCS radiation signal distributions.

图6、a) Test samples and testing site. b) RL curves of B2’. c) Summary of RLmin and EABmax for all test samples. d) Comparison of RLmin and EABmax of different graphene-based EMW absorbing materials that have been reported. e) TG curve of B2 in an air atmosphere. TG curve of f) B2 and g) PI fibers in a nitrogen atmosphere. h) EMW loss mechanism of the G-PI@F20/CNTx.

图7、a) Components of the EMW absorption performance demonstration. b) Scenario demonstration and validation of the aerogel's comprehensive performance. c) Spectrum analyzer signal display before and after aerogel coverage. d) Surface temperature fluctuation curve of the aerogel under ultralow temperature conditions. e) Surface temperature fluctuation curve of the aerogel under high-temperature conditions.

3小结

通过采用原位 PI 焊接技术，解决了传统石墨烯基气凝胶的多个界面特性与其抗疲劳性能之间的矛盾。所制备的具有 PI 纤维交联网络的石墨烯气凝胶可在较宽的温度范围内（-196 至 160 °C）承受 90% 的应变压缩循环，变形损失小于 5%。这种气凝胶具有独特的分层多孔结构，具有 4.35mg·cm-3 的超低密度，在厚度为 4.1mm时可达到 12.48 GHz 的 EAB，在厚度为 20.3 毫米时可达到覆盖 2.76-18 千兆赫的超宽带吸收，RLmin 为 -43.49 分贝。分层多孔结构可抑制声子传输和空气对流，产生 0.0313 W m-¹ K-¹ 的超低导热系数，以及 V-0 级阻燃性。总体而言，G-PI@F20/CNTx 材料因其出色的超弹性、电磁波吸收能力、隔热性和阻燃性，在航空航天和其他先进应用领域展现出巨大潜力。这项研究还为解决其他纳米材料组件在极端环境下的机械弹性问题提供了宝贵的参考。

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