1成果简介
航空航天、电子通信与交通运输系统对高性能动能吸收与电磁屏蔽材料提出了迫切需求，但在维持超低密度的同时提升动能吸收性能仍是该领域的核心挑战。本文，中国科学院苏州纳米技术与纳米仿生研究所王锦 研究员、胡东梅 研究员等在《Small Methods》期刊发表名为"Bioinspired Superlight Carbon Nanotube Aerogel With Exceptionally High Kinetic Energy Absorption up to 385.47 MJ/m³"的论文，研究通过模拟竹子内部结构，采用分段沉积（segmented deposition）策略将银（Ag）沉积于碳纳米管气凝胶（CNTA）之上，构筑了银功能化碳纳米管气凝胶（ACNTA）。其中，具有宏观孔隙结构的CNTA主链赋予材料固有的低密度和大变形能力，而银的附着则增强了碳纳米管纤维之间的抗滑移性能和导电性。由此获得了密度仅为 9.3 mg cm⁻³ 的超轻 ACNTA，在 8500 s⁻¹ 应变速率下动能吸收达 385.47 MJ m⁻³；此外，ACNTA 的电磁屏蔽性能达 99.65 dB，较原始 CNTA 提升 22%。该仿生竹结构设计的气凝胶还具有一定的隔热、吸声与降噪性能。该仿生设计为电子与装备外部防护材料提供了多功能超轻材料的潜力。
2图文导读
图1. (a) Schematic diagram of ACNTA synthesis process; (b) Schematic diagram of bamboo step density; (c) Macroscopic image of ACNTA (d) SEM image of CNTA132 step density.
图2、(a) Schematic diagram of Hopkinson pressure bar; Stress–strain curves of CNTA at (b) 6800 s−1, (c)7800 s−1, (d)8500 s−1 strain rate; (e) Comparison chart of sample volume energy absorption values (The maximum stress of CNTA123 at a strain rate of 6800, 7700, and 8500 s−1 is 485.363 ± 19.545, 567.070 ± 15.418, 624.075 ± 13.010 MPa, and the energy absorption values are 108.533 ± 5.490, 145.246 ± 10.955, 275.840 ± 9.417 MJ m−3, respectively; The maximum stress of CNTA132 at a strain rate of 6800, 7700, and 8500 s−1 is 431.703 ± 42.611, 471.945 ± 56.599, 510.362 ± 41.205 MPa, and the energy absorption values are 93.750 ± 16.736, 113.913 ± 16.652, 200.788 ± 18.604 MJ m−3, respectively; The maximum stress of CNTA312 at a strain rate of 6800, 7700, and 8500 s−1 is 390.241 ± 26.347, 456.695 ± 49.057, 589.630 ± 23.261 MPa, and the energy absorption values are 84.733 ± 10.210, 142.085 ± 15.529, 162.541 ± 21.064 MJ m−3, respectively; Error bars represent mean ± SD (n = 5)); (f) Comparison of dynamic energy absorption with other materials; (g) Schematic diagram of static cyclic compression.
图3、(a) Dynamic compression mechanism diagram of CNTA; (b) XRD images of CNTA and ACNTA; (c) XPS images of CNTA and ACNTA; (d) Comparison chart of Ag analysis XPS of ACNTA; (e) Ag spectral changes of ACNTA123-1.2; Surface SEM image of (f) CNTA123, (g)ACNTA123-0.2, (h) ACNTA123-0.4, (i) ACNTA123-0.6, (j) ACNTA123-0.8, (k) ACNTA123-1.0, (l) ACNTA123-1.2; (m) EDS image of ACNTA123-1.2.
图4、(a) The resistivity and conductivity of different materials; (b) Electromagnetic shielding performance of different materials; (c) Comparison of SET, SEA, and SER values for different materials; (d) The A, T, and R coefficients of different materials; (e) Enlarged T-coefficients of different materials; (f) Comparison chart of electromagnetic shielding performance and thickness relationship with other materials; (g) Analysis diagram of electromagnetic shielding mechanism.
图5、(a) Stress–strain diagrams of CNTA123 and ACNTA123-0.8 at different strain rates; (b) Comparison of dynamic energy absorption and toughness between CNTA123 and ACNTA123-0.8 at different strain rates; (c) Infrared spectra of temperature changes under different voltages of ACNTA123-0.8; (d) Comparison chart of temperature changes under different voltages of ACNTA123-0.8; (e) Schematic diagram of step temperature under material electric heating; (f) Noise reduction and sound absorption images of ACNTA123-0.8 (n = 3); (g) Thermal conductivity comparison chart of ACNTA123-0.8 and other materials; (h) Thermal insulation infrared image of materials; (i) Application diagram of materials.
3小结
综上所述，本研究设计了一种仿生竹结构，并成功制备了具有阶梯式密度的银修饰碳纳米管气凝胶。该材料增强的动能吸收能力源于两个关键因素：(1) 通过调整碳沉积时间实现的梯度密度设计。这使得较软的段落能在受冲击时通过大幅变形吸收能量，而较硬的层则提供支撑，并通过坍塌和碎裂进一步消散能量。(2) 银元素的引入增强了纤维间的接触，并抑制了碳纳米管在冲击下的滑移，从而进一步消散动能。因此，在各种应变速率范围内，该ACNTA的动能吸收能力提高了40%–166%。此外，银的引入增强了碳纳米管网络导电路径内的电磁波吸收和反射能力，从而实现了高达99.65 dB的电磁屏蔽效能。该气凝胶还具备隔热、电加热、吸音和降噪性能。这种仿生设计方法为未来防护材料的设计提供了宝贵的启示，并为克服单功能材料固有的局限性开辟了一条充满希望的途径。
文献：
https://doi.org/10.1002/smtd.70820
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