Acid-Assisted Toughening Aramid Aerogel Monoliths with Ultralow Thermal Conductivity and Superior Tensile Toughness,Advanced Functional Materials

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Acid-Assisted Toughening Aramid Aerogel Monoliths with Ultralow Thermal Conductivity and Superior Tensile Toughness
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2023-09-24 , DOI: 10.1002/adfm.202307072
Jianpeng Wu ₁ , Junshuo Zhang ₁ , Min Sang ₁ , Zimu Li ₁ , Jianyu Zhou ₁ , Yu Wang ₁ , Shouhu Xuan _{1,

2} , Ken Cham‐Fai Leung ₃ , Xinglong Gong _{1,

2}

Affiliation

Resisting extreme loading and thermal ablation encountered by aerospace devices demands for high performance engineering materials. Aerogels have achieved satisfactory thermal insulation but the intrinsic brittleness of porous skeletons fail to ensure their normal operation under severe stress fields. Herein, aramid nanofibers (ANFs) are processed into tough 3D aerogel monoliths via a multi-scale toughening strategy, involving unidirectional freeze-casting-enabled microstructure orientation and acid-assisted nanofiber cross-linking. Scalable production of ANFs aerogels is realized through fast air-drying without excessive energy consumption. The aligned sheets in ANFs aerogels enable extreme thermal conductivity of 15.8 mW m⁻¹ K⁻¹, superinsulation from −130 to 300 °C, and durable combustion protection for 20 min. Particularly, highly aggregated nanofibers assemble into dense ANFs skeletons, endowing the tough aerogels with superior specific tensile strength (89 MPa cm³ g⁻¹), ultra-high toughness (1.3 MJ m⁻³), and impressive fracture energy (7.36 kJ m⁻²). Such mechanical properties are highly resistant to harsh environments, including water erosion (7 days) and high temperature baking (30 days). Moreover, ANFs aerogels exhibit two to three times more energy dissipation than commercial foams against ballistic impact at 140 m s⁻¹. This integrated mechanical and thermal robustness may pioneer the potential application in impact-thermal coupled safeguard for aerogel materials.

中文翻译：

具有超低导热率和优异拉伸韧性的酸辅助增韧芳纶气凝胶整体

航空航天设备需要高性能工程材料来抵抗极端负载和热烧蚀。气凝胶已经实现了令人满意的隔热性能，但多孔骨架固有的脆性无法保证其在严重应力场下的正常工作。在此，芳纶纳米纤维 (ANF) 通过多尺度增韧策略加工成坚韧的 3D 气凝胶整体，包括单向冷冻铸造微结构取向和酸辅助纳米纤维交联。ANFs气凝胶的规模化生产是通过快速风干实现的，无需过多的能源消耗。ANF 气凝胶中的排列片材可实现 15.8 mW m ⁻¹ K ⁻¹的极端导热率、-130 至 300 °C 的超隔热性以及 20 分钟的持久燃烧保护。特别是，高度聚集的纳米纤维组装成致密的ANF骨架，赋予坚韧气凝胶优异的比拉伸强度（89 MPa cm ³ g ^-1）、超高韧性（1.3 MJ m ^-3）和令人印象深刻的断裂能（7.36 kJ m ⁻² )。这种机械性能对恶劣环境具有很强的抵抗力，包括水侵蚀（7天）和高温烘烤（30天）。^{此外，ANF气凝胶在140 ms -1}的弹道冲击下表现出比商用泡沫高两到三倍的能量耗散。这种综合的机械和热鲁棒性可能会开创气凝胶材料在冲击热耦合防护方面的潜在应用。

更新日期：2023-09-24

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