碳化物衍生碳法制备中空碳纤维架构，用于极端航空航天隔热

摘要：碳基隔热材料在高超音速飞行器和深空任务等极端环境下的热保护系统（TPS）中具有显著的应用潜力。这归功于它们的超轻结构、优异的隔热性能和出色的高温稳定性。然而，传统的碳气凝胶在制造过程中经常会出现明显的体积收缩，这给优化其结构和热性能带来了挑战。受中空纤维结构所

1成果简介

碳基隔热材料在高超音速飞行器和深空任务等极端环境下的热保护系统（TPS）中具有显著的应用潜力。这归功于它们的超轻结构、优异的隔热性能和出色的高温稳定性。然而，传统的碳气凝胶在制造过程中经常会出现明显的体积收缩，这给优化其结构和热性能带来了挑战。受中空纤维结构所带来的性能提升的启发，

本文，湖南大学Jinshui Liu、申克教授团队在《ADVANCED FUNCTIONAL MATERIALS》期刊发表名为“Hollow Carbon Fiber Architectures Fabricated via Carbide-Derived Carbon Strategy for Ultra-Lightweight Thermal Protection Systems”的论文，研究采用碳化物衍生碳（CDC）策略来制造基于碳纤维的中空多孔绝热材料（CF-H）；碳纤维毡（CF）被用作结构模板。CDC 策略将模板方法与保形转化机制相结合，实现了最小的体积收缩率（10.22%）和高孔隙率（98.84%）。

中空纤维框架降低了密度（19mg·cm−3），最大限度地减少了热传导，并提供了较低的热导率（300 °C 时为 0.09553W·m−1·K−1）。此外，CF-H还保留了 CF 模板的针刺结构，因此在机械应力下表现出优异的弹性。总之，应用 CDC策略开发轻质、高性能碳基隔热材料为设计和开发应用于极端航空航天条件的TPS隔热材料提供了一个新的视角。

2图文导读

图1、a) The design strategy and preparation process of CF-H. b) SEM images of the biomimetic hollow carbon fiber microstructure of CF-H. c) Measurement of the apparent density of CF-H. d) Optical image of CF-H (19 mg cm−3) self-standing at the tip of a dandelion. e) Compressive deformation and recoverability of CF-H with a 2000 g weight. f) Optical images of CF-H samples processed into different shapes.

图2、SEM images of products at different stages of CF-H preparation at various magnifications: a) CF, b) SiC@CF, c) SiC-H, d) CF-H.

图3、a) XRD pattern of products at different stages of CF-H preparation. b) Apparent density of samples. (c) Ellingham diagram for reactions 1-3 under standard conditions. d–f) Raman spectra of CF, SiC-H, and CF-H. g) Shrinkage rates of samples at each stage. h) Pore size distribution of CF and CF-H measured using the mercury intrusion method. i) Comparison of volumetric shrinkage rates of CF-H with different carbon aerogels。

图4、a) Schematic diagram of SiC-H etched by Cl radicals. b) Optical images of SiC-H etched by Cl radicals at different temperatures. c) TEM images of SiC-H. d,e) Elemental mapping of SiC-H. f) TEM images of CF-H. g,h) Elemental mapping and content of CF-H. i) Nitrogen adsorption–desorption isotherms of products at different stages. j) DFT pore size distribution. k) Schematic diagram of the pore structure of CF-H obtained by etching SiC-H with Cl radicals. l) Schematic diagram of carbon atom rearrangement during CDC synthesis.

图5、a) Comparison of infrared thermal imaging of CF-H and CF with the heat source applied perpendicular to the fiber direction. b) The heat source applied parallel to the fiber direction. c) Temperature-time curves of CF-H and CF with the heat source applied perpendicular to the fiber direction. d) Temperature–time curves of CF-H and CF with the heat source applied parallel to the fiber direction. e) Schematic diagram of thermal conductivity anisotropy testing. f) Comparison of thermal conductivity anisotropy between CF-H and CF. g) Anisotropy factors of CF-H and CF. h) Thermal conductivity of CF-H in different directions at temperatures ranging from 25 to 300 °C. i) Thermal insulation mechanism diagram of CF-H. j) Comparison of thermal conductivity of CF-H with different carbon-based thermal insulation materials.

图6、a) Optical images of CF-H under compression at different strain. b) Stress–strain curves of a CF-H (19 mg cm−3) compressed to 20–80% strain. c) Compressive stress–strain curves of a CF-H at 60% strain for 300 cycles. d) Maximum stress, modulus of CF-H for different compressive cycles. f) Schematic illustration of the needle-punched fiber structure construction. g) SEM observation of the microstructure evolution of CF-H. h) Schematic illustration of the elasticity mechanism of CF-H. i) Optical photograph indicating the compressive elasticity of CF-H in liquid nitrogen (−196 °C). j) Comparison of compressive strength between CF-H and other aerogels at 60% compressive strain。

3小结

总之，我们利用 CDC 策略成功合成了一种新型多孔隔热材料 CF-H，它具有中空碳纤维结构。将基于模板生成碳化硅涂层的方法与采用保形转化机制的 CDC 策略相结合，确保了 CF-H 的制备具有极低的体积收缩率。CF-H 是以碳纤维毡为模板构建的中空纤维结构。这种方法产生了极高的孔隙率，有助于实现材料的低密度和轻质化。此外，中空纤维结构的加入大大降低了垂直于纤维方向的固相热传导效率。同时，由于碳化硅晶格中的硅原子被去除，中空结构以及中空碳纤维内部形成的微孔和中孔增强了多孔网络对热辐射的吸收和散射。这使得 CF-H 具有显著的导热各向异性。即使在极高的温度条件下，CF-H 也能保持其中空纤维形态，在广泛的温度范围内保持其卓越的隔热性能。

中空纤维框架降低了密度（19 mg cm-3），最大限度地减少了热传导，并提供了较低的热导率（300 °C 时为0.09553 W m-1 K-1）。此外，通过在 CF 模板中引入深针刺纤维结构，CF-H 被赋予了一个坚固的弹簧状网络，该网络中的针刺纤维束沿施加载荷的方向排列。这种结构设计确保了在 20%-80% 的压缩范围内具有优异的压缩回弹性，证明了材料在机械应力下的弹性。我们相信，应用 CDC 策略制造具有复杂孔隙结构的碳基隔热材料，是开发先进隔热材料的一种前景广阔的设计方法。这些材料特别适用于极端运行环境中的 TPS，如航空航天应用和高温工业环境，在这些环境中，卓越的耐热性和机械耐久性至关重要。

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