As high-performance thermal protection and structure enhancement materials, oxide ceramic fibers have become indispensable in numerous areas, ranging from deep-sea exploration to supersonic aircraft. However, under extreme energy input, abnormal grain growth and inevitable vermiculate structure would break the fiber integrity, causing catastrophic structure failure. Nowadays, the design of nanoceramics brings potential answers for strengthening of mechanical properties, but with the diameter downsized to the nanoscale, the increasing structural susceptibility of ceramic fiber to phase transformation and grain growth becomes a huge barrier. Here, we propose a strong carboxylic ligand confinement strategy by the combination of formic and acetic acids to control the inorganic colloid growth for fabricating robust α-alumina nanofibers. The rapid hydrolysis and coordination of the carboxylate groups with aluminum together with subsequent concentration synergistically promote the formation of small and compact precursor colloids, laying a solid foundation for suppressing abnormal grain growth and achieving refined alumina grain structure. The local disorder induced by silica and boron oxide surrounding α-alumina grains imparts excellent mechanical properties and flexibility with no fractures observed even after 500 buckling cycles and a wide range of temperatures from −196 to 1100 °C, providing an enlightening paradigm for ceramic fiber strengthening.

中文翻译：

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通过配体约束与局部无序调整相结合实现稳健的 α-Alumina 纳米纤维


氧化物陶瓷纤维作为高性能的热保护和结构增强材料，在从深海勘探到超音速飞机的许多领域中都不可或缺。然而，在极端能量输入下，异常的晶粒生长和不可避免的蛭状结构会破坏纤维的完整性，导致灾难性的结构失效。如今，纳米陶瓷的设计为增强机械性能带来了潜在的答案，但随着直径缩小到纳米级，陶瓷纤维对相变和晶粒生长的结构敏感性增加成为一个巨大的障碍。在这里，我们提出了一种强羧基配体限制策略，通过甲酸和乙酸的组合来控制无机胶体生长，以制造坚固的α-氧化铝纳米纤维。羧酸盐基团与铝的快速水解和配位以及随后的浓缩协同促进小而紧凑的前驱体胶体的形成，为抑制异常晶粒生长和实现细化氧化铝晶粒结构奠定了坚实的基础。α氧化铝颗粒周围的二氧化硅和氧化硼引起的局部无序赋予了优异的机械性能和柔韧性，即使在 500 次屈曲循环和 -196 至 1100 °C 的宽温度范围后也没有观察到断裂，为陶瓷纤维增强提供了启发性的范式。