Electrospun polyacrylonitrile (PAN) nanofibers have been widely used as a precursor to fabricate high-quality carbon nanofibers (CNFs). However, the low degree of cyclization and breakage of fibers during the stabilization process severely restrict the mechanical properties of the final CNFs. In this work, we propose a novel strategy to enhance the cyclization by introducing carboxyl groups via hydrolysis. This treatment significantly reduces the cyclization energy barrier by facilitating an ionic pathway rather than a radical pathway. As a result, the degree of stabilization effectively increases from ∼45 % to over 60 %. Simultaneously, the cyclization temperature also reduces from 288 to 260 °C, corresponding to a gentler cyclization reaction, that can avoid stress concentration and thus eliminate the fiber breakage during heat treatments. These features lead to a remarkable enhancement on the tensile strength for CNF films, from 26.0 to 70.4 MPa. This hydrolysis-based stabilization optimization provides a straightforward method to strengthen CNFs, thereby extending their applications.

中文翻译：

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通过水解诱导的低能垒环化反应强化聚丙烯腈基碳纳米纤维


静电纺丝聚丙烯腈 （PAN） 纳米纤维已被广泛用作制造高质量碳纳米纤维 （CNF） 的前体。然而，在稳定过程中纤维的低环化和断裂程度严重限制了最终 CNF 的机械性能。在这项工作中，我们提出了一种新的策略，通过水解引入羧基来增强环化。这种处理通过促进离子途径而不是自由基途径来显着降低环化能垒。因此，稳定度有效地从 ∼45 % 增加到 60 % 以上。同时，环化温度也从 288 °C 降低到 260 °C，对应于更温和的环化反应，可以避免应力集中，从而消除热处理过程中的纤维断裂。这些特性使 CNF 薄膜的拉伸强度显著提高，从 26.0 MPa 提高到 70.4 MPa。这种基于水解的稳定优化提供了一种直接的方法来增强 CNF，从而扩展其应用。