Organic monolayers disrupt plastic flow in metals.
Organic monolayers disrupt plastic flow in metals.
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有机单层破坏金属中的塑料流。
DOI：
10.1126/sciadv.abc8900
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发表时间：
2020-12
期刊：
影响因子：
13.6
通讯作者：
Chandrasekar S
中科院分区：
文献类型：
--
作者：
Sugihara T;Udupa A;Viswanathan K;Davis JM;Chandrasekar S
吸附的单分子有机薄膜通过诱导表面应力使延性金属脆化。吸附薄膜经常影响表面的力学行为，导致众所周知的机械力化学现象，如液态金属脆化和环境辅助开裂。在这里，我们演示了一种机械力化学现象，在这种现象中，吸附的长链有机单层破坏了金属的大应变塑性变形。利用高速原位成像和事后分析，我们发现单分子膜诱导了从韧性到脆性的转变。弯曲流动是延性金属的特征，而准周期断裂是脆性材料的典型特征，变形力减少了85%。通过分子自组装独立地改变表面能和分子链长，我们认为这种“脆化”是由吸附诱导的表面应力驱动的，而不是表面能降低的。我们的观察得到了建模和分子模拟的支持，可以为解释固体中的各种机械力化学现象提供基础。研究结果对机械加工、粉碎和磨损等制造工艺也有影响。
Adsorbed monomolecular organic films are shown to embrittle ductile metals via an induced surface stress. Adsorbed films often influence mechanical behavior of surfaces, leading to well-known mechanochemical phenomena such as liquid metal embrittlement and environment-assisted cracking. Here, we demonstrate a mechanochemical phenomenon wherein adsorbed long-chain organic monolayers disrupt large-strain plastic deformation in metals. Using high-speed in situ imaging and post facto analysis, we show that the monolayers induce a ductile-to-brittle transition. Sinuous flow, characteristic of ductile metals, gives way to quasi-periodic fracture, typical of brittle materials, with 85% reduction in deformation forces. By independently varying surface energy and molecule chain length via molecular self-assembly, we argue that this “embrittlement” is driven by adsorbate-induced surface stress, as against surface energy reduction. Our observations, backed by modeling and molecular simulations, could provide a basis for explaining diverse mechanochemical phenomena in solids. The results also have implications for manufacturing processes such as machining and comminution, and wear.
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