Atomistic observation on diffusion-mediated friction between single-asperity contacts
Atomistic observation on diffusion-mediated friction between single-asperity contacts
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DOI：
10.1038/s41563-021-01091-3
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发表时间：
2021-10
期刊：
影响因子：
41.2
通讯作者：
Yang He;Ding-shun She;Zhenyu Liu;Xiang Wang;L. Zhong;Chongmin Wang;Guofeng Wang;S. Mao
中科院分区：
文献类型：
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作者：
Yang He;Ding-shun She;Zhenyu Liu;Xiang Wang;L. Zhong;Chongmin Wang;Guofeng Wang;S. Mao
纳米摩擦学领域长期以来一直无法直接观察滑动界面上发生的情况。虽然基于原子力显微镜的技术已经确定了许多纳米级的摩擦现象，许多解释的陷阱仍然来自接触表面的间接或非原位表征。在这里，我们结合了原位高分辨率透射电子显微镜和原子力显微镜测量，提供直接的实时观察原子尺度的界面结构在摩擦过程中，并发现形成一个松散的填充界面层之间的两个金属凸体，使低摩擦下的拉伸应力。分子动力学模拟证实了这一发现。在压缩应力作用下，界面层在平衡距离处形成有序层，从而导致从低摩擦运动向耗散高摩擦运动的转变。这项工作直接揭示了原子扩散在金属接触摩擦中的独特作用。
The field of nanotribology has long suffered from the inability to directly observe what takes place at a sliding interface. Although techniques based on atomic force microscopy have identified many friction phenomena at the nanoscale, many interpretative pitfalls still result from the indirect or ex situ characterization of contacting surfaces. Here we combined in situ high-resolution transmission electron microscopy and atomic force microscopy measurements to provide direct real-time observations of atomic-scale interfacial structure during frictional processes and discovered the formation of a loosely packed interfacial layer between two metallic asperities that enabled a low friction under tensile stress. This finding is corroborated by molecular dynamic simulations. The loosely packed interfacial layer became an ordered layer at equilibrium distances under compressive stress, which led to a transition from a low-friction to a dissipative high-friction motion. This work directly unveils a unique role of atomic diffusion in the friction of metallic contacts.