Hu Hengqian, Wang Jin, Tian Kaiwen, Zheng Quanshui, Ma Ming
Department of Mechanical Engineering, Tsinghua University, Beijing, China.
State Key Laboratory of Tribology in Advanced Equipment, Tsinghua University, Beijing, China.
Nat Commun. 2024 Dec 30;15(1):10830. doi: 10.1038/s41467-024-55069-1.
Structural superlubricity (SSL), a state of ultralow friction and no wear between two solid surfaces in contact, offers a fundamental solution for reducing friction and wear. Recent studies find that the edge pinning of SSL contact dominates the friction. However, its nature remains mysterious due to the lack of direct characterizations on atomic scale. Here, for microscale graphite mesa, we unambiguously reveal the atomic structure and chemical composition of the disordered edge. The friction stress for each contact condition, namely, edge/edge, edge/surface, and surface/surface contacts are quantified, with the ratio being 10:10:1. The mechanism is revealed by all-atom molecular dynamic simulations, which reproduce the measured friction qualitatively. Inspired by such understanding, through fabricating SiN caps with tensile stress, we further eliminate the friction caused by the edges through disengaging the edges from the substrate. As a result, an SSL contact with ultralow friction stress of 0.1 kPa or lower is achieved directly.
结构超润滑（SSL）是指两个相互接触的固体表面之间处于超低摩擦且无磨损的状态，为减少摩擦和磨损提供了一种基本解决方案。最近的研究发现，SSL接触中的边缘钉扎主导着摩擦力。然而，由于缺乏原子尺度上的直接表征，其本质仍然神秘。在此，对于微米级石墨台面，我们明确揭示了无序边缘的原子结构和化学成分。对每种接触条件下的摩擦应力进行了量化，即边缘/边缘、边缘/表面和表面/表面接触，其比例为10:10:1。通过全原子分子动力学模拟揭示了该机制，该模拟定性地再现了测量到的摩擦力。受此理解启发，通过制造具有拉伸应力的氮化硅帽，我们进一步通过使边缘与基底脱离来消除边缘引起的摩擦。结果，直接实现了超低摩擦应力为0.1kPa或更低的SSL接触。
