Abstract Diamond-like-carbon (DLC) is a promising material for tribological applications such as hard disk, automotive, machine tool, and aerospace coatings. We performed in-situ transmission electron microscopy (TEM) and molecular dynamics (MD) studies of nanoscale single-asperities made of tetrahedral amorphous carbon (ta-C, a type of DLC with high strength) contacting single-crystal diamond, to understand the factors controlling adhesion. Visualization of the contacts in TEM enabled us to correlate the asperity's geometry and the adhesion measurements. MD simulations allowed the atomic-scale mechanisms of adhesion to be elucidated and correlated with the TEM observations. Experimentally-determined pull-in forces show less scatter than pull-off forces. The magnitude of the pull-in forces is consistent with adhesion arising from van der Waals (VDW) interactions, allowing us to estimate the ta-C/diamond Hamaker constant. MD simulations with the AIREBO potential confirmed that including VDW interactions leads to less scatter in adhesive forces in approach than in separation. MD simulations with the REBO+S potential demonstrate that the large scatter in pull-off forces observed experimentally arises from the complex nature of covalent bonding between substrate and tip, influenced by the local energy landscape, hydrogen coverage, and the number of repeated contact events. The scatter in pull-off force also tends to decrease with increasing roughness.

中文翻译：

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化学键对类金刚石碳纳米级粘附变异性的影响

摘要 类金刚石碳 (DLC) 是一种很有前途的摩擦学材料，如硬盘、汽车、机床和航空航天涂层。我们对由接触单晶金刚石的四面体无定形碳（ta-C，一种高强度 DLC）制成的纳米级单凹凸面进行了原位透射电子显微镜 (TEM) 和分子动力学 (MD) 研究，以了解控制附着力的因素。TEM 中接触的可视化使我们能够关联粗糙的几何形状和粘附测量。MD 模拟允许阐明粘附的原子级机制并与 TEM 观察相关联。实验确定的牵引力比牵引力显示出更少的分散。拉入力的大小与范德华 (VDW) 相互作用产生的粘附力一致，使我们能够估计 ta-C/金刚石哈梅克常数。具有 AIREBO 势能的 MD 模拟证实，与分离时相比，包括 VDW 相互作用会导致接近时粘附力的分散更少。具有 REBO+S 电位的 MD 模拟表明，实验观察到的拉脱力的大分散是由于基板和尖端之间共价键的复杂性质，受局部能量景观、氢覆盖率和重复接触事件次数的影响. 随着粗糙度的增加，拉脱力的分散也趋于减少。具有 AIREBO 势能的 MD 模拟证实，与分离时相比，包括 VDW 相互作用会导致接近时粘附力的分散更少。具有 REBO+S 电位的 MD 模拟表明，实验观察到的拉脱力的大分散是由于基板和尖端之间共价键的复杂性质，受局部能量景观、氢覆盖率和重复接触事件次数的影响. 随着粗糙度的增加，拉脱力的分散也趋于减少。具有 AIREBO 势能的 MD 模拟证实，与分离时相比，包括 VDW 相互作用会导致接近时粘附力的分散更少。具有 REBO+S 电位的 MD 模拟表明，实验观察到的拉脱力的大分散是由于基板和尖端之间共价键的复杂性质，受局部能量景观、氢覆盖率和重复接触事件次数的影响. 随着粗糙度的增加，拉脱力的分散也趋于减少。氢覆盖率，以及重复接触事件的数量。随着粗糙度的增加，拉脱力的分散也趋于减少。氢覆盖率，以及重复接触事件的数量。随着粗糙度的增加，拉脱力的分散也趋于减少。