Orders of Magnitude Changes in the Friction of an Ionic Liquid on Carbonaceous Surfaces,The Journal of Physical Chemistry C

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Orders of Magnitude Changes in the Friction of an Ionic Liquid on Carbonaceous Surfaces
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2018-01-19 00:00:00 , DOI: 10.1021/acs.jpcc.7b10173
Nicolas Voeltzel _{1,

2} , Nicolas Fillot ₁ , Philippe Vergne ₁ , Laurent Joly ₂

Affiliation

The fast development of ionic liquids as new lubricants and carbon-based coatings as performant tribological surfaces calls for the characterization of their frictional and interfacial hydrodynamic behavior. Here we use molecular dynamics simulations to explore the response under shear of an ionic liquid confined between various carbon-based surfaces and an iron oxide surface for comparison. We show that extremely low fluid friction and giant hydrodynamic slippage can be obtained on graphite and to a lesser extent on diamond, but that friction on amorphous carbon surfaces is comparable to that on iron oxide. We relate these differences to the atom-scale roughness of the surfaces. In particular, although amorphous carbon surfaces are apolar, their nanometric roughness is enough to generate a fluid friction comparable to that of the extremely smooth but polar iron oxide surface. We also show that, at high shear rates, seemingly small differences in viscosity and interfacial friction can result in a significant change of the slip length. We finally discuss the consequences of the ultralow fluid friction that we observed on the macroscopic behavior of lubricated contacts.

中文翻译：

碳质表面上离子液体摩擦的量级变化

离子液体作为新型润滑剂的快速发展以及碳基涂料作为高性能的摩擦表面的迅速发展要求对其摩擦和界面流体动力学行为进行表征。在这里，我们使用分子动力学模拟来探索限制在各种碳基表面和氧化铁表面之间的离子液体在剪切作用下的响应，以进行比较。我们表明，可以在石墨上获得极低的流体摩擦和巨大的流体动力滑移，而在金刚石上获得的滑动程度较小，但无定形碳表面上的摩擦与氧化铁上的摩擦可比。我们将这些差异与表面的原子尺度粗糙度联系起来。特别是，尽管无定形碳表面是非极性的，它们的纳米粗糙度足以产生与极光滑但极性的氧化铁表面相当的流体摩擦。我们还表明，在高剪切速率下，粘度和界面摩擦的细微差别似乎会导致滑移长度的显着变化。最后，我们讨论了在润滑触点的宏观行为上观察到的超低流体摩擦的后果。

更新日期：2018-01-19

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