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Towards superlubricity in nanostructured surfaces: the role of van der Waals forces

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Abstract

Hydrogenated amorphous carbon (a-C:H) thin films have a unique combination of properties that are fundamental in mechanical and electromechanical devices aimed at energy efficiency issues. The literature brings a wealth of information about the ultra-low friction (superlubricity) mechanism in a-C:H thin films. However, there is persistent controversy concerning the physicochemical mechanisms of contact mechanics at the atomic/molecular level and the role of electrical interactions at the sliding interface is still a matter of debate. We find that the hydrogenation of the outermost nanostructured surface atomic layers of a-C:H thin films is proportional to the surface potential and also to the friction forces arising at the sliding interface. A higher hydrogen-to-carbon ratio reduces the surface potential, directly affecting frictional forces by a less effective long-term interaction. The structural ultra-low friction (superlubricity) is attributed to a lower polarizability at the outermost nanostructured layer of a-C:H thin films due to a higher hydrogen density, which renders weaker van der Waals forces, in particular London dispersion forces. More hydrogenated nanodomains at the surface of a-C:H thin films are proposed to be used to tailor superlubricity.

Graphical abstract: Towards superlubricity in nanostructured surfaces: the role of van der Waals forces

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Publication details

The article was received on 19 Apr 2018, accepted on 27 Jul 2018 and first published on 27 Jul 2018


Article type: Paper
DOI: 10.1039/C8CP02508H
Citation: Phys. Chem. Chem. Phys., 2018, Advance Article
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    Towards superlubricity in nanostructured surfaces: the role of van der Waals forces

    F. G. Echeverrigaray, S. R. S. de Mello, L. M. Leidens, M. E. H. Maia da Costa, F. Alvarez, T. A. L. Burgo, A. F. Michels and C. A. Figueroa, Phys. Chem. Chem. Phys., 2018, Advance Article , DOI: 10.1039/C8CP02508H

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