AVS 60th International Symposium and Exhibition
    Tribology Focus Topic Tuesday Sessions
       Session TR+SE-TuM

Invited Paper TR+SE-TuM9
Low Friction on Metals – Glide Planes and Molecular Lubricants

Tuesday, October 29, 2013, 10:40 am, Room 203 C

Session: Low Friction Materials
Presenter: R. Bennewitz, INM - Leibniz-Institute for New Materials, Germany
Correspondent: Click to Email
Nanotribological investigations of flat crystalline metal surfaces by means of friction force microscopy often result in extremely low friction coefficients. Experimental results indicate that the actual glide occurs between the low-indexed crystalline surface and a metallic neck, which forms by transfer of metal to the tip of the force microscope [1]. In the case of Au(111) surfaces, the apparently simple gliding process requires surfaces diffusion to operate, as evident from a failure of atomic friction mechanisms at lower temperatures [2]. Friction coefficients measured by friction force microscopy approach values known from macroscopic experiments when the tip plastically deforms the surface by scratching [3].

Electrochemical methods allow for an in-situ modification of surfaces by electrochemical oxidation, reduction, ion adsorption, or change in surface reconstruction. All of these influence nanometer-scale friction. For example, variation of the surface reconstruction reveals that friction increases with atomic-scale roughness [4]. Friction experiments in ionic liquids demonstrate that the preferential adsorption of anions or cations opens an opportunity for reversible switching of lubrication [5].

[1] N.N. Gosvami et al., Microscopic Friction Studies on Metal Surfaces, Tribol Lett 39 (2010) 19

[2] N.N. Gosvami et al., Ageing of a Microscopic Sliding Gold Contact at Low Temperatures, Phys. Rev. Lett. 107 (2011) 144303

[3] M. Mishra et al., Friction model for single-asperity elastic-plastic contacts, Phys. Rev. B 86 (2012) 045452

[4] F. Hausen et al., Surface structures and frictional properties of Au(100) in an electrochemical environment, Surf. Sci., 607 (2013) 20

[5] J. Sweeney et al., Control of Nanoscale Friction on Gold in an Ionic Liquid by a Potential-Dependent Ionic Lubricant Layer, Phys. Rev. Lett., 109 (2012) 155502