From microscopic nonlinear dynamics to macroscopic friction: low-friction sliding of nanocrystals

by Dr Astrid de Wijn (SU Fysikum/Kemisk Fysik)

Tuesday 22 Feb 2011, 13:30 → 14:30 Europe/Stockholm

122:026

Structural incompatibility (incommensurability) of two contacting solids leads to low-friction sliding. However, there is experimental evidence that the incommensurate low-friction state of a nanoscale contact is destroyed by rotation of the sliding flake[1], leading to a commensurate state with high friction.
We study the rotational dynamics and the stability of incommensurate sliding of nanocrystals on crystalline subtrates. By means of a simple, analytically soluble model, we show that stable incommensurate sliding states exist for different types of substrates and nanocrystals, but that their long-term survival under experimental conditions is delicate[2]. We compare our results to experimental data for friction of graphene flakes on graphite[1] and gold crystals on graphite. We propose experimental conditions which produce more robust low-friction states[3]. Using numerical simulations and simple theoretical arguments, we demonstrate how the low-friction states can influence the effectiveness of solid lubrication of macroscopic interfaces with nanocrystals.

[1] A. E. Filippov, M. Dienwiebel, J. W. M. Frenken, J. Klafter, M. Urbakh, Torque and twist against superlubricity, Phys. Rev. Lett. 100, 046102 (2008).
[2] Astrid S. de Wijn, C. Fusco, and Annalisa Fasolino, Stability of superlubric sliding on graphite, Physical Review E 81, 046105 (2010).
[3] Astrid S. de Wijn and Annalisa Fasolino, Stability of low-friction surface sliding of nanocrystal with rectangular symmetry and application to W on NaF(001), Tribology Letters 39, 91 (2010).