The phenomenon of friction permeates the vast majority of mechanical systems, but despite its ubiquity, the basic mechanisms leading to friction are currently not very well understood. Instead, the characterization of friction is mostly limited to phenomenological descriptions.A promising way to improve on the comprehension of friction on a fundamental level is guided by the fact that macroscopic contacts in general can be broken down into many smaller sub-contacts. It thus is imperative to investigate friction of these smallest units, the so-called single asperity nanoscale contacts, to gain insight into the basic principles governing friction. An essential issuein this context is the emergence of contact ageing, which i.a. is the cause for static friction. Contact ageing is observed in macroscopic friction experiments on a regular basis, but its existence in nanoscale contacts could only recently be demonstrated for the first time.Nanoparticles manipulated under vacuum conditions using friction force microscopes represent an excellent experimental model system in this endeavor to study frictional properties of single asperity contacts. In this work, experimental methods to manipulate nanoparticles and to study their frictional characteristics were developed and implemented. This framework allowed to conduct fundamental experiments regarding the friction kinetics of antimony nanoparticles on graphite substrates with respect to their velocity- and temperature-dependence.By carrying out Monte Carlo simulations of a newly devised nanoscale friction model, two competing processes were identified as having a major impact on the friction kinetics, namely thermal activation as well as ageing of the contacts. The observation of stick-slip-type friction in consecutive experiments allowed to directly quantify contact ageing in nanoparticle friction, exposing an ageing law with logarithmic dependence on stationary hold times.Complementary measurements revealed two qualitatively different contact ageing phenomena for point-like contacts at varied temperatures. In silica-gold contacts, ageing during lateral movement due to gold neck shearing could be registered, while silica-silica contacts exhibited ageing of stationary contacts, comparable to the contact ageing found for antimony nanoparticles.All findings highlight the fundamental significance of contact ageing in nanoscale friction, especially for the case of nanoparticle kinetics.
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