Load- and Size Effects of the Diamond Friction Coefficient at the Nanoscale
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ORIGINAL PAPER
Load- and Size Effects of the Diamond Friction Coefficient at the Nanoscale Hanzhong Liu1 · Wenjun Zong1 · Xiao Cheng1 Received: 24 June 2020 / Accepted: 18 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The friction coefficient, an important parameter to evaluate the dynamic properties of friction pairs, has been widely used in macro engineering fields. However, it is probably inappropriate to characterize the tribological properties at the nanoscale due to the strong size effect, and the conventional formula cannot reveal its determinants owing to its oversimple form. Therefore, in the present work, a new formula is deduced to overcome these shortcomings. The established formula for the friction coefficient considers the adhesion and discloses the relationship between the friction coefficient and the material properties of diamond. It effectively suppresses the dependency of the friction coefficient on the load, although such a dependency cannot be eliminated completely. Therefore, another new formula, independent of the loading force, is derived. Interestingly, the results indicate that the size effect is invariably observed in the friction coefficients derived from the three formulas due to different accumulation effects of debris atoms, which is verified by molecular dynamics simulations.
* Wenjun Zong [email protected] Hanzhong Liu [email protected] 1
Center for Precision Engineering, Harbin Institute of Technology, P.O. Box 413, Harbin 150001, People’s Republic of China
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Vol.:(0123456789)
120
Page 2 of 13
Tribology Letters
(2020) 68:120
Graphic Abstract
Keywords Diamond friction · Nanofriction coefficient · Adhesive force · Size effect
1 Introduction Diamond has a tetrahedral cubic structure constructed from carbon atoms. This atomic structure provides diamond with excellent mechanical properties, e.g., an ultrahigh hardness, high strength and unmatched wear resistance [1], which lead to the widespread industrial applications of diamond, ranging from cutting tools to bearings in microelectromechanical systems (MEMS) [2]. In addition, functional parts with sliding surfaces, e.g., piston rings [3] and triboelectric nanogenerators [4], are usually coated with a thin diamond film to enhance the wear resistance and consequently increase the service life. The latest report [5] declared that it can effectively reduce
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the discomfort experienced by patients when they undergo surgery by utilizing a scalpel coated with a diamond film because of its outstanding friction performance. The excellent tribological properties lead to widespread application potentials of diamond in new high-tech fields [6], and this material is attracting a substantial amount of attention. Their attempts and findings have provided insights into the tribological properties of diamond, which can be summarized as follows. At the macroscale, the friction coefficient of a diamond friction pair is far lower than that of most materials in the atmosphere, and i
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