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Open Access Publications from the University of California

Tribological Phenomena at the Atomic Scale Interface: 2D materials and beyond

  • Author(s): Ye, Zhijiang
  • Advisor(s): Martini, Ashlie
  • et al.
Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Public License

Tribology is the science and engineering of friction, adhesion, wear and lubrication of sliding/interacting interfaces. It is truly interdisciplinary, as tribological properties (friction, wear, etc.) are directly related to the mechanical properties, thermal transport, electrical properties, and chemical reactions at interfaces. Generally, nanotribological studies, or examination of tribological phenomena at the nanometer length-scale, are important for two reasons: first, for fundamental understanding of interfacial phenomena on a small scale; and second, for the enhanced performance of nanoscale mechanical components as well as the development of next generation devices.

Lubricants are an important component of tribology for their ability to reduce friction and wear to save energy while increasing a machine's useful life. Solid lubricants, such as 2D materials (graphene, molybdenum disulfide, boron nitride) and soft metals/metal alloys, are especially useful for lubricating machine components that operate under extreme conditions (such as very high temperatures, very high applied pressures and very fast/slow sliding speeds). Under these conditions, most liquid/oil-based lubricants fail due to decomposition or oxidization at very high temperatures, or have reduced performance at very high pressure and very low sliding speeds. In this thesis, we use molecular dynamics simulations and atomic force microscope experiments to investigate tribological properties of solid lubricants under various conditions and additionally address some of the atomic scale mechanisms that contribute to thermal and electrical phenomena at the interface. Specifically, we discuss (1) tribological behavior on flat surfaces, (2) tribological behavior on surfaces with defects, (3) tribological behavior under extreme conditions, and (4) thermal and electrical transport at nanoscale interfaces. Our study provides insight to the molecular origins of interfacial phenomena and their application to next generation devices.

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