Ultrastrong Carbon Thin Films from Diamond to Graphene under Extreme Conditions: Probing Atomic-Scale Interfacial Mechanisms to Achieve Ultralow Friction and Wear

Abstract

The project goal was to gain a fundamental understanding of how to achieve low friction and wear in ultrastrong carbon-based materials. Experimentally, an in situ nanotribometry method was used, which enables nanoscale visualization of sliding contacts inside the transmission electron microscope (TEM). These experiments are in turn modelled computationally using molecular dynamics, allowing better understanding of the atomic-scale processes controlling friction and wear. The focus was on the behavior of silicon-silicon, silicon-diamond, and diamond-like-carbon (DLC)-diamond interfaces. For silicon-silicon interfaces, nanocontacts showed a sliding-history and stress-dependent adhesion, where sliding increased adhesion by more than 16 times. This effect was enhanced by the applied normal stress. This is explained in terms of stress-activated covalent bond breaking that only occurs during sliding. For silicon in sliding contact with diamond, the observed adhesion increases with applied stress and speed. This dependence is explained in terms of tip geometry changes due to atomic-scale plasticity. For DLC interfaces, wear during sliding and the evolution of adhesion forces were characterized. Wear was measured as a function of load and sliding distance. Gradual wear with sliding was observed with the wear rate increasing with the average contact stress, but not following the classic Archard's wear law nor to recently observed behavior following transition state theory. The wear behavior over the full range of stresses is well described by multi-bond wear model that exhibits a change from Archard-like behavior at high stresses to a transition state theory description at lower stresses.

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Document Details

Document Type
Technical Report
Publication Date
Mar 19, 2019
Accession Number
AD1077386

Entities

People

  • Reau-ren Jeng

Organizations

  • National Chung Cheng University

Tags

Communities of Interest

  • Advanced Electronics

DTIC Thesaurus Topics

  • Air Force Research Laboratories
  • Chemical Reactions
  • Covalent Bonds
  • Electron Microscopy
  • Friction
  • Mechanical Engineering
  • Mechanical Properties
  • Mechanics
  • Modulus Of Elasticity
  • Molecular Dynamics
  • Raman Spectra
  • Raman Spectroscopy
  • Spectroscopy
  • Surface Properties
  • Surface Roughness
  • Two Dimensional
  • United States Naval Academy

Readers

  • Materials Science and Engineering.
  • Tribology (the study of the boundary interaction between sliding surfaces, lubrication, wear and friction).

Technology Areas

  • Microelectronics