| AVS 62nd International Symposium & Exhibition | |
| Tribology Focus Topic | Thursday Sessions |
| Session TR+AS+NS+SS-ThA |
| Session: | Molecular Origins of Friction |
| Presenter: | Judith Harrison, United States Naval Academy |
| Authors: | J.A. Harrison, United States Naval Academy M. Fallet, United States Naval Academy K.E. Ryan, United States Naval Academy T. Knippenberg, High Point University S.H. Kim, Pennsylvania State University A. Al-Azizi, Pennsylvania State University |
| Correspondent: | Click to Email |
Atomic-scale wear in nanoscale contacts is of particular importance for tip-based nanomanufacturing applications. As a result, wear resistant materials, such as diamond-like carbon (DLC), have been used to coat AFM tips to improve the lifespan and reliability of AFM probes and surfaces. Unfortunately, the tribological performance of these materials is known to depend on environmental conditions, such as humidity levels. We have performed macroscopic and atomic force microscopy friction experiments and molecular dynamics (MD) simulations aimed at examining adhesion and wear of DLC in humid environments.
Macro-scale friction tests showed friction and transfer film dependence on humid conditions. Low humidity suppresses transfer film formation while keeping the friction low. Intermediate humidity, however, does not reduce transfer film formation and increases the friction. The effect of humidity on friction was found to agree with the adhesion dependence on relative humidity as measured with atomic force microscopy.
Because it is difficult to elucidate atomic-scale mechanisms via experimental methods, molecular dynamics simulations have been employed to examine this behavior. Adhesion and sliding simulations of non-hydrogenated, ultrananocrystalline diamond (UNCD) and DLC surfaces with various levels of hydrogen in the presence of water using the qAIREBO and the ReaxFF potentials have been performed. Because both of these potentials are able to model chemical reactions, the atomic-scale mechanisms responsible for adhesion and wear can be identified. Results obtained with both potentials will be compared to the experimental results.