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O: Fachverband Oberflächenphysik

O 88: Symposium Nanotribology

O 88.4: Hauptvortrag

Freitag, 26. März 2010, 11:45–12:15, H1

Friction at the Nanoscale: Insights from Atomistic Simulations — •Izabela Szlufarska, Yifei Mo, Yun Liu, and Maneesh Mishra — Department of Materials Science & Engineering, University of Wisconsin, Madison, WI 53706

Controlling tribological properties requires understanding a bewildering array of interrelated mechanisms, including elastic instabilities, plastic deformation, fracture, and chemical reactions. Large scale atomistic simulations have been used to unravel some of these mechanisms. Tribological studies are typically divided into a wearless regime, where deformation is primarily elastic, and a wear regime where permanent deformation occurs. For wearless contacts, I will use the example of H-terminated diamond surface to illustrate the breakdown of continuum mechanics at the nanoscale and to demonstrate that nanoscale contacts can be described using macroscale roughness theories. This discovery lays a foundation for unified friction laws across all length scales. I will also discuss effects of surface chemistry on friction, such as frictional dissipation in the presence of trace moisture. In the wear regime I will focus on the origins of recently observed ductile wear in nominally brittle SiC. Although this ductile wear holds potential for greatly enhancing the ease of machining of high-performance ceramics, its origin is still an open question. I will evaluate potential mechanisms for ductile wear, including the possibility of transformation to more ductile phases, dislocation mediated plasticity, and nanoindentation-induced amorphization.