Speaker
Dr
Astrid de Wijn
(SU Fysikum/Kemisk Fysik)
Description
Mechanical properties of crystalline materials are
ultimately determined by their atomic structure. A direct
consequence of the symmetry of the atomic surface structure
is anisotropy of friction and wear. We investigate the
anisotropy of friction theoretically, as well as
experimentally on graphitic surfaces. We find that the
anisotropy does not depend on the geometry of the sliding
object, only on that of the substrate. Friction vectors can
deviate significantly from the pulling directions. For
graphitic substrates, the strongest deviations are found for
pulling directions which lie almost along one zigzag
direction of the honeycomb structure, the preferred sliding
directions. Numerical simulation and further theory reveal
the role of temperature and of the two-dimensional character
of the surface potential for the friction anisotropy. The
friction is determined by atomic stick-slip events along and
across molecular rows determine direction and magnitude of
friction.
(Collaboration with Balakrishna S. G. and R. Bennewitz, INM
- Leibniz Institute for New Materials, Germany)
[1] Preferential sliding directions on graphite, Balakrishna
S.G., Astrid S. de Wijn, and Roland Bennewitz, Phys. Rev. B
89, 245440 (2014).
