a1 Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California—Berkeley, Berkeley, California 94720
a2 Ames Laboratory & Department of Chemistry, Iowa State University, Ames, Iowa 50011
a3 Austrian Centre of Competence for Tribology Research GmbH, A-2700 Wiener Neustadt, Austria; and Austrian Research Centre-Seibersdorf Research GmbH, A-2444 Seibersdorf, Austria
a4 Laboratoire de Science et Génie des Matériaux et de Métallurgie (LSG2M), Institut Jean Lamour [FR2797 Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Lorraine (INPL)-Université Henri Poincaré (UHP)], Nancy-Université Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France
We show that friction anisotropy is an intrinsic property of the atomic structure of Al–Ni–Co decagonal quasicrystals and not only of clean and well-ordered surfaces that can be prepared in vacuum [J.Y. Park et al., Science 309, 1354 (2005)]. Friction anisotropy is manifested in both nanometer-size contacts obtained with sharp atomic force microscope tips and macroscopic contacts produced in pin-on-disk tribometers. We show that the friction anisotropy, which is not observed when an amorphous oxide film covers the surface, is recovered when the film is removed due to wear. Equally important is the loss of the friction anisotropy when the quasicrystalline order is destroyed due to cumulative wear. These results reveal the intimate connection between the mechanical properties of these materials and their peculiar atomic structure.
(Received January 10 2008)
(Accepted February 26 2008)