Novel Quasicrystal Friction Properties

Quasicrystals, solid materials possessing an odd five-fold or ten-fold symmetry (making the ten-fold solid partly periodic and partly aperiodic) and which form dodecahedral grains, seem to present less friction than do many other materials. For the past ten years no explanation for this has been found; does it arise from some macroscopic cause---hardness or surface chemistry, say---or from some fundamental property related to the exotic quasicrystal structure. J.Y. Park and his colleagues at LBL and Ames Lab have looked at this issue by dragging a probe microscope across a sample.

At last week's AVS Science & Technology symposium in Anaheim, Park reported finding was a highly anisotropic friction for his Al-Ni-Co quasicrystal: low friction when sliding the probe in the aperiodic direction and high friction when sliding along the periodic direction (jypark@lbl.gov, see website at stm.lbl.gov/research/Quasicrystal/Quasicrystal.html). (Paper NS-WeA9, laypaper at http://www2.avs.org/symposium/anaheim/pressroom/park.pdf )