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 (email@example.com,
see website at stm.lbl.gov/research/Quasicrystal/Quasicrystal.html).
(Paper NS-WeA9, laypaper at http://www2.avs.org/symposium/anaheim/pressroom/park.pdf