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Sapphire: a kinking nonlinear elastic solid
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|Title: ||Sapphire: a kinking nonlinear elastic solid|
|Authors: ||Basu, S.|
Barsoum, Michel W.
Kalidindi, Surya R.
|Issue Date: ||16-Mar-2006|
|Publisher: ||American Institute of Physics|
|Citation: ||Journal of Applied Physics 99: pp. 063501-7.|
|Abstract: ||Kinking nonlinear elastic (KNE) solids are a recently identified large class of solids that deform
fully reversibly by the formation of dislocation-based kink bands [Barsoum et al. Phys. Rev. Lett.
92, 255508 2004 .] We further conjectured that a high c/a ratio—that ensures that only basal slip
is operative—is a sufficient condition for a solid to be KNE. The c/a ratio of sapphire is 2.73 and
thus, if our conjecture is correct, it should be a KNE solid. Herein by repeatedly loading—up to 30
times—the same location of sapphire single crystals of two orientations—A and C—with a 1 m
radius spherical nanoindenter, followed by atomic force microscopy, we showed that sapphire is
indeed a KNE solid. After pop-ins of the order of 100 nm, the repeated loadings give rise to fully
reversible, reproducible hysteresis loops wherein the energy dissipated per unit volume per cycle Wd
is of the order of 0.5 GJ/m3. Wd is due to the back and fro motion of the dislocations making up the
incipient kink bands that are fully reversible. The results presented here strongly suggest that—like
in graphite and mica—kink bands play a more critical role in the room temperature constrained
deformation of sapphire than had hitherto been appreciated. Our interpretation is also in agreement
with, and can explain most, recent nanoindentation results on sapphire.|
|Appears in Collections:||Faculty Research and Publications (MSE)|
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