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Condensed Matter Seminars

ics Condensed Matter
Thursday, November 8, 2001
4:00 PM
Physics Building, Room 204
Note special time.
Note special room.
Robert F. Berg [Host: G. Hess]
NIST
"Polymer-like viscosity near the critical point of xenon"
ABSTRACT:
This talk will describe two measurements of viscosity very close to xenon's critical point. The first experiment measured the viscosity increase caused by near-critical conditions. It revealed that, close to the critical point, xenon is partly elastic: It can stretch as well as flow. The second experiment, planned for 2002, will look for the shear-rate-induced viscosity decrease predicted by theory. Such "viscoelasticity" and "shear-thinning" are ordinarily seen only in much more complicated fluids such as polymer solutions. Both experiments are designed for the Space Shuttle. We required the Space Shuttle's microgravity because Earth's gravity compresses any fluid near its critical point. A layer of fluid even as thin as a dime collapses under its own weight, increasing the density at the bottom of the sample and distorting the data. Conducting the experiments on the Space Shuttle reduces these density differences by a factor of 100.

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