HR: 15:25h
AN: MR13A-08    [Abstracts]
TI: Diamond-Cell Measurements of Fluid Viscosity and Activation Energy at High Pressures
AU: * Grocholski, B
EM: brent@eps.berkeley.edu
AF: Department of Earth and Planetary Science, University of California, Berkeley, CA 94720 United States
AU: Jeanloz, R
EM: jeanloz@berkeley.edu
AF: Department of Earth and Planetary Science, University of California, Berkeley, CA 94720 United States
AB: Significant advances in high pressure-temperature experiments now make it possible to measure the viscosity of fluids at deep-planetary conditions. This is important because viscosity is often the rate-limiting factor for internal planetary dynamics, yet it is poorly understood from a theoretical perspective. New rolling-sphere measurements on methanol and a 4:1 methanol:ethanol mixture, using a resistance-heated diamond-cell, yield an activation energy and volume of 18 to 99 ($\pm$ 5) kJ/mol and 4.5 to 3.2 ($\pm$ 0.4) cm$^{3}$/mol over the pressure-temperature range of 0 to 6.5 GPa and 298 to 338 K. These alcohols are potential analogs for structured liquids, such as the silicate melts of the Earth's interior, and are also important as pressure transmitting media in diamond-cell experiments. Our data are in good agreement with previous measurements at room temperature, and we find that both activated-state (Arrhenius) and free-volume models fit the data within our uncertainties. Extrapolation based on these models yields glass-transition pressures (10$^{12}$ Pa s) of 19.7 ($\pm$ 0.5) GPa and 11.0 ($\pm$ 0.8) GPa at room temperature. Note that our measurements extend beyond the equilibrium crystallization pressure of methanol, 3.6 GPa at 300 K, so provide information about viscous relaxation of the metastable liquid state.
DE: 3909 Elasticity and anelasticity
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
DE: 3994 Instruments and techniques
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting