HR: 1340h
AN: MR13A-0056    [Abstracts]
TI: Effect of pressure on viscosity of liquid Fe-alloys up to 16 GPa
AU: * Terasaki, H
EM: terasaki@ganko.tohoku.ac.jp
AF: Institute of Mineralogy, Petrology and Economic Geology, Tohoku University, Aoba-ku, Aramaki, Aoba, Sendai, 980-8578 Japan
AU: Ohtani, E
EM:
AF: Institute of Mineralogy, Petrology and Economic Geology, Tohoku University, Aoba-ku, Aramaki, Aoba, Sendai, 980-8578 Japan
AU: Suzuki, A
EM:
AF: Institute of Mineralogy, Petrology and Economic Geology, Tohoku University, Aoba-ku, Aramaki, Aoba, Sendai, 980-8578 Japan
AU: Nishida, K
EM:
AF: Institute of Mineralogy, Petrology and Economic Geology, Tohoku University, Aoba-ku, Aramaki, Aoba, Sendai, 980-8578 Japan
AU: Sakamaki, T
EM:
AF: Institute of Mineralogy, Petrology and Economic Geology, Tohoku University, Aoba-ku, Aramaki, Aoba, Sendai, 980-8578 Japan
AU: Shindo, S
EM:
AF: Institute of Mineralogy, Petrology and Economic Geology, Tohoku University, Aoba-ku, Aramaki, Aoba, Sendai, 980-8578 Japan
AU: Funakoshi, K
EM:
AF: Japan Synchrotron Research Institute, Kouto 1-1-1, Mikazuki, Hyogo, 679-5198 Japan
AB: Viscosity of liquid Fe-alloy is closely related to a convection behavior of the Earth's liquid outer core and also time scale of planetary core formation. In previous studies, viscosity of liquid Fe-S has been measured up to 7 GPa using X-ray radiography falling sphere method [Terasaki et al. 2001]. However, some technical problems, such as chemical reaction between the metal marker sphere and the Fe-alloy sample and insufficient image recording time for less viscous material, have been suggested. In this study, we have measured the viscosity of Fe-S and Fe-C liquids without those problems by using novel techniques combined with in situ X-ray radiography falling sphere method and extended the pressure range to 16 GPa. Falling sphere viscometry was carried out under high pressure and temperature using high speed CCD camera with 1500 ton Kawai-type multi-anvil device at BL04B1, SPring-8 in Japan. Starting compositions of Fe-alloy were Fe₇₈S₂₂ and Fe₈₆C₁₄ which correspond to near eutectic compositions at the experimental pressures. Viscosity marker sphere, which was made of Re or Pt, was coated by alumina in order to prevent the reaction between the sphere and the Fe-alloy sample. Falling sphere images were obtained with recording rate of 50 - 125 frame/second. Viscosity of liquid Fe-S was measured up to 16.1 GPa and 1763 K. Measured viscosity coefficients were in the range of 8.8 - 9.2 mPa-s which indicates that the activation volume of viscous flow is approximately a half of the previous estimations (1.5 cm³/mol). Viscosity of liquid Fe-C was measured up to 5 GPa and 1843 K. Viscosity coefficients are 4.7 - 4.9 mPa-s. Activation volume of Fe-C liquid is estimated to be 0.8 cm³/mol. This pressure dependence is consistent with the result of Lucas (1964) measured at ambient pressure. Consequently, viscosity of Fe-alloy liquids are likely to stay small in the Earth's interior and there is no large difference in viscosity coefficient and activation volume between Fe-S and Fe-C eutectic liquids in the range of measurements.
DE: 1015 Composition of the core
DE: 3924 High-pressure behavior
DE: 5139 Transport properties
DE: 8125 Evolution of the Earth (0325)
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005