HR: 1340h
AN: MR13A-0060    [Abstracts]
TI: In situ viscosity measurements of liquid Fe-S alloys at high pressures
AU: * Funakoshi, K
EM: funakosi@spring8.or.jp
AF: Japan Synchrotron Radiation Institute, Koto 1-1-1, Mikazuki, Sayo-gun, Hyogo, 679-5198 Japan
AU: Nozawa, A
EM: nozawa@spring8.or.jp
AF: Japan Synchrotron Radiation Institute, Koto 1-1-1, Mikazuki, Sayo-gun, Hyogo, 679-5198 Japan
AB: The viscosity of liquid Fe-S alloys is an important for understanding the properties and dynamics of the Earth's outer core. Recent measurements of the viscosity of liquid Fe-S alloys have showed the very low values (<10^-2 Pa-s), however, the accuracies are not so good for determining the precise activation energy and activation volume at high pressure. An X-ray radiography technique with synchrotron radiation is very useful for the falling sphere viscosity measurement, because it enables us in situ observation of the sinking process and determination of the reliable viscosity coefficient. We measured the viscosities of liquid Fe-S alloys (Fe₇₃S₂₇, Fe₈₀S₂₀, Fe₉₀S₁₀) combining with the X-ray radiography and a multi-anvil press (SPEED-1500) at the SPring-8 (BL04B1 beamline). Precise viscosities have been obtained up to 14 GPa, and the viscosities decrease with increasing the temperature and the sulfur content. These take a minimum value at close to the 20% sulfur content (eutectic composition). The activation energy and the activation volume have been determined from the P-T dependences of the viscosities using a non-linear least square fitting. The activation energies of liquid Fe-S alloys increase with the iron content. The viscosities of the Earth's outer core have been calculated between the inner core boundary and the core-mantle boundary using the activation energy and the activation volume of Fe₉₀S₁₀. They are four orders of magnitude higher than the viscosities of liquid iron. These results imply that the addition of sulfur into the liquid iron is significantly large effect of the viscosity in the Earth's outer core.
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: Fall Meeting 2005