Japan Geoscience Union Meeting 2018

Presentation information

[EE] Oral

S (Solid Earth Sciences) » S-IT Science of the Earth's Interior & Tectonophysics

[S-IT18] Planetary cores: Structure, formation, and evolution

Mon. May 21, 2018 1:45 PM - 3:15 PM A11 (Tokyo Bay Makuhari Hall)

convener:Hidenori Terasaki(Graduate School of Science, Osaka University), Eiji Ohtani(Department of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University), William F McDonough (共同), George Helffrich(Earth-Life Science Institute, Tokyo Institute of Technology), Chairperson:Terasaki Hidenori, McDonough William(University of Maryland / Tohoku University)

2:30 PM - 2:45 PM

[SIT18-04] Elastic wave velocity of Fe-Si alloy at high pressure

*Tatsuya Sakamaki1, Hidenori Terasaki2, Yuki Shibazaki1, Hiromu Tobe1, Yuta Shimoyama2, Yuji Higo3, Akio Suzuki1 (1.Tohoku University, 2.Osaka University, 3.JASRI)

Keywords:iron-silicon alloy, elastic wave velocity, high pressure

As an approach to understanding planetary cores, a determination of the elastic property of iron-alloys is powerful. Here, we report both of elastic velocity and density of Fe-Si alloy up to 6 GPa and 1873 K using ultrasonic technique combining with synchrotron x-ray at BL04B1 of SPring-8. In this experiment, Fe-10at%Si system showed three phases (bcc, fcc, bcc+fcc) depending on pressure and temperature conditions. This indicated that a stability field of fcc phase is large compared to ambient condition. Based on the velocity measurements, negative temperature effect on the velocity was found clearly. The phase transition from bcc to fcc around 6 GPa and 1000 K caused small changes in properties: the density and velocity (Vp) jump are 1.2% and 0.8%, respectively. Comparing with pure-iron (bcc), the bcc-Fe-Si is 10% faster at the same density. These knowledges can help us to analyze new planetary observations in the near future.