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Toshimori Sekine, Seminar, 3:00 PM, Mar. 13, 2014

Published: March 10, 2014

Topic:

High-pressure Phase Boundary, Hugoniot, and Thermodynamics

Background:

There are many known high-pressure phases transformations in solids. The phase boundary between low-pressure phase and high-pressure phase is defined thermodynamically based on the experimental data. Hugoniot measurements provide information of the phase transition, and discontinuity or kink in the plots of pressure-density and shock velocity-particle velocity may indicate a high-pressure structural change with a significant volume change. Some of the phase boundaries are inconsistent with the static high-pressure and high temperature data. There are several types of Hugoniots that indicate high-pressure phase transitions, depending on material and the reaction and phase transition mechanism. We summarize the relationship between Hugoniot and the thermodynamic phase boundary, taking into account some recent results on a hydrous magnesium silicate of antigorite. Recently a dense hydrous magnesium silicate phase (phase H) has been predicted and confirmed experimentally. A comparison of Hugoniot compression curve and sound velocity between the measured and calculated values has indicated that the dynamic decomposition products include phase H at pressures of 40-70 GPa and that water fluid comes out above a pressure of ~70 GPa. The phase boundary for phase H has a negative slope in the pressure-temperature plot. The Hugoniot curve for antigorite that display a phase transition to phase H is a characteristic feature that differs from the phase transitions with positive slopes. We will discuss the decomposition reactions for antigorite under shock loadings. Our findings have important implications for the role of antigorite as a water carrier into deeper mantle of the Earth and to hotter planets near the Sun.


Personal Profile:

Toshimori Sekine received his B. S. from Tokyo Institute of Technology (1976), and Ph.D. from Tokyo Institute of Technology (1979). He was awarded a distinguished achievement award of minister of science and technology, Japan, 2000 and Fellow of the American Physical Society, USA, 2003 for his work on thermodynamics of reactions at high pressure and high temperature. His research interest is focus on experimental investigation of interactions between materials and shock wave, Shock wave chemistry, and Geochemistry on impacts. His research was introduced in Nature v.391, p539 (1998), Nature Geoscience v2 January Backstroy (2009) and Nature Asia-pacific web February issue (2009).


He joined National Institute for Research in Inorganic Materials (Currently National Institute of Materials Science) at 1985, and is a senior scientist at the Institution since 2005. Now, He is a professor at Graduate School of Science, Hiroshima University, Japan. His total publications are more than 200 including patents and he is often received invited speeches in the APS conference on shock compression of condensed matter.


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