日時 ： ２００９年５月２８日（金）※16：30～
場所 ： 愛媛大学総合研究棟Ⅰ 4F 共通会議室（理学部構内）
要 旨
MgSiO3 is one of the most common rock-forming components in the Earth. However, due to its refractory nature and fragility in the molten state, direct investigation of melt properties at extreme pressures and temperatures are exceedingly challenging. Alternatively, properties of the (supercooled) liquid at high pressure can be investigated by relaxing the glass on heating near the glass transition temperature (region), Tg. Volumetric and structural changes in MgSiO3 glass under sub-Tg to super-Tg conditions between 2.0 and 8.5 GPa provide insights into structural relaxation for fragile liquids under compression.
MgSiO3 glass was prepared by melting crystalline MgSiO3 at ~1873 K and quenching the liquid in air. Glass cylinders are heat-treated at high pressure in the Walker 6/8 multi anvil apparatus. Samples were compressed to the desire pressure and heated to the annealing temperature where they were held for 5 minutes. Pressure was released at >10 GPa/min immediately following the quench. Densities of recovered samples were measured by the Archimedes methods. Additionally, Raman and NMR spectroscopy were performed to examine the structural change with density.
The general trend of the densification with temperature are similar for each pressure and can be categorized as follows: (1) a low temperature interval where density changes on compression are recovered within 0.7% of the initial density, (2) an intermediate temperature interval where permanent densification with temperature is greatest and (3) a high temperature interval where the change in density with annealing temperature is significantly reduced. Since the relaxation begins abruptly just below the Tg at the pressure, the temperature at which the slope of densification changes suggests a limiting temperature for Tg. This limit is found to decrease with increasing pressure expanding the temperature interval of the glass transition. The result of Raman and NMR spectroscopy, which show the structural change of MgSiO3 glass with pressure and temperature will be also presented.
問い合わせ先：土屋 卓久 TEL （089）927-8198
E-mail takut@sci.ehime-u.ac.jp
