Volume 09, No.3
目次 / Table of Contents
May issue 2004
1. SPring-8の現状／PRESENT STATUS OF SPring-8
2. 最近の研究から／FROM LATEST RESEARCH
愛媛大学 地球深部ダイナミクス研究センター Geodynamics Research Center, Ehime University
- Abstract
- Carbonates are important constituents of marine sediments and play an important role in the long-term recycling of carbon in the Earth’s deep interior via subduction of oceanic plates. We studied the stability of magnesite, the major carbonate in the mantle, by in situ X-ray diffraction measurements using a combination of laser-heated diamond anvil cell (LHDAC) and synchrotron radiation at BL10XU. We found that magnesite is stable at pressure up to ~115 GPa, at temperatures of ~ 2100 - 2200K, whereas it transforms to a new phase at higher pressures. The diffraction data of the new phase, magnesiteⅡ, are reasonably indexed on the basis of an orthorhombic system, yielding a density of 5.2 g/cm3 at 119 GPa, at room temperature. The present results suggest that magnesite and its high-pressure form are the major hosts for carbon throughout the most parts of the Earth’s lower mantle.
[1]（財）高輝度光科学研究センター 利用研究促進部門Ⅰ Materials Science Division, JASRI、[2]日本原子力研究所 中性子利用研究センター Neutron Science Research Center, Japan Atomic Energy Research Institute、[3]東京理科大学 基礎工学部 Faculty of Industrial Science and Technology, Tokyo University of Science
- Abstract
- Inorganic glasses normally exhibit a network of interconnected covalent-bonded structural elements that has no long-range order. In silicate glasses the network formers are based on SiO4-tetrahedra of which the interconnectivity is realized by sharing the oxygen atoms at the corners. Conventional wisdom then implies that alkaline and alkaline-earth orthosilicate materials cannot be vitrified because they do not contain sufficient network forming SiO2 to establish the needed interconnectivity. We have studied a bulk magnesium orthosilicate glass obtained by levitation melting- and-cooling. We find that the role of network former is largely taken on by corner- and edge-sharing ionic magnesium species that adopt 4-, 5- and 6-coordination with oxygen.
京都大学 工学研究科 Graduate School of Engineering, Kyoto University
3. 研究会等報告／WORKSHOP AND COMMITTEE REPORT
4. 談話室・ユーザー便り／OPEN HOUSE・A LETTER FROM SPring-8 USERS
（財）高輝度光科学研究センター 総務部 Personnel Section General Affairs Division, JASRI
5. 告知板／ANNOUNCEMENTS
6. 播磨科学公園都市ガイドブック／HANDY TIPS AROUND HARIMA SCIENCE GARDEN CITY
その他／MISC
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