A5030317011- High-pressure geophysics and materials
- Glass properties and applications
- Geological and Geochemical Analysis
- Crystal Structures and Properties
- Mineralogy and Gemology Studies
- Advanced NMR Techniques and Applications
- X-ray Diffraction in Crystallography
- Nuclear materials and radiation effects
- earthquake and tectonic studies
- Solid-state spectroscopy and crystallography
- Advanced ceramic materials synthesis
- Zeolite Catalysis and Synthesis
- Advanced Condensed Matter Physics
- NMR spectroscopy and applications
- Material Dynamics and Properties
- Clay minerals and soil interactions
- Metallurgical Processes and Thermodynamics
- Hydrocarbon exploration and reservoir analysis
- Microwave Dielectric Ceramics Synthesis
- Boron and Carbon Nanomaterials Research
- Phase Equilibria and Thermodynamics
- Methane Hydrates and Related Phenomena
- Chemical Synthesis and Characterization
- Inorganic Fluorides and Related Compounds
- Ferroelectric and Piezoelectric Materials
Okayama University
2014-2024
Planetary Science Institute
2016-2022
Okayama Prefecture
2016
Tokyo Institute of Technology
1991-2011
Tohoku University
1996
Tokyo Metropolitan Institute of Gerontology
1996
University of Alberta
1989-1993
Institute of Inorganic Chemistry of the Slovak Academy of Sciences
1992
State University of New York
1989-1990
Stony Brook University
1989-1990
Subduction-zone magmatism is triggered by the addition of H 2 O-rich slab-derived components: aqueous fluid, hydrous partial melts, or supercritical fluids from subducting slab. Geochemical analyses island arc basalts suggest two signatures a melt and fluid. These liquids unite to fluid under pressure temperature conditions beyond critical endpoint. We ascertain endpoints between sediment high-Mg andesite (HMA) melts located, respectively, at 83-km 92-km depths using an in situ observation...
Coordination and local geometry around Si cations in silicate liquids are of primary importance controlling the chemical physical properties magmas. Pressure-induced changes from fourfold to sixfold coordination glass samples quenched has been detected with (29)Si magic-angle spinning nuclear magnetic resonance spectrometry. Samples Na(2)Si(2)O(5) 8 gigapascals 1500 degrees C contained about 1.5 percent octahedral Si, which was demonstrably part a homogeneous, amorphous phase. The dominant...
The second critical endpoint in the peridotite‐H 2 O system has been determined using an X‐ray radiography technique together with a Kawai‐type, double‐stage, multianvil driven by DIA‐type cubic press (SPEED‐1500) installed at SPring‐8, Japan. pressure of was appearance and disappearance round shape radiographic images changing experimental pressure. In experiments up to 3.6 GPa, two fluid phases (i.e., aqueous hydrous silicate melt) were observed. At 4.0 however, we could not distinguish...
Solid‐state 1 H nuclear magnetic resonance (NMR) spectroscopy has developed into a versatile, high‐resolution method for elucidating the detailed structures of both crystalline and amorphous materials. Here, we summarize our recent endeavors in applying this to glassy silicates related inorganic We first present updated correlations between chemical shift O⋯O H⋯O distances O–H⋯O hydrogen bonds, derived from comprehensive database containing original high‐quality fast magic angle spinning...
We have studied quenched high pressure phases in the CaSiO 3 system by x‐ray diffraction (XRD) and 29 Si MAS NMR, XRD study of previously reported “ε‐CaSiO phase” synthesized at 12 GPa 1500 °C reveals that it is actually a mixture β‐Ca 2 SiO 4 (larnite) unknown CaSi O 5 phase. This result supported NMR spectra. Furthermore, both data suggest phase may titanite (CaTiSiO ) structure which Ti replaced an octahedral Si. Samples from 15 1500°C consist mostly amorphous phase, but small amount...
In order to shed light on the proton distributions and order/disorder in high-pressure delta-Al(OH)3 delta-AlOOH phases, two-dimensional, high-resolution 1H CRAMPS (FSLG)-MAS NMR 27Al 3QMAS spectra have been obtained. For delta-Al(OH)3, CRAMPS-MAS revealed two peaks with an intensity ratio close 2:1. The MAS suggest a single Al site well-defined local structure. delta-AlOOH, indicate presence of H each. These results are consistent crystal structures refined from X-ray diffraction....
In situ observations of the ilmenite‐perovskite transition in MgSiO 3 were carried out a multianvil high‐pressure apparatus interfaced with synchrotron radiation. The phase boundary between ilmenite and perovskite temperature range 1300–1600 K was determined to be P (GPa) = 28.4(±0.4) ‐ 0.0029(± 0.0020)T (K) based on Jamieson's equation state gold [Jamieson et al., 1982] 27.3(±0.4) 0.0035(±0.0024)T Anderson's [Anderson 1989]. consistency our results, using state, previous studies obtained by...
Most of the earth's mantle is made up high-pressure silicate minerals that contain octahedrally coordinated silicon (Si VI ), but many thermodynamically important details cation site ordering remain unknown. Silicon-29 nuclear magnetic resonance (NMR) spectroscopy potentially very useful for determining short-range structure. A systematic study silicon-29 chemical shifts Si has revealed empirical correlations between shift and structure are in understanding several new calcium silicates. The...
Abstract We performed 1 H and 29 Si NMR infrared measurements, first-principles calculations to clarify the nature of OH defects in MgSiO 3 orthoenstatite. An orthoenstatite sample synthesized at 7 GPa 1200 °C from a composition + 0.1 wt% 2 O yielded two MAS peaks near 5.9 7.6 ppm that are correlated 2D spectra, bands 3361 3066 cm − correspond previously reported A3 A4 bands. The confirmed they due pair protons Mg (M2) vacancy. A1 A2 3687 3592 for low silica activities were arise four SiB...
Liquid B2O3 represents an archetypical oxide melt with a superhigh viscosity at the melting temperature. We present results of in situ x-ray diffraction study and measurements liquid under high pressure up to 8 GPa. Additionally, 11B solid state NMR spectroscopy glasses quenched from five different pressures has been carried out. Taken together, obtained provide understanding nature structural transformations B2O3. The fraction boroxol rings structure rapidly decreases pressure. From about...
We have applied one-dimensional (1D) 1H MAS NMR, 27Al → CP as well 2D triple-quantum (3Q) heteronuclear correlation (HETCOR) and high-resolution 3QMAS/HETCOR NMR techniques to KAlSi3O8 (Or), NaAlSi3O8 (Ab) NaAlSiO4 (Ne) glasses containing 0~2 wt% H2O shed light on the dissolution mechanisms of water in aluminosilicate melts (glasses). An Al Q3-OH group, characterized by chemical shifts 1.3-1.9 ppm, was identified for all hydrous glasses. Its abundance increases with bulk Al/Si ratio. The...