Phase Changes Induced by Guest Orientational Ordering on Methane and Hydrogen Hydrates under Low Temperatures and High Pressures

Low-temperature and high-pressure experiments were performed with filled ice structures of methane hydrate and hydrogen hydrate under pressure and temperature conditions of 2.0-77 GPa and 30-300 K and 5.0-50 GPa and 10-300 K, respectively, using diamond anvil cell and helium-refrigerator cryostat. I...

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Bibliographic Details
Published inThe Review of High Pressure Science and Technology Vol. 24; no. 4; pp. 278 - 287
Main Authors HIRAI, Hisako, TANAKA, Takehiko, KAGAWA, Shingo, MATSUOKA, Takahiro, OHISHI, Yasuo, HIRAO, Naohisa, YAGI, Takehiko, OHTAKE, Michika, YAMAMOTO, Yoshitaka
Format Journal Article
LanguageJapanese
English
Published Tokyo The Japan Society of High Pressure Science and Technology 01.01.2014
Japan Science and Technology Agency
Subjects
DAC
Diamond anvil cells
Diffraction
guest orientational ordering
high pressure
Hydrates
Hydrogen
hydrogen hydrate
low temperature
Methane
methane hydrate
Methane hydrates
Order disorder
phase transition
X-rays
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Summary:Low-temperature and high-pressure experiments were performed with filled ice structures of methane hydrate and hydrogen hydrate under pressure and temperature conditions of 2.0-77 GPa and 30-300 K and 5.0-50 GPa and 10-300 K, respectively, using diamond anvil cell and helium-refrigerator cryostat. In-situ X-ray diffractometry and Raman spectroscopy revealed that orientational ordering of guest molecules occurred from disordered-rotation state at low temperature and high pressure, and that the guest ordering induced structural changes. For hydrogen hydrate, cubic structure was deformed to a tetragonal structure, while for methane hydrate axial ratios of orthorhombic structure were remarkably changed within the same orthorhombic structure.
Bibliography:ObjectType-Article-1
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ISSN:0917-639X
1348-1940
DOI:10.4131/jshpreview.24.278