Inelastic Neutron Scattering and Neutron Diffraction Studies of Gas Hydrates
Gas hydrates (clathrates) are elevated-pressure (P) and low-temperature (T) solid phases in which gas molecule guests are physically incorporated into hydrogen-bonded, cage-like ice host frameworks. Natural clathrates have been found worldwide in permafrost and in ocean floor sediments, as well as i...
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ftunivarizona:oai:repository.arizona.edu:10150/194926 2023-05-15T16:37:51+02:00 Inelastic Neutron Scattering and Neutron Diffraction Studies of Gas Hydrates Tait, Kimberly Downs, Robert T. Johnson, Roy Seedorff, Eric Daemen, Luke Prewitt, Charles 2007 http://hdl.handle.net/10150/194926 EN eng The University of Arizona. http://hdl.handle.net/10150/194926 659747157 2044 Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. text Electronic Dissertation 2007 ftunivarizona 2020-06-14T08:04:46Z Gas hydrates (clathrates) are elevated-pressure (P) and low-temperature (T) solid phases in which gas molecule guests are physically incorporated into hydrogen-bonded, cage-like ice host frameworks. Natural clathrates have been found worldwide in permafrost and in ocean floor sediments, as well as in the outer solar system (comets, Mars, satellites of the gas giant planets). Diffraction patterns have been collected of gas hydrates at various methane and ethane compositions by preparing samples in an ex situ gas hydrate synthesis apparatus, and CO₂ gas hydrates were prepared in situ to look at the kinetics of formation. Storage of hydrogen in molecular form within a clathrate framework has been one of the suggested methods for storing hydrogen fuel safely, but pure hydrogen clathrates H₂(H₂O)₂ form at high pressures. It has been found that mixed clathrates (a stabilizer molecule in the large cage) and hydrogen gas together can reduce the pressures and temperatures at which these materials form. In situ neutron inelastic scattering experiments on hydrogen adsorbed into a fully deuterated tetrahydrofuran water ice clathrate show that the adsorbed hydrogen has three rotational excitations (transitions between J = 0 and 1 states) at approximately 14 meV in both energy gain and loss. These transitions could be unequivocally assigned the expected slow conversion from ortho- to para-hydrogen resulted in a neutron energy gain signal at 14 meV, at a temperature of 5 K (kT= 0.48 meV). A doublet in neutron energy loss at approximately 28.5 meV are interpreted as J = 1 → 2 transitions. In situ neutron inelastic scattering experiments on hydrogen adsorbed into ethylene oxide, a structure I former, were also carried out at the Los Alamos Neutron Scattering Center (LANSCE). There is convincing evidence (shifted rotational mode of molecular hydrogen) that hydrogen is capable of diffusing in the small cages of ethylene oxide clathrate. Values are also obtained for the librational modes of enclathrated ethylene oxide and several water translation modes. Also reported for the first time are the internal modes (higher frequencies) of ethylene oxide in ethylene oxide clathrate as measured by inelastic neutron scattering. Doctoral or Postdoctoral Thesis Ice permafrost The University of Arizona: UA Campus Repository |
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The University of Arizona: UA Campus Repository |
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English |
description |
Gas hydrates (clathrates) are elevated-pressure (P) and low-temperature (T) solid phases in which gas molecule guests are physically incorporated into hydrogen-bonded, cage-like ice host frameworks. Natural clathrates have been found worldwide in permafrost and in ocean floor sediments, as well as in the outer solar system (comets, Mars, satellites of the gas giant planets). Diffraction patterns have been collected of gas hydrates at various methane and ethane compositions by preparing samples in an ex situ gas hydrate synthesis apparatus, and CO₂ gas hydrates were prepared in situ to look at the kinetics of formation. Storage of hydrogen in molecular form within a clathrate framework has been one of the suggested methods for storing hydrogen fuel safely, but pure hydrogen clathrates H₂(H₂O)₂ form at high pressures. It has been found that mixed clathrates (a stabilizer molecule in the large cage) and hydrogen gas together can reduce the pressures and temperatures at which these materials form. In situ neutron inelastic scattering experiments on hydrogen adsorbed into a fully deuterated tetrahydrofuran water ice clathrate show that the adsorbed hydrogen has three rotational excitations (transitions between J = 0 and 1 states) at approximately 14 meV in both energy gain and loss. These transitions could be unequivocally assigned the expected slow conversion from ortho- to para-hydrogen resulted in a neutron energy gain signal at 14 meV, at a temperature of 5 K (kT= 0.48 meV). A doublet in neutron energy loss at approximately 28.5 meV are interpreted as J = 1 → 2 transitions. In situ neutron inelastic scattering experiments on hydrogen adsorbed into ethylene oxide, a structure I former, were also carried out at the Los Alamos Neutron Scattering Center (LANSCE). There is convincing evidence (shifted rotational mode of molecular hydrogen) that hydrogen is capable of diffusing in the small cages of ethylene oxide clathrate. Values are also obtained for the librational modes of enclathrated ethylene oxide and several water translation modes. Also reported for the first time are the internal modes (higher frequencies) of ethylene oxide in ethylene oxide clathrate as measured by inelastic neutron scattering. |
author2 |
Downs, Robert T. Johnson, Roy Seedorff, Eric Daemen, Luke Prewitt, Charles |
format |
Doctoral or Postdoctoral Thesis |
author |
Tait, Kimberly |
spellingShingle |
Tait, Kimberly Inelastic Neutron Scattering and Neutron Diffraction Studies of Gas Hydrates |
author_facet |
Tait, Kimberly |
author_sort |
Tait, Kimberly |
title |
Inelastic Neutron Scattering and Neutron Diffraction Studies of Gas Hydrates |
title_short |
Inelastic Neutron Scattering and Neutron Diffraction Studies of Gas Hydrates |
title_full |
Inelastic Neutron Scattering and Neutron Diffraction Studies of Gas Hydrates |
title_fullStr |
Inelastic Neutron Scattering and Neutron Diffraction Studies of Gas Hydrates |
title_full_unstemmed |
Inelastic Neutron Scattering and Neutron Diffraction Studies of Gas Hydrates |
title_sort |
inelastic neutron scattering and neutron diffraction studies of gas hydrates |
publisher |
The University of Arizona. |
publishDate |
2007 |
url |
http://hdl.handle.net/10150/194926 |
genre |
Ice permafrost |
genre_facet |
Ice permafrost |
op_relation |
http://hdl.handle.net/10150/194926 659747157 2044 |
op_rights |
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
_version_ |
1766028148110000128 |