An ex-situ study of retained structural changes and densification in oxide glasses recovered from high pressure and temperature using NMR spectroscopy
Abstract/Contents
- Abstract
- This study attempts to understand the pressure effects on the structure and density of glasses recovered from 1-3 GPa pressure using 27Al, 11B, 29Si and 23Na MAS NMR spectroscopy. A quantitative spectroscopic study of the pressure-induced structural changes and densification is conducted on aluminosilicate and aluminoborosilicate glass compositions. We have demonstrated that high-pressure experiments in solid media pressure apparatus conducted at high-pressure and near the glass transition temperature retain much of the pressure-induced structural changes and densification compared to high-pressure experiments above the melting temperature. Our study of Na, Ca and Mg aluminosilicate glasses show that the role of non-bridging oxygen (NBO) in pressure-induced structural changes varies systematically upon changing modifier from Na to Ca to Mg. The network cation coordination (Al) increase are larger for the NBO-rich composition compared to NBO-poor composition in Na aluminosilicate glasses, while both NBO-rich and poor Mg aluminosilicate glasses showed no apparent difference in aluminum coordination increase. In Ca aluminoborosilicate glasses with varying B/Si ratio, we observe both aluminum and boron coordination to rise with pressure. However, the average aluminum coordination and densification increases were larger for the high boron composition compared to that of low boron. In this thesis, we propose a mechanism that describe such interaction between boron and aluminum network cations. We also look at aluminoborosilicate glasses with varying modifier from Ca2+ to La3+ to Y3+ studying the effect of modifier field strength on network cation coordination increases with pressure. Our results show that network cation coordination increases (B and Al) are dramatically larger for smaller and highly charged modifier cations (La and Y) compared to Ca.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2017 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Bista, Saurav |
|---|---|
| Associated with | Stanford University, Department of Geological and Environmental Sciences. |
| Primary advisor | Stebbins, Jonathan Farwell |
| Thesis advisor | Stebbins, Jonathan Farwell |
| Thesis advisor | Brown, Gordon |
| Thesis advisor | Mao, Wendy (Wendy Li-wen) |
| Advisor | Brown, Gordon |
| Advisor | Mao, Wendy (Wendy Li-wen) |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Saurav Bista. |
|---|---|
| Note | Submitted to the Department of Geological and Environmental Sciences. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2017. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2017 by Saurav Bista
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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