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Long-term fuel solutions : a solid state NMR investigation of borosilicate glasses and the development of ZSM-22 coatings
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Barnsley, Kristian Edward (2020) Long-term fuel solutions : a solid state NMR investigation of borosilicate glasses and the development of ZSM-22 coatings. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3517950~S15
Abstract
With the global fossil fuel supply running on borrowed time, it is clear that the development of alternative energy solutions is of vital importance. Clean renewable energy sources are often the preference when selecting alternatives, however limitations on the implementation of technologies such as wind and solar energy means that nuclear energy and more classical fuelbased methods remain a key component of any solution. The work presented in this thesis
concerns the development of two materials central to such solutions.
The first group of materials of interest are borosilicate glasses, which can serve as a waste form for high-level nuclear waste. Given how long nuclear waste can remain hazardous for, effective and efficient waste storage is vital for nuclear power to remain a long-term solution. These materials were studied in two stages using solid state NMR. Firstly, a set of more
compositionally simple glasses were studied, containing only boron, silicon and sodium oxides. This was done since the amorphous nature of the glasses can mean that structural insights gained though NMR can be limited by chemical disorder. By simplifying the glass
composition, the disorder can be reduced, and more accurate measurement of the fundamental structural blocks can be achieved. This study utilised fields ranging between 2.3 and 14.1 T as well as MQMAS and DOR NMR to identify and characterise four key structural boron units present in the glasses. The DOR NMR data also indicated the presence of a fifth, previously unobserved unit in one of these glasses. The second stage of this study looked at a more complex set of glasses, closer to the composition of a waste form glass, containing eight oxides. Here the effects of inserting rare-earth elements (REE) into the glass was investigated using 11B, 23Na 29Si and 95Mo NMR. A pronounced shift in the boron speciation was observed moving from tetrahedral to trigonal planar structures with the insertion of REE. This was explained via the movement of charge balancing Na+ ions away from the boron units and into the silicon network, grouping around the REE. The effects on boron speciation were observed to be more pronounced for smaller ionic radius REE. An improvement in the glasses chemical stability was also observed in correlation with these changes, something that is of great importance to safe nuclear waste storage.
The second group of materials of interest are zeolite catalysts for the conversion of methanol
to hydrocarbons (MTH). This catalytic process allows the creation of gasoline and other
valuable hydrocarbons to be produced from methanol, which in turn can easily be made from
any biomass. This study focuses on the formation of ZSM22 coatings, a zeolite that has been
receiving recent academic attention, to provide superior heat transfer during the MTH reaction. The novel synthesis of ZSM22 as a coating onto a titanium substrate was successfully achieved by use of a substrate housing and optimisation of autoclave rotation to provide maximum nutrient flow over nucleation sites. For this to be possible a separate fluid dynamics study was undertaken to understand the complex motion of the substrate housing within the rotating autoclave. This was done using an acrylic simulation apparatus and video data processing to establish and characterise the rotational regimes of the system. The rotational rate boundaries between these regimes were then established for a range of viscosities to allow these results to be translated to synthesis systems. This system also proved to be independently interesting from a fluid dynamics perspective, exhibiting the rare property of fluid hysteresis. Whilst this project had initially intended to then study these coatings using NMR, the full complexity of their production had not been foreseen and as such considerably more time would be required for a further structural investigation.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QC Physics Q Science > QD Chemistry T Technology > TP Chemical technology |
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Library of Congress Subject Headings (LCSH): | Glass -- Research, Boron, Silicon, Organic solid state chemistry, Nuclear magnetic resonance | ||||
Official Date: | September 2020 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Hanna, John V. ; Rebrov, Evgeny | ||||
Sponsors: | Pacific Northwest Laboratory ; University of Warwick | ||||
Extent: | xx, 163 leaves : illustrations, charts | ||||
Language: | eng |
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