Chikani, Bharvi;
(2023)
Amorphous mixtures of small hydrocarbons and ice.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Water is a highly relevant molecule for a range of critical processes including clathrate hydrates, icy comets and hydration shells of hydrophobic moieties. Carbon, a “building block of life”, often likes to coexist with water. With respect to water’s and carbon’s chemical and physical properties, they are very different from one another. This project explores and establishes important processes happening at the interface between these species. This research initially focuses on the thermal desorption properties of amorphous mixtures and layered films of H2O and toluene at various ratios by incorporating the research on thin films with a film thickness of ~55 Langmuir and by comparing to the thick films synthesised with film thickness ranging from ~72 to 172 µm to observe changes in the desorption behaviour. It also highlights the influence of four other hydrocarbons, tetramethylbutane (TMB), dimethylbutane (DMB), tetramethylcyclopropane (TMCP) and cyclohexane (CYH) at various ratios and their impact on the properties of H2O. A range of analytical techniques have been considered to investigate the behaviour of amorphous hydrocarbon/H2O mixtures at temperatures ranging from ~100 to 260 K including differential scanning calorimetry, powder X-ray diffraction, small-angle X-ray scattering and Fourier-Transform infrared spectroscopy. From these analytical techniques, they have shown that a small amount of hydrocarbon can have a substantial impact on the crystallisation temperature from 162 K for pure ASW to 175 K for the cyclohexane/H2O 1:34 ratio. Each hydrocarbon/H2O mixture also shows a different stacking disordered ice XRD pattern once the sample has crystallised which is indicated from the profile of the peaks. From the FT-IR spectra, structural changes can be observed upon heating and differences in the hydrogen bonding of the as-made samples. Finally, the designing and implementation of an incubator setup is carried out to investigate the kinetics of clathrate hydrate formation in which it was found that new clathrate hydrates have been synthesised. The impact that these results would have, would serve the wider community ranging from chemistry to astrophysics to atmospheric sciences. It would also be highly relevant for understanding the properties of H2O in nanoconfinements as well as for optimising computational models considering H2O.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Amorphous mixtures of small hydrocarbons and ice |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10158700 |
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