Fast Scanning Calorimetry Studies of Deeply Supercooled Water and Aqueous Solutions
Open AccessThis dissertation describes the results of FSC studies of the fundamental properties of ASW. Motivation for fundamental studies of condensed aqueous phases, modern experimental approaches, and current terminology and theories relevant to liquids and glasses are described in Chapter 1. Chapter 2 provides an in-depth description of the experimental apparatus, along with basic experimental procedures and critical tests.Chapter 3 describes the results of FSC experiments designed to establish quantitative relationships between the kinetic parameters of supercooled liquids and experimental variables; thereby, validating the central assumption of the FSC approach, i.e., the assumption that the inverse of the heating rate is equal to the relaxation time at the temperature where the glass transition is observedIn Chapter 4, the FSC was employed to investigate the glass transition phenomena in vapor deposited ASW films doped with CH3COOH, C5H11OH, C2H5OH, and CCl4. Systematic FSC measurements of Tg and Cp dependence on the concentration of impurities indicate the possible existence of two distinct non-crystalline phases of H2O in binary aqueous solutions. I discuss the implications of these findings for past studies of molecular kinetics in pure vitreous water and in binary aqueous solutions.Chapter 5 presents and discusses the results of FSC experiments utilized to investigate the glass transition phenomena in ~2 micrometer thick ASW films doped with a 0.1 molar ratio of CH3COOH with heating rates varying from 5 kK/s to 650 kK/s. Based on the Adams-Gibbs analysis of the results, I argue that the impact of impurities on the molecular kinetics in supercooled water is similar to that of nanopore confinement and that it can be rationalized in terms of limitations imposed on water's cooperative rearrangement scale by dopant species. In Chapter 6, variable rate FSC was used to estimate the characteristic crystallization time of ASW during rapid heating with rates from 3*103 K/s to 1.6*106 K/s. The resulting dependence of tCR on temperature conforms to Arrhenius Law (Ea ~68 ± 2 kJ/mol). Based on this observation, I argue that pure ASW is a strong glass over the entire temperature range from the 228 K down to cryogenic temperatures.
- All rights reserved
Notice to Authors
If you are the author of this work and you have any questions about the information on this page, please use the Contact form to get in touch with us.
| Thumbnail | Title | Date Uploaded | Visibility | Actions |
|---|---|---|---|---|
|
|
McCartney_gwu_0075A_10264.pdf | 2018-01-16 | Open Access |
|