Linn Thrane PhD Dissertation Defense
- Wednesday, November 14, 2018 at 12:00pm
- Animal Biosciences Building, 138 - view map
Nuclear Magnetic Resonance Studies to Characterize Phase Transitions in Porous Systems
Nuclear magnetic resonance (NMR) allows for in-situ non-invasive studies of a wide range of systems at microscopic time and length scales. NMR relaxometry and diffusometry techniques along with magnetic resonance imaging (MRI) are applied to explore and characterize various phase transitions in complex systems. NMR techniques are highly sensitive to the thermodynamic phase of the system as well as restrictions on molecular motion, and the ability to detect and monitor phase transitions non-invasively is of great interest for various industrial applications High resolution MRI along with T1-T2 magnetic relaxation correlation experiments and pulsed gradient stimulated echo (PGStE) NMR methods are demonstrated to characterize hydrate formation. MRI monitors the spatial heterogeneity of the system as well as local hydrate growth rates. Using T1-T2 correlation NMR and spectrally resolved diffusometry, the transition from mobile to restricted dynamics is observed simultaneously for both water and cyclopentane throughout the hydrate formation process. The combination of these MR techniques allows for exploration of the complex molecular dynamics involved in hydrate formation processes. NMR frequency spectra and 1D T2 relaxation measurements are used to characterize the presence of an amorphous drug and its liquid-solid phase transition. T1-T2 magnetic relaxation correlation experiments monitor the impact of long-time storage at high relative humidity on the drug in a porous silica tablet. The results indicate the ability of non-solid-state NMR to characterize crystalline and amorphous solid structural phases, and the potential for drug quality control by NMR methods. Using a low-field NMR system, microbially induced calcite precipitation (MICP) processes in granular media are explored by means of 1D T2 relaxation measurements. The 1D T2 distributions allowed for in-situ monitoring of the mineral precipitation progress and, accompanied by post-study SEM images, indicates a decrease in total pore volume, the formation of a gas interface, and a change in the surface mineralogy of the granular media. The results confirm the potential for detailed characterization of MICP progression in engineering applications. Ultimately, NMR is demonstrated as an effective method for detecting, characterizing, and monitoring several distinct phase transitions at various time- and length-scales.
- Department of Mechanical & Industrial Engineering