Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 29 for “"pulsed field gradient"”.
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Pulsed field gradient magnetic resonance measurements of lithium-ion diffusion
… and the resulting macroscopic transport. Gradient nuclear magnetic resonance measurements are a mature and effective means of investigating macroscopic transport phenomena and posses several advantages over competing measures of transport in ionic solids. However, short coherence times, …
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Microscopic diffusion measurements with nanoporous materials: complementary benefits of infrared microimaging and pulsed field gradient NMR
… namely infrared (IR) microimaging and pulsed field gradient (PFG) NMR. The dissertation contains mainly five chapters. The first chapter introduces diffusion phenomena in general and concisely explains the importance and the current challenges of the investigation of molecular diffusion …
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The measurement of the diffusion coefficient of water in poly (ethylene oxide) water solutions using a nuclear magnetic resonance pulsed field gradient technique
… solutions as a function of concentration using a pulsed field gradient NMR technique, for values of the concentration of poly-ox in H2O from to 1.2 gm poly-ox/gm. Near zero poly-ox concentration, the slope of the D vs. concentration curve is quite large. As the concentration increases, the slope …
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Polymer dynamics in bulk, adsorbed and solution by NMR methods
… of small molecules in polymer solutions by pulsed field-gradient proton nuclear magnetic resonance (PGSE ¹H NMR). The diffusion of solvents in polymer solutions is investigated. The diffusion of N-N, dimethylformamide in polystyrene is studied as a function of concentration and temperature. …
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Multiscale Tortuous Diffusion in Anion- and Cation-Exchange Membranes: Exploration of Counterions, Water Content, and Polymer Functionality
… on water transport in AEMs and CEMs using pulsed-field-gradient (PFG) NMR diffusometry. Water diffusion in both AEMs and CEMs exhibit specific trends as a function of water uptake (wt%), indicating morphological similarities across common chemical structures. Furthermore, restricted …
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Cation and Anion Transport in a Dicationic Imidazolium-Based Plastic Crystal Ion Conductor
… means of multi-nuclear solid-state (SS) NMR and pulsed-field-gradient (PFG) NMR. We quantify distinct cation and anion diffusion coefficients as well as the diffusion activation energies (Ea) in this dicationic imidazolium-based OIPC. Our studies suggest a change in transport mechanism for the …
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Tuning polymeric chiral surfactants for enhanced enantiomeric recognition in micellar electrokinetic chromatography
… the polymeric surfactants was obtained by use of pulsed field gradient-NMR (PFG-NMR). A superior chromatographic performance in MEKC was demonstrated by the modified polymeric surfactants as compared to the non-modified polymeric surfactants. A correlation between the polarity and the size of the …
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Transport properties of micellar solutions and microemulsions.
… were made by the NMR spin-echo method with a pulsed field gradient using the nucleus 1H. The results indicated that the surfactant is aggregated and water plus oxyethvlene chains form the continuum up to 100% surfactant. Phase diagrams were determined for the C[12]S[4]-H[2]O-heptane system and …
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EFFECTS OF OSMOLYTES ON THE CONFORMATIONAL STABILITY AND HYDRODYNAMIC RADII OF IMMUNITY PROTEIN 9 AND HUMAN SERUM ALBUMIN
… and hydrodynamic radii (Rh) were measured with pulsed-field gradient NMR. The unfolding curves of Im9 and HSA are shifted to higher urea concentration so that Urea1/2 and GH2O increased, as the osmolyte concentration was increased indicating that Im9 and HSA are more stable in the presence of …
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Process Applications of NMR
… lineshape observed in an inhomogeneous magnetic field is poorly fitted by a Lorentzian lineshape, so a new model lineshape is developed based on the distribution of resonance frequencies across the sample. Volume selective NMR spectroscopy using the STEAM and PROJSAT pulse sequences is optimised …
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Multiscale Transport and Dynamics in Ion-Dense Organic Electrolytes and Copolymer Micelles
… techniques. By employing variable temperature pulsed-field-gradient (PFG) NMR diffusometry, which can probe molecular transport over nm – μm length scales, I first explore transport and morphology on a series of ion-conducting materials: an organic ionic plastic crystal, a proton-exchange …
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Acetate-based Electrolytes for Aqueous Zinc-ion Batteries: An Investigation of the Zinc Anode
… a combination of molecular dynamics simulations, pulsed-field-gradient NMR, and rotating-disk-electrode electrochemistry, I first show how increasing KOAc concentration from 5 m to 27 m transforms the solvation environment into an ion-coordinated network that dramatically slows HER/OER kinetics …
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Diffusion and Relaxometry Studies in Mesoporous Systems using Nuclear Magnetic Resonance
… branching on diffusion has been examined using Pulsed Field Gradient (PFG) NMR. This includes a diffusion study of binary mixtures consisting of *n*-dodecane and one of octane isomers. It has shown that linear octane diffuses distinctively faster than branched octane isomers, indicating physical …
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Novel Techniques and Electrolytes for Energy Storage Devices
… electrochemical impedance spectroscopy, pulsed field gradient nuclear magnetic resonance and viscometry. Collectively, these results have been used to quantitatively identify promising candidates for applications in SIBs. Supercapacitors are high power energy storage devices that store …
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Microporous Polymer-Metal Organic Framework (MOF) Hybrid Materials for Separations
… self-diffusivities of gases were measured using pulsed-field gradient nuclear magnetic resonance and compared to macroscopic diffusivities obtained from permeation and sorption analysis. The PIM–MOF material platform was also extended to solvent-based separations.To understand solvent transport …
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Transport and Anisotropy inside Ionic Polymer Membranes
… of a standard protocol for calibrating high pulsed-field-gradient NMR. I show that high gradient calibration using low γ nuclei is not amenable to measurements on slow diffusing high γ nuclei. Then I employ NMR diffusometry to investigate transport and anisotropy for a series of ionic …
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Signal sampling and processing in magnetic resonance applications
… is presented. The method is validated against pulsed field gradient NMR diffusion data of two experimental systems. In the first experimental system, the sampling pattern is optimised for the most accurate estimation of the lognormal distribution parameters of an emulsion droplet size …
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Vapour-Liquid Equilibria within Nanoporous Media
… designed to operate inside the strong magnetic fields of an NMR spectrometer. NMR spectroscopy, relaxation and pulsed field gradient (PFG) diffusion experiments were performed on each of the systems discussed in this report. Cyclohexane was initially studied inside a porous titania catalyst …
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Magnetic Resonance Studies of the Diffusion Dynamics of Molecular Systems Relevant to Fischer-Tropsch Catalysis
… number distributions of confined mixtures using Pulsed-Field Gradient (PFG) Nuclear Magnetic Resonance (NMR) techniques. An advancement on this calibration technique is used to show that the diffusion mechanism of these liquids, in addition to the activation energy and molecular free volume, …
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NMR studies of carbon dioxide sequestration in porous media
… contributes to the knowledge in this field by investigating the two-phase flow and entrapment processes of CO2, as well as other relevant fluids, in porous media at the pore- and centimetre-scales using a combination of lab-based nuclear magnetic resonance (NMR) experimental techniques …
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