Hyperpolarised noble gas nuclear magnetic resonance and magnetic resonance imaging studies of complex porous mediaTools Hill-Casey, Fraser (2018) Hyperpolarised noble gas nuclear magnetic resonance and magnetic resonance imaging studies of complex porous media. PhD thesis, University of Nottingham.
AbstractThe ability to non-invasively probe void spaces is an extremely valuable tool for applications ranging from chemical engineering to biomedical, pulmonary imaging studies. Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) provide such a methodology. To achieve suitable signal intensity from the magnetic resonance experiment, a probe molecule such as H2O is introduced to the void space to generate enough detectable signal for an MR system. The use of liquids, however, restricts the time scales accessible and confines characterisation of diffusion to that of the molecular regime. In recent years, gas phase measurements have been made with probe molecules such as sulphur hexafluoride SF6 but such measurements typically require high pressures to achieve suitable sensitivity and as such are subject to the same limitations as liquid measurements. However, via use of hyperpolarisation (hp) techniques such as Spin Exchange Optical Pumping (SEOP) it is possible to perform measurements of noble gases at atmospheric pressure and room temperature. As such, it is possible to utilise these hp gasses to investigate low-density, gas-phase mass-transport, such that the diffusion may be studied in the Knudsen regime. Understanding of diffusion processes are particularly valuable to the design of hierarchical porous media such as catalysed diesel particulate filters (DPF) and other industrial catalytic processes. The characterisation of the structure-transport relationships of porous solids is extremely valuable for the design of new advanced catalysed materials for a range of applications.
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