Relaxometry water mobility

Abstract We use Nuclear Magnetic Resonance relaxometry (i.e. the frequency variation of the NMR relaxation rates) of quadrupolar nucleus ( Na) and H Pulsed Gradient Spin Echo NMR to determine the mobility of the counterions and the water molecules within aqueous dispersions of clays. The local ordering of isotropic dilute clay dispersions is investigated by NMR relaxometry. In contrast, the NMR spectra of the quadrupolar nucleus and the anisotropy of the water self-diffusion tensor clearly exhibit the occurrence of nematic ordering in dense aqueous dispersions. Multi-scale numerical models exploiting molecular orbital quantum calculations, Grand Canonical Monte Carlo simulations, Molecular and Brownian Dynamics are used to interpret the measured water mobility and the ionic quadrupolar relaxation measurements. 

Xu et al. investigated the interaction of water with NAFION under acid, sodium, and potassium forms using NMR relaxometry techniques in terms of dispersion R co) reveahng two types of bound water, the expected bound water and water with considerably reduced mobility in the driest NAFION [105]. Lee et al. applied NMR spin-lattice relaxation techniques to characterize the molecular motion of H20 in NAFION 117, AQUIVION E87-05, and sulfonated-RADEL proton exchange membranes [106]. It was concluded that the motion of H20 is affected by the acidity and mobihty of the sulfonic acid groups to which the water molecules are coordinated at low hydration level. At higher levels of hydration, the molecular motion of H20 is affected by the phase separation of the hydrophihc/hydrophobic domains and the size of the hydrophilic domains. 

The degree to which there is hydrogen in silanol groups of C-S-H hydrates remains a matter of contention. Regarding NMR relaxometry, such OH groups at pore surfaces may be associated with relatively (rotationally ) mobile Ca ions in solution (Nonat 2004 Richardson 2008) and therefore appear within (contribute to) the relaxation of the pore water. 

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