パルス磁場勾配NMRを用いた水の自己拡散係数の計測 : 原理と粘土ゲルへの応用例

概要

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Principles of the measurement of the diffusion coefficients by the pulsed-field-gradient (PFG) proton nuclear magnetic resonance (NMR) spectroscopy were reviewed. In the PFG NMR method developed by Stejskal and Tanner, the randomwalk displacement of the target nuclei is encoded as a phase of the spin precession and detected as the decrease in the NMR spin-echo signal intensity with increasing pulsed magnetic field gradients. An example of the measurement of H_2O selfdiffusion in water-rich hectorite gels was shown. The obtained diffusion data were explained by a model that free or unbound H_2O molecules diffuse in the porous gel by avoiding the randomly placed obstacles (clay platelets sandwiched by bound or immobilized H_2O layers). Because nondestructive, quick, high -precision, and three-dimensional measurements of self-diffusion tensors of H_2O are possible, PFG NMR is a powerful tool in the clay science.
日本粘土学会の論文
2002-08-24