Mitchell J, Griffith J D, Collins J H P, Sederman A J, Gladden L F, Johns M L
Department of Chemical Engineering, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom.
J Chem Phys. 2007 Dec 21;127(23):234701. doi: 10.1063/1.2806178.
Two-dimensional T(2)-T(2) NMR relaxation exchange spectroscopy has been applied to model porous media composed of mixtures of nonporous borosilicate and soda lime glass spheres in water. The spheres had a mean diameter of 100 microm, thus providing an approximately constant characteristic pore dimension throughout the structures, while the use of two glass types ensured that water in different pore-space regions had significantly different T(2) relaxation rates. The packed beds were constructed in various ways with controlled glass type domain sizes to rigorously validate a model for region-to-region exchange of water. From the determined exchange times, the corresponding length scales were calculated based on the molecular self-diffusion of water; these agreed to better than +/-25% with the expected domain sizes. Furthermore, exchange distances on the order of the pore size were observed in thoroughly mixed systems. Depending on the relaxation rates present in the sample, this technique can provide estimates of length scales ranging from microns to millimeters.
二维T(2)-T(2)核磁共振弛豫交换光谱已应用于模拟由无孔硼硅酸盐和钠钙玻璃球在水中混合而成的多孔介质。这些球体的平均直径为100微米，从而在整个结构中提供了大致恒定的特征孔隙尺寸，而使用两种玻璃类型确保了不同孔隙空间区域中的水具有显著不同的T(2)弛豫率。填充床以各种方式构建，具有可控的玻璃类型域尺寸，以严格验证水的区域间交换模型。根据确定的交换时间，基于水的分子自扩散计算相应的长度尺度；这些与预期的域尺寸的吻合度优于±25%。此外，在充分混合的系统中观察到了与孔径相当的交换距离。根据样品中存在的弛豫率，该技术可以提供从微米到毫米范围内的长度尺度估计。
