Neutron scattering study on dynamics of water molecules in MCM-41. 2. Determination of translational diffusion coefficient
Neutron scattering study on dynamics of water molecules in MCM-41. 2. Determination of translational diffusion coefficient
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DOI：
10.1021/jp046036l
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发表时间：
2005-06-09
影响因子：
3.3
通讯作者：
Bellissent-Funel, MC
中科院分区：
文献类型：
--
作者：
Takahara, S;Sumiyama, N;Bellissent-Funel, MC
在238-298 K温度范围和0.31-0.99埃（-1）动量传递范围内，测量了水填充MCM-41（孔径为21.4和28.4埃）样品的准弹性中子散射（QENS）谱，以研究受限水分子的动力学行为。的光谱，其中主要包括从水分子的平移扩散的贡献，通过使用洛伦兹和拉伸指数函数进行了分析。拟合比较表明，后者的分析比前者更可靠。位于孔壁附近的不动水分子的分数，这给出了一个弹性组件，被发现是0.044-0.061在两个孔。拉伸指数β测定为0.66 ± 0.80。结果表明，水分子在孔隙中的平移扩散被约束减速，并且减速随着孔径的减小而变得显著。常温下承压水与本体水平移扩散系数之比D-T在0.47 ~ 0.63之间。
Quasielastic neutron scattering (QENS) spectra of water-filled MCM-41 samples (pore diameters: 21.4 and 28.4 angstrom) were measured over the temperature range 238-298 K and the momentum transfer range 0.31-0.99 angstrom(-1) to investigate the dynamics of confined water molecules. The spectra, which consist mainly of contributions from the translational diffusion of water molecules, were analyzed by using the Lorentzian and the stretched exponential functions. Comparison of the fits indicated that the latter analysis is more reliable than the former one. The fraction of immobile water molecules located in the vicinity of the pore walls, which give an elastic component, was found to be 0.044-0.061 in both pores. The stretch exponent beta was determined as 0.660.80. It was shown that the translational diffusion of water molecules in the pores is decelerated by confinement and that the deceleration becomes marked with a decrease in pore size. The ratios of the translational diffusion coefficient D-T of confined water to that of bulk water at room temperature were within a range of 0.47-0.63.