Effects of the counterion on dielectric spectroscopy of a montmorillonite suspension over the frequency range 10(5)-10(10) Hz.
Effects of the counterion on dielectric spectroscopy of a montmorillonite suspension over the frequency range 10(5)-10(10) Hz.
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DOI：
10.1016/s0021-9797(03)00688-x
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发表时间：
2003-12
影响因子：
9.9
通讯作者：
T. Ishida;M. Kawase;K. Yagi;J. Yamakawa;K. Fukada
中科院分区：
文献类型：
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作者：
T. Ishida;M. Kawase;K. Yagi;J. Yamakawa;K. Fukada
进行了介电测量上的蒙脱石粘土与三种不同的抗衡离子交换的悬浮液：钠，铵，和四甲基铵（TMA）。对于TMA反离子的粘土样品，只有两个介电吸收峰可以被识别，而对于两种无机反离子，发现了三个峰。从弛豫时间和弛豫强度来看，在10 GHz左右观察到的介电过程是由于大量水分子的取向所致。松弛强度的过程中发生在10 MHz左右的绝热压缩系数从超声速度测量进行了比较。随着压缩性的降低，松弛强度的增加表明，在10 MHz左右的过程是由粘土样品上的结合水分子的取向引起的。对于TMA样品，在10 MHz左右发生的过程的弛豫强度非常小。此外，结合水分子的网络结构可以通过TMA样品特有的性质来表征，考虑到其Cole-Cole参数的值。在100 kHz左右发生的过程的弛豫强度的结果进行了比较与电泳迁移率。这种比较表明，结合离子和离子之间的歧视扩散双层是重要的，和松弛和电泳的结果可以令人满意地解释粘土的表面极化。
Dielectric measurements were carried out on suspensions of montmorillonite clay exchanged with three different counterions: sodium, ammonium, and tetramethylammonium (TMA). Only two dielectric absorption peaks could be identified for the clay sample with the TMA counterion, whereas three peaks were found for the two inorganic counterions. The dielectric process observed at around 10 GHz is due to the orientation of bulk water molecules, judging from the relaxation time and relaxation strength. The relaxation strength of the process occurring at around 10 MHz was compared with the coefficient of adiabatic compressibility obtained from ultrasound velocity measurements. The increase in the relaxation strength with decreasing compressibility indicates that the process at around 10 MHz is caused by the orientation of bound water molecules on the clay samples. The relaxation strength of the process occurring at around 10 MHz for the TMA sample was remarkably small. Furthermore, the network structure of the bound water molecules can be characterized by a property peculiar to the TMA sample, taking into account the value of its Cole–Cole parameter. Results for the relaxation strength of the process occurring at around 100 kHz were compared with those for electrophoretic mobility. This comparison revealed that discrimination between bound ions and ions in the diffuse double layer is important, and both the relaxation and electrophoretic results could be satisfactorily explained by surface polarization of the clay.