Viscosity of Dilute Na-Montmorillonite Suspensions in Electrostatically Stable Condition under Low Shear Stress
Viscosity of Dilute Na-Montmorillonite Suspensions in Electrostatically Stable Condition under Low Shear Stress
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低剪切应力下静电稳定条件下稀钠蒙脱石悬浮液的粘度
DOI：
10.1016/j.colsurfa.2012.11.005
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Yasuhisa Adachi
中科院分区：
文献类型：
--
作者：
Yoko Tsujimoto;Motoyoshi Kobayashi;Yasuhisa Adachi
本文研究了静电分散钠基蒙脱土稀悬浮液的流变行为，以阐明在零应力极限条件下电粘性效应的重要性。使用原始螺旋型粘度计测量悬浮液的粘度，该粘度计由两个与一米长的毛细管连接的量筒组成。实验中使用了体积分数为2.0 × 10− 4至2.0 × 10−3的极稀悬浮液。悬浮液的离子强度被控制为小于0.001 M。因此，形成了充分发展的双电层。据证实，所测得的悬浮液的粘度随着其离子强度的降低而增加，根据电粘性效应的表现。在无盐条件下，由于二次电粘效应，粘度显著增加。为了分析这种影响，我们专注于悬浮蒙脱石颗粒的有效半径。我们估计他们的有效半径，通过拟合的Dougherty-Krieger方程的粘度数据。我们发现，所获得的有效半径依赖于显着的离子强度在低Peclet数制度，这是类似的理论依赖性的有效半径确定从流体动力学，静电和扩散能量的粒子之间的相互作用平衡。因此，随着离子强度的降低，有效半径的增加引起电排斥力的扩大，导致该粘土悬浮液的粘度增加。此外，有效半径的大小大于德拜长度。这表明，即使当蒙脱石颗粒之间的距离大于德拜长度时，电排斥力也会影响颗粒之间的相互作用。
We have studied the rheological behavior of dilute suspensions of electrostatically dispersed Na-montmorillonite to elucidate the importance of the electroviscous effect under the condition of zero stress limits. The viscosities of the suspensions were measured using an original spiral-type viscometer that consisted of two measuring cylinders connected with a one-meter-long capillary tube. Extremely dilute suspensions, whose volume fractions ranged from 2.0 × 10−4to 2.0 × 10−3, were used for the experiments. The ionic strength of the suspensions was controlled to be less than 0.001 M. Thus, a fully developed electrical double layer was formed. It was confirmed that the measured viscosities of the suspensions increased with a decrease in their ionic strength, in accordance with a manifestation of the electroviscous effect. The viscosity increased markedly owing to the secondary electroviscous effect under the limit of the salt-free condition. To analyze this effect, we focused on the effective radii of the suspended montmorillonite particles. We estimated their effective radii by fitting the Dougherty–Krieger equation to the viscosity data. We found that the obtained effective radii depended significantly on the ionic strength in the low Peclet number regime, which was similar to the theoretical dependence of the effective radii determined from the interaction balance between the particles governed by hydrodynamic, electrostatic, and diffusive energies. Thus, the increase in the effective radius with a decrease in the ionic strength gives rise to the expansion of the electric repulsive force, resulting in an increase of the viscosity of this clay suspension. In addition, the magnitudes of the effective radii were greater than the Debye length. This indicates that even when the distance between the montmorillonite particles is greater than the Debye length, the electrical repulsive force affects the interaction between the particles.