Department of Chemistry and Materials, Faculty of Textile Science and Technology , Shinshu University , Tokida 3-15-1 , Ueda , Nagano 386-8567 , Japan.
Langmuir. 2018 Jul 24;34(29):8464-8471. doi: 10.1021/acs.langmuir.8b01336. Epub 2018 Jul 13.
In spite of the fact that a flow is often present in the liquid in which charged particles are dispersed, the effect of a flow on the forces controlling the dispersion is not clear. Here, we used a combined atomic force microscope-peristaltic pump system to determine the effect of a flow in aqueous solutions between a negatively charged silica particle and a negatively charged silicon wafer on the forces in the system. The effect of a flow on the forces in water or aqueous solutions of NaCl or MgCl·6HO was studied for salt concentrations lower than the concentrations needed to invert the charge of the silica and silicon surfaces. This was done to prevent the formation of a reversed flow in the system due to a charge inversion of the silica surface. A flow was seen to decrease the intersurface repulsive forces, if the water contained salt (NaCl or MgCl·6HO). An increased bulk salt concentration was also seen to decrease the repulsive forces further in the presence of a liquid flow. The surface potentials and effective ionic concentrations of the systems were determined by comparing the experimental curves with the theoretically calculated ones. The surface potentials and effective ionic concentrations were seen to decrease and increase, respectively, as the flow rate and bulk salt concentrations were increased. This change was explained by the shrinking of the diffuse layers by the liquid flow, due to part of the diffuse layer being washed away by the flowing liquid.
尽管在带电荷粒子分散的液体中通常存在流动，但流动对控制分散的力的影响尚不清楚。在这里，我们使用原子力显微镜-蠕动泵组合系统来确定带负电荷的二氧化硅颗粒和带负电荷的硅片之间在水溶液中流动对系统力的影响。研究了在低于使二氧化硅和硅表面电荷反转所需浓度的盐浓度下，水或 NaCl 或 MgCl·6HO 水溶液中流动对力的影响。这样做是为了防止由于二氧化硅表面电荷反转而在系统中形成反向流动。如果水中含有盐（NaCl 或 MgCl·6HO），则流动会减小界面间的排斥力。在存在液体流动的情况下，增加本体盐浓度也会进一步减小排斥力。通过将实验曲线与理论计算曲线进行比较，确定了系统的表面电势和有效离子浓度。随着流速和本体盐浓度的增加，观察到表面电势和有效离子浓度分别减小和增加。这种变化是由于部分扩散层被流动的液体冲走，液体流动导致扩散层收缩所致。
