Xu W, Nikolov A, Wasan DT
Department of Chemical Engineering, Illinois Institute of Technology, Chicago, Illinois, 60616
J Colloid Interface Sci. 1998 Jan 1;197(1):160-9. doi: 10.1006/jcis.1997.5249.
An experimental investigation was made of the sedimentation rate of low-charged monodisperse silica and polystyrene latex particle dispersions as a function of the particle volume fraction. It was found that the normalized sedimentation velocity U/U0, corrected for the effect of the two-body hydrodynamic interaction, increases with the particle volume fraction, which indicates that the degree of particle aggregation inside the dispersions increases with the particle volume fraction. This phenomenon results from attractive many-body hydrodynamic interactions between colloidal particles. It is reported for the first time that the many-body hydrodynamic interaction becomes important at the particle concentration of 6.5 vol% in monodisperse dispersions, and the many-body thermodynamic interaction is negligible at a low particle concentration, i.e., less than 15 vol%. The effect of many-body hydrodynamic interaction on the particle microstructure was also experimentally examined by using a nondestructive Kossel diffraction technique based on the principle of back-light scattering. It was found that the particle packing structure inside the dispersion initially becomes more ordered with the increase of the particle volume fraction. However, there is less increase in the particle ordering structure after 6 vol%. Furthermore, after the particle concentration reaches 10 vol%, the particle packing structure decreases to a value lower than that of 6 vol% due to the increased particle aggregation, as found in the sedimentation experiments. Predictions of a statistical thermodynamic model were compared with the experimental data on structure factors. It is found that particle dimerization occurs around 10 vol%, which agrees with the sedimentation results. Copyright 1998 Academic Press. Copyright 1998Academic Press
对低电荷单分散二氧化硅和聚苯乙烯乳胶颗粒分散体的沉降速率随颗粒体积分数的变化进行了实验研究。结果发现，经两体流体动力学相互作用影响校正后的归一化沉降速度U/U0随颗粒体积分数增加，这表明分散体内颗粒的聚集程度随颗粒体积分数增加。这种现象源于胶体颗粒之间有吸引力的多体流体动力学相互作用。首次报道在单分散分散体中，当颗粒浓度为6.5体积%时多体流体动力学相互作用变得重要，而在低颗粒浓度即小于15体积%时多体热力学相互作用可忽略不计。还基于背散射原理使用无损科塞尔衍射技术通过实验研究了多体流体动力学相互作用对颗粒微观结构的影响。发现分散体内颗粒堆积结构最初随颗粒体积分数增加变得更有序。然而，在6体积%之后颗粒有序结构的增加较少。此外，如沉降实验中所发现的，在颗粒浓度达到10体积%之后，由于颗粒聚集增加，颗粒堆积结构降低到低于6体积%时的值。将统计热力学模型的预测结果与关于结构因子的实验数据进行了比较。发现颗粒二聚化在10体积%左右发生，这与沉降结果一致。版权所有1998年学术出版社。版权所有1998年学术出版社
