Lee Myung Han, Furst Eric M
Department of Chemical Engineering, University of Delaware, Colburn Laboratory, 150 Academy Street, Newark, Delaware 19716, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2006 Sep;74(3 Pt 1):031401. doi: 10.1103/PhysRevE.74.031401. Epub 2006 Sep 7.
The coupled aggregation and sedimentation of colloidal particles with short-range attractions are investigated. Nonadsorbing polymer is used to induce depletion interactions between the hard-sphere particles. Gravitational forces, caused by a density mismatch between the particles and the suspending fluid, result in the sedimentation of particles and aggregates, as well as the compaction and rearrangement of the final sediment layer. At low polymer concentrations CP, or low initial volume fractions phio, clusters formed during the period of fast sedimentation are small, and the structure of the final sediment is dense. Conversely, at high CP, or high phio, large clusters form during sedimentation, and the resulting sediment structure is significantly less dense, with large void volumes. The size of the presediment aggregates depends on CP and phio with a functional form that resembles other thermally activated barrier hopping processes in colloidal systems, such as the delayed sedimentation of colloidal gels. Finally, when the particles are weakly attractive, gravitational stresses are found to induce compaction of the sediment over long periods of time. However, sediments composed of particles that are strongly attractive resist rearrangements and compaction, even when the sediment layers have a relatively large amount of free volume.
研究了具有短程吸引力的胶体颗粒的耦合聚集和沉降。使用非吸附性聚合物来诱导硬球颗粒之间的耗尽相互作用。颗粒与悬浮液之间的密度不匹配所产生的重力，导致颗粒和聚集体的沉降，以及最终沉积层的压实和重排。在低聚合物浓度CP或低初始体积分数phio时，快速沉降期间形成的团簇较小，最终沉积物的结构致密。相反，在高CP或高phio时，沉降过程中会形成大团簇， resulting sediment structure is significantly less dense, with large void volumes. 预沉积聚集体的大小取决于CP和phio，其函数形式类似于胶体系统中的其他热激活势垒跳跃过程，如胶体凝胶的延迟沉降。最后，当颗粒具有弱吸引力时，发现重力应力会在很长一段时间内导致沉积物压实。然而，由具有强吸引力的颗粒组成的沉积物即使在沉积层具有相对大量自由体积的情况下也能抵抗重排和压实。
