Department of Chemical and Biomolecular Engineering, University of Illinois, Urbana, IL 60801, USA.
J Phys Condens Matter. 2011 Jan 26;23(3):035102. doi: 10.1088/0953-8984/23/3/035102. Epub 2010 Dec 10.
The effect of weak particle anisotropy on the onset of fluidity in dense suspensions of glasses of repulsive, weakly attractive and strongly attractive spherical and dumbbell shaped particles is explored. Yield stresses are found to scale with volume fraction showing a divergence at random close packing for all systems. However the onsets of yielding in suspensions of spherical and dumbbell shaped particles are shown to display qualitatively different behaviors. Suspensions of hard spheres exhibit a single yield stress (strain) while suspensions of spheres experiencing short range attractions in dense gels display two yielding events. Double yielding occurs when attractions between particles are only a few kT and the suspensions are sufficiently dense. For dumbbell suspensions, single yielding is observed for hard dumbbell glasses in a region where the glasses are expected to be plastic while double yielding is observed when the particles are expected to have localized centers of mass and localized orientations. Double yielding is also observed for dense dumbbell suspensions that experience attractions while only single yielding events are observed in strongly attractive gels for both dumbbells and spheres. These results are discussed in the light of recent theories and simulations of mechanisms of localization in suspensions of spherical and weakly anisotropic particles.
探讨了弱粒子各向异性对排斥性、弱吸引力和强吸引力的球形和哑铃形粒子的玻璃密集悬浮液流变性开始的影响。发现屈服应力与体积分数相关，对于所有系统，在随机密堆积时都会出现发散。然而，球形和哑铃形粒子悬浮液的屈服起始显示出定性不同的行为。硬球悬浮液表现出单一的屈服应力（应变），而在密集凝胶中经历短程吸引力的球体悬浮液显示出两个屈服事件。当粒子间的吸引力只有几个 kT 且悬浮液足够密集时，会发生双重屈服。对于哑铃悬浮液，在预期为塑性的硬哑铃玻璃区域观察到单一屈服，而当预期颗粒具有局部质心和局部取向时，观察到双重屈服。在经历吸引力的密集哑铃悬浮液中也观察到双重屈服，而在强吸引力凝胶中，哑铃和球体都只观察到单一屈服事件。这些结果是根据最近关于球形和弱各向异性粒子悬浮液中局部化机制的理论和模拟讨论的。
