Application of functional property generated with the anisotropic shear induced structure of suspension and colloidal systems

我们研究了悬浮体和胶体体系的流致结构及其对流动特性的影响，涉及到作为功能流体的应用。在第一次浓缩悬浮液试验中，我们关注了大应变振荡流动中剪切反转后颗粒结构的重排过程。不管施加的剪切速率是什么，这个过程都是一个固体行为，因为它只取决于应变。非定常影响准稳态振荡流过瞬变期后的表观粘度。也就是说，在高频条件下，表观流动性增加，这一趋势在单分散体系中明显观察到。此外，双分散体系在振荡流动中的粘度对体积分数的依赖关系与在定常流动中得到的明显不同。在浓缩悬浮液的压缩试验中，我们发现表观屈服应力，即类似固体的特性，随着往复挤压运动的增加而增加。结果表明，在挤压速度、颗粒形状等不同条件下，由于过滤作用，在挤压流的中心区域产生了浓度和较强的粘结结构。在胶体体系实验中，我们对聚苯乙烯微球通过小孔的稀胶分散进行了实验研究，得到了胶体颗粒对孔口流动的稳定或不稳定的影响，这取决于电解液的浓度。测量到的流量随强烈的静电斥力而波动。随着电解液密度的增加，孔口流量趋于稳定，而过高的电解液密度会引起流量的不稳定。

We have investigated the flow-induced structures of suspension and colloidal systems and those influence on the flow characteristics, relating to the application as the functional fluids.In the first test with concentrated suspensions, we had concerned with the rearrangement process of the particle structure after a shear reversal in oscillatory flow with large strain. Regardless of the shear rate applied, the process was a solid like behavior because it was only depended on the strain. The apparent viscosity estimated in the quasi-steady oscillatory flow after the transient period was affected with the unsteadiness. That is, the apparent fluidity was increased in high frequency conditions and this tendency was conspicuously observed in the mono-dispersed systems. Moreover, the dependency of the viscosity evaluated in the oscillatory flow on the rate of the volume fraction in bi-disperse systems was remarkably different with that obtained in steady flow.In the squeezing test of the concentrated suspensions, we had found that the apparent yield stress, that is solid like property, was increased with the reciprocated squeezing motion. The results obtained with the different conditions in squeezing velocity, particle shape and so on show that the concentration and the stronger cohesive structure was generated at the center region of squeezing flow due to the filtration effectsIn the test of colloidal systems, we have experimentally studied the dilute colloidal dispersion of the fine polystystyrene spheres passing through a small orifice, where it was obtained that the colloidal particles gave a stability or an instability effect on the orifice flow depending on the electrolyte density. This measured flow rates fluctuated with strong electrostatic repulsion. The increase in the electrolyte density stabilized the orifice flow, whereas excessively high electrolyte density caused instability in the flow rates.