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

我们研究了悬浮液和胶体体系的流动诱导结构及其对流动特性的影响，并将其应用于功能流体。在第一次浓悬液试验中，我们研究了大应变振荡流剪切逆转后颗粒结构的重排过程。无论施加的剪切速率如何，该过程都是类似固体的行为，因为它只取决于应变。瞬态后准稳态振荡流的视粘度估计受非定常影响。也就是说，表观流动性在高频条件下增加，这种趋势在单分散体系中明显观察到。此外，在振荡流动中评估的粘度对双分散体系体积分数速率的依赖关系与在稳定流动中获得的结果有显著不同。在浓缩悬浮液的挤压试验中，我们发现随着往复挤压运动，表观屈服应力，即固体性质的增加。在不同的挤压速度、颗粒形状等条件下得到的结果表明，由于过滤作用，在挤压流的中心区域产生了浓度和更强的粘性结构。在胶体体系的测试中，我们实验研究了聚苯乙烯细球通过小孔口时的稀胶体分散。根据电解质密度的不同，胶体颗粒对孔板流动有稳定或不稳定的影响。这种测量的流量随强烈的静电斥力而波动。电解质密度的增加稳定了孔板流动，而过高的电解质密度会导致流速的不稳定。

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.