Lattuada Enrico, Buzzaccaro Stefano, Piazza Roberto
Department of Chemistry, Materials Science, and Chemical Engineering (CMIC), Politecnico di Milano, Edificio 6, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
J Phys Condens Matter. 2018 Jan 31;30(4):044005. doi: 10.1088/1361-648X/aaa2d1.
We have investigated the stationary sedimentation profiles of colloidal gels obtained by an arrested phase-separation process driven by depletion forces, which have been compressed either by natural gravity or by a centrifugal acceleration ranging between 6g and 2300g. Our measurements show that the gel rheological properties display a drastic change when the gel particle volume fraction exceeds a value [Formula: see text], which barely depends on the strength of the interparticle attractive forces that consolidate the network. In particular, the gel compressive yield stress [Formula: see text], which increases as [Formula: see text] for [Formula: see text], displays a diverging behaviour for [Formula: see text], with an asymptotic value that is close to the random close packing value for hard spheres. The evidence we obtained suggests that [Formula: see text] basically coincides with the liquid (colloid-rich) branch of the metastable coexistence curve, rather than with the lower (and ϕ-dependent) values expected for an attractive glass line penetrating inside the coexistence region.
我们研究了通过耗尽力驱动的受阻相分离过程获得的胶体凝胶的静态沉降剖面，这些凝胶通过自然重力或6g至2300g之间的离心加速度进行压缩。我们的测量结果表明，当凝胶颗粒体积分数超过一个值[公式：见正文]时，凝胶的流变特性会发生剧烈变化，该值几乎不依赖于巩固网络的颗粒间吸引力的强度。特别是，凝胶压缩屈服应力[公式：见正文]，对于[公式：见正文]，其随[公式：见正文]增加，而对于[公式：见正文]则表现出发散行为，其渐近值接近硬球的随机密堆积值。我们获得的证据表明，[公式：见正文]基本上与亚稳共存曲线的液体（富含胶体）分支重合，而不是与预期穿透共存区域内部的吸引玻璃线的较低（且与ϕ相关）值重合。
