We report a study combining x-ray photon correlation spectroscopy (XPCS) with in situ rheology to investigate the microscopic dynamics and mechanical properties of aqueous suspensions of the synthetic hectorite clay Laponite, which is composed of charged, nanometer-scale, disk-shaped particles. The suspensions, with particle concentrations ranging from 3.25 to 3.75 wt %, evolve over time from a fluid to a soft glass that displays aging behavior. The XPCS measurements characterize the localization of the particles during the formation and aging of the soft-glass state. The fraction of localized particles, $f_0$, increases rapidly during the early formation stage and grows more slowly during subsequent aging, while the characteristic localization length $r_{\mathrm{loc}}$ steadily decreases. Despite the strongly varying rates of aging at different concentrations, both $f_0$ and $r_{\mathrm{loc}}$ scale with the elastic shear modulus $G^{\prime }$ in a manner independent of concentration. During the later aging stage, the scaling between $r_{\mathrm{loc}}$ and $G^{\prime }$ agrees quantitatively with a prediction of naive mode coupling theory. Breakdown of agreement with the theory during the early formation stage indicates the prevalence of dynamic heterogeneity, suggesting the soft solid forms through precursors of dynamically localized clusters.

中文翻译：

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微观遍历破坏性决定了形成玻璃的纳米粘土悬浮液的弹性的出现和演化

我们报告了一项结合x射线光子相关光谱（XPCS）和原位流变学的研究，以研究合成锂蒙脱石粘土皂石的水悬浮液的微观动力学和力学性能，该锂皂石粘土由带电的纳米级圆盘状颗粒组成。颗粒浓度在3.25至3.75 wt％范围内的悬浮液会随着时间的推移从流体演变成显示老化行为的软玻璃。XPCS测量表征了软玻璃状态形成和老化过程中颗粒的定位。局部粒子的比例，$F_0$，在早期形成阶段迅速增加，在随后的老化过程中缓慢增长，而特征化的定位长度 ${\mathrm{[R}}_{\mathrm{位置}}$稳步下降。尽管不同浓度下的衰老率差异很大，但两者$F_0$ 和 ${\mathrm{[R}}_{\mathrm{位置}}$ 与弹性剪切模量成比例 $G^{\prime }$以与专注无关的方式。在后期的老化阶段，${\mathrm{[R}}_{\mathrm{位置}}$ 和 $G^{\prime }$在定量上与朴素模式耦合理论的预测吻合。在早期形成阶段，与理论的一致性破坏表明存在动态异质性，表明通过动态局部团簇的前体形成了软固体形式。