胶体与湿颗粒体系的聚集行为及其结构转变的力学谱研究

复杂体系（胶体、颗粒物质等）的聚集行为及其结构转变研究是软凝聚态物理的前沿领域之一。胶体和颗粒物质在一定的体积分数/堆积密度下会发生液-固转变。然而，关于胶体和颗粒物质在外界因素诱导下的各种聚集行为及其液-固转变的弛豫特征与机制的研究进展较为缓慢。本课题在前期工作基础上，基于内耗技术研究胶体（硬球、软球）以及湿颗粒体系的聚集行为及其液-固转变的动力学特征与耦合机制。通过测量体系的力学性质（模量和力学损耗）随体积分数/堆积密度、温度、频率与应变振幅的变化曲线，探讨粒子大小、形状与弹性系数等因素对体系的聚集行为及其液-固转变的影响。分析力学损耗的具体来源，获得其对研究体系具体材料参数的定量或半定量的依赖关系。基于耦合模型获得胶体与湿颗粒体系液-固转变的耦合特征与规律，揭示这两种体系的聚集行为及其液-固转变的耦合机制和内在关联。该项目对深入理解玻璃化转变有重要意义，同时拓展了内耗学科的研究领域。

Investigation on aggregation behaviors and structural changes of complex systems such as colloids and granular matters is one of the frontier areas in soft condensed physics. The liquid-solid transition of colloidal and granular systems usually occurs at a certain volume fraction or packing density. However, the aggregation behaviors and the relaxation characteristics and mechanism of colloidal and granular systems under the environmental conditions are still not well understood. Therefore, based on the previous work, we have proposed a project to study the aggregation behaviors as well as dynamics and cooperative mechanism of liquid-solid transition in colloidal (hard sphere and soft sphere) and wet granular systems by mechanical spectroscopy. Through the measurements of mechanical properties such as modulus and mechanical loss of the systems with increasing volume fraction/packing density, temperature, frequency and amplitude, the effects of different factors such as the sizes, shapes and elastic coefficient of particles on the aggregation behaviors and the liquid-solid transition of colloidal and wet granular systems will be investigated. The origin of mechanical loss will be analyzed and a quantitative or semi-quantitative relationship between mechanical loss and material parameters of different systems will be obtained. Based on the coupling model, the coupling behaviors and variation rules of liquid-solid transition of colloidal and wet granular systems will be obtained, and the aggregation behaviors and cooperative mechanism and intrinsic connection of the liquid-solid transition for these two systems will be clarified. This research will have important implications for deeply understanding the glass transition, and develop the research field of internal friction.