|Alternative Title||Microstructural Study of Aggregation Process and Shear Deformation in The Interfacial Colloidal System|
|Place of Conferral||北京|
|Keyword||水油界面 胶体聚集 二元 剪切流动 相互作用 微观结构|
Colloidal suspensions are widely used in industrial production and daily life, such as cosmetics, ink, paints and so on. The aggregation behavior of colloidal systems has always been a hot issue of research, which is related to the stability and rheology of colloidal systems, and has been widely used in petrochemical, biomedical and environmental management. Therefore, studying colloidal aggregation behavior has both profound theoretical significance and strong practical value.
In recent years, interface systems formed by two kinds of insoluble liquids have often been used to study colloidal aggregation behavior. The main reasons are as follows:
(1) Colloidal particles are confined in a two-dimensional plane due to interfacial tension, and all information of the microstructure can be contained in one plane so that the microscopic structures and aggregation processes in 2D suspensions are much more easily and clearly observed compared to the three-dimensional suspensions.
(2) A large number of studies have shown that the interaction between colloids can be tailored by various means. Colloidal particles can form a variety of rich structures at the interface, like soap forths, particle loop and aggregates with different morphology.
At present, the research of colloidal particles at the inteface mainly focuses on two aspects. On the one hand, the origin and mechanism of various types of interaction forces between colloidal particles at the interface were widely studied. By changing the electrolyte concentration and surfactant in the liquids, the interaction force between colloidal particles in different systems can be measured and the potential energy curve plotted. On the other hand, many researches were about how to change the microstructure of aggregates or gel network formed by the colloidal particles at the interface. There are few analyses of the dynamic process and microscopic aggregation behavior of colloidal particles on the interface under different conditions. However, previous studies mainly focused on simply one-component systems with mono-charged and mono-sized particles. Little is known about the mixed systems composed of particles with different interactions, which are more generally existed in nature and industry. And the performance of the heterogeneous particle-mixed monolayer membrane is more abundant, which opens up a new way for controling structures.
In this paper, the liquid-liquid interface formed by water (or salt solution) and decane was used to study the aggregation process of charged colloidal spheres at different electrolyte concentrations and surface coverage, and the dynamic behavior of particles or aggregates and structural evolution were quantitatively characterized. Besides, the microstructure scale and morphology of charged colloidal particles with different salt solution concentrations and different surface coverages were compared and analyzed. It is found that the addition of salt in the aqueous phase can reduce the interparticle repulsion and accelerate the aggregation speed. The shape of the cluster on the initial interface affects the aggregation process. The fractal dimension of the aggregated network decreases with increasing concentration of salt solution. And the regimes of aggregating change from RLCA to DLCA.
The influence of the doping ratio of hard spheres and charged particles on the interfacial collidal structures was also studied. In order to prepare binary colloidal systems with different area fraction ratios, we mixed two kinds of colloidal particle suspensions according to the required volume ratio, and then respectively diffused at the pure water-oil interface and the salt solution-oil interface, tracked the colloidal particles and accumulating the aggregate structure. The analysis was conducted to find the correlation between the degree of doping and the degree of aggregation. The experimental results and analysis show that the introduction of hard spheres can induce the aggregation of charged spheres at the pure water-oil interface. Changing the mixing ratio of particles with different potentials can change the path, rate and state of particle aggregation.
In this paper, the deformation of the interfacial gel network under shear was also studied. Previous studies have focused on their mechanical behavior, such as yield, elastic strain, and changes in macroscopic shape under load, such as the size and density of clusters. These studies lack the study of the microscopic mechanism of deformation. In this paper, a self-designed interface shearing device is used to apply shear to the static gel on the interface. We pay attention to the deformation of the interfacial gel microstructure under shearing, and summarize the several deformation modes corresponding to different morphological microstructures. It is hoped that there will be some reference for more complex multi-scale microstructures.
|谢天. 界面胶体体系聚集机制及剪切形变的微观结构研究[D]. 北京. 中国科学院大学,2019.|
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