Polydispersity Effects in a Colloidal Dispersion Fluid

由于多分散胶体流体是一个复杂的体系，因此不可避免地需要引入一个合适的模型来研究该体系的基本性质。此外，为了提高对系统的理解，获得可用的物理量表达式是很重要的。在本项目中，我们使用硬球Yukawa模型，并利用Ornstein-Zernike方程的解析MSA解，成功地获得了静态结构因子、中子(或光)散射截面和热力学参数的解析表达式。所得到的表达式是有用的和紧凑的，它们提示我们将其应用于多分散流体。利用这些表达式，我们实际研究了大小和相互作用多分散性对可观测量的影响。主要工作如下：1.相互作用多分散性对描述胶体PA-…密度波动的结构因子的影响颗粒数越多，与粒度多分散性的影响定性相同，但前者的影响弱于后者。相互作用多分散性对气液转变临界点附近的状态方程等温线有明显的特征影响，而相互作用多分散性效应的大小和方向则相反。研究了胶体硬球二元系多分散流体的可测结构因子。发现该因子有一个奇特的峰。峰对大小的多分散性非常敏感，并逐渐向已知的多分散度增大的驼峰方向变化。讨论了这种特殊结构与胶体颗粒内部物质分布的密切关系，并研究了溶剂中胶体颗粒之间的相互作用。讨论了溶剂介导的相互作用可能比范德华相互作用范围更长、更重要。但是，这项工作还需要进一步调查和改进。较少

Since a polydisperse colloidal fluid is a complex system, it is inevitable to introduce an appropriate model which makes it possible to work essential properties of the system. Moreover, in order to improve understanding of the system it is important to obtain available expressions of physical quantities. In the present project, we employed the hard sphere Yukawa model for the system, and using the analytical MSA solution of the Ornstein-Zernike equation we succeeded to obtain analytical expressions for the static structure factor, the neutron (or light) scattering cross section and the thermodynamical quantities. The expressions obtained is useful and compact, and they prompt us to apply to the polydisperse fluids. Using the expressions, we actually worked the size and interaction polydispersity effects on observable quantities. The abstract of the work is as follows:1. The interaction polydispersity effect on the structure factor describing the density fluctuation in the colloidal pa … More rticle numbers is qualitatively the same effect as the size polydispersity has, but the former effect is weaker than the latter.2. The interaction polydispersity has a characteristic effect on the isotherm of the equation of state near the critical point of the gas-liquid transition, and the directions of the size and interaction polydispersity-effects are opposite.3. The measurable structure factor was investigated for the binary-pecies polydisperse fluid of colloidal hard spheres. It was found that the factor has a peculiar peak. The peak is very sensitive to the size polydispersity and changes gradually to the hump already known as the polydispersity increases. It was discussed that the peculiar structure is closely related to material distribution inside colloidal particles.The interaction between colloidal particles in a solvent was worked. It was discussed that the solvent-mediated interaction could be longer-range and more important than the van der Waals interaction. However, this work needs further investigation and improvement. Less