Thermodynamics and Structure of Plate-Like Particle Dispersions

Abstract: A considerable amount of mineral particles are found to have a plate-like shape. The work in this thesis concerns theoretical investigations, using Monte Carlo method, of the properties of such particles in aqueous solutions. The objectives were first to create a model that could capture the essential physics of clay suspensions and also to understand the role of thermodynamics in certain chemical processes. For all investigations, the results are related to experimental studies. The acid-base behavior of clays have been studied, using the primitive model, and an excellent agreement between simulated and experimental curves was found. The formation of gel phases as a function of the charge anisotropy have also been investigated. Liquid-gel and sol-gel transitions are found to occur for high and moderate charge anisotropy respectively. There transitions were also found to be size and salt dependent. In absence of charge anisotropy, a liquid-glass transition is reported. The formation of smectic and columnar liquid crystals phases with plate-like particles has been found to be favored by a strong charge anisotropy, in opposition to what was observed for nematic phases. New liquid-crystal phases were also reported. The stability and growth of nanoplatelets is discussed. It was found that the internal Coulombic repulsion could be the cause of the limited growth of C-S-H platelets. The influence of thermodynamics on the aggregation mode of such platelets was also investigated.