Characteristics of Molecular Forces for Freezing Including Fine Particles

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When water and water solution involving foreign fine particles freeze, the freezing process can be divided into two cases whether particles are trapped in the freezing layer or particles are swept out from the freezing layer. The trapped and swept phenomenon of foreign particles due to freezing is widely an important problem related to the freezing process of sludge, frost heaving and the solidification of metal including foreign particles.In this study, we have investigated this phenomenon due to freezing experimentally and theoretically. The trapped and swept phenomenon largely depends on the freezing rate, the size of particle and the surface electric charge of particle. The critical freezing rate is defined as the maximum freezing rate where particles are swept out from the freezing layer. In order that a foreign particle is swept out from the ice layer, a film of liquid of sufficient thickness should exist between a particle and ice, layer. Namely, the repulsive force should act between a particle and ice layer in order to transport water towards the growing ice surface behind the particle. We have presented a model of the trapped and swept phenomenon of fine particles due to freezing, based on electric double layer force, van der Waals force, viscous force and gravity force as the force acting on a particle. The calculated results for the critical freezing rate were in agreement with the experimental results using various particles.Next, we have investigated the swept and trapped phenomena of dissolved gas in water due to freezing. The ice layer including gas strongly depends on the freezing direction, the freezing rate and the volume of dissolved gas in water.