We discuss that the bulk crystal growth from the melt is dominated by the bulk melt regardless of the variation of the interface phenomena. During crystal growth from the oxide melt the ionic species are segregated in the diffusion boundary layer where the quantitative ratio of the metal to oxygen is not stoichiometric and thus, the oxygen is an independent component, resulting in increment of degree of freedom by one. This changes the population and segregation of ionic species at the interface, however, the composition of grown crystal is not affected by this change but is predominated by the bulk melt. This is also the case with the growth under a current injection to the interface region yielding the interface electric field of ~ 1 V/cm. On the other hand, when an external field is applied to the interface region to introduce the energy of several kJ/mol, a new phase relationship is attained between the solid and liquid. For instance, an electrostatic electric field with the magnitude of ~ 104 V/cm becomes the third parameter following those of composition and temperature in the phase diagram, which provides one degree of freedom enabling the conversion of the incongruent material to congruent.
In this paper, we introduce a mean-field theory to describe phase separations in mixtures of a nematic liquid crystal and a colloidal particle. The theory takes into account an orientational ordering of liquid crystals and a crystalline ordering of colloidal particles. We calculate phase diagrams on the temperature-concentration plane, depending on interactions between a liquid crystal and a colloidal surface. We find various phase separation processes, such as a nematic-crystal phase separation and nematic-isotropic-crystal triple point. Inside the binodal curves, we have new unstable and metastable regions which are important in phase ordering dynamics of colloidal dispersions.
Crystallization of 4He quantum crystals in superfluid advances very rapidly at low temperatures owing to the fast mass transport via superflow and the negligibly small latent heat. Rapid crystallization allows the fundamental physics of crystal shape and growth to be explored in a measurable time scale in laboratories and the peculiar interfacial phenomena such as the crystallization wave propagation to be realized. Rapid crystallization also means that 4He crystals can response to tiny driving forces which have been neglected for ordinary classical crystals. Here, we report the effects of novel driving forces, such as gravity change, superflow, wettability and acoustic radiation pressure. Subjected to these driving, 4He crystals were strongly deformed and brought to highly non-equilibrium states, showing various kinds of extraordinary crystallization and relaxation processes in the superfluid. Furthermore, huge 4He crystals were successfully obtained in zero gravity and their shape was analyzed by the theory of equilibrium shapes.
Position of crystal/melt interface is determined by temperature distribution, and growth rate can be controlled by cooling rate. When the growth rate was zero or small, a straight crystal/melt interface formed parallel to the isothermal line. On the other hand, crystal/melt interface changed to zigzag faceted morphology when the growth rate increased. It will be explained how the interface morphology transition has been occurred by using direct observed movie. And, this experimental method can be applied to measurement of the effective thermal conductivity around grain boundaries.
This paper reviews a recent study on the melt crystallization mechanism analyzed with a method of dimensional reduction for high-dimensional data representing distribution functions, which are obtained by a molecular dynamics simulation for crystallization of a Lennard-Jones melt. Owing to this method, the nucleation of a crystal with a distorted structure and the reconstruction of the distorted crystal to a crystal with a more energetically stable structure, which can hardly be recognized by visual inspection of the structure and distribution functions, are visually confirmed. This method can also evaluate the time evolution of local structural order distribution in the melt during crystallization.