Topology and numerical simulation of phase separation in sodium silicate glasses

• Liquid/liquid phase separation lead to the formation of droplets.
• The droplets possess a lower viscosity in comparison to the matrix phase.
• A core/shell structure is formed leading to non-linear droplet growth.
• An increase of the viscosity in the shell with the radius of the droplet is stated.

Liquid/liquid phase separation in glasses may lead to heterogeneities in the nanometer scale. The droplet phase can be nucleated from a homogeneous liquid. The chemical composition of the nanoscale phase separation changes with temperature in contrast to the nanocrystallization. The understanding of topological changes in the glass networks is of importance for the changes in viscosity and the microscopic changes in the growth rate during the course of the phase separation process. This work considers a glass system in which one of the separated phases is much more rigid than the other and the formed new phase possesses a lower viscosity in comparison to the matrix phase. The chemical composition of the matrix changes only in a thin layer around the growing droplets. A shell with increased rigidity is formed which decelerates the growth by encapsulation.

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