Hydrodynamic coarsening in phase-separated silicate melts

TL;DR

This study uses in-situ synchrotron tomography to reveal that phase separation in silicate melts exhibits linear coarsening driven by viscous flow, with domain size growth governed by surface tension and viscosity ratios.

Contribution

It provides the first direct 3D visualization and quantitative analysis of viscous flow-driven coarsening in phase-separated silicate melts, contrasting with diffusive growth models.

Findings

Linear domain growth observed over time.

Viscous flow dominates over diffusion in coarsening.

Domain geometry remains statistically similar when scaled by size.

Abstract

Using in-situ synchrotron tomography, we investigate the coarsening dynamics of barium borosilicate melts during phase separation. The 3-D geometry of the two interconnected phases is determined thanks to image processing. We observe a linear growth of the size of domains with time, at odds with the sublinear diffusive growth usually observed in phase-separating glasses or alloys. Such linear coarsening is attributed to viscous flow inside the bicontinuous phases, and quantitative measurements show that the growth rate is well explained by the ratio of surface tension over viscosity. The geometry of the domains is shown to be statistically similar at different times, provided that the microstructure is rescaled by the average domain size. Complementary experiments on melts with a droplet morphology demonstrate that viscous flow prevails over diffusion in the large range of domain sizes measured in our experiments (1 - 80 microns).