Time lapse, three dimensional in situ imaging of ice crystal growth in a colloidal silica suspension

TL;DR

This study employs fast X-ray computed tomography to visualize ice crystal growth in colloidal silica suspensions in three dimensions over time, revealing how particle concentration influences the freezing process.

Contribution

It introduces a novel in situ imaging technique for observing ice growth in colloidal suspensions, providing new insights into the effects of particle concentration on freezing behavior.

Findings

Local colloid concentration does not affect crystal growth until particles are densely packed.

Concentrated colloids behave like a viscous liquid with a concentration-dependent freezing point.

The method enables real-time, 3D visualization of ice formation in complex suspensions.

Abstract

The freezing of colloidal suspensions is encountered in many natural and engineering processes such as the freezing of soils, food engineering, and cryobiology. It can also be used as a bio-inspired, versatile, and environmentally-friendly processing route for porous materials and composites. Yet, it is still a puzzling phenomenon with many unexplained features, due to the complexity of the system and the space and time scales at which the process should be investigated. We demonstrate here the interest of fast X-ray computed tomography to provide time-lapse, three-dimensional, in situ imaging of ice crystal growth in a colloidal silica suspension. The experimental measurements show that the local increase of colloid concentration does not affect the growth kinetics of the crystals, until the colloidal particles become closely packed. For particles much smaller than ice crystals, the concentrated colloidal suspension is equivalent to a simple liquid phase with higher viscosity and a freezing point determined by the concentration of colloidal particles.