Multiphase imaging of freezing particle suspensions by confocal microscopy

TL;DR

This paper demonstrates the use of confocal microscopy for in situ multiphase imaging of particle segregation and ice growth during the ice-templating process, providing new insights into microstructure formation.

Contribution

It introduces confocal microscopy as a novel in situ technique for observing particle-scale microstructures in ice-templating, enhancing understanding of solidification microstructures.

Findings

Confocal microscopy enables detailed observation of ice growth and particle organization.

Temperature gradient and growth rate significantly influence microstructure.

Addition of PVA affects the solidification microstructures.

Abstract

Ice-templating is a well-established processing route for porous ceramics. Because of the structure/properties relationships, it is essential to better understand and control the solidification microstructures. Ice-templating is based on the segregation and concentration of particles by growing ice crystals. What we understand so far of the process is based on either observations by optical or X-ray imaging techniques, or on the characterization of ice-templated materials. However, in situ observations at particle-scale are still missing. Here we show that confocal microscopy can provide multiphase imaging of ice growth and the segregation and organization of particles. We illustrate the benefits of our approach with the observation of particles and pore ice in the frozen structure, the dynamic evolution of the freeze front morphology, and the impact of PVA addition on the solidification microstructures. These results prove in particular the importance of controlling both the temperature gradient and the growth rate during ice-templating.