In Situ X-Ray Radiography and Tomography Observations of the Solidification of Alumina Particles Suspensions. Part I: Initial Instants

TL;DR

This study uses in situ X-ray imaging to observe the initial solidification behavior of alumina particle suspensions, revealing mechanisms of interface evolution and particle redistribution crucial for freeze-casting processes.

Contribution

It provides new insights into the early-stage solidification mechanisms of colloidal suspensions, highlighting the role of crystal type and interface dynamics without requiring Mullins-Sekerka instabilities.

Findings

Particle redistribution depends on crystal type.

Interface pattern evolution does not require Mullins-Sekerka instabilities.

Initial solidification phenomena influence subsequent crystal growth.

Abstract

This paper investigates by in situ high-resolution X-ray radiography and tomography the behaviour of colloidal suspensions of alumina particles during directional solidification by freezing. The combination of these techniques provided both qualitative and quantitative information about the propagation kinetic of the solid/liquid interface, the particles redistribution between the crystals and a particle enriched phase and the 3D organisation of the ice crystals. In this first part of two companion papers, the precursor phenomena leading to directional crystallisation during the first instants of solidification is studied. Mullins-Sekerka instabilities are not necessary to explain the dynamic evolution of the interface pattern. Particle redistribution during these first instants is dependent on the type of crystals growing into the suspension. The insights gained into the mechanisms of solidification of colloidal suspensions may be valuable for the materials processing routes derived for this type of directional solidification (freeze-casting), and of general interest for those interested in the interactions between solidification fronts and inert particles.