In Situ X-Ray Radiography and Tomography Observations of the Solidification of Alumina Particles Suspensions. Part II: Steady State

TL;DR

This study uses in situ X-ray imaging to analyze how alumina particles are redistributed during steady state ice crystal growth in colloidal suspensions, revealing direct interface interactions as the main mechanism.

Contribution

It demonstrates that particle redistribution during steady state solidification is driven by direct interface interactions, not diffusion or constitutional supercooling, and identifies key controlling parameters.

Findings

Particles are redistributed by direct interaction with the moving interface.

Diffusion does not determine concentration profiles at the studied velocities.

Parameters like interface velocity, particle size, and crystal orientation influence redistribution.

Abstract

This paper investigates the behaviour of colloidal suspensions of alumina particles during directional solidification, by in situ high-resolution observations using X-ray radiography and tomography. This second part is focussed on the evolution of ice crystals during steady state growth (in terms of interface velocity) and on the particles redistribution taking place in this regime. In particular, it is shown that diffusion cannot determine the concentration profile and the particles redistribution in this regime of interface velocities (20-40 microns/s); constitutional supercooling arguments cannot be invoked to interpret particles redistribution. Particles are redistributed by a direct interaction with the moving solidification interface. Several parameters controlling the particles redistribution were identified, namely the interface velocity, the particle size, the shape of the ice crystals and the orientation relationships between the crystals and the temperature gradient.