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

This paper investigates the behavior 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 particle redistribution taking place in this regime. In particular, it is shown that particle diffusion cannot determine the particle concentration profile in this regime of interface velocities (20-40 mu m/s). Particles are redistributed by a direct interaction with the moving solidification interface. Several parameters controlling the particle 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.