Structural properties of materials created through freeze casting

Upon freezing of an aqueous suspension of colloidal particles, ice platelets or dendrites with high aspect ratios are formed that engulf or reject the particles, depending on their size and the velocity of the advancing ice front. As the particles are pushed between the growing crystals, concentrated regions of colloidal particles are formed. Recent experiments have exploited this to create strong, porous materials with a well-controlled microstructure. We investigate this process by means of molecular dynamics simulations, focusing on the effect of the ice front velocity on the structure of the resulting material. We develop a model that accounts for particle engulfment or rejection by the ice front, and study both columnar and lamellar geometries. The degree of order of the resulting solid and the thickness of the walls surrounding the pores are shown to be determined by front velocity and initial particle concentration in the suspension.