Phase-Field Modeling of Microstructural Evolution by Freeze-Casting

Freeze-casting has attracted great attention as a potential method for manufacturing bioinspired materials with excellent flexibility in microstructure control. The solidification of ice crystals in ceramic colloidal suspensions plays an important role during the dynamic process of freeze-casting. During solidification, the formation of a microstructure results in a dendritic pattern within the ice-template crystals, which determines the macroscopic properties of materials. In this paper, the authors propose a phase-field model that describes the crystallization in an ice template and the evolution of particles during anisotropic solidification. Under the assumption that ceramic particles represent mass flow, namely a concentration field, the authors derive a sharp-interface model and then transform the model into a continuous initial boundary value problem via the phase-field method. The adaptive finite-element technique and generalized single-step single-solve (GSSSS) time-integration method are employed to reduce computational cost and reconstruct microstructure details. The numerical results are compared with experimental results, which demonstrate good agreement. Finally, a microstructural morphology map is constructed to demonstrate the effect of different concentration fields and input cooling rates. The authors observe that at particle concentrations ranging between 25 and 30% and cooling rate lower than -5 degrees min(-1) generates the optimal dendrite structure in freeze casting process.