Computational Phase-Field Modeling for Microstructural Evolution in Bioinspired Material from Freeze-Casting Process

In this research, a numerical model for microstructure evolution in the freeze-casting process is established. The theoretical mechanism behind the ceramic colloidal suspension solidification process is revealed; also, the relationship between the critical factors and the porous structures is quantitatively described. The model is benchmarked with experimental results and found to be in good agreement. In recent decades, freeze-casting, with an excellent flexibility in microstructure control, has attracted great attention as a potential manufacture method of bioinspired materials. Solidification of ice crystal in ceramic colloidal suspension is found as an important role in freeze-casting dynamical process. The formation of microstructure in solidification results in a dendritic pattern within the ice-template crystallization, determining the macroscopic properties of the materials. In this dissertation, a phase-field model is proposed to describe the crystallization of the ice-template and the particle evolution during the solidification. The ceramic particle is regarded as a mass flow, namely a concentration field. Following the 1D freeze-casting model by Peppin and a general phase-field model for binary alloy casting, a sharp interface model is built up and transformed into a continuous boundary value problem by the phase-field method. The adaptive finite element technique is employed to decrease the computational cost; furthermore, the algorithm reconstructs the details of microstructure, and the influence of the anisotropy may be exhibited. Finally, the numerical results are compared with the experimental data, which demonstrate a good agreement. Both results identify several essential physical parameters controlling the ice-template morphology and the formation of microstructure, such as front velocity, temperature gradient, and particle concentration. The first numerical model to simulate the structural detail in freeze-casting is constructed in the study; moreover, significant perspectives on designing the bioinspired material is presented.