Freezing colloidal suspensions: ice segregation and pattern formation
Dr. Anthony Anderson (University of Cambridge)
Thursday 14th March, 2013 14:00-15:00 Maths 203
Colloidal suspensions do not freeze uniformly; rather, the frozen phase (e.g. ice) becomes segregated, trapping bulk regions of the colloid within, which leads to a fascinating variety of patterns that are of both practical and mathematical interest. Yet, despite the central importance of ice segregation in several applications, its physics are still poorly understood. In this talk, I will identify the key physical processes involved in freezing colloids, with an eye towards the development of general mathematical models. In this vain, I will review previous work on the micro-scale physics that govern the interaction of a single inert particle with a solid-liquid interface where phase change is occurring. From this foundation, I will discuss attempts to formulate homogenized continuum theories to model the freezing behaviour of concentrated suspensions. While these continuum theories provide insight into the possible mechanisms of pattern formation caused by ice segregation, we've recently conducted directional solidification experiments that reveal some key inadequacies of these theories. I will discuss these experimental observations and present a case study of periodic ice-lensing using a 1D dynamical model. This model reproduces several of the experimental observations and has some important implications in frost heave.