Solidification of Suspended Colloids at Nonplanar Interfaces

Abstract

Summary Freeze‐drying has been widely used to deliver wide varieties of porous structures because of its processing ease and environment‐friendly nature. However, freezing of colloidal suspensions is also complex that depends on interplay of multiple parameters including the rate of processing, the magnitude of temperature gradient, and the portion of each component in the liquid mixture. While these parameters are relatively easy to measure and control, the mutual interaction between the growing solid‐liquid interface and the solute content in the suspension is much harder to evaluate. We present a two‐dimensional numerical model to simulate this latter scenario in a unidirectional freezing process, with a focus of colloidal particle motions at self‐evolving nonplanar solid‐liquid interface. This growing interface is determined by a real‐time thermal and constitutional supercooling in the liquid medium. We found colloidal particles can be rejected by the interface if the repelling from the interface is strong and freezing speed is low. Microscale liquid medium among colloidal particle gaps can freeze when particles are highly packed between frozen solid tips, with small pores easily frozen than larger ones. Noting all these findings are revealed by coupling our simulation with a visualization module though high performance GPU devices.

Stability of ice lenses in saline soils

“…While it is known that frost heave (the uplift of the soil surface in winter) is caused by the formation of ice lenses, the physical mechanisms governing their initiation and growth have yet to be fully explained (O'Neill 1983;Rempel 2010;Peppin & Style 2013;Wettlaufer 2019). In soils with a high clay content, ice lenses can become non-planar, forming complex polygonal and reticulate vein structures (Taber 1929;Mackay 1974;Arenson et al 2006;Peppin, Elliott & Worster 2006;Deville 2013;El Hasadi & Kodadadi 2015;Wang et al 2016;Xu et al 2016;You, Wang & Worster 2018b). In addition, most soils and colloidal suspensions contain dissolved solutes in the pore fluid, which significantly influence the freezing process (Hallet 1978;Chamberlain 1983;Arenson et al 2006;Pekor 2014;Schollick et al 2016;Wang et al 2016;You et al 2018a;Ginot et al 2019).…”