Boundary-induced inhomogeneity of particle layers in the solidification of suspensions

Abstract

When a suspension freezes, a compacted particle layer builds up at the solidification front with noticeable implications on the freezing process. In a directional solidification experiment of monodisperse suspensions in thin samples, we evidence a link between the thickness of this layer and the sample depth. We attribute it to an inhomogeneity of particle density that is attested by the evidence of crystallization at the plates and of random close packing far from them. A mechanical model based on the resulting modifications of permeability enables us to relate the layer thickness to this inhomogeneity and to select the distribution of particle density that yields the best fit to our data. This distribution involves an influence length of sample plates of about eleven particle diameters. Altogether, these results clarify the implications of boundaries on suspension freezing. They may be useful to model polydisperse suspensions with large particles playing the role of smooth boundaries with respect to small ones.

Ultrastrong Hierarchical Porous Materials via Colloidal Assembly and Oxidation of Metal Particles

“…In this process, the aqueous suspension is cast in a customized setup that allows for the controlled growth of ice crystals via unidirectional freezing (Figure 4B). [ 60 ] The ice crystals are subsequently removed from the solid frozen structure through a standard freeze‐drying process. To reach the low viscosity required for controlled ice growth, we used an aqueous suspension containing aluminum particles, the dispersant citric acid and poly(vinyl alcohol) as organic binder.…”

A New Era of Integrative Ice Frozen Assembly into Multiscale Architecturing of Energy Materials

“…[138] Notably, the growth rate can increase with respect to high thermal conductivity, [140] small size of solute particles, [141] low solute concentration, and ionic salt strength. [137] Thus, the kinetics of the assembly process plays a vital role in determining the final porous structure.…”

“…Given by that the structural changes with definite porous arrangements depend on the growth speed of solid freezing front during a freezing process, the kinetics can be controlled by various factors such as, heat flow, temperature, freezing velocity, critical velocity, solute, and solvent. [ 137 ] The particle in colloidal suspension can be either rejected and pushed ahead or trapped in the liquid‐solid interface, varying the freezing velocity, so‐called the movement rate of the freezing front during solidification. Solving Equations (1) and (3), the critical point of the freezing velocity, that is, critical velocity ( v c ), can be derived as below.…”

Stability of ice lenses in saline soils

“…Pressures are defined relative to atmospheric (gauge), so that p r = 0 for a reservoir at atmospheric pressure. A linear temperature gradient is imposed on the system, and a constant freezing speed V. This can be achieved by ramping the temperatures at the top and base (Penner 1986;Konrad 1989a) or by moving the soil at speed V through a fixed temperature gradient (Watanabe & Mizoguchi 2000;Peppin, Wettlaufer & Worster 2008;Anderson & Worster 2014;Schollick et al 2016;You et al 2018a;Saint-Michel et al 2019). At steady state the ice lens growth speed V il is equal to V.…”

“…Microscale experiments capable of observing the pore contents during freezing, such as Raman spectroscopy (Watanabe & Mizoguchi 2000), X-ray scattering (Spannuth et al 2011) and confocal microscopy Ginot et al 2019;Saint-Michel et al 2019) will play an important role in clarifying the situation.…”