Speed-dependent ice bandings in freezing colloidal suspensions

Abstract

Formation mechanism of speed-dependent ice bandings in freezing colloidal suspensions, of significance in frost heaving and materials science, remains a mystery. With quantitative experiments, we propose a possible mechanism of speed-dependent ice bandings by focusing on the particle packing density and dynamic interface undercooling. The particle packing density ahead of the freezing interface decreases with increasing pulling speeds, attributed to the speed-dependent packing of particles. Through affecting the curvature undercooling of pore ices, the speed-dependent packing of particles can be used to explain speed-dependent thicknesses of ice bandings. The dynamic interface undercooling was obtained to explore curvature undercooling of pore ices and quantitative details of transient interface positions, speeds and undercooling were given. All the evidences imply that the speed-dependent particle packing and dynamic interface undercooling are responsible for speed-dependent ice bandings. (Xin Lin) 2 / 16 direction of the thermal gradient. These perpendicular segregated patterns are of great importance due to their effects on the dynamics of frost heaving [10-12] and mechanical properties of freeze casting porous materials [3,13].Recently, Anderson et al.[9] discovered pulling-speed-dependent ice bandings

Experimental and numerical studies on freezing of droplets under effects of nanoparticles and magnetic fields

“…The scaling model can predict the shape change features of nanofluid droplets with low particle volumetric concentrations (C0 < 1.0%) well. However, the theoretical calculations and experimental data differ at higher particle volumetric concentrations (C0 ≥ 1.0%) because of the accumulation of particles in the liquid phase near the freezing front increases to a constant packing density at high particle volumetric concentrations [10,148,216,217]. Further increases in the initial concentration cannot change the concentration near the freezing front.…”

“…The freezing process of a colloidal suspension is very Chapter 1 2 different from that of pure water due to the complex interactions between the dispersed particles and the liquid-solid interfaces. The engulfment/rejection of particles and the alignment of particles due to the freezing front can always occur during the solidification process in colloidal suspensions [10][11][12].…”

“…Analogous to the multiphase flow model, the evolution equation for the temperature distribution function can be expressed as (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) where i  is the weight coefficient, which is given as ( ) ST denotes the source term in Eq. (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), which is given by [283,284] ,0 The enthalpy can be calculated with the temperature and solid volume fraction as ( ) ( ) domains, respectively, and the symbol * represents the state before streaming.…”

“…10 The morphologies of freezing fronts in the freezing of aqueous suspensions with montmorillonite clay (a) -(c) and kaolinite clay (d)-(f)[146,147].The existence of transverse crystals, which are normal to the freezing direction, indicates the appearance of unstable structures in the observed domain inFigure 2-11(a). Global instabilities (denoted by black arrows) and localised instabilities (denoted by white arrows) are used to describe these unstable structures.…”

“…Eq (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). into Eq (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14),. the scales of the horizontal velocity u can be obtained as in the central region is the result of the horizontal flow and can be calculated as…”