A Buoyancy-Assisted Mechanism of Scalable Colloidal Crystallization

ME Torki and VS Deshpande, ADVANCED POWDER TECHNOLOGY, 34, 104099 (2023).

DOI: 10.1016/j.apt.2023.104099

An ingenious mechanism of scalable grain crystallization inside a 3D colloidal domain is proposed. The mechanism is materialized by random vibration either on a jammed particle assembly or on freefalling particle fronts traveling inside a colloidal domain under the influence of near-zero or limited buoyancy. Brownian dynamics is invoked by employing a generalized Langevin's thermostat equation, which solves for a time-variant state of particles undergoing moderate random vibration under the effect of a viscose solvent until full occupancy of the box is reached at fixed temperature. The contacting particles admit a simple mass-spring-dashpot discrete-element model with negligible sliding friction. The problem seeks optimized states with the highest overall crystallinity and lowest grain-boundary effect by parametrization of the sedimentation domain geometry as well as the particles' and solvent's properties. The parametric study investigates the effects of geometry (box height, length and cross-sectional mismatch), particle density and solvent viscosity on evolving and ultimate-state crystallinity, chiefly quantified by an overall crystallinity ratio. Buoyancy-assisted sedimentation reflects the formation of FCC-dominant particle submanifolds, and is further suggestive of optimum ranges of box height, solvent viscosity and particle density as opposed to critical ranges of box length and in-plane aspect ratio. Depending on the desired level of crystallinity, the proposed mechanism can be regarded as supplant or supplement for other crystallization mechanisms including aging, magnetization, etc. & COPY; 2023 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights reserved.

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