Microstructures and mechanics in the colloidal film drying process
Abstract
We use Brownian Dynamics (BD) simulations and continuum models to study the microstructures and mechanics in the colloidal film drying process. Colloidal suspensions are compressed between a planar moving interface and a stationary substrate. In the BD simulations, we develop a new Energy Minimization Potential-Free (EMPF) algorithm to enforce the hard-sphere potential in confined systems and to accurately measure the stress profile. The interface moves either at a constant velocity Uw or via a constant imposed normal stress Σe. Comparing the interface motions to the particle Brownian motion defines the Péclet numbers PeU = Uwa/d0 and PeΣ = Σea3/kBT, respectively, where d0 = kBT/ζ with kBT the thermal energy scale, ζ the single-particle resistance, and a the particle radius. With a constant interface velocity, thermodynamics drives the suspension behavior when PeU ≪ 1, and homogeneous crystallization appears when the gap spacing between the two boundaries pushes the volume fraction above the equilibrium phase boundary. In contrast, when PeU ≫ 1, local epitaxial crystal growth appears adjacent to the moving interface even for large gap sizes. Interestingly, the most amorphous film microstructures are found at moderate PeU. The f...Continue Reading
References
Brownian Dynamics Simulation of Film Formation of Mixed Polymer Latex in the Water Evaporation Stage
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