Effect of Temperature Cycling on Ostwald Ripening.

We study the effect of temperature cycling on the rate of Ostwald ripening (or coarsening) of spherical particles dispersed in a binary solution. A widespread view, which states a temperature cycle generally enhances the rate of Ostwald ripening by first dissolving the smallest particles (heating) and then regrowing the dissolved amount of material on the remaining particles (cooling), is shown to be inadequate as it does not include transient effects. On the basis of a simulation method that assumes mass transfer as the limiting growth mechanism, we show that each temperature cycle is followed by a significant relaxation of the particle-size distribution, during which the number of particles remains constant, and the average particle size .

Predicting the Kinetics of Ice Recrystallization in Aqueous Sugar Solutions.

The quality of stored frozen products such as foods and biomaterials generally degrades in time due to the growth of large ice crystals by recrystallization. While there is ample experimental evidence that recrystallization within such products (or model systems thereof) is often dominated by diffusion-limited Ostwald ripening, the application of Ostwald-ripening theories to predict measured recrystallization rates has only met with limited success. For a model system of polycrystalline ice within an aqueous solution of sugars, we here show recrystallization rates be predicted on the basis of Ostwald ripening theory, provided (1) the theory accounts for the fact the solution can be nonideal, nondilute and of different density than the crystals, (2) the effect of ice-phase volume fraction on the diffusional flux of water between crystals is accurately described, and (3) all relevant material properties (involving binary Fick diffusion coefficients, the thermodynamic factor of the solution, and the surface energy of ice) are carefully estimated.

Mesoscale simulation of semiflexible chains. II. Evolution dynamics and stability of fiber bundle networks.

Network formation of associative semiflexible fibers and mixtures of fibers and colloidal particles is simulated for the Johnson-Kendall-Roberts model of elastic contacts, and a phase diagram in terms of particle elasticity and surface energy is presented. When fibers self-assemble, they form a network for sufficiently large fiber-solvent surface energy. If the surface energy is above the value where single particles crystallize, the adhesion forces drive diffusion-limited aggregation.

Mesoscale simulation of semiflexible chains. I. Endpoint distribution and chain dynamics.

The endpoint distribution and dynamics of semiflexible fibers are studied by numerical simulation. A brief overview is given over the analytical theory of flexible and semiflexible polymers. In particular, a closed expression is given for the relaxation spectrum of wormlike chains, which determines polymer diffusion and rheology.

How to impose stick boundary conditions in coarse-grained hydrodynamics of Brownian colloids and semi-flexible fiber rheology.

Long-range hydrodynamics between colloidal particles or fibers is modelled by the fluid particle model. Two methods are considered to impose the fluid boundary conditions at colloidal surfaces. In the first method radial and transverse friction forces between particle and solvent are applied such that the correct friction and torque follows for moving or rotating particles.

Close packing density of polydisperse hard spheres.

The most efficient way to pack equally sized spheres isotropically in three dimensions is known as the random close packed state, which provides a starting point for many approximations in physics and engineering. However, the particle size distribution of a real granular material is never monodisperse. Here we present a simple but accurate approximation for the random close packing density of hard spheres of any size distribution based upon a mapping onto a one-dimensional problem.

Mesoscopic model for colloidal particles, powders, and granular solids.

A simulation model is presented, comprising elastic spheres with a short-range attraction. Besides conservative forces, radial and shear friction, and radial noise are added. The model can be used to simulate colloids, granular solids, and powders, and the parameters may be related to experimental systems via the range of attraction and the adhesion energy.

A Local Galilean Invariant Thermostat.

The thermostat introduced recently by Stoyanov and Groot (J. Chem. Phys.

From molecular dynamics to hydrodynamics: a novel Galilean invariant thermostat.

This paper proposes a novel thermostat applicable to any particle-based dynamic simulation. Each pair of particles is thermostated either (with probability P) with a pairwise Lowe-Andersen thermostat [C. P.