Two-Steps Versus One-Step Solidification Pathways of Binary Metallic Nanodroplets.

The solidification of AgCo, AgNi, and AgCu nanodroplets is studied by molecular dynamics simulations in the size range of 2-8 nm. All these systems tend to phase separate in the bulk solid with surface segregation of Ag. Despite these similarities, the simulations reveal clear differences in the solidification pathways.

Study of the aggregation behavior of Janus particles by coupling experiments and Brownian dynamics simulations.

Hypothesis: New colloids such as inverse patchy particles or Janus particles are considered as smart building blocks in the development of innovative and performant materials. For example, the control of the self-assembly of oxide-based charged Janus particles is interesting for ceramic shaping. Thus, the synthesis of silica based Janus particles as well as a detailed study of their behavior in suspension are presented in this paper.

Self-Organization of Large Alumina Platelets and Silica Nanoparticles by Heteroaggregation and Sedimentation: Toward an Alternative Shaping of Nacre-Like Ceramic Composites.

Nacre-like ceramic composites are of importance in a wide range of applications, because of their mechanical properties, combining high mechanical strength and high fracture toughness. Those mechanical properties are the result of strongly aligned platelets glued in a matrix. Different methods exist to shape such a "brick-and-mortar" hierarchical structure.

Brownian dynamics simulations of one-patch inverse patchy particles.

Inverse patchy particles are promising colloids to develop new architectures in ceramic materials based on their self-assembly. Nonetheless, a good understanding of their aggregation is required. Several previous studies have shown that the behavior of ceramic colloids can be well described by the DLVO interaction potential.

Role of Electrostatic Interactions in Oil-in-Water Emulsions Stabilized by Heteroaggregation: An Experimental and Simulation Study.

Oil-in-water emulsion stabilization by heteroaggregation of hydrophilic particles without a surfactant is of importance in a wide range of applications; however, the stabilization mechanism is little described. To shed light on the early stage of the stabilization mechanism, a model system composed of an oil wax phase dispersed in water with oppositely charged colloidal particles is studied experimentally and numerically. Experiments show that the colloids do not penetrate deeply in the oil phase, suggesting that adsorption of the colloidal particles on the wax droplets is mainly due to electrostatic interactions.

Influence of different surfactants on Pickering emulsions stabilized by submicronic silica particles.

Hypothesis: Pickering emulsions were prepared using wax and silica submicronic particles (650 nm), as a first step towards the synthesis of Janus particles. Surfactants added to silica particles control the emulsion stability and particles arrangement, i.e.

Computer simulations of heteroaggregation with large size asymmetric colloids.

Hypothesis: Hetero-aggregation of inorganic colloids is influenced by numerous parameters, which dictate the suspension properties. When particles are different in size, the suspension can be either stable or unstable according to concentration of components, ionic strength, and pH. Experimentally, understanding the role of each parameter is sometimes difficult because parameters cannot easily be modified independently.

Early Dynamics and Stabilization Mechanisms of Oil-in-Water Emulsions Containing Colloidal Particles Modified with Short Amphiphiles: A Numerical Study.

Emulsions stabilized by mixtures of particles and amphiphilic molecules are relevant for a wide range of applications, but their dynamics and stabilization mechanisms on the colloidal level are poorly understood. Given the challenges to experimentally probe the early dynamics and mechanisms of droplet stabilization, Brownian dynamics simulations are developed here to study the behavior of oil-in-water emulsions stabilized by colloidal particles modified with short amphiphiles. Simulation parameters are based on an experimental system that consists of emulsions obtained with octane as the oil phase and a suspension of alumina colloidal particles modified with short carboxylic acids as the continuous aqueous medium.

Interdiffusion and crystallization of oppositely charged colloids.

The aggregation of oppositely charged colloids, usually denoted as heteroaggregation, is often used in colloidal processing, for which a precise control of the basic mechanisms of aggregate formation is of crucial importance. A promising way to achieve a better degree of control is to guide heteroaggregation by imposing geometric constraints. Here, we consider this possibility by simulating the heteroaggregation of two oppositely charged suspensions which are initially separated and then put into contact through a planar interface.

Shear viscosity in hard-sphere and adhesive colloidal suspensions with reverse non-equilibrium molecular dynamics.

We employ the reverse non-equilibrium molecular dynamics method (RNEMD) of Müller-Plathe [Phys. Rev. E, 1999, 59, 4894] to calculate the shear viscosity of colloidal suspensions within the stochastic rotation dynamics-molecular dynamics (SRD-MD) simulation method.

Aggregation of binary colloidal suspensions on attractive walls.

The adsorption of colloidal particles from a suspension on a solid surface is of fundamental importance to many physical and biological systems. In this work, Brownian Dynamics simulations are performed to study the aggregation in a suspension of oppositely charged colloidal particles in the presence of an attractive wall. For sufficiently strong attractions, the wall alters the microstructure of the aggregates so that B2 (CsCl-type) structures are more likely obtained instead of B1 (NaCl-type) structures.

How colloid-colloid interactions and hydrodynamic effects influence the percolation threshold: A simulation study in alumina suspensions.

The percolation behavior of alumina suspensions is studied by computer simulations. The percolation threshold ϕc is calculated, determining the key factors that affect its magnitude: the strength of colloid-colloid attraction and the presence of hydrodynamic interactions (HIs). To isolate the effects of HIs, we compare the results of Brownian Dynamics, which do not include hydrodynamics, with those of Stochastic Rotation Dynamics-Molecular Dynamics, which include hydrodynamics.

Compact and ordered colloidal clusters from assembly-disassembly cycles: a numerical study.

Brownian dynamics simulations are used to investigate the assembly of attractive colloids whose interaction potential well is periodically changed over time. Our system is composed of spherical, mono-disperse, highly charged, alumina particles whose interactions are modeled by the DLVO theory. The depth of the potential well is periodically changed by varying the ionic strength of the liquid medium.

Numerical and experimental study of suspensions containing carbon blacks used as conductive additives in composite electrodes for lithium batteries.

Suspensions of carbon blacks and spherical carbon particles are studied experimentally and numerically to understand the role of the particle shape on the tendency to percolation. Two commercial carbon blacks and one lab-synthesized spherical carbon are used. The percolation thresholds in suspensions are experimentally determined by two complementary methods: impedance spectroscopy and rheology.

Brownian dynamics simulations of colloidal suspensions containing polymers as precursors of composite electrodes for lithium batteries.

Dilute aqueous suspensions of silicon nanoparticles and sodium carboxymethylcellulose salt (CMC) are studied experimentally and numerically by brownian dynamics simulations. The study focuses on the adsorption of CMC on silicon and on the aggregation state as a function of the suspension composition. To perform simulations, a coarse-grained model has first been developed for the CMC molecules.

Granulating titania powder by colloidal route using polyelectrolytes.

A new, convenient, and inexpensive approach to process and granulate titania powders by a chemical route is proposed. It is based on the use of a formulation that includes a polyanion such as poly(sodium 4-styrenesulfonate) (PSS). Such a polyelectrolyte is most often considered to achieve dispersion of oxide powders in water.