Influence of mixing characteristics for water encapsulation by self-assembling hydrophobic silica nanoparticles

Water encapsulation using silica nanoparticles was assessed using two different types of single step mixing processes. The influential mixing characteristics have been determined. Direct mixing at high rotational speed requires high shear and vigorous stirring properties. Progressive water atomisation using gentle mixing process requires high atomisation pressure and rapid surface refreshing of the mixed material. Mechanisms of powder formation were also proposed. Encapsulation of micrometric water droplets in shell-like structure is respectively obtained by either progressive size reduction of macroscopic particulates or direct coating of pre-formed microscopic droplets. These mechanisms resulting from the interactions between a solid particle and a liquid highly depend on parameters such as particle's hydrophobicity, surface tension or kinetic energy.

Graphical abstractWater encapsulation using silica nanoparticles was studied using two different types of mixing processes. In high shear processes, dry water is produced by size reduction of water droplets coated with silica nanoparticles. In low shear processes, the same structure is obtained by spontaneous solid particles coating of water droplets produced by the atomisation. Non-coating or in the contrary mousse formation phenomena was frequently observed.Figure optionsDownload full-size imageDownload as PowerPoint slide