Tuning the stabilization mechanism of nanoparticle-regulated complex fluids

Abstract

In nanoparticle haloing, charged nanoparticles have been found to enhance the stability of colloidal suspensions by forming a non-adsorbing layer surrounding neutral colloids which induces an electrostatic repulsion between them. However, there has been some debate that nanoparticles may directly deposit onto the colloidal surfaces and that the stabilization mechanism relies on nanoparticle adsorption. In this study, we have found that these two mechanisms control the stability of colloidal suspensions across a continuum over increasing nanoparticle concentrations.AFM force measurements showed that highly charged zirconia nanoparticles built up an electrostatic repulsion between negligibly charged silica surfaces, preventing them from aggregating. The follow-up adsorption measurements and force modeling indicated that minor adsorption of nanoparticles is expected at volume fractions of 10 -5 to 10 -3 , but the amount of nanoparticle adsorption dramatically increases with increasing the nanoparticle volume fraction beyond 10 -3 . Based on these results, we propose that the fundamental mechanism of nanoparticleregulated stabilization is nanoparticle haloing at low nanoparticle concentrations which transitions to adsorption at higher concentrations. Accordingly, at a nanoparticle volume fraction of around 10 -3 where the transition happens, the stabilization can be influenced by both nanoparticle haloing and adsorption.

Nonlinear Agglomeration of Bimodal Colloids under Microgravity

“…The zeta potential of the larger particles is set at its isoelectric point, in which the only intermolecular forces acting upon the microparticles are van der Waals forces, while the nanoparticles are highly charged. At particular proportions of nano-and microparticles, nanoparticles both adhere to and form halos around the microparticles to create an effective electrostatic repulsive barrier to screen the van der Waals forces and stabilize the suspension (Moradi et al, 2019a). At this state, the suspension is metastable and forms an ordered crystalline solid phase.…”

Ammoniacal Carbonate Leaching: Effect of Dissolved Sulfur in the Distillation Operation

“…Aqueous suspension stabilization can be controlled by the mechanisms electrostatic, steric, electrosteric and nanoparticle haloing stabilization, by the following methods: adjusting either ionic strength or pH of the electrolyte solution; adding a component like a surfactant or polymer that adsorbs on the colloidal particles and changes their surface properties; a polyelectrolyte that impart electrostatic and steric stabilization to a given colloidal dispersion; or highly charged nanoparticles by forming a nonadsorbing nanoparticle layer around neutral colloidal particle, which presents as an effective surface charge and produces an electrostatic repulsion that mitigates the inherent van der Waals attraction between them. 17,18 A method for purifying Basic Nickel Carbonate of Na + , Clions and other impurities on its surface was clarified by the electric double layer model and it was proposed a washing-drying-rewashing-drying process, 19 but other studies have not been performed about colloidal processing or sulfur removal of Ni(II)-NH 3 -CO 2 -SO 2 -H 2 O system.…”