![]() ![]() Particle bridges can subsequently be removed by applying low shear or by modifying the particle wettability.Īggregating droplets Aggregating emulsion Droplet adhesion Particle bridging Particle-stabilized emulsions Pickering emulsions Process conditions Shear history.Ĭopyright © 2014 The Authors. In rheology, shear thinning is the non-Newtonian behavior of a fluid in which the viscosity decreases under shear strain. Particles with a slight preference for the continuous phase are required for bridging to occur, and the degree of bridging increases with increasing shear rate but decreases with increasing particle volume fraction. This aggregating state can be accessed by varying several different parameters, including particle wettability and particle volume fraction. We have created strongly aggregating Pickering emulsions using our model system. We have looked for direct evidence of droplets sharing particles using freeze fracture scanning electron microscopy. ![]() We have used light scattering and microscopy to study the degree to which emulsions are bridged, and how this is affected by parameters including particle volume fraction, particle wettability and shear rate. The high internal phase emulsion stabilized by solid particles is also called high internal phase Pickering emulsion (HIPPE), and the oil concentration is generally >74 ( 4 ). A mixture of dodecane and isopropyl myristate was used as the oil phase. Pickering emulsions, as solid particle stabilized emulsions, show to have long-term stability and many unique advantages over ordinary emulsions ( 1 3 ). ![]() We have developed a model oil-in-water system for studying particle bridging in Pickering emulsions stabilised by fluorescent Stöber silica. Firstly, the main stabilization mechanisms of Pickering emulsion are reviewed, and then the preparation, properties, and applications of Pickering emulsions stabilized by protein-based solid particles, microgels, fibrils and hollow nanoparticles are summarized (Fig. Zeta potential ( ) and yield stress ( B ) values were used to characterize the influence of the salt concentration ( C NaCl ) on the interactions between the fumed silica particles used to stabilize the emulsions. They can subsequently be broken by low shear or by modifying the particle wettability. This work explores the effect of disrupting the drop-particle network by shear flow on the stability of Pickering emulsions. *American Chemical Society, Petroleum Research Fund (PRF No.Particle bridges form in Pickering emulsions when the oil-water interfacial area generated by an applied shear is greater than that which can be stabilised by the available particles and the particles have a slight preference for the continuous phase. 1998: Society of Petroleum Engineers Richardson, TX.Ģ. The goal of this work was to assess the stability of w/w Pickering emulsions (under simple shear flow) stabilized with nanoparticles of different size and to correlate the relationship between emulsion stability and particle size. Green DW, Willhite GP, Enhanced oil recovery. The formation of Pickering emulsions by using Janus nanoparticles is also investigated, as are the synergetic effects of Janus particles and surfactants.ġ. The issue of the stability of Pickering emulsions is tackled at a mesoscopic level using dissipative particle dynamics simulations within the Adiabatic Biased Molecular Dynamics framework. Increasing the surfactant concentration leads to a reduction of the required shear rate, as does a hydrophilic solid wall. Particle-stabilised or Pickering emulsions are versatile systems. Without surfactant, the oil cannot be mobilized, but with the presence of sodium dodecyl sulfate surfactants the oil detaches from the solid surface to create oil-in-water emulsion. The system is then sheared in a Couette flow simulation. Oil is represented by hexadecane that is adsorbed on the wall of a microcavity in an aqueous environment. Here, the formation of emulsions using dissipative particle dynamics (DPD) simulations and the effects of shear on oil mobilization are studied. Recently, the potential of Janus nanoparticles has also been studied for use in EOR. As pointed by Wei et al., the Pickering emulsion system is a type of power-law fluid that follows Ostwaldde Waele’s relationship. In enhanced oil recovery (EOR) surfactant solutions are pumped into a reservoir to mobilize trapped oil. For all Pickering emulsions, the apparent viscosity () gradually decreased with an increase in the shear rate from 0.1 to 10 s 1, indicating the shear-thinning behavior of all emulsions. One of the interesting features of particle-stabilized (Pickering) emulsions is the long-term (kinetic) stability of the drops to coalescence 1. ![]()
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