Magnetorheological characterization of oil-in-oil magnetic Pickering emulsions

A magnetic Pickering emulsion is a type of emulsion stabilized by magnetic nanoparticles that accumulate at the droplet interface. This makes the emulsion easy to control using an external magnetic field, which, in turn, makes it useful in many applications. Research and development in this field are ongoing, but regardless of the application, control of the formation process is necessary. Rheological measurements are one of techniques used for evaluating the internal structure and stability of emulsions. The main focus of the current research is to investigate the magnetorheological effect of the rarely tested oil-in-oil (O/O) magnetic Pickering emulsions and compare them with better-characterized oil-based magnetic fluids. The magnetoviscous effect typically occurs when magnetic nanoparticles or magnetic Pickering emulsions align with the magnetic field, and this effect depends mainly on the internal structure, such as the size and shape of the particles and droplets. The experimental results indicate that the magnetic emulsion fabricated utilizing ultrasound and an additional electric field exhibits higher dynamic yield stress as a function of the magnetic field compared with the partially covered droplets. This suggests that the stable emulsion becomes a more rigid system and is more resistant to deformation when a magnetic field is applied. Besides that, the magnetoviscous effect of the magnetic emulsions was lower compared with that of magnetic suspensions with the same mass fraction of magnetic nanoparticles.