Ultrasound measurements of particle shells in magnetic Pickering emulsions

Abstract

A magnetic Pickering emulsion is an emulsion stabilized by magnetic nanoparticles that accumulate at the droplet interface to form a shell. The physical characterization of a Pickering emulsion, particularly the size of the stabilizing layer and the size of Pickering droplets, is essential for many applications. This report presents the findings of a theoretical and experimental study of ultrasound attenuation involving magnetic Pickering emulsions. Specifically, the ultrasound scattering theory based on the so-called core–shell model was utilized to interpret data obtained from ultrasonic measurements. In this model, the additional phase, i.e., the particle shell covering the oil core of a Pickering droplet, was considered for acoustic wave propagation in emulsions. The attenuation of an ultrasonic wave in the function of wavenumber multiplied by core radius (kb), wavenumber multiplied by shell thickness (kc), and frequency was numerically calculated for different concentrations of the droplets. The theoretical results and measurements were compared using a novel approach based on ultrasound spectroscopy to determine the stability and the size of the magnetic Pickering droplets.