Magnetorheological behavior of Pickering emulsions stabilized by surface-modified Fe3O4 nanoparticles

Silane-modified Fe 3 O 4 nanoparticles can stabilize emulsions of both polar and non-polar oils, and the rheological behavior of these emulsions has been investigated as a function of oil volume fraction ( ϕ o ), oil polarity and magnetic field intensity ( ψ ). All the emulsions show a similar elastic response with a modulus plateau at low frequency and a small phase angle (<15°) in dynamic oscillatory shear, and shear-thinning behavior in steady shear measurements. This is independent of ϕ o , oil polarity and ψ . The dynamic modulus ( G ′) and complex viscosity ( η *) increase with an increase in ϕ o and oil polarity, due to enhanced droplet packing and flocculation and particle aggregation on droplet surfaces. The presence of a magnetic field promotes particle attractions and associations and enhances the strength of the three-dimensional particle and droplet networks, thus remarkably increasing G ′ and η * and raising the yield stress. The increase in modulus, viscosity and yield stress are beneficial for the elevation of the stability of these functional emulsions.