Magnetorheological behavior of Pickering emulsions stabilized by surface-modified Fe₃O₄ nanoparticles
2012
Qiao, Xiuying | Zhou, Jun | Binks, Bernard P. | Gong, Xinglong | Sun, Kang
Silane-modified Fe₃O₄ 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 (ϕₒ), 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 ϕₒ, oil polarity and ψ. The dynamic modulus (G′) and complex viscosity (η*) increase with an increase in ϕₒ 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.
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