According to recent research reports, addition of small amounts of a secondary fluid to a suspension could dramatically increase viscosity of suspension. Results of this study indicate another interesting behavior that the secondary fluid could form a thin hydrophobic membrane around particle surface and significantly decrease the viscosity and yield stress of the suspension. To enhance the surface hydrophobicity, hydrophobic nanoparticles (nano-CaCO3) were added to the hydrophobic membrane of particles to improve the surface roughness, and to generate composite particles having a hierarchical structure similar to the micromorphology of lotus leaf. This composite particle has a higher contact angle, and the suspension of composite particles has a lower viscosity and a lower yield stress.
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