Sedimentation and precipitation of nanoparticles in power-law fluids

Our experiment reported here adopts water, alcohol (100 %), carboxymethyl cellulose (CMC) aqueous solution with different concentrations as the base-fluid of nano-fluids. We show diffusion, aggregation and precipitation of nano-size particles in the optical quartz glass Petri dishes filled with nano-fluids flat with the help of a rotating cone. The experimental results illustrate that nanoparticles are preferably suspended in CMC aqueous solution than in water or alcohol, which means the effective Hamaker constant of water- or alcohol-particle suspensions is bigger than that of CMC-particle suspension. In the experiment with CMC as the base solution, increasing the viscosity of the solution can alleviate the settling velocity of particles and make the suspension better. The experiment also discovers that in static condition, the mutual attractive force between nanoparticles plays an important role in the suspension; however, if external forces, which are higher than the attraction, exist, they are decisive parts. In addition, Al2O3 solution is much more sensitive than the Cu solution with the varying concentration and status in the experiment because the density of Al2O3 particles is smaller than that of Cu-nanoparticles.