Dispersion of Nanoparticle Clusters in a Rotor−Stator Mixer

The unique properties of nanoparticles and nanoparticle clusters show high potential for nanomaterials to be formulated into numerous products. In this paper, nanosuspensions are formulated by breaking up nanoparticle clusters (called agglomerates) in high-shear flows. A new breakage model is introduced to interpret erosive dispersion of agglomerates, and the population balance modeling is applied to account for effects of breakage on agglomerate size distribution. Effects of suspension structure on its rheology and flow are included in modeling. The population balance equations are solved using the quadrature method of moments (QMOM) that is linked directly to the k−ε model of the computational fluid dynamics (CFD) code FLUENT. In dispersion experiments, the aqueous suspensions of fumed silica particles, Aerosil 200V, are used. The test rig consists of an in-line Silverson rotor−stator mixer and a stirred tank. The head is a two-stage rotor−stator design with the inner stator consisting of round holes and the outer stator consisting of smaller square holes. Experimental results are compared with model predictions.