Dispersion of Nanoparticle Clusters in a Rotor−Stator Mixer

Abstract

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.

Comparative performance of in-line rotor-stators for deagglomeration processes

“…These support that aggregates, which are the smallest fragments, are eroded off the surface of agglomerates during processing. These results relating to both the mechanism of breakup and the smallest attainable size are in line with our previous findings (Bałdyga et al, 2008a;Özcan-Taşkin et al, 2009;Padron et al, 2008) and it may therefore be anticipated that for this test system, breakup will occur through erosion with other rotor-stator designs as well. …”

“…Of these, aggregates are held together by sintering bridges and cannot be broken up, but agglomerates, which are held together by weaker bonds such as, van-der-Waals and hydrogen bonds, can be disintegrated further provided that the energy input in the processing environment is sufficiently high (Bałdyga et al, 2008a). The following expression proposed by Tang et al (2001) based on the earlier work by Rumpf (1962) has commonly been used to calculate the tensile strength of agglomerates, T, (Baldyga et al, 2006;2007a and2007b;Özcan-Taşkın et al, 2009) which is related to the porosity of the clusters, a:…”

A Soft Strain Sensor Based on Ionic and Metal Liquids

“…In order to minimize the loss of elasticity, we used nanoparticles with a high aspect ratio, since such geometry is known to provide good conductivity at lower filler volumes [32]. The particle chosen was a nickel nanostrand (NiNs, length 30 μm, Conductive Composites inc.).…”

Test Reactions to Study Efficiency of

“…However, rotorstators mixers are widely used, which includes the creation of emulsions a) b) Hall et al, 2011a;Hall et al, 2013;Jasińska et al, 2012;Jasińska et al, 2013b;Jasińska et al, 2013c;Jasińska and Bałdyga, 2014;Jasińska et al, 2014b) and suspensions (Bałdyga et al, 2008).…”