Based on a selective dimension scale-out method, a high-throughput oscillating feedback minireactor (OFM) was developed to prepare uniform Mg(OH) 2 nanoparticles using a precipitation method. Three-dimensional unsteady simulations indicated that three secondary flows (i.e., vortex, feedback, and oscillation) could effectively induce chaotic advection, and OFM could improve mixing performance compared to those using the microreactor before amplification. The Villermaux−Dushman experiments showed that high-efficiency micromixing could be achieved within 3.9 ms. The average size of the Mg(OH) 2 nanoparticles decreased with the increase of total flow rate (Q total ), as well as with the decrease of precursor concentration and C(Mg 2+ )/C(OH − ) ratio. Mg(OH) 2 with an average particle size of 53.0 nm and narrow particle size distribution (PSD) was obtained at a high throughput of 180 mL/min. Compared with the products obtained in the initial microreactor, the product quality was maintained or even improved, suggesting that the scale-out method is reliable and effective.
A four-stage oscillating feedback millireactor with splitters (S-OFM) was designed to improve the mixing performance based on chaotic advection. Three-dimensional CFD simulations were used to investigate its flow characteristics and mixing performance, and the generation mechanisms of secondary flows were examined. The results show that the mixing index (MI cup ) increased with the increase in the Reynolds number (Re), and MI cup could reach 99.8% at Re = 663. Poincarémapping and Kolmogorov entropy were adopted to characterize the chaotic advection intensity, which indicates that there is a intensity increase with the increase in Re. In addition, the results of Villermaux−Dushman experiments demonstrate that S-OFM performs excellently, and the mixing time could reach 1.04 ms at Re = 2764. Finally, S-OFM was successfully used to synthesize CdS nanoparticles with cubic hexagonal phase junctions. At a flow rate of 180 mL/min, the average particle size was 10.5 nm and the particle size distribution was narrow (with a coefficient of variation of 0.14).
A high-throughput (105.5 g/h) passive four-stage asymmetric oscillating feedback microreactor using chaotic mixing mechanism was developed to prepare aggregated Barium sulfate (BaSO 4 ) particles of high primary nanoparticle size uniformity. Threedimensional unsteady simulations showed that chaotic mixing could be induced by three unique secondary flows (i.e., vortex, recirculation, and oscillation), and the fluid oscillation mechanism was examined in detail. Simulations and Villermaux-Dushman experiments indicate that almost complete mixing down to molecular level can be achieved and the prepared BaSO 4 nanoparticles were with narrow primary particle size distribution (PSD) having geometric standard deviation, σ g , less than 1.43 when the total volumetric flow rate Q total was larger than 10 ml/min. By selecting Q total and reactant concentrations, average primary particle size can be controlled from 23 to 109 nm as determined by microscopy. An average size of 26 nm with narrow primary PSD (σ g = 1.22) could be achieved at Q total of 160 ml/min.
A high-throughput (105.5 g/h) passive four-stage asymmetric oscillating
feedback microreactor using chaotic mixing mechanism was developed to
prepare aggregated BaSO4 particles of high primary nanoparticle size
uniformity. Three-dimensional unsteady simulations showed that chaotic
mixing could be induced by three unique secondary flows (i.e., vortex,
recirculation, and oscillation), and the fluid oscillation mechanism was
examined in detail. Simulations and Villermaux-Dushman experiments
indicate that almost complete mixing down to molecular level can be
achieved and the prepared BaSO4 nanoparticles were with narrow primary
particle size distribution (PSD) having geometric standard deviation,
σg, less than 1.43 when the total volumetric flow rate Qtotal was larger
than 10 mL/min. By selecting Qtotal and reactant concentrations, average
primary particle size can be controlled from 23 to 109 nm as determined
by microscopy. An average size of 26 nm with narrow primary PSD (σg =
1.22) could be achieved at Qtotal of 160 mL/min.
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