Turbulence-assisted shear regulatable synthesis of Ag nanoparticles using a counter axial-swirling impinging jet flow reactor

Abstract

Achieving a controllable synthesis of metal nanoparticles depends very much on the hydrodynamics of the synthesis process, in particular the local turbulence that has been considered to have a significant impact on the synthesised nano particle size and morphology. This paper reports the study on turbulence induced shear regulatable synthesis of the silver nanoparticles (AgNPs) using a counter axial-swirling impinging jet flow reactor (CASIJR), exploring the effect of turbulent shear stress on the formation of AgNPs. The micro-mixing and turbulence induced shear in the flow inside the CASIJR reactor were evaluated using Reynolds Average Navier-Stokes (RANS) modelling coupled with the Reynolds Stress Model (RSM). It was indicated from the simulations that an increase in the axial-swirling circular pipe flow diameter based Reynolds number from 3300 to 4900 would enhance the mixing and local turbulence induced shear, characterising by an increase in the mixing index. It was also found from the AgNPs synthesis experiments that there exists a strong correlation between the turbulent shear stress $\overline{u^{\prime }{v}^{\prime }}$ and the synthesised AgNPs size. The average synthesised nano particle size, size distribution, and morphology of AgNPs are affected by the micro-mixing and anisotropic turbulence induced shear in the CASIJR.