Investigation and simulation of droplet breakup and iron oxide nanoparticle formation in spray-flame synthesis

Abstract

Particle formation from an iron-based precursor dissolved in ethanol and 2-ethylhexanoic acid was studied via population balance simulations of the SpraySyn burner. Monte-Carlo population balance modeling was used to estimate droplet evaporation and breakup, while particle nucleation and growth were calculated using a pivot method. To investigate common particle formation pathways a precursor chemistry model was formulated and discussed for the cases of instantaneous and absent thermal decomposition in the liquid phase. Following this, the droplet breakup time was calculated to determine when precursor and particle transfer into the gas phase occurs. The simulation results show good agreement with experimental data from literature for different precursor concentrations. However, in the cases where thermal decomposition is absent in the liquid phase, the model underestimates particle size and polydispersity. The primary conclusion is that nanoparticles smaller than 10 nm most likely formed in the liquid phase. Moreover, particle formation in the liquid phase increases polydispersity through the formation of an accumulation mode near the droplet surface.