Effects of temperature-time history on the flame synthesis of nanoparticles in a swirl-stabilized tubular burner with two feeding modes

Abstract

This work examines the effect of temperature-time history on the flame synthesis of titania nanoparticles using a specially designed swirl-stabilized tubular burner with two kinds of precursor feeding modes, the tangential inlet and the central jet inlet. When the Damköhler number is less than unity, a rapidly mixed type tubular flame is well-formed, which is chosen to be the condition for flame synthesis. The ex situ characterization of the synthesized TiO2 nanoparticles shows that the particle samples from the tangential inlet feeding mode are mainly anatase (up to 84.3%) with a mean primary particle size of 13.0 ± 3.2 nm, whereas those from the central jet inlet feeding mode are large polydisperse rutile (up to 74%) nanoparticles with a mean size of 16.9 ± 8.8 nm. The significant differences in particle size and crystal phase are attributed to the varied temperature-time histories of two feeding modes, as the residence time of nanoparticles in high-temperature zone of the central jet inlet mode is much longer with larger variation than that of the tangential inlet feeding mode. Finally, the well-dispersed Pd/TiO2 nanocatalysts are generated by elaborately feeding palladium acetate through the central jet inlet and titanium tetraisopropoxide through the tangential inlets, respectively, to better match the temperature-time histories with the decomposition properties of two different precursors. The study demonstrates the potential of this swirl-stabilized burner for producing tailored single- and multi-component nanomaterials for a variety of applications.