Experimental investigation on microexplosion of single isolated burning droplets containing titanium tetraisopropoxide for nanoparticle production

The microexplosion and nanoparticle formation of single isolated burning droplets using titanium tetraisopropoxide (TTIP) as nanoparticle precursor are investigated experimentally. Spherical along with fine agglomerated titanium dioxide (TiO2) nanoparticles are obtained from the single droplet combustion of TTIP dissolved in pure xylene, pure ethanol and the mixture of xylene and ethanol. Strong, global, and continuous microexplosions are observed during the combustion of TTIP/xylene droplet and TTIP/xyleneethanol droplet. We proposed a hypothesis of droplet microexplosions as follows: hydrolysis of TTIP at or in the droplet surface leads to formation of TiO2 nanoparticles, which together with the low volatility component near the droplet surface creates an impermeable shell for the high volatility component. The high volatility component in the interior is superheated to induce heterogeneous nucleation of bubbles beneath the shell, which increases the pressure inside the shell until microexplosion occurs. These insights are very important mechanisms for the well- established flame spray pyrolysis (FSP) process. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.