The effect of external electric fields during flame synthesis of titania

The evolution of nanoparticle growth inside electrically assisted flames is studied by thermophoretic sampling (TS) followed by transmission electron microscopy (TEM) and statistical evaluation of the counted images. Up to 11 g/h titania particles are produced by titanium tetraisopropoxide (TTIP) oxidation in a CH4/O2 premixed flame. An electric DC-field of 1.5 kV/cm is established across the flame with two plate electrodes. At each TS location, the flame temperature is measured by Fourier transform infrared (FTIR) spectroscopy while the product powder is analyzed with nitrogen adsorption (BET), X-ray diffraction (XRD), TEM and small-angle X-ray scattering (SAXS) that is used to estimate the extent of agglomeration. External electric fields decrease most dramatically the flame temperature downstream of the electric field controlling particle size, crystallinity and morphology and contribute to the formation of soft agglomerates.