Parametric study of operating conditions of low-pressure premixed flame (ethylene/hydrogen/oxygen) synthesis using titanium tetra-isopropoxide (TTIP) precursor is investigated, specifically examining as-synthesized nanopowder phase and properties. The Sandia SPIN code is used to simulate the synthesis flow field to guide and compare with experiments. Strategic dilution of inert gases is used to adjust the characteristic flame temperature. As-produced samples are thermally stable without any sign of phase change, as characterized using TGA and DSC, up to 500°C. X-ray photoelectron spectroscopy (XPS) indicates Ti4+ valence and presence of carbon (13 -- 30 atomic %), with absence of Ti3+, Ti-C, and nitrogen. SEM and TEM confirm mixed micro- and nano-meter features. XRD and SAED divulge srilankite, rutile, and anatase phases produce under different experimental conditions.

Temperatures ranging from 1560K to 2650K, ambient pressures from 20 to 40 torr, and burner flow velocities from 150 to 300 cm/s are investigated, producing nanoparticles ranging from 3-10nm +/- 3nm with mixed srilankite and rutile titania phases. Oxygen concentration effects are also studied from equivalence ratios of 1.08 to 0.37. Fuel-lean conditions produce anatase-rutile mixed nanopowders, while fuel-rich conditions yielded srilankite-rutile mixed nanopowders. By modifying the composition of the precursor (e.g. by adding ethylene), the phase of the product can be changed, likely because of carbon-doping stabilizing a specific phase.