Crystalline phases and particle characteristics of the combustion- synthesized TiO₂ nanoparticles

TiO₂ nanoparticles were synthesized with using N ₂-diluted and O₂-enriched coflow hydrogen diffusion flames. We investigated the effects of the flame temperature on the crystalline phases and particle characteristics of the TiO₂ nanoparticles that were formed. For the higher temperature conditions, the maximum centerline temperatures that were measured were greater than approximately 1,600K, and TiO₂ nanoparticles, which had spherical shapes with diameters of approximately 60nm, were synthesized. For the lower temperature conditions, the maximum centerline temperatures that were measured were less than approximately 1,600K, and the diameters of the nanoparticles that were formed had unclear boundaries that ranged from 35 to 50nm. From the XRD analyses, it was believed that the crystalline structures of the nanoparticles that were formed were divided into two types. For the higher temperature cases, the fractions of the TiO₂ nanoparticles that were synthesized, which had anatase-phase crystalline structures, increased with the increase of the flame temperatures. On the contrary, for the lower temperature cases, the fraction of anatase-phase nanoparticles increased with the decrease of the flame temperatures.