Research On Influencing Factor Of Titania Nanoparticle Size

As an important nanosized material, TiO₂ nano-particle is applicable to production and living widely.Its photocatalytic activity is widely used for solar battery and photocatalytic synthesization and so on.Particle characteristics like size and size distribution mainly influence the final product quality and photocatalytic activity of TiO₂.This emphasizes the need for discussion and control for the influencing factor of particle size.The CVD method is used to produce TiO₂ nano-particle in the propane-air diffusion flame. The effect of different operating conditions on particle size and crystal form is investigated. There are four different operating conditions analyzed. The results show that temperature is influenced mainly by the rate of propane and air; the higher the rate of propane is, the bigger particle size is, while the higher the rate of air is, the less particle size is; besides particle size is consistent with the rate of TiCl₄; while the influence of the rate of carried gas on particle size is negligible.Using the commercial CFD-code FLUENT and the additional fluid-particle dynamics (Pratsinis, 1998), the simulation of the effect of surface oxidation reaction , dilution and thermophoretic on particle size is performed. The result show that, mean particle diameter with surface oxidation reaction considered is bigger at the same position. Meanwhile the influence of surface oxidation reaction on particle size is obvious at the beginning of reaction but negligible at the outlet because of the relation between precursor and oxidant concentration. The increase of particle size is evidently restrained by dilution in the flame region, but hardly in the non-flame region due to the little effect of dilution. If we take the surface oxidation reaction and dilution into consideration, the dilution restrains obviously the velocity growth and affects deeply the particle size, while surface oxidation reaction effect merely particle size near the centerline.we also find that thermophoretic just have a little influence on particle size inside the flame.