Rapid Thermal Synthesis of Nano Titanium Dioxide Powders Using a Plasma Torch

Received: October 6, 2012
Revised: February 4, 2013
Accepted: February 4, 2013
Download Citation: RIS|BibTeX|https://doi.org/10.4209/aaqr.2012.10.0269  

Cite this article:
Wang, Y.F., Yen, H.Y., Tsai, Y.I., Chen, H.M. and Tsai, C.H. (2013). Rapid Thermal Synthesis of Nano Titanium Dioxide Powders Using a Plasma Torch. Aerosol Air Qual. Res. 13: 1313-1320. https://doi.org/10.4209/aaqr.2012.10.0269

ABSTRACT

Spherical TiO₂ nano- to microparticles are rapidly synthesized by spraying clear stock solution as a nano aerosol into an atmospheric-pressure microwave plasma torch at 550–600°C. The stock solution was prepared by an initial H₂O/TiCl₄ (titanium tetrachloride) volume ratio of 8. At about 0.15 s, anatase TiO₂ powders were produced and collected by 14-stage impactors. The size distribution shows that 98.47% of the particles in number were in the < 10-nm impactor, with the normalized particle number percentage (dn'/dlogDp) of 327.1, although the mass distribution of the powders was mainly in the size range of 2.5–6.2 μm. Scanning electron microscopy and transmission electron microscopy images show that most of the spherical TiO₂ particles had a primary particle size of about 10 nm. Moreover, larger secondary particles (several μm), likely aggregated small particles were also presented. The chemical composition and elemental analyses show that the structure of the powders is mainly composed of TiO₂ with traces of TiO₂-xNx. Hence, the total reaction pathway is proposed as Ti(OH)_xCl_4-x + H₂O + N₂ + O₂ → TiO₂ nuclei + HCl + other byproducts. Moreover, the ultraviolet-visible absorption spectrum and photocatalytic performance of the synthesized powders during exposure to ultraviolet or visible light are comparable to those of commercial TiO₂ powders.

Keywords: Nanoparticles; Size distribution; Synthesis; Photocatalyst; Discharge