Synthesis of crystalline micron spheres of titanium dioxide by thermal plasma oxidation of titanium carbide

Spherical micron particles of crystalline titanium dioxide (TiO2) were synthesized by inflight oxidation of titanium carbide (TiC) micron powders (mean diameter: 28 mum) in argon-oxygen thermal plasma. The extent of oxidation of TiC powders increases with the flow rate of oxygen in the plasma gases (Ar + O-2), and a nearly complete oxidation was achieved at a higher oxygen input (10 L/min) yielding TiO2 powders as the oxidized product. Morphology examination showed that the particles generated by this process are monodispersed and are perfectly spherical. Particle sizes of the as-produced powders range from submicron to several tens of micrometers and are characterized by a bimodal size distribution. A simple sedimentation treatment was applied to separate the as-formed powders with alcohol solvent to give uniform spherical particles with monomodal size distributions. Microstructure analysis of individual particle by aid of selected area Raman spectrum revealed that all the spherical particles are totally crystalline, comprised of either rutile or anatase or their composite. The formation mechanism of the TiO2 particles in the plasma oxidation was discussed.