The study of the effect of external additives on the synthesis of fumed TiO2 with a high content of rutile structure by the novel natural dropping thermal treatment.

• The effect of external additive on fumed TiO 2 was studied by the thermal treatment. • The TiO 2 with SiO 2 showed high rutile content and excellent dispersibility. • The TiO 2 with calcium stearate showed high rutile content and low dispersibility. • The rutile content is related to the agglomerate of TiO 2 before thermal treatment. The effect of external additives on the synthesis of fumed TiO 2 with a high rutile structure content was studied. The focus of this investigation was on the external additive species, agglomerates of the fumed TiO 2 before and after the thermal treatment. The transformation ratio from the anatase to rutile structure of the thermally-treated fumed TiO 2 was investigated as a function of the fumed TiO 2 agglomerate before the thermal treatment. Small agglomerated powders resulted in a decrease of transformation temperature. Two novel results were obtained in this investigation. One was a new fumed TiO 2 with a 100% rutile structure having an excellent dispersibility being successfully synthesized by the thermal treatment of AEROXIDE® TiO 2 P 25 with a small portion of AEROSIL® R 972. The other was the remarkable acceleration of the transformation from the anatase to rutile structure and grain growth/sintering of the thermally-treated fumed TiO 2 observed at a relatively low thermal treatment temperature by the oxidation reaction of calcium stearate as an external additive. [ABSTRACT FROM AUTHOR]