Development of the fumed TiO2 having high content of rutile structure and dispesibility using the dry-type of surface modification and the thermal treatment

The effect of dry-type surface modification of a fumed TiO₂ and the thermal treatment were studied to synthesize the new fumed TiO₂ having a high content of rutile structure and high dispersibility. The fumed TiO₂ was modified with various metallic alkoxides to prepare precursors and next the resulted precursors were thermally-treated by the novel natural dropping method with a very short heating time, less than 1 s. The focus of this investigation was on the metallic alkoxide species as a surface modification agent and morphologies of both the precursor and thermally-treated fumed TiO₂. The morphologies and nanostructures of the obtained fumed TiO₂ were characterized. The carbon content and agglomerate of the precursor influenced on the transformation ratio from anatase to rutile structure. It was confirmed that the dry-type surface modification with tetraethoxysilane (TEOS) and titanium tetra-isopropoxide (TTIP) at room temperature is very effective method to prepare precursors for the next thermal treatment. The thermally-treated fumed TiO₂ modified with TTIP showed 100% rutile structure with pure TiO₂ composition at 1400 °C. The thermally-treated fumed TiO₂ modified with small quantities of TEOS exhibited both 100% rutile structure and excellent dispersibility. This high dispersibility caused from a sponge-like structural characteristic of the agglomerate and static electricity repellence by coated SiO₂ layer. The thermally-treated fumed TiO₂ modified with TEOS and TTIP showed the color tone shift can be attributed to rutile structure. It was revealed that the combination of dry-type surface modification and natural dropping thermal treatment is an attractive method to prepare the new fumed TiO₂ with 100% rutile structure maintaining the high dispersiblity.