Preparation of a microsphere SiO2/TiO2 composite pigment: The mechanism of improving pigment properties by SiO2

In this study, a microsphere SiO2/TiO2 composite pigment (M-SiO2/TiO2) was prepared through a facile grinding and calcination process. The structure and properties of M-SiO2/TiO2 were characterized in detail, and the mechanism governing the improvement of pigment properties by M-SiO2 was proposed. The results of this study show that M-SiO2 and TiO2 are successfully compounded, and their combination is inferred to be achieved by the formation of Si-O-Ti bonds through the hydroxyl groups on their surface. The M-SiO2/TiO2 has almost the same pigment properties as pure titanium dioxide, while the weight fraction of TiO2 in M-SiO2/TiO2 is 70%, which can significantly reduce the consumption of TiO2. In M-SiO2/TiO2, the introduction of M-SiO2 leads to the improvement of the rutile-phase conversion of TiO2, as well as reducing TiO2 particle size; thus, this step can further improve the pigment properties. When the calcination temperature is 900 °C, the TiO2 in M-SiO2/TiO2 is primarily rutile (rutile conversion rate is 88.57%) with a particle size of 0.1-0.3 μm, exhibiting good dispersion. In contrast, pure TiO2 is primarily composed of anatase (rutile conversion rate is 11.39%) with a particle size of 0.2-0.6 μm, exhibiting serious agglomeration. The M-SiO2/TiO2 composite is expected to be applied in the fields of paint, plastic, and papermaking in an effort to significantly reduce the cost and consumption of TiO2 pigment.