Effect of La3+ on evolution of TiO2 coating layers on lamellar sericite and
their pigmentary properties
their pigmentary properties
(Faculty of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013, China)
Abstract: TiO2-coated sericite powders were prepared by the chemical deposition method starting from lamellar sericite and TiCl4 in the presence of La3+. After calcination at 900 ℃ for 1 h, the resultant TiO2 nanoparticles on the sericite surfaces exist in anatase phase. The light scattering indexes of the TiO2-coated lamellar sericite powders are dozens of times higher than those of the naked lamellar sericite powders, varying with different contents of La3+. The presence of La3+ in the deposition solution is beneficial to the formation of the small-sized anatase TiO2 nanoparticles. The presence of La3+ also favors the formation of the dense and uniform island-like TiO2 coating layers in a large range of the mass ratio of TiO2 to sericite from 5% to 20%. XPS analysis shows that when La3+ is absent in the reaction solution, TiO2 coating layers anchor on the sericite surface via Ti—O—Si and Ti—O—Al bonds. The presence of La3+ causes the formation of Si—O—La and Al—O—La bonds on the sericite surface and Ti—O—La bond on the surface of TiO2 coating layers.
Key words: lamellar sericite; TiO2 coating; lanthanum