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Abstract: Rutile TiO2-coated sericite powders were prepared by the chemical deposition method starting from lamellar sericite and TiCl4 in the presence of Sn4+. After calcination at 850°C for 4h, TiO2 nanolayers in rutile phase were formed on the sericite surfaces. The presence of Sn4+ induced the phase transformation of amorphous to rutile TiO2, giving the formation of TiO2 nanolayers composed of small-sized rutile TiO2 nanoparticles. XPS analysis shows that Sn4+ cations were anchored at the sericite surfaces by formation of Al–O–Sn and Si–O–Sn bonds, and the aluminum and silicon sites on the sericite surfaces were dominantly occupied by Sn4+ cations. TiO2 coating layers were subsequently anchored at the sericite surfaces via Ti–O–Sn bonds. The TiO2-coated sericite powders had higher light scattering indexes than the naked sericite powders. The brightness, whiteness, and light scattering index of the rutile TiO2-coated sericite powders were slightly higher than those of the anatase TiO2-coated sericite powders. [ABSTRACT FROM AUTHOR]

Abstract: Binary Al2O3/SiO2-coated rutile TiO2 composites were prepared by a liquid-phase deposition method starting from Na2SiO3·9H2O and NaAlO2. The chemical structure and morphology of binary Al2O3/SiO2 coating layers were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, TG–DSC, Zeta potential, powder X-ray diffraction, and transmission electron microscopy techniques. Binary Al2O3/SiO2 coating layers both in amorphous phase were formed at TiO2 surfaces. The silica coating layers were anchored at TiO2 surfaces via Si–O–Ti bonds and the alumina coating layers were probably anchored at the SiO2-coated TiO2 surfaces via Al–O–Si bonds. The formation of continuous and dense binary Al2O3/SiO2 coating layers depended on the pH value of reaction solution and the alumina loading. The binary Al2O3/SiO2-coated TiO2 composites had a high dispersibility in water. The whiteness and brightness of the binary Al2O3/SiO2-coated TiO2 composites were higher than those of the naked rutile TiO2 and the SiO2-coated TiO2 samples. The relative light scattering index was found to depend on the composition of coating layers. [ABSTRACT FROM AUTHOR]

Abstract: Alumina-coated rutile TiO2 samples were prepared starting from NaAlO2 by the chemical liquid deposition method. The alumina nanofilms existed in amorphous hydrated alumina phase and anchored at the surfaces of TiO2 particles via Ti–O–Al bonding. The formation of continuous and dense alumina nanofilms on the TiO2 surface depended on the pH value of the reaction solution and the alumina loading. After coated by alumina nanofilms, the whiteness and brightness of the alumina-coated TiO2 samples increased with the increase of the alumina loading while the relative light scattering index was found to depend upon the alumina loading. [Copyright &y& Elsevier]

Abstract: The evolution of alumina coating layers on rutile TiO2 particle surfaces was investigated starting from aluminum sulfate by a chemical liquid deposition method. The morphology of the alumina coating layers was determined by transmission electron microscopy. The chemical structure and the evolution mechanism of the alumina coating layers on TiO2 surfaces were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and powder X-ray diffraction techniques. The dispersibility of the alumina-coated TiO2 powders was determined by dynamic laser scattering (DLS) mode. The alumina coating layers existed in boehmite phase, AlOOH, and anchored at the surfaces of TiO2 via Ti–O–Al bond. The formation of alumina coating layers on TiO2 surfaces depended on the pH value of the deposition solution and the alumina loading. After coated by alumina layer, the dispersibility, whiteness, brightness, and light scattering index of the resultant samples were promoted. [Copyright &y& Elsevier]