Evolution mechanism of alumina nanofilms on rutile TiO2 starting from sodium metaaluminate and the pigmentary properties

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.