Nano-TiO2/Diatomite Composite: Synthesis, Structure and Heat Resistance

Nano-TiO2/diatomite composite (DDT) has been prepared (nano-sized TiO2 particles have been deposited on a Moldovan diatomite as substrate) by a modified heterogeneous hydrolysis with TiCl4 as precursor of TiO2. The as-prepared composites DDT were calcined at different temperatures in a range of 200–1000°C. The characterization of the structure and microscopic appearance of nano-TiO2 has been performed by X-ray powder diffraction, scanning electron microscopy X-ray photoelectron spectroscopy, energy dispersive spectroscopy, Fourier-transform infrared spectroscopy, and nitrogen adsorption/desorption measurements. It has been shown that TiO2 in the anatase phase is deposited on the surface of the macropores walls of diatomite. The thermal stability of the prepared material was studied. An increase in the calcination temperature leads to an increase in the size of TiO2 nanoparticles and to a decrease in the specific surface and pore volume associated with shrinkage of the mesoporous structure. However, the whole structure remains mesoporous up to 800°C; the thermal stability is thus improved compared with pure TiO2. Diatomite improves the thermal stability of TiO2 crystals and inhibits the phase transformation of anatase to rutile. All samples contain anatase phase without impurities of rutil phase up to 800°C. At 1000°C, the composite is non-porous and contains a mixture of crystalline anatase and rutile nanoparticles with an average diameter of 5 to 10 nm.