Structure and Properties of Porous SiO_2-TiO_2 Blocks

Porous Si02-Ti02 blocks were successfully synthesized by polymerization of tetraethy-oxysilane and tetrabutyl titanate in the presence of polyethylene glycol via a sol-gel route. Their infrared spectra, pore distribution and chemical durability were mainly studied. The results showed that the residual organic component can be removed after heat-treated at 500 ℃ for 2h, and then a vitreous structure with Si-O and Ti-O bonds was formed. The porous materials containing Ti had a narrower pore distribution and the peak of the pore distribution curve shifted to the smaller pore diameter. With the increase of TiO2 content, the density of porous blocks increased, whereas open porosity and adsorbed water ratio decreased at the same time. After immersion in water at 80 ℃for 72h, the type and shape of adsorption-desorption curves changed slightly. Since the change of specific surface area, pore volume and average pore diameter for the obtained materials decreased with the increase of Ti content, it indicated an improvement of water resistance. The durability of porous blocks in 1% NaOH basic solutions at 95 ℃ was apparently improved due to an addition of titanium as compared with SiO2 porous block which was collapsed in such solution. However, anti-acid resistance of porous materials in 20% H2SO4 solutions at 98 ℃ can not be improved by an addition of titanium.