Effect of Ti concentration on the structure and texture of SiTiOC glasses

Five different silicon-titanium organic-inorganic hybrid materials were prepared by the reaction of tetraethoxysilane, titanium tetrabutoxide and silanol-terminated polydimethylsiloxane. Si-Ti oxycarbide glasses were prepared by pyrolysis of the hybrid materials in nitrogen atmosphere in the range of 400 to 1500 °C. The obtained Si-Ti oxycarbide materials were characterized by Fourier Transform-Infra Red spectroscopy, X-ray-diffraction, mercury porosimetry and SEM. The study indicated that the reactivity towards water increases up to 1000 °C, at higher temperatures it decreases for all samples. During the pyrolysis, Ti atoms were incorporated into the silicate network leading to the formation of Si-Ti oxycarbide glasses, except with sample containing 7% of Ti which presented also the formation of β-SiC and TiC crystalline phases. The porosity was increased up to 600 °C and then decreased tending to disappear at 1500 °C. When the titanium concentration increased from 1 to 3% in the oxycarbide glass, the porosity decreased; for higher concentration, an increase in the porosity was observed.