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 deg. 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 deg. 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 deg. C and then decreased tending to disappear at 1500 deg. 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.