Structural Evolution During Pyrolysis of Sol-Gel Derived Hybrid Materials

Siloxane-titania materials have been prepared starting from diethoxydimethylsilane and titanium isopropoxide. The transparent starting gels can be described as nanocomposites formed with siloxane chains and TiO2-based particles. The pyrolysis process under argon atmosphere up to 1600 degrees C has been followed by various techniques such as infrared and solid state NMR spectroscopies, X-ray diffraction and Ti K-edge X-ray Absorption. Si-C bond cleavage begins at low temperature leading to redistribution reactions with the formation of new Si-O bonds. Crystallization of TiO2 at low temperature is prevented and titanium carbide starts to form around 800 degrees C. Samples pyrolyzed at 1600 degrees C show the presence of SiO2 and TiC crystalline phases.