Preparation and Characterization of Si-C-O Aerogels Using Tetraethoxysilane and Dimethyldiethoxysilane as Precursors

Nano-porous monolithic Si-C-O aerogels were synthesized by the reaction of tetraethoxysilane with dimethyldiethoxysilane via sol-gel process, supercritical drying and pyrolysis at 1200 degrees C. The composition and structure of the Si-C-O aerogels was investigated by TG-DTA, SEM and NMR. The results show that the appearance of Si-C-O aerogel changes from white to black when it is carbonized at 1200 degrees C. The density and surface area of the aerogel are about 0.3 g/cm(3) and 217 m(2)/g, respectively. The carbon element in the Si-C-O aerogel exists as amorphous SiCO3 and free carbon phase. The empirical formula of the Si-C-O aerogels is SiC0.15O1.7+0.23C(free). Si-C-O aerogel consists of interconnected nano size spherical particles. Due to the partial substitution of oxygen by carbides carbon (Si-C), Si-C-O aerogel exhibits better thermal stability than SiO2 aerogel, and the surface area of Si-C-O aerogel at 1000 degrees C is 208.6 m(2)/g.