Structural characterization of sol-gel composites using TEOS/MEMO as precursors

An organic/inorganic hybrid SiO₂-matrix composite was prepared through sol-gel process using TEOS and MEMO as precursors. The structures and thermal stability of the composites were investigated by various complementary techniques. The results indicate that both TEOS and MEMO hydrolyze and polymerize in sols to gelatinize and form silica-matrix materials after being baked at 60 °C. Increase of the MEMO concentration in the sols results in reduction of low-molecular compounds (such as H₂O, CH₃OH, etc.) incorporated in baked gels, thus significantly decreasing the thermal weight-loss at temperature lower that 400 °C. On the other hand, the organic functional groups bonded with -Si-O in MEMO polymerize and gelatinize to change the atomic structures and chemical states of Si in the composites. The sol-gel composites induced by TEOS/MEMO gelatinization process become pure silica after thermal treatment over 500 °C, due to decomposition and evaporation of the incorporated organic groups. It is interesting to note that from the sol containing TEOS and MEMO precursors, hydrolyzed product from MEMO precursor preferably dip-deposits compared with that from TEOS. The detailed structure analysis and mechanisms of thermal stability are analyzed in the paper.