Akademik Veri Yönetim Sistemi
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, cilt.73, sa.1, ss.171-180, 2015 (SCI-Expanded)
New silicon boron oxycarbide (SiBOC) preceramic polymers were synthesized via sol-gel method by using n-butyltrimethoxysilane and iso-butyltrimethoxysilane as silicon sources, triethylborate and boric acid as boron sources to obtain SiBOC ceramics. The effect of different molar ratios of Boron/Silica (B/Si) and ultrasonic application were investigated on gelation time. Influence of the microwave application on gelation time was performed for the first time, and compared with ultrasonic application. The changes in the structure of SiBOC preceramic with amount of boron, addition of glycerol, ultrasonic and microwave applications were also investigated by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction technique and Si-29 MAS NMR spectroscopy. It was observed that the gelation time (t(gel)) is reduced with higher amount of boron in the structure as well as ultrasonic and microwave application. Reduction of gelation time with increasing boron amount was related to formation of more Si-O-B (borosiloxane) bonds in the structure. Furthermore, decreases of gelation time with ultrasonic or microwave application may be owing to the acceleration of the hydrolysis and condensation reactions. Pyrolysis of obtained gels under nitrogen atmosphere up to 1,400 A degrees C by 10 K/min heating rate produced solid homogeneous ceramic powders.