Borosiloksan (SİBOC) gel synthesis by sol-gel method, characterization and ceramic formation investigation

In this study, silicon boron oksikarbür (SiBOC) precursor polymer gels were synthesized by sol-gel method and organoborosiloksan polymers were synthesized by hydroboration reaction. SiBOC ceramics were obtained by the pyrolysis of this polymers in an inert atmosphere. Polymers and ceramic powders that have not been in the literature were synthesized using different parameters. Structure, thermal properties and crystallization behavior of them were investigated by Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), and X-Ray Diffraction (XRD) technique. To obtain SiBOC precursor polymer gels, different silanes, boron compounds and B/Si molar ratio were used. The effect of addition of glycerine during the reaction and ultrasonic and microwave application at the end of the reaction to the polymer gelation times and decomposition temperature of ceramic powders were investigated. In addition, structure of the used siloxane to produce the organoborosiloxane polymers and siloxane/borane molar ratio were investigated in terms of the effect to the structure and the decomposition temperature of ceramic powders. As a conclusion, the decrease in branching of the organic groups, the increase of the percentage of boron in the structure, the use of triethylborate (TEB) as boron sources, the addition of glycerin and the application of ultrasonic and microwave reduced the gelation time (tgel). XRD analysis results show that, ß-SiC crystal were observed in the all ceramic powders at 1400°C and amorphous SiBOC ceramics with stability at high temperatures were obtained.