Abstract
In this work, polycyclic silazane/siloxane networks bearing Si O and Si N bonds were synthesized, via hydrosilylation reaction, from cyclotrisilazane, [CH 2 CH(CH 3)SiNH] 3, and cyclotetrasiloxane, [CH 3(H)SiO] 4, with different Si H:Si vinyl molar ratios. The resulting polymers were pyrolyzed up to 1000 °C, in N 2 atmosphere, producing SiOCN glasses. The polymer-to-ceramic transformation was studied by thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), and chemical analysis. The 1000–1500 °C, high temperature structural evolution was also studied using X-ray diffraction (XRD) and FTIR. The hydrosilylation reaction produced ethylenic bridge crosslinked polymeric precursors with good thermal stability. The SiOCN glasses obtained with ceramic yields higher than 80 wt% showed spectra absorptions of Si N, Si O, and Si C bonds in FTIR. The XRD patterns of the products obtained at 1500 °C displayed diffraction peaks characteristic of β-SiC and a broad halo centered at 22° (2 θ), due to the amorphous silica phase. β-SiC diffraction peaks in the XRD patterns were more intense for the precursor richer in polysiloxane units, although absorptions of Si N, Si C, and Si O bonds were also observed in the FTIR spectra. Thus, the final materials were characterized as SiC/SiOCN composites in nano/amorphous phases.
Published Version
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