Glasses in the SiOCN system produced by pyrolysis of polycyclic silazane/siloxane networks

Autor: I. Valéria P. Yoshida, Marco Antônio Schiavon, Katia J. Ciuffi
Rok vydání: 2007
Předmět:
Zdroj: Journal of Non-Crystalline Solids. 353:2280-2288
ISSN: 0022-3093
DOI: 10.1016/j.jnoncrysol.2007.03.004
Popis: 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.
Databáze: OpenAIRE
Externí odkaz: