PMS/DVB/activated charcoal hybrid polymers-derived sicxoy glasses

Full text: This study focuses on the preparation of silicon oxycarbide glasses (SiOC) derived from hybrid polymeric precursors such as poly(methylsiloxane) (PMS), divinylbenzene (DVB) and activated charcoal (C) in different compositions. The polymers derived from PMS and DVB were obtained by Pt-catalysed hydrosilylation reaction in PMS:DVB molar ratios of 80:20 and 20:80, in the presence or absence of C (0, 1 and 3 wt%). The resulting polymers were post-cured and pyrolysed in Ar atmosphere at 1000 deg C, giving rise to corresponding glasses containing high- and low-PMS content. The polymers were characterized by thermogravimetry and the glasses by infrared and Raman spectroscopies, X-ray diffractometry and scanning electron microscopy. Samples with high- PMS content presented ceramic yields higher than low-PMS samples, as expected. The presence of C reduced the ceramic yield for all samples, showing less influence for those with high-PMS content. Infrared spectra exhibited well-defined absorptions at 1020, 800 and 480 cm^-1, associated to Si-O and Si-C, typical of mineralized materials. XRD patterns presented a broad halo centered at 23° (2θ), typical of non-crystalline SiOC, and a weak but distinct diffraction at 26.5° and a broad one at around 43°, mainly for low-PMS glasses. The first diffraction signal corresponds to graphitic carbon, whereas the second one originates from graphene sheets, characteristic for disordered carbons. Raman spectra exhibited broad D and G peaks around 1330 and 1590 cm^-1, respectively, indicating the presence of disordered carbon phase [1]. The increase of both DVB and C showed a tendency of reduction of the carbon-cluster size. SEM images demonstrated the typical smooth surface of SiOC glasses with circular and elliptical macropores and some rough regions with river-shaped patterns [2]. References: [1] Kleebe, H.-J.; et al. Int. J. Mat. Res. 96 (2006) 699-709. [2]Haußmann, M.; et al.J. Anal. Appl. Pyrolysis 91 (2011) 224-231.(author)