Influence of molecular architecture of Si-containing precursors and HF chemical treatment on structural and textural features of silicon oxycarbide (SiOC) materials

Abstract

Silicon oxycarbide (SiOC) ceramics were obtained from two polymeric precursors to investigate the influence of pyrolysis temperature and HF chemical treatment on their structures and textural features. DVDH polycyclic polymer was prepared from 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, and 2,4,6,8-tetramethylcyclotetrasiloxane, whilst PMFV linear from poly [dimethylsiloxane-co-diphenylsiloxane] divinyl terminated. SiOC-based ceramics were obtained by pyrolysis under argon at 1000 and 1500 °C and also etched in HF solution. FT-IR, TG, XRD, N2 gas physisorption at 77 K and elemental analyses were used to characterize the obtained materials. The results revealed information about controlling chemical structure of SiOC ceramics through the combination of adequate precursor, thermal and chemical treatment. The study demonstrated the dependence of the polymeric precursors structure over the ceramic yield and Cgraphitic and β-SiC crystalline phases produced. HF etching allowed the fabrication of porous materials containing carbon conducting and SiC semiconducting phases more exposed into SiOC matrices, thus revealing potentialities to future electrochemical investigations.