Dense bulk silicon oxycarbide glasses obtained by spark plasma sintering

Dense silicon oxycarbide glasses (SiOC) have been produced by spark plasma sintering (SPS) of SiOC powders. Raw powders were obtained by pyrolysis under nitrogen at 1100 °C of tetraethylorthosilcate/polydimethylsiloxane (TEOS/PDMS) hybrids. SPS experiments were carried out at 1300 and 1500 °C at 10 and 80 MPa and then were studied by chemical analysis, 29Si and 13C MAS NMR, ATR, Raman, XRD, FE-SEM, density, porosity, microhardness (Hv) and thermal conductivity (K). The SiOC materials are formed by SixOC4−x units within a silica matrix where silicon carbide and graphite nanodomains are also present. After the SPS treatment the silicon carbide crystallite size is close to 2.5 nm. At 1300 °C and 1500 °C the carbon nanodomain size is close to 3 nm and 2 nm, respectively. Hv values vary from 3.4 to 9.15 GPa, for 30% and 1% of porosity, respectively. Finally, K is always close to 1.38 W m−1 K−1.