Influence of processing conditions in TEOS/PDMS derived silicon oxycarbide materials. Part 1: Microstructure and properties

Fully dense bulk silicon oxycarbide (SiOC) derived materials have been prepared using the conventional ceramic route. Tetraethylortosilicate/Polydimethylsiloxane (TEOS/PDMS) organic–inorganic hybrids were used as starting materials. These hybrids were thermal treated, attrition milled and pyrolyzed at 1100 °C. SiOC powders were shaped employing uniaxial and/or isostatic pressing and finally were sintered up to 1550 °C for 4, 8 and 16 h. Bulky defect free SiOC ceramics without porosity were obtained displaying enhanced both mechanical properties and oxidation resistance compared to silica glasses. These SiOC materials present maximum values of microindentation hardness and flexural strength of 11.7 GPa and 153 MPa, respectively, and a high oxidation resistance at 1550 °C for 100 h, a very low coefficient of thermal expansion of 1.35 × 10−6 °C−1, a high glass transition temperature of 1325 °C, and an electrical resistivity of 3.15 × 105 Ω m.