Influence of the gas atmosphere on the composition and phase development of polymer-derived SiOC-Ceramics

Silicon oxycarbide (SiOC)-based ceramics were synthesized by pyrolysis of a commercial polysiloxane containing MoSi2 and ceramic filler particles. The influence of different gas atmospheres on the chemical composition and on the phase formation of the filled Si-O-C ceramic during the pyrolysis process up to elevated temperatures of above 1200 degrees C has been studied. The pyrolysis gas composition in the furnace during pyrolysis was measured with an in situ gas analyzer. Both the core and the surface of bulk samples were investigated with respect to composition in order to take the changes on the rim area of the specimens into account. The influence of hydrogen gas on the compositional gradient of the resulting ceramic material was derived from samples investigated by polarization microscopy, X-ray diffraction (XRD), and micro-XRD (mu-XRD).