Silicon oxycarbide-based composites produced from pyrolysis of polysiloxanes with active Ti filler

Abstract

Phenyl (PPS) and methyl (PMS) containing polysiloxanes were pyrolyzed at elevated temperatures (900-1500 degrees C) under argon atmosphere to investigate the phase developments within the polymers. It was found that pyrolysis of the polymers under inert atmosphere up to 1300 degrees C leads to amorphous silicon oxycarbide (SiOxCy) ceramics. Conversions at higher temperatures results in the transformations into the crystalline beta-SiC phases. Ceramic matrix composites (CMCs) were developed based on the active filler controlled pyrolysis (AFCOP) of polysiloxanes with active Ti filler additions. CMC monoliths were prepared with 60-80 wt.% of active Ti particulates blended into polymer precursors. Green bodies of the composites were made by warm pressing under 15 MPa pressure and ceramics were obtained by pyrolysis at elevated temperatures between 900 and 1500 degrees C under argon atmosphere. The results showed that due to the incorporation of active Ti fillers, formation of crystalline phases such as TiC, TiSi, and TiO occured within the amorphous matrix due to the reactions between the Ti and the polymer decomposition products. The microstructural and mechanical characterization results of the composites are presented within the paper. (c) 2005 Elsevier Ltd. All rights reserved.