Phenyl (PPS) and methyl (PMS) containing polysiloxanes were pyrolyzed at elevated temperatures (900-1500• 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• C leads to amorphous silicon oxycarbide (SiO x C y ) ceramics. Conversions at higher temperatures results in the transformations into the crystalline ␤-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• 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.

Abstract. Pyrolytic conversion of a preceramic polymer, poly(phenyl)siloxane has been investigated to develop ceramic matrix composites (CMCs) at low temperatures with high dimensional stability. Furthermore, the thermal transformation of the polymer precursor under inert atmosphere was monitored. For this purpose, poly(phenyl)siloxanes were cured at about 200 °C for 2 hours under air and pyrolysed at various temperatures in the range of 900 -1500 °C for 1 hour under inert argon atmosphere. The products of the pyrolytic conversion were analyzed using X-ray diffraction (XRD), thermal analysis (TG and DTA) and scanning electron microscopy (SEM) coupled with EDX analyzer. It was found that pyrolysis under inert atmosphere up to 1300 °C led to amorphous silicon oxycarbide (SiO x C y ) ceramics. Conversions at higher temperatures caused the transformation into the crystalline β-SiC phases. Moreover, to obtain composite monoliths inert Al 2 O 3 and active Ti and Si particulates were incorporated into the polymer as fillers employing compressive moulding at moderate temperatures. During pyrolysis, cross-linked green compacts of the particulate/polymer system were converted into ceramic body and the microstructural parameters and the effects of the filler type on the microstructure were investigated.