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• 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.

Manufacturing of ceramic matrix composite using a hybrid process combining TiSi2 active filler infiltration and preceramic impregnation and pyrolysis

“…The repetition of numerous impregnation and pyrolysis cycles is then necessary to obtain a dense material [7] . P. Greil suggested overcoming this problem with the addition of active fillers, which react during pyrolysis under reactive atmosphere to form oxides, carbides or nitrides leading to significant volume expansions [8][9][10][11][12][13][14][15][16][17][18] . These reactions occur with a volume expansion that can compensate for the polymer shrinkage.…”

Ceramic Matrix Composites Manufactured by Multistep Densification of Si‐O‐C Fibre Preform

“…However, the repetition of numerous impregnation and pyrolysis cycles is then necessary to obtain a dense material [10] . As it has been suggested by P. Greil in the case of ceramic preparation, this problem could be overcome with the use of active fillers, which react during pyrolysis under reactive atmosphere to form oxides, carbides or nitrides leading to a significant volume expansion that can decrease the matrix porosity [11][12][13][14][15][16][17][18][19][20] . Among various expansion agents, titanium disilicide powder (TiSi 2 ) is identified as an interesting active filler [20][21][22][23] .…”

Polysiloxane‐Derived Ceramics Containing Nanowires with Catalytically Active Tips

“…Above those temperatures, amorphous ceramic materials are obtained and, beyond 1200°C, thermodynamically stable phases start to form as nano‐sized crystals . Besides the diversity of possible precursors, the final material properties can be influenced by reactive or inert additives . Introduction of metallic elements may influence the pyrolytic conversion and stabilize phases, for example, carbon nanotubes or 1D nanostructures of SiC, Si 3 N 4 , etc .…”