Implications of coupled crystallization and decomposition reactions for CMC processing using polymer derived ceramics

Conference Dates

November 5-9, 2017


The wider adoption of SiC-based ceramic matrix composites (CMCs) for thermo-structural applications is limited in part by the challenges encountered in processing dense matrices without low melting temperature or oxidation-sensitive phases (i.e. free Si or C). Manufacturing routes utilizing polymer-derived ceramics (PDC) are being developed as a cost-effective method to manufacture CMCs with improved temperature capability. The notional approach involves repeated infiltration of the CMC preform with a preceramic polymer followed by pyrolysis to form an amorphous Si-(O-N)-C matrix. A heat treatment at a higher temperature is necessary to crystallize the PDC, which improves the thermal conductivity, thermal stability, and oxidation resistance compared to the amorphous polymer derived phase. Crystallization occurs by precipitation of SiC, C, and/or Si3N4 while concomitant decomposition reactions produce gaseous SiO and CO.

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