EFFECT OF PYROLYSIS PARAMETERS ON SILICON CARBIDE-FORMING COMPOSITE MIXTURES

High-performance ceramics are often used for reusable spacecraft Thermal Protection Systems (TPS). Pre-ceramic polymers provide a suitable route for fabricating silicon carbide (SiC)–based TPS. It is known that different phases of SiC form upon pyrolysis depending on the temperature. This research investigates the effects of pyrolysis temperature and nucleation aids on SiC forming pre-ceramic polymers and how they influence the final phases. It is possible that the addition of seed powders consisting of microscale and nanoscale SiC powders can aid growth of crystalline SiC at lower temperatures and influence the final composition in mixtures of SiC-forming polymers with crystalline SiC powders and graphite. For this research, pre-ceramic polymer mixtures with various nucleation aids were cured slowly in a furnace and pyrolyzed at various temperatures into a ceramic. The effects of temperature were investigated for six different sample configurations: pure polymer sample, micron crystalline SiC powder layer with polymer fill, nano SiC powder with polymer fill, micron SiC powder and polymer mixture (85 wt%), 3D printed amorphous carbon-loaded polylactic acid layer with SiC polymer fill, and crystalline graphite mixed with a UV-curable polymer (65 wt.%) mixed with SiC polymer. Material characterization was conducted via SEM to identify the phases. These results can improve processing procedures for these ceramics with better strength and thermal diffusivity for TPS.Ensign, United States NavyApproved for public release. Distribution is unlimited