Straightforward Design Strategy toward 3D Near-Net-Shape Stoichiometric SiC Parts

Fused deposition modeling (FDM), traditionally reserved for thermoplastics, is modified here with a granule-based extrusion head to be extended to advanced nonoxide ceramics via a straightforward design strategy that considers the shaping opportunities and the chemical richness offered by preceramic polymers. Specifically, 3D near-net-shape stoichiometric silicon carbide (SiC) objects are designed by manipulating the key features of a commercially available polycarbosilane (fusibility, high carbon content, relatively high SiC yield). In the early stage of the process, the carbon-rich polycarbosilane is first mixed with Si and SiC fillers and then thermolyzed at 120 degrees C to increase polymer branching while offering tailored rheological properties during the subsequent extrusion process at 90 degrees C and adequate shape retention once extruded. This allows for the design of tailored and complex 3D complex polycarbosilane-based architectures with features down to 400 mu m. Polymer-based parts are further converted into 3D stoichiometric SiC objects with quasi-near-net-shape-a volume shrinkage reduced to 9.1% is measured-by heat treatment at a temperature as low as 1400 degrees C (argon flow). Given the flexibility to tune the preceramic polymer chemical and rheological properties, a new combined design approach is leveraged to generate bespoke advanced ceramics with a high freedom in geometry complexity. A straightforward design strategy coupling a granule-based fused deposition modeling process and preceramic polymer manipulation highlights the production of 3D near-net-shape stoichiometric SiC parts with a high potential impact in adverse environments as mirrors for lightweight opto-mechanical systems, as high-flux concentrated solar receivers and as heat exchangers for thermal management.image