Develop SiC/Carbon ceramic matrix composites by direct ink writing and low-temperature pyrolysis

Background: Ceramic matrix composites (CMCs) consisting of reinforced fibers and ceramics as matrix materials have been designed to possess significantly greater fracture toughness and thermal shock resistance, showing potential in turbine and combustion engines, hypersonic vehicles, and satellites. Additional manufacturing of CMCs allows the printing of complex geometry for component design. However, the fiber alignment is challenging in printed parts, and the sintering temperature of ceramics is high.

Methods: The team hypothesized from other studies an initial ink formula for testing. Direct Ink Writing (DIW) will be used to print the parts for this study. The initial ink formula for the DIW paste consists of a(n): preceramic polymer (poly(methyl-silsesquioxane) Silres MK); solvent (isopropanol), inert filler (SiC powder Starceram S Grade UF10), dispersant agent (BYK 180), reinforcement agent (commercialized, chopped, uncoated carbon fibers), crosslinking catalyst (Geniosil GF91), and the rheology modifier (hydrophobic fumed silica, Aerosil R106). Rheological analysis will be done to analyze the specific effects of the components so that it is possible to better understand each of the components' individual contributions to the ink’s rheology. The Tronxy 2, a direct ink writing printer, will print parts that will be placed in a sintering furnace for crosslinking and pyrolysis. Once pyrolysis is completed the sample will be subject to mechanical testing, and then microscopic analysis of the failed parts will be conducted.

Conclusion: This work will employ SiC/Carbon fiber CMCs to demonstrate that (a) the rheology property can guide for shear thinning, which is critical for direct ink writing; (2) the low-temperature pyrolysis (<1000^oC) of SiC/C CMCs is efficient to form dense structure, which will be discussed in detail.