STTR Phase I: Additive manufacturing of ceramic composites for next generation gas turbines

The broader impact/commercial potential of this project lies in next generation gas turbines where the heart of the engine, the combustor and the blade, are constructed from ceramic matrix composites (CMCs). These developments will spell a new phase of air transportation beyond the current engines that rely upon nickel-base superalloys, which have reached their maximum capability. The ceramic engines are eventually expected to be 25% more efficient. The CMCs are constructed from fibers of silicon-carbide that are spun into net shape and then infiltrated with an equally robust high temperature matrix, also made from silicon carbide-based ceramics. The fiber composites overcome the inherent brittleness of monolithic ceramics while retaining their mechanical and corrosion resistance in aggressive environments. These composites will have applications beyond gas turbines. They can become the critical breakthrough for the solar collector on Concentrated Solar Power systems, and have the potential to be used as cladding for nuclear fuels for greater safety and accident tolerance. The key innovation in this Phase I project is the development of an additive manufacturing process for creating a dense and defect free matrix from polymer precursors that convert into silicon carbide-based ceramics. This Small Business Technology Transfer Research (STTR) Phase I project employs additive manufacturing to fabricate dense and defect free matrices for ceramic matrix composites (CMCs). These composites are constructed from fibers of silicon carbide (SiC). The innovation in this project lies in constructing the matrix from polymer precursors where nanoscale layers are deposited in quick succession to create the matrix. These silicon-based polymer precursors convert into ceramics when heated to ~800 oC. Nominal processing, also known as polymer-infiltration-and-pyrolysis, produces cracks in the matrix despite 24 hour curing cycles. These cracks degrade the strength of the composite. In this project nanoscale coatings are deposited in the form of thin layers of liquid and then pyrolyzed into the ceramic in just one or two seconds. The coatings are defect free and dense. The short curing time allows rapid deposition of layers. The CMC can be prepared from SiC fiber preforms in about four hours. The feasibility of the process has been demonstrated with carbon fibers under a grant from Ceramics Program at NSF. In this SBIR project, American Manufacturing LLC seeks to demonstrate the fabrication of CMCs made from silicon-carbide fibers, and demonstrate their viability for high temperature applications.