Faculty Sponsor's Department(s):
SiC-based ceramic matrix composites (CMCs) are of interest in many applications due to their high strength, low density, and ability to withstand very high temperatures. This unique set of properties has the potential to enable greater overall engine efficiency in aircraft, rockets, land-based turbines, and hypersonic flight vehicles. An important group of these materials is fabricated by reactive melt infiltration of Si into carbonaceous material filling the spaces between the SiC fibers. However, the operating temperatures are currently limited by the presence of unreacted Si, which has a lower melting point than SiC. The goal of this project is to develop an improved route for the synthesis of SiC-based matrices that are fully dense and minimize the amount of residual silicon. SiC compacts are prepared via spark plasma sintering (SPS), which uses pressure and the heat from an electric current to compress powder into a pellet with variable density. SPS parameters, including the heating rate, temperature, and dwell time, will be optimized to achieve 40-50% relative density. These specimens will then be infiltrated with C precursors to produce a porous network of carbon, which would then be exposed to Si vapor to yield a SiC surface that can be wetted by molten Si, which will be subsequently infiltrated on the vapor-treated preform. These experiments will lead to a better understanding of the kinetics of Si infiltration and the mechanism of reaction. Electron microscopy will be used to measure the reaction layer and characterize defect evolution in the product. Results from this work will support the development of advanced ceramic materials and help meet the demand for more efficient turbine engines.