Vapor-mediated synthesis of silicon carbide matrices for ceramic matrix composites by reactive melt infiltration

Abstract

A two-step synthesis of SiC including initial exposure of carbon surfaces to Si vapor, followed by Si melt infiltration, is described herein. Interrupted differential thermal analysis (DTA) of amorphous C and Si powder mixtures and microstructure characterization are used to identify the stages of the reaction. Exposure to Si vapor yields a SiC layer with nanoscale porosity driven by the volume change associated with the reaction. This forms a continuous pore network that promotes subsequent melt access to the reaction front with the C. While the pores remain open, the vapor phase reaction proceeds at a nearly-constant rate and exhibits a strong temperature sensitivity, the latter due largely to the temperature sensitivity of the Si vapor pressure. The implications for enhancing the reactive melt infiltration process and fabrication of SiC matrices for ceramic composites are discussed.