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.

Abstract: A series of alloys of Co, Ni, Al, W, Ta, and Cr, wherein the alloy comprises a solid solution of gamma and gamma prime alloy phases, the Ni content is greater than 25% at. %, the Al content is greater than 10 at. %, the Cr content is greater than 2 at. %, and the Ni:Co ratio is between 0.5 and 1.5. In one or more examples, the alloy further comprises one or more of C, B, and a reactive element metal. Embodiments of the alloy simultaneously possess a high solvus temperature, a high fraction of the strengthening ??-L12 phase, good oxidation resistance and highly favorable solidification characteristics.

Abstract: A series of alloys of Co, Ni, Al, W, Ta, and Cr, wherein the alloy comprises a solid solution of gamma and gamma prime alloy phases, the Ni content is greater than 25% at. %, the Al content is greater than 10 at. %, the Cr content is greater than 2 at. %, and the Ni:Co ratio is between 0.5 and 1.5. In one or more examples, the alloy further comprises one or more of C, B, and a reactive element metal. Embodiments of the alloy simultaneously possess a high solvus temperature, a high fraction of the strengthening ??-L12 phase, good oxidation resistance and highly favorable solidification characteristics.

Abstract: An oxide-based ceramic matrix composite and a method of making oxide-based ceramic composite are provided. The oxide-based ceramic matrix composite comprises a ceramic fiber and a mullite-alumina impregnating the ceramic fiber, wherein the mullite-alumina ceramic matrix comprises of 10-70 wt % mullite-alumina mixture.