Faculty Sponsor's Department:
SiC/SiC ceramic matrix composites (CMCs) are promising to use for high temperature stable products like turbine blades. Furthermore, Y-Si alloys offer significant advantages when used instead of silicon in a process called reactive melt infiltration (RMI) to create these SiC/SiC CMCs. In the process, excess carbon in the preform reacts with silicon from the infiltrating liquid to produce SiC, but some amount of residual silicon or silicide is left behind. This investigation serves to elucidate the thermodynamic stability of the silicides (YSi, Y3Si5 and YSi2) that are likely to be formed when a Y-Si alloy is used in this process. It seeks to clarify whether Y3Si5 and YSi2 are both stable phases, and it also endeavors to determine whether a possible equilibrium between YSi and SiC exists at certain temperatures. The silicides for these experiments are manufactured with an arc melter. Diffusion couples are created and heat treated in a hot press to encourage reaction between the components. Characterization of the samples is accomplished by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The initial results support previous research that indicates that YSi2 and Y3Si5 are distinct phases. Being able to clarify the phase diagram of Y-Si has the potential of helping the development of robust SiC/SiC CMCs.