Date of Award
Master of Science
The processing of ZrB2-ZrC-ZrxSiy composite by reactive metal penetration was investigated as a successor to the ZrB2-SiC composites for hypersonic vehicles application, which cannot be used for extended time at temperatures greater than 1600C due to formation of SiO and CO gases. Zirconium (Zr), zirconium disilicide (ZrSi2), and boron carbide (B4C) were reacted in graphite crucibles for 60, 120, 180, and 240 minutes. Microscopy and x-ray diffraction (XRD) deduced the formation of a heterogeneous microstructure of ZrB2-ZrC-ZrxSiy precipitates surrounded by a solidified Zr-Si melt. Unreacted boron carbide was observed in samples held at 1860C for 60 minutes and 120 minutes, so thermodynamic equilibrium was not achieved. The reaction for the composite formation is as follows:
The most consistent microstructures were seen on the samples heated for 180 minutes and 240 minutes, in which the free B4C completely decomposed to zirconium boride and carbide. Also, because of the closeness of the initial compositions of Zr and Si (12 wt% and 14 wt%) on the Zr-Si phase diagram, there was not much difference in the final phases obtained in both compositions.
Received from ProQuest
Nischel B. Maheswaraiah
Maheswaraiah, Nischel B., "Processing Of ZrB2-ZrC-ZrxSiy Ceramic By Reactive Metal Penetration" (2010). Open Access Theses & Dissertations. 2725.