Compatibility of Refractory Metal Boride/Oxide Composites at Ultra-High Temperatures.

摘要

The compatibility of the HfO2/HfSi2/HfB2 phases has been investigated in an argon atmosphere at 1800 deg, 1700 deg and 1600 deg C. At the three temperatures investigated, HfB 2 was determined to be relatively inert to either the oxide or silicide phases when examined with the scanning electron microscope and optical microscope. At 1800 deg C, a reactive product was found between the hafnia and hafnium dislicide phases with a wavy interface moving, parabolically with respect to time. The microstructural analysis of the interface suggests that liquid contributes to the interfacial reactions. In addition, two-solid phases (Hf 2 Si and HfSi) were formed at temperature along with silicide and silicate liquids located between HfSi2 and HfO2. At 1600 deg C for annealing times from 4 to 50 hours, the HfSi 2 /HfO 2 interface does not react as inferred from the acquired constant thickness of the silicide layer. Ceramic Composites, High Temperatures Materials Boride-Oxide Composites, Compatibility, Silicide-Oxide Composites.