Abstract Scope |
Ultra-high temperature ceramics (UHTCs) are capable of withstanding extreme temperatures. Specifically, hafnium carbide (HfC) and tantalum carbide (TaC) have the highest melting points amongst UHTCs, however, rapid oxidation of these materials is a persistent problem. In this work, HfC, TaC, and nominally single phase (Hf,Ta)C mixtures were densified using spark plasma sintering. Oxidation exposures were conducted in a resistive heating system at 1400°C in 1% oxygen/argon for times up to 10 minutes. Scanning electron microscopy and energy dispersive spectroscopy were used to characterize the oxide morphology, composition, and to determine the oxide thickness. Oxide thickness results demonstrated that pure TaC oxidizes more rapidly than pure HfC. The resulting oxide of the mixed (Hf,Ta) carbides was denser and thinner compared to the end members. X-Ray diffraction analysis showed that the complex oxide Hf6Ta2O17 was the predominant oxide phase, contributing to the change in oxide morphology and reduced oxide thickness. |