About this Abstract |
| Meeting |
MS&T25: Materials Science & Technology
|
| Symposium
|
Materials Under Extreme Environment
|
| Presentation Title |
Design of Oxidation Resistant HfC-TaC Ultra-High Temperature Ceramics Based on Thermodynamic and Kinetic Modeling of the Hf-Ta-C-O System |
| Author(s) |
Rahim M. Zaman, Elizabeth J. Opila, Bi-Cheng Zhou |
| On-Site Speaker (Planned) |
Rahim M. Zaman |
| Abstract Scope |
The hafnium-tantalum-carbon-oxygen system is modeled to develop novel oxidation mechanism descriptions of HfC-TaC ultra-high temperature ceramics. Research objectives include CALculation of PHAse Diagrams (CALPHAD) model development of the Hf-Ta-C-O system and HfO2-Ta2O5 isoplethal section supported by first-principles calculations, performance of first-principles calculations of oxygen vacancy formation and diffusion in thermally grown HfO2, Ta2O5, and Hf6Ta2O17, and development of continuum models to describe oxidation of HfC-TaC ceramics. Hf(n-5)/2Ta2On is entropically stabilized with larger structure size and has slower oxygen transport than HfO2 and Ta2O5 due to its dense atomic packing, despite forming oxygen vacancies more readily. Optimally oxidation resistant 3 HfC : 1 TaC is predicted to form a carbon-containing Hf6Ta2O17 scale between 1000 and 1381 °C and a pure Hf6Ta2O17 scale between 1381 and 2190 °C. Improving the oxidation resistance of HfC and TaC will benefit aerospace initiatives and contribute to knowledge regarding materials for extreme chemical and thermal conditions. |