| About this Abstract |
| Meeting |
MS&T21: Materials Science & Technology
|
| Symposium
|
Thermodynamics of Materials in Extreme Environments
|
| Presentation Title |
High-temperature Structure and Thermodynamics of Cerium Silicates, A-Ce2Si2O7, and Ce4.67(SiO4)3O |
| Author(s) |
Andrew Charles Strzelecki, Kyle Kriegsman, Paul Estevenon, Vitaliy G. Goncharov, Jianming Bai, Stephanie Szenknect, Adel Mesbah, Di Wu, John S. McCloy, Nicolas Dacheux, Xiaofeng Guo |
| On-Site Speaker (Planned) |
Andrew Charles Strzelecki |
| Abstract Scope |
Lanthanide disilicates and oxyapatites have potential roles in high temperature applications as thermal (TBC) and environmental barrier coatings (EBC). In this work, structural and thermodynamic investigations on A-Ce2Si2O7 (tetragonal, P4<sub>1</sub>) and Ce4.67(SiO4)3O (hexagonal, P6<sub>3</sub>/m) were performed. The high temperature structural behaviors and coefficients of thermal expansion were determined by in situ high temperature synchrotron XRD and TGA-DSC. A-Ce2Si2O7 was found to be stable in N2 and air up to ~1483 K with an isotropic thermal expansion. Ce4.67(SiO4)3O had a slow partial oxidation between 533 K and 873 K, followed by a thermal decomposition to CeO2 and SiO2 at ~1000 K in air. By using high temperature oxide melt solution calorimetry, the standard enthalpy of formation was determined for A-Ce2Si2O7 (-3825.1 ± 6.0 kJ/mol) and Ce4.67(SiO4)3O (-7391.3 ± 9.5 kJ/mol). These thermodynamic parameters were used in examining each phases chemical stability in high temperature environments relevant to aeronautical applications. |