About this Abstract |
Meeting |
2021 TMS Annual Meeting & Exhibition
|
Symposium
|
Computational Thermodynamics and Kinetics
|
Presentation Title |
Stability and Phase Transition of Cristobalite in SiO2 |
Author(s) |
Ying Chen, Nguyen-Dung Tran, Hao Wang, Masanori Kohyama, Satoshi Kitaoka, Tetsuo Mohri |
On-Site Speaker (Planned) |
Ying Chen |
Abstract Scope |
SiO2 has many polymorphs with plentiful phase transformations. The present work focus on the Cristobalite phases of SiO2 which is taken as a promising oxidation protective film in environmental barrier coating. β-Cristobalite is stable at high temperature, while the phase transition to α-Cristobalite happens accompanying a large volume shrinkage at 270°C, which leads to the SiO2 film broken or peeled off. First-principles calculation has been conducted to get a guideline to suppress such α-β Cristobalite phase transition. Electronic structure, phonon vibration calculation are conducted on α-Cristobalite, β-Cristobalite and α-Quartz to investigate the stability and the tendency of phase transformation. Nitrogen-doping is then attempted and a structure with Si-N-N-Si-O ring formed from the pair N2 substituting two oxygen atoms at the vertexes of neighboring O-O-O-Si tetrahedron gives obviously lower energy than other configurations, this mechanism can be explained by analysis of local energy density and local stress density. |
Proceedings Inclusion? |
Planned: |