| 研究課題/領域番号 |
21K14393
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| 研究機関 | 東北大学 |
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研究代表者 |
DAVEY THERESA 東北大学, 工学研究科, 特任助教 (10816987)
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| 研究期間 (年度) |
2021-04-01 – 2024-03-31
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| キーワード | zirconium carbide / zirconia / ordering / CALPHAD / point defects |
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| 研究実績の概要 |
Density functional theory (DFT) calculations were used to explore the stability of ordered and disordered phases in the carbon-oxygen-zirconium-vacancy system at 0 K. Cluster expansion method (CEM) calculations of the C-O-Zr system and C-Zr-vacancy system were performed to examine stable ordered phases and vacancy ordering. Special quasirandom structures (SQS) were generated to examine disordered phases. These calculations extend our understanding of the effect of impurities on low temperature ordered phases. First-principles calculations exploring the maximum solubility of oxygen and carbon in zirconium carbide and zirconia respectively were also performed. Finite temperature first-principles calculations (phonon calculations) for some parts of the carbon-oxygen-zirconium-vacancy system were performed to examine the thermal disordering processes.
First-principles calculations examining the effects of oxygen on carbon vacancy ordering in zirconium carbide were performed and published in RSC Advances. Additionally, an invited review paper including these results was published in the International Journal of Ceramic Engineering and Science. Results were presented at virtual international conferences (MH21, PACRIM, TMS, ICACC) and at an invited lecture at 第60回セラミックス基礎科学討論会. Due to the ongoing COVID-19 pandemic, in-person participation in international meetings was not possible, but will resume as soon as possible.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
The planned calculations to explore the carbon-oxygen-zirconium-vacancy system in brief have been started and are progressing as anticipated, and several other interesting phenomena have been observed with potential for further investigation. The obtained results are very promising and have attracted interest from experimental researchers in the field following presentations at international conferences and publication of two papers.
Although several presentations were made at virtual international conferences and in-person domestic conferences this year, the ongoing COVID-19 pandemic has limited conference attendance for community discussion. Dissemination of the results via papers has been prioritised to counter the effects of the COVID-19 pandemic.
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| 今後の研究の推進方策 |
In FY2022, calculations will continue to further elucidate the oxidation pathway between zirconium carbide and zirconia as a function of temperature, extending the previous results. Further trends in the interstitial oxygen ordering in hcp and bcc zirconium will be examined at finite temperatures. The coexistence of zirconium carbide and zirconia and their interfaces will be explored using first-principles calculations in the ground state and at finite temperature, mapping the lattice parameter (volume) and elastic (mechanical) properties in the composition and temperature space. Geometric constraints on the mixing of the carbide and oxide phases will be examined. Preliminary CALPHAD modelling of the O-Zr phase diagram (incorporating new insights) will be performed.
In FY2023, CALPHAD modelling of the C-O-Zr ternary system will be performed, incorporating insights from calculations in previous years. Short-range-ordering in the liquid phase will be considered via the MQM, considering short-range atomic interactions. CALPHAD modelling of the O-Zr and C-Zr binary liquids will be considered incorporating any short-range-ordering effects.
Results are planned to be presented at domestic and international conferences virtually, or in-person if possible (MS&T (USA), ICACC (USA), TMS (USA), Ceramic Society of Japan meetings), and further results will be published.
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| 次年度使用額が生じた理由 |
Software licences planned for purchase in FY2021 have not yet been required, so their purchase has been deferred to subsequent years. Significant amounts of the budget were planned to be used for travel to international conferences to disseminate information, and to host visitors to allow collaborations. Unfortunately, due to the ongoing COVID-19 pandemic, international travel has not been possible in the last year, therefore these expenses have been delayed until such meetings and in-person collaborations are possible.
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