Effect of synthetic method on the structure of pyrochlore- and zirconolite-type oxides
Bibliographic record
Abstract
Ceramic materials such as pyrochlore-and zirconolite-type oxides have been studied for several decades due to their applications in catalysis, ferromagnetism, luminescence, ionic conductivity, and radioactive waste sequestration.The studies presented in this thesis investigated the effects of solution-based synthesis methods (coprecipitation and sol-gel) on the long-and short-range structures of pyrochlore-and zirconolite-type oxides annealed at various temperatures and the structural stability of these materials upon irradiation.Powder X-ray diffraction (XRD) was used to confirm the formation of the desired phases at all temperatures studied (pyrochlore: 700 to 1400 °C; zirconolite: 700 to 1400 °C).Changes in the long-range structure of the materials were evaluated by Rietveld refinement of the diffraction patterns.Scanning electron microscopy (SEM) showed an increase in grain size with annealing temperature.X-ray absorption near edge spectroscopy (XANES) was used to probe the local structure of Ti and Zr within the materials.Examination of the Ti K-and Zr K-edge XANES spectra showed no significant change in the structure of the pyrochlore-and zirconolite-type materials annealed at temperatures as low as 800 and 900 °C, respectively.Pellets of pyrochlore-and zirconolite-type materials prepared by the three synthesis methods (ceramic, coprecipitation, and sol-gel) were implanted with high energy Au -ions to simulate radiation-induced structural damage.Ti K-edge glancing angle XANES showed no change in the radiation resistance of zirconolite prepared by any of the synthesis methods.The pyrochlore-type materials exhibited reduced radiation resistance when the synthesis method was changed from ceramic or coprecipitation to sol-gel.This effect could be due to an increase in the porosity of the material.Therefore, it has been shown that pyrochlore-and zirconolite-type materials can be synthesized at temperatures as low as 800 and 900 °C, respectively, by using a coprecipitation or sol-gel method, due to the atomic scale mixing of reactants which occurs in solution.However, use of these synthesis methods could decrease the ability of the materials to withstand radiation-induced structural damage.The reduction of the annealing temperatures required to form pyrochlore-and zirconolite-type materials results in more cost-efficient processing which is ideal for industrial scaling.Advanced Photon Source (APS) for XANES collection.The Canadian Foundation for Innovation (CFI) is thanked for providing funds to purchase the PANalytical Empyrean powder X-ray diffractometer that was used in this project.This research used resources of the Advanced Photon
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".