Surface Fluorination of Nuclear Graphite Exposed to Molten 2LiF–BeF<sub>2</sub> (FLiBe) Salt and Its Cover Gas at 700 °C
Bibliographic record
Abstract
High Resolution Image Download MS PowerPoint Slide This study demonstrates that the reaction of Li 2 BeF 4 (FLiBe) with graphite both in the liquid phase and the gas phase of the molten salt leads to the formation of covalent and semi-ionic carbon–fluorine bonds at the graphite surface and is accompanied by surface microstructural changes, removal of C–O groups, and deposition of metallic beryllium, based on XPS, Raman, and glow discharge mass spectroscopy characterization. At 700 °C, the observed surface density of C–F is higher after 240 h than after 12 h of exposure to molten FLiBe salt; the kinetics of covalent C–F formation is slower than that of semi-ionic C–F formation, and the relative amount of semi-ionic C–F content increases with depth. The graphite sample exposed to the cover gas exhibits less surface fluorination than the salt-exposed sample, with predominantly semi-ionic C–F. Based on these observations and the observed LiF/BeF 2 ratio by surface XPS, the hypotheses that fluorination of the salt-exposed graphite occurs via a gas-phase mechanism or that it requires salt intrusion are refuted; future studies are warranted on the transport of C–F semi-ionic and covalent species in graphite at high temperatures.
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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 | 0.000 |
| 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) | 0.003 | 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".