Primary phases in aluminous slags produced by the aluminothermic reduction of pyrochlore
Bibliographic record
Abstract
Abstract Phases present in slags from Araxá (Brazil), Oka (Quebec) and Fen (Norway) resulting from the production of ferroniobium by the aluminothermic reduction of pyrochlore-group minerals are a function of composition of the pyrochlore feed and the diverse fluxes (CaO, CaF2) added to the alumina and iron oxide used in the reduction process. Absent from all slags investigated are Fe-bearing compounds. All of the slags are modally-dominated by prismatic crystals of β-alumina or hibonite, with a wide variety of Th-Ba-Ti-Nb-Al-oxide compounds and silico-aluminate glasses occurring in the interstices between these crystals. Slag from Fen consists of a framework of β-alumina (Ba and/or CaTi varieties) with a barian titanian niobate, considered to be an highly reduced Nb 3+ - and Ti 3+ -bearing anion deficient perovskite, as the first oxide phase to crystallize. This was followed by a Zr-Ti-Th-niobate (21.7–24.1 wt.% ThO 2 ), a Nb-rich, Thbearing zirconolite-like phase (17.7–21.2 wt.%; Nb 2 O 5 ; 6.8–9.5 wt.% ThO 2 ) and diverse Th-Nb-rich, Alpoor (< 1 wt.% Al 2 O 3 ) perovskites (29.4–40.5 wt.% Nb 2 O 5 ; 3.3–11.4 wt.% ThO 2 ). The latter represents a NaNbO 3 –CaTiO 3 –Na 2/3 Th 1/3 TiO 3 –ThTi 2 O 6 solid solution. Late Na-rich silicate glass contains celsian. Slag from Araxá also consists of a framework of β-alumina (Ti-poor). Interstitial compounds differ from Fen in being predominantly rare-earth element (REE)-Nb-Al-Th-perovskites belonging to a REEAlO 3 –Ca 2 AlNbO 6 –CaTiO 3 –ThTi 2 O 6 solid solution with minor NaNbO 3 and CaZrO 3 , and compositionally diverse barium calcium aluminates [(Ba, Ca)Al 2 O 4 ] set in a F-bearing (6–7 wt.%) Na-Ba-Si-aluminate glass with minor Ba 4 Nb 2 O 9 , CaF 2 , BaF 2 and NaF. Slag from Oka consists of a framework of hibonite [(Ca, REE) (Al, Ti, Mg) 12 O 19 ] zoned with respect to the REE content. Interstitial compounds are CaZr 4 O 9 , Nb-Th-poor perovskites belonging to the REEAlO 3 –CaTiO 3 series with minor CaZrO 3 set in a F-bearing (5–6 wt.%) calcium aluminate glass. These data demonstrate that during ferroniobium production REE, Zr, Th, U and significant amounts of Nb are sequestered in the oxide phases in accord with their lithophile geochemical character. None of these elements are present as compounds in the siderophillic ferroniobium alloys. These data demonstrate that the aluminothermic reduction process results in the loss of significant amounts of Nb to the slag. Perovskite-group compounds are present in all of the slags but differ widely in their composition as a result of compositional differences in the feed pyrochlores and fluxes added to the smelting process. Slags originating from ferroniobium production are enriched in Th and U and could be considered as an environmental hazard if these elements are mobilized during chemical weathering of slag.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.001 | 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 teacher head, 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".