Thermal stability and hydrogen storage properties of Hf0.75Ti0.25NbVZr and TiNbVZr high entropy alloys
Bibliographic record
Abstract
This study examines the thermal stability and hydrogen storage performance of Hf 0.75 Ti 0.25 NbVZr and TiNbVZr high-entropy alloys (HEAs). Heat treatments were conducted at 1300°C for 24 and 48 hours and at 600°C for 1 and 2 months. X-ray diffraction (XRD) analysis revealed that Hf 0.75 Ti 0.25 NbVZr transitioned from a mixture of BCC and C15 Laves phases to a single BCC phase at 1300°C. At 600°C, a combination of BCC, C14 Laves, and HCP phases was detected, with phase compositions remaining stable over time. Hydrogen absorption tests showed that heat-treated samples required activation at 250°C. After 2 months at 600°C, Hf 0.75 Ti 0.25 NbVZr alloy had a hydrogen uptake of 0.95 wt.% while TiNbVZr treated at 1300°C for 24 hours absorbed 1.10 wt.% of hydrogen. In contrast, the as-cast alloys absorbed 2.05 wt.% and 2.7 wt.%, respectively, at room temperature. Hydrogenation induced phase transformations, notably causing significant expansion in the C14 Laves phase. The highest hydrogen absorption was observed in the as-synthesized arc-melted alloys, which outperformed heat-treated samples in storage capacity. These findings demonstrate that heat treatment lowers hydrogen storage efficiency due to phase transformations and reduced BCC phase content.
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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) | 0.001 | 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".