Lattice distortion in nanocrystalline Fe powder studied by positron annihilation and X-ray diffraction
Bibliographic record
Abstract
X-ray diffraction and positron annihilation measurements were performed on the ball-milled nanocrystalline Fe powder over a wide range of crystallite sizes (9–90 nm). With increasing milling time, the crystallite size reduction was accompanied by a monotonic increase of the lattice parameter of Fe (i.e. lattice expansion). The positron lifetime increased significantly due to enhanced positron annihilation from the defects (excess vacancies, vacancy-clusters, etc.) generated at the Fe grain boundaries and intercrystalline regions with progressive milling up to 24 h (crystallite size ∼ 12 nm). The observed lattice expansion has been successfully simulated using a theoretical model taking account of the excess free volume associated with the excess vacancies/vacancy-clusters at the grain boundaries in nanocrystalline Fe. Prolonged ball milling up to 36 h (crystallite size < 10 nm) led to an anomalous decrease of all positron lifetime parameters. The X-ray diffraction line profiles of ball-milled Fe powder exhibited anisotropic broadening due to the high density of dislocations in Fe. Milling duration ≥ 24 h further led to asymmetric broadening of Fe diffraction peaks indicating heterogeneous dislocation structure in the severely plastically deformed ball-milled Fe. Further analysis of asymmetrically broadened peak reflections revealed deformation induced tetragonal distortion of body centered cubic Fe lattice in the 36 h ball-milled Fe powder.
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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) | 0.000 | 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".