Sintering Behavior and Microstructure Development of Porous Silicon Nitride Ceramics Prepared in an Air Atmosphere Furnace
Bibliographic record
Abstract
Porous silicon nitride (Si 3 N 4 ) ceramics have been sintered in a conventional air atmosphere furnace at temperatures between 1500°C and 1700°C, with sintering additions of either 5 or 10 wt% yttria (Y 2 O 3 ). The use of a protective α‐Si 3 N 4 powder bed helps to prevent significant oxidation of the samples during sintering in air, keeping oxidation weight gains below 4 wt% (typically <2.5 wt%). This compares with more typical weight losses when sintering in nitrogen. Samples prepared with a protective α‐Si 3 N 4 powder bed exhibited sintered densities up to ∼89% of the theoretical, which was notably higher than for similar compositions prepared in a controlled nitrogen atmosphere (i.e., ∼70% of theoretical). Increased densification is proposed to arise from the formation of a thin SiO 2 surface layer on individual α‐Si 3 N 4 particles, through passive oxidation, which is expected to promote viscous‐flow densification at lower temperatures. The excess of SiO 2 , relative to the starting composition, is also reflected in the final phase assembly, with Si 2 N 2 O formed in addition to the transformation of α‐ to β‐Si 3 N 4 , when sintering above ∼1550°C. A Si 2 N 2 O gradient occurs, with the surface being approximately 80 vol% Si 2 N 2 O and the bulk predominantly Si 3 N 4 , for samples sintered at 1600°C and 1700°C. Conversely, Si 2 N 2 O is not observed in any measurable volume for similar samples sintered in nitrogen.
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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".