High-Speed Morphology Control of Boehmite Nanoparticles by Supercritical Hydrothermal Treatment with Carboxylic Acids
Bibliographic record
Abstract
This study demonstrates that the morphology of boehmite (AlOOH) nanoparticles can be controlled over a short timespan by supercritical hydrothermal treatment in the presence of alkyl carboxylic acids including hexanoic, octanoic, decanoic, tetradecanoic, and octadecanoic acids. Boehmite nanoparticles were treated with carboxylic acid in supercritical water at 400 °C and at a water density of 0.35 g/cm 3 in a batch-type reactor. When the carboxylic acid was not added, the particles were shaped as rhombic plates. However, the addition of carboxylic acid changed the crystal morphology to hexagonal plates. The aspect ratio (i.e., [length along the a -axis]/[length along the c -axis]) of the rhombic plates increased with a treatment time of 2–30 min, which is a much shorter timespan than that used for conventional hydrothermal crystallization. The aspect ratio of the hexagonal plates increased with increasing concentration of alkyl carboxylic acids. These results clearly indicate that carboxylic acids enhance the dissolution and recrystallization of boehmite. The aspect ratio increased with decreasing length of the alkyl chain of alkyl-carboxylic acid added to the system. Thermogravimetric analysis (TGA) showed that carboxylic acids modified the surface of the boehmite particles. The coverage of the alkyl carboxylic acid on the surface of the nanoparticles was evaluated from the weight loss curve obtained from TGA, and the surface area was evaluated from transmission electron microscopy, which showed that the aspect ratio of the particles increased with increasing the coverage. The results suggest that the carboxylic acid suppresses crystal growth along the shorter axis through surface-capping, thus enhancing dissolution and crystal growth along the a -axis.
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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) | 0.000 | 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 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".