Synthesis of Hematite Crystals from Natural Iron Sand: The Influence of Heating on Optical and Magnetic Properties
Bibliographic record
Abstract
The objective of this study was to synthesize α-Fe2O3 (hematite) crystals through a mechanical precipitation approach and investigate the influence of elevated annealing temperatures on their optical and magnetic properties.Initially, iron sand was mechanically ground into fine powder using an agate mortar.This powder was then solubilized in 400 mL of 37% HCl and subsequently filtered using Whatman filter paper No. 42.The resulting filtrate was stirred magnetically at 200 rpm while ammonium hydroxide was gradually introduced until a pH of 8 was achieved, precipitating the desired product.The precipitate was separated, washed with deionized water, and dried on a hot plate at 100℃ for one hour.The dried product was divided into four samples and each was subjected to annealing at temperatures of 300℃, 400℃, 500℃, and 550℃ for one hour, respectively.X-ray diffraction (XRD) analysis, corroborated by the Crystallographic Open Database (COD), confirmed that the synthesized hematite crystals exhibited a hexagonal structure belonging to the R-3c space group.A notable decrease in grain size was observed with increasing annealing temperature, shrinking from approximately 0.44 µm at 300℃ to around 0.36 µm at 500℃.This trend suggests that higher temperatures facilitate the disintegration of aggregates into finer particles.Vibrating Sample Magnetometry (VSM) revealed that the hematite crystals possessed high coercivity and remanence, both of which decreased with rising annealing temperatures, indicative of their ferromagnetic nature.UV-Visible spectroscopy identified maximum absorption within the 200-202 nm range, with the peak absorption occurring at 201.56 nm for crystals annealed at 500℃.Additionally, bandgap energy was observed to increase from 2.632 eV at an annealing temperature of 300℃ to 3.708 eV at 550℃.In conclusion, the mechanical precipitation method effectively produced ferromagnetic hematite microparticles from natural iron sand, with their properties significantly influenced by the annealing temperature.These findings offer insights into the tunable nature of hematite's optical and magnetic characteristics, with implications for their application in various technological domains.
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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 | 0.001 |
| 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".