Obtaining of hematite from industrial steel waste using dry-milling and high temperature
| Autor: | K. F. Ulbrich, Carlos Eduardo Maduro de Campos |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Thermogravimetric analysis
Mill scale Materials science Morin transition TJ807-830 Environmental engineering High-temperature Building and Construction Thermal treatment TA170-171 Hematite Iron oxides Renewable energy sources Nanocrystalline material X-ray diffraction Chemical engineering visual_art visual_art.visual_art_medium Crystallite Electrical and Electronic Engineering Ball mill Milling Phase transition |
| Zdroj: | Cleaner Engineering and Technology, Vol 5, Iss, Pp 100327-(2021) |
| ISSN: | 2666-7908 |
| DOI: | 10.1016/j.clet.2021.100327 |
| Popis: | In this work, the mill scale (MS) of hot rolling, a waste of steel processing, composed by a complex mixture of iron oxides, is transformed in a nanocrystalline powder containing only the hematite (α-Fe2O3) phase. For that, the MS was dry-milled using a high-energy ball mill for 30 min and heat-treated up to 1200 °C for 25 min. The samples of this study were characterized by X-ray diffraction, Thermogravimetric Analysis and Vibrating Sample Magnetometry. The milling process decreases the amount of FeO phase content (FeO:Fe3O4 phase ratio from 3:1 to 1:1), reduces the average crystallite size and increases the micro-strain of the iron oxides. The high-temperature experiments showed the complete transformation of the Fe3O4 and FeO nanophases to the nanocrystalline α-Fe2O3 with average crystalline domains greater than 180 nm after few hours of heat treatment. The thermal expansion coefficient of the α-Fe2O3 nanophase was obtained considering anisotropic effects, mainly for the a-axis. Thermogravimetric analysis shows the oxidation of Fe3O4 to α-Fe2O3. The milled MS sample shows a mixed magnetism that transforms to a weak ferromagnetism (or antiferromagntism) after thermal treatment. The temperature of the Morin transition of the α-Fe2O3 nanophase at 110 K and a second magnetic transition at 50 K, related to a spin-glass state, seems to be strongly affected by the nanometric size of crystalline domains (about 180 nm). |
| Databáze: | OpenAIRE |
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