Production of amorphous Fe-B alloy and α-Fe by chemical reduction of hematite using sodium borohydride

Natural and well-crystallized hematite was suspended in water and treated at room-temperature (RT) with sodium borohydride in acid medium. The product of the reaction is a highly magnetic black powder, which is stable at RT. The NaBH4 treatment converts about half of the hematite to an amorphous Fe–...

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Bibliographic Details
Published in:Journal of materials science 2006-10, Vol.41 (20), p.6843-6854
Main Authors: DE RESENDE, V. G, DA COSTA, G. M, DE GRAVE, E, DATAS, L
Format: Article
Language:English
Subjects:
Amorphous alloys
Borohydrides
Boron oxides
Chemical reduction
Cross-disciplinary physics: materials science
rheology
Crystallization
Exact sciences and technology
Hematite
Iron oxides
Materials science
Morphology
Nodules
Organic chemistry
Other topics in materials science
Oxidation
Physics
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Summary:Natural and well-crystallized hematite was suspended in water and treated at room-temperature (RT) with sodium borohydride in acid medium. The product of the reaction is a highly magnetic black powder, which is stable at RT. The NaBH4 treatment converts about half of the hematite to an amorphous Fe–B alloy and to a small fraction of sub-micron sized, amorphous metallic-Fe nodules. Heating at 400 °C of this composite has resulted in the crystallization and/or oxidation of more than half of the amorphous Fe–B phase to α-Fe and Fe3O4 and B2O3, respectively. Further, the already present superficial, amorphous metallic Fe is converted to α-Fe and the original, plate like morphology of the hematite has changed to a mix of nodular and acicular particles. After treatment at 800 °C, the metallic Fe and the amorphous Fe–B have completely vanished, and the resulting product consists of hematite and FeBO3 embedded in a matrix of α-Fe2O3.
ISSN:0022-2461
1573-4803
DOI:10.1007/s10853-006-0953-3