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Production of Fe nanoparticles from γ-Fe2O3 by high-pressure hydrogen reduction

Dirba, Imants and Schwöbel, C. A. and Zintler, Alexander and Komissinskiy, Philipp and Molina-Luna, Leopoldo and Gutfleisch, Oliver (2020):
Production of Fe nanoparticles from γ-Fe2O3 by high-pressure hydrogen reduction.
In: Nanoscale Advances, 2 (10), pp. 4777-4784. Royal Society of Chemistry, ISSN 2516-0230,
DOI: 10.1039/D0NA00635A,
[Article]

Abstract

In this work, the reduction of iron oxide γ-Fe2O3 nanoparticles by hydrogen at high pressures is studied. Increasing the hydrogen pressure enables reduction of γ-Fe2O3 to α-Fe at significantly lower temperatures. At low pressures, a temperature of 390 °C is necessary whereas at 530 bar complete reduction can be realized at temperatures as low as 210 °C. This leads to significant improvement in the final particle morphology, maintaining high surface-to-volume ratio of the nanoparticles with an average size of 47 ± 5 nm which is close to that of the precursor γ-Fe2O3. Neck formation, coalescence and growth during reduction can be significantly suppressed. Investigations of magnetic properties show that saturation magnetization of the reduced α-Fe nanoparticles decreases with particle size from 209 A m2 kg−1 at 390 °C reduction temperature to 204 A m2 kg−1 at 210 °C. Coercivity for the fine iron particles reaches 0.076 T which exceeds the theoretical anisotropy field. This is attributed to nano-scale surface effects.

Item Type: Article
Erschienen: 2020
Creators: Dirba, Imants and Schwöbel, C. A. and Zintler, Alexander and Komissinskiy, Philipp and Molina-Luna, Leopoldo and Gutfleisch, Oliver
Title: Production of Fe nanoparticles from γ-Fe2O3 by high-pressure hydrogen reduction
Language: English
Abstract:

In this work, the reduction of iron oxide γ-Fe2O3 nanoparticles by hydrogen at high pressures is studied. Increasing the hydrogen pressure enables reduction of γ-Fe2O3 to α-Fe at significantly lower temperatures. At low pressures, a temperature of 390 °C is necessary whereas at 530 bar complete reduction can be realized at temperatures as low as 210 °C. This leads to significant improvement in the final particle morphology, maintaining high surface-to-volume ratio of the nanoparticles with an average size of 47 ± 5 nm which is close to that of the precursor γ-Fe2O3. Neck formation, coalescence and growth during reduction can be significantly suppressed. Investigations of magnetic properties show that saturation magnetization of the reduced α-Fe nanoparticles decreases with particle size from 209 A m2 kg−1 at 390 °C reduction temperature to 204 A m2 kg−1 at 210 °C. Coercivity for the fine iron particles reaches 0.076 T which exceeds the theoretical anisotropy field. This is attributed to nano-scale surface effects.

Journal or Publication Title: Nanoscale Advances
Journal volume: 2
Number: 10
Publisher: Royal Society of Chemistry
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Advanced Electron Microscopy (aem)
11 Department of Materials and Earth Sciences > Material Science > Advanced Thin Film Technology
11 Department of Materials and Earth Sciences > Material Science > Functional Materials
Date Deposited: 09 Sep 2020 05:52
DOI: 10.1039/D0NA00635A
Projects: This work was supported by the German Federal Ministry of Education and Research (BMBF) within the project 03X3582., This work was also supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), Project ID No. 405553726, TRR 270.
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