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

• Published in: Nanoscale advances Vol. 2; no. 1; pp. 4777 - 4784
• Main Authors: Dirba, I, Schwöbel, C. A, Zintler, A, Komissinskiy, P, Molina-Luna, L, Gutfleisch, O
• Format: Journal Article
• Language: English
• Published: 13-10-2020
• ISSN: 2516-0230
• DOI: 10.1039/d0na00635a

In this work, the reduction of iron oxide γ-Fe
2
O
3
nanoparticles by hydrogen at high pressures is studied. Increasing the hydrogen pressure enables reduction of γ-Fe
2
O
3
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-Fe
2
O
3
. 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 m
2
kg
−1
at 390 °C reduction temperature to 204 A m
2
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.
In this work, the reduction of iron oxide γ-Fe
2
O
3
nanoparticles by hydrogen at high pressures is studied.