Surface-induced reversal of a phase transformation for the synthesis of ε-Fe2O3 nanoparticles with high coercivity
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2020
Authors
Tadić, MarinMilošević, Irena
Kralj, Slavko
Hanžel, Darko
Barudžija, Tanja
Motte, Laurence
Makovec, Darko
Article (Published version)
,
© 2020 Acta Materialia Inc.
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A metastable ε-polymorph of iron(III) oxide (ε-Fe2O3) is a very attractive material from the technological, engineering, and scientific points of view. In comparison with other iron oxides, it is characterized by unusual magnetic properties and a giant coercivity of ~20 kOe, which is the largest value among metal oxides. The routine method of ε-Fe2O3 formation is based on the thermal annealing of maghemite (γ-Fe2O3) nanoparticles confined in a silica matrix where the ε-Fe2O3 appears as an intermediate phase between the maghemite and an α-polymorph (α-Fe2O3) hematite (γ→ε→α pathway). In this study, it is demonstrated that the ε→α transformation can be reversed when hematite nanoparticles with an anisotropic hollow morphology are annealed above 600 °C. The observed reversal of the phase stability is explained in terms of an increased nanoparticle surface area and surface energy related to the hollow structure. This study demonstrates the applicability of surface-induced phase transformat...ion to stabilize and control ε-Fe2O3 nanostructures with anisotropic shape and high coercivity ~1600 kA/m that is one of the key properties of functional magnetic materials for information processing and storage. The understanding of ε-Fe2O3 formation mechanism can provide a new viewpoint and guidance for designing metastable polymorphs and applicative properties. © 2020 Acta Materialia Inc.
Keywords:
Nanostructure / Transformation / Oxide / Magnetic properties / Transmission electron microscopySource:
Acta Materialia, 2020, 188, 16-22Funding / projects:
- Magnetic and radionuclide labeled nanostructured materials for medical applications (RS-MESTD-Integrated and Interdisciplinary Research (IIR or III)-45015)
- Project CNRS-MSTD [25793]
- Bilateral Project [Bi-RS/1415-24]
- Slovenian Research Agency - Slovenia [P2-0089]
- Slovenian Research Agency - Slovenia [P1-0112]
- Slovenian Research Agency - Slovenia [J17302]
- Slovenian Research Agency - Slovenia [J3-7494]
DOI: 10.1016/j.actamat.2020.01.058
ISSN: 1359-6454
WoS: 000527826500002
Scopus: 2-s2.0-85079280935
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VinčaTY - JOUR AU - Tadić, Marin AU - Milošević, Irena AU - Kralj, Slavko AU - Hanžel, Darko AU - Barudžija, Tanja AU - Motte, Laurence AU - Makovec, Darko PY - 2020 UR - https://vinar.vin.bg.ac.rs/handle/123456789/8824 AB - A metastable ε-polymorph of iron(III) oxide (ε-Fe2O3) is a very attractive material from the technological, engineering, and scientific points of view. In comparison with other iron oxides, it is characterized by unusual magnetic properties and a giant coercivity of ~20 kOe, which is the largest value among metal oxides. The routine method of ε-Fe2O3 formation is based on the thermal annealing of maghemite (γ-Fe2O3) nanoparticles confined in a silica matrix where the ε-Fe2O3 appears as an intermediate phase between the maghemite and an α-polymorph (α-Fe2O3) hematite (γ→ε→α pathway). In this study, it is demonstrated that the ε→α transformation can be reversed when hematite nanoparticles with an anisotropic hollow morphology are annealed above 600 °C. The observed reversal of the phase stability is explained in terms of an increased nanoparticle surface area and surface energy related to the hollow structure. This study demonstrates the applicability of surface-induced phase transformation to stabilize and control ε-Fe2O3 nanostructures with anisotropic shape and high coercivity ~1600 kA/m that is one of the key properties of functional magnetic materials for information processing and storage. The understanding of ε-Fe2O3 formation mechanism can provide a new viewpoint and guidance for designing metastable polymorphs and applicative properties. © 2020 Acta Materialia Inc. T2 - Acta Materialia T1 - Surface-induced reversal of a phase transformation for the synthesis of ε-Fe2O3 nanoparticles with high coercivity VL - 188 SP - 16 EP - 22 DO - 10.1016/j.actamat.2020.01.058 ER -
@article{ author = "Tadić, Marin and Milošević, Irena and Kralj, Slavko and Hanžel, Darko and Barudžija, Tanja and Motte, Laurence and Makovec, Darko", year = "2020", abstract = "A metastable ε-polymorph of iron(III) oxide (ε-Fe2O3) is a very attractive material from the technological, engineering, and scientific points of view. In comparison with other iron oxides, it is characterized by unusual magnetic properties and a giant coercivity of ~20 kOe, which is the largest value among metal oxides. The routine method of ε-Fe2O3 formation is based on the thermal annealing of maghemite (γ-Fe2O3) nanoparticles confined in a silica matrix where the ε-Fe2O3 appears as an intermediate phase between the maghemite and an α-polymorph (α-Fe2O3) hematite (γ→ε→α pathway). In this study, it is demonstrated that the ε→α transformation can be reversed when hematite nanoparticles with an anisotropic hollow morphology are annealed above 600 °C. The observed reversal of the phase stability is explained in terms of an increased nanoparticle surface area and surface energy related to the hollow structure. This study demonstrates the applicability of surface-induced phase transformation to stabilize and control ε-Fe2O3 nanostructures with anisotropic shape and high coercivity ~1600 kA/m that is one of the key properties of functional magnetic materials for information processing and storage. The understanding of ε-Fe2O3 formation mechanism can provide a new viewpoint and guidance for designing metastable polymorphs and applicative properties. © 2020 Acta Materialia Inc.", journal = "Acta Materialia", title = "Surface-induced reversal of a phase transformation for the synthesis of ε-Fe2O3 nanoparticles with high coercivity", volume = "188", pages = "16-22", doi = "10.1016/j.actamat.2020.01.058" }
Tadić, M., Milošević, I., Kralj, S., Hanžel, D., Barudžija, T., Motte, L.,& Makovec, D.. (2020). Surface-induced reversal of a phase transformation for the synthesis of ε-Fe2O3 nanoparticles with high coercivity. in Acta Materialia, 188, 16-22. https://doi.org/10.1016/j.actamat.2020.01.058
Tadić M, Milošević I, Kralj S, Hanžel D, Barudžija T, Motte L, Makovec D. Surface-induced reversal of a phase transformation for the synthesis of ε-Fe2O3 nanoparticles with high coercivity. in Acta Materialia. 2020;188:16-22. doi:10.1016/j.actamat.2020.01.058 .
Tadić, Marin, Milošević, Irena, Kralj, Slavko, Hanžel, Darko, Barudžija, Tanja, Motte, Laurence, Makovec, Darko, "Surface-induced reversal of a phase transformation for the synthesis of ε-Fe2O3 nanoparticles with high coercivity" in Acta Materialia, 188 (2020):16-22, https://doi.org/10.1016/j.actamat.2020.01.058 . .