Deformations of the α-Fe<sub>2</sub>O<sub>3</sub> rhombohedral lattice across the Néel temperature

Fabrykiewicz, Piotr; Stękiel, Michał; Sosnowska, I.; Przeniosło, R.

doi:10.1107/s2052520616017935

Cited by 10 publications

(6 citation statements)

References 28 publications

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“…Therefore, the ZFC-FC relations plotted in Figure 7(c) present an irreversible process of magnetizing such a system, which can be treated as a bulk magnet. Nonetheless, it should be noted that a kink in the ZFC curve between 250 K and 260 K denotes the Morin transition usually observed in hematite at T∼260 K, [67,68] which confirms the presence of this phase in the annealed NFO sample. Figure 7(d) presents ZFC-FC curves for the annealed NFO@SiO 2 sample measured at 100 and 1000 Oe.…”

Section: Fc-zfc Magnetizationsupporting

confidence: 61%

Tuning Physical Properties of NiFe2O4 and NiFe2O4@SiO2 Nanoferrites by Thermal Treatment

Bajorek

Berger

Dulski

et al. 2022

Metall Mater Trans A

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The comparison between NiFe2O4 (co-precipitation) and NiFe2O4@SiO2 (co-precipitation and microemulsion) ferrite nanoparticles in their as-received and annealed form is presented. The structural characterization revealed the gradual crystallization of as-received samples induced by thermal treatment. The existence of cubic inverse spinel ferrite structure with tetrahedral and octahedral iron occupancy is confirmed in all samples by the comprehensive study. The Fourier-transform infrared (FTIR) spectroscopy confirmed the typical spinel structure and other Fe-based states, whereas the presence of nonstoichiometric hematite is detected in the annealed NiFe2O4 sample. In the case of nanoparticles embedded into the silica matrix, the crystallization of initially amorphous silica is revealed in structural and microstructural characterization. As shown by FTIR, the applied thermal treatment reduces the water molecules and hydroxyl units compared to the initial material. The separation of the rhombohedral hematite α-Fe2O3 phase in the NiFe2O4 ferrite evidenced during the annealing process is demonstrated in structural and magnetic studies. The analysis of saturation magnetization pointed to the spin canting phenomenon in the surface layer with a slight change of the so-called dead layer upon heating. The room temperature superparamagnetic state (SPM) is modified in the NiFe2O4 sample across annealing as an effect of ferrite crystallization and grain growth as well as hematite separation. For as-received NiFe2O4, with temperature decrease, the blocking process preceded by the freezing process is observed. The silica shell is recognized as the sustaining cover for the SPM state. The electronic structure studies confirmed the complex nature of the Fe-based states.

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Section: Fc-zfc Magnetizationsupporting

confidence: 61%

Tuning Physical Properties of NiFe2O4 and NiFe2O4@SiO2 Nanoferrites by Thermal Treatment

Bajorek

Berger

Dulski

et al. 2022

Metall Mater Trans A

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“…The further calcination at higher temperatures (500 • C) resulted in nearly pure hematite. Thus, the diffraction peaks were attributed to 96.9, 100, and 98.7% of the polycrystalline structure of hematite for the calcination times 2, 4, and 5 h, respectively (Figure 1b and Table 2) [46,51,56,62,64].…”

Section: Xrdmentioning

confidence: 98%

“…On the other hand, the increase in calcination temperature caused a pronounced change in the Fe x O y -NP type, which resulted in a greater proportion of hematite. For example, the diffraction peaks of GS-NPs calcined at 300 • C for 2, 4, and 5 h were attributed to 55.0, 57.1, and 86.6% of polycrystalline hematite, respectively (Table 2) [46,47,50,51,53,54], while the diffraction peaks of the GS-NPs calcined at 500 • C for 2, 4 and 5 h were assigned to 25.4, 91.3, and 62.4% of monoclinic, cubic, and trigonal with hexagonal axis hematite [46,47,[49][50][51][52][55][56][57][58][59][60].…”

Section: Xrdmentioning

confidence: 99%

“…The diffraction peaks of the CS-NPs calcined at 200 • C for 2, 4, and 5 h were attributed to 91.1, 92.9, and 95.5% of the polycrystalline structure of hematite, respectively (Figure 1b and Table 2) [46,56,[61][62][63]. A temperature increment to 300 • C generated a change in nanoparticles, finding 88.6, 93.5, and 98.1% of the polycrystalline structure of hematite for the calcination times 2, 4, and 5 h, respectively (Figure 1b and Table 2) [46,51,56,61,64]. The further calcination at higher temperatures (500 • C) resulted in nearly pure hematite.…”

Section: Xrdmentioning

confidence: 99%

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Effect of Calcination Temperature and Time on the Synthesis of Iron Oxide Nanoparticles: Green vs. Chemical Method

et al. 2023

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Nowadays, antioxidants and antibacterial activity play an increasingly vital role in biosystems due to the biochemical and biological reactions that involve free radicals and pathogen growth, which occur in many systems. For this purpose, continuous efforts are being made to minimize these reactions, including the use of nanomaterials as antioxidants and bactericidal agents. Despite such advances, iron oxide nanoparticles still lack knowledge regarding their antioxidant and bactericidal capacities. This includes the investigation of biochemical reactions and their effects on nanoparticle functionality. In green synthesis, active phytochemicals give nanoparticles their maximum functional capacity and should not be destroyed during synthesis. Therefore, research is required to establish a correlation between the synthesis process and the nanoparticle properties. In this sense, the main objective of this work was to evaluate the most influential process stage: calcination. Thus, different calcination temperatures (200, 300, and 500 °C) and times (2, 3, and 5 h) were studied in the synthesis of iron oxide nanoparticles using either Phoenix dactylifera L. (PDL) extract (green method) or sodium hydroxide (chemical method) as the reducing agent. The results show that calcination temperatures and times had a significant influence on the degradation of the active substance (polyphenols) and the final structure of iron oxide nanoparticles. It was found that, at low calcination temperatures and times, the nanoparticles exhibited small sizes, fewer polycrystalline structures, and better antioxidant activities. In conclusion, this work highlights the importance of green synthesis of iron oxide nanoparticles due to their excellent antioxidant and antimicrobial activities.

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“…Additional peaks at 2θ values of 45.55 and 59.29° were assigned to monoclinic magnetite, corresponding to the crystallographic planes (030) and (049), respectively. The peaks at 21.08, 23.48, 39.33, 40.04, and 54.47° were attributed to monoclinic hematite, with the crystallographic planes (11-1), (20-2), (40-6), (021), and (512), respectively, and the space group C 1 2/c 1 (15) according to the JCPDS card number 00-210-8028 [ 67 ].…”

Section: Resultsmentioning

confidence: 99%

Agro-Waste Sweet Pepper Extract-Magnetic Iron Oxide Nanoparticles for Antioxidant Enrichment and Sustainable Nanopackaging

López-Alcántara,

Colindres-Vásquez,

Fodil

et al. 2024

Polymers

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This study synthesizes magnetic iron oxide nanoparticles from agro-waste sweet pepper extract, exploring their potential as antioxidant additives and in food preservation. Iron (III) chloride hexahydrate is the precursor, with sweet pepper extract as both a reducing and capping agent at pH 7.5. Characterization techniques, including microscopy and spectroscopy, analyze the sweet pepper extract-magnetic iron oxide nanoparticles. Antioxidant capacities against 2,2-diphenyl-1-picrylhydrazyl are assessed, incorporating nanoparticles into banana-based bioplastic for grape preservation. Microscopy reveals cubic and quasi-spherical structures, and spectroscopy confirms functional groups, including Fe–O bonds. X-ray diffraction identifies cubic and monoclinic magnetite with a monoclinic hematite presence. Sweet pepper extract exhibits 100% inhibitory activity in 20 min, while sweet pepper extract-magnetic iron oxide nanoparticles show an IC50 of 128.1 µg/mL. Furthermore, these nanoparticles, stabilized with banana-based bioplastic, effectively preserve grapes, resulting in a 27.4% lower weight loss rate after 144 h compared to the control group (34.6%). This pioneering study encourages institutional research into the natural antioxidant properties of agro-waste sweet pepper combined with magnetic iron and other metal oxide nanoparticles, offering sustainable solutions for nanopackaging and food preservation. Current research focuses on refining experimental parameters and investigating diverse applications for sweet pepper extract-magnetic iron oxide nanoparticles in varied contexts.

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Deformations of the α-Fe₂O₃ rhombohedral lattice across the Néel temperature

Cited by 10 publications

References 28 publications

Tuning Physical Properties of NiFe2O4 and NiFe2O4@SiO2 Nanoferrites by Thermal Treatment

Tuning Physical Properties of NiFe2O4 and NiFe2O4@SiO2 Nanoferrites by Thermal Treatment

Effect of Calcination Temperature and Time on the Synthesis of Iron Oxide Nanoparticles: Green vs. Chemical Method

Agro-Waste Sweet Pepper Extract-Magnetic Iron Oxide Nanoparticles for Antioxidant Enrichment and Sustainable Nanopackaging

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Deformations of the α-Fe2O3 rhombohedral lattice across the Néel temperature

Cited by 10 publications

References 28 publications

Tuning Physical Properties of NiFe2O4 and NiFe2O4@SiO2 Nanoferrites by Thermal Treatment

Tuning Physical Properties of NiFe2O4 and NiFe2O4@SiO2 Nanoferrites by Thermal Treatment

Effect of Calcination Temperature and Time on the Synthesis of Iron Oxide Nanoparticles: Green vs. Chemical Method

Agro-Waste Sweet Pepper Extract-Magnetic Iron Oxide Nanoparticles for Antioxidant Enrichment and Sustainable Nanopackaging

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Product

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Deformations of the α-Fe₂O₃ rhombohedral lattice across the Néel temperature