Thermomagnetometric evidence of γ-Fe2O3 as an intermediate in the oxidation of magnetite

Sanders, J.P.; Gallagher, P. K.

doi:10.1016/s0040-6031(03)00250-8

Cited by 40 publications

(12 citation statements)

References 2 publications

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“…On TGA curve of Fe3O4 it can be seen a slight mass increase (ca. 0.6%) up to 340 ºC, due to oxidation of magnetite phase to maghemite phase (Fe 2+ O.Fe2 3+ O3 → -Fe2O3) [18,19].This fact is related to the first exothermic event in the DTA curve of magnetite at the same temperature, while the second peak at 650 ºC indicates conversion to hematite phase ( -Fe2O3) without any mass change [19].…”

Section: Ir and Raman Spectramentioning

confidence: 95%

Photodegradation of herbicide Metsulfuron-methyl with TiO2 supported on magnetite particles coated with SiO2

Montañez

Heredia

Sham

et al. 2018

Journal of Environmental Chemical Engineering

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Natural watercourses may be significantly contaminated due to the increase of agricultural activities, making it necessary to develop new methodologies for the remediation of agrochemicals, including herbicides. To this effect, photodegradation with TiO2 is a very effective process. However, this semiconductor cannot be easily removed from the treated aqueous medium. Supporting the photocatalyst on different materials facilitates its removal by several methods, including magnetic attraction. According to this goal, this work reports the synthesis of TiO2 photocatalysts supported on SiO2-coated magnetite particles (Fe3O4) by a low-temperature sol-gel process (75 °C). By varying the aging time of the TiO2 sol, materials with different structural properties and combinations of anatase-brookite phases were obtained. Of all the synthesized solids, the one with the highest photocatalytic activity in the degradation of model compounds was the TiO2/SiO2/Fe3O4 catalyst with a 47.4/13.6/39.0 wt % respectively. Under optimal working conditions and at a pH value close to neutrality (conditions in which Metsulfuron-methyl is persistent in an aqueous medium) this catalyst degraded 70% of the herbicide initial concentration in three and a half hours of artificial irradiation with an activity similar to the mass TiO2. The aging time significantly influenced on structural properties of supported TiO2. With its increase, the degree of crystallinity of the samples also increased but its specific surface decreased. The catalyst with higher photoactivity blends the best combination of both factors and is, therefore, a good alternative for the remediation of contaminated effluents with commercial formulations of this herbicide. Also, its magnetic support facilitates its subsequent removal from treated water samples.

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Section: Ir and Raman Spectramentioning

confidence: 95%

Photodegradation of herbicide Metsulfuron-methyl with TiO2 supported on magnetite particles coated with SiO2

Montañez

Heredia

Sham

et al. 2018

Journal of Environmental Chemical Engineering

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“…The process is found to be complex and suggested to involve the metastable spinel, γ-Fe 2 O 3 , as an intermediate. The formation of the intermediate is supported by thermomagnetometric evidence (89). Labus et al (90) have studied the phase transitions and thermal effects occurring during annealing CrO x (x g 2.4) in air.…”

Section: Inorganicsmentioning

confidence: 94%

Thermal Analysis

Vyazovkin

2004

Anal. Chem.

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“…This result is consistent with the XRD data analysis, which indicates the presence of only the α-Fe 2 O 3 phase for samples annealed at temperatures at 450 °C and higher temperatures, as discussed below. It is worth mentioning that the phase transformation from Fe 3 O 4 to γ-Fe 2 O 3 which is expected to occur at temperatures ≈160 °C-320 °C [25] could not be clearly observed in the TGA/DSC curves, possibly obscured by the concurrent weight loss from the removal of organic compounds. The second process is mainly associated with the improvement of the crystallinity of hematite NPs and it corresponds to an exothermic process, as evidenced by the peak at ∼567 °C.…”

Section: Tga and Dsc Curvesmentioning

confidence: 99%

Synthesis and characterization of α-Fe₂O₃ nanoparticles showing potential applications for sensing quaternary ammonium vapor at room temperature

Quispe¹,

Luza-Mamani²,

Baldárrago-Alcántara³

et al. 2022

Nanotechnology

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P-type and n-type metal oxide semiconductors are widely used in the manufacture of gas sensing materials, due to their excellent electronic, electrical and electrocatalytic properties. Hematite (α-Fe2O3) compound has been reported as a promising material for sensing broad types of gases, due to its affordability, good stability and semiconducting properties. In the present work, the efficient and easy-to-implement sol-gel method has been used to synthesize α-Fe2O3 nanoparticles (NPs). The TGA-DSC characterizations of the precursor gel provided information about the phase transformation temperature and the mass percentage of the hematite NPs. XRD, TEM and XPS data analyses indicated the formation of two iron oxide phases (hematite and magnetite) when the NPs are subjected to thermal treatment at 400 °C. Meanwhile, only the hematite phase was determined for thermal annealing above 500 °C up to 800 °C. Besides, the crystallite size shows an increasing trend with the thermal annealing and no defined morphology. A clear reduction of surface defects, associated with oxygen vacancies was also evidenced when the annealing temperature was increased, resulting in changes on the electrical properties of hematite NPs. Resistive gas-sensing tests were carried out using hematite NPs + glycerin paste, to detect quaternary ammonium compounds. Room-temperature high sensitivity values (Sr ~ 4) have been obtained during the detection of ~1mM quaternary ammonium compounds vapor. The dependence of the sensitivity on the particle size, the mass ratio of NPs with respect to the organic ligand, changes in the dielectric properties, and the electrical conduction mechanism of gas sensing was discussed.

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Thermomagnetometric evidence of γ-Fe2O3 as an intermediate in the oxidation of magnetite

Cited by 40 publications

References 2 publications

Photodegradation of herbicide Metsulfuron-methyl with TiO2 supported on magnetite particles coated with SiO2

Photodegradation of herbicide Metsulfuron-methyl with TiO2 supported on magnetite particles coated with SiO2

Thermal Analysis

Synthesis and characterization of α-Fe₂O₃ nanoparticles showing potential applications for sensing quaternary ammonium vapor at room temperature

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Thermomagnetometric evidence of γ-Fe2O3 as an intermediate in the oxidation of magnetite

Cited by 40 publications

References 2 publications

Photodegradation of herbicide Metsulfuron-methyl with TiO2 supported on magnetite particles coated with SiO2

Photodegradation of herbicide Metsulfuron-methyl with TiO2 supported on magnetite particles coated with SiO2

Thermal Analysis

Synthesis and characterization of α-Fe2O3 nanoparticles showing potential applications for sensing quaternary ammonium vapor at room temperature

Contact Info

Product

Resources

About

Synthesis and characterization of α-Fe₂O₃ nanoparticles showing potential applications for sensing quaternary ammonium vapor at room temperature