Powders with superparamagnetic Fe<sub>3</sub>C particles studied with Mössbauer spectrometry

David, B.; Schneeweiss, O.; Dumitrache, Florian; Fleaca, C.; Alexandrescu, R.; Morjan, I.

doi:10.1088/1742-6596/217/1/012097

Cited by 11 publications

(8 citation statements)

References 12 publications

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“…Data from Fe3C collected below 55 K was not included in this work, due to the spectral change seen in the 50 K spectrum of Figure 5. The nature of this spectral change is not currently known, but can be seen in the 2009 work by David et al [12] For comparison of Debye temperatures, it appears that different methods of calculation, and the experimental approach used has profound effects on the outcome, as summarised in Table 8 for Fe3C. As such, the values stated in this work are for consideration of Mössbauer data, and the mathematical approach using the Debye model as detailed. This wide range of existing values may be due to the nature in which the Fe3C is being studied, while that studied in this work is ex situ as nanoparticles.…”

Section: Analysis and Discussionmentioning

confidence: 94%

Variable Temperature 57Fe-Mössbauer Spectroscopy Study of Nanoparticle Iron Carbides

Scrimshire¹,

Lobera²,

Kultyshev³

et al. 2015

Croat. Chem. Acta

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Near-phase-pure nanoparticle iron carbides (Fe3C and Fe5C2) were synthesised. Debye model calculations were used with hyperfine parameters gathered by 57 Fe Mössbauer spectroscopy within a temperature range of 10 K to 293 K, with analysis providing Debye temperatures of 422 K and 364 K for two Fe sites in Fe5C2 and 355 K for ferromagnetic Fe3C. The intrinsic isomer shifts were calculated as 0.45 mm s −1 and 0.43 mm s −1 for iron sites 1 and 2 respectively in Fe5C2 and 0.42 mm s −1 for Fe3C. Recoil-free fractions for the two iron sites were also calculated at f300 0.785 and 0.726 for site 1 and 2 respectively.

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Section: Analysis and Discussionmentioning

confidence: 94%

Variable Temperature 57Fe-Mössbauer Spectroscopy Study of Nanoparticle Iron Carbides

Scrimshire¹,

Lobera²,

Kultyshev³

et al. 2015

Croat. Chem. Acta

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“…As the remaining quantities are related to side phases they should either remain unchanged or contribute to an irreversible process. Component 6b overlays with D1 for FeNC porph and FeNC ppy, due to the superparamagnetic effect of Fe 3 C. [ 65 ] This is important to note, as consequently during the in situ experiment, it is clear that not the overall absorption area assigned to D1 but only a partial fraction is expected to change by electroreduction of FeN 4 moieties.…”

Section: Resultsmentioning

confidence: 99%

Active Site Identification in FeNC Catalysts and Their Assignment to the Oxygen Reduction Reaction Pathway by In Situ⁵⁷Fe Mössbauer Spectroscopy

Gallenkamp

Paul

et al. 2021

Adv Energy and Sustain Res

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FeNC catalysts are the most promising substitutes for Pt‐based catalysts for the oxygen reduction reaction in proton exchange fuel cells. However, it remains unclear which FeN4 moieties contribute to the reaction mechanism and in which way. The origin of this debate could lie in various preparation routes, and therefore the aim of this work is to identify whether the active site species differ in different preparation routes or not. To answer this question, three FeNC catalysts, related to the three main preparation routes, are prepared and thoroughly characterized. Three transitions A–C that are distinguished by a variation in the local environment of the deoxygenated state are defined. By in situ 57Fe Mössbauer spectroscopy, it can be shown that all three catalysts exhibit a common spectral change assigned to one of the transitions that constitutes the dominant contribution to the direct electroreduction of oxygen. Moreover, the change in selectivity can be attributed to the presence of a variation within additional species. Density functional theory calculations help to explain the observed trends and enable concrete suggestions on the nature of nitrogen coordination in the two FeN4 moieties involved in the oxygen reduction reaction of FeNC catalysts.

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“…In the case of FCB3N sample the MS measured at 293 K exhibited very low absorption (the lowest value of relative transmission was 0.994) [8]. This spectrum was fitted with the ferromagnetic Fe 3 C sextet (B HF = 20.5 T, ε Q = 0.01 mm/s, δ = 0.19 mm/s, A = 0.28) [7], a doublet (δ = 0.19 mm/s, ∆E Q = 0.51 mm/s, A = 0.64) and the superparamagnetic Fe 3 O 4 doublet (δ = 0.68 mm/s, ∆E Q = 0.70 mm/s, A = 0.08).…”

Section: Resultsmentioning

confidence: 94%

“…The Mössbauer spectrum (MS) of FCB1 sample measured at 293 K was fitted with three components [8]: a narrow doublet probably of superparamagnetic In the corresponding MS measured at 27 K (Fig. 1) the sextet of ferromagnetic Fe 3 C (B HF = 24.5 T, ε Q = 0.07 mm/s, δ = 0.36 mm/s, A = 0.74) dominated the spectrum [3].…”

Section: Resultsmentioning

confidence: 99%

Low-Temperature Magnetic Properties of Nanocomposites Containing Superparamagnetic Fe₃C Particles

et al. 2010

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Two nanopowders containing superparamagnetic Fe3C particles, superparamagnetic Fe3O4/γ-Fe2O3 particles and carbon black phase were synthesised by the method of laser-induced homogeneous pyrolysis of gaseous precursors. Both were characterised by X-ray diffraction, Mössbauer spectrometry and standard magnetic measurements. The mean crystallite size of Fe3C was 3 nm for the first sample and 10 nm for the second sample. Mössbauer spectra measured at 27 K and zero-field cooled/field cooled curves measured down to 4 K are reported.

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Powders with superparamagnetic Fe₃C particles studied with Mössbauer spectrometry

Cited by 11 publications

References 12 publications

Variable Temperature 57Fe-Mössbauer Spectroscopy Study of Nanoparticle Iron Carbides

Variable Temperature 57Fe-Mössbauer Spectroscopy Study of Nanoparticle Iron Carbides

Active Site Identification in FeNC Catalysts and Their Assignment to the Oxygen Reduction Reaction Pathway by In Situ⁵⁷Fe Mössbauer Spectroscopy

Low-Temperature Magnetic Properties of Nanocomposites Containing Superparamagnetic Fe₃C Particles

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Powders with superparamagnetic Fe3C particles studied with Mössbauer spectrometry

Cited by 11 publications

References 12 publications

Variable Temperature 57Fe-Mössbauer Spectroscopy Study of Nanoparticle Iron Carbides

Variable Temperature 57Fe-Mössbauer Spectroscopy Study of Nanoparticle Iron Carbides

Active Site Identification in FeNC Catalysts and Their Assignment to the Oxygen Reduction Reaction Pathway by In Situ57Fe Mössbauer Spectroscopy

Low-Temperature Magnetic Properties of Nanocomposites Containing Superparamagnetic Fe3C Particles

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Product

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Powders with superparamagnetic Fe₃C particles studied with Mössbauer spectrometry

Active Site Identification in FeNC Catalysts and Their Assignment to the Oxygen Reduction Reaction Pathway by In Situ⁵⁷Fe Mössbauer Spectroscopy

Low-Temperature Magnetic Properties of Nanocomposites Containing Superparamagnetic Fe₃C Particles