Recoil User Manual -- Mossbauer spectral analysis software for Windows
Abstract
This is the user manual for the Mossbauer spectral analysis software "Recoil", developed in the research group of Professor Denis G. Rancourt, Department of Physics, University of Ottawa, Ottawa, Canada.
... Mössbauer spectra of complexes 1-3, Figure 5, with natural abundance 57 Fe were collected at 77 K. The Mössbauer parameters are given in Table 2. ...
... The spectra were fitted to the sum of Lorentzians by a least-squares refinement using or Recoil 1.05 Mössbauer Analysis Software. [57] All isomer shifts refer to α-Fe at room temperature. Absence of any oxide impurities was checked by high velocity transmission measurements (v max = 12 mm/s). ...
The new pyridazine containing iron complexes, (N,N,N',N'‐tetrakis(3‐pyridazylmethyl)propylenediamine)iron(II)(PF6)2 (1) and (N,N'‐bis(2‐pyridazylmethyl)‐N,N'‐bis(2‐pyridylmethyl)propylenediamine)iron(II) (PF6)2 (2) were synthesized and their reactivity towards protonation was compared to the analogous tetrapyridine complex (N,N,N',N'‐tetrakis(2‐pyridylmethyl)propylenediamine)iron(II)(PF6)2 (3). The solution and solid state structures were confirmed by NMR and X‐ray crystallographic studies. For 1‐3, the ligands bind in a hexadentate fashion giving similar octahedral structures with an N6 coordination environment. Across the series, the increasing number of pyridazines has only modest effects on the spectroscopic and electrochemical properties of the metal. Nevertheless, their reactivity towards protonation is drastically different. While 2 and 3 decompose in the presence of strong acids, 1 is able to be stably protonated as a result of cooperative second sphere interactions.
... At 5 K a sextet characteristic for maghemite (g-Fe 2 O 3 ) appears. 37 Hyperfine magnetic fields on 57 Fe nuclei are between 509 and 517 kOe and correspond to Fe 3+ in tetrahedral and octahedral sites of the maghemite structure. Full pattern profile analysis (''Rietveld refinement'') of the powder diffraction data identified the iron oxide phase as maghemite (Fig. 3). ...
... Simulations of the experimental data were performed with the Recoil software. 57 X-Ray powder diffraction. To determine the crystalline phase contributions of the NCs powder XRD as well as Mössbauer spectroscopy were used. ...
The effect of surface functionalization on the structural and magnetic properties of catechol-functionalized iron oxide magnetic (γ-Fe2O3) nanocrystals were investigated. γ-Fe2O3 nanocrystals (NCs) were synthesized from iron acetyl acetonate in phenyl ether with 1,2-tetradecanediol, oleic acid, and oleylamine. X-ray powder diffraction in combination with Mössbauer spectroscopy revealed the presence of γ-Fe2O3 (maghemite) particles only. Replacement of oleic acid (OA) with catechol-type 3,4-dihydroxyhydrocinnamic acid (DHCA) or polydentate polydopamine acrylate (PDAm) surface ligands lead to a pronounced change of the magnetic behavior of the γ-Fe2O3 nanocrystals and separated them into two distinctive magnetic entities. XPS and Mössbauer spectroscopy revealed the shell to be reduced with a magnetite (Fe3O4) contribution of up to 33% of the total mass while the core remained maghemite (γ-Fe2O3). The magnetic interaction between the maghemite core and the magnetite shell strongly reduced the anisotropy constant of the nanocrystals and the effective magnetization. Our experiments show that the surface chemistry strongly affects the phase distribution and the macroscopic magnetic properties of iron oxide nanopowders.
... M€ ossbauer spectrum of a-Fe foil was used to calibrate the centre position of the spectrum and hyperfine parameters. All peaks were fitted using the RECOIL software package (Lagarec & Rancourt, 1998) by using Lorentzian line-shape (e.g. Gorski & Scherer, 2010). ...
The iron stable isotope compositions (δ56Fe) and iron valence states of ultrahigh-pressure (UHP) eclogites from Bixiling in the Dabie orogen belt, China, were measured to trace changes of geochemical conditions during vertical transportation of earth materials, for example, oxygen fugacity. The bulk Fe3+/ΣFe ratios of retrograde eclogites, determined by Mössbauer spectroscopy, are consistently higher than those of fresh eclogites, suggesting oxidation during retrograde metamorphism and fluid infiltration. The studied eclogites (five samples) display limited MORB-like (~0.10 ‰) δ56Fe values, which are indistinguishable from their protoliths, i.e., gabbro cumulates formed through differentiation of mantle-derived basaltic magma. This suggests that Fe isotope fractionation during continental subduction is limited. Garnet separates display limited δ56Fe variation ranging from -0.08 ± 0.07 ‰ to 0.02 ± 0.07‰, whereas coexisting omphacite displays a large variation of δ56Fe values from 0.15 ± 0.07 ‰ to 0.47 ± 0.07 ‰. Omphacite also has highly variable Fe3+/ΣFe ratios from 0.367 ± 0.025 to 0.598 ± 0.024, indicating modification after peak metamorphism. Omphacite from retrograde eclogites has elevated Fe3+/ΣFe ratios (0.54 - 0.60) compared to that from fresh eclogites (~0.37), whereas garnet displays a narrow range of ferric iron content with Fe3+/ΣFe ratios from 0.039 ± 0.013 to 0.065 ± 0.022. The homogenous δ56Fe values and Fe3+/ΣFe ratios of garnet suggest that it survived the retrograde metamorphism and preserved its Fe isotopic features and ferric contents of peak metamorphism. Because of similar diffusion rates of Fe & Mg in garnet and omphacite, and constant Δ26Mgomphacite-garnet values (1.14 ± 0.04‰), equilibrium iron isotope fractionation between garnet and omphacite was probably achieved during peak metamorphism. Elevated Fe3+/ΣFe ratios of omphacite from retrograde eclogites and variant Δ56Feomphacite-garnet values of the studied eclogites (0.13 ± 0.10 ‰ to 0.48 ± 0.10 ‰) indicate that oxidized geofuild infiltration resulted in elevation of δ56Fe values of omphacite during retrograde metamorphism. This article is protected by copyright. All rights reserved.
... Isomer shifts are quoted relative to the centroid of metallic iron at 298 K. The Recoil-Mössbauer Spectral Analysis Software for windows was used for quantitative evaluation of the Mössbauer spectra [21]. ...
Nanocrystalline Mn²⁺-doped magnetite (Fe3O4) particles of the composition MnxFe3−yO4\(\left (x = 0.0, 0.1, 0.2, 0.3, 0.4 \text { and } 0.5; y = \frac {2x}{3}\right )\), prepared using chemical precipitation under reflux with the Mn²⁺ ions substituting for Fe³⁺ ions rather than Fe²⁺ ones, are characterized mainly with XRD and ⁵⁷Fe Mössbauer spectroscopy. All samples were found to have spinel-related structures with average lattice parameters that increase linearly with the Mn²⁺ concentration, x. The particle size for the samples varied from ∼8 nm to 23 nm. The oxidation of Fe²⁺ to Fe³⁺ at surface layers of the Fe3O4 nanoparticles leading to the formation of maghemite (γ-Fe2O3) was found to considerably weaken with increasing Mn²⁺ concentration. The percentage of the nanoparticles that exhibit short range magnetic ordering due to cationic clustering and/or superparamagnetism increases from 17% to 32% with increasing x. The dependence of isomer shifts of the ⁵⁷Fe nuclei at the tetrahedral and octahedral sites on dopant Mn²⁺ concentration is emphasized. The electric quadrupole shifts indicate that the MnxFe3−yO4 particles undergo Verwey transition. The effective hyperfine magnetic fields at both crystallographic sites decrease with increasing Mn²⁺ concentration reflecting a size effect as well as a weakening in the magnetic super-exchange interaction. The Mössbauer data indicate that for x ≤ 0.2, the dopant Mn²⁺ ions substitute solely for octahedral Fe³⁺ ions whereas for x > 0.2 they substitute for Fe³⁺ at both tetrahedral and octahedral sites.
... These diffractograms ( Figure 1) showed well-formed spots with no evidence for streaking in the regions investigated. Structural solution was performed using charge flipping, as implemented in TOPAS Academic, 21 with Pbam symmetry imposed, using high-resolution PXRD data collected with the I11 instrument. The algorithm was successful in identifying the locations of all ions in the unit cell, allowing the identity of the ions on each site to be ...
Sr2Fe3Se2O3 is a localized-moment iron oxide selenide in which two unusual coordinations for Fe2+ ions form two sublattices in a 2:1 ratio. In the paramagnetic region at room temperature, the compound adopts the crystal structure first reported for Sr2Co3S2O3, crystallizing in space group Pbam with a = 7.8121 Å, b = 10.2375 Å, c = 3.9939 Å, and Z = 2. The sublattice occupied by two-thirds of the iron ions (Fe2 site) is formed by a network of distorted mer-[FeSe3O3] octahedra linked via shared Se2 edges and O vertices forming layers, which connect to other layers by shared Se vertices. As shown by magnetometry, neutron powder diffraction, and Mössbauer spectroscopy measurements, these moments undergo long-range magnetic ordering below TN1 = 118 K, initially adopting a magnetic structure with a propagation vector (1/2 - δ, 0, 1/2) (0 ≤ δ ≤ 0.1) which is incommensurate with the nuclear structure and described in the Pbam1 '( a01/2)000 s magnetic superspace group, until at 92 K ( TINC) there is a first order lock-in transition to a structure in which these Fe2 moments form a magnetic structure with a propagation vector (1/2, 0, 1/2) which may be modeled using a 2 a × b × 2 c expansion of the nuclear cell in space group 36.178 B a b21 m (BNS notation). Below TN2 = 52 K the remaining third of the Fe2+ moments (Fe1 site) which are in a compressed trans-[FeSe4O2] octahedral environment undergo long-range ordering, as is evident from the magnetometry, the Mössbauer spectra, and the appearance of new magnetic Bragg peaks in the neutron diffractograms. The ordering of the second set of moments on the Fe1 sites results in a slight reorientation of the majority moments on the Fe2 sites. The magnetic structure at 1.5 K is described by a 2 a × 2 b × 2 c expansion of the nuclear cell in space group 9.40 I a b (BNS notation).
... Figures (a) and (b) have the same scale bar valuesTable 1providing few correlations between the selected synthesis conditions and chemical compositions obtained from Mössbauer spectra. It should be noted that all the spectra were folded and baseline corrected relative to the 10 m thick α-Fe foil at room-temperature (RT) and subsequently fitted using Voigtian shaped line profiles in Recoil[23][24][25]. Voigtian linewidths have been used to represent Gaussian distributions of Lorentzian lines, and so reflect a distribution of hyperfine fields. ...
For the first time, Mössbauer parameters of mixed cubic spinel NiFe2O4 nanoparticles, prepared by using a one-stage process via evaporation of levitating iron–nickel droplets into a mix of helium–air gas flow accompanied with the application of a DC electric field of up to 210 kV m⁻¹, are reported. © 2018 Springer Science+Business Media, LLC, part of Springer Nature
... 57 Co in Rh was used as γ-ray source for Mössbauer radiation. Recoil spectral analysis software was employed for the quantitative analysis of the Mössbauer spectra [27]. The velocity scale and isomer shifts were calibrated using a metallic α-Fe foil absorber at room temperature. ...
Mullite-type Bi2(Ga1-xFex)4O9 solid solutions, with 0.1 ≤ x ≤ 0.9, have been synthesized by a combination of mechanical and thermal treatments of a Bi2O3/Ga2O3/α-Fe2O3 stoichiometric mixture. The microstructure of the as-prepared materials on the long-range and local atomic scales was investigated by X-ray diffraction and ⁵⁷Fe Mössbauer spectroscopy, respectively. The XRD data analysis revealed in all cases linear dependence of the lattice parameters related on x. Due to the ability of the applied Mössbauer spectroscopy to probe the local environment of Fe cations, the local structural disorder in investigated solid solutions is provided. It was shown that the presence of Fe³⁺ cations in octahedral sites of the orthorhombic structure causes a local distortion of polyhedra in the material. The preferential occupation of Fe in octahedral site was revealed. Detailed quantitative information on both the cation distribution and the bond lengths provided is discussed in relation to the derived hyperfine parameters.
... 32 Transmission Mössbauer spectroscopy was performed with a variable temperature Hecooled system with a 57 Co source. Unless otherwise noted, Mössbauer spectra were collected at 140 K. Spectra were t using the Recoil soware 35 and procedures outlined by Gorski and Scherer. 32 To prepare samples and avoid oxidation, we sealed samples with Kapton tape in the glovebox. ...
... Measurements were done with a 100 mCi 57 Co source in a Rh matrix, which was driven at a constant acceleration rate in a triangular mode at room temperature. The spectra were recorded in 512 channels and the Lorentzian lines of the folded data were fitted using the Recoil software [20]. The spectrometer was calibrated with the room temperature spectrum of an a-Fe foil. ...
In this work, rare-earth orthoferrites polycrystalline compounds REFeO3 (REFO) with RE = rare-earth La, Pr, Nd and Sm were synthesized by the self-combustion method. A direct correlation between the magnitude of the magnetic hyperfine field and the FeO1Fe bond angles was observed. From transmission Mössbauer spectra recorded at room-temperature, relative recoilless F-factors for these REFO compounds were estimated. The method applied to perform this calculation was based on the determination of two subspectral areas present in a mixture of known amounts of the compound under study and a standard sample (α-Fe). For that purpose spectra were thickness-corrected and fitted using lorentzian lines. The so obtained factors were F-REFeO3 (RE = rare-earth La, Pr, Nd and Sm): 1.30 ± 0.02, 1.08 ± 0.04, 1.15 ± 0.05, 1.18 ± 0.08 respectively. The absolute recoilless factors obtained by this method had an average relative error around 11% in comparison with the values predicted by the Debye model.
... The natural iron sample was used for the calibration of the Mössbauer spectrometer. The fitting of the Mössbauer spectra were performed by using the Recoil program [39]. In all the spectra the solid lines and the solid circles represent the simulated curves and experimental data points, respectively. ...
Herein, we report the role of mechanical activation in modifying the structural, microstructural, magnetic and hyperfine parameters of nanosized Co0.3Zn0.7Fe2O4 having average particle size ∼16.6 nm synthesized via coprecipitation method followed by high energy ball milling with cation distribution (Zn²⁺0.61Fe³⁺0.39)A [Co²⁺0.3Zn²⁺0.09Fe³⁺1.61]BO4. The values of the blocking temperature and Curie temperature of the sample are 220 and 270 K, respectively. The values of saturation magnetization at 300 and 5 K are 59 and 88 emu g⁻¹and those of the coercivity at 100 and 5 K are 400 and 5000 Oe, respectively. The values of the magnetic parameters of the sample are greater than those of its counterparts synthesized by chemical methods. A model for precise estimation of the cation distribution of ferrites has been proposed. Moreover, the memory effect obtained in the dc magnetization of the sample can be used for generating, storing and retrieving binary bit pattern.
... The velocity scale was calibrated relative to 57 Fe in Rh. Mössbauer spectral analysis software "Recoil" [14] was used for the quantitative evaluation of the spectra. The Voigt-based fitting method was applied. ...
The composite materials prepared from clay and iron oxides in different weight ratios and temperatures denoted as A85 and E20 were heated at 300 °C in reductive atmosphere and up to 650 °C in inert atmosphere. The changes in the structure, surface and pore properties were examined by XRD, N2 adsorption method and TG, DTA method. The morphology was studied using scanning electron microscope. The heating of composites up to temperature 300 °C in the reductive atmosphere caused the transformation of the present oxide phases. The distribution curve of the heated composites is narrower and is shifted to the lower pores. The composites heated up to 650 °C in the N2 atmosphere showed to the transformation of iron oxide phases to hematite; the composites contained less pores, became denser and due to sintering of iron oxides particles a decrease in specific surface area was observed.
... 32 Transmission Mössbauer spectroscopy was performed with a variable temperature Hecooled system with a 57 Co source. Unless otherwise noted, Mössbauer spectra were collected at 140 K. Spectra were t using the Recoil soware 35 and procedures outlined by Gorski and Scherer. 32 To prepare samples and avoid oxidation, we sealed samples with Kapton tape in the glovebox. ...
Here we revisit whether the common mixed-valent Fe mineral, magnetite, is a viable reductant for the abiotic natural attenuation of perchloroethylene (PCE) and trichloroethylene (TCE) in anoxic groundwater plumes. We measured PCE and TCE reduction by stoichiometric magnetite as a function of pH and Fe(II) concentration. In the absence of added Fe(II), stoichiometric magnetite does not reduce PCE and TCE over a three month period under anoxic conditions. When Fe(II) is added to magnetite suspensions, PCE and TCE are reduced under Fe(II) and pH conditions that appear to be controlled by the solubility of ferrous hydroxide, Fe(OH)2(s). Reduction rates are slow with only 1 to 30% carbon products (primarily acetylene) accumulating over several months. We conducted a similar set of experiments with Fe(OH)2(s) alone and found that, compared to in the presence of magnetite, Fe(OH)2(s) reduces PCE and TCE only at Fe(II) concentrations that are too high (≥13 mM, 726 mg L⁻¹) to be representative of natural aquifer conditions. Our results suggest that magnetite present in aquifer sediments alone is unlikely to reduce PCE and TCE sufficiently fast to contribute to natural attenuation of PCE and TCE. The lack of compelling evidence for PCE and TCE reduction by magnetite raises important questions regarding the current application of using magnetic susceptibility as a potential indicator for abiotic natural attenuation. Dynamic conditions and high Fe(II) concentrations that favor active precipitation of minerals, such as Fe(OH)2(s) in the presence of magnetite (or other Fe minerals), however, may lead to PCE and TCE reduction that could help attenuate PCE and TCE plumes.
... All centroid shifts, d, are given with respect to metallic a-iron at room temperature. The spectra were least square fitted using Recoil software [26]. ...
A systematic investigation of magnetic nanoparticles and the formation of a core-shell structure, consisting of multiple maghemite (γ-Fe2O3) nanoparticles as the core and silica as the shell, has been performed using various techniques. High-resolution transmission electron microscopy clearly shows isolated maghemite nanoparticles with an average diameter of 13 nm and the formation of a core-shell structure. Low temperature Mössbauer spectroscopy reveals the presence of pure maghemite nanoparticles with all vacancies at the B-sites. Isothermal magnetization and zero-field-cooled and field-cooled measurements are used for investigating the magnetic properties of the nanoparticles. The magnetization results are in good accordance with the contents of the magnetic core and the non-magnetic shell. The multiple-core γ-Fe2O3 nanoparticles show similar behavior to isolated particles of the same size.
... Mössbauer Analysis Software ( Lagarec and Rancourt, 1998 for Hg using 10 µg L -1 Ga internal standard. The equilibrium concentrations and adsorption isotherms were fitted to Freundlich and Langmuir models, given in Equations 7.2 And 7.3 respectively. ...
Recycling is considered a key strategy to meet an ever-growing demand of raw materials for the development of novel technologies. While established for solid fractions, metals also have various pathways, both natural or anthropogenic, for mitigation into aquatic streams, making removal and recovery from liquid media desired. Distinct cases are considered throughout this dissertation in which trace elements are present in aqueous streams. These streams were characterized with great attention to the chemical fractionation and speciation, as different fractions and species of a single element show a different behavior in treatment processes. The oxidation state, chemical structure or complexation of trace elements, to which the pH and concentration of other compounds (such as chloride or OM) have a large contribution, can be determined by analytical methods or predicted by mathematical modelling. Processes were optimized aiming at the maximum recovery of metal(loid)s, or at minimizing economic expenditures to chemicals by taking into account the price-elasticity on the residual concentration.
Medicinal use of platinum based antineoplastics in chemotherapy of cancer patients releases intact platinum compounds and their degradation products in the urine. Therefore, the pharmacokinetic excretion of total platinum concentration upon administration of cisplatin and carboplatin was monitored through a clinical study. The platinum speciation arising from the in vivo degradation was compared to the ex vivo degradation, in which carboplatin was shown to be the most stable. Cisplatin and oxaliplatin rapidly undergo degradation according to an exponential decay. From a technical point of view, recovery of platinum species is most favorable directly from collected urine fractions, before severe dilution occurs and the complexity of the stream increases by the mixing with (municipal) wastewater downstream. The potential use of biosorbents to recover Pt was evaluated for cancerostatic platinum compounds (CPC) cisplatin, carbo-platin and oxaliplatin. A minimum adsorbent dose of 10 g/L was required for proper removal and used in all further tests. In comparison with biochar and wood ash, chitosan possesses the highest Pt(IV) adsorption capacity (0.97 mg/g), although a further increase is expected upon chemical modification. The adsorption mechanism is pH dependent and is generally optimal in the neutral range between 6 and 8. The heavy matrix loading in synthetic human urine (83.72 g/LTDS) significantly influenced the removal efficiency. This was also observed during continuous percolation of urine, collected from patients receiving cisplatin and carboplatin, through a column packed with activated carbon. The final, low-concentrated fractions of urine percolating through the column caused desorption of platinum previously loaded onto the column into the effluent.
In wastewater generated by mirror production, excess silver from its spray dosing at the glass surface was found to make up 2.5 mg/L in solution. At the alkaline pH of 11.74, speciation modelling predicted cationic Ag+ to be the main species. Coagulants polyaluminium chloride and sodium poly-acrylated aluminium chloride were found well suited for minimization of residual Ag concentrations below the discharge standard of 0.50 mg/L applicable to the specific industrial sector in Flanders (Belgium). Optimal conditions resulted in remaining silver concentration as low as 0.004 mg/L and sludge containing 42.4 ± 3.4 m% silver on a dry matter basis, which can be used for further pyrometallurgical refining. The catalytic activator for AgNO3 reduction, PdCl2, is collected in a side-stream. Its particulate nature made it well susceptible for physical treatment by sedimentation or, faster, sand filtration. The main residual dissolved species of palladium is PdCl2 (aq), which occurs besides smaller fractions of PdCl+, [PdCl3]- and [PdCl4]2-. It was removed by the 1:1 volume-based combination of ion-exchange resins with sulfonic acid and tertiary amine functionalities. In total, as much as 99.9 ± 0.2 % of palladium could be recovered.
In the lower concentration range, adsorption was selected as a suitable technique for removal of dissolved trace elements. In striving to suppress arsenic contamination in drinking water below the safety standard of 10 μg/L, synthetic nanomaterials were developed and applied. MIL-101(Cr), a metal organic framework (MOF) of high porosity, was used as host for the encapsulation of in situ synthesized iron oxide nanoparticles. Despite the somehow reduced Langmuir surface area (-29.1 %), Fe3O4 nanoparticles could be stabilized in water, preventing their aggregation while still excelling in adsorption capacity of 121.5 mg/g and 80.0 mg/g towards arsenite (H3AsO3) and arsenate (H2AsO4- and HAsO42) respectively. The same removal efficiency was maintained in the presence of excessive Ca2+, Mg2+, phosphate or NOM concentrations and in actual ground and surface water.
As metal concentrations are proportional to the profitability of resource recovery, treatment near each emission source was technically favored. This implies to separate side-streams of controllable flow rate, unaffected by the dilution by other wastewater unless to counter high concentrations of salts and other compounds, for instance present in urine, that may affect the removal efficiency and/or cause early adsorbent saturation. The described collection and pre-concentration procedures, compatible to consecutive pyrometallurgical processes, hence contribute at lifting the overall recycling rate of critical and precious metals in a sustainable manner.
... The velocity scale was calibrated relative to 57 Fe in Rh. Mössbauer spectral analysis software "Recoil" [28] was used for the quantitative evaluation of the spectra. The Voigt-based fitting method was applied for all spectra to determine the line positions, line widths and peak intensities. ...
The natural clay bentonite (B) as adsorbent of lead cations was studied. To enhance its adsorption
capacity, the coating by iron oxide particles, in two selected weight ratios: 2:1 (BM1) and 4:1(BM2),
was used. The changes of the textural and surface parameters after the modification were studied by the
low temperature nitrogen adsorption, XRD and SEM method, Mössbauer spectroscopy. The Pb(II)
adsorption experiments were studied under the different conditions, such as pH of the model solutions,
contact time and initial metal ion concentration. Higher adsorption rates of BM1 and BM2 samples
were observed for lower initial metal ion concentrations.
... 42 Uncertainties of the fitted parameters are derived from the co-variance matrix used in the Levenberg− Marquardt algorithm implemented in the Recoil fitting routine and reported as 95% confidence errors. 43 Sequential Extraction. Reactors containing ∼2 mM Fe(II) were also prepared with Fe(II)Cl 2 having a natural isotope abundance and were subjected to a sequential extraction procedure as previously described. ...
Iron-containing clay minerals are ubiquitous in soils, sediments, and water and provide a significant source of redox-active Fe that is known to influence metal sorption, contaminant fate, and nutrient cycling. While biological reduction of clay minerals has been known for some time, it has only recently been shown that Fe(II) can abiotically reduce Fe(III) in clay minerals. Here we used Mössbauer spectroscopy to show that Fe(II) reduces an extensive amount of Fe(III) in a low Fe clay mineral (Wyoming montmorillonite SWy-2, 2.3 wt% Fe). The extent of reduction ranges from 12 to 78% over a pH range of 4.0 to 7.5 and Fe(II) concentration from 0.4 to 2.2 mM and increases as the amount of sorbed Fe(II) increases until about half of the mineral is reduced. It is unclear how such extensive reduction occurs in an Fe-bearing clay mineral with such a low Fe concentration. With only 2.3 wt% Fe in SWy-2, Fe atoms in the clay mineral are spatially isolated and electron conduction or hopping between neighboring Fe atoms seems unlikely and is also supported by Mössbauer spectroscopy collected over a range of temperatures. The lack of evidence for electron hopping in SWy-2 raises the intriguing question of how the electrons access the Fe deep in the clay mineral structure. Data from Mössbauer spectroscopy and chemical extraction suggest that electron transfer through the basal plane rather than edge sites may explain how such extensive reduction occurs in SWy-2. Electron transfer through the basal plane would provide access to the Fe atoms throughout the structure without requiring electrons to move in the structure via hopping or conduction. Our work demonstrates that Fe(II) reduction of clay minerals can occur across a range of geochemically relevant conditions and that extensive reduction can occur in low Fe clay minerals possibly via electron transfer through the basal plane.
... Room-temperature Mössbauer spectra were taken in transmission geometry using a 57 Co/Rh c-ray source. The velocity scale was calibrated relative to Fe. Recoil spectral analysis software [38] was used for the quantitative evaluation of the Mössbauer spectra. The X-ray diffraction (XRD) patterns were collected using a PW1820 Philips powder diffractometer (Philips, Eindhoven, Netherlands) with Cu Ka radiation. ...
The studies on the mechanochemical synthesis and electrochemical characterization of orthorhombic calcium ferrite (CaFe 2 O 4) are reported in this paper. Stoichi-ometric mixtures of a-Fe 2 O 3 and granulated Ca metal were used as the starting materials for the synthesis process. The synthesized calcium ferrite was characterized by room-temperature Mössbauer spectra, XRD and TEM. The electrochemical characterisation was carried out using cyclic voltammetry studies. Mössbauer spectra provide the yield of the reaction, information on the charge status, the local symmetry and the magnetic state of the iron ions in the mechanosynthesized ferrite material. XRD analysis of the CaFe 2 O 4 compound reveals the orthorhombic crystal structure with an average crystalline size of about 28 nm. TEM micrographs reveal the nanoparticles with irregular crystal morphology ranging from 8 to 30 nm. The elec-trochemical studies clearly show that the calcium ferrite compound can act as an electrocatalyst for Oxygen Evolution Reaction (OER).
... The spectrometer was calibrated with an α-Fe foil at room temperature and the sample temperature was varied from 5 K to 30 K using a liquid helium cryostat. All spectra were fitted using the Recoil software [14]. ...
We have investigated the low temperature magnetic properties of Dy 2 Fe 2 Si 2 C by using magnetisation, specific heat, x-ray diffraction, neutron powder diffraction and 57 Fe Mössbauer spectroscopy measurements over the temperature range 1.5 K–300 K. Dy 2 Fe 2 Si 2 C exhibits two magnetic transitions at low temperatures: an antiferromagnetic transition at ##IMG## [http://ej.iop.org/images/0953-8984/29/11/115806/cmaa52f9ieqn001.gif] {${T_textN}}sim 26$ K and a spin-reorientation transition at ##IMG## [http://ej.iop.org/images/0953-8984/29/11/115806/cmaa52f9ieqn002.gif] {$T_t}sim 6$ K. The magnetic structure above T t can be described with a propagation vector ##IMG## [http://ej.iop.org/images/0953-8984/29/11/115806/cmaa52f9ieqn003.gif] {$mathbfk~=~left(0~0~frac12}right)$ with the ordering of the Dy magnetic moments along the monoclinic b -axis whereas on cooling below T t the Dy moment tips away from the b -axis towards the ac -plane. We find that the spin-reorientation in Dy 2 Fe 2 Si 2 C is mainly driven by the competition between the second-order crystal field term B 20 and the higher-order terms, in particular B 40 and B 64 .
... A triangular drive velocity was used for all spectra and the spectra were recorded in 1024 channels. Mössbauer spectra were least-squares fitted using the RECOIL software [12] and all isomer shifts quoted hereafter are relative to the α-Fe foil (12.5 μm thickness) calibration spectrum obtained at room temperature (fitting with Lorentzian lines yields an 'inner-pair' linewidth of 3−4 = 0.26(1)mm/s). For the purposes of the Mössbauer fitting, the paramagnetic doublets of the olivine and pyroxene components were constrained to be symmetric, even though both phases have two sites available to the Fe. ...
The Lynch 001 meteorite was found in the Nullarbor Plain region of Western Australia in 1977. This meteorite is classified as an ordinary chondrite of the petrologic group L5/6 that has undergone ‘minor to moderate’ terrestrial weathering. Here, we characterize the Fe-bearing phases in this chondrite using ⁵⁷Fe Mössbauer spectroscopy carried out over the temperature range 13 K to room temperature (295 K). The paramagnetic doublets of olivine, pyroxene and a superparamagnetic ferric phase dominate the room temperature Mössbauer spectrum. On the basis of the room temperature quadrupole splitting of the olivine component, we estimate its composition to be Fa 30(5). Besides the paramagnetic ferric component, accounting for ∼15 % of the spectral area at room temperature, magnetically ordered ferric phases were also detected. The total relative proportion of the Fe ³⁺ components allows us to estimate the terrestrial age of Lynch 001 to be 6,500 ± 1,500 yr, consistent with the value of 6,700 ± 1,300 yr determined by ¹⁴C dating.
... The samples were sealed in aluminum foil or in a plastic container. The spectra were fitted to the sum of Lorentzian by a least-squares refinement using or Recoil 1.05 Mössbauer Analysis Software (Lagarec and Rancourt, 1998). All isomer shifts refer to α-Fe at room temperature. ...
Hydrotalcites containing Ni(II) and Fe(III) was synthesized using co-precipitation method to demonstrate their use as a support material for the homogeneous deposition of Au and Au-Pd nanoparticles via sol-immobilization. Detailed characterization performed by UV–Vis, ATR-FTIR, TGA, Mössbauer spectroscopy, SEM, Cryo-TEM, BET analysis evidenced the structural, morphological and textural properties of the passive support and decoration of nanoparticles on the surface of LDH and evidenced the property to be used as photocatalysts. These materials proved to be efficient photocatalysts for the degradation of environmentally important Orange II dye (OII) as a model pollutant. Different experimental parameters influencing the photocatalytic activity viz., catalyst dosage, initial dye concentration and reusability of the catalyst were studied. Langmuir-Hinshelwood model was used to analyze the kinetics of the photocatalytic process. Heteronuclear Au-Pd nanoparticles immobilized on NiFeCO3 LDH was found to be the best photocatalyst degrading about 95% of the dye (25 mg/L) after 60 min and this activity remains to be nearly the same after recycling the catalyst. This enhancement in the activity was attributed to the presence of Au-Pd Nps, with specific surface area (80 m2/g), and band gap (2.7 eV). Our study shows the prepared photocatalyst anticipates being a promising candidate for other photocatalytic applications.
... Mössbauer spectra for all the samples were collected in a transmission configuration at a maximum velocity of 12 mm/s and a constant accelerating mode, with a radioactive source 57 Co in a Rh matrix. Mössbauer data were fitted using the Recoil software [45]. VSM for the mechanically alloyed powders was measured using a Microsens type EV9 vibrating sample magnetometer at an external magnetic field applied up to ± 20 kOe. ...
The effect of ethanol as a process control agent (PCA) on the mechanical alloying (MA) of Fe-20 at. % Al powders is presented. MA was performed at room temperature in an oscillation ball mill and its dynamic was studied by changing the milling frequency and time. We characterized the milled powders using X-ray diffraction (XRD), Mössbauer spectroscopy, and vibrating sample magnetometry (VSM). X-ray patterns for the milled powders without PCA showed a rapid formation of the disordered Fe(Al) solid solution after 25 Hz for 6 h of milling. Mössbauer spectroscopy confirmed two ferromagnetic sites related to the α-Fe phase and Fe(Al) disordered solid solution. However, intense cold welding of the powders to the milling tools for all milling frequencies led to a powder recovery of only 40% on average. The addition of ethanol as a PCA at a 25 Hz increased the powder recovery up to 96% even for different milling times, whereas X-ray diffraction and Mössbauer spectra showed a single α-Fe phase. VSM results exhibit the presence of a soft ferromagnetic character, in which a correlation between the structural parameters with the coercive field and saturation magnetization was deduced. Thus, while ethanol increases the powder recovery rate it also modifies the milling kinetics affecting the domain walls’ movement and the corresponding magnetic interactions between iron atoms.
... All measurements were carried out at room temperature over a velocity range of ± 4 mm s −1 , and were calibrated relative to α-Fe foil. Spectral data were fitted using the Recoil software package [31], using Lorentzian line shapes. The low S/N obtained for each sample was caused by strong absorption of incident gamma-rays by the sample (due to very high bismuth contents). ...
Glasses with nominal molar composition 20B2O3 – (80−x)Bi2O3 – xFe2O3 (where x = 0–40) were successfully prepared by melt-quenching. These glasses were characterised by multiple techniques including density, X-ray diffraction (XRD), X-Ray fluorescence (XRF), Raman, FT-IR and Mössbauer spectroscopies, dilatometry and differential thermal analysis (DTA). Partial replacement of Bi2O3 by Fe2O3 leads to decreasing density and molar volume and a substantial increase in thermal stability, as measured by several parameters, with maximum improvements achieved when x = 10–20. These improvements are accompanied by modest increases in dilatometric softening point. FT-IR and Raman spectra confirm the presence of BO3 and BiO6 structural units in all glasses, with glass structure apparently little affected by Fe2O3. Mössbauer spectroscopy confirms that iron is present partly as 4-fold coordinated Fe³⁺ in all glasses, with some 5- and/or 6- coordinated Fe³⁺ sites also present.
... Fitting and quantification are done with the Recoil spectral analysis software, adapted as needed for the epidemiological context (Lagarec and Rancourt, 1998;Rancourt, 2019). ...
We analyzed historic and recent all-cause mortality data for France, and other jurisdictions for comparison, using model fitting to quantify winter-burden deaths, and deaths from exceptional events. In this way, COVID-19 is put in historic perspective. We prove that the "COVID-peak" feature that is present in the all-cause mortality data of certain mid-latitude Northern hemisphere jurisdictions, including France, cannot be a natural epidemiological event occurring in the absence of a large non-pathogenic perturbation. We are certain that this "COVID-peak" is artificial because it: i. occurs sharply (one-month width) at an unprecedented location in the seasonal cycle of all-cause mortality (centered at the end of March), 2 ii. is absent in many jurisdictions (34 of the USA States have no "COVID-peak"), and iii. varies widely in magnitude from jurisdiction to jurisdiction in which it occurs. We suggest that: • the unprecedented strict mass quarantine and isolation of both sick and healthy elderly people, together and separately, killed many of them, • that this quarantine and isolation is the cause of the "COVID-peak" event that we have quantified, • and that the medical mechanism is mainly via psychological stress and social isolation of individuals with health vulnerabilities. According to our calculations, this caused some 30.2 K deaths in France in March and April 2020. However, even including the "COVID-peak", the 2019-2020 winter-burden all-cause mortality is not statistically larger than usual. Therefore SARS-CoV-2 is not an unusually virulent viral respiratory disease pathogen. By analyzing the all-cause mortality data from 1946 to 2020, we also identified a large and steady increase in all-cause mortality that began in approximately 2008, which is too large to be explained by population growth in the relevant age structure, and which may be related to the economic crash of 2008 and its long-term societal consequences. ---- Résumé en français : Nous avons analysé les données historiques et récentes de mortalité toutes causes confondues pour la France et d'autres juridictions à des fins de comparaison, en lissant une courbe théorique pour quantifier les décès dus à la charge hivernale et les décès dus à des événements exceptionnels. De cette façon, on peut observer le COVID-19 avec une perspective historique. Ainsi, nous prouvons que le « pic COVID » présent dans les données de mortalité toutes causes confondues de certaines juridictions de l'hémisphère Nord à moyenne latitude, y compris la France, ne peut pas être un événement épidémiologique naturel ayant survenu de façon naturelle, en l'absence d'une grande perturbation non pathogène. Nous sommes convaincus que le « pic COVID » est artificiel car : i. il s'est produit brusquement (largeur d'un mois) à une date sans précédent dans le cycle saisonnier de mortalité toutes causes confondues (milieu du pic à la fin mars), ii. il est absent dans de nombreuses juridictions (34 des États américains n'ont pas de « pic COVID »), et iii. l'ampleur de ce pic varie considérablement d'une juridiction à l'autre. Nous suggérons que : • la quarantaine de masse et l'isolement strict sans précédent des personnes âgées malades et en bonne santé, ensemble et séparément, a tué beaucoup d'entre eux, 4 • que cette quarantaine et cet isolement sont la cause de l'événement « pic-COVID » que nous avons quantifié, • et que le mécanisme médical expliquant ce pic passe principalement par le stress psychologique et l'isolement social des personnes vulnérables au niveau de leur santé. Selon nos calculs, ces mesures ont provoqué quelques 30,2 K décès en France en mars et avril 2020. Cependant, même en incluant le « pic COVID », la charge hivernale de mortalité toutes causes confondues pour l'hiver 2019-2020 n'est pas statistiquement supérieure aux charges hivernales habituelles, ce qui nous amène à affirmer que le SARS-CoV-2 n'est pas un virus responsable de maladies respiratoires inhabituellement virulent. En analysant les données de mortalité toutes causes confondues de 1946 à 2020, nous avons également identifié une augmentation importante et régulière de la mortalité toutes causes confondues qui a commencé vers 2008, trop importante pour être expliquée par la croissance de la population étant donné la pyramide des âges, mais qui pourrait être liée à la crise économique de 2008 et à ses conséquences sociétales sur le long terme.
... Spectra were collected at −260 and 25 • C. Measurements at low temperatures were performed working with a closed-cycle cryogenic system (Model DE-202, ARS, Macungie, PA, USA). Each spectrum was folded to minimize geometric effects; the experimental data were fitted using Recoil [50], a commercial program with constraints. ...
A series of iron functionalized hydroxyapatite (Fe/HAP) samples with different metal loading (2 < wt.% Fe < 13) was prepared by a flash ionic exchange procedure from iron(III) nitrate as precursor and tested in some environmental air-quality protection reactions such as the catalytic reduction of NOx by NH3 (NH3-SCR), catalytic oxidation of NH3 (NH3-SCO) and catalytic N2O decomposition. The catalytic performances of the Fe/HAP catalysts were determined under flow conditions as a function of temperature and using reactant concentrations typical of polluting gaseous emissions from industrial vents. Physico-chemical characterization with various techniques of study (UV-DR and Mössbauer spectroscopies, NH3 titration, N2-physisorption, and XRPD analyses) provided valuable information on Fe-speciation, acidity, morphology, and structure of the samples. In general, highly dispersed Fe3+ centers were the predominant species, irrespective of Fe-loading, while just low percentage (≤15%) of FexOy nanoclusters (2 < size/nm < 4) was detected on the samples. As expected, the differences in iron concentration produced a diversified effect of both catalyst properties and catalytic activity, comprising the conversion and selectivity profiles, different for each reaction considered. The obtained results indicate a good potentiality for the eco-friendly Fe-catalysts for some environmental reactions of air protection.
... All measurements were calibrated relative to α-Fe foil. Spectral data were fitted using the Recoil software package, 21 using Lorentzian line shapes. ...
Synchrotron X-ray powder diffraction data indicate that La_{0.5}Sr_{0.5}Mn_{0.5}Rh_{0.5}O_{3} and La_{0.5}Sr_{0.5}Fe_{0.5}Rh_{0.5}O_{3} adopt distorted perovskite structures (space group Pnma) with A-site and B-site cation disorder. A combination of XPS and {57}^Fe Mössbauer data indicate the transition metal cations in the two phases adopt Mn3+/Rh4+ and Fe3+/Rh4+ oxidation state combinations respectively. Transport data indicate both phases are insulating, with ρ vs. T dependences consistent with 3D variable-range hopping. Magnetisation data reveal that La_{0.5}Sr_{0.5}Mn_{0.5}Rh_{0.5}O_{3} adopts a ferromagnetic state below T_{c} ~ 60 K, which is rationalized on the basis of coupling via a dynamic Jahn–Teller distortion mechanism. In contrast, magnetic data reveal La_{0.5}Sr_{0.5}Fe_{0.5}Rh_{0.5}O_{3} undergoes a transition to a spin-glass state at T ∼ 45 K, attributed to frustration between nearest-neighbour Fe–Rh and next-nearest-neighbour Fe–Fe couplings
... Measurements were taken in the range ± 11 mm s −1 . The hyperfine interaction parameters were determined by fitting the experimental spectra by a least-squares method using the Recoil software [20]. The center shifts were reported with respect to that of 25 µm-thick α-Fe foil at room temperature. ...
Iron and manganese are ubiquitous in the natural environment. FeII-FeIII layered double hydroxide, commonly called green rust (GR), and MnIII-MnIV birnessite (Bir) are also well known to be reactive solid compounds. Therefore, studying the chemical interactions between Fe and Mn species could contribute to understanding the interactions between their respective biogeochemical cycles. Moreover, ferromanganese solid compounds are potentially interesting materials for water treatment. Here, a {Fe(OH)2, FeIIaq} mixture was oxidized by Bir in sulphated aqueous media in the presence or absence of dissolved O2. In oxic conditions for an initial FeII/OH− ratio of 0.6, a single GR phase was obtained in a first step; the oxidation kinetics being faster than without Bir. In a second step, GR was oxidised into various final products, mainly in a spinel structure. A partial substitution of Fe by Mn species was suspected in both GR and the spinel. In anoxic condition, GR was also observed but other by-products were concomitantly formed. All the oxidation products were characterized by XRD, XPS, and Mössbauer spectroscopy. Hence, oxidation of FeII species by Bir can be considered as a new chemical pathway for producing ferromanganese spinels. Furthermore, these results suggest that Bir may participate in the formation of GR minerals.
... Room-temperature 57 Fe Mössbauer spectra were collected relative to a-Fe over a velocity range of ±12 or ±6 mm s -1 using a constant acceleration spectrometer with a 25 mCi source of 57 Co in Rh. Attempts were made to fit the spectra using Lorentzian as well as Extended Voigt-Based Fitting (xVBF) paramagnetic doublets consistent with Fe 3+ and/or Fe 2+ , using the Recoil analysis software package (Rancourt 1998). The area ratio of the doublets was established, enabling estimation of the (Fe 3+ /SFe) redox ratio based on fitted peak areas and assuming that the recoil-free fraction ratio f(Fe 3+ )/f(Fe 2+ ) = 1.0. ...
The crystallization of iron-containing sodium silicate phases holds particular importance, both in the management of high-level nuclear wastes and in geosciences. Here, we study three as-quenched glasses and their heat-treated chemical analogs, NaFeSiO4, NaFeSi2O6, and NaFeSi3O8 (with nominal stoichiometries from feldspathoid, pyroxene, and feldspar mineral groups, i.e., Si/Fe = 1, 2, and 3, respectively) using various techniques. Phase analyses revealed that as-quenched NaFeSiO4 could not accommodate all Fe in the glass phase (some Fe crystallizes as Fe3O4), whereas as-quenched NaFeSi2O6 and NaFeSi3O8 form amorphous glasses. NaFeSi2O6 glass is the only composition that crystallizes into its respective isochemical crystalline polymorph, i.e., aegirine, upon isothermal heat-treatment. As revealed by Mössbauer spectroscopy, iron is predominantly present as fourfold-coordinated Fe3+ in all glasses, though it is present as sixfold-coordinated Fe3+ in the aegirine crystals (NaFeSi2O6), as expected from crystallography. Thus, Na-Fe silicate can form a crystalline phase in which it is octahedrally coordinated, even though it is mostly tetrahedrally coordinated in the parent glasses. Thermal behavior, magnetic properties, iron redox state (including Fe K-edge X-ray absorption), and vibrational properties (Raman spectra) of the above compositions are discussed.
... Curve fitting was performed using a Gaussian/Lorentzian (70/30) peak shape after ranging from -11 to +11 mm s −1 . The hyperfine interaction parameters were determined by fitting the experimental using the software Recoil and its Voigt-based fitting model [18]. The center shifts are given with respect to metallic α-iron foil at room temperature. ...
We report the effect of the synthesis route of starch-functionalized magnetite nanoparticles (NPs) on their adsorption properties of As(V) and As(III) from aqueous solutions. NP synthesis was achieved by two different routes implying the alkaline precipitation of either a mixed Fe²⁺/Fe³⁺ salt solution (MC samples) or a Fe²⁺ salt solution in oxidative conditions (MOP samples). Syntheses were carried out with starch to Fe mass ratio (R) ranging from 0 to 10. The crystallites of starch-free MC NPs (14 nm) are smaller than the corresponding MOP (67 nm), which leads to higher As(V) sorption capacity of0.3 mmol gFe⁻¹ to compare with respect to 0.1 mmol gFe⁻¹ for MOP at pH=6. MC and MOP starch-functionalized NPs exhibit higher sorption capacities than pristine one and the difference in sorption capacities between MOP and MC samples decreases with increasing R values. Functionalization tends to reduce the size of the magnetite crystallites and to prevent their agglomeration. Size reduction is more pronounced for MOP samples (67 nm (R0) to 12 nm (R10)) than for MC samples (14 nm (R0) to 9 nm (R10)). Therefore, due to close crystallite size, both MC and MOP samples, when prepared at R=10, display similar As(V) (respectively, As(III)) sorption capacities close to 1.3 mmol gFe⁻¹ (respectively, 1.0 mmol gFe⁻¹). Additionally, according to the effect of pH on arsenic trapping, the electrostatic interactions appear as a major factor controlling As(V) adsorption while surface complexation may control As(III) adsorption
... The best fit, with a χ 2 of 0.643 was obtained using four ferric doublets with Lorentzian lineshapes. Fitting of the new spectrum with the program RECOIL (developed by Lagarec and Rancourt, 1998). gave the fit shown in Fig. 4, and the parameters reported in Table 1. ...
Jahnsite-(CaMnZn), CaMn ²⁺ Zn 2 Fe ³⁺ 2 (PO 4 ) 4 (OH) 2 ⋅8H 2 O, is a new jahnsite-group mineral associated with alteration of phosphophyllite at the Hagendorf-Süd pegmatite, Bavaria. It forms as thin yellow crusts and brown epitactic growths on altered phosphophyllite, both of which comprise lath-like crystals in orthogonal orientation, up to 100 μm long. The crystals contain intergrowths of jahnsite-(CaMnZn) and jahnsite-(CaMnMn) on a scale of ~50 μm. The calculated density is 2.87 g cm ⁻³ based on the empirical formula. Optically it is biaxial (–), with α = 1.675(2), β = 1.686(2) and γ = 1.691(2) (white light). The calculated 2V is 68°. Dispersion could not be observed, and the optical orientation is Z = b . Pleochroism was imperceptible. Electron microprobe analyses together with results from Mössbauer spectroscopy gives the formula (Ca 0.59 Mn 0.24 ) Σ0.83 Mn(Zn 0.74 Mn ²⁺ 0.48 Mg 0.18 Fe ²⁺ 0.13 Fe ³⁺ 0.47 ) Σ2 Fe ³⁺ 2 (P 0.995 O 4 ) 4 (OH) 2.03 (H 2 O) 7.97 .
Jahnsite-(CaMnZn) is monoclinic, P 2/ a , with a = 15.059(1), b = 7.1885(6), c = 10.031(2) Å, β = 111.239(8)° and V = 1012.1(2) Å ³ . The recent International Mineralogical Association approved nomenclature system for jahnsite-group minerals was applied to establish jahnsite-(CaMnZn) from the empirical formula. The structural flexibility of jahnsite-group minerals to accommodate cations of quite different sizes in the X and M 1 sites is discussed in terms of rotations about the 7 Å axis of two independent octahedra centred at the M 3 sites.
... Mössbauer spectrum of Mt 950°C was collected between ± 12 mm/s. All the spectra were numerically analyzed using a commercial program that takes into account hyperfine magnetic fields and quadrupole splitting distributions (Lagarec and Rancourt 1998). ...
To improve hexavalent chromium (Cr(VI)) retention of montmorillonite (Mt) at pH 3, Mt sample was subjected to different treatments: thermal ones at 600 °C or 950 °C, 2 h, or mechanical grinding for 300 s. Then, the obtained products were loaded with different octadecyl trimethyl ammonium loading and 50% and 100% of Mt cation exchange capacity (CEC). The samples were characterized by several techniques at each stage. Differential thermogravimetric analysis (DTGA) performed on the products allowed determining the actual surfactant amount related to the internal or external surface by cation exchange and Van der Waals (VdW) mechanisms, respectively, taking into account the CEC of the thermal or mechanical pretreated Mt base sample used. X-ray diffraction (XRD) analyses revealed that the surfactant loading allowed the reversal of the collapsed interlayer after both treatments. The samples subjected to the thermal treatment at 600 °C and the raw Mt samples exhibit higher positive zeta potential values than the mechanical pretreated Mt ones with 100% of the CEC surfactant loaded at pH 3. This was directly related to the external surface covered by the surfactant. The agreement between the results of the surfactant coverage on the external surface and Cr(VI) removal at pH 3 indicates that the electrostatic mechanism is the main driving force for the sorption of Cr(VI). These synthesized sorbents achieve similar Cr(VI) retention using less than half the surfactant amount of already published studies.
... The spectrometer was calibrated by using the spectrum of natural iron. The M€ ossbauer spectra were fitted by the Recoil program [30]. The i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( x x x x ) x x x center shift values (CS) are quoted relative to the natural iron (CS ¼ 0). ...
LiAlH4 is a promising material for hydrogen storage, having the theoretical gravimetric density of 10.6 wt% H2. In order to decrease the temperature where hydrogen is released, we investigated the catalytic influence of Fe2O3 on LiAlH4 dehydrogenation, as a model case for understanding the effects transition oxide additives have in the catalysis process. Quick mechanochemical synthesis of LiAlH4 + 5 wt% Fe2O3 led to the significant decrease of the hydrogen desorption temperature, and desorption of over 7 wt%H2 in the temperature range 143–154 °C. Density functional theory (DFT)-based calculations with Tran-Blaha modified Becke-Johnson functional (TBmBJ) address the electronic structure of LiAlH4 and Li3AlH6. ⁵⁷Fe Mössbauer study shows the change in the oxidational state of iron during hydrogen desorption, while the ¹H NMR study reveals the presence of paramagnetic species that affect relaxation. The electron transfer from hydrides is discussed as the proposed mechanism of destabilization of LiAlH4 + 5 wt% Fe2O3.
... Calibration was performed with a 12-µm-thick α-Fe foil to which isomer shift values are referred. The Mössbauer spectra were numerically analyzed using a computer program that takes into account hyperfine magnetic fields and quadrupole splitting distributions (Lagarec and Rancourt 1998). ...
To help understand the dynamics of peatlands forming on the Southern Serra do Espinhaço, Brazil, the occurring natural (²²⁶Ra, ²³²Th, ⁴⁰K) and anthropogenic (¹³⁷Cs) activity of gamma-ray emitters located at three sites, namely the localities of São João da Chapada (CH), Pinheiro (PIN) and Pau de Fruta (PDF), was studied. The iron compounds were characterized by ⁵⁷Fe Mössbauer spectroscopy. Differences on natural radionuclide levels and distributions were found among the peatland sites, indicating differences on mineral composition, hydric regimes and living. Significant correlation was found only for ²³²Th–²²⁶Ra activity values (Pearson correlation coefficient of − 0.5), which is different from other South American soils, where significant positive correlations among all radionuclides were determined. In PDF and CH, the dose rate results are lower than the worldwide mean value, but in PIN, they are higher because of the relatively high ²²⁶Ra concentration. The only anthropogenic radionuclide is ¹³⁷Cs. The convection–diffusion model fits the CH and PDF activity profiles, although the PIN profile is likely affected by other soil mechanisms as well. Mössbauer spectra reveal Fe³⁺ in two different local environments and the occurrence of hematite in the upper samples of the CH site. The iron concentration decreases with depth. Contrary to soils of other regions, no significant correlation was found between iron species and the natural radioactivity. The studied peatlands exhibit clear differences between their natural and anthropogenic radionuclide distributions to those of mineral soils.
... The velocity scale was calibrated using an a-iron metal foil absorber at room temperature. The spectra were fitted using the Recoil program (Lagarec and Rancourt 1998). All experimental M€ ossbauer spectra were fitted with Lorentzian lines. ...
Mössbauer spectra of equilibrated ordinary chondrites ?consist of two doublets due to paramagnetic iron present in olivines and pyroxenes and two sextets due to magnetically ordered iron present in metallic phases and troilite. The spectral areas of the different mineralogical phases found by Mössbauer spectroscopy in meteorites are proportional to the number of iron atoms in this mineralogical phase. This property of Mössbauer spectra can be the basis for constructing a method for the classification of ordinary chondrites. This idea was first explored at the Mössbauer Laboratory in Kanpur. This group suggested a qualitative method based on 2‐dimensional plots of Mössbauer spectral areas and thus classified properly some meteorites. We constructed a quantitative method using Mössbauer spectral areas, multidimensional discriminant analysis, and Mahalanobis distance (4M method) to determine the probability of a meteorite to be of type H, L, or LL. Based on 59 Mössbauer spectra, we calculated by the 4M method, Scluster, the level of similarity of the Goronyo meteorite to the clusters. On the plot of ferrosilite versus fayalite, the point representing Goronyo is located on the border between H and L areas. Calculated by the 4M method, the meteorite Goronyo is 32% similar to type H, 75% to type L, and 11% to type LL. Additional mineralogical analyses suggested that the Goronyo meteorite would be classified as type L, although it was originally reported as type H in the Meteoritical Bulletin Database.
... Measurements were taken at the wide range of velocities ± 11 mm/s or ± 4 mm/s for experiments at room temperature (RT). The hyperfine interaction parameters were determined by fitting the experimental spectra by a least-squares method using the Recoil software (Lagarec and Rancourt, 1998) with Voigt-based fitting analysis or Lorentzian model except in the case of the appearance of a magnetic order for Fe(II) phases (siderite), whereas the full static Hamiltonian site model is required at very low temperature (15 K or 4 K) to solve the mixed hyperfine interactions. The center shifts were reported with respect to that of 25 μm-thick α-Fe foil at RT. Similarly, iron speciation of fresh samples and oxidized samples, before and after the kinetic weathering cells, were analyzed using Fe Ledge X-ray absorption near-edge spectroscopy (XANES) spectra using the Spherical Grating Monochromator (SGM) beamline 11ID-1 at the Canadian Light Source in Saskatoon, Canada (Regier et al., 2007). ...
Mine tailings exposed to water and oxygen generate acid mine drainage (AMD) when the neutralizing minerals are insufficient to buffer the acid produced by sulfide oxidation. Mineral reactivity, such as sulfide oxidation and carbonate dissolution, leads to several changes within mine tailings in terms of their physical, mineralogical, and geochemical properties, which may lead to the release of metal(oid)s (e.g., As, Cu, Zn, Fe, S) into the environment. Fresh and oxidized tailings were sampled at two vertical profiles in a tailings storage facility (TSF). The TSF contains tailings from gold ore processing at a mine that has been closed for more than 25 years. Oxidized tailings have formed by in-situ oxidation of fresh tailings over more than 20 years. The collected samples were analyzed for: i) chemical composition by inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray fluorescence (XRF), and total S/C; and ii) mineralogical composition by X-ray diffraction (XRD), Mineral Liberation Analyzer (MLA), Mossbauer spectroscopy, and Fe L-edge X-ray absorption near-edge spectroscopy (XANES). Mineralogically, the fresh tailings included more than 22 wt.% carbonates and more than 10 wt.% sulfides. In contrast, the oxidized tailings were composed mainly of secondary minerals such as iron oxy-hydroxides and gypsum. Geochemically, the fresh tailings exhibited a circumneutral behavior during weathering cell experiments and contaminants such as As were negligibly released (<0.3 mg/L). The latter is explained by formation of secondary iron oxy-hydroxides, which are known for the capacity to uptake several contaminants from the leachate. Long term oxidation of fresh tailings will lead to highly oxidized tailings similar to those collected in situ. The oxidized tailings exhibited an acidic behavior despite sulfide depletion due to latent acidity. The geochemical behavior was strongly controlled by the reactivity of secondary minerals (e.g., dissolution of gypsum and iron oxy-hydroxides). Quantitively, the oxidized tailings released 163 mg/kg Fe, around 12,000 mg/kg S, and around 6 mg/kg Zn.
... The 57 Fe mössbauer spectrum recorded at room temperature (RT) for α-Fe 2 O 3 nanorods sample is shown in Fig. 5 and shows sextet pattern confirming the appearance of magnetic behaviour in the sample. The spectrum was fitted based on the software RECOIL [43] and the 57 Fe mössbauer parameters of the sample were extracted. The value of hyperfine field B hf obtained is 51.4(3) T which is associated with the haematite phase α-Fe 2 O 3 [44]. ...
... The 57 Fe Mössbauer spectra recorded at 300 K (room temperature) for the samples A and B are presented in Figure 6; both samples display magnetic ordering. The spectra were analysed using the analysis code RECOIL software [39] and the 57 Fe extracted Mössbauer parameters at room temperature are listed in Table.1. The transmission mössbauer spectroscopy of the samples A and B (Figure 6) reveals only single sextet indicating magnetically ordered state. ...
The aim of this study, beside the development of an eco-friendly method for the synthesis α-Fe 2 O 3 nanoparticles, is to study the effects of using different precursors on the main properties of the α-Fe 2 O 3 nanoparticles synthesized. In this regards, we have used a biosynthesis method to synthesis two α-Fe 2 O 3 samples from two different salts as precursors, namely, ferric nitrate and ferric chloride. XRD results confirmed a rhombohedral (hexagonal) structure with the space group R3¯c in all samples. TEM morphology analysis revealed different shapes for the different samples based on different precursors. The ferric nitrate sample showed quasi-spherical shape with average particles size of 70 nm, while ferric chloride showed growth of a nanorod-based structure with average diameter of 50 nm and length of 400 nm. UV study revealed that the ferric nitrate sample exhibits better optical properties than the ferric chloride sample. The energy band gap E g obtained from the optical study is 2.53 eV for the ferric nitrate sample and 2.70 eV for the ferric chloride sample. FT-IR study confirms the phase purity and chemical bonds of the nanoparticles synthesized. Mössbauer spectroscopy investigation revealed the weak ferromagnetic nature of the samples.
... Fe spectra were subjected to linear combination fitting (LCF) using Athena software (Ravel and Newville, 2005) and shell-byshell fitting in Viper software (Klementev, 2001). Additionally, red floc Fe mineralogy was determined with 57 Fe Mössbauer spectroscopy at 77 K and subsequent spectra fitting using Recoil software, Voigt-based fitting routine (Lagarec and Rancourt, 1998). White flocs were further subjected to sulfide (Cline, 1969) and elemental S (S 0 ; Wan et al., 2014) quantification in the Geomicrobiology Laboratory, University of Tuebingen, Germany, and to polysulfide quantification (Rizkov et al., 2004;Kamyshny et al., 2006) in the Environmental Geochemistry Laboratory, University of Bayreuth, Germany. ...
For much of the Precambrian era, the bulk ocean was anoxic and Fe(II) rich (ferruginous), except for the first development of shallow ocean oxygenation and temporally/spatially restricted sulfide-rich waters (euxinia) along productive continental margins in the late Archean, which prevailed throughout much of the remaining Precambrian. There is little detail pertaining to transition zones between ferruginous, euxinic, and oxic seawater over the continental shelf that may have played an important role in shaping the composition of the underlying sediment. Here we present spectroscopic data on the Fe and sulfur mineralogy in the Arvadi Spring (Switzerland), a proposed analogue for such conditions. Our study reveals green rust, ferrihydrite, and lepidocrocite as the main Fe minerals. Because the reactivity of green rust differs from that of ferric hydroxides and Fe(II) sulfides, it is important to understand its role in the transfer of metals and nutrients from seawater to underlying sediments, if those sediments are to be used as chemical archives of paleo-seawater. We observed elemental sulfur (S ⁰ ) as the dominant sulfur precipitate and found indications for its role in pyrite formation, implying that S ⁰ could have had a similar role in Precambrian deposition of pyrite-poor or pyrite-rich sediments.
Micas from mafic ultrapotassic rocks with lamproitic affinity from several localities of the Central Mediterranean region were studied through single-crystal X-ray diffraction (SC-XRD), electron microprobe analysis (EMPA) and Secondary Ion Mass Spectrometry (SIMS); Mössbauer Spectroscopy (MöS), when feasible, was also applied to minimise the number of unknown variables and uncertainties. Lamproitic samples analysed cover the most important Central Mediterranean type localities, from Plan d'Albard (Western Alps) to Sisco (Corsica), Montecatini Val di Cecina and Orciatico (Tuscany, Italy) and Torre Alfina (Northern Latium, Italy). The studied crystals show distinctive chemical and structural features; all of them belong to the phlogopite-annite join and crystallise in the 1 M polytype, except for micas from Torre Alfina, where both 1 M and 2 M1 polytypes were found. Studied micas have variable but generally high F and Ti contents, with Mg/(Mg + Fe) ranging from ~ 0.5 to ~ 0.9; 2M1 crystals from Torre Alfina radically differ in chemical composition, showing high contents of Ti and Fe as well as of Al in both tetrahedra and octahedra, leading to distinctive structural distortions, especially in tetrahedral sites.
In the present work, the oxidation and spin state of Fe and the local structure around Fe in the supercapacitor birnessite with different contents of the Fe dopant were investigated using Mössbauer spectroscopy. It was found that Fe ions were exclusively present as high spin Fe3+ in octahedral coordination with about 70% iron occupying the Mn3+ positions and about 30% iron occupying the Mn4+ positions in the [MnO6] octahedra for all Fe-doped birnessite samples. Based on these new findings, the trend of typical cell parameters, selected bond lengths of the Fe-doped birnessites and their corresponding quadrupole splittings in the Mössbauer spectra were well explained by considering both the weakened Jahn–Teller effect during the replacement of Mn3+ by Fe3+ and the expansion of octahedra during the replacement of Mn4+ by Fe3+. The present work offers some new insights into the understanding of the mechanism of the heterogeneous atomic doping on the crystal structure of birnessite, with importance for both mineralogy and material science.
Our study targets some of the long-standing questions concerning the somewhat mysterious properties of chalcopyrite CuFeS2. We show that defect chemistry in connection with charge transfer within the structure is responsible for the unusual electronic and magnetic properties of CuFeS2. Specifically, our model addresses weak ferromagnetism and the high mobility of carriers on the background of a rigid antiferromagnetic structure. We show that defect structure can, counterintuitively, boost the mobility of free carriers due to defect-modified charge transfer. Further, the defect-modified charge transfer induces the weak ferromagnetism both in the Cu- and Fe-sublattice. This new view opens up space for further investigations and applications of charge transfer compounds.
The phase Na 5 FeSi 4 O 12 [pentasodium iron(III) silicate] crystallizes readily from the Na 2 O–Fe 2 O 3 –SiO 2 glass system in a relatively large compositional range. However, its crystal structure and properties have not been studied in detail since its discovery in 1930. In this work, the Na 5 FeSi 4 O 12 phase was crystallized from a host glass with 5Na 2 O·Fe 2 O 3 ·8SiO 2 stoichiometry, and both the glass and the crystal were studied. It was found that the Na 5 FeSi 4 O 12 phase crystallizes at ∼720 °C from the glass and melts at ∼830 °C when heated at a rate of 10 °C min ⁻¹ . The crystal structure was solved using single-crystal X-ray diffraction and the refined data are reported for the first time for the Na 5 FeSi 4 O 12 phase. It exhibits trigonal symmetry, space group R \overline{3} c , with a = 21.418 and c = 12.2911 Å. The Na atoms located between adjacent structural channels exhibit positional disorder and splitting which was only refined by using low-temperature data collection (150 K). While ∼7% of the total Fe cations occur as Fe ²⁺ in the glass, four-coordinated Fe ³⁺ constitutes ∼93% of the total Fe cations. However, iron in the crystal, which exhibits a paramagnetic behavior, is solely present as six-coordinated Fe ³⁺ . The magnetic and vibrational properties of the glass and crystal are discussed to provide additional insight into the structure.
We report line broadening in the 77 K 57Fe Mössbauer spectra of some commercially available medicines based on ferrous sulfates and on ferrous fumarates. While introducing only a single ferrous doublet is required to fit the RT spectra of all samples, on the contrary the line shapes of the 77 K spectra are properly described with two ferrous doublets. We discuss eight different static and dynamic hypotheses as possible physical origins for these two doublets, but finally we propose that the reasons are similar for the ferrous sulfates and for the ferrous fumarates containing medicines, and it can be due to the presence of easily dehydrated and hydrated ferrous compounds. The presence of several hydrated sulfates was confirmed by RT Raman spectroscopy. Possible implications of these results related with the hydrated character by which the active parts of the medicines are fabricated by the pharmaceutical companies are also discussed.
In this paper the synthesis of the LaBiFe2O6 material by the modified Pechini method is reported. Structural, morphologic, magnetic and optic experimental studies were performed. Rietveld refinement of x-ray diffraction patterns revealed that LaBiFe2O6 crystallizes in an orthorhombic perovskite structure (space group Pnma, # 62). Scanning electron microscopy images showed the nanometric feature of grains. X-ray dispersive spectroscopy permitted to infer the obtaining of the LaBiFe2O6 expected stoichiometry. Results of magnetic susceptibility as a function of temperature and field magnetization evidenced mixed ferromagnetism and superparamagnetism behavior at T=300 K. Mössbauer spectroscopy supported the superparamagnetic and ferromagnetic responses as a result of the nanogranular morphology and anisotropy effects. Spectrum of diffuse reflectance suggest that this material behaves as a semiconductor with energy gap Eg=2.13 eV.
The present work reports chemical and structural data of actinolite asbestos from Aurina Valley, Bolzano (Italy). The chemical composition was determined using EMPA and TG analysis, and the Fe3+/Fetot ratio was accurately evaluated with independent ⁵⁷Fe Mössbauer spectroscopy. Morphology and crystallinity were also investigated through SEM and TEM investigations. Crystal structure was refined using high-resolution synchrotron XRPD data. The iron content of Aurina Valley sample is lower compared to two representative asbestiform actinolite samples (with structure refinement) taken from the literature (FeOtot 7.77 wt% against 12÷13 wt%, respectively), accounting for the reduced cell volume here measured (910.29 ų against 912÷918 ų, respectively). Refined site scattering values of Aurina Valley sample are in agreement with those calculated from chemical compositions, and the optimized structural formula is: K0.02Na0.05(Na0.08Ca1.92)∑=2.00(Mg3.80Fe²⁺0.79Fe³⁺0.11Al0.20Mn0.05Ni0.02Cr0.01)∑=4.98(Si7.67Al0.25)∑=7.92O21.69(OH)2.31. The C sites M(1), M(2) and M(3) are occupied by Mg and Fe in a proportion of ∼4:1, whereas the M(4) site contains mainly Ca and a very small amount of Na. Iron exclusively occupies the octahedral C sites, with Fe²⁺ ions occurring at the M(1, 2, 3) sites and the small amount of Fe³⁺ (13% of Fetot) ordered at the M(2) site. The refined crystal structure and cation distribution are fully consistent with results previously obtained on asbestiform and non-asbestiform samples belonging to the tremolite-actinolite-ferro- actinolite substitutional series.
The 1D chain [Fe(Etutrz)3](ClO4)2 ⋅ 1.5H2O (2) (Etutrz = 1-ethyl-3-(4H-1,2,4-triazol-4-yl) thiourea), displays pronounced thermochromism with a purple color at 77 K while the sample is white at 300 K. Investigation of magnetic properties reveal an abrupt spin transition around 227 K. Differential scanning calorimetry studies on cooling display a first order phase transition at around 200 K with an entropy variation of ΔS = 61.3 J mol− 1 K− 1. ⁵⁷Fe Mössbauer spectroscopy of 2 confirms a complete spin transition with a 100% high-spin population at 300 K (isomer shift δHS = 1.04(1) mm/s, quadrupole splitting ΔEQ = 2.86(2) mm/s). The Fe(II) ions convert to the low-spin state at 78K (δLS = 0.53(2) mm/s). The quadrupole splitting, ΔEQ = 0.29(2) mm/s, confirms the presence of distorted octahedra within the 1D chain. The 1D chain [Fe(Etutrz)3](BF4)2 ⋅2MeOH (1) exhibits a different magnetic behavior with a gradual spin conversion at T1/2 = 221 K, whereas thermochromic properties are maintained.
A mesoporous SBA‐15 solid was doped with Li, K or Cs. These systems were used as supports of iron nanoparticles and each composite was utilized as catalyst in the Fischer‐Tropsch synthesis. After the activation treatment the same Fe species were detected in all solids: Fe3O4, α‐Fe and Fe²⁺ inside SBA‐15 walls. However, the species percentages and their distribution were different according to the dopant present. In all “working” catalysts a mixture of carbides ε`‐Fe2.2C and χ‐Fe2C5, Fe3O4 and ions Fe+ 2 inside the SBA‐15 walls were found. Alkali cations produce different amount and strength of basic sites. At 1 atm and T=703 K, the catalytic activity order was: Li> K> no doped > Cs and the alkali metals favored the production of olefins. At 20 atm, the activity was considerably higher, even at a temperature as low as 543 K, which was attributed to structural properties of the support and to diffusional effects. All catalysts showed a promising hydrocarbon production in the gasoline range. The influence of alkali metals was discussed in terms of electrostatic effects and the limited hydrocarbon chain growth was attributed to the control over size of active iron species.
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In submerged soils and sediments, clay minerals are often exposed to anoxic waters containing ferrous iron (Fe²⁺). Here, we investigated the sorption of Fe²⁺ onto a synthetic montmorillonite (Syn-1) low in structural Fe (<0.05 mmol Fe per kg) under anoxic conditions and the effects of subsequent oxidation. Samples were prepared at two Fe-loadings (0.05 and 0.5 mol Fe added per kg clay) and equilibrated for 1 and 30 days under anoxic conditions (O2 < 0.1 ppm), followed by exposure to ambient air. Iron solid-phase speciation and mineral identity was analysed by ⁵⁷Fe Mössbauer spectroscopy and synchrotron X-ray absorption spectroscopy (XAS). Mössbauer analyses showed that Fe(II) was partially oxidized (14–100% of total added Fe²⁺) upon sorption to Syn-1 under anoxic conditions. XAS results revealed that the added Fe²⁺ mainly formed precipitates (layered Fe minerals, Fe(III)-bearing clay minerals, ferrihydrite, and lepidocrocite) in different quantities depending on the Fe-loading. Exposing the suspensions to ambient air resulted in rapid and complete oxidation of sorbed Fe(II) and the formation of Fe(III)-phases (Fe(III)-bearing clay minerals, ferrihydrite, and lepidocrocite), demonstrating that the clay minerals were unable to protect ferrous Fe from oxidation, even when equilibrated 30 days under anoxic conditions prior to oxidation. Our findings clarify the role of clay minerals in the formation and stability of Fe-bearing solid phases during redox cycles in periodically anoxic environments.
Pseudo-spherical cubic-shaped nanoparticles of spinel ferrite CuFe2O4 have been prepared using a two-stage process. At first, an evaporation of levitating copper–iron drop into mix of helium–air gas flow took place, which resulting in copper ferrite-based powders. Then, such powders were additionally oxidized trough the heterogeneous auto-wave combustion in open air. We studied the effect of performing the synthesis in either an air or a helium environment on the phase composition of nanoparticles, and how the use of a post-synthesis annealing step modifies this, using room temperature ⁵⁷Fe Mössbauer spectroscopy. By applying this technique, we are able to distinguish between the normal (non-magnetic) and inverse cubic (magnetic) phases of CuFe2O4, which is usually inaccessible using X-ray diffraction, as well as quantifying their relative amounts within each sample. Furthermore, we have been able to quantify trace amounts of the tetragonal CuFe2O4, phases that are typically obscured by line-broadening effects within our X-ray diffraction data, which indicates that annealing using a propane flame can also cause a cubic to tetragonal distortion in the crystal structure of the spinel lattice. Finally, by combining our Mössbauer parameters, which are sensitive to the Fe-containing phases only, with X-ray diffraction data, which are sensitive to all phases, we report on the full phase composition for the first time for nanoparticles produced via this synthesis route.
We report on the epitaxial growth and the characterization of thin FePt films and the subsequent patterning of magnetic lattice structures. These structures can be used to trap ultracold atoms for quantum simulation experiments. We use molecular beam epitaxy to deposit monocrystalline FePt films with a thickness of 50 nm. The films are characterized with X-ray scattering and Mössbauer spectroscopy to determine the long range order parameter and the hard magnetic axes. A high monocrystalline fraction was measured as well as a strong remanent magnetization of M = 900 kA/m and coercivity of 0.4 T. Using electron beam lithography and argon ion milling, we create lattice patterns with a period down to 200 nm, and a resolution of 30 nm. The resulting lattices are imaged in a scanning electron microscope in the cross-section created by a focused ion beam. A lattice with continuously varying lattice constant ranging from 5 μm down to 250 nm has been created to show the wide range of length scales that can now be created with this technique.
Antimony (Sb) is a naturally occurring element; it is enriched in the environment by anthropogenic activities. Like other metalloid species, Sb partitions to mineral phases such as oxyhydroxides. In reducing environments, Fe(III) may serve as a terminal electron acceptor during dissimilatory iron reduction leading to its transformation. Relatively little is known concerning the effect of Sb(V) on the precipitation of biogenic minerals in relation to microbiologically mediated redox reactions. To further our understanding, Sb-bearing ferrihydrites (0.5 g) with variable Sb/(Fe + Sb) molar ratios of 0.04, 0.06 and 0.1, were incubated in the presence of Shewanella oneindensis MR-1 (1 x 10⁸ cell mL⁻¹) under N2 atmosphere. Additionally, we synthesized abiotic GR1(CO3²⁻) in the presence of Sb(V) to examine the effect of Sb(V) on this mineral formation and stabilization. A combination of wet chemistry and solid analysis techniques (XRD, Mössbauer and Raman spectroscopies) was used to characterize the reactions.
The Sb loading affected the rate and the extent of bio-reduction compared with pure ferrihydrite. Only a minor fraction of the total Sb, less than 0.5 %, was released into the solution by the end of the incubation period, suggesting that the metalloid partitioned mainly in a newly formed phase. Furthermore, XPS analyses showed the presence of Sb(V) and Sb(III) species on the biogenic minerals. Magnetite was the main biogenic precipitate (91 %) in the absence of Sb(V). Increasing of the molar ratios [Sb/(Fe + Sb)] to 0.1 resulted mainly in the precipitation of carbonated green (47 %) rust and goethite (37 %). Abiotic green rust synthesis carried out in the presence of Sb(V) indicated the latter’s stabilizing effect on the green rust structure, as for phosphate species. Thus, it is likely that Sb(V) preserve biogenic green rust, hindering its transformation to more thermodynamically stable phases.
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