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Using different iron sources of industrial iron oxide, loess, slag, and golden soil, iron elements were introduced into the formula respectively, and celadon samples were prepared in a reducing atmosphere. To reveal the influence of iron source on glaze color, the celadon samples were analyzed by Spectrophotometer, X-ray fluorescence spectroscopy, X-ray diffractometer, scanning electron microscope, and X-ray photoelectron spectrometer. The results show that the glaze color of the samples is quite different, samples using iron oxide and golden soil as iron source raw materials are sky-green, the loess sample is olive green, and the slag sample is similar to the bean green. There are many quartz crystals in the glaze of iron oxide samples, and the turbidity is high. The liquid-liquid phase separation size close to the quartz crystal is large, and far away from the crystal is small. Industrial iron oxide is the easiest to reduce, followed by goethite in golden soil, and reduction of hematite in slag and the iron in loess in the form of isomorphic is successively more difficult. The difference in the form of occurrence of iron is the most essential factor that causes the difference in glaze color. [ABSTRACT FROM AUTHOR]

Jun ware is stoneware created in the late Northern Song dynasty (12th century) with a blue glaze combining transparent-blue and whitish-opaque submillimetric areas. The glaze has a glass nanostructure with lime-rich droplets in a silica-rich matrix resulting from a high temperature liquid-liquid phase separation. Calcium-rich opaque and calcium-poor transparent areas are combined. Iron is more oxidised in the calcium rich areas (≈17–20% Fe2+) than in the calcium poor areas (≈60–70% Fe2+) of the glaze. Therefore, iron is oxidised in the lime-rich droplets and reduced in the silica-rich matrix. The sky- like appearance of the glaze is due to the combination of the light absorption in the transparent-dark-blue Fe2+ rich areas and scattering in the white-yellowish Fe3+ rich areas. Copper appears mainly oxidised but in the red areas a few small copper nanoparticles are present and iron appears more oxidised. The result indicates the simultaneous reduction of copper and oxidation of iron. • Lime-rich and silica-rich glass nanostructure. • Iron is mainly oxidised in the lime-rich droplets and reduced in the silica matrix. • Copper is mainly present as Cu+. • Simultaneous reduction of copper and oxidation of iron in the red areas. [ABSTRACT FROM AUTHOR]

A variety of Magnetic Resonance Imaging (MRI) techniques are known to be sensitive to brain iron content. In principle, iron sensitive MRI techniques are based on local magnetic field variations caused by iron particles in tissue. The purpose of this study was to investigate the sensitivity of MR relaxation and magnetization transfer parameters to changes in iron oxidation state compared to changes in iron concentration. Therefore, quantitative MRI parameters including R1, R2, R2∗, quantitative susceptibility maps (QSM) and magnetization transfer ratio (MTR) of post mortem human brain tissue were acquired prior and after chemical iron reduction to change the iron oxidation state and chemical iron extraction to decrease the total iron concentration. All assessed parameters were shown to be sensitive to changes in iron concentration whereas only R2, R2∗ and QSM were also sensitive to changes in iron oxidation state. Mass spectrometry confirmed that iron accumulated in the extraction solution but not in the reduction solution. R2∗ and QSM are often used as markers for iron content. Changes in these parameters do not necessarily reflect variations in iron content but may also be a result of changes in the iron’s oxygenation state from ferric towards more ferrous iron or vice versa.

Electronic states of iron in the lower mantle's dominant mineral, (Mg,Fe,Al)(Fe,Al,Si)O3 bridgmanite, control physical properties of the mantle including density, elasticity, and electrical and thermal conductivity. However, the determination of electronic states of iron has been controversial, in part due to different interpretations of Mössbauer spectroscopy results used to identify spin state, valence state, and site occupancy of iron. We applied energy-domain Mössbauer spectroscopy to a set of four bridgmanite samples spanning a wide range of compositions: 10–50% Fe/total cations, 0–25% Al/total cations, 12–100% Fe3+/total Fe. Measurements performed in the diamond-anvil cell at pressures up to 76 GPa below and above the high to low spin transition in Fe3+ provide a Mössbauer reference library for bridgmanite and demonstrate the efects of pressure and composition on electronic states of iron. Results indicate that although the spin transition in Fe3+ in the bridgmanite B-site occurs as predicted, it does not strongly affect the observed quadrupole splitting of 1.4 mm/s, and only decreases center shift for this site to 0 mm/s at ~70 GPa. Thus center shift can easily distinguish Fe3+ from Fe2+ at high pressure, which exhibits two distinct Mössbauer sites with center shift ~1 mm/s and quadrupole splitting 2.4–3.1 and 3.9 mm/s at ~70 GPa. Correct quantification of Fe3+/total Fe in bridgmanite is required to constrain the efects of composition and redox states in experimental measurements of seismic properties of bridgmanite. In Fe-rich, mixed-valence bridgmanite at deep-mantle-relevant pressures, up to ~20% of the Fe may be a Fe2.5+ charge transfer component, which should enhance electrical and thermal conductivity in Fe-rich heterogeneities at the base of Earth's mantle. [ABSTRACT FROM AUTHOR]

Mg-Al-Si-O glassy systems have a great importance in a wide range of industrial applications, specifically as an electrolyte for molten oxide electrolysis processes in steelmaking. Understanding how the iron oxidation state of the raw material (Fe2+/Fe3+) and its corresponding amount influence this glassy system's properties will be the aim of the current work. Iron oxides (as Fe 2 O 3 or Fe 3 O 4) were used to dope Mg-Al-Si-O system obtaining amorphous materials through an unconventional method: Laser Floating Zone (LFZ). Above 8% mol of Fe formation of magnetic phases or iron clusters, were observed in the glass matrix. Samples with Fe 2 O 3 showed a higher crystal concentration, when compared with Fe 3 O 4. The electron paramagnetic resonance measurements show a strong dependence on the iron source (Fe 3 O 4 or Fe 2 O 3). In addition, the magnetization decreases linearly with iron content, independently of iron oxidation state, except for samples with a higher concentration of Fe 2 O 3 (15% mol), due to sample crystallization. Moreover, with Fe 3 O 4 as raw material there is an improvement (~250 times) of the electrical conductivity when compared with Fe 2 O 3. The results show that the presence of Fe2+ on the glass influences the electrical conductivity, which could have impact in the efficiency of molten oxide electrolysis process. [ABSTRACT FROM AUTHOR]

Ferrous ( Fe 2 + ) and ferric ( Fe 3 + ) iron content in mineral samples was determined from total iron (as obtained, for instance, from X-ray fluorescence analysis) and mass increase upon switching the purge gas from inert to oxidizing, at high temperature, in a thermogravimetric analysis. The method was validated using analytical-grade ilmenite ( FeTiO 3 , or Fe 2 + O · TiO 2 ) and magnetite ( Fe 3 O 4 , or Fe2+ · Fe23+O3). The estimated mass percentages of FeO are less than the expected values, according to chemical composition, by 1.1 and 1.2 percentage points for ilmenite and magnetite, respectively. The application of this method is further illustrated by determining the Fe 2 + and Fe 3 + content, expressed as FeO and Fe 2 O 3 , in three samples of igneous rocks. [ABSTRACT FROM AUTHOR]

The X‐ray crystal structure of tris[N‐(2‐hydroxyethyl)‐2,2′‐iminodiethanolato]tris(2,2′,2′′‐nitrilotriethanolato)tetrairon(II)triiron(III) bis(perchlorate), [Fe7(C6H12NO3)3(C6H13NO3)3](ClO4)2 or [Fe7(tea)3(tea‐H)3](ClO4)2 (tea‐H3 is triethanolamine), is known from the literature [Liu et al. (2008). Z. Anorg. Allg. Chem.634, 778–783] as a heptanuclear coordination cluster. The space group was given as I213 and is reinvestigated in the present study. We find a new space‐group symmetry of Pa and could detect O—H hydrogens, which were missing in the original publication. Consequences on the Fe oxidation states are investigated with the bond‐valence method, resulting in a mixed‐valence core of four FeII and three FeIII centres. Symmetry relationships between the two space groups and the average supergroup Ia are discussed in detail. [ABSTRACT FROM AUTHOR]

We have used X-ray photoelectron spectroscopy (XPS) as a novel method to investigate the causes of colour changes in a reddish limestone under irradiation by a Q-switched Nd:YAG 1064 nm laser. We irradiated clean dry and wet surfaces of Pidramuelle Roja , a building stone frequently used in the Asturian heritage, at fluences ranging from 0.12 to 1.47 J cm −2 . We measured the colour coordinates and undertook XPS analysis of the state of oxidation of iron both before and after irradiation. Visible colour changes and potential aesthetic damage occurred on dry surfaces from a fluence of 0.31 J cm −2 , with the stone showing a greening effect and very intense darkening. The colour change on dry surfaces was considerably higher than on wet surfaces, which at the highest fluence (1.47 J cm −2 ) was also above the human visual detection threshold. The use of XPS demonstrated that the change in colour (chroma and hue) is associated with a reduction in the iron oxidation state on dry surfaces during laser irradiation. This points out to a potential routinary use of XPS to analyse causes of colour changes during laser cleaning in other types of coloured building stones. [ABSTRACT FROM AUTHOR]

To develop Raman spectroscopy as a quantitative tool in both geosciences and planetary sciences the effect of iron oxidation state (Fe3+/Fetot) on the Raman spectra of basaltic and pantelleritic glasses has been investigated. We have used remelted pantellerite from Pantelleria Island and synthetic iron-rich basaltic glasses [from Chevrel et al. (2014)]. The Raman spectra of pantelleritic glasses reveal dramatic changes in the high wavelength region of the spectrum (800-1200 cm-1) as iron oxidation state changes. In particular the 970 cm-1 band intensity increases with increasing oxidation state of the glass (Fe3+/Fetot ratio from 0.24 to 0.83). In contrast, Raman spectra of the basaltic glasses do not show the same oxidation state sensitivity (Fe3+/Fetot ratio from 0.15 to 0.79). A shift, however, of the 950 cm-1 band to high wavenumber with decreasing iron oxidation state can be observed. We present here two empirical parameterizations (for silica- and alkali-rich pantelleritic glasses and for iron-rich basaltic glasses) to enable estimation of the iron oxidation state of both anhydrous and hydrous silicate glasses (up to 2.4 wt% H2O). The validation of the models derived from these parameterizations have been obtained using the independent characterization of these melt samples plus a series of external samples via wet chemistry. The "pantelleritic" model can be applied within SiO2, FeO, and alkali content ranges of ~69-75, ~7-9, and ~8-11 wt%, respectively. The "basaltic" model is valid within SiO2, FeO, and alkali content ranges of ~42-54, ~10-22, and ~3-6 wt%, respectively. The results of this study contribute to the expansion of the compositionally dependent database previously presented by Di Genova et al. (2015) for Raman spectra of complex silicate glasses. The applications of these models range from microanalysis of silicate glasses (e.g., melt inclusions) to handheld in situ terrestrial field investigations and studies under extreme conditions such as extraterrestrial (i.e., Mars), volcanic, and submarine environments. [ABSTRACT FROM AUTHOR]

Analysis of the oxidation state and coordination geometry using pre-edge analysis is attractive for heterogeneous catalysis and materials science, especially for in situ and time-resolved studies or highly diluted systems. In the present study, focus is laid on iron-based catalysts. First a systematic investigation of the pre-edge region of the Fe K-edge using staurolite, FePO4, FeO and α-Fe2O3 as reference compounds for tetrahedral Fe2+, tetrahedral Fe3+, octahedral Fe2+ and octahedral Fe3+, respectively, is reported. In particular, high-resolution and conventional X-ray absorption spectra are compared, considering that in heterogeneous catalysis and material science a compromise between high-quality spectroscopic data acquisition and simultaneous analysis of functional properties is required. Results, which were obtained from reference spectra acquired with different resolution and quality, demonstrate that this analysis is also applicable to conventionally recorded pre-edge data. For this purpose, subtraction of the edge onset is preferentially carried out using an arctangent and a first-degree polynomial, independent of the resolution and quality of the data. For both standard and high-resolution data, multiplet analysis of pre-edge features has limitations due to weak transitions that cannot be identified. On the other hand, an arbitrary empirical peak fitting assists the analysis in that non-local transitions can be isolated. The analysis of the oxidation state and coordination geometry of the Fe sites using a variogram-based method is shown to be effective for standard-resolution data and leads to the same results as for high-resolution spectra. This method, validated by analysing spectra of reference compounds and their well defined mixtures, is finally applied to track structural changes in a 1% Fe/Al2O3 and a 0.5% Fe/BEA zeolite catalyst during reduction in 5% H2/He. The results, hardly accessible by other techniques, show that Fe3+ is transformed into Fe2+, while the local Fe-O coordination number of 4-5 is maintained, suggesting that the reduction involves a rearrangement of the oxygen neighbours rather than their removal. In conclusion, the variogram-based analysis of Fe K-edge spectra proves to be very useful in catalysis research. [ABSTRACT FROM AUTHOR]

Self foaming cellular glass–ceramics were obtained by sintering mixtures of a basalt scoria and soda lime cullet for 15 min at 1050 and 1100 °C. The effect of polyvalent ions (Fe 3 + /Fe 2 + ) on porosity (from 53 to 86 vol.%) and crystallization was studied for different mixtures subjected to different thermal treatments. Due to the range of mechanical strength values (crushing strength from 2 to 50 MPa) and total porosity achieved, these porous glass–ceramics could be applied as building materials, as lightweight aggregate for concrete or as lightweight panels. [ABSTRACT FROM AUTHOR]

BACKGROUND Electro-Fenton technology has demonstrated great potential for the degradation of recalcitrant organic contaminants in polluted wastewaters. In this technology, the decomposition of hydrogen peroxide is catalysed by the presence of iron, and powerful oxidants, hydroxyl radicals, are generated. However, there is concern over the reduction of iron released in the treated effluent. Therefore, retention of catalyst is required, and advances in electro-Fenton heterogeneous catalysis are necessary. In this study, the use of polyacrylamide hydrogel was evaluated as a support for the iron, and the performance of the catalyst (Fe- PH) developed was assayed in the electro-Fenton degradation of two dyes, Reactive Black 5 and Blue Sella Solid. RESULTS First, the synthesis of Fe- PH catalyst was studied. The results showed that the loaded hydrogel with a mixture of Fe( II) and Fe( III) in 1:2 molar ratio reached the highest decolourization efficiency. The performance of the optimized Fe- PH catalyst was evaluated in the decolourization of the selected dyes. These studies demonstrated the satisfactory performance of electro-Fenton using Fe- PH catalyst as well as its reusability. CONCLUSION In summary, the Fe- PH catalyst developed gives the promise of wastewater treatment by means of an electro-Fenton process. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: Sandstone-hosted unconformity-related U deposits in the Athabasca Basin at McArthur River Zone 4 and Maurice Bay as well as barren alteration systems at Wheeler River Zone “K” and Spring Point are surrounded by an outer, peripheral zone of illite and an inner, central zone of chlorite alteration. The oxidation state of Fe determined by 57Fe Mössbauer spectroscopy of illite, sudoite, and clinochlore from these systems indicates that pre-ore illite contains mostly Fe3+ (Fe3+/ΣFe=0.77–1.00), reflecting formation from a predominantly oxidizing basinal fluid. Lower Fe3+/ΣFe ratios are recorded by late pre-ore sudoite and clinochlore occurring near faulted unconformities, consistent with the contribution to the chlorites from reducing basement-derived fluids. Sudoite and clinochlore in the alteration halo of barren systems are more reduced (Fe3+/ΣFe median=0.3–0.4) than sudoite from mineralized systems (Fe3+/ΣFe median=0.45–0.55). Sudoite from both systems becomes broadly more oxidized with increasing distance from the fault zone. Variations in the Fe3+/ΣFe ratios of sudoite and clinochlore support a mechanism in which Fe2+ transported by reducing basement-derived fluids is partially oxidized to Fe3+ by basinal fluids prior to incorporation into the chlorite. Thus, scarcity of oxidizing U-bearing basinal fluids available for interaction with reducing basement fluids is a critical factor precluding U mineralization in barren systems. Trends of decreasing Fe3+/ΣFe ratios in sudoite coupled with decreasing 207Pb/206Pb ratios of leachable Pb can be used as geochemical vectors to the sites of potential U mineralization. [Copyright &y& Elsevier]

Abstract: We investigated the ferric iron (Fe3+) concentration in (Mg,Fe)O ferropericlase using the flank method applied to Mg–Fe interdiffusion couples of ferropericlase. Diffusion couples with Mg/(Mg+Fe) in the range 0.44 to 1 were annealed at temperatures of 1673–1873K and pressures of 5–24GPa over a wide range of oxygen fugacities. Oxygen fugacity was controlled by Fe, Ni, Mo, and Re metal capsules and their corresponding oxide phases. Based on our results and available experimental data, we derived an equation for the Fe3+ solubility in ferropericlase applicable to depths at the top of the lower mantle: [Fe3+]=C (X Fe 4 f O2) m exp{−((1−X Fe)E⁎Mg+X Fe E*Fe+PV*)/RT}, where C=2.6(1)×10−3, m=0.114(3), E*Mg=−35(3) [kJ/mol], E*Fe=−98(2) [kJ/mol], and V*=2.09(3) [cm3/mol]. The value of the oxygen fugacity exponent m implies that Fe3+ mostly occupies tetrahedral sites under these conditions, which is consistent with the results of previously reported Mössbauer spectroscopy studies. Based on this relationship, we calculated the redox conditions of ferropericlase inclusions in diamonds believed to have come from the lower mantle. The estimated oxygen fugacities are close to the upper stability limit of diamond in mantle peridotite at the top of the lower mantle at adiabatic or slightly superadiabatic temperatures, which suggests that ferropericlase inclusions recorded and preserved the conditions at which diamond was precipitated from carbonates or carbonatite melts near the top of the lower mantle. [Copyright &y& Elsevier]

Abstract: Knowing the redox state of polyvalent elements in glass is important for understanding and controlling the glass properties. In this work we demonstrate the applicability of X-ray photoelectron spectroscopy (XPS) in the determination of the iron redox state in a multicomponent glass having a basalt-like composition. The XPS measurements reveal an entropy-driven reduction of ferric iron to ferrous iron upon increasing melt temperature. Furthermore, the local ferric iron enriched domains, i.e., a kind of inhomogeneity in the glass, is identified by means of XPS. It is proved that XPS is a useful and reliable tool for probing both the average redox state and inhomogeneities in glassy materials. [Copyright &y& Elsevier]

We report application of the flank method using the electron microprobe to a suite of twelve (Mg,Fe)O samples with composition 2-47 wt% Fe and Fe/ΣFe = 1 to 11%, where Fe/ΣFe was determined independently using Mössbauer spectroscopy on the same grains used for the flank method measurements. A calibration curve of the form Fe = A + B × (ΣFe) + C × (Lβ/Lα) was fit to the data and gave excellent agreement between Fe/ΣFe calculated from the flank method and Fe/ΣFe determined using Mössbauer spectroscopy. We found the method to be sufficiently sensitive to determine meaningful variations in Fe/ΣFe for geophysically relevant compositions of (Mg,Fe)O (<25 wt% Fe), and calibration parameters remained constant within experimental uncertainty over the course of the entire study (20 months). Flank method measurements on an inhomogeneous sample of synthetic (Mg,Fe)O showed evidence of diffusion processes resulting from rupture of the capsule during the high-pressure experiment and the possibility to measure Lβ/Lα variations with a spatial resolution of a few microns. We detected the presence of exsolved magnesioferrite in a suite of (Mg,Fe)O single crystals using transmission electron microscopy and Mössbauer spectroscopy. Flank method measurements on the same suite of single crystals showed enhanced Fe/ΣFe values, consistent with the presence of magnesioferrite even though the grains were too small to be resolved by conventional electron microprobe measurements. [ABSTRACT FROM AUTHOR]

Supported bimetallic PtFe catalyst is one of the most promising candidates for preferential CO oxidation (PROX) in H2 for fuel cells. We are interested in developing novel PtFe catalysts which have special architectures and are more excellent in catalytic performance for the PROX reaction. In the present study, three kinds of novel alumina-supported PtFe, PtFe2 and PtFe3 alloy nanoparticles were prepared from Pt(acac)2 and Fe(acac)3 reduced by ethylene glycol in Ar atmosphere at 185 °C. The catalytic experiments showed that the three materials were more active for the PROX reaction under pretreatment both in He and H2 atmospheres as compared to that of Pt/Al2O3 prepared by the same chemical route. Their structural property and iron state were investigated by X-ray diffraction and 57Fe Mössbauer spectroscopy. The obtained results proved that the novel as-prepared PtFe/Al2O3, PtFe2/Al2O3 and PtFe3/Al2O3 materials are clearly different in the architecture and the oxidation state of iron as compared to the conventionally prepared one. [ABSTRACT FROM AUTHOR]

Abstract: The mechanism of formation of [FeIV(O)(N4Py)]2+ (2, N4Py= N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) from the reaction of [FeII(N4Py)(CH3CN)]2+ (1) with m-chloroperbenzoic acid (mCPBA) in CH2Cl2 at −30°C has been studied on the basis of the visible spectral changes observed and the reaction stoichiometry. It is shown that the conversion of 1 to 2 in 90% yield requires 1.5equiv. peracid and takes place in two successive one-electron steps via an [FeIII(N4Py)OH]2+(3) intermediate. The first oxidation step uses 0.5equiv. peracid and produces 0.5equiv. 3-chlorobenzoic acid, while the second step uses 1equiv. peracid and affords byproducts derived from chlorophenyl radical. We conclude that the FeII(N4Py) center promotes O–O bond heterolysis, while the FeIII(N4Py) center favors O–O bond homolysis, so the nature of O–O bond cleavage is dependent on the iron oxidation state. [Copyright &y& Elsevier]

A quasi-on-line method of measurement of the oxidation states of iron coupled with a GFAAS analysis is reported for the trace conditions found in atmospheric waters. This technique is based on the formation of a specific complex [Fe(FZ)3]4- between Fe(II) and ferrozine (FZ). tC18 solid-phase extraction cartridges (Sep-Pak) are used to separate the [Fe(FZ)3]4- and Fe(III) so as to limit the risk of redox evolution of the sample. The adaptation to dilute aqueous media, via acidification at pH = 2 of rainwater sample, and atmospheric interferences are discussed, and the Fe(II) recovery in rainwaters is determined. This method coupled with a quasi-on-line sampling protocol has been tested on rains collected in Guadeloupe Island (Caribbean Sea, 16°N, 61°W) during a field campaign in May 2005. Our results show that the proposed method can satisfactorily be applied to the determination of Fe(II) and Fe(III) in atmospheric waters under in situ conditions. [ABSTRACT FROM AUTHOR]

We have established a method to determine the oxidation state of Fe using the electron microprobe--the "flank method." This method has the possibility to analyze simultaneously the major-element chemistry on the same spot. The method is based on FeL X-ray emission spectra that show a concomitant change of both the intensity and the wavelength of the soft FeLα and FeLβ emission lines. The method has been developed for garnets using well-characterized synthetic samples, and an empirical correction scheme has been established for self-absorption of the FeL X-ray emission. This enables the unambiguous correlation of measured intensity ratios of FeLα/FeLβ X-ray emission to the oxidation state in garnet. The flank method can be used with routine microprobe settings (e.g., 15 kV, 60 nA) and, for garnets, with minimum beam size. This way, Fe3+/ΣFe and major and trace elements can be determined within 10 minutes on the microscale. The resulting accuracy of Fe3+/ΣFe is then ±0.04 for garnets at 10 wt% total Fe. Application to natural garnet megacrysts with 8 wt% total Fe and Fe3+ known from Mössbauer spectroscopy yields excellent agreement between the two methods. For practical application, the calibration can be achieved by using three natural standards and fitting the data to Fe2+ and Fe3+ with linear equations. Through repeated measurements on homogeneous samples, the error in Fe3+/ΣFe becomes approximately ±0.02 (1σ). Optimization of analytical parameters such as beam current, measurement time, and repetition of analyses, will further lower the uncertainty. [ABSTRACT FROM AUTHOR]

X-ray absorption near edge structure spectroscopy was applied in order to investigate differences in iron chemical state between the nerve cells of substantia nigra (SN) representing Parkinson’s disease (PD) and those of control cases. Autopsy samples were cut using a cryotome, and were not fixed and not embedded in paraffin. The comparison of the absorption spectra near the iron K-edge measured in melanized neurons from SN of PD and control samples did not show significant differences in iron oxidation state. Measurements of inorganic reference materials containing iron in the second and third oxidation states indicate that most of the iron in all the nerve cell bodies examined was oxidized and occurred as trivalent ferric iron (Fe3+). [ABSTRACT FROM AUTHOR]

Abstract: The Li1.746Nd4.494FeO9.493 (LNF) ternary phase, located in the Li2O-rich part of the Li2O–Nd2O3–Fe2O3 system, crystallizes with a cubic unit cell of dimension and the space group . Refinement on F resulted in . The structure is comprised of a network of corners, edges and faces sharing the coordination polyhedra of neodymium. In between this skeleton the regular octahedra of oxygen-coordinated iron and trigonal prisms of lithium are located. The Mössbauer spectra revealed the presence of Fe3+, Fe4+ and Fe5+ ions distributed on two symmetry-independent lattice positions. [Copyright &y& Elsevier]

The sandwich (black core) structure in the production of Etruscan-Padan type pottery was investigated. Petrographic, X-ray diffraction (XRD) and Mössbauer data showed that colour changes from core to margin are related to differences in both Fe oxidation state and abundance of maghemite, hercynite and hematite. The occurrence of maghemite and hercynite and the higher quantity of Fe(II) in the cores suggest poor oxygen diffusion in the potsherds during firing. This is congruent with the occurrence of high fractions of paramagnetic Fe in octahedral sites, located in the amorphous phase probably derived from chlorite breakdown, and with the wide range of grain-size distribution of oxidic particles, indicated by the slowing down of superparamagnetic relaxation as temperatures are lowered. [Copyright &y& Elsevier]

The measurement of the soft FeLα and FeLβ X-ray emission spectra by electron microprobe (flank method) allows the determination of the iron oxidation state in minerals if our new method for self-absorption correction is applied. It can be shown that the FeLβ/FeLα ratios obtained with the flank method correlate with Mössbauer quadrupole splitting and crystallographic data. This can be explained by the successive distortion of the iron coordination polyhedra with cation substitution. Thus, the electron microprobe data unexpectedly reveal details of the electrostatic field at the crystallographic site. Although the resolution with respect to hyperfine parameters is lower compared to other methods, the Fe2+/Fe3+ determination by electron microprobe bears several advantages: (i) the small sample amount needed, (ii) the small sampling volume ≤1 μm3, (iii) the simultaneous in situ Fe2+/Fe3+ determination and quantitative chemical analysis, (iv) the easy routine sample preparation, (v) the ready availability of an electron microprobe in comparison to a synchrotron. [ABSTRACT FROM AUTHOR]

The dependence of the ferric–ferrous ratio in silicate melts on oxygen fugacity was studied in the system SiO2(Qz)–NaAlSi3O8(Ab)–CaAl2Si2O8(An)–H2O using Mo¨ssbauer spectroscopy. Experiments were performed under water-saturated conditions at 500 MPa, and at temperatures of 850 and 950 °C, covering a range typical for magmatic processes. The oxygen fugacity was varied in the fO2 range from Cu–Cu2O buffer to slightly more reducing conditions than the wu¨stite–magnetite buffer. The iron redox ratio was determined by analyzing the Mo¨ssbauer parameter distribution that was modeled based on experimental spectra collected at room temperature on the quenched samples. The obtained iron redox ratios show a linear dependence on oxygen fugacity on a logarithmic scale for both temperatures. The iron redox ratio (Fe3+/Fe2+) decreases with temperature for a given oxygen fugacity. The spectroscopic data at 850 °C are in good agreement with Fe3+/Fe2+ ratios derived from element partitioning but show considerable deviations from iron redox ratios predicted by the empirical equation given by Kress and Carmichael [Contrib. Mineral. Petrol. 108 (1991) 82]. This indicates that an extrapolation of this equation to such low temperatures may have large errors. A sample quenched slowly through the temperature range near and below Tg shows considerable differences in the obtained Mo¨ssbauer spectra compared to more rapidly cooled samples, indicating ordering of the iron environment at least in the mesoscopic range. The oxidation state, however, does not differ when compared to the more rapidly quenched melts. [Copyright &y& Elsevier]

The oxidation state of iron in minerals is an important part of analysis. Especially for minerals used as a raw material for metallurgical processes, the oxidation state has a significant impact on the process. One crucial impact is the varying carbon requirement in smelting furnaces, which can be significantly different if the oxidation state is not assessed correctly. Compared to methods usually used to determine the oxidation state, a relatively simple and fast thermogravimetric method is proposed in this article. As a sample, a detailed analyzed chromite sample from Turkey is used. Bulk chemical analysis, Raman spectroscopy, X-ray diffraction, and QEMSCAN® are used to determine the preconditions of the sample. Mössbauer spectroscopy is used as a reference method to determine the oxidation state of iron in the sample. Uncertified wet chemical methods are investigated as well in this paper and the results are compared with the reference measurement. Using a thermochemical simulation tool, parameters for the thermogravimetric method are investigated and the limitation of this method is examined. The mean ferrous ratio in the sample determined by the proposed method is 75.205%, which is only slightly lower than the ferrous ratio of 76% determined by Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]

Micro - X-ray Absorption Near Edge Structure (μXANES) at the Fe K-edge of biological tissues after admission of superparamagnetic iron oxide nanoparticles (SPIONs) has been used to monitor the iron oxidation state in the nanoparticles and in the native tissues. It was found that μXANES technique with submicron spatial resolution is sensitive enough to allow a separation of the contributions from the iron atoms present in SPIONs from the contribution of the atoms representing iron contained in the tissues of the body before the introduction of nanoparticles. The analysis of μXANES showed that SPIONs studied in the present research is found to be quite stable and retains its properties after interaction with tissues in vivo. Thus, such SPIONs are promising for further use in the theranostics for oncology. • μXRF located the areas of high Fe concentration in mice lungs after SPIONs injection. • μXANES distinguished contributions from SPIONs and native iron in the lung tissue. • SPIONs showed chemical and structural stability after in vivo application. [ABSTRACT FROM AUTHOR]

The iron coordination, its oxidation state (Fe2+/Fe tot.), and alkali ratio [Na/(Na + K)] greatly influence the structure and thus the viscosity of volcanic melts, which is known to play a key role in the dynamics of volcanic eruptions. Furthermore, it has been recently reported that volcanic melts can contain iron-bearing nanocrystals and this makes it difficult to isolate and quantify the chemical contribution to the viscosity of magmas. Here, we present Raman spectroscopic and differential scanning calorimetry (DSC) data on nanocrystal-free peralkaline rhyolites with different Fe2+/Fe tot. (0.15–0.84) and Na/(Na + K) (0–1) molar ratios. Raman spectra are used to infer the structural changes occurring with varying iron oxidation state and alkali content, whereas the combination of Raman spectroscopy and DSC measurements allow the characterization of the anhydrous nanocrystal-free viscosity as a function of temperature. Results suggest that at similar and high Fe2+/Fe tot. ratio the Raman spectral feature controlled by the iron coordination changes with Na/(Na + K). Conversely, the change of alkali content at a fixed Fe2+/Fe tot. ratio results in a variation of the spectral feature that reflects the size distribution of rings of tetrahedra in the melt structure. We further discuss the implications of our findings for magma transport and estimate that the viscosity of anhydrous peralkaline rhyolites at the eruptive temperature of 750 °C can increase up to 3.5 log units when Fe2+/Fe tot. and Na/(Na + K) ratios decrease contemporaneously from 0.84 to 0.15 and from 1 to 0, respectively. Finally, the comparison of our viscosity data with those from the literature suggests that the DSC-approach presented and adopted in this study is independent on chemical composition and thus can be used also to retrieve the effect of nanocrystals on the viscosity of volcanic melts. The results presented here have profound implications for the modelling of magma viscosity. • Nanocrystal-free melt viscosity can be retrieved by DSC measurements. • Viscosity increases up to 3 log units with changing Fe2+/Fe tot and Na/(Na/K). • Structural effect of Fe2+/Fe tot and Na/(Na/K) are identified by Raman spectroscopy. • Raman features correlate with viscosity increase. • Glass characterization by Raman spectroscopy is essential for reliable viscosity data. [ABSTRACT FROM AUTHOR]

• The cryo-XANES spectroscopy for fresh, non-fixed, frozen human specimens were applied. • Ovarian tumours with different malignancies were studied. • From one patients two type of samples were analysed: cystic fluid and corresponding tissue. • Specimens contain both chemical form of iron, but substantial is fraction of Fe3+. • The tendency that the malignant tumours contain more fraction Fe2+ compared with the non-malignant ones. Ovarian cancer is one of the most frequent types of gynaecological malignancy among women. Despite the advances in diagnostic techniques, ovarian tumours are still detected at a late stage, thus the survival rate is very low. Iron is an essential metal in the human body, yet its potential role in ovarian carcinogenesis is yet to be determined. The aim of this study was to check if iron oxidation state in tissue and cystic fluid can be treated as an indicator of the malignancy of the ovarian tumours. Another aspect of this study was to investigate the role of iron in carcinogenesis mechanism in ovarian tumour transformation. Synchrotron radiation X-ray absorption near edge structure (SR-XANES) spectroscopy was used to analyze the human ovarian tumour tissues and cystic fluids of different types and grades of malignancy. Fresh, non-fixed, frozen samples were used to analyze the state of iron oxidation in all the biological materials. The samples were obtained from patients requiring surgical intervention. The High Energy X-ray Absorption Spectroscopy (XANES) measurements were performed at the beamline P65 at Petra III Extension, DESY – Deutsches Elektronen - Synchrotron. Fe XANES spectra were collected at selected points of a few different regions of the samples. For each specimen, an average of these points was probed. Having been measured, the spectra were compared with organic and inorganic reference materials. Also, the position of the absorption edge was calculated using the integration method. In all specimens, iron occurred in the oxidation states, Fe2+ and Fe3+, although the fraction of iron in the third oxidation state was substantial, especially in malignant cases. The results also show differences in the chemical form of iron in the tissue and cystic fluids of the same patient. The cryo-XANES measurement carried out for ovarian cancer tissues and cystic fluids showed changes in the chemical form of iron between non-malignant and malignant tumours. For both types of sample can be observed that they contain iron on second and iron on third oxidation state. Moreover, the tendency was observed that malignant tumours of the ovary contain a larger fraction of iron in the second oxidation state compared to non-malignant ones. [ABSTRACT FROM AUTHOR]

A new general model that takes into account the pressure and redox state effect is presented to calculate melt viscosities of natural Fe-bearing melts. This new model is applicable to melts that span a wide range of temperatures (from 733 to 1873 K), pressures (0.001-15 kbar), H2O content (from 0 calculated to be ±0.23 log units of viscosity, which is within or close to experimental uncertainty. The transport properties, including glass transition temperature and melt fragility, can also be calculated from this model. A spreadsheet to calculate the viscosity is provided in an Electronic Supplement. [ABSTRACT FROM AUTHOR]