Mössbauer and X-ray fluorescence study of sediments from Samana Bay,Dominican Republic

The chemical state of iron in sediments collected from Samana Bay has been determined by Mössbauer spectroscopy. The Mössbauer spectra were composed of two paramagnetic doulets, which correspond to high=spin ferric and ferrous components. Based on the Mössbauer spectra, the possible origin of the different types of sediments are discussed. The mercury contamination calculated from X-ray fluorescence results for some sediments is shown in a comparative form.     

Analysis of the iron state in iron containing vitamins and dietary supplements by Mössbauer spectroscopy

An analysis of iron in some commercial products of vitamins and dietary supplements containing ferrous fumarate, ferrous bisglycinate chelate (Ferrochel^®) and ferrous sulfate was made by Mössbauer spectroscopy. Various ferric and ferrous impurities were found. Two vitamin products contained major iron compounds that did not correspond to ferrous fumarate or ferrous bisglycinate chelate announced by the manufacturer.     

Mössbauer spectroscopic studies of tungsten ores

Tungsten ores from Degana, Rajashthan State, India are studied using Mössbauer spectroscopy. The low grade ore exhibits two types of mineral assemblages as per chemical states of iron. The relation between ferrous/ferric ratio and tungsten concentration also supports the existence of two types of mineral assemblages. The Mössbauer spectroscopy of concentrate ore samples has shown the absence of iron. The energy dispersive X-ray fluorescence spectroscopy on the contrary has evidenced the presence of iron in concentrate ore samples but at lower concentration on comparison with low grade ores. These differences in behaviour in the above spectroscopic studies may be additionally due to higher attenuation of -radiations and higher atomic weight material in the ore concentrates.     

Identification of crystalline structures using Mössbauer parameters and artificial neural network

Mössbauer spectroscopy is a useful technique for characterizing the valencies, electronic and magnetic states, coordination symmetries and site occupancies of Fe cations. The Mössbauer parameters of Isomer Shift (I.S.) and Quadrupole Splitting (Q.S.) are useful to distinguish paramagnetic ferrous and ferric ions in several substances, while the internal magnetic field provides information on the crystallinity. A correlation is being sought between Mössbauer parameters and several structure properties of some iron-containing minerals using Artificial Neural Networks (ANN). Distinct regions of crystalline structures are defined when any two parameters are plotted, but in several cases superposition of these regions leads to erroneous conclusions. We have tried to eliminate this difficulty by using convenient axes. These axes form n-dimensional vectors as input to our ANN. In recent years ANN has shown to be a powerful technique to solve problems as pattern recognition, optimization, preview ups and downs in stock market, automatic control and identification of a mineral from a Mössbauer spectrum or Mössbauer data bank. Using ANN we have been successful in identification of crystalline structures from plots of Mössbauer spectral parameters of I.S., Q.S., and structure properties of mean metal-oxygen distance in coordination site. Results using ANN in identification of crystalline structures using Mössbauer parameters of I.S., Q.S., and polyhedral volume of a coordination site are presented.     

Surface structure of Fe(III)-containing binary hydroxide systems

A brief overview is given of recently obtained data on the surface structure and composition of various iron(III)-containing nickel hydroxide systems, as studied using transmission Mössbauer spectroscopy supplemented by atomic absorption, Auger electron and Fourier transform infrared spectroscopic data. The systems studied include coprecipitated binary Ni(II)–Fe(III) hydroxides in a wide range of compositions, ferric hydroxide precipitated on the surface of -Ni(OH)₂ crystallites, ferric hydroxo complexes adsorbed onto nickel hydroxides from alkaline electrolytes and the products of their hydrolysis.     

Emission Mössbauer spectroscopic studies on mixed-valence states of57Fe atoms produced in57Co-labeled trinuclear cobalt-iron carboxylates

Mixed-valence states of⁵⁷Fe-atoms produced after EC-decay of⁵⁷Co in oxo-centered trinuclear cobalt-iron carboxylates have been studied by means of emission Mössbauer spectroscopy. The emission Mössbauer spectra show nearly the same temperature dependence of the mixed-valence state as found in the absorption Mössbauer spectra of the corresponding trinuclear iron carboxylates. The results indicate that most of the decayed atoms keep their position at the sites of original⁵⁷Co atoms.     

Untersuchung eisenhaltiger Fertigarzneimittel mit Hilfe der M?ssbauer-Spektroskopie

Zusammenfassung Die Möglichkeiten der Mössbauer Spektroskopie zur qualitativen und quantitativen Charakterisierung eisenhaltiger Fertigarzneimittel und Naturprodukte werden anhand einiger experimenteller Beispiele aufgezeigt und diskutiert. Das Verfahren ermöglicht rasche Aussagen über den Oxidationszustand des Eisens sowie eventuelle Verunreinigungen durch andere Eisenverbindungen.

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Examination of iron containing medicaments by means of Mössbauer spectroscopy

Summary The possibilities of Mössbauer spectroscopy for the qualitative and quantitative characterization of iron contained in medicaments and natural tonica are demonstrated and discussed by several experimental examples. The method provides a means for rapid elucidation of the oxidation state of iron and the possible presence of other contaminating iron compounds.

Herrn Prof. Dr. R. Bock zum 65. Geburtstag in Dankbarkeit gewidmet     

Etude par effet Mössbauer des composés de type “bronzes fluorés” MxFeF3 (M = K,Rb, Cs,NH4)

The hexagonal, tetragonal and pyrochlore-type nonstoichiometric iron fluorides M_xFeF₃ (M = K, Rb, Cs, NH₄) have been studied by Mössbauer spectroscopy over the temperature range 4.2 to 295 K. The magnetic transition temperatures have been determined. The ferrous and ferric ions remain in discrete oxidation states indicating the absence of charge hopping. The broadened lines of the spectra of the hexagonal and tetragonal phases are consistent with the disordering of Fe²⁺ and Fe³⁺ in the structure. By contrast, the narrow linewidths of the spectra of the pyrochlore-type phases characterize a structural ordering between the ferrous and ferric ions.     

Oxide Transformation During Preparation of Black Pottery in Hungary

Traditional black pottery produced in Nádudvar, E-Hungary, was studied by ⁵⁷Fe Mössbauer spectroscopy, X-ray diffractometry and microscopy. Quartz, feldspar, clay minerals (kaolinite, smeetite, illite) and calcite were identified in the basic clay material by X-ray diffractometry (XRD). Mössbauer spectroscopy (MS) of the original clay revealed that about 35% of iron compounds were present in goethite while the rest in clay minerals (illite and smectite). After firing the clay in air using an electric furnace (red pottery is prepared in the same way), the Mössbauer spectra showed hematite as the only iron oxide or hydroxide phase, being in good agreement with X-ray diffractometry. In the black product itself, fired in the traditional open-flame furnace, the Mössbauer spectra reflected the presence of iron in magnetite and in sheet silicates with approximately the same relative ratio of oxides and silicates as in the starting material. This can be interpreted as a result of the transformation of goethite to hematite in the first step of firing (in air), and as a reduction of hematite to magnetite in the second step of firing (closed from air). A significant difference was found in the distribution of iron at the Fe²⁺ and Fe³⁺ cation sites in the black surface (more Fe²⁺) and at the dark gray bulk of the fired pottery (less Fe²⁺), showing that the reduction of Fe³⁺ occurs in the silicates instead of further reduction of the magnetite (e.g., to wüstite).     

Methyl methacrylate-n-butyl methacrylate copolymer containing ferric chloride: Mössbauer study

Methyl methacrylate /MMA/-n-butyl methacrylate /nBuMA/ copolymer containing anhydrous ferric chloride was prepared by free radical polymerization at 70 °C. TGA studies showed that the addition of ferric chloride increases the thermal stability of copolymer by 90 °C. Mössbauer studies of the copolymer were carried out to determine the oxidation state and environments of iron in the copolymer. Mössbauer studies of the copolymer heated at 150 °C, 300 °C and 500 °C for 1 h showed that during the thermal degradation, no reduction of Fe³⁺ takes place.     

Determination of thin surface layers in-situ by the conversion electron mössbauer spectroscopy /CEMS/, using a parallel plate avalanche counter /PPAC/

In the present paper we describe a technique for the determination of thin layer thicknesses by the conversion electron Mössbauer spectroscopy /CEMS/, using a new alternative method, a parallel plate avalanche counter /PPAC/, operating with the ketone gas in the ionization chamber. We determined the thickness of iron and magnetite on steel.     

Quantitative multielemental analysis of titaniferous magnetites

Two representative titaniferous magnetite samples procured from Moulabhanj, Orissa, India have been studied by PIXE, EDXRF, Mössbauer spectroscopy, and XRD techniques. Major iron-bearing phases identified in the samples by Mössbauer spectroscopy and XRD are magnetite, hematite, ferrous ilmenite and ferric ilmenite. The Fe²⁺/Fe³⁺ ratio and the relative percentages of different minerals were determined from the resonance areas of Mössbauer spectra. Quantitative multielemental analysis was carried out by energy dispersive X-ray fluorescence (EDXRF) and proton induced X-ray emission (PIXE). Nineteen minor and trace elements have been quantified by EDXRF whereas by PIXE eighteen elements have been analyzed quantitatively. Concentrations of trace elements determined by EDXRF and PIXE were used in interpreting the physico-chemical condition of the depositional basin.     

The charge distribution of iron complexes studied by XPS,Mössbauer spectroscopy,and SCC-MO calculations

A series of iron complexes has been studied by XPS and Mössbauer spectroscopy. Atomic charges and iron atom populations have been estimated from the experimental results and compared with iterative extended Hückel (IEH) calculations as well as with calculations based on a modified form of this method (MIEH).     

Mössbauer and X-ray analysis of corrosion products from surface equipment of oil production well

Wellhead equipment corrosion samples including internal surface of choke were analyzed by means of Mössbauer spectroscopy and X-ray diffractometry. The samples include some impurities of quartz, dolomite and calcite. The resulted analysis shows some iron oxides and oxyhydroxides as surface equipment corrosion products.     

Mössbauer studies of styrene-acrylonitrile copolymers containing ferric chloride

Acrylonitrile-styrene /AN-St/ copolymers of different compositions were prepared, with and without ferric chloride by free radical polymerization. It was found using Mössbauer spectroscopy that reduction of Fe³⁺ to Fe²⁺ takes place during the polymerization. The addition of ferric chloride and the reduction of Fe³⁺ was found to influence the thermal stability of the copolymers.     

Characterization of silica supported Rh-Fe catalysts by Mössbauer technique

Silica supported Rh–Fe catalysts were characterized by means of in situ⁵⁷Fe Mössbauer spectroscopy. The Mössbauer spectra indicated that iron on the silica support existed either as Fe/O/ in the Rh–Fe alloy or as Fe³⁺ in Rh–Fe metal cluster compounds. The (Fe³⁺/Fe/O/) ratio and Mössbauer parameters were found to depend on the (Fe/Rh) atomic ratio in the catalysts. Such dependence corresponded to the change of catalytic properties of the supported Rh–Fe catalyst with the varying (Fe/Rh) ratio.     

Mössbauer spectroscopic study of the temperature dependence of the intramolecular mobility of a cross-linked polymeric cation-exchanger based on acrylic acid

Conclusions The temperature transition of a solvated cross-linked polymer (the SGK-7 carboxyl cation-exchanger, which contains iron(III) ions) from the solid state to a state characterized by intense intramolecular motions was detected and studied by Mössbauer spectroscopy. Triggering of two types of motions was demonstrated: high-frequency vibrations of atoms with a higher amplitude (manifested by a sharp decrease in the probability of the Mössbauer effect) and slower (conformational) motions (manifested by a change in the shape of the spectrum). The parameters of the motions were determined within the framework of the lattice model and the effect of the solvating liquid on the nature of the transition was demonstrated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1740–1745, August, 1985.     

Mössbauer spectroscopic study of the reductive decomposition of iron(III) complexes

Iron injections containing high spin iron(III) complexes may undergo a reductive decomposition during preparation or storage. This process was investigated by the Mössbauer spectroscopy of ice samples prepared by quick-freezing of the injection. The comparison of three model compounds and the correlation between the osmotic pressure of the solutions and their iron(II) concentration formed in the decomposition process and determined by Mössbauer measurements revealed the reason and mechanism of the decomposition.     

Mössbauer study of hydrogenated Fe-Zr amorphous alloys

The effect of electrochemical hydrogenation was investigated in Fe₉₀Zr₁₀ and Fe₈₉Zr₁₁ amorphous alloys by means of⁵⁷Fe Mössbauer spectroscopy. Significant changes in the Mössbauer spectra as well as in the hyperfine field distribution of hydrogenated samples were found with increasing hydrogen concentration. It was established that the dependence of Curie temperature on hydrogen content had a maximum, and the hydrogen had two mean localization sites. By comparing the Mössbauer spectra of hydrogenated samples as-quenched and annealed before hydrogenation it was shown that low-temperature relaxation processes were going on at aging temperature as low as 150°C in this amorphous alloy and the low-temperature relaxation processes modify the localization of hydrogen. The combination of the hydrogenation and Mössbauer techniques gives a very sensitive method for detecting structural changes.     

Mössbauer and ESR study of the formation of phthalocyanineiron(II) pyridine adduct in the supercage of NaY,KY, and RbY zeolite

Phthalocyanineiron(II) (FePc) and phthalocyaninato[(2-)bispyridine]iron(II) (FePc(py)₂) synthesized in supercage of NaY, KY and RbY zeolite have been characterized by Mössbauer and ESR spectroscopy. The yield of formation of the pyridine adduct depends on the ionic radius of the alkali ions introduced into the supercage, but not on the number of iron ions trapped in the cages, suggesting that free space in the supercage was the most important factor for the formation of the FePc-py-adducts.