Search

The polycrystalline compound EuBa 1.3 Pr 0.7 Cu 3 O 7− δ has been prepared and investigated by the means of 141 Pr Mossbauer spectroscopy. The observed 141 Pr Mossbauer isomer shift, δ (at T =4.2 K)=0.10 (15) mm/s relative to PrF 3 , reflect a valence state of 3+ for Pr located at the Ba site in EuBa 1.3 Pr 0.7 Cu 3 O 7− δ . Magnetic order of the Pr sublattice was not observed at T =4.2 K in contrast with the compound Eu 0.3 Pr 0.7 Ba 2 Cu 3 O 7− δ where magnetic order of the Pr sublattice appears at T =12 K. Our results explain why Pr behaves very similar to other 3+ cations (La, Nd) when substituted for Ba in this system, and suggests that suppression of superconductivity by Pr substituted at the rare earth site is a consequence of the hole filling effect.

Potentiodynamic and chronoamperometric polarization measurements, 57Fe conversion electron Mössbauer spectroscopy, X-ray diffractometry and electron microprobe measurements were performed on amorphous and microcsrystalline Fe–25Ni–25Cr alloys coatings electrochemically deposited at varying times in comparison with a thermally prepared alloy of the same composition. Significant differences were found among the Mössbauer spectra of electrodeposited alloys reflecting differences in the short range ordering of the dominant ferromagnetic phases. The potentiodynamic polarization curves revealed a higher ability to spontaneous passivation for the more disordered deposit while anodic dissolution was characteristic for the more ordered electrodeposits and for the crystalline thermally prepared alloy. The onset of the passivation of amorphous alloy was enhanced either by the decreased anodic dissolution or the increased hydrogen evolution rate. At the early stage of passivation, consistent passivation characterization was found both by chronoamperometric and potentiodynamic curves and by polarization resistance measurements performed at open circuit potential. Keywords: Amorphous/microcrystalline electrodeposited Fe–Ni–Cr alloys, Spontaneous passivation, Corrosion rate, and transient electrochemical polarization, Conversion electron Mössbauer spectroscopy, X-ray diffractometry

Radiation effects of energetic heavy ion irradiation in Fe–Zr amorphous alloys were investigated by the help of Mössbauer spectroscopy, X-ray diffraction and electrolytical hydrogenation. The electrolytical hydrogenation of non-irradiated and irradiated samples was carried out by a unique cathodic potential (−1000 mV versus SHE). The combination of electrolytical hydrogenation and Mössbauer analysis gives a very sensitive method for detecting structural changes of these amorphous alloys. It was found that the structural changes in the amorphous state, which are undetectable without hydrogenation by Mössbauer spectroscopy, modify the localization and the concentration of introduced hydrogen, and are reflected in a significant change of magnetic hyperfine interaction. The results can be associated with structural changes due to the effect of energetic heavy ion irradiation. Keywords: Electrolytical hydrogenation, 57Fe Mössbauer spectroscopy, Fe–Zr amorphous alloys, Heavy ion irradiation

The thermal decomposition of zirconium molybdate, tungstate and arsenate were investigated. The total mass losses of the investigated materials were 12.5, 11 and 8.5%, respectively. Despite having different crystal dimensions and structure the thermal decomposition of the samples takes place in a similar way. During heating two main endothermic processes with mass loss were observed. At the end of the thermal decomposition, oxides of the original materials were observed. The mentioned mass losses originate partly from the crystal water loss of the materials. The calculated crystal water content in the original molecule was 1.3 and 1 mole/molecule unit, respectively. Furthermore, for zirconium arsenate, a sublimation process was recorded above 960 K.

57Fe transmission Mossbauer spectroscopy and X-ray diffractometry were used to study clay mineral samples originated from two different regions (Um-arrazm and Alkawasim) of Libya in order to get information about their mineralogical composition to assess their potential for use in the Libyan oil industry. In the samples originated from Um-arrazm calcite, akaganeite and nontronite while in the samples originated from Alkawasim quartz, akaganeite, montmorillonite, kaolinite, illite, mica and hematite were identified with different ratios by using diffraction method. The differences in the phase composition of iron-containing phases of samples from different localities have reflected in the complex Mossbauer spectra at both 300 K and 80 K. For the samples originated from Um-arrazm the Mossbauer parameters of subspectra were identified as nontronite and akaganeite.

57Fe Mossbauer spectroscopy measurements were performed on the perovskite compounds Eu0.7Pr0.3Ba2(Cu0.9957Fe0.01)3O7-δ, EuBa1.5Pr0.5(Cu0.9957Fe0.01)3O7-δ and EuBa1.3Pr0.7(Cu0.9957Fe0.01)3O7-δ. The observed 57Fe Mossbauer spectra provided an evidence for the correct site assignment of subspectra originating from 57Fe in different microenvironments. Apart from a minor component which was assigned to the 57Fe in the Cu(2) site of the copper oxide plane, all the subspectra could be attributed to the 57Fe in the Cu(1) copper oxide chain site with a fourfold (doublet D1), fivefold (doublet D2) or sixfold (doublet D3) oxygen coordination. In contrast, in the compound EuBa2(Cu0.9957Fe0.01)3O7-δ the 6-coordinated (D3) species has not been observed. The substitution of Pr for Eu or for Ba resulted in an increased occupancy of the O(5) antichain oxygen sites, which was explained by the charge neutrality criterion. Especially, the replacement of Ba2+ with Pr3+ led to an unusually high degree of occupancy of O(5) sites. In the 57Fe Mossbauer spectra the relative area of the 6-coordinated species (D3) increased, and that of the 4-coordinated one (D1) vanished completely in the case when Pr was substituted for Ba. Furthermore, the proportion of the 6-coordinated (D3) species increased at the expense of the 5-coordinated (D2) one with an increasing concentration of Pr at the Ba site. These experimental results are consistent with the variety of Mossbauer results reported so far.

Sediments from the Admiralty Bay, King George Island, Antarctica, were investigated by 57Fe Mossbauer spectroscopy, X-ray diffractometry, and radiometry. Quartz, feldspar, chlorite, calcite, dolomite, mica, kaolinite, hematite and magnetite were identified as constituent minerals in the sediment samples. The phase composition and the iron distribution among the crystallographic sites of iron-bearing minerals (silicates, magnetite and hematite) of samples from different location have been derived from the complex Mossbauer spectra. At different locations sediments had significant characteristic differences in the mineral composition, in the iron distribution among the crystallographic site of silicates, and in the specific radioactivity of Cs radionuclides. These results indicate differences in the rock formation and alteration by the sediments in this maritime part of Antarctica. There is a much higher amount of iron oxides in the sediments from south part of the geological fault across the Admiralty Bay than in the north part. This can be associated with much more alteration in the rocks in the south part compared to the northern one. This finding can contribute to the question of the history of the formation and alteration of volcanic rocks in the border of Antarctica.

The paper offers three applications of nuclear methods in the research of chemical structure. First, progress in positron annihilation spectroscopy is illustrated by a positron beamline study, which obtained results that are not available through conventional experiments. The positron beam was used for the study of Langmuir-Blodgett (LB) films containing 4-58 layers of arachidic acid and its salts. These measurements have shown that this emerging technique is capable of characterizing even such elusive systems. Second, the potential of Mossbauer spectroscopy to answer current challenges of solid state chemistry are shown in a study on perovskites of recent interest. 151Eu Mossbauer spectroscopy was used to study the effect of Pr substitution in EuBa2Cu3O7-δ. It was shown that the introduction of Pr into the rare earth site as well as into the Ba site results in the appearance of extra electrons both in the copper oxide planes and at the 4f shell of Eu cations. The observed effects were explained by the hole filling effect of Pr. Finally, a survey is presented on the recently developed techniques for nuclear resonant scattering of synchrotron radiation, an exciting and very rapidly developing extension to conventional Mossbauer spectroscopy. An interesting new result is that nuclear inelastic scattering experiments performed on solutions of 57Fe complexes show contribution from vibrations rather than from diffusion to the inelastic spectra.

Mossbauer, FTIR and XRD analyses showed that in aqueous medium in air in the presence of L-tryptophan (Trp) or indole-3-acetic acid (IAA) the ambient-temperature ageing of the precipitates formed from ferrous sulphate at pH∼7 gave composite phases with varying proportions of γ-FeOOH (a dominating crystalline phase), α-FeOOH (both fine-grained, showing superparamagnetic behaviour at 298 K, and relatively better crystallized) and amorphous ferric hydroxide. The experimental data suggested a competition for adsorption sites at the oxyhydroxide surface in the suspension during phase transformations, as well as the transformation of γ-FeOOH (and/or amorphous ferric hydroxide) to α-FeOOH via the dissolution-reprecipitation mechanism. The formation of certain ferric oxyhydroxide phases in the presence of Trp and IAA — released e.g., in the course of bacterial and plant metabolism — can contribute to the regulation of soil mineral composition.

57Fe and 151Eu Mossbauer spectroscopy as well as RF susceptibility measurements were applied to study the effects of Pr substitution either into the rare earth or into the Ba site in Eu1−x Pr x Ba2Cu3O7−δ and EuBa2−x Pr x Cu3O7−δ, respectively. Site mixing of Pr between the rare earth and Ba sites could be excluded by the utilization of 57Fe Mossbauer spectroscopy. It was found that there exists a correlation between the 151Eu isomer shift and the onset temperature of the superconducting transition independent of the location of Pr. RF susceptibility measurements provide an evidence for a difference in the magnetic moment of Pr substituted for the Eu or Ba sites. The obtained results can be explained by hole filling as the dominant effect of Pr substitution.

A real specimen originating from the primary circuit of a VVER-440 type pressurized water cooled nuclear reactor has been studied by Conversion Electron Mossbauer Spectroscopy (CEMS) in order to find out how the AP-CITROX decontamination procedure modifies the structure and composition of the surface oxide layer of stainless steel which is used in the steam generator. Other methods like voltammetry, gravimetry, and SEM-EDAX were also applied to characterize the samples and to help the interpretation of CEMS results. It was found that, in contradiction with expectations, the presence of the surface magnetite layer could not be convincingly identified even on the non-decontaminated sample. This finding together with the relatively weak Mossbauer signals indicated that the surface oxide layer is strongly Fe-depleted. It was also concluded that the upper layer of the bulk steel (under the oxide layer) has an altered composition probably due to irradiation-enhanced diffusion of the metallic constituents. It was established that the AP-CITROX decontamination procedure does not exert detrimental effects on the thickness and composition of the surface oxide layer.

151Eu Mossbauer spectrum of IR-transmitting calcium aluminate glass, 60CaO·32Al2O3·5Fe2O3·3Eu2O3, consists of a broad peak due to distorted Eu(III) with δ and Δ values of 0.91 and −2.02 mm·s−1, respectively. Debye temperatures (θD) of 360 and 320 K were obtained from the temperature dependence of absorption area (A) and that of δ, respectively. These θD values indicate that Eu(III) atoms occupy substitutional sites of distorted Al(III)O4 tetrahedra in calcium aluminate glass. The δ value of 0.62 mm/s obtained from the heat-treated sample (glass ceramic) indicates that Eu(III)-O bonds became less covalent. A smaller Δ value of −1.20 mm·s−1 was obtained for Eu(III) in the glass ceramic, indicating less distorted Eu(III)O4 tetrahedra.

119Sn conversion electron Mossbauer spectroscopy, X-ray diffractometry and energy dispersive X-ray analysis (EDAX) were employed to investigate microstructure, composition and phases present in as-electroplated Sn-Cr and Sn-Cr-Zn alloys deposited on copper substrates. In the Sn-Cr deposits Cu, β-Sn, Cr-Sn phases can be identified by X-ray diffractometry. The phase composition is significantly different between the samples prepared with relatively higher and lower current densities. In the diffractograms of Sn-Cr-Zn deposits Cu, β-Sn, Zn phases can be well identified. A small intensity amorphous peak is also present, which can perhaps be associated with the presence of some amorphous Zn and Sn alloy. 119Sn Mossbauer spectra of Sn-Cr deposits exhibit an asymmetric broad main line centered near the isomer shift characteristic of β-Sn as well as they contain a small component near the zero velocity which can be attributed to a SnO2 phase based upon its characteristic. 119Sn Mossbauer spectra of Sn-Cr-Zn deposits are roughly similar to those of Sn-Cr deposits although the Mossbauer parameters of the third phase are different and vary with the Zn content. The presence of SnO2 on the surface mainly in the Sn-Cr samples can be attributed to the corrosion process in the air.

Traditional black pottery produced in Nadudvar, E-Hungary, was studied by 57Fe Mossbauer 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). Mossbauer 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 Mossbauer 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 Mossbauer 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 wustite).

Introduction of the Mossbauer nuclei 57Fe into Hg-1223 phase and that of 57Fe and 151Eu into Tl-1212 and Tl-1223 superconductors were investigated. Samples of high phase purity were obtained. Scanning electron microscopy and optical microscopy in normal and polarized light were employed to study the microstructure of the specimens. Energy dispersive X-ray analysis showed that 57Fe in the Hg-based samples and 57Fe as well as 151Eu in the Tl-based compounds, entered superconducting phases. Incorporation of Eu3+ into the superconducting phase favored the formation of the Tl-1212 phase. Mossbauer spectroscopy showed that Eu3+ entered the Ca-site. Two doublets found in the 57Fe Mossbauer spectra in both the Hg-1223 and the Tl-1223 phase referred to two different micro-environments of Fe3+. The assignment of the 57Fe Mossbauer spectra was made under the assumption that Fe favored the 1223 phase. Fe3+ may replace Cu in both the square pyramidal, five-fold oxygen coordinated Cu sites between the Ca and Ba-(Sr)-O layers, and in the square planar, four-fold oxygen coordinated Cu sites the Ca layers in the superconducting phases in both the Hg- and the Tl-based materials. From the relative areas of the two doublets, we concluded that the Fe3+ preferred the square planar Cu site.

Zirconium phosphate ( α -type), and zirconium phosphate-phosphite, and their silica containing forms were prepared. The products of syntheses and their purities and crystallinities were characterized by XRD diffraction. Thereafter the samples were irradiated with γ -rays (to 3×10 6 Gy absorbed dose), after which irradiation the samples were again characterized. Comparison of the diffractograms reveals that irradiation does not result in detectable structural changes. Thus, application of these materials as sorbents and as ion exchangers is suggested in processes taking place under irradiation.

Triphenyltin(IV) complexes ofN-acetylglycine,N-acetyl-L-leucine,N-acetyl-L-asparagine andN-acetyl-L-tyrosine were prepared by two methods and characterized by means of different spectroscopic methods (FTIR, multinuclear,1H,13C and119Sn NMR and119Sn Mossbauer). The spectroscopic data indicated that theN-acetylglycine complex adopts a trigonal-bipyramidal structure in which the monodentate carboxylate and the amide-C=O group are bound to the same organotin(IV) moiety. The other three complexes are linear oligomers in which the planar Ph3Sn(IV) is coordinated axially by a monodentate carboxylate and an amide-C=O from two different ligands. At theC-terminal end of the oligomer chain there is a tetracoordinated tin(IV) with a monodentate carboxylate as donor group.

The data on the coordination and structure of iron(II) and iron(III) anthranilates in the solid state and in aqueous medium are presented and discussed, as studied using Mossbauer (for solid products and frozen solutions) and FTIR spectroscopy (for solid samples). Whereas, in slightly acidic nitrate solutions under aerobic conditions ferric ions can still be gradually reduced by anthranilic (o-aminobenzoic) acid, which may have some ecological significance, in circumneutral media this process is retarded. Mossbauer parameters calculated for iron(II) and iron(III) anthranilates, as well as characteristic vibration modes of certain functional groups involved in coordination with iron cations are discussed. The FTIR data obtained for ferrous anthranilates, as compared to anthranilic acid, definitely exhibit the direct involvement of both the carboxylic and the amino groups of anthranilic acid in coordination with iron. q 1999 Elsevier Science B.V. All rights reserved.

The thermal behaviour of Co(II), Ni(II) and Zn(II)-containing zirconium phosphate of α type was investigated. XRPD analysis revealed that, for the samples containing Co(II) or Ni(II), the first reflection of the solid phase is split into a doublet. In contrast, when Zn(II) is present, a single solid phase system is formed. The thermal behaviour of the materials followed this sequence. For the samples containing Co(II) or Ni(II), phase-transition processes were found and there was also a loss of crystal water, but for the sample containing Zn(II) there was only one endothermic effect, which corresponded to the decomposition of phosphate groups.

Eight di-n-butyltin(IV) complexes with glycolic, 2-hydroxy-propionic, succinic and malic acids, have been prepared by two different procedures. The compounds were characterised by elemental analysis, FTIR, Raman and119Sn Mossbauer spectroscopy. The IR and Raman data indicated the presence of bidentate and/or monodentate carboxylate groups, non linear C−Sn−C bonds, and Sn−O bonds within the complexes. The results of Mossbauer spectroscopic measurements, based on point-charge model calculations, have shown the occurrence of trigonal bipyramidal environment in the central tin(IV) atom, besides the octahedral and tetrahedral structure.

Electrodeposited Fe-Ni-Cr alloys irradiated with 209 MeV energy 84Kr ions were investigated by conversion electron Mossbauer spectroscopy, X-ray diffraction and electron microprobe analysis. Significant dose dependent changes were found between Mossbauer spectra of the irradiated and non-irradiated deposits. These changes reflect the dose dependent transformation of the metastable ferromagnetic phase to the paramagnetic one.

Using Mossbauer spectroscopy and X-ray diffraction as analytical tools, an "anomalous" α-γ phase transformation observed previously in steels was studied. It was shown in this work that this phase transformation is a feature of the Fe-12Cr-4Ni ternary alloy, and the ageing-time dependence of the γ-phase formation follows Avrami kinetics representing a diffusion controlled process. The activation energy of the process was also determined. The equilibrium composition of the samples could be interpreted in terms of calculated phase diagrams of the Fe-Cr-Ni system. On the basis of the hyperfine-field distributions derived from the spectra it was shown that two processes take place in the ferromagnetic α-phase during the ageing at different rates in which the slower one is in accordance with a decrease of the chromium concentration in the α-phase owing to the γ-phase formation.

New user-friendly software for analysis of Mossbauer-spectra has been developed. Evolution Algorithm is used for global search of Mossbauer parameters in order to enhance the reliability of the obtained results. Fitting of Lorentzians, Pseudo-Voigt line profiles, deriving hyperfine-field distributions including correlations and combinations and Mossbauer Line Sharpening by Fourier transformation provide a wide range of applicability.

Human liver ferritin and its pharmaceutical analogue, Ferrum Lek, containing nanosized hydrous ferric oxides cores in the forms of ferrihydrite and akaganeite, respectively, were studied using Mossbauer spectroscopy with a high velocity resolution in the temperature range of 295-90 K. To simplify comparison, these spectra were fitted using one quadrupole doublet within the homogeneous iron core model. An unusual line broadening with a temperature decrease was observed in this way for human liver ferritin below ∼150 K and for Ferrum Lek below ∼130 K. Some anomalies were also observed below these temperatures for spectral area and quadrupole splitting. The Debye temperature for both iron cores was evaluated from temperature dependence of isomer shift using the temperature dependence of the second-order Doppler shift.

Nanoparticles (NPs) of Fe3O4 and γFe2O3 synthesized by hydrothermal reaction were characterized by X-ray diffractometry (XRD), 57Fe-Mossbauer spectroscopy and field emission scanning electron microscopy (FE-SEM). A decrease in concentration of methylene blue (MB) aqueous solution due to bulk Fe0-NP γFe2O3 mixture with the mass ratio of 3:7 was measured by ultraviolet-visible light absorption spectroscopy (UV-Vis). The Mossbauer spectrum of NP Fe3O4 prepared from hydrothermal reaction was composed of two sextets with absorption area (A), isomer shift (δ) and internal magnetic field (Hint) of 56.3 %, 0.34±0.03 mm s − 1 and 49.0±0.30 T for tetrahedral (Td) FeIII, and 43.7 %, 0.66±0.11 mm s − 1 and 44.0±0.71 T for octahedral (Oh) FeII + III. The FeII/FeIII ratio was determined to be 0.280 for NP Fe3O4, giving ‘x’ of 0.124 in Fe3 − xO4. These results show that NP Fe3O4 prepared by hydrothermal reaction was not regular but nonstoichiometric Fe3O4. Consistent results were observed for XRD patterns of NP Fe3 − xO4 indicating sharp intense peaks at 2Θ of 30.2, 35.7 and 43.3° with a large linewidth of 0.44°, yielding the crystallite size of 29–37 nm from the Scherrer’s equation. Iso-thermal annealing of NP Fe3 − xO4 at 250 °C for 30 min resulted in the precipitation of NP γFe2O3 with δ of 0.33±0.03 mm s − 1 and Hintof 46.4±0.27 T due to magnetic tetrahedral FeIII. The Debye temperature of NP Fe3 − xO4 was respectively estimated to be 267±5.45 K for Fe\(^{\mathrm{III}}(T_{\mathrm{d}})\) and 282±7.17 K for Fe\(^{\mathrm{II+III}}(O_{\mathrm{h}})\), both of which were smaller than that obtained for bulk Fe3O4 of 280±4.15 K and 307±5.70 K, indicating that the chemical environment of iron of NPs is less rigid than that of the bulk compounds. A leaching test using methylene blue (MB) and mixture of bulk Fe0-NP γFe2O3 (3:7) showed a remarkable decrease in MB concentration from 1.90 × 10 − 2 to 9.49 × 10 − 4 mM for 24 h with the first order rate constant (kMB) of 2.1 × 10 − 3 min − 1. This result verifies that MB decomposing ability is enhanced by using NP γFe2O3 compared with the kMB of 1.1 × 10 − 4 min − 1 previously obtained from the leaching test using MB and bulk mixture of Fe0 − γFe2O3 (3:7).

Anatase type TiO is well known as a photo- catalyst activated by the UV light. It will be more effective to develop photo-catalyst which shows photo catalysis under visible light irradiation. Recently, Kubuki et al. revealed that 15Na2O•15CaO•xFe2O3•(70–x)SiO with ‘x’ between 10 and 50 mass% exhibited chemical oxygen demand (COD) decomposing ability. This result implies that iron silicate glass might be utilized as a purifier of polluted water. In this study, we report a relationship between local structure and visible light activated photo-catalytic effect of xFe2O3·(100–x)SiO2 glass prepared by sol-gel method. method. Iron silicate glass with a composition of xFe2O3·(100–x)SiO (in mass %, x = 10-50) were prepared by a sol-gel method. Reagent chemicals of Si(OC2H5)4, Fe(NO3)3·9H2O, 7.8 M HNO3, and C2H5OH were poured into a beaker and well mixed for 2 h at RT. After having been agitated by refluxheat method at 80ºC for 2h, the solution was poured into a glass vial and dried at 60ºC for 3 days to prepare gel samples of dark brown color. It was annealed at 1000ºC for 3 h in air. For evaluation of photo-catalytic effect, 40mg of well-pulverized annealed samples were soaked into 20 ml of methylene blue aqueous solution (MBaq) with a concentration of 20µΜ. Irradiation test was carried out for 2 h at RT in a darkroom using a glass vial irradiated with a visible light having the wavelength range of 420-750 nm. Absorbance (Abs.) of MBag before and after the irradiation test was determined by UV-VIS. 57^Fe-Mössbauer spectra were measured by a constant acceleration mode with a source of Co(Rh) and a reference of α-Fe. Absorption area (A) for the magnetic sextet with isomer shift and internal magnetic field (Hint) of 0.37 mm s^-1 and 51.4 T increased from 0.0 to 10.3 and 100 % with Fe2O3 content (x), indicating an increase in the fraction of hematite (α-Fe2O3). Decrease in the Abs. of MB became larger after 2h-irradiation test with an increase of ‘x’. It is concluded that MB-decomposing ability is associated with the amount of α-Fe phase precipitated in the annealed iron silicate glass.

A relationship between local structure and methylene blue (MB) decomposing ability of nanoparticles (NPs) of metallic iron (Fe0) and maghemite (γ‐Fe2O3) was investigated by 57Fe Mossbauer spectroscopy, X-ray diffractometry and UV-visible light absorption spectroscopy. γ‐Fe2O3 NPs were successfully prepared by mixing (NH4)2Fe(SO4)2⋅6H2O (Mohr's salt) and (NH4)3Fe(C2O4)3⋅3H2O aqueous solution at 30 °C for 1 h, while those of Fe0 were obtained by the reduction of Mohr's salt with NaBH4. From the Scherrer's equation, the smallest crystallite sizes of γ‐Fe2O3 NPs and Fe0 NPs were determined to be 9.7 and 1.5 nm, respectively. 57Fe Mossbauer spectrum of γ‐Fe2O3 NPs consists of a relaxed sextet with isomer shift (δ) of 0.33±0.01 mm s−1, internal magnetic field (Hint) of 25.8±0.5 T, and linewidth (Γ) of 0.62±0.04 mm s−1. 57Fe Mossbauer spectrum of Fe0 NP is mainly composed of a sextet having δ, Δ, and Hint of 0.00±0.01 mm s−1 0.45±0.01 mm s−1, and 22.8±0.1 T, respectively. A bleaching test of the mixture of Fe0 a...

Based on earlier experiences with α- and γ-zirconium phosphate, zirconium phosphate–phosphite (ZrPP) containing silica (ZrSiPP) has been prepared, and its structure identified by XRD. The thermal behaviour and specific surface area have also been determined. On the basis of experimental data for SiZrPP, the following monoclinic cell parameters of: a=0.7622 nm, b=0.5956 nm, c=2.2105 nm and β=111.4° (different from those of ZrPP) were calculated. SiZrPP has five times higher specific surface area (52.6 m2·g−1) than ZrPP and it shows characteristic thermal decomposition.

A new user-friendly software for analysis of Mossbauer-spectra has been developed. The program makes use of the advantages provided by the current generation of fast personal computers. An Evolution Algorithm1,2 is used for global search of Mossbauer parameters in order to enhance the reliability of the obtained results. Fitting of Lorentzians, Pseudo-Voigt line profiles, and deriving hyperfine-field distributions including correlations and combinations and Mossbauer Line Sharpening by Fourier transformation provide a wide range of applicability.

The discovery of radioactivity started the nuclear research. The nuclear techniques are very powerful tools in structural chemistry, as well. We would like to support this statement by two examples in this paper. We present a series of Mossbauer measurements which give information about the coordination structure of some dibutyltin (IV) complexes of carbohydrate derivates. The other example will demonstrate how the positron lifetime spectra can reflect the temperature dependence of water structure.

57Fe Mossbauer spectroscopy was used to study the effects of heavy ion irradiation on (Bi0.93Pb0.17)Sr1.9Ca2.05(Cu1.02Fe0.01)3Oy superconductors. The Mossbauer spectra of the irradiated superconductor showed significant changes in the subspectra belonging to different Cu microenvironments into which Fe ions were substituted. The relative occurrence of Fe occupying the square pyramidal fivefold oxygen coordinated Cu sites decreased while Fe3+ substituting the square planar fourfold oxygen coordinated Cu sites increased upon bombardment by 246 MeV 86Kr8+ ions. This observation was interpreted on the basis of partial replacement of the apical oxygen atoms in the square pyramids surrounding one of the Cu sites. Such oxygen vacancies create additional square planar coordination sites for Cu. These results also support the covalent character of Cu-O bonds in the superconducting layer as well as the ionic character of bond of apical oxygen to Cu.

The effect of the structure of a mixture of industrially produced iron and iron oxide on the decomposition of trichloroethylene (TCE) was investigated by gas chromatography, scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray analysis, X-ray diffractometry, and 57Fe-Mössbauer spectroscopy. The concentration of 10 mg L−1 TCE aqueous solution decreased to 0.41, 0.52, 0.26, and 0.09 mg L−1 when stirred for 7 days with iron–iron oxide mixtures having mass ratios of 2:8, 3:7, 4:6, and 5:5, respectively. The Mössbauer spectra of the mixtures after leaching were composed of two sextets with respective isomer shifts (δ) and internal magnetic fields (H) of 0.29±0.01 mm s−1 and 48.8±0.1 T, and 0.64±0.01 mm s−1 and 45.5±0.1 T, attributed to the Fe3+ species in tetrahedral (T d) and the Fe2+ and Fe3+ mixed species (Fe2.5+) in octahedral (O h) sites, respectively. Mössbauer spectra of a 3:7 mass ratio iron–iron oxide mixture showed a gradual decrease in the absorption area (A) of zero valent iron (Fe0) from 40.6. to 12.6, 13.2, 3.8 2.8, and 1.0±0.5 % and an increase in A of Fe3O4 from 31.8 to 59.4, 71.4, 93.2, 95.6, and 98.0±0.5 % after leaching with 10 mg L−1 TCE aqueous solution for 1, 2, 3, 7, and 10 days, respectively. Consistent values of the first-order rate constant were calculated as 0.32 day−1 for Fe0 oxidation, 0.34 day−1 for Fe3O4 production, and 0.30 day−1 for TCE decomposition, which indicates that the oxidation of Fe0 was the rate-controlling factor for Fe3O4 production and TCE decomposition. It is concluded from the experimental results that an iron–iron oxide mixture is very effective for the decomposition of TCE.

Complex formation equilibria of diethyltin(IV) with five N-D-gluconylamino acids in aqueous solution (I = 0.1 M, NaClO4) were studied and the stabilities of the species were determined by potentiometric titrations. Diethyltin(IV) complexes of α-amino acid derivatives are water-soluble in the physiological pH range, while in the presence of N-D-gluconyl-β-alanine a precipitate is formed, which dissolves with increasing pH. 13C NMR measurements showed that in the N-D-gluconyl-α-amino acid complexes the ligand is coordinated through its deprotonated carboxylate oxygen, amide nitrogen and C(2)-hydroxy group, while for the soluble N-D-gluconyl-β-alanine complex the ligand is coordinated via the deprotonated carboxylate and C(3)-, C(4)-, C(5)-hydroxy groups. Mössbauer measurements reflected the geometry of the complexes formed.

Dibenzyltin(IV) complexes of carbohydrate derivatives were prepared and studied by Mossbauer and FTIR spectroscopy and by thermogravimetry. The Mossbauer studies indicated that the reaction between dibenzyltin(IV)-dichloride and sugar-type ligands led to reaction products containing tin(IV)-oxide. beside the dibenzyltin(IV) sugar complex. These two type of species were shown to be in weak interaction. Comparison of the experimental quadrupole splitting values with those calculated on the basis of the partial quadrupole splitting concept revealed the steric arrangements of the coordination sphere of tin(IV) in the sugar complexes.

The emission ((57)Co) variant of Mössbauer spectroscopy, rarely used in biology-related studies, was applied to study binding and possible transformations of (57)Co(II) traces in live and dead (hydrothermally treated) cells of the rhizobacterium Azospirillum brasilense (strain Sp7) at T=80 K in frozen aqueous suspensions and as their dried residues. The Mössbauer parameters calculated from the spectra were compared with the similarly obtained data reported earlier for another A. brasilense strain, Sp245 (which differs from strain Sp7 by the ecological niche occupied in the rhizosphere and was found earlier to exhibit different metabolic responses under similar environmental conditions). Similarly to strain Sp245, live cells of strain Sp7, rapidly frozen 2 min and 1 h after their contact with (57)Co(2+) (measured in frozen suspensions), showed marked differences in their Mössbauer parameters, reflecting metabolic transformations of (57)Co(2+) occurring within an hour. However, the parameters for strains Sp7 (this work) and Sp245 (reported earlier), obtained under similar conditions, were found to significantly differ, implying dissimilarity in their metabolic response to Co(2+). This is in line with their different metabolic responses to several heavy metals, including Co(2+), detected earlier using Fourier transform infrared spectroscopy.

Decomposition mechanism of methylene blue (MB) caused by a mixture of metallic iron-maghemite (Fe0-γFe2O3) was investigated by means of 57Fe-Mossbauer spectroscopy, X-ray diffractometry (XRD), Ultraviolet-Visible Absorption Spectroscopy (UV-vis) and electrospray-ionization mass spectroscopy (ESI-MS). Ten day-leaching test of 10 μmol L − 1 MB aqueous solution and Fe0-γFe2O3 mixture (mass ratio 3:7) showed a decrease in the concentration from 10.5 to 4.45 μmol L − 1 with first-order rate constant (k) of $1.5_{7} \times 10^{-1}$ day − 1. An ESI-MS study of Fe0-γFe2O3 mixture (3:7) after the leaching test revealed new peaks at m/z of 100, 110 and 137 due to fragmentation of MB, in addition to those observed at m/z of 284, 270 and 256 which were ascribed to MB, Azure B and Azure A, respectively. 57Fe-Mossbauer spectra of Fe0-γFe2O3 mixture (3:7) resulted in a decrease in absorption area (A) for Fe0 (δ = 0.00±0.01 mm s − 1, H int = 33.0±0.1 T) from 37.5 to 21.3, 9.7, 7.9, 7.0 and 4.5±0.5 %, together with an increase in A from 0.0 to 5.0, 13.8, 17.2, 21.0 and 22.4±0.5 % for octahedral (O h) iron (FeII + FeIII) of Fe3O4. XRD study of these samples indicated that the peak intensity at 2Θ of 44.7° being ascribed to Fe0 was decreased, while that of 35.6° due to Fe3O4 was almost constant; relative peak ratio of Fe $^{0}/\mathrm{Fe}_{3}$ O4 was decreased from 26.3 to 2.76 after the leaching, indicating that Fe0 in the Fe0-γFe2O3 mixture was oxidized to Fe3O4. These experimental results suggest that Fe0-γFe2O3 mixture could be utilized for the cleaning or decomposition of toxic organic compounds like trichloroethylene.

Mossbauer spectroscopy, X-ray diffractometry and DSC measurements were used to study the as-quenched state and the crystallization of Fe83P17 amorphous alloys quenched at several different cooling rates. The melt temperatures investigated were 1100 and 1250 °C. We have found changes in the hyperfine field distribution curves as a function of the quenching rate. These changes can be attributed to relaxation effects which are more considerable than those observed in Ni(Fe)P alloys. On the other hand, we have found differences in the phase composition of the partially crystallized alloys kept at different melt temperatures (but quenched at the same rate) at the same stage of crystallization. These can be associated with the similar effect of long-term melting as found earlier in Ni(Fe)P and FeB alloys. This effect can also be expected theoretically in the investigated temperature range.

The crystallization kinetics of Fe83P17 amorphous alloy has been studied by Mossbauer spectroscopy and X-ray diffractometry. The samples were annealed isothermally at two different temperatures (315 °C and 325 °C). During isothermal annealing of the samples three phases were observed: crystalline Fe3P phase, crystalline α-Fe phase and the amorphous phase. The value of the Avrami exponent was found to be about 2.0 at each annealing temperature. This suggests that the growth rate of the crystals is controlled by volume diffusion and the nucleation rate decreases during crystallization. The activation energy obtained for the overall crystallization process was 193±43 kJ mol−1.

Mossbauer spectroscopy, X-ray diffractometry and differential scanning calorimetry were used to study the effect of the preparation parameters on the short range ordering of Fe83P17 amorphous alloys. The samples were quenched with different quenching rates from the melt which was kept either at 1100°C or 1250°C for 20 min. The short range order of the amorphous samples was found to depend on the quenching rate due to the relaxation taking place during rapid quenching of the melt. In one case, in the sample quenched with the lowest quenching rate from the melt of 1250°C, crystalline phases identified as Fe3P and α-Fe were also found. This phase separation can be understood by taking into consideration the effect of both the melt temperature and the quenching rate. In this case, the cooling time can be long enough for separation of the phases which can be expected within the range of 1040–1250°C according to the phase diagram.

The uptake and accumulation of iron in cucumber roots exposed to cadmium were investigated with Fe sufficient and deficient cucumber plants using Mossbauer spectroscopy, Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and ferric chelate reductase activity measurements. Both Fe sufficient and Fe deficient plants were applied. In the case of Fe sufficient cucumber roots grown in nutrient solution with 10 μM Cd no changes were found in the occurrence of Fe species (mostly hydrous ferric oxides and ferric-carboxylate complexes) compared to the control where no Cd was added. In the Fe deficient roots pretreated with 0, 0.1, 1, 10 and 100 μM Cd for 3 h then supplied also with 0.5 mM 57Fe-citrate for 30 min, FeII was identified in a hexaaqua complex form. The relative amount of FeII was decreasing simultaneously with increasing Cd concentration, while the relative occurrence of FeIII species and total Fe concentration were increasing. The results support the inhibitory effect of Cd on Fe-chelate reduction. Although the reductase activity at 10 and 100 μM Cd treatment was lower than in the iron sufficient control plants, FeII could be identified by Mossbauer spectroscopy whereas in the Fe sufficient control, this form was below detection limit. These data demonstrate that the influx and the reoxidation of FeII was decreased by Cd, consequently, they refer to the competition of Cd2+ and Fe2+ during the membrane transport and the inhibition of the reoxidation process.

Mossbauer spectroscopy was used in order to study the influence of electrochemical behaviour of electrochemically deposited Fe—8P amorphous alloy. Electrochemically deposited amorphous samples were exposed to corrosion in the solution of H2SO4 and Na2SO4 containing NaHSO3 at pH=3.5. CEM spectra of as-deposited samples exhibit a typical sextet of ferromagnetic amorphous state. Even with samples being kept under corrosion condition for 10 minutes, the Mossbauer spectra reveal an extra Fe(III) component.

151Eu and 141Pr Mossbauer spectroscopy was applied to study the effects of Pr substitution for Eu or Ba atoms in Eu1-xPrxBa2Cu3O7-δ and EuBa2-xPrxCu3O7-δ, respectively. It was found that there exists a correlation between the 151Eu isomer shift and the onset temperature of the superconducting transition, independent of the location of Pr. This shows that the extra electrons provided by the Pr increase the electronic density in the copper oxide planes and in the 4f orbitals of Eu31, simultaneously. The polycrystalline compound EuBa1.3Pr0.7Cu3O7-δ has been investigated by 141Pr Mossbauer spectroscopy. The observed 141Pr isomer shift, δ(4.2 K) = 0.10(15) mm/s relative to PrF3, reflects a valence state of 3+ for the Pr located at the Ba site in EuBa1.3Pr0.7Cu3O7-δ, being in contrast to the valence state of 3.4+ found earlier for Pr which was situated at the rare earth site. This means that the valence state of Pr substituted for Eu is different from that of Pr substituted for Ba. These results suggest that the suppression of superconductivity by Pr substituted for the rare earth atoms is a consequence of the hole filling effect.