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Sample records for 57fe moessbauer studies

  1. {sup 57}Fe and {sup 119}Sn Moessbauer Effect Study of Fe-Sn-B Amorphous Alloys

    SciTech Connect

    Miglierini, M.; Rusakov, V. S.

    2010-07-13

    Ribbons of Fe{sub 100-x}Sn{sub 5}B{sub x} (x = 15, 17, 20) metallic glass are studied using {sup 57}Fe and {sup 119}Sn Moessbauer spectrometry. The obtained Moessbauer spectra are evaluated by distributions of hyperfine magnetic fields in addition to crystalline components. The as-quenched alloys are XRD amorphous for x =15 and 17 whereas for x =20, traces of quenched-in crystallites are revealed. Progress of crystallization is followed on samples annealed for 30 min at temperatures that cover the first crystallization peak. The evolution of crystalline fraction as well as average values of hyperfine magnetic fields and isomer shifts are discussed as a function of the alloy composition and temperature of annealing.

  2. Copper(II) cyanido-bridged bimetallic nitroprusside-based complexes: Syntheses, X-ray structures, magnetic properties, {sup 57}Fe Moessbauer spectroscopy and thermal studies

    SciTech Connect

    Travnicek, Zdenek; Herchel, Radovan; Mikulik, Jiri; Zboril, Radek

    2010-05-15

    Three heterobimetallic cyanido-bridged copper(II) nitroprusside-based complexes of the compositions [Cu(tet)Fe(CN){sub 5}NO].H{sub 2}O (1), where tet=N,N'-bis(3-aminopropyl)ethylenediamine, [Cu(hto)Fe(CN){sub 5}NO].2H{sub 2}O (2), where hto=1,3,6,9,11,14-hexaazatricyclo[12.2.1.1{sup 6,9}]octadecane and [Cu(nme){sub 2}Fe(CN){sub 5}NO].H{sub 2}O (3), where nme=N-methylethylenediamine, were synthesized and characterized by elemental analyses, {sup 57}Fe Moessbauer and FTIR spectroscopies, thermal analysis, magnetic measurements and single-crystal X-ray analysis. The products of thermal degradation processes of 2 and 3 were studied by XRD, {sup 57}Fe Moessbauer spectroscopy, SEM and EDS, and they were identified as mixtures of CuFe{sub 2}O{sub 4} and CuO. - Three heterobimetallic cyano-bridged copper(II) nitroprusside-based complexes of the general compositions of [Cu(L)Fe(CN){sub 5}NO].xH{sub 2}O, where L=N,N'-bis(3-aminopropyl)ethylenediamine (complex 1), 1,3,6,9,11,14-hexaazatricyclo[12.2.1.1{sup 6,9}]-octadecane (complex 2) and N-methylethylenediamine (complex 3), were synthesized, and fully structurally and magnetically characterized. SEM, EDS, XRD and {sup 57}Fe Moessbauer experiments were used for characterization of thermal decomposition products of complexes 2 and 3.

  3. Constraints on the oxidation state of the mantle: An electrochemical and sup 57 Fe Moessbauer study of mantle-derived ilmenites

    SciTech Connect

    Virgo, D.; Luth, R.W. ); Moats, M.A.; Ulmer, G.C. )

    1988-07-01

    Ilmenite samples from four kimberlite localities were studied using electrochemical, Moessbauer spectroscopic, and microprobe analytical techniques in order to infer the oxidation state of their source regions in the mantle. The values of Fe{sup 3+}/{Sigma}Fe calculated from analyses, using three different electron microanalytical instruments assuming ilmenite stoichiometry, are consistently higher than those derived from the Moessbauer data, by as much as 100%. Furthermore, the range in Fe{sup 3+}/{Sigma}Fe calculated using the analyses from different instruments and/or different correction schemes is nearly as large. Thus Fe{sup 3+}/{Sigma}Fe calculated from microprobe analyses should be taken with caution, even if the precision appears high. {sup 57}Fe Moessbauer spectroscopy on the electrochemical experiment run products demonstrates that Fe{sup 3+}/{Sigma}Fe is significantly lower than it is for the natural C-bearing ilmenites. In contrast, the ilmenite that lacked C did not change Fe{sup 3+}/{Sigma}Fe during the electrochemical experiment. Examination of the reduced samples with SEM established that the natural, single-phase ilmenites exsolved during the electrochemical experiment to form ilmenite{sub ss} + spinel{sub ss}. The initial, reduced trends in the electrochemical experiments for the C-bearing ilmenites are attributed to disequilibrium interactions between the decomposing sample and the evolved gas in the electrochemical cell and do not represent the quenched mantle memory nor the intrinsic f{sub O{sub 2}} of the sample prior to reduction. Furthermore, the oxidized f{sub O{sub 2}} trend is interpreted, for the carbon-bearing samples, are representing the f{sub O{sub 2}} of the ilmenite{sub ss} + spinel{sub ss} assemblage and not the intrinsic f{sub o{sub 2}} of the mantle-derived ilemnite{sub ss}.

  4. Metal valences in electron-doped (Sr,La){sub 2}FeTaO{sub 6} double perovskite: A {sup 57}Fe Moessbauer spectroscopy study

    SciTech Connect

    Rautama, E.-L.; Linden, J.; Yamauchi, H.; Karppinen, M.

    2007-02-15

    Substitution of divalent Sr by trivalent La is found to affect the valence states of both of the two B-site cations, Fe and Ta, in the double perovskite oxide (Sr{sub 1-} {sub x} La {sub x} ){sub 2}FeTaO{sub 6}. Moreover, it improves the degree of order of these cations. From {sup 57}Fe Moessbauer spectra the average Fe valence was found to decrease with increasing La substitution level, x. However, the valence of Fe decreased less than expected if the valence of Ta was assumed to remain constant. Hence, we conclude that also the valence of Ta decreases. - Graphical abstract: Both the degree of order and the valence states of Fe and Ta are controlled in the (Sr{sub 1-} {sub x} La {sub x} ){sub 2}FeTaO{sub 6} double perovskite oxide through aliovalent La{sup III}-for-Sr{sup II} substitution.

  5. Phase evolution in {sup 57}Fe/Al multilayers studied through dc magnetization, conversion electron Moessbauer spectroscopy, and transmission electron microscopy

    SciTech Connect

    Jani, Snehal; Lakshmi, N.; Venugopalan, K.; Sebastian, Varkey; Reddy, V. R.; Gupta, Ajay; Lalla, N. P.

    2008-12-15

    Fe/Al multilayer thin films with an overall atomic concentration ratio of Fe:Al=1:2 have been prepared by ion-beam sputtering. Phase formation and microstructural evolution with thermal annealing have been studied by x-ray reflectivity, cross-sectional transmission electron microscopy, dc magnetization, and conversion electron Moessbauer spectroscopy. These studies show that although the starting composition is Al rich, the intermixing of Fe and Al at the interfaces leads to the formation of a magnetic Fe{sub 3}Al-like region at the interface. Thus, the magnetic contribution in the as-deposited multilayer structure (MLS) is not only from pure Fe but also from an Fe{sub 3}Al-like region formed at the interface. On annealing the MLS, a stable nonmagnetic MLS consisting of intermetallic B2Fe{sub 50}Al{sub 50} separated by thin Al layers is formed. Further annealing only induces better ordering of Fe{sub 50}Al{sub 50} and does not destroy the MLS.

  6. {sup 57}Fe Moessbauer and x-ray magnetic circular dichroism study of magnetic compensation of the rare-earth sublattice in Nd{sub 2-x}Ho{sub x}Fe{sub 14}B compounds

    SciTech Connect

    Chaboy, J.; Piquer, C.; Plugaru, N.; Bartolome, F.; Laguna-Marco, M. A.

    2007-10-01

    We present here a study of the magnetic properties of the Nd{sub 2-x}Ho{sub x}Fe{sub 14}B series. The macroscopic properties of these compounds evolve continuously from those of Nd{sub 2}Fe{sub 14}B to those of Ho{sub 2}Fe{sub 14}B as Ho gradually replaces Nd. The system shows a compensation of the rare-earth sublattice magnetization for a critical concentration, x{sub c}=0.55, that is reflected into the anomalous behavior of both macroscopic and microscopic magnetic probes. The combined analysis of magnetization, {sup 57}Fe Moessbauer spectroscopy and Fe K-edge x-ray magnetic circular dichroism (XMCD) measurements suggests that the origin of the anomalous magnetic behavior found at x{sub c}=0.55 is mainly due to the Ho sublattice. Moreover, the analysis of the Fe K-edge XMCD signals reveal the presence of a rare-earth contribution, reflecting the coupling of the rare-earth and Fe magnetic moments, which can lead to the possibility of disentangling the magnetic behavior of both Fe and R atoms using a single absorption edge.

  7. Moessbauer investigation of {sup 57}Fe doped La{sub 4}Ni{sub 3}O{sub 10{+-}}{sub y} phases

    SciTech Connect

    Carvalho, M.D.; Bassat, J.M.

    2009-01-15

    {sup 57}Fe doped La{sub 4}Ni{sub 2.97}Fe{sub 0.03}O{sub 9.95} was synthesized by a citrate method and, afterwards, successfully oxidized and reduced by electrochemical methods. The compounds obtained were investigated by X-ray diffraction, electrical measurements and Moessbauer spectroscopy. The study allowed to follow the variation of the two nickel sites environment with the oxygen stoichiometry and a deeper understanding of the electrical behavior versus oxygen non-stoichiometry was achieved. The Moessbauer study revealed that after both oxidation and reduction treatments, the major modifications were observed on the octahedra adjacent to the La{sub 2}O{sub 2} layers, while the middle octahedra of the triple perovskite block remained almost unchanged. The oxygen intercalation (oxidized treatment) takes place essentially in the La{sub 2}O{sub 2} layers and the oxygen desintercalation (reduction treatment) occurs in the octahedral sites adjacent to those layers. - Grapical abstract: Moessbauer spectra of oxidized and reduced Ruddlesden-Popper compounds La{sub 4}Ni{sub 2.97}Fe{sub 0.03}O{sub 10{+-}}{sub y}.

  8. Structure and oscillational motion of /sup 57/Fe atoms in interstitial sites in Al as determined from interference of Moessbauer. gamma. radiation

    SciTech Connect

    Pauling, L.

    1981-12-01

    The first excited site of the /sup 57/Fe atom entrapped in an interstitial site in aluminum, as reported by W. Petry, G. Vogl, and W. Mansel (Phys. Rev. Lett. 45, 1862 (1980)) from a Moessbauer spectroscopic study of a single crystal, is analyzed by consideration of the value of the Hooke's law constant of the Fe-Al bonds obtained from the values for elemental Fe and Al. The eight wavefunctions for the eightfold nearly degenerate excited state are described as 2s1p1d1f hybrids of three-dimensional harmonic oscillator wavefunctions relative to the center of the undistorted Al/sub 6/ octahedron or as localized 1s functions relative to the center of the distorted octahedron. These considerations provide a qualitative understanding of the observations on this system.

  9. Investigations of Iron Minerals Formed by Dissimilatory Alkaliphilic Bacterium with {sup 57}Fe Moessbauer Spectroscopy

    SciTech Connect

    Chistyakova, N. I.; Rusakov, V. S.; Shapkin, A. A.; Zhilina, T. N.; Zavarzina, D. G.; Kohout, J.

    2010-07-13

    Anaerobic alkaliphilic bacterium of Geoalkalibacter ferrihydriticus type (strain Z-0531), isolated from a bottom sediment sample from the weakly mineralized soda Lake Khadyn, have been analyzed. The strain uses the amorphous Fe(III)-hydroxide (AFH) as an electron acceptor and acetate CH{sub 3}COO{sup -} as an electron donor. Moessbauer investigations of solid phase samples obtained during the process of the bacterium growth were carried out at room temperature, 77.8 K, 4.2 K without and with the presence of an external magnetic field (6 T) applied perpendicular to the {gamma}-bebam.

  10. Nuclear Bragg scattering studies in [sup 57]Fe with synchrotron radiation

    SciTech Connect

    Haustein, P.E.

    1993-01-01

    Studies of nuclear Bragg x-ray scattering of synchrotron radiation, using crystals of [alpha]-[sup 57]Fe[sub 2]O[sub 3], have been carried out at the NSLS at Brookhaven National Laboratory and at the Cornell University CHESS facility. These studies have demonstrated that nuclear resonance states can be used to produce filtered x-ray beams which have extremely narrow bandwidth, small angular divergence and unique polarization and temporal properties. this combination of characteristics, unobtainable with radioactive sources, makes synchrotron-based Moessbauer spectroscopy feasible and is an important complement to existing methods. A review of the experimental methodology is presented. As well as come suggestions for fuller exploitation of this new technique.

  11. Nuclear Bragg scattering studies in {sup 57}Fe with synchrotron radiation

    SciTech Connect

    Haustein, P.E.

    1993-03-01

    Studies of nuclear Bragg x-ray scattering of synchrotron radiation, using crystals of {alpha}-{sup 57}Fe{sub 2}O{sub 3}, have been carried out at the NSLS at Brookhaven National Laboratory and at the Cornell University CHESS facility. These studies have demonstrated that nuclear resonance states can be used to produce filtered x-ray beams which have extremely narrow bandwidth, small angular divergence and unique polarization and temporal properties. this combination of characteristics, unobtainable with radioactive sources, makes synchrotron-based Moessbauer spectroscopy feasible and is an important complement to existing methods. A review of the experimental methodology is presented. As well as come suggestions for fuller exploitation of this new technique.

  12. Assessment of the optimum degree of Sr{sub 3}Fe{sub 2}MoO{sub 9} electron-doping through oxygen removal: An X-ray powder diffraction and {sup 57}Fe Moessbauer spectroscopy study

    SciTech Connect

    Lopez, Carlos A.; Viola, Maria del C.; Pedregosa, Jose C.; Mercader, Roberto C.

    2010-10-15

    We describe the preparation and structural characterization by X-ray powder diffraction (XRPD) and Moessbauer spectroscopy of three electron-doped perovskites Sr{sub 3}Fe{sub 2}MoO{sub 9-{delta}} with Fe/Mo = 2 obtained from Sr{sub 3}Fe{sub 2}MoO{sub 9}. The compounds were synthesized by topotactic reduction with H{sub 2}/N{sub 2} (5/95) at 600, 700 and 800 {sup o}C. Above 800 {sup o}C the Fe/Mo ratio changes from Fe/Mo = 2-1 < Fe/Mo < 2. The structural refinements of the XRPD data for the reduced perovskites were carried out by the Rietveld profile analysis method. The crystal structure of these phases is cubic, space group Fm3-bar m, with cationic disorder at the two different B sites that can be populated in variable proportions by the Fe atoms. The Moessbauer spectra allowed determining the evolution of the different species formed after the treatments at different temperatures and confirm that Fe ions in the samples reduced at 600, 700 and 800 {sup o}C are only in the high-spin Fe{sup 3+} electronic state.

  13. 57Fe Moessbauer Spectroscopic Investigations on the Brownmillerite Series Ca2(Fe2-xAlx)O5

    SciTech Connect

    Redhammer, G.J.; Roth, G.

    2005-04-26

    Several compounds along the Brownmillerite solid solution series Ca2Fe2-xAlxO5 with 0.0 {<=} x {<=} 1.34 have been synthesized by slow cooling from the melt and subsequent quenching. These samples were studied by Moessbauer spectroscopy at different absorber temperatures. Samples up to x = 1.00 are antiferromagnetically ordered at room temperature and can be evaluated by one octahedral and one tetrahedral magnetically split subspectra. With increasing temperature or increasing Al3+-content, respectively, the local magnetic fields decrease and finally collapse (TN = 518 K for x = 0.0 and TN = 298 K for x = 1.06, respectively). Despite the change of space group symmetry, quadrupole splittings at both positions increase almost linearly with increasing Al3+-content. This can be referred to structural changes reported. Even at low Al3+-contents, there always is a distribution of Fe3+ and Al3+ over the tetrahedral and octahedral positions in contrast to earlier results. Fe3+ prefers the octahedral and Al3+ prefers the tetrahedral positions.

  14. 57Fe-labeled octamethylferrocenium tetrafluoroborate. X-ray crystal structures of conformational isomers, hyperfine interactions, and spin-lattice relaxation by Moessbauer spectroscopy.

    PubMed

    Schottenberger, Herwig; Wurst, Klaus; Griesser, Ulrich J; Jetti, Ram K R; Laus, Gerhard; Herber, Rolfe H; Nowik, Israel

    2005-05-11

    X-ray structure determinations of two different single crystals of octamethylferrocenium tetrafluoroborate (OMFc(+)BF(4)(-)) revealed conformational polymorphism with ligand twist angles of 180 degrees and 108 degrees , respectively. Their concomitant occurrence could be explained by the small lattice energy difference of 3.2 kJ mol(-1). Temperature-dependent Moessbauer spectroscopy of (57)Fe-labeled OMFc(+)BF(4)(-) over the range 90 < T < 370 K did not show the anomalous sudden increase in the motion of the metal atom as observed in neutral OMFc. Broadened absorption curves characteristic of relaxation spectra were obtained with an isomer shift of 0.466(6) mm s(-1) at 90 K. The temperature dependence of the isomer shift corresponded to an effective vibrating mass of 79 +/- 10 Da and, in conjunction with the temperature dependence of the recoil-free fraction, to a Moessbauer lattice temperature of 89 K. The spin relaxation rate could be better described by an Orbach rather than a Raman process. At 400 K, a reversible solid-solid transition to a plastic crystalline mesophase was noted. PMID:15869302

  15. 57Fe quadrupole splitting and isomer shift in various oxyhemoglobins: study using Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Berkovsky, A. L.; Kumar, A.; Kundu, S.; Vinogradov, A. V.; Konstantinova, T. S.; Semionkin, V. A.

    2010-04-01

    A comparative study of normal human, rabbit and pig oxyhemoglobins and oxyhemoglobin from patients with chronic myeloleukemia and multiple myeloma using Mössbauer spectroscopy with a high velocity resolution demonstrated small variations of the 57Fe quadrupole splitting and isomer shift. These variations may be a result of small structural differences in the heme iron stereochemistry of various hemoglobins.

  16. 57Fe Mössbauer study of Lu2Fe3Si5 iron silicide superconductor

    DOE PAGESBeta

    Ma, Xiaoming; Ran, Sheng; Pang, Hua; Li, Fashen; Canfield, Paul C.; Bud'ko, Sergey L.

    2015-08-01

    With the advent of Fe–As based superconductivity it has become important to study how superconductivity manifests itself in details of 57Fe Mössbauer spectroscopy of conventional, Fe-bearing superconductors. The iron-based superconductor Lu2Fe3Si5 has been studied by 57Fe Mössbauer spectroscopy over the temperature range from 4.4 K to room temperature with particular attention to the region close to the superconducting transition temperature (Tc=6.1 K). Consistent with the two crystallographic sites for Fe in this structure, the observed spectra appear to have a pattern consisting of two doublets over the whole temperature range. Furthermore, the value of Debye temperature was estimated from temperaturemore » dependence of the isomer shift and the total spectral area and compared with the specific heat capacity data. Neither abnormal behavior of the hyperfine parameters at or near Tc, nor phonon softening were observed.« less

  17. 57Fe Mössbauer study of Lu2Fe3Si5 iron silicide superconductor

    DOE PAGESBeta

    Ma, Xiaoming; Ran, Sheng; Pang, Hua; Li, Fashen; Canfield, Paul C.; Bud'ko, Sergey L.

    2015-03-28

    With the advent of Fe–As based superconductivity it has become important to study how superconductivity manifests itself in details of 57Fe Mössbauer spectroscopy of conventional, Fe-bearing superconductors. The iron-based superconductor Lu2Fe3Si5 has been studied by 57Fe Mössbauer spectroscopy over the temperature range from 4.4 K to room temperature with particular attention to the region close to the superconducting transition temperature (Tc=6.1 K). Furthermore, consistent with the two crystallographic sites for Fe in this structure, the observed spectra appear to have a pattern consisting of two doublets over the whole temperature range. The value of Debye temperature was estimated from temperaturemore » dependence of the isomer shift and the total spectral area and compared with the specific heat capacity data. As a result, neither abnormal behavior of the hyperfine parameters at or near Tc, nor phonon softening were observed.« less

  18. 57FE Mössbauer spectroscopy studies of Tektites from Khon Kaen, Ne Thailand

    NASA Astrophysics Data System (ADS)

    Costa, B. F. O.; Klingelhöfer, G.; Alves, E. I.

    2014-01-01

    Room temperature 57Fe Mössbauer effect spectroscopy has been used to investigate the local Fe environment in a set of indochinite tektites from Thailand. A MIMOS II spectrometer in backscattering geometry has been used in the study, so that no sample preparation at all was required. The spectra have been analysed in terms of discrete spectral components using Voigt functions. The results are similar to those obtained with analysis done with quadrupole splitting distributions. In all cases the Mössbauer spectra show a broadened asymmetric quadrupole split doublet. The Fe 2+ sites have been distinguished in Fe with octahedral and tetrahedral coordination. The Fe3+ /Fe2+ and Fe2+ tetrahedral/octahedral ratios have been determined from the relative areas of the various spectral components. Their values have been discussed in the light of actual literature.

  19. Short-range order in iron alloys studied by 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Idczak, R.; Konieczny, R.; Chojcan, J.

    2013-04-01

    The room temperature Mössbauer spectra of 57Fe were measured for dilute iron-based solid solutions FeD (D=Co, Cr, Mn, Mo, Ni, Pt, Re, Ti). Analysis of the obtained spectra gave clear evidence that the distribution of impurity atoms in the two first coordination shells of 57Fe nuclei is not homogenous and it cannot be described in terms of binomial distribution. Quantitatively, the effects were described in terms of the short-range order parameters.

  20. DFT study of the hyperfine parameters and magnetic properties of ZnO doped with 57Fe

    NASA Astrophysics Data System (ADS)

    Abreu, Y.; Cruz, C. M.; Piñera, I.; Leyva, A.; Cabal, A. E.; Van Espen, P.

    2014-05-01

    Magnetic state of 57Fe implanted and doped ZnO samples have been reported and studied by Mössbauer spectroscopy at different temperatures. The Mössbauer spectra mainly showed four doublets and three sextets, but some ambiguous identification remains regarding the probe site location and influence of defects in the hyperfine and magnetic parameters. In the present work some possible implantation configurations are suggested and evaluated using Monte Carlo simulation and electronic structure calculations within the density functional theory. Various implantation environments were proposed and studied considering the presence of defects. The obtained 57Fe hyperfine parameters show a good agreement with the reported experimental values for some of these configurations. The possibility of Fe pair formation, as well as a Zn site vacancy stabilization between the second and third neighborhood of the implantation site, is supported.

  1. 57Fe-Mössbauer study of electrically conducting barium iron vanadate glass after heat treatment

    NASA Astrophysics Data System (ADS)

    Kubuki, Shiro; Sakka, Hiroshi; Tsuge, Kanako; Homonnay, Zoltán; Sinkó, Katalin; Kuzmann, Ernő; Yasumitsu, Hiroki; Nishida, Tetsuaki

    2008-07-01

    Local structure and thermal durability of semiconducting xBaO·(90 - x)V2O5 · 10Fe2O3 glasses ( x = 20, 30 and 40), NTA glass TM, before and after isothermal annealing were investigated by 57Fe-Mössbauer spectroscopy and differential thermal analysis (DTA). An identical isomer shift (mathit{δ}) of 0.39 ± 0.01 mm s - 1 and a systematic increase in the quadrupole splitting ( Δ) were observed from 0.70 ± 0.02 to 0.80 ± 0.02 mm s - 1 with an increasing BaO content, showing an increase in the local distortion of FeIIIO4 tetrahedra. From the slope of the straight line in the T g Δ plot of NTA glass TM, it proved that FeIII plays a role of network former. Large Debye temperature ( Θ D) values of 1000 and 486 K were respectively obtained for 20BaO · 70V2O5 · 10Fe2O3 glass before and after isothermal annealing at 400°C for 60 min, respectively. This result also suggests that FeIII atoms constitute the glass network composed of tetrahedral FeO4, tetrahedral VO4 and pyramidal VO5 units. The electric conductivity of 20BaO · 70V2O5 · 10Fe2O3 glass increased from 1.6 × 10 - 5 to 5.8 × 10 - 2 S cm - 1 after isothermal annealing at 450°C for 2,000 min. These results suggest that the drastic increase in the electric conductivity caused by heat treatment is closely related to the structural relaxation of the glass network structure.

  2. Magnetic anisotropy in FeSb studied by 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Komędera, K.; Jasek, A. K.; Błachowski, A.; Ruebenbauer, K.; Krztoń-Maziopa, A.

    2016-02-01

    The Fe1+xSb compound has been synthesized close to stoichiometry with x=0.023(8). The compound was investigated by 57Fe Mössbauer spectroscopy in the temperature range 4.2-300 K. The antiferromagnetic ordering temperature was found as 232 K i.e. much higher than for the less stoichiometric material. Regular iron was found to occupy two different positions in proportion 2:1. They differ by the electric quadrupole coupling constants and both of them exhibit extremely anisotropic electric field gradient tensor (EFG) with the asymmetry parameter η ≈ 1 . The negative component of both EFGs is aligned with the c-axis of the hexagonal unit cell, while the positive component is aligned with the <120> direction. Hence, a model describing deviation from the NiAs P63/mmc symmetry group within Fe-planes has been proposed. Spectra in the magnetically ordered state could be explained by introduction of the incommensurate spin spirals propagating through the iron atoms in the direction of the c-axis with a complex pattern of the hyperfine magnetic fields distributed within a-b plane. Hyperfine magnetic field pattern of spirals due to major regular iron is smoothed by the spin polarized itinerant electrons, while the minor regular iron exhibits hyperfine field pattern characteristic of the highly covalent bonds to the adjacent antimony atoms. The excess interstitial iron orders magnetically at the same temperature as the regular iron, and magnetic moments of these atoms are likely to form two-dimensional spin glass with moments lying in the a-b plane. The upturn of the hyperfine field for minor regular iron and interstitial iron is observed below 80 K. Magneto-elastic effects are smaller than for FeAs, however the recoilless fraction increases significantly upon transition to the magnetically ordered state.

  3. Mechanically-induced disorder in CaFe2As2: A 57Fe Mössbauer study

    DOE PAGESBeta

    Ma, Xiaoming; Ran, Sheng; Canfield, Paul C.; Bud'ko, Sergey L.

    2015-10-17

    57Fe Mössbauer spectroscopy was used to perform a microscopic study on the extremely pressure and strain sensitive compound, CaFe2As2, with different degrees of strain introduced by grinding and annealing. At the base temperature, in the antiferromagnetic/orthorhombic phase, compared to a sharp sextet Mössbauer spectrum of single crystal CaFe2As2, which is taken as an un-strained sample, an obviously broadened sextet and an extra doublet were observed for ground CaFe2As2 powders with different degrees of strain. The Mössbauer results suggest that the magnetic phase transition of CaFe2As2 can be inhomogeneously suppressed by the grinding induced strain to such an extent that themore » antiferromagnetic order in parts of the grains forming the powdered sample remain absent all the way down to 4.6 K. However, strain has almost no effect on the temperature dependent hyperfine magnetic field in the grains with magnetic order. Additional electronic and asymmetry information was obtained from the isomer shift and quadrupole splitting. Similar isomer shift values in the magnetic phase for samples with different degrees of strain, indicate that the stain does not bring any significant variation of the electronic density at 57Fe nucleus position. As a result, the absolute values of quadrupole shift in the magnetic phase decrease and approach zero with increasing degrees of strain, indicating that the strain reduces the average lattice asymmetry at Fe atom position.« less

  4. 57 Fe Mössbauer spectroscopy studies of chondritic meteorites from the Atacama Desert, Chile: Implications for weathering processes

    NASA Astrophysics Data System (ADS)

    Munayco, P.; Munayco, J.; Valenzuela, M.; Rochette, P.; Gattacceca, J.; Scorzelli, R. B.

    2014-01-01

    Some terrestrial areas have climatic and geomorphologic features that favor the preservation, and therefore, accumulation of meteorites. The Atacama Desert in Chile is among the most important of such areas, known as dense collection areas. This desert is the driest on Earth, one of the most arid, uninhabitable locals with semi-arid, arid and hyper-arid conditions. The meteorites studied here were collected from within the dense collection area of San Juan at the Central Depression and Coastal Range of Atacama Desert. 57Fe Mössbauer spectroscopy was used for quantitative analysis of the degree of weathering of the meteorites, through the determination of the proportions of the various Fe-bearing phases and in particular the amount of oxidized iron in the terrestrial alteration products. The abundance of ferric ions in weathered chondrites can be related to specific precursor compositions and to the level of terrestrial weathering. The aim of the study was the identification, quantification and differentiation of the weathering products in the ordinary chondrites found in the San Juan area of Atacama Desert.

  5. Structural and 57Fe Mössbauer study of EuCr1 - x Fe x O3 nanocrystalline particles

    NASA Astrophysics Data System (ADS)

    Widatallah, H. M.; Al-Shahumi, T. M. H.; Gismelseed, A. M.; Klencsár, Z.; Al-Rawas, A. D.; Al-Omari, I. A.; Elzain, M. E.; Yousif, A. A.; Pekala, M.

    2012-03-01

    A structural and Mössbauer study of mechanosynthesized EuCr1 - xFexO3 nanocrystalline particles (˜20-30 nm) is presented. The lattice parameters increase with increasing x-value leading to an increasingly distorted structure. The crystallite sizes range between 20 nm and 30 nm. Magnetic and 57Fe Mössbauer measurements show the samples with x < 0.7 to be paramagnetic and those with x ≥ 0.7 to be partially superparamagnetic at 298 K. The 78 K Mössbauer spectra of the samples with x = 0.3-1.0 are composed of well-resolved two sextets that are explicable in terms of the structural model that we recently have proposed for the EuCrO3 nanoparticles according to which the transition metal ions and Eu3 + partly exchange their usual sites in the perovskite-related structure (Widatallah et al. J Phys D Appl Phys 44:265403, 2011). Consequently, the two sextets obtained at 78 K refer to Fe3 + ions at the usual B-octahedral site and the A-dodecahedral site usually occupied by Eu3 + .

  6. Mechanically - induced disorder in CaFe2As2: a 57Fe Mössbauer study

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoming; Ran, Sheng; Canfield, Paul C.; Bud'Ko, Sergey L.

    57 Fe Mössbauer spectroscopy was used to study an extremely pressure and strain sensitive compound, CaFe2As2, with different degrees of strain introduced by grinding and annealing. At the base temperature, in the antiferromagnetic/orthorhombic phase, compared to a sharp sextet Mössbauer spectrum of single crystal CaFe2As2, which is taken as an un-strained sample, an obviously broadened sextet and an extra doublet were observed for ground CaFe2As2 powders with different degrees of strain. The Mössbauer results suggest that the magnetic phase transition of CaFe2As2 can be inhomogeneously suppressed by the grinding induced strain to such an extent that the antiferromagnetic order in parts of the grains forming the powdered sample remain absent all the way down to 4.6 K. However, strain has almost no effect on the temperature dependent hyperfine magnetic field in the grains with magnetic order. The quadrupole shift in the magnetic phase approachs zero with increasing degrees of strain, indicating that the strain reduces the average lattice asymmetry at Fe atom position. Supported by US DOE under the Contract No. DE-AC02-07CH11358 and by the China Scholarship Council.

  7. A study of thermodynamic properties of dilute Fe-Ru alloys by 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Idczak, R.; Konieczny, R.; Chojcan, J.

    2016-12-01

    The room temperature Mössbauer spectra of 57Fe were measured for Fe1- x Ru x solid solutions with x in the range 0.01 ≤ x ≤ 0.08. The obtained data were analysed in terms of short-range order parameter (SRO) and the binding energy E b between two ruthenium atoms in the studied materials using the extended Hrynkiewicz-Królas idea. The extrapolated value of E b for x = 0 was used to compute the enthalpy of solution H FeRu of Ru in Fe matrix. The result was compared with corresponding values given in the literature which were derived from experimental calorimetric data as well as with the value resulting from the cellular atomic model of alloys by Miedema. It was found that all the H FeRu values are negative or Ru atoms interact repulsively. At the same time, the Mössbauer data were used to determine values of the short-range order parameter α 1. For the as-obtained samples in which atoms are frozen-in high temperature state, close to the melting point, the negative α 1 values were found. The findings indicates ordering tendencies in such specimens. On the other hand, in the case of the annealed samples where the observed distributions of atoms should be frozen-in state corresponding to the temperature 700 K, the Fe1- x Ru x alloys with x ≥ 0.05 exhibit clustering tendencies (a predominance of Fe-Fe and Ru-Ru bonds), which manifest themselves by positive values of the calculated SRO parameter. The clustering process leads to a local increase in ruthenium concentration and nucleation of a new ruthenium-rich phase with the hcp structure.

  8. Mössbauer spectroscopic study of 57Fe metabolic transformations in the rhizobacterium Azospirillum brasilense Sp245

    NASA Astrophysics Data System (ADS)

    Kamnev, Alexander A.; Tugarova, Anna V.; Kovács, Krisztina; Biró, Borbála; Homonnay, Zoltán; Kuzmann, Ernő

    2014-04-01

    Preliminary 57Fe transmission Mössbauer spectroscopic data were obtained for the first time for live cells of the plant-growth-promoting rhizobacterium Azospirillum brasilense (wild-type strain Sp245) grown aerobically with 57FeIII-nitrilotriacetate (NTA) complex as a sole source of iron. The results obtained have shown that live cells actively reduce part of the assimilated iron(III) to iron(II), the latter amounting up to 33 % of total cellular iron after 18 h of growth, and 48 % after additional 3 days of storage of the dense wet cell suspension in nutrient-free saline solution in air at room temperature (measured at 80 K). The cellular iron(II) was found to be represented by two quadrupole doublets of different high-spin forms, while the parameters of the cellular iron(III) were close to those typical for bacterioferritins.

  9. Study of 57 Fe Mössbauer effect in RFe2Zn20 ( R = Lu, Yb, Gd)

    DOE PAGESBeta

    Bud’ko, Sergey L.; Kong, Tai; Ma, Xiaoming; Canfield, Paul C.

    2015-08-04

    In this document we report measurements of 57Fe Mössbauer spectra for RFe2Zn20 (R = Lu, Yb, Gd) from ~ 4.5 K to room temperature. The obtained isomer shift values are very similar for all three compounds, their temperature dependence was analyzed within the Debye model and resulted in an estimate of the Debye temperatures of 450-500 K. The values of quadrupole splitting at room temperature change with the cubic lattice constant a in a linear fashion. For GdFe2Zn20, ferromagnetic order is seen as an appearance of a sextet in the spectra. The 57Fe site hyperfine field for T → 0more » was evaluated to be ~ 2.4 T.« less

  10. Progressive oxidation of pyrite in five bituminous coal samples: An As XANES and 57Fe Mössbauer spectroscopic study

    USGS Publications Warehouse

    Kolker, Allan; Huggins, Frank E.

    2007-01-01

    Naturally occurring pyrite commonly contains minor substituted metals and metalloids (As, Se, Hg, Cu, Ni, etc.) that can be released to the environment as a result of its weathering. Arsenic, often the most abundant minor constituent in pyrite, is a sensitive monitor of progressive pyrite oxidation in coal. To test the effect of pyrite composition and environmental parameters on the rate and extent of pyrite oxidation in coal, splits of five bituminous coal samples having differing amounts of pyrite and extents of As substitution in the pyrite, were exposed to a range of simulated weathering conditions over a period of 17 months. Samples investigated include a Springfield coal from Indiana (whole coal pyritic S = 2.13 wt.%; As in pyrite = detection limit (d.l.) to 0.06 wt.%), two Pittsburgh coal samples from West Virginia (pyritic S = 1.32–1.58 wt.%; As in pyrite = d.l. to 0.34 wt.%), and two samples from the Warrior Basin, Alabama (pyritic S = 0.26–0.27 wt.%; As in pyrite = d.l. to 2.72 wt.%). Samples were collected from active mine faces, and expected differences in the concentration of As in pyrite were confirmed by electron microprobe analysis. Experimental weathering conditions in test chambers were maintained as follows: (1) dry Ar atmosphere; (2) dry O2 atmosphere; (3) room atmosphere (relative humidity ∼20–60%); and (4) room atmosphere with samples wetted periodically with double-distilled water. Sample splits were removed after one month, nine months, and 17 months to monitor the extent of As and Fe oxidation using As X-ray absorption near-edge structure (XANES) spectroscopy and 57Fe Mössbauer spectroscopy, respectively. Arsenic XANES spectroscopy shows progressive oxidation of pyritic As to arsenate, with wetted samples showing the most rapid oxidation. 57Fe Mössbauer spectroscopy also shows a much greater proportion of Fe3+ forms (jarosite, Fe3+ sulfate, FeOOH) for samples stored under wet conditions, but much less

  11. Structural, electrical, magnetic and 57Fe Mössbauer study of polycrystalline multiferroic DyFeO3

    NASA Astrophysics Data System (ADS)

    Reddy, S. Shravan Kumar; Raju, N.; Reddy, Ch. Gopal; Reddy, P. Yadagiri; Reddy, K. Rama; Reddy, V. Raghavendra

    2015-12-01

    Structural, Raman spectroscopy, leakage current density, temperature dependent magnetization and Mössbauer measurements of polycrystalline DyFeO3 (DFO) prepared through sol-gel route are reported in this paper. Phase purity and structure of the prepared sample is confirmed from x-ray diffraction and Raman spectroscopy measurements. The room temperature leakage current density (J-E) measurements indicate that Ohmic contribution and space charge limited conduction are the dominating mechanisms at low and high applied electric fields respectively. Signatures of Fe3+ spin reorientation transition (TSR) and the antiferromagnetic ordering of Dy3+ ions are observed from the temperature dependent (10-350 K) magnetization data. The M-H data measured at 2 K shows the field induced metamagnetic transition. Internal hyperfine field obtained from temperature dependent (5-300 K) 57Fe Mössbauer measurements is observed to decrease below the TSR and further found to increase till 5 K indicating the contribution of Dy3+ magnetic ordering on the hyperfine field of Fe nucleus.

  12. 57Fe Mössbauer and electrical studies of the (NiO)-(Cr2O3) x-(Fe2O3)2-x system

    NASA Astrophysics Data System (ADS)

    Fayek, M. K.; Ata-Allah, S. S.

    2003-08-01

    From 57Fe Mössbauer measurements carried out on the spinel ferrite under study, the ratio of the integrated intensities of 57Fe A- and B-site subspectra can be evaluated. The composition of the ferrite has been established as (Fe3+)[Ni2+Cr3+xFe3+1-x] for 0.0 ≤ x ≤ 0.6. The composition dependence of the Mössbauer hyperfine parameters (center shift and quadrupole splitting) displays no features in this composition range that would result from a qualitative change in electronic structure. The ac conductivity measurements re-veal a semiconducting behavior with a transition in the conductivity versus temperature curve. The transi-tion temperature is found to decrease linearly with increasing Cr concentration x. The dielectric parameters (and loss (tan δ)) of the studied samples exhibit dipolar relaxation effects. The results of conductivity and dielectric parameters are explained in the light of hopping conduction at the octahedral B sites.

  13. Multiple superhyperfine fields in a {DyFe2Dy} coordination cluster revealed using bulk susceptibility and (57)Fe Mössbauer studies.

    PubMed

    Peng, Yan; Mereacre, Valeriu; Anson, Christopher E; Powell, Annie K

    2016-08-01

    A [DyFeDy(μ3-OH)2(pmide)2(p-Me-PhCO2)6] coordination cluster, where pmideH2 = N-(2-pyridylmethyl)iminodiethanol, has been synthesized and the magnetic properties studied. The dc magnetic measurements reveal dominant antiferromagnetic interactions between the metal centres. The ac measurements reveal zero-field quantum tunnelling of the magnetisation (QTM) which can be understood, but not adequately modelled, in terms of at least three relaxation processes when appropriate static (dc) fields are applied. To investigate this further, (57)Fe Mössbauer spectroscopy was used and well-resolved nuclear hyperfine structures could be observed, showing that on the Mössbauer time scale, without applied field or else with very small applied fields, the iron nuclei experience three or more superhyperfine fields arising from the slow magnetisation reversal of the strongly polarized fields of the Dy(III) ions. PMID:27424877

  14. Thermal decomposition and reconstruction of CaFe-layered double hydroxide studied by X-ray diffractometry and 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Bugris, Valéria; Ádok-Sipiczki, Mónika; Anitics, Tamás; Kuzmann, Ernő; Homonnay, Zoltán; Kukovecz, Ákos; Kónya, Zoltán; Sipos, Pál; Pálinkó, István

    2015-06-01

    In spite of numerous investigations on the various processes of the thermal decomposition and rehydration of layered double hydroxides (LDHs) by a variety sophisticated experimental means, many details are still unexplored and some contradictions are still unresolved. In this work, our efforts were focussed on clarifying the composition, structure and properties of thermally decomposed metaphases originating from CaFe-LDH, heat treated in the 373-973 K temperature range. The structure reconstruction ability of mixed metal oxide phases obtained after heat treatments was also investigated, mainly concentrating on the changes in the microenvironment of Fe(III), in the presence of controlled amount of water vapour (i.e., at different relative humidities). All samples were characterised by X-ray diffractometry, and the iron-containing phases were studied by 57Fe Mössbauer spectroscopy.

  15. Moessbauer effect: Study of disordered magnetic systems

    SciTech Connect

    Chang, Xiao Sha.

    1989-01-01

    This dissertation describes Moessbauer spectroscopy studies of two chemically disordered binary, crystalline alloys having the composition A{sub 1-x}B{sub x}. Both systems are random 3d Heisenberg ferromagnets. In each case both A and B atoms carry a magnetic moment. The first study concerns a Moessbauer absorber experiment on Fe{sub 1-x} V{sub x}, in which the disorder in the critical region is of the annealed random exchange type. To eliminate the effect of concentration inhomogeneity, the measurement of the critical exponent {beta} was done on the alloy with x = 0.125, where dT{sub C}/dx = 0, yielding {beta} = 0.362(8) over the reduced temperature range 1.4 {times} 10{sup {minus}3} < t < 4.88 {times} 10{sup {minus}1}. This result confirms the theoretical prediction that the annealed disorder is irrelevant to critical behavior in this case. As expected the critical exponent {beta} is consistent with the expectation for the 3d Heisenberg model as well as the measured exponent of pure Fe. The second study involves a Moessbauer source experiment on {sup 57} CoPd{sub 0.80}Co{sub 0.20}, in which disorder is of the quenched random exchange type perturbed by a very weak random anisotropy interaction. The critical exponent {beta} deduced over the range 1 {times} 10{sup {minus}2} < t < 2 {times} 10{sup {minus}1} is 0.385(20), and is consistent with the theoretical prediction for quenched disordered 3d Heisenberg systems: the disorder is irrelevant to the critical behavior. However, because of the restricted range of reduced temperature, the result is insufficiently asymptotic to serve as a conclusive test of the theory. Outside the critical region the distribution of Fe{sup 57} hyperfine field in Pd{sub 0.80}Co{sub 0.20} is observed to have an anomalous temperature dependence characterized by a linear increase in the width of the field distribution for T/T{sub C} {ge} 0.6.

  16. The 57Fe hyperfine interactions in iron storage proteins in liver and spleen tissues from normal human and two patients with mantle cell lymphoma and acute myeloid leukemia: a Mössbauer effect study

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Alenkina, I. V.; Vinogradov, A. V.; Konstantinova, T. S.; Semionkin, V. A.

    2015-04-01

    Study of human spleen and liver tissues from healthy persons and two patients with mantle cell lymphoma and acute myeloid leukemia was carried out using Mössbauer spectroscopy with a high velocity resolution. Small variations in the 57Fe hyperfine parameters for normal and patient's tissues were detected and related to small variations in the 57Fe local microenvironment in ferrihydrite cores. The differences in the relative parts of more crystalline and more amorphous core regions were also supposed for iron storage proteins in normal and patients' spleen and liver tissues.

  17. Elementary diffusion jump of iron atoms in intermetallic phases studied by Moessbauer spectroscopy; 1: Fe-Al close to equiatomic stoichiometry

    SciTech Connect

    Vogl, G.; Sepiol, B. . Inst. fuer Festkoerperphysik)

    1994-09-01

    The authors have studied the quasielastic broadening of the [sup 57]Fe Moessbauer resonance in the intermetallic compound FeAl in order to determine the diffusion jump mechanism of the Fe atoms. From the angular dependence of the line broadening relative to an oriented single crystal they deduce that the Fe atoms jump effectively to different neighbor sites on the Fe sublattice. The jump is, however, not a direct one, but rather a combination of a jump into a nearest neighbor vacancy--leading to short-time occupation of an antistructure site on the Al sublattice--and a jump into a vacancy back on the Fe sublattice.

  18. The electronic structure of the H-cluster in the [FeFe]-hydrogenase from Desulfovibrio desulfuricans: a Q-band 57Fe-ENDOR and HYSCORE study.

    PubMed

    Silakov, Alexey; Reijerse, Eduard J; Albracht, Simon P J; Hatchikian, E Claude; Lubitz, Wolfgang

    2007-09-19

    The active site of the (57)Fe-enriched [FeFe]-hydrogenase (i.e., the "H-cluster") from Desulfovibrio desulfuricans has been examined using advanced pulse EPR methods at X- and Q-band frequencies. For both the active oxidized state (H(ox)) and the CO inhibited form (H(ox)-CO) all six (57)Fe hyperfine couplings were detected. The analysis shows that the apparent spin density extends over the whole H-cluster. The investigations revealed different hyperfine couplings of all six (57)Fe nuclei in the H-cluster of the H(ox)-CO state. Four large 57Fe hyperfine couplings in the range 20-40 MHz were found (using pulse ENDOR and TRIPLE methods) and were assigned to the [4Fe-4S](H) (cubane) subcluster. Two weak (57)Fe hyperfine couplings below 5 MHz were identified using Q-band HYSCORE spectroscopy and were assigned to the [2Fe](H) subcluster. For the H(ox) state only two different 57Fe hyperfine couplings in the range 10-13 MHz were detected using pulse ENDOR. An (57)Fe line broadening analysis of the X-band CW EPR spectrum indicated, however, that all six (57)Fe nuclei in the H-cluster are contributing to the hyperfine pattern. It is concluded that in both states the binuclear subcluster [2Fe](H) assumes a [Fe(I)Fe(II)] redox configuration where the paramagnetic Fe(I) atom is attached to the [4Fe-4S](H) subcluster. The (57)Fe hyperfine interactions of the formally diamagnetic [4Fe-4S](H) are due to an exchange interaction between the two subclusters as has been discussed earlier by Popescu and Münck [Popescu, C.V.; Münck, E., J. Am. Chem. Soc. 1999, 121, 7877-7884]. This exchange coupling is strongly enhanced by binding of the extrinsic CO ligand. Binding of the dihydrogen substrate may induce a similar effect, and it is therefore proposed that the observed modulation of the electronic structure by the changing ligand surrounding plays an important role in the catalytic mechanism of [FeFe]-hydrogenase. PMID:17722921

  19. Moessbauer Study of Electrodeposited Fe/Fe-Oxide Multilayers

    SciTech Connect

    Kuzmann, E.; Homonnay, Z.; Klencsar, Z.; Vertes, A.; Lakatos-Varsanyi, M.; Miko, A.; Varga, L.K.; Kalman, E.; Nagy, F.

    2005-04-26

    Iron has been deposited electrochemically by short current pulses in Na-saccharin containing FeII-chloride and sulphate solution electrolytes. Combined electrochemical techniques with initial pulse plating of iron nanolayer and its subsequent anodic oxidation under potential control have been used for production of Fe/Fe-oxide multilayers. 57Fe CEM spectra of pulse plated iron revealed the presence of a minor doublet attributed mainly to {gamma}-FeOOH in addition to the dominant sextet of {alpha}-iron. In the case of anodically oxidized pulse plated iron and of samples after repeated deposition of anodically oxidized pulse plated iron an additional minor doublet, assigned to ferrous chloride, also appears in the Moessbauer spectra. A significant change in the magnetic anisotropy of {alpha}-iron was observed with the anodic oxidation. The thickness of the layers were estimated from the CEM spectrum data by a modified computer program of the Liljequist method. The coercive field and the power loss versus frequency data showed that the pulse plated iron cores are good inductive elements up to several kHz frequencies.

  20. Fe-57 Moessbauer study of tektites

    NASA Technical Reports Server (NTRS)

    Evans, B. J.; Leung, L. K.

    1976-01-01

    Moessbauer measurements were made on selected moldavite, australite, philippinite, and Georgia tektites. The spectra consist of two apparent lines, but at least two quadrupole doublets can be fitted to these spectra. The Moessbauer parameters for these doublets indicate that they arise from Fe2+ ions with local environments, which are relatively rich and relatively poor in calcium, respectively, similar to those in clinopyroxenes. No evidence for Fe3+/Fe2+ ratios above 0.01 (estimated detection limit) have been found in any tektite. Tektites are considerably more reduced than previously believed, and the extent of the reduction shows little or no variation among different types of tektites. These results limit the source materials of tektites to minerals in which the iron is uniformly highly reduced and in which the iron is contained clinopyroxene-like phases.

  1. Provenance study of obsidians from the archaeological site of La Maná (Ecuador) by electron spin resonance (ESR), SQUID magnetometry and 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Duttine, M.; Scorzelli, R. B.; Poupeau, G.; Bustamante, A.; Bellido, A. V.; Lattini, R. M.; Guillaume-Gentil, N.

    2007-02-01

    Obsidians from major Ecuadorian sources (outcrops) were analyzed by electron spin resonance, SQUID magnetometry and 57Fe Mössbauer spectroscopy. If the last technique allows to discriminate obsidians from the Quiscatola source, an association of ESR with SQUID magnetometry permits to differentiate obsidians from the sources of Cotopaxi volcano, from the Quiscatola and Mullumica-Callejones sources of the Chacana caldera and to infer that the 12 analyzed obsidians from the pre-Hispanic site of La Maná come from the Mullumica-Callejones source.

  2. Effects of time and temperature of firing on Fe-rich ceramics studied by Moessbauer spectroscopy and two-dimensional {sup 1}H-nuclear magnetic resonance relaxometry

    SciTech Connect

    Casieri, Cinzia; De Luca, Francesco; Nodari, Luca; Russo, Umberto; Terenzi, Camilla; Tudisca, Valentina

    2012-10-15

    The combined effects of firing temperature and soaking time on the microstructure of iron-rich porous ceramics have been studied by {sup 57}Fe-Moessbauer spectroscopy and 2D {sup 1}H nuclear magnetic resonance (NMR) relaxometry using a single-sided probe. Examining water-saturated ceramics using the relaxation correlation method, where longitudinal (T{sub 1}) and transverse (T{sub 2}) relaxation times are measured concurrently, provides information about firing-induced changes in both porosity (related to T{sub 1}) and magnetic properties (related to T{sub 2}). Comparing the information obtained from {sup 1}H-NMR analyses with that obtained from Moessbauer spectroscopy (which characterizes changes in iron-bearing species) shows that the T{sub 1}-T{sub 2} NMR correlation technique is very sensitive to even subtle modifications in the magnetic behavior of Fe-bearing species. Moreover, the single-sided NMR approach allows us to perform millimeter-scale depth-resolved measurements, which can be used to non-invasively study the microstructural heterogeneities associated with non-uniform firing effects inside ceramics. This is in contrast to Moessbauer spectroscopy, which requires that the ceramic samples be ground.

  3. Moessbauer Study of Soil Profiles in Industrial Region of Ukraine

    SciTech Connect

    Kopcewicz, B.; Jelenska, M.; Hasso-Agopsowicz, A.; Kopcewicz, M.

    2005-04-26

    Moessbauer spectroscopy was applied to study the influence of industrial activity on soil composition. Comparing the Moessbauer spectra of separate layers for the Mariupol sampling site (highly polluted industrial region of South -- East Ukraine) we observed: i) appearance of the Fe3O4 compound at top soil layers: 16.6% of relative spectral area (RA) at (0 - 10 cm) layer, 5.3% of RA at (30 - 40 cm) layer and no magnetite component at deeper layers, ii) a significant increase of the contribution of the magnetically split spectral components: from 10.9% of RA for (120 - 130 cm) layer to 32.8% of RA for (0-10 cm) layer. The differences in RA of the magnetically split spectral components between top soil layer and the (120 - 130 cm) layer at the Homutovski steppe sampling site (non-polluted area) are much smaller, 13.7% and 9.8%, respectively. From the temperature dependence of the Moessbauer spectra it was concluded that part of the iron-containing compounds appears in the form of ultra fine particles in the superparamagnetic state. The observed increase of total concentration of the magnetic minerals for polluted sampling sites is caused by an increase of the content of coarse fraction of the magnetic particles.

  4. /sup 57/Fe Mossbauer spectroscopy of U/sub 6/Fe

    SciTech Connect

    Lemon, G.; Boolchand, P.; Stevens, M.; DeLong, L.E.; Huber, J.G.; Marcuso, M.

    1986-04-01

    Samples of U/sub 6/Fe were prepared by arc melting U and enriched /sup 57/Fe. The samples display superconducting transitions which are sensitive to long-term exposure to air. Room temperature spectra of U/sub 6/Fe typically display a majority site A (quadrupole splitting ..delta.. = 0.749(3) mm/s, isomer shift delta = 0.482(6) mm/s relative to Cu) and a minority site B (..delta.. = 0.55(3) mm/s, sigma = 0.12(3) mm/s) with the site intensity ratio (I/sub B//I/sub A/) typically 0.05 to 0.10. The I/sub B//I/sub A/ intensity ratio increases upon air exposure of the samples. We have studied Moessbauer spectra as a function of temperature T in the range 15/sup 0/K less than or equal to T less than or equal to 310/sup 0/K paying particular attention to the T-variation of the isomer-shift and recoil-free-fraction of the majority site A. Results indicate a consistent softening of lattice vibrations of U/sub 6/Fe at T approx. = 170/sup 0/K.

  5. Study of Vitamins and Dietary Supplements Containing Ferrous Fumarate and Ferrous Sulfate Using Moessbauer Spectroscopy

    SciTech Connect

    Oshtrakh, M. I.; Novikov, E. G.; Semionkin, V. A.; Dubiel, S. M.

    2010-07-13

    A study of several samples of vitamins and dietary supplements containing ferrous fumarate and ferrous sulfate was carried out using Moessbauer spectroscopy with a high velocity resolution. A presence of ferrous and ferric impurities was revealed. Small variations of Moessbauer hyperfine parameters were found for both ferrous fumarates and ferrous sulfates in the investigated medicines.

  6. Moessbauer studies of Sr{sub 2}FeO{sub 4} to pressures of 20 GPa

    SciTech Connect

    Hearne, G.R. |; Pasternak, M.P.; Rozenberg, G.

    1995-09-01

    The transport and magnetic properties of the antiferromagnetic semiconductor Sr{sub 2}FeO{sub 4} (Fe{sup 4+}, d{sup 4}) were probed by resistance studies and {sup 57}Fe Moessbauer spectroscopy to 20 GPa using a diamond-anvil cell. The main conclusions of this work are that beyond the onset of the semiconductor-metal transition at {approx}17(1) GPa determined in the resistance studies: (1) the compound is still magnetic and, (2) there is no charge disproportionation of the form: 2Fe{sup 4+} {yields} Fe{sup 3+} + Fe{sup 5+}. The quadrupole splitting ({delta}E{sub Q}) at room temperature (RT) decreases from 0.42 mm/s at ambient pressure to a minimum of 2.2 mm/s at {approx}5.5 GPa. Beyond 5.5 GPa {delta}E{sub Q} at RT increases monotonically reaching 0.5 mm/s at 20 GPa. In the 0-10 GPa pressure range the Neel temperature T{sub N}, is pinned at 60-70 K reaching values of 135(5) K at 19 GPa where the compound is metallic. At 19 GPa and T {much_lt} T{sub N} a simplified magnetic spectrum having an internal magnetic field of {approx}25 T and a substantial quadrupole interaction is obtained.

  7. Moessbauer studies of two-electron centers with negative correlation energy in crystalline and amorphous semiconductors

    SciTech Connect

    Bordovsky, G. A.; Nemov, S. A.; Marchenko, A. V.; Seregin, P. P.

    2012-01-15

    The results of the study of donor U{sup -}-centers of tin and germanium in lead chalcogenides by Moessbauer emission spectroscopy are discussed. The published data regarding the identification of amphoteric U{sup -}-centers of tin in glassy binary arsenic and germanium chalcogenides using Moessbauer emission spectroscopy, and in multicomponent chalcogenide glasses using Moessbauer absorption spectroscopy are considered. Published data concerning the identification of two-atom U{sup -}-centers of copper in lattices of semimetal copper oxides by Moessbauer emission spectroscopy are analyzed. The published data on the detection of spatial inhomogeneity of the Bose-Einstein condensate in superconducting semiconductors and semimetal compounds, and on the existence of the correlation between the electron density in lattice sites and the superconducting transition temperature are presented. The principal possibility of using Moessbauer U{sup -}-centers as a tool for studying the Bose-Einstein condensation of electron pairs during the superconducting phase transition in semiconductors and semimetals is considered.

  8. Mössbauer study of exogenous iron redistribution between the brain and the liver after administration of 57Fe3O4 ferrofluid in the ventricle of the rat brain

    NASA Astrophysics Data System (ADS)

    Polikarpov, Dmitry; Gabbasov, Raul; Cherepanov, Valery; Loginova, Natalia; Loseva, Elena; Nikitin, Maxim; Yurenia, Anton; Panchenko, Vladislav

    2015-04-01

    Iron clearance pathways after the injection of 57Fe3O4-based ferrofluid into the brain ventricles were studied histologically and by Mössbauer spectroscopy. It was found that the dextran coated initial nanobeads of the ferrofluid disintegrated in the brain into separate superparamagnetic nanoparticles within a week after the injection. The exogenous iron completely exited all ventricular cavities of the brain within a week after the injection but remained in the white matter for months. Kupffer cells with the exogenous iron appeared in the rat liver 2 hours after the injection. Their concentration reached its maximum on the third day and dropped to zero within a week. The exogenous iron appeared in the spleen a week after the injection and remained in the spleen for months.

  9. The 57Fe hyperfine interactions in the iron bearing phases in different fragments of Chelyabinsk LL5 meteorite: a comparative study using Mössbauer spectroscopy with a high velocity resolution

    NASA Astrophysics Data System (ADS)

    Maksimova, A. A.; Oshtrakh, M. I.; Petrova, E. V.; Grokhovsky, V. I.; Semionkin, V. A.

    2015-04-01

    A comparative study of the 57Fe hyperfine interactions in iron bearing phases of Chelyabinsk LL5 ordinary chondrite fragments with different lithology was carried out using Mössbauer spectroscopy with a high velocity resolution. The obtained values of hyperfine parameters for the same iron bearing phases in different fragments demonstrated small variations. These differences were related to small variations in the Fe local microenvironments in both M1 and M2 sites in olivine and pyroxene, to deviation from stoichiometry in troilite with increase in Fe vacancies and to differences in Ni concentrations in α-Fe(Ni, Co) and γ-Fe(Ni, Co) phases in the metal grains. The obtained differences may indicate a breccia structure of Chelyabinsk LL5 ordinary chondrite.

  10. The {sup 57}Fe nuclear magnetic resonance shielding in ferrocene revisited. A density-functional study of orbital energies, shielding mechanisms, and the influence of the exchange-correlation functional

    SciTech Connect

    Schreckenbach, G.

    1999-06-01

    The {sup 57}Fe nuclear magnetic resonance (NMR) shielding and chemical shift in ferrocene, Fe(C{sub 5}H{sub 5}){sub 2}, are studied using density functional theory (DFT) and gauge-including atomic orbitals (GIAO). Electronic factors contributing to the chemical shift are discussed in detail. It is shown that the chemical shift is entirely determined by paramagnetic contributions which in turn are dominated by metal based occupied-virtual d{r_arrow}d couplings. In particular, the HOMO-1(a{sub 1}{sup {prime}}) and the HOMO (e{sub 2}{sup {prime}}) couple with the LUMO (e{sub 1}{sup {double_prime}}). It is argued that the {sup 57}Fe nucleus in ferrocene is less shielded than in the reference compound (iron pentacarbonyl) due to a smaller HOMO-LUMO gap, resulting in stronger interactions between occupied and virtual orbitals. The influence of the XC functional on the calculated molecular orbital (MO) energies of frontier orbitals is discussed. Different generalized gradient approximations (GGA) give similar results whereas hybrid functionals that incorporate part of the Hartree{endash}Fock exchange stabilize occupied MOs strongly and destabilize virtual MOs. HOMO-LUMO gaps are nearly doubled as a result. The previously noted {open_quotes}dramatic influence{close_quotes} of different exchange-correlation (XC) functionals on the calculated chemical shifts is analyzed. The influence of the XC functional is realized through the paramagnetic part of the shielding; hybrid functionals increase it in absolute terms as compared to pure DFT (GGA). It is argued that three factors are responsible. These are (i) the increased occupied-virtual gaps, (ii) the more diffuse nature of virtual orbitals, and (iii) the coupling due to the Hartree{endash}Fock exchange in hybrid functionals. The last two factors increase the paramagnetic part of the shielding, and this effect is only partly reversed by the increased occupied-virtual gaps that result in reduced interactions. It is suggested

  11. Structural magnetic and Mossbauer study of 57Fe doped La2/3Ca1/3Mn1-xFexO3 (0≥x≥0.1) manganites

    NASA Astrophysics Data System (ADS)

    Sánchez, L. C.; Durango, D.; Arnache, O.

    2016-02-01

    We have studied the effect of 57Fe substitution on structural and magnetic properties of La2/3Ca1/3Mn1-xFexO3 (LCMFO; x=0, 5 and 10%) manganites. The powders were prepared by the solid state reaction method, and the final products were characterized by X-Ray Diffraction (XRD), Mössbauer Spectrometry and Magnetic Measurements. Only one single phase corresponding to the manganite phase was detected without the presence of impurities or iron phases. The hyperfine parameters of Mossbauer spectra (MS), taken at different temperatures for the doped samples, reveal the only presence of Fe3+ ions in octahedral coordination. At low temperatures, the MS spectra were fitted with a model of three components associated to three magnetic phases of iron (ferromagnetic and paramagnetic states). These ordered and not ordered magnetic phases are related to the effects of grain size distribution in LCMFO samples. Finally, significant changes were observed in the saturation magnetization, Curie temperature and coercivity field with increasing of iron doping level.

  12. In situ x-ray reflectivity and grazing incidence x-ray diffraction study of L 1(0) ordering in (57)Fe/Pt multilayers.

    PubMed

    Raghavendra Reddy, V; Gupta, Ajay; Gome, Anil; Leitenberger, Wolfram; Pietsch, U

    2009-05-01

    In situ high temperature x-ray reflectivity and grazing incidence x-ray diffraction measurements in the energy dispersive mode are used to study the ordered face-centered tetragonal (fct) L 1(0) phase formation in [Fe(19 Å)/Pt(25 Å)]( × 10) multilayers prepared by ion beam sputtering. With the in situ x-ray measurements it is observed that (i) the multilayer structure first transforms to a disordered FePt and subsequently to an ordered fct L 1(0) phase, (ii) the ordered fct L 1(0) FePt peaks start to appear at 320 °C annealing, (iii) the activation energy of the interdiffusion is 0.8 eV and (iv) ordered fct FePt grains have preferential out-of-plane texture. The magneto-optical Kerr effect and conversion electron Mössbauer spectroscopies are used to study the magnetic properties of the as-deposited and 400 °C annealed multilayers. The magnetic data for the 400 °C annealed sample indicate that the magnetization is at an angle of ∼50° from the plane of the film. PMID:21825468

  13. Moessbauer studies of complex materials: Energy versus time domain

    SciTech Connect

    Planckaert, N.; Callens, R.; Demeter, J.; Temst, K.; Vantomme, A.; Laenens, B.; Meersschaut, J.; Sturhahn, W.; Kharlamova, S.

    2009-06-01

    We present a critical comparison between conventional Moessbauer spectroscopy on the one hand and energy and time resolved nuclear resonant scattering on the other hand. The three Moessbauer techniques are evaluated by the characterization of the complex magnetic structure of an Fe{sub 3}Al alloy. It is shown how the different scattering processes and detection schemes, which are involved in the respective configurations, determine the specific strengths of the three techniques and how they are optimally suited for the characterization of materials of varying complexity and reduced sizes.

  14. SEM, optical, and Moessbauer studies of submicrometer chromite in Allende

    NASA Astrophysics Data System (ADS)

    Housley, R. M.

    New scanning electron and optical microscope results are presented showing that sub-micrometer chromite is abundant along healed cracks and grain boundaries in Allende chondrule olivine. Some wider healed cracks also contain pentlandite and euhedral Ni3Fe grains. Also reported are Moessbauer measurements on Allende HF-HCl residues confirming a high Fe(+++)/Fe(++) ratio.

  15. SEM, optical, and Moessbauer studies of submicrometer chromite in Allende

    NASA Technical Reports Server (NTRS)

    Housley, R. M.

    1982-01-01

    New scanning electron and optical microscope results are presented showing that sub-micrometer chromite is abundant along healed cracks and grain boundaries in Allende chondrule olivine. Some wider healed cracks also contain pentlandite and euhedral Ni3Fe grains. Also reported are Moessbauer measurements on Allende HF-HCl residues confirming a high Fe(+++)/Fe(++) ratio.

  16. The (Na,Li)FeGe2O6 clinopyroxene-type series: a temperature-dependent single-crystal X-ray diffraction and 57Fe Mössbauer spectroscopic study

    NASA Astrophysics Data System (ADS)

    Redhammer, Günther J.; Tippelt, Gerold

    2016-01-01

    Pyroxene-type compounds along the solid solution series LiFeGe2O6 ( P21/ c space group symmetry) and NaFeGe2O6 ( C2/ c) have been synthesized at 1273-1373 K and investigated by single-crystal X-ray diffraction at 298 K and between 105 and 298 K for Li0.4Na0.6FeGe2O6 in order to study structural variations associated with the chemical- and temperature-driven P21/ c ⇔ C2/ c phase transition. 57Fe Mössbauer spectroscopy, differential thermal analysis, and determination of thermal expansion coefficients from high-temperature powder X-ray diffraction data complete the investigations. The C2/ c phase is stabilized with increasing Na+ content and temperature, and the phase boundary is found at 789 K in pure LiFeGe2O6, decreasing to 109 K in the compound Li0.3Na0.7FeGe2O6. From the available data, a T- X structural phase diagram is constructed. The P21/ c ⇔ C2/ c phase transition is accompanied by distinct variations in lattice parameters, rearrangements in M2 site coordination as well as changes in tetrahedral site chain kinking. Also, chemical strain and the thermal expansion tensor change in size and orientation with Li+ by Na+ replacement. The study will provide a detailed description of the observed variations in bond lengths, bond angles, and distortion parameters.

  17. TEM and Moessbauer Study of Nano Sized Fe{sub 2}MnAl Flakes

    SciTech Connect

    Vinesh, A.; Sudheesh, V. D.; Lakshmi, N.; Venugopalan, K.

    2011-07-15

    Magnetic and structural properties of L21 ordered Fe{sub 2}MnAl Heusler alloy have been studied by X-ray diffraction, Transmission electron microscopy (TEM), Moessbauer spectroscopy and DC magnetization. Structural texturing induced by ball milling is destroyed on heating while Moessbauer and DC magnetization studies show magnetic texturing persists after thermal treatment. TEM shows large distribution in particle size with an average size of 27 nm. Thermal annealing of ball milled sample results L2{sub 1} ordering and the needle shaped particle contributes spin texturing.

  18. Moessbauer spectroscopic studies of iron-doped rutile.

    NASA Technical Reports Server (NTRS)

    Stampfl, P. P.; Travis, J. C.; Bielefeld, M. J.

    1973-01-01

    Moessbauer spectra were obtained of single crystal and powdered samples of rutile (TiO2) doped to about one percent by weight in isotopically enriched iron. It is shown that the oxidation state may be reversibly altered in situ. After reduction, the oxygen neighbors of the dopant ion are apparently shifted to accomodate the larger ferrous ion. The agreement of calculated quadrupole splittings with experimental results suggests that impurities and oxygen vacancies are uniformly distributed in powdered samples, giving the dopant ions an 'ideal lattice' local environment. The differences between the single crystal and powder sample hyperfine parameters are attributed to variations in stoichiometry, charge compensation mechanisms, or other diffusion related parameters.

  19. Antiferromagnetism in Co-57-doped La2CuO(4-y) studied by Moessbauer spectroscopy

    NASA Technical Reports Server (NTRS)

    Jha, S.; Mitros, C.; Lahamer, Amer; Yehia, Sherif; Julian, Glenn M.

    1989-01-01

    Moessbauer effect studies of Co-57-doped La2CuO(4-y) were performed at temperatures between 4.2 K and room temperature. These confirm the antiferromagnetic ordering of these compounds below room temperature. Temperature dependence of the quadrupole splitting shows that the hyperfine field is at an angle with the c-axis.

  20. Moessbauer study in thin films of FeSi2 and FeSe systems

    NASA Technical Reports Server (NTRS)

    Escue, W. J.; Aggarwal, K.; Mendiratta, R. G.

    1978-01-01

    Thin films of FeSi2 and FeSe were studied using Moessbauer spectroscopy information regarding dangling bond configuration and nature of crystal structure in thin films was derived. A significant influence of crystalline aluminum substrate on film structure was observed.

  1. Use of Moessbauer spectroscopy to study reaction products of polyphenols and iron compounds

    SciTech Connect

    Gust, J. ); Suwalski, J. )

    1994-05-01

    Moessbauer spectroscopy was used to study parameters of the reaction products of iron compounds (Fe[sup III]) and polyphenols with hydroxyl (OH) groups in ortho positions. Polyphenols used in the reaction were catechol, pyrogallol, gallic acid, and oak tannin. The Fe-containing compounds were hydrated ferric sulfate (Fe[sub 2][SO[sub 4

  2. Synthesis and vibrational spectroscopy of 57Fe-labeled models of [NiFe] hydrogenase: first direct observation of a nickel–iron interaction† †Electronic supplementary information (ESI) available: Experimental procedures, spectral data, computational chemistry details, animated vibrational modes as GIFs. See DOI: 10.1039/c4cc04572f Click here for additional data file. Click here for additional data file.

    PubMed Central

    Pelmenschikov, Vladimir; Wang, Hongxin; Meier, Florian; Gee, Leland B.; Yoda, Yoshitaka; Kaupp, Martin; Rauchfuss, Thomas B.

    2014-01-01

    A new route to iron carbonyls has enabled synthesis of 57Fe-labeled [NiFe] hydrogenase mimic (OC)3 57Fe(pdt)Ni(dppe). Its study by nuclear resonance vibrational spectroscopy revealed Ni–57Fe vibrations, as confirmed by calculations. The modes are absent for [(OC)3 57Fe(pdt)Ni(dppe)]+, which lacks Ni–57Fe bonding, underscoring the utility of the analyses in identifying metal–metal interactions. PMID:25237680

  3. Vibration DOS of 57Fe and Zn doped rutile Sn(Sb) oxides

    NASA Astrophysics Data System (ADS)

    Nomura, Kiyoshi; Rykov, Alexandre; Németh, Zoltán; Yoda, Yoshitaka

    2012-03-01

    Sn oxides co-doped with Zn, Sb and 57Fe were prepared by sol-gel method, and especially the doping effect of non-magnetic Zn ions was studied. The bulk saturation magnetization is in accordance with the intensity of the magnetic component in Mössbauer spectra. The nuclear inelastic scattering (NIS) spectra of these compounds were measured in SPring 8. The vibration density of states (VDOS) of 57Fe doped Sn(Sb) oxides showed that the softening peaks around 15-20 meV appeared by doping less than 10% Zn ions. The clusters of non-magnetic ZnFe2O4 may be most probably formed under the limit of XRD detections. The results suggest that the strengthening of ferromagnetism, which appears in the dilute Zn doping, may occur due to the spin arrangement of dilute Fe3 + through magnetic defects rather than the formation of magnetic iron oxides.

  4. Bulk and thin films of FeTe: A Moessbauer study

    NASA Technical Reports Server (NTRS)

    Escue, W. T.; Aggarwal, K.; Mendiratta, R. G.

    1977-01-01

    Studies of bulk and thin films of FeTe using Moessbauer spectroscopy showed that FeTe has one noncubic Fe (+2) site which is 3d2 4s 4p3 hybridized. The presence of dangling bands was indicated in spectra of FeTe thin films. The films showed a tendency of texture formation. The substrate was observed to influence the film structure and nature of bonds in films.

  5. A hydrogen bond study in tobacco mosaic virus using Moessbauer spectroscopy.

    PubMed

    Haffner, H; Appel, H; Holmes, K C

    1986-01-01

    The Moessbauer method was applied to obtain information on a suggested hydrogen bond in tobacco mosaic virus (TMV), between the hydroxyl group of Tyr 139 and a carboxyl oxygen of Glu 22 in a neighbouring subunit. Spectra of 129I were taken of 3,5-di-iodo-L-tyrosine as a free amino acid and in situ in TMV. The increase of the pK value of 3,5-di-iodo-L-tyrosine by 0.8 units at position 139 in TMV compared to the free value is a strong argument in favour of the existence of a hydrogen bond via the relevant hydroxyl group. The reported study demonstrates the surprising sensitivity of the observable Moessbauer parameters to details of the electronic configuration in the neighbourhood of the probe nucleus. PMID:3816698

  6. Moessbauer spectroscopy studies of carbon-encapsulated magnetic nanoparticles obtained by different routes

    SciTech Connect

    Bystrzejewski, M.; Huczko, A.; Lange, H.; Grabias, A.; Borysiuk, J.

    2008-09-01

    Carbon-encapsulated magnetic nanoparticles (CEMNPs) are nanomaterials with a core-shell structure. Their intrinsic properties result both from the unique nature of the encapsulated magnetic phases and the high chemical stability of the external carbon shells. CEMNPs may find many prospective applications, e.g., in magnetic data storage, catalysis, xerography, magnetic resonance imaging, and in biomedical applications. Herein, we present detailed structural studies of such nanostructures by Moessbauer spectroscopy, x-ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy. CEMNPs have been obtained by three different techniques: carbon arc, combustion synthesis, and radio frequency thermal plasma. The evaluation of the phase composition of the products was strongly limited due to the broadening and overlapping of the lines in XRD diffraction patterns. The presence of the semicrystalline phases, which could not been identified by XRD, was established by Moessbauer spectroscopy. Furthermore, the magnetic core phase composition was evaluated quantitatively. The products were purified before structural analyses to remove the nonencapsulated particles. The purification caused significant changes in the mass and the saturation magnetization. The Moessbauer spectra of the purified products were compared with the literature data concerning the as-produced CEMNPs.

  7. Moessbauer spectroscopic study of the initial stages of iron-core formation in horse spleen apoferritin: Evidence for both isolated Fe(III) atoms and oxo-bridged Fe(III) dimers as early intermediates

    SciTech Connect

    Bauminger, E.R.; Nowik, I. ); Harrison, P.M.; Treffry, A. )

    1989-06-27

    Ferritin stores iron within a hollow protein shell as a polynuclear Fe(III) hydrous oxide core. Although iron uptake into ferritin has been studied previously, the early stages in the creation of the core need to be clarified. These are dealt with in this paper by using Moessbauer spectroscopy, a technique that enables several types of Fe(II) and Fe(III) to be distinguished. Systematic Moessbauer studies were performed on samples prepared by adding {sup 57}Fe(II) atoms to apoferritin as a function of pH (5.6-7.0), n (the number of Fe/molecule (4-480)), and t{sub f} (the time the samples were held at room temperature before freezing). Four different Fe(III) species were identified: solitary Fe(III) atoms giving relaxation spectra, which can be identified with the species observed before by EPR and UV difference spectroscopy; oxo-bridged dimers giving doublet spectra with large splitting, observed for the first time in ferritin; small Fe(III) clusters giving doublets of smaller splitting and larger antiferromagnetically coupled Fe(III) clusters, similar to those found previously in larger ferritin iron cores, which, for samples with n {ge} 40, gave magnetically split spectra at 4.1 K. Both solitary Fe(III) and dimers diminished with time, suggesting that they are intermediates in the formation of the iron core. Two kinds of divalent iron were distinguished for n = 480, which may correspond to bound and free Fe(II).

  8. A Moessbauer-effect study of a series of R sub 2 Fe sub 14 C hard magnetic materials

    SciTech Connect

    Long, G.J.; Pringle, O.A.; Marasinghe, G.K. Department of Physics, University of Missouri-Rolla, Rolla, Missouri 65401 ); Grandjean, F. ); Buschow, K.H.J. )

    1991-04-15

    The {sup 57}Fe Moessbauer-effect spectra of the series of hard magnetic materials, R{sub 2}Fe{sub 14}C, where R is Nd, Gd, Tb, Dy, Ho, and Lu, have been measured at 295 K. All of these carbides exhibit uniaxial magnetic anisotropy. The spectra resemble those obtained for the related R{sub 2}Fe{sub 14}B compounds and have been fit with the model used earlier for Nd{sub 2}Fe{sub 14}B. The magnitude of the hyperfine field on each site, as a function of rare earth, parallels the Curie temperature; the maximum hyperfine fields and the maximum Curie temperature are observed for Gd{sub 2}Fe{sub 14}C. A linear correlation is observed between the hyperfine fields on the six sites in the analogous borides and carbides; however, these fields are systematically smaller in the carbides. The decrease in the tetragonal unit cell {ital c}-axis length in the carbides apparently reduces the exchange interactions between the 8{ital j} and 16{ital k} iron layers and hence reduces the moments. The isomer shift on each site decreases as the atomic number of the rare earth increases, whereas the quadrupole interactions are independent of rare earth.

  9. In-field {sup 57}Fe Mössbauer spectroscopy below spin-flop transition in powdered troilite (FeS) mineral

    SciTech Connect

    Cuda, Jan Tucek, Jiri; Filip, Jan; Malina, Ondrej; Krizek, Michal; Zboril, Radek

    2014-10-27

    Powdered troilite (FeS), extracted from the Cape York IIIA octahedrite meteorite, was investigated employing in-field {sup 57}Fe Mössbauer spectroscopy. The study identified a typical behavior of polycrystalline antiferromagnetic material under external magnetic fields. The in-field evolution of the {sup 57}Fe Mössbauer spectra showed that the spin-flop transition in the FeS system occurs at a field higher than 5 T.

  10. Moessbauer spectroscopic studies of iron compounds in coal and related materials

    SciTech Connect

    Twardowska, H.

    1980-01-01

    A selection of Illinois coals, related materials, and coal process residues were investigated by means of Moessbauer spectroscopy. The purpose of the study is to characterize the iron compounds in the materials and the iron chemistry which occurs when the coal is processed. The predominant iron mineral occurring in the coals was pyrite. Marcasite also occurred in the coals although it was frequently obscured by pyrite. Jarosite was found in the weathered coals. The study also considered pyrrhotite. An important chemical process in the charring and liquefaction of coal is the conversion of pyrite to pyrrhotite. (JMT)

  11. Determination of the Lamb-Moessbauer factors of LiFePO{sub 4} and FePO{sub 4} for electrochemical in situ and operando measurements in Li-ion batteries

    SciTech Connect

    Aldon, L.

    2010-01-15

    {sup 57}Fe Moessbauer spectroscopy is a powerful tool to investigate redox reactions during in electrochemical lithium insertion/extraction processes. Electrochemical oxidation of LiFe{sup II}PO{sub 4} (triphylite) in Li-ion batteries results in Fe{sup III}PO{sub 4} (heterosite). LiFePO{sub 4} was synthesized by solid state reaction at 800 deg. C under Ar flow from Li{sub 2}CO{sub 3}, FeC{sub 2}O{sub 4}.2H{sub 2}O and NH{sub 4}H{sub 2}PO{sub 4} precursors in stoichiometric composition. FePO{sub 4} was prepared from chemical oxidation of LiFePO{sub 4} using bromine as oxidative agent. For both materials a complete {sup 57}Fe Moessbauer study as a function of the temperature has been carried out. The Debye temperatures are found to be theta{sub M}=336 K for LiFePO{sub 4} and theta{sub M}=359 K for FePO{sub 4}, leading to Lamb-Moessbauer factors f{sub 300K}=0.73 and 0.77, respectively. These data will be useful for a precise estimation of the relative amounts of each species in a mixture. - Graphical abstract: Relative amount of FePO{sub 4} obtained by Moessbauer and electrochemical data. We have corrected Moessbauer spectral intensities with our f factor of both LiFePO{sub 4} and FePO{sub 4}. Open (filled) squares correspond to values obtained during charging (discharging) process. The dashed line, given as a guideline for the eye, corresponds to the ideal case were amounts deduced from different experimental measurements are equal.

  12. Electron proportional gas counter for linear and elliptical Moessbauer polarimetry

    SciTech Connect

    Tancziko, F.; Sajti, Sz.; Deak, L.; Merkel, D. G.; Endro''czi, G.; Nagy, D. L.; Bottyan, L.; Olszewski, W.; Szymanski, K.

    2010-02-15

    Design, characterization, and selected applications of a novel electron detector dedicated to conventional perpendicular- and low-angle-incidence conversion electron Moessbauer spectroscopy are presented. The setup is suitable for varying the incident angle and external magnetic fields on Moessbauer source and absorber. Test experiments were performed on {alpha}-{sup 57}Fe films using a conventional single-line {sup 57}Co(Rh) and magnetically split, {sup 57}Co({alpha}-Fe) Moessbauer sources. The integral ''blackness effect'' in conversion-electron Moessbauer spectra of {sup 57}Fe isotope-enriched absorbers is demonstrated and shown to be pronounced at shallow angles of incidence. In order to determine the alignment and sign of the hyperfine field in an isotope-enriched absorber, the blackness effect is accounted for in a semiempirical way by using single-line source/absorber experimental relative intensities determined independently. This method works with high accuracy for linear polarimetry; however it is only a rough approximation in the case of nearly circular polarimetry.

  13. Study of Fe-Co Nanocomposite Films

    SciTech Connect

    Lancok, A.; Klementova, M.; Kohout, J.; Miglierini, M.; Fendrych, F.; Lancok, J.

    2010-07-13

    Moessbauer study of nanogranular ferromagnetic FeCo films is presented. Two ways of production of nanocomposite systems were employed: (i) hollow cathode plasma jet deposition process, and (ii) laser ablation from Fe-Co metallic targets by means of a KrF excimer laser and r.f. magnetron sputtering. Complementary information on the composition of the samples were obtained by nuclear magnetic resonance of {sup 57}Fe and {sup 59}Co nuclei, conversion electron Moessbauer spectroscopy, and high resolution transmission electron microscopy. The films contain crystalline nanoparticles, 5-20 nm in size, embedded in an amorphous matrix.

  14. Iron-oxide Aerogel and Xerogel Catalyst Formulations: Characterization by 57Fe Mössbauer and XAFS Spectroscopies

    SciTech Connect

    Huggins, F.; Bali, S; Huffman, G; Eyring, E

    2010-01-01

    Iron in various iron-oxide aerogel and xerogel catalyst formulations ({ge}85% Fe{sub 2}O{sub 3}; {le}10% K, Co, Cu, or Pd) developed for possible use in Fischer-Tropsch synthesis (FTS) or the water-gas-shift (WGS) reaction has been examined by {sup 57}Fe Moessbauer spectroscopy. The seventeen samples consisted of both as-prepared and calcined aerogels and xerogels and their products after use as catalysts for FTS or the WGS reaction. Complementary XAFS spectra were obtained on the occurrence of the secondary elements in some of the same materials. A broad, slightly asymmetric, two-peak Moessbauer spectrum was obtained from the different as-prepared and calcined catalyst formulations in the majority of cases. Such spectra could only be satisfactorily fit with three quadrupole doublet components, but no systematic trends in the isomer shift and quadrupole splitting parameters and area ratios of the individual components could be discerned that reflected variations in the composition or preparation of the aerogel or xerogel materials. However, significant reductions were noted in the Moessbauer effective thickness (recoilless absorption effect per unit mass of iron) parameter, {chi}{sub eff}/g, determined at room temperature, for aerogels and xerogels compared to bulk iron oxides, reflecting the openness and lack of rigidity of the aerogel and xerogel structures. Moessbauer measurements for two aerogels over the range from 15 to 292 K confirmed the greatly diminished nature of this parameter at room temperature. Major increases in the effective thickness parameter were observed when the open structure of the aerogel or xerogel collapsed during calcination resulting in the formation of iron oxides (hematite, spinel ferrite). Similar structural changes were indicated by increases in this parameter after use of iron-oxide aerogels as catalysts for FTS or the WGS reaction, during which the iron-oxide aerogel was converted to a mixture of nonstoichiometric magnetite and

  15. Nuclear Bragg x-ray scattering of synchrotron radiation by sup 57 Fe sub 2 O sub 3

    SciTech Connect

    Haustein, P.E.; Berman, L.E.; Faigel, G.; Grover, J.R.; Hastings, J.B.; Siddons, D.P.

    1989-01-01

    A program of studies of nuclear Bragg x-ray scattering with {sup 57}Fe{sub 2}O{sub 3} at the National Synchrotron Light Source at Brookhaven National Laboratory and at the Cornell University CHESS facility is reviewed. Two main areas, instrumentation development and studies of dynamical diffraction processes, are described. The latter area has included: measurements of the temporal behaviour of nuclear collective decay mode and direct observation of polarization mixing. 7 refs., 5 figs.

  16. The 57Fe Synchrotron Mössbauer Source at the ESRF.

    PubMed

    Potapkin, Vasily; Chumakov, Aleksandr I; Smirnov, Gennadii V; Celse, Jean Philippe; Rüffer, Rudolf; McCammon, Catherine; Dubrovinsky, Leonid

    2012-07-01

    The design of a (57)Fe Synchrotron Mössbauer Source (SMS) for energy-domain Mössbauer spectroscopy using synchrotron radiation at the Nuclear Resonance beamline (ID18) at the European Synchrotron Radiation Facility is described. The SMS is based on a nuclear resonant monochromator employing pure nuclear reflections of an iron borate ((57)FeBO(3)) crystal. The source provides (57)Fe resonant radiation at 14.4 keV within a bandwidth of 15 neV which is tunable in energy over a range of about ±0.6 µeV. In contrast to radioactive sources, the beam of γ-radiation emitted by the SMS is almost fully resonant and fully polarized, has high brilliance and can be focused to a 10 µm × 5 µm spot size. Applications include, among others, the study of very small samples under extreme conditions, for example at ultrahigh pressure or combined high pressure and high temperature, and thin films under ultrahigh vacuum. The small cross section of the beam and its high intensity allow for rapid collection of Mössbauer data. For example, the measuring time of a spectrum for a sample in a diamond anvil cell at ∼100 GPa is around 10 min, whereas such an experiment with a radioactive point source would take more than one week and the data quality would be considerably less. The SMS is optimized for highest intensity and best energy resolution, which is achieved by collimation of the incident synchrotron radiation beam and thus illumination of the high-quality iron borate crystal within a narrow angular range around an optimal position of the rocking curve. The SMS is permanently located in an optics hutch and is operational immediately after moving it into the incident beam. The SMS is an in-line monochromator, i.e. the beam emitted by the SMS is directed almost exactly along the incident synchrotron radiation beam. Thus, the SMS can be easily utilized with all existing sample environments in the experimental hutches of the beamline. Owing to a very strong

  17. Verwey transition of nano-sized magnetite crystals investigated by 57Fe NMR

    NASA Astrophysics Data System (ADS)

    Lim, Sumin; Choi, Baek Soon; Lee, Soon Chil; Hong, Jaeyoung; Lee, Jisoo; Hyeon, Taeghwan; Kim, Taehun; Jeong, Jaehong; Park, Je-Geun

    It is well known that magnetite crystals undergo a metal-insulator transition at the Verwey transition temperature, TV = 123 K. In this work, we studied the Verwey transition of nano-sized crystals with 57Fe NMR. In the metallic state above Tv, the NMR spectrum shows a single sharp peak, which broadens below TV indicating the Verwey transition. We measured the spectra of the nano-crystals with radii of 16 nm, 25 nm, and 40 nm and compared with that of a bulk. The transition temperature obtained from the NMR spectra depends on both the crystal size and crystallinity. When the crystal size decreases from bulk to 16 nm, the transition temperature drops from 123 K to 100 K. The transition temperature of the samples kept dry air decrease due to aging.

  18. Search for resonant absorption of solar axions emitted in M1 transition in 57Fe nuclei

    NASA Astrophysics Data System (ADS)

    Derbin, A. V.; Egorov, A. I.; Mitropol'Sky, I. A.; Muratova, V. N.; Semenov, D. A.; Unzhakov, E. V.

    2009-08-01

    A search for resonant absorption of 14.4 keV solar axions by a 57Fe target was performed. The Si(Li) detector placed inside the low-background setup was used to detect the γ-quanta appearing in the deexcitation of the 14.4 keV nuclear level: A+57Fe→57Fe*→57Fe+ γ. The new upper limit for the hadronic axion mass has been obtained of m A ≤159 eV (95% c.l.) ( S=0.5, z=0.56).

  19. 57Fe Mössbauer spectroscopy used to develop understanding of a diamond preservation index model

    NASA Astrophysics Data System (ADS)

    Yambissa, M. T.; Forder, S. D.; Bingham, P. A.

    2016-12-01

    57Fe Mössbauer spectroscopy has provided precise and accurate iron redox ratios Fe2+/Fe3+ in ilmenite, FeTiO3, found within kimberlite samples from the Catoca and Camatxia kimberlite pipes from N.E. Angola. Ilmenite is one of the key indicator minerals for diamond survival and it is also one of the iron-bearing minerals with iron naturally occurring in one or both of the oxidation states Fe3+ and Fe2+. For this reason it is a good indicator for studying oxygen fugacities ( fO2) in mineral samples, which can then be related to iron redox ratios, Fe2+/Fe3+. In this paper we demonstrate that the oxidation state of the ilmenite mineral inclusion from sampled kimberlite rock is a key indicator of the oxidation state of the host kimberlite assemblage, which in turn determines the genesis of diamond, grade variation and diamond quality. Ilmenite samples from the two different diamondiferous kimberlite localities (Catoca and Camatxia) in the Lucapa graben, N.E. Angola, were studied using Mössbauer spectroscopy and X-Ray Diffractometry, in order to infer the oxidation state of their source regions in the mantle, oxygen partial pressure and diamond preservation conditions. The iron redox ratios, obtained using Mössbauer spectroscopy, show that the Catoca diamond kimberlite is more oxidised than kimberlite found in the Camatxia pipe, which is associated within the same geological tectonic structure. Here we demonstrate that57Fe Mössbauer spectroscopy can assist geologists and mining engineers to effectively evaluate and determine whether kimberlite deposits are economically feasible for diamond mining.

  20. Moessbauer spectroscopy study on the corrosion resistance of plasma nitrided ASTM F138 stainless steel in chloride solution

    SciTech Connect

    Souza, S.D. de; Olzon-Dionysio, M.; Basso, R.L.O.; Souza, S. de

    2010-10-15

    Plasma nitriding of ASTM F138 stainless steel samples has been carried out using dc glow discharge under 80% H{sub 2}-20% N{sub 2} gas mixture, at 673 K, and 2, 4, and 7 h time intervals, in order to investigate the influence of treatment time on the microstructure and the corrosion resistance properties. The samples were characterized by scanning electron microscopy, glancing angle X-ray diffraction and conversion electron Moessbauer spectroscopy, besides electrochemical tests in NaCl aerated solution. A modified layer of about 6 {mu}m was observed for all the nitrided samples, independent of nitriding time. The X-ray diffraction analysis shows broad {gamma}{sub N} phase peaks, signifying a great degree of nitrogen supersaturation. Besides {gamma}{sub N,} the Moessbauer spectroscopy results indicated the occurrence of {gamma}' and {epsilon} phases, as well as some other less important phases. Corrosion measurements demonstrate that the plasma nitriding time affects the corrosion resistance and the best performance is reached at 4 h treatment. It seems that the {epsilon}/{gamma}' fraction ratio plays an important role on the resistance corrosion. Additionally, the Moessbauer spectroscopy was decisive in this study, since it was able to identify and quantify the iron phases that influence the corrosion resistance of plasma nitrided ASTM F138 samples.

  1. Moessbauer and Electron Microprobe Studies of Density Separates of Martian Nakhlite Mil03346: Implications for Interpretation of Moessbauer Spectra Acquired by the Mars Exploration Rovers

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; McKay, G. A.; Agresti, D. G.; Li, Loan

    2008-01-01

    Martian meteorite MIL03346 is described as an augite-rich cumulate rock with approx.80%, approx.3%, and approx.21% modal phase proportions of augite (CPX), olivine and glassy mesostasis, respectively, and is classified as a nakhlite [1]. The Mossbauer spectrum for whole rock (WR) MIL 03346 is unusual for Martian meteorites in that it has a distinct magnetite subspectrum (7% subspectral area) [2]. The meteorite also has products of pre-terrestrial aqueous alteration ("iddingsite") that is associated primarily with the basaltic glass and olivine. The Mossbauer spectrometers on the Mars Exploration Rovers have measured the Fe oxidation state and the Fe mineralogical composition of rocks and soils on the planet s surface since their landing in Gusev Crater and Meridiani Planum in January, 2004 [3,4]. The MIL 03346 meteorite provides an opportunity to "ground truth" or refine Fe phase identifications. This is particularly the case for the so-called "nanophase ferric oxide" (npOx) component. NpOx is a generic name for a ferric rich product of oxidative alteration. On Earth, where we can take samples apart and study individual phases, examples of npOx include ferrihydrite, schwertmannite, akagaaneite, and superparamagnetic (small particle) goethite and hematite. It is also possible for ferric iron to be associated to some unknown extent with igneous phases like pyroxene. We report here an electron microprobe (EMPA) and Moessbauer (MB) study of density separates of MIL 03346. The same separates were used for isotopic studies by [5]. Experimental techniques are described by [6,7].

  2. Moessbauer study of iron-carbide growth and Fischer-Tropsch activity

    SciTech Connect

    Rao, K.R.P.M.; Huggins, F.E.; Huffman, G.P.

    1995-12-31

    There is a need to establish a correlation between the Fischer-Tropsch (FT) activity of an iron-based catalyst and the catalyst phase during FT synthesis. The nature of iron phases formed during activation and FT synthesis is influenced by the gas used for activation. Moessbauer investigations of iron-based catalysts subjected to pretreatment in gas atmospheres containing mixtures of CO, H{sub 2}, and He have been carried out. Studies on UCI 1185-57 catalyst indicate that activation of the catalyst in CO leads to the formation of 100% magnetite and the magnetite formed gets rapidly converted to at least 90% of x-Fe{sub 5}C{sub 2} during activation. The x-Fe{sub 5}C{sub 2} formed during activation gets partly (= 25%) converted back to Fe{sub 3}O{sub 4} during FT synthesis and both x-Fe{sub 5}C{sub 2} and Fe{sub 3}O{sub 4} reach constant values. On the other hand, activation of the catalyst in synthesis gas leads to formation of Fe{sub 3}O{sub 4} and which is slowly converted to x-Fe{sub 5}C{sub 2} and e-Fe{sub 2.2}C during activation, and both carbide phases increase slowly during FT synthesis. FT synthesis activity is found to give rise to {approx} 70% (H2+CO) conversion in the case of CO activated catalyst as compared to {approx} 20% (H2+CO) conversion in the case of synthesis gas-activated catalyst.

  3. A 57Fe Mössbauer characterization of Fe-biopolymer complexes and their relevance to biological molecules

    NASA Astrophysics Data System (ADS)

    Bhatia, Subhash C.; Cardelino, Beatriz H.; Ravi, Natarajan

    2005-09-01

    57Fe Mössbauer spectroscopy is used to study the interactions, geometry, and the coordination characteristics of the Fe-complexes of biopolymers such as chitosan, glucosamine, and chondritin sulfate. In addition, a computational effort is undertaken for predicting the geometries and energies of the metal complexes by the Density Functional Theory (DFT) methods as implemented in the Gaussian 2003 quantum mechanical program. Both experimental and computational results suggest that the structure of the metal complexes resemble closely the structure of the active sites of metalloenzymes in 2+ or 3+ oxidation states and is at least tetracoordinated and can possibly have six ligands.

  4. Study of excess Fe metal in the lunar fines by magnetic separation, Moessbauer spectroscopy, and microscopic examination.

    NASA Technical Reports Server (NTRS)

    Housley, R. M.; Grant, R. W.; Abdel-Gawad, M.

    1972-01-01

    A simple and convenient method of making quantitative magnetic separations has been applied to the lunar fines. The fractions obtained form groups containing distinctively different particle types; thus, it appears that magnetic separation in itself many be a useful way of characterizing lunar fines. Moessbauer studies of fines 10084 show that the metal cannot contain more than about 1.5% Ni, implying that by far the bulk of the metal results from reduction rather than from direct meteoritic addition. Microscopic examination of magnetic separates from 15101 fines suggests that reduction of Fe accompanies every major impact event on the moon.

  5. Structural properties of magnetite under high pressure studied by Moessbauer spectroscopy

    SciTech Connect

    Kobayashi, Hisao; Isogai, Ichiro; Kamimura, Takashi; Hamada, Noriaki; Onodera, Hideya; Todo, Sakae; Mori, Nobuo

    2006-03-01

    We have measured the Moessbauer spectra of magnetite (Fe{sub 3}O{sub 4}) under a pressure of up to 18 GPa at room temperature using nonenriched high-quality samples. An analysis of the observed Moessbauer spectra confirms that Fe{sub 3}O{sub 4} does not undergo a magnetic or crystalline structural transition up to 18 GPa at room temperature. In the pressure dependences of the refined hyperfine interaction parameters, however, small but distinct anomalies are found at 7.0 GPa in the center shifts of two crystallographically nonequivalent Fe sites, which are caused by the discontinuous decrease of an oxygen internal coordinate in the cubic inverse spinel structure. We believe that the pressure-induced discontinuous change of the Fe-O bond length is related to the absence of a metal-insulator transition above 7.5 GPa.

  6. Moessbauer studies on LaNi(4.7)Sn(0.3) and its hydride

    NASA Technical Reports Server (NTRS)

    Oliver, F. W.; Morgan, W.; Hammond, E. C.; Wood, S.; May, L.

    1985-01-01

    Moessbauer measurements were made on LaNi(4.7)Sn(0.3) at room and liquid nitrogen temperatures. Experimental data yielded a singlet at room temperature and a doublet at liquid-nitrogen temperature. Spectra of the hydrided sample yielded a doublet at liquid-nitrogen temperature with an increase in the quadrupole splitting compared to the unhydrided spectra, but no change in the isomer shift. These data indicate that there is no significant interaction between the tin and the hydrogen. The magnetic character remained the same down to liquid-nitrogen temperature as evidenced by the Moessbauer data. X-ray diffraction measurements on the hydride showed an expanded lattice with the same structure as found for the unhydrided sample. A decrease in particle size was observed upon hydriding.

  7. Mössbauer evidence of 57Fe3O4 based ferrofluid biodegradation in the brain

    NASA Astrophysics Data System (ADS)

    Polikarpov, D.; Cherepanov, V.; Chuev, M.; Gabbasov, R.; Mischenko, I.; Nikitin, M.; Vereshagin, Y.; Yurenia, A.; Panchenko, V.

    2014-04-01

    The ferrofluid, based on 57Fe isotope enriched Fe3O4 nanoparticles, was synthesized, investigated by Mössbauer spectroscopy method and injected transcranially in the ventricle of the rat brain. The comparison of the Mössbauer spectra of the initial ferrofluid and the rat brain measured in two hours and one week after the transcranial injection allows us to state that the synthesized magnetic 57Fe3O4 nanoparticles undergo intensive biodegradation in live brain and, therefore, they can be regarded as a promising target for a new method of radionuclide-free Mössbauer brachytherapy.

  8. Correlation of Coal Calorific Value and Sulphur Content with 57Fe Mössbauer Spectral Absorption

    NASA Astrophysics Data System (ADS)

    Wynter, C. I.; May, L.; Oliver, F. W.; Hall, J. A.; Hoffman, E. J.; Kumar, A.; Christopher, L.

    Coal is the most abundant, most economical and widely distributed fossil fuel in the world today. It is also the principal form of reductant in the iron and steel industry. This study was undertaken to not only add to the growing use of Mössbauer spectroscopy application in industry but also to increase the chemistry and physics knowledge base of coal. Coal is 40 to 80 percent carbon with small amounts of sulphur and iron as pyrite and ferrous sulphate. The environmental concern associated with mining and burning of coal has long been a subject of investigation with emphasis on the sulphur content. We examined five ranks of coal: anthracite, Eastern bituminous, bituminous, sub-bituminous, and lignite. Relationships were investigated between the Calorific Value (CV) of coal and inorganic sulphur content, 57Fe Mössbauer absorption, and ratio of pyrite (FeS2) to FeSO4. Twenty-eight samples of the five different types of coal had CVs ranging from 32,403 to 16,100 kJ/kg and sulphur concentrations ranging from 0.28 to 2.5 percent. CV appeared to be positively correlated with concentrations of sulphur and of iron-sulphur salts, although there appears to be little connection with the distribution of their oxidation states.

  9. Moessbauer study of iron-carbide growth and Fischer-Tropsch activity

    SciTech Connect

    Rao, K.R.P.M.; Huggins, F.E.; Huffman, G.P.

    1995-12-31

    There is a need to establish a correlation between the Fischer-Tropsch (FT) activity of an iron-based catalyst and the catalyst phase during FT synthesis. The nature of iron phases formed during activation and FT synthesis is influenced by the nature of the gas and pressure apart from other parameters like temperature, flow rate etc., used for activation. Moessbauer investigations of iron-based catalysts subjected to pretreatment at two different pressures in gas atmospheres containing mixtures of CO, H{sub 2}, and He have been carried out. Studies on UCI 1185-57 (64%Fe{sub 2}O{sub 3}/5%CuO/1%K{sub 2}O/30% Kaolin) catalyst indicate that activation of the catalyst in CO at 12 atms. leads to the formation of 100% magnetite and the magnetite formed gets rapidly converted to at least 90% of {chi}-Fe{sub 5}C{sub 2} during activation. The FT activity was found to be good at 70-80% of (H{sub 2}+CO) conversion. On the other hand, activation. The FT activity was found to be good at 70-80% of (H{sub 2}+CO) conversion. On the other hand, activation of the catalyst in synthesis gas at 12 atms. leads to formation of Fe{sub 3}O{sub 4} and it gets sluggishly converted to {chi}-Fe{sub 5}C{sub 2} and {epsilon}-Fe{sub 2.2}C during activation and both continue to grow slowly during FT synthesis. FT activity is found to be poor. Pretreatment of the catalyst, 100fe/3.6Si/0.71K at a low pressure of 1 atms. in syngas gave rise to the formation of {chi}-Fe{sub 5}C{sub 2} and good FT activity. On the other hand, pretreatment of the catalyst, 100Fe/3.6Si/0.71K at a relatively high pressure of 12 atms. in syngas did not give rise to the formation any carbide and FT activity was poor.

  10. Probe Mössbauer spectroscopy of mechanical alloying in binary Cr‐{sup 57}Fe(1 at%) system

    SciTech Connect

    Elsukov, Evgeny P. Kolodkin, Denis A. Ul'yanov, Alexander L. Porsev, Vitaly E.

    2014-10-27

    Solid state reactions during mechanical alloying (MA) in a binary mixture of powdered Cr and {sup 57}Fe in atomic ratio of 99:1 have been studied using {sup 57}Fe Mössbauer spectroscopy, X-ray diffraction and Auger spectrometry. The proposed model of MA includes formation of Cr(Fe){sub x}O{sub y} oxides at the contact places of Cr and Fe particles, formation of nanostructure with simultaneous dissolution of the oxides, penetration of Fe atoms along grain boundaries in close-to-boundary distorted zones of interfaces in a substitutional position, formation of the substitutional solid solution of Fe in Cr in the body of grains. It was shown that the increase in the BCC lattice parameter on increasing the milling time is due to the dissolution of oxides and formation of interstitial solid solution of O in Cr. There were established substantial differences in consumption of BCC Fe in a Mg → Al → Si → Cr sequence due to the major role of chemical interaction of Mg(Al,Si,Cr) with Fe.

  11. Mössbauer investigations of hyperfine interactions features of {sup 57}Fe nuclei in BiFeO{sub 3} ferrite

    SciTech Connect

    Sobolev, Alexey Presniakov, Igor Rusakov, Vyacheslav Matsnev, Mikhail; Gorchakov, Dmitry; Glazkova, Iana; Belik, Alexey

    2014-10-27

    New results of {sup 57}Fe Mössbauer studies on BiFeO{sub 3} powder sample performed at various temperatures above and below magnetic phase transitions point T{sub N} ≈ 640K are reported. We have performed self-consistent calculations of the lattice contributions to the EFG tensor, taking into account dipole moments of the O{sup 2−} and Bi{sup 3+} ions. Low-temperature {sup 57}Fe Mössbauer spectra recorded at T < T{sub N} were analyzed assuming an anharmonic cycloidal modulation of the Fe{sup 3+} magnetic moments. The cycloidal modulation of the iron spin was described with the elliptic Jacobi function sn[(±4K(m)/λ)x,m]. The good fit of the experimental spectra was obtained for the anharmonicity m = 0.44 ± 0.04 (T = 4.9K) resulting from the easy-axis magnetic anisotropy.

  12. 57 Fe Mössbauer probe of spin crossover thin films on a bio-membrane

    NASA Astrophysics Data System (ADS)

    Naik, Anil D.; Garcia, Yann

    2012-03-01

    An illustrious complex [Fe(ptz)6](BF4)2 (ptz = 1-propyl-tetrazole) ( 1) which was produced in the form of submicron crystals and thin film on Allium cepa membrane was probed by 57Fe Mossbauer spectroscopy in order to follow its intrinsic spin crossover. In addition to a weak signal that corresponds to neat SCO compound significant amount of other iron compounds are found that could have morphed from 1 due to specific host-guest interaction on the lipid-bilayer of bio-membrane. Further complimentary information about biogenic role of membrane, was obtained from variable temperature Mossbauer spectroscopy on a ~5% enriched [57Fe(H2O)6](BF4)2 salt on this membrane.

  13. Moessbauer and SANS Studies of Anti-Invar Fe-Ni-C Alloy under Magnetic Field

    SciTech Connect

    Nadutov, V. M.; Kosintsev, S. G.; Svystunov, Ye. O.; Garamus, V. M.; Willumeit, R.; Eckerlebe, H.; Ericsson, T.; Annersten, H.

    2010-07-13

    Anti-Invar effect in the f.c.c.-Fe-25.3%Ni-C alloy was revealed, i.e., enhanced thermal expansion coefficient (TEC)({approx}20x10{sup -6} K{sup -1}) which was accompanied by almost temperature-insensitive behavior in a temperature range of 122-525 K that was considerably expanded to the low temperature range due to alloying with carbon. The Moessbauer and small-angle neutron scattering (SANS) experiments with the varying temperature and in an external magnetic field of 1.5-5 T have revealed an existence of inhomogeneous magnetic order in anti-Invar alloy below and above the magnetic transition point. The anti-Invar behavior correlates with the thermally induced change in the magnetic order and interspin interaction.

  14. Moessbauer studies of pressure-induced amorphization in the molecular crystal SnBr{sub 4}

    SciTech Connect

    Hearne, G.R.; Pasternak, M.P. |; Taylor, R.D.

    1995-10-01

    A single line spectrum is characteristic of the Moessbauer data obtained in the 0--5 GPa range, indicating the preservation of fourfold symmetry of the SnBr{sub 4} molecule in the crystal. Above 5 GPa, near {ital P}{sub {ital c}}, a {ital quadruple} {ital interaction} takes place concurrent with a dramatic increase in the {ital recoil{minus}free} {ital fraction} $({ital f})---. The value of the quadrupole splitting reaches a maximum of 0.9 mm/s at {ital P}{similar_to}15 GPa and remains constant thereafter. By {similar_to}9 GPa the absorption area, which is proportional to {ital f}, increases by 30--40 % over the lowest pressure value and then remains constant at higher pressure. These results are consistent with the formation of a molecular species, e.g., a (SnBr{sub 4}){sub 2} dimer, lacking the {ital T}{sub {ital d}} symmetry at the original Sn{sup 4+} site and having optical phonons {ital hard} enough not to be excited by the nuclear recoil process. Molecular association into (SnBr{sub 4}){sub 2} dimers, the building block of the high-pressure disordered state, also explains many of the experimental features of the Raman data. Upon decompression, Moessbauer (and Raman) data suggest that these dimers dissociate into monomers at {similar_to}5 GPa; however, a disordered structure of SnBr{sub 4} persists as pressure is decreased further. Crystallization is fully recovered below 1 GPa. The nature of the pressure-induced amorphization of the insulator SnBr{sub 4} is discussed in terms of the structural and valence properties of the analogous metallic SnI{sub 4}.

  15. Level Densities and Radiative Strength Functions in 56FE and 57FE

    SciTech Connect

    Tavukcu, E

    2002-12-10

    Understanding nuclear level densities and radiative strength functions is important for pure and applied nuclear physics. Recently, the Oslo Cyclotron Group has developed an experimental method to extract level densities and radiative strength functions simultaneously from the primary {gamma} rays after a light-ion reaction. A primary {gamma}-ray spectrum represents the {gamma}-decay probability distribution. The Oslo method is based on the Axel-Brink hypothesis, according to which the primary {gamma}-ray spectrum is proportional to the product of the level density at the final energy and the radiative strength function. The level density and the radiative strength function are fit to the experimental primary {gamma}-ray spectra, and then normalized to known data. The method works well for heavy nuclei. The present measurements extend the Oslo method to the lighter mass nuclei {sup 56}Fe and {sup 57}Fe. The experimental level densities in {sup 56}Fe and {sup 57}Fe reveal step structure. This step structure is a signature for nucleon pair breaking. The predicted pairing gap parameter is in good agreement with the step corresponding to the first pair breaking. Thermodynamic quantities for {sup 56}Fe and {sup 57}Fe are derived within the microcanonical and canonical ensembles using the experimental level densities. Energy-temperature relations are considered using caloric curves and probability density functions. The differences between the thermodynamics of small and large systems are emphasized. The experimental heat capacities are compared with the recent theoretical calculations obtained in the Shell Model Monte Carlo method. Radiative strength functions in {sup 56}Fe and {sup 57}Fe have surprisingly high values at low {gamma}-ray energies. This behavior has not been observed for heavy nuclei, but has been observed in other light- and medium-mass nuclei. The origin of this low {gamma}-ray energy effect remains unknown.

  16. Effect of 57Fe-goethite Amendment on Microbial Community Composition and Dynamics During the Transition from Iron to Sulfate Reduction

    NASA Astrophysics Data System (ADS)

    Moon, H.; McGuiness, L.; Kukkadapu, R. K.; Peacock, A.; Komlos, J.; Kerkhof, L.; Long, P. E.; Jaffe, P. R.

    2009-12-01

    Due to an increasing interest in microbial biostimulation for the purpose of U(VI) bioreduction, which proceeds via iron reduction, there is a growing need for a better understanding of the associated biogeochemical dynamics. This includes Fe(III) availability as well as the microbial community changes, including the activity of iron-reducers during the biostimulation period even after the onset of sulfate reduction. An up-flow column experiment was conducted with Old Rifle site sediments, where half of the columns had sediment that was augmented with 57Fe-goethite to track minute goethite changes after the onset of sulfate reduction, and to study the effects of increased Fe(III) levels on the overall biostimulation dynamics. The addition of the 57Fe-goethite did not delay the onset of sulfate reduction, but slightly suppressed the overall rate of sulfate reduction and hence acetate utilization. Mossbauer analyses confirmed that there was bioavailable iron present after the onset of sulfate reduction and that iron was still being reduced during sulfate reduction. Addition of the 57Fe-goethite to the sediment had a noticeable effect on the overall composition of the microbial population. 16S rRNA analyses of biostimulatd sediment using TRFLP showed that Geobacter sp. were still active and replicating after sulfate reduction had occurred for over 30 days. DNA fingerprints of the sediment-attached microbial communities were dominated by 5 TRFs, that comprised 25-57 % of the total profile. Augmentation of sediments with the 57Fe-goethite resulted in somewhat higher numbers of Geobacter-like species throughout the experiment, and during sulfate reduction slightly lower numbers of sulfate reducers. These columns also had a slightly improved U(VI) removal efficiency, which might be attributed to the higher Geobacter-like numbers.

  17. Moessbauer and magnetic study of Mn, Zr and Cd substituted W-type hexaferrites prepared by co-precipitation

    SciTech Connect

    Iqbal, Muhammad Javed; Khan, Rafaqat Ali; Mizukami, Shigemi; Miyazaki, Terunobu

    2011-11-15

    Highlights: {yields} Zr and Cd ions substitute tetrahedral 4e and 4f{sub IV} sites while Mn ions occupy octahedral 6g and 4f sites. {yields} Doping of W-type hexaferrites with Mn, Zr and Cd improves the values of M{sub s} and M{sub r}. {yields} The enhancement of magnetic characteristic togetherwith the formation of rice shaped W-type hexaferrites nanoparticles is promising for imaging and sensing devices. {yields} The synthesized materials are suitable for magnetic data storage with high density. -- Abstract: BaCo{sub 2-x}Mn{sub x}Fe{sub 16-2y}(Zr-Cd){sub y}O{sub 27} (x = 0-0.5 and y = 0-1.0) hexaferrite nanocrystallites of average sizes in the range of 33-42 nm are synthesized by the chemical co-precipitation method. The synthesized materials are characterized using different techniques including X-ray diffraction (XRD), energy dispersive X-ray florescence (ED-XRF), scanning electron microscope (SEM), Moessbauer spectrometer and vibrating-sample magnetometer (VSM). Based on analysis of the data obtained from Moessbauer spectral studies, doping is believed to have occurred preferably in the vicinity of 12k sub-lattice, i.e. f{sub IV} (4e, 4f{sub IV}), 2b (6g, 4f) and 2d site. Variations in the saturation magnetization (77.1-60.9 emu g{sup -1}), remanent magnetization (22.08-31.23 emu g{sup -1}) and coercivity (1570.1-674.7 Oe) exhibit tunable behavior with dopant content and therefore can be useful for application in various magnetic devices.

  18. Specific features of magnetic states of impurity iron ions in the perovskite La0.75Sr0.25Co0.98 57Fe0.02O3

    NASA Astrophysics Data System (ADS)

    Pokatilov, V. S.; Rusakov, V. S.; Makarova, A. O.; Pokatilov, V. V.; Matsnev, M. E.

    2016-02-01

    Single-phase polycrystalline La0.75Sr0.25Co0.98 57Fe0.02O3 samples have been prepared by solidstate ceramic technology. The samples have the rhombohedral structure (space group Rbar 3c). The studies of perovskite La0.75Sr0.25Co0.98 57Fe0.02O3 by Mössbauer spectroscopy on impurity 57Fe nuclei in the temperature range of 5-293 K have revealed the existence of a superparamagnetic relaxation in the temperature range of 100-210 K. The parameters of hyperfine interactions (hyperfine magnetic fields, line shifts, and quadrupole shifts) and the anisotropy energy have been measured, and the frequencies of magnetic moment relaxation of iron ions have been estimated.

  19. Moessbauer Footprint in the Soil

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This 3-D image taken by the microscopic imager onboard the Mars Exploration Rover Opportunity shows a circular imprint left in the Meridiani Planum soil by the rover's Moessbauer spectrometer, an instrument located on its arm that detects iron-bearing minerals. Scientists are studying the curiously rounded grains for clues about the soil's history. The observed area is 3 centimeters (1.2 inches) across.

  20. Moessbauer Nose Print

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image was taken by the microscopic imager, an instrument located on the Mars Exploration Rover Opportunity 's instrument deployment device, or 'arm.' The image shows the imprint of the donut-shaped plate on the rover's Moessbauer spectrometer instrument, also located on the 'arm.' The Moessbauer spectrometer was deployed within the trench to investigate the fine-grained soil for iron-bearing minerals. The area in this image measures approximately 3 centimeters (1.2 inches) across.

  1. Magnetic and Moessbauer studies of Apollo 16 rock chips 60315,51 and 62295,27

    NASA Technical Reports Server (NTRS)

    Brecher, A.; Vaughan, D. J.; Burns, R. G.

    1973-01-01

    Analysis of the Moessbauer spectra of two Apollo 16 rocks showed that 60315,51 is much richer in iron metal and troilite, but poorer in olivine, than 62295,27. The values of magnetic parameters, derived from hysteresis loops at 175 and 300 K, indicate the high metal contents and the predominance of coarse multidomain grains in both rocks. These coexist with a superparamagnetic grain fraction in 60315 and with a small single-domain grain fraction in 62295. The high Fe(0)/Fe(2+) ratios, the nonlinear acquisition of laboratory thermoremanence, and the drastic changes in magnetic parameters upon heating support the proposed formation of both rocks from the lunar regolith, with incorporation of shocked meteoritic metal grains during high-temperature impact events and simultaneous acquisition of magnetic remanence. Values estimated for ancient lunar magnetic fields by comparing the natural remanence with laboratory thermoremanence acquired in fields of 0.05 and 0.5 Oe, range from 0.01 to more than 1 Oe.

  2. EPR and (57)Fe ENDOR investigation of 2Fe ferredoxins from Aquifex aeolicus.

    PubMed

    Cutsail, George E; Doan, Peter E; Hoffman, Brian M; Meyer, Jacques; Telser, Joshua

    2012-12-01

    We have employed EPR and a set of recently developed electron nuclear double resonance (ENDOR) spectroscopies to characterize a suite of [2Fe-2S] ferredoxin clusters from Aquifex aeolicus (Aae Fd1, Fd4, and Fd5). Antiferromagnetic coupling between the Fe(II), S = 2, and Fe(III), S = 5/2, sites of the [2Fe-2S](+) cluster in these proteins creates an S = 1/2 ground state. A complete discussion of the spin-Hamiltonian contributions to g includes new symmetry arguments along with references to related FeS model compounds and their symmetry and EPR properties. Complete (57)Fe hyperfine coupling (hfc) tensors for each iron, with respective orientations relative to g, have been determined by the use of "stochastic" continuous wave and/or "random hopped" pulsed ENDOR, with the relative utility of the two approaches being emphasized. The reported hyperfine tensors include absolute signs determined by a modified pulsed ENDOR saturation and recovery (PESTRE) technique, RD-PESTRE-a post-processing protocol of the "raw data" that comprises an ENDOR spectrum. The (57)Fe hyperfine tensor components found by ENDOR are nicely consistent with those previously found by Mössbauer spectroscopy, while accurate tensor orientations are unique to the ENDOR approach. These measurements demonstrate the capabilities of the newly developed methods. The high-precision hfc tensors serve as a benchmark for this class of FeS proteins, while the variation in the (57)Fe hfc tensors as a function of symmetry in these small FeS clusters provides a reference for higher-nuclearity FeS clusters, such as those found in nitrogenase. PMID:22872138

  3. The Use of Moessbauer Spectroscopy in Metallurgy

    SciTech Connect

    Forder, S.D.

    2005-04-26

    This review will present examples of the varied way in which Moessbauer spectroscopy has been used, with complementary analytical techniques, to gain information about metals and alloys, with cases chosen to illustrate how this information can be valuable to industry.The Moessbauer investigations reviewed have been divided into three categories:1) Monitoring the effect of deliberate modification of the metal by processing, either at the pre-treatment stage, e.g. metal ion etching of steel surfaces prior to coating or during the modification of structure and properties, such as the formation of Al-Fe surface alloys formed by ion implantation of Fe in Al.2) Monitoring changes in the metal not caused deliberately, i.e. the side-effects of processing. Examples reviewed include Moessbauer studies of reactor steels, and phase transformation during intensive plastic deformation. Also the Moessbauer Effect has helped to determine the cause of staining occurring on electrogalvanized steel.3) Obtaining information to enable fundamental understanding of metals and alloys. These examples include Moessbauer spectroscopy used to study the formation of intermetallic phases in industrial alloys, the influence of metal ions on iron oxide rusts and the study of quasi-crystalline alloys.The information gained has helped the improvement of properties, the monitoring of changes in structures, as well as the development of fundamental understanding of metals and alloys.

  4. Moessbauer-Fresnel zone plate as nuclear monochromator

    SciTech Connect

    Mooney, T.M.; Alp, E.E.; Yun, W.B.

    1992-06-01

    Zone plates currently used in x-ray optics derive their focusing power from (a spatial variation of) the electronic refractive index -- that is, from the collective effect of electronic x-ray-scattering amplitudes. Nuclei also scatter x rays, and resonant nuclear-scattering amplitudes, particularly those associated with Moessbauer fluorescence, can dominate the refractive index for x-rays whose energies are very near the nuclear-resonance energy. A zone plate whose Fresnel zones are filled alternately with {sup 57}Fe and {sup 56}Fe ({sup 57}Fe has a nuclear resonance of natural width {Gamma} = 4.8 nano-eV at 14.413 keV; {sup 56}Fe has no such resonance) has a resonant focusing efficiency; it focuses only those x-rays whose energies are within several {Gamma} of resonance. When followed by an absorbing screen with a small pinhole, such a zone plate can function as a synchrotron-radiation monochromator with an energy resolution of a few parts in 10{sup 12}. The energy-dependent focusing efficiency and the resulting time-dependent response of a resonant zone plate are discussed.

  5. Surface analysis of mixed-conducting ferrite membranes by the conversion-electron Moessbauer spectroscopy

    SciTech Connect

    Waerenborgh, J.C.; Tsipis, E.V.; Yaremchenko, A.A.; Kharton, V.V.

    2011-09-15

    Conversion-electron Moessbauer spectroscopy analysis of iron surface states in the dense ceramic membranes made of {sup 57}Fe-enriched SrFe{sub 0.7}Al{sub 0.3}O{sub 3-{delta}} perovskite, shows no traces of reductive decomposition or carbide formation in the interfacial layers after operation under air/CH{sub 4} gradient at 1173 K, within the limits of experimental uncertainty. The predominant trivalent state of iron cations at the membrane permeate-side surface exposed to flowing dry methane provides evidence of the kinetic stabilization mechanism, which is only possible due to slow oxygen-exchange kinetics and enables long-term operation of the ferrite-based ceramic reactors for natural gas conversion. At the membrane feed-side surface exposed to air, the fractions of Fe{sup 4+} and Fe{sup 3+} are close to those in the powder equilibrated at atmospheric oxygen pressure, suggesting that the exchange limitations to oxygen transport are essentially localized at the partially reduced surface. - Graphical Abstract: Conversion-electron Moessbauer spectroscopy analysis of dense ceramic membranes made of {sup 57}Fe-enriched SrFe{sub 0.7}Al{sub 0.3}O{sub 3-{delta}} perovskite, shows no reductive decomposition in thin interfacial layers after testing under air/CH{sub 4} gradient, enabling stable operation of the ferrite-based ceramic reactors for partial oxidation of methane. Highlights: > Conversion-electron Moessbauer spectroscopy is used for mixed-conducting membranes. > No decomposition is detected in the membrane surface layers under air/CH{sub 4} gradient. > Due to kinetic stabilization, Fe{sup 3+} states prevail at the surface exposed to methane. > Transmission Moessbauer spectra show perovskite decomposition on equlibration in CH{sub 4}. > Ferrite-based ceramic reactors can stably operate under air/CH{sub 4} gradient.

  6. Test of level density models from reactions of {sup 6}Li on {sup 58}Fe and {sup 7}Li on {sup 57}Fe

    SciTech Connect

    Oginni, B. M.; Grimes, S. M.; Voinov, A. V.; Adekola, A. S.; Brune, C. R.; Carter, D. E.; Heinen, Z.; Jacobs, D.; Massey, T. N.; O'Donnell, J. E.; Schiller, A.

    2009-09-15

    The reactions of {sup 6}Li on {sup 58}Fe and {sup 7}Li on {sup 57}Fe have been studied at 15 MeV beam energy. These two reactions produce the same compound nucleus, {sup 64}Cu. The charged particle spectra were measured at backward angles. The data obtained have been compared with Hauser-Feshbach model calculations. The level density parameters of {sup 63}Ni and {sup 60}Co have been obtained from the particle evaporation spectra. We also find contributions from the break up of the lithium projectiles to the low energy region of the {alpha} spectra.

  7. The road to Fe16N2 formation in N + implanted 57Fe enriched films

    NASA Astrophysics Data System (ADS)

    Leroy, E.; Djega-Mariadassou, C.; Bernas, H.; Kaitasov, O.; Krishnan, R.; Tessier, M.

    1995-07-01

    20 keV N+ ions have been implanted on 57Fe enriched Fe films and RF deposited on glass and NaCl substrates with various fluences up to 3.0×1016 N+/cm2. Conversion electron Mossbauer spectroscopy and transmission electron microscopy measurements performed at room temperature on the as-implanted samples reveal the presence of α-Fe, α'-martensite, and ɛ-Fe3-xN phases. α″-Fe16N2 is only detected after a subsequent annealing at 220 °C; α'-martensite with a low nitrogen content appears as the precursor of α″, The additional nitrogen content needed for this process is supplied by the ɛ phase.

  8. The Contribution of 57Fe Mössbauer Spectrometry to Investigate Magnetic Nanomaterials

    NASA Astrophysics Data System (ADS)

    Greneche, Jean-Marc

    Fe containing nanomaterials and nanoparticles are quite important because their unusual physical properties make them excellent candidates for different applications. 57Fe Mössbauer spectrometry appears as an excellent tool to provide structural and magnetic data through the hyperfine parameters. After a short definition of nanostructures and their main characteristics originated from confinement effects, we established the relevant features to understand nanoscale magnetism. Some examples have been thus selected to illustrate first how Mössbauer spectrometry contributes to understand the chemical, structural and magnetic nature of nanostructures and the role of surface and grain boundaries. Then, they also demonstrate also how the fitting procedure remains a delicate task to model the hyperfine structure and does require on the one hand large experimental data basis obtained from different techniques including structural, morphological and magnetic parameters and on the other hand materials with high knowledge and control of synthesis conditions.

  9. Mark of the Moessbauer

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image, taken by an instrument called the microscopic imager on the Mars Exploration Rover Spirit, reveals an imprint left by another instrument, the Moessbauer spectrometer. The imprint is at a location within the rover wheel track named 'Middle of Road.' Both instruments are located on the rover's instrument deployment device, or 'arm.'

    Not only was the Moessbauer spectrometer able to gain important mineralogical information about this site, it also aided in the placement of the microscopic imager. On hard rocks, the microscopic imager uses its tiny metal sensor to determine proper placement for best possible focus. However, on the soft martian soil this guide would sink, prohibiting proper placement of the microscopic imager. After the Moessbauer spectrometer's much larger, donut-shaped plate touches the surface, Spirit can correctly calculate where to position the microscopic imager.

    Scientists find this image particularly interesting because of the compacted nature of the soil that was underneath the Moessbauer spectrometer plate. Also of interest are the embedded, round grains and the fractured appearance of the material disturbed within the hole. The material appears to be slightly cohesive. The field of view in this image, taken on Sol 43 (February 16, 2004), measures approximately 3 centimeters (1.2 inches) across.

  10. Moessbauer on Mars

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken at Meridiani Planum, Mars, by the panoramic camera on the Mars Exploration Rover Opportunity shows the rover's Moessbauer spectrometer (circular device in center), located on its instrument deployment device, or 'arm.' The image was acquired on the ninth martian day or sol of the rover's mission.

  11. Phenomenological simulation and density functional theory prediction of 57 Fe Mössbauer parameters: application to magnetically coupled diiron proteins

    NASA Astrophysics Data System (ADS)

    Rodriguez, Jorge H.

    2013-04-01

    The use of phenomenological spin Hamiltonians and of spin density functional theory for the analysis and interpretation of Mössbauer spectra of antiferromagnetic or ferromagnetic diiron centers is briefly discussed. The spectroscopic parameters of the hydroxylase component of methane monooxygenase (MMOH), an enzyme that catalyzes the conversion of methane to methanol, have been studied. In its reduced diferrous state (MMOH Red ) the enzyme displays 57Fe Mössbauer and EPR parameters characteristic of two ferromagnetically coupled high spin ferrous ions. However, Mössbauer spectra recorded for MMOH Red from two different bacteria, Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b, display slightly different electric quadrupole splittings (Δ E Q ) in apparent contradiction to their essentially identical active site crystallographic structures and biochemical functions. Herein, the Mössbauer spectral parameters of MMOH Red have been predicted and studied via spin density functional theory. The somewhat different Δ E Q recorded for the two bacteria have been traced to the relative position of an essentially unbound water molecule within their diiron active sites. It is shown that the presence or absence of the unbound water molecule mainly affects the electric field gradient at only one iron ion of the binuclear active sites.

  12. Moessbauer study of microstructural and chemical changes in Fe-9Ni steel during two-phase tempering

    SciTech Connect

    Fultz, B.; Morris, J.W. Jr.

    1980-11-01

    Two-phase tempering of martensitic Fe-9Ni steel serves to enhance the low temperature toughness and forms austenite precipitates in this material. Hyperfine field effects in Fe-Ni alloys were systematized so that tempering induced chemical composition changes in the martensite could be quantified by Moessbauer spectrometry. The kinetics of segregation of alloy elements from the martensite into the fresh austenite can be determined simultaneously with the amount of austenite which was formed.

  13. Moessbauer Study and Macroscopic/Global Magnetic Behavior of Powdered Ilmenite (FeTiO{sub 3}) Sample

    SciTech Connect

    Cuda, J.; Prochazka, V.; Zboril, R.; Tucek, J.; Maslan, M.

    2010-07-13

    In this article, the commercial synthetic powdered sample of ilmenite (FeTiO{sub 3}) has been re-examined by Moessbauer spectroscopy in the paramagnetic regime from 77 K to 280 K and in a magnetically ordered state below 57 K. The effective vibrating mass and the Debye temperature was found to be (78{+-}3) amu and (359{+-}27) K, respectively. The two sextet components were used for correct fitting of the Moessbauer spectra recorded at 5 K and 45 K in an external magnetic field of 5 T. Moreover, the macroscopic magnetic measurements were carried out by an MPMS XL-7 magnetometer to determine a temperature dependence of the molar susceptibility and hysteresis loops of this sample. The Moessbauer spectra and magnetization measurements confirm that below the ordering temperature of ilmenite, it behaves as a non-ideal antiferromagnetic material with a significant magnetic hardening at low temperatures. In addition, the magnetic molar susceptibility follows a Curie-Weiss law with C{sub m=5.8x10{sup -5}Km{sup 3}/mol}, and Weiss temperature {theta}{sub p} = 30.6 K.

  14. Moessbauer Close-Up

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This close-up image of the Mars Exploration Rover Spirit's instrument deployment device, or 'arm,' shows the donut-shaped plate on the Moessbauer spectrometer. This image makes it easy to recognize the imprint left by the instrument in the martian soil at a location called 'Peak' on sol 43 (February 16, 2004). This image was taken by the rover's panoramic camera on sol 39 (February 11, 2004).

  15. Ordering and oxygen content effects in YBa sub 2 (Cu sub 1 minus x Fe sub x ) sub 3 O sub 7 samples observed by high-temperature Moessbauer spectroscopy

    SciTech Connect

    Saitovitch, E.B.; Scorzelli, R.B.; Azevedo, I.S.; dos Santos, C.A. )

    1990-05-01

    We report here {ital in} {ital situ} high-temperature {sup 57}Fe Moessbauer measurements on YBa{sub 2}(Cu{sub 1{minus}{ital x}}Fe{sub {ital x}}){sub 3}O{sub 7} samples in controlled oxygen atmosphere, in air, or in vacuum. In these conditions, fundamental information can be obtained related to the thermal stability of the different Fe species, as well as the mechanism of oxygen loss.

  16. Moessbauer spectroscopy study of iron-based catalysts used in Fischer-Tropsch synthesis

    SciTech Connect

    Rao, K.R.P.M.; Huggins, F.E.; Huffman, G.P.

    1995-12-01

    Mossbauer investigations of iron-based catalysts containing the promoters K, and Cu, and binders consisting of oxides of Al, Si and Zr were carried out. Catalysts subjected to pretreatment in gas atmospheres containing mixtures of CO, H{sub 2}, and He have been studied. It is shown that the nature of binders, promoters and pretreatment of a catalyst influence the iron-phases formed during pretreatment and FT synthesis. Activation of the catalysts in CO leads to rapid and almost complete formation of {chi}-Fe{sub 5}C{sub 2} during activation and gives rise to high (H{sub 2}+CO) conversion. On the other hand, activation of the catalysts in synthesis gas leads to slow and incomplete formation of carbides and low (H{sub 2}+CO) conversion.

  17. Map of Moessbauer Placement

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This elevation map of a soil target called 'Peak' was created from images taken by the microscopic imager located on the Mars Exploration Rover Spirit's instrument deployment device or 'arm.' The image reveals the various high and low points of this spot of soil after the Moessbauer spectrometer, another instrument on the rover's arm, was gently placed down on it. The blue areas are farthest away from the instrument; the red areas are closest. The variation in distance between blue and red areas is only 2 millimeters, or .08 of an inch. The images were acquired on sol 39 (February 11, 2004).

  18. Observation of Enhancement of the Morin Transition Temperature in Iridium-Doped α-Fe2O3 Thin Film by 57Fe-Grazing Incidence Synchrotron Radiation Mössbauer Spectroscopy

    NASA Astrophysics Data System (ADS)

    Mitsui, Takaya; Mibu, Ko; Seto, Makoto; Kurokuzu, Masayuki; Pati, Satya Prakash; Nozaki, Tomohiro; Sahashi, Masashi

    2016-06-01

    The Morin transition of a (0001)-oriented iridium-doped α-Fe2O3 thin film deposited on an Al2O3(0001) substrate was studied by 57Fe-grazing incidence synchrotron radiation Mössbauer spectroscopy (GISRMS). Temperature-dependent spectra proved that the iridium doping markedly enhanced the Morin temperature of the α-Fe2O3 thin film; the iron spin directions were perpendicular to the film plane at temperatures below 100 °C, while they were in-plane at temperatures above 150 °C. The antiferromagnetic ordering was maintained far above 400 °C. The results demonstrated the availabilities of 57Fe-GISRMS, which enables a very quick evaluation of the magnetism in antiferromagnetic ultrathin films at high temperatures.

  19. Moessbauer spectroscopy study of the aging and tempering of high nitrogen quenched Fe-N alloys: Kinetics of formation of Fe{sub 16}N{sub 2} nitride by interstitial ordering in martensite

    SciTech Connect

    Fall, I.; Genin, J.M.R. |

    1996-08-01

    The distribution of nitrogen atoms in austenite and during the different stages of aging and tempering of martensite is studied by Moessbauer spectroscopy, X-ray diffraction, and transmission electron microscopy (TEM). Transmission Moessbauer spectroscopy (TMS) and conversion electron Moessbauer spectroscopy (CEMS) are used for studying the austenite phase where the distribution of nitrogen atoms is found to depend on the nitriding method, gas nitriding in the authors` case, or ion implantation. Conversion electron Moessbauer spectroscopy, which concerns a depth predominantly less than 200 nm, reveals a nitrogen atom distribution different from that found in the bulk by TMS. The identification and kinetics of the stages of aging and tempering of martensite are followed by TMS measurements, and the phase characterization is confirmed by X-ray diffraction and TEM. The major stages are the early ordering of nitrogen atoms, which leads to small coherent precipitates of {alpha}-Fe{sub 16}N{sub 2}; the passage by thickening to semicoherent precipitates of {alpha}-Fe{sub 16}N{sub 2}; the dissolution of {alpha}-Fe{sub 16}N{sub 2} with the concomitant formation of {gamma}-Fe{sub 4}N; and the decomposition of retained austenite by tempering. The three first stages correspond to activation energies of 95, 126, and 94 kJ/mole, respectively, consistent with the nitrogen diffusion for the first and third stages and the dislocation pipe diffusion of iron for the second.

  20. Hyperfine fields at 57Fe in dilute iron-based alloys determined by Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Idczak, R.; Konieczny, R.; Chojcan, J.

    2015-04-01

    The room temperature Mössbauer spectra of 57Fe were measured for several dilute iron-based alloys, Fe1-xDx (D = Co, Cr, Mn, Mo, Pt, Re, Ta, V, W), annealed at 1270 K for 2 h before the measurements. The analysis of the spectra shows that the effective hyperfine field B at 57Fe nuclei depends on the concentration x of the minority component of the alloys under consideration and the dependence is different for iron nuclei having unlike numbers of impurities in their neighbourhood. The latter is at variance with previously published data, which suggest that the general B(x) dependence is common for all impurity configurations present in the vicinity of iron nuclei.

  1. Noncollinear Fe spin structure in (Sm-Co)/Fe exchange-spring bilayers: layer-resolved {sup 57}Fe Mssbauer spectroscopy and electronic structure calculations.

    SciTech Connect

    Uzdin, V. M.; Vega, A.; Khrenov, A.; Keune, W.; Kuncser, V. E.; Jiang, J. S.; Bader, S. D.

    2012-01-01

    Magnetization reversal in nanoscale (Sm-Co)/Fe (hard/soft) bilayer exchange-spring magnets with in-plane uniaxial magnetic anisotropy was investigated by magnetometry, conversion-electron Moessbauer spectroscopy (CEMS) and atomistic Fe spin-structure calculations. Magnetization loops along the easy direction exhibit signatures typical of exchange-spring magnets. In-field CEMS at inclined {gamma}-ray incidence onto thin (2 nm) {sup 57}Fe probe layers embedded at various depths in the 20-nm-thick natural (soft) Fe layer provides depth-dependent information (via the line-intensity ratio R{sub 23} as a function of the applied field H) about the in-plane rotation of Fe spins. A minimum in the R{sub 23}-vs-H dependence at (H{sub min}, R{sub min}) determines the field where Fe magnetic moments roughly adopt an average perpendicular orientation during their reversal from positive to negative easy-axis orientation. A monotonic decrease of H{sub min} with distance from the hard/soft interface is observed. Rotation of Fe spins takes place even in the interface region in applied fields far below the field of irreversible switching, H{sub irr}, of the hard phase. Formation of an Fe-Co alloy is detected in the interface region. For comparison, the noncollinear Fe spin structure during reversal and the resulting R{sub 23} ratio were obtained by electronic-structure calculations based on a quantum-mechanical Hamiltonian for itinerant electrons. The coupling at the hard/soft interface is described by the uniaxial exchange-anisotropy field, hint, as a parameter. Our calculated R{sub 23} ratios as a function of the (reduced) applied field h exhibit similar features as observed in the experiment, in particular a minimum at (h{sub min}, R{sub min}). R{sub min} is found to increase with hint, thus providing a measure of the interface coupling. Evidence is provided for the existence of fluctuations of the interface coupling. The calculations also show that the Fe spin spiral formed

  2. Observation of Flux-Grown α-Fe2O3 Single Crystal at the Morin Transition by 57Fe Synchrotron Radiation Mössbauer Diffraction

    NASA Astrophysics Data System (ADS)

    Mitsui, Takaya; Nakamura, Shin; Ikeda, Naoshi; Fujiwara, Kosuke; Masuda, Ryo; Kobayashi, Yasuhiro; Seto, Makoto

    2016-05-01

    The Morin transition of a high-quality flux-grown single crystal of α-Fe2O3 was studied by 57Fe synchrotron radiation Mössbauer diffraction. The measured rocking curves and Mössbauer spectra gave direct evidence that the coexistence of magnetic phases during the Morin transition occurred over a wide temperature range. The complex magnetic structure at the phase coexistence induced a large magnetostrictive distortion in the α-Fe2O3 crystal surface. In contrast, however, when the antiferromagnetic phase was dominant at low temperatures, the distortion disappeared, and the initial high crystal perfection was recovered. The spectral line shapes were discussed in terms of the interference between electronic and nuclear scatterings.

  3. New limit on the mass of 14.4-keV solar axions emitted in an M1 transition in 57Fe nuclei

    NASA Astrophysics Data System (ADS)

    Derbin, A. V.; Muratova, V. N.; Semenov, D. A.; Unzhakov, E. V.

    2011-04-01

    Axions of energy 14.4 keV that originated from the M1 transition in 57Fe nuclei in the Sun were sought by using the resonance-absorption reaction A+57Fe57Fe* → 57Fe+ γ (14.4 keV). Asectioned Si(Li) detector arranged in a low-background facility was used to record photons from this reaction. This resulted in setting a new limit on the axion couplings to nucleons, |-1.19 g {/AN 0} + g {/AN 3}| ≤ 3.0×10-6. Within the hadronic-axion model, the respective constraint on the axion mass is m A ≤ 145 eV (at a 95% C.L.).

  4. Neutron Cross section Covariances in the Resonance region: 50,53Cr, 54,57Fe and 60Ni

    SciTech Connect

    Oblozinsky, P.; Cho,Y.-S.; Mattoon,C.M.; Mughabghab,S.F.

    2010-11-23

    We evaluated covariances in the neutron resonance region for capture and elastic scattering cross sections on minor structural materials, {sup 50,53}Cr, {sup 54,57}Fe and {sup 60}Ni. Use was made of the recently developed covariance formalism based on kernel approximation along with data in the Atlas of Neutron Resonances. Our results of most interest for advanced fuel cycle applications, elastic scattering cross section uncertainties at energies around 100 keV, are on the level of about 7-10%.

  5. Fe-57 and Sn-119 Moessbauer study of La2CuO(4-y), YBa2Cu3O(7-y) and SmBa2Cu3O(7-y)

    NASA Technical Reports Server (NTRS)

    Jha, S.; Mitros, C.; Yehia, S.; Lahamer, Amer; Julian, Glenn M.

    1988-01-01

    Moessbauer studies reveal antiferromagnetic order in doped La2CuO(4-7): at 77 K, H = 476 kOe at Fe-57 and H is less that 10 kOe at Sn-119. Split-source and conventional absorber experiments on RBa2Cu3O(7-y) (R = Y, Sm) are consistent with occupation of 3 sites by Fe-57, the relative population depending on sample preparation and Fe concentration.

  6. Inelastic scattering in condensed matter with high intensity Moessbauer radiation

    SciTech Connect

    Yelon, W.B.; Schupp, G.

    1993-02-01

    The QUEGS facility at MURR has produced a number of new results and demonstrated the range of potential applications of high resolution, high intensity Moessbauer scattering. This work has been carried out by both MU and Purdue researchers and includes published results on Na, W, pentadecane, polydimethylsiloxane and other systems, manuscripts submitted on alkali halides (Phys. Rev. B) and accurate Moessbauer lineshape measurements (Phys. Rev. C), and manuscripts in preparation on glycerol, NiAl and Moessbauer spectra obtained by modulating a scattering crystal. Recently, new collaborations have been initiated which will substantially enhance our efforts. These are with W. Steiner (Vienna), G. Coddens (Saclay), and R. D. Taylor (Los Alamos). Steiner is experienced with Fe-57 Moessbauer scattering, while Coddens specializes in quasielastic neutron scattering; both of these areas naturally complement our work. R. D. Taylor has pioneered Moessbauer spectroscopy from the time of its discovery and has already made important contributions to our study of lattice dynamics and superconductivity for lead alloyed with small quantities of tin. At the same time, a significant instrument upgrade is underway, funded in part by the DOE-URIP program.

  7. Large low-energy M1 strength for ^{56,57}Fe within the nuclear shell model.

    PubMed

    Brown, B Alex; Larsen, A C

    2014-12-19

    A strong enhancement at low γ-ray energies has recently been discovered in the γ-ray strength function of ^{56,57}Fe. In this work, we have for the first time obtained theoretical γ decay spectra for states up to ≈8  MeV in excitation for ^{56,57}Fe. We find large B(M1) values for low γ-ray energies that provide an explanation for the experimental observations. The role of mixed E2 transitions for the low-energy enhancement is addressed theoretically for the first time, and it is found that they contribute a rather small fraction. Our calculations clearly show that the high-ℓ(=f) diagonal terms are most important for the strong low-energy M1 transitions. As such types of 0ℏω transitions are expected for all nuclei, our results indicate that a low-energy M1 enhancement should be present throughout the nuclear chart. This could have far-reaching consequences for our understanding of the M1 strength function at high excitation energies, with profound implications for astrophysical reaction rates. PMID:25554878

  8. 57Fe Mössbauer spectroscopy, X-ray single-crystal diffractometry, and electronic structure calculations on natural alexandrite

    NASA Astrophysics Data System (ADS)

    Weber, Sven-Ulf; Grodzicki, Michael; Lottermoser, Werner; Redhammer, Günther J.; Tippelt, Gerold; Ponahlo, Johann; Amthauer, Georg

    2007-09-01

    Natural alexandrite Al2BeO4:Cr from Malyshevo near Terem Tschanka, Sverdlovsk, Ural, Russia, has been characterized by 57Fe Mössbauer spectroscopy, electron microprobe, X-ray single-crystal diffractometry and by electronic structure calculations in order to determine oxidation state and location of iron. The sample contains 0.3 wt% of total iron oxide. The 57Fe Mössbauer spectrum can be resolved into three doublets. Two of them with hyperfine parameters typical for octahedrally coordinated high-spin Fe3+ and Fe2+, respectively, are assigned to iron substituting for Al in the octahedral M2-site. The third doublet is attributed to Fe3+ in hematite. Electronic structure calculations in the local spin density approximation are in reasonable agreement with experimental data provided that expansion and/or distortion of the coordination octahedra are presumed upon iron substitution. The calculated hyperfine parameters of Fe3+ are almost identical for the M1 and M2 positions, but the calculated ligand-field splitting is by far too large for high-spin Fe3+ on M1.

  9. Low temperature fluorination of Sr{sub 3}Fe{sub 2}O{sub 7-x} with polyvinylidine fluoride: An X-ray powder diffraction and Moessbauer spectroscopy study

    SciTech Connect

    Hancock, Cathryn A.; Herranz, Tirma; Marco, Jose F.; Berry, Frank J.; Slater, Peter R.

    2012-02-15

    Fluorination of the Ruddlesden Popper phase, Sr{sub 3}Fe{sub 2}O{sub 7-x} by heat treatment with polyvinylidine fluoride (PVDF) gives a range of novel oxide fluoride compounds. Fluorination with 1 mol equivalent PVDF leads to a filling of the normal Ruddlesden Popper structure anion sites and a material of composition Sr{sub 3}Fe{sub 2}O{sub 5+x}F{sub 2-x} (x Almost-Equal-To 0.28(4)) which contains both Fe{sup 4+} and Fe{sup 3+}. Increasing the amount of PVDF to 2 mol equivalent leads to an increase in anion content due to filling of half the interstitial sites within the structure, with iron being completely reduced to Fe{sup 3+} leading to a composition Sr{sub 3}Fe{sub 2}O{sub 4}F{sub 4}. An increase in the amount of PVDF to Almost-Equal-To 3 mol equivalent leads to a further increase in unit cell volume, attributed to complete filling of the interstitial sites and a composition Sr{sub 3}Fe{sub 2}O{sub 3}F{sub 6}. {sup 57}Fe Moessbauer spectra in the temperature range 10-300 K demonstrated the complexity of the magnetic interactions in each of the three phases which reflect different local compositions of oxygen and fluorine around the iron ions thus influencing the superexchange pathways. - Graphical abstract: Low temperature (375 Degree-Sign C) fluorination of Sr{sub 3}Fe{sub 2}O{sub 7-x} with poly(vinylidene fluoride) leads to the production of three new Ruddlesden Popper oxide fluorides with progressive filling of the anion sites within the structure. Highlights: Black-Right-Pointing-Pointer The fluorination of Sr{sub 3}Fe{sub 2}O{sub 7-x} using PVDF. Black-Right-Pointing-Pointer The control of the fluorine content with amount of PVDF used. Black-Right-Pointing-Pointer The synthesis of three new Fe based oxide fluorides. Black-Right-Pointing-Pointer The identification of the structures of these oxide fluorides.

  10. Moessbauer spectroscopy studies of iron-catalysts used in Fischer-Tropsch (FT) processes. Quarterly technical progress report, January--March, 1995

    SciTech Connect

    Huffman, G.P.; Rao, K.R.P.M.

    1995-10-01

    Moessbauer spectroscopy investigations were carried out on 14 iron-based catalysts during the period under review. The catalyst 100Fe/4.4Si/0.71K (all atomic ratios) was subjected to activation first in syngas and subsequently in CO gas atmosphere. Fischer-Tropsch (FT) synthesis was carried out on the above catalyst. Another catalyst 100Fe/4.4Si/2.6Cu/0.71K (all atomic ratios) activated in syngas and subjected to FT synthesis was also studied to understand the effect of added Cu on the phase distribution and its effect on the FT activity. The following trends were observed: (1) activation of the catalyst in syngas, H{sub 2}/CO, lead to the formation of Fe{sub 3}O{sub 4} and no carbides were formed, the FT activity was found to be low at 9--12% (H{sub 2}+CO) conversion; (2) activation of the catalyst in CO for 22hrs lead to the formation of 33% of {chi}-carbide and the FT activity was found to be high at 88% maximum; (3) addition of copper to the catalyst has improved the FT activity for those catalysts pretreated in syngas at elevated pressures.

  11. The Miniaturized Moessbauer Spectrometer MIMOS II for the Asteroid Redirect Mission(ARM): Quantative Iron Mineralogy And Oxidation States

    NASA Technical Reports Server (NTRS)

    Schroeder, C.; Klingelhoefer, G; Morris, R. V.; Yen, A. S.; Renz, F.; Graff, T. G.

    2016-01-01

    The miniaturized Moessbauer spectrometer MIMOS II is an off-the-shelf instrument with proven flight heritage. It has been successfully deployed during NASA’s Mars Exploration Rover (MER) mission and was on-board the UK-led Beagle 2 Mars lander and the Russian Phobos-Grunt sample return mission. A Moessbauer spectrometer has been suggested for ASTEX, a DLR Near-Earth Asteroid (NEA) mission study, and the potential payload to be hosted by the Asteroid Redirect Mission (ARM). Here we make the case for in situ asteroid characterization with Moessbauer spectroscopy on the ARM employing one of three available fully-qualified flight-spare Moessbauer instruments.

  12. (Gamma scattering in condensed matter with high intensity Moessbauer radiation)

    SciTech Connect

    Not Available

    1992-01-01

    This report discusses: quasielastic scattering studies on glycerol; gamma-ray scattering from alkali halides; lattice dynamics in metals; Moessbauer neutron scattering, x-ray diffraction, and macroscopic studies of high {Tc} superconductors containing tungsten; NiAl scattering studies; and atomic interference factors and nuclear Casimir effect.

  13. The quantitative determination of FeS2 phases in coal by means of 57Fe Mössbauer spectroscopy

    USGS Publications Warehouse

    Evans, B.J.; King, Hobart M.; Renton, John J.; Stiller, A.

    1990-01-01

    A knowledge of the concentration of pyrite and marcasite in coals can provide important insight into the genesis of coal deposits. Determinations of the relative amounts of pyrite and marcasite by traditional methods of coal analysis are, however, beset with many difficulties. Using 57Fe Mössbauer spectroscopy and a mild chemical treatment with hydrofluoric acid, a technique has been devised for the quantitative determination of the relative concentrations of pyrite and marcasite in samples of whole coals or their low-temperature ashes. The sample preparation procedure is comparable to less accurate methods. Good qualitative agreement has been obtained between ore microscopic and Mössbauer spectroscopic techniques for a series of extensively investigated whole coal samples.

  14. Multilevel relaxation model for describing the Moessbauer spectra of nanoparticles in a magnetic field

    SciTech Connect

    Chuev, M. A.

    2012-04-15

    A theory is developed for the Moessbauer absorption spectra of an ensemble of single-domain particles in a magnetic field. This theory is based on the generalization of a relaxation model with a quantummechanical description of the stationary states of a particle and on the formalism of Liouville operators for describing the hyperfine interaction for a hyperfine field changing in both the magnitude and direction for various stationary states. The general scheme of calculating relaxation Moessbauer spectra in terms of a standard stochastic approach is substantially optimized using operations with block matrices and a unique tridiagonalization of high-rank non-Hermitian matrices with a simple nonorthogonal transformation in the calculation procedure. The resulting model can easily be implemented on a personal computer. It considers the physical mechanisms of formation of a hyperfine structure in a spectrum of nanoparticles in a real situation and self-consistently describes the qualitative features of the nontrivial evolution of spectra with the temperature and the magnetic-field direction and strength, which has been detected in {sup 57}Fe nucleus experiments performed on magnetic nanoparticles for half a century.

  15. Equilibrium and pre-equilibrium processes in the {sup 55}Mn({sup 6}Li,xp) and {sup 57}Fe({alpha},xp) reactions

    SciTech Connect

    Voinov, A. V.; Grimes, S. M.; Brune, C. R.; Massey, T. N.; Buerger, A.; Goergen, A.; Guttormsen, M.; Larsen, A. C.; Siem, S.; Kalbach, C.

    2011-05-15

    Spectra of outgoing neutrons and protons from the {sup 6}Li + {sup 55}Mn reaction and protons from the {alpha} + {sup 57}Fe reaction have been measured with beams of 15-MeV {sup 6}Li ions and 30-MeV {alpha} particles. These reactions proceed through the same {sup 61}Ni nucleus at the same excitation energy, thus allowing the difference in reaction mechanisms to be studied. It is shown that spectra from the first reaction measured at backward angles are due to emission from a traditional compound nucleus reaction, in which the intermediate nucleus has reached statistical equilibrium; the spectra from the second reaction contain a significant fraction of pre-equilibrium emission at all angles. Level density parameters of the residual nucleus {sup 60}Co have been obtained from the first reaction. Both emission spectra and angular distributions have been measured for the second reaction. It was found that the pre-equilibrium component exhibits a forward-peaked angular distribution, as expected, but with a steeper slope than predicted and with an unusual slight rise at angles above 120 deg. The backward-angle rise is explained qualitatively by the dominance of the multistep compound mechanism at backward angles.

  16. Features of the Quantitative Analysis in Moessbauer Spectroscopy

    SciTech Connect

    Semenov, V. G.; Panchuk, V. V.; Irkaev, S. M.

    2010-07-13

    The results describing the effect of different factors on errors in quantitative determination of the phase composition of studied substances by Moessbauer spectroscopy absorption are presented, and the ways of using them are suggested. The effectiveness of the suggested methods is verified by an example of analyzing standard and unknown compositions.

  17. Synchrotron-Radiation-Based Moessbauer Spectroscopy

    SciTech Connect

    Seto, Makoto; Masuda, Ryo; Mitsui, Takaya; Higashitaniguchi, Satoshi; Kitao, Shinji; Kobayashi, Yasuhiro; Inaba, Chika; Yoda, Yoshitaka

    2009-05-29

    We have developed a new method that yields Moessbauer absorption spectra using synchrotron radiation (SR); this method is applicable for almost all Moessbauer nuclides including those that cannot be measured by previous methods using radioisotope (RI) sources. The Moessbauer spectrum of the 68.752 keV excited state of {sup 73}Ge, which cannot be measured using a RI source, was measured using SR. Our results show that this method can be used to perform advanced Moessbauer spectroscopy measurements owing to the excellent features of SR.

  18. Evaluation of Fe uptake and translocation in transgenic and non-transgenic soybean plants using enriched stable (57)Fe as a tracer.

    PubMed

    Oliveira, Silvana R; Menegário, Amauri A; Arruda, Marco A Z

    2014-10-01

    A tracer experiment is carried out with transgenic T (variety M 7211 RR) and non-transgenic NT (variety MSOY 8200) soybean plants to evaluate if genetic modification can influence the uptake and translocation of Fe. A chelate of EDTA with enriched stable (57)Fe is applied to the plants cultivated in vermiculite plus substrate and the (57)Fe acts as a tracer. The exposure of plants to enriched (57)Fe causes the dilution of the natural previously existing Fe in the plant compartments and then the changed Fe isotopic ratio ((57)Fe/(56)Fe) is measured using a quadrupole-based inductively coupled plasma mass spectrometer equipped with a dynamic reaction cell (DRC). Mathematical calculations based on the isotope dilution methodology allow distinguishing the natural abundance Fe from the enriched Fe (incorporated during the experiment). The NT soybean plants acquire higher amounts of Fe from natural abundance (originally present in the soil) and from enriched Fe (coming from the (57)Fe-EDTA during the experiment) than T soybean ones, demonstrating that the NT soybean plants probably absorb higher amounts of Fe, independently of the source. The percentage of newly incorporated Fe (coming from the treatment) was approximately 2.0 and 1.1% for NT and T soybean plants, respectively. A higher fraction (90.1%) of enriched Fe is translocated to upper parts, and a slightly lower fraction (3.8%) is accumulated in the stems by NT plants than by T ones (85.1%; 5.1%). Moreover, in both plants, the Fe-EDTA facilitates the transport and translocation of Fe to the leaves. The genetic modification is probably responsible for differences observed between T and NT soybean plants. PMID:25079128

  19. 57Fe emission Mössbauer spectroscopy following dilute implantation of 57Mn into In 2O3

    NASA Astrophysics Data System (ADS)

    Mokhles Gerami, A.; Johnston, K.; Gunnlaugsson, H. P.; Nomura, K.; Mantovan, R.; Masenda, H.; Matveyev, Y. A.; Mølholt, T. E.; Ncube, M.; Shayestehaminzadeh, S.; Unzueta, I.; Gislason, H. P.; Krastev, P. B.; Langouche, G.; Naidoo, D.; Ólafsson, S.

    2016-12-01

    Emission Mössbauer spectroscopy has been utilised to characterize dilute 57Fe impurities in In 2O3 following implantation of 57Mn ( T 1/2 = 1.5 min.) at the ISOLDE facility at CERN. From stoichiometry considerations, one would expect Fe to adopt the valence state 3 + , substituting In 3+, however the spectra are dominated by spectral lines due to paramagnetic Fe2+. Using first principle calculations in the framework of density functional theory (DFT), the density of states of dilute Fe and the hyperfine parameters have been determined. The hybridization between the 3d-band of Fe and the 2p band of oxygen induces a spin-polarized hole on the O site close to the Fe site, which is found to be the cause of the Fe2+ state in In 2O3. Comparison of experimental data to calculated hyperfine parameters suggests that Fe predominantly enters the 8b site rather than the 24d site of the cation site in the Bixbyite structure of In 2O3. A gradual transition from an amorphous to a crystalline state is observed with increasing implantation/annealing temperature.

  20. Sensitivity of 57Fe emission Mössbauer spectroscopy to Ar and C induced defects in ZnO

    NASA Astrophysics Data System (ADS)

    Bharuth-Ram, K.; Mølholt, T. E.; Langouche, G.; Geburt, S.; Ronning, C.; Doyle, T. B.; Gunnlaugsson, H. P.; Johnston, K.; Mantovan, R.; Masenda, H.; Naidoo, D.; Ncube, M.; Gislason, H.; Ólafsson, S.; Weyer, G.

    2016-12-01

    Emission Mössbauer Spectroscopy (eMS) measurements, following low fluence (<1012 cm-2) implantation of 57Mn (t 1/2 = 1.5 min.) into ZnO single crystals pre-implanted with Ar and C ions, has been utilized to test the sensitivity of the 57Fe eMS technique to the different types of defects generated by the different ion species. The dominant feature of the Mössbauer spectrum of the Ar implanted ZnO sample was a magnetic hyperfine field distribution component, attributed to paramagnetic Fe3+, while that of the C implanted sample was a doublet attributed to substitutional Fe2+ forming a complex with the C dopant ions in the 2- state at O vacancies. Magnetization measurements on the two samples, on the other hand, yield practically identical m(H) curves. The distinctly different eMS spectra of the two samples display the sensitivity of the probe nucleus to the defects produced by the different ion species.

  1. Mechanical strength and local structure of 'new' Hagi porcelain investigated by 57Fe-Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Kubuki, S.; Uehara, H.; Akagi, K.; Mikuni, A.; Isobe, N.; Homonnay, Z.; Sinkó, K.; Kuzmann, E.; Nishida, T.

    2010-03-01

    A relationship between the local structure and mechanical strength of 'new' Hagi porcelain 'A' and 'B' prepared by sintering two types of iron containing aluminosilicate soils under oxidizing and reducing atmospheres were investigated by means of 57Fe-Mössbauer spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), as well as three point bending test. The largest mechanical strength (σ) value of 64.3±3.1 MPa was estimated from the three-point bending test of reductively sintered Hagi porcelain 'A'. The Mössbauer spectrum was composed of two paramagnetic doublets due to tetrahedral FeII FeIII with the isomer shift (δ) values of 1.13±0.02 and 0.31±0.01 mm s-1. On the other hand, a paramagnetic doublet and a magnetic sextet with the δ values of 0.30±0.01 and 0.35±0.02 mm s-1 were observed from the Mössbauer spectra of other samples. It can be concluded that the mechanically strengthened Hagi porcelain was successfully fabricated by choosing soil 'A' and by sintering under a reducing atmosphere.

  2. Mössbauer spectra and electric properties of 57Fe-enriched BiFeO3 thin films

    NASA Astrophysics Data System (ADS)

    Tanaka, Kiyotaka; Fujita, Yuya; Okamura, Soichiro; Yoshida, Yutaka

    2014-09-01

    57Fe-enriched BiFeO3 (BFO) thin films are fabricated on Pt/Ti/SiO2/Si substrates from a stoichiometric precursor solution by chemical solution deposition process. The microstructure of the thin films is controlled by a changing the sintering time at 550 °C. The polycrystalline thin film fabricated at 550 °C for 5 min shows well-saturated polarization-electric field (P-E) hysteresis loops and the remnant polarization Pr and coercive field Ec at room temperature are 52 µC/cm2 and 365 kV/cm, respectively, at an applied electric field of 1200 kV/cm. The Mössbauer spectra show that the BFO thin film has the valence state of Fe3+ only, consisting of antiferromagnetic and paramagnetic components. The paramagnetic component with an area fraction from 11 to 18%, which is not amorphous or Bi2Fe4O9, seems to distribute in the surface shell of the grains and the grain boundaries. This component must strongly influence the ferroelectric properties at room temperature.

  3. Search for 14.4 keV solar axions from M1 transition of 57Fe with CUORE crystals

    NASA Astrophysics Data System (ADS)

    CUORE Collaboration

    2013-05-01

    We report the results of a search for axions from the 14.4 keV M1 transition from 57Fe in the core of the sun using the axio-electric effect in TeO2 bolometers. The detectors are 5 × 5 × 5 cm3 crystals operated at about 10 mK in a facility used to test bolometers for the CUORE experiment at the Laboratori Nazionali del Gran Sasso in Italy. An analysis of 43.65 kgṡd of data was made using a newly developed low energy trigger which was optimized to reduce the energy threshold of the detector. An upper limit of 0.58 cṡkg-1ṡd-1 is established at 95% C.L., which translates into lower bounds fA >= 3.12 × 105 GeV 95% C.L. (DFSZ model) and fA >= 2.41 × 104 GeV 95% C.L. (KSVZ model) on the Peccei-Quinn symmetry-breaking scale, for a value of S = 0.5 of the flavor-singlet axial vector matrix element. These bounds can be expressed in terms of axion masses as mA <= 19.2 eV and mA <= 250 eV at 95% C.L. in the DFSZ and KSVZ models respectively. Bounds are given also for the interval 0.35 <= S <= 0.55.

  4. 57 Fe Mössbauer and X-ray characterisation of sandstones

    NASA Astrophysics Data System (ADS)

    Mulaba-Bafubiandi, A. F.; Waanders, F. B.

    2013-04-01

    Sandstones from the Free State province in South Africa have been mined and processed mainly by small scale and artisanal miners in the rural areas. In the present investigation basic fire proof and water absorption tests, X-ray and γ-ray based characterisation techniques were used to study the sandstones. The collected samples were grouped according to their apparent colour in day light conditions and the elemental analysis showed the presence of a high amount of oxygen (>52%) and silicon (>38%) with Mn, Al, Fe and Ca as major elements in proportions related to the colour distribution of the various sandstones. The uniaxial compressive stress was found to be the highest (56 MPa) for the greyish sandstone and the lowest (8 MPa) for the white sandstone sample, also associated with the lowest (Al+Fe)/Si value of 0.082. The humidity test showed that the 6 % water absorption was lower than the recommended ASTM value of 8 %. The sandstone samples were also subjected to various high temperatures to simulate possible fire conditions and it was found that the non alteration of the mineral species might be one of the reasons why the sandstones are regarded as the most refractory amongst the building materials typically used. Mössbauer spectroscopy revealed that iron is present in all the sandstones, mainly as Fe3 + with the black sandstone showing an additional presence of 3 % Fe2 + indicating that a higher iron content coupled to higher silicon content, contributes to an increase in the uniaxial compressive strength.

  5. Study of C-coated LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} as positive electrode material for Li-ion batteries

    SciTech Connect

    Perea, A.; Castro, L.; Aldon, L.; Stievano, L.; Dedryvere, R.; Gonbeau, D.; Tran, N.; Nuspl, G.; Breger, J.; Tessier, C.

    2012-08-15

    Commercial C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} positive electrode material has been investigated by {sup 57}Fe Moessbauer Spectroscopy (MS), X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The combined use of these experimental techniques provides a better understanding of the electrochemical reaction involved during cycling. {sup 57}Fe MS is very efficient to directly follow oxidation state of Fe in the electrode, and gives surprisingly indirect information on the oxidation state of Mn as observed by XAS and XPS. The electrochemical mechanism is proposed based from in situ and operando investigations using both MS and XAS, and is consistent with XPS surface studies. XPS analysis of the electrodes at the end of charge (4.4 V) reveals enhanced electrode/electrolyte interface reactivity at this high potential. Aging of C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4}/Li cells after 50 cycles at 60 Degree-Sign C indicates a rather good electrochemical behavior (low capacity fading) of the electrode material. Both {sup 57}Fe MS and XPS (Mn 2p and Fe 2p) clearly show no modification on Fe and Mn oxidation state compared to fresh electrode confirming the good electrochemical performances. - Graphical abstrct: Quantitative evaluation of the Fe{sup 3+} and Mn{sup 3+} content during the first charge/discharge cycle obtained from K-edge XANES spectra of C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} recorded upon cell operation at RT with C/10 rate. During the charge co-existence of Fe and Mn oxidation is observed between points 2 and 4 of the potential curve. At the end of the charge the cut-off voltage limits the oxidation at about 93%. Highlights: Black-Right-Pointing-Pointer C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} electrode material upon cycling vs. metallic lithium. Black-Right-Pointing-Pointer {sup 57}Fe Moessbauer spectroscopy is a (in)direct probe for Fe(Mn) oxidation state. Black-Right-Pointing-Pointer Both K-Fe and K-Mn edges XAS show a simultaneous

  6. Cross sections of the 57Fe(n,α)54Cr and 63Cu(n,α)60Co reactions in the MeV region

    NASA Astrophysics Data System (ADS)

    Gledenov, Yu. M.; Sedysheva, M. V.; Stolupin, V. A.; Zhang, Guohui; Han, Jinhua; Wang, Zhimin; Fan, Xiao; Liu, Xiang; Chen, Jinxiang; Khuukhenkhuu, G.; Szalanski, P. J.

    2014-06-01

    Cross sections of the 57Fe(n,α)54Cr reaction are measured for the first time, and those of the 63Cu(n,α)60Co reaction are measured in the megaelectron volt region by the direct experimental method. Experiments were performed at the 4.5-MV Van de Graaff Accelerator of Peking University. Monoenergetic neutrons (5.0, 5.5, 6.0, and 6.5 MeV) were produced through the 2H(d,n)3He reaction with a deuterium gas target. Measurements were carried out using a double-section-gridded ionization chamber and back-to-back double 57Fe and 63Cu samples. Foreground and background were measured in separate runs. A 238U sample and a BF3 long counter were utilized for absolute neutron flux calibration and for neutron flux normalization, respectively. Present results are compared with talys-1.4 code predictions, existing measurements, and evaluations.

  7. Electric field gradient at 57Fe in scandium and systematics of the electric field gradient at impurities in transition-metal hosts

    NASA Astrophysics Data System (ADS)

    Nair, N. V.; Nair, K. Vijayakumaran

    1986-05-01

    The electric field gradient (EFG) at 57Fe probe atoms in hcp transition-metal scandium is measured using Mössbauer spectroscopy, with 57Fe as a dilute impurity in pure scandium metal. The quadrupole splitting obtained is 0.26(2) mm/s and the corresponding EFG is 1.3(1)×1017 V/cm2 at the probe site in scandium. The ratio eqel/eqion is in fairly good agreement with the universal correlation proposed by Raghavan et al. The results are compared with the theoretical value of the EFG calculated using the conduction-electron charge-shift model. Also, a systematic scheme, which can be used to determine eqel and the sign of EFG in transition-metal hosts, is proposed.

  8. Calibration of modern density functional theory methods for the prediction of 57Fe Mössbauer isomer shifts: meta-GGA and double-hybrid functionals.

    PubMed

    Römelt, Michael; Ye, Shengfa; Neese, Frank

    2009-02-01

    Five density functionals including GGA (generalized gradient approximation) (BP86), meta-GGA (TPSS), hybrid meta-GGA (TPSSh), hybrid (B3LYP), and double-hybrid functionals (B2PLYP) were calibrated for the prediction of 57Fe Mössbauer isomer shifts on a set of 20 iron-containing molecules. The influence of scalar relativistic effects and the basis set dependence of the predictions were investigated. PMID:19102678

  9. Fe-implanted 6H-SiC: Direct evidence of Fe{sub 3}Si nanoparticles observed by atom probe tomography and {sup 57}Fe Mössbauer spectroscopy

    SciTech Connect

    Diallo, M. L.; Fnidiki, A. Lardé, R.; Cuvilly, F.; Blum, I.; Lechevallier, L.; Debelle, A.; Thomé, L.; Viret, M.; Marteau, M.; Eyidi, D.; Declémy, A.

    2015-05-14

    In order to understand ferromagnetic ordering in SiC-based diluted magnetic semiconductors, Fe-implanted 6H-SiC subsequently annealed was studied by Atom Probe Tomography, {sup 57}Fe Mössbauer spectroscopy and SQUID magnetometry. Thanks to its 3D imaging capabilities at the atomic scale, Atom Probe Tomography appears as the most suitable technique to investigate the Fe distribution in the 6H-SiC host semiconductor and to evidence secondary phases. This study definitely evidences the formation of Fe{sub 3}Si nano-sized clusters after annealing. These clusters are unambiguously responsible for the main part of the magnetic properties observed in the annealed samples.

  10. Moessbauer studies in zinc-manganese ferrites for use in measuring small velocities and accelerations with great precision

    NASA Technical Reports Server (NTRS)

    Escue, W. T.; Gupta, R. G.; Mendiratta, R. G.

    1975-01-01

    Mossbauer spectroscopy was used for a systematic study of the magnetic behavior of manganese and zinc in mixed ferrites. It was observed that Zn2+ has preference to substitute Mn2+ at interstitial sites where the metal ions are tetrahedrally coordinated with four oxygen neighbors. The internal magnetic hyperfine field at the tetrahedral iron site is larger than that at the octahedral site. The relaxation effects were observed to play an important role as the zinc contents were increased, while the spin-correlation time and the magnetic field were observed to decrease in strength. It is concluded that Mossbauer effect data on complex materials, when used in conjunction with other data, can provide useful insight into the origin of the microscopic properties of magnetic materials.

  11. Spatial spin-modulated structure and hyperfine interactions of 57Fe nuclei in multiferroics BiFe1- x T x O3 ( T = Sc, Mn; x = 0, 0.05)

    NASA Astrophysics Data System (ADS)

    Rusakov, V. S.; Pokatilov, V. S.; Sigov, A. S.; Matsnev, M. E.; Gapochka, A. M.; Kiseleva, T. Yu.; Komarov, A. E.; Shatokhin, M. S.; Makarova, A. O.

    2016-01-01

    The results of the Mössbauer studies on 57Fe nuclei in multiferroics BiFe1- x T x O3 ( T = Sc, Mn; x = 0, 0.05) in the temperature range of 5.2-300 K have been presented. The Mössbauer spectra have been analyzed in terms of the model of an incommensurate spatial spin-modulated structure of cycloid type. Information has been obtained about the effect of the substitution of Sc and Mn atoms for Fe atoms on the hyperfine parameters of the spectrum: the shift and the quadrupole shift of the Mössbauer line, the isotropic and anisotropic contributions to the hyperfine magnetic field, and also the parameter of anharmonicity of the spatial spin-modulated structure.

  12. Iron-oxide aerogel and xerogel catalyst formulations: Characterization by 57Fe Mössbauer and XAFS spectroscopies

    NASA Astrophysics Data System (ADS)

    Huggins, Frank E.; Bali, Sumit; Huffman, Gerald P.; Eyring, Edward M.

    2010-06-01

    Iron in various iron-oxide aerogel and xerogel catalyst formulations (≥85% Fe 2O 3; ≤10% K, Co, Cu, or Pd) developed for possible use in Fischer-Tropsch synthesis (FTS) or the water-gas-shift (WGS) reaction has been examined by 57Fe Mössbauer spectroscopy. The seventeen samples consisted of both as-prepared and calcined aerogels and xerogels and their products after use as catalysts for FTS or the WGS reaction. Complementary XAFS spectra were obtained on the occurrence of the secondary elements in some of the same materials. A broad, slightly asymmetric, two-peak Mössbauer spectrum was obtained from the different as-prepared and calcined catalyst formulations in the majority of cases. Such spectra could only be satisfactorily fit with three quadrupole doublet components, but no systematic trends in the isomer shift and quadrupole splitting parameters and area ratios of the individual components could be discerned that reflected variations in the composition or preparation of the aerogel or xerogel materials. However, significant reductions were noted in the Mössbauer effective thickness (recoilless absorption effect per unit mass of iron) parameter, χeff/ g, determined at room temperature, for aerogels and xerogels compared to bulk iron oxides, reflecting the openness and lack of rigidity of the aerogel and xerogel structures. Mössbauer measurements for two aerogels over the range from 15 to 292 K confirmed the greatly diminished nature of this parameter at room temperature. Major increases in the effective thickness parameter were observed when the open structure of the aerogel or xerogel collapsed during calcination resulting in the formation of iron oxides (hematite, spinel ferrite). Similar structural changes were indicated by increases in this parameter after use of iron-oxide aerogels as catalysts for FTS or the WGS reaction, during which the iron-oxide aerogel was converted to a mixture of nonstoichiometric magnetite and the Hägg carbide, χ-Fe 5C

  13. Zero-Field Spin-Echo Nuclear Magnetic Resonance and Moessbauer Spectroscopy Studies on the Enhancement of the Magnetic Properties of the SAMARIUM(2)

    NASA Astrophysics Data System (ADS)

    Potenziani, Ernest, II

    The Sm(,2)(Co,Fe,Cu,Zr,Cr)(,14.8) - type permanent magnets have been investigated by ('57)Fe Mossbauer spectroscopy and ('149)Sm and ('59)Co zero-field spin-echo NMR techniques. A complete set of samples, varying in complexity and heat treatment, were prepared and examined. The following findings were obtained: (1) the addition of copper serves to precipitate out iron and cobalt with the replacement of the transition metals by the copper, (2) the addition of iron causes some substitutional displacement of the cobalt with the remaining iron forming an Fe-Co phase, (3) a further removal of the free iron is accomplished by the addition of zirconium and a subsequent step anneal, (4) the second and more important role of the zirconium is known to be an increase in the coercive force. The results herein indicate that the zirconium preferentially substitutes into the 1:5 phase, replacing the samarium, and degrading the magnetic properties of the cellular boundary 1:5 phase--causing it to exert a more effective pinning of the domain walls, in agreement with experimental findings, (5) the addition of chromium with zirconium causes a preferential substitution of iron into the 4f crystal site of the 2:17 phase, thereby increasing the anisotropy and facilitating the removal of the Fe-Co phase.

  14. Material Research Using Moessbauer Spectroscopy With Exotic Nuclei

    SciTech Connect

    Kobayashi, Y.

    2009-05-04

    We have succeeded to obtain in-beam Moessbauer spectra using a short-lived {sup 57}Mn (T{sub 1/2} = 1.45 min) probes implanted into some different types of samples, in order to study the chemical states of the excited atoms produced just after nuclear decays and/or the dynamic behaviors of isolated single atoms in a semiconductor. {sup 57}Mn was produced as a radioactive beam following a nuclear projectile-fragmentation reaction of {sup 58}Fe{sup 21+} beams (E = 63 MeV/nucleon) with Be production target, and separated by the in-flight isotope separator at the accelerators in RIKEN Nishina Center. From the temperature dependence of obtained Moessbauer parameters of the isomer shift (I.S.), the quadrupole splitting (Q.S.), and the linewidth (I), the chemical species and the dynamic behavior of the isolated atoms could be discussed. The in-beam Moessbauer technique combined with a short-lived RI beam is a very powerful tool to investigate the products after nuclear transformations and the dynamics of dilute impurities in solids.

  15. Moessbauer Effect Study of Bi2O3. Na2O. B2O3. Fe2O3 Glass System

    SciTech Connect

    Salah, S.H.; Kashif, I.; Salem, S.M.; Mostafa, A.G.; El-Manakhly, K.A.

    2005-04-26

    Sodium-tetra-borate host glass containing both bismuth and iron cations were prepared obeying the composition (Na2B4O7)0.75 (Fe2O3)0.25-x (Bi2O3)x [where x = 0.0, 0.05, 0.10, 0.15, 0.20, and 0.25 mol.%]. X-ray diffraction indicated that all samples were in a homogeneous glassy phase. Moessbauer effect results showed that all iron ions appeared as Fe3+ ions occupying tetrahedral coordination state. The covalency of the Fe-O bond increased as bismuth oxide was gradually increased. IR measurements indicated the presence of some non-bridging oxygens and confirmed that iron ions occupy the tetrahedral coordination state. It was found also that, as Bi2O3 was gradually increased both magnetic susceptibility and specific volume decreased, while both density and molar volume increased.

  16. The dynamics of 57Fe nuclei in Fe(II)-DNA and [Fe(II)(1-methyl-2-mercaptoimidazole)2]-DNA condensates.

    PubMed

    Silvestri, Arturo; Ruisi, Giuseppe; Girasolo, Maria Assunta

    2002-11-25

    Alcoholic solutions of FeCl(2) and Fe(II)(Hmmi)(2)Cl(2) (Hmmi=1-methyl-2-mercaptoimidazole) induce calf thymus DNA condensation from aqueous solutions buffered at pH 7.4. A 1:1 Fe(II)-(DNA monomer) stoichiometry is assumed. The (57)Fe Mössbauer hyperfine parameters suggest an octahedral coordination environment, severely distorted, in both Fe(II)-(DNA monomer) and [Fe(II)(Hmmi)(2)]-(DNA monomer) condensates. The dynamic properties of iron nuclei in freeze-dried samples were investigated by means of variable temperature (57)Fe Mössbauer spectroscopy. Mean square displacements, (T), were calculated, such as the effective vibrating mass and the Mössbauer lattice temperature of the solids. increases linearly with the temperature in the whole temperature range explored; the absolute values are typical for lattice or solid-state vibrations. Very similar values for the effective vibrating masses were extracted, suggesting comparable covalency of the bonding interaction between the metal atom and its ligands, while the Mössbauer lattice temperatures show a softening of the lattice for [Fe(II)(Hmmi)(2)]-(DNA monomer) with respect to Fe(II)-(DNA monomer) condensate. PMID:12433425

  17. Moessbauer Spectroscopy on the Martian Surface: Predictions

    NASA Technical Reports Server (NTRS)

    Schaefer, M. W.; Dyar, M. D.

    2003-01-01

    Moessbauer spectrometers will be used on the upcoming MER/Athena and Mars Express/ Beagle 2 landers to identify and quantify relative amounts of iron-bearing minerals and determine Fe3+/Fe2+ ratios, allowing more realistic modeling of Martian mineralogy and geochemistry. To properly interpret the spectra acquired by these instruments, we must understand the Mossbauer parameters of minerals that we might expect to find on Mars. We present here a summary of predicted Fe-bearing minerals that might be observed by the MER Moessbauer spectrometers, based upon previous and our own on-going work.

  18. Gamma scattering in condensed matter with high intensity Moessbauer radiation

    SciTech Connect

    Not Available

    1990-01-01

    We give a progress report for the work which has been carried out in the last three years with DOE support. A facility for high-intensity Moessbauer scattering is now fully operational at the University of Missouri Research Reactor (MURR) as well as a facility at Purdue, using special isotopes produced at MURR. High precision, fundamental Moessbauer effect studies have been carried out using scattering to filter the unwanted radiation. These have led to a new Fourier transform method for describing Moessbauer effect (ME) lineshape and a direct method of fitting ME data to the convolution integral. These methods allow complete correction for source resonance self absorption (SRSA) and the accurate representation of interference effects that add an asymmetric component to the ME lines. We have begun applying these techniques to attenuated ME sources whose central peak has been attenuated by stationary resonant absorbers, to more precisely determine interference parameters and line-shape behavior in the resonance asymptotic region. This analysis is important to both the fundamental ME studies and to scattering studies for which a deconvolution is essential for extracting the correct recoilless fractions and interference parameters. A number of scattering studies have been successfully carried out including a study of the thermal diffuse scattering in Si, which led to an analysis of the resolution function for gamma-ray scattering. Also studied was the anharmonic motion in Na and the satellite reflection Debye-Waller factor in TaS{sub 2}, which indicate phason rather than phonon behavior. We have begun quasielastic diffusion studies in viscous liquids and current results are summarized. These advances, coupled to our improvements in MIcrofoil Conversion Electron spectroscopy lay the foundation for the proposed research outlined in this request for a three-year renewal of DOE support.

  19. Inelastic scattering in condensed matter with high intensity Moessbauer radiation

    SciTech Connect

    Yelon, W.B.; Schupp, G.

    1990-10-01

    We give a progress report for the work which has been carried out in the last three years with DOE support. A facility for high-intensity Moessbauer scattering is now fully operational at the University of Missouri Research Reactor (MURR) as well as facility at Purdue, using special isotopes produced at MURR. High precision, fundamental Moessbauer effect studies have been carried out using scattering to filter the unwanted radiation. These have led to a new Fourier transform method for describing Moessbauer effect (ME) lineshape and a direct method of fitting ME data to the convolution integral. These methods allow complete correction for source resonance self absorption (SRSA) and the accurate representation of interference effects that add an asymmetric component to the ME lines. We have begun applying these techniques to attenuated ME sources whose central peak has been attenuated by stationary resonant absorbers, to more precisely determine interference parameters and line-shape behavior in the resonance asymptotic region. This analysis is important to both the fundamental ME studies and to scattering studies for which a deconvolution is essential for extracting the correct recoilless fractions and interference parameters. A number of scattering studies have been successfully carried out including a study of the thermal diffuse scattering in Si, which led to an analysis of the resolution function for gamma-ray scattering. Also studied was the anharmonic motion in Na and the satellite reflection Debye-Waller factor in TaS{sub 2}, which indicate phason rather than phonon behavior. We have begun quasielastic diffusion studies in viscous liquids and current results are summarized. These advances, coupled to our improvements in MIcrofoil Conversion Electron spectroscopy lay the foundation for the proposed research outlined in this request for a three-year renewal of DOE support.

  20. Moessbauer spectroscopy studies of iron-catalysts used in Fischer-Tropsch (FT) processes. Quarterly technical progress report, October 1, 1996--December 31, 1996

    SciTech Connect

    Huffman, G.P.; Rao, K.R.P.M.

    1996-12-31

    The U.S. Department of Energy has currently a program to develop Fischer-Tropsch catalysts which are active at low H{sub 2}/Co ratio of 0.67. The Center for Applied Energy Research, University of Kentucky and Texas A&M University have been developing Fischer- Tropsch catalysts which are active at a low H{sub 2}/Co ratio of 0.67. It is of interest to find out any relationships that may exist between the iron phases that are produced during activation and FT synthesis and the activity of the catalysts. Moessbauer spectroscopy investigations were carried out on 32 iron-base catalysts during the period under review. Eleven catalysts withdrawn from slurry type of reactors during and at the end of FT synthesis were received from the University of Kentucky. Twenty one catalysts withdrawn at the end of the run from both the slurry and fixed-bed reactors were received from Texas A&M University.

  1. Fe-57 Moessbauer Spectroscopy of Fulgurites: Implications for Chemical Reduction

    NASA Technical Reports Server (NTRS)

    Sheffer, A. A.; Dyar, M. D.

    2004-01-01

    The high temperature (superliquidus) processing of silicates often results in very reduced products, such as Si-bearing Fe metal in type-1 chondrules and in lunar regolith agglutinates. Previous work on fulgurites (the glassy products of the lightning strike fusion of sand, soil, or rock) found silicon metal and iron-silicon alloys inside the silicate glass. The mechanism for this extreme reduction is not yet understood. In this work, we begin a Fe-57 Moessbauer spectroscopy study as well as continuing a microprobe study of several fulgurites in order to better constrain the extent and process of Fe reduction.

  2. Time-differential perturbed-angular-correlation and emission Moessbauer studies on {sup 99}Ru dispersed in YBa{sub 2}Cu{sub 3}O{sub 6.8} and YBa{sub 2}Cu{sub 3}O{sub 6}

    SciTech Connect

    Ohkubo, Y.; Kobayashi, Y.; Harasawa, K.; Ambe, S.; Okada, T.; Ambe, F.; Asai, K.; Shibata, S.

    1995-06-29

    The hyperfine interactions at {sup 99}Ru({sup $IMP@99}Rh) dispersed in YBa{sub 2}Cu{sub 3}O{sub 6.8} and YBa{sub 2}Cu{sub 3}O{sub 6} were studied by means of time-differential perturbed-angular-correlation (TDPAC) and emission Moessbauer spectroscopy. The TDPAC and Moessbauer measurements show that Ru ions are in the tetravalent state and exclusively occupy the Cu-1 sites, which form one-dimensional Cu-O chains in the orthorhombic phase. The oxygen coordinations around the Ru ions are discussed on the basis of the observed electric field gradients at {sup 99}Ru in YBa{sub 2}Cu{sub 3}O{sub 6.8} and YBa{sub 2}Cu{sub 3}O{sub 6}. 35 refs., 6 figs., 1 tab.

  3. Analysis of Moessbauer Data from Mars: A Database and Artificial Neural Network for Identification of Iron-bearing Phases

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; deSouza, P. A.; Morris, R. V.; Klingelhoefer, G.

    2003-01-01

    The exploration of the planet Mars is one of the major goals within the Solar system exploration programs of the US-American space agency NASA and the European Space Agency ESA. In particular the search for water and life and understanding of the history of the surface and atmosphere will be the major tasks of the upcoming space missions to Mars. The miniaturized Moessbauer spectrometer MIMOS II has been selected for the NASA Mars-Exploration-Rover twin-mission to Mars in 2003 and the ESA 2003 Mars-Express Beagle 2 mission. Reduced in size and weight, in comparison to ordinary laboratory setup, the sensor head just weights approximately 400 g, with a volume of (50x50x90) cu mm, and holds two gamma-ray sources: the stronger for experiments and the weaker for calibrations. The collimator (in sample direction) also shields the primary radiation off the detectors. Around the drive four detectors are mounted. The detectors are made of Si-PIN-photodiodes in chip form (100 sq mm, thickness of 0.5 mm). The control unit is located in a separate electronics board. This board is responsible for the power supply, generation of the drive's velocity reference signal, read of the detector pulses to record the spectrum, data storage and communication with the host computer. After more than four decades from the discovery of the Moessbauer effect, more than 400 minerals were studied at different temperatures. Their Moessbauer parameters were reported in the literature, and have been recently collected in a data bank. Previous Mars-missions, namely Viking and Mars Pathfinder, revealed Si, Al, Fe, Mg, Ca, K, Ti, S and Cl to be the major constituents in soil and rock elemental composition of the red planet. More than 200 minerals already studied by Moessbauer spectroscopy contain significant amounts of these elements. A considerable number of Moessbauer studies were also carried out on meteorites and on Moon samples. Looking backward in the studies of the whole Moessbauer community

  4. Search for 14.4 keV solar axions emitted in the M1-transition of {sup 57}Fe nuclei with CAST

    SciTech Connect

    Andriamonje, S.; Aune, S.; Dafni, T.; Ferrer-Ribas, E.; Autiero, D.; Barth, K.; Davenport, M.; Lella, L. Di; Belov, A.; Beltrán, B.; Carmona, J.M.; Cebrián, S.; Bräuninger, H.; Englhauser, J.; Friedrich, P.; Collar, J.I.; Eleftheriadis, C.; Fanourakis, G.; Fischer, H.; Franz, J.; Collaboration: CAST collaboration; and others

    2009-12-01

    We have searched for 14.4 keV solar axions or more general axion-like particles (ALPs), that may be emitted in the M1 nuclear transition of {sup 57}Fe, by using the axion-to-photon conversion in the CERN Axion Solar Telescope (CAST) with evacuated magnet bores (Phase I). From the absence of excess of the monoenergetic X-rays when the magnet was pointing to the Sun, we set model-independent constraints on the coupling constants of pseudoscalar particles that couple to two photons and to a nucleon g{sub aγ}|−1.19g{sub aN}{sup 0}+g{sub aN}{sup 3}| < 1.36 × 10{sup −16} GeV{sup −1} for m{sub a} < 0.03 eV at the 95% confidence level.

  5. Nuclear resonant scattering measurements on {sup 57}Fe by multichannel scaling with a 64-pixel silicon avalanche photodiode linear-array detector

    SciTech Connect

    Kishimoto, S. Haruki, R.; Mitsui, T.; Yoda, Y.; Taniguchi, T.; Shimazaki, S.; Ikeno, M.; Saito, M.; Tanaka, M.

    2014-11-15

    We developed a silicon avalanche photodiode (Si-APD) linear-array detector for use in nuclear resonant scattering experiments using synchrotron X-rays. The Si-APD linear array consists of 64 pixels (pixel size: 100 × 200 μm{sup 2}) with a pixel pitch of 150 μm and depletion depth of 10 μm. An ultrafast frontend circuit allows the X-ray detector to obtain a high output rate of >10{sup 7} cps per pixel. High-performance integrated circuits achieve multichannel scaling over 1024 continuous time bins with a 1 ns resolution for each pixel without dead time. The multichannel scaling method enabled us to record a time spectrum of the 14.4 keV nuclear radiation at each pixel with a time resolution of 1.4 ns (FWHM). This method was successfully applied to nuclear forward scattering and nuclear small-angle scattering on {sup 57}Fe.

  6. Inelastic scattering in condensed matter with high intensity Moessbauer radiation. Final technical report, December 1, 1989--November 30, 1992

    SciTech Connect

    Yelon, W.B.; Schupp, G.

    1993-02-01

    The QUEGS facility at MURR has produced a number of new results and demonstrated the range of potential applications of high resolution, high intensity Moessbauer scattering. This work has been carried out by both MU and Purdue researchers and includes published results on Na, W, pentadecane, polydimethylsiloxane and other systems, manuscripts submitted on alkali halides (Phys. Rev. B) and accurate Moessbauer lineshape measurements (Phys. Rev. C), and manuscripts in preparation on glycerol, NiAl and Moessbauer spectra obtained by modulating a scattering crystal. Recently, new collaborations have been initiated which will substantially enhance our efforts. These are with W. Steiner (Vienna), G. Coddens (Saclay), and R. D. Taylor (Los Alamos). Steiner is experienced with Fe-57 Moessbauer scattering, while Coddens specializes in quasielastic neutron scattering; both of these areas naturally complement our work. R. D. Taylor has pioneered Moessbauer spectroscopy from the time of its discovery and has already made important contributions to our study of lattice dynamics and superconductivity for lead alloyed with small quantities of tin. At the same time, a significant instrument upgrade is underway, funded in part by the DOE-URIP program.

  7. Sensitivity of the CUORE detector to 14.4 keV solar axions emitted by the M1 nuclear transition of 57Fe

    NASA Astrophysics Data System (ADS)

    Li, Dawei; Creswick, Richard J.; Avignone, Frank T., III; Wang, Yuanxu

    2016-02-01

    In this paper we present a calculation of the sensitivity of the CUORE detector to the monoenergetic 14.4 keV solar axions emitted by the M1 nuclear transition of 57Fe in the Sun and detected by inverse coherent Bragg-Primakoff conversion in single-crystal TeO2 bolometers. The expected counting rate is calculated using density functional theory for the electron charge density of TeO2 and realistic background and energy resolution of CUORE. Monte Carlo simulations for 5y × 741 kg=3705 kg y of exposure are analyzed using time correlation of individual events with the theoretical time-dependent counting rate. We find an expected model-independent limit on the product of the axion-photon coupling and the axion-nucleon coupling gaγγgaNeff < 1.105 × 10-16 /GeV for axion masses less than 500 eV with 95% confidence level.

  8. Magnetic hysteresis properties and 57Fe Mössbauer spectroscopy of iron and stony-iron meteorites: Implications for mineralogy and thermal history

    NASA Astrophysics Data System (ADS)

    Dos Santos, E.; Gattacceca, J.; Rochette, P.; Scorzelli, R. B.; Fillion, G.

    2015-05-01

    Since the solid matter in our solar system began to assemble 4.57 billion years ago, meteorites have recorded a large range of processes, including metamorphism, melting, irradiation and hypervelocity impacts. These processes as well as solar system magnetic fields can be accessed through the investigation of magnetic properties of meteorites. In this work, we present magnetic hysteresis properties, isothermal remanent magnetization acquisition curves and 57Fe Mössbauer spectra for nineteen iron and eleven stony-iron meteorites. These data will be the background for a discussion about the thermal and shock history of these meteorites. Although Mössbauer spectroscopy and hysteresis measurements are not able to provide cooling rates like the conventional metallographic method does, we show that the combination of the ordering degree of taenite phase measured by Mössbauer spectroscopy and hysteresis properties are useful for constraining the thermal and shock history of meteorites. In particular, strong shock and the associated thermal event that result in disordering of tetrataenite can be easily identified.

  9. Remarkable improvement of the signal-to-noise ratio of 57Mn/ 57Fe in-beam Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Nagatomo, T.; Kobayashi, Y.; Kubo, M. K.; Yamada, Y.; Mihara, M.; Sato, W.; Miyazaki, J.; Sato, S.; Kitagawa, A.

    2011-02-01

    In-beam Mössbauer spectroscopy utilizing unstable 57Mn beams is a powerful method to extract physical and chemical properties at the atomic scale. A parallel plate avalanche counter (PPAC), optimized to detect conversion electrons generated by the Mössbauer effect, can be employed to suppress higher-energy background γ rays. However, β rays are emitted by the 57Mn parent nuclei of 57Fe, which can significantly degrade the spectrum quality. In the present work, we have developed a new anti-coincidence-detection system with a thin plastic scintillation counter (0.5 mmt), which can be used to detect β rays and reject them from the recorded PPAC events. To demonstrate the anti-coincidence system, we carried out Mössbauer spectroscopy utilizing 57Mn nuclei that were implanted into a non-magnetic aluminum metal plate at room temperature. Using the anti-coincidence method, we obtained a typical Mössbauer spectrum of high quality, despite a very low number of implanted 57Mn atoms, of ˜5 × 10 9. The signal to noise ratio of the obtained spectrum was increased remarkably, and the relative peak height above the baseline increased from 10% to 220% using the anti-coincidence method. The developed detection system is applicable to investigation of in situ properties, and avoids the potentially problematic agglomeration of probes in a sample.

  10. Transition to collapsed tetragonal phase in CaFe2As2 single crystals as seen by 57Fe Mössbauer spectroscopy

    DOE PAGESBeta

    Bud'ko, Sergey L.; Ma, Xiaoming; Tomić, Milan; Ran, Sheng; Valentí, Roser; Canfield, Paul C.

    2016-01-21

    Temperature dependent measurements of 57Fe Mössbauer spectra on CaFe2As2 single crystals in the tetragonal and collapsed tetragonal phases are reported. Clear features in the temperature dependencies of the isomer shift, relative spectra area, and quadrupole splitting are observed at the transition from the tetragonal to the collapsed tetragonal phase. From the temperature dependent isomer shift and spectral area data, an average stiffening of the phonon modes in the collapsed tetragonal phase is inferred. The quadrupole splitting increases by ~25% on cooling from room temperature to ~100 K in the tetragonal phase and is only weakly temperature dependent at low temperaturesmore » in the collapsed tetragonal phase, in agreement with the anisotropic thermal expansion in this material. In order to gain microscopic insight about these measurements, we perform ab initio density functional theory calculations of the electric field gradient and the electron density of CaFe2As2 in both phases. By comparing the experimental data with the calculations we are able to fully characterize the crystal structure of the samples in the collapsed-tetragonal phase through determination of the As z coordinate. Furthermore, based on the obtained temperature dependent structural data we are able to propose charge saturation of the Fe-As bond region as the mechanism behind the stabilization of the collapsed-tetragonal phase at ambient pressure.« less

  11. Transition to collapsed tetragonal phase in CaFe2As2 single crystals as seen by 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Bud'ko, Sergey L.; Ma, Xiaoming; Tomić, Milan; Ran, Sheng; Valentí, Roser; Canfield, Paul C.

    2016-01-01

    Temperature dependent measurements of 57Fe Mössbauer spectra on CaFe2As2 single crystals in the tetragonal and collapsed tetragonal phases are reported. Clear features in the temperature dependencies of the isomer shift, relative spectra area, and quadrupole splitting are observed at the transition from the tetragonal to the collapsed tetragonal phase. From the temperature dependent isomer shift and spectral area data, an average stiffening of the phonon modes in the collapsed tetragonal phase is inferred. The quadrupole splitting increases by ˜25 % on cooling from room temperature to ˜100 K in the tetragonal phase and is only weakly temperature dependent at low temperatures in the collapsed tetragonal phase, in agreement with the anisotropic thermal expansion in this material. In order to gain microscopic insight about these measurements, we perform ab initio density functional theory calculations of the electric field gradient and the electron density of CaFe2As2 in both phases. By comparing the experimental data with the calculations we are able to fully characterize the crystal structure of the samples in the collapsed-tetragonal phase through determination of the As z coordinate. Based on the obtained temperature dependent structural data we are able to propose charge saturation of the Fe-As bond region as the mechanism behind the stabilization of the collapsed-tetragonal phase at ambient pressure.

  12. Moessbauer spectrometer for mineralogical analysis of the Mars surface: Moessbauer source considerations

    NASA Technical Reports Server (NTRS)

    Evlanov, E. N.; Frolov, V. A.; Prilutskii, O. F.; Veselova, G. V.; Rodin, A. M.; Klingelhoefer, G.

    1993-01-01

    Development of space rocketry and cosmic instrument making has made it possible to create interplanetary stations to be sent to the solar system bodies. In the last decade of the century the planet Mars will be in the focus of planetary science problems. Russia, USA (the NASA) and Europe (the ESA) plan to do a new step in the study of the planetary system by spacecraft missions to Mars. One part of the programs of these missions is Martian surface measurements of iron, which is a dominant element in both the Martian soil and rocks (about 13 percent by weight). The chemistry of iron in space is strongly coupled to the chemistry of abundant elements (to begin with hydrogen, carbon, oxygen) and it is this coupling of chemical cycles of abundant elements that gives us the possibility of understanding some features of the chemical evolution of matter. In this connection of extremely great importance for the understanding of the evolution of the solar system are the oxidation state of the iron and its mineral composition of the Mars surface. Being highly successful, the Viking landers had no instrumentation to answer these questions. Such instrumentation has to be specifically sensitive to mineralogy. For this purpose the back scattering Moessbauer spectrometer (MS-96) was proposed to be installed on a rover to be launched on board the Russian spacecraft Mars-96 mission to Mars. Due to power and mass restrictions three systems of the device MS-96 (velocity transducer, detector and electronic components) have been extremely miniaturized in comparison to a standard system. In this paper we intend to place for consideration a radioactive source to find out what characteristics it should have to be suitable for purposes of the experiment.

  13. XRD and {sup 119}Sn Moessbauer spectroscopy characterization of SnSe obtained from a simple chemical route

    SciTech Connect

    Bernardes-Silva, Ana Claudia . E-mail: anaclaudiabs2000@yahoo.com.br; Mesquita, A.F.; Moura de Neto, E.; Porto, A.O. . E-mail: arilzaporto@yahoo.com.br; Ardisson, J.D.; Lameiras, F.S.

    2005-09-01

    Crystalline tin selenide semiconductor was synthesized by a chemical route. Selenium powder reacted with potassium boronhydride, giving a soluble selenium species potassium seleniumhydride. The reaction of potassium seleniumhydride with tin chloride produced crystalline tin selenide, which was characterized by X-ray diffraction, {sup 119}Sn Moessbauer spectroscopy and scanning electronic microscopy. The material was thermally treated, in nitrogen flow, at 300 and 600 deg. C for 2 h and the particle size evolution was studied by X-ray diffraction. The X-ray diffraction and {sup 119}Sn Moessbauer results showed that a mixture of tin oxides and orthorhombic tin selenide was obtained.

  14. Redox condition of the late Neoproterozoic pelagic deep ocean: 57Fe Mössbauer analyses of pelagic mudstones in the Ediacaran accretionary complex, Wales, UK

    NASA Astrophysics Data System (ADS)

    Sato, Tomohiko; Sawaki, Yusuke; Asanuma, Hisashi; Fujisaki, Wataru; Okada, Yoshihiro; Maruyama, Shigenori; Isozaki, Yukio; Shozugawa, Katsumi; Matsuo, Motoyuki; Windley, Brian F.

    2015-11-01

    We report geological and geochemical analysis of Neoproterozoic pelagic deep-sea mudstones in an accretionary complex in Lleyn, Wales, UK. Ocean plate stratigraphy at Porth Felen, NW Lleyn, consists of mid-ocean ridge basalt (> 4 m), bedded dolostone (2 m), black mudstone (5 m), hemipelagic siliceous mudstone (1 m,) and turbiditic sandstone (15 m), in ascending order. The absence of terrigenous clastics confirms that the black and siliceous mudstone was deposited in a pelagic deep-sea. Based on the youngest U-Pb age (564 Ma) of detrital zircons separated from overlying sandstone, the deep-sea black mudstone was deposited in the late Ediacaran. The 5 m-thick black mudstone contains the following distinctive lithologies: (i) black mudstone with thin pyritic layers (0.8 m), (ii) alternation of black mudstone and gray/dark gray siliceous mudstone (2.4 m), (iii) thinly-laminated dark gray shale (1 m), and (iv) black mudstone with thin pyritic layers (1 m). 57Fe Mössbauer spectroscopy confirms that these black mudstones contain pyrite without hematite. In contrast, red bedded claystones (no younger than 542 Ma) in the neighboring Braich section contain hematite as their main iron mineral. These deep-sea mudstones in the Lleyn Peninsula record a change of redox condition on the pelagic deep-sea floor during the Ediacaran. The black mudstone at Porth Felen shows that deep-sea anoxia existed in the late Ediacaran. The eventual change from a reducing to an oxidizing deep-sea environment likely occurred in the late Ediacaran (ca. 564-542 Ma).

  15. The importance of a Ni correction with ion counter in the double spike analysis of Fe isotope compositions using a 57Fe/58Fe double spike

    NASA Astrophysics Data System (ADS)

    Finlayson, V. A.; Konter, J. G.; Ma, L.

    2015-12-01

    We present a new method capable of measuring iron isotope ratios of igneous materials to high precision by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) using a 57Fe-58Fe double spike. After sample purification, near-baseline signal levels of nickel are still present in the sample solution, acting as an isobaric interference on 58 amu. To correct for the interference, the minor 60Ni isotope is monitored and used to subtract a proportional 58Ni signal from the total 58 amu beam. The 60Ni signal is difficult to precisely measure on the Faraday detector due to Johnson noise occurring at similar magnitude. This noise-dominated signal is subtracted from the total 58 amu beam, and its error amplified during the double spike correction. Placing the 60Ni beam on an ion counter produces a more precise measurement, resulting in a near-threefold improvement in δ56Fe reproducibility, from ±0.145‰ when measured on Faraday to 0.052‰. Faraday detectors quantify the 60Ni signal poorly, and fail to discern the transient 20Ne40Ar interference visible on the ion counter, which is likely responsible for poor reproducibility. Another consideration is instrumental stability (defined herein as drift in peak center mass), which affects high-resolution analyses. Analyses experiencing large drift relative to bracketing standards often yield nonreplicating data. Based on this, we present a quantitative outlier detection method capable of detecting drift-affected data. After outlier rejection, long-term precision on individual runs of our secondary standard improves to ±0.046‰. Averaging 3-4 analyses further improves precision to 0.019‰, allowing distinction between ultramafic minerals.

  16. Electronic structure of the unique [4Fe-3S] cluster in O2-tolerant hydrogenases characterized by 57Fe Mossbauer and EPR spectroscopy.

    PubMed

    Pandelia, Maria-Eirini; Bykov, Dmytro; Izsak, Robert; Infossi, Pascale; Giudici-Orticoni, Marie-Thérèse; Bill, Eckhard; Neese, Frank; Lubitz, Wolfgang

    2013-01-01

    Iron-sulfur clusters are ubiquitous electron transfer cofactors in hydrogenases. Their types and redox properties are important for H(2) catalysis, but, recently, their role in a protection mechanism against oxidative inactivation has also been recognized for a [4Fe-3S] cluster in O(2)-tolerant group 1 [NiFe] hydrogenases. This cluster, which is uniquely coordinated by six cysteines, is situated in the proximity of the catalytic [NiFe] site and exhibits unusual redox versatility. The [4Fe-3S] cluster in hydrogenase (Hase) I from Aquifex aeolicus performs two redox transitions within a very small potential range, forming a superoxidized state above +200 mV vs. standard hydrogen electrode (SHE). Crystallographic data has revealed that this state is stabilized by the coordination of one of the iron atoms to a backbone nitrogen. Thus, the proximal [4Fe-3S] cluster undergoes redox-dependent changes to serve multiple purposes beyond classical electron transfer. In this paper, we present field-dependent (57)Fe-Mössbauer and EPR data for Hase I, which, in conjunction with spectroscopically calibrated density functional theory (DFT) calculations, reveal the distribution of Fe valences and spin-coupling schemes for the iron-sulfur clusters. The data demonstrate that the electronic structure of the [4Fe-3S] core in its three oxidation states closely resembles that of corresponding conventional [4Fe-4S] cubanes, albeit with distinct differences for some individual iron sites. The medial and distal iron-sulfur clusters have similar electronic properties as the corresponding cofactors in standard hydrogenases, although their redox potentials are higher. PMID:23267108

  17. Search for 14.4 keV solar axions from M1 transition of {sup 57}Fe with CUORE crystals

    SciTech Connect

    2013-05-01

    We report the results of a search for axions from the 14.4 keV M1 transition from {sup 57}Fe in the core of the sun using the axio-electric effect in TeO{sub 2} bolometers. The detectors are 5 × 5 × 5 cm{sup 3} crystals operated at about 10 mK in a facility used to test bolometers for the CUORE experiment at the Laboratori Nazionali del Gran Sasso in Italy. An analysis of 43.65 kg⋅d of data was made using a newly developed low energy trigger which was optimized to reduce the energy threshold of the detector. An upper limit of 0.58 c⋅kg{sup −1}⋅d{sup −1} is established at 95% C.L., which translates into lower bounds f{sub A} ≥ 3.12 × 10{sup 5} GeV 95% C.L. (DFSZ model) and f{sub A} ≥ 2.41 × 10{sup 4} GeV 95% C.L. (KSVZ model) on the Peccei-Quinn symmetry-breaking scale, for a value of S = 0.5 of the flavor-singlet axial vector matrix element. These bounds can be expressed in terms of axion masses as m{sub A} ≤ 19.2 eV and m{sub A} ≤ 250 eV at 95% C.L. in the DFSZ and KSVZ models respectively. Bounds are given also for the interval 0.35 ≤ S ≤ 0.55.

  18. Moessbauer search for ferric oxide phases in lunar materials and simulated lunar materials

    NASA Technical Reports Server (NTRS)

    Forester, D. W.

    1973-01-01

    Moessbauer studies were carried out on lunar fines and on simulated lunar glasses containing magnetic-like precipitates with the primary objective of determining how much, if any, ferric oxide is present in the lunar soils. Although unambiguous evidence of lunar Fe(3+) phases was not obtained, an upper limit was estimated from different portions of the Moessbauer spectra to be between 0.1 and 0.4 wt.% (as Fe3O4). A smaller than 62 microns fraction of 15021,118 showed 0.5 wt.% ferromagnetic iron at 300 K in as-returned condition. After heating to 650 C in an evacuated, sealed quartz tube for 1400 hours, the same sample exhibited 1 wt.% ferromagnetic iron at room temperature. An accompanying decrease in excess absorption area near zero velocity was noted. Thus, the result of the vacuum heat treatment was to convert fine grained iron to larger particles, apparently without the oxidation effects commonly reported.

  19. Moessbauer analysis of heat affected zones of an SA 508 steel weld

    SciTech Connect

    Kwon, S.J.; Oh, S.J.; Kim, S.; Lee, S.; Kim, J.H.

    1998-12-18

    Microstructure of a heat affected zone (HAZ) in a weld is influenced by many factors such as chemical composition, welding condition, and peak temperature. It is more complex under multi-pass welding because of the repeated heat input. For the analysis of the HAZ microstructure, optical microscope, electron microscope, and X-ray diffraction techniques have been widely used. However, their application is limited since they can hardly make quantitative analysis of HAZ where numerous phases such as martensite, bainite, ferrite, pearlite, austenite, and carbides are co-existing. Moessbauer spectroscopy, in such a case, is particularly useful due to the capability of quantitative analysis on the fraction of each phase. In this study, phases present in the HAZ of an SA 508 steel were identified, and their fractions were quantitatively determined by Moessbauer spectroscopy in conjunction with microscopic observations.

  20. Moessbauer studies in Zn(2+)0.3 Mn(2+)0.7 Mn(3+) (2-y) Fe(3+) (2-y) O4

    NASA Technical Reports Server (NTRS)

    Gupta, R. G.; Mendiratta, R. G.; Escue, W. T.

    1975-01-01

    The Mossbauer effect has proven to be effective in the study of nuclear hyperfine interactions. Ferrite systems having the formula (Zn(2+)0.3)(Mn(2+)0.7)(Mn(3+)y)(Fe(3+)2-y)(O4) were prepared and studied. These systems can be interpreted as mangacese-doped zinc and a part of iron ions. A systematic study of these systems is presented to promote an understanding of their microstructure for which various theories were proposed.

  1. Effect of nanocrystallization on the electrical conductivity enhancement and Moessbauer hyperfine parameters of iron based glasses

    SciTech Connect

    El-Desoky, M.M.; Ibrahim, F.A.; Mostafa, A.G.; Hassaan, M.Y.

    2010-09-15

    Selected glasses of Fe{sub 2}O{sub 3}-PbO{sub 2}-Bi{sub 2}O{sub 3} system have been transformed into nanomaterials by annealing at temperature close to crystallization temperature (T{sub c}) for 1 h. The effects of the annealing of the present samples on its structural and electrical properties were studied by Moessbauer spectroscopy, transmission electron micrograph (TEM), differential scanning calorimeter (DSC) and dc conductivity ({sigma}). Moessbauer spectroscopy was used in order to determine the states of iron and its hyperfine structure. The effect of nanocrystalization on the Moessbauer hyperfine parameters did not exhibit significant modifications in present glasses. However, in case of glass ceramic nanocrystals show a distinct decrease in the quadrupole splitting ({Delta}) is observed, reflecting an evident decrease in the distortion of structural units like FeO{sub 4} units. In general, the Moessbauer parameters of the nano-crystalline phase exhibit tendency to increase with PbO{sub 2} content. TEM of as-quenched glasses confirm the homogeneous and essentially featureless morphology. TEM of the corresponding glass ceramic nanocrystals indicates nanocrystals embedded in the glassy matrix with average particle size of about 32 nm. The crystallization temperature (T{sub c}) was observed to decrease with PbO{sub 2} content. The glass ceramic nanocrystals obtained by annealing at T{sub c} exhibit improvement of electrical conductivity up to four orders of magnitude than the starting glasses. This considerable improvement of electrical conductivity after nanocrystallization is attributed to formation of defective, well-conducting phases 'easy conduction paths' along the glass-crystallites interfaces.

  2. Mineralogical and Geochemical Analyses of Antarctic Lake Sediments: A Reflectance and Moessbauer Spectroscopy Study with Applications for Remote Sensing on Mars

    NASA Technical Reports Server (NTRS)

    Froeschl, Heinz; Lougear, Andre; Trautwein, Alfred X.; Newton, Jason; Doran, Peter T.; Koerner, Wilfried; Koeberl, Christian; Bishop, Janice (Technical Monitor); DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Lakebottom sediments from the Dry Valleys region of Antarctica have been analyzed here in order to study the influence of water chemistry on the mineralogy and geochemistry of these sediments, as well as to evaluate techniques for remote spectral identification of potential biomarker minerals on Mars. Lakes from the Dry Valleys region of Antarctica have been investigated as possible analogs for extinct lake environments on early Mars. Sediment cores were collected in the present study from perennially ice-covered Lake Hoare in the Taylor Valley. These sediments were taken from a core in an oxic region of the lake and another core in an anoxic zone. Differences between the two cores were observed in the sediment color, Fe(II)/Fe(III) ratio, the presence of pyrite, the abundance of Fe, S and some trace elements, and the C, N and S isotope fractionation patterns. The results of visible-infrared reflectance spectroscopy (0.3-25 microns) Mossbauer spectroscopy (77 and 4 K) and X-ray diffraction are combined to determine the mineralogy and composition of these samples. The sediments are dominated by plagioclase, K-feldspar, quartz and pyroxene. Algal mats grow on the bottom of the lake and organic material has been found throughout the cores. Calcite is abundant in some layers of the aerobic core (shallow region) and pyrite is abundant in some layers of the anaerobic core (deep region). Analysis of the spectroscopic features due to organics and carbonates with respect to the abundance of organic C and carbonate contents was performed in order to select optimal spectral bands for remote identification of these components in planetary regoliths. Carbonate bands near 4 and 6.8 microns (approx.2500 and 1500/cm) were detected for carbonate abundances as low as 0.1 wt.% CO2. Organic features at 3.38, 3.42 and 3.51 microns (2960, 2925 and 2850/cm) were detected for organic C abundances as low as 0.06 wt.% C. The d13C trends show a more complex organic history for the anaerobic

  3. Moessbauer Spectrometer in the PXI/CompactPCI Modular System

    SciTech Connect

    Pechousek, Jiri; Mashlan, Miroslav; Zboril, Radek

    2005-04-26

    Two commercially available modules, a digital oscilloscope (NI 5102) and a function generator (NI 5401) in the PXI (PCI eXtension for Instrumentation) or PCI standard from National Instruments Inc., supported by the driver software, have been used for building a computer-based Moessbauer spectrometer. The RTSI (Real-Time System Integration) bus is used for synchronizing the accumulation of the detector impulses to the Moessbauer spectrum with velocity of the 'source-sample' relative motion. The amplitude selection of the impulses from the detector output is based on the use of the Waveform Peak Detection.vi function. This function is available in the graphical programming environment LabVIEW 7 Express which serves for an implementation of the virtual instrument of the Moessbauer spectrometer. Moessbauer spectra can be accumulated in the constant and variable velocity modes; moreover, there is a possibility to register gamma-ray spectra in the multichannel analyzer mode. Two types of the detectors (a NaI(Tl) and a resonance scintillation detector) have been used with the new Moessbauer spectrometer.

  4. Prototype Backscatter Moessbauer Spectrometer for Measurement of Martian Surface Mineralogy

    NASA Technical Reports Server (NTRS)

    Shelfer, T. D.; Morris, R. V.; Agresti, D. G.; Nguyen, T.; Wills, E. L.; Shen, M. H.

    1993-01-01

    We have designed and successfully tested a prototype of a backscatter Moessbauer spectrometer (BaMS) targeted for use on the Martian surface to (1) determine oxidation states of iron, and (2) identify and determine relative abundances of iron-bearing mineralogies. No sample preparation is required to perform measurements; it is only necessary to bring sample and instrument into physical contact. The prototype meets our projected specification for a flight instrument in terms of mass, power, and volume. A Moessbauer spectrometer on the Martian surface would provide wide variety of information about the current state of the Martian surface, and this information is described.

  5. Moessbauer Spectroscopy of Martian and Sverrefjell Carbonates

    NASA Technical Reports Server (NTRS)

    Agresti, David G.; Morris, Richard V.

    2011-01-01

    Mars, in its putative "warmer, wetter: early history, could have had a CO2 atmosphere much denser than its current value of <10 mbar. The question of where all this early CO2 has gone has long been debated. Now, several instruments on Mars Exploration Rover (MER) Spirit, including its Moessbauer spectrometer MIMOS II, have identified Mg-Fe carbonate in rock outcrops at Comanche Spur in the Columbia Hills of Gusev Crater. With this finding, carbonate cements in volcanic breccia collected on Sverrefjell Volcano on Spitzbergen Island in the Svalbard Archipelago (Norway) during the AMASE project are mineralogical and possible process analogues of the newly discovered martian carbonate. We report further analyses of Mossbauer spectra from Comanche Spur and discuss their relationship to Mossbauer data acquired on Sverrefjell carbonates. The spectra were velocity calibrated with MERView and fit using MERFit. Instead of the "average temperature" Comanche spectrum (data from all temperature windows summed), we refit the Comanche data for QS within each temperature window, modeling as doublets for Fe2+(carbonate), Fe2+(olivine), and Fe3+(npOx). The temperature dependences of QS for the Comanche carbonate and for a low-Ca carbonate from Chocolate Pots in Yellowstone National Park (YNP) are shown; they are the same within error. For Comanche carbonate summed over 210-270 K, (CS, QS) = (1.23, 1.95) mm/s. The value of QS for Sverrefjell carbonate at 295 K, (CS, QS) = (1.25, 1.87) mm/s, is also plotted, and the plot shows that the QS for the Sverrefjell carbonate agrees within error with the Comanche data extrapolated to 295 K. This agreement is additional evidence that the Sverrefjell carbonates are Mossbauer analogues for the Comanche carbonates, and that both carbonates might have precipitated from solutions that became carbonate rich by passing through buried carbonate deposits.

  6. Molecular dynamics in cytochrome c oxidase Moessbauer spectra deconvolution

    SciTech Connect

    Bossis, Fabrizio; Palese, Luigi L.

    2011-01-07

    Research highlights: {yields} Cytochrome c oxidase molecular dynamics serve to predict Moessbauer lineshape widths. {yields} Half height widths are used in modeling of Lorentzian doublets. {yields} Such spectral deconvolutions are useful in detecting the enzyme intermediates. -- Abstract: In this work low temperature molecular dynamics simulations of cytochrome c oxidase are used to predict an experimentally observable, namely Moessbauer spectra width. Predicted lineshapes are used to model Lorentzian doublets, with which published cytochrome c oxidase Moessbauer spectra were simulated. Molecular dynamics imposed constraints to spectral lineshapes permit to obtain useful information, like the presence of multiple chemical species in the binuclear center of cytochrome c oxidase. Moreover, a benchmark of quality for molecular dynamic simulations can be obtained. Despite the overwhelming importance of dynamics in electron-proton transfer systems, limited work has been devoted to unravel how much realistic are molecular dynamics simulations results. In this work, molecular dynamics based predictions are found to be in good agreement with published experimental spectra, showing that we can confidently rely on actual simulations. Molecular dynamics based deconvolution of Moessbauer spectra will lead to a renewed interest for application of this approach in bioenergetics.

  7. Speciation of triphenyltin compounds using Moessbauer spectroscopy. Final report

    SciTech Connect

    Eng, G.

    1993-11-01

    Organotin compounds have been used widely as the active agent in antifouling marine paints. Organotin compounds, i.e., tributyltin compounds (TBTs) and triphenyltin compounds (TPTs) have been found to be effective in preventing the unwanted attachment and development of aquatic organisms such as barnacles, sea grass and hydroids on ships, hulls and underwater surfaces. However, these organotin compounds have been found to be toxic to non-targeted marine species as well. While speciation of tributyltins in environmental water systems has received much attention in the literature, little information concerning the speciation of triphenyltins is found. Therefore, it would be important to study the fate of TPTs in the aquatic environment, particularly in sediments, both oxic and anoxic, in order to obtain speciation data. Since marine estuaries consist of areas with varying salinity and pH, it is important to investigate the speciation of these compounds under varying salinity conditions. In addition, evaluation of the speciation of these compounds as a function of pH would give an insight into how these compounds might interact with sediments in waters where industrial chemical run-offs can affect the pH of the estuarine environment. Finally, since organotins are present in both salt and fresh water environments, the speciation of the organotins in seawater and distilled water should also be studied. Moessbauer spectroscopy would provide a preferred method to study the speciation of triphenyltins as they leach from marine paints into the aquatic environment. Compounds used in this study are those triphenyltin compounds that are commonly incorporated into marine paints such as triphenyltin fluoride (TPTF), triphenyltin acetate (TPTOAc), triphenyltin chloride (TPTCl) and triphenyltin hydroxide (TPTOH).

  8. The Miniaturized Moessbauer Spectrometers MIMOS II on MER: Four Years of Operation - A Summary

    NASA Technical Reports Server (NTRS)

    Fleischer, I.; Klingelhoefer, G.; Morris, R. V.; Rodionov, D.; Blumers, M.; Bernhardt, B.; Schroeder, C.; Ming, D. W.; Yen, A. S.; Cohen, B. A.; McCoy, T. J.; Mittlefehldt, D. W.; Schmidt, M. E.; Girones Lopez, J.; Studlek, G.; Brueckner, J.; Gellert, R.; d'Uston, C.

    2008-01-01

    The two Miniaturized Moessbauer Spectrometers (MIMOS II) on board the two Mars Exploration Rovers Spirit and Opportunity have now been collecting important scientific data for more than four years. The spectrometers provide information about Fe-bearing mineral phases and determine Fe oxidation states. The total amount of targets analized exceeds 600, the total integration time exceeds 260 days for both rovers. Since landing, more than five half-lives of the Co-57 MB sources have past (intensity at the time of landing approx. 150 mCi). Current integration times are about 50 hours in order to achieve reasonable statistics as opposed to 8 hours at the beginning of the mission. In total, 13 different mineral phases were detected: Olivine, pyroxene, hematite, magnetite and nanophase ferric oxide were detected at both landing sites. At Gusev, ilmenite, goethite, a ferric sulfate phase and a yet unassigned phase (in the rock Fuzzy Smith) were detected. At Meridiani, jarosite, metallic iron in meteoritic samples (kamacite), troilite, and an unassigned ferric phase were detected. Jarosite and goethite are of special interest, as these minerals are indicators for water activity. In this abstract, an overview of Moessbauer results will be given, with a focus on data obtained since the last martian winter. The MER mission has proven that Moessbauer spectroscopy is a valuable tool for the in situ exploration of extraterrestrial bodies and for the study of Febearing samples. The experience gained through the MER mission makes MIMOS II a obvious choice for future missions to Mars and other targets. Currently, MIMOS II is on the scientific payload of two approved future missions: Phobos Grunt (Russian Space Agency; 2009) and ExoMars (European Space Agency; 2013).

  9. Identification of Iron-Bearing Phases on the Martian Surface and in Martian Meteorites and Analogue Samples by Moessbauer Spectroscopy

    NASA Technical Reports Server (NTRS)

    Klingelhoefer, G.; Agresti, D. G.; Schroeder, C.; Rodionov, D.; Yen, A.; Ming, Doug; Morris, Richard V.

    2007-01-01

    The Moessbauer spectrometers on the Mars Exploration Rovers (MER) Spirit (Gusev Crater) and Opportunity (Meridiani Planum) have each analyzed more than 100 targets during their ongoing missions (>1050 sols). Here we summarize the Fe-bearing phases identified to date and compare the results to Moessbauer analyses of martian meteorites and lunar samples. We use lunar samples as martian analogues because some, particularly the low-Ti Apollo 15 mare basalts, have bulk chemical compositions that are comparable to basaltic martian meteorites [1,2]. The lunar samples also provide a way to study pigeonite-rich samples. Pigeonite is a pyroxene that is not common in terrestrial basalts, but does often occur on the Moon and is present in basaltic martian meteorites

  10. Moessbauer Spectroscopy on the Martian Surface: Constraints on Interpretation of MER Data

    NASA Technical Reports Server (NTRS)

    Dyar, M. D.; Schaefer, M. W.

    2003-01-01

    Moessbauer spectrometers will be used on martian landers and rovers to identify and quantify relative amounts of Fe-bearing minerals, as well as to determine their Fe(3+)/Fe(2+) ratios, allowing more realistic modeling of martian mineralogy and evolution. However, derivation of mineral modes, Fe(3+)/Fe(2+) ratios, and phase identification via Moessbauer spectroscopy (MS) does have limitations. We discuss here the exciting potential of MS for remote planetary exploration, as well as constraints on interpretation of remote Moessbauer data.

  11. Moessbauer Mineralogy on the Moon: The Lunar Regolith

    NASA Technical Reports Server (NTRS)

    Morris, Richard V.; Korotev, Randy L..; Shelfer, Tad D.; Klingelhoefer, Goestar

    1997-01-01

    A first-order requirement for spacecraft missions that land on solid planetary objects is instrumentation for mineralogical analyses. For purposes of providing diagnostic information about naturally-occurring materials, the element iron is particularly important because it is abundant and multivalent. Knowledge of the oxidation state of iron and its distribution among iron-bearing mineralogies tightly constrains the types of materials present and provides information about formation and modification (weathering) processes. Because Moessbauer spectroscopy is sensitive to both the valence of iron and its local chemical environment, the technique is unique in providing information about both the relative abundance of iron-bearing phases and oxidation state of the iron. The Moessbauer mineralogy of lunar regolith samples (primarily soils from the Apollo 16 and 17 missions to the Moon) were measured in the laboratory to demonstrate the strength of the technique for in situ mineralogical exploration of the Moon. The regolith samples were modeled as mixtures of five iron-bearing phases: olivine, pyroxene, glass, ilmenite, and metal. Based on differences in relative proportions of iron associated with these phases, volcanic ash regolith can be distinguished from impact-derived regolith, impact-derived soils of different geologic affinity (e.g., highlands, maria) can be distinguished on the basis of their constituent minerals, and soil maturity can be estimated. The total resonant absorption area of the Moessbauer spectrum can be used to estimate total FeO concentrations.

  12. Moessbauer Characterization of Magnetite/Polyaniline Magnetic Nanocomposite

    SciTech Connect

    Rodriguez, Anselmo F. R.; Faria, Fernando S. E. D. V.; Lopez, Jorge L.; Mesquita, Antonio G. G.; Coaquira, Jose A. H.; Oliveira, Aderbal C.; Morais, Paulo C.; Azevedo, Ricardo B.; Araujo, Ana C. V. de; Alves, Severino Jr.; Azevedo, Walter M. de

    2010-12-02

    Aniline surface coated Fe{sub 3}O{sub 4} nanoparticles have been successfully synthesized by UV irradiation varying the time and the acid media (HCl, HNO{sub 3}, or H{sub 2}SO{sub 4}). The synthesized material represents a promising platform for application in nerve regeneration. XRD patterns are consistent with the crystalline structure of magnetite. Nevertheless, for UV irradiation times longer than 2 h, extra XRD lines reveal the presence of goethite. The mean crystallite size of uncoated particles is estimated to be 25.4 nm, meanwhile that size is reduced to 19.9 nm for the UV irradiated sample in HCl medium for 4 h. Moessbauer spectra of uncoated nanoparticles reveal the occurrence of thermal relaxation at room temperature, while the 77 K-Moessbauer spectrum suggests the occurrence of electron localization effects similar to that expected in bulk magnetite. The Mossbauer spectra of UV irradiated sample in HCl medium during 4 h, confirms the presence of the goethite phase. For this sample, the thermal relaxation is more evident, since the room temperature spectrum shows larger spectral area for the nonmagnetic component due to the smaller crystallite size. Meanwhile, the 77 K-Moessbauer spectrum suggests the absence of the electron localization effect above 77 K.

  13. Determination of the Moessbauer parameters of rare-earth nitroprussides: Evidence for new light-induced magnetic excited state (LIMES) in nitroprussides

    SciTech Connect

    Rusanov, V.; Stankov, S.; Ahmedova, A.; Trautwein, A.X.

    2009-05-15

    Nitroprussides of the rare-earth elements and some mixed rare-earth-sodium nitroprussides are studied by Moessbauer spectroscopy at ambient and lower temperatures. The high precision Moessbauer measurements reveal fine changes in the electronic configurations of the nitroprusside anions. A small increase of the quadrupole splitting reveals charge polarization effects in the nitroprusside anion caused by the oblate or prolate shape of the rare-earth ion and the lanthanide contraction. Despite the very large magnetic moment of holmium a magnetic phase transition is not observed down to 300 mK. The population of the metastable states SI and SII are evidenced in europium and scandium nitroprussides, and most likely they can be populated in all rare-earth nitroprussides. No distinct correlation between the Moessbauer parameters and the decay temperatures T{sub c} of the metastable states are found. In a very thin surface layer strong color change, which remains stable at room temperature, is detected. A quadrupole doublet with Moessbauer parameters typical for Fe(III), low spin S=1/2 state is related to a new colored photoproduct. The photoproduct is called light-induced magnetic excited state (LIMES) and explained with a photochemical redox reaction, which changes the valence, spin, and magnetic state of 4f-3d bimetallic complexes. - Graphical abstract: Rare-earth nitroprussides are studied by Moessbauer spectroscopy. Population of metastable states in a thin surface layer, and another state which remains stable at room temperature, are detected. The latter is a photoproduct which is called light-induced magnetic excited state (LIMES) and explained with a photochemical redox reaction, which changes the valence, spin, and magnetic state of 4f-3d bimetallic complexes.

  14. 57Fe Mössbauer spectroscopy investigations of iron oxidation states in the Harmattan dust nutrient contribution to West African soils

    NASA Astrophysics Data System (ADS)

    Adetunji, Jacob

    2014-12-01

    A variety of investigations have been carried out on Harmattan dust over many decades demonstrating the continuing importance of the Harmattan dust phenomenon. The investigations have included elemental enrichment factors, mineralogical nutrient input through dust deposition on the soil, meteorological studies, etc. Harmattan dust is important, not only for its impact on radio communication and low visibility in the shipping lanes over the Atlantic, but also on the livelihood and health of people living in countries over which the dust-laden Harmattan wind blows. However, so far, the aspect of nutrient mineral deposition on the soil has not been thoroughly investigated and requires attention, since the majority of people living in West Africa rely heavily on agriculture. It is therefore relevant to know the useful nutrients in the Harmattan dust deposited on soils of the region. This study is therefore aimed at determining the ferric-ferrous ratio of the iron-bearing minerals contained in the Harmattan dust, so their nutritional contribution can be considered. The Mössbauer technique is a powerful tool for studying the ferric-ferrous ratio and has therefore been used, for the first time, to determine the oxidation states of iron in the dust samples. The results of the analysis show that the Harmattan dust is seriously deficient in ferrous iron, which is the more soluble Fe-ion, needed in the soil for healthy crops and plants in general.

  15. Design of the MsAa-4 Moessbauer Spectrometer

    SciTech Connect

    Blachowski, A.; Ruebenbauer, K.; Zukrowski, J.; Gornicki, R.

    2008-10-28

    An entirely new Moessbauer spectrometer MsAa-4 is currently being under design and construction. New features as compared to the basic features of the previous generation MsAa-3 spectrometer could be summarized as follows. Completely digital processing of the {gamma}-ray detector signal beyond the Gaussian shape filter/amplifier is to be implemented. The spectrometer is going to be able to accommodate external multiple detector heads. Up to 128 {gamma}-ray spectra in 16384 channels of 32-bit each and up to 512 Moessbauer spectra in 4096 channels of 32-bit each could be collected simultaneously, provided the proper external multiple detector head is used. The count-rate per single detector is limited to about 10{sup 5} counts per second in total. Improved precision of the reference function from 12-bit to 16-bit is to be provided. The reference function is stored in 8192 channels per a complete cycle. Addition of the random noise to the reference corner prism of the Michelson-Morley calibration interferometer is to be introduced to avoid spurious fringes due to the phase lock-up. An integrated universal temperature controller being able to use a variety of the temperature sensors is to be interconnected properly with the spectrometer. The spectrometer is now a stand-alone network device as it is equipped with the Ethernet connection to the outside world. Fast and high precision digital oscilloscope is to be incorporated to the spectrometer as the intrinsic unit. This oscilloscope could monitor signals at various crucial points of the internal spectrometer electronics. Modular design and use of the strict standards allows easy reconfiguration for other applications than Moessbauer spectroscopy.

  16. High pressure Moessbauer spectroscopy in diamond anvil cells

    SciTech Connect

    Taylor, R.D. ); Pasternak, M.P. . School of Physics and Astronomy Los Alamos National Lab., NM )

    1991-01-01

    Diamond anvil cells provide a means to obtain near-hydrostatic pressures from the kilobar to the megabar regime. Moessbauer spectroscopy (MS) nicely complements the optical and X-ray measurements usually made. After a brief summary of the techniques applicable to MS, we present several examples of high pressure MS including hysteresis in the {sub {alpha}}-{sub {var epsilon}} transition in Fe, metallization in molecular crystals and the insulator-metal Mott transition in NiI{sub 2} and CoI{sub 2}. 25 refs., 7 figs.

  17. Calibration of DFT Functionals for the Prediction of 57Fe Mössbauer Spectral Parameters in Iron-Nitrosyl and Iron-Sulfur Complexes: Accurate Geometries Prove Essential

    PubMed Central

    Sandala, Gregory M.; Hopmann, Kathrin H.; Ghosh, Abhik

    2011-01-01

    Six popular density functionals in conjunction with the conductor-like screening (COSMO) solvation model have been used to obtain linear Mössbauer isomer shift (IS) and quadrupole splitting (QS) parameters for a test set of 20 complexes (with 24 sites) comprised of nonheme nitrosyls (Fe–NO) and non-nitrosyl (Fe–S) complexes. For the first time in an IS analysis, the Fe electron density was calculated both directly at the nucleus, ρ(0)N, which is the typical procedure, and on a small sphere surrounding the nucleus, ρ(0)S, which is the new standard algorithm implemented in the ADF software package. We find that both methods yield (near) identical slopes from each linear regression analysis but are shifted with respect to ρ(0) along the x-axis. Therefore, the calculation of the Fe electron density with either method gives calibration fits with equal predictive value. Calibration parameters obtained from the complete test set for OLYP, OPBE, PW91, and BP86 yield correlation coefficients (r2) of approximately 0.90, indicating that the calibration fit is of good quality. However, fits obtained from B3LYP and B3LYP* with both Slater-type and Gaussian-type orbitals are generally found to be of poorer quality. For several of the complexes examined in this study, we find that B3LYP and B3LYP* give geometries that possess significantly larger deviations from the experimental structures than OLYP, OPBE, PW91 or BP86. This phenomenon is particularly true for the di- and tetranuclear Fe complexes examined in this study. Previous Mössbauer calibration fit studies using these functionals have usually included mononuclear Fe complexes alone, where these discrepancies are less pronounced. An examination of spin expectation values reveals B3LYP and B3LYP* approach the weak-coupling limit more closely than the GGA exchange-correlation functionals. The high degree of variability in our calculated S2 values for the Fe–NO complexes highlights their challenging electronic

  18. Chemostratigraphy and Fe Mineralogy of the Victoria Crater Duck Bay Section: Opportunity APXS and Moessbauer Results

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, D. W.; Schroeder, C.; Gellert, R.; Klingelhoefer, G.; Jolliff, B. L.; Morris, R. V.

    2008-01-01

    Meridiani Planum is a vast plain of approximately horizontally bedded sedimentary rocks composed of mixed and reworked basaltic and evaporitic sands containing secondary, diagenetic minerals [e.g., 1-5]. Because bedding planes are subparallel to topography, investigation of contiguous stratigraphy requires examining exposures in impact craters. Early in the mission (sols 130-317), Opportunity was commanded to do detailed study of exposed outcrops in Endurance crater, including the contiguous Karatepe section at the point of ingress. Just over 1000 sols later and roughly 7 km to the south, the rover is being commanded to do a similar study of the Duck Bay section of Victoria crater. Here we report on the preliminary results from the Alpha Particle X-ray Spectrometer (APXS) and Moessbauer instruments.

  19. Moessbauer Spectroscopy of Soils and Rocks at Gusev Crater and Meridiani Planum

    NASA Technical Reports Server (NTRS)

    Klingelhoefer, G.; Morris, R. V.; Bernhardt, B.; Schroeder, C.; Rodionov, D.; deSouza, P. A., Jr.; Yen, A.; Renz, F.; Wdowiak, T.; Squyres, S.

    2004-01-01

    For the first time in history a Moessbauer spectrometer was placed on the surface of another planet. The miniaturized Moessbauer spectrometer MIMOS II is part of the Athena payload of NASA's twin Mars Exploration Rovers (MER) Spirit,and Opportunity. It determines the Fe-bearing mineralogy of Martian soils and rocks at the Rovers respective landing sites, Gusev crater and Meridiani Planum. First results of soil and rock measurements at both landing sites confirm a generally basaltic composition of Martian surface materials.

  20. Extraterrestrial Moessbauer Spectroscopy: More than Three Years of Mars Exploration and Developments for Future Missions

    NASA Technical Reports Server (NTRS)

    Schroeder, Christian; Klingelhoefer, Goestar; Morris, Richard V.; Rodionov, Daniel S.; Fleischer, Iris; Blumers, Mathias

    2007-01-01

    The NASA Mars Exploration Rovers (MER), Spirit and Opportunity, landed on the Red Planet in January 2004. Both rovers are equipped with a miniaturized Moessbauer spectrometer MIMOS II. Designed for a three months mission, both rovers and both Moessbauer instruments are still working after more than three years of exploring the Martian surface. At the beginning of the mission, with a landed intensity of the Moessbauer source of 150 mCi, a 30 minute touch and go measurement produced scientifically valuable data while a good quality Moessbauer spectrum was obtained after approximately eight hours. Now, after about five halflives of the sources have passed, Moessbauer integrations are routinely planned to last approx.48 hours. Because of this and other age-related hardware degradations of the two rover systems, measurements now occur less frequently, but are still of outstanding quality and scientific importance. Summarizing important Moessbauer results, Spirit has traversed the plains from her landing site in Gusev crater and is now, for the greater part of the mission, investigating the stratigraphically older Columbia Hills. Olivine in rocks and soils in the plains suggests that physical rather than chemical processes are currently active.

  1. Iron Moessbauer spectroscopy: Superparamagnetism in hydrothermal vents and the search for evidence of past life on Mars

    NASA Technical Reports Server (NTRS)

    Agresti, David G.; Wdowiak, Thomas J.

    1992-01-01

    In view of the demonstrated value of Iron Moessbauer Spectroscopy (FeMS) in the study of extraterrestrial iron and the fact that, after silicon and oxygen, iron is the most abundant element on the surface of Mars, we proposed, and have under development, a backscatter Moessbauer spectrometer with x ray fluorescence capability (BaMS/XRF) for use on Mars as a geophysical prospecting instrument. Specifically, we have proposed BaMS/XRF as part of the geochemistry instrumentation on NASA's Mars Environment Survey (MESUR) mission. BaMS/XRF will have applications in: (1) the study of past environments through the examination of sedimentary material; (2) the study of the contemporary Martian environment; and (3) the study of iron-containing minerals of possible biogenic origin. Development of a reference library from a geophysical point of view for putative Martian surface materials at appropriate temperatures is now underway. We carried out preliminary optical reflectance and FeMS measurements on mineral products (iron oxyhydroxides) of deep-sea hydrothermal activity. Various aspects of this investigation are presented.

  2. Moessbauer spectroscopy and scanning electron microscopy of the Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Brown, Christopher L.; Oliver, Frederick W.; Hammond, Ernest C., Jr.

    1989-01-01

    Meteorites provide a wealth of information about the solar system's formation, since they have similar building blocks as the Earth's crust but have been virtually unaltered since their formation. Some stony meteorites contain minerals and silicate inclusions, called chondrules, in the matrix. Utilizing Moessbauer spectroscopy, we identified minerals in the Murchison meteorite, a carbonaceous chondritic meteorite, by the gamma ray resonance lines observed. Absorption patterns of the spectra were found due to the minerals olivine and phyllosilicate. We used a scanning electron microscope to describe the structure of the chondrules in the Murchison meteorite. The chondrules were found to be deformed due to weathering of the meteorite. Diameters varied in size from 0.2 to 0.5 mm. Further enhancement of the microscopic imagery using a digital image processor was used to describe the physical characteristics of the inclusions.

  3. The big and little of fifty years of Moessbauer spectroscopy at Argonne.

    SciTech Connect

    Westfall, C.

    2005-09-20

    Using radioactive materials obtained by chance, a turntable employing gears from Heidelberg's mechanical toy shops, and other minimal equipment available in post World War II Germany, in 1959 Rudolf Moessbauer confirmed his suspicion that his graduate research had yielded ground-breaking results. He published his conclusion: an atomic nucleus in a crystal undergoes negligible recoil when it emits a low energy gamma ray and provides the entire energy to the gamma ray. In the beginning Moessbauer's news might have been dismissed. As Argonne nuclear physicist Gilbert Perlow noted: ''Everybody knew that nuclei were supposed to recoil when emitting gamma rays--people made those measurements every day''. If any such effect existed, why had no one noticed it before? The notion that some nuclei would not recoil was ''completely crazy'', in the words of the eminent University of Illinois condensed matter physicist Frederich Seitz. Intrigued, however, nuclear physicists as well as condensed matter (or solid state) physicists in various locations--but particularly at the Atomic Energy Research Establishment at Harwell in Britain and at Argonne and Los Alamos in the U.S.--found themselves pondering the Moessbauer spectra with its nuclear and solid state properties starting in late 1959. After an exciting year during which Moessbauer's ideas were confirmed and extended, the physics community concluded that Moessbauer was right. Moessbauer won the Nobel Prize for his work in 1961. In the 1960s and 1970s Argonne physicists produced an increasingly clear picture of the properties of matter using the spectroscopy ushered in by Moessbauer. The scale of this traditional Moessbauer spectroscopy, which required a radioactive source and other simple equipment, began quite modestly by Argonne standards. For example Argonne hosted traditional Moessbauer spectroscopy research using mostly existing equipment in the early days and equipment that cost $100,000 by the 1970s alongside work at

  4. The Miniaturized Moessbauer Spectrometer MIMOS II of the Athena Payload for the 2003 MER Missions

    NASA Technical Reports Server (NTRS)

    Klingelhoefer, G.; Morris, R. V.; deSouza, P. A., Jr.; Bernhardt, B.

    2003-01-01

    A first-order requirement of spacecraft missions that land on Mars is instrumentation for in situ mineralogical analysis. Moessbauer Spectroscopy is a powerful tool for quantitative analysis of Fe-bearing materials. The Athena Moessbauer spectrometer MIMOS II on the martian surface will provide: (1) identification of iron-bearing phases (e.g., oxides, silicates, sulfides, sulfates, and carbonates), (2) quantitative measurement of the distribution of iron among its oxidation states (e.g., Fe(2+)/Fe(3+) ratio), and (3) quantitative measurement of the distribution of iron among iron-bearing phases (e.g., the relative proportions of iron in olivine, pyroxene, and magnetite in a basalt) in rocks and soils. Moessbauer data will also be highly complementary with chemical analyses from the APXS and the Mini-TES compositional data. Mars is a particularly good place to do Moessbauer mineralogy because its surface is iron rich (approx. 20% Fe as Fe2O3). Moessbauer spectrometers that are built with backscatter measurement geometry require no sample preparation, a factor important for in situ planetary measurements.

  5. Moessbauer effect measurement in single crystal iron subjected to cyclic stress

    NASA Technical Reports Server (NTRS)

    Singh, J. J.

    1976-01-01

    Backscattered Moessbauer spectra were recorded at different fatigue levels in cyclically fatigued high-purity single-crystal iron specimens in the form of rectangular strips with appropriate concentrators in the midplane. The Moessbauer spectra were submitted to a least-squares analysis to determine the isomer shift, quadrupole shift, hyperfine field, and peak spectral widths in each spectrum. It is shown that the quadrupole shift and the isomer shift changed little with fatigue, whereas the effective internal field and the associate line widths exhibit significant variation as a function of fatigue level. It is concluded that the impurity concentration builds up slowly with increasing fatigue level in the region of stress concentration. Since there is a direct correlation between crack initiation and defect concentration level, it is expected that Moessbauer measurements in the test specimen can provide a means of monitoring the impurity buildup presumed to be the eventual cause of fatigue crack initiation and failure.

  6. Moessbauer spectroscopy of Mg(0.9)Fe(0.1)SiO3 perovskite

    NASA Technical Reports Server (NTRS)

    Jeanloz, Raymond; O'Neill, Bridget; Pasternak, Moshe P.; Taylor, R. D.; Bohlen, Steven R.

    1992-01-01

    Ambient pressure Moessbauer spectra of Mg(0.9)Fe-57(0.1)SiO3 perovskite synthesized at pressure-temperature conditions of about 50 GPa and 1700 K show that the iron is entirely high-spin Fe(2+) and appears to be primarily located in the octahedral site within the crystal structure. We observe broad Moessbauer lines, suggesting a distribution of electric-field gradients caused by disorder associated with the Fe ions. Also, the perovskite exhibits magnetic ordering at temperatures lower than 5 K, implying that there is a magnetic contribution to the absolute ('third-law') entropy of this phase.

  7. Moessbauer spectroscopy evidence of a spinodal mechanism for the thermal decomposition of fcc FeCu

    SciTech Connect

    Crespo, P. |; Barro, M.J.; Hernando, A.; Escorial, A.G.; Menendez, N.; Tornero, J.D.; Barandiaran, J.M.

    1998-07-24

    Moessbauer spectroscopy shows the existence of compositional fluctuations, where different Fe environments coexist, during decomposition upon heat treatment of metastable f.c.c. FeCu solid solution. The presence of isolated Fe atoms in the Cu matrix, f.c.c. Fe{sub rich}Cu, f.c.c. FeCu{sub rich} and b.c.c. Fe has been detected in early decomposition stages. At later decomposition stages, low temperature Moessbauer spectroscopy indicates the presence of a broad distribution of Curie temperatures, coexisting with isolated Fe atoms in the Cu matrix, f.c.c. Fe and b.c.c. Fe.

  8. Cronstedtite and iron sulfide mineralogy of CM-type carbonaceous chondrites from cryogenic Moessbauer spectra

    NASA Technical Reports Server (NTRS)

    Fisher, Duncan S.; Burns, Roger G.

    1993-01-01

    Determinations of oxidation states and the crystal chemistry of iron-bearing minerals in CM meteorites by Moessbauer spectroscopy are complicated by thermally-induced electron hopping in cronstedtite and by ill-defined contributions from the hydrous iron sulphide phase believed to be tochilinite. Moessbauer spectral measurements at 30 K of several cronstedtite and tochilinite specimens have enabled modal proportions of these minerals, as well as Fe(3+)/Fe(2+) ratios, to be determined quantitatively for a suite of CM-type carbonaceous chondrites that included Murchison, Murray, Cold Bokkeveld, ALH 83100, and LEW 90500.

  9. Synthesis and investigation of iron (II) dioximates with arsine derivatives by Moessbauer and IR spectroscopy

    SciTech Connect

    Zubareva, V.E.; Turte, K.I.; Shafranskii, V.N.; Bulgak, I.I.; Batyr, D.G.; Stukan, R.A.

    1988-06-01

    New compounds with the formula (Fe/sup II/(dioximate)/sub 2/L/sub 2/), where dioximate stands for monodeprotonated anions of dimethylglyoxime (dmgH), diphenylglyoxime (dfgH), 1,2-cyclohexanedione dioxime (nioxH), and ..cap alpha..-furildioxime (furgH), and L stands for di-n-butylphenylarsine (AsBut/sub 2/Ph) and triethylarsine (AsEt/sub 3/), have been investigated by Moessbauer and IR spectroscopy. The Moessbauer spectra of the compounds indicated at 80 and 300/sup 0/K consist of doublets, whose parameters correspond to the low-spin state of iron (II).

  10. An Overview of Moessbauer Mineralogy at Gusev Crater, Mars

    NASA Technical Reports Server (NTRS)

    Klingelhoefer, G.; Schroeder, C.; Rodionov, D.; Yen, A.

    2006-01-01

    The Mars Exploration Rover (MER) Spirit landed on the plains of Gusev Crater on 4 January 2004 [1]. The scientific objective of the Moessbauer (MB) spectrometer on Spirit is to provide quantitative information about the distribution of Fe among its oxidation and coordination states, identification of Fe-bearing phases, and relative distribution of Fe among those phases. The speciation and distribution of Fe in Martian rock and soil constrains the primary rock types, redox conditions under which primary minerals crystallized, the extent of alteration and weathering, the type of alteration and weathering products, and the processes and environmental conditions for alteration and weathering.We discuss the Fe-bearing phases detected by Spirit s MB instrument during its first 540 sols of exploration [2,3]. Spirit roved eastward across the plains from its landing site to the Columbia Hills during the first approx.150 sols. Rocks are unweathered to weakly weathered olivine basalt, with olivine, pyroxene (Ol > Px), magnetite (Mt), and minor hematite (Hm) and nanophase ferric oxide (npOx) as their primary Fe-bearing minerals. Soils are generally similar basaltic materials, except that the proportion of npOx is much higher (up to approx.40%). NpOx is an oct-Fe3+ alteration product whose concentration is highest in fine-grained soils and lowest in rock interiors exposed by grinding with the Rock Abrasion Tool (RAT). Spirit explored the lower slopes of the Columbia Hills (West Spur) during sols approx.150-320. West Spur rocks are highly altered, even for interior surfaces exposed by grinding (Fe3+/FeT approx.0.56-0.84). High concentrations of npOx, Hm, and Mt are present. One rock (Clovis) contains significant quantities of goethite (alpha-FeOOH; approx.40% of total Fe). The detection of goethite is very significant because it is a mineralogical marker for aqueous alteration.

  11. Some Improvements in the Design of a CA/CV Moessbauer Velocity Drive

    SciTech Connect

    Seberini, Milan

    2008-10-28

    A constant velocity Moessbauer drive was built with velocity range {+-}15 mm/s and velocity resolution 0.005 mm/s. Based on good experience with its performance, a new universal CA/CV drive was designed. The new drive is supposed to have velocity range of {+-}80 mm/s with a velocity resolution below 0.002 mm/s.

  12. Moessbauer medium with a hidden nuclear population inversion and negative absorption of gamma quanta

    SciTech Connect

    Rivlin, Lev A

    2011-06-30

    We consider physical foundations of an eventual experiment aimed at observing stimulated gamma-photon emission of long-lived Moessbauer isomers through selective frequency modulation of gamma-resonances establishing hidden population inversion without exceeding the number of excited nuclei over unexcited ones and without additional pumping. The examples of suitable nuclei and numerical estimates of the parameters are presented. (active media)

  13. Investigation of the Moessbauer Spectrum Quality as a Dependence on the Frequency of the Velocity Signal

    SciTech Connect

    Pechousek, J.

    2010-07-13

    This paper is focused on a quality characterizing the Moessbauer spectra measured for various frequencies of the velocity signal. Standard electromechanical double-loudspeaker drive and digital PID velocity controller were used for calibration spectra measurement in the frequency interval from 4 up to 100 Hz. Several parameters were evaluated for recommendation of the suitable velocity signal frequency.

  14. In-situ Moessbauer Spectroscopy of Supported Iron Fischer-Tropsch Catalysts During Activation

    SciTech Connect

    Motjope, Thato R.; Dlamini, Thulani H.

    2005-04-26

    The behavior of Fe based catalysts supported on ZrO2, SiO2, {gamma}-Al2O3, CeO2 and TiO2 during calcination, reduction and FT synthesis have been studied via in situ Moessbauer spectroscopy. It was found that the type of metal support interaction i.e. surface migration or bulk diffusion during calcination was dependant on the type of support used. Surface migration of Fe3+ during calcination was dominant for ZrO2, CeO2 and {gamma}-Al2O3 and this resulted in the sintering of {alpha}-Fe2O3 crystallites. Whereas bulk diffusion was observed mainly for the catalysts prepared using SiO2 and TiO2, causing a stabilization of the small crystallites of Fe3+ that interacted strongly with the support. Upon reduction, the large crystallites of {alpha}-Fe2O3 were found to reduce readily compared to the small crystallites of Fe3+, except for the catalyst prepared using {gamma}-Al2O3, as a support, where the presence of Al3+ resulted in the formation of spinel like species with the formula (Fe{sup 3+}{sub 2-x}Al{sup 3+}{sub x}Fe{sup 2+})O{sub 4} which are resistant to reduction. Upon exposure to synthesis gas, it was found that catalysts supported on ZrO2 and CeO2 carburized readily resulting in the formation of circa 80% {chi}-Fe2.5C. From this study it was observed that {gamma}-Al2O3 is not the preferred support for Fe based FT catalysts, as it forms the least amount of Fe carbides during FT synthesis.

  15. Hematite at Meridiani Planum and Gusev Crater as identified by the Moessbauer Spectrometer MIMOS II

    NASA Technical Reports Server (NTRS)

    Klingelhoefer, G.; Morris, R. V.; Rodionov, D.; Schroeder, C.; de Souza, P. A.; Yen, A.; Renz, F.; Wdowiak, T.

    2006-01-01

    The Moessbauer (MB) spectrometers on the MER rovers Opportunity and Spirit, which landed on Mars in January 2004, have identified the iron-containing mineral hematite (a-Fe2O3) at both landing sites. On Earth, hematite can occur either by itself or with other iron oxides as massive deposits, in veins , and as particles dispersed through a silicate or other matrix material. Hematite particle size can range from nanophase (superparamagnetic) to multidomain and particle shape ranges from equant to acicular to platy. Fine-grained hematite is red in color and is a pigmenting agent. Coarse-grained hematite can be spectrally neutral (gray) at visible wavelengths. Substitutional impurities, particularly Al, are common in hematite. Chemically pure, coarse-grained, and well-crystalline hematite has a magnetic transition (the Morin transition) at 260 K. Moessbauer spectra, recorded as a function of temperature, provide a way to characterize Martian hematite with respect to some of the physical and chemical characteristics. At Meridiani Planum besides the iron-sulfate mineral jarosite also the Fe-oxide hematite has been identified by the Moessbauer spectrometer, mainly in three distinct types of reservoir: - outcrop matrix material dominated by the mineral jarosite in the MB spectrum, certain basaltic soils, and mm-sized spherules dubbed blueberries. Moessbauer spectra of each reservoir yield a distinct set of hyperfine parameters for hematite, suggesting different degrees of crystallinity and particle size. The hematite found by MB instrument MIMOS II in the outcrop material shows the Morin transition at relatively high temperatures (ca. 250 K) which is an indication of pure and well-crystallized hematite. The source of the hematite in the Blueberries as identified by Moessbauer spectroscopy, and also by MiniTES, is not known. These spherules, covering nearly the whole landing site area (Eagle crater, plains, Endurance crater), may be concretions formed in the outcrop

  16. Investigation of potential analytical methods for redox control of the vitrification process. [Moessbauer

    SciTech Connect

    Goldman, D.S.

    1985-11-01

    An investigation was conducted to evaluate several analytical techniques to measure ferrous/ferric ratios in simulated and radioactive nuclear waste glasses for eventual redox control of the vitrification process. Redox control will minimize the melt foaming that occurs under highly oxidizing conditions and the metal precipitation that occurs under highly reducing conditions. The analytical method selected must have a rapid response for production problems with minimal complexity and analyst involvement. The wet-chemistry, Moessbauer spectroscopy, glass color analysis, and ion chromatography techniques were explored, with particular emphasis being placed on the Moessbauer technique. In general, all of these methods can be used for nonradioactive samples. The Moessbauer method can readily analyze glasses containing uranium and thorium. A shielded container was designed and built to analyze fully radioactive glasses with the Moessbauer spectrometer in a hot cell environment. However, analyses conducted with radioactive waste glasses containing /sup 90/Sr and /sup 137/Cs were unsuccessful, presumably due to background radiation problems caused by the samples. The color of glass powder can be used to analyze the ferrous/ferric ratio for low chromium glasses, but this method may not be as precise as the others. Ion chromatography was only tested on nonradioactive glasses, but this technique appears to have the required precision due to its analysis of both Fe/sup +2/ and Fe/sup +3/ and its anticipated adaptability for radioactivity samples. This development would be similar to procedures already in use for shielded inductively coupled plasma emission (ICP) spectrometry. Development of the ion chromatography method is therefore recommended; conventional wet-chemistry is recommended as a backup procedure.

  17. The Role of Iron in the Enhancement of Negative Magnetoresistance in La0.8Sr0.2FexCo1-xO3-z

    SciTech Connect

    Nemeth, Z.; Homonnay, Z.; Vertes, A.; Hakl, J.; Vad, K.; Meszaros, S.; Lackner, B.; Kellner, K.; Gritzner, G.; Greneche, J.M.; Lindbaum, A.

    2005-04-26

    The role of iron in enhancing the magnetoresistance in the compounds La0.8Sr0.2FexCo1-xO3-z was investigated by studying the electronic and magnetic structure of La0.8Sr0.2FexCo1-xO3-z as a function of temperature. For this purpose 57Fe transmission Moessbauer spectroscopy, magnetoresistance, as well as AC and DC magnetization measurements were applied. The detailed study of the temperature dependence of 57Fe Moessbauer parameters gave possibility to explore correlations between the local electronic and magnetic state of iron and the magnetic susceptibility as well as magnetoresistance in La0.8Sr0.2FexCo1-xO3-z. On the basis of the obtained results an attempt was made to explain the exotic magnetic and MR properties of these perovskites.

  18. Hematite at Meridiani Planum and Gusev Crater as identified by the Moessbauer Spectrometer MIMOS II

    NASA Astrophysics Data System (ADS)

    Klingelhoefer, G.; Morris, R. V.; Rodionov, D.; Schroeder, C.; de Souza, P. A.; Yen, A.; Renz, F.; Wdowiak, T.

    2004-12-01

    The Moessbauer (MB) spectrometers on the MER rovers Opportunity and Spirit, which landed on Mars in January 2004, have identified the iron-containing mineral hematite (a-Fe2O3) at both landing sites. On Earth, hematite can occur either by itself or with other iron oxides as massive deposits, in veins , and as particles dispersed through a silicate or other matrix material. Hematite particle size can range from nanophase (superparamagnetic) to multidomain and particle shape ranges from equant to acicular to platy. Fine-grained hematite is red in color and is a pigmenting agent. Coarse-grained hematite can be spectrally neutral (gray) at visible wavelengths. Substitutional impurities, particularly Al, are common in hematite. Chemically pure, coarse-grained, and well-crystalline hematite has a magnetic transition (the Morin transition) at ~260 K. Moessbauer spectra, recorded as a function of temperature, provide a way to characterize Martian hematite with respect to some of the physical and chemical characteristics. At Meridiani Planum besides the iron-sulfate mineral jarosite also the Fe-oxide hematite has been identified by the Moessbauer spectrometer, mainly in three distinct types of reservoir: - outcrop matrix material dominated by the mineral jarosite in the MB spectrum, certain basaltic soils, and mm-sized spherules dubbed blueberries. Moessbauer spectra of each reservoir yield a distinct set of hyperfine parameters for hematite, suggesting different degrees of crystallinity and particle size. The hematite found by MB instrument MIMOS II in the outcrop material shows the Morin transition at relatively high temperatures (ca. 250 K) which is an indication of pure and well-crystallized hematite. The source of the hematite in the `Blueberries' as identified by Moessbauer spectroscopy, and also by MiniTES, is not known. These spherules, covering nearly the whole landing site area (Eagle crater, plains, Endurance crater), may be concretions formed in the outcrop

  19. Reflectivity (visible and near IR), Moessbauer, static magnetic, and X ray diffraction properties of aluminum-substituted hematites

    NASA Technical Reports Server (NTRS)

    Morris, Richard V.; Schulze, Darrell G.; Lauer, Howard V., Jr.; Agresti, David G.; Shelfer, Tad D.

    1992-01-01

    The effect of substituting iron by aluminum in polymorphs of Fe2O3 and FeOOH on their reflectivity characteristics was investigated by comparing data on visible and NIR reflectivities and on static magnetic, XRD, and Moessbauer properties for a family of aluminum-substituted hematites alpha-(Fe,Al)2O3, with compositions where the values of the Al/(Al+Fe) ratio were up to 0.61. Samples were prepared by oxidation of magnetite, dehydroxylation of goethite, and direct precipitation. The analytical methods used for obtaining diffuse reflectivity spectra (350-2200 nm), Moessbauer spectra, and static magnetic data are those described by Morris et al. (1989).

  20. Mineralogical diversity (spectral reflectance and Moessbauer data) in compositionally similar impact melt rocks from Manicouagan Crater, Canada

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Bell, J. F., III; Golden, D. C.; Lauer, H. V., Jr.

    1993-01-01

    Meteoritic impacts under oxidizing surface conditions occur on both earth and Mars. Oxidative alteration of impact melt sheets is reported at several terrestrial impact structures including Manicouagan, West Clearwater Lake, and the Ries Basin. A number of studies have advocated that a significant fraction of Martian soil may consist of erosional products of oxidatively altered impact melt sheets. If so, the signature of the Fe-bearing mineralogies formed by the process may be present in visible and near infrared reflectivity data for the Martian surface. Of concern is what mineral assemblages form in impact melt sheets produced under oxidizing conditions and what their spectral signatures are. Spectral and Moessbauer data for 19 powder samples of impact melt rock from Manicouagan Crater are reported. Results show for naturally occurring materials that composite hematite-pyroxene bands have minima in the 910-nm region. Thus many of the anomalous Phobos-2 spectra, characterized by a shallow band minimum in the near-IR whose position varies between approximately 850 and 1000 nm, can be explained by assemblages whose endmembers (hematite and pyroxene) are accepted to be present on Mars. Furthermore, results show that a mineralogically diverse suite of rocks can be generated at essentially constant composition, which implies that variations in Martian surface mineralogy do not necessarily imply variations in chemical composition.

  1. Characterization of magnetite in silico-aluminous fly ash by SEM, TEM, XRD, magnetic susceptibility, and Moessbauer spectroscopy

    SciTech Connect

    Gomes, S.; Francois, M.; Abdelmoula, M.; Refait, P.; Pellissier, C.; Evrard, O.

    1999-11-01

    Spinel magnetite contained in a silico-aluminous fly ash (originating from la Maxe's power plant, near Metz in the east of France) issued from bituminous coal combustion has been studied by scanning and transmission electron microscopy linked with energy dispersive spectroscopy. X-ray diffraction, susceptibility measurements, and Moessbauer spectroscopy. The results show that in this magnetite Mg is strongly substituted for Fe and the chemical formula is closer to MgFe{sub 2}O{sub 4} than Fe{sub 3}O{sub 4}. Magnetite also contains Mn, Ca, and Si elements, but at a lower proportion. The results are compatible with the chemical formula Fe{sub 2.08}Mg{sub 0.75}Mn{sub 0.11}Ca{sub 0.04}Si{sub 0.02}O{sub 4} and crystallochemical formula [Fe{sup 2{minus}}{sub 0.92}Ca{sup 2+}{sub 0.06}Si{sup 4+}{sub 0.02}]{sup tetra}[Fe{sup 3+}Fe{sup 2+}{sub 0.16}Mg{sup 2+}{sub 0.73}Mn{sup 2+}{sub 0.11}]{sup octa}O{sub 4}, showing the cation distribution on octahedral and tetrahedral sites of the spinel structure. The reason Mg element is not incorporated in soluble surface salt and in glass composition of the silico-aluminous fly ashes is now understood.

  2. Acidic properties of binary oxide catalysts. II. Moessbauer spectroscopy and pyridine adsorption for iron supported on magnesia, alumina, and titania

    SciTech Connect

    Connell, G.; Dumesic, J.A.

    1986-11-01

    The acidic properties of MgO, Al/sub 2/O/sub 3/, and TiO/sub 2/ were studied using pyridine adsorption. Infrared spectroscopy and gravimetric adsorption measurements indicate no acid sites on MgO, while Lewis acid sites were observed on the surfaces of Al/sub 2/O/sub 3/ and TiO/sub 2/. Doping Fe onto MgO and Al/sub 2/O/sub 3/ was shown by Moessbauer spectroscopy to produce only highly coordinated Fe (e.g., sixfold coordination). A small amount of low coordination iron (e.g., fourfold coordination) was observed on TiO/sub 2/. Pyridine adsorption measurements showed that addition of Fe on MgO did not generate acidity, whereas iron produced a small number of sites on Al/sub 2/O/sub 3/ and iron addition caused a selective poisoning and strengthening of the acid sites on TiO/sub 2/. All acids in this series of single component and binary component oxides were Lewis acids. A model of Lewis acidity is proposed in that the existence of coordinatively unsaturated cations responsible for the acidic properties can be predicted using Pauling's electrostatic bond strength rules. This model is also shown to be valid for iron cations deposited on SiO/sub 2/.

  3. Magnetic properties and Moessbauer analyses of glass from the K-T boundary, Beloc, Haiti

    NASA Technical Reports Server (NTRS)

    Senftle, F. E.; Thorpe, A. N.; May, L.; Barkatt, A.; Adel-Hadadi, M. A.; Marbury, G. S.; Izett, G.; Sigurdsson, H.; Maurasse, F. J.-M. R.

    1993-01-01

    The experimental magnetic susceptibility, the temperature-independent component of the magnetic susceptibility, the magnetization, and the Curie constant have been measured for a number of specimens of glass from the K-T boundary found at Beloc, Haiti, and the results are compared with those of similar measurements of tektites. Because the Fe(3+)/Fe(2+) ratio is needed to calculate the magnetic parameters, Moessbauer spectroscopic measurements were also made. The data were consistent with the classification of the Beloc glasses as tektites.

  4. Combined backscatter Moessbauer spectrometer/x ray fluorescence analyzer (BaMS/XRF) for extraterrestrial surfaces

    NASA Technical Reports Server (NTRS)

    Shelfer, T. D.; Wills, E. L.; Agresti, D. G.; Pimperl, M. M.; Shen, M. H.; Morris, R. V.; Nguyen, T.

    1993-01-01

    We have designed and tested a prototype combined backscatter Moessbauer spectrometer and x-ray fluorescence analyzer (BaMS/XRF). A space qualified instrument based on this design would be suitable for in-situ use on planetary missions to the surfaces of the Moon (Artemis and lunar outpost), Mars (MESUR), asteroids, or other solid solar system objects. The BaMS/XRF instrument is designed to be capable of concurrent sample analyses for the mineralogy of iron-bearing phases and elemental composition without the need for sample preparation.

  5. Coordination of Fe, Ga and Ge in high pressure glasses by Moessbauer, Raman and X-ray absorption spectroscopy, and geological implications

    NASA Technical Reports Server (NTRS)

    Fleet, M. E.; Henderson, G. S.; Herzberg, C. T.; Crozier, E. D.; Osborne, M. D.; Scarfe, C. M.

    1984-01-01

    For some time, it has been recognized that the structure of silicate liquids has a great bearing on such magma properties as viscosity, diffusivity, and thermal expansion and on the extrapolation of thermodynamic quantities outside of the experimentally measurable range. In this connection it is vital to know if pressure imposes changes in melt structure similar to the pressure-induced reconstructive transformations in crystals. In the present study on 1 bar and high pressure glasses, an investigation is conducted regarding the coordination of Fe(3+) in Fe silicate glasses by Moessbauer spectroscopy. Raman spectroscopy is employed to explore the coordinations of Ge(4+) in GeO2 glasses and of Ga(3+) in NaGa silicate glasses, while the coordination of Ga(3+) in NaGaSiO4 glasses is studied with the aid of methods of X-ray absorption spectroscopy.

  6. Ultra-soft magnetic properties and correlated phase analysis by 57Fe Mössbauer spectroscopy of Fe74Cu0.8Nb2.7Si15.5B7 alloy

    NASA Astrophysics Data System (ADS)

    Manjura Hoque, S.; Liba, S. I.; Anirban, A.; Choudhury, Shamima; Akhter, Shireen

    2016-02-01

    A detailed study of magnetic softness has been performed on FINEMENT type of ribbons by investigating the BH loop with maximum applied field of 960 A/m. The ribbon with the composition of Fe74Cu0.8Nb2.7Si15.5B7 was synthesized by rapid solidification technique and the compositions volume fraction was controlled by changing the annealing condition. Detail phase analysis was performed through X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Vibrating sample magnetometer (VSM) and Mössbauer spectroscopy in order to correlate the ultrasoft magnetic properties with the volume fraction of amorphous and α-Fe(Si) soft nano composites. Bright (BF) and dark field (DF) image with selective area diffraction (SAD) patterns by the transmission electron microscopy (TEM) of the sample annealed for the optimized annealed condition at 853 K for 3 min reveals nanocrystals with an average size between 10-15 nm possessing the bcc structure which matches with the grain size revealed by the X-ray diffraction. Kinetics of crystallization of α-Fe(Si) phases has been determined by DSC curves. Extremely small coercivity of 30.9 A/m and core loss of 2.5 W/Kg for the sample annealed at 853 K for 3 min was found. Similar values for other crystalline conditions were determined by using BH loop tracer with a maximum applied field of around 960 A/m. Mössbauer spectroscopy was used to determine chemical shift, hyperfine field distribution (HFD), and peak width of different phases. The volume fractions of the relative amount of amorphous and crystalline phases are also determined by Mössbauer spectroscopy. High saturation magnetization along with ultrasoft magnetic properties exhibits very high potentials technological applications.

  7. Hyperfine interactions in soybean and lupin oxy-leghemoglobins studied using Mössbauer spectroscopy with a high velocity resolution

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Alenkina, I. V.; Zakharova, A. P.; Oshtrakh, M. I.; Semionkin, V. A.

    2015-04-01

    A comparative study of monomeric soybean and lupin leghemoglobins in the oxy-form was carried out using Mössbauer spectroscopy with a high velocity resolution at 90 K. The 57Fe hyperfine parameters of measured spectra were evaluated and compared with possible structural differences in the heme Fe(II)-O 2 bond.

  8. Moessbauer spectra of olivine-rich achondrites - Evidence for preterrestrial redox reactions

    NASA Technical Reports Server (NTRS)

    Burns, R. G.; Martinez, S. L.

    1991-01-01

    Moessbauer spectral measurements at 4.2 K were made on several ureilites and the two shergottites found in Antarctica, as well as two ureilite falls, three SNC meteorite falls, and two finds in order to distinguish products of preterrestrial redox reactions from phases formed during oxidative weathering on the earth. The spectra indicated that several ureilites contain major proportions of metallic iron, much of which resulted from preterrestrial carbon-induced reduction of ferrous iron in the outermost 10-100 microns of olivine grains in contact with carbonaceous material in the ureilites. The cryptocrystalline nature of these Fe inclusions in olivine renders the metal extremely vulnerable to aerial oxidation, even in ureilites collected as falls. It is inferred that the nanophase ferric oxides or oxyhydroxides identified in Brachina and Lafayette were produced by terrestrial weather of olivines before the meteorites were found. The absence of goethite in two olivine-bearing Antarctic shergottites suggests that the 2 percent ferric iron determined in their Moessbauer spectra also originated from oxidation on Mars.

  9. An East to West Mineralogical Trend in Mars Exploration Rover Spirit Moessbauer Spectra of Home Plate

    NASA Technical Reports Server (NTRS)

    Schroder, C.; Di, K.; Morris, R. V.; Klingelhofer, G.; Li, R.

    2008-01-01

    Home Plate is a light-toned plateau approx.90 m in diameter within the Inner Basin of the Columbia Hills in Gusev crater on Mars. It is the most extensive exposure of layered bedrock encountered by Spirit to date, and it is composed of clastic rocks of moderately altered alkali basalt composition, enriched in some highly volatile elements. Textural observations suggest an explosive origin and geochemical observations favor volcanism, probably a hydrovolcanic explosion [1]. Since it first arrived at Home Plate on sol 744, Spirit has circumnavigated the plateau (Fig. 1) and is now, since sol 1410, resting at its Winter Haven 3 location at the north end of Home Plate. Results: The MER Moessbauer spectrometers determine Fe oxidation states, identify Fe-bearing mineral phases and quantify the distribution of Fe among oxidation states and mineral phases [2]. Moessbauer spectra of Home Plate bedrock were obtained in five different locations from nine different targets (Fig. 1): Barnhill Ace, Posey Manager, and James Cool Papa Bell Stars at the northwest side of Home Plate; Pesapallo, June Emerson, and Elizabeth Emery on the east side; Texas Chili on the south side; Pecan Pie on the west side; and Chanute on the north side.

  10. The miniaturised Moessbauer spectrometer MIMOS II: future developments.

    NASA Astrophysics Data System (ADS)

    Rodionov, D.; Blumers, M.; Klingelhöfer, G.; Bernhardt, B.; Fleischer, I.; Schröder, C.; Morris, R.; Girones Lopez, J.

    2007-08-01

    In January 2004, the first in situ extraterrestrial Mössbauer spectrum was received from the Martian surface. At the present time (May 2007) two Miniaturized Mössbauer Spectrometers (MIMOS II) on board of the two Mars Exploration Rovers "Spirit" and "Opportunity" continue to collect valuable scientific data. Both spectrometers are operational after more than 3 years of work. Originally, the mission was expected to last for 90 days. To date more than 600 spectra were obtained with a total integration time for both rovers exceeding 260 days. The MER mission has proven that Mössbauer spectroscopy is a valuable technique for the in situ exploration of extraterrestrial bodies and the study of Fe-bearing samples. The Mössbauer team at the University of Mainz has accumulated a lot of experience and learned many lessons during last three years. All that makes MIMOS II a feasible choice for the future missions to Mars and other targets. Currently MIMOS II is on the scientific payload of two missions: Phobos Grunt (Russian Space Agency) and ExoMars (European Space Agency). Phobos Grunt is scheduled to launch in 2009. The main goals of the mission are: a) Phobos regolith sample return, b) Phobos in situ study, c) Mars and Phobos remote sensing. MIMOS II will be installed on the arm of a landing module. Currently, we are manufacturing an engineering model for testing purposes. The ESA "ExoMars" mission involves the development of a MER-like rover with more complex scientific payload (Pasteur exobiology instruments, including a drilling system). Its aim is to further characterise the biological environment in preparation for robotic missions and eventually human exploration. Data from the mission will provide invaluable input to the field of exobiology - the study of the origin, the evolution and distribution of life in the universe. The launch date is scheduled for 2013. Like on MER, the MIMOS II instrument will be mounted on a robotic arm. Advanced and improved version of

  11. Development of the Fast Scintillation Detector with Programmable High Voltage Adjustment Suitable for Moessbauer Spectroscopy

    SciTech Connect

    Prochazka, R.; Frydrych, J.; Pechousek, J.

    2010-07-13

    This work is focused on a development of a compact fast scintillation detector suitable for Moessbauer spectroscopy (low energy X-ray/{gamma}-ray detection) where high counting rates are inevitable. Optimization of this part was necessary for a reliable function, better time resolution and to avoid a detector pulses pile-up effect. The pile-up effect decreases the measurement performance, significantly depends on the source activity and also on the pulse duration. Our new detection unit includes a fast scintillation crystal YAP:Ce, an R6095 photomultiplier tube, a high voltage power supply socket C9028-01 assembly, an AD5252 digital potentiometer with an I2C interface and an AD8000 ultra fast operation preamplifier. The main advantages of this solution lie in a short pulse duration (less than 200 ns), stable operation for high activities, programmable gain of the high voltage supply and compact design in the aluminum housing.

  12. Moessbauer analysis of Lewisville, Texas, archaeological site lignite and hearth samples. Environmental geology notes

    SciTech Connect

    Shiley, R.H.; Hughes, R.E.; Cahill, R.A.; Konopka, K.L.; Hinckley, C.C.

    1985-01-01

    The Lewisville site, located in Denton County on the Trinity River north of Dallas, Texas, was thought to provide evidence of the earliest human activity in the western hemisphere. Radiocarbon dates of 37,000 to 38,000 B.P. determined for the site in the late 1950s conflicted with the presence of a Clovis point, which would fix the age of the site between 11,000 and 11,500 B.P. It was hypothesized (Johnson, 1982) that Clovis people were burning lignite from nearby outcrops: lignite in hearth residues would give older than actual ages by radiocarbon dating. X-ray diffraction and instrumental neutron-activation analysis proved inconclusive; however, Moessbauer spectroscopy indicated that hematite, a pyrite combustion product, was present in the ash. From this evidence the authors conclude that there is some support for the hypothesis.

  13. Fe-Bearing Phases Indentified by the Moessbauer Spectrometers on the Mars Exploration Rovers: An Overview

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Klingelhoefer, G.; Ming, D. W.; Schroeder, C.; Rodionov, D.; Yen, A.; Gellert, R.

    2006-01-01

    The twin Mars Exploration Rovers Spirit and Opportunity have explored the martian surface at Gusev Crater (GC) and Meridiani Planum (MP), respectively, for about two Earth years. The Moessbauer (MB) spectrometers on both rovers have analyzed an aggregate of approx.200 surface targets and have returned to Earth information on the oxidation state of iron, the mineralogical composition of Fe-bearing phases, and the distribution of Fe among oxidation states and phases at the two landing sites [1-7]. To date, 15 component subspectra (10 doublets and 5 sextets) have been identified and most have been assigned to mineralogical compositions. Two subspectra are assigned to phases (jarosite and goethite) that are marker minerals for aqueous processes because they contain hydroxide anion in their structures. In this paper, we give an overview of the Febearing phases identified and their distributions at Gusev crater and Meridiani Planum.

  14. Fe-Bearing Phases Identified by the Moessbauer Spectrometers on the Mars Exploration Rovers: An Overview

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Klingelhoefer, G.; Rodionov, D.; Yen, A.; Gellert, R.

    2006-01-01

    The twin Mars Exploration Rovers Spirit and Opportunity have explored the martian surface at Gusev Crater (GC) and Meridiani Planum (MP), respectively, for about two Earth years. The Moessbauer (MB) spectrometers on both rovers have analyzed an aggregate of 200 surface targets and have returned to Earth information on the oxidation state of iron, the mineralogical composition of Febearing phases, and the distribution of Fe among oxidation states and phases at the two landing sites [1-7]. To date, 15 component subspectra (10 doublets and 5 sextets) have been identified and most have been assigned to mineralogical compositions. Two subspectra are assigned to phases (jarosite and goethite) that are marker minerals for aqueous processes because they contain hydroxide anion in their structures. In this paper, we give an overview of the Febearing phases identified and their distributions at Gusev crater and Meridiani Planum.

  15. Interpretation of the Moessbauer Spectra of the Magnetic Nanoparticles in Mouse Spleen

    SciTech Connect

    Chuev, Mikhail A.; Cherepanov, Valery M.; Polikarpov, Mikhail A.; Panchenko, Vladislav Y.; Deyev, Sergey M.; Mischenko, Iliya N.; Nikitin, Maxim P.

    2010-12-02

    We have developed a stochastic model for description of relaxation effects in the system of homogeneously magnetized single-domain particles and applied the model to the analysis of Moessbauer spectra of magnetic nanoparticles (Chemicell ARA) and mouse spleen after i.v. injection into animals. We estimate that the fraction of exogenous iron in nanoparticles in the mouse spleen 3 months after injection was 0.27{+-}0.03. The spectra of the residual nanoparticles in the spleen had almost the same isomer shift but smaller mean hyperfine magnetic field values indicating decrease in the magnetic anisotropy energy (size) of the particles compared to the initial ones in the course of biodegradation. Concentration of ferritin-like iron was about three-fold higher than that in the spleen of untreated animals showing ferritin-like forms in the mouse spleen.

  16. Mineralogy at Gusev Crater and Meridiani Planum from the Moessbauer Spectrometers on the Mars Exploration Rovers

    NASA Technical Reports Server (NTRS)

    Morris, Richard V.; Klingelhoefer, Goestar

    2006-01-01

    The Moessbauer spectrometers on the twin MER rovers Spirit and Opportunity have provided significant new information on the distribution of iron among its oxidation states, the identification of the mineralogical composition of iron-bearing phases, and the distribution of iron among those phases for rock and soil at Gusev Crater and Meridiani Planum. The plains of Gusev Crater are dominated by olivine-bearing basalt (approximately Fo(60)) and Fe(3+)/Fe(total)=0.1 - 0.5. The oxide mineral generally present is magnetite. In contrast, initial results for the Columbia Hills are consistent with the presence of hematite and a ferrous iron phase, possibly pyroxene. Gusev spectra also have a ferric doublet (not jarosite) that is tentatively associated with nano-phase ferric oxide. A wider diversity of material is present at Meridiani Planum. Significantly, jarosite-bearing outcrop is present throughout the region, with good exposures in impact craters such as Eagle and Endurance (Fe(3+)/Fe (total) approx. 0.9). The Moessbauer identification of jarosite (a hydroxyl-bearing sulfate mineral) is evidence for aqueous, acid-sulfate processes on Mars. Hematite is observed within the outcrop matrix and in the spheroidal particles (Blueberries) found within the outcrop and as a surface lag. An isolated rock (Bounce Rock) was the only sample at either landing site whose iron-bearing phase was dominated by pyroxene. The basaltic sand in the central portion of Eagle crater, in the intercrater plains, and between slabs of outcrop at both Eagle and Endurance craters is olivine-bearing basalt. The widespread occurrence of olivine-bearing basalt at both MER landing sites implies that physical, rather than chemical, weathering processes dominate at the surface of contemporary Mars.

  17. Design and Construction of an Autonomous Low-Cost Pulse Height Analyzer and a Single Channel Analyzer for Moessbauer Spectroscopy

    SciTech Connect

    Velasquez, A.A.; Trujillo, J.M.; Morales, A.L.; Tobon, J.E.; Gancedo, J.R.; Reyes, L.

    2005-04-26

    A multichannel analyzer (MCA) and a single channel-analyzer (SCA) for Moessbauer spectrometry application have been designed and built. Both systems include low-cost digital and analog components. A microcontroller manages, either in PHA or MCS mode, the data acquisition, data storage and setting of the pulse discriminator limits. The user can monitor the system from an external PC through the serial port with the RS232 communication protocol. A graphic interface made with the LabVIEW software allows the user to adjust digitally the lower and upper limits of the pulse discriminator, and to visualize as well as save the PHA spectra in a file. The system has been tested using a 57Co radioactive source and several iron compounds, yielding satisfactory results. The low cost of its design, construction and maintenance make this equipment an attractive choice when assembling a Moessbauer spectrometer.

  18. Synthesis of iron(II) dioximates with phosphine derivatives and their investigation by Moessbauer and IR spectroscopy

    SciTech Connect

    Turte, K.I.; Zubareva, V.E.; Shafranskii, V.N.; Bulgak, I.I.; Batyr, D.G.; Timokhin, B.V.; Dmitriev, V.I.

    1988-03-01

    Newly synthesized compounds with the general formula (Fe/sup II/(dioxH)/sub 2/L/sub 2/), where dioxH stands for the monodeprotonated anions of dimethylglyoxime (dmgH) diphenylglyoxime (dpgH), 1,2-cyclohexanedione dioxime (nioxH), and ..cap alpha..-furildioxime (furgH), and L stands for n-butyldiphenylphosphine (PBuPh/sub 2/) and di-n-butylphenylphosphine (PBu/sub 2/Ph), have been investigated by Moessbauer and IR spectroscopy. The Moessbauer spectra of all the compounds at 80 and 300/sup 0/K consist of doublets, whose parameters correspond to the low-spin state of iron(II). The replacement of an axial ligand of PPh/sub 3/ by PBuPh/sub 2/ or PBu/sub 2/Ph results in a decreasing the magnitude of the quadrupole splitting by approx. 30%. It has been found that PBuPh/sub 2/ and PBu/sub 2/Ph have stronger sigma-donor and ..pi..-acceptor properties in comparison to PPH/sub 3/. The data from the IR and Moessbauer spectra confirm the existence of cis influence of the ligands in the complexes investigated.

  19. Neutron Diffraction Study of LaSr3Fe3O10 in the Temperature Range 25 - 650 deg. C

    SciTech Connect

    Neov, S.; Prokhnenko, O.; Velinov, N.; Kozhukharov, V.; Neov, D.; Dabrowski, L.

    2007-04-23

    The effect of high temperature on the structure of LaSr3Fe3O10 has been studied by neutron diffraction. Neutron data have been correlated with Moessbauer spectroscopy results and electrical conductivity measurements.

  20. A Backscatter Moessbauer Spectrometer (BaMS) for use on Mars

    NASA Technical Reports Server (NTRS)

    Agresti, D. G.; Morris, R. V.; Wills, E. L.; Shelfer, T. D.; Pimperl, M. M.; Shen, M.-H.; Nguyen, T.

    1992-01-01

    The use of Moessbauer spectroscopy for in situ analysis on the surface of Mars was proposed and the design and implementation of a backscatter Moessbauer spectrometer (BaMS) instrument suitable for planetary missions to the surfaces of Mars (MESUR), the Moon (Artemis and lunar outpost), asteroids, or other solid solar system objects is discussed. The BaMS instrument is designed to be capable of analysis of a sample for the mineralogy of its iron-bearing phases without any sample preparation. A requirement of lander missions to Mars is instrumentation for in situ mineralogical analyses. Such analyses provide data needed for primary characterization as to the type of surface materials present and by inference the processes that formed and subsequently modified them. For purposes of providing diagnostic information about naturally occurring materials, the element iron is particularly important because it is abundant and multivalent (primarily 0, +2, and +3 oxidation states). Knowledge of the oxidation state of iron and its distribution among iron-bearing mineralogies tightly constrains the types of materials present. The pivotal role of iron was already recognized in 1978 by COMPLEX, who recommended development of flight instruments that would identify mineralogy and the oxidation state of iron in planetary surface materials. The near-term U.S. strategy for the exploration of Mars is the MESUR (Mars Environmental SURvey) program, which entails emplacement of a network of small, long-lived surface landers. For the Moon, BaMS was recommended as part of a three-instrument landed payload for the Artemis missions, targeted for 1997. BaMS would prospect for ilmenite, an oxygen resource material, and provide data to assess the maturity of lunar soil. Because instrumental characteristics are low mass, low volume, and low power consumption, BaMS is suitable for implementation on even small landers and rovers, as are being envisioned in MESUR and Artemis concepts. In addition

  1. Mössbauer study on iron-polygalacturonate coordination compounds

    NASA Astrophysics Data System (ADS)

    Fodor, Judit; Kuzmann, Ernö; May, Zoltán; Vértes, Attila; Homonnay, Zoltán; Szentmihályi, Klára

    2008-07-01

    57Fe Mössbauer spectroscopy was used to determine the oxidation state and microenvironments of iron in the Fe-polygalacturonate compound prepared by a novel method from pectin. ICP analysis was applied to study the iron content of the coordination compounds. It was found that there are two ferrous and one ferric microenvironments in the compound. In the iron- polygalacturonate compound the ferrous forms occur dominantly. A model for the bonding of Fe in the polygalacturonate chains is proposed.

  2. Chemical decomposition of iron in Spanish coal pyrolysis identified by Moessbauer spectroscopy at different temperatures

    SciTech Connect

    Ahmed, M.A.; Blesa, M.J.; Moliner, R.

    2007-07-01

    Three chars from lignite (Se), sub bituminous (AA6), bituminous (BCA) Spanish coals produced at 673 K, 773 K, and 873 K were analyzed by Moessbauer spectroscopy at room temperature, and 80 K, except BCA char produced at 873 K, its analysis was extended down to 10 K. Least square fit analysis for the spectra of Se chars showed that, jarosite/Fe{sup 3+} was hydrolyzed into rozenite/Fe2+ at 873 K. Pyrite was reduced to troilite (FeS) at 773 K. Both jarosite and very broad doublet were observed at T = 673 K. The hyperfine parameters of this phase gave close values to microcrystalline iron in either Fe (II) or Fe (III) states. On the other hand, the spectral analysis of AA6 chars ascertained that rozenite was hydrolyzed to goethite (FeOOH) in the range of 773 K-873 K, whereas pyrite was reduced to pyrrohotite (Fe{sub 1-x}S). However, no chemical changes were observed for jarosite in all AA6-chars. Likewise, siderite was changed into magnetite in the BCA chars produced at 673 K and 773 K. Spectrum performed at 10 K for char produced at 873 K proved the presence of ferrihydrite (H = 489.2 kOe), troilite (H = 355.3 kOe) and a broad paramagnetic doublet belonging to an organic iron. These phases and still remaining siderite inferred also that such transformations are incomplete.

  3. Moessbauer Effects and Magnetic Properties of Mixed Valent Europium Sulfide, EuPd

    SciTech Connect

    Wakeshima, Makoto; Doi, Yoshihiro; Hinatsu, Yukio

    2001-02-15

    EuPd{sub 3}S{sub 4} with a NaPt{sub 3}O{sub 4}-type structure was investigated by X-ray diffraction, {sup 151}Eu Moessbauer spectroscopy, magnetic susceptibility, and specific heat measurements. In this compound, Eu{sup 2+} and Eu{sup 3+} ions exist in the ratio of ca. 1:1. The Debye temperatures of Eu{sup 2+} and Eu{sup 3+} were determined to be 195 and 220 K, respectively. The isomer shift of Eu{sup 2+} in this EuPd{sub 3}S{sub 4} at 300 K is largest among Eu{sup 2+} sulfides because of the compression effect of the Eu{sup 2+} sites. The temperature dependence of the isomer shifts suggests that a hopping of the electron between Eu{sup 2+} and Eu{sup 3+} occurs in EuPd{sub 3}S{sub 4}. The Eu{sup 2+} ion was found to be in the antiferromagnetic state below 3 K from both the magnetic susceptibility and specific heat measurements.

  4. Iron Mineralogy and Aqueous Alteration on Mars from the MER Moessbauer Spectrometers. Chapter 15

    NASA Technical Reports Server (NTRS)

    Morris, Richard V.; Klingelhoefer, Goestar

    2007-01-01

    The twin Mars Exploration Rovers Spirit (Gusev crater) and Opportunity (Meridiani Planum) used MIMOS II Moessbauer spectrometers to analyze martian surface materials in the first application of extraterrestrial Moessbauer spectroscopy. The instruments acquired spectra that identified the speciation of Fe according to oxidation state, coordination state, and mineralogical composition and provided quantitative information about the distribution of Fe among oxidation states, coordination states, and Fe-bearing phases. A total of 12 unique Fe-bearing phases were identified: Fe(2+) in olivine, pyroxene, and ilmenite; Fe(2+) and Fe(3+) in magnetite and chromite; Fe(3+) in nanophase ferric oxide (npOx), hematite, goethite, jarosite, an unassigned Fe3+ sulfate, and an unassigned Fe(3+) phase associated with jarosite; and Fe(0) in kamacite. Weakly altered basalts at Gusev crater (SO3 = 2.5 +/- 1.4 wt.% and Fe(3+)/Fe(sub T) = 0.24 +/- 0.11) are widespread on the Gusev plains and occur in less abundance on West Spur and Husband Hill in the Columbia Hills. Altered low-S rocks (SO3 = 5.2 +/- 2.0 wt.% and Fe(3+)/Fe(sub T) = 0.63 +/- 0.18) are the most common type of rock in the Columbia Hills. Ilm-bearing, weakly altered basalts were detected only in the Columbia Hills, as was the only occurrence of chromite in an altered low-S rock named Assemblee. Altered high-S rocks (SO3 > 14.2 wt.% and Fe(3+)/Fe(sub T) = 0.83 +/- 0.05) are the outcrop rocks of the ubiquitous Burns formation at Meridiani Planum. Two Fe(0)-bearing rocks at Meridiani Planum (Barberton and Heat Shield Rock) are meteorites. Laguna Class soil is weakly altered (SO3 = 6 +/- 2 wt.% and Fe(3+)/Fe(sub T) = 0.29 +/- 0.08) and widely distributed at both Gusev crater and Meridiani Planum, implying efficient global mixing processes or a global distribution of precursor rocks with comparable Fe mineralogical compositions. Paso Robles Class soil is heavily altered (SO3 approx. 31 wt.% and Fe(3+)/Fe(sub T) = 0.83 +/- 0

  5. Moessbauer Spectroscopy for Lunar Resource Assessment: Measurement of Mineralogy and Soil Maturity

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Agresti, D. G.; Shelfer, T. D.; Pimperl, M. M.; Shen, M.-H.; Gibson, M. A.; Wills, E. L.

    1992-01-01

    First-order assessment of lunar soil as a resource includes measurement of its mineralogy and maturity. Soils in which the mineral ilmenite is present in high concentrations are desirable feedstock for the production of oxygen at a lunar base. The maturity of lunar soils is a measure of their relative residence time in the upper 1 mm of the lunar surface. Increasing maturity implies increasing load of solar wind species (e.g., N, H, and He-3), decreasing mean grain size, and increasing glass content. All these physicochemical properties that vary in a regular way with maturity are important parameters for assessing lunar soil as a resource. For example, He-3 can be extracted and potentially used for nuclear fusion. A commonly used index for lunar soil maturity is I(sub s)/FeO, which is the concentration of fine-grained metal determined by ferromagnetic resonance (I(sub s)) normalized to the total iron content (as FeO). I(sub s)/FeO has been measured for virtually every soil returned by the Apollo and Luna missions to the Moon. Because the technique is sensitive to both oxidation state and mineralogy, iron Moessbauer spectroscopy (FeMS) is a viable technique for in situ lunar resource assessment. Its utility for mineralogy is apparent from examination of published FeMS data for lunar samples. From the data published, it can be inferred that FeMS data can also be used to determine soil maturity. The use of FeMS to determine mineralogy and maturity and progress on development of a FeMS instrument for lunar surface use are discussed.

  6. Moessbauer Mineralogical Evidence for Aqueous Processes at Gusev Crater and Meridiani Planum

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Klingelhoefer, G.

    2006-01-01

    The Moessbauer spectrometers on the MER rovers have measured the relative abundances of iron with respect to both oxidation state and iron-bearing phase at Gusev Crater (Spirit rover) and Meridiani Planum (Opportunity rover). The assemblage of phases indicates aqueous alteration processes at both landing sites. Although the rock and soil of the Gusev Crater plains are dominated by Fe(2+) in olivine-bearing basalt (approx.Fo60), a Fe(3+)-rich component (nanophase ferric oxide, np-Ox) has significant abundance in surface soils (13-28% of total Fe) and in the surface coatings (rinds) of certain rocks (39%) but not in rock interiors exposed by grinding (5-6%). The mode of occurrence of np-Ox implies that it is the product of oxidative alteration of Fe(2+) silicate and oxide phases in the presence of H2O. The ubiquitous presence of sulfur in soil and in rock coatings, as determined by the MER-A APXS instrument, suggests that the alteration occurred under acid-sulfate conditions, so that both hydrolytic and sulfatic reactions are viable. A possible source for the weathering agents is volcanic emanations rich in H2O and SO2. Generally, rocks in the Columbia Hills are significantly more altered than those in the Gusev plains, with a higher proportion of Fe(3+) oxide phases compared to Fe(2+) silicate phases. This mineralogical dichotomy implies a difference in the timing, rate, duration, and/or mechanism of alteration for basaltic material in the Gusev plains compared to basaltic material in the Columbia Hills. It is possible, for example, that the basaltic material in the Columbia Hills underwent aqueous alteration in a paleoclimate that favored nearly complete alteration and that the basaltic material of the Gusev plains will not achieve the degree of alteration exhibited by the Columbia Hills under current martian surface conditions.

  7. Synthesis and Moessbauer-spectroscopic investigation of coordination compounds of tin(IV) with ligands based on thiosemicarbazide

    SciTech Connect

    Gerbeleu, N.V.; Rochev, V.Ya.; Turte, K.I.; Bologa, O.A.; Bobkova, S.A.; Lozan, V.I.; Lavrinyuk, I.P.

    1987-03-01

    Coordination compounds of Sn(IV) of the type SnX/sub 4/L/sub 2/, where X = Cl and Br, and L stands for pyruvic acid thiosemicarbazone (pyth), carboxybenzaldehyde thiosemicarbazone (beth), and thiosemicarbazidediacetic acid (thda), respectively, have been investigated by Moessbauer spectroscopy. The gamma-resonance spectra have the form of unbroadened singlet lines with values of the isomer shifts at 92/sup 0/K equal to 0.56 for SnCl/sub 4/ (pyth)/sub 2/, 0.52 for SnCl/sub 4/ (beth)/sub 2/, 0.65 for SnCl/sub 4/ (thda)/sub 2/, 0.78 for SnBr/sub 4/ (pyth)/sub 2/, and 0.91 mm/sec for SnBr/sub 4/ (thda)/sub 2/. An analysis of the IR spectra and Moessbauer spectra led to the conclusion that in all the compounds synthesized L acts as a neutral monodentate ligand, in which the sulfur atom is the donor site.

  8. Mössbauer study of the iron atom state in modified chromium dioxide

    NASA Astrophysics Data System (ADS)

    Bondarevskii, S. I.; Eremin, V. V.; Panchuk, V. V.; Semenov, V. G.; Osmolovsky, M. G.

    2016-01-01

    Powders of modified chromium dioxide produced by the hydrothermal method were studied using 57Fe Mössbauer spectroscopy at a temperature of 298 K. The content of the modifier, i.e., 57Fe compound, was varied from 2 to 10 mmol/mol Cr at a Sb content of 2.2 and 10 mmol/mol Cr. It was shown that, independently of concentrations, Fe3+ ions are distributed between three magnetic solid solutions (sextets): based on CrO2 (bulk material and iron-enriched surface layer), based on Cr2O3, and surface β-CrOOH (doublet). In this case, chromium atoms were not substituted in the CrSbO4 nucleation (12 nm in size) phase with an accuracy up to the Mössbauer factor. It was assumed that the powder coercivity, in addition to the size factor, is controlled by the iron concentration in the CrO2 surface layer.

  9. Site location of Co in {beta}-FeSi{sub 2}

    SciTech Connect

    Dezsi, I.; Fetzer, Cs.; Kiss, M.; Degroote, S.; Vantomme, A.

    2005-10-01

    In order to reveal cationic site preference in {beta}-FeSi{sub 2}, Co-substituted samples synthesized by various techniques such as molecular beam epitaxy, ion implantation, and chemical vapor transport were investigated by {sup 57}Fe conversion electron Moessbauer (CEM) as well as {sup 57}Co Moessbauer emission (ME) spectroscopy. Literature on the structure of {beta}-FeSi{sub 2} is somewhat contradictory, especially on the point of the population of the two iron sites in the orthorhombic structure. {sup 57}Co ME and {sup 57}Fe CEM spectra both showed two quadrupole split spectral components in the crystalline phase. Hyperfine parameters indicate that Co atoms substitute Fe in both Fe positions in the orthorhombic lattice. The aim of the present study was to get reliable results on the relative population of the two iron sites and determine the substitution of the iron sites by Co atoms in the {beta}-FeSi{sub 2} lattice. The relative intensities of the two components in the absorption and emission Moessbauer spectra were found to be very similar for the samples prepared by different techniques, indicating a homogeneous distribution of Co on both Fe sites.

  10. Magnetic, ferroelectric, and spin phonon coupling studies of Sr3Co2Fe24O41 multiferroic Z-type hexaferrite

    NASA Astrophysics Data System (ADS)

    Raju, N.; Shravan Kumar Reddy, S.; Ramesh, J.; Gopal Reddy, Ch.; Yadagiri Reddy, P.; Rama Reddy, K.; Sathe, V. G.; Raghavendra Reddy, V.

    2016-08-01

    The magnetic, Raman, ferroelectric, and in-field 57Fe Mössbauer studies of polycrystalline multiferroic Sr3Co2Fe24O41 are reported in this paper. From the magnetization studies, it is observed that the sample is soft magnetic in nature with low temperature magnetic spin transitions like longitudinal to transverse conical structure around 130 K and change in magnetic crystalline anisotropy from conical to planar structure at 250 K. Ferroelectric studies of the sample exhibit the spontaneous polarization at low temperature. Strong spin phonon and spin lattice coupling is observed through low temperature Raman spectroscopy. From the in-field 57Fe Mössbauer spectroscopy, spin up and spin down site occupations of Fe ions are calculated in the unit cell.

  11. A study of the domain structure of ferrites in the vicinity of the compensation point by Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Aliev, Sh. M.; Kamilov, I. K.; Aliev, M. Sh.; Ibaev, Zh. G.

    2016-02-01

    A single-crystal sample of gadolinium ferrite garnet Gd3Fe5O12 was studied by Mössbauer spectroscopy near compensation point T cm ( T cm = 286 K). The relative intensities of absorption lines in 57Fe Mössbauer spectra allow it to be concluded that the domain sizes in ferrite grow with the temperature approaching T cm, with domain structure in the sample disappearing at compensation point T cm.

  12. {sup 151}Eu and {sup 121}Sb Moessbauer spectroscopy of EuSbSe{sub 3} and EuBiSe{sub 3}

    SciTech Connect

    Schappacher, Falko M.; Poettgen, Rainer Bang Jin, Geng; Albrecht-Schmitt, Thomas E.

    2007-11-15

    {sup 151}Eu and {sup 121}Sb Moessbauer spectroscopy of EuSbSe{sub 3} and EuBiSe{sub 3} were measured at different temperatures. The presence of divalent europium and trivalent antimony were confirmed. The largely negative values of the isomer shift in {sup 151}Eu spectrum show highly ionic bonding within these two compounds. Both of them show magnetic hyperfine field splitting at 4.2 K, which indicates a change in the orientation of the EFG principal axis with respect to the magnetic hyperfine field direction. EuSbSe{sub 3} has slightly smaller electron density at the antimony nuclei, compared to Sb{sub 2}Se{sub 3.} - Graphical abstract: Experimental and simulated {sup 121}Sb Moessbauer spectrum of EuSbSe{sub 3} at 77 K.

  13. Zn-exchange and Mössbauer studies on the [Fe-Fe] derivatives of the purple acid Fe(III)-Zn(II)-phosphatase from kidney beans.

    PubMed

    Suerbaum, H; Körner, M; Witzel, H; Althaus, E; Mosel, B D; Müller-Warmuth, W

    1993-05-15

    In order to perform Mössbauer studies, Zn(II) in the Fe(III)-Zn(II) purple acid phosphatase of the red kidney bean has been exchanged by incubating the semiapoenzyme with 57Fe(II). The resulting Fe(III)-57Fe(II) enzyme has 125% activity, compared with that of the Zn(II) enzyme. It can be oxidized by H2O2 or peroxydisulfate to the Fe(III)-57Fe(III) species with a 30-times lower activity. Incubation of the metal-free apoenzyme with 57Fe(II) in the presence of O2 leads to the 57Fe(III)-57Fe(II) species which is stable in dilute solutions, but partially oxidized during the concentration procedure to the 57Fe(III)-57Fe(III) enzyme. Limited reduction of the oxidized enzyme with ascorbate delivers a mixture of the Fe(II)-Fe(II)/Fe(III)-Fe(III) species, but not the mixed valent Fe(III)-Fe(II) species, indicating that after the transfer of the first electron the second electron of the ascorbate radical is immediately transferred to the second Fe(III). The Mössbauer spectra of the oxidized species show at 4.2 K two quadrupole doublets with delta of 0.51 mm/s and 0.53 mm/s and delta E of 1.46 and 0.96 mm/s indicating high spin Fe(III) in two different binding sites, obviously with a higher asymmetry in the chromophoric Fe(III) site. The values are too low for a mu-oxo bridge. The mixed-valent Fe(III)-Fe(II) species shows two quadrupole doublets with delta values of 0.55 mm/s and 1.14 mm/s and delta E values of 1.43 mm/s and 3.01 mm/s at 70 K for high spin Fe(II) and Fe(III), but the signal of the Fe(II) component shows magnetic patterns at 4.2 K indicating a half-integer spin system with antiferromagnetic coupling. The Fe(II)-Fe(II) system exhibits two quadrupole doublets with delta values of 1.18 mm/s and 1.22 mm/s and with delta E values of 3.69 mm/s and 2.68 mm/s again indicating a higher asymmetry in the originally chromophoric Fe(III)-binding site. Addition of phosphate shows only minor differences in the oxidized enzyme and in the mixed valent Fe(III)-Fe(II) system

  14. The structure and stability of CaFe layered double hydroxides with various Ca:Fe ratios studied by Mössbauer spectroscopy, X-ray diffractometry and microscopic analysis

    NASA Astrophysics Data System (ADS)

    Sipiczki, M.; Kuzmann, E.; Homonnay, Z.; Megyeri, J.; Pálinkó, I.; Sipos, P.

    2013-07-01

    The effects of the Ca(II)/Fe(III) ratios on the structure and Fe microenvironments have been studied in layered double hydroxides comprising of Ca(II) and Fe(III) (CaFe-LDH) prepared by the co-precipitation method. The Ca(II)/Fe(III) ratios were varied systematically from 2 to 6 and for characterisation 57Fe Mössbauer spectroscopy, powder X-ray diffractometry and scanning electron microscopy were applied. XRD patterns of the samples at all Ca(II)/Fe(III) ratios exhibited reflections corresponding to CaFe-LDH and 57Fe Mössbauer measurements revealed that Fe(III) was in a high-spin, somewhat disordered octahedral environment. Above the Ca(II)/Fe(III) ratio of 2 the reflections of Ca(OH)2 also appeared. This phase was found to stabilise the LDH phase, while the phase-pure LDH decomposed on ageing.

  15. The Incredible Diversity of Fe-bearing Phases at Gusev Crater, Mars, According to the Mars Exploration Rover Moessbauer Spectrometer

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Klingelhoefer, G.; Schroeder, C.; Rodionov, D. S.; Ming, D. W.; Yen, A.

    2006-01-01

    The Mars Exploration Rover (MER) Spirit landed on the plains of Gusev Crater on 4 January 2004. One primary scientific objective for the mission is to characterize the mineralogical and elemental composition of surface materials, searching for evidence of water and clues for assessing past and current climates and their suitability for life [1]. The role of the Moessbauer (MB) spectrometer on Spirit is to provide quantitative information about the distribution of Fe among its oxidation and coordination states, identification of Fe-bearing phases, and relative distribution of Fe among those phases. The speciation and distribution of Fe in Martian rock and soil constrains the primary rock types, redox conditions under which primary minerals crystallized, the extent of alteration and weathering, the type of alteration and weathering products, and the processes and environmental conditions for alteration and weathering. In this abstract, we discuss the incredible diversity of Fe-bearing phases detected by Spirit s MB instrument during its first 540 sols of exploration at Gusev crater [2,3].

  16. Combined Backscatter Moessbauer Spectrometer and X Ray Fluorescence analyzer (BaMS/XRF) for planetary surface materials

    NASA Technical Reports Server (NTRS)

    Agresti, D. G.; Shelfer, T. D.; Pimperl, M. M.; Wills, E. L.; Morris, R. V.

    1991-01-01

    A backscatter Moessbauer spectrometer (BaMS) with included x ray fluorescence (XRF) capability for the Mars Environment Survey (MESUR) Mission, which has been proposed by NASA for 1998, is being developed. The instrument will also be suitable for other planetary missions such as those to the Moon, asteroids, and other solid solar-system objects. The BaMS would be unique for MESUR in providing information about iron mineralogy in rocks, clays, and other surface materials, including relative proportions of iron-bearing minerals. It requires no sample preparation and can identify all the normal oxidation states of iron (3+, 2+, 0). Thus, BaMS is diagnostic for weathering and other soil-forming processes. Backscatter design allows the addition of XRF elemental analysis with little or no modification. The BaMS/XRF instrument complements the thermal analyzer with evolved gas analyzer (TA-EGA) and the alpha-proton x-ray spectrometer (APXS) proposed (along with BaMS) for geochemical analysis on MESUR.

  17. [Application of Mossbauer spectroscopy to the study of hemoglobinopathies. Preliminary experience].

    PubMed

    Abreu, M S; Sanchís, M E; Peñalver, J A; Kanter, F

    1989-10-01

    37Fe Moessbauer spectroscopy has been applied to the study of iron deposits in patients with altered iron metabolism. Haematological parameters were also studied in order to analyse their relationship with Moessbauer results. Within the aim of this research, 12 samples of packed red blood cells were analysed: 6 with beta-thalassaemia major, 2 with S-beta-thalassaemia, 1 with sickle cell anaemia and 3 from normal subjects used as control for Moessbauer spectroscopy. Moessbauer spectra of 6 red blood cells samples showed that besides the two components, i.e., oxy and deoxy haemoglobin present in samples of normal subjects, appears a third component with Moessbauer parameters corresponding to ferritin-like iron. Correlation of % transferrin saturation (TS %) with ferritin-like iron (r = 0.90, p less than 0.05) as well as between TS % and the ratio ferritin-like iron/Hb iron (r = 0.91, p less than 0.05) was found. A tendency to correlation of serum ferritin (SF) with ferritin-like iron (r = 0.90, p less than 0.05) as well as between TS % and the ratio ferritin-like iron/Hb iron (r = 0.91, p less than 0.05) was found. A tendency to correlation of SF with ferritin-like iron (r = 0.78) and with the ratio ferritin-like iron/Hb iron, was also observed. It can be concluded that Moessbauer spectroscopy could be a useful technique in the study of this kind of pathology. PMID:2617381

  18. MOKE Study of Fe/Co/Al Multilayers

    SciTech Connect

    Jani, Snehal; Lakshmi, N.; Venugopalan, K.; Rajput, Parasmani; Zajaoc, M.; Rueffer, R.; Reddy, V. R.; Gupta, Ajay

    2011-07-15

    The multilayer system (MLS)-[{sup 57}Fe{sub 25}A/Co{sub 11}A/Al{sub 17}A]x20 has been deposited by Ion beam sputtering (IBS) technique. The MLS has been annealed at 700 deg. C for 1 h. Overall composition of as deposited and annealed MLS have been characterized by EDX and magnetic properties have been studied through angular dependent magneto optic Kerr effect (MOKE) hysteresis curves. The study shows that the as-deposited MLS has excellent soft magnetic properties coupled with perpendicular magnetic isotropy which is destroyed on annealing.

  19. A {sup 151}Eu Moessbauer spectroscopic and magnetic susceptibility investigation of the intermetallic compounds EuTIn (T = Zn, Pd, Pt, Au)

    SciTech Connect

    Muellmann, R.; Mosel, B.D.; Eckert, H.; Kotzyba, G.; Poettgen, R.

    1998-04-01

    The title compounds were investigated by magnetic susceptibility measurements and {sup 151}Eu Moessbauer spectroscopy. EuZnIn and EuPtIn show Curie-Weiss behavior above 60 K with experimental magnetic moments of 7.80(5) and 8.0(1) {mu}{sub B}/Eu, respectively, indicating divalent europium. The zinc compound orders antiferromagnetically at T{sub N} = 8.0(5) k and two metamagnetic transitions are detected at the critical field strengths B{sub C1} = 1.1(1) T and B{sub C2} = 2.6(2) T. At 5 K the saturation magnetic moment amounts to 7.0(1) {mu}{sub B}/Eu, suggesting a full parallel spin alignment. EuPdIn and EuAuIn order antiferromagnetically at 13.0(5) and 21.0(5) K in low external magnetic fields, respectively. The four compounds are metallic conductors. The Moessbauer measurements of the EuTIn compounds show {sup 151}Eu isomer shifts typical of divalent europium. The isomer shifts are found to linearly correlated with the closest Eu-Eu distance in the structure. Based on the Moessbauer data the onset of magnetic order is observed at T{sub N}(EuZnIn) = 9.5(5) K, T{sub N}(EuPdIn) = 15.5(5) K, T{sub N}(EuAuIn) = 20.0(5) K, and T{sub N}(EuPtIn) = 20.0(5) K, respectively. The magnetically split spectrum of EuZnIn reveals evidence of Eu site inequivalence.

  20. Moessbauer spectroscopy and magnetic characteristics of Zn{sub 1-x}Co{sub x}Fe{sub 2}O{sub 4} (x = 0-1) nanoparticles

    SciTech Connect

    Ghasemi, Ali; Sepelak, Vladimir; Shirsath, Sagar E.; Liu Xiaoxi; Morisako, Akimitsu

    2011-04-01

    Zn{sub 1-x}Co{sub x}Fe{sub 2}O{sub 4} (x = 0-1 in a step of 0.2) nanoparticles with different range of particle size including 5-10 nm and 200-250 nm have been prepared by sol-gel process. Moessbauer spectra at room temperature indicated that, with increasing cobalt content, there is a transition from paramagnetic to magnetically ordered-ferrimagnetic state. Magnetic properties were measured at 300 and 10 K using a Quantum Design MPMS-5S SQUID magnetometer. It was found that with an increase in cobalt content the saturation magnetization and coercivity increase.

  1. Effect of uniaxial tensile stress on the isomer shift of 57Fe in fcc stainless steels

    NASA Astrophysics Data System (ADS)

    Ratner, E.; Ron, M.

    1982-05-01

    The electron wave-function response to uniaxial tensile stress in fcc steels (SS310 and SS316) was investigated through the isomer shift of the Mössbauer effect. Stresses up to 12 kbar (the ultimate tensile stress is approximately 14 kbar) were applied at room temperature. The isomer shift changes linearly in these circumstances. It is concluded that, as in the case of hydrostatic pressure, the paramount factor here is the volume strain of the wave functions of 4S electrons.

  2. The 57Fe Mössbauer parameters of pyrite and marcasite with different provenances

    USGS Publications Warehouse

    Evans, B.J.; Johnson, R.G.; Senftle, F.E.; Cecil, C.B.; Dulong, F.

    1982-01-01

    The Mössbauer parameters of pyrite and marcasite exhibit appreciable variations, which bear no simple relationship to the geological environment in which they occur but appear to be selectively influenced by impurities, especially arsenic, in the pyrite lattice. Quantitative and qualitative determinations of pyrite/marcasite mechanical mixtures are straightforward at 298 K and 77 K but do require least-squares computer fittings and are limited to accuracies ranging from ±5 to ±15 per cent by uncertainties in the parameter values of the pure phases. The methodology and results of this investigation are directly applicable to coals for which the presence and relative amounts of pyrite and marcasite could be of considerable genetic significance.

  3. Spectroscopic studies of superconductors. Part B: Tunneling, photoelectron, and other spectra

    SciTech Connect

    Bozovic, I.; Marel, D. van der

    1996-12-31

    Part B is divided into the following sections: (1) tunneling, photoelectron, and other spectra; (2) tunneling spectra: theoretical studies; (3) photoelectron spectra; and (4) other spectra (XAFS, RBS, ESR, Moessbauer, thermoreflectance, etc.). Separate abstracts were prepared for most papers in this volume.

  4. Mössbauer study of novel iron(II)-dioxime complexes with branched alkyl chains

    NASA Astrophysics Data System (ADS)

    Kuzmann, E.; Lengyel, A.; Homonnay, Z.; Várhelyi, Cs.; Klencsár, Z.; Kubuki, S.; Szalay, R.

    2014-04-01

    Novel iron(II) oxime complexes with dimethyl-glyoxime, methyl-ethyl-glyoxime, methyl-isopropyl-glyoxime, [Fe(DioxH)2L2] with and without axial ligands have been synthesized. 57Fe Mössbauer spectroscopy showed different spin states in complexes with short alkyl chain and with branched alkyl chain, respectively. It was shown that the asymmetry observed in the doublet line intensity of iron-bis-glyoximes is due to the texture effect. The effect of back-coordination was also studied in the case of iron-bis-dioxime complexes with branched alkyl chains, having different axial ligands.

  5. YPdSn and YPd{sub 2}Sn: Structure, {sup 89}Y solid state NMR and {sup 119}Sn Moessbauer spectroscopy

    SciTech Connect

    Hoeting, Christoph; Eckert, Hellmut; Langer, Thorsten; Schellenberg, Inga; Poettgen, Rainer

    2012-06-15

    The stannides YPdSn and YPd{sub 2}Sn were synthesized by high-frequency melting of the elements in sealed tantalum tubes. Both structures were refined on the basis of single crystal X-ray diffractometer data: TiNiSi type, Pnma, a=715.4(1), b=458.8(1), c=789.1(1) pm, wR2=0.0461, 510 F{sup 2} values, 20 variables for YPdSn and MnCu{sub 2}Al type, Fm3 Macron m, a=671.44(8), wR2=0.0740, 55 F{sup 2} values, 5 parameters for YPd{sub 2}Sn. The yttrium atoms in the new stannide YPdSn are coordinated by two tilted Pd{sub 3}Sn{sub 3} hexagons (ordered AlB{sub 2} superstructure). In the Heusler phase YPd{sub 2}Sn each yttrium atom has octahedral tin coordination and additionally eight palladium neighbors. The cubic site symmetry of yttrium is reflected in the {sup 119}Sn Moessbauer spectrum which shows no quadrupole splitting. In contrast, YPdSn shows a single signal at {delta}=1.82(1) mm/s subjected to quadrupole splitting of {Delta}E{sub Q}=0.93(1) mm/s. Both compounds have been characterized by high-resolution {sup 89}Y solid state NMR spectroscopy, which indicates the presence of strong Knight shifts. The spectrum of YPd{sub 2}Sn is characterized by an unusually large linewidth, suggesting the presence of a Knight shift distribution reflecting local disordering effects. The range of {sup 89}Y Knight shifts of several binary and ternary intermetallic yttrium compounds is briefly discussed. - Graphical abstract: YPdSn and YPd{sub 2}Sn: Structure, {sup 89}Y solid state NMR and {sup 119}Sn Moessbauer spectroscopy. Highlights: Black-Right-Pointing-Pointer Synthesis and structure of ternary stannides YPdSn and YPd{sub 2}Sn. Black-Right-Pointing-Pointer {sup 119}Sn Moessbauer spectroscopic investigation of YPdSn and YPd{sub 2}Sn. Black-Right-Pointing-Pointer {sup 89}Y solid state NMR of intermetallics.

  6. Innovative instrumentation for mineralogical and elemental analyses of solid extraterrestrial surfaces: The Backscatter Moessbauer Spectrometer/X Ray Fluorescence analyzer (BaMS/XRF)

    NASA Technical Reports Server (NTRS)

    Shelfer, T. D.; Morris, Richard V.; Nguyen, T.; Agresti, D. G.; Wills, E. L.

    1994-01-01

    We have developed a four-detector research-grade backscatter Moessbauer spectrometer (BaMS) instrument with low resolution x-ray fluorescence analysis (XRF) capability. A flight-qualified instrument based on this design would be suitable for use on missions to the surfaces of solid solar-system objects (Moon, Mars, asteroids, etc.). Target specifications for the flight instrument are as follows: mass less than 500 g; volumes less than 300 cu cm; and power less than 2 W. The BaMS/XRF instrument would provide data on the oxidation state of iron and its distribution among iron-bearing mineralogies and elemental composition information. This data is a primary concern for the characterization of extraterrestrial surface materials.

  7. To the problem about the origin of lunar maria and continents (Moessbauer investigations)

    NASA Technical Reports Server (NTRS)

    Malysheva, T. V.

    1977-01-01

    A comparative study of Mossbauer spectra of regolith returned by the Luna 16 and Luna 20 spacecraft is presented. The Mossbauer spectra of the mare regolith differs significantly for all fractions from the spectra for the same fractions of continental regolith. The total quantity of iron is 1.85 times greater in the mare regolith. There is 2.4 times less olivine in the mare region than in the continental region. The pyroxene component of the mare regolith is less homogeneous in composition (contains more augite and glass) and is present in larger quantities. Ilmenite was found only in the mare regolith. In the continental region, the predominant titanium-containing phase is ulvospinel. The mare regolith contains more metallic iron, which is more finely dispersed and contains less nickel. Troilite is found in the maria region. Based on these differences, it is concluded that the formation of continental rocks occurred at an earlier stage of crystallization from the melt and at higher temperatures and higher partial pressures of oxygen. The mare basalts crystallized from a more reduced magma, apparently in a later process.

  8. Exploration of synchrotron Mossbauer micrscopy with micrometer resolution: forward and a new backscattering modality on natural samples

    SciTech Connect

    Yan, L.; Zhao, J.; Toellner, T.S.; Divan, R.; Xu, S.; Cai, Z.; Boesenberg, J.S.; Freidrich, J.M.; Cramer, S.P.; Alp, E.E.

    2012-01-01

    New aspects of synchrotron Moessbauer microscopy are presented. A 5 {micro}m spatial resolution is achieved, and sub-micrometer resolution is envisioned. Two distinct and unique methods, synchrotron Moessbauer imaging and nuclear resonant incoherent X-ray imaging, are used to resolve spatial distribution of species that are chemically and magnetically distinct from one another. Proof-of-principle experiments were performed on enriched {sup 57}Fe phantoms, and on samples with natural isotopic abundance, such as meteorites.

  9. Pressure-induced phase transition of Fe{sub 2}TiO{sub 4}: X-ray diffraction and Moessbauer spectroscopy

    SciTech Connect

    Wu Ye; Wu Xiang; Qin Shan

    2012-01-15

    X-ray diffraction and Moessbauer spectroscopy were employed to investigate structural stability of Fe{sub 2}TiO{sub 4} under high pressure. Measurements were performed up to about 24 GPa at room temperature using diamond anvil cell. Experimental results demonstrate that Fe{sub 2}TiO{sub 4} undergoes a series of phase transitions from cubic (Fd3-bar m) to tetragonal (I4{sub 1}/amd) at 8.7 GPa, and then to orthorhombic structure (Cmcm) at 16.0 GPa. The high-pressure phase (Cmcm) of Fe{sub 2}TiO{sub 4} is kept on decompression to ambient pressure. In all polymorphs of Fe{sub 2}TiO{sub 4}, iron cations present a high-spin ferrous property without electric charge exchange with titanium cations at high pressure supported by Moessbauer evidences. - Graphical abstract: A series of phase transition of Fe{sub 2}TiO{sub 4} occurs from cubic (a) to tetragonal (b and c) then to orthorhombic phase (d-f) at high pressure. Highlights: Black-Right-Pointing-Pointer High pressure behaviors of Fe{sub 2}TiO{sub 4} were investigated. Black-Right-Pointing-Pointer Phase transitions were observed from cubic to tetragonal and then to orthorhombic. Black-Right-Pointing-Pointer Orthorhombic phase can be kept on decompression. Black-Right-Pointing-Pointer In all polymorphs of Fe{sub 2}TiO{sub 4}, iron ions are ferrous with high-spin state.

  10. Evidence for pigmentary hematite on Mars based on optical, magnetic, and Moessbauer studies of superparamagnetic (nanocrystalline) hematite

    NASA Technical Reports Server (NTRS)

    Morris, Richard V.; Agresti, David G.; Newcomb, Jeffery A.; Shelfer, Tad D.; Lauer, Howard V., Jr.

    1989-01-01

    Samples containing variable amounts of superparamagnetic hematite (sp-Hm) were prepared by a method in which the sp-Hm particles were dispersed throughout larger particles of silica gel, and the optical and magnetic properties of these samples were compared with those of larger-diameter hematite (bulk-Hm). It is shown that the optical properties of sp-Hm are different from those of bulk-Hm. Implications of the results for mineralogical interpretations of spectral data for the Martian surface and its terrestrial analogues are discussed. It is concluded that features resulting from ferric iron in the Martian spectral data and the results of the Viking magnetic properties experiment are both consistent with hematite present as both sp-Hm and bulk-Hm; the hematite particles most likely occur in pigmentary form, i.e., as particles dispersed throughout the volume of a spectrally neutral material.

  11. Evidence for pigmentary hematite on Mars based on optical, magnetic, and Moessbauer studies of superparamagnetic (nanocrystalline) hematite

    NASA Astrophysics Data System (ADS)

    Morris, R. V.; Agresti, D. G.; Lauer, H. V.; Newcomb, J. A.; Shelfer, T. D.; Murali, A. V.

    1989-03-01

    Samples containing variable amounts of superparamagnetic hematite (sp-Hm) were prepared by a method in which the sp-Hm particles were dispersed throughout larger particles of silica gel, and the optical and magnetic properties of these samples were compared with those of larger-diameter hematite (bulk-Hm). It is shown that the optical properties of sp-Hm are different from those of bulk-Hm. Implications of the results for mineralogical interpretations of spectral data for the Martian surface and its terrestrial analogues are discussed. It is concluded that features resulting from ferric iron in the Martian spectral data and the results of the Viking magnetic properties experiment are both consistent with hematite present as both sp-Hm and bulk-Hm; the hematite particles most likely occur in pigmentary form, i.e., as particles dispersed throughout the volume of a spectrally neutral material.

  12. Differential Moessbauer spectrometer

    SciTech Connect

    Kurinyi, Yu.A.; Grotov, Yu.D.

    1988-07-01

    A spectrometer is described that permits hardware differentiation of spectra with respect to the energy of gamma radiation, specimen temperature, etc. Differentiation is performed by secondary modulation of source motion with subsequent phase-sensitive detection at the harmonics. The spectrometer is CAMAC-compatible and permits simultaneous measurement of the first four harmonics.

  13. Iron Isotope Variations in Reduced Groundwater and in Drinking Water Supplies: A Case Study of Hanoi, Vietnam

    NASA Astrophysics Data System (ADS)

    Teutsch, N.; Berg, M.; von Gunten, U.; Halliday, A.

    2004-12-01

    In reduced groundwater iron is involved in biotic and abiotic transformation processes, both of which could lead to iron isotope fractionation. The reduced groundwater aquifers in the area of the Vietnamese capital of Hanoi are the main drinking water sources for the city. These groundwaters contain arsenic, which imposes a serious health threat to millions of people. Dissolved arsenic is related to the reducing conditions prevalent in the groundwater, and iron and arsenic contents are correlated in the sediments. We are employing iron isotope composition as a tool to better understand the processes leading to the transformation of iron in the groundwater and its role in various biogeochemical processes in reduced environments. Drinking water is supplied to the city of Hanoi from several water treatment plants (WTP) which pump the raw groundwater from a lower aquifer, while the rural surroundings pump untreated groundwater from an upper aquifer by private tubewells. Surface water from the Red River delta is the main source of recharge to these two aquifers. Due to high content of particulate natural organic matter (NOM) in the sediment leading to extensive microbial activity, the groundwaters are anoxic and rich in dissolved iron(II). The iron(II) removal in the WTPs is carried by a multi-step treatment including aeration, settling, filtration, and chlorination. We have collected natural groundwater samples for isotopic analysis from two aquifers at several locations, a groundwater depth profile and its corresponding sediment phases from the upper aquifer and the underlying aquitard, raw and treated water from several WTPs, as well as the corresponding iron(III) precipitates. The iron concentrations of groundwaters analysed in this study range from 3 to 28 mg/L and δ 57Fe (57/54 deviation from IRMM 014) values vary between -1.2 and +1.5 ‰ . The sediment depth profile has a δ 57Fe around +0.3 ‰ , which implies that the high values obtained in the groundwater

  14. Mossbauer Studies of Some Iron

    NASA Astrophysics Data System (ADS)

    Boyd, Darwin Lee

    ^{57}Fe Mossbauer spectroscopy was used to investigate several iron(III) spin crossover systems as well as a cold cholesteric liquid crystal. Tris thioseleno- and tris diselenocarbamates were found to be similar to their corresponding tris monothio and tris dithio complexes, showing increasing magnetic moment with increasing isomer shift and decreasing magnetic moment with increasing quadrupole splitting. These observations indicate that the tris thioseleno- and tris diselenocarbamates are, like their dithio analogs, spin crossover systems. Several mixed ligand thioseleno complexes were also studied and found to be similar to the corresponding dithio complexes. A possible trihydrate of Fe(S_2CN(CH _2CH_2OH) _2)_3 was investigated. Repeated attempts to reproduce a recently published four line Mossbauer spectrum for the trihydrate failed. It was concluded that the published methods actually result in the anhydrous complex. Heating of this complex in accordance with the published methods to produce the anhydrous complex resulted in decomposition. Anhydrous preparations of Fe(S_2CN(CH _2CH_2OH) _2)_3 when recrystallized from methanol without heating produced four line Mossbauer spectra at low temperatures. The temperature dependencies of the isomer shift, quadrupole splitting, and peak area indicate that, in this case, the interconversion rate between the two spin states has slowed to below the inverse of the Mossbauer time scale. This slowing is believed to be caused by partial solvation by small, nonstoichiometric, quantities of methanol. Cholesterol-2-(2-ethoxy ethoxy) ethyl carbonate was investigated via Mossbauer spectroscopy by dissolving into it 0.16wt% ^{57 }Fe enriched 1,1^' -diacetylferrocene. A glass transition temperature of 177 K and a Mossbauer Debye temperature of 32.7 K were measured. An increase in the average half width of the resonance lines above the glass transition temperature indicates the onset of diffusion in the supercooled liquid. A lack of

  15. Field-induced spin reorientation in [Fe/Cr ] n multilayers studied by nuclear resonance reflectivity

    NASA Astrophysics Data System (ADS)

    Andreeva, M.; Gupta, A.; Sharma, G.; Kamali, S.; Okada, K.; Yoda, Y.

    2015-10-01

    We present depth-resolved nuclear resonance reflectivity studies of the magnetization evolution in [57Fe(3nm ) /Cr (1.2 nm ) ] 10 multilayer under applied external field. The measurements have been performed at the station BL09XU of SPring-8 at different values of the external field (0-1500 Oe). We apply the joint fit of the delayed reflectivity curves and the time spectra of the nuclear resonance reflectivity measured at different grazing angles for enhancement of the depth resolution and reliability of results. We show that the azimuth angle, which is used in all papers devoted to the magnetization profile determination, has a more complicated physical sense due to the partially coherent averaging of the scattering amplitudes from magnetic lateral domains. We describe how to select the true azimuth angle from the determined "effective azimuth angle." Finally we obtain the noncollinear twisted magnetization depth profiles where the spin-flop state appears sequentially in different 57Fe layers at increasing applied field.

  16. Analysis of 6.4 KEV Moessbauer Spectra Obtained with MIMOS II on MER on Cobbles at Meridiani Planum, Mars and Considerations on Penetration Depths

    NASA Technical Reports Server (NTRS)

    Fleischer, I.; Klingelhoefer, G.; Morris, R. V.; Schroder, C.; Rodionov, D.; deSouza, P.

    2008-01-01

    The miniaturized Moessbauer (MB) spectrometers MIMOS II [1] on board of the two Mars Exploration Rovers Spirit and Opportunity have obtained more than 600 spectra of more than 300 different rock and soil targets [2-7]. Both instruments have simultaneously collected 6.4 keV X-ray and 14.4 keV .-ray spectra in backscattering geometry [1]. With Spirit's MB spectrometer, 6.4 keV and 14.4 keV spectra have been obtained for all targets through sol 461. After this date, only 14.4 keV spectra were collected. With Opportunity's spectrometer, 6.4 keV and 14.4 keV spectra have been collected for all targets to date. The Fe-mineralogy of rock and soil targets at both landing sites reported to date has been exclusively extracted from 14.4 keV spectra [2-5]. The comparison of 6.4 keV and 14.4 keV spectra provides depth selective information about a sample, but interpretation is not always straightforward [8].

  17. Magnetite in Martian Meteorite Mil 03346 and Gusev Adirondack Class Basalt: Moessbauer Evidence for Variability in the Oxidation State of Adirondack Lavas

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; McKay, G. A.; Ming, D. W.; Klingelhoefer, G.; Schroeder, C.; Rodionov, D.; Yen, A.

    2006-01-01

    The Moessbauer spectrometers on the Mars Exploration Rovers Spirit (Gusev crater) and Opportunity (Meridiani Planum) have returned information on the oxidation state of iron, the mineralogical composition of Fe-bearing phases, and the distribution of Fe among oxidation states and phases [1,2,3]. To date, 100 and 85 surface targets have been analyzed by the Spirit and Opportunity spectrometers, respectively. Twelve component subspectra (8 doublets and 4 sextets) have been identified and most have been assigned to mineralogical compositions [4]. Two sextet subspectra result from the opaque and strongly magnetic mineral magnetite (Fe3O4 for the stoichiometric composition), one each for the crystallographic sites occupied by tetrahedrally-coordinated Fe3+ and by octahedrally-coordinated Fe3+ and Fe2+. At Gusev crater, the percentage of total Fe associated with magnetite for rocks ranges from 0 to 35% (Fig. 1) [3]. The range for soils (5 to 12% of total Fe from Mt, with one exception) is narrower. The ubiquitous presence of Mt in soil firmly establishes the phase as the strongly magnetic component in martian soil

  18. The Study of ( n,d) Reaction Cross Sections for Some Medium Weight Targets up to 30 MeV

    NASA Astrophysics Data System (ADS)

    Aydin, A.; Şahan, M.; Tel, E.; Şahan, H.; Uğur, F. A.

    2011-08-01

    In this study, neutron incident reaction cross sections for some medium target nuclei ( 44 Ca, 65 Cu, 54 Fe, 56 Fe, 57 Fe, 58 Ni, 60 Ni and 67 Zn) have been investigated for the ( n,d) reaction cross sections. These new calculations on the excitation functions of 44 Ca(n,d) 43 K, 65 Cu(n,d) 44 Ni, 54 Fe(n,d) 53 Mn, 56 Fe(n,d) 55 Mn, 57 Fe(n,d) 56 Mn, 58 Ni(n,d) 57 Co, 60 Ni(n,d) 59 Co and 67 Zn(n,d) 66 Cu reactions have been carried out up to 30 MeV incident neutron energy. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The PEQ calculations involve the new evaluated the Geometry Dependent Hybrid model. Equilibrium effects are calculated according to the Weisskopf-Ewing model. By using the new cross sections formulae for ( n,d) reactions developed by Aydin et al., the obtained results have been discussed and compared with the available experimental data taken from EXFOR database.

  19. Anisotropic hyperfine field fluctuation in La{sub 0.67}Ca{sub 0.33}Mn{sub 0.99}Fe{sub 0.01}O{sub 3}

    SciTech Connect

    Kim, C.S.; Park, S.I.; Sur, J.C.; Lee, B.W.

    1999-09-01

    Colossal magnetoresistance (CMR), Moessbauer spectra, and neutron diffraction of the iron-doped manganite, La{sub 0.67}Ca{sub 0.33}Mn{sub 0.99} {sup 57}Fe{sub 0.01}O{sub 3}, have been studied. The crystal structure is found to be cubic perovskite with the lattice parameter a{sub 0} = 3.868 {angstrom}. It is notable that the Curie temperature, T{sub c} = 270 K, line broadening and 1,6 and 3,4 line-width difference appear to suggest anisotropic hyperfine field fluctuation. The temperature dependence of the effective anisotropy energy is also found to decrease rapidly with increasing temperature.

  20. Moessbauer spectroscopic investigations of bimetallic FeCo, FeNi, and FeRu model catalysts supported on magnesium hydroxide carbonate

    SciTech Connect

    Nagorny, K.; Bubert, S.

    1987-11-01

    FeCo, FeNi, and FeRu alloys supported on basic magnesium carbonate have been prepared by precipitation from salt solutions at 340 K onto the support using ion exchange and have been subsequently annealed for 20 h under argon. The reduction, oxidation, and sintering behavior of the samples under H/sub 2/ or CO exposure has been investigated at 723 K by means of Moessbauer spectroscopy. The comparison of the resonance absorption areas of the spectra taken at 4 and 295 K allowed the calculation of the Debye temperatures and Debye-Waller factors of the different components. From the Debye-Waller factors the relative fractions could be extrapolated to the conditions at 0 K. The kinetics of the H/sub 2/ exposure showed an increase in the reduction velocity as well as in the degree of reduction in the sequence FeCo < FeNi < FeRu. Above a critical particle diameter a phase separation occurred because of the segregation of an iron-rich phase at the surface of the alloy particles. The kinetics of the CO exposure demonstrated that with FeCo clusters iron(III) surface oxide layers form, whereas with FeNi clusters iron(II) surface oxide layers are generated. FeCo clusters with a cobalt content of 25% form only unstable surface carbides, whereas clusters with a cobalt content of about 5% form stable bulk carbides. The velocity of carbide formation increases with decreasing particle size. Based on the present data a model is proposed which explains the behavior of FeMe/magnesium hydroxide carbonates catalysts in H/sub 2/ and CO atmospheres.

  1. Setting temperature effect in polycrystalline exchange-biased IrMn/CoFe bilayers

    SciTech Connect

    Fernandez-Outon, L. E.; Araujo Filho, M. S.; Araujo, R. E.; Ardisson, J. D.; Macedo, W. A. A.

    2013-05-07

    We study the effect of atomic interdiffusion on the exchange bias of polycrystalline IrMn/({sup 57}Fe + CoFe) multilayers due to the thermal setting process of exchange coupling during field annealing. Depth-resolved {sup 57}Fe conversion electron Moessbauer spectroscopy was used to quantify atomic interdiffusion. Vibrating sample magnetometry was used to monitor the variation of exchange bias and magnetisation. It was found that interface sharpness is only affected above {approx}350 Degree-Sign C. Three different stages for the setting of exchange bias can be inferred from our results. At the lower setting temperatures (up to 350 Degree-Sign C), the effect of field annealing involves alignment of spins and interfacial coupling due to the setting of both antiferromagnetic (AF) bulk and interface without significant interdiffusion. At a second stage (350-450 Degree-Sign C), where AF ordering dominates over diffusion effects, atomic migration and increased setting of AF spins co-exist to produce a peak in exchange bias field and coercivity. On a third stage (>450 Degree-Sign C), severe chemical intermixing reduces significantly the F/AF coupling.

  2. EuTZn (T=Pd, Pt, Au) with TiNiSi-type structure-Magnetic properties and {sup 151}Eu Moessbauer spectroscopy

    SciTech Connect

    Mishra, Trinath; Hermes, Wilfried; Harmening, Thomas; Eul, Matthias; Poettgen, Rainer

    2009-09-15

    The europium compounds EuTZn (T=Pd, Pt, Au) were synthesized from the elements in sealed tantalum tubes in an induction furnace. These intermetallics crystallize with the orthorhombic TiNiSi-type structure, space group Pnma. The structures were investigated by X-ray diffraction on powders and single crystals: a=732.3(2), b=448.5(2), c=787.7(2) pm, R{sub 1}/wR{sub 2}=0.0400/0.0594, 565 F{sup 2} values for EuPdZn, a=727.8(3), b=443.7(1), c=781.7(3) pm, R{sub 1}/wR{sub 2}=0.0605/0.0866, 573 F{sup 2} values for EuPtZn, and a=747.4(2), b=465.8(2), c=789.1(4) pm, R{sub 1}/wR{sub 2}=0.0351/0.0590, 658 F{sup 2} values for EuAuZn, with 20 variables per refinement. Together the T and zinc atoms build up three-dimensional [TZn] networks with short T-Zn distances. The EuTZn compounds show Curie-Weiss behavior in the temperature range from 75 to 300 K with mu{sub eff}=7.97(1), 7.70(1), and 7.94(1) mu{sub B}/Eu atom and theta{sub P}=18.6(1), 34.9(1), and 55.5(1) K for T=Pd, Pt, and Au, respectively, indicating divalent europium. Antiferromagntic ordering was detected at 15.1(3) K for EuPdZn and canted ferromagnetic ordering at 21.2(3) and 51.1(3) K for EuPtZn and EuAuZn. {sup 151}Eu Moessbauer spectroscopic measurements confirm the divalent nature of the europium atoms by isomer shift values ranging from -8.22(8) (EuPtZn) to -9.23(2) mm/s (EuAuZn). At 4.2 K full magnetic hyperfine field splitting is observed in all three compounds due to magnetic ordering of the europium magnetic moments. - Graphical abstract: Europium coordination in EuPdZn, EuPtZn, and EuAuZn.

  3. Resonant nuclear scattering of synchrotron radiation: Detector development and specular scattering from a thin layer of {sup 57}Fe

    SciTech Connect

    Baron, A.Q.R.

    1995-04-01

    This thesis explores resonant nudear scattering of synchrotron radiation. An introductory chapter describes some useful concepts, such as speedup and coherent enhancement, in the context of some basic physical principles. Methods of producing highly monochromatic synchrotron beams usmg either electronic or nuclear scattering are also discussed. The body of the thesis concentrates on detector development and specular scattering from iynthetic layered materials. A detector employing n-dcrochannel plate electron multipliers is shown to have good ({approximately}50%) effidency for detecting 14.4 key x-rays incident at small ({approximately}0.5 degree) grazing angles onto Au or CsI photocathodes. However, being complicated to use, it was replaced with a large area (>=lan2) avalanche photodiode (APD) detector. The APD`s are simpler to use and have comparable (30--70%) efficiencies at 14.4 key, subnanosecond time resolution, large dynan-dc range (usable at rates up to {approximately}10{sup 8} photons/second) and low (<{approximately}0.01 cts/sec) background rates. Maxwell`s equations are used to derive the specular x-ray reflectivity of layered materials with resonant transitions and complex polarization dependencies. The effects of interfadal roughness are treated with some care, and the distorted wave Born approximation (DWBA) used to describe electronic scattering is generalized to the nuclear case. The implications of the theory are discussed in the context of grazing incidence measurements with emphasis on the kinematic and dynamical aspects of the scattering.

  4. Cation distribution in Ni–Cu–Zn nanoferrites from {sup 57}Fe in-field Mössbauer spectra

    SciTech Connect

    Prameela, P.; Kumar, A. Mahesh; Choudary, G.S.V.R.K.; Rao, K.H.; Reddy, V.R.

    2014-11-15

    Highlights: • Occupancy of copper ions at about 20% towards tetrahedral sites. • Distribution is proposed on the basis of % of Fe ions at both A and B sites. • Distribution is checked by estimating the theoretical lattice constant values. - Abstract: The nanoparticles of Ni{sub 1−x}Cu{sub x}Zn{sub 0.35}Fe{sub 2}O{sub 4} were synthesized by sol–gel method using polyvinyl alcohol as a chelating agent. X-ray diffraction patterns of all the samples confirmed the single phase spinel structure. The site occupancy of copper in the nanosized nickel–zinc ferrite spinels was investigated with the help of in-field Mössbauer spectroscopy. Cation distribution for the whole series of compositions was proposed by considering the amounts of iron ions present at both tetrahedral and octahedral interstitial sites in the spinel lattice. Confirmation of the proposed distributions was done by estimating quantitatively the lattice parameters for these compositions and comparing their values with those of the experimentally observed ones.

  5. Mössbauer spectroscopic studies in U-Fe and U-Fe-Zr alloys

    NASA Astrophysics Data System (ADS)

    Panda, Alaka; Singh, L. Herojit; Rajagopalan, S.; Govindaraj, R.; Ramachandran, Renjith; Kalavathi, S.; Amarendra, G.

    2016-05-01

    57Fe Mössbauer studies have been carried out in an alloy of U and Fe with atomic percentage in the ratio of 68%:32% in order to understand the local structure and valence of Fe atoms associated with different phases that may get formed. The effect of changes in the hyperfine parameters such as isomer shift and quadrupole splitting at Fe sites due to additional alloying of Zr has been studied in an alloy of U, Fe and Zr in the ratio of 44%:33%:23% respectively with respect to that of the U-Fe alloy chosen in the present study. Possible effect of solute clustering in these systems has been addressed in an analogous alloy of uranium and zirconium using positron lifetime spectroscopy.

  6. Mössbauer Studies of Thermal Power Plant Coal and Fly Ash

    NASA Astrophysics Data System (ADS)

    Taneja, S. P.

    Iron-57 Mössbauer spectroscopic studies were carried out at room temperature on samples of coal, slag (bottom ash) and mechanical ash collected from Bhatinda (India) thermal power plant. Hyperfine parameters such as isomer shift, quadrupole splitting and total internal magnetic field of 57Fe nuclei were used to characterize various iron-bearing minerals. The observed parameters indicate the presence of pyrite, siderite and ankerite in coal sample while magnetic fractions of mechanical ash and slag samples show the formation of hematite and Al-substituted magnesio-ferrite. The non-magnetic fraction of slag ash shows the dominance of Fe2+ phases while that of mechanical ash demonstrates the formation of both Fe2+ and Fe3+ phases. These findings are compared with Mössbauer and magnetic susceptibility studies on fly ash samples of Panipat (India) thermal power plant reported earlier.

  7. Bricks in historical buildings of Toledo City: characterisation and restoration

    SciTech Connect

    Lopez-Arce, Paula; Garcia-Guinea, Javier; Gracia, Mercedes; Obis, Joaquin

    2003-01-15

    Two different types of ancient bricks (12th to 14th centuries) collected from historical buildings of Toledo (Spain) were characterised by optical microscopy, scanning electron microscopy/energy-dispersive X-ray spectrometers (SEM/EDS), electron probe microanalysis (EM), X-ray diffraction (XRD), differential thermal analysis (DTA) and {sup 57}Fe-Moessbauer spectroscopy. Physical properties such as water absorption and suction, porosity, density and compression strength were also determined. Several minerals found in the brick matrix, such as garnet, let us infer raw material sources; calcite, dolomite, illite and neoformed gehlenite and diopside phases, on temperature reached in firing; secondary calcite, on first cooling scenarios; and manganese micronodules, on late pollution environments. XRD and DTA of original and refired samples supply information about firing temperatures. Additional data on firing conditions and type of the original clay are provided by the Moessbauer study. Physical properties of both types of bricks were compared and correlated with raw materials and fabric and firing technology employed. The physicochemical characterisation of these bricks provides valuable data for restoration purposes to formulate new specific bricks using neighbouring raw materials.

  8. Magnetic dilution of the iron sublattice in CoFe{sub 2-x}Sc{sub x}O{sub 4} (0{<=}x{<=}1)

    SciTech Connect

    Lefevre, C.; Roulland, F.; Viart, N.; Greneche, J.M.; Pourroy, G.

    2010-11-15

    Substitution of Fe for Sc in CoFe{sub 2}O{sub 4} spinel structure is presented. All CoFe{sub 2-x}Sc{sub x}O{sub 4} compounds crystallize in the spinel type structure (space group Fd3-bar m). By using X-ray diffraction studies, magnetic measurements and in-field {sup 57}Fe Moessbauer spectrometry, the limit of substitution has been determined to be equal to x=0.56. An increase in the cell parameter and the strains and a decrease in the apparent crystallites size are observed. For x>0.3, a partial oxidation of cobalt is evidenced and Co{sup 3+} is stabilized in the structure. A ferromagnetic behavior has been observed for all investigated compounds. As x increases, the Curie temperature and the hyperfine fields decrease. Following the Stephenson model, the diminution of T{sub C} is ascribed to a decrease of the main J{sub AB} interaction. -- Graphical abstract: Evolution of the cell parameters, the magnetic properties and the Moessbauer spectra in CoFe{sub 2-r}Sc{sub r}O{sub 4} (0{<=}r{<=}1). Display Omitted

  9. Mössbauer spectroscopic studies of Fe-20 wt.% Cr ball milled alloy

    NASA Astrophysics Data System (ADS)

    Pandey, Brajesh; Rao, M. Ananda; Verma, H. C.; Bhargava, S.

    2006-04-01

    Interesting differences were noticed in the alloying process during ball milling of Fe-10 wt.% Cr and Fe-20 wt.% Cr alloys by 57Fe Mössbauer spectroscopic studies. In both cases, there is almost no diffusion of Fe in Cr or vice versa up to 20 h of milling time. As the powders are milled for another 20 h substantive changes occur in the Mössbauer spectra showing atomic level mixing. But the two compositions behave differently with respect to alloying. Fe-20 wt.% Cr sample does not differ much in the hyperfine field distribution as it is milled from 40 to 100 h. On the other hand, the hyperfine field distribution keeps on changing with milling time for Fe-10 wt.% Cr sample even up to 100 h of milling. The average crystallite size is found to be 7.5 nm for Fe-10 wt.% Cr and 6.5 nm in Fe-20 wt.% Cr after milling.

  10. Mössbauer spectroscopic studies of Fe-20 wt.% Cr ball milled alloy

    NASA Astrophysics Data System (ADS)

    Pandey, Brajesh; Ananda Rao, M.; Verma, H. C.; Bhargava, S.

    Interesting differences were noticed in the alloying process during ball milling of Fe-10 wt.% Cr and Fe-20 wt.% Cr alloys by 57Fe Mössbauer spectroscopic studies. In both cases, there is almost no diffusion of Fein Cr or vice versa up to 20 h of milling time. As the powders are milled for another 20 h substantive changes occur in the Mössbauer spectra showing atomic level mixing. But the two. compositions behave differently with respect to alloying. Fe-20 wt.% Cr sample does not differ much in the hyperfine field distribution as it is milled from 40 to 100 h. On the other hand, the hyperfine field distribution keeps on changing with milling time for Fe-10 wt.% Cr sample even up to 100 h of milling. The average crystallite size is found to be 7.5 nm for Fe-10 wt.% Cr and 6.5 nm in Fe-20 wt.% Cr after milling.

  11. Mössbauer study of cobalt and iron in the cyanobacterium (blue green alga)

    NASA Astrophysics Data System (ADS)

    Ambe, Shizuko

    1990-07-01

    Mössbauer emission and absorption studies have been performed on cobalt and iron in the cyanobacterium (blue-green alga). The Mössbauer spectrum of the cyanobacterium cultivated with57Co is decomposed into two doublets. The parameters of the major doublet are in good agreement with those of cyanocobalamin (vitamin B12) labeled with57Co. The other minor doublet has parameters close to those of Fe(II) coordinated with six nitrogen atoms. These suggest that cobalt is used for the biosynthesis of vitamin B12 or its analogs in the cyanobacterium. The spectra of the cyanobacterium grown with57Fe show that iron is in the high-spin trivalent state and possibly in the form of ferritin, iron storage protein.

  12. Mössbauer studies of medium-carbon, high-chromium martensitic steels

    NASA Astrophysics Data System (ADS)

    Peters, J. A.; Kolk, B.; Bleloch, A. L.

    1986-02-01

    57Fe Mössbauer effect spectroscopy is employed to determine the relationship between the microstructure and the mechanical properties of martensitic steels with base composition Fe-10wt%Cr-0,26wt%C. The microstructure consists predominantly of two phases: martensite and austenite. The effect of low concentrations of both Mn and Ni on the structure and the mechanical properties of these steels is studied. The results indicate that Mn and Ni additions are equally effective in increasing the fraction of retained austenite. The austenite is an important phase since it is considered to be beneficial to the toughness of steel. However, we find that the impact toughness first decreases and then increases as a function of the fraction of austenite.

  13. Effect of cycled combustion ageing on a cordierite burner plate

    SciTech Connect

    Garcia, Eugenio

    2010-11-15

    A combination of {sup 57}Fe-Moessbauer spectroscopy and X-ray Powder Diffraction analysis has been employed to study modifications in chemical and mechanical stability occurring in a cordierite burner aged under combustion conditions which simulate the working of domestic boilers. Moessbauer study shows that Fe is distributed into the structural sites of the cordierite lattice as Fe{sup 2+} and Fe{sup 3+} ions located mostly at octahedral sites. Ferric oxide impurities, mainly hematite, are also present in the starting cordierite material accounting for {approx_equal}40% of the total iron phases. From Moessbauer and X-ray diffraction data it can be deduced that, under the combustion conditions used, new crystalline phases were formed, some of the substitutional Fe{sup 3+} ions existing in the cordierite lattice were reduced to Fe{sup 2+}, and ferric oxides underwent a sintering process which results in hematite with higher particle size. All these findings were detected in the burner zone located in the proximity of the flame and were related to possible chemical reactions which might explain the observed deterioration of the burner material. Research Highlights: {yields}Depth profile analyses used as a probe to understand changes in refractory structure. {yields}All changes take place in the uppermost surface of the burner, close to the flame. {yields}Reduction to Fe{sup 2+} of substitutional Fe{sup 3+} ions and partial cordierite decomposition. {yields}Heating-cooling cycling induces a sintering of the existing iron oxide particles. {yields}Chemical changes can explain the alterations observed in the material microstructure.

  14. Influence of Sn{sup 4+} and Sn{sup 4+}/Mg{sup 2+} doping on structural features and visible absorption properties of {alpha}-Fe{sub 2}O{sub 3} hematite

    SciTech Connect

    Gaudon, M.; Pailhe, N.; Majimel, J.; Wattiaux, A.; Abel, J.; Demourgues, A.

    2010-09-15

    Pure, Sn-doped and Mg/Sn co-doped {alpha}-Fe{sub 2}O{sub 3} hematite samples were synthesized by precipitation process. Fe{sub 2}O{sub 3} is the most popular red mineral pigment which is used largely in traditional ceramics, tar and concrete. The compounds were characterized by powder X-ray diffraction (XRD), scanning transmission electronic microscopy (energy dispersive X-ray cartography), Moessbauer spectroscopy, magnetic investigations versus temperature and visible-NIR spectroscopy. Both {sup 57}Fe and {sup 119}Sn Moessbauer analyses combined with rietveld XRD refinements are the ideal techniques to characterize tin-iron oxides. Hence, thanks to these techniques it was shown how the synthesis temperature influences directly the grain size and the dopants concentration limit which can be incorporated into the host hematite matrix. The stabilization of these tetravalent and divalent dopants into the hematite framework leads to reduce the crystal growth and to limit the (AF) ordering due to the formation of cationic vacancies. The study of the Morin magnetic transition emphasizes this demonstration. In a second part, the influence of the dopants incorporation on the material color was investigated in order to show which key parameters allow improving the red color saturation of iron oxides. In order to improve the red color of the hematites, it was shown that the introduction of cationic vacancies-limiting the octahedral distortion thanks to the interruption of the dissymmetric metal-metal orbital coupling-is the key point. Vacancies are created by Sn{sup 4+}, doping for an increase of the introduced Sn{sup 4+} concentration; it acts to the detriment of the color saturation. - Graphical Abstract: Sn-doped or Sn/Mg-doped Fe{sub 2}O{sub 3} hematites, were analyzed by X-ray diffraction refinement, Moessbauer spectroscopy, magnetic characterization and TEM investigations. Their color is correlated to the doping ions concentration.

  15. Local atomic arrangement in mechanosynthesized Co x Fe1-x-y Ni y alloys studied by Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Pikula, Tomasz

    2014-07-01

    Mechanosynthesized Co x Fe1-x-y Ni y alloys were examined using X-ray diffraction (XRD) and Mössbauer spectroscopy. In order to explain the shape of hyperfine magnetic field (HMF) distributions for the alloys, a local environment model based on a multinomial distribution was proposed. The model was in agreement with the XRD data and confirmed that the studied alloys were disordered solid solutions. It was successfully applied to describe the samples with bcc and fcc crystalline lattice type within the relatively broad range of components concentration. The results showed that the change of the crystalline lattice type does not cause an abrupt change of the HMF value. Moreover, a mean number of unpaired spins for the first coordination sphere may be used as a parameter to describe the HMF value experienced by 57Fe nucleus. Finally, a set of the most probable atomic configurations and their corresponding contributions to the HMF distribution were obtained.

  16. Mössbauer study of the effect of pH on Fe valence in iron-polygalacturonate as a medicine for human anaemia

    NASA Astrophysics Data System (ADS)

    Kuzmann, E.; Garg, V. K.; de Oliveira, A. C.; Klencsár, Z.; Szentmihályi, K.; Fodor, J.; May, Z.; Homonnay, Z.

    2015-02-01

    Iron-polygalacturonate complexes have been synthesized from polygalacturonic acid by applying a novel preparation method in order to develop medicine suitable for the effective iron supplementation of the human body in the case of anemia. Since the iron uptake depends on the oxidation state of iron, 57Fe Mössbauer spectroscopy was used to study the occurrence of different valence states in the iron-polygalacturonate complexes prepared under different circumstances. The Mössbauer-spectra indicated the presence of iron both in FeII and FeIII states in the investigated iron-polygalacturonate compounds, the occurrence of which varied with the preparation parameters. A correlation of the relative occurrence of iron valence states with the pH has been found. The relative occurrence of FeIII was found to increase with increasing pH. The knowledge of this correlation can help find optimum preparation conditions of iron-polygalacturonates to cure human anemia.

  17. Crystal and molecular structure and Raman and sup 127 I Moessbauer spectra of iodine(III) bis(fluorosulfate) iodide, I(OSO sub 2 F) sub 2 I

    SciTech Connect

    Birchall, T.; Denes, G.; Faggiani, R.; Frampton, C.S.; Gillespie, R.J.; Kapoor, R.; Vekris, J.E. )

    1990-04-18

    Iodine is oxidized by peroxodisulfuryl difluoride, S{sub 2}O{sub 6}F{sub 2}, to give I(OSO{sub 2}F){sub 2}I. The crystal structure of the orthorhombic type crystal is reported. The structure was solved by means of Patterson functions and refined by least squares to final agreement indices of R{sub 1} = 0.0353 and R{sub 2} = 0.0374 for 1,600 independent reflections. There are three primary bonds to the central iodine, I(1), (I(1)-OSO{sub 2}F = 2.086 (7) and 2.258 (7) {angstrom}; I(1)-I(2) = 2.676 (1) {angstrom}), which create a distorted T=shaped AX{sub 3}E{sub 2} geometry. The second iodine, I(2), has a primary bond to I(1) and a strong intermolecular secondary I(2)-O bond of length 2.655 (8) {angstrom} to one of the fluorosulfate groups that is colinear with the primary bond, giving an AXYE{sub 3} geometry about I(2). The Raman spectrum of the solid and the {sup 127}I Moessbauer spectrum are in full agreement with the structure found. 30 refs., 3 figs., 4 tabs.

  18. Mössbauer study of hyperfine interactions in EuFe2(As1-xPx)2 and BaFe2(As1-xPx)2

    NASA Astrophysics Data System (ADS)

    Sklyarova, A.; Tewari, G. C.; Lindén, J.; Mustonen, O.; Rautama, E.-L.; Karppinen, M.

    2015-03-01

    The magnetic properties of the pnictide superconductors with the nominal composition of BaFe2(As0.68P0.32)2 and EuFe2(As0.8P0.2)2 were studied by 57Fe Mössbauer spectroscopy. A superconducting transition at 30 K was detected and coexistence of magnetism and superconductivity at low temperatures was observed. The Mössbauer spectra show two iron-atom surroundings, which are attributed to undoped AFe2As2 and substituted AFe2(As1-xPx)2, with at least one phosphorus atom in the tetragonal iron environment, (A = Ba or Eu). These two iron-atom surroundings were attributed to one macroscopic AFe2(As1-xPx)2 phase.

  19. Moessbauer Mineralogy of Rock, Soil, and Dust at Gusev Crater, Mars: Spirit's Journey through Weakly Altered Olivine Basalt on the Plains and Pervasively Altered Basalt in the Columbia Hills

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Klingelhoefer, G.; Schroeder, C.; Rodionov, D. S.; Yen, A.; Ming, D. W.; deSouza, P. A., Jr.; Fleischer, I.; Wdowiak, T.; Gellert, R.; Bernhardt, B.; Evlanov, E. N.; Zubkov, B.; Foh, J.; Bonnes, U.; Kankeleit, E.; Guetlich, P.; Renz, F.; Squyres, S. W.; Arvidson, R. E.

    2006-01-01

    The Moessbauer spectrometer on Spirit measured the oxidation state of Fe, identified Fe-bearing phases, and measured relative abundances of Fe among those phases for surface materials on the plains and in the Columbia Hills of Gusev crater. Eight Fe-bearing phases were identified: olivine, pyroxene, ilmenite, magnetite, nanophase ferric oxide (npOx), hematite, goethite, and a Fe(3+)-sulfate. Adirondack basaltic rocks on the plains are nearly unaltered (Fe(3+)/Fe(sub T)<0.2) with Fe from olivine, pyroxene (Ol>Px), and minor npOx and magnetite. Columbia Hills basaltic rocks are nearly unaltered (Peace and Backstay), moderately altered (WoolyPatch, Wishstone, and Keystone), and pervasively altered (e.g., Clovis, Uchben, Watchtower, Keel, and Paros with Fe(3+)/Fe(sub T) approx.0.6-0.9). Fe from pyroxene is greater than Fe from olivine (Ol sometimes absent), and Fe(2+) from Ol+Px is 40-49% and 9-24% for moderately and pervasively altered materials, respectively. Ilmenite (Fe from Ilm approx.3-6%) is present in Backstay, Wishstone, Keystone, and related rocks along with magnetite (Fe from Mt approx. 10-15%). Remaining Fe is present as npOx, hematite, and goethite in variable proportions. Clovis has the highest goethite content (Fe from Gt=40%). Goethite (alpha-FeOOH) is mineralogical evidence for aqueous processes because it has structural hydroxide and is formed under aqueous conditions. Relatively unaltered basaltic soils (Fe(3+)/Fe(sub T) approx. 0.3) occur throughout Gusev crater (approx. 60-80% Fe from Ol+Px, approx. 10-30% from npOx, and approx. 10% from Mt). PasoRobles soil in the Columbia Hills has a unique occurrence of high concentrations of Fe(3+)-sulfate (approx. 65% of Fe). Magnetite is identified as a strongly magnetic phase in Martian soil and dust.

  20. ⁵⁷Fe polarization-dependent synchrotron Mössbauer spectroscopy using a diamond phase plate and an iron borate nuclear Bragg monochromator.

    PubMed

    Mitsui, Takaya; Imai, Yasuhiko; Masuda, Ryo; Seto, Makoto; Mibu, Ko

    2015-03-01

    Energy-domain (57)Fe polarization-dependent synchrotron radiation Mössbauer spectroscopy was developed by using a diamond X-ray phase plate and an iron borate nuclear Bragg monochromator. The former controls the polarization of the incident synchrotron radiation X-rays and the latter filters the (57)Fe-Mössbauer radiation with a narrow bandwidth of ∼3.4 Γ0 (Γ0 ≃ 4.7 neV: natural linewidth of the (57)Fe nucleus) from the broadband synchrotron radiation. The developed nuclear diffraction optics allowed (57)Fe-Mössbauer studies to be performed with various polarization states, i.e. linear polarization, circular polarization and non-polarization. In this paper, the spectrometer system, beam characterization, performance-test experiments and a grazing-incidence Mössbauer measurement of an isotope-enriched ((57)Fe: 95%) iron thin film are described. PMID:25723944

  1. EPR Spectroscopic Studies of [FeFe]-Hydrogenase Maturation

    PubMed Central

    Suess, Daniel L. M.

    2015-01-01

    Proton reduction and H2 oxidation are key elementary reactions for solar fuel production. Hydrogenases interconvert H+ and H2 with remarkable efficiency and have therefore received much attention in this context. For [FeFe]-hydrogenases, catalysis occurs at a unique cofactor called the H-cluster. In this article, we discuss ways in which EPR spectroscopy has elucidated aspects of the bioassembly of the H-cluster, with a focus on four case studies: EPR spectroscopic identification of a radical en route to the CO and CN− ligands of the H-cluster, tracing 57Fe from the maturase HydG into the H-cluster, characterization of the auxiliary Fe–S cluster in HydG, and isotopic labeling of the CN− ligands of HydA for electronic structure studies of its Hox state. Advances in cell-free maturation protocols have enabled several of these mechanistic studies, and understanding H-cluster maturation may in turn provide insights leading to improvements in hydrogenase production for biotechnological applications. PMID:26508821

  2. Mössbauer spectra study on Xiu-Yan Jade

    NASA Astrophysics Data System (ADS)

    Qiu, Zhaoming; Rang, Mei; Huang, Junjie

    1992-04-01

    Having beautiful colours and fine features, Xiu-Yan Jade is famous in the world. Mineralogically, Xiu-Yan Jade is serpentine jade. XRD, IR and TEM study indicate that the jade consists mainly of antigorite (m{Mg3(1-1/m)[Si2O5](OH)1+3(1-2/m)}) with a minor amount of chrysotile. Two favourite samples (PXA, PX1-t) are chosen for research on57Fe Mössbauer spectra. Two sets of quadrupole doublets are obtained from the spectra, The parameters of two samples, 1. 124 mm/s and 1. 119 mm/s of I. S. and 2. 732mm/s and 2. 716mm/s of Q. S. for Fe2+ in the octahedral and 0. 364mm/s and 0. 351mm/s of I. S. 0. 632 and 0. 546mm/s of Q. S. for Fe3+ in the octahedral, are only antigorite. Studies indicate that: (1) iron—ion in antigorite enters the lattice as impurity: (2)Fe2+ and Fe3+ substitute for Mg in the coordination octahedron: and (3) the colour of jade is related to content of Fe, and Fe3+/Fe2+≤1 is favourite for colour—forming.

  3. Structural transitions in La 0.95 Ba 0.05 Mn 0.98 57 Fe 0.02 O 3 under heat treatment

    NASA Astrophysics Data System (ADS)

    Sedykh, V.; Rusakov, V.

    2014-04-01

    Structural transitions in polycrystalline Ba-doped lanthanum manganite La0.95Ba0.05Mn0.98Fe0.02O3 + δ have been investigated under different cooling conditions after vacuum annealing (fast and slow cooling) by Mössbauer spectroscopy and X-ray diffraction (XRD) analysis. A rhombohedral structure of the synthesized La0.95Ba0.05Mn0.98Fe0.02O3 + δ sample transfers into a mixture of the orthorhombic PnmaI, PnmaII* and PnmaII phases (common space group Pnma) with a stoichiometric oxygen composition under vacuum annealing. The further vacuum annealing leads to fluctuations in a partial relation of the orthorhombic phases on fast cooling. This unusual behavior of the structural transitions are discussed.

  4. Insights into iron sources and pathways in the Amazon River provided by isotopic and spectroscopic studies

    NASA Astrophysics Data System (ADS)

    Mulholland, Daniel Santos; Poitrasson, Franck; Boaventura, Geraldo Resende; Allard, Thierry; Vieira, Lucieth Cruz; Santos, Roberto Ventura; Mancini, Luiz; Seyler, Patrick

    2015-02-01

    The present study investigated the weathering and transport mechanisms of Fe in the Amazon River. A particular emphasis was placed on Fe partitioning, speciation, and isotopic fractionation in the contrasting waters of the Solimões and Negro rivers and their mixing zone at the beginning of the Amazon River. Samples collected in the end-member rivers and thirteen sites distributed throughout the mixing zone were processed through frontal vacuum filtration and tangential-flow ultrafiltration to separate the different suspended solid fractions, i.e., particulate (P > 0.45 μm and P > 0.22 μm), colloidal (0.22 μm > C > 5 kDa) and truly dissolved elements (TD < 5 kDa). The Fe isotopic composition and electron paramagnetic resonance (EPR) species were measured on these different pore-sized fractions. The acidic and organo-Fe-rich waters of the Negro River displayed dissolved and colloidal fractions enriched in heavy isotopes (∼1.2‰, in δ57Fe values relative to IRMM-14), while the particulate fractions yielded light isotopic compositions of -0.344‰ for P > 0.22 μm and -0.104‰ for P > 0.45 μm fractions). The mineral particulate-rich waters of the Solimões River had dissolved and colloidal fractions with light isotopic composition (-0.532‰ and -0.176‰, respectively), whereas the particulate fractions yielded δ57Fe values close to those of the continental crust (i.e., -0.029‰ for P > 0.22 μm and 0.028‰ for P > 0.45 μm). Ten kilometers downstream from the Negro and Solimões junction, the concentrations of colloidal and dissolved Fe species deviate markedly from conservative mixing. A maximum Fe loss of 43 μg/L (i.e., 50% of the dissolved and colloidal Fe) is observed 110 km downstream from the rivers junction. The contrasting Negro and Solimões Rivers isotopic compositions along the pore-sized water fractions is attributable to the biogeochemical processes involving different types of upland soils and parental materials. For instance, the isotopic

  5. Mössbauer spectroscopy studies of selected conducting polypyrroles

    NASA Astrophysics Data System (ADS)

    Proń, A.; Kucharski, Z.; Budrowski, C.; Zagórska, M.; Krichene, S.; Suwalski, J.; Dehe, G.; Lefrant, S.

    1985-12-01

    Polypyrrole obtained by chemical oxidation of pyrrole in ethanol-water solution containing FeCl3 can be reduced chemically in Na+Naph-/THF solution and then reoxidized with FeCl3, SnCl4, and SbCl5. 57Fe and 119Sn Mössbauer spectra of the reaction products show only one type of iron and tin with Mössbauer parameters characteristic of FeCl-4 and SnCl-5. In the case of the oxidation with SbCl5, two nonequivalent antimony nuclei have been detected by 121Sb. The calculated isomer shift and quadrupole splitting values are consistent with SbCl-6 and SbCl3. The resonant absorption in all three systems studied is strongly temperature dependent and can be observed only at temperatures significantly lower than RT. This behavior indicates a low Mössbauer lattice temperature and an extremely loose bonding between the inserted anions and polymer chains.

  6. Nuclear dynamical diffraction using synchrotron radiation

    SciTech Connect

    Brown, D.E.

    1993-05-01

    The scattering of synchrotron radiation by nuclei is extensively explored in this thesis. From the multipole electric field expansion resulting from time-dependent nonrelativistic perturbation theory, a dynamical scattering theory is constructed. This theory is shown, in the many particle limit, to be equivalent to the semi-classical approach where a quantum mechanical scattering amplitude is used in the Maxwell inhomogeneous wave equation. The Moessbauer specimen whose low-lying energy levels were probed is a ferromagnetic lattice of {sup 57}Fe embedded in a yttrium iron garnet (YIG) crystal matrix. The hyperfine fields in YIG thin films were studied at low and room temperature using time-resolved quantum beat spectroscopy. Nuclear hyperfine structure quantum beats were measured using a fast plastic scintillator coincidence photodetector and associated electronics having a time resolution of 2.5 nsec. The variation of the quantum beat patterns near the Bragg [0 0 2] diffraction peak gave a Lamb-Moessbauer factor of 8.2{plus_minus}0.4. Exploring characteristic dynamical features in the higher order YIG [0 0 10] reflection revealed that one of the YIG crystals had bifurcated into two different layers. The dynamics of nuclear superradiance was explored. This phenomenon includes the radiative speedup exhibited by a collective state of particles, and, in striking concurrence, resonance frequency shifts. A speedup of a factor of 4 in the total decay rate and a beat frequency shift of 1{1/2} natural resonance linewidths were observed. Nuclear resonance scattering was also found to be a useful way of performing angular interferometry experiments, and it was used to observe the phase shift of a rotated quantum state. On the whole, nuclear dynamical diffraction theory has superbly explained many of the fascinating features of resonant magnetic dipole radiation scattered by a lattice of nuclei.

  7. Magnetic measurements of the transuranium elements and charge state characterization of actinides in monazite. Progress report

    SciTech Connect

    Huray, P. G.

    1980-01-01

    A micromagnetic susceptometer for the purpose of measuring extremely small sample quantities (on the microgram level) was designed, constructed, and calibrated in previous years. (The 1979 progress report gives details of its operation.) This device has operated without significant downtime in this funding period, and much progress has been made in the magnetic characterization of elements beyond Am in the periodic table. This program has roughly doubled man's knowledge of magnetism in Cm, Bk, and Cf, and includes the only Es magnetic measurements to date. The incorporation of an automatic data collection system in this period has made analysis much more accurate, and has allowed quicker turnaround of compounds and metals for study. Results obtained for the compounds and metals studied this year are summarized. The lanthanide orthophosphates are being investigated as an alternate means of primary containment for high-level actinide wastes. Researchers at the Oak Ridge National Laboratory are involved in preparation of actinide-doped compounds for all of the lanthanide transition series (La through Lu) for a study of leaching characteristics and E.S.R. classification. To aid this study the charge state of /sup 237/Np or /sup 57/Fe has been identified, either in the as-prepared compounds or following radioactive decay of /sup 241/Am via the Moessbauer Effect. The final charge state will be an influential variable in the immobilization characteristics of the waste products stored in this synthetic monazite form. 10 figures, 1 table. (RWR)

  8. Resonance Counters as the Best Tool for the Investigations in Material Science

    SciTech Connect

    Belyaev, A. A.; Irkaev, S. M.; Panchuck, V. V.; Semenov, V. G.; Volodin, V. S.

    2008-10-28

    Sensitivity and resolution play a crucial role when Moessbauer spectroscopy is used in the materials science. Application of resonance counters in Moessbauer spectrometers allows us to increase the parameters mentioned above, and also signal-to-noise ratio considerably. The last one provides diminishing the time needed for obtaining given statistical accuracy. We carried out investigations of development of optimal counters for following isotopes: {sup 57}Fe, {sup 119}Sn, and {sup 151}Eu. Influence of different parameters of resonant radiation converters on experimental results was considered theoretically. Optimization of design has been performed using mathematical modeling based on Monte-Carlo method. Comparison of different types of counters used for resonant detecting was carried out. Results of experimental works on selection of efficient radiation converters are given. Comparison of scintillation and gas resonance counters was carried out. FeAl and FeGe{sub 2} alloys and K{sub 2}MgFe(CN){sub 6} have been used as converters for experiments with {sup 57}Fe-isotope, CaSnO{sub 3} has been used for {sup 119}Sn and Eu{sub 2}O{sub 3} and EuF{sub 3}--for {sup 151}Eu isotope. Gamma-optical scheme for versatile spectrometer, which expands the range of application of resonant detection for other Moessbauer isotopes, was suggested.

  9. NiO/Fe(001): Magnetic anisotropy, exchange bias, and interface structure

    SciTech Connect

    Mlynczak, E.; Luches, P.

    2013-06-21

    The magnetic and structural properties of NiO/Fe epitaxial bilayers grown on MgO(001) were studied using magnetooptic Kerr effect (MOKE) and conversion electron Moessbauer spectroscopy (CEMS). The bilayers were prepared under ultra high vacuum conditions using molecular beam epitaxy with oblique deposition. Two systems were compared: one showing the exchange bias (100ML-NiO/24ML-Fe), ML stands for a monolayer, and another where the exchange bias was not observed (50ML-NiO/50ML-Fe). For both, the magnetic anisotropy was found to be complex, yet dominated by the growth-induced uniaxial anisotropy. The training effect was observed for the 100ML-NiO/24ML-Fe system and quantitatively described using the spin glass model. The composition and magnetic state of the interfacial Fe layers were studied using {sup 57}Fe-CEMS. An iron oxide phase (Fe{sup 3+}{sub 4}Fe{sup 2+}{sub 1}O{sub 7}), as thick as 31 A, was identified at the NiO/Fe interface in the as-deposited samples. The ferrimagnetic nature of the interfacial iron oxide film explains the complex magnetic anisotropy observed in the samples.

  10. Lattice dynamics in the FeSb[subscript 3] skutterudite

    SciTech Connect

    Moechel, A.; Sergueev, I.; Nguyen, N.; Long, Gary J.; Grandjean, Fernande; Johnson, D.C.; Hermann, R.P.

    2011-11-17

    Thin films of FeSb{sub 3} were characterized by electronic transport, magnetometry, x-ray diffraction, {sup 57}Fe and {sup 121}Sb nuclear inelastic scattering, and {sup 57}Fe Moessbauer spectroscopy. Resistivity and magnetometry measurements reveal semiconducting behavior with a 16.3(4) meV band gap and an effective paramagnetic moment of 0.57(6) {mu}B, respectively. A systematic comparison of the lattice dynamics with CoSb{sub 3} and EuFe{sub 4}Sb{sub 12} reveals that the Fe{sub 4}Sb{sub 12} framework is softer than the Co{sub 4}Sb{sub 12} framework, and that the observed softening and the associated lowering of the lattice thermal conductivity in the RFe{sub 4}Sb{sub 12} filled skutterudites are not only related to the filler but also to the Fe{sub 4}Sb{sub 12} framework.

  11. Behavior of iron in (Mg,Fe)SiO[subscript 3] post-perovskite assemblages at Mbar pressures

    SciTech Connect

    Jackson, Jennifer M.; Sturhahn, Wolfgang; Tschauner, Oliver; Lerche, Michael; Fei, Yingwei

    2010-10-04

    The electronic environment of the iron sites in postperovskite (PPv) structured ({sup 57}Fe,Mg)SiO{sub 3} has been measured in-situ at 1.12 and 1.19 Mbar at room temperature using {sup 57}Fe synchrotron Moessbauer spectroscopy. Evaluation of the time spectra reveals two distinct iron sites, which are well distinguished by their hyperfine fields. The dominant site is consistent with an Fe{sup 3+}-like site in a high spin state. The second site is characterized by a small negative isomer shift with respect to {alpha}-iron and no quadrupole splitting, consistent with a metallic iron phase. Combined with SEM/ EDS analyses of the quenched assemblage, our results are consistent with the presence of a metallic iron phase coexisting with a ferric-rich PPv. Such a reaction pathway may aid in our understanding of the chemical evolution of Earth's core-mantle-boundary region.

  12. Charge Transfer in FeOCl Intercalation Compounds and its Pressure Dependence: An X-ray Spectroscopic Study

    SciTech Connect

    I Jarrige; Y Cai; S Shieh; H Ishii; N Hiraoka; S Karna; W Li

    2011-12-31

    We present a study of charge transfer in Na-intercalated FeOCl and polyaniline-intercalated FeOCl using high-resolution x-ray absorption spectroscopy and resonant x-ray emission spectroscopy at the Fe-K edge. By comparing the experimental data with ab initio simulations, we are able to unambiguously distinguish the spectral changes which appear due to intercalation into those of electronic origin and those of structural origin. For both systems, we find that about 25% of the Fe sites are reduced to Fe{sup 2+} via charge transfer between FeOCl and the intercalate. This is about twice as large as the Fe{sup 2+} fraction reported in studies using Moessbauer spectroscopy. This discrepancy is ascribed to the fact that the charge transfer occurs on the same time scale as the Moessbauer effect itself. Our result suggests that every intercalated atom or molecule is involved in the charge-transfer process, thus making this process a prerequisite for intercalation. The Fe{sup 2+} fraction is found to increase with pressure for polyaniline-FeOCl, hinting at an enhancement of the conductivity in the FeOCl intercalation compounds under pressure.

  13. A computer program for Moessbauer data processing

    NASA Technical Reports Server (NTRS)

    Howser, L. M.; Singh, J. J.; Smith, R. E., Jr.

    1972-01-01

    A computer program to analyze Mossbauer data is presented in detail. The least-squares curve fitting techniques described apply to single line spectra, single hyperfine spectra, or when the constituent spectra are separated well enough to let the individual absorption peaks stand alone. The present program is not adapted for complex spectra resulting from the existence of several local environments in the absorber iron alloy. Sample problems are presented to aid the user in setting up and running the program. The program is written in FORTRAN 4 language for the Control Data 6000 series digital computer with the SCOPE 3.0 operating system and requires approximately 115,000 octal locations of core storage. A typical case with one absorption peak runs in 20 seconds, and a typical problem with six absorption peaks requires 50 seconds.

  14. MOESSBAUER EFFECT IN HEMOGLOBIN WITH DIFFERENT LIGANDS.

    PubMed

    GONSER, U; GRANT, R W; KREGZDE, J

    1964-02-14

    Recoil-free nuclear gamma-ray resonance adsorption was observed in the iron-57 of blood. The spectral parameters are dependent on the ligand bound to the iron atoms in hemoglobin. The results are interpreted in terms of isomeric shifts and quad rupole splittings. PMID:14081237

  15. Moessbauer mineralogy of calcined Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Morris, Richard V.; Zolensky, M. E.; Hiroi, T.; Lipschutz, M. E.

    1994-01-01

    The three Antarctic meteorites B7904, Y82162, and Y86720 are unusual because they have characteristics in common with both CI and CM groups and because they apparently underwent thermal alteration after hydrous alteration on their parent body. They are also spectrally similar (visible and near-IR) to C, G, B, and F asteroids, which may imply that the surface materials on those asteroids may have undergone thermal alteration. Based on the reflectance spectra of samples of Murchison (CM2 carbonaceous chondrite) that were thermally altered in the laboratory (cryopumped and initial 10(exp -5) atm H2), Hiroi et al. concluded that putative thermal alteration occurred at temperatures of 600 to 1000 C. Similar experiments have been done on Murchison and reported mineralogical changes based on data from transmission electron diffraction microscopy, electron diffraction, and analytical electron microscopy. We report here the Mossbauer mineralogy of the same samples of thermally-altered Murchison. Mossbauer mineralogy gives the molar distribution of Fe among its oxidation states and iron-bearing mineralogies.

  16. Moessbauer spectroscopy of the SNC meteorite Zagami

    NASA Technical Reports Server (NTRS)

    Agerkvist, D. P.; Vistisen, L.

    1993-01-01

    We have performed Mossbauer spectroscopy on two different pieces of the meteorite Zagami belonging to the group of SNC meteorites. In one of the samples we found a substantial amount of olivine inter grown with one kind of pyroxene, and also another kind of pyroxene very similar to the pyroxene in the other sample we examined. Both samples showed less than 1 percent of Fe(3+) in the silicate phase. The group of SNC meteorites called shergottites, to which Zagami belongs, are achondrites whose texture, mineralogy and composition resembles those of terrestrial diabases. The results from the investigation are presented.

  17. Nuclear forward scattering vs. conventional Mossbauer studies of atomically tailored Eu-based materials.

    SciTech Connect

    Konjhodzic, A.; Adamczyk, A.; Hasan, Z.; Alp, E. E.; Sturhahn, W.; Zhao, J.; Carroll, J. J.; Vagizov, F.; Univ. of Philadelphia; Youngstown State Univ.

    2006-01-01

    With the decrease in size of devices, rapid characterization of nano-devices is an inevitable necessity. It is shown that Moessbauer spectroscopy using synchrotron radiation from the advanced photon source provides such a tool of investigation. Results are presented and compared for conventional Moessbauer and Nuclear Forward Scattering for {sup 151}Eu-doped magnesium sulfide as an example, especially at low concentrations.

  18. An FTIR and ESR study of iron doped calcium borophosphate glass-ceramics

    NASA Astrophysics Data System (ADS)

    Karabulut, M.; Popa, A.; Borodi, G.; Stefan, R.

    2015-12-01

    A series of glasses in the xFe2O3-(100-x) [42B2O3-24CaO-34P2O5] system has been prepared for x = 0-10. Structure of as casted glasses and their heat treated counterparts have been studied by X-ray diffraction, infrared and electron spin resonance spectroscopies. Amorphous nature of all of the compositions studied is confirmed by the XRPD spectra. After the heat treatment, besides the main BPO4 phase, CaBPO5 and Ca(PO3) crystalline phases were identified in the iron free glass while B0.57Fe0.43PO4 phase was also observed in the XRD pattern of iron containing samples. FTIR spectra indicate changes in the glass network upon iron addition. X-band ESR spectra exhibits resonance signals at g ∼ 2.0 and g ∼ 4.3 for all analyzed samples. A supplementary line centered at g ∼ 6 appears after the thermal treatment. The nature of ESR absorption signals and influence of iron content on the evolution of ESR parameters are discussed.

  19. Recent advances in biosynthetic modeling of nitric oxide reductases and insights gained from nuclear resonance vibrational and other spectroscopic studies

    DOE PAGESBeta

    Chakraborty, Saumen; Reed, Julian; Sage, Timothy; Branagan, Nicole C.; Petrik, Igor D.; Miner, Kyle D.; Hu, Michael Y.; Zhao, Jiyong; Alp, E. Ercan; Lu, Yi

    2015-08-14

    This Forum Article focuses on recent advances in structural and spectroscopic studies of biosynthetic models of nitric oxide reductases (NORs). NORs are complex metalloenzymes found in the denitrification pathway of Earth's nitrogen cycle where they catalyze the proton-dependent twoelectron reduction of nitric oxide (NO) to nitrous oxide (N2O). While much progress has been made in biochemical and biophysical studies of native NORs and their variants, a. clear mechanistic understanding of this important metalloenzyme related to its function is still elusive. We report herein UV vis and nuclear resonance vibrational spectroscopy (NRVS) studies of mononitrosylated intermediates of the NOR reaction ofmore » a biosynthetic model. The ability to selectively substitute metals at either heme or nonheme metal sites allows the introduction of independent 57Fe probe atoms at either site, as well as allowing the preparation of analogues of stable reaction intermediates by replacing either metal with a redox inactive metal. Together with previous structural and spectroscopic results, we summarize insights gained from studying these biosynthetic models toward understanding structural features responsible for the NOR activity and its mechanism. As a result, the outlook on NOR modeling is also discussed, with an emphasis on the design of models capable of catalytic turnovers designed based on close mimics of the secondary coordination sphere of native NORs.« less

  20. Recent advances in biosynthetic modeling of nitric oxide reductases and insights gained from nuclear resonance vibrational and other spectroscopic studies.

    PubMed

    Chakraborty, Saumen; Reed, Julian; Sage, J Timothy; Branagan, Nicole C; Petrik, Igor D; Miner, Kyle D; Hu, Michael Y; Zhao, Jiyong; Alp, E Ercan; Lu, Yi

    2015-10-01

    This Forum Article focuses on recent advances in structural and spectroscopic studies of biosynthetic models of nitric oxide reductases (NORs). NORs are complex metalloenzymes found in the denitrification pathway of Earth's nitrogen cycle where they catalyze the proton-dependent two-electron reduction of nitric oxide (NO) to nitrous oxide (N2O). While much progress has been made in biochemical and biophysical studies of native NORs and their variants, a clear mechanistic understanding of this important metalloenzyme related to its function is still elusive. We report herein UV-vis and nuclear resonance vibrational spectroscopy (NRVS) studies of mononitrosylated intermediates of the NOR reaction of a biosynthetic model. The ability to selectively substitute metals at either heme or nonheme metal sites allows the introduction of independent (57)Fe probe atoms at either site, as well as allowing the preparation of analogues of stable reaction intermediates by replacing either metal with a redox inactive metal. Together with previous structural and spectroscopic results, we summarize insights gained from studying these biosynthetic models toward understanding structural features responsible for the NOR activity and its mechanism. The outlook on NOR modeling is also discussed, with an emphasis on the design of models capable of catalytic turnovers designed based on close mimics of the secondary coordination sphere of native NORs. PMID:26274098

  1. Novel rhenium gasket design for nuclear resonant inelastic x-ray scattering at high pressure

    SciTech Connect

    Tanis, Elizabeth A.; Giefers, Hubertus; Nicol, Malcolm F.

    2008-02-15

    For the first time, a highly absorbing element, rhenium, has been proven to be a strong, reliable, and safe gasket material for achieving high pressure in nuclear resonant inelastic x-ray scattering (NRIXS) experiments. Rhenium foil was cut into rectangular slices and in order to reduce absorption, the elevated imprint due to preindenting of the gasket is removed using electrical discharge machining. By utilizing this novel gasket design, transmission losses were mitigated while performing NRIXS experiments conducted on the {sup 119}Sn and {sup 57}Fe Moessbauer isotopes.

  2. Techniques for inelastic x-ray scattering with {mu}eV resolution.

    SciTech Connect

    Rohlsberger, R.

    1998-10-23

    We introduce a novel type of spectrometer that provides a {micro}eV bandpass together with a tunability over a few meV. The technique relies on nuclear resonant scattering (Moessbauer effect) of synchrotrons radiation at the 14.4-keV resonance of {sup 57}Fe. Energy tuning is achieved by the Doppler effect in high speed rotary motion. The resonantly scattered monochromatic radiation is extracted by a polarization filtering technique or by spatial separation due to the ''nuclear lighthouse effect''.

  3. Backscattering Mössbauer MIMOS II and XRF studies on tektites from different strewn fields

    NASA Astrophysics Data System (ADS)

    Costa, B. F. O.; Klingelhöfer, G.; Panthöfer, M.; Alves, E. I.

    2014-04-01

    Room temperature 57Fe Mössbauer spectroscopy has been used to obtain information on the redox and coordination of iron in tektites. A MIMOS II spectrometer in backscattering geometry has been used in the study, so that no sample preparation at all was required. X-ray fluorescence has been used to determine the composition of the tektites. Mössbauer spectra have been deconvoluted using three extended Voigt-based profiles to allow quantitative analysis of iron atoms valence and coordination. In all tektites, the Fesites have been distinguished in Fe with octahedral and tetrahedral coordination. The Feoctahedral sites show a region of isomer shift (IS) and quadrupole splitting (QS), IS 1.02-1.14 mm/s and QS 1.82-2.12 mm/s, relative to -Fe. The Fetetrahedral sites show a region of hyperfine parameters of IS = 0.59-0.89 mm/s and QS = 1.14-1.60 mm/s. The Fe3+sites show IS = 0.11-0.33 mm/s and QS = 0.02-0.04 mm/s. The Fe3+/Fe2+ ratio was found to be 0.025-0.149.

  4. Mössbauer Study of Graphite-Containing Iron Oxide Nanoparticles

    NASA Astrophysics Data System (ADS)

    Sorescu, Monica; Trotta, Richard

    2016-03-01

    Graphite-doped hematite and magnetite nanoparticles systems (~50 nm) were prepared by mechanochemical activation for milling times ranging from 2 to 12 hours. Their structural and magnetic properties were studied by 57Fe Mössbauer spectroscopy. The spectra corresponding to the hematite milled samples were analyzed by considering two sextets, corresponding to the incorporation of carbon atoms into the iron oxide structure. For ball-milling time of 12 hours a quadrupole split doublet has been added, representing the contribution of ultrafine particles. The Mössbauer spectra of graphite-doped magnetite were resolved considering a sextet and a magnetic hyperfine field distribution, corresponding to the tetrahedral and octahedral sublattices of magnetite, respectively. A quadrupole split doublet was incorporated in the fitting of the 12-hour milled sample. The recoilless fraction for all samples was determined using our previously developed dual absorber method. It was found that the recoilless fraction of the graphite-doped hematite nanoparticles decreases as function of ball-milling time. The f factor of graphite-containing magnetite nanoparticles for the tetrahedral sites stays constant, while that of the octahedral sublattice decreases as function of ball-milling time. These findings reinforce the idea that carbon atoms exhibit preference for the octahedral sites of magnetite.

  5. Mössbauer and EPR Study of Reaction Intermediates of Cytochrome P450

    NASA Astrophysics Data System (ADS)

    Schünemann, V.; Trautwein, A. X.; Jung, C.; Terner, J.

    2002-06-01

    We present a complementary Mössbauer and EPR study on reaction intermediates of substrate-free and substrate-bound cytochrome P450cam from Pseudomonas putida prepared by the freeze-quench method from 57Fe-labeled P450cam using peroxy acetic acid as oxidizing agent. When reacting the substrate-free P450cam for 8 ms reaction time the reaction mixture consists of ˜85% of ferric low-spin iron (Fe(III)) with g-factors and hyperfine parameters of the starting material; the remaining ˜15% are identified as ferryl iron (Fe(IV); S Fe=1) by its Mössbauer signature. Parallel to the ferryl iron a tyrosine radical ( S rad=1/2) is formed. The two paramagnetic species are not exchange-coupled; however, they are close enough to significantly influence the (EPR) relaxation behavior of the radical spin. In the case of substrate-bound P450cam only trace amounts of the tyrosine radical are formed within 8 ms (<3%); within the accuracy of Mössbauer spectroscopy (5%) iron(IV) can not be detected. The results point to Tyr-96, which is hydrogen-bonded to the substrate camphor, as the candidate for the observed tyrosine radical.

  6. Magnetization and Mössbauer study of partially oxidized iron cluster films deposited on HOPG

    NASA Astrophysics Data System (ADS)

    Tarras-Wahlberg, Nils; Kamali, Saeed; Andersson, Mats; Johansson, Christer; Rosén, Arne

    2014-10-01

    Iron clusters produced in a laser vaporization source were deposited to form cluster-assembled thin films with different thicknesses on highly oriented pyrolytic graphite substrates. The development of oxidation of the clusters with time, up to three years, was investigated by magnetic measurements using an alternating gradient magnetometer. Furthermore, to receive information about the oxidation states, clusters of 57Fe were studied using Mössbauer spectroscopy. The magnetic analysis shows a time evolution of the saturation magnetization, remanence, and coercivity, determined from the hysteresis curves characteristic of a progressing oxidation. The different thicknesses of the iron cluster films as well as a protective layer of vanadium influence the magnetic properties when the samples are subjected to oxidation with time. While the saturation magnetization and remanence decrease and reach half the initial values for almost all the samples after three years, the coercivity increases for all samples and is more substantial for the thickest sample with a vanadium protective layer. This value is three folded after three years. Furthermore, based on a core-shell model and using the saturation magnetization values we have been able to quantitatively calculate the amount of the increase of Fe-oxide as a function of time. The Mössbauer spectroscopy shows peaks corresponding to iron metal and maghemite.

  7. Iron absorption in raw and cooked bananas: a field study using stable isotopes in women

    PubMed Central

    García, Olga P.; Martínez, Mara; Romano, Diana; Camacho, Mariela; de Moura, Fabiana F.; Abrams, Steve A.; Khanna, Harjeet K.; Dale, James L.; Rosado, Jorge L.

    2015-01-01

    Background Banana is a staple food in many regions with high iron deficiency and may be a potential vehicle for iron fortification. However, iron absorption from bananas is not known. Objective The objective of this study was to evaluate total iron absorption from raw and cooked bananas. Design Thirty women (34.9±6.6 years) from rural Mexico were randomly assigned to one of two groups each consuming: 1) 480 g/day of raw banana for 6 days, or 2) 500 g/day of cooked banana for 4 days. Iron absorption was measured after extrinsically labeling with 2 mg of 58Fe and a reference dose of 6 mg 57Fe; analysis was done using ICP-MS. Results Iron content in cooked bananas was significantly higher than raw bananas (0.53 mg/100 g bananas vs. 0.33 mg/100 mg bananas, respectively) (p<0.001). Percent iron absorption was significantly higher in raw bananas (49.3±21.3%) compared with cooked banana (33.9±16.2%) (p=0.035). Total amount of iron absorbed from raw and cooked bananas was similar (0.77±0.33 mg vs. 0.86±0.41 mg, respectively). Conclusion Total amount of absorbed iron is similar between cooked and raw bananas. The banana matrix does not affect iron absorption and is therefore a potential effective target for genetic modification for iron biofortification. PMID:25660254

  8. Fe and Cu isotope fractionation between chalcopyrite and dissolved metal species during hydrothermal recrystallization: An experimental study at 350°C and 500 bars

    NASA Astrophysics Data System (ADS)

    Syverson, D. D.; Luhmann, A. J.; Tan, C.; Borrok, D. M.; Ding, K.; Seyfried, W. E., Jr.

    2015-12-01

    The equilibrium Fe and Cu isotope fractionation factor between chalcopyrite and dissolved metal species was determined under hydrothermal conditions at 350°C and 500 bars. The experiments took advantage of gold-cell reaction technology, allowing time-series sampling of solution during the hydrothermal recrystallization of chalcopyrite over 3000 hours. One of the recrystallization experiments utilized an anomalous 57Fe spike in solution to quantify the degree and rate of isotopic exchange towards equilibrium between mineral and fluid reservoirs. The time-series 57Fe spike data suggests that chalcopyrite exchanges rapidly with dissolved Fe and Cu in solution and the isotopic fractionation between each metal-bearing reservoir throughout reaction progress, upon dissolution and recrystallization, represents close to equilibrium conditions. The isotope data indicate that the equilibrium fractionation between chalcopyrite and dissolved Fe and Cu at 350°C, Δ56FeCpy-Fe(aq), is 0.129±0.171‰ and Δ65CuCpy-Fe(aq), is -0.201±0.341‰ (2σ), and are in good agreement with recent theoretical equilibrium predictions. Comparison of the experimental data from this study with conjugate chalcopyrite and dissolved Fe and Cu pairs from a variety of hydrothermal systems along the mid-ocean ridge system indicates that chalcopyrite precipitates and recrystallizes at isotopic equilibrium with the fluid during cooling upon ascent to the seafloor. The rapid exchange between the mineral and fluid metal-reservoirs suggests that chalcopyrite effectively records the isotopic composition of the coexisting hydrothermal fluid during the evolution of hydrothermal systems. In addition, the pyrite-chalcopyrite equilibrium Fe isotope fractionation, Δ56FePyr-Cpy, at 350°C is quantified by combination of pyrite-Fe2+(aq) equilibrium fractionation data from Syverson et al., [2013] with chalcopyrite-Fe2+(aq) from this study, resulting in a fractionation of 0.861±0.337‰ (2σ). The empirical

  9. H-bonding scheme and cation partitioning in axinite: a single-crystal neutron diffraction and Mössbauer spectroscopic study

    NASA Astrophysics Data System (ADS)

    Gatta, G. Diego; Redhammer, Günther J.; Guastoni, Alessandro; Guastella, Giorgio; Meven, Martin; Pavese, Alessandro

    2016-05-01

    The crystal chemistry of a ferroaxinite from Colebrook Hill, Rosebery district, Tasmania, Australia, was investigated by electron microprobe analysis in wavelength-dispersive mode, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), 57Fe Mössbauer spectroscopy and single-crystal neutron diffraction at 293 K. The chemical formula obtained on the basis of the ICP-AES data is the following: ^{X1,X2} {{Ca}}_{4.03} Y ( {{{Mn}}_{0.42} {{Mg}}_{0.23} {{Fe}}^{2 + }_{1.39} } )_{Σ 2.04} ^{Z1,Z2} ( {{{Fe}}^{3 + }_{0.15} {{Al}}_{3.55} {{Ti}}_{0.12} } )_{Σ 3.82} ^{T1,T2,T3,T4} ( {{{Ti}}_{0.03} {{Si}}_{7.97} } )_{Σ 8} ^{T5} {{B}}_{1.96} {{O}}_{30} ( {{OH}} )_{2.18} . The 57Fe Mössbauer spectrum shows unambiguously the occurrence of Fe2+ and Fe3+ in octahedral coordination only, with Fe2+/Fe3+ = 9:1. The neutron structure refinement provides a structure model in general agreement with the previous experimental findings: the tetrahedral T1, T2, T3 and T4 sites are fully occupied by Si, whereas the T5 site is fully occupied by B, with no evidence of Si at the T5, or Al or Fe3+ at the T1- T5 sites. The structural and chemical data of this study suggest that the amount of B in ferroaxinite is that expected from the ideal stoichiometry: 2 a.p.f.u. (for 32 O). The atomic distribution among the X1, X2, Y, Z1 and Z2 sites obtained by neutron structure refinement is in good agreement with that based on the ICP-AES data. For the first time, an unambiguous localization of the H site is obtained, which forms a hydroxyl group with the oxygen atom at the O16 site as donor. The H-bonding scheme in axinite structure is now fully described: the O16- H distance (corrected for riding motion effect) is 0.991(1) Å and an asymmetric bifurcated bonding configuration occurs, with O5 and O13 as acceptors [i.e. with O16··· O5 = 3.096(1) Å, H··· O5 = 2.450(1) Å and O16- H··· O5 = 123.9(1)°; O16··· O13 = 2.777(1) Å, H··· O13 = 1.914(1) Å and O16- H··· O13 = 146

  10. Unusual 5f magnetism in the U2Fe3Ge ternary Laves phase: a single crystal study.

    PubMed

    Henriques, M S; Gorbunov, D I; Waerenborgh, J C; Havela, L; Shick, A B; Diviš, M; Andreev, A V; Gonçalves, A P

    2013-02-13

    Magnetic properties of the intermetallic compound U(2)Fe(3)Ge were studied on a single crystal. The compound crystallizes in the hexagonal Mg(2)Cu(3)Si structure, an ordered variant of the MgZn(2) Laves structure (C14). U(2)Fe(3)Ge displays ferromagnetic order below the Curie temperature T(C) = 55 K and presents an exception to the Hill rule, as the nearest inter-uranium distances do not exceed 3.2 Å. Magnetic moments lie in the basal plane of the hexagonal lattice, with the spontaneous magnetic moment M(s) = 1.0 μ(B)/f.u. at T = 2 K. No anisotropy within the basal plane is detected. In contrast to typical U-based intermetallics, U(2)Fe(3)Ge exhibits very low magnetic anisotropy, whose field does not exceed 10 T. The dominance of U in the magnetism of U(2)Fe(3)Ge is suggested by the (57)Fe Mössbauer spectroscopy study, which indicates very low or even zero Fe moments. Electronic structure calculations are in agreement with the observed easy-plane anisotropy but fail to explain the lack of an Fe contribution to the magnetism of U(2)Fe(3)Ge. PMID:23315489

  11. Unusual 5f magnetism in the U2Fe3Ge ternary Laves phase: a single crystal study

    NASA Astrophysics Data System (ADS)

    Henriques, M. S.; Gorbunov, D. I.; Waerenborgh, J. C.; Havela, L.; Shick, A. B.; Diviš, M.; Andreev, A. V.; Gonçalves, A. P.

    2013-02-01

    Magnetic properties of the intermetallic compound U2Fe3Ge were studied on a single crystal. The compound crystallizes in the hexagonal Mg2Cu3Si structure, an ordered variant of the MgZn2 Laves structure (C14). U2Fe3Ge displays ferromagnetic order below the Curie temperature TC = 55 K and presents an exception to the Hill rule, as the nearest inter-uranium distances do not exceed 3.2 Å. Magnetic moments lie in the basal plane of the hexagonal lattice, with the spontaneous magnetic moment Ms = 1.0 μB/f.u. at T = 2 K. No anisotropy within the basal plane is detected. In contrast to typical U-based intermetallics, U2Fe3Ge exhibits very low magnetic anisotropy, whose field does not exceed 10 T. The dominance of U in the magnetism of U2Fe3Ge is suggested by the 57Fe Mössbauer spectroscopy study, which indicates very low or even zero Fe moments. Electronic structure calculations are in agreement with the observed easy-plane anisotropy but fail to explain the lack of an Fe contribution to the magnetism of U2Fe3Ge.

  12. Constraining the origins of the magnetism of lepidocrocite (γ-FeOOH): a Mössbauer and magnetisation study

    NASA Astrophysics Data System (ADS)

    Guyodo, Yohan; Bonville, Pierre; Till, Jessica; Ona-Nguema, Georges; Lagroix, France; Menguy, Nicolas

    2016-03-01

    Lepidocrocite, a widespread environmentally relevant iron oxyhydroxide, has been investigated for decades using 57Fe Mössbauer spectroscopy and magnetic measurements. However, a coherent and comprehensive interpretation of all the data is still lacking due to seemingly contradictory interpretations. On one hand, temperature dependence of magnetic susceptibility and Mössbauer spectra resemble those of superparamagnetic nanoparticles with diameters less than 10 nm even though physically particles are lath-shaped with lengths on the order of 100-300 nm. On the other hand, in-field Mössbauer spectra show that lepidocrocite is an antiferromagnet and becomes paramagnetic above 50-70 K, a temperature close to the blocking temperature deduced from susceptibility data. The present study investigates a well-characterized synthetic sample of lepidocrocite, includes modelling of Mössbauer spectra and dc and ac magnetization data, and proposes a solution to this paradox. The new data are coherent with the presence of two entities in lepidocrocite: a bulk antiferromagnetic matrix and sparse ferrimagnetic nanosized inclusions (d = 3.4 nm), akin to maghemite, embedded within. The presence of nanosized ferrimagnetic inclusions is confirmed for the first time by Mössbauer spectroscopy.

  13. Studies of iron impurities in YxPr1-xBa2Cu3O7-delta

    NASA Technical Reports Server (NTRS)

    Swartzendruber, L. J.; Bennett, L. H.; Ritter, J.; Rubinstein, M.; Harford, M. Z.

    1990-01-01

    Pr is the only rare earth which, when substituted for Y in YBa2Cu3O7, significantly alters the superconducting transition temperature T(sub c) without changing the crystal structure. For YxPr1-xBa2Cu3O7-delta with delta approx. equal to 0, T(sub c) is reduced rapidly as x is increased, reaching zero for x about 0.5. For x above 0.5 the compound is antiferromagnetic with a Neel temperature that increases with increasing x, rising to above room temperature for x near 1. A similar behavior is observed when the oxygen deficit delta is increased from zero to 1 with x=0. For the case of Pr substitution, the drop in T(sub c) is believed due to magnetic interactions. For the case of varying delta with x=0, the drop can be attributed to a combination of magnetic interactions, band filling, and changes in crystal structure. To study these effects, the Mossbauer effect of 57 Fe atoms substituted for the Cu atoms has been observed as a function of delta, x, and temperature. The observed spectra are all well described by a two quadrupole-split pairs, a central singlet, and a six-line magnetic hyperfine field pattern. For several Pr compositions both delta and temperature were varied, and the results support the hypothesis that a magnetic interaction exists between the Fe in the Cu lattice and the substitutional Pr atoms.

  14. Mössbauer and magnetization studies of A0.8Fe2 - ySe2 (A = K, Rb and K/Tl)

    NASA Astrophysics Data System (ADS)

    Nowik, I.; Felner, I.; Zhang, M.; Wang, A. F.; Chen, X. H.

    2011-09-01

    57Fe Mössbauer spectroscopy and dc magnetization studies of the magneto-superconducting tetragonal A0.8Fe2 - ySe2 (A = K, Rb and K/Tl, y = 0.2-0.3) materials at temperatures of 5-550 K have been performed. Below the superconducting transition, magnetization studies performed under low applied fields (H), on both Rb0.8Fe2 - ySe2 and K0.3Tl0.5Fe2 - ySe2 single crystals, show a positive field-cooled branch known as the paramagnetic-Meissner effect for H\\parallel ab but not for H\\parallel c . This paramagnetic-Meissner effect is attributed to a peculiar isothermal hysteresis loop obtained for H\\parallel ab . Despite being superconducting, due to the antiferromagnetic nature of the materials, Mössbauer spectroscopy studies exhibit well-defined sextets at low temperatures. The full diagonalization of the hyperfine interaction spin Hamiltonian shows clearly that the iron moments are tilted by θ ~ 40°-45° away from the c-axis of the low-temperature tetragonal type structure. Moreover, long-term Mössbauer spectroscopy measurements at elevated temperatures suppress the antiferromagnetic state, and the materials measured after cooling to ambient temperatures exhibit a paramagnetic doublet only; its origin is discussed.

  15. Moessbauer effect and X-ray distribution function analysis in complex Na{sub 2}O-CaO-ZnO-Fe{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-SiO{sub 2} glasses and glass-ceramics

    SciTech Connect

    Romero, M.; Rincon, J.M.; Musik, S.; Kozhukharov, V.

    1999-05-01

    Moessbauer spectroscopy at room temperature was carried out to determine the state of iron ions in complex glasses and glass-ceramics in the SiO{sub 2}-CaO-ZnO-Na{sub 2}O-Fe{sub 2}O{sub 3}-Al{sub 2}O{sub 3} system. Isomer shift values of the glasses suggest that Fe{sup 3+} and Fe{sup 2+} are in tetrahedral and octahedral coordination, respectively. The spectrum of the glass-ceramic shows that about 60 wt% total iron is in the magnetite phase. The Fe{sup +3}/Fe{sup +2} ratio varies with the total iron oxide content of the glasses, indicating that the vitreous network is more distorted when the iron content is greater. X-ray diffraction measurements were carried out to obtain the radial distribution function (RDF). The interatomic distances for Si-Si and Si-O have been determined. The complex composition of these glasses does not allow the estimation of Al-O and Fe-O distances.

  16. Study of the surface chemistry and morphology of single walled carbon nanotube-magnetite composites

    SciTech Connect

    Marquez-Linares, F.; Uwakweh, O.N.C.; Lopez, N.; Chavez, E.; Polanco, R.; Morant, C.; Sanz, J.M.; Elizalde, E.; Neira, C.; Nieto, S.; Roque-Malherbe, R.

    2011-03-15

    The study of the morphologies of the single walled carbon nanotube (SWCNT), magnetite nanoparticles (MNP), and the composite based on them was carried with combined X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). These techniques together with thermogravimetric analyses (TGA) and diffuse reflectance infrared transform spectroscopy (DRIFTS) confirmed the production of pure single phases, and that the composite material consisted of MNP attached to the outer surface of the SWCNT. The Moessbauer spectroscopy (MS) research showed the presence of a large quantity of Lewis acid sites in the highly dispersed magnetite particles supported on the SWCNT outer surface. The DRIFTS carbon dioxide adsorption study of the composites revealed significant adsorption of carbon dioxide, fundamentally in the Lewis acid sites. Then, the Lewis acid sites were observed to be catalytically active. Further, the electron exchange between the Lewis acid sites and the basic or amphoteric adsorbed molecules could influence the magnetic properties of the magnetite. Consequently, together with this first ever use of MS in the study of Lewis acid sites, this investigation revealed the potential of the composites for catalytic and sensors applications. -- Graphical abstract: A large amount of Lewis acid sites were found in the highly dispersed magnetite which is supported on the SWCNT outer surface. Display Omitted Research highlights: {yields} The obtained materials were completely characterized with XRD, Raman and SEM-TEM. {yields} DRIFT, TGA and adsorption of the composites allowed understand the material formation. {yields} This is the first report of a study of Lewis sites by Moessbauer spectroscopy.

  17. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy.

    PubMed

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B; Gee, Leland B; Scott, Aubrey D; Yoda, Yoshitaka; Tanaka, Yoshihito; Lubitz, Wolfgang; Cramer, Stephen P

    2015-01-01

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the (57)Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique 'wagging' mode involving H(-) motion perpendicular to the Ni(μ-H)(57)Fe plane was studied using (57)Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)(57)Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe-CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)(57)Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)(57)Fe(CO)3](+) and DFT calculations, which collectively indicate a low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H(-) binding Ni more tightly than Fe. The present methodology is also relevant to characterizing Fe-H moieties in other important natural and synthetic catalysts. PMID:26259066

  18. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy

    NASA Astrophysics Data System (ADS)

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B.; Gee, Leland B.; Scott, Aubrey D.; Yoda, Yoshitaka; Tanaka, Yoshihito; Lubitz, Wolfgang; Cramer, Stephen P.

    2015-08-01

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique `wagging' mode involving H- motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)57Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe-CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)57Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)57Fe(CO)3]+ and DFT calculations, which collectively indicate a low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H- binding Ni more tightly than Fe. The present methodology is also relevant to characterizing Fe-H moieties in other important natural and synthetic catalysts.

  19. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy

    SciTech Connect

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B.; Gee, Leland B.; Scott, Aubrey D.; Yoda, Yoshitaka; Lubitz, Wolfgang; Cramer, Stephen P.

    2015-08-10

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique ‘wagging’ mode involving H- motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)57Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe–CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)57Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)57Fe(CO)3]+ and DFT calculations, which collectively indicate a low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H- binding Ni more tightly than Fe. Lastly, the present methodology is also relevant to characterizing Fe–H moieties in other important natural and synthetic catalysts.

  20. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy

    DOE PAGESBeta

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B.; Gee, Leland B.; Scott, Aubrey D.; et al

    2015-08-10

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique ‘wagging’ mode involving H- motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)57Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe–CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)57Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)57Fe(CO)3]+ and DFT calculations, which collectively indicate amore » low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H- binding Ni more tightly than Fe. Lastly, the present methodology is also relevant to characterizing Fe–H moieties in other important natural and synthetic catalysts.« less

  1. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy

    PubMed Central

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B.; Gee, Leland B.; Scott, Aubrey D.; Yoda, Yoshitaka; Tanaka, Yoshihito; Lubitz, Wolfgang; Cramer, Stephen P.

    2015-01-01

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique ‘wagging' mode involving H− motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)57Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe–CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)57Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)57Fe(CO)3]+ and DFT calculations, which collectively indicate a low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H− binding Ni more tightly than Fe. The present methodology is also relevant to characterizing Fe–H moieties in other important natural and synthetic catalysts. PMID:26259066

  2. Phase separation in Ca(1-x)La(x)Fe₂As₂ superconductors: a ⁵⁷Fe Mössbauer study.

    PubMed

    Liu, Xiaoxing; Li, Yang; Wan, Jianmei; Li, Zhiwei; Pang, Hua

    2016-03-31

    We report a detailed 57Fe Mössbauer study of lanthanum doped CaFe2As2 superconductors. The quadrupole splitting distribution (QSD) method was adopted to analyze the Mössbauer spectra of Ca(1-x) La(x)Fe2As2 (x  =  0.2, 0.3) single crystals. For both compounds we observed two QSD contributions centered at 0.31 mm s(-1) and  -0.32 mm s(-1) at room temperature. The first principles calculations of the electronic structures and the electric field gradient (EFG) of Ca(1-y)La(y)Fe2As2 model systems reveal that the EFG changes from positive to negative with increasing dopant concentration, indicating that the La atoms distribute heterogeneously in the compounds. The two QSD components behave differently with decreasing temperature. The minority La-rich phase undergoes superconducting transition, while short range spin fluctuations and/or spin-phonon coupling appear in the majority La-poor phase. Our experiments provide new evidence of the phase separation picture at low temperatures in Ca(1-x)La(x)Fe2As2 superconductors. PMID:26910879

  3. XRD and Mössbauer studies of crystallographic and magnetic transformations in synthesized Zn-substituted Cu-Ga-Fe compound

    NASA Astrophysics Data System (ADS)

    Ata-Allah, S. S.

    2004-12-01

    System of samples in the form of Cu 1-xZn xFe 2-yGa yO 4 with ( 0.0⩽x⩽1.0, y=0.0 and 1.0) is synthesized. X-ray diffraction study confirms the presence of a single-phase structure, where tetragonal unit cell is obtained for samples CuFe 2O 4 and CuGaFeO 4 with c/a>1. At compositional parameter x⩾0.25, tetragonal-to-cubic transformation occurs. The determined lattice parameter a for the cubic samples is found to decrease with increasing Zn content x. 57Fe Mössbauer measurements at 293, 77 and 12 K show characteristic spectra of paramagnetic, magnetic, and electronic types for the different compositions. Cation distribution obtained from the spectral analysis at 12 K revealed transformation from the ferrimagnetic inverse spinel of CuFe 2O 4 to the antiferromagnetic normal spinel of ZnFe 2O 4. Hyperfine parameters are found to be strongly dependent on temperature and concentration parameter x. Low-temperature measurements are carried out using installed and well-calibrated closed-cycle variable temperature cryostat Model REF-399-D22. Low vibration is obtained through bellows, spacer, and exchange gas isolation and a difference of 0.018 mm s -1 between the FWHM of a pure iron foil at room temperature and 12 K is achieved.

  4. Magnetic composites from minerals: study of the iron phases in clay and diatomite using Mössbauer spectroscopy, magnetic measurements and XRD

    NASA Astrophysics Data System (ADS)

    Cabrera, M.; Maciel, J. C.; Quispe-Marcatoma, J.; Pandey, B.; Neri, D. F. M.; Soria, F.; Baggio-Saitovitch, E.; de Carvalho, L. B.

    2014-01-01

    Magnetic particles as matrix for enzyme immobilization have been used and due to the enzymatic derivative can be easily removed from the reaction mixture by a magnetic field. This work presents a study about the synthesis and characterization of iron phases into magnetic montmorillonite clay (mMMT) and magnetic diatomaceous earth (mDE) by 57Fe Mössbauer spectroscopy (MS), magnetic measurements and X-ray diffraction (XRD). Also these magnetic materials were assessed as matrices for the immobilization of invertase via covalent binding. Mössbauer spectra of the magnetic composites performed at 4.2 K showed a mixture of magnetite and maghemite about equal proportion in the mMMT, and a pure magnetite phase in the sample mDE. These results were verified using XRD. The residual specific activity of the immobilized invertase on mMMT and mDE were 83 % and 92.5 %, respectively. Thus, both magnetic composites showed to be promising matrices for covalent immobilization of invertase.

  5. Selective Dissolution Techniques, X-Ray Diffraction and Mössbauer Spectroscopy Studies of Forms of Fe in Particle-Size Fractions of an Entic Haplustoll

    NASA Astrophysics Data System (ADS)

    Acebal, S. G.; Aguirre, M. E.; Santamaría, R. M.; Mijovilovich, A.; Petrick, S.; Saragovi, C.

    2003-06-01

    Particle-size fractions (∅ = mean diameter, 5-2 μm, 2-1 μm, and <1 μm) from the Ap horizon of an Entic Haplustoll from Argentina were treated with the selective-dissolution techniques ammonium oxalate (OX), dithionite-citrate-bicarbonate (DCB), NaOH, and Na-pyrophosphate (PY), and studied by X-ray powder diffraction (XRD) and 57Fe Mössbauer spectroscopy (MS). Quartz, feldspar, smectite, illite and interstratified illite-smectite are the dominant minerals whereas Fe oxides and oxy-hydroxides are present in low concentration but increase as particle size decreases. Poorly crystallized oxides (highly Al-substituted hematite and goethite) amounts are lower, comparable to or slightly higher than the hematite amounts in the ∅ = 5-2 μm, 2-1 μm and <1 μm fractions respectively. This hematite is well crystallized but presents some degree of Al-substitution. Magnetite/maghemite was identified in the 2-1 μm fraction. Paramagnetic Fe3+ and Fe2+ are associated to the clay minerals and/or hydroxyl-interlayered 2:1 type material present; part of this Fe3+ is located in the hydroxy-interlayers its amount being higher in the smallest fraction. Any possible changes after the PY and NaOH treatments were not detected by MS.

  6. Iron-rich Oxides at the Core-mantle Boundary

    NASA Astrophysics Data System (ADS)

    Wicks, J. K.; Jackson, J. M.; Sturhahn, W.; Bower, D. J.; Zhuravlev, K. K.; Prakapenka, V.

    2013-12-01

    Seismic observations near the base of the core-mantle boundary (CMB) have detected 5-20 km thick patches in which the seismic wave velocities are reduced by up to 30%. These ultra-low velocity zones (ULVZs) have been interpreted as aggregates of partially molten material (e.g. Williams and Garnero 1996, Hernlund and Jellinek, 2010) or as solid, iron-enriched residues (e.g. Knittle and Jeanloz, 1991; Mao et al., 2006; Wicks et al., 2010), typically based on proposed sources of velocity reduction. The stabilities of these structure types have been explored through dynamic models that have assembled a relationship between ULVZ stability and density (Hernlund and Tackley, 2007; Bower et al., 2010). Now, to constrain the chemistry and mineralogy of ULVZs, more information is needed on the relationship between density and sound velocity of candidate phases. We present the pressure-volume-temperature equation of state of (Mg0.06 57Fe0.94)O determined up to pressures of 120 GPa and temperatures of 2000 K. Volume was measured with X-ray diffraction at beamline 13-ID-D of the Advanced Photon Source (APS), where high pressures and temperatures are achieved in a diamond anvil cell with in-situ laser heating. Sample assemblies were prepared using dehydrated NaCl as an insulator and neon as a pressure transmitting medium. We present results with and without iron as a buffer and thermal pressure gauge. We have also determined the room temperature Debye velocity (VD) of (Mg0.06 57Fe0.94)O using nuclear resonant inelastic x-ray scattering and in-situ X-ray diffraction, up to 80 GPa at 3-ID-B of the APS. The effect of the electronic environment of the iron sites on the velocities was tracked in-situ using synchrotron Moessbauer spectroscopy. Using our measured equation of state, the seismically relevant compressional (VP) and shear (VS) wave velocities were calculated from the Debye velocities. We combine these studies with a simple mixing model to predict the properties of a solid

  7. MSATT Workshop on Innovative Instrumentation for the In Situ Study of Atmosphere-Surface Interactions on Mars

    NASA Technical Reports Server (NTRS)

    Fegley, Bruce, Jr. (Editor); Waenke, Heinrich (Editor)

    1992-01-01

    Papers accepted for the Mars Surface and Atmosphere Through Time (MSATT) Workshop on Innovative Instruments for the In Situ Study of Atmosphere-Surface Interaction of Mars, 8-9 Oct. 1992 in Mainz, Germany are included. Topics covered include: a backscatter Moessbauer spectrometer (BaMS) for use on Mars; database of proposed payloads and instruments for SEI missions; determination of martian soil mineralogy and water content using the Thermal Analyzer for Planetary Soils (TAPS); in situ identification of the martian surface material and its interaction with the martian atmosphere using DTA/GC; mass spectrometer-pyrolysis experiment for atmospheric and soil sample analysis on the surface of Mars; and optical luminescence spectroscopy as a probe of the surface mineralogy of Mars.

  8. Study of the effect of plasma-striking atmosphere on Fe-oxidation in thermal dc arc-plasma processing

    SciTech Connect

    Banerjee, I.; Khollam, Y. B.; Mahapatra, S. K.; Das, A. K.; Bhoraskar, S. V.

    2010-11-15

    The effect of plasma-striking atmosphere: air and air+Ar-gas on the crystallization of Fe-oxide phases was studied using dc thermal arc-plasma processing route. The powders were characterized by x-ray diffraction, vibrating sample magnetometry, transmission electron microscopy, and Moessbauer spectroscopy techniques. At room temperature and O{sub 2} rich atmosphere, arc-evaporated Fe{sup 2+} ions oxidize into either {gamma}-Fe{sub 2}O{sub 3} or Fe{sub 3}O{sub 4} depending upon the combining ratio of Fe with molecular O{sub 2}. Fe/O ratio could be adjusted using proper flow rate of Ar gas to crystallize the pure {gamma}-Fe{sub 2}O{sub 3}.

  9. Structural, magnetic and electrical properties of the hexagonal ferrites MFeO{sub 3} (M=Y, Yb, In)

    SciTech Connect

    Downie, Lewis J.; Goff, Richard J.; Kockelmann, Winfried; Forder, Sue D.; Parker, Julia E.; Morrison, Finlay D.; Lightfoot, Philip

    2012-06-15

    The hexagonal ferrites MFeO{sub 3} (M=Y, Yb, In) have been studied using a combination of neutron and X-ray powder diffraction, magnetic susceptibility, dielectric measurements and {sup 57}Fe Moessbauer spectroscopy. This study confirms the previously reported crystal structure of InFeO{sub 3} (YAlO{sub 3} structure type, space group P6{sub 3}/mmc), but YFeO{sub 3} and YbFeO{sub 3} both show a lowering of symmetry to at most P6{sub 3}cm (ferrielectric YMnO{sub 3} structure type). However, Moessbauer spectroscopy shows at least two distinct Fe sites for both YFeO{sub 3} and YbFeO{sub 3} and we suggest that the best model to rationalise this involves phase separation into more than one similar hexagonal YMnO{sub 3}-like phase. Rietveld analysis of the neutron diffraction data was carried out using two hexagonal phases as a simplest case scenario. In both YFeO{sub 3} and YbFeO{sub 3}, distinct dielectric anomalies are observed near 130 K and 150 K, respectively. These are tentatively correlated with weak anomalies in magnetic susceptibility and lattice parameters, for YFeO{sub 3} and YbFeO{sub 3}, respectively, which may suggest a weak magnetoelectric effect. Comparison of neutron and X-ray powder diffraction shows evidence of long-range magnetic order in both YFeO{sub 3} and YbFeO{sub 3} at low temperatures. Due to poor sample crystallinity, the compositional and structural effects underlying the phase separation and possible magnetoelectric phenomena cannot be ascertained. - Graphical abstract: Hexagonal MFeO{sub 3} (M=Y, Yb) exhibit phase separation into two YMnO{sub 3}-like phases. Variable temperature crystallographic, electrical and magnetic studies suggest weak correlations between electrical and magnetic responses and long-range magnetic order at low temperature. Highlights: Black-Right-Pointing-Pointer Multi-technique study of multiferroic hexagonal MFeO{sub 3}. Black-Right-Pointing-Pointer Phase separation into two similar hexagonal phases. Black

  10. A Mössbauer spectroscopic study of the iron redox transition in eastern Mediterranean sediments

    NASA Astrophysics Data System (ADS)

    van der Zee, Claar; Slomp, Caroline P.; Rancourt, Denis G.; de Lange, Gert J.; van Raaphorst, Wim

    2005-01-01

    Fe cycling at two sites in the Mediterranean Sea (southwest of Rhodes and in the North Aegean) has been studied, combining the pore water determination of nutrients, manganese, and iron, citrate-bicarbonate-dithionite (CDB) and total sediment extractions, X-ray diffraction, and 57Fe Mössbauer spectroscopy (MBS). At the Rhodes site, double peaks in the CDB-extractable Mn and Fe profiles indicate non-steady-state diagenesis. The crystalline iron oxide hematite, identified at both sites by room temperature (RT) MBS, appears to contribute little to the overall Fe reduction. MBS at liquid helium temperature (LHT) revealed that the reactive sedimentary Fe oxide phase was nanophase goethite, not ferrihydrite as is usually assumed. The pore water data at both sites indicates that upon reductive dissolution of nanophase goethite, the upward diffusing dissolved Fe 2+ is oxidized by Mn oxides, rather than by nitrate or oxygen. The observed oxidation of Fe 2+ by Mn oxides may be more common than previously thought but not obvious in sediments where the nitrate penetration depth coincides with the Mn oxide peak. At the Rhodes site, the solid-phase Fe(II) increase occurred at a shallower depth than the accumulation of dissolved Fe 2+ in the pore water. The deeper relict Mn oxide peak acts as an oxidation barrier for the upward diffusing dissolved Fe 2+, thereby keeping the pore water Fe 2+ at depth. At the North Aegean site, the solid-phase Fe(II) increase occurs at approximately the same depth as the increase in dissolved Fe 2+ in the pore water. Overall, the use of RT and cryogenic MBS provided insight into the solid-phase Fe(II) gradient and allowed identification of the sedimentary Fe oxides: hematite, maghemite, and nanophase goethite.

  11. Magnetic studies of mesoporous nanostructured iron oxide materials synthesized by one-step soft-templating.

    PubMed

    Jin, Jing; Hines, William A; Kuo, Chung-Hao; Perry, David M; Poyraz, Altug S; Xia, Yan; Zaidi, Taha; Nieh, Mu-Ping; Suib, Steven L

    2015-07-14

    A combined magnetization and (57)Fe spin-echo nuclear magnetic resonance (NMR) study has been carried out on mesoporous nanostructured materials consisting of the magnetite (Fe3O4) and maghemite (γ-Fe2O3) phases. Two series of samples were synthesized using a recently developed one-step soft-templating approach with systematic variations in calcination temperature and reaction atmosphere. Nuclear magnetic resonance has been shown to be a valuable tool for distinguishing between the two magnetic iron oxide spinel phases, Fe3O4 and γ-Fe2O3, on the nanoscale as well as monitoring phase transformation resulting from oxidation. For the Fe3O4 and γ-Fe2O3 phases, peaks in the NMR spectra are attributed to Fe in the tetrahedral (A) sites and octahedral (B) sites. The magnetic field dependence of the peaks was observed and confirmed the site assignments. Fe3O4 on a nanoscale readily oxidizes to form γ-Fe2O3 and this was clearly evident in the NMR spectra. As evidenced by transmission electron microscope (TEM) images, the porous mesostructure for the iron oxide materials is formed by a random close-packed aggregation of nanoparticles; correspondingly, superparamagnetic behavior was observed in the magnetic measurements. Although X-ray diffraction (XRD) shows the spinel structure for the Fe3O4 and γ-Fe2O3 phases, unlike NMR, it is difficult to distinguish between the two phases with XRD. Nitrogen sorption isotherms characterize the mesoporous structures of the materials, and yield BET surface area values and limited BJH pore size distribution curves. PMID:26067028

  12. (TAML)Fe**IV=O Complex in Aqueous Solution: Synthesis And Spectroscopic And Computational Characterization

    SciTech Connect

    Chanda, A.; Shan, X.; Chakrabarti, M.; Ellis, W.C.; Popescu, D.L.; Oliveira, F.Tiago de; Wang, D.; Que, L.; Jr.; Collins, T.J.; Munck, E.; Bominaar, E.L.

    2009-05-12

    Recently, we reported the characterization of the S = 1/2 complex [Fe{sup V}(O)B*]{sup -}, where B* belongs to a family of tetraamido macrocyclic ligands (TAMLs) whose iron complexes activate peroxides for environmentally useful applications. The corresponding one-electron reduced species, [Fe{sup IV}(O)B*]{sup 2-} (2), has now been prepared in >95% yield in aqueous solution at pH > 12 by oxidation of [Fe{sup III}(H{sub 2}O)B*]{sup -} (1), with tert-butyl hydroperoxide. At room temperature, the monomeric species 2 is in a reversible, pH-dependent equilibrium with dimeric species [B*Fe{sup IV}?O?Fe{sup IV}B*]{sup 2-} (3), with a pK{sub a} near 10. In zero field, the Moessbauer spectrum of 2 exhibits a quadrupole doublet with {Delta}E{sub Q} = 3.95(3) mm/s and {delta} = ?0.19(2) mm/s, parameters consistent with a S = 1 Fe{sup IV} state. Studies in applied magnetic fields yielded the zero-field splitting parameter D = 24(3) cm{sup -1} together with the magnetic hyperfine tensor A/g{sub n}{beta}{sub n} = (?27, ?27, +2) T. Fe K-edge EXAFS analysis of 2 shows a scatterer at 1.69 (2) {angstrom}, a distance consistent with a Fe{sup IV} = O bond. DFT calculations for [Fe{sup IV}(O)B*]{sup 2-} reproduce the experimental data quite well. Further significant improvement was achieved by introducing hydrogen bonding of the axial oxygen with two solvent-water molecules. It is shown, using DFT, that the {sup 57}Fe hyperfine parameters of complex 2 give evidence for strong electron donation from B* to iron.

  13. Atypical iron storage in marine brown algae: a multidisciplinary study of iron transport and storage in Ectocarpus siliculosus

    PubMed Central

    Matzanke, Berthold F.; Küpper, Frithjof C.; Carrano, Carl J.

    2012-01-01

    Iron is an essential element for all living organisms due to its ubiquitous role in redox and other enzymes, especially in the context of respiration and photosynthesis. The iron uptake and storage systems of terrestrial/higher plants are now reasonably well understood, with two basic strategies for iron uptake being distinguished: strategy I plants use a mechanism involving induction of Fe(III)-chelate reductase (ferrireductase) and Fe(II) transporter proteins, while strategy II plants utilize high-affinity, iron-specific, binding compounds called phytosiderophores. In contrast, little is known about the corresponding systems in marine, plant-like lineages, particularly those of multicellular algae (seaweeds). Herein the first study of the iron uptake and storage mechanisms in the brown alga Ectocarpus siliculosus is reported. Genomic data suggest that Ectocarpus may use a strategy I approach. Short-term radio-iron uptake studies verified that iron is taken up by Ectocarpus in a time- and concentration-dependent manner consistent with an active transport process. Upon long-term exposure to 57Fe, two metabolites have been identified using a combination of Mössbauer and X-ray absorption spectroscopies. These include an iron–sulphur cluster accounting for ~26% of the total intracellular iron pool and a second component with spectra typical of a polymeric (Fe3+O6) system with parameters similar to the amorphous phosphorus-rich mineral core of bacterial and plant ferritins. This iron metabolite accounts for ~74% of the cellular iron pool and suggests that Ectocarpus contains a non-ferritin but mineral-based iron storage pool. PMID:22945940

  14. In-beam Mössbauer spectroscopy of {sup 57}Fe/{sup 57}Mn in MgO and NaF at Heavy-Ion Medical Accelerator in Chiba

    SciTech Connect

    Kubo, M. K.; Kobayashi, Y.; Yamada, Y.; Mihara, M.; Nagatomo, T.; Sato, W.; Miyazaki, J.; Sato, S.; Kitagawa, A.

    2014-02-15

    Development of efficient ion supply of {sup 58}Fe from {sup 58}Fe(C{sub 5}H{sub 5}){sub 2}, and quick switching between therapy and material science at the Heavy-Ion Medical Accelerator in Chiba realized a new {sup 57}Mn in-beam emission Mössbauer spectroscopy measurement system. Application to simple binary chemical compounds, MgO and NaF, proved the usefulness of the system to probe chemical and physical behaviors of trace impurities in solids. Annealing of lattice defects produced by the implantation and β-decay of {sup 57}Mn and/or γ-ray emission recoil was observed by a local probe.

  15. Structural, thermal, magnetic and electrical studies of the iron oxophosphate Rb{sub 7}Fe{sub 7}(PO{sub 4}){sub 8}O{sub 2}.2H{sub 2}O

    SciTech Connect

    Hidouri, Mourad; Lajmi, Besma; Gmati, Nadia; Wattiaux, Alain; Nenert, Gwilherm; Ritter, Clemens; Fournes, Leopold; Darriet, Jacques; Lopez, Maria Luisa; Pico, Carlos; Amara, Mongi B.

    2010-09-15

    A new iron oxophosphate of composition Rb{sub 7}Fe{sub 7}(PO{sub 4}){sub 8}O{sub 2}.2H{sub 2}O has been synthesized and studied by X-ray diffraction, TG and DTA analysis, magnetic susceptibility, neutron diffraction, Moessbauer spectroscopy and ionic conductivity. This compound crystallizes in the monoclinic system with the P2{sub 1}/c space group and the unit cell parameters a = 8.224(8) A, b = 22.162(6) A, c = 9.962(6) A and {beta} = 109.41(8){sup o}. Its structure is built up from Fe{sub 7}O{sub 32} clusters of edge- and corner-sharing FeO{sub 5} and FeO{sub 6} polyhedra. Neighboring clusters are connected by the phosphate tetrahedra to form a three-dimensional framework. The Rb{sup +} cations and the water molecules are occupying intersecting tunnels parallel to a and c. The presence of water molecules was confirmed by TG and DTA analysis. The magnetic susceptibility measurements have shown the existence of antiferromagnetic ordering below 22 K with a weak ferromagnetic component. Additionally, these measurements show evidence for a strong magnetic frustration characterized by |{theta}/T{sub N}| {approx} 12. Powder neutron diffraction study confirms the presence of a long range antiferromagnetic order coupled to a weak ferromagnetic component along the b-axis. The strongly reduced magnetic moments extracted from the refinement support the existence of a magnetically frustrated ground state. The Moessbauer spectroscopy results confirmed the presence of only Fe{sup 3+} ions in both five and six coordination. The ionic conductivity measurements led to activation energy of 0.81 eV, a value that agrees with the obtained for other rubidium phosphates.

  16. Mossbauer studies of complex materials: energy versus time domain.

    SciTech Connect

    Planckaert, N.; Callens, R.; Demeter, J.; Laenens, B.; Sturhahn, W.; Kharlamova, S.; Temst, K.; Vantomme, A.

    2009-06-01

    We present a critical comparison between conventional Moessbauer spectroscopy on the one hand and energy and time resolved nuclear resonant scattering on the other hand. The three Moessbauer techniques are evaluated by the characterization of the complex magnetic structure of an Fe{sub 3}Al alloy. It is shown how the different scattering processes and detection schemes, which are involved in the respective configurations, determine the specific strengths of the three techniques and how they are optimally suited for the characterization of materials of varying complexity and reduced sizes.

  17. Enzyme Substrate Complex of the H200C Variant of Homoprotocatechuate 2,3-Dioxygenase: Mössbauer and Computational Studies.

    PubMed

    Meier, Katlyn K; Rogers, Melanie S; Kovaleva, Elena G; Lipscomb, John D; Bominaar, Emile L; Münck, Eckard

    2016-06-20

    The extradiol, aromatic ring-cleaving enzyme homoprotocatechuate 2,3-dioxygenase (HPCD) catalyzes a complex chain of reactions that involve second sphere residues of the active site. The importance of the second-sphere residue His200 was demonstrated in studies of HPCD variants, such as His200Cys (H200C), which revealed significant retardations of certain steps in the catalytic process as a result of the substitution, allowing novel reaction cycle intermediates to be trapped for spectroscopic characterization. As the H200C variant largely retains the wild-type active site structure and produces the correct ring-cleaved product, this variant presents a valuable target for mechanistic HPCD studies. Here, the high-spin Fe(II) states of resting H200C and the H200C-homoprotocatechuate enzyme-substrate (ES) complex have been characterized with Mössbauer spectroscopy to assess the electronic structures of the active site in these states. The analysis reveals a high-spin Fe(II) center in a low symmetry environment that is reflected in the values of the zero-field splitting (ZFS) (D ≈ - 8 cm(-1), E/D ≈ 1/3 in ES), as well as the relative orientations of the principal axes of the (57)Fe magnetic hyperfine (A) and electric field gradient (EFG) tensors relative to the ZFS tensor axes. A spin Hamiltonian analysis of the spectra for the ES complex indicates that the magnetization axis of the integer-spin S = 2 Fe(II) system is nearly parallel to the symmetry axis, z, of the doubly occupied dxy ground orbital deduced from the EFG and A-values, an observation, which cannot be rationalized by DFT assisted crystal-field theory. In contrast, ORCA/CASSCF calculations for the ZFS tensor in combination with DFT calculations for the EFG- and A-tensors describe the experimental data remarkably well. PMID:27275865

  18. Dimeric Fe (II, III) complex of quinoneoxime as functional model of PAP enzyme: Mössbauer, magneto-structural and DNA cleavage studies

    NASA Astrophysics Data System (ADS)

    Salunke-Gawali, Sunita; Ahmed, Khursheed; Varret, François; Linares, Jorge; Zaware, Santosh; Date, Sadgopal; Rane, Sandhya

    2008-07-01

    Purple acid phosphatase, ( PAP), is known to contain dinuclear Fe2 + 2, + 3 site with characteristic Fe + 3 ← Tyr ligand to metal charge transfer in coordination. Phthiocoloxime (3-methyl-2-hydroxy-1,4-naphthoquinone-1-oxime) ligand L, mimics (His/Tyr) ligation with controlled and unique charge transfers resulting in valence tautomeric coordination with mixed valent diiron site in model compound Fe-1: [μ-OH-Fe2 + 2, + 3 ( o-NQCH3ox) ( o-NSQCH3ox)2 (CAT) H2O]. Fe-2: [Fe + 3( o-NQCH3ox) ( p-NQCH3ox)2]2 a molecularly associated dimer of phthiocoloxime synthesized for comparison of charge transfer. 57Fe Mössbauer studies was used to quantitize unusual valences due to ligand in dimeric Fe-1 and Fe-2 complexes which are supported by EPR and SQUID studies. 57Fe Mössbauer spectra for Fe-1 at 300 K indicates the presence of two quadrupole split asymmetric doublets due to the differences in local coordination geometries of [Fe + 3]A and [Fe + 2]B sites. The hyperfine interaction parameters are δ A = 0.152, (Δ E Q)A = 0.598 mm/s with overlapping doublet at δ B = 0.410 and (Δ E Q)B = 0.468 mm/s. Due to molecular association tendency of ligand, dimer Fe-2 possesses 100% Fe + 3(h.s.) hexacoordinated configuration with isomer shift δ = 0.408 mm/s. Slightly distorted octahedral symmetry created by NQCH3ox ligand surrounding Fe + 3(h.s.) state generates small field gradient indicated by quadrupole split Δ E Q = 0.213 mm/s. Decrease of isomer shifts together with variation of quadrupole splits with temperature in Fe-1 dimer compared to Fe-2 is result of charge transfers in [Fe2 + 2, + 3 SQ] complexes. EPR spectrum of Fe-1 shows two strong signals at g 1 = 4.17 and g 2 = 2.01 indicative of S = 3/2 spin state with an intermediate spin of Fe + 3(h.s.) configuration. SQUID data of χ _m^{corr} .T were best fitted by using HDVV spin pair model S = 2, 3/2 resulting in antiferromagnetic exchange ( J = -13.5 cm - 1 with an agreement factor of R = 1.89 × 10 - 5). The lower J

  19. Moessbauer Spectroscopy of Mineral Separates from SNC Meteorites

    NASA Technical Reports Server (NTRS)

    Dyar, M. D.

    2003-01-01

    Numerous workers have recently focused attention on the issue of the oxygen fugacity (f(sub O2)) of martian samples. Estimates of fO2 based on Fe-Ti oxides and D(sub Eu)/D(sub Gd) and D(sub Eu)/D(sub Sm) ratios suggest a range of fO2 values for SNC meteorites from IW+2.5 - IW+3.5 for Shergotty to IW- 2.0 - IW+0.2 for QUE94201. Fe(3+)/Fe(2+) is also a function of f(sub O2), and synchrotron micro-XANES values for olivine, pyroxene, and feldspar Fe(3+) have been reported. However, the relationship between the reported Fe(3+) values and the other methods for estimating f(sub O2) is not clear, and further measurements of Fe(3+)/Fe(2+) by a more conventional technique have been needed. Accordingly, in this project, new Mossbauer spectroscopy data on mineral separates handpicked from 10 SNC meteorites are reported.

  20. Moessbauer spectra of ferrite catalysts used in oxidative dehydrogenation

    NASA Technical Reports Server (NTRS)

    Cares, W. R.; Hightower, J. W.

    1971-01-01

    Room temperature Mossbauer spectroscopy was used to examine bulk changes which occur in low surface area CoFe2O4 and CuFe2O4 catalysts as a result of contact with various mixtures of trans-2-butene and O2 during oxidative dehydrogenation reactions at about 420 C. So long as there was at least some O2 in the gas phase, the CoFe2O4 spectrum was essentially unchanged. However, the spectrum changed from a random spinel in the oxidized state to an inverse spinel as it was reduced by oxide ion removal. The steady state catalyst lies very near the fully oxidized state. More dramatic solid state changes occurred as the CuFe2O4 underwent reduction. Under severe reduction, the ferrite was transformed into Cu and Fe3O4, but it could be reversibly recovered by oxidation. An intense doublet located near zero velocity persisted in all spectra of CuFe2O4 regardless of the state of reduction.

  1. Mössbauer spectroscopic studies of the moment distribution in Fe73.5Cu1Nb3Si13.5B9

    NASA Astrophysics Data System (ADS)

    Aghamohammadzadeh, H.; Williams, J. M.; Gibbs, M. R. J.; Parmar, B. S.; Davies, H. A.

    2000-05-01

    57Fe Mössbauer spectroscopy can be used to determine the distribution of moment directions in magnetic materials. Here, we have applied this technique to a study of Fe73.5Cu1Nb3Si13.5B9 (isocompositional with FINEMET). We are particularly interested in establishing the distribution of moment directions in the nanophase material, obtained by devitrification from an amorphous precursor. The nanophase material consists of Fe-Si grains embedded in an amorphous matrix. Current understanding of the resulting magnetic properties, which involves application of the random anisotropy model to these materials, assumes that the magnetization in the grains is exchange coupled to neighbors, giving a long exchange length compared with the nanometer grain size. We present data for the amorphous precursor, the standard nanophase material, and nanophase material devitrified in an external magnetic field. If σu and σv represent the Gaussian widths of the out-of-plane and in-plane moment direction distributions respectively, we have found that σu=14° and σv=68° for the amorphous precursor, σu=14° and σv=92° for the standard nanophase material, and σu=22° and σv=79° for a magnetic field aligned specimen. We interpret these data as demonstrating that standard devitrification does result in grains with a wide spread of moment direct ions over the volume sampled by this technique, even allowing for exchange coupling. These results and the implications for macroscopic magnetic properties such as anisotropy will be discussed.

  2. Hyperfine fields in Fe-Ni-X alloys and their application to a study of tempering of 9Ni steel

    SciTech Connect

    Fultz, B.; Morris, J.W. Jr.

    1984-12-01

    Hyperfine interactions due to solutes in Fe-Ni-X alloys were systematized, and interpreted with a model of linear response of hyperfine magnetic fields to magnetic moments. The effects of solutes on the /sup 57/Fe hmf were used for chemical analysis of the austenite formed in 9Ni steel during tempering. Diffusion kinetics of the Ni and X solutes were found to play an important role in the formation of the austenite particles.

  3. Chemical mixing at “Al on Fe” and “Fe on Al” interfaces

    SciTech Connect

    Süle, P.; Horváth, Z. E.; Kaptás, D.; Bujdosó, L.; Balogh, J.; Nakanishi, A.

    2015-10-07

    The chemical mixing at the “Al on Fe” and “Fe on Al” interfaces was studied by molecular dynamics simulations of the layer growth and by {sup 57}Fe Mössbauer spectroscopy. The concentration distribution along the layer growth direction was calculated for different crystallographic orientations, and atomically sharp “Al on Fe” interfaces were found when Al grows over (001) and (110) oriented Fe layers. The Al/Fe(111) interface is also narrow as compared to the intermixing found at the “Fe on Al” interfaces for any orientation. Conversion electron Mössbauer measurements of trilayers—Al/{sup 57}Fe/Al and Al/{sup 57}Fe/Ag grown simultaneously over Si(111) substrate by vacuum evaporation—support the results of the molecular dynamics calculations.

  4. Behavioral response of pyrite structured Co0.2Fe0.8S2 nano-wires under high-pressure up to 8 GPa - Mössbauer spectroscopic and electrical resistivity studies

    NASA Astrophysics Data System (ADS)

    Chandra, U.; Sharma, P.; Parthasarathy, G.; Sreedhar, B.

    2016-02-01

    Pyrite-structured Co0.2Fe0.8S2 nano wires with aspect ratio 45:1, synthesized using solution colloid method were studied under high pressure up to 8 GPa using 57Fe Mössbauer spectroscopy (using diamond anvil cell) and electrical resistivity (using tungsten carbide cell) techniques. Room temperature S K-edge XANES studies at INFN-LNF synchrotron beam line signified the changes in the electronic structure owing to Co substitution. Magnetic measurements at 5 K demonstrated disordered ferromagnetic behavior similar to Griffith phase. The value of isomer shift identified Fe in divalent, low spin state corresponding to pyrite structure. Higher value of quadrupole splitting observed at ambient condition was due to large lattice strain and electric field gradient generated by large surface to volume ratio of the nano size of the system. With applied pressure, the value followed the expected trend of increase up to 4.3 GPa, then to decrease till 6.4 GPa. Such change in the trend suggested a phase transition. On decompression to ambient pressure, the system seemed to retain high pressure phase and nano structure. The pressure coefficient of electrical resistivity varying from -0.0454 to -0.166 Ω-cm/GPa across the transition pressure of ~4.5 GPa was sluggish suggesting second order phase transition. The pressure-dependent variations by Mössbauer parameters and electrical resistivity showed identical result. This is the first report of pressure effect on nano sized Co0.2Fe0.8S2. Effect of particle size on transition pressure could not be evaluated due to lack of available reports on bulk system.

  5. Influence of the nature of the ligand on the structure and spectra of boron-containing iron(II) dioximates

    SciTech Connect

    Pol'shin, E.V.; Trachevskii, V.V.; Tyukhtenko, S.I.; Nazarenko, A.Yu.; Voloshin, Ya.Z.

    1987-11-01

    The Moessbauer (/sup 57/Fe) and NMR (/sup 1/H, /sup 13/C, /sup 11/B) spectra of the macrobicyclic dioximates FeD/sub 3/(BF)/sub 2/, where H/sub 2/D stands for glyoxime, methylglyoxime, 1,2-cyclohexanedione dioxime (Nioxime), furildioxime, and benzil dioxime, have been investigated. The values of the isomer shifts for these compounds range from 0.31 to 0.37 mm/sec relative to sodium nitroprusside, and the Raman scattering ranges from 0.6 to 0.9 for the aliphatic oximes and is equal to approx. 0.2 for the aromatic oximes. The changes in the Raman scattering have been related to the angle of distortion of the trigonal prism. The greatest changes in the /sup 13/C and /sup 1/H NMR spectra are observed for the atoms of the substituents.

  6. Formation of magnetic nanoparticles studied during the initial synthesis stage

    NASA Astrophysics Data System (ADS)

    Kraken, M.; Masthoff, I.-C.; Borchers, A.; Litterst, F. J.; Garnweitner, G.

    2014-01-01

    The formation of iron oxide nanoparticles in course of a sol-gel preparation process was traced by UV/Vis and 57Fe Mössbauer absorption spectroscopy. Samples were extracted at different stages of the reaction. While spectra measured on samples extracted at low reactor temperatures showed the starting materials Fe(acac)3 diluted in benzyl alcohol undergoing slow paramagnetic relaxation, a sample extracted at a reactor temperature of 180 °C gave clear evidence for emerging iron oxide nanoparticles. A prolonged stay at 200 °C results in a complete transformation from Fe(acac)3 to maghemite nanoparticles.

  7. Recoilless fraction studies of iron near the Curie temperature

    NASA Astrophysics Data System (ADS)

    Kolk, B.; Bleloch, A. L.; Hall, D. B.

    1986-02-01

    The recoilless fraction f of57Fe in iron is determined as a function of temperature T in the vicinity of the Curie temperature Tc using a source of57Co diffused in a foil of 100% enriched56Fe. Our results show that f does not undergo an abrupt change at Tc, but that in the ferromagnetic phase |d f/d T| is larger than in the non-ferromagnetic phase. This indicates that the ferromagnetic interaction increases the bond between the iron atoms, and thus contributes to the stability of the iron lattice below Tc.

  8. Effect of Gd substitution on the structure and magnetic properties of YFeO{sub 3} ceramics

    SciTech Connect

    Yuan, Xueping; Sun, Yue; Xu, Mingxiang

    2012-12-15

    High quality Gd-doped YFeO{sub 3} polycrystalline samples were synthesized by solid-state reaction method. The crystal structure of the samples can be described by the space group of Pbnm (No. 62). {sup 57}Fe Moessbauer spectra show that only the high spin Fe{sup 3+} exists and the samples are magnetic ordering at room temperature. The spontaneous magnetization at room temperature was observed and the paramagnetic contribution from Gd{sup 3+} ions was confirmed by the significant enhancement of the magnetization. Temperature-dependent magnetization data correlate with the Gd concentration x and follow the Curie-Weiss law above the ferromagnetic transition temperature. Magnetic measurements suggest that the substitution of Y{sup 3+} ions by Gd{sup 3+} ions effectively enhance the magnetization of YFeO{sub 3}. This is achieved by the additional Gd-Gd interactions, Gd-Fe interactions and the variation of Fe-O-Fe superexchange bond caused by distortion of the crystal structure. - Graphical abstract: The crystallographic structure of YFeO{sub 3} and the magnetic hysteresis loops of Y{sub 1-x}Gd{sub x}FeO{sub 3} (x=0, 0.1, 0.5, and 1) samples at room temperature. Highlights: Black-Right-Pointing-Pointer Y{sub 1-x}Gd{sub x}FeO{sub 3} (0{<=}x{<=}1) ceramics were synthesized by solid state reaction method. Black-Right-Pointing-Pointer Y{sub 1-x}Gd{sub x}FeO{sub 3} (0{<=}x{<=}1) samples are ferromagnetic ordering at room temperature. Black-Right-Pointing-Pointer Results of {sup 57}Fe Moessbauer spectra are typical for Fe{sup 3+} high spin state. Black-Right-Pointing-Pointer Substitution of Y{sup 3+} ions by Gd{sup 3+} ions enhances the magnetization of YFeO{sub 3} obviously.

  9. Structure and magnetic properties of the cubic oxide fluoride BaFeO{sub 2}F

    SciTech Connect

    Berry, Frank J.; Coomer, Fiona C.; Hancock, Cathryn; Helgason, Orn; Moore, Elaine A.; Slater, Peter R.; Wright, Adrian J.; Thomas, Michael F.

    2011-06-15

    Fluorination of the parent oxide, BaFeO{sub 3-{delta}}, with polyvinylidine fluoride gives rise to a cubic compound with a=4.0603(4) A at 298 K. {sup 57}Fe Moessbauer spectra confirmed that all the iron is present as Fe{sup 3+}. Neutron diffraction data showed complete occupancy of the anion sites, indicating a composition BaFeO{sub 2}F, with a large displacement of the iron off-site. The magnetic ordering temperature was determined as T{sub N}=645{+-}5 K. Neutron diffraction data at 4.2 K established G-type antiferromagnetism with a magnetic moment per Fe{sup 3+} ion of 3.95 {mu}{sub B}. However, magnetisation measurements indicated the presence of a weak ferromagnetic moment that is assigned to the canting of the antiferromagnetic structure. {sup 57}Fe Moessbauer spectra in the temperature range 10-300 K were fitted with a model of fluoride ion distribution that retains charge neutrality of the perovskite unit cell. - Graphical abstract: The cubic oxide fluoride of composition BaFeO{sub 2}F has been synthesised and characterised. Highlights: > Fluorination of BaFeO{sub 3-{delta}} with polyvinylidene fluoride gives a cubic oxide fluoride of composition BaFeO{sub 2}F. > BaFeO{sub 2}F adopts a canted antiferromagnetic structure and is different from the related phase of composition SrFeO{sub 2}F. > A model of fluoride ion distribution about iron in BaFeO{sub 2}F has been explored.

  10. Preparation and Characterization of Ultrathin Stainless Steel Films

    SciTech Connect

    Sahoo, B.; Schlage, K.; Roehlsberger, R.; Major, J.; Hoersten, U. von; Keune, W.; Wende, H.

    2011-06-30

    We report on the preparation of polycrystalline austenitic 310 ({sup 57}Fe{sub 0.55}Cr{sub 0.25}Ni{sub 0.20}) stainless steel (SS) thin films on Si substrates and the characterization of their residual magnetism via {sup 57}Fe conversion-electron Moessbauer spectroscopy (CEMS). The films were structurally characterized at room temperature by X-ray diffraction (XRD). The virgin films were found to be structurally disordered. Subsequent annealing at moderate temperatures in ultrahigh vacuum produces the ordered martensitic and austenitic SS phases. Further annealing at higher temperatures (up to temperatures where long-range diffusion into the substrate is still weak) transforms the films into the austenitic phase with no trace of a magnetic hyperfine interaction. However, when a 2 nm thick SS thin film is embedded between two carbon layers, the as prepared disordered SS film does not transform to the martensitic or austenitic SS phase irrespective of the annealing temperature, probably because the interdiffusion with C prohibits the formation of these phases.

  11. In situ small-angle x-ray and nuclear resonant scattering study of the evolution of structural and magnetic properties of an Fe thin film on MgO (001)

    NASA Astrophysics Data System (ADS)

    Sharma, Gagan; Gupta, Ajay; Gupta, Mukul; Schlage, Kai; Wille, H.-C.

    2015-12-01

    Growth of magnetron sputtered Fe films on clean single crystalline MgO (001) substrate has been studied using in situ grazing incidence small angle x-ray scattering (GISAXS) and grazing incidence nuclear resonant scattering (GINRS) measurements. While GISAXS provides information about morphological changes, GINRS provides information about structural and magnetic properties, thus making it possible to correlate the evolution of magnetic properties with that of morphology and structure of the film. The film exhibits a Volmer-Weber type growth, with percolation transition occurring around 2 nm film thickness. Presence of a finite quadrupole splitting, as seen in GINRS measurements, suggests a significant distortion from cubic symmetry up to a film thickness of 3.5 nm, which can be attributed to hybridization between Fe 3 d and O 2 p orbitals at the interface as well as in-plane tensile strain induced as a result of coalescence of islands. Initially Fe islands exhibit superparamagnetic relaxation, while finite magnetic moment appears upon formation of macroscopic percolation islands. The film exhibits a weak perpendicular magnetic anisotropy (PMA), which vanishes concurrently with disappearance of structural distortion, suggesting that the observed PMA at least partly originates from inherent strain in the film. No presence of any known oxide of Fe was detected at the interface. More precise information about topological and magnetic structure of the interfaces between Fe and MgO layers is obtained using combined x-ray reflectivity and nuclear resonance reflectivity measurements on a 57Fe/MgO multilayer. Measurements show that about two monolayers of Fe at the interface have a reduced hyperfine field, providing evidence for hybridization with O atoms, as predicted by theory.

  12. Determination of manganese-53 by neutron activation and other miscellaneous studies on lunar dust.

    PubMed

    Herr, W; Herpers, U; Hess, B; Skerra, B; Woelfle, R

    1970-01-30

    A highly sensitive determination of spallogenic (53)Mn (T = 2 x 106 yr) was accomplished in 0.99 g of lunar soil. The chemical yield of Mn is determined with "carrier-free" (52)Mn tracer. During a 23-day reactor irradiation the (53)Mn is transformed into (54)Mn (T = 300 days). Appropriate chemical recycling was done by ion exchange and distillation. Interferences of the (n,p) and the (n,2n) nuclear reactions were carefully studied. A (53)Mn disintegration rate of 30.3 +/- 5.5 dpm/kg results. This extremely economic method is proposed for further detailed lunar profile measurements. The Re content, which is of possible cosmochemical interest, was determined to be 11 ppb. Appropriate separation techniques were used. The rather weak and complex thermoluminescence properties made a more basic study advisable. Thermogravimetric analysis, mass spectroscopy, and Moessbauer spectroscopy were applied. The presence of ilmenite, metallic Fe etc., and of an unidentified Fe(2+)-containing compound was deduced. Natural thermoluminescence could not be proved with certainty in our surface sample. However, the complexity of the artificial thermoluminescence demands better defined mineral fractions. The fission track method was used to measure U distribution in glass spherules etc. PMID:17781575

  13. MAGNETO-CHEMICAL CHARACTER STUDIES OF NOVEL FE CATALYSTS FOR COAL LIQUEFACTION

    SciTech Connect

    Murty A. Akundi

    1997-10-01

    Co-precipitation is the major method proposed for synthesis of molybdenum oxide supported Fe, Fe/Co, and Fe/Cu catalysts. However, many variables may effect the particle size and surface properties of the synthesized catalysts, such as pH of molybdate solution, precipitation temperature and pH, Fe/Mo atomic ratio, pH of the washing solution, aging of the freshly prepared samples, and the length and temperature of calcination. In this period, we have been working on precipitation between iron(III) nitrate solution and ammonium para-molybdate solution under controlled pH condition, and with different Me/Fe atomic ratio. The effect of aging time on the property of the samples was also studied. The samples with the ratio of Fe/MoO{sub 3}: 6.5%, 20%, 26%, and 30% were prepared using above mentioned method. The samples with 6.5% and 26% were characterized with thermal analysis, infrared spectroscopy, magnetization, Moessbauer and X-ray diffraction before and after calcination at 400 C. FTIR was examined on precipitate, calacined and reduced samples as well as CO adsorbed and desorbed samples. Magnetization Studies were made on precipitated, calacined, and reduced samples. Their synthesis and characterization are presented in this report.

  14. Atomic scale study of magnetic phase transitions in (Co,Ti;Sc) substituted nanosize barium hexaferrite

    NASA Astrophysics Data System (ADS)

    Krezhov, Kiril

    BaFe12O19 and related isostructural (M-type) hexaferrites derived by single or double cation substitution for Fe3+ with preservation of the formal valence are a recognized group of oxides for their remarkable properties. The magnetic interactions may be tuned by suitable substitutions resulting in notable magnetic properties utilized extensively for permanent magnets, microwave devices and perpendicular recording media. We report on the magnetic structure evolution accompanying the magnetic anisotropy change, from a combined magnetic (SQUID), x-ray and neutron diffraction, and magnetic field dependent 57Fe Mössbauer study on BaFe12O19 at selected cation substitutions. The short and long range atomic and magnetic order in powder samples of nanosize particles prepared by soft chemistry routes were studied and compared with own and literature data for the parent BaFe12O19 compound prepared by solid state reaction. Refinements based on diffraction data show that the magnetic structures of BaFe12-xXxO19 (X=Co,Ti; Sc) hexaferrites are largely temperature and substitution dependent. Between 200 and 300K the (Co,Ti)-hexaferrites (x=0.4, 0.7, 0.8, 0.85) display ferrimagnetic structures where the canting of the magnetic moments depends on the substitution rate. When lowering the temperature the magnetic structure for x=0.45 remains ferrimagnetic down to 10 K, while for x=0.7 and x=0.8 a complex conical magnetic structures is finally established. For x=0.85 significant distortions in the local oxygen surrounding of ferric cation sites were established, while the grain-size effect on the structural parameters was considerably smaller. The thermal expansion coefficient exhibits a strong anisotropy. The refined magnetic moments are considerably lower than the theoretical spin only moments, especially for the 4e and 12k sites, indicating a local noncollinearity with short-range ordering. The five-cation sublattice collinear ferrimagnetic structure of uniaxial type known as

  15. Structural study and physical properties of a new phosphate KCuFe(PO{sub 4}){sub 2}

    SciTech Connect

    Badri, Abdessalem; Hidouri, Mourad; Lopez, Maria Luisa; Pico, Carlos; Wattiaux, Alain; Ben Amara, Mongi

    2011-04-15

    Single crystals of a new phosphate KCuFe(PO{sub 4}){sub 2} have been prepared by the flux method and its structural and physical properties have been investigated. This compound crystallizes in the monoclinic system with the space group P2{sub 1}/n and its parameters are: a=7.958(3) A, b=9.931(2) A, c=9.039(2) A, {beta}=115.59(3){sup o} and Z=4. Its structure consists of FeO{sub 6} octahedra sharing corners with Cu{sub 2}O{sub 8} units of edge-sharing CuO{sub 5} polyhedra to form undulating chains extending infinitely along the b-axis. These chains are connected by the phosphate tetrahedra giving rise to a 3D framework with six-sided tunnels parallel to the [101] direction, where the K{sup +} ions are located. The Moessbauer spectroscopy results confirm the exclusive presence of octahedral Fe{sup 3+} ions. The magnetic measurements show the compound to be antiferromagnetic with C{sub m}=5.71 emu K/mol and {theta}=-156.5 K. The derived experimental effective moment {mu}{sub ex}=6.76{mu}{sub B} is somewhat higher than the theoretical one of {mu}{sub th}=6.16{mu}{sub B}, calculated taking only into account the spin contribution for Fe{sup 3+} and Cu{sup 2+} cations. Electrical measurements allow us to obtain the activation energy (1.22 eV) and the conductivity measurements suggest that the charge carriers through the structure are the potassium cations. -- Graphical abstract: A projection along the [101] direction of the structure showing the six-edged tunnels, occupied by the K{sup +} ions. Display Omitted Highlights: {yields} The reported structure is of a new type. {yields} The structural model is supported by a Moessbauer spectroscopy study. {yields} The magnetic susceptibility results are reported. {yields} The electrical properties are discussed.

  16. Nuclear Resonant Scattering Studies Under High Pressure and HighTtemperature

    NASA Astrophysics Data System (ADS)

    Sturhahn, W.; Lin, J.; Shen, G.; Jackson, J. M.; Zhao, J.; Prakapenka, V.; Lerche, M.; Bass, J. D.; Mao, H.

    2004-12-01

    Nuclear resonant scattering techniques have been applied very successfully to iron-bearing alloys [1-3] and silicates [4] under pressures in the Mbar regime using diamond anvil cells. The two main methods, nuclear resonant inelastic x-ray scattering (NRIXS) and synchrotron Mössbauer spectroscopy (SMS), will be discussed in their potential for the geophysical problem area. In general, NRIXS provides the phonon density of states [5] and sound velocities [6], whereas SMS gives access to the abundance of ferric iron and the spin state of iron in minerals and their polymorphs. % The introduction of Laser heating in combination with NRIXS and SMS at sector 3-ID of the Advanced Photon Source permits us now to conduct these studies under high pressure \\textit{and} high temperature. Here we will address two examples of this powerful, new opportunity. The reduction of sound velocities with increasing temperature, in particular for the shear wave, observed from NRIXS on hot, compressed iron metal in a pressure range of 40 GPa to 60 GPa. We find that the sound velocities do not depend on density alone but show an explicit temperature dependence. In a second experiment, we analyzed valence and spin state of iron in magnesium silicates. The starting material, orthoenstatite 57Fe0.1Mg0.9SiO3, was compressed in several steps up to 31 GPa in a diamond anvil cell. Each step involved laser annealing and the collection of SMS spectra at several temperatures. With x-ray diffraction we confirmed the creation of high-clinoenstatite, ringwoodite, ilmenite, and perovskite structures. Unique data on the iron behavior in each polymorph was obtained. % This work is supported by the U.S. DOE-BES, Office of Science, under Contract No. W-31-109-Eng-38 and by NSF through COMPRESS. % {}[1] H.K.Mao et al., Science \\textbf{292}, 914 (2001) [1mm] % {}[2] J.-F.Lin et al., Geophysical Research Letters \\textbf{30}, 2112 (2003) [1mm] % {}[3] W.L.Mao et al., Geophysical Research Letters \\textbf{31

  17. Diffusion studies with synchrotron Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Jackson, J. M.

    2011-12-01

    Knowledge of diffusion properties is critical for understanding many physical and chemical processes in planetary interiors. For example, diffusion behavior provides constraints on chemical exchange and viscosity. Nuclear resonances open the window for observing diffusion properties under the extreme conditions that exist deep inside the Earth. Synchrotron Mössbauer spectroscopy (viz. nuclear forward scattering) makes use of synchrotron radiation coherently scattered in the forward direction after nuclear resonant excitation. The decay of the forward-scattered radiation is faster when atoms move on the time scale of the excited-state lifetime because of a loss of coherence. Such diffusion-activated processes lead to accelerated decay and line broadening in the measured signal. In the case of the Mössbauer active isotope 57Fe, the nuclear resonance at 14.4 keV has a natural lifetime of 141 ns. Therefore, one can observe diffusion events ranging from approximately one-sixth to 100 times the natural lifetime of 57Fe, which corresponds to diffusion coefficients of 10-16 and 10-13 m2/s, respectively and a two to three order of magnitude range of suitability. In this contribution, we will describe such measurements that access the microscopic details of the diffusion process for iron-bearing phases.

  18. Iron deficiency, but not anemia, upregulates iron absorption in breast-fed Peruvian infants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Iron absorption in adults is regulated by homeostatic mechanisms that decrease absorption when iron status is high. There are few data, however, regarding the existence of a similar homeostatic regulation in infants. We studied 2 groups of human milk-fed infants using (57)Fe (given as ferrous sulfat...

  19. Pseudo-discontinuities in the isomer shift near magnetic transitions

    NASA Astrophysics Data System (ADS)

    Kolk, B.; Hall, D. B.; Zheng, Y.; Lumetta, J. T.

    1983-12-01

    It is shown that a relatively small non-linear behavior of the velocity drive system used in Mössbauer effect studies yields pseudo-discontinuities in the isomer shift near the critical temperature T c of a magnetic-paramagnetic transition. The anomaly of the57Fe isomer shift in iron is attributed to this effect.

  20. Intermultiplet transitions in optically opaque EuBa{sub 2}Cu{sub 3}O{sub 7}: An inelastic neutron scattering study

    SciTech Connect

    Staub, U.; Soderholm, L.; Osborn, R.; Guillaume, M.; Furrer, A.; Trounov, V.

    1994-06-01

    We report the results of inelastic neutron scattering (INS) studies of the J=0 to J=1 magnetic transitions in EuBa{sub 2}Cu{sub 3}O{sub 7}. The low J values of these multiplets restrict our crystal field analysis to the second order crystalline electric field (CEF) parameters B{sub o}{sup 2} and B{sub 2}{sup 2} obtained by fitting the splitting of the J=l multiplet, and the spin-orbit coupling parameter, which is used to fit the energy of the J=0 to J=l multiplet splitting. We compare our results to those derived from other INS studies on different rare earths, as well as with B{sub o}{sup 2} and B{sub 2}{sup 2} derived from Moessbauer studies. The J=O to J=l splitting observed here is smaller than previously seen by optical spectroscopic studies on a variety of transparent, ionic compounds, necessitating the inclusion of a free-ion parameter in the fitting procedure. This work represents the first time that a complete excited multiplet has been seen for R in RBa{sub 2}CU{sub 3}O{sub 7}. These results are particularly germane to crystal field analyses of the light rare earth ions in optically opaque materials, where assumptions about free-ion parameters are essential for a meaningful analysis.

  1. Thermal decomposition of iron(VI) oxides, K{sub 2}FeO{sub 4} and BaFeO{sub 4}, in an inert atmosphere

    SciTech Connect

    Madarasz, Janos; Zboril, Radek; Homonnay, Zoltan . E-mail: vsharma@fit.edu; Pokol, Gyoergy

    2006-05-15

    The thermal decomposition of solid samples of iron(VI) oxides, K{sub 2}FeO{sub 4}.0.088 H{sub 2}O (1) and BaFeO{sub 4}.0.25H{sub 2}O (2) in inert atmosphere has been examined using simultaneous thermogravimetry and differential thermal analysis (TG/DTA), in combination with in situ analysis of the evolved gases by online coupled mass spectrometer (EGA-MS). The final decomposition products were characterized by {sup 57}Fe Moessbauer spectroscopy. Water molecules were released first, followed by a distinct decomposition step with endothermic DTA peak of 1 and 2 at 273 and 248 deg. C, respectively, corresponding to the evolution of molecular oxygen as confirmed by EGA-MS. The released amounts of O{sub 2} were determined as 0.42 and 0.52 mol pro formula of 1 and 2, respectively. The decomposition product of K{sub 2}FeO{sub 4} at 250 deg. C was determined as Fe(III) species in the form of KFeO{sub 2}. Formation of an amorphous mixture of superoxide, peroxide, and oxide of potassium may be other products of the thermal conversion of iron(VI) oxide 1 to account for less than expected released oxygen. The thermogravimetric and Moessbauer data suggest that barium iron perovskite with the intermediate valence state of iron (between III and IV) was the product of thermal decomposition of iron(VI) oxide 2.

  2. Vibrational entropy of spinodal decomposition in FeCr

    SciTech Connect

    Swan-Wood, T.L.; Delaire, O.; Fultz, B.

    2005-07-01

    Inelastic neutron-scattering spectra were measured on stoichiometric Fe{sub 0.50}Cr{sub 0.50} prepared as a body-centered-cubic (bcc) solid solution, and after increasing amounts of chemical unmixing on the bcc lattice induced by annealing the solid solution at 773 K. These spectra were reduced by a conventional procedure to a neutron-weighted vibrational density of states. Moessbauer spectrometry was used to characterize the extent of decomposition after annealing. A neutron-weight correction was performed, using results from the Moessbauer spectra and recent data on inelastic nuclear resonant scattering from {sup 57}Fe-Cr. The vibrational entropy of decomposition was found to be -0.17{+-}0.01k{sub B}/atom, nearly equal to the change in configurational entropy after spinodal decomposition. Effects of vibrational entropy on the thermodynamics of unmixing are analyzed, showing a large effect on the free energy with the formation of Cr-rich zones, and a large effect on the critical temperature for spinodal decomposition for equiatomic Fe{sub 0.50}Cr{sub 0.50}.

  3. Nanogranular Fe{sub x}Ni{sub 23-x}B{sub 6} phase formation during devitrification of nickel-rich Ni{sub 64}Fe{sub 16}Zr{sub 7}B{sub 12}Au{sub 1} amorphous alloy

    SciTech Connect

    Idzikowski, B.; Szajek, A.; Greneche, J.-M.; Kovac, J.

    2004-08-23

    Nickel-rich amorphous precursors with chemical composition of Ni{sub 64}Fe{sub 16}Zr{sub 7}B{sub 12}Au{sub 1} were produced by melt-spinning technique and then heat treated at temperatures ranging from 435 to 600 deg. C for 1 h to form a nanostructure. Properties of the amorphous and the nanocrystalline samples were investigated by the differential scanning calorimetry, the x-ray diffraction (XRD), the vibrating sample magnetometry, and Moessbauer techniques. The annealing favors the emergence of cubic Fe{sub x}Ni{sub 23-x}B{sub 6} crystalline grains (10-25 nm in diameter). Magnetic measurements made at 4.2-1100 K reveal rather high value of saturation magnetization (nearly 60 and 40 Am{sup 2}/kg at 4.2 K and room temperature, respectively) in amorphous as well as in nanocrystalline states. These facts are consistent with 300 K {sup 57}Fe Moessbauer effect results which are well supported by the calculations of Ni and Fe magnetic moments in Ni{sub 23}B{sub 6} and Fe{sub 23}B{sub 6} phases, using the spin polarized tight binding linear muffin-tin orbital method. However, anomalous high magnetic moments of Fe atoms were found in some inequivalent positions in the crystal structure.

  4. Exchange interactions in Dy{sub x}Tm{sub 1{minus}x}Fe{sub 10}Si{sub 2} compounds

    SciTech Connect

    Stefanski, P.; Kowalczyk, A.; Budzynski, M.

    1994-03-01

    Moessbauer measurements were performed on Dy{sub x}Tm{sub 1{minus}x}Fe{sub 10}Si{sub 2} samples (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0). The hyperfine magnetic fields at {sup 57}Fe nuclei were investigated, their changes caused by replacement of Tm by Dy atoms. Measurements were performed in transmission geometry using a constant acceleration Moessbauer spectrometer. The substitution of Tm atoms by the Dy atoms causes an increase of internal magnetic fields. In pure TmFe{sub 10}Si{sub 2} the hyperfine magnetic fields at 8(i), 8(j) and 8(f) positions are respectively equal to 25.3, 23.0 and 21.2 T. The complete substitution of Tm by Dy gives the average increase of hyperfine magnetic field magnitude equal to 0.6 T. The molecular field approximation was applied to calculate the intra- and intersublattice exchange interactions considering experimental Curie temperatures of the investigated compounds. The calculated exchange coupling constants between rare earth and iron sublattices increase when substituting Tm by Dy.

  5. Mössbauer Effect Study of Seawater-Neutralized Red Mud and its Adsorption Properties

    NASA Astrophysics Data System (ADS)

    Coyle, C. M.; Cashion, J. D.

    2005-04-01

    The 57Fe Mössbauer spectra of seawater-neutralized red mud from the Gladstone, Queensland, alumina refinery was found to be due almost entirely to SPM and magnetically split hematite, for which the Morin transition had been suppressed below 5 K. Adsorption of metal ions from solutions with varying concentrations of Cd, Cr, Cu, Mn, Pb and Zn either enhanced or reduced the magnetic relaxation frequency in small concentrations, depending on the ion, but always reduced the relaxation frequency at large concentrations. Precipitation of hydrocerussite, Pb3(OH)2(CO3)2 was identified from the XRD spectrum.

  6. Mössbauer study of dissimilatory reduction of iron contained in glauconite by alkaliphilic bacteria

    NASA Astrophysics Data System (ADS)

    Chistyakova, Nataliya I.; Rusakov, Vyacheslav S.; Shapkin, Alexey A.; Zhilina, Tatyana N.; Zavarzina, Darya G.

    2012-03-01

    57Fe Mössbauer investigations of glauconite and new solid phases formed during the process of the bacterial growth in alkaline environment were carried out at room temperature, 78 K and 4.8 K. The magnetically ordered phase formed during bioleaching of glauconite by G. ferrihydriticus in pure culture or in combination with Cl. alkalicellulosi represented as a mixture of off-stoichiometric magnetite and maghemite. In case of combined binary bacterium culture growth the relative content of magnetically ordered phase was more than for the G. ferrihydriticus growth.

  7. Mössbauer and XRD study of intercalated CaFe-layered double hydroxides

    NASA Astrophysics Data System (ADS)

    Sipiczki, Mónika; Kuzmann, Ernő; Pálinkó, István; Homonnay, Zoltán; Sipos, Pál; Kukovecz, Ákos; Kónya, Zoltán

    2014-04-01

    N-containing fully saturated (L-prolinate) or aromatic (indole-2-carboxylate) heterocyclic anions were immobilised in CaFe-layered double hydroxide with the dehydration-rehydration method from aqueous ethanol or acetone. The structure of the resulting organic-inorganic hybrids was characterised mainly with powder X-ray diffraction and 57Fe Mössbauer spectroscopy, and as supplementary analysis scanning electron microscopy, energy dispersive X-ray spectroscopy with elemental mapping and molecular modelling were also applied. It was found that the solvent mixture used for the synthesis caused enormous difference in the interlayer spacings of the obtained inorganic-organic hybrids.

  8. Photoelectron, nuclear gamma-ray and infrared absorption spectroscopic studies of neptunium in sodium silicate glass

    SciTech Connect

    Veal, B.W.; Carnall, W.T.; Dunlap, B.D.; Mitchell, A.W.; Lam, D.J.

    1986-04-01

    The valence state of neptunium ions in sodium silicate glasses prepared under reducing and oxidizing conditions has been investigated by the x-ray photoelectron, Moessbauer and optical absorption spectroscopic techniques. Results indicate that the Np ions are tetravalent in glasses prepared under reducing conditions and pentavalent in glasses prepared under oxidizing conditions.

  9. A study of defects in iron-based binary alloys by the Mössbauer and positron annihilation spectroscopies

    SciTech Connect

    Idczak, R. Konieczny, R.; Chojcan, J.

    2014-03-14

    The room temperature positron annihilation lifetime spectra and {sup 57}Fe Mössbauer spectra were measured for pure Fe as well as for iron-based Fe{sub 1−x}Re{sub x}, Fe{sub 1−x}Os{sub x}, Fe{sub 1−x}Mo{sub x}, and Fe{sub 1−x}Cr{sub x} solid solutions, where x is in the range between 0.01 and 0.05. The measurements were performed in order to check if the known from the literature, theoretical calculations on the interactions between vacancies and solute atoms in iron can be supported by the experimental data. The vacancies were created during formation and further mechanical processing of the iron systems under consideration so the spectra mentioned above were collected at least twice for each studied sample synthesized in an arc furnace— after cold rolling to the thickness of about 40 μm as well as after subsequent annealing at 1270 K for 2 h. It was found that only in Fe and the Fe-Cr system the isolated vacancies thermally generated at high temperatures are not observed at the room temperature and cold rolling of the materials leads to creation of another type of vacancies which were associated with edge dislocations. In the case of other cold-rolled systems, positrons detect vacancies of two types mentioned above and Mössbauer nuclei “see” the vacancies mainly in the vicinity of non-iron atoms. This speaks in favour of the suggestion that in iron matrix the solute atoms of Os, Re, and Mo interact attractively with vacancies as it is predicted by theoretical computations and the energy of the interaction is large enough for existing the pairs vacancy-solute atom at the room temperature. On the other hand, the corresponding interaction for Cr atoms is either repulsive or attractive but smaller than that for Os, Re, and Mo atoms. The latter is in agreement with the theoretical calculations.

  10. Mono- and Dinuclear Iron Complexes of Bis(1-methylimidazol-2-yl)ketone (bik): Structure, Magnetic Properties and Catalytic Oxidation Studies

    PubMed Central

    Bruijnincx, Pieter C. A.; Buurmans, Inge L. C.; Huang, Yuxing; Juhász, Gergely; Viciano-Chumillas, Marta; Quesada, Manuel; Reedijk, Jan; Lutz, Martin; Spek, Anthony L.; Münck, Eckard; Bominaar, Emile L.; Klein Gebbink, Robertus J. M.

    2011-01-01

    The newly synthesized dinuclear complex [FeIII2(μ-OH)2(bik)4](NO3)4 (1) (bik, bis(1-methylimidazol-2-yl)ketone) shows rather short Fe···Fe (3.0723(6) Å) and Fe–O distances (1.941(2)/1.949(2) Å) compared to other unsupported FeIII2(μ-OH)2 complexes. The bridging hydroxide groups of 1 are strongly hydrogen bonded to a nitrate anion. The 57Fe isomer shift (δ = 0.45 mm s−1) and quadrupole splitting (ΔEQ = 0.26 mm s−1) obtained from Mössbauer spectroscopy are consistent with the presence of two identical high-spin iron(III) sites. Variable temperature magnetic susceptibility studies revealed antiferromagnetic exchange (J = 35.9 cm−1 and = JS1·S2) of the metal ions. The optimized DFT geometry of the cation of 1 in the gas phase agrees well with the crystal structure, but both the Fe···Fe and Fe-OH distances are overestimated (3.281 and 2.034 Å, respectively). The agreement in these parameters improves dramatically (3.074 and 1.966 Å) when the hydrogen-bonded nitrate groups are included, reducing the value calculated for J by 35%. Spontaneous reduction of 1 was observed in methanol, yielding a blue [FeII(bik)3]2+ species. Variable temperature magnetic susceptibility measurements of [FeII(bik)3](OTf)2 (2) revealed spin crossover behavior. Thermal hysteresis was observed with 2, due to a loss of co-crystallized solvent molecules, as monitored by thermogravimetric analysis. The hysteresis disappears once the solvent is fully depleted by thermal cycling. [FeII(bik)3](OTf)2 (2) catalyzes the oxidation of alkanes with t-BuOOH. High selectivity for tertiary C-H bond oxidation was observed with adamantane (3°/2° value of 29.6); low alcohol/ketone ratios in cyclohexane and ethylbenzene oxidation, a strong dependence of total turnover number on the presence of O2, and a low retention of configuration in cis-1,2-dimethylcyclohexane oxidation were observed. Stereoselective oxidation of olefins with dihydrogen peroxide yielding epoxides was observed under

  11. Mössbauer and vibrational DOS studies of diluted magnetic tin oxides and nano iron oxides

    NASA Astrophysics Data System (ADS)

    Nomura, K.; Rykov, A. I.; Navarro, A. M. Mudarra; Torres, C. E. Rodriguez; Errico, L. A.; Barrero, C. A.; Yoda, Y.

    2013-04-01

    The magnetic properties and Mössbauer results for SnO2 doped with 57Fe are reviewed, and the values of isomer shift and quadrupole splitting are compared with the results obtained by ab initio calculations. It is concluded that the exchange interactions between oxygen defects and magnetic atoms are responsible for long range magnetic interactions of dilute Fe ions dispersed in SnO2. Fe atom precipitated clusters may be formed in highly Fe doped SnO2 samples by annealing at relatively high temperatures for several hours. The reduction of the particle size to nano-scale dimensions induces magnetization, which can be associated with oxygen defects. We have measured the nuclear inelastic scattering (NIS) spectra of Fe oxides, and 57Fe and (Co or Mn) doped SnO2 synthesized mainly by sol-gel methods and we have derived the vibration density of states (VDOS). The local phonons are sensitive to the presence of precipitated clusters.

  12. Mössbauer and vibrational DOS studies of diluted magnetic tin oxides and nano iron oxides

    NASA Astrophysics Data System (ADS)

    Nomura, K.; Rykov, A. I.; Navarro, A. M. Mudarra; Torres, C. E. Rodriguez; Errico, L. A.; Barrero, C. A.; Yoda, Y.

    2014-01-01

    The magnetic properties and Mössbauer results for SnO2 doped with 57Fe are reviewed, and the values of isomer shift and quadrupole splitting are compared with the results obtained by ab initio calculations. It is concluded that the exchange interactions between oxygen defects and magnetic atoms are responsible for long range magnetic interactions of dilute Fe ions dispersed in SnO2. Fe atom precipitated clusters may be formed in highly Fe doped SnO2 samples by annealing at relatively high temperatures for several hours. The reduction of the particle size to nano-scale dimensions induces magnetization, which can be associated with oxygen defects. We have measured the nuclear inelastic scattering (NIS) spectra of Fe oxides, and 57Fe and (Co or Mn) doped SnO2 synthesized mainly by sol-gel methods and we have derived the vibration density of states (VDOS). The local phonons are sensitive to the presence of precipitated clusters.

  13. Mössbauer study of spin structure transformation from an incommensurate to a commensurate state

    NASA Astrophysics Data System (ADS)

    Choi, Kang Ryong; Park, Seung-Iel; Kim, Sam Jin; Kim, Chul Sung

    2009-01-01

    We present crystallographic and magnetic properties of NiCr1.98 57Fe0.02O4 by using X-ray diffractometry (XRD), vibrating sample magnetometry (VSM), and Mössbauer spectroscopy. The lattice constants a0 were determined to be 8.318 Å. The ferrimagnetic Neel temperature ( T N) for NiCr1.98 57Fe0.02O4 is determined to be 90 K. The Mössbauer absorption spectra for all chromites at 4.2 K show two well developed sextets superposed with small difference of hyperfine fields ( H hf) caused by Cr3 + ions in two different magnetic sites. The values of the isomer shifts show that the charge states of Fe are Fe3 + for all temperature range. Ni-chromites Mössbauer spectra below T N present aline broadening due to a Jahn-Teller distortion and show that spin structure behavior of Cr ions change from an incommensurate to a commensurate state.

  14. Structure and magnetic properties of the Al{sub 1-x}Ga{sub x}FeO{sub 3} family of oxides: A combined experimental and theoretical study

    SciTech Connect

    Saha, Rana; Shireen, Ajmala; Bera, A.K.; Shirodkar, Sharmila N.; Sundarayya, Y.; Kalarikkal, Nandakumar; Yusuf, S.M.; Waghmare, Umesh V.; Sundaresan, A.; Rao, C.N.R

    2011-03-15

    Magnetic properties of the Al{sub 1-x}Ga{sub x}FeO{sub 3} family of oxides crystallizing in a non-centrosymmetric space group have been investigated in detail along with structural aspects by employing X-ray and neutron diffraction, Moessbauer spectroscopy and other techniques. The study has revealed the occurrence of several interesting features related to unit cell parameters, site disorder and ionic size. Using first-principles density functional theory based calculations, we have attempted to understand how magnetic ordering and related properties in these oxides depend sensitively on disorder at the cation site. The origin and tendency of cations to disorder and the associated properties are traced to the local structure and ionic sizes. -- Graphical abstract: We have studied both experimentally and theoretically the important role of disorder at the cation site on magnetic and related properties of the Al{sub 1-x}Ga{sub x}FeO{sub 3} family of oxides crystallizing in a non-centrosymmetric space group. Display Omitted Research highlights: {yields} Interesting observations on cation site disorder, cell parameters and ionic size. {yields} Cation site disorder explains magnetic ordering. {yields} Demonstrates the importance of the A-site cations.

  15. Mossbauer study of the Allende meteorite

    NASA Astrophysics Data System (ADS)

    Oliver, F. W.; Isuk, E. E.; Wynter, C.

    1984-03-01

    A room temperature spectrum of a Moessbauer investigation of the Allende III carbonaceous chondrite is presented. Analysis demonstrates that the iron minerals are predominantly olivine, and that there exists a small quantity of a phyllosilicate or goethite. The magnitude of the isomer shift relative to iron foil (1.43 + or - .01 mm/s) for the olivine shows iron to be in the Fe(2) state. Quadrupole splitting of the olivine is 2.92 + or - .01 m/s. Nothing suggests appreciable quantities of ferromagnetic materials.

  16. Mössbauer study of nanostructured iron fluoride powders

    NASA Astrophysics Data System (ADS)

    Guérault, H.; Tamine, M.; Grenèche, J. M.

    2000-11-01

    Nanostructured iron fluoride powders were prepared using the grinding route for different times and different intensities. Their structural, microstructural and magnetic properties are investigated by means of both transmission Mössbauer spectrometry as a function of temperature and in-field 57Fe Mössbauer spectrometry. We report a fitting procedure which successfully describes the zero-field Mössbauer spectra recorded at different temperatures. It allows us to describe the powders as crystalline grains and grain boundaries which behave as antiferromagnets and speromagnets, respectively. Such arrangements are confirmed by in-field Mössbauer spectrometry. According to x-ray diffraction data, the size of grains and the thickness of grain boundaries are found to be strongly dependent on the grinding conditions. The occurrence of superparamagnetic effects at high temperature gives clear evidence for the role of grain boundaries in the magnetic coupling of crystalline grains.

  17. Studies of Fe/sup 2 +/. -->. Fe/sup 3 +/ transitions during the process of rock weathering by nuclear gamma-resonance spectroscopy

    SciTech Connect

    Vasil'ev, S.P.; Babanin, V.F.; Solov'ev, A.A.

    1986-11-01

    This paper presents a method for the mineral and weathering assessment of rocks and carbonaceous matter based in gamma spectroscopy and transitions between iron ions. The method is applied to rocks collected near the Teberda preserve. Four latitudinal bands of rocks parallel to the Greater Caucasus Ridge are identified in this territory. Isomer shift and hyperfine parameters of the Moessbauer spectra are given.

  18. Mössbauer Properties of the Diferric Cluster and the Differential Iron(II)-Binding Affinity of the Iron Sites in Protein R2 of Class Ia Escherichia coli Ribonucleotide Reductase: A DFT/Electrostatics Study

    PubMed Central

    Han, Wen-Ge; Sandala, Gregory M.; Giammona, Debra Ann; Bashford, Donald; Noodleman, Louis

    2013-01-01

    The R2 subunit of class-Ia ribonucleotide reductase (RNR) from Escherichia coli (E. coli) contains a diiron active site. Starting from the apo-protein and Fe(II) in solution at low Fe(II)/apoR2 ratios, mononuclear Fe(II) binding is observed indicating possible different Fe(II) binding affinities for the two alternative sites. Further, based on their Mössbauer spectroscopy and two-iron-isotope reaction experiments, Bollinger et al. (J. Am. Chem. Soc., 1997, 119, 5976–5977) proposed that the site Fe1, which bonds to Asp84, should be associated with the higher observed 57Fe Mössbauer quadrupole splitting (2.41 mm s−1) and lower isomer shift (0.45 mm s−1) in the Fe(III)Fe(III) state, site Fe2, which is further from Tyr122, should have a greater affinity for Fe(II) binding than site Fe1, and Fe(IV) in the intermediate X state should reside at site Fe2. In this paper, using density functional theory (DFT) incorporated with the conductor like screening (COSMO) solvation model and with the finite-difference Poisson-Boltzmann self-consistent reaction field (PB-SCRF) methodologies, we have demonstrated that the observed large quadrupole splitting for the diferric state R2 does come from site Fe1(III) and it is mainly caused by the binding position of the carboxylate group of Asp84 sidechain. Further, a series of active site clusters with mononuclear Fe(II) binding at either site Fe1 or Fe2 have been studied, which show that with single dielectric medium outside the active site quantum region, there is no energetic preference for Fe(II) binding at one site over another. However, when including the explicit extended protein environment in the PB-SCRF model, the reaction field favors the Fe(II) binding at site Fe2 rather than at site Fe1 by ~9 kcal mol−1. Therefore our calculations support the proposal of the previous Mössbauer spectroscopy and two-iron-isotope reaction experiments by Bollinger et al. PMID:21837345

  19. An inelastic nuclear resonant scattering study of partial entropies of ordered and disordered Fe{sub 3}Al

    SciTech Connect

    Fultz, B.; Sturhahn, W.; Toellner, T. S.; Alp, E. E.

    1999-11-29

    Inelastic nuclear resonant scattering spectra were measured on alloys of Fe{sub 3}Al that were chemically disordered, partially-ordered, and DO{sub 3}-ordered. The phonon partial DOS for {sup 57}Fe atoms were extracted from these data, and the change upon disordering in the partial vibrational entropy of Fe atoms was obtained. By comparison to previous calorimetry measurements, it is shown that the contribution of the Fe atoms to the vibrational entropy is a factor of 10 smaller than that of the Al atoms. With the assistance of Born - von Karman model calculations on the ordered alloy, it is shown that differences in the vibrational entropy originate primarily with changes in the optical modes upon disordering. The phonon DOS of {sup 57}Fe was found to change systematically with chemical short range order in the alloy. It is argued that changes in the vibrational entropy originate primarily with changes in the chemical short-range order in the alloy, as opposed to long-range order.

  20. Non-Heme Iron Absorption and Utilization from Typical Whole Chinese Diets in Young Chinese Urban Men Measured by a Double-Labeled Stable Isotope Technique

    PubMed Central

    Yang, Lichen; Zhang, Yuhui; Wang, Jun; Huang, Zhengwu; Gou, Lingyan; Wang, Zhilin; Ren, Tongxiang; Piao, Jianhua; Yang, Xiaoguang

    2016-01-01

    Background This study was to observe the non-heme iron absorption and biological utilization from typical whole Chinese diets in young Chinese healthy urban men, and to observe if the iron absorption and utilization could be affected by the staple food patterns of Southern and Northern China. Materials and Methods Twenty-two young urban men aged 18–24 years were recruited and randomly assigned to two groups in which the staple food was rice and steamed buns, respectively. Each subject received 3 meals containing approximately 3.25 mg stable 57FeSO4 (the ratio of 57Fe content in breakfast, lunch and dinner was 1:2:2) daily for 2 consecutive days. In addition, approximately 2.4 mg 58FeSO4 was administered intravenously to each subject at 30–60 min after dinner each day. Blood samples were collected from each subject to measure the enrichment of the 57Fe and 58Fe. Fourteen days after the experimental diet, non-heme iron absorption was assessed by measuring 57Fe incorporation into red blood cells, and absorbed iron utilization was determined according to the red blood cell incorporation of intravenously infused 58Fe SO4. Results Non-heme iron intake values overall, and in the rice and steamed buns groups were 12.8 ±2.1, 11.3±1.3 and 14.3±1.5 mg, respectively; the mean 57Fe absorption rates were 11±7%, 13±7%, and 8±4%, respectively; and the mean infused 58Fe utilization rates were 85±8%, 84±6%, and 85±10%, respectively. There was no significantly difference in the iron intakes, and 57Fe absorption and infused 58Fe utilization rates between rice and steamed buns groups (all P>0.05). Conclusion We present the non-heme iron absorption and utilization rates from typical whole Chinese diets among young Chinese healthy urban men, which was not affected by the representative staple food patterns of Southern and Northern China. This study will provide a basis for the setting of Chinese iron DRIs. PMID:27099954

  1. Relevance of supramolecular interactions, texture and lattice occupancy in the designer iron(II) spin crossover complexes

    SciTech Connect

    Naik, Anil D.; Tinant, Bernard; Muffler, Kai; Wolny, Juliusz A.; Schuenemann, Volker; Garcia, Yann

    2009-06-15

    New Fe{sup II} complexes of formula [Fe(3-Br-phen){sub 2}(NCS){sub 2}].Solvent (Solvent=0.5 CH{sub 3}OH (1), 2 CH{sub 2}Cl{sub 2} (2), desolvation of 2 (3), 0.5 CH{sub 3}COCH{sub 3} (4) and 0 (5)) have been synthesized. {sup 57}Fe Moessbauer and magnetic investigation reveal unique features atypical of classic [Fe(phen){sub 2}(NCS){sub 2}] polymorphs. Complex 1, prepared by precipitation in MeOH, undergoes upon cooling below room temperature an incomplete and gradual thermally induced spin conversion, while 4 prepared by an extraction method remains mostly in the low-spin state. The non solvated compounds 3 and 5, display a more abrupt spin crossover on cooling around T{sub 1/2}=175 K and T{sub 1/2}=198 K, respectively. Defects/soft lattice inclusion due to different methods of material synthesis, extent of aging, reaction medium and associated solvent molecules have enormous influence on the particle size and magnetic properties of these complexes. Scanning electron micrographs helps to establish a logical relationship among methods employed for synthesis, texture of materials and their effect on magnetic properties. The crystal structure of 2 determined in the monoclinic space group P2/c (100 K) reveals a mononuclear complex consisting of a distorted FeN{sub 6} octahedron in the low-spin state, constructed from two 3-bromo-1, 10-phenanthroline and two isothiocyanato anions in cis position. Intermolecular interactions between mononuclear units of the S...Br, S...C(H) and pi-pi type afford a 2D supramolecular network. DFT calculations for the single molecule 2 reveals an energy difference between high-spin and low-spin isomers of 7 kJ/mol suggesting a slight destabilization of the low-spin state compared to [Fe(phen){sub 2}(NCS){sub 2}]. Normal co-ordinate analysis was also carried out for 3 and compared with experimental temperature dependent Raman spectra for 5. - Graphical abstract: New Fe{sup II} complexes of formula [Fe(3-Br-phen){sub 2}(NCS){sub 2}].Solvent

  2. Synthetic Coprecipitates of Exopolysaccharides and Ferrihydrite. Part I: Characterization

    SciTech Connect

    Mikutta,C.; Mikutta, R.; Bonneville, S.; Wagner, F.; Voegelin, A.; Christl, I.; Kretzschmar, R.

    2008-01-01

    Iron(III) (hydr)oxides formed at extracellular biosurfaces or in the presence of exopolymeric substances of microbes and plants may significantly differ in their structural and physical properties from their inorganic counterparts. We synthesized ferrihydrite (Fh) in solutions containing acid polysaccharides [polygalacturonic acid (PGA), alginate, xanthan] and compared its properties with that of an abiotic reference by means of X-ray diffraction, transmission electron microscopy, gas adsorption (N2, CO2), X-ray absorption spectroscopy, 57Fe Moessbauer spectroscopy, and electrophoretic mobility measurements. The coprecipitates formed contained up to 37 wt% polymer. Two-line Fh was the dominant mineral phase in all precipitates. The efficacy of polymers to precipitate Fh at neutral pH was higher for polymers with more carboxyl C (PGA {approx} alginate > xanthan). Pure Fh had a specific surface area of 300 m2/g; coprecipitation of Fh with polymers reduced the detectable mineral surface area by up to 87%. Likewise, mineral micro- (<2 nm) and mesoporosity (2-10 nm) decreased by up to 85% with respect to pure Fh, indicative of a strong aggregation of Fh particles by polymers in freeze-dried state. C-1s STXM images showed the embedding of Fh particles in polymer matrices on the micrometer scale. Iron EXAFS spectroscopy revealed no significant changes in the local coordination of Fe(III) between pure Fh and Fh contained in PGA coprecipitates. 57Fe Moessbauer spectra of coprecipitates confirmed Fh as dominant mineral phase with a slightly reduced particle size and crystallinity of coprecipitate-Fh compared to pure Fh and/or a limited magnetic super-exchange between Fh particles in the coprecipitates due to magnetic dilution by the polysaccharides. The pHiep of pure Fh in 0.01 M NaClO4 was 7.1. In contrast, coprecipitates of PGA and alginate had a pHiep < 2. Considering the differences in specific surface area, porosity, and net charge between the coprecipitates and pure Fh

  3. Mössbauer study of metallic iron and iron oxide nanoparticles having environmental purifying ability

    NASA Astrophysics Data System (ADS)

    Kubuki, Shiro; Watanabe, Yuka; Akiyama, Kazuhiko; Ristić, Mira; Krehula, Stjepko; Homonnay, Zoltán; Kuzmann, Ernő; Nishida, Tetsuaki

    2014-10-01

    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 Mössbauer spectroscopy, X-ray diffractometry and UV-visible light absorption spectroscopy. γ- Fe2O3 NPs were successfully prepared by mixing ( NH4)2Fe ( SO4)2ṡ6H2O (Mohr's salt) and ( NH4)3Fe ( C2O4)3ṡ3H2O 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 Mössbauer 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 Mössbauer 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 and γ- Fe2O3 NPs (3:7 ratio, 100 mg) in MB aqueous solution (20 mL) for 6 h showed a remarkable decrease of MB concentration with the first-order rate constant (kMB) of 6.7 × 10-1 h-1. This value is larger than that obtained for the bleaching test using bulk Fe0+γ- Fe2O3 (3:7) mixture (kMB= 6.5×10-3h-1) . These results prove that MB decomposing ability is enhanced by the NPs mixture of Fe0 and γ- Fe2O3.

  4. Level Densities of Residual Nuclei from particle evaporation of {sup 64}Cu

    SciTech Connect

    Oginni, B. M.; Grimes, S. M.; Voinov, A. V.; Adekola, A. S.; Brune, C. R.; Carter, D.; Heinen, Z.; Jacobs, D.; Massey, T. N.; O'Donnell, J.

    2009-07-06

    The reactions of {sup 6}Li on {sup 58}Fe and {sup 7}Li on {sup 57}Fe have been studied at beam energy 15 MeV. These two reactions produce the same compound nucleus, {sup 64}Cu. The neutron, proton, and alpha spectra were measured at backward angles. The data obtained have been compared with Hauser Fesh-bach model calculations. The level density parameters of the residual nuclei have been obtained from the particle evaporation spectra.

  5. Mössbauer spectra obtained using β - γ coincidence method after 57Mn implantation into LiH and LiD

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Kobayashi, Y.; Yamada, Y.; Kubo, M. K.; Mihara, M.; Nagatomo, T.; Sato, W.; Miyazaki, J.; Tanigawa, S.; Natori, D.; Sato, S.; Kitagawa, A.

    2016-12-01

    Highly energetic 57Mn ( T 1/2 = 1.45 m) was generated by nuclear projectile fragmentation in a heavy-ion accelerator, and implanted into lithium hydride (LiH) and lithium deuteride (LiD) at 578 K. Mössbauer spectroscopy with β - γ coincidence detection was then carried out on the 57Fe obtained from β -decay of the 57Mn to study the time dependence of the site distributions and coordination environments of dilute Fe atoms implanted in the LiH and LiD. The results suggest that the Fe atoms can substitute for either the Li and H or D atoms within 100 ns. Additionally, the displacement behavior of the substitutional 57Fe atoms on the lattice sites is discussed.

  6. High-temperature Mössbauer-effect measurements with a precision furnace

    NASA Astrophysics Data System (ADS)

    Kolk, B.; Bleloch, A.; Hall, D. B.; Zheng, Y.; Patton-Hall, K. E.

    1985-08-01

    A furnace system is presented for Mössbauer-effect spectroscopy at temperatures up to 1200 K with a temperature stability better than 0.03 K. This system allows the study of samples at high temperatures in an external magnetic field of a few kG with a homogeneity of better than 1%. Our measurements show that a few degrees above the Curie temperature TC, such an external field induces a considerable hyperfine field at 57Fe nuclei in iron. In addition, the magnetic hyperfine field and the isomer shift of 57Fe in metallic iron are measured over a temperature range of 300 to 1100 K. It is shown that a relatively small nonlinear behavior of the Mössbauer velocity drive system may result in a pseudodiscontinuity in the isomer shift δ near the Curie temperature, explaining the anomalous behavior observed for δ of iron and of some iron alloys in this region.

  7. A study of the influence of crystallite size on the electrical and magnetic properties of CuFe{sub 2}O{sub 4}

    SciTech Connect

    Iqbal, Muhammad Javed; Yaqub, Nadia; Sepiol, Bogdan; Ismail, Bushra

    2011-11-15

    Graphical abstract: A plot of crystallite size against the normalized values of resistivity, dielectric constant and the drift mobility of the CuFe{sub 2}O{sub 4} materials. Highlights: {yields} The CuFe{sub 2}O{sub 4} materials of different crystallite sizes of <100 nm are prepared by sol-gel method and others of the size of >100 nm by combustion method. {yields} The synthesized samples are characterized for different electrical, dielectrical, magnetic and structural properties. {yields} The results show a sudden change in dc-electrical resistivity, Curie temperature, dielectric parameters, etc. when their crystallite size approaches 84 nm. {yields} This study shows transition from bulk to the nano regime takes place at the particle size of 84 nm. -- Abstract: An attempt has been made to clarify the fundamental assumption that the properties of materials change as the crystallite size of the material is reduced below 100 nm. CuFe{sub 2}O{sub 4} samples of different crystallite sizes were prepared by the sol-gel and combustion methods and then analyzed by X-ray diffraction (XRD), thermal analyses (TGA/DTG) and scanning electron microscopy (SEM) techniques. The magnetic properties were studied by measuring the AC magnetic susceptibility ({chi}) and the Moessbauer spectroscopy. The DC electrical resistivity, dielectric constant, dielectric loss tangent, Curie temperature and hyperfine splitting of the samples change with the crystallite size. The change in the electrical properties is attributed to the formation of discrete energy levels instead of the bands. However, the magnetic parameters change due to the existence of non magnetic surface layers. The isomer shift and the hyperfine splitting show gradual increase with the increase in crystallite sizes.

  8. A Calorimetric Study of Almandine: Are the Thermodynamic Properties of the End-Member Aluminosilicate Garnets Finally Known Quantitatively?

    NASA Astrophysics Data System (ADS)

    Dachs, E.; Geiger, C. A.; Benisek, A.

    2012-12-01

    The aluminosilicate garnets (E3Al2Si3O12 with E = Fe2+, Mn2+, Ca, Mg) form an important rock-forming mineral group. Much study has been directed toward determining their thermodynamic properties. The iron end-member almandine (Fe3Al2Si3O12) is a key phase in many petrologic investigations. As part of an ongoing calorimetric and thermodynamic study of the aluminosilicate garnets, the heat capacity of three synthetic well-characterized polycrystalline almandine garnets and one natural almandine-rich single crystal was measured. The various garnets were characterized by optical microscopy, electron-microprobe analysis, X-ray powder diffraction and 57Fe Mössbauer spectroscopy. Heat capacity measurements were performed in the temperature range 3 to 300 K using relaxation calorimetry and between 282 and 764 K using DSC methods. From the former, So values between 336.7 ± 0.8 and 337.8 ± 0.8 J/molK are calculated for the different samples. The smaller value is considered the best So for end-member stoichiometric almandine, because it derives from the "best" Fe3+-free synthetic sample. The Cp behavior for almandine at T > 298 K is given by the polynomial (in J/molK): Cp = 649.06(±4) - 3837.57(±122)T-0.5 - 1.44682(±0.06)107T-2 + 1.94834(±0.09)109T-3, which is calculated using DSC data together with one published heat-content datum determined by transposed-drop calorimetry along with a new determination that gives H1181K - H302K = 415.0 ± 3.2 kJ/mole. Almandine shows a λ-type heat-capacity anomaly at low temperatures resulting from a paramagnetic-antiferromagnetic phase transition at about 9 K. The lattice heat capacity was calculated using the single-parameter phonon dispersion model of Komada and Westrum (1997), which allows the non-lattice heat capacity (Cex) behavior to be modelled. An analysis shows the presence of an electronic heat-capacity contribution (Cel - Schottky anomaly) around 17 K that is superimposed on a larger magnetic heat-capacity effect (Cmag

  9. Thermal low spin-high spin equilibrium of Fe(II) in thiospinels CuFe{sub 0.5}(Sn{sub (1-x)}Ti{sub x}){sub 1.5}S{sub 4} (0{<=}x{<=}1)

    SciTech Connect

    Womes, M.; Reibel, C.; Mari, A.; Zitoun, D.

    2011-04-15

    A series of spinel compounds with composition CuFe{sub 0.5}(Sn{sub (1-x)}Ti{sub x}){sub 1.5}S{sub 4} (0{<=}x{<=}1) is analysed by X-ray diffraction, measurements of magnetic susceptibilities and {sup 57}Fe Moessbauer spectroscopy. All samples show a temperature-dependent equilibrium between an electronic low spin 3d(t{sub 2g}){sup 6}(e{sub g}){sup 0} and a high spin 3d(t{sub 2g}){sup 4}(e{sub g}){sup 2} state of the Fe(II) ions. The spin crossover is of the continuous type and extends over several hundred degrees in all samples. The Sn/Ti ratio influences the thermal equilibrium between the two spin states. Substitution of Sn(IV) by the smaller Ti(IV) ions leads to a more compact crystal lattice, which, in contrast to many metal-organic Fe(II) complexes, does not stabilise the low spin state, but increases the residual high spin fraction for T{yields}0 K. The role played by antiferromagnetic spin coupling in the stabilisation of the high spin state is discussed. The results are compared with model calculations treating the effect of magnetic interactions on spin state equilibria. -- Graphical Abstract: Comparison of fractions of high spin Fe(II) from Moessbauer spectra (circles) with plots of {chi}{sub m}T (dots) versus T. Discrepancies between both methods indicate anti-ferromagnetic spin coupling. Display Omitted Research highlights: {yields} Many Fe(II) complexes show thermally induced high spin-low spin crossover. {yields} Spin crossover in spinel compounds is extremely scarce. {yields} Usually, lattice contraction favours the low spin state in Fe(II) complexes. {yields} In these spinels, lattice contraction favours the high spin state. {yields} The stabilisation of the high spin state is explained by spin-spin interactions.

  10. Mössbauer, electron paramagnetic resonance, and magnetic susceptibility studies on members of a new family of cyano-bridged 3d-4f complexes. Demonstration of anisotropic exchange in a Fe-Gd complex.

    PubMed

    Stoian, Sebastian A; Paraschiv, Carmen; Kiritsakas, Nathalie; Lloret, Francesc; Münck, Eckard; Bominaar, Emile L; Andruh, Marius

    2010-04-01

    The synthesis and crystallographic characterization of a new family of M(mu-CN)Ln complexes are reported. Two structural series have been prepared by reacting in water rare earth nitrates (Ln(III) = La, Pr, Nd, Sm, Eu, Gd, Dy, Ho) with K(3)[M(CN)(6)] (M(III) = Fe, Co) in the presence of hexamethylenetetramine (hmt). The first series consists of six isomorphous heterobinuclear complexes, [(CN)(5)M-CN-Ln(H(2)O)(8)].2hmt ([FeLa] 1, [FePr] 2, [FeNd] 3, [FeSm] 4, [FeEu] 5, [FeGd] 6), while the second series consists of four isostructural ionic complexes, [M(CN)(6)][Ln(H(2)O)(8)].hmt ([FeDy] 7, [FeHo] 8, [CoEu] 9, [CoGd] 10). The hexamethylenetetramine molecules contribute to the stabilization of the crystals by participating in an extended network of hydrogen bond interactions. In both series the aqua ligands are hydrogen bonded to the nitrogen atoms from both the terminal CN(-) groups and the hmt molecules. The [FeGd] complex has been analyzed with (57)Fe Mossbauer spectroscopy and magnetic susceptibility measurements. We have also analyzed the [FeLa] complex, in which the paramagnetic Gd(III) is replaced by diamagnetic La(III), with (57)Fe Mossbauer spectroscopy, electron paramagnetic resonance (EPR), and magnetic susceptibility measurements, to obtain information about the low-spin Fe(III) site that is not accessible in the presence of a paramagnetic ion at the complementary site. For the same reason, the [CoGd] complex, containing diamagnetic Co(III), was studied with EPR and magnetic susceptibility measurements, which confirmed the S = 7/2 spin of Gd(III). Prior knowledge about the paramagnetic sites in [FeGd] allows a detailed analysis of the exchange interactions between them. In particular, the question of whether the exchange interaction in [FeGd] is isotropic or anisotropic has been addressed. Standard variable-temperature magnetic susceptibility measurements provide only the value for a linear combination of J(x), J(y), and J(z) but contain no information

  11. Fe isotope behaviours during sulfide-dominated skarn-type mineralisation

    NASA Astrophysics Data System (ADS)

    Wang, Yue; Zhu, Xiang-kun; Cheng, Yanbo

    2015-05-01

    Fe isotope compositions of mineral separates and bulk samples from Dongguashan and Fenghuangshan skarn type Cu-Fe deposits in Tongling District, Middle-Lower Yangtze Valley Cu-Fe-Au-Mo polymetallic belt have been investigated. Differences in δ57Fe values exist in co-precipitated bornite-chalcopyrite and pyrite-chalcopyrite mineral pairs. The bornite is enriched in light iron isotopes relative to coexisting chalcopyrite, whereas pyrite samples show a tendency of heavy isotopes enrichment relative to chalcopyrite. Moreover, the δ57Fe values of endoskarn and the earliest formed Fe-mineral phase magnetite of the three deposits investigated in Tongling district are consistently lower relative to ore-related igneous rocks, suggesting Fe isotopic fractionation occurs during fluid exsolution and exsolved fluid is enriched in light Fe isotopes relative to the stock. Furthermore, spatial and temporal variations in δ57Fe values within single mineral phases are observed, suggesting iron isotopic fractionation occurs between mineral and fluid phases as a result of precipitation of Fe-bearing minerals during fluid evolution. Overall, according to Fe isotope compositions of three representative skarn deposits formed under the same geological setting in Tongling district, this study indicates that Fe isotopes have the potential to unraveling ore-forming processes, as well as constraining the metal sources of skarn deposits. Combining with results of previous studies, a protocol for using Fe isotopes to trace skarn-type metallogeny is proposed.

  12. Magnetic Texturing of Xenon-Irradiated Iron Films Studied by Magnetic Orientation Mössbauer Spectroscopy

    NASA Astrophysics Data System (ADS)

    Müller, G. A.; Lieb, K. P.; Carpene, E.; Zhang, K.; Schaaf, P.; Faupel, J.; Krebs, H. U.

    2004-11-01

    Modifications of magnetic properties upon heavy-ion irradiation have been recently investigated for films of ferromagnetic 3d-elements (Fe, Ni, Co) and alloys (permendur, permalloy), in relation to changes of their microstructure. Here we report on Xe-ion irradiation of a highly textured iron film prepared via pulsed-laser deposition on a MgO(100) single crystal and containing a thin 57Fe marker layer for magnetic orientation Mössbauer spectroscopy (MOMS). We compare the results with those obtained for a polycrystalline Fe/Si(100) sample produced by electron evaporation and premagnetized before Xe-irradiation in a 300 Oe external field. Characterization of the samples also included magneto-optical Kerr effect (MOKE), Rutherford backscattering spectroscopy (RBS) and X-ray diffraction (XRD).

  13. Local structure study of Fe dopants in Ni-deficit Ni3Al alloys

    DOE PAGESBeta

    V. N. Ivanovski; Umicevic, A.; Belosevic-Cavor, J.; Lei, Hechang; Li, Lijun; Cekic, B.; Koteski, V.; Petrovic, C.

    2015-08-24

    We found that the local electronic and magnetic structure, hyperfine interactions, and phase composition of polycrystalline Ni–deficient Ni 3-x FexAl (x = 0.18 and 0.36) were investigated by means of 57 Fe Mössbauer spectroscopy. The samples were characterized by X–ray diffraction and magnetization measurements. The ab initio calculations performed with the projector augmented wave method and the calculations of the energies of iron point defects were done to elucidate the electronic structure and site preference of Fe doped Ni 3 Al. Moreover, the value of calculated electric field gradient tensor Vzz=1.6 1021Vm-2 matches well with the results of Mössbauer spectroscopymore » and indicates that the Fe atoms occupy Ni sites.« less

  14. Mineralogy of SNC Meteorite EET79001 by Simultaneous Fitting of Moessbauer Backscatter Spectra

    NASA Technical Reports Server (NTRS)

    Morris, Richard V.; Agresti, D. G.

    2010-01-01

    We have acquired M ssbauer spectra for SNC meteorite EET79001 with a MIMOS II backscatter M ssbauer spectrometer [1] similar to those now operating on Mars as part of the Mars Exploration Rover (MER) missions. We are working to compare the Fe mineralogical composition of martian meteorites with in-situ measurements on Mars. Our samples were hand picked from the >1 mm size fraction of saw fines on the basis of lithology, color, and grain size (Table 1). The chips were individually analyzed at approx.300K by placing them on a piece of plastic that was in turn supported by the contact ring of the instrument (oriented vertically). Tungsten foil was used to mask certain areas from analysis. As shown in Figure 1, a variety of spectra was obtained, each resulting from different relative contributions of the Fe-bearing minerals present in the sample. Because the nine samples are reasonably mixtures of the same Fe-bearing phases in variable proportions, the nine spectra were fit simultaneously (simfit) with a common model, adjusting parameters to a single minimum chi-squared convergence criterion [2]. The starting point for the fitting model and values of hyperfine parameters was the work of Solberg and Burns [3], who identified olivine, pyroxene, and ferrous glass as major, and ilmenite and a ferric phase as minor (<5%), Fe-bearing phases in EET79001.

  15. a Spin Relaxation Model for the Moessbauer Spectra of Barium Tin

    NASA Astrophysics Data System (ADS)

    Irwin, George Michael

    The stochastic relaxation theory of Anderson and Sack is applied to the Mossbauer spectra of seven samples of BaSn_{rm x}Ti _{rm 2-x}Fe _4O_{11} with compositions x = 0.0, 0.4, 0.6, 0.8, 1.2, 1.6, and 2.0. The spectra were obtained at room temperature and in the temperature range 20 K to 170 K. The broad, low temperature spectra were analysed using least square fitting to a simple model for Fe^{3+} in which the ionic moment is subject to a molecular field and a perpendicular random field which induces transitions between spin states. The resulting fits rival the results of analyses on similar systems using static hyperfine field distributions while requiring only two free parameters to mimic the temperature dependence of the spectral lineshapes. The results verify a magnetic double transition in the sample with x = 0.0 which disappears as Sn is added, but suggests that the samples with x = 1.2, 1.6, and 2.0 also show a double transition that has not been observed using other methods.

  16. Moessbauer and SEM characterization of the scale on type 304 stainless steel

    SciTech Connect

    Waanders, F.B.; Vorster, S.W.; Engelbrecht, A.

    2000-05-10

    Defects that form on stainless steels during production cause reworking, leading to higher production costs associated with production delays. Primarily wrong casting, rolling, grinding, annealing and pickling practices cause typical metallurgical defects such as the formation of residual scale. In the present investigation the problem of residual scale development on austenitic stainless steel (type AISI 304, with typical composition 19%Cr, 8%Ni, 1.5%Mn, <1%Si and the balance Fe) was investigated. Scale that is not removed during the pickling process is referred to as residual scale. Characterization of the surface scale is a prerequisite for effective measures aimed at minimizing scale formation and the design of efficient descaling procedures. The scale consists of an outer layer of iron oxides and an inner layer composed of small grains of FeCr{sub 2}O{sub 4} with the scale-metal interface not uniform and oxidation occurring along grain boundaries. Internal oxidation is found near the scale-metal interface with the amount of unoxidized metal increasing toward the scale-metal interface. If the scale is not removed from the hot steel it may be rolled into the product surface which will then require additional processing. Descaling presently used for stainless steel comprises of acid pickling, mechanical descaling and electrolytic pickling.

  17. Non-traditional stable isotope behaviors in immiscible silica-melts in a mafic magma chamber

    PubMed Central

    Zhu, Dan; Bao, Huiming; Liu, Yun

    2015-01-01

    Non-traditional stable isotopes have increasingly been applied to studies of igneous processes including planetary differentiation. Equilibrium isotope fractionation of these elements in silicates is expected to be negligible at magmatic temperatures (δ57Fe difference often less than 0.2 per mil). However, an increasing number of data has revealed a puzzling observation, e.g., the δ57Fe for silicic magmas ranges from 0‰ up to 0.6‰, with the most positive δ57Fe almost exclusively found in A-type granitoids. Several interpretations have been proposed by different research groups, but these have so far failed to explain some aspects of the observations. Here we propose a dynamic, diffusion-induced isotope fractionation model that assumes Si-melts are growing and ascending immiscibly in a Fe-rich bulk magma chamber. Our model offers predictions on the behavior of non-traditional stable isotope such as Fe, Mg, Si, and Li that are consistent with observations from many A-type granitoids, especially those associated with layered intrusions. Diffusion-induced isotope fractionation may be more commonly preserved in magmatic rocks than was originally predicted. PMID:26620121

  18. Non-traditional stable isotope behaviors in immiscible silica-melts in a mafic magma chamber.

    PubMed

    Zhu, Dan; Bao, Huiming; Liu, Yun

    2015-01-01

    Non-traditional stable isotopes have increasingly been applied to studies of igneous processes including planetary differentiation. Equilibrium isotope fractionation of these elements in silicates is expected to be negligible at magmatic temperatures (δ(57)Fe difference often less than 0.2 per mil). However, an increasing number of data has revealed a puzzling observation, e.g., the δ(57)Fe for silicic magmas ranges from 0‰ up to 0.6‰, with the most positive δ(57)Fe almost exclusively found in A-type granitoids. Several interpretations have been proposed by different research groups, but these have so far failed to explain some aspects of the observations. Here we propose a dynamic, diffusion-induced isotope fractionation model that assumes Si-melts are growing and ascending immiscibly in a Fe-rich bulk magma chamber. Our model offers predictions on the behavior of non-traditional stable isotope such as Fe, Mg, Si, and Li that are consistent with observations from many A-type granitoids, especially those associated with layered intrusions. Diffusion-induced isotope fractionation may be more commonly preserved in magmatic rocks than was originally predicted. PMID:26620121

  19. Non-traditional stable isotope behaviors in immiscible silica-melts in a mafic magma chamber

    NASA Astrophysics Data System (ADS)

    Zhu, Dan; Bao, Huiming; Liu, Yun

    2015-12-01

    Non-traditional stable isotopes have increasingly been applied to studies of igneous processes including planetary differentiation. Equilibrium isotope fractionation of these elements in silicates is expected to be negligible at magmatic temperatures (δ57Fe difference often less than 0.2 per mil). However, an increasing number of data has revealed a puzzling observation, e.g., the δ57Fe for silicic magmas ranges from 0‰ up to 0.6‰, with the most positive δ57Fe almost exclusively found in A-type granitoids. Several interpretations have been proposed by different research groups, but these have so far failed to explain some aspects of the observations. Here we propose a dynamic, diffusion-induced isotope fractionation model that assumes Si-melts are growing and ascending immiscibly in a Fe-rich bulk magma chamber. Our model offers predictions on the behavior of non-traditional stable isotope such as Fe, Mg, Si, and Li that are consistent with observations from many A-type granitoids, especially those associated with layered intrusions. Diffusion-induced isotope fractionation may be more commonly preserved in magmatic rocks than was originally predicted.

  20. Low temperature behavior of hyperfine fields in amorphous and nanocrystalline FeMoCuB

    SciTech Connect

    Kohout, Jaroslav; Křišt'an, Petr; Kubániová, Denisa; Kmječ, Tomáš; Závěta, Karel; Štepánková, Helena; Lančok, Adriana; Sklenka, L'ubomír; Matúš, Peter; and others

    2015-05-07

    Low temperature (4.2 K) magnetic behavior of Fe{sub 76}Mo{sub 8}Cu{sub 1}B{sub 15} metallic glass was studied by {sup 57}Fe Mössbauer spectrometry (MS) and {sup 57}Fe NMR. Distributions of hyperfine magnetic fields P(B) were determined for as-quenched and annealed (nanocrystalline) samples with relative fraction of the grains about 43%. P(B) distributions were derived for both the amorphous matrix and nanocrystalline grains. NMR of alloys with natural and {sup 57}Fe enriched Fe enabled to assess the contribution of {sup 11}B to the total NMR signal. P(B) distribution of the as-quenched alloy derived from MS matches reasonably well the one from NMR of the enriched sample. NMR signal from the sample with natural Fe exhibits contributions from {sup 11}B nuclei. The principal NMR lines of the annealed alloys at 47 MHz correspond to bcc Fe nanocrystals. Small asymmetry of the lines towards higher frequencies might be an indication of possible impurity atoms in the bcc structure. The observed differences between natural and enriched samples are attributed to higher sensitivity in the latter. Positions of the lines attributed to bcc Fe nanocrystals obtained from MS and NMR are in perfect agreement.

  1. Crystal chemical properties of synthetic lazulite-scorzalite solid-solution series

    NASA Astrophysics Data System (ADS)

    Schmid-Beurmann, P.; Knitter, St.; Cemič, L.

    Members of the lazulite-scorzalite (MgAl2- (PO4)2(OH)2-FeAl2(PO4)2(OH)2) solid-solution series were synthesized in compositional steps of 12.5mol% at T=485°C and P=0.3GPa under hydrothermal conditions and controlled oxygen fugacities of the Ni/NiO-buffer. X-ray powder diffraction and 57Fe-Mössbauer studies show that under these conditions a complete solid-solution series is formed which is characterized by the substitution of Mg2+ and Fe2+ on the octahedral Me2+ site. The 57Fe-Mössbauer spectra which reveal the presence of both ferrous and ferric iron and the compositional data were interpreted in terms of a defect model with a distribution of the ferric ions over both the Me2+ and the Al3+ positions and vacancies on the Me2+ site. The 57Fe-Mössbauer parameters of the synthetic compounds correspond to those of natural lazulites except for the total absorption ratio of the ferric iron A(Fe3+)/(A(Fe3+)+A(Fe2+)), which is significantly higher in natural lazulites of the same composition. The total absorption ratio of the ferric iron increases from 4% in pure scorzalite to 15% in a Mg-rich solid-solution with xFe=12(1)%

  2. Hydride Properties and IRON-57 Mossbauer Effect Studies in TITANIUM(COPPER(1-Y)IRON(Y)) Intermetallic Compounds.

    NASA Astrophysics Data System (ADS)

    Zakaria, Ahmad

    1987-12-01

    The hydrogen absorption properties of the Ti(Cu _{rm 1-y}Fe _{rm y}) (0 <=q y <=q 1) intermetallic compound were systematically investigated. X-ray diffraction data indicated that the intermetallic compound adopted the gammaTiCu structure for 0 <=q y <=q.1 and crystallized in the TiFe structure for.5 <=q y <=q 1. A mixture of these two phases was observed for 0.1 < y <.5. The lattice parameters for the pure intermetallic compounds and hydrided samples were measured. The heat of hydride formation, DeltaH, as a function of Fe content was determined from pressure-composition isotherms and the Van't Hoff relation. In the composition range 0 <=q y <=q.1 the value of DeltaH varied from -74.3 kJ (mole H_{2 })^{-1} to -59.1 kJ (mole H_{2})^{ -1}. For.5 <=q y <=q 1 it went from -49.5 kJ (mole H_{2})^{-1} to -27.3 kJ (mole H_ {2})^{-1}. We have found that DeltaH values derived from a model proposed by Shilov et al. for calculating DeltaH of the multicomponent hydrides were in good agreement with the experimental data by about 3%. Other properties of the hydride such as hydrogen storage capacity and hysteresis effect were also found to be y dependent. Systematic ^{57}Fe Mossbauer effect studies were also carried out in the intermetallic compound and hydride systems with the emphasis on the isomer shift measurements. The total s-electron densities at the Fe nucleus (|psi_{ rm s}({rm o})|^ {2}) increases when the Fe content y decreases in the pure intermetallic compounds. | psi_{rm s}({rm o })|^{2} decreases with the introduction of the hydrogen. In the hydride system |psi_{rm s}({rm o})|^{2 } was found to be y independent. Interpretation of the data was based on the changes in | psi_{rm s}({rm o })|^{2} due to expansion and contraction of the host lattice and the electronic structure differences. The decrease in | psi_{rm s}({rm o })|^{2} due to the hydrogenation in the TiCu-like hydride (0 <=q y <=q.1) could be accounted for by the volume effect only. For TiFe-like hydride

  3. Study of the carburization of an iron catalyst during the Fischer-Tropsch synthesis: influence on its catalytic activity

    SciTech Connect

    Pijolat, M.; Perrichon, V.; Bussiere, P.

    1987-09-01

    The fast transformation of an ironalumina catalyst into Fe/sub 2+x/C during the H/sub 2/ + CO reaction was followed by in situ Moessbauer spectroscopy at 523 K and the behavior was compared with changes in catalytic activity for Fischer-Tropsch synthesis. After a few hours of synthesis, no metallic iron could be detected by either Moessbauer or IR spectroscopy, whereas the CO conversion was still half of that observed initially. The nature of the sites responsible for the remaining activity is discussed. The interpretation of the Moessbauer spectra has permitted the determination of the stoichiometry of the Fe/sub 2+x/C carbide (0 less than or equal to x less than or equal to 0.4), and hence the following of the change of x during the reaction. Thus, the activity in CO hydrogenation could be related to the number of carbon vacancies in the iron carbide, i.e., to the extent of the metallic character of this carbide. This concept of the variation of hydrogenating properties of the carbide with the carbon content has been supported by similar catalytic results obtained in the room temperature hydrogenation of ethylene performed on carbides of different stoichiometry

  4. Iron isotope fractionation in sulfides: constraints on mechanisms of sulfide formations in hydrothermal and magmatic systems.

    NASA Astrophysics Data System (ADS)

    Polyakov, Veniamin; Soultanov, Dilshod

    2010-05-01

    deposit of Crasberg igneous complex (GIC) [8]. In this case, pyrite is enriched in heavy iron isotope relative to chalcopyrite that is in agreement with direction of iron isotope fractionation in equilibrium. Using these data [8] and appropriate iron β-factors obtained from INRXS- and Moessbauer experiments, we estimated temperatures of pyrite and chalcopyrite formation. We obtained reasonable temperatures varying between 180 and 650oC for different intrusions of GIC, which are in agreement with other estimations [9,10] Conclusions: Iron β-factors for chalcopyrite CuFeS2 were calculated from 57Fe PDOS obtained in INRXS synchrotron radiation experiments [1]. Iron β-factors for mackinawite were calculated from the Moessbauer SOD shift based on experiments [4]. Using new value of chalcopyrite and mackinawite and/or troilite iron β-factors, it was shown that isotope composition of pyrite in hydrothermal seafloor processes is controlled by equilibrium isotope fractionation between FeS phase (pyrite precursor) and hydrothermal fluid. Fe isotope equilibrium between pyrite and chalcopyrite may be attained in magmatic processes. References: Kobayashi H., Umemura J., Kazekami Y. and Sakai N. Phys. Rev. B. (2007) 76, 134108. Polyakov V. B., Mineev S. D., Clayton R. N., Hu G. and Mineev K. S. Geochim. Cosmochim. Acta (2005) 69, 5531-5536. Polyakov V. B., Clayton R. N., Horita J. and Mineev S.D. Geochim. Cosmochim. Acta (2007) 71, 3833-3846. Bertaut E. F., Burlet P. and Chappert J. Solid State Comm. (1965) 3, 335 - 338. Polyakov V. B. Geochim. Cosmochim. Acta (1997)61, 4213 - 4217. Polyakov V.B. and Mineev S. D. Geochim. Cosmochim. Acta (2000) 64, 849 - 865 Rouxel O., Shanks III W. C., Bach W. and Edwards K. J. Chem. Geol. (2008) 252, 214 - 227 Graham S., Pearson N., Jackson S., Griffin W. and O'Reilly S. Y. Chem. Geol. (2004) 204, 147 - 169 Heinrich C. A. Mineralium Deposita (2005) 39, 864-889 Pollard P.J. and Taylor R.G. Mineralium Deposita (2004) 37, 117-136. .

  5. Magnetic properties of cobalt-ferrite nanoparticles embedded in polystyrene resin

    SciTech Connect

    Vaishnava, P. P.; Senaratne, U.; Buc, E.; Naik, R.; Naik, V. M.; Tsoi, G.; Wenger, L. E.; Boolchand, P.

    2006-04-15

    Samples of maghemite and cobalt-ferrite nanoparticles (sizes, 3-10 nm) were prepared by cross-linking sulfonated polystyrene resin with aqueous solutions of (1) FeCl{sub 2}, (2) 80%FeCl{sub 2}+20%CoCl{sub 2}, (3) FeCl{sub 3}, and (4) 80%FeCl{sub 3}+20%CoCl{sub 2} by volume. Chemical analysis, x-ray powder-diffraction, and {sup 57}Fe Moessbauer spectroscopic measurements show that samples 1 and 3 consist of {gamma}-Fe{sub 2}O{sub 3} nanoparticles (sizes, {approx}10 and 3 nm) and sample 2 and 4 consist of Co{sub x}Fe{sub 3-x}O{sub 4} nanoparticles (sizes, {approx}10 and 4 nm). The temperature dependence of the zero-field-cooled and field-cooled magnetizations at low temperatures, together with a magnetic hysteresis in the M versus H data below blocking temperatures, demonstrate superparamagnetic behavior. The introduction of Co in the iron oxide-resin matrix results in an increase in the blocking temperature of nanoparticles.

  6. Extracellular iron-sulfur precipitates from growth of Desulfovibrio desulfuricans

    SciTech Connect

    Antonio, M. R.; Tischler, M. L.; Witzcak, D.

    1999-12-20

    The authors have examined extracellular iron-bearing precipitates resulting from the growth of Desulfovibrio desulfuricans in a basal medium with lactate as the carbon source and ferrous sulfate. Black precipitates were obtained when D. desulfuricans was grown with an excess of FeSO{sub 4}. When D. desulfuricans was grown under conditions with low amounts of FeSO{sub 4}, brown precipitates were obtained. The precipitates were characterized by iron K-edge XAFS (X-ray absorption fine structure), {sup 57}Fe Moessbauer-effect spectroscopy, and powder X-ray diffraction. Both were noncrystalline and nonmagnetic (at room temperature) solids containing high-spin Fe(III). The spectroscopic data for the black precipitates indicate the formation of an iron-sulfur phase with 6 nearest S neighbors about Fe at an average distance of 2.24(1) {angstrom}, whereas the brown precipitates are an iron-oxygen-sulfur phase with 6 nearest O neighbors about Fe at an average distance of 1.95(1) {angstrom}.

  7. Structure and magnetic properties of Y{sub 1-x}Lu{sub x}FeO{sub 3} (0 {<=} x {<=} 1) ceramics

    SciTech Connect

    Yuan Xueping; Tang Yankun; Sun Yue; Xu Mingxiang

    2012-03-01

    Polycrystalline Lu-doped YFeO{sub 3} samples with perovskite structure were synthesized by solid-state reaction. Powder X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray analysis manifest the high quality of the samples. Room temperature {sup 57}Fe Moessbauer spectra indicate that only the Fe{sup 3+} exists in the samples, which excludes the formation of multiple valence of Fe. The large effective magnetic moments of Fe{sup 3+} obtained from the temperature dependence of magnetization data can be explained in terms of the formation of ferromagnetic clusters. Field-dependent magnetization reveals that all the samples show weak ferromagnetic property due to the small canting of the Fe{sup 3+} moments. The field-induced spin-reorientation was detected on YFeO{sub 3} and was gradually suppressed by Lu{sup 3+} doping. Polarization hysteresis loops of Y{sub 1-x}Lu{sub x}FeO{sub 3} (0 {<=} x {<=} 1) were observed at room temperature. Our results suggest that the multiferroic properties may exist in the Y{sub 1-x}Lu{sub x}FeO{sub 3} (0 {<=} x {<=} 1) ceramics.

  8. Pressure-induced magnetic transition and sound velocities of Fe(3)c : implications for carbon in the earth's inner core.

    SciTech Connect

    Gao, L.; Chen, B.; Wang, J.; Alp, E.E.; Zhao, J.; Lerche, M.; Sturhahn, W.; Scott, H.P.; Huang, F.; Ding, Y.; Sinogeikin, S.V.; Lundstrom, C.C.; Bass, J.D.; Li, J.; X-Ray Science Division; Univ. of Illinois; Carnegie Inst. of Washington; Indiana Univ.

    2008-09-11

    We have carried out nuclear resonant scattering measurements on {sup 57}Fe-enriched Fe{sub 3}C between 1 bar and 50 GPa at 300 K. Synchrotron Moessbauer spectra reveal a pressure-induced magnetic transition in Fe{sub 3}C between 4.3 and 6.5 GPa. On the basis of our nuclear resonant inelastic X-ray scattering spectra and existing equation-of-state data, we have derived the compressional wave velocity V{sub p} and shear wave velocity V{sub s} for the high-pressure nonmagnetic phase, which can be expressed as functions of density ({rho}): V{sub p} (km/s) = -3.99 + 1.29{rho}(g/cm{sup 3}) and V{sub s} (km/s) = 1.45 + 0.24{rho}(g/cm{sup 3}). The addition of carbon to iron-nickel alloy brings density, V{sub p} and V{sub s} closer to seismic observations, supporting carbon as a principal light element in the Earth's inner core.

  9. The influence of microstructure on magnetic properties of nanocrystalline Fe-Pt-Nb-B permanent magnet ribbons

    SciTech Connect

    Randrianantoandro, N.; Greneche, J. M.; Crisan, A. D.; Crisan, O.; Marcin, J.; Kovac, J.; Hanko, J.; Skorvanek, I.; Svec, P.; Chrobak, A.

    2010-11-15

    A FePt-based hard-magnetic nanocomposite of exchange spring type was prepared by isothermal annealing of melt-spun Fe{sub 52}Pt{sub 28}Nb{sub 2}B{sub 18} (atomic percent) ribbons. The relationship between microstructure and magnetic properties was investigated by qualitative and quantitative structural analysis based on the x-ray diffraction, transmission electron microscopy, and {sup 57}Fe Moessbauer spectrometry on one hand and the superconducting quantum interference device magnetometry on the other hand. The microstructure consists of L1{sub 0}-FePt hard-magnetic grains (15-45 nm in diameter) dispersed in a soft magnetic medium composed by A1 FePt, Fe{sub 2}B, and boron-rich (FeB)PtNb remainder phase. The ribbons annealed at 700 deg. C for 1 h exhibit promising hard-magnetic properties at room temperature: M{sub r}/M{sub s}=0.69; H{sub c}=820 kA/m and (BH){sub max}=70 kJ/m{sup 3}. Strong exchange coupling between hard and soft magnetic phases was demonstrated by a smooth demagnetizing curve and positive {delta}M-peak in the Henkel plot. The magnetic properties measured from 5 to 750 K reveals that the hard characteristics remains rather stable up to 550 K, indicating a good prospect for the use of these permanent magnets in a wide temperature range.

  10. Magnetic study and thermal analysis of a metastable Fe-Zr-based alloy: Influence of process control agents

    NASA Astrophysics Data System (ADS)

    Pilar, M.; Escoda, L.; Suñol, J. J.; Greneche, J. M.

    In this work a Fe 60Co 10(Ni 70Zr 30) 15B 15 nanocrystalline alloy was produced by mechanical alloying. Powders were milled using hexane or cyclohexane as process control agents (PCAs) and their properties compared with those of alloy developed without PCA. Structural and magnetic analysis was performed using X-ray diffraction (XRD), transmission 57Fe Mössbauer spectrometry (TMS) and vibrating sample magnetometry (VSM). High magnetization of saturation and low coercitive field values correspond to an alloy milled with hexane. Thermal analysis was performed by differential scanning calorimetry (DSC). High thermal stability characterizes alloys milled with PCA. Annealing treatments at 400 °C improve magnetic behavior of all samples. Compositional analysis shows low-milling media (<1.1 at.%) and C contamination (<0.2 at.%).

  11. Structural and magnetic study of Al{sup 3+} doped Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4} nanoferrites

    SciTech Connect

    Wang, L.; Rai, B.K.; Mishra, S.R.

    2015-05-15

    Graphical abstract: Hyperfine field of individual sites (inset) and weighted average hyperfine field as a function of Al{sup 3+} content for Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4}. - Highlights: • Grain size reduction with Al{sup 3+} substitution. • Preferred occupancy of Al{sup 3+} at B site for higher Al{sup 3+} content. • Reduction in Ms, Tc, and hyperfine field with increasing Al{sup 3+} content. • Size dependent variation in coercivity. • Changes in isomer shift due to competing effect of volume and substitution. - Abstract: Nanostructured Al{sup 3+} doped Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) ferrites were synthesized via the wet chemical method. X-ray diffraction, transmission electron microscopy, and magnetization measurements have been used to investigate the structural and magnetic properties of spinel ferrites calcined at 950 °C. With the doping of Al{sup 3+}, the particle size of Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4} first increased to 47 nm at x = 0.4 and then decreased down to 37 nm at x = 1. The main two absorption bands in IR spectra were observed around 600 cm{sup −1} and 400 cm{sup −1} corresponding to stretching vibration of tetrahedral and octahedral group Fe{sup 3+}–O{sup 2−}. Saturation magnetization and hyperfine field values decreased linearly with Al{sup 3+} due to magnetic dilution and the relative strengths of Fe–O–Me (Me = Fe, Ni, Zn, and Al) superexchanges. The coercive field showed an inverse dependence on ferrite particle size with minimum value of 82 Oe for x = 0.4. A continuous drop in Curie temperature was observed with the Al{sup 3+} substitution. From the Moessbauer spectral analysis and X-ray diffraction analysis, it is deduced that Al{sup 3+} for x < 0.4 has no obvious preference for either tetrahedral or octahedral site but has a greater preference for the B site for x > 0.4. In nutshell the study presents detailed

  12. Microbial Reduction of Uranium under Iron- and Sulfate-reducing Conditions: Effect of Amended Goethite on Microbial Community Composition and Dynamics

    SciTech Connect

    Moon, Hee Sun; McGuinness, L.; Kukkadapu, Ravi K.; Peacock, Aaron D.; Komlos, John; Kerkhoff, Lee; Long, Philip E.; Jaffe, Peter R.

    2010-07-01

    There is a growing need for a better understanding of the biogeochemical dynamics involved in microbial U(VI) reduction due to an increasing interest in using biostimulation via electron donor addition as a means to remediate uranium contaminated sites. U(VI) reduction has been observed to be maximized during iron reducing conditions and to decrease upon commencement of sulfate reducing conditions. There are many unknowns regarding the impact of iron/sulfate biogeochemistry on U(VI) reduction. This includes Fe(III) availability as well as the microbial community changes, including the activity of iron-reducers during the uranium biostimulation period even after the onset of sulfate reduction. Up-flow column experiments were conducted with Old Rifle site sediments containing Fe-oxides, Fe-clays, and sulfate rich groundwater. Half of the columns had sediment that was augmented with small amounts of small-particle 57Fe-goethite to track continuously minute goethite changes, and to study the effects of increased Fe(III) levels on the overall biostimulation dynamics. The addition of the 57Fe-goethite did not delay the onset of sulfate reduction, but slightly suppressed the overall rate of sulfate reduction and hence acetate utilization, it did not affect the bacterial numbers of Geobacter-like species throughout the experiment, but did lower the numbers of sulfate reducers in the sediments. 57Fe-Mössbauer analyses (a 57Fe-specific technique) confirmed that there was bioavailable iron present after the onset of sulfate reduction and that iron was still being reduced during sulfate reduction. Addition of the 57Fe-goethite to the sediment had a noticeable effect on the overall composition of the microbial population. 16S rRNA analyses of biostimulated sediment using TRFLP (terminal restriction fragment length polymorphism) showed that Geobacter sp. (a known Fe-reducer) was still active and replicating during the period of significant sulfate reduction. DNA fingerprints of

  13. Abiotic U(VI) Reduction by Sorbed Fe(II) on Natural Sediments

    SciTech Connect

    Fox, Patricia M.; Davis, James A.; Kukkadapu, Ravi K.; Singer, David M.; Bargar, John R.; Williams, Kenneth H.

    2013-09-15

    Laboratory experiments were performed as a function of aqueous Fe(II) concentration to determine the uptake and oxidation of Fe(II), and Fe(II)-mediated abiotic reduction of U(VI) by aquifer sediments from the Rifle IFRC field site in Colorado, USA. Mössbauer analysis of the sediments spiked with aqueous 57Fe(II) showed that 57Fe(II) was oxidized on the mineral surfaces to 57Fe(III) and most likely formed a nano-particulate Fe(III)-oxide or ferrihydrite-like phase. The extent of 57Fe oxidation decreased with increasing 57Fe(II) uptake, such that 100 % was oxidized at 7.3 μmol/g Fe and 52 % at 39.6 μmol/g Fe, indicating that the sediments had a finite capacity for oxidation of Fe(II). Abiotic U(VI) reduction was observed by XANES spectroscopy only when the Fe(II) uptake was greater than approximately 20 μmol/g and surface-bound Fe(II) was present. The level of U(VI) reduction increased with increasing Fe(II)- loading above this level to a maximum of 18 and 36 % U(IV) at pH 7.2 (40.7 μmol/g Fe) and 8.3 (56.1 μmol/g Fe), respectively in the presence of 400 ppm CO2. Greater U(VI) reduction was observed in CO2 free systems [up to 44 and 54 % at pH 7.2 (17.3 μmol/g Fe) and 8.3 (54.8 μmol/g Fe), respectively] compared to 400 ppm CO2 systems, presumably due to differences in aqueous U(VI) speciation. While pH affects the amount of Fe(II) uptake onto the solid phase, with greater Fe(II) uptake at higher pH, similar amounts of U(VI) reduction were observed at pH 7.2 and 8.3 for a similar Fe(II) uptake. Thus, it appears that abiotic U(VI) reduction is controlled primarily by Fe(II) concentration and aqueous U(VI) speciation. The range of Fe(II) loadings tested in this study are within the range observed in bioreduced sediments, suggesting that Fe(II)-mediated abiotic U(VI) reduction may indeed play a role in field settings.

  14. Abiotic U(VI) reduction by sorbed Fe(II) on natural sediments

    NASA Astrophysics Data System (ADS)

    Fox, Patricia M.; Davis, James A.; Kukkadapu, Ravi; Singer, David M.; Bargar, John; Williams, Kenneth H.

    2013-09-01

    Laboratory experiments were performed as a function of aqueous Fe(II) concentration to determine the uptake and oxidation of Fe(II), and Fe(II)-mediated abiotic reduction of U(VI) by aquifer sediments from the DOE Rifle field research site in Colorado, USA. Mössbauer analysis of the sediments spiked with aqueous 57Fe(II) showed that 57Fe(II) was oxidized on the mineral surfaces to 57Fe(III) and most likely formed a nano-particulate Fe(III)-oxide or ferrihydrite-like phase. The extent of 57Fe oxidation decreased with increasing 57Fe(II) uptake, such that 98% was oxidized at 7.3 μmol/g Fe and 41% at 39.6 μmol/g Fe, indicating that the sediments had a limited capacity for oxidation of Fe(II). Abiotic U(VI) reduction was observed by XANES spectroscopy only when the Fe(II) uptake was greater than approximately 20 μmol/g and surface-bound Fe(II) was present, possibly as oligomeric Fe(II) surface species. The degree of U(VI) reduction increased with increasing Fe(II)-loading above this level to a maximum of 18% and 36% U(IV) at pH 7.2 (40.7 μmol/g Fe) and 8.3 (56.1 μmol/g Fe), respectively in the presence of 400 ppm CO2. Greater U(VI) reduction was observed in CO2-free systems [up to 44% and 54% at pH 7.2 (17.3 μmol/g Fe) and 8.3 (54.8 μmol/g Fe), respectively] compared to 400 ppm CO2 systems, presumably due to differences in aqueous U(VI) speciation. While pH affects the amount of Fe(II) uptake onto the solid phase, with greater Fe(II) uptake at higher pH, similar amounts of U(VI) reduction were observed at pH 7.2 and 8.3 for a similar Fe(II) uptake. Thus, it appears that abiotic U(VI) reduction is controlled primarily by sorbed Fe(II) concentration and aqueous U(VI) speciation. The range of Fe(II) loadings tested in this study are within the range observed in biostimulation experiments at the Rifle site, suggesting that Fe(II)-mediated abiotic U(VI) reduction could play a significant role in field settings.

  15. Copper stable isotopes as tracers of metal-sulphide segregation and fractional crystallisation processes on iron meteorite parent bodies

    NASA Astrophysics Data System (ADS)

    Williams, Helen M.; Archer, Corey

    2011-06-01

    We report high precision Cu isotope data coupled with Cu concentration measurements for metal, troilite and silicate fractions separated from magmatic and non-magmatic iron meteorites, analysed for Fe isotopes (δ 57Fe; permil deviation in 57Fe/ 54Fe relative to the pure iron standard IRMM-014) in an earlier study ( Williams et al., 2006). The Cu isotope compositions (δ 65Cu; permil deviation in 65Cu/ 63Cu relative to the pure copper standard NIST 976) of both metals (δ 65Cu M) and sulphides (δ 65Cu FeS) span much wider ranges (-9.30 to 0.99‰ and -8.90 to 0.63‰, respectively) than reported previously. Metal-troilite fractionation factors (Δ 65Cu M-FeS = δ 65Cu M - δ 65Cu FeS) are variable, ranging from -0.07 to 5.28‰, and cannot be explained by equilibrium stable isotope fractionation coupled with either mixing or reservoir effects, i.e. differences in the relative proportions of metal and sulphide in the meteorites. Strong negative correlations exist between troilite Cu and Fe (δ 57Fe FeS) isotope compositions and between metal-troilite Cu and Fe (Δ 57Fe M-FeS) isotope fractionation factors, for both magmatic and non-magmatic irons, which suggests that similar processes control isotopic variations in both systems. Clear linear arrays between δ 65Cu FeS and δ 57Fe FeS and calculated Cu metal-sulphide partition coefficients (D Cu = [Cu] metal/[Cu] FeS) are also present. A strong negative correlation exists between Δ 57Fe M-FeS and D Cu; a more diffuse positive array is defined by Δ 65Cu M-FeS and D Cu. The value of D Cu can be used to approximate the degree of Cu concentration equilibrium as experimental studies constrain the range of D Cu between Fe metal and FeS at equilibrium to be in the range of 0.05-0.2; D Cu values for the magmatic and non-magmatic irons studied here range from 0.34 to 1.11 and from 0.04 to 0.87, respectively. The irons with low D Cu values (closer to Cu concentration equilibrium) display the largest Δ 57Fe M-FeS and the

  16. Magnetic properties study on Fe-doped calcium phosphate

    NASA Astrophysics Data System (ADS)

    Silva, C. C.; Vasconcelos, I. F.; Sombra, A. S. B.; Valente, M. A.

    2009-11-01

    Calcium phosphates are very important for applications in medicine due to their properties such as biocompatibility and bioactivity. In order to enhance these properties, substitution of calcium with other ions has been proposed. Partial substitution of calcium by different ions has been made in order to improve the properties of the calcium phosphates and also to allow new applications of apatite in medicine. In this work, hydroxyapatite [Ca10(PO4)6(OH)2—HAP] was prepared by high-energy dry milling (20 h) and mixed with iron oxide (5 wt.%). The mixture was calcinated at 900 °C for 5 h with a heating rate of 3 °C min-1 in an attempt to introduce iron oxide into the HAP structure. The sintered sample was characterized using x-ray diffraction (XRD) and magnetization. The 57Fe-Mössbauer spectra of the calcium phosphate oxides were also measured, revealing the presence of iron in three different phases: Ca2Fe2O5, Fe2O3 and hydroxyapatite.

  17. Mössbauer study of conductive oxide glass

    NASA Astrophysics Data System (ADS)

    Matsuda, Koken; Kubuki, Shiro; Nishida, Tetsuaki

    2014-10-01

    Heat treatment of barium iron vanadate glass, BaO - Fe2O3- V2O5, at temperatures higher than crystallization temperature causes a marked decrease in resistivity (ρ) from several MΩcm to several Ωcm. 57Fe Mössbauer spectrum of heat-treated vanadate glass shows a marked decrease in quadrupole splitting (Δ) of FeIII, reflecting a structural relaxation, i.e., an increased symmetry of "distorted" FeO4 and VO4 tetrahedra which are connected to each other by sharing corner oxygen atoms. Structural relaxation of 3D-network of vanadate glass accompanies a decrease in the activation energy for the conduction, reflecting a decreased energy gap between the donor level and conduction band. A marked increase in the conductivity was observed in CuO- or Cu2O -containing barium iron vanadate glass after heat treatment at 450 °C for 30 min or more. "n-type semiconductor model combined with small polaron hopping theory" was proposed in order to explain the high conductivity.

  18. Mössbauer study of conductive oxide glass

    SciTech Connect

    Matsuda, Koken; Kubuki, Shiro; Nishida, Tetsuaki

    2014-10-27

    Heat treatment of barium iron vanadate glass, BaO‐Fe{sub 2}O{sub 3}‐V{sub 2}O{sub 5}, at temperatures higher than crystallization temperature causes a marked decrease in resistivity (ρ) from several MΩcm to several Ωcm. {sup 57}Fe Mössbauer spectrum of heat-treated vanadate glass shows a marked decrease in quadrupole splitting (Δ) of Fe{sup III}, reflecting a structural relaxation, i.e., an increased symmetry of 'distorted' FeO{sub 4} and VO{sub 4} tetrahedra which are connected to each other by sharing corner oxygen atoms. Structural relaxation of 3D-network of vanadate glass accompanies a decrease in the activation energy for the conduction, reflecting a decreased energy gap between the donor level and conduction band. A marked increase in the conductivity was observed in CuO- or Cu{sub 2}O-containing barium iron vanadate glass after heat treatment at 450 °C for 30 min or more. 'n-type semiconductor model combined with small polaron hopping theory' was proposed in order to explain the high conductivity.

  19. Spin freezing process in a reentrant ferromagnet studied by neutron depolarization analysis

    SciTech Connect

    Sato, T.; Shinohara, T.; Ogawa, T.; Takeda, M.

    2004-10-01

    The spin freezing process and the magnetic nature of reentrant spin-glass (RSG) and the ferromagnetic (FM) phases of a typical reentrant ferromagnet Ni{sub 78}Mn{sub 22} were investigated based on neutron depolarization analysis, and the results were compared with the previous Moessbauer measurements [Phys. Rev. B 64, 184432 (2001)]. The wavelength-dependent polarization, under a field cooled (FC) condition, showed the damped oscillatory behavior in both the RSG and FM phases, except in the temperature region just above the RSG temperature T{sub RSG}{approx}60 K. At a temperature of around 80 K, however, it showed a double oscillatory behavior. The field integral I, which is proportional to the mean local magnetic induction, was deduced as a function of the temperature. Two branches of temperature-dependent field integrals were found: a low-temperature I{sub low}-branch, which has a small value of I, stopped at a temperature below the Curie temperature T{sub C}{approx}160 K, and a high temperature I{sub high}-branch, which has a large value of I, appeared just below 80 K. This means that there are two kinds of magnetic environments, and they have different values of magnetization. This is consistent with the observation of the double peak spectrum of the hyperfine field in the previous Moessbauer measurements. The present neutron data and the Moessbauer data can be interpreted along a scenario of reentrant behavior, which consists of the low-temperature spin canting state and the ''melting of frustrated spins'' mechanism introduced by Saslow and Parker [Phys. Rev. Lett. 56, 1074 (1986)], except for the absence of the observation of singularity in the temperature-dependent magnetization. Based on such considerations, we constructed a comprehensive picture of the spin freezing process and the magnetic nature of the RSG and FM phases in the reentrant ferromagnet.

  20. RAPID COMMUNICATION: Studies of the magnetostriction of as-prepared and annealed glass-coated Co-rich amorphous microwires by SAMR method

    NASA Astrophysics Data System (ADS)

    Zhukova, V.; Blanco, J. M.; Zhukov, A.; Gonzalez, J.

    2001-11-01

    The saturation magnetostriction constant, λs, of as-prepared and current annealed glass-covered Co57Fe6.1Ni10B15.9Si11, Co67.5Fe4Ni1.5B14Si12Mo1, Co69.1Fe5.2Ni1B14.8Si9.9 and Co69.5Fe3.9Ni1B12.8Si10.8Mo2 amorphous microwires has been measured by the small angle magnetization rotation method. As-prepared samples exhibit negative λs ranging between -0.9×10-6 and -0.3×10-6. Current annealing results in a significant change of λs, that is, a general tendency to increase towards zero.

  1. Crystal structure and Mössbauer studies of the isotypic Fe6-cluster compounds RE15[Fe8C25], RE=Dy, Ho

    NASA Astrophysics Data System (ADS)

    Davaasuren, Bambar; Dashjav, Enkhtsetseg; Kreiner, Guido; Borrmann, Horst; Weber, Sven-Ulf; Becker, Klaus-Dieter; Jochen Litterst, Fred; Kniep, Rüdiger

    2015-05-01

    The carboferrates RE15[Fe8C25] (RE=Dy, Ho) were prepared from mixtures of the elements by arc-melting followed with subsequent annealing at 1373 K. The crystal structures were determined from single crystal X-ray diffraction data and revealed an isotypic relationship to Er15[Fe8C25] (hP48, P321). The main feature of the crystal structure is given by Fe6 cluster units characterized by covalent Fe-Fe bonding interactions. 57Fe Mössbauer spectra of Dy15[Fe8C25] were fitted by three subspectra with relative spectral weights of about 3:3:2 which is in general agreement with the crystal structure. Below 50 K, an onset of magnetic hyperfine fields at the three iron sites is observed which is supposed to be caused by dipolar fields arising from neighboring, slowly relaxing Dy magnetic moments.

  2. Mössbauer study of metallic iron and iron oxide nanoparticles having environmental purifying ability

    SciTech Connect

    Kubuki, Shiro Watanabe, Yuka Akiyama, Kazuhiko; Ristić, Mira; Krehula, Stjepko; Homonnay, Zoltán; Kuzmann, Ernő; Nishida, Tetsuaki

    2014-10-27

    A relationship between local structure and methylene blue (MB) decomposing ability of nanoparticles (NPs) of metallic iron (Fe{sup 0}) and maghemite (γ‐Fe{sub 2}O{sub 3}) was investigated by {sup 57}Fe Mössbauer spectroscopy, X-ray diffractometry and UV-visible light absorption spectroscopy. γ‐Fe{sub 2}O{sub 3} NPs were successfully prepared by mixing (NH{sub 4}){sub 2}Fe(SO{sub 4}){sub 2}⋅6H{sub 2}O (Mohr's salt) and (NH{sub 4}){sub 3}Fe(C{sub 2}O{sub 4}){sub 3}⋅3H{sub 2}O aqueous solution at 30 °C for 1 h, while those of Fe{sup 0} were obtained by the reduction of Mohr's salt with NaBH{sub 4}. From the Scherrer's equation, the smallest crystallite sizes of γ‐Fe{sub 2}O{sub 3} NPs and Fe{sup 0} NPs were determined to be 9.7 and 1.5 nm, respectively. {sup 57}Fe Mössbauer spectrum of γ‐Fe{sub 2}O{sub 3} NPs consists of a relaxed sextet with isomer shift (δ) of 0.33{sub ±0.01} mm s{sup −1}, internal magnetic field (H{sub int}) of 25.8{sub ±0.5} T, and linewidth (Γ) of 0.62{sub ±0.04} mm s{sup −1}. {sup 57}Fe Mössbauer spectrum of Fe{sup 0} NP is mainly composed of a sextet having δ, Δ, and H{sub int} of 0.00{sub ±0.01} mm s{sup −1} 0.45{sub ±0.01} mm s{sup −1}, and 22.8{sub ±0.1} T, respectively. A bleaching test of the mixture of Fe{sup 0} and γ‐Fe{sub 2}O{sub 3} NPs (3:7 ratio, 100 mg) in MB aqueous solution (20 mL) for 6 h showed a remarkable decrease of MB concentration with the first-order rate constant (k{sub MB}) of 6.7 × 10{sup −1} h{sup −1}. This value is larger than that obtained for the bleaching test using bulk Fe{sup 0}+γ‐Fe{sub 2}O{sub 3} (3:7) mixture (k{sub MB} = 6.5×10{sup −3}h{sup −1}). These results prove that MB decomposing ability is enhanced by the NPs mixture of Fe{sub 0} and γ‐Fe{sub 2}O{sub 3}.

  3. Structural, magnetic and Mössbauer studies of (BiFeO3)0.7-(SrFe12O19)0.3 nanocomposite prepared by a sol-gel route

    NASA Astrophysics Data System (ADS)

    Das, A.; Roychowdhury, A.; Pati, S. P.; Bandyopadhyay, S.; Das, D.

    2014-04-01

    The nanocomposite (BiFeO3)0.7-(SrFe12O19)0.3 has been prepared by a sol-gel route and characterized by XRD, TEM, TGA/DTA, dc magnetization and 57Fe Mössbauer spectroscopy. The hyperfine parameters obtained from Mössbauer spectroscopy indicate formation of pure hexaferrite phase of SrFe12O19 (SRF) in the nanocomposite (NC). The NC exhibits typical hysteresis loops with significantly altered magnetization parameters (saturation magnetization, coercivity and remnant magnetization) in comparison with that of the pristine SRF and BiFeO3 (BFO) nanoparticles (NPs). The ZFC-FC curves show a divergence in low temperature region which confirms the irreversible character of magnetization.

  4. Mossbauer and spectral (visible and near-IR) data for Fe(3+)-substituted rutile

    NASA Technical Reports Server (NTRS)

    Lauer, H. V., Jr.; Morris, R. V.; Vempati, R. K.

    1994-01-01

    Titanohematite and rutile containing some Fe(3+) are possible highly oxidized weathering products of ilmenite and titanomagnetities. We report here Moessbauer and reflectivity data (visible and near-IR) for Fe(3+)-substituted rutile as a part of our continuing studies of ferric-substituted minerals that might have bearing on the interpretation of Martian spectral data.

  5. Crystal structure and Mössbauer studies of the isotypic Fe{sub 6}-cluster compounds RE{sub 15}[Fe{sub 8}C{sub 25}], RE=Dy, Ho

    SciTech Connect

    Davaasuren, Bambar; Dashjav, Enkhtsetseg; Kreiner, Guido; Borrmann, Horst; Weber, Sven-Ulf; Becker, Klaus-Dieter; Jochen Litterst, Fred; Kniep, Rüdiger

    2015-05-15

    The carboferrates RE{sub 15}[Fe{sub 8}C{sub 25}] (RE=Dy, Ho) were prepared from mixtures of the elements by arc-melting followed with subsequent annealing at 1373 K. The crystal structures were determined from single crystal X-ray diffraction data and revealed an isotypic relationship to Er{sub 15}[Fe{sub 8}C{sub 25}] (hP48, P321). The main feature of the crystal structure is given by Fe{sub 6} cluster units characterized by covalent Fe–Fe bonding interactions. {sup 57}Fe Mössbauer spectra of Dy{sub 15}[Fe{sub 8}C{sub 25}] were fitted by three subspectra with relative spectral weights of about 3:3:2 which is in general agreement with the crystal structure. Below 50 K, an onset of magnetic hyperfine fields at the three iron sites is observed which is supposed to be caused by dipolar fields arising from neighboring, slowly relaxing Dy magnetic moments. - Graphical abstract: Fe{sub 6}-cluster in the crystal structure of RE{sub 15}[Fe{sub 8}C{sub 25}], RE=Dy, Ho. - Highlights: • New carboferrates RE{sub 15}[Fe{sub 8}C{sub 25}] with RE=Dy, Ho have been synthesized. • The crystal structures were refined using single crystal X-ray data. • An orientational relationship between Fe{sub 6}-clusters and Fe in γ-Fe is outlined. • {sup 57}Fe Mössbauer spectra are in agreement with structural data from X-rays. • Magnetic hyperfine fields below 50 K are explained by dipolar fields from Dy atoms.

  6. Enhancement of spin relaxation in an FeDy2 Fe coordination cluster by magnetic fields.

    PubMed

    Peng, Guo; Mereacre, Valeriu; Kostakis, George E; Wolny, Juliusz A; Schünemann, Volker; Powell, Annie K

    2014-09-22

    Two [FeLn2 Fe(μ3 -OH)2 (teg)2 (N3 )2 (C6 H5 COO)4 ] compounds (where Ln=Y(III) and Dy(III) ; teg=triethylene glycol anion) have been synthesized and studied using SQUID and Mössbauer spectroscopy. The magnetic measurements on both compounds indicate dominant antiferromagnetic interactions between the metal centers. Analysis of the (57) Fe Mössbauer spectra complement the ac magnetic susceptibility measurements, which show how a static magnetic field can quench the slow relaxation of magnetization generated by the anisotropic Dy(III) ions. PMID:25197018

  7. Characterization of mechanical nanocrystallization process of amorphous Fe{endash}Mo{endash}Si{endash}B alloy by transmission Moessbauer spectroscopy

    SciTech Connect

    Liu, X.D.; Lu, K.; Umemoto, M.

    1997-03-01

    The nanocrystallization process of the amorphous Fe{endash}Mo{endash}Si{endash}B alloy under ball milling is characterization by means of transmission M{umlt o}ssbauer spectroscopy in the present paper. It was found that a single {alpha}-Fe phase with the bcc structure is formed under ball-milling the amorphous Fe{endash}Mo{endash}Si{endash}B alloy. A significant increase in the relative area of the subspectra of 8 Fenn and 7 Fenn and a remarkable decrease in isomer shift and half linewidth of the subspectra of various Fe configurations, especially in the case of 6 Fenn, were observed during the ball milling process. The diffusion of metalloid atoms from the bcc {alpha}-Fe phase to the remaining amorphous phase and {alpha}-Fe/{alpha}-Fe grain boundaries is suggested to occur during the mechanical crystallization of the current amorphous alloy based on the above TMES investigations. {copyright} {ital 1997 Materials Research Society.}

  8. Moessbauer/XRF MIMOS Instrumentation and Operation During the 2012 Analog Field Test on Mauna Kea Volcano, Hawaii

    NASA Technical Reports Server (NTRS)

    Graff, Trevor G.; Morris, R. V.; Klingelhofer, G.; Blumers, M.

    2013-01-01

    Field testing and scientific investigations were conducted on the Mauna Kea Volcano, Hawaii, as part of the 2012 Moon and Mars Analog Mission Activities (MMAMA). Measurements were conducted using both stand-alone and rover-mounted instruments to determine the geophysical and geochemical properties of the field site, as well as provide operational constraints and science considerations for future robotic and human missions [1]. Reported here are the results from the two MIMOS instruments deployed as part of this planetary analog field test.

  9. Decay of {sup 161m1,m2}Dy isomers under conditions of a resonance environment (Moessbauer Screen)

    SciTech Connect

    Loginov, Yu. E. Zinoviev, V. G.; Kabina, L. P.; Lisin, S. S.; Maljutenkov, Ed. I.

    2013-06-15

    The half-lives of the isomers {sup 161m1}Dy and {sup 161m2}Dy (E = 25.6 keV and T{sub 1/2} {approx} 30 ns for the former and E = 74.6 keV and T{sub 1/2} {approx} 3 ns for the latter) placed in a {sup 160}Gd{sub 2}O{sub 3} crystal lattice at T = 300 K and surrounded by stable {sup 161}Dy nuclei in the composition of {sup 161}Dy{sub 2}O{sub 3} were measured by the method of ({beta}-{gamma}) coincidences in the beta-decay process {sup 161}Tb {yields} {sup 161}Dy. Nuclei of {sup 161m1,m2}Dy were obtained according to the chain {sup 160}Gd(n, {gamma}){sup 161}Gd {yields} {sup 161}Tb {yields} {sup 161}Dy from {sup 160}Dy{sub 2}O{sub 3} weighted portions irradiated at the PWR-M reactor of the Petersburg Nuclear Physics Institute (PNPI, Gatchina, Russia). The T{sub 1/2} value observed for the isomer {sup 161m1}Dy was found to be correlated with the number of surrounding {sup 161}Dy nuclei. The presence of this correlation in {sup 161m1}Dy can be explained by the multiple resonance scattering of photons from isomer decay within the sample used. No such correlation was observed for {sup 161m2}Dy. The half-lives measured for the isomers {sup 161m1}Dy and {sup 161m2}Dy in the absence of the above environment are 29.2(1) and 3.50(1) ns, respectively.

  10. Mechanistic studies of the reaction of reduced methane monooxygenase hydroxylase with dioxygen and substrates

    SciTech Connect

    Valentine, A.M.; Stahl, S.S.; Lippard, S.J.

    1999-04-28

    Soluble methane monooxygenase (sMMO) catalyzes the oxidation of methane to methanol. Single-turnover reactions of sMMO from Methylococcus capsulatus (Bath) were studied by stopped-flow optical spectroscopy to examine further the activated dioxygen intermediates and their reactions with hydrocarbon substrates. A diiron(III) peroxo species designated H{sub peroxo} is the first intermediate observed in the reaction between the chemically reduced hydroxylase (H{sub red}) and dioxygen. The optical spectrum of this species determined by diode array detection is presented for the first time and exhibits visible absorption bands with {lambda}{sub max} {approx} 420 nm ({epsilon} = 4,000 M{sup {minus}1} cm{sup {minus}1}) and {lambda}{sub max} = 725 nm ({epsilon} = 1,800 M{sup {minus}1} cm{sup {minus}1}). The temperature dependences of the rate constants for formation and decay of H{sub peroxo} and for the subsequent intermediate, Q, were examined in the absence and in the presence of hydrocarbon substrates, and activation parameters for these reactions were determined. For single-turnover reaction kinetics monitored at 420 nm, the {lambda}{sub max} for Q, a nonlinear Eyring plot was obtained when acetylene or methane was present in sufficiently high concentration. This behavior reflects a two-step mechanism, Q formation followed by Q decay, in which the rate-determining step changes depending on the temperature. The rate of H{sub peroxo} formation does not depend on dioxygen concentration, indicating that an effectively irreversible step involving dioxygen precedes formation of the diiron(III) peroxo species. The rate constant observed at 4 C for H{sub peroxo} formation, 1--2 s{sup {minus}1}, is slower than that determined previously by Moessbauer and optical spectroscopy, {approximately}20--25 s{sup {minus}1} (Liu, K. E., et al. J. Am. Chem. Soc. 1995, 117, 4997--4998; 10174--10185). Possible explanations for this discrepancy include the existence of two distinct peroxo

  11. Raman and Mossbauer spectroscopy and X-ray diffractometry studies on quenched copper-ferri-aluminates.

    PubMed

    Modi, Kunal B; Raval, Pooja Y; Shah, Suraj J; Kathad, Chetan R; Dulera, Sonal V; Popat, Mansi V; Zankat, Kiritsinh B; Saija, Kiran G; Pathak, Tushar K; Vasoya, Nimish H; Lakhani, Vinay K; Chandra, Usha; Jha, Prafulla K

    2015-02-16

    Four spinel ferrite compositions of the CuAl(x)Fe(2-x)O4, x = 0.0, 0.2, 0.4, 0.6, system prepared by usual double-sintering ceramic route and quenched (rapid thermal cooling) from final sintering temperature (1373 K) to liquid nitrogen temperature (80 K) were investigated by employing X-ray powder diffractometry, (57)Fe Mossbauer spectroscopy, and micro-Raman spectroscopy at 300 K. The Raman spectra collected in the wavenumber range of 100-1000 cm(-1) were analyzed in a systematic manner and showed five predicted modes for the spinel structure and splitting of A1g Raman mode into two/three energy values, attributed to peaks belonging to each ion (Cu(2+), Fe(3+), and Al(3+)) in the tetrahedral positions. The suppression of lower-frequency peaks was explained on the basis of weakening in magnetic coupling and reduction in ferrimagnetic behavior as well as increase in stress induced by square bond formation on Al(3+) substitution. The enhancement in intensity, random variation of line width, and blue shift for highest frequency peak corresponding to A1g mode were observed. The ferric ion (Fe(3+)) concentration for different compositions determined from Raman spectral analysis agrees well with that deduced by means of X-ray diffraction line-intensity calculations and Mossbauer spectral analysis. An attempt was made to determine elastic and thermodynamic properties from Raman spectral analysis and elastic constants from cation distribution. PMID:25594232

  12. Eu doping in multiferroic BiFeO3 ceramics studied by Mossbauer and EXAFS spectroscopy.

    PubMed

    Kothari, Deepti; Raghavendra Reddy, V; Gupta, Ajay; Meneghini, Carlo; Aquilanti, Giuliana

    2010-09-01

    Bismuth ferrite ceramics (BiFeO(3)) are multifunctional materials classified as multiferroics for their special magnetic and electric properties that can be modified by substitutional doping at the Bi and/or Fe sites. Understanding the relation between magnetoelectric response and structural/electronic modification upon doping is a relevant issue. In this work, the structure of Eu-doped multiferroic systems (Bi(1-x)Eu(x)FeO(3), x = 0, 0.5, 0.1, 0.15) as well as the valence state of Fe and Eu ions have been investigated combining Mossbauer and x-ray absorption fine structure (XAFS) spectroscopy techniques. The Eu(3+) doping at the Bi site results in better magnetic properties. High temperature (57)Fe Mossbauer data and Fe K-edge XAFS results show that FeO(6) octahedron distortions reduce with Eu(3+) doping. It is conclusively shown that the observed magnetic properties in BiFeO(3) with chemical substitution (Eu) are mainly due to the structural distortions and not due to Fe multiple valence. (151)Eu Mossbauer measurements show that the Eu(3+)(Bi(3+)) site is magnetically inactive in BiFeO(3). PMID:21403301

  13. Eu doping in multiferroic BiFeO3 ceramics studied by Mossbauer and EXAFS spectroscopy

    NASA Astrophysics Data System (ADS)

    Kothari, Deepti; Raghavendra Reddy, V.; Gupta, Ajay; Meneghini, Carlo; Aquilanti, Giuliana

    2010-09-01

    Bismuth ferrite ceramics (BiFeO3) are multifunctional materials classified as multiferroics for their special magnetic and electric properties that can be modified by substitutional doping at the Bi and/or Fe sites. Understanding the relation between magnetoelectric response and structural/electronic modification upon doping is a relevant issue. In this work, the structure of Eu-doped multiferroic systems (Bi1 - xEuxFeO3, x = 0, 0.5, 0.1, 0.15) as well as the valence state of Fe and Eu ions have been investigated combining Mossbauer and x-ray absorption fine structure (XAFS) spectroscopy techniques. The Eu3 + doping at the Bi site results in better magnetic properties. High temperature 57Fe Mossbauer data and Fe K-edge XAFS results show that FeO6 octahedron distortions reduce with Eu3 + doping. It is conclusively shown that the observed magnetic properties in BiFeO3 with chemical substitution (Eu) are mainly due to the structural distortions and not due to Fe multiple valence. 151Eu Mossbauer measurements show that the Eu3 + (Bi3 + ) site is magnetically inactive in BiFeO3.

  14. Rhyolite-dacite-trachyandesite association: a Mössbauer spectroscopy study

    NASA Astrophysics Data System (ADS)

    Hassan, K. M.

    2009-07-01

    Three volcanic dykes, rhyolite, dacite and trachyandesite cutting a radioactive granite, located between Latitudes 22° 47' 396″-22° 47' 884″ N and Longitudes 31° 54' 883″-31° 54' 894″ E in the south Western Desert of Egypt were sampled and analyzed by X-ray diffraction, 57Fe Mössbauer spectroscopy and chemical method. They are consisted of feldspar and quartz together with some paramagnetic minerals including aegirine plus minor riebeckite in the rhyolite; aegirine plus some riebeckite in the dacite; and riebeckite plus trace aegirine in the trachyandesite, respectively. The bulk content of iron in each dyke has characteristic ferric-quadrupole splitting and oxidation values: 0.29 millimeters per second (mm/s) and 100% for rhyolite; 0.31 mm/s and 82% for dacite; and 0.35 mm/s and 0.69% for trachyandesite. Variations in the quadrupole splitting have been attributed to changes from the local crystal chemistry, while the oxidation variations are source-related.

  15. Fe Isotope Composition of Neoproterozoic Post-Glacial "Cap Dolostones"

    NASA Astrophysics Data System (ADS)

    Halverson, G. P.

    2005-12-01

    The largest variations in the Fe isotope composition in the geological record are found in sedimentary rocks, presumably as the result of redox transformations of iron during mineral precipitation, microbial processing, and diagenesis (Johnson et al., Cont. Min. Petrol., 2003). Systematic trends in the variability of the Fe isotope composition of sulfide minerals formed in ancient marine black shales broadly mirror patterns in sulfur isotope data (Δ33S, Δ34S), which are consistent with geological and other geochemical evidence for the progressive oxidation of the earth's surface during the Precambrian (Rouxel et al., Science, 2005). Therefore, the record of the Fe isotope composition of minerals formed in the marine environment appears to be a promising proxy for the redox evolution of the ocean. We have developed a method to extract the marine Fe isotope composition from carbonates in an attempt to establish higher resolution records of changes in marine redox changes than permitted by black shale geochemistry. We have applied this method to the study of ca. 635 Ma iron-rich dolostones, which are found in Neoproterozoic successions worldwide and immediately post-date a purported snowball (Marinoan) glaciation during which time the deep ocean is thought to have become anoxic (Hoffman et al., Science, 1998), allowing its Fe isotopic composition to evolve towards the composition of relatively light (δ57Fe vs. IRMM-14 ~ -0.6‰) hydrothermal iron (Beard et al., Geology, 2003). Fe isotope compositions were measured relative to IRMM-14 in medium-resolution mode on a Neptune MC-ICP-MS with a long-term external (2σ) reproducibility of < 0.04‰/amu. Preliminary data on dolomite samples from Svalbard, northern Namibia and northwest Canada show a range in δ57Fe values from -0.65 to 0.04‰, similar to the range found in siderite and Fe-rich dolomite in ancient BIFs (Johsnon et al., 2003) and to values for the Namibian cap dolostone reported by Leighton et al

  16. Ferrous Carbonyl Dithiolates as Precursors to FeFe, FeCo, and FeMn Carbonyl Dithiolates

    PubMed Central

    2015-01-01

    Reported are complexes of the formula Fe(dithiolate)(CO)2(diphos) and their use to prepare homo- and heterobimetallic dithiolato derivatives. The starting iron dithiolates were prepared by a one-pot reaction of FeCl2 and CO with chelating diphosphines and dithiolates, where dithiolate = S2(CH2)22– (edt2–), S2(CH2)32– (pdt2–), S2(CH2)2(C(CH3)2)2– (Me2pdt2–) and diphos = cis-C2H2(PPh2)2 (dppv), C2H4(PPh2)2 (dppe), C6H4(PPh2)2 (dppbz), C2H4[P(C6H11)2]2 (dcpe). The incorporation of 57Fe into such building block complexes commenced with the conversion of 57Fe into 57Fe2I4(iPrOH)4, which then was treated with K2pdt, CO, and dppe to give 57Fe(pdt)(CO)2(dppe). NMR and IR analyses show that these complexes exist as mixtures of all-cis and trans-CO isomers, edt2– favoring the former and pdt2– the latter. Treatment of Fe(dithiolate)(CO)2(diphos) with the Fe(0) reagent (benzylideneacetone)Fe(CO)3 gave Fe2(dithiolate)(CO)4(diphos), thereby defining a route from simple ferrous salts to models for hydrogenase active sites. Extending the building block route to heterobimetallic complexes, treatment of Fe(pdt)(CO)2(dppe) with [(acenaphthene)Mn(CO)3]+ gave [(CO)3Mn(pdt)Fe(CO)2(dppe)]+ ([3d(CO)]+). Reduction of [3d(CO)]+ with BH4– gave the Cs-symmetric μ-hydride (CO)3Mn(pdt)(H)Fe(CO)(dppe) (H3d). Complex H3d is reversibly protonated by strong acids, the proposed site of protonation being sulfur. Treatment of Fe(dithiolate)(CO)2(diphos) with CpCoI2(CO) followed by reduction by Cp2Co affords CpCo(dithiolate)Fe(CO)(diphos) (4), which can also be prepared from Fe(dithiolate)(CO)2(diphos) and CpCo(CO)2. Like the electronically related (CO)3Fe(pdt)Fe(CO)(diphos), these complexes undergo protonation to afford the μ-hydrido complexes [CpCo(dithiolate)HFe(CO)(diphos)]+. Low-temperature NMR studies indicate that Co is the kinetic site of protonation. PMID:24803716

  17. Measurement of hair iron concentration as a marker of body iron content

    PubMed Central

    SAHIN, CEM; PALA, CIGDEM; KAYNAR, LEYLAGUL; TORUN, YASEMIN ALTUNER; CETIN, AYSUN; KURNAZ, FATIH; SIVGIN, SERDAR; SAHIN, FATIH SERDAR

    2015-01-01

    The aim of the present study was to define the possible association between blood parameters and hair iron concentration in patient groups showing a difference in body iron content. The study population comprised subjects with iron deficiency anaemia and transfusion-related anaemia with different body iron contents and a healthy control group. All the cases included in the study were examined with respect to hair iron concentration, serum iron, total iron-binding capacity (TIBC), transferrin saturation and erythrocyte markers in the total blood count with ferritin values. Differences in hair iron concentration were evaluated between the groups. Correlation analysis was applied to define the association between the laboratory values used as markers of body iron content and hair iron concentration. A statistically significant difference was determined in hair iron 56Fe and 57Fe concentrations between the group with transfusion-related anaemia, the iron deficiency anaemia group and the healthy control group (P<0.001). In addition, a positive correlation was determined between hair iron 56Fe and 57Fe concentrations and serum iron, ferritin level, transferrin saturation, mean erythrocyte volume and mean erythrocyte haemoglobin values and a negative correlation with TIBC. In conclusion, the results of the present study showed a statistically significant difference in the hair iron concentrations of the patient groups with different body iron content and these values were correlated to the laboratory markers of body iron content. PMID:26137241

  18. Biofeasibility Study.

    ERIC Educational Resources Information Center

    Chaparian, Michael

    1995-01-01

    Discusses the use of bioremediation as a method for disposing of contaminants by exploiting natural biodegradation processes. The process of conducting a biofeasibility study and a case study are reviewed. (LZ)

  19. Intelligence Studies

    ERIC Educational Resources Information Center

    Monaghan, Peter

    2009-01-01

    To make an academic study of matters inherently secret and potentially explosive seems a tall task. But a growing number of scholars are drawn to understanding spycraft. The interdisciplinary field of intelligence studies is mushrooming, as scholars trained in history, international studies, and political science examine such subjects as the…

  20. Social Studies.

    ERIC Educational Resources Information Center

    Bieber, Edward

    The product of a Special Studies Institute, this teacher developed resource guide for the emotionally handicapped (K-6) presents social study concepts and activities relative to education in the urban out-of-doors. Focus is on the study of man (past, present, and future) interacting with his environment. Listed below are activity examples: (1)…

  1. College Studying.

    ERIC Educational Resources Information Center

    Nist, Sherrie L.; Simpson, Michele

    2002-01-01

    Notes that many students enter postsecondary institutions unprepared to meet the studying demands placed on them. Examines models and taxonomies that have guided researchers as they have investigated studying. Reviews research factors related to studying at the college level: course characteristics, learner characteristics, and learning…

  2. Toxicity Studies.

    PubMed

    2016-01-01

    Toxicity studies in the animal models are done to determine the dose level recommended for the treatment of disease as drug. This guideline enables the characterization of adverse effects following repeated daily inhalation exposure to a test. This chapter includes oral and dermal toxicity studies which are discussed as per OECD guidelines. Both acute and subacute toxicity studies are given special emphasis. PMID:26939270

  3. Dielectric behaviors at microwave frequencies and Mössbauer effects of chalcedony, agate, and zultanite

    NASA Astrophysics Data System (ADS)

    Paralı, Levent; Şabikoǧlu, İsrafil; Tucek, Jiri; Pechousek, Jiri; Novak, Petr; Navarik, Jakub

    2015-05-01

    In this study, dielectric properties within 8-12 GHz microwave frequencies, inductively coupled plasma-atomic emission spectrometry, Fourier transform infrared spectrometry, synchronized two thermal analyses, and 57Fe Mössbauer spectroscopy analysis of chalcedony, agate, and zultanite samples from Turkey are presented. Agate and chalcedony show the same nine vibrational absorption peaks obtained unlike zultanite from FTIR spectra in the 350 cm-1 to 4000 cm-1 range, ɛ‧ values of chalcedony, agate and zultanite derived at 10.5 GHz were 4.67, 4.41, and 7.34, respectively, ɛ‧ and ɛ″ values of the studied samples at the microwave frequencies are related to the percentage weight of their constituent parts in their chemical compositions. 57Fe Mössbauer spectroscopy results confirm the existence of iron-containing islands in the crystal structure of zultanite, agate, and chalcedony samples, equipped them with magnetic features typical for magnetic nanoparticles including superparamagnetism. The presence of iron-containing islands significantly affects the magnetic, dielectric, and optical properties of studied samples that are not observed for pure minerals without any foreign inclusions. Project supported by the Project LO1305 and Operational Program Education for Competitiveness-European Social Fund of the Ministry of Education, Youth and Sports of the Czech Republic (Grant No. CZ.1.07/2.3.00/20.0155), and the Internal Student Grant IGA of Palacky University in Olomouc, Czech Republic (Grant No. IGA PrF 2014017).

  4. Application of emission ( 57Co) Mössbauer spectroscopy in bioscience

    NASA Astrophysics Data System (ADS)

    Kamnev, Alexander A.

    2005-06-01

    Cobalt is an essential trace element with a broad range of physiological and biochemical functions. However, biochemical speciation of cobalt and structural investigations of cobalt-containing complexes with biomacromolecules are challenging, as the participation of cobalt in physiological processes is limited by its very low concentrations. Emission Mössbauer spectroscopy (EMS), with the radioactive 57Co isotope as the most widely used nuclide, is several orders of magnitude more sensitive than its 57Fe absorption variant which has had a rich history of applications in bioscience. Nevertheless, owing to specific difficulties related to the necessity of using radioactive 57Co in samples under study, applications of EMS in biological fields have so far been sparse. In this communication, the EMS applicability to studying biological objects as well as some specific aspects of the EMS methodology are considered in order to draw attention to the unique structural information which can be obtained non-destructively in situ. Chemical consequences (after-effects) of the nuclear transition ( 57Co→ 57Fe), which provide additional information on the electron acceptor properties of the proximate chemical microenvironment of the metal ions, are also considered. The data presented demonstrate that EMS is a sensitive tool for monitoring the chemical state and coordination of cobalt species in biological matter and in biomacromolecular complexes (metalloenzymes), providing valuable structural information at the atomic level.

  5. Hexagonal ferrites of X-, W-, and M-type in the system Sr-Fe-O: A comparative study

    NASA Astrophysics Data System (ADS)

    Töpfer, Jörg; Seifert, Daniela; Le Breton, Jean-Marie; Langenhorst, Falko; Chlan, Vojtech; Kouřil, Karel; Štěpánková, Helena

    2015-03-01

    Three hexagonal ferrites from the Fe-rich part of the pseudo-binary system SrO-Fe2O3 were investigated. Besides the well-known M-type SrFe12O19 two other ferrites were found to exist at high temperatures: W-type SrFe22 + Fe163 + O27 and X-type Sr2 Fe22 + Fe283 + O46 ferrites. A detailed characterization of the X-type Sr-ferrite is reported here for the first time using XRD, HRTEM, magnetization measurements, Mössbauer and 57Fe NMR spectroscopies and ab initio calculations of the electronic structure. The results are compared to those of W- and M-type Sr ferrites. Mössbauer spectra were analyzed with six Fe contributions in the case of the X-type, seven Fe-sites for the W-type and five Fe sites for the M-type in agreement with crystal structure arrangements. Based on a detailed analysis of the NMR spectra in comparison with ab initio calculations the NMR lines were assigned to individual crystal sites. A preferential occupation of ferrous ions in the S blocks of the X- and W-type ferrites was elucidated from Mössbauer and NMR data as well as ab initio calculations.

  6. Aerosal studies

    NASA Technical Reports Server (NTRS)

    Harris, F. S., Jr.

    1976-01-01

    Various methods of measuring aerosols were studied in terms of the best methods to use, the instruments or techniques actually employed, and those techniques applied in field measurements on air quality as influenced by rocket launch effluents, and in an urban environment. Further studies were initiated on the remote sensing of aerosols by satellites and the influence of aerosols on visibility. The characterization of aerosols by measurement of scattered light was studied on Mie theory calculations.

  7. Stream Studies.

    ERIC Educational Resources Information Center

    Hamilton City Board of Education (Ontario).

    This manual provides teachers with some knowledge of ecological study methods and techniques used in collecting data when plants and animals are studied in the field. Most activities deal with the interrelatedness of plant and animal life to the structure and characteristics of a stream and pond. Also included in this unit plan designed for the…

  8. Women's Studies.

    ERIC Educational Resources Information Center

    Davis, James E., Ed.; Davis, Hazel K., Ed.

    1981-01-01

    The 16 articles in this journal issue deal with women's studies within the English curriculum. Topics discussed in the articles include (1) the feminist challenge to the male-centered curriculum in higher education; (2) the women's movement and women's studies; (3) connotations of the word "girl"; (4) women in English education; (5) the new…

  9. Study Skills.

    ERIC Educational Resources Information Center

    Thomas, Anne

    1993-01-01

    Three developments lend support to the idea that schools must help teach study skills: (1) advances in cognitive psychology that suggest children are active learners; (2) society's concern for at-risk students; and (3) growing demands for improved student performance. There is evidence that systematic study skills instruction does improve academic…

  10. Studying Zooarchaeology

    ERIC Educational Resources Information Center

    Moore, Molly; Wolf, Deborah; Butler, Virginia L.

    2012-01-01

    Children often associate the study of bones with dinosaurs or crime scenes. This unit introduces students to "zooarchaeology," the study of animal remains from archaeological sites. Students in grades 3-5 engage in hands-on activities examining bones, shells, and other "hard parts" of animals. They use their observations as a starting point for…

  11. SISTER STUDY

    EPA Science Inventory

    The Sister Study will investigate the role of genetic, environmental, and lifestyle factors on the risk of breast cancer and other diseases in sisters of women with breast cancer. This research study will enroll 50,000 women who live in the United States and who are the cancer-fr...

  12. Social Studies.

    ERIC Educational Resources Information Center

    White, Cam, Ed.

    This document contains the following papers on social studies instruction and technology: (1) "Waking the Sleeping Giant: Social Studies Teacher Educators Collaborate To Integrate Technology into Methods' Courses" (Cheryl Mason, Marsha Alibrandi, Michael Berson, Kara Dawson, Rich Diem, Tony Dralle, David Hicks, Tim Keiper, and John Lee); (2)…

  13. Iron isotope composition of the suspended matter along depth and lateral profiles in the Amazon River and its tributaries

    NASA Astrophysics Data System (ADS)

    dos Santos Pinheiro, Giana Márcia; Poitrasson, Franck; Sondag, Francis; Vieira, Lucieth Cruz; Pimentel, Márcio Martins

    2013-07-01

    Samples of suspended matter were collected at different locations, seasons, depths and lateral profiles in the Amazon River and three of its main tributaries, the Madeira, the Solimões and the Negro rivers. Their iron isotope compositions were studied in order to understand the iron cycle and investigate the level of isotopic homogeneity at the river cross-section scale. Samples from four depth profiles and three lateral profiles analyzed show suspended matter δ57Fe values (relative to IRMM-14) between -0.501 ± 0.075‰ and 0.196 ± 0.083‰ (2SE). Samples from the Negro River, a blackwater river, yield the negative values. Samples from other stations (whitewater rivers, the Madeira, the Solimões and the Amazon) show positive values, which are indistinguishable from the average composition of the continental crust (δ57FeIRMM-14 ˜ 0.1‰). Individual analyses of the depth and lateral profiles show no significant variation in iron isotope signatures, indicating that, in contrast to certain chemical or other isotopic tracers, one individual subsurface sample is representative of river deeper waters. This also suggests that, instead of providing detailed information on the riverine iron cycling, iron isotopes of particulate matter in rivers will rather yield a general picture of the iron sources.

  14. Energy calibration issues in nuclear resonant vibrational spectroscopy: observing small spectral shifts and making fast calibrations.

    PubMed

    Wang, Hongxin; Yoda, Yoshitaka; Dong, Weibing; Huang, Songping D

    2013-09-01

    The conventional energy calibration for nuclear resonant vibrational spectroscopy (NRVS) is usually long. Meanwhile, taking NRVS samples out of the cryostat increases the chance of sample damage, which makes it impossible to carry out an energy calibration during one NRVS measurement. In this study, by manipulating the 14.4 keV beam through the main measurement chamber without moving out the NRVS sample, two alternative calibration procedures have been proposed and established: (i) an in situ calibration procedure, which measures the main NRVS sample at stage A and the calibration sample at stage B simultaneously, and calibrates the energies for observing extremely small spectral shifts; for example, the 0.3 meV energy shift between the 100%-(57)Fe-enriched [Fe4S4Cl4](=) and 10%-(57)Fe and 90%-(54)Fe labeled [Fe4S4Cl4](=) has been well resolved; (ii) a quick-switching energy calibration procedure, which reduces each calibration time from 3-4 h to about 30 min. Although the quick-switching calibration is not in situ, it is suitable for normal NRVS measurements. PMID:23955030

  15. Energy calibration issues in nuclear resonant vibrational spectroscopy: observing small spectral shifts and making fast calibrations

    PubMed Central

    Wang, Hongxin; Yoda, Yoshitaka; Dong, Weibing; Huang, Songping D.

    2013-01-01

    The conventional energy calibration for nuclear resonant vibrational spectroscopy (NRVS) is usually long. Meanwhile, taking NRVS samples out of the cryostat increases the chance of sample damage, which makes it impossible to carry out an energy calibration during one NRVS measurement. In this study, by manipulating the 14.4 keV beam through the main measurement chamber without moving out the NRVS sample, two alternative calibration procedures have been proposed and established: (i) an in situ calibration procedure, which measures the main NRVS sample at stage A and the calibration sample at stage B simultaneously, and calibrates the energies for observing extremely small spectral shifts; for example, the 0.3 meV energy shift between the 100%-57Fe-enriched [Fe4S4Cl4]= and 10%-57Fe and 90%-54Fe labeled [Fe4S4Cl4]= has been well resolved; (ii) a quick-switching energy calibration procedure, which reduces each calibration time from 3–4 h to about 30 min. Although the quick-switching calibration is not in situ, it is suitable for normal NRVS measurements. PMID:23955030

  16. Flooding impairs Fe uptake and distribution in Citrus due to the strong down-regulation of genes involved in Strategy I responses to Fe deficiency in roots.

    PubMed

    Martínez-Cuenca, Mary-Rus; Quiñones, Ana; Primo-Millo, Eduardo; Forner-Giner, M Ángeles

    2015-01-01

    This work determines the ffects of long-term anoxia conditions--21 days--on Strategy I responses to iron (Fe) deficiency in Citrus and its impact on Fe uptake and distribution. The study was carried out in Citrus aurantium L. seedlings grown under flooding conditions (S) and in both the presence (+Fe) and absence of Fe (-Fe) in nutritive solution. The results revealed a strong down-regulation (more than 65%) of genes HA1 and FRO2 coding for enzymes proton-ATPase and Ferric-Chelate Reductase (FC-R), respectively, in -FeS plants when compared with -Fe ones. H+-extrusion and FC-R activity analyses confirmed the genetic results, indicating that flooding stress markedly repressed acidification and reduction responses to Fe deficiency (3.1- and 2.0-fold, respectively). Waterlogging reduced by half Fe concentration in +FeS roots, which led to 30% up-regulation of Fe transporter IRT1, although this effect was unable to improve Fe absorption. Consequently, flooding inhibited 57Fe uptake in +Fe and -Fe seedlings (29.8 and 66.2%, respectively) and 57Fe distribution to aerial part (30.6 and 72.3%, respectively). This evidences that the synergistic action of both enzymes H+-ATPase and FC-R is the preferential regulator of the Fe acquisition system under flooding conditions and, hence, their inactivation implies a limiting factor of citrus in their Fe-deficiency tolerance in waterlogged soils. PMID:25897804

  17. (p,α) Reaction Cross Sections Calculations of Fe and Ni Target Nuclei Using New Developed Semi-empirical Formula

    NASA Astrophysics Data System (ADS)

    Tel, E.; Akca, S.; Kara, A.; Yiğit, M.; Aydın, A.

    2013-10-01

    Iron (Fe) and nickel (Ni) are important fusion structural materials in reactor technology. The gas production in the metallic structure arising from many different types of nuclear reactions has been a significant damage mechanism in structural components of fusion reactors. The hydrogen and its isotopes at high temperatures leave out of the metallic lattice but the alpha (α) particles that remain in the lattice generate helium (He) gas bubbles. In other words, the α particles can cause serious changes in the physical and mechanical properties of the fusion structural materials. In this study, the excitation functions of 54,57Fe(p,α) and 58,60,61,64Ni(p,α) reactions have been investigated in the incident proton energy range of 10-40 MeV to estimate the radiation damage effects on fusion structural materials used in the construction of the first walls and core of the reactor. The calculations of (p,α) reaction cross sections on 54,57Fe and 58,60,61,64Ni have been made by using PCROSS code and CEM95 code. The full exciton and cascade exciton model (CEM95) for pre-equilibrium calculations and Weisskopf-Ewing model for equilibrium calculations are used. Besides, the semi-empirical cross section formula with new coefficient obtained by Tel et al. (Pramana J Phys 74:931-943, 2010) has been applied for (p,α) reactions at 17.9 MeV proton incident energy.

  18. Interstitial Fe in MgO

    SciTech Connect

    Mølholt, T. E. Gislason, H. P.; Ólafsson, S.; Mantovan, R.; Gunnlaugsson, H. P.; Svane, A.; Weyer, G.; Masenda, H.; Naidoo, D.; Bharuth-Ram, K.; Fanciulli, M.; Johnston, K.; Sielemann, R.

    2014-01-14

    Isolated {sup 57}Fe atoms were studied in MgO single-crystals by emission Mössbauer spectroscopy following implantation of {sup 57}Mn decaying to {sup 57}Fe. Four Mössbauer spectral components were found corresponding to different Fe lattice positions and/or charge states. Two components represent Fe atoms substituting Mg as Fe{sup 2+} and Fe{sup 3+}, respectively; a third component is due to Fe in a strongly implantation-induced disturbed region. The fourth component, which is the focus of this paper, can be assigned to Fe at an interstitial site. Comparison of its measured isomer shift with ab initio calculations suggests that the interstitial Fe is located on, or close to, the face of the rock-salt MgO structure. To harmonize such an assignment with the measured near-zero quadrupole interaction a local motion process (cage motion) of the Fe has to be stipulated. The relation of such a local motion as a starting point for long range diffusion is discussed.

  19. X-ray and [gamma]-ray spectroscopy of solids under pressure

    SciTech Connect

    Ingalls, R.L.

    1993-04-30

    The following studies are described that were either completed during this 3-year period or are well underway: XAFS study of pressure-induced transition in Rb-W bronze (Rb[sub 0.31]WO[sub 3]); XAFS study of bcc-hcp transition in Fe; XAFS search for valence change in thallium perhenate (TlReO[sub 4]) at high pressure; XANES analysis of alkali halides; pair potentials in alkali halides studied via EXAFS; EXAFS determination of bond angles in ReO[sub 3]; XAFS study of mixed-valence transition in SmSe; Moessbauer studies of Fe hydride at high pressure; and Moessbauer and x-ray studies of Fe silicate spinel at high pressure. (DLC)

  20. X-ray and {gamma}-ray spectroscopy of solids under pressure. Annual technical progress report, October 1990--October 1993

    SciTech Connect

    Ingalls, R.L.

    1993-04-30

    The following studies are described that were either completed during this 3-year period or are well underway: XAFS study of pressure-induced transition in Rb-W bronze (Rb{sub 0.31}WO{sub 3}); XAFS study of bcc-hcp transition in Fe; XAFS search for valence change in thallium perhenate (TlReO{sub 4}) at high pressure; XANES analysis of alkali halides; pair potentials in alkali halides studied via EXAFS; EXAFS determination of bond angles in ReO{sub 3}; XAFS study of mixed-valence transition in SmSe; Moessbauer studies of Fe hydride at high pressure; and Moessbauer and x-ray studies of Fe silicate spinel at high pressure. (DLC)

  1. Culture Studies: Hawaiian Studies Project.

    ERIC Educational Resources Information Center

    Hazama, Dorothy, Ed.

    Reports and materials from the Hawaiian Studies Project are presented. The document, designed for elementary school teachers contains two major sections. The first section describes the planning phase of the project, the Summer Institute for Hawaiian Culture Studies (1976) and the follow-up workshops and consultant help (1976-77). The appendix to…

  2. NEUROTOXICITY STUDIES

    EPA Science Inventory

    The neurotoxicity of DBPs in general has not been well characterized. The literature provides reports of neurotoxicity of DCA following exposures to relatively high doses. Studies completed at EPA, however, have shown that relatively low doses of DCA (as low as 16 mg/kg/day; simi...

  3. Readability Study.

    ERIC Educational Resources Information Center

    White, Robert; Jordan, William

    A readability study for the Albuquerque Technical-Vocational Institute (T-VI) was undertaken to provide information regarding the reading ability required to complete training and to function in entry-level jobs. Readability formulas were applied to materials used in training and on the job. In addition, students were tested for level of reading,…

  4. Case Studies

    ERIC Educational Resources Information Center

    Ritter, Lois A., Ed.; Sue, Valerie M., Ed.

    2007-01-01

    This article presents two case studies using online surveys for evaluation. The authors begin with an example of a needs assessment survey designed to measure the amount of help new students at a university require in their first year. They then discuss the follow-up survey conducted by the same university to measure the effectiveness of the…

  5. MEDIEVAL STUDIES.

    ERIC Educational Resources Information Center

    MARTONFFY, ANDREA PONTECORVO; AND OTHERS

    A CURRICULUM GUIDE ON MEDIEVAL STUDIES IS PRESENTED, INCLUDING TEACHER MATERIALS AND STUDENT PROBLEM SETS. THE TEACHER MATERIALS DESCRIBE AND EXPLAIN THE ECONOMIC, SOCIAL, AND POLITICAL ASPECTS OF MANORIAL LIFE--THE PREDOMINANT FORM OF AGRICULTURAL LIFE IN NORTHERN FRANCE, ENGLAND, AND GERMANY DURING THE PERIOD FROM APPROXIMATELY 800 TO 1300 A.D.…

  6. IMMUNOTOXICITY STUDIES

    EPA Science Inventory

    Few D/DBPs have been evaluated for effects on the immune system, but certain studies suggest that immunosuppression may follow exposure to D/DBPs. Suppressed immune function is associated with increased susceptibility to infectious disease and certain types of cancer in humans a...

  7. Discipline Study.

    ERIC Educational Resources Information Center

    Queer, Glenn E.

    This report discusses a study designed to elicit opinions from Pittsburgh School District principals, parents, and teachers concerning corporal punishment and other disciplinary action. Questionnaires were aimed at (1) determining reactions to current regulations governing the use of corporal punishment, (2) eliciting instances of experience or…

  8. Research Study

    ERIC Educational Resources Information Center

    Glick, Ashley

    2010-01-01

    Background: Action Research about my 2nd grade classroom in the Buffalo School District. I examined three areas of interest and tried to find some conclusions related to behavior management. Purpose: The purpose of this study is how will implementing procedures, rules, and consequences help improve student behavior. Research Design: Descriptive;…

  9. Consortium study of the unusual H chondrite regolith breccia, Noblesville

    NASA Technical Reports Server (NTRS)

    Lipschutz, Michael E.; Wolf, Stephen F.; Vogt, Stephan; Michlovich, Edward; Lindstrom, Marilyn M.; Zolensky, Michael E.; Mittlefehldt, David W.; Satterwhite, Cecilia; Schultz, Ludolf; Loeken, Thomas

    1993-01-01

    The Noblesville meteorite is a genomict, regolith breccia (H6 clasts in H4 matrix). Moessbauer analysis confirms that Noblesville is unusually fresh, not surprising in view of its recovery immediately after its fall. It resembles 'normal' H4-6 chondrites in its chemical composition and induced thermoluminescence (TL) levels. Thus, at least in its contents of volatile trace elements, Noblesville differs from other H chondrite, class A regolith breccias. Noblesville's small pre-atmospheric mass and fall near solar maximum and/or its peculiar orbit (with perihelion less than 0.8 AU as shown by natural TL intensity) may partly explain its levels of cosmogenic radionuclides. Its cosmic ray exposure age of about 44 Ma is long, is equalled or exceeded by less than 3 percent of all H chondrites, and also differs from the 33 +/- 3 Ma mean exposure age peak of other H chondrite regolith breccias. While Noblesville is now among the chondritic regolithic breccias richest in solar gases, elemental ratios indicate some loss, especially of He, perhaps by impacts in the regolith that heated individual grains. While general shock-loading levels in Noblesville did not exceed 4 GPa, individual clasts record shock levels of 5-10 GPa, doubtless acquired prior to lithification of the whole-rock meteoroid.

  10. A Study of the Magnetic and Thermal Properties of Ln

    SciTech Connect

    Harada, Daijitsu; Hinatsu, Yukio

    2001-05-01

    Crystal structures, and magnetic, electric, and thermal properties of fluorite related compounds Ln{sub 3}RuO{sub 7} (Ln=Sm, Eu) have been investigated. For Eu{sub 3}RuO{sub 7}, a magnetic transition due to Ru{sup 5+} ions is found at T{sub N}=22.5 K on the susceptibility-temperature curve. Specific heat measurements also exhibit a {lambda}-type anomaly at the same temperature. The Moessbauer spectrum measured at 10 K shows broadening of the line corresponding to magnetic splitting. For Sm{sub 3}RuO{sub 7}, two magnetic anomalies have been observed at 10.5 and 22.5 K from its magnetic susceptibility measurements. Below 22.5 K Ru{sup 5+} ions are antiferromagnetically coupled, and when the temperature is decreased through 10.5 K the ordering of Sm{sup 3+} ions occurs rapidly. Specific heat measurements show first-order transition peaks at T=280 and 190 K for Eu{sub 3}RuO{sub 7} and Sm{sub 3}RuO{sub 7}, respectively. T he results of magnetic susceptibility and electric resistivity measurements indicate that these transitions are structural phase transitions.

  11. Study Design for Sequencing Studies.

    PubMed

    Honaas, Loren A; Altman, Naomi S; Krzywinski, Martin

    2016-01-01

    Once a biochemical method has been devised to sample RNA or DNA of interest, sequencing can be used to identify the sampled molecules with high fidelity and low bias. High-throughput sequencing has therefore become the primary data acquisition method for many genomics studies and is being used more and more to address molecular biology questions. By applying principles of statistical experimental design, sequencing experiments can be made more sensitive to the effects under study as well as more biologically sound, hence more replicable. PMID:27008009

  12. Retrospective studies.

    PubMed

    Silveira, Patrícia Pelufo; Manfro, Gisele Gus

    2015-01-01

    Large retrospective, epidemiological studies accumulated in the late 1980s, providing increasing evidence to the deeply rooted thought that perinatal events could persistently affect the individual's functioning and health/disease patterns throughout the lifetime. Evidences of such associations can be found in the literature since the beginning of the twentieth century, but studies from Barker, Hales, and colleagues serve as an important hallmark. They proposed the "thrifty phenotype" hypothesis, stating that poor nutrition in fetal and early infant life is detrimental to the development and function of the individuals' organism, predisposing them to the later development of adult chronic diseases. At first used to explain the increased risk for type 2 diabetes in low birth weight individuals, the hypothesis was soon adapted to other systems, becoming one of the core assumptions of the Developmental Origins of Adult Health and Disease (DOHaD) model. The central nervous system is also vulnerable to the effects of environmental variation during fetal or neonatal life. Many researchers have explored the effects of perinatal programming on the human neurodevelopment, and some aspects of the brain structure and/or functioning (such as cognitive function, physiological reactivity to stress, and the risk for behavioral disorders or psychopathology) were shown to be modifiable by the exposure to certain adverse events early in life such as neonatal infections, exposure to gestational psychosocial stress, nutrition during gestation, exposure to drugs, or tobacco smoking during pregnancy. Until recently, most studies focused on birth weight as a strong surrogate of the intrauterine environment, investigating the effects of low birth weight (as a marker of suboptimal fetal environment) on a variety of neurodevelopmental outcomes. Despite the fact that literature reviews on this topic are as old as 1940, the more recent retrospective studies are summarized in this chapter

  13. Cholera studies*

    PubMed Central

    Pollitzer, R.

    1956-01-01

    The first portion of this study describes in detail the different aspects of stool examinations, including the collection, preservation, and pooling of specimens, macroscopic and bacterioscopic examination, enrichment methods, and cultivation on a variety of solid media. The author also deals with the examination of vomits and of water. The performance and value of different identification tests (agglutination, haemolysis, and bacteriophage) and confirmatory tests are then considered. An annex is included on bacteriological procedures in the laboratory diagnosis of cholera. PMID:13356145

  14. Mössbauer and EPR Study of Iron in Vacuoles from Fermenting Saccharomyces cerevisiae

    PubMed Central

    Cockrell, Allison L.; Holmes-Hampton, Gregory P.; McCormick, Sean P.; Chakrabarti, Mrinmoy; Lindahl, Paul A.

    2011-01-01

    Vacuoles were isolated from fermenting yeast cells grown on minimal medium supplemented with 40 µM 57Fe. Absolute concentrations of Fe, Cu, Zn, Mn, Ca, and P in isolated vacuoles were determined by ICP-MS. Mössbauer spectra of isolated vacuoles were dominated by two spectral features; a mononuclear magnetically isolated high-spin (HS) FeIII species coordinated primarily by hard/ionic (mostly or exclusively oxygen) ligands, and superparamagnetic FeIII oxyhydroxo nanoparticles. EPR spectra of isolated vacuoles exhibited a gave ~ 4.3 signal typical of HS FeIII with E/D ~ 1/3. Chemical reduction of the HS FeIII species was possible, affording a Mössbauer quadrupole doublet with parameters consistent with O/N ligation. Vacuolar spectral features were present in whole fermenting yeast cells; however, quantitative comparisons indicated that Fe leaches out of vacuoles during isolation. The in vivo vacuolar Fe concentration was estimated to be ~1.2 mM while the Fe concentration of isolated vacuoles was ~220 µM. Mössbauer analysis of FeIII polyphosphate exhibited properties similar to those of vacuolar Fe. At the vacuolar pH of 5, FeIII polyphosphate was magnetically isolated, while at pH 7, it formed nanoparticles. This pH-dependent conversion was reversible. FeIII polyphosphate could also be reduced to the FeII state, affording similar Mössbauer parameters to that of reduced vacuolar Fe. These results are insufficient to identify the exact coordination environment of the FeIII species in vacuoles, but they suggest a complex closely related to FeIII polyphosphate. A model for Fe trafficking into/out of yeast vacuoles is proposed. PMID:22047049

  15. In situ spectroscopic applications to the study of rechargeable lithium batteries. Final report

    SciTech Connect

    Barbour, R.; Kim, Sunghyun; Tryk, D.; Scherson, D.A.

    1993-08-01

    In situ attenuated total reflection Fourier transform infrared spectroscopy (ATR/FTIR) has been employed to examine the reactivity of lithium toward polyethylene oxide (PEO) at ca. 60{degree}C. Uncertainties regarding the cleanliness of the Li surfaces were, minimized by electrodepositing a film of metallic Li directly onto a thin layer of gold (ca. 60 {Angstrom}) vapor deposited on a Ge ATR optical element during the spectroscopic measurements. The ATR/FTIR features observed upon stripping the Li layer were consistent with the formation of alkoxide-type moieties resulting from the Li-induced cleavage of the ether-type functionalities. Electronic and structural aspects of the electrochemical insertion of lithium from non-aqueous electroyltes into FeS{sub 2} have been investigated using in situ Fe K-edge X-ray absorption fine structure (XAFS). The results obtained indicate that the incorporation of Li{sup +} in the pyrite lattice brings about a marked decrease in the amplitude of the extended XAFS (EXAFS) oscillations, particularly for shells associated with distant atoms and a rounding of the, X-ray absorption near edge structure (XANES) region. An analysis of the EXAFS spectra yielded a value for the FeS distance of 2.29 {plus_minus} 0.02 {Angstrom}. On this basis and additional in situ room temperature {sup 57}Fe Mossbauer effect spectroscopy data for the same system it has been proposed that the electrically formed material involves a highly disordered (possibly amorphous) form of Fe{sub l-x}S (with Li+ counterbalancing the charge).

  16. Studying mechanosynthesized Hägg carbide (χ-Fe5C2)

    NASA Astrophysics Data System (ADS)

    Barinov, V. A.; Protasov, A. V.; Surikov, V. T.

    2015-08-01

    Methods of thermomagnetic analysis and Mössbauer experiments (57Fe) were used to investigate the formation of Hägg carbide (χ-Fe5C2) under the conditions of mechanical milling of α-Fe in a medium of liquid hydrocarbons. It has been established that, with the employed parameters of milling, the synthesis of χ carbide begins after the completion of the stage of the formation of cementite (θ phase). The borderline of temperature stability of the monophase state of the χ carbide has been determined to be no more than 800 K. At T > 800 K, χ carbide decomposes into cementite and free carbon. The optimum temperature of heating of the synthesized Hägg carbide at which the population of the crystallographically nonequivalent positions of the Fe atoms is close to the ideal (0.2: 0.4: 0.4) is 775 K; the Curie temperature is T C = 520 K. The analysis of the Mössbauer data and of the results of a geometrical simulation of the configurations of Fe atoms in the the χ carbide unit cell made it possible to establish that the above relationship between the populations of positions is satisfied with the allowance for the anisotropic component h an of the field of hyperfine interaction. Under the effect of h an, the crystallographically equivalent atoms Fe(4 e) become nonequivalent (Fe( e 1) and Fe( e 2)) in the magnetic sense. This specific feature manifests in the appearance in the presence of the distribution of hyperfine fields P( H) of two Mössbauer contributions, i.e., p( e 1) and p( e 2) with equal fractions of iron atoms in each of the contributions f Fe( e 1) = = f Fe( e 2) = 0.1 with the magnitudes of the fields H ≈ 11 and 16 T, respectively.

  17. Cholera studies*

    PubMed Central

    Pollitzer, R.

    1957-01-01

    Discussing the symptomatology of cholera, the author deals first with the incubation period, the clinical types, choleraic diarrhoea, and cholerine; he then considers in detail the various stages of cholera gravis and the relapses and complications that may be met. This is followed by sections on diagnosis and differential diagnosis, and on prognosis and the various factors influencing it. The author's highly detailed review of the treatment of cholera which concludes this study is divided into three parts, dealing with attempts at specific therapy, with infusion treatment, and with adjuvant treatment. PMID:13426761

  18. Anticorrosion studies

    NASA Technical Reports Server (NTRS)

    Boerio, J.

    1986-01-01

    The aging behavior of chemically bonded interfaces between metals and pottants, such as ethylene vinyl acetate (EVA) was studied using the Dow Corning primer systems. It was observed that the primers seem to function as anticorrosive agents on metal surfaces. It was demonstrated that EVA, and the A-11861 EVA/glass primer stops corrosion of the aluminum used on the back surfaces of crystalline silicon solar cells. However, this same treatment does not work for the aluminum on the back surfaces of amorphous silicon solar cells.

  19. Ethnobotanical Study.

    PubMed

    2016-01-01

    Ethnobotany is the study of interrelationships between human cultures and plants, animals, and other organisms in their environment. It also creates an awareness of the link between biodiversity and cultural diversity. From the beginning of civilization, people have been using plants for various purposes like food, shelter, medicines, etc. Ethnobotanists play a key role in exploring these kinds of information from indigenous people which creates a gateway for formulating a novel drug. The content in this chapter deals with these aspects in an approachable manner. PMID:26939258

  20. Anticorrosion studies

    NASA Astrophysics Data System (ADS)

    Boerio, J.

    The aging behavior of chemically bonded interfaces between metals and pottants, such as ethylene vinyl acetate (EVA) was studied using the Dow Corning primer systems. It was observed that the primers seem to function as anticorrosive agents on metal surfaces. It was demonstrated that EVA, and the A-11861 EVA/glass primer stops corrosion of the aluminum used on the back surfaces of crystalline silicon solar cells. However, this same treatment does not work for the aluminum on the back surfaces of amorphous silicon solar cells.