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Sample records for dose mn fe

  1. Anomalous positive exchange bias in nanostructured FeMn/Co/FeMn networks

    NASA Astrophysics Data System (ADS)

    Jiang, Changjun; Xue, Desheng; Fan, Xiaolong; Guo, Dangwei; Liu, Qingfang

    2007-08-01

    FeMn/Co/FeMn multilayers are sputtered onto porous alumina templates and silicon, respectively. The FeMn/Co/FeMn multilayer on the porous alumina templates forms an interconnected network nanostructure, while the FeMn/Co/FeMn multilayer on the silicon substrate forms a continuous film. The SQUID testing results show that the exchange bias (HE) and coercivity (Hc) of the FeMn/Co/FeMn multilayer on the porous alumina templates strongly depend on the temperature. A positive exchange bias loops shift is observed at 250 K under field-cooled conditions. However, this is not found in the FeMn/Co/FeMn multilayer on silicon for the same layer thickness. We attribute the positive exchange bias loops shift of the network nanostructured FeMn/Co/FeMn multilayer to the decreased exchange coupling due to the existence of the holes in the interconnected nanostructure.

  2. Tough cryogenic alloys from the Fe-Mn and Fe-Mn-Cr systems

    NASA Technical Reports Server (NTRS)

    Schanfein, M. J.; Zackay, V. F.; Morris, J. W., Jr.

    1974-01-01

    By adjusting composition, metastable gamma (austenite) and epsilon (hexagonal) martensite may be retained in Fe-Mn and Fe-Mn-Cr alloys and used to impact toughness through the TRIP mechanism. The resulting alloys have excellent toughness at cryogenic temperatures. The best alloys obtained to date are: Fe-20Mn, with sigma (sub y) = 79ksi and K sub IC = 275ksi square root of (in) at 77 K, and Fc-16Mn-8Cr, with sigma sub y = 85ksi and K sub IC = 72ksi square root of (in) at 77 K.

  3. Guidelines for finding concretionary Mn-Fe oxides in streams

    USGS Publications Warehouse

    Nowlan, G.A.

    1982-01-01

    Concretionary Mn-Fe oxides in streams form at interfaces between oxidizing and reducing environments. A reducing environment produces waters high in dissolved Mn and Fe, and an oxidizing environment causes precipitation. Mineralogical, microprobe, and optical studies of concretionary Mn-Fe oxides may further our understanding of the role of Mn-Fe oxides in determining the trace-element geochemistry of stream sediments. ?? 1982.

  4. Noncollinear magnetism of Mn nanowires on Fe(1 1 0).

    PubMed

    Igarashi, R N; Miranda, I P; Eleno, L T F; Klautau, A B; Petrilli, H M

    2016-08-17

    Magnetic properties of Mn linear nanochains on a bcc Fe(1 1 0) surface have been studied using the first-principles real space-linear muffin-tin orbital atomic sphere approximation (RS-LMTO-ASA) method. We have considered up to nine Mn atoms deposited on bcc Fe(1 1 0). Our ab initio calculations reveal the competition between the antiferromagnetic Mn-Mn and Mn-Fe couplings, presenting a behavior which is very different from Mn nanowires on Fe(0 0 1), as shown in a previous publication. Due to this competition and non-negligible Dzyaloshinskii-Moriya interaction, noncollinear magnetic structures are stabilized as ground states for the Mn nanochains on Fe(1 1 0). PMID:27346457

  5. Low hysteresis FeMn-based top spin valve.

    PubMed

    Ustinov, V V; Krinitsina, T P; Milyaev, M A; Naumova, L I; Proglyado, V V

    2012-09-01

    FeMn-based top spin valves Ta/[FeNi/CoFe]/Cu/CoFe/FeMn/Ta with different Cu and FeMn layers thicknesses were prepared by DC magnetron sputtering at room temperature. It was shown that low field hysteresis due to free layer magnetization reversal can be reduced down to (0.1 divided by 0.2) Oe keeping the GMR ratio higher 8% by using both layers thicknesses optimization and non-collinear geometry of magnetoresistance measurements. Dependence of low field hysteresis and GMR ratio on the angle between applied magnetic field and pinning direction are presented. PMID:23035516

  6. Noncollinear magnetism of Mn nanowires on Fe(1 1 0)

    NASA Astrophysics Data System (ADS)

    Igarashi, R. N.; Miranda, I. P.; Eleno, L. T. F.; Klautau, A. B.; Petrilli, H. M.

    2016-08-01

    Magnetic properties of Mn linear nanochains on a bcc Fe(1 1 0) surface have been studied using the first-principles real space-linear muffin-tin orbital atomic sphere approximation (RS–LMTO–ASA) method. We have considered up to nine Mn atoms deposited on bcc Fe(1 1 0). Our ab initio calculations reveal the competition between the antiferromagnetic Mn–Mn and Mn–Fe couplings, presenting a behavior which is very different from Mn nanowires on Fe(0 0 1), as shown in a previous publication. Due to this competition and non-negligible Dzyaloshinskii–Moriya interaction, noncollinear magnetic structures are stabilized as ground states for the Mn nanochains on Fe(1 1 0).

  7. Dissimilatory Fe(III) and Mn(IV) reduction.

    PubMed Central

    Lovley, D R

    1991-01-01

    The oxidation of organic matter coupled to the reduction of Fe(III) or Mn(IV) is one of the most important biogeochemical reactions in aquatic sediments, soils, and groundwater. This process, which may have been the first globally significant mechanism for the oxidation of organic matter to carbon dioxide, plays an important role in the oxidation of natural and contaminant organic compounds in a variety of environments and contributes to other phenomena of widespread significance such as the release of metals and nutrients into water supplies, the magnetization of sediments, and the corrosion of metal. Until recently, much of the Fe(III) and Mn(IV) reduction in sedimentary environments was considered to be the result of nonenzymatic processes. However, microorganisms which can effectively couple the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV) have recently been discovered. With Fe(III) or Mn(IV) as the sole electron acceptor, these organisms can completely oxidize fatty acids, hydrogen, or a variety of monoaromatic compounds. This metabolism provides energy to support growth. Sugars and amino acids can be completely oxidized by the cooperative activity of fermentative microorganisms and hydrogen- and fatty-acid-oxidizing Fe(III) and Mn(IV) reducers. This provides a microbial mechanism for the oxidation of the complex assemblage of sedimentary organic matter in Fe(III)- or Mn(IV)-reducing environments. The available evidence indicates that this enzymatic reduction of Fe(III) or Mn(IV) accounts for most of the oxidation of organic matter coupled to reduction of Fe(III) and Mn(IV) in sedimentary environments. Little is known about the diversity and ecology of the microorganisms responsible for Fe(III) and Mn(IV) reduction, and only preliminary studies have been conducted on the physiology and biochemistry of this process. PMID:1886521

  8. Investigations of Fe and Mn Bioreduction in Unconsolidated Clastic Sediments

    NASA Astrophysics Data System (ADS)

    McKinley, J. P.; Zachara, J. M.; Fredrickson, J. K.; Heald, S. M.

    2003-12-01

    We studied the microbial reduction of Mn and Fe in sediments from Oak Ridge, TN, and the Hanford Site, WA. Bioreduction was by incubation of 1 g sediment in 10 ml of 30 mM pH 7 bicarbonate buffer with 7-9 x 107 cells/ml {it S. putrefaciens} CN32 and 10 mM sodium lactate as electron donor. Solution chemistry was monitored during incubation and sediments were pasteurized before characterization. For the unconsolidated clay-rich saprolite from Oak Ridge, Fe reduction occurred after Mn reduction was essentially complete. In sediments from the Pliocene Ringold Fm. (Hanford), incubated under the same conditions, Fe reduction was inhibited, and Mn(III/IV) was incompletely reduced. When Ringold sediments were incubated under conditions with greater available electron donor, more Fe was reduced after reduction of almost all of the available Mn(IV). Transmission and scanning electron microscopy and X-ray microprobe and XANES analysis of Ringold sediments were used to determine the spatial and temporal distribution of Mn. Initially, Mn(III/IV) was present as fragments of phyllomanganate minerals and as interlammelar precipitates with Fe oxides in micas and on silicate clast surfaces. The precipitates were botryoidal and chemically heterogeneous at the sub-micron scale. Precipitates within micas had expanded and deformed the sheet structure of each flake. With the lesser available donor, Mn reduction essentially ceased after 43 days of incubation, and the bulk Mn XANES spectrum indicated residual Mn(III/IV). X-ray microprobe mapping indicated all of the remaining Mn was associated with interlamellar and grain-surface iron oxides, and microXANES showed that the Mn valence within a single mica clast was heterogeneously distributed, and varied from Mn(III/IV) to Mn(II). At longer incubation times, the Mn nearer to the clast exterior tended to be more uniformly reduced than Mn in the interior. The Mn in clast interiors was apparently not readily bioavailable, but could act to

  9. Thermodynamics of nitrogen in Mn-Fe-C melts

    NASA Astrophysics Data System (ADS)

    Lee, Young E.

    2003-12-01

    The present study assesses the available experimental data in the Unified Interaction Parameter (UIP) formalism and proposes a thermodynamic model to describe the solubility of nitrogen over the entire composition range in Mn-Fe-C melts. The solubility of nitrogen was investigated from equilibrium between gaseous nitrogen and nitrogen dissolved in Mn-Fe-C melts. 1/2N_2 (g) + \\underset{raise0.3emsmashriptscriptstyle-}{N} (x,liq.Mn)K = x_N γ _N /P_{N_2^{1/2} } The equilibrium constant, K, and the activity coefficient of nitrogen, γ N, in the UIP formalism were determined taking a liquid Mn and infinite dilution of N in a Mn melt as the standard states for Mn and N, respectively. In K=-5.633+5770/T (1544 to 1841 K) ln K = - 5.633 + 5770/T (1544 to 1841 K)[Figure not available: see fulltext.

  10. Molecular orbital (SCF-X-α-SW) theory of Fe2+-Mn3+, Fe3+-Mn2+, and Fe3+-Mn3+ charge transfer and magnetic exchange in oxides and silicates

    USGS Publications Warehouse

    Sherman, David M.

    1990-01-01

    Metal-metal charge-transfer and magnetic exchange interactions have important effects on the optical spectra, crystal chemistry, and physics of minerals. Previous molecular orbital calculations have provided insight on the nature of Fe2+-Fe3+ and Fe2+-Ti4+ charge-transfer transitions in oxides and silicates. In this work, spin-unrestricted molecular orbital calculations on (FeMnO10) clusters are used to study the nature of magnetic exchange and electron delocalization (charge transfer) associated with Fe3+-Mn2+, Fe3+-Mn3+, and Fe2+-Mn3+ interactions in oxides and silicates. 

  11. Local Observation of the Site Occupancy of Mn in a MnFePSi Compound

    NASA Astrophysics Data System (ADS)

    Neish, M. J.; Oxley, M. P.; Guo, J.; Sales, B. C.; Allen, L. J.; Chisholm, M. F.

    2015-03-01

    MnFePSi compounds are promising materials for magnetic refrigeration as they exhibit a giant magnetocaloric effect. From first principles calculations and experiments on bulk materials, it has been proposed that this is due to the Mn and Fe atoms preferentially occupying two different sites within the atomic lattice. A recently developed technique was used to deconvolve the obscuring effects of both multiple elastic scattering and thermal diffuse scattering of the probe in an atomic resolution electron energy-loss spectroscopy investigation of a MnFePSi compound. This reveals, unambiguously, that the Mn atoms preferentially occupy the 3 g site in a hexagonal crystal structure, confirming the theoretical predictions. After deconvolution, the data exhibit a difference in the Fe L2 ,3 ratio between the 3 f and 3 g sites consistent with differences in magnetic moments calculated from first principles, which are also not observed in the raw data.

  12. Magnetic and microwave properties of CoFe/PtMn/CoFe multilayer films

    NASA Astrophysics Data System (ADS)

    Pettiford, C. I.; Zeltser, A.; Yoon, S. D.; Harri, V. G.; Vittoria, C.; Sun, N. X.

    2006-04-01

    CoFe/PtMn/CoFe films were deposited on seed layers of Ru or NiFeCr with CoFe film compositions being either Co-10 at. %Fe or Co-16 at. %Fe. Eight periods of the CoFe/PtMn/CoFe trilayers were also prepared. The magnetic properties and ferromagnetic resonance (FMR) of these films were characterized with vibrating-sample magnetometer, and field-sweep FMR system at X band (~9.5 GHz). The Ru-seeded CoFe/PtMn/CoFe sandwich films show excellent magnetic softness with a low hard axis coercivity of 2-4 Oe, an easy axis Mr/Ms of >98%, and a significantly enhanced in-plane anisotropy of 57-123 Oe when CoFe layer thickness is above 200 A˚. Contrary to what was observed in the ferromagnetic/antiferromagnetic bilayer systems that have reduced FMR linewidth with the increase of film thickness, the CoFe/PtMn/CoFe trilayers with Ru seed layer show a minimum FMR linewidth of 45 Oe at an intermediate CoFe layer thickness of 300 A˚ at ~9.5 GHz.

  13. Hydrogen Embrittlement Susceptibility of Fe-Mn Binary Alloys with High Mn Content: Effects of Stable and Metastable ɛ-Martensite, and Mn Concentration

    NASA Astrophysics Data System (ADS)

    Koyama, Motomichi; Okazaki, Shota; Sawaguchi, Takahiro; Tsuzaki, Kaneaki

    2016-06-01

    To obtain a basic understanding of hydrogen embrittlement associated with ɛ-martensite, we investigated the tensile behavior of binary Fe-Mn alloys with high Mn content under cathodic hydrogen charging. We used Fe-20Mn, Fe-28Mn, Fe-32Mn, and Fe-40Mn alloys. The correlation between the microstructure and crack morphology was clarified through electron backscatter diffraction measurements and electron channeling contrast imaging. ɛ-martensite in the Fe-20Mn alloy critically deteriorated the resistance to hydrogen embrittlement owing to transformation to α'-martensite. However, when ɛ-martensite is stable, hydrogen embrittlement susceptibility became low, particularly in the Fe-32Mn alloys, even though the formation of ɛ-martensite plates assisted boundary cracking. The Fe-40Mn alloys, in which no martensite forms even after fracture, showed higher hydrogen embrittlement susceptibility compared to the Fe-32Mn alloy. Namely, in Fe-Mn binary alloys, the Mn content has an optimal value for hydrogen embrittlement susceptibility because of the following two reasons: (1) The formation of stable ɛ-martensite seems to have a positive effect in suppressing hydrogen-enhanced localized plasticity, but causes boundary cracking, and (2) an increase in Mn content stabilizes austenite, suppressing martensite-related cracking, but probably decreases the cohesive energy of grain boundaries, causing intergranular cracking. As a consequence, the optimal Mn content was 32 wt pct in the present alloys.

  14. Magnetic interactions in BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices

    PubMed Central

    Xu, Qingyu; Sheng, Yan; Khalid, M.; Cao, Yanqiang; Wang, Yutian; Qiu, Xiangbiao; Zhang, Wen; He, Maocheng; Wang, Shuangbao; Zhou, Shengqiang; Li, Qi; Wu, Di; Zhai, Ya; Liu, Wenqing; Wang, Peng; Xu, Y. B.; Du, Jun

    2015-01-01

    The clear understanding of exchange interactions between magnetic ions in substituted BiFeO3 is the prerequisite for the comprehensive studies on magnetic properties. BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices have been fabricated by pulsed laser deposition on (001) SrTiO3 substrates. Using piezoresponse force microscopy (PFM), the ferroelectricity at room temperature has been inferred from the observation of PFM hysteresis loops and electrical writing of ferroelectric domains for both samples. Spin glass behavior has been observed in both samples by temperature dependent magnetization curves and decay of thermo-remnant magnetization with time. The magnetic ordering has been studied by X-ray magnetic circular dichroism measurements, and Fe-O-Mn interaction has been confirmed to be antiferromagnetic (AF). The observed spin glass in BiFe0.5Mn0.5O3 films has been attributed to cluster spin glass due to Mn-rich ferromagnetic (FM) clusters in AF matrix, while spin glass in BiFeO3/BiMnO3 superlattices is due to competition between AF Fe-O-Fe, AF Fe-O-Mn and FM Mn-O-Mn interactions in the well ordered square lattice with two Fe ions in BiFeO3 layer and two Mn ions in BiMnO3 layer at interfaces. PMID:25766744

  15. 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

  16. Structure and magnetism of FeMnO3

    NASA Astrophysics Data System (ADS)

    Rayaprol, S.; Kaushik, S. D.; Babu, P. D.; Siruguri, V.

    2013-02-01

    The compound FeMnO3 crystallizing in the mineral bixbyite structure has been prepared by mechanochemical synthesis achieved by high energy ball milling of starting compounds. The structure and magnetism have been studied using powder neutron diffraction and magnetization measurements. Magnetization measurements exhibits ferrimagnetism at 300 K and antiferromagnetic (TN) ordering around 36 K. Magnetic structure has been determined from the Rietveld analysis of the neutron diffraction pattern recorded at 300 K. Fe and Mn occupy both 8b and 24d sites in 1:1 ratio. Interaction between Fe and Mn atoms is antiferromagnetic. The ferrimagnetism arises due to anti-parallel alignment of unequal moments on 8b and 24d sites.

  17. Study of intergranular embrittlement in Fe-12Mn alloys

    SciTech Connect

    Lee, H.J.

    1982-06-01

    A high resolution scanning Auger microscopic study has been performed on the intergranular fracture surfaces of Fe-12Mn steels in the as-austenitized condition. Fracture mode below the ductile-brittle transition temperature was intergranular whenever the alloy was quenched from the austenite field. The intergranular fracture surface failed to reveal any consistent segregation of P, S, As, O, or N. The occasional appearance of S or O on the fracture surface was found to be due to a low density precipitation of MnS and MnO/sub 2/ along the prior austenite boundaries. An AES study with Ar/sup +/ ion-sputtering showed no evidence of manganese enrichment along the prior austenite boundaries, but a slight segregation of carbon which does not appear to be implicated in the tendency toward intergranular fracture. Addition of 0.002% B with a 1000/sup 0/C/1h/WQ treatment yielded a high Charpy impact energy at liquid nitrogen temperature, preventing the intergranular fracture. High resolution AES studies showed that 3 at. % B on the prior austenite grain boundaries is most effective in increasing the grain boundary cohesive strength in an Fe-12Mn alloy. Trace additions of Mg, Zr, or V had negligible effects on the intergranular embrittlement. A 450/sup 0/C temper of the boron-modified alloys was found to cause tempered martensite embrittlement, leading to intergranular fracture. The embrittling treatment of the Fe-12Mn alloys with and without boron additions raised the ductile-brittle transition by 150/sup 0/C. This tempered martensite embrittlement was found to be due to the Mn enrichment of the fracture surface to 32 at. % Mn in the boron-modified alloy and 38 at. % Mn in the unmodified alloy. The Mn-enriched region along the prior austenite grain boundaries upon further tempering is believed to cause nucleation of austenite and to change the chemistry of the intergranular fracture surfaces. 61 figures.

  18. The corrosion behavior of Fe-Mn-Al weld metals

    NASA Astrophysics Data System (ADS)

    Aidun, Daryush K.

    2001-02-01

    The corrosion resistance of a newly developed iron-base, Fe-Mn-Al austenitic, and duplex weld metal has been examined in the NACE solution consisting of 5 wt.% NaCl, 0.5 wt.% acetic acid, and the balance distilled water. The electrochemical techniques such as potentiodynamic polarization, Tafel plots, linear polarization, cyclic polarization, and open-circuit potential versus time were employed. The Fe-Mn-Al weld metals did not passivate and exhibited high corrosion rates. Fe-Cr-Ni (310 and 316) weld and base metals were also examined in the NACE solution at room temperature. The 310 and 316 base metals were more resistant to corrosion than the as-welded 310 and 316 weld metals. Postweld heat treatment (PWHT) improved the corrosion performance of the Fe-Mn-Al weld metals. The corrosion resistance of Fe-Mn-Al weld metals after PWHT was still inferior to that of the 310 and 316 weld and base metals.

  19. Effect of on-site Coulomb interaction (U) on the electronic and magnetic properties of Fe2MnSi, Fe2MnAl and Co2MnGe

    NASA Astrophysics Data System (ADS)

    Sharma, Sonu; Pandey, Sudhir K.

    2016-04-01

    The electronic band structures, density of states' plots and magnetic moments of Fe2MnSi, Fe2MnAl, and Co2MnGe are studied by using the first principles calculation. The FM solutions using LSDA without U show the presence of half-metallic ferromagnetic (HFM) ground state in Fe2MnSi, whereas the ground state of Fe2MnAl is found to be metallic. In both compounds the maximum contribution to the total magnetic moment is from the Mn atom, while the Fe atom contributes very less. The electronic structures and magnetic moments of Fe-based compounds are affected significantly by U under around-the-mean-field (AMF) double counting scheme, whereas its effect is very less on Co2MnGe. The magnetic moment of Fe atom in Fe2MnSi (Fe2MnAl) increased by ∼70% (∼75%) and in Mn atom it decreases by ∼50% (∼70%) when the value of U is increased from 1 to 5 eV. Hund's like exchange interactions are increasing in Fe atom while decreasing in Mn atom with increase in U. The Fe and Mn moments are ferromagnetically coupled in Fe2MnSi for all values of U, whereas in Fe2MnAl they are coupled antiferromagnetically below U=2 eV and ferromagnetically above it. Above U=2 eV the metallic ground state of Fe2MnAl changes to semiconducting ground state and the ferromagnetic coupling between Fe and Mn atoms appears to be responsible for this. This shows that the validity of AFM double counting scheme is not robust for the entire range of U in the Fe2MnAl compound.

  20. Magnetic properties and atomic ordering of BCC Heusler alloy Fe2MnGa ribbons

    NASA Astrophysics Data System (ADS)

    Xin, Yuepeng; Ma, Yuexing; Luo, Hongzhi; Meng, Fanbin; Liu, Heyan

    2016-05-01

    The electronic structure, atomic disorder and magnetic properties of the Heusler alloy Fe2MnGa have been investigated experimentally and theoretically. BCC Fe2MnGa ribbon samples were prepared. Experimentally, a saturation magnetic moment (3.68 μB at 5 K) much larger than the theoretical value (2.04 μB) has been reported. First-principles calculations indicate that the difference is related to the Fe-Mn disorder between A, B sites, as can also be deduced from the XRD pattern. L21 type Fe2MnGa is a ferrimagnet with antiparallel Fe and Mn spin moments. However, when Fe-Mn disorder occurs, part of Mn moments will be parallel to Fe moments, and the Fe moments also clearly increase simultaneously. All this results in a total moment of 3.74 μB, close to the experimental value.

  1. Paramagnetic properties of Fe-Mn and Fe-V alloys: a DMFT study

    NASA Astrophysics Data System (ADS)

    Belozerov, Alexander S.; Anisimov, Vladimir I.

    2016-09-01

    We calculate magnetic susceptibility of paramagnetic bcc Fe-Mn and Fe-V alloys by two different approaches. The first approach employs the coherent potential approximation (CPA) combined with the dynamical mean-field theory (DMFT). The material-specific Hamiltonians in the Wannier function basis are obtained by density functional theory. In the second approach, we construct supercells modeling the binary alloys and study them using DMFT. Both approaches lead to a qualitative agreement with experimental data. In particular, the decrease of Curie temperature with Mn content and a maximum at about 10 at.% V are well described in units of the Curie temperature of pure iron. In contrast to the Mn impurities, the V ones are found to be antiferromagnetically coupled to Fe atoms. Our calculations for the two-band Anderson–Hubbard model indicate that the antiferromagnetic coupling is responsible for a maximum in the concentration dependence of Curie temperature in Fe-V alloys.

  2. Paramagnetic properties of Fe-Mn and Fe-V alloys: a DMFT study.

    PubMed

    Belozerov, Alexander S; Anisimov, Vladimir I

    2016-09-01

    We calculate magnetic susceptibility of paramagnetic bcc Fe-Mn and Fe-V alloys by two different approaches. The first approach employs the coherent potential approximation (CPA) combined with the dynamical mean-field theory (DMFT). The material-specific Hamiltonians in the Wannier function basis are obtained by density functional theory. In the second approach, we construct supercells modeling the binary alloys and study them using DMFT. Both approaches lead to a qualitative agreement with experimental data. In particular, the decrease of Curie temperature with Mn content and a maximum at about 10 at.% V are well described in units of the Curie temperature of pure iron. In contrast to the Mn impurities, the V ones are found to be antiferromagnetically coupled to Fe atoms. Our calculations for the two-band Anderson-Hubbard model indicate that the antiferromagnetic coupling is responsible for a maximum in the concentration dependence of Curie temperature in Fe-V alloys. PMID:27355416

  3. Scavenging of Cd through Fe/Mn oxides within natural surface coatings.

    PubMed

    Li, Yu; Huang, Guo-he; Zhang, Bai-yu; Guo, Shu-hai

    2006-01-01

    The dynamics of Cd scavenging from solutions by Fe/Mn oxides in natural surface coatings (NSCs) was investigated under laboratory conditions. Selective extraction methods were employed to estimate the contributions of Fe/Mn oxides, where hydroxylamine hydrochloride (0.01 mol/L NH2OH x HCl + 0.01 mol/L HNO3), sodium dithionite (0.4 mol/L Na2S2O4) and nitric acid (10% HNO3) were used as extraction reagents. The Cd scavenging was accomplished with developing periods of the NSCs (totally 21 data sets). The resulting process dynamics fitted well to the Elovich equation, demonstrating that the amount of Cd scavenged was proportional to the increments of Fe/Mn oxides that were accumulated in the NSCs. The amount of Cd bound to Fe oxides (M,,) and Mn oxides (MCdMn could be quantified by solving two equations based on the properties of two extraction reagents. The amount of Cd scavenged by Fe/Mn oxides could also be estimated using MCdFe and MCdMn, divided by the total amounts of Fe and Mn oxides in the NSCs, respectively. The results indicated that the Cd scavenging by Fe/Mn oxides was dominated by Fe oxides, with less roles attributed to Mn oxides. The estimated levels of Cd scavenging through Fe and Mn oxides agreed well with those predicted through additive-adsorption and linear-regression models. PMID:17294965

  4. Electrochemical sensing property of Mn doped Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Suresh, R.; Giribabu, K.; Manigandan, R.; Vijayalakshmi, L.; Stephen, A.; Narayanan, V.

    2013-02-01

    The Mn doped Fe3O4 nanoparticles were synthesized by hydrothermal method. The prepared nanoparticles were characterized by X-ray diffraction (XRD) analysis, UV-Visible spectroscopy (UV-Vis) and field emission scanning electron microscopy (FE-SEM). The electrochemical sensing property of pure and Mn doped Fe3O4 nanoparticles were examined using uric acid (UA) as an analyte. The obtained results indicated that the Mn doped Fe3O4 nanoparticles exhibited higher electrocatalytic activity towards UA.

  5. Ferromagnetic interactions and martensitic transformation in Fe doped Ni-Mn-In shape memory alloys

    SciTech Connect

    Lobo, D. N.; Priolkar, K. R.; Emura, S.; Nigam, A. K.

    2014-11-14

    The structure, magnetic, and martensitic properties of Fe doped Ni-Mn-In magnetic shape memory alloys have been studied by differential scanning calorimetry, magnetization, resistivity, X-ray diffraction (XRD), and EXAFS. While Ni{sub 2}MnIn{sub 1−x}Fe{sub x} (0 ≤ x ≤ 0.6) alloys are ferromagnetic and non martensitic, the martensitic transformation temperature in Ni{sub 2}Mn{sub 1.5}In{sub 1−y}Fe{sub y} and Ni{sub 2}Mn{sub 1.6}In{sub 1−y}Fe{sub y} increases for lower Fe concentrations (y ≤ 0.05) before decreasing sharply for higher Fe concentrations. XRD analysis reveals presence of cubic and tetragonal structural phases in Ni{sub 2}MnIn{sub 1−x}Fe{sub x} at room temperature with tetragonal phase content increasing with Fe doping. Even though the local structure around Mn and Ni in these Fe doped alloys is similar to martensitic Mn rich Ni-Mn-In alloys, presence of ferromagnetic interactions and structural disorder induced by Fe affect Mn-Ni-Mn antiferromagnetic interactions resulting in suppression of martensitic transformation in these Fe doped alloys.

  6. Fieldlike spin-orbit torque in ultrathin polycrystalline FeMn films

    NASA Astrophysics Data System (ADS)

    Yang, Yumeng; Xu, Yanjun; Zhang, Xiaoshan; Wang, Ying; Zhang, Shufeng; Li, Run-Wei; Mirshekarloo, Meysam Sharifzadeh; Yao, Kui; Wu, Yihong

    2016-03-01

    Fieldlike spin-orbit torque in FeMn/Pt bilayers with ultrathin polycrystalline FeMn has been characterized through planar Hall effect measurements. A large effective field of 2.05 ×10-5 to 2.44 ×10-5Oe (A-1cm2) is obtained for FeMn in the thickness range of 2-5 nm. The experimental observations can be reasonably accounted for by using a macrospin model under the assumption that the FeMn layer is composed of two spin sublattices with unequal magnetizations. The large effective field corroborates the spin Hall origin of the effective field, considering the much smaller uncompensated net moments in FeMn as compared to NiFe. The effective absorption of spin current by FeMn is further confirmed by the fact that spin current generated by Pt in NiFe/FeMn/Pt trilayers can only travel through the FeMn layer with a thickness of 1-4 nm. By quantifying the fieldlike effective field induced in NiFe, a spin diffusion length of 2 nm is estimated in FeMn, consistent with values reported in the literature by ferromagnetic resonance and spin-pumping experiments.

  7. The Mn-Fe negative correlation in olivines in ALHA 77257 ureilite

    NASA Astrophysics Data System (ADS)

    Miyamoto, M.; Furuta, T.; Fujii, N.; McKay, D. S.; Lofgren, G. E.; Duke, M. B.

    1993-03-01

    An electron probe microanalyzer is used to measure the Mn, Fe, and oxygen zoning profiles of olivines in the ALHA 77257 ureilite. This is done to study the effects of reduction on the Mn-Fe value, as ureilite olivines exhibit thin reduced rims. Since the Mn content gradually increases toward the rim of ureilite olivines, while the Fa (= 100 x Fe/(Mg + Fe), mol percent) component decreases, the Mn-Fe content of olivine is likely related to redox conditions. The results of melting experiments suggest that the Mn-Fe positive correlation is related to temperature and that the negative correlation of Mn-Fe in olivine and low-Ca pyroxene is related to reduction.

  8. Electronic structure and magnetic properties of Mn, Co, and Ni substitution of Fe in Fe4N

    NASA Astrophysics Data System (ADS)

    Monachesi, Patrizia; Björkman, Torbjörn; Gasche, Thomas; Eriksson, Olle

    2013-08-01

    The magnetic properties of Mn, Co, and Ni substituted Fe4N are calculated from first principles theory. It is found that the generalized gradient approximation reproduces with good accuracy the magnetic moment and equilibrium volume for the parent Fe4N structure, with the atomic moment largest for the Fe atom furthest away from the N atom (Fe I site), approaching a value of 3 μB/atom, whereas the Fe atom closer to the N atom (Fe II site) has a moment closer to that of bcc Fe. The substitution of Fe for Mn, Co, or Ni, shows an intricate behavior in which the Mn substitution clearly favors the Fe II site, Ni favors substitution on the Fe I site, and Co shows no strong preference for either lattice site. The Ni and Co substitution results in a ferromagnetic coupling to the Fe atoms, whereas Mn couples antiferromagnetically on the Fe II site and ferromagnetically on the Fe I site. For all types of doping, the total magnetic moment is enhanced compared to Fe4N only in the energetically very unfavorable case of Mn doping at the Fe I site.

  9. Relative Biological Effectiveness of HZE Fe Ions for Induction ofMicro-Nuclei at Low Doses

    SciTech Connect

    Groesser, Torsten; Chun, Eugene; Rydberg, Bjorn

    2007-01-16

    Dose-response curves for induction of micro-nuclei (MN) was measured in Chinese hamster V79 and xrs6 (Ku80-) cells and in human mammary epithelial MCF10A cells in the dose range of 0.05-1 Gy. The Chinese Hamster cells were exposed to 1 GeV/u Fe ions, 600 MeV/u Fe ions, and 300 MeV/u Fe ions (LETs of 151, 176 and 235 keV/{micro}m respectively) as well as with 320 kVp X-rays as reference. Second-order polynomials were fitted to the induction curves and the initial slopes (the alpha values) were used to calculate RBE. For the repair proficient V79 cells the RBE at these low doses increased with LET. The values obtained were 3.1 (LET=151 keV/{micro}m), 4.3 (LET = 176 keV/{micro}m) and 5.7 (LET = 235 keV/{micro}m), while the RBE was close to 1 for the repair deficient xrs6 cells regardless of LET. For the MCF10A cells the RBE was determined for 1 GeV/u Fe ions and found to be 5.4, slightly higher than for V79 cells. To test the effect of shielding, the 1 GeV/u Fe ion beam was intercepted by various thickness of high-density polyethylene plastic absorbers, which resulted in energy loss and fragmentation. It was found that the MN yield for V79 cells placed behind the absorbers decreased in proportion to the decrease in dose both before and after the Fe ion Bragg peak (excluding the area around the Fe-ion Bragg peak itself), indicating that RBE did not change significantly due to shielding. At the Bragg peak the effectiveness for MN formation per unit dose was decreased, indicating an 'overkill' effect by low-energy very high-LET Fe ions.

  10. Mixing antiferromagnets to tune NiFe-[IrMn/FeMn] interfacial spin-glasses, grains thermal stability, and related exchange bias properties

    SciTech Connect

    Akmaldinov, K.; Ducruet, C.; Portemont, C.; Joumard, I.; Prejbeanu, I. L.; Dieny, B.; Baltz, V.

    2014-05-07

    Spintronics devices and in particular thermally assisted magnetic random access memories require a wide range of ferromagnetic/antiferromagnetic (F/AF) exchange bias (EB) properties and subsequently of AF materials to fulfil diverse functionality requirements for the reference and storage. For the reference layer, large EB energies and high blocking temperature (T{sub B}) are required. In contrast, for the storage layer, mostly moderate T{sub B} are needed. One of the present issues is to find a storage layer with properties intermediate between those of IrMn and FeMn and in particular: (i) with a T{sub B} larger than FeMn for better stability at rest-T but lower than IrMn to reduce power consumption at write-T and (ii) with improved magnetic interfacial quality, i.e., with reduced interfacial glassy character for lower properties dispersions. To address this issue, the EB properties of F/AF based stacks were studied for various mixed [IrMn/FeMn] AFs. In addition to EB loop shifts, the F/AF magnetic interfacial qualities and the AF grains thermal stability are probed via measurements of the low- and high-temperature contributions to the T{sub B} distributions, respectively. A tuning of the above three parameters is observed when evolving from IrMn to FeMn via [IrMn/FeMn] repetitions.

  11. Assessment of Mn-Fe-Si-C Melt in Unified Interaction Parameter Formalism

    NASA Astrophysics Data System (ADS)

    Shin, Jung Pil; Lee, Young E.

    2016-02-01

    The solubility of C in Mn-Fe-Si-C melt decreases with increasing Si content, and its decrease becomes greater when the phase in equilibrium with Mn-Fe-Si-C melt changes from carbon to SiC. Such behavior has an industrial implication for low carbon products and processes of steels and Mn alloys. Li and Morris assessed the solution properties of Mn-Fe-Si-C system in the UIP formalism, but the effectiveness of their assessment was limited in applicable ranges of composition to Mn-rich solution and of temperature to around 1673 K (1400 °C). This study develops the information of activity coefficients of C and Si of Mn-Fe-Si-C system from the consistent experimental solubility of C and assesses them in the UIP formalism. This assessment of Mn-Fe-Si-C system describes confidently the behavior of solution properties in a wide range of composition and temperature.

  12. Chemistry of arsenic removal during coagulation and Fe-Mn oxidation

    SciTech Connect

    Edwards, M. . Dept. of Civil Engineering)

    1994-09-01

    Arsenic removal during coagulation or Fe-Mn oxidation is examined to aid utilities that desire to improve arsenic removal. Fundamental mechanisms of arsenic removal are discussed, optimization strategies are forwarded, and some new insights are provided to guide future research. Specifically, As(III) removals by coagulation are primarily controlled by coagulant dose and relatively unaffected by solution pH, whereas the converse is true for As(V). When compared on the basis of moles iron or aluminum hydroxide solid formed during coagulation, iron and aluminum coagulants are of demonstrably equal effectiveness in removing As(V) at pH < 7.5. However, iron-based coagulants are advantageous if soluble metal residuals are problematic, if pH is > 7.5, or if the raw water contains As(III). Arsenic removal during Fe-Mn oxidation is controlled by the quantity of iron removed [Fe(OH)[sub 3] formed] and is relatively independent of the quantity of manganese removed (MnOOH formed). 63 refs.

  13. A Mn(IV)/Fe(IV) Intermediate in Assembly of the Mn(IV)/Fe(III) Cofactor of Chlamydia trachomatis Ribonucleotide Reductase†

    PubMed Central

    Jiang, Wei; Hoffart, Lee M.; Krebs, Carsten; Bollinger, J. Martin

    2008-01-01

    We recently showed that the class Ic ribonucleotide reductase from the human pathogen, Chlamydia trachomatis, uses a MnIV/FeIII cofactor to generate protein and substrate radicals in its catalytic mechanism [Jiang, W., Yun, D., Saleh, L., Barr, E. W., Xing, G., Hoffart, L. M., Maslak, M.-A., Krebs, C., and Bollinger, J. M., Jr. (2007) Science 316, 1188-1191]. Here, we have dissected the mechanism of formation of this novel heterobinuclear redox cofactor from the MnII/FeII cluster and O2. An intermediate with a g = 2 EPR signal that shows hyperfine coupling to both 55Mn and 57Fe accumulates almost quantitatively in a second order reaction between O2 and the reduced R2 complex. The otherwise slow decay of the intermediate to the active MnIV/FeIII-R2 complex is accelerated by the presence of the one-electron reductant, ascorbate, implying that the intermediate is more oxidized than MnIV/FeIII. Mössbauer spectra show that the intermediate contains a high-spin FeIV center. Its chemical and spectroscopic properties establish that the intermediate is a MnIV/FeIV-R2 complex with an S = 1/2 electronic ground state arising from antiferromagnetic coupling between the MnIV (SMn = 3/2) and high-spin FeIV (SFe = 2) sites. PMID:17616152

  14. Origin of concretionary Mn-Fe-oxides in stream sediments of Maine, U.S.A.

    USGS Publications Warehouse

    Nowlan, G.A.; McHugh, J.B.; Hessin, T.D.

    1983-01-01

    Studies of stream and sediment-pore waters largely explain the genesis of concretionary Mn-Fe-oxides in Maine. Waters of two small streams near Jackman, Maine, were studied in terms of pH, Eh, dissolved oxygen, dissolved organic carbon, dissolved Mn, total dissolved Fe, and ferrous and ferric Fe. Pyrite Creek has profuse concretions and coatings of Mn-Fe-oxides, whereas West Pyrite Creek has only sparse Mn-Fe-oxide stains. Pyrite Creek drains boggy terrain and West Pyrite Creek drains well-drained terrain. In West Pyrite Creek, stream and subjacent pore waters have chemical characteristics that do not differ greatly. However, dissolved Mn, ferrous Fe, dissolved oxygen, and in situ Eh measurements show that a steep Eh gradient exists between stream and subjacent pore waters of Pyrite Creek. The steep Eh gradient is manifested by the common zonation of coatings and stains on rocks in stream sediment. The bottom zone has no deposition of oxides, the middle zone is red and consists mostly of Fe-oxides, and the upper zone is black or dark-brown and consists of Mn-oxides with varying amounts of Fe-oxides. The zonation agrees with theoretical predictions of oxide stability as one moves from a reducing to an oxidizing environment. At locations where concretionary Mn-Fe-oxides form, pore waters are depleted of oxygen because of abundant decaying organic material in the stream sediment. The pore waters are charged with dissolved Mn and Fe because mechanically deposited Mn-Fe-oxides are remobilized due to the low-Eh conditions. Groundwaters also contribute dissolved Mn and Fe. Stream waters, on the other hand, are oxygenated and the high-Eh conditions result in low concentrations of dissolved Mn and Fe in stream waters because of the insolubility of Mn-Fe-oxides in high-Eh environments. Therefore, concretionary Mn-Fe-oxides form at the interface between pore and stream waters because Mn- and Fe-rich pore waters, which are undersaturated with respect to Mn-Fe-oxides, mix with

  15. Close correlation between magnetic properties and the soft phonon mode of the structural transition in BaFe>2mn>As>2mn> and SrFe>2mn>As>2mn>

    SciTech Connect

    Parshall, D.; Pintschovius, L.; Niedziela, Jennifer L.; Castellan, J. -P.; Lamago, D.; Mittal, R.; Wolf, Th.; Reznik, Dmitry

    2015-04-27

    Parent compounds of Fe-based superconductors undergo a structural phase transition from a tetragonal to an orthorhombic structure. We investigated the temperature dependence of the frequencies of TA phonons that extrapolate to the shear vibrational mode at the zone center, which corresponds to the orthorhombic deformation of the crystal structure at low temperatures in BaFe>2mn>As>2mn> and SrFe>2mn>As>2mn>. We found that acoustic phonons at small wave vectors soften gradually towards the transition from high temperatures, tracking the increase of the size of slowly fluctuating magnetic domains. On cooling below the transition to base temperature the phonons harden, following the square of the magnetic moment (which we find is proportional to the anisotropy gap). Finally, our results provide evidence for close correlation between magnetic and phonon properties in Fe-based superconductors.

  16. Magnetic and magnetocaloric exploration of Fe rich (Mn,Fe)2(P,Ge)

    NASA Astrophysics Data System (ADS)

    Leitão, J. V.; van der Haar, M.; Lefering, A.; Brück, E.

    2013-10-01

    We explored the Fe rich side of the (Mn,Fe)2(P,Ge) magnetocaloric system. The transition temperature of this system is extremely easy to tune with careful manipulation of Fe and Ge content as well as stoichiometrical proportions, which give rise to the real possibility of lowering the price of this compound and thus make it economically viable for practical magnetocaloric applications. Novel and unexpected magnetic properties observed in this system suggest an exciting potential for permanent magnet application in a limited concentration range.

  17. Fabrication and Characterization of MnBi/Co and MnBi/FeCo Nanocomposite Bulk Magnets

    NASA Astrophysics Data System (ADS)

    Poudyal, Narayan; Gandha, Kinjal; Wang, Wei; Liu, Xiaotong; Qiu, Zhaoguo; Elkins, Kevin; Liu, J. Ping; Cui, Jun; Department of Physics, University of Texas at Arlington, Texas 76019, USA Team; Energy; Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington USA Collaboration

    2015-03-01

    We report the fabrication of MnBi/Co and MnBi/FeConanocomposite bulk magnets by consolidating the hard and the soft phase powder particles under a magnetic field followed by subsequent sintering process. The anisotropic micro and submicron hard magnetic MnBi particles were first prepared by low energy cryo ball milling at liquid nitrogen temperature. MnBi/Co and MnBi/FeCo nanocomposite powders were then prepared by using different fraction of chemically synthesized Co nanowires and FeCo nanoparticles as the soft magnetic phase. The saturation magnetization (Ms) of the composite magnets increases with addition of the soft phase while the coercivity first increases and then decreases. The MnBi/Co and MnBi/FeCo nanocomposite bulk magnets have reached an enhanced magnetization value (Ms = 78 and 80.6 emu/g) with 30 wt. % of Co nanowires and FeCo nanoparticles, respectively compared to the single phase MnBi bulk magnet (Ms = 52 emu/g).

  18. Magnetic properties and thermal stability of MnBi/NdFeB hybrid bonded magnets

    NASA Astrophysics Data System (ADS)

    Cao, S.; Yue, M.; Yang, Y. X.; Zhang, D. T.; Liu, W. Q.; Zhang, J. X.; Guo, Z. H.; Li, W.

    2011-04-01

    Magnetic properties and thermal stability were investigated for the MnBi/NdFeB (MnBi = 0, 20, 40, 60, 80, and 100 wt.%) bonded hybrid magnets prepared by spark plasma sintering (SPS) technique. Effect of MnBi content on the magnetic properties of the hybrid magnets was studied. With increasing MnBi content, the coercivity of the MnBi/NdFeB hybrid magnets increases rapidly, while the remanence and maximum energy product drops simultaneously. Thermal stability measurement on MnBi magnet, NdFeB magnet, and the hybrid magnet with 20 wt.% MnBi indicates that both the NdFeB magnet and the MnBi/NdFeB hybrid magnet have a negative temperature coefficient of coercivity, while the MnBi magnet has a positive one. The (BH)max of the MnBi/NdFeB magnet (MnBi = 20 wt.%) is 5.71 MGOe at 423 K, which is much higher than 3.67 MGOe of the NdFeB magnet, indicating a remarkable improvement of thermal stability.

  19. Magnetic properties and thermal stability of MnBi/NdFeB hybrid bonded magnets

    SciTech Connect

    Cao, S.; Yue, M.; Yang, Y. X.; Zhang, D. T.; Liu, W. Q.; Zhang, J. X.; Guo, Z. H.; Li, W.

    2011-04-01

    Magnetic properties and thermal stability were investigated for the MnBi/NdFeB (MnBi = 0, 20, 40, 60, 80, and 100 wt.%) bonded hybrid magnets prepared by spark plasma sintering (SPS) technique. Effect of MnBi content on the magnetic properties of the hybrid magnets was studied. With increasing MnBi content, the coercivity of the MnBi/NdFeB hybrid magnets increases rapidly, while the remanence and maximum energy product drops simultaneously. Thermal stability measurement on MnBi magnet, NdFeB magnet, and the hybrid magnet with 20 wt.% MnBi indicates that both the NdFeB magnet and the MnBi/NdFeB hybrid magnet have a negative temperature coefficient of coercivity, while the MnBi magnet has a positive one. The (BH){sub max} of the MnBi/NdFeB magnet (MnBi = 20 wt.%) is 5.71 MGOe at 423 K, which is much higher than 3.67 MGOe of the NdFeB magnet, indicating a remarkable improvement of thermal stability.

  20. Magnetic epoxy nanocomposites with superparamagnetic MnFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Huang, Jiangnan; Cao, Yonghai; Zhang, Xi; Li, Yutong; Guo, Jiang; Wei, Suying; Peng, Xiangfang; Shen, Tong D.; Guo, Zhanhu

    2015-09-01

    Manganese iron oxide (MnFe2O4) nanoparticles successfully served as nanofillers for obtaining magnetic epoxy nanocomposites. The viscosities of MnFe2O4/epoxy resin liquid suspensions increased with increasing the nanoparticles loading except the suspension with 5.0 and 1.0 wt% loading, whose viscosities were lower than that of pure epoxy. The introduction of MnFe2O4 nanoparticles showed a lower onset decomposition temperature and glass transition temperature (Tg), which decreased with increasing the nanoparticles loading. The storage modulus and tensile strength of 1.0 wt% MnFe2O4/epoxy were a little higher than that of pure epoxy. The coercivity of MnFe2O4/epoxy nanocomposites with 5.0 wt% (44.7 Oe) and 10.0 wt% (43.9 Oe) displayed much higher than that of pure MnFe2O4 nanoparticles (14.94 Oe). The magnetic moment (m) of nanocomposites (1.354 μB for 10 wt% MnFe2O4/epoxy) are higher than that of pure MnFe2O4 nanoparticles (1.244 μB). The increased real permittivity observed in the nanocomposites was attributed to the interfacial polarization. The intrinsic permittivity of the MnFe2O4 nanoparticles was also calculated.

  1. Fe-species-loaded mesoporous MnO2 superstructural requirements for enhanced catalysis.

    PubMed

    Huang, Ruting; Liu, Yanyu; Chen, Zhiwen; Pan, Dengyu; Li, Zhen; Wu, Minghong; Shek, Chan-Hung; Wu, C M Lawrence; Lai, Joseph K L

    2015-02-25

    In this work, a novel catalyst, Fe-species-loaded mesoporous manganese dioxide (Fe/M-MnO2) urchinlike superstructures, has been fabricated successfully in a two-step technique. First, mesoporous manganese dioxide (M-MnO2) urchinlike superstructures have been synthesized by a facile method on a soft interface between CH2Cl2 and H2O without templates. Then the M-MnO2-immobilized iron oxide catalyst was obtained through wetness impregnation and calcination. Microstructural analysis indicated that the M-MnO2 was composed of urchinlike hollow submicrospheres assembled by nanorod building blocks with rich mesoporosity. The Fe/M-MnO2 retained the hollow submicrospheres, which were covered by hybridized composites with broken and shortened MnO2 nanorods. Energy-dispersive X-ray microanalysis was used to determine the availability of Fe loading processes and the homogeneity of Fe in Fe/M-MnO2. Catalytic performances of the M-MnO2 and Fe/M-MnO2 were evaluated in catalytic wet hydrogen peroxide oxidation of methylene blue (MB), a typical organic pollutant in dyeing wastewater. The catalytic degradation displayed highly efficient discoloration of MB when using the Fe/M-MnO2 catalyst, e.g., ca. 94.8% of MB was decomposed when the reaction was conducted for 120 min. The remarkable stability of this Fe/M-MnO2 catalyst in the reaction medium was confirmed by an iron leaching test and reuse experiments. Mechanism analysis revealed that the hydroxyl free radical was responsible for the removal of MB and catalyzed by M-MnO2 and Fe/M-MnO2. MB was transformed into small organic compounds and then further degraded into CO2 and H2O. The new insights obtained in this study will be beneficial for the practical applications of heterogeneous catalysts in wastewater treatments. PMID:25626157

  2. Thermodynamic Assessment of the Aluminum Corner of the Al-Fe-Mn-Si System

    NASA Astrophysics Data System (ADS)

    Lacaze, Jacques; Eleno, Luiz; Sundman, Bo

    2010-09-01

    A new assessment of the aluminum corner of the quaternary Al-Fe-Mn-Si system has been made that extends beyond the COST-507 database. This assessment makes use of a recent, improved description of the ternary Al-Fe-Si system. In the present work, modeling of the Al-rich corner of the quaternary Al-Fe-Mn-Si system has been carried out by introducing Fe solubility into the so-called alpha-AlMnSi and beta-AlMnSi phases of the Al-Mn-Si system. A critical review of the data available on the quaternary system is presented and used for the extension of the description of these ternary phases into the quaternary Al-Fe-Mn-Si.

  3. Cu-Mn-Fe alloys and Mn-rich amphiboles in ancient copper slags from the Jabal Samran area, Saudi Arabia: With synopsis on chemistry of Fe-Mn(III) oxyhydroxides in alteration zones

    NASA Astrophysics Data System (ADS)

    Surour, Adel A.

    2015-01-01

    In the Jabal Samran area (western Saudi Arabia), secondary copper mineralization in a NE-trending shear zone in which the arc metavolcanic host rocks (dacite-rhyodacite) show conjugate fractures and extensive hydrothermal alteration and bleaching. The zones contain frequent Fe-Mn(III) oxyhydroxides (FeOH-MnOH) that resulted from oxidation of pyrite and Mn-bearing silicates. In the bleached part, the groundmass is represented by Fe-bearing interstratified illite-smectite with up to 4.02 wt% FeOt. FeOH-MnOH are pre-weathering phases formed by hydrothermal alteration in a submarine environment prior to uplifting. Five varieties of FeOH are distinguished, four of them are exclusively hydrothermal with ∼20 wt% H2O whereas the fifth contains ∼31-33 wt% H2O and might represent reworking of earlier hydrothermal FeOH phases by weathering. FeOH fills thin fractures in the form of veinlets and crenulated laminae or as a pseudomorph for pyrite, goethite and finally ferrihydrite, and this oxyhydroxide is characterized by positive correlation of Fe2O3 with SiO2 and Al2O3. On the other hand, MOH shows positive correlation between MnO2 and Al2O3 whereas it is negative between Fe2O3 and SiO2. Paratacamite is the most common secondary copper mineral that fills fractures and post-dates FeOH and MnOH. It is believed that Cl- in the structure of paratacamite represents inherited marine storage rather than from surfacial evaporates or meteoric water. The mineralogy of slags suggests a complicated mineral assemblage that includes native Cu prills, synthetic spinifixed Mn-rich amphiboles with 16.73 wt% MnO, brown glass and Ca-Mn-Fe phase close to the olivine structure. EMPA indicate that the some Cu prills have either grey discontinuous boarder zone of S-rich Mn-Cu alloy (with up to 21.95 wt% S and 19.45 wt% Mn) or grey Cu-Mn-Fe alloy (with up to 15.9 wt% Cu, 39. 12 wt% Mn and 61.64 wt% Fe). Mn in the Cu prills is expelled inward as Cu-Mn-Fe alloy inclusions whereas S is expelled

  4. Magnetism of NiMn2O4-Fe3O4 spinel interfaces

    SciTech Connect

    Arenholz, Elke; Nelson-Cheeseman, B. B.; Chopdekar, R. V.; Bettinger, J. S.; Arenholz, E.; Suzuki, Y.

    2007-09-13

    We investigate the magnetic properties of the isostructural spinel-spinel interface of NiMn{sub 2}O{sub 4}(NMO)-Fe{sub 3}O{sub 4}. Although the magnetic transition temperature of the NMO film is preserved, both bulk and interface sensitive measurements demonstrate that the interface exhibits strong interfacial magnetic coupling up to room temperature. While NMO thin films have a ferrimagnetic transition temperature of 60 K, both NiFe{sub 2}O{sub 4} and MnFe{sub 2}O{sub 4} are ferrimagnetic at room temperature. Our experimental results suggest that these magnetic properties arise from a thin interdiffused region of (Fe,Mn,Ni){sub 3}O{sub 4} at the interface, leading to Mn and Ni magnetic properties similar to those of MnFe{sub 2}O{sub 4} and NiFe{sub 2}O{sub 4}.

  5. The improvement of cryogenic mechanical properties of Fe-12 Mn and Fe-8 Mn alloy steels through thermal/mechanical treatments

    NASA Technical Reports Server (NTRS)

    Hwang, S. K.; Morris, J. W., Jr.

    1979-01-01

    An investigation has been made to improve the low temperature mechanical properties of Fe-8Mn and Fe-12Mn-0.2 Ti alloy steels. A reversion annealing heat treatment in the two-phase (alpha + gamma) region following cold working has been identified as an effective treatment. In an Fe-12Mn-0.2Ti alloy a promising combination of low temperature (-196 C) fracture toughness and yield strength was obtained by this method. The improvement of properties was attributed to the refinement of grain size and to the introduction of a uniform distribution of retained austenite (gamma). It was also shown that an Fe-8Mn steel could be grain-refined by a purely thermal treatment because of its dislocated alpha-prime martensitic structure and absence of epsilon martensite. As a result, a significant reduction of ductile to brittle transition temperature was obtained.

  6. Structural, magnetic and dielectric properties of polyaniline/MnCoFe2O4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Chitra, Palanisamy; Muthusamy, Athianna; Jayaprakash, Rajan

    2015-12-01

    Ferromagnetic PANI containing MnCoFe2O4 nanocomposites were synthesized by in-situ chemical polymerization of aniline incorporated MnCoFe2O4 nanoparticles (20%, 10% w/w of fine powders) with and without ultrasonic treatment. The MnCoFe2O4 nanoparticles were synthesized by auto combustion method. The PANI/MnCoFe2O4 nanocomposites were characterized with Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The average particle size of the resulting PANI/MnCoFe2O4 nanocomposites was confirmed from the TEM and XRD analysis. The structure and morphology of the composites were confirmed by FT-IR spectroscopy, XRD and SEM. In addition, the electrical and magnetic properties of the nanocomposites were investigated. The PANI/MnCoFe2O4 nanocomposites under applied magnetic field exhibited the hysteresis loops of ferromagnetic nature at room temperature. The variation of Dielectric constant, Dielectric loss, and AC conductivity of PANI/MnCoFe2O4 nanocomposites at room temperature as a function of frequency in the range 50 Hz-5 MHz has been studied. Effect of ultrasonication on the PANI/MnCoFe2O4 nanocomposites was also investigated.

  7. Observations on the formation of [var epsilon] martensite in an Fe-23. 2%Mn alloy

    SciTech Connect

    Akguen, I.; Durlu, T.N. . Dept. of Physics)

    1994-11-15

    In Fe-Mn binary alloys the formation behavior of [var epsilon] martensite is quite sensitive to the Mn percentage and although both [var epsilon] and [alpha][prime] type martensites are formed in low Mn alloys, mostly [gamma] [yields] [var epsilon] transformation occur as the Mn concentration is increased. The present study was undertaken to examine the formation of thermally induced and also strain-induced [var epsilon] martensites, and their intersections in a Fe-23.2%Mn alloy by using transmission electron microscopy techniques.

  8. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOEpatents

    Brager, Howard R.; Garner, Francis A.

    1987-09-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  9. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOEpatents

    Brager, Howard R.; Garner, Francis A.

    1987-01-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  10. Application of damping mechanism model and stacking fault probability in Fe-Mn alloy

    SciTech Connect

    Huang, S.K.; Wen, Y.H.; Li, N. Teng, J.; Ding, S.; Xu, Y.G.

    2008-06-15

    In this paper, the damping mechanism model of Fe-Mn alloy was analyzed using dislocation theory. Moreover, as an important parameter in Fe-Mn based alloy, the effect of stacking fault probability on the damping capacity of Fe-19.35Mn alloy after deep-cooling or tensile deformation was also studied. The damping capacity was measured using reversal torsion pendulum. The stacking fault probability of {gamma}-austenite and {epsilon}-martensite was determined by means of X-ray diffraction (XRD) profile analysis. The microstructure was observed using scanning electronic microscope (SEM). The results indicated that with the strain amplitude increasing above a critical value, the damping capacity of Fe-19.35Mn alloy increased rapidly which could be explained using the breakaway model of Shockley partial dislocations. Deep-cooling and suitable tensile deformation could improve the damping capacity owning to the increasing of stacking fault probability of Fe-19.35Mn alloy.

  11. Study of magnetic properties in ball-milled MnFeCo

    NASA Astrophysics Data System (ADS)

    Cornejo, D. R.; Padrón Hernández, E.; Rechenberg, H. R.; Azevedo, A.; Rezende, S. M.

    2004-05-01

    A study of the magnetic properties in mechanical alloyed nanocrystalline MnO+FeCo was carried out. As-milled and annealed samples show a noticeable improvement of the coercivity, even at room temperature. A strong effect over the spin wave stiffness constant of the ferromagnetic α -FeCo, probably induced by the antiferromagnetic ordering of the MnO around to 120K (the Néel temperature of MnO) was observed.

  12. Magnetic anisotropy and spin wave relaxation in CoFe/PtMn/CoFe trilayer films

    NASA Astrophysics Data System (ADS)

    Ren, Y. H.; Wu, C.; Gong, Y.; Pettiford, C.; Sun, N. X.

    2009-04-01

    We investigated the magnetic anisotropic properties and the spin wave relaxation in trilayer films of CoFe/PtMn/CoFe grown on the seed layer Ru or NiFeCr with CoFe compositions being Co-16 at. % Fe. The measurements were taken in samples with the ferromagnetic layers of CoFe varying from 10 to 500 Å by the ferromagnetic resonance (FMR) technique. The magnetic anisotropic parameters were investigated by rotating the field aligned axis with respect to the spectral field in the configurations of both in plane and out of plane. We determine the effective in-plane anisotropy field of ˜0.005 T, the uniaxial out-of-plane anisotropy of ˜-0.3 T, and the exchange stiffness D of ˜512 meV Å2. Moreover, spin wave damping was estimated by analyzing the FMR linewidth and line shape as a function of the angle between the external field and easy axis and as a function of the thickness of the CoFe layers. We identify an extrinsic contribution of the damping parameter dominated by two-magnon scattering in addition to the intrinsic Gilbert term with a damping parameter, α =0.012. Further, we reveal that a significant linewidth broadening could also be caused by the overlap of the surface and the uniform spin wave excitations. The FMR lines show a strong dependence of the surface anisotropy contribution of free energy in trilayer films.

  13. The distribution of Fe and Mn between chlorite and fluid: Evidence from fluid inclusions

    SciTech Connect

    Bottrell, S.H.; Yardley, B.W.D. )

    1991-01-01

    The Fe/Mn ratio of fluid inclusions from low-grade metamorphic quartz veins has been analyzed by an improved crush-leach method. When compared with Fe and Mn in coexisting vein chlorites, exchange between fluid and chlorite is shown to vary with the redox state of the wall rocks, but is independent of the salinity of the fluid. Agreement between our results and theoretical predictions of Fe/Mn partitioning between fluid and chlorite are good for veins from relatively oxidized rocks, but vein fluids from reduced hosts are enriched in Fe.

  14. The synthesis of open-shell, bimetallic Mn/Fe trinuclear clusters

    PubMed Central

    Powers, Tamara M.; Gu, Nina; Fout, Alison R.; Baldwin, Anne M.; Sánchez, Raúl Hernández; Alfonso, Denise M.; Chen, Yu-Sheng; Zheng, Shao-Liang

    2013-01-01

    Concomitant deprotonation and metallation of hexadentate ligand platform tbsLH6 (tbsLH6 = 1,3,5-C6H9(NHC6H4-o-NHSiMe2 tBu)3) with divalent transition metal starting materials Fe2(Mes)4 (Mes = mesityl) or Mn3(Mes)6 in the presence of tetrahydrofuran (THF) resulted in isolation of homotrinuclear complexes (tbsL)Fe3(THF) and (tbsL)Mn3(THF) respectively. In the absence of coordinating solvent (THF) the deprotonation and metallation exclusively afforded dinuclear complexes of the type (tbsLH2)M2 (M = Fe or Mn). The resulting dinuclear species were utilized as synthons to prepare bimetallic trinuclear clusters. Treatment of (tbsLH2)Fe2 complex with divalent Mn source (Mn2(N(SiMe3)2)4) afforded the bimetallic complex (tbsL)Fe2Mn(THF) which established the ability of hexamine ligand tbsLH6 to support mixed metal clusters. The substitutional homogeneity of (tbsL)Fe2Mn(THF) was determined by 1H NMR, 57Fe Mössbauer, and X-ray fluorescence. Anomalous scattering measurements were critical for the unambiguous assignment of the trinuclear core composition. Heating a solution of (tbsLH2)Mn2 with a stoichiometric amount of Fe2(Mes)4 (0.5 mol equiv) affords a mixture of both (tbsL)Mn2Fe(THF) and (tbsL)Fe2Mn(THF) as a result of the thermodynamic preference for heavier metal substitution within the hexa-anilido ligand framework. These results demonstrate for the first time the assembly of mixed metal cluster synthesis in an unbiased ligand platform. PMID:23984911

  15. Directional short range order in L10 FeMnPt magnetic thin films

    NASA Astrophysics Data System (ADS)

    Sun, Cheng-Jun; Xu, Dongbin; Heald, Steve M.; Chen, Jingsheng; Chow, Gan-Moog

    2011-10-01

    A method for investigating the directional short range order (DSRO) of an element of interest in L10 FeMnPt thin films using polarization-dependent x-ray absorption near edge structure (XANES) spectroscopy is described. The XANES calculations for both L10 FePt and L10 MnPt phases indicate that the height of the low-energy shoulder of the polarization-dependent XANES is proportional to the degree of DSRO of the element of interest in the case of L10 FePt and MnPt systems. The experimentally observed DSROs of Fe and Mn in L10 FeMnPt magnetic thin films are consistent with a decrease of ordering parameter with increasing Mn doping. We demonstrate theoretically and experimentally that the heights of the low-energy shoulder in the FeK- and MnK-edge polarization-dependent XANES are proportional to the DSROs of Fe and Mn, respectively.

  16. Degradation behavior of biodegradable Fe35Mn alloy stents.

    PubMed

    Sing, N B; Mostavan, A; Hamzah, E; Mantovani, D; Hermawan, H

    2015-04-01

    This article reports a degradation study that was done on stent prototypes made of biodegradable Fe35Mn alloy in a simulated human coronary arterial condition. The stent degradation was observed for a short-term period from 0.5 to 168 h, which simulates the early period of stenting procedure. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to quantify degradation rate and surface property of the stents. Results showed that signs of degradation were visible on both crimped and expanded stents after 1 h of test, mostly located on the stent's curvatures. The degradation rate of stent was higher compared to that of the original alloy, indicating the surface altering effect of stent fabrication processing to degradation. A single oxide layer was formed and detected as a porous structure with capacitive behavior. Expanded stents exhibited lower polarization resistance compared to the nonexpanded ones, indicating the cold work effect of expansion procedure to degradation. PMID:24954069

  17. Exchange bias in sputtered FeNi/FeMn systems: Effect of short low-temperature heat treatments

    NASA Astrophysics Data System (ADS)

    Savin, Peter; Guzmán, Jorge; Lepalovskij, Vladimir; Svalov, Andrey; Kurlyandskaya, Galina; Asenjo, Agustina; Vas'kovskiy, Vladimir; Vazquez, Manuel

    2016-03-01

    Short (5 min) post-deposition thermal treatments under magnetic field at low temperature (up to 200 °C) performed in exchange-coupled FeNi(40 nm)/FeMn(20 nm) bilayer thin films prepared by magnetron sputtering are shown to be effective to significantly modify their exchange field (from around 40 Oe down to 27 Oe) between FeNi and FeMn layers. A similar exchange field decrease was observed for the first deposited FeNi layer of the FeNi(40 nm)/FeMn(20 nm)/FeNi(40 nm) trilayer films after the same thermal treatments. The exchange field value for the second FeNi layer was not substantially changed. The X-ray diffraction patterns indicates that such a heat treatment has no effect on the grain size and crystalline texture of the films, while atomic force microscope studies reveal an increase of the surface roughness after the treatment which is more noticeable in the case of the trilayer film. Analysis of the experimental results leads us to conclude that the variations of the exchange field after heat treatment are likely caused by a modification of interfacial roughness and/or interfacial magnetic structure, but unlikely by the changes in the microstructure and/or changes of composition of the antiferromagnetic FeMn layer.

  18. Dilute ferrimagnetism of ilmenites Mn3FeTiSbO9 and Mn4FeTi2SbO12

    NASA Astrophysics Data System (ADS)

    Bazuev, G. V.; Korolev, A. V.; Golovkin, B. G.

    2016-07-01

    Metastable solid solutions (SS) Mn3FeTiSbO9 and Mn4FeTi2SbO12 with the ilmenite structure (space group R bar 3) have been prepared by quenching at normal conditions. The compositions of the compounds have been justified using EDX spectroscopy and X-ray diffraction. The magnetic properties of SSs have been analyzed by comparison with ferrimagnetic ilmenite Mn2FeSbO6 ( T N = 269 K) as a natural mineral and ceramics obtained at high pressure and high temperature. The solid solutions have been characterized as dilute magnetic systems formed as a result of substitution of nonmagnetic cations Ti4+ for a part of Fe3+ and Sb5+ cations. Mn3FeTiSbO9 is considered as a ferromagnetic with T N = 171 K and Mn4FeTi2SbO12 as a magnetic with the concentration of magnetic clusters below the percolation threshold.

  19. Fe content effects on electrochemical properties of Fe-substituted Li 2MnO 3 positive electrode material

    NASA Astrophysics Data System (ADS)

    Tabuchi, Mitsuharu; Nabeshima, Yoko; Takeuchi, Tomonari; Tatsumi, Kuniaki; Imaizumi, Junichi; Nitta, Yoshiaki

    Fe-substituted Li 2MnO 3 including a monoclinic layered rock-salt structure (C2/ m), (Li 1+ x(Fe yMn 1- y) 1- xO 2, 0 < x < 1/3, 0.1 ≤ y ≤ 0.5) was prepared by coprecipitation-hydrothermal-calcination method. The sample was assigned as two-phase composite structure consisting of the cubic rock-salt (F m 3 bar m) and monoclinic ones at high Fe content above 30% (y ≥ 0.3), while the sample was assigned as a monoclinic phase (C2 /m) at low Fe content less than 20%. In the monoclinic Li 2MnO 3-type structure, the Fe ion tends to substitute a Li (2 b) site, which corresponds to a center position of Mn 4+ hexagonal network in Mn-Li layer. The electrochemical properties including discharge characteristics under high current density (<3600 mA g -1 at 30 °C) and low temperature (<-20 °C at 40 mA g -1) were severely affected by chemical composition (Fe content and Li/(Fe + Mn) ratio), crystal structure (monoclinic phase content) and powder property (specific surface area). Under the optimized Fe content (0.2 < y < 0.4), the Li/sample cells showed high initial discharge capacity (240-300 mAh g -1) and energy density (700-950 mWh g -1) between 1.5 and 4.8 V under moderate current density, 40 mA g -1 at 30 °C. Results suggest that Fe-substituted Li 2MnO 3 would be a non-excludable 3 V positive electrode material.

  20. Influence of substrate rocks on Fe-Mn crust composition

    USGS Publications Warehouse

    Hein, J.R.; Morgan, C.L.

    1999-01-01

    Principal Component and other statistical analyses of chemical and mineralogical data of Fe-Mn oxyhydroxide crusts and their underlying rock substrates in the central Pacific indicate that substrate rocks do not influence crust composition. Two ridges near Johnston Atoll were dredged repetitively and up to seven substrate rock types were recovered from small areas of similar water depths. Crusts were analyzed mineralogically and chemically for 24 elements, and substrates were analyzed mineralogically and chemically for the 10 major oxides. Compositions of crusts on phosphatized substrates are distinctly different from crusts on substrates containing no phosphorite. However, that relationship only indicates that the episodes of phosphatization that mineralized the substrate rocks also mineralized the crusts that grew on them. A two-fold increase in copper contents in crusts that grew on phosphatized clastic substrate rocks, relative to crusts on other substrate rock types, is also associated with phosphatization and must have resulted from chemical reorganization during diagenesis. Phosphatized crusts show increases in Sr, Zn, Ca, Ba, Cu, Ce, V, and Mo contents and decreases in Fe, Si, and As contents relative to non-phosphatized crusts. Our statistical results support previous studies which show that crust compositions reflect predominantly direct precipitation from seawater (hydrogenetic), and to lesser extents reflect detrital input and diagenetic replacement of parts of the older crust generation by carbonate fluorapatite.

  1. Impact of Mn on the solution enthalpy of hydrogen in austenitic Fe-Mn alloys: a first-principles study.

    PubMed

    von Appen, Jörg; Dronskowski, Richard; Chakrabarty, Aurab; Hickel, Tilmann; Spatschek, Robert; Neugebauer, Jörg

    2014-12-01

    Hydrogen interstitials in austenitic Fe-Mn alloys were studied using density-functional theory to gain insights into the mechanisms of hydrogen embrittlement in high-strength Mn steels. The investigations reveal that H atoms at octahedral interstitial sites prefer a local environment containing Mn atoms rather than Fe atoms. This phenomenon is closely examined combining total energy calculations and crystal orbital Hamilton population analysis. Contributions from various electronic phenomena such as elastic, chemical, and magnetic effects are characterized. The primary reason for the environmental preference is a volumetric effect, which causes a linear dependence on the number of nearest-neighbour Mn atoms. A secondary electronic/magnetic effect explains the deviations from this linearity. PMID:25250795

  2. Antiferromagnetic FeMn alloys electrodeposited from chloride-based electrolytes.

    PubMed

    Ruiz-Gómez, Sandra; Ranchal, Rocío; Abuín, Manuel; Aragón, Ana María; Velasco, Víctor; Marín, Pilar; Mascaraque, Arantzazu; Pérez, Lucas

    2016-03-01

    The capability of synthesizing Fe-based antiferromagnetic metal alloys would fuel the use of electrodeposition in the design of new magnetic devices such as high-aspect-ratio spin valves or new nanostructured hard magnetic composites. Here we report the synthesis of high quality antiferromagnetic FeMn alloys electrodeposited from chloride-based electrolytes. We have found that in order to grow homogeneous FeMn films it is necessary to incorporate a large concentration of NH4Cl as an additive in the electrolyte. The study of the structure and magnetic properties shows that films with composition close to Fe50Mn50 are homogeneous antiferromagnetic alloys. We have established a parameter window for the synthesis of FeMn alloys that show antiferromagnetism at room temperature. PMID:26925594

  3. The Charpy impact behavior of Fe{sub 3}Al and Fe{sub 3}Al-20 at % Mn alloys

    SciTech Connect

    Liu, J.N.; Yan, W.; Ma, J.L.; Wu, K.H.

    1997-12-31

    A series of experiments were conducted to investigate the impact fracture behavior of Fe{sub 3}Al and Fe{sub 3}Al-20 Mn alloys. The results of this study indicated that: (i) The addition of Mn introduces an ordered L1{sub 2}-type phase in the Fe{sub 3}Al-based alloys. On the other hand, the addition of Mn decreases the order parameter of the DO{sub 3} {alpha} phase. (ii) The total-impact energy of an Fe{sub 3}Al alloy increases with the temperature at the low-temperature range (<600 C), then drops around 700 C, and finally increases again as the temperature further elevates. (iii) The trend of the variation of the impact energy of Fe{sub 3}Al-20 at % Mn alloy with temperature is the same as that of the Fe{sub 3}Al alloy. (iv) And the addition of Mn significantly improves the impact energy of the Fe{sub 3}Al-based alloy, and changes the variation of the crack-growth energy with the testing temperature when the temperature is above 700 C.

  4. Ab initio study of Fe{sub 2}MnZ (Al, Si, Ge) Heusler alloy using GGA approximation

    SciTech Connect

    Jain, Vivek Kumar Jain, Vishal Lakshmi, N. Venugopalan, K.

    2014-04-24

    Density functional theory based on FP-LAPW method used to investigate the electronic structure of Fe{sub 2}MnZ, shows that the total spin magnetic moment shows a trend consistent with the Slater–Pauling curve. The Fe and Mn magnetic moment depend on choice of Z element although the magnetic moment of Z element is negative and less than 0.1 μ{sub B}. Spin polarization calculations evidence 100% spin polarization for Fe{sub 2}MnSi. Fe{sub 2}MnAl and Fe{sub 2}MnGe show metallic behavior with 93%, 98% spin polarization.

  5. Controlling phosphate releasing from poultry litter using stabilized Fe-Mn binary oxide nanoparticles.

    PubMed

    Xie, Wenbo; Zhao, Dongye

    2016-01-15

    Animal wastes contain high concentrations of phosphorus (P), most of which is lost into the environment due to uncontrolled release rates. Polysaccharide stabilized Fe-Mn binary oxide nanoparticles were prepared and tested for phosphate adsorption from water and for controlling leachability of P from poultry litter. A water soluble starch and carboxymethyl cellulose (CMC) were used as a stabilizer. Both the Freundlich and Langmuir models were able to adequately interpret the isotherm data. The Langmuir maximum capacity was determined at 252, 298 and 313 mg-P/g for bare, CMC- and starch-stabilized nanoparticles, respectively. The presence of the stabilizers not only enhanced the sorption capacity, but facilitated delivery and dispersion of the nanoparticles in poultry litter (PL) and in soil. High phosphate sorption capacity was observed over a broad pH range of 4-9. FTIR analyses indicated that inner sphere surface complexation (Fe-O-P) was the key mechanism for the enhanced uptake of P. When applied to poultry litter, the stabilized nanoparticles reduced water leachable phosphate by >86% at a dose of 0.2 g/L as Fe, and simultaneously, water leachable arsenic by >87-95%. Under conditions of simulated land application of PL, the nanoparticle amendment of PL reduced the water soluble P from 66% (for untreated PL) to 4.4%, and lowered the peak soluble P concentration from 300 to <20 mg/L. By transferring the peak soluble P to the nanoparticle-bound P, the nanoparticles not only greatly reduce the potential runoff loss of P from PL, but also provide a long-term slow-releasing nutrient source. Fortuitously, the nanoparticle treatment was able to immobilize arsenic from PL. With excellent adsorption capacity, easy deliverability, low cost and environmental innocuousness, the stabilized Fe-Mn nanoparticles appear promising for controlling P releases from poultry litter or other animal wastes and for phosphate recovery from water. PMID:26442720

  6. Structural and magnetic properties of (Fe/Mn) exchange-biased multilayers

    NASA Astrophysics Data System (ADS)

    El Bahoui, A.; Genevois, C.; Juraszek, J.; Bordel, C.; Ledue, D.

    2013-05-01

    Exchange-biasing of ferromagnetic (F) Fe layers by adjacent antiferromagnetic (AF) Mn layers has been investigated in (Fe/Mn)10 multilayered films. This study has been focused on the relationship between the evolution of the exchange-bias field and the evolution of the film microstructure as a function of the deposition temperature. The increase of the deposition temperature results in the formation of an Fe-Mn alloy at the interfaces and columnar features whose size increases with the deposition temperature. In parallel, the exchange-bias field decreases significantly, due to interface roughness.

  7. Ni spin switching induced by magnetic frustration in FeMn/Ni/Cu(001)

    SciTech Connect

    Wu, J.; Choi, J.; Scholl, A.; Doran, A.; Arenholz, E.; Hwang, Chanyong; Qiu, Z. Q.

    2009-03-08

    Epitaxially grown FeMn/Ni/Cu(001) films are investigated by Photoemission Electron Microscopy and Magneto-Optic Kerr Effect. We find that as the FeMn overlayer changes from paramagnetic to antiferromagnetic state, it could switch the ferromagnetic Ni spin direction from out-of-plane to in-plane direction of the film. This phenomenon reveals a new mechanism of creating magnetic anisotropy and is attributed to the out-of-plane spin frustration at the FeMn-Ni interface.

  8. Perpendicular exchange bias behaviors of CoPt/IrMn and CoPt/FeMn bilayers: A comparative study

    SciTech Connect

    Tsai, C. Y.; Lin, K. F.; Hsu, Jen-Hwa

    2015-05-07

    In this study, FeMn was introduced as an antiferromagnetic (AFM) layer to couple with a single-layered Co{sub 49}Pt{sub 51} alloy thin film, and it was compared with a Co{sub 49}Pt{sub 51}/IrMn bilayer system in exchange bias (EB) effect, to explore the mechanism of spontaneous perpendicular exchange bias (PEB), which has been recently observed in CoPt/IrMn bilayers. Bilayers of CoPt/IrMn and CoPt/FeMn were prepared under the same conditions by sputtering at room temperature without any inducing field. Although PEB was observed in as-grown CoPt/FeMn bilayers, the loop shape and PEB behavior were found to exhibit different characteristics from those of CoPt/IrMn bilayers. The CoPt (5 nm)/FeMn (10 nm) bilayer has a sheared loop that is similar to a double-shifted loop and a much lower squareness ratio (SQR = 0.52) and exchange bias field (H{sub e} = 180 Oe) than the CoPt (5 nm)/IrMn (10 nm) system, which has a rectangular loop shape and a high SQR of 0.97 and large H{sub e} of 290 Oe. The two systems present entirely different dependences of PEB on the thickness of the AFM layer. CoPt/IrMn exhibits behavior that is typical of most EB systems, but for CoPt/FeMn, this dependence is more complicated with an unusual peak at an AFM layer thickness of 10 nm. Based on the dissimilar loop shapes and dependences of PEB on AFM thickness, the mechanisms of the spontaneously established PEB in these two systems are considered to differ. Investigations of cross-sectional transmission electron microscopy revealed no apparent difference between the interfacial microstructures of the two systems. X-ray diffraction studies demonstrated the 〈111〉 texture of both systems. Therefore, different interfacial spin configurations may be responsible for the dissimilar PEB behaviors in these two FM/AFM bilayer systems.

  9. Observation of hyperfine structure of D022-Mn3‑ x Fe x Ga by Mössbauer effect

    NASA Astrophysics Data System (ADS)

    Koeba, Akira; Shima, Toshiyuki; Doi, Masaaki

    2016-07-01

    In this work, to obtain the design guideline for a magnet made of a Mn-based alloy, Mn3‑ x Fe x Ga alloys were prepared by arc melting and the magnetic state of Fe in the alloys and hyperfine structure were investigated on the basis of the Mössbauer effect. As a result, D022-Mn2.2Fe0.5Ga alloys were obtained by annealing at 350 °C for 2 days. From the Mössbauer spectrum of Mn2.2Fe0.5Ga, it was clear that Fe replaced Mn in the Mn II site of the D022 structure. In addition, it was also found that the hyperfine field of Fe is extremely lower in the Mn II site than in the Mn I site.

  10. Magnetic interactions in BiFe₀.₅Mn₀.₅O₃ films and BiFeO₃/BiMnO₃ superlattices.

    PubMed

    Xu, Qingyu; Sheng, Yan; Khalid, M; Cao, Yanqiang; Wang, Yutian; Qiu, Xiangbiao; Zhang, Wen; He, Maocheng; Wang, Shuangbao; Zhou, Shengqiang; Li, Qi; Wu, Di; Zhai, Ya; Liu, Wenqing; Wang, Peng; Xu, Y B; Du, Jun

    2015-01-01

    The clear understanding of exchange interactions between magnetic ions in substituted BiFeO3 is the prerequisite for the comprehensive studies on magnetic properties. BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices have been fabricated by pulsed laser deposition on (001) SrTiO3 substrates. Using piezoresponse force microscopy (PFM), the ferroelectricity at room temperature has been inferred from the observation of PFM hysteresis loops and electrical writing of ferroelectric domains for both samples. Spin glass behavior has been observed in both samples by temperature dependent magnetization curves and decay of thermo-remnant magnetization with time. The magnetic ordering has been studied by X-ray magnetic circular dichroism measurements, and Fe-O-Mn interaction has been confirmed to be antiferromagnetic (AF). The observed spin glass in BiFe0.5Mn0.5O3 films has been attributed to cluster spin glass due to Mn-rich ferromagnetic (FM) clusters in AF matrix, while spin glass in BiFeO3/BiMnO3 superlattices is due to competition between AF Fe-O-Fe, AF Fe-O-Mn and FM Mn-O-Mn interactions in the well ordered square lattice with two Fe ions in BiFeO3 layer and two Mn ions in BiMnO3 layer at interfaces. PMID:25766744

  11. Preparation of a novel graphene oxide/Fe-Mn composite and its application for aqueous Hg(II) removal.

    PubMed

    Tang, Jingchun; Huang, Yao; Gong, Yanyan; Lyu, Honghong; Wang, Qilin; Ma, Jianli

    2016-10-01

    A novel graphene oxide/Fe-Mn (GO/Fe-Mn) composite was synthesized (molar ratio of Fe/Mn=3/1 and mass ratio of Fe/GO=1/7.5) and investigated for the sorption characteristics and mechanisms of aqueous mercury (Hg(2+)) as well as the biological effects to wheat and rice. Characterization tests showed that Fe-Mn oxides were impregnated onto GO sheets in an amorphous form through oxygen-containing functional groups (i.e., CO, epoxy COC, carboxyl OCO, and CO) and π-π interactions. GO/Fe-Mn possessed large surface area, surface enhanced Raman scattering with more sp(3) defects, and greater thermal stability than GO. XPS analysis revealed that Fe2O3, FeOOH, MnO2, MnOOH, and MnO were the dominant metal oxides in GO/Fe-Mn. Pseudo-second-order kinetic model and Sips isotherm model fitted well with the sorption kinetic and isotherm data. The maximum sorption capacity for mercury was 32.9mg/g. Ligand exchange and surface complexation were the dominant mechanisms for mercury removal. GO/Fe-Mn greatly reduced the bioavailability of mercury to wheat and rice, even promoted the seedling growth. This work suggests that GO/Fe-Mn can be used as an effective and environmental-friendly adsorbent in heavy metal remediation. PMID:27232726

  12. Magnetic properties and loss separation in FeSi/MnZnFe2O4 soft magnetic composites

    NASA Astrophysics Data System (ADS)

    Lauda, M.; Füzer, J.; Kollár, P.; Strečková, M.; Bureš, R.; Kováč, J.; Baťková, M.; Baťko, I.

    2016-08-01

    We investigated composites that have been prepared from FeSi powders covered with MnZnFe2O4 (MnZn ferrite), which was prepared by sol-gel synthesis accompanied with the auto-combustion process. The aim of this paper is to analyze the complex permeability and core losses of prepared samples with different amount of MnZn ferrite. The microstructure and the powder morphology were examined by scanning electron microscopy. Magnetic measurements on bulk samples were carried out using a vibrating sample magnetometer, an impedance analyzer and hysteresisgraphs. The results indicate that the composites with 2.6 wt% MnZn ferrite show better soft magnetic properties than the composites with about 6 wt% MnZn ferrite.

  13. Zn Speciation in two Fe-Mn Banded Systems

    NASA Astrophysics Data System (ADS)

    Marcus, M.; Manceau, A.; Kersten, M.; Tazaki, K.

    2002-12-01

    We have used micro-EXAFS spectroscopy to study the speciation of Zn in two shallow-water Fe-Mn banded structures. One of the samples is from the Baltic Sea and contains anthropogenic Zn in a matrix which is believed to be banded due to annual oscillations in oxygen content, pH and other variables of water chemistry (Hlawatsch, et. al., 2002). The other sample, from Akayu Hot Springs off the coast of a volcanic island (Satsuma-Iwo Jima) at the southern tip of Japan, is a hardened biomat in which the compositional oscillations are at least partly due to bacterial action, and in which the Zn content is natural (Tazaki, 2000). By using a beam as small as 5μm in diameter, we can look at details of metal distribution and speciation on a spatial scale much finer than the banding, which has wavelengths of order 100μm. In both samples, the Zn is associated with the high-Mn layers, though the layer-to-layer contrast is lower in the Japan sample. However, the speciation of Zn is different in the two samples. The Baltic sample shows Zn only in one form - sorbed on a layered phyllomanganate resembling birnessite with Zn tetrahedrally coordinated and sorbed to vacant octahedral sites of the Mn layer. This species was also found in soil (Manceau et. al., 2000). The Japan sample also has tetrahedral Zn in birnessite-like phyllomanganate as well as Zn in at least two other forms. The phyllomanganate species is thus seen to be a ubiquitous sink for Zn in the environment. We will discuss some possible reasons for the differences and similarities of Zn speciation in these two systems. Hlawatsch, S., Garbe-Schönberg, C.D., Lechtenberg, F., Manceau, A., Tamura, N., Kulik, D.A., Kersten, M. (2002) Trace metal fluxes to ferromanganese nodules from the western Baltic Sea as a record for long-term environmental changes. Chemical Geology, 182 697-709. Manceau A., Lanson B., Schlegel M.L., Hargé J.C., Musso M., Eybert-Bérard L., Hazemann J.L., Chateigner D., Lamble G.M. (2000

  14. FeMn/Fe/Co/Cu(1,1,10) films studied using the magneto-optic Kerr effect and photoemission electron microscopy

    SciTech Connect

    Meng, Y.; Li, J.; Tan, A.; Park, J.; Jin, E.; Son, H.; Doran, A.; Scholl, A.; Arenholz, E.; Zhao, H. W.; Hwang, Chanyong; Qiu, Z. Q.

    2011-07-31

    FeMn/Fe/Co/Cu(1,1,10) films were grown epitaxially and investigated using the magneto-optic Kerr effect and photoemission electron microscopy. We found that FeMn/Fe/Co/Cu(1,1,10) exhibits the same properties as FeMn/Co/Cu(1,1,10) for the ferromagnetic phase of the face centered cubic (fcc) Fe film but a different property for the non-ferromagnetic phase of the fcc Fe film. This result indicates that the characteristic property reported in the literature for FeMn/Co/Cu(001) comes from the FeMn spin structure and is independent of the ferromagnetic layer.

  15. Thermal Decay and Reversal of Exchange Bias Field of CoFe/PtMn Bilayer after Ga+ Irradiation

    NASA Astrophysics Data System (ADS)

    Zhou, Guang-Hong; Zhu, Yu-Fu; Lin, Yue-Bin

    2011-05-01

    An applied field is used to perform Ga+ ion irradiation on a CoFe/PtMn bilayer. Effects of the applied field and energy transfer between Ga+ ions and antiferromagnetic (AFM) atoms on the exchange bias field Hex are investigated. A partially reversed Hex is found in CoFe/PtMn specimens irradiated at a dose of 1 × 1014 ions/cm2 with an applied field anti-parallel to the original exchange bias direction. We believe that the rapid energy transfer and local temperature increase originating from the interaction between Ga+ ions and AFM atoms result in spin reversal and the formation of reversed AFM domains when specimens are irradiated with anti-parallel fields. The decrease in Hex when annealing the film in a negative saturation field indicates a thermal decay process. The AFM moments are reversed by thermal activation over an energy barrier distribution, which may change in some way as the temperature increases.

  16. Precipitation and fracture behaviour of Fe-Mn-Ni-Al alloys

    NASA Astrophysics Data System (ADS)

    Heo, Yoon-Uk; Lee, Hu-Chul

    2013-12-01

    The effects of Al addition on the precipitation and fracture behaviour of Fe-Mn-Ni alloys were investigated. With the increasing of Al concentration, the matrix and grain boundary precipitates changed from L10 θ-MnNi to B2 Ni2MnAl phase, which is coherent and in cube-to-cube orientation relationship with the α‧-matrix. Due to the suppression of the θ-MnNi precipitates at prior austenite grain boundaries (PAGBs), the fracture mode changed from intergranular to transgranular cleavage fracture. Further addition of Al resulted in the discontinuous growth of Ni2MnAl precipitates in the alloy containing 4.2 wt.% Al and fracture occurred by void growth and coalescence, i.e. by ductile dimple rupture. The transition of the fracture behaviour of the Fe-Mn-Ni-Al alloys is discussed in relation to the conversion of the precipitates and their discontinuous precipitation behaviour at PAGBs.

  17. Substituting Fe for two of the four Mn ions in photosystem II-effects on water-oxidation.

    PubMed

    Semin, Boris K; Seibert, Michael

    2016-06-01

    We have investigated the interaction of Fe(II) cations with Ca-depleted PSII membranes (PSII[-Ca,4Mn]) in the dark and found that Fe(II) incubation removes 2 of 4 Mn ions from the tetranuclear Mn cluster of the photosynthetic O2-evolving complex (OEC). The reduction of Mn ions in PSII(-Ca,4Mn) by Fe(II) and the concomitant release of two Mn(II) cations is accompanied by the binding of newly generated Fe(III) in at least one vacated Mn site. Flash-induced chlorophyll (Chl) fluorescence yield measurements of this new 2Mn/nFe cluster (PSII[-Ca,2Mn,nFe]) show that charge recombination in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) occurs between Qa (-) and the remaining Mn/Fe cluster (but not YZ (●)) in the OEC, and extraction of 2 Mn occurs uniformly in all PSII complexes. No O2 evolution is observed, but the heteronuclear metal cluster in PSII(-Ca,2Mn,nFe) samples is still able to supply electrons for reduction of the exogenous electron acceptor, 2,6-dichlorophrenolindophenol, by photooxidizing water and producing H2O2 in the absence of an exogenous donor as seen previously with PSII(-Ca,4Mn). Selective extraction of Mn or Fe cations from the 2Mn/nFe heteronuclear cluster demonstrates that the high-affinity Mn-binding site is occupied by one of the iron cations. It is notable that partial water-oxidation function still occurs when only two Mn cations are present in the PSII OEC. PMID:26847716

  18. Eutectic equilibria in the quaternary system Fe-Cr-Mn-C

    NASA Technical Reports Server (NTRS)

    Nowotny, H.; Wayne, S.; Schuster, J. C.

    1982-01-01

    The constitution of the quaternary system, Fe-Cr-Mn-C and to a lesser extent of the quinary system, Fe-Cr-Mn-Al-C were examined for in situ composite alloy candidates. Multivariant eutectic compositions were determined from phase equilibria studies wherein M7C3 carbides (approximately 30% by volume) formed from the melt within gamma iron. An extended field of the hexagonal carbide, (Cr, Fe, Mn)7 C3, was found without undergoing transformation to the orthorhombic structure. Increasing stability for this carbide was found for higher ratios of Cr/Fe(+) Cr + Mn. Aluminum additions promoted a ferritic matrix while manganese favored the desired gamma austenitic matrix. In coexistence with the matrix phase, chromium enters preferentially the carbide phase while manganese distributes equally between the gamma matrix and the M7C3 carbide. The composition and lattice parameters of the carbide and matrix phases were determined to establish their respective stabilities.

  19. Structural and magnetic characterization of the ball-milled α-Fe 2O 3-Mn 2O 3 and α-Fe-Mn 2O 3 systems

    NASA Astrophysics Data System (ADS)

    de Medeiros, S. N.; Luciano, A.; Cótica, L. F.; Santos, I. A.; Paesano, A.; da Cunha, J. B. M.

    2004-10-01

    In this work, the (Fe2O3)x(Mn2O3)1-x and Fey(Mn2O3)1-y systems were mechanically processed in a high-energy ball-mill. The as-milled powders were structurally and magnetically characterized by X-ray diffraction, Mössbauer spectroscopy and magnetic measurements. Under similar milling settings and conditions, dissimilar behaviors were observed in the studied systems. In the oxide-oxide system, only the bixbyite (Mn,Fe)2O3 phase was obtained in all the analysed samples, whereas in the metal-oxide system, a sharp compositional dependence for the final milling products was observed. For y⩽0.40, the FeMn2O4 spinel phase was detected and, for y>0.40, a wustite-like phase of the (Fe, Mn)1-yO type was formed. It was observed that magnetization in both systems increased with the nominal concentration, x or y, of the magnetic precursors, up to half of the concentration maximum and then it decreased as a result of structural phase transformations.

  20. Magnetic and magnetocaloric properties of LuFe2- x Mn x O4 + δ multiferroics

    NASA Astrophysics Data System (ADS)

    Gamzatov, A. G.; Aliev, A. M.; Markelova, M. N.; Burunova, N. A.; Kaul', A. R.; Semisalova, A. S.; Perov, N. S.

    2016-06-01

    The magnetic and magnetocaloric properties of the LuFe2- x Mn x O4 + δ ( x = 0, 0.05, 0.12) system have been studied. A partial substitution of manganese for iron leads to a noticeable decrease in the magnetization and the magnetocaloric effect. It has been shown that the magnetocaloric effect in LuFe2- x Mn x O4 + δ samples is determined by several mechanisms.

  1. Ternary NiFeMn layered double hydroxides as highly-efficient oxygen evolution catalysts.

    PubMed

    Lu, Zhiyi; Qian, Li; Tian, Yang; Li, Yaping; Sun, Xiaoming; Duan, Xue

    2016-01-18

    Layered double hydroxides (LDHs) are a family of layer materials that receive heightened attention. Herein a ternary NiFeMn-LDH is investigated with superior oxygen evolution activity, which is attributed to the Mn(4+) doping in the intralayer, which modifies the electronic structure and improves the conductivity of the electrocatalyst. PMID:26579843

  2. Atomic structural and electrochemical impact of Fe substitution on nano porous LiMnPO4

    NASA Astrophysics Data System (ADS)

    Seo, Inseok; Senthilkumar, B.; Kim, Kwang-Ho; Kim, Jae-Kwang; Kim, Youngsik; Ahn, Jou-Hyeon

    2016-07-01

    The atomic structural and electrochemical properties of Fe substituted nano porous LiMn1-xFexPO4 (x = 0-0.8) composites are investigated and compared. X-ray scattering method is used for atomic structural investigation. Rietveld refinement shows that all Fe substituted composites have the same olivine structure (Pnma) with lithium occupying octahedral 4a sites, Fe2+ replacing Mn2+ at the octahedral 4c sites. The a, b, c parameters and cell volume decrease with the addition of Fe2+. When the nano porous LiMn1-xFexPO4 composites are evaluated as cathode materials in lithium cells at room temperature, x = 0.6, and 0.8 resulted in the best overall electrochemical performance, exhibiting stable cycling and high discharge capacities of 149 and 154 mA h g-1, respectively. The composites with above x = 0.4 show a fast lithium ions transfer with high electronic conductivity because Fe transition metal substitution reduce the partly occupation of Mn in the M1 (LiO6) sites and thereby Mn block the lithium ion diffusion pathway. We here firstly find the antisite defect in the high Mn content in porous LiMn1-xFexPO4 composites.

  3. Structural and magnetic properties of MnPd/Fe grown on MgO(100) substrate: Ab initio studies

    NASA Astrophysics Data System (ADS)

    Malonda-Boungou, B. R.; Magnoungou, J. H. J.; M'Passi-Mabiala, B.; Demangeat, C.

    2016-07-01

    Structural and magnetic properties of ultrathin films MnPd/Fe grown on MgO(001) are investigated using a self-consistent pseudopotential plane waves method based on density functional theory in the Perdew-Burke-Ernzerhof generalized gradient approximation. The results obtained reveal the presence of an antiferromagnetic coupling between successive Mn [100] rows, combined with a ripple where Mn outward atoms exhibit a positive magnetic moment, in the case of Mn overlayer on Fe/MgO(001). In the case of MnPd monolayer ordered alloy, the c(2 × 2) structure formation is more favorable than the p(1 × 2) one, exhibiting a ferromagnetic coupling between Mn neighbor atoms with a positive induced ferromagnetic moment on Pd atoms. Pd atoms are pushed outward. For 1-ML MnxPd1 - x on Fe/MgO, the Mn absolute mean magnetization per atom increases as x coverage increases, whereas the Pd mean induced magnetic moment decreases. For systems alternating Mn and Pd monolayers on Fe/MgO(001), a complex magnetic structure is shown on Mn monolayers: changing from Mn neighboring antiferromagnetic coupling to Mn [010] rows antiferromagnetic behavior. The correlation is made between the electronic structure and the magnetic properties, by comparing filled with partially filled components (Pd, Mn and Fe) d-bands. The magnetization easy-axis changes between the in-plane and the out-of-plane orientations from Fe/MgO to MnPd/Fe/MgO systems.

  4. Fe and Mn removal from mining drainage using goaf filling materials obtained from coal mining process.

    PubMed

    Zhang, Liping; Chen, Aolei; Qu, Hongbin; Xu, Shouqiang; Zhang, Xue; He, Xuwen

    2015-01-01

    Coal gangue, sandy soil and clay (mass ratio 45:4:1) as goaf filling materials acquired from coal mining processes were applied to remove Fe and Mn effectively from mining drainage. The results of an adsorption kinetic study showed that the Fe adsorption equation was y=21.454y+8.4712, R2=0.9924 and the Mn adsorption equation was y=7.5409x+0.905, R2=0.9957. Meanwhile, the goaf filling materials had low desorption capacity (Fe 6.765 μg/g, Mn 1.52 μg/g) and desorption ratio (Fe 8.98%, Mn 11.04%). Experiments demonstrated that Fe and Mn from mining drainage could be removed stably at a flow rate of 1.2 L/min, Fe inlet concentration of less than 40 mg/L, Mn inlet concentration of less than 2 mg/L and neutral or alkaline conditions. During a procedure of continuous experiments, the effluent quality could meet the requirement of the 'Code for Engineering Design of Sewage Regeneration-GB503352-2002'. A real-application project using goaf filling materials to treat mining drainage in Shendong coal mine showed that the average cost per ton of mining drainage was about 0.55 RMB, which could bring about considerable economic benefit for coal mining enterprises. PMID:26606087

  5. Catalytic ozonation of petroleum refinery wastewater utilizing Mn-Fe-Cu/Al2O 3 catalyst.

    PubMed

    Chen, Chunmao; Yoza, Brandon A; Wang, Yandan; Wang, Ping; Li, Qing X; Guo, Shaohui; Yan, Guangxu

    2015-04-01

    There is of great interest to develop an economic and high-efficient catalytic ozonation system (COS) for the treatment of biologically refractory wastewaters. Applications of COS require options of commercially feasible catalysts. Experiments in the present study were designed to prepare and investigate a novel manganese-iron-copper oxide-supported alumina-assisted COS (Mn-Fe-Cu/Al2O3-COS) for the pretreatment of petroleum refinery wastewater. The highly dispersed composite metal oxides on the catalyst surface greatly promoted the performance of catalytic ozonation. Hydroxyl radical mediated oxidation is a dominant reaction in Mn-Fe-Cu/Al2O3-COS. Mn-Fe-Cu/Al2O3-COS enhanced COD removal by 32.7% compared with a single ozonation system and by 8-16% compared with Mn-Fe/Al2O3-COS, Mn-Cu/Al2O3-COS, and Fe-Cu/Al2O3-COS. The O/C and H/C ratios of oxygen-containing polar compounds significantly increased after catalytic ozonation, and the biodegradability of petroleum refinery wastewater was significantly improved. This study illustrates potential applications of Mn-Fe-Cu/Al2O3-COS for pretreatment of biologically refractory wastewaters. PMID:25649390

  6. Microstructure and mechanical behavior of Fe30Ni 20Mn35Al15 and modified Fe30Ni 20Mn35Al15 alloys

    NASA Astrophysics Data System (ADS)

    Meng, Fanling

    A novel alloy with nominal composition Fe30Ni 20Mn35Al15 has been found to show good room-temperature strength and significant ductility. The current project is to study the wear properties of as-cast Fe30Ni20Mn35Al 15 and discuss the possibility of further improving the mechanical properties of this alloy. The dry sliding wear of as-cast Fe30Ni20Mn 35Al15 was studied in in four different environments, i.e. air, dry oxygen, dry argon and a 4% hydrogen/nitrogen mixture. Two-body and three-body abrasive wear mechanism was found for tests in oxygen-containing environments, while plastic flow mechanisms dominated the wear behavior for tests in argon. Hydrogen embrittlement led to 1000% increase of wear loss by causing more rapid crack nucleation of the asperities. The effects of different additions of chromium (≤ 8 at. %) on both microstructure and fracture behavior of Fe30Ni20Mn 35Al15 were investigated. All alloys consisted of (Ni, Al)-rich B2 and (Fe, Mn)-rich f.c.c. phases with most of the Cr residing in the f.c.c. phase. The addition of 6 at. % Cr not only increased the room temperature ductility, but also completely suppressed the environmental embrittlement observed in the Cr-free alloy at low strain rates. The effects of varying the Al concentration on the microstructures and tensile properties of six two-phase FeNiMnAl alloys with a composition close to Fe30Ni20Mn35Al15 were studied. The increase in f.c.c. volume fraction and f.c.c. lamellar width led to an increase in ductility and a decrease in yield strength. The correlation between the yield stress and f.c.c. lamellar spacing lambda obeyed a Hall-Petch-type relationship, i.e. sigmay=252+0.00027lambda-1, where the units for sigmay and lambda are MPa and meter, respectively. FeNiMnAl alloy with B2 and f.c.c. phases aligned along was reported to show high strength at room temperature. The mechanical properties of Fe 28Ni18Mn33Al21, consisting of (Ni, Al)-enriched B2 and (Fe, Mn)-enriched f.c.c. phases with

  7. Synthesis and high-efficiency methylene blue adsorption of magnetic PAA/MnFe2O4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Ding, Zui; Cai, Minhan; Jian, Haitao; Zeng, Zhiqiao; Li, Feng; Liu, J. Ping

    2015-08-01

    MnFe2O4 nanoparticles and polyacrylic acid PAA/MnFe2O4 nanocomposites were synthesized by a hydrothermal method and ultrasonic mixing process. The obtained materials were characterized by XRD, FTIR, SEM, TEM, and VSM. XRD patterns indicate that the synthesized MnFe2O4 nanoparticles have a single cubic spinel phase. SEM images confirm the existence of three types of basic morphology of MnFe2O4 nanoparticles: octahedral, flower-like, and plate-like particles. High saturation magnetization Ms (up to 74.6 emu/g) of the as-synthesized MnFe2O4 nanoparticles was obtained. Experiments demonstrate that the variation of the hydrothermal reaction time does not remarkably affect the magnetic properties of MnFe2O4 nanoparticles. In PAA/MnFe2O4 nanocomposites, the coating of PAA leads to a slight decrease in magnetization of MnFe2O4 nanoparticles. Additionally, PAA coating greatly enhances the adsorption properties of MnFe2O4 nanoparticles for Methylene Blue (MB) dye. Especially, the removal efficiency reaches 96.3%. This research indicates that the as-synthesized PAA/MnFe2O4 nanocomposites exhibit excellent magnetic properties and can be taken as a promising adsorbent for removal of MB dye in industrial scale.

  8. Transition metal redox and Mn disproportional reaction in LiMn0.5Fe0.5PO4 electrodes cycled with aqueous electrolyte

    NASA Astrophysics Data System (ADS)

    Zhuo, Zengqing; Hu, Jiangtao; Duan, Yandong; Yang, Wanli; Pan, Feng

    2016-07-01

    We performed soft x-ray absorption spectroscopy (sXAS) and a quantitative analysis of the transition metal redox in the LiMn0.5Fe0.5PO4 electrodes upon electrochemical cycling. In order to circumvent the complication of the surface reactions with organic electrolyte at high potential, the LiMn0.5Fe0.5PO4 electrodes are cycled with aqueous electrolyte. The analysis of the transitional metal L-edge spectra allows a quantitative determination of the redox evolution of Mn and Fe during the electrochemical cycling. The sXAS analysis reveals the evolving Mn oxidation states in LiMn0.5Fe0.5PO4. We found that electrochemically inactive Mn2+ is formed on the electrode surface during cycling. Additionally, the signal indicates about 20% concentration of Mn4+ at the charged state, providing a strong experimental evidence of the disproportional reaction of Mn3+ to Mn2+ and Mn4+ on the surface of the charged LiMn0.5Fe0.5PO4 electrodes.

  9. Preparation and magnetic properties of anisotropic bulk MnBi/NdFeB hybrid magnets

    NASA Astrophysics Data System (ADS)

    Ma, Y. L.; Liu, X. B.; Nguyen, V. V.; Poudyal, N.; Yue, M.; Liu, J. P.

    2016-08-01

    Anisotropic hybrid bulk magnets of MnBi/NdFeB with different composition ratio have been prepared with starting MnBi and Nd2Fe14B powders as well as epoxy resin as a binder in case it is needed to form bulk samples. It has been found that the ratio between the two phases in content has a remarkable influence on the magnetic properties, the thermal stability and the density of the bulk magnets. With increasing MnBi content the binder addition can be reduced. When the MnBi content is larger than 30 wt%, no binder is needed. On the other hand, the coercivity and saturation magnetization were increased significantly with increasing NdFeB content. When the NdFeB content was increased from 0% to 50%, the maximum energy product was enhanced from 4.7 to 10.0 MGOe, respectively. The energy product then decreased gradually with the NdFeB content due to the reduced density of the hybrid magnet. The thermal stability measurements showed that the temperature coefficient of coercivity grew with the MnBi content and became positive with MnBi=80 wt%.

  10. Electrical manipulation of ferromagnetic NiFe by antiferromagnetic IrMn

    NASA Astrophysics Data System (ADS)

    Tshitoyan, V.; Ciccarelli, C.; Mihai, A. P.; Ali, M.; Irvine, A. C.; Moore, T. A.; Jungwirth, T.; Ferguson, A. J.

    2015-12-01

    We demonstrate that an antiferromagnet can be employed for a highly efficient electrical manipulation of a ferromagnet. In our study, we use an electrical detection technique of the ferromagnetic resonance driven by an in-plane ac current in a NiFe/IrMn bilayer. At room temperature, we observe antidampinglike spin torque acting on the NiFe ferromagnet, generated by an in-plane current driven through the IrMn antiferromagnet. A large enhancement of the torque, characterized by an effective spin-Hall angle exceeding most heavy transition metals, correlates with the presence of the exchange-bias field at the NiFe/IrMn interface. It highlights that, in addition to the strong spin-orbit coupling, the antiferromagnetic order in IrMn governs the observed phenomenon.

  11. Structural, thermal and magnetic properties of Ni 1-xMn xFe 2O 4 nanoferrites

    NASA Astrophysics Data System (ADS)

    Shobana, M. K.; Sankar, S.

    2009-07-01

    In this paper, the structural, thermal and magnetic properties of Ni 1-xMn xFe 2O 4 are presented. It is observed that high concentration of Mn 2+ ions into NiFe 2O 4 tends to reduce the particle size. Calcination at 500 °C has resulted in the growth of Ni 1-xMn xFe 2O 4 nanoparticles, but the calcination at 900 °C has led to the evaporation of the majorities of the polyvinyl alcohol. After calcination at 900 °C, crystallographically oriented NiMnFe 2O 4 nanoparticles are formed. These Ni 1-xMn xFe 2O 4 nanoparticles show hysteresis behaviour upon magnetization. On the other hand, saturation magnetization (Ms) values decreases with increasing Mn content in ferrite due to the influence of Mn 2+ ion in the sub lattice.

  12. FeMn Metal Droplet Behavior in the MnO-SiO2-CaO Slag System

    NASA Astrophysics Data System (ADS)

    Jang, Hyoung-Soon; Ryu, Jae Wook; Sohn, Il

    2015-04-01

    Optimization of the MnO-SiO2-CaO-based slag composition in the FeMn decarburization refining process to minimize metal droplet entrainment has been studied. FeMn spherical droplets with average diameter of 2.5 mm were dispersed within the refining slag of the medium carbon grade ferro-manganese alloy process. Approximately 4.2 pct of the slag existed as FeMn droplets contributing to the overall metal yield loss in the current process. Sedimentation tests of slags with various SiO2 content ranging from 26 to 47 pct using Al2O3 crucibles held at 1773 K (1500 °C) for 30 minutes showed an improvement of the metal/slag separation. Estimated and measured viscosity of the slags showed SiO2 at 32 pct to be optimal for metal/slag separation. Changes in the SiO2 content to 32 pct in actual plant trials allowed significant decrease in the amount of metal droplet entrainment resulting in a decrease of metal in slag to 1.3 pct. Refining times for this optimized slag composition required at least 20 minutes holding for increased separation according to Stokes' law.

  13. Magnetic self-assembly for the synthesis of magnetically exchange coupled MnBi/Fe-Co composites

    NASA Astrophysics Data System (ADS)

    Xu, Xia; Hong, Yang-Ki; Park, Jihoon; Lee, Woncheol; Lane, Alan M.; Cui, Jun

    2015-11-01

    Exchange coupled hard/soft MnBi/Fe-Co core/shell structured composites were synthesized using a magnetic self-assembly process. MnBi particles were prepared by arc-melting, and Fe-Co nanoparticles were synthesized by an oleic acid assisted chemical reduction method. Grinding a mixture of micron-sized MnBi and Fe-Co nanoparticles in hexane resulted in MnBi/Fe-Co core/shell structured composites. The MnBi/Fe-Co (95/5 wt%) composites showed smooth magnetic hysteresis loops, enhanced remanent magnetization, and positive values in the ΔM curve, indicating exchange coupling between MnBi and Fe-Co particles.

  14. The role of biogenic Fe-Mn oxides formed in situ for arsenic oxidation and adsorption in aquatic ecosystems.

    PubMed

    Bai, Yaohui; Yang, Tingting; Liang, Jinsong; Qu, Jiuhui

    2016-07-01

    As(III&V), Mn(II), and Fe(II) may occur simultaneously in some groundwater and surface water. Studying their redox reactions and interactions is essential to unravel the biogeochemical cycles of these metal ions in aquatic ecosystems and to find effective methods to remove them simultaneously in drinking water treatment. Here, the formation of biogenic Fe-Mn oxides (BFMO, defined as a mixture of biogenic Mn oxide (BMO) and Fe oxide) as well as its oxidation and adsorption of As in a Fe(II)-Mn(II)-As(III&V)-Mn-oxidizing microbe (Pseudomonas sp. QJX-1) system were investigated. Batch experiments and structure characterization revealed that the BFMO was formed via a sequential precipitation of Fe oxide and BMO. The first formed Fe oxide was identified as FeOOH (lepidocrocite) and the latter formed BMO was identified as MnO2 (similar to hexagonal birnessite). In the BFMO mixture, the BMO part was mainly responsible for As(III) oxidation, and the Fe oxide part dominated As adsorption. Remarkably, the BMO could oxidize Fe(II) to form FeOOH, which may improve As adsorption. The optimum Mn(II)/Fe(II) ratio for As removal was approximately 1:3 (mol/mol). Taken together, in Fe(II)-Mn(II)-As(III&V)-Mn-oxidizing microbe ecosystems, the in situ formation of BFMO could eliminate or decrease Fe(II), Mn(II), and As(III&V) species simultaneously. Therefore, based on this study, new approaches may be developed for As removal from water containing high concentrations of Fe(II) and Mn(II). PMID:27088246

  15. Damage annealing in low temperature Fe/Mn implanted ZnO

    NASA Astrophysics Data System (ADS)

    Gunnlaugsson, H. P.; Bharuth-Ram, K.; Johnston, K.; Langouche, G.; Mantovan, R.; Mølholt, T. E.; Naidoo, D.; Ólafsson, O.; Weyer, G.

    2015-04-01

    57Fe Emission Mössbauer spectra obtained after low fluence (<1012 cm -2) implantation of 57Mn ( T 1/2= 1.5 min.) into ZnO single crystal held at temperatures below room temperature (RT) are presented. The spectra can be analysed in terms of four components due to Fe 2+ and Fe 3+ on Zn sites, interstitial Fe and Fe in damage regions (Fe D ). The Fe D component is found to be indistinguishable from similar component observed in emission Mössbauer spectra of higher fluence (˜1015 cm -2)57Fe/ 57Co implanted ZnO and 57Fe implanted ZnO, demonstrating that the nature of the damage regions in the two types of experiments is similar. The defect component observed in the low temperature regime was found to anneal below RT.

  16. Level density and mechanism of deuteron-induced reactions on Fe>54mn>,>56mn>,>58mn>

    SciTech Connect

    Ramirez, A. P. D.; Voinov, A. V.; Grimes, S. M.; Byun, Y.; Brune, C. R.; Massey, T. N.; Akhtar, S.; Dhakal, S.; Parker, C. E.

    2015-07-06

    Here, deuteron elastic cross sections, as well as neutron, proton, and α-particle emission spectra, from d+54,56,58Fe reactions have been measured with deuteron beam energies of 5, 7, and 9 MeV. Optical model parameters have been tested against our experimental data. The fraction of total reaction cross section responsible for the formation of compound nuclei has been deduced from the angular distributions. The degree of discrepancy between calculated and experimental compound cross sections was found to increase with increasing neutron number. The nuclear level densities of the residual nuclei 55Co, 57Co, 55Fe, 57Fe, 52Mn, and 54Mn have been deduced from the compound double differential cross sections. The Gilbert-Cameron model with Iljinov parameter systematics [A. S. Iljinov and M. V. Mebel, Nucl. Phys. A 543, 517 (1992)] was found to have a good agreement with our results.

  17. Magnetic order near 270 K in mineral and synthetic Mn2FeSbO6 ilmenite

    NASA Astrophysics Data System (ADS)

    Mathieu, R.; Ivanov, S. A.; Bazuev, G. V.; Hudl, M.; Lazor, P.; Solovyev, I. V.; Nordblad, P.

    2011-05-01

    The structural and magnetic properties of Mn2FeSbO6 single-crystalline mineral and ceramic samples synthesized under thermobaric treatment have been investigated, and compared to theoretical predictions based on first-principles electronic structure calculations. This ilmenite system displays a sharp magnetic transition just below the room temperature related to a ferrimagnetic ordering of the Mn2+ and Fe3+ cations, which makes Mn2FeSbO6 a promising candidate for designing functional magnetic materials.

  18. A new particulate Mn-Fe-P-shuttle at the redoxcline of anoxic basins

    NASA Astrophysics Data System (ADS)

    Dellwig, Olaf; Leipe, Thomas; März, Christian; Glockzin, Michael; Pollehne, Falk; Schnetger, Bernhard; Yakushev, Evgeniy V.; Böttcher, Michael E.; Brumsack, Hans-Jürgen

    2010-12-01

    Pelagic redoxclines of anoxic basins and deeps form the suboxic transition between oxygenated surface and anoxic or even sulfidic bottom waters. Intense element cycling, favoured by elevated microbial activity, causes steep gradients of physico-chemical parameters, nutrients and redox-sensitive trace metals. This study presents a conceptual model for authigenic particle formation at pelagic redoxclines, which is based on the tight coupling of Mn, Fe, and P cycles. Besides the well-known occurrence of Mn-oxides, textural (SEM-EDX) and geochemical (ICP-OES, ICP-MS) analyses of particles from the redoxclines of the Black Sea and the Baltic Sea (Gotland Basin, Landsort Deep) evidence the existence of earlier postulated Fe-oxyhydroxo-phosphates and emphasize mixed phases consisting of Mn-oxides and Fe-oxyhydroxo-phosphates as a new solid species. Most of the analyzed particles are star-shaped, of about 5 μm in size, and occur as single particles or aggregates without any morphological differences between Mn-oxides, Fe-oxyhydroxo-phosphates, and mixed phases. Throughout the redoxcline, these minerals show a general succession with maximum abundance of Mn-oxides above the redoxcline followed by mixed phases and almost pure Fe-phosphates within and below the redoxcline, respectively. Molar Fe/P ratios of single particles argue against the formation of known pure Fe-phosphates like vivianite or strengite at the lower end of the redox transition zone, but are consistent with recent experimental findings for colloidal P-bearing hydrous ferric oxides. Moreover, morphological similarities suggest the formation of irregular Fe-oxyhydroxo coatings due to oxidation of upward diffusing Fe 2+ by oxygen and stepwise replacement of Mn(IV) by Fe(III) on sinking MnO x particles followed by immediate adsorption or even co-precipitation of phosphate. Batch-type experiments using biogenic MnO x particles demonstrate the efficient potential of Fe 2+ oxidation by sinking MnO x particles

  19. Influence of the porewater geochemistry on Fe and Mn assimilation in Laternula elliptica at King George Island (Antarctica)

    NASA Astrophysics Data System (ADS)

    Poigner, Harald; Monien, Patrick; Monien, Donata; Kriews, Michael; Brumsack, Hans-Jürgen; Wilhelms-Dick, Dorothee; Abele, Doris

    2013-12-01

    A high input of lithogenic sediment from glaciers was assumed to be responsible for high Fe and Mn contents in the Antarctic soft shell clam Laternula elliptica at King George Island. Indeed, withdrawal experiments indicated a strong influence of environmental Fe concentrations on Fe contents in bivalve hemolymph, but no significant differences in hemolymph and tissue concentrations were found among two sites of high and lower input of lithogenic debris. Comparing Fe and Mn concentrations of porewater, bottom water, and hemolymph from sampling sites, Mn appears to be assimilated as dissolved species, whereas Fe apparently precipitates as ferrihydrite within the oxic sediment or bottom water layer prior to assimilation by the bivalve. Hence, we attribute the high variability of Fe and Mn accumulation in tissues of L. elliptica around Antarctica to differences in the geochemical environment of the sediment and the resulting Fe and Mn flux across the benthic boundary.

  20. Magnetic characteristics of a high-layer-number NiFe/FeMn multilayer

    NASA Astrophysics Data System (ADS)

    Paterson, G. W.; Gonçalves, F. J. T.; McFadzean, S.; O'Reilly, S.; Bowman, R.; Stamps, R. L.

    2015-11-01

    We report the static and dynamic magnetic characteristics of a high-layer-number NiFe/FeMn multilayer test structure with potential applications in broadband absorber and filter devices. To allow fine control over the absorption linewidths and to understand the mechanisms governing the resonances in a tailored structure similar to that expected to be used in real world applications, the multilayer was intentionally designed to have layer thickness and interface roughness variations. Magnetometry measurements show that the sample has complex hysteresis loops with features consistent with single ferromagnetic film reversals. Characterisation by transmission electron microscopy allows us to correlate the magnetic properties with structural features, including the film widths and interface roughnesses. Analysis of resonance frequencies from broadband ferromagnetic resonance measurements as a function of field magnitude and orientation provide values of the local exchange bias, rotatable anisotropy, and uniaxial anisotropy fields for specific layers in the stack and explain the observed mode softening. The linewidths of the multilayer are adjustable around the bias field, approaching twice that seen at larger fields, allowing control over the bandwidth of devices formed from the structure.

  1. Magnetic characteristics of a high-layer-number NiFe/FeMn multilayer

    SciTech Connect

    Paterson, G. W. Gonçalves, F. J. T.; McFadzean, S.; Stamps, R. L.; O'Reilly, S.; Bowman, R.

    2015-11-28

    We report the static and dynamic magnetic characteristics of a high-layer-number NiFe/FeMn multilayer test structure with potential applications in broadband absorber and filter devices. To allow fine control over the absorption linewidths and to understand the mechanisms governing the resonances in a tailored structure similar to that expected to be used in real world applications, the multilayer was intentionally designed to have layer thickness and interface roughness variations. Magnetometry measurements show that the sample has complex hysteresis loops with features consistent with single ferromagnetic film reversals. Characterisation by transmission electron microscopy allows us to correlate the magnetic properties with structural features, including the film widths and interface roughnesses. Analysis of resonance frequencies from broadband ferromagnetic resonance measurements as a function of field magnitude and orientation provide values of the local exchange bias, rotatable anisotropy, and uniaxial anisotropy fields for specific layers in the stack and explain the observed mode softening. The linewidths of the multilayer are adjustable around the bias field, approaching twice that seen at larger fields, allowing control over the bandwidth of devices formed from the structure.

  2. Mn, Fe, Zn and As speciation in a fast-growing ferromanganese marine nodule

    SciTech Connect

    Marcus, Matthew A.; Manceau, Alain; Kersten, Michael

    2004-04-01

    The speciation of Mn, Fe, As and Zn in a fast-growing (0.02mm/yr), shallow-marine ferromanganese nodule has been examined by micro X-ray fluorescence, micro X-ray diffraction, and micro X-ray absorption spectroscopy. This nodule exhibits alternating Fe-rich and Mn-rich layers reflecting redox variations in water chemistry. Fe occurs as two-line ferrihydrite. The As is strictly associated with Fe and is mostly pentavalent, with an environment similar to that of As sorbed on or coprecipitated with synthetic ferrihydrite. The Mn is in the form of turbostratic birnessite with {approx} 10 percent trivalent manganese in the layers and probably {approx} 8 percent corner-sharing metal octahedra in the interlayers. The Zn is enriched on the rim of the nodule, associated with Mn. The Zn is completely (>90 percent) tetrahedrally coordinated and sorbed in the interlayers of birnessite on vacant layer Mn sites. The Zn and Mn species are similar to ones found in soils, suggesting common structural principles, despite the differing formation conditions in these systems.

  3. Sulfur evolution in chemical looping combustion of coal with MnFe2O4 oxygen carrier.

    PubMed

    Wang, Baowen; Gao, Chuchang; Wang, Weishu; Zhao, Haibo; Zheng, Chuguang

    2014-05-01

    Chemical looping combustion (CLC) of coal has gained increasing attention as a novel combustion technology for its advantages in CO2 capture. Sulfur evolution from coal causes great harm from either the CLC operational or environmental perspective. In this research, a combined MnFe2O4 oxygen carrier (OC) was synthesized and its reaction with a typical Chinese high sulfur coal, Liuzhi (LZ) bituminous coal, was performed in a thermogravimetric analyzer (TGA)-Fourier transform infrared (FT-IR) spectrometer. Evolution of sulfur species during reaction of LZ coal with MnFe2O4 OC was systematically investigated through experimental means combined with thermodynamic simulation. TGA-FTIR analysis of the LZ reaction with MnFe2O4 indicated MnFe2O4 exhibited the desired superior reactivity compared to the single reference oxides Mn3O4 or Fe2O3, and SO2 produced was mainly related to oxidization of H2S by MnFe2O4. Experimental analysis of the LZ coal reaction with MnFe2O4, including X-ray diffraction and X-ray photoelectron spectroscopy analysis, verified that the main reduced counterparts of MnFe2O4 were Fe3O4 and MnO, in good agreement with the related thermodynamic simulation. The obtained MnO was beneficial to stabilize the reduced MnFe2O4 and avoid serious sintering, although the oxygen in MnO was not fully utilized. Meanwhile, most sulfur present in LZ coal was converted to solid MnS during LZ reaction with MnFe2O4, which was further oxidized to MnSO4. Finally, the formation of both MnS and such manganese silicates as Mn2SiO4 and MnSiO3 should be addressed to ensure the full regeneration of the reduced MnFe2O4. PMID:25079636

  4. Magnetic properties of transition metal Mn, Fe and Co dimers on monolayer phosphorene.

    PubMed

    Khan, Imran; Hong, Jisang

    2016-09-23

    We studied the geometries, electronic structure and magnetic properties of substitutional doping and adsorption of transition metal (Mn, Fe and Co) dimers on phosphorene monolayer in the framework of the generalized gradient approximation (GGA) and GGA + U. Electronic band structures and magnetic properties were dependent on the doping type and dopant materials. For Mn and Fe substitutional and adsorption dimers, we obtained semiconducting band structures with spin polarization. However, we found a half-metallic feature in Co substitutional dimer while the Co adsorption dimer showed a semiconducting behavior without any spin polarization. With GGA + U, all the systems showed spin polarized semiconducting band structures except Co adsorption dimer which remained unaffected. The hybridization between transition metal (TM) and phosphorene sheet contributed to suppressing the magnetic moment of TM dimers. For instance, the total magnetic moments of -2.0, 4.24 and 1.28 μ B/cell for Mn, Fe and Co substitutional dimers were obtained while the Mn and Fe adsorption dimers showed magnetic moments of -1.69 and 0.46 μ B/cell. These magnetic moments were enhanced with GGA + U. The same magnetic ground states were obtained both from GGA and GGA + U approaches except for the Mn dimers. We observed that the Mn and Fe substitutional dimers showed an out-of-plane magnetization while an in-plane magnetization was observed in Co substitutional dimer. The Mn adsorption dimer still displayed a perpendicular magnetization whereas the Fe adsorption dimer had an in-plane magnetization. We found that the both GGA and GGA + U showed the same magnetization direction in all the systems. PMID:27512907

  5. Magnetic properties of transition metal Mn, Fe and Co dimers on monolayer phosphorene

    NASA Astrophysics Data System (ADS)

    Khan, Imran; Hong, Jisang

    2016-09-01

    We studied the geometries, electronic structure and magnetic properties of substitutional doping and adsorption of transition metal (Mn, Fe and Co) dimers on phosphorene monolayer in the framework of the generalized gradient approximation (GGA) and GGA + U. Electronic band structures and magnetic properties were dependent on the doping type and dopant materials. For Mn and Fe substitutional and adsorption dimers, we obtained semiconducting band structures with spin polarization. However, we found a half-metallic feature in Co substitutional dimer while the Co adsorption dimer showed a semiconducting behavior without any spin polarization. With GGA + U, all the systems showed spin polarized semiconducting band structures except Co adsorption dimer which remained unaffected. The hybridization between transition metal (TM) and phosphorene sheet contributed to suppressing the magnetic moment of TM dimers. For instance, the total magnetic moments of ‑2.0, 4.24 and 1.28 μ B/cell for Mn, Fe and Co substitutional dimers were obtained while the Mn and Fe adsorption dimers showed magnetic moments of ‑1.69 and 0.46 μ B/cell. These magnetic moments were enhanced with GGA + U. The same magnetic ground states were obtained both from GGA and GGA + U approaches except for the Mn dimers. We observed that the Mn and Fe substitutional dimers showed an out-of-plane magnetization while an in-plane magnetization was observed in Co substitutional dimer. The Mn adsorption dimer still displayed a perpendicular magnetization whereas the Fe adsorption dimer had an in-plane magnetization. We found that the both GGA and GGA + U showed the same magnetization direction in all the systems.

  6. Magnetic susceptibilities of liquid Cr-Au, Mn-Au and Fe-Au alloys

    SciTech Connect

    Ohno, S.; Shimakura, H.; Tahara, S.; Okada, T.

    2015-08-17

    The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr{sub 1-c}Au{sub c} with 0.5 ≤ c and Mn{sub 1-c}Au{sub c} with 0.3≤c obeyed the Curie-Weiss law with regard to their dependence of χ on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of χ for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of χ for liquid Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of χ{sub 3d} due to 3d electrons for liquid binary TM-M (M=Au, Al, Si, Sb), and investigated the relationship between χ{sub 3d} and E{sub F} in liquid binary TM-M alloys at a composition of 50 at% TM.

  7. Effect of Mn substitution on the transport properties of co-sputtered Fe{sub 3−x}Mn{sub x}Si epilayers

    SciTech Connect

    Tang, M.; Jin, C.; Bai, H. L.

    2014-11-07

    Motivated by the theoretical calculations that Fe{sub 3−x}Mn{sub x}Si can simultaneously exhibit a high spin polarization with a high Curie temperature to be applied in spintronic devices, and in order to further study the effect of Mn contents on the physical properties of Fe{sub 3−x}Mn{sub x}Si, we have investigated the effect of Mn substitution on the transport properties of epitaxial Fe{sub 3−x}Mn{sub x}Si (0≤x≤1) films systematically. The Fe{sub 3−x}Mn{sub x}Si films were epitaxially grown on MgO(001) plane with 45° rotation. The magnetization for various x shows enhanced irreversibility, implying the antiferromagnetic ordering induced by the substitution of Mn. A metal-semiconductor crossover was observed due to the enhanced disorders of interactions and the local lowering of symmetry induced by the substitution of Mn. The single-domain state in the Fe{sub 3−x}Mn{sub x}Si films leads to twofold symmetric curves of the anisotropic magnetoresistance and planar Hall resistivity.

  8. Magnetic and structural properties of ferromagnetic Fe5PB2 and Fe5SiB2 and effects of Co and Mn substitutions

    DOE PAGESBeta

    McGuire, Michael A.; Parker, David S.

    2015-10-22

    Crystallographic and magnetic properties of Fe5PB2, Fe4CoPB2, Fe4MnPB2, Fe5SiB2, Fe4CoSiB2, and Fe4MnSiB2 are reported. All adopt the tetragonal Cr5B3 structure-type and are ferromagnetic at room temperature with easy axis of magnetization along the c-axis. The spin reorientation in Fe5SiB2 is observed as an anomaly in the magnetization near 170 K, and is suppressed by substitution of Co or Mn for Fe. The silicides are found to generally have larger magnetic moments than the phosphides, but the data suggests smaller magnetic anisotropy in the silicides. Cobalt substitution reduces the Curie temperatures by more than 100 K and ordered magnetic moments bymore » 16-20%, while manganese substitution has a much smaller effect. This suggests Mn moments align ferromagnetically with the Fe and that Co does not have an ordered moment in these structures. Anisotropic thermal expansion is observed in Fe5PB2 and Fe5SiB2, with negative thermal expansion seen along the c-axis of Fe5SiB2. First principles calculations of the magnetic properties of Fe5SiB2 and Fe4MnSiB2 are reported. The results, including the magnetic moment and anisotropy, and are in good agreement with experiment.« less

  9. Magnetic and structural properties of ferromagnetic Fe5PB2 and Fe5SiB2 and effects of Co and Mn substitutions

    NASA Astrophysics Data System (ADS)

    McGuire, Michael A.; Parker, David S.

    2015-10-01

    Crystallographic and magnetic properties of Fe5PB2, Fe4CoPB2, Fe4MnPB2, Fe5SiB2, Fe4CoSiB2, and Fe4MnSiB2 are reported. All adopt the tetragonal Cr5B3 structure-type and are ferromagnetic at room temperature with easy axis of magnetization along the c-axis. The spin reorientation in Fe5SiB2 is observed as an anomaly in the magnetization near 170 K and is suppressed by substitution of Co or Mn for Fe. The silicides are found to generally have larger magnetic moments than the phosphides, but the data suggest smaller magnetic anisotropy in the silicides. Cobalt substitution reduces the Curie temperatures by more than 100 K and ordered magnetic moments by 16%-20%, while manganese substitution has a much smaller effect. This suggests Mn moments align ferromagnetically with the Fe and that Co does not have an ordered moment in these structures. Anisotropic thermal expansion is observed in Fe5PB2 and Fe5SiB2, with negative thermal expansion seen along the c-axis of Fe5SiB2. First principles calculations of the magnetic properties of Fe5SiB2 and Fe4MnSiB2 are reported. The results, including the magnetic moment and anisotropy, are in good agreement with experiment.

  10. Effects of Oral Administration of CrCl3 on the Contents of Ca, Mg, Mn, Fe, Cu, and Zn in the Liver, Kidney, and Heart of Chicken.

    PubMed

    Liu, Yanhan; Zhao, Xiaona; Zhang, Xiao; Zhao, Xuejun; Liu, Yongxia; Liu, Jianzhu

    2016-06-01

    This study aimed to investigate the effects of oral administration of trivalent chromium on the contents of Ca, Mg, Mn, Fe, Cu, and Zn in the heart, liver, and kidney. Different levels of 1/8, 1/4, and 1/2 LD50 (LD50 = 5000 mg/kg body mass) CrCl3 milligrams per kilogram body mass daily were added into the water to establish the chronic poisoning model. Ca, Mg, Mn, Fe, Cu, and Zn were detected with the flame atomic absorption spectrometry in the organs exposed 14, 28, and 42 days to CrCl3, respectively. Results showed that Cr was accumulated in the heart, liver, and kidney significantly (P < 0.05) with extended time and dose. The contents of Ca and Fe increased, whereas those of Mg, Mn, Cu, and Zn decreased in the heart, liver, and kidney of each treated group, which had a dose- and time-dependent relationship, but the contents of Mg and Zn in the heart took on a fluctuated change. These particular observations were different from those in the control group. In conclusion, the oral administration of CrCl3 could change the contents of Ca, Mg, Mn, Fe, Cu, and Zn in the heart, liver, and kidney, which may cause disorders in the absorption and metabolism of the metal elements of chickens. PMID:26537118

  11. Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica

    NASA Astrophysics Data System (ADS)

    Aquilina, Alfred; Homoky, William B.; Hawkes, Jeffrey A.; Lyons, Timothy W.; Mills, Rachel A.

    2014-07-01

    Short sediment cores were collected from ∼1100 m water depth at the top of Hook Ridge, a submarine volcanic edifice in the Central Basin of the Bransfield Strait, Antarctica, to assess Fe and Mn supply to the water column. Low-temperature hydrothermal fluids advect through these sediments and, in places, subsurface H2S is present at high enough concentrations to support abundant Sclerolinum sp., an infaunal tubeworm that hosts symbiotic thiotrophic bacteria. The water column is fully oxic, and oxygen penetration depths at all sites are 2-5 cmbsf. Pore water Fe and Mn content is high within the subsurface ferruginous zone (max. 565 μmol Fe L-1, >3-7 cmbsf)-14-18 times higher than values measured at a nearby, background site of equivalent water depth. Diffusion and advection of pore waters supply significant Fe and Mn to the surface sediment. Sequential extraction of the sediment demonstrates that there is a significant enrichment in a suite of reactive, authigenic Fe minerals in the upper 0-5 cm of sediment at one site characterised by weathered crusts at the seafloor. At a site with only minor authigenic mineral surface enrichment we infer that leakage of pore water Fe and Mn from the sediment leads to enriched total dissolvable Fe and Mn in bottom waters. An Eh sensor mounted on a towed package mapped a distinct Eh signature above this coring site which is dispersed over several km at the depth of Hook Ridge. We hypothesise that the main mechanism for Fe and Mn efflux from the sediment is breach of the surface oxic layer by the abundant Sclerolinum sp., along with episodic enhancements by physical mixing and resuspension of sediment in this dynamic volcanic environment. We propose that Hook Ridge sediments are an important source of Fe and Mn to the deep waters of the Central Basin in the Bransfield Strait, where concentrations are sustained by the benthic flux, and Fe is stabilised in the water column as either colloidal phases or ligand-bound dissolved

  12. Thermal decomposition study of Mn doped Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Malek, Tasmira J.; Chaki, S. H.; Tailor, J. P.; Deshpande, M. P.

    2016-05-01

    Fe3O4 is an excellent magnetic material among iron oxides. It has a cubic inverse spinel structure exhibiting distinguished electric and magnetic properties. In this paper the authors report the synthesis of Mn doped Fe3O4 nanoparticles by wet chemical reduction technique at ambient temperature and its thermal characterization. Ferric chloride hexa-hydrate (FeCl3•6H2O), manganese chloride tetra-hydrate (MnCl2•4H2O) and sodium boro-hydrate (NaBH4) were used for synthesis of Fe3O4 nanoparticles at ambient temperature. The elemental composition of the as-synthesized Mn doped Fe3O4 nanoparticles were determined by energy dispersive analysis of X-rays (EDAX) technique. Thermogravimetric (TG) and differential thermal analysis (DTA) were carried out on the Mn doped Fe3O4 nanoparticles in the temperature range of ambient to 1124 K. The thermo-curves revealed that the particles decompose by four steps. The kinetic parameters were evaluated using non-mechanistic equations for the thermal decomposition.

  13. Post-irradiation annealing behavior of neutron-irradiated FeCu, FeMnNi and FeMnNiCu model alloys investigated by means of small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Bergner, F.; Ulbricht, A.; Lindner, P.; Keiderling, U.; Malerba, L.

    2014-11-01

    Neutron irradiation of reactor pressure vessel steels gives rise to the formation of thermodynamically stable and unstable nano-features. The present work is focused on the stability of Cu-, Mn- and Ni-containing solute clusters in model alloys exposed to post-irradiation annealing. Fe0.1Cu, Fe1.2Mn0.7Ni and Fe1.2Mn0.7Ni0.1Cu (wt%) model alloys irradiated up to neutron exposures of 0.1 and 0.19 dpa (displacements per atom) were annealed at stepwise increasing temperatures in the range from 300 °C (i.e. near irradiation temperature) to 500 °C and characterized by means of small-angle neutron scattering (SANS). We have found characteristic differences in the annealing behavior of the alloys. In particular, there is a non-trivial (synergistic-antagonistic) interplay of Mn/Ni and Cu.

  14. Interfacial strain and defects in asymmetric Fe-Mn oxide hybrid nanoparticles.

    PubMed

    Mayence, Arnaud; Wéry, Madeleine; Tran, Dung Trung; Wetterskog, Erik; Svedlindh, Peter; Tai, Cheuk-Wai; Bergström, Lennart

    2016-08-01

    Asymmetric Fe-Mn oxide hybrid nanoparticles have been obtained by a seed-mediated thermal decomposition-based synthesis route. The use of benzyl ether as the solvent was found to promote the orientational growth of Mn1-xO onto the iron oxide nanocube seeds yielding mainly dimers and trimers whereas 1-octadecene yields large nanoparticles. HRTEM imaging and HAADF-STEM tomography performed on dimers show that the growth of Mn1-xO occurs preferentially along the edges of iron oxide nanocubes where both oxides share a common crystallographic orientation. Fourier filtering and geometric phase analysis of dimers reveal a lattice mismatch of 5% and a large interfacial strain together with a significant concentration of defects. The saturation magnetization is lower and the coercivity is higher for the Fe-Mn oxide hybrid nanoparticles compared to the iron oxide nanocube seeds. PMID:27385323

  15. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel by Atom Probe Tomography

    NASA Astrophysics Data System (ADS)

    Pereloma, E. V.; Stohr, R. A.; Miller, M. K.; Ringer, S. P.

    2009-12-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 °C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe)3Ti and (Ni,Fe)3(Al,Mn) precipitates eventually form after isothermal aging for ~60 seconds. The morphology of the (Ni,Fe)3Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe)3(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe)3Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  16. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel using Atom Probe Tomography

    SciTech Connect

    Pereloma, E. V.; Stohr, R A; Miller, Michael K; Ringer, S. P.

    2009-01-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe){sub 3}Ti and (Ni,Fe){sub 3}(Al,Mn) precipitates eventually form after isothermal aging for {approx}60 seconds. The morphology of the (Ni,Fe){sub 3}Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe){sub 3}(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe){sub 3}Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  17. Interfacial strain and defects in asymmetric Fe-Mn oxide hybrid nanoparticles

    NASA Astrophysics Data System (ADS)

    Mayence, Arnaud; Wéry, Madeleine; Tran, Dung Trung; Wetterskog, Erik; Svedlindh, Peter; Tai, Cheuk-Wai; Bergström, Lennart

    2016-07-01

    Asymmetric Fe-Mn oxide hybrid nanoparticles have been obtained by a seed-mediated thermal decomposition-based synthesis route. The use of benzyl ether as the solvent was found to promote the orientational growth of Mn1-xO onto the iron oxide nanocube seeds yielding mainly dimers and trimers whereas 1-octadecene yields large nanoparticles. HRTEM imaging and HAADF-STEM tomography performed on dimers show that the growth of Mn1-xO occurs preferentially along the edges of iron oxide nanocubes where both oxides share a common crystallographic orientation. Fourier filtering and geometric phase analysis of dimers reveal a lattice mismatch of 5% and a large interfacial strain together with a significant concentration of defects. The saturation magnetization is lower and the coercivity is higher for the Fe-Mn oxide hybrid nanoparticles compared to the iron oxide nanocube seeds.Asymmetric Fe-Mn oxide hybrid nanoparticles have been obtained by a seed-mediated thermal decomposition-based synthesis route. The use of benzyl ether as the solvent was found to promote the orientational growth of Mn1-xO onto the iron oxide nanocube seeds yielding mainly dimers and trimers whereas 1-octadecene yields large nanoparticles. HRTEM imaging and HAADF-STEM tomography performed on dimers show that the growth of Mn1-xO occurs preferentially along the edges of iron oxide nanocubes where both oxides share a common crystallographic orientation. Fourier filtering and geometric phase analysis of dimers reveal a lattice mismatch of 5% and a large interfacial strain together with a significant concentration of defects. The saturation magnetization is lower and the coercivity is higher for the Fe-Mn oxide hybrid nanoparticles compared to the iron oxide nanocube seeds. Electronic supplementary information (ESI) available: Materials characterization, powder X-ray diffraction, EFTEM images, EELS spectra, HAADF-STEM. See DOI: 10.1039/c6nr01373b

  18. Structural And Magnetic Properties Of Mn And Zn Doped Fe3O4 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Varshney, Dinesh; Verma, Kavita; Yogi, A.

    2011-07-01

    Mn and Zn doped Fe3O4 nanoparticles of size 7.36 and 12.52 nm were prepared by co precipitation method. X-ray diffraction (XRD) pattern infers that both the samples are in single phase with Fd3m space group, which was further confirmed by Rietveld refinement. Transmission Mössbauer spectra reveals ferrimagnetic nature for Mn doping concentration while into that for Zn doping concentration it shows diamagnetic behaviour. Zn doped nanoparticles shows the superparamagnetic property.

  19. Spark plasma sintering and microwave electromagnetic properties of MnFe2O4 ceramics

    NASA Astrophysics Data System (ADS)

    Penchal Reddy, M.; Mohamed, A. M. A.; Venkata Ramana, M.; Zhou, X. B.; Huang, Q.

    2015-12-01

    MnFe2O4 ferrite powder was synthesized by a facile one-pot hydrothermal route and then consolidated into dense nanostructured compacts by the spark plasma sintering (SPS) technique. The effect of sintering temperature, on densification, morphology, magnetic and microwave absorption properties was examined. Spark plasma sintering resulted in uniform microstructure, as well as maximum relative density of 98%. The magnetic analysis indicated that the MnFe2O4 ferrite nanoparticles showed ferrimagnetic behavior. Moreover, the dielectric loss and magnetic loss properties of MnFe2O4 ferrite nanoparticles were both enhanced due to its better dipole polarization, interfacial polarization and shape anisotropy. It is believed that such spark plasma sintered ceramic material will be applied widely in microwave absorbing area.

  20. Rotational hysteresis of the exchange anisotropy direction in Co /FeMn thin films

    NASA Astrophysics Data System (ADS)

    Olamit, Justin; Liu, Kai

    2007-05-01

    The effects of rotating an applied field on the exchange anisotropy in Co /FeMn thin films have been investigated. When the applied field is initially along the cooling field direction, the longitudinal hysteresis loop has a maximum coercivity and the transverse hysteresis loop is flat, indicating that the exchange field is along the cooling field direction. When the applied field angle is rotated away and then restored to the original field cooling direction, the exchange anisotropy direction has changed. The rotation of the exchange field direction trails the applied field and is hysteretic. The rotational hysteresis of the exchange field direction is due to the weak anisotropy in thin FeMn layers and decreases with increasing FeMn thickness.

  1. Fractionation and risk assessment of Fe and Mn in surface sediments from coastal sites of Sonora, Mexico (Gulf of California).

    PubMed

    Jara-Marini, Martín E; García-Camarena, Raúl; Gómez-Álvarez, Agustín; García-Rico, Leticia

    2015-07-01

    The aim of this study was to evaluate Fe and Mn distribution in geochemical fractions of the surface sediment of four oyster culture sites in the Sonora coast, Mexico. A selective fractionation scheme to obtain five fractions was adapted for the microwave system. Surface sediments were analyzed for carbonates, organic matter contents, and Fe and Mn in geochemical fractions. The bulk concentrations of Fe ranged from 10,506 to 21,918 mg/kg (dry weight, dry wt), and the bulk concentrations of Mn ranged from 185.1 to 315.9 mg/kg (dry wt) in sediments, which was low and considered as non-polluted in all of the sites. The fractionation study indicated that the major geochemical phases for the metals were the residual, as well as the Fe and Mn oxide fractions. The concentrations of metals in the geochemical fractions had the following order: residual > Fe and Mn oxides > organic matter > carbonates > interchangeable. Most of the Fe and Mn were linked to the residual fraction. Among non-residual fractions, high percentages of Fe and Mn were linked to Fe and Mn oxides. The enrichment factors (EFs) for the two metals were similar in the four studied coasts, and the levels of Fe and Mn are interpreted as non-enrichment (EF < 1) because the metals concentrations were within the baseline concentrations. According to the environmental risk assessment codes, Fe and Mn posed no risk and low risk, respectively. Although the concentrations of Fe and Mn were linked to the residual fraction, the levels in non-residual fractions may significantly result in the transference of other metals, depending on several physico-chemical and biological factors. PMID:26116197

  2. Thermoelectric properties of Fe and Al double substituted MnSiγ (γ~1.73)

    NASA Astrophysics Data System (ADS)

    Barczak, S. A.; Downie, R. A.; Popuri, S. R.; Decourt, R.; Pollet, M.; Bos, J. W. G.

    2015-07-01

    Two series of Fe and Al double substituted MnSiγ chimney ladders with a nominal valence electron count, VEC=14 per transition metal were prepared (γ=1.75). Simultaneous replacement of Mn with Fe and Si with Al yielded the Mn1-xFexSi1.75-xAlx series while the second Mn1-xFexSi1.75-1.75xAl2x series follows the pseudo-binary between MnSi1.75 and FeAl2. Scanning electron microscopy and elemental mapping revealed that ~60% of the nominal Al content ends up in the product with the remainder lost to sublimation, and that up to 7% Al can be substituted in the main group sublattice. Profile analysis of X-ray powder diffraction data revealed gradual changes in the cell metrics, consistent with the simultaneous substitution of Fe and Al in a fixed ratio. All samples are p-type with VEC≈13.95 from the structural data and ~1×1021 holes cm-3 from variable temperature Seebeck measurements. The substituted samples have lower electrical resistivities (ρ300 K=2-5 mΩ cm) due to an improved microstructure. This leads to increased thermoelectric power factors (largest S2/ρ=1.95 mW m-1 K-2) compared to MnSiγ. The thermal conductivity for the Mn0.95Fe0.05Si1.66Al0.1 sample is 2.7 W m-1 K-1 between 300 and 800 K, and is comparable to literature data for the parent material.

  3. Phase transformations during deformation of Fe-Ni and Fe-Mn alloys produced by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Cherdyntsev, V. V.; Pustov, L. Yu.; Kaloshkin, S. D.; Tomilin, I. A.; Shelekhov, E. V.; Laptev, A. I.; Baldokhin, Yu. V.; Estrin, E. I.

    2007-10-01

    Compositions of Fe(100 - x)Mn x ( x = 10 and 12 at. %) and Fe(100 - y)Ni y ( y = 18 and 20 at. %) were produced by combined mechanical alloying of pure-metal powders and annealed in the austenitic field. After annealing and cooling to room temperature, the alloys had a single-phase austenitic structure. During deformation, the γ phase partially transforms into the α 2 phase (and/or ɛ phase in Fe-Mn alloys). The phase composition of the alloys after deformation depends on the amount of alloying elements and the predeformation annealing regime. The amount of martensite in the structure of a bulk alloy obtained by powder compacting grows proportionally to the degree of deformation of the sample.

  4. Different magnetic origins of (Mn, Fe)-codoped ZnO powders and thin films

    SciTech Connect

    Fan, Jiuping; Jiang, Fengxian; Quan, Zhiyong; Qing, Xiufang; Xu, Xiaohong

    2012-11-15

    Graphical abstract: The effects of the sample forms, fabricated methods, and process conditions on the structural and magnetic properties of (Mn, Fe)-codoped ZnO powders and films were systematically studied. The origins of ferromagnetism in the vacuum-annealed powder and PLD-deposited film are different. The former originates from the impurities of magnetic clusters, whereas the latter comes from the almost homogenous phase. Highlights: ► The magnetic natures of Zn{sub 0.98}Mn{sub 0.01}Fe{sub 0.01}O powders and thin films come from different origins. ► The ferromagnetism of the powder is mainly from the contribution of magnetic clusters. ► Whereas the ferromagnetic behavior of the film comes from the almost homogenous phase. -- Abstract: The structural and magnetic properties of (Mn, Fe)-codoped ZnO powders as well as thin films were investigated. The X-ray diffraction and magnetic measurements indicated that the higher sintering temperature facilitates more Mn and Fe incorporation into ZnO. Magnetic measurements indicated that the powder sintered in air at 800 °C showed paramagnetic, but it exhibited obvious room temperature ferromagnetism after vacuum annealing at 600 °C. The results revealed that magnetic clusters were the major contributors to the observed ferromagnetism in vacuum-annealed Zn{sub 0.98}Mn{sub 0.01}Fe{sub 0.01}O powder. Interestingly, the room temperature ferromagnetism was also observed in the Zn{sub 0.98}Mn{sub 0.01}Fe{sub 0.01}O film deposited via pulsed laser deposition from the air-sintered paramagnetic target, but the secondary phases in the film were not detected from X-ray diffraction, transmission electron microscopy, and zero-field cooling and field cooling. Apparently, the magnetic natures of powders and films come from different origins.

  5. Preparation and Magnetic Studies of Mn Substituted Analogues of BiFeO3

    NASA Astrophysics Data System (ADS)

    Choudhary, B. L.; Kumar, Sudhish; Krishnamurthy, Anjali; Srivastava, Bipin K.

    2011-11-01

    Manganese substituted samples (for iron) in the multiferroic BiFeO3 have been prepared using solid state ceramic route. It has been possible to prepare a sample with the highest 40% Mn content. Reitveld analysis of the X-ray diffraction patterns shows that the substituted analogues crystallize in rhombohedral symmetry in R-3¯c space group. Effort to prepare 50 atomic% Mn substituted sample did not succeed. Magnetization measurements have been made in the temperature range 20K-300K and in fields upto 8 kOe. Magnetic nature of the 40 atomic% Mn substituted sample is alike that of 30 atomic% Mn substituted one. Mn induces weak ferromagnetism with the average magnetic moment increasing with its concentration.

  6. DFT calculation and experimental investigation of Mn doping effect in Fe16N2

    NASA Astrophysics Data System (ADS)

    Jiang, Yanfeng; Himmetoglu, Burak; Cococcioni, Matteo; Wang, Jian-Ping

    2016-05-01

    An effective dopant to improve the thermal stability of a Fe16N2 permanent magnet is proposed in this paper. It is demonstrated both theoretically and experimentally that manganese is a promising candidate as dopant in Fe16N2 magnet to improve the thermal stability. Firstly, the atomic moments of the Fe ions with respect to N is investigated by using first-principles DFT calculation. Two possible candidates of elements, including Co and Mn, are compared in terms of its preferred position and magnetic coupling mode. It is found that Mn prefers Fe1 position and ferromagnetic coupling in the Fe16N2 lattice. So Mn is considered as a promising dopant in Fe16N2 magnet to improve its thermal stability. Based on theoretical results, experiments are conducted by a cold-crucible method to prepare (Fe1-xMnx) N bulk samples. The samples are thermal treated at different temperatures to observe their thermal stabilities. X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) are characterized on the samples.

  7. Adsorption of antimony(V) onto Mn(II)-enriched surfaces of manganese-oxide and FeMn binary oxide.

    PubMed

    Liu, Ruiping; Xu, Wei; He, Zan; Lan, Huachun; Liu, Huijuan; Qu, Jiuhui; Prasai, Tista

    2015-11-01

    Manganese(IV) oxide [Mn(IV)] potentially oxidizes antimony(III) [Sb(III)] to antimony(V) [Sb(V)] and improves Sb removal by FeMn binary oxide (FMBO) through an oxidation-adsorption mechanism. This study focused on the effect of Mn(IV) reductive dissolution by potassium sulfite (K2SO3) on Sb(V) adsorption onto manganese oxide (Mn-oxide) and FMBO. The maximum Sb(V) adsorption (Qmax,Sb(V)) increased from 1.0 to 1.1 mmol g(-1) for FMBO and from 0.4 to 0.6 mmol g(-1) for Mn-oxide after pretreatment with 10 mmol L(-1) K2SO3. The addition of 2.5 mmol L(-1) Mn(2+) also significantly improved Sb(V) adsorption, and the observed Qmax,Sb(V) increased to 1.4 and 1.0 mmol g(-1) for FMBO and Mn-oxide, respectively, with pre-adsorbed Mn(2+). Neither K2SO3 nor Mn(2+) addition had any effect on Sb(V) adsorption onto iron oxide (Fe-oxide). Mn(2+) introduced by either Mn(IV) dissolution or addition tended to form outer-sphere surface complexes with hydroxyl groups on Mn-oxide surfaces (MnOOH). Mn(2+) at 2.5 mmol L(-1) shifted the isoelectric point (pHiep) from 7.5 to 10.2 for FMBO and from 4.8 to 9.2 for Mn-oxide and hence benefited Sb(V) adsorption. The adsorption of Sb(V) onto Mn(2+)-enriched surfaces contributed to the release of Mn(2+), and the X-ray photoelectron spectra also indicated increased binding energy of Mn 2p3/2 after the adsorption of Sb(V) onto K2SO3-pretreated FMBO and Mn-oxide. Sb(V) adsorption involved the formation of inner-sphere complexes and contributed to the release of Mn(2+). In the removal of Sb(III) by Mn-based oxides, the oxidation of Sb(III) to Sb(V) by Mn(IV) oxides had an effect; however, Mn(IV) dissolution and Mn(2+)-enrichment also played an important role. PMID:26218341

  8. Mechanical properties of weldments in experimental Fe-12Mn-0.2Ti and Fe-12Mn-1Mo-0.2Ti alloys for cryogenic service

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.; Devletian, J. H.

    1981-01-01

    Mechanical properties of weldments in two Fe-12Mn experimental alloys designed for cryogenic service were evaluated. Weldments were made using the GTA welding process. Tests to evaluate the weldments were conducted at -196 C and included: equivalent energy fracture toughness tests; autogenous transverse weld, notched transverse weld, and longitudinal weld tensile tests; and all-weld-metal tensile tests. The Fe-12Mn-0.2Ti and Fe-12Mn-1Mo-0.2Ti alloys proved weldable for cryogenic service, with weld metal and heat-affected zone properties comparable with those of the base metal. Optimum properties were achieved in the base alloys, weld metals, and heat-affected zones after a two-step heat treatment consisting of austenitizing at 900 C followed by tempering at 500 C. The Mo-containing alloy offered a marked improvement in cryogenic properties over those of the Mo-free alloy. Molybdenum increased the amount of retained austenite and reduced the amount of epsilon martensite observed in the microstructure of the two alloys.

  9. Electrochemical deposition and microstructural characterization of AlCrFeMnNi and AlCrCuFeMnNi high entropy alloy thin films

    NASA Astrophysics Data System (ADS)

    Soare, V.; Burada, M.; Constantin, I.; Mitrică, D.; Bădiliţă, V.; Caragea, A.; Târcolea, M.

    2015-12-01

    Al-Cr-Fe-Mn-Ni and Al-Cr-Cu-Fe-Mn-Ni high entropy alloy thin films were prepared by potentiostatic electrodeposition and the microstructure of the deposits was investigated. The thin films were co-deposited in an electrolyte based on a DMF (N,N-dimethylformamide)-CH3CN (acetonitrile) organic compound. The energy dispersive spectrometry investigation (EDS) indicated that all the five respectively six elements were successfully co-deposited. The scanning electron microscopy (SEM) analysis revealed that the film consists of compact and uniform particles with particle sizes of 500 nm to 4 μm. The X-ray diffractometry (XRD) patterns indicated that the as-deposited thin films were amorphous. Body-centered-cubic (BCC) structures were identified by XRD after the films were annealed at various temperatures under inert Ar atmosphere. The alloys adhesion on the substrate was determined by the scratch-testing method, with higher values obtained for the Al-Cr-Cu-Fe-Mn-Ni alloy.

  10. 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer spin valve component investigated by polarized neutron reflectometry

    SciTech Connect

    Callori, S. J. Bertinshaw, J.; Cortie, D. L.; Cai, J. W. Zhu, T.; Le Brun, A. P.; Klose, F.

    2014-07-21

    We have observed 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer system using polarized neutron reflectometry. Magnetometry results show magnetic switching for both the biased and free NiFe layers, the latter of which reverses at low applied fields. As these measurements are only capable of providing information about the total magnetization within a sample, polarized neutron reflectometry was used to investigate the reversal behavior of the NiFe layers individually. Both the non-spin-flip and spin-flip neutron reflectometry signals were tracked around the free NiFe layer hysteresis loop and were used to detail the evolution of the magnetization during reversal. At low magnetic fields near the free NiFe coercive field, a large spin-flip signal was observed, indicating magnetization aligned perpendicular to both the applied field and pinned layer.

  11. The microstructure of near-equiatomic B2/f.c.c. FeNiMnAl alloys

    SciTech Connect

    Baker, I.; Wu, H.; Wu, X.; Miller, M.K.; Munroe, P.R.

    2011-10-15

    A microstructural analysis of two FeNiMnAl alloys, Fe{sub 30}Ni{sub 20}Mn{sub 30}Al{sub 20} and Fe{sub 25}Ni{sub 25}Mn{sub 30}Al{sub 20}, was performed by a combination of atom probe tomography and transmission electron microscopy techniques. Although the microstructures of both alloys, which consist of alternating platelets aligned along < 100> of the B2-ordered phase, are similar to B2/b.c.c. two-phase alloys previously observed in the FeNiMnAl system, the two phases present in the current alloys are B2-ordered and f.c.c., with the latter phase being heavily twinned. Very fine ({approx} 5 nm) precipitates, whose chemistry was similar to that of the f.c.c. (Fe, Mn)-rich phase, were found within the B2 (Ni, Al)-rich phase in both alloys. - Highlights: {yields} The microstructures of the novel alloys Fe{sub 30}Ni{sub 20}Mn{sub 30}Al{sub 20} and Fe{sub 25}Ni{sub 25}Mn{sub 30}Al{sub 20} were characterized. {yields} Atom probe tomography and transmission electron microscopy were used in the study. {yields} A < 100>-aligned B2-ordered phase and heavily-twinned f.c.c. phase were present. {yields} Very fine (Fe, Mn)-rich precipitates were found within the B2 (Ni, Al)-rich phase.

  12. Preparation, characterization, and phosphate removal and recovery of magnetic MnFe2O4 nano-particles as adsorbents.

    PubMed

    Xia, Shumei; Xu, Xiaoming; Xu, Changsong; Wang, Hongshuai; Zhang, Xiaowei; Liu, Guangmin

    2016-01-01

    Phosphate removal is an important method for controlling eutrophication in bodies of water. Adsorption is an effective phosphate removal approach. In this research, the adsorbent, namely, MnFe2O4, was prepared through the improved co-precipitation method and investigated in terms of phosphate removal. MnFe2O4 was characterized by scanning electron microscopy, vibrating sample magnetometry, X-ray diffraction, and Fourier transform infrared spectroscopy. Phosphate adsorption by MnFe2O4, desorption of adsorbed MnFe2O4 with the regeneration of desorbed MnFe2O4, and phosphate recovery were researched. Experimental results showed that adding the appropriate amount of polyethylene glycol to MnFe2O4 precursors during preparation inhibited the agglomeration of MnFe2O4 between particles because of the magnetic property of MnFe2O4 etc. High crystallinity and strong magnetism were achieved by MnFe2O4 at low temperatures. Average particle size was 5.1 nm. The hysteresis loops confirmed the ferrimagnetic behaviour of MnFe2O4 with a high saturation magnetization (i.e. 26.27 emu/g). The adsorption mechanism of phosphate was mainly physical. The prepared MnFe2O4 had a spinel structure. The proposed technique achieved a phosphate removal rate of 96.06%. A considerable amount of phosphate was desorbed from the adsorbed MnFe2O4 in 15 w/v% NaOH solution. The adsorption capacity of the desorbed MnFe2O4 could be restored to 96.73% in 10 w/v% NaNO3 solution through ion exchange. A sustainable phosphate source was recovered via hydroxyapatite crystallization in the desorption solution, which contained an abundant amount of phosphate as seed for suitable recovery condition. This finding suggested that MnFe2O4 could be a promising adsorbent for efficient phosphate removal. PMID:26292922

  13. The Microstructure of Near-Equiatomic B2/f.c.c. FeNiMnAl Alloys

    SciTech Connect

    Baker, Ian; Wu, H; Wu, Xiaolan; Miller, Michael K; Munroe, P R

    2011-01-01

    A microstructural analysis of two FeNiMnAl alloys, Fe{sub 30}Ni{sub 20}Mn{sub 30}Al{sub 20} and Fe{sub 25}Ni{sub 25}Mn{sub 30}Al{sub 20}, was performed by a combination of atom probe tomography and transmission electron microscopy techniques. Although the microstructures of both alloys, which consist of alternating platelets aligned along <100> of the B2-ordered phase, are similar to B2/b.c.c. two-phase alloys previously observed in the FeNiMnAl system, the two phases present in the current alloys are B2-ordered and f.c.c., with the latter phase being heavily twinned. Very fine ({approx} 5 nm) precipitates, whose chemistry was similar to that of the f.c.c. (Fe, Mn)-rich phase, were found within the B2 (Ni, Al)-rich phase in both alloys.

  14. Ductile-brittle-ductile transition and grain boundary segregation of Mn and Ni in an Fe-6Mn-12Ni alloy

    SciTech Connect

    Heo, N.H.

    1996-05-15

    Recently, Heo and Lee reported a ductile-brittle-ductile (DBD) transition in an Fe-8Mn-7Ni ternary alloy, which was caused by manganese segregation to the grain boundaries and its desegregation into the matrix. More recently Heo theoretically analyzed the nonequilibrium segregation behaviors of the elements in the Fe-8Mn-7Ni alloy. The aim of the present study is to investigate whether other Fe-6Mn-12Ni ternary alloy also shows the ductile-brittle-ductile transition, and is additionally to ascertain whether calculated results are consistent with experimental data. The study encompasses experimental procedures and a modeling based on the previous research. A general discussion will show that such an approach allows a comprehensive understanding of the ductile-brittle-ductile transition in the Fe-Mn-Ni ternary alloys.

  15. Biocompatibility of Mn0.4Zn0.6Fe2O4 Magnetic Nanoparticles and Their Thermotherapy on VX2-Carcinoma-Induced Liver Tumors.

    PubMed

    Yuan, Chun-Yan; Tang, Qiu-Sha; Zhang, Dong-Sheng

    2015-01-01

    Malignant tumors are the most serious threat to human health. Much research has focused on revealing the characteristics of this disease and developing methods of treatment. Because tumor cells are more sensitive to heat than normal cells, thermotherapy for the treatment of tumors has attracted much attention. In this paper, we presented functional Mn-Zn ferrite nanoparticles with the molecular composition of Mn0.4Zn0.6Fe2O4 as the magnetic response material for the thermotherapy. The suggested Mn-Zn ferrite nanoparticles were with a self-regulation temperature of 43 degrees C which was ideal for tumor thermotherapy. The biocompatibility and anti-tumor effect of this material were well investigated. It was found that the Mn0.4Zn0.6Fe2O4 nanoparticles have no hemolysis activity, no genotoxic effects and cytotoxicity. Its Median Lethal Dose (LD50) arrived at 6.026 g/kg and it did not induce any abnormal clinical signs in laboratory animals. Moreover, the suggested nanoparticles can increase the inhibitory ratio of weight and volume of tumors, cause tumor tissues necrosis and show the therapeutic effect on the xenograft live cancers in vivo. Based on these results, we could envision the valuable application of the Mn0.4Zn0.6Fe2O4 nanoparticles for the practical thermotherapy. PMID:26328307

  16. Effects of Mn content on the deformation behavior of Fe-Mn-Al-C TWIP steels — A computational study

    SciTech Connect

    Wang, Yuan; Sun, Xin; Wang, Y. D.; Zbib, Hussein M.

    2015-04-01

    This paper presents a double-slip/double-twin polycrystal plasticity model using finite element solution to investigate the kinetics of deformation twinning of low-to-medium manganese (Mn) twinning-induced plasticity (TWIP) steels. Empirical equations are employed to estimate the stacking fault energy (SFE) of TWIP steels and the critical resolved shear stress (CRSS) for dislocation slip and deformation twinning, respectively. The results suggest that the evolution of twinning in Fe-xMn-1.4Al-0.6C (x=11.5, 13.5, 15.5, 17.5 and 19.5) TWIP steels, and its relation to the Mn content, can explain the effect of Mn on mechanical properties.the stress-strain. By comparing the double-slip/double-twin model to a double-slip model, the predicted results essentially reveal that the interaction behavior between dislocation slip and deformation twinning can lead to an additional work hardening. Also, numerical simulations are carried out to study the influence of boundary conditions on deformation behavior and twin formation. The nucleation and growth of twinning are found to depend on internal properties (e.g., mismatch orientation of grains and stress redistribution) as well as on external constraints (e.g., the applied boundary conditions) of the material.

  17. Effect of Manganese on Microstructures and Solidification Modes of Cast Fe-Mn-Si-Cr-Ni Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Peng, Huabei; Wen, Yuhua; Du, Yangyang; Yu, Qinxu; Yang, Qin

    2013-10-01

    We investigated microstructures and solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys to clarify whether Mn was an austenite former during solidification. Furthermore, we examined whether the Creq/Nieq equations (Delong, Hull, Hammer and WRC-1992 equations) and Thermo-Calc software® together with database TCFE6 were valid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys. The results have shown that the solidification modes of Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni alloys changed from the F mode to the FA mode with increasing the Mn concentration. Mn is an austenite former during the solidification for the cast Fe-Mn-Si-Cr-Ni shape memory alloys. The Delong, Hull, Hammer, and WRC-1992 equations as well as Thermo-Calc software® together with database TCFE6 are invalid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni SMAs. To predict the solidification modes of cast Fe-Mn-Si-Cr-Ni alloys, a new Creq/Nieq equation should be developed or the thermodynamic database of Thermo-Calc software® should be corrected.

  18. Investigation of magnetic properties of MnBi/Co and MnBi/Fe65Co35 nanocomposite permanent magnets by micro-magnetic simulation

    NASA Astrophysics Data System (ADS)

    Li, Y. Q.; Yue, M.; Wang, T.; Wu, Q.; Zhang, D. T.; Gao, Y.

    2015-11-01

    Demagnetization curves of anisotropic nanocomposite MnBi/Co and MnBi/Fe65Co35 permanent magnets were investigated by micro-magnetic finite element method. Effects of volume ratio, deviation degree of orientation and intrinsic magnetic properties of the soft magnetic phase on the magnetic properties of the magnets were investigated. From the viewpoint of practical applications, to meet the requirement of hardness parameters, ĸ=K/(μ0MS2)1/2>1, the calculation maximum (BH)max of MnBi/Co and MnBi/Fe65Co35 magnets are about 199 kJ/m3 (V(Co)=22 vol%) and 196 kJ/m3 (V(FeCo)=14 vol%), respectively, indicating their good potential in application. Compared with single phase MnBi magnet, the (BH)max of nanocomposite MnBi/Co and MnBi/Fe65Co35 magnets increases by 66% and 63%, respectively. The remanence and coercivity of MnBi/Co nanocomposite magnets reduce as appearing a deviation degree of orientation, result of greatly decrease of the magnetic energy product.

  19. Charge and magnetic states of Mn-, Fe-, and Co-doped monolayer MoS{sub 2}

    SciTech Connect

    Lin, Xianqing; Ni, Jun

    2014-07-28

    First-principles calculations have been performed to investigate the electronic and magnetic properties of monolayer MoS{sub 2} substitutionally doped with Mn, Fe, and Co in possible charge states (q). We find that the Mn, Fe, and Co dopants substituting for a Mo atom in monolayer MoS{sub 2} (Mn@Mo, Fe@Mo, and Co@Mo) are all magnetic in their neutral and charge states except in the highest positive charge states. Mn@Mo, Fe@Mo, and Co@Mo have the same highest negative charge states of q=−2 for chemical potential of electron just below the conduction band minimum, which corresponds to the electron doping. In the q=−2 state, Mn@Mo has a much larger magnetic moment than its neutral state with the antiferromagnetic coupling between the Mn dopant and its neighboring S atoms maintained, while Fe@Mo and Co@Mo have equal or smaller magnetic moments than their neutral states. The possible charge states of Mn@Mo, Fe@Mo, and Co@Mo and the variation of the magnetic moments for different dopants and charge states are due to the change of the occupation and energy of the anti-bonding defect levels in the band gap. The rich magnetic properties of the neutral and charge states suggest possible realization of the substitutionally Mn-, Fe-, and Co-doped monolayer MoS{sub 2} as dilute magnetic semiconductors.

  20. Mechanical and hardness evaluations of Fe-18Cr-18Mn alloys

    SciTech Connect

    Rawers, J.C.; Duttlinger, N.W.

    2008-01-01

    A series of Fe-18Cr-18Mn-N-C alloys was produced and evaluated to determine their mechanical and hardness properties. In one group, different levels of nitrogen and carbon were added to a base composition of Fe-18Cr-18Mn. The base Fe-18Cr-18Mn alloy had a fcc-bcc duplex microstructure. The addition of nitrogen and carbon stabilised the fcc phase. These alloys had increasing room temperature hardness, strength, and failure energy with increasing interstitial concentrations. At cryogenic and elevated temperatures, these alloys had increasing hardness (and by implication, increased strength) with increasing interstitial concentrations. In a second group, different levels of nitrogen and carbon were added to the base Fe-18Cr-18Mn composition to which minor solid solution additions of silicon, molybdenum, and nickel had been added. Minor alloy additions made only nominal improvement to mechanical and hardness properties. Nitrogen remained interstitial. However, these minor solid solution additions reduced carbon solubility resulting in the formation of M23C6 precipitates that, while increasing alloy hardness and strength, greatly reduced fracture toughness. The present study suggests that replacing nickel with manganese in stainless steels results not only in more economical alloys but also in alloys with higher strength and hardness.

  1. Microstructural, mechanical, corrosion and cytotoxicity characterization of the hot forged FeMn30(wt.%) alloy.

    PubMed

    Čapek, Jaroslav; Kubásek, Jiří; Vojtěch, Dalibor; Jablonská, Eva; Lipov, Jan; Ruml, Tomáš

    2016-01-01

    An interest in biodegradable metallic materials has been increasing in the last two decades. Besides magnesium based materials, iron-manganese alloys have been considered as possible candidates for fabrication of biodegradable stents and orthopedic implants. In this study, we prepared a hot forged FeMn30 (wt.%) alloy and investigated its microstructural, mechanical and corrosion characteristics as well as cytotoxicity towards mouse L 929 fibroblasts. The obtained results were compared with those of iron. The FeMn30 alloy was composed of antiferromagnetic γ-austenite and ε-martensite phases and possessed better mechanical properties than iron and even that of 316 L steel. The potentiodynamic measurements in simulated body fluids showed that alloying with manganese lowered the free corrosion potential and enhanced the corrosion rate, compared to iron. On the other hand, the corrosion rate of FeMn30 obtained by a semi-static immersion test was significantly lower than that of iron, most likely due to a higher degree of alkalization in sample surrounding. The presence of manganese in the alloy slightly enhanced toxicity towards the L 929 cells; however, the toxicity did not exceed the allowed limit and FeMn30 alloy fulfilled the requirements of the ISO 10993-5 standard. PMID:26478385

  2. Nickel-free Fe-12Mn-0.2Ti alloy steel for cryogenic applications

    NASA Technical Reports Server (NTRS)

    Hwang, S.; Jin, S.; Morris, J. W., Jr.

    1976-01-01

    A nickel-free Fe-12Mn-0.2Ti alloy steel was investigated for cryogenic applications. The systematic control of the grain size and the microstructural distribution of the retained gamma phase was made through alpha plus gamma heat treatments in combination with mechanical working. Substantial improvements of important low temperature mechanical properties were obtained by these processings.

  3. The Formation of Crystal Defects in a Fe-Mn-Si Alloy Under Cyclic Martensitic Transformations.

    PubMed

    Bondar, Vladimir I; Danilchenko, Vitaliy E; Iakovlev, Viktor E

    2016-12-01

    Formation of crystalline defects due to cyclic martensitic transformations (CMT) in the iron-manganese Fe-18 wt.% Mn-2 wt.% Si alloy was investigated using X-ray diffractometry. Conditions for accumulation of fragment sub-boundaries with low-angle misorientations and chaotic stacking faults in crystal lattice of austenite and ε-martensite were analyzed. PMID:26960743

  4. Superhalogen Behavior of FeO4 MnO_4

    NASA Astrophysics Data System (ADS)

    Gutsev, G. L.; Khanna, S. N.; Jena, P.; Rao, B. K.

    2000-03-01

    Superhalogens are a class of cluster compounds that possess electron affinities in excess of 3.6 eV which is the electron affinity of chlorine, the most electronegative element in the periodic table. For clusters containing oxygen, a superhalogen has to satisfy the composition MO_n, where 2n=k+1. Here k is the maximal valence of the central atom M and n is the number of oxygen atoms. This requirement is fulfilled for MnO4 as the maximal valence of Mn is 7. However, FeO4 should be a closed shell system as the maximal valence of Fe is 8. Consequently, it should possess a relatively low electron affinity. We have performed self-consistent calculations of the total energy and geometry of FeO4 and MnO4 clusters in the neutral and anionic configurations using gradient corrected density functional theory and molecular orbital approach. The electron affinity of MnO4 was found to be 5 eV and as expected, is a superhalogen. Contrary to expectation, FeO4 too was found to have a large electron affinity, namely 3.8 eV and thus, belongs to the superhalogen class. The origin of this large electron affinity of a closed shell system is shown to be a manifestation of the special bonding characterstic of d-electron systems.

  5. Effect of Fe doping on the electrochemical capacitor behavior of MnO2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Poonguzhali, R.; Shanmugam, N.; Gobi, R.; Senthilkumar, A.; Viruthagiri, G.; Kannadasan, N.

    2015-10-01

    In this work, the influence of Fe doping on the capacitance behavior of MnO2 nanoparticles synthesized by chemical precipitation was investigated. During the doping process the concentration of Fe was increased from 0.025 M to 0.125 M in steps of 0.025 M. The products obtained were characterized by X-ray diffraction, Fourier infrared spectroscopy, scanning electron microscopy and N2 adsorption-desorption isotherms. To demonstrate the suitability of Fe-doped MnO2 for capacitor applications, cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance were recorded. Among the different levels of doping, the specific capacitance of 912 F/g was delivered by 0.075 M of Fe-doped MnO2 at a scan rate of 10 mV/s, which is almost more than fourfold that of the bare MnO2 electrode (210 F/g). Moreover, for the same concentration the charge, discharge studies revealed the highest specific capacitance of 1084 F/g at a current density of 10 A/g.

  6. Elasticity and magnetocaloric effect in MnFe4Si3

    NASA Astrophysics Data System (ADS)

    Herlitschke, M.; Klobes, B.; Sergueev, I.; Hering, P.; Perßon, J.; Hermann, R. P.

    2016-03-01

    The room temperature magnetocaloric material MnFe4Si3 was investigated with nuclear inelastic scattering (NIS) and resonant ultrasound spectroscopy (RUS) at different temperatures and applied magnetic fields in order to assess the influence of the magnetic transition and the magnetocaloric effect on lattice dynamics. The NIS data give access to phonons with energies above 3 meV, whereas RUS probes the elasticity of the material in the MHz frequency range and thus low-energy, ˜ neV, phonon modes. A significant influence of the magnetic transition on the lattice dynamics is observed only in the low-energy, long-wavelength limit. MnFe4Si3 and other compounds in the Mn5 -xFexSi3 series were also investigated with vibrating sample magnetometry, resistivity measurements, and Mössbauer spectroscopy in order to study the magnetic transitions and to complement the results obtained on the lattice dynamics.

  7. Precipitates and Grain Boundary Strength of an Fe-Mn-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Heo, Yoon-Uk; Jang, Jae Hoon; Lee, Hu-Chul

    2012-11-01

    The effect of grain boundary (GB) precipitates on the GB strength of an age-hardened Fe-7.8Mn-8.2Ni alloy was investigated. Premature intergranular fracture was observed after age hardening due to the precipitation of θ-MnNi precipitates at prior austenite grain boundaries. However, the conversion of GB θ precipitates to austenite by a short second aging at 793 K (520 °C) after peak aging at 713 K (440 °C) resulted in a remarkable improvement of GB strength. The result strongly supports the proposition that the weak bonding of GB θ precipitates to the matrix is the main reason for GB embrittlement in age-hardened Fe-Mn-Ni alloys.

  8. Elasticity and magnetocaloric effect in MnFe4Si3

    DOE PAGESBeta

    Herlitschke, Marcus; Klobes, B.; Sergueev, I.; Hering, Paul; Persson, Joerg; Hermann, Raphael P.

    2016-03-16

    The room temperature magnetocaloric material MnFe4Si3 was investigated with nuclear inelastic scattering (NIS) and resonant ultrasound spectroscopy (RUS) at different temperatures and applied magnetic fields in order to assess the infuence of the magnetic transition and the magnetocaloric effect on the lattice dynamics. The NIS data give access to phonons with energies above 3 meV, whereas RUS probes the elasticity of the material in the MHz frequency range and thus low energy, ~5 neV, phonon modes. A significant infuence of the magnetic transition on the lattice dynamics is observed only in the low energy region. Here, MnFe4Si3 and other compoundsmore » in the Mn5-xFexSi3 series were also investigated with vibrating sample magnetometry, resistivity measurements and Moessbauer spectroscopy in order to study the magnetic transitions and to complement the obtained results on the lattice dynamics.« less

  9. Structural stability, half-metallicity and magnetism of the CoFeMnSi/GaAs(0 0 1) interface

    NASA Astrophysics Data System (ADS)

    Feng, Yu; Chen, Xiaorui; Zhou, Ting; Yuan, Hongkuan; Chen, Hong

    2015-08-01

    The ferromagnet/semiconductor interface plays a crucial role in the performance of advanced magnetic tunnel junctions (MTJs) built of ferromagnetic electrodes and semiconductor as a spacer. We investigate the interface character between LiMgPbSb-type Heusler alloy CoFeMnSi and semiconductor GaAs by using the first-principles density functional simulations. In our calculations, we build two kinds of interface structures, namely the top-type and the bridge-type structure by connecting the termination of nine CoFeMnSi layers to the top of the As-terminated GaAs layer and the bridge site between interface As atoms, respectively. The calculated phase diagram indicated that the CoFe-terminated interface is more stable in the bridge-type structure than in the top-type structure, and a favored MnMn- or MnSi-terminated interface will appear in the top-type structure instead of the bridge-type structure under Fe-rich conditions. Besides, our calculation reveals that interface Mn and interface Fe atoms prefer to extend outward and their atom-resolved spin magnetic moments are enhanced due to the rehybridization caused by the symmetry breaking at the interface, while interface Co atoms shrink inward and their moments are decreased compared with the bulk value. Further analysis on DOS and PDOS indicates that owing to the interface effect, the half metallicity of CoFe-, MnSi-, and SiSi-terminated interfaces is completely destroyed. However, the MnMn-terminated interface in the top-type structure preserves 100% spin polarization, indicating that the CoFeMnSi/GaAs heterostructure with the top-type MnMn-terminated interface has more advantages than other atomic terminations in spintronics applications.

  10. Effect of CoFe insertion in Co{sub 2}MnSi/CoFe/n-GaAs junctions on spin injection properties

    SciTech Connect

    Ebina, Yuya; Akiho, Takafumi; Liu, Hong-xi; Yamamoto, Masafumi; Uemura, Tetsuya

    2014-04-28

    The CoFe thickness (t{sub CoFe}) dependence of spin injection efficiency was investigated for Co{sub 2}MnSi/CoFe/n-GaAs junctions. The ΔV{sub NL}/I value, which is a measure of spin injection efficiency, strongly depended on t{sub CoFe}, where ΔV{sub NL} is the amplitude of a nonlocal spin-valve signal, and I is an injection current. Importantly, the maximum value of ΔV{sub NL}/I for a Co{sub 2}MnSi/CoFe/n-GaAs junction was one order of magnitude higher than that for a CoFe/n-GaAs junction, indicating that a Co{sub 2}MnSi electrode works as a highly polarized spin source. No clear spin signal, on the other hand, was observed for a Co{sub 2}MnSi/n-GaAs junction due to diffusion of Mn atoms into the GaAs channel. Secondary ion mass spectrometry analysis indicated that the CoFe insertion effectively suppressed the diffusion of Mn into GaAs, resulting in improved spin injection properties compared with those for a Co{sub 2}MnSi/n-GaAs junction.

  11. The synthesized and thermally modified Mn-Ca-FeOOH composite in persulfate system: Its role to discolor methylene blue

    NASA Astrophysics Data System (ADS)

    Jo, Young-Hoon; Hong, Seong-Ho; Park, Tae-Jin; Do, Si-Hyun

    2014-05-01

    Methylene blue (MB) discoloration was performed using persulfate (PS) activated with the synthesized composites. Four types of composites, which were synthesized by the immobilization of Mn on iron oxides (hematite and goethite) using either NaOH or Ca(OH)2, were evaluated as PS activator. The synthesized Mn-Ca-FeOOH composite was selected and it was thermally modified at 300 and 700 °C (denoted Mn-Ca-FeOOH_300 and Mn-Ca-FeOOH_700). The BET surface area of Mn-Ca-FeOOH_300 was similar to that of Mn-Ca-FeOOH while that of Mn-Ca-FeOOH_700 was dramatically lower. XRD and XPS analysis indicated that the thermal modification transformed iron oxides from goethite to hematite and changed amorphous manganese oxide to crystalline. MB discoloration at pH 3 indicated that Mn-Ca-FeOOH acted as an oxidant to degrade MB, and the thermally modified composites (i.e. Mn-Ca-FeOOH_300 and Mn-Ca-FeOOH_700) acted as a catalyst to activate PS. Moreover, incomplete MB discoloration was observed in PS/composite system at pH 3. However, a whole tested wavelength of MB was reduced when MB discoloration was tested in PS/composite system above pH 7. Moreover, the increasing pH of solution increased MB discoloration. The higher MB discoloration in heterogeneous system at pH 12 could suggest that superoxide anion (O2•-) was dominant reactive oxygen species.

  12. Perpendicular exchange bias effect in sputter-deposited CoFe/IrMn bilayers

    SciTech Connect

    Chen, J. Y. Thiyagarajah, Naganivetha; Xu, H. J.; Coey, J. M. D.

    2014-04-14

    CoFe/IrMn bilayers with perpendicular magnetization for various IrMn layer thicknesses exhibit unusual two-step hysteresis loops with both positive and negative loop shifts. Observed at room temperature in the as-grown state, they provide direct evidence of large antiferromagnetic domain formation at the IrMn interface. The exchange bias field reaches 100 mT with an IrMn layer thickness of 4 nm after field annealing at 200 °C–300 °C in 800 mT, which is at least three times as large as the coercivity, and may be useful for reference layers of spin-valves or magnetic tunnel junctions with perpendicular magnetic anisotropy.

  13. Exchange bias effects in Heusler alloy Ni2MnAl/Fe bilayers

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Tomoki; Kubota, Takahide; Sugiyama, Tomoko; Huminiuc, Teodor; Hirohata, Atsufumi; Takanashi, Koki

    2016-06-01

    Ni2MnAl Heusler alloy thin films were epitaxially grown on MgO(1 0 0) single crystal substrates by ultra-high-vacuum magnetron sputtering technique. X-ray diffraction and transmission electron microscopy observation revealed that the structures of all the Ni2MnAl thin films were B2-ordered regardless of the deposition temperature ranging from room temperature to 600 °C. The temperature dependence of electrical resistivity showed a kink about 280 K, which was consistent with a reported value of the Néel temperature for antiferromagnetic B2-Ni2MnAl. The magnetization curves of Ni2MnAl/Fe bilayer samples showed a shift caused by the interfacial exchange interaction at 10 K. The maximum value of the exchange bias field H ex was 55 Oe corresponding to the exchange coupling energy J k of 0.03 erg cm‑2.

  14. MnFe2O4@C Nanofibers as High-Performance Anode for Sodium-Ion Batteries.

    PubMed

    Liu, Yongchang; Zhang, Ning; Yu, Chuanming; Jiao, Lifang; Chen, Jun

    2016-05-11

    MnFe2O4 nanodots (∼3.3 nm) homogeneously dispersed in porous nitrogen-doped carbon nanofibers (denoted as MFO@C) were prepared by a feasible electrospinning technique. Meanwhile, MFO@C with the character of flexible free-standing membrane was directly used as binder- and current collector-free anode for sodium-ion batteries, exhibiting high electrochemical performance with high-rate capability (305 mA h g(-1) at 10000 mA g(-1) in comparison of 504 mA h g(-1) at 100 mA g(-1)) and ultralong cycling life (ca. 90% capacity retention after 4200 cycles). The Na-storage mechanism was systematically studied, revealing that MnFe2O4 is converted into metallic Mn and Fe after the first discharge (MnFe2O4 + 8Na(+) + 8e(-) → Mn + 2Fe + 4Na2O) and then to MnO and Fe2O3 during the following charge (Mn + 2Fe + 4Na2O → MnO + Fe2O3 + 8Na(+) + 8e(-)). The subsequent cycles occur through reversible redox reactions of MnO + Fe2O3 + 8Na(+) + 8e(-) ↔ Mn + 2Fe + 4Na2O, of which the reduction/oxidation of MnO/Mn takes place at a lower potential than that of Fe2O3/Fe. Furthermore, a soft package sodium-ion full battery with MFO@C anode and Na3V2(PO4)2F3/C cathode was assembled, delivering a stable capacity of ∼400 mA h g(-1) for MFO@C (with 100 cycles at 500 mA g(-1)) and a promising energy density of 77.8 Wh kg(-1) for the whole battery. This is owing to the distinctive structure of very-fine MnFe2O4 nanodots embedded in porous N-doped carbon nanofibers, which effectively improves the utilization rate of active materials, facilitates the transportation of electrons and Na(+) ions, and prevents the particle pulverization/agglomeration upon prolonged cycling. PMID:27050390

  15. Phosphorites, Co-rich Mn nodules, and Fe-Mn crusts from Galicia Bank, NE Atlantic: Reflections of Cenozoic tectonics and paleoceanography

    NASA Astrophysics Data System (ADS)

    González, Francisco Javier; Somoza, Luis; Hein, James R.; Medialdea, Teresa; León, Ricardo; Urgorri, Victoriano; Reyes, Jesús; Martín-Rubí, Juan Antonio

    2016-02-01

    A wide variety of marine mineral deposits were recovered from 750 to 1400 m water depths on Galicia Bank, Iberian margin. Mineral deposits include: (1) carbonate fluorapatite phosphorite slabs and nodules that replaced limestone and preserved original protolith fabric. (2) Ferromanganese vernadite crusts with high Mn and Fe (Mn/Fe = 1) contents, and thick stratabound layers consisting mainly of Mn (up to 27% MnO) and Fe (15% Fe2O3), which impregnated and replaced the phosphorite. (3) Co-rich Mn nodules are composed of romanechite and todorokite laminae. Mn-rich layers (up to 58% MnO) contain up to 1.8% Co. (4) Goethite nodules with Fe up to 67% Fe2O3 have low Mn and trace metals. We interpret this mineralization paragenesis to be related to major changes in oceanographic and tectonic regimes. Three phosphatization generations formed hardgrounds dated by 87Sr/86Sr isotopes as late Oligocene, early Miocene, and latest early Miocene. During the latest early Miocene, the hardground was fractured and breached due to regional intraplate tectonism, which was coeval with a widespread regional erosional unconformity. The stratabound layers and Co-rich manganese nodules were derived from low-temperature geothermally driven hydrothermal fluids, with fluid conduits along reactivated faults. During middle and late Miocene, the introduction of vigorous deep water flow from the Arctic generated growth of hydrogenetic ferromanganese crusts. Finally, growth of diagenetic Fe-rich nodules (late Pliocene) was promoted by the introduction of hypersaline Mediterranean Outflow Water into the Atlantic Ocean.

  16. Elevated Temperature Deformation of Fe-39.8Al and Fe-15.6Mn-39.4Al

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel

    2004-01-01

    The elevated temperature compressive properties of binary Fe-39.8 at % Al and Fe-15.6Mn-39.4Al have been measured between 1000 and 1300 K at strain rates between 10(exp 7) and 10(exp 3)/ s. Although the Mn addition to iron aluminide did not change the basic deformation characteristics, the Mn-modified alloy was slightly weaker. In the regime where deformation of FeAl occurs by a high stress exponent mechanism (n = 6), strength increases as the grain size decreases at least for diameters between approx. 200 and approx. 10 microns. Due to the limitation in the grain size-flow stress-temperature-strain rate database, the influence of further reductions of the grain size on strength is uncertain. Based on the appearance of subgrains in deformed iron aluminide, the comparison of grain diameters to expected subgrain sizes, and the grain size exponent and stress exponent calculated from deformation experiments, it is believed that grain size strengthening is the result of an artificial limitation on subgrain size as proposed by Sherby, Klundt and Miller.

  17. Phase Field Modeling of Cyclic Austenite-Ferrite Transformations in Fe-C-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Chen, Hao; Zhu, Benqiang; Militzer, Matthias

    2016-08-01

    Three different approaches for considering the effect of Mn on the austenite-ferrite interface migration in an Fe-0.1C-0.5Mn alloy have been coupled with a phase field model (PFM). In the first approach (PFM-I), only long-range C diffusion is considered while Mn is assumed to be immobile during the phase transformations. Both long-range C and Mn diffusions are considered in the second approach (PFM-II). In the third approach (PFM-III), long-range C diffusion is considered in combination with the Gibbs energy dissipation due to Mn diffusion inside the interface instead of solving for long-range diffusion of Mn. The three PFM approaches are first benchmarked with isothermal austenite-to-ferrite transformation at 1058.15 K (785 °C) before considering cyclic phase transformations. It is found that PFM-II can predict the stagnant stage and growth retardation experimentally observed during cycling transformations, whereas PFM-III can only replicate the stagnant stage but not the growth retardation and PFM-I predicts neither the stagnant stage nor the growth retardation. The results of this study suggest a significant role of Mn redistribution near the interface on reducing transformation rates, which should, therefore, be considered in future simulations of austenite-ferrite transformations in steels, particularly at temperatures in the intercritical range and above.

  18. Phase Field Modeling of Cyclic Austenite-Ferrite Transformations in Fe-C-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Chen, Hao; Zhu, Benqiang; Militzer, Matthias

    2016-06-01

    Three different approaches for considering the effect of Mn on the austenite-ferrite interface migration in an Fe-0.1C-0.5Mn alloy have been coupled with a phase field model (PFM). In the first approach (PFM-I), only long-range C diffusion is considered while Mn is assumed to be immobile during the phase transformations. Both long-range C and Mn diffusions are considered in the second approach (PFM-II). In the third approach (PFM-III), long-range C diffusion is considered in combination with the Gibbs energy dissipation due to Mn diffusion inside the interface instead of solving for long-range diffusion of Mn. The three PFM approaches are first benchmarked with isothermal austenite-to-ferrite transformation at 1058.15 K (785 °C) before considering cyclic phase transformations. It is found that PFM-II can predict the stagnant stage and growth retardation experimentally observed during cycling transformations, whereas PFM-III can only replicate the stagnant stage but not the growth retardation and PFM-I predicts neither the stagnant stage nor the growth retardation. The results of this study suggest a significant role of Mn redistribution near the interface on reducing transformation rates, which should, therefore, be considered in future simulations of austenite-ferrite transformations in steels, particularly at temperatures in the intercritical range and above.

  19. Tailoring Mg(x)Mn(1-x)Fe(2)O(4) superparamagnetic nanoferrites for magnetic fluid hyperthermia applications.

    PubMed

    Jeun, Minhong; Park, Sungwook; Jang, Gun Hyuk; Lee, Kwan Hyi

    2014-10-01

    A superparamagnetic nanoferrite (SPNF) with high magnetic moment, AC magnetically induced heating (AC-heating) capacity, and good biocompatibility is the most vital part of magnetic fluid hyperthermia for utilizing it in the clinics. Herein, we precisely tune magnetic properties and AC-heating characteristics of MgxMn1-xFe2O4 SPNF via chemically controlling the cations' concentration and distribution to develop a tailored MgxMn1-xFe2O4 SPNF as a potential magnetic fluid hyperthermia agent. The magnetic and AC-heating characteristics of the tailored MgxMn1-xFe2O4 SPNF are strongly dependent on the Mg/Mn cations' concentration and distribution, and Mg0.285Mn0.715Fe2O4 SPNF exhibits the highest saturation magnetization and AC-heating capacity as well as high biocompatibility. PMID:25238143

  20. The magneto-structural transition in Mn1-x Fe x CoGe

    NASA Astrophysics Data System (ADS)

    Ren, Q. Y.; Hutchison, W. D.; Wang, J. L.; Studer, A. J.; Din, M. F. Md; Muñoz Pérez, S.; Cadogan, J. M.; Campbell, S. J.

    2016-05-01

    Large refrigeration capacities, between 212(30) J kg-1 and 261(40) J kg-1 for a magnetic field change from 0 T to 5 T, were obtained in Mn1-x Fe x CoGe (x  =  0.01, 0.02, 0.03 and 0.04) compounds. A partial magnetic phase diagram has been derived on the basis of magnetic transition and martensitic transformation temperatures determined from differential scanning calorimetry (200 K to 450 K), variable temperature x-ray diffraction (20 K to 310 K) and magnetisation measurements (5 K to 340 K 0.01 T). Mn1-x Fe x CoGe compounds with compositions in the range x  =  0.01 to 0.03 exhibit magneto-structural transitions. Neutron diffraction experiments were carried out on the Mn0.98Fe0.02CoGe sample over the temperature range of 5 K to 450 K. The diffraction patterns were analysed based on irreducible representation theory which confirms a ferromagnetic structure in the sample with an atomic magnetic moment of 3.7(1)μ B at 5 K on the Mn sublattice, oriented along the orthorhombic c axis. More significantly, a magneto-structural transition around T M ~ 297(1) K with a full width at half maximum of 29 K is demonstrated directly via neutron diffraction. Larger magnetic entropy changes are obtained for the Mn1-x Fe x CoGe (x  =  0.01, 0.02 and 0.03) samples than for Mn0.96Fe0.04CoGe which has separate structural and magnetic transitions. In addition, it is noted that standard Arrott plots do not provide unambiguous insight to the nature of the magneto-structural transition in the Mn1-x Fe x CoGe compounds.

  1. Molecular controls on Cu and Zn isotopic fractionation in Fe-Mn crusts

    NASA Astrophysics Data System (ADS)

    Little, S. H.; Sherman, D. M.; Vance, D.; Hein, J. R.

    2014-06-01

    The isotopic systems of the transition metals are increasingly being developed as oceanic tracers, due to their tendency to be fractionated by biological and/or redox-related processes. However, for many of these promising isotope systems the molecular level controls on their isotopic fractionations are only just beginning to be explored. Here we investigate the relative roles of abiotic and biotic fractionation processes in controlling modern seawater Cu and Zn isotopic compositions. Scavenging to Fe-Mn oxides represents the principal output for Cu and Zn to sediments deposited under normal marine (oxic) conditions. Using Fe-Mn crusts as an analogue for these dispersed phases, we investigate the phase association and crystal chemistry of Cu and Zn in such sediments. We present the results of an EXAFS study that demonstrate unequivocally that Cu and Zn are predominantly associated with the birnessite (δ-MnO2) phase in Fe-Mn crusts, as previously predicted from sequential leaching experiments (e.g., Koschinsky and Hein, 2003). The crystal chemistry of Cu and Zn in the crusts implies a reduction in coordination number in the sorbed phase relative to the free metal ion in seawater. Thus, theory would predict equilibrium fractionations that enrich the heavy isotope in the sorbed phase (e.g., Schauble, 2004). In natural samples, Fe-Mn crusts and nodules are indeed isotopically heavy in Zn isotopes (at ∼1‰) compared to deep seawater (at ∼0.5‰), consistent with the predicted direction of equilibrium isotopic fractionation based on our observations of the coordination environment of sorbed Zn. Further, ∼50% of inorganic Zn‧ is chloro-complexed (the other ∼50% is present as the free Zn2+ ion), and complexation by Cl- is also predicted to favour equilibrium partitioning of light Zn isotopes into the dissolved phase. The heavy Zn isotopic composition of Fe-Mn crusts and nodules relative to seawater can therefore be explained by an inorganic fractionation during

  2. High Curie temperature of Ce-Fe-Si compounds with ThMn12 structure

    SciTech Connect

    Zhou, C; Pinkerton, FE; Herbst, JF

    2015-01-15

    We report the discovery of ternary CeFe(12-x)Si(x)compounds possessing the ThMn12 structure. The samples were prepared by melt spinning followed by annealing. In contrast to other known Ce Fe-based binary and ternary compounds, CeFe12-xSix compounds exhibit exceptionally high Curie temperatures whose values increase with added Si substitution. The highest T. = 583 K in CeFe10Si2 rivals that of the well-established Nd2Fe14B compound. We ascribe the T-c behavior to a combination of Si-induced 3d band structure changes and partial Ce3+ stabilization. (C) 2014 Published by Elsevier Ltd.

  3. Carbon-coated Fe-Mn-O composites as promising anode materials for lithium-ion batteries.

    PubMed

    Li, Tao; Wang, Yue-Ya; Tang, Rui; Qi, Yong-Xin; Lun, Ning; Bai, Yu-Jun; Fan, Run-Hua

    2013-10-01

    Fe-Mn-O composite oxides with various Fe/Mn molar ratios were prepared by a simple coprecipitation method followed by calcining at 600 °C, and carbon-coated oxides were obtained by pyrolyzing pyrrole at 550 °C. The cycling and rate performance of the oxides as anode materials are greatly associated with the Fe/Mn molar ratio. The carbon-coated oxides with a molar ratio of 2:1 exhibit a stable reversible capacity of 651.8 mA h g(-1) at a current density of 100 mA g(-1) after 90 cycles, and the capacities of 567.7, 501.3, 390.7, and 203.8 mA h g(-1) at varied densities of 200, 400, 800, and 1600 mA g(-1), respectively. The electrochemical performance is superior to that of single Fe3O4 or MnO prepared under the same conditions. The enhanced performance could be ascribed to the smaller particle size of Fe-Mn-O than the individuals, the mutual segregation of heterogeneous oxides of Fe3O4 and MnO during delithiation, and heterogeneous elements of Fe and Mn during lithiation. PMID:24007324

  4. The centralized control of elemental mercury emission from the flue gas by a magnetic rengenerable Fe-Ti-Mn spinel.

    PubMed

    Liao, Yong; Xiong, Shangchao; Dang, Hao; Xiao, Xin; Yang, Shijian; Wong, Po Keung

    2015-12-15

    A magnetic Fe-Ti-Mn spinel was developed to adsorb gaseous Hg(0) in our previous study. However, it is currently extremely restricted in the control of Hg(0) emission from the flue gas for at least three reasons: sorbent recovery, sorbent regeneration and the interference of the chemical composition in the flue gas. Therefore, the effect of SO2 and H2O on the adsorption of gaseous Hg(0) on the Fe-Ti-Mn spinel and the regeneration of spent Fe-Ti-Mn spinel were investigated in this study. Meanwhile, the procedure of the centralized control of Hg(0) emission from the flue gas by the magnetic Fe-Ti-Mn spinel has been analyzed for industrial application. The spent Fe-Ti-Mn spinel can be regenerated by water washing followed by the thermal treatment at 450 °C with no obvious decrease of its ability for Hg(0) capture. Meanwhile, gaseous Hg(0) in the flue gas can be remarkably concentrated during the regeneration, facilitating its safe disposal. Initial pilot test demonstrated that gaseous Hg(0) in the real flue gas can be concentrated at least 100 times by the Fe-Ti-Mn spinel. Therefore, Fe-Ti-Mn spinel was a novel magnetic regenerable sorbent, which can be used for the centralized control of Hg(0) emission from the flue gas. PMID:26298264

  5. Mn abundances in the stars of the Galactic disc with metallicities -1.0 < [Fe/H] < 0.3

    NASA Astrophysics Data System (ADS)

    Mishenina, T.; Gorbaneva, T.; Pignatari, M.; Thielemann, F.-K.; Korotin, S. A.

    2015-12-01

    In this work, we present and discuss the observations of the Mn abundances for 247 FGK dwarfs, located in the Galactic disc with metallicity -1 < [Fe/H] < +0.3. The observed stars belong to the substructures of the Galaxy thick and thin disks, and to the Hercules stream. The observations were conducted using the 1.93 m telescope at Observatoire de Haute-Provence (OHP, France) equipped with the echelle-type spectrographs ELODIE and SOPHIE. The abundances were derived under the LTE approximation, with an average error for the [Mn/Fe] ratio of 0.10 dex. For most of the stars in the sample, Mn abundances are not available in the literature. We obtain an evolution of [Mn/Fe] ratio with the metallicity [Fe/H] consistent with previous data compilations. In particular, within the metallicity range covered by our stellar sample, the [Mn/Fe] ratio is increasing with the increase of metallicity. This due to the contribution to the Galactic chemical evolution of Mn and Fe from thermonuclear supernovae. We confirm the baseline scenario where most of the Mn in the Galactic disc and in the Sun is made by thermonuclear supernovae. In particular, the effective contribution from core-collapse supernovae to the Mn in the Solar system is about 10-20 per cent. However, present uncertainties affecting the production of Mn and Fe in thermonuclear supernovae are limiting the constraining power of the observed [Mn/Fe] trend in the Galactic discs on, e.g. the frequency of different thermonuclear supernovae populations. The different production of these two elements in different types of thermonuclear supernovae needs to be disentangled by the dependence of their relative production on the metallicity of the supernova progenitor.

  6. Differential coordination demands in Fe vs Mn water-soluble cationic metalloporphyrins translates into remarkably different aqueous redox chemistry and biology

    PubMed Central

    Tovmasyan, Artak; Weitner, Tin; Sheng, Huaxin; Lu, MiaoMiao; Rajic, Zrinka; Warner, David S.; Spasojevic, Ivan; Reboucas, Julio S.; Benov, Ludmil; Batinic-Haberle, Ines

    2013-01-01

    on fairly similar log kcat(O2.− values, very similar effect on the growth of SOD-deficient E. coli was anticipated by both metalloporphyrins. Yet, while MnTE-2-PyP5+ was fully efficacious at ≥20 μM, the Fe analog, FeTE-2-PyP5+ supported SOD-deficient E. coli growth at 200-fold lower doses in the range of 0.1 to 1 μM. Moreover the pattern of SOD-deficient E. coli growth was different with Mn- and Fe porphyrins. Such results suggested different mode of action of these metalloporphyrins. Further exploration demonstrated that: (1) 0.1 μM FeTE-2-PyP5+ provided similar growth stimulation as 0.1 μM Fe salt, while 20 μM Mn salt provides no protection to E. coli; and (2) 1 μM Fe porphyrin is fully degraded by 12 hours in E. coli cytosol and growth medium; while Mn porphyrin is not. Stimulation of the aerobic growth of SOD-deficient E. coli by the Fe porphyrin is therefore due to iron acquisition. Our data suggest that in vivo, redox-driven degradation of Fe porphyrins resulting in Fe release plays a major role in their biological action. Possibly, iron reconstitutes enzymes bearing [4Fe-4S] clusters as active sites. Under same experimental conditions, (OH)(H2O)FePs do not cause mouse arterial hypotension, whereas (H2O)2MnPs do, which greatly limits the application of Mn porphyrins in vivo. PMID:23646875

  7. Effect of Tb-Mn substitution on the magnetic and electrical properties of BiFeO3 ceramics

    NASA Astrophysics Data System (ADS)

    Saravana Kumar, K.; Aswini, P.; Venkateswaran, C.

    2014-09-01

    Tb-Mn co-substituted BiFeO3 of stoichiometry Bi1-xTbxFe1-xMnxO3 (x=0, 0.10, 0.15, 0.20) has been synthesized by a solid-state reaction method. Inferences from X-ray photoelectron spectroscopy indicate the presence of Fe in mixed oxidation states i.e., Fe3+ and Fe2+. But in the Tb-Mn substituted samples, Fe is predominantly in +3 oxidation state and Mn is found to be in +3 state. There is a decrease in cell volume due to Tb3+ substitution as Mn3+ ions have similar ionic radii as that of Fe3+. The grains of substituted samples have regular dimensions with agglomeration when compared to irregular shaped grains of BiFeO3. No major characteristic transitions are found in substituted samples as observed from the thermal measurements, but BiFeO3 shows a ferroelectric-paraelectric transition at ~820 °C. A weak magnetic ordering is observed from the magnetization measurements at room temperature with the increase in substitution percentage. Impedance spectroscopy studies show the impact of Tb-Mn substitution on the conductivity of BiFeO3. The ferroelectric loop and leakage current studies with an applied electric field on samples also supplement the results obtained from impedance measurements.

  8. Ab initio investigation of competing antiferromagnetic structures in low Si-content FeMn(PSi) alloy

    NASA Astrophysics Data System (ADS)

    Li, Guijiang; Eriksson, Olle; Johansson, Börje; Vitos, Levente

    2016-06-01

    The antiferromagnetic structures of a low Si-content FeMn(PSi) alloy were investigated by first principles calculations. One possible antiferromagnetic structure in supercell along the c-axis was revealed in FeMnP0.75Si0.25 alloy. It was found that atomic disorder occupation between Fe atom on 3f and Mn atoms on 3g sites is responsible for the formation of antiferromagnetic structures. Furthermore the magnetic competition and the coupling between possible AFM supercells along the c and a-axis can promote a non-collinear antiferromagnetic structure. These theoretical investigations help to deeply understand the magnetic order in FeMn(PSi) alloys and benefit to explore the potential magnetocaloric materials in Fe2P-type alloys.

  9. Ab initio investigation of competing antiferromagnetic structures in low Si-content FeMn(PSi) alloy.

    PubMed

    Li, Guijiang; Eriksson, Olle; Johansson, Börje; Vitos, Levente

    2016-06-01

    The antiferromagnetic structures of a low Si-content FeMn(PSi) alloy were investigated by first principles calculations. One possible antiferromagnetic structure in supercell along the c-axis was revealed in FeMnP0.75Si0.25 alloy. It was found that atomic disorder occupation between Fe atom on 3f and Mn atoms on 3g sites is responsible for the formation of antiferromagnetic structures. Furthermore the magnetic competition and the coupling between possible AFM supercells along the c and a-axis can promote a non-collinear antiferromagnetic structure. These theoretical investigations help to deeply understand the magnetic order in FeMn(PSi) alloys and benefit to explore the potential magnetocaloric materials in Fe2P-type alloys. PMID:27143642

  10. Effect of doping and elastic properties in (Mn,Fe ) 2(Si ,P )

    NASA Astrophysics Data System (ADS)

    Roy, P.; Torun, E.; de Groot, R. A.

    2016-03-01

    Mixed magnetism (the coexistence of strong and weak magnetism in one material) is regarded as the origin of the giant magnetocaloric effect (GMCE). A good example is (Mn,Fe ) 2(Si ,P ), which is established as one of the best magnetocaloric materials available. Tuning the material properties are essential for optimizing its performance, and a straightforward way to do that is by doping. In this article, an ab initio electronic structure method was used to calculate the structure and magnetic properties of 3 d -transition-metal-doped (Mn,Fe ) 2(Si ,P ) materials for magnetocaloric applications (transition metals are Cr, Co, Mn, Ni, Cu). For a steady performance, the material should be mechanically stable. A detailed analysis of the elastic constants shows that the mechanical stability of the (Mn,Fe ) 2(Si ,P ) system increases significantly by doping with boron without affecting the magnetic properties. Insights of the influence of doping enable future studies to understand and predict better magnetocaloric materials.

  11. The investigation of Fe-Mn-based alloys with shape memory effect by small-angle scattering of polarized neutrons

    NASA Astrophysics Data System (ADS)

    Kopitsa, G. P.; Runov, V. V.; Grigoriev, S. V.; Bliznuk, V. V.; Gavriljuk, V. G.; Glavatska, N. I.

    2003-07-01

    The small-angle polarized neutron scattering (SAPNS) technique has been used to study a nuclear and magnetic homogeneity in the distribution of both substituent (Si, Cr, Ni) and interstitial (C, N) alloying elements on the mesoscopic range in Fe-Mn-based alloys with shape memory effect (SME). The four groups of alloys with various basic compositions: FeMn 18 (wt%), FeMn 20Si 6, FeMn 20Cr 9N 0.2 and FeMn 17Cr 9Ni 4Si 6 were investigated. It was found that the small-angle scattering of neutrons and depolarization on these alloys are very small altogether. The scattering did not exceed 1.5% from the incident beam and depolarization ∼2% for all samples. It means that these alloys are well nuclear and magnetically homogeneous on the scale of 10-1000 Å. However, the difference in the homogeneity depending on the compositions still takes place. Thus, the adding of Si in FeMn 18 and FeMn 20Cr 9N 0.2 alloys improves the homogeneity pronouncedly. At once, the effect of the doping by C or N atoms on the homogeneity in FeMn 20Si 6 and FeMn 17Cr 9Ni 4Si 6 alloys is multivalued and depend on the presence of substitutional atoms (Ni and Cr). The capability of SAPNS as a method for the study of mesoscopic homogeneity in materials with SME and testing of the quality of their preparation is discussed.

  12. 238U-234U-230Th disequilibrium in hydrogenous oceanic Fe-Mn crusts: Palaeoceanographic record or diagenetic alteration?

    USGS Publications Warehouse

    Chabaux, F.; O'Nions, R. K.; Cohen, A.S.; Hein, J.R.

    1997-01-01

    A detailed TIMS study of (234Uexc/238U), (230Th/232Th), and Th/U ratios have been performed on the outermost margin of ten hydrogenous Fe-Mn crusts from the equatorial Pacific Ocean and west-central Indian Ocean. Th/U concentration ratios generally decrease from the crust's surface down to 0.5-1 mm depth and growth rates estimated by uranium and thorium isotope ratios are significantly different in Fe-Mn crusts from the Peru Basin and the west-central Indian Ocean. Fe-Mn crusts from the same geographical area define a single trend in plots of Ln (234Uexc/238U) vs. Ln(230Th/232Th) and Th/U ratios vs. age of the analysed fractions. Results suggest that (1) hydrogenous Fe-Mn crusts remain closed-systems after formation, and consequently (2) the discrepancy observed between the 230Th and 234U chronometers in Fe-Mn crusts, and the variations of the Th/U ratios through the margin of Fe-Mn crusts, are not due to redistribution of uranium and thorium isotopes after oxyhydroxide precipitation, but rather to temporal variations of both Th/U and initial thorium activity ratios recorded by the Fe-Mn layers. Implications of these observations for determination of Fe-Mn crust growth-rates are discussed. Variations of both Th/U and initial Th activity ratios in Fe-Mn crusts might be related to changes in particle input to seawater and/or changes in ocean circulation during the last 150 ka. Copyright ?? 1997 Elsevier Science Ltd.

  13. Magnetic order near 270 K in mineral and synthetic Mn{sub 2}FeSbO{sub 6} ilmenite

    SciTech Connect

    Mathieu, R.; Hudl, M.; Nordblad, P.; Ivanov, S. A.; Bazuev, G. V.; Lazor, P.; Solovyev, I. V.

    2011-05-16

    The structural and magnetic properties of Mn{sub 2}FeSbO{sub 6} single-crystalline mineral and ceramic samples synthesized under thermobaric treatment have been investigated, and compared to theoretical predictions based on first-principles electronic structure calculations. This ilmenite system displays a sharp magnetic transition just below the room temperature related to a ferrimagnetic ordering of the Mn{sup 2+} and Fe{sup 3+} cations, which makes Mn{sub 2}FeSbO{sub 6} a promising candidate for designing functional magnetic materials.

  14. Study of the Thermodynamics of Chromium(III) and Chromium(VI) Binding to Fe3O4 and MnFe2O4 nanoparticles

    PubMed Central

    Luther, Steven; Brogfeld, Nathan; Kim, Jisoo; Parsons, J.G.

    2013-01-01

    Removal of chromium(III) or (VI) from aqueous solution was achieved using Fe3O4, and MnFe2O4 nanomaterials. The nanomaterials were synthesized using a precipitation method and characterized using XRD. The size of the nanomaterials was determined to be 22.4 ± 0.9 nm (Fe3O4) and 15.5 ± 0.5 nm (MnFe2O4). The optimal binding pH for chromium(III) and chromium(VI) were pH 6 and pH 3. Isotherm studies were performed, under light and dark conditions, to determine the capacity of the nanomaterials. The capacities for the light studies with MnFe2O4 and Fe3O4 were determined to be 7.189 and 10.63 mg/g, respectively, for chromium(III). The capacities for the light studies with MnFe2O4 and Fe3O4 were 3.21 and 3.46 mg/g, respectively, for chromium(VI). Under dark reaction conditions the binding of chromium(III) to the MnFe2O4 and Fe3O4 nanomaterials were 5.74 and 15.9 mg/g, respectively. The binding capacity for the binding of chromium(VI) to MnFe2O4 and Fe3O4 under dark reaction conditions were 3.87 and 8.54 mg/g, respectively. The thermodynamics for the reactions showed negative ΔG values, and positive ΔH values. The ΔS values were positive for the binding of chromium(III) and for chromium(VI) binding under dark reaction conditions. The ΔS values for chromium(VI) binding under the light reaction conditions were determined to be negative. PMID:23558081

  15. Magnetic properties of Fe-Mn-Pt for heat assisted magnetic recording applications

    SciTech Connect

    Park, Jihoon; Hong, Yang-Ki; Kim, Seong-Gon; Gao, Li; Thiele, Jan-Ulrich

    2015-02-07

    We calculate the electronic structures of FePt and Fe{sub 0.5}Mn{sub 0.5}Pt using first-principles calculations based on density functional theory within the local-spin-density approximation. The Curie temperature (T{sub c}) was calculated by mean field approximation. Composition dependence of the Cure temperature (T{sub c}(x)) of Fe{sub 1−x}Mn{sub x}Pt was used to identify a composition to meet the desired T{sub c} in the range of 600–650 K. The identified composition (0.0294 ≤ x ≤ 0.0713) gives saturation magnetization (M{sub s}) in the range of 1041–919 emu/cm{sup 3} and magnetocrystalline anisotropy constant (K) in the range of 9.96–8.36 × 10{sup 6 }J/m{sup 3} at 0 K. Temperature dependent M(T) and K(T) of Fe{sub 1−x}Mn{sub x}Pt (0.0294 ≤ x ≤ 0.0713) were calculated using the Brillouin function and Callen-Callen experimental relation, respectively. Fe{sub 1−x}Mn{sub x}Pt (0.0294 ≤ x ≤ 0.0713) shows 930–800 emu/cm{sup 3} of M{sub s} and 7.18–5.61 × 10{sup 6 }J/m{sup 3} of K at 300 K, thereby satisfying desired magnetic properties for heat-assisted magnetic recording media to achieve 4 Tb/in.{sup 2} areal density.

  16. Fe(II)-mediated reduction and repartitioning of structurally incorporated Cu, Co, and Mn in iron oxides.

    PubMed

    Frierdich, Andrew J; Catalano, Jeffrey G

    2012-10-16

    The reduction of trace elements and contaminants by Fe(II) at Fe(III) oxide surfaces is well documented. However, the effect of aqueous Fe(II) on the fate of redox-active trace elements structurally incorporated into iron oxides is unknown. Here, we investigate the fate of redox-active elements during Fe(II)-activated recrystallization of Cu-, Co-, and Mn-substituted goethite and hematite. Enhanced release of Cu, Co, and Mn to solution occurs upon exposure of all materials to aqueous Fe(II) relative to reactions in Fe(II)-free fluids. The quantity of trace element release increases with pH when Fe(II) is present but decreases with increasing pH in the absence of Fe(II). Co and Mn release from goethite is predicted well using a second-order kinetic model, consistent with the release of redox-inactive elements such as Ni and Zn. However, Cu release and Co and Mn release from hematite require the sum of two rates to adequately model the kinetic data. Greater uptake of Fe(II) by Cu-, Co-, and Mn-substituted iron oxides relative to analogues containing only redox-inactive elements suggests that net Fe(II) oxidation occurs. Reduction of Cu, Co, and Mn in all materials following reaction with Fe(II) at pHs 7.0-7.5 is confirmed by X-ray absorption near-edge structure spectroscopy. This work shows that redox-sensitive elements structurally incorporated within iron oxides are reduced and repartitioned into fluids during Fe(II)-mediated recrystallization. Such abiotic reactions likely operate in tandem with partial microbial and abiotic iron reduction or during the migration of Fe(II)-containing fluids, mobilizing structurally bound contaminants and micronutrients in aquatic systems. PMID:22970760

  17. Al-Mn coating electrodeposited from ionic liquid on NdFeB magnet with high hardness and corrosion resistance

    NASA Astrophysics Data System (ADS)

    Ding, Jingjing; Xu, Bajin; Ling, Guoping

    2014-06-01

    Al-Mn coatings were electrodeposited on sintered NdFeB permanent magnet in MnCl2-AlCl3-1-ethyl-3-methylim-idazolium chloride (MnCl2-AlCl3-EMIC) ionic liquid at room temperature. The coatings were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The adhesion strength of the coating on NdFeB substrate was evaluated by thermal shock and scratch test. The hardness and corrosion behavior of Al-Mn coating were measured by a Knoop microhardness tester, immersion test and neutral salt spray test respectively. The results showed that the amorphous structure of the deposits was obtained at the current density of 6 mA/cm2, while higher current densities resulted in a mixed structure of amorphous and crystalline. The Al-Mn coating showed excellent adhesion strength on NdFeB substrate with the thermal shock test over 30 cycles and Lc > 80 N. The hardness of Al-Mn coating was up to 5.4 GPa. The amorphous Al-Mn coating showed an anodic sacrificial protection with a low corrosion rate for NdFeB. Meanwhile, the magnetic properties measured by an AMT-4 magnetic measurement device showed that Al-Mn coating did not deteriorate the magnetic property of NdFeB.

  18. Formation and evolution of MnNi clusters in neutron irradiated dilute Fe alloys modelled by a first principle-based AKMC method

    NASA Astrophysics Data System (ADS)

    Ngayam-Happy, R.; Becquart, C. S.; Domain, C.; Malerba, L.

    2012-07-01

    An atomistic Monte Carlo model parameterised on electronic structure calculations data has been used to study the formation and evolution under irradiation of solute clusters in Fe-MnNi ternary and Fe-CuMnNi quaternary alloys. Two populations of solute rich clusters have been observed, which can be discriminated by whether or not the solute atoms are associated with self-interstitial clusters. Mn-Ni-rich clusters are observed at a very early stage of the irradiation in both modelled alloys, whereas the quaternary alloys contain also Cu-containing clusters. Mn-Ni-rich clusters nucleate very early via a self-interstitial-driven mechanism, earlier than Cu-rich clusters; the latter, however, which are likely to form via a vacancy-driven mechanism, grow in number much faster than the former, helped by the thermodynamic driving force to Cu precipitation in Fe, thereby becoming dominant in the low dose regime. The kinetics of the number density increase of the two populations is thus significantly different. Finally the main conclusion suggested by this work is that the so-called late blooming phases might as well be neither late, nor phases.

  19. First-principles investigation of the stability of MN and CrMN precipitates under coherency strains in α-Fe (M = V, Nb, Ta)

    NASA Astrophysics Data System (ADS)

    Fors, Dan H. R.; Wahnström, Göran

    2011-06-01

    We perform a systematic ab initio study of the interface energetics of thin coherent rocksalt (nacl) structured MN and tetragonal CrMN films in bcc Fe (M = V, Nb, Ta), motivated by the vital role of MN and CrMN precipitates for the long-term creep resistance in 9%-12%Cr steels. The similarities and differences in the work of separations and the elastic costs for the coherency strains are identified, and the possibility for formation of coherent films are discussed. Our findings provide valuable information of the interface energetics, which in continuation can be combined with thermodynamical modeling to obtain a better understanding of the initial nucleation stage of the MN and CrMN precipitates, and their influence on the long-term microstructural evolution in 9%-12%Cr steels.

  20. Discontinuous coarsening behavior of Ni(2)MnAl intermetallic compound during isothermal aging treatment of Fe-Mn-Ni-Al alloys.

    PubMed

    Heo, Yoon-Uk; Takeguchi, Masaki; Furuya, Kazuo; Lee, Hu-Chul

    2010-08-01

    The discontinuous reaction of the Ni(2)MnAl intermetallic phase was investigated during the aging of a solution-treated Fe-8.3Mn-8.2Ni-4.2Al alloy. During aging, Ni(2)MnAl lamellae formed at the prior austenite grain boundaries and twin boundaries and grew into the neighboring grains. The presence of continuously precipitated fine Ni(2)MnAl particles before the growth of the discontinuously precipitated lamellae was confirmed by dark-field transmission electron microscopy, and it was concluded that the present reaction is a type of discontinuous coarsening process, alpha' + Ni(2)MnAl (continuous precipitation) --> alpha + Ni(2)MnAl (discontinuous coarsening). The chemical driving force and the reduction of the total coherent strain energy were suggested to be the driving force for the discontinuous coarsening reaction. PMID:20551447

  1. Large exchange bias in polycrystalline MnN/CoFe bilayers at room temperature

    NASA Astrophysics Data System (ADS)

    Meinert, Markus; Büker, Björn; Graulich, Dominik; Dunz, Mareike

    2015-10-01

    We report on the new polycrystalline exchange bias system MnN/CoFe, which shows exchange bias of up to 1800 Oe at room temperature with a coercive field around 600 Oe. The room-temperature values of the interfacial exchange energy and the effective uniaxial anisotropy are estimated to be Jeff=0.41 mJ /m2 and Keff=37 kJ /m3 . The thermal stability was found to be tunable by controlling the nitrogen content of MnN. The maximum blocking temperature exceeds 325 ∘C, however the median blocking temperature in the limit of thick MnN is 160 ∘C . Good oxidation stability through self-passivation was observed, enabling the use of MnN in lithographically defined microstructures. As a proof of principle we demonstrate a simple giant magnetoresistance stack exchange biased with MnN, which shows clear separation between parallel and antiparallel magnetic states. These properties come along with a surprisingly simple manufacturing process for the MnN films.

  2. Genetic and biochemical effects induced by iron ore, Fe and Mn exposure in tadpoles of the bullfrog Lithobates catesbeianus.

    PubMed

    Veronez, Alexandra Caroline da Silva; Salla, Rômulo Victor; Baroni, Vinícius Dadalto; Barcarolli, Indianara Fernanda; Bianchini, Adalto; Dos Reis Martinez, Claudia Bueno; Chippari-Gomes, Adriana Regina

    2016-05-01

    For decades, the extraction of minerals has intensified in order to meet the demand of industry. Iron ore deposits are important sources of metals, such as iron (Fe) and manganese (Mn). The particulate ores can be dispersed during extraction, transport and storage, with potential to induce biological impacts. Amphibians are very sensitive to environmental stressors. Therefore, the present study aimed to assess the effects of iron ore, Fe and Mn exposure during the metamorphosis of Lithobates catesbeianus. Endpoints analyzed included morphological (biometrical and developmental analyses), whole body Fe and Mn concentration in, plasma ferritin concentration, erythrocyte DNA damage (measured through comet assay and micronucleus test) and liver activity of enzymes involved in oxidative status [glutathione S-transferase (GST) and catalase (CAT)]. Tadpoles were kept under control condition (no contaminant addition) or exposed to iron ore (3.79mg/L as fine particulate matter); Fe (nominal concentration: 0.51mg/L Fe as C10H12FeN2NaO8; Fe-EDTA); and Mn (nominal concentration: 5.23mg/L Mn as 4H2O.MnCl2) for 30 days. Virtually, no mortality was observed, except for one tadpole found dead in the iron ore treatment. However, tadpoles exposed to iron ore had longer tail than those kept under control conditions while tadpoles exposed to manganese chloride showed higher body length than control ones. Exposure to Fe and Mn induced a delay in tadpole metamorphosis, especially when these metals are presented not as a mixture (iron ore). Tadpoles exposed to iron ore had increased whole body Fe and Mn while those exposed to Fe and Mn accumulated each metal individually. Tadpoles exposed to any of the contaminants tested showed a significant increase in erythrocyte DNA damage and frequency of micronuclei. In addition, they showed higher liver GST activity respect with those kept under control conditions. Plasma ferritin concentration and liver CAT activity were higher only in tadpoles

  3. Role of the antiferromagnetic pinning layer on spin wave properties in IrMn/NiFe based spin-valves

    NASA Astrophysics Data System (ADS)

    Gubbiotti, G.; Tacchi, S.; Del Bianco, L.; Bonfiglioli, E.; Giovannini, L.; Tamisari, M.; Spizzo, F.; Zivieri, R.

    2015-05-01

    Brillouin light scattering (BLS) was exploited to study the spin wave properties of spin-valve (SV) type samples basically consisting of two 5 nm-thick NiFe layers (separated by a Cu spacer of 5 nm), differently biased through the interface exchange coupling with an antiferromagnetic IrMn layer. Three samples were investigated: a reference SV sample, without IrMn (reference); one sample with an IrMn underlayer (10 nm thick) coupled to the bottom NiFe film; one sample with IrMn underlayer and overlayer of different thickness (10 nm and 6 nm), coupled to the bottom and top NiFe film, respectively. The exchange coupling with the IrMn, causing the insurgence of the exchange bias effect, allowed the relative orientation of the NiFe magnetization vectors to be controlled by an external magnetic field, as assessed through hysteresis loop measurements by magneto-optic magnetometry. Thus, BLS spectra were acquired by sweeping the magnetic field so as to encompass both the parallel and antiparallel alignment of the NiFe layers. The BLS results, well reproduced by the presented theoretical model, clearly revealed the combined effects on the spin dynamic properties of the dipolar interaction between the two NiFe films and of the interface IrMn/NiFe exchange coupling.

  4. Fabrication and properties of Mn 0.5Zn 0.5Fe 2O 4 nanofibers

    NASA Astrophysics Data System (ADS)

    Li, Qiailing; Wang, Wenting

    2010-08-01

    Zn-doped α-FeOOH nanofiber was synthesized by coprecipitation method. Then the α-FeOOH was enwraped by the complex of the Mn 2+ and citric acid. The morphology of α-FeOOH did not transform after the calcination process and Mn 0.5Zn 0.5Fe 2O 4 nanofiber was successfully prepared. The phase, morphology, particle diameter and the magnetic properties of samples were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The results indicated that Mn 0.5Zn 0.5Fe 2O 4 nanofibers with an aspect ratio over 40 and a diameter of 20 nm were prepared. Compared with the amorphous Mn 0.5Zn 0.5Fe 2O 4, the anisotropy of the Mn 0.5Zn 0.5Fe 2O 4 nanofiber increased, resulting in the higher coercivity and magnetization of the obtained sample. With an increase in the calcination temperature, the diameter and the saturation magnetization of the sample increased, while the aspect ratio and coercivity decreased. The coercivity of the sample obtained at 700 °C was maximal (up to 185.4 Oe). The saturation magnetization of the sample obtained at 900 °C was maximal (up to 65.3 emu/g). The use of citric acid method prevented the presence of Mn(OH) 2, resulting in the decrease of the calcination temperature.

  5. Superior magnetic and mechanical property of MnFe3N driven by electron correlation and lattice anharmonicity

    NASA Astrophysics Data System (ADS)

    Wu, Hao; Sun, Hong; Chen, Changfeng

    2015-02-01

    Manganese-substitution-doped iron nitride MnFe3N holds great promise for applications in high-density magnetic recording and spintronic devices. However, existing theory contradicts experimental results on the structural and magnetic stability of MnFe3N , and the underlying mechanisms remain elusive. Here we demonstrate by first-principles calculations that the ferromagnetic state with enhanced magnetization in MnFe3N is driven by the electron correlation effect not previously considered. We further reveal a large nonlinear shear plasticity, which produces an unexpectedly high shear strength in MnFe3N despite its initial ductile nature near the equilibrium structure. Moreover, we identify strong lattice anharmonicity that plays a pivotal role in stabilizing MnFe3N under high pressures at room temperature. These remarkable properties stem from the intriguing bonding nature of the parent compound Fe4N . Our results explain experimental results and offer insights into the fundamental mechanisms for the superior magnetic and mechanical properties of MnFe3N .

  6. Role of the antiferromagnetic pinning layer on spin wave properties in IrMn/NiFe based spin-valves

    SciTech Connect

    Gubbiotti, G. Tacchi, S.; Del Bianco, L.; Bonfiglioli, E.; Giovannini, L.; Spizzo, F.; Zivieri, R.; Tamisari, M.

    2015-05-07

    Brillouin light scattering (BLS) was exploited to study the spin wave properties of spin-valve (SV) type samples basically consisting of two 5 nm-thick NiFe layers (separated by a Cu spacer of 5 nm), differently biased through the interface exchange coupling with an antiferromagnetic IrMn layer. Three samples were investigated: a reference SV sample, without IrMn (reference); one sample with an IrMn underlayer (10 nm thick) coupled to the bottom NiFe film; one sample with IrMn underlayer and overlayer of different thickness (10 nm and 6 nm), coupled to the bottom and top NiFe film, respectively. The exchange coupling with the IrMn, causing the insurgence of the exchange bias effect, allowed the relative orientation of the NiFe magnetization vectors to be controlled by an external magnetic field, as assessed through hysteresis loop measurements by magneto-optic magnetometry. Thus, BLS spectra were acquired by sweeping the magnetic field so as to encompass both the parallel and antiparallel alignment of the NiFe layers. The BLS results, well reproduced by the presented theoretical model, clearly revealed the combined effects on the spin dynamic properties of the dipolar interaction between the two NiFe films and of the interface IrMn/NiFe exchange coupling.

  7. Quaternary PtMnCuX/C (X = Fe, Co, Ni, and Sn) and PtMnMoX/C (X = Fe, Co, Ni, Cu and Sn) alloys catalysts: Synthesis, characterization and activity towards ethanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Ammam, Malika; Easton, E. Bradley

    2012-10-01

    In this account, two series of quaternary PtMnCuX/C (X = Fe, Co, Ni, and Sn) and PtMnMoX/C (X = Fe, Co, Ni, Cu and Sn) alloys catalysts have been synthesized and characterized by ICP, XRD, XPS, TEM and cyclic voltammetry. XRD spectra of each series illustrated that PtMnCuX/C (X = Fe, Co and Ni) and PtMnMoX/C (X = Fe, Co, Ni and Cu) alloys have been formed without significant free Mn, Cu, Mo or X co-catalysts. For PtMnCuSn/C and PtMnMoSn/C, in addition to alloy formation, significant free Sn-oxides are present in each catalyst. Cyclic voltammetry and chronoamperometry revealed that all quaternary showed superior electrocatalytic activity towards ethanol oxidation compared to the ternary precursor. Also, shift of the onset potential of ethanol oxidation towards less positive values were also recorded with the quaternary alloys, demonstrating a facilitated oxidation with the quaternary alloys compared to ternary alloy precursor. The magnitude of the gain in potential depend on the alloy composition and PtMnMoSn/C was found to be the best of all synthetized quaternary alloys with an onset potential of ethanol oxidation of only 0.059 V vs. Ag/AgCl.

  8. Ferromagnetic interfacial interaction and the proximity effect in a Co2FeAl/(Ga,Mn)As bilayer.

    PubMed

    Nie, S H; Chin, Y Y; Liu, W Q; Tung, J C; Lu, J; Lin, H J; Guo, G Y; Meng, K K; Chen, L; Zhu, L J; Pan, D; Chen, C T; Xu, Y B; Yan, W S; Zhao, J H

    2013-07-12

    The magnetic properties of a Co2FeAl/(Ga,Mn)As bilayer epitaxied on GaAs (001) are studied both experimentally and theoretically. Unlike the common antiferromagnetic interfacial interaction existing in most ferromagnet-magnetic semiconductor bilayers, a ferromagnetic interfacial interaction in the Co2FeAl/(Ga,Mn)As bilayer is observed from measurements of magnetic hysteresis and x-ray magnetic circular dichroism. The Mn ions in a 1.36 nm thick (Ga,Mn)As layer remain spin polarized up to 400 K due to the magnetic proximity effect. The minor loops of the Co2FeAl/(Ga,Mn)As bilayer shift with a small ferromagnetic interaction field of +24 Oe and -23 Oe at 15 K. The observed ferromagnetic interfacial coupling is supported by ab initio density functional calculations. These findings may provide a viable pathway for designing room-temperature semiconductor spintronic devices through magnetic proximity effect. PMID:23889435

  9. Ferromagnetic Interfacial Interaction and the Proximity Effect in a Co2FeAl/(Ga,Mn)As Bilayer

    NASA Astrophysics Data System (ADS)

    Nie, S. H.; Chin, Y. Y.; Liu, W. Q.; Tung, J. C.; Lu, J.; Lin, H. J.; Guo, G. Y.; Meng, K. K.; Chen, L.; Zhu, L. J.; Pan, D.; Chen, C. T.; Xu, Y. B.; Yan, W. S.; Zhao, J. H.

    2013-07-01

    The magnetic properties of a Co2FeAl/(Ga,Mn)As bilayer epitaxied on GaAs (001) are studied both experimentally and theoretically. Unlike the common antiferromagnetic interfacial interaction existing in most ferromagnet-magnetic semiconductor bilayers, a ferromagnetic interfacial interaction in the Co2FeAl/(Ga,Mn)As bilayer is observed from measurements of magnetic hysteresis and x-ray magnetic circular dichroism. The Mn ions in a 1.36 nm thick (Ga,Mn)As layer remain spin polarized up to 400 K due to the magnetic proximity effect. The minor loops of the Co2FeAl/(Ga,Mn)As bilayer shift with a small ferromagnetic interaction field of +24Oe and -23Oe at 15 K. The observed ferromagnetic interfacial coupling is supported by ab initio density functional calculations. These findings may provide a viable pathway for designing room-temperature semiconductor spintronic devices through magnetic proximity effect.

  10. Nanostructure evolution under irradiation in FeMnNi alloys: A "grey alloy" object kinetic Monte Carlo model

    NASA Astrophysics Data System (ADS)

    Chiapetto, M.; Malerba, L.; Becquart, C. S.

    2015-07-01

    This work extends the object kinetic Monte Carlo model for neutron irradiation-induced nanostructure evolution in Fe-C binary alloys developed in [1], introducing the effects of substitutional solutes like Mn and Ni. The objective is to develop a model able to describe the nanostructural evolution of both vacancy and self-interstitial atom (SIA) defect cluster populations in Fe(C)MnNi neutron-irradiated model alloys at the operational temperature of light water reactors (∼300 °C), by simulating specific reference irradiation experiments. To do this, the effects of the substitutional solutes of interest are introduced, under simplifying assumptions, using a "grey alloy" scheme. Mn and Ni solute atoms are not explicitly introduced in the model, which therefore cannot describe their redistribution under irradiation, but their effect is introduced by modifying the parameters that govern the mobility of both SIA and vacancy clusters. In particular, the reduction of the mobility of point-defect clusters as a consequence of the presence of solutes proved to be key to explain the experimentally observed disappearance of detectable defect clusters with increasing solute content. Solute concentration is explicitly taken into account in the model as a variable determining the slowing down of self-interstitial clusters; small vacancy clusters, on the other hand, are assumed to be significantly slowed down by the presence of solutes, while for clusters bigger than 10 vacancies their complete immobility is postulated. The model, which is fully based on physical considerations and only uses a few parameters for calibration, is found to be capable of reproducing the experimental trends in terms of density and size distribution of the irradiation-induced defect populations with dose, as compared to the reference experiment, thereby providing insight into the physical mechanisms that influence the nanostructural evolution undergone by this material during irradiation.

  11. The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

    The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life.

  12. Fe-Si-Mn-oxyhydroxide encrustations on basalts at east pacific rise near 13°N: An SEM-EDS study

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoyuan; Zeng, Zhigang; Qi, Haiyan; Chen, Shuai; Yin, Xuebo; Yang, Baoju

    2014-12-01

    Fe-Si-Mn-oxyhydroxide encrustations at the East Pacific Rise (EPR) near 13°N were analyzed using the scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS). These encrustations are mainly composed of amorphous Fe-Si-Mn-oxyhydroxides forming laminated, spherical, porous aggregates with some biodetritus, anhydrite, nontronite, and feldspar particles. Anhydrite particles and nontronite crystals in the Fe-Si-Mn-oxyhydroxide encrustations imply that the Fe-Si-Mn-oxyhydroxide may have formed under relatively low- to high-temperature hydrothermal conditions. The Fe-Si-Mn-oxyhydroxide encrustations on pillow basalts are 1-2 mm thick. The growth rate of ferromanganese crusts in the survey area suggests that these encrustations are an unlikely result of hydrogenic deposition alone having a hydrothermal and (Fe/Mn ratio up to 7.7 and Fe/(Fe+Mn+Al) ratio exceeding 0.78) hydrogenic origin (0.22 Fe/Mn ratio close to the mean value of 0.7 for open-ocean seamount crusts). The varying Fe/Mn ratios indicate that the Fe-Si-Mn-oxyhydroxide encrustations have formed through several stages of seafloor hydrothermalism. It is suggested that, at the initial formation stage, dense Fe-Si-oxyhydroxides with low Mn content deposit from a relatively reducing hydrothermal fluid, and then the loose Fe-Si-Mn-oxyhydroxides deposit on the Fe-Si-oxyhydroxides. As the oxidation degree of hydrothermal fluid increases and Si-oxide is inhibited, Mn-oxide will precipitate with Fe-oxyhydroxides.

  13. Structure and magnetism of Mn, Fe, or Co adatoms on monolayer and bilayer black phosphorus

    NASA Astrophysics Data System (ADS)

    Wang, Hongbo; Zhu, Shasha; Fan, Fengren; Li, Zhengwei; Wu, Hua

    2016-03-01

    Black phosphorus (BP) is an emergent layered material and is currently explored for its potential applications in nanoelectronics. Here using density functional calculations, we investigate the structure and magnetism of transition metal (TM) adatoms (Mn, Fe, and Co) on the monolayer and bilayer BP. We find that while the TM adatoms prefer to occupy a valley site of the puckered monolayer BP and have a low-spin magnetic state, they could move to an interlayer interstitial site of the bilayer BP and turn into a high-spin state. In particular, Mn adatom at the valley site of monolayer BP has also a metastable high-spin state, and moreover, a low-spin to high-spin magnetic transition can readily be induced by a strain along the armchair direction. Then Mn adsorbed BP monolayer has a strain-tuning spin switch.

  14. Synergetic effects of Mn and Si in the interaction with point defects in bcc Fe

    NASA Astrophysics Data System (ADS)

    Bakaev, A.; Terentyev, D.; He, X.; Van Neck, D.

    2014-12-01

    The interaction of Mn, Si and Cr with a vacancy and self-interstitial defects in BCC Fe has been analyzed using ab initio calculations. While the interaction of the considered solute clusters with a single vacancy is linearly additive, there is a considerable synergetic effect in the case of self-interstitial atoms, found to bind strongly with Mn-Si pairs. The latter therefore act as deep trapping configurations for self-interstitials. At the same time, the presence of the point defects nearby weakly attractive Mn-Si pairs significantly enhances the solute-solute binding. The revealed effects are rationalized on the basis of charge density and local magnetic moment distributions.

  15. Magnetic and mechanical properties of Ni-Mn-Ga/Fe-Ga ferromagnetic shape memory composite

    NASA Astrophysics Data System (ADS)

    Tan, Chang-Long; Zhang, Kun; Tian, Xiao-Hua; Cai, Wei

    2015-05-01

    A ferromagnetic shape memory composite of Ni-Mn-Ga and Fe-Ga was fabricated by using spark plasma sintering method. The magnetic and mechanical properties of the composite were investigated. Compared to the Ni-Mn-Ga alloy, the threshold field for magnetic-field-induced strain in the composite is clearly reduced owing to the assistance of internal stress generated from Fe-Ga. Meanwhile, the ductility has been significantly improved in the composite. A fracture strain of 26% and a compressive strength of 1600 MPa were achieved. Projects supported by the National Natural Science Foundation of China (Grant Nos. 51271065 and 51301054), the Program for New Century Excellent Talents in Heilongjiang Provincial Education Department, China (Grant No. 1253-NCET-009), the Youth Academic Backbone in Heilongjiang Provincial Education Department, China (Grant No. 1251G022), the Projects of Heilongjiang, China, and China Postdoctoral Science Foundation.

  16. Comparative Studies of Cation Doping of ZnO with Mn, Fe, and Co

    NASA Astrophysics Data System (ADS)

    Jug, Karl; Tikhomirov, Viatcheslav A.

    2009-08-01

    MSINDO calculations were performed to elucidate the effect of doping and defects on the electronic properties of zinc oxide. The cyclic cluster Zn48O48 served as a model for the bulk. Band gaps and stabilities of spin states were determined for doping with Mn, Fe, and Co. It was found that a substantial lowering of the band gap occurs for Mn and Co doping. In contrast, the Fe doping has a rather insignificant effect on the band gap. Additional defects such as oxygen vacancy, zinc interstitial, or zinc vacancy were also studied. In the case of substitution of zinc by two transition metal atoms, various spin states arise which can be classified as antiferromagnetic, ferrimagnetic, or ferromagnetic. We find that the spin state with the lowest multiplicity, antiferromagentic or ferrimagnetic, is more stable than the high-multiplicity ferromagnetic state in most considered cases, but additional zinc vacancies or mixed doping may reverse this trend.

  17. Metal-ceramic microstructures in the Fe-Mn-O system -- Morphology control by impurity addition

    SciTech Connect

    Subramanian, R.; Uestuendag, E.; Sass, S.L.; Dieckmann, R.

    1995-10-01

    The influence of the addition of impurities and changes in the oxygen partial pressure on the formation of metal-ceramic microstructures by partial reduction of ternary or higher ceramic oxides was experimentally investigated in the model system Fe-Mn-O at constant temperature and total pressure. Electron microscopy studies were performed for microstructural characterization, phase identification and chemical analysis. It was observed that the addition of dopants such as BaO, CaO, MgO, SrO, Al{sub 2}O{sub 3}, Cr{sub 2}O{sub 3} or ZrO{sub 2} to the initial, polycrystalline oxide solid solution (Fe{sub 1{minus}x}Mn{sub x}){sub 1{minus}{Delta}}O strongly influences the location and rate of metal precipitation during reduction. Experimental observations are discussed based on solubility limits and the segregation of dopants.

  18. Enhanced Thermoelectric Properties of W- and Fe-Substituted MnSi γ

    NASA Astrophysics Data System (ADS)

    Ghodke, Swapnil; Hiroishi, Naoya; Yamamoto, Akio; Ikuta, Hiroshi; Matsunami, Masaharu; Takeuchi, Tsunehiro

    2016-06-01

    We have investigated the effect of heavy-element (W) substitution on the thermoelectric properties of higher manganese silicide (HMS). Samples were prepared by arc melting followed by liquid quenching, where the latter assisted in achieving higher solubility for tungsten. We observed that Mn34.6W1.8Si63.6 was a p-type material, whereas simultaneous substitution of 12 at.% Fe made the higher manganese silicide an n-type material. The optimal carrier concentration was obtained by simultaneous substitution of Fe and W for Mn atoms. Although the samples were metastable, we successfully obtained bulk samples by a low-temperature (970 K), high-pressure (>100 MPa), long-duration sintering process. The lattice thermal conductivity was effectively reduced by W substitution, and the ZT value was improved to above 0.5 for both n- and p-type samples.

  19. Giant exchange bias in Mn2FeGa with hexagonal structure

    NASA Astrophysics Data System (ADS)

    Liu, Z. H.; Zhang, Y. J.; Zhang, H. G.; Zhang, X. J.; Ma, X. Q.

    2016-07-01

    In this study, we present the experimental observation that polycrystalline Mn2+xFe1-xGa (x = -0.2, 0, 0.2, 0.4) compounds can be synthesized to be D019-type (Ni3Sn-type) hexagonal structure with space group P63/mmc. A giant exchange bias field up to 1.32 kOe was achieved in hexagonal Mn2FeGa alloy at 5 K. A cluster glass state is confirmed by ac susceptibility measurement under different driving frequencies. Interestingly, robust horizontal and vertical shifts in magnetic hysteresis loop were simultaneously observed at 5 K under high cooling field up to 90 kOe. The large exchange bias is originated from the large exchange anisotropy between cluster glass phase and ferrimagnetic matrix. The vertical shift is thought to be attributed to the incomplete reversal of frozen cluster spins.

  20. Strain development during the phase transition of La(Fe,Mn,Si)13Hz

    NASA Astrophysics Data System (ADS)

    Neves Bez, Henrique; Nielsen, Kaspar K.; Smith, Anders; Norby, Poul; Stâhl, Kenny; Bahl, Christian R. H.

    2016-08-01

    We use powder X-ray diffraction to evaluate the temperature dependence of the crystalline properties during the magnetic phase transition of La(Fe,Mn,Si)13Hz as a function of the Fe/Mn/Si ratio. Both the paramagnetic and ferromagnetic phases were observed as peak overlaps in the patterns around the Curie temperature (TC) occurring continuously in a temperature range of about 5 K around TC. Using the Williamson-Hall method, we evaluate the strain developing in the crystallites during the transition and find that it is associated with the growth of the paramagnetic phase as the transition occurs. Based on our measurements and microstructure analyses, we propose that cracking during the phase transition is due to or aggravated by the small content of a La-rich phase.

  1. Nonvolatile photorefractive properties in triply doped stoichiometric Mg:Fe:Mn:LiTaO3 crystals

    NASA Astrophysics Data System (ADS)

    Sun, Ting; Zhang, Xiao-Dong; Sun, Liang; Wang, Rui

    2014-01-01

    We have grown triply doped Mg:Fe:Mn:LiTaO3 crystals with near stoichiometry using the top seeded solution growth technique. The defect structure was investigated by infrared absorption spectra and Curie temperature. Using a blue laser as the source, excellent photorefractive properties were obtained. Nonvolatile holographic storage properties were investigated using the dual wavelength technique. We got a very high fixed diffraction efficiency and nonvolatile holographic storage sensitivity. The blue light has more than enough energy to excite holes of deep (Mn) and shallow (Fe) trap centers with the same phase, which enhance dramatically the blue photorefractive properties and the nonvolatile holographic storage. Mg2+ ion is no longer damage resistant at blue laser, but enhances photorefractive characteristics.

  2. Structural, magnetic, and electron transport properties of MnBi:Fe thin films

    SciTech Connect

    Kharel, P.; Skomski, R.; Sellmyer, D. J.; Li, X. Z.; Shah, V. R.; Al-Aqtash, N.; Tarawneh, K.; Sabirianov, R. F.

    2012-04-01

    The structural, magnetic, and electron transport properties of Mn{sub 55-x}Fe{sub x}Bi{sub 45} (x = 0, 2, 4, 5, 8, 11, 13, 16) films prepared by multilayer deposition and annealing using e-beam evaporation have been investigated. Fe doping has produced a significant change in the magnetic properties of the samples including the decrease in saturation magnetization and magnetocrystalline anisotropy and increase in coercivity. Although the magnetization shows a smooth decrease with increasing Fe concentration, the coercivity jumps abruptly from 8.5 kOe to 22 kOe as Fe content changes from 4% to 5%, but the change in coercivity is small as the concentration goes beyond 5%. The temperature dependence of resistivity shows that the samples with low Fe concentration ({<=}4%) are metallic, but the resistivity increases unexpectedly as the concentration reaches 5%, where the resistance increases with decreasing temperature below 300 K. First-principle calculations suggest that the observed magnetic properties can be understood as the consequences of competing ferromagnetic and antiferromagnetic exchange interactions between the interstitial atom and the rest of the MnBi lattice.

  3. Galvanomagnetic properties of Fe2YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-01

    The Hall effect and the magnetoresistance of Fe2YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3 d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit ( H > 10 kOe), the value and the sign of the normal ( R 0) and anomalous ( R s ) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R s in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio ( R s ∝ ρ 0 3.1 ), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  4. Galvanomagnetic properties of Fe{sub 2}YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    SciTech Connect

    Kourov, N. I. Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-15

    The Hall effect and the magnetoresistance of Fe{sub 2}YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit (H > 10 kOe), the value and the sign of the normal (R{sub 0}) and anomalous (R{sub s}) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R{sub s} in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio (R{sub s} ∝ ρ{sub 0}{sup 3.1}), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  5. Mechanical Properties and Microstructure of the CoCrFeMnNi High Entropy Alloy Under High Strain Rate Compression

    NASA Astrophysics Data System (ADS)

    Wang, Bingfeng; Fu, Ao; Huang, Xiaoxia; Liu, Bin; Liu, Yong; Li, Zezhou; Zan, Xiang

    2016-07-01

    The equiatomic CoCrFeMnNi high entropy alloy, which crystallizes in the face-centered cubic (FCC) crystal structure, was prepared by the spark plasma sintering technique. Dynamic compressive tests of the CoCrFeMnNi high entropy alloy were deformed at varying strain rates ranging from 1 × 103 to 3 × 103 s-1 using a split-Hopkinson pressure bar (SHPB) system. The dynamic yield strength of the CoCrFeMnNi high entropy alloy increases with increasing strain rate. The Zerilli-Armstrong (Z-A) plastic model was applied to model the dynamic flow behavior of the CoCrFeMnNi high entropy alloy, and the constitutive relationship was obtained. Serration behavior during plastic deformation was observed in the stress-strain curves. The mechanism for serration behavior of the alloy deformed at high strain rate is proposed.

  6. Mechanical Properties and Microstructure of the CoCrFeMnNi High Entropy Alloy Under High Strain Rate Compression

    NASA Astrophysics Data System (ADS)

    Wang, Bingfeng; Fu, Ao; Huang, Xiaoxia; Liu, Bin; Liu, Yong; Li, Zezhou; Zan, Xiang

    2016-05-01

    The equiatomic CoCrFeMnNi high entropy alloy, which crystallizes in the face-centered cubic (FCC) crystal structure, was prepared by the spark plasma sintering technique. Dynamic compressive tests of the CoCrFeMnNi high entropy alloy were deformed at varying strain rates ranging from 1 × 103 to 3 × 103 s-1 using a split-Hopkinson pressure bar (SHPB) system. The dynamic yield strength of the CoCrFeMnNi high entropy alloy increases with increasing strain rate. The Zerilli-Armstrong (Z-A) plastic model was applied to model the dynamic flow behavior of the CoCrFeMnNi high entropy alloy, and the constitutive relationship was obtained. Serration behavior during plastic deformation was observed in the stress-strain curves. The mechanism for serration behavior of the alloy deformed at high strain rate is proposed.

  7. Partitioning and structural role of Mn and Fe ions in ionic sulfophosphate glasses

    SciTech Connect

    Möncke, Doris; Wondraczek, Lothar; Sirotkin, Sergey; Stavrou, Elissaios; Kamitsos, Efstratios I.

    2014-12-14

    Ionic sulfophosphate liquids of the type ZnO-Na{sub 2}O-Na{sub 2}SO{sub 4}-P{sub 2}O{sub 5} exhibit surprising glass forming ability, even at slow or moderate cooling rate. As a concept, they also provide high solubility of transition metal ions which could act as cross-linking sites between the sulfate and phosphate entities. It is therefore investigated how the replacement of ZnO by MnO and/or FeO affects the glass structure and the glass properties. Increasing manganese levels are found to result in a monotonic increase of the transition temperature T{sub g} and most of the mechanical properties. This trend is attributed to the change of metal-ion coordination from four-fold around Zn{sup 2+} to six-fold around Mn{sup 2+} ions. The higher coordination facilitates cross-linking of the ionic structural entities and subsequently increases T{sub g}. Raman and infrared spectroscopy show that the structure of these glasses involves only SO{sub 4}{sup 2−} and PO{sub 4}{sup 3−} monomers as well as P{sub 2}O{sub 7}{sup 4-} dimers. Replacement of ZnO by MnO is found to favour PO{sub 4}{sup 3−} over P{sub 2}O{sub 7}{sup 4-} species, a trend which is enhanced by co-doping with FeO. Both transition metal ions show, like Zn{sup 2+}, a preference to selectively coordinate to phosphate anionic species, as opposed to sodium ions which coordinate mainly to sulfate anions. EPR spectroscopy finally shows that divalent Mn{sup 2+} ions are present primarily in MnO{sub 6}-clusters, which, in the studied sulfophosphate glasses, convert upon increasing MnO content from corner-sharing to edge-sharing entities.

  8. First-principles study on the ferrimagnetic half-metallic Mn{sub 2}FeAs alloy

    SciTech Connect

    Qi, Santao; Zhang, Chuan-Hui; Chen, Bao; Shen, Jiang; Chen, Nanxian

    2015-05-15

    Mn-based full-Heusler alloys are kinds of promising candidates for new half-metallic materials. Basing on first principles, the electronic structures and magnetic properties of the Mn{sub 2}FeAs full-Heusler alloy have been investigated in detail. The Hg{sub 2}CuTi-type Mn{sub 2}FeAs compound obeys the Slater-Pauling rule, while the anti-parallel alignment atomic magnetic moments of Mn locating at different sites indicate it a ferrimagnetic alloy. The calculated spin-down bands behave half-metallic character, exhibiting a direct gap of 0.46 eV with a 100% spin polarization at the Fermi level. More studies show the compound would maintain half-metallic nature in a large range of variational lattice constants. We expect that our calculated results may trigger Mn{sub 2}FeAs applying in the future spintronics field. - Graphical abstract: The d orbitals of Mn and Fe atoms split into multi-degenerated levels which create new bonding and nonbonding states. These exchange splitting shift the Fermi level to origin band gap.▪ - Highlights: • The electronic structure and magnetic properties of Mn{sub 2}FeAs full-Heusler alloy were studied. • A total magnetic moment of 3μ{sub B} was obtained for Mn{sub 2}FeAs alloy, following the SP rule M{sub t}=Z{sub t}−24. • The origin of ferrimagnetism and half-metallic character in Mn{sub 2}FeAs were discussed.

  9. Mechanism and kinetics of interaction of Fe, Cr, Mo, and Mn atoms with molecular oxygen

    SciTech Connect

    Akhmadov, U.S.; Zaslonko, I.S.; Smirnov, V.N.

    1988-09-01

    By means of resonance atomic absorption in shock waves, rate constants have been measured for the interaction of atoms of a number of transition metals (Fe, Cr, Mo, and Mn) with molecular oxygen. A new method is proposed and used for determining the exponent ..gamma.. in the modified Lambert-Beer law D = element of(ZN)/sup ..gamma../. The bond strength in CrO and MoO molecules has been estimated.

  10. Design of dual-phase Fe/Mn/C steel for low-temperature application

    SciTech Connect

    Kim, N.J.

    1981-09-01

    An investigation has been made to improve the impact properties of a dual phase Fe/1.5Mn/.06C steel for potential low temperature application. The research involved establishing the microstructure-property relationships, especially with regard to the morphology of the constituents. Dual phase processing was done in two ways, viz., controlled rolling and intercritical annealing of the as-hot-rolled structure.

  11. Pack-boriding of Fe-Mn binary alloys: Characterization and kinetics of the boride layers

    SciTech Connect

    Bektes, M.; Calik, A.; Ucar, N.; Keddam, M.

    2010-02-15

    In this work, the boronizing of Fe-Mn binary alloys at 0.42, 0.76 and 0.94 wt.% Mn was carried out in a solid medium using the powder pack method. In this method, commercial Ekabor-II boron source and activator (ferro-silicon) were thoroughly mixed to form the boriding medium. The samples were boronized in an electrical resistance furnace for exposure times of 2, 4, 6 and 8 h at 1173 K under atmospheric pressure and a series of boronized samples in the temperature range 1073-1373 K for 3 h. After the furnace process, boronized samples were removed from the furnace and cooled in air. Afterwards, the boride layers generated by the pack-boronizing process were characterized by optical microscopy, scanning electron microscopy, XRD analysis, Vickers microhardness and tensile testing. The generated boride layers, showing a saw-tooth morphology, had a surface microhardness in the range 1400-1270 HV0.1. It was shown that the values of yield stresses and ultimate tensile stresses were increased as the Mn content increases in the boronized Fe-Mn binary alloys. In contrast, the values of elongations determined from the stress-strain curves were decreased. Furthermore, it was found that the calculated mean value of the activation energy of boron diffusion was close to 119 J/mol.

  12. Dipolar centers in incipient ferroelectrics: Mn and Fe in KTaO3

    NASA Astrophysics Data System (ADS)

    Venturini, E. L.; Samara, G. A.; Laguta, V. V.; Glinchuk, M. D.; Kondakova, I. V.

    2005-03-01

    The influence of lattice disorder produced by Mn and Fe substitution on the dielectric properties of the incipient ferroelectric KTaO3 were investigated. Both substituents produce dipolar centers that exhibit relaxational behavior in the audio frequency range. At a concentration of 0.01 at. %, i.e., in the very dilute limits, the Mn center is reflected in a dielectric loss ( ∈″ or tanδ ) peak, but not to a measurable degree in the real part (∈') of the dielectric function, but a concentration of 0.3 at. % Mn produces measurable anomalies in both ∈'(T) and the dielectric loss. In the case of Fe, a concentration of 0.3 at. % produces anomalies in the dielectric loss, but not in ∈'(T) . Hydrostatic pressure has a considerable influence on the static and dynamic properties of these materials and provides insights into the physics. The results are discussed in terms of microscopic models for these dipolar centers, and it is shown that all the properties can be understood in terms of the temperature and pressure dependences of the correlation length for dipolar interactions in the highly polarizable KTaO3 host lattice—properties unique to soft ferroelectric mode hosts. A model theory was used to describe the influence of random dipolar fields on the reorientation dynamics. The calculations are found to be in good agreement with the experimental data on the 0.3 % Mn where there are weak dipolar correlations.

  13. Compositional dependence of antiferromagnetic anisotropy in IrMn/CoFe exchange bias systems

    NASA Astrophysics Data System (ADS)

    Aley, N. P.; O'Grady, K.

    2011-04-01

    We report on a study of the effect of Ir content on the loop shift (HEX) and anisotropy constant (KAF) in the CoFe/IrMn system. The sample structure investigated was Si/NiCr(5 nm)/Ru(5 nm)/IrxMn1-x/CoFe(2 nm)/Ta(3 nm). All samples were produced by sputtering and the Ir and Mn levels were varied using a specially made composite target and deposited at ˜120 °C. The composition of the samples was analyzed using energy dispersive x-ray analysis. KAF was calculated from thermal activation measurements using the York Protocols. A plateau in HEX was found for Ir levels between 16- 20.5 at. %. HEX was found to decrease by 50% on either side of this window. This result is consistent with previous studies where the enhancement of HEX was attributed to an increase in the atomic ordering of the IrMn alloy. However, KAF decreases linearly with increasing Ir concentration and does not appear to correlate with the change in HEX.

  14. The effect of the concentration of the Mn2+ ions on the optical and magnetic properties of the ZnS:Fe2+(1%) nanowires

    NASA Astrophysics Data System (ADS)

    Cao, Jian; Fan, Lin; Yang, Jinghai; Yan, Yongsheng; Wei, Maobin; Yang, Lili; Feng, Bo; Han, Donglai; Wang, Bingji; Fu, Hao

    2013-05-01

    In this paper, the wurtzite-type Fe/Mn co-doped ZnS nanowires were prepared by a simple hydrothermal method at 180 °C without any surface-active agent. The results showed that both the Fe2+ and Mn2+ ions were incorporated into the ZnS host and the maximum concentration of the Mn2+ ions in the ZnS:Fe2+(1%) nanowires was 5.1%. After adding Mn2+ ions into the ZnS:Fe2+(1%) nanowires, the emission peak centered at 2.14 eV corresponding to the Mn2+4T1-6A1 transition can be observed. As the Mn2+ doped ratio increased, the concentration quenching effect can be observed. The ferromagnetism property of the ZnS:Fe2+Mn2+ nanowires was observed around room temperature, which became weaker as the Mn2+ doped ratio increased.

  15. A new Fe-Mn-Si alloplastic biomaterial as bone grafting material: In vivo study

    NASA Astrophysics Data System (ADS)

    Fântânariu, Mircea; Trincă, Lucia Carmen; Solcan, Carmen; Trofin, Alina; Strungaru, Ştefan; Şindilar, Eusebiu Viorel; Plăvan, Gabriel; Stanciu, Sergiu

    2015-10-01

    Designing substrates having suitable mechanical properties and targeted degradation behavior is the key's development of bio-materials for medical application. In orthopedics, graft material may be used to fill bony defects or to promote bone formation in osseous defects created by trauma or surgical intervention. Incorporation of Si may increase the bioactivity of implant locally, both by enhancing interactions at the graft-host interface and by having a potential endocrine like effect on osteoblasts. A Fe-Mn-Si alloy was obtained as alloplastic graft materials for bone implants that need long recovery time period. The surface morphology of the resulted specimens was investigated using scanning electrons microscopy (VegaTescan LMH II, SE detector, 30 kV), X-ray diffractions (X'Pert equipment) or X-ray dispersive energy analyze (Bruker EDS equipment). This study objective was to evaluate in vivo the mechanisms of degradation and the effects of its implantation over the main metabolic organs. Biochemical, histological, plain X radiography and computed tomography investigations showed good compatibility of the subcutaneous implants in the rat organism. The implantation of the Fe-Mn-Si alloy, in critical size bone (tibiae) defect rat model, did not induced adverse biological reactions and provided temporary mechanical support to the affected bone area. The biodegradation products were hydroxides layers which adhered to the substrate surface. Fe-Mn-Si alloy assured the mechanical integrity in rat tibiae defects during bone regeneration.

  16. Latent heat of magnetization for MnFeSi0 . 33P0 . 66

    NASA Astrophysics Data System (ADS)

    Roy, Prasenjit; de Groot, Robert A.; Theoretical Chemistry Team

    2015-03-01

    Magnetic refrigeration is a very promising environmental-friendly method to encounter the energy shortage of the world by implementing the magnetocaloric effect. MnFeSiP series of materials are distinguishable magnetocaloric meterial for the use of non-toxic, inexpensive elements as well as high efficiency. There are several ways to measure the efficiency of the MCE, viz.- measuring the adiabatic temperature change or measuring the entropy change at the transition. MnFeSiP materials show a first order magneto-elastic phase transition at the Curie temperature (TC). This simultaneous occourance of the magnetic and elastic transition in this material account for a higher ΔTad (or high entropy change), which is linearly proportional to the Latent heat (L) of magnetization. Experimentally L can be determined with techniques such as Differential Scanning Calorimetry. In our study we use VASP in addition to the Phonopy package, to determine the finite temperature properties of the system. Quasi Harmonic Approximation was applied successfully to determine the Gibbs free energy of MnFeSi0.33 P0.66. Hence we show a phase transition around 425 K. From the temperature derivative of G , the specific heat was obtained and finally the latent heat was obtained. Foundation for fundamental research on matter.

  17. Study on CO2 laser weldability of Fe-Mn-Si shape memory alloy

    NASA Astrophysics Data System (ADS)

    Zhou, Chaoyu; Lin, Chengxin; Liu, Linlin

    2011-11-01

    In this study, a cross-flow laser with maximum out power of 5kW was applied to the welding of Fe-Mn-Si shape memory alloys (SMA). The optimal welding processing parameters of 1mm thick Fe-Mn-Si SMA were established by orthogonal experiment. With the optimal processing parameters, power 1600W, welding speed 2.2m/min, defocusing distance 0.6mm, the tensile strength of the welded joint can achieve 93.5% of the base material, and the weld undercut and reinforcement transfer smoothly on the surface of the welding seam and the cross-section of the welding seam morphology presents "X" shape. The fracture appears in the weld fusion zone, so this area is weak during the laser welding. By the metallographic observation, the weld center structure is small equated, and the region of fusion zone is thick cellular crystal that decreases the strength of the welded joint, and the X-ray diffraction (XRD) test proves that the laser welding promotes the grain refinement. The micro-hardness analysis shows that the hardness of the fusion zone is lower than the other area clearly which is also associated to the weld structure. By the fracture scanning electron microscope (SEM) analysis, it is found that the fracture of Fe-Mn-Si SMA shows many small dimples with the optimal parameters, and the result is accorded with the base material which belongs to plastic fracture.

  18. Study on CO2 laser weldability of Fe-Mn-Si shape memory alloy

    NASA Astrophysics Data System (ADS)

    Zhou, Chaoyu; Lin, Chengxin; Liu, Linlin

    2012-04-01

    In this study, a cross-flow laser with maximum out power of 5kW was applied to the welding of Fe-Mn-Si shape memory alloys (SMA). The optimal welding processing parameters of 1mm thick Fe-Mn-Si SMA were established by orthogonal experiment. With the optimal processing parameters, power 1600W, welding speed 2.2m/min, defocusing distance 0.6mm, the tensile strength of the welded joint can achieve 93.5% of the base material, and the weld undercut and reinforcement transfer smoothly on the surface of the welding seam and the cross-section of the welding seam morphology presents "X" shape. The fracture appears in the weld fusion zone, so this area is weak during the laser welding. By the metallographic observation, the weld center structure is small equated, and the region of fusion zone is thick cellular crystal that decreases the strength of the welded joint, and the X-ray diffraction (XRD) test proves that the laser welding promotes the grain refinement. The micro-hardness analysis shows that the hardness of the fusion zone is lower than the other area clearly which is also associated to the weld structure. By the fracture scanning electron microscope (SEM) analysis, it is found that the fracture of Fe-Mn-Si SMA shows many small dimples with the optimal parameters, and the result is accorded with the base material which belongs to plastic fracture.

  19. [Determination the chemical speciation of Cu, Zn, Fe and Mn in Radix Scutellariae by AAS].

    PubMed

    Miao, Shan; Sun, Ji-yuan; Xie, Yan-hua; Wang, Jian-bo; Shi, Xiao-peng; Ding, Yuan-yuan; Bi, Lin-lin; Gao, Shuang-bin; Wang, Si-wang

    2009-05-01

    An analysis method was developed to determine the chemical speciation of Cu, Zn, Fe and Mn in radix scutellariae decoction using atomic absorption spectroscopy(AAS). The decoction can be divided into suspension and soluble species by 0.45 microm filter membrane and the soluble species can be separated into organism and inorganic species by LSA-10 macroporous resin. These elements in water-soluble test samples can be divided into alcohol-soluble and water-soluble by adopting n-octyl alcohol-water allocation system in man-made gastric acidity. Then, the concentration of these elements was determined by AAS, which provided more chemical speciation information about these elements instead of the total amount of them only in radix scutellariae. Deteotion limit of Cu, Zn and Mn by using the method was all 0.01 microg x mL(-1) and was 0.02 microg x mL(-1) for Fe. The RSD was in the range of 1.5%-3.6% (n=11) and the recovery rate of soluble species and inorganic species were in range of 96.7%-105.0%. The method has been successfully applied to determine the chemical speciation of Cu, Zn, Fe and Mn in radix scutellariae, which was very important for overall study of radix scutellariae. PMID:19650506

  20. A new mineral species ferricoronadite, Pb[Mn6 4+(Fe3+, Mn3+)2]O16: mineralogical characterization, crystal chemistry and physical properties

    NASA Astrophysics Data System (ADS)

    Chukanov, Nikita V.; Aksenov, Sergey M.; Jančev, Simeon; Pekov, Igor V.; Göttlicher, Jörg; Polekhovsky, Yury S.; Rusakov, Vyacheslav S.; Nelyubina, Yuliya V.; Van, Konstantin V.

    2016-04-01

    A new mineral ferricoronadite with the simplified formula Pb(Mn6 4+Fe2 3+)O16 was discovered in the orogenetic zone related to the "Mixed Series" metamorphic complex near the Nežilovo village, Pelagonian massif, Republic of Macedonia. Associated minerals are franklinite, gahnite, hetaerolite, roméite, almeidaite, Mn-analogue of plumboferrite, zincohögbomite analogue with Fe3+ > Al, zincochromite, Zn-bearing talc, Zn-bearing muscovite, baryte, quartz and zircon. Ferricoronadite is a late hydrothermal mineral forming veinlets up to 8 mm thick in granular aggregate predominantly composed by zinc-dominant spinels. The new mineral is opaque, black, with brownish black streak. The luster is strong submetallic to metallic. The micro-indentation hardness is 819 kg/mm2. Distinct cleavage is observed on (100). Ferricoronadite is brittle, with uneven fracture. The density calculated from the empirical formula is 5.538 g/cm3. In reflected light, ferricoronadite is light gray. The reflectance values [R max/R min, % (λ, nm)] are: 28.7/27.8 (470), 27.6/26.6 (546), 27.2/26.1 (589), 26.5/25.5 (650). The IR spectrum shows the absence of H2O and OH groups. According to the Mössbauer spectrum, all iron is trivalent. The Mn K-edge XANES spectroscopy shows that Mn is predominantly tetravalent, with subordinate Mn3+. The chemical composition is (wt%; electron microprobe, Mn apportioned between MnO2 and Mn2O3 based on the charge-balance requirement): BaO 5.16, PbO 24.50, ZnO 0.33, Al2O3 0.50, Mn2O3 9.90, Fe2O3 11.45, TiO2 4.19, MnO2 44.81, total 100.84. The empirical formula based on 8 cations Mn + Fe + Ti + Al + Zn pfu is Pb1.03Ba0.32(Mn{4.85/4+}Fe{1.35/3+}Mn{1.18/3+}Ti0.49Al0.09Zn0.04)Σ8.00O16. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is tetragonal, space group I4/m, a = 9.9043(7), c = 2.8986(9) Å, V = 284.34(9) Å3, Z = 1. In ferricoronadite, double chains of edge-sharing (Mn, Fe, Ti)-centered octahedra are connected via

  1. A new mineral species ferricoronadite, Pb[Mn6 4+(Fe3+, Mn3+)2]O16: mineralogical characterization, crystal chemistry and physical properties

    NASA Astrophysics Data System (ADS)

    Chukanov, Nikita V.; Aksenov, Sergey M.; Jančev, Simeon; Pekov, Igor V.; Göttlicher, Jörg; Polekhovsky, Yury S.; Rusakov, Vyacheslav S.; Nelyubina, Yuliya V.; Van, Konstantin V.

    2016-07-01

    A new mineral ferricoronadite with the simplified formula Pb(Mn6 4+Fe2 3+)O16 was discovered in the orogenetic zone related to the "Mixed Series" metamorphic complex near the Nežilovo village, Pelagonian massif, Republic of Macedonia. Associated minerals are franklinite, gahnite, hetaerolite, roméite, almeidaite, Mn-analogue of plumboferrite, zincohögbomite analogue with Fe3+ > Al, zincochromite, Zn-bearing talc, Zn-bearing muscovite, baryte, quartz and zircon. Ferricoronadite is a late hydrothermal mineral forming veinlets up to 8 mm thick in granular aggregate predominantly composed by zinc-dominant spinels. The new mineral is opaque, black, with brownish black streak. The luster is strong submetallic to metallic. The micro-indentation hardness is 819 kg/mm2. Distinct cleavage is observed on (100). Ferricoronadite is brittle, with uneven fracture. The density calculated from the empirical formula is 5.538 g/cm3. In reflected light, ferricoronadite is light gray. The reflectance values [ R max/ R min, % ( λ, nm)] are: 28.7/27.8 (470), 27.6/26.6 (546), 27.2/26.1 (589), 26.5/25.5 (650). The IR spectrum shows the absence of H2O and OH groups. According to the Mössbauer spectrum, all iron is trivalent. The Mn K-edge XANES spectroscopy shows that Mn is predominantly tetravalent, with subordinate Mn3+. The chemical composition is (wt%; electron microprobe, Mn apportioned between MnO2 and Mn2O3 based on the charge-balance requirement): BaO 5.16, PbO 24.50, ZnO 0.33, Al2O3 0.50, Mn2O3 9.90, Fe2O3 11.45, TiO2 4.19, MnO2 44.81, total 100.84. The empirical formula based on 8 cations Mn + Fe + Ti + Al + Zn pfu is Pb1.03Ba0.32(Mn 4.85 4+ Fe 1.35 3+ Mn 1.18 3+ Ti0.49Al0.09Zn0.04)Σ8.00O16. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is tetragonal, space group I4/ m, a = 9.9043(7), c = 2.8986(9) Å, V = 284.34(9) Å3, Z = 1. In ferricoronadite, double chains of edge-sharing (Mn, Fe, Ti)-centered octahedra are connected

  2. Construction of the Magnetic Phase Diagram of FeMn/Ni/Cu(001) Using Photoemission Electron Microscopy

    SciTech Connect

    Wu, J.; Scholl, A.; Arenholz, E.; Hwang, C.; Qiu, Z. Q.

    2011-01-04

    Single crystalline FeMn/Ni bilayer was epitaxially grown on Cu(001) substrate and investigated by photoemission electron microscopy (PEEM). The FeMn and Ni films were grown into two cross wedges to facilitate an independent control of the FeMn (0-20 ML) and Ni (0-20 ML) film thicknesses. The Ni magnetic phases were determined by Ni domain images as a function of the Ni thickness (d{sub Ni}) and the FeMn thickness (d{sub FeMn}). The result shows that as the Ni thickness increases, the Ni film undergoes a paramagnetic-to-ferromagnetic state transition at a critical thickness of d{sub FM} and an in-plane to out-of-plane spin reorientation transition at a thicker thickness d{sub SRT}. The phase diagram shows that both d{sub FM} and d{sub SRT} increase as the FeMn film establishes its antiferromagnetic order.

  3. MnFe2O4 as a gas sensor towards SO2 and NO2 gases

    NASA Astrophysics Data System (ADS)

    Rathore, Deepshikha; Mitra, Supratim

    2016-05-01

    The chemical co-precipitation method was used to synthesize MnFe2O4 nanoparticles. Single cubic phase formation of nanoparticles was confirmed by X-ray diffraction technique. The average particle size of MnFe2O4 nanoparticles was found to be 10.7 nm using Scherrer formula. The ultrafine powder of MnFe2O4 nanoparticles was pressed to design pellet of 10 mm diameter and 1mm thickness. Copper electrodes have been deposited on the surface of pellet using silver paste in the form of capacitor. Fabricated gas sensing device of MnFe2O4 nanoparticles was tested towards SO2 and NO2 gases. Cole-Cole plot of MnFe2O4 was investigated with the help of electrochemical workstation. The performance of the sensors including sensitivity, response and recovery time was also determined. It was observed that the MnFe2O4 nanoparticles are more sensible for NO2 gas as compared to SO2 gas.

  4. Magnetism in La₂O₃(Fe₁₋xMnx)₂Se₂ tuned by Fe/Mn ratio

    SciTech Connect

    Lei, Hechang; Bozin, Emil S.; Llobet, A.; Ivanovski, V.; Koteski, V.; Belosevic-Cavor, J.; Cekic, B.; Petrovic, C.

    2012-09-17

    We report the evolution of structural and magnetic properties in La₂O₃(Fe₁₋xMnx)₂Se₂. Heat capacity and bulk magnetization indicate an increased ferromagnetic component of the long-range magnetic order and possible increased degree of frustration. Atomic disorder on Fe(Mn) sites suppresses the temperature of the long-range order whereas intermediate alloys show a rich magnetic phase diagram.

  5. 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.

  6. Enhanced half-metallicity of off-stoichiometric quaternary Heusler alloy C o2(Mn ,Fe )Si investigated through saturation magnetization and tunneling magnetoresistance

    NASA Astrophysics Data System (ADS)

    Moges, Kidist; Honda, Yusuke; Liu, Hong-xi; Uemura, Tetsuya; Yamamoto, Masafumi; Miura, Yoshio; Shirai, Masafumi

    2016-04-01

    We investigated the factors that critically affect the half-metallicity of the quaternary Heusler alloy C o2(Mn ,Fe )Si (CMFS) by examining the film composition dependence of the saturation magnetization per formula unit, μs, of CMFS thin films and the tunneling magnetoresistance (TMR) ratio of CMFS/MgO/CMFS magnetic tunnel junctions (MTJs). We also investigated the origin of the giant TMR ratio of up to 2610% at 4.2 K (429% at 290 K) obtained for CMFS MTJs with Mn-rich, lightly Fe-doped CMFS electrodes. Co antisites at the nominal Mn/Fe sites (C oMn /Fe antisites) can consistently explain the μs for (Mn + Fe)-deficient CMFS thin films being lower than the half-metallic Zt-24 value and the TMR ratio for MTJs with (Mn + Fe)-deficient CMFS electrodes being lower than that for MTJs with (Mn + Fe)-rich CMFS electrodes. It was revealed that the C oMn /Fe antisite is detrimental to the half-metallicity of the CMFS quaternary alloy, as it is in the Co2MnSi (CMS) ternary alloy. It was also shown that (Mn +Fe ) -rich compositions are critical to suppressing these harmful antisites and to retaining the half-metallic electronic state. In addition, a relatively small Fe ratio, rather than a large one, in the total (Mn +Fe ) composition led to a more complete half-metallic electronic state. Half-metallicity was more strongly enhanced by increasing the Mn composition in Mn-rich, lightly Fe-doped CMFS than in Mn-rich CMS. This phenomenon is the cause of the giant TMR ratio recently reported for CMFS MTJs. Our findings indicate that the approach to controlling off-stoichiometry and film composition is promising for fully utilizing the half-metallicity of quaternary CMFS thin films as spin source materials.

  7. Planar Hall effect in Y{sub 3}Fe{sub 5}O{sub 12}/IrMn films

    SciTech Connect

    Zhang, X. Zou, L. K.

    2014-12-29

    The planar Hall effect of IrMn on an yttrium iron garnet (YIG = Y{sub 3}Fe{sub 5}O{sub 12}) was measured in the magnetic field rotating in the film plane. The magnetic field angular dependence of planar Hall resistance (PHR) was observed in YIG/IrMn bilayer at different temperatures, while the Gd{sub 3}Ga{sub 5}O{sub 12}/IrMn film shows constant PHR for different magnetic field angles at both 10 K and 300 K. This provides evidence that IrMn has interfacial spins which can be led by ferrimagnetic layer in YIG/IrMn structure. A hysteresis can be observed in PHR-magnetic field angle loop of YIG/IrMn film at 10 K, indicative of the irreversible switching of IrMn interfacial spins at low temperature.

  8. Synthesis of MnFe2O4@Mn-Co oxide core-shell nanoparticles and their excellent performance for heavy metal removal.

    PubMed

    Ma, Zichuan; Zhao, Dongyuan; Chang, Yongfang; Xing, Shengtao; Wu, Yinsu; Gao, Yuanzhe

    2013-10-21

    Magnetic nanomaterials that can be easily separated and recycled due to their magnetic properties have received considerable attention in the field of water treatment. However, these nanomaterials usually tend to aggregate and alter their properties. Herein, we report an economical and environmentally friendly method for the synthesis of magnetic nanoparticles with core-shell structure. MnFe2O4 nanoparticles have been successfully coated with amorphous Mn-Co oxide shells. The synthesized MnFe2O4@Mn-Co oxide nanoparticles have highly negatively charged surface in aqueous solution over a wide pH range, thus preventing their aggregation and enhancing their performance for heavy metal cation removal. The adsorption isotherms are well fitted to a Langmuir adsorption model, and the maximal adsorption capacities of Pb(II), Cu(II) and Cd(II) on MnFe2O4@Mn-Co oxide are 481.2, 386.2 and 345.5 mg g(-1), respectively. All the metal ions can be completely removed from the mixed metal ion solutions in a short time. Desorption studies confirm that the adsorbent can be effectively regenerated and reused. PMID:23945878

  9. Enhanced Thermal Stability and Magnetic Properties in NaCl-Type FePt-MnO Binary Nanocrystal Superlattices

    SciTech Connect

    Dong, AG; Chen, J; Ye, XC; Kikkawa, JM; Murray, CB

    2011-08-31

    We report the growth of NaCl-type binary nanocrystal (NC) superlattice membranes by coassembly of FePt and MnO NCs at the liquid-air interface. The constituent FePt NCs were converted into the hard magnetic L1(0) phase by thermal annealing at 650 degrees C without degradation of the long-range NC ordering. In contrast, both FePt-only NC superlattices and FePt-MnO disordered NC mixtures showed substantial FePt sintering under the same annealing conditions. Our results demonstrate that the incorporation of FePt NCs into binary superlattices can solve the problems of FePt sintering during conversion to the L1(0) phase, opening a new route to the fabrication of ordered ferromagnetic NC arrays on a desired substrate for high-density data storage applications.

  10. Exchange-bias phenomena and modeling in nanocrystalline powders of MnO/FeCo and NiO/Fe

    NASA Astrophysics Data System (ADS)

    Cornejo, D. R.; Padrón Hernández, E.; Azevedo, A.; Rezende, S. M.

    2005-05-01

    An approach towards the modeling of the magnetic behavior in heterogeneous systems of exchange-coupled antiferromagnetic (AF) and ferromagnetic (FM) particles with composition (AF)x+(FM)1-x is presented. The model is based on the Preisach hysteresis model and correctly predicts the correlation between the exchange-bias field and the mean grain size of the material, as established from the measurements of the hysteresis loops in mechanically alloyed (MnO)+(α-FeCo). The model was also used to calculate the unidirectional anisotropy interface energies in both this and (NiO)x+(α-Fe)1-x system; in the latter case, the predicted value was in full agreement with that reported for antiferromagnetic layers of NiO.

  11. Self-current induced spin-orbit torque in FeMn/Pt multilayers

    PubMed Central

    Xu, Yanjun; Yang, Yumeng; Yao, Kui; Xu, Baoxi; Wu, Yihong

    2016-01-01

    Extensive efforts have been devoted to the study of spin-orbit torque in ferromagnetic metal/heavy metal bilayers and exploitation of it for magnetization switching using an in-plane current. As the spin-orbit torque is inversely proportional to the thickness of the ferromagnetic layer, sizable effect has only been realized in bilayers with an ultrathin ferromagnetic layer. Here we demonstrate that, by stacking ultrathin Pt and FeMn alternately, both ferromagnetic properties and current induced spin-orbit torque can be achieved in FeMn/Pt multilayers without any constraint on its total thickness. The critical behavior of these multilayers follows closely three-dimensional Heisenberg model with a finite Curie temperature distribution. The spin torque effective field is about 4 times larger than that of NiFe/Pt bilayer with a same equivalent NiFe thickness. The self-current generated spin torque is able to switch the magnetization reversibly without the need for an external field or a thick heavy metal layer. The removal of both thickness constraint and necessity of using an adjacent heavy metal layer opens new possibilities for exploiting spin-orbit torque for practical applications. PMID:27185656

  12. Self-current induced spin-orbit torque in FeMn/Pt multilayers.

    PubMed

    Xu, Yanjun; Yang, Yumeng; Yao, Kui; Xu, Baoxi; Wu, Yihong

    2016-01-01

    Extensive efforts have been devoted to the study of spin-orbit torque in ferromagnetic metal/heavy metal bilayers and exploitation of it for magnetization switching using an in-plane current. As the spin-orbit torque is inversely proportional to the thickness of the ferromagnetic layer, sizable effect has only been realized in bilayers with an ultrathin ferromagnetic layer. Here we demonstrate that, by stacking ultrathin Pt and FeMn alternately, both ferromagnetic properties and current induced spin-orbit torque can be achieved in FeMn/Pt multilayers without any constraint on its total thickness. The critical behavior of these multilayers follows closely three-dimensional Heisenberg model with a finite Curie temperature distribution. The spin torque effective field is about 4 times larger than that of NiFe/Pt bilayer with a same equivalent NiFe thickness. The self-current generated spin torque is able to switch the magnetization reversibly without the need for an external field or a thick heavy metal layer. The removal of both thickness constraint and necessity of using an adjacent heavy metal layer opens new possibilities for exploiting spin-orbit torque for practical applications. PMID:27185656

  13. Structural, magnetic, and electron transport properties of MnBi:Fe thin films

    SciTech Connect

    Kharel, P; Li, XZ; Shah, VR; Al-Aqtash, N; Tarawneh, K; Sabirianov, RF; Skomski, R; Sellmyer, DJ

    2012-04-01

    The structural, magnetic, and electron transport properties of Mn55-xFexBi45 (x = 0, 2, 4, 5, 8, 11, 13, 16) films prepared by multilayer deposition and annealing using e-beam evaporation have been investigated. Fe doping has produced a significant change in the magnetic properties of the samples including the decrease in saturation magnetization and magnetocrystalline anisotropy and increase in coercivity. Although the magnetization shows a smooth decrease with increasing Fe concentration, the coercivity jumps abruptly from 8.5 kOe to 22 kOe as Fe content changes from 4% to 5%, but the change in coercivity is small as the concentration goes beyond 5%. The temperature dependence of resistivity shows that the samples with low Fe concentration (<= 4%) are metallic, but the resistivity increases unexpectedly as the concentration reaches 5%, where the resistance increases with decreasing temperature below 300 K. First-principle calculations suggest that the observed magnetic properties can be understood as the consequences of competing ferromagnetic and antiferromagnetic exchange interactions between the interstitial atom and the rest of the MnBi lattice. (C) 2012 American Institute of Physics. [doi:10.1063/1.3675615

  14. LiMO{sub 2} (M=Mn, Fe, and Co): Energetics, polymorphism and phase transformation

    SciTech Connect

    Wang Miaojun; Navrotsky, Alexandra . E-mail: anavrotsky@ucdavis.edu

    2005-04-15

    LiMO{sub 2} materials (M=Mn, Fe, and Co) with different structures were synthesized and their enthalpies of formation from oxides (Li{sub 2}O and M{sub 2}O{sub 3}, M=Mn and Fe), or from oxides (Li{sub 2}O and CoO) plus oxygen at 25{sup o}C were determined by high-temperature oxide melt solution calorimetry. The relative stability of the polymorphs of the compound LiMO{sub 2} was established based on their enthalpies of formation. Phase transformations in LiFeO{sub 2} were investigated by differential scanning calorimetry and high-temperature oxide melt solution calorimetry. The phase transition enthalpies at 25{sup o}C for {beta}->{alpha}, {gamma}->{beta}, and {gamma}->{alpha} are 4.9+/-0.7, 4.3+/-0.8 and 9.2+/-0.9kJ/mol, respectively. Thus the {gamma} phase (ordered cations) is the stable form of LiFeO{sub 2} at room temperature, the {alpha} phase (disordered cations) is stable at high temperature and the {beta} phase may have a stability field at intermediate temperatures.

  15. Synthesis of Waste Form in the Gd-Fe-Al-Ni-Mn-Cr-O System

    SciTech Connect

    Chae, S.C.; Jang, Y.N.; Bae, I.K.; Ryu, K.W.

    2006-07-01

    Poly-phase waste form which was the mixture of Gd{sub 3}Fe{sub 2}Al{sub 3}O{sub 12} and (Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4} was synthesized. Also, we are intended to examine phase relation and physicochemical properties of coexisted phases in the compositions and to confirm accommodation relation of elements and phases. Two types of phase series were observed: Garnet-perovskite-spinel and Garnet-spinel. The compositions of garnets and spinels were nonstoichiometric, and especially, this poly-phase ceramics may be in a good waste form. The excessive Gd in garnets indicated the immobilization of higher content of actinides. The nonstoichiometric compositions of garnet and spinel were attributed to the formation of perovskite in that perovskite contained Gd, Fe and Al from garnet and Cr from spinel. (authors)

  16. Evaluation of Fe, Mn promoted sulfated zirconia catalyst by x-ray and infrared spectroscopies

    SciTech Connect

    Tabora, J.E.; Davis, R.J.

    1995-12-01

    Sulfated zirconia promoted with Fe and Mn is two orders of magnitude more active than an unpromoted catalyst for butane isomerization at low temperature. In this work, the atomic structures of the unpromoted and promoted superacid catalysts were investigated using x-ray absorption spectroscopy at the Zr and Fe K-edges. In addition, infrared spectroscopy was used to probe the structure of the surface sulfate groups on the superacids. Infrared spectroscopy of adsorbed pyridine and carbon monoxide was also used to determine the types and strengths of acid sites on the two samples. Results indicated that Fe atoms do not substitute into tetragonal zirconia and that both Bronsted and Lewis acid sites were present on the materials. Furthermore, no obvious difference in acid strength was observed. Implications of these results for catalysis by zirconia-based superacids will be discussed.

  17. Controlled synthesis and magnetic properties of bimagnetic spinel ferrite CoFe2O4 and MnFe2O4 nanocrystals with core-shell architecture.

    PubMed

    Song, Qing; Zhang, Z John

    2012-06-20

    A combination of hard phase CoFe(2)O(4) and soft phase MnFe(2)O(4) as the bimagnetic nanocrystals in a core-shell architecture has been synthesized, and their magnetic properties have been systematically studied. Both HRTEM and EDS results confirmed the formation of bimagnetic core-shell structured nanocrystals. On the basis of the systematic and comparative studies of the magnetic properties of a mechanical mixture of pure CoFe(2)O(4) and MnFe(2)O(4) nanocrystals, chemically mixed Co(1-x)Mn(x)Fe(2)O(4) nanocrystals, and bimagnetic core-shell CoFe(2)O(4)@MnFe(2)O(4) and MnFe(2)O(4)@CoFe(2)O(4) nanocrystals, the bimagnetic core-shell nanocrystals show very unique magnetic properties, such as the blocking temperature and coercivity. Our results show that the coercivity correlates with the volume fraction of the soft phase as the theoretical hard-soft phase model has suggested. Furthermore, switching the hard phase CoFe(2)O(4) from the core to the shell shows great changes in the coercivity of the nanocrystals. The bimagnetic core-shell nanocrystals evidently demonstrate the rational design capability to separately control the blocking temperature and the coercivity in magnetic nanocrystals by varying the materials, their combination, and the volume ratio between the core and the shell and by switching hard or soft phase materials between the core and shell. Such controls via a bimagnetic core-shell architecture are highly desirable for magnetic nanocrystals in various applications. PMID:22621435

  18. Density Functional Theory Analysis of Structure, Energetics, and Spectroscopy for the Mn-Fe Active Site of Chlamydia trachomatis Ribonucleotide Reductase in Four Oxidation States

    PubMed Central

    Han, Wen-Ge; Giammona, Debra Ann; Bashford, Donald; Noodleman, Louis

    2010-01-01

    Models for the Mn-Fe active site structure of ribonucleotide reductase (RNR) from pathogenic bacteria Chlamydia trachomatis (Ct) in different oxidation states have been studied in this paper, using broken-symmetry density functional theory (DFT) incorporated with the conductor like screening (COSMO) solvation model and also with the finite-difference Poisson-Boltzmann self-consistent reaction field (PB-SCRF) calculations. The detailed structures for the reduced Mn(II)-Fe(II), the met Mn(III)-Fe(III), the oxidized Mn(IV)-Fe(III) and the superoxidized Mn(IV)-Fe(IV) states are predicted. The calculated properties, including geometries, 57Fe Mössbauer isomer shifts and quadrupole splittings, and 57Fe and 55Mn ENDOR hyperfine coupling constants, are compared with the available experimental data. The Mössbauer and energetic calculations show that the (μ-oxo, μ-hydroxo) models better represent the structure of the Mn(IV)-Fe(III) state than the di-μ-oxo models. The predicted Mn(IV)-Fe(III) distances (2.95 and 2.98 Å) in the (μ-oxo, μ-hydroxo) models are in agreement with the EXAFS experimental value of 2.92 Å (Younker, et al. J. Am. Chem. Soc. 2008, 130, 15022-15027). The effect of the protein and solvent environment on the assignment of the Mn metal position is examined by comparing the relative energies of alternative mono-Mn(II) active site structures. It is proposed that if the Mn(II)-Fe(II) protein is prepared with prior addition of Mn(II) or with Mn(II) richer than Fe(II), Mn is likely positioned at metal site 2, which is further from Phe127. PMID:20604534

  19. Fe-Ca-phosphate, Fe-silicate, and Mn-oxide minerals in concretions from the Monterey Formation

    USGS Publications Warehouse

    Medrano, M.D.; Piper, D.Z.

    1997-01-01

    Concentrically zoned phosphatic-enriched concretions were collected at three sites from the Monterey Formation. The following minerals were identified: vivianite, lipscombite, rockbridgeite, leucophosphite, mitridatite, carbonate fluorapatite, nontronite, todorokite, and barite. The mineralogy of the concretions was slightly different at each of the three collection sites. None of the concretions contains all of the minerals, but the spatial distribution of minerals in individual concretions, overlapping mineralogies between different concretions, and the geochemical properties of the separate minerals suggest a paragenesis represented by the above order. Eh increased from the precipitation of vivianite to that of rockbridgeite/lipscombite. The precipitation of leucophosphite, then mitridatite, carbonate fluorapatite and todorokite/Fe-oxide indicates increasing pH. Concretion growth culminated with the precipitation of todorokite, a Mn oxide, and minor amounts of barite along microfractures. Conspicuously absent are Fe-sulfide and Mn-phosphate minerals. The concretions are hosted by finely laminated diatomite. The laminations exhibit little to no deformation around the concretions, requiring that the concretions formed after compaction. We interpret this sediment feature and the paragenesis as recording the evolving pore-water chemistry as the formation was uplifted into the fresh-ground-water zone.

  20. Is the enrichment of metals in Mn-Fe nodules from the central Pacific correlated with glacial-interglacial stages?

    NASA Astrophysics Data System (ADS)

    Wegorzewski, A.; Kuhn, T.

    2012-12-01

    Polymetallic nodules and crusts contain high concentrations of Mn, Fe, Ni, Cu, Co and HFSE. The BGR has been exploring a German license area between the Clarion- and Clipperton Fracture Zone (CCFZ) in the Pacific for nodule abundance and metal content. Nodules are Mn-Fe oxy-hydroxide precipitations consisting of concentrically banded microlayers of different chemical and mineralogical composition. There are layers with high Mn/Fe ratios (3-400) and high Ni+Cu (2-6 wt%) but low Co contents (0.01-0.2 wt%). Mineralogically these layers consists of todorokite and birnessite. In contrast there are layers with low Mn/Fe ≤ 3 and low Ni+Cu (~1 wt%) but increased Co content (0.2-0.5 wt%) and consist mineralogically of Fe-rich vernadite which is epitaxial intergrown with feroxyhyte nanoparticles (Bodei et al., 2007). The different composition of the layers is depending on different growth processes, such as hydrogenetic (metal precipitation from the water column under oxic conditions; Mn/Fe ≤ 3) or diagenetic (metal precipitation from the sediment pore water under oxic (Mn/Fe 3-10) or suboxic (Mn/Fe ≥ 10) conditions; Halbach et al., 1988). X-ray Photoelectron Spectroscopy analyses of recently precipitated outer layers show low Mn/Fe ratios (1.4-2.8). The Ni+Cu content range from 0.34-1.86 wt% and Co shows concentrations between 0.33-1.42 wt%. These results are typical for hydrogenetic processes. They may indicate that in the oxic pore water the same metal enrichment processes prevail as in oxic seawater. Oxygen measurements of near-bottom and pore water proved that the nodules are currently growing under oxic conditions (Mewes, K.,unpub. data). Layers with Mn/Fe ratios of 3-400 cannot grow under such oxic conditions. The high fractionation of Mn and Fe is only possible under suboxic conditions as they are currently predominating in the Peru Basin (PB). Similar growth structures and Mn/Fe ratios of individual layers from CCFZ and PB nodules indicate suboxic conditions

  1. Catalytic conversion of syngas to mixed alcohols over Zn-Mn promoted Cu-Fe based catalyst

    DOE PAGESBeta

    Lu, Yongwu; Yu, Fei; Hu, Jin; Liu, Jian

    2012-04-12

    Zn-Mn promoted Cu-Fe based catalyst was synthesized by the co-precipitation method. Mixed alcohols synthesis from syngas was studied in a half-inch tubular reactor system after the catalyst was reduced. Zn-Mn promoted Cu-Fe based catalyst was characterized by SEM-EDS, TEM, XRD, and XPS. The liquid phase products (alcohol phase and hydrocarbon phase) were analyzed by GC-MS and the gas phase products were analyzed by GC. The results showed that Zn-Mn promoted Cu-Fe based catalyst had high catalytic activity and high alcohol selectivity. The maximal CO conversion rate was 72%, and the yield of alcohol and hydrocarbons were also very high. Cumore » (111) was the active site for mixed alcohols synthesis, Fe2C (101) was the active site for olefin and paraffin synthesis. The reaction mechanism of mixed alcohols synthesis from syngas over Zn-Mn promoted Cu-Fe based catalyst was proposed. Here, Zn-Mn promoted Cu-Fe based catalyst can be regarded as a potential candidate for catalytic conversion of biomass-derived syngas to mixed alcohols.« less

  2. Structural and magnetic properties of epitaxial FeMn2O4 film on MgO (100)

    NASA Astrophysics Data System (ADS)

    Duong van, Thiet; Nguyen, Thi Minh Hai; Nguyen, Anh Phuong; Dang Duc, Dung; Duong, Anh Tuan; Nguyen van, Quang; Cho, Sunglae

    FeM2X4 spinel structures, where M is a transition metal and X is oxygen or sulfur, are candidate materials for spin filters, one of the key devices in spintronics. On the other hand, the electronic and magnetic properties of these spinel structures could be modified via the control of cation distribution. Among the spinel oxides, iron manganese oxide is one of promising materials for applications. FeMn2O4 shows inverse spinel structure above 390 K and ferrimagnetic properties below the temperature. In this work, we report on the structural and magnetic properties of epitaxial FeMn2O4 thin film on MgO(100) substrate. The reflection high energy electron diffraction (RHEED) and X-ray diffraction (XRD) results indicated that films were epitaxially grown on MgO(100) without the impurity phases. The valance states of Fe and Mn in the FeMn2O4film were carried out using x-ray photoelectron spectrometer (XPS). The magnetic properties were measured by vibrating sample magnetometer (VSM), indicating that the samples are ferromagnetic at room temperature. The structural detail and origin of magnetic ordering in FeMn2O4 will be discussed.

  3. Catalytic conversion of syngas to mixed alcohols over Zn-Mn promoted Cu-Fe based catalyst

    SciTech Connect

    Lu, Yongwu; Yu, Fei; Hu, Jin; Liu, Jian

    2012-04-12

    Zn-Mn promoted Cu-Fe based catalyst was synthesized by the co-precipitation method. Mixed alcohols synthesis from syngas was studied in a half-inch tubular reactor system after the catalyst was reduced. Zn-Mn promoted Cu-Fe based catalyst was characterized by SEM-EDS, TEM, XRD, and XPS. The liquid phase products (alcohol phase and hydrocarbon phase) were analyzed by GC-MS and the gas phase products were analyzed by GC. The results showed that Zn-Mn promoted Cu-Fe based catalyst had high catalytic activity and high alcohol selectivity. The maximal CO conversion rate was 72%, and the yield of alcohol and hydrocarbons were also very high. Cu (111) was the active site for mixed alcohols synthesis, Fe2C (101) was the active site for olefin and paraffin synthesis. The reaction mechanism of mixed alcohols synthesis from syngas over Zn-Mn promoted Cu-Fe based catalyst was proposed. Here, Zn-Mn promoted Cu-Fe based catalyst can be regarded as a potential candidate for catalytic conversion of biomass-derived syngas to mixed alcohols.

  4. Effects of Manganese Content on Solidification Structures, Thermal Properties, and Phase Transformation Characteristics in Fe-Mn-C Steels

    NASA Astrophysics Data System (ADS)

    Yang, Jian; Wang, Yu-Nan; Ruan, Xiao-Ming; Wang, Rui-Zhi; Zhu, Kai; Fan, Zheng-Jie; Wang, Ying-Chun; Li, Cheng-Bin; Jiang, Xiao-Fang

    2015-02-01

    The solidification structures and the thermal properties of Fe-Mn-C steel ingots containing different manganese contents have been investigated and the phase transformation characteristics have been revealed by Thermo-Calc to assist development of the continuous casting technology of Fe-Mn-C steels. The results show that the thermal conductivity of the 0Mn steel is higher than that of the 3Mn steel. The thermal conductivity of the 6Mn steel is the lowest in the three kinds of steels below 1023 K (750 °C) and the highest above 1173 K (900 °C). The 0Mn steel has the highest value of the proportion of equiaxed grain zone area in the three kinds of steels, whereas the 3Mn steel has the lowest value of it in the steels. Manganese has the effect of promoting the coarsening of grains. The microstructure is martensite and a little retained austenite (3.8 mass pct) in the 6Mn steel, whereas the microstructure is bainite in the 3Mn steel. The 0Mn steel is characterized by ferrite and pearlite. The mean thermal expansion coefficients of the steels are in the range from 1.0 × 10-5 to 1.6 × 10-5 K-1, and the determinations of mold tapers of the 6Mn and 3Mn steels can refer to low-carbon steel. Using RA <60 pct as the criterion, the third brittle temperature region of the 6Mn steel is 873 K to 1073 K (600 °C to 800 °C), whereas those of the 3Mn steel and the 0Mn steel are 873 K to 1123 K (600 °C to 850 °C) and 873 K to 1173 K (600 °C to 900 °C), respectively. In the 6Mn and 3Mn steels, the deformation-induced ferrite (DIF) forms in sufficient quantities cause the recovery of the ductility at the low temperature end. However, since low strains are present when straightening, sufficient quantities of DIF cannot be formed. Thus, the ductility of the 6Mn and 3Mn steels cannot be improved during the continuous casting process. Manganese has the effect of enlarging the austenite phase region and reducing the δ-ferrite phase region and α-ferrite phase region.

  5. Giant magnetoresistance in the half-metallic double-perovskite ferrimagnet Mn2FeReO6.

    PubMed

    Li, Man-Rong; Retuerto, Maria; Deng, Zheng; Stephens, Peter W; Croft, Mark; Huang, Qingzhen; Wu, Hui; Deng, Xiaoyu; Kotliar, Gabriel; Sánchez-Benítez, Javier; Hadermann, Joke; Walker, David; Greenblatt, Martha

    2015-10-01

    The first transition-metal-only double perovskite compound, Mn(2+) 2 Fe(3+) Re(5+) O6 , with 17 unpaired d electrons displays ferrimagnetic ordering up to 520 K and a giant positive magnetoresistance of up to 220 % at 5 K and 8 T. These properties result from the ferrimagnetically coupled Fe and Re sublattice and are affected by a two-to-one magnetic-structure transition of the Mn sublattice when a magnetic field is applied. Theoretical calculations indicate that the half-metallic state can be mainly attributed to the spin polarization of the Fe and Re sites. PMID:26235744

  6. Crystal structure and magnetism of YbFeMnO 5: A neutron diffraction and Mössbauer spectroscopy study

    NASA Astrophysics Data System (ADS)

    Martínez-Lope, M. J.; Retuerto, M.; Alonso, J. A.; García-Hernández, M.; Krezhov, K.; Spirov, I.; Ruskov, T.; Fernández-Díaz, M. T.

    2009-04-01

    We have studied the crystal structure and magnetic properties of Y bFeMnO 5 obtained by substituting Fe 3+ for Mn 3+ in the parent Y bMn 2O 5 compound, through x-ray (XRD) and neutron (NPD) powder diffraction, magnetometry and Mössbauer spectroscopy. The samples were prepared in polycrystalline form by a soft chemistry route, followed by thermal treatments under high-oxygen pressure. The Rietveld analysis of diffraction data shows that Y bFeMnO 5 is isostructural with the oxides of stoichiometry RMn 2O 5 (R=rare earth, Y or Bi); the crystal structure is orthorhombic, Pbam space group, formed by chains of edge-sharing Mn 4+O 6 octahedra linked together by dimer groups of square pyramids Fe 3+O 5 and Y b 3+O 8 scalenohedra. A low level of disorder was established between the two transition metal positions 4 f and 4 h, occupied ideally by Mn 4+ and by Fe 3+: about 6% of Mn cations is replaced by Fe and 16% of Fe by Mn. Mössbauer spectroscopy data confirm the existence of two distinct crystallographic sites for Fe 3+. One of them corresponds to almost regular octahedra (at 4 f positions), characterized by nearly equal Mn/Fe-O distances of 1.890 Å at RT (from NPD data), giving a quadrupole doublet in the Mössbauer spectra at RT, broadened by the Fe/Mn disorder over this site. The second environment for Fe 3+ contributes to a less broadened, but more intensive doublet in the Mössbauer spectra, which corresponds to a distorted square pyramid Fe 3+O 5 (at 4h sites), for which NPD data demonstrates an axial distortion with three sets of Fe-O distances at 2.010(2) Å, 1.859(5) Å and 1.925(3) Å. Magnetic studies and the thermal evolution of the NPD patterns show that below a transition temperature Tc˜178 K a long-range magnetic order is developed, resolved from NPD data as a ferrimagnetic structure with propagation vector k=0. The spin arrangements for the Mn 4+ ions ( 4f site) and Fe 3+ ions ( 4h site) are given by the basis vectors ( 0,0,Fz) and ( 0,0,Fz

  7. Alloying effects on the microstructure and phase stability of Fe-Cr-Mn steels

    SciTech Connect

    Rawers, J.C.

    2008-05-01

    Austenitic Fe–Cr–Mn stainless steels interstitially alloyed with nitrogen have received considerable interest lately, due to their many property improvements over conventional Fe–Cr–Ni alloys. The addition of nitrogen to Fe–Cr–Mn stabilizes the fcc structure and increases the carbon solubility. The benefits of increased interstitial nitrogen and carbon content include: enhanced strength, hardness, and wear resistance. This study examines the effect of carbon, silicon, molybdenum, and nickel additions on the phase stability and tensile behavior of nitrogen-containing Fe–Cr–Mn alloys. Nitrogen and carbon concentrations exceeding 2.0 wt.% were added to the base Fe–18Cr–18Mn composition without the formation of nitride or carbide precipitates. Minor additions of molybdenum, silicon, and nickel did not affect nitrogen interstitial solubility, but did reduce carbon solubility resulting in the formation of M23C6 (M=Cr, Fe, Mo) carbides. Increasing the interstitial content increases the lattice distortion strain, which is directly correlated with an increase in yield stress.

  8. Influence of solute drag on the growth of proeutectoid ferrite in Fe-C-Mn alloy

    SciTech Connect

    Enomoto, M.

    1999-10-08

    The diffusion-controlled growth of proeutectoid ferrite ({alpha}) from austenite ({gamma}) in an Fe-C-Mn alloy was simulated incorporating the possible drag effect of Mn on the migration of {alpha}:{gamma} interphase boundaries. The magnitude of drag force or the dissipation of free energy by drag was evaluated by means of Cahn and Purdy-Brechet models. The growth rate of ferrite was calculated from the flux balance equation for carbon taking into account the fact that the carbon concentration at the boundary in austenite varied with time. Whereas the time exponent of growth deviated from one-half at each moment, the overall time dependence was dictated by carbon volume diffusion in austenite. The reported differences of experimental growth rates from those calculated assuming paraequilibrium were reduced considerably by incorporating the drag of Mn, although simulation results may largely depend on the shape and depth of solute interaction potential with {alpha}:{gamma} boundaries and Mn diffusivity within the boundary, etc.

  9. Redox Dynamics of Mixed Metal (Mn, Cr, and Fe) Ultrafine Particles

    PubMed Central

    Nico, Peter S.; Kumfer, Benjamin M.; Kennedy, Ian M.; Anastasio, Cort

    2008-01-01

    The impact of particle composition on metal oxidation state, and on changes in oxidation state with simulated atmospheric aging, are investigated experimentally in flame-generated nanoparticles containing Mn, Cr, and Fe. The results demonstrate that the initial fraction of Cr(VI) within the particles decreases with increasing total metal concentration in the flame. In contrast, the initial Mn oxidation state was only partly controlled by metal loading, suggesting the importance of other factors. Two reaction pathways, one reductive and one oxidative, were found to be operating simultaneously during simulated atmospheric aging. The oxidative pathway depended upon the presence of simulated sunlight and O3, whereas the reductive pathway occurred in the presence of simulated sunlight alone. The reductive pathway appears to be rapid but transient, allowing the oxidative pathway to dominate with longer aging times, i.e. greater than ∼8 hours. The presence of Mn within the particles enhanced the importance of the oxidative pathway, leading to more net Cr oxidation during aging implying that Mn can mediate oxidation by removal of electrons from other particulate metals. PMID:20046215

  10. Redox Dynamics of Mixed Metal (Mn, Cr, and Fe) Ultrafine Particles

    SciTech Connect

    Nico, Peter S.; Kumfer, Benjamin M.; Kennedy, Ian M.; Anastasio, Cort

    2008-08-01

    The impact of particle composition on metal oxidation state, and on changes in oxidation state with simulated atmospheric aging, are investigated experimentally in flame-generated nanoparticles containing Mn, Cr, and Fe. The results demonstrate that the initial fraction of Cr(VI) within the particles decreases with increasing total metal concentration in the flame. In contrast, the initial Mn oxidation state was only partly controlled by metal loading, suggesting the importance of other factors. Two reaction pathways, one reductive and one oxidative, were found to be operating simultaneously during simulated atmospheric aging. The oxidative pathway depended upon the presence of simulated sunlight and O{sub 3}, whereas the reductive pathway occurred in the presence of simulated sunlight alone. The reductive pathway appears to be rapid but transient, allowing the oxidative pathway to dominate with longer aging times, i.e. greater than {approx}8 hours. The presence of Mn within the particles enhanced the importance of the oxidative pathway, leading to more net Cr oxidation during aging implying that Mn can mediate oxidation by removal of electrons from other particulate metals.

  11. Scrutinizing Hall Effect in Mn_{1-x}Fe_{x}Si: Fermi Surface Evolution and Hidden Quantum Criticality.

    PubMed

    Glushkov, V V; Lobanova, I I; Ivanov, V Yu; Voronov, V V; Dyadkin, V A; Chubova, N M; Grigoriev, S V; Demishev, S V

    2015-12-18

    Separating between the ordinary Hall effect and anomalous Hall effect in the paramagnetic phase of Mn_{1-x}Fe_{x}Si reveals an ordinary Hall effect sign inversion associated with the hidden quantum critical (QC) point x^{*}∼0.11. The effective hole doping at intermediate Fe content leads to verifiable predictions in the field of fermiology, magnetic interactions, and QC phenomena in Mn_{1-x}Fe_{x}Si. The change of electron and hole concentrations is considered as a "driving force" for tuning the QC regime in Mn_{1-x}Fe_{x}Si via modifying the Ruderman-Kittel-Kasuya-Yosida exchange interaction within the Heisenberg model of magnetism. PMID:26722936

  12. Strain Localization in Thin Films of Bi(Fe,Mn)O3 Due to the Formation of Stepped Mn(4+)-Rich Antiphase Boundaries.

    PubMed

    MacLaren, I; Sala, B; Andersson, S M L; Pennycook, T J; Xiong, J; Jia, Q X; Choi, E-M; MacManus-Driscoll, J L

    2015-12-01

    The atomic structure and chemistry of thin films of Bi(Fe,Mn)O3 (BFMO) films with a target composition of Bi2FeMnO6 on SrTiO3 are studied using scanning transmission electron microscopy imaging and electron energy loss spectroscopy. It is shown that Mn(4+)-rich antiphase boundaries are locally nucleated right at the film substrate and then form stepped structures that are approximately pyramidal in three dimensions. These have the effect of confining the material below the pyramids in a highly strained state with an out-of-plane lattice parameter close to 4.1 Å. Outside the area enclosed by the antiphase boundaries, the out-of-plane lattice parameter is much closer to bulk values for BFMO. This suggests that to improve the crystallographic perfection of the films whilst retaining the strain state through as much of the film as possible, ways need to be found to prevent nucleation of the antiphase boundaries. Since the antiphase boundaries seem to form from the interaction of Mn with the Ti in the substrate, one route to perform this would be to grow a thin buffer layer of pure BiFeO3 on the SrTiO3 substrate to minimise any Mn-Ti interactions. PMID:26474888

  13. Magnetism of hexagonal Mn{sub 1.5}X{sub 0.5}Sn (X = Cr, Mn, Fe, Co) nanomaterials

    SciTech Connect

    Fuglsby, R.; Kharel, P.; Zhang, W.; Sellmyer, D. J.; Valloppilly, S.; Huh, Y.

    2015-05-07

    Mn{sub 1.5}X{sub 0.5}Sn (X = Cr, Mn, Fe, Co) nanomaterials in the hexagonal Ni{sub 2}In-type crystal structure have been prepared using arc-melting and melt spinning. All the rapidly quenched Mn{sub 1.5}X{sub 0.5}Sn alloys show moderate saturation magnetizations with the highest value of 458 emu/cm{sup 3} for Mn{sub 1.5}Fe{sub 0.5}Sn, but their Curie temperatures are less than 300 K. All samples except the Cr containing one show spin-glass-like behavior at low temperature. The magnetic anisotropy constants calculated from the high-field magnetization curves at 100 K are on the order of 1 Merg/cm{sup 3}. The vacuum annealing of the ribbons at 550 °C significantly improved their magnetic properties with the Curie temperature increasing from 206 K to 273 K for Mn{sub 1.5}Fe{sub 0.5}Sn.

  14. Strain Localization in Thin Films of Bi(Fe,Mn)O3 Due to the Formation of Stepped Mn4+-Rich Antiphase Boundaries

    NASA Astrophysics Data System (ADS)

    MacLaren, I.; Sala, B.; Andersson, S. M. L.; Pennycook, T. J.; Xiong, J.; Jia, Q. X.; Choi, E.-M.; MacManus-Driscoll, J. L.

    2015-10-01

    The atomic structure and chemistry of thin films of Bi(Fe,Mn)O3 (BFMO) films with a target composition of Bi2FeMnO6 on SrTiO3 are studied using scanning transmission electron microscopy imaging and electron energy loss spectroscopy. It is shown that Mn4+-rich antiphase boundaries are locally nucleated right at the film substrate and then form stepped structures that are approximately pyramidal in three dimensions. These have the effect of confining the material below the pyramids in a highly strained state with an out-of-plane lattice parameter close to 4.1 Å. Outside the area enclosed by the antiphase boundaries, the out-of-plane lattice parameter is much closer to bulk values for BFMO. This suggests that to improve the crystallographic perfection of the films whilst retaining the strain state through as much of the film as possible, ways need to be found to prevent nucleation of the antiphase boundaries. Since the antiphase boundaries seem to form from the interaction of Mn with the Ti in the substrate, one route to perform this would be to grow a thin buffer layer of pure BiFeO3 on the SrTiO3 substrate to minimise any Mn-Ti interactions.

  15. Effects of Fe content on the microstructure and properties of CuNi10FeMn1 alloy tubes fabricated by HCCM horizontal continuous casting

    NASA Astrophysics Data System (ADS)

    Jiang, Yan-bin; Xu, Jun; Liu, Xin-hua; Xie, Jian-xin

    2016-04-01

    Heating-cooling combined mold (HCCM) horizontal continuous casting technology developed by our research group was used to produce high axial columnar-grained CuNi10FeMn1 alloy tubes with different Fe contents. The effects of Fe content (1.08wt%-2.01wt%) on the microstructure, segregation, and flushing corrosion resistance in simulated flowing seawater as well as the mechanical properties of the alloy tubes were investigated. The results show that when the Fe content is increased from 1.08wt% to 2.01wt%, the segregation degree of Ni and Fe elements increases, and the segregation coefficient of Ni and Fe elements falls from 0.92 to 0.70 and from 0.92 to 0.63, respectively. With increasing Fe content, the corrosion rate of the alloy decreases initially and then increases. When the Fe content is 1.83wt%, the corrosion rate approaches the minimum and dense, less-defect corrosion films, which contain rich Ni and Fe elements, form on the surface of the alloy; these films effectively protect the α-matrix and reduce the corrosion rate. When the Fe content is increased from 1.08wt% to 2.01wt%, the tensile strength of the alloy tube increases from 204 MPa to 236 MPa, while the elongation to failure changes slightly about 46%, indicating the excellent workability of the CuNi10FeMn1 alloy tubes.

  16. Temporal and spatial variability of Fe and Mn in perched groundwater flowing through weathered argillite underlying a steep forested hillslope

    NASA Astrophysics Data System (ADS)

    Kim, H.; Bishop, J. K.

    2013-12-01

    Groundwater flowing through weathered bedrock dictates the runoff chemistry to streams in many catchments yet; its chemical evolution has been rarely documented. In particular, observations of Fe and Mn dynamics in groundwater are extremely challenging due to their high reactivity. To preserve the sample integrity for these elements we have developed a new sampling scheme that is applicable to autosamplers; a gravitational filtration system (GFS). GFS is capable of filtering samples by gravity within 30 minutes after the sampling. The GFS samples showed a good agreement with reference samples, which were collected following the standard sampling method for trace metals (i.e. immediate filtration and acidification). Since October 2011, GFS has been employed to monitor Fe and Mn in perched groundwater that moves through weathered argillite in an intensively instrumented hillslope (Rivendell), in the Angelo Coast Range Reserve. The study site is located at the headwaters of the Eel River, northern California, characterized by a typical coastal Californian Mediterranean climate. We collected groundwater samples at 3 wells along the hillslope (upslope (W10), mid-slope (W3) and near the creek (W1)) with 1-3 day intervals. Additionally, rainwater and throughfall samples were collected at a meadow near the hillslope and at the middle of the hillslope, respectively. The results from our observations indicate that Fe and Mn exhibit distinct spatial and temporal behavior under variable hydrologic conditions. The concentrations of Fe in throughfall vs. rainwater were similar (0.45μM vs. 0.49μM), but Mn in throughfall was 10-fold higher than that in rainwater (1.2 μM vs. 0.1 μM). In the early rainy season, W10's water table was deep (-18m) and Fe and Mn in W10 were 30-150 nM and 1-2 μM, respectively. As the rainy season proceeds, W10's water table rose by 4-6m, indicating the arrival of new water. At this time, Mn in W10 decreased to ~0.1 μM, synchronizing with the water

  17. X-ray magnetic circular dichroism on La2/3Ca1/3Mn0.97Fe0.03O3 thin films

    NASA Astrophysics Data System (ADS)

    Figueroa, Adriana I.; Campillo, Gloria E.; Baker, Alexander A.; Osorio, Jaime A.; Arnache, Oscar L.; van der Laan, Gerrit

    2015-11-01

    The element-selective technique of X-ray magnetic circular dichroism (XMCD) has been used to study the magnetic properties of La2/3Ca1/3Mn0.97Fe0.03O3 (LCMFO) thin films. XMCD measurements below the ferromagnetic ordering temperature at the Mn and Fe L2,3 absorption edges allow the determination of the contributions and relative orientations of the Mn and Fe magnetic moments. A reduction in the Mn L2,3 XMCD signal of the LCMFO sample compared to that for the parent La2/3Ca1/3MnO3 (LCMO) system reveals important modifications in the electronic and magnetic properties with the presence of Fe. The Fe L2,3 X-ray absorption (XAS) for the LCMFO film is characteristic of Fe3+, and the comparison with multiplet calculations shows that the Fe dopants occupy octahedral sites in the crystal, which is consistent with Fe3+ substituting Mn3+ in LCMO. The magnetic moments of Mn and Fe are found to align antiparallel, which suggests the presence of Mn-O-Fe superexchange coupling. This result is consistent with macroscopic magnetometry measurements on the LCMFO system, which show a decrease in saturation magnetization of LCMO with Fe doping.

  18. Synthesis and study of the crystallographic and magnetic structure of DyFeMnO{sub 5}: A new ferrimagnetic oxide

    SciTech Connect

    Martinez-Lope, M.J.; Retuerto, M.; Alonso, J.A. Pomjakushin, V.

    2008-09-15

    The title oxide has been obtained by replacing Mn{sup 3+} by Fe{sup 3+} in the parent oxide DyMn{sub 2}O{sub 5}. The crystallographic and magnetic structures have been analysed from neutron powder diffraction (NPD) data, in complement with susceptibility and magnetic measurements. DyFeMnO{sub 5} is orthorhombic, belonging to the Pbam space group as the parent compound. The crystal structure contains infinite chains of edge-sharing Mn{sup 4+}O{sub 6} octahedra, interconnected by dimer units of Fe{sup 3+}O{sub 5} square pyramids. There is a certain antisite disorder in the crystal structure, with 8.0% of the Mn{sup 4+} sites occupied by Fe cations, and 8.2% of the Fe{sup 3+} positions occupied by Mn{sup 3+} cations. The magnetization measurements show that DyFeMnO{sub 5} presents magnetic order below T{sub C}{approx}178 K; a study of the magnetic structure from the low-temperature NPD patterns indicates an antiferromagnetic coupling of the Mn{sup 4+} and Fe{sup 3+} spins, with the polarization of the Dy{sup 3+} magnetic moments parallel to the those of the Fe sublattice. - Graphical abstract: DyFeMnO{sub 5} is orthorhombic (Pbam) as the parent DyMn{sub 2}O{sub 5} oxide. The crystal structure contains infinite chains of edge-sharing Mn{sup 4+}O{sub 6} octahedra, interconnected by dimer units of Fe{sup 3+}O{sub 5} square pyramids. It is ferrimagnetic below T{sub C}{approx}178 K; a NPD study indicated an antiferromagnetic coupling of the Mn{sup 4+} and Fe{sup 3+} spins, with Dy{sup 3+} magnetic moments parallel to those of Fe.

  19. Numerical Study of Microstructural Evolution During Homogenization of Al-Si-Mg-Fe-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Priya, Pikee; Johnson, David R.; Krane, Matthew J. M.

    2016-09-01

    Microstructural evolution during homogenization of Al-Si-Mg-Fe-Mn alloys occurs in two stages at different length scales: while holding at the homogenization temperature (diffusion on the scale of the secondary dendrite arm spacing (SDAS) in micrometers) and during quenching to room temperature (dispersoid precipitation at the nanometer to submicron scale). Here a numerical study estimates microstructural changes during both stages. A diffusion-based model developed to simulate evolution at the SDAS length scale predicts homogenization times and microstructures matching experiments. That model is coupled with a Kampmann Wagner Neumann-based precipitate nucleation and growth model to study the effect of temperature, composition, as-cast microstructure, and cooling rates during posthomogenization quenching on microstructural evolution. A homogenization schedule of 853 K (580 °C) for 8 hours, followed by cooling at 250 K/h, is suggested to optimize microstructures for easier extrusion, consisting of minimal α-Al(FeMn)Si, no β-AlFeSi, and Mg2Si dispersoids <1 μm size.

  20. Immobilization of selenite in soil and groundwater using stabilized Fe-Mn binary oxide nanoparticles.

    PubMed

    Xie, Wenbo; Liang, Qiqi; Qian, Tianwei; Zhao, Dongye

    2015-03-01

    Stabilized Fe-Mn binary oxide nanoparticles were synthesized and tested for removal and in-situ immobilization of Se(IV) in groundwater and soil. A water-soluble starch or food-grade carboxymethyl cellulose (CMC) was used as a stabilizer to facilitate in-situ delivery of the particles into contaminated soil. While bare and stabilized nanoparticles showed rapid sorption kinetics, starch-stabilized Fe-Mn offered the greatest capacity for Se(IV). The Langmuir maximum capacity was determined to be 109 and 95 mg-Se/g-Fe for starch- and CMC-stabilized nanoparticles, respectively, and the high Se(IV) uptake was observed over the typical groundwater pH range of 5-8. Column breakthrough tests indicated that the stabilized nanoparticles were deliverable in a model sandy soil while non-stabilized particles were not. When a Se(IV)-spiked soil was treated in situ with the nanoparticles, >90% water leachable Se(IV) was transferred to the nanoparticle phase, and thereby immobilized as the particles were retained in the downstream soil matrix. The nanoparticle amendment reduced the TCLP (toxicity characteristic leaching procedure) leachability and the California WET (waste extraction test) leachability of Se(IV) by 76% and 71%, respectively. The technology holds the potential to fill a major technology gap in remediation of metals-contaminated soil and groundwater. PMID:25577492

  1. Numerical Study of Microstructural Evolution During Homogenization of Al-Si-Mg-Fe-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Priya, Pikee; Johnson, David R.; Krane, Matthew J. M.

    2016-06-01

    Microstructural evolution during homogenization of Al-Si-Mg-Fe-Mn alloys occurs in two stages at different length scales: while holding at the homogenization temperature (diffusion on the scale of the secondary dendrite arm spacing (SDAS) in micrometers) and during quenching to room temperature (dispersoid precipitation at the nanometer to submicron scale). Here a numerical study estimates microstructural changes during both stages. A diffusion-based model developed to simulate evolution at the SDAS length scale predicts homogenization times and microstructures matching experiments. That model is coupled with a Kampmann Wagner Neumann-based precipitate nucleation and growth model to study the effect of temperature, composition, as-cast microstructure, and cooling rates during posthomogenization quenching on microstructural evolution. A homogenization schedule of 853 K (580 °C) for 8 hours, followed by cooling at 250 K/h, is suggested to optimize microstructures for easier extrusion, consisting of minimal α-Al(FeMn)Si, no β-AlFeSi, and Mg2Si dispersoids <1 μm size.

  2. Itinerant Antiferromagnetism in FeMnP0.8Si0.2

    DOE PAGESBeta

    Sales, Brian C.; Susner, Michael A.; Conner, Benjamin S.; Yan, Jiaqiang Q.; May, Andrew F.

    2015-09-25

    Compounds based on the Fe2P structure have continued to attract interest because of the interplay between itinerant and localized magnetism in a noncentrosymmetric crystal structure, and because of the recent developments of these materials for magnetocaloric applications. We report the growth and characterization of millimeter-sized single crystals of FeMnP0.8Si0.2 with the Fe2P structure. Single-crystal x-ray diffraction, magnetization, resistivity, and Hall and heat capacity data are reported. The crystals exhibit itinerant antiferromagnetic order below 158 K with no hint of ferromagnetic behavior in the magnetization curves and with the spins ordered primarily in the ab plane. The room-temperature resistivity is closemore » to the Ioffe-Regel limit for a metal. Single-crystal x-ray diffraction indicates a strong preference for Mn to occupy the larger pyramidal 3g site. The cation site preference in the as-grown crystals and the antiferromagnetism were not changed after high-temperature anneals and a rapid quench to room temperature« less

  3. Annealing texture of a cold-rolled Fe-Mn-Al-Si-C alloy

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Basudev; Ray, Ranjit Kumar

    2015-09-01

    The study of recrystallization texture of a cold deformed Fe-Mn-Al-Si-C alloy, with about 30% Mn, has been discussed in this paper. The alloy is fully austenitic at room temperature, and therefore, principal FCC rolling textures were developed in this material at different stages of cold rolling. The present study was undertaken to observe the transformation of FCC rolling texture during recrystallization of a heavily cold deformed specimen. It was observed that isothermal annealing at 750 °C led to a weak recrystallisation texture, which was quite similar to the deformation texture developed at the early stage of cold rolling. During recovery stage, a strong Bs/Goss-type texture was developed, which was identified as a new observation in this work.

  4. Fe and Mn oxidation states by TEM-EELS in fine-particle emissions from a Fe-Mn alloy making plant.

    PubMed

    Marris, Hélène; Deboudt, Karine; Flament, Pascal; Grobéty, Bernard; Gieré, Reto

    2013-10-01

    Fine particles were sampled both inside the chimneys and in the near-field of an Fe-Mn-alloy manufacturing plant. The transfer from one point to another point in the environment, as well as the bioavailability and toxicity of these two metals, depend above all on their speciation. The oxidation states of iron and manganese in the collected particles were determined by using transmission electron microscopy coupled with electron energy-loss spectroscopy (TEM-EELS). The mineralogical identity of these metal-rich particles was determined by selected area electron diffraction (SAED) coupled with energy-dispersive X-ray spectroscopy (EDX). This study shows that both iron and manganese in metallic particles are prone to oxidation reactions via gas/particle conversion mechanisms, which take place in the flue gases within the smoke stacks. This phenomenon is more pronounced for the smallest Fe-rich particles. However, no further change of oxidation state of the two elements was observed in the near-field of the plant, after emission into the atmosphere (within <2000 m of the smoke stacks). The oxidation states of iron and manganese remain mainly between +II and +III, which is probably due to short residence time of these particles in the pollution plume. PMID:24000787

  5. Magnetic properties of Fe-Mn-Pt for heat assisted magnetic recording applications

    NASA Astrophysics Data System (ADS)

    Park, Jihoon; Hong, Yang-Ki; Kim, Seong-Gon; Gao, Li; Thiele, Jan-Ulrich

    2015-02-01

    We calculate the electronic structures of FePt and Fe0.5Mn0.5Pt using first-principles calculations based on density functional theory within the local-spin-density approximation. The Curie temperature (Tc) was calculated by mean field approximation. Composition dependence of the Cure temperature (Tc(x)) of Fe1-xMnxPt was used to identify a composition to meet the desired Tc in the range of 600-650 K. The identified composition (0.0294 ≤ x ≤ 0.0713) gives saturation magnetization (Ms) in the range of 1041-919 emu/cm3 and magnetocrystalline anisotropy constant (K) in the range of 9.96-8.36 × 106 J/m3 at 0 K. Temperature dependent M(T) and K(T) of Fe1-xMnxPt (0.0294 ≤ x ≤ 0.0713) were calculated using the Brillouin function and Callen-Callen experimental relation, respectively. Fe1-xMnxPt (0.0294 ≤ x ≤ 0.0713) shows 930-800 emu/cm3 of Ms and 7.18-5.61 × 106 J/m3 of K at 300 K, thereby satisfying desired magnetic properties for heat-assisted magnetic recording media to achieve 4 Tb/in.2 areal density.

  6. Coexistence of Fe(II)- and Mn(II)-oxidizing bacteria govern the formation of deep sea umber deposits

    NASA Astrophysics Data System (ADS)

    Peng, Xiaotong; Ta, Kaiwen; Chen, Shun; Zhang, Lijuan; Xu, Hengchao

    2015-11-01

    The genesis of umber deposits has remained controversial for several decades. Recently, microbial Fe(II) oxidation associated with low-temperature diffuse venting has been identified as a key process for the formation of umber deposits, but the exact biogeochemical mechanisms involved to the precipitation of Mn oxides in umber deposits still remain unknown. Here, we used nano secondary ion mass spectrometer, synchrotron-based X-ray absorption spectroscopy, electron microscopy, and molecular techniques to demonstrate the coexistence of two types of metal-oxidizing bacteria within deep-sea hydrothermal umber deposits at the South Mid-Atlantic Ridge, where we found unique spheroids composed of biogenic Fe oxyhydroxides and Mn oxides in the deposits. Our data show that Fe oxyhydroxides and Mn oxides are metabolic by-products of lithotrophic Fe(II)-oxidizing bacteria and heterotrophic Mn(II)-oxidizing bacteria, respectively. The hydrothermal vents fuel lithotrophic microorganisms, which constitute a trophic base that might support the activities of heterogenic Mn(II)-oxidizing bacteria. The biological origin of umber deposits shed light on the importance of geomicrobiological interaction in triggering the formation of metalliferous deposits, with important implications for the generation of submarine Mn deposits and crusts.

  7. Enhanced Stability of the Fe(II)/Mn(II) State in a Synthetic Model of Heterobimetallic Cofactor Assembly.

    PubMed

    Kerber, William D; Goheen, Joshua T; Perez, Kaitlyn A; Siegler, Maxime A

    2016-01-19

    Heterobimetallic Mn/Fe cofactors are found in the R2 subunit of class Ic ribonucleotide reductases (R2c) and R2-like ligand binding oxidases (R2lox). Selective cofactor assembly is due at least in part to the thermodynamics of M(II) binding to the apoprotein. We report here equilibrium studies of Fe(II)/Mn(II) discrimination in the biomimetic model system H5(F-HXTA) (5-fluoro-2-hydroxy-1,3-xylene-α,α'-diamine-N,N,N',N'-tetraacetic acid). The homobimetallic F-HXTA complexes [Fe(H2O)6][1]2·14H2O and [Mn(H2O)6][2]2·14H2O (1 = [Fe(II)2(F-HXTA)(H2O)4](-); 2 = [Mn(II)2(F-HXTA)(H2O)4](-)) were characterized by single crystal X-ray diffraction. NMR data show that 1 retains its structure in solution (2 is NMR silent). Metal exchange is facile, and the heterobimetallic complex [Fe(II)Mn(II)(F-HXTA)(H2O)4](-) (3) is formed from mixtures of 1 and 2. (19)F NMR was used to quantify 1 and 3 in the presence of excess M(II)(aq) at various metal ratios, and equilibrium constants for Fe(II)/Mn(II) discrimination were calculated from these data. Fe(II) is preferred over Mn(II) with K1 = 182 ± 13 for complete replacement (2 ⇌ 1). This relatively modest preference is attributed to a hard-soft acid-base mismatch between the divalent cations and the polycarboxylate ligand. The stepwise constants for replacement are K2 = 20.1 ± 1.3 (2 ⇌ 3) and K3 = 9.1 ± 1.1 (3 ⇌ 1). K2 > K3 demonstrates enhanced stability of the heterobimetallic state beyond what is expected for simple Mn(II) → Fe(II) replacement. The relevance to Fe(II)/Mn(II) discrimination in R2c and R2lox proteins is discussed. PMID:26709740

  8. Thermoelectric properties of Fe and Al double substituted MnSi{sub γ} (γ~1.73)

    SciTech Connect

    Barczak, S.A.; Downie, R.A.; Popuri, S.R.; Decourt, R.; Pollet, M.; Bos, J.W.G.

    2015-07-15

    Two series of Fe and Al double substituted MnSi{sub γ} chimney ladders with a nominal valence electron count, VEC=14 per transition metal were prepared (γ=1.75). Simultaneous replacement of Mn with Fe and Si with Al yielded the Mn{sub 1−x}Fe{sub x}Si{sub 1.75−x}Al{sub x} series while the second Mn{sub 1−x}Fe{sub x}Si{sub 1.75–1.75x}Al{sub 2x} series follows the pseudo-binary between MnSi{sub 1.75} and FeAl{sub 2}. Scanning electron microscopy and elemental mapping revealed that ~60% of the nominal Al content ends up in the product with the remainder lost to sublimation, and that up to 7% Al can be substituted in the main group sublattice. Profile analysis of X-ray powder diffraction data revealed gradual changes in the cell metrics, consistent with the simultaneous substitution of Fe and Al in a fixed ratio. All samples are p-type with VEC≈13.95 from the structural data and ~1×10{sup 21} holes cm{sup −3} from variable temperature Seebeck measurements. The substituted samples have lower electrical resistivities (ρ{sub 300} {sub K}=2–5 mΩ cm) due to an improved microstructure. This leads to increased thermoelectric power factors (largest S{sup 2}/ρ=1.95 mW m{sup −1} K{sup −2}) compared to MnSi{sub γ}. The thermal conductivity for the Mn{sub 0.95}Fe{sub 0.05}Si{sub 1.66}Al{sub 0.1} sample is 2.7 W m{sup −1} K{sup −1} between 300 and 800 K, and is comparable to literature data for the parent material. - Graphical abstract: The crystal structure, microstructure and thermoelectric properties of Fe and Al double substituted MnSi{sub γ} (γ~1.73) have been investigated. - Highlights: • Up to 7% Al can be substituted in MnSi{sub γ} when co-doped with Fe. • Improved microstructure and reduced electrical resistivities for Al substituted samples. • Largest power factor 1.95 mW m{sup −1} K{sup −2} and best estimated ZT=0.5.

  9. Synthesis, structural and dielectric properties of double perovskite Ho2FeMnO6

    NASA Astrophysics Data System (ADS)

    Chakraborty, Tirthankar; Elizabeth, Suja

    2016-05-01

    A new double perovskite Ho2FeMnO6 was grown by nitrate route. Temperature dependent dielectric response was recorded at different frequencies. Relaxor-like-behavior is observed whose activation energy was calculated using Arrhenius equation. The dispersion is very small at room temperature. The Nyquist plot over a broad frequency range at room temperature provides evidence for the presence of three relaxations from sample electrode interface, grain boundary and grain. The corresponding values of resistance and capacitance were calculated from the equivalent circuit model analysis of the Nyquist plot.

  10. Magnetic vortex in epitaxially-grown Co2(Fe,Mn)Si alloy

    NASA Astrophysics Data System (ADS)

    Yamamoto, T.; Seki, T.; Kotsugi, M.; Takanashi, K.

    2016-04-01

    We report magnetic vortex formation in epitaxially grown Co2Fe0.4Mn0.6Si (CFMS) Heusler alloy discs that was confirmed using photoemission electron microscopy and the magneto-optical Kerr effect. The phase diagram of magnetic domain structures as functions of the disc thickness (t) and diameter (D) indicates that the magnetic vortex is stable in wide ranges of t and D even for the epitaxial CFMS. The annihilation field of vortex core depended not only on the disc aspect ratio but also on t. Numerical simulation suggests that this t dependence results from extrinsic pinning of a vortex core due to the epitaxial growth.

  11. 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.

  12. Perpendicular magnetic anisotropy in Co2Fe0.4Mn0.6Si

    NASA Astrophysics Data System (ADS)

    Ludbrook, B. M.; Ruck, B. J.; Granville, S.

    2016-07-01

    We report perpendicular magnetic anisotropy (PMA) in the half-metallic ferromagnetic Heusler alloy Co2Fe0.4Mn0.6Si (CFMS) in a MgO/CFMS/Pd trilayer stack. PMA is found for CFMS thicknesses between 1 and 2 nm, with a magnetic anisotropy energy density of KU=1.5 ×106 erg/cm3 for tCFMS=1.5 nm. Both the MgO and Pd layer are necessary to induce the PMA. We measure a tunable anomalous Hall effect, where its sign and magnitude vary with both the CFMS and Pd thickness.

  13. Multiscale twin hierarchy in NiMnGa shape memory alloys with Fe and Cu

    DOE PAGESBeta

    Barabash, Rozaliya I.; Barabash, Oleg M.; Popov, Dmitry; Shen, Guoyin; Park, Changyong; Yang, Wenge

    2015-01-31

    X-ray microdiffraction and scanning electron microscopy studies reveal 10 M martensitic structure with a highly correlated multiscale twin hierarchy organization in NiMnGaFeCu shape memory alloys. In this paper, high compatibility is found at the twin interfaces resulting in a highly correlated twinned lattice orientation across several laminate levels. The lattice unit cell is described as monoclinic I-centered with a = 4.28 Å, b = 4.27 Å, c = 5.40 Å, γ = 78.5°. The modulation is found parallel to the b axis. Finally, thin tapered needle-like lamellae and branching are observed near the twin boundaries.

  14. Thermodynamics of Nitrogen in Fe-Mn-Al-Si-C Alloy Melts

    NASA Astrophysics Data System (ADS)

    Paek, Min-Kyu; Chatterjee, Saikat; Pak, Jong-Jin; Jung, In-Ho

    2016-04-01

    Thermodynamic behavior of nitrogen in the entire range of the Fe-Mn-Al-Si-C liquid solution was modeled based on the critical evaluation and optimization of all available experimental data. The Gibbs energy of liquid solution was described using the Modified Quasichemical Model (MQM) in the pair approximation, instead of classical Wagner Interaction Parameter Formalism, to consider the strong interactions between species in liquid state. In particular, the dissolution behavior of N and formation of AlN in the entire ternary and higher order liquids were accurately predicted from the MQM only with binary model parameters of N.

  15. Influence of Carbon on the Microstructure of a Fe-Mn-Si-Cr-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Mostafa, Khaled M.; de Baerdemaeker, J.; van Caenegem, N.; Segers, D.; Houbaert, Y.

    2009-08-01

    The influence of the addition of C to the Fe-Mn-Si-Cr-Ni base material is investigated at room temperature. Steel samples were deformed during a tensile experiment up to a strain of 17%. Light optical microscopy (OM) and x-ray diffraction (XRD) gave information about the different micro-structural phases that exist in the deformed and the undeformed alloys. The evolution of the defect structure is followed by positron annihilation techniques such as Doppler broadening of annihilation radiation spectroscopy (DBAR) and the positron annihilation lifetime spectroscopy (PALS). During deformation a martensitic ɛ-phase is induced. The size of the martensite plates increases with increasing deformation.

  16. Enhanced arsenic removal by in situ formed Fe-Mn binary oxide in the aeration-direct filtration process.

    PubMed

    Wu, Kun; Liu, Rui-Ping; Liu, Hui-Juan; Lan, Hua-Chun; Qu, Jiu-Hui

    2012-11-15

    Field studies were conducted to evaluate the feasibility of an in situ formed Fe-Mn binary oxide (in situ FMBO) for improving arsenic (As) removal in the aeration-direct filtration process. The transformation and transportation of As, Fe, and Mn in the filter bed were also investigated. The in situ FMBO increased the As removal efficiency by 20-50% to keep the residual As below 10 μg/L. The optimum FMBO dosage was determined to be 0.55 mg/L with the Fe/Mn ratio as 10:1. The removal of Fe, Mn, turbidity, and particles was also improved to a large extent. The in situ FMBO favored the transformation of soluble As, Fe, and Mn into the solid phases, benefiting the removal of these pollutants by the subsequent filtration. Moreover, the deposited precipitates onto the filter media were characterized, as indicated by the analyses of SEM/EDS and particle size distribution. The long-term experiments exhibited decreased head loss growth and prolonged run length, suggesting an enhanced pollutant catching capacity of the filter media. The full-scale field study with a flow of 10,000 m3/d confirmed positive effects of in situ FMBO on As removal, with the average effluent As concentration reduced from 20 μg/L to 6 μg/L (reagent cost=0.006 ¥/m3). PMID:23017236

  17. Mn(ii) mediated degradation of artemisinin based on Fe3O4@MnSiO3-FA nanospheres for cancer therapy in vivo

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Zhang, Weijie; Zhang, Min; Guo, Zhen; Wang, Haibao; He, Mengni; Xu, Pengping; Zhou, Jiajia; Liu, Zhenbang; Chen, Qianwang

    2015-07-01

    Artemisinin (ART) is a natural drug with potent anticancer activities related with Fe2+ mediated cleavage of the endoperoxide bridge in ART. Herein, we reported that Mn2+ could substitute for Fe2+ to react with ART and generate toxic products, inducing a much higher anticancer efficiency. On this basis, we prepared pH-responsive Fe3O4@MnSiO3-FA nanospheres which can efficiently deliver hydrophobic ART into tumors in mice models. Mn2+ was released in acidic tumor environments and intracellular lysosomes, interacting with ART to kill cancer cells. The ART-loaded nanocarriers could suppress tumor growth more efficiently than free ART, which could be further illustrated by magnetic resonance imaging (MRI). Histological analysis revealed that the drug delivery system had no obvious effect on the major organs of mice. ART has been reported to have lower toxicity than chemotherapeutics. The ART-loaded nanocarriers are promising to be used in improving the survival of chemotherapy patients, providing a novel method for clinical tumor therapy.Artemisinin (ART) is a natural drug with potent anticancer activities related with Fe2+ mediated cleavage of the endoperoxide bridge in ART. Herein, we reported that Mn2+ could substitute for Fe2+ to react with ART and generate toxic products, inducing a much higher anticancer efficiency. On this basis, we prepared pH-responsive Fe3O4@MnSiO3-FA nanospheres which can efficiently deliver hydrophobic ART into tumors in mice models. Mn2+ was released in acidic tumor environments and intracellular lysosomes, interacting with ART to kill cancer cells. The ART-loaded nanocarriers could suppress tumor growth more efficiently than free ART, which could be further illustrated by magnetic resonance imaging (MRI). Histological analysis revealed that the drug delivery system had no obvious effect on the major organs of mice. ART has been reported to have lower toxicity than chemotherapeutics. The ART-loaded nanocarriers are promising to be used in

  18. Tuning of structural and magnetic properties of Mn-doped CoFe{sub 2}O{sub 4} nanoparticles

    SciTech Connect

    Rani, Stuti; Varma, G. D.

    2015-06-24

    In the present manuscript, Mn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) nanoparticles have been synthesized with co-precipitation method by annealing at 900 °C and studied the structural and magnetic properties. X ray diffraction pattern reveals the formation of single phase cubic spinel structure with the space group Fd-3m. An impurity peak of α-Fe{sub 2}O{sub 3} has been observed in the XRD patterns of samples with Mn composition, x ≥ 0.4. However, this impurity phase of α-Fe{sub 2}O{sub 3} is not observed in the MnFe{sub 2}O{sub 4} sample synthesized by annealing at 500 °C. FESEM results indicate the formation of nano-sized particles. Magnetic measurements show ferrimagnetic interaction in Mn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} (x≥0) nanoparticles at room temperature. However, MnFe{sub 2}O{sub 4} sample synthesized by annealing at 500 °C shows superparamagnetic behavior. We have fitted the M-H curve of MnFe{sub 2}O{sub 4} synthesized by annealing at 500 °C with modified Langvenin function to confirm superparamagnetism. The correlation between the structural and observed magnetic properties of as synthesized samples nanoparticles will be described and discussed in this paper.

  19. Using granular C0-AI2O3 spacer for optimization of functional parameters of the FeMn/Fe20Ni80 magnetoresistive films

    NASA Astrophysics Data System (ADS)

    Gorkovenko, A. N.; Lepalovskij, V. N.; Adanakova, O. A.; Vas'kovskiy, V. O.

    2016-03-01

    In this paper we studied the possibility of tailoring the functional properties of the multilayer magnetoresistive medium with unidirectional anisotropy and the anisotropic magnetoresistance effect (AMR). Objects of the research were composite Co-Al2O3 films and Ta/Fe20Ni80/Fe50Mn50/Fe20Ni80/Co-Al2O3/Fe20Ni80/Ta multilayers structures obtained by magnetron sputtering and selectively subjected vacuum annealing. Structure, magnetic and magnetoresistive properties of the films in the temperature range 77÷440 K were investigated.

  20. Ferrimagnetism in MnFeF/sub 5/. 2H/sub 2/O

    SciTech Connect

    Jones, E.R. Jr.; Van Hine, C.; Datta, T.; Cathey, L.; Karraker, D.G.

    1985-11-06

    The magnetic susceptibility of MnFeF/sub 5/.2H/sub 2/O was measured at temperatures from 5 to 300 K for applied fields of up to 1 kOe with a SQUID susceptometer. A ferrimagnetic phase transition was observed at 38 +/- 0.25 K. At temperatures between 200 and 300 K the susceptibility followed a Curie-Weiss law chi = C/(T-Theta) with Theta = -164 K and an effective magnetic moment of 7.4 +/- 0.1 ..mu../sub B/. The Moessbauer resonance spectrum gave a quadrupole-split doublet with an isomer shift of 0.483 mm/s relative to ..cap alpha..-iron, indicating that all of the iron was Fe/sup 3 +/. 13 references, 4 figures, 2 tables.

  1. Million-Fold Electrical Conductivity Enhancement in Fe2(DEBDC) versus Mn2(DEBDC) (E = S, O)

    PubMed Central

    2015-01-01

    Reaction of FeCl2 and H4DSBDC (2,5-disulfhydrylbenzene-1,4-dicarboxylic acid) leads to the formation of Fe2(DSBDC), an analogue of M2(DOBDC) (MOF-74, DOBDC4– = 2,5-dihydroxybenzene-1,4-dicarboxylate). The bulk electrical conductivity values of both Fe2(DSBDC) and Fe2(DOBDC) are ∼6 orders of magnitude higher than those of the Mn2+ analogues, Mn2(DEBDC) (E = O, S). Because the metals are of the same formal oxidation state, the increase in conductivity is attributed to the loosely bound Fe2+ β-spin electron. These results provide important insight for the rational design of conductive metal–organic frameworks, highlighting in particular the advantages of iron for synthesizing such materials. PMID:25932955

  2. Million-Fold Electrical Conductivity Enhancement in Fe2(DEBDC) versus Mn2(DEBDC) (E = S, O).

    PubMed

    Sun, Lei; Hendon, Christopher H; Minier, Mikael A; Walsh, Aron; Dincă, Mircea

    2015-05-20

    Reaction of FeCl2 and H4DSBDC (2,5-disulfhydrylbenzene-1,4-dicarboxylic acid) leads to the formation of Fe2(DSBDC), an analogue of M2(DOBDC) (MOF-74, DOBDC(4-) = 2,5-dihydroxybenzene-1,4-dicarboxylate). The bulk electrical conductivity values of both Fe2(DSBDC) and Fe2(DOBDC) are ∼6 orders of magnitude higher than those of the Mn(2+) analogues, Mn2(DEBDC) (E = O, S). Because the metals are of the same formal oxidation state, the increase in conductivity is attributed to the loosely bound Fe(2+) β-spin electron. These results provide important insight for the rational design of conductive metal-organic frameworks, highlighting in particular the advantages of iron for synthesizing such materials. PMID:25932955

  3. Fischer Tropsch synthesis : influence of Mn on the carburization rates and activities of Fe-based catalysts by TPR-EXAFS/XANES and catalyst testing.

    SciTech Connect

    Ribeiro, M. C.; Jacobs, G.; Pendyala, R.; Davis, B. H.; Cronauer, D. C.; Kropf, A. J.; Marshall, C. L.

    2011-03-24

    Fe-based catalysts containing different amounts of Mn were tested for Fischer-Tropsch synthesis using a stirred tank reactor at 270 C, 1.21 MPa, and H{sub 2}:CO = 0.7. Catalyst activation by carburization with 10% CO/He was followed by Temperature Programmed Reduction/X-ray Absorption Spectroscopy (TPR-EXAFS/XANES) from room temperature to 300 C. {gamma}-Fe{sub 2}O{sub 3} was converted into iron carbides, whereas MnO{sub x} was reduced to oxygen deficient MnO. Mn hindered Fe carburization, such that the carburized catalyst displayed higher Fe{sub 3}O{sub 4} content than the catalyst without Mn. EXAFS fitting indicates that the carburized catalyst contained a mixture of Hgg carbide, Fe{sub 3}O{sub 4}, and Mn oxides. Increasing Mn content led to higher CH{sub 4} and light product selectivities, and lower light olefin selectivities. Higher and stable conversions were obtained with a catalyst containing an almost equimolar Fe/Mn ratio relative to the catalyst without Mn. Selectivity trends are attributed to the higher WGS rates observed on the FeMn catalysts, consistent with the structural differences observed.

  4. Fe-Mn substance in ocean as reason of regulation radionuclide pollution

    NASA Astrophysics Data System (ADS)

    Asavin, Alex; Martynov, Konstantin; Konstantinova, Lia

    2013-04-01

    Distribution of radionuclide in marine sediments as yet little studied [Choppin & Wong 1998]. The work mainly focused on effects of nuclear test fallout. In the works are examined isotopes of Pu - 238; Th - 232; U -234;238; Pu - 239,240,241; Am - 241; Np - 237; Cm -244 [Holm 1995]. It has been shown that seems to accumulate radionuclides in marine sediments. In particular, the importance attached to carbonate complexes (corals, etc.). But questions about the possibility of re-mobilization of radionuclide, forms their concentration, their participation in global geochemical cycles in the ocean, remain open. We believe a major factor controlling the distribution of heavy metals is the formation of ocean ferromanganese crusts and nodules hydrogenic at the bottom of the ocean and seamounts. It is likely that the process of formation of Fe-manganese hydrogenic can play a major role in the control of radioactive contamination in the oceanic sediment. At least for the U number of works on the subject [Sherman et al. 2008]. The high sensitivity of the Fe-manganese crust is known to the isotopic composition of lead [Loranger & Zayed 1994, Collen et al 2011]. Recent work [Wilkins etal 2006, Renshaw etal 2009] show a large role; Fe (III)-and Mn (IV)-reducing organisms that anaerobic bacteria in oxidation and therefore changes in mobility systems U and Pu. So much interest is data for sorption of radionuclide on hydroxides Fe and Mn. Unfortunately we are not aware of works on the subject. We have therefore taken their own experimental studies on sorption of radionuclide on natural Fe-Mn crusts (sample from Magellan seamount Pacific ocean) [Martynov et al 2012]. The results showed high sorption ability of material crusts for fixation of radionuclides: U-233, Np-237, Pu-238, Am-241. For all radionuclide experiment absorption has been reached already in the first hour it was 96.0% of total substance radionuclide absorbed from the solution, and after the first day it was reached

  5. Evolution of Intermetallics, Dispersoids, and Elevated Temperature Properties at Various Fe Contents in Al-Mn-Mg 3004 Alloys

    NASA Astrophysics Data System (ADS)

    Liu, K.; Chen, X.-G.

    2015-12-01

    Nowadays, great interests are rising on aluminum alloys for the applications at elevated temperature, driven by the automotive and aerospace industries requiring high strength, light weight, and low-cost engineering materials. As one of the most promising candidates, Al-Mn-Mg 3004 alloys have been found to possess considerably high mechanical properties and creep resistance at elevated temperature resulted from the precipitation of a large number of thermally stable dispersoids during heat treatment. In present work, the effect of Fe contents on the evolution of microstructure as well as high-temperature properties of 3004 alloys has been investigated. Results show that the dominant intermetallic changes from α-Al(MnFe)Si at 0.1 wt pct Fe to Al6(MnFe) at both 0.3 and 0.6 wt pct Fe. In the Fe range of 0.1-0.6 wt pct studied, a significant improvement on mechanical properties at elevated temperature has been observed due to the precipitation of dispersoids, and the best combination of yield strength and creep resistance at 573 K (300 °C) is obtained in the 0.3 wt pct Fe alloy with the finest size and highest volume fraction of dispersoids. The superior properties obtained at 573 K (300 °C) make 3004 alloys more promising for high-temperature applications. The relationship between the Fe content and the dispersoid precipitation as well as the materials properties has been discussed.

  6. Effect of gamma ray irradiation on the structural and electrical transport properties of PrFe{sub 1−x}Mn{sub x}O{sub 3}

    SciTech Connect

    Sultan, Khalid Ikram, M.; Asokan, K.

    2014-04-24

    The effect of gamma ray irradiation on the structural and transport properties of polycrystalline bulk samples of PrFe{sub 1−x}Mn{sub x}O{sub 3} (x = 0.0, 0.1, 0.5) were investigated. The samples were synthesized by solid state reaction method and exposed to {sup 60}Co gamma radiation to accumulated dose of 625 KGy. From the Raman study, the modes exhibit a blue shift with broadening of spectral features in the irradiated samples. The dielectric constant (ε′) was also studied as a function of frequency. The dielectric constant and ac conductivity increases with Mn doping but decrease on irradiation. Exposure to gamma radiation results in substantial modification in the physical properties of these compounds.

  7. Cubic structure and canted antiferromagnetism of CaMn7O12 doped with trivalent cations (Fe, Al, Cr)

    NASA Astrophysics Data System (ADS)

    Motin Seikh, Md.; Caignaert, V.; Lebedev, O. I.; Raveau, B.

    2014-02-01

    In this study, we show the dramatic effect of the doping of the octahedral sites with M3+ cations (Fe3+, Al3+ and Cr3+) upon the structure and magnetism of the rhombohedral double perovskite CaMn7O12. In the oxides CaMn7-xMxO12, charge ordering between Mn3+ and Mn4+ octahedral sites is destroyed leading to the cubic structure (Im-3), whereas the initial magnetic properties (TN~90 K) have disappeared leading to canted antiferromagnetism (TN≈50-70 K) for small x values (x ~0.2-1). A spin glass like behaviour is also observed for larger values (x~1) in the case of Fe substitution.

  8. From ferromagnetic{endash}ferromagnetic to ferromagnetic{endash}antiferromagnetic exchange coupling in NiFe/MnNi bilayers

    SciTech Connect

    Spenato, David; Youssef, Jamal Ben; Le Gall, Henri; Ostorero, Jean

    2001-06-01

    The effect of the growth conditions and the Mn concentration on the exchange coupling between a ferromagnetic (F) NiFe and an antiferromagnetic (AF) MnNi layers were studied. We found that an F/AF coupling appears in the bilayers when the Mn concentration is more than 45%. Beyond this critical concentration the exchange field shows a maximum then decreases. The correlation between the exchange field and the microstructure of the film is discussed. We show that: (1) the enhancement of the exchange field is associated with the enhancement of the antiferromagnetic grain size and (2) the existence of the exchange field is associated with a third x-ray peak which may be an FeMnNi ternary allow type. This result was associated with interfacial diffusion confirmed by magnetization variation measurements before and after annealing. {copyright} 2001 American Institute of Physics.

  9. Investigation of the mechanical properties of FeNiCrMnSi high entropy alloy wear resistant

    NASA Astrophysics Data System (ADS)

    Buluc, G.; Florea, I.; Chelariu, R.; Popescu, G.; Carcea, I.

    2016-06-01

    In this paper we investigated microstructure, hardness and wear resistance for FeNiCrMnAl, high entropy alloy. The FeNiCrMnSi, high entropy alloy was elaborated in a medium induction furnace, by choosing the silicon, as an alliance element within the equi- atomic high entropy alloy, we managed to obtain a dendritic structure, the formation of intermetallic compounds or separated silicon. The medium hardness value of the investigated alloy was 948.33 HV and the medium value of the friction coefficient was 0.6655 in the first 20 seconds and 0.5425 for 1667 seconds. The volume loss of the high entropy alloy FeNiCrMnSi was 0.0557 mm3.

  10. Magnetic properties of Co 1- xM xPt 3 (M  Mn, Fe) compounds with competing interactions

    NASA Astrophysics Data System (ADS)

    Kim, T. H.; Dinia, A.; Cadeville, M. C.

    1995-02-01

    Magnetic properties of the pseudo-binary Co 1- xM xPt 3 (M  Mn, Fe) compounds have been investigated. Under adequate preparation conditions, these compounds display the L1 2 structure. For M  Mn the magnetic phase diagram presents a continuous ferromagnetic region from CoPt 3 to MnPt 3 with a re-entrant spin glass (RSG) phase emerging at low T and H between x = 0.2 and 0.6. For M  Fe, a spin glass (SG) phase separates the ferromagnetic region on the Co-rich side, from the antiferromagnetic region on the Fe-rich side. The results are qualitatively discussed in terms of the three dominant competing magnetic interactions JCoCo, JCoM, JMM.

  11. Synthesis and electromagnetic absorption properties of Ag-coated reduced graphene oxide with MnFe2O4 particles

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Wu, Xinming; Zhang, Wenzhi; Huang, Shuo

    2016-04-01

    A ternary composite of Ag/MnFe2O4/reduced graphene oxide (RGO) was synthesized by a facile hydrothermal method. The morphology, microstructure, magnetic and electromagnetic properties of as-prepared Ag/MnFe2O4/RGO composite were characterized by means of XRD, TEM, XPS, VSM and vector network analyzer. The maximum reflection loss (RL) of Ag/ MnFe2O4/RGO composite shows maximum absorption of -38 dB at 6 GHz with the thickness of 3.5 mm, and the absorption bandwidth with the RL below -10 dB is up to 3.5 GHz (from 3.7 to 7.2 GHz). The result demonstrates that the introduction of Ag significantly leads to the multiple absorbing mechanisms. It is believed that such composite could serve as a powerful candidate for microwave absorber.

  12. Calculations of structural, elastic, electronic, magnetic and phonon properties of FeNiMnAl by the first principles

    SciTech Connect

    Uğur, Şule; İyigör, Ahmet

    2014-10-06

    The electronic, elastic and dynamical properties of the quaternary alloy FeNiMnAl have been investigated using a pseudopotential plane wave method within the generalized gradient approximation (GGA). We determined the lattice parameters and the bulk modulus B. In addition, the elastic properties such as elastic constans (C{sub 11}, C{sub 12} and C{sub 44}), the shear modulus G, the young modulus E, the poisson's ratio σ and the B/G ratio are also given. The FeNiMnAl Heusler alloy exhibit a ferromagnetic half-metallic behavior with the total magnetic moment of 4.02 μ{sub B}. The phonon dispersion of FeNiMnAl has been performed using the density functional theory and the direct method with 2×2×2 supercell.

  13. Magnetic structures and magnetic phase transitions in the Mn-doped orthoferrite TbFeO3 studied by neutron powder diffraction

    NASA Astrophysics Data System (ADS)

    Nair, Harikrishnan S.; Chatterji, Tapan; Kumar, C. M. N.; Hansen, Thomas; Nhalil, Hariharan; Elizabeth, Suja; Strydom, André M.

    2016-02-01

    The magnetic structures and the magnetic phase transitions in the Mn-doped orthoferrite TbFeO3 studied using neutron powder diffraction are reported. Magnetic phase transitions are identified at TN Fe / Mn ≈ 295 K where a paramagnetic-to-antiferromagnetic transition occurs in the Fe/Mn sublattice, TS R Fe / Mn ≈ 26 K where a spin-reorientation transition occurs in the Fe/Mn sublattice and TN R ≈ 2 K where Tb-ordering starts to manifest. At 295 K, the magnetic structure of the Fe/Mn sublattice in TbFe 0.5 Mn 0.5 O3 belongs to the irreducible representation Γ 4 ( G x A y F z or P b ' n ' m ). A mixed-domain structure of ( Γ 1 + Γ 4 ) is found at 250 K which remains stable down to the spin re-orientation transition at TS R Fe / Mn ≈ 26 K. Below 26 K and above 250 K, the majority phase ( > 80 % ) is that of Γ 4 . Below 10 K the high-temperature phase Γ 4 remains stable till 2 K. At 2 K, Tb develops a magnetic moment value of 0.6(2) μ B / f.u. and orders long-range in Fz compatible with the Γ 4 representation. Our study confirms the magnetic phase transitions reported already in a single crystal of TbFe 0.5 Mn 0.5 O3 and, in addition, reveals the presence of mixed magnetic domains. The ratio of these magnetic domains as a function of temperature is estimated from Rietveld refinement of neutron diffraction data. Indications of short-range magnetic correlations are present in the low-Q region of the neutron diffraction patterns at T < TS R Fe / Mn . These results should motivate further experimental work devoted to measure electric polarization and magnetocapacitance of TbFe 0.5 Mn 0.5 O3.

  14. Modeling specific heat and entropy change in La(Fe-Mn-Si)13-H compounds

    NASA Astrophysics Data System (ADS)

    Piazzi, Marco; Bennati, Cecilia; Curcio, Carmen; Kuepferling, Michaela; Basso, Vittorio

    2016-02-01

    In this paper we model the magnetocaloric effect of LaFexMnySiz-H1.65 compound (x + y + z = 13), a system showing a transition temperature finely tunable around room temperature by Mn substitution. The thermodynamic model takes into account the coupling between magnetism and specific volume as introduced by Bean and Rodbell. We find a good qualitative agreement between experimental and modeled entropy change - Δs(H , T). The main result is that the magnetoelastic coupling drives the phase transition of the system, changing it from second to first order by varying a model parameter η. It is also responsible for a decrease of - Δs at the transition, due to a small lattice contribution to the entropy counteracting the effect of the magnetic one. The role of Mn is reflected exclusively in a decrease of the strength of the exchange interaction, while the value of the coefficient β, responsible for the coupling between volume and exchange energy, is independent on the Mn content and it appears to be an intrinsic property of the La(Fe-Si)13 structure.

  15. The Solidification Mode of Fe-Mn-Al-C Lightweight Steel

    NASA Astrophysics Data System (ADS)

    Lee, Chan-Young; Lee, Young-Kook

    2014-09-01

    Solidification behavior and solid-state transformation were investigated in Fe-Mn-Al-C lightweight steel. The solidification mode of the Fe-9.3Mn-5.6Al-0.2C (wt.%) lightweight steel was predicted to be the F mode (liquid → liquid + δ-ferrite → δ-ferrite → δ-ferrite + γ-austenite), according to the classification of the solidification modes of stainless steels. However, the microstructures of an ingot of the lightweight steel showed that the solidification occurred by the FA mode (liquid → liquid + δ-ferrite → liquid + δ-ferrite + γ-austenite → δ-ferrite + γ-austenite). To examine the difference between predicted and actual solidification modes, some specimens were annealed at various temperatures ranging from 1200°C to 1450°C for 10 min and then quenched. The microstructures of the annealed specimens exhibited that there were the narrow ranges of single δ-ferrite and solidification sections. This result indicates that the solidification mode of the present steel was the F mode, matching well with the predicted solidification mode. The reason for the FA mode, which was observed in the ingot, was because the liquid passed by a narrow solidification section and a single δ-ferrite region, and it directly entered the dual-phase region of δ-ferrite and γ-austenite during cooling.

  16. Phase Evolution in Fe-Mn-Si Shape Memory Alloys due to Forging Speed

    NASA Astrophysics Data System (ADS)

    Eskil, Murat; Kanca, Erdogan

    2013-09-01

    The objective of this investigation is to compare the crystallographic characteristics of two different compositions of Fe-Mn-Si alloys forged with the newly designed and constructed High Energy Rate Forming (HERF) hammer with conventional hydraulic and mechanical presses. The degree of martensite formation may depend on metal forming conditions. For both of the alloys, one of the specimens was investigated in as "prepared form", the other specimen was investigated after air cooling with homogenization treatment and three specimens were deformed in different velocities after homogenization treatments. The changes which occurred in the transformation parameters of two FeMnSi alloys with different compositions due to the effects of thermal and mechanical procedures have been studied by using X-ray diffraction. In the alloy specimens cooled to different conditions from the high-temperature γ phase region, γ→ɛ and γ→ɛ→α‧ martensitic transformations were observed. The lattice parameters (LP) of fcc γ and hcp ɛ structures were determined, and changes in forging speed on the LPs were found.

  17. Rapid Solidification Behavior of Fe-Cr-Mn-Mo-Si-C Alloys

    NASA Astrophysics Data System (ADS)

    Ranganathan, Sathees; Makaya, Advenit; Fredriksson, Hasse; Savage, Steven

    2007-12-01

    The rapid solidification behavior of alloys in the Fe-Cr-Mn-Mo-Si-C system was investigated for different compositions and cooling rates. The C content was varied and alloying additions of Mo and B were studied with respect to their effect on the microstructure. The alloys were cast as either melt-spun ribbons or as 1-mm-thick plates after levitation or as rods 2 to 4 mm in diameter by injection into copper molds. A homogeneous single-phase structure was obtained for the alloy of composition 72.8Fe-8Cr-6Mn-5Si-5Mo-3.2C (wt pct), for a sample diameter of 2.85 mm, at a cooling rate of ≈1100 K/s. The single-phase structure was identified as a metastable solid solution, exhibiting the characteristics of the ɛ phase. Upon reheating, decomposition of the single-phase structure into fine bainite plates and secondary carbides was observed between 600 °C and 700 °C. The annealed structure obtained showed high hardness values (>850 HV).

  18. Electrochemical study of aqueous asymmetric FeWO4/MnO2 supercapacitor

    NASA Astrophysics Data System (ADS)

    Goubard-Bretesché, Nicolas; Crosnier, Olivier; Buvat, Gaëtan; Favier, Frédéric; Brousse, Thierry

    2016-09-01

    The concept of an asymmetric FeWO4/MnO2 electrochemical capacitor cycled in a neutral aqueous electrolyte is presented for the first time. Commercially available cryptomelane-type MnO2 and synthesized nanocrystalline FeWO4 were used as positive and negative electrode materials, respectively. Prior to assembling the cell, the electrodes have been individually tested in a 5 M LiNO3 electrolyte solution to define both the adequate balance of active material in the supercapacitor and the proper working voltage window. Then, the full asymmetric device has been cycled between 0 and 1.4 V for over 40,000 cycles and subjected to accelerated ageing tests under floating conditions at different voltages, without any significant change on its electrochemical behavior. This remarkable stability shows the interest of developing full oxide-based asymmetric supercapacitors operating in non-toxic aqueous electrolytes that could compete with commercial carbon-based electrochemical double-layer capacitors.

  19. Microstructural stability and mechanical behavior of FeNiMnCr high entropy alloy under ion irradiation

    DOE PAGESBeta

    Leonard, Keith J.; Bei, Hongbin; Zinkle, Steven J.; Kiran Kumar, N. A. P.; Li, C.

    2016-05-13

    In recent years, high entropy alloys (HEAs) have attracted significant attention due to their excellent mechanical properties and good corrosion resistance, making them potential candidates for high temperature fission and fusion structural applications. However there is very little known about their radiation resistance, particularly at elevated temperatures relevant for energy applications. In the present study, a single phase (face centered cubic) concentrated solid solution alloy of composition 27%Fe-28%Ni-27%Mn-18%Cr was irradiated with 3 or 5.8 MeV Ni ions at temperatures ranging from room temperature to 700 °C and midrange doses from 0.03 to 10 displacements per atom (dpa). Transmission electron microscopymore » (TEM), scanning transmission electron microscopy with energy dispersive x-ray spectrometry (STEM/EDS) and X-ray diffraction (XRD) were used to characterize the radiation defects and microstructural changes. Irradiation at higher temperatures showed evidence of relatively sluggish solute diffusion with limited solute depletion or enrichment at grain boundaries. The main microstructural feature at all temperatures was high-density small dislocation loops. Voids were not observed at any irradiation condition. Nano-indentation tests on specimens irradiated at room temperature showed a rapid increase in hardness ~35% and ~80% higher than the unirradiated value at 0.03 and 0.3 dpa midrange doses, respectively. The irradiation-induced hardening was less pronounced for 500 °C irradiations (<20% increase after 3 dpa). Overall, the examined HEA material exhibits superior radiation resistance compared to conventional single phase Fe-Cr-Ni austenitic alloys such as stainless steels. Furthermore, the present study provides insight on the fundamental irradiation behavior of a single phase HEA material over a broad range of irradiation temperatures.« less

  20. Atomic structure and magnetic properties of MnFe2O4 nanoparticles produced by reverse micelle synthesis

    NASA Astrophysics Data System (ADS)

    Carpenter, Everett E.; O'Connor, Charles J.; Harris, Vincent G.

    1999-04-01

    Using the aqueous cores of reverse micelles as nanoreactors, nanoparticles (d˜10 nm) of the mixed ferrite MnFe2O4 were produced. Seven processing trials were performed where the concentration of ammonium hydroxide, reaction temperature, and the oxidizing agent were varied. All trials result in Mn-ferrite particles with varying chemistry and structure. The Mn concentration in the resulting ferrite is strongly enhanced by both the presence of H2O2 as an oxidizing agent and a surplus of ammonium hydroxide. The increased Mn concentration correlates with a higher fraction of octahedrally coordinated Mn cations. When near-stoic amounts of ammonium hydroxide are used, the resulting ferrites are nearly stoichiometric with a more equitable distribution of Mn cations on the octahedral and tetrahedral sublattices. In all ferrite nanoparticles, the Mn cations have a preference for octahedral site occupancy that is larger than the 20% measured in bulk Mn-ferrite. We attribute the cation filling trends to the stabilization of excess trivalent Mn during processing.

  1. Secondary Fe- and Mn-Oxides Associated with Faults Near Moab, Utah: Records of Past Fluid Flow

    NASA Astrophysics Data System (ADS)

    Garcia, V. H.; Reiners, P. W.

    2015-12-01

    Secondary Fe- and Mn-oxides are locally common near faults and fractures, and as cements within sandstones of the Colorado Plateau, and provide evidence of past fluid-flow. Here we describe textural, mineralogic, and geochronologic observations from fault-zone Fe- and Mn-oxide mineralization in Flat Iron Mesa, near Moab, Utah. Several hypotheses have been proposed for their origin, including reactions associated with the mixing of deep reduced and near-surface oxygenated waters. We integrate field observations, detailed SEM and petrographic observations, geochemical models, (U-Th)/He and Ar/Ar dating, and other data to develop interpretations of the formation of these deposits. SEM imaging shows that sandstone matrix cement adjacent to the faults follows two precipitation sequences: Fe-oxide followed by barite and Fe-oxide followed by Mn-oxide. Dense oxide layers also accumulated in cm-scale fractures near faults, and show the following precipitation sequence: Fe-oxide, barite, Ba rich Mn-oxide, and pure Mn-oxide. The latter sequence is observed at larger scale across faults in one site in Flat Iron Mesa. Our new He dates for Mn-oxides are 1.7-2.9 Ma while Fe-oxide dates are 2.7-3.0 Ma. If these dates represent formation ages, they are consistent with the interpreted precipitation sequence but would require protracted mineralization over Ma-timescales. Alternatively, they may represent varying degrees of He retentivity in earlier formed deposits. Previous Ar/Ar dates have been interpreted as a 20-25 Ma formation age. Ongoing Ar/Ar and He diffusion studies will resolve this discordance. Assuming the previous Ar dates do not reflect contamination by detrital K-bearing phases and do reflect oxide formation, potential interpretations for the younger He ages include recent U-Th addition, recrystallization, later oxide growth, or large diffusive He loss at low temperatures.

  2. Magnetization reversal in epitaxial exchange-biased IrMn/FeGa bilayers with anisotropy geometries controlled by oblique deposition

    NASA Astrophysics Data System (ADS)

    Zhang, Yao; Zhan, Qingfeng; Zuo, Zhenghu; Yang, Huali; Zhang, Xiaoshan; Dai, Guohong; Liu, Yiwei; Yu, Ying; Wang, Jun; Wang, Baomin; Li, Run-Wei

    2015-05-01

    We fabricated epitaxial exchange biased (EB) IrMn/FeGa bilayers by oblique deposition and systematically investigated their magnetization reversal. Two different configurations with the uniaxial magnetic anisotropy Ku parallel and perpendicular to the unidirectional anisotropy Ke b were obtained by controlling the orientation of the incident FeGa beam during deposition. A large ratio of Ku/Ke b was obtained by obliquely depositing the FeGa layer to achieve a large Ku while reducing the IrMn thickness to obtain a small Ke b. Besides the previously reported square loops, conventional asymmetrically shaped loops, and one-sided and two-sided two-step loops, unusual asymmetrically shaped loops with a three-step magnetic transition for the descending branch and a two-step transition for the ascending branch and biased three-step loops were observed at various field orientations in the films of both IrMn (tIrMn=1.5 to 20 nm)/FeGa (10 nm) with Ku⊥ Ke b and IrMn (tIrMn≤2 nm)/FeGa (10 nm) with Ku|| Ke b . Considering the geometries of anisotropies, a model based on domain wall nucleation and propagation was employed to quantitatively describe the angular dependent behaviors of IrMn/FeGa bilayers. The biased three-step magnetic switching was predicted to take place when | Ku|> ɛ90°+Ke b , where ɛ90° is the 90° domain wall nucleation energy, and the EB leads to the appearance of the unusual asymmetrically shaped hysteresis loops.

  3. Kinetic modeling of 52Fe/52mMn-citrate at the blood-brain barrier by positron emission tomography.

    PubMed

    Calonder, C; Würtenberger, P I; Maguire, R P; Pellikka, R; Leenders, K L

    1999-11-01

    The kinetics of iron at the blood-brain barrier of the monkey were studied in vivo using positron emission tomography (PET) and the tracer 52Fe/52mMn-citrate. 52mMn is the beta(+)-emitting daughter nuclide of 52Fe and therefore contributes to the observed signal and background in the PET images and may influence the quantification of physiological relevant iron parameters. The kinetics of pure (52m)Mn-citrate at the blood-brain barrier of the monkey were studied experimentally, and the analysis of the data with a reasonable compartment model led to equal efflux and influx parameters for Mn (1.35 +/- 0.3 x 10(-2) min(-1)). By using complexes between Mn and diethylenetriaminepentaacetic acid, the validity of the proposed model could be confirmed. To describe the observed kinetics of 52Fe/(52m)Mn-citrate, the manganese model was coupled to an iron model, which finally allowed the quantification of two iron-specific parameters: an input rate into global brain tissue of 7.15 +/- 2.6 x 10(-4) min(-1) and a time delay of roughly 24 min to account for the observed activities. The simpler linearization procedure has been proposed and could be applied to all our data sets and is able to replace the complicated nonlinear iron/manganese tracer kinetic model neglecting any influence of manganese on the analysis. PMID:10537064

  4. Solid-state transformation of Fe-rich intermetallic phases in Al–5.0Cu–0.6Mn squeeze cast alloy with variable Fe contents during solution heat treatment

    SciTech Connect

    Lin, Bo; Zhang, Weiwen; Zhao, Yuliang; Li, Yuanyuan

    2015-06-15

    The Al–5.0 wt.% Cu–0.6 wt.% Mn alloys with a variable Fe content were prepared by squeeze casting. Optical microscopy (OM), Deep etching technique, scanning electron microscopy(SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to examine the solid-state transformation of Fe-rich intermetallics during the solution heat treatment. The results showed that the Chinese script-like α-Fe, Al{sub 6}(FeMn) and needle-like Al{sub 3}(FeMn) phases transform to a new Cu-rich β-Fe (Al{sub 7}Cu{sub 2}(FeMn)) phase during solution heat treatment. The possible reaction and overall transformation kinetics of the solid-state phase transformation for the Fe-rich intermetallics were investigated. - Graphical abstract: Display Omitted - Highlights: • The α-Fe, Al{sub 6}(FeMn) and Al{sub 3}(FeMn) phases change to the β-Fe phases. • Possible reactions of Fe phases during solution heat treatment are discussed. • The overall fractional transformation rate follows an Avrami curve.

  5. Characterization of Fe-Mn concretions from a Luvisol irrigated by mine water in a semi-arid agricultural area

    NASA Astrophysics Data System (ADS)

    Ettler, Vojtech; Mihaljevic, Martin; Kribek, Bohdan; Veselovsky, Frantisek; Sracek, Ondra; Vanek, Ales; Penizek, Vit; Mapani, Ben; Kamona, Fred

    2016-04-01

    We studied Fe-Mn concretions from Cutanic Luvisol in the northern part of Namibia, where agricultural fields are irrigated with the drainage water from the Kombat Cu-Pb-Zn mine (pH 7, metal concentrations in ug/L: Fe 7, Mn 10, Zn 7, Cu 18). Concretions (0.5-2 cm in size) were mostly found towards the basis of the soil profile (BC horizon, depth 100-120 cm). Comparisons with the bulk chemical composition of the soil matrix indicated that Fe-Mn concretions were enriched with metals, metalloids and other trace elements (enrichment factor EFs varied in the range 1.3-6.4). Concentrations of the elements of interest in the Fe-Mn concretions were the following (mg/kg): As 23.1, Ba 3840, Cd 6.83, Cu 450, Pb 597, Zn 137. The X-ray diffraction analysis indicated that concretions were composed of quartz, goethite, hematite, illite/mica, lithiophorite (LiAl2Mn3O6(OH)6) and birnessite. The SEM observation confirmed that internal structure with concentric rings reflecting seasonal changes in redox conditions occurred within the concretions. Spot analyses and X-ray elemental maps performed using EDS spectrometry showed that concentrations of metalloids were rather low and slightly elevated Ba concentrations were only observed within the Mn-oxide zones. Selective extractions were used to understand the binding of trace elements onto individual target phases. Whereas Mn-oxide phases sequestered the majority of Cd (up to 98%), Ba, Pb and REEs (up to 78%), other metals such as Cu and Zn exhibited much lower values (47-65%) and were also significantly bound to Fe-oxides. The pH-static leaching test conducted in the pH range of 2-12 indicated that the majority of trace elements were mostly leached under acidic conditions with the exception of As, which was highly solubilized at pH 12 (up to 17%). Whereas Ba, Cd, Cu and Zn were significantly released under acidic conditions (up to 12%), the leaching of Pb was almost negligible over the entire pH range. Our results show that Fe-Mn

  6. Improving the High-Voltage Li2FeMn3O8 Cathode by Chlorine Doping.

    PubMed

    Dai, Jiaqi; Zhou, Lihui; Han, Xiaogang; Carter, Marcus; Hu, Liangbing

    2016-05-01

    High-capacity and high-voltage cathode materials are desirable for high-energy-density lithium ion batteries. Among various cathode materials, Li2FeMn3O8 is attractive due to its high working voltage, low toxicity, and low cost. However, its superior electrochemical properties are significantly limited by the intrinsic defects in the Li2FeMn3O8 cathode, which makes the theoretical working voltage (4.9 V) and capacity (148 mAh/g) hard to reach. In this paper, we demonstrated that Cl doping can effectively increase the capacity and working voltage of the Li2FeMn3O8 cathode. X-ray photoelectron spectroscopy reveals that Cl doping reduced the valence state and increased the electron binding energy in cations and thus increased the voltage and enhanced the capacity of the Li2FeMn3O8 cathode. Our results also indicate that Cl doping can be a promising low-cost method to improve the electrochemical performance of various oxide cathode materials, including LiCoO2 and LiMn2O4. PMID:27046350

  7. Photoinduced electrical properties of Mn-doped BiFeO3 thin films prepared by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Yoshida, Kenji; Sakamoto, Wataru; Moriya, Makoto; Yogo, Toshinobu

    2014-09-01

    Polycrystalline Mn-doped BiFeO3 thin films with a relatively narrow band gap were prepared on Pt/TiOx/SiO2/Si and MgO(100) substrates by chemical solution deposition. Their photoinduced electrical properties under visible light irradiation (400-700 nm) were characterized. The rapid on/off response of the photocurrent to light in unpoled BiFeO3-based thin films was demonstrated. From the direction of the electric current, the internal bias electric field caused by the space charge distribution in the unpoled film is considered to have an important effect on photocurrent generation and photovoltaic phenomena. Although Mn doping did not greatly affect the band gap and ferroelectric remanent polarization, it had an influence on the photocurrent behavior and photovoltaic properties. The magnitude of the photoinduced current of the film decreased with increasing Mn doping. In this case, the energy level created in BiFeO3 by Mn doping traps carriers generated by photoexcitation. The interfacial state between the thin film and the top or bottom electrode and the electrical resistivity at low applied voltages were also found to be related to the photoinduced behavior of the Mn-doped BiFeO3 thin films.

  8. Magnetovolume effect in Ho{sub 2}Fe{sub 17-x}Mn{sub x} compounds

    SciTech Connect

    Wang, J. L.; Studer, A. J.; Kennedy, S. J.; Zeng, R.; Dou, S. X.; Campbell, S. J.

    2012-04-01

    The structural and magnetic properties of seven compounds in the Ho{sub 2}Fe{sub 17-x}Mn{sub x} series (x = 0-5) have been investigated. The spontaneous magnetization M{sub s} at 10 K exhibits a minimum at x{approx_equal} 3.8 while the 3d-sublattice magnetization M{sub T} is found to decrease at {approx} -3.4 {mu}{sub B}/per Mn atom compared with the rate of {approx}-2.0 {mu}{sub B}/per Mn atom expected from a simple dilution model. All of the Ho{sub 2}Fe{sub 17-x}Mn{sub x} compounds exhibit anisotropic thermal expansion below their Curie temperatures leading to the presence of strong magnetovolume effects and Invar-type behavior below T{sub C}. An approximately zero volume thermal expansion has been detected between 10 K and 270 K for Ho{sub 2}Fe{sub 17}. The maximum magnetic entropy changes for Ho{sub 2}Fe{sub 17-x}Mn{sub x} with x = 0 and 2.0 are 3.2 J kg{sup -1} K{sup -1} around T{sub C} {approx} 336 K and 2.7 J kg{sup -1} K{sup -1} around T{sub C} {approx} 302 K, respectively, for magnetic field change of B = 0-5 T.

  9. High-field magnetization of heusler alloys Fe2 XY ( X = Ti, V, Cr, Mn, Fe, Co, Ni; Y = Al, Si)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Belozerova, K. A.; Weber, H. W.

    2015-10-01

    The magnetization curves of ferromagnetic Heusler alloys Fe2 XY (where X = Ti, V, Cr, Mn, Fe, Co, Ni are transition 3 d elements and Y = Al, Si are the s and p elements of the third period of the Periodic Table) have been measured at T = 4.2 K in the field range H ≤ 70 kOe. It has been shown that the high-field ( H ≥ 20 kOe) magnetization is described within the Stoner model.

  10. Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi

    NASA Astrophysics Data System (ADS)

    Ang, Andrew Siao Ming; Berndt, Christopher C.; Sesso, Mitchell L.; Anupam, Ameey; S, Praveen; Kottada, Ravi Sankar; Murty, B. S.

    2015-02-01

    High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.

  11. Perpendicularly magnetized ferrimagnetic [Mn50Ga50/Co2FeAl] superlattice and the utilization in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Ma, Q. L.; Zhang, X. M.; Miyazaki, T.; Mizukami, S.

    2015-08-01

    The ferrimagnetic superlattice (SL) [MnGa/Co2FeAl]n exhibiting perpendicular magnetic anisotropy opened a new method for spintronics materials used in magnetic random access memory, because of the high anisotropy, small damping constant and tunable magnetization. In this work, we fabricated SLs with different MnGa composition and studied the MnGa composition dependence of the structure and magnetic properties of the SLs. Furthermore, we fabricated fully perpendicular magnetic tunnel junctions with SLs as both top and bottom electrodes. A clear tunnel magnetoresistance (TMR) effect with TMR ratio of 1.3% at room temperature was observed.

  12. Microstructural Evolution and Functional Properties of Fe-Mn-Al-Ni Shape Memory Alloy Processed by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Niendorf, Thomas; Brenne, Florian; Krooß, Philipp; Vollmer, Malte; Günther, Johannes; Schwarze, Dieter; Biermann, Horst

    2016-06-01

    In the current study, a Fe-Mn-Al-Ni shape memory alloy is processed by additive manufacturing for the first time. Microstructural evolution upon processing is strongly affected by thermal gradients and solidification velocity and, thus, by processing parameters and the actual specimen geometry. By single-step solutionizing heat treatment pronounced grain growth is initiated leading to microstructures showing good reversibility. The compressive stress-strain response revealed maximum reversible pseudo-elastic strain of about 7.5 pct. Critical steps toward further optimization of additively manufactured Fe-Mn-Al-Ni shape memory alloys are discussed.

  13. Microstructural Evolution and Functional Properties of Fe-Mn-Al-Ni Shape Memory Alloy Processed by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Niendorf, Thomas; Brenne, Florian; Krooß, Philipp; Vollmer, Malte; Günther, Johannes; Schwarze, Dieter; Biermann, Horst

    2016-03-01

    In the current study, a Fe-Mn-Al-Ni shape memory alloy is processed by additive manufacturing for the first time. Microstructural evolution upon processing is strongly affected by thermal gradients and solidification velocity and, thus, by processing parameters and the actual specimen geometry. By single-step solutionizing heat treatment pronounced grain growth is initiated leading to microstructures showing good reversibility. The compressive stress-strain response revealed maximum reversible pseudo-elastic strain of about 7.5 pct. Critical steps toward further optimization of additively manufactured Fe-Mn-Al-Ni shape memory alloys are discussed.

  14. The effects of annealing on the microstructure and mechanical properties of Fe28Ni18Mn33Al21

    DOE PAGESBeta

    Meng, Fanling; Qiu, Jingwen; Baker, Ian; Bei, Hongbin

    2015-08-20

    In this paper, As-cast Fe28Ni18Mn33Al21, which consists of aligned, 50 nm, (Ni, Al)-rich B2, and (Fe, Mn)-rich f.c.c. phases, was annealed at a variety of temperatures up to 1423 K and the microstructure and mechanical properties were examined. It was shown that the as-cast microstructure arises from a eutectoid transformation at ~1300 K. Annealing at temperatures ≤1073 K produces β-Mn-structured precipitates and hardness values up to 816 HV, while annealing at temperatures >1073 K leads to dramatic coarsening of the two-phase B2/f.c.c. microstructure (up to 5.5 µm after 50 h at 1273 K), but does not lead to β-Mn precipitation.more » Interestingly, annealing at temperatures >1073 K delays the onset of β-Mn precipitation during subsequent anneals at lower temperatures. Coarsening the B2/f.c.c. lamellar structure by annealing at higher temperatures softens it and leads to increases in ductility from fracture before yield to ~8 % elongation. Finally, the presence of β-Mn precipitates makes the very fine, brittle B2/f.c.c. microstructures even more brittle, but significant ductility (8.4 % elongation) is possible even with β-Mn precipitates present if the B2/f.c.c. matrix is coarse and, hence, more ductile.« less

  15. Correlation between particle size and magnetic characteristics of Mn-substituted ZnFe2O4 ferrites

    NASA Astrophysics Data System (ADS)

    Zawar, Sidra; Atiq, Shahid; Riaz, Saira; Naseem, Shahzad

    2016-05-01

    We report synthesis of Zn1-xMnxFe2O4 (x = 0.0, 0.1, 0.3, 0.4 & 0.5) ferrites using sol-gel auto-combustion route while citric acid is used as a fuel. The study is aimed to explore the influence of Mn contents on structural parameters, morphological characteristics and magnetic properties of ZnFe2O4 ferrite samples while the impact of average grain dimensions on magnetic properties inferred from multi domain and single domain particle's effect is also analyzed. X-ray diffraction confirmed the configuration of single phase pure crystalline structure with low concentration of Mn while some impurity peaks were found for higher Mn contents. Lattice parameter was found to increase with increasing Mn contents while crystallite size was decreased. Average grain size was decreased from 240 to 150 nm with increasing Mn concentration which directly affected the magnetic properties. A decrease in saturation magnetization (from 52.35 to 45.80 emu/g) and an increase in coercivity (from 44 to 262 Oe) was observed with increasing Mn contents. A decrease in initial permeability and increase in hysteresis loss with increasing Mn contents was also evident. Coercive field and hysteresis losses were increased with decreasing average grain size while initial permeability was found to decrease with decrease in average grain size.

  16. Thermally induced magnetization switching in Fe/MnAs/GaAs(001): selectable magnetic configurations by temperature and field control

    PubMed Central

    Spezzani, Carlo; Vidal, Franck; Delaunay, Renaud; Eddrief, Mahmoud; Marangolo, Massimiliano; Etgens, Victor H.; Popescu, Horia; Sacchi, Maurizio

    2015-01-01

    Spintronic devices currently rely on magnetization control by external magnetic fields or spin-polarized currents. Developing temperature-driven magnetization control has potential for achieving enhanced device functionalities. Recently, there has been much interest in thermally induced magnetisation switching (TIMS), where the temperature control of intrinsic material properties drives a deterministic switching without applying external fields. TIMS, mainly investigated in rare-earth–transition-metal ferrimagnets, has also been observed in epitaxial Fe/MnAs/GaAs(001), where it stems from a completely different physical mechanism. In Fe/MnAs temperature actually modifies the surface dipolar fields associated with the MnAs magnetic microstructure. This in turn determines the effective magnetic field acting on the Fe overlayer. In this way one can reverse the Fe magnetization direction by performing thermal cycles at ambient temperatures. Here we use element selective magnetization measurements to demonstrate that various magnetic configurations of the Fe/MnAs/GaAs(001) system are stabilized predictably by acting on the thermal cycle parameters and on the presence of a bias field. We show in particular that the maximum temperature reached during the cycle affects the final magnetic configuration. Our findings show that applications are possible for fast magnetization switching, where local temperature changes are induced by laser excitations. PMID:25631753

  17. Potential parent compound of superconductor: Sr 2CuM 2As 2O 2 (M = Mn, Fe)

    NASA Astrophysics Data System (ADS)

    Wang, Guangtao; Zhang, Minping; Zheng, Lihua; Yang, Zongxian

    2010-10-01

    The electronic structure of Sr 2CuMn 2As 2O 2 and Sr 2CuFe 2As 2O 2 are studied by the first-principle calculations. These compounds have a body-centered-tetragonal crystal structure that consists of the CuO 2 layers similar to those in the high- T cuprate superconductor, and intermetallic MAs (M = Mn, or Fe) layers similar to the FeAs layers in high- T pnictides. Such special structure makes them as interesting candidates for new type of superconductor since they have two types of superconducting layers. However, our calculations indicate that the states in the range from -2.0 eV to +2.0 eV are dominated by Mn-3d or Fe-3d states, while the states of Cu-3d are far away from the Fermi level (in the range from -3.0 eV to -1.0 eV). Such results are significantly different with the Cu-based superconductor, like La 2CuO 4, where the states around Fermi level are dominated by Cu-3d states. Besides, we find that the mean-field magnetic ground state is the checkerboard antiferromagnetic in Cu sublattice and the stripe antiferromagnetic in Fe (or Mn) sublattice.

  18. Thermally induced magnetization switching in Fe/MnAs/GaAs(001): selectable magnetic configurations by temperature and field control.

    PubMed

    Spezzani, Carlo; Vidal, Franck; Delaunay, Renaud; Eddrief, Mahmoud; Marangolo, Massimiliano; Etgens, Victor H; Popescu, Horia; Sacchi, Maurizio

    2015-01-01

    Spintronic devices currently rely on magnetization control by external magnetic fields or spin-polarized currents. Developing temperature-driven magnetization control has potential for achieving enhanced device functionalities. Recently, there has been much interest in thermally induced magnetisation switching (TIMS), where the temperature control of intrinsic material properties drives a deterministic switching without applying external fields. TIMS, mainly investigated in rare-earth-transition-metal ferrimagnets, has also been observed in epitaxial Fe/MnAs/GaAs(001), where it stems from a completely different physical mechanism. In Fe/MnAs temperature actually modifies the surface dipolar fields associated with the MnAs magnetic microstructure. This in turn determines the effective magnetic field acting on the Fe overlayer. In this way one can reverse the Fe magnetization direction by performing thermal cycles at ambient temperatures. Here we use element selective magnetization measurements to demonstrate that various magnetic configurations of the Fe/MnAs/GaAs(001) system are stabilized predictably by acting on the thermal cycle parameters and on the presence of a bias field. We show in particular that the maximum temperature reached during the cycle affects the final magnetic configuration. Our findings show that applications are possible for fast magnetization switching, where local temperature changes are induced by laser excitations. PMID:25631753

  19. Preparation and application of Mn-substituted δ-FeOOH for oxidative adsorption of As(III)

    NASA Astrophysics Data System (ADS)

    Chon, C.; Yang, H.; Cho, D.; Kim, Y.; Schwartz, F.; Lee, E.; Jeon, B.; Song, H.

    2013-12-01

    Iron oxides are one of the commonly used media for arsenic treatment, but they have significantly low adsorption capacity for As(III) than As(V), rendering limited applicability to treat groundwater possessing relatively high level of As(III). In this study, we prepared a Mn-substituted iron oxyhydroxide and demonstrated its applicability for enhancing As(III) removal. Four synthetic samples of Mn-substituted δ-FeOOH (MSF) with different ratios of Mn:Fe (0, 10, 30, and 50%) were prepared by oxidative hydrolysis of Fe(II) and Mn(II) salts with very rapid oxidation using H2O2. X-ray diffraction and Rietveld refinement analysis revealed that the crystal structures of MSFs resembles those of feroxyhyte (δ'-FeOOH), with the c unit cell parameter proportionally decreasing with increasing Mn-substitution, resulting in formation of δ-(Fe1-x, Mnx)OOH like structure. Adsorption batch experiments with MSF revealed that As(III) was oxidized into As(V) by surface oxidation of MSF, suggesting Mn-mediated oxidative adsorption of As(III). This oxidative removal of As(III) is consistent with previous studies that reported removal of As(III) by iron minerals containing MnOOH or reduced species of Mn. However, the adsorption capacities decreased from 20.0 to 10.8 mg/g with increasing Mn ratio from 0 to 50%. This indicates the loss of available adsorption sites by increased occupancy of Mn on the surface sites. Arsenic removal by iron oxides has been reported to occur via co-precipitation of As(III) and an inner-sphere complexation of As(V) that involves Fe atoms on the surface. Therefore, it appears Mn-substitution on Fe is for the decrease of arsenic sorption.. The adsorption of arsenic on MSF containing 10% Mn exhibited 93.8 % removal within the first 70 min and reaching sorption equilibrium after 530 min for initial As(III) concentration of 19.5 mg/L. Adsorption capacities of MSF were 18.3, 44.5, and 55.3 mg/g for the initial concentrations of 19.5, 52.7 and 96.7 mg

  20. Mechanism of N2O formation during the low-temperature selective catalytic reduction of NO with NH3 over Mn-Fe spinel.

    PubMed

    Yang, Shijian; Xiong, Shangchao; Liao, Yong; Xiao, Xin; Qi, Feihong; Peng, Yue; Fu, Yuwu; Shan, Wenpo; Li, Junhua

    2014-09-01

    The mechanism of N2O formation during the low-temperature selective catalytic reduction reaction (SCR) over Mn-Fe spinel was studied. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and transient reaction studies demonstrated that the Eley-Rideal mechanism (i.e., the reaction of adsorbed NH3 species with gaseous NO) and the Langmuir-Hinshelwood mechanism (i.e., the reaction of adsorbed NH3 species with adsorbed NOx species) both contributed to N2O formation. However, N2O selectivity of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism was much less than that through the Eley-Rideal mechanism. The ratio of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism remarkably increased; therefore, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the decrease of the gas hourly space velocity (GHSV). As the gaseous NH3 concentration increased, N2O selectivity of NO reduction over Mn-Fe spinel increased because of the promotion of NO reduction through the Eley-Rideal mechanism. Meanwhile, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the increase of the gaseous NO concentration because the formation of NH on Mn-Fe spinel was restrained. Therefore, N2O selectivity of NO reduction over Mn-Fe spinel was related to the GHSV and concentrations of reactants. PMID:25105802

  1. Preparation and characterization of MnFe{sub 2}O{sub 4} in the solvothermal process: Their magnetism and electrochemical properties

    SciTech Connect

    Lin, Xiaomei; Lv, Xin; Wang, Limin; Zhang, Feifei; Duan, Lianfeng

    2013-07-15

    Graphical abstract: - Highlights: • Effect of CTAB on the morphology and crystallization of MnFe{sub 2}O{sub 4}. • The lowest coercivity of MnFe{sub 2}O{sub 4} polyhedron is 11.9 Oe. • MnFe{sub 2}O{sub 4} as anode for LIB shows good reversible capacity and cycle performances. - Abstract: The uniform different morphologies MnFe{sub 2}O{sub 4}, including cube, truncated cube, polyhedron and octahedron, were successfully synthesized via a solvothermal route using cetyltrimethylammonium bromide. The results of control experiments revealed that the concentration of cetyltrimethylammonium bromide was an important factor, which affected the morphology and crystallization of MnFe{sub 2}O{sub 4} submicro-crystals. All the prepared samples exhibited soft-magnetic behavior at room temperature. Especially, the coercivity of MnFe{sub 2}O{sub 4} polyhedron with 200 nm diameter was 11.9 Oe, which was among the lowest values reported so far. Moreover, MnFe{sub 2}O{sub 4} submicro-crystals with special morphologies demonstrated higher reversible capacity (about 1000 mAh g{sup −1}) and different cycle performances. After 50 cycles, polyhedron structure remained 428 mAh/g. The MnFe{sub 2}O{sub 4} would have a potential application as anode material for lithium ion batteries.

  2. XRD and Mössbauer spectroscopy investigation of Mn substituted CuFe2O4 nanoparticles.

    PubMed

    Rai, A; Banerjee, M

    2008-08-01

    The effect of Mn substitution in Cu ferrite may present a challenge, as there are three transition metals ions distributed among the two available crystallographic sub lattices. This system also presents complicated super exchange interactions. In this study a series of five powdered samples with composition Cu(1-x)Mn(x)Fe2O4 were investigated using XRD and transmission Mössbauer spectroscopy. The variation of lattice parameter, crystallite size, and Mössbauer parameters of the product formed with the variation in the concentration of Mn has been studied. XRD study revealed the formation of pure phase spinels with FCC cubic structure having particle size ranging from 7.2 nm to 20 nm. Lattice constant value showed constant increase with increasing Mn concentration. AFM image confirms the formation of spherical shaped nanoparticles. Mössbauer spectroscopy proves to be an excellent tool for probing the local environment of Fe atoms present in such materials. Results show two sets of six finger patterns for all the samples with two double line pattern obtained for the composition with x = 0.75 and 1.0, indicating the presence of Fe in both A and B site. Increase in Mn concentration first increases the hyperfine field and then it gradually decreases. This effect is observed at both the sites. This effect is due to the relative strengths of Fe-O-X super exchange (X = Fe, Mn, Cu) as well as number of different nearest neighbour of A and B sites. The unexpected behaviour for the last two compositions can be explained by the presence of particle size distribution that results in superparamagnetic behaviour. PMID:19049197

  3. Discussion on the Alloying Element Partition and Growth Kinetics of Proeutectoid Ferrite in Fe-C-Mn-X Alloys

    NASA Astrophysics Data System (ADS)

    Wei, R.; Enomoto, M.

    2011-12-01

    Experimental data on alloying element partition and growth kinetics of proeutectoid ferrite in quaternary Fe-C-Mn-Si, Ni, and Co alloys were reanalyzed using an approximate method, which permits a quick evaluation of alloy partitioning to be made. The method yielded results in good agreement with DICTRA and is applicable to Fe-C base multicomponent alloys. Differences of the predicted local condition at the α/ γ boundary from those previously presented in the alloys are noted.

  4. Stress induced anisotropy in CoFeMn soft magnetic nanocomposites

    SciTech Connect

    Leary, A. M. Keylin, V.; McHenry, M. E.; Ohodnicki, P. R.

    2015-05-07

    The use of processing techniques to create magnetic anisotropy in soft magnetic materials is a well-known method to control permeability and losses. In nanocomposite materials, field annealing below the Curie temperature results in uniaxial anisotropy energies up to ∼2 kJ/m{sup 3}. Higher anisotropies up to ∼10 kJ/m{sup 3} result after annealing Fe-Si compositions under stress due to residual stress in the amorphous matrix acting on body centered cubic crystals. This work describes near zero magnetostriction Co{sub 80−x−y}Fe{sub x}Mn{sub y}Nb{sub 4}B{sub 14}Si{sub 2} soft magnetic nanocomposites, where x and y < 8 at.% with close packed crystalline grains that show stress induced anisotropies up to ∼50 kJ/m{sup 3} and improved mechanical properties with respect to Fe-Si compositions. Difference patterns measured using transmission X-ray diffraction show evidence of affine strain with respect to the stress axis.

  5. 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.

  6. Microwave adsorption of Sr(MnTi)xFe12-2xO19 particles

    NASA Astrophysics Data System (ADS)

    Yuan, C. L.; Tuo, Y. S.

    2013-09-01

    MnTi-substituted strontium ferrite particles of Sr(MnTi)xFe12-2xO19, (x=0-2.0), were synthesized using the aqueous combustion method. The structural character and the thermal properties of the sol-gel were investigated using Fourier transform infrared spectroscopy and thermogravimetric analysis, and the effects of the chemical composition and annealing temperature on the crystalline structure, the magnetic properties, and the morphology of ZnTi-substituted strontium ferrite particles were studied using X-ray diffraction, vibrating sample magnetometer measurements, and high-resolution scanning electron microscopy. X-ray diffraction indicated that M-type and Y-type hexagonal phases coexist in Sr-ferrites annealed at 1000 °C/2 h. However, a single phase of M-type hexagonal ferrite was obtained by heating the prepared powder at 1200 °C/2 h. The saturation magnetization at 300 K was found to greatly increase from 43.7 emu/g in SrFe12O19 ferrite to 59.0 emu/g in Sr(MnTi)0.5Fe11O19 ferrite. In contrast, the intrinsic coercivity was found to rapidly decrease from 4.32 kG in SrFe12O19 ferrite to 3.25 kG in Sr(MnTi)0.5Fe11O19 ferrite. The composite specimens of Sr(MnTi)xFe12-2xO19 and thermal plastic resin showed wide-band microwave absorption due to reflection losses from -15.7 to -22.7 dB at frequencies between 18 and 40 GHz as observed by a high-frequency network analyzer.

  7. Synthesis and characterizations of water-based ferrofluids of substituted ferrites [Fe 1-xB xFe 2O 4, B=Mn, Co ( x=0-1)] for biomedical applications

    NASA Astrophysics Data System (ADS)

    Giri, Jyotsnendu; Pradhan, Pallab; Somani, Vaibhav; Chelawat, Hitesh; Chhatre, Shreerang; Banerjee, Rinti; Bahadur, Dhirendra

    Nanomagnetic particles have great potential in the biomedical applications like MRI contrast enhancement, magnetic separation, targeting delivery and hyperthermia. In this paper, we have explored the possibility of biomedical applications of [Fe 1-xB xFe 2O 4, B=Mn, Co] ferrite. Superparamagnetic particles of substituted ferrites [Fe 1-xB xFe 2O 4, B=Mn, Co ( x=0-1)] and their fatty acid coated water base ferrofluids have been successfully prepared by co-precipitation technique using NH4OH/TMAH (Tetramethylammonium hydroxide) as base. In vitro cytocompatibility study of different magnetic fluids was done using HeLa (human cervical carcinoma) cell lines. Co 2+-substituted ferrite systems (e.g. CoFe 2O 4) is more toxic than Mn 2+-substituted ferrite systems (e.g. MnFe 2O 4, Fe 0.6Mn 0.4Fe 2O 4). The later is as cytocompatible as Fe 3O 4. Thus, Fe 1-xMn xFe 2O 4 could be useful in biomedical applications like MRI contrast agent and hyperthermia treatment of cancer.

  8. Thermophysical properties of BiFeO3, Bi0.91Nd0.09FeO3, and BiFe0.91Mn0.09O3 multiferroics at high temperatures

    NASA Astrophysics Data System (ADS)

    Klyndyuk, A. I.; Khort, A. A.

    2016-06-01

    The thermal diffusion, heat capacity, and thermal conductivity of BiFeO3, Bi0.91Nd0.09FeO3, and BiFe0.91Mn0.09O3 multiferroics have been studied at high temperatures (300-1120 K). The dominant mechanisms of phonon transfer in the regions of the antiferromagnetic and ferroelectric phase transitions have been determined. The temperature dependence of the mean free path of phonons has been found.

  9. Studies on transition metals and alloy Fischer-Tropsch catalysts, their electronic and bulk properties. (I: Fe/MnO; II: Fe/TiO/sub 2/; III: Fe/Mord. ). Final report, July 1, 1982-September 30, 1983

    SciTech Connect

    Mulay, L.N.

    1983-11-01

    The objectives were: (1) to characterize samples D1, 10% FeO/90% MnO, and D2, 48% FeO/52% MnO, under varying conditions of reduction (at 250/sup 0/C or 350/sup 0/C in H/sub 2/) and of syngas reaction 1:1 of CO:H/sub 2/ at 290/sup 0/C) and in some cases use CO only for reduction and to identify species by Moessbauer Spectroscopy and Magnetization (sigma/sub s) measurement; (2) similarly, to see if there is any metal (oxide)/support (Mordenite) interaction by the same techniques. The characterization was carried out with above techniques and the kinetic results for syngas were obtained on the above systems mostly at PETC. During reduction of Fe-oxide/Mn-oxide an intermediate Mn-ferrite phase was detected. After reduction, species such as Fe/sup 0/+Fe/sup 3 +/+Fe/sup 2 +/ in varying total proportions (45% at 290/sup 0/C and Fe/sup 0/+Fe/sup 2 +/ 75% were found at 350/sup 0/C). Syngas conversion showed Fe-carbides (Fe/sub 2/C/sub 2/+Fe/sub 3/C) depending on the reaction conditions, and the composition of D/sub 1/ and D/sub 2/. With the fresh ..gamma..-Fe/sub 2/O/sub 3/ (identified by Moessbauer) on Mordenites with varying ratios of SiO/sub 2//Al/sub 2/O/sub 3/, a decrease in (sigma/sub s/) was found with lowering of the ratios from 60 to 17. At 17% ratio (sigma/sub s/) was smallest and the change in the isomer shift was maximum, which established an interaction with the Broensted cities. 24 figures.

  10. Mn(II) mediated degradation of artemisinin based on Fe3O4@MnSiO3-FA nanospheres for cancer therapy in vivo.

    PubMed

    Chen, Jian; Zhang, Weijie; Zhang, Min; Guo, Zhen; Wang, Haibao; He, Mengni; Xu, Pengping; Zhou, Jiajia; Liu, Zhenbang; Chen, Qianwang

    2015-08-01

    Artemisinin (ART) is a natural drug with potent anticancer activities related with Fe(2+) mediated cleavage of the endoperoxide bridge in ART. Herein, we reported that Mn(2+) could substitute for Fe(2+) to react with ART and generate toxic products, inducing a much higher anticancer efficiency. On this basis, we prepared pH-responsive Fe3O4@MnSiO3-FA nanospheres which can efficiently deliver hydrophobic ART into tumors in mice models. Mn(2+) was released in acidic tumor environments and intracellular lysosomes, interacting with ART to kill cancer cells. The ART-loaded nanocarriers could suppress tumor growth more efficiently than free ART, which could be further illustrated by magnetic resonance imaging (MRI). Histological analysis revealed that the drug delivery system had no obvious effect on the major organs of mice. ART has been reported to have lower toxicity than chemotherapeutics. The ART-loaded nanocarriers are promising to be used in improving the survival of chemotherapy patients, providing a novel method for clinical tumor therapy. PMID:26140326

  11. Magnetic properties of Fe0.4Mn0.6/Co2FeAl bilayers grown on GaAs by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Meng, K. K.; Nie, S. H.; Yu, X. Z.; Wang, S. L.; Yan, W. S.; Zhao, J. H.

    2011-11-01

    Polycrystalline Fe0.4Mn0.6 layers with the different thickness are deposited on 4-nm-thick single-crystalline Co2FeAl layers, which are grown on GaAs (001) substrates at room temperature by molecular-beam epitaxy. Both the exchange bias and the in-plane magnetic anisotropies of the bilayers are strongly dependent on the thickness of the Fe0.4Mn0.6 layer. The former is described using a granular level model. A modified Stoner-Wohlfarth model is used to explain the in-plane magnetic anisotropies observed at 5 K, while one possible reason for the magnetic anisotropies measured at 300 K is the complex interfacial magnetic properties proved by x-ray magnetic circular dichroism measurements.

  12. Solidification Microstructure, Segregation, and Shrinkage of Fe-Mn-C Twinning-Induced Plasticity Steel by Simulation and Experiment

    NASA Astrophysics Data System (ADS)

    Lan, Peng; Tang, Haiyan; Zhang, Jiaquan

    2016-06-01

    A 3D cellular automaton finite element model with full coupling of heat, flow, and solute transfer incorporating solidification grain nucleation and growth was developed for a multicomponent system. The predicted solidification process, shrinkage porosity, macrosegregation, grain orientation, and microstructure evolution of Fe-22Mn-0.7C twinning-induced plasticity (TWIP) steel match well with the experimental observation and measurement. Based on a new solute microsegregation model using the finite difference method, the thermophysical parameters including solid fraction, thermal conductivity, density, and enthalpy were predicted and compared with the results from thermodynamics and experiment. The effects of flow and solute transfer in the liquid phase on the solidification microstructure of Fe-22Mn-0.7C TWIP steel were compared numerically. Thermal convection decreases the temperature gradient in the liquid steel, leading to the enlargement of the equiaxed zone. Solute enrichment in front of the solid/liquid interface weakens the thermal convection, resulting in a little postponement of columnar-to-equiaxed transition (CET). The CET behavior of Fe-Mn-C TWIP steel during solidification was fully described and mathematically quantized by grain morphology statistics for the first time. A new methodology to figure out the CET location by linear regression of grain mean size with least-squares arithmetic was established, by which a composition design strategy for Fe-Mn-C TWIP steel according to solidification microstructure, matrix compactness, and homogeneity was developed.

  13. Site-mixing effect on the XMCD spectrum in double perovskite Bi2FeMnO6

    NASA Astrophysics Data System (ADS)

    Ahmed, Towfiq; Chen, Aiping; McFarland, Brian; Wang, Qiang; Ohldag, Hendrik; Sandberg, Richard; Jia, Quanxi; Yarotski, Dmitry A.; Zhu, Jian-Xin

    2016-06-01

    We investigate magnetization in double perovskite multiferroic Bi2FeMnO6 (BFMO) thin film using density functional theory (DFT) simulations, and X-ray magnetic circular dichroism (XMCD) measurements. The exchange interaction between Fe and Mn sites gives rise to a ferrimagnetic ordering in BFMO. When grown without structural defects, distinct XMCD signal is expected from this system. The site resolved magnetization, thus, can be extracted using XMCD sum rules. Although our theoretical calculations are consistent with this expectation for the ideal BFMO system, experimental measurements find evidence of anomalous peak for the L2 and L3 edges of XMCD signals, and thus, the XMCD sum rules are no longer valid. We theoretically explain this phenomenon by considering both tetragonal (near interface), and monoclinic (bulk) phases of BFMO system, with Fe and Mn ions interchanged between their respective sites. Such site-mixing between magnetic cations are commonly found during the synthesis process. Our DFT calculations of XMCD for site interchanged Fe and Mn ions in the bulk phase (monoclinic) of BFMO are in good agreement with experimental XMCD signal and reproduce the anomalous peak features at L2/L3 edges.

  14. Structural transitions, magnetic properties, and electronic structures of Co(Fe)-doped MnNiSi compounds

    SciTech Connect

    Li, Y.; Wei, Z. Y.; Liu, E. K. Wang, S. G.; Wang, W. H.; Wu, G. H.; Liu, G. D.

    2015-05-07

    The structural transitions, magnetic properties, and electronic structures of Co(Fe)-doped MnNiSi compounds are investigated by x-ray powder diffraction, differential scanning calorimetry (DSC), magnetic measurements, and first-principles calculations. Results indicate that all samples undergo a martensitic transition from the Ni{sub 2}In-type parent phase to TiNiSi-type orthorhombic phase at high temperatures. The substitution of Co(Fe) for Mn in Mn{sub 1−x}Co{sub x}NiSi (x = 0.2, 0.3, and 0.4) and Mn{sub 1−y}Fe{sub y}NiSi (y = 0.26, 0.30, 0.36, 0.46, and 0.55) samples decreases the structural transition temperature and Curie temperature of martensite. The martensite phases show a typical ferromagnetic behavior with saturation field being basically unchanged with increasing Co(Fe) content, while the saturation magnetization shows a decreasing tendency. The theoretically calculated moments are in good agreement with the experimentally measured results. The orbital hybridizations between different 3d elements are analyzed from the distribution of density of states.

  15. Bioaccessibility of Cr, Cu, Fe, Mg, Mn, Mo, Se and Zn from nutritional supplements by the unified BARGE method.

    PubMed

    Tokalıoğlu, Serife; Clough, Robert; Foulkes, Mike; Worsfold, Paul

    2014-05-01

    In this study, the Unified Bioaccessibility Research Group of Europe (BARGE) in vitro method was used to assess the bioaccessibility of Cr, Cu, Fe, Mg, Mn, Mo, Se, and Zn in ten nutritional supplement samples and three certified reference materials. The total digest, gastric phase and gastro-intestinal phase concentrations of Cu, Fe, Mg, Mn and Zn were determined by ICP-OES and Cr, Mo and Se by ICP-MS. The bioaccessible fractions of the elements in the gastric phase for the nutritional supplements were in the range 13-89% for Cr, 9-79% for Cu, 55-99% for Fe, 33-95% for Mg, 83-94% for Mn, 42-101% for Mo, 74-125% for Se and 81-104% for Zn. The range for the gastrointestinal phase was 6-65% for Cr, 27-66% for Cu, 3-14% for Fe, 34-91% for Mg, 53-62% for Mn, 40-109% for Mo, 53-146% for Se and 3-35% for Zn. PMID:24360457

  16. Biosorption of Fe(II) and Mn(II) Ions from Aqueous Solution by Rice Husk Ash

    PubMed Central

    Zhao, Jiaying; Jiang, Zhao; Shan, Dexin; Lu, Yan

    2014-01-01

    Rice husk ash (RHA), an agricultural waste, was used as biosorbent for the removal of Iron(II) and Manganese(II) ions from aqueous solutions. The structural and morphological characteristics of RHA and its elemental compositions before and after adsorption of Fe(II) and Mn(II) were determined by scanning electron microscopic (SEM) and X-ray fluorescence (XRF) analyses. Batch experiments were carried out to determine the influence of initial pH, contact time, adsorbent dosage, and initial concentration on the removal of Fe(II) and Mn(II) ions. Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherm of the metal ions by RHA. The correlation coefficient (R2) of Langmuir and Freundlich isotherm models equals 0.995 and 0.901 for Fe(II), 0.9862 and 0.8924 for Mn(II), respectively, so the Langmuir model fitted the equilibrium data better than the Freundlich isotherm model. The mean free energy values evaluated from the D-R model indicated that the biosorption of Fe(II) and Mn(II) onto RHA was physical in nature. Experimental data also showed that the biosorption processes of both metal ions complied with the pseudo-second-order kinetics. PMID:24982918

  17. Magnetocaloric effect, cyclability and coefficient of refrigerant performance in the MnFe(P, Si, B) system

    NASA Astrophysics Data System (ADS)

    Guillou, F.; Yibole, H.; Porcari, G.; Zhang, L.; van Dijk, N. H.; Brück, E.

    2014-08-01

    MnFeP0.595Si0.33B0.075 has recently been presented as a top class magnetocaloric material combining a large magnetocaloric entropy change, a large temperature change, limited thermal hysteresis, and an enhanced mechanical stability. By providing practical rules to control the transition temperature in the MnFe(P,Si,B) system, we demonstrate that this new material was not a single composition and that a giant magnetocaloric effect (MCE) can be observed over a broad temperature range, a point of great interest for applications. As important prerequisite is the cyclability of the MCE. The thermal hysteresis and the recovery of the MCE during field oscillations have been addressed for MnFe(P,Si,B) materials. It is found that when the thermal hysteresis becomes about as large as the field induced shift of the transition, the MCE becomes partially irreversible and a strong decrease in the cyclic temperature change occurs. For an intermediate field change, typically 1 T, the limit for thermal hysteresis is about δThyst ≈ 4 K in the MnFe(P,Si,B) system. Finally, the interest of this material class for magnetic refrigeration is discussed in terms of the coefficient of refrigerant performance.

  18. The ternary MnFe2O4/graphene/polyaniline hybrid composite as negative electrode for supercapacitors

    NASA Astrophysics Data System (ADS)

    Sankar, Kalimuthu Vijaya; Selvan, Ramakrishnan Kalai

    2015-02-01

    The ternary MnFe2O4/graphene/polyaniline (PANI) composite was successfully prepared for the negative electrode in hybrid supercapacitors. The MnFe2O4 particles are synthesized by polymer assisted solution combustion method without any high temperature calcinations. Similarly, the flexible graphene and PANI are prepared by eco-friendly hydrothermal and in situ polymerization method, respectively. The presence of possible functional groups and the existence of individual constituents in the composite were identified through Fourier transform infra-red spectra (FT-IR) and Raman spectra. Transmission electron microscope (TEM) image reveals that the MnFe2O4 particles are dispersed on the flexible graphene sheet and are wrapped by PANI. The ternary composite electrode delivered a specific capacitance of 241 F g-1 at 0.5 mA cm-2, which was 7.5 times higher than MnFe2O4. The calculated b-value elucidates that the charge storage mechanism in the ternary system is based on the capacitive behavior rather than intercalation. The increase in ratio between capacitive and intercalation current with respect to scan rate corroborates that the pseudocapacitive charge storage mechanism is dominant. Further, the fabricated hybrid supercapacitor provides the maximum specific capacitance and energy density of 48.5 F g-1 at 0.5 mA cm-2 and 17 Wh kg-1, respectively. In addition, the hybrid supercapacitor exhibits excellent cyclic stability of up to 5000 successive cycles.

  19. Tip Growth Of Carbon Nanotubes Obtained By Pyrolyzation Of Camphor Oil With Zeolite Embedded With Fe/Ni/Mn Catalyst

    NASA Astrophysics Data System (ADS)

    Azira, A. A.; Zainal, N. F. A.; Nik, S. F.; Rusop, M.

    2009-06-01

    Highly efficient synthesis of carbon nanotubes (CNTs) have been synthesized by thermal decomposition of camphor oil, on a zeolite support impregnated with Fe/Ni/Mn (molar ratio of Fe:Ni:Mn = 1:1:1) catalyst in the temperature range from 550-950° C by the thermal CVD method. Besides the surface fluidization of the catalyst nanoparticles themselves, assistance of the metal oxides embedded in zeolite supports is supposed to be responsible for high activity and selectivity of the Fe/Ni/Mn catalyst over which carbon source (camphor oil) successfully decomposes. The CNT yield was higher at 850° C and can be considered as the optimum deposition temperature. This result demonstrates that zeolite impregnated with the catalyst Fe/Ni/Mn is a suitable support for effective formation of CNTs. The morphological studies support `tip growth mechanism' for the growth of the CNT's in our case. The as-grown CNTs were characterized by FESEM and FTIR spectroscopy.

  20. Observed And Modeled Seasonal Trends In Dissolved And Particulate Cu, Fe, Mn, And Zn In A Mining-Impacted Stream

    EPA Science Inventory

    North Fork Clear Creek (NFCC) in Colorado, an acid-mine drainage (AMD) impacted stream, was chosen to examine the distribution of dissolved and particulate Cu, Fe, Mn, and Zn in the water column, with respect to seasonal hydrologic controls. NFCC is a high-gradient stream with d...

  1. Structural, optical, and magnetic properties of Mn and Fe-doped Co{sub 3}O{sub 4} nanoparticles

    SciTech Connect

    Stella, C. Soundararajan, N.; Ramachandran, K.

    2015-08-15

    Mn and Fe-doped Co{sub 3}O{sub 4} nanoparticles were prepared by a simple precipitation method. The synthesized particles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and vibrating sample magnetometer (VSM) techniques. XRD analysis showed the cubic structure of Co{sub 3}O{sub 4}. SEM and TEM images confirmed the formation of interconnected nanoparticles. Mn and Fe-doped Co{sub 3}O{sub 4} showed broad absorption in the visible region compared to undoped sample and the band gap values are red shifted. Five Raman active modes were observed from the Raman spectra. FTIR spectra confirmed the spinel structure of Co{sub 3}O{sub 4} and the doping of Mn and Fe shifts the vibrational modes to lower wave number region. The magnetic measurements confirmed that Fe-doped Co{sub 3}O{sub 4} shows a little ferromagnetic behavior compared to undoped and Mn-doped Co{sub 3}O{sub 4}, which could be related to the uncompensated surface spins and the finite size effects.

  2. GEOCHEMICAL PARTITIONING OF PB, ZN, CU, FE, AND MN ACROSS THE SEDIMENT-WATER INFERFACE IN LARGE LAKES

    EPA Science Inventory

    The early diagenetic remobilization of Mn, Fe, Zn, Cu, and Pb was evaluated by studying the geochemical partitioning of the metals among hydromorphic phases (as operationally defined by sequential-chemical extractions) in interfacial sediment (fluff) and in the sediment column, a...

  3. Solidification Microstructure, Segregation, and Shrinkage of Fe-Mn-C Twinning-Induced Plasticity Steel by Simulation and Experiment

    NASA Astrophysics Data System (ADS)

    Lan, Peng; Tang, Haiyan; Zhang, Jiaquan

    2016-04-01

    A 3D cellular automaton finite element model with full coupling of heat, flow, and solute transfer incorporating solidification grain nucleation and growth was developed for a multicomponent system. The predicted solidification process, shrinkage porosity, macrosegregation, grain orientation, and microstructure evolution of Fe-22Mn-0.7C twinning-induced plasticity (TWIP) steel match well with the experimental observation and measurement. Based on a new solute microsegregation model using the finite difference method, the thermophysical parameters including solid fraction, thermal conductivity, density, and enthalpy were predicted and compared with the results from thermodynamics and experiment. The effects of flow and solute transfer in the liquid phase on the solidification microstructure of Fe-22Mn-0.7C TWIP steel were compared numerically. Thermal convection decreases the temperature gradient in the liquid steel, leading to the enlargement of the equiaxed zone. Solute enrichment in front of the solid/liquid interface weakens the thermal convection, resulting in a little postponement of columnar-to-equiaxed transition (CET). The CET behavior of Fe-Mn-C TWIP steel during solidification was fully described and mathematically quantized by grain morphology statistics for the first time. A new methodology to figure out the CET location by linear regression of grain mean size with least-squares arithmetic was established, by which a composition design strategy for Fe-Mn-C TWIP steel according to solidification microstructure, matrix compactness, and homogeneity was developed.

  4. The design of an Fe-12Mn-O.2Ti alloy steel for low temperature use

    NASA Technical Reports Server (NTRS)

    Hwang, S. K.; Morris, J. W., Jr.

    1977-01-01

    An investigation was made to improve the low temperature mechanical properties of Fe-8 approximately 12% Mn-O 2Ti alloy steels. A two-phase(alpha + gamma) tempering in combination with cold working or hot working was identified as an effective treatment. A potential application as a Ni-free cryogenic steel was shown for this alloy. It was also shown that an Fe-8Mn steel could be grain-refined by a purely thermal treatment because of its dislocated martensitic structure and absence of epsilon phase. A significant reduction of the ductile-brittle transition temperature was obtained in this alloy. The nature and origin of brittle fracture in Fe-Mn alloys were also investigated. Two embrittling regions were found in a cooling curve of an Fe-12Mn-O 2Ti steel which was shown to be responsible for intergranular fracture. Auger electron spectroscopy identified no segregation during solution-annealing treatment. Avoiding the embrittling zones by controlled cooling led to a high cryogenic toughness in a solution-annealed condition.

  5. Effect of Ti addition on the microstructure and mechanical properties of a cast Fe-Ni-Mo-Mn maraging steel

    NASA Astrophysics Data System (ADS)

    Nejad, S. Hossein; Nili Ahmadabadi, M.

    2003-10-01

    To study the effect of Ti on the age hardening behavior of Fe-Ni-Mn maraging steels, a Fe-Ni-Mo-Mn steel was alloyed with Ti then mechanical properties and aging behavior of two cast steels were investigated. In this regard, two heats of nominal compositions of Fe-10Ni-6Mo-3Mn and Fe-lONi-6Mo-3Mn-0. 7Ti were induction melted in air and vacuum respectively and cast in iron mold. After homogenizing at 1473K for 21.6ks and water quenching, solution annealing was performed at 1223K for 3.6ks followed by air cooling. Age hardening behavior at 773Kin the range of 0.36-172. 8 ks was determined. Tensile properties and Charpy impact toughness were measured in the solution annealed and peak-aged conditions. Fractographic features were studied by scanning electron microscope equipped with EDX microanalyses. Tensile properties of the alloys in the peakaged condition were in the range of grade 200 standard maraging steel. It has been found that Ti addition resulted in increasing of hardness and strength in aged condition and decreasing of Charpy impact toughness in both solution annealed and aged conditions. Ti addition also changes type and morphology of inclusions and fracture mechanism from semi-ductile intergranular mode to semi-ductile transgranular one.

  6. The magnetic phase transition in Mn1.1Fe0.9P1-xGex magnetocaloric alloys

    NASA Astrophysics Data System (ADS)

    Chen, X.; Ramanujan, R. V.

    2015-02-01

    Mn-Fe-P-Ge alloys are promising, low cost, high performance candidates for magnetic cooling applications based on the magnetocaloric effect. These alloys undergo a magnetic phase transition which induces a large entropy change (ΔS). Experimental and modeling studies were conducted to study this transition for varying Ge content. Landau theory and the Bean-Rodbell model were applied to Mn1.1Fe0.9P1-xGex (x = 0.26, 0.3, and 0.32) melt spun ribbons to model the phase transition and the associated entropy change. The critical behavior of these alloys was studied. The critical composition range at which the cross over from first order to second order magnetic transition occurs was determined. The calculated thermodynamic values and critical temperatures were in good agreement with our experimental results. A high maximum entropy change (ΔS) of ˜44.9 J kg-1 K-1 was observed in Mn1.1Fe0.9P0.74Ge0.26 in a 5 T applied magnetic field. The results suggest that Mn-Fe-P-Ge alloys are very attractive materials for near room temperature magnetic cooling.

  7. Enhanced switching characteristics and piezoelectric response in epitaxial BiFeO3-TbMnO3 thin films

    NASA Astrophysics Data System (ADS)

    Li, Wei; Wang, Yiping; Nie, Pengxiao; Hu, Querui; Yang, Ying; Yuan, Guoliang

    2015-06-01

    High-quality (001) oriented epitaxial 0.9BiFeO3-0.1TbMnO3 thin films were grown on La2/3Sr1/3MnO3 and SrRuO3 buffered SrTiO3 substrate using pulsed laser deposition. X-ray diffraction showed that the films are single-phase perovskite without secondary impurity phases. Domain structures and upward ferroelectric self-poling phenomenon were distinctly observed in both films with compressive epitaxial strains. Furthermore, the upward self-poling disappears in polycrystalline 0.9BiFeO3-0.1TbMnO3 thin film on Pt/TiO2/SiO2/Si substrates. Through local switching spectroscopy measurements, the evidence of enhanced ferroelectric switching and piezoelectric response characteristics have been provided.

  8. Mechanical milling assisted synthesis of Ba-Mn co-substituted BiFeO3 ceramics and their properties

    NASA Astrophysics Data System (ADS)

    Saravana Kumar, K.; Venkateswaran, C.; Kannan, D.; Tiwari, Brajesh; Ramachandra Rao, M. S.

    2012-10-01

    Samples of composition Bi1-xBaxFe1-xMnxO3 (x = 0, 0.1, 0.2) were synthesized by initial mixing of precursors by high-energy ball milling and subsequent sintering of the milled powders. The co-substitution of Ba-Mn controls the formation of impurity phases, as evident from x-ray diffraction analysis. Evidence of Fe in mixed oxidation states of +3 and +2 and Mn in +3 state is found from x-ray photoelectron spectroscopy. Electron microscopy exhibits a decrease in grain size due to inhibition in grain growth by Ba-Mn co-substitution. The magnetization value at 20 kOe increases as the percentage of substitution increases. The x = 0.2 sample exhibits a comparable and stable resistivity curve in the experimental temperature range and has a higher value of remanent polarization (Pr) when compared with the x = 0 sample.

  9. Process of prototyping coronary stents from biodegradable Fe-Mn alloys.

    PubMed

    Hermawan, Hendra; Mantovani, Diego

    2013-11-01

    Biodegradable stents are considered to be a recent innovation, and their feasibility and applicability have been proven in recent years. Research in this area has focused on materials development and biological studies, rather than on how to transform the developed biodegradable materials into the stent itself. Currently available stent technology, the laser cutting-based process, might be adapted to fabricate biodegradable stents. In this work, the fabrication, characterization and testing of biodegradable Fe-Mn stents are described. A standard process for fabricating and testing stainless steel 316L stents was referred to. The influence of process parameters on the physical, metallurgical and mechanical properties of the stents, and the quality of the produced stents, were investigated. It was found that some steps of the standard process such as laser cutting can be directly applied, but changes to parameters are needed for annealing, and alternatives are needed to replace electropolishing. PMID:23665503

  10. Enhanced photovoltaic properties in bilayer BiFeO3/Bi-Mn-O thin films.

    PubMed

    Chakrabartty, Joyprokash; Nechache, Riad; Harnagea, Catalin; Li, Shun; Rosei, Federico

    2016-05-27

    We report an external solar power conversion efficiency of ∼1.43% in BiFeO3(BFO)/BiMnO3(BMO) bilayer thin films. Both films are epitaxially grown on (111) oriented niobium doped SrTiO3 (NSTO) single crystal substrates by pulsed laser deposition. By illuminating the BFO/BMO films under 1 Sun (AM 1.5 G), we found a remarkably high fill factor of ∼0.72, much higher than values reported for devices based on BFO or BMO alone. In addition, we demonstrate that the photocurrent density and photovoltage are tunable by changing the polarization direction in the BFO/BMO bilayer, as confirmed by the macroscopic polarization-voltage (P-V) hysteresis loop. This effect is described in terms of a more favorable energy band alignment of the electrode/bilayer/NSTO heterostructure junction, which controls photocarrier separation. PMID:27094952

  11. Enhanced photovoltaic properties in bilayer BiFeO3/Bi-Mn-O thin films

    NASA Astrophysics Data System (ADS)

    Chakrabartty, Joyprokash; Nechache, Riad; Harnagea, Catalin; Li, Shun; Rosei, Federico

    2016-05-01

    We report an external solar power conversion efficiency of ∼1.43% in BiFeO3(BFO)/BiMnO3(BMO) bilayer thin films. Both films are epitaxially grown on (111) oriented niobium doped SrTiO3 (NSTO) single crystal substrates by pulsed laser deposition. By illuminating the BFO/BMO films under 1 Sun (AM 1.5 G), we found a remarkably high fill factor of ∼0.72, much higher than values reported for devices based on BFO or BMO alone. In addition, we demonstrate that the photocurrent density and photovoltage are tunable by changing the polarization direction in the BFO/BMO bilayer, as confirmed by the macroscopic polarization–voltage (P–V) hysteresis loop. This effect is described in terms of a more favorable energy band alignment of the electrode/bilayer/NSTO heterostructure junction, which controls photocarrier separation.

  12. Nanomechanical Behavior of CoCrFeMnNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Mridha, Sanghita; Das, Santanu; Aouadi, Samir; Mukherjee, Sundeep; Mishra, Rajiv S.

    2015-08-01

    The nanomechanical behavior of the Co20Cr20Fe20Mn20Ni20 high-entropy alloy was investigated in as-cast, rolled, annealed, and thin-film forms. Dislocation nucleation was studied by repeated indents at a low load for each of the different processing conditions. Distinct displacement bursts (pop in) were observed in the loading curve marked by incipient plasticity for all the samples. The as-cast and annealed samples showed pop ins for 100% of the indents, whereas the rolled and thin-film samples showed a much lower fraction of displacement bursts. This was explained by the high density of dislocations for the cold-worked and thin-film conditions. The strong depth dependence of hardness was explained by geometrically necessary dislocations. The nanomechanical behavior and twinned microstructure indicate low stacking-fault energy for this high-entropy alloy.

  13. Mechanical cycling effects at Fe-Mn-Si-Cr-Ni SMAs obtained by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Pricop, B.; Söyler, U.; Comčneci, R. I.; Özkal, B.; Bujoreanu, L. G.

    Specimens from Fe-Mn-Si-Cr-Ni SMA, obtained by powder metallurgy and compacted through hot rolling, were subjected to tensile loading-unloading cycles. The pseudoelastic parameters were determined based on recorded stress-strain curves, and their variation tendency with increasing the number of mechanical cycles was discussed. The gauges of tensile specimens were cut after mechanical cycling and were subjected to structural and dilatometric analysis. The structure was analyzed by XRD and SEM, aiming to reveal mechanical cycling effects. The thermomechanical response on heating, of mechanically cycled specimens, was recorded by dilatometry and revealed a tendency to enhance thermal expansion as an effect of increasing the number of cycles. The microstructural changes, induced by mechanical cycling, consisted in the stress induced formation of α' martensite.

  14. High spin polarization in CoFeMnGe equiatomic quaternary Heusler alloy

    SciTech Connect

    Bainsla, Lakhan; Suresh, K. G.; Nigam, A. K.; Manivel Raja, M.; Varaprasad, B. S. D. Ch. S.; Takahashi, Y. K.; Hono, K.

    2014-11-28

    We report the structure, magnetic property, and spin polarization of CoFeMnGe equiatomic quaternary Heusler alloy. The alloy was found to crystallize in the cubic Heusler structure (prototype LiMgPdSn) with considerable amount of DO{sub 3} disorder. Thermal analysis result indicated the Curie temperature is about 750 K without any other phase transformation up to melting temperature. The magnetization value was close to that predicted by the Slater-Pauling curve. Current spin polarization of P = 0.70 ± 0.01 was deduced using point contact andreev reflection measurements. The temperature dependence of electrical resistivity has been fitted in the temperature range of 5–300 K in order to check for the half metallic behavior. Considering the high spin polarization and Curie temperature, this material appears to be promising for spintronic applications.

  15. Electron paramagnetic resonance linewidths and line shapes for the molecular magnets Fe8 and Mn12

    NASA Astrophysics Data System (ADS)

    Park, Kyungwha; Novotny, M. A.; Dalal, N. S.; Hill, S.; Rikvold, P. A.

    2002-05-01

    We study theoretically electron paramagnetic resonance (EPR) linewidths for single crystals of the molecular magnets Fe8 and Mn12 as functions of energy eigenstates Ms, frequency, and temperature when a magnetic field along the easy axis is swept at fixed excitation frequency. This work was motivated by recent EPR experiments. To calculate the linewidths, we use density-matrix equations, including dipolar interactions and distributions of the uniaxial anisotropy parameter D and the Landé g factor. Our calculated linewidths agree well with the experimental data. We also examine the line shapes of the EPR spectra due to local rotations of the magnetic anisotropy axes caused by defects in samples. Our preliminary results predict that this effect leads to asymmetry in the EPR spectra.

  16. Exchange anisotropy and spin-wave damping in CoFe/IrMn bilayers

    NASA Astrophysics Data System (ADS)

    Rezende, S. M.; Lucena, M. A.; Azevedo, A.; de Aguiar, F. M.; Fermin, J. R.; Parkin, S. S. P.

    2003-05-01

    The magnetic properties and the spin-wave damping in FM/AF bilayers of CoFe/IrMn have been investigated with magneto-optic Kerr effect magnetometry, ferromagnetic resonance (FMR), and Brillouin light scattering (BLS). As observed in other systems, the values of the interlayer exchange field obtained with different techniques are discrepant, but they all exhibit the expected t-1 dependence with the FM film thickness t. On the other hand the spin-wave relaxation rates measured by BLS and FMR are fit with a t-2 dependence plus a constant term. This is interpreted as the sum of two independent contributions, an intrinsic mechanism dominated by Gilbert damping and an extrinsic mechanism dominated by two-magnon scattering due to fluctuations of the interlayer exchange coupling caused by interface roughness.

  17. Proof of intercrystallite ionic transport in LiMPO(4) electrodes (M = Fe, Mn).

    PubMed

    Lee, Kyu Tae; Kan, Wang H; Nazar, Linda F

    2009-05-01

    Homogeneous-sized LiMPO(4) (M = Fe, Mn) nanorods and bulk particles were synthesized, and the thermodynamic characteristics of their mixtures as electrodes were analyzed to study the lithiation/delithiation mechanism for the general case of nanoparticles with a heterogeneous particle size distribution. We show that ionic transport occurs between nano and bulk particles in a cell at equilibrium, due to their electrochemical potential difference that originates from their different thermodynamic properties. This means that one phase in a single particle is preferred to two phases in a single particle during lithiation/delithiation of LiMPO(4) from the viewpoint of thermodynamics if the electrode is composed of differing particle sizes. PMID:19366201

  18. Microstructural characterization of transformable Fe-Mn alloys at different length scales

    SciTech Connect

    Liang, X.; Wang, X.; Zurob, H.S.

    2009-11-15

    The as-annealed and deformed Microstructure of transformable Fe-Mn alloys were, comprehensively, characterized over a wide range of length scales. Differential interference contrast optical metallography, combined with a tinting etching method, was employed to examine the grain morphology. A new specimen preparation method, involving electro-polishing and electro-etching, was developed for scanning electron microscopy and electron back-scattered diffraction analysis. This method leads to a very good imaging contrast and thus bridges the length scale gap between optical metallography and transmission electron microscopy. Moreover, it enables simultaneous scanning electron microscopy and electron backscatter diffraction analysis which allows correlations among morphology, crystal orientation and phase analysis in the length scale of microns. Transmission electron microscopy investigations were also made to evaluate the thermal and mechanical transformation products as well as defect structures.

  19. Antiparallel interface coupling evidenced by negative rotatable anisotropy in IrMn/NiFe bilayers

    SciTech Connect

    Schafer, D.; Grande, P. L.; Pereira, L. G.; Azevedo, G. M.; Harres, A.; Geshev, J.; Sousa, M. A. de; Pelegrini, F.

    2015-06-07

    Negative rotatable anisotropy is estimated via ferromagnetic resonance measurements in as-made, annealed, and ion-irradiated IrMn{sub 3}/Ni{sub 81}Fe{sub 19} bilayers. Opposite to previous observations, inverse correlation between rotatable anisotropy and coercivity is observed. The exchange-bias field, determined from hysteresis loop measurements, is higher than that obtained from ferromagnetic resonance for all samples. The results are discussed in terms of majority antiparallel coupling and magnetic-field-induced transitions from antiparallel to parallel states of uncompensated spins at ferromagnet/antiferromagnet interface. We affirm that an observation of negative rotatable anisotropy evidences antiparallel coupling even in systems presenting conventional exchange bias.

  20. Competing effects of magnetocrystalline anisotropy and exchange bias in epitaxial Fe/IrMn bilayers

    SciTech Connect

    Zhang, Wei; Bowden, Mark E.; Krishnan, Kannan M.

    2011-03-01

    We systematically investigated the possible magnetization reversal behavior in well-characterized, epitaxial, Fe/IrMn exchange-biased bilayers as a function of the antiferromagnetic (AF) layer thickness. Several kinds of multi-step loops were observed for the samples measured at various field orientations. The angular dependence of the switching fields, observed using longitudinal and transverse magneto-optic Kerr effect (MOKE), were shown to depend on the competition between the magnetocrystalline anisotropy and the exchange bias (EB). A modified ‘effective field’ model was applied to quantitatively describe the evolution of the magnetic behavior and correctly predict the occurrence of different magnetic switching processes. The dependence of the effective anisotropy fields on the AF layer thickness directly reflects the competing effects of the pinned and rotatable antiferromagnetic spins at the EB interface.

  1. The content of Ca, Cu, Fe, Mg and Mn and antioxidant activity of green coffee brews.

    PubMed

    Stelmach, Ewelina; Pohl, Pawel; Szymczycha-Madeja, Anna

    2015-09-01

    A simple and fast method of the analysis of green coffee infusions was developed to measure total concentrations of Ca, Cu, Fe, Mg and Mn by high resolution-continuum source flame atomic absorption spectrometry. The precision of the method was within 1-8%, while the accuracy was within -1% to 2%. The method was used to the analysis of infusions of twelve green coffees of different geographical origin. It was found that Ca and Mg were leached the easiest, i.e., on average 75% and 70%, respectively. As compared to the mug coffee preparation, the rate of the extraction of elements was increased when infusions were prepared using dripper or Turkish coffee preparation methods. Additionally, it was established that the antioxidant activity of green coffee infusions prepared using the mug coffee preparation was high, 75% on average, and positively correlated with the total content of phenolic compounds and the concentration of Ca in the brew. PMID:25842341

  2. Little Ice Age Recorded in Mn/Fe Precipitates by Pb and Nd Isotopes

    NASA Astrophysics Data System (ADS)

    Liebetrau, V.; Eisenhauer, A.; Frei, R.; Bock, B.; Kronz, A.; Hansen, B. T.; Leipe, T.

    2002-12-01

    Ferromanganese precipitates of the Baltic Sea can be dated by the 226Raexcess/Ba-method (Liebetrau et al., 2002). Recent investigations have shown that these precipitates may represent perfect archives for the postglacial history of the circum Baltic area. In particular, these precipitates offer the possibility to study short term variations of the Scandinavian shield erosion and climate change during the Little Ice Age. The Nd isotope record of a selected Mn/Fe crust from the Mecklenburg Bay of the Baltic Sea shows a significant change of the ɛ Nd-value from around -13 for ages older than 1100 years AD to approx. -18 around 1600 years AD. This shift can be explained by increased erosion and input of Nd from Archean Scandinavian sources and/or a reduced inflow of North Atlantic water (ɛ Nd = -13) to the Baltic Sea. Comparison with a temperature reconstruction for Fennoscandia (Mann, 2001) documents a close relationship of the ɛ Nd record with temperature variations during the Little Ice Age because negative ɛ Nd-value tend to correlate with lower temperature during the last 1000 years. In contrast, the pattern of 207Pb/206Pb record closely correlates with historically known changes of anthropogenic activities during the industrial revolution and times of enhanced Ag and Pb mining. Nd and Pb are correlated before 1100 AD but are decoupled after at about 1100 years AD. We propose that Pb appears to be more sensitive to anthropogenic activities since about 1100 AD. Liebetrau V., Eisenhauer A., Gussone N., W”rner G., Hansen B.T., and Leipe T., 2002, 226Raexcess/Ba growth rates and U-Th-Ra-Ba systematic of Baltic Mn/Fe crusts, Geochim. Cosmochim. Acta, 66, 73-83 Mann M.E., 2001, The Little Ice Age, in: Encyclopedia of Environmental Global Change

  3. Controlling disorder-mediated exchange bias in (Mn,Zn,Fe)3O4 thin films

    NASA Astrophysics Data System (ADS)

    Alaan, U. S.; Sreenivasulu, G.; Yu, K. M.; Jenkins, C.; Shafer, P.; Arenholz, E.; Srinivasan, G.; Suzuki, Y.

    2016-05-01

    We report exchange bias in (Mn,Zn,Fe)3O4 thin films that are compositionally homogeneous. We show that exchange bias in these Mn-Zn ferrite (MZFO) films can be tuned quite easily through annealing of the as-deposited films. The annealing process increases the crystallinity, as measured by X-ray diffraction (XRD). This improvement in crystallinity is accompanied by lower coercive fields, lower exchange bias fields, and higher saturation magnetizations. Exchange bias in these nominally homogeneous ferrite films is correlated with the degree of both structural and magnetic disorder. Based on the annealing experiments, we believe that these MZFO films may consist of crystalline regions that are separated from one another by disordered regions of the same nominal composition. The disordered regions serve to exchange bias the more structurally and magnetically ordered crystalline MZFO grains, leading to a shift of the magnetic hysteresis loop. Together these results indicate that the magnitude of the exchange bias can be controlled by tuning the degree of crystallinity in the system.

  4. Microstructural Developments and Tensile Properties of Lean Fe-Mn-Al-C Lightweight Steels

    NASA Astrophysics Data System (ADS)

    Sohn, S. S.; Lee, S.; Lee, B.-J.; Kwak, J.-H.

    2014-09-01

    Concepts of Fe-Al-Mn-C-based lightweight steels are fairly simple, but primary metallurgical issues are complicated. In this study, recent studies on lean-composition lightweight steels were reviewed, summarized, and emphasized by their microstructural development and mechanical properties. The lightweight steels containing a low-density element of Al were designed by thermodynamic calculation and were manufactured by conventional industrial processes. Their microstructures consisted of various secondary phases as κ-carbide, martensite, and austenite in the ferrite matrix according to manufacturing and annealing procedures. The solidification microstructure containing segregations of C, Mn, and Al produced a banded structure during the hot rolling. The (ferrite + austenite) duplex microstructure was formed after the annealing, and the austenite was retained at room temperature. It was because the thermal stability of austenite nucleated from fine κ-carbide was quite high due to fine grain size of austenite. Because these lightweight steels have outstanding properties of strength and ductility as well as reduced density, they give a promise for automotive applications requiring excellent properties.

  5. Monte Carlo study of decorated dislocation loops in FeNiMnCu model alloys

    NASA Astrophysics Data System (ADS)

    Bonny, G.; Terentyev, D.; Zhurkin, E. E.; Malerba, L.

    2014-09-01

    Radiation-induced embrittlement of bainitic steels is the lifetime limiting factor of reactor pressure vessels in existing nuclear light water reactors. The primary mechanism of embrittlement is the obstruction of dislocation motion by nano-metric defects in the bulk of the material due to irradiation. Such features are known to be solute clusters that may be attached to point defect clusters. In this work we study the thermal stability of solute clusters near edge dislocation lines and loops with Burgers vector b = ½[1 1 1] and b = [1 0 0] in FeNiMnCu model alloys by means of Metropolis Monte Carlo simulations. It is concluded that small dislocation loops may indeed act as points for heterogeneous nucleation of solute precipitates in reactor pressure vessel steels and increase their thermodynamic stability up to and above normal reactor operating temperatures. We also found that, in the presence of dislocation-type defects, the Ni content determines the thermodynamic driving force for precipitation, rather than the Mn content.

  6. Distributed microbially- and chemically-mediated redox processes controlling arsenic dynamics within Mn-/Fe-oxide constructed aggregates

    NASA Astrophysics Data System (ADS)

    Ying, Samantha C.; Masue-Slowey, Yoko; Kocar, Benjamin D.; Griffis, Sarah D.; Webb, Samuel; Marcus, Matthew A.; Francis, Christopher A.; Fendorf, Scott

    2013-03-01

    The aggregate-based structure of soils imparts physical heterogeneity that gives rise to variation in microbial and chemical processes which influence the speciation and retention of trace elements such as As. To examine the impact of distributed redox conditions on the fate of As in soils, we imposed various redox treatments upon constructed soil aggregates composed of ferrihydrite- and birnessite-coated sands presorbed with As(V) and inoculation with the dissimilatory metal reducing bacterium Shewanella sp. ANA-3. Aeration of the advecting solution surrounding the aggregates was varied to simulate environmental conditions. We find that diffusion-limited transport within high dissolved organic carbon environments allows reducing conditions to persist in the interior of aggregates despite aerated advecting external solutes, causing As, Mn, and Fe to migrate from the reduced aggregate interiors to the aerated exterior region. Upon transitioning to anoxic conditions in the external solutes, pulses of As, Mn and Fe are released into the advecting solution, while, conversely, a transition to aerated conditions in the exterior resulted in a cessation of As, Mn, and Fe release. Importantly, we find that As(III) oxidation by birnessite is appreciable only in the presence of O2; oxidation of As(III) to As(V) by Mn-oxides ceases under anaerobic conditions apparently as a result of microbially mediated Mn(IV/III) reduction. Our results demonstrate the importance of considering redox conditions and the physical complexity of soils in determining As dynamics, where redox transitions can either enhance or inhibit As release due to speciation shifts in both sorbents (solubilization versus precipitation of Fe and Mn oxides) and sorbates (As).

  7. Influence of boron doping on magnetic properties and microwave characteristics of MnIr/FeCoB multilayers

    NASA Astrophysics Data System (ADS)

    Phuoc, Nguyen N.; Ong, C. K.

    2012-04-01

    A detailed investigation of the influence of B doping on the magnetic properties and high frequency characteristics of FeCoB/MnIr multilayered thin films was carried out. Exchange bias was found to decrease monotonically with B doping possibly due to less favorable of AF phase of MnIr in the samples with rich B concentration. However, with small amount of doping up to 9% of B concentration, the MnIr fcc (111) peaks become more prominent and the real part of permeability enhanced. Our results suggest no correlation between the structural phase of MnIr and the exchange bias. Also, the influences of B doping on several static and dynamic parameters, such as rotational magnetic anisotropy field, coercivity, saturation magnetization, resonance frequency, and effective damping factor are presented and discussed. Our results support the claim that the coercivity enhancement and the arising of rotational anisotropy may have the same physical origin.

  8. Influence of boron doping on magnetic properties and microwave characteristics of MnIr/FeCoB multilayers

    SciTech Connect

    Phuoc, Nguyen N.; Ong, C. K.

    2012-04-15

    A detailed investigation of the influence of B doping on the magnetic properties and high frequency characteristics of FeCoB/MnIr multilayered thin films was carried out. Exchange bias was found to decrease monotonically with B doping possibly due to less favorable of AF phase of MnIr in the samples with rich B concentration. However, with small amount of doping up to 9% of B concentration, the MnIr fcc (111) peaks become more prominent and the real part of permeability enhanced. Our results suggest no correlation between the structural phase of MnIr and the exchange bias. Also, the influences of B doping on several static and dynamic parameters, such as rotational magnetic anisotropy field, coercivity, saturation magnetization, resonance frequency, and effective damping factor are presented and discussed. Our results support the claim that the coercivity enhancement and the arising of rotational anisotropy may have the same physical origin.

  9. Mechanism of Austenite Formation from Spheroidized Microstructure in an Intermediate Fe-0.1C-3.5Mn Steel

    NASA Astrophysics Data System (ADS)

    Lai, Qingquan; Gouné, Mohamed; Perlade, Astrid; Pardoen, Thomas; Jacques, Pascal; Bouaziz, Olivier; Bréchet, Yves

    2016-05-01

    The austenitization from a spheroidized microstructure during intercritical annealing was studied in a Fe-0.1C-3.5Mn alloy. The austenite grains preferentially nucleate and grow from intergranular cementite. The nucleation at intragranular cementite is significantly retarded or even suppressed. The DICTRA software, assuming local equilibrium conditions, was used to simulate the austenite growth kinetics at various temperatures and for analyzing the austenite growth mechanism. The results indicate that both the mode and the kinetics of austenite growth strongly depend on cementite composition. With sufficiently high cementite Mn content, the austenite growth is essentially composed of two stages, involving the partitioning growth controlled by Mn diffusion inside ferrite, followed by a stage controlled by Mn diffusion within austenite for final equilibration. The partitioning growth results in a homogeneous distribution of carbon within austenite, which is supported by NanoSIMS carbon mapping.

  10. Mechanism of Austenite Formation from Spheroidized Microstructure in an Intermediate Fe-0.1C-3.5Mn Steel

    NASA Astrophysics Data System (ADS)

    Lai, Qingquan; Gouné, Mohamed; Perlade, Astrid; Pardoen, Thomas; Jacques, Pascal; Bouaziz, Olivier; Bréchet, Yves

    2016-07-01

    The austenitization from a spheroidized microstructure during intercritical annealing was studied in a Fe-0.1C-3.5Mn alloy. The austenite grains preferentially nucleate and grow from intergranular cementite. The nucleation at intragranular cementite is significantly retarded or even suppressed. The DICTRA software, assuming local equilibrium conditions, was used to simulate the austenite growth kinetics at various temperatures and for analyzing the austenite growth mechanism. The results indicate that both the mode and the kinetics of austenite growth strongly depend on cementite composition. With sufficiently high cementite Mn content, the austenite growth is essentially composed of two stages, involving the partitioning growth controlled by Mn diffusion inside ferrite, followed by a stage controlled by Mn diffusion within austenite for final equilibration. The partitioning growth results in a homogeneous distribution of carbon within austenite, which is supported by NanoSIMS carbon mapping.

  11. Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr18 FCC solid solution alloy

    DOE PAGESBeta

    Wu, Z.; Bei, H.

    2015-07-01

    Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with amore » composition of FeNiMnCr18 was successfully developed. This near-equiatomic FeNiMnCr18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.« less

  12. Solvothermal synthesis of MnFe2O4-graphene composite-Investigation of its adsorption and antimicrobial properties

    NASA Astrophysics Data System (ADS)

    Chella, Santhosh; Kollu, Pratap; Komarala, Eswara Vara P. R.; Doshi, Sejal; Saranya, Murugan; Felix, Sathiyanathan; Ramachandran, Rajendran; Saravanan, Padmanapan; Koneru, Vijaya Lakshmi; Venugopal, Velmurugan; Jeong, Soon Kwan; Nirmala Grace, Andrews

    2015-02-01

    Graphene manganese ferrite (MnFe2O4-G) composite was prepared by a solvothermal process. The as-prepared graphene manganese ferrite composite was tested for the adsorption of lead (Pb(II)) and cadmium (Cd(II)) ions by analytical methods under diverse experimental parameters. With respect to contact time measurements, the adsorption of Pb and Cd ions increased and reached equilibrium within 120 and 180 min at 37 °C with a maximum adsorption at pH 5 and 7 respectively. The Langmuir model correlates to the experimental data showing an adsorption capacity of 100 for Pb(II) and 76.90 mg g-1 for Cd(II) ions. Thermodynamic studies revealed that the adsorption of Pb and Cd ions onto MnFe2O4-G was spontaneous, exothermic and feasible in the range of 27-47 °C. Cytotoxicity behavior of graphene against bacterial cell membrane is well known. To better understand its antimicrobial mechanism, the antibacterial activity of graphene and MnFe2O4-G nanocomposite was compared. Under similar concentration and incubation conditions, nanocomposite MnFe2O4-G dispersion showed the highest antibacterial activity of 82%, as compared to graphene showing 37% cell loss. Results showed that the prepared composite possess good adsorption efficiency and thus could be considered as an excellent material for removal of toxic heavy metal ions as explained by adsorption isotherm. Hence MnFe2O4-G can be used as an adsorbent as well as an antimicrobial agent.

  13. Decay properties of 68,69,70Mn: Probing collectivity up to N = 44 in Fe isotopic chain

    NASA Astrophysics Data System (ADS)

    Benzoni, G.; Morales, A. I.; Watanabe, H.; Nishimura, S.; Coraggio, L.; Itaco, N.; Gargano, A.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y.; Lorusso, G.; Patel, Z.; Rice, S.; Sinclair, L.; Söderström, P.-A.; Sumikama, T.; Wu, J.; Xu, Z. Y.; Yokoyama, R.; Baba, H.; Avigo, R.; Bello Garrote, F. L.; Blasi, N.; Bracco, A.; Camera, F.; Ceruti, S.; Crespi, F. C. L.; de Angelis, G.; Delattre, M.-C.; Dombradi, Zs.; Gottardo, A.; Isobe, T.; Kuti, I.; Matsui, K.; Melon, B.; Mengoni, D.; Miyazaki, T.; Modamio-Hoybjor, V.; Momiyama, S.; Napoli, D. R.; Niikura, M.; Orlandi, R.; Sakurai, H.; Sahin, E.; Sohler, D.; Taniuchi, R.; Taprogge, J.; Vajta, Zs.; Valiente-Dobón, J. J.; Wieland, O.; Yalcinkaya, M.

    2015-12-01

    The β decays 68Mn →68Fe, 69Mn →69Fe and 70Mn →70Fe have been measured at the RIBF facility at RIKEN using the EURICA γ spectrometer combined with an active stopper consisting of a stack of Si detectors. The nuclei were produced as fission fragments from a beam of 238U at a bombarding energy of 345 MeV/nucleon impinging on a Be target and selected using the BigRIPS separator. Half-lives and β-delayed neutron emission probabilities have been extracted for these decays, together with first experimental information on excited states populated in 69,70Fe. The data indicate a continuously increasing deformation for Fe isotopes up to A = 70. This is interpreted, as for Cr isotopes, in terms of the interplay between the quadrupole correlations of the ν 1d5/2 and ν 0g9/2 orbitals and the monopole component of the π 0f7/2- ν 0f5/2 interaction.

  14. Oxygen-participated electrochemistry of new lithium-rich layered oxides Li3MRuO5 (M = Mn, Fe).

    PubMed

    Laha, S; Natarajan, S; Gopalakrishnan, J; Morán, E; Sáez-Puche, R; Alario-Franco, M Á; Dos Santos-Garcia, A J; Pérez-Flores, J C; Kuhn, A; García-Alvarado, F

    2015-02-01

    We describe the synthesis, crystal structure and lithium deinsertion-insertion electrochemistry of two new lithium-rich layered oxides, Li3MRuO5 (M = Mn, Fe), related to rock salt based Li2MnO3 and LiCoO2. The Li3MnRuO5 oxide adopts a structure related to Li2MnO3 (C2/m) where Li and (Li0.2Mn0.4Ru0.4) layers alternate along the c-axis, while the Li3FeRuO5 oxide adopts a near-perfect LiCoO2 (R3[combining macron]m) structure where Li and (Li0.2Fe0.4Ru0.4) layers are stacked alternately. Magnetic measurements indicate for Li3MnRuO5 the presence of Mn(3+) and low spin configuration for Ru(4+) where the itinerant electrons occupy a π*-band. The onset of a net maximum in the χ vs. T plot at 9.5 K and the negative value of the Weiss constant (θ) of -31.4 K indicate the presence of antiferromagnetic superexchange interactions according to different pathways. Lithium electrochemistry shows a similar behaviour for both oxides and related to the typical behaviour of Li-rich layered oxides where participation of oxide ions in the electrochemical processes is usually found. A long first charge process with capacities of 240 mA h g(-1) (2.3 Li per f.u.) and 144 mA h g(-1) (1.38 Li per f.u.) is observed for Li3MnRuO5 and Li3FeRuO5, respectively. An initial sloping region (OCV to ca. 4.1 V) is followed by a long plateau (ca. 4.3 V). Further discharge-charge cycling points to partial reversibility (ca. 160 mA h g(-1) and 45 mA h g(-1) for Mn and Fe, respectively). Nevertheless, just after a few cycles, cell failure is observed. X-ray photoelectron spectroscopy (XPS) characterisation of both pristine and electrochemically oxidized Li3MRuO5 reveals that in the Li3MnRuO5 oxide, Mn(3+) and Ru(4+) are partially oxidized to Mn(4+) and Ru(5+) in the sloping region at low voltage, while in the long plateau, O(2-) is also oxidized. Oxygen release likely occurs which may be the cause for failure of cells upon cycling. Interestingly, some other Li-rich layered oxides have been reported to

  15. Thermodynamics of Fe3O4-Co3O4 and Fe3O4-Mn3O4 spinel solid solutions at the bulk and nanoscale.

    PubMed

    Sahu, Sulata K; Huang, Baiyu; Lilova, Kristina; Woodfield, Brian F; Navrotsky, Alexandra

    2015-09-14

    High temperature oxide melt solution calorimetry has been performed to investigate the enthalpies of mixing (ΔmixH) of bulk and nanophase (1 -x)Fe3O4-xM3O4 (M = Co, Mn) spinel solid solutions. The entropies of mixing (ΔmixS) were calculated from the configurational entropies based on cation distributions, and the Gibbs free energies of mixing (ΔmixG) were obtained. The ΔmixH and ΔmixG for the (1 -x)Fe3O4-xCo3O4 system are negative over the complete solid solution range, for both macroscopic and nanoparticulate materials. In (1 -x)Fe3O4-xMn3O4, the formation enthalpies of cubic Fe3O4 (magnetite) and tetragonal Mn3O4 (hausmannite) are negative for Mn3O4 mole fractions less than 0.67 and slightly positive for higher manganese content. Relative to cubic Fe3O4 and cubic Mn3O4 (stable at high temperature), the enthalpies and Gibbs energies of mixing are negative over the entire composition range. A combination of measured mixing enthalpies and reported Gibbs energies in the literature provides experimental entropies of mixing. The experimental entropies of mixing are consistent with those calculated from cation distributions for x > 0.3 but are smaller than those predicted for x < 0.3. This discrepancy may be related to the calculations, having treated Fe(2+) and Fe(3+) as distinguishable species. The measured surface energies of the (1 -x)Fe3O4-xM3O4 solid solutions are in the range of 0.6-0.9 J m(-2), similar to those of many other spinels. Because the surface energies are relatively constant, the thermodynamics of mixing at a given particle size throughout the solid solution can be considered independent of the particular particle size, thus confirming and extending the conclusions of a recent study on iron spinels. PMID:26245233

  16. Enhanced GMI effect in Fe 73.5-xMn xSi 13.5B 9Nb 3Cu I (x=1,3,5) nanocomposites due to Mn substitution for Fe

    NASA Astrophysics Data System (ADS)

    Phan, Manh-Huong; Peng, Hua-Xin; Yu, Seong-Cho; Tho, Nguyen D.; Chau, Nguyen

    2006-03-01

    Influence of Mn partial substitution for Fe on the magnetic and magnetoimpedance properties of Fe 73.5-xMn xSi 13.5B 9Nb 3Cu I (x = 1, 3, and 5) nanocomposite ribbons were investigated. The results indicated that the Mn addition led to an improved exchange coupling between grains and hence in the magnetic softness. Consequently, the giant magnetoimpedance (GMI) effect was significantly enhanced in these nanocomposites. In the frequency range of 0.1-10 Mhz, the GMI ratio reached the highest values of 83%, 94%, and 130% at the frequency of 2 MHz for x = 1, 3, and 5 compositions, respectively. The corresponding field sensitivity of GMI reached the highest values of 6, 7, and 16 %/Oe, respectively. These indicate that Fe 73.5-xMn xSi 13.5B 9Nb 3Cu I (x = 1, 3, and 5) nanocomposites are potential candidate materials for making GMI sensors.

  17. Annealing effects on the structural and magnetic properties of off-stoichiometric Fe-Mn-Ga ferromagnetic shape memory alloys

    DOE PAGESBeta

    Chen, Yan; Bei, Hongbin; Dela Cruz, Clarina R; Wang, Yandong; An, Ke

    2016-05-07

    Annealing plays an important role in modifying structures and properties of ferromagnetic shape memory alloys (FSMAs). The annealing effect on the structures and magnetic properties of off-stoichiometric Fe45Mn26Ga29 FSMA has been investigated at different elevated temperatures. Rietveld refinements of neutron diffraction patterns display that the formation of the γ phase in Fe45Mn26Ga29 annealed at 1073 K increases the martensitic transformation temperature and reduces the thermal hysteresis in comparison to the homogenized sample. The phase segregation of a Fe-rich cubic phase and a Ga-rich cubic phase occurs at the annealing temperature of 773 K. The atomic occupancies of the alloys aremore » determined thanks to the neutron's capability of differentiating transition metals. The annealing effects at different temperatures introduce a different magnetic characteristic that is associated with distinctive structural changes in the crystal.« less

  18. Rapid liquid phase sintered Mn doped BiFeO3 ceramics with enhanced polarization and weak magnetization

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Yadav, K. L.

    2007-12-01

    Single-phase BiFe1-xMnxO3 multiferroic ceramics have been synthesized by rapid liquid phase sintering method to study the influence of Mn substitution on their crystal structure, dielectric, magnetic, and ferroelectric behaviors. From XRD analysis it is seen that Mn substitution does not affect the crystal structure of the BiFe1-xMnxO3 system. An enhancement in magnetization was observed for BiFe1-xMnxO3 ceramics. However, the ferooelectric hysteresis loops were not really saturated, we observed a spontaneous polarization of 10.23μC /cm2 under the applied field of 42kV/cm and remanent polarization of 3.99μC/cm2 for x =0.3 ceramic.

  19. First principles study on spin and orbital magnetism of 3d transition metal monatomic nanowires (Mn, Fe and Co).

    PubMed

    Sargolzaei, Mahdi; Samaneh Ataee, S

    2011-03-30

    We have demonstrated the electronic structure and magnetic properties of 3d transition metal nanowires (Mn, Fe and Co) in the framework of relativistic density functional theory. The equilibrium bond lengths were optimized using the generalized gradient approximation. In a full relativistic regime individual spin and orbital moments induced from spin polarization via spin-orbit coupling were calculated. In order to get an upper estimate for orbital moments, we used an orbital polarization correction to our exchange-correlation functional. We found that the orbital magnetic moments of Fe and Co linear chains are strongly enhanced in the presence of an orbital polarization correction. We have calculated the exchange coupling parameters between two nearest-neighbor magnetic atoms according to a Heisenberg-like model in the presence of the orbital polarization correction. We found that the Co and Fe nanowires behave like a ferromagnetic linear chain whereas a Mn monatomic nanowire remains antiferromagnetic. PMID:21378443

  20. Exchange bias of MnFe2O4@γFe2O3 and CoFe2O4@γFe2O3 core/shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Cabreira-Gomes, R.; G. Silva, F.; Aquino, R.; Bonville, P.; Tourinho, F. A.; Perzynski, R.; Depeyrot, J.

    2014-11-01

    We compare here exchange bias (EB) properties of chemically synthesized core-shell nanoparticles (NPs), based either on a core of soft ferrite (MnFe2O4) or hard ferrite (CoFe2O4) protected by a maghemite shell (γ-Fe2O3). These NPs dispersed in acidic solutions are electrostatically stabilized, yielding to stable colloidal dispersions with a strong interparticle repulsion and negligible dipolar interactions in the probed range of temperatures. Field cooled (FC) magnetic hysteresis loops of non-textured frozen dispersions (with magnetic anisotropy axis of NPs distributed at random) and those of a powder based on the same NPs present a shift along the H-axis, expressing the coupling between the spin-ordered cores and the disordered surface layer of the NPs. The bias field is found to present a maximum, larger for NPs based on harder ferrite core. It is obtained for a cooling field of the order of one half of the anisotropy field, which is much larger for the CoFe2O4 cores than for MnFe2O4 ones. In powders, particles are in contact leading to an interparticle exchange which is not present in the dilute solutions where exchange bias properties are only due to an intraparticle exchange between core and surface. The thermal dependence of the bias field is well described by a reduced exponential behavior with a characteristic freezing temperature of about 8 K.

  1. Influence of manganese on sintering processes in the Ti-Fe system. 1. Volume changes in sintering of Ti-Fe-Mn compacts

    SciTech Connect

    Kivalo, L.I.; Skorokhod, V.V.

    1986-05-01

    An investigation was made of the influence of manganese on the sintering processes in the titanium-iron system in the area of temperatures of existence of the first ternary eutectic point. Powders of titanium obtained by hydride-calcium reduction, ferromanganese, and types PZh4M2 and V3 iron were used. A figure presents data on the character of the volume changes in sintering of compacts of mixtures of titanium and iron powders with and without manganese. The x-ray analysis was made on a DRON-0.5 instrument. The profiles of intensities of the x-ray lines of Ti(Fe, Mn) phase present in specimens of mixture II are shown. With an increase in sintering temperature the line, which is diffuse at 1050 degrees C, gradually narrows, and at 1250 degrees C a doublet appears. At the time, the lattice parameter changes from 0.2976 for unalloyed TiFe to 0.2991 nm for Ti(Fe, Mn) obtained at 1250 degrees C. To obtain Ti(Fe, Mn) compounds of the required composition, it is necessary to take into account the amount of evaporated manganese.

  2. Effect of Cr and Mn ions on the structure and magnetic properties of GaFeO{sub 3}: Role of the substitution site

    SciTech Connect

    Saha, Rana; Shireen, Ajmala; Shirodkar, Sharmila N.; Waghmare, Umesh V.; Sundaresan, A.; Rao, C.N.R.

    2011-09-15

    Effect of substitution of Cr and Mn in the Fe and Ga sites of GaFeO{sub 3} on the structural parameters and magnetic properties has been investigated by preparing GaFe{sub 1-x}Cr{sub x}(Mn{sub x})O{sub 3} and Ga{sub 1-x}Cr{sub x}(Mn{sub x})FeO{sub 3} starting with appropriate oxide precursors. It is shown that, starting with Cr or Mn substituted Ga{sub 2}O{sub 3}, one obtains Ga{sub 1-x}Cr{sub x}(Mn{sub x})FeO{sub 3}, while reaction of Cr or Mn substituted {alpha}-Fe{sub 2}O{sub 3} with Ga{sub 2}O{sub 3} yields GaFe{sub 1-x}Cr{sub x}(Mn{sub x})O{sub 3}. The structural parameters and magnetic properties vary significantly with the substitution site of Cr showing a large decrease in the unit cell parameters as well as the T{sub C} and other magnetic properties when the substitution is at the octahedral Fe (1, 2) site. Substitution of Cr at the octahedral Ga2 site results in marginal changes. Substitution of Mn in the Ga and Fe sites also show differences although the changes themselves are much smaller. First-principles calculations confirm such site-specificity and show how Cr substitution affects the properties differently when substituted at the Ga2 and Fe1 sites. - Graphical abstract: The important role of site-specific substitution of transition metal ions on the structure and magnetic properties of GaFeO{sub 3} has been investigated experimentally and theoretically. Highlights: > Substitution of transition metal ions to specific cation site. > Ionic radii of the cation dictate the disorder associated with the specific site. > Site-specificity explains magnetic ordering and structural parameters.

  3. FeTiMn alloy granulate in a pressure container for storage of hydrogen and deuterium

    SciTech Connect

    Klatt, K.; Wenzl, H.

    1982-01-19

    Oxygen is incorporated into an FeTiMn granulate in an amount sufficient to form double oxides of titanium and manganese therein, but insufficient to form oxides containing iron. As the result, the granules are embrittled, favoring the formation of microcracks to such an extent that activation of the granules by hydrogen takes place, after initial evacuation, at room temperature, after which the granulate can be used in a pressure container for storage and discharge of hydrogen and/or deuterium over long periods of operation. The oxygen content is to be kept in an atomic ratio with reference to the manganese content of the alloy lying between 1:3 and 1:3.5 and the ratio of titanium not bound by formation of a metal oxide to the iron should be equal to or greater than 1:1 on an atomic basis, with the FeTi content of the alloy constituting 90 to 95% by weight of the alloy.

  4. Exchange bias of spin valve structure with a top-pinned Co{sub 40}Fe{sub 40}B{sub 20}/IrMn

    SciTech Connect

    You, C. Y.; Furubayashi, T.; Takahashi, Y. K.; Goripati, H. S.; Hono, K.

    2008-07-07

    We have investigated the exchange bias of a directly top-pinned Co{sub 40}Fe{sub 40}B{sub 20}/IrMn structure. An exchange bias was realized on the as-deposited samples, in which Co{sub 40}Fe{sub 40}B{sub 20} exhibits a fully amorphous structure. A current-in-plane giant magnetoresistance effect was demonstrated on simple Ru/CoFeB/Cu/CoFeB/IrMn/Ru stacks prior to and after annealing. The amorphous CoFeB layer partially crystallized from the interface with a Cu spacer layer after annealed at 280 deg. C.

  5. In vitro study on apoptotic cell death by effective magnetic hyperthermia with chitosan-coated MnFe2O4

    NASA Astrophysics Data System (ADS)

    Oh, Yunok; Lee, Nohyun; Kang, Hyun Wook; Oh, Junghwan

    2016-03-01

    Magnetic nanoparticles (MNPs) have been widely investigated as a hyperthermic agent for cancer treatment. In this study, thermally responsive Chitosan-coated MnFe2O4 (Chitosan-MnFe2O4) nanoparticles were developed to conduct localized magnetic hyperthermia for cancer treatment. Hydrophobic MnFe2O4 nanoparticles were synthesized via thermal decomposition and modified with 2,3-dimercaptosuccinic acid (DMSA) for further conjugation of chitosan. Chitosan-MnFe2O4 nanoparticles exhibited high magnetization and excellent biocompatibility along with low cell cytotoxicity. During magnetic hyperthermia treatment (MHT) with Chitosan-MnFe2O4 on MDA-MB 231 cancer cells, the targeted therapeutic temperature was achieved by directly controlling the strength of the external AC magnetic fields. In vitro Chitosan-MnFe2O4-assisted MHT at 42 °C led to drastic and irreversible changes in cell morphology and eventual cellular death in association with the induction of apoptosis through heat dissipation from the excited magnetic nanoparticles. Therefore, the Chitosan-MnFe2O4 nanoparticles with high biocompatibility and thermal capability can be an effective nano-mediated agent for MHT on cancer.

  6. Synthesis of Mn1-xZnxFe2O4 ferrite powder by co-precipitation method

    NASA Astrophysics Data System (ADS)

    Irfan, Salma; Ajaz-un-Nabi, M.; Jamil, Yasir; Amin, Nasir

    2014-06-01

    Ferrimagnetic substances referred to as ferrites are ionic crystals whose chemical composition is of the form XFe2 O4 where X signifies a divalent metal. Magnetic Nano sized ferrites have found a significant potential in many applications, such as magnetic recording media, Ferro fluids and radar absorbing coating. Ferrites are widely used in many industrial applications due to their spontaneous magnetization. Soft ferrites of Mn-Zn, Ni-Zn and Mg-Mn are well known for their high magnetic permeability. In the present research work we have prepared fine Mn1-xZnxFe2O4 ferrite powder with varying x concentrations (0.25-0.75) by metal chloride precursors through a co-precipitation technique by pipette drop method using aqueous NaOH solution for comparing their spontaneous magnetization and particle size. The co-precipitation technique is a high way to produce chemically homogeneous powder with fine particle size in nanometers (22.5nm-74.5nm).The effect of x-concentration on the particle size of the Mn(1-x) Zn(x) ferrite has been discussed on the basis of XRD. The crystalline phases have been identified by X-ray diffraction with Cu-Kα radiations. The XRD patterns have verified that the specimen has spinal type structure. The observable peaks are broad since the size of the particles is small. We have concluded that at constants temperature particle size increases with increasing x-concentrations. Effect of different concentrations of x (Zn+2) on the spontaneous magnetization of different Mn(1-x) Zn(x) Fe2O4 sample is determined. We have reached the conclusion that all the samples of Mn(1-x) Zn(x) Fe2 O4 ferrites were magnetic either of low or high magnetization. The maximum spontaneous magnetization and minimum particle size is obtained at x=0.25 (at digestion temperature=65°C).

  7. Electronic structural flexibility of heterobimetallic Mn/Fe cofactors: R2lox and R2c proteins.

    PubMed

    Shafaat, Hannah S; Griese, Julia J; Pantazis, Dimitrios A; Roos, Katarina; Andersson, Charlotta S; Popović-Bijelić, Ana; Gräslund, Astrid; Siegbahn, Per E M; Neese, Frank; Lubitz, Wolfgang; Högbom, Martin; Cox, Nicholas

    2014-09-24

    The electronic structure of the Mn/Fe cofactor identified in a new class of oxidases (R2lox) described by Andersson and Högbom [Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 5633] is reported. The R2lox protein is homologous to the small subunit of class Ic ribonucleotide reductase (R2c) but has a completely different in vivo function. Using multifrequency EPR and related pulse techniques, it is shown that the cofactor of R2lox represents an antiferromagnetically coupled Mn(III)/Fe(III) dimer linked by a μ-hydroxo/bis-μ-carboxylato bridging network. The Mn(III) ion is coordinated by a single water ligand. The R2lox cofactor is photoactive, converting into a second form (R2loxPhoto) upon visible illumination at cryogenic temperatures (77 K) that completely decays upon warming. This second, unstable form of the cofactor more closely resembles the Mn(III)/Fe(III) cofactor seen in R2c. It is shown that the two forms of the R2lox cofactor differ primarily in terms of the local site geometry and electronic state of the Mn(III) ion, as best evidenced by a reorientation of its unique (55)Mn hyperfine axis. Analysis of the metal hyperfine tensors in combination with density functional theory (DFT) calculations suggests that this change is triggered by deprotonation of the μ-hydroxo bridge. These results have important consequences for the mixed-metal R2c cofactor and the divergent chemistry R2lox and R2c perform. PMID:25153930

  8. The role of tree uprooting dynamics on the dynamics of Fe (Mn, Al and Si) forms in different forest soils

    NASA Astrophysics Data System (ADS)

    Tejnecký, V.; Samonil, P.; Boruvka, L.; Nikodem, A.; Drabek, O.; Valtera, M.

    2013-12-01

    Tree uprooting dynamics plays an important role in the development of forest ecosystems. This process causes bioturbation of soils and creates new microenvironments which consist of pits and mounds. These microtopographical forms could persist for some thousands of years. Pits and mounds undergo different pedogenesis in comparison to adjacent undisturbed soils. The stage of pedogenesis can be assessed according to the results of fractionation of Fe and also partially Mn, Al and Si. The main aim of this contribution is to assess the fractionation of Fe, Mn, Al and Si for three different soil regions. Soil samples were collected at three localities occurred along hypothetical gradient of soil weathering and leaching processes: The first was a (spruce)-fir-beech natural forest in the Razula region. The second location is the same type of natural forest in Zofin; however it has contrasting lithology. Both these natural forests are located in the Czech Republic (CZ). The third forest was a northern hardwood forest in Upper Peninsula, Michigan, USA. The prevailing soil types - Haplic Cambisols have formed on flysch parent materials in the Razula reserve; Entic Podzols have developed on granite residuum at the Zofin reserve, and Albic Podzols occurred in outwash parent materials at the Michigan sites (Šamonil et al., in press). In total 790 soil samples were analysed. These samples were collected from 5 depths (0-10, 15, 30, 50 and 100 cm) within the pit, mound and control, currently undisturbed position. For each sample, content of Fe (and Mn, Al, Si) forms: exchangeable, crystalline, and amorphous together with organically complexed Fe were determined. We generally observed an increased content of Fe soil forms in the pits of studied treethrows. The content of Fe forms increased along depth gradient at the disturbed sites. However, exchangeable Fe was most abundant in the 0-10cm layer which corresponds to the A horizon. Naturally, if present, the E horizon exhibited

  9. Polyol synthesis of Mn3+ substituted Fe3O4 nanoparticles: Cation distribution, structural and electrical properties

    NASA Astrophysics Data System (ADS)

    Amir, Md.; Ünal, B.; Shirsath, Sagar E.; Geleri, M.; Sertkol, M.; Baykal, A.

    2015-09-01

    In this study, MnxFe2-xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) nanoparticles were synthesized by polyol route and the effect of Mn3+ substitution on structural and dielectric properties of Fe3O4 was studied. X-ray powder diffraction (XRD) patterns confirmed the single spinel ferrite phase formation (Rietveld analysis). Crystallite size of the synthesized materials lie in the range of 12-25 nm as calculated X-ray diffraction patterns using Scherrer's formula. The microstructural features were examined by SEM images. Cation distribution calculations confirmed Fe3+ ions have both tetrahedral and ochedral site preferences whereas Mn3+ ions mostly occupies tetrahedral A-site. The ac electrical and dielectric properties of Mn3+ ion substituted Fe3O4 nanoparticle show that there were significant changes in both conductivity and complex permittivity as well as dielectric loss tangent as Mn3+ ion concentration is varied from zero to unity. It is clearly seen that conductivity increases with increase in temperature which may be due to increase in hopping capability of charge carriers at higher temperatures. Detailed evaluation of analysis reveals that at higher frequencies there is less effect of temperature on conductivity which can be interpreted on the basis of interfacial, dipolar, ionic and electronic polarization as detailed above section in explanation of variation of dielectric loss. The dielectric permittivity shows dielectric behavior can be clarified on the basis of Koop's interpretations in accordance with two layer Maxwell-Wagner model by accounting for surface charges. The electrical and dielectric properties, i.e. ac/dc conductivity, real/complex dielectric permittivity, and dielectric loss (tan δ) decrease with Mn3+ ion doping in some aspects.

  10. Enhanced magnetic fluid hyperthermia by micellar magnetic nanoclusters composed of Mn(x)Zn(1-x)Fe(2)O(4) nanoparticles for induced tumor cell apoptosis.

    PubMed

    Qu, Yang; Li, Jianbo; Ren, Jie; Leng, Junzhao; Lin, Chao; Shi, Donglu

    2014-10-01

    Monodispersed MnxZn1-xFe2O4 magnetic nanoparticles of 8 nm are synthesized and encapsulated in amphiphilic block copolymer for development of the hydrophilic magnetic nanoclusters (MNCs). These MNCs exhibit superparamagnetic characteristics, high specific absorption rate (SAR), large saturation magnetization (Ms), excellent stability, and good biocompatibility. MnFe2O4 and Mn0.6Zn0.4Fe2O4 are selected as optimum compositions for the MNCs (MnFe2O4/MNC and Mn0.6Zn0.4Fe2O4/MNC) and employed for magnetic fluid hyperthermia (MFH) in vitro. To ensure biosafety of MFH, the parameters of alternating magnetic field (AMF) and exposure time are optimized with low frequency, f, and strength of applied magnetic field, Happlied. Under optimized conditions, MFH of MnFe2O4/MNC and Mn0.6Zn0.4Fe2O4/MNC result in cancer cell death rate up to 90% within 15 min. The pathway of cancer cell death is identified as apoptosis, which occurs in mild hyperthermia near 43 °C. Both MnFe2O4/MNC and Mn0.6Zn0.4Fe2O4/MNC show similar efficiencies on drug-sensitive and drug-resistant cancer cells. On the basis of these findings, those MnxZn1-xFe2O4 nanoclusters can serve as a promising candidate for effective targeting, diagnosis, and therapy of cancers. The multimodal cancer treatment is also possible as amphiphilic block copolymer can encapsulate, in a similar fashion, different nanoparticles, hydrophobic drugs, and other functional molecules. PMID:25204363

  11. Ordering of atoms in 3d sublattice of the intermetallic quasibinary system Dy(Fe/sub 1-x/Mn/sub x/)/sub 2/

    SciTech Connect

    Ilyushin, A.S.; Kastro, D.A.; Makhmud, I.A.

    1986-12-01

    Methods of x-ray analysis and nuclear ..gamma..-resonance (Moessbauer effect) have been used to study the distribution of iron and manganese atoms in the intermetallic quaisbinary system Dy(Fe/sub 1-x/Mn/sub x/)/sub 2/, which is isostructural to the Laves phase C15. Ordering of atoms of transition metals has been found in 3d sublattice of intermetallic compounds Dy(Fe/sub 1-x/Mn/sub x/)/sub 2/ with the formation of triple superstructure having the stoichiometric composition Dy(Fe/sub 0 x 25/Mn/sub 0 x 75/)/sub 2/

  12. Interfacial exchange coupling in cubic Heusler Co2FeZ (Z = Al and Si)/tetragonal Mn3Ga bilayers

    NASA Astrophysics Data System (ADS)

    Ranjbar, R.; Suzuki, K.; Sugihara, A.; Ma, Q. L.; Zhang, X. M.; Miyazaki, T.; Ando, Y.; Mizukami, S.

    2015-05-01

    We have fabricated bilayer films of tetragonal Heusler-like D022 Mn3Ga and cubic Heusler Co2FeZ (Z = Si and Al) on (100) single-crystalline MgO substrates and investigated their structural and interfacial exchange coupling. The coupling in the Mn3Ga/Co2FeAl bilayer was either ferromagnetic or antiferromagnetic, depending on annealing temperature, whereas only antiferromagnetic exchange coupling was observed in the Mn3Ga/Co2FeSi bilayers. The effects of annealing on the structure and coupling strength in the bilayers are discussed.

  13. Reduction of Fe(III), Mn(IV), and Toxic Metals at 100°C by Pyrobaculum islandicum

    PubMed Central

    Kashefi, Kazem; Lovley, Derek R.

    2000-01-01

    It has recently been noted that a diversity of hyperthermophilic microorganisms have the ability to reduce Fe(III) with hydrogen as the electron donor, but the reduction of Fe(III) or other metals by these organisms has not been previously examined in detail. When Pyrobaculum islandicum was grown at 100°C in a medium with hydrogen as the electron donor and Fe(III)-citrate as the electron acceptor, the increase in cell numbers of P. islandicum per mole of Fe(III) reduced was found to be ca. 10-fold higher than previously reported. Poorly crystalline Fe(III) oxide could also serve as the electron acceptor for growth on hydrogen. The stoichiometry of hydrogen uptake and Fe(III) oxide reduction was consistent with the oxidation of 1 mol of hydrogen resulting in the reduction of 2 mol of Fe(III). The poorly crystalline Fe(III) oxide was reduced to extracellular magnetite. P. islandicum could not effectively reduce the crystalline Fe(III) oxide minerals goethite and hematite. In addition to using hydrogen as an electron donor for Fe(III) reduction, P. islandicum grew via Fe(III) reduction in media in which peptone and yeast extract served as potential electron donors. The closely related species P. aerophilum grew via Fe(III) reduction in a similar complex medium. Cell suspensions of P. islandicum reduced the following metals with hydrogen as the electron donor: U(VI), Tc(VII), Cr(VI), Co(III), and Mn(IV). The reduction of these metals was dependent upon the presence of cells and hydrogen. The metalloids arsenate and selenate were not reduced. U(VI) was reduced to the insoluble U(IV) mineral uraninite, which was extracellular. Tc(VII) was reduced to insoluble Tc(IV) or Tc(V). Cr(VI) was reduced to the less toxic, less soluble Cr(III). Co(III) was reduced to Co(II). Mn(IV) was reduced to Mn(II) with the formation of manganese carbonate. These results demonstrate that biological reduction may contribute to the speciation of metals in hydrothermal environments and could

  14. Fabrication and Characterization of Mn0.5Zn0.5Fe2O4 Magnetic Nanofibers

    NASA Astrophysics Data System (ADS)

    Xiang, Jun; Shen, Xiang-Qian; Song, Fu-Zhan; Meng, Xian-Feng

    2010-01-01

    Mn0.5Zn0.5Fe2O4 Magnetic nanofibers were fabricated by calcining electrospun polymer/inorganic composite nanofibers and characterized by thermogravimetric and differential thermal analysis, x-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy and a vibrating sample magnetometer. The experimental results show that the pure spinel structure is basically formed when the composite nanofibers are calcined at 450°C for 2h. With the increasing calcination temperature, both the saturation magnetization and coercivity of nanofiber samples increase initially along with the growth of Mn0.5Zn0.5Fe2O4 nanocrystals contained in the nanofibers. However, when the calcination temperature reaches 550°C, the saturation magnetization of nanofibers starts to dramatically decrease owing to the formation of the α-Fe2O3 phase at this temperature. The prepared Mn0.5Zn0.5Fe2O4 nanofibers calcined at 500°C for 2h have diameters ranging from 100 to 200nm. Their saturation magnetization and coercivity are 12.37 emu/g and 4.81 kA/m at room temperature, respectively.

  15. The embrittlement and de-embrittlement of grain boundaries in an Fe-Mn-Ni alloy due to grain boundary segregation of Mn

    SciTech Connect

    Heo, N.H.; Lee, H.C.

    1996-04-01

    A ductile-brittle-ductile (DBD) transition behavior in an age-hardenable Fe-8Mn-7Ni alloy has been analyzed in light of segregation and desegregation of alloying elements at prior austenite grain boundaries. The DBD transition in the alloy can be distinguished by two C-type curves: one corresponding to the start of zero tensile elongation and the other to the finish. The activation energies for ductile-to-brittle and brittle-to-ductile transitions are in close agreement with that for age hardening. Manganese content at the prior austenite grain boundaries was analyzed by Auger electron spectroscopy, and intergranular fracture strength at the brittle fracture region showed inverse trends with Mn concentration at the grain boundaries. All these observations strongly suggest that manganese segregation and its desegregation are responsible for the DBD transition of this alloy.

  16. -decay measurements for N > 40 Mn nuclei and inference of collectivity for neutron-rich Fe isotopes

    SciTech Connect

    Daugas, J; Delaroche, J. P.; Pfutzner, M.; Sawicka, M.; Becker, F.; Belier, G.; Bingham, C. R.; Borcea, C.; Bouchez, E.; Buta, A.; Dragulescu, E.; Georgiev, G.; Giovinazzo, J.; Grawe, H.; Grzywacz, R.; Hammache, F.; Libert, J.; Meot, V.; Negoita, F.; de Oliveira Santos, F.; Perru, O.; Roig, O.; Rykaczewski, Krzysztof Piotr; Saint-Laurent, M. G.; Sauvestre, J. E.; Sorlin, O.; Stanoiu, M.; Stefan, I.; Theisen, Ch.

    2011-01-01

    A decay spectroscopic study of the neutron-rich isotopes has been performed using fragmentation of a 86Kr primary beam. Fragments from this reaction have been selected by the LISE2000 spectrometer at the Grand Acc el erateur National d Ions Lourds (GANIL). Half-lives of 29 isotopes, including the first ones identified for 61Ti (15 4 ms), 64V (19 8 ms), and 71Fe (28 5 ms), have been determined and compared with model predictions. 67,68Mn -delayed rays were observed for the first time. The branching for the -delayed neutron emission was measured to be greater than 10(5)% in the 67Mn decay. The 67Fe isomeric level is firmly determined at higher energy than assigned in previous works. The excitation energies of the first (2+) and (4+) states of 68Fe are suggested to lie at 522(1) and 1389(1) keV, respectively, thus bringing confirmation of assignments based on in-beam -ray spectroscopy. Beyond-mean-field calculations with the Gogny D1S force have been performed for even-mass nuclei through the Fe isotopic chain. Not only 68Fe but most of the neutron-rich Fe isotopes with neutron numbers below N = 50 are interpreted as soft rotors. The calculated mean occupancy of the neutron g9/2 and d5/2 orbitals in correlated ground states is steadily growing with increasing neutron number throughout the isotopic chain. Interpretation of 67Fe data is based upon the present calculations for the 66Fe and 68Fe even cores.

  17. Interlinked multiphase Fe-doped MnO2 nanostructures: a novel design for enhanced pseudocapacitive performance

    NASA Astrophysics Data System (ADS)

    Wang, Ziya; Wang, Fengping; Li, Yan; Hu, Jianlin; Lu, Yanzhen; Xu, Mei

    2016-03-01

    Structure designing and morphology control can lead to high performance pseudocapacitive materials for supercapacitors. In this work, we have designed interlinked multiphase Fe-doped MnO2 nanostructures (α-MnO2/R-MnO2/ε-MnO2) to enhance the electrochemical properties by a facile method. These hierarchical hollow microspheres assembled by interconnected nanoflakes, and with plenty of porous nanorods radiating from the spherical shells were hydrothermally obtained. The supercapacitor electrode prepared from the unique construction exhibits outstanding specific capacitance of 267.0 F g-1 even under a high mass loading (~5 mg cm-2). Obviously improved performances compared to pure MnO2 are also demonstrated with a good rate capability, high energy density (1.30 mW h cm-3) and excellent cycling stability of 100% capacitance retention after 2000 cycles at 2 A g-1. The synergistic effects of alternative crystal structures, appropriate crystallinity and optimal morphology are identified to be responsible for the observations. This rational multiphase composite strategy provides a promising idea for materials scientists to design and prepare scalable electrode materials for energy storage devices.Structure designing and morphology control can lead to high performance pseudocapacitive materials for supercapacitors. In this work, we have designed interlinked multiphase Fe-doped MnO2 nanostructures (α-MnO2/R-MnO2/ε-MnO2) to enhance the electrochemical properties by a facile method. These hierarchical hollow microspheres assembled by interconnected nanoflakes, and with plenty of porous nanorods radiating from the spherical shells were hydrothermally obtained. The supercapacitor electrode prepared from the unique construction exhibits outstanding specific capacitance of 267.0 F g-1 even under a high mass loading (~5 mg cm-2). Obviously improved performances compared to pure MnO2 are also demonstrated with a good rate capability, high energy density (1.30 mW h cm-3) and

  18. Osmium isotope variations in the oceans recorded by Fe-Mn crusts

    USGS Publications Warehouse

    Burton, K.W.; Bourdon, B.; Birck, J.-L.; Allegre, C.J.; Hein, J.R.

    1999-01-01

    This study presents osmium (Os) isotope data for recent growth surfaces of hydrogenetic ferromanganese (Fe-Mn) crusts from the Pacific, Atlantic and Indian Oceans. In general, these data indicate a relatively uniform Os isotopic composition for modern seawater, but suggest that North Atlantic seawater is slightly more radiogenic than that of the Pacific and Indian Oceans. The systematic difference in the Os isotopic composition between the major oceans probably reflects a greater input of old continental material with a high Re/Os ratio in the North Atlantic Ocean, consistent with the distribution of Nd and Pb isotopes. This spatial variation in the Os isotope composition in seawater is consistent with a residence time for Os of between 2 and 60 kyr. Indian Ocean samples show no evidence of a local source of radiogenic Os, which suggests that the present-day riverine input from the Himalaya-Tibet region is not a major source for Os. Recently formed Fe-Mn crusts from the TAG hydrothermal field in the North Atlantic yield an Os isotopic composition close to that of modern seawater, which indicates that, in this area, the input of unradiogenic Os from the hydrothermal alteration of oceanic crust is small. However, some samples from the deep Pacific (???4 km) possess a remarkably unradiogenic Os isotope composition (187Os/186Os ratios as low as 4.3). The compositional control of Os incorporation into the crusts and mixing relationships suggest that this unradiogenic composition is most likely due to the direct incorporation of micrometeoritic or abyssal peridotite particles, rather than indicating the presence of an unradiogenic deep-water mass. Moreover, this unradiogenic signal appears to be temporary, and local, and has had little apparent effect on the overall evolution of seawater. These results confirm that input of continental material through erosion is the dominant source of Os in seawater, but it is not clear whether global Os variations are due to the input

  19. Magnetic anisotropy of Fe1-yXyPt-L10 [X = Cr, Mn, Co, Ni, Cu] bulk alloys

    NASA Astrophysics Data System (ADS)

    Cuadrado, R.; Klemmer, Timothy J.; Chantrell, R. W.

    2014-10-01

    We demonstrate by means of fully relativistic first principles calculations that, by substitution of Fe by Cr, Mn, Co, Ni, or Cu in FePt-L10 bulk alloys, with fixed Pt content, it is possible to tune the magnetocrystalline anisotropy energy by adjusting the content of the non-magnetic species in the material. The changes in the geometry due to the inclusion of each element induces different values of the tetragonality and hence changes in the magnetic anisotropy and in the net magnetic moment. The site resolved magnetic moments of Fe increase with the X content while those of Pt and X are simultaneously reduced. The calculations are in good quantitative agreement with experimental data and demonstrate that models with fixed band structure but varying numbers of electrons per unit cell are insufficient to describe the experimental data for doped FePt-L10 alloys.

  20. 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.

  1. Respective role of Fe and Mn oxide contents for arsenic sorption in iron and manganese binary oxide: an X-ray absorption spectroscopy investigation.

    PubMed

    Zhang, Gaosheng; Liu, Fudong; Liu, Huijuan; Qu, Jiuhui; Liu, Ruiping

    2014-09-01

    In our previous studies, a synthesized Fe-Mn binary oxide was found to be very effective for both As(V) and As(III) removal in aqueous phase, because As(III) could be easily oxidized to As(V). As(III) oxidation and As(V) sorption by the Fe-Mn binary oxide may also play an important role in the natural cycling of As, because of its common occurrence in the environment. In the present study, the respective role of Fe and Mn contents present in the Fe-Mn binary oxide on As(III) removal was investigated via a direct in situ determination of arsenic speciation using X-ray absorption spectroscopy. X-ray absorption near edge structure results indicate that Mn atoms exist in a mixed valence state of +3 and +4 and further confirm that MnOx (1.5 < x < 2) content is mainly responsible for oxidizing As(III) to As(V) through a two-step pathway [reduction of Mn(IV) to Mn(III) and subsequent Mn(III) to Mn(II)] and FeOOH content is dominant for adsorbing the formed As(V). No significant As(III) oxidation by pure FeOOH had been observed during its sorption, when the system was exposed to air. The extended X-ray absorption fine structure results reveal that the As surface complex on both the As(V)- and As(III)-treated sample surfaces is an inner-sphere bidentate binuclear corner-sharing complex with an As-M (M = Fe or Mn) interatomic distance of 3.22-3.24 Å. In addition, the MnOx and FeOOH contents exist only as a mixture, and no solid solution is formed. Because of its high effectiveness, low cost, and environmental friendliness, the Fe-Mn binary oxide would play a beneficial role as both an efficient oxidant of As(III) and a sorbent for As(V) in drinking water treatment and environmental remediation. PMID:25093452

  2. Alternating magnetic anisotropy of Li2(Li1 -xTx )N (T =Mn ,Fe ,Co ,andNi )

    NASA Astrophysics Data System (ADS)

    Jesche, A.; Ke, L.; Jacobs, J. L.; Harmon, B.; Houk, R. S.; Canfield, P. C.

    2015-05-01

    Substantial amounts of the transition metals Mn, Fe, Co, and Ni can be substituted for Li in single crystalline Li2(Li1 -xTx)N . Isothermal and temperature-dependent magnetization measurements reveal local magnetic moments with magnitudes significantly exceeding the spin-only value. The additional contributions stem from unquenched orbital moments that lead to rare-earth-like behavior of the magnetic properties. Accordingly, extremely large magnetic anisotropies have been found. Most notably, the magnetic anisotropy alternates as easy plane→easy axis→easy plane→easy axis when progressing from T =MnFe →Co →Ni . This behavior can be understood based on a perturbation approach in an analytical, single-ion model. The calculated magnetic anisotropies show surprisingly good agreement with the experiment and capture the basic features observed for the different transition metals.

  3. Study of the effect of annealing on defects in Fe Mn Si Cr Ni C alloy by slow positron beam

    NASA Astrophysics Data System (ADS)

    Mostafa, Khaled. M.; De Baerdemaeker, J.; Van Caenegem, N.; Segers, D.; Houbaert, Y.

    2008-10-01

    FeMnSi shape memory alloys (SMAs) have received much attention as one-way SMAs due to their cost-effectiveness. Variable-energy (0-30 keV) positron beam studies have been carried out on a Fe-Mn-Si-Cr-Ni-C alloy with different degrees of deformation. Doppler broadening profiles of the positron annihilation as a function of incident positron energy were shown to be quite sensitive to defects introduced by deformation. The variation of the nature and the concentration of defects are studied as a function of isochronal annealing temperature. These results are correlated with the data measured with the positron annihilation lifetime spectroscopy (PALS). The positron annihilation results are compared to XRD and optical microscopy (OM).

  4. Alternating magnetic anisotropy of Li2(Li1–xTx)N (T = Mn, Fe, Co, and Ni)

    DOE PAGESBeta

    Jesche, A.; Ke, L.; Jacobs, J. L.; Harmon, B.; Houk, R. S.; Canfield, P. C.

    2015-05-11

    Substantial amounts of the transition metals Mn, Fe, Co, and Ni can be substituted for Li in single crystalline Li2(Li1–xTx)N. Isothermal and temperature-dependent magnetization measurements reveal local magnetic moments with magnitudes significantly exceeding the spin-only value. The additional contributions stem from unquenched orbital moments that lead to rare-earth-like behavior of the magnetic properties. Accordingly, extremely large magnetic anisotropies have been found. Most notably, the magnetic anisotropy alternates as easy plane→easy axis→easy plane→easy axis when progressing from T = MnFe → Co → Ni. This behavior can be understood based on a perturbation approach in an analytical, single-ion model.more » As a result, the calculated magnetic anisotropies show surprisingly good agreement with the experiment and capture the basic features observed for the different transition metals.« less

  5. Synthesis of SiO2-coated ZnMnFe2O4 nanospheres with improved magnetic properties.

    PubMed

    Wang, Jun; Zhang, Kai; Zhu, Yuejin

    2005-05-01

    A core-shell structured composite, SiO2 coated ZnMnFe2O4 spinel ferrite nanoparticles (average diameter of approximately 80 nm), was prepared by hydrolysis of tetraethyl orthosilicate (TEOS) in the presence of ZnMnFe2O4 nanoparticles (average diameter of approximately 10 nm) synthesized by a hydrothermal method. The obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM). The magnetic measurements were carried out on a vibrating sample magnetometer (VSM), and the measurement results indicate that the core-shell samples possess better magnetic properties at room temperature, compared with paramagnetic colloids with a magnetic core by a coprecipitation method. These core-shell nanospherical particles with self-assembly under additional magnetic fields could have potential application in biomedical systems. PMID:16010937

  6. Divergent Coupling of Alcohols and Amines Catalyzed by Isoelectronic Hydride Mn(I) and Fe(II) PNP Pincer Complexes.

    PubMed

    Mastalir, Matthias; Glatz, Mathias; Gorgas, Nikolaus; Stöger, Berthold; Pittenauer, Ernst; Allmaier, Günter; Veiros, Luis F; Kirchner, Karl

    2016-08-22

    Herein, we describe an efficient coupling of alcohols and amines catalyzed by well-defined isoelectronic hydride Mn(I) and Fe(II) complexes, which are stabilized by a PNP ligand based on the 2,6-diaminopyridine scaffold. This reaction is an environmentally benign process implementing inexpensive, earth-abundant non-precious metal catalysts, and is based on the acceptorless alcohol dehydrogenation concept. A range of alcohols and amines including both aromatic and aliphatic substrates were efficiently converted in good to excellent isolated yields. Although in the case of Mn selectively imines were obtained, with Fe-exclusively monoalkylated amines were formed. These reactions proceed under base-free conditions and required the addition of molecular sieves. PMID:27377955

  7. Reply to comment on "Molecular controls on Cu and Zn isotopic fractionation in Fe-Mn crusts"

    NASA Astrophysics Data System (ADS)

    Sherman, David M.; Little, Susan H.; Vance, Derek

    2015-02-01

    In our paper "Molecular controls on Cu and Zn isotopic fractionation in Fe-Mn crusts", we present an explanation for the observed isotopic fractionations of Cu and Zn in seawater. We hypothesise that the isotopic fractionation of Cu and Zn is driven by the scavenging of these metals by particulate Fe-Mn oxides as reflected in the isotopic composition of Zn and Cu in marine ferromanganese crusts. Zn sorbed to ferromanganese crusts is isotopically heavier than dissolved Zn in seawater by 0.5‰. EXAFS spectra show that Zn in ferromanganese crusts is sorbed to birnessite and in tetrahedral coordination. Dissolved inorganic Zn in seawater, however, is primarily octahedrally coordinated as Zn(H2O)+26. The difference in the Zn coordination environment gives a qualitative explanation for the sorption (scavenging) of isotopically heavy Zn by ferromanganese crusts (predominantly birnessite).

  8. Microstructure and shape recovery characteristics in a TIG-welded Fe-Mn-Si-Cr-Ni shape memory alloy

    NASA Astrophysics Data System (ADS)

    Qiao, Zhixia; Li, Lianjin; Wang, Dongai; Li, Zongmin

    2007-07-01

    Microstructure of an Fe-Mn-Si-Cr-Ni shape memory alloy (SMA) after being TIG (tungsten-insert gas welding) welded was investigated using scanning electron microscope (SEM) and X-ray diffractometer. The results show that dendrite crystals composed of cellular sub-structures form in the weld zone due to remelting. There is no obvious change in microstructure of the heat-affected zone (HAZ) except for some degree of growth of austenite grains. Since both the weld zone and HAZ consist of single phase of austenite (γ), pre-strain can still induce the γ-->ɛ martensite transformation in welding joints of the alloy. Effect of TIG welding on shape recovery characteristics of the alloy was examined by bending tests and it was found that the TIG-welded Fe-Mn-Si-Cr-Ni alloy exhibits almost the same excellent SME as the base material.

  9. Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels

    NASA Astrophysics Data System (ADS)

    Mahmudi, Abbas; Nedjad, Syamak Hossein; Behnam, Mir Masud Jabbari

    2011-10-01

    Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied. To investigate the microstructure and mechanical properties, optical microscopy, scanning electron microscopy, X-ray diffraction, tensile test, and hardness test were used. The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of submicrocrystalline Fe2(Mo, Ti) Laves phase particles, which are stable at high temperatures. These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment.

  10. Large enhancement of Blocking temperature by control of interfacial structures in Pt/NiFe/IrMn/MgO/Pt multilayers

    SciTech Connect

    Chen, Xi; Wang, Shouguo Han, Gang; Jiang, Shaolong; Yang, Kang; Liu, Qianqian; Yu, Guanghua; Liu, Jialong; Wang, Rongming

    2015-09-15

    The Blocking temperature (T{sub B}) of Pt/NiFe/IrMn/MgO/Pt multilayers was greatly enhanced from far below room temperature (RT) to above RT by inserting 1 nm thick Mg layer at IrMn/MgO interface. Furthermore, the exchange bias field (H{sub eb}) was increased as well by the control of interfacial structures. The evidence for a significant fraction of Mn-O bonding at IrMn/MgO interface without Mg insertion layer was provided by X-ray photoelectron spectroscopy. The bonding between Mn and O can decrease the antiferromagnetism of IrMn film, leading to lower value of T{sub B} in Pt/NiFe/IrMn/MgO/Pt multilayers. Ultrathin Mg film inserted at IrMn/MgO interface acting as an oxygen sinking layer can suppress the oxidation reactions between Mn and O and reduce the formation of Mn-O bonding greatly. The oxidation suppression results in the recovery of the antiferromagnetism of IrMn film, which can enhance T{sub B} and H{sub eb}. Furthermore, the high resolution transmission electron microscopy demonstrates that the Mg insertion layer can efficiently promote a high-quality MgO (200) texture. This study will enhance the understanding of physics in antiferromagnet-based spintronic devices.

  11. Large enhancement of Blocking temperature by control of interfacial structures in Pt/NiFe/IrMn/MgO/Pt multilayers

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Wang, Shouguo; Han, Gang; Jiang, Shaolong; Yang, Kang; Liu, Qianqian; Liu, Jialong; Wang, Rongming; Yu, Guanghua

    2015-09-01

    The Blocking temperature (TB) of Pt/NiFe/IrMn/MgO/Pt multilayers was greatly enhanced from far below room temperature (RT) to above RT by inserting 1 nm thick Mg layer at IrMn/MgO interface. Furthermore, the exchange bias field (Heb) was increased as well by the control of interfacial structures. The evidence for a significant fraction of Mn-O bonding at IrMn/MgO interface without Mg insertion layer was provided by X-ray photoelectron spectroscopy. The bonding between Mn and O can decrease the antiferromagnetism of IrMn film, leading to lower value of TB in Pt/NiFe/IrMn/MgO/Pt multilayers. Ultrathin Mg film inserted at IrMn/MgO interface acting as an oxygen sinking layer can suppress the oxidation reactions between Mn and O and reduce the formation of Mn-O bonding greatly. The oxidation suppression results in the recovery of the antiferromagnetism of IrMn film, which can enhance TB and Heb. Furthermore, the high resolution transmission electron microscopy demonstrates that the Mg insertion layer can efficiently promote a high-quality MgO (200) texture. This study will enhance the understanding of physics in antiferromagnet-based spintronic devices.

  12. Depositional cycles and Fe/Mn ratio in Upper Absheron substage succession in the western flank of the South Khazarian/Caspian depression of the Azerbaijan Republic

    NASA Astrophysics Data System (ADS)

    Amirov, Elnur

    2016-04-01

    depositional environment during its sedimentation. Bedset I (a) is subdivided into 10 interbeds with total thickness 3m 82 cm. Lithologically represented by alternation of shelly sandstone, sandstone, sandy silt, sandy organogenic limestone, and sandy shales. We consider this series as transgressive system tract. Bedset I (b) is subdivided into 8 interbeds with total thickness 2m 98 cm. Lithologically represented by alternation of sandy silt, sandy organogenic limestone, shelly sandstone and sandy shales. We consider this series as transgressive system tract. In this bedset the measurement of Fe/Mn ratio was made only from 4 interbeds: Fe/Mn= 16,1 (Interbed 2); Fe/Mn = 27,8 (Interbed 4); Fe/Mn = 4,2 (Interbed 6); Fe/Mn = 15,8 (Interbed 8). Bedset I (c) is startigraphically younger portion of the same unit and displays lateral facial replacement of proximal, possible, shore face setting by distal shelf environment. Bedset consists of 22 interbeds with total thickness 1m 78 cm. Lithologically represented by alternation of sandy silts and sandstones with two interlayers of sandy limestones. Angle of dipping varies from 9° to 11°. We consider this series as transgressive system tract. In this bedset the measurement of Fe/Mn ratio was made from 19 interbeds: Fe/Mn = 17,6 (Interbed 2); Fe/Mn = 52,6 (Interbed 4); Fe/Mn = 8 (Interbed 5); Fe/Mn = 6,8 (Interbed 6); Fe/Mn = 41,3 (Interbed 7); Fe/Mn = 75,1 (Interbed 8); Fe/Mn = 22,2 (Interbed 9); Fe/Mn = 32,7 (Interbed 10); Fe/Mn = 24,4 (Interbed 11); Fe/Mn = 44,6 (Interbed 13); Fe/Mn = 12,8 (Interbed 14); Fe/Mn = 4,3 (Interbed 15); Fe/Mn = 7,6 (Interbed 16); Fe/Mn = 18,6 (Interbed 17); Fe/Mn = 59,8 (Interbed 18); Fe/Mn = 51,1 (Interbed 19); Fe/Mn = 29,1 (Interbed 20); Fe/Mn = 12,3 (Interbed 21); Fe/Mn = 48,5 (Interbed 22). Bedset II is the massive and homogeneous, thickness 80cm. Lithologically represented by organogenic limestones. Thickness of the bedset increases along striking from 22cm to 85cm. Bedset II lies with angular

  13. A simplified determination of total concentrations of Ca, Fe, Mg and Mn in addition to their bioaccessible fraction in popular instant coffee brews.

    PubMed

    Stelmach, Ewelina; Szymczycha-Madeja, Anna; Pohl, Pawel

    2016-04-15

    A direct analysis of instant coffee brews with HR-CS-FAAS spectrometry to determine the total Ca, Fe, Mg and Mn content has been developed and validated. The proposed method is simple and fast; it delivers good analytical performance; its accuracy being within -3% to 3%, its precision--2-3% and detection limits--0.03, 0.04, 0.004 and 0.01 mg l(-1) for Ca, Fe, Mg and Mn, respectively. In addition, Ca, Fe, Mg and Mn bioaccessibility in instant coffee brews was measured by means of the in vitro gastrointestinal digestion with the use of simulated gastric and intestinal juice solutions. Absorption of metals in intestinal villi was simulated by means of ultrafiltration over semi-permeable membrane with a molecular weight cut-off of 5 kDa. Ca, Fe, Mg and Mn concentrations in permeates of instant coffee gastrointestinal incubates were measured with HR-CS-FAA spectrometry. PMID:26616965

  14. Magnetic properties and anisotropic magnetoresistance of antiperovskite nitride Mn{sub 3}GaN/Co{sub 3}FeN exchange-coupled bilayers

    SciTech Connect

    Sakakibara, H. Ando, H.; Kuroki, Y.; Kawai, S.; Ueda, K.; Asano, H.

    2015-05-07

    Epitaxial bilayers of antiferromagnetic Mn{sub 3}GaN/ferromagnetic Co{sub 3}FeN with an antiperovskite structure were grown by reactive magnetron sputtering, and their structural, magnetic, and electrical properties were investigated. Exchange coupling with an exchange field H{sub ex} of 0.4 kOe at 4 K was observed for Mn{sub 3}GaN (20 nm)/Co{sub 3}FeN (5 nm) bilayers. Negative anisotropic magnetoresistance (AMR) effect in Co{sub 3}FeN was observed and utilized to detect magnetization reversal in exchange-coupled Mn{sub 3}GaN/Co{sub 3}FeN bilayers. The AMR results showed evidence for current-induced spin transfer torque in antiferromagnetic Mn{sub 3}GaN.

  15. 15R SrMn(1-)(x)()Fe(x)()O(3)(-)(delta) (x approximately 0.1); A New Perovskite Stacking Sequence.

    PubMed

    Cussen, Edmund J.; Sloan, Jeremy; Vente, Jaap F.; Battle, Peter D.; Gibb, Terence C.

    1998-11-16

    A polycrystalline sample of a new phase in the Sr-Fe-Mn-O system has been prepared by standard solid-state techniques. Characterization at room temperature by X-ray diffraction, high-resolution electron microscopy, Mössbauer spectroscopy and neutron diffraction has led to it being described as a 15-layered, rhombohedral (15R) perovskite [space group R&thremacr;m: a = 5.4489(1) Å, c = 33.8036(7) Å] with a previously unobserved structure. The pseudo close-packed SrO(3) layers have a (cchch)(3) stacking sequence such that the occupation of the interstitial 6-coordinate sites by Mn (or Fe) leads to the formation of Mn(2)O(9) units which are linked to each other either directly by a common vertex, or indirectly via a single, vertex-sharing MnO(6) octahedron. The stoichiometry of the compound was determined to be SrMn(0.915(5))Fe(0.085(5))O(2.979(3)). The face-sharing sites are occupied by 0.957(3)Mn/0.043(3)Fe while the exclusively corner-linked sites show a higher Fe occupation; 0.745(4)Mn/ 0.255(4)Fe. A neutron diffraction experiment carried out at 3 K indicated the presence of long-range magnetic order with the Mn(4+) cations aligned antiferromagnetically with an ordered moment of 2.26(3)&mgr;(B)/Mn(4+). Both the neutron and the susceptibility data are consistent with the Fe cations remaining magnetically disordered to 3 K. The latter data show T(N) = 220 K, and suggest that some spin frustration is present at low temperatures. PMID:11670745

  16. Magnetism in La₂O₃(Fe₁₋xMnx)₂Se₂ tuned by Fe/Mn ratio

    DOE PAGESBeta

    Lei, Hechang; Bozin, Emil S.; Llobet, A.; Ivanovski, V.; Koteski, V.; Belosevic-Cavor, J.; Cekic, B.; Petrovic, C.

    2012-09-17

    We report the evolution of structural and magnetic properties in La₂O₃(Fe₁₋xMnx)₂Se₂. Heat capacity and bulk magnetization indicate an increased ferromagnetic component of the long-range magnetic order and possible increased degree of frustration. Atomic disorder on Fe(Mn) sites suppresses the temperature of the long-range order whereas intermediate alloys show a rich magnetic phase diagram.

  17. [Accumulation of Fe, Cu, Zn, Mg, Mn and Co in the ovary of Carcinus maenas L. during ovogenesis].

    PubMed

    Martin, J L; Ceccaldi, H J

    1976-01-01

    During ovogenesis the ovary of Carcinus maenas shows a continuous accumulation of Fe, Cu, Mg, Mn and Co. For Zn the accumulation seems to stop for gonad indexes near 6.5. The goal of this accumulation is not determined. Nevertheless we suppose that it is in relation with the role of organic reserves that possess the female sexual cells in decapods and with the synthesis of enzymes and hemocyanin. PMID:134766

  18. Specific heat and entropy change at the first order phase transition of La(Fe-Mn-Si)13-H compounds

    NASA Astrophysics Data System (ADS)

    Basso, Vittorio; Küpferling, Michaela; Curcio, Carmen; Bennati, Cecilia; Barzca, Alexander; Katter, Matthias; Bratko, Milan; Lovell, Edmund; Turcaud, Jeremy; Cohen, Lesley F.

    2015-08-01

    In this paper, we present the results of an experimental investigation on the magnetocaloric properties of hydrogenated La(Fe-Mn-Si)13-H with Mn substituting Fe to finely tune the transition temperature. We measured the specific heat under magnetic field cp(H, T) and the magnetic field induced isothermal entropy change Δs(H, T) of a series of compounds by direct Peltier calorimetry. Results show that increasing Mn from 0.06 to 0.46 reduces the transition temperature from 339 K to 270 K whilst the total entropy change due to a 1.5 T field is depressed from 18.7 J kg-1 K-1 to 10.2 J kg-1 K-1 and the thermal hysteresis similarly is reduced from 1.5 K to zero. In the paper, we interpret the results in terms of a magnetic phase transition changing from the first to the second order with increasing Mn content, and we discuss the value of the results for magnetic cooling applications.

  19. Influence of Mn substitution on the magnetic properties of Ho sub 2 Fe sub 14 C compounds

    SciTech Connect

    Verhoef, R.; de Boer, F.R. ); Jacobs, T.H.; Buschow, K.H.J. )

    1990-05-01

    The crystallographic and magnetic properties of the compounds Ho{sub 2}Fe{sub 14{minus}{ital x}}Mn{sub {ital x}}C have been investigated by means of x-ray diffraction and magnetic measurements. Magnetization measurements made in fields up to 38 T showed that the saturation moment exhibits a minimum at a Mn concentration corresponding to about {ital x}=2. The occurrence of this minimum is explained by antiparallel coupling between the Ho and 3{ital d} sublattice magnetization, the latter becoming strongly reduced with increasing Mn concentration. Most of the Ho{sub 2}Fe{sub 14{minus}{ital x}}Mn{sub {ital x}}C compounds investigated have a break in the magnetization curves measured at 4.2 K. This break is interpreted as the onset of decoupling between the antiparallel coupling between the rare-earth and 3{ital d} sublattice. A mean-field analysis was used to derive the intersublattice molecular-field coefficients {ital n}{sub {ital RT}}.

  20. Determination of the recovery stress under constraint in Fe29Mn7Si5Cr SMA

    NASA Astrophysics Data System (ADS)

    van Caenegem, N.; Duprez, L.; Verbeken, K.; Houbaert, Y.; Segers, D.; van Humbeeck, J.

    2008-05-01

    Ferrous shape memory alloys (SMAs) do not possess a complete shape recovery. Several attempts to improve the shape recovery still fail to achieve 100% recovery. For some applications, however, the recovery stress under constraint might be more important. In this work, a procedure was designed to measure these stresses under constraint in a Fe29MnSiCr SMA. The net recovery stress was defined as the maximal difference between the stresses developed in deformed and an undeformed sample. The calculation of σthermal(T) = E(T)α(T)(T-T0) can replace the measurement of the stress developed in the undeformed sample. The effect of partially free recovery before recovery under constraint is also investigated. It was remarkable that after annealing at 200°C, the net stress did not decrease although about 50% of the shape recovery has already taken place. This allows to use this alloy as a pipe joint, where the diameter of the joint can be larger than the one of the pipes, since the free recovery will hardly lower the recovery stresses under constraint.

  1. Microstructure Formation during Solidification of Melt-Spun Co-Fe-Mn-Si Alloys

    NASA Astrophysics Data System (ADS)

    Zollinger, J.; Adam, O.; Daloz, D.

    2012-01-01

    Cobalt-based alloys ribbons for the fabrication of cored wires require high elongation, e.g. a good metallurgical quality associated with a fine grain structure. The melt-spinning process allows fabricating the 200 μm thick ribbons in a single casting step. However, the properties of such ribbon suffer from the presence of casting defects, leading to early fractures in the material. The present study investigates the microstructure and defect formation in melt-spun Co-6.5Fe-2.6Mn-(0-1.6)Si alloys (in wt.%). These alloys exhibit uncommon intrinsic behaviour and properties such as high nucleation undercoolings (up to 295K in DTA experiments) or reduced solidification interval (10 < T0 < 25 K). It is found that the main defect leading to fracture is micro-shrinkage due to the solutal dendrite growth at low nucleation undercooling. Low silicon additions (0.6 wt.%) are found to reduce the size and the occurrence of shrinkage and increase the elongation, whereas larger silicon additions (1.6 wt.%) are detrimental to the ribbon properties.

  2. Magnetic properties of MnFe2O4 nano-aggregates dispersed in paraffin wax

    NASA Astrophysics Data System (ADS)

    Aslibeiki, B.; Kameli, P.

    2015-07-01

    Manganese ferrite, MnFe2O4 nanoparticles with average size of ∼6.5 nm were synthesized by using a thermal decomposition method. The nanoparticles were aggregated which was confirmed by FESEM and TEM images. The aggregates with a diameter of ∼50 nm showed interacting superspin glass (SSG) behavior. The powders were dispersed in the molten paraffin wax by using ultrasonic bath. Samples with different paraffin/ferrite weight ratios of P/F= 0, 1, 5, 10 and 20 were prepared. M-H curves of the samples revealed presence of superparamagnetic state at 300 K. Saturation magnetization (Ms) decreased from 26.6 to 1.3 emu/g by increasing the P/F value from 0 to 20, respectively. Furthermore, the VSM measurements showed a decrease in surface spin disorder of paraffin-embedded nanoparticles in comparison with bare particles. The AC magnetic susceptibility peak temperature, TP increased from 230 to >300 K with increasing the paraffin content in the samples. The present study showed that by dispersing the particles in a non-magnetic matrix, the blocking temperature could be increased.

  3. Thermal-history dependent magnetoelastic transition in (Mn,Fe){sub 2}(P,Si)

    SciTech Connect

    Miao, X. F. Dijk, N. H. van; Brück, E.; Caron, L.; Gercsi, Z.; Daoud-Aladine, A.

    2015-07-27

    The thermal-history dependence of the magnetoelastic transition in (Mn,Fe){sub 2}(P,Si) compounds has been investigated using high-resolution neutron diffraction. As-prepared samples display a large difference in paramagnetic-ferromagnetic (PM-FM) transition temperature compared to cycled samples. The initial metastable state transforms into a lower-energy stable state when the as-prepared sample crosses the PM-FM transition for the first time. This additional transformation is irreversible around the transition temperature and increases the energy barrier which needs to be overcome through the PM-FM transition. Consequently, the transition temperature on first cooling is found to be lower than on subsequent cycles characterizing the so-called “virgin effect.” High-temperature annealing can restore the cycled sample to the high-temperature metastable state, which leads to the recovery of the virgin effect. A model is proposed to interpret the formation and recovery of the virgin effect.

  4. Magnetisation configuration at the interface of Fe_0.5Mn_0.5/Co(111)

    NASA Astrophysics Data System (ADS)

    Ujfalussy, Balazs; Schultess, T. C.; Stocks, G. M.; Canning, A.

    2002-03-01

    The microscopic understanding of the interface of a ferromagnet and an antiferromagnet is of fundamental importance in the problem of exchange bias. Of particular interest is the interface between Fe_0.5Mn_0.5/Co(111) however, it is rather difficult to study it experimentally. We performed an ab-initio spin-dynamics calculation to determine the magnetization configuration of this interface. We find that the magnetization changes from a 3Q-like state to a 1Q-like state which is perpendicular to the magnetization of the Co at the interface. We comment on the range of the interaction and possible mechanism of exchange bias. This work was supported by the Division of Materials Sciences and Engineering, and by the Director, Office of Advanced Scientific Computing Research, Division of Mathematical Information and Computational Sciences Division, of the U.S. Department of Energy, under contract number DE-AC03-76SF00098 and subcontract DE-AC05-00OR22725 with UT-Battelle LLC.

  5. ABO3 (A = La, Ba, Sr, K; B = Co, Mn, Fe) perovskites for thermochemical energy storage

    NASA Astrophysics Data System (ADS)

    Babiniec, Sean M.; Coker, Eric N.; Ambrosini, Andrea; Miller, James E.

    2016-05-01

    The use of perovskite oxides as a medium for thermochemical energy storage (TCES) in concentrating solar power systems is reported. The known reduction/oxidation (redox) active perovskites LaxSr1-xCoyMn1-yO3 (LSCM) and LaxSr1-xCoyFe1-yO3 (LSCF) were chosen as a starting point for such research. Materials of the LSCM and LSCF family were previously synthesized, their structure characterized, and thermodynamics reported for TCES operation. Building on this foundation, the reduction onset temperatures are examined for LSCM and LSCF compositions. The reduction extents and onset temperatures are tied to the crystallographic phase and reaction enthalpies. The effect of doping with Ba and K is discussed, and the potential shortcomings of this subset of materials families for TCES are described. The potential for long-term stability of the most promising material is examined through thermogravimetric cycling, scanning electron microscopy, and dilatometry. The stability over 100 cycles (450-1050 °C) of an LSCM composition is demonstrated.

  6. Effect of Complex Inclusion Particles on the Solidification Structure of Fe-Ni-Mn-Mo Alloy

    NASA Astrophysics Data System (ADS)

    Park, Jun Seok; Lee, Changhee; Park, Joo Hyun

    2012-12-01

    The effect of combinations of several deoxidizers, i.e., Mg-Al, Mg-Ti, Al-Ti, and Ce-Al, on the solidification structure of Fe-2 mass pct Ni-1 mass pct Mn-1 mass pct Mo alloy melt was investigated using a melt sampling and quenching method. Using this method, we evaluated the catalytic potency of several complex inclusion particles by taking the inclusion evolution process into account. Fine equiaxed crystals were obtained in the Mg-Ti-deoxidized steel wherein the MgO(MgAl2O4)-TiN complex compounds formed. However, the longer the holding time at high temperatures, the larger the fraction of Ti2O3, and very fine TiN formed because of microsegregation during solidification, resulting in poor equiaxed crystals. When the steel was deoxidized with Mg-Al, the initial structure was dominantly columnar. However, the longer the holding time, the larger the fraction of MgAl2O4 spinel, resulting in the formation of fine equiaxed crystals. Ce-Al complex deoxidation provided a relatively small portion of equiaxed crystals, whereas Ti-Al deoxidation produced the fewest equiaxed crystals because of the formation of alumina. The effectiveness of each inoculant particle for the crystallization of the primary δ-iron was explained well by the lattice disregistry concept.

  7. Mn-doped ZnFe{sub 2}O{sub 4} nanoparticles with enhanced performances as anode materials for lithium ion batteries

    SciTech Connect

    Tang, Xiaoqin; Hou, Xianhua; Yao, Lingmin; Hu, Shejun; Liu, Xiang; Xiang, Liangzhong

    2014-09-15

    Highlights: • Mn-doped ZnFe{sub 2}O{sub 4} nanoparticles have been synthesized by hydrothermal method. • Zn{sub 0.96}Mn{sub 0.04}Fe{sub 2}O{sub 4} electrode shows the highest reversible capacity of 1157 mA h g{sup −1}. • The Zn{sub 0.96}Mn{sub 0.04}Fe{sub 2}O{sub 4} electrode shows promising cycling stability. - Abstract: Nanocrystalline Zn{sub 1−x}Mn{sub x}Fe{sub 2}O{sub 4} (x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) have been successfully synthesized by one-step hydrothermal method. The morphologies and electrochemical performance of Mn-doped ZnFe{sub 2}O{sub 4} in various proportions were investigated at room temperature, respectively. The Zn{sub 1−x}Mn{sub x}Fe{sub 2}O{sub 4} (x = 0.04) electrode in the as-synthesized samples showed the highest specific capacity of 1547 mA h g{sup −1} and 1157 mA h g{sup −1} in the initial discharge/charge process, with a coulombic efficiency of 74.8%. Additionally, excellent cycling stability was performed with a 1214 mA h g{sup −1} capacity retention at a current density of 100 mA g{sup −1} after 50 cycles. The corresponding mechanism was proposed which indicated that the Mn-doped ZnFe{sub 2}O{sub 4} nanoparticles experienced an aggregation thermochemical reaction among ZnO, MnO and Fe{sub 2}O{sub 3} subparticles.

  8. Heat capacities and entropies of rhodochrosite (MnCO3) and siderite (FeCO3) between 5 and 600 K.

    USGS Publications Warehouse

    Robie, R.A.; Haselton, H.T., Jr.; Hemingway, B.S.

    1984-01-01

    The heat capacities of rhodochrosite, (Mn0.994Fe0.005Mg0.001)CO3, and siderite, 171(Fe0.956Mn0.042Mg0.002)CO3, were measured between 5 and 550 K by combined cryogenic-adiabatic and differential scanning calorimetry. These new data were used to reanalyse the thermodynamic properties of these phases.-J.A.Z.

  9. Efficient removal of arsenic from water using a granular adsorbent: Fe-Mn binary oxide impregnated chitosan bead.

    PubMed

    Qi, Jianying; Zhang, Gaosheng; Li, Haining

    2015-10-01

    A novel sorbent of Fe-Mn binary oxide impregnated chitosan bead (FMCB) was fabricated through impregnating Fe-Mn binary oxide into chitosan matrix. The FMCB is sphere-like with a diameter of 1.6-1.8 mm, which is effective for both As(V) and As(III) sorption. The maximal sorption capacities are 39.1 and 54.2 mg/g, respectively, outperforming most of reported granular sorbents. The arsenic was mainly removed by adsorbing onto the Fe-Mn oxide component. The coexisting SO4(2-), HCO3(-) and SiO3(2-) have no great influence on arsenic sorption, whereas, the HPO4(2-) shows negative effects. The arsenic-loaded FMCB could be effectively regenerated using NaOH solution and repeatedly used. In column tests, about 1500 and 3200 bed volumes of simulated groundwater containing 233 μg/L As(V) and As(III) were respectively treated before breakthrough. These results demonstrate the superiority of the FMCB in removing As(V) and As(III), indicating that it is a promising candidate for arsenic removal from real drinking water. PMID:26141284

  10. Serration Behavior and Pop-in Phenomena in AlxCrCuFeMnNi High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Diao, Haoyan; Xie, Xie; Chen, Shuying; Wang, Gongyao; Yang, Fuqian; Dahmen, Karin; Liaw, Peter

    2015-03-01

    Recently, high-entropy alloys (HEAs), based on achieving a high configuration entropy of mixing among alloying elements, have been developed. Many of these alloys contain expensive elements, such as Co. Substituting these elements for less expensive elements, such as Mn, without compromising the mechanical performance is crucial to make HEAs commercially viable. The AlxCrCuFeMnNi (x = 0.1, 0.3, and 0.8) system is one such alloy that displays encouraging mechanical results in both compression and nanoindentation experiments. Discrete, jerky stress-drop bursts (serrations) are even found at room temperature. The mean-field-interaction model predicts the scaling behavior of the distribution, D(S), of avalanche sizes in the experiments. D(S) follows a power law multiplied by an exponentially-decaying scaling function. The size of the largest observed avalanche depends on experimental parameters, such as aluminum content, strain rate, or temperature. In nanoindentation, a strain burst is manifested by a sudden displacement excursion or `pop-in', following the initial elastic Hertzian contact. The pop-in phenomena becomes more frequent and regular, as the indentation load is greater than 35 mN. A quantitative theory for the serration behavior and pop-in phenomena is a critical issue for understanding the deformation characteristics of HEAs. This work was supported by the Department of Energy No. DE-FE-0008855 and DE-FE-0011194.

  11. Growth of epitaxial AlN films on (Mn,Zn)Fe 2O 4 substrates by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Ohta, J.; Fujioka, H.; Takahashi, H.; Oshima, M.

    2002-09-01

    We have grown AlN on (Mn,Zn)Fe 2O 4 substrates by pulsed laser deposition (PLD) and investigated their structural properties using high resolution X-ray diffraction (HRXRD), reflection high energy electron diffraction (RHEED), and atomic force microscopy (AFM). We have observed the transition of the RHEED pattern from sharp streaks into clear spots at the early stage of the film growth, which indicates that the growth mode of AlN changed from the two-dimensional mode to the three-dimensional mode due to the stress buildup. RHEED and XRD observations have revealed that hexagonal AlN (0 0 0 1) grows on (Mn,Zn)Fe 2O 4 (1 1 1) with the in-plane epitaxial relationship of [1 1 -2 0]AlN//[0 1 -1](Mn,Zn)Fe 2O 4. The lattice mismatch for this alignment is calculated to be 6%. The FWHM value of the AlN (0 0 0 2) X-ray rocking curve is as low as 77 arcsec, which indicates that the density of the threading screw dislocations in the AlN film is quite low.

  12. Stabilization of the HCP [var epsilon] phase in an Fe-21%Mn alloy subjected to cathodic hydrogen charging

    SciTech Connect

    Aikawa, T.; Nishino, Y.; Asano, S. )

    1993-07-01

    Cathodic hydrogen charging induces some phase transformation in the surface layer of FCC iron alloys. Such a hydrogen-induced phase transformation has extensively been studied for austenitic stainless steels, where the FCC [gamma] phase transforms partially into an HCP [var epsilon][sub H] phase. The formation of the [var epsilon][sub H] phase has also been found in FCC Fe-Mn alloys and Fe-Ni-Mn alloys. The [var epsilon][sub H] phase is unstable in the absence of hydrogen and decomposes to an [var epsilon] martensite in the metastable FCC alloys. In order to make clear the nature of the [var epsilon][sub H] phase, it is necessary to reveal the stability of the [var epsilon] phase in FCC iron alloys during cathodic hydrogen charging. In the present study, the authors employed an Fe-21%Mn alloy which consisted of a mixture of the [gamma] and [var epsilon] phases in an as-quenched state. For this two-phase alloy, the [var epsilon] [r arrow] [gamma] transformation has so far been examined by a high-pressure equilibration method in a hydrogen-gas atmosphere. The purpose of this study is to compare the stability of the [gamma] phases in the two-phase alloy subjected to cathodic hydrogen charging in an aqueous solution. The influence of hydrogen on the [var epsilon] phase stability will be discussed, including the transformation in a hydrogen-gas atmosphere.

  13. Development and application of a microfluidic in-situ analyzer for dissolved Fe and Mn in natural waters.

    PubMed

    Milani, Ambra; Statham, Peter J; Mowlem, Matt C; Connelly, Douglas P

    2015-05-01

    The redox sensitive trace metals iron and manganese are two important elements that help shape the biogeochemistry of aquatic systems and thus their measurement is important. Current laboratory methods are expensive, time consuming and cannot provide the spatial and temporal resolution needed to characterize these elements in natural waters. Here we describe the first autonomous analyzer capable of providing vertical profiles as well as routine in-situ determinations of dissolved Fe(II) and Mn in aquatic environments. The spectrophotometric sensor uses microfluidic methods (Lab-on-a-chip technology) and mixes reagents and samples using a novel in-cell diffusion process. Fe(II) and Mn can be measured with a frequency of up to 12 and 6 samples per hour respectively with limits of detection of 27nM for Fe(II), 2.1% precision (n=20), and 28nM for Mn, 2.4% precision (n=19). The device combines relatively low cost, low power usage, low reagent consumption, portability, and tolerance to pressures up to at least 170 bars, with high precision and accuracy. We present data from a successful demonstration of the sensor during a cruise to the Gotland and Landsort Deep Basins of the Baltic Sea. PMID:25702979

  14. Improved shape memory properties and internal structures in Fe-Mn-Si-based alloys containing Nb and C

    NASA Astrophysics Data System (ADS)

    Baruj, A.; Kikuchi, T.; Kajiwara, S.; Shinya, N.

    2003-10-01

    It bas recently been found that the shape memory properties of Fe-Mn-Si-based alloys are notably improved by addition of small amounts of Nb and C elements. In these newly modified alloys, the so-called “training process" is replaced by a simpler thermomechanical treatment. For example, in an Fe-28Mn-6Si-5Cr-0.5NbC alloy (mass %), a combination of pre-rolling at 870K followed by 10min ageing at 1070K results in a shape recovery of 90% for 4% initial strain and a shape recovery stress of 295MPa for 4.5% initial strain. In this work, we present the shape memory properties of the samples pre-rolled up to 20% in Fe-28Mn-6Si-5Cr-0.5NbC, and atomic force microscopy (AFM) and transmission electron microscopy (TEM) observations of the stressinduced martensite. Detailed discussion is made on the relations between the microstructures observed by AFM and TEM and the shape recovery and shape recovery stress, and the main factors responsible for drastic improvement of the shape memory properties in this alloy system are drawn.

  15. Magnetic and structural properties of ferromagnetic Fe{sub 5}PB{sub 2} and Fe{sub 5}SiB{sub 2} and effects of Co and Mn substitutions

    SciTech Connect

    McGuire, Michael A. Parker, David S.

    2015-10-28

    Crystallographic and magnetic properties of Fe{sub 5}PB{sub 2}, Fe{sub 4}CoPB{sub 2}, Fe{sub 4}MnPB{sub 2}, Fe{sub 5}SiB{sub 2}, Fe{sub 4}CoSiB{sub 2}, and Fe{sub 4}MnSiB{sub 2} are reported. All adopt the tetragonal Cr{sub 5}B{sub 3} structure-type and are ferromagnetic at room temperature with easy axis of magnetization along the c-axis. The spin reorientation in Fe{sub 5}SiB{sub 2} is observed as an anomaly in the magnetization near 170 K and is suppressed by substitution of Co or Mn for Fe. The silicides are found to generally have larger magnetic moments than the phosphides, but the data suggest smaller magnetic anisotropy in the silicides. Cobalt substitution reduces the Curie temperatures by more than 100 K and ordered magnetic moments by 16%–20%, while manganese substitution has a much smaller effect. This suggests Mn moments align ferromagnetically with the Fe and that Co does not have an ordered moment in these structures. Anisotropic thermal expansion is observed in Fe{sub 5}PB{sub 2} and Fe{sub 5}SiB{sub 2}, with negative thermal expansion seen along the c-axis of Fe{sub 5}SiB{sub 2}. First principles calculations of the magnetic properties of Fe{sub 5}SiB{sub 2} and Fe{sub 4}MnSiB{sub 2} are reported. The results, including the magnetic moment and anisotropy, are in good agreement with experiment.

  16. Magnetic and structural properties of ferromagnetic Fe5PB2 and Fe5SiB2 and effects of Co and Mn substitutions

    SciTech Connect

    McGuire, Michael A.; Parker, David S.

    2015-10-22

    Crystallographic and magnetic properties of Fe5PB2, Fe4CoPB2, Fe4MnPB2, Fe5SiB2, Fe4CoSiB2, and Fe4MnSiB2 are reported. All adopt the tetragonal Cr5B3 structure-type and are ferromagnetic at room temperature with easy axis of magnetization along the c-axis. The spin reorientation in Fe5SiB2 is observed as an anomaly in the magnetization near 170 K, and is suppressed by substitution of Co or Mn for Fe. The silicides are found to generally have larger magnetic moments than the phosphides, but the data suggests smaller magnetic anisotropy in the silicides. Cobalt substitution reduces the Curie temperatures by more than 100 K and ordered magnetic moments by 16-20%, while manganese substitution has a much smaller effect. This suggests Mn moments align ferromagnetically with the Fe and that Co does not have an ordered moment in these structures. Anisotropic thermal expansion is observed in Fe5PB2 and Fe5SiB2, with negative thermal expansion seen along the c-axis of Fe5SiB2. First principles calculations of the magnetic properties of Fe5SiB2 and Fe4MnSiB2 are reported. The results, including the magnetic moment and anisotropy, and are in good agreement with experiment.

  17. Threshold effects for resistance to optical damage and nonvolatile holographic storage properties in In:Mn:Fe:LiNbO3 crystals

    SciTech Connect

    Zhen Xihe; Li Qiang; Xu Yuheng

    2005-07-20

    The threshold concentration for In2O3 was found in In:Mn:Fe:LiNbO3 crystals by measurement of the infrared spectra of the crystals. The resistance of the In:Mn:Fe:LiNbO3 crystals to optical damage is characterized by changes in photoinduced birefringence as well as by distortion of the transmitted beam pattern. The resistance increases remarkably when the concentration of In2O3 exceeds its threshold. The resistance to optical damage of a In(3.0 mol. %):Mn:Fe:LiNbO3 crystal is 2 orders of magnitude higher that of a Mn:Fe:LiNbO3 crystal. The dependence of defects on the resistance to optical damage of the In:Mn:Fe:LiNbO3 crystals is discussed in detail. Nonvolatile holographic storage was achieved for all crystals, and the sensitivity of the In(3.0 mol. %):Mn:Fe:LiNbO3 crystal is much higher than that of the others.

  18. Molecular evidence for microorganisms participating in Fe, Mn, and S biogeochemical cycling in two low-temperature hydrothermal fields at the Southwest Indian Ridge

    NASA Astrophysics Data System (ADS)

    Li, Jiwei; Peng, Xiaotong; Zhou, Huaiyang; Li, Jiangtao; Sun, Zhilei

    2013-06-01

    We examined two low-temperature hydrothermal deposits rich in Fe-Si-Mn collected from the recently discovered hydrothermal fields at the Southwest Indian Ridge using mineralogical, geochemical, and molecular biological techniques. The mineralogical and geochemical analyses indicated that the low-temperature hydrothermal fields would provide a warm and chemical species-rich habitat for chemosynthetic-based hydrothermal ecosystems. Analyses of 16S rRNA sequences showed that ζ-Proteobacteria, Pseudoalteromonas, Leptothrix, and Pseudomonas were potential Fe and Mn oxidizers in the low-temperature hydrothermal environments, but they were not present in equal abundance among the subniches. Some potential Fe and Mn reducers were also recovered; they were more commonly found in the exterior black Fe-Mn oxides. The difference between the exterior black Fe-Mn oxides and the interior Opal-A could be related to differences in in situ physicochemical conditions. We also identified microbial players that may participate in sulfur (S) geochemical cycling in these low-temperature hydrothermal environments via analyses of 16S rRNA sequences and the aprA functional gene. The results indicated that members of γ-Proteobacteria and α-Proteobacteria were involved in the S oxidation process, while members of δ-Proteobacteria, Nitrospirae, Firmicutes, and Archaea might participate in the S reduction process. Fe, Mn, and S oxidizers and reducers might actively participate in hydrothermal biogeochemical processes, which could influence the transfer of chemical species and the formation of biogenic minerals.

  19. Interlinked multiphase Fe-doped MnO2 nanostructures: a novel design for enhanced pseudocapacitive performance.

    PubMed

    Wang, Ziya; Wang, Fengping; Li, Yan; Hu, Jianlin; Lu, Yanzhen; Xu, Mei

    2016-03-24

    Structure designing and morphology control can lead to high performance pseudocapacitive materials for supercapacitors. In this work, we have designed interlinked multiphase Fe-doped MnO2 nanostructures (α-MnO2/R-MnO2/ε-MnO2) to enhance the electrochemical properties by a facile method. These hierarchical hollow microspheres assembled by interconnected nanoflakes, and with plenty of porous nanorods radiating from the spherical shells were hydrothermally obtained. The supercapacitor electrode prepared from the unique construction exhibits outstanding specific capacitance of 267.0 F g(-1) even under a high mass loading (∼5 mg cm(-2)). Obviously improved performances compared to pure MnO2 are also demonstrated with a good rate capability, high energy density (1.30 mW h cm(-3)) and excellent cycling stability of 100% capacitance retention after 2000 cycles at 2 A g(-1). The synergistic effects of alternative crystal structures, appropriate crystallinity and optimal morphology are identified to be responsible for the observations. This rational multiphase composite strategy provides a promising idea for materials scientists to design and prepare scalable electrode materials for energy storage devices. PMID:26977698

  20. Combined effects of Bi deficiency and Mn substitution on the structural transformation and functionality of BiFeO{sub 3} films

    SciTech Connect

    Chen, Jingyi; Wang, Yao Deng, Yuan

    2014-11-07

    Mn-doped BiFeO{sub 3} films with Mn contents of 5 and 10 mol. % were prepared via a chemical route. A carefully controlled amount of Bi deficiency was introduced to further tune the lattice structure and the functionality of multiferroic BiFeO{sub 3}. The crystal structure of Bi{sub 1−δ}Fe{sub 1−x}Mn{sub x}O{sub 3} films was investigated by X-ray diffraction and Raman spectra; a rhombohedral-to-orthorhombic phase transition was revealed. The observed double hysteresis loops and two capacitance maxima from polarization vs electric field and capacitance-voltage measurements indicate an antiferroelectric-like behavior. Additionally, the coexistence of ferroelectric (FE) and antiferroelectric (AFE) phases in Bi{sub 1−δ}Fe{sub 1−x}Mn{sub x}O{sub 3} films was revealed from the domain structures obtained by piezoelectric force microscopy. The effects of Mn substitution in conjunction with Bi deficiency on the FE-AFE phase transition and electrical behavior of BiFeO{sub 3} films are discussed in detail. Meanwhile, magnetic and photoluminescence measurements on the films illustrate that Mn substitution gives rise to the net magnetic moment and the defects induced by both Bi deficiency and Mn substitution influence the electronic structure of BiFeO{sub 3} films. This study thus shows a simple and effective way to control the functionalities of BiFeO{sub 3} films.

  1. Structural transformation and multiferroic properties of Ba-Mn co-doped BiFeO3

    NASA Astrophysics Data System (ADS)

    Rout, Jyoshna; Choudhary, R. N. P.

    2016-01-01

    Pure BiFeO3 and Bi1-xBaxFe1-xMnxO3 (x = 0.10, 0.20) fine ceramics were synthesized using mechano-synthesis route. The influence of co-doping (Ba-Mn) on structural and multiferroic properties of BiFeO3 has been studied in different experimental conditions. X-ray diffraction patterns, Rietveld structural refinement of XRD patterns and Fourier transform infrared (FTIR) spectra reveal the structural transition from rhombohedral (R3c) to the biphasic structure (R3c + P4mm) on co-doping. The co-doping improves surface morphology and also reduces the particle size. The room temperature M-H loops of all samples showed antiferromagnetic/weak ferromagnetic behavior. Magnetoelectric coupling coefficient determination is carried out to reveal extent of intimate interaction between electric and magnetic dipoles interaction in the samples. Room temperature occurrence of ferromagnetism, ferroelectricity and magnetoelectric effect supports the observation of multiferroism and magnetoelectric coupling in BiFeO3. Thus, co-doping at Bi- and Fe-sites of BiFeO3 can improve multiferroic properties of BiFeO3 for various applications.

  2. Tuning of net magnetic moment in BiFeO3 multiferroics by co-substitution of Nd and Mn

    NASA Astrophysics Data System (ADS)

    Kumar, Pawan; Kar, Manoranjan

    2014-09-01

    The structural and magnetic properties of Bi1-xNdxFe1-xMnxO3 ceramics prepared by the tartaric acid modified sol-gel technique have been studied to understand the effect of structural modification on the magnetic Properties of BiFeO3. The co-substitution of Nd and Mn at Bi and Fe sites respectively in BiFeO3 significantly suppress the impurity phases (Bi25FeO40, Bi2Fe4O9 etc.). The Rietveld analysis of X-ray diffraction (XRD) patterns indicates the existence of compositional driven crystal structure transformation from rhombohederal (R3c space group, higher crystal symmetry) to the orthorhombic (Pbnm space group, lower crystal symmetry) with the increase in substitution concentration due to excess chemical pressure (lattice strain). The quantitative crystallographic phase analysis has been carried out by Rietveld analysis of all the XRD patterns. Magnetic measurements reveal that co-substituted BiFeO3 nanoparticles for x=0.050 have enhanced remnant magnetization about 21 times as compared to pure one. The remnant magnetization reaches a maximum value at the morphological phase boundary (x=0.050) and further increase (x>0.050) in substitution concentration results in the reduction of remnant magnetization due to the appearance of complete antiferromagnetic ordering in the orthorhombic structure because of the significant contribution from the crystallographic phase of Pbnm space group (as obtained from the quantitative crystallographic phase contribution by the Rietveld analysis).

  3. Redox centers evolution in phospho-olivine type (LiFe0.5Mn0.5 PO4) nanoplatelets with uniform cation distribution.

    PubMed

    Paolella, Andrea; Bertoni, Giovanni; Dilena, Enrico; Marras, Sergio; Ansaldo, Alberto; Manna, Liberato; George, Chandramohan

    2014-03-12

    In phospho-olivine type structures with mixed cations (LiM1M2PO4), the octahedral M1 and M2 sites that dictate the degree of intersites order/disorder play a key role in determining their electrochemical redox potentials. In the case of LiFexMn1-xPO4, for example, in micrometer-sized particles synthesized via hydrothermal route, two separate redox centers corresponding to Fe(2+)/Fe(3+) (3.5 V vs Li/Li(+)) and Mn(2+)/Mn(3+) (4.1 V vs Li/Li(+)), due to the collective Mn-O-Fe interactions in the olivine lattice, are commonly observed in the electrochemical measurements. These two redox processes are directly reflected as two distinct peak potentials in cyclic voltammetry (CV) and equivalently as two voltage plateaus in their standard charge/discharge characteristics (in Li ion batteries). On the contrary, we observed a single broad peak in CV from LiFe0.5Mn0.5PO4 platelet-shaped (∼10 nm thick) nanocrystals that we are reporting in this work. Structural and compositional analysis showed that in these nanoplatelets the cations (Fe, Mn) are rather homogeneously distributed in the lattice, which is apparently the reason for a synergetic effect on the redox potentials, in contrast to LiFe0.5Mn0.5PO4 samples obtained via hydrothermal routes. After a typical carbon-coating process in a reducing atmosphere (Ar/H2), these LiFe0.5Mn0.5PO4 nanoplatelets undergo a rearrangement of their cations into Mn-rich and Fe-rich domains. Only after such cation rearrangement (via segregation) in the nanocrystals, the redox processes evolved at two distinct potentials, corresponding to the standard Fe(2+)/Fe(3+) and Mn(2+)/Mn(3+) redox centers. Our experimental findings provide new insight into mixed-cation olivine structures in which the degree of cations mixing in the olivine lattice directly influences the redox potentials, which in turn determine their charge/discharge characteristics. PMID:24564785

  4. Reoxidation of Aluminum in Fe- Al- M (M = C, Mn, and Ti) melts with CaO-Al2 O3-Fe t O (3 mass pct) slags

    NASA Astrophysics Data System (ADS)

    Lee, Kwang Ro; Suito, Hideaki

    1996-06-01

    An Fe-0.01 to 0.5 mass pct Al alloy and an Fe-0.003 to 0.71 mass pct Al-1 mass pct M (M = C, Mn, and Ti) alloy were reoxidized with the CaO-Al2O3-FetO (3 mass pct) slags at 1873 K in an Al2O3 or CaO crucible for 5 and 60 minutes. The contents of acid-insoluble Al, total O, and alloying element M in metal as well as those of M and FetO in slag were measured as a function of total Al content. On the basis of the present and previous results for Fe- Al- Te alloys, the effect of alloying elements on the degree of supersaturation with respect to the Al2O3 precipitation was studied. As a result, the supersaturation phenomenon was observed in all experiments at 5 minutes, but in the experiments at 60 minutes, it was observed only in Fe- Al and Fe- Al- Ti alloys. No supersaturation was observed in the reoxidation of Si in Fe-0.13 to 0.98 mass pct Si alloys with the CaO-SiO2-FetO (3 mass pct) slags in a CaO crucible at 5 and 60 minutes.

  5. Effects of exogenous pyoverdines on Fe availability and their impacts on Mn(II) oxidation by Pseudomonas putida GB-1

    PubMed Central

    Lee, Sung-Woo; Parker, Dorothy L.; Geszvain, Kati; Tebo, Bradley M.

    2014-01-01

    Pseudomonas putida GB-1 is a Mn(II)-oxidizing bacterium that produces pyoverdine-type siderophores (PVDs), which facilitate the uptake of Fe(III) but also influence MnO2 formation. Recently, a non-ribosomal peptide synthetase mutant that does not synthesize PVD was described. Here we identified a gene encoding the PVDGB-1 (PVD produced by strain GB-1) uptake receptor (PputGB1_4082) of strain GB-1 and confirmed its function by in-frame mutagenesis. Growth and other physiological responses of these two mutants and of wild type were compared during cultivation in the presence of three chemically distinct sets of PVDs (siderotypes n°1, n°2, and n°4) derived from various pseudomonads. Under iron-limiting conditions, Fe(III) complexes of various siderotype n°1 PVDs (including PVDGB-1) allowed growth of wild type and the synthetase mutant, but not the receptor mutant, confirming that iron uptake with any tested siderotype n°1 PVD depended on PputGB1_4082. Fe(III) complexes of a siderotype n°2 PVD were not utilized by any strain and strongly induced PVD synthesis. In contrast, Fe(III) complexes of siderotype n°4 PVDs promoted the growth of all three strains and did not induce PVD synthesis by the wild type, implying these complexes were utilized for iron uptake independent of PputGB1_4082. These differing properties of the three PVD types provided a way to differentiate between effects on MnO2 formation that resulted from iron limitation and others that required participation of the PVDGB-1 receptor. Specifically, MnO2 production was inhibited by siderotype n°1 but not n°4 PVDs indicating PVD synthesis or PputGB1_4082 involvement rather than iron-limitation caused the inhibition. In contrast, iron limitation was sufficient to explain the inhibition of Mn(II) oxidation by siderotype n°2 PVDs. Collectively, our results provide insight into how competition for iron via siderophores influences growth, iron nutrition and MnO2 formation in more complex environmental

  6. Mechanisms controlling Cu, Fe, Mn, and Co profiles in peat of the Filson Creek Fen, northeastern Minnesota

    USGS Publications Warehouse

    Walton-Day, K.; Filipek, L.H.; Papp, C.S.E.

    1990-01-01

    Filson Creek Fen, located in northeastern Minnesota, overlies a Cu-Ni sulfide deposit. A site in the fen was studied to evaluate the hydrogeochemical mechanisms governing the development of Fe, Mn, Co, and Cu profiles in the peat. At the study site, surface peat approximately 1 m thick is separated from the underlying mineralized bedrock by a 6-12 m thickness of lake and glaciofluvial sediments and till. Concentrations of Fe, Mn, Co, and Cu in peat and major elements in pore water delineate a shallow, relatively oxidized, Cu-rich zone overlying a deeper, reduced, Fe-, Mn-, and Co-rich zone within the peat. Sequential metal extractions from peat samples reveal that 40-55% of the Cu in the shallow zone is associated with organic material, whereas the remaining Cu is distributed between iron-oxide, sulfide, and residual fractions. Sixty to seventy percent of the Fe, Mn, and Co concentrated in the deeper zone occur in the residual phase. The metal profiles and associations probably result from non-steady-state input of metals and detritus into the fen during formation of the peat column. The enrichment of organic-associated Cu in the upper, oxidized zone represents a combination of Cu transported into the fen with detrital plant fragments and soluble Cu, derived from weathering of outcrop and subcrop of the mineral deposit, transported into the fen, and fixed onto organic matter in the peat. The variable stratigraphy of the peat indicates that weathering processes and surface vegetation have changed through time in the fen. The Fe, Mn, and Co maxima at the base of the peat are associated with a maximum in detrital matter content of the peat resulting from a transition between the underlying inorganic sedimentary environment to an organic sedimentary environment. The chemistry of sediments and ground water collected beneath the peat indicate that mobilization of metals from sulfide minerals in the buried mineral deposit or glacial deposits is minimal. Therefore, the

  7. Impact of FeCl₃ dosing on AnMBR treatment of municipal wastewater.

    PubMed

    Dong, Qirong; Parker, Wayne; Dagnew, Martha

    2015-09-01

    The long-term (90 days) impact of dosing FeCl3 on bioprocess performance and membrane performance in a pilot AnMBR fed with authentic sewage was evaluated. The addition of 26 mg/L of FeCl3 enhanced the performance of the AnMBR with respect to removal efficiencies of COD and BOD5, but did not have a significant influence on the removal efficiencies of TKN and TP and the methane yield. The membrane was operated at a constant flux of 17 LMH and its performance was significantly improved by dosing FeCl3. This was demonstrated by a reduction in the fouling that withstood scouring stresses to values lower than 5 kPa and negligible reversible fouling for the first 75 days. The superior membrane performance was consistent with the shift of particle size distribution to the particulate fraction and the reduced colloidal and soluble substances in the sludge, especially the soluble protein, carbohydrate, Ca and S. CLSM tests showed that the addition of FeCl3 resulted in a thicker foulant layer and the deposition of protein and carbohydrate on the membrane surface was significantly reduced. Therefore a more porous foulant layer was formed and this prevented the development of a strongly-attached cake layer and pore blocking. A recovery cleaning study indicated FeCl3 dosing enhanced the efficiency of the recovery cleaning protocol. The foulants formed with the Fe-dosed sludge had greater inorganic content, as 75% of the foulant resistance was removed by citric acid. The superior membrane performance during the operation combined with enhanced cleaning efficiency by FeCl3 dosing would significantly improve the sustainability of AnMBR in municipal wastewater treatment. PMID:26005788

  8. Effects of D-strain, g-strain, and dipolar interactions on EPR linewidths of the molecular magnets Fe8 and Mn12

    NASA Astrophysics Data System (ADS)

    Park, Kyungwha; Novotny, M. A.; Dalal, N. S.; Hill, S.; Rikvold, P. A.

    2002-01-01

    Electron paramagnetic resonance measurements on single crystals of the molecular magnets Fe8 and Mn12 reveal complex nonlinearities in the linewidths as functions of energy eigenstate, frequency, and temperature. Using a density-matrix equation with distributions of the uniaxial anisotropy parameter D, the Landé g factor, and dipolar interactions, we obtain linewidths in good agreement with experiments. Our study shows that the distribution in D is common to the examined molecular magnets Fe8 and Mn12 regardless of the qualities of the samples. This could provide the basis for a proposed tunneling mechanism due to lattice defects. The distribution in g is also quite significant for Mn12.

  9. Broken ergodicity, memory effect, and rejuvenation in Taylor-phase and decagonal Al3(Mn,Pd,Fe) complex intermetallics

    NASA Astrophysics Data System (ADS)

    Dolinšek, J.; Slanovec, J.; Jagličić, Z.; Heggen, M.; Balanetskyy, S.; Feuerbacher, M.; Urban, K.

    2008-02-01

    The Taylor-phase complex intermetallic compound T-Al3Mn , its solid solutions with Pd and Fe, T-Al3(Mn,Pd) and T-Al3(Mn,Fe) , and the related decagonal d-Al-Mn-Fe quasicrystal belong to the class of magnetically frustrated spin systems that exhibit rich out-of-equilibrium spin dynamics in the nonergodic phase below the spin-freezing temperature Tf . Performing large variety of magnetic experiments as a function of temperature, magnetic field, aging time tw , and different thermal histories, we investigated broken-ergodicity phenomena of (i) a difference in the field-cooled and zero-field-cooled susceptibilities, (ii) the frequency-dependent freezing temperature, Tf(ν) , (iii) hysteresis and remanence, (iv) ultraslow decay of the thermoremanent magnetization, (v) the memory effect (a state of the spin system reached upon isothermal aging can be retrieved after a negative temperature cycle), and (vi) “rejuvenation” (small positive temperature cycle within the nonergodic phase erases the effect of previous aging). We show that the phenomena involving isothermal aging periods (the memory effect, rejuvenation, and the ultraslow decay of the thermoremanent magnetization) get simple explanation by considering that during aging under steady external conditions, localized spin regions quasiequilibrate into more stable configurations, so that higher thermal energy is needed to destroy these regions by spin flipping, as compared to the thermal energy required to reverse a frustrated spin in a disordered spin-glass configuration that forms in the case of no aging. Common to all the investigated broken-ergodicity phenomena is the slow approach of a magnetically frustrated spin system toward a global equilibrium, which can never be reached on accessible experimental time scales due to macroscopic equilibration times.

  10. Proteins involved in electron transfer to Fe(III) and Mn(IV) oxides by Geobacter sulfurreducens and Geobacter uraniireducens.

    PubMed

    Aklujkar, M; Coppi, M V; Leang, C; Kim, B C; Chavan, M A; Perpetua, L A; Giloteaux, L; Liu, A; Holmes, D E

    2013-03-01

    Whole-genome microarray analysis of Geobacter sulfurreducens grown on insoluble Fe(III) oxide or Mn(IV) oxide versus soluble Fe(III) citrate revealed significantly different expression patterns. The most upregulated genes, omcS and omcT, encode cell-surface c-type cytochromes, OmcS being required for Fe(III) and Mn(IV) oxide reduction. Other electron transport genes upregulated on both metal oxides included genes encoding putative menaquinol : ferricytochrome c oxidoreductase complexes Cbc4 and Cbc5, periplasmic c-type cytochromes Dhc2 and PccF, outer membrane c-type cytochromes OmcC, OmcG and OmcV, multicopper oxidase OmpB, the structural components of electrically conductive pili, PilA-N and PilA-C, and enzymes that detoxify reactive oxygen/nitrogen species. Genes upregulated on Fe(III) oxide encode putative menaquinol : ferricytochrome c oxidoreductase complexes Cbc3 and Cbc6, periplasmic c-type cytochromes, including PccG and PccJ, and outer membrane c-type cytochromes, including OmcA, OmcE, OmcH, OmcL, OmcN, OmcO and OmcP. Electron transport genes upregulated on Mn(IV) oxide encode periplasmic c-type cytochromes PccR, PgcA, PpcA and PpcD, outer membrane c-type cytochromes OmaB/OmaC, OmcB and OmcZ, multicopper oxidase OmpC and menaquinone-reducing enzymes. Genetic studies indicated that MacA, OmcB, OmcF, OmcG, OmcH, OmcI, OmcJ, OmcM, OmcV and PccH, the putative Cbc5 complex subunit CbcC and the putative Cbc3 complex subunit CbcV are important for reduction of Fe(III) oxide but not essential for Mn(IV) oxide reduction. Gene expression patterns for Geobacter uraniireducens were similar. These results demonstrate that the physiology of Fe(III)-reducing bacteria differs significantly during growth on different insoluble and soluble electron acceptors and emphasize the importance of c-type cytochromes for extracellular electron transfer in G. sulfurreducens. PMID:23306674

  11. Mn(2+)-mediated homogeneous Fenton-like reaction of Fe(III)-NTA complex for efficient degradation of organic contaminants under neutral conditions.

    PubMed

    Li, Yifan; Sun, Jianhui; Sun, Sheng-Peng

    2016-08-01

    In this work, we report a novel Mn(2+)-mediated Fenton-like process based on Fe(III)-NTA complex that is super-efficient at circumneutral pH range. Kinetics experiments showed that the presence of Mn(2+) significantly enhanced the effectiveness of Fe(III)-NTA complex catalyzed Fenton-like reaction. The degradation rate constant of crotamiton (CRMT), a model compound, by the Fe(III)- NTA_Mn(2+) Fenton-like process was at least 1.6 orders of magnitude larger than that in the absence of Mn(2+). Other metal ions such as Ca(2+), Mg(2+), Co(2+) and Cu(2+) had no impacts or little inhibitory effect on the Fe(III)-NTA complex catalyzed Fenton-like reaction. The generation of hydroxyl radical (HO) and superoxide radical anion (O2(-)) in the Fe(III)-NTA_Mn(2+) Fenton-like process were suggested by radicals scavenging experiments. The degradation efficiency of CRMT was inhibited significantly (approximately 92%) by the addition of HO scavenger 2-propanol, while the addition of O2(-) scavenger chloroform resulted in 68% inhibition. Moreover, the results showed that other chelating agents such as EDTA- and s,s-EDDS-Fe(III) catalyzed Fenton-like reactions were also enhanced significantly by the presence of Mn(2+). The mechanism involves an enhanced generation of O2(-) from the reactions of Mn(2+)-chelates with H2O2, indirectly promoting the generation of HO by accelerating the reduction rate of Fe(III)-chelates to Fe(II)- chelates. PMID:27070388

  12. The role of the (111) texture on the exchange bias and interlayer coupling effects observed in sputtered NiFe/IrMn/Co trilayers

    SciTech Connect

    Castro, I. L.; Nascimento, V. P.; Passamani, E. C.; Takeuchi, A. Y.; Larica, C.; Tafur, M.; Pelegrini, F.

    2013-05-28

    Magnetic properties of sputtered NiFe/IrMn/Co trilayers grown on different seed layers (Cu or Ta) deposited on Si (100) substrates were investigated by magnetometry and ferromagnetic resonance measurements. Exchange bias effect and magnetic spring behavior have been studied by changing the IrMn thickness. As shown by X-ray diffraction, Ta and Cu seed layers provoke different degrees of (111) fcc-texture that directly affect the exchange bias and indirectly modify the exchange spring coupling behavior. Increasing the IrMn thickness, it was observed that the coupling angle between the Co and NiFe ferromagnetic layers increases for the Cu seed system, but it reduces for the Ta case. The results were explained considering (i) different anisotropies of the Co and IrMn layers induced by the different degree of the (111) texture and (ii) the distinct exchange bias set at the NiFe/IrMn and IrMn/Co interfaces in both systems. The NiFe and Co interlayer coupling angle is strongly correlated with both exchange bias and exchange magnetic spring phenomena. It was also shown that the highest exchange bias field occurs when an unstressed L1{sub 2} IrMn structure is stabilized.

  13. Fatigue Crack Propagation in Intercritically Tempered Fe-9Ni-0.1C and Fe-4Mn-0.15C

    NASA Astrophysics Data System (ADS)

    Choi, H. J.; Schwartz, L. H.

    1983-06-01

    Fatigue crack propagation was studied for two intercritically tempered cryogenic steels, Fe-9Ni-0.1C and Fe-4Mn-0.15C, at both intermediate (stage II) and low (stage I, near threshold) stress intensity ranges. Propagation rates were determined for varying intercritical tempering times corresponding to varying amounts of retained austenite and untempered martensite. The results show that the heat treatments that optimize impact fracture properties in the nickel steel are also beneficial with respect to the fatigue crack propagation rate in stage I, while no beneficial effect beyond that attributable to carbon redistribution was observed for stage II. For the manganese steel, heat treatments leading to increased concentrations of retained austenite also increased the threshold stress even though no improvement in fracture toughness was observed. To clarify the origin of this improved behavior, the fracture surface was analyzed by Mössbauer Spectroscopy and Auger Electron Microprobe. The Mössbauer results indicated that the retained austenite in the crack path is transformed to martensite as was earlier shown in this laboratory for Charpy specimens. Auger composition analysis suggested a tendency for a stage I crack tip to avoid the mechanically induced brittle untempered martensite in the Fe-Mn steel, while no such preference was observed for stage II.

  14. Examination of the magnetism dynamics from intermixing effects in γ-Fe{sub 2}O{sub 3}/MnO core-shell nanoparticles

    SciTech Connect

    Skoropata, E. Lierop, J. van; Su, T. T.; Ouyang, H.; Freeland, J. W.

    2015-05-07

    We have examined the effects of core-shell intermixing on the dynamical magnetism of γ-Fe{sub 2}O{sub 3}/MnO nanoparticles. The core and shell phases were identified using x-ray diffraction, and x-ray absorption spectroscopy identified Mn ions in both octahedral and tetrahedral sites, consistent with a significant amount of substitution at the core-shell interface to form an Fe/Mn-ferrite. The dynamical response was probed by Mössbauer spectroscopy, which decouples surface and core spins, and suggested a change in the relaxation behaviour among the spin populations within γ-Fe{sub 2}O{sub 3}/MnO relative to the γ-Fe{sub 2}O{sub 3} seed particles. Interestingly, the magnetic relaxation effects at the atomic scale, measured via Mössbauer spectroscopy, were enhanced, indicating that the addition of an MnO shell and intermixing affected the dynamical freezing process which altered the surface magnetism of the γ-Fe{sub 2}O{sub 3} core. Our results show that both the MnO shell and the interfacial intermixed layer are important in determining the core-shell nanoparticle magnetism.

  15. Fe(3)O(4)/MnO hybrid nanocrystals as a dual contrast agent for both T(1)- and T(2)-weighted liver MRI.

    PubMed

    Im, Geun Ho; Kim, Soo Min; Lee, Dong-Gyu; Lee, Won Jae; Lee, Jung Hee; Lee, In Su

    2013-03-01

    To investigate whether it is possible to develop a dual magnetic resonance (MR) contrast agent, Fe(3)O(4)/MnO hybrid nanocrystals were modified to integrate the T(1) and T(2) contrast-enhancing abilities of each compound, and their characteristics as MR contrast agents were investigated. In vitro and in vivo investigations revealed that the Fe(3)O(4)/MnO dumbbell-shaped nanocrystal exerted a negative T(2) contrast effect in its intact form and also gave rise to a positive contrast effect in T(1)-weighted MR imaging by releasing Mn(2+) ions in a low pH environment. This induced organ-specific contrast enhancement for both T(1)- and T(2)-weighted in vivo MR imaging. The usefulness of the Fe(3)O(4)/MnO hybrid nanocrystals as dual contrast agents was evaluated by in vivo MR imaging of an orthotopic xenograft model of human hepatocellular carcinoma (HCC). After injection of the Fe(3)O(4)/MnO hybrid nanocrystals, dual contrast-enhanced MR images that synergistically combined the T(2) and T(1) contrast effects from the Fe(3)O(4) grain and released Mn(2+) ions were obtained by a single acquisition of MR imaging. This facilitated the detection of HCC with a high degree of conspicuity that could not be achieved with any single contrast agent. PMID:23246062

  16. Observation of the large magnetocaloric effect and suppression of orbital entropy change in Fe-doped MnV{sub 2}O{sub 4}

    SciTech Connect

    Huang, Z. H.; Luo, X. E-mail: ypsun@issp.ac.cn; Hu, L.; Tan, S. G.; Liu, Y.; Yuan, B.; Chen, J.; Song, W. H.; Sun, Y. P. E-mail: ypsun@issp.ac.cn

    2014-01-21

    We present the structural and magnetic properties of Mn{sub 1−x}Fe{sub x}V{sub 2}O{sub 4} (x = 0.1, 0.2, and 0.3), and investigate the magnetocaloric effect in those compounds. The ferrimagnetic spin ordering is enhanced with the Fe doping at Mn site of MnV{sub 2}O{sub 4}, while the orbital ordering is suppressed. Large magnetic entropy changes up to 3.8 J/kg K as well as the relative cooling power up to 110 J/kg at the field change of 0-2 T for Mn{sub 1−x}Fe{sub x}V{sub 2}O{sub 4} are calculated from the isothermal magnetization measurements. The large orbital entropy change of MnV{sub 2}O{sub 4} is suppressed by the Fe doping, while the spin entropy contribution arising from the strong spin-orbit coupling remains. Moreover, the doping of Fe broadens the temperature span of the large magnetic entropy change and increases the relative cooling power of MnV{sub 2}O{sub 4} by 2.4 times.

  17. Nanostructure evolution under irradiation of Fe(C)MnNi model alloys for reactor pressure vessel steels

    NASA Astrophysics Data System (ADS)

    Chiapetto, M.; Becquart, C. S.; Domain, C.; Malerba, L.

    2015-06-01

    Radiation-induced embrittlement of bainitic steels is one of the most important lifetime limiting factors of existing nuclear light water reactor pressure vessels. The primary mechanism of embrittlement is the obstruction of dislocation motion produced by nanometric defect structures that develop in the bulk of the material due to irradiation. The development of models that describe, based on physical mechanisms, the nanostructural changes in these types of materials due to neutron irradiation are expected to help to better understand which features are mainly responsible for embrittlement. The chemical elements that are thought to influence most the response under irradiation of low-Cu RPV steels, especially at high fluence, are Ni and Mn, hence there is an interest in modelling the nanostructure evolution in irradiated FeMnNi alloys. As a first step in this direction, we developed sets of parameters for object kinetic Monte Carlo (OKMC) simulations that allow this to be done, under simplifying assumptions, using a "grey alloy" approach that extends the already existing OKMC model for neutron irradiated Fe-C binary alloys [1]. Our model proved to be able to describe the trend in the buildup of irradiation defect populations at the operational temperature of LWR (∼300 °C), in terms of both density and size distribution of the defect cluster populations, in FeMnNi model alloys as compared to Fe-C. In particular, the reduction of the mobility of point-defect clusters as a consequence of the presence of solutes proves to be key to explain the experimentally observed disappearance of detectable point-defect clusters with increasing solute content.

  18. Effect of mineral-enriched diet and medicinal herbs on Fe, Mn, Zn, and Cu uptake in chicken

    PubMed Central

    2012-01-01

    Background The goal of our study was to evaluate the effects of different medicinal herbs rich in polyphenol (Lemon balm, Sage, St. John's wort and Small-flowered Willowherb) used as dietary supplements on bioaccumulation of some essential metals (Fe, Mn, Zn and Cu) in different chicken meats (liver, legs and breast). Results In different type of chicken meats (liver, legs and breast) from chickens fed with diets enriched in minerals and medicinal herbs, beneficial metals (Fe, Mn, Zn and Cu) were analysed by flame atomic absorption spectrometry. Fe is the predominant metal in liver and Zn is the predominant metal in legs and breast chicken meats. The addition of metal salts in the feed influences the accumulations of all metals in the liver, legs and breast chicken meat with specific difference to the type of metal and meat. The greatest influences were observed in legs meat for Fe and Mn. Under the influence of polyphenol-rich medicinal herbs, accumulation of metals in the liver, legs and breast chicken meat presents specific differences for each medicinal herb, to the control group that received a diet supplemented with metal salts only. Great influence on all metal accumulation factors was observed in diet enriched with sage, which had significantly positive effect for all type of chicken meats. Conclusions Under the influence of medicinal herbs rich in different type of polyphenol, accumulation of metals in the liver, legs and breast chicken meat presents significant differences from the group that received a diet supplemented only with metal salts. Each medicinal herb from diet had a specific influence on the accumulation of metals and generally moderate or poor correlations were observed between total phenols and accumulation of metals. This may be due to antagonism between metal ions and presence of other chelating agents (amino acids and protein) from feeding diets which can act as competitor for complexation of metals and influence accumulation of metals

  19. Metastable (Bi, M)2(Fe, Mn, Bi)2O(6+x) (M = Na or K) pyrochlores from hydrothermal synthesis.

    PubMed

    Daniels, Luke M; Playford, Helen Y; Grenèche, Jean-Marc; Hannon, Alex C; Walton, Richard I

    2014-12-15

    The hydrothermal syntheses, structures, and magnetism of two new pyrochlore oxides of compositions (Na0.60Bi1.40)(Fe1.06Mn0.17Bi0.77)O6.87 and (K0.24Bi1.51)(Fe1.07Mn0.15Bi0.78)O6.86 are described. With preparation at 200 °C for 6 h in solutions of sodium or potassium hydroxide, the alkali metals introduced from these mineralizers are essential to the synthesis of the phases. The average long-range order of the pyrochlore structure, with space group Fd3̅m, was investigated and refined against X-ray and neutron diffraction data, and it was shown that disorder is present in both the metal and coordinating oxygen positions, along with metal-mixing across both the A and B sites of the structure. XANES analysis confirms the presence of Mn(4+), mixed valence Bi(3+) and Bi(5+), and Fe(3+), the last also verified by (57)Fe Mössbauer spectroscopy. Magnetic measurements show a lack of long-range magnetic ordering that is typical of geometrically frustrated pyrochlores. The observed glasslike interactions occur at low temperatures, with the onset temperature depending upon the magnitude of the applied external field. Variable temperature X-ray diffraction shows that these pyrochlores are metastable and collapse on heating at ca. 395 °C, which suggests that their formation by conventional solid-state synthesis would be impossible. PMID:25413441

  20. Experimental investigation of off-stoichiometry and 3d transition metal (Mn, Ni, Cu)-substitution in single-crystalline FePt thin films

    NASA Astrophysics Data System (ADS)

    Ono, Takuya; Nakata, Hitoshi; Moriya, Tomohiro; Kikuchi, Nobuaki; Okamoto, Satoshi; Kitakami, Osamu; Shimatsu, Takehito

    2016-05-01

    In L10 (fct)-FePt thin films, both tuning Fe and Pt concentrations and substitution with third-metal were studied for magnetic characteristic optimization. We investigated single-crystalline FePt-X (X = Mn, Ni, Cu) thin films grown epitaxially on MgO(001) substrates at a substrate temperature of 350 °C by changing Fe, Pt, and X contents, and explored the effects of off-stoichiometry and 3d-metal-substitution. The magnetic moment per atom (m) of FePt-X films as a function of the effective number of valence electrons (neff) in 3d metal sites follows the Slater-Pauling-type trend, by which m decreases by the neff deviation from neff = 8, independently of the X metal and the Pt concentration. The magnetic anisotropy (Ku) exhibits neff dependence similar to m. This trend was almost independent of the Pt concentration after compensation using the theoretical prediction on the relation between Ku and Fe/Pt concentrations. Such a trend has been proved for stoichiometric FePt-X films, but it was clarified as robust against off-stoichiometry. The compensated Ku ( Ku comp ) of FePt-Mn and FePt-Cu followed a similar trend to that predicted by the rigid-band model, although the Ku comp of the FePt-Mn thin films dropped more rapidly than the rigid band calculation. However, it followed the recent first-principles calculation.

  1. Corrosion Behavior of High Nitrogen Nickel-Free Fe-16Cr-Mn-Mo-N Stainless Steels

    NASA Astrophysics Data System (ADS)

    Chao, K. L.; Liao, H. Y.; Shyue, J. J.; Lian, S. S.

    2014-04-01

    The purpose of the current study is to develop austenitic nickel-free stainless steels with lower chromium content and higher manganese and nitrogen contents. In order to prevent nickel-induced skin allergy, cobalt, manganese, and nitrogen were used to substitute nickel in the designed steel. Our results demonstrated that manganese content greater than 14 wt pct results in a structure that is in full austenite phase. The manganese content appears to increase the solubility of nitrogen; however, a lower corrosion potential was found in steel with high manganese content. Molybdenum appears to be able to increase the pitting potential. The effects of Cr, Mn, Mo, and N on corrosion behavior of Fe-16Cr-2Co-Mn-Mo-N high nitrogen stainless steels were evaluated with potentiodynamic tests and XPS surface analysis. The results reveal that anodic current and pits formation of the Fe-16Cr-2Co-Mn-Mo-N high nitrogen stainless steels were smaller than those of lower manganese and nitrogen content stainless steel.

  2. Boric acid flux synthesis, structure and magnetic property of MB12O14(OH)10 (M=Mn, Fe, Zn)

    NASA Astrophysics Data System (ADS)

    Yang, Dingfeng; Cong, Rihong; Gao, Wenliang; Yang, Tao

    2013-05-01

    Three new borates MB12O14(OH)10 (M=Mn, Fe, Zn) have been synthesized by boric acid flux methods, which are isotypic to NiB12O14(OH)10. Single-crystal XRD was performed to determine the crystal structures in detail. They all crystallize in the monoclinic space group P21/c. The size of MO6 (M=Mg, Mn, Fe, Co, Ni, Zn) octahedron shows a good agreement with the Shannon effective ionic radii of M2+. Magnetic measurements indicate MnB12O14(OH)10 is antiferromagnetic without a long-range ordering down to 2 K. The values of its magnetic superexchange constants were evaluated by DFT calculations, which explain the observed magnetic behavior. The UV-vis diffuse reflectance spectrum of ZnB12O14(OH)10 suggests a band gap ˜4.6 eV. DFT calculations indicate it has a direct band gap 4.9 eV. The optical band gap is contributed by charge transfers from the occupied O 2p to the unoccupied Zn 4s states.

  3. Adsorption of arsenite and selenite using an inorganic ion exchanger based on Fe-Mn hydrous oxide.

    PubMed

    Szlachta, Małgorzata; Gerda, Vasyl; Chubar, Natalia

    2012-01-01

    The adsorption behaviour and mechanism of As(III) and Se(IV) oxyanion uptake using a mixed inorganic adsorbent were studied. The novel adsorbent, based on Fe(III)-Mn(III) hydrous oxides and manganese(II) carbonate, was synthesised using a hydrothermal precipitation approach in the presence of urea. The inorganic ion exchanger exhibited a high selectivity and adsorptive capacity towards As(III) (up to 47.6 mg/g) and Se(IV) (up to 29.0 mg/g), even at low equilibrium concentration. Although pH effects were typical for anionic species (i.e., the adsorption decreased upon pH increase), Se(IV) was more sensitive to pH changes than As(III). The rates of adsorption of both oxyanions were high. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) studies showed that the ion exchange adsorption of both anions took place via OH(-) groups, mainly from Fe(III) but also Mn(III) hydrous oxides. MnCO(3) did not contribute directly to As(III) and Se(IV) removal. A higher adsorptive capacity of the developed material towards As(III) was partly due to partial As(III) oxidation during adsorption. PMID:21968401

  4. Micromagnetic analysis of the hardening mechanisms of nanocrystalline MnBi and nanopatterned FePt intermetallic compounds.

    PubMed

    Kronmüller, H; Yang, J B; Goll, D

    2014-02-12

    The uniaxial intermetallic compounds of L10-FePt and the low temperature NiAs structure of MnBi are suitable alloys for application as high-density recording materials or as high-coercivity permanent magnets. Single domain particles of these materials are characterized by coercive fields above 1 T over a large temperature range. In particular MnBi shows a coercive field of 2 T at 450 K. Its extraordinary magnetic properties in the temperature range up to 600 K are due to an increase of the magnetocrystalline anisotropy constant from 1.2 MJ m(-3) at 300 K to 2.4 MJ m(-3) at 450 K. In spite of the large coercivities obtained for both type of materials their experimental values deviate considerably from the theoretical values Hc = 2K1/Js valid for a homogeneous rotation process in spherical particles. As is well known these discrepancies are due to the deteriorating effects of the microstructure. For an analysis of the coercive fields the Stoner-Wohlfarth theory has to be expanded with respect to higher anisotropy constants and to microstructural effects such as misaligned grains and grain surfaces with reduced anisotropy constants. It is shown that the temperature dependence and the angular dependence of Hc for FePt as well as MnBi can be quantitatively interpreted by taking into account the above mentioned intrinsic and microstructural effects. PMID:24469256

  5. Investigations on Laser Beam Welding Dissimilar Material Combinations of Austenitic High Manganese (FeMn) and Ferrite Steels

    NASA Astrophysics Data System (ADS)

    Behm, Velten; Höfemann, Matthias; Hatscher, Ansgar; Springer, André; Kaierle, Stefan; Hein, David; Otto, Manuel; Overmeyer, Ludger

    For the past few years the customer's demand for more fuel efficient and at the same time safer vehicles has steadily increased. Consequently, light weight design has become one of the main interests in engineering. With regard to sheet metal components, a new class of high manganese steels, based on the TWIP (twinning induced plasticity) effect, provides the opportunity of shaping light weight designedthin and complex sheet metal geometries with advanced crash performance. In terms of weldability, due to their thermo-physical properties (high content of C, Mn, Al, Si), FeMn steels have to be handled differently in comparison to conventional steel grades. Particularly dissimilar material combinations of FeMn and ferrite steels are in the center of interest for industrial applications. This study reveals that metallurgical properties of dissimilar welding seams can be influenced considerably by laser beam welding, resulting in a change of the mechanical properties of the seam which is practicable without using filler material as described in (Flügge et al., 2011).

  6. Arsenic release from Fe/Mn oxide-rich (model) soils/sediments - A comparison of single extraction procedures

    NASA Astrophysics Data System (ADS)

    Vanek, A.; Komarek, M.; Galuskova, I.

    2012-04-01

    Arsenic extractability in As-modified Fe(III) and Mn(III,IV) oxide-coated sands was tested using five widely used 2-h single extraction procedures: deionised water, 0.01 M CaCl2, 1 M NH4NO3, 0.1 M Na2HPO4 and 0.005 DTPA. In general, the highest As recoveries reaching 39-50% of total As concentration were observed for all extracting media in the birnessite (delta-MnO2) system, indicating relatively weak adsorption of As onto the Mn oxides. The Na2HPO4 extracts from the Fe oxide systems (i.e., associated with ferrihydrite and goethite) were highest in As, accounting for up to 34% of total As amount. Surprisingly, comparable recoveries of As (14-20%) yielded deionised water, CaCl2, NH4NO3, DTPA as extracting media for both ferrihydrite and goethite coatings. Deionised water and Na2HPO4 extractions are suggested for quick estimation of easily soluble, exchangeable and/or specifically adsorbed As in real soil/sediment samples.

  7. Sediment fractionation of Cu, Ni, Zn, Cr, Mn, and Fe in one experimental and three natural marshes

    SciTech Connect

    Lindau, C.W.; Hossner, L.R.

    1982-07-01

    Dredged sediments from the Gulf Intracoastal Waterway near Galveston, Tex., were used as a substrate material in the construction of an experimental intertidal salt marsh. Selected substrate properties were compared with those of established marshes. Clay mineralogical properties of the experimental marsh were compared with those of three nearby natural marshes. A sequential chemical extraction procedure was used to obtain data on the partitioning of micronutrients and heavy metals among selected marsh substrate fractions. Clay minerals found in the sediments of the experimental marsh were equivalent to those identified in the natural marshes. Total elemental substrate concentrations of Cu, Ni, Cr, Zn, Mn, and Fe averaged 7.9, 8.6, 25.5, 25.2, 123, and 12,200 ..mu..g/g, respectively, over the four marsh sites. Copper, nickel, zinc, and chromium displayed only minor variations in substrate partitioning between the experimental and natural marsh samples. Micronutrients and heavy metal concentrations in the exchangeable and water-soluble fraction were low compared with other fractions. Approximately 30% of the total substrate Cu, Ni, and Zn was associated with the organic matter fraction. Metals fixed within the lattice structures of clay and silicate minerals ranged from 20% Mn for experimental marsh samples to 90% Cr for one of the natural marshes. Major differences in Mn and Fe substrate partitioning were observed when the experimental marsh samples were compared with those of the natural marshes.

  8. Formation and diffusion of vacancy-polaron complex in olivine-type LiMnPO4 and LiFePO4

    NASA Astrophysics Data System (ADS)

    Asari, Yusuke; Suwa, Yuji; Hamada, Tomoyuki

    2011-10-01

    Formation and diffusion of a vacancy-polaron complex in olivine-type cathode-active materials, namely, LiMPO4 (M = Fe, Mn), were theoretically investigated by using the first-principles density functional theory within a framework of GGA + U method. It is shown that a lithium vacancy and a corresponding hole-polaron form the complex at the fully lithiated limit owing to lattice distortion and Coulomb interaction between them. It is also shown that the formation energy of the complex in LiMnPO4 is 0.19 eV higher than that in LiFePO4, since a hole polaron in LiMnPO4 is not sufficiently relaxed. As a result, the nucleation rate of MnPO4 phase in LiMnPO4 is 10-3 times slower than that in LiFePO4 and represents the main difference between the kinetics in the initial stage of charging of the two olivine materials. It was also found that the activation energy of the complex diffusion is limited by vacancy hopping in LiMnPO4, while it is determined by both vacancy hopping and polaron hopping in LiFePO4. The activation energy in LiMnPO4, 0.38 eV, is comparable with that in LiFePO4, 0.42 eV. The calculated potential energy profile, showed that the minimum energy path of the diffusing lithium in LiMnPO4 has the same winding shape as that in LiFePO4.

  9. Photoluminescence and Raman studies for the confirmation of oxygen vacancies to induce ferromagnetism in Fe doped Mn:ZnO compound

    NASA Astrophysics Data System (ADS)

    Das, J.; Mishra, D. K.; Srinivasu, V. V.; Sahu, D. R.; Roul, B. K.

    2015-05-01

    With a motivation to compare the magnetic property, we synthesised undoped, transition metal (TM) Mn doped and (Mn:Fe) co-doped ZnO ceramics in the compositions ZnO, Zn0.98Mn0.02O and Zn0.96(Mn0.02Fe0.02)O. Systematic investigations on the structural, microstructural, defect structure and magnetic properties of the samples were performed. Low temperature as well as room temperature ferromagnetism has been observed for all our samples, however, enhanced magnetisation at room temperature has been noticed when ZnO is co-doped with Fe along with Mn. Particularly the sample with the composition Zn0.96Mn0.02Fe0.02O showed a magnetisation value more than double of the sample with composition Zn0.98Mn0.02O, indicating long range strong interaction between the magnetic impurities leading to higher ferromagnetic ordering. Raman and PL studies reveal presence of higher defects in form of oxygen vacancy clusters created in the sample due to Fe co doping. PL study also reveals enhanced luminescence efficiency in the co doped sample. Temperature dependent magnetisation study of this sample shows the spin freezing temperature around 39 K indicating the presence of small impurity phase of Mn2-xZnxO3 type. Electron Spin Resonance signal obtained supports ferromagnetic state in the co doped sample. Enhancement of magnetisation is attributed to interactions mediated by magnetic impurities through large number of oxygen vacancies created by Fe3+ ions forming bound magnetic polarons (BMP) and facilitating long range ferromagnetic ordering in the co- doped system.

  10. Divergent Modification of Low-Dose 56Fe-Particle and Proton Radiation on Skeletal Muscle

    PubMed Central

    Shtifman, Alexander; Pezone, Matthew J.; Sasi, Sharath P.; Agarwal, Akhil; Gee, Hannah; Song, Jin; Perepletchikov, Aleksandr; Yan, Xinhua; Kishore, Raj; Goukassian, David A.

    2014-01-01

    It is unknown whether loss of skeletal muscle mass and function experienced by astronauts during space flight could be augmented by ionizing radiation (IR), such as low-dose high-charge and energy (HZE) particles or low-dose high-energy proton radiation. In the current study adult mice were irradiated whole-body with either a single dose of 15 cGy of 1 GeV/n 56Fe-particle or with a 90 cGy proton of 1 GeV/n proton particles. Both ionizing radiation types caused alterations in the skeletal muscle cytoplasmic Ca2+ ([Ca2+]i) homeostasis. 56Fe-particle irradiation also caused a reduction of depolarization-evoked Ca2+ release from the sarcoplasmic reticulum (SR). The increase in the [Ca2+]i was detected as early as 24 h after 56Fe-particle irradiation, while effects of proton irradiation were only evident at 72 h. In both instances [Ca2+]i returned to baseline at day 7 after irradiation. All 56Fe-particle irradiated samples revealed a significant number of centrally localized nuclei, a histologic manifestation of regenerating muscle, 7 days after irradiation. Neither unirradiated control or proton-irradiated samples exhibited such a phenotype. Protein analysis revealed significant increase in the phosphorylation of Akt, Erk1/2 and rpS6k on day 7 in 56Fe-particle irradiated skeletal muscle, but not proton or unirradiated skeletal muscle, suggesting activation of pro-survival signaling. Our findings suggest that a single low-dose 56Fe-particle or proton exposure is sufficient to affect Ca2+ homeostasis in skeletal muscle. However, only 56Fe-particle irradiation led to the appearance of central nuclei and activation of pro-survival pathways, suggesting an ongoing muscle damage/recovery process. PMID:24131063

  11. Effect of Mn Substitution for Multiferroic BiFeO3 Probed by High-Resolution Soft-X-Ray Spectroscopy

    SciTech Connect

    Higuchi, Tohru; Higuchi, T.; Hattori, T.; Sakamoto, W.; Itoh, N.; Shimura, T.; Yogo, T.; Yao, P.; Liu, Y.; Glans, P.; Chang, C.; Wu, Z.; Guo, Jinghua

    2008-07-11

    The electronic structures of BiFeO{sub 3} (BF) and Mn-doped BiFeO{sub 3} (BF(Mn)) have been studied by X-ray absorption spectroscopy (XAS) and soft-X-ray emission spectroscopy (SXES). The BF and BF(Mn) have the mixed valence state of Fe{sup 2+} and Fe{sup 3+}. The valence band is mainly composed of O 2p state hybridized with the majority-spin t{sub 2g} and e{sub g} orbitals of Fe 3d state. The conduction band is composed of the minority-spin t{sub 2g} and e{sub g} orbitals of Fe 3d. The band gaps of BF and BF(Mn) are estimated to be 1.3 eV and 2.7 eV, respectively. The increase of band gap with Mn substitution contributes to the change of bandwidth of valence band.

  12. Penetration depth and absorption mechanisms of spin currents in Ir{sub 20}Mn{sub 80} and Fe{sub 50}Mn{sub 50} polycrystalline films by ferromagnetic resonance and spin pumping

    SciTech Connect

    Merodio, P.; Ghosh, A.; Lemonias, C.; Gautier, E.; Ebels, U.; Chshiev, M.; Béa, H. E-mail: helene.bea@cea.fr; Baltz, V. E-mail: helene.bea@cea.fr

    2014-01-20

    Spintronics relies on the spin dependent transport properties of ferromagnets (Fs). Although antiferromagnets (AFs) are used for their magnetic properties only, some fundamental F-spintronics phenomena like spin transfer torque, domain wall motion, and tunnel anisotropic magnetoresistance also occur with AFs, thus making AF-spintronics attractive. Here, room temperature critical depths and absorption mechanisms of spin currents in Ir{sub 20}Mn{sub 80} and Fe{sub 50}Mn{sub 50} are determined by F-resonance and spin pumping. In particular, we find room temperature critical depths originating from different absorption mechanisms: dephasing for Ir{sub 20}Mn{sub 80} and spin flipping for Fe{sub 50}Mn{sub 50}.

  13. Effect of Mn and Ti substitution on the reflection loss characteristic of Ba0.6Sr0.4Fe11-zMnTizO19 (z = 0, 1, 2 and 3)

    NASA Astrophysics Data System (ADS)

    Gunanto, Y. E.; Cahyadi, L.; Adi, W. Ari

    2016-04-01

    The synthesis and characterization of composition Ba0.6Sr0.4Fe11-zMnTizO19 (z = 0; 1; 2 and 3) compound by solid state reaction using mechanical milling have been performed. The raw materials were BaCO3, SrCO3, Fe2O3, MnCO3, and TiO2. The mixed powder was compacted and sintered at 1000°C for 5 hours. X-ray diffraction studies indicate expansion of hexagonal unit cell and compression of atomic density with substitution of Mn2+ and Ti4+ ions. Effect of substitution upon magnetic properties revealed that total magnetization, remanence, and coercivity changed with substitution due to preferential site occupancy of substituted Mn2+ and Ti4+ ions. Since the coercivity and total magnetization may be controlled by substitution while maintaining resistive properties, this material is useful for microwave absorber.

  14. Neutral catecholate derivatives of manganese and iron: Synthesis and characterization of the metal-oxygen cubane-like species M sub 4 (DBCat) sub 4 (py) sub 6 (M = Mn, Fe), the trinuclear complex Mn sub 3 (DBCat) sub 4 (py) sub 4 , and the dimers M sub 2 (DBCat) sub 2 (py) sub n (M = Mn, n = 6; M = Fe, n = 4, 6)

    SciTech Connect

    Shoner, S.C.; Power, P.P. )

    1992-03-18

    The synthesis and characterization of several new catecholate derivatives of manganese and iron are described. The reaction of 3,5-di-tert-butylcatechol (DBCatH{sub 2}) with the amides M(N(SiMe{sub 3}){sub 2}){sub 2} (M = Mn, Fe) in the presence of pyridine (py) affords the title compounds in high yield. The dimers Mn{sub 2}(DBCat){sub 2}(py){sub 6} (1) and Fe{sub 2}(DBCat){sub 2}(py){sub n} (n = 4 (4a), 6 (4b)) are obtained by treatment of catechol with the appropriate amide in pyridine. In hexane or toluene, this reaction gives the tetrametallic species M{sub 4}(DBCat){sub 4}(py){sub 6} (M = Mn (2), Fe (5)) upon the addition of 2 equiv of pyridine or, in the case of 2, by recrystallization of the dimer from toluene. Mn{sub 3}(DBCat){sub 4}(py){sub 4} (3) is obtained by slow air oxidation of 2 or by addition of 1/3 equiv of 3,5-di-tert-butyl-o-benzoquinone to the reaction of Mn(N(SiMe{sub 3}){sub 2}){sub 2} with DBCatH{sub 2} in hexane with subsequent addition of pyridine. Compounds 1-5 were characterized by infrared, UV-visible, {sup 1}H NMR, and EPR spectroscopy and X-ray crystallography.

  15. Itinerant Antiferromagnetism in FeMnP0.8Si0.2

    SciTech Connect

    Sales, Brian C.; Susner, Michael A.; Conner, Benjamin S.; Yan, Jiaqiang Q.; May, Andrew F.

    2015-01-01

    Compounds based on the Fe2P structure have continued to attract interest because of the interplay between itinerant and localized magnetism in a noncentrosymmetric crystal structure, and because of the recent developments of these materials for magnetocaloric applications. We report the growth and characterization of millimeter-sized single crystals of FeMnP0.8Si0.2 with the Fe2P structure. Single-crystal x-ray diffraction, magnetization, resistivity, and Hall and heat capacity data are reported. The crystals exhibit itinerant antiferromagnetic order below 158 K with no hint of ferromagnetic behavior in the magnetization curves and with the spins ordered primarily in the ab plane. The room-temperature resistivity is close to the Ioffe-Regel limit for a metal. Single-crystal x-ray diffraction indicates a strong preference for Mn to occupy the larger pyramidal 3g site. The cation site preference in the as-grown crystals and the antiferromagnetism were not changed after high-temperature anneals and a rapid quench to room temperature

  16. Recycling bacteria for the synthesis of LiMPO4 (M = Fe, Mn) nanostructures for high-power lithium batteries.

    PubMed

    Zhou, Yanping; Yang, Dan; Zeng, Yi; Zhou, Yan; Ng, Wun Jern; Yan, Qingyu; Fong, Eileen

    2014-10-15

    In this work, a novel waste-to-resource strategy to convert waste bacteria into a useful class of cathode materials, lithium metal phosphate (LiMPO4; M = Fe, Mn), is presented. Escherichia coli (E. coli) bacteria used for removing phosphorus contamination from wastewater are harvested and used as precursors for the synthesis of LiMPO4. After annealing, LiFePO4 and LiMnPO4 nanoparticles with dimensions around 20 nm are obtained. These particles are found to be enveloped in a carbon layer with a thickness around 3-5 nm, generated through the decomposition of the organic matter from the bacterial cell cytoplasm. The battery performance for the LiFePO4 is evaluated. A high discharge capacity of 140 mAh g(-1) at 0.1 C with a flat plateau located at around 3.5 V is obtained. In addition, the synthesized particles display excellent stability and rate capabilities. Even under a high C rate of 10 C, a stable discharge capacity of 75.4 mAh g(-1) can still be achieved. PMID:24930375

  17. Hydrothermal synthesis, evolution, and electrochemical performance of LiMn0.5Fe0.5PO4 nanostructures.

    PubMed

    Xiang, Wei; Zhong, Yan-Jun; Ji, Jun-Yi; Tang, Yan; Shen, HuiHui; Guo, Xiao-Dong; Zhong, Ben-He; Dou, Shi Xue; Zhang, Zhi-Ye

    2015-07-28

    LiMn0.5Fe0.5PO4 (LMFP) materials are synthesized by the hydrothermal approach in an organic-free and surfactant-free aqueous solution. The phase and morphological evolution of the material intermediates at different reaction temperatures and times are characterized by XRD, SEM and TEM, respectively. The results show that during temperature increase, the solubility product (Ksp) of the precursors (Li3PO4, Fe3(PO4)2 and (Mn,Fe)3(PO4)2) is the decisive parameter for the precipitation processes. Once the temperature locates at the range of 100-110 °C, the unstable precursors dissolve quickly and then LMFP nuclei are formed, followed by a dissolution-reprecipitation process. As the reaction progresses, the primary particles self-aggregate to form rod or plate particles to reduce the overall surface energy through oriented attachment (OA) and the Ostwald ripening (OR) mechanism. Moreover, the resultant concentration of the precursor significantly affects the crystal size of LMFP by altering the supersaturation degree of solution at the nucleation stage. The carbon coated LMFP nanostructure synthesized at 0.6 mol L(-1) (resultant concentration of PO4(3-)) delivers discharge capacities of 155, 100 and 81 mA h g(-1) at 0.1, 5 and 20 C rate, respectively. The understanding of nanostructural evolution and its influence on the electrochemical performance will pave a way for a high-performance LMFP cathode. PMID:26119980

  18. Variation of spin–orbit coupling and related properties in skyrmionic system Mn{}_{1{--}x}Fe x Ge

    NASA Astrophysics Data System (ADS)

    Kanazawa, N.; Shibata, K.; Tokura, Y.

    2016-04-01

    We report a systematic study of the magnetic and magnetotransport properties in skyrmionic compounds Mn{}1-xFe x Ge. Helical-spin or skyrmion orders are formed in all the compositions, which allows us to study electron band-filling dependence of those periodically-winding spin textures. Magnetization characteristics reflect the variation in Dzyaloshinskii–Moriya interaction or spin–orbit coupling with chemical composition, typically as a change in the critical magnetic field. This tunable spin–orbit coupling enables control of skyrmion formation, such as its size, helicity and topology. Anomalous Hall effect in Mn{}1-xFe x Ge can also be a good measure of the strength of spin–orbit coupling. Anomalous Hall conductivity {σ }{xy}A={S}HM is moderately temperature-dependent, obeying the magnetization variation, except for those at low temperatures in FeGe accompanied by skew contribution. The constancy of anomalous Hall coefficient S H against temperature manifests that the contribution from reciprocal space Berry phase induced by spin–orbit coupling is dominant in anomalous Hall conductivity. Strength of Dzyaloshinskii–Moriya interaction and anomalous Hall coefficient show a similar tendency in their band-filling dependence. Spin–orbit coupling plays a fundamental role behind both of the chiral magnetism and spin-dependent transport phenomena in this system.

  19. Itinerant Antiferromagnetism in FeMnP0.8Si0.2

    SciTech Connect

    Sales, Brian C.; Susner, Michael A.; Conner, Benjamin S.; Yan, Jiaqiang Q.; May, Andrew F.

    2015-09-25

    Compounds based on the Fe2P structure have continued to attract interest because of the interplay between itinerant and localized magnetism in a noncentrosymmetric crystal structure, and because of the recent developments of these materials for magnetocaloric applications. We report the growth and characterization of millimeter-sized single crystals of FeMnP0.8Si0.2 with the Fe2P structure. Single-crystal x-ray diffraction, magnetization, resistivity, and Hall and heat capacity data are reported. The crystals exhibit itinerant antiferromagnetic order below 158 K with no hint of ferromagnetic behavior in the magnetization curves and with the spins ordered primarily in the ab plane. The room-temperature resistivity is close to the Ioffe-Regel limit for a metal. Single-crystal x-ray diffraction indicates a strong preference for Mn to occupy the larger pyramidal 3g site. The cation site preference in the as-grown crystals and the antiferromagnetism were not changed after high-temperature anneals and a rapid quench to room temperature

  20. Theory of nonequilibrium segregation in an Fe-Mn-Ni ternary alloy and a ductile-brittle-ductile transition

    SciTech Connect

    Heo, N.H.

    1996-07-01

    In an Fe-8Mn-7Ni ternary alloy, age-hardened by coherently formed face-centered tetragonal MnNi intermetallic compounds within the matrix, a modeling based on a regular solution model is performed to formulate the nonequilibrium grain boundary segregation behaviors of the alloying elements, followed by a ductile-brittle-ductile transition in the alloy. An equation is derived representing the segregation kinetics. It is confirmed from the calculations that the segregation behaviors of the elements are directly controlled by the precipitation reaction in the matrix. The nonequilibrium segregation behaviors are characterized by time-temperature diagrams, which show maximum segregation levels of the elements in an intermediate aging time and temperature range. The calculated results explain theoretically and semiquantitatively the relationship between the nonequilibrium segregation of the elements and the ductile-brittle-ductile transition.

  1. Alloy Design, Combinatorial Synthesis, and Microstructure-Property Relations for Low-Density Fe-Mn-Al-C Austenitic Steels

    NASA Astrophysics Data System (ADS)

    Raabe, D.; Springer, H.; Gutierrez-Urrutia, I.; Roters, F.; Bausch, M.; Seol, J.-B.; Koyama, M.; Choi, P.-P.; Tsuzaki, K.

    2014-09-01

    We present recent developments in the field of austenitic steels with up to 18% reduced mass density. The alloys are based on the Fe-Mn-Al-C system. Here, two steel types are addressed. The first one is a class of low-density twinning-induced plasticity or single phase austenitic TWIP (SIMPLEX) steels with 25-30 wt.% Mn and <4-5 wt.% Al or even <8 wt.% Al when naturally aged. The second one is a class of κ-carbide strengthened austenitic steels with even higher Al content. Here, κ-carbides form either at 500-600°C or even during quenching for >10 wt.% Al. Three topics are addressed in more detail, namely, the combinatorial bulk high-throughput design of a wide range of corresponding alloy variants, the development of microstructure-property relations for such steels, and their susceptibility to hydrogen embrittlement.

  2. Ab Initio Construction of Magnetic Phase Diagrams in Alloys: The Case of Fe(1-x)Mn(x)Pt.

    PubMed

    Pujari, B S; Larson, P; Antropov, V P; Belashchenko, K D

    2015-07-31

    A first-principles approach to the construction of concentration-temperature magnetic phase diagrams of metallic alloys is presented. The method employs self-consistent total energy calculations based on the coherent potential approximation for partially ordered and noncollinear magnetic states and is able to account for competing interactions and multiple magnetic phases. Application to the Fe(1-x)Mn(x)Pt "magnetic chameleon" system yields the sequence of magnetic phases at T=0 and the c-T magnetic phase diagram in good agreement with experiment, and a new low-temperature phase is predicted at the Mn-rich end. The importance of non-Heisenberg interactions for the description of the magnetic phase diagram is demonstrated. PMID:26274437

  3. Temperature-induced martensite in magnetic shape memory Fe{sub 2}MnGa observed by photoemission electron microscopy

    SciTech Connect

    Jenkins, Catherine; Scholl, Andreas; Kainuma, R.; Elmers, Hans-Joachim; Omori, Toshihiro

    2012-01-18

    The magnetic domain structure in single crystals of a Heusler shape memory compound near the composition Fe{sub 2}MnGa was observed during phase transition by photoelectron emission microscopy at Beamline 11.0.1.1 of the Advanced Light Source. The behavior is comparable with recent observations of an adaptive martensite phase in prototype Ni{sub 2}MnGa, although the pinning in the recent work is an epitaxial interface and in this work the e ective pinning plane is a boundary between martensitic variants that transform in a self-accommodating way from the single crystal austenite phase present at high temperatures. Temperature dependent observations of the twinning structure give information as to the coupling behavior between the magnetism and the structural evolution.

  4. Synthesis and characterization of Mn0.5Zn0.5Fe2O4 and Fe3O4 nanoparticle ferrofluids for thermo-electric conversion

    NASA Astrophysics Data System (ADS)

    Sansom, C. L.; Jones, P.; Dorey, R. A.; Beck, C.; Stanhope-Bosumpim, A.; Peterson, J.

    2013-06-01

    Ferrofluids containing nanoparticles of Mn0.5Zn0.5Fe2O4 (MZ5) and Fe3O4 (magnetite) have been examined as potential thermal transport media and energy harvesting materials. The ferrofluids were synthesized by chemical co-precipitation and characterized by EDX to determine composition and by TEM to determine particle size and agglomeration. A range of particle coatings and carrier fluids were used to complete the fluid preparation. Commercially available ferrofluids were tested in custom built rigs to demonstrate both thermal pumping (for waste heat removal applications) and power induction (for power conversion and energy harvesting applications). The results indicate that simple ferrofluids possess the necessary properties to remove waste heat, either into thermal storage or for conversion to electrical power.

  5. Lattice dynamics in austenitic stainless steels Fe 18Cr 12Ni 2Mo and Fe 18Cr 16Ni 10Mn

    NASA Astrophysics Data System (ADS)

    Rajevac, V.; Hoelzel, M.; Danilkin, S. A.; Hoser, A.; Fuess, H.

    2004-04-01

    Phonon dispersion curves of austenitic stainless steels Fe-18Cr-16Ni-10Mn and Fe-18Cr-12Ni-2Mo have been measured by triple-axis neutron spectroscopy. The data were analysed using Born-von Karman interactions as well as calculations including the contribution of conduction electrons on the lattice dynamics. An appropriate description of the experimental data was obtained by taking into account two-neighbour shells plus the contribution of the electron gas. The elastic constants and moduli obtained are close to reported results by ultrasonic studies on polycrystalline samples. The phonon densities of states in both systems calculated from the dispersion curves agree well with results obtained by time-of-flight neutron spectroscopy on polycrystalline samples. The Debye temperature THgr(T) shows a minimum around 40 K, similar to copper and nickel.

  6. Bi deficiency-tuned functionality in multiferroic Bi1-δFe0.95Mn0.05O3 films.

    PubMed

    Chen, Jingyi; Wang, Yao; Wang, Hui; Zhang, Shuangmei; Deng, Yuan

    2016-01-01

    Structural evolution and ferroelectric (FE)-to-antiferroelectric (AFE) transition behaviors were observed in Bi1-δFe0.95Mn0.05O3 (100)-textured films with a carefully controlled Bi deficiency concentration δ. Raman spectra revealed an orthorhombic structural transition induced by Mn substitution. The polarization-electric field hysteresis loops and capacitance-voltage loops of Bi1-δFe0.95Mn0.05O3 films clearly demonstrated antiferroelectric behavior with increasing δ. The responses of the domain structure of the Bi1-δFe0.95Mn0.05O3 film under positive and negative applied voltages directly suggested the coexistence of FE and AFE phases. The existence of (100) superstructure reflections and antiparallel displacements of the Bi atoms along the [100] direction observed by transmission electron microscopy unambiguously reveal the AFE phase. The chemical substitution-induced orthorhombic structural transition in BiFe0.95Mn0.05O3 film implies that as the δ concentration increases, the changes in Bi-O bonding and the stereochemical activity of Bi 6s lone pair affect both the ferroelectric distortion and the antiferrodistortive rotation and therefore drive the Bi1-δFe0.95Mn0.05O3 crystal lattice to form a PbZrO3-type orthorhombic phase with an AFE order. A continuing increase in Bi deficiency creates defect dipole complexes which produce an internal field leading to a preferred direction of the ferroelectric domain. The Bi deficiency in multiferroic BiFeO3 provides a new route by which to tune functionality. PMID:26775621

  7. Bi deficiency-tuned functionality in multiferroic Bi1-δFe0.95Mn0.05O3 films

    PubMed Central

    Chen, Jingyi; Wang, Yao; Wang, Hui; Zhang, Shuangmei; Deng, Yuan

    2016-01-01

    Structural evolution and ferroelectric (FE)-to-antiferroelectric (AFE) transition behaviors were observed in Bi1-δFe0.95Mn0.05O3 (100)-textured films with a carefully controlled Bi deficiency concentration δ. Raman spectra revealed an orthorhombic structural transition induced by Mn substitution. The polarization-electric field hysteresis loops and capacitance-voltage loops of Bi1-δFe0.95Mn0.05O3 films clearly demonstrated antiferroelectric behavior with increasing δ. The responses of the domain structure of the Bi1-δFe0.95Mn0.05O3 film under positive and negative applied voltages directly suggested the coexistence of FE and AFE phases. The existence of (100) superstructure reflections and antiparallel displacements of the Bi atoms along the [100] direction observed by transmission electron microscopy unambiguously reveal the AFE phase. The chemical substitution-induced orthorhombic structural transition in BiFe0.95Mn0.05O3 film implies that as the δ concentration increases, the changes in Bi-O bonding and the stereochemical activity of Bi 6s lone pair affect both the ferroelectric distortion and the antiferrodistortive rotation and therefore drive the Bi1-δFe0.95Mn0.05O3 crystal lattice to form a PbZrO3-type orthorhombic phase with an AFE order. A continuing increase in Bi deficiency creates defect dipole complexes which produce an internal field leading to a preferred direction of the ferroelectric domain. The Bi deficiency in multiferroic BiFeO3 provides a new route by which to tune functionality. PMID:26775621

  8. Bi deficiency-tuned functionality in multiferroic Bi1-δFe0.95Mn0.05O3 films

    NASA Astrophysics Data System (ADS)

    Chen, Jingyi; Wang, Yao; Wang, Hui; Zhang, Shuangmei; Deng, Yuan

    2016-01-01

    Structural evolution and ferroelectric (FE)-to-antiferroelectric (AFE) transition behaviors were observed in Bi1-δFe0.95Mn0.05O3 (100)-textured films with a carefully controlled Bi deficiency concentration δ. Raman spectra revealed an orthorhombic structural transition induced by Mn substitution. The polarization-electric field hysteresis loops and capacitance-voltage loops of Bi1-δFe0.95Mn0.05O3 films clearly demonstrated antiferroelectric behavior with increasing δ. The responses of the domain structure of the Bi1-δFe0.95Mn0.05O3 film under positive and negative applied voltages directly suggested the coexistence of FE and AFE phases. The existence of (100) superstructure reflections and antiparallel displacements of the Bi atoms along the [100] direction observed by transmission electron microscopy unambiguously reveal the AFE phase. The chemical substitution-induced orthorhombic structural transition in BiFe0.95Mn0.05O3 film implies that as the δ concentration increases, the changes in Bi-O bonding and the stereochemical activity of Bi 6s lone pair affect both the ferroelectric distortion and the antiferrodistortive rotation and therefore drive the Bi1-δFe0.95Mn0.05O3 crystal lattice to form a PbZrO3-type orthorhombic phase with an AFE order. A continuing increase in Bi deficiency creates defect dipole complexes which produce an internal field leading to a preferred direction of the ferroelectric domain. The Bi deficiency in multiferroic BiFeO3 provides a new route by which to tune functionality.

  9. Growth kinetics of grain boundary allotriomorphs of proeutectoid ferrite in Fe-C-Mn-X{sub 2} alloys

    SciTech Connect

    Tanaka, T.; Aaronson, H.I.; Enomoto, M.

    1995-03-01

    The parabolic rate constant for the thickening of grain boundary ferrite allotriomorphs at the faces of austenite grain boundaries was measured as a function of isothermal transformation temperature in three Fe-C-X{sub 1}-X{sub 2} alloys where X{sub 1} is Mn and X{sub 2} is successively Si, Ni, and Co. The results were compared with the predictions of the local equilibrium model for multi-component systems and with those derived from the theory of growth under paraequilibrium conditions. The distribution of Mn and Si in ferrite and austenite in the Fe-C-Mn-Si alloy was also measured as a function of reaction temperature with transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The observed temperature below which alloying element partition ceased was in good agreement with the local equilibrium model. Whereas the parabolic rate constant for thickening was considerably larger than the amount predicted by this theory in the alloying element diffusion-controlled regime, the opposite was true in the carbon diffusion-controlled regime. Similarly, the calculated paraequilibrium constant was usually considerably larger than that measured experimentally. Synergistic enhancements of the effects of Mn and X{sub 2} in diminishing thickening kinetics were observed for each X{sub 2}. The time-temperature-transformation (TTT) curves for the beginning of transformation were calculated from a modified Cahn analysis for the overall kinetics of grain-boundary-nucleated reactions using values of the nucleation rate and the parabolic growth rate constant computed from various models and compared with experimentally determined TTT curves.

  10. Aluminum Deoxidation Equilibria in Liquid Iron: Part III—Experiments and Thermodynamic Modeling of the Fe-Mn-Al-O System

    NASA Astrophysics Data System (ADS)

    Paek, Min-Kyu; Do, Kyung-Hyo; Kang, Youn-Bae; Jung, In-Ho; Pak, Jong-Jin

    2016-06-01

    Deoxidation equilibria in high-Mn- and high-Al-alloyed liquid steels were studied over the entire Fe-Mn-Al composition range by both experiments and thermodynamic modeling. Effect of Mn on the Al deoxidation equilibria in liquid iron was measured by the different experimental techniques depending on the Al content. In order to confirm the reproducibility of the experimental results, the deoxidation experiments were carried out reversibly from high oxygen state by addition of Al as a deoxidizer, and from low oxygen state by addition of Fe2O3 or MnO as an oxygen source. For the Al-rich side, CaO flux was added on top of liquid iron in order to remove suspended Al2O3 inclusions in the melt. Based on the present experimental result and available critically evaluated literature data, the Al deoxidation equilibria in Fe-Mn-Al-O liquid alloy were thermodynamically modeled. The Modified Quasichemical Model was used in order to take into account a strong short-range ordering of atoms in molten state. Deoxidation equilibria and inclusion stability diagram for entire Fe-Mn-Al melt were successfully reproduced by the present model.

  11. Ferromagnetism and Nonmetallic Transport of Thin-Film α-FeSi>2mn> : A Stabilized Metastable Material

    SciTech Connect

    Cao, Guixin; Singh, D. J.; Zhang, X. -G.; Samolyuk, German; Qiao, Liang; Parish, Chad; Jin, Ke; Zhang, Yanwen; Guo, Hangwen; Tang, Siwei; Wang, Wenbin; Yi, Jieyu; Cantoni, Claudia; Siemons, Wolter; Payzant, E. Andrew; Biegalski, Michael; Ward, T. Z.; Mandrus, David; Stocks, G. M.; Gai, Zheng

    2015-04-07

    The epitaxially stabilized metallic α-FeSi>2mn> thin films on Si(001) were grown using pulsed laser deposition. While the bulk material of α-FeSi>2mn> is a high temperature metastable phase and nonmagnetic, the thin film is stabilized at room temperature and shows unusual electronic transport and magnetic properties due to strain modification. The transport renders two different conducting states with a strong crossover at 50 K accompanied by an onset of ferromagnetism as well as a substantial magnetocaloric effect and magnetoresistance. These experimental results are discussed in terms of the unusual electronic structure of α-FeSi>2mn> obtained within density functional calculations and Boltzmann transport calculations with and without strain. Our findings provide an example of a tailored material with interesting physics properties for practical applications.

  12. Comparative Studies of Spinel MnFe2O4 Nanostructures: Structural, Morphological, Optical, Magnetic and Catalytic Properties.

    PubMed

    Jacintha, A Mary; Manikandan, A; Chinnaraj, K; Antony, S Arul; Neeraja, P

    2015-12-01

    Spinel MnFe2O4 nanostructures with two different morphologies such as nanoflakes (NFs) and nanoparticles (NPs) were synthesized by a simple microwave-assisted combustion (MACM) and conventional combustion (CCM) methods respectively. Powder X-ray diffraction (XRD) study showed that the samples have pure cubic spinel phase and the average crystallite size is found to be 15.13 ± 2 nm and 24.38 ± 13 nm for NFs and NPs respectively. The calculated lattice parameter values of the samples NFs and NPs are 8.476 and 8.474 Å respectively. The morphology of the samples was recorded using high resolution scanning electron microscope (HR-SEM) analysis and was found that nanoflakes and nanoparticles morphologies by MACM and CCM methods respectively. Energy dispersive X-ray (EDX) results showed that the composition of the elements was relevant as expected from these combustion methods. The optical properties of the as-prepared nanostructures were also investigated by UV-Visible Diffuse Reflectance Spectroscopy (DRS) and Photoluminescence (PL) Spectroscopy. The energy band gap (E(g)) of the sample NFs is 1.78 eV, whereas the sample NPs has 1.75 eV. The magnetic properties were investigated using the Vibrating Sample Magnetometer (VSM) at room temperature and the hysteresis loops confirmed the super-paramagnetic behavior for both samples with saturation magnetization (M(s)) values in the range of 59.29 ± 11 and 66.78 ± 06 emu/g for the samples NFs and NPs respectively. The oxidation of benzyl alcohol into benzaldehyde reached a maximum of 87.65% for MnFe2O4 NFs, whereas for MnFe2O4 NPs, the conversion was only 69.43% with 100% selectivity. PMID:26682405

  13. Effects of strain amplitude and temperature on the damping capacity of an Fe-19Mn alloy with different microstructures

    SciTech Connect

    Huang Shuke; Zhou Danchen; Liu Jianhui; Teng Jin; Li Ning; Wen Yuhua

    2010-11-15

    The influences of strain amplitude (10{sup -5}-10{sup -4}) and temperature (25 deg. C-500 deg. C) on the internal friction of a cold-drawn and solution treated Fe-19Mn alloy were investigated. The internal friction was measured using reversal torsion pendulum and multifunction internal friction equipment. The microstructure was observed using scanning electron microscopy. The phase transformation temperatures were determined using differential scanning calorimetry. The results indicated that the internal friction of the solution treated alloy was related to strain amplitude, which could be explained using the movement of Shockley partial dislocations (bowing out and breaking away). But the internal friction of the cold-drawn alloy was independent of strain amplitude because of high density dislocations formed by cold forming. Moreover, when the temperature was changed between 25 deg. C and 500 deg. C, the internal friction of the cold-drawn alloy increased slowly from 25 deg. C to 375 deg. C, and then increased quickly from 375 deg. C to 500 deg. C. However, for the solution treated alloy, there was an internal friction peak at about 210 deg. C in the heating process (from 25 deg. C to 500 deg. C), and there was another internal friction peak at about 150 deg. C in the cooling process. These peaks could be explained using the heat-assisted movement of dislocations. - Research Highlights: {yields}Internal friction of solution treated Fe-19Mn alloy is related to strain amplitude. {yields}Internal friction of cold-drawn Fe-19Mn alloy is independent of strain amplitude. {yields}IF of cold-drawn alloy increases from RT to 500 deg. C. {yields}There is an IF peak of solution treated alloy in heating and cooling process separately. {yields}The results can be explained using the movement of dislocations.

  14. Precipitation sensitivity to alloy composition in Fe-Cr-Mn austenitic steels developed for reduced activation for fusion application

    SciTech Connect

    Maziasz, P.J.; Klueh, R.L.

    1988-01-01

    Special austenitic steels are being designed in which alloying elements like Mo, Nb, and Ni are replaced with Mn, W, V, Ti, and/or Ta to reduce the long-term radioactivity induced by fusion reactor irradiation. However, the new steels still need to have properties otherwise similar to commercial steels like type 316. Precipitation strongly affects strength and radiation-resistance in austenitic steels during irradiation at 400--600/degree/C, and precipitation is also usually quite sensitive to alloy composition. The initial stage of development was to define a base Fe-Cr-Mn-C composition that formed stable austenite after annealing and cold-working, and resisted recovery or excessive formation of coarse carbide and intermetallic phases during elevated temperature annealing. These studies produced a Fe-12Cr-20Mn-0.25C base alloy. The next stage was to add the minor alloying elements W, Ti, V, P, and B for more strength and radiation-resistance. One of the goals was to produce fine MC precipitation behavior similar to the Ti-modified Fe-Cr-Ni prime candidate alloy (PCA). Additions of Ti+V+P+B produced fine MC precipitation along network dislocations and recovery/recrystallization resistance in 20% cold worked material aged at 800/degree/C for 166h, whereas W, Ti, W+Ti, or Ti+P+B additions did not. Addition of W+Ti+V+P+B also produced fine MC, but caused some sigma phase formation and more recrystallization as well. 29 refs., 14 figs., 9 tabs.

  15. Mössbauer studies on Mn substituted CoFe2O4/SiO2 nanocomposites synthesized by sol-gel method

    NASA Astrophysics Data System (ADS)

    Hua, Jie; Liu, Yang; Wang, Li; Feng, Ming; Zhao, Jialong; Li, Haibo

    2016-03-01

    Mn-substituted CoFe2O4 nanoparticles dispersed in SiO2 matrix (Co1-xMnxFe2O4/SiO2) were synthesized by a sol-gel method. The effects of Mn2+ content and annealing temperature on their structural and magnetic properties as well as cation distribution were studied in detail by X-ray diffraction, vibrating sample magnetometer and Mössbauer spectroscopy at room temperature. The results show that the Co1-xMnxFe2O4 in the samples annealed at above 700 °C exhibits cubic spinel structure. The lattice constant of Co1-xMnxFe2O4 nanoparticles increases with increasing Mn2+ content because of the substitution of Co2+ ion with a small ionic radius by Mn2+ ion with a relatively large ionic radius and most of Mn2+ ions tend to substitute Co2+ ions at octahedral B sites. The saturation magnetization, coercivity and hyperfine fields for Co1-xMnxFe2O4/SiO2 nanocomposites increase with increasing Mn2+ content when x≤0.2, and then decrease for higher Mn2+ content, these changes are strongly dependent on the cation distribution. Furthermore, with increasing annealing temperature, the crystallite size, saturation magnetization and coercivity of the samples increase, the sample transfers from the mixed state of superparamagnetic and magnetic order to the completely magnetic order and Mn2+ ions migrate from the tetrahedral A sites to octahedral B sites.

  16. Geometric and Electronic Structure of the Mn(IV)Fe(III) Cofactor in Class Ic Ribonucleotide Reductase: Correlation to the Class Ia Binuclear Non-Heme Iron Enzyme

    PubMed Central

    Kwak, Yeonju; Jiang, Wei; Dassama, Laura M.K.; Park, Kiyoung; Bell, Caleb B.; Liu, Lei V.; Wong, Shaun D.; Saito, Makina; Kobayashi, Yasuhiro; Kitao, Shinji; Seto, Makoto; Yoda, Yoshitaka; Alp, E. Ercan; Zhao, Jiyong; Bollinger, J Martin; Krebs, Carsten; Solomon, Edward I.

    2013-01-01

    The class Ic ribonucleotide reductase (RNR) from Chlamydia trachomatis (Ct) utilizes a Mn/Fe hetero-binuclear cofactor, rather than the Fe/Fe cofactor found in the β (R2) subunit of the class Ia enzymes, to react with O2. This reaction produces a stable MnIVFeIII cofactor that initiates a radical, which transfers to the adjacent α (R1) subunit and reacts with the substrate. We have studied the MnIVFeIII cofactor using nuclear resonance vibrational spectroscopy (NRVS) and absorption (Abs) / circular dichroism (CD) / magnetic CD (MCD) / variable temperature, variable field (VTVH) MCD spectroscopies to obtain detailed insight into its geometric/electronic structure and to correlate structure with reactivity; NRVS focuses on the FeIII, whereas MCD reflects the spin-allowed transitions mostly on the MnIV. We have evaluated 18 systematically varied structures. Comparison of the simulated NRVS spectra to the experimental data shows that the cofactor has one carboxylate bridge, with MnIV at the site proximal to Phe127. Abs/CD/MCD/VTVH MCD data exhibit 12 transitions that are assigned as d-d, and oxo and OH− to metal charge transfer (CT) transitions. Assignments are based on MCD/Abs intensity ratios, transition energies, polarizations, and derivative-shaped pseudo-A term CT transitions. Correlating these results with TD-DFT calculations defines the MnIVFeIII cofactor as having a µ-oxo, µ-hydroxo core and a terminal hydroxo ligand on the MnIV. From DFT calculations, the MnIV at site 1 is necessary to tune the redox potential to a value similar to that of the tyrosine radical in class Ia RNR, and the OH− terminal ligand on this MnIV provides a high proton affinity that could gate radical translocation to the α (R1) subunit. PMID:24131208

  17. Cycling of trace metals (Mn, Fe, Mo, U, V, Cr) in deep pore waters of intertidal flat sediments

    NASA Astrophysics Data System (ADS)

    Beck, Melanie; Dellwig, Olaf; Schnetger, Bernhard; Brumsack, Hans-Jürgen

    2008-06-01

    Trace metals (Mn, Fe, Mo, U, Cr, V) were studied in pore waters of an intertidal flat located in the German Wadden Sea. The study system is an example of a permeable tidal flat system where pore water exchange is affected by tidal driven pressure gradients besides diffusion. Permanently installed in situ samplers were used to extract pore waters down to 5 m depth throughout one year. The samplers were either located close to the tidal flat margin or in central parts of the tidal flat. Despite dynamic sedimentological and hydrological conditions, the general trends with depth in deep tidal flat pore waters are remarkably similar to those observed in deep sea environments. Rates of trace metal cycling must be comparably large in order to maintain the observed pore water profiles. Trace metals further show similar general trends with depth close to the margin and in central parts of the tidal flat. Seasonal sampling revealed that V and Cr vary concurrent with seasonal changes in dissolved organic carbon (DOC) concentration. This effect is most notable close to the tidal flat margin where sulphate, DOC, and nutrients vary with season down to some metres depth. Seasonal variations of Mn, Fe, Mo, and U are by contrast limited to the upper decimetres of the sediment. Their seasonal patterns depend on organic matter supply, redox stratification, and particulate matter deposited on sediment surfaces. Pore water sampling within one tidal cycle provides evidence for pore water advection in margin sediments. During low tide pore water flow towards the creekbank is generated by a hydraulic gradient suggesting that deep pore waters may be seeping out of creekbank sediments. Owing to the enrichment of specific elements like Mn in pore water compared to sea water, seeping pore waters may have an impact on the chemistry of the open water column. Mass balance calculations reveal that the impact of deep pore waters on the Mn budget in the open water column is below 4%. Mn deep pore

  18. Mechanism of selenite removal by a mixed adsorbent based on Fe-Mn hydrous oxides studied using X-ray absorption spectroscopy.

    PubMed

    Chubar, Natalia; Gerda, Vasyl; Szlachta, Małgorzata

    2014-11-18

    Selenium cycling in the environment is greatly controlled by various minerals, including Mn and Fe hydrous oxides. At the same time, such hydrous oxides are the main inorganic ion exchangers suitable (on the basis of their chemical nature) to sorb (toxic) anions, separating them from water solutions. The mechanism of selenite adsorption by the new mixed adsorbent composed of a few (amorphous and crystalline) phases [maghemite, MnCO3, and X-ray amorphous Fe(III) and Mn(III) hydrous oxides] was studied by extended X-ray absorption fine structure (EXAFS) spectroscopy [supported by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) data]. The complexity of the porous adsorbent, especially the presence of the amorphous phases of Fe(III) and Mn(III) hydrous oxides, is the main reason for its high selenite removal performance demonstrated by batch and column adsorption studies shown in the previous work. Selenite was bound to the material via inner-sphere complexation (via oxygen) to the adsorption sites of the amorphous Fe(III) and Mn(III) oxides. This anion was attracted via bidentate binuclear corner-sharing coordination between SeO3(2-) trigonal pyramids and both FeO6 and MnO6 octahedra; however, the adsorption sites of Fe(III) hydrous oxides played a leading role in selenite removal. The contribution of the adsorption sites of Mn(III) oxide increased as the pH decreased from 8 to 6. Because most minerals have a complex structure (they are seldom based on individual substances) of various crystallinity, this work is equally relevant to environmental science and environmental technology because it shows how various solid phases control cycling of chemical elements in the environment. PMID:25325790

  19. Processing, Microstructure and Mechanical Properties of the CrMnFeCoNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Gludovatz, Bernd; George, Easo P.; Ritchie, Robert O.

    2015-08-01

    Equiatomic multi-component alloys, referred to variously as high-entropy alloys, multi-component alloys, or compositionally complex alloys in the literature, have recently received significant attention in the materials science community. Some of these alloys can display a good combination of mechanical properties. Here, we review recent work on the processing, microstructure and mechanical properties of one of the first and most studied high-entropy alloys, namely the single-phase, face-centered cubic alloy CrMnFeCoNi, with emphasis on its excellent damage tolerance (strength with toughness) in the temperature range from room temperature down to liquid nitrogen temperature.

  20. Short-range magnetic correlations and spin dynamics in the paramagnetic regime of (Mn,Fe)2(P,Si)

    NASA Astrophysics Data System (ADS)

    Miao, X. F.; Caron, L.; Cedervall, J.; Gubbens, P. C. M.; Dalmas de Réotier, P.; Yaouanc, A.; Qian, F.; Wildes, A. R.; Luetkens, H.; Amato, A.; van Dijk, N. H.; Brück, E.

    2016-07-01

    The spatial and temporal correlations of magnetic moments in the paramagnetic regime of (Mn,Fe ) 2(P ,Si ) have been investigated by means of polarized neutron diffraction and muon-spin relaxation techniques. Short-range magnetic correlations are present at temperatures far above the ferromagnetic transition temperature (TC). This leads to deviations of paramagnetic susceptibility from Curie-Weiss behavior. These short-range magnetic correlations extend in space, slow down with decreasing temperature, and finally develop into long-range magnetic order at TC.