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Sample records for cr mn fe

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  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. 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.

  12. 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.

  13. 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)

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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).

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  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. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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).

  19. First-principles study on the magnetism and electronic structure in 3d transition metal (X=Sc, V, Cr, Mn, Fe, Ni, Cu) doped CoO

    NASA Astrophysics Data System (ADS)

    Liu, R. X.; Wang, X. C.; Chen, G. F.; Yang, B. H.

    2016-03-01

    We have studied the electronic structure and magnetism of the single transitional metal element X=Sc, V, Cr, Mn, Fe, Ni, Cu-doped CoO systems by first-principles calculations. At X=Sc, Cr, Cu, the binding energy of the doped systems is lower than pure CoO, suggesting that these systems are energetically stable. In the Sc, V, Cr, Mn, Fe, Ni, Cu-doped 2×2×2 CoO supercells, the total magnetic moments are 3.03, 5.64, 6.80, 7.70, 6.93, 2.30 and 1.96 μB, respectively. At X=Cr and Fe, the doped CoO systems are half-metallic with a high spin polarization. The large magnetic moment and high spin polarization in the Cr and Fe-doped CoO are important for the design of the spintronic devices.

  20. 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.

  1. 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.

  2. Electronic structure, magnetism, and antisite disorder in CoFeCrGe and CoMnCrAl quaternary Heusler alloys

    SciTech Connect

    Enamullah, .; Venkateswara, Y.; Gupta, Sachin; Varma, Manoj Raama; Singh, Prashant; Suresh, K. G.; Alam, Aftab

    2015-12-10

    In this study, we present a combined theoretical and experimental study of two quaternary Heusler alloys CoFeCrGe (CFCG) and CoMnCrAl (CMCA), promising candidates for spintronics applications. Magnetization measurement shows the saturation magnetization and transition temperature to be 3 μB, 866 K and 0.9 μB, 358 K for CFCG and CMCA respectively. The magnetization values agree fairly well with our theoretical results and also obey the Slater-Pauling rule, a prerequisite for half metallicity. A striking difference between the two systems is their structure; CFCG crystallizes in fully ordered Y-type structure while CMCA has L21 disordered structure. The antisite disorder adds a somewhat unique property to the second compound, which arises due to the probabilistic mutual exchange of Al positions with Cr/Mn and such an effect is possibly expected due to comparable electronegativities of Al and Cr/Mn. Ab initio simulation predicted a unique transition from half metallic ferromagnet to metallic antiferromagnet beyond a critical excess concentration of Al in the alloy.

  3. Electronic structure, magnetism, and antisite disorder in CoFeCrGe and CoMnCrAl quaternary Heusler alloys

    DOE PAGESBeta

    Enamullah, .; Venkateswara, Y.; Gupta, Sachin; Varma, Manoj Raama; Singh, Prashant; Suresh, K. G.; Alam, Aftab

    2015-12-10

    In this study, we present a combined theoretical and experimental study of two quaternary Heusler alloys CoFeCrGe (CFCG) and CoMnCrAl (CMCA), promising candidates for spintronics applications. Magnetization measurement shows the saturation magnetization and transition temperature to be 3 μB, 866 K and 0.9 μB, 358 K for CFCG and CMCA respectively. The magnetization values agree fairly well with our theoretical results and also obey the Slater-Pauling rule, a prerequisite for half metallicity. A striking difference between the two systems is their structure; CFCG crystallizes in fully ordered Y-type structure while CMCA has L21 disordered structure. The antisite disorder adds amore » somewhat unique property to the second compound, which arises due to the probabilistic mutual exchange of Al positions with Cr/Mn and such an effect is possibly expected due to comparable electronegativities of Al and Cr/Mn. Ab initio simulation predicted a unique transition from half metallic ferromagnet to metallic antiferromagnet beyond a critical excess concentration of Al in the alloy.« less

  4. 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.

  5. 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.

  6. Increasing the ordering temperatures in oxalate-based 3D chiral magnets: the series [Ir(ppy)2(bpy)][M(II)M(III)(ox)3] x 0.5 H2O (M(II)M(III) = MnCr, FeCr, CoCr, NiCr, ZnCr, MnFe, FeFe); bpy = 2,2'-bipyridine; ppy = 2-phenylpyridine; ox = oxalate dianion).

    PubMed

    Clemente-León, Miguel; Coronado, Eugenio; Gómez-García, Carlos J; Soriano-Portillo, Alejandra

    2006-07-10

    The synthesis, structure, and physical properties of a novel series of oxalate-based bimetallic magnets obtained by using the Ir(ppy)2(bpy)]+ cation as a template of the bimetallic [M(II)M(III)(ox)3]- network are reported. The compounds can be formulated as [Ir(ppy)2(bpy)][M(II)Cr(III)(ox)3] x 0.5 H2O (M(II) = Ni, Mn, Co, Fe, and Zn) and [Ir(ppy)2(bpy)]-[M(II)Fe(III)(ox)3] x 0.5 H2O (M(II) = Fe, Mn) and crystallize in the chiral cubic space group P4(1)32 or P4(3)32. They show the well-known 3D chiral structure formed by M(II) and M(III) ions connected through oxalate anions with [Ir(ppy)2(bpy)]+ cations and water molecules in the holes left by the oxalate network. The M(II)Cr(III) compounds behave as soft ferromagnets with ordering temperatures up to 13 K, while the Mn(II)Fe(III) and Fe(II)Fe(III) compounds behave as a weak ferromagnet and a ferrimagnet, respectively, with ordering temperatures of 31 and 28 K. These values represent the highest ordering temperatures so far reported in the family of 3D chiral magnets based on bimetallic oxalate complexes. PMID:16813431

  7. Nano-twin Mediated Plasticity in Carbon-containing FeNiCoCrMn High Entropy Alloys

    SciTech Connect

    Wu, Zhenggang; Bei, Hongbin; Parish, Chad M

    2015-06-14

    Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. Moreover, the effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. We found that these materials can be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (~70% at 77 K and ~40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys.

  8. Nano-twin Mediated Plasticity in Carbon-containing FeNiCoCrMn High Entropy Alloys

    DOE PAGESBeta

    Wu, Zhenggang; Bei, Hongbin; Parish, Chad M

    2015-06-14

    Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. Moreover, the effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. We found that these materials canmore » be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (~70% at 77 K and ~40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys.« less

  9. Influence of Plasma Remelting on the Microstructure and Cavitation Resistance of Arc-Sprayed Fe-Mn-Cr-Si Alloy

    NASA Astrophysics Data System (ADS)

    Pukasiewicz, A. G. M.; Alcover, P. R. C.; Capra, A. R.; Paredes, R. S. C.

    2014-01-01

    Surface remelting is an important technique for modifying the microstructure of thermally sprayed coatings as it reduces the porosity and promotes a metallurgical bond between substrate and coating. Many studies have been carried out in the field of materials selection and surface engineering in an attempt to reduce cavitation damage. In this work, an Fe-Mn-Cr-Si alloy was deposited by arc spraying and then remelted by a plasma-transferred arc process. The base metal was a soft martensitic stainless steel. The influence of remelting current on coating and base metal microstructure and cavitation resistance was studied. The use of a lower mean current and a pulsed arc reduced the thickness of the heat-affected zone. In specimens remelted with constant arc current, dendrites were aligned parallel to the path followed by the plasma torch; while in those remelted with a pulsed plasma arc, the alignment of the microstructure was disrupted. The use of a higher peak current in pulsed-current plasma transferred arc remelting reduced mass loss due to cavitation. Fe-Mn-Cr-Si coatings exhibited cavitation-induced hardening, with martensite formation during cavitation tests. This transformation helps to increase the cavitation resistance of the remelted coating compared with the soft martensitic stainless steel base metal.

  10. Magnetic properties of Sm2(Fe0.95M0.05)17Nx (M=Cr and Mn) anisotropic coarse powders with high coercivity

    NASA Astrophysics Data System (ADS)

    Ito, Mikio; Majima, Kazuhiko; Shimuta, Toru; Katsuyama, Shigeru; Nagai, Hiroshi

    2002-09-01

    Sm2(Fe0.95Cr0.05)17Nx and Sm2(Fe0.95Mn0.05)17Nx coarse powders 10-70 mum in size were synthesized by crushing mother alloy ingots into 32-74 mum in particle size and subsequent nitrogenation at 748 K in a flowing mixed gas of 60 vol % H2+40 vol % NH3. The effects of Cr or Mn substitution for Fe on the nitrogenation rate, magnetic properties, and microstructure of the Sm2Fe17Nx hard magnetic material were investigated. Cr and Mn substitution was quite effective for accelerating nitrogenation. When the powders were nitrogenated beyond x=3, amorphous phase formation was observed as the x value increased. The magnetic properties of the nitrogenated powders were significantly improved by Cr and Mn substitution, and these powders also possessed a satisfactory magnetic anisotropy. The maximum coercivity in this study, 0.59 MA/m, was obtained for the Sm2(Fe0.95Mn0.05)17N5.0 powder in spite of its large particle size. The high coercivity of the coarse powders was caused by a cell-like microstructure composed of fine 2-17 crystalline grains 20-30 nm in size surrounded by an amorphous phase.

  11. Effect of one-step recrystallization on the grain boundary evolution of CoCrFeMnNi high entropy alloy and its subsystems.

    PubMed

    Chen, Bo-Ru; Yeh, An-Chou; Yeh, Jien-Wei

    2016-01-01

    In this study, the grain boundary evolution of equiatomic CoCrFeMnNi, CoCrFeNi, and FeCoNi alloys after one-step recrystallization were investigated. The special boundary fraction and twin density of these alloys were evaluated by electron backscatter diffraction analysis. Among the three alloys tested, FeCoNi exhibited the highest special boundary fraction and twin density after one-step recrystallization. The special boundary increment after one-step recrystallization was mainly affected by grain boundary velocity, while twin density was mainly affected by average grain boundary energy and twin boundary energy. PMID:26923713

  12. Effect of one-step recrystallization on the grain boundary evolution of CoCrFeMnNi high entropy alloy and its subsystems

    PubMed Central

    Chen, Bo-Ru; Yeh, An-Chou; Yeh, Jien-Wei

    2016-01-01

    In this study, the grain boundary evolution of equiatomic CoCrFeMnNi, CoCrFeNi, and FeCoNi alloys after one-step recrystallization were investigated. The special boundary fraction and twin density of these alloys were evaluated by electron backscatter diffraction analysis. Among the three alloys tested, FeCoNi exhibited the highest special boundary fraction and twin density after one-step recrystallization. The special boundary increment after one-step recrystallization was mainly affected by grain boundary velocity, while twin density was mainly affected by average grain boundary energy and twin boundary energy. PMID:26923713

  13. 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

  14. Effect of Pre-straining on the Shape Recovery of Fe-Mn-Si-Cr-Ni Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Maji, Bikas C.; Krishnan, Madangopal; Verma, Amit; Basu, R.; Samajdar, I.; Ray, Ranjit K.

    2015-02-01

    The effect of pre-straining on the shape recovery behavior of Fe-14Mn-6Si-9Cr-5Ni (wt pct) shape memory alloy (SMA) has been studied. The shape recovery associated with the reverse ɛ martensitic transformation, i.e., ɛ → γ, was characterized by dilatometry using specimens which were pre-strained to different extent (0 to 14 pct). Dilatometric studies revealed that in Fe-Mn-Si-Cr-Ni SMA, the shape recovery takes place in two stages: (i) in the first stage, the unpinned fraction of stress-induced ɛ martensite reverts back to parent phase γ in the temperature regime of 353 K to 653 K (80 °C to 380 °C) and (ii) in the second stage the remaining "pinned" ɛ martensite is unpinned by the decomposition of deformation-induced α' martensite in the temperature range of 743 K to 893 K (470 °C to 620 °C). The amount of recovery in the first stage decreases with pre-strain, whereas it increases in the second stage. The ɛ → γ transformation finish temperature, A f, increases with increase in pre-strain amount, though the reverse transformation start temperature, A S, remains unaffected. Microstructural characterization revealed that the amount of deformation-induced α' martensite depends on the mode of straining and the crystallographic texture of the starting material. The reversion of α' martensite is seen to occur by the precipitation of Fe5Ni3Si2-type intermetallic π-phase within these plates.

  15. Characterization of the surface of Fe-19Mn-18Cr-C-N during heat treatment in a high vacuum - An XPS study

    SciTech Connect

    Zumsande, K.; Weddeling, A.; Hryha, E.; Huth, S.; Nyborg, L.; Weber, S.; Krasokha, N.; Theisen, W.

    2012-09-15

    Nitrogen-containing CrMn austenitic stainless steels offer evident benefits compared to CrNi-based grades. The production of high-quality parts by means of powder metallurgy could be an appropriate alternative to the standard molding process leading to improved properties. The powder metallurgical production of CrMn austenitic steel is challenging on account of the high oxygen affinity of Mn and Cr. Oxides hinder the densification processes and may lower the performance of the sintered part if they remain in the steel after sintering. Thus, in evaluating the sinterability of the steel Fe-19Mn-18Cr-C-N, characterization of the surface is of great interest. In this study, comprehensive investigations by means of X-ray photoelectron spectroscopy and scanning electron microscopy combined with energy dispersive X-ray spectroscopy were performed to characterize the surface during heat treatment in a high vacuum. The results show a shift of oxidation up to 600 Degree-Sign C, meaning transfer of oxygen from the iron oxide layer to Mn-based particulate oxides, followed by progressive reduction and transformation of the Mn oxides into stable Si-containing oxides at elevated temperatures. Mass loss caused by Mn evaporation was observed accompanied by Mn oxide decomposition starting at 700 Degree-Sign C. - Highlights: Black-Right-Pointing-Pointer Surface characterization by means of XPS, SEM, and EDX analyses. Black-Right-Pointing-Pointer Heat treatment of a high CrMn powder. Black-Right-Pointing-Pointer Transfer of oxygen from the iron oxide layer to manganese-based particulate oxides. Black-Right-Pointing-Pointer Progressive reduction of Mn oxides. Black-Right-Pointing-Pointer Transformation of the Mn oxides into stable Si-containing oxides.

  16. Weathering and precipitation after meteorite impact of Ni, Cr, Fe, Ca and Mn in K-T boundary clays from Stevns Klint

    NASA Astrophysics Data System (ADS)

    Miyano, Yumiko; Yoshiasa, Akira; Tobase, Tsubasa; Isobe, Hiroshi; Hongu, Hidetomo; Okube, Maki; Nakatsuka, Akihiko; Sugiyama, Kazumasa

    2016-05-01

    Ni, Cr, Fe, Ca and Mn K-edge XANES and EXAFS spectra were measured on K-T boundary clays from Stevns Klint in Denmark. According to XANES spectra and EXAFS analyses, the local structures of Ni, Cr and Fe in K-T boundary clays is similar to Ni(OH)2, Cr2O3 and FeOOH, respectively. It is assumed that the Ni, Cr and Fe elements in impact related glasses is changing into stable hydrate and oxide by the weathering and diagenesis at the surface of the Earth. Ca in K-T boundary clays maintains the diopside-like structure. Local structure of Ca in K-T clays seems to keep information on the condition at meteorite impact. Mn has a local structure like MnCO3 with divalent state. It is assumed that the origin on low abundant of Mn in the Fe-group element in K-T clays was the consumption by life activity and the diffusion to other parts.

  17. Magnetism, structures and stabilities of cluster assembled TM@Si nanotubes (TM = Cr, Mn and Fe): a density functional study.

    PubMed

    Dhaka, Kapil; Bandyopadhyay, Debashis

    2016-08-01

    The present study reports transition metal (TM = Cr, Mn and Fe) doped silicon nanotubes with tunable band structures and magnetic properties by careful selection of cluster assemblies as building blocks using the first-principles density functional theory. We found that the transition metal doping and in addition, the hydrogen termination process can stabilize the pure silicon nanoclusters or cluster assemblies and then it could be extended as magnetic nanotubes with finite magnetic moments. Study of the band structures and density of states (DOS) of different empty and TM doped nanotubes (Type 1 to Type 4) show that these nanotubes are useful as metals, semiconductors, semi-metals and half-metals. These designer magnetic materials could be useful in spintronics and magnetic devices of nanoscale order. PMID:27430742

  18. 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

  19. Effect of hydrogen on internal friction and Young`s modulus of Fe-Cr-Mn austenitic stainless steel

    SciTech Connect

    Usui, Makoto; Asano, Shigeru

    1996-06-01

    The internal friction technique has so far been applied to studies on hydrogen behavior in iron and steel. The hydrogen cold-work peak is well known for pure iron and has also been observed in BCC iron alloys such as ferritic stainless steel and maraging steel. It provides important information about the hydrogen- dislocation interaction in the BCC iron lattice. Meanwhile, for FCC iron alloys such as austenitic stainless steel, another characteristic hydrogen internal friction peak has been found by authors` group and confirmed by several other investigators. In the present study, type 205 austenitic stainless steel (Fe-17Cr-15Mn) was chosen as a nickel-free FCC iron alloy, in which manganese is totally substituted for nickel in type 304 steel. This steel has an unstable FCC lattice as is the case of type 304 steel, in which hydrogen-induced phase transformation depends on the austenite stability. However, the present steel was confirmed to form the {var_epsilon}{sub H} phase after cathodic hydrogen charging in a similar manner to the stable FCC lattice of type 310 steel. In addition, the Fe-Cr-Mn alloy shows a marked anomaly in the temperature dependence of Young`s modulus: an abrupt drop near the Neel temperature T{sub N} and successive lowering below T{sub N}, as has been reported in the literature for some antiferromagnetic materials. The effect of hydrogen on Young`s modulus was studied by several investigators, but there was great inconsistency among their experimental results. The purpose of this paper is to confirm the hydrogen peak of internal friction in type 205 steel and to examine the effect of hydrogen on Young`s modulus of this steel.

  20. Multiferroic approach for Cr,Mn,Fe,Co,Ni,Cu substituted BaTiO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Verma, Kuldeep Chand; Kotnala, R. K.

    2016-05-01

    Multiferroic magnetoelectric (ME) at room temperature is significant for new design nano-scale spintronic devices. We have given a comparative study to report multiferroicity in BaTM0.01Ti0.99O3 [TM = Cr,Mn,Fe,Co,Ni,Cu (1 mol% each) substituted BaTiO3 (BTO)] nanoparticles. The TM ions influenced both nano-size and lattice distortion of Ti–O6 octahedra to the BTO. X ray diffraction study indicates that the dopant TM could influence lattice constants, distortion, tetragonal splitting of diffraction peaks (002/200) as well as peak shifting of diffraction angle in the BTO lattice. This can induce lattice strain which responsible to oxygen defects formation to mediate ferromagnetism. Also, the lattice strain effect could responsible to reduce the depolarization field of ferroelectricity and provide piezoelectric and magnetostrictive strains to enhance ME coupling. The size of BTO nanoparticles is varied in 13–51 nm with TM doping. The room temperature magnetic measurement indicates antiferromagnetic exchange interactions in BTO lattice with TM ions. The zero-field cooling and field cooling magnetic measurement at 500 Oe indicates antiferromagnetic to ferromagnetic transition. It also confirms that the substitution of Cr, Fe and Co into BTO could induce strong antiferromagnetic behavior. However, the substitutions of Mn, Ni and Cu have weak antiferromagnetic character. The temperature dependent dielectric measurements indicates polarization enhancement that influenced with both nano-size as well TM ions and exhibits ferroelectric phase transition with relaxor-like characteristics. Dynamic ME coupling is investigated, and the longitudinal ME voltage coefficient, α ME is equivalent to linear ME coupling coefficient, α (={\\varepsilon }{{o}}{\\varepsilon }{{r}}{α }{{ME}}) is also calculated.

  1. Hot Ductility Behaviors in the Weld Heat-Affected Zone of Nitrogen-Alloyed Fe-18Cr-10Mn Austenitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Moon, Joonoh; Lee, Tae-Ho; Hong, Hyun-Uk

    2015-04-01

    Hot ductility behaviors in the weld heat-affected zone (HAZ) of nitrogen-alloyed Fe-18Cr-10Mn austenitic stainless steels with different nitrogen contents were evaluated through hot tension tests using Gleeble simulator. The results of Gleeble simulations indicated that hot ductility in the HAZs deteriorated due to the formation of δ-ferrite and intergranular Cr2N particles. In addition, the amount of hot ductility degradation was strongly affected by the fraction of δ-ferrite.

  2. Exact ab initio transport coefficients in bcc Fe-X (X=Cr, Cu, Mn, Ni, P, Si) dilute alloys

    NASA Astrophysics Data System (ADS)

    Messina, Luca; Nastar, Maylise; Garnier, Thomas; Domain, Christophe; Olsson, Pär

    2014-09-01

    Defect-driven diffusion of impurities is the major phenomenon leading to formation of embrittling nanoscopic precipitates in irradiated reactor pressure vessel (RPV) steels. Diffusion depends strongly on the kinetic correlations that may lead to flux coupling between solute atoms and point defects. In this work, flux coupling phenomena such as solute drag by vacancies and radiation-induced segregation at defect sinks are systematically investigated for six bcc iron-based dilute binary alloys, containing Cr, Cu, Mn, Ni, P, and Si impurities, respectively. First, solute-vacancy interactions and migration energies are obtained by means of ab initio calculations; subsequently, self-consistent mean field theory is employed in order to determine the exact Onsager matrix of the alloys. This innovative multiscale approach provides a more complete treatment of the solute-defect interaction than previous multifrequency models. Solute drag is found to be a widespread phenomenon that occurs systematically in ferritic alloys and is enhanced at low temperatures (as for instance RPV operational temperature), as long as an attractive solute-vacancy interaction is present, and that the kinetic modeling of bcc alloys requires the extension of the interaction shell to the second-nearest neighbors. Drag occurs in all alloys except Fe(Cr); the transition from dragging to nondragging regime takes place for the other alloys around (Cu, Mn, Ni) or above (P, Si) the Curie temperature. As far as only the vacancy-mediated solute migration is concerned, Cr depletion at sinks is foreseen by the model, as opposed to the other impurities which are expected to enrich up to no less than 1000 K. The results of this study confirm the current interpretation of the hardening processes in ferritic-martensitic steels under irradiation.

  3. Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr18 FCC solid solution alloy

    SciTech Connect

    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 a 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.

  4. Thermodynamic Stability of Transition-Metal-Substituted LiMn2-x Mx O4 (M=Cr, Fe, Co, and Ni) Spinels.

    PubMed

    Lai, Chenying; Chen, Jiewei; Knight, James C; Manthiram, Arumugam; Navrotsky, Alexandra

    2016-07-01

    The formation enthalpies from binary oxides of LiMn2 O4 , LiMn2-x Crx O4 (x=0.25, 0.5, 0.75 and 1), LiMn2-x Fex O4 (x=0.25 and 0.5), LiMn2-x Cox O4 (x=0.25, 0.5, and 0.75) and LiMn1.75 Ni0.25 O4 at 25 °C were measured by high temperature oxide melt solution calorimetry and were found to be strongly exothermic. Increasing the Cr, Co, and Ni content leads to more thermodynamically stable spinels, but increasing the Fe content does not significantly affect the stability. The formation enthalpies from oxides of the fully substituted spinels, LiMnMO4 (M=Cr, Fe and Co), become more exothermic (implying increasing stability) with decreasing ionic radius of the metal and lattice parameters of the spinel. The trend in enthalpy versus metal content is roughly linear, suggesting a close-to-zero heat of mixing in LiMn2 O4 -LiMnMO4 solid solutions. These data confirm that transition-metal doping is beneficial for stabilizing these potential cathode materials for lithium-ion batteries. PMID:27017448

  5. Effects of anodic passivation on the constitution, stability and resistance to corrosion of passive film formed on an Fe-24Mn-4Al-5Cr alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Y. S.; Zhu, X. M.; Liu, M.; Che, R. X.

    2004-01-01

    The effects of anodic aging time and potential on the corrosion resistance, stability and constitution of the passive film formed on an Fe-24Mn-4Al-5Cr alloy in 50% HNO 3 solution were studied by using combined electrochemical measurements and Auger electron spectroscopic (AES)/X-ray photoelectron spectroscopic (XPS) analysis. In the anodic passive region, prolonged anodic aging time or increased passivating potential can induce better protective and stable properties of the passive film and better resistance to corrosion. With increasing aging time from 15 min to 5 h, the time required for the potential decay from the passive to active state increases from about 300 up to above 12,000 s, and the corrosion resistance in 1 mol l -1 Na 2SO 4 solution of Fe-24Mn-4Al-5Cr alloy, characterized by polarization curves, is superior to that of Fe-13% Cr-0.1% C stainless steel. AES and XPS analyses of the aging passive film show that these improvements of properties are related to modifications of the passive layer with time. The increase of resistance to corrosion is attributed to Al 2O 3 and Cr 2O 3 enrichment and oxides of Fe and Mn depletion in the passive film and a thickening of the effective barrier layer of oxides.

  6. Novel High-Speed High Pressure Torsion Technology for Obtaining Fe-Mn-Si-Cr Shape Memory Alloy Active Elements

    NASA Astrophysics Data System (ADS)

    Gurău, Gheorghe; Gurău, Carmela; Potecaşu, Octavian; Alexandru, Petrică; Bujoreanu, Leandru-Gheorghe

    2014-07-01

    This paper introduces an adapted high-speed high pressure torsion (HS-HPT) method of severe plastic deformation applied for obtaining shape memory alloy (SMA) active elements with revolution symmetry, able to develop axial displacement/force. Billets with circular crown forms were cut from Fe-28Mn-6Si-5Cr (mass%) SMA ingots and, by means of HS-HPT technology, were directly turned into modules, with truncated cone shell configurations. This process was performed, during time intervals of seconds, under the effect of high pressure (up to 1 GPa) cumulated with high rotation speed (hundreds of rotations per minute) applied on the active surfaces of sintered-carbide anvils, specially designed for this purpose. Due to pressure and friction, generated by rotation, the entire sample volume is heated and simultaneously deformed to final shape. During the process, microstructure fragmentation occurred enabling to obtain (ultra)fine grains and nanocrystalline areas, in spite of the heat developed by friction, which was removed by conduction at the contact surface between sample and anvils, before the occurrence of any recrystallization phenomena. When compressed between flat surfaces, the truncated cone modules developed a superelastic-like response, unique among Fe -Mn-Si base SMAs and, when heated in compressed state, they were able to develop either axial strokes or recovery forces by either free or constrained recovery shape memory effect (SME), respectively. By means of optical (OM) and scanning electron microscopy (SEM) marked structural changes caused by HT-HPT were revealed, along with fine and ultrafine crystalline grains. The presence of stress-induced ɛ-hexagonal close-packed ( hcp) martensite, together with nanocrystalline areas were confirmed by x-ray diffraction.

  7. Lunar highland rocks - Element partitioning among minerals. II - Electron microprobe analyses of Al, P, Ca, Ti, Cr, Mn and Fe in olivine

    NASA Technical Reports Server (NTRS)

    Smith, J. V.; Hansen, E. C.; Steele, I. M.

    1980-01-01

    Lunar olivines from anorthosites, granulitic impactites, and rocks in the Mg-rich plutonic trend were subjected to electron probe measurements for Al, P, Ca, Ti, Cr and Mn, which show that the FeO/MnO ratio for lunar olivines lies between 80 and 110 with little difference among the rock types. The low values of Ca in lunar olivines indicate slow cooling to subsolidus temperatures, with blocking temperatures of about 750 C for 67667 and 1000 C for 60255,73-alpha determined by the Finnerty and Boyd (1978) experiments. An important paradox is noted in the low Ti content of Fe-rich olivines from anorthosites, although both Ti and Fe tend to become enriched in liquid during fractional distillation. Except for Ca and Mn, olivine from anorthosites has lower minor element values than other rock types. Formation from a chemically distinct system is therefore implied.

  8. 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

  9. Electronic structures of the ferrimagnetic double-perovskites Sr2XReO6 (X = Cr, Mn, Fe, Ni) with the modified Becke-Johnson potential

    NASA Astrophysics Data System (ADS)

    Guo, San-Dong

    2015-04-01

    We investigate the electronic structures and magnetic properties of the ferrimagnetic double-perovskites Sr2XReO6 (X = Cr, Mn, Fe, Ni) by using Tran and Blaha's modified Becke and Johnson exchange potential. The calculated results show that Sr2XReO6 (X = Cr, Fe) are half-metals, and Sr2XReO6 (X = Mn, Ni) are insulators, which is in accordance with the experimental results. By using the ionic picture, we explain the trend in the density of states and total magnetic moment with X changing from Cr to Ni. We find that the insulating property is associated with X2 +, while the metallic character is associated with X3 +. The Re t2g splitting in the minority channel leads to insulativity of Sr2XReO6 (X = Mn, Ni), and the Re t2g splitting of Sr2MnReO6 is caused by lattice distortion, while Sr2NiReO6's splitting is due to the heavier atomic mass of Ni. When spin-orbit coupling is included, the spin polarization of Sr2XReO6 (X = Cr, Fe) drifts off 100%, and the related gaps of Sr2XReO6 (X = Mn, Ni) become narrow. The spin-orbit coupling results in a significant increase in the total magnetic moment due to an unquenched Re orbital moment. Our calculated energy band structures show that Sr2MnReO6 is a spin gapless semiconductor, which can realize fully polarized spin-down electrons and spin-up holes.

  10. Valence Stabilization, Mixed Crystal Chemistry, and Electronic Transitions in Tetrahedral Oxo and Hydroxo Cr(IV), Mn(V), and Fe(VI) Clusters: A Theoretic Investigation

    NASA Astrophysics Data System (ADS)

    Atanasov, M.; Adamsky, H.; Eifert, K.

    1997-01-01

    Ab initioHartree-Fock SCF (HF-SCF) and multiconfiguration complete active space SCF (CSCF) calculations have been carried out on tetrahedral M(OH) 4zand MO 4z' model clusters ( M, z, z': Cr IV,0, -4; Mn V, 1, -3; Fe VI, 2, -2) in their 3A2ground state and in selected triplet and singlet ligand field and charge transfer excited states. Ground state orbital energies and charge distributions supplemented with calculations using asemiempirical approach (Jørgensen) help characterize the stabilization of Cr IV, Mn V, and Fe VIin terms of competing ionic and covalent forces. The crucial role of the Madelung energy in stabilizing these unusual oxidation states is emphasized. Frozen orbitals as obtained by state averaging over d2triplet and singlet states are used to compare results from Hartree-Fock and ligand field treatments. Calculations using these orbitals show that interelectronic repulsion parameters in tetra-oxo coordinated Cr IV, Mn V, and Fe VIare considerably reduced compared to their free ionic values. Charge transfer states are found to further modify energy levels of d2type, leading to an effective lowering of Coulomb repulsion parameters in the order of the e2, e1t21, and t22strong field configurations. Theories of isomorphic substitution for ionic solids are not applicable for the systems under consideration. Comparison between available structural and spectral data shows that Cr IV, Mn V, and Fe VIions in dilute mixed crystals with isovalent tetrahedral host ions, such as Si IV, P V, and S VI, assume geometries close to those known for stoichiometric phases with CrO 44-, MnO 43-, and FeO 42-tetrahedra. Covalent contributions to the lattice energy from guest ( d2) and host tetrahedra are additive, and mixing enthalpies are small or negligible, allowing for continuous solid solutions even when guest and host ions, such as Mn Vand P V, Fe VIand S VI, differ considerably in their size.

  11. Electronic and magnetic properties of a new diluted magnetic semiconductor Li(Zn,TM)As (TM:V, Cr, Mn, Fe, Co and Ni)

    NASA Astrophysics Data System (ADS)

    Tao, H. L.; Lin, L.; Zhang, Z. H.; He, M.; Song, B.

    2016-07-01

    First-principles calculations were performed to study electronic structures and magnetic properties of transition metal (TM) doped LiZnAs system. V, Mn, Fe and Co doped LiZnAs preferred anti-ferromagnetic states while no magnetisms were found for Cr and Ni-doped LiZnAs system. In contrast, V/Li, Cr/Li, Mn/Li, Fe/Li and Co/Li codoped LiZnAs preferred ferromagnetic couplings between the TM atoms other than the anti-ferromagnetic states. Thus off-stoichiometry of Li is very essential for the preparation of ferromagnetic LiZnAs materials. For Ni/Li-codoped LiZnAs, anti-ferromagnetic is more stable, which is resulted from the through-bond spin polarization mechanism.

  12. Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

    PubMed Central

    Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X.; George, Easo P.; Yu, Qian; Ritchie, Robert O.

    2015-01-01

    Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ∼1 GPa, excellent ductility (∼60–70%) and exceptional fracture toughness (KJIc>200 MPa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. We further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip. PMID:26647978

  13. Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

    SciTech Connect

    Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X.; George, Easo P.; Yu, Qian; Ritchie, Robert O.

    2015-12-09

    Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ~1 GPa, excellent ductility (~60–70%) and exceptional fracture toughness (KJIc>200M Pa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. In conclusion, we further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip.

  14. Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

    DOE PAGESBeta

    Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X.; George, Easo P.; Yu, Qian; Ritchie, Robert O.

    2015-12-09

    Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ~1 GPa, excellent ductility (~60–70%) and exceptional fracture toughness (KJIc>200M Pa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening andmore » ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. In conclusion, we further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip.« less

  15. Thermal Behavior of Mechanically Alloyed Powders Used for Producing an Fe-Mn-Si-Cr-Ni Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Pricop, B.; Söyler, U.; Lohan, N. M.; Özkal, B.; Bujoreanu, L. G.; Chicet, D.; Munteanu, C.

    2012-11-01

    In order to produce shape memory rings for constrained-recovery pipe couplings, from Fe-14 Mn-6 Si-9 Cr-5 Ni (mass%) powders, the main technological steps were (i) mechanical alloying, (ii) sintering, (iii) hot rolling, (iv) hot-shape setting, and (v) thermomechanical training. The article generally describes, within its experimental-procedure section, the last four technological steps of this process the primary purpose of which has been to accurately control both chemical composition and the grain size of shape memory rings. Details of the results obtained in the first technological step, on raw powders employed both in an initial commercial state and in a mixture state of commercial and mechanically alloyed (MA) powders, which were subjected to several heating-cooling cycles have been reported and discussed. By means of differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and X-ray diffraction (XRD), the thermal behaviors of the two sample powders have been analyzed. The effects of the heating-cooling cycles, on raw commercial powders and on 50% MA powders, respectively, were argued from the point of view of specific temperatures and heat variations, of elemental diffusion after thermal cycling and of crystallographic parameters, determined by DSC, SEM, and XRD, respectively.

  16. Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi.

    PubMed

    Zhang, ZiJiao; Mao, M M; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X; George, Easo P; Yu, Qian; Ritchie, Robert O

    2015-01-01

    Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ∼ 1 GPa, excellent ductility (∼ 60-70%) and exceptional fracture toughness (KJIc>200 MPa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. We further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip. PMID:26647978

  17. Temperature dependencies of the elastic moduli and thermal expansion coefficient of an equiatomic, single-phase CoCrFeMnNi high-entropy alloy

    DOE PAGESBeta

    Laplanche, G.; Gadaud, P.; Horst, O.; Otto, F.; Eggeler, G.; George, E.

    2014-11-15

    The equiatomic CoCrFeMnNi alloy is now regarded as a model face-centered cubic single-phase high-entropy alloy. Consequently, determination of its intrinsic properties such as the temperature dependencies of elastic moduli and thermal expansion coefficient are important to improve understanding of this new class of material. Lastly, these temperature dependencies were measured over a large temperature range (200–1270 K) in this study.

  18. The Mechanical and Corrosion Behaviors of As-cast and Re-melted AlCrCuFeMnNi Multi-Component High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Soare, Vasile; Mitrica, Dumitru; Constantin, Ionut; Popescu, Gabriela; Csaki, Ioana; Tarcolea, Mihai; Carcea, Ioan

    2015-04-01

    A multi-component AlCrCuFeMnNi high-entropy alloy, prepared by vacuum induction melting, was investigated for structural, mechanical, and corrosion characteristics, before and after the re-melting process. Optical microscopy analysis revealed a dendritic solidification behavior. The interdendritic area contains two main phases and occasionally small hard phases. The re-melting process produced a finer dendritic structure, with rounded dendrites and reduced interdendritic hard phases. The SEM-EDAX analysis showed that the dendrite region contains a Widmanstatten type of structure and are composed of Cr-Fe rich phases, whereas the interdendrite region contains Cu and Mn rich phases. XRD analysis revealed two disordered BCC type A2 structures with high Cr and Fe content and an FCC A12 type of structure for the Cu and Mn rich interdendritic phase. The lattice constants, determined by X-ray diffraction, are 2.87 and 2.91 Å for the A2 phases and 3.67 Å for A1 phase. The Vickers micro hardness increased with the homogeneity of the alloy, having a maximum value of 4370 MPa for the re-melted sample. Corrosion tests carried out in 3.5 wt pct sodium chloride aerated solution indicated that the corrosion resistance improved with the re-melting process, being 1.5 to 2 times better than that of 304 stainless steel.

  19. Density functional theory study of Mo-doped M@(BN)48 (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) clusters

    NASA Astrophysics Data System (ADS)

    Liang, Wenjuan; Jia, Jianfeng; Lv, Jin; Wu, Haishun

    2016-03-01

    The structure and magnetic properties of Mo-doped M@(BN)48 (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) clusters were calculated at BPW91/LanL2DZ level. The magnetic nature of the clusters M@(BN)48 significantly changed when doping with Mo atom, except for Co@(BN)48. Only the magnetic moment for the CrMo@(BN)48 cluster was decreased to zero. Thus, M@(BN)48 clusters can be selected as the model system to detect Mo atom by the change of the magnetic moment.

  20. Magnetic and Mössbauer study of Mg0.9Mn0.1Cr x Fe2-x O4 ferrites

    NASA Astrophysics Data System (ADS)

    Elzain, M.; Widatallah, H.; Gismelseed, A.; Bouziane, K.; Yousif, A.; Al Rawas, A.; Al-Omari, I.; Sellai, A.

    The ferrites Mg0.9Mn0.1Cr x Fe2-x O4 (O≤x≤0.9) were prepared using the conventional double sintering method. The XRD showed that the samples maintain a single spinel cubic phase. The Mössbauer measurements were carried out at room and liquid nitrogen temperatures. From the area ratios of the A and B sites, it was found that the Fe cation population of the A and B sites decreases in proportion to Cr concentration. The contact hyperfine fields at the A and B sites were found to decrease with increasing Cr contents. This was found to be in approximate agreement with the results of magnetization measurement. The distributions of Mg and Mn cations versus Cr concentration were also determined using the Mössbauer and magnetization results. The Curie temperatures were determined and found to agree with the reported values. As the Cr contents increases the relative magnetization, was found to increase at low temperatures and decreases at higher temperatures.

  1. Characterization of a New Fe-C-Mn-Si-Cr Bearing Alloy: Tempered Martensite Embrittlement Susceptibility

    NASA Astrophysics Data System (ADS)

    Marcomini, J. B.; Goldenstein, H.

    2014-03-01

    Bearing steels containing 1% C and 1.5% Cr have been the usual material of choice for machine components submitted to rolling and contact fatigue, for more than a century. As a rule these steels are quenched from the intercritical gamma + carbide region and tempered at low temperatures (less than 250 °C), in order to retain the high hardness of the martensite matrix and avoid the tempered martensite embrittlement (TME) phenomena, which compromise the toughness of steels tempered at higher temperatures. A new high Si alloy was developed for bearing applications. The inhibiting and/or retarding effect of Si on the kinetics of cementite precipitation leads to a higher temperature of TME occurrence, allowing the tempering of the components at a higher temperature, thus increasing the toughness, without sacrificing the high hardness. The purpose of this work was to confirm the TME resistance of the new alloy. In this work, impact tests result for commercial SAE/AISI 52100 (0.25% Si) and for a modified 52100 containing 1.74% Si, were compared. No evidence of TME was detected on the Si-modified steel.

  2. Influence of the addition of transition metals (Cr, Zr, Mo) on the properties of MnOx-FeOx catalysts for low-temperature selective catalytic reduction of NOx by Ammonia.

    PubMed

    Zhou, Changcheng; Zhang, Yaping; Wang, Xiaolei; Xu, Haitao; Sun, Keqin; Shen, Kai

    2013-02-15

    The co-precipitation and citric acid methods were employed to prepare MnO(x)-FeO(x) catalysts for the low-temperature selective catalytic reduction (SCR) of NO(x) by ammonia. It was found that the Mn-Fe (CP) sample obtained from the co-precipitation method, which exhibited low crystalline of manganese oxides on the surface, high specific surface area and abundant acid sites at the surface, had better catalytic activity. The effects of doping different transition metals (Mo, Zr, Cr) in the Mn-Fe (CP) catalysts were further investigated. The study suggested that the addition of Cr can obviously reduce the take-off temperature of Mn-Fe catalyst to 90°C, while the impregnation of Zr and Mo raised that remarkably. The texture and micro-structure analysis revealed that for the Cr-doped Mn-Fe catalysts, the active components had better dispersion with less agglomeration and sintering and the largest BET surface specific area. In situ FTIR study indicated that the addition of Cr can increase significantly the surface acidity, especially, the Lewis acid sites, and promote the formation of the intermediate -NH(3)(+). H(2)-TPR results confirmed the better low-temperature redox properties of Mn-Fe-Cr. PMID:23142012

  3. Optical and dielectric properties of BiMn1-xAExO3 (AE=Cr, Fe, Co, and Zn; x=0, 0.1) nanoparticles synthesized by sol-gel technique

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Neha; Gaur, Anurag; Yadav, Kamlesh

    2015-08-01

    BiMnO3 is a multiferroic material which means that it shows both the ferroelectricity and ferromagnetism. Present study deals about the study of optical and dielectric properties of BiMnO3 and doped BiMnO3. The magnetic and non magnetic ions are introduced as dopants in place of Mn sublattice, BiMn1-xAExO3 (where x=0.1 and AE= Cr, Fe, Co, and Zn). We have synthesized nanoparticles of BiMnO3 and BiMn1-xAExO3 (where x=0.1 and AE= Cr, Fe, Co, and Zn) by sol-gel technique. Optical properties have been studied by using FTIR (Fourier Transform Infrared) spectroscopy. FTIR (Fourier Transform Infrared Spectroscopy) analysis showed that there is an increase in the band gap of BiMn1-xAExO3 (where x=0.1 and AE= Cr, Fe, Co, and Zn) than pure BiMnO3 for the samples synthesized by sol-gel technique. The increase in band gap on doping is due to the radius to charge ratio. Ferroelectric hysteresis loop confirms the presence of ferroelectricity in BiMnO3. From the ferroelectric hysteresis loop the parameters like coericivity, saturation polarization and remanant polarization has been calculated. Nanoparticles of BiMnO3 have applications in memory storage devices.

  4. Microstructures and Mechanical Performance of Plasma-Nitrided Al0.3CrFe1.5MnNi0.5 High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Tang, Wei-Yeh; Chuang, Ming-Hao; Lin, Su-Jien; Yeh, Jien-Wei

    2012-07-01

    This study investigates the effect of plasma nitriding at 798 K (525 °C) on microstructures and the mechanical performance of Al0.3CrFe1.5MnNi0.5 high-entropy alloys (HEAs) obtained using different cast and wrought processing. All the alloys can be well nitride, with a thickness of around 80 μm, and attain a peak hardness level around Hv 1300 near the surface. The main nitride phases are CrN, AlN, and (Mn, Fe)4N. Those of the substrates are bcc, fcc, Al-, and Ni-rich B2 precipitates, and ρ phase. Their relative amounts depend on the prior processing and also change under the heat treatment during nitriding. The formation of ρ phase during nitriding could in-situ harden the substrate to attain the suitable level required for wear applications. This gives the advantage in simplifying the processing for making a wear-resistance component or a mold since austenitizing, quench hardening, and tempering required for steels such as SACM and SKD steels are no longer required and final finishing can be accomplished before nitriding. Nitrided Al0.3CrFe1.5MnNi0.5 samples have much better wear resistance than un-nitrided ones by 49 to 80 times and also exhibit superior adhesive wear resistance to conventional nitrided alloys: nitriding steel SACM-645 (AISI 7140), 316 stainless steel, and hot-mold steel SKD-61 (AISI H13) by 22 to 55 times depending on prior processing. The superiority is due to the fact that the present nitrided alloys possess a much thicker highly hardened layer than the conventional alloys.

  5. Structural, spectral, DFT, pH-metric and biological studies on Cr(III), Mn(II) and Fe(III) complexes of dithione heterocyclic thiosemicarbazide ligand

    NASA Astrophysics Data System (ADS)

    Abu El-Reash, Gaber M.; El-Gammal, Ola A.; El-Gamil, Mohammed M.

    2013-03-01

    Cr(III), Mn(II) and Fe(III) complexes derived from the quadruple potential dithione heterocyclic thiosemicarbazide ligand (H2PET) have been prepared and characterized by conventional techniques. The isolated complexes were assigned the formulae, [Cr(HPET)(H2O)2Cl2]·3H2O, [Mn(HPET)(H2O)Cl]2 and [Fe(HPET)(H2O)2Cl2]·H2O, respectively. IR data revealed that the ligand behaves as monobasic bidentate through (Cdbnd N)py and (Csbnd S) groups in both Cr(III) and Fe(III) complexes. In the binuclear Mn(II) complex, H2PET acts as NSNS monobasic tetradente via (Cdbnd N)py, (Csbnd S), (Cdbnd S) and the new azomethine, (Ndbnd C)* groups. An octahedral geometry for all complexes was proposed. The bond lengths, bond angles, HOMO, LUMO and dipole moment have been calculated by DFT using materials studio program to confirm the geometry of H2PET and its metal complexes. The ligand association constant and the stability constants of its complexes in addition to the thermodynamic parameters were calculated from pH metrically at 298, 308 and 318°K in 50% dioxane-water mixture, respectively. Also, the kinetic and thermodynamic parameters for the different thermal degradation steps of the complexes were determined by Coats-Redfern and Horowitz-Metzger methods. Moreover, the anti-oxidant (using ABTS and DPPH methods), anti-hemolytic, and cytotoxic activities of the compounds have been tested.

  6. Specific features of the electrical resistivity of half-metallic ferromagnets Co2 MeAl ( Me = Ti, V, Cr, Mn, Fe)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Perevozchikova, Yu. A.; Weber, H. W.; Marchenkov, V. V.

    2016-07-01

    The transport properties of half-metallic ferromagnetic Heusler alloys Co2 MeAl ( Me = Ti, V, Cr, Mn, Fe are transition 3 d metals) have been measured in the temperature range of 4-900 K. The specific features of the behavior of the resistivity have been considered in the framework of the two-current model of conductivity that takes into account the existence of the energy gap in the electronic spectra of the alloys near the Fermi level of one of electron subbands that differs in the spin direction.

  7. Influence of roll and solution treatment processing on shape memory effect of Fe-14Mn-5Si-9Cr-5Ni alloy

    SciTech Connect

    Li, C.L.; Jin, Z.H.

    1998-10-01

    The shape memory effect was studied in an Fe-14Mn-5Si-9Cr-5Ni alloy rerolled at 1123 K after hot rolling at 1423 K, followed by solution treatment at different temperatures. It was found that the alloy exhibits a maximum degree of shape recovery in a bending test and a complete recovery tensile strain of 2.2% in samples that were solution heated at 973 K for 600 s and then quenched in water. The rerolled processing at 1123 K after hot rolling at 1423 K and the microstructure under solution treatment state are important for obtaining a good shape memory effect in the alloy.

  8. A Novel Training-Free Processed Fe-Mn-Si-Cr-Ni Shape Memory Alloy Undergoing δ → γ Phase Transformation

    NASA Astrophysics Data System (ADS)

    Peng, Huabei; Wang, Gaixia; Du, Yangyang; Wang, Shanling; Chen, Jie; Wen, Yuhua

    2016-04-01

    We not only suppress the formation of twin boundaries but also introduce a high density of stacking faults by taking advantage of δ → γ phase transformation in a processed Fe-19.38Mn-5.29Si-8.98Cr-4.83Ni shape memory alloy. As a result, its shape memory effect is remarkably improved after heating at 1533 K (1260 °C) (single-phase region of δ ferrite) and air cooling due to δ → γ phase transformation.

  9. A Novel Training-Free Processed Fe-Mn-Si-Cr-Ni Shape Memory Alloy Undergoing δ → γ Phase Transformation

    NASA Astrophysics Data System (ADS)

    Peng, Huabei; Wang, Gaixia; Du, Yangyang; Wang, Shanling; Chen, Jie; Wen, Yuhua

    2016-07-01

    We not only suppress the formation of twin boundaries but also introduce a high density of stacking faults by taking advantage of δ → γ phase transformation in a processed Fe-19.38Mn-5.29Si-8.98Cr-4.83Ni shape memory alloy. As a result, its shape memory effect is remarkably improved after heating at 1533 K (1260 °C) (single-phase region of δ ferrite) and air cooling due to δ → γ phase transformation.

  10. Catalytic oxidation of 2-Propanol over (Cr,Mn,Fe)-Pt/gamma-Al2O3 bimetallic catalysts and modeling of experimental results by artificial neural networks.

    PubMed

    Niaei, A; Salari, D; Aghazadeh, F; Caylak, N; Sepehrianazar, A

    2010-01-01

    The catalytic activity of transition metals (Cr,Mn,Fe) supported on the Pt/gamma -Al(2)O(3) industrial catalyst was investigated to bring about the complete oxidation of 2-Propanol. Catalytic studies were carried out under atmospheric pressure in a fixed bed reactor. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and ICP-AES techniques were used to characterize a series of catalysts. Results showed that the Pt-Mn/gamma -Al(2)O(3) (3.88 wt.%Mn) at calcination temperature of 300 degrees C was the most promising catalyst based on activity, which might be contributed to the quantity of manganese loading, the favorable synergetic effects between Pt and Mn and the well-dispersed bimetallic phase. An artificial neural networks (ANN) model was developed to predict the performance of catalytic oxidation process over Pt-Mn/gamma -Al(2)O(3) bimetallic catalyst based on experimental data. For this purpose the Levenberg-Marquardt (LM) learning algorithm was employed to train the model by using laboratory experimental data. A comparison between the predicted results of the designed ANN model and experimental data was also conducted. The developed model can describe the catalytic oxidation over bimetallic catalysts under different conditions. PMID:20390890

  11. First-principles study of the inversion thermodynamics and electronic structure of Fe M2X4 (thio)spinels (M =Cr , Mn, Co, Ni; X =O , S)

    NASA Astrophysics Data System (ADS)

    Santos-Carballal, David; Roldan, Alberto; Grau-Crespo, Ricardo; de Leeuw, Nora H.

    2015-05-01

    Fe M2X4 spinels, with the magnetite structure, 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. We present here a computational study of the inversion thermodynamics and the electronic structure of these (thio)spinels for M =Cr ,Mn ,Co ,Ni , using calculations based on the density functional theory with on-site Hubbard corrections (DFT +U ). The analysis of the configurational free energies shows that different behavior is expected for the equilibrium cation distributions in these structures: FeC r2X4 and FeM n2S4 are fully normal, FeN i2X4 and FeC o2S4 are intermediate, and FeC o2O4 and FeM n2O4 are fully inverted. We have analyzed the role played by the size of the ions and by the crystal field stabilization effects in determining the equilibrium inversion degree. We also discuss how the electronic and magnetic structure of these spinels is modified by the degree of inversion, assuming that this could be varied from the equilibrium value. We have obtained electronic densities of states for the completely normal and completely inverse cation distribution of each compound. FeC r2X4 ,FeM n2X4 ,FeC o2O4 , and FeN i2O4 are half-metals in the ferrimagnetic state when Fe is in tetrahedral positions. When M is filling the tetrahedral positions, the Cr-containing compounds and FeM n2O4 are half-metallic systems, while the Co and Ni spinels are insulators. The Co and Ni sulfide counterparts are metallic for any inversion degree together with the inverse FeM n2S4 . Our calculations suggest that the spin filtering properties of the Fe M2X4 (thio)spinels could be modified via the control of the cation distribution through variations in the synthesis conditions.

  12. Chemical vapor deposition and electric characterization of perovskite oxides LaMO{sub 3} (M=Co, Fe, Cr and Mn) thin films

    SciTech Connect

    Ngamou, Patrick Herve Tchoua; Bahlawane, Naoufal

    2009-04-15

    Oxides with a perovskite structure are important functional materials often used for the development of modern devices. In view of extending their applicability, it is necessary to efficiently control their growth as thin films using technologically relevant synthesis methods. Pulsed spray evaporation CVD was used to grow several perovskite-type oxides on planar silicon substrates at temperatures ranging from 500 to 700 deg. C. The optimization of the process control parameters allows the attainment of the perovskite structure as a single phase. The electrical characterization using the temperature-dependent conductivity and thermopower indicates the p-type conduction of the grown films and shows a decreasing concentration of the charge carrier, mobility and band gap energy in the sequence LaCoO{sub 3}>LaMnO{sub 3}>LaCrO{sub 3}>LaFeO{sub 3}. The investigation of the electric properties of the obtained perovskite thin films shows the versatility of CVD as a method for the development of innovative devices. - Graphical abstract: We report a single step deposition of perovskite thin films LaMO{sub 3} (M: Co, Mn, Cr, Fe) using pulsed spray evaporation chemical vapor deposition. Electrical and thermopower properties, similar to these of bulk materials, could promote the development of modern thermoelectric devices based on thin films technology.

  13. Mössbauer and magnetic study of Mn2+- and Cr3+-substituted spinel magnesioferrites of the composition Mg1-xMnxFe2-2xCr2xO4

    NASA Astrophysics Data System (ADS)

    Widatallah, H. M.; Al-Omari, I. A.; Gismelseed, A. M.; Yassin, O. A.; Al-Rawas, A. D.; Elzain, M. E.; Yousif, A. A.; Osman, O. A.

    Chromium and manganese co-substituted spinel magnesioferrites of the composition Mg1-x Mn x Fe2-2 x Cr2x O4 (x=O.O, 0.1, 0.2, 0.3, and 0.5) were investigated with X-ray diffraction (XRD), Mössbauer spectroscopy and magnetic measurements. The cation distribution inferred suggests that Mn2+ and Cr3+ ions dominantly occupy the A- and Bsites respectively. The gradual decrease of the hyperfine fields and Curie temperatures with increasing x reflects a gradual weakening in the AB exchange interaction. Mössbauer data of the sample with x=0.5 is suggestive of cation clustering and/or superparamagnetism. The magnetization data is suggestive of Yafet-Kittel-type canted magnetism.

  14. Ternary titanium transition metal bismuthides Ti{sub 4}TBi{sub 2} with T = Cr, Mn, Fe, Co, and Ni

    SciTech Connect

    Richter, C.G.; Jeitschko, W.; Kuennen, B.; Gerdes, M.H.

    1997-11-01

    The title compounds were prepared by reaction of the elemental components and with the exception of the isotypic chromium compound their tetragonal V{sub 4}SiSb{sub 2}-type crystal structures (I4/mcm, Z = 4) were determined and refined from single-crystal X-ray data. Ti{sub 4}CrBi{sub 2}: a = 1051.6(l), c = 506.7(1) pm; Ti{sub 4}Mn Bi{sub 2}: a = 1049.1 (1), c = 497.8 (1) pm, R = 0.031 for 176 structure factors; Ti{sub 4}FeBi{sub 2}: a = 1048.6(1), c = 493.3(1) pm, R = 0.013 (274 F values); Ti{sub 4}CoBi{sub 2}: a = 1050.6(2), c = 488.2(1) pm, R = 0.038 (472 F values); Ti{sub 4}NiBi{sub 2}: a = 1055.4(1), c = 481.4(1) pm, R = 0.020(373 F values), and 14 variable parameters each. The compounds are isotypic with V{sub 4}SiSb{sub 2}, a structure which is isopointal with U{sub 6}Mn and closely related to the structures of W{sub 5}Si{sub 3} and TlTe. All atoms have high coordination numbers. Unusual features of the structure are channels formed solely by the bismuth atoms and linear chains of the heavier transition metal ions with bond distances varying between 253.3 (Cr-Cr) and 240.7 pm (Ni-Ni). The electrical conductivities of Ti{sub 4}TBi{sub 2} (T= Fe,Co, Ni)--determined with a four-probe technique for sintered polycrystalline samples between 4 K and room temperature--indicate metallic behavior. The magnetic susceptibilities of the five compounds were determined with a SQUID magnetometer. Ti{sub 4}CrBi{sub 2}, T{sub i}4FeBi{sub 2}, and Ti{sub 4}NiBi{sub 2} are Pauli paramagnetic. The magnetic susceptibilities of Ti{sub 4}MnBi{sub 2} and Ti{sub 4}CoBi{sub 2} are strongly temperature dependent. The evaluation of these data according to a modified Curie-Weiss law suggests that both compounds contain one unpaired electron per formula unit. A brief discussion of chemical bonding in these compounds leads to the conclusion that considerable Ti-Ti bonding must be present in these bismuthides, in spite of the fact that the shortest Ti-Ti bonds are as long as 299 pm.

  15. Investigation of magnetic properties and electronic structure of layered-structure borides AlT{sub 2}B{sub 2} (T=Fe, Mn, Cr) and AlFe{sub 2–x}Mn{sub x}B{sub 2}

    SciTech Connect

    Chai, Ping; Stoian, Sebastian A.; Tan, Xiaoyan; Dube, Paul A.; Shatruk, Michael

    2015-04-15

    The ternary phases AlT{sub 2}B{sub 2} (T=Fe, Mn, Cr) and quaternary phases AlFe{sub 2–x}Mn{sub x}B{sub 2} have been synthesized by arc-melting and characterized by powder X-ray diffraction, magnetic measurements, Mössbauer spectroscopy, and electronic band structure calculations. All the compounds adopt the AlFe{sub 2}B{sub 2}-type structure, in which infinite zigzag chains of B atoms are connected by Fe atoms into [Fe{sub 2}B{sub 2}] slabs that alternate with layers of Al atoms along the b axis. The magnetic measurements reveal that AlFe{sub 2}B{sub 2} is a ferromagnet with T{sub C}=282 K while AlMn{sub 2}B{sub 2} and AlCr{sub 2}B{sub 2} do not show magnetic ordering in the studied temperature range of 1.8–400 K. A systematic investigation of solid solutions AlFe{sub 2−x}Mn{sub x}B{sub 2} showed a non-linear change in the structural and magnetic behavior. The ferromagnetic ordering temperature is gradually decreased as the Mn content (x) increases. The Mössbauer spectra reveal the presence of non-magnetic (NM) and ferromagnetic (FM) spectral components in all Mn-containing samples, with the amount of NM fraction increasing as the Mn content increases. While for the AlFe{sub 2−x}Mn{sub x}B{sub 2} samples with x=0.0 and 0.4 the hyperfine splitting of the FM spectral component collapses at temperatures close to the Curie temperatures determined from the magnetic measurements, for the x=1.2 and 1.6 samples the FM fraction exhibits a sizable unquenched hyperfine splitting at room temperature, a finding that is inconsistent with the observed magnetic properties. Along with the increase in the amount of the NM fraction, this observation suggests formation of Fe-rich and Mn-rich regions in the structure of the solid solutions. Quantum-chemical calculations and crystal orbital Hamilton population analysis provide a clear explanation of the distinction in properties for this series of compounds and also reveal the importance of electronic factors in modifying the

  16. Composition Dependence of Phase Stability, Deformation Mechanisms, and Mechanical Properties of the CoCrFeMnNi High-Entropy Alloy System

    NASA Astrophysics Data System (ADS)

    Tasan, C. C.; Deng, Y.; Pradeep, K. G.; Yao, M. J.; Springer, H.; Raabe, D.

    2014-10-01

    The proposal of configurational entropy maximization to produce massive solid-solution (SS)-strengthened, single-phase high-entropy alloy (HEA) systems has gained much scientific interest. Although most of this interest focuses on the basic role of configurational entropy in SS formability, setting future research directions also requires the overall property benefits of massive SS strengthening to be carefully investigated. To this end, taking the most promising CoCrFeMnNi HEA system as the starting point, we investigate SS formability, deformation mechanisms, and the achievable mechanical property ranges of different compositions and microstructural states. A comparative assessment of the results with respect to room temperature behavior of binary Fe-Mn alloys reveals only limited benefits of massive SS formation. Nevertheless, the results also clarify that the compositional requirements in this alloy system to stabilize the face-centered cubic (fcc) SS are sufficiently relaxed to allow considering nonequiatomic compositions and exploring improved strength-ductility combinations at reduced alloying costs.

  17. Composition Dependence of Phase Stability, Deformation Mechanisms, and Mechanical Properties of the CoCrFeMnNi High-Entropy Alloy System

    NASA Astrophysics Data System (ADS)

    Tasan, C. C.; Deng, Y.; Pradeep, K. G.; Yao, M. J.; Springer, H.; Raabe, D.

    2014-09-01

    The proposal of configurational entropy maximization to produce massive solid-solution (SS)-strengthened, single-phase high-entropy alloy (HEA) systems has gained much scientific interest. Although most of this interest focuses on the basic role of configurational entropy in SS formability, setting future research directions also requires the overall property benefits of massive SS strengthening to be carefully investigated. To this end, taking the most promising CoCrFeMnNi HEA system as the starting point, we investigate SS formability, deformation mechanisms, and the achievable mechanical property ranges of different compositions and microstructural states. A comparative assessment of the results with respect to room temperature behavior of binary Fe-Mn alloys reveals only limited benefits of massive SS formation. Nevertheless, the results also clarify that the compositional requirements in this alloy system to stabilize the face-centered cubic (fcc) SS are sufficiently relaxed to allow considering nonequiatomic compositions and exploring improved strength-ductility combinations at reduced alloying costs.

  18. Acceleration of ordering transformation of a new Fe{sub 2}(Mn,Cr)Si Heusler-alloy film by very high frequency plasma irradiation process during radio frequency sputter deposition

    SciTech Connect

    Yoshimura, S.; Kobayashi, H.; Egawa, G.; Saito, H.; Ishida, S.

    2011-04-01

    A new Heusler alloy, Fe{sub 2}(Mn,Cr)Si, that is likely to have high spin polarization (P) and high damping constant ({alpha}) was proposed to obtain high magneto-resistance ratio and low spin torque noise in a magnetic read head with a current-perpendicular-to-plane (CPP) giant magneto-resistance (GMR) multilayer. A very high frequency (VHF) plasma irradiation process during radio frequency (RF) sputter deposition was investigated to form the highly ordered structure of the Heusler alloy film with low thermal treatment temperature. The main results are as follows: (1) P and magnetic moment of Fe{sub 2}(Mn{sub 0.5}Cr{sub 0.5})Si with an L2{sub 1} structure were estimated at 0.99 and 2.49 {mu}{sub B}/f.u., respectively, and {alpha} was also estimated to be larger compared with the case of Co{sub 2}MnSi, according to density of states (DOS) calculations. (2) The ordering (at least B2 structure) temperature of Fe{sub 2}(Mn{sub 0.6}Cr{sub 0.4})Si film decreased from 500 to 300 deg. C by using the VHF plasma irradiation process with optimized condition. (3) The surface roughness of Fe{sub 2}(Mn{sub 0.6}Cr{sub 0.4})Si film also reduced from 1.7 to 0.5 nm by using the VHF plasma irradiation process. It is found that the Fe{sub 2}(Mn,Cr)Si Heusler alloy and the VHF plasma irradiation process with optimized condition seems to be applicable for fabrication of high-performance magnetic read head with CPP-GMR device.

  19. Characterization of La2/3Ca1/3xMnO3 with Low Doping of Fe and Cr (abstract)

    NASA Astrophysics Data System (ADS)

    Giratá, D.; Quintero, D. L.; Arnache, O.; Hoffmann, A.

    2009-04-01

    We have characterized magnetization, transport, and structure of La2/3Ca1/3MnO3 thin films and bulk powder samples undoped and with low doping of 57Fe (1% and 3%) and Cr (6%, 7%, and 8%). The powder samples were synthesized by solid-state reaction and thin films grown on (100)-SrTiO3 STO, and (100)-LaAlO3 LAO single-crystal substrates by high O2 pressure (500 mTorr) using dc magnetron sputtering. We found changes in the values of the magnetoresistance and metal-insulator transition temperatures, as well as the magnetization and Curie temperatures. These behaviors are dependent of the composition of the samples. However, we observed from the hysteresis loops that the coercitive field did not change significantly with Cr or Fe addition at different temperatures. Doping decreased the double exchange and the ferromagnetic order, possibly due to the competing influences from the strain relaxation.

  20. Substitution in ce2tsi3 intermetallic compositions with t = (Cr, Mn, Fe, Co, or Ni) x (Pd or Au) 1-x. Technical report No. 30

    SciTech Connect

    1996-07-10

    Alloys of composition Ce2(3d/T)Si3, with `3d` one of Cr, Mn, Fe, Co or Ni and `T` being Pd or Au, were separated and examined by powder x-ray diffraction. Select single phase compositions were further examined by magnetic susceptibility, by resistivity for the Pd and Co end-members and by specific heat for Ce2CoSi3. For compounds not containing cobalt, effective cerium moments consistent with trivalent cerium were observed. A re-examination of the AlB2 related structure of Ce2CoSi3 by single crystal methods revealed ordering of cobalt within the CoSi3 hexagonal layer. Magnetic susceptibility, resistance and specific heat measurements suggest valence fluctuation behavior of the cerium in Ce2CoSi3. A return to trivalent cerium magnetic behavior occurs on increasing palladium or gold substitution for cobalt.

  1. Free energy landscape approach to aid pure phase synthesis of transition metal (X=Cr, Mn and Fe) doped bismuth titanate (Bi2Ti2O7)

    NASA Astrophysics Data System (ADS)

    Mayfield, Cedric L.; Huda, Muhammad N.

    2016-06-01

    A density functional theory study of Cr, Mn and Fe substitutions in Bi2Ti2O7 (BTO) photocatalysts is presented. We performed a stability analysis from our total energy calculations and have determined formations of dopant inspired phases are detrimental to the overall photocatalytic performance of X-doped BTO. From our calculated formation energies and electronic structures it is shown that X substitution of Ti is least stable and should be associated with formation of secondary phases more so than X substitution of Bi. This result contradicts the many experimental studies which suggest transition metal dopants always substitute Ti in BTO, but on the other hand, explains the poor photocatalytic response beyond what has become known as the critical dopant concentration.

  2. Influence of transition metals (Cr, Mn, Fe, Co and Ni) on the methane combustion over Pd/Ce-Zr/Al 2O 3 catalyst

    NASA Astrophysics Data System (ADS)

    Yue, Baohua; Zhou, Renxian; Wang, Yuejuan; Zheng, Xiaoming

    2006-06-01

    The effects of transition metals (Cr, Mn, Fe, Co and Ni) on the catalytic properties of Pd/Ce-Zr/Al 2O 3 catalyst for methane combustion have been investigated. The supported Pd catalysts are characterized by BET, XRD, TEM, TPR, TPO and TPSR measurements. Activity tests in methane combustion show that Pd/Ce-Zr-Ni/Al 2O 3 has the highest catalytic activity and thermal stability among all catalysts. The results of TEM show that the addition of Ni to Pd/Ce-Zr/Al 2O 3 increases the dispersion of Pd component and inhibits the site growth. The results of TPO and TPSR show that the addition of Ni inhibits the decomposition of PdO particles and improves the reduction-reoxidation properties of the active PdO species, which increases the catalytic activity and thermal stability of the Pd/Ce-Zr/Al 2O 3 catalyst.

  3. Influence of deformation on the structure and the mechanical properties of a high-entropy Fe25Cr20Ni20Co10Mn15Al10 alloy

    NASA Astrophysics Data System (ADS)

    Gorban', B. F.; Nazarenko, V. A.; Danilenko, N. I.; Karpets, M. V.; Krapivka, N. A.; Firstov, S. A.; Makarenko, E. S.

    2014-10-01

    The phase composition, the hardness, and the elasticity modulus of a high-entropy Fe25Cr20Ni20Co10Mn15Al10 alloy have been studied in the as-cast state, after rolling deformation, and after subsequent high-temperature annealing. The alloy consists of the following two phases: solid substitutional solutions with bcc and fcc crystal lattices; in the as-cast state and after annealing the bcc solid solution is ordered according to B2 type (CsCl). The mixture rule is applied for the calculation of the electron density, the atomic radius, and the melting point at grain boundaries and in the grain volume of the alloy after deformation and annealing. The obtained data demonstrate that the alloy is thermally stable.

  4. Characterization of Structural Properties of LiMxFe5-xO8 (M=Al, Cr, Mn) Spinel Solid Solutions

    NASA Astrophysics Data System (ADS)

    Darul, J.

    2008-08-01

    The structural properties of series spinel oxides with the general formula, LiM0.5Fe4.5O8 (M = Mn, Cr, Al), are investigated. The effect of limited substitution of manganese, chromium and aluminum ions in the lithium ferrite samples on the order-disorder phase transition in the spinel crystal lattice at room temperature is presented. In these materials it is found that the ordered structures have not been isolated as single phases under the present experimental conditions and this fact will certainly influence the magnetic behavior of the compounds. The Rietveld refinements of the synchrotron X-ray diffraction data revealed that transition metal ions hinders the ordering process and Al3+ ion was shown to be least effective in removing of order.

  5. Peculiarities of the phase composition and structure of the high-entropy FeWMoCrVSiMnC multicomponent steel

    NASA Astrophysics Data System (ADS)

    Pushin, V. G.; Kuranova, N. N.; Nikolaeva, N. V.; Uksusnikov, A. N.; Ustyugov, Yu. M.; Belosludtseva, E. S.; Pushin, A. V.; Svirid, A. E.

    2015-07-01

    We report on the results of analysis of the phase composition, structure, and hardness of high-entropy FeWMoCrVSiMnC multicomponent steel subjected to synthesis and subsequent thermal treatment. Analysis is carried out using the methods of analytic transmission and scanning structural and orientational electron microscopy, optical metallography, X-ray energy-dispersive spectroscopy, X-ray phase and structural analyses, and Rockwell measurements of hardness. It is found that steel has a high hardness (62 HRC) and is in ultra-fine-disperse composite martensite-multicarbide state. All carbides are distributed uniformly over the steel volume and have nano- and submicrometer scales depending on the carbide type.

  6. Thermodynamic laws of the oxygen solubility in liquid metals (Ni, Co, Fe, Mn, Cr) and the formation of oxygen-containing solutions in the alloys based on them

    NASA Astrophysics Data System (ADS)

    Paderin, S. N.; Shil'nikov, E. V.

    2015-12-01

    The solubility of oxygen in liquid Ni, Co, Fe, Mn, and Cr metals (Group IV in the periodic table) has been found for the first time. Linear dependences of the oxygen solubility on the standard Gibbs energy for the oxidation reaction of a liquid metal with gaseous oxygen are found. The revealed function of oxygen solubility is of scientific importance and allows one to develop a theory of oxygen solutions in liquid metals and liquid multicomponent metallic compositions and to calculate the energies of mixing of liquid metals with oxygen from Δ G MO ° for metal oxidation reactions with allowance for pseudoregular-solution model equations. Using the energies of mixing and metal compositions, we calculated the equilibrium oxygen concentrations in a metal molten pool at the end of oxidation stage of melting 08Kh18N10T steel in an arc furnace. This fact indicates practical importance of the found function of the oxygen solubility in metals.

  7. First-principles study of one-dimensional sandwich wires [(P)5TM]∞ (TM = Ti, V, Cr, Mn, Fe, Co)

    NASA Astrophysics Data System (ADS)

    Ma, Yandong; Dai, Ying; Li, Xinru; Li, Zhujie; Huang, Baibiao

    2013-10-01

    Since the discovery of ferrocene, many one-dimensional metallic sandwich molecular wires have been identified. However, most of the known systems are assembled from organic molecules. Suffering from many drawbacks has, however, hampered their widespread applications. With the goal of breaking this logjam, we provide a blueprint for the designing of a variety of novel sandwich molecular wires ([(P)5TM]∞, TM = Ti, V, Cr, Mn, Fe, and Co) assembled from ferrocene-like inorganic molecules (P)5TM, offering evidence of the existence of inorganic molecular wires in this class. We present first-principles calculations to investigate systematically the electronic and magnetic properties of such novel inorganic sandwich molecular wires. Compared with the organic molecular wires, all the inorganic [(P)5TM]∞ wires are of large magnetic moment. Among them, we find that [(P)5V]∞, [(P)5Cr]∞ and [(P)5Mn]∞ display ferromagnetic character, while for [(P)5Ti]∞, [(P)5Fe]∞ and [(P)5Co]∞, the magnetic coupling is antiferromagnetic. More remarkably, the TM atoms distributed in these wires show regular docking and lead to structures with ordered spin signals, which is a long-term dream of spintronics. We propose that the difference in magnetic coupling for the studied systems is related to the competition between two exchange interactions of TM atoms. Specifically, we propound that the general mechanism for the formation of stable 1D [(P)5TM]∞ involves the transfer of one electron from the TM atom to the P5 ligand forming ({P})_{5}^{-} and TM+ alternating structure.

  8. Effect of Cr substitution on the magnetic and magnetic-transport properties of Fe{sub 2}Mn{sub 1-x}Cr{sub x}Si alloys

    SciTech Connect

    Pal, Lakhan; Gupta, Sachin; Suresh, K. G.; Nigam, A. K.

    2014-05-07

    Fe{sub 2}Mn{sub 1-x}Cr{sub x}Si (x = 0, 0.1, and 0.2) alloys were investigated for their magnetic and transport properties in view of the expected half metallicity. It is found that Cr substitution suppresses the antiferromagnetic phase present in parent Fe{sub 2}MnSi, which completely disappears for x = 0.2. Curie temperature of the alloys increases from 230 K to 299 K as x is increased from 0 to 0.2. The value of the Rhodes-Wohlfarth ratio indicates that the system shows iterant magnetism. Resistivity measurements also show absence of antiferromagnetic phase for x = 0.2. Resistivity data have been fitted by considering the electron-phonon and electron-magnon scattering contributions, which indicates the presence of half metallicity in these compounds. Temperature dependence of resistivity data shows magnetoresistance of −3% and −2.5% at Curie temperature with applied field of 50 kOe for x = 0.1 and 0.2, respectively.

  9. Electron capture of strongly screening nuclides 56Fe, 56Co, 56Ni, 56Mn,56Cr and 56V in pre-supernovae

    NASA Astrophysics Data System (ADS)

    Liu, Jing-Jing

    2013-08-01

    According to the shell-model Monte Carlo method, based on the random-phase approximation and linear response theory, we carried out an estimation of electron capture (EC) of the strongly screening nuclides 56Fe, 56Co, 56Ni, 56Mn,56Cr and 56V during strong electron screening (SES) in pre-supernovae. The EC rates are decreased greatly and may even exceed 21.5 per cent in the case of SES. We also compare our results with those calculated by the method of Aufderheide in the case of SES. Our results agree reasonably well with those of Aufderheide in higher density and temperature surroundings (e.g. ρ7 > 60, T9 = 15.40) and the maximum error is ˜0.5 per cent. However, the maximum error is ˜13.0 per cent in lower density surroundings (e.g. 56Cr at ρ7 = 10, T9 = 15.40, Ye = 0.41). We also compared our results for SES with those of Fuller, Fowler & Newman and Nabi, which apply to a case without SES. The comparisons show that our results are lower than those of Fuller, Fowler & Newman by more than one order of magnitude and about 7.23 per cent lower than those of Nabi.

  10. Highly (002) textured large grain bcc Cr{sub 80}Mn{sub 20} seed layer on Cr{sub 50}Ti{sub 50} amorphous layer for FePt-C granular film

    SciTech Connect

    Jeon, Seong-Jae Saito, Shin; Hinata, Shintaro; Takahashi, Migaku

    2015-05-07

    Effect of bcc Cr{sub 80}Mn{sub 20} seed layer and Cr{sub 50}Ti{sub 50} amorphous texture inducing layer on the heteroepitaxy system in FePt-C granular film was studied by introducing a new concept of the layered structure. The concept suggested that the large grain seed layer in which the crystallographic texture was initially formed on an amorphous layer in the layered structure can reduce the angular distribution of (002) c-axis crystal orientation in the FePt-C granular film owing to heteroepitaxial growth. Structure analysis by X-ray diffraction revealed that (1) when the substrate heating temperature was elevated from 300 °C to 500 °C, grain size in the seed layer increased from 9.8 nm to 11.6 nm, and then decreased with further increasing the substrate temperature. The reduction of the grain size over 500 °C corresponds to the crystallization of the amorphous texture inducing layer, (2) when the grain size increased from 9.8 nm to 11.6 nm, the angular distribution of the (002) orientation in the seed layer dramatically decreased from 13.7° to 4.1°. It was shown that the large grain seed layer increased the perpendicular hysteresis in FePt-C granular film.

  11. Effects of Cr, Zr, V, Mn, Fe, and Co to the hydride properties of Laves phase-related body-centered-cubic solid solution alloys

    NASA Astrophysics Data System (ADS)

    Young, K.; Ouchi, T.; Nei, J.; Meng, T.

    2015-05-01

    Chemical composition modifications of a Laves phase-related BCC solid solution base alloy, Ti15.6Zr2.1V44Cr11.2Mn6.9Fe2.7Co1.4Ni15.7Al0.3, were investigated in order to study the function of each constituent element on the structural, gaseous phase and electrochemical hydrogen storage properties of these alloys. In general, removal of Fe and decrease in V-content in exchange for higher Ni-content were found to improve both the electrochemical capacity and high-rate dischargeability, which are related to the decrease in C14-content and increase in TiNi-content. However, total elimination of the C14 phase by removal of Zr resulted in a reduced discharge capacity, a prolonged activation period, and a less catalytic surface for electrochemical reaction. Besides the BCC and C14 phases, the TiNi phase was also found in every alloy in this study, contributing positively to the bulk diffusion of hydrogen while hindering the surface electrochemical reaction.

  12. 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.

  13. Chemical bonding in the ternary transition metal bismuthides Ti{sub 4}TBi{sub 2} with T=Cr, Mn, Fe, Co, and Ni

    SciTech Connect

    Rytz, R.; Hoffman, R.

    1999-04-05

    The electronic structure and chemical bonding in the ternary transition metal bismuthides Ti{sub 4}TBi{sub 2} (T = Cr, Mn, Fe, Co, and Ni) is investigated by approximate MO calculations of the extended Hueckel tight-binding type. These intermetallic compounds crystallize in a layer structure, repeating sequence T-Ti/Bi-T-Ti/Bi, stacking along c; the late transition metals form linear chains with short T-T bonds. Other important structural elements are face-sharing chains of Ti{sub 4}Bi{sub 2} octahedra and Bi channels. The decrease of the T-T bond lengths from Cr to Ni is more pronounced than expected from the decrease of the metallic radii alone. The analysis of the electronic structure indicates that this behavior arises from the titanium-titanium and titanium-bismuth interlayer interactions. Diminution of the titanium-titanium interlayer distances as one goes from Ti{sub 4}CrBi{sub 2} to Ti{sub 4}NiBi{sub 2} is due to Ti(d)-Ti(d) bonding, which increases with increasing electron filling of the titanium d levels. The titanium-bismuth interactions remain strong along this series, as can also be seen by the constant intralayer/titanium-bismuth distances. A distinguishing feature of the title compounds is the channels formed by bismuth atoms. These channels are filled by Bi-centered, essentially unhybridized 6p orbitals forming a 2D net stacking along c and interacting with each other, stronger in the c direction than perpendicular to it. The possibility of intercalating electrophilic species into these electron-filled voids is also investigated.

  14. New cyanide-bridged Mn(III)-M(III) heterometallic dinuclear complexes constructed from [M(III)(AA)(CN)4]- building blocks (M = Cr and Fe): synthesis, crystal structures and magnetic properties.

    PubMed

    Nastase, Silviu; Maxim, Catalin; Andruh, Marius; Cano, Joan; Ruiz-Pérez, Catalina; Faus, Juan; Lloret, Francesc; Julve, Miguel

    2011-05-14

    Three Mn(III)-M(III) (M = Cr and Fe) dinuclear complexes have been obtained by assembling [Mn(III)(SB)(H(2)O)](+) and [M(III)(AA)(CN)(4)](-) ions, where SB is the dianion of the Schiff-base resulting from the condensation of 3-methoxysalicylaldehyde with ethylenediamine (3-MeOsalen(2-)) or 1,2-cyclohexanediamine (3-MeOsalcyen(2-)): [Mn(3-MeOsalen)(H(2)O)(µ-NC)Cr(bipy)(CN)(3)]·2H(2)O (1), [Mn(3-MeOsalen)(H(2)O)(µ-NC)Cr(ampy)(CN)(3)][Mn(3-MeOsalen)(H(2)O)(2)]ClO(4)·2H(2)O (2) and [Mn(3-MeOsalcyen)(H(2)O)(µ-NC)Fe(bpym)(CN)(3)]·3H(2)O (3) (bipy = 2,2'-bipyridine, ampy = 2-aminomethylpyridine and bpym = 2,2'-bipyrimidine). The [M(AA)(CN)(4)](-) unit in 1-3 acts as a monodentate ligand towards the manganese(III) ion through one of its four cyanide groups. The manganese(III) ion in 1-3 exhibits an elongated octahedral stereochemistry with the tetradentate SB building the equatorial plane and a water molecule and a cyanide-nitrogen atom filling the axial positions. Remarkably, the neutral mononuclear complex [Mn(3-MeOsalen)(H(2)O)(2)]ClO(4) co-crystallizes with the heterobimetallic unit in 2. The values of the Mn(III)-M(III) distance across the bridging cyanide are 5.228 (1), 5.505 (2) and 5.265 Å (3). The packing of the neutral heterobimetallic units in the crystal is governed by the self-complementarity of the [Mn(SB)(H(2)O)](+) moieties, which interact each other through hydrogen bonds established between the aqua ligand from one fragment with the set of phenolate- and methoxy-oxygens from the adjacent one. The magnetic properties of the three complexes have been investigated in the temperature range 1.9-300 K. Weak antiferromagnetic interactions between the Mn(III) and M(III) ions across the cyanido bridge were found: J(MnM) = -5.6 (1), -0.63 (2) and -2.4 cm(-1) (3) the Hamiltonian being defined as H = -JS(Mn)·S(M). Theoretical calculations based on density functional theory (DFT) have been used to substantiate both the nature and magnitude of the exchange

  15. Investigation of Dipodal oxy-Schiff base and its salen and salophen Fe(III)/Cr(III)/Mn(III) Schiff bases (N2O2) caped complexes and their magnetic and thermal behaviors

    NASA Astrophysics Data System (ADS)

    Çelikbilek, Şeyma; Koç, Ziya Erdem

    2014-05-01

    Six new dinuclear Fe(III)/Cr(III)/Mn(III) complexes have been involved tetradentate (N2O2) Schiff bases (salenH2) and (salophenH2) with 2,4-bis(4-hydroxyphenylimino-4‧-formylphenoxy)-6-methoxy-1,3,5-triazine have been synthesized. The complexes were characterized as high-spin (S = 5/2) distorted trigonal bipyramidal salen/salophenFe(III) bridged, distorted trigonal bipyramidal (S = 3/2) salen/salophenCr(III) and high-spin distorted trigonal bipyramidal (S = 2) salen/salophenMn(III) by OH- groups. The structures of ligand and complexes were identified by using elemental analysis, thermal analysis, magnetic susceptibility, LC-MS, ICP-AES, 1H NMR and FT-IR spectral data.

  16. Cyclic Deformation Behavior of Fe-18Cr-18Mn-0.63N Nickel-Free High-Nitrogen Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Shao, C. W.; Shi, F.; Li, X. W.

    2015-04-01

    Cyclic deformation and damage behavior of a Ni-free high-nitrogen austenitic stainless steel with a composition of Fe-18Cr-18Mn-0.63N (weight pct) were studied, and the internal stress and effective stress were estimated by partitioning the hysteresis loop during cyclic straining at total strain amplitudes ranging from 3.0 × 10-3 to 1.0 × 10-2. It is found that immediate cyclic softening takes place at all strain amplitudes and subsequently a saturation or quasi-saturation state develops and occupies the main part of the whole fatigue life. The internal stress increases with increasing strain amplitude, while the variation of effective stress with strain amplitude is somewhat complicated. Such a phenomenon is discussed in terms of dislocation structures and the short-range ordering caused by the interaction between nitrogen atoms and substitutional atoms. The relationship of fatigue life vs plastic strain amplitude ( N f-Δ ɛ pl/2) follows a bilinear Coffin-Manson rule, resulting from the variation in slip deformation mode with the applied strain amplitude. At the low strain amplitude, cracks initiate along slip bands, and planar slip dislocation configurations dominate the major characteristic of internal microstructures. At high strain amplitudes, intergranular (mostly along grain boundaries and few along twin boundaries) cracks are generally found, and the deformation microstructures are mainly composed of dislocation cells, stacking faults and a small amount of deformation twins, in addition to planar slip dislocation structures.

  17. Studies on some salicylaldehyde Schiff base derivatives and their complexes with Cr(III), Mn(II), Fe(III), Ni(II) and Cu(II).

    PubMed

    Abdel-Latif, S A; Hassib, H B; Issa, Y M

    2007-07-01

    The formation constants of some transition metal ions Cr(III), Mn(II), Fe(III), Ni(II) and Cu(II) binary complexes containing Schiff bases resulting from condensation of salicylaldehyde with aniline (I), 2-aminopyridine (II), 4-aminopyridine (III) and 2-aminopyrimidine (IV) were determined pH-metrically in ethanolic medium (80%, v/v). The formation constants were determined for all binary complexes. The important infrared (IR) spectral bands corresponding to the active groups in the four ligands and the solid complexes under investigation were studied. The solid complexes have been synthesized and studied by thermogravimetric analysis. The thermal dehydration and decomposition of these complexes were studied kinetically using the integral method applying the Coats-Redfern equation. It was found that the thermal decomposition of the complexes follow second order kinetics. The thermodynamic parameters of the decomposition are also reported. The electronic absorption spectra of the investigated ligands were carried out to determine the pK(a) values spectrophotometrically. PMID:17084104

  18. Studies on some salicylaldehyde Schiff base derivatives and their complexes with Cr(III), Mn(II), Fe(III), Ni(II) and Cu(II)

    NASA Astrophysics Data System (ADS)

    Abdel-Latif, S. A.; Hassib, H. B.; Issa, Y. M.

    2007-07-01

    The formation constants of some transition metal ions Cr(III), Mn(II), Fe(III), Ni(II) and Cu(II) binary complexes containing Schiff bases resulting from condensation of salicylaldehyde with aniline (I), 2-aminopyridine (II), 4-aminopyridine (III) and 2-aminopyrimidine (IV) were determined pH-metrically in ethanolic medium (80%, v/v). The formation constants were determined for all binary complexes. The important infrared (IR) spectral bands corresponding to the active groups in the four ligands and the solid complexes under investigation were studied. The solid complexes have been synthesized and studied by thermogravimetric analysis. The thermal dehydration and decomposition of these complexes were studied kinetically using the integral method applying the Coats-Redfern equation. It was found that the thermal decomposition of the complexes follow second order kinetics. The thermodynamic parameters of the decomposition are also reported. The electronic absorption spectra of the investigated ligands were carried out to determine the p Ka values spectrophotometrically.

  19. Microwave-assisted synthesis: A fast and efficient route to produce LaMO{sub 3} (M = Al, Cr, Mn, Fe, Co) perovskite materials

    SciTech Connect

    Prado-Gonjal, J.; Arevalo-Lopez, A.M.; Moran, E.

    2011-02-15

    Research highlights: {yields} Lanthanum perovskites can be prepared by microwave irradiation in a domestic set-up. {yields} Microwave-assisted synthesis yields well crystallized and pure materials, sometimes nanosized. {yields} Rietveld analysis has been performed to refine the structures. {yields} Magnetic and electric measurements are similar to those previously reported. {yields} Microwave-assisted synthesis is a fast and efficient method for the synthesis of lanthanum perovskites. -- Abstract: A series of lanthanum perovskites, LaMO{sub 3} (M = Al, Cr, Mn, Fe, Co), having important technological applications, have been successfully prepared by a very fast, inexpensive, reproducible, environment-friendly method: the microwave irradiation of the corresponding mixtures of nitrates. Worth to note, the microwave source is a domestic microwave oven. In some cases the reaction takes place in a single step, while sometimes further annealings are necessary. For doped materials the method has to be combined with others such as sol-gel. Usually, nanopowders are produced which yield high density pellets after sintering. Rietveld analysis, oxygen stoichiometry, microstructure and magnetic measurements are presented.

  20. In quest of cathode materials for Ca ion batteries: the CaMO3 perovskites (M = Mo, Cr, Mn, Fe, Co, and Ni).

    PubMed

    Arroyo-de Dompablo, M E; Krich, C; Nava-Avendaño, J; Palacín, M R; Bardé, F

    2016-07-20

    Basic electrochemical characteristics of CaMO3 perovskites (M = Mo, Cr, Mn, Fe, Co, and Ni) as cathode materials for Ca ion batteries are investigated using first principles calculations at the Density Functional Theory level (DFT). Calculations have been performed within the Generalized Gradient Approximation (GGA) and GGA+U methodologies, and considering cubic and orthorhombic perovskite structures for CaxMO3 (x = 0, 0.25, 0.5, 0.75 and 1). The analysis of the calculated voltage-composition profile and volume variations identifies CaMoO3 as the most promising perovskite compound. It combines good electronic conductivity, moderate crystal structure modifications, and activity in the 2-3 V region with several intermediate CaxMoO3 phases. However, we found too large barriers for Ca diffusion (around 2 eV) which are inherent to the perovskite structure. The CaMoO3 perovskite was synthesized, characterized and electrochemically tested, and results confirmed the predicted trends. PMID:27398629

  1. Selective solid-phase extraction and analysis of trace-level Cr(III), Fe(III), Pb(II), and Mn(II) Ions in wastewater using diethylenetriamine-functionalized carbon nanotubes dispersed in graphene oxide colloids.

    PubMed

    Zhu, Xiangbing; Cui, Yuemei; Chang, Xijun; Wang, Hua

    2016-01-01

    Multi-walled carbon nanotubes (MCNTs) were dispersed in graphene oxide (GO) colloids to be further functionalized with diethylenetriamine (DETA), resulting in GO-MCNTs-DETA nanocomposites for the solid-phase extraction and analysis of Cr(III), Fe(III), Pb(II), and Mn(II) ions at the trace levels in wastewater. Inductively coupled plasma optical emission spectrometry (ICP-OES) indicates that this new solid-phase sorbent could facilitate the maximum static adsorption capacities of 5.4, 13.8, 6.6 and 9.5 mg g(-1) for Cr(III), Fe(III), Pb(II), and Mn(II) ions, respectively, showing the adsorption capacity up to 95% within about 30 min. Moreover, the detection limits of the GO-MCNTs-DETA-based analysis method were found to be 0.16, 0.50, 0.24 and 0.38 ng mL(-1) for Cr(III), Fe(III), Pb(II), and Mn(II) ions, respectively, with the relative standard deviation of lower than 3.0% (n=5). Importantly, common coexisting ions showed no significant interference on the separation and pre-concentration of these heavy metal ions at pH 4.0. Subsequently, the GO-MCNTs-DETA sorbent was successfully employed for the separation and analysis of trace-level Cr(III), Fe(III), Pb(II), and Mn(II) ions in wastewater samples yielding 75-folds concentration factors. PMID:26695275

  2. Electron-impact excitation of H-like Cr, Mn, Fe, Co, and Ni for applications in modeling X-ray astrophysical sources

    NASA Astrophysics Data System (ADS)

    Malespin, C.; Ballance, C. P.; Pindzola, M. S.; Witthoeft, M. C.; Kallman, T. R.; Loch, S. D.

    2011-02-01

    Context. Accurate atomic data for the less abundance Fe-peak elements are required for use in X-ray astrophysical studies. Aims: We calculate high quality electron-impact excitation collision strengths and effective collision strengths for hydrogenic Cr, Mn, Fe, Co, and Ni. Methods: We use the Dirac R-matrix method, the intermediate coupling frame transformation R-matrix method, the semi-relativistic distorted-wave method and the fully-relativistic distorted-wave method to calculate collision strengths for each of the ions. The ADAS collisional-radiative codes are used to produce photon emissivity coefficients for each ion. Results: Results are presented for atomic energy levels, spontaneous emission coefficients, electron-impact excitation collision strengths and associated effective collision strengths for each of the five species under consideration. We find relativistic effects can contribute an approximate 10% increase to the background cross section in relation to semi-relativistic collision calculations. We also confirm that radiation damping plays a prominent role for certain near threshold resonances. In order check the integration of our results within collisional-radiative modeling codes, we have used the ADAS package for some preliminary modeling of photon emissivities. The atomic data shall be made available online through the OPEN-ADAS site and the CFADC database Final datasets for each ion are only available in electronic form at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A115

  3. Synthesis and characterization of dopamine substitue tripodal trinuclear [(salen/salophen/salpropen)M] (Mdbnd Cr(III), Mn(III), Fe(III) ions) capped s-triazine complexes: Investigation of their thermal and magnetic properties

    NASA Astrophysics Data System (ADS)

    Uysal, Şaban; Koç, Ziya Erdem

    2016-04-01

    In this work, we aimed to synthesize and characterize a novel tridirectional ligand including three catechol groups and its novel tridirectional-trinuclear triazine core complexes. For this purpose, we used melamine (2,4,6-triamino-1,3,5-triazine) (MA) as starting material. 2,4,6-tris(4-carboxybenzimino)-1,3,5-triazine (II) was synthesized by the reaction of an equivalent melamine (I) and three equivalent 4-carboxybenzaldehyde. 4,4‧,4″-((1E,1‧E,1″E)-((1,3,5-triazine-2,4,6-triyl)tris(azanylylidene))tris(methanylylidene))tris(N-(3,4-dihydroxyphenethyl)benzamide) L (IV) was synthesized by the reaction of one equivalent (II) and three equivalent dopamine (3,4-dihydroxyphenethylamine) (DA) by using two different methods. (II, III, IV) and nine novel trinuclear Cr(III), Mn(III) and Fe(III) complexes of (IV) were characterized by means of elemental analyses, 1H NMR, FT-IR spectrometry, LC-MS (ESI+) and thermal analyses. The metal ratios of the prepared complexes were performed using Atomic Absorption Spectrophotometry (AAS). We also synthesized novel tridirectional-trinuclear systems and investigated their effects on magnetic behaviors of [salen, salophen, salpropen Cr(III)/Mn(III)/Fe(III)] capped complexes. The complexes were determined to be low-spin distorted octahedral Mn(III) and Fe(III), and distorted octahedral Cr(III) all bridged by catechol group.

  4. Phase relationships in the quaternary systems MS-Cr/sub 2/S/sub 3/-In/sub 2/S/sub 3/ (M=Mn,Fe,Co,Ni), miscibility gaps in spinel solid solutons

    SciTech Connect

    Lutz, H.D.; Jung, M.; Wussow, K.

    1986-02-01

    The phase diagrams of the quanternary systems MS-Cr/sub 2/S/sub 3/-In/sub 2/S/sub 3/ wth M=MN,Fe,Ni were studied by x-ray powder photographs of quenched samples. In the quasibinary sections MnIn/sub 2/S/sub 4/-MnCr/sub 2/S/sub 4/ and FeIn/sub 2/S/sub 4/-FeCr/sub 2/S/sub 4/, immiscibility domes exist below 800 and 850/sup 0/C, respectively. At higher temperatures complete series of spinel type solid solutions are formed, which can be quenched to ambient temperature without decomposition. In the NiIn/sub 2/S/sub 4/-NiCr/sub 2/S/sub 4/ section, spinel-type solid solutions are formed in the range from NiIn/sub 2/S/sub 4/ to NiCr/sub 1.7/In/sub 0.3/S/sub 4/ (800/sup 0/C). At lower temperatures decomposition to chromium and indium rich spinel solid solutions occurs. The phase width of Cr/sub 3/S/sub 4/ type NiCr/sub 2/S/sub 4/ is very small. The system NiCr/sub 2/S/sub 4/-In/sub 2/S/sub 3/ is similar to the NiCr/sub 2/S/sub 4/-NiIn/sub 2/S/sub 4/ system, but probably no quasibinary. The fir spectra of the NiCr/sub 2-2X/In/sub 2X/S/sub 4/ (and NiCr/sub 2-2X/Ga/sub 2X/S/sub 4/) solid solutions reveal that the hypothetical spinel NiCr/sub 2/S/sub 4/ is probably metallic. In the sections CoS-In/sub 2/S/sub 3/ and NiS-In/sub 2/S/sub 3/, spinel type solid solutions are formed in the range from In/sub 2/S/sub 3/ to MIN/sub 2/S/sub 4/. The unusually small reaction rates of the solid state equilibration reaction are discussed in terms of the Gibb's enthalpies of forming the spinel mixed crystals and the kinetic retardation of such reactions.

  5. Ab initio GGA+U study of oxygen evolution and oxygen reduction electrocatalysis on the (001) surfaces of lanthanum transition metal perovskites LaBO₃ (B = Cr, Mn, Fe, Co and Ni).

    PubMed

    Lee, Yueh-Lin; Gadre, Milind J; Shao-Horn, Yang; Morgan, Dane

    2015-09-01

    In this work, we performed density functional theory (DFT) calculations with inclusion of Hubbard U corrections for the transition metal d-electrons, to investigate stability and electrocatalytic activities of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) for the ABO3 (A = La; B = Cr, Mn, Fe, Co, and Ni) (001) surfaces. We showed surface binding energies of relevant ORR/OER species are coupled strongly to surface polarity and local oxidation states, giving large (∼1 eV scale per adsorbate) differences in binding between (001) AO and BO2 surfaces, where the more oxidized BO2 bare surfaces in general exhibit weak coverage dependence, while the more reduced AO bare surfaces of the LaCrO3, LaMnO3, and LaFeO3 perovskites with lower d-electron filling show strong/moderate coverage dependences. We then predicted that surface coverage can play a key role in determining surface stability, and when coverage effects are included the AO and BO2(001) surfaces have either similar stability or the AO surface is more stable, as found for 1 monolayer HO* covered AO surfaces of LaCrO3 and LaFeO3 under ORR conditions and 1 monolayer O* covered LaNiO3 AO surface under OER conditions. For the (001) AO surfaces with strong coverage dependent surface adsorption, we predicted a decrease in ORR overpotential of 1-2 V with proper treatment of coverage effects as compared to those of the bare surface simulations. Our results indicated that the GGA+U method and proper treatment of coverage effects more accurately predict ORR and OER overpotentials relative to experimental values as compared to the GGA method and bare surfaces. The overall ORR activity trends vs. the LaBO3 series were predicted to be Co > Mn ≈ Ni > Fe > Cr. PMID:26227442

  6. The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy

    SciTech Connect

    Otto, Frederik; Dlouhy, A.; Somsen, Ch.; Bei, Hongbin; Eggeler, G.; George, Easo P

    2013-01-01

    An equiatomic CoCrFeMnNi high-entropy alloy, which crystallizes in the face-centered cubic (FCC) crystal structure, was produced by arc melting and drop casting. The drop-cast ingots were homogenized, cold rolled, and recrystallized to obtain single-phase microstructures with three different grain sizes in the range 4~160 m. Quasi-static tensile tests were then performed at temperatures between 77 and 1073 K. Yield strength, ultimate tensile strength and ductility all increased with decreasing temperature. During the initial stages of plasticity (up to ~2% strain), deformation occurs by planar dislocation glide on the normal FCC slip system {111} 110 at all temperatures and grain sizes investigated. Undissociated 1/2 110 dislocations were observed, as were numerous stacking faults, which imply the dissociation of several of these dislocations into 1/6 112 Shockley partials. At later stages ( 20% strain), nanoscale deformation twins were observed after interrupted tests at 77 K, but not in specimens tested at room temperature where plasticity occurred exclusively by dislocations which organized into cells. Deformation twinning, by continually decreasing the mean free path of dislocations during tensile testing, produces a high degree of work hardening and a significant increase in the ultimate tensile strength. This increased work hardening prevents the early onset of necking instability and is a reason for the enhanced ductility observed at 77 K. A second way in which twinning can contribute to ductility is by providing an additional deformation mode to accommodate plasticity. However, it cannot explain the increase in yield strength with decreasing temperature in our high-entropy alloy since twinning was not observed in the early stages of plastic deformation. Since strong temperature dependencies of yield strength are also seen in binary FCC solid solution alloys, it may be an inherent solute effect, which needs further study.

  7. Photoionization study of Ne-like K9+, Ca10+, Sc11+, Ti12+, V13+, Cr14+, Mn15+, and Fe16+ ions using the screening constant by unit nuclear charge method

    NASA Astrophysics Data System (ADS)

    Goyal, Arun; Khatri, Indu; Sow, Malick; Sakho, Ibrahima; Aggarwal, Sunny; Singh, A. K.; Mohan, Man

    2016-08-01

    Photoionization of the 2s22p6 (1S0) ground state of the Ne-like (Z=19-29) ions is presented in this paper. Resonance energies and total natural width of the 2s2p6np 1P series of the Ne-like K9+, Ca10+, Sc11+, Ti12+, V13+, Cr14+, Mn15+, and Fe16+are reported. All the calculations are made using the Screening constant by unit nuclear charge (SCUNC) formalism. New data for Ne-like K9+, Sc11+, Ti12+, V13+, Cr14+, and Mn15+ions are tabulated. Good agreements are found with available literature data.

  8. Magnetic anisotropy of Fe{sub 1−y}X{sub y}Pt-L1{sub 0} [X = Cr, Mn, Co, Ni, Cu] bulk alloys

    SciTech Connect

    Cuadrado, R.; Chantrell, R. W.; Klemmer, Timothy J.

    2014-10-13

    We demonstrate by means of fully relativistic first principles calculations that, by substitution of Fe by Cr, Mn, Co, Ni, or Cu in FePt-L1{sub 0} 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-L1{sub 0} alloys.

  9. Solidification structure of C{sub 2.08}Cr{sub 25.43}Si{sub 1.19}Mn{sub 0.43}Fe{sub 70.87} powders fabricated by high pressure gas atomization

    SciTech Connect

    Dai Yongxiang; Yang Min; Song Changjiang; Han, Qingyou; Zhai Qijie

    2010-01-15

    Powders of hypoeutectic high chromium white cast iron (C{sub 2.08}Cr{sub 25.43}Si{sub 1.19}Mn{sub 0.43}Fe{sub 70.87}) were produced by high pressure gas atomization. The microstructure of the powders was characterized using light microscopy, scanning electron microscopy and X-ray diffraction. The results showed that the as-atomized powders were mainly composed of austenite and M{sub 7}C{sub 3} (M = Fe, Cr) type carbide, and became ferrite and carbide after annealing. With the decrease of the powder diameter, the number of austenite grains, primary dendrite length and second dendrite arm spacing were decreased. The relationship between cooling rate and microstructure was also determined.

  10. Electrochemical and corrosion properties of YNi{sub 2.5}M{sub 0.5} (M = Ni, Al, Fe, Cr, Cu, Co, Mn) hybride-forming alloys

    SciTech Connect

    Korobov, I.I.; Vasina, S.Ya.; Petrii, O.A.

    1995-06-01

    Hydrogen sorption by electrode materials based on YNi{sub 2.5}M{sub 0.5} (M = Ni, Al, Fe, Cr, Co, Cu, Mn) intermetallic compounds (IMC) with Cu and PTFE binders is studied in 1 M NaOH solution. The obtained reversible electrochemical capacities correspond to YNi{sub 2.5}M{sub 0.5}H{sub 1.3-1.7} hybrides which are stable at room temperature and atmospheric pressure. The application of Cu binder allows one to more completely use the material sorption capacity and promotes both extraction and sorption of hydrogen by IMC.

  11. New series of triple molybdates AgA3R(MoO4)5 (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) with framework structures and mobile silver ion sublattices

    NASA Astrophysics Data System (ADS)

    Kotova, Irina Yu.; Solodovnikov, Sergey F.; Solodovnikova, Zoya A.; Belov, Dmitry A.; Stefanovich, Sergey Yu.; Savina, Aleksandra A.; Khaikina, Elena G.

    2016-06-01

    Triple molybdates AgA3R(MoO4)5 (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg3In(MoO4)5 type were synthesized and single crystals of AgMg3R(MoO4)5 (R=Cr, Fe) were grown. In their structures, the MoO4 tetrahedra, pairs and trimers of edge-shared (Mg, R)O6 octahedra are connected by common vertices to form a 3D framework. Large framework cavities involve Ag+ cations disordered on three nearby positions with CN=3+1 or 4+1. Alternating (Mg, R)O6 octahedra and MoO4 tetrahedra in the framework form quadrangular windows penetrable for Ag+ at elevated temperatures. Above 653-673 K, the newly obtained molybdates demonstrate abrupt reduction of the activation energy to 0.4-0.6 eV. At 773 K, AgMg3Al(MoO4)5 shows electric conductivity 2.5·10-2 S/cm and Ea=0.39 eV compatible with characteristics of the best ionic conductors of the NASICON type.

  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. Correlation of Fe/Cr phase decomposition process and age-hardening in Fe-15Cr ferritic alloys

    NASA Astrophysics Data System (ADS)

    Chen, Dongsheng; Kimura, Akihiko; Han, Wentuo

    2014-12-01

    The effects of thermal aging on the microstructure and mechanical properties of Fe-15Cr ferritic model alloys were investigated by TEM examinations, micro-hardness measurements and tensile tests. The materials used in this work were Fe-15Cr, Fe-15Cr-C and Fe-15Cr-X alloys, where X refers to Si, Mn and Ni to simulate a pressure vessel steel. Specimens were isothermally aged at 475 °C up to 5000 h. Thermal aging causes a significant increase in the hardness and strength. An almost twice larger hardening is required for embrittlement of Fe-15Cr-X relative to Fe-15Cr. The age-hardening is mainly due to the formation of Cr-rich α‧ precipitates, while the addition of minor elements has a small effect on the saturation level of age-hardening. The correlation of phase decomposition process and age-hardening in Fe-15Cr alloy was interpreted by dispersion strengthened models.

  14. Effect of Cr on electronic and magnetic properties of χ-carbide (Fe,Cr)5C2

    NASA Astrophysics Data System (ADS)

    Wang, B.; Zhang, Q.; Zhang, Z. F.; Lv, Z. Q.; Fu, W. T.

    2015-10-01

    From density-function theory calculation, the structural, electronic and magnetic properties of χ-carbides (Fe,Cr)5C2 are investigated. With the increase of Cr content in χ-carbides (Fe,Cr)5C2, the formation energy of χ carbide gradually decrease and energy stability of them increase. The formation energy of Cr5C2 is -0.354 eV/f.u, and the stability of Cr5C2 is higher than other χ carbides (Fe,Cr)5C2, Mn5C2 and Fe5C2. There exists charges transfer from metal cation (Fe/Cr) to C atoms in χ-carbides, and this reveals an ionic contribution to the bonds. The addition of Cr decreases the magnetic moments of χ carbide, and the magnetic moments (Ms) of Cr2Cr2FeC2 and Cr5C2 are 0 μB/f.u., while it expresses opposite magnetic characters of the same atom at different sites in the other χ type (Fe,Cr)5C2 carbides. The 3d states of metal atoms in the majority states (up) move to above the Femi level and some metal atoms (Fe/Cr) in χ type (Fe,Cr)5C2 are undergone the anti-ferromagnetic transformation.

  15. Bis(azulene) "submarine" metal dimer sandwich compounds (C10H8)2M2(M = Ti, V, Cr, Mn, Fe, Co, Ni): Parallel and opposed orientations.

    PubMed

    Wang, Hongyan; Wang, Hui; King, R Bruce; Schaefer, Henry F

    2016-01-15

    The opposed and parallel structures for the binuclear bis(azulene) "submarine" sandwiches (C10H8)2M2 (M = Ti, V, Cr, Mn, Fe, Co, Ni) have been optimized using density functional theory. The lowest energy (C10H8)2 M2 structures of the early transition metals Ti, V, Cr, and Mn have the azulene units functioning as bis(pentahapto) ligands to each metal atom similar to the azulene ligand in the long-known molybdenum carbonyl complex (η(5),η(5)-C10H8 )Mo2 (CO)6 . The metal-metal bonds in these early transition metal structures have distances and Wiberg bond indices consistent with the formal bond orders required to give each metal atom an 18-electron configuration for the singlet structures and a 17-electron configuration for the triplet structures. For the later transition metals Fe, Co, and Ni, the lowest energy (C10H8)2 M2 structures contain pentahapto-trihapto azulene ligands with an uncomplexed C=C double bond, similar to that in the long-known iron carbonyl complex (η(5),η(3)-C10H8)Fe2 (CO)5 . The parallel (η(5),η(3)-C10H8 )2M2 (M = Fe, Co, Ni) structures contain metallocene subunits with their metal atoms at long nonbonding distances of 3.5-3.9 Å from the other metal atom, which is located between the azulene C7 rings. Higher energy opposed (C10H8)2 Fe2 structures contain an unprecedented distorted η(6) ,η(4) -azulene ligand using six carbon atoms for bonding to one iron atom as a hexahapto fulvene ligand and the remaining four carbon atoms for bonding to the other iron atom as a tetrahapto diene ligand. PMID:26213099

  16. Varied roles of Pb in transition-metal PbMO3 perovskites (M = Ti, V, Cr, Mn, Fe, Ni, Ru)

    NASA Astrophysics Data System (ADS)

    Goodenough, John B.; Zhou, Jianshi

    2015-06-01

    Different structural chemistries resulting from the Pb2+ lone-pair electrons in the PbMO3 perovskites are reviewed. The Pb2+ lone-pair electrons enhance the ferroelectric transition temperature in PbTiO3, stabilize vanadyl formation in PbVO3, and induce a disproportionation reaction of CrIV in PbCrO3. A Pb2+ + NiIV = Pb4+ + NiII reaction in PbNiO3 stabilizes the LiNbO3 structure at ambient pressure, but an A-site Pb4+ in an orthorhombic perovskite PbNiO3 is stabilized at modest pressures at room temperature. In PbMnO3, a ferroelectric displacement due to the lone pair electron effect is minimized by the spin-spin exchange interaction and the strong octahedral site preference of the MnIV/III cation. PbRuO3 is converted under pressure from the defective pyrochlore to the orthorhombic (Pbnm) perovskite structure where Pb-Ru interactions via a common O -2p orbital stabilize at low temperature a metallic Imma phase at ambient pressure. Above Pc ≃ ~32 GPa, a covalent Pb-Ru bond is formed by Pb2+ + RuIV = Pb4+ + RuII electron sharing.

  17. Atmospheric metal pollution (Cr, Cu, Fe, Mn, Ni, Pb and Zn) in Oporto city derived from results for low-volume aerosol samplers and for the moss Sphagnum auriculatum bioindicator.

    PubMed

    Vasconcelos, M T; Tavares, H M

    1998-03-01

    A low-volume aerosol sampler with filters and bags of Sphagnum auriculatum were exposed, in parallel, to the atmosphere of Oporto city for approx. 2 months in 1994, during a dry weather period. The levels of Cr, Cu, Fe, Mn, Ni, Pb and Zn in the moss (weekly samples) and in the filters (daily samples) were determined by atomic absorption spectrophotometry and the results were compared. For all the heavy metals, the rate of metal uptake by moss was significantly correlated with the metal concentration in atmospheric aerosols. The results indicated that moss bags of S. auriculatum can provide a quantitative estimation of the concentration of different heavy metals in urban atmospheres, when specific calibration by mechanic monitoring, at the same sampling point, is performed during a first stage of biomonitoring. The mean aerosol metal concentrations found in the Oporto atmosphere were similar to those observed in other urban atmospheres in different countries. The relative order of the mean metal concentrations was Fe (1.8 micrograms/m3) > Zn > Pb > Cu > Cr > Mn > Ni (20 ng/m3). The aerosol Pb levels were monitored at different sampling points over various periods of time between 1991 and 1997. The mean Pb levels were < or = 0.5 microgram/m3 and approximately constant at each sample point up to January 1996. After that date it decreased by approx. 50%, in consequence of the reduction of the Pb concentration in leaded gasoline. PMID:9525044

  18. Electronic structure and bonding of the 3d transition metal borides, MB, M =Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu through all electron ab initio calculations

    NASA Astrophysics Data System (ADS)

    Tzeli, Demeter; Mavridis, Aristides

    2008-01-01

    The electronic structure and bonding of the ground and some low-lying states of all first row transition metal borides (MB), ScB, TiB, VB, CrB, MnB, FeB, CoB, NiB, and CuB have been studied by multireference configuration interaction (MRCI) methods employing a correlation consistent basis set of quintuple cardinality (5Z). It should be stressed that for all the above nine molecules, experimental results are essentially absent, whereas with the exception of ScB and CuB the remaining seven species are studied theoretically for the first time. We have constructed full potential energy curves at the MRCI/5Z level for a total of 27 low-lying states, subsequently used to extract binding energies, spectroscopic parameters, and bonding schemes. In addition, some 20 or more states for every MB species have been examined at the MRCI/4Z level of theory. The ground state symmetries and corresponding binding energies (in kcal/mol) are Σ-5(ScB), 76; Δ6(TiB), 65; Σ+7(VB), 55; Σ+6(CrB), 31; Π5(MnB), 20; Σ-4(FeB), 54; Δ3(CoB), 66; Σ+2(NiB), 79; and Σ+1(CuB), 49.

  19. Long-Term Corrosion Testing of Thermal Spray Coatings of Amorphous Metals: Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 and Fe48Mo14Cr15Y2C15B6

    SciTech Connect

    Farmer, J; Day, D; Lian, T; Saw, C; Hailey, P; Payer, J; Aprigliano, L; Beardsley, B; Branagan, D

    2007-07-09

    Amorphous alloys identified as SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of SAM2X5 also made it an effective neutron absorber, and suitable for criticality control applications.

  20. Oxide Transformation in Cr-Mn-Prealloyed Sintered Steels: Thermodynamic and Kinetic Aspects

    NASA Astrophysics Data System (ADS)

    Hryha, Eduard; Nyborg, Lars

    2014-04-01

    The main obstacle for utilization of Cr and Mn as alloying elements in powder metallurgy is their high oxygen affinity leading to oxidation risk during powder manufacturing, handling, and especially during further consolidation. Despite the high purity of the commercially available Cr- and Mn-prealloyed iron powder grades, the risk of stable oxide formation during the sintering process remains. Thermodynamic and kinetic simulation of the oxide formation/transformation on the former powder surface during heating and sintering stages using thermodynamic modeling tools (Thermo-Calc and HSC Chemistry) was performed. Simulation is based on the results from the analysis of amount, morphology, and composition of the oxide phases inside the inter-particle necks in the specimens from interrupted sintering trials utilizing advanced analysis tools (HRSEM + EDX and XPS). The effect of the processing parameters, such as sintering atmosphere composition, temperature profile as well as graphite addition on the possible scenarios of oxide reduction/formation/transformation for Fe-Cr-Mn-C powder systems, was evaluated. Results indicate that oxide transformation occurs in accordance with the thermodynamic stability of oxides as follows: Fe2O3 → FeO → Fe2MnO4 → Cr2FeO4 → Cr2O3 → MnCr2O4 → MnO/MnSiO x → SiO2. Spinel MnCr2O4 was identified as the most stable oxide phase at applied sintering conditions up to 1393 K (1120 °C). Controlled conditions during the heating stage minimize the formation of stable oxide products and produce oxide-free sintered parts.

  1. Metal distribution and disorder in the crystal structure of [NH2Et2][Cr7MF8((t)BuCO2)16] wheel molecules for M = Mn, Fe, Co, Ni, Cu, Zn and Cd.

    PubMed

    Larsen, Finn Krebs; Overgaard, Jacob; Christensen, Mogens; McIntyre, Garry James; Timco, Grigore; Winpenny, Richard E P

    2014-12-01

    The homometallic wheel compound [Cr8F8(O2CCMe3)16] formed with fluorine and pivalic acid ligands can be modified by introducing in the synthesis process a divalent cation M capable of octahedral coordination instead of one of the trivalent Cr centres in the ring. Heterometallic mono-anionic species [Cr7MF8(O2CCMe3)16](-) can form diethylammonium salts and be crystallized from ethylacetate solution as compounds with the general formula [NH2Et2][Cr7MF8((t)BuCO2)16][C4H8O2]0.5 for M = Mn, Fe, Co, Ni, Cu, Zn and Cd. Their structures are isomorphous, belonging to the space group P21/c. The study has determined the degree of order for the individual M heterometal over the possible metal positions of the ring in the crystal structure by modelling based on X-ray diffraction data. The model took into account disorder in tert-butyl groups of the pivalate ligands and in the position and orientation of the ethylacetate solvent molecule. The heterometal turned out to be partly ordered in the crystal structure. PMID:25449616

  2. Electronic structure of CrAs and FeAs

    NASA Astrophysics Data System (ADS)

    Podloucky, Raimund

    1984-08-01

    As in a recent study for MnAs a two centre tight binding model consisting of itinerant metal d-states hybridizing with non-metal p-states was applied for CrAs and FeAs to calculate unpolarized and spin polarized local densities of states, ferromagnetic moments and band energies. The factor for the change of the d-band width relative to MnAs was estimated to be 1.3 for CrAs and 0.8 for FeAs. The self-consistent separation of the p- and d-band centres amounts to -1.3 eV for CrAs and -0.5 eV for FeAs providing a charge transfer of 0.8 and 0.6 electrons from the metal to the As atoms, correspondingly. One B8 1 structure and two B31 structures according to low and high temperature phases were studied for each compound. For CrAs self-consistent magnetic moments of 1.58 and 1.2μ B were obtained, respectively. For FeAs no ferromagnetic moment could be stabilized unless the d-band width was substantially reduced. The results are discussed with respect to MnAs. The model is able to reproduce the increase and breakdown of the magnetic moment for the series CrAs-MnAs-FeAs. Furthermore, the correct structural trend B31-B8 1-B31 is obtained if the band energy differences are corrected by a constant of 0.3 eV. This correction is attributed to the failure of the model to provide absolute differences of total energies.

  3. Spectroscopic and thermal degradation behavior of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes with thiopental sodium anesthesia drug

    NASA Astrophysics Data System (ADS)

    Refat, Moamen S.

    2013-04-01

    A new series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized with thiopental sodium anesthesia drug. The elemental analyses of the complexes are confined to stoichiometry of the formulas [M(TPL)3]ṡnH2O (M = Cr(III) or Fe(III); n = 6 or 5), [M(TPL)2(H2O)2]ṡnH2O (M = Mn(II), Co(II) or Ni(II); n = 0 or 4), and [M(TPL)2] (M = Cu(II) or Zn(II); n = 2 or 0) respectively, where TPL is thiopental chelating agent. Structures have been discussed and suggested upon elemental analyses, infrared, Raman, electronic, electron spin resonance, 1H NMR spectral data and magnetic studies. The X-ray powder diffraction (XRD) was performed of metal complexes. The XRD patterns indicate crystalline nature for the complexes. The measured low molar conductance values in dimethylsulfoxide indicate that the complexes are non-electrolyte nature. Spectroscopic discussion refer that coordination take place through three types: Cdbnd N (pyrimidine moiety) nitrogen and C2sbnd S (2-thiolate group) for Cr(III), Mn(II) and Fe(III), C6dbnd O (amido group) oxygen and C2sbnd S (2-thiolate group) for Co(II) and Ni(II), and Cu(II) and Zn(II) ions coordinated via Cdbnd N (pyrimidine moiety) nitrogen, C2dbnd S (2-thiolate group) and C6dbnd O (amido group) oxygen, respectively. The thermal behavior (TG/DTG/DTA) of the complexes was studied and kinetic parameters were determined by Horowitz-Metzger and Coats-Redfern methods. The thiopental and its complexes have been screened for their antimicrobial (G+ and G-) bacteria (Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa) and fungi (Aspergillus flavus and Candida albicans) activities by minimum inhibitory concentration (MIC) method.

  4. Bulk modulus and specific heat of B-site doped (La0.3Pr0.7)0.65Ca0.35Mn1-xBxO3 (B=Fe, Cr, Ru, Al, Ga)

    NASA Astrophysics Data System (ADS)

    Srivastava, Archana; Thakur, Rasna; Gaur, N. K.

    2014-04-01

    Specific heat (Cp) thermal expansion (α) and Bulk modulus (BT) of lightly doped Rare Earth manganites (La0.3Pr0.7)0.65Ca0.35Mn1-xBxO3 (B3+ = Fe3+,Cr3+,Ga3+,Al3+,Ru4+); (0.3Mn0.97Fe0.03O3 as a function of temperature (10K≤T≤ 200K) is found to be in agreement with the published data. The trend of variation of Debye temperature with B-site cationic radius is predicted probably for the first time for the B-site doped rare earth manganites.

  5. 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.

  6. The effect of the B-site cation and oxygen stoichiometry on the local and average crystal and magnetic structures of Sr2Fe1.9M0.1O5+y (M = Mn, Cr, Co; y = 0, 0.5)

    SciTech Connect

    Ramezanipour, Farshid; Greedan, John; Cranswick, Lachlan M.D.; Garlea, Vasile O; Siewenie, Joan; King, Graham; Llobet, Anna; Donaberger, R. L.

    2012-01-01

    Six compounds with formula Sr2Fe1.9M0.1O5+y (M = Mn, Cr, Co; y = 0, 0.5) were synthesized in air and argon, exhibiting surprisingly different properties depending on the B-cation type in spite of the low (5%) doping level. All argon synthesized phases, y 0, have long range brownmillerite ordering of oxygen vacancies with Icmm symmetry as shown by neutron diffraction (ND). All show long-range G-type antiferromagnetic order with N el temperatures, TN, from variable temperature ND of 649(3)K, 636(2)K and 668(5)K for Cr, Mn and Co-compounds, respectively, compared with Sr2Fe2O5, TN = 693 K. Competing ferromagnetic interactions may be responsible for the anomalously low value in the M = Mn case. The air synthesized phases with y 0.5 show surprising variation with M as investigated by X-ray, TOF and constant wavelength neutron diffractions. The M = Co compound is isostructural with Sr4Fe4O11 (Sr2Fe2O5.5), Cmmm, while the M = Cr phase is cubic, Pm-3m, and that for M = Mn appears to be cubic but the reflections are systematically broadened in a manner which suggests a local Cmmm structure. NPDF studies show that the local structure of the Cr phase is better described in terms of a Cmmm ordering of oxygen vacancies with Fe O coordination numbers of five and six. The M = Co material shows C-type antiferromagnetic long-range magnetic order at 4 K as found for Sr4Fe4O11. TN 230 K is inferred from a ZFC-FC magnetic susceptibility divergence compared with TN = 232 K for un-doped Sr4Fe4O11. The M = Cr and Mn compounds show no long-range magnetic ordering down to 4 K, but the divergence of ZFC and FC susceptibility data indicative of spin glass-like transitions occur at 60 K and 45 K for Cr and Mn, respectively. ND shows both diffuse and sharp Bragg magnetic reflections at positions consistent with a Cmmm cell for the M = Mn phase. For the M = Cr material, a very weak magnetic Bragg peak indexed as (1/2 1/2 1/2), consistent with a G-type AF order, is found at 4 K. These results

  7. An investigation of Cr(VI) removal with metallic iron in the co-presence of sand and/or MnO2.

    PubMed

    Gheju, M; Balcu, I; Vancea, C

    2016-04-01

    This study focused on the influence of sand and/or MnO2 co-presence on the mechanism and kinetics of Cr(VI) removal with Fe(0). The process was investigated under acidic and well-mixed conditions, over the temperature range of 6-32 °C. It was shown that both mechanism and kinetics of the removal process were highly dependent on composition and dose of reactive mixture added to Cr(VI) solution. At 22 °C, indirect chemical reduction with Fe(II) was the main removal path in H2O-Fe(0)-Cr(VI) and H2O-Fe(0)-Sand-Cr(VI) system, while in H2O-Fe(0)-MnO2-Cr(VI) and H2O-Fe(0)-MnO2-Sand-Cr(VI) system removal of Cr(VI) occurred mainly via adsorption on MnO2. The pseudo zero-order kinetic model provided the best match for H2O-Fe(0)-Cr(VI) and H2O-Fe(0)-Sand-Cr(VI) system, while in H2O-Fe(0)-MnO2-Cr(VI) and H2O-Fe(0)-MnO2-Sand-Cr(VI) system the process fitted well to the pseudo second-order model. Temperature influenced the efficiency and kinetics of the process in all investigated systems, and the removal mechanism only in H2O-Fe(0)-MnO2-Cr(VI) and H2O-Fe(0)-MnO2-Sand-Cr(VI) system. PMID:26826456

  8. Magnetic coupling in neutral and charged Cr{sub 2}, Mn{sub 2}, and CrMn dimers

    SciTech Connect

    Desmarais, N.; Reuse, F. A.; Khanna, S. N.

    2000-04-01

    Theoretical ab initio studies of neutral, cationic and anionic Cr{sub 2}, Mn{sub 2}, and CrMn dimers have been carried out to explore the progression of magnetic coupling with the number of electrons. It is shown that while Cr{sub 2} and Cr{sub 2}{sup -} have antiferromagnetically coupled atomic spins, Cr{sub 2}{sup +} has a ferromagnetic ground state closely followed by an antiferromagnetic state. On the other hand, all Mn{sub 2} dimers are ferromagnetic, irrespective of the charge. The neutral CrMn is ferrimagnetic while the charged CrMn are antiferromagnetic. In all cases, the charged dimers are found to be more stable than the neutral ones. The results are compared with available calculations and experiments and the difficulties associated with theoretical description and the experimental interpretations are discussed. (c) 2000 American Institute of Physics.

  9. Electron spin resonance and magnetization studies on Bi0.5Ca0.5Mn0.95TM0.05O3 (TM = Cr, Fe, Co and Ni)

    NASA Astrophysics Data System (ADS)

    Vijayan, D.; Kurian, Joji; Singh, R.

    2012-04-01

    In this work, we present the temperature dependent ESR and magnetization measurements on 3d TM doped Bi-manganite samples of composition Bi0.5Ca0.5Mn0.95TM0.05O3 (TM = Cr, Fe, Co and Ni) synthesized by solid state reaction method. The temperature dependent double integrated intensity (DI) of the ESR signal and the magnetic moment (M) have been used to estimate the charge ordering temperature (TCO), antiferromagnetic ordering (AFM) onset temperature TO and Neel temperature, TN. The 1/DI and 1/M versus T plots show FM correlations in the temperature range T > TCO and coexistence of ferromagnetic (FM) and AFM correlations in the temperature range TCO > T > TO. The magnetization data give TCO values close to the values obtained from ESR data. The data are analyzed in view of electronic phase separation model. The suppression of charge ordering is explained in view of the changes in short range magnetic interactions between Mn ions and the possible change in the band structure as a result of TM ion doping.

  10. Synthesis and Characterization of Cr(III), Mn(III), Fe(III), VO(IV), Zr(IV) and UO2(VI) Complexes of Schiff Base Derived from Isonicotinoyl Hydrazone

    PubMed Central

    Gawande, Pranita U.; Mandlik, P. R.; Aswar, A. S.

    2015-01-01

    2-hydroxy-5-chloro-3-nitroacetophenone isonicotinoyl hydrazone as a Schiff base ligand and its complexes with Cr(III), Mn(III), Fe(III), VO(IV), Zr(IV) and UO2(VI) metal ions have been synthesized. The ligands as well as their metal complexes were well characterized using various physicochemical techniques such as elemental analyses, molar conductance measurements, magnetic measurements, thermal analysis, electronic and IR spectral studies. On the basis of these studies, square pyramidal stereochemistry for Mn(III) and VO(IV) complexes while octahedral stereochemistry for all the other complexes have been suggested. The complexes were found to be stable up to 60-70° and thermal decomposition of the complexes ended with respective metal oxide as a final product. The thermal data have been analyzed for kinetic parameters using Broido and Horowitz-Metzger methods. The synthesized Schiff base ligand and its complexes were also tested for their antimicrobial activity using various microorganisms. PMID:26664052

  11. Anomalous Hall effect in Cr doped FeSi

    NASA Astrophysics Data System (ADS)

    Yadam, Sankararao; Lakhani, Archana; Singh, Durgesh; Prasad, Rudra; Ganesan, V.

    2016-05-01

    Investigations of economically affordable bulk materials for the spin based electronics are in huge demand. In this direction, electrical and Hall transport properties of the polycrystalline Cr doped Kondo insulator FeSi, i.e Fe0.975Cr0.025Si is reported. Well agreement between temperature dependence of the Hall and linear resistivity are observed. The observed minimum at ~19K in the resistivity is attributed to the ferromagnetic transition temperature (TC). Anomalous Hall resistivity is seen in the itinerant ferromagnet, Fe0.975Cr0.025Si well below the TC. The obtained Hall resistivity is comparable with that of the spintronic material Fe0.9Co0.1Si. The present study proves that the electrical transport properties of bulk materials made by low cost elements such as Fe, Cr and Si exhibits large magnetic field effects and are useful for the spintronics applications, unlike spintronics material (Ga, Mn)As that demand higher costs.

  12. The influence of cooling rate and Fe/Cr content on the evolution of Fe-rich compounds in a secondary Al-Si-Cu diecasting alloy

    NASA Astrophysics Data System (ADS)

    Fabrizi, A.; Timelli, G.

    2016-03-01

    This study investigates the morphological evolution of primary α-Al(Fe,Mn,Cr)Si phase in a secondary Al-Si-Cu alloy with respect to the initial Fe and Cr contents as well as to the cooling rate. The solidification experiments have been designed in order to cover a wide range of cooling rates, and the Fe and Cr contents have been varied over two levels. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes occurring at different experimental conditions. The morphological evolution of the α-Fe phase has been also analysed by observing deep etched samples. By changing the cooling rate, α-Al15(Fe,Mn,Cr)3Si2 dodecahedron crystals, as well as Chinese- script, branched structures and dendrites form, while primary coarse β-Al5(Fe,Mn)Si needles appear in the alloy with the highest Fe content at low cooling rates.

  13. A Study of Different Doped Metal Cations on the Physicochemical Properties and Catalytic Activities of Ce20 M1 Ox (M=Zr, Cr, Mn, Fe, Co, Sn) Composite Oxides for Nitric Oxide Reduction by Carbon Monoxide.

    PubMed

    Deng, Changshun; Li, Min; Qian, Junning; Hu, Qun; Huang, Meina; Lin, Qingjin; Ruan, Yongshun; Dong, Lihui; Li, Bin; Fan, Minguang

    2016-08-01

    This work is mainly focused on investigating the effects of different doped metal cations on the formation of Ce20 M1 Ox (M=Zr, Cr, Mn, Fe, Co, Sn) composite oxides and their physicochemical and catalytic properties for NO reduction by CO as a model reaction. The obtained samples were characterized by using N2 physisorption, X-ray diffraction, laser Raman spectroscopy, UV/Vis diffuse reflectance spectroscopy, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction by hydrogen and by oxygen (H2 -TPR and O2 -TPD), in situ diffuse reflectance infrared Fourier transform spectroscopy, and the NO+CO model reaction. The results imply that the introduction of M(x+) into the lattice of CeO2 increases the specific surface area and pore volume, especially for variable valence metal cations, and enhances the catalytic performance to a great extent. In this regard, increases in the oxygen vacancies, reduction properties, and chemisorbed O2 (-) (and/or O(-) ) species of these Ce20 M1 Ox composite oxides (M refers to variable valence metals) play significant roles in this reaction. Among the samples, Ce20 Cr1 Ox exhibited the best catalytic performance, mainly because it has the best reducibility and more chemisorbed oxygen, and significant reasons for these attributes may be closely related to favorable synergistic interactions of the vacancies and near-surface Ce(3+) and Cr(3+) . Finally, a possible reaction mechanism was tentatively proposed to understand the reactions. PMID:27435470

  14. 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.

  15. CrMn underlayers for CoCrPt thin film media

    SciTech Connect

    Lee, L.L.; Laughlin, D.E.; Lambeth, D.N.

    1998-07-01

    An improved CoCrPt thin film medium or longitudinal magnetic recording which has a coercivity significantly greater than prior CoCrPt thin film media was investigated. A CrMn alloy underlayer was used, instead of the conventional Cr underlayer. A coercivity value of 4,280 Oe was easily reached in a CoCrPt film on a 50 nm thick CrMn underlayer as compared to 2,810 Oe with a pure Cr underlayer. It was found that the coercivity increase due to the Mn addition was realized if the substrates were preheated before the sputtering. Grain boundary interdiffusion of Mn from the underlayer to the magnetic layer may be the cause for the coercivity increase.

  16. Structural and physical properties of the ferromagnetic tris-dithiooxalato compounds, A[M(II)Cr(III)(C(2)S(2)O(2))(3)], with A(+) = N(n-C(n)()H(2)(n)(+1))(4)(+) (n = 3-5) and P(C(6)H(5))(4)(+) and M(II) = Mn, Fe, Co, and Ni.

    PubMed

    Bradley, Justin M; Carling, Simon G; Visser, Dirk; Day, Peter; Hautot, Dimitri; Long, Gary J

    2003-02-24

    The structural and magnetic properties of the tris-dithiooxalato salts, A[M(II)Cr(C(2)S(2)O(2))(3)], have been investigated with A(+) = PPh(4)(+), N(n-C(n)()H(2)(n)()(+1))(4)(+), with n = 3-5, where M(II) is Mn, Fe, Co, and Ni. With the exception of A[MnCr(C(2)S(2)O(2))(3)], all the salts are ferromagnets with Curie temperatures, T(c), between 5 and 16 K. In contrast to the corresponding oxalates which are ferromagnetic, the A[MnCr(C(2)S(2)O(2))(3)] compounds are paramagnetic above 2 K. Powder neutron diffraction studies of d(20)-PPh(4)[FeCr(C(2)S(2)O(2))(3)] indicate that no structural phase transitions occur between 2.4 and 285 K and that the coefficient of linear expansion is four times larger for the c-axis than for the a-axis. The crystal structure refined from powder neutron diffraction data confirms the honeycomb layer arrangement observed in the related bimetallic tris-oxalate salts. The Mössbauer spectra reveal that the iron(II) in PPh(4)[FeCr(C(2)S(2)O(2))(3)] is coordinated mainly to six oxygen atoms of the dithiooxalato ligand but with a minor component of sulfur coordination that increases with aging of the sample; the iron(II) is high-spin in both cases. Powder neutron diffraction profiles of d(20)-PPh(4)[FeCr(C(2)S(2)O(2))(3)] below T(c) show magnetic intensity with a q = 0 propagation vector, confirming the presence of ferromagnetic order. PMID:12588130

  17. Reactivity of hydrated monovalent first row transition metal ions M(+)(H2O)n, M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, toward molecular oxygen, nitrous oxide, and carbon dioxide.

    PubMed

    van der Linde, Christian; Hemmann, Sonja; Höckendorf, Robert F; Balaj, O Petru; Beyer, Martin K

    2013-02-14

    The reactions of hydrated monovalent transition metal ions M(+)(H(2)O)(n), M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, toward molecular oxygen, nitrous oxide, and carbon dioxide were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Clusters containing monovalent chromium, cobalt, nickel, or zinc were reactive toward O(2), while only hydrated cobalt was reactive toward N(2)O. A strongly size dependent reactivity was observed. Chromium and cobalt react very slowly with carbon dioxide. Nanocalorimetric analysis, (18)O(2) exchange, and collision induced dissociation (CID) experiments were done to learn more about the structure of the O(2) products. The thermochemistry for cobalt, nickel, and zinc is comparable to the formation of O(2)(-) from hydrated electrons. These results suggest that cobalt, nickel, and zinc are forming M(2+)/O(2)(-) ion pairs in the cluster, while chromium rather forms a covalently bound dioxygen complex in large clusters, followed by an exothermic dioxide formation in clusters with n ≤ 5. The results show that hydrated singly charged transition metal ions exhibit highly specific reactivities toward O(2), N(2)O, and CO(2). PMID:22506540

  18. 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.

  19. Synthesis and Characterization of Poly-phase Waste Form: Gd{sub 3}Fe{sub 5}O{sub 12}+(Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4}

    SciTech Connect

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

    2006-07-01

    The synthesis of poly-phase waste form, which is an immobilization matrix for the HLW, was performed with the mixed composition of garnet and spinel (Gd{sub 3}Fe{sub 5}O{sub 12}+(Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4}) at temperatures in the range of 1200 deg. C to 1400 deg. C. The phases synthesized from all stoichiometric compositions were garnet, perovskite, and spinel. Especially, garnet was synthesized only in the composition of the highest content of Fe(y=0.9), whereas it was not synthesized in other compositions. This result indicated that the content of Fe was closely related to the formation of garnet. The composition of garnet revealed that the content of Gd was exceeded and that of Fe was depleted. Preferential distribution of elements in the phases can be attributed to the nonstoichiometric composition of garnet. (authors)

  20. X-ray photoelectron spectroscopic analysis of oxidized Fe-16Cr-16Ni-2Mn-1Mo-2Si austenitic stainless steel

    SciTech Connect

    Poston, J.A., Jr.; Siriwardane, R.V.; Dunning, J.S.; Alman, D.E.; Rawers, J.C.

    2007-03-30

    Depth profile analysis (argon ion etching/X-ray photoelectron spectroscopy) was conducted on a series of Fe–16Cr–16Ni–2Mn–1Mo–2Si austenitic stainless steel samples oxidized at 973 and 1073 K with exposure times of 25, 100, 193, 436 and 700 h. Surface and near surface rearrangement following oxidation resulted in a region of high Cr concentration on all oxidized samples. Temperature and time dependence to O2 penetration depth was observed. In general, O2 penetration depth was found to increase with increasing exposure up to 436 h. No increase in depth was observed between 436 and 700 h exposure time.

  1. Influence of Bulk Chemical Composition on Relative Sensitivity Factors for 55Mn/52Cr by SIMS: Implications for the 53Mn-53Cr Chronometer

    SciTech Connect

    Matzel, J; Jacobsen, B; Hutcheon, I D; Kita, N; Ryerson, F J

    2009-09-09

    The {sup 53}Mn-{sup 53}Cr systematics of meteorite samples provide an important high resolution chronometer for early solar system events. Accurate determination of the initial abundance of {sup 53}Mn ({tau}{sub 1/2} = 3.7 Ma) by secondary ion mass spectrometry (SIMS) is dependent on properly correcting for differing ion yields between Mn and Cr by use of a relative sensitivity factor (RSF). Ideal standards for SIMS analysis should be compositionally and structurally similar to the sample of interest. However, previously published Mn-Cr studies rely on few standards (e.g., San Carlos olivine, NIST 610 glass) despite significant variations in chemical composition. We investigate a potential correlation between RSF and bulk chemical composition by determining RSFs for {sup 55}Mn/{sup 52}Cr in 11 silicate glass and mineral standards (San Carlos olivine, Mainz glasses KL2-G, ML3B-G, StHs6/80-G, GOR128-G, BM90/21-G, and T1-G, NIST 610 glass, and three LLNL pyroxene-composition glasses). All standards were measured on the Cameca ims-3f ion microprobe at LLNL, and a subset were also measured on the Cameca ims-1270 ion microprobe at the Geological Survey of Japan. The standards cover a range of bulk chemical compositions with SiO{sub 2} contents of 40-71 wt.%, FeO contents of 0.05-20 wt.% and Mn/Cr ratios between 0.4 and 58. We obtained RSF values ranging from 0.83 to 1.15. The data obtained on the ims-1270 ion microprobe are within {approx}10% of the RSF values obtained on the ims-3f ion microprobe, and the RSF determined for San Carlos olivine (0.86) is in good agreement with previously published data. The typical approach to calculating an RSF from multiple standard measurements involves making a linear fit to measured {sup 55}Mn/{sup 52}Cr versus true {sup 55}Mn/{sup 52}Cr. This approach may be satisfactory for materials of similar composition, but fails when compositions vary significantly. This is best illustrated by the {approx}30% change in RSF we see between

  2. Evaluation of hardening behaviors in ion-irradiated Fe-9Cr and Fe-20Cr alloys by nanoindentation technique

    NASA Astrophysics Data System (ADS)

    Li, Shilei; Wang, Yanli; Dai, Xianyuan; Liu, Fang; Li, Jinyu; Wang, Xitao

    2016-09-01

    The ion irradiation hardening behaviors of Fe-9 wt% Cr and Fe-20 wt% Cr model alloys were investigated by nanoindentation technique. The specimens were irradiated with 3 MeV Fe11+ ions at room temperature up to 1 and 5 dpa for Fe-9Cr alloy and 1 and 2.5 for Fe-20Cr alloy. The ratio of average hardness in the same depth of irradiated and unirradiated (Hirr. av/Hunirr. av) was used to determine the critical indentation depth hcrit to eliminate the softer substrate effect. The Nix-Gao model was used to explain the indentation size effect. Irradiation hardening is clearly observed in both Fe-9Cr alloy and Fe-20Cr alloy after ion irradiation. The differences of ISE and irradiation hardening behaviors between Fe-9Cr and Fe-20Cr alloys are considered to be due to their different microstructures and microstructural evolution under ion irradiation.

  3. Exploring the Cr2+ doping effect on structural, vibrational and dielectric properties of Mn-Zn ferrites

    NASA Astrophysics Data System (ADS)

    Choudhary, Pankaj; Tyagi, Tarun; Dar, M. A.; Varshney, Dinesh

    2016-05-01

    A series of Cr doped Mn-Zn ferrites with compositional formula Mn0.5Zn0.5-xCrxFe2O4 (x = 0, 0.3, 0.5) were prepared by solid-state reaction route. X-ray diffraction (XRD) analysis reveals that the samples prepared are polycrystalline cubic spinel in structure (Fd3m) with some secondary phase of α-Fe2O3. Slight variation in the lattice parameter of Cr doped Mn0.5Zn0.5Fe2O4 has been observed due to difference in ionic radii of cations. Small shift in Raman modes towards higher wave number has been observed. Further the line width decreases with the doping ions. A giant dielectric constant ~104 is observed for parent Mn0.5Zn0.5Fe2O4 which is found to decrease with increase in Cr2+ doping. Low dielectric loss is observed for Mn0.5Zn0.5Fe2O4 and improves with Cr2+ doping at Zn2+ site.

  4. The effect of interstitial carbon on the mechanical properties and dislocation substructure evolution in Fe40.4Ni11.3Mn34.8Al7.5Cr6 high entropy alloys

    DOE PAGESBeta

    Wang, Zhangwei; Baker, Ian; Cai, Zhonghou; Chen, Si; Poplawsky, Jonathan D.; Guo, Wei

    2016-09-01

    A systematic study of the effects of up to 1.1 at. % carbon on the mechanical properties and evolution of the dislocation substructure in a series of a high entropy alloys (HEA) based on Fe40.4Ni11.3Mn34.8Al7.5Cr6 is presented. Transmission electron microscopy (TEM), synchrotron X-ray diffraction (XRD) and atom probe tomography (APT) were used to show that all the alloys are single-phase f.c.c. random solid solutions. The lattice constant, determined from synchrotron XRD measurements, increases linearly with increasing carbon concentration, which leads to a linear relationship between the yield strength and the carbon concentration. The dislocation substructures, as determined by a TEM,more » show a transition from wavy slip to planar slip and, at higher strains, and from cell-forming structure (dislocations cells, cell blocks and dense dislocation walls) to non-cell forming structure (Taylor lattice, microbands and domain boundaries) with the addition of carbon, features related to the increase in lattice friction stress. The stacking fault energy (measured via weak-beam imaging of the separation of dislocation partials) decreases with increasing carbon content, which also contributes to the transition from wavy slip to planar slip. The formation of non-cell forming structure induced by carbon leads to a high degree of strain hardening and a substantial increase in the ultimate tensile strength. In conclusion, the consequent postponement of necking due to the high strain hardening, along with the plasticity accommodation arising from the formation of microbands and domain boundaries, result in an increase of ductility due to the carbon addition.« less

  5. 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

  6. 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

  7. Interstitial loop transformations in FeCr

    DOE PAGESBeta

    Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.; Xu, Haixuan

    2015-03-27

    Here, we improve the Self-Evolving Atomistic Kinetic Monte Carlo (SEAKMC) algorithm by integrating the Activation Relaxation Technique nouveau (ARTn), a powerful open-ended saddle-point search method, into the algorithm. We use it to investigate the reaction of 37-interstitial 1/2[1 1 1] and 1/2[View the MathML source] loops in FeCr at 10 at.% Cr. They transform into 1/2[1 1 1], 1/2[View the MathML source], [1 0 0] and [0 1 0] 74-interstitial clusters with an overall barrier of 0.85 eV. We find that Cr decoration locally inhibits the rotation of crowdions, which dictates the final loop orientation. Moreover, the final loop orientationmore » depends on the details of the Cr decoration. Generally, a region of a given orientation is favored if Cr near its interface with a region of another orientation is able to inhibit reorientation at this interface more than the Cr present at the other interfaces. Also, we find that substitutional Cr atoms can diffuse from energetically unfavorable to energetically favorable sites within the interlocked 37-interstitial loops conformation with barriers of less than 0.35 eV.« less

  8. Interstitial loop transformations in FeCr

    SciTech Connect

    Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.; Xu, Haixuan

    2015-03-27

    Here, we improve the Self-Evolving Atomistic Kinetic Monte Carlo (SEAKMC) algorithm by integrating the Activation Relaxation Technique nouveau (ARTn), a powerful open-ended saddle-point search method, into the algorithm. We use it to investigate the reaction of 37-interstitial 1/2[1 1 1] and 1/2[View the MathML source] loops in FeCr at 10 at.% Cr. They transform into 1/2[1 1 1], 1/2[View the MathML source], [1 0 0] and [0 1 0] 74-interstitial clusters with an overall barrier of 0.85 eV. We find that Cr decoration locally inhibits the rotation of crowdions, which dictates the final loop orientation. Moreover, the final loop orientation depends on the details of the Cr decoration. Generally, a region of a given orientation is favored if Cr near its interface with a region of another orientation is able to inhibit reorientation at this interface more than the Cr present at the other interfaces. Also, we find that substitutional Cr atoms can diffuse from energetically unfavorable to energetically favorable sites within the interlocked 37-interstitial loops conformation with barriers of less than 0.35 eV.

  9. Diffusion kinetics of Cr in spinel: Experimental studies and implications for 53Mn-53Cr cosmochronology

    NASA Astrophysics Data System (ADS)

    Posner, Esther S.; Ganguly, Jibamitra; Hervig, Richard

    2016-02-01

    The 53Mn-53Cr decay system, in which 53Mn decays to 53Cr (t1/2 = 3.7 Ma) has been widely used to construct 53Cr/52Cr vs. 55Mn/52Cr isochrons and thus determine relative ages of early solar system objects or events, assuming that the initial Cr isotopic ratio, (53Cr/52Cr)o, equals (53Mn/52Cr)o. With the primary objective of interpretation of these ages within a diffusion kinetic framework, we have determined the tracer diffusion coefficient of Cr in natural spinels, which are very close to the MgAl2O4 end-member composition, as a function of temperature and oxygen fugacity (f(O2)). It is found that the diffusion coefficient of Cr, D(Cr), in two stocks of spinels (referred to as cut-gems and gem-gravels) with very similar major element chemistry is consistently different, but the data in each stock yield well defined Arrhenius relations that show a difference of log D of 0.6-1.0, depending on temperature, with the D(Cr) in gem-gravel being higher than that in the cut-gem stock. The D(Cr) was found to have a positive dependence on f(O2) in the range of f(O2) of around ±2 log units relative to that of the wüstite-magnetite buffer. The difference in the D(Cr) between the two stocks and the observed D(Cr) vs. f(O2) relation has been explained in terms of a change of point defect concentration resulting from heterovalent substitution of trace elements and equilibration with the imposed f(O2) conditions, respectively. Assuming a homogeneous semi-infinite matrix, the closure temperature (Tc) of Cr diffusion in spinel has been calculated as a function of grain size, cooling rate, peak temperature (To) and f(O2). Also the dependence of D(Cr) and Tc(Cr) on the Cr# (i.e. Cr/(Cr + Al) ratio) has been accounted for using available D(Cr) vs. Cr# data in Suzuki et al. (2008). We argue, on the basis of crystal chemical considerations and available diffusion kinetic data for minerals, that the Tc for Mn should be much lower than that for Cr in spinel, olivine and orthopyroxene, and

  10. Corrosion Behavior of 35CrMn and Q235 Steel in Simulated Acid Rain Conditions

    NASA Astrophysics Data System (ADS)

    Zuo, Xiu-li; Xiang, Bin; Li, Xing; Wei, Zi-dong

    2012-04-01

    Effects of pH value, chloride ion concentration and alternation of wetting and drying time in acid rain on the corrosion of 35CrMn and Q235 steel were investigated through the measurement of polarization curves, electrochemical impedance spectroscopy, x-ray diffraction, and quantum mechanical calculations. The corrosion rate of 35CrMn and Q235 steel increased with decreasing pH values of the simulated acid rain, whereas the corrosion potential of 35CrMn and Q235 steel became more negative. The impedance became higher and the corrosion rate decreased with increasing test time. The dissolution rate of samples increased with chloride ion concentration. Results suggested that the corrosion rate of 35CrMn steel was obviously lower than that of Q235 steel for a more compact rust, α-FeOOH. Quantum chemical calculations further revealed that the increase in corrosion rate of the steel resulted from pitting corrosion caused by the corrosive chloride ion.

  11. 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.

  12. 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

  13. 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.

  14. Corrosion Behavior of Thermally Sprayed NiCrBSi Coating on 16MnR Low-Alloy Steel in KOH Solution

    NASA Astrophysics Data System (ADS)

    Zeng, Q.; Sun, J.; Emori, W.; Jiang, S. L.

    2016-05-01

    NiCrBSi coatings were selected as protective material and air plasma-sprayed on 16MnR low-alloy steel substrates. Corrosion behavior of 16MnR substrates and NiCrBSi coatings in KOH solution were evaluated by polarization resistance ( R p), potentiodynamic polarization curves, electrochemical impedance spectroscopy, and immersion corrosion tests. Electrolytes were solutions with different KOH concentrations. NiCrBSi coating showed superior corrosion resistance in KOH solution compared with the 16MnR. Corrosion current density of 16MnR substrate was 1.7-13.0 times that of NiCrBSi coating in the given concentration of KOH solution. By contrast, R p of NiCrBSi coating was 1.2-8.0 times that of the substrate, indicating that the corrosion rate of NiCrBSi coating was much lower than that of 16MnR substrate. Capacitance and total impedance value of NiCrBSi coating were much higher than those of 16MnR substrate in the same condition. This result indicates that corrosion resistance of NiCrBSi coating was better than that of 16MnR substrate, in accordance with polarization results. NiCrBSi coatings provided good protection for 16MnR substrate in KOH solution. Corrosion products were mainly Ni/Fe/Cr oxides.

  15. Radiation effects on interface reactions of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni)

    NASA Astrophysics Data System (ADS)

    Shao, Lin; Chen, Di; Wei, Chaochen; Martin, Michael S.; Wang, Xuemei; Park, Youngjoo; Dein, Ed; Coffey, Kevin R.; Sohn, Yongho; Sencer, Bulent H.; Rory Kennedy, J.

    2015-01-01

    We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 °C or 550 °C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reach the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick's laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.

  16. Radiation effects on interface reactions of U/Fe, U/(Fe+Cr), and U/(Fe+Cr+Ni)

    SciTech Connect

    Shao, Lin; Chen, Di; Wei, Chaochen; Martin, Michael S.; Wang, Xuemei; Park, Youngjoo; Dein, Ed; Coffey, Kevin R.; Sohn, Yongho; Sencer, Bulent H.; Rory Kennedy, J.

    2014-10-01

    We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 C or 550 C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reach the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick’s laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.

  17. Radiation effects on interface reactions of U/Fe, U/(Fe+Cr), and U/(Fe+Cr+Ni)

    DOE PAGESBeta

    Shao, Lin; Chen, Di; Wei, Chaochen; Martin, Michael S.; Wang, Xuemei; Park, Youngjoo; Dein, Ed; Coffey, Kevin R.; Sohn, Yongho; Sencer, Bulent H.; et al

    2014-10-01

    We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 C or 550 C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reachmore » the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick’s laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.« less

  18. Magnetotransport in La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/CuCr{sub 2}O{sub 4}/Fe{sub 3}O{sub 4} magnetic junctions

    SciTech Connect

    Iwata-Harms, Jodi M.; Suzuki, Yuri; Chopdekar, Rajesh V.; Wong, Franklin J.; Nelson-Cheeseman, Brittany B.; Jenkins, Catherine A.; Arenholz, Elke

    2015-01-05

    We demonstrate distinct magnetic and resistive switching with junction magnetoresistance up to −6% in magnetic tunnel junctions with a CuCr{sub 2}O{sub 4} barrier. Junction magnetoresistance is inversely related to barrier thickness and reveals a maximum at a finite applied bias that converges to zero bias at low temperatures for all barrier thicknesses. The non-monotonic bias dependence is attributed to a charge gap from the Fe{sub 3}O{sub 4} electrode and possible spin filtering from the spin-split conduction band of the ferrimagnetic CuCr{sub 2}O{sub 4} barrier.

  19. 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).

  20. 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

  1. Elastic anomalies in Fe-Cr alloys.

    PubMed

    Zhang, Hualei; Wang, Guisheng; Punkkinen, Marko P J; Hertzman, Staffan; Johansson, Börje; Vitos, Levente

    2013-05-15

    Using ab initio alloy theory, we determine the elastic parameters of ferromagnetic and paramagnetic Fe(1-c)Cr(c) (0 ≤ c ≤ 1) alloys in the body centered cubic crystallographic phase. Comparison with the experimental data demonstrates that the employed theoretical approach accurately describes the observed composition dependence of the polycrystalline elastic moduli. The predicted single-crystal elastic constants follow complex anomalous trends, which are shown to originate from the interplay between magnetic and chemical effects. The nonmonotonic composition dependence of the elastic parameters has marked implications on the micro-mechanical properties of ferrite stainless steels. PMID:23604218

  2. Ferromagnetic Fe2CrAl Nanowires

    NASA Astrophysics Data System (ADS)

    Dulal, Rajendra; Dahal, Bishnu; Pegg, Ian L.; Philip, John

    Heusler alloy Fe2CrAl (FCA) nanowires were grown on silicon substrates. Nanowires have diameters in the range 50 to 200 nm and lengths up to 100 µm. They exhibit cubic L21 and A2 type structure with a space group, Pm m. Magnetic characterization reveals that they display ferromagnetic behavior and has a Curie temperature above 400 K. Magnetic behavior of FCA nanowires is different from the reported bulk behavior. Bulk FCA with L21 structure has a Curie temperature around 274 K. National Science Foundation under ECCS-0845501 and NSF-MRI, DMR-0922997.

  3. 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

  4. Collinear spin-density-wave ordering in Fe/Cr multilayers and wedges

    SciTech Connect

    Fishman, R.S.; Shi, Z.

    1999-06-01

    {acute e}el temperature. Model II also predicts that the {ital I} SDW may undergo a single phase transition from n=m to m{minus}1 before disappearing above T{sub N}(N). This behavior has recently been confirmed by neutron-scattering measurements on CrMn/Cr multilayers. While model I very successfully predicts the behavior of Fe/Cr/Fe wedges, a refined version of model II describes some properties of sputtered Fe/Cr multilayers. {copyright} {ital 1999} {ital The American Physical Society}

  5. Bioaccumulation of Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn in trophosome and vestimentum of the tube worm Riftia pachyptila from Guaymas basin, Gulf of California

    NASA Astrophysics Data System (ADS)

    Ruelas-Inzunza, J.; Páez-Osuna, F.; Soto, Luis A.

    2005-07-01

    Twenty two specimens of vestimentiferan tube worms Riftia pachyptila were collected from Guaymas Basin. The distribution of ten trace metals in trophosome and vestimentum was investigated. Highest mean concentrations of Co, Cu and Fe were detected in the trophosome; while higher mean levels of Cd, Hg, Mn, Ni, Pb and Zn were measured in the vestimentum. However, the t-student test resulted in significant differences (p<0.05) only in the case of Co. Cd and Fe concentrations in vestimentum increased accordingly with the size of specimens. With respect to vent fluids, extreme uptake seems to be a characteristic of R. pachyptila in the case of Cu and Zn but not for the rest of the analyzed metals. Studies concerning accumulation mechanisms of trace metals in R. pachyptila are needed, particularly on the capacity of this organism to tolerate elevated levels of elements considered as non-essential.

  6. Interaction UMo fuel with Fe and FeCr

    NASA Astrophysics Data System (ADS)

    Nikitin, S. N.; Shornikov, D. P.; Tarasov, B. A.; Baranov, V. G.

    2016-04-01

    Uranium-molybdenum alloys are perspective nuclear fuel for fast reactors. In this work, a study was conducted of the interaction of uranium-molybdenum alloy with iron and chromium steel at an elevated temperature of 750 °C for 5 hours. It was found that the constant rate of the interaction layer growth for diffusion couple UMo/FeCr is about 5.4-10-12 m2/s at 750 °C. The phase composition of the interaction layers for the both diffusion couples was determined. The interaction comes along the grain boundaries, there are not interacts UMo alloy grain in the structure of the diffusion zone.

  7. 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

  8. Cr(III) Oxidation Coupled With Microbially-Mediated Mn(II) Oxidation

    SciTech Connect

    Youxian Wu; Baolin Deng

    2006-04-05

    Cr(VI) can be reduced to less toxic and mobile Cr(III) species through abiotic and biological processes. Reductive immobilization of Cr(VI) has been widely explored as a cost effective technology for site remediation; Mn oxides are regarded as primary oxidants for Cr(III) oxidation in the environment; and Generation of Mn oxides from Mn(II) in natural environments is believed to be biologically catalyzed.

  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. Ring head recording on perpendicular media: Output spectra for CoCr and CoCr/NiFe media

    NASA Astrophysics Data System (ADS)

    Stubbs, D. P.; Whisler, J. W.; Moe, C. D.; Skorjanec, J.

    1985-04-01

    The recording density response for sputtered CoCr (thickness=0.5 μm) and CoCr/NiFe (t=0.25 μm/0.5 μm) as well as evaporated CoNi (t=0.12 μm) and Co surface-doped iron oxide particulate media has been measured by reading and writing with Mn-Zn ferrite heads (gap length=0.375 μm, track width=37 μm) in contact with the media. Measurements to 200 kfc/i (thousand flux changes per inch) show a gap null around 115 kfc/i. The data have been normalized by dividing out the head sensitivity to obtain the value of spacing plus transition width (d+a) for the various media. For the CoCr media this value varied from 0.075-0.088 μm; for CoNi, 0.100 μm, and for the particulate medium, 0.163 μm. In addition, testing with a larger gapped Mn-Zn ferrite head (g=2.43 μm) shows that the head fields are distorted by the soft magnetic underlayer in dual layer CoCr/NiFe samples when the gap length is large compared to the distance to the underlayer.

  11. Nanoparticles of pure and substituted maghemites (gamma-M(x)Fe(2_x)O3 where M = Al, Cr, Mn, Zn and 0 < or = x < or = 1.3): a comparative study.

    PubMed

    Prasad, N K; Gohri, V; Bahadur, D

    2011-03-01

    Magnetic nanoparticles of pure and substituted iron oxides are prepared by single step autocombustion or by wet chemical methods. The nanoparticles prepared by the first process had mixed phase of hematite and maghemite whereas the later essentially gives maghemite phase. XRD patterns and TEM micrographs of the pure and substituted maghemites samples suggest about their monophasic nature and inverse spinel structure. Further, the size of the particles for the above iron oxide samples was found to be in the range of 4 to 30 nm. Saturation magnetization value for the samples was observed to be varying with the type and the amount of substitution. For example, magnetization value initially increased and then decreased for Al- and Mn-substitutions but it continuously decreased for Cr- and Zn-substitutions. Contrary to the saturation magnetization value, the Curie temperature decreased continuously with increased substitutions irrespective of the type of substitutions. Due to higher magnetization value of Mn-substituted maghemite (for x = 0.2, 78 Am2/kg), it has higher heating ability and specific absorption rate compared to Al-substituted maghemite (for x = 0.07, 70 Am2/kg) and pure maghemite (62 Am2/kg). PMID:21449460

  12. Textures of strip cast Fe16%Cr

    SciTech Connect

    Raabe, D.; Reher, F.; Luecke, K. ); Hoelscher, M. )

    1993-07-01

    Ferritic stainless steels with a Cr content of 16% are mainly manufactured by continuous casting, hot rolling, cold rolling and final recrystallization. The recent development of the strip casting method, which provides sheets with an equivalent geometry, i.e. thickness and width as the hot rolled band, yields significant improvements in comparison to the conventional processing. The weak initial strip texture and the homogeneous microstructure through the sample thickness have shown evidence of avoiding the well known ridging phenomenon of the finally rolled and annealed product. The occurrence of ridging in conventionally processed FeCr steel has been attributed to the collective shear of grains with (hkl)<110>, i.e. [alpha]-fibre orientations, which become oriented and topologically arranged during hot rolling. In the present paper the textures of a stainless ferritic steel with 16% Cr and 0.02% C, strip casted (SC) as well as hot rolled (HR), were thus investigated. The textures were examined by measuring the four incomplete pole figures (110), (200), (112) and (103) in the back reflection mode. The orientation distribution function (ODF) was calculated by the series expansion method (1[sup max]=22). In the case of cubic crystal symmetry and orthorhombic sample symmetry an orientation can then be presented by the three Euler angles [var phi][sub 1], [var phi], [var phi][sub 2] in the reducted Euler space. Since bcc steels tend to develop characteristic fibre textures, it is favorable to present the ODFs as isointensity diagrams in [var phi][sub 1]-sections through the Eulerspace. In this work the [alpha]-fibre and the [gamma]-fibre are of major interest.

  13. 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. 

  14. A novel low Cr-containing Fe-Cr-Co alloy for metallic interconnects in planar intermediate temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, Wenying; Yan, Dong; Yang, Jie; Chen, Jing; Chi, Bo; Pu, Jian; Li, Jian

    2014-12-01

    A newly developed low-Cr containing Fe-Cr-Co alloy, named as FeCro, is evaluated as a candidate material of metallic interconnects for intermediate temperature solid oxide fuel cells (IT-SOFCs). This alloy possesses excellent oxidation resistance and adequate electrical conductivity at 750 °C in air, and shows slight Cr deposition in/around La0.72Sr0.18MnO3(LSM) electrode under a harsh accelerating condition of 400 mA cm-2 and 850 °C. The thickness of the oxide scale thermally grown at 750 °C in air for 1000 his less than 1 μm, presenting a double-layered structure with dense (Mn, Cr)3O4 on the top of Cr2O3. The oxidation kinetics at 750 °C obeys the parabolic law with a low rate constant of1.42 × 10-15 g2 cm-4 s-1. The Cr deposition in/around the LSM electrode in the presence of the FeCro alloy is remarkably reduced, compared to the commercial Crofer 22H alloy. The measured area specific resistance (ASR) at 750 °C in air after 1000 h isothermal oxidation is 14 mΩ cm2. It is the unique microstructure of the formed oxide scale that significantly enhances the resistances of the FeCro alloy to oxidation and Cr volatilization.

  15. Electrochemical Studies of Passive Film Stability on Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 Amorphous Metal in Seawater at 90oCElectrochemical Studies of Passive Film Stability on Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 Amorphous Metal in Seawater at 9

    SciTech Connect

    Farmer, J C; Haslam, J; Day, S D; Lian, T; Saw, C K; Hailey, P D; Choi, J S; Rebak, R B; Yang, N; Payer, J H; Perepezko, J H; Hildal, K; Lavernia, E J; Ajdelsztajn, L; Branagan, D J; Buffa, E J; Aprigliano, L F

    2007-04-25

    An iron-based amorphous metal, Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4} (SAM2X5), with very good corrosion resistance was developed. This material was prepared as a melt-spun ribbon, as well as gas atomized powder and a thermal-spray coating. During electrochemical testing in several environments, including seawater at 90 C, the passive film stability was found to be comparable to that of high-performance nickel-based alloys, and superior to that of stainless steels, based on electrochemical measurements of the passive film breakdown potential and general corrosion rates. This material also performed very well in standard salt fog tests. Chromium (Cr), molybdenum (Mo) and tungsten (W) provided corrosion resistance, and boron (B) enabled glass formation. The high boron content of this particular amorphous metal made it an effective neutron absorber, and suitable for criticality control applications. This material and its parent alloy maintained corrosion resistance up to the glass transition temperature, and remained in the amorphous state during exposure to relatively high neutron doses.

  16. 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.

  17. Cyclic and isothermal oxidation behavior at 1100 and 1200 C of Ni-20Cr, Ni-20Cr-3Mn, Ni-20Cr-3Si, and Ni-40Cr alloys

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.

    1973-01-01

    Alloys of Ni-20Cr, Ni-20Cr-3Mn, Ni-20Cr-3Si, and Ni-40Cr were cyclically oxidized at 1100 and 1200 C for up to 100 hours. Oxidation behavior was judged by sample thickness and weight change, metallography, diffraction, and microprobe analysis. The least attacked were Ni-40Cr and Ni-20Cr-3Si. The alloy Ni-20Cr-3Mn was much less attacked than Ni-20Cr, but more than the other alloys. The formation of Cr2O3 accounted for the increased resistance of Ni-Cr and Ni-20Cr-3Si, and the formation of MnCr2O4 accounts for the improvement in Ni-20Cr-3mn over Ni-20Cr.

  18. Cr(OH)₃(s) Oxidation Induced by Surface Catalyzed Mn(II) Oxidation

    SciTech Connect

    Namgung, Seonyi; Kwon, M.; Qafoku, Nikolla; Lee, Gie Hyeon

    2014-09-16

    This study examined the feasibility of Cr(OH)₃(s) oxidation mediated by surface catalyzed Mn(II) oxidation under common groundwater pH conditions as a potential pathway of natural Cr(VI) contaminations. Dissolved Mn(II) (50 μM) was reacted with or without synthesized Cr(OH)₃(s) (1.0 g/L) at pH 7 – 9 under oxic or anoxic conditions. In the absence of Cr(OH)₃(s), homogeneous Mn(II) oxidation by dissolved O₂ was not observed at pH ≤ 8.0 for 50 d. At pH 9.0, by contrast, dissolved Mn(II) was completely removed within 8 d and precipitated as hausmannite. When Cr(OH)₃(s) was present, this solid was oxidized and released substantial amounts of Cr(VI) as dissolved Mn(II) was added into the suspension at pH ≥ 8.0 under oxic conditions. Our results suggest that Cr(OH)₃(s) was readily oxidized by a newly formed Mn oxide as a result of Mn(II) oxidation catalyzed on Cr(OH)₃(s) surface. XANES analysis of the residual solids after the reaction between 1.0 g/L Cr(OH)₃(s) and 204 μM Mn(II) at pH 9.0 for 22 d revealed that the product of surface catalyzed Mn(II) oxidation resembled birnessite. The rate and extent of Cr(OH)₃(s) oxidation was likely controlled by those of surface catalyzed Mn(II) oxidation as the production of Cr(VI) increased with increasing pH and initial Mn(II) concentrations. This study evokes the potential environmental hazard of sparingly soluble Cr(OH)₃(s) that can be a source of Cr(VI) in the presence of dissolved Mn(II).

  19. Inverse and oscillatory magnetoresistance in Fe(001)/MgO/Cr/Fe magnetic tunnel junctions

    SciTech Connect

    Zhang, J.; Wang, Y.; Zhang, Xiaoguang; Han, Prof. X. F.

    2010-01-01

    The effect of Cr(001) insertion layers in Fe(001)/MgO/Cr/Fe magnetic tunneling junctions (MTJs) is studied from first-principles. It is shown that with the increase of the Cr(001) layer thickness, the tunneling magnetoresistance (TMR) first decreases rapidly and then oscillates with a two-monolayer period. At some thicknesses, the oscillation leads to a sign reversal of the TMR. The oscillatory interfacial Cr moment at the Cr-MgO interface as a function of the Cr layer thickness, which arises from the layer-anti-ferromagnetic ordering of Cr, is the cause for the oscillatory TMR.

  20. 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.

  1. Resistance of Nanostructured Fe-Cr Alloys to Oxidative Degradation: Role of Zr and Cr Contents

    NASA Astrophysics Data System (ADS)

    Mahesh, B. V.; Singh Raman, R. K.; Koch, C. C.

    2015-04-01

    This article investigates the effect of grain size and Cr concentration on the oxidation resistance of nanocrystalline Fe-Cr alloys having varying Cr contents between 2 and 10 wt pct. The results have been compared with microcrystalline Fe-Cr alloys with 10 and 20 wt pct Cr. Pellets of nanocrystalline and microcrystalline Fe-Cr alloys were prepared by mechanical alloying followed by hot compaction and sintering, and then oxidized at 823 K (550 °C) for 150-hours. Oxidation kinetics was determined by measuring the weight gain during oxidation, and the post-oxidation characterization of the oxide scales was performed using secondary ion mass spectroscopy. The chromium content at the inner oxide scale of nanocrystalline Fe-Cr alloys (with >7 pct Cr) was found to be comparable with that of microcrystalline 20 pctCr alloy, which suggests that nanocrystalline grain size distribution can be exploited to develop highly oxidation resistant alloys with much lower amounts of expensive alloying element (Cr). A mechanistic understanding of the high temperature oxidation in nanostructured alloys has been presented and the critical amount of bulk Cr content required to form a protective chromia layer has been calculated. The paper also investigates the role of a reactive element Zr on the high temperature oxidation resistance of nanocrystalline Fe-Cr. The beneficial effect is more pronounced at low bulk Cr (2 to 4 pct) concentrations (compared to higher Cr (>7 pct) concentration), however, at low bulk Cr, insufficient Cr enrichment occurs to establish a protective chromium oxide layer.

  2. Bulk modulus and specific heat of B-site doped (La{sub 0.3}Pr{sub 0.7}){sub 0.65}Ca{sub 0.35}Mn{sub 1−x}B{sub x}O{sub 3} (B=Fe, Cr, Ru, Al, Ga)

    SciTech Connect

    Srivastava, Archana; Thakur, Rasna; Gaur, N. K.

    2014-04-24

    Specific heat (C{sub p}) thermal expansion (α) and Bulk modulus (B{sub T}) of lightly doped Rare Earth manganites (La{sub 0.3}Pr{sub 0.7}){sub 0.65}Ca{sub 0.35}Mn{sub 1−x}B{sub x}O{sub 3} (B{sup 3+} = Fe{sup 3+},Cr{sup 3+},Ga{sup 3+},Al{sup 3+},Ru4+); (0.3Mn{sub 0.97}Fe{sub 0.03}O{sub 3} as a function of temperature (10K≤T≤ 200K) is found to be in agreement with the published data. The trend of variation of Debye temperature with B-site cationic radius is predicted probably for the first time for the B-site doped rare earth manganites.

  3. Optimizing NiCr and FeCr HVOF Coating Structures for High Temperature Corrosion Protection Applications

    NASA Astrophysics Data System (ADS)

    Oksa, M.; Metsäjoki, J.

    2015-02-01

    In order to achieve a desired dense structure for coatings employed in high temperature corrosion conditions, thermal spray process optimization with diagnostic tools can be applied. In this study, NiCr (51Ni-46Cr-2Si-1Fe) and FeCr (Fe-19Cr-9W-7Nb-4Mo-5B-2C-2Si-1Mn) powders were sprayed with HVOFGF (gas-fueled) and HVOFLF (liquid-fueled) systems, and the spray processes were monitored with diagnostic tools, including SprayWatch for measuring the temperature and velocity of the spray stream, and in situ coating property (ICP measurement) for measuring the stress state. Various spray parameters were applied to attain the best coating characteristics for high temperature applications. Selected coatings were exposed to high temperature corrosion conditions both in laboratory and actual power plant. The coatings were analyzed by microscopic means and mechanical testing. The application of process-structure-properties-performance methodology with the process monitoring, analysis of the coating characteristics, and results of corrosion performance are presented in this paper.

  4. Negative-Electrode Catalysts for Fe/Cr Redox Cells

    NASA Technical Reports Server (NTRS)

    Gahn, R. F.; Hagedorn, N.

    1987-01-01

    Electrodes perform more consistently and less expensive. Surfaces catalyzed by bismuth and bismuth/lead developed for application on chromium electrode in iron/chromium redox electrochemical energy storage system. NASA Fe/Cr storage system incorporates two soluble electrodes consisting of acidified solutions of iron chloride (FeC13 and FeC12) and chromium chloride (CrC13 and CrC12) oxidized and reduced in power-conversion unit to store and produce electricity. Electrolytes circulated with pumps and stored in external tanks.

  5. Amorphization of C-implanted Fe(Cr) alloys

    SciTech Connect

    Knapp, J.A.; Follstaedt, D.M.; Sorensen, N.R.; Pope, L.E.

    1990-01-01

    The amorphous phase formed by implanting C into Fe alloyed with Cr, which is prototype for the amorphous phase formed by implanting C into stainless steels, is compared to that formed by implanting C plus Ti into Fe and steels. The composition range of the phase has been examined; higher Cr and C concentrations are required than needed with Ti and C. The friction and wear benefits obtained by implanting stainless steels with C alone do not persist for the long durations and high wear loads found with Ti and C. However, the amorphous Fe-Cr-C alloys exhibits good aqueous corrosion resistance. 9 refs., 3 figs., 1 tabs.

  6. CASSCF/CI calculations for first row transition metal hydrides - The TiH(4-phi), VH(5-delta), CrH(6-sigma-plus), MnH(7-sigma-plus), FeH(4,6-delta) and NiH(2-delta) states

    NASA Technical Reports Server (NTRS)

    Walch, S. P.; Bauschlicher, C. W., Jr.

    1983-01-01

    Calculations are performed for the predicted ground states of TiH(4-phi), VH(5-delta), CrH(6-sigma-plus), MnH(7-sigma-plus), Fett(4,6-delta) and NiH(2-delta). For FeH both the 6-delta and 4-delta states are studied, since both are likely candidates for the ground state. The ground state symmetries are predicted based on a combination of atomic coupling arguments and coupling of 4s(2)3d(n) and 4s(1)3d(n+1) terms in the molecular system. Electron correlation is included by a CASSCF/CI (SD) treatment. The CASSCF includes near-degeneracy effects, while correlation of the 3d electrons in included at the CI level.

  7. Nucleation of Cr precipitates in Fe-Cr alloy under irradiation

    SciTech Connect

    Dai, Y. Y.; Ao, L.; Sun, Qing- Qiang; Yang, L.; Nie, JL; Peng, SM; Long, XG; Zhou, X. S.; Zu, Xiaotao; Liu, L.; Sun, Xin; Terentyev, Dimtry; Gao, Fei

    2015-04-01

    The nucleation of Cr precipitates induced by overlapping of displacement cascades in Fe-Cr alloys has been investigated using the combination of molecular dynamics (MD) and Metropolis Monte Carlo (MMC) simulations. The results reveal that the number of Frenkel pairs increases with the increasing of overlapped cascades. Overlapping cascades could promote the formation of Cr precipitates in Fe-Cr alloys, as analyzed using short range order (SRO) parameters to quantify the degree of ordering and clustering of Cr atoms. In addition, the simulations using MMC approach show that the presence of small Cr clusters and vacancy clusters formed within cascade overlapped region enhance the nucleation of Cr precipitates, leading to the formation of large Cr dilute precipitates.

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. V, Cr, and Mn in the earth, moon, EPB, and SPB and the origin of the moon - Experimental studies

    NASA Technical Reports Server (NTRS)

    Drake, Michael J.; Capobianco, Christopher J.; Newsom, Horton E.

    1989-01-01

    The abundances of V, Cr, and Mn inferred for the mantles of the earth and moon decrease in that order and are similar in both mantles (but distinct from those in the mantles of the Eucrite Parent Body and Shergottite Parent Body), suggesting a common origin for the mantles of the earth and the moon. This hypothesis was investigated on the basis of a comparison between the depletions of V, Cr, and Mn in the mantles of the earth and the moon, and the metal/silicate partition coefficients of these elements at 1260 C and 1 bar pressure among a S-bearing metallic liquid, a silicate melt, and a FeNi alloy. It was found that the earth and the moon depletions of V, Cr, and Mn are not correlated with metal/silicate partition coefficients; the V and Cr partitioned into S-rich metallic liquids under reducing conditions more strongly than Mn, consistent with the relative volatilities of these elements. This indicates that the depletion patterns of these elements in the mantles of the earth and moon cannot be attributed primarily to terrestrial core formation.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Mn-Cr systematics in primitive meteorites: Insights from mineral separation and partial dissolution

    NASA Astrophysics Data System (ADS)

    Göpel, Christa; Birck, Jean-Louis; Galy, Albert; Barrat, Jean-Alix; Zanda, Brigitte

    2015-05-01

    Cr isotopic compositions have been measured on carbonaceous chondrites (CC): Tafassasset, Paris, Niger I, NWA 5958, NWA 8157 and Jbilet Winselwan. In bulk samples, the 54Cr/52Cr ratios (expressed as ε54Cr) range from 0.93 to 1.58 ε units. These values are in agreement with values characteristic for distinct petrologic types. Despite this 54Cr heterogeneity, the variability in the 53Cr/52Cr ratios (expressed as ε53Cr) of 0.2 ε units and the Mn/Cr ratios is consistent with the previous finding of an isochron in the Mn-Cr evolution diagram. The Mn/Cr ratio in CC corresponds to variable abundances of high-T condensate formed and separated at the beginning of the solar system, thus the canonical 53Mn/55Mn ratio can be defined. Based on a consistent chronology for U-Pb and Mn-Cr between the earliest objects formed in the solar nebula and the D'Orbigny angrite we define a canonical 53Mn/55Mn ratio and ε53Cri of 6.8 × 10-6 and -0.177, respectively. The internal Mn/Cr systematics in Tafassasset and Paris were studied by two approaches: leaching technique and mineral separation. Despite variable ε54Cr values (up to >30 ε) linear co-variations were found between ε53Cr and Mn/Cr ratio. The mineral separates as well as the leachates of Tafassasset fall on a common isochron indicating that (1) cooling of the Tafassasset's parent body occurred at 4563.5 ± 0.25 Ma, and that (2) 54Cr is decoupled from the other isotopes even though temperatures >900 °C have been reached during metamorphism. In the case of Paris, the leachates form an alignment with a 53Mn/55Mn ratio higher than the canonical value. This alignment is not an isochron but rather a mixing line. Based on leachates from various CM and CI, we propose the occurrence of three distinct Cr reservoirs in meteoritic material: PURE54, HIGH53 and LOW53 characterized by a ε53Cr and ε54Cr of 0 and 25,000, -2.17 and 8, and 0.5 and -151, respectively. PURE54 has already been described and is carried by highly refractory

  18. Quantification of corrosion resistance of a new-class of criticality control materials: thermal-spray coatings of high-boron iron-based amorphous metals - Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4

    SciTech Connect

    Farmer, J C; Choi, J S; Shaw, C K; Rebak, R; Day, S D; Lian, T; Hailey, P; Payer, J H; Branagan, D J; Aprigliano, L F

    2007-03-28

    An iron-based amorphous metal, Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4} (SAM2X5), with very good corrosion resistance was developed. This material was produced as a melt-spun ribbon, as well as gas atomized powder and a thermal-spray coating. Chromium (Cr), molybdenum (Mo) and tungsten (W) provided corrosion resistance, and boron (B) enabled glass formation. The high boron content of this particular amorphous metal made it an effective neutron absorber, and suitable for criticality control applications. Earlier studies have shown that ingots and melt-spun ribbons of these materials have good passive film stability in these environments. Thermal spray coatings of these materials have now been produced, and have undergone a variety of corrosion testing, including both atmospheric and long-term immersion testing. The modes and rates of corrosion have been determined in the various environments, and are reported here.

  19. Oxidation of Fe-Cr-Al and Fe-Cr-Al-Y Single Crystals

    NASA Astrophysics Data System (ADS)

    Grabke, H. J.; Siegers, M.; Tolpygo, V. K.

    1995-03-01

    Single crystal samples of the alloy Fe-20%Cr-5%Al with and without Y-doping were used to study the "reactive element" (RE) effect, which causes improved oxidation behaviour and formation of a protective Al2O3 layer on this alloy. The oxidation was followed by AES at 10-7 mbar O2 up to about 1000 °C. Most observations were peculiar for this low pO2 environment, but yttrium clearly favors the formation of Al-oxide and stabilizes it also under these conditions, probably by favoring its nucleation. The oxides formed are surface compounds of about monolayer thickness, not clearly related to bulk oxides. Furthermore, the morphologies of oxide scales were investigated by SEM, after oxidation at 1000°C for 100 h at 133 mbar O2. On Fe-Cr-Al the scale is strongly convoluted and tends to spalling, whereas the presence of Y leads to flat scales which are well adherent. This difference is explained by a change in growth mechanism. The tendency for separation of oxide and metal was highest for the samples with low energy metal surface, i.e. (100) and (110), the scale was better adherent on the (111) oriented surface and on the polycrystalline specimen, since in the latter cases the overall energy for scale/metal separation is higher. All observations, from the low and from the high pO2 experiments, are discussed in relation to the approximately ten mechanisms proposed in the literature for explanation of the RE effects.

  20. Synthesis and characterization of MnCrO4, a new mixed-valence antiferromagnet.

    PubMed

    Nalbandyan, Vladimir B; Zvereva, Elena A; Yalovega, Galina E; Shukaev, Igor L; Ryzhakova, Anastasiya P; Guda, Alexander A; Stroppa, Alessandro; Picozzi, Silvia; Vasiliev, Alexander N; Whangbo, Myung-Hwan

    2013-10-21

    A new orthorhombic phase, MnCrO4, isostructural with MCrO4 (M = Mg, Co, Ni, Cu, Cd) was prepared by evaporation of an aqueous solution, (NH4)2Cr2O7 + 2 Mn(NO3)2, followed by calcination at 400 °C. It is characterized by redox titration, Rietveld analysis of the X-ray diffraction pattern, Cr K edge and Mn K edge XANES, ESR, magnetic susceptibility, specific heat and resistivity measurements. In contrast to the high-pressure MnCrO4 phase where both cations are octahedral, the new phase contains Cr in a tetrahedral environment suggesting the charge balance Mn(2+)Cr(6+)O4. However, the positions of both X-ray absorption K edges, the bond lengths and the ESR data suggest the occurrence of some mixed-valence character in which the mean oxidation state of Mn is higher than 2 and that of Cr is lower than 6. Both the magnetic susceptibility and the specific heat data indicate an onset of a three-dimensional antiferromagnetic order at TN ≈ 42 K, which was confirmed also by calculating the spin exchange interactions on the basis of first principles density functional calculations. Dynamic magnetic studies (ESR) corroborate this scenario and indicate appreciable short-range correlations at temperatures far above TN. MnCrO4 is a semiconductor with activation energy of 0.27 eV; it loses oxygen on heating above 400 °C to form first Cr2O3 plus Mn3O4 and then Mn1.5Cr1.5O4 spinel. PMID:24090277

  1. 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.

  2. Electronic properties of excess Cr at Fe site in FeCr{sub 0.02}Se alloy

    SciTech Connect

    Kumar, Sandeep Singh, Prabhakar P.

    2015-06-24

    We have studied the effect of substitution of transition-metal chromium (Cr) in excess on Fe sub-lattice in the electronic structure of iron-selenide alloys, FeCr{sub 0.02}Se. In our calculations, we used Korringa-Kohn-Rostoker coherent potential approximation method in the atomic sphere approximation (KKR-ASA-CPA). We obtained different band structure of this alloy with respect to the parent FeSe and this may be reason of changing their superconducting properties. We did unpolarized calculations for FeCr{sub 0.02}Se alloy in terms of density of states (DOS) and Fermi surfaces. The local density approximation (LDA) is used in terms of exchange correlation potential.

  3. Long afterglow properties of Zn2GeO4:Mn2+, Cr3+ phosphor

    NASA Astrophysics Data System (ADS)

    Cong, Yan; He, Yangyang; Dong, Bin; Xiao, Yu; Wang, Limei

    2015-04-01

    Zn2GeO4:Mn2+, Cr3+ phosphors were prepared by conventional solid state reaction and the photoluminescence properties were investigated. The Mn2+ activated Zn2GeO4 phosphors exhibited green emission at 533 nm due to the 4T1(4G) → 6A1(6S) transition of Mn2+ ions. With Cr3+ co-doping in Zn2GeO4 host, long afterglow characteristics were found from the same transition of Mn2+. The TL results revealed the presence of same traps in the phosphor, and the doping of Cr3+ ions deepened the VGe traps. The native defect VGe as a hole traps is responsible for the long afterglow emission in Zn2GeO4:Mn2+, Cr3+ phosphor. The possible mechanism of this phosphor has also been discussed.

  4. 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.

  5. 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

  6. Effects of Cr on the interdiffusion between Ce and Fe-Cr alloys

    NASA Astrophysics Data System (ADS)

    Lo, Wei-Yang; Silva, Nicolas; Wu, Yuedong; Winmann-Smith, Robert; Yang, Yong

    2015-03-01

    Fuel cladding chemical interaction (FCCI) has been a long-standing issue for the metallic fuel with a steel cladding in a sodium-cooled fast reactor, particularly for a high burnup fuel. Although the FCCI has been largely improved by alloying the fuels with Zr or Pd elements, applying a physical diffusion barrier between fuel and cladding, and employing advanced ferritic/martensitic (F/M) claddings, there is a scientific knowledge gap in understanding the behavior of chromium and its effects on the interdiffusion between lanthanides and advanced F/M steels that contain 9-12 wt.% Cr. In this paper, we systematically studied the interdiffusion between cerium and Fe-Cr model alloys with Cr contents of 6, 9 and 12 wt.%. Following the thermal annealing at 560 °C for up to 100 h, detailed microstructural characterizations were performed to determine the interdiffusion microstructures, compositional distributions, diffusion kinetics, and phase structures in the interdiffusion zone. This study unambiguously disclosed that, as the Ce diffuses into Fe-Cr model alloys, Cr segregates and precipitates into Cr-rich σ phase consisted of Fe and Cr instead of forming a ternary phase together with Fe and Ce. The precipitation of those nano-sized σ phase particles at the Ce diffusion front would effectively slow down the interdiffusion.

  7. 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.

  8. Ferromagnetic ordering of Cr and Fe doped p-type diamond: An ab initio study

    SciTech Connect

    Benecha, E. M.; Lombardi, E. B.

    2014-02-21

    Ferromagnetic ordering of transition metal dopants in semiconductors holds the prospect of combining the capabilities of semiconductors and magnetic systems in single hybrid devices for spintronic applications. Various semiconductors have so far been considered for spintronic applications, but low Curie temperatures have hindered room temperature applications. We report ab initio DFT calculations on the stability and magnetic properties of Fe and Cr impurities in diamond, and show that their ground state magnetic ordering and stabilization energies depend strongly on the charge state and type of co-doping. We predict that divacancy Cr{sup +2} and substitutional Fe{sup +1} order ferromagnetically in p-type diamond, with magnetic stabilization energies (and magnetic moment per impurity ion) of 16.9 meV (2.5 μ{sub B}) and 33.3 meV (1.0 μ{sub B}), respectively. These magnetic stabilization energies are much larger than what has been achieved in other semiconductors at comparable impurity concentrations, including the archetypal dilute magnetic semiconductor GaAs:Mn. In addition, substitutional Fe{sup +1} exhibits a strong half-metallic character, with the Fermi level crossing bands in only the spin down channel. These results, combined with diamond’s extreme properties, demonstrate that Cr or Fe dopedp-type diamond may successfully be considered in the search for room temperature spintronic materials.

  9. Hydrogen-Resistant Fe/Ni/Cr-Base Superalloy

    NASA Technical Reports Server (NTRS)

    Bhat, Biliyar N.; Chen, Po-Shou; Panda, Binayak

    1994-01-01

    Strong Fe/Ni/Cr-base hydrogen- and corrosion-resistant alloy developed. Superalloy exhibits high strength and exceptional resistance to embrittlement by hydrogen. Contains two-phase microstructure consisting of conductivity precipitated phase in conductivity matrix phase. Produced in wrought, weldable form and as castings, alloy maintains high ductility and strength in air and hydrogen. Strength exceeds previously known Fe/Cr/Ni hydrogen-, oxidation-, and corrosion-resistant alloys. Provides higher strength-to-weight ratios for lower weight in applications as storage vessels and pipes that must contain hydrogen.

  10. Study on the growth and corrosion resistance of manganese phosphate coatings on 30CrMnMoTi alloy steel

    NASA Astrophysics Data System (ADS)

    Fang, Liang; Xie, Liang-bo; Hu, Jia; Li, Yun; Zhang, Wen-ting

    Due to containing some alloy elements such as chromium, 30CrMnMoTi steel is usually difficult to be phosphated. In present paper, the growth process of the phosphate coating on 30CrMnMoTi alloy steel fabricated by a high temperature manganese phosphating was investigated. The microstructure, surface morphology, composition and corrosion resistance of the phosphate coatings were analyzed by XRD, SEM, EDS and electrochemical polarization method, respectively. The time dependence of open circuit potential (OCP) and the weight of the coating were also measured. It is found that the phosphate coating is mainly composed of (Mn,Fe)5H2(PO4)4·4H2O and consists of a lot of close packed lump crystallites. Based on the time dependence of morphology and the weight of phosphate films, it shows that the phosphating process mainly includes three stages: corrosion of the substrate, creation and growth of phosphate crystal nucleus and thickening of phosphate coating. For 30CrMnMoTi steel, it takes at least 30 seconds and 3 minutes for the first and second step, respectively: at the beginning stage of phospahting process, a lot of bubbles emit, then a complete film will form at the end of bubbling, and the nucleation of phosphate film is inhomogeneous, phosphate crystal nucleus usually forms preferentially at grain boundary. The coating weight-time curve is similar to that of the parabolic growth. The electrochemical polarization measurement shows that the corrosion potentials of the phosphated steel shifted positively about 480 mV than the bare steel and the results of neutral salt spray test (NSS) could reach 24 h, indicating the phosphating improved the corrosion resistance of the 30CrMnMoTi alloy steel.

  11. Carbon Nanostructures Grown on Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Čaplovičová, Mária; Čaplovič, Ľubomír; Búc, Dalibor; Vinduška, Peter; Janík, Ján

    2010-11-01

    The morphology and nanostructure of carbon nanotubes (CNTs), synthesized directly on Fe-Cr-Al-based alloy substrate using an alcohol catalytic chemical vapour deposition method (ACCVD), were examined by transmission electron microscopy (TEM). The grown CNTs were entangled with chain-like, bamboo-like, and necklace-like morphologies. The CNT morphology was affected by the elemental composition of catalysts and local instability of deposition process. Straight and bended CNTs with bamboo-like nanostructure grew mainly on γ-Fe and Fe3C particles. The synthesis of necklace-like nanostructures was influenced by silicon oxide, and growth of chain-like nanostructures was supported by a catalysts consisting of Fe, Si, oxygen and trace of Cr. Most of nanotubes grew according to base growth mechanism.

  12. Effect of vacancies on the spin density waves onset in Fe/Cr superlattices

    NASA Astrophysics Data System (ADS)

    Parlebas, J. C.; Demangeat, C.; Mokrani, A.; Yartsev, S. V.; Ustinov, V. V.; Yartseva, N. S.

    2011-05-01

    The spin density wave's onset in Cr based superlattices is considered within proximity of Fe interlayer boundaries and the effect of randomly located vacancies in Cr monolayers is examined. The study is performed for Fe/Cr, Fe/Cr/V superlattices with odd and even number of Cr monolayers. It is shown that the number of Cr monolayer determines the spin density wave's nodes onset in the perfect Fe/Cr super lattices. Pinning of Cr magnetic moments on vacancies destroys this determination and leads to appearance or disappearance of nodes.

  13. Magnetic interaction reversal in watermelon nanostructured Cr-doped Fe nanoclusters

    SciTech Connect

    Kaur, Maninder; Qiang, You; Dai, Qilin; Tang, Jinke; Bowden, Mark; Engelhard, Mark; Wu, Yaqiao

    2013-11-11

    Cr-doped core-shell Fe/Fe-oxide nanoclusters (NCs) were synthesized at varied atomic percentages of Cr from 0 at. % to 8 at. %. The low concentrations of Cr (<10 at. %) were selected in order to inhibit the complete conversion of the Fe-oxide shell to Cr{sub 2}O{sub 3} and the Fe core to FeCr alloy. The magnetic interaction in Fe/Fe-oxide NCs (∼25 nm) can be controlled by antiferromagnetic Cr-dopant. We report the origin of σ-FeCr phase at very low Cr concentration (2 at. %) unlike in previous studies, and the interaction reversal from dipolar to exchange interaction in watermelon-like Cr-doped core-shell NCs.

  14. Interlayer coupling in Fe/Cr/Gd multilayer structures

    SciTech Connect

    Drovosekov, A. B. Kreines, N. M.; Savitsky, A. O.; Kravtsov, E. A.; Blagodatkov, D. V.; Ryabukhina, M. V.; Milyaev, M. A.; Ustinov, V. V.; Pashaev, E. M.; Subbotin, I. A.; Prutskov, G. V.

    2015-06-15

    The effect of the chromium layer thickness on the magnetic state of an [Fe/Cr/Gd/Cr]{sub n} multilayer structure is studied. A series of Fe/Cr/Gd structures with Cr spacer thicknesses of 4–30 Å is studied by SQUID magnetometry and ferromagnetic resonance in the temperature range 4.2–300 K. The obtained experimental results are described in terms of an effective field model, which takes into account a biquadratic contribution to the interlayer coupling energy and a nonuniform magnetization distribution inside the gadolinium layer (which was detected earlier). Depending on the magnetic field and temperature, the following types of magnetic ordering are identified at various chromium layer thicknesses: ferromagnetic, antiferromagnetic, and canted ordering. A comparison of the experimental and calculated curves allowed us to determine the dependence of the bilinear (J{sub 1}) and biquadratic (J{sub 2}) exchange constants on chromium layer thickness t{sub Cr}. Weak oscillations at a period of about 18 Å are detected in the J{sub 1}(t{sub Cr}) dependence in the range 8–30 Å. The interlayer coupling oscillations in the system under study are assumed to be related to the RKKY exchange interaction mechanism via the conduction electrons of Cr.

  15. 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

  16. 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.

  17. 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.

  18. Migration of Cr-Vacancy Clusters and Interstitial Cr in Alpha-Fe using the Dimer Method

    SciTech Connect

    Chen, Dong; Gao, Fei; Hu, Wangyu; Hu, Shenyang Y.; Terentyev, Dimtry; Sun, Xin; Heinisch, Howard L.; Henager, Charles H.; Khaleel, Mohammad A.

    2010-02-01

    The migration mechanisms and the corresponding activation energies of Cr-vacancy (Cr-V) clusters and Cr interstitials in α-Fe have been investigated using the dimer and the nudged elastic band methods. Dimer searches are employed to find the possible transition states of these defects, and the lowest energy paths are used to determine the energy barriers for migration. A substitutional Cr atom can migrate to a nearest neighbor vacancy through an energy barrier of 0.56 eV, but this simple mechanism alone is unlikely to lead to the long-distance migration of Cr unless there is a supersaturated concentration of vacancies in the system. The Cr-vacancy clusters can lead to long-distance migration of a Cr atom that is accomplished by Fe and Cr atoms successively jumping to nearest neighbor vacancy positions, defined as a self-vacancy-assisted migration mechanism, with the migration energies ranging from 0.64 to 0.89 eV. In addition, a mixed Cr-Fe dumbbell interstitial can easily migrate through Fe lattices, with the migration energy barrier of 0.17, which is lower than that of the Fe-Fe interstitial. The on-site rotation of the Cr-Fe interstitial and Cr atom hopping from one site to another are believed to comprise the dominant migration mechanism. The calculated binding energies of Cr-V clusters are strongly dependent on the size of clusters and the concentration of Cr atoms in clusters.

  19. Importance of doping and frustration in itinerant Fe-doped Cr2Al

    DOE PAGESBeta

    Susner, M. A.; Parker, D. S.; Sefat, A. S.

    2015-05-12

    We performed an experimental and theoretical study comparing the effects of Fe-doping of Cr2Al, an antiferromagnet with a N el temperature of 670 K, with known results on Fe-doping of antiferromagnetic bcc Cr. (Cr1-xFex)2Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing TN to 170 K for x=0.10. Antiferromagnetic behavior disappears entirely at x≈0.125 after which point increasing paramagnetic behavior is exhibited. Moreover, this is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which TN gradually decreases followed by the appearance of a ferromagnetic state. Theoretical calculations explainmore » that the Cr2Al-Fe suppression of magnetic order originates from two effects: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr2Al. In pure-phase Cr2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr2Al and Fe-doped Cr2Al.« less

  20. 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.

  1. Hydrogen permeation characteristics of some Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Van Deventer, E. H.; Maroni, V. A.

    1983-01-01

    Hydrogen permeation data are reported for two Fe-Cr-Al alloys, Type-405 SS (Cr 14-A1 0.2) and a member of the Fecralloy family of alloys (Cr 16-A1 5). The hydrogen permeability of each alloy (in a partially oxidized condition) was measured over a period of several weeks at randomly selected temperatures (between 150 and 850°C) and upstream H 2 pressures (between 2 and 1.5 × 10 4 Pa). The permeabilities showed considerable scatter with both time and temperature and were 10 2 to 10 3 times lower than those of pure iron, even in strongly reducing environments. The exponent, n, for the relationship between upstream H 2 pressure, P, and permeability, φ, ( φ ~ Pn) was closer to 0.7 than to the expected 0.5, indicating a process limited by surface effects (e.g., surface oxide films) as opposed to bulk material effects. Comparison of these results with prior permeation measurements on other Fe-Cr-Al alloys, on Fe-Cr alloys, and on pure iron shows that the presence of a few weight percent aluminum offers the best prospects for achieving low tritium permeabilities with martensitic and ferritic steels used in fusion-reactor first wall and blanket applications.

  2. The resistance to cavitation erosion of CrMnN stainless steels

    SciTech Connect

    Fu, W.T.; Jing, T.F.; Zheng, Y.Z.; Yang, Y.B.; Yao, M.

    1998-12-01

    The resistance to cavitation erosion (CE) was measured using a magnetostrictive device and a rotating disk device for some CrMnN stainless steels (Chinese patent ZL 90 1 02197.0). The microstructural changes in the surface layer before and after CE were analyzed by use of Mossbauer spectra. Results show that the resistance to CE of duplex austenitic-martensitic CrMnN stainless steels is much better than that of ZG0Cr13Ni4-6Mo and ZG0Cr16Ni5Mo steel, which are in common use for hydraulic turbine runners. The metastable austenite and its changes in the process of CE are the key factors why the CrMnN stainless steels have excellent resistance to cavitation erosion.

  3. Host Atom Diffusion in Ternary Fe-Cr-Al Alloys

    NASA Astrophysics Data System (ADS)

    Rohrberg, Diana; Spitzer, Karl-Heinz; Dörrer, Lars; Kulińska, Anna J.; Borchardt, Günter; Fraczkiewicz, Anna; Markus, Torsten; Jacobs, Michael H. G.; Schmid-Fetzer, Rainer

    2014-01-01

    In the Fe-rich corner of the Fe-Cr-Al ternary phase diagram, both interdiffusion experiments [1048 K to 1573 K (775 °C to 1300 °C)] and 58Fe tracer diffusion experiments [873 K to 1123 K (600 °C to 850 °C)] were performed along the Fe50Cr50-Fe50Al50 section. For the evaluation of the interdiffusion data, a theoretical model was used which directly yields the individual self-diffusion coefficients of the three constituents and the shift of the original interface of the diffusion couple through inverse modeling. The driving chemical potential gradients were derived using a phenomenological Gibbs energy function which was based on thoroughly assessed thermodynamic data. From the comparison of the individual self-diffusivities of Fe as obtained from interdiffusion profiles and independent 58Fe tracer diffusivities, the influence of the B2-A2 order-disorder transition becomes obvious, resulting in a slightly higher activation enthalpy for the bcc-B2 phase and a significantly lower activation entropy for this phase.

  4. 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.

  5. Mn-Cr Systematics in Sphalerites and Niningerites From Qingzhen and Yamato69001: Implications Regarding Their Formation Histories

    NASA Astrophysics Data System (ADS)

    El Goresy, A.; Wadhwa, M.; Zinner, E. K.; Nagel, H.-J.; Janicke, J.; Crozaz, G.

    1992-07-01

    Recent Cr isotopic measurements of sphalerites and alabandites in three EL3 chondrites MAC88136, MAC88180, and MAC88184 and of sphalerites in the EH4 chondrite Indarch (El Goresy et al., 1992) revealed ^53Cr excesses (^53Cr*), resulting from the in situ decay of ^53Mn (tau(sub)1/2=3.7 Ma), in most grains analysed. However, the initial ^53Mn/^55Mn ratios calculated for these grains were quite variable, and it was concluded that redistribution of ^53Cr* by diffusional processes was the most likely cause for these variations. In a continuation of the previous work (El Goresy et al., 1992), we report new mineral-chemical and Cr-isotopic data for two EH3 chondrites, Qingzhen and Yamato 69001. The distribution of Fe, Mg, and Mn in niningerites and sphalerites occurring in individual sulfide assemblages was determined by electron microprobe analysis. Among the meteorites of the EH3 subgroup, Qingzhen and Yamato 69001 are unique in that niningerites in both meteorites display normal as well as reversed zoning, indicating complex thermal histories (Ehlers and El Goresy, 1988; Lin et al., 1989; Lin, 1991; Nagel, 1991). Niningerites have different MnS contents (9.2-32.6 mol% MnS in Qingzhen vs. 4.2- 6.3 mol% MnS in Yamato 69001), as do the sphalerites (4.0-9.2 mol% MnS in Qingzhen vs. 2.0-3.5 mol% in Yamato 69001). Sphalerites in both meteorites are normally zoned, with 46.0-49.8 mol% FeS in sphalerites from Qingzhen, and 42.3-49.7 mol% FeS in sphalerites from Yamato 69001. The spatial distributions of Fe and Mg in niningerites and of Fe and Mn in sphalerites indicate complex processes that may have occurred before accretion and/or during later metamorphic events in the parent body (El Goresy and Ehlers, 1989; Lin, 1991; Nagel, 1991). Ion microprobe measurements of 6 sphalerites and 3 niningerites in Qingzhen and of 3 sphalerites and 2 niningerites in Yamato 69001 showed that ^55Mn/^52Cr ratios in these sulfide phases are significantly lower than in sphalerites and

  6. Exchange bias in Fe/Cr double superlattices.

    SciTech Connect

    Jiang, J. S.; Felcher, G. P.; Inomata, A.; Goyette, R.; Nelson, C.; Bader, S. D.

    1999-11-30

    Utilizing the oscillatory interlayer exchange coupling in Fe/Cr superlattices, we have constructed ''double superlattice'' structures where a ferromagnetic (F) and an antiferromagnetic (AF) Fe/Cr superlattice are coupled through a Cr spacer. The minor hysteresis loops in the magnetization are shifted from zero field, i.e., the F superlattice is exchange biased by the AF one. The double superlattices are sputter-deposited with (211) epitaxy and possess uniaxial in-plane magnetic anisotropy. The magnitude of the bias field is satisfactorily described by the classic formula for collinear spin structures. The coherent structure and insensitivity to atomic-scale roughness makes it possible to determine the spin distribution by polarized neutron reflectivity, which confirms that the spin structure is collinear. The magnetic reversal behavior of the double superlattices suggests that a realistic model of exchange bias needs to address the process of nucleating local reverse domains.

  7. Preparation, structural and magnetic characterization of DyCrMnO{sub 5}

    SciTech Connect

    Martinez-Lope, M.J.; Retuerto, M. Garcia-Hernandez, M.; Alonso, J.A.

    2009-03-15

    The title compound has been first synthesized by a citrate technique followed by thermal treatments under moderate oxygen pressure conditions, and characterized by X-ray and neutron powder diffraction (NPD) and magnetization measurements. The crystal structure of DyCrMnO{sub 5} has been refined from NPD data in the space group Pbam; a=7.2617(6) A, b=8.5161(6) A, and c=5.7126(5) A at 295 K. This oxide is isostructural with RMn{sub 2}O{sub 5} oxides (R=rare earths) and it contains infinite chains of (Cr, Mn){sup 4+}O{sub 6} octahedra-sharing edges, linked together by (Mn, Cr){sup 3+}O{sub 5} pyramids and DyO{sub 8} units. The high degree of antisite disordering exhibited by DyCrMnO{sub 5} is noteworthy. The octahedral positions are occupied by roughly 50% of Mn and Cr cations, and the pyramidal groups contain two thirds of Mn and one third of Cr cations. We assume that Mn and Cr cations at the octahedral positions exhibit a tetravalent oxidation state, whereas the metals at the pyramidal positions are trivalent, in order to preserve the electroneutrality of this oxide. The susceptibility vs temperature curve of DyCrMnO{sub 5} does not suggest the establishment of a long-range magnetic structure even at low temperatures; the NPD technique does not provide any signal of magnetic ordering, since the reflections do not show any magnetic contribution. - Graphical abstract: DyCrMnO{sub 5} is isostructural with DyMn{sub 2}O{sub 5}, belonging to the Pbam space group. The crystal structure contains infinite chains of edge-sharing Mn{sup 4+}O{sub 6} octahedra, interconnected by dimer units of Cr{sup 3+}O{sub 5} square pyramids. The low-temperature neutron powder diffraction (NPD) patterns do not show any magnetic contribution, indicating that a full long-range magnetic ordering is not established down to low temperature, although the Dy{sup 3+} magnetic moments are susceptible to be polarized by an external magnetic field at the lowest temperature of 5 K.

  8. Influence of the presence of pre-existing thermal [var epsilon]-martensite on the formation of stress-induced [var epsilon]-martensite and on the shape memory effect of a Fe-Mn-Cr-Si-Ni shape memory alloy

    SciTech Connect

    Federzoni, L.; Guenin, G. )

    1994-07-01

    At present, many investigations are done on Fe-Mn-based shape memory alloys because of their particularly good one-way type shape memory effect and their low cost. With addition of Cr and Ni, it is possible to reach a good corrosion resistance, which confers to this type of alloys a commercial significance. The shape memory effect is associated with the formation of stress-induced [var epsilon]-martensite by deformation of an austenitic ([gamma]) sample. The reversion by heating of the [var epsilon]-martensite provides the shape memory effect. It is generally admitted that the presence of thermal [var epsilon]-martensite before deformation has a negative influence on the formation of the stress-induced martensite and on the shape memory effect. The authors' purpose is to evaluate the real influence of the pre-existing thermal [var epsilon]-martensite on the formation of the stress-induced [var epsilon]-martensite, its recovery and on the shape memory effect.

  9. 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.

  10. Corrosion Resistance of Amorphous Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 coating - a new criticality-controlled material

    SciTech Connect

    Farmer, J C; Choi, J S; Saw, C K; Rebak, R; Day, S D; Lian, T; Hailey, P; Payer, J H; Branagan, D J; Aprigliano, L F

    2007-03-28

    An iron-based amorphous metal with good corrosion resistance and a high absorption cross-section for thermal neutrons has been developed and is reported here. This amorphous alloy has the approximate formula Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4} and is known as SAM2X5. Chromium (Cr), molybdenum (Mo) and tungsten (W) were added to provide corrosion resistance, while boron (B) was added to promote glass formation and the absorption of thermal neutrons. Since this amorphous metal has a higher boron content than conventional borated stainless steels, it provides the nuclear engineer with design advantages for criticality control structures with enhanced safety. While melt-spun ribbons with limited practical applications were initially produced, large quantities (several tons) of gas atomized powder have now been produced on an industrial scale, and applied as thermal-spray coatings on prototypical half-scale spent nuclear fuel containers and neutron-absorbing baskets. These prototypes and other SAM2X5 samples have undergone a variety of corrosion testing, including both salt-fog and long-term immersion testing. Modes and rates of corrosion have been determined in various relevant environments, and are reported here. While these coatings have less corrosion resistance than melt-spun ribbons and optimized coatings produced in the laboratory, substantial corrosion resistance has been achieved.