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Sample records for cr cu mn

  1. Adjustment of temperature coefficient of resistance in NiCr/CuNi(Mn)/NiCr films

    NASA Astrophysics Data System (ADS)

    Brückner, W.; Baunack, St.; Elefant, D.; Reiss, G.

    1996-06-01

    The thin-film system Ni0.37Cr0.63/Cu0.57Ni0.42Mn0.01/Ni0.37Cr0. 63 with a typical thickness of 1 μm is used for low-ohmic precision resistors. The necessary adjustment of the temperature coefficient of resistance (TCR) by annealing has been studied by investigating the irreversible changes of the resistance during various annealing steps of NiCr/CuNi(Mn)/NiCr multilayers in comparison with single layers of CuNi(Mn) and NiCr. Auger depth profiles showed that the interdiffusion of CuNi(Mn) and NiCr results in an impoverishment of Ni in CuNi(Mn), explaining the TCR shift by comparison with data of Cu1-xNix bulk material. The decrease of the resistivity and the reduction of the width of the copper-nickel conductive layer by formation of a Ni0.6Cr0.2Cu0.2 interdiffusion zone phase (in accordance with the Cu-Ni-Cr phase diagram) cause a significant curvature of the resistance-temperature curve. As main result, it is shown that the NiCr base and cover layers and their interdiffusion with CuNi(Mn) play the decisive role in adjusting the TCR. It was checked that oxidation and topography effects have no remarkable influences.

  2. New type of Schottky diode-based Cu-Al-Mn-Cr shape memory material films

    NASA Astrophysics Data System (ADS)

    Aksu Canbay, C.; Dere, A.; Mensah-Darkwa, Kwadwo; Al-Ghamdi, Ahmed; Karagoz Genç, Z.; Gupta, R. K.; Yakuphanoglu, F.

    2016-07-01

    Cr-doped CuAlMn shape memory alloys were produced by arc melting method. The effects of Cr content on microstructure and transformation parameters of were investigated. The alloys were characterized by X-ray analysis, optical microscope observations and differential scanning calorimetry measurements. The grain size of the alloys was decreased by the addition of Cr into CuAlMn alloy system. The martensite transformation temperature was shifted both the lower temperature and higher temperature with the addition of chromium. This change was explained on the basis of the change in the thermodynamics such as enthalpy, entropy and activation energy values. The obtained results indicate that the phase transformation temperatures of the CuAlMn alloy system can be controlled by addition of Cr. We fabricated a Schottky barrier diode and observed that ideality factor and barrier height increase with increasing temperature. The diodes exhibited a thermal sensor behavior. This indicates that Schottky diode-based Cu-Al-Mn-Cr shape memory material films can be used as a sensor in high-temperature measurement applications.

  3. Auger electron spectroscopy study of interdiffusion, oxidation and segregation during thermal treatment of NiCr/CuNi(Mn)/NiCr thin films

    NASA Astrophysics Data System (ADS)

    Baunack, S.; Brückner, W.; Pitschke, W.; Thomas, J.

    1999-04-01

    The effect of annealing on sputter deposited thin-films NiCr/CuNi(Mn)/NiCr is studied by Auger electron depth profiling. The samples were annealed to maximum temperatures of 300°C to 550°C and investigated at ambient temperature. Auger transitions of Cu and Ni are separated by target factor analysis, principal component analysis and linear least squares fit to standard spectra. For the CuNi(Mn) layer in the as-received state AES results shows a Cu depletion caused by bombardment induced segregation. After annealing the measured Cu concentration has increased due to Ni diffusion to the interfaces. The NiCr layer is degraded with increasing annealing temperature due to formation of a chromium oxide and diffusion of Ni from the CuNi(Mn) layer. A sequence with nominal compositions near Cr 2Ni, CrNi and CrNi 2 is found. At the NiCr/CuNi(Mn) interface an interdiffusion zone phase Ni 0.6Cr 0.2Cu 0.2 is formed.

  4. Wear behavior of self-lubricating Fe-Cr-C-Mn-Cu alloys: Smearing effect of second phase particles

    NASA Astrophysics Data System (ADS)

    Kim, Ki Nam; Kim, Byung Sik; Shin, Gyeong Su; Park, Myung Chul; Lee, Deok Hyun; Kim, Seon Jin

    2011-08-01

    Newly developed self-lubricating Fe-Cr-C-Mn-Cu cast composite alloys were investigated to study the role of Cu-rich second phase particles which smear on the wear surface during sliding. The wear resistance of the material was improved with an increasing copper concentration. The improved wear resistance was probably obtained by forming a protective tribofilm, which prevented metal-to-metal contact through smearing of the embedded Cu-rich second phase particles. This formation of protective oxide films during sliding is likely to improve the wear resistance of austenitic Fe-Cr-C-Mn-Cu cast composite alloys.

  5. Precipitation behavior of dispersoids in Al-Mg-Si-Cu-Mn-Cr alloy during homogenization annealing

    NASA Astrophysics Data System (ADS)

    Han, Yi; Ma, Ke; Wang, Chuyan; Nagaumi, Hiromi

    The precipitation behavior of dispersoids containing Mn and Cr in Al-Mg-Si-Cu-Mn-Cr alloy during homogenization annealing with different heating rate was investigated in this paper. Scanning transmission electron microscopy (STEM) was used to measure the difference in the size and number density of dispersoids after the two treatments. The effect of homogenization treatment on the recrystallization fraction and grain size was determined by examining hot forged and solution treated specimens using electron back-scatter diffraction (EBSD). It was found that the slow homogenization heating rate promotes to an increase in the average dispersoid number density and decrease in particle size. The enhanced dispersoids distribution resulting from the slow homogenization heating rate leads to a reduction in the recrystallization fraction (24 29% lower) and grain size (18 22% smaller).

  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. The accumulation of metal (Co, Cr, Cu, Mn and Zn) in freshwater Ulva (Chlorophyta) and its habitat.

    PubMed

    Rybak, Andrzej; Messyasz, Beata; Łęska, Bogusława

    2013-04-01

    The possibility of using freshwater Ulva (Chlorophyta) as a bioaccumulator of metals (Co, Cr, Cu, Mn and Zn) in lake and river water was examined weekly in the summer of 2010 in three types of samples: the water, the sediment and the thalli of Ulva. Samples of freshwater Ulva were collected from two aqueous ecosystems lie 250 km away from the basin of the Baltic Sea and 53 km from each other. A flow lake located in the centre of the big city was the first water reservoir (ten sites) and second, the suburban river (six sites). The mean metal concentrations in the Ulva tissue from the river and the lake decreased in the following order: Mn > Zn > Cr > Cu > Co and Mn > Cr > Zn > Cu > Co, respectively. Moreover, a negative and statistically significant correlation between Mn concentrations in the Ulva thalli and the river water was observed. Additionally, numerous correlations were noted between the different concentrations of metals within the Ulva thalli, in the water and in the sediment. The great concentrations of Mn and Zn and the smallest of Co were found in thalli of Ulva, irrespective of the type of the ecosystem from which samples of algal thalli originated. Freshwater Ulva populations examined in this study were clearly characterized a dozen or so times by the higher Mn and Cr accumulation than taxa from that genera coming from sea ecosystems. The calculated bioconcentration factor confirm the high potential for freshwater Ulva to be a bioaccumulator of trace metals in freshwater ecosystems.

  8. Study of the effect of different fermenting microorganisms on the Se, Cu, Cr, and Mn contents in fermented goat and cow milks.

    PubMed

    Quintana, Aida Verónica; Olalla-Herrera, Manuel; Ruiz-López, María Dolores; Moreno-Montoro, Miriam; Navarro-Alarcón, Miguel

    2015-12-01

    The aim of this study was to determine the Se, Cu, Cr, and Mn concentrations of different types of goat- and cow-milk fermented products and evaluate the influence of fermenting bacteria (classical fermenting starters and a probiotic strain) on these concentrations. Atomic absorption spectrometry with hydride generation was used to measure Se and electrothermal atomization to measure Cu, Cr and Mn. Analytical parameters determined in the fermented milks demonstrated that the procedures used were adequate for Se, Cu, Cr, and Mn analyses. Se levels were significantly lower in fermented goat milk products than in fermented cow milk products (p<0.05). Se, Cu, Cr, and Mn levels did not differ as a function of the fermenting bacteria used in commercial fermented goat or cow milks or in the lab-produced goat yoghurt. Given the Se, and Cr intakes for healthy adults, goat and cow yogurts may be important dietary sources. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. 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.

  10. Determination of ratios of Auger electrons emission probabilities and K-L shell vacancy transfer probability of Cr, Mn, Fe, Co, Ni, Cu and Zn compounds

    NASA Astrophysics Data System (ADS)

    Küçükönder, Adnan; Kavşut, Onur

    2017-02-01

    Ratios of emission probabilities of Auger electrons [u = p(KLX)/p(KLL), ν = p(KXY)/p(KLL)] and the vacancy transfer probabilities from K to L shell, ηKL for Cr, Mn, Fe, Co,Ni, Cu and Zn compounds were obtained using the experimental Kx-ray emission ratios and K-shell fluorescence yields. We were used the experimental Kβ/Kα intensity ratios and K shell fluorescence yields WK. Ratios of emission probabilities of Auger electrons and the vacancy transfer probabilities are changed by chemical effect for different for Cr, Mn, Fe, Co,Ni, Cu and Zn compounds.

  11. Magnetism and superconductivity in MxFe1+yTe1-zSez (M = Cr, Mn, Co, Ni, Cu, and Zn) single crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Z. T.; Yang, Z. R.; Li, L.; Zhang, C. J.; Pi, L.; Tan, S.; Zhang, Y. H.

    2011-04-01

    High-quality single crystals with nominal composition M0.05Fe0.95Te0.8Se0.2 (M = Cr, Mn, Co, Ni, Cu, and Zn) have been grown, through which the doping effect on magnetism and superconductivity is studied. Elementary analysis reveals that Cu, Co, and Ni, with smaller ionic radii for valence state 2+, can substitute effectively for Fe with doping levels near 5%. In contrast, the solid solution of Cr, Mn, and Zn in the host system is low. Magnetic and electronic investigations show that the substitution of Co, Ni, or Cu for Fe leads to the formation of spin-glass state and suppression of superconductivity. The superconductivity is partly suppressed by Co doping, while completely destroyed by Ni and Cu doping. Compared with Cu- and Ni-doped samples, the Co-doped sample has the smallest lattice constant, indicating that the superconductivity might be also modulated by the changes of microstructure.

  12. Synthesis, Crystal Structures, and Magnetic Properties of Two Novel Cyanido-Bridged Heterotrimetallic {Cu(II)Mn(II)Cr(III)} Complexes.

    PubMed

    Alexandru, Maria-Gabriela; Visinescu, Diana; Shova, Sergiu; Andruh, Marius; Lloret, Francesc; Julve, Miguel

    2017-02-20

    The self-assembly process between the heteroleptic [Cr(III)(phen)(CN)4](-) and [Cr(III)(ampy)(CN)4](-) metalloligands and the heterobimetallic {Cu(II)(valpn)Mn(II)}(2+) tecton afforded two heterotrimetallic complexes of formula [{Cu(II)(valpn)Mn(II)(μ-NC)2Cr(III)(phen)(CN)2}2{(μ-NC)Cr(III)(phen)(CN)3}2]·2CH3CN (1) and {[Cu(II)(valpn)Mn(II)(μ-NC)2Cr(III)(ampy)(CN)2]2·2CH3CN}n (2) [phen = 1,10-phenanthroline, ampy = 2-aminomethylpyridine, and H2valpn = 1,3-propanedyilbis(2-iminomethylene-6-methoxyphenol)]. The crystal structure of 1 consists of neutral Cu(II)2Mn(II)2Cr(III)4 octanuclear units, where two [Cr(phen)(CN)4](-) anions act as bis-monodentate ligands through cyanide groups toward two manganese(II) ions from two [Cu(II)(valpn)Mn(II)](2+) units to form a [{Cu(valpn)Mn}2Cr2(CN)4](6+) square motif. Two [Cr(phen)(CN)4](-) pendant anions in 1 are bound to the copper(II) ions with cis-trans geometry with respect to the bridging [Cr(phen)(CN)4](-) anion. Compound 2 is a sheet-like coordination polymer, where chains constituted by {Cr(III)(ampy)(CN)4} spacers act as bis-monodentate ligands toward the manganese(II) ions belonging to the {Cu(II)(valpn)Mn(II)} nodes, which are interlinked by another {Cr(III)(ampy)(CN)4} unit that acts as a bridge between the copper(II) and manganese(II) ions of adjacent chains. Magnetic susceptibility measurements in the temperature range of 1.9-300 K were performed for 1 and 2. An overall antiferromagnetic behavior is observed for 1, the ground spin state being described by a spin triplet from the square motif plus two magnetically isolated spin triplets from the two peripheral chromium(III) ions. Ferrimagnetic chains with interacting spins 1/2 (resulting spin of the trimetallic {Cu(II)(valpn)Mn(II)(μ-NC)Cr(III)} fragment) and 3/2 (spin from the bis-monodentate [Cr(III)(ampy)(CN)4](-) with weak interchain ferromagnetic interactions across the cyanide bridge between the chromium(III) and the copper(II) ion from adjacent chains [

  13. 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.

  14. Immobilization of heavy metals (Pb, Cu, Cr, Zn, Cd, Mn) in the mineral additions containing concrete composites.

    PubMed

    Giergiczny, Zbigniew; Król, Anna

    2008-12-30

    The presented work determines the level of heavy metals (Pb+2, Cu+2, Zn+2, Cr+6, Cd+2, Mn+2) immobilization in the composites produced using Ordinary Portland Cement (OPC) as well as of binders containing large amount of mineral additives in its composition-siliceous fly ash (FA), fluidized bed combustion ash (FFA) and ground granulated blast furnace slag (GGBFS). Heavy metals were introduced to cementitious materials in the form of soluble salts as well as components of hazardous wastes (medical ash, metallurgical dust). It has been stated, that the level of heavy metals immobilization is combined with composites composition. Majority of analyzed heavy metals, added to binders' composition in the form of heavy metal salts achieves high level of immobilization, in mortar based on binder with 85% GGBFS and 15% OPC. The lowest immobilization level was reached for chromium Cr+6 added to hardening mortars as Na2Cr2O72H2O. The level ranges from 85.97% in mortars made on blended binder (20% OPC, 30% FFA and 50% GGBFS) to 93.33% in mortar produced on OPC. The increase of the so-called immobilization degree with time of hardened material maturing was found. This should be attributed to the pozzolanic or pozzolanic/hydraulic properties of components used; their effect on microstructure of hardened material is also important. Mineral additions enter the hydration reactions in the mixtures and favor the formation of specific microstructure promoting the immobilization of hazardous elements.

  15. High-pressure preparation and characterization of new metastable oxides: the case of NdCu3Mn3MO12 (M = Fe, Cr)

    NASA Astrophysics Data System (ADS)

    Sánchez-Benítez, J.; Kayser, P.; Martínez-Lope, M. J.; de la Calle, C.; Retuerto, M.; Fernandez-Díaz, M. T.; Alonso, J. A.

    2011-10-01

    High-pressure synthesis is a powerful technique to stabilize metastable oxides, either containing transition metals in unusual oxidation states, or favouring the formation of dense perovskite-related phases. Happily, many solids synthesized at high pressure-high temperature conditions (where they are fhermodynamically stable) can be "quenched" to ambient conditions, where they are termodynamically metaestable, yet they remain indefinitely kinetically stable. In this paper we illustrate the example of a new family of oxides derived from the CaCu3Mn4O12 perovskite. We have studied the series of nominal composition NdCu3(Mn3M)O12 (M = Fe, Cr) where Mn is replaced by Fe(Cr) cations in the ferrimagnetic perovskite NdCu3Mn4O12. These materials have been synthesized in poly crystalline form under moderate pressure conditions of 2 GPa, in the presence of KClO4 as oxidizing agent. All the samples have been studied by neutron powder diffraction (NPD) below and above the ferromagnetic Curie temperatures. These oxides crystallize in the cubic space group Imbar 3 (No. 204). Mn4+/Mn3+ and Fe3+(Cr3+) occupy at random the octahedral B positions of the perovskite structure. The materials have also been characterized by magnetic and magnetotransport measurements. All the samples are ferrimagnetic and show a decrease of TC upon Fe(Cr) introduction since these ions disturb the ferromagnetic interactions within this magnetic sublattice. The introduction of Fe changes the resistivity response from metallic to a semiconductor behavior. However, the magnetoresistance is still considerable at 300 K upon Fe doping, and it is enhanced at 100 K probably due to the decrease in the number of charge carriers from the pure oxide to the Fe-doped compound.

  16. Effect of deep cryogenic treatment on the microstructure and wear performance of Cr-Mn-Cu white cast iron grinding media

    NASA Astrophysics Data System (ADS)

    Vidyarthi, M. K.; Ghose, A. K.; Chakrabarty, I.

    2013-12-01

    The phase transformation and grinding wear behavior of Cr-Mn-Cu white cast irons subjected to destabilization treatment followed by air cooling or deep cryogenic treatment were studied as a part of the development program of substitute alloys for existing costly wear resistant alloys. The microstructural evolution during heat treatment and the consequent improvement in grinding wear performance were evaluated with optical and scanning electron microscopy, X-ray diffraction analysis, bulk hardness, impact toughness and corrosion rate measurements, laboratory ball mill grinding wear test etc. The deep cryogenic treatment has a significant effect in minimizing the retained austenite content and converts it to martensite embedded with fine M7C3 alloy carbides. The cumulative wear losses in cryotreated alloys are lesser than those with conventionally destabilized alloys followed by air cooling both in wet and dry grinding conditions. The cryotreated Cr-Mn-Cu irons exhibit comparable wear performance to high chromium irons.

  17. Elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys studied by the combinatorial thin film approach and ab initio calculations.

    PubMed

    Reeh, S; Kasprzak, M; Klusmann, C D; Stalf, F; Music, D; Ekholm, M; Abrikosov, I A; Schneider, J M

    2013-06-19

    The elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys with additions of up to 8 at.% X were studied by combinatorial thin film growth and characterization and by ab initio calculations using the disordered local moments (DLM) approach. The lattice parameter and Young's modulus values change only marginally with X. The calculations and experiments are in good agreement. We demonstrate that the elastic properties of transition metal alloyed Fe-Mn can be predicted by the DLM model.

  18. Electronic structure and half-metallicity in new Heusler alloys CoYO2 (Y = Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, and Zn)

    NASA Astrophysics Data System (ADS)

    Esteki, S.; Ahmadian, F.

    2017-09-01

    First-principles calculations based on density functional theory (DFT) using the self-consistent full-potential linearized augmented plane wave (FPLAPW) method were applied to study the electronic structures and magnetic properties of new Heusler alloys CoYO2 (Y = Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, and Zn). The calculated formation energies of these compounds were negative, therefore, they can be synthesized experimentally. All compounds were stable in ferromagnetic AlCu2Mn-type structure. In AlCu2Mn-type structure, CoScO2, CoFeO2, and CoNiO2 compounds were HM ferromagnets, CoCuO2 was a nearly half-metal, CoZnO2 was a spin gapless semiconductor, and other compounds were conventional ferromagnets. In CuHg2Ti-type structure, CoTiO2 compound had a nearly HM characteristic, CoVO2 was a spin gapless semiconductor, and other compounds were conventional ferromagnets. The origin of the half-metallic band gap for CoScO2 alloy Heusler alloy was well understood. The total magnetic moments of the three HM compounds obeyed Slater-Pauling rules (Mtot = 22-Ztot and Mtot = 32-Ztot). CoScO2 had the widest region of half-metallicity between the three half-metals indicating its high robustness of half-metallicity with respect to the variation of lattice constants.

  19. Phytoremediation of Cd, Cr, Cu, Mn, Fe, Ni, Pb and Zn from aqueous solution using Phragmites cummunis, Typha angustifolia and Cyperus esculentus.

    PubMed

    Chandra, Ram; Yadav, Sangeeta

    2011-07-01

    A comparative bioaccumulation pattern and ultra structural changes were studied in Phragmites cummunis, Typha angustifolia and Cyperus esculentus in mixed metals solution of cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn). P. cummunis was observed to be a shoot accumulator for Cr, Fe, Mn, Ni, Pb, and Zn. However, T. angustifolia was found to be a root accumulator for Cd, Cr, Cu, Fe, Ni and Pb. In addition, C. esculentus also accumulated most of the tested heavy metals in the roots, while Mn and Fe were translocated up to leaves. Further, the long term metal treatment showed maximum accumulation of all heavy metals in P. cummunis followed by T. angustifolia and C. esculentus. Among heavy metals, Fe was accumulated maximum, i.e., >1000 microg g(-1) by all three plants. Simultaneously, the adverse effects on biochemical parameters were noted earlier in C. esculentus than T. angustifolia and P. cummunis. Ultra structural observation showed the cellular changes in wetland plants after longer exposure. Results revealed that P. cummunis and T. angustifolia had more potential for tested metals than C. esculentus. This study established that these wetland plants could be used for heavy metals phytoremediation from metal containing industrial wastewater.

  20. The life-table demographic response of freshwater rotifer Brachionus calyciflorus to multi-metal (Cu, Zn, Cd, Cr, and Mn) mixture interaction.

    PubMed

    Xu, Xiao-Ping; Xi, Yi-Long; Huang, Lin; Xiang, Xian-Ling

    2014-08-01

    The effects of multi-metal mixtures on the life-table demography of rotifers are not well known. In this study, the freshwater rotifer Brachionus calyciflorus was exposed to mixture of Cu, Zn, Cd, Cr, and Mn, and the life-table demographic parameters including net reproductive rate, generation time, life expectancy at hatching, and intrinsic rate of population increase were calculated. The results showed that interactions between a given element concentration, except Mn, and the other four elements mixture concentration affected the intrinsic rate of population increase (p < 0.01). Interactions between Zn concentration, as well as Mn, and the other four elements mixture concentration affected the net reproductive rate and the life expectancy at hatching, respectively (p < 0.05). The variation of parameters with the rise of the other four elements mixture concentrations from 0 to high was mainly attributed to the difference of interaction among the five metals mixture with different ratio of concentrations.

  1. Effect of plasma-catalyst system on NO removal using M-Cu (M = Mn, Ce, Cr, Co, and Fe) catalysts

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Liu, Han-Zi; Yang, Bin; Sun, Bao-Min; Xiao, Hai-Ping; Zhang, Yong-Sheng

    2016-11-01

    A series of M-Cu (M = Mn, Ce, Cr, Co, and Fe) bimetal oxide catalysts combined with plasma were prepared for NO x removal at various temperatures. All catalysts combined with plasma exhibited excellent deNO x activity. The Mn-Cu catalyst showed the highest selective catalytic reduction (SCR) activity; the NO removal efficiency of the Mn-Cu catalyst could reach 90% at a gas temperature of 25 °C. E/N increased as gas temperature increased; the mean electron energy and the proportion of high-energy electrons also increased considerably, producing more active radicals. Without any catalyst, the increase in temperature inhibited NO removal owing to O3 consumption. As the temperature increased, NO removal efficiency decreased below 100 °C however, it increased in the range of 100-300 °C, and then decreased above 300 °C in the plasma-catalyst system. NO2 concentration decreased markedly at 150 °C via the fast SCR reaction.

  2. Transient Liquid Phase Bonding of Cu-Cr-Zr-Ti Alloy Using Ni and Mn Coatings: Microstructural Evolution and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Venkateswaran, T.; Ravi, K. R.; Sivakumar, D.; Pant, Bhanu; Janaki Ram, G. D.

    2017-08-01

    High-strength copper alloys are used extensively in the regenerative cooling parts of aerospace structures. Transient liquid phase (TLP) bonding of a Cu-Cr-Zr-Ti alloy was attempted in the present study using thin layers of elemental Ni and Mn coatings applied by electroplating. One of the base metals was given a Ni coating of 4 µm followed by a Mn coating of 15 µm, while the other base metal was given only the Ni coating (4 µm). The bonding cycle consisted of the following: TLP stage—heating to 1030 °C and holding for 15 min; homogenization stage—furnace cooling to 880 °C and holding for 2 h followed by argon quenching to room temperature. Detailed microscopy and electron probe microanalysis analysis of the brazed joints were carried out. The braze metal was found to undergo isothermal solidification within the 15 min of holding time at 1030 °C. At the end of TLP stage, the braze metal showed a composition of Cu-17Ni-9Mn (wt.%) at the center of the joint with a steep gradient in Ni and Mn concentrations from the center of the braze metal to the base metal interfaces. After holding for 2 h at 880 °C (homogenization stage), the compositional gradients were found to flatten significantly and the braze metal was found to develop a homogeneous composition of Cu-11Ni-7Mn (wt.%) at the center of the joint. In lap-shear tests, failures were always found to occur in the base metal away from the brazed region. The copper alloy base metal was found to undergo significant grain coarsening due to high-temperature exposure during brazing and, consequently, suffer considerable reduction in yield strength.

  3. Concentrations of Mn, Fe, Cu, Zn, Cr, Cd, Pb, Ni in selected Nigerian tubers, legumes and cereals and estimates of the adult daily intakes.

    PubMed

    Akinyele, I O; Shokunbi, O S

    2015-04-15

    This study was designed to determine the levels of microminerals (manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), chromium (Cr)) and heavy metals (cadmium (Cd), lead (Pb) and nickel (Ni)) in some tubers, legumes and cereals obtained from the markets in Abeokuta city, South-West Nigeria. The food samples were digested by dry ashing procedure and their minerals were determined by atomic absorption spectrophotometer. The results show mean values of 1.67-32.00, 7.25-61.58, 1.59-10.56, 6.65-46.99, 0.02-0.58, <0.01-0.09, <0.08, and 0.06-0.14 mg/kg for Mn, Fe, Cu, Zn, Cr, Cd, Pb and Ni respectively. The levels of these metals in all the samples analysed were within the ranges reported for similar tubers, legumes and cereals from various parts of the world. The daily intakes of the metals through tubers, legumes and cereals were found to be lower than the provisional tolerable daily intakes proposed by Joint FAO/WHO Expert Committee on Food Additives.

  4. Assessment of heavy metal (Cu, Ni, Fe, Co, Mn, Cr, Zn) pollution in effluent dominated rivulet water and their effect on glycogen metabolism and histology of Mastacembelus armatus.

    PubMed

    Javed, Mehjbeen; Usmani, Nazura

    2013-01-01

    The present study was conducted to examine the contamination of rivulet situated at Kasimpur, Aligarh (27.218° N; 79.378° E). It receives the wastewater of Harduaganj Thermal Power Plant (HTPS) containing fly ash and heavy metals. Among the heavy metals estimated in the rivulet water, Fe (8.71 mgL(-1)) was present in the highest concentration followed by Cu (0.86 mgL(-1)), Zn (0.30 mgL(-1)) Mn (0.21 mgL(-1)), Ni (0.12 mgL(-1)), Co (0.11 mgL(-1)) and Cr (0.10 mgL(-1)). The values for the heavy metals such as Fe, Ni and Mn were beyond the limits set by UNEPGEMS. Bioaccumulation of these heavy metals was detected in tissues such as gills, liver, kidney, muscle and integument of the fish Mastacembelus armatus. Accumulation of Fe (213.29 - 2601.49 mgkg(-1).dw) was highest in all the organs. Liver was the most influenced organ and integument had the least metal load. The accumulation of Fe, Zn, Cu and Mn, observed in the tissues were above the values recommended by FAO/WHO. Biochemical estimation related to blood glucose, liver and muscle glycogen conducted showed significant (p < 0.01) elevation in blood glucose content over control (17.73%), whereas liver glycogen dropped significantly (p < 0.01) over control (-89.83%), and similarly muscle glycogen also decreased significantly (p < 0.05) over control (-71.95%), suggesting enhanced glycolytic capacity to fuel hepatic metabolism. Histopathological alterations were also observed in selected organs (gills, liver and kidney) of Mastacembelus armatus.

  5. The Deformation Behavior and Microstructure Evolution of a Mn- and Cr-Containing Al-Mg-Si-Cu Alloy During Hot Compression and Subsequent Heat Treatment

    NASA Astrophysics Data System (ADS)

    Xu, Yi; Nagaumi, Hiromi; Han, Yi; Zhang, Gongwang; Zhai, Tongguang

    2017-03-01

    Hot compression tests on a newly developed Mn- and Cr-containing Al-Mg-Si-Cu alloy were carried out at temperatures ranging from 623 K (350 °C) to 823 K (550 °C) and strain rates between 0.001 and 1 s-1 after casting and subsequent homogenization heat treatment. The true stress-true strain curves of the alloy exhibited a peak stress at a small plastic strain followed by dynamic flow softening. Using the constitutive equation containing the strain rate, peak stress, and temperature, the activation energy for hot deformation in the alloy was determined to be 249.67 kJ/mol, much higher than that (143.4 kJ/mol) for self-diffusion in pure Al. Scanning transmission electron microscopy experiments revealed that Mn- and Cr-containing α-dispersoids formed during homogenization showed a strong pinning effect on dislocations and grain boundaries, which was responsible for the increase in activation energy for hot deformation in the alloy. A threshold stress was consequently introduced and determined in the constitutive equation to count for the dispersoid hardening effect on hot deformation in the alloy. Electron back-scatter diffraction measurements revealed that the softening occurred in the alloy was mainly due to dynamic recovery taking place at relatively large Z values, and that it was dominated by continuous dynamic recrystallization at relatively low Z. In subsequent annealing after hot deformation at large Z, abnormal grain growth could occur, as a result of the critical strain-annealing effect. After upsetting at higher temperatures, the alloy showed superior tensile properties due to a high non-recrystallized area fraction.

  6. The Deformation Behavior and Microstructure Evolution of a Mn- and Cr-Containing Al-Mg-Si-Cu Alloy During Hot Compression and Subsequent Heat Treatment

    NASA Astrophysics Data System (ADS)

    Xu, Yi; Nagaumi, Hiromi; Han, Yi; Zhang, Gongwang; Zhai, Tongguang

    2017-01-01

    Hot compression tests on a newly developed Mn- and Cr-containing Al-Mg-Si-Cu alloy were carried out at temperatures ranging from 623 K (350 °C) to 823 K (550 °C) and strain rates between 0.001 and 1 s-1 after casting and subsequent homogenization heat treatment. The true stress-true strain curves of the alloy exhibited a peak stress at a small plastic strain followed by dynamic flow softening. Using the constitutive equation containing the strain rate, peak stress, and temperature, the activation energy for hot deformation in the alloy was determined to be 249.67 kJ/mol, much higher than that (143.4 kJ/mol) for self-diffusion in pure Al. Scanning transmission electron microscopy experiments revealed that Mn- and Cr-containing α-dispersoids formed during homogenization showed a strong pinning effect on dislocations and grain boundaries, which was responsible for the increase in activation energy for hot deformation in the alloy. A threshold stress was consequently introduced and determined in the constitutive equation to count for the dispersoid hardening effect on hot deformation in the alloy. Electron back-scatter diffraction measurements revealed that the softening occurred in the alloy was mainly due to dynamic recovery taking place at relatively large Z values, and that it was dominated by continuous dynamic recrystallization at relatively low Z. In subsequent annealing after hot deformation at large Z, abnormal grain growth could occur, as a result of the critical strain-annealing effect. After upsetting at higher temperatures, the alloy showed superior tensile properties due to a high non-recrystallized area fraction.

  7. Cu-Cr Literature Review

    SciTech Connect

    Need, Ryan F.

    2012-08-09

    Cu-Cr alloys are part of a class of face-centered cubic (FCC)-body-centered cubic (BCC) composites that includes similar alloys, such as Cu-Nb and Cu-Ta. When heavily deformed, these FCC-BCC materials create 'in situ' composites with a characteristic structure-nanoscale BCC filaments in a ductile FCC matrix. The strength of these composites is vastly greater than predicted by the rule of mixtures, and has been shown to be inversely proportional to the filament spacing. Lower raw materials costs suggest that Cu-Cr alloys may offer more economical solution to high-strength, high-conductivity wire than either their Nb or Ta counterparts. However, Cr is also more brittle and soluble in Cu than Nb or Ta. These qualities necessitate thermal treatments to remove solute atoms from the Cu matrix, improve conductivity, and maintain the ductility of the Cr filaments. Through the use of different thermomechanical processing routes or the addition of select dopants, alloys with strength in excess of 1 GPa at 70% IACS have been achieved. To date, previous research on Cu-Cr alloys has focused on a relatively small number of alloy compositions and processing methods while the effects of dopants and ageing treatments have only been studied independently. Consequently, there remains considerable opportunity for the development and optimization of these alloys as a leading high-strength, high-conductivity material.

  8. Succulent species differ substantially in their tolerance and phytoextraction potential when grown in the presence of Cd, Cr, Cu, Mn, Ni, Pb, and Zn.

    PubMed

    Zhang, Chengjun; Sale, Peter W G; Clark, Gary J; Liu, Wuxing; Doronila, Augustine I; Kolev, Spas D; Tang, Caixian

    2015-12-01

    Plants for the phytoextraction of heavy metals should have the ability to accumulate high concentrations of such metals and exhibit multiple tolerance traits to cope with adverse conditions such as coexistence of multiple heavy metals, high salinity, and drought which are the characteristics of many contaminated soils. This study compared 14 succulent species for their phytoextraction potential of Cd, Cr, Cu, Mn, Ni, Pb, and Zn. There were species variations in metal tolerance and accumulation. Among the 14 succulent species, an Australian native halophyte Carpobrotus rossii exhibited the highest relative growth rate (20.6-26.6 mg plant(-1) day(-1)) and highest tolerance index (78-93%), whilst Sedum "Autumn Joy" had the lowest relative growth rate (8.3-13.6 mg plant(-1) day(-1)), and Crassula multicava showed the lowest tolerance indices (<50%). Carpobrotus rossii and Crassula helmsii showed higher potential for phytoextraction of these heavy metals than other species. These findings suggest that Carpobrotus rossii is a promising candidate for phytoextraction of multiple heavy metals, and the aquatic or semiterrestrial Crassula helmsii is suitable for phytoextraction of Cd and Zn from polluted waters or wetlands.

  9. Solid-state reactions during mechanical alloying of ternary Fe-Al-X (X=Ni, Mn, Cu, Ti, Cr, B, Si) systems: A review

    NASA Astrophysics Data System (ADS)

    Hadef, Fatma

    2016-12-01

    The last decade has witnessed an intensive research in the field of nanocrystalline materials due to their enhanced properties. A lot of processing techniques were developed in order to synthesis these novel materials, among them mechanical alloying or high-energy ball milling. In fact, mechanical alloying is one of the most common operations in the processing of solids. It can be used to quickly and easily synthesize a variety of technologically useful materials which are very difficult to manufacture by other techniques. One advantage of MA over many other techniques is that is a solid state technique and consequently problems associated with melting and solidification are bypassed. Special attention is being paid to the synthesis of alloys through reactions mainly occurring in solid state in many metallic ternary Fe-Al-X systems, in order to improve mainly Fe-Al structural and mechanical properties. The results show that nanocrystallization is the common result occurring in all systems during MA process. The aim of this work is to illustrate the uniqueness of MA process to induce phase transformation in metallic Fe-Al-X (X=Ni, Mn, Cu, Ti, Cr, B, Si) systems.

  10. Assessment of heavy metals/metalloid (As, Pb, Cd, Ni, Zn, Cr, Cu, Mn) concentrations in edible fish species tissue in the Pearl River Delta (PRD), China.

    PubMed

    Leung, H M; Leung, A O W; Wang, H S; Ma, K K; Liang, Y; Ho, K C; Cheung, K C; Tohidi, F; Yung, K K L

    2014-01-15

    The major aim of this study was to investigate heavy metal content of edible fish in the PRD. Eleven species of fish (consisting of 711 individuals) [catfish (Clarias fuscus), tilapia (Oreochromis mossambicus), grass carp (Ctenopharyngodon idellus), bighead carp (Aristichthys nobilis), mandarin fish (Siniperca kneri), snakehead (Channa asiatiea), black bass (Micropterus salmoides), mangrove snapper (Lutjanus griseus), star snapper (Lutjanu stellatus), snubnose pompano (Trachinotus blochii) and orange-spotted grouper (Epinephelus coioides)] were collected for the analyses of heavy metals. Overall concentrations (mg/kg, ww) in the fish muscles were: As (0.03-1.53), Pb (0.03-8.62), Cd (0.02-0.06), Ni (0.44-9.75), Zn (15.7-29.5), Cr (0.22-0.65), Cu (0.79-2.26), Mn (0.82-6.91). Significant level of Pb were found in tilapia at all locations. It is recommended that heavy metal concentrations in different fish species must be determined on a regular basis in the future so as to reduce human health risks from acute and chronic food intoxication.

  11. Modeling of the corrosion behavior and its interrelation with the deformation behavior and microstructure in a newly developed 7.5Mn-5Cr-1.5Cu alloy white iron

    NASA Astrophysics Data System (ADS)

    Patwardhan, A. K.; Jain, N. C.

    1991-10-01

    Corrosion rate, (CR), compressive strength (CS), and percent strain were determined for different microstructures generated by heat-treating a newly designed 7.5Mn-5Cr-1.5Cu alloy white iron intended to be used for making castings to resist aqueous corrosion under marine conditions. The microstructures were characterized on the basis of size, shape, and distribution of the second phase, which in the present study comprised dispersed (DCs) and massive carbides (MCs). A new term, “distribution factor” (DF), has been evolved to characterize DCs. This factor proved useful in establishing a relationship between microstructure and CR, which can be represented by the expression CR = [C1 + C2(VMC) + C3(VMC)2] * (DF)4

  12. Monitoring trace elements (Al, As, Cr, Cu, Fe, Mn, Ni and Zn) in deep and surface waters of the estuary of the Nerbioi-Ibaizabal River (Bay of Biscay, Basque Country)

    NASA Astrophysics Data System (ADS)

    Fernández, Silvia; Villanueva, Unai; de Diego, Alberto; Arana, Gorka; Madariaga, Juan Manuel

    2008-07-01

    Deep water samples (in contact with the sediment) were collected at eight different points of the estuary of the Nerbioi-Ibaizabal River (Bay of Biscay, Basque Country), both at low and high tides, during four sampling campaigns (May, September and December 2005 and March 2006). Superficial water was also sampled in March 2006. Temperature, pH, redox potential, dissolved oxygen and electrical conductivity corresponding to each sample were measured in situ at each sampling point using a multiparametric probe. The physico-chemical parameters found are typical of highly stratified estuaries, with an acceptable oxygenation level. After filtering and acidifying the samples, they were analysed by inductively coupled plasma/mass spectrometry (ICP/MS) to simultaneously determine the total concentration of Al, As, Cr, Cu, Fe, Mn, Ni and Zn. Concentrations in the μg kg - 1 level were found in all cases ( cCr and cNi, 1-10; cAl, cAs and cZn, 10-50; cCu and cMn, 10-100 and cFe, 100-400 μg kg - 1 ). A probable net input of Al, Cr, Mn and Zn via the main (Nerbioi-Ibaizabal) and some of the tributary rivers (Galindo, Asua and Gobela) was identified. Evidence of a common source of Al and Zn to the estuary was found. Correlation analysis of data revealed connections between variables (concentration of Cu, Fe and As with salinity, as well as cAl with cZn, cCu with cFe, cAs with cFe, and cAs with cCu). Principal Component Analysis (PCA) of data allowed the samples to be grouped according to sampling campaign, with two principal components accounting for 62% of the total variance. In addition, plots of element concentration against salinity suggested a conservative behaviour for As, Cu and Fe and a non-conservative one for Cr. Not clear mixing behaviour was observed for the rest of elements.

  13. Effects of the Oral Administration of K2Cr2O7 and Na2SeO3 on Ca, Mg, Mn, Fe, Cu, and Zn Contents in the Heart, Liver, Spleen, and Kidney of Chickens.

    PubMed

    Chen, Peng; Zhu, Yiran; Wan, Huiyu; Wang, Yang; Hao, Pan; Cheng, Ziqiang; Liu, Yongxia; Liu, Jianzhu

    2017-03-28

    This study aimed to investigate the effects of selenium on the ion profiles in the heart, liver, spleen, and kidney through the oral administration of hexavalent chromium. Approximately 22.14 mg/kg b.w. K2Cr2O7 was added to water to establish a chronic poisoning model. Different selenium levels (0.00, 0.31, 0.63, 1.25, 2.50, and 5.00 mg Na2SeO3/kg b.w.) around the safe dose were administered to the experimental group model. Ca, Mg, Mn, Fe, Cu, and Zn were detected in the organs through flame atomic absorption spectrometry after these organs were exposed to K2Cr2O7 and Na2SeO3 for 14, 28, and 42 days. Results showed that these elements exhibited various changes. Ca contents declined in the heart, liver, and spleen. Ca contents also decreased on the 28th day and increased on the 42nd day in the kidney. Mn contents declined in the heart and spleen but increased in the kidney. Mn contents also decreased on the 28th day and increased on the 42nd day in the liver. Cu contents declined in the heart and spleen. Cu contents increased on the 28th day and decreased on the 42nd day in the liver and kidney. Zn contents declined in the heart and spleen. Zn contents increased on the 28th day and decreased on the 42nd day in the liver and kidney. Fe contents decreased in the heart and liver. Fe contents increased on the 28th day and decreased on the 42nd day in the spleen and kidney. Mg contents did not significantly change in these organs. Appropriate selenium contents enhanced Mn and Zn contents, which were declined by chromium. Conversely, appropriate selenium contents reduced Ca, Fe, and Cu contents, which were increased by chromium. In conclusion, the exposure of chickens to K2Cr2O7 induced changes in different trace elements, and Na2SeO3 supplementation could alleviate this condition.

  14. Usual dietary intakes of selected trace elements (Zn, Cu, Mn, I, Se, Cr, and Mo) and biotin revealed by a survey of four-season 7-consecutive day weighed dietary records in middle-aged Japanese dietitians.

    PubMed

    Imaeda, Nahomi; Kuriki, Kiyonori; Fujiwara, Nakako; Goto, Chiho; Tokudome, Yuko; Tokudome, Shinkan

    2013-01-01

    We aimed to identify food sources of selected trace elements (Zn, Cu, Mn, I, Se, Cr, Mo) and biotin in the Japanese diet and to assess usual dietary intakes based on the ratios of within-person to between-person variance. Subjects were 98 middle-aged dietitians living in central Japan who participated in a survey of four-season 7 consecutive day weighed diet records. Based on the latest Standard Tables of Food Composition in Japan published in 2010, food sources of selected nutrients were located according to a contribution analysis, and computed usual dietary intakes. Dietary intakes were checked with the Dietary Reference Intakes for Japanese 2010. Prevalence of inadequacy in a group was determined using the Estimated Average Requirement cut-point method. The major contributors to selected trace elements and biotin were not only meat and milk, but also traditional Japanese food items, including rice, tofu and tofu products, fish, seaweed, chicken eggs, fermented soy bean seasonings, and green tea. Medians of usual intakes were estimated for Zn (men 8.9 mg, women 8.4 mg), Cu (1.32 mg, 1.21 mg), Mn (3.73 mg, 3.76 mg), I (312 μg, 413 μg), Se (97 μg, 94 μg), Cr (10 μg, 9 μg), Mo (226 μg, 184 μg), and biotin (51.7 μg, 47.6 μg). The prevalence of inadequacy of dietary intakes was high for Zn, Cu and Cr. Regarding I, the proportion above the Tolerant Upper Level was overestimated based on the crude mean value. We first identified food sources of selected trace elements and biotin in the Japanese diet, and assessed the usual intakes.

  15. Effect of microstructure on the corrosion and deformation behavior of a newly developed 6Mn-5Cr-1.5Cu corrosion-resistant white iron

    NASA Astrophysics Data System (ADS)

    Rao, P. N. V. R. S. S. V. Prasada; Patwardhan, A. K.; Jain, N. C.

    1993-02-01

    An experimental study has been made of the effect of heat treatment on the transformation behavior of a 4.8 pct Cr white iron, alloyed with 6 pct Mn and 1.5 pct Cu, by employing optical metallography, X-ray diffractometry, and differential thermal analysis (DTA) techniques, with a view to assess the suitability of the different microstructures in resisting aqueous corrosion. The matrix microstructure in the as-cast condition, comprising pearlite + bainite/martensite, transformed to austenite on heat-treating at all the temperatures between 900 °C and 1050 °C. Increasing the soaking period at each of the heat-treating temperatures led to an increase in the volume fraction and stability of austenite. M3C was the dominant carbide present in the as-cast condition. On heat-treating, different carbides formed: M23C6 carbide was present on heat-treating at 900 °C and 950 °C; on heat-treating at 1000 °C, M7C3 formed and persisted even on heattreating at 1050 °C. The possible formation of M5C2 carbide in the as-cast and heat-treated conditions (900 °C and 950 °C) is also indicated. Dispersed carbides (DC), present in austenite up to 950 °C, mostly comprised M3C and M5C2. On stress relieving of the heat-treated samples, M7C3-type DC also formed. The hardness changes were found to be consistent with the micro-structural changes occurring on heat-treating. The as-cast state was characterized by a reasonable resistance to corrosion in 5 pct NaCl solution. On heat-treating, the corrosion resistance improved over that in the as-cast state. After 4 hours soaking, increasing the temperature from 900 °C to 1050 °C led to an improvement in corrosion resistance. However, after 10 hours soaking, corrosion resistance decreased on increasing the temperature from 900 °C to 950 °C and improved thereafter on increasing the heat-treating temperature. Deformation behavior responded to the microstructure on similar lines as the corrosion behavior. Although in an early stage of

  16. Co-electrolysis of steam and CO2 in a solid oxide electrolysis cell with La0.75Sr0.25Cr0.5Mn0.5O3-δ -Cu ceramic composite electrode

    NASA Astrophysics Data System (ADS)

    Xing, Ruimin; Wang, Yarong; Zhu, Yongqiang; Liu, Shanhu; Jin, Chao

    2015-01-01

    Cu impregnation has been performed to improve electronic conductivity of La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) material in reducing atmosphere, and solid oxide electrolysis cells (SOECs) with the configuration of LSCF|LSGM|LSCM-Cu are prepared and evaluated for high temperature steam and carbon dioxide co-electrolysis. Electrochemical impedance spectra (EIS) and voltage-current curves are carried out to characterize the cell performances. Compared with LSCF|LSGM|LSCM cell without Cu impregnation for steam electrolysis under the same conditions, EIS results show that LSCF|LSGM|LSCM-Cu cell not only displays lower ohmic resistance and better electrochemical performances, but also their resistance increases with the percentage of the fed CO2 under open circuit voltage, in which the polarization resistance dominates. With the applied electrolysis voltage of 1.65 V and the operating temperature of 750 °C, the maximum consumed current density increases from 1.31 A cm-2 without CO2 to 1.82 A cm-2 with 37.5% CO2. Although there is an increase of 2.0% in the applied electrolysis voltage, the cell has exhibited an excellent durability test for more than 50 h with the electrolysis current density of 0.33 A cm-2 and the gas mixture of 50% AH-25% H2-25% CO2 at 750 °C.

  17. 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.

  18. An anti CuO2-type metal hydride square net structure in Ln2M2As2H(x) (Ln=La or Sm, M=Ti, V, Cr, or Mn).

    PubMed

    Mizoguchi, Hiroshi; Park, SangWon; Hiraka, Haruhiro; Ikeda, Kazutaka; Otomo, Toshiya; Hosono, Hideo

    2015-03-02

    Using a high pressure technique and the strong donating nature of H(-), a new series of tetragonal La2Fe2Se2O3-type layered mixed-anion arsenides, Ln2M2As2H(x), was synthesized (Ln=La or Sm, M=Ti, V, Cr, or Mn; x≈3). In these compounds, an unusual M2H square net, which has anti CuO2 square net structures accompanying two As(3-) ions, is sandwiched by (LaH)2 fluorite layers. Notably, strong metal-metal bonding with a distance of 2.80 Å was confirmed in La2Ti2As2H2.3, which has metallic properties. In fact, these compounds are situated near the boundary between salt-like ionic hydrides and transition-metal hydrides with metallic characters.

  19. Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) new complexes of 5-aminosalicylic acid: Spectroscopic, thermal characterization and biological activity studies

    NASA Astrophysics Data System (ADS)

    Soliman, Madiha H.; Mohamed, Gehad G.

    2013-04-01

    The complexing behavior of mesalazine (5-aminosalicylic acid; 5-ASA) towards the transition metal ions namely, Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) have been examined by elemental analyses, magnetic measurements, electronic, IR and 1H NMR. Thermal properties and decomposition kinetics of all complexes are investigated. The interpretation, mathematical analyses and evaluation of kinetic parameters of all thermal decomposition stages have been evaluated using Coats-Redfern equation. The free ligand and its metal complexes have been tested in vitro against Aspergillus fumigatus and Candida albicans fungi and Pseudomonas aeruginosa, Escherichia coli, Bacillis subtilies and Staphylococcus aureus bacteria in order to assess their antimicrobial potential. The results indicate that the metal complexes are also found to have more antimicrobial activity than the parent 5-ASA drug.

  20. 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.

  1. Determination of labile species of As(V), Ba, Cd, Co, Cr(III), Cu, Mn, Ni, Pb, Sr, V(V), and Zn in natural waters using diffusive gradients in thin-film (DGT) devices modified with montmorillonite.

    PubMed

    Dos Anjos, Vanessa E; Abate, Gilberto; Grassi, Marco T

    2017-03-01

    A binding phase based on the clay mineral montmorillonite (MT) was used as a sorbent in this work, which employed diffusive gradients in thin-film (DGT) devices to determine the lability of trace elements in natural waters. Montmorillonite exhibits low cost, wide availability, ease of handling, high ion-exchange capacity, and reusability. As(V), Ba(2+), Cd(2+), Co(2+), Cr(III), Cu(2+), Mn(2+), Ni(2+), Pb(2+), Sr(2+), V(V), and Zn(2+) were quantitatively sorbed by MT and eluted with 1.0 mol L(-1) HNO3, which provided efficiency above 70% of recovery. Validation tests were performed with synthetic solutions. The recovery of known concentrations ranged from 83 to 110%. The performance of modified DGT was compared with conventional DGT devices in experiments lasting 6 and 48 h. The results obtained with both DGT devices showed no significant differences with 95% confidence. DGT samplers with MT were deployed in the determination of labile forms of the elements in water samples from Iguaçu River (Paraná, Brazil). The measured masses of elements in MT for various durations showed good fit to a theoretical line, indicating that the results agreed with the principle of the DGT technique. The concentrations of labile species in the sample proceeded as follows; Sr > Cd > Ba > Cu > Cr > Mn > Zn > Pb. The results suggest that DGT devices with MT are an effective alternative for speciation analysis of a wide range of elements (cations as well as anions) in natural waters.

  2. Effect of CaO on retention of S, Cl, Br, As, Mn, V, Cr, Ni, Cu, Zn, W and Pb in bottom ashes from fluidized-bed coal combustion power station.

    PubMed

    Bartoňová, Lucie; Klika, Zdeněk

    2014-07-01

    This work was conducted to evaluate whether Ca-bearing additives used during coal combustion can also help with the retention of some other elements. This work was focused on the evaluation of bottom ashes collected during four full-scale combustion tests at an operating thermal fluidized-bed power station. Bottom ashes were preferred to fly ashes for the study to avoid interference from condensation processes usually occurring in the post-combustion zone. This work focused on the behaviors of S, Cl, Br, As, Mn, V, Cr, Ni, Cu, Zn, W, and Pb. Strong positive correlations with CaO content in bottom ashes were observed (for all four combustion tests) for S, As, Cl and Br (R=0.917-0.999). Strong inverse proportionality was calculated between the contents of Pb, Zn, Ni, Cr and Mn and CaO, so these elements showed association to materials other than Ca-bearing compounds (e.g., to aluminosilicates, organic matter, etc.). Somewhat unclear behaviors were observed for W, Cu, and V. Their correlation coefficients were evaluated as statistically "not significant", i.e., these elements were not thought to be significantly associated with CaO. It was also discovered that major enrichment of CaO in the finest bottom ash fractions could be advantageously used for simple separation of elements strongly associated with these fractions, mainly S and As, but also Cl or Br. Removal of 5% of the finest ash particles brings about a decrease in As concentration down to 77%-80% of its original bulk ash content, which can be conveniently used e.g., when high As content complicates further ash utilization.

  3. Raman and infrared studies of La1-ySryMn1-xMxO3 ( M=Cr , Co, Cu, Zn, Sc or Ga): Oxygen disorder and local vibrational modes

    NASA Astrophysics Data System (ADS)

    Dubroka, A.; Humlíček, J.; Abrashev, M. V.; Popović, Z. V.; Sapiña, F.; Cantarero, A.

    2006-06-01

    We present results of our study of polarized Raman scattering and infrared reflectivity of rhombohedral ceramic La1-ySryMn1-xMxO3 manganites in the temperature range between 77 and 320K . In our samples, a part of the Mn atoms is substituted by M=Cr , Co, Cu, Zn, Sc, or Ga with x in the range 0-0.1. The hole concentration was kept at the optimal value of about 32% by tuning the Sr content y . We have monitored distortions of the oxygen sublattice by the presence of broad bands in the Raman spectra, the increase of dc resistivity extracted from the infrared reflectivity, and the change of the critical temperature of the ferromagnetic transition. Our results support the idea that these properties are mainly determined by the radius of the substituent ion, its electronic and magnetic structure playing only a minor role. Furthermore, the Raman spectra exhibit an additional Ag -like high frequency mode attributed to the local breathing vibration of oxygens surrounding the substituent ion. Its frequency and intensity strongly depend on the type of the substituent. In the Co-substituted sample, the mode anomalously softens when going from 300to77K . The frequency of the bulk A1g mode depends linearly on the angle of the rhombohedral distortion.

  4. Influence of the type of tree habitat on the character of co-occurrence of Fe, Mn, Zn, Cu, Pb, Ni, Cr and Co in the soil of the Tatra Mountain National Park.

    PubMed

    Kwapuliński, Jerzy; Paprotny, Łukasz; Paukszto, Andrzej; Kowol, Jolanta; Rochel, Robert; Nogaj, Ewa; Musielińska, Renata; Celiński, Rafał

    2013-01-01

    The objective of the research was to determine the effect of habitat type of selected species of trees on the nature of co-occurrence of Fe, Mn, Zn, Cu, Pb, Cd, Ni, Cr and Co. The presence of speciation forms of these metals was investigated, with reference to the species composition of tree stands in selected areas of the Tatra Mountain National Park (Chochołowska Valley, Strążyska Valley, Kościeliska Valley, as well as Mała Łąka Valley).Contents of selected metals in samples were determined by the flame ASA method, with an accuracy of 0.1 µg/g. In habitats dominated by maples, the Pb content in the Chochołowska Valley, unlike Kościeliska Valley covered with beeches, the Pb content in the form directly bioavailable, was twice as high. This was clearly proved in the case of Strążyska Valley where the soil in beech tree habitats contained larger quantities of exchangeable forms of Pb, than that in the Chochołowska Valley. The soil of the valleys, including the Mała Łąka Valley, showed peculiar characteristic averaging of the contents of selected speciation forms of metals in the soil. Content corresponding to 10 percentile and geometrical average may be regarded as benchmarks in future studies of the Tatra Mountain National Park, or other protected areas.

  5. Statistical theory of diffusion in concentrated bcc and fcc alloys and concentration dependencies of diffusion coefficients in bcc alloys FeCu, FeMn, FeNi, and FeCr

    SciTech Connect

    Vaks, V. G.; Khromov, K. Yu. Pankratov, I. R.; Popov, V. V.

    2016-07-15

    The statistical theory of diffusion in concentrated bcc and fcc alloys with arbitrary pairwise interatomic interactions based on the master equation approach is developed. Vacancy–atom correlations are described using both the second-shell-jump and the nearest-neighbor-jump approximations which are shown to be usually sufficiently accurate. General expressions for Onsager coefficients in terms of microscopic interatomic interactions and some statistical averages are given. Both the analytical kinetic mean-field and the Monte Carlo methods for finding these averages are described. The theory developed is used to describe sharp concentration dependencies of diffusion coefficients in several iron-based alloy systems. For the bcc alloys FeCu, FeMn, and FeNi, we predict the notable increase of the iron self-diffusion coefficient with solute concentration c, up to several times, even though values of c possible for these alloys do not exceed some percent. For the bcc alloys FeCr at high temperatures T ≳ 1400 K, we show that the very strong and peculiar concentration dependencies of both tracer and chemical diffusion coefficients observed in these alloys can be naturally explained by the theory, without invoking exotic models discussed earlier.

  6. Enhancement of ferromagnetism by Cr doping in Ni-Mn-Cr-Sb Heusler alloys

    NASA Astrophysics Data System (ADS)

    Khan, Mahmud; Dubenko, Igor; Stadler, Shane; Jung, J.; Stoyko, S. S.; Mar, Arthur; Quetz, Abdiel; Samanta, Tapas; Ali, Naushad; Chow, K. H.

    2013-03-01

    A series of Mn rich Ni50Mn37-xCrxSb13 Heusler alloys have been investigated by dc magnetization and electrical resistivity measurements. Due to the weakening of the Ni-Mn hybridization, the martensitic transition shifts to lower temperatures with increasing Cr concentration, while the saturation magnetization at 5 K increases. The magnetoresistance and exchange bias properties are dramatically suppressed with increasing Cr concentration. The observed behaviors suggest that substitution of Cr for Mn in Ni50Mn37-xCrxSb13 Heusler alloys not only destabilizes the martensitic phase but also enhances ferromagnetism in the system. The possible mechanisms responsible for the observed behavior are discussed.

  7. Thermodynamic Modeling of the Al-Cr-Mn Ternary System

    NASA Astrophysics Data System (ADS)

    Cui, Senlin; Jung, In-Ho

    2017-03-01

    The phase diagram information available in the literature on the Al-Cr-Mn system was comprehensively evaluated and optimized for the first time to obtain a set of Gibbs energies of all the solid and liquid phases in the Al-Cr-Mn system. The Modified Quasi-chemical Model (MQM) was utilized to describe the Gibbs energy of the liquid phase of the Al-Cr-Mn system. The Compound Energy Formalism (CEF) was used to model the solid solution phases. A revision of the Al-Mn system was simultaneously conducted to consider the γ_H (Al8Mn5) phase. The liquid Cr-Mn phase was also remodeled using the Modified Quasi-chemical Model (MQM) to obtain a consistent description of the ternary Al-Cr-Mn liquid phase. Accurate description of the phase diagram of the entire Al-Cr-Mn system was obtained from the thermodynamic models with optimized parameters in the present study, and the model parameters can be used to predict the thermodynamic properties of the ternary system.

  8. Unexpected crystal and magnetic structures in MnCu4In and MnCu4Sn

    SciTech Connect

    Provino, A; Paudyal, D; Fornasini, ML; Dhiman, I; Dhar, SK; Das, A; Mudryk, Y; Manfrinetti, P; Pecharsky, VK

    2013-01-29

    We discovered a new compound MnCu4In with its own hexagonal structure type (hP12-P63mc, ternary ordered derivative of the hexagonal MgZn2-type) that becomes ferromagnetic at TC = 540 K. This transition temperature is higher than that found in the MnCu2In and MnCu2Sn alloys. In contrast, the homologous compound MnCu4Sn, which crystallizes in the cubic MgCu4Sn-type, orders antiferromagnetically with TN = 110 K. The neutron diffraction studies show ferromagnetic spin orientation in the {1 0 1} plane in MnCu4In with a magnetic moment of 4.5 μB/Mn at 22 K, and a corresponding value of 4.7 μB/Mn in the antiferromagnetic MnCu4Sn with propagation vector View the MathML source. The first-principles electronic structure calculations show that the unexpected difference in both magnetic and crystal structures of MnCu4In and MnCu4Sn is due to the difference in the Mn-3d bands and exchange interactions relating to different crystal anisotropy, coordination numbers, and interatomic distances.

  9. Chemical speciation of Fe, Mn, Pb, Zn, Cd, Cu, Co, Ni and Cr in the suspended particulate matter off the Mejerda River Delta (Gulf of Tunis, Tunisia)

    NASA Astrophysics Data System (ADS)

    Helali, Mohamed Amine; Oueslati, Walid; Zaaboub, Noureddine; Added, Ayed; Aleya, Lotfi

    2016-06-01

    Fluxes of suspended particulate matter (SPM) and their associated metals were performed off the Mejerda River Delta during both the wet (March) and the dry (July) seasons in 2012, using sediment traps at study stations at depths of 10, 20 and 40 m. Fluxes nearest to the Mejerda outlet were more significant, especially during winter (36 g m-2 day-1), but dissipated further offshore, 24.5-6 g m-2 day-1 at the 20 m and 21.8-4.8 g m-2 day-1 at the 40 m stations. Many variations observed in seasonal and spatial metal fluxes are similar to those of SPM, in particular Pb and Zn, probably because they are associated with the mining activity characteristic of the Mejerda catchment. Chemical speciation reveals that most of the metals (20-100%) are bound to the residual fraction. The most toxic metals (Pb, Zn) are bound in part to the exchangeable fraction (20-50% for Pb and 5-15% for Zn) making them relatively bioavailable and therefore potentially toxic. While Cu and Cd fluxes are not always clearly established according to season, both metals are apparently sequestered deep in the sediment, bound especially to clays (40-80% for Cd and up to 100% for Cu).

  10. Strengthening in rapidly solidified age hardened Cu-Cr and Cu-Cr-Zr alloys

    SciTech Connect

    Correia, J.B.; Davies, H.A.; Sellars, C.M.

    1997-01-01

    Cu-Cr and Cu-Cr-Zr alloy powders were produced by water atomization and consolidated by warm extrusion. Coherent Cr precipitation is associated with the peak hardness condition in these alloys. The mechanical properties obtained after aging treatments, namely the peak hardness, and the corresponding proof stress are related to the concentration of the alloying element initially in solid solution in the powders. The strengthening observed is interpreted in terms of theories of precipitation and dispersion strengthening and compared with similar analyses reported previously in the literature for these alloy systems.

  11. 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.

  12. 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.

  13. Effect of heat treatment on the hardness-microstructure inter-relation in a 7.5Mn-5Cr-1.5Cu alloy white iron: A modeling approach

    NASA Astrophysics Data System (ADS)

    Jain, N. C.; Patwardhan, A. K.

    1992-03-01

    An experimental study has been made on the effect of heat-treating temperature (800 °C 850 °C 900 °C, 950 °C, 1000 °C, and 1050 °C) and time (2, 4, 6, 8, and 10 hours) on the transformation behavior of a 7.5Mn-5Cr-1.5Cu white cast iron developed to resist aqueous corrosion in different environments. Structural changes on heat treating were monitored using hardness measurements. It was observed that on heat treating from 800 °C, hardness increased marginally with soaking period. Hardness was independent of soaking period on heat treating at 850 °C and 900 °C. On heat treating from 950 °C and higher, hardness decreased with time, the effect being pronounced at 1000 °C and 1050 °C. These changes are consistent with the resultant microstructural changes. The hardness (H) vs time (t) plots at any temperature are linear and can be represented by H = C1 + C 2t (T °C) The hardness vs temperature plots as influenced by time, which, in effect, represented how effectively the alloy sustained hardness, are most appropriately represented by a third-order polynomial: H = C1 + C2T + C3T2 + C4T3 (t s) leading to a horizontal “S” shape. Based on fundamental considerations, the final model interrelating hardness with temperature and time is H = 61.8 e2442.5/T + (0.0188 -1.6 × 10-5· T)t where T = temperature in K; t = time in seconds; and H = Vickers hardness number, 30 kgf (VHN30). The overall validity and usefulness of the model have been discussed.

  14. Magnetic properties of Cr and Mn powders (abstract)

    NASA Astrophysics Data System (ADS)

    Zhukov, A. P.; Ivanov, S. A.; Nudelman, M. A.; Ponomarev, B. K.; Kaloshkin, S. D.; Shatov, A. A.

    1993-05-01

    Mn and Cr powders were produced from electrolytic Mn and Cr by ball milling in a stainless steel container with carbon steel balls. The milling time, t, varied from 5 min to 8 h. Structures were investigated by x-ray and electron microscopy. Chemical compositions of samples were checked by flame atomic absorption spectrometry. The magnetization was measured by induction method in a pulsed magnetic field up to 10 T. The main part of Mn and Cr powder volume was occupied by α-Mn and b.c.c. Cr, respectively. Diffraction peaks became vaster and more asymmetric with increasing t due to the onset of defects of the structure. The presence of MnO was observed in the Mn sample after 8 h of milling. The size of Mn and Cr particles over same critical t (for chromium t=100 min) was no more than 1 mm. A noticeable Fe content, which increases at higher t, was observed. The Mössbauer spectra of Cr and Mn samples showed the lines of α-Fe and γ-Fe. High values of saturation magnetization, σ, up to 5.4 emu/g, and susceptibility and existence of the hysteresis in low fields at temperatures up to 360 K, indicate ferromagnetic ordering of the samples. Within the range of 78-360 K σ only slightly depends on temperature, but noticeably grows with increasing t at fixed temperature in Cr powders, remaining practically constant in Mn powders. No correlation could be observed between Fe content and σ : the latter remained the same in Mn with Fe concentration increasing, but in Cr, as Fe concentration increased sevenfold, it grew by four times. Spontaneous magnetization per mass unit of Fe, σ, was sufficiently lower than that of pure α-Fe (220 emu/g). The obtained values of σ correspond neither to Fe solid solution nor to pure Cr or Mn. Elucidation of the obtained results can be done both by the presence of α-Fe particles and by variation of exchange interactions caused by sample defects. A noticeable difference of σ values from those properties of bulk α-Fe can be explained by

  15. 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.

  16. Observations of a Cast Cu-Cr-Zr Alloy

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    2006-01-01

    Prior work has demonstrated that Cu-Cr-Nb alloys have considerable advantages over the copper alloys currently used in regeneratively cooled rocket engine liners. Observations indicated that Zr and Nb have similar chemical properties and form very similar compounds. Glazov and Zakharov et al. reported the presence of Cr2Zr in Cu-Cr-Zr alloys with up to 3.5 wt% Cr and Zr though Zeng et al. calculated that Cr2Zr could not exist in a ternary Cu-Cr-Zr alloy. A cast Cu-6.15 wt% Cr-5.25 wt% Zr alloy was examined to determine if the microstructure developed would be similar to GRCop-84 (Cu-6.65 wt% Cr-5.85 wt% Nb). It was observed that the Cu-Cr-Zr system did not form any Cr2Zr even after a thermal exposure at 875 C for 176.5 h. Instead the alloy consisted of three phases: Cu, Cu5Zr, and Cr.

  17. Magnetic resonance in a Cu-Cr-S structure

    SciTech Connect

    Vorotynov, A. M. Abramova, G. M.; Pankrats, A. I.; Petrakovskii, G. A.; Zharkov, S. M.; Zeer, G. M.; Tugarinov, V. I.; Rautskii, M. V.; Sokolov, V. V.

    2013-11-15

    A layered Cu-Cr-S structure composed of single-crystal CuCrS{sub 2} layers and thin CuCr{sub 2}S{sub 4} plates embedded in them has been investigated by the magnetic resonance and scanning electron microscopy methods. The Curie temperature and saturation magnetization of the spinel phase of the investigated samples have been determined. The thickness of the CuCr{sub 2}S{sub 4} layers has been estimated. The dependence of the growncrystal topology on synthesis conditions has been established. An interpretation of the anomalous behavior of the magnetostatic oscillation intensity is offered.

  18. 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

  19. Rational serendipity: "undirected" synthesis of a large {MnCu} complex from pre-formed Mn(II) building blocks.

    PubMed

    Frost, Jamie M; Kettles, Fraser J; Wilson, Claire; Murrie, Mark

    2016-11-15

    Use of an aminopolyalcohol-based Mn(II) complex in solvothermal Cu(II) chemistry leads to a rare example of a high nuclearity heterometallic {MnCu} system, in which four Cu(II)(H1Edte) units trap an inner {MnCu(II)} oxide core.

  20. Spin density waves in dilute CuMn alloys

    SciTech Connect

    Cable, J.W. ); Tsunoda, Y. )

    1992-01-01

    Neutron scattering studies on concentrated CuMn alloys show static spin density waves (SDW) that are incommensurate with the lattice and which become dynamic above the freezing temperature T[sub f] with a dispersion relation that is essentially vertical. We have examined the existence of both the static and the dynamic SDW in dilute CuMn alloys where the Mn atoms may be separated beyond the range of SDW stability. There is no such cutoff range in the Overhauser SDW model where the transition temperature is simply linear with concentration, but a recent calculation by loffe and Feigel'man gives magnetic order that does depend on an interaction range and the density of spins on the lattice. For CuMn alloys, they obtain spin-glass ordering at low Mn concentration with a crossover to short-range helical order near 10% Mn. Our neutron scattering measurements were made on single crystals of CuMn alloys containing 1.4 and 3.0% Mn. Elastic scans along <1[zeta]0> at temperatures well below T[sub f] yield the same type of intensity distribution as that previously observed for the more concentrated alloys and show the existence of static SDW at dilutions down to 1.4% Mn. Inelastic scans in the same Q region for the Cu-3% Mn alloy clearly show the presence of dynamic SDW at temperatures up to T/T[sub f] = 7.5. These results favor the SDW model of Overhauser as the best description of the magnetic order in dilute CuMn alloys.

  1. Spin density waves in dilute CuMn alloys

    SciTech Connect

    Cable, J.W.; Tsunoda, Y.

    1992-12-01

    Neutron scattering studies on concentrated CuMn alloys show static spin density waves (SDW) that are incommensurate with the lattice and which become dynamic above the freezing temperature T{sub f} with a dispersion relation that is essentially vertical. We have examined the existence of both the static and the dynamic SDW in dilute CuMn alloys where the Mn atoms may be separated beyond the range of SDW stability. There is no such cutoff range in the Overhauser SDW model where the transition temperature is simply linear with concentration, but a recent calculation by loffe and Feigel`man gives magnetic order that does depend on an interaction range and the density of spins on the lattice. For CuMn alloys, they obtain spin-glass ordering at low Mn concentration with a crossover to short-range helical order near 10% Mn. Our neutron scattering measurements were made on single crystals of CuMn alloys containing 1.4 and 3.0% Mn. Elastic scans along <1{zeta}0> at temperatures well below T{sub f} yield the same type of intensity distribution as that previously observed for the more concentrated alloys and show the existence of static SDW at dilutions down to 1.4% Mn. Inelastic scans in the same Q region for the Cu-3% Mn alloy clearly show the presence of dynamic SDW at temperatures up to T/T{sub f} = 7.5. These results favor the SDW model of Overhauser as the best description of the magnetic order in dilute CuMn alloys.

  2. 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.

  3. Preparation of W/CuCrZr mono-block test mock-up using vacuum brazing technique

    NASA Astrophysics Data System (ADS)

    Premjit Singh, K.; Khirwadkar, S.; Bhope, Kedar; Patel, Nikunj; Mokaria, Prakash

    2017-04-01

    Development of the joining for W/CuCrZr mono-block PFC test mock-up is an interesting area in Fusion R&D. W/Cu bimetallic material has been prepared using OFHC Copper casting approach on the radial surface of W mono-block tile surface. The W/Cu bimetallic material has been joined with CuCrZr tube (heat sink) material with the vacuum brazing route. Vacuum brazing of W/Cu-CuCrZr has been performed @ 970°C for 10 min using NiCuMn-37 filler material under deep vacuum environment (10-6 mbar). Graphite fixture was used for OFHC Copper casting and vacuum brazing experiments. The joint integrity of W/Cu-CuCrZr mono-block mock-up of W/Cu and Cu-CuCrZr interface has been checked using ultrasonic immersion technique. The result of the experimental work is presented in the paper.

  4. Reversion phenomena of Cu-Cr alloys

    NASA Technical Reports Server (NTRS)

    Nishikawa, S.; Nagata, K.; Kobayashi, S.

    1985-01-01

    Cu-Cr alloys which were given various aging and reversion treatments were investigated in terms of electrical resistivity and hardness. Transmission electron microscopy was one technique employed. Some results obtained are as follows: the increment of electrical resistivity after the reversion at a constant temperature decreases as the aging temperature rises. In a constant aging condition, the increment of electrical resistivity after the reversion increases, and the time required for a maximum reversion becomes shorter as the reversion temperature rises. The reversion phenomena can be repeated, but its amount decreases rapidly by repetition. At first, the amount of reversion increases with aging time and reaches its maximum, and then tends to decrease again. Hardness changes by the reversion are very small, but the hardness tends to soften slightly. Any changes in transmission electron micrographs by the reversion treatment cannot be detected.

  5. Oxalate-based soluble 2D magnets: the series [K(18-crown-6)]3[M(II)3(H2O)4{M(III)(ox)3}3] (M(III) = Cr, Fe; M(II) = Mn, Fe, Ni, Co, Cu; ox = C2O4(2-); 18-crown-6 = C12H24O6).

    PubMed

    Coronado, Eugenio; Galán-Mascarós, José R; Martí-Gastaldo, Carlos; Waerenborgh, João C; Gaczyński, Piotr

    2008-08-04

    The synthesis and magnetic properties of the oxalate-based molecular soluble magnets with general formula [K(18-crown-6)] 3[M (II) 3(H 2O) 4{M (III)(ox) 3} 3] (M (III) = Cr, Fe; M (II) = Mn, Fe, Ni, Co, Cu; ox = C 2O 4 (2-)) are here described. All the reported compounds are isostructural and built up by 2D bimetallic networks formed by alternating M (III) and M (II) ions connected through oxalate anions. Whereas the Cr (III)M (II) derivatives behave as ferromagnets with critical temperatures up to 8 K, the Fe (III)M (II) present ferri- or weak ferromagnetic ordering up to 26 K.

  6. Photoemission of Mn6Cr single-molecule magnets

    NASA Astrophysics Data System (ADS)

    Heinzmann, U.; Merschjohann, F.; Helmstedt, A.; Gryzia, A.; Winter, A.; Steppeler, S.; Müller, N.; Brechling, A.; Sacher, M.; Richthofen, C.-G. Freiherr v.; Glaser, T.; Voss, S.; Fonin, M.; Rüdiger, U.

    2009-11-01

    We present the status of new experimental studies of X-ray absorption spectroscopy, magnetic circular dichroism in photoemission and spin-resolved photoelectron spectroscopy of Mn6Cr single-molecule magnet systems by use of circularly-polarized synchrotron radiation of the electron storage rings in Maxlab Lund, Sweden und BESSY, Berlin, Germany.

  7. Spin density waves in dilute CuMn alloys

    SciTech Connect

    Cable, J.W. ); Tsunoda, Y. )

    1993-05-15

    Neutron scattering studies on concentrated CuMn alloys show static spin density waves (SDW) that are incommensurate with the lattice and which become dynamic above the freezing temperature [ital T][sub [ital f

  8. Structure and growth of Cr on Cu(100)

    NASA Astrophysics Data System (ADS)

    Jandeleit, J.; Gauthier, Y.; Wuttig, M.

    1994-11-01

    The structure, growth and morphology of ultrathin Cr films on Cu(100) were investigated using Auger electron spectroscopy (AES), and low and medium energy electron diffraction (LEED and MEED). From the LEED pattern and the measurements of LEED {I}/{V} curves the structure of the Cr films was determined. By comparison with full dynamical calculations the resulting structure is identified as bcc Cr which grows with the (110) surface parallel to the Cu(100) substrate. The atomic positions within the film closely resemble the positions of bulk Cr. MEED and AES reveal that Cr grows in three-dimensional islands on the Cu(100) surface for the temperature range studied (200-470 K). The structure and growth of the Cr films is compared with the similar epitaxial system of Fe on Cu(100).

  9. Corrosion behavior of Au and Ag modified Cu-Ni-Mn alloys.

    PubMed

    Wright, S R; Cocks, F H; Gettleman, L

    1980-04-01

    The linear electrochemical polarization method was used to provide quantitative in vitro measurements of corrosion rates as a function of exposure time for Cu-Ni-Mn, Cu-Ni-Mn-Au, Cu-Ni-Mn-Ag, and Cu-Ni-Mn-Au-Ag alloys in artificial saliva. Both Au and Ag additives to dental-cast Cu-Ni-Mn alloys lowered the corrosion rate significantly.

  10. Effect of chemical fertilizers on the fractionation of Cu, Cr and Ni in contaminated soil

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Duan, Chang-Qun; Zhu, Yi-Nian; Zhang, Xue-Hong; Wang, Cheng-Xian

    2007-08-01

    Effect of chemical fertilizers (urea, NH4Cl, Ca(NO3)2, KCl and KH2PO4) on the fractionation of Cu, Cr and Ni was studied by a 4-month incubation experiment. Using sequential extraction procedure, it was found that the application of fertilizers could change the distribution of Cu, Cr and Ni in the fractions of soil. Applying urea (CO(NH2)2) significantly decreased the concentrations of Cu, Cr and Ni in water soluble plus exchangeable (WE) fraction, but increased those in Fe-Mn oxides bound (FM) fraction ( p < 0.01). However, application of NH4Cl caused an increase in the WE fraction by 27.7% for Cu, 111.5% for Cr and 20.4% for Ni. The CO(NH2)2 raised the soil pH from 4.51 to 4.96, whereas NH4Cl lowered the pH of soil by 0.44 units. The WE fraction of the three heavy metals was significantly increased, while the FM fraction was significantly decreased by adding KCl ( p < 0.01). Moreover, the supply of KH2PO4 reduced the WE and carbonate bound (CB) fractions of Cu, Cr and Ni in the soil, however, it raised Cu and Ni in the residual (RS) fraction and Cr in the FM fraction. In addition, the mobility index indicated that KCl and NH4Cl increased the mobility of Cu, Cr and Ni in the soil, whereas urea and KH2PO4 decreased the mobility of the three metals in the soil. These results suggest that applying chemical fertilizers does not only provide plant nutrients, but may also change the speciation and mobility of heavy metals in the soil.

  11. Kinetic parameters and structural variations in Cu-Al-Mn and Cu-Al-Mn-Mg shape memory alloys

    NASA Astrophysics Data System (ADS)

    Canbay, Canan Aksu

    2017-02-01

    In this work polycrystalline Cu-Al-Mn and Cu-Al-Mn-Mg SMAs were fabricated by arc melting. The thermal analysis was made to determine the characteristic transformation temperatures of the samples and kinetic parameters. Also the effect of Mg on transformation temperatures and kinetic parameters detected. The structural analysis was made to designate the diffraction planes of martensite phase at room temperature and this was supported by optical measurement observations.

  12. Observations Of A Cast Cu-Cr-Zr Alloy

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    2006-01-01

    The calculated phase diagram and observations of Zeng et al were confirmed. 1) Additional X-ray diffraction peaks for aged sample indicates possibility that additional metastable phases may form; 2) Cu5Zr was observed rather than the Cu9Zr2 proposed for the binary Cu-Zr phase diagram. Despite similarities between Zr and Nb, Cu-Cr-Zr does not appear to be a good candidate alloy system for rocket engine applications.

  13. Mesoporous delafossite CuCrO2 and spinel CuCr2O4: synthesis and catalysis

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Shi, Yifeng; Chi, Miaofang; Park, Jung-Nam; Stucky, Galen D.; McFarland, Eric W.; Gao, Lian

    2013-08-01

    Delafossite CuCrO2 and spinel CuCr2O4 with mesoporous structures have been successfully synthesized using nanocasting methods based on a KIT-6 template. The functional activity of the mesoporous materials was evaluated in applications as heterogeneous catalysts. The activity for photocatalytic hydrogen production of the delafossite structures with different morphologies was characterized and the oxidation state changes associated with photocorrosion of Cu+ investigated using electron energy loss spectroscopy (EELS). Mg2+ doping was found to facilitate the casting of ordered structures for CuCrO2 and improves the photocorrosion resistance of delafossite structures. The mesoporous spinel CuCr2O4 nanostructures were found to be active for low temperature CO oxidation.

  14. Magnetically induced ferroelectricity in Cu2MnSnS4 and Cu2MnSnSe4

    NASA Astrophysics Data System (ADS)

    Fukushima, Tetsuya; Yamauchi, Kunihiko; Picozzi, Silvia

    2010-07-01

    We investigate magnetically induced ferroelectricity in Cu2MnSnS4 by means of Landau theory of phase transitions and of ab initio density-functional theory. As expected from the Landau approach, ab initio calculations show that a nonzero ferroelectric polarization P along the y direction (on the order of a tenth of μC/cm2 ) is induced by the peculiar antiferromagnetic (AFM) configuration of Mn spins occurring in Cu2MnSnS4 . The comparison between P , calculated either via density-functional theory or according to Landau approach, clearly shows that ferroelectricity is mainly driven by Heisenberg-exchange terms and only to a minor extent by relativistic terms. At variance with previous examples of collinear antiferromagnets with magnetically induced ferroelectricity (such as AFM-E HoMnO3 ), the ionic displacements occurring upon magnetic ordering are very small, so that the exchange-striction mechanism (i.e., displacement of ions so as to minimize the magnetic-coupling energy) is not effective here. Rather, the microscopic mechanism at the basis of polarization has mostly an electronic origin. In this framework, we propose the small magnetic moment at Cu sites induced by neighboring Mn magnetic moments to play a relevant role in inducing P . Finally, we investigate the effect of the anion by comparing Cu2MnSnSe4 and Cu2MnSnS4 : Se4p states, more delocalized compared to S3p states, are able to better mediate the Mn-Mn interaction, in turn leading to a higher ferroelectric polarization in the Se-based compound.

  15. Magnetoelasticity in ACr2O4 spinel oxides (A= Mn, Fe, Co, Ni, and Cu)

    NASA Astrophysics Data System (ADS)

    Kocsis, V.; Bordács, S.; Varjas, D.; Penc, K.; Abouelsayed, A.; Kuntscher, C. A.; Ohgushi, K.; Tokura, Y.; Kézsmárki, I.

    2013-02-01

    Dynamical properties of the lattice structure were studied by optical spectroscopy in ACr2O4 chromium spinel oxide magnetic semiconductors over a broad temperature region of T=10-335 K. The systematic change of the A-site ions (A= Mn, Fe, Co, Ni and Cu) showed that the occupancy of 3d orbitals on the A site has strong impact on the lattice dynamics. For compounds with orbital degeneracy (FeCr2O4, NiCr2O4, and CuCr2O4), clear splitting of infrared-active phonon modes and/or activation of silent vibrational modes have been observed upon the Jahn-Teller transition and at the onset of the subsequent long-range magnetic order. Although MnCr2O4 and CoCr2O4 show multiferroic and magnetoelectric character, no considerable magnetoelasticity was found in spinel compounds without orbital degeneracy as they closely preserve the high-temperature cubic spinel structure even in their magnetic ground state. Aside from lattice vibrations, intra-atomic 3d-3d transitions of the A2+ ions were also investigated to determine the crystal field and Racah parameters and the strength of the spin-orbit coupling.

  16. Hidden transition in multiferroic and magnetodielectric CuCrO2 evidenced by ac-susceptibility

    NASA Astrophysics Data System (ADS)

    Shukla, Kaushak K.; Pal, Arkadeb; Singh, Abhishek; Singh, Rahul; Saha, J.; Sinha, A. K.; Ghosh, A. K.; Patnaik, S.; Awasthi, A. M.; Chatterjee, Sandip

    2017-04-01

    Ferroelectric polarization, magnetic-field dependence of the dielectric constant and ac and dc magnetizations of frustrated CuCrO2 have been measured. A new spin freezing transition below 32 K is observed which is thermally driven. The nature of the spin freezing is to be a single-ion process. Dilution by the replacements of Cr ions by magnetic Mn ions showed suppression of the spin freezing transition suggesting it to be fundamentally a single-ion freezing process. The observed freezing, which is seemingly associated to geometrical spin frustration, represents a novel form of magnetic glassy behavior.

  17. The electronic and magnetic properties of wurtzite Mn:CdS, Cr:CdS Mn:Cr:CdS: first principles calculations

    NASA Astrophysics Data System (ADS)

    Nabi, Azeem; Akhtar, Zarmeena; Iqbal, Tahir; Ali, Atif; Arshad Javid, Muhammad

    2017-07-01

    In this article, density functional theory (DFT) based on generalized gradient approximation (GGA) and GGA+U, U is Hubbard term, is used to study the electronic properties of CdS doped with different dopants (Cr, Mn). The calculations are carried out for Mn-doped CdS, Cr-doped CdS, and co-doping of Mn/Cr in CdS simultaneously. It is found that hopping of electrons is possible with Cr:CdS and Mn:Cr:CdS while Mn:CdS does not allow the hopping of electrons. Moreover, double exchange interactions are observed in Cr:CdS and d-d super-exchange interactions are observed in Mn:CdS. Now the problem becomes interesting when one magnetic ion (Cr) supporting double exchange interactions and another ion (Mn) supporting d-d super-exchange interactions are doped simultaneously in the same system (CdS). The co-doped CdS is more stable even at high Curie temperature due to p-d double exchange interactions and d-d super exchange interactions. Furthermore, the Cr-3d and Mn-3d states present in-between the band gap are responsible for inner shell transitions and hence for optical properties. Therefore, the co-doped system is taken into account to enhance its applications in the field of spintronic and magneto-optical devices.

  18. Mn-Cr isotopic systematics of Chainpur chondrules and bulk ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Nyquist, L.; Lindstrom, D.; Wiesmann, H.; Bansal, B.; Shih, C.-Y.; Mittlefehldt, D.; Martinez, R.; Wentworth, S.

    1994-01-01

    We report on ongoing study of the Mn-Cr systematics of individual Chainpur (LL3.4) chondrules and compare the results to those for bulk ordinary chondrites. Twenty-eight chondrules were surveyed for abundances of Mn, Cr, Na, Fe, Sc, Hf, Ir, and Zn by INAA. Twelve were chosen for SEM/EDX and high-precision Cr-isotopic studies on the basis of LL-chondrite-normalized Mn(LL), Sc(LL), (Mn/Fe)(LL), and (Sc/Fe)(LL) as well as their Mn/Cr ratios. Classification into textural types follows from SEM/EDX examination of interior surfaces.

  19. Structure and Electrical Properties of Mn-Cu-O Spinels

    NASA Astrophysics Data System (ADS)

    Bobruk, M.; Durczak, K.; Dąbek, J.; Brylewski, T.

    2017-03-01

    The study presents the results of structural and electrical conductivity investigations of a Cu1.3Mn1.7O4 spinel obtained using EDTA gel processes. An amorphous gel was synthesized and calcinated for 5 h in air at temperatures of 673, 773, 873, and 973 K. When calcinating the gel at temperatures below 973 K, the obtained powders consisted of two phases—the regular Cu1.5Mn1.5O4 spinel and manganese(III) oxide. At 973 K, Mn2O3 was no longer observed, but a new Mn3O4 phase appeared in addition to the Cu1.5Mn1.5O4 spinel. Green bodies prepared from these powders were sintered for 2 h in air at 1393 K. The obtained sinters had a porosity of around 12% and were composed predominantly of the spinel phase, with minor amounts of Mn3O4 and, in the case of three of four sinters—CuO. Electrical conductivity measurements were taken over the temperature range of 300-1073 K. A change in the character of conductivity of the studied sinters was observed in the range of 400-430 K, and it was associated with an increase in activation energy from 0.20 to 0.56 eV. The electrical conductivity of the studied sinters ranged from 74.8 to 88.4 S cm-1, which makes the Cu1.3Mn1.7O4 material suitable for application as a protective-conducting coating in IT-SOFC ferritic stainless steel interconnects.

  20. Structure and Electrical Properties of Mn-Cu-O Spinels

    NASA Astrophysics Data System (ADS)

    Bobruk, M.; Durczak, K.; Dąbek, J.; Brylewski, T.

    2017-04-01

    The study presents the results of structural and electrical conductivity investigations of a Cu1.3Mn1.7O4 spinel obtained using EDTA gel processes. An amorphous gel was synthesized and calcinated for 5 h in air at temperatures of 673, 773, 873, and 973 K. When calcinating the gel at temperatures below 973 K, the obtained powders consisted of two phases—the regular Cu1.5Mn1.5O4 spinel and manganese(III) oxide. At 973 K, Mn2O3 was no longer observed, but a new Mn3O4 phase appeared in addition to the Cu1.5Mn1.5O4 spinel. Green bodies prepared from these powders were sintered for 2 h in air at 1393 K. The obtained sinters had a porosity of around 12% and were composed predominantly of the spinel phase, with minor amounts of Mn3O4 and, in the case of three of four sinters—CuO. Electrical conductivity measurements were taken over the temperature range of 300-1073 K. A change in the character of conductivity of the studied sinters was observed in the range of 400-430 K, and it was associated with an increase in activation energy from 0.20 to 0.56 eV. The electrical conductivity of the studied sinters ranged from 74.8 to 88.4 S cm-1, which makes the Cu1.3Mn1.7O4 material suitable for application as a protective-conducting coating in IT-SOFC ferritic stainless steel interconnects.

  1. Defect-induced magnetic structure of CuMnSb

    NASA Astrophysics Data System (ADS)

    Máca, F.; Kudrnovský, J.; Drchal, V.; Turek, I.; Stelmakhovych, O.; Beran, P.; Llobet, A.; Marti, X.

    2016-09-01

    The observed ground state for the CuMnSb alloy is the antiferromagnetic (111) phase as confirmed by neutron diffraction experiments. Ab initio total energy calculations for ideal, defect-free CuMnSb contradict this result and indicate that other magnetic structures can have their total energies lower. It is known that Heusler alloys usually contain various defects depending on the sample preparation. We have therefore investigated magnetic phases of CuMnSb assuming the most common defects which exist in real experimental conditions. The full-potential supercell approach and a Heisenberg model approach using the coherent potential approximation are adopted. The results of the total energy supercell calculations indicate that defects that bring Mn atoms close together promote the antiferromagnetic (111) structure already for a low critical defect concentrations (≈3 %). A detailed study of exchange interactions between Mn moments further supports the above stabilization mechanism. Finally, the stability of the antiferromagnetic (111) order is enhanced by inclusion of electron correlations in narrow Mn bands. The present refinement structure analysis of the neutron scattering experiment supports theoretical conclusions.

  2. Antiferromagnetic structure in tetragonal CuMnAs thin films

    PubMed Central

    Wadley, P.; Hills, V.; Shahedkhah, M. R.; Edmonds, K. W.; Campion, R. P.; Novák, V.; Ouladdiaf, B.; Khalyavin, D.; Langridge, S.; Saidl, V.; Nemec, P.; Rushforth, A. W.; Gallagher, B. L.; Dhesi, S. S.; Maccherozzi, F.; Železný, J.; Jungwirth, T.

    2015-01-01

    Tetragonal CuMnAs is an antiferromagnetic material with favourable properties for applications in spintronics. Using a combination of neutron diffraction and x-ray magnetic linear dichroism, we determine the spin axis and magnetic structure in tetragonal CuMnAs, and reveal the presence of an interfacial uniaxial magnetic anisotropy. From the temperature-dependence of the neutron diffraction intensities, the Néel temperature is shown to be (480 ± 5) K. Ab initio calculations indicate a weak anisotropy in the (ab) plane for bulk crystals, with a large anisotropy energy barrier between in-plane and perpendicular-to-plane directions. PMID:26602978

  3. Antiferromagnetic structure in tetragonal CuMnAs thin films.

    PubMed

    Wadley, P; Hills, V; Shahedkhah, M R; Edmonds, K W; Campion, R P; Novák, V; Ouladdiaf, B; Khalyavin, D; Langridge, S; Saidl, V; Nemec, P; Rushforth, A W; Gallagher, B L; Dhesi, S S; Maccherozzi, F; Železný, J; Jungwirth, T

    2015-11-25

    Tetragonal CuMnAs is an antiferromagnetic material with favourable properties for applications in spintronics. Using a combination of neutron diffraction and x-ray magnetic linear dichroism, we determine the spin axis and magnetic structure in tetragonal CuMnAs, and reveal the presence of an interfacial uniaxial magnetic anisotropy. From the temperature-dependence of the neutron diffraction intensities, the Néel temperature is shown to be (480 ± 5) K. Ab initio calculations indicate a weak anisotropy in the (ab) plane for bulk crystals, with a large anisotropy energy barrier between in-plane and perpendicular-to-plane directions.

  4. First-principles spin-transfer torque in CuMnAs |GaP |CuMnAs junctions

    NASA Astrophysics Data System (ADS)

    Stamenova, Maria; Mohebbi, Razie; Seyed-Yazdi, Jamileh; Rungger, Ivan; Sanvito, Stefano

    2017-02-01

    We demonstrate that an all-antiferromagnetic tunnel junction with current perpendicular to the plane geometry can be used as an efficient spintronic device with potential high-frequency operation. By using state-of-the-art density functional theory combined with quantum transport, we show that the Néel vector of the electrodes can be manipulated by spin-transfer torque. This is staggered over the two different magnetic sublattices and can generate dynamics and switching. At the same time the different magnetization states of the junction can be read by standard tunneling magnetoresistance. Calculations are performed for CuMnAs |GaP |CuMnAs junctions with different surface terminations between the antiferromagnetic CuMnAs electrodes and the insulating GaP spacer. We find that the torque remains staggered regardless of the termination, while the magnetoresistance depends on the microscopic details of the interface.

  5. 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.

  6. 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).

  7. Mn-Cr ages of Fe-rich olivine in two Rumuruti (R) chondrites

    NASA Astrophysics Data System (ADS)

    Sugiura, N.; Miyazaki, A.

    2006-05-01

    Mn-Cr systematics in olivine of two Rumuruti (R) chondrites was investigated. Mn/52Cr ratios up to 1800 and 1300, and δ53Cr of up to 25° and 7° were observed for NWA 753 and Sahara 99531, respectively. All data points of NWA 753 show a linear correlation between δ53Cr values and Mn/52Cr ratios on the isochron diagram. The inferred initial 53Mn/55Mn ratio for NWA 753 is (1.84 ± 0.42(2σ)) × 10-6. In the case of Sahara 99531, a positive correlation interpreted as an isochron for 53Mn/55Mn = 2.75 ± 1.55 (2σ) × 10-6 was obtained for only one chondrule. Data from other chondrules in Sahara 99531 give an upper limit of 53Mn/55Mn = 0.49 × 10-6. The Mn-Cr ages of NWA 753 and a chondrule in Sahara 99531 are slightly older than that of the angrite LEW 86010 (Lugmair and Shukolyukov, 1998). Other chondrules in Sahara 99531 are at least 5 Ma younger than the LEW 86010. The Mn-Cr ages of olivine in R chondrites correspond to the time when olivine became a closed system either during slow cooling from the peak metamorphic temperature or during rapid cooling by impact excavation. In either case the olivine closure occurred earlier than the final assembly of the brecciated chondrites.

  8. Preparation and characterization of Mn and (Mn, Cu) co-doped ZnO nanostructures.

    PubMed

    Wang, H B; Wang, H; Zhang, C; Yang, F J; Duan, J X; Yang, C P; Gu, H S; Zhou, M J; Li, Q; Jiang, Y

    2009-05-01

    We report on the ferromagnetic characteristics of Zn(1-x)Mn(x)O nanorods synthesized by a seed-mediated solution method. The as-doped ZnO nanorods had a length about 200 nm and a diameter ranging from 20 to 30 nm. Magnetic property measurements revealed that the Zn(1-x)Mn(x)O nanorods exhibited weak ferromagnetism at 305 K. Similar solution method were also employed to fabricate the (Mn, Cu) co-doped nanostructures. The presence of Cu2+ was found to change the nanorod morphology (in the case of pure ZnO) to nanoparticle. On the other hand, not only the hysteresis curve saturated at lower magnetic field, but also the saturation magnetization was increased with the Cu doping. Transmission electron microscopy, X-ray photoelectron spectroscopy and Photoluminescence analysis suggested that the room temperature (RT) ferromagnetism could be originated from the Mn2+ doped into the ZnO lattice, and additional carriers due to the Cu co-doping may enhance the room temperature ferromagnetism in the Mn:ZnO system.

  9. Glassy dynamics in CuMn thin-film multilayers

    NASA Astrophysics Data System (ADS)

    Zhai, Qiang; Harrison, David C.; Tennant, Daniel; Dalhberg, E. Dan; Kenning, Gregory G.; Orbach, Raymond L.

    2017-02-01

    Thin-film multilayered spin-glass CuMn/Cu structures display glassy dynamics. The freezing temperature Tf was measured for 40 layers of CuMn films of thickness L =4.5 ,9.0 , and 20.0 nm, sandwiched between nonmagnetic Cu layers of thickness ≈60 nm. The Kenning effect, Tf∝lnL , is shown to follow from power-law dynamics where the correlation length grows from nucleation as ξ (t ,T ) =c1a0(t/τ0) c2(T /Tg) , leading to [(Tf/Tg) c2ln(tco/τ0) ] +lnc1=ln(L /a0) . Here, Tg is the bulk spin-glass temperature, c1 and c2 are constants determined from the spin-glass dynamics, tco is the time for the correlation length to grow to the film thickness, τ0 is a characteristic exchange time ≈ℏ /kBTg , and a0 is the average Mn-Mn separation. For t ≥tco , the magnetization dynamics are simple activated, with a single activation energy Δmax(L ) /kBTg=(1 /c2) [ln(L /a0) -lnc1] that does not change with time. Values for all these parameters are found for the three values of L explored in these measurements. We find experimentally Δmax(L ) /kB =907 , 1246, and 1650 K, respectively, for the three CuMn thin-film multilayer thicknesses, consistent with power-law dynamics. We perform a similar analysis based on the activated dynamics of the droplet model and find a much larger spread for Δmax(L ) than found experimentally.

  10. Structural Investigations of Nanocrystalline Cu-Cr-Mo Alloy Prepared by High-Energy Ball Milling

    NASA Astrophysics Data System (ADS)

    Kumar, Avanish; Pradhan, Sunil Kumar; Jayasankar, Kalidoss; Debata, Mayadhar; Sharma, Rajendra Kumar; Mandal, Animesh

    2017-02-01

    Cu-Cr-Mo alloy could be a suitable candidate material for collector electrodes in high-power microwave tube devices. An attempt has been made to synthesize ternary Cu-Cr-Mo alloys by mechanical alloying of elemental Cu, Cr, and Mo powders, to extend the solid solubility of Cr and Mo in Cu, using a commercial planetary ball mill. For the first ternary alloy, a mixture of 80 wt.% Cu, 10 wt.% Cr, and 10 wt.% Mo was mechanically milled for 50 h. For the second ternary alloy, a mixture of 50 wt.% Cr and 50 wt.% Mo was mechanically milled for 50 h to obtain nanocrystalline Cr(Mo) alloy, which was later added to Cu powder and milled for 40 h to obtain Cu-20 wt.%Cr(Mo) alloy. Both nanocrystalline Cu-Cr-Mo ternary alloys exhibited crystallite size below 20 nm. It was concluded that, with addition of nanocrystalline Cr(Mo) to Cu, it was possible to extend the solid solubility of Cr and Mo in Cu, which otherwise was not possible by mechanical alloying of elemental powders. The resulting microstructure of the Cu-20 wt.%Cr(Mo) alloy comprised a homogeneous distribution of fine and hard (Cr, Mo) particles in a copper matrix. Furthermore, Cu-20 wt.%Cr(Mo) alloy showed better densification compared with Cu-10 wt.%Cr-10 wt.%Mo alloy.

  11. Electrochemical Behavior of Ion-Plated TiN and Cu-Cr Coatings

    DTIC Science & Technology

    1993-09-01

    results show that Cu-Cr alloys containing up to about 25 atomic percent CR consist of single phase FCC structure . The alloys containing more than 60...19), curve 4 for CuCr(40), and curve 5 for Cu-Cr(85)]. Note that Curves 1, 2, and 3 are from FCC structure , curve 4 from dual-phase structure, and

  12. 53Mn-53Cr Chronometry of Cb Chondrite: Evidence for Uniform Distribution of 53Mn in the Early Solar System

    NASA Astrophysics Data System (ADS)

    Yamashita, Katsuyuki; Maruyama, Seiji; Yamakawa, Akane; Nakamura, Eizo

    2010-11-01

    High-precision Cr isotope ratios for chondrules and metal grain separated from CB chondrite Gujba were determined. The ɛ54Cr values (ɛiCr = [(iCr/52Cr)sample/(iCr/52Cr)standard - 1] × 104) for all samples were identical within the analytical uncertainty, with a mean value of +1.29 ± 0.02. Uniform ɛ54Cr signatures of both chondrules and metal grains imply that the Cr isotope systematics of the meteorite was once completely equilibrated. The ɛ53Cr values of the chondrules and metal grain, on the other hand, display a strong correlation with the 55Mn/52Cr ratio. The 53Mn/55Mn calculated from the slope of the isochron is (3.18 ± 0.52) × 10-6. This corresponds to absolute ages of 4563.7 ± 1.2 Ma and 4563.5 ± 1.1 Ma using angrites D'Orbigny and LEW 86010, respectively, as time anchors. These ages are consistent with the ages obtained using other short- and long-lived radio nuclides, supporting the uniform distribution of 53Mn in the early solar nebula.

  13. Calorimetric Investigation of Thermal Stability of 304H Cu (Fe-17.7Cr-9.3Ni-2.95Cu-0.91Mn-0.58Nb-0.24Si-0.1C-0.12N-Wt Pct) Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Tripathy, Haraprasanna; Subramanian, Raju; Hajra, Raj Narayan; Rai, Arun Kumar; Rengachari, Mythili; Saibaba, Saroja; Jayakumar, Tammana

    2016-12-01

    The sequence of phase instabilities that take place in a Fe-17.7Cr-9.3Ni-0.58Nb-2.95Cu-0.12N (wt pct) austenitic stainless steel (304H Cu grade) as a function of temperature has been investigated using dynamic calorimetry. The results obtained from this investigation are supplemented by Thermocalc-based equilibrium and Scheil-Gulliver nonequilibrium solidification simulation. The following phase transformation sequence is found upon slow cooling from liquid: L → L + γ → L + γ + MX → γ + MX + δ → γ +MX + M23C6 → γ + MX + M23C6 + Cu. Under slow cooling, the solidification follows austenite + ferrite (AF) mode, which is in accordance with Thermocalc prediction and Scheil-Gulliver simulation. However, higher cooling rates result in skeletal δ-ferrite formation, due to increased segregation tendency of Nb and Cr to segregate to interdendritic liquid. The solidification mode is found to depend on combined Nb + Cu content. Experimental estimates of enthalpy change associated with melting and secondary phase precipitation are also obtained. In addition a semi-quantitative study on the dissolution kinetics of M23C6 type carbides has also been investigated. The standard solution treatment at 1413 K (1140 °C) is found to be adequate to dissolve both Cu and M23C6 into γ-austenite; but the complete dissolution of MX type carbonitrides occurs near the melting region.

  14. Effect of Age-Hardening Treatment on Microstructure and Sliding Wear-Resistance Performance of WC/Cu-Ni-Mn Composite Coatings

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Yang, Shuai; Liu, Kai; Gui, Chibin; Xia, Weisheng

    2017-06-01

    The Cu-Ni-Mn alloy-based hardfacing coatings reinforced by WC particles (WC/Cu-Ni-Mn) were deposited on a steel substrate by a manual oxy-acetylene weld hardfacing method. A sound interfacial junction was formed between the WC particles and the Cu-Ni-Mn alloy metal matrix binder even after the age-hardening treatment. The friction and wear behavior of the hardfacing coatings was investigated. With the introduction of WC particles, the sliding wear resistance of the WC/Cu-Ni-Mn hardfacing coatings was sharply improved: more than 200 times better than that of the age-hardening-treated Cu-Ni-Mn alloy coating. The sliding wear resistances of the as-deposited and the age-hardening-treated WC/Cu-Ni-Mn hardfacing coatings were 1.83 and 2.26 times higher than that of the commercial Fe-Cr-C hardfacing coating, which is mainly ascribed to the higher volume fraction of carbide reinforcement. Owing to the precipitation of the NiMn secondary phase in the Cu-Ni-Mn metal matrix, the age-hardening-treated coating had better wear resistance than that of the as-deposited coating. The main sliding wear mechanisms of the age-hardening-treated coatings are adhesion and abrasion.

  15. The Mn-Cr Isotope Systematics in the Ureilites Kenna and LEW 85440

    NASA Astrophysics Data System (ADS)

    Shukolyukov, A.; Lugmair, G. W.

    2006-03-01

    The ureilite parent body is characterized by an anomalous 54Cr/52Cr ratio that is deficient in 54Cr. Thus, its precursor material was different from the known carbonaceous chondrite classes. The Mn-Cr system in Kenna and LEW85440 closed late.

  16. Microstructures and mechanical properties of sputtered Cu/Cr multilayers

    SciTech Connect

    Misra, A.; Kung, H.; Mitchell, T.E.; Jervis, T.R.; Nastasi, M.

    1998-03-01

    The microstructures and mechanical properties of Cu/Cr multilayers prepared by sputtering onto {l_brace}100{r_brace} Si substrates at room temperature are presented. The films exhibit columnar grain microstructures with nanoscale grain sizes. The interfaces are planar and abrupt with no intermixing, as expected from the phase diagram. The multilayers tend to adopt a Kurdjumov-Sachs (KS) orientation relationship: {l_brace}110{r_brace}Cr // {l_brace}111{r_brace}Cu, <111>Cr // <110>Cu. The hardness of the multilayered structures, as measured by nanoindentation, increase with decreasing layer thickness for layer thicknesses ranging from 200 nm to 50 nm, whereas for lower thicknesses the hardness of the multilayers is independent of the layer thickness. Dislocation-based models are used to interpret the variation of hardness with layer periodicity. The possible effects of factors such as grain size within the layers, density and composition of films and residual stress in the multilayers are highlighted. Comparisons are made to the mechanical properties of sputtered polycrystalline Cu/Nb multilayers which, like Cu/Cr, exhibit sharp fcc/bcc interfaces with no intermixing and a KS orientation relationship, but have a small shear modulus mismatch.

  17. Mn-Cr isotope systematics of the D'Orbigny angrite

    NASA Astrophysics Data System (ADS)

    Glavin, D. P.; Kubny, A.; Jagoutz, E.; Lugmair, G. W.

    2004-05-01

    We have conducted a detailed study of the Mn-Cr systematics of the angrite D'Orbigny. Here, we report Cr isotopic abundances and Mn/Cr ratios in olivine, pyroxene, glass, chromite, and bulk rock samples from D'Orbigny. 53Cr excesses in these samples correlate well with their respective Mn/Cr ratios and define an isochron with a slope that corresponds to an initial 53Mn/55Mn ratio = (3.24 ± 0.04) - 10-6 and initial 53Cr/52Cr ratio of e(53) = 0.30 ± 0.03 at the time of isotopic closure. The 53Mn/55Mn ratio of the D'Orbigny bulk rock is more than two-fold the 53Mn/55Mn ratio of the angrites Lewis Cliff 86010 (LEW) and Angra dos Reis (ADOR) and implies an older Mn-Cr age of 4562.9 ± 0.6 Ma for D'Orbigny relative to a Pb-Pb age of 4557.8 ± 0.5 Ma for LEW and ADOR. One of the most unusual aspects of D'Orbigny is the presence of glass, a phase that has not been identified in any of the other angrites. The Mn-Cr data for glass and a pyroxene fraction found in druses indicate that they formed contemporaneously with the main phases of the meteorite. Since the Mn-Cr age of D'Orbigny is ~5 Ma years older than the angrites LEW and ADOR, D'Orbigny likely represents an earlier stage in the evolution of the angrite parent body.

  18. Structure and growth of Mn on Cu(100)

    NASA Astrophysics Data System (ADS)

    Flores, T.; Hansen, M.; Wuttig, M.

    1992-12-01

    The structure and growth of manganese on Cu(100) was studied using Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and medium energy electron diffraction (MEED). Depending upon the film thickness and the sample temperature during deposition a variety of superstructures is observed. At growth temperatures below 270 K the first Mn layer wets the Cu substrate and grows in a c(8 × 2) structure with hexagonal atomic arrangement. Above 1 ML Mn, the films become increasingly more disordered and rearrange into a c(12 × 8) structure. Manganese is incorporated into the surface above 270 K. This leads to the formation of two ordered surface alloys at growth temperatures above 270 K: a c(2 × 2) structure around 0.5 ML Mn and a p2mg(4 × 2) structure above 1 ML Mn. Irreversible phase transitions upon annealing have been studied for the low temperature structures. This confirms that incorporation of Mn is the essential step to form the ordered surface alloys.

  19. Mechanical properties of Cr-Cu coatings produced by electroplating

    NASA Astrophysics Data System (ADS)

    Riyadi, Tri Widodo Besar; Sarjito, Masyrukan, Riswan, Ricky Ary

    2017-06-01

    Hard chromium coatings has long been considered as the most used electrodeposited coating in several industrial applications such as in petrochemistry, oil and gas industries. When hard coatings used in fastener components, the sliding contact during fastening operation produces high tensile stresses on the surface which can generate microcracks. For component used in high oxidation and corrosion environment, deep cracks cannot be tolerated. In this work, a laminated structure of Cr-Cu coating was prepared using electroplating on carbon steel substrates. Two baths of chrome and copper electrolyte solutions were prepared to deposit Cr as the first layer and Cu as the second layer. The effect of current voltages on the thickness, hardness and specific wear rate of the Cu layer was investigated. The results show that an increase of the current voltages increased the thickness and hardness of the Cu layer, but reduced the specific wear rate. This study showed that the use of Cu can be a potential candidate as a laminated structure Cr-Cu for chromium plating.

  20. Novel CuCr2O4 embedded CuO nanocomposites for efficient photodegradation of organic dyes

    NASA Astrophysics Data System (ADS)

    Mageshwari, K.; Sathyamoorthy, R.; Lee, Jeong Yong; Park, Jinsub

    2015-10-01

    Novel photocatalyst based on CuO-CuCr2O4 nanocomposites was synthesized for different Cr3+ concentration by reflux condensation method, and their photocatalytic activity was evaluated by monitoring the photodegradation of methyl orange (MO) and methylene blue dyes (MB) under UV light irradiation. Phase evolution by X-ray diffraction showed monoclinic CuO and tetragonal CuCr2O4 as the components of the prepared nanocomposites. Morphological analysis by scanning electron microscope and transmission electron microscope revealed that the incorporation of Cr3+ in CuO lattice alters the morphology of CuO from microsphere to cluster shape. Photoluminescence spectra of CuO-CuCr2O4 nanocomposites exhibited reduced PL emissions compared to pure CuO, indicating the low recombination rate of photogenerated electrons and holes. As expected, the CuCr2O4 loaded CuO showed enhanced photocatalytic activity for MO and MB dyes, and the kinetic studies suggest that the degradation follows pseudo-first-order kinetics. The enhanced photocatalytic activity of CuO-CuCr2O4 nanocomposites can be attributed to the presence of CuCr2O4 as an electron acceptor, which improves the effective charge separation in CuO.

  1. Manufacturing and High Heat Flux Testing of Brazed Flat-Type W/CuCrZr Plasma Facing Components

    NASA Astrophysics Data System (ADS)

    Lian, Youyun; Liu, Xiang; Feng, Fan; Chen, Lei; Cheng, Zhengkui; Wang, Jin; Chen, Jiming

    2016-02-01

    Water-cooled flat-type W/CuCrZr plasma facing components with an interlayer of oxygen-free copper (OFC) have been developed by using vacuum brazing route. The OFC layer for the accommodation of thermal stresses was cast onto the surface of W at a temperature range of 1150 °C-1200 °C in a vacuum furnace. The W/OFC cast tiles were vacuum brazed to a CuCrZr heat sink at 940 °C using the silver-free filler material CuMnSiCr. The microstructure, bonding strength, and high heat flux properties of the brazed W/CuCrZr joint samples were investigated. The W/Cu joint exhibits an average tensile strength of 134 MPa, which is about the same strength as pure annealed copper. High heat flux tests were performed in the electron beam facility EMS-60. Experimental results indicated that the brazed W/CuCrZr mock-up experienced screening tests of up to 15 MW/m2 and cyclic tests of 9 MW/m2 for 1000 cycles without visible damage. supported by National Natural Science Foundation of China (No. 11205049) and the National Magnetic Confinement Fusion Science Program of China (No. 2011GB110004)

  2. Role of Cu-Ion Doping in Cu-α-MnO2 Nanowire Electrocatalysts for the Oxygen Reduction Reaction

    DOE PAGES

    Davis, Danae J.; Lambert, Timothy N.; Vigil, Julian A.; ...

    2014-07-09

    The role of Cu-ion doping in α-MnO2 electrocatalysts for the oxygen reduction reaction in alkaline electrolyte was investigated. Copper doped α-MnO2 nanowires (Cu-α-MnO2) were prepared with varying amounts of Cu2+ using a solvothermal method. The electrocatalytic dataindicates that Cu-α-MnO2 nanowires have higher terminal current densities, enhanced kinetic rate constants, and improved charge transfer resistances that trend with Cu-content, exceeding values attained by α-MnO2 alone. The observed improvement in catalytic behavior correlates with an increase in Mn3+ content for the Cu-α-MnO2 nanowires. The Mn3+/Mn4+ couple is themediator for the rate-limiting redox driven O2-/OH- exchange. It is proposed that O2 adsorbs viaanmore » axial site (the eg orbital on the Mn3+ d4 ion) at the surface, or at edge defects, of the nanowireand that the increase in covalent nature of the nanowire with Cu-ion doping leads to stabilization of O2 adsorbates and faster rates of reduction. This work is applicable to other manganese oxide electrocatalysts and shows for the first time there is a correlation for manganese oxides between electrocatalytic activity for the ORR in alkaline electrolyte and an increase in Mn3+ character of the oxide.« less

  3. Mn-Cr intersite independent magnetic behavior and electronic structures of LaMn3Cr4O12: Study from first-principles

    NASA Astrophysics Data System (ADS)

    Lv, Shuhui; Li, Hongping; Liu, Xiaojuan; Meng, Jian

    2011-07-01

    The magnetic and electronic structures of LaMn3Cr4O12 are investigated using the full-potential linearized augmented plane wave method within both the generalized gradient approximation (GGA) and GGA + U (electronic correlation) methods. The calculated results indicate that LaMn3Cr4O12 is an antiferromagnetic insulator. The magnetic ordering is demonstrated to be G-type within both Mn-site and Cr-site spins. However, there is no obvious magnetic coupling between Mn-site and Cr-site sublattices, which is verified by the separate distribution of their corresponding partial density of states. Moreover, the magnetic coupling constants of JCr-Cr and JMn-Mn are predicted to be - 5.0 (- 2.8) and - 0.83 (- 0.63) meV within GGA (GGA + U), respectively, consistent with the experimentally observed two independent Néel temperatures (TN1 and TN2). The calculated densities of states reveal the experimentally reported charge formula of LaMn3+3Cr3+4O12.

  4. Thermomechanical Processing and Roll Bonding of Tri-Layered Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn Composite

    NASA Astrophysics Data System (ADS)

    Kim, Hobyung; Kang, Gyeong Tae; Hong, Sun Ig

    2016-05-01

    Tri-layered Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn composite was processed by roll bonding and the effect of thermomechanical processing on the mechanical performance and electrical conductivity was studied. Roll-bonded composite exhibited the brief work hardening and subsequent rapid work softening because of the high stored deformation energy, leading to failure at the plastic strain of 8 to 10 pct. The mechanical instability of as-roll-bonded composites was abated by heat treatment (HT) at 723 K (450 °C) and the extended work hardening with enhanced ductility compared to that of the as-roll-bonded composites was observed after HT. The strength and electrical conductivity of clad composite is dependent on the precipitation strengthening of Cu-Cr and recovery softening of Cu-Ni-Zn during post-roll-bonding HT. The increase of roll-bonding temperature enhances the precipitation kinetics and it takes shorter time to reach maximum hardness in Cu-Cr layer during post-roll-bonding HT. The toughness of as-roll-bonded Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn clad composite at 773 K (500 °C) [42 MJ/mm3] is greater than those at 723 K (450 °C) [24 MJ/mm3] and 823 K (550 °C) [38 MJ/mm3]. The maximum toughness [100 MJ/mm3] with the electrical conductivity of 68 pct IACS was obtained in the Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn clad composite roll-bonded at 773 K (500 °C) and subsequently heat-treated at 723 K (450 °C).

  5. Exchange anisotropy in NiFe layers coupled with multilayered MnFe/MnFeCr (abstract)

    NASA Astrophysics Data System (ADS)

    Kung, Kenneth T.-Y.; Campbell, Richard T.

    1991-11-01

    The exchange anisotropy in a ferromagnetic NiFe layer coupled with an antiferromagnetic MnFe layer can be used to stabilize the single domain state of a magnetoresistive sensor,1 but this technology may be limited by the high corrosion sensitivity of MnFe. It is possible to improve the corrosion resistance of MnFe through impurity doping, e.g., MnFeCr with Cr concentrations of 3-12 at. %,2 but this technique will at the same time degrade the exchange anisotropy. In this work, we have investigated the exchange anisotropy in NiFe layers coupled with multilayered MnFe/MnFeCr. The samples had a configuration of glass substrates, followed by a NiFe (300 Å) layer, followed by a MnFe(x Å)/MnFeCr(y Å) multilayer, where the antiferromagnetic multilayer had either MnFe or MnFeCr interfacing with the NiFe and had a fixed total thickness of 240 Å. They were prepared by rf diode sputtering and, after a Ta (200 Å) protective layer deposition, were thermally cycled to a maximum temperature of 250 °C. The results can be summarized as follows: (1) The anisotropy energy, EUA, near the room temperature ranged from 0.03 to 0.10 erg/cm2; it was determined mostly by the antiferromagnetic layer (MnFe or MnFeCr) at the NiFe interface and was essentially independent of the rest of antiferromagnetic structure. (2) The critical temperature, TC, range from 90 to 160 °C; it was determined mostly by the relative amounts of MnFe and MnFeCr in the entire antiferromagnetic structure and not just at the NiFe interface. These results implied that, while one could improve the anisotropy energy at lower temperatures simply by improving the antiferromagnetic layer near the NiFe interface, to improve the anisotropy energy at higher temperatures one must improve the entire antiferromagnetic layer.

  6. Effect of MnCuFe2O4 content on magnetic and dielectric properties of poly (O-Phenylenediamine)/MnCuFe2O4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Kannapiran, Nagarajan; Muthusamy, Athianna; Chitra, Palanisamy

    2016-03-01

    Poly o-phenylenediamine (PoPD)/MnCuFe2O4 nanocomposites with three different ratios of MnCuFe2O4 (10%, 20%, 30% w/w) were synthesized by in-situ oxidative chemical polymerization method ammonium persulphate used as oxidant, while MnCuFe2O4 nanoparticles was prepared by auto-combustion method. The structure, morphology and magnetic properties of synthesized PoPD/MnCuFe2O4 nanocomposites were characterized by FT-IR, UV-visible absorption spectra, X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) and Vibrating sample magnetometer (VSM). FTIR spectra and XRD were confirmed the formation of the PoPD/MnCuFe2O4 nanocomposites. The morphology of PoPD/MnCuFe2O4 nanocomposites is visualized through SEM and TEM. The spherical morphology of the PoPD was confirmed using SEM analysis. Dielectric properties of PoPD/MnCuFe2O4 nanocomposites at different temperatures have been performed in the frequency range of 50 Hz-5 MHz. The optical absorption experiments of PoPD/MnCuFe2O4 nanocomposites reveal that the direct transition with an energy band gap is around 2 eV.

  7. Magnetic resonance in a gallium-doped Cu-Cr-S structure

    NASA Astrophysics Data System (ADS)

    Vorotynov, A. M.; Pankrats, A. I.; Abramova, G. M.; Velikanov, D. A.; Bovina, A. F.; Sokolov, V. V.; Filatova, I. Yu.

    2016-04-01

    A layered Cu-Cr-S structure doped with Ga ions and consisting of single-crystal CuCrS2 layers, embedded with thin plates of spinel phases CuCr2S4 and CuGa x Cr2- x S4, has been studied using the magnetic resonance and magnetic susceptibility methods. The Curie temperature and the saturation magnetization of the spinel phases of the samples have been determined. The spinel phase layer thickness has been estimated.

  8. 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

  9. A discrete Cu cluster and a 3D Mn(II)-Cu(II) framework based on assembly of Mn2Cu4 clusters: synthesis, structure and magnetic properties.

    PubMed

    Chakraborty, Anindita; Escuer, Albert; Ribas, Joan; Maji, Tapas Kumar

    2016-10-04

    The synthesis, single-crystal structure characterization and detailed magnetic study of a homometallic hexanuclear Cu(II) cluster [Cu6(μ3-OH)2(ppk)6(H2O)2(NO3)4] (1) and a three-dimensional (3D) compound [{MnCu2(dpkO2H)2(dpkO2)N3}·(NO3)·H2O]n (2) (ppk = phenyl-2-pyridyl ketoxime; dpk = di-2-pyridyl ketone) consisting of heterometallic Mn(II)-Cu(II) hexanuclear cores as secondary building units are reported in this paper. In compound 1, two symmetry-related Cu3 triangles consisting of a hydroxido-bridged trinuclear unit, [Cu3(μ3-OH)(ppk)3(H2O)(NO3)](+), are assembled through nitrate bridging giving rise to the homometallic Cu6 cluster. Compound 2 contains heterometallic {MnCu} cores, which are further connected to each other through an azido bridging ligand in all the crystallographic directions, resulting in a 3D metal-organic framework. Construction of such a heterometallic 3D framework from {MnCu} units is until now, unknown. Magnetic studies of both 1 and 2 were performed in detail and both compounds show dominant antiferromagnetic interaction in the respective clusters. Compound 1 reveals significant spin frustration and anti-symmetric exchange interaction in the trinuclear cores, with a significantly high value of Jav (-655 cm(-1)). Furthermore, compound 2 exhibits a dominant antiferromagnetic interaction, which is also supported by an extensive magneto-structural correlation which considers the different magnetic pathways.

  10. Mechanical and Thermal Properties of Two Cu-Cr-Nb Alloys and NARloy-Z

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Michal, Gary M.

    1996-01-01

    A series of creep tests were conducted on Cu-8 Cr-4 Nb (Cu-8 at.% Cr-4 at.% Nb), Cu-4 Cr-2 Nb (Cu-4 at.% Cr-2 at% Nb), and NARloy-Z (Cu-3 wt.% Ag-0.5 wt.% Zr) samples to determine their creep properties. In addition, a limited number of low cycle fatigue and thermal conductivity tests were conducted. The Cu-Cr-Nb alloys showed a clear advantage in creep life and sustainable load over the currently used NARloy-Z. Increases in life at a given stress were between 100% and 250% greater for the Cu-Cr-Nb alloys depending on the stress and temperature. For a given life, the Cu-Cr-Nb alloys could support a stress between 60% and 160% greater than NARloy-Z. Low cycle fatigue lives of the Cu-8 Cr-4 Nb alloy were equivalent to NARloy-Z at room temperature. At elevated temperatures (538 C and 650 C), the fatigue lives were 50% to 200% longer than NARloy-Z samples tested at 538 C. The thermal conductivities of the Cu-Cr-Nb alloys remained high, but were lower than NARloy-Z and pure Cu. The Cu-Cr-Nb thermal conductivities were between 72% and 96% that of pure Cu with the Cu-4 Cr-2 Nb alloy having a significant advantage in thermal conductivity over Cu-8 Cr4 Nb. In comparison, stainless steels with equivalent strengths would have thermal conductivities less than 25% the thermal conductivity of pure Cu. The combined results indicate that the Cu-Cr-Nb alloys offer an attractive alternative to current high temperature Cu-based alloys such as NARloy-Z.

  11. How Deep and Hot was Earth's Magma Ocean? Combined Experimental Datasets for the Metal-silicate Partitioning of 11 Siderophile Elements - Ni, Co, Mo, W, P, Mn, V, Cr, Ga, Cu and Pd

    NASA Technical Reports Server (NTRS)

    Righter, Kevin

    2008-01-01

    variable oxygen fugacity. Preliminary results confirm that D(Ni) and D(Co) converge at pressures near 25-30 GPa and approximately 2200 K, and show that D(Pd) and D(Cu) become too low at the PT conditions of the deepest models. Furthermore, models which force fit V and Cr mantle concentrations by metal-silicate equilibrium overlook the fact that at early Earth mantle fO2, these elements will be more compatible in Mg-perovskite and (Fe,Mg)O than in metal. Thus an intermediate depth magma ocean, at 25-30 GPa, 2200 K, and at IW-2, can explain more mantle siderophile element concentrations than other models.

  12. How Deep and Hot was Earth's Magma Ocean? Combined Experimental Datasets for the Metal-silicate Partitioning of 11 Siderophile Elements - Ni, Co, Mo, W, P, Mn, V, Cr, Ga, Cu and Pd

    NASA Technical Reports Server (NTRS)

    Righter, Kevin

    2008-01-01

    variable oxygen fugacity. Preliminary results confirm that D(Ni) and D(Co) converge at pressures near 25-30 GPa and approximately 2200 K, and show that D(Pd) and D(Cu) become too low at the PT conditions of the deepest models. Furthermore, models which force fit V and Cr mantle concentrations by metal-silicate equilibrium overlook the fact that at early Earth mantle fO2, these elements will be more compatible in Mg-perovskite and (Fe,Mg)O than in metal. Thus an intermediate depth magma ocean, at 25-30 GPa, 2200 K, and at IW-2, can explain more mantle siderophile element concentrations than other models.

  13. High temperature coarsening of Cr2Nb precipitates in Cu-8 Cr-4 Nb alloy

    NASA Technical Reports Server (NTRS)

    Anderson, Kenneth Reed

    1996-01-01

    A new high-temperature-strength, high-conductivity Cu-Cr-Nb alloy with a CrNb ratio of 2:1 was developed to achieve improved performance and durability. The Cu-8 Cr4 Nb alloy studied has demonstrated remarkable thermal and microstructural stability after long exposures at temperatures up to 0.98 T(sub m). This stability was mainly attributed to the slow coarsening kinetics of the Cr2Nb precipitates present in the alloy. At all temperatures, the microstructure consists of a bimodal and sometimes trimodal distribution of strengthening Cr2Nb precipitates, depending on precipitation condition, i.e. from liquid or solid solution, and cooling rates. These precipitates remain in the same size range, i.e. large precipitates of approximately I pm, and small precipitates less dm 300 nm, and effectively pin the grain boundaries thus retaining a fine grain size of 2.7 micro-m after 100 h at 1323 K. (A relatively small number of Cr-rich and Nb-rich particles were also present.) This grain boundary pinning and sluggish coarsening of Cr2Nb particles explain the retention of good mechanical properties after prolonged holding at very high temperatures, e.g., 75% of the original hardness after aging for 100 h at 1273 K. Application of LSW-based coarsening models indicated that the coarsening kinetics of the large precipitates are most likely governed by grain boundary diffsion and, to a lesser extent, volume diffusion mechanisms.

  14. Electronic structure and magnetism of Mn 2CuAl: A first-principles study

    NASA Astrophysics Data System (ADS)

    Li, S. T.; Ren, Z.; Zhang, X. H.; Cao, C. M.

    2009-07-01

    The electronic structure and magnetism of a new Mn-based Heusler alloys Mn 2CuAl has been studied by first-principles calculations. The calculations suggest that Mn 2CuAl crystallizes in the Hg 2CuTi type of structure, in which the Cu atoms have Al as nearest neighbors. As a consequence, the Mn atoms occupy two nearest neighbor sublattices A and B. Like the well known Heusler alloy Cu 2MnAl, the magnetic moment of Mn 2CuAl also comes from the two Mn atoms in the lattice, while the Cu atom is almost nonmagnetic. At equilibrium lattice constant, Mn 2CuAl is a ferrimagnet with moment of 0.22μ B. The partial spin moments of Mn (A) and Mn (B) are -3.52μ B and 3.74μ B, respectively. The small total moment comes from the antiparallel configurations of the Mn partial moments. With a small contraction of the lattice, the total moment becomes near zero and a half-metallic antiferromagnetic state is observed.

  15. 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.

  16. 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.

  17. Two-dimensional ferromagnetism and spin filtering in Cr and Mn-doped graphdiyne

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Gao, Pengfei; Guo, Lei; Wen, Yanni; Zhang, Yang; Zhang, Shengli

    2017-06-01

    Ferromagnetism in half-metallic two-dimensional material can lead to unique spintronics application. In this work, Cr-doped single-layer graphdiyne is predicted to be two-dimensional ferromagnetic semiconductor, and Mn-doped graphdiyne is predicted to be ferromagnetic conductor using first-principle calculations. Cr and Mn adatoms could be stabilized on the corner sites of graphdiyne sheet due to high migration barriers. The currents through Cr- and Mn-doped graphdiyne possess spin polarization feature. For Cr-doped graphdiyne system, the transmission polarization is up to 100% and could be controlled by the gate voltage. Cr-/Mn-doped graphdiyne with spin-polarized semiconductor/conductor properties could be promising material for combined usage in spintronics application.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  19. Scrutinizing Al-like 10+51V, 11+53Cr, 12+55Mn, 13+57Fe, 14+59Co, 15+61Ni, and 16+63Cu 1ions for atomic clocks with uncertainties below the 10-19 level

    NASA Astrophysics Data System (ADS)

    Yu, Yan-mei; Sahoo, B. K.

    2016-12-01

    We investigate the transition between the fine structure levels of the ground state, 3 p 2P1 /2→3 p 2P3 /2 , of the highly charged Al-like 10+51V, 11+53Cr, 12+55Mn, 13+57Fe, 14+59Co, 15+61Ni, and 16+63Cu ions for frequency standards. To comprehend them as prospective atomic clocks, we determine their transition wavelengths, quality factors, and various plausible systematics during the measurements. Since most of these ions have nuclear spin I =3 /2 , uncertainties due to dominant quadrupole shifts can be evaded in the F =0 hyperfine level of the 3 p 2P3 /2 state. Other dominant systematics such as quadratic Stark and black-body radiation shifts have been evaluated precisely demonstrating the feasibility of achieving high accuracy, below 10-19 fractional uncertainty, atomic clocks using the above transitions. Moreover, relativistic sensitivity coefficients are determined to find out the aptness of these proposed clocks to investigate possible temporal variation of the fine structure constant. To carry out these analysis, a relativistic coupled-cluster method considering Dirac-Coulomb-Breit Hamiltonian along with lower-order quantum electrodynamics interactions is employed and many spectroscopic properties are evaluated. These properties are also of immense interest for astrophysical studies.

  20. Geochemistry and crystallochemistry of oceanic hydrothermal manganese oxyhydroxides showing Mn-Cu association

    SciTech Connect

    Stouff, P.; Boulegue, J. )

    1989-04-01

    Hydrothermal iron and manganese oxides have been found in association with sulfides dredged on the E.P.R. near 7{degree}N. The Mn phase, mainly a 10-7 {angstrom} phyllomanganate, presents a very important enrichment in Cu (up to 30% as weight of oxide). The Fe phase, mainly hydro-goethite, has a very low content of metals of economic interest. Also Mn-Cu oxide particles have been collected in sediment traps near the hydrothermal vents at 13{degree}N. Using the Mn oxide samples of 7{degree}N, Cu shows two simultaneous oxidation states: +I and +II (ESCA and XAS edge measurements). Cu is adsorbed on the Mn(O,OH){sub 2} layers and partially belongs to the water layers (EXAFS results). This seems to be the first report of naturally occurring Cu-buserite in this environment. Lead isotope abundances, the presence of Cu(I), thermodynamic considerations on the stability of the Mn-Cu oxyhydroxides and unsuccessful attempts made with synthetic 10-7 {angstrom} phyllomanganates (buserite and birnessite types) at low temperature in order to stabilize Cu(I) and incorporate it in the interlamellar space of the manganate, lead the authors to accept a high temperature origin for the formation of the Mn-Cu oxyhydroxides. They present a transport model for Cu and Mn precipitation from oceanic hydrothermal fluid, to explain the formation of Mn-Cu oxyhydroxides.

  1. Creep and oxidation behavior of modified CF8C-plus with W, Cu, Ni, and Cr

    DOE PAGES

    Unocic, Kinga A.; Dryepondt, Sebastien N.; Yamamoto, Yukinori; ...

    2016-02-01

    Here, the microstructures of modified CF8C-Plus (Fe-19Cr-12Ni-0.4W-3.8Mn-0.2Mo-0.6Nb-0.5Si-0.9C) with W and Cu (CF8CPWCu) and CF8CPWCu enhanced with 21Cr + 15Ni or 22Cr + 17.5Ni were characterized in the as-cast condition and after creep testing. When imaged at lower magnifications, the as-cast microstructure was similar among all three alloys as they all contained a Nb-rich interdendritic phase and Mn-based inclusions. Transmission electron microscopy (TEM) analysis showed the presence of nanoscale Cu-rich nanoprecipitates distributed uniformly throughout the matrix of CF8CPWCu, whereas in CF8CPWCu22/17, Cu precipitates were found primarily at the grain boundaries. The presence of these nanoscale Cu-rich particles, in addition to W-richmore » Cr23C6, nanoscale Nb carbides, and Z-phase (Nb2Cr2N2), improved the creep strength of the CF8CPWCu steel. Modification of CF8CPWCu with Cr and Ni contents slightly decreased the creep strength but significantly improved the oxidation behavior at 1073 K (800 °C). In particular, the addition of 22Cr and 17.5Ni strongly enhanced the oxidation resistance of the stainless steel resulting in a 100 degrees or greater temperature improvement, and this composition provided the best balance between improving both mechanical properties and oxidation resistance.« less

  2. Creep and oxidation behavior of modified CF8C-plus with W, Cu, Ni, and Cr

    SciTech Connect

    Unocic, Kinga A.; Dryepondt, Sebastien N.; Yamamoto, Yukinori; Maziasz, Philip J.

    2016-02-01

    Here, the microstructures of modified CF8C-Plus (Fe-19Cr-12Ni-0.4W-3.8Mn-0.2Mo-0.6Nb-0.5Si-0.9C) with W and Cu (CF8CPWCu) and CF8CPWCu enhanced with 21Cr + 15Ni or 22Cr + 17.5Ni were characterized in the as-cast condition and after creep testing. When imaged at lower magnifications, the as-cast microstructure was similar among all three alloys as they all contained a Nb-rich interdendritic phase and Mn-based inclusions. Transmission electron microscopy (TEM) analysis showed the presence of nanoscale Cu-rich nanoprecipitates distributed uniformly throughout the matrix of CF8CPWCu, whereas in CF8CPWCu22/17, Cu precipitates were found primarily at the grain boundaries. The presence of these nanoscale Cu-rich particles, in addition to W-rich Cr23C6, nanoscale Nb carbides, and Z-phase (Nb2Cr2N2), improved the creep strength of the CF8CPWCu steel. Modification of CF8CPWCu with Cr and Ni contents slightly decreased the creep strength but significantly improved the oxidation behavior at 1073 K (800 °C). In particular, the addition of 22Cr and 17.5Ni strongly enhanced the oxidation resistance of the stainless steel resulting in a 100 degrees or greater temperature improvement, and this composition provided the best balance between improving both mechanical properties and oxidation resistance.

  3. Creep and Oxidation Behavior of Modified CF8C-Plus with W, Cu, Ni, and Cr

    NASA Astrophysics Data System (ADS)

    Unocic, Kinga A.; Dryepondt, Sebastien; Yamamoto, Yukinori; Maziasz, Philip J.

    2016-04-01

    The microstructures of modified CF8C-Plus (Fe-19Cr-12Ni-0.4W-3.8Mn-0.2Mo-0.6Nb-0.5Si-0.9C) with W and Cu (CF8CPWCu) and CF8CPWCu enhanced with 21Cr + 15Ni or 22Cr + 17.5Ni were characterized in the as-cast condition and after creep testing. When imaged at lower magnifications, the as-cast microstructure was similar among all three alloys as they all contained a Nb-rich interdendritic phase and Mn-based inclusions. Transmission electron microscopy (TEM) analysis showed the presence of nanoscale Cu-rich nanoprecipitates distributed uniformly throughout the matrix of CF8CPWCu, whereas in CF8CPWCu22/17, Cu precipitates were found primarily at the grain boundaries. The presence of these nanoscale Cu-rich particles, in addition to W-rich Cr23C6, nanoscale Nb carbides, and Z-phase (Nb2Cr2N2), improved the creep strength of the CF8CPWCu steel. Modification of CF8CPWCu with Cr and Ni contents slightly decreased the creep strength but significantly improved the oxidation behavior at 1073 K (800 °C). In particular, the addition of 22Cr and 17.5Ni strongly enhanced the oxidation resistance of the stainless steel resulting in a 100 degrees or greater temperature improvement, and this composition provided the best balance between improving both mechanical properties and oxidation resistance.

  4. Deep Drawing Behavior of CoCrFeMnNi High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Bae, Jae Wung; Moon, Jongun; Jang, Min Ji; Ahn, Dong-Hyun; Joo, Soo-Hyun; Jung, Jaimyun; Yim, Dami; Kim, Hyoung Seop

    2017-07-01

    Herein, the deep drawability and deep drawing behavior of an equiatomic CoCrFeMnNi HEA and its microstructure and texture evolution are first studied for future applications. The CoCrFeMnNi HEA is successfully drawn to a limit drawing ratio (LDR) of 2.14, while the planar anisotropy of the drawn cup specimen is negligible. The moderate combination of strain hardening exponent and strain rate sensitivity and the formation of deformation twins in the edge region play important roles in successful deep drawing. In the meanwhile, the texture evolution of CoCrFeMnNi HEA has similarities with conventional fcc metals.

  5. Deep Drawing Behavior of CoCrFeMnNi High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Bae, Jae Wung; Moon, Jongun; Jang, Min Ji; Ahn, Dong-Hyun; Joo, Soo-Hyun; Jung, Jaimyun; Yim, Dami; Kim, Hyoung Seop

    2017-09-01

    Herein, the deep drawability and deep drawing behavior of an equiatomic CoCrFeMnNi HEA and its microstructure and texture evolution are first studied for future applications. The CoCrFeMnNi HEA is successfully drawn to a limit drawing ratio (LDR) of 2.14, while the planar anisotropy of the drawn cup specimen is negligible. The moderate combination of strain hardening exponent and strain rate sensitivity and the formation of deformation twins in the edge region play important roles in successful deep drawing. In the meanwhile, the texture evolution of CoCrFeMnNi HEA has similarities with conventional fcc metals.

  6. In-beam mechanical testing of CuCrZr

    NASA Astrophysics Data System (ADS)

    Marmy, P.

    2004-08-01

    In the ITER design, CuCrZr has been selected as the heat sink material for components of the first wall and the divertor. The objective of this work is to check the material fatigue performance when the CuCrZr alloy is cyclically deformed concurrently with irradiation, using an in situ testing machine placed in a 590 MeV proton accelerator. Three fatigue experiments have been conducted at 100 °C, under strain control, at a total strain range of 0.8%. The in-beam specimen reached the longest life. The post-irradiation tested specimen had the shortest life. The total plastic strain measured in the in-beam specimen was larger than the plastic strain measured in the statically irradiated specimen or in the unirradiated specimen.

  7. XANES evidence for oxidation of Cr(III) to Cr(VI) by Mn-oxides in a lateritic regolith developed on serpentinized ultramafic rocks of New Caledonia.

    PubMed

    Fandeur, Dik; Juillot, Farid; Morin, Guillaume; Olivi, Luca; Cognigni, Andrea; Webb, Samuel M; Ambrosi, Jean-Paul; Fritsch, Emmanuel; Guyot, François; Brown, Gordon E

    2009-10-01

    Although several laboratory studies showed that Mn-oxides are capable of oxidizing Cr(II) to Cr(VI), very few have reported evidence for such a reaction in natural systems. This study presents new evidence for this redox reaction between Cr(III) and Mn-oxides in a lateritic regolith developed on ultramafic rocks in New Caledonia. The studied lateritic regolith presents several units with contrasting amounts of major (Fe, Al, Si, and Mg) and trace (Mn, Cr, Ni, Co) elements, which are related to varying mineralogical compositions. Bulk XANES analyses show the occurrence of Cr(VI) (up to 20 wt % of total chromium) in the unit of the regolith which is also enriched in Mn (up to 21.7 wt % MnO), whereas almost no Cr(VI) is detected elsewhere. X-ray powder diffraction indicates that the large amounts of Mn in this unit of the regolith are due to the occurrence of Mn-oxides (identified as a mixture of asbolane, lithiophorite and birnessite) and Mn K-edge XANES data indicate that Mn occurs mainly as Mn(IV) in this unit, although small amounts of Mn(III) could also be detected. These results strongly suggest a direct role of the Mn-oxides on the occurrence of Cr(VI) through a redox reaction between Cr(III) and Mn(IV) and/or Mn(III). Owing to the much larger toxicity and solubility of Cr(VI), such a co-occurrence of Cr and Mn-oxides in these soils could then represent an important risk for the environment. However, the significant amounts of Cr(VI) released after reacting the samples from the studied sequence with a 0.1 M (NH)4H2PO4 solution, designed to remove tightly sorbed chromate species, suggest that Cr(VI) mainly occurs as sorption complexes. This hypothesis is reinforced by spatially resolved XANES analyses, which show that Cr(VI) is associated with both Mn- and Fe-oxides, and especially at the boundary between these two mineral species. Such a distribution of Cr(VI) suggests a possible readsorption of Cr(VI) onto surrounding Fe-oxyhydroxides (mainly goethite) after

  8. 53Mn-53Cr radiometric dating of secondary carbonates in CR chondrites: Timescales for parent body aqueous alteration

    NASA Astrophysics Data System (ADS)

    Jilly-Rehak, Christine E.; Huss, Gary R.; Nagashima, Kazuhide

    2017-03-01

    We present 53Mn-53Cr ages of secondary carbonates in Renazzo-like (CR) chondrites, determined by secondary ion mass spectrometry. The timing of aqueous alteration in CR chondrites has been unconstrained in the literature. We measured 53Mn-53Cr isotope systematics in carbonates from three different CR-chondrite lithologies. Calcite in the interchondrule matrix of Renazzo, calcite in the matrix of GRO 95577, and dolomite in a dark inclusion of Renazzo all show excesses in 53Cr, interpreted as the daughter product from the decay of 53Mn. The Renazzo calcite yields an initial ratio of (53Mn/55Mn)0 = (3.6 ± 2.7) × 10-6, and the Renazzo dark inclusion dolomite ranges from (53Mn/55Mn)0 = (3.1 ± 1.4) × 10-6 (corrected to the RSF of a calcite standard) to (3.7 ± 1.7) × 10-6 (corrected to an inferred dolomite RSF). When anchored to the D'Orbigny angrite, the Renazzo carbonates yield ages between 4563.6 and 4562.6 Ma, or ∼4.3-5.3 Myr after the formation of CV CAIs. Calcite measured in the heavily altered specimen GRO 95577 yields a shallower slope of (53Mn/55Mn)0 = (7.9 ± 2.8) × 10-7, corresponding to a much younger age of 4555.4 Ma, or ∼12.6 Myr after CAI formation. The two Renazzo ages are contemporaneous with Mn-Cr ages of carbonates in Tagish Lake, CI, and CM chondrites, but the GRO 95577 age is uniquely young. These findings suggest that early aqueous alteration on chondritic parent bodies was a common occurrence, likely driven by internal heating from 26Al decay after accretion. The young carbonate ages of GRO 95577 suggest that either the CR parent body was sufficiently large to sustain heating from 26Al for ∼8 Myr, or that late-stage impact events supplied heat to the region where GRO 95577 originated.

  9. Elastocaloric effect in CuAlZn and CuAlMn shape memory alloys under compression.

    PubMed

    Qian, Suxin; Geng, Yunlong; Wang, Yi; Pillsbury, Thomas E; Hada, Yoshiharu; Yamaguchi, Yuki; Fujimoto, Kenjiro; Hwang, Yunho; Radermacher, Reinhard; Cui, Jun; Yuki, Yoji; Toyotake, Koutaro; Takeuchi, Ichiro

    2016-08-13

    This paper reports the elastocaloric effect of two Cu-based shape memory alloys: Cu68Al16Zn16 (CuAlZn) and Cu73Al15Mn12 (CuAlMn), under compression at ambient temperature. The compression tests were conducted at two different rates to approach isothermal and adiabatic conditions. Upon unloading at a strain rate of 0.1 s(-1) (adiabatic condition) from 4% strain, the highest adiabatic temperature changes (ΔTad) of 4.0 K for CuAlZn and 3.9 K for CuAlMn were obtained. The maximum stress and hysteresis at each strain were compared. The stress at the maximum recoverable strain of 4.0% for CuAlMn was 120 MPa, which is 70% smaller than that of CuAlZn. A smaller hysteresis for the CuAlMn alloy was also obtained, about 70% less compared with the CuAlZn alloy. The latent heat, determined by differential scanning calorimetry, was 4.3 J g(-1) for the CuAlZn alloy and 5.0 J g(-1) for the CuAlMn alloy. Potential coefficients of performance (COPmat) for these two alloys were calculated based on their physical properties of measured latent heat and hysteresis, and a COPmat of approximately 13.3 for CuAlMn was obtained.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'. © 2016 The Author(s).

  10. Oxidation of CoCrFeMnNi High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Holcomb, Gordon R.; Tylczak, Joseph; Carney, Casey

    2015-06-01

    Eight model high entropy alloys (HEAs) in the CoCrFeMnNi family (including one alloy each in the CoCrFeNi and CoFeMnNi subfamilies) were made, prepared, and exposed to laboratory air for 1100 h at 650°C and 750°C. Two commercial alloys, nickel-base superalloy 230 (N06230) and austenitic stainless steel 304H (S30409), were simultaneously exposed for comparison. Mass change oxidation kinetics were measured and cross-sections of exposed samples were observed. Seven of these HEAs contained much more Mn (12-24 wt.%) than is found in commercial heat-resistant stainless steels and superalloys. The oxidation resistance of CoCrFeNi was excellent and comparable to 304H at 650°C and only slightly worse at 750°C. The thin oxide scale on CoCrFeNi was primarily Cr oxide (presumably Cr2O3) with some Mn oxide at the outer part of the scale. The CoCrFeMnNi HEAs all experienced more rapid oxidation than CoCrFeNi and, especially at 750°C, experienced oxide scale spallation. The addition of Y in the alloy to lower S improved the oxidation resistance of these HEAs. Alloy CoFeMnNi, without Cr, experienced much higher oxidation rates and scale spallation than the Cr-containing alloys. A linear regression analysis of the log of the parabolic rate constant, log(kp), as functions of wt.% Cr and Mn found a good correlation for the compositional dependence of the oxidation rate constant, especially at 650°C. Mn was found to be more detrimental increasing log(k p) than Cr was helpful reducing log(k p). If CoCrFeMnNi HEAs are to be used in high temperature oxidizing environments, then examining lower levels of Mn, while maintaining Cr levels, should be pursued.

  11. Cu-Mn-Ce ternary mixed-oxide catalysts for catalytic combustion of toluene.

    PubMed

    Lu, Hanfeng; Kong, Xianxian; Huang, Haifeng; Zhou, Ying; Chen, Yinfei

    2015-06-01

    Cu-Mn, Cu-Mn-Ce, and Cu-Ce mixed-oxide catalysts were prepared by a citric acid sol-gel method and then characterized by XRD, BET, H2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene combustion reaction. Results showed that the Cu-Mn-Ce ternary mixed-oxide catalyst with 1:2:4 mole ratios had the highest catalytic activity, and 99% toluene conversion was achieved at temperatures below 220°C. In the Cu-Mn-Ce catalyst, a portion of Cu and Mn species entered into the CeO2 fluorite lattice, which led to the formation of a ceria-based solid solution. Excess Cu and Mn oxides existed on the surface of the ceria-based solid solution. The coexistence of Cu-Mn mixed oxides and the ceria-based solid solution resulted in a better synergetic interaction than the Cu-Mn and Cu-Ce catalysts, which promoted catalyst reducibility, increased oxygen mobility, and enhanced the formation of abundant active oxygen species.

  12. Cr Isotope Variation in the Components of Unequilibrated Chondrite QUE 97008 (L3.05) and Implications for 53Mn-53Cr Dating of Unequilibrated Chondrites

    NASA Astrophysics Data System (ADS)

    Kadlag, Y.; Becker, H.

    2016-08-01

    In this study, we report Cr isotope variation in physically separated components of unequilibrated chondrite QUE 97008. Decoupling of 54Cr and 53Cr and Mn/Cr indicate the presence of at least two types of 54CR depleted and enriched carriers.

  13. Asymmetric reversal in aged high concentration CuMn alloy.

    PubMed

    Barnsley, L C; MacA Gray, E; Webb, C J

    2013-02-27

    The magnetic hysteresis loops of an aged Cu(81.2)Mn(18.8) alloy sample exhibit significant asymmetric reversal at low temperatures, with high sensitivity to the cooling field. Much of the observed behaviour was explained by considering an ensemble of coherent, ferromagnetically aligned clusters interacting with a randomized spin glass component. A modified Stoner-Wohlfarth model was successfully applied to the data using Monte Carlo simulations, in order to gain insight into the dependence of the cluster shape anisotropy and exchange anisotropy on the cooling field. This model suggested that ferromagnetic clusters grow as the cooling field increases.

  14. 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.

  15. 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.

  16. Preparation and Performance of Cu-Cr Contact Materials for Vacuum Switches with Low Contact Pressure

    NASA Astrophysics Data System (ADS)

    Chang, Yanli; Zheng, Wei; Zhou, Zhiming; Zhai, Yuxiang; Wang, Yaping

    2016-11-01

    Insufficient anti-welding properties limit the application of Cu-Cr contact material in vacuum switches with low contact pressure. The CuCr-W-C alloys that are prepared are for decreasing welding tendencies and keeping the voltage withstand by addition of W and C elements. It is found that the average welding force of CuCr-W-C alloys is reduced more than 50% compared with that of the Cu50 Cr50 alloy. Especially for CuCrW3.0C0.3 and CuCrW1.0C0.5, the welding forces reduce to only 10% of Cu50Cr50. Arc erosion areas of CuCr-W-C alloys are enlarged by five times more than that of the Cu50Cr50 alloy in the same arcing conditions. The results of type tests were qualified. The results suggested that the CuCrW2.0C1.0 alloy could be used in vacuum switches with low contact pressure to replace the W-Cu type contacts.

  17. Exchange bias effect in NiMnSb/CrN heterostructures deposited by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Sharma Akkera, Harish; Barman, Rahul; Kaur, Navjot; Choudhary, Nitin; Kaur, Davinder

    2013-05-01

    Exchange bias has been studied in various Ni50Mn36.8Sb13.2/CrN heterostructures with different CrN thicknesses (15 nm-80 nm), grown on Si (100) substrate using magnetron sputtering. The shift in hysteresis loop up to 51 Oe from the origin was observed at 10 K for Ni-Mn-Sb film without CrN layer. On the other hand, a significant shifting of hysteresis loop was observed with antiferromagnetic (AFM) CrN layer in Ni50Mn36.8Sb13.2/CrN heterostructure. The exchange coupled 140 nm Ni50Mn36.8Sb13.2/35 nm CrN heterostructure exhibited a relatively large exchange coupling field of 148 Oe at 10 K compared to other films, which may be related to uncompensated and pinned AFM spins at FM-AFM interface and different AFM domain structures for different thicknesses of CrN layer. Further nanoindentation measurements revealed the higher values of hardness and elastic modulus of about 12.7 ± 0.38 GPa and 179.83 ± 1.24 GPa in Ni50Mn36.8Sb13.2/CrN heterostructures making them promising candidate for various multifunctional MEMS devices.

  18. Large enhancement of ferromagnetism by Cr doping in Mn3O4 nanowires

    NASA Astrophysics Data System (ADS)

    Li, GaoMin; Tang, XiaoBing; Lou, ShiYun; Zhou, ShaoMin

    2014-04-01

    The Mn3O4 nanostructures having low temperature Curie point (45 K) disqualify them for most practical applications. In this work, single-crystalline Cr-doped Mn3O4 nanowires with ferromagnetic Curie point at room temperature (305 K) have been investigated. Our experimental results show an increase in effective magnetic moment per gram as Cr3+ replaces Mn3+ and oxygen vacancies, which result in a transition from paramagnetic (Mn3O4) to ferromagnetic. The doped Cr3+ and oxygen vacancies reveal the remarkable ferromagnetic in Mn3-xCrxO4 nanowires may be ascribed to bound magnetic polarons model. Our experimental results suggest these obtained nanowires are promising nanoscale building blocks in spintronic devices.

  19. Ferromagnetism-dependent polytypism: CrAs versus MnAs

    NASA Astrophysics Data System (ADS)

    Benaissa, H.; Zaoui, A.; Ferhat, M.

    2016-12-01

    Density spin-polarized functional theory using pseudopotential plane wave method is used here to explore the structural and magnetic properties of 3C, 4H, 6H and 2H polytypes of transition metal arsenides: CrAs and MnAs. The results reveal that CrAs manifest weak dependence of the lattice parameter a and the c/a ratio versus hexagonality, but for MnAs, the lattice parameters display strong dependence on crystal polytype. Most importantly, our results show that the different crystal 3C, 4H, 6H and 2H polytypes exhibit significant distinct magnetism in CrAs and MnAs. While the total spin moments induced in CrAs is strongly independent of the crystal structure adopted, the ferromagnetism in MnAs is found sensitive to polytypism.

  20. First-principles study on the band structure, magnetic and elastic properties of half-metallic Cr2MnAl

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    In this study, we have investigated the structural, electronic, magnetic and elastic properties of the full-Heusler Cr2MnAl alloy in the framework of density functional theory with generalized gradient approximation (GGA). The calculated results showed that Cr2MnAl was stable in ferrimagnetic configuration and crystallized in the Hg2CuTi-type structure. From the band structure and density of states calculation results, we concluded that Cr2MnAl belongs to a kind of half-metallic compound with an indirect band gap of 0.37 eV. Immediately thereafter, we have analyzed the origin of half-metallic band gap. The total magnetic moment of Cr2MnAl at the stable state is - 2μB per formula unit, obeying the Slater-Pauling rule Mt = Zt - 24. In addition, various mechanical properties have been obtained and discussed based on the three principle elastic tensor elements C11,C12 and C44 for the first time in the present work. We expect that our calculated results may trigger the application of Cr2MnAl in future spintronics field.

  1. Structure-activity relationship of CuO/MnO2 catalysts in CO oxidation

    NASA Astrophysics Data System (ADS)

    Qian, Kun; Qian, Zhaoxia; Hua, Qing; Jiang, Zhiquan; Huang, Weixin

    2013-05-01

    A series of CuO/MnO2 catalysts with different CuO loadings were synthesized by the incipient wetness impregnation method. The catalysts were characterized by N2 adsorption-desorption isotherms, powder X-ray diffraction, X-ray photoelectron spectroscopy, H2-temperature programmed reduction, CO-temperature programmed reduction and scanning electron microscope. The CuO/MnO2 catalysts with CuO loading of 1-40% exhibit almost the same catalytic performance toward CO oxidation while those with higher CuO loadings exhibit a much poorer catalytic activity. The structural characterization results demonstrate that the CuO-MnO2 interface is the active site for CO oxidation in CuO/MnO2 catalysts and CO oxidation over CuO/MnO2 probably follows the interfacial reaction mechanism in which CO chemisorbed on CuO reacts with oxygen species on MnO2 at the CuO-MnO2 interface.

  2. 53Mn-53Cr chronology of Ca-Fe silicates in CV3 chondrites

    NASA Astrophysics Data System (ADS)

    MacPherson, Glenn J.; Nagashima, Kazuhide; Krot, Alexander N.; Doyle, Patricia M.; Ivanova, Marina A.

    2017-03-01

    High precision secondary ion mass-spectrometry (SIMS) analyses of kirschsteinite (CaFeSiO4) in the reduced CV3 chondrites Vigarano and Efremovka yield well resolved 53Cr excesses that correlate with 55Mn/52Cr, demonstrating in situ decay of the extinct short-lived radionuclide 53Mn. To ensure proper correction for relative sensitivities between 55Mn+ and 52Cr+ ions, we synthesized kirschsteinite doped with Mn and Cr to measure the relative sensitivity factor. The inferred initial ratio (53Mn/55Mn)0 in chondritic kirschsteinite is (3.71 ± 0.50) × 10-6. When anchored to 53Mn-53Cr relative and U-corrected 207Pb-206Pb absolute ages of the D'Orbigny angrite, this ratio corresponds to kirschsteinite formation 3.2-0.7+08 Ma after CV Ca-, Al-rich inclusions. The kirschsteinite data are consistent within error with the data for aqueously-formed fayalite from the Asuka 881317 CV3 chondrite as reported by Doyle et al. (2015), supporting the idea that Ca-Fe silicates in CV3 chondrites are cogenetic with fayalite (and magnetite) and formed during metasomatic alteration on the CV3 parent body. Concentrically-zoned crystals of kirschsteinite and hedenbergite indicate that they initially formed as near end-member compositions that became more Mg-rich with time, possibly as a result of an increase in temperature.

  3. 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.

  4. Contribution of Ca^{2+} ions influx in Cu (II) or Cr (VI) induced hepatocyte cytotoxicity

    NASA Astrophysics Data System (ADS)

    Pourahmad, J.; O'Brien, P. J.

    2003-05-01

    Previously we showed that hepatocyte lysis induced by Cu (II) or Cr (VI) could be partly attributed to membrane lipid peroxidation induced by Cu (II) or Cr (VI) [1, 2]. Changes in Na^+ and Ca^{+2} homeostasis induced when Cu^{+2} or Cr VI were incubated with hepatocytes. Na^+ omission from the media or addition of the Na^+/H^+ exchange inhibitor 5-(N, N-dimethyl)-amiloride markedly increased Cu (II) or Cr (VI) cytotoxicity even though Cu (II) or Cr (VI) did not increase hepatocyte Na^+ when the media contained Na^+. The omission of CI^- from the media or addition of glycine, a CI^- channel blocker also enhanced Cu (II) or Cr (VI) induced cytotoxicity. Intracellular Ca^{+2} levels however were markedly increased when the hepatocytes were incubated with Cu^{+2} or Cr VI in a Na^+ free media and removing media Ca^{+2} with EGTA also prevented Cu (II) or Cr (VI) induced hepatocyte cytotoxicity. This suggests that intracellular Ca^{+2} accumulation contributes to Cu (II) or Cr (VI) induced cytotoxicity and a Na^+_- dependent Ca^{+2} transporter is involved in controlling excessive Ca^{+2} accumulation caused by Cu (II) or Cr (VI).

  5. First-principles study on stability and magnetism of NdFe11M and NdFe11M N for M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn

    NASA Astrophysics Data System (ADS)

    Harashima, Yosuke; Terakura, Kiyoyuki; Kino, Hiori; Ishibashi, Shoji; Miyake, Takashi

    2016-11-01

    Recently synthesized NdFe12N has excellent magnetic properties, while it is thermodynamically unstable. Using the first-principles method, we study the effect of substitutional 3d transition metal elements to the mother compound NdFe12. We find that Co has a positive effect on the stability of the ThMn12 structure. In contrast to Ti substitution, Co substitution does not reduce the magnetization significantly. The crystal field parameter A20 is nearly unchanged by Co substitution, and nitrogenation to NdFe11Co greatly enhances A20 . This suggests that Co is a good candidate as a substitutional element for NdFe12N.

  6. 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.

  7. Free standing CuO-MnO2 nanocomposite for room temperature ammonia sensing

    NASA Astrophysics Data System (ADS)

    Bhuvaneshwari, S.; Papachan, Seethal; Gopalakrishnan, N.

    2017-05-01

    CuO nanostructures and CuO-MnO2 nanocomposite were successfully synthesized using hydrothermal method without any aid of growth controlling agents. The synthesized CuO nanostructures have monoclinic structure. The XRD pattern of CuO-MnO2 observed with mixed phases of monoclinic CuO and birnessite-type MnO2 which confirms the formation of nanocomposite. SEM images revealed the turmeric-like morphology for CuO and intercalated sheets with flowers on the surface for CuO-MnO2. The length and breadth of turmeric-like structure is about 642.2 nm and 141.8 nm, respectively. The band gap of 1.72 eV for CuO nanostructure and 1.9 eV for CuO-MnO2 nanocomposite were observed from the absorption spectra. The free standing devices of CuO-MnO2 showed nearly a 3 fold increase sensing response to ammonia at room temperature when compared to the constituent CuO. The composite sensor showed response time of 120 s and recovered within 600 s. This enhanced response can be asserted to the peculiar morphology of the composite that provides more adsorption site for gas diffusion to take place.

  8. Antibacterial Cr-Cu-O films prepared by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Musil, J.; Blažek, J.; Fajfrlík, K.; Čerstvý, R.; Prokšová, Š.

    2013-07-01

    The paper reports on the effect of Cu content in the Cr-Cu-O film and its structure on its antibacterial activity and mechanical properties. The Cr-Cu-O films were prepared by reactive magnetron sputtering from composed Cr/Cu targets using a dual magnetron. The antibacterial activity of Cr-Cu-O films was tested on the killing of Escheria coli bacteria. Correlations between the structure of the Cr-Cu-O film, the content of Cu in the film and its (i) antibacterial efficiency and (ii) mechanical properties were investigated in detail. It was found that the 100% efficiency of the killing of E. coli bacteria on the surface of the Cr-Cu-O film is achieved if (1) the Cu content in the film is ≥15 at.% and (2) the film is either X-ray amorphous or crystalline with the CuCrO2 delafossite structure. These Cr-Cu-O films need no excitation and very effectively kill E. coli bacteria in the daylight as well as in the dark. The X-ray amorphous Cr-Cu-O films with ~20 at.% Cu exhibit a higher (i) hardness H ≈ 4 GPa, (ii) effective Young's modulus E* ≈ 72 GPa and (iii) elastic recovery We ≈ 37% compared with the crystalline Cr-Cu-O film with the CuCrO2 delafossite structure exhibiting H ≈ 1.2 GPa, E* ≈ 21 GPa and We ≈ 21%. Both films very effectively kill the E. coli bacteria, however, exhibit a low ratio H/E* < 0.1.

  9. Precipitation in 9Ni-12Cr-2Cu maraging steels

    SciTech Connect

    Stiller, K.; Haettestrand, M.; Danoix, F.

    1998-11-02

    Two maraging steels with the compositions 9Ni-12Cr-2Cu-4Mo (wt%) and 9Ni-12Cr-2Cu and with small additions of Al and Ti were investigated using atom probe field ion microscopy. Tomographic atom probe investigations were performed to clarify the spatial distribution of elements in and close to the precipitates. Materials heat treated at 475 C for 5, 25 min, 1, 2, 4 and 400 h were analyzed. Precipitates in the Mo-rich material were observed already after 5 min of aging, while in the material without MO, precipitation started later. In both materials precipitation begins with the formation of Cu-rich particles which work as nucleation sites for a Ni-rich phase of type Ni{sub 3}(Ti,Al). A Mo-rich phase was detected in the Mo-rich steel after 2 h of aging. The distribution of alloying elements in the precipitates, their role in the precipitation process, and the mechanism of hardening in the two materials are discussed.

  10. The Mn-53-Cr-53 System in CAIs: An Update

    NASA Technical Reports Server (NTRS)

    Papanastassiou, D. A.; Wasserburg, G. J.; Bogdanovski, O.

    2005-01-01

    High precision techniques have been developed for the measurement of Cr isotopes on the Triton mass spectrometer, at JPL. It is clear that multiple Faraday cup, simultaneous ion collection may reduce the uncertainty of isotope ratios relative to single Faraday cup ion collection, by the elimination of uncertainties from ion beam instabilities (since ion beam intensities for single cup collection are interpolated in time to calculate isotope ratios), and due to a greatly increased data collection duty cycle, for simultaneous ion collection. Efforts to measure Cr by simultaneous ion collection have not been successful in the past. Determinations on Cr-50-54Cr, by simultaneous ion collection on the Finnigan/ MAT 262 instrument at Caltech, resulted in large variations in extrinsic precision, for normal Cr, of up to 1% in Cr-53/Cr-52 (data corrected for mass fractionation, using Cr-50/Cr-52).

  11. 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.

  12. The effect of Mn on the activities of Fe, Ni, and Cr in an Fe-Ni-Cr base alloy

    SciTech Connect

    Lee, M.C.Y. . Div. of Mineral Commodities)

    1993-11-01

    A combination Knudsen cell-mass spectrometer apparatus developed by the Bureau of Mines is accurate enough to permit the activity of many alloy components to be measured directly as the ratio of the ion currents of an appropriate isotope evaporated from the alloy and from the pure component. This apparatus has been used to determine the activities of Fe, Ni, and Cr as functions of temperature in 71Fe-20Ni-6Cr-3Mn (at. pct). A comparison of the data with data obtained earlier from other Fe-Ni-Cr base alloys indicates that partial substitution of Mn for Cr causes the activity coefficient of Fe to decrease and to deviate negatively above 1,550 K. The activity coefficient of Ni is markedly increased by the substitution decreases both the activity coefficient of Cr and the temperature dependence of this coefficient. The oxidation behavior of Fe-Ni-Cr base alloys, the stability of the austenitic phase in such alloys, and the Ni equivalent of Mn are discussed in light of these changes in activity coefficient.

  13. 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.

  14. Effect of Doping on Thermoelectric Properties of Delafossite-Type Oxide CuCrO2

    NASA Astrophysics Data System (ADS)

    Hayashi, Kei; Sato, Ken-ichi; Nozaki, Tomohiro; Kajitani, Tsuyoshi

    2008-01-01

    We have studied the effects of doping on the high-temperature thermoelectric properties of the delafossite-type oxide CuCrO2. The single or double doping of divalent cations for Cr3+ ions was carried out to introduce hole carriers. For the first step, we measured the electrical conductivity σ and Seebeck coefficient S of single-doped samples, and calculated the power factor P=σS2. Mg-, Zn-, Ca-, Ni-, and Co-doped samples showed a higher power factor than CuCrO2, while the Fe-, V-, and Mn-doped samples exhibited a lower power factor. The maximum power factor P=2.36×10-4 W/mK2 at 1100 K was obtained with the Mg-doped sample. The above tendencies of the power factor are well explained by the valence states and ionic radii of the dopants. For the next step, Mg and M (M = Zn, Ca, Ni, or Co) double-doped samples were prepared. Since there was no impurity phase in the Mg+Ni cases, we have elucidated the structure and high-temperature thermoelectric properties of CuCr0.97-xMg0.03NixO2 (0Cu 3d orbitals. Since the Cu-O bond distance of the double-doped samples is shorter than that of the Mg-doped sample, it was found that hole carriers are introduced into the Cu site by the double doping. The shorter Cu-O bond distance also results in the increase in the overlapping integral between Cu 3d and O 2p orbitals. Because of the increase in the overlapping integral between the electronic orbitals caused by the topological reason and the increase in the number of hole carriers in the Cu site, the double-doped samples exhibited a higher electrical conductivity than the Mg-doped sample. The maximum electrical conductivity 45 S/cm around 1000 K was obtained for the sample of x=0.04. The Seebeck coefficient of the double-doped samples was higher than that of the Mg-doped sample, in which the total number of hole carriers (i.e., the sum of the hole

  15. Magnetic structure and electromagnetic properties of LnCrAsO with a ZrCuSiAs-type structure (Ln = La, Ce, Pr, and Nd).

    PubMed

    Park, Sang-Won; Mizoguchi, Hiroshi; Kodama, Katsuaki; Shamoto, Shin-ichi; Otomo, Toshiya; Matsuishi, Satoru; Kamiya, Toshio; Hosono, Hideo

    2013-12-02

    We report the synthesis, structure, and electromagnetic properties of Cr-based layered oxyarsenides LnCrAsO (Ln = La, Ce, Pr, and Nd) with a ZrCuSiAs-type structure. All LnCrAsO samples showed metallic electronic conduction. Electron doping in LaCrAsO by Mn-substitution for the Cr sites gave rise to a metal-insulator transition. Analysis of powder neutron diffraction data revealed that LaCrAsO had G-type antiferromagnetic (AFM) ordering, i.e., a checkerboard-type AFM ordering in the CrAs plane and antiparallel spin coupling between the adjacent CrAs planes, at 300 K with a large spin moment of 1.57 μB along the c axis. The magnetic susceptibility of LaCrAsO was very small (on the order of 10(-3) emu/mol) and showed a broad hump at ∼550 K. First-principles density functional theory calculations of LaCrAsO explained its crystal structure and metallic nature well, but could not replicate the antiparallel spin coupling between the CrAs layers. The electronic structure of LaCrAsO is discussed with regard to those of related compounds LaFeAsO and LaMnAsO.

  16. Magnetic phase transitions in PrMn 2- xCr xGe 2

    NASA Astrophysics Data System (ADS)

    Dincer, I.; Elerman, Y.; Elmali, A.; Ehrenberg, H.; Fuess, H.; Duman, E.; Acet, M.

    2002-07-01

    The structural and magnetic properties of PrMn 2- xCr xGe 2 (0⩽ x⩽1.0) were studied by X-ray diffraction and magnetization measurements. The powder samples crystallize in the ThCr 2Si 2-type structure, and the lattice constants at room temperature show almost no variation as Cr substitutes Mn. The observed phase transitions are summarized in a proposed magnetic x- T phase diagram and compared with previous Moessbauer spectroscopy and neutron diffraction results for x=0.

  17. Ligational behaviour of lomefloxacin drug towards Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Th(IV) and UO(2)(VI) ions: synthesis, structural characterization and biological activity studies.

    PubMed

    Abd el-Halim, Hanan F; Mohamed, Gehad G; el-Dessouky, Maher M I; Mahmoud, Walaa H

    2011-11-01

    Nine new mononuclear Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Th(IV) and UO(2)(VI) complexes of lomefloxacin drug were synthesized. The structures of these complexes were elucidated by elemental analyses, IR, XRD, UV-vis, (1)H NMR as well as conductivity and magnetic susceptibility measurements and thermal analyses. The dissociation constants of lomefloxacin and stability constants of its binary complexes have been determined spectrophotometrically in aqueous solution at 25±1°C and at 0.1 M KNO(3) ionic strength. The discussion of the outcome data of the prepared complexes indicate that the lomefloxacin ligand behaves as a neutral bidentate ligand through OO coordination sites and coordinated to the metal ions via the carbonyl oxygen and protonated carboxylic oxygen with 1:1 (metal:ligand) stoichiometry for all complexes. The molar conductance measurements proved that the complexes are electrolytes. The powder XRD study reflects the crystalline nature for the investigated ligand and its complexes except Mn(II), Zn(II) and UO(2)(II). The geometrical structures of these complexes are found to be octahedral. The thermal behaviour of these chelates is studied where the hydrated complexes lose water molecules of hydration in the first steps followed by decomposition of the anions, coordinated water and ligand molecules in the subsequent steps. The activation thermodynamic parameters are calculated using Coats-Redfern and Horowitz-Metzger methods. A comparative study of the inhibition zones of the ligand and its metal complexes indicates that metal complexes exhibit higher antibacterial effect against one or more bacterial species than the free LFX ligand. The antifungal and anticancer activities were also tested. The antifungal effect of almost metal complexes is higher than the free ligand. LFX, [Co(LFX)(H(2)O)(4)]·Cl(2) and [Zn(LFX)(H(2)O)(4)]·Cl(2) were found to be very active with IC50 values 14, 11.2 and 43.1, respectively. While, other

  18. Ligational behaviour of lomefloxacin drug towards Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Th(IV) and UO 2(VI) ions: Synthesis, structural characterization and biological activity studies

    NASA Astrophysics Data System (ADS)

    El-Halim, Hanan F. Abd; Mohamed, Gehad G.; El-Dessouky, Maher M. I.; Mahmoud, Walaa H.

    2011-11-01

    Nine new mononuclear Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Th(IV) and UO 2(VI) complexes of lomefloxacin drug were synthesized. The structures of these complexes were elucidated by elemental analyses, IR, XRD, UV-vis, 1H NMR as well as conductivity and magnetic susceptibility measurements and thermal analyses. The dissociation constants of lomefloxacin and stability constants of its binary complexes have been determined spectrophotometrically in aqueous solution at 25 ± 1 °C and at 0.1 M KNO 3 ionic strength. The discussion of the outcome data of the prepared complexes indicate that the lomefloxacin ligand behaves as a neutral bidentate ligand through OO coordination sites and coordinated to the metal ions via the carbonyl oxygen and protonated carboxylic oxygen with 1:1 (metal:ligand) stoichiometry for all complexes. The molar conductance measurements proved that the complexes are electrolytes. The powder XRD study reflects the crystalline nature for the investigated ligand and its complexes except Mn(II), Zn(II) and UO 2(II). The geometrical structures of these complexes are found to be octahedral. The thermal behaviour of these chelates is studied where the hydrated complexes lose water molecules of hydration in the first steps followed by decomposition of the anions, coordinated water and ligand molecules in the subsequent steps. The activation thermodynamic parameters are calculated using Coats-Redfern and Horowitz-Metzger methods. A comparative study of the inhibition zones of the ligand and its metal complexes indicates that metal complexes exhibit higher antibacterial effect against one or more bacterial species than the free LFX ligand. The antifungal and anticancer activities were also tested. The antifungal effect of almost metal complexes is higher than the free ligand. LFX, [Co(LFX)(H 2O) 4]·Cl 2 and [Zn(LFX)(H 2O) 4]·Cl 2 were found to be very active with IC50 values 14, 11.2 and 43.1, respectively. While, other complexes had

  19. Stress oscillations and surface alloy formation during the growth of FeMn on Cu(001)

    NASA Astrophysics Data System (ADS)

    Pan, Wei; Sander, Dirk; Lin, Minn-Tsong; Kirschner, Jürgen

    2003-12-01

    In situ stress and medium-energy electron-diffraction (MEED) measurements have been performed simultaneously during the deposition of FeMn on Cu(001). For a thickness above 5 layers, stress and MEED exhibit coherent layer-by-layer oscillations with a period of one atomic layer, where the largest compressive stress corresponds to the filled layer. In this thickness regime, the average stress is -0.59±0.02 GPa. From this, we deduce the biaxial modulus of FeMn layers as 148 (±5) GPa, which agrees well with the respective bulk value. For a FeMn thickness below 1.5 layers, the resulting stress is qualitatively ascribed to the sum of the individual stress contributions from Fe on Cu(001) and Mn on Cu(001). A c(2×2) low-energy electron diffraction pattern in this thickness regime indicates the formation of a c(2×2) MnCu surface alloy in the initial growth of FeMn on Cu(001), which induces a compressive surface stress of -0.7 N/m for the initial deposition of the FeMn alloy. This surface alloy formation leads to a Fe-rich FeMn alloy near the Cu interface. This compositional change might modify the antiferromagnetic coupling of the 1:1 FeMn alloy.

  20. CuCrZr alloy microstructure and mechanical properties after hot isostatic pressing bonding cycles

    NASA Astrophysics Data System (ADS)

    Frayssines, P.-E.; Gentzbittel, J.-M.; Guilloud, A.; Bucci, P.; Soreau, T.; Francois, N.; Primaux, F.; Heikkinen, S.; Zacchia, F.; Eaton, R.; Barabash, V.; Mitteau, R.

    2014-04-01

    ITER first wall (FW) panels are a layered structure made of the three following materials: 316L(N) austenitic stainless steel, CuCrZr alloy and beryllium. Two hot isostatic pressing (HIP) cycles are included in the reference fabrication route to bond these materials together for the normal heat flux design supplied by the European Union (EU). This reference fabrication route ensures sufficiently good mechanical properties for the materials and joints, which fulfil the ITER mechanical specifications, but often results in a coarse grain size for the CuCrZr alloy, which is not favourable, especially, for the thermal creep properties of the FW panels. To limit the abnormal grain growth of CuCrZr and make the ITER FW fabrication route more reliable, a study began in 2010 in the EU in the frame of an ITER task agreement. Two material fabrication approaches have been investigated. The first one was dedicated to the fabrication of solid CuCrZr alloy in close collaboration with an industrial copper alloys manufacturer. The second approach investigated was the manufacturing of CuCrZr alloy using the powder metallurgy (PM) route and HIP consolidation. This paper presents the main mechanical and microstructural results associated with the two CuCrZr approaches mentioned above. The mechanical properties of solid CuCrZr, PM CuCrZr and joints (solid CuCrZr/solid CuCrZr and solid CuCrZr/316L(N) and PM CuCrZr/316L(N)) are also presented.

  1. Effects of Mn on the mechanical properties and high temperature oxidation of 9Cr2WVTa steel

    NASA Astrophysics Data System (ADS)

    Jin, Xiaojie; Chen, Shenghu; Rong, Lijian

    2017-10-01

    The mechanical properties and high temperature oxidation behaviors of 9Cr2WVTa steels with Mn contents in the range of 0.04-0.93 wt% were investigated. There are no obvious differences in the tensile properties at room temperature and high temperature, only a slight reduction in the impact toughness when Mn content reaches 0.93 wt%. Remarkably, the high temperature oxidation resistance is significantly improved with an increase of Mn content. After 500 h of oxidation, a (Fe0.6Cr0.4)2O3 oxide scale is developed on the steel with 0.04 wt% Mn, Mn1.5Cr1.5O4 oxides are occasionally detected when Mn content reaches 0.47 wt%, while a thin compact scale with a mixture of Mn1.5Cr1.5O4 and Cr1.3Fe0.7O3 oxides is formed on the steel containing 0.93 wt% Mn. Addition of Mn promotes the formation of Mn-oxides, which lowers oxygen partial pressure and accelerates external oxidation of Cr. At last, the presence of Mn-Cr spinels and Cr-rich oxides improves the oxidation resistance.

  2. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al. Part 1; Oxidation Kinetics

    NASA Technical Reports Server (NTRS)

    Raj, S. V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu-17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9+/-9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17%Cr-5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR-5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

  3. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17%Cr and Cu-17%Cr-5%Al. Part 1; Oxidation Kinetics

    NASA Technical Reports Server (NTRS)

    Raj. Sai V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu- 17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 +/- 9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17%Cr- 5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR- 5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

  4. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17%Cr and Cu-17%Cr-5%Al. Part 1; Oxidation Kinetics

    NASA Technical Reports Server (NTRS)

    Raj. Sai V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu- 17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 9.5 kJ mol-1. In contrast, the oxidation kinetics for the Cu-17%Cr- 5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR- 5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

  5. Magnetic properties of CuCr2Se4 and CuCr1.5Ti0.5Se4

    NASA Astrophysics Data System (ADS)

    Behera, P. Suchismita; Bhobe, P. A.; Nigam, A. K.

    2016-05-01

    CuCr2Se4 is a potentially attractive versatile material, from the point of view of spintronics application. It shows characteristics of a ferromagnetic conductor at room temperature and with suitable doping it is proposed to show half-metallicity. With an aim to understand the effect of doping at Cr-site by a non-magnetic ion, we carried out investigation of magnetic and crystal structure properties of polycrystalline CuCr2Se4 and CuCr1.5Ti0.5Se4 spinel. These materials were prepared by solid state synthesis and characterized using room temperature powder XRD and measurement of magnetic properties. The XRD patterns were analyzed using Rietveld technique and lattice constants were estimated. Formation of a small amount of Cr3Se4 phase was identified from the XRD profiles. However, the magnetic properties do not seem to be affected much by it. Compared to parent compound, CuCr2Se4, the ferromagnetic Curie temperature TC in CuCr1.5Ti0.5Se4 was found to decrease to 208 K. But its magnetic moment (μB/f.u.) determined from the saturation magnetization value measured at 5 K, differed only slightly from that of CuCr2Se4. Our preliminary results are presented here.

  6. Synthesis, Structure and Properties of Tetragonal Sr2M3As2O2 (M3 = Mn3, Mn2Cu and MnZn2) Compounds Containing Alternating CuO2-Type and FeAs-Type Layers

    SciTech Connect

    Nath, R; Garlea, Vasile O; Goldman, Alan; Johnston, david C

    2010-01-01

    Polycrystalline samples of Sr2Mn2CuAs2O2, Sr2Mn3As2O2, and Sr2Zn2MnAs2O2 were synthesized. Their temperature- and applied magnetic field-dependent structural, transport, thermal, and magnetic properties were characterized by means of x-ray and neutron diffraction, electrical resistivity , heat capacity, magnetization and magnetic susceptibility measurements. These compounds have a body-centered-tetragonal crystal structure (space group I 4/mmm) that consists of MO2 (M = Zn and/or Mn) oxide layers similar to the CuO2 layers in high superconducting transition temperature Tc cuprate superconductors, and intermetallic MAs (M = Cu and/or Mn) layers similar to the FeAs layers in high-Tc pnictides. These two types of layers alternate along the crystallographic c-axis and are separated by Sr atoms. The site occupancies of Mn, Cu and Zn were studied using Rietveld refinements of x-ray and neutron powder diffraction data. The temperature dependences of suggest metallic character for Sr2Mn2CuAs2O2 and semiconducting character for Sr2Mn3As2O2 and Sr2Zn2MnAs2O2. Sr2Mn2CuAs2O2 is inferred to be a ferrimagnet with a Curie temperature TC = 95(1) K. Remarkably, we find that the magnetic ground state structure changes from a G-type antiferromagnetic structure in Sr2Mn3As2O2 to an A-type ferrimagnetic structure in Sr2Mn2CuAs2O2 in which the Mn ions in each layer are ferromagnetically aligned, but are antiferromagnetically aligned between layers.

  7. Prediction of half-metallic properties for the Heusler alloys Mn 2CrZ (Z=Al, Ga, Si, Ge, Sb): A first-principles study

    NASA Astrophysics Data System (ADS)

    Luo, Hongzhi; Zhu, Zhiyong; Liu, Guodong; Xu, Shifeng; Wu, Guangheng; Liu, Heyan; Qu, Jingping; Li, Yangxian

    First-principles FLAPW calculations were performed on the Mn 2CrZ ( Z=Al, Ga, Si, Ge and Sb) alloys. Based on these results we predict two half-metallic ferromagnets (HMFs) namely Mn 2CrAl and Mn 2CrSb, and also find an energy gap in Mn 2CrGa which lies near the Fermi level. The energy gap lies in the majority spin band for Mn 2CrAl and Mn 2CrGa, whereas in the minority one for Mn 2CrSb. The calculated total spin magnetic moments Mtcal are -1 μB per unit cell for Mn 2CrAl and Mn 2CrGa, +1 μB per unit cell for Mn 2CrSb and zero for Mn 2CrSi and Mn 2CrGe, which agree with the Slater-Pauling rule. The calculation indicates a large and localized magnetic moment of Cr at B site. This is meaningful for searching for new half-metallic antiferromagnets in Heusler alloys. The magnetic moment of Cr is found to increase with increasing atomic number of Z and is antiparallel to that of Mn. The change of Mn and Cr spin moments compensates each other and keeps the total spin moment as an integer when the Z atom is changed.

  8. Constraining the Material that Formed the Moon: The Origin of Lunar V, CR, and MN Depletions

    NASA Technical Reports Server (NTRS)

    Chabot, N. L.; Agee, C. B.

    2002-01-01

    The mantles of the Earth and Moon are similarly depleted in V, Cr, and Mn relative to chondritic values. Core formation deep within the Earth was suggested by as the origin of the depletions. Following Earth's core formation, the Moon was proposed to have inherited its mantle from the depleted mantle of the Earth by a giant impact event. This theory implied the Moon was primarily composed of material from the Earth's mantle. Recent systematic metal-silicate experiments of V, Cr, and Mn evaluated the behavior of these elements during different core formation scenarios. The study found that the V, Cr, and Mn depletions in the Earth could indeed be explained by core formation. The conditions of core formation necessary to deplete V, Cr, and Mn in the Earth's mantle were consistent with the deep magma ocean proposed to account for the Earth's mantle abundances of Ni and Co. Using the parameterizations of for the metal-silicate partition coefficients (D) of V, Cr, and Mn, we investigate here the conditions needed to match the depletions in the silicate Moon and determine if such conditions could have been present on the giant impactor.

  9. Physical properties of the tetragonal CuMnAs: A first-principles study

    NASA Astrophysics Data System (ADS)

    Máca, F.; Kudrnovský, J.; Drchal, V.; Carva, K.; Baláž, P.; Turek, I.

    2017-09-01

    Electronic, magnetic, and transport properties of the antiferromagnetic (AFM) CuMnAs alloy with tetragonal structure, promising for the AFM spintronics, are studied from first principles using the Vienna ab initio simulation package. We investigate the site occupation of sublattices and the lattice parameters of three competing phases. We analyze the factors that determine which of the three conceivable structures will prevail. We then estimate formation energies of possible defects for the experimentally prepared lattice structure. MnCu and CuMn antisites as well as MnCu swaps and vacancies on Mn or Cu sublattices were identified as possible candidates for defects in CuMnAs. We find that the interactions of the growing thin film with the substrate and with vacuum as well as the electron correlations are important for the phase stability while the effect of defects is weak. In the next step, using the tight-binding linear muffin-tin orbital method for the experimental structure, we estimate transport properties for systems containing defects with low formation energies. Finally, we determine the exchange interactions and estimate the Néel temperature of the AFM-CuMnAs alloy using the Monte Carlo approach. A good agreement of the calculated resistivity and Néel temperature with experimental data makes it possible to draw conclusions concerning the competing phases.

  10. The General Isothermal Oxidation Behavior of Cu-8Cr-4Nb

    NASA Technical Reports Server (NTRS)

    Thomas-Ogbuji, L. U.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Oxidation kinetics of Cu-8Cr-4Nb was investigated by TGA (thermogravimetric) exposures between 500 and 900-C (at 25-50 C intervals) and the oxide scale morphologies examined by microscopy and micro-analysis. Because Cu-8Cr-4Nb is comprised of fine Cr2Nb precipitates in a Cu matrix, the results were interpreted by comparison with the behavior of copper (OFHC) and 'NARloy-Z' (a rival candidate material for thrust cell liner applications in advanced rocket engines) under the same conditions. While NARloy-Z and Cu exhibited identical oxidation behavior, Cu-8Cr-4Nb differed markedly in several respects: below approx. 700 C its oxidation rates were significantly lower than those of Cu; At higher temperatures its oxidation rates fell into two categories: an initial rate exceeding that of Cu, and a terminal rate comparable to that of Cu. Differences in oxide morphologies paralleled the kinetic differences at higher temperature: While NARloy-Z and Cu produced a uniform oxide scale of Cu2O inner layer and CuO outer layer, the inner (Cu2O) layer on Cu-8Cr-4Nb was stratified, with a highly porous/spongy inner stratum (responsible for the fast initial kinetics) and a dense/blocky outer stratum (corresponding to the slow terminal kinetics). Single and spinel oxides of Nb and Cr were found at the interface between the oxide scale and Cu-8Cr-4Nb substrate and it appears that these oxides were responsible for its suppressed oxidation rates at the intermediate temperatures. No difference was found between Cu-8Cr-4Nb oxidation in air and in oxygen at 1.0 atm.

  11. Pressure-induced superconductivity in CrAs and MnP

    NASA Astrophysics Data System (ADS)

    Cheng, Jinguang; Luo, Jianlin

    2017-09-01

    Transition-metal monopnictides, CrAs and MnP, were studied over 50 years ago due to the presence of interesting magnetic properties: CrAs forms a double-helical magnetic structure below T N  ≈  270 K accompanied by a strong first-order structural transition, while MnP first undergoes a ferromagnetic transition at T C  ≈  290 K and then adopts a similar double-helical order below T s  ≈  50 K. Both compounds are correlated metals and exhibit distinct anomalies at these characteristic magnetic transitions. By using high pressure as a clean tuning knob, we recently observed superconductivity with a maximum superconducting transition temperature of T c  ≈  2 K and 1 K when their helimagnetic orders are suppressed under a critical pressure of P c  ≈  0.8 and 8 GPa for CrAs and MnP, respectively. Despite a relatively low T c, CrAs and MnP are respectively the first superconductor among the Cr- and Mn-based compounds in that the electronic density of states at the Fermi energy are dominated by Cr/Mn-3d electrons. These discoveries, in particular the close proximity of superconductivity to the helimagnetic order reminiscent of many unconventional superconducting systems, have attracted considerable attention in the community of superconductivity. The evolution of the helimagnetic order under pressure and its relationship with superconductivity have been actively investigated recently. Much effort has also been devoted to exploring more novel Cr- or Mn-based superconductors, leading to the discovery of quasi-1D A2Cr3As3 (A  =  K, Rb, Cs) superconductors. In this review article, we will summarize the current progress achieved regarding superconductivity in CrAs and MnP.

  12. Pressure-induced superconductivity in CrAs and MnP.

    PubMed

    Cheng, Jinguang; Luo, Jianlin

    2017-09-27

    Transition-metal monopnictides, CrAs and MnP, were studied over 50 years ago due to the presence of interesting magnetic properties: CrAs forms a double-helical magnetic structure below T N  ≈  270 K accompanied by a strong first-order structural transition, while MnP first undergoes a ferromagnetic transition at T C  ≈  290 K and then adopts a similar double-helical order below T s  ≈  50 K. Both compounds are correlated metals and exhibit distinct anomalies at these characteristic magnetic transitions. By using high pressure as a clean tuning knob, we recently observed superconductivity with a maximum superconducting transition temperature of T c  ≈  2 K and 1 K when their helimagnetic orders are suppressed under a critical pressure of P c  ≈  0.8 and 8 GPa for CrAs and MnP, respectively. Despite a relatively low T c, CrAs and MnP are respectively the first superconductor among the Cr- and Mn-based compounds in that the electronic density of states at the Fermi energy are dominated by Cr/Mn-3d electrons. These discoveries, in particular the close proximity of superconductivity to the helimagnetic order reminiscent of many unconventional superconducting systems, have attracted considerable attention in the community of superconductivity. The evolution of the helimagnetic order under pressure and its relationship with superconductivity have been actively investigated recently. Much effort has also been devoted to exploring more novel Cr- or Mn-based superconductors, leading to the discovery of quasi-1D A2Cr3As3 (A  =  K, Rb, Cs) superconductors. In this review article, we will summarize the current progress achieved regarding superconductivity in CrAs and MnP.

  13. Aging Characteristics of Sn-Ag Eutectic Solder Alloy with the Addition of Cu, In, and Mn

    NASA Astrophysics Data System (ADS)

    Ghosh, M.; Kar, Abhijit; Das, S. K.; Ray, A. K.

    2009-10-01

    In the present investigation, three types of solder alloy, i.e., Sn-Ag-Cu, Sn-Ag-In, and Sn-Ag-Cu-Mn, have been prepared and joined with Cu substrate. In the reflowed condition, the joint interface is decorated with Cu6Sn5 intermetallic in all cases. During aging at 100 °C for 50 to 200 hours, Cu3Sn formation took place in the diffusion zone of the Sn-Ag-Cu and Sn-Ag-In vs Cu assembly, which was not observed for the Sn-Ag-Cu-Mn vs Cu joint. Aging also leads to enhancement in the width of reaction layers; however, the growth is sluggish (~134 KJ/mol) for the Sn-Ag-Cu-Mn vs Cu transition joint. In the reflowed condition, the highest shear strength is obtained for the Sn-Ag-Cu-Mn vs Cu joint. Increment in aging time results in decrement in shear strength of the assemblies; yet small reduction is observed for the Sn-Ag-Cu-Mn vs Cu joint. The presence of Mn in the solder alloy is responsible for the difference in microstructure of the Sn-Ag-Cu-Mn solder alloy vs Cu assembly in the reflowed condition, which in turn influences the microstructure of the same after aging with respect to others.

  14. Experimental Study on Dynamic Mechanical Properties of 30CrMnSiNi2A Steel.

    NASA Astrophysics Data System (ADS)

    Huang, Fenglei; Yao, Wei; Wu, Haijun; Zhang, Liansheng

    2009-06-01

    Under dynamic conditions, the strain-rate dependence of material response and high levels of hydrostatic pressure cause the material behavior to be significantly different from what is observed under quasi-static condition. The curves of stress and strain of 30CrMnSiNi2A steel in different strain rates are obtained with SHPB experiments. Metallographic analyses show that 30CrMnSiNi2A steel is sensitive to strain rate, and dynamic compression leads to shear failure with the angle 45^o as the small carbide which precipitates around grain boundary changes the properties of 30CrMnSiNi2A steel. From the SHPB experiments and quasi-static results, the incomplete Johnson-Cook model has been obtained: σ=[1587+382.5(ɛ^p)^0.245][1+0.017ɛ^*], which can offer parameters for theory application and numerical simulation.

  15. Electronic structure, magnetic structure, and metal-atom site preferences in CrMnAs

    NASA Astrophysics Data System (ADS)

    Lutz, Laura Christine

    Density functional theory was used to examine stoichiometric CrMnAs, one of a class of 3d-metal arsenides that exhibit cooperative magnetic ordering. CrMnAs is a tetragonal structure with two inequivalent metal sites: M(I), which is tetrahedral coordinate, and M(II), which is square pyramidal coordinate. CrMnAs thus presents a "coloring problem," the question of how the two types of metal atoms are distributed between the two types of metal sites. Previous diffraction studies have determined that CrMnAs is antiferromagnetic with the M(I) site primarily occupied by Cr. TB-LMTO-ASA local density approximation (LDA) calculations showed indications of instability in the nonmagnetic structure, which could be resolved either by structural distortion or by spin polarization. LDA crystal orbital Hamilton population (COHP) curves were used to predict the nature of particular direct-exchange interactions upon spin polarization. Spin-polarized total energy calculations were performed using VASP with the generalized gradient approximation (GGA). The lowest-energy structure had Mn at the M(I) site and a different antiferromagnetic ordering than previously observed. The structure with the second-lowest calculated total energy also had Mn at M(I). Next lowest were four structures with Cr at M(I), including the experimentally observed structure. Those four had calculated total energies ranging from 154.2 to 167.8 meV/f.u. higher than the lowest-energy case. The number of possible structures with small energy differences suggests that the observed magnetic ordering and coloring may be due to entropy rather than reflecting a true electronic ground state.

  16. Cu and Cu(Mn) films deposited layer-by-layer via surface-limited redox replacement and underpotential deposition

    NASA Astrophysics Data System (ADS)

    Fang, J. S.; Sun, S. L.; Cheng, Y. L.; Chen, G. S.; Chin, T. S.

    2016-02-01

    The present paper reports Cu and Cu(Mn) films prepared layer-by-layer using an electrochemical atomic layer deposition (ECALD) method. The structure and properties of the films were investigated to elucidate their suitability as Cu interconnects for microelectronics. Previous studies have used primarily a vacuum-based atomic layer deposition to form a Cu metallized film. Herein, an entirely wet chemical process was used to fabricate a Cu film using the ECALD process by combining underpotential deposition (UPD) and surface-limited redox replacement (SLRR). The experimental results indicated that an inadequate UPD of Pb affected the subsequent SLRR of Cu and lead to the formation of PbSO4. A mechanism is proposed to explain the results. Layer-by-layer deposition of Cu(Mn) films was successfully performed by alternating the deposition cycle-ratios of SLRR-Cu and UPD-Mn. The proposed self-limiting growth method offers a layer-by-layer wet chemistry-based deposition capability for fabricating Cu interconnects.

  17. Cu- and Mn-bearing tourmalines from Brazil and Mozambique: crystal structures, chemistry and correlations.

    PubMed

    Ertl, Andreas; Giester, Gerald; Schüssler, Ulrich; Brätz, Helene; Okrusch, Martin; Tillmanns, Ekkehart; Bank, Hermann

    Cu- and Mn-bearing tourmalines from Brazil and Mozambique were characterised chemically (EMPA and LA-ICP-MS) and by X-ray single-crystal structure refinement. All these samples are rich in Al, Li and F (fluor-elbaite) and contain significant amounts of CuO (up to ~1.8 wt%) and MnO (up to ~3.5 wt%). Structurally investigated samples show a pronounced positive correlation between the distances and the (Li + Mn(2+) + Cu + Fe(2+)) content (apfu) at this site with R(2) = 0.90. An excellent negative correlation exists between the distances and the Al2O3 content (R(2) = 0.94). The samples at each locality generally show a strong negative correlation between the X-site vacancies and the (MnO + FeO) content. The Mn content in these tourmalines depends on the availability of Mn, on the formation temperature, as well as on stereochemical constraints. Because of a very weak correlation between MnO and CuO we believe that the Cu content in tourmaline is essentially dependent on the availability of Cu and on stereochemical constraints.

  18. Cu- and Mn-bearing tourmalines from Brazil and Mozambique: crystal structures, chemistry and correlations

    NASA Astrophysics Data System (ADS)

    Ertl, Andreas; Giester, Gerald; Schüssler, Ulrich; Brätz, Helene; Okrusch, Martin; Tillmanns, Ekkehart; Bank, Hermann

    2013-04-01

    Cu- and Mn-bearing tourmalines from Brazil and Mozambique were characterised chemically (EMPA and LA-ICP-MS) and by X-ray single-crystal structure refinement. All these samples are rich in Al, Li and F (fluor-elbaite) and contain significant amounts of CuO (up to ~1.8 wt%) and MnO (up to ~3.5 wt%). Structurally investigated samples show a pronounced positive correlation between the < Y-O> distances and the (Li + Mn2+ + Cu + Fe2+) content (apfu) at this site with R 2 = 0.90. An excellent negative correlation exists between the < Y-O> distances and the Al2O3 content ( R 2 = 0.94). The samples at each locality generally show a strong negative correlation between the X-site vacancies and the (MnO + FeO) content. The Mn content in these tourmalines depends on the availability of Mn, on the formation temperature, as well as on stereochemical constraints. Because of a very weak correlation between MnO and CuO we believe that the Cu content in tourmaline is essentially dependent on the availability of Cu and on stereochemical constraints.

  19. Crystal structure and magnetic properties of titanium-based CuTi2-xMxS4 and CuCr2-xTixSe4 chalcospinels

    NASA Astrophysics Data System (ADS)

    Barahona, P.; Galdámez, A.; López-Vergara, F.; Manríquez, V.; Peña, O.

    2014-04-01

    CuTi2-xMxS4 (M=Fe, Mn, Co; x=0.3, 0.5) and CuCr2-xTixSe4 (x=0.3, 0.5, 0.7) chalcospinels were synthesized by conventional solid-state reactions. Their crystal structures were determined by single-crystal X-ray diffraction. All of the phases crystallized in cubic spinel-type structures (space group, Fd 3 bar m). For all of the chalcospinel compounds, the edge-length distortion parameter (ELD) indicated that the most distorted polyhedron was Q[(Ti,M)3Cu], which displayed an ~8% distortion from an ideal tetrahedron structure (Q=S or Se). The Mn-based thiospinel CuMn0.3Ti1.7S4 is paramagnetic, whereas the Fe-based thiospinels (CuTi2-xFexS4; x=0.3 and 0.7) are strongly antiferromagnetic due to their spin-glass states. The magnetic susceptibility measurements indicated ferromagnetic behavior for the selenospinels (CuCr2-xTixSe4; x=0.3, 0.5 and 0.7).

  20. Oxidation behavior of cubic phases formed by alloying Al3Ti with Cr and Mn

    NASA Technical Reports Server (NTRS)

    Parfitt, L. J.; Nic, J. P.; Mikkola, D. E.; Smialek, J. L.

    1991-01-01

    Gravimetric, SEM, and XRD data are presented which document the significant improvement obtainable in the oxidation resistance of Al3Ti-containing alloys through additions of Cr. The L1(2) Al(67)Cr(8)Ti25 alloy exhibited excellent cyclic oxidation resistance at 1473 K, with the primary oxide formed being the ideally protective alpha-Al2O3. The Al(67)Mn(8)Ti(25) alloy also tested for comparison exhibited poor cyclic oxidation resistance, with substantial occurrence of TiO2 in the protective scales. Catastrophic oxidation was also encountered in the quaternary alloy Al(67)Mn(8)Ti(22)V(3).

  1. Multiferroicity in B-site ordered double perovskite Y2MnCrO6

    NASA Astrophysics Data System (ADS)

    Fang, Yong; Yan, Shi-Ming; Qiao, Wen; Wang, Wei; Wang, Dun-Hui; Du, You-Wei

    2014-11-01

    Double perovskite manganite Y2MnCrO6 ceramic is synthesized and its multiferroic properties are investigated. Novel multiferroic properties are displayed with respect to other multiferroics, such as high ferroelectric phase transition temperature, and the coexistence of ferrimagnetism and ferroelectricity. Moreover, the ferroelectric polarization of Y2MnCrO6 below the magnetic phase temperature can be effectively tuned by an external magnetic field, showing a remarkable magnetoelectric effect. These results open an effective avenue to explore magnetic multiferroics with spontaneous magnetization and ferroelectricity, as well as a high ferroelectric transition temperature.

  2. Oxidation behavior of cubic phases formed by alloying Al3Ti with Cr and Mn

    NASA Technical Reports Server (NTRS)

    Parfitt, L. J.; Nic, J. P.; Mikkola, D. E.; Smialek, J. L.

    1991-01-01

    Gravimetric, SEM, and XRD data are presented which document the significant improvement obtainable in the oxidation resistance of Al3Ti-containing alloys through additions of Cr. The L1(2) Al(67)Cr(8)Ti25 alloy exhibited excellent cyclic oxidation resistance at 1473 K, with the primary oxide formed being the ideally protective alpha-Al2O3. The Al(67)Mn(8)Ti(25) alloy also tested for comparison exhibited poor cyclic oxidation resistance, with substantial occurrence of TiO2 in the protective scales. Catastrophic oxidation was also encountered in the quaternary alloy Al(67)Mn(8)Ti(22)V(3).

  3. Microdomain Structure of Cr-Doped Manganites: Nd 1/2Ca 1/2(Mn,Cr)O 3

    NASA Astrophysics Data System (ADS)

    Machida, Akihiko; Moritomo, Yutaka; Nishibori, Eiji; Takata, Masaki; Sakata, Makoto; Ohoyama, Kenji; Mori, Shigeo; Yamamoto, Naoki; Nakamura, Arao

    2000-11-01

    Crystal and magnetic structures of Cr-doped manganites, Nd1/2Ca1/2Mn1-yCryO3 (y=0.00 and 0.03), have been investigated by synchrotron radiation (SR) x-ray powder diffraction as well as neutron powder diffraction measurements.A detailed analysis of the high-resolution x-ray profile has revealed that the Cr-doped compound exhibits broad extra reflections, suggesting the formation of microdomains below the charge-ordering temperature T CO.The origin of the microdomain structure is discussed in terms of the charge separation.

  4. Mn-53-Cr-53 Systematics of R-Chondrite NWA 753

    NASA Technical Reports Server (NTRS)

    Jogo, K.; Shih, C-Y.; Reese, Y. D.; Nyquist, L. E.

    2006-01-01

    Chondrules and chondrites are interpreted as objects formed in the early solar system, and it is important to study them in order to elucidate its evolution. Here, we report the study of the Mn-Cr systematics of the R-Chondrite NWA753 and compare the results to other chondrite data. The goal was to determine Cr isotopic and age variations among chondrite groups with different O-isotope signatures. The Mn-53-Cr-53 method as applied to individual chondrules [1] or bulk chondrites [2] is based on the assumption that 53Mn was initially homogeneously distributed in that portion the solar nebula where the chondrules and/or chondrites formed. However, different groups of chondrites formed from regions of different O-isotope compositions. So, different types of chondrites also may have had different initial Mn-53 abundances and/or Cr isotopic compositions. Thus, it is important to determine the Cr isotopic systematics among chondrites from various chondrite groups. We are studying CO-chondrite ALH83108 and Tagish Lake in addition to R-Chondrite NWA753. These meteorites have very distinct O-isotope compositions (Figure 1).

  5. Characterization of transparent conductive delafossite-CuCr1-xO2 films

    NASA Astrophysics Data System (ADS)

    Chen, Hong-Ying; Chang, Kuei-Ping; Yang, Chun-Chao

    2013-05-01

    In this study, the CuCr1-xO2 films with x = 0.00-0.25 were prepared on a quartz substrate by sol-gel processing. The films were first deposited onto a quartz substrate by spin-coating. The specimens were annealed at 500 °C in air for 1 h and post-annealed in N2 at 700 °C for 2 h. As the films were post-annealed in N2, a pure delafossite-CuCrO2 phase appeared in the CuCr1-xO2 films below x = 0.20. However, an additional CuO phase appeared at x = 0.25. The pure delafossite-CuCrO2 phase can exist within x ≤ 0.20 in CuCr1-xO2 films. The binding energies of Cu-2p3/2 and Cr-2p3/2 in the CuCr1-xO2 films with the pure delafossite-CuCrO2 phase were 932.1 ± 0.2 eV and 576.0 ± 0.2 eV, respectively. The surface exhibited elongated grain features when the pure delafossite-CuCrO2 phase was present in the CuCr1-xO2 films. The maximum transmittance of the CuCr1-xO2 films with the pure delafossite-CuCrO2 phase was approximately 80%, which moved toward the visible region with the increasing x-value. The film absorption edges were observed at 400 nm, which were sharper with the increasing x-value. The optical bandgaps of CuCr1-xO2 films with the pure delafossite-CuCrO2 phase were approximately 3.0 eV. The electrical conductivity of CuCr1-xO2 films with the pure delafossite-CuCrO2 phase was 1.1 × 10-3 S cm-1 (x = 0.00), and increased to 0.16 S cm-1 (x = 0.20). The corresponding carrier concentration of CuCr1-xO2 films with the pure delafossite-CuCrO2 phase was 2.8 × 1014 cm-3 (x = 0.00), and markedly increased to 1.8 × 1016 cm-3 (x = 0.20). The Cr-deficient condition in delafossite-CuCrO2 films enhances film electrical conductivity and carrier concentration, but retains the film's high-visible transparency.

  6. Cr, Cu, Mn, Mo, Ni, and Steel Price Drivers

    USGS Publications Warehouse

    Papp, John F.; Corathers, Lisa A.; Edelstein, Daniel L.; Fenton, Michael D.; Kuck, Peter H.; Magyar, Michael J.

    2007-01-01

    Summary This report contains the 55 slide images from a presentation made by the author at the meeting of the Metal Powder Industries Federation held in Denver, CO, on May 15, 2007. The Metal Powder Industries Federation (MPIF) invited the U.S. Geological Survey (USGS) to speak at their annual meeting about the price drivers for chromium, copper, manganese, molybdenum, nickel, and steel. These metals are of interest to MPIF because the prices of these raw materials used by their industry were at historically high levels. Because the USGS closely monitors, yet neither buys nor sells, metal commodities, it is an unbiased source of metal price information and analysis. The authors used information about these and other metals collected and published by the USGS (U.S. production, trade, stocks, and prices) and about consumption and stocks internationally by country from industry organizations that publish such information, because metal markets are influenced by activities and events over the entire globe. By seeking a common cause for common behavior among the various metal commodities, the authors found that major price drivers on metal commodities were inflation, major international events such as wars and recessions, and major national events such as the dissolution of the Soviet Union in 1991 and economic growth in China, which started with the open door policy in the 1970s but did not have significant market impact until starting in the 1990s. Metal commodity prices also responded to commodity-specific events.

  7. Magnetic and crystallographic properties of ZrM2-delta Zn20+delta (M=Cr-Cu)

    DOE PAGES

    Svanidze, E.; Kindy II, M; Georgen, C.; ...

    2016-10-15

    Single crystals of the cubic Laves ternaries ZrM2-delta Zn20+delta (M=Mn, Fe, Co, Ni and Cu, 0 <= delta <= 1) have been synthesized using a self-flux method. The magnetic properties of these compounds were compared with structurally similar cubic binaries ZrM2 (M=Mn, Fe, Co, Ni and Cu). A transition from local to itinerant moment magnetism was observed for M=Fe and M=Mn, while all other ternaries exhibit weakly para- or diamagnetic behavior. The local-to-itinerant crossover can be explained by a nearly two-fold increase of the M-M bond length d(M-M) in ZrM2-delta Zn20+delta compounds, as compared with the ZrM2 binaries. Additionally, wemore » report two new compounds in this series ZrCrZn21 and ZrCu2Zn20. Analysis of crystallographic and magnetic trends in these materials will aid in understanding of magnetism in general and 3d intermetallics in particular. (C) 2016 Elsevier B.V. All rights reserved.« less

  8. Magnetic and crystallographic properties of ZrM2-delta Zn20+delta (M=Cr-Cu)

    SciTech Connect

    Svanidze, E.; Kindy II, M; Georgen, C.; Fulfer, B.; Lapidus, S. H.; Chan, J. Y.; Morosan, E.

    2016-10-15

    Single crystals of the cubic Laves ternaries ZrM2-delta Zn20+delta (M=Mn, Fe, Co, Ni and Cu, 0 <= delta <= 1) have been synthesized using a self-flux method. The magnetic properties of these compounds were compared with structurally similar cubic binaries ZrM2 (M=Mn, Fe, Co, Ni and Cu). A transition from local to itinerant moment magnetism was observed for M=Fe and M=Mn, while all other ternaries exhibit weakly para- or diamagnetic behavior. The local-to-itinerant crossover can be explained by a nearly two-fold increase of the M-M bond length d(M-M) in ZrM2-delta Zn20+delta compounds, as compared with the ZrM2 binaries. Additionally, we report two new compounds in this series ZrCrZn21 and ZrCu2Zn20. Analysis of crystallographic and magnetic trends in these materials will aid in understanding of magnetism in general and 3d intermetallics in particular. (C) 2016 Elsevier B.V. All rights reserved.

  9. Magnetic and crystallographic properties of ZrM2-δZn20+δ (M=Cr-Cu)

    NASA Astrophysics Data System (ADS)

    Svanidze, E.; , M. Kindy, II; Georgen, C.; Fulfer, B. W.; Lapidus, S. H.; Chan, J. Y.; Morosan, E.

    2016-10-01

    Single crystals of the cubic Laves ternaries ZrM2-δZn20+δ (M=Mn, Fe, Co, Ni and Cu, 0 ≤ δ ≤ 1) have been synthesized using a self-flux method. The magnetic properties of these compounds were compared with structurally similar cubic binaries ZrM2 (M=Mn, Fe, Co, Ni and Cu). A transition from local to itinerant moment magnetism was observed for M=Fe and M=Mn, while all other ternaries exhibit weakly para- or diamagnetic behavior. The local-to-itinerant crossover can be explained by a nearly two-fold increase of the M- M bond length dM-M in ZrM2-δZn20+δ compounds, as compared with the ZrM2 binaries. Additionally, we report two new compounds in this series ZrCrZn21 and ZrCu2Zn20. Analysis of crystallographic and magnetic trends in these materials will aid in understanding of magnetism in general and 3 d intermetallics in particular.

  10. Density functional investigation of the magnetic superstructure of Cu2MnSnS4

    NASA Astrophysics Data System (ADS)

    Koo, Hyun-Joo

    2012-09-01

    The cause for the ordered magnetic structure of Cu2MnSnS4 below TN=8.8 K was examined by evaluating the spin exchange interactions on the basis of density functional electronic structure calculations. The Mn-S…S-Mn super-superexchange interactions of Cu2MnSnS4 are all calculated to be antiferromagnetic. In the (2a, b, 2c) magnetic superstructure observed from the neutron diffraction, only one spin exchange contributes to the energy lowering. This makes the (2a, b, c) antiferromagnetic superstructure identical in energy with the (2a, b, 2c) antiferromagnetic superstructure, implying that the magnetic Bragg peaks of Cu2MnSnS4 below TN have contributions from both (2a, b, c) and (2a, b, 2c) superstructures.

  11. Protection of Advanced Copper Alloys With Lean Cu-Cr Coatings

    NASA Technical Reports Server (NTRS)

    Greenbauer-Seng, L. (Technical Monitor); Thomas-Ogbuji, L.

    2003-01-01

    Advanced copper alloys are used as liners of rocket thrusters and nozzle ramps to ensure dissipation of the high thermal load generated during launch, and Cr-lean coatings are preferred for the protection of these liners from the aggressive ambient environment. It is shown that adequate protection can be achieved with thin Cu-Cr coatings containing as little as 17 percent Cr.

  12. The role of organics in the oxidative release of Cr(VI) from Cr(OH)3 by δ-MnO2

    NASA Astrophysics Data System (ADS)

    Watts, M. P.; Hanssen, E.; Moreau, J. W.

    2015-12-01

    The environmental release of the toxic and mobile Cr(VI) from poorly soluble and non-toxic Cr(III) mineral phases primarily occurs via oxidation by Mn(IV) oxides. This process accounts for the contamination of a number of natural and anthropogenically perturbed environments. The mechanism and controls upon the reaction of Mn(IV) oxides with insoluble Cr(III) minerals remain poorly understood. Further to this, despite near ubiquity in nature and a number of studies investigating Mn(IV) oxides reactivity towards natural organic compounds, few studies have assessed the impact of organics upon the oxidation of Cr(III) minerals by Mn(IV) oxides. This study aimed to determine the changes in redox state of the Cr and Mn during reactions between the environmentally dominant Cr(OH)3 and δ-MnO2 minerals, under circum-neutral conditions, in the presence and absence of organic and humic acids. We used a combination of aqueous analytical techniques, alongside cryo-TEM-EELS which enabled mapping of the Cr and Mn redox state of the solid phases at the nanometre scale. In the absence of organic compounds, a steady but significant release of Cr(VI) occurred prior to cessation of the reaction, despite the presence of a large pool of un-reacted Cr(III) and Mn(IV). Analysis using cryo-TEM-EELS suggests a passivation mechanism, through the detection of Mn(II) at the Cr and Mn mineral surface. The presence of oxalate and citrate variably promoted and inhibited Cr(VI) release, depending upon their concentrations relative to the mineral phases. The presence of humic acids, however, invariably promoted Cr(VI) release under the conditions tested. The complex impacts of organics on Cr(VI) release by δ-MnO2-mediated oxidation of Cr(OH)3 result from the various roles that organics can play in the reaction, acting as complexants, reductants and adsorbing species.

  13. {sup 53}Mn-{sup 53}Cr CHRONOMETRY OF CB CHONDRITE: EVIDENCE FOR UNIFORM DISTRIBUTION OF {sup 53}Mn IN THE EARLY SOLAR SYSTEM

    SciTech Connect

    Yamashita, Katsuyuki; Yamakawa, Akane; Nakamura, Eizo; Maruyama, Seiji

    2010-11-01

    High-precision Cr isotope ratios for chondrules and metal grain separated from CB chondrite Gujba were determined. The {epsilon}{sup 54}Cr values ({epsilon}{sup i}Cr = [({sup i}Cr/{sup 52}Cr){sub sample}/({sup i}Cr/{sup 52}Cr){sub standard} - 1] x 10{sup 4}) for all samples were identical within the analytical uncertainty, with a mean value of +1.29 {+-} 0.02. Uniform {epsilon}{sup 54}Cr signatures of both chondrules and metal grains imply that the Cr isotope systematics of the meteorite was once completely equilibrated. The {epsilon}{sup 53}Cr values of the chondrules and metal grain, on the other hand, display a strong correlation with the {sup 55}Mn/{sup 52}Cr ratio. The {sup 53}Mn/{sup 55}Mn calculated from the slope of the isochron is (3.18 {+-} 0.52) x 10{sup -6}. This corresponds to absolute ages of 4563.7 {+-} 1.2 Ma and 4563.5 {+-} 1.1 Ma using angrites D'Orbigny and LEW 86010, respectively, as time anchors. These ages are consistent with the ages obtained using other short- and long-lived radio nuclides, supporting the uniform distribution of {sup 53}Mn in the early solar nebula.

  14. Optical spectroscopy of the Triangular Lattice Antiferromagnets CuCrO2 and α-CaCr2O4

    NASA Astrophysics Data System (ADS)

    Schmidt, Michael; Wang, Zhe; Mayr, F.; Toth, S.; Lake, B.; Islam, A. T. M. N.; Tsurkan, V.; Loidl, A.; Deisenhofer, J.

    2012-02-01

    We will compare and discuss our results obtained by optical spectroscopy on CuCrO2 and α-CaCr2O4. While CuCrO2 is famous for its multiferroicity [1], in α-CaCr2O4 a polarization can only be observed under the application of electric or magnetic field, despite having a closely related structure [2]. At near infrared and visible light frequencies we observe Cr^3+ crystal field absorptions and below TN excitons and exciton-magnon-transitions appear. The width of these exciton-magnon transitions is analyzed with respect to the existence of Z2 vortices as proposed by Kojima et al. [3]. [4pt] [1] S. Seki et al., Phys. Rev. Lett. 101, 067240 (2008)[0pt] [2] K. Singh et al., Phys. Rev. B 84, 064129 (2011)[0pt] [3] N. Kojima et al., J. Phys. Soc. Jpn. 62, 4137 (1993)

  15. Neutron diffraction studies on single crystals in the NiAs-type system MnSb-CrSb

    NASA Astrophysics Data System (ADS)

    Reimers, W.; Hellner, E.; Treutmann, W.; Brown, P. J.; Heger, G.

    1980-01-01

    A more detailed magnetic phase diagram of the system MnSb-CrSb has been established. A polarised neutron diffraction study has been performed on a Mn 1.10Sb crystal. Some ideas on the electronic structure of the system Mn 1+σSb (0 ⩽ σ ⩽ 0.22) are given.

  16. 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.

  17. Naturally Occurring Cr and Ni in the Sacramento Valley: II. Mn Oxides and the Mobility of Cr(VI) and Ni

    NASA Astrophysics Data System (ADS)

    Mills, C. T.; Morrison, J. M.; Goldhaber, M. B.; Foster, A. L.; Wolf, R. E.; Wanty, R. B.

    2007-12-01

    Soil manganese oxides can strongly affect the mobility and redox state of several toxic trace metals. We are studying the biogeochemical origin of Mn oxides and their association with Cr and Ni in soils of the Sacramento Valley, California. Both Cr and Ni are likely derived from ultramafic rocks that underlie Coast Range drainages to the west of the study area. The impact of weathering and erosion of these rocks is evident in the high levels of total Cr (80 to 1420 μg g-1) and nickel (65 to 224 μg g-1) that occur broadly in western Sacramento Valley soils. Although much of the Cr is bound in refractory spinels as Cr(III), some mobilization of Cr is apparent in the coincidence of enriched soils with high contents of Cr(VI) in ground water. Data from the National Water Information System (NWIS) shows 7 of 12 sampled wells within a 600 km2 area in the Sacramento Valley having Cr(VI) concentrations between 60 and 100% of the CA maximum contaminant level for drinking water (50 μg l-1). A 3-meter depth soil profile collected within the lower Putah Creek watershed was examined to investigate processes contributing to the oxidation and mobilization of natural Cr(III). Hydroxylamine hydrochloride-reducible Mn was determined for 8 depth intervals as a measure of manganese oxide occurrence. Concentrations of reducible Mn varied between 360 and 690 μg g-1 with depth and peaked at 2.7 m below the surface. Concentrations of anion exchangeable Cr(VI) were as high as 6 ng g-1 and were positively correlated (r2=0.59; p=0.07) with reducible Mn. Scanning electron microscopy of soil minerals from the 2.9 to 3.0 m interval showed Cr-bearing spinel grains enclosed within Mn oxide micro concretions suggesting a potential mechanism for the oxidation of natural Cr(III) to mobile Cr(VI). Consistent with the known tendency of Ni to sorb on Mn oxides, substantial Ni (13 to 45 μg g-1) was released in the reducible Mn fraction and it strongly correlates (r2=0.76; p=0.005) with reducible Mn

  18. Electrical properties of perovskite-type La(Cr 1- xMn x)O 3+ δ

    NASA Astrophysics Data System (ADS)

    Taguchi, Hideki; Matsu-ura, Shin-ichiro; Nagao, Mahiko; Kido, Hiroyasu

    1999-10-01

    Perovskite-type La(Cr 1- xMn x)O 3+ δ (0.0⩽ x⩽1.0) was synthesized using a sol-gel process. The crystal structure of La(Cr 1- xMn x)O 3+ δ changes from orthorhombic to rhombohedral at x=0.6. The Mn 4+ ion content increases monotonically in the range 0.2⩽ x⩽1.0. The magnetic measurement of La(Cr 1- xMn x)O 3+ δ indicates that a Mn 3+ ion is a high-spin state with (d ε) 3(d γ) 1. The variation of the average (Cr, Mn)-O distance is explained by ionic radii of the Cr 3+, the Mn 3+, the Mn 4+ ions. Since the log σT-1/ T curve is linear and the Seebeck coefficient ( α) is independent of temperature, it is considered that La(Cr 1- xMn x)O 3+ δ is a p-type semiconductor and exhibits the hopping conductivity.

  19. Electronic Structure of Halogen Doped CuCr2Se4

    SciTech Connect

    Arenholz, Elke; Liberati, M.; Neulinger, J. R.; Chopdekar, R.V.; Bettinger, J.S.; Arenholz, E.; Butler, W.; Stacy, A.M.; Idzerda, Y.I.; Suzuki, Y.

    2008-09-13

    We have employed element and chemically sensitive X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) in order to address a long standing controversy regarding the electronic and magnetic state of CuCr{sub 2}Se{sub 4} via halogen doping of the Se anion site in CuCr{sub 2}Se{sub 4-x}Y{sub x} (Y=Cl and Br). Long range magnetic order is observed above room temperature for all samples. The Cr L{sub 2,3} XAS spectra show a prevalent 3+ valence for the Cr ions independent of doping concentration and doping agent. The Cu L{sub 2,3} XAS spectra show a combination of 1+ and 2+ valence states for all samples. XMCD spectra indicate the presence of a magnetic moment associated with the Cu ions that is aligned antiparallel to the Cr moment.

  20. A new Cu-8 Cr-4 Nb alloy for high temperature applications

    SciTech Connect

    Ellis, D.L.; Michal, G.M.; Dreshfield, R.L.

    1995-06-01

    Various applications exist where a high conductivity alloy with good strength and creep resistance are required. NASA LeRC has developed a Cu-8 at. percent Cr-4 at. percent Nb (Cu-8 Cr-4 Nb) alloy for these applications. The alloy is designed for use up to 700 C and shows exceptional strength, low cycle fatigue (LCF) resistance, and creep resistance. Cu-8 Cr-4 Nb also has a thermal conductivity of at least 72 percent that of pure Cu. Furthermore, the microstructure and mechanical properties of the alloy are very stable. In addition to the original application in combustion chambers, Cu-8 Cr-4 Nb shows promise for welding electrodes, brazing fixtures, and other applications requiring high conductivity and strength at elevated temperatures.

  1. A new Cu-8 Cr-4 Nb alloy for high temperature applications

    NASA Technical Reports Server (NTRS)

    Ellis, D. L.; Michal, G. M.; Dreshfield, R. L.

    1995-01-01

    Various applications exist where a high conductivity alloy with good strength and creep resistance are required. NASA LeRC has developed a Cu-8 at. percent Cr-4 at. percent Nb (Cu-8 Cr-4 Nb) alloy for these applications. The alloy is designed for use up to 700 C and shows exceptional strength, low cycle fatigue (LCF) resistance, and creep resistance. Cu-8 Cr-4 Nb also has a thermal conductivity of at least 72 percent that of pure Cu. Furthermore, the microstructure and mechanical properties of the alloy are very stable. In addition to the original application in combustion chambers, Cu-8 Cr-4 Nb shows promise for welding electrodes, brazing fixtures, and other applications requiring high conductivity and strength at elevated temperatures.

  2. Room temperature magnetocaloric effect in Ni-Mn-In-Cr ferromagnetic shape memory alloy thin films

    NASA Astrophysics Data System (ADS)

    Akkera, Harish Sharma; Singh, Inderdeep; Kaur, Davinder

    2017-02-01

    The influence of Cr substitution for In on the martensitic phase transformation and magnetocaloric effect (MCE) has been investigated in Ni-Mn-Cr-In ferromagnetic shape memory alloy (FSMA) thin films fabricated by magnetron sputtering. Temperature dependent magnetization (M-T) measurements demonstrated that the martensitic transformation temperatures (TM) monotonously increase with the increase of Cr content due to change in valence electron concentration (e/a) and cell volume. From the study of isothermal magnetization curves (M-H), magnetocaloric effect around the martensitic transformation has been investigated in these FSMA thin films. The magnetic entropy change ∆SM of 7.0 mJ/cm3-K was observed in Ni51.1Mn34.9In9.5Cr4.5 film at 302 K in an applied field of 2 T. Further, the refrigerant capacity (RC) was also calculated for all the films in an applied field of 2 T. These findings indicate that the Cr doped Ni-Mn-In FSMA thin films are potential candidates for room temperature micro-length-scale magnetic refrigeration applications.

  3. Structure, magnetism, and electron-transport properties of Mn2CrGa-based nanomaterials

    NASA Astrophysics Data System (ADS)

    Zhang, Wenyong; Kharel, Parashu; Skomski, Ralph; Valloppilly, Shah; Li, Xingzhong; Sellmyer, David J.

    2016-05-01

    Mn2CrGa in the disordered cubic structure has been synthesized using rapid quenching and subsequent annealing. The cubic phase transforms to a stable tetragonal phase when a fraction of Cr or Ga is replaced by Pt or Al, respectively. All samples are ferrimagnetic with high Curie temperatures (Tc); Mn2CrGa exhibits the highest Tc of about 813 K. The tetragonal samples have appreciable values of magnetocrystalline anisotropy energy, which leads to an increase in coercivity (Hc) that approaches about 10 kOe in the Pt-doped sample. The Hc linearly increases with a decrease of temperature, concomitant with the anisotropy change with temperature. All samples are metallic and show negative magnetoresistance with room-temperature resistivities on the order of 1 mΩcm. The magnetic properties including high Tc and low magnetic moment suggest that these tetragonal materials have potential for spin-transfer-torque-based devices.

  4. Ferromagnetic behavior of nanocrystalline Cu-Mn alloy prepared by ball milling

    NASA Astrophysics Data System (ADS)

    Mondal, B. N.; Sardar, G.; Nath, D. N.; Chattopadhyay, P. P.

    2014-12-01

    50Cu-50Mn (wt%) alloy was produced by ball milling. The milling was continued up to 30 h followed by isothermal annealing over a four interval of temperature from 350 to 650 °C held for 1 h. Crystallite size, lattice strain, lattice parameter were determined by Rietveld refinement structure analysis of X-ray diffraction data. The amount of dissolved/precipitated Mn (wt%) after ball milling/milling followed by annealing was calculated by quantative phase analysis (QPA). The increase of coercivity could be attributed to the introduction of lattice strain and reduction of crystallite size as a function of milling time. Electron paramagnetic resonance and superconducting quantum interface device analysis indicate that soft ferromagnetic behavior has been achieved by ball milled and annealed Cu-Mn alloy. The maximum coercivity value of Cu-Mn alloy obtained after annealing at 350 °C for 1 h is 277 Oe.

  5. Novel synthesis and shape-dependent catalytic performance of Cu-Mn oxides for CO oxidation

    NASA Astrophysics Data System (ADS)

    Li, Zhixun; Wang, Honglei; Wu, Xingxing; Ye, Qinglan; Xu, Xuetang; Li, Bin; Wang, Fan

    2017-05-01

    Transition metal oxides with large specific surface area are attractive for high-activity catalysts, and hierarchical structures of transition metal oxides with porous feature possess the structural advantage in the transfer of gaseous reactant and product. In this work, porous Cu-Mn oxides with high surface area were successfully obtained through low-temperature coprecipitation method in alcohol/water solvent and then post-annealing. The addition of alcohol showed great influences on the shape and catalytic performances for CO oxidation. Dumbbell-like Cu-Mn oxide particles with splitting ends displayed high catalytic activity and a complete conversion of CO was achieved at 45 °C, suggesting a shape-dependent catalytic activity. The oxidative activity was attributed to a combination of factors including specific surface area, active surface oxygen species and Mn(IV) cations. The results may supply a new thought to design high-performance Cu-Mn oxide catalysts.

  6. Reentrant behavior in Cr doped bilayer manganite LaSr2Mn2O7

    NASA Astrophysics Data System (ADS)

    Bhatia, S. N.; Mohapatra, Niharika

    2017-07-01

    We have studied the effect of replacing Mn3+ by Cr3+ on the structure, transport and magnetism in the bilayered manganite LaSr2Mn2O7. Although no structural transition was observed in LaSr2Mn2-yCryO7 (0.1 ≤ y ≤ 0.6), the electrical transport and the magnetic properties were found to be affected significantly by this substitution. Substitution of Cr3+ reduces the conductivity by restricting the hopping of small polarons. Magnetization increases with increasing Cr3+ concentration suggesting that Cr3+-ions induce ferromagnetic moments. The ferromagnetic and an antiferromagnetic phase observed above ∼60 K merge into an inhomogeneous phase below this temperature. Thermopower yields an essentially concentration independent charge density nearly equal to its value for chromium free composition inspite of its expected decrease with this substitution suggesting that the small charge density of the insulating AFM phase is supplemented by the free carriers in the FM phase. The inhomogeneous phase shows a relaxor type behavior which contrasts with the spin glass behavior seen in La0.46Sr0.54Mn0.98Cr0.02O3 having an identical AFM magnetic state. The difference is attributed to the non-JT character of Cr-ions which reduce the distortion of the Mnsbnd O octahedra located within the FM domains. With a higher lattice strain in the surrounding AFM matrix the carriers remain confined within the FM domains leading to the relaxor type behavior.

  7. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al Part II: Scale Microstructures

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. Details of the oxidation kinetics of these alloys were discussed in Part I. This paper analyzes the microstructures of the scale and its composition in an attempt to elucidate the oxidation mechanisms in these alloys. The scales formed on Cu-17%Cr specimens oxidized between 773 and 973 K consisted of external CuO and subsurface Cu2O layers. The total thickness of these scales varied from about 10 m at 773 K to about 450 m at 973 K. In contrast, thin scales formed on Cu-17%Cr-5%Al alloys oxidized between 773 and 1173 K. The exact nature of these scales could not be determined by x-ray diffraction but energy dispersive spectroscopy analyses were used to construct a scale composition map. Phenomenological oxidation mechanisms are proposed for the two alloys.

  8. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al. Part 2; Scale Microstructures

    NASA Technical Reports Server (NTRS)

    Raj, S. V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. Details of the oxidation kinetics of these alloys were discussed in Part I. This paper analyzes the microstructures of the scale and its composition in an attempt to elucidate the oxidation mechanisms in these alloys. The scales formed on Cu-17%Cr specimens oxidized between 773 and 973 K consisted of external CuO and subsurface Cu2O layers. The total thickness of these scales varied from about 10 m at 773 K to about 450 m at 973 K. In contrast, thin scales formed on Cu-17%Cr-5%Al alloys oxidized between 773 and 1173 K. The exact nature of these scales could not be determined by x-ray diffraction but energy dispersive spectroscopy analyses were used to construct a scale composition map. Phenomenological oxidation mechanisms are proposed for the two alloys.

  9. First-principles investigation of structural and magnetic disorder in CuNiMnAl and CuNiMnSn Heusler alloys

    DOE PAGES

    Aron-Dine, S.; Pomrehn, G. S.; Pribram-Jones, A.; ...

    2017-01-10

    Two quaternary Heusler alloys, equiatomic CuNiMnAl and CuNiMnSn, are studied using density functional theory to understand their tendency for atomic disorder on the lattice and the magnetic effects of disorder. Disordered structures with antisite defects of atoms of the same and different sublattices are considered, with the level of atomic disorder ranging from 3% to 25%. Formation energies and magnetic moments are calculated relative to the ordered ground state and combined with a simple thermodynamical model to estimate temperature effects. We predict the relative levels of disordering in the two equiatomic alloys with good correlation to experimental x-ray diffraction results.more » In conclusion, the effect of swaps involving Mn is also discussed.« less

  10. First-principles investigation of structural and magnetic disorder in CuNiMnAl and CuNiMnSn Heusler alloys

    NASA Astrophysics Data System (ADS)

    Aron-Dine, S.; Pomrehn, G. S.; Pribram-Jones, A.; Laws, K. J.; Bassman, L.

    2017-01-01

    Two quaternary Heusler alloys, equiatomic CuNiMnAl and CuNiMnSn, are studied using density functional theory to understand their tendency for atomic disorder on the lattice and the magnetic effects of disorder. Disordered structures with antisite defects of atoms of the same and different sublattices are considered, with the level of atomic disorder ranging from 3% to 25%. Formation energies and magnetic moments are calculated relative to the ordered ground state and combined with a simple thermodynamical model to estimate temperature effects. We predict the relative levels of disordering in the two equiatomic alloys with good correlation to experimental x-ray diffraction results. The effect of swaps involving Mn is also discussed.

  11. Influence of ternary addition of transition elements (Cr, Si and Mn) on the microstructure and magnetic properties of nano-structured CuCo alloy

    NASA Astrophysics Data System (ADS)

    Mondal, B. N.; Chabri, S.; Basumallick, A.; Chattopadhyay, P. P.

    2012-09-01

    The current state of studies presents the effect of ternary addition of transition elements such as Mn, Cr and Si (10 wt%) on the mechanically driven non-equilibrium solubility of 40 wt% Co containing Cu-Co alloy. X-ray powder diffraction analysis indicates that addition of Mn has been found to be the most effective in enhancing the solubility and formation of a complete solid solution between Co and Cu in a short duration (30 h) of ball milling. The microstructure of the ball milled CuCoMn alloy was found to be stable after the isothermal annealing up to a temperature of 450 °C for 1 h. The magnetic properties such as magnetic saturation, coercivity and remanence of ball milled CuCo alloy in the presence of Mn significantly altered after annealing in the temperature range 350-650 °C for 1 h. The best combination of magnetic properties of CuCoMn alloy has been found after annealing at 550 °C for 1 h.

  12. Microstructures and Thermal Properties of Cold-Sprayed Cu-Cr Composite Coatings

    NASA Astrophysics Data System (ADS)

    Kikuchi, S.; Yoshino, S.; Yamada, M.; Fukumoto, M.; Okamoto, K.

    2013-08-01

    Copper-based composites for thermal conductive components were prepared via the cold spray process, and the deposition efficiency and adhesion morphology of feedstock powders on Cu substrate were evaluated. Cu-based composites were fabricated using Cu-Cr mixed powders with their mixture ratio of 20, 35, 50, and 65 mass% Cr onto oxygen-free copper substrate with N2 carrier gas. Cu-Cr composite coatings were investigated for their Cr content ratio, microstructures, and thermal conductivity. The Cr content ratio in the coating was approximately 50-60% of feedstock mixture ratio due to the low formability of the hard particles. Transmission electron microscopy characterizations revealed that an oxygen-rich layer exists at the Cr particle/Cu substrate interface, which contributes to the deposition of the Cr particles. After the heat treatment at 1093 K, the coatings showed denser cross-sectional structures than those before the heat treatment, and the thermal conductivity was improved as a result of the recrystallization of Cu matrix.

  13. Control of magnetic properties of MnBi and MnBiCu thin films by Kr{sup +} ion irradiation

    SciTech Connect

    Xu Qianqian; Kanbara, Ryutarou; Kato, Takeshi; Iwata, Satoshi; Tsunashima, Shigeru

    2012-04-01

    Mn{sub 52}Bi{sub 48} (15 nm) and Mn{sub 54}Bi{sub 24}Cu{sub 21} (15 nm) thin films were prepared by the magnetron sputtering and vacuum annealing at 350 deg. C, and the variations of their structures and magnetic properties with 30 keV Kr{sup +} ion irradiation were studied. The MnBi and MnBiCu films exhibited saturation magnetizations M{sub s} of 180 emu/cc and 210 emu/cc, the coercivities H{sub c} of 10 kOe and 3.4 kOe, respectively. The M{sub s} and H{sub c} of the MnBi abruptly vanished by the irradiation of ion dose at 3 x 10{sup 14} ions/cm{sup 2}, while those of the MnBiCu film gradually decreased with increasing the ion dose and became zero at 5 x 10{sup 13} ions/cm{sup 2}. The different trend on the ion irradiation between MnBi and MnBiCu films is understood by the surface structure of the film, i.e., the MnBi has convex islands on its surface, which protect the underneath NiAs-type MnBi from the irradiation, while the MnBiCu has rather flat surface, and its crystal structure was uniformly modified by the irradiation. From the surface flatness and the uniformity of the MnBiCu film, as well as the low annealing temperature of 350 deg. C, it was concluded that the MnBiCu film is one of the attractive materials for high-density ion irradiation bit patterned media.

  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. Magnetic properties of the CrMnFeCoNi high-entropy alloy

    DOE PAGES

    Schneeweiss, Oldřich; Friák, Martin; Dudová, Marie; ...

    2017-07-28

    In this paper, we present experimental data showing that the equiatomic CrMnFeCoNi high-entropy alloy undergoes two magnetic transformations at temperatures below 100 K while maintaining its fcc structure down to 3 K. The first transition, paramagnetic to spin glass, was detected at 93 K and the second transition of the ferromagnetic type occurred at 38 K. Field-assisted cooling below 38 K resulted in a systematic vertical shift of the hysteresis curves. Strength and direction of the associated magnetization bias was proportional to the strength and direction of the cooling field and shows a linear dependence with a slope of 0.006more » ± 0.001 emu T. The local magnetic moments of individual atoms in the CrMnFeCoNi quinary fcc random solid solution were investigated by ab initio (electronic density functional theory) calculations. Results of the numerical analysis suggest that, irrespective of the initial configuration of local magnetic moments, the magnetic moments associated with Cr atoms align antiferromagnetically with respect to a cumulative magnetic moment of their first coordination shell. The ab initio calculations further showed that the magnetic moments of Fe and Mn atoms remain strong (between 1.5 and 2 μB), while the local moments of Ni atoms effectively vanish. Finally, these results indicate that interactions of Mn- and/or Fe-located moments with the surrounding magnetic structure account for the observed macroscopic magnetization bias.« less

  17. Electroless deposition of NiCrB diffusion barrier layer film for ULSI-Cu metallization

    NASA Astrophysics Data System (ADS)

    Wang, Yuechun; Chen, Xiuhua; Ma, Wenhui; Shang, Yudong; Lei, Zhengtao; Xiang, Fuwei

    2017-02-01

    NiCrB films were deposited on Si substrates using electroless deposition as a diffusion barrier layer for Cu interconnections. Samples of the prepared NiCrB/SiO2/Si and NiCrB/Cu/NiCrB/SiO2/Si were annealed at temperatures ranging from 500 °C to 900 °C. The reaction mechanism of the electroless deposition of the NiCrB film, the failure temperature and the failure mechanism of the NiCrB diffusion barrier layer were investigated. The prepared samples were subjected to XRD, XPS, FPP and AFM to determine the phases, composition, sheet resistance and surface morphology of samples before and after annealing. The results of these analyses indicated that the failure temperature of the NiCrB barrier film was 900 °C and the failure mechanism led to crystallization and grain growth of the NiCrB barrier layer after high temperature annealing. It was found that this process caused Cu grains to reach Si substrate through the grain boundaries, and then the reaction between Cu and Si resulted in the formation of highly resistive Cu3Si.

  18. Spin dependent transport properties of Mn-Ga/MgO/Mn-Ga magnetic tunnel junctions with metal(Mg, Co, Cr) insertion layer

    SciTech Connect

    Liang, S. H.; Tao, L. L.; Liu, D. P. Han, X. F.; Lu, Y.

    2014-04-07

    We report a first principles theoretical investigation of spin polarized quantum transport in Mn{sub 2}Ga/MgO/Mn{sub 2}Ga and Mn{sub 3}Ga/MgO/Mn{sub 3}Ga magnetic tunneling junctions (MTJs) with the consideration of metal(Mg, Co, Cr) insertion layer effect. By changing the concentration of Mn, our calculation shows a considerable disparity in transport properties: A tunneling magnetoresistance (TMR) ratio of 852% was obtained for Mn{sub 2}Ga-based MTJs, however, only a 5% TMR ratio for Mn{sub 3}Ga-based MTJs. In addition, the influence of insertion layer has been considered in our calculation. We found the Co insertion layer can increase the TMR of Mn{sub 2}Ga-based MTJ to 904%; however, the Cr insertion layer can decrease the TMR by 668%; A negative TMR ratio can be obtained with Mg insertion layer. Our work gives a comprehensive understanding of the influence of different insertion layer in Mn-Ga based MTJs. It is proved that, due to the transmission can be modulated by the interfacial electronic structure of insertion, the magnetoresistance ratio of Mn{sub 2}Ga/MgO/Mn{sub 2}Ga MTJ can be improved by inserting Co layer.

  19. Chemical separation and mass spectrometry of Cr, Fe, Ni, Zn, and Cu in terrestrial and extraterrestrial materials using thermal ionization mass spectrometry.

    PubMed

    Yamakawa, Akane; Yamashita, Katsuyuki; Makishima, Akio; Nakamura, Eizo

    2009-12-01

    A sequential chemical separation technique for Cr, Fe, Ni, Zn, and Cu in terrestrial and extraterrestrial silicate rocks was developed for precise and accurate determination of elemental concentration by the isotope dilution method (ID). The technique uses a combination of cation-anion exchange chromatography and Eichrom nickel specific resin. The method was tested using a variety of matrixes including bulk meteorite (Allende), terrestrial peridotite (JP-1), and basalt (JB-1b). Concentrations of each element was determined by thermal ionization mass spectrometry (TIMS) using W filaments and a Si-B-Al type activator for Cr, Fe, Ni, and Zn and a Re filament and silicic acid-H3PO4 activator for Cu. The method can be used to precisely determine the concentrations of these elements in very small silicate samples, including meteorites, geochemical reference samples, and mineral standards for microprobe analysis. Furthermore, the Cr mass spectrometry procedure developed in this study can be extended to determine the isotopic ratios of 53Cr/52Cr and 54Cr/52Cr with precision of approximately 0.05epsilon and approximately 0.10epsilon (1epsilon = 0.01%), respectively, enabling cosmochemical applications such as high precision Mn-Cr chronology and investigation of nucleosynthetic isotopic anomalies in meteorites.

  20. Cyclic Oxidation Behavior of CuCrAl Cold-Sprayed Coatings for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, Sai; Karthikeyan, J.

    2009-01-01

    The next generation of reusable launch vehicles is likely to use GRCop-84 [Cu-8(at.%)Cr-4%Nb] copper alloy combustion liners. The application of protective coatings on GRCop-84 liners can minimize or eliminate many of the environmental problems experienced by uncoated liners and significantly extend their operational lives and lower operational cost. A newly developed Cu- 23 (wt.%) Cr-5% Al (CuCrAl) coating, shown to resist hydrogen attack and oxidation in an as-cast form, is currently being considered as a protective coating for GRCop-84. The coating was deposited on GRCop-84 substrates by the cold spray deposition technique, where the CuCrAl was procured as gas-atomized powders. Cyclic oxidation tests were conducted between 773 and 1,073 K to characterize the coated substrates.

  1. Electrical conductivity and mechanical properties of Cu-0.7wt% Cr and Cu-1.0wt% Cr alloys processed by severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Kommel, L.; Pokatilov, A.

    2014-08-01

    As-cast Cu-0.7wt% Cr and Cu-1.0wt% Cr alloys were subjected to equal-channel angular pressing (ECAP), hard cyclic viscoplastic (HCV) deformation and post deformation heat treatment for receiving an ultrafine grained material with a combination of high strength, good wear resistance and high electric conductivity. Samples from Cu-0.7wt% Cr alloy were processed up to six passes and Cu-1wt% Cr alloy samples were processed up to four passes of ECAP via Bc route. HCV deformation of samples was conducted by frequency of 0.5 Hz for 20 cycles at tension-compression strain amplitudes of +/-0.05%, +/-0.1%, +/-0.5%, +/-1% and +/-1.5%, respectively. During HCV deformation, as-cast Cu-0./wt% Cr alloy show fully viscoelastic behavior at strain/stress amplitude of +/-0.05% while ECAP processed material show the same behavior at strain amplitude of +/-0.1%. The Young modulus was increased from ~120 GPa up to ~150 GPa. The results illustrated that specific volume wear decrease with increasing of hardness but the measured coefficient of friction (COF ~ 0.6) was approximately the same for all samples at the end of wear testing. The hardness after ECAP for 6 passes by Bc route was 192HV0.1 and electric conduction 74.16% IACS, respectively. By this the as-cast Cu-0./wt% Cr alloy (heat treated at 1000 °C for 2h) has microhardness ~70HV0.1 and electrical conductivity of ~40% IACS. During aging at the temperatures in the interval of 250-550 °C for 1h the hardness and electrical conductivity were stabilized to mean values of 120+/-5HV0.1 and to 93.4+/-0.3% IACS, respectively. The hardness and electric conductivity took decrease by temperature increase over ~550 °C, respectively. The results of present experimental investigation show that UFG Cu- 0.7wt% Cr alloy with compare to Cu-1.0% Cr alloy is a highly electrical conductive and high temperature wear resistant material for using in electrical industry.

  2. Sol gel synthesis and characterization studies of Cupromanganite CaCu3Mn4O12

    NASA Astrophysics Data System (ADS)

    Nurulhuda, A.; Warikh, A. R. M.; Hafizzal, Y.

    2017-08-01

    A single-phase CaCu3Mn4O12 electroceramic had been prepared via sol gel method and fairly well densified at relative low temperature under atmospheric condition where the crystallization of CaCu3Mn4O12 occurred due to amorphous polymeric mixture. The precursor was prepared by mixing the solutions with 0.6 M citric acid (C6H8O7) as a chelating reagent with the mol ratio 1:2. The precursor gel formed was calcined and sintered at range 400 °C to 800°C by varying dwell time. Material formations under the reported conditions have been confirmed by X-ray diffraction (XRD). The results show that the formation of CaCu3Mn4O12 started at 500 ° C and was formed completely at 700 ° C for 18 hours. The microstructure of all CaCu3Mn4O12 was analysed using field emission scanning electron microscopy (FESEM). A smaller particle size with higher grain boundary was obtained at sintering 700°C to 800°C. FESEM results show the significant influence of calcinations and sintering parameter on the microstructure behaviour of CaCu2Mn4O12.

  3. Coupled antiferromagnetic spin- <mn>1mn>>2mn> chains in green dioptase Cu>6mn>[Si>6mn>O>18mn>]·>6mn>H>2mn>O

    SciTech Connect

    Podlesnyak, Andrey A; Larry M. Anovitz; Kolesnikov, Alexander I; Matsuda, Masaaki; Prisk, Timothy R; Toth, Sandor; Ehlers, Georg

    2016-02-01

    In this paper, we report inelastic neutron scattering measurements of the magnetic excitations of green dioptase Cu6[Si6O18]∙6H2O. The observed spectrum contains two magnetic modes and a prominent spin gap that is consistent with the ordered ground state of Cu moments coupled antiferromagnetically in spiral chains along the c axis and ferromagnetically in ab planes on the hexagonal cell. The data are in excellent agreement with a spin- <mn>1mn>>2mn>Hamiltonian that includes antiferromagnetic nearest-neighbor intrachain coupling Jc=10.6(1) meV, ferromagnetic interchain coupling Jab=₋1.2 (1) meV, and exchange anisotropy ΔJc=0.14(1) meV. We calculated the sublattice magnetization to be strongly reduced, ~0.39μB. This appears compatible with a reduced Néel temperature, TN=14.5K<c, and can be explained by a presence of quantum spin fluctuations

  4. Giant Magnetoresistance and Coercivity of electrodeposited multilayered FeCoNi/Cu and CrFeCoNi/Cu

    NASA Astrophysics Data System (ADS)

    Shakya, P.; Cox, B.; Davis, D.

    2012-02-01

    The effect of Cr addition on electrodeposited multilayered nanowires CrFeCoNi/Cu was investigated from a magnetic property perspective: current perpendicular to the plane-Giant Magnetoresistance (CPP-GMR) and Coercivity (BH loops). The magnetic behavior of multilayered nanowires of CrFeNiCo/Cu was also affected by the alloy deposition potential, alloy pulsing time (layer thickness) and number of bilayers. Furthermore, the addition of Cr influenced both the nanowires GMR and Coercivity. Cr addition to the ferromagnetic FeCoNi layer induced a reduction in the room temperature GMR from 10.64% to 5.62%; however, the magnetic saturation field decreased from 0.45 to 0.27 T. The increase in the number of bilayers, from 1000 to 2500, resulted in a higher GMR value, 14.56% with 0.35 T magnetic saturation field. Addition of Cr to the ferromagnetic layer decreased the coercivity from 0.015 to 0.0054 T. Low saturation field CPP-GMR nanowires showing low coercivity at room temperature opens a new door for magnetic sensing devices. To the best of our knowledge, this is the first study on electrodeposited CrFeCoNi/Cu multilayered nanowires.

  5. Mn-Cr isotopic systematics of individual Chainpur chondrules. [Abstract only

    NASA Technical Reports Server (NTRS)

    Nyquist, L.; Lindstrom, D.; Wiesmann, H.; Martinez, R.; Bansal, B.; Mittlefehldt, D.; Shih, C.-Y.; Wentworth, S.

    1994-01-01

    Twenty-eight chondrules separated from Chainpur (LL3.4) were surveyed for abundances of Mn, Cr, Na, Fe, Sc, Hf, Ir, and Zn by Instrumental Neutron Activation Analysis (INAA). Six, weighting 0.6-1.5 mg each, were chosen for Scanning Electron Microscopy (SEM)/Energy Dispersive X-ray (EDX) and high-precision Ce-isotopic studies. LL-chondrite-normalized (Mn/Fe)(sub LL) and (Sc/Fe)(sub LL) were found to be useful in categorizing them. Five chondrules (CH-16, -17, -18, -23, and -28) were in the range 0.5 less than (Mn/Fe)(sub LL) less than 1. 4 and 0.5 less than (Sc/Fe)(sub LL) less than 1.4. The sixth (CH-25) had (Mn/Fe)(sub LL) and (Sc/Fe)(sub LL) ratios of 0.40 and 8.1, respectively, and was enriched in the refractory lithophile elements Sc and Hf and the refractory siderophile element Ir by 2.7 and 4.4x LL abundances respectively. SEM/EDX of exterior surfaces of the chondrules showed they consisted of varying proportions of low- and high-Ca pyroxenes, olivine, glass, kamacite/taenite, and Fe-sulfides. Chromium-53/chromium-52 for the six chondrules and bulk Chainpur (WR) are presented. Chromium-54/chromium-52 is close to terrestrial and does not correlate with Mn/Cr. We provisionally ignore the possibility of initial Cr isotopic heterogeneities among the chondrules. Omitting both the CH-25 and WR data, a linear regression gives initial (Mn-53/Mn-55)(sub I) = 8 +/- 4 x 10(exp -6), corresponding to chondrule formation at Delta(t)(sub LEW) = -9 +/- 4 Ma prior to igneous crystallization of the LEW 86010 angrite. If initial (Mn-53/Mn-55)(sub 0) in the solar system were as high as approximately 4.4 x 10(exp -5) when Allende CAI formed, our data suggest Chainpur chondrules formed approximately 9 Ma later, in qualitative agreement with 'late' I-Xe formation ages for most Chainpur chondrules.

  6. Efficient carbon dioxide electrolysis with metal nanoparticles loaded La0·75Sr0·25Cr0·5Mn0·5O3-δ cathodes

    NASA Astrophysics Data System (ADS)

    Zhu, Changli; Hou, Linxi; Li, Shisong; Gan, Lizhen; Xie, Kui

    2017-09-01

    Solid oxide electrolysis cells with La0·75Sr0·25Cr0·5Mn0·5O3-δ (LSCM) cathode can electrolyze CO2 to generate chemical fuels. Nevertheless, the cathode performance is limited by its electrocatalytic activity. In this work, metal nanoparticles including Ni, Cu and NiCu metals are successfully impregnated in LSCM electrode to improve its activity. XRD, XPS, SEM and TEM together confirm the metal nanocatalysts are homogeneously distributed on LSCM backbone and therefore create active electrochemical interface for CO2 splitting. Electrical properties of LSCM with impregnated metal nanoparticles are investigated and correlated to electrode performances. Electrochemical measurements show that the NiCu-LSCM demonstrates the optimum performance without degradation after operation for ∼100 h and ∼10 redox cycles. It is believed that the enhanced performance of CO2 electrolysis may be attributed to the synergetic effect of metal nanocatalyst and LSCM ceramic electrode.

  7. Simulations of irradiated-enhanced segregation and phase separation in Fe-Cu-Mn alloys

    NASA Astrophysics Data System (ADS)

    Li, Boyan; Hu, Shenyang; Li, Chengliang; Li, Qiulin; Chen, Jun; Shu, Guogang; Henager, Chuck, Jr.; Weng, Yuqing; Xu, Ben; Liu, Wei

    2017-09-01

    For reactor pressure vessel steels, the addition of Cu, Mn, and Ni has a positive effect on their mechanical, corrosion and radiation resistance properties. However, experiments show that radiation-enhanced segregation and/or phase separation is one of the important material property degradation processes. In this work, we develop a model integrating rate theory and phase-field approaches to investigate the effect of irradiation on solute segregation and phase separation. The rate theory is used to describe the accumulation and clustering of radiation defects, while the phase-field approach describes the effect of radiation defects on phase stability and microstructure evolution. The Fe-Cu-Mn ternary alloy is taken as a model system. The free energies used in the phase-field model are from CALPHAD. Spatial dependent radiation damage from atomistic simulations is introduced into the simulation cell for a given radiation dose rate. The radiation effect on segregation and phase separation is taken into account through the defect concentration dependence of solute mobility. Using the model, the effect of temperature and radiation rates on Cu and Mn segregation and Cu-rich phase nucleation were systematically investigated. The segregation and nucleation mechanisms were analyzed. The simulations demonstrate that the nucleus of Cu precipitates has a core-shell composition profile, i.e. Cu-rich at the center and Mn-rich at the interface, in good agreement with theoretical calculations as well as experimental observations.

  8. Laser weldability of 21Cr-6Ni-9Mn stainless steel: Part II - Weldability diagrams

    SciTech Connect

    Tate, Stephen B.; Javernick, Daniel Anthony; Lienert, Thomas J.; Liu, Stephen

    2016-11-02

    In this second part of the study, weldability diagrams developed to relate solidification crack susceptibility and chemical composition for laser welded type 21Cr-6Ni-9Mn (21-6-9) stainless steel are presented. Sigmajig testing on 14 commercial 21-6-9 alloys, 20 experimental 21-6-9 alloys, and 7 other high-N, high-Mn austenitic stainless steels was used to develop weldability diagrams for solidification crack susceptibility for laser welding of type 21-6-9. Three travel speeds were used to show the changes in minimum Creq/Nieq for primary ferrite solidification as solidification rate increase d with travel speed . Primary austenite solidification was observed below 1.55 Creq/Nieq (Espy equivalents) at 21 mm/s travel speed. At 42 mm/s travel speed , a mix of solidification modes were displayed for alloys from 1.55-1.75 Creq/Nieq. Primary ferrite solidification was observed above 1.75 Creq/Nieq at both 42 and 85 mm/s travel speeds. No solidification cracking was observed for alloys with primary ferrite solidification. Lastly, variable cracking behavior was found in alloys with primary austenite solidification, but in general cracking was observed in alloys with greater than 0.02 wt-% combined impurity content according to (P+0.2S).

  9. Tensile and Fracture Toughness Properties of Neutron-Irradiated CuCrZr

    SciTech Connect

    Sokolov, Mikhail A; Zinkle, Steven J; Li, Meimei

    2009-01-01

    Tensile and fracture toughness properties of a precipitation-hardened CuCrZr alloy were investigated in two heat treatment conditions: solutionized, water quenched and aged (CuCrZr SAA), and hot isostatic pressed, solutionized, slow-cooled and aged (CuCrZr SCA). The second heat treatment simulated the manufacturing cycle for large components, and is directly relevant for the ITER divertor components. Specimens were neutron irradiated at {approx}80 C to two fluences, 2 x 10{sup 24} and 2 x 10{sup 25} n/m{sup 2} (E > 0.1 MeV), corresponding to displacement doses of 0.15 and 1.5 displacements per atom (dpa). Tensile and fracture toughness tests were carried out at room temperature. Significant irradiation hardening and plastic instability at yield occurred in both heat treatment conditions with a saturation dose of {approx}0.1 dpa. Neutron irradiation slightly reduced fracture toughness in CuCrZr SAA and CuCrZr SCA. The fracture toughness of CuCrZr remained high up to 1.5 dpa (J{sub Q} > 200 kJ/m{sup 2}) for both heat treatment conditions.

  10. Investigation of vacuum properties of CuCrZr alloy for high-heat-load absorber

    NASA Astrophysics Data System (ADS)

    Shueh, C.; Chan, C. K.; Chang, C. C.; Sheng, I. C.

    2017-01-01

    The Taiwan Photon Source (TPS) uses high-heat-load (HHL) absorbers to protect downstream ultrahigh-vacuum chambers from overheating. In this work, we propose to use the CuCrZr alloy (ASTM C18150) for the HHL absorber body and the ConFlat flanges. We use the throughput method to measure the thermal outgassing rate and a helium leak detector to verify the vacuum seal between the CuCrZr alloy and stainless-steel flanges. The measured outgassing rate of the CuCrZr alloy was 5.8×10-10 Pa m/s after 72 h of pumping and decreased to 2.0 × 10-10 Pa m/s after 100 h of pumping. The leak rate through the vacuum seal between a CuCrZr flange and a stainless-steel flange was less than 1 × 10-10 Pa m3/s even after mounting and unmounting the flanges ten times and baking them at 250 °C. These results indicate that CuCrZr alloy is suitable for integrating HHL components with ConFlat CuCrZr flanges for the absorption of the synchrotron radiation generated by the TPS.

  11. Characterization of transparent superconductivity Fe-doped CuCrO2 delafossite oxide

    NASA Astrophysics Data System (ADS)

    Taddee, Chutirat; Kamwanna, Teerasak; Amornkitbamrung, Vittaya

    2016-09-01

    Delafossite CuCr1-xFexO2 (0.0 ≤ x ≤ 0.15) semiconductors were synthesized using a self-combustion urea nitrate process. The effects of Fe concentration on its microstructural, optical, magnetic, and electrical properties were investigated. X-ray diffraction (XRD) analysis results revealed the delafossite structure in all the samples. The lattice spacing of CuCr1-xFexO2 slightly increased with increasing substitution of Fe at the Cr sites. The optical properties measured at room temperature using UV-visible spectroscopy showed a weak absorbability in the visible light and near IR regions. The corresponding direct optical band gap was about 3.61 eV, exhibiting transparency in the visible region. The magnetic hysteresis loop measurements showed that the Fe-doped CuCrO2 samples exhibited ferromagnetic behavior at room temperature. This indicated that the substitution of Fe3+ for Cr3+ produced a mixed effect on the magnetic properties of CuCrO2 delafossite oxide. The temperature dependent resistivity measurements clearly revealed the presence of superconductivity in the CuCr1-xFexO2 with a superconducting transition up to 118 K.

  12. Bandgap- and Radial-Position-Dependent Mn-Doped Zn-Cu-In-S/ZnS Core/Shell Nanocrystals.

    PubMed

    Peng, Lucheng; Huang, Keke; Zhang, Zhuolei; Zhang, Ying; Shi, Zhan; Xie, Renguo; Yang, Wensheng

    2016-03-03

    This paper presents a mechanistic study on the doping of Zn-Cu-In-S/ZnS core/shell quantum dots (QDs) with Mn by changing the Zn-Cu-In-S QD bandgap and dopant position inside the samples (Zn-Cu-In-S core and ZnS shell). Results show that for the Mn:Zn-Cu-In-S/ZnS system, a Mn-doped emission can be obtained when the bandgap value of the QDs is larger than the energy of Mn-doped emission. Conversely, a bandgap emission is only observed for the doped system when the bandgap value of QDs is smaller than the energy gap of the Mn-doped emission. In the Zn-Cu-In-S/Mn:ZnS systems, doped QDs show dual emissions, consisting of bandgap and Mn dopant emissions, instead of one emission band when the value of the host bandgap is larger than the energy of the Mn-doped emission. These findings indicate that the emission from Mn-doped Zn-Cu-In-S/ZnS core/shell QDs depends on the bandgap of the QDs and the dopant position inside the core/shell material. The critical bandgap of the host materials is estimated to have the same value as the energy of the Mn d-d transition. Subsequently, the mechanism of photoluminescence properties of the Mn:Zn-Cu-In-S/ZnS and Zn-Cu-In-S/Mn:ZnS core/shell QD systems is proposed. Control experiments are then carried out by preparing Mn-doped Zn(Cu)-In-S QDs with various bandgaps, and the results confirm the reliability of the suggested mechanism. Therefore, the proposed mechanism can aid the design and synthesis of novel host materials in fabricating doped QDs.

  13. Carbides in iron-rich Fe-Mn-Cr-Mo-Al-Si-C systems

    NASA Technical Reports Server (NTRS)

    Lemkey, F. D.; Gupta, H.; Nowotny, H.; Wayne, S. F.

    1984-01-01

    The optimization of high carbon iron-base superalloy properties with duplex microstructure gamma + M7C3 carbide requires analysis in the context of a seven-component system. Data are first provided here for the Fe-Mn-Cr-Mo-C quinary system, at 30 at. pct carbon. A characterization of competing carbides, according to a pseudoternary phase diagram at 35 wt pct iron, is made from isothermal sections. It is noted that while M7C3 and M3C carbides' occurrences are respectively favored at the Cr and Mn corners, the M2C carbide and molybdenum cementite are predominant with increasing amounts of Mo. Lattice parameters are reported for the various carbides.

  14. Carbides in iron-rich Fe-Mn-Cr-Mo-Al-Si-C systems

    NASA Technical Reports Server (NTRS)

    Lemkey, F. D.; Gupta, H.; Nowotny, H.; Wayne, S. F.

    1984-01-01

    The optimization of high carbon iron-base superalloy properties with duplex microstructure gamma + M7C3 carbide requires analysis in the context of a seven-component system. Data are first provided here for the Fe-Mn-Cr-Mo-C quinary system, at 30 at. pct carbon. A characterization of competing carbides, according to a pseudoternary phase diagram at 35 wt pct iron, is made from isothermal sections. It is noted that while M7C3 and M3C carbides' occurrences are respectively favored at the Cr and Mn corners, the M2C carbide and molybdenum cementite are predominant with increasing amounts of Mo. Lattice parameters are reported for the various carbides.

  15. Galvanomagnetic properties of Heusler alloy Co2 YAl ( Y = Ti, V, Cr, Mn, Fe, and Ni)

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    The Hall effect and the magnetoresistance of ferromagnetic Heusler alloys Co2 YAl, where Y = Ti, V, Cr, Mn, Fe, and Ni have been studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. Normal R 0 and anomalous R S Hall coefficients are shown to be maximal in magnitudes in the middle of the 3 d period of the periodic table of elements. Coefficient R 0 changes the negative sign to positive sign in going from weak ( Y = Ti, V) to strong ( Y = Cr, Mn, Fe, and Ni) ferromagnetic alloys. Constant R S is positive and proportional to ρ2.9 in all the alloys. The magnetoresistance of the alloys is not higher than several percent and its magnitude is changed fairly significantly in the dependence on the number of valence electrons z; the magnetoresistance signs vary arbitrarily.

  16. High-Strength Ultra-Fine-Grained Hypereutectic Al-Si-Fe-X (X = Cr, Mn) Alloys Prepared by Short-Term Mechanical Alloying and Spark Plasma Sintering

    PubMed Central

    Průša, Filip; Bláhová, Markéta; Vojtěch, Dalibor; Kučera, Vojtěch; Bernatiková, Adriana; Kubatík, Tomáš František; Michalcová, Alena

    2016-01-01

    In this work, Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn (wt %) alloys were prepared by a combination of short-term mechanical alloying and spark plasma sintering. The microstructure was composed of homogeneously dispersed intermetallic particles forming composite-like structures. X-ray diffraction analysis and TEM + EDS analysis determined that the α-Al along with α-Al15(Fe,Cr)3Si2 or α-Al15(Fe,Mn)3Si2 phases were present, with dimensions below 130 nm. The highest hardness of 380 ± 7 HV5 was observed for the Al-20Si-10Fe-6Mn alloy, exceeding the hardness of the reference as-cast Al-12Si-1Cu-1 Mg-1Ni alloy (121 ± 2 HV5) by nearly a factor of three. Both of the prepared alloys showed exceptional thermal stability with the hardness remaining almost the same even after 100 h of annealing at 400 °C. Additionally, the compressive strengths of the Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn alloys reached 869 MPa and 887 MPa, respectively, and had virtually the same values of 870 MPa and 865 MPa, respectively, even after 100 h of annealing. More importantly, the alloys showed an increase in ductility at 400 °C, reaching several tens of percent. Thus, both of the investigated alloys showed better mechanical properties, including superior hardness, compressive strength and thermal stability, as compared to the reference Al-10Si-1Cu-1Mg-1Ni alloy, which softened remarkably, reducing its hardness by almost 50% to 63 ± 8 HV5. PMID:28774094

  17. Creep Testing of High-Temperature Cu-8 Cr-4 Nb Alloy Completed

    NASA Technical Reports Server (NTRS)

    1995-01-01

    A Cu-8 at.% Cr-4 at.% Nb (Cu-8 Cr-4 Nb) alloy is under development for high-temperature, high heatflux applications, such as actively cooled, hypersonic vehicle heat exchangers and rocket engine combustion chambers. Cu-8 Cr-4 Nb offers a superior combination of strength and conductivity. It has also shown exceptional low-cycle fatigue properties. Following preliminary testing to determine the best processing route, a more detailed testing program was initiated to determine the creep lives and creep rates of Cu-8 Cr-4 Nb alloy specimens produced by extrusion. Testing was conducted at the NASA Lewis Research Center with constant-load vacuum creep units. Considering expected operating temperatures and mission lives, we developed a test matrix to accurately determine the creep properties of Cu-8 Cr-4 Nb between 500 and 800 C. Six bars of Cu-8 Cr-4 Nb were extruded. From these bars, 54 creep samples were machined and tested. The figure on the left shows the steady-state, or second-stage, creep rates for the samples. Comparison data for NARloy-Z (Cu-3 wt % Ag-0.5 wt % Zr), the alloy currently used in combustion chamber liners, were not unavailable. Therefore the steady-state creep rates for Cu at similar temperatures are presented. As expected, in comparison to pure Cu, the creep rates for Cu-8 Cr-4 Nb are much lower. The lives of the samples are presented in the figure on the right. As shown, Cu-8 Cr-4 Nb at 800 C is comparable to NARloy-Z at 648 C. At equivalent temperatures, Cu-8 Cr-4 Nb enjoys a 20 to 50 percent advantage in stress for a given life and 1 to 3 orders of magnitude greater life at a given stress. The improved properties allow for design tradeoffs and improvements in new and existing heat exchangers such as the next generation of combustion chamber liners. Average creep rates for Cu-8 Cr-4 Nb and pure Cu are shown. Average creep lives for Cu-8 Cr- 4 Nb and NARloy-Z are also shown. Currently, two companies are interested in the commercial usage of the Cu

  18. Giant magnetic coercivity in CaCu5-type SmNi3TSi (T=Mn-Cu) solid solutions

    NASA Astrophysics Data System (ADS)

    Yao, Jinlei; Yan, Xu; Morozkin, A. V.

    2015-12-01

    The effects of transition metal substitution for Ni on the magnetic properties of the CaCu5-type SmNi3TSi (T=Mn, Fe, Co, Cu) solid solutions have been investigated. SmNi3MnSi, SmNi3FeSi, SmNi3CoSi and SmNi3CuSi show ferromagnetic ordering at 125 K, 190 K, 46 K and 12 K and field induced transitions at 65 K, 110 K, 30 K and 6 K, respectively. The magnetocaloric effects of SmNi3TSi (T=Mn, Fe, Co, Cu) were calculated in terms of isothermal magnetic entropy change (ΔSm). The magnetic entropy ΔSm reaches value of -1.1 J/kg K at 130 K for SmNi3MnSi, -0.4 J/kg K at 180 K for SmNi3FeSi, -0.37 J/kg K at 45 K for SmNi3CoSi and -0.5 J/kg K at 12 K for SmNi3CuSi in field change of 0-50 kOe around the ferromagnetic ordering temperature. They show positive ΔSm of +2.4 J/kg K at 30 K for SmNi3MnSi, -2.6 J/kg K at 65 K for SmNi3FeSi, +0.73 J/kg K at 15 K for SmNi3CoSi and -0.5 J/kg K at 6 K for SmNi3CuSi in field change of 0-50 kOe around the metamagnetic-like transition temperature. Below the field induced transition temperature, SmNi3TSi (T=Mn, Fe, Co, Cu) exhibits giant magnetic coercivity of 80 kOe at 20 K for SmNi3MnSi, 87 kOe at 40 K for SmNi3FeSi, 27 kOe at 20 K for SmNi3CoSi and 54 kOe at 5 K for SmNi3CuSi. Below the field induced transition temperature, SmNi3TSi (T=Mn, Fe, Co, Cu) exhibits giant magnetic coercivity of 80 kOe at 20 K for SmNi3MnSi, 87 kOe at 40 K for SmNi3FeSi, 27 kOe at 20 K for SmNi3CoSi and 54 kOe at 5 K for SmNi3CuSi.

  19. Tetragonal phase of epitaxial room-temperature antiferromagnet CuMnAs.

    PubMed

    Wadley, P; Novák, V; Campion, R P; Rinaldi, C; Martí, X; Reichlová, H; Zelezný, J; Gazquez, J; Roldan, M A; Varela, M; Khalyavin, D; Langridge, S; Kriegner, D; Máca, F; Mašek, J; Bertacco, R; Holý, V; Rushforth, A W; Edmonds, K W; Gallagher, B L; Foxon, C T; Wunderlich, J; Jungwirth, T

    2013-01-01

    Recent studies have demonstrated the potential of antiferromagnets as the active component in spintronic devices. This is in contrast to their current passive role as pinning layers in hard disk read heads and magnetic memories. Here we report the epitaxial growth of a new high-temperature antiferromagnetic material, tetragonal CuMnAs, which exhibits excellent crystal quality, chemical order and compatibility with existing semiconductor technologies. We demonstrate its growth on the III-V semiconductors GaAs and GaP, and show that the structure is also lattice matched to Si. Neutron diffraction shows collinear antiferromagnetic order with a high Néel temperature. Combined with our demonstration of room-temperature-exchange coupling in a CuMnAs/Fe bilayer, we conclude that tetragonal CuMnAs films are suitable candidate materials for antiferromagnetic spintronics.

  20. Diffusion bonding of beryllium to CuCrZr for ITER applications.

    SciTech Connect

    Cadden, Charles H.; Puskar, Joseph David; Goods, Steven Howard

    2008-08-01

    Low temperature diffusion bonding of beryllium to CuCrZr was investigated for fusion reactor applications. Hot isostatic pressing was accomplished using various metallic interlayers. Diffusion profiles suggest that titanium is effective at preventing Be-Cu intermetallics. Shear strength measurements suggest that acceptable results were obtained at temperatures as low as 540C.

  1. [CrIII(NCMe)6]3+--a labile CrIII source enabling formation of Cr[M(CN)6] (M=V, Cr, Mn, Fe) Prussian blue-type magnetic materials.

    PubMed

    Nelson, Kendric J; Daniels, Matthew C; Reiff, William M; Troff, Shayla A; Miller, Joel S

    2007-11-26

    The kinetic inertness of the hexaaquachromium(III) (kH2O=2.4x10(-6) s(-1)) has led to challenges with respect to incorporating CrIII ions into Prussian blue-type materials; however, hexakis(acetonitrile)chromium(III) was shown to be substantially more labile (approximately 10(4) times) and enables a new synthetic route for the synthesis of these materials via nonaqueous solvents. The synthesis, spectroscopic, and physical properties of Cr[M(CN)6] (M=V, Cr, Mn, Fe) Prussian blue analogues synthesized from [CrIII(NCMe)6]3+ and the corresponding [MIII(CN)6]3- are described. All these compounds {(NEt4)0.02CrIII[VIII(CN)6]0.98(BF4)(0.08).0.10MeCN (1), CrIII[CrIII(CN)6].0.16MeCN (2), CrIII[MnIII(CN)6].0.10MeCN (3), and (NEt4)0.04CrIII0.64CrIV0.40[FeII(CN)6]0.40[FeIII(CN)6]0.60(BF4)(0.16).1.02MeCN (4)} are ferrimagnets exhibiting cluster-glass behavior. Strong antiferromagnetic coupling was observed for M=V, Cr, and Mn with Weiss constants (theta) ranging from -132 to -524 K; and in 2, where the strongest coupling is observed (theta=-524 K), the highest Tc (110 K) value was observed. Weak antiferromagnetic coupling was observed for M=Fe (theta=-12 K) leading to the lowest Tc (3 K) value in this series. Weak coupling and the low Tc value observed in 4 were additionally contributed by the presence of both [FeII(CN)6]4- and [FeIII(CN)6]3- as confirmed by 57Fe-Mössbauer spectroscopy.

  2. Two-Stage Heat Treatment of Steel 30CrMnSi and Its Optimization

    NASA Astrophysics Data System (ADS)

    Nekouei, Rasoul Khayyam; Akhaghi, Reza; Tahmasebi, Rouhollah; Ravanbakhsh, Arsalan; Moghaddam, Ali Jafari

    2016-09-01

    The effect of cooling medium on the microstructure and mechanical properties of steel 30CrMnSi is studied after different heat treatment. Microstructure is studied by scanning electron microscopy, energy dispersion analysis, and fractography. Impact strength, shear punch stress, friction coefficient, and wear resistance in pin-on-disk tests are determined. Phase transformations with tempering are studied by dilatometry. A heat treatment regime providing an optimum set of steel properties is proposed.

  3. Numerical analysis of rheological and tribological behavior influence on 16MnCr5 forging fibering

    NASA Astrophysics Data System (ADS)

    Gavrus, A.; Pintilie, D.; Nedelcu, R.

    2016-10-01

    The present research work is focus on the influence of the rheological constitutive equation and friction law formulation on 16MnCr5 forging fibering. Numerical analysis using FE Forge® and Abaqus code show the importance of the rheological softening terms on the metals fibers morphology and position coordinate. Calibration of friction law and sensitivity of softening parameters corresponding to a Hansel-Spittel rheological equation have been studied.

  4. Magnetic and magnetoelastic properties of M-substituted cobalt ferrites (M=Mn, Cr, Ga, Ge)

    SciTech Connect

    Song, Sang-Hoon

    2007-12-15

    Magnetic and magnetoelastic properties of a series of M-substituted cobalt ferrites, CoMxFe2-xO4 (M=Mn, Cr, Ga; x=0.0 to 0.8) and Ge-substituted cobalt ferrites Co1+xGexFe2-2xO4 (x=0.0 to 0.6) have been investigated.

  5. Microstructure and corrosion properties of CrMnFeCoNi high entropy alloy coating

    NASA Astrophysics Data System (ADS)

    Ye, Qingfeng; Feng, Kai; Li, Zhuguo; Lu, Fenggui; Li, Ruifeng; Huang, Jian; Wu, Yixiong

    2017-02-01

    Equimolar CrMnFeCoNi high entropy alloy (HEA) is one of the most notable single phase multi-component alloys up-to-date with promising mechanical properties at cryogenic temperatures. However, the study on the corrosion behavior of CrMnFeCoNi HEA coating has still been lacking. In this paper, HEA coating with a nominal composition of CrMnFeCoNi is fabricated by laser surface alloying and studied in detail. Microstructure and chemical composition are determined by X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) are used to investigate the corrosion behavior. The coating forms a simple FCC phase with an identical dendritic structure composed of Fe/Co/Ni-rich dendrites and Mn/Ni-rich interdendrites. Both in 3.5 wt.% NaCl solution and 0.5 M sulfuric acid the coating exhibits nobler corrosion resistance than A36 steel substrate and even lower icorr than 304 stainless steel (304SS). EIS plots coupled with fitted parameters reveal that a spontaneous protective film is formed and developed during immersion in 0.5 M sulfuric acid. The fitted Rt value reaches its maximum at 24 h during a 48 h' immersion test, indicating the passive film starts to break down after that. EDS analysis conducted on a corroded surface immersed in 0.5 M H2SO4 reveals that corrosion starts from Cr-depleted interdendrites.

  6. Compositional Zoning and Mn-Cr Systematics in Carbonates from the Y791198 CM2 Carbonaceous Chondrite

    NASA Technical Reports Server (NTRS)

    Brearley, Adrian J.; Hutcheon, Ian D.; Browning, Lauren

    2001-01-01

    Cathodoluminescence and microprobe analyses show that carbonates in Y791198 exhibit complex zoning. Cr-Mn dating suggests formation of carbonates 10 Ma after CAI formation Additional information is contained in the original extended abstract..

  7. Compositional Zoning and Mn-Cr Systematics in Carbonates from the Y791198 CM2 Carbonaceous Chondrite

    NASA Technical Reports Server (NTRS)

    Brearley, Adrian J.; Hutcheon, Ian D.; Browning, Lauren

    2001-01-01

    Cathodoluminescence and microprobe analyses show that carbonates in Y791198 exhibit complex zoning. Cr-Mn dating suggests formation of carbonates 10 Ma after CAI formation Additional information is contained in the original extended abstract..

  8. 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.

  9. Compressive deformation behavior of CrMnFeCoNi high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Jang, Min Ji; Joo, Soo-Hyun; Tsai, Che-Wei; Yeh, Jien-Wei; Kim, Hyoung Seop

    2016-11-01

    The compressive deformation behavior of a single phase CrMnFeCoNi high-entropy alloy (HEA) is investigated using experimental and theoretical approaches. The equiaxed microstructures are observed using optical microscope, electron backscattered diffraction, and synchrotron X-ray diffraction (XRD) techniques. Compressive results reveal that the CrMnFeCoNi HEA has a high strain-hardening exponent in spite of its large grain size due to increased dislocation density and severe lattice distortion. The compressive texture of the HEA resembles those of typical FCC metals. The phenomenological dislocation-based constitutive model well describes the compressive deformation behavior. The predicted dislocation density is in good quantitative agreement with the experimental value measured using whole-profile fitting of synchrotron XRD peaks. It can be confirmed from the experimental and theoretical findings that the deformation mechanism of the CrMnFeCoNi HEA is the conventional dislocation glide and mechanical twinning is negligible contrary to general belief.

  10. Anomalous power dependence in the zero-field resonance for the molecular nanomagnet Cr7Mn

    NASA Astrophysics Data System (ADS)

    Collett, C. A.; Timco, G. A.; Winpenny, R. E. P.; Friedman, J. R.

    We report electron-spin resonance studies of the paramagnetic ring [(CH3)2NH2][Cr7MnF8((CH3)3CCOO)16] (''Cr7Mn''), a spin S=1 molecular nanomagnet with a large zero-field ground-state tunnel splitting of ~4 GHz. We perform parallel-mode electron-spin-resonance (ESR) spectroscopy with loop-gap resonators (LGRs) with resonance frequencies of 4-6 GHz. A crystal of Cr7Mn is placed on the loop of the LGR with the sample's easy axis parallel to the field. We observe an ESR peak at zero dc field. With increasing radiation power, a pronounced dip develops in the center of the resonance peak, indicating a decoupling of the sample from the resonator with increased power. The onset of this decoupling depends on both the temperature and the applied power, with greater power required to observe the dip at higher temperatures. By pulsing the radiation, we can rule out that the dip is related to sample heating or saturation of the resonance. Power, temperature, and frequency dependence of the decoupling will be presented, and possible explanations will be discussed.

  11. 53Mn-53Cr dating of aqueously formed carbonates in the CM2 lithology of the Sutter's Mill carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Jilly, Christine E.; Huss, Gary R.; Krot, Alexander N.; Nagashima, Kazuhide; Yin, Qing-Zhu; Sugiura, Naoji

    2014-11-01

    Radiometric dating of secondary minerals can be used to constrain the timing of aqueous alteration on meteoritic parent bodies. Dolomite is a well-documented secondary mineral in CM chondrites, and is thought to have formed by precipitation from an aqueous fluid on the CM parent body within several million years of accretion. The petrographic context of crosscutting dolomite veins indicates that aqueous alteration occurred in situ, rather than in the nebular setting. Here, we present 53Mn-53Cr systematics for dolomite grains in Sutter's Mill section SM51-1. The Mn-Cr isotope data show well-resolved excesses of 53Cr correlated with 55Mn/52Cr ratio, which we interpret as evidence for the in situ decay of radioactive 53Mn. After correcting for the relative sensitivities of Mn and Cr using a synthetic Mn- and Cr-bearing calcite standard, the data yield an isochron with slope corresponding to an initial 53Mn/55Mn ratio of 3.42 ± 0.86 × 10-6. The reported error includes systematic uncertainty from the relative sensitivity factor. When calculated relative to the U-corrected Pb-Pb absolute age of the D'Orbigny angrite, Sutter's Mill dolomites give a formation age between 4564.8 and 4562.2 Ma (2.4-5.0 Myr after the birth of the solar system). This age is contemporaneous with previously reported ages for secondary carbonates in CM and CI chondrites. Consistent carbonate precipitation ages between the carbonaceous chondrite groups suggest that aqueous alteration was a common process during the early stages of parent body formation, probably occurring via heating from internal 26Al decay. The high-precision isochron for Sutter's Mill dolomite indicates that late-stage processing did not reach temperatures that were high enough to further disturb the Mn-Cr isochron.

  12. Effect of Thermomagnetic Treatment on Structure and Properties of Cu-Al-Mn Alloy

    NASA Astrophysics Data System (ADS)

    Titenko, A. N.; Demchenko, L. D.; Perekos, A. O.; Gerasimov, O. Yu

    2017-04-01

    The paper studies the influence of magnetic field on magnetic and mechanical properties of Cu-Mn-Al alloy under annealing. The comparative analysis of the magnetic field orientation impact on solid solution decomposition processes in a fixed annealing procedure is held using the methods of low-field magnetic susceptibility, specific magnetization, and microhardness test. The paper highlights changes in the magnetic and mechanical properties of Cu-Al-Mn alloy as the result of change in a critical size of forming precipitated ferromagnetic phase and determines correlation in the behavior of magnetic and mechanical properties of the alloy, depending on a critical nucleus size of forming precipitated ferromagnetic phase.

  13. Epitaxy of MnO on Cu l brace 001 r brace

    SciTech Connect

    Tian, D.; Li, H.; Wu, S.C.; Quinn, J.; Li, Y.S.; Jona, F. ); Marcus, P.M. )

    1992-09-15

    Deposition of 2--3 layer equivalents of Mn on a clean Cu{l brace}001{r brace} surface followed by exposure to oxygen and brief anneals at 450 {degree}C--475 {degree}C leads to the growth of MnO islands which are epitaxial to, but incommensurate with, the Cu substrate. The proof is provided by a quantitative analysis of low-energy electron-diffraction intensities and is confirmed by angle-integrated and angle-resolved valence-band photoemission experiments.

  14. Thermally stimulated luminescence studies of undoped, Cu- and Mn-doped CaSO4 compounds

    NASA Astrophysics Data System (ADS)

    Manam, J.; Das, S.

    Thermally stimulated luminescence (TSL) of undoped and doped CaSO4 with activators such as Cu and Mn has been investigated. The polycrystalline samples of undoped and doped CaSO4 are prepared by the melting method. The formation of CaSO4 compound is confirmed by X-ray diffraction and Fourier transform infrared studies. Scanning electron microscopic studies of CaSO4 are also carried out. The TSL glow curves of undoped CaSO4, Cu- and Mn-doped CaSO4 are studied. Comparison of the thermoluminescence (TL) intensity of the most intensive glow peak of Cu-doped CaSO4 compound with that of undoped CaSO4 shows that addition of Cu impurity in CaSO4 compound enhances the TL intensity by about four times. However, the addition of Mn impurity to undoped CaSO4 increases the TL intensity by about three times when compared with that of undoped CaSO4. The TL-dose dependence of all three samples was studied and was observed to be almost linear in the studied range of irradiation time. Among the samples studied, namely undoped CaSO4 and Cu- and Mn-doped CaSO4, Cu-doped CaSO4 is found to be the most sensitive. The trap parameters, namely order of kinetics (b), activation energy (E) and frequency factor (s) associated with the most intensive glow peaks of CaSO4:Mn, CaSO4:Cu and CaSO4 phosphors were determined using the glow curve shape (Chen's) method.

  15. Investigation of structural stability and elastic properties of CrH and MnH: A first principles study

    NASA Astrophysics Data System (ADS)

    Kanagaprabha, S.; Rajeswarapalanichamy, R.; Sudhapriyanga, G.; Murugan, A.; Santhosh, M.; Iyakutti, K.

    2015-06-01

    The structural and mechanical properties of CrH and MnH are investigated using first principles calculation based on density functional theory as implemented in VASP code with generalized gradient approximation. The calculated ground state properties are in good agreement with previous experimental and other theoretical results. A structural phase transition from NaCl to NiAs phase at a pressure of 76 GPa is predicted for both CrH and MnH.

  16. Pulse Electrodeposition of Cu-ZnO and Mn-Cu-ZnO Nanowires

    SciTech Connect

    Gupta, Mayank; Pinisetty, D.; Flake, John C.; Spivey, James J.

    2010-07-09

    Cu–ZnO and Mn–Cu–ZnO nanowires are attractive catalysts for alcohol synthesis from CO hydrogenation reactions. Nanowire alloys are pulse electrodeposited into track etched polycarbonate membranes using aqueous electrolytes including Mn(NO3)2, Cu(NO3)2, Zn(NO3)2, and NH4 NO3. Pulse waveforms with a cathodic current density of 50.7mAcm -2 for 50 ms (on-time), with varying off-times (400, 500, and 600 ms), are used to fabricate nanowire arrays (400 nm diameter, 25μm long, and pore density of 1.5×108pores cm-2 ). Pulse waveforms allow significantly higher copper concentrations and better control of zinc and manganese concentrations within nanowires. X-ray diffraction results show preferential growth in the (111) direction and crystallite size increases with an increase in off-time. Waveforms with longer off-times (500 and 600 ms) resulted in nanowires with relatively higher copper concentrations due to improved copper transport in nanopores. The nanowire surface has no manganese; however, the core shows manganese, which increases with the decrease in off-time. The effect of deposition conditions and electrolyte composition on nanowire properties are explained and discussed.

  17. Spectro-photometric determinations of Mn, Fe and Cu in aluminum master alloys

    NASA Astrophysics Data System (ADS)

    Rehan; Naveed, A.; Shan, A.; Afzal, M.; Saleem, J.; Noshad, M. A.

    2016-08-01

    Highly reliable, fast and cost effective Spectro-photometric methods have been developed for the determination of Mn, Fe & Cu in aluminum master alloys, based on the development of calibration curves being prepared via laboratory standards. The calibration curves are designed so as to induce maximum sensitivity and minimum instrumental error (Mn 1mg/100ml-2mg/100ml, Fe 0.01mg/100ml-0.2mg/100ml and Cu 2mg/100ml-10mg/ 100ml). The developed Spectro-photometric methods produce accurate results while analyzing Mn, Fe and Cu in certified reference materials. Particularly, these methods are suitable for all types of Al-Mn, Al-Fe and Al-Cu master alloys (5%, 10%, 50% etc. master alloys).Moreover, the sampling practices suggested herein include a reasonable amount of analytical sample, which truly represent the whole lot of a particular master alloy. Successive dilution technique was utilized to meet the calibration curve range. Furthermore, the workout methods were also found suitable for the analysis of said elements in ordinary aluminum alloys. However, it was observed that Cush owed a considerable interference with Fe, the later one may not be accurately measured in the presence of Cu greater than 0.01 %.

  18. Solid-state synthesis and thermoelectric properties of Cr-doped MnSi1.73

    NASA Astrophysics Data System (ADS)

    Shin, Dong-Kil; You, Sin-Wook; Kim, Il-Ho

    2014-11-01

    Cr-doped HMSs (higher manganese silicides), MnSi1.73 : Cr x ( x = 0, 0.005, 0.01, 0.02, 0.03), were prepared by using a solid-state reaction and hot pressing. X-ray diffraction analysis and Rietveld refinement confirmed the synthesis of MnSi1.73. The Cr atoms were confirmed to be soluble in the HMS structure because the lattice constant increased with increasing Cr content ( x), and the solid solubility limit of Cr was estimated as x = 0.01. All specimens showed p-type conduction and exhibited degenerate semiconductor characteristics at all temperatures examined (323-823 K). The Seebeck coefficient was decreased and the electrical conductivity was increased by Cr doping. The dimensionless thermoelectric figure of merit ZT was obtained as 0.36 at 823 K for MnSi1.73 : Cr0.005 and MnSi1.73 : Cr0.01 because the power factor was increased and the thermal conductivity was decreased by Cr doping.

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

    SciTech Connect

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

    2009-03-08

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

  20. Novel Cu-Cr alloy matrix CNT composites with enhanced thermal conductivity

    NASA Astrophysics Data System (ADS)

    Kong, Jian; Zhang, Chao-ying; Cheng, Xiang

    2013-09-01

    Carbon nanotubes (CNTs) are incorporated into the Cu-Cr matrix to fabricate bulk CNT/Cu-Cr composites by means of a powder metallurgy method, and their thermal conductivity behavior is investigated. It is found that the formation of Cr3C2 interfacial layer improves the interfacial bonding between CNTs and Cu-Cr matrix, producing a reduction of interfacial thermal resistance, and subsequently enhancing the thermal conductivity of the composites. The thermal conductivity of the composites increases by 12 % and 17 % with addition of 5 vol.% and 10 vol.% CNTs, respectively. The experimental results are also theoretically analyzed using an effective medium approximation (EMA) model, and it is found that the EMA model combined with a Debye model can provide a satisfactory agreement to the experimental data.

  1. Luminescence (M=Mn2+, Cu2+) and Esr (M=Gd3+, Mn2+, Cu2+) of Na2ZnP2O7: M

    NASA Astrophysics Data System (ADS)

    Kumar, B. Vijaya; Vithal, M.

    2012-06-01

    We report the synthesis of sodium zinc diphosphate (Na2ZnP2O7) using a domestic microwave oven (2.45 GHz) and metal ion doped sodium zinc diphosphate (Na1.88Gd0.04ZnP2O7/Na1.92M0.04ZnP2O7 (M=Mn and Cu)) by a solid state metathesis reaction. All the materials were characterized by powder X-ray diffraction (XRD) and infrared spectroscopy (IR). These metal doped diphosphates were crystallized in a tetragonal lattice with space group P42/mnm. The IR spectra of all the samples were characterized by bands due to the P2O74- group. The powder electron spin resonance (ESR) spectrum of Na1.88Gd0.04ZnP2O7 gave a characteristic “U” type spectrum. The powder ESR spectrum of Na1.92Mn0.04ZnP2O7 consists of six lines while Na1.92Cu0.04ZnP2O7 gave a broad profile. All the doped metal ions occupy the Na+ site in the diphosphate lattice. The broad emission band at 614 nm (red band) observed for Na1.92Mn0.04ZnP2O7 is assigned to an electronic transition T14(G4)→A16(S6) of Mn2+ in distorted octahedral coordination.

  2. Microstructure and Mechanical Properties of Vacuum Plasma Sprayed Cu-8Cr-4Nb

    NASA Technical Reports Server (NTRS)

    Holmes, Richard; Ellis, David; McKechnie, Timothy; Hickman, Robert

    1997-01-01

    This paper compares the tensile properties of Cu-8Cr-4Nb material produced by VPS to material previously produced by extrusion. The microstructure of the VPS material is also presented. The combustion chamber liner of rocket motors represents an extreme materials application. The liner hot wall is exposed to a 2760 C (5000 F) flame while the cold side is exposed to cryogenic hydrogen liquid. Materials for use in the combustion chamber liner require a combination of high temperature strength, creep resistance, and low cycle fatigue resistance along with high thermal conductivity. The hot side is also subject to localized cycles between reducing and oxidizing environments that degrade the liner by a process called blanching. A new Cu-8 at.% Cr-4 at% Nb (Cu-8Cr-4Nb) alloy has been developed at NASA Lewis Research Center as a replacement for the currently used alloy, NARloy-z (Cu-3 wt.% Ag-0.5 wt.% Zr). The alloy is strengthened by a fine dispersion of Cr2Nb particles. The alloy has better mechanical properties than NARloy-Z while retaining most of the thermal conductivity of pure copper. The alloy has been successfully consolidated by extrusion and hot isostatic pressing (HIPing). However, vacuum plasma spraying (VPS) offers several advantages over prior consolidation methods. VPS can produce a near net shape piece with the profile of the liner. In addition, oxidation resistant and thermal barrier coatings can be incorporated as an integral part of the liner hot wall during the VPS deposition. The low oxygen VPS Cu-8Cr-4Nb exhibits a higher strength than Cu-8Cr-4Nb produced by extrusion at elevated temperatures and a comparable strength at room temperature. Moduli and ductility were not significantly different. However, the ability to produce parts to near-net shape and maintain the good elevated temperature tensile properties of the extruded Cu-8Cr-4Nb makes VPS an attractive processing method for fabricating rocket engine combustion liners.

  3. Microstructure and Mechanical Properties of Vacuum Plasma Sprayed Cu-8Cr-4Nb

    NASA Technical Reports Server (NTRS)

    Holmes, Richard; Ellis, David; McKechnie, Timothy; Hickman, Robert

    1997-01-01

    This paper compares the tensile properties of Cu-8Cr-4Nb material produced by VPS to material previously produced by extrusion. The microstructure of the VPS material is also presented. The combustion chamber liner of rocket motors represents an extreme materials application. The liner hot wall is exposed to a 2760 C (5000 F) flame while the cold side is exposed to cryogenic hydrogen liquid. Materials for use in the combustion chamber liner require a combination of high temperature strength, creep resistance, and low cycle fatigue resistance along with high thermal conductivity. The hot side is also subject to localized cycles between reducing and oxidizing environments that degrade the liner by a process called blanching. A new Cu-8 at.% Cr-4 at% Nb (Cu-8Cr-4Nb) alloy has been developed at NASA Lewis Research Center as a replacement for the currently used alloy, NARloy-z (Cu-3 wt.% Ag-0.5 wt.% Zr). The alloy is strengthened by a fine dispersion of Cr2Nb particles. The alloy has better mechanical properties than NARloy-Z while retaining most of the thermal conductivity of pure copper. The alloy has been successfully consolidated by extrusion and hot isostatic pressing (HIPing). However, vacuum plasma spraying (VPS) offers several advantages over prior consolidation methods. VPS can produce a near net shape piece with the profile of the liner. In addition, oxidation resistant and thermal barrier coatings can be incorporated as an integral part of the liner hot wall during the VPS deposition. The low oxygen VPS Cu-8Cr-4Nb exhibits a higher strength than Cu-8Cr-4Nb produced by extrusion at elevated temperatures and a comparable strength at room temperature. Moduli and ductility were not significantly different. However, the ability to produce parts to near-net shape and maintain the good elevated temperature tensile properties of the extruded Cu-8Cr-4Nb makes VPS an attractive processing method for fabricating rocket engine combustion liners.

  4. Structural and magnetic characterization of the complete delafossite solid solution (CuAlO₂)₁-x(CuCrO₂)x.

    PubMed

    Barton, Phillip T; Seshadri, Ram; Knöller, Andrea; Rosseinsky, Matthew J

    2012-01-11

    We have prepared the complete delafossite solid solution series between diamagnetic CuAlO(2) and the t(2g)(3)frustrated antiferromagnet CuCrO(2). The evolution with composition x in CuAl(1-x)Cr(x)O(2) of the crystal structure and magnetic properties has been studied and is reported here. The room-temperature unit cell parameters follow the Végard law and increase with x as expected. The μ(eff) is equal to the Cr(3+) spin-only S = 3/2 value throughout the entire solid solution. Θ(CW) is negative, indicating that the dominant interactions are antiferromagnetic, and its magnitude increases with Cr substitution. For dilute Cr compositions, the nearest-neighbor exchange coupling constant J(BB) was estimated by mean-field theory to be 3.0 meV. Despite the sizable Θ(CW), long-range antiferromagnetic order does not develop until x is almost 1, and is preceded by glassy behavior. The data presented here, and those on dilute Al substitution from Okuda et al, suggest that the reduction in magnetic frustration due to the presence of non-magnetic Al does not have as dominant an effect on magnetism as chemical disorder and dilution of the magnetic exchange. For all samples, the 5 K isothermal magnetization does not saturate in fields up to 5 T and minimal hysteresis is observed. The presence of antiferromagnetic interactions is clearly evident in the sub-Brillouin behavior with a reduced magnetization per Cr atom. An inspection of the scaled Curie plot reveals that significant short-range antiferromagnetic interactions occur in CuCrO(2) above its Néel temperature, consistent with its magnetic frustration. Uncompensated short-range behavior is present in the Al-substituted samples and is likely a result of chemical disorder.

  5. Size-dependent dual emission of Cu,Mn:ZnSe QDs: Controlling both emission wavelength and intensity.

    PubMed

    Xu, Shuhong; Jiang, Han; Dong, Renjie; Lv, Changgui; Wang, Chunlei; Cui, Yiping

    2017-06-01

    Cu,Mn:ZnSe quantum dots (QDs) of tunable size, controllable photoluminescence (PL) intensity ratio and PL range were prepared. A study of the experimental conditions confirmed that the size of Cu,Mn:ZnSe QDs is affected by the pH of the solution, the speed at which the Zn solution is injected and the reaction temperature. In general, high pH, low injection speed and high reaction temperature are optimal for preparing large QDs. Based on this knowledge, different sizes of Cu,Mn:ZnSe QDs were synthesized. Moreover, white emission Cu,Mn:ZnSe QDs were designed by controlling the experimental conditions and the feeding mole ratio of Mn:Cu. Copyright © 2017 John Wiley & Sons, Ltd.

  6. One-pot synthesis of Mn-doped TiO2 grown on graphene and the mechanism for removal of Cr(VI) and Cr(III).

    PubMed

    Chen, Zengping; Li, Yaru; Guo, Meng; Xu, Fengyun; Wang, Peng; Du, Yu; Na, Ping

    2016-06-05

    Mn-doped TiO2 grown on reduced graphene oxide(rGO) was synthesized by one-pot hydrothermal method and the photocatalytic removal of Cr by the material was investigated under sunlight. The materials were characterized by a combination of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, Brunauer-Emmett-Teller method, UV-vis diffuse reflectance spectra, photoluminescence spectra, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. Cr(total) removal efficiency of the material is 97.32% in 30min and 99.02% in 60min under sunlight irradiation, as the initial concentration of Cr(VI) is 20mg/L. The high photocatalytic activity under visible light is considered mainly due to the Mn-doping, and rGO plays an important role in the synergetic effect of adsorption and photocatalysis to sustain the high efficient removal of Cr(VI) and Cr(III). Cr(VI) adsorbed on the surface of rGO is reduced to Cr(III) by photo electrons which are transported through rGO, and the reaction product Cr(III) continues to be adsorbed. The process contributes to the release of abundant photocatalytic sites of Mn-TiO2 and improves photocatalytic efficiency. The excellent adsorption and photocatalytic effect with the explanation of the synergetic mechanism are very useful not only for fundamental research but also for the potential practical applications.

  7. A series of M(II)Cu(II)3 stars (M = Mn, Ni, Cu, Zn) exhibiting unusual magnetic properties.

    PubMed

    Mondal, Suraj; Mandal, Shuvankar; Carrella, Luca; Jana, Arpita; Fleck, Michel; Köhn, Andreas; Rentschler, Eva; Mohanta, Sasankasekhar

    2015-01-05

    The work in this report describes the syntheses, electrospray ionization mass spectromtery, structures, and experimental and density functional theoretical (DFT) magnetic properties of four tetrametallic stars of composition [M(II)(Cu(II)L)3](ClO4)2 (1, M = Mn; 2, M = Ni; 3, M = Cu; 4, M = Zn) derived from a single-compartment Schiff base ligand, N,N'-bis(salicylidene)-1,4-butanediamine (H2L), which is the [2 + 1] condensation product of salicylaldehyde and 1,4-diaminobutane. The central metal ion (Mn(II), Ni(II), Cu(II), or Zn(II)) is linked with two μ2-phenoxo bridges of each of the three [Cu(II)L] moieties, and thus the central metal ion is encapsulated in between three [Cu(II)L] units. The title compounds are rare or sole examples of stars having these metal-ion combinations. In the cases of 1, 3, and 4, the four metal ions form a centered isosceles triangle, while the four metal ions in 2 form a centered equilateral triangle. Both the variable-temperature magnetic susceptibility and variable-field magnetization (at 2-10 K) of 1-3 have been measured and simulated contemporaneously. While the Mn(II)Cu(II)3 compound 1 exhibits ferromagnetic interaction with J = 1.02 cm(-1), the Ni(II)Cu(II)3 compound 2 and Cu(II)Cu(II)3 compound 3 exhibit antiferromagnetic interaction with J = -3.53 and -35.5 cm(-1), respectively. Variable-temperature magnetic susceptibility data of the Zn(II)Cu(II)3 compound 4 indicate very weak antiferromagnetic interaction of -1.4 cm(-1), as expected. On the basis of known correlations, the magnetic properties of 1-3 are unusual; it seems that ferromagnetic interaction in 1 and weak/moderate antiferromagnetic interaction in 2 and 3 are possibly related to the distorted coordination environment of the peripheral copper(II) centers (intermediate between square-planar and tetrahedral). DFT calculations have been done to elucidate the magnetic properties. The DFT-computed J values are quantitatively (for 1) or qualitatively (for 2 and 3) matched

  8. Large exchange bias enhancement in (Pt(or Pd)/Co)/IrMn/Co trilayers with ultrathin IrMn thanks to interfacial Cu dusting

    SciTech Connect

    Vinai, G.; Moritz, J.; Bandiera, S.; Prejbeanu, I. L.; Dieny, B.

    2014-04-21

    The magnitude of exchange bias (H{sub ex}) at room temperature can be significantly enhanced in IrMn/Co and (Pt(or Pd)/Co)/IrMn/Co structures thanks to the insertion of an ultrathin Cu dusting layer at the IrMn/Co interface. The combination of trilayer structure and interfacial Cu dusting leads to a three-fold increase in H{sub ex} as compared to the conventional IrMn/Co bilayer structure, with an increased blocking temperature (T{sub B}) and a concave curvature of the temperature dependence H{sub ex}(T), ideal for improved Thermally Assisted-Magnetic Random Access Memory storage layer. This exchange bias enhancement is ascribed to a reduction of the spin frustration at the IrMn/Co interface thanks to interfacial Cu addition.

  9. Role of Cu-Ion Doping in Cu-α-MnO2 Nanowire Electrocatalysts for the Oxygen Reduction Reaction

    SciTech Connect

    Davis, Danae J.; Lambert, Timothy N.; Vigil, Julian A.; Rodriguez, Mark A.; Brumbach, Michael T.; Coker, Eric N.; Limmer, Steven J.

    2014-07-09

    The role of Cu-ion doping in α-MnO2 electrocatalysts for the oxygen reduction reaction in alkaline electrolyte was investigated. Copper doped α-MnO2 nanowires (Cu-α-MnO2) were prepared with varying amounts of Cu2+ using a solvothermal method. The electrocatalytic dataindicates that Cu-α-MnO2 nanowires have higher terminal current densities, enhanced kinetic rate constants, and improved charge transfer resistances that trend with Cu-content, exceeding values attained by α-MnO2 alone. The observed improvement in catalytic behavior correlates with an increase in Mn3+ content for the Cu-α-MnO2 nanowires. The Mn3+/Mn4+ couple is themediator for the rate-limiting redox driven O2-/OH- exchange. It is proposed that O2 adsorbs viaan axial site (the eg orbital on the Mn3+ d4 ion) at the surface, or at edge defects, of the nanowireand that the increase in covalent nature of the nanowire with Cu-ion doping leads to stabilization of O2 adsorbates and faster rates of reduction. This work is applicable to other manganese oxide electrocatalysts and shows for the first time there is a correlation for manganese oxides between electrocatalytic activity for the ORR in alkaline electrolyte and an increase in Mn3+ character of the oxide.

  10. Microstructures of phased-in Cr-Cu/Cu/Au bump-limiting metallization and its soldering behavior with high Pb content and eutectic PbSn solders

    NASA Astrophysics Data System (ADS)

    Pan, G. Z.; Liu, Ann A.; Kim, H. K.; Tu, K. N.; Totta, Paul A.

    1997-11-01

    The microstructure of phased-in Cr-Cu/Cu/Au multilayer thin films and their solderability with high Pb-content PbSn solder (95/5%) and eutectic PbSn solder (37/63%) were studied by using cross-sectional transmission electron microscopy and scanning electron microscopy. We found that the phased-in Cr-Cu layer is intermixed and grains of both Cr and Cu are elongated along the growth direction. This special compositionally graded or functionally graded microstructure presents a lock-in effect of the Cr and Cu grains. It has succeeded in preventing the spalling of Cu3Sn in solder joints formed using the 95/5% solder, but failed in preventing the spalling of Cu6Sn5 in those formed using the eutectic solder. We suggest that the difference may be due to the different dissolution rates of the two compounds in the solders.

  11. Tunable emission of Cu (Mn)-doped ZnInS quantum dots via dopant interaction.

    PubMed

    Zhu, Jiatao; Mei, Shiliang; Yang, Wu; Zhang, Guilin; Chen, Qiuhang; Zhang, Wanlu; Guo, Ruiqian

    2017-11-15

    In this work, transition metal ion- doped zinc-based quantum dots (QDs) are synthesized via a greener controllable method to avoid the toxicity of the traditional cadmium-based QDs and broaden the tunable emission. Herein, the tunable emission of Cu-doped ZnInS/ZnS core-shell QDs (Cu:ZnInS/ZnS) can cover from 500 to 620nm by varying the Cu dopant concentration from 1 to 20% and the maximum quantum yield can reach 49.8%. Based on the single-doped QDs, Cu,Mn co-doped ZnInS/ZnS core-shell QDs (Cu,Mn:ZnInS/ZnS) with a photoluminance (PL) quantum yield of 30.4% are obtained. All the as-synthesized QDs have the zinc blende structure and the average size is about 3.55nm. Besides, the interaction mechanism between the Cu and Mn dopant luminescence centers is proposed in this work, which is rarely investigated in the previous report. Diffusion priority and energy transfer between these two dopants are supposed to play an important role in the co-doped QDs and Cu ions could affect the splitting of Mn d states. Color coordinates of these doped QDs show the line-tunability from (0.200, 0.397) to (0.408, 0.508) on the Commission Internationale de L'Eclairage (CIE) chromatic diagram, showing a promising potential in high-quality white light output by integration of these QDs with blue chips. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. Magnetic properties of Cu substituted NdMn2Si2 intermetallics

    NASA Astrophysics Data System (ADS)

    Elmali, A.; Dincer, I.; Elerman, Y.; Ehrenberg, H.; Fuess, H.

    2005-05-01

    The structure and magnetic properties of NdMn2-xCuxSi2 (0.2 x 1) were studied by X-ray powder diffraction and magnetization measurements. In this study, we investigate the variations in the magnetic properties of NdMn2-xCuxSi2 as a function of Cu concentration by examing the evolution of the features in the temperature dependence of the magnetization. Earlier neutron diffraction experiments showed that the ferromagnetic Mn planes are ordered antiparallel along the c-axis below 380 K and the Nd sublattice orders at 33 K in NdMn2Si2. The ordering of the Nd sublattice reconfigures the ordering in Mn sublattice and leads to ferromagnetic ordering. With increasing amount of Cu, the Curie temperature has a maximum value of 120 K at x = 0.7 and decreases for the samples with x 0.8.

  13. Cu, Cr and As distribution in soils adjacent to pressure-treated decks, fences and poles.

    PubMed

    Chirenje, Tait; Ma, L Q; Clark, C; Reeves, M

    2003-01-01

    Chromated copper arsenate (CCA)-treated wood has been widely used in the Southeastern United States to protect wood products from microbial and fungal decay. The aims of this study were to (1). determine the distribution of arsenic (As), chromium (Cr), and copper (Cu), in soils surrounding CCA-treated wood structures such as decks, fences and poles; and (2). evaluate the impacts of these structures on As, Cr and Cu loading of the soils. Profile and lateral soil samples were collected under CCA-treated decks and adjacent to poles and fences. The results showed elevation of As, Cr and Cu concentrations close to and under the structures, with mean As concentrations as high as 23 mg x kg(-1) close to utility poles compared with less than 3 mg x kg (-1) at distances of about 1.5 m away. Concentrations of As, Cr, and Cu decreased with depth in areas close to CCA-treated poles. However, these results were only apparent in relatively new structures. A combination of weathering and leaching with time may have reduced the impact in older poles. Increased concentrations of As, Cu and Cr were also observed close to CCA-treated decks and fences, with age showing a similar impact. These results are helpful for CCA-treated wood product users to determine the safe use of these structures.

  14. Investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al alloy with Ag and Mn additions

    SciTech Connect

    Silva, R.A.G.; Paganotti, A.; Gama, S.; Adorno, A.T.; Carvalho, T.M.; Santos, C.M.A.

    2013-01-15

    The investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al, Cu-11%Al-3%Ag, Cu-11%Al-10%Mn and Cu-11%Al-10%Mn-3%Ag alloys was made using microhardness measurements, differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy, energy dispersion X-ray spectroscopy and magnetic moment change with applied field measurement. The results indicated that the Mn addition changes the phase stability range, the microhardness values and makes undetectable the eutectoid reaction in annealed Cu-11%Al and Cu-11%Al-3%Ag alloys while the presence of Ag does not modify the phase transformation sequence neither microhardness values of the annealed Cu-11%Al and Cu-11%Al-10%Mn alloys, but it increases the magnetic moment of this latter at about 2.7 times and decreases the rates of eutectoid and peritectoid reactions of the former. - Highlights: Black-Right-Pointing-Pointer The microstructure of Cu-Al alloy is modified in the Ag presence. Black-Right-Pointing-Pointer ({alpha} + {gamma}) phase is stabilized down to room temperature when Ag is added to Cu-Al alloy. Black-Right-Pointing-Pointer Ag-rich phase modifies the magnetic characteristics of Cu-Al-Mn alloy.

  15. Zn, Cu, and Mn levels in the liver of the dogfish exposed to Zn

    SciTech Connect

    Sanpera, C.; Vallribera, M.; Crespo, S.

    1983-10-01

    To investigate the effects of Zn contamination on the hepatic distribution of these trace elements, Zn, Cu, and Mn levels were determined by atomic absorption spectrophotometry in the liver of the dogfish Scyliorhinus canicula exposed to 80 and 10 ppm of zinc.

  16. Effect of Mn on the Microstructure and Magnetic Properties in Cu-Fe-Co Alloys

    NASA Astrophysics Data System (ADS)

    Mondal, B. N.; Basu Mallick, A.; Nath, D. N.; Chattopadhyay, P. P.

    2011-02-01

    An attempt was made to study the effect of Mn addition on the formation of supersaturated solid solution of Co and Fe in Cu during ball milling and precipitation of the solute-rich phases during subsequent annealing of the ball-milled product. It is demonstrated that the addition of Mn in the ternary CuFeCo powder blend enhances the metastable solubility of Fe and Co in Cu and facilitates the formation of the nanocrystalline supersaturated single-phase solid solution. Field emission-scanning electron microscopy (FE-SEM) also revealed notable influence of Mn on the morphological evolution of the ball-milled and annealed alloy powders. X-ray diffraction (XRD) analysis revealed that the FeCo phase having the bcc Bravais lattice forms after annealing at and above 620 K (350 °C) in both alloys. Estimation of magnetic properties showed that Mn addition in the CuFeCo alloy improved the coercivity, remanence, and magnetic saturation.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  18. Alloyed Mn-Cu-In-S nanocrystals: a new type of diluted magnetic semiconductor quantum dots.

    PubMed

    Liu, Qinghui; Deng, Ruiping; Ji, Xiangling; Pan, Daocheng

    2012-06-29

    A new type of Mn-Cu-In-S diluted magnetic semiconductor quantum dots was synthesized and reported for the first time. The quantum dots, with no highly toxic elements, not only show the same classic diluted magnetic behavior as Mn-doped CdSe, but also exhibit tunable luminescent properties in a relatively large window from 542 to 648 nm. An absolute photoluminescence quantum yield up to 20% was obtained after the shell growth of ZnS. This kind of magnetic/luminescent bi-functional Mn-Cu-In-S/ZnS core/shell quantum dot might serve as promising nanoprobes for use in dual-mode optical and magnetic resonance imaging techniques.

  19. Alloyed Mn-Cu-In-S nanocrystals: a new type of diluted magnetic semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Liu, Qinghui; Deng, Ruiping; Ji, Xiangling; Pan, Daocheng

    2012-06-01

    A new type of Mn-Cu-In-S diluted magnetic semiconductor quantum dots was synthesized and reported for the first time. The quantum dots, with no highly toxic elements, not only show the same classic diluted magnetic behavior as Mn-doped CdSe, but also exhibit tunable luminescent properties in a relatively large window from 542 to 648 nm. An absolute photoluminescence quantum yield up to 20% was obtained after the shell growth of ZnS. This kind of magnetic/luminescent bi-functional Mn-Cu-In-S/ZnS core/shell quantum dot might serve as promising nanoprobes for use in dual-mode optical and magnetic resonance imaging techniques.

  20. CrCuAgN PVD nanocomposite coatings: Effects of annealing on coating morphology and nanostructure

    NASA Astrophysics Data System (ADS)

    Liu, Xingguang; Iamvasant, Chanon; Liu, Chang; Matthews, Allan; Leyland, Adrian

    2017-01-01

    CrCuAgN PVD nanocomposite coatings were produced using pulsed DC unbalanced magnetron sputtering. This investigation focuses on the effects of post-coat annealing on the surface morphology, phase composition and nanostructure of such coatings. In coatings with nitrogen contents up to 16 at.%, chromium exists as metallic Cr with N in supersaturated solid solution, even after 300 °C and 500 °C post-coat annealing. Annealing at 300 °C did not obviously change the phase composition of both nitrogen-free and nitrogen-containing coatings; however, 500 °C annealing resulted in significant transformation of the nitrogen-containing coatings. The formation of Ag aggregates relates to the (Cu + Ag)/Cr atomic ratio (threshold around 0.2), whereas the formation of Cu aggregates relates to the (Cu + Ag + N)/Cr atomic ratio (threshold around 0.5). The primary annealing-induced changes were reduced solubility of Cu, Ag and N in Cr, and the composition altering from a mixed ultra-fine nanocrystalline and partly amorphous phase constitution to a coarser, but still largely nanocrystalline structure. It was also found that, with sufficient Cu content (>12 at.%), annealing at a moderately high temperature (e.g. 500 °C) leads to transportation of both Cu and Ag (even at relatively low concentrations of Ag, ≤3 at.%) from inside the coating to the coating surface, which resulted in significant reductions in friction coefficient, by over 50% compared to that of the substrate (from 0.31 to 0.14 with a hemispherical diamond indenter, and from 0.83 to 0.40 with an alumina ball counterface, respectively). Results indicate that the addition of both Cu and Ag (in appropriate concentrations) to nitrogen-containing chromium is a viable strategy for the development of 'self-replenishing' silver-containing thin film architectures for temperature-dependent solid lubrication requirements or antimicrobial coating applications.

  1. Magnetization reversal and giant coercivity in Co(Cr0.7Mn0.3)2O4

    NASA Astrophysics Data System (ADS)

    Padam, R.; Kumar, R.; Grover, A. K.; Pal, D.

    2014-04-01

    We demonstrate the evaluation of temperature and magnetic field dependent magnetization of single phase sample of cubic spinel Co(Cr0.7Mn0.3(2O4. It has been noticed that 30% Mn substitution for Cr in CoCr2O4 leads to the huge reversal of temperature dependent magnetization below compensation temperature, Tcomp ˜ 82.9 K. In addition to this, sample is found to exhibit giant coercivity, reaching about 1.54 T at 3K, similar to hard magnetic materials. These intriguing phenomena are ascribed to the presence of magneto-crystalline anisotropy in the sample.

  2. Searching for 0+ states in 50Cr: Implications for the superallowed β decay of 50Mn

    NASA Astrophysics Data System (ADS)

    Leach, K. G.; Garrett, P. E.; Ball, G. C.; Bender, P. C.; Bildstein, V.; Brown, B. A.; Burbadge, C.; Faestermann, T.; Hadinia, B.; Holt, J. D.; Laffoley, A. T.; Jamieson, D. S.; Jigmeddorj, B.; Radich, A. J.; Rand, E. T.; Stroberg, S. R.; Svensson, C. E.; Towner, I. S.; Wirth, H.-F.

    2016-07-01

    A 52Cr(p ,t )50Cr two-neutron pickup reaction was performed using the Q3D magnetic spectrograph at the Maier-Leibnitz-Laboratorium in Garching, Germany. Excited states in 50Cr were observed up to an excitation energy of 5.3 MeV. Despite significantly increased sensitivity and resolution over previous work, no evidence of the previously assigned first excited 0+ state was found. As a result, the 02+ state is reassigned at an excitation energy of Ex=3895.0 (5 ) keV in 50Cr. This reassignment directly impacts direct searches for a nonanalog Fermi β+ decay branch in 50Mn. These results also show better systematic agreement with the theoretical predictions for the 0+ state spectrum in 50Cr using the same formalism as the isospin-symmetry-breaking correction calculations for superallowed nuclei. The experimental data are also compared to ab-initio shell-model predictions using the IM-SRG formalism based on N N and 3 N forces from chiral-EFT in the p f -shell for the first time.

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

    NASA Astrophysics Data System (ADS)

    Ammam, Malika; Easton, E. Bradley

    2012-10-01

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

  4. Synthesis, dielectric behavior and impedance measurement studies of Cr-substituted Zn-Mn ferrites

    SciTech Connect

    Hankare, P.P.; Patil, R.P.; Garadkar, K.M.; Sasikala, R.; Chougule, B.K.

    2011-03-15

    Graphical abstract: Variation of dielectric constant with frequency. Research highlights: {yields} Sol-gel route synthesized spherical crystalline nanoparticles of ZnMn{sub 1-x}Cr{sub x}FeO{sub 4}. {yields} XRD, DTA, FTIR, SEM, dielectric and impedance study. {yields} The ferrites show concentration dependence of ac electrical conductivity. {yields} Impedance response is dominated by grain boundary behavior. -- Abstract: Nanocrystalline ZnMn{sub 1-x}Cr{sub x}FeO{sub 4} (1.0 {>=} x {>=} 0) ferrites were synthesized by sol-gel technique. X-ray diffraction (XRD) confirmed the formation of single phasic cubic spinel lattice for all the compositions studied. Lattice parameter shows a decreasing trend with an increase in Cr content in the compositions. Formation of spherical nanoparticles was revealed by scanning electron microscopy (SEM) analysis. Infrared spectroscopic studies revealed two main absorption bands in the range 400-800 cm{sup -1} arising due to tetrahedral (A) and octahedral (B) site vibrations. Dielectric constant, dielectric loss tangent, ac conductivity and complex impedance were measured as a function of frequency in the range 20 Hz to 1 MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. The role of chromium in modifying structural and dielectric properties of these ferrites has been explained.

  5. Recrystallization Behavior of CoCrCuFeNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Park, Nokeun; Watanabe, Ikuto; Terada, Daisuke; Yokoyama, Yoshihiko; Liaw, Peter K.; Tsuji, Nobuhiro

    2015-04-01

    We investigated the recrystallization behavior of a cold-rolled CoCrCuFeNi high-entropy alloy (HEA). Two different face-centered cubic phases having different chemical compositions and lattice constants in the as-cast specimen have different chemical compositions: One phase was the Cu-lean matrix and the other was the Cu-rich second phase. The second phase remained even after a heat treatment at 1373 K (1100 °C) and Cu enriched more in the Cu-rich second phase. The calculated mixing enthalpies of both Cu-lean and Cu-rich phases in the as-cast and heat-treated specimens explained that Cu partitioning during the heat treatment decreased the mixing enthalpy in both phases. In the specimens 90 pct cold rolled and annealed at 923 K, 973 K, and 1073 K (650 °C, 700 °C, and 800 °C), recrystallization proceeded with increasing the annealing temperature, and ultrafine recrystallized grains with grain sizes around 1 μm could be obtained. The microhardness tended to decrease with increasing the fraction recrystallized, but it was found that the microhardness values of partially recrystallized specimens were much higher than those expected by a simple rule of mixture between the initial and cold-rolled specimens. The reason for the higher hardness was discussed based on the ultrafine grain size, sluggish diffusion expected in HEAs, and two-phase structure in the CoCrCuFeNi alloy.

  6. Ti3CrCu4: A possible 2-D ferromagnetic spin fluctuating system

    NASA Astrophysics Data System (ADS)

    Dhar, S. K.; Provino, A.; Manfrinetti, P.; Kulkarni, R.; Goyal, Neeraj; Paudyal, D.

    2016-05-01

    Ti3CrCu4 is a new ternary compound which crystallizes in the tetragonal Ti3Pd5 structure type. The Cr atoms form square nets in the a-b plane (a = 3.124 Å) which are separated by an unusually large distance c = 11.228 Å along the tetragonal axis, thus forming a -2-D Cr-sublattice. The paramagnetic susceptibility is characterized by a low effective moment, μeff = 1.1 μB, a low paramagnetic Curie temperature θP (below 7 K) and a temperature independent χ0 = 6.7 x 10-4 emu/mol. The magnetization at 1.8 K increases rapidly with field nearly saturating to 0.2 μB/f.u. The zero field heat capacity C/T shows an upturn below 7 K (˜190 mJ/mol K2 at ˜0.1K) which is suppressed in applied magnetic fields and interpreted as suggesting the presence of spin fluctuations. The resistivity at low temperatures shows non-Fermi liquid behavior. Overall, the experimental data thus reveal an unusual magnetic state in Ti3CrCu4, which likely has its origin in the layered nature of the Cr sub-lattice and ferromagnetic spin fluctuations. Density functional theoretical calculations reveal a sharp Cr density of states peak just above the Fermi level, indicating the propensity of Ti3CrCu4 to become magnetic.

  7. Electron scattering mechanisms in Cu-Mn films for interconnect applications

    NASA Astrophysics Data System (ADS)

    Misják, F.; Nagy, K. H.; Lobotka, P.; Radnóczi, G.

    2014-08-01

    Electrical properties and corresponding structural features of Cu-Mn alloy films with potential application as barrier and interconnect layers were studied. Cu-Mn films were deposited by DC magnetron sputtering at room temperature on SiO2 substrates. Electrical resistivity measurements were made as a function of film composition and temperature. The specific resistivity varies linearly with the Mn content showing a maximum of 205 μΩcm at 80 at. % Mn. The temperature coefficient of resistance (TCR) of all alloy films is low, showing non-metallic conductivity for most compositions. Also a minimum TCR has been observed in the 40-80 at. % Mn range which was attributed to a magnetic transformation around 200-300 K. Electrical resistivity measurements are correlated with the film structure revealed by transmission electron microscopy to clarify the phase regions throughout the composition range. In the 20-40 at. % and 70-80 at. % Mn ranges, two-phase structures were identified, where Cu- or Mn-rich solid solution grains were surrounded by a thin amorphous covering layer. Based on the revealed phase regions and morphologies electron scattering mechanisms in the system were evaluated by combining the Matthiessen's rule and the Mayadas-Schatzkes theory. Grain boundary reflectivity coefficients (r = 0.6-0.8) were calculated from fitting the model to the measurements. The proposed model indicates that, in a binary system, the special arrangement of the two phases results in new scattering mechanisms. The results are of value in optimizing the various parameters needed to produce a suitable barrier layer.

  8. Electron scattering mechanisms in Cu-Mn films for interconnect applications

    SciTech Connect

    Misják, F.; Nagy, K. H.; Radnóczi, G.; Lobotka, P.

    2014-08-28

    Electrical properties and corresponding structural features of Cu-Mn alloy films with potential application as barrier and interconnect layers were studied. Cu-Mn films were deposited by DC magnetron sputtering at room temperature on SiO{sub 2} substrates. Electrical resistivity measurements were made as a function of film composition and temperature. The specific resistivity varies linearly with the Mn content showing a maximum of 205 μΩcm at 80 at. % Mn. The temperature coefficient of resistance (TCR) of all alloy films is low, showing non-metallic conductivity for most compositions. Also a minimum TCR has been observed in the 40–80 at. % Mn range which was attributed to a magnetic transformation around 200–300 K. Electrical resistivity measurements are correlated with the film structure revealed by transmission electron microscopy to clarify the phase regions throughout the composition range. In the 20–40 at. % and 70–80 at. % Mn ranges, two-phase structures were identified, where Cu- or Mn-rich solid solution grains were surrounded by a thin amorphous covering layer. Based on the revealed phase regions and morphologies electron scattering mechanisms in the system were evaluated by combining the Matthiessen's rule and the Mayadas-Schatzkes theory. Grain boundary reflectivity coefficients (r = 0.6–0.8) were calculated from fitting the model to the measurements. The proposed model indicates that, in a binary system, the special arrangement of the two phases results in new scattering mechanisms. The results are of value in optimizing the various parameters needed to produce a suitable barrier layer.

  9. Abundances of O, Mg, S, Cr, Mn, Ti, Ni and Zn from absorption lines of neutral gas in the Large Magellanic Cloud in front of R136

    NASA Technical Reports Server (NTRS)

    De Boer, K. S.; Fitzpatrick, E. L.; Savage, B. D.

    1985-01-01

    Weak absorption lines of C I, O I, Mg I, Mg II, Si I, Si II, P I, Cl I, Cr II, Mn II, Fe I, Ni II, Zn II, CO and C2 are detected in neutral gas in front of the 30 Doradus H II region by IUE spectra of R 136. The Large Magellanic Cloud abundances from the absorption lines are a factor of 2 or 3 below those of the Milky Way, in agreement with emission line study results. Neutral gas density and temperature are estimated from the observed excitation and ionization to be about 300/cu cm and 100 K, respectively; this implies a gas pressure of 30,000/cu cm K.

  10. Transparent ferrimagnetic semiconducting CuCr2O4 thin films by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Tripathi, T. S.; Yadav, C. S.; Karppinen, M.

    2016-04-01

    We report the magnetic and optical properties of CuCr2O4 thin films fabricated by atomic layer deposition (ALD) from Cu(thd)2, Cr(acac)3, and ozone; we deposit 200 nm thick films and anneal them at 700 °C in oxygen atmosphere to crystallize the spinel phase. A ferrimagnetic transition at 140 K and a direct bandgap of 1.36 eV are determined for the films from magnetic and UV-vis spectrophotometric measurements. Electrical transport measurements confirm the p-type semiconducting behavior of the films. As the ALD technique allows the deposition of conformal pin-hole-free coatings on complex 3D surfaces, our CuCr2O4 films are interesting material candidates for various frontier applications.

  11. Half-metallic antiferromagnetism in double perovskite BiPbCrCuO{sub 6}

    SciTech Connect

    Weng, Ke-Chuan; Wang, Y. K.

    2015-05-07

    The electronic structure and magnetic properties of BiPbCrCuO{sub 6} double perovskite are investigated based on first-principles density functional calculations with generalized gradient approximation (GGA) and GGA incorporated with Coulomb correlation interaction U (GGA + U). The results suggest the half-metallic (HM) and antiferromagnetic (AFM) properties of BiPbCrCuO{sub 6} double perovskite. The HM-AFM property of the double perovskite is caused by the double-exchange mechanism between neighboring Cr{sup 5+}(t{sub 2g}{sup 1}↓) and Cu{sup 2+}(t{sub 2g}{sup 3}↑t{sub 2g}{sup 3}↓e{sub g}{sup 2}↑e{sub g}↓) via the intermediate O{sup 2−}(2s{sup 2}2p{sup 6}) ion.

  12. Hot and cold rolling of high nitrogen Cr-Ni and Cr-Mn austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Ilola, R.; Hänninen, H.; Kauppi, T.

    1998-10-01

    Behavior of austenitic Cr-Ni-(0.14-0.50)N and Cr-Mn-(0.78-1.00)N steels in hot and cold rolling was investigated by rolling experiments and mechanical testing. Structure of the steels in the as-cast condition and fracture surfaces after the rolling experiments were investigated using optical and scanning electron microscopy (SEM). Resistance to deformation was calculated using rolling forces in hot rolling. Increase in strength in the rolling experiments was related to the nitrogen content of the steels. Resistance to deformation during hot rolling increased with decreasing rolling temperature and with increasing nitrogen content. In some steels, hot rolling led to edge cracking, which was more a function of impurity than nitrogen content. Microscopy revealed that the edge cracking occurred along grain boundaries and second phase particles. For the cold-rolled steels, the highest achievable reductions were limited due to a “crocodiling” phenomenon, that is, opening of the strip end. Fracture type at the opened strip end was a brittle-like fracture.

  13. Hot and cold rolling of high nitrogen Cr-Ni and Cr-Mn austenitic stainless steels

    SciTech Connect

    Iiola, R.; Hanninen, H.; Kauppi, T.

    1998-10-01

    Behavior of austenitic Cr-Ni-(0.14--0.50)N and Cr-Mn-(0.78--1.00)N steels in hot and cold rolling was investigated by rolling experiments and mechanical testing. Structure of the steels in the as-cast condition and fracture surfaces after the rolling experiments were investigated using optical and scanning electron microscopy (SEM). Resistance to deformation was calculated using rolling forces in hot rolling. Increase in strength in the rolling experiments was related to the nitrogen content of the steels. Resistance to deformation during hot rolling increased with decreasing rolling temperature and with increasing nitrogen content. In some steels, hot rolling led to edge cracking, which was more a function of impurity than nitrogen content. Microscopy revealed that the edge cracking occurred along grain boundaries and second phase particles. For the cold-rolled steels, the highest achievable reductions were limited due to a crocodiling phenomenon, that is, opening of the strip end. Fracture type at the opened strip end was a brittle-like fracture.

  14. Transformation of tetracyclines mediated by Mn(II) and Cu(II) ions in the presence of oxygen.

    PubMed

    Chen, Wan-Ru; Huang, Ching-Hua

    2009-01-15

    Complexation of tetracyclines (TCs) with dissolved Mn(II) and Cu(II) ions were found to significantly enhance the transformation of these antibiotics in the presence of oxygen at pH 8-9.5 and pH 4-6, respectively. In the TC-Mn(II)-O2 system, oxidation of the TC-complexed Mn(II) to Mn(III) by oxygen occurs, followed by oxidation of TC by Mn(III) to regenerate Mn(II). In the TC-Cu(II)-O2 system, Cu(II) oxidizes TC within the complex and the yielded Cu(I) is reoxidized by the present oxygen. Opposite reactivity trends were observed with the two metals: OTC (oxytetracycline) > TTC (tetracycline) > iso-CTC (iso-chlorotetracycline) for the Mn(II)-mediated reaction, whereas CTC > TTC > OTC > epimers for the Cu(II)-mediated reaction. The reactivity results and examination of TC-metal ion complexation and transformation products suggest that the BCD-ring and A-ring of TC are crucial to interact with Mn(II) and Cu(II), respectively. This study highlights that the fate of TCs in aquatic environments may differ significantly by their strong interactions with different metal species present in the systems.

  15. Anti-wetting Cu/Cr coating with micro-posts array structure fabricated by electrochemical approaches

    NASA Astrophysics Data System (ADS)

    Zhou, Yufeng; Hang, Tao; Li, Feng; Li, Ming

    2013-04-01

    Microposts structured Cu/Cr multilayer coating was prepared by a simple two-step approach combining electroless and electro deposition. Surface morphologies of the as-prepared Cu/Cr multilayer coating characterized by field emission scanning electron microscopy show that this multilayer coating exhibits micro-posts arrayed structure with a layer of Cr uniformly covering the circular conical surface of Cu micro-cones array. The wettability test shows that the contact angle of Cu/Cr multilayer surface with water drop can be greater than 140° by optimizing the electrodeposition time of Cr. The mechanism of hydrophobicity of both the micro-cones arrayed and micro-posts arrayed structures was briefly discussed by comparing two different wetting modes. Due to its good anti-wetting property and unique structure, the micro-posts arrayed Cu/Cr multilayer coating is expected for extensive practical applications.

  16. Concentrations of heavy metals (Mn, Co, Ni, Cr, Ag, Pb) in coffee.

    PubMed

    Nędzarek, Arkadiusz; Tórz, Agnieszka; Karakiewicz, Beata; Clark, Jeremy Simon; Laszczyńska, Maria; Kaleta, Agnieszka; Adler, Grażyna

    2013-01-01

    Technologies involved in roasting coffee beans, as well as the methods used to prepare infusions, vary according to culture, and contribute to differences in the concentration of elements in the drink. Concentrations of six elements: manganese (Mn), cobalt (Co), nickel (Ni), chrome (Cr), silver (Ag) and lead (Pb) were investigated in coffee infusions from eleven samples of coffee, roasted and purchased in four countries: Bosnia and Herzegovina, Brazil, Lebanon and Poland. Metal concentrations were determined using an induction coupled plasma technique in combination with mass spectrometry (ICP-MS, Perkin Elmer) which measures total metal (ionic and non-ionic) content. Metal intake estimated for individual countries (in the respective order; mean consumption per person per year) was as follows: Mn: 26.8-33.1, 28.3-29.5, 29.7, 12.6-18.9 mg; Co: 0.33-0.48, 0.42-0.35, 0.32, 0.12-0.17 mg; Ni: 3.83-5.68, 4.85-5.51, 4.04, 2.06-2.24 mg; Cr: 0.17-0.41, 0.21-0.47, 0.17, 0.09-0.28 mg; Ag: 0.16-1.13, 0.26-0.70, 0.61, 0.33-1.54 mg, Pb: 4.76-7.56, 3.59-5.13, 3.33, 1.48-2.43 mg. This finding gives new data for Mn, Co, Ni, Cr, and Ag intake from coffee , and suggests that the amounts are negligible. However, the data for Pb consumption in heavy drinkers, for example in Bosnia and Herzegovina, indicate that Pb intake from coffee may contribute to the disease burden. The high lead level in some coffees suggests the need for a more precise control of coffee contamination.

  17. Effects of chelated Zn/Cu/Mn on redox status, immune responses and hoof health in lactating Holstein cows

    PubMed Central

    Zhao, Xue-Jun; Li, Zhong-Peng; Wang, Jun-Hong; Xing, Xiang-Ming; Wang, Zhen-Yong

    2015-01-01

    To evaluate the effects of chelated Zn/Cu/Mn on redox status, immune responses and hoof health in lactating Holstein cows, 48 head in early lactation were divided into healthy or lame groups according to their gait score. Cows were fed the same amount of Zn/Cu/Mn as sulfate salts or in chelated forms for 180 days, and foot-and-mouth disease (FMD) vaccine was injected at day 90. The results showed that lame cows had lower antioxidant function, serum Zn/Mn levels, hair Cu levels, and hoof hardness. Moreover, increased antioxidant status, FMD antibody titers, serum and hair levels of Zn/Cu/Mn, and hoof hardness and decreased milk fat percent and arthritis biomarkers were observed in cows fed chelated Zn/Cu/Mn. In summary, supplementation with chelated Zn/Cu/Mn improved antioxidant status and immune responses, reduced arthritis biomarkers, and increased accumulation of Zn/Cu/Mn in the body and hoof hardness in dairy cows. PMID:26040614

  18. Cu(II) Catalytic Reduction of Cr(VI) by Tartaric Acid Under the Irradiation of Simulated Solar Light

    PubMed Central

    Li, Ying; Qin, Chao; Zhang, Jing; Lan, Yeqing; Zhou, Lixiang

    2014-01-01

    Abstract Cu(II) catalytic reduction of Cr(VI) by tartaric acid under the irradiation of simulated solar light was investigated through batch experiments at pHs from 3 to 6 and at temperatures from 15°C to 35°C. Results demonstrated that introduction of Cu(II) could markedly improve reduction of Cr(VI) in comparison with tartaric acid alone. Optimal removal of Cr(VI) was achieved at pH 4. Reduction of Cr(VI) increased with increasing temperatures and initial concentrations of Cu(II) and tartaric acid. The catalytic role of Cu(II) in the reduction of Cr(VI) was ascribed to the formation of Cu(II)-tartaric acid complex, which generated active reductive intermediates, including Cu(I) and tartaric acid radicals through a pathway of metal–ligand–electron transfer with light. Cu(II) photocatalytic reduction of Cr(VI) by tartaric acid followed pseudo zero-order kinetics with regard to Cr(VI), and the activation energy was calculated to be 21.48 kJ/mol. To date, such a role of Cu(II) has not been reported. The results from the present study are helpful in fully understanding the photochemical reductive behavior of Cr(VI) in the presence of both tartaric acid and Cu(II) in soil and aquatic environments. PMID:25125941

  19. Cu(II) Catalytic Reduction of Cr(VI) by Tartaric Acid Under the Irradiation of Simulated Solar Light.

    PubMed

    Li, Ying; Qin, Chao; Zhang, Jing; Lan, Yeqing; Zhou, Lixiang

    2014-08-01

    Cu(II) catalytic reduction of Cr(VI) by tartaric acid under the irradiation of simulated solar light was investigated through batch experiments at pHs from 3 to 6 and at temperatures from 15°C to 35°C. Results demonstrated that introduction of Cu(II) could markedly improve reduction of Cr(VI) in comparison with tartaric acid alone. Optimal removal of Cr(VI) was achieved at pH 4. Reduction of Cr(VI) increased with increasing temperatures and initial concentrations of Cu(II) and tartaric acid. The catalytic role of Cu(II) in the reduction of Cr(VI) was ascribed to the formation of Cu(II)-tartaric acid complex, which generated active reductive intermediates, including Cu(I) and tartaric acid radicals through a pathway of metal-ligand-electron transfer with light. Cu(II) photocatalytic reduction of Cr(VI) by tartaric acid followed pseudo zero-order kinetics with regard to Cr(VI), and the activation energy was calculated to be 21.48 kJ/mol. To date, such a role of Cu(II) has not been reported. The results from the present study are helpful in fully understanding the photochemical reductive behavior of Cr(VI) in the presence of both tartaric acid and Cu(II) in soil and aquatic environments.

  20. Weldability of a high entropy CrMnFeCoNi alloy

    SciTech Connect

    Wu, Zhenggang; David, Stan A.; Feng, Zhili; Bei, Hongbin

    2016-07-19

    We present the high-entropy alloys are unique alloys in which five or more elements are all in high concentrations. In order to determine its potential as a structural alloy, a model face-centered-cubic CrMnFeCoNi alloy was selected to investigate its weldability. Welds produced by electron beam welding show no cracking. The grain structures within the fusion zone (FZ) are controlled by the solidification behavior of the weld pool. The weldment possesses mechanical properties comparable to those of the base metal (BM) at both room and cryogenic temperatures. Finally, compared with the BM, deformation twinning was more pronounced in the FZ of the tested alloy.

  1. Weldability of a high entropy CrMnFeCoNi alloy

    SciTech Connect

    Wu, Zhenggang; David, Stan A.; Feng, Zhili; Bei, Hongbin

    2016-07-19

    We present the high-entropy alloys are unique alloys in which five or more elements are all in high concentrations. In order to determine its potential as a structural alloy, a model face-centered-cubic CrMnFeCoNi alloy was selected to investigate its weldability. Welds produced by electron beam welding show no cracking. The grain structures within the fusion zone (FZ) are controlled by the solidification behavior of the weld pool. The weldment possesses mechanical properties comparable to those of the base metal (BM) at both room and cryogenic temperatures. Finally, compared with the BM, deformation twinning was more pronounced in the FZ of the tested alloy.

  2. A Study of Free Recovery in a Fe - Mn - Si - Cr Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Spiridon, I.-P.; Lohan, N.-M.; Suru, M.-G.; Mihalache, E.; Bujoreanu, L.-G.; Pricop, B.

    2016-01-01

    Video recording of the free recovery of "hot shape" (typical for the austenitic domain) in shape-memory alloy Fe - 28% Mn - 6% Si - 5% Cr during heating of specimens with a "cold shape" typical for the martensitic domain is performed. Prior to each measurement the specimens are deformed by caliber bending at room temperature in martensitic condition. The thermomechanical training consists in 10 cycles of bending - heating - cooling. Displacements of the free ends of the specimens are plotted as a function of the temperature and the plots are used to determine the critical temperatures of the reverse martensitic transformation.

  3. 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.

  4. Effects of Thermal and Mechanical Processing on Microstructures and Desired Properties of Particle-Strengthened Cu-Cr-Nb Alloys

    NASA Technical Reports Server (NTRS)

    Anderson, Kenneth Reed

    2000-01-01

    Ternary Cu-Cr-Nb alloys, particularly Cu-8 Cr-4 Nb (in at.%), have demonstrated good thermal stability as well as high strength and conductivity at elevated temperatures. The initial powder material has a bimodal size distribution of Cr2Nb precipitates. Primary Cr2Nb precipitates are approx. 1 micron, and secondary Cr2Nb particles are 30-200 nm. The particle coarsening was analyzed and found to follow LSW-type behavior, This study provides a detailed examination of the stability and strengthening effects of Cr2Nb particles. This investigation also revealed that the primary particles provide direct grain boundary pinning and indirect grain boundary strengthening but virtually no Orowan strengthening. The secondary particles found within grains do provide Orowan strengthening. For extruded material, grain bound-ary strengthening (Hall-Petch effect) accounts for two-thirds of the strength with Orowan effects contributing the remainder. The proven advantages of Cu-Cr-Nb were the motivation to improve these attributes via microstructural refinement. Mechanical milling (MM) of Cu- 4 Cr-2 Nb and Cu-8 Cr-2 Nb produced an increase in hot pressed Vickers hardness of 122% and 96%, respectively. The increase in hardness was more due to Cu grain-size refinement than to Cr,,Nb refinement. This study also demonstrated enhanced stability of MM Cu-4 Cr-2 Nb. Hot pressed 4 h milled Cu-4 Cr-2 Nb experienced only a 22% drop in hardness when annealed at 1273 K for 50 h versus a 30% drop for extruded Cu-8 Cr-4 Nb. The goal of improving the strength and stability of Cu-4 Cr-2 Nb to better than such properties for as- extruded Cu-8 Cr-4 Nb has been met. In addition, a figure-of-merit (FOM) coupling hardness and thermal conductivity was maximized for the case of 4 h milled Cu-4 Cr-2 Nb material. Overall, Cu-Cr-Nb alloys not only possess high strength, conductivity and thermal stability but also can be further developed to improve strength and stability.

  5. Equation of State of an AlCoCrCuFeNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Li, Gong; Xiao, Daihong; Yu, Pengfei; Zhang, Lijun; Liaw, Peter K.; Li, Yanchun; Liu, Riping

    2015-08-01

    The pressure-volume (P-V) relationship of the AlCoCrCuFeNi high-entropy alloy (HEA) at room temperature has been studied using in situ high-pressure energy-dispersive x-ray diffraction with synchrotron radiation at high pressures. The equation of state of the AlCoCrCuFeNi HEA is determined by the calculation of the radial distribution function. The experimental results indicate that the HEA keeps a stable face-centered-cubic + body-centered-cubic structure in the experimental pressure range from 0 GPa to 24 GPa.

  6. Factors affecting chelating extraction of Cr, Cu, and As from CCA-treated wood.

    PubMed

    Chang, Fang-Chih; Wang, Ya-Nang; Chen, Pin-Jui; Ko, Chun-Han

    2013-06-15

    The disposal of chromated copper arsenate (CCA)-treated waste wood is becoming a serious problem in many countries due to potential leaching of hazardous elements from in-service use in the environment or disposal of solutions after remediation; therefore, it is necessary to develop proper remediation techniques. The effects of concentration, extraction period, temperature, and sequential extraction on the extraction of Cr, Cu, and As from CCA-treated wood using [S,S]-ethylenediaminedisuccinic acid (EDDS), ethylenediaminetetraacetic acid (EDTA), and nitrilotriacetic acid (NTA) were studied. Mobility of metal in the samples was evaluated by using a sequential extraction scheme that could give the information needed to explain different extraction efficiencies for different metals. Results of long-term leaching tests of CCA-treated wood before and after EDDS extraction were used to evaluate Cr, Cu, and As leachability. Kinetic experiments showed that 6 h was the optimum extraction time for all metals and CCA-treated wood. Experimental results showed that EDDS is a very effective chelating agent for the extraction of Cr, Cu, and As from CCA-treated wood. Increased temperature significantly enhanced the extraction efficiency of CCA metals, especially Cr and As. The much better extractability of Cu compared to Cr and As by chelating agents can be attributed to the presence of larger weakly bound fractions. The CCA-treated woods after EDDS extraction have met the EPA's TCLP regulatory limit and could be classified as a non-hazardous waste according to identification standard of hazardous wastes.

  7. Chemical zoning and diffusion of Ca, Al, Mn, and Cr in olivine of springwater pallasite

    NASA Technical Reports Server (NTRS)

    Zhou, Y.; Steele, Ian M.

    1993-01-01

    The pallasites, consisting mainly of Fe-Ni metal and olivine, are thought to represent the interior of a planetary body which slowly cooled from high temperature. Although the olivines are nearly homogeneous, ion microprobe studies revealed variations of Ca, Ti, Co, Cr, and Ni near grain edges. These variations were thought to represent diffusion in response to falling temperature of the parent body. Pallasite cooling rates have been estimated based on kamacite taenite textures but results differ by x100. In principle elemental profiles in olivine can allow estimates of cooling rate if diffusion coefficients are known; in addition, given a cooling rate, diffusion coefficients could be derived. Data are presented which show that apparent diffusion profiles can be measured for Al, Ca, Cr, and Mn which qualitatively agree with expected diffusion rates and have the potential of providing independent estimates of pallasite cooling rates.

  8. 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)

  9. Chemical zoning and diffusion of Ca, Al, Mn, and Cr in olivine of springwater pallasite

    NASA Technical Reports Server (NTRS)

    Zhou, Y.; Steele, Ian M.

    1993-01-01

    The pallasites, consisting mainly of Fe-Ni metal and olivine, are thought to represent the interior of a planetary body which slowly cooled from high temperature. Although the olivines are nearly homogeneous, ion microprobe studies revealed variations of Ca, Ti, Co, Cr, and Ni near grain edges. These variations were thought to represent diffusion in response to falling temperature of the parent body. Pallasite cooling rates have been estimated based on kamacite taenite textures but results differ by x100. In principle elemental profiles in olivine can allow estimates of cooling rate if diffusion coefficients are known; in addition, given a cooling rate, diffusion coefficients could be derived. Data are presented which show that apparent diffusion profiles can be measured for Al, Ca, Cr, and Mn which qualitatively agree with expected diffusion rates and have the potential of providing independent estimates of pallasite cooling rates.

  10. Grain Refinement and Mechanical Properties of Cu-Cr-Zr Alloys with Different Nano-Sized TiCp Addition.

    PubMed

    Zhang, Dongdong; Bai, Fang; Wang, Yong; Wang, Jinguo; Wang, Wenquan

    2017-08-08

    The TiCp/Cu master alloy was prepared via thermal explosion reaction. Afterwards, the nano-sized TiCp/Cu master alloy was dispersed by electromagnetic stirring casting into the melting Cu-Cr-Zr alloys to fabricate the nano-sized TiCp-reinforced Cu-Cr-Zr composites. Results show that nano-sized TiCp can effectively refine the grain size of Cu-Cr-Zr alloys. The morphologies of grain in Cu-Cr-Zr composites changed from dendritic grain to equiaxed crystal because of the addition and dispersion of nano-sized TiCp. The grain size decreased from 82 to 28 μm with the nano-sized TiCp content. Compared with Cu-Cr-Zr alloys, the ultimate compressive strength (σUCS) and yield strength (σ0.2) of 4 wt% TiCp-reinforced Cu-Cr-Zr composites increased by 6.7% and 9.4%, respectively. The wear resistance of the nano-sized TiCp-reinforced Cu-Cr-Zr composites increased with the increasing nano-sized TiCp content. The wear loss of the nano-sized TiCp-reinforced Cu-Cr-Zr composites decreased with the increasing TiCp content under abrasive particles. The eletrical conductivity of Cu-Cr-Zr alloys, 2% and 4% nano-sized TiCp-reinforced Cu-Cr-Zr composites are 64.71% IACS, 56.77% IACS and 52.93% IACS, respectively.

  11. Structural and magnetic modulations in CaCu(x)Mn(7 - x)O(12).

    PubMed

    Sławiński, W; Przeniosło, R; Sosnowska, I; Bieringer, M

    2010-05-12

    Low temperature atomic position modulations and magnetic moment modulations are reported for CaCu(x)Mn(7 - x)O(12) (x = 0.0, 0.1 and 0.23) using neutron powder diffraction. Both modulations are described with propagation vectors (0, 0, q) parallel to the c-axis in the hexagonal setting. The present neutron diffraction studies confirm the quantitative model describing the atomic position modulations in CaCu(x)Mn(7 - x)O(12) (x = 0.0 and 0.1) as derived from synchrotron based powder x-ray diffraction studies (Sławiński et al 2009 Acta Crystallogr. B 65 535). Neutron diffraction studies confirm the relation between the atomic position modulation length L(p) and the magnetic modulation length L(m) = 2L(p) between 50 K and the Néel temperature T(N). CaCu(x)Mn(7 - x)O(12) (x = 0.1 and 0.23) shows a magnetic phase transition near 50 K associated with considerable changes of the magnetic modulation length and the magnetic coherence length, similar to that observed in the parent CaMn(7)O(12).

  12. Magnetic refrigeration capabilities of magnetocaloric Ni2Mn:75Cu:25Ga

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Jenkins, C. A.; Dubenko, I.; Samanta, T.; Ali, N.; Roy, S.

    2013-03-01

    Doping-driven competition between energetically similar ground states leads to many exciting materials phenomena such as the emergence of high-Tc superconductivity, diluted magnetic semiconductors, and colossal magnetoresistance. Doped Ni2MnGa Heusler alloy, which is a multifunctional ferromagnetic alloy with various exotic physical properties demonstrates this notion of rich phenomenology via modified ground spin states. Adopting this generic concept, here we will present a novel doped Ni2Mn.75Cu.25Ga alloy that offers unprecedented co-existence of the magnetocaloric effect and fully controlled ferromagnetism at room temperature. Application of site engineering enables us to manipulate the ground spin state that leads to the decrease in magnetic transition temperature and also increases the delocalization of the Mn magnetism. SQUID magnetometery suggests that Cu doping enhances the saturation magnetization, coercive field and clarity of magnetic hysteresis loops. By exploiting x-ray absorption techniques and measuring element specific magnetic hysteresis loops, here we will describe the microscopic origin of enhnaced magnetocaloric properties and d-d interaction driven charge transfer effects in Ni2Mn.75Cu.25Ga This work was supported by DOE Grant No. DE-FG02-06ER46291

  13. Synthesis and Electrochemical Characterization of M2Mn3O8 (M=Ca,Cu) Compounds and Derivatives

    SciTech Connect

    Park, Yong Joon; Doeff, Marca M.

    2005-08-25

    M{sub 2}Mn{sub 3}O{sub 8} (M=Ca{sup 2+}, Cu{sup 2+}) compounds were synthesized and characterized in lithium cells. The M{sup 2+} cations, which reside in the van der Waal's gaps between adjacent sheets of Mn{sub 3}O{sub 8}{sup 4-}, may be replaced chemically (by ion-exchange) or electrochemically with Li. More than 7 Li{sup +}/Cu{sub 2}Mn{sub 3}O{sub 8} may be inserted electrochemically, with concomitant reduction of Cu{sup 2+} to Cu metal, but less Li can be inserted into Ca{sub 2}Mn{sub 3}O{sub 8}. In the case of Cu{sup 2+}, this process is partially reversible when the cell is charged above 3.5 V vs. Li, but intercalation of Cu{sup +} rather than Cu{sup 2+} and Li{sup +}/Cu{sup +} exchange occurs during the subsequent discharge. If the cell potential is kept below 3.4 V, the Li in excess of 4Li{sup +}/Cu{sub 2}Mn{sub 3}O{sub 8} can be cycled reversibly. The unusual mobility of +2 cations in a layered structure has important implications both for the design of cathodes for Li batteries and for new systems that could be based on M{sup 2+} intercalation compounds.

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

    NASA Astrophysics Data System (ADS)

    Surour, Adel A.

    2015-01-01

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

  16. Investigation of electronic structure, magnetic and transport properties of half-metallic Mn2CuSi and Mn2ZnSi Heusler alloys

    NASA Astrophysics Data System (ADS)

    Bhat, Idris Hamid; Yousuf, Saleem; Mohiuddin Bhat, Tahir; Gupta, Dinesh C.

    2015-12-01

    The electronic and magnetic properties of Mn2CuSi and Mn2ZnSi Heusler alloys have been investigated using full-potential linearized augmented plane wave method. The optimized equilibrium lattice parameters in stable F-43m configuration are found to be 5.75 Å for Mn2CuSi and 5.80 Å for Mn2ZnSi. Spin-resolved calculations show that the Mn atoms at inequivalent Wyckoff positions have different contributions to the total magnetic moment in the unit cell. The anti-parallel magnetic moments of inequivalent Mn atoms sum to an integer with total magnetic moment per unit cell. The 100% spin-polarization at Fermi energy together with the total magnetic moment of 1.0 μB for Mn2CuSi and 2.0 μB for Mn2ZnSi per unit cell, predict that the materials follow MT=ZT - 28 Slater-Pauling rule. Both the materials under study exhibit half-metallicity with an energy gap in the spin-down channels. In the study, we predict a rather fine value of Seebeck coefficient. Further, the decreasing electrical conductivity with temperature shows a metallic character in spin-up configurations, while the electrical conductivity of spin-down states follows a semiconductor-like trend.

  17. Structure, Magnetism, and Transport of CuCr2Se4 Thin Films

    SciTech Connect

    Bettinger, J.S.; Chopdekar, R.V.; Liberati, M.; Neulinger, J.R.; Chshiev, M.; Takamura, Y.; Alldredge, L.M.B.; Arenholz, E.; Idzerda,Y.U.; Stacy, A.M.; Butler, W.H.; Suzuki, Y.

    2007-04-01

    We report the successful growth of highly spin-polarized chalcogenide thin films of CuCr{sub 2}Se{sub 4}, which are promising candidates for spin-based electronic applications. We also present electronic structure calculations for CuCr{sub 2}Se{sub 4} that, together with magnetic and transport data, imply that the stoichiometric compound is a metallic ferromagnet with a relatively low density of hole-like carriers at the Fermi energy. These calculations also predict that a deficiency of Se will deplete the minority density of states at the Fermi energy perhaps leading to a half-metal. We have successfully grown thin films of CuCr{sub 2}Se{sub 4} by pulsed laser deposition on isostructural MgAl{sub 2}O{sub 4} substrates followed by an anneal in a Se-rich environment. X-ray diffraction confirms the structure of CuCr{sub 2}Se{sub 4} on MgAl{sub 2}O{sub 4} substrates as well as a secondary phase of Cr{sub 2}Se{sub 3}. X-ray absorption spectroscopy indicates that the chemical structure at the surface of the films is similar to that of bulk CuCr{sub 2}Se{sub 4} single crystals. Magnetization measurements indicate that these films saturate with a magnetic moment close to 5 {micro}{sub B} per formula unit and a T{sub c} above 400 K. X-ray magnetic circular dichroism shows that the magnetism persists to the surface of the film. Resistivity and Hall effect measurements are consistent with a p-type ferromagnetic metallic behavior and with the electronic structure calculations.

  18. Vacuum Plasma Spray of CuCrNb Alloy for Advanced Liquid - Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank

    2000-01-01

    The copper-8 atomic percent chromium-4 atomic percent niobium (CuCrNb) alloy was developed by Glenn Research Center (formally Lewis Research Center) as an improved alloy for combustion chamber liners. In comparison to NARloy-Z, the baseline (as in Space Shuttle Main Engine) alloy for such liners, CuCrNb demonstrates mechanical and thermophysical properties equivalent to NARloy-Z, but at temperatures 100 C to 150 C (180 F to 270 F) higher. Anticipated materials related benefits include decreasing the thrust cell liner weight 5% to 20%, increasing the service life at least two fold over current combustion chamber design, and increasing the safety margins available to designers. By adding an oxidation and thermal barrier coating to the liner, the combustion chamber can operate at even higher temperatures. For all these benefits, however, this alloy cannot be formed using conventional casting and forging methods because of the levels of chromium and niobium, which exceed their solubility limit in copper. Until recently, the only forming process that maintains the required microstructure of CrNb intermetallics is powder metallurgy formation of a billet from powder stock, followed by extrusion. This severely limits its usefulness in structural applications, particularly the complex shapes required for combustion chamber liners. Vacuum plasma spray (VPS) has been demonstrated as a method to form structural articles including small combustion chambers from the CuCrNb alloy. In addition, an oxidation and thermal barrier layer can be formed integrally on the hot wall of the liner that improve performance and extend service life. This paper discusses the metallurgy and thermomechanical properties of VPS formed CuCrNb versus the baseline powder metallurgy process, and the manufacturing of small combustion chamber liners at Marshall Space Flight Center using the VPS process. The benefits to advanced propulsion initiatives of using VPS to fabricate combustion chamber liners

  19. Vacuum Plasma Spray of CuCrNb Alloy for Advanced Liquid - Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank

    2000-01-01

    The copper-8 atomic percent chromium-4 atomic percent niobium (CuCrNb) alloy was developed by Glenn Research Center (formally Lewis Research Center) as an improved alloy for combustion chamber liners. In comparison to NARloy-Z, the baseline (as in Space Shuttle Main Engine) alloy for such liners, CuCrNb demonstrates mechanical and thermophysical properties equivalent to NARloy-Z, but at temperatures 100 C to 150 C (180 F to 270 F) higher. Anticipated materials related benefits include decreasing the thrust cell liner weight 5% to 20%, increasing the service life at least two fold over current combustion chamber design, and increasing the safety margins available to designers. By adding an oxidation and thermal barrier coating to the liner, the combustion chamber can operate at even higher temperatures. For all these benefits, however, this alloy cannot be formed using conventional casting and forging methods because of the levels of chromium and niobium, which exceed their solubility limit in copper. Until recently, the only forming process that maintains the required microstructure of CrNb intermetallics is powder metallurgy formation of a billet from powder stock, followed by extrusion. This severely limits its usefulness in structural applications, particularly the complex shapes required for combustion chamber liners. Vacuum plasma spray (VPS) has been demonstrated as a method to form structural articles including small combustion chambers from the CuCrNb alloy. In addition, an oxidation and thermal barrier layer can be formed integrally on the hot wall of the liner that improve performance and extend service life. This paper discusses the metallurgy and thermomechanical properties of VPS formed CuCrNb versus the baseline powder metallurgy process, and the manufacturing of small combustion chamber liners at Marshall Space Flight Center using the VPS process. The benefits to advanced propulsion initiatives of using VPS to fabricate combustion chamber liners

  20. Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil.

    PubMed

    Shaheen, Sabry M; Rinklebe, Jörg

    2017-01-15

    The impact of sugar beet factory lime (SBFL) on the release dynamics and mobilization of toxic metals (TMs) under dynamic redox conditions in floodplain soils has not been studied up to date. Therefore, the aim of this study was to verify the scientific hypothesis that SBFL is able to immobilize Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn under different redox potentials (EH) in a contaminated floodplain soil. For this purpose, the non-treated contaminated soil (CS) and the same soil treated with SBFL (CS+SBFL) were flooded in the laboratory using a highly sophisticated automated biogeochemical microcosm apparatus. The experiment was conducted stepwise from reducing (-13 mV) to oxidizing (+519 mV) soil conditions. Soil pH decreased under oxic conditions in CS (from 6.9 to 4.0) and in CS+SBFL (from 7.5 to 4.4). The mobilization of Cu, Cr, Pb, and Fe were lower in CS+SBFL than in CS under both reducing/neutral and oxic/acidic conditions. Those results demonstrate that SBFL is able to decrease concentrations of these elements under a wide range of redox and pH conditions. The mobilization of Cd, Co, Mn, Mo, Ni, and Zn were higher in CS+SBFL than in CS under reducing/neutral conditions; however, these concentrations showed an opposite behavior under oxic/acidic conditions and were lower in CS+SBFL than in CS. We conclude that SBFL immobilized Cu, Cr, Pb, and Fe under dynamic redox conditions and immobilized Cd, Co, Mn, Mo, Ni, and Zn under oxic acidic conditions; however, the latter elements were mobilized under reducing neutral conditions in the studied soil. Therefore, the addition of SBFL to acid floodplain soils contaminated with TMs might be an important alternative for ameliorating these soils with view to a sustainable management of these soils.

  1. A novel coping metal material CoCrCu alloy fabricated by selective laser melting with antimicrobial and antibiofilm properties.

    PubMed

    Ren, Ling; Memarzadeh, Kaveh; Zhang, Shuyuan; Sun, Ziqing; Yang, Chunguang; Ren, Guogang; Allaker, Robert P; Yang, Ke

    2016-10-01

    The aim of this study was to fabricate a novel coping metal CoCrCu alloy using a selective laser melting (SLM) technique with antimicrobial and antibiofilm activities and to investigate its microstructure, mechanical properties, corrosion resistance and biocompatibility. Novel CoCrCu alloy was fabricated using SLM from a mixture of commercial CoCr based alloy and elemental Cu powders. SLM CoCr without Cu served as control. Antibacterial activity was analyzed using standard antimicrobial tests, and antibiofilm properties were investigated using confocal laser scanning microscope. Cu distribution and microstructure were determined using scanning electron microscope, optical microscopy and X-ray diffraction. Corrosion resistance was evaluated by potential dynamic polarization and biocompatibility measured using an MTT assay. SLM CoCrCu alloys were found to be bactericidal and able to inhibit biofilm formation. Other factors such as microstructure, mechanical properties, corrosion resistance and biocompatibility were similar to those of SLM CoCr alloys. The addition of appropriate amounts of Cu not only maintains normal beneficial properties of CoCr based alloys, but also provides SLM CoCrCu alloys with excellent antibacterial and antibiofilm capabilities. This material has the potential to be used as a coping metal for dental applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Structural, optical, dielectric and antibacterial studies of Mn doped Zn0.96Cu0.04O nanoparticles.

    PubMed

    Sangeetha, R; Muthukumaran, S; Ashokkumar, M

    2015-06-05

    Zn(0.96-x)Cu0.04Mn(x)O (0⩽x⩽0.04) nanoparticles were synthesized by sol-gel method. The X-ray diffraction pattern indicated that doping of Mn and Cu did not change the ZnO hexagonal wurtzite structure. The Mn doped nanoparticles had smaller average crystallite size than un-doped Zn0.96Cu0.04O nanoparticles due to the distortion in the host ZnO lattice. This distortion prevented the subsequent growth and hence the size reduced by Mn doping. The changes in lattice parameters, average crystallite size, peak position and peak intensity confirmed the Mn substitution in Zn-Cu-O lattice. The Mn and Cu co-doping increased the charge carrier density in ZnO nanoparticles which led to increase the dielectric constant. The dielectric constant also varied by depend the size of the nanoparticles. The change in morphology by Mn-doping was studied by transmission electron microscope. The optical absorption and band gap were changed with respect to both compositional and size effects. The band gap was initially increased from 3.65 to 3.73 eV at 1% of Mn doping, while decreasing trend in band gap was noticed for further increase of Mn. The band gap was decreased from 3.73 to 3.48 eV when Mn concentration was increased from 2% to 4%. Presence of chemical bonding and purity of the nanoparticles were confirmed by FTIR spectra. The antibacterial study revealed that that the antibacterial activity of Zn0.96Cu0.04O is enhanced by Mn doping.

  3. Enhanced Photovoltage Response of Hematite-X-Ferrite Interfaces (X = Cr, Mn, Co, or Ni)

    NASA Astrophysics Data System (ADS)

    Bian, Liang; Li, Hai-long; Li, Yu-jin; Nie, Jia-nan; Dong, Fa-qin; Dong, Hai-liang; Song, Mian-xin; Wang, Li-sheng; Zhou, Tian-liang; Zhang, Xiao-yan; Li, Xin-xi; Xie, Lei

    2017-02-01

    High-fluorescent p-X-ferrites (XFe2O4; XFO; X = Fe, Cr, Mn, Co, or Ni) embedded in n-hematite (Fe2O3) surfaces were successfully fabricated via a facile bio-approach using Shewanella oneidensis MR-1. The results revealed that the X ions with high/low work functions modify the unpaired spin Fe2+-O2- orbitals in the XFe2O4 lattices to become localized paired spin orbitals at the bottom of conduction band, separating the photovoltage response signals (73.36 455.16/-72.63 -32.43 meV). These (Fe2O3)-O-O-(XFe2O4) interfacial coupling behaviors at two fluorescence emission peaks (785/795 nm) are explained via calculating electron-hole effective masses (Fe2O3-FeFe2O4 17.23 × 10-31 kg; Fe2O3-CoFe2O4 3.93 × 10-31 kg; Fe2O3-NiFe2O4 11.59 × 10-31 kg; Fe2O3-CrFe2O4 -4.2 × 10-31 kg; Fe2O3-MnFe2O4 -11.73 × 10-31 kg). Such a system could open up a new idea in the design of photovoltage response biosensors.

  4. Synthesis, structures and magnetic properties of the dimorphic Mn2CrSbO6 oxide.

    PubMed

    Dos santos-García, Antonio J; Solana-Madruga, Elena; Ritter, Clemens; Ávila-Brande, David; Fabelo, Oscar; Sáez-Puche, Regino

    2015-06-21

    The perovskite polymorph of Mn(2)CrSbO(6) compound has been synthesized at 8 GPa and 1473 K. It crystallizes in the monoclinic P21/n space group with cell parameters a = 5.2180 (2) Å, b = 5.3710(2) Å, c = 7.5874(1) Å and β = 90.36(1)°. Magnetic susceptibility and magnetization measurements show the simultaneous antiferromagnetic ordering of Mn(2+) and Cr(3+) sublattices below TN = 55 K with a small canting. Low temperature powder neutron diffraction reveals a commensurate magnetic structure with spins confined to the ac-plane and a propagation vector κ = [1/2 0 1/2]. The thermal treatment of this compound induces an irreversible phase transition to the ilmenite polymorph, which has been isolated at 973 K and crystallizes in R3[combining macron] space group with cell parameters a = 5.2084 (4) Å and c = 14.4000 (11) Å. Magnetic susceptibility, magnetization and powder neutron diffraction data confirm the antiferromagnetic helical ordering of spins in an incommensurate magnetic structure with κ = [00 0.46] below 60 K, and the temperature dependence of the propagation vector up to κ = [00 0.54] at about 10 K.

  5. 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).

  6. Cu-Zn powders as potential Cr(VI) adsorbents for drinking water.

    PubMed

    Kaprara, E; Seridou, P; Tsiamili, V; Mitrakas, M; Vourlias, G; Tsiaoussis, I; Kaimakamis, G; Pavlidou, E; Andritsos, N; Simeonidis, K

    2013-11-15

    This work examines the possibility of applying CuZn alloys as a reducing medium for the efficient removal of hexavalent chromium from drinking water. In an effort to develop a route for producing powders of CuZn alloys under mild conditions and investigate the optimum composition for such application, a series of alloys in the form of powders were prepared, by a sequence of Cu and Zn ball-milling and low temperature annealing. Batch Cr(VI) removal tests, performed to evaluate and compare the efficiency of the products under typical natural water parameters (pH 7 and natural-like water), indicated that the best performing material have a composition around 50 wt% Cu. The dominant reduction mechanisms are both the corrosion of the alloy surface and the electron transfer to the solution. The behavior of granulated CuZn media was tested in rapid-scale column tests using the commercial KDF which verified the high potential of CuZn alloys in Cr(VI) removal. Nevertheless, Cu and Zn leaching problems should be also considered. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. Thermoelectric Properties of CuAgSe doped with Co, Cr

    NASA Astrophysics Data System (ADS)

    Czajka, Peter; Yao, Mengliang; Opeil, Cyril

    Thermoelectric materials represent one way that reliable cooling below the boiling point of nitrogen can be realized. Current materials do not exhibit sufficiently high efficiencies at cryogenic temperatures, but significant progress is being made. One material that has generated significant interest recently is CuAgSe. It has been demonstrated (Ishiwata et al., Nature Mater. 2013) that doping CuAgSe with 10% Ni at the Cu sites increases the material's thermoelectric figure of merit (ZT) at 100 K from 0.02 to 0.10. This is intriguing not just because of the dramatic effect that the Ni doping produces, but also because CuAgSe is a semimetal and semimetals are not usually able to exhibit the kind of asymmetric carrier activation necessary for strong thermoelectric performance. In order to further investigate the unusual nature of thermoelectricity in CuAgSe and its strong dependence on chemical composition, we have synthesized and measured the thermoelectric properties of a series of CuAgSe samples doped with Co and Cr. Temperature-dependent magnetic and thermoelectric transport properties of CuAgSe as a function of Co and Cr doping will be discussed. This work is supported by the Department of Defense, AFOSR, MURI Program Contract # FA9550-10-1-0533 and the Trustees of Boston College.

  8. Synthesis and characterization of La(Cr,Fe,Mn)O3 nanoparticles obtained by co-precipitation method

    NASA Astrophysics Data System (ADS)

    Fabian, F. A.; Pedra, P. P.; Filho, J. L. S.; Duque, J. G. S.; Meneses, C. T.

    2015-04-01

    Magnetic and structural properties have been investigated in La(Cr,Fe,Mn)O3 nanoparticles obtained by co-precipitation method. The X-ray diffraction measurements allied to Rietveld method confirm the formation of LaCrO3, LaFeO3 and LaMnO3 nanoparticles with crystal structure orthorhombic (Pbnm), orthorhombic (Pnma) and rhombohedral (R-3c), respectively. We also verified an decreasing in the average crystallite size from 73 to 26 nm, depending of the transition metal. The magnetic measurements reveal an antiferromagnetic behavior for the LaCrO3 sample with TN~289 K, and a weak ferromagnetic ordering for the LaMnO3 sample with Tc~200 K.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  10. Multiple magnetic transitions, Griffiths-like phase, and magnetoresistance in La2CrMnO6

    NASA Astrophysics Data System (ADS)

    Palakkal, Jasnamol Pezhumkattil; Raj Sankar, Cheriyedath; Varma, Manoj Raama

    2017-08-01

    DC and AC magnetic measurements indicate the presence of multiple magnetic transitions arising from the competing magnetic interaction between Cr and Mn in the perovskite La2CrMnO6. Ferromagnetic and spin glass transitions are observed in La2CrMnO6. The material also has a Griffith-like phase with the occurrence of ferromagnetic short range correlations above TC. The system ultimately turns into paramagnetic at the Griffiths temperature 180 K. A combination of variable range hopping, and the nearest neighbor small polaron hopping governs the conduction mechanism in the material. A negative magnetoresistance of 22% at 105 K is observed for the material at 90 kOe which increases to 29% near 110 K and reduces gradually to zero on further increase in the temperature.

  11. Wetting and interface phenomena in the molten Sn/CuFeNiCoCr high-entropy alloy system

    NASA Astrophysics Data System (ADS)

    Ma, G. F.; Li, Z. K.; Ye, H.; He, C. L.; Zhang, H. F.; Hu, Z. Q.

    2015-11-01

    The wetting behavior and the interfacial characteristics of the molten Sn on a CuFeNiCoCr high-entropy alloy (HEA) substrate were investigated by the sessile drop method. Oxidation of the CuCoNiFeCr HEA surface inhibited the interaction between the molten Sn and the CuCoNiFeCr HEA substrate, leading to a very poor wetting at 573 K, 623 K and 673 K. However, the equilibrium contact angle decreased monotonously with the temperature increasing in the temperature range of 673-923 K. Moreover, the interfacial microstructure depended on temperature. An intermetallic compound existed at the interface between the molten Sn and the CuFeNiCoCr HEA substrate, and the interface thickness varied with the wetting temperature. The wetting process of the molten Sn on the CuFeNiCoCr HEA substrate consisted of three stages according to the wetting temperature.

  12. Synthesis and characterization of (smif)2M(n) (n = 0, M = V, Cr, Mn, Fe, Co, Ni, Ru; n = +1, M = Cr, Mn, Co, Rh, Ir; smif =1,3-di-(2-pyridyl)-2-azaallyl).

    PubMed

    Frazier, Brenda A; Bartholomew, Erika R; Wolczanski, Peter T; DeBeer, Serena; Santiago-Berrios, Mitk'El; Abruña, Hector D; Lobkovsky, Emil B; Bart, Suzanne C; Mossin, Susanne; Meyer, Karsten; Cundari, Thomas R

    2011-12-19

    A series of Werner complexes featuring the tridentate ligand smif, that is, 1,3-di-(2-pyridyl)-2-azaallyl, have been prepared. Syntheses of (smif)(2)M (1-M; M = Cr, Fe) were accomplished via treatment of M(NSiMe(3))(2)(THF)(n) (M = Cr, n = 2; Fe, n = 1) with 2 equiv of (smif)H (1,3-di-(2-pyridyl)-2-azapropene); ortho-methylated ((o)Mesmif)(2)Fe (2-Fe) and ((o)Me(2)smif)(2)Fe (3-Fe) were similarly prepared. Metatheses of MX(2) variants with 2 equiv of Li(smif) or Na(smif) generated 1-M (M = Cr, Mn, Fe, Co, Ni, Zn, Ru). Metathesis of VCl(3)(THF)(3) with 2 Li(smif) with a reducing equiv of Na/Hg present afforded 1-V, while 2 Na(smif) and IrCl(3)(THF)(3) in the presence of NaBPh(4) gave [(smif)(2)Ir]BPh(4) (1(+)-Ir). Electrochemical experiments led to the oxidation of 1-M (M = Cr, Mn, Co) by AgOTf to produce [(smif)(2)M]OTf (1(+)-M), and treatment of Rh(2)(O(2)CCF(3))(4) with 4 equiv Na(smif) and 2 AgOTf gave 1(+)-Rh. Characterizations by NMR, EPR, and UV-vis spectroscopies, SQUID magnetometry, X-ray crystallography, and DFT calculations are presented. Intraligand (IL) transitions derived from promotion of electrons from the unique CNC(nb) (nonbonding) orbitals of the smif backbone to ligand π*-type orbitals are intense (ε ≈ 10,000-60,000 M(-1)cm(-1)), dominate the UV-visible spectra, and give crystals a metallic-looking appearance. High energy K-edge spectroscopy was used to show that the smif in 1-Cr is redox noninnocent, and its electron configuration is best described as (smif(-))(smif(2-))Cr(III); an unusual S = 1 EPR spectrum (X-band) was obtained for 1-Cr.

  13. Characterization of Cold Sprayed CuCrAl Coated GRCop-84 Substrates for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, S . V.; Barrett, C. A.; Lerch, B. A.; Karthikeyan, J.; Ghosn, L. J.; Haynes, J.

    2005-01-01

    An advanced Cu-8(at.%)Cr-4%Nb alloy developed at NASA's Glenn Research Center, and designated as GRCop-84, is currently being considered for use as combustor liners and nozzles in NASA's future generations of reusable launch vehicles (RLVs). Despite the fact that this alloy has superior mechanical and oxidation properties compared to many commercially available copper alloys, it is felt that its high temperature and environmental resistance capabilities can be further enhanced with the development and use of suitable coatings. Several coatings and processes are currently being evaluated for their suitability and future down selection. A newly developed CuCrAl has shown excellent oxidation resistance compared to current generation Cu-Cr coating alloys. Cold spray technology for depositing the CuCrAl coating on a GRCop-84 substrate is currently being developed under NASA's Next Generation Launch Technology (NGLT) Propulsion Research and Technology (PR&T) project. The microstructures, mechanical and thermophysical properties of overlay coated GRCop-84 substrates are discussed.

  14. Electrokinetic Treatment of Cr-, Cu-, and Zn-Contaminated Sediment: Cathode Modification

    PubMed Central

    Rajić, Ljiljana; Dalmacija, Božo; Perović, Svetlana Ugarčina; Krčmar, Dejan; Rončević, Srđan; Tomašević, Dragana

    2013-01-01

    Abstract Enhanced electrokinetic (EK) removal of Cr, Cu, and Zn from sediment by using original and modified integrated ion exchange (IIX™) cathodes was investigated. IIX cathode design and EK device process modifications were made to improve performance: separation of IIX cathode components (IIXS), combination of modified IIX cathode with pulsed electric field (IIXSP), and separation of IIX cathode components with addition of an anion exchange resin compartment (IIXA). After using the IIXSP, overall Cr, Cu, and Zn removal efficacies were significantly improved compared with the other treatments investigated. No improvements in overall Cr, Cu, and Zn removal efficacies were achieved by utilization of IIXA. Nevertheless, significant removal efficacies occurred at the anode region since distribution of the alkaline front was prevented. However, metal accumulation in the cathode region occurred. This was a consequence of metal cation complexation with Cl− released from the anion exchange resin that changed the direction of metal migration. Enhancing EK remediation of Cr-, Cu-, and Zn-contaminated sediment can be achieved by using a modified IIX cathode. PMID:24381480

  15. Electrokinetic Treatment of Cr-, Cu-, and Zn-Contaminated Sediment: Cathode Modification.

    PubMed

    Rajić, Ljiljana; Dalmacija, Božo; Perović, Svetlana Ugarčina; Krčmar, Dejan; Rončević, Srđan; Tomašević, Dragana

    2013-12-01

    Enhanced electrokinetic (EK) removal of Cr, Cu, and Zn from sediment by using original and modified integrated ion exchange (IIX™) cathodes was investigated. IIX cathode design and EK device process modifications were made to improve performance: separation of IIX cathode components (IIXS), combination of modified IIX cathode with pulsed electric field (IIXSP), and separation of IIX cathode components with addition of an anion exchange resin compartment (IIXA). After using the IIXSP, overall Cr, Cu, and Zn removal efficacies were significantly improved compared with the other treatments investigated. No improvements in overall Cr, Cu, and Zn removal efficacies were achieved by utilization of IIXA. Nevertheless, significant removal efficacies occurred at the anode region since distribution of the alkaline front was prevented. However, metal accumulation in the cathode region occurred. This was a consequence of metal cation complexation with Cl(-) released from the anion exchange resin that changed the direction of metal migration. Enhancing EK remediation of Cr-, Cu-, and Zn-contaminated sediment can be achieved by using a modified IIX cathode.

  16. First-principles calculations of the stability and hydrogen storage behavior of C14 Laves phase compound TiCrMn

    NASA Astrophysics Data System (ADS)

    Nong, Zhi-Sheng; Zhu, Jing-Chuan; Yang, Xia-Wei; Cao, Yong; Lai, Zhong-Hong; Liu, Yong; Sun, Wen

    2014-06-01

    The structural, elastic properties, electronic structure and hydrogen storage behavior of TiCrMn with a hexagonal C14 structure were investigated by the first-principles calculations within the frame work of DFT. The calculated lattice constants were consistent with the experimental values, and obtained cohesive energy and formation enthalpy showed TiCrMn is of the structural stability. These results also indicated that Mn atoms would optionally substitute on the Cr sites of TiCr2 phase to form the ternary intermetallic TiCrMn. The five independent elastic constants as well as polycrystalline elastic parameters (bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratio ν and anisotropy value A) were calculated, and then the ductility and elastic anisotropy of TiCrMn were discussed in details. Furthermore, the electronic DOS and charge density distribution of TiCrMn were also calculated, which revealed the underlying mechanism of structural stability and chemical bonding. Finally, the binding energy of hydrogen in hydride TiCrMn(H3) was investigated, confirming the better hydrogen storage behavior of C14 Laves phase TiCrMn.

  17. Shape evolution of Cu-doped Mn{sub 3}O{sub 4} spinel microcrystals: influence of copper content

    SciTech Connect

    Wang, Fan; Wu, Haiqiu; Lin, Ziting; Han, Shuaiyuan; Wang, Dan; Xue, Ying; Sun, Yunlong; Sun, Jian; Li, Bin

    2010-11-15

    Spinel-type Cu-doped Mn{sub 3}O{sub 4} microcrystals with various shapes were synthesized by hydrothermal method. The interrelation between the preparative conditions and the composition, structure, and morphology of the products were investigated using various analytical techniques, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermal gravimetric analysis. Results revealed that the introduction of Cu{sup 2+} ions into the reaction system promoted the formation of single phase Cu-doped Mn{sub 3}O{sub 4}. A gradual shape evolution from polyhedron to octahedron occurred upon increasing the additive copper content. Complete decolorization of organic dye (methylene blue) aqueous solution was achieved by treating the dye with Cu-doped Mn{sub 3}O{sub 4} in acidic media, which shows the possible application of doped Mn{sub 3}O{sub 4} as effective reagents for the degradation of organic contaminants in water.

  18. Structural, elastic, electronic, magnetic and vibrational properties of CuCoMnGa under pressure

    SciTech Connect

    İyigör, Ahmet; Uğur, Şule

    2014-10-06

    First principles calculations for the structural, electronic, elastic and phonon properties of the cubic quaternary heusler alloy CuCoMnGa on pressure have been reported by density functional theory (DFT) within generalized gradient approximation (GGA). The calculated values of the elastic constants were used for estimations of the Debye temperatures, the bulk modulus, the shear modulus, the young modulus E, the poisson's ratio σ and the B/G ratio. The elastic constants satisfy all of the mechanical stability criteria. The electronic structures of the ferromagnetic configuration for CuCoMnGa have a metallic character. The estimated magnetic moment per formula unit is 3.76 μ{sub B}. The phonon dispersion is studied using the supercell approach, and the stable nature at 0.2 GPa pressure is observed.

  19. Magnetic properties of Mn1.9Cu0.1Sb under high pressure

    NASA Astrophysics Data System (ADS)

    Matsumoto, Yoshihiro; Matsubayashi, Kazuyuki; Uwatoko, Yoshiya; Hiroi, Masahiko; Mitsui, Yoshifuru; Koyama, Keiichi

    2016-08-01

    Magnetization measurements were carried out for polycrystalline Mn1.9Cu0.1Sb in magnetic fields up to 5 T in the 10-300 K temperature range under high pressures up to 1 GPa in order to investigate the magnetic properties and the thermal transformation arrest (TTA) phenomenon under high pressures. The spin-reorientation temperature increased from 202 K for 0.1 MPa to 244 K for 1 GPa, whereas the transition temperature from the ferrimagnetic (FRI) to antiferromagnetic (AFM) state did not drastically change at ˜116 K. The magnetic relaxation behavior from the FRI to AFM state was observed in 10 < T ≤ 70 K, which was analyzed using the Kohlrausch-Williams-Watts model. Obtained results indicated that the TTA phenomenon of Mn1.9Cu0.1Sb was suppressed by the application of high pressures.

  20. Pressure- and Temperature-Dependent Study of Heusler Alloys Cu2MGa (M = Cr and V)

    NASA Astrophysics Data System (ADS)

    Gupta, Dinesh C.; Ghosh, Sukriti

    2017-04-01

    Full-potential computation of the electronic, magnetic, elastic and thermodynamic properties of Cu2MGa (M = Cr and V) alloys has been performed in the most stable Fm-3 m phase. The equilibrium lattice parameter is 5.9660 Å for Cu2CrGa and 5.9629 Å for Cu2VGa in the stable state. The application of mBJ potential has also found no energy gap in these alloys in either of the spin channels, hence they are metallic. The total and partial density of states, second-order elastic constants and their combinations are computed to show the electronic, magnetic, stability and brittle or ductile nature of these alloys, which are reported for the first time. Cauchy's pressure and Pugh's index predict Cu2CrGa to be brittle and Cu2VGa to be ductile. Both the materials are stiff enough to break. We have found that both the compounds are anisotropic, ferromagnetic and metallic in nature. We have used quasi-harmonic approximations to study the pressure and temperature variation of the thermodynamic properties of these alloys.

  1. Iron-base superalloys - A phase analysis of the multicomponent system (Fe-Mn-Cr-Mo-Nb-Al-Si-C)

    NASA Technical Reports Server (NTRS)

    Gupta, H.; Nowotny, H.; Lemkey, F. D.

    1988-01-01

    In the course of studies on the iron-rich multicomponent system Fe-Mn-Cr-Mo-Nb-Al-Si-C, work was concentrated on pertinent quinary and six-component combinations namely Fe-Mn-Al-Si-C, Fe-Cr-Al-Si-C and Fe-Mn-Cr-Al-Si-C which had been elaborated at 65, 72, and 80 wt pct Fe. Manganese acts as a strong stabilizer for the cementite carbide. Chromium seems to stabilize the iron aluminide Fe2Al5 which forms in a considerable amount within an alloy of nominal composition Fe(65)Mn(15)Cr(12)Al(5)Si(2)C(1) (percent by weight). Although the Mn3AlC carbide is, like Fe3AlC, a perovskite carbide, manganese does not appear to favor the formation of the perovskite carbide. Because of the relatively low sintering temperature (700 C), for al large portion of the samples equilibria conditions are not always reached.

  2. 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.

  3. First-principles and Monte Carlo studies of the Ni2(Mn,Cr)Ga Heusler alloys electronic and magnetic properties

    NASA Astrophysics Data System (ADS)

    Zagrebin, M. A.; Sokolovskiy, V. V.; Smolyakova, E. E.; Buchelnikov, V. D.

    2017-02-01

    Structural, magnetic and electronic properties of a series of Ni2Mn1-x Cr x Ga Heusler alloys have been studied by means of ab initio calculations and Monte Carlo simulations. The optimized lattice parameters of all investigated compositions are close to 5.81 Å and weakly depend on Cr excess. The martensitic transformation in Ni-Mn-Cr-Ga alloys occurs in all compositional range. Tetragonal distortions weakly depend on Cr concentration. Besides, an increase in energy difference between austenite and martensite with increasing Cr content was observed. For electronic and magnetic properties, it was observed that Ni2Mn1-x Cr x Ga demonstrate the metallic behavior. Using the SPR-KKR calculations of magnetic exchange constants, we have shown that the largest contribution to the total exchange energy is associated between nearest neighbor Ni-Mn pair. These inter-sublattice interactions in austenitic phase are higher then intra-sublattice interactions (Ni-Ni and Mn(Cr)-Mn(Cr)). Estimated Curie temperatures for Ni2Mn1-x Cr x Ga are found to decrease with increasing Cr content. All obtained results are in good agreement with experimental data.

  4. Structural, optical, dielectric and antibacterial studies of Mn doped Zn0.96Cu0.04O nanoparticles

    NASA Astrophysics Data System (ADS)

    Sangeetha, R.; Muthukumaran, S.; Ashokkumar, M.

    2015-06-01

    Zn0.96-xCu0.04MnxO (0 ⩽ x ⩽ 0.04) nanoparticles were synthesized by sol-gel method. The X-ray diffraction pattern indicated that doping of Mn and Cu did not change the ZnO hexagonal wurtzite structure. The Mn doped nanoparticles had smaller average crystallite size than un-doped Zn0.96Cu0.04O nanoparticles due to the distortion in the host ZnO lattice. This distortion prevented the subsequent growth and hence the size reduced by Mn doping. The changes in lattice parameters, average crystallite size, peak position and peak intensity confirmed the Mn substitution in Zn-Cu-O lattice. The Mn and Cu co-doping increased the charge carrier density in ZnO nanoparticles which led to increase the dielectric constant. The dielectric constant also varied by depend the size of the nanoparticles. The change in morphology by Mn-doping was studied by transmission electron microscope. The optical absorption and band gap were changed with respect to both compositional and size effects. The band gap was initially increased from 3.65 to 3.73 eV at 1% of Mn doping, while decreasing trend in band gap was noticed for further increase of Mn. The band gap was decreased from 3.73 to 3.48 eV when Mn concentration was increased from 2% to 4%. Presence of chemical bonding and purity of the nanoparticles were confirmed by FTIR spectra. The antibacterial study revealed that that the antibacterial activity of Zn0.96Cu0.04O is enhanced by Mn doping.

  5. NiFe/CoFe/Cu/CoFe/MnIr spin valves studied by ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Timopheev, A. A.; Sobolev, N. A.; Pogorelov, Y. G.; Bunyaev, S. A.; Teixeira, J. M.; Cardoso, S.; Freitas, P. P.; Kakazei, G. N.

    2013-05-01

    Ion-beam deposited (Glass/Ta/NiFe/CoFe/Cu/CoFe/MnIr/Ta) spin valves (SVs) with a Cu-spacer thickness (tCu) varying from 14 to 28 Å have been studied by ferromagnetic resonance (FMR) and magnetoresistance (MR) measurements. With respect to the interlayer coupling strength between the free and fixed ferromagnetic layers, the samples have been divided in those with a weak coupling (for tCu > 16 Å) and a strong coupling regimes (for tCu ≤ 16 Å). The FMR behavior in these two regimes is quite different. For the weakly coupled series, there are two well-defined FMR peaks stemming from the free and fixed layers. Their in-plane angular dependences exhibit 180° and 360° symmetries, respectively. For the strongly coupled SVs, the resonance modes are hybridized and possess features of both layers simultaneously. The main coupling mechanism between the two layers, as concluded from the FMR and MR measurements, is the Néel "orange-peel" magnetostatic interaction, accompanied by a direct exchange due to pinholes in the Cu spacer for tCu < 17 Å.

  6. Temperature dependences of the structural and the mechanical properties of a CdMnCrTe quaternary alloy

    NASA Astrophysics Data System (ADS)

    Hwang, Younghun; Um, Youngho

    2012-11-01

    We investigated the structural and the mechanical properties of single crystals of the diluted magnetic semiconductor (DMS) Cd1- x- y Mn x Cr y Te ( x = 0.37, 0 ≤ y ≤ 0.03) grown by using the vertical Bridgman method. High-temperature X-ray diffraction (XRD) and microhardness measurements were carried out during heating processes at temperatures from room temperature to 750 K. The lattice constants increased with increasing temperature whereas the lattice constants decreased with increasing Cr composition y. The hardness of the Cd1- x- y Mn x Cr y Te crystal increased exponentially with decreasing temperature for T ≤ 600 K, and it remained constant for T ≥ 700 K. The Vickers hardness, H V , decreased with increasing temperature and increased with increasing Cr composition y. The activation energy for the dislocation motion was determined from the relation between temperature and hardness.

  7. A high performance quasi-solid-state supercapacitor based on CuMnO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Arif, Muhammad; Duan, Guorong; Chen, Shenming; Liu, Xiaoheng

    2017-07-01

    Mixed metal or transition metal oxides hold an unveiled potential as one of the most promising energy storage material because of their excellent stability, reliable conductivity, and convenient use. In this work, CuMnO2 nanoparticles are successfully prepared by a facile hydrothermal process with the help of dispersing agent cetyltrimethylammonium bromide (CTAB). CuMnO2 nanoparticles possess a uniform quadrilateral shape, small size (approximately 25 × 25 nm-35 × 35 nm), excellent dispersity, and large specific surface specific (56.9 m2 g-1) with an interparticle mesoporous structure. All these characteristics can bring benefit for their application in supercapacitor. A quasi-solid-state symmetric supercapacitor device is assembled by using CuMnO2 nanoparticles as both positive electrode and negative electrode. The device exhibits good supercapacitive performance with a high specific capacitance (272 F g-1), a maximum power density of 7.56 kW kg-1 and a superior cycling stability of 18,000 continuous cycles, indicating an excellent potential to be used in energy storage device.

  8. Solubility and magnetic properties enhancement in bi-phase nanostructure Cu-Fe-Mn alloy

    NASA Astrophysics Data System (ADS)

    Mondal, B. N.; Basumallick, A.; Nath, D. N.; Chattopadhyay, P. P.

    2013-09-01

    In order to improve solubility and magnetic properties, the ball milling technology was used for the production of 50Cu-40Fe-10Mn (wt%) alloy. The effect of Mn content on the microstructure and magnetic properties of Cu-Fe alloy was also investigated in detail. Microstructure and magnetic properties of the alloy were analyzed by X-ray diffraction, differential scanning calorimetry, high resolution transmission electron microscopy and superconducting quantum interface device magnetometry. The results showed that a complete solid solution of the alloy was produced after 30 h of milling. Quantitative phase analysis of X-ray diffraction data revealed that the milled alloy obtained after isothermal annealing at 550 °C for 1 h consisted of Cu (54.52 wt%), α-Fe (36.49 wt%) and MnO (8.99 wt%). The milled alloy obtained after annealing at 450 °C for 1 h leads to the maximum values of magnetic properties such as coercivity=438 Oe, remanent magnetization=14.3 emu/g, and saturation magnetization=51 emu/g.

  9. Multicolor luminescence from transition metal ion (Mn2+ and Cu2+) doped ZnS nanoparticles.

    PubMed

    Datta, Anuja; Biswas, Subhajit; Kar, Soumitra; Chaudhuri, Subhadra

    2007-10-01

    Mn and Cu doped ZnS nanoparticles in powder form were prepared by a simple solvothermal route. Particle size and crystal structure of the products were investigated through X-ray diffraction study revealing the formation of cubic ZnS nanoparticles of average diameter 2.5 nm. Particle size was also verified by the high resolution transmission electron microscopic images. Blue emission at approximately 445 nm was observed from the undoped sample, which was attributed to the presence of large surface defects. With increasing doping concentration the defect related emission gradually quenches and subsequently the impurity related emissions appeared. Mn doped samples exhibited orange emission at approximately 580 nm which may be attributed to the transition between (4)T1 and (6)A1 energy levels of the Mn2+ 3d states. Whereas, the Cu doped ZnS nanoparticles exhibited a red shifted strong blue emission at approximately 466 nm which is attributed to the transition of the electrons from the surface states to the 't2' levels of Cu impurities.

  10. Dynamic mechanical analyze of superelastic CuMnAl shape memory alloy

    NASA Astrophysics Data System (ADS)

    (Dragoș Ursanu, A. I.; Stanciu, S.; Pricop, B.; Săndulache, F.; Cimpoeșu, N.

    2016-08-01

    A new shape memory alloy was obtain from high purity Cu, Mn and Al elements using a induce furnace. The intelligent material present negative transformation temperatures and an austenite like state at room temperature. The austenite state of CuMnAl shape memory alloy present superelasticity property. Five kilograms ingot was obtain of Cu10Mn10Al alloy. From the base material (melted state) were cut samples with 6 mm thickness using a mechanical saw. After an homogenization heat treatment the samples were hot rolled through four passes with a reduction coefficient of 20%. Experimental lamellas were obtained with 1.5 mm thickness and 90x10 mm length and width. After the hot rolled treatment the materials were heat treated at 800°C for 20 minutes and chilled in water. Four samples, one just laminated and three heat treated by aging, were analyzed with a Netzsch DMA equipment to establish the elastic modulus and the internal friction values of the materials. Metallic materials microstructure was analyzed using a scanning electron microscope Vega Tescan LMH II type. After the aging heat treatment a decrease of internal friction is observed on the entire analyze range which is assigned to formation of Al-based precipitates that block the internal movement of the alloy characteristic phases.

  11. Low temperature spin dynamics in Cr{sub 7}Ni-Cu-Cr{sub 7}Ni coupled molecular rings

    SciTech Connect

    Bordonali, L.; Furukawa, Y.; Mariani, M.; Sabareesh, K. P. V.; Garlatti, E.; Borsa, F.

    2014-05-07

    Proton Nuclear Magnetic Resonance (NMR) relaxation measurements have been performed down to very low temperature (50 mK) to determine the effect of coupling two Cr{sub 7}Ni molecular rings via a Cu{sup 2+} ion. No difference in the spin dynamics was found from nuclear spin lattice relaxation down to 1.5 K. At lower temperature, the {sup 1}H-NMR line broadens dramatically indicating spin freezing. From the plot of the line width vs. magnetization, it is found that the freezing temperature is higher (260 mK) in the coupled ring with respect to the single Cr{sub 7}Ni ring (140 mK)

  12. Cu2Mn1-xCoxSnS4: Novel kësterite type solid solutions

    NASA Astrophysics Data System (ADS)

    López-Vergara, F.; Galdámez, A.; Manríquez, V.; Barahona, P.; Peña, O.

    2013-02-01

    A new family of Cu2Mn1-xCoxSnS4 chalcogenides has been synthesized by conventional solid-state reactions at 850 °C. The reactions products were characterized by powder X-ray diffraction (XRD), energy-dispersive X-ray analysis (SEM-EDS), Raman spectroscopy and magnetic susceptibility. The crystal structures of two members of the solid solution series Cu2Mn0.4Co0.6SnS4 and Cu2Mn0.2Co0.8SnS4 have been determined by single-crystal X-ray diffraction. Both phases crystallize in the tetragonal kësterite-type structure (space group I4¯). The distortions of the tetrahedral volume of Cu2Mn0.4Co0.6SnS4 and Cu2Mn0.2Co0.8SnS4 were calculated and compared with the corresponding differences in the Cu2MnSnS4 (stannite-type) end-member. The compounds show nearly the same Raman spectral features. Temperature-dependent magnetization measurements (ZFC/FC) and high-temperature susceptibility indicate that these solid solutions are antiferromagnetic.

  13. Speciation of organic carbon, Cu and Mn in the River Marne (France): the role of colloids

    NASA Astrophysics Data System (ADS)

    Jaïry, A.; Garban, B.; Blanchard, M.; Chesterikoff, A.

    1999-02-01

    The distribution of organic carbon (OC) and of some metals (Cu, Mn) amongst the particulate (>0·2 m), colloidal (10 kDa-0·2 m) and the truly dissolved (<10 kDa) fractions of the River Marne was investigated during the phytoplankton spring bloom. A tangential ultrafiltration (UF) device was utilized to separate the colloidal fraction. On average, 22% of the OC, 31% of the Cu and 53% of the Mn, usually assigned to the so-called dissolved fraction, were found in the colloidal fraction. The colloidal fraction exhibited a behaviour different from that of the particulate and truly dissolved fractions. Autochthonous production led to enrichment in the colloidal and particulate OC pools: up to 47% of the total dissolved OC was in the colloidal fraction. An increase in the colloidal metal fraction, concomitant with a fall in the truly dissolved fraction, coincided with peaks in phytoplankton during the bloom. These phenomena might be related either to an increase in pH associated with photosynthetic activity, resulting in the precipitation of truly dissolved forms into the colloidal fraction, or to scavenging of the truly dissolved metals by the algal species of colloidal size.The interaction between the colloidal and the truly dissolved phases was very important. The partition coefficients of the Cu and Mn between the colloidal and truly dissolved fractions were higher than between the particulate and the truly dissolved fractions. This pattern is consistent with a greater specific surface area of colloids than macroparticles. Consequently, the adsorption and complexation capacities are enhanced in the colloidal fraction of the particulate matter.The extraction of hydrophobic complexes with Cu using C18 Sep-Pak columns, showed that the Cu occurring in colloidal, total dissolved or truly dissolved forms was significantly complexed by the organic matter. The truly dissolved fraction might be complexed up to 100% during a phytoplankton bloom.

  14. Ti3CrCu4: A possible 2-D ferromagnetic spin fluctuating system

    DOE PAGES

    Dhar, S. K.; Provino, A.; Manfrinetti, P.; ...

    2016-03-09

    Ti3CrCu4 is a new ternary compound which crystallizes in the tetragonal Ti3Pd5 structure type. The Cr atoms form square nets in the a-b plane (a = 3.124 Å) which are separated by an unusually large distance c = 11.228 Å along the tetragonal axis, thus forming a -2-D Cr-sublattice. The paramagnetic susceptibility is characterized by a low effective moment, μeff = 1.1 μB, a low paramagnetic Curie temperature θP (below 7 K) and a temperature independent χ0 = 6.7 x 10–4 emu/mol. The magnetization at 1.8 K increases rapidly with field nearly saturating to 0.2 μB/f.u. The zero field heatmore » capacity C/T shows an upturn below 7 K (~190 mJ/mol K2 at ~0.1K) which is suppressed in applied magnetic fields and interpreted as suggesting the presence of spin fluctuations. The resistivity at low temperatures shows non-Fermi liquid behavior. Overall, the experimental data thus reveal an unusual magnetic state in Ti3CrCu4, which likely has its origin in the layered nature of the Cr sub-lattice and ferromagnetic spin fluctuations. Here, density functional theoretical calculations reveal a sharp Cr density of states peak just above the Fermi level, indicating the propensity of Ti3CrCu4 to become magnetic.« less

  15. The effect of substitution of Mn by Fe and Cr on the martensitic transition in the Ni50Mn34In16 alloy.

    PubMed

    Sharma, V K; Chattopadhyay, M K; Nath, S K; Sokhey, K J S; Kumar, R; Tiwari, P; Roy, S B

    2010-12-08

    The potential shape memory alloy Ni(50)Mn(34)In(16) is studied with partial substitution of Mn with Fe and Cr to investigate the effect of such substitution on the martensitic transition in the Ni-Mn-In alloy system. The results of ac susceptibility, magnetization and electrical resistivity measurements show that while the substitution with Cr increases the martensitic transition temperature, the substitution with Fe decreases it. Possible reasons for this shift in martensitic transition are discussed. Evidence of kinetic arrest of the austenite to martensite phase transition in the Fe substituted alloys is also presented. Unlike the kinetic arrest of the austenite to martensite phase transition in the parent Ni(50)Mn(34)In(16) alloy which takes place in the presence of high external magnetic field, the kinetic arrest of the austenite to martensite phase transition in the Fe doped alloy occurs even in zero magnetic field. The Cr substituted alloys, on the other hand, show no signature of kinetic arrest of this phase transition.

  16. Visible Light-Induced Electron Transfer from Di-mu-oxo Bridged Dinuclear Mn Complexes to Cr Centers in Silica Nanopores

    SciTech Connect

    Frei, Heinz; Weare, Walter W.; Pushkar, Yulia; Yachandra, Vittal K.; Frei, Heinz

    2008-06-03

    The compound (bpy)2MnIII(mu-O)2MnIV(bpy)2, a structural model relevant for the photosynthetic water oxidation complex, was coupled to single CrVI charge-transfer chromophores in the channels of the nanoporous oxide AlMCM-41. Mn K-edge EXAFS spectroscopy confirmed that the di-mu-oxo dinuclear Mn core of the complex is unaffected when loaded into the nanoscale pores. Observation of the 16-line EPR signal characteristic of MnIII(mu-O)2MnIV demonstrates that the majority of the loaded complexes retained their nascent oxidation state in the presence or absence of CrVI centers. The FT-Raman spectrum upon visible light excitation of the CrVI-OII --> CrV-OI ligand-to-metal charge-transfer reveals electron transfer from MnIII(mu-O)2MnIV (Mn-O stretch at 700 cm-1) to CrVI, resulting in the formation of CrV and MnIV(mu-O)2MnIV (Mn-O stretch at 645 cm-1). All initial and final states are directly observed by FT-Raman or EPR spectroscopy, and the assignments corroborated by X-ray absorption spectroscopy measurements. The endoergic charge separation products (DELTA Eo = -0.6 V) remain after several minutes, which points to spatial separation of CrV and MnIV(mu-O)2MnIV as a consequence of hole (OI) hopping as a major contributing mechanism. This is the first observation of visible light-induced oxidation of a potential water oxidation complex by a metal charge-transfer pump in a nanoporous environment. These findings will allow for the assembly and photochemical characterization of well defined transition metal molecular units, with the ultimate goal of performing endothermic, multi-electron transformations that are coupled to visible light electron pumps in nanostructured scaffolds.

  17. Effect of Cu Addition on Precipitation and Growth Behavior of MnS in Silicon Steel Sheets

    NASA Astrophysics Data System (ADS)

    Ueshima, Nobufumi; Maeda, Takuya; Oikawa, Katsunari

    2017-08-01

    The influence of Cu addition on MnS precipitation and growth behavior in Fe-2.88Si-0.1Mn- xCu ( x = 0, 0.25) has been investigated. SEM observation clarified that Cu addition has no effect on the morphology of MnS or its growth rate at early stage. In contrast, Cu addition suppresses the growth rate at the Ostwald ripening stage. At the early stage of growth, a plateau region was observed both with and without Cu addition. Neither the conventional diffusion limited growth nor the Ostwald ripening theory adequately explains these observations. Using the Kampmann-Wagner Numerical (KWN) model, it was possible to successfully reproduce such behavior, including the plateau region. The interfacial energy between ferrite and the MnS was evaluated by the KWN-model, and good agreement was found with previously reported values. The suppression in the growth rate at the Ostwald ripening stage by Cu addition can be explained by a 15 pct reduction in the interfacial energy which possibly occurs due to the segregation of Cu at the interface between MnS and ferrite. This segregation was experimentally confirmed by STEM-EDX analysis.

  18. Rational synthesis and magnetic properties of a family of low-dimensional heterometallic Cr-Mn complexes based on the versatile building block [Cr(2,2'-bipyridine)(CN)4]-.

    PubMed

    Zhang, Yuan-Zhu; Gao, Song; Wang, Zhe-Ming; Su, Gang; Sun, Hao-Ling; Pan, Feng

    2005-06-27

    Six heterometallic compounds based on the building block [Cr(bpy)(CN)4]- (bpy = 2,2'-bipyridine) with secondary and/or tertiary coligands as modulators, {Mn(H2O)2[Cr(bpy)(CN)4]2}n (1), {Mn(bpy)(H2O)[Cr(bpy)(CN)4]2 x H2O}n (2), [Mn(bpy)2][Cr(bpy)(CN)4]2 x 5H2O (3), {[Mn(dca)(bpy)(H2O)][Cr(bpy)(CN)4] x H2O}n (4) (dca = N(CN)2(-)), {Mn(N3)(CH3OH)[Cr(bpy)(CN)4] x 2H2O}n (5), and {Mn(bpy)(N3)(H2O)[Cr(bpy)(CN)4] x H2O}2 (6), have been prepared and characterized structurally and magnetically. X-ray crystallography reveals that the compounds 1, 2, 4, and 5 consist of one-dimensional (1D) chains with different structures: a 4,2-ribbon-like chain, a branched zigzag chain, a 2,2-CC zigzag chain, and a 3,3-ladder-like chain, respectively. It also reveals that compound 3 has a trinuclear [MnCr2] structure, and compound 6 has a tetranuclear [Mn2Cr2] square structure. Magnetic studies show antiferromagnetic interaction between Cr(III) and Mn(II) ions in all compounds. All of the chain compounds exhibit metamagnetic behaviors with different critical temperatures (Tc) and critical fields (Hc; at 1.8 K): 3.2 K and 3.0 kOe for 1; 2.3 K and 4.0 kOe for 2; 2.1 K and 1.0 kOe for 4; and 4.7 K and 5.0 kOe for 5, respectively. The noncentrosymmetric compound 2 is also a weak ferromagnet at low temperature because of spin canting. The magnetic analyses reveal Cr-Mn intermetallic magnetic exchange constants, J, of -4.7 to -9.4 cm(-1) (H = -JS(Cr) x S(Mn)). It is observed that the antiferromagnetic interaction through the Mn-N-C-Cr bridge increases as the Mn-N-C angle (theta) decreases to the range of 155-180 degrees, obeying an empirical relationship: J = -40 + 0.2theta. This result suggests that the best overlap between t(2g) (high-spin Mn(II)) and t(2g) (low-spin Cr(III)) occurs at an angle of approximately 155 degrees.

  19. 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.

  20. Catalytic behavior and synergistic effect of nanostructured mesoporous CuO-MnOx-CeO2 catalysts for chlorobenzene destruction

    NASA Astrophysics Data System (ADS)

    He, Chi; Yu, Yanke; Shen, Qun; Chen, Jinsheng; Qiao, Nanli

    2014-04-01

    Mesoporous CuO-MnOx-CeO2 composite metal oxides with different copper and manganese loadings were prepared by a urea-assistant hydrothermal method, and were further adopted for the complete catalytic combustion of chlorobenzene. The effects of reaction conditions such as inlet reagent concentration and water feed concentration on chlorobenzene combustion were also studied. The structure and textural properties of the synthesized catalysts were characterized via the XRD, N2 adsorption/desorption, FE-SEM, TEM, H2-TPR, O2-TPD, and XPS techniques. The characterization results reveal that the presence of a small amount of Mn species can facilitate the incorporation of Cu and Mn ions into ceria lattice to form Cu-Mn-Ce-O solid solution. The synergistic effect of Cu and Mn species can reduce the redox potential of the composite catalysts, and produce large amounts of oxygen vacancies in the interface of CuOx, MnOx, and CeO2 oxides. The catalyst with Cu/Mn atomic ratio of 1/1 exhibits the best chlorobenzene elimination capability, oxidizing about 95% of the inlet chlorobenzene at 264 °C with CO2 selectivity higher than 99.5%. The concentration and mobility of the chemically adsorbed oxygen are vital for the effective removal of surface Cl species, which inhibits the dissociation of oxygen molecules and decreases the reducibility of the copper and manganese species. It can be rationally concluded that the superior catalytic performance and durability of the mesoporous CuO-MnOx-CeO2 composite oxides are primarily attributed to the higher surface oxygen concentration and better active oxygen mobility.

  1. Excitation dependent multicolor emission and photoconductivity of Mn, Cu doped In2S3 monodisperse quantum dots.

    PubMed

    Ghosh, Sirshendu; Saha, Manas; Ashok, Vishal Dev; Chatterjee, Arijit; De, S K

    2016-04-15

    Indium sulphide (In2S3) quantum dots (QDs) of average size 6 ± 2 nm and hexagonal nanoplatelets of average size 37 ± 4 nm have been synthesized from indium myristate and indium diethyl dithiocarbamate precursors respectively. The absorbance and emission band was tuned with variation of nanocrytal size from very small in the strong confinement regime to very large in the weak confinement regime. The blue emission and its shifting with size has been explained with the donor-acceptor recombination process. The 3d element doping (Mn(2+) and Cu(2+)) is found to be effective for formation of new emission bands at higher wavelengths. The characteristic peaks of Mn(2+) and Cu(2+) and the modification of In(3+) peaks in the x-ray photoelectric spectrum (XPS) confirm the incorporation of Mn(2+) and Cu(2+) into the In2S3 matrix. The simulation of the electron paramagnetic resonance signal indicates the coexistence of isotropic and axial symmetry for In and S vacancies. Moreover, the majority of Mn(2+) ions and sulphur vacancies (VS ) reside on the surface of nanocrystals. The quantum confinement effect leads to an enhancement of band gap up to 3.65 eV in QDs. The formation of Mn 3d levels between conduction band edge and shallow donor states is evidenced from a systematic variation of emission spectra with the excitation wavelength. In2S3 QDs have been established as efficient sensitizers to Mn and Cu emission centers. Fast and slow components of photoluminescence (PL) decay dynamics in Mn and Cu doped QDs are interpreted in terms of surface and bulk recombination processes. Fast and stable photodetctors with high photocurrent gain are fabricated with Mn and Cu doped QDs and are found to be faster than pure In2S3. The fastest response time in Cu doped QDs is an indication of the most suitable system for photodetector devices.

  2. Excitation dependent multicolor emission and photoconductivity of Mn, Cu doped In2S3 monodisperse quantum dots

    NASA Astrophysics Data System (ADS)

    Ghosh, Sirshendu; Saha, Manas; Ashok, Vishal Dev; Chatterjee, Arijit; De, S. K.

    2016-04-01

    Indium sulphide (In2S3) quantum dots (QDs) of average size 6 ± 2 nm and hexagonal nanoplatelets of average size 37 ± 4 nm have been synthesized from indium myristate and indium diethyl dithiocarbamate precursors respectively. The absorbance and emission band was tuned with variation of nanocrytal size from very small in the strong confinement regime to very large in the weak confinement regime. The blue emission and its shifting with size has been explained with the donor-acceptor recombination process. The 3d element doping (Mn2+ and Cu2+) is found to be effective for formation of new emission bands at higher wavelengths. The characteristic peaks of Mn2+ and Cu2+ and the modification of In3+ peaks in the x-ray photoelectric spectrum (XPS) confirm the incorporation of Mn2+ and Cu2+ into the In2S3 matrix. The simulation of the electron paramagnetic resonance signal indicates the coexistence of isotropic and axial symmetry for In and S vacancies. Moreover, the majority of Mn2+ ions and sulphur vacancies (VS ) reside on the surface of nanocrystals. The quantum confinement effect leads to an enhancement of band gap up to 3.65 eV in QDs. The formation of Mn 3d levels between conduction band edge and shallow donor states is evidenced from a systematic variation of emission spectra with the excitation wavelength. In2S3 QDs have been established as efficient sensitizers to Mn and Cu emission centers. Fast and slow components of photoluminescence (PL) decay dynamics in Mn and Cu doped QDs are interpreted in terms of surface and bulk recombination processes. Fast and stable photodetctors with high photocurrent gain are fabricated with Mn and Cu doped QDs and are found to be faster than pure In2S3. The fastest response time in Cu doped QDs is an indication of the most suitable system for photodetector devices.

  3. Effect of Cu and Zn Substitutions on MnSb Properties

    SciTech Connect

    Mitsiuk, V. I.; Ryzhkovskii, V. M.; Tkachenka, T. M.

    2008-10-28

    The NiAs-type solid solutions based on manganese antimonide Mn{sub 1.1}Sb with Zn or Cu (up to 10 at % of substituting component) have been studied by {sup 57}Fe Moessbauer spectroscopy. It has been shown that the replacement of the manganese antimonide by Cu or Zn does not appreciably affect the main Moessbauer parameters in comparison to those of the parent compound. Two different values of hyperfine magnetic field at Fe are present in all the samples and can be attributed to the metal atoms located in MeI and MeII positions. The substitution of Cu or Zn for manganese antimonide leads to the redistribution of the metal atoms between two cation sublattices.

  4. Exchange bias through a Cu interlayer in an IrMn/Co system

    NASA Astrophysics Data System (ADS)

    Geshev, J.; Nicolodi, S.; Pereira, L. G.; Nagamine, L. C. C. M.; Schmidt, J. E.; Deranlot, C.; Petroff, F.; Rodríguez-Suárez, R. L.; Azevedo, A.

    2007-06-01

    Ferromagnetic resonance (FMR) and magnetization (MAG) measurements were used to study the exchange interaction between the antiferromagnetic and ferromagnetic layers in an IrMn/Cu/Co system as a function of the Cu spacer thickness. Although the experimental angular variations of the exchange-bias fields HebFMR and HebMAG coincide, the coupling strengths J and the Co layers’ anisotropy fields HU , obtained via numerical simulations, are different. For all Cu thicknesses JFMR>JMAG and HUFMR

  5. 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.

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

    DOE PAGES

    Enamullah, .; Venkateswara, Y.; Gupta, Sachin; ...

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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 L 21 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.

  8. Effects of biaxial strain on stability and half-metallicity of Cr and Mn pnictides and chalcogenides in the zinc-blende structure

    NASA Astrophysics Data System (ADS)

    Miao, M. S.; Lambrecht, Walter R. L.

    2005-08-01

    The effects of biaxial strain, imposed by epitaxial growth conditions, on the half-metallicity properties of Cr and Mn pnictides and chalcogenides were investigated using local spin-density-functional calculations. The minority band gaps were found to decrease significantly under the biaxial strain, whereas the spin-flip gaps changed only slightly. The calculations show that under epitaxial conditions for any choice of substrate, CrSe, MnAs, MnSe, and MnTe cannot be half metallic; CrAs and CrTe are barely half metallic as their SF gap is close to zero; and only CrSb and MnSb remain distinct half metals with spin-flip gaps of 0.9 and 0.3eV , respectively.

  9. Investigation of the nanostructure and wear properties of physical vapor deposited CrCuN nanocomposite coatings

    SciTech Connect

    Baker, M.A.; Kench, P.J.; Tsotsos, C.; Gibson, P.N.; Leyland, A.; Matthews, A.

    2005-05-01

    This article presents results on CrCuN nanocomposite coatings grown by physical vapor deposition. The immiscibility of Cr (containing a supersaturation of nitrogen) and Cu offers the potential of depositing a predominantly metallic (and therefore tough) nanocomposite, composed of small Cr(N) metallic and/or {beta}-Cr{sub 2}N ceramic grains interdispersed in a (minority) Cu matrix. A range of CrCuN compositions have been deposited using a hot-filament enhanced unbalanced magnetron sputtering system. The stoichiometry and nanostructure have been studied by x-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, and x-ray diffraction. Hardness, wear resistance, and impact resistance have been determined by nanoindentation, reciprocating-sliding, and ball-on-plate high-cycle impact. Evolution of the nanostructure as a function of composition and correlations of the nanostructure and mechanical properties of the CrCuN coatings are discussed. A nanostructure comprised of 1-3 nm {alpha}-Cr(N) and {beta}-Cr{sub 2}N grains separated by intergranular regions of Cu gives rise to a coating with significantly enhanced resistance to impact wear.

  10. Weldability of a high entropy CrMnFeCoNi alloy

    DOE PAGES

    Wu, Zhenggang; David, Stan A.; Feng, Zhili; ...

    2016-07-19

    We present the high-entropy alloys are unique alloys in which five or more elements are all in high concentrations. In order to determine its potential as a structural alloy, a model face-centered-cubic CrMnFeCoNi alloy was selected to investigate its weldability. Welds produced by electron beam welding show no cracking. The grain structures within the fusion zone (FZ) are controlled by the solidification behavior of the weld pool. The weldment possesses mechanical properties comparable to those of the base metal (BM) at both room and cryogenic temperatures. Finally, compared with the BM, deformation twinning was more pronounced in the FZ ofmore » the tested alloy.« less

  11. Texture evolution of cold rolled and reversion annealed metastable austenitic CrMnNi steels

    NASA Astrophysics Data System (ADS)

    Weidner, A.; Fischer, K.; Segel, C.; Schreiber, G.; Biermann, H.

    2015-04-01

    A thermo-mechanical process consisting of cold rolling and subsequent reversion annealing was applied to high-alloy metastable austenitic CrMnNi steels with different nickel contents. As a result of the reversion annealing ultrafine grained material with a grain size in the range between 500 nm up to 4 μm were obtained improving the strength behavior of the material. The evolution of the texture of both the cold rolled states and the reversion-annealed states was studied either by X-ray diffraction or by EBSD measurements. The nickel content has a significant influence on the austenite stability and consequently also on the amount of the martensitic phase transformation. However, the developed textures in both steel variants with different austenite stability revealed the same behavior. In both investigated steels the texture of the reverted austenite is a pronounced Bs-type texture as developed also for the deformed austenite

  12. Nanomechanical Behavior of CoCrFeMnNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Mridha, Sanghita; Das, Santanu; Aouadi, Samir; Mukherjee, Sundeep; Mishra, Rajiv S.

    2015-08-01

    The nanomechanical behavior of the Co20Cr20Fe20Mn20Ni20 high-entropy alloy was investigated in as-cast, rolled, annealed, and thin-film forms. Dislocation nucleation was studied by repeated indents at a low load for each of the different processing conditions. Distinct displacement bursts (pop in) were observed in the loading curve marked by incipient plasticity for all the samples. The as-cast and annealed samples showed pop ins for 100% of the indents, whereas the rolled and thin-film samples showed a much lower fraction of displacement bursts. This was explained by the high density of dislocations for the cold-worked and thin-film conditions. The strong depth dependence of hardness was explained by geometrically necessary dislocations. The nanomechanical behavior and twinned microstructure indicate low stacking-fault energy for this high-entropy alloy.

  13. Positron Annihilation Spectroscopy and Small Angle Neutron Scattering Characterization of Nanostructural Features in Irradiated Fe-Cu-Mn Alloys

    SciTech Connect

    Wirth, B D; Asoka-Kumar, P; Howell, R H; Odette, G R; Sterne, P A

    2001-01-01

    Radiation embrittlement of nuclear reactor pressure vessel steels results from a high number density of nanometer sized Cu-Mn-Ni rich precipitates (CRPs) and sub-nanometer matrix features, thought to be vacancy-solute cluster complexes (VSC). However, questions exist regarding both the composition of the precipitates and the defect character and composition of the matrix features. We present results of positron annihilation spectroscopy (PAS) and small angle neutron scattering (SANS) characterization of irradiated and thermally aged Fe-Cu and Fe-Cu-Mn alloys. These complementary techniques provide insight into the composition and character of both types of nanoscale features. The SANS measurements indicate populations of CRPs and VSCs in both alloys. The CRPs are coarser in the Fe-Cu alloy and the number densities of CRP and VSC increase with the addition of Mn. The PAS involved measuring both the positron lifetimes and the Doppler broadened annihilation spectra in the high momentum region to provide elemental sensitivity at the annihilation site. The spectra in Fe-Cu-Mn specimens thermally aged to peak hardness at 450 C and irradiated at 288 C are nearly identical to elemental Cu. Positron lifetime and spectrum measurements in Fe-Cu specimens irradiated at 288 C clearly show the existence of long lifetime ({approx}500 ps) open volume defects, which also contain Cu. Thus the SANS and PAS provide a self-consistent picture of nanostructures composed of CRPs and VSCs and tend to discount high Fe concentrations in the CRPs.

  14. Effect of Cr addition on the structural, magnetic and mechanical properties of magnetron sputtered Ni-Mn-In ferromagnetic shape memory alloy thin films

    NASA Astrophysics Data System (ADS)

    Akkera, Harish Sharma; Kaur, Davinder

    2016-12-01

    The effect of Cr substitution for In on the structural, martensitic phase transformation and mechanical properties of Ni-Mn-In ferromagnetic shape memory alloy (FSMA) thin films was systematically investigated. X-ray diffraction results revealed that the Ni-Mn-In-Cr thin films possessed purely austenitic cubic L21 structure at lower content of Cr, whereas higher Cr content, the Ni-Mn-In-Cr thin films exhibited martensitic structure at room temperature. The temperature-dependent magnetization ( M- T) and resistance ( R- T) results confirmed that the monotonous increase in martensitic transformation temperatures ( T M) with the addition of Cr content. Further, the room temperature nanoindentation studies revealed the mechanical properties such as hardness ( H), elastic modulus ( E), plasticity index ( H/ E) and resistance to plastic deformation ( H 3/ E 2) of all the samples. The addition of Cr content significantly enhanced the hardness (28.2 ± 2.4 GPa) and resistance to plastic deformation H 3/ E 2 (0.261) of Ni50.4Mn34.96In13.56Cr1.08 film as compared with pure Ni-Mn-In film. As a result, the appropriate addition of Cr significantly improved the mechanical properties with a decrease in grain size, which could be further attributed to the grain boundary strengthening mechanism. These findings indicate that the Cr-doped Ni-Mn-In FSMA thin films are potential candidates for microelectromechanical systems applications.

  15. Magnetic ordering of the Pr sublattice with the substitution of Cu for Mn in PrMn2Si2 intermetallics

    NASA Astrophysics Data System (ADS)

    Elmali, A.; Dincer, I.; Elerman, Y.; Ehrenberg, H.; Fuess, H.

    2004-12-01

    The magnetic properties of PrMn2-xCuxSi2 (0 \\le x \\le 1 ) were studied by field-cooled and zero-field-cooled magnetization measurements in the temperature range 5 K \\le T \\le 350 K in low external fields (5 mT) and by magnetic-field-dependent magnetization measurements in fields up to 5.5 T. Substitution of Cu for Mn leads to a linear decrease in the lattice constant c and the unit cell volume V and a linear increase in the lattice constant a. Earlier neutron diffraction experiments showed that Pr does not order down to 1.6 K in PrMn2Si2 while the ferromagnetic Mn planes are ordered antiparallel along the c axis. With the increasing Cu content, the magnetization increases rapidly at low temperatures for the samples with 0.4 \\le x \\le 1 . Cu substitution strongly changes the magnetic properties and leads to the magnetic ordering of the Pr sublattice. This is mainly deduced from the discussion of the values of the magnetic moments at low temperatures. Below the Curie temperatures TC, the spins in the Mn sublattice are arranged parallel to the Pr sublattice. With increasing Cu, TC(x) has a maximum value of 155 K at x = 0.6 and decreases for samples with x \\ge 0.7 .

  16. Critical behavior and reversible magnetocaloric effect in multiferroic MnCr2O4

    NASA Astrophysics Data System (ADS)

    Dey, K.; Indra, A.; Majumdar, S.; Giri, S.

    2017-08-01

    Magnetocaloric effect (MCE) in multiferroic cubic spinel MnCr2O4 (space group Fd 3 bar m, no. 227, cF56), has been investigated using dc magnetization studies. The values of maximum magnetic entropy change (ΔSMmax) and the adiabatic temperature change (Δ Tad) are ∼5.3 J kg-1 K-1 and ∼2 K, respectively, at ∼42.8 K for the magnetic field change of 50 kOe. The dc magnetization data near the transition temperature were analyzed by the modified Arrott plots, the Kouvel-Fisher method, log M vs log H, and the scaling analysis. Critical exponents β = 0.3932 ± 0.0287, γ = 1.0256 ± 0.0239, and δ = 3.55 ± 0.26 are obtained around the critical temperature ∼ 42.88 K. The critical exponents are in excellent agreement with the single scaling equation of state M (H, ɛ) =ɛ 0.3932 ± 0.0287 f± (H /ɛ ((0.3932 ± 0.0287) + (1.0256 ± 0.0239))); with f+ for T > 42.88 K, f- for T < 42.88 K, and ɛ = (T - 42.88)/42.88. At T = 42.88 K, the exponent δ relates the magnetization with applied filed by M =H 1 / (3.55 ± 0.26) . Scaling analysis shows that calculated critical exponents as well as critical temperature are intrinsic to the system. Theoretically, the value of β is close to 3D Heisenberg model, while values of γ and δ are close to those of the mean field model. So the values of critical exponents indicate that the critical behavior of MnCr2O4 cannot be described within the framework of existing universality classes and probably belong to a separate class.

  17. Enhanced Photovoltage Response of Hematite-X-Ferrite Interfaces (X = Cr, Mn, Co, or Ni).

    PubMed

    Bian, Liang; Li, Hai-Long; Li, Yu-Jin; Nie, Jia-Nan; Dong, Fa-Qin; Dong, Hai-Liang; Song, Mian-Xin; Wang, Li-Sheng; Zhou, Tian-Liang; Zhang, Xiao-Yan; Li, Xin-Xi; Xie, Lei

    2017-12-01

    High-fluorescent p-X-ferrites (XFe2O4; XFO; X = Fe, Cr, Mn, Co, or Ni) embedded in n-hematite (Fe2O3) surfaces were successfully fabricated via a facile bio-approach using Shewanella oneidensis MR-1. The results revealed that the X ions with high/low work functions modify the unpaired spin Fe(2+)-O(2-) orbitals in the XFe2O4 lattices to become localized paired spin orbitals at the bottom of conduction band, separating the photovoltage response signals (73.36~455.16/-72.63~-32.43 meV). These (Fe2O3)-O-O-(XFe2O4) interfacial coupling behaviors at two fluorescence emission peaks (785/795 nm) are explained via calculating electron-hole effective masses (Fe2O3-FeFe2O4 17.23 × 10(-31) kg; Fe2O3-CoFe2O4 3.93 × 10(-31) kg; Fe2O3-NiFe2O4 11.59 × 10(-31) kg; Fe2O3-CrFe2O4 -4.2 × 10(-31) kg; Fe2O3-MnFe2O4 -11.73 × 10(-31) kg). Such a system could open up a new idea in the design of photovoltage response biosensors.

  18. 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.

  19. The Effect of Core-Mantle Differentiation on V, Cr, and Mn: Experimental Metal/Silicate Partitioning Results

    NASA Technical Reports Server (NTRS)

    Chabot, N. L.; Agee, C. B.

    2001-01-01

    The abundances of V, Cr, and Mn are similarly depleted in the Earth and Moon. We present metal/silicate partitioning results which examine if the depletions can be explained by a core formation event. Additional information is contained in the original extended abstract.

  20. Further Observations of Fe-60-Ni-60 and Mn-53-Cr-53 Isotopic Systems in Sulfides from Enstatite Chondrites

    NASA Technical Reports Server (NTRS)

    Guan, Y.; Huss, G. R.; Leshin, L. A.

    2004-01-01

    Recent studies have shown that short-lived Fe-60 (t(sub 1/2) = 1.5 Ma) was present in some components of ordinary and enstatite chondrites when they formed. Here we report additional data on Fe-60 from sulfides in enstatite chondrites and on the potential relationship between the Fe-60-Ni-60 and Mn-53-Cr-53 systems.

  1. The Effect of Core-Mantle Differentiation on V, Cr, and Mn: Experimental Metal/Silicate Partitioning Results

    NASA Technical Reports Server (NTRS)

    Chabot, N. L.; Agee, C. B.

    2001-01-01

    The abundances of V, Cr, and Mn are similarly depleted in the Earth and Moon. We present metal/silicate partitioning results which examine if the depletions can be explained by a core formation event. Additional information is contained in the original extended abstract.

  2. High-field magnetization of band ferromagnets Co2 YAl ( Y = Ti, V, Cr, Mn, Fe, Ni)

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    The temperature dependences of the magnetization of ferromagnetic Heusler alloys Co2 YAl, where Y = Ti, V, Cr, Mn, Fe, and Ni have been studied at H = 50 kOe in the range 2 K < T < 1100 K. It is shown that the high-field ( H ≥ 20 kOe) magnetization is described within the Stoner model.

  3. Preparation and thermoelectric properties of ternary superionic conductor CuCrS{sub 2}

    SciTech Connect

    Chen Yuexing; Zhang Boping; Ge Zhenhua; Shang Pengpeng

    2012-02-15

    Transition metal chalcogenide CuCrS{sub 2} powder was synthesized by mechanical alloying (MA) and then consolidated by spark plasma sintering (SPS) technique at 673-1073 K. The phase structure, microstructure and thermoelectric properties of samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Seebeck coefficient/electrical conductivity measuring system, respectively. All the bulks indicated a single phase CuCrS{sub 2}, while the high relative density over 90% were attained for the samples sintered at 873-1073 K. The electrical conductivity of bulk samples displayed a typical characteristic of semiconductor. With increasing measuring temperature, the conductive behaviour of bulk samples sintered over 973 K showed a semiconductor transformation from n-type to p-type due to the changes of main carrier type. The sample obtained by applying SPS at 873 K got the highest power factor 83.2 {mu}W m{sup -1} K{sup -2}, and the largest ZT value 0.11 at 673 K. - Graphical abstract: The samples sintered above 873 K, both of the Seebeck coefficient and electrical conductivity exhibit an increase tendency with increasing temperature, which is due to the mechanism of mix-conduction for CuCrS{sub 2}. Highlights: Black-Right-Pointing-Pointer Single phase CuCrS{sub 2} powder was synthesized by ball-milling at 425 rpm for 40 h. Black-Right-Pointing-Pointer Dense CuCrS{sub 2} bulks were fabricated using SPS techniques at sintering temperature 873-1073 K. Black-Right-Pointing-Pointer Seebeck coefficient of CuCrS{sub 2} samples sintered over 973 K change the signs. Black-Right-Pointing-Pointer Highest power factor reached 83.2 {mu}W m{sup -1} K{sup -2} at 673 K for the sample sintered at 873 K. Black-Right-Pointing-Pointer ZT value was 0.11 at 673 K for the sample sintered at 873 K.

  4. CuMnOS Nanoflowers with Different Cu(+)/Cu(2+) Ratios for the CO2-to-CH3OH and the CH3OH-to-H2 Redox Reactions.

    PubMed

    Chen, Xiaoyun; Abdullah, Hairus; Kuo, Dong-Hau

    2017-01-24

    A conservative CO2-Methanol (CH3OH) regeneration cycle, to capture and reutilize the greenhouse gas of CO2 by aqueous hydrogenation for industry-useful CH3OH and to convert aqueous CH3OH solution by dehydrogenation for the clean energy of hydrogen (H2), is demonstrated at normal temperature and pressure (NTP) with two kinds of CuMnOS nanoflower catalysts. The [Cu(+)]-high CuMnOS led to a CH3OH yield of 21.1 mmol·g(-1)catal.·h(-1) in the CuMnOS-CO2-H2O system and the other [Cu(+)]-low one had a H2 yield of 7.65 mmol·g(-1)catal.·h(-1) in the CuMnOS-CH3OH-H2O system. The successful redox reactions at NTP rely on active lattice oxygen of CuMnOS catalysts and its charge (hole or electron) transfer ability between Cu(+) and Cu(2+). The CO2-hydrogenated CH3OH in aqueous solution is not only a fuel but also an ideal liquid hydrogen storage system for transportation application.

  5. CuMnOS Nanoflowers with Different Cu+/Cu2+ Ratios for the CO2-to-CH3OH and the CH3OH-to-H2 Redox Reactions

    NASA Astrophysics Data System (ADS)

    Chen, Xiaoyun; Abdullah, Hairus; Kuo, Dong-Hau

    2017-01-01

    A conservative CO2-Methanol (CH3OH) regeneration cycle, to capture and reutilize the greenhouse gas of CO2 by aqueous hydrogenation for industry-useful CH3OH and to convert aqueous CH3OH solution by dehydrogenation for the clean energy of hydrogen (H2), is demonstrated at normal temperature and pressure (NTP) with two kinds of CuMnOS nanoflower catalysts. The [Cu+]-high CuMnOS led to a CH3OH yield of 21.1 mmol·g‑1catal.·h‑1 in the CuMnOS-CO2-H2O system and the other [Cu+]-low one had a H2 yield of 7.65 mmol·g‑1catal.·h‑1 in the CuMnOS-CH3OH-H2O system. The successful redox reactions at NTP rely on active lattice oxygen of CuMnOS catalysts and its charge (hole or electron) transfer ability between Cu+ and Cu2+. The CO2-hydrogenated CH3OH in aqueous solution is not only a fuel but also an ideal liquid hydrogen storage system for transportation application.

  6. CuMnOS Nanoflowers with Different Cu+/Cu2+ Ratios for the CO2-to-CH3OH and the CH3OH-to-H2 Redox Reactions

    PubMed Central

    Chen, Xiaoyun; Abdullah, Hairus; Kuo, Dong-Hau

    2017-01-01

    A conservative CO2-Methanol (CH3OH) regeneration cycle, to capture and reutilize the greenhouse gas of CO2 by aqueous hydrogenation for industry-useful CH3OH and to convert aqueous CH3OH solution by dehydrogenation for the clean energy of hydrogen (H2), is demonstrated at normal temperature and pressure (NTP) with two kinds of CuMnOS nanoflower catalysts. The [Cu+]-high CuMnOS led to a CH3OH yield of 21.1 mmol·g−1catal.·h−1 in the CuMnOS-CO2-H2O system and the other [Cu+]-low one had a H2 yield of 7.65 mmol·g−1catal.·h−1 in the CuMnOS-CH3OH-H2O system. The successful redox reactions at NTP rely on active lattice oxygen of CuMnOS catalysts and its charge (hole or electron) transfer ability between Cu+ and Cu2+. The CO2-hydrogenated CH3OH in aqueous solution is not only a fuel but also an ideal liquid hydrogen storage system for transportation application. PMID:28117456

  7. The microstructure of an Fe-Mn-Si-Cr-Ni stainless steel shape memory alloy

    NASA Astrophysics Data System (ADS)

    Maji, Bikas C.; Krishnan, Madangopal; Rama Rao, V. V.

    2003-05-01

    The microstructure and phase stability of the Fe-15Mn-7Si-9Cr-5Ni stainless steel shape memory alloy in the temperature range of 600 °C to 1200 °C was investigated using optical and transmission electron microscopy, X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and chemical analysis techniques. The microstructural studies show that an austenite single-phase field exists in the temperature range of 1000 °C to 1100 °C, above 1100 °C, there exists a three-phase field consisting of austenite, δ-ferrite, and the (Fe,Mn)3Si intermetallic phase; within the temperature range of 700 °C to 1000 °C, a two-phase field consisting of austenite and the Fe5Ni3Si2 type intermetallic phase exists; and below 700 °C, there exists a single austenite phase field. Apart from these equilibrium phases, the austenite grains show the presence of athermal ɛ martensite. The athermal α' martensite has also been observed for the first time in these stainless steel shape memory alloys and is produced through the γ-ɛ-α' transformation sequence.

  8. Laser weldability of 21Cr-6Ni-9Mn stainless steel: Part II - Weldability diagrams

    DOE PAGES

    Tate, Stephen B.; Javernick, Daniel Anthony; Lienert, Thomas J.; ...

    2016-11-02

    In this second part of the study, weldability diagrams developed to relate solidification crack susceptibility and chemical composition for laser welded type 21Cr-6Ni-9Mn (21-6-9) stainless steel are presented. Sigmajig testing on 14 commercial 21-6-9 alloys, 20 experimental 21-6-9 alloys, and 7 other high-N, high-Mn austenitic stainless steels was used to develop weldability diagrams for solidification crack susceptibility for laser welding of type 21-6-9. Three travel speeds were used to show the changes in minimum Creq/Nieq for primary ferrite solidification as solidification rate increase d with travel speed . Primary austenite solidification was observed below 1.55 Creq/Nieq (Espy equivalents) at 21more » mm/s travel speed. At 42 mm/s travel speed , a mix of solidification modes were displayed for alloys from 1.55-1.75 Creq/Nieq. Primary ferrite solidification was observed above 1.75 Creq/Nieq at both 42 and 85 mm/s travel speeds. No solidification cracking was observed for alloys with primary ferrite solidification. Lastly, variable cracking behavior was found in alloys with primary austenite solidification, but in general cracking was observed in alloys with greater than 0.02 wt-% combined impurity content according to (P+0.2S).« less

  9. Site preference and compensation behavior in Co(Cr, Mn){sub 2}O{sub 4} system

    SciTech Connect

    Zhang, H. G.; Wang, Z.; Yue, M.; Liu, E. K.; Wang, W. H.; Wu, G. H.

    2015-05-07

    Site preference of doped Mn ions in CoCr{sub 2−x}Mn{sub x}O{sub 4} (x = 0–2) series has been derived separately from structure and magnetic measurement. It shows that parts of the doped Mn ions occupy the A (Co) sites when x < 0.5. And then, it takes the two B (Cr) sites in turn before and after x = 1.3. This site preference behavior results in a role conversion of the magnetic contributors and, thus, leads to the composition dependent magnetic compensation. Temperature induced compensation and negative magnetization have also been found in several samples, which is attributed to the large energy barrier between the ferromagnetic and antiferromagnetic spin arrangement. A structure transition from cubic to tetragonal symmetry has been detected.

  10. Enhanced magnetism of Cu{sub n} clusters capped with N and endohedrally doped with Cr

    SciTech Connect

    Datta, Soumendu; Banerjee, Radhashyam; Mookerjee, Abhijit

    2015-01-14

    The focus of our work is on the production of highly magnetic materials out of Cu clusters. We have studied the relative effects of N-capping as well as N mono-doping on the structural stability and electronic properties of the small Cu clusters using first principles density functional theory based electronic structure calculations. We find that the N-capped clusters are more promising in producing giant magnetic moments, such as 14 μ{sub B} for the Cu{sub 6}N{sub 6} cluster and 29 μ{sub B} for the icosahedral Cu{sub 13}N{sub 12} cluster. This is accompanied by a substantial enhancement in their stability. We suggest that these giant magnetic moments of the capped Cu{sub n} clusters have relevance to the observed room temperature ferromagnetism of Cu doped GaN. For cage-like hollow Cu-clusters, an endohedral Cr-doping together with the N-capping appears as the most promising means to produce stable giant magnetic moments in the copper clusters.

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

    SciTech Connect

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

    2012-04-12

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

  12. Study of magnetic compensation behavior in Mn(Cr1-xFex)2O4

    NASA Astrophysics Data System (ADS)

    Barman, Junmoni; Ravi, S.

    2017-09-01

    We report the preparation of single phase samples of Mn(Cr1-xFex)2O4 for x = 0-0.50 and study of their structural and magnetic properties. These samples are found to crystallize in cubic structure with Fd 3 bar m space group with typical lattice constant varying from a = 8.4396 Å for x = 0 to 8.4588 Å for x = 0.50. The ferrimagnetic transition temperature as per magnetic measurements is found to increase from 46 K for x = 0 to 402 K for x = 0.50 due to the strengthening of the superexchange interaction. The Saturation magnetization value is found to decrease monotonously with increase in Fe concentration beyond x = 0.10 and approaches magnetic compensation at x = 0.40. In addition to composition induced magnetic compensation, we have observed magnetic compensation due to change in temperature for x = 0.40 with a compensation temperature of 267 K. This is explained by considering the substitution of Fe3+ ions in one of the Cr3+ sites and the different temperature dependence of two sublattice moments.

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

    DOE PAGES

    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

  14. Magnetic and electron transport properties of Cr-doped (Nd, Sr)MnO 3 single crystals

    NASA Astrophysics Data System (ADS)

    Takeuchi, Jun; Dhakal, Tara P.; Hirahara, Seitaro; Miyoshi, Kiyotaka

    2002-02-01

    The effect of Cr-doping on the Mn site in Nd 1- ySr yMnO 3 ( y=0.33 and 0.5) single crystals grown by the floating zone method has been studied. The y=0.33 system exhibits a transition at Curie temperature ( TC=250 K) to ferromagnetic metal (FMM). The doping of Cr 3+ ions up to 6 at% enhances the colossal magnetoresistance effect. The y=0.5 system exhibits a transition at TC=260 K to FMM and at Néel temperature ( TN=160 K) to antiferromagnetic insulator (AFMI). The doping of 5 at% Cr 3+ ions lowers TC to be 250 K and completely suppresses the AFMI state.

  15. Study of Fe-12Cr-20Mn-W-C austenitic steels irradiated in the SM-2 reactor

    NASA Astrophysics Data System (ADS)

    Shamardin, V. K.; Bulanova, T. M.; Neustroyev, V. S.; Ostrovsky, Z. E.; Kosenkov, V. M.; Ivanov, L. I.; Djomina, E. V.

    1992-09-01

    A comparison has been made between the mechanical properties and swelling of austenitic stainless steels EP-838 (Fe-Cr-Mn) and 316SS (Fe-Cr-Ni) irradiated in the mixed-neutron spectrum of the SM-2 reactor in the temperature range 400-800°C (every 100°C) to 16 dpa dose with 1000 and 3000 appm helium generation correspondingly, determined by nickel content. EP-838 exhibited less susceptibility to void swelling and radiation hardening. Fe-12Cr-20Mn-W-0.1C steel without nickel irradiated at 100°C to 21 dpa exhibited significant radiation hardening accompanied by α-phase formation in the steel structure.

  16. Surface precipitation of chromium in rapidly solidified Cu-Cr alloys

    NASA Astrophysics Data System (ADS)

    Bizjak, Milan; Karpe, Blaž; Jakša, Gregor; Kovač, Janez

    2013-07-01

    Rapidly solidified ribbons of Cu-Cr alloys with 2.27 and 4.20 at.% of chromium were produced using the melt-spinning method. Alloys were analyzed by electron microscopy for complete solubility of Cr in copper matrix. To avoid disturbing effects of Cr phase particles, the kinetics and the sequence of microstructural transformations during heating were analyzed only the sample with 2.27 at.% of chromium with complete Cr solubility in the copper matrix. We then investigated the precipitation process for this alloy that was subsequently heated at a constant rate. The increased solid solubility obtained allowed the extensive precipitation of a Cr-rich phase. The kinetics and the sequence of microstructural changes that occurred during the heating were analyzed using an in situ measurement of the electrical resistance. The quenched microstructure was analyzed at transition points using scanning and transmission electron microscopy. X-ray photoelectron spectroscopy, as a very surface-sensitive method, was applied to study the changes in the chemical composition of the surface for the Cu-Cr alloy ribbons in the temperature range 400-700 °C during an in situ heat treatment in an ultra-high vacuum. The results show a relatively rapid precipitation of chromium to the surface, which starts at 400 °C and is correlated with a change in the microstructure and the electrical resistance. The Cr-precipitation is faster at higher temperatures and follows the parabolic law. The resistivity results for the supersaturated binary alloy were analyzed using the Ozawa method to give an activation energy for the precipitation of 196 ± 10 kJ mol-1.

  17. Growth, structure, and magnetism of single-crystalline NixMn100-x films and NiMn/Co bilayers on Cu(001)

    NASA Astrophysics Data System (ADS)

    Tieg, C.; Kuch, W.; Wang, S. G.; Kirschner, J.

    2006-09-01

    The growth and structure of single-crystalline NixMn100-x films on Cu(001) were studied for concentrations of x⩾13 and thicknesses of 0 15 monolayer (ML). Medium energy electron diffraction (MEED) curves revealed a layer-by-layer growth mode at a substrate temperature of T=300K for alloy films with 40Mn content increases. We find a characteristic c(2×2) superstructure by low-energy electron diffraction (LEED) for alloy compositions in the vicinity of the equiatomic region. A kinematic analysis of specular LEED intensity curves was employed to determine the average interlayer spacing d , yielding a decreasing d with Ni content from 1.90Å for x=13 to 1.73Å for pure Ni on Cu(001). For equiatomic c(2×2) NiMn/Cu(001) we propose a bulklike L10 crystal structure, which is characterized by an in-plane orientation of the bulk c axis. We show that Co grows layer by layer and assumes a p(1×1) structure on equiatomic c(2×2) NiMn/Cu(001) . Using Co/Cu(001) as a substrate for equiatomic NiMn leads to a non-layer-by-layer growth of the alloy film and a diffuse LEED pattern with weak c(2×2) spots. The investigation of such bilayer structures by magneto-optical Kerr effect measurements (MOKE) indicates the presence of an antiferromagnetic (AFM) order in NixMn100-x films with x close to the equiatomic composition and thicknesses above 8 ML at 300K , as concluded from the coercivity enhancement.

  18. Creep of Uncoated and Cu-Cr Coated NARloy-Z

    NASA Technical Reports Server (NTRS)

    Walter, R. J.; Chiang, K. T.

    1998-01-01

    Stress rupture creep tests were performed on uncoated and Cu-30vol%Cr coated NARloy-Z copper alloy specimens exposed to air at 482 C to 704 C. The results showed that creep failure in air of unprotected NARloy-Z was precipitated by brittle intergranular surface cracking produced by strain assisted grain boundary oxidation (SAGBO) which in turn caused early onset of tertiary creep. For the protected specimens, the Cu-Cr coating remained adherent throughout the tests and was effective in slowing down the rate of oxygen absorption, particularly at the higher temperatures, by formation of a continuous chromium oxide scale. As the result of reducing oxygen ingress, the coating prevented SAGBO initiated early creep failure, extended creep deformation and increased the creep rupture life of NARloy-Z over the entire 482 C to 704 C test temperature range.

  19. Enhanced Magnetization of CuCr2O4 Thin Films by Substrate-Induced Strain

    SciTech Connect

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

    2008-09-17

    We report the synthesis of epitaxial spinel CuCr{sub 2}O{sub 4} thin films that display enhanced magnetization in excess of 200% of the bulk values when grown on single-crystal (110) MgAl{sub 2}O{sub 4} substrates. Bulk CuCr{sub 2}O{sub 4} is a ferrimagnetic insulator with a net magnetic moment of 0.5 {micro}{sub B} due to its distorted tetragonal unit cell (c/a= 1.29) and frustrated triangular moment configuration. We show that through epitaxial growth and substrate-induced strain, it is possible to tune the magnetic functionality of our films by reducing the tetragonal distortion of the unit cell which effectively decreases the frustration of the magnetic moments allowing for an overall greater net moment.

  20. Magnetic properties of delafossite oxide: CuCr1-xTixO2

    NASA Astrophysics Data System (ADS)

    Majee, M. K.; Bhobe, P. A.; Nigam, A. K.

    2016-05-01

    In order to increase the possibility for technological applications of CuCrO2, there have been attempts to introduce ferromagnetic (FM) order by doping at B-site. With this aim, we present here study of polycrystalline CuCr1-xTixO2 with x=0.0, 0.05, 0.1. The samples have been prepared using solid state synthesis method and characterized for its crystal structure and magnetic properties. All the samples crystallize in the 2H delafossite structure with R-3m space group. Ti substitution causes the expansion of unit cell with increase in both the lattice constants. Antiferromagnetic ordering temperature is seen to decrease with increasing Ti. Ferromagnetic-like signature is obtained in one of the compositions at low applied magnetic field of 100 Oe.

  1. Crystal structure and magnetic properties of the Cr-doped spiral antiferromagnet BiMnFe{sub 2}O{sub 6}

    SciTech Connect

    Batuk, Dmitry; De Dobbelaere, Christopher; Tsirlin, Alexander A.; Abakumov, Artem M.; Hardy, An; Van Bael, Marlies K.; Greenblatt, Martha; Hadermann, Joke

    2013-09-01

    Graphical abstract: - Highlights: • The substitution of Cr for Mn in BiMnFe{sub 2}O{sub 6} is possible by the solution–gel method. • The BiCr{sub x}Mn{sub 1−x}Fe{sub 2}O{sub 6} solid solution is obtained for the x values up to 0.3. • Increasing Cr content lowers the temperature of the antiferromagnetic ordering. - Abstract: We report the Cr{sup 3+} for Mn{sup 3+} substitution in the BiMnFe{sub 2}O{sub 6} structure. The BiCr{sub x}Mn{sub 1−x}Fe{sub 2}O{sub 6} solid solution is obtained by the solution–gel synthesis technique for the x values up to 0.3. The crystal structure investigation using a combination of X-ray powder diffraction and transmission electron microscopy demonstrates that the compounds retain the parent BiMnFe{sub 2}O{sub 6} structure (for x = 0.3, a = 5.02010(6)Å, b = 7.06594(7)Å, c = 12.6174(1)Å, S.G. Pbcm, R{sub I} = 0.036, R{sub P} = 0.011) with only a slight decrease in the cell parameters associated with the Cr{sup 3+} for Mn{sup 3+} substitution. Magnetic susceptibility measurements suggest strong similarities in the magnetic behavior of BiCr{sub x}Mn{sub 1−x}Fe{sub 2}O{sub 6} (x = 0.2; 0.3) and parent BiMnFe{sub 2}O{sub 6}. Only T{sub N} slightly decreases upon Cr doping that indicates a very subtle influence of Cr{sup 3+} cations on the magnetic properties at the available substitution rates.

  2. Electronic effects at interfaces in Cu - Cr, Mo, Ta, Re Multilayers

    SciTech Connect

    Barbee, T W; Bello, A F; Klepeis, J E; Van Buuren, T

    1999-06-28

    In this study we characterize electronic effects in short-period ({approx}20 {angstrom}) metallic multilayer films in which 40% of the atoms are at an interface using near-edge (L{sub 3,2}) x-ray absorption. This study investigates Cu/TM where TM = Cr, MO, W, Ta, Re. These immiscible elemental pairs are ideal to study as they form no compounds and exhibit terminal solid solubility. An interest in the charge transfer between elements in alloys and compounds has led to studies using x-ray absorption as described above. Near edge x-ray absorption fine structure (NEXAFS), a technique used for analyzing x-ray absorption near the absorption edge of the element, is especially suited to study the amount of unoccupied states in the conduction band of a metal. The d-metals spectra show large peaks at the absorption edges called ''white lines.'' These are due to the unoccupied d-states just above the Fermi level in these metals. A study of the white lines in the 3d metals show that as the d-band is increasingly occupied the white lines decrease in intensity. Starting with Ti (3d{sup 2} 4s{sup 2}), which has an almost empty d-band and shows strong white lines, the white-line intensities decrease across the Periodic Chart to Cu (3d{sup 10} 4s{sup 1}), which has a full d-band and no white lines. Systematic measurement of the L{sub 3,2} absorption spectra of bulk elemental Cu and Cu in the Cu/TM multilayers enabled measurement of the charge transfer. NEXAFS on metallic multilayers has received less attention than alloys because of the difficulty in synthesizing multilayers with controllability up to the monolayer level and because there is little difference between the signal from the bulk and from longer period (> 30 {angstrom}) multilayers. For high-quality short period multilayers, however, the difference is clear. This is highlighted in a study of short period Co/Cu multilayers, where the electronic density of states of Cu in Cu/Co greatly differed from that of bulk Cu. The

  3. Evaluation of the bioaccessible fractions of Fe, Zn, Cu and Mn in baby foods.

    PubMed

    do Nascimento da Silva, Emanueli; Leme, Ana Beatriz Perriello; Cidade, Mirla; Cadore, Solange

    2013-12-15

    The bioaccessibility of four essential micronutrients (iron, zinc, copper and manganese) in some baby foods was evaluated using an in vitro gastrointestinal digestion model. For all of the flour-based foods evaluated, the bioaccessibility of Zn was low, while the bioaccessibility of Cu was above 50%. For these samples, the bioaccessibility of Mn was lower than 50%. Two samples composed of oat and rice flour and whole wheat flour demonstrated a lower bioaccessible fraction of Fe (less than 35%), while the sample made with wheat flour showed high Fe bioaccessibility (approximately 80%). For vegetable- and meat-based baby foods, the Fe bioaccessibility was greater than 80% in samples that contained meat and chicken and approximately 20% for the banana-based sample. The bioaccessibility of Zn was small for all of the foods studied, and in some cases, no Zn appeared to be released. The sample containing banana showed 100% Cu bioaccessibility, in contrast to meat and chicken-based samples, whose Cu bioaccessibility values were less than 50%. The opposite effect occurred for Mn, in which samples containing meat and chicken presented a bioaccessible fraction greater than 50% while the banana-based sample had a fraction less than 50%. © 2013 Elsevier B.V. All rights reserved.

  4. 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.

  5. High-energy magnetic excitations in Mn{sub 90}Cu{sub 10}

    SciTech Connect

    Fernandez-Baca, J.A.; Nicklow, R.M.; Hagen, M.E. |; Perring, T.G.; Tsunoda, Y.

    1992-12-01

    The study of the magnetic excitations in Mn-rich alloys should be a good test of the multiband calculations of the spin dynamics of pure {gamma}-Mn, which is a prototypical itinerantelectron antiferromagnet. In this paper we report the results of recent neutron inelastic scattering measurements performed on Mn{sub 90}Cu{sub 10} at room temperature (T = 0.63 T{sub N}) and up to 300 meV of energy transfer. These measurements were performed using the HET chopper-spectrometer at the ISIS spallation neutron source, Rutherford Appleton Laboratory, U.K. The results have been compared with calculations using a model scattering function convoluted with the full HET resolution function. In this model there is a steep linear spin-wave dispersion (D {approx} 250 meV-{Angstrom}) for wavevectors up to {approx} {1/2} of the Brillouin zone and a strong damping which is linear in the wavevector q. For larger wavevectors the spin-wave energies are constant at about 190 meV. These features are qualitatively similar to the predictions of Cade and Yeung for pure {gamma}-Mn.

  6. High-energy magnetic excitations in Mn[sub 90]Cu[sub 10

    SciTech Connect

    Fernandez-Baca, J.A.; Nicklow, R.M. ); Hagen, M.E. . Dept. of Physics Rutherford Appleton Lab., Chilton . ISIS Science Div.); Perring, T.G. . ISIS Science Div.); Tsunoda, Y. . Faculty of Science)

    1992-01-01

    The study of the magnetic excitations in Mn-rich alloys should be a good test of the multiband calculations of the spin dynamics of pure [gamma]-Mn, which is a prototypical itinerantelectron antiferromagnet. In this paper we report the results of recent neutron inelastic scattering measurements performed on Mn[sub 90]Cu[sub 10] at room temperature (T = 0.63 T[sub N]) and up to 300 meV of energy transfer. These measurements were performed using the HET chopper-spectrometer at the ISIS spallation neutron source, Rutherford Appleton Laboratory, U.K. The results have been compared with calculations using a model scattering function convoluted with the full HET resolution function. In this model there is a steep linear spin-wave dispersion (D [approx] 250 meV-[Angstrom]) for wavevectors up to [approx] [1/2] of the Brillouin zone and a strong damping which is linear in the wavevector q. For larger wavevectors the spin-wave energies are constant at about 190 meV. These features are qualitatively similar to the predictions of Cade and Yeung for pure [gamma]-Mn.

  7. Dynamic Embrittlement in Cu-Cr-Zr-Ti Alloy: Evidence of Intergranular Segregation of Sulphur

    NASA Astrophysics Data System (ADS)

    Chenna Krishna, S.; Radhika, K. V.; Tharian, K. Thomas; Swathi Kiranmayee, M.; Sudarshan Rao, G.; Jha, Abhay K.; Pant, Bhanu

    2013-08-01

    In the present investigation, Cu-0.6Cr-0.005Zr-0.0045Ti alloy was subjected to different heat treatment and thermomechanical treatment (TMT) to simulate the conditions experienced during brazing and forming, respectively. Grain coarsening was observed in the samples subjected to heat treatment, and grain refinement was observed in the samples subjected to TMT. Tensile tests conducted with these samples at room temperature and 600 °C have shown that Cu-Cr-Zr-Ti alloy was susceptible to dynamic embrittlement (DE). However, the observation was limited to coarse-grained samples (280-350 μm) at 600 °C. On the other hand, the fine-grained samples (20-40 μm) showed good ductility. Electron microscopy studies conducted on the tensile-tested specimens prone to DE indicated the presence of sulfur on the fractured surface and intergranular segregation of sulfur. Therefore, it can be inferred from the results that DE due to sulfur can occur in Cu-Cr-Zr-Ti alloy at elevated temperature for coarse-grained samples.

  8. Monolithic Cu-Cr-Nb Alloys for High Temperature, High Heat Flux Applications

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Locci, Ivan E.; Michal, Gary M.; Humphrey, Derek M.

    1999-01-01

    Work during the prior four years of this grant has resulted in significant advances in the development of Cu-8 Cr4 Nb and related Cu-Cr-Nb alloys. The alloys are nearing commercial use in the Reusable Launch Vehicle (RLV) where they are candidate materials for the thrust cell liners of the aerospike engines being developed by Rocketdyne. During the fifth and final year of the grant, it is proposed to complete development of the design level database of mechanical and thermophysical properties and transfer it to NASA Glenn Research Center and Rocketdyne. The database development work will be divided into three main areas: Thermophysical Database Augmentation, Mechanical Testing and Metallography and Fractography. In addition to the database development, work will continue that is focussed on the production of alternatives to the powder metallurgy alloys currently used. Exploration of alternative alloys will be aimed at both the development of lower cost materials and higher performance materials. A key element of this effort will be the use of Thermo-Calc software to survey the solubility behavior of a wide range of alloying elements in a copper matrix. The ultimate goals would be to define suitable alloy compositions and processing routes to produce thin sheets of the material at either a lower cost, or, with improved mechanical and thermal properties compared to the current Cu-Cr-Nb powder metallurgy alloys.

  9. Effects of Ce Addition on High Temperature Deformation Behavior of Cu-Cr-Zr Alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Volinsky, Alex A.; Tran, Hai T.; Chai, Zhe; Liu, Ping; Tian, Baohong

    2015-10-01

    Hot deformation behavior of the Cu-Cr-Zr and Cu-Cr-Zr-Ce alloys was investigated by compressive tests using the Glee-ble-1500D thermomechanical simulator at 650-850 °C and 0.001-10 s-1 strain rate. The flow stress decreased with the deformation temperature at a given stain rate. However, the flow stress increased with the strain rate at the same deformation temperature. The constitutive equations for two kinds of alloys were obtained by correlating the flow stress, the strain rate and temperature using stepwise regression analysis. The addition of Ce can refine the grain and effectively accelerate dynamic recrystallization. The processing maps were established, based on the dynamic material model. Instability zones in the flow behavior can be easily recognized. Hot deformation optimal processing parameters were obtained in the range of this experiment. The hot deformation characteristics and microstructure were also analyzed by the processing maps. The addition of Ce can optimize hot workability of the Cu-Cr-Zr alloy.

  10. Investigation on the microstructure and mechanical properties of CuCrZr after manufacturing thermal cycle for plasma facing component

    NASA Astrophysics Data System (ADS)

    Park, Jeong-Yong; Jung, Yang-Il; Choi, Byung-Kwon; Lee, Jung-Suk; Jeong, Yong Hwan; Hong, Bong Guen

    2011-10-01

    The effects of manufacturing thermal cycle on the various mechanical properties of CuCrZr were investigated. Vickers hardness was changed with an aging temperature in an identical manner with the strength change in a wide range of heat treatment. The change of Charpy impact energy with an aging temperature exhibited an opposite trend to the changes of the strength and hardness. At least in terms of the impact energy of CuCrZr, aging at a higher temperate would be preferable if the strength of CuCrZr could be maintained higher than the limitation value after the completion of the fabrication of ITER first wall. The fatigue life of CuCrZr was influenced to a certain extent by the cooling rate and the aging temperature. Especially in the higher strain amplitude, the contribution of the elastic and plastic components to the fatigue response was dependent on the yield strength which is determined by the aging temperature.

  11. Positron Annihilation Spectroscopy and Small Angle Neutron Scattering Characterization of the Effect of Mn on the Nanostructural Features formed in Irradiated Fe-Cu-Mn Alloys

    SciTech Connect

    Glade, S C; Wirth, B D; Asoka-Kumar, P; Odette, G R; Sterne, P A; Howell, R H

    2003-02-27

    The size, number density and composition of the nanometer defects responsible for the hardening and embrittlement in irradiated Fe-0.9wt.% Cu and Fe-0.9wt.% Cu-1.0wt% Mn model reactor pressure vessel alloys were measured using small angle neutron scattering and positron annihilation spectroscopy. These alloys were irradiated at 290 C to relatively low neutron fluences (E > 1 MeV, 6.0 x 10{sup 20} to 4.0 x 10{sup 21} n/m{sup 2}) in order to study the effect of manganese on the nucleation and growth of copper rich precipitates and secondary defect features. Copper rich precipitates were present in both alloys following irradiation. The Fe-Cu-Mn alloy had smaller precipitates and a larger number density of precipitates, suggesting Mn segregation at the iron matrix-precipitate interface which reduces the interfacial energy and in turn the driving force for coarsening. Mn also retards the precipitation kinetics and inhibits large vacancy cluster formation, suggesting a strong Mn-vacancy interaction which reduces radiation enhanced diffusion.

  12. Mn-Cr dating of Fe- and Ca-rich olivine from 'quenched' and 'plutonic' angrite meteorites using Secondary Ion Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    McKibbin, Seann J.; Ireland, Trevor R.; Amelin, Yuri; Holden, Peter

    2015-05-01

    Angrite meteorites are suitable for Mn-Cr relative dating (53Mn decays to 53Cr with a half life of 3.7 Myr) using Secondary Ion Mass Spectrometry (SIMS) because they contain olivine and kirschsteinite with very high 55Mn/52Cr ratios arising from very low Cr concentrations. Discrepant Mn-Cr and U-Pb time intervals between the extrusive or 'quenched' angrite D'Orbigny and some slowly cooled or 'plutonic' angrites suggests that some have been affected by secondary disturbances, but this seems to have occurred in quenched rather than in slow-cooled plutonic angrites, where such disturbance or delay of isotopic closure might be expected. Using SIMS, we investigate the Mn-Cr systematics of quenched angrites to higher precision than previously achieved by this method and extend our investigation to non-quenched (plutonic or sub-volcanic) angrites. High values of 3.54 (±0.18) × 10-6 and 3.40 (±0.19) × 10-6 (2-sigma) are found for the initial 53Mn/55Mn of the quenched angrites D'Orbigny and Sahara 99555, which are preserved by Cr-poor olivine and kirschsteinite. The previously reported initial 53Mn/55Mn value of D'Orbigny obtained from bulk-rock and mineral separates is slightly lower and was probably controlled by Cr-rich olivine. Results can be interpreted in terms of the diffusivity of Cr in this mineral. Very low Cr concentrations in Ca-rich olivine and kirschsteinite are probably charge balanced by Al; this substitutes for Si and likely diffuses at a very slow rate because Si is the slowest-diffusing cation in olivine. Diffusion in Cr-rich Mg-Fe olivine is probably controlled by cation vacancies because of deficiency in charge-balancing Al and is therefore more prone to disturbance. The higher initial 53Mn/55Mn found by SIMS for extrusive angrites is more likely to reflect closure of Cr in kirschsteinite at the time of crystallisation, simultaneous with closure of U-Pb and Hf-W isotope systematics for these meteorites obtained from pyroxenes. For the younger

  13. Dependency of simultaneous Cr(VI), Cu(II) and Cd(II) reduction on the cathodes of microbial electrolysis cells self-driven by microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Yu, Lihua; Wu, Dan; Huang, Liping; Zhou, Peng; Quan, Xie; Chen, Guohua

    2015-01-01

    Microbial fuel cells (MFCs) using either Cr(VI) (MFCsCr) or Cu(II) (MFCsCu) as a final electron acceptor, are stacked to self-drive microbial electrolysis cells (MECs) using Cd(II) (MECsCd) as an electron acceptor for simultaneous reduction of Cr(VI) in MFCsCr, Cu(II) in MFCsCu and Cd(II) in MECsCd with no external energy consumption. Titanium sheet (TS) and carbon rod (CR) as the cathodes of MECsCd are assessed for efficient system performance. MFCsCr and MFCsCu in series is superior to the parallel configuration, and higher Cd(II) reduction along with simultaneous Cr(VI) and Cu(II) reduction supports TS function as a good cathode material. Conversely, CR can not entirely proceed Cd(II) reduction in MECsCd despite of more Cr(VI) and Cu(II) reduction in the same serial configuration than either system alone. While a decrease in cathode volume in both MFCsCr and MFCsCu with serial connection benefits to reduction of Cr(VI) in MFCsCr and Cu(II) in MFCsCu, Cd(II) reduction in MECsCd is substantially enhanced under a decrease in cathode volume in individual MFCsCr and serially connected with volume-unchanged MFCsCu. This study demonstrates simultaneous Cr(VI), Cu(II) and Cd(II) recovery from MFCsCr-MFCsCu-MECsCd self-driven system is feasible, and TS as the cathodes of MECsCd is critical for efficient system performance.

  14. Suppressed 3D conductivity in Mn doped Cu0.5Tl0.5Ba2Ca2-yMnyCu3O10-δ superconductors

    NASA Astrophysics Data System (ADS)

    Qurat-ul-Ain, Khan, Nawazish A.

    2013-04-01

    We have synthesised Mn-doped Cu0.5Tl0.5Ba2(Ca2-yMny)Cu3O10-δ superconducting samples and studied their Fluctuation Induced Conductivity (FIC) analysis. The Tc(R = 0) and magnitude of diamagnetism are suppressed with increased Mn-doping in the final compound. FIC analyses have shown a suppression of 3D Lawrence and Doniach (LD) regime and a significant enhancement of 2D LD regime of Mn-doping of y = 0.35. In the sample with Mn-doping of y = 0.5, the 3D LD regime vanishes altogether and only 2D LD regime is observed, showing the confinement of superconductivity in the two dimensional planes. The coherence length along the c-axis and the Fermi velocity of the carriers are suppressed with increased Mn doping. Using the Ginzburg-Landau (GL) number [NG] and GL equations, the thermodynamic critical magnetic field Bc(0), the lower critical field Bc1(0), the upper critical field Bc2(0), the critical current density Jc(0), and penetration depth λp.d are determined. The values of critical fields Bc(0) and Bc1(0) increases, despite suppression in the Tc(R = 0) with increased Mn-doping. The values of Jc(0), the penetration depth Λp.d, and inter-layer coupling are suppressed with enhanced Mn-doping. These observations suggested that Mn ions act as sub-nano-scale pinning centers between the CuO2 planes and their presence at the Ca-sites promote the de-coupling of CuO2 planes.

  15. Electronic structure of metastable bcc Cu-Cr alloy thin films: Comparison of electron energy-loss spectroscopy and first-principles calculations.

    PubMed

    Liebscher, C H; Freysoldt, C; Dennenwaldt, T; Harzer, T P; Dehm, G

    2016-07-12

    Metastable Cu-Cr alloy thin films with nominal thickness of 300nm and composition of Cu67Cr33 (at%) are obtained by co-evaporation using molecular beam epitaxy. The microstructure, chemical phase separation and electronic structure are investigated by transmission electron microscopy (TEM). The thin film adopts the body-centered cubic crystal structure and consists of columnar grains with ~50nm diameter. Aberration-corrected scanning TEM in combination with energy dispersive X-ray spectroscopy confirms compositional fluctuations within the grains. Cu- and Cr-rich domains with composition of Cu85Cr15 (at%) and Cu42Cr58 (at%) and domain size of 1-5nm are observed. The alignment of the interface between the Cu- and Cr-rich domains shows a preference for {110}-type habit plane. The electronic structure of the Cu-Cr thin films is investigated by electron energy loss spectroscopy (EELS) and is contrasted to an fcc-Cu reference sample. The experimental EEL spectra are compared to spectra computed by density functional theory. The main differences between bcc-and fcc-Cu are related to differences in van Hove singularities in the electron density of states. In Cu-Cr solid solutions with bcc crystal structure a single peak after the L3-edge, corresponding to a van Hove singularity at the N-point of the first Brillouin zone is observed. Spectra computed for pure bcc-Cu and random Cu-Cr solid solutions with 10at% Cr confirm the experimental observations. The calculated spectrum for a perfect Cu50Cr50 (at%) random structure shows a shift in the van Hove singularity towards higher energy by developing a Cu-Cr d-band that lies between the delocalized d-bands of Cu and Cr.

  16. Two-dimensional assembly of [Mn(III)₂Mn(II)₂] single-molecule magnets and [Cu(pic)₂] linking units (Hpic = picolinic acid).

    PubMed

    Jeon, Ie-Rang; Ababei, Rodica; Lecren, Lollita; Li, Yang-Guang; Wernsdorfer, Wolfgang; Roubeau, Olivier; Mathonière, Corine; Clérac, Rodolphe

    2010-05-28

    In an attempt to develop novel coordination networks of SMMs, a Cu(II) picolinate complex has been used to coordinate S(T) = 9 tetranuclear Mn-based SMMs resulting in an intriguing 2D framework exhibiting a magnet-like behavior at low temperature.

  17. Fluctuations of chemical composition of austenite and their consequence on shape memory effect in Fe-Mn-(Si, Cr, Ni, C, N) alloys

    SciTech Connect

    Bliznuk, V.V.; Gavriljuk, V.G. . E-mail: gavr@imp.kiev.ua; Kopitsa, G.P.; Grigoriev, S.V.; Runov, V.V.

    2004-09-20

    Polycrystalline samples of shape memory iron-based alloys containing 17, and 30 mass% Mn and alloyed with Si, Cr, Ni, C, N were studied by means of small angle scattering of polarized neutrons (SAPNS). A direct correlation between chemical homogeneity of the Fe-Mn, Fe-Mn-Si, Fe-Mn-Si-Cr, Fe-Mn-Si-Cr-Ni solid solutions and the values of reversible strain caused by the {gamma} {yields} {epsilon} {yields} {gamma} martensitic transformation was found. The addition of silicon to the Fe-Mn alloys significantly improves chemical homogeneity of the fcc solid solution on the scale of larger than several nm, which correlates with the essential increase of reversible strain. A similar to silicon but weaker effect was observed in the case of nitrogen addition to the Fe-Mn-Si-Cr, Fe-Mn-Si-Cr-Ni alloys. Based on the obtained experimental data and in consistency with the previously expressed idea by Sade et al., the positive effect of silicon and nitrogen on chemical homogeneity and SME in Fe-Mn alloys is attributed to the short-range atomic ordering induced by these elements.

  18. Effects of interfacial roughness on the planar Hall effect in NiFe/Cu/IrMn multilayers

    NASA Astrophysics Data System (ADS)

    Li, Xu-Jing; Feng, Chun; Chen, Xi; Liu, Yang; Liu, Yi-Wei; Li, Ming-Hua; Yu, Guang-Hua

    2015-02-01

    This paper reports that the planar Hall effect in NiFe/Cu/IrMn multilayers was strongly influenced by the Cu spacer thickness ( t Cu), which was due to the variation of interfacial roughness. With t Cu increasing, a peculiar change of planar Hall voltage was observed. The reason for the voltage behaviors was that the interfacial roughness influenced the spin-asymmetry of spin-polarized electrons in ferromagnetic metals. The diffuse scattering to the electrons turned to specular scattering when the interface became flat, leading to the variation of resistivity change (Δ ρ). As the increase in t Cu, the extremum field was reduced because of the weaken exchange coupling between NiFe and IrMn layers.

  19. Superoxide radical anion scavenging and dismutation by some Cu2+ and Mn2+ complexes: A pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Joshi, Ravi

    2017-10-01

    Copper (Cu) and manganese (Mn) ions are catalytic centers, in complexed form, in scavenging and dismutation process of superoxide radicals anion (O2.-) by superoxide dismutase enzyme. In the present work, fast reaction kinetics and mechanism of scavenging and dismutation of O2.- by Cu2+, Mn2+ and their complexes formed with some natural ligands have been studied using pulse radiolysis technique. Catechol, gentisic acid, tetrahydroxyquinone, tyrosine, tryptophan, embelin and bilirubin have been used as low molecular weight natural ligands for Cu2+ and Mn2+ to understand superoxide radical scavenging and dismutation reactions. These complexes have been found to be efficient scavengers of O2.- (k 107-109 M-1 s-1). The effects of nature of metal ion and ligand, and stoichiometry of complex on scavenging reaction rate constants are reported. Higher scavenging rate constants have been observed with complexes of: (1) Cu2+ as compared to Mn2+, and (2) at [ligand]/[metal] ratio of one as compared to two. A clear evidence of O2.- dismutation by free metal ions and some of the complexes has been observed. The study suggests that complexes of Cu2+ and Mn2+ with small natural ligands can also act as SOD mimics.

  20. Influence of MnC2O4 microadditives on combustion characteristics of CuO/Al nanoenergetics

    NASA Astrophysics Data System (ADS)

    Painuly, Madhusudan; Patel, Vinay Kumar; Bhattacharya, Shantanu

    2016-05-01

    In this work, we have investigated the catalytic effect of MnC2O4 microrods on combustion characteristics of CuO/nAl nanoenergetic composites. CuO nanorods were prepared by solid state synthesis method using the nonionic surfactant of poly(ethylene)glycol of molecular weight 400 (PEG400). The crystal information and microstructure of CuO/nAl nanoenergetics were studied by X-ray diffractometry and Transmission Electron microscopy. Microrods shaped manganese oxalate (MnC2O4) were fabricated by using mild thermal precipitation and aging process and confirmed by energy dispersive X-ray spectroscopy (EDS). The microstructures of MnC2O4 microrods and the nanoenergetic composites of CuO/nAl/MnC2O4 were characterized by Field emission scanning electron microscopy (FE-SEM) imaging. The addition of MnC2O4 microrods has demonstrated a significant enhancement in dynamic pressure-time characteristics of CuO/nAl nanoenergetics.

  1. Synthesis and high temperature transport properties of new quaternary layered selenide NaCuMnSe{sub 2}

    SciTech Connect

    Pavan Kumar, V.; Varadaraju, U.V.

    2014-04-01

    Synthesis and high temperature transport properties of NaCu{sub 1+x}Mn{sub 1−x}Se{sub 2}, (x=0−0.75) a new quaternary layered selenide, are reported. NaCuMnSe{sub 2} crystallizes in a trigonal unit cell with space group of P-3m1 (a=4.1276 Å, c=7.1253 Å). The isovalent substitution of Mn{sup 2+} by Cu{sup 2+} is carried out. All the compositions show semiconducting nature, whereas the Seebeck coefficient increases gradually over the entire measured temperature range. Compositions with x=0 and 0.025 follow thermally activated behavior. With increase in copper concentration the conduction mechanism transforms to 2D variable range hopping (VRH) for x=0.05 and 0.075. - Graphical abstract: Crystal structure of NaCuMnSe{sub 2}. - Highlights: • A new quaternary layered selenide NaCuMnSe{sub 2} is synthesized. • All the compositions show semiconducting nature, whereas the Seebeck coefficient increases gradually over the entire measured temperature range. • Conduction mechanism transforms from thermally activated behavior to 2D variable range hopping with increase in copper concentration.

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

    DOE PAGES

    Lu, Yongwu; Yu, Fei; Hu, Jin; ...

    2012-04-12

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

  3. Synthesis and luminescence properties of ZnS and metal (Mn, Cu)-doped-ZnS ceramic powder

    NASA Astrophysics Data System (ADS)

    Ummartyotin, S.; Bunnak, N.; Juntaro, J.; Sain, M.; Manuspiya, H.

    2012-03-01

    ZnS and metal (Mn, Cu)-doped-ZnS were successfully prepared by wet chemical synthetic route. The understanding of substituted metal ions (Mn, Cu) into ZnS leads to transfer the luminescent centre by small amount of metal dopant (Mn, Cu). Fourier transform infrared and X-ray diffraction were used to determine chemical bonding and crystal structure, respectively. It showed that small amount of metal (Mn, Cu) can be completely substituted into ZnS lattice. X-ray fluorescence was used to confirm the existence of metal-doped ZnS. Scanning electron microscope revealed that their particles exhibits blocky particle with irregular sharp. Laser confocal microscope and photoluminescence spectroscopy showed that ZnS and metal-doped-ZnS exhibited intense, stable, and tunable emission covering the blue to red end of the visible spectrum. ZnS, Mn-doped-ZnS and Cu-doped-ZnS generated blue, yellow and green color, respectively.

  4. Magnetic properties of CaCu5-type RNi3TSi (R=Gd and Tb, T=Mn, Fe, Co and Cu) compounds

    NASA Astrophysics Data System (ADS)

    Morozkin, A. V.; Knotko, A. V.; Yapaskurt, V. O.; Yao, Jinlei; Yuan, Fang; Mozharivskyj, Y.; Nirmala, R.; Quezado, S.; Malik, S. K.

    2015-12-01

    Magnetic properties and magnetocaloric effect of CaCu5-type RNi3TSi (R=Gd and Tb, T=Mn, Fe, Co and Cu) compounds have been investigated. Magnetic measurements of RNi3TSi display the increasing of Curie temperature and the decreasing of magnetocaloric effect and saturated magnetic moment in the row of 'RNi3CuSi-RNi3NiSi-RNi3CoSi-RNi3MnSi-RNi3FeSi'. In contrast to GdNi3{Mn, Fe, Co}Si, TbNi3{Mn, Fe, Co}Si exhibit significant magnetic hysteresis. The coercive field increases from TbNi4Si ( 0.5 kOe) to TbNi3CoSi (4 kOe), TbNi3MnSi (13 kOe) and TbNi3FeSi (16 kOe) in field of 50 kOe at 5 K, whereas TbNi3CuSi exhibits a negligible coercive field.

  5. Neutron scattering study of spin ordering and stripe pinning in superconducting La<mn>1.93mn>Sr>0.07mn>CuO>4mn>

    SciTech Connect

    Jacobsen, H.; Zaliznyak, I. A.; Savici, A. T.; Winn, B. L.; Chang, S.; Hücker, M.; Gu, G. D.; Tranquada, J. M.

    2015-11-20

    The relationships among charge order, spin fluctuations, and superconductivity in underdoped cuprates remain controversial. We use neutron scattering techniques to study these phenomena in La<mn>1.93mn>Sr>0.07mn>CuO>4mn> a superconductor with a transition temperature of Tc = 20 K. At T<< Tc, we find incommensurate spin fluctuations with a quasielastic energy spectrum and no sign of a gap within the energy range from 0.2 to 15 meV. A weak elastic magnetic component grows below ~ 10 K, consistent with results from local probes. Regarding the atomic lattice, we have discovered unexpectedly strong fluctuations of the CuO6 octahedra about Cu-O bonds, which are associated with inequivalent O sites within the CuO2 planes. Moreover, we observed a weak elastic (3 30) superlattice peak that implies a reduced lattice symmetry. The presence of inequivalent O sites rationalizes various pieces of evidence for charge stripe order in underdoped La2-xSrxCuO4. The coexistence of superconductivity with quasi-static spin-stripe order suggests the presence of intertwined orders; however, the rotation of the stripe orientation away from the Cu-O bonds might be connected with evidence for a finite gap at the nodal points of the superconducting gap function.

  6. Magnetic properties of CaCu{sub 5}-type RNi{sub 3}TSi (R=Gd and Tb, T=Mn, Fe, Co and Cu) compounds

    SciTech Connect

    Morozkin, A.V.; Knotko, A.V.; Yapaskurt, V.O.; Yao, Jinlei; Yuan, Fang; Mozharivskyj, Y.; Nirmala, R.; Quezado, S.; Malik, S.K.

    2015-12-15

    Magnetic properties and magnetocaloric effect of CaCu{sub 5}-type RNi{sub 3}TSi (R=Gd and Tb, T=Mn, Fe, Co and Cu) compounds have been investigated. Magnetic measurements of RNi{sub 3}TSi display the increasing of Curie temperature and the decreasing of magnetocaloric effect and saturated magnetic moment in the row of ‘RNi{sub 3}CuSi–RNi{sub 3}NiSi–RNi{sub 3}CoSi–RNi{sub 3}MnSi–RNi{sub 3}FeSi’. In contrast to GdNi{sub 3}{Mn, Fe, Co}Si, TbNi{sub 3}{Mn, Fe, Co}Si exhibit significant magnetic hysteresis. The coercive field increases from TbNi{sub 4}Si (~0.5 kOe) to TbNi{sub 3}CoSi (4 kOe), TbNi{sub 3}MnSi (13 kOe) and TbNi{sub 3}FeSi (16 kOe) in field of 50 kOe at 5 K, whereas TbNi{sub 3}CuSi exhibits a negligible coercive field. - Graphical abstract: Magnetic measurements of RNi{sub 3}TSi show the increasing of Curie temperature and the decreasing of magnetocaloric effect and saturated magnetic moment in the row of 'RNi{sub 3}CuSi–RNi{sub 3}NiSi–RNi{sub 3}CoSi–RNi{sub 3}MnSi–RNi{sub 3}FeSi'. In contrast to GdNi{sub 3}{Mn, Fe, Co}Si, TbNi{sub 3}{Mn, Fe, Co}Si exhibit significant magnetic hysteresis. The coercive field increases from TbNi{sub 4}Si (~0.5 kOe) to TbNi{sub 3}CoSi (4 kOe), TbNi{sub 3}MnSi (13 kOe) and TbNi{sub 3}FeSi (16 kOe) in field of 50 kOe at 5 K, whereas TbNi{sub 3}CuSi exhibits a negligible coercive field. - Highlights: • CaCu{sub 5}-type RNi{sub 3}TSi show ferromagnetic ordering (R=Gd, Tb, T=Mn–Co, Cu). • Curie point increases in ‘RNi{sub 3}CuSi–RNi{sub 3}NiSi–RNi{sub 3}CoSi–RNi{sub 3}MnSi–RNi{sub 3}FeSi’ row. • MCE decreases in ‘RNi{sub 3}CuSi–RNi{sub 3}NiSi–RNi{sub 3}CoSi–RNi{sub 3}MnSi–RNi{sub 3}FeSi’ row. • TbNi{sub 3}{Mn, Fe, Co}Si exhibit significant magnetic hysteresis. • The coercive field of TbNi{sub 3}MnSi and TbNi{sub 3}FeSi reach 13 kOe and 16 kOe at 5 K.

  7. Imaging Current-Induced Switching of Antiferromagnetic Domains in CuMnAs

    NASA Astrophysics Data System (ADS)

    Grzybowski, M. J.; Wadley, P.; Edmonds, K. W.; Beardsley, R.; Hills, V.; Campion, R. P.; Gallagher, B. L.; Chauhan, J. S.; Novak, V.; Jungwirth, T.; Maccherozzi, F.; Dhesi, S. S.

    2017-02-01

    The magnetic order in antiferromagnetic materials is hard to control with external magnetic fields. Using x-ray magnetic linear dichroism microscopy, we show that staggered effective fields generated by electrical current can induce modification of the antiferromagnetic domain structure in microdevices fabricated from a tetragonal CuMnAs thin film. A clear correlation between the average domain orientation and the anisotropy of the electrical resistance is demonstrated, with both showing reproducible switching in response to orthogonally applied current pulses. However, the behavior is inhomogeneous at the submicron level, highlighting the complex nature of the switching process in multidomain antiferromagnetic films.

  8. Imaging Current-Induced Switching of Antiferromagnetic Domains in CuMnAs.

    PubMed

    Grzybowski, M J; Wadley, P; Edmonds, K W; Beardsley, R; Hills, V; Campion, R P; Gallagher, B L; Chauhan, J S; Novak, V; Jungwirth, T; Maccherozzi, F; Dhesi, S S

    2017-02-03

    The magnetic order in antiferromagnetic materials is hard to control with external magnetic fields. Using x-ray magnetic linear dichroism microscopy, we show that staggered effective fields generated by electrical current can induce modification of the antiferromagnetic domain structure in microdevices fabricated from a tetragonal CuMnAs thin film. A clear correlation between the average domain orientation and the anisotropy of the electrical resistance is demonstrated, with both showing reproducible switching in response to orthogonally applied current pulses. However, the behavior is inhomogeneous at the submicron level, highlighting the complex nature of the switching process in multidomain antiferromagnetic films.

  9. Acoustic characteristics of high damping Mn73Cu20Ni5Fe2 alloy

    NASA Astrophysics Data System (ADS)

    Fukuhara, M.; Yin, F.; Kawahara, K.

    2004-02-01

    The acoustic characteristics for high damping Mn73Cu20Ni5Fe2 (M2052) alloy were investigated in terms of frequency-dependent complex dynamics, using an ultrasonic pulse method. The longitudinal and transverse waves show maximum decrements of about 2 and 1.8 at around 1.8 and 0.8 MHz, respectively, derived from a single relaxation process. Frequency dispersion leads to increase in dynamic modulus and delay in phase, suggesting growth (microkinking) of microtwin phases analogous to the stretching by micro-Brownian rotation in rubbers.

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

    DOE PAGES

    Barabash, Rozaliya I.; Barabash, Oleg M.; Popov, Dmitry; ...

    2015-01-31

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

  11. Paramagnetic to antiferromagnetic transition in epitaxial tetragonal CuMnAs (invited)

    SciTech Connect

    Hills, V.; Wadley, P. Campion, R. P.; Beardsley, R.; Edmonds, K. W.; Gallagher, B. L.; Novak, V.; Ouladdiaf, B.; Jungwirth, T.

    2015-05-07

    In this paper, we use neutron scattering and electrical transport to investigate the paramagnetic to antiferromagnetic phase transition in tetragonal CuMnAs films on GaP(001). X-ray diffraction and cross-sectional transmission electron microscopy measurements show that the films are chemically ordered with high structural quality. The temperature dependence of the structurally forbidden (100) neutron scattering peak is used to determine the Néel temperature, T{sub N}. We then demonstrate the presence of a clear peak in the temperature derivative of the resistivity around T{sub N}. The effect of disorder-induced broadening on the shape of the peak is discussed.

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

    SciTech Connect

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

    2015-01-31

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

  13. 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.

  14. 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.

  15. Effects of Mn, Si, and purity on the design of 3.5NiCrMoV, 1CrMoV, and 2.25Cr-1Mo bainitic alloy steels

    NASA Astrophysics Data System (ADS)

    Bodnar, R. L.; Ohhashi, T.; Jaffee, R. I.

    1989-08-01

    Three high-temperature bainitic alloy steels were evaluated in the laboratory to determine the effects of Mn, Si, and impurities ( i.e., S, P, Sn, As, and Sb) on microstructure and mechanical properties. The alloy steels were 3.5NiCrMoV and CrMoV, which are used for turbine rotors, and 2.25Cr-1Mo, which is used in pressure vessel applications. The important effects of Mn, Si, and impurities, which should control the design of these high-temperature bainitic steels, are presented. Key results are used to illustrate the influence of these variables on cleanliness, overheating, austenitizing, hardenability, tempering, ductility, toughness, temper embrittlement, creep rupture, and low-cycle fatigue. Low levels of Mn, Si, and impurities not only result in improved temper embrittlement resistance in these steels but also lead to an improvement in creep rupture properties ( i.e., improved strength and ductility). These results have produced some general guidelines for the design of high-temperature bainitic steels. Examples illustrating the implementation of the results and the effectiveness of the design guidelines are provided. Largely based on the benefits shown by this work, a high-purity 3.5NiCrMoV steel, which is essentially free of Mn, Si, and impurities, has been developed and is already being used commercially.

  16. Complexes of arabinogalactan of Pereskia aculeata and Co2+, Cu2+, Mn2+, and Ni2+.

    PubMed

    Merce, A L; Landaluze, J S; Mangrich, A S; Szpoganicz, B; Sierakowski, M R

    2001-01-01

    The main interest in the biopolymer arabinogalactan is that it is edible. Complementing its high protein percentage, when complexed to essential metal ions, widens the use in food and pharmacology industries and technologies. The binding constants of Co2+, Cu2+, Mn2+ and Ni2+ with arabinogalactan, extracted from the leaves of Pereskia aculeata from Brazil were determined by potentiometric titrations and also the speciation according to pH values. The complexed species proposed by potentiometric titrations and the unique complexing ability of galacturonic acid groups towards Cu2+ and Ni2+ in the tridimensional web structure of arabinogalactan were confirmed by IR and EPR spectroscopies. The thermal stability of the complexed species also varied with the metal ion employed in the complexation when compared to the biopolymer alone. These complexes are new sources of additives for the food and pharmacology industries and carriers of essential metal ions to animal and vegetal biochemistry.

  17. Structure and magnetic properties of CuIn1-xTxTe2 (T=Co,Mn)

    NASA Astrophysics Data System (ADS)

    Guo, Yongquan; Li, Shuai; Wang, Tai; Xie, Nana

    2017-08-01

    The crystal structures, magnetic and optical properties of the 3d transition metals of Co or Mn doped CuInTe2 have been investigated using X-ray diffraction, magnetic measurements, ultraviolet and visible spectrophotometers. It is found that CuIn1-xTxTe2 (T=Co, Mn) crystallize in tetragonal chalcopyrite structure in a doping range of x=0-0.2. The structural analyses show that the 3d transition metal of Mn or Co prefers to occupy the 4b crystal position. Mn-doped CuIn1-xMnxTe2 (x=0-0.3) show paramagnetic characteristics at room temperature with the susceptibilities of about 10-5. However, lightly Co-doping into CuIn1-xCoxTe2 shows ferromagnetism at room temperature under a low applied field. This phenomenon is suggested to result from the spin-spin interactions between Co atoms which lead to the ferromagnetism. CuIn0.9Co0.1Te2 with ferromagnetism at room temperature under a low field revealed in this work indicates that it a good candidate for photovoltaic cells application since its bandgap matches well with that of CuIn1-xGaxSe2 with high conversion efficiency.

  18. X-ray absorption study of the ferromagnetic Cu moment at the YBa2Cu3O7/La2 /3Ca1 /3MnO3 interface and variation of its exchange interaction with the Mn moment

    NASA Astrophysics Data System (ADS)

    Sen, K.; Perret, E.; Alberca, A.; Uribe-Laverde, M. A.; Marozau, I.; Yazdi-Rizi, M.; Mallett, B. P. P.; Marsik, P.; Piamonteze, C.; Khaydukov, Y.; Döbeli, M.; Keller, T.; Biškup, N.; Varela, M.; Vašátko, J.; Munzar, D.; Bernhard, C.

    2016-05-01

    With x-ray absorption spectroscopy and polarized neutron reflectometry we studied how the magnetic proximity effect at the interface between the cuprate high-TC superconductor YBa2Cu3O7 (YBCO) and the ferromagnet La2 /3Ca1 /3MnO3 (LCMO) is related to the electronic and magnetic properties of the LCMO layers. In particular, we explored how the magnitude of the ferromagnetic Cu moment on the YBCO side depends on the strength of the antiferromagnetic (AF) exchange coupling with the Mn moment on the LCMO side. We found that the Cu moment remains sizable if the AF coupling with the Mn moments is strongly reduced or even entirely suppressed. The ferromagnetic order of the Cu moments thus seems to be intrinsic to the interfacial CuO2 planes and related to a weakly ferromagnetic intraplanar exchange interaction. The latter is discussed in terms of the partial occupation of the Cu 3 d3 z2-r2 orbitals, which occurs in the context of the so-called orbital reconstruction of the interfacial Cu ions.

  19. Preliminary assessment of metal-porcelain bonding strength of CoCrW alloy after 3wt.% Cu addition.

    PubMed

    Lu, Yanjin; Zhao, Chaoqian; Ren, Ling; Guo, Sai; Gan, Yiliang; Yang, Chunguang; Wu, Songquan; Lin, Junjie; Huang, Tingting; Yang, Ke; Lin, Jinxin

    2016-06-01

    In this work, a novel Cu-bearing CoCrW alloy fabricated by selective laser melting for dental application has been studied. For its successful application, the bonding strength of metal-porcelain is essential to be systematically investigated. Therefore, the aim of this study was to evaluate the metal-porcelain bonding strength of CoCrWCu alloy by three-point bending test, meanwhile the Ni-free CoCrW alloy was used as control. The oxygen content was investigated by an elemental analyzer; X-ray photoelectron spectroscopy (XPS) was used to analyze the surface chemical composition of CoCrW based alloy after preoxidation treatment; the fracture mode was investigated by X-ray energy spectrum analysis (EDS) and scanning electron microscope (SEM). Result from the oxygen content analysis showed that the content of oxygen dramatically increased after the Cu addition. And the XPS suggested that Co-oxidation, Cr2O3, CrO2, WO3, Cu2O and CuO existed on the preoxidated surface of the CoCrWCu alloy; the three-point bending test showed that the bonding strength of the CoCrWCu alloy was 43.32 MPa, which was lower than that of the CoCrW group of 47.65 MPa. However, the average metal-porcelain bonding strength is significantly higher than the minimum value in the ISO 9693 standard. Results from the SEM images and EDS indicated that the fracture mode of CoCrWCu-porcelain was mixed between cohesive and adhesive. Based on the results obtained in this study, it can be indicated that the Cu-bearing CoCrW alloy fabricated by the selective laser melting is a promising candidate for use in dental application.

  20. Influence of annealing conditions on microstructure and phase occurrence in high-alloy CrMnN steels

    SciTech Connect

    Bakajova, Jana; Domankova, Maria; Cicka, Roman; Eglsaeer, Sabine; Janovec, Jozef

    2010-10-15

    The influence of annealing at 750, 800, 850, 900 and 950 deg. C for 4 h on the microstructure and the phase occurrence in two high-alloy CrMnN austenitic stainless steels was investigated using light microscopy, transmission electron microscopy, and thermodynamic calculations. Austenite, {sigma}, and Cr{sub 2}N were identified in both steels experimentally. The experimental results were found to be in good agreement with the thermodynamic predictions. In one of the steels, M{sub 23}C{sub 6} as a non-equilibrium probably residual phase was found. Cr{sub 2}N appeared in the steels either in the form of discrete particles or as a part of cells consisting of alternate lamellae of Cr{sub 2}N and austenite.

  1. EPR Study of Cr5+ and Cu2+ in Some Zeolites Introduced by Solid- and Liquid-State Reactions

    NASA Astrophysics Data System (ADS)

    Köksal, Fevzi; Ucun, Fatih; Kartal, İbrahim

    1996-04-01

    This study reports on the EPR of Cr5+ and Cu2+ ions, introduced by solid- and liquid-state reactions with the synthetic zeolites 3A, 4A and 5A, and the natural zeolite clinoptilolite. Cr3+ was oxidized to Cr5+ in the samples, the coordination around Cr5+ being square pyramidal. Super-hyperfine (shf) interaction of Cr5+ with 27Al nucleus was observed in both solid-and liquid-state-introduced 5A zeolite, whereas this shf could not be observed for the solid-state introduced 4A zeolite. The liquid-state Cr-introduced 4A zeolite needed a heat treatment at 473 K for ½ h for the appearance of shfs. Furthermore, it has been found that the coordination structure around the Cu2+ is square pyramidal in solid-state introduced samples, whereas it is octahedral in the liquid-state introduced ones.

  2. Enhanced room temperature ferromagnetism and photoluminescence behavior of Cu-doped ZnO co-doped with Mn

    NASA Astrophysics Data System (ADS)

    Ashokkumar, M.; Muthukumaran, S.

    2015-05-01

    Cu, Mn co-doped ZnO nanoparticles were successfully synthesized by the sol-gel technique. XRD pattern described that Mn-doping did not affect the hexagonal wurtzite structure of the samples and no secondary phases were found. The reduced crystallite size at Mn=2% is due to the suppression of grain surface growth by foreign impurity. The enhancement of crystal size after Mn=2% is due to the expansion of lattice volume produced by the distortion around the dopant ion. The better dielectric constant and conductivity noticed at Mn=2% are explained by charge carrier density and crystallite size. The suppression of broad UV band by Mn-doping is discussed based on the generation of non-radiative recombination centers. Hysteresis loop showed the clear room temperature ferromagnetism in all the samples and the magnetization increased with Mn-doping. Better electrical and magnetic behavior of Zn0.94Cu0.04Mn0.02O sample is suggested for effective opto-magnetic devices.

  3. Electronic structure and magnetism of Ge(Sn)TMXTe1-X (TM = V, Cr, Mn): A first principles study

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Bose, S. K.; Kudrnovský, J.

    2016-12-01

    This work presents the results of first principles calculations of the electronic and magnetic properties of the compound SnTe and GeTe in zinc blende (ZB) and rock salt (RS) structures, doped with 3d transition metal V, Cr, and Mn. The present study, initiated from the viewpoint of potential application in spintronics, is motivated by our earlier work involving these two compounds, where the doping was limited to the Sn and Ge sublattices. In view of some discrepancies between our calculated results and the available experimental data, in this work we have examined the effect of the Te-sublattice doping. The case of Mn-doping, where the previous results of calculations seemed to differ most from the experimentally available data, is examined further by looking at the effect of Mn atoms partially occupying interstitial sites as well. From the standpoint of potential application in spintronics, we look for half-metallic (HM) states and tabulate their properties in both rock salt and zinc blende structures. ZB structure is found to be more conducive to HM state in general. Among the binary compounds we identify several HM candidates: VGe, VSn, MnGe, MnSn and MnTe at their equilibrium volumes and all in ZB structure. Estimates of the Curie temperature for the ferromagnetic compounds including the half-metals are presented. It is shown that despite the ferromagnetic (FM) nature of the Mn-Mn interaction for the Te-doped case, a simultaneous doping of both Ge(Sn)- and Te-sublattice with Mn atoms would leave the material predominantly antiferromagnetic (AFM).

  4. Comparative study of supported CuOx and MnOx catalysts for the catalytic wet air oxidation of β-naphthol

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Yu, Chaoying; Zhao, Peiqing; Chen, Gexin

    2012-09-01

    MnOx/nano-TiO2, MnOx/Al2O3-TiO2 (Al-Ti), CuOx/nano-TiO2 and CuOx/Al-Ti were prepared and their application in catalytic wet air oxidation (CWAO) of β-naphthol were investigated. The catalysts had been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) measurements. Phases of CuO, Cu2O, CuAl2O4, MnO2 and Mn2O3 could be found on the surface of the aforementioned catalysts. Significant differences in activities were observed among the prepared catalysts. Compared to CuOx/nano-TiO2, the combined action of highly dispersed CuO as well as CuAl2O4 of CuOx/Al-Ti helped to achieve higher activity for the CWAO of β-naphthol, while the Cu2O component lead to lower efficiency of CuOx/nano-TiO2. On the surface of MnOx/nano-TiO2, both the larger amount of highly dispersed MnO2 and the stronger electron transfer between MnO2 and Mn2O3 were helpful to promote the activity for the degradation of β-naphthol. However, the higher amount of bulk MnO2 and the weaker electron transfer for MnOx/Al-Ti were unfavorable to increase its efficiency. Among the four catalysts as-prepared, MnOx/nano-TiO2 was identified the highest activity with 93.7% COD removal.

  5. Inelastic-neutron-scattering studies of spin-wave excitations in the pnictides MnSb and CrSb

    SciTech Connect

    Radhakrishna, P.; Cable, J.W.

    1996-11-01

    The spin-wave dispersion relations in the ferromagnet MnSb, and the antiferromagnet CrSb, have been measured, by neutron inelastic scattering, along high-symmetry directions in reciprocal space, as a function of temperature. The effect of composition is discussed. The dispersion in CrSb is found to rise very steeply as a function of {ital q}, and a gap in the excitation spectrum occurs at {ital q}=0. The results for these itinerant electron magnetic materials are compared with previous experimental and theoretical work. {copyright} {ital 1996 The American Physical Society.}

  6. Inelastic-neutron-scattering studies of spin-wave excitations in the pnictides MnSb and CrSb

    NASA Astrophysics Data System (ADS)

    Radhakrishna, P.; Cable, J. W.

    1996-11-01

    The spin-wave dispersion relations in the ferromagnet MnSb, and the antiferromagnet CrSb, have been measured, by neutron inelastic scattering, along high-symmetry directions in reciprocal space, as a function of temperature. The effect of composition is discussed. The dispersion in CrSb is found to rise very steeply as a function of q, and a gap in the excitation spectrum occurs at q=0. The results for these itinerant electron magnetic materials are compared with previous experimental and theoretical work.

  7. Mechanical characteristics and swelling of austenitic Fe-Cr-Mn steels irradiated in the SM-2 and BOR-60 reactors

    NASA Astrophysics Data System (ADS)

    Shamardin, V. K.; Bulanova, T. M.; Neustroev, V. S.; Ivanov, L. I.; Djomina, E. V.; Platov, Yu. M.

    1991-03-01

    Three types of austenitic Fe-Cr-Mn stainless steels were irradiated simultaneously with Fe-Cr-Ni austenitic steel at temperatures from 400 to 800°C in the mixed spectrum of the high flux SM-2 reactor to 10 dpa and 700 appm of He and in the BOR-60 reactor to 60 dpa without He generation. The paper presents the swelling and mechanical properties of steels irradiated in the BOR-60 and SM-2 as a function of the concentration of transmuted He and the value of atomic displacement.

  8. Iron-rich low-cost superalloys. [Cr(15)-Mn(15)-Mo(2)-C(1. 5)-Si(1. 0)-Nb(1. 0)-Fe(bal. ) and Cr(20)-Mn(10)-C(3. 4)-Fe(bal. )

    SciTech Connect

    Wayne, S.F.

    1985-01-01

    An iron-rich low-cost superalloy has been developed in conjunction with United Technologies Research Center under the NASA program, Conservation of Strategic Aerospace Materials. The alloy, when processed by conventional chill casting, has physical and mechanical properties that compare favorably with existing nickel - and cobalt-based superalloys while containing significantly lower amounts of strategic elements. The composition of the alloy is Cr(15)-Mn(15)-Mo(2)-C(1.5)-Si(1.0)-Nb(1.0)-Fe(bal.), and it can be produced with chromite ore deposits located within the United States. Studies were also made on the properties of Cr(20)-Mn(10)-C(3.4)-Fe(bal.), a eutectic alloy processed by chill casting and directional solidification (D.S.) which produced an aligned microstructure consisting of M/sub 7/C/sub 3/ fibers in an ..gamma..-Fe matrix. This good alignment vanishes when molybdenum or aluminum is added in higher concentrations. Thermal expansion of the M/sub 7/C/sub 3/ (M = Fe, Cr, Mn) carbide lattice was measured up to 800/sup 0/C and found to be highly anisotropic, with the a-axis being the predominant mode of expansion. Repetitive impact-sliding wear experiments performed with the Fe-rich eutectic alloy showed that the directionally solidified microstructure greatly improved the alloy's wear resistance as compared to the chill-cast microstructure and conventional nickel-base superalloys.

  9. Fate of Cu, Cr, and As during combustion of impregnated wood with and without peat additive

    SciTech Connect

    Karin Lundholm; Dan Bostroem; Anders Nordin; Andrei Shchukarev

    2007-09-15

    The EU Directive on incineration of waste regulates the harmful emissions of particles and twelve toxic elements, including copper, chromium, and arsenic. Using a 15 kW pellets-fueled grate burner, experiments were performed to determine the fate of copper, chromium, and arsenic during combustion of chromate copper arsenate (CCA) preservative wood. The fate and speciation of copper, chromium, and arsenic were determined from analysis of the flue gas particles and the bottom ash using SEM-EDS, XRD, XPS, and ICP-AES. Chemical equilibrium model calculations were performed to interpret the experimental findings. The results revealed that about 5% copper, 15% chromium, and 60% arsenic were volatilized during combustion of pure CCA-wood, which is lower than predicted volatilization from the individual arsenic, chromium, and copper oxides. This is explained by the formation of more stable refractory complex oxide phases for which the stability trends and patterns are presented. When co-combusted with peat, an additional stabilization of these phases was obtained and thus a small but noteworthy decrease in volatilization of all three elements was observed. The major identified phases for all fuels were CuCrO{sub 2}(s), (Fe,Mg,Cu)(Cr,Fe,Al)O{sub 4}(s), Cr{sub 2}O{sub 3}(s), and Ca{sub 3}(AsO{sub 4}){sub 2}(s). Arsenic was also identified in the fine particles as KH{sub 2}AsO{sub 4}(s) and As{sub 2}O{sub 3}). A strong indication of hexavalent chromium in the form of K{sub 2}CrO{sub 4} or as a solid solution between K{sub 3}Na(CrO{sub 4}){sub 2} and K{sub 3}Na(SO{sub 4}){sub 2} was found in the fine particles. Good qualitative agreement was observed between experimental data and chemical equilibrium model calculations. 38 refs., 6 figs., 2 tabs.

  10. 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.

  11. Effects of different manganese precursors as promoters on catalytic performance of CuO-MnOx/TiO2 catalysts for NO removal by CO.

    PubMed

    Sun, Chuanzhi; Tang, Yingjie; Gao, Fei; Sun, Jingfang; Ma, Kaili; Tang, Changjin; Dong, Lin

    2015-06-28

    Two different precursors, manganese nitrate (MN) and manganese acetate (MA), were employed to prepare two series of catalysts, i.e., xCuyMn(N)/TiO2 and xCuyMn(A)/TiO2, by a co-impregnation method. The catalysts were characterized by XRD, LRS, CO-TPR, XPS and EPR spectroscopy. The results suggest that: (1) both xCuyMn(N)/TiO2 and xCuyMn(A)/TiO2 catalysts exhibit much higher catalytic activities than an unmodified Cu/TiO2 catalyst in the NO + CO reaction. Furthermore, the activities of catalysts modified with the same amount of manganese are closely dependent on manganese precursors. (2) The enhancement of activities for Mn-modified catalysts should be attributed to the formation of the surface synergetic oxygen vacancy (SSOV) Cu(+)-□-Mn(y+) in the reaction process. Moreover, since the formation of the SSOV (Cu(+)-□-Mn(3+)) in the xCuyMn(N)/TiO2 catalyst is easier than that (Cu(+)-□-Mn(2+)) in the xCuyMn(A)/TiO2 catalyst, the activity of the xCuyMn(N)/TiO2 catalyst is higher than that of the xCuyMn(A)/TiO2 catalyst. This conclusion is well supported by the XPS and EPR results.

  12. Effect of aluminum substitution on structural and electromagnetic properties of nanocrystalline MgCuMn ferrites

    SciTech Connect

    Ramesh, T. E-mail: ramanasarabu@gmail.com; Kumar, S. Senthil; Shinde, R. S.; Murthy, S. R.

    2015-06-24

    The effect of substitution of nonmagnetic Al{sup 3+} ions on the structural and electromagnetic properties were studied in nanocrystalline ferrite series of Mg{sub 0.8}Cu{sub 0.2}Al{sub x}Fe{sub 1.95-x}Mn{sub 0.05}O{sub 4} where x varies 0-0.4 in steps of 0.1. This series was synthesized by using microwave hydrothermal method. The nanocrystalline ferrite phase was observed at temperature 150°C/40 min. Synthesized powders were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The synthesized powders were densified using microwave sintering method at 950°C/40 min. The sintered samples were characterized using XRD. Surface morphology was observed by using field effective scanning electron microscopy (FESEM). The electrical and magnetic properties were measured at room temperature. These results led us to interfere that the values of d.c resistivity increases and dielectric constant, initial permeability, saturation magnetization and Curie temperature were observed to be decreased with the substitution of Al{sup 3+} ions with those of Fe{sup 3+}. The low dielectric and magnetic losses and low magnetization exhibited by aluminum substituted MgCuMn ferrites makes them find applications in microwave devices.

  13. [CoCuMnOx Photocatalyzed Oxidation of Multi-component VOCs and Kinetic Analysis].

    PubMed

    Meng, Hai-long; Bo, Long-li; Liu, Jia-dong; Gao, Bo; Feng, Qi-qi; Tan, Na; Xie, Shuai

    2016-05-15

    Solar energy absorption coating CoCuMnOx was prepared by co-precipitation method and applied to photodegrade multi- component VOCs including toluene, ethyl acetate and acetone under visible light irradiation. The photocatalytic oxidation performance of toluene, ethyl acetate and acetone was analyzed and reaction kinetics of VOCs were investigated synchronously. The research indicated that removal rates of single-component toluene, ethyl acetate and acetone were 57%, 62% and 58% respectively under conditions of 400 mg · m⁻³ initial concentration, 120 mm illumination distance, 1 g/350 cm² dosage of CoCuMnOx and 6 h of irradiation time by 100 W tungsten halogen lamp. Due to the competition among different VOCs, removal efficiencies in three-component mixture were reduced by 5%-26% as compared with single VOC. Degradation processes of single-component VOC and three-component VOCs both fitted pseudo first order reaction kinetics, and kinetic constants of toluene, ethyl acetate and acetone were 0.002, 0.002 8 and 0.002 33 min⁻¹ respectively under single-component condition. Reaction rates of VOCs in three-component mixture were 0.49-0.88 times of single components.

  14. Application of Cu-Al-Mn superelastic alloy bars as reinforcement elements in concrete beams

    NASA Astrophysics Data System (ADS)

    Shrestha, Kshitij C.; Araki, Yoshikazu; Nagae, Takuya; Yano, Hayato; Koetaka, Yuji; Omori, Toshihiro; Sutou, Yuji; Kainuma, Ryosuke; Ishida, Kiyohito

    2012-04-01

    Experimental works are done to assess the seismic behavior of concrete beams reinforced with superelastic alloy (SEA) bars. Applicability of newly developed Cu-Al-Mn SEA bars, characterized by large recovery strain, low material cost, and high machinability, have been proposed as partial replacements for conventional steel bars in order to reduce residual deformations in structures during and after intense earthquakes. Four-point reverse-cyclic bending tests were done on 1/3 scale concrete beams comprising three different types of specimens - conventional steel reinforced concrete (ST-RC), SEA reinforced concrete (SEA-RC), and SEA reinforced concrete with pre-tensioning (SEA-PC). The results showed that SEA reinforced concrete beams demonstrated significant enhancement in crack recovery capacity in comparison to steel reinforced beam. Average recovery of cracks for each of the specimens was 21% for ST-RC, 84% for SEA-RC, and 86% for SEA-PC. In addition, SEA-RC and SEA-PC beams demonstrated strong capability of recentering with comparable normalized strength and ductility relative to conventional ST-RC beam specimen. ST-RC beam, on the other hand, showed large residual cracks due to progressive reduction in its re-centering capability with each cycle. Both the SEA-RC and SEA-PC specimens demonstrated superiority of Cu-Al-Mn SEA bars to conventional steel reinforcing bars as reinforcement elements.

  15. XRD and XANES study of some Cu-doped MnBi materials

    NASA Astrophysics Data System (ADS)

    Mishra, Ashutosh; Patil, Harsha

    2016-10-01

    High purity MnBi low temperature phase has been prepared and analyzed using X- ray diffraction (XRD) and X-ray absorption near edge structure (XANES) measurements. The X-ray diffraction measurements were carried out using Bruker D8 Advance X-ray diffractometer. The X-rays were produced using a sealed tube and the wavelength of X-ray was 154 nm (Cu K-alpha). and X-rays were detected using a fast counting detector based on Silicon strip technology (Bruker LynxEye detector)[1]. and the X-ray absorption spectra has emerged as a powerful technique for local structure determination, which can be applied to any type of material. The X-ray absorption measurements of two Cu-doped MnBi alloys have been performed at the recently developed BL-8 Dispersive EXAFS beam line at 2.5 GeV Indus-2 synchrotron at RRCAT, Indore, India[2]. The X-ray absorption near edge structure (XANES) data obtained has been processed using data analysis program Athena. The energies of the K absorption edge, chemical shifts, edge-widths, shifts of the principal absorption maximum in the alloys have been determined.

  16. Adsorption of Cu and Mn on covalently cross-linked alginate gel beads.

    PubMed

    Gotoh, Takeshi; Matsushima, Keiei; Kikuchi, Ken-Ichi

    2004-04-01

    The covalently cross-linked alginate gel beads were prepared by the reactions of Ca(2+)-doped alginate gel beads, which were formed by spraying a viscous alginate solution into a calcium chloride solution, with cyanogen bromide and following 1,6-diaminohexane. The cross-linking of alginate matrix decreased the mean bead diameter by about 30% and made the beads durable in some extent under alkaline conditions. The adsorption of metal ions on the covalently cross-linked alginate gel beads was rapid and reached at equilibrium within 30 min at 25 degrees C. Adsorption isotherms of Cu(II), Mn(II), and Ca2+ on the beads possessed a stepwise shape, which was firstly determined by Rorrer et al. [Ind. Eng. Chem. Res. 32 (1993) 2170] for cross-linked chitosan gel beads and explained by a pore-blockage mechanism. Higher selectivity was determined against Cu(II) over Mn(II) and Ca2+, especially at a low concentration region. These metal adsorption profiles for the covalently cross-linked alginate gel beads was almost the same as those for the un-cross-linked beads, indicating that the cross-linking reactions were performed without interfering the adsorption characteristics of alginate gel beads.

  17. Magnetic properties of the intermetallic compounds MMscriptX(M=Cr,Mn, Mscript=Ru,Rh,Pd, and X=P,As)

    NASA Astrophysics Data System (ADS)

    Kanomata, T.; Kawashima, T.; Utsugi, H.; Goto, T.; Hasegawa, H.; Kaneko, T.

    1991-04-01

    Magnetization, magnetic susceptibility, and crystal structure are investigated on the ternary chromium arsenides CrM'As (M'=Ru,Rh,Pd) and ternary manganese phosphides and arsenides MnM'P(M'=Rh,Pd) and MnM'As(M'=Ru,Pd). MnRhP, MnRuAs, and MnPdAs are ferromagnets with a Curie temperature of Tc=401, 496, and 210 K, respectively. CrRhAs is an antiferromagnet with a Néel temperature of TN=165 K. MnPdP and CrPdAs show spin-glass-like freezing. A magnetic order-order transition is observed for CrRuAs. Susceptibility χ versus temperature curves are well expressed by a formula χ =C'/(T - θ'P)γ for all present compounds. The values of γ are about 3/2 for manganese compounds and CrPdAs, and about 1/2 for CrRuAs and CrRhAs.

  18. The Effects of Helium Bubble Microstructure on Ductility in Annealed and HERF 21Cr-6Ni-9Mn Stainless Steel

    SciTech Connect

    Tosten, M.H.; Morgan, M.J.

    1998-01-01

    This study examined the effects of microstructure on the ambient temperature embrittlement from hydrogen isotopes and decay helium in 21Cr-6Ni-9Mn stainless steel. Hydrogen and tritium-exposed 21Cr-6Ni-9Mn stainless steel tensile samples were pulled to failure and then characterized by transmission electron microscopy (TEM) and optical microscopy. This study determined that ductility differences between annealed and high-energy-rate-forged (HERF) stainless steel containing tritium and its decay product, helium, could be related to differences in the helium bubble microstructures. The HERF microstructures were more resistant to tritium-induced embrittlement than annealed microstructures because the high number density of helium bubbles on dislocations trap tritium within the matrix and away from the grain boundaries.

  19. Microstructure and Mechanical Properties After Shock Wave Loading of Cast CrMnNi TRIP Steel

    NASA Astrophysics Data System (ADS)

    Eckner, Ralf; Krüger, L.; Ullrich, C.; Rafaja, D.; Schlothauer, T.; Heide, G.

    2016-10-01

    The mechanical response of shock wave-prestrained high-alloy Cr16-Mn7-Ni6 TRIP steel was investigated under compressive and tensile loading at room temperature. Previous shock wave loading was carried out using a flyer-plate assembly with different amounts of explosives in order to achieve shock pressures of 0.3, 0.6, 0.9, and 1.2 Mbar. A significant increase in hardness and strength was observed as compared with the initial as-cast condition. In contrast, a slight decrease in strain hardening rates was measured together with a decrease in fracture elongation in the tensile test. Microstructural analyses of the shock-loaded samples were performed by light optical and scanning electron microscopy. The microstructure revealed a high density of deformation bands consisting of separated stacking faults, ɛ-martensite, or twins. Significant amounts of deformation-induced α'-martensite were only present at the highest shock pressure of 1.2 Mbar. The thickness of the deformation bands and the number of martensite nuclei at their intersections increased with increasing shock pressure. In all shock-loaded specimens, pronounced phase transformation occurred during subsequent mechanical testing. Consequently, the amount of the deformation-induced α'-martensite in the shock-loaded specimens was higher than in the unshocked as-cast samples.

  20. Structural and magnetic properties of a prospective spin gapless semiconductor MnCrVAl

    NASA Astrophysics Data System (ADS)

    Huh, Y.; Gilbert, S.; Kharel, P.; Jin, Y.; Lukashev, P.; Valloppilly, S.; Sellmyer, D. J.

    Recently a new class of material, spin gapless semiconductors (SGS), has attracted much attention because of their potential for spintronic devices. We have synthesized a Heusler compound, MnCrVAl, which is theoretically predicted to exhibit SGS by arc melting, rapid quenching and thermal annealing. First principles calculations are employed to describe its structural, electronic and magnetic properties. X-ray diffraction indicates that the rapidly quenched samples crystallize in the disordered cubic structure. The crystal structure is stable against heat treatment up to 650oC. The samples show very small saturation magnetization, 0.3 emu/g, at room temperature under high magnetic field, 30 kOe. Above room temperature, the magnetization increases with increasing temperature undergoing a magnetic transition at 560oC, similar to an antiferromagnetic-to-paramagnetic transition. The prospect of this material for spintronic applications will be discussed. This research is supported by SDSU Academic/Scholarly Excellence Fund, and Research/Scholarship Support Fund. Research at UNL is supported by DOE (DE-FG02-04ER46152, synthesis, characterization), NSF (ECCS-1542182, facilities), and NRI.

  1. Factors Affecting the Hydrogen Embrittlement Resistance of Ni-Cr-Mn-Nb Welds

    SciTech Connect

    G.A. Young; C.K. Battige; N. Liwis; M.A. Penik; J. Kikel; A.J. Silvia; C.K. McDonald

    2001-03-18

    Nickel based alloys are often welded with argon/hydrogen shielding gas mixtures to minimize oxidation and improve weld quality. However, shielding gas mixtures with {ge} 1% hydrogen additions can result in hydrogen concentrations greater than 5 wt. ppm in the weld metal and reduce ductility via hydrogen embrittlement. For the conditions investigated, the degree of hydrogen embrittlement is highly variable between 5 and 14 wt. ppm. investigation of hydrogen embrittlement of EN82H GTAW welds via tensile testing, light microscopy, transmission electron microscopy, orientation imaging microscopy, and thermal desorption spectroscopy shows that this variability is due to the inhomogeneous microstructure of the welds, the presence of recrystallized grains, and complex residual plastic strains. Specifically, research indicates that high residual strains and hydrogen trapping lower the ductility of Ni-Cr-Mn-Nb weld metal when dissolved hydrogen concentrations are greater than 5 wt. ppm. The inhomogeneous microstructure contains columnar dendritic, cellular dendritic, and recrystallized grains. The decreased tensile ductility observed in embrittled samples is recovered by post weld heat treatments that decrease the bulk hydrogen concentration below 5 wt. ppm.

  2. Study on Protection Mechanism of 30CrMnMo-UHMWPE Composite Armor.

    PubMed

    Zhou, Yu; Li, Guoju; Fan, Qunbo; Wang, Yangwei; Zheng, Haiyang; Tan, Lin; Xu, Xuan

    2017-04-12

    The penetration of a 30CrMnMo ultra-high molecular weight polyethylene armor by a high-speed fragment was investigated via experiments and simulations. Analysis of the projectile revealed that the nose (of the projectile) is in the non-equilibrium state at the initial stage of penetration, and the low-speed regions undergo plastic deformation. Subsequently, the nose-tail velocities of the projectile were virtually identical and fluctuated together. In addition, the effective combination of the steel plate and polyethylene (PE) laminate resulted in energy absorption by the PE just before the projectile nose impacts the laminate. This early absorption plays a positive role in the ballistic performance of the composite armor. Further analysis of the internal energy and mass loss revealed that the PE laminate absorbs energy via the continuous and stable failure of PE fibers during the initial stages of penetration, and absorbs energy via deformation until complete penetration occurs. The energy absorbed by the laminate accounts for 68% of the total energy absorption, indicating that the laminate plays a major role in energy absorption during the penetration process.

  3. Study on Protection Mechanism of 30CrMnMo-UHMWPE Composite Armor

    PubMed Central

    Zhou, Yu; Li, Guoju; Fan, Qunbo; Wang, Yangwei; Zheng, Haiyang; Tan, Lin; Xu, Xuan

    2017-01-01

    The penetration of a 30CrMnMo ultra-high molecular weight polyethylene armor by a high-speed fragment was investigated via experiments and simulations. Analysis of the projectile revealed that the nose (of the projectile) is in the non-equilibrium state at the initial stage of penetration, and the low-speed regions undergo plastic deformation. Subsequently, the nose-tail velocities of the projectile were virtually identical and fluctuated together. In addition, the effective combination of the steel plate and polyethylene (PE) laminate resulted in energy absorption by the PE just before the projectile nose impacts the laminate. This early absorption plays a positive role in the ballistic performance of the composite armor. Further analysis of the internal energy and mass loss revealed that the PE laminate absorbs energy via the continuous and stable failure of PE fibers during the initial stages of penetration, and absorbs energy via deformation until complete penetration occurs. The energy absorbed by the laminate accounts for 68% of the total energy absorption, indicating that the laminate plays a major role in energy absorption during the penetration process. PMID:28772764

  4. Superoxide radical generation and Mn- and Cu-Zn superoxide dismutases activities in human leukemic cells.

    PubMed

    Kato, Masahiko; Minakami, Hisanori; Kuroiwa, Minoru; Kobayashi, Yasuyuki; Oshima, Shigeru; Kozawa, Kunihisa; Morikawa, Akihiro; Kimura, Hirokazu

    2003-03-01

    Mn- and Cu-Zn superoxide dismutase (SOD) activities and generation of superoxide radicals (O(2) (-)) were assessed in leukemic cells from 10 patients with acute myeloid or monocytic leukemia (AML) and 10 patients with acute lymphoblastic leukemia (ALL), using a sensitive, specific chemiluminescence method. Leukemic cells were classified according to the French-American-British classification. M4 AML cells from two patients produced some O(2) (-) upon stimulation with opsonized zymosan (OZ), phorbol myristate acetate (PMA) or N-formyl-methionyl-leucyl-phenylalanine (FMLP), but less than normal granulocytes or monocytes. M5b AML cells from one patient produced as much O(2) (-) in response to these stimulants as normal monocytes. No O(2) (-) generation was induced in other types of leukemic cells. Total SOD activity in AML cells was significantly greater in normal granulocytes, but was only half of the activity in ALL cells. Mn-SOD in AML cells was very low or undetectable. These results suggest that except in M5b cells, decreased O(2) (-) production may contribute to susceptibility to infections in AML patients. Decreased Mn-SOD activity in AML cells may predispose them to oxidative stress. Copyright 2002 John Wiley & Sons, Ltd.

  5. [The recycling rate and budget of trace element Mn and Cu in agroecosystem using ICP-AES].

    PubMed

    Zhou, Hua; Xu, Yong-Gang; Jiang, Chun-Ming

    2011-10-01

    The recycling rate and budget of Mn and Cu under different fertilization regimes by using long-term field experiment and ICP-AES analysis were investigated in the present paper. The results showed that the recycling rates of Mn and Cu were greater than 80% because of sediment recycling type, and the values increased with the amount of feed stuffs increasing. Both the two elements under different fertilization regimes showed budget deficit, with the deficit order of M< (or < or =)NPK + M < CK < NPK, showing that chemical fertilizer application might induce severe deficit, while application of recycling organic matter might minimize the unbalance.

  6. [Specificity of activity antioxidative enzymes at protein deficiency and excessive content Cu, Zn, Mn, Se in the food].

    PubMed

    Ivakhnenko, V I; Mal'tsev, G Iu; Vasil'ev, A V; Gmoshinskiĭ, I V

    2007-01-01

    The research of kinetic properties (Km u Vmax) of two enzymes: Superoxide Dismutase and Glutathione Peroxidase from rats liver and blood and lipid peroxidation induced by both a low protein diet (8%) and 2-fold concentration Cu, Zn, Mn, Se in diet. There was a change of Km and Vmax: the reduction of Km(GPH) was in liver at 28 d and the increase of Km(SOD) was in liver in group with 2-fold concentration Cu, Zn, Mn, Se in diet. The analysis of Km and Vmax of Superoxide Dismutase and Glutathione Peroxidase in different alimentary influence may be as one of methods for assessment individualization of diet therapy.

  7. Microstructural refinement and strengthening of Cu-4 Cr-2 Nb alloy by mechanical milling

    SciTech Connect

    Anderson, K.R.; Groza, J.R.; Ulmer, D.G.

    1997-07-15

    Lately, a variety of dispersion strengthened (DS) copper alloys that provide a good combination of thermal/electrical conductivity and mechanical strength have been developed. Strengthening is usually achieved by the introduction of a ceramic, refractory metal or intermetallic secondary phase. Cu-Cr-Nb is one such DS alloy in which strengthening is provided by Cr{sub 2}Nb intermetallic particles. Mechanical milling of as-atomized Cu-4 Cr-2 Nb alloy powders substantially increases the mechanical strength (hardness) of the starting material. This is achieved through a drastic grain size, as well as large precipitate size refinement. A more uniform precipitate distribution is also attained. Whether milling is performed with steel or WC vial and balls the hardness saturates at approximately 100 HRB after about 4 hr milling. However, this benefit of MM was offset by an equally severe decrease in electrical conductivity. This decrease is attributed to impurities/contamination from the milling media introduced into the milled powder, primarily, Fe and C, or, WC and Co.

  8. Study of Carbon Nanotubes in Cu-Cr Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Gill, Puneet; Munroe, Norman

    2012-11-01

    A novel metal matrix composite (MMC), Cu-Cr-MWCNT (copper-chromium-multiwalled carbon nanotube), was manufactured using a powder metallurgy technique. Cu-Cr alloy is widely adopted for contacts in vacuum circuit breakers. MWCNT was incorporated in an effort to enhance electrical conductivity and decrease the usage of Cr as strategic metal. Optimized milling conditions and sintering profiles were utilized to minimize any significant damage to the MWCNTs but yet provide homogeneous distribution of all constituents. Raman spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used to determine the crystal structure orientation, microstructure, and morphology, respectively, of the composite. Raman peak shift and intensity ratios assessed the stresses induced and the degree of disorder of MWCNTs in the composite. TEM indicated carbide and oxide formations in the composite. SEM images revealed the presence of MWCNTs within the metal matrix. The corrosion resistances of the composite with and without MWCNTs was determined by cyclic potentiodynamic polarization (ASTM F 2129-08) in phosphate buffer saline solution at 37 °C.

  9. [Study on the determination of trace Cu and Mn in foodstuff preconcentration by precipitate flotation and FAAS].

    PubMed

    Li, Chun-xiang; Chen, Ting-yu; Yan, Yong-sheng

    2007-10-01

    In the present paper, the use of 8-hydroxyquinoline(oxine, HQ) complexs in precipitate flotation to separate and preconcentrate Cu and Mn, using SDBS as collector, followed by AAS spectrophotometric determination is proposed. The optimum conditions of precipitate flotation were studied. The effects of several parameters of flotation processes condition on single metal ions precipitation-flotation and multi-metal ions coprecipitation-flotation of Cu and Mn at pH 9 were investigated. The experimental results show that the flotation rate of Cu is supreme with pH 9. Under the condition of pH 9 and changing the ratio of concentration, when Mn/Cu> or =8, the recovery rate of Cu is less than 90%. This method is simple, rapid, accurate, sensitive and precise and avoids using the virulent organic solvent. The linear range of Cu is 0.5-5.0 microg x mL(-1) with the correlative coefficient of 0.9996, detection limit of this method was found to be 1.59 x 10(-3) microg x mL(-1), the linear range of Mn is 0.5-5.0 microg x mL(-1) with the correlative coefficient of 0.9987, and the detection limit of this method was found to be 3.52 x 10(-3) microg x mL(-1). The method was applied to the determination of Cu and Mn in foodstuff, and the recovery is 87.6%-100.7%. The result was satisfactory.

  10. Sorption of Cu, Pb and Cr on Na-montmorillonite: competition and effect of major elements.

    PubMed

    Zhu, Jun; Cozzolino, Vincenza; Pigna, Massimo; Huang, Qiaoyun; Caporale, Antonio Giandonato; Violante, Antonio

    2011-07-01

    The competitive sorption among Cu, Pb and Cr in ternary system on Na-montmorillonite at pH 3.5, 4.5 and 5.5 and at different heavy metal concentrations, and the effect of varying concentrations of Al, Fe, Ca and Mg on the sorption of heavy metals were studied. Competitive sorption of Cu, Pb and Cr in ternary system on montmorillonite followed the sequence of Cr≫Cu>Pb. Moreover, the competition was weakened by the increase of pH while was intensified by the increase of heavy metal concentration. The sorption of heavy metal on montmorillonite was inhibited by the presence of Ca and Mg, while Al and Fe showed different patterns in affecting heavy metal sorption. Aluminum and Fe generally inhibited the sorption of heavy metal when the pH and/or concentration of major elements were relatively low. However, promoting effects on heavy metal sorption by Al and Fe were found at relatively high pH and/or great concentration of major elements. The inhibition of major elements on heavy metal sorption generally followed the order of Al>Fe>Ca⩾Mg, while Fe was more efficient than Al in promoting the sorption of heavy metals. These findings are of fundamental significance for evaluating the mobility of heavy metals in polluted environments.

  11. Swelling of solute-modified Fe-Cr-Mn alloys in FFTF (Fast Flux Test Facility)-MOTA

    SciTech Connect

    Garner, F.A.

    1986-10-01

    Density change data continue to be accumulated on solute-modified and commercial Fe-Cr-Mn alloys irradiated at 520/sup 0/C and 50 dpa. The tendency toward saturation of density change observed in the simple ternary alloys in the annealed condition is accentuated by cold-working and solute addition. Irradiation at 420/sup 0/C appears to further accelerate the tendency toward saturation.

  12. Effect of Co doping on optical properties of chemically synthesized delafossite structured CuCrO2 thin film

    NASA Astrophysics Data System (ADS)

    Bera, A.; Deb, K.; Sarkar, K.; Saha, B.

    2017-05-01

    In this communication, thin films of delafossite structured oxide material of CuCrO2 with different concentration of cobalt (0%, 1%, 2% and 3%) have been grown on quartz substrate by sol-gel spin coating method. Prepared films were annealed at 800 °C in ambient condition for 5 hours. The microstructure, surface topography and optical properties of as prepared Co doped CuCrO2 thin films were analyzed by using X-ray diffractometer (XRD) with Cu-Kα radiation, Atomic Force Microscopy (AFM) and UV-Vis NIR photospectrometer respectively. Maximum transparency was found to be 50% from transmittance spectra. Red shifts of optical energy band gap have been observed due to increase of carrier concentration of cobalt in CuCrO2 thin films. The doping of cobalt in CuCrO2 thin films have a significant influence on the optical properties of CuCrO2 which can be used to shape up smart semiconductor devices.

  13. Structure and electrical properties of Cu-doped Mn-Co-O spinel prepared via soft chemistry and its application in intermediate-temperature solid oxide fuel cell interconnects

    NASA Astrophysics Data System (ADS)

    Brylewski, T.; Kruk, A.; Bobruk, M.; Adamczyk, A.; Partyka, J.; Rutkowski, P.

    2016-11-01

    The study describes CuxMn1.25-0.5xCo1.75-0.5xO4 (x = 0, 0.1, 0.3 and 0.5) spinels synthesized using EDTA gel processes in order to optimize the performance of high-quality spinel protective-conducting films deposited on steel interconnects. The powders obtained after 12 h of calcination in air at 1073 K are solely cubic spinels. Sintering these spinels for 12 h in air at 1423 K also leads to the formation of small amounts of CoO, Mn2O3 or CuO; the type of phase depends on the quantity of copper introduced into the manganese-cobalt lattice. The highest electrical conductivity at 1073 K is observed for Cu0.3Mn1.1Co1.6O4 (162 S·cm-1), which is closely correlated with the lowest activation energy of conduction over the entire temperature range (373≤T≤1073 K); the lowest conductivity is measured for Mn1.25Co1.75O4 (84 Sṡcm-1). The study confirms the suitability of the Cu0.3Mn1.1Co1.6O4 spinel as a potential material for the preparation of protective-conducting coatings on the surface of the DIN 50049 ferritic steel applied in IT-SOFC interconnects. The area-specific resistance of coated steel is 0.08 Ω·cm2, which is lower than that of bare steel after 300 h of oxidation at 1073 K. Cr vaporization tests show that the Cu0.3Mn1.1Co1.6O4 coating is efficient at blocking the outward diffusion of chromium.

  14. Towards consistent chronology in the early Solar System: high resolution 53Mn-53Cr chronometry for chondrules.

    SciTech Connect

    Yin, Q; Jacobsen, B; Moynier, F; Hutcheon, I D

    2007-05-02

    New high-precision {sup 53}Mn-{sup 53}Cr data obtained for chondrules extracted from a primitive ordinary chondrite, Chainpur (LL3.4), define an initial {sup 53}Mn/{sup 55}Mn ratio of (5.1 {+-} 1.6) x 10{sup -6}. As a result of this downward revision from an earlier higher value of (9.4 {+-} 1.7) x 10{sup -6} for the same meteorite (Nyquist et al. 2001), together with an assessment of recent literature, we show that a consistent chronology with other chronometers such as the {sup 26}Al-{sup 26}Mg and {sup 207}Pb-{sup 206}Pb systems emerges in the early Solar System.

  15. 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.

  16. Low temperature transport anomaly in Cr substituted (La0.67Sr0.33)MnO3 manganites

    NASA Astrophysics Data System (ADS)

    Tank, Tejas M.; Shelke, Vilas; Das, Sarmistha; Rana, D. S.; Thaker, C. M.; Samatham, S. S.; Ganesan, V.; Sanyal, S. P.

    2017-06-01

    The structural, electrical, and magnetic properties of La0.67Sr0.33Mn1-xCrxO3 (0 ≤ x ≤ 0.10) manganites have been studied by substitution of antiferromagnetic trivalent Cr ion at Mn-site. Systematic efforts have been carried out to understand the electrical resistivity behavior in the ferromagnetic metallic and paramagnetic semi-conducting phases of Cr substituted La0.67Sr0.33Mn1-xCrxO3 manganites. Polycrystalline samples show a resistivity minimum at a temperature (Tmin) of <40 K in the ferromagnetic metallic phase. Tmin shifts to higher temperatures on application of magnetic fields. The appearance of this resistivity minimum was analyzed by fittings the data according to the model that considers e-e scattering caused by enhanced Coulombic interactions. The electrical resistivity data has been best fitted in the metallic and semiconducting regime using various models. Present results suggest that intrinsic magnetic inhomogeneity like Cr3+ ions in these strongly electron-correlated manganite systems is originating due to the existence of the ferromagnetic interactions.

  17. Geochemical studies of Fe, Mn, Co, As, Cr, Sb, Zn, Sc and V in surface sediments from Jiaozhou Bay

    NASA Astrophysics Data System (ADS)

    Wu, Run; Li, Pei-Quan; Miao, Lu-Tian; Zhang, Shu-Xin; Tian, Wei-Zhi

    1994-12-01

    The contents of nearly forty-elements in surface sediments in Jiaozhou Bay were determined using a Neutron Activation Analysis Technique (Grancini, et al., 1976; Li Peiquan et al., 1985, 1986; Li Xiuxia et al., 1986). This paper's detailed discussion on only nine elements (Fe, Mn, Co, Cr, Sc, As, Sb, Zn and V) includes their distributions, concentrations, correlationships, material sources, background, etc. Based on Zavaristski's classification method, Fe, Mn, Co, Cr and V belong to the second group; As and Sb to the eighth groups: Sc and Zn to the third and sixth groups. It was found that their notably good correlationship is mainly due to the similarity of their ionic structures and that their variation is controlled by the Fe content (except Mn). The source of sediments is mainly terristrial material, and the composition of sediment is similar to that of shale and shale+clay. The contents for a large number of elements are within the scope of the background level, but there still is pollution of Zn and Cr, at least in a few stations.

  18. Ultra-robust high-field magnetization plateau and supersolidity in bond-frustrated MnCr2S4.

    PubMed

    Tsurkan, Vladimir; Zherlitsyn, Sergei; Prodan, Lilian; Felea, Viorel; Cong, Pham Thanh; Skourski, Yurii; Wang, Zhe; Deisenhofer, Joachim; von Nidda, Hans-Albrecht Krug; Wosnitza, Joahim; Loidl, Alois

    2017-03-01

    Frustrated magnets provide a promising avenue for realizing exotic quantum states of matter, such as spin liquids and spin ice or complex spin molecules. Under an external magnetic field, frustrated magnets can exhibit fractional magnetization plateaus related to definite spin patterns stabilized by field-induced lattice distortions. Magnetization and ultrasound experiments in MnCr2S4 up to 60 T reveal two fascinating features: (i) an extremely robust magnetization plateau with an unusual spin structure and (ii) two intermediate phases, indicating possible realizations of supersolid phases. The magnetization plateau characterizes fully polarized chromium moments, without any contributions from manganese spins. At 40 T, the middle of the plateau, a regime evolves, where sound waves propagate almost without dissipation. The external magnetic field exactly compensates the Cr-Mn exchange field and decouples Mn and Cr sublattices. In analogy to predictions of quantum lattice-gas models, the changes of the spin order of the manganese ions at the phase boundaries of the magnetization plateau are interpreted as transitions to supersolid phases.

  19. Electrokinetic recovery of Cd, Cr, As, Ni, Zn and Mn from waste printed circuit boards: effect of assisting agents.

    PubMed

    Xiu, Fu-Rong; Zhang, Fu-Shen

    2009-10-15

    The printed circuit boards (PCBs) contains large number of heavy metal such as Cd, Cr, As, Ni, Zn and Mn. In this study, the use of electrokinetic (EK) treatment with different assisting agents has been investigated to recover the heavy metals from waste PCBs, and the effectiveness of different assisting agents (HNO(3), HCl, citric acid) was evaluated. The PCBs were first pre-treated by supercritical water oxidation (SCWO) process, then subjected to EK process. The heavy metal speciation, migration and recovery efficiency in the presence of different assisting agents during EK process were discussed. The mass loss of Cd, Cr, As and Zn during the SCWO process was negligible, but approximately 52% of Ni and 56% of Mn were lost in such a process. Experimental results showed that different assisting agents have significant effect on the behavior and recovery efficiency of different heavy metals. HCl was highly efficient for the recovery of Cd in waste PCBs due to the low pH and the stable complexation of Cl(-). Citric acid was highly efficient for the recovery of Cr, Zn and Mn. HNO(3) was low efficient for recovery of most heavy metals except for Ni.

  20. Tracing Cr, Pb, Fe and Mn occurrence in the Bahía Blanca estuary through commercial fish species.

    PubMed

    La Colla, Noelia S; Botté, Sandra E; Oliva, Ana L; Marcovecchio, Jorge E

    2017-05-01

    Over the last decades the anthropogenic contamination impact has substantially increased in the Bahía Blanca estuarine area, and scarce information exists regarding metals in the biotic compartment of this estuary. Thus, fish tissues were used to evaluate metal accumulation within this aquatic environment. The study focused on the determination of Cr, Pb, Fe and Mn in the gills, liver and muscle tissues of six commercial fish species (Brevoortia aurea, Odontesthes argentinensis, Micropogonias furnieri, Cynoscion guatucupa, Mustelus schmitti and Paralichthys orbignyanus). From the results it can be summarized that C. guatucupa tends to accumulate higher metal levels in the liver tissues, mostly Cr and Fe, than the other studied species. O. argentinensis and P. orbignyanus, both permanent inhabitants of the BBE, achieved the highest metal values in the gill tissues, mostly in comparison to M. schmitti. The gill tissues were found to be the main organ of Mn and Ni accumulation for most species, whereas in general, minimum concentrations were found for all the analyzed metals in the muscle tissues. Nevertheless, and according to the guidelines, all fish species showed at least one sample with concentrations of Mn and/or Cr above the permissible levels for human consumption. Finally, it was highlighted the usefulness of selecting these fish species as bioindicators of metal pollution, since they are either permanent inhabitants of the estuary or, according to the sizes under analyses, spend much of their time in this coastal waters.

  1. Effect of the ITER FW Manufacturing Process on the Microstructure and Properties of a CuCrZr Alloy

    NASA Astrophysics Data System (ADS)

    Liu, Danhua; Wang, Pinghuai; Song, Yi; Li, Qian; Chen, Jiming

    2015-10-01

    The first wall (FW) is one of the core components in ITER. As the heat sink material, the CuCrZr alloy shall be properly jointed with beryllium and stainless steel. At present, the grains of CuCrZr are prone to coarsen seriously in the thermal cycle process of FW manufacturing, which has become a critical issue for ITER parties. To investigate the mirostructure and mechanical properties of the optimized CuCrZr alloy in the first wall fabricating thermal cycle, simulative experiments have been done in this study. The alloy ingot was forged and hot rolled into plates, and then solid solution annealed, cold rolled and aged for strengthening. Several heat treatments were done to the CuCrZr samples, and the changes of microstructure, micro-hardness and tensile strength were investigated. The results indicated that the original elongated grains had changed into equiaxed ones, and the vickers hardness had declined to about 60 after experiencing the process of CuCrZr/316L(N) bi-metallic plate manufacturing, either by hot isostatic pressing at a higher temperature or by explosion welding followed by solution annealing. Joining Be/CuCrZr by hot isostatic pressing acts as an aging process for CuCrZr, so after the simulated heat treatment, the hardness of the alloy increased to about 110 HV and the tensile yield strength at 250°C rose to about 170 MPa. Meanwhile, the average grain size was controlled below 200 μm. supported by the International Nuclear Thermonuclear Experimental Reactor (ITER) Specific Program of China (No. 2014GB126000)

  2. Feasibility of constructed wetland planted with Leersia hexandra Swartz for removing Cr, Cu and Ni from electroplating wastewater.

    PubMed

    You, Shao-Hong; Zhang, Xue-Hong; Liu, Jie; Zhu, Yi-Nian; Gu, Chen

    2014-01-01

    As a low-cost treatment technology for effluent, the constructed wetlands can be applied to remove the heavy metals from wastewater. Leersia hexandra Swartz is a metal-accumulating hygrophyte with great potential to remove heavy metal from water. In this study, two pilot-scale constructed wetlands planted with L. hexandra (CWL) were set up in greenhouse to treat electroplating wastewater containing Cr, Cu and Ni. The treatment performance of CWL under different hydraulic loading rates (HLR) and initial metal concentrations were also evaluated. The results showed that CWL significantly reduced the concentrations of Cr, Cu and Ni in wastewater by 84.4%, 97.1% and 94.3%, respectively. High HLR decreased the removal efficiencies of Cr, Cu and Ni; however, the heavy metal concentrations in effluent met Emission Standard of Pollutants for Electroplating in China (ESPE) at HLR less than 0.3 m3/m2 d. For the influent of 5 mg/L Cr, 10 mg/L Cu and 8 mg/L Ni, effluent concentrations were below maximum allowable concentrations in ESPE, indicating that the removal of Cr, Cu and Ni by CWL was feasible at considerably high influent metal concentrations. Mass balance showed that the primary sink for the retention of contaminants within the constructed wetland system was the sediment, which accounted for 59.5%, 83.5%, and 73.9% of the Cr, Cu and Ni, respectively. The data from the pilot wetlands support the view that CWL could be used to successfully remove Cr, Cu and Ni from electroplating wastewater.

  3. The use of diffusion multiples to explore the Co-Cr-Fe-Mn-Ni high entropy system

    NASA Astrophysics Data System (ADS)

    Wilson, Paul Nathaniel

    High entropy alloys (HEAs) or Multi-principal element alloys (MEAs) are a relatively new class of alloys. These alloys are defined as having at least five major alloying elements in atomic percent from 5% to 35%. There are hundreds of thousands of equiatomic compositions possible and only a fraction have been explored. This project examines diffusion multiples as a method to accelerate alloy development in these systems. The system chosen for this experiment is the Co-Cr-Fe-Mn-Ni system. The methodology developed for creating these diffusion multiples involved a two-step process. In the first step two binary alloys (50at-% Fe-Mn and 50 at%- Ni-Co ) were diffusion bonded together. In the second step, under uniaxial compression, was used to bond Cr to diffusion couple prepared in Step I. Successful diffusion multiples were created by this method. An auxiliary method named differential melting liquid impingement (DMLI) was developed that created diffusion multiples using liquid processing methods that will be described. After creation of these multiples, the ternary and quinary interface regions were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and nanoindentation. The Cr/NiCo region experienced interdiffusion but no intermediate phase formation retaining the FCC / BCC interface at the hot-pressing temperature (1200 °C). However, upon cooling from 1200 °C, the BCC region adjacent to the interface decomposed into BCC + sigma. In contrast, the Cr/FeMn interface region developed a layered structure of FCC/sigma/BCC suggesting that sigma is stable at 1200 °C in contradiction to the published 1200 °C ternary phase diagram. Upon cooling, the sigma present at 1200 °C decomposed into FCC + sigma, except in samples that were contaminated with C; in those cases, FCC + M23C6 was observed as the decomposition product. The quinary regions were evaluated using the various HEA parameters, namely

  4. Trigonal-bipyramidal and square-pyramidal chromium-manganese chalcogenide clusters, [E2CrMn2(CO)n](2-) (E=S, Se, Te; n=9, 10): synthesis, electrochemistry, UV/Vis absorption, and computational studies.

    PubMed

    Shieh, Minghuey; Yu, Chun-Hsien; Chu, Yen-Yi; Guo, Yu-Wen; Huang, Chung-Yi; Hsing, Kai-Jieah; Chen, Pei-Chi; Lee, Chung-Feng

    2013-05-01

    The reactions of E powder (E=S, Se) with a mixture of Cr(CO)6 and Mn2(CO)10 in concentrated solutions of KOH/MeOH produced two new mixed Cr-Mn-carbonyl clusters, [E2CrMn2(CO)9](2-) (E=S, 1; Se, 2). Clusters 1 and 2 were isostructural with one another and each displayed a trigonal-bipyramidal structure, with the CrMn2 triangle axially capped by two μ3-E atoms. The analogous telluride cluster, [Te2CrMn2(CO)9](2-) (3), was obtained from the ring-closure of Te2Mn2 ring complex [Te2Mn2Cr2(CO)18](2-) (4). Upon bubbling with CO, clusters 2 and 3 were readily converted into square-pyramidal clusters, [E2CrMn2(CO)10](2-) (E=Se, 5; Te, 6), accompanied with the cleavage of one Cr-Mn bond. According to SQUID analysis, cluster 6 was paramagnetic, with S=1 at room temperature; however, the Se analogue (5) was spectroscopically proposed to be diamagnetic, as verified by TD-DFT calculations. Cluster 6 could be further carbonylated, with cleavage of the Mn-Mn bond to produce a new arachno-cluster, [Te2CrMn2(CO)11](2-) (7). The formation and structural isomers, as well as electrochemistry and UV/Vis absorption, of these clusters were also elucidated by DFT calculations.

  5. Ultrasonic spray-pyrolyzed CuCrO2 thin films

    NASA Astrophysics Data System (ADS)

    Sánchez-Alarcón, R. I.; Oropeza-Rosario, G.; Gutierrez-Villalobos, A.; Muro-López, M. A.; Martínez-Martínez, R.; Zaleta-Alejandre, E.; Falcony, C.; Alarcón-Flores, G.; Fragoso, R.; Hernández-Silva, O.; Perez-Cappe, E.; Mosqueda Laffita, Yodalgis; Aguilar-Frutis, M.

    2016-05-01

    In this paper the optical, structural and electrical properties of CuCrO2 thin films deposited by ultrasonic spray pyrolysis at temperatures from 400 to 600 °C in steps of 50 °C are presented. Copper and chromium acetylacetonates were chosen as sources of Cu and Cr, respectively, and N,N-dimethylformamide was used as the solvent. X-ray results confirmed that the films as deposited showed the CuCrO2 phase without any post-deposition thermal annealing. The surface morphology was observed to be mirror like, and as the films were deposited at different temperatures, they gradually revealed the presence of small crystallites. The best film’s optical percentage transmission (in the visible region), about 58%, was obtained in films deposited at 450 °C, and the highest band gap energy (3.17 eV) was measured in films deposited at 400 °C. The electrical properties of the films were obtained by the Hall effect. A hole concentration in the range 1019-1021 cm-3, conductivity as high as 35 S cm-1, and mobility lower than 1 cm2 V-1 s-1 were obtained in the films. p-type conductivity was confirmed using the hot point probe arrangement, and the Seebeck coefficient was estimated. The hole conductivity is thought to be due to excess oxygen in the films. Finally, the minimum energy required to transfer carriers from acceptor level to the valence band in the films was estimated by impedance spectroscopy.

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

    PubMed

    Frierdich, Andrew J; Catalano, Jeffrey G

    2012-10-16

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

  7. Lattice dynamics and thermal transport in multiferroic CuCrO2

    DOE PAGES

    Bansal, Dipanshu; Niedziela, Jennifer L.; May, Andrew F.; ...

    2017-02-09

    Inelastic neutron and x-ray scattering measurements of phonons and spin waves in CuCrO2 were performed over a wide range of temperature, and complemented with first-principles simulations. The phonon dispersions and density of states are well reproduced by our density functional cal- culations, and reveal a strong anisotropy of Cu vibrations, with large amplitudes of low-frequency in-plane motions. In addition, we find that spin fluctuations persist above 300 K, far above the N eel temperature for long-range antiferromagnetic order, TN. Modeling of the thermal conductivity, based on our phonon measurements and simulations, reveals a significant anisotropy and indicates that the spinmore » fluctuations above TN constitute a strong source of phonon scattering.« less

  8. Overview spectra and axial distribution of spectral line intensities in a high-current vacuum arc with CuCr electrodes

    SciTech Connect

    Lisnyak, M.; Pipa, A. V.; Gorchakov, S. E-mail: weltmann@inp-greifswald.de; Iseni, S.; Franke, St.; Khapour, A.; Methling, R.; Weltmann, K.-D. E-mail: weltmann@inp-greifswald.de

    2015-09-28

    Spectroscopic investigations of free-burning vacuum arcs in diffuse mode with CuCr electrodes are presented. The experimental conditions of the investigated arc correspond to the typical system for vacuum circuit breakers. Spectra of six species Cu I, Cu II, Cu III, Cr I, Cr II, and Cr III have been analyzed in the wavelength range 350–810 nm. The axial intensity distributions were found to be strongly dependent on the ionization stage of radiating species. Emission distributions of Cr II and Cu II can be distinguished as well as the distributions of Cr III and Cu III. Information on the axial distribution was used to identify the spectra and for identification of overlapping spectral lines. The overview spectra and some spectral windows recorded with high resolution are presented. Analysis of axial distributions of emitted light, which originates from different ionization states, is presented and discussed.

  9. Raman spectroscopy of the superconductor CuCrO2 delafossite oxide

    NASA Astrophysics Data System (ADS)

    Monteiro, J. F. H. L.; Jurelo, A. R.; Siqueira, E. C.

    2017-02-01

    Polycrystalline CuCrO2 samples were successfully prepared by traditional solid-state reaction method and using self-combustion urea nitrate process. The crystal structure and the effect of the sample preparation on the Raman vibrational modes were systematically investigated. Raman spectra at room temperature were obtained with light focused on several points inside a single grain. Phonon modes allowed by symmetry were identified, besides of some additional lines. Significant differences in phonon modes between samples prepared by solid state reaction method and self-combustion urea nitrate process were observed.

  10. Nanostructured Cu-Cr alloy with high strength and electrical conductivity

    SciTech Connect

    Islamgaliev, R. K. Nesterov, K. M.; Bourgon, J.; Champion, Y.; Valiev, R. Z.

    2014-05-21

    The influence of nanostructuring by high pressure torsion (HPT) on strength and electrical conductivity in the Cu-Cr alloy has been investigated. Microstructure of HPT samples was studied by transmission electron microscopy with special attention on precipitation of small chromium particles after various treatments. Effect of dynamic precipitation leading to enhancement of strength and electrical conductivity was observed. It is shown that nanostructuring leads to combination of high ultimate tensile strength of 790–840 MPa, enhanced electrical conductivity of 81%–85% IACS and thermal stability up to 500 °C. The contributions of grain refinement and precipitation to enhanced properties of nanostructured alloy are discussed.

  11. Relaxor-like dielectric response of spin liquid CuCrO{sub 2}

    SciTech Connect

    Mazumder, N. Roy, R.; Ghorai, U. K.; Saha, S.; Chattopadhyay, K. K.

    2014-04-24

    Broadband dielectric analysis (10{sup −2}-10{sup 7} Hz) of layered triangular lattice CuCrO{sub 2} is performed (123 K - 473 K) and analyzed in connection with recently observed spin frustration in this multiferroic [M. Poienar et al. Phys. Rev. B 81, 104411, (2010); M. Frontzek et al. Phys. Rev. B 84, 094448, (2011)]. Most unexpectedly, this well known delafossite has found to have nontrivial charge degrees of freedom, being characterized by a relaxor-like dielectric relaxation around 375 K with FWHM of ∼100K. The result strongly suggests the existence of intermolecular Coulomb interaction between charge disproportionation induced electric dipoles.

  12. Oxidation Behavior of GRCop-84 (Cu-8Cr-4Nb) at Intermediate and High Temperatures

    NASA Technical Reports Server (NTRS)

    Thomas-Ogbuji, Linus U.; Humphrey, Donald L.; Greenbauer-Seng, Leslie (Technical Monitor)

    2000-01-01

    The oxidation behavior of GRCop-84 (Cu-8 at %Cr-4 at %Nb) has been investigated in air and in oxygen, for durations of 0.5 to 50 hours and temperatures ranging from 500 to 900 C. For comparison, data was also obtained for the oxidation of Cu and NARloy-Z (Cu-3 wt% Ag-0.5 wt% Zr) under the same conditions. Arrhenius plots of those data showed that all three materials had similar oxidation rates at high temperatures (> 750 C). However, at intermediate temperatures (500 to 750 C) GRCop exhibited significantly higher oxidation resistance than Cu and NARloy-Z. The oxidation kinetics of GRCop-84 exhibited a sharp and discontinuous jump between the two regimes. Also, in the high temperature regime GRCop-84 oxidation rate was found to change from a high initial value to a significantly smaller terminal value at each temperature, with progress of oxidation; the two different oxidation rates were found to correlate with a porous intial oxide and a dense final oxide, respectively.

  13. Ab-initio study of structural, elastic, thermal, electronic and magnetic properties of quaternary Heusler alloys CoMnCrZ (Z = Al, As, Si, Ge)

    NASA Astrophysics Data System (ADS)

    Mohamedi, Mohamed Walid; Chahed, Abbes; Amar, Amina; Rozale, Habib; Lakdja, Abdelaziz; Benhelal, Omar; Sayede, Adlane

    2016-12-01

    First-principles approach is used to study the structural, electronic and magnetic properties of CoMnCrZ (Z = Al, Si, Ge and As) quaternary Heusler compounds, using full-potential linearized augmented plane wave (FP-LAPW) scheme within the generalized gradient approximation (GGA). The computed equilibrium lattice parameters agree well with the available theoretical data. The obtained negative formation energy shows that CoMnCrZ (Z = Al, Si, Ge, As) compounds have strong structural stability. The elastic constants Cij are calculated using the total energy variation with strain technique. The polycrystalline elastic moduli (namely: the shear modulus, Young's modulus, Poisson's ratio, sound velocities, Debye temperature and melting temperature were derived from the obtained single-crystal elastic constants. The ductility mechanism for the studied compounds is discussed via the elastic constants Cij. Our calculations with the GGA approximation predict that CoMnCrGe, CoMnCrAl, CoMnCrSi and CoMnCrAs are half-metallic ferrimagnets (HMFs) with a half-metallic gap EHM of 0.03 eV, 0.19 eV, 0.34 eV and 0.50 eV for, respectively. We also find that the half-metallicity is maintained on a wide range of lattice constants.

  14. Structural, magnetic, and superconducting properties of pulsed-laser-deposition-grown La<mn>1.85mn> Sr<mn>0.15mn> CuO>4mn> / La<mn>2mn>/>3mn> Ca<mn>1mn>/>3mn> MnO>3mn> superlattices on (001)-oriented LaSrAlO<mn>4mn> substrates

    SciTech Connect

    Das, S.; Sen, K.; Marozau, I.; Uribe-Laverde, M. A.; Biskup, N.; Varela, M.; Khaydukov, Y.; Soltwedel, O.; Keller, T.; Döbeli, M.; Schneider, C. W.; Bernhard, C.

    2014-03-12

    Epitaxial La<mn>1.85mn> Sr<mn>0.15mn> CuO>4mn> / La<mn>2mn>/>3mn> Ca<mn>1mn>/>3mn> MnO>3mn> (LSCO/LCMO) superlattices (SL) on (001)- oriented LaSrAlO4 substrates have been grown with pulsed laser deposition (PLD) technique. Their structural, magnetic and superconducting properties have been determined with in-situ reflection high energy electron diffraction (RHEED), x-ray diffraction, specular neutron reflectometry, scanning transmission electron microscopy (STEM), electric transport, and magnetization measurements. We find that despite the large mismatch between the in-plane lattice parameters of LSCO (a = 0.3779 nm) and LCMO (a = 0.387 nm) these superlattices can be grown epitaxially and with a high crystalline quality. While the first LSCO layer remains clamped to the LSAO substrate, a sizeable strain relaxation occurs already in the first LCMO layer. The following LSCO and LCMO layers adopt a nearly balanced state in which the tensile and compressive strain effects yield alternating in-plane lattice parameters with an almost constant average value. No major defects are observed in the LSCO layers, while a significant number of vertical antiphase boundaries are found in the LCMO layers. The LSCO layers remain superconducting with a relatively high superconducting onset temperature of Tconset ≈ 36 K. The macroscopic superconducting response is also evident in the magnetization data due to a weak diamagnetic signal below 10 K for H ∥ ab and a sizeable paramagnetic shift for H ∥ c that can be explained in terms of a vortex-pinning-induced flux compression. The LCMO layers maintain a

  15. Cu-Cr-Nb-Zr Alloy for Rocket Engines and Other High-Heat- Flux Applications

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    2013-01-01

    Rocket-engine main combustion chamber liners are used to contain the burning of fuel and oxidizer and provide a stream of high-velocity gas for propulsion. The liners in engines such as the Space Shuttle Main Engine are regeneratively cooled by flowing fuel, e.g., cryogenic hydrogen, through cooling channels in the back side of the liner. The heat gained by the liner from the flame and compression of the gas in the throat section is transferred to the fuel by the liner. As a result, the liner must either have a very high thermal conductivity or a very high operating temperature. In addition to the large heat flux (>10 MW/sq m), the liners experience a very large thermal gradient, typically more than 500 C over 1 mm. The gradient produces thermally induced stresses and strains that cause low cycle fatigue (LCF). Typically, a liner will experience a strain differential in excess of 1% between the cooling channel and the hot wall. Each time the engine is fired, the liner undergoes an LCF cycle. The number of cycles can be as few as one for an expendable booster engine, to as many as several thousand for a reusable launch vehicle or reaction control system. Finally, the liners undergo creep and a form of mechanical degradation called thermal ratcheting that results in the bowing out of the cooling channel into the combustion chamber, and eventual failure of the liner. GRCop-84, a Cu-Cr-Nb alloy, is generally recognized as the best liner material available at the time of this reporting. The alloy consists of 14% Cr2Nb precipitates in a pure copper matrix. Through experimental work, it has been established that the Zr will not participate in the formation of Laves phase precipitates with Cr and Nb, but will instead react with Cu to form the desired Cu-Zr compounds. It is believed that significant improvements in the mechanical properties of GRCop-84 will be realized by adding Zr. The innovation is a Cu-Cr-Nb-Zr alloy covering the composition range of 0.8 to 8.1 weight

  16. Visible Light-Induced Electron Transfer From Di-Mu-Oxo-Bridged Dinuclear Mn Complexes to Cr Centers in Silica Nanopores

    SciTech Connect

    Weare, W.W.; Pushkar, Y.; Yachandra, V.K.; Frei, H.

    2009-05-26

    The compound (bpy){sub 2}Mn{sup III}({mu}-O){sub 2}Mn{sup IV}(bpy){sub 2}, a structural model relevant for the photosynthetic water oxidation complex, was coupled to single Cr{sup VI} charge-transfer chromophores in the channels of the nanoporous oxide AlMCM-41. Mn K-edge EXAFS spectroscopy confirmed that the di-{mu}-oxo dinuclear Mn core of the complex is unaffected when loaded into the nanoscale pores. Observation of the 16-line EPR signal characteristic of Mn{sup III}({mu}-O){sub 2}Mn{sup IV} demonstrates that the majority of the loaded complexes retained their nascent oxidation state in the presence or absence of Cr{sup VI} centers. The FT-Raman spectrum upon visible light excitation of the Cr{sup VI}-O{sup II} {yields} Cr{sup V}-O{sup I} ligand-to-metal charge transfer reveals electron transfer from Mn{sup III}({mu}-O){sub 2}Mn{sup IV} (Mn-O stretch at 700 cm{sup -1}) to Cr{sup VI}, resulting in the formation of Cr{sup V} and Mn{sup IV}({mu}-O){sub 2}Mn{sup IV} (Mn-O stretch at 645 cm{sup -1}). All initial and final states are directly observed by FT-Raman or EPR spectroscopy, and the assignments are corroborated by X-ray absorption spectroscopy measurements. The endoergic charge separation products ({Delta}E{sub o} = -0.6 V) remain after several minutes, which points to spatial separation of Cr{sup V} and Mn{sup IV}({mu}-O){sub 2}Mn{sup IV} as a consequence of hole (O{sup I}) hopping as a major contributing mechanism. This is the first observation of visible light-induced oxidation of a potential water oxidation complex by a metal charge-transfer pump in a nanoporous environment. These findings will allow for the assembly and photochemical characterization of well-defined transition metal molecular units, with the ultimate goal of performing endothermic, multielectron transforma