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Sample records for cr cu mn

  1. 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.

  2. 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.

  3. Bioaccessibility of Cr, Cu, Fe, Mg, Mn, Mo, Se and Zn from nutritional supplements by the unified BARGE method.

    PubMed

    Tokalıoğlu, Serife; Clough, Robert; Foulkes, Mike; Worsfold, Paul

    2014-05-01

    In this study, the Unified Bioaccessibility Research Group of Europe (BARGE) in vitro method was used to assess the bioaccessibility of Cr, Cu, Fe, Mg, Mn, Mo, Se, and Zn in ten nutritional supplement samples and three certified reference materials. The total digest, gastric phase and gastro-intestinal phase concentrations of Cu, Fe, Mg, Mn and Zn were determined by ICP-OES and Cr, Mo and Se by ICP-MS. The bioaccessible fractions of the elements in the gastric phase for the nutritional supplements were in the range 13-89% for Cr, 9-79% for Cu, 55-99% for Fe, 33-95% for Mg, 83-94% for Mn, 42-101% for Mo, 74-125% for Se and 81-104% for Zn. The range for the gastrointestinal phase was 6-65% for Cr, 27-66% for Cu, 3-14% for Fe, 34-91% for Mg, 53-62% for Mn, 40-109% for Mo, 53-146% for Se and 3-35% for Zn. PMID:24360457

  4. An experimental and thermodynamic equilibrium investigation of the Pb, Zn, Cr, Cu, Mn and Ni partitioning during sewage sludge incineration.

    PubMed

    Liu, Jingyong; Fu, Jiewen; Ning, Xun'an; Sun, Shuiyu; Wang, Yujie; Xie, Wuming; Huang, Shaosong; Zhong, Sheng

    2015-09-01

    The effects of different chlorides and operational conditions on the distribution and speciation of six heavy metals (Pb, Zn, Cr, Cu, Mn and Ni) during sludge incineration were investigated using a simulated laboratory tubular-furnace reactor. A thermodynamic equilibrium investigation using the FactSage software was performed to compare the experimental results. The results indicate that the volatility of the target metals was enhanced as the chlorine concentration increased. Inorganic-Cl influenced the volatilization of heavy metals in the order of Pb>Zn>Cr>Cu>Mn>Ni. However, the effects of organic-Cl on the volatility of Mn, Pb and Cu were greater than the effects on Zn, Cr and Ni. With increasing combustion temperature, the presence of organic-Cl (PVC) and inorganic-Cl (NaCl) improved the transfer of Pb and Zn from bottom ash to fly ash or fuse gas. However, the presence of chloride had no obvious influence on Mn, Cu and Ni. Increased retention time could increase the volatilization rate of heavy metals; however, this effect was insignificant. During the incineration process, Pb readily formed PbSiO4 and remained in the bottom ash. Different Pb compounds, primarily the volatile PbCl2, were found in the gas phase after the addition of NaCl; the dominant Pb compounds in the gas phase after the addition of PVC were PbCl2, Pb(ClO4)2 and PbCl2O4. PMID:26354691

  5. 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. PMID:26041187

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  8. The structure, Raman spectroscopy and evidence of ferromagnetic transition in CuCr1-xMxO2 (M=Mn and Rh) compounds

    NASA Astrophysics Data System (ADS)

    Elkhouni, T.; Amami, M.; Colin, C. V.; Strobel, P.; Ben Salah, A.

    2014-04-01

    The CuCr1-xMxO2 (M=Mn, Rh) polycrystalline powders were synthesized by the direct solid state reaction of Cu2O and M2O3 (M=trivalent cation or mixer of trivalent cation for transition metal). The magnetic susceptibility was measured in the temperature range of 0-300 K. It was found that the magnetic susceptibility (χ) increases rapidly with the doping of Cr3+ by Mn3+ and Rh3+ ions with existence of paramagnetic substance at low temperature. With the substitution of magnetic Mn3+ and Rh3+ for Cr3+ (S=3/2), the antiferromagnetic (AF) transition becomes broader and the transition temperature increases. However, at low temperature, the magnetic data for CuCr1-xMxO2 (M=Mn, Rh) show evidence for weak ferromagnetic (FM) transition between 100 K and 130 K. Clear hysteresis loops indicate that FM order exists in both of them Mn or Rh-doped samples at 4 K. All samples behave like semiconductors. The ferromagnetism properties can be attributed to the double exchange interaction between the Mn3+ or Rh3+ and Cr3+ semiconductors compounds.

  9. 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.

  10. Ab Initio Characterization of the Electrostatic Complexes Formed by H2 Molecule and Cr(+), Mn(+), Cu(+), and Zn(+) Cations.

    PubMed

    Artiukhin, Denis G; Bieske, Evan J; Buchachenko, Alexei A

    2016-07-14

    Equilibrium structures, dissociation energies, and rovibrational energy levels of the electrostatic complexes formed by molecular hydrogen and first-row S-state transition metal cations Cr(+), Mn(+), Cu(+), and Zn(+) are investigated ab initio. Extensive testing of the CCSD(T)-based approaches for equilibrium structures provides an optimal scheme for the potential energy surface calculations. These surfaces are calculated in two dimensions by keeping the H-H internuclear distance fixed at its equilibrium value in the complex. Subsequent variational calculations of the rovibrational energy levels permits direct comparison with data obtained from equilibrium thermochemical and spectroscopic measurements. Overall accuracy within 2-3% is achieved. Theoretical results are used to examine trends in hydrogen activation, vibrational anharmonicity, and rotational structure along the sequence of four electrostatic complexes covering the range from a relatively floppy van der Waals system (Mn(+)···H2) to an almost a rigid molecular ion (Cu(+)···H2). PMID:26914616

  11. Serration Behavior and Pop-in Phenomena in AlxCrCuFeMnNi High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Diao, Haoyan; Xie, Xie; Chen, Shuying; Wang, Gongyao; Yang, Fuqian; Dahmen, Karin; Liaw, Peter

    2015-03-01

    Recently, high-entropy alloys (HEAs), based on achieving a high configuration entropy of mixing among alloying elements, have been developed. Many of these alloys contain expensive elements, such as Co. Substituting these elements for less expensive elements, such as Mn, without compromising the mechanical performance is crucial to make HEAs commercially viable. The AlxCrCuFeMnNi (x = 0.1, 0.3, and 0.8) system is one such alloy that displays encouraging mechanical results in both compression and nanoindentation experiments. Discrete, jerky stress-drop bursts (serrations) are even found at room temperature. The mean-field-interaction model predicts the scaling behavior of the distribution, D(S), of avalanche sizes in the experiments. D(S) follows a power law multiplied by an exponentially-decaying scaling function. The size of the largest observed avalanche depends on experimental parameters, such as aluminum content, strain rate, or temperature. In nanoindentation, a strain burst is manifested by a sudden displacement excursion or `pop-in', following the initial elastic Hertzian contact. The pop-in phenomena becomes more frequent and regular, as the indentation load is greater than 35 mN. A quantitative theory for the serration behavior and pop-in phenomena is a critical issue for understanding the deformation characteristics of HEAs. This work was supported by the Department of Energy No. DE-FE-0008855 and DE-FE-0011194.

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

    PubMed

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

    2016-06-01

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

  13. Magnetic anisotropy of Fe1-yXyPt-L10 [X = Cr, Mn, Co, Ni, Cu] bulk alloys

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    We demonstrate by means of fully relativistic first principles calculations that, by substitution of Fe by Cr, Mn, Co, Ni, or Cu in FePt-L10 bulk alloys, with fixed Pt content, it is possible to tune the magnetocrystalline anisotropy energy by adjusting the content of the non-magnetic species in the material. The changes in the geometry due to the inclusion of each element induces different values of the tetragonality and hence changes in the magnetic anisotropy and in the net magnetic moment. The site resolved magnetic moments of Fe increase with the X content while those of Pt and X are simultaneously reduced. The calculations are in good quantitative agreement with experimental data and demonstrate that models with fixed band structure but varying numbers of electrons per unit cell are insufficient to describe the experimental data for doped FePt-L10 alloys.

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

    NASA Astrophysics Data System (ADS)

    Verma, Kuldeep Chand; Kotnala, R. K.

    2016-05-01

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

  15. 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. PMID:18423859

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  19. Electrochemically assisted sorption on oxidized multiwalled carbon nanotubes for preconcentration of Cr, Mn, Co, Ni, Cu and Zn from water samples.

    PubMed

    Zawisza, Beata; Sitko, Rafal

    2013-04-21

    The rapid development in nanomaterials and nanotechnologies has provided many new opportunities in the area related to analytical chemistry. In this paper the unique properties of these materials were used in order to preconcentrate heavy metals prior to detection by spectroscopic techniques. A novel, simple and highly reliable method for the preconcentration of trace amounts of chromium, manganese, cobalt, nickel, copper and zinc using electrochemically assisted sorption on oxidized multiwalled carbon nanotubes (MWCNTs) is developed. The proposed method is based on the application of an electric field to support the sorption process on oxidized MWCNTs. The proposed method was used to preconcentrate trace elements from water of pH = 4. After the preconcentration process, oxidized MWCNTs were directly measured using an energy dispersive X-ray fluorescence (EDXRF) spectrometer that reduces the number of chemicals required and minimizes sample handling. Besides EDXRF, any spectroscopy technique allowing the measurement of solid samples can be applied. The various parameters including pH of the solution, amounts of oxidized MWCNTs, sample volume and the influence of voltage as well as the time of assisted electric field on the sorption process were investigated for the optimization of the analytical procedure. Under optimized conditions the proposed preconcentration method offers a high recovery of 99% (Cr), 97% (Mn), 94% (Co), 96% (Ni), 92% (Cu) and 93% (Zn) and good precision of sample preparation (RSD) within 3.5-7%. If measurements are performed using the EDXRF spectrometer, the detection limits are 1 ng mL(-1), 5 ng mL(-1), 5 ng mL(-1), 7 ng mL(-1), 1 ng mL(-1), 8 ng mL(-1) for Cr(III), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II), respectively. PMID:23476917

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

    SciTech Connect

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

    1995-06-01

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

  1. 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.

  2. 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. PMID:26201657

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

    PubMed

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

    2007-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Tzeli, Demeter; Mavridis, Aristides

    2008-01-01

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

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

    PubMed

    Vasconcelos, M T; Tavares, H M

    1998-03-01

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

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

    PubMed

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

    2014-12-01

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

  8. 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.

  9. 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.

  10. 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.

  11. Partitioning of Mo, P and other siderophile elements (Cu, Ga, Sn, Ni, Co, Cr, Mn, V, and W) between metal and silicate melt as a function of temperature and silicate melt composition

    NASA Astrophysics Data System (ADS)

    Righter, K.; Pando, K. M.; Danielson, L.; Lee, Cin-Ty

    2010-03-01

    Metal-silicate partition coefficients can provide information about the earliest differentiation histories of terrestrial planets and asteroids. Systematic studies of the effects of key parameters such as temperature and melt composition are lacking for many elements. In particular, data for Mo is scarce, but given its refractory nature, is of great value in interpreting metal-silicate equilibrium. Two series of experiments have been carried out to study Mo and P partitioning between Fe metallic liquid and basaltic to peridotitic silicate melt, at 1 GPa and temperatures between 1500 and 1900 °C. Because the silicate melt utilized was natural basalt, there are also measurable quantities of 9 other siderophile elements (Ni, Co, W, Sn, Cu, Mn, V, Cr, Ga and Zn). The Ni and Co data can be used to assess consistency with previous studies. In addition, the new data also allow a first systematic look at the temperature dependence of Cu, Ga, Sn, Cr, Mn V and W for basaltic to peridotitic melts. Many elements exhibit an increase in siderophile behavior at higher temperature, contrary to popular belief, but consistent with predictions from thermodynamics. Using these new data we examine DMomet/sil and DPmet/sil in detail and show that increasing temperature causes a decrease in the former and an increase in the latter, whereas both increase with MgO content of the silicate melt. The depletions of Mo and P in the mantle of the Earth can be explained by metal-silicate equilibrium at magma ocean conditions — both elements are satisfied at PT conditions of an intermediate depth magma ocean for the Earth 22.5 GPa and 2400 °C.

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

    PubMed

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

    2013-10-21

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

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

    SciTech Connect

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

    2000-04-01

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

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

    PubMed

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

    2013-02-14

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

  15. CrMn underlayers for CoCrPt thin film media

    SciTech Connect

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

    1998-07-01

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

  16. 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.

  17. 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.

  18. 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).

  19. 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.

  20. 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.

  1. Room-temperature antiferromagnetism in CuMnAs

    NASA Astrophysics Data System (ADS)

    Máca, F.; Mašek, J.; Stelmakhovych, O.; Martí, X.; Reichlová, H.; Uhlířová, K.; Beran, P.; Wadley, P.; Novák, V.; Jungwirth, T.

    2012-04-01

    We report on an experimental and theoretical study of CuMn-V compounds. In agreement with previous works we find low-temperature antiferromagnetism with Néel temperature of 50 K in the cubic half-Heusler CuMnSb. We demonstrate that the orthorhombic CuMnAs is a room-temperature antiferromagnet. Our results are based on X-ray diffraction, magnetization, transport, and differential thermal analysis measurements, and on density-functional theory calculations of the magnetic structure of CuMn-V compounds. In the discussion part of the paper we make a prediction, based on our density-functional theory calculations, that the electronic structure of CuMn-V compounds makes a transition from a semimetal to a semiconductor upon introducing the lighter group-V elements.

  2. 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.

  3. 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

  4. On reversion phenomena in Cu-Zr-Cr alloys

    NASA Technical Reports Server (NTRS)

    Suzuki, H.; Kitano, H.; Kanno, M.

    1985-01-01

    Reversion phenomena in aged Cu-0.12% Zr-0.28% Cr alloy were investigated by means of resistivity measurement and transmission electron microscopy and compared with those of Cu-0.30% Zr and Cu-0.26% Cr alloys. Specimens in the form of a 0.5 mm sheet were solution-treated at 950 F for 1 hr water-quenched, aged, and finally reversed. The reversion phenomena were confirmed to exist in Cu-Zr and Cu-Zr-Cr alloys as well as Cu-Cr alloys, at aging temperatures of 300 to 500 F. The critical aging temperature for the reversion was not observed in all the alloys. Split aging increased the amount of reversion, particularly in Cu-Zr and Cu-Zr-Cr alloys, compared with that by conventional aging. The amount of reversion in Cu-Zr-Cr alloy was greatly affected by the resolution of Cr precipitate formed by preaging. Structural changes in Cu-Zr-Cr alloy due to the reversion were hardly observed by transmission electron microscopy.

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

    NASA Astrophysics Data System (ADS)

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

    2005-07-01

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

  6. Evaluation of Ti-Cr-Cu alloys for dental applications

    NASA Astrophysics Data System (ADS)

    Koike, Marie; Okabe, Toru; Itoh, Masayuki; Okuno, Osamu; Kimura, Kohei; Takeda, Osamu; Okabe, Toru H.

    2005-12-01

    This study examined the characteristics of as-cast Ti-Cr(7 19%)-Cu(3 7%) (all percentages in this article are mass%) alloys to evaluate their suitability for dental applications; studies on the alloy structures and mechanical properties, grindability, and corrosion behavior were included in the investigation. The alloys were centrifugally cast and bench-cooled in investment molds. The x-ray diffractometry of the as-cast alloys bench-cooled in the molds indicated the following phases: α+β+ω in the 7% Cr and 7% Cr+3% Cu; β+ω in the 13%Cr; and β in the 13%Cr+3% Cu through the 19%Cr+3% Cu alloys. The strengths of the binary β Ti-Cr and ternary β Ti-Cr-Cu alloys with 13 and 19% Cr were approximately two times higher than those of CP Ti. The alloy ductility was dependent on the chemical composition and thus, the microstructure. The 7% Cr alloys were extremely brittle and hard due to the ω phase, but the ductility was restored in the 13 and 19% Cr alloys. The hardness (HV) of the cast 13 and 19% Cr alloys was approximately 300 350 compared with a value of 200 for CP Ti. The grindability of the cast alloys was examined using a rotating SiC wheel at speeds (circumferential) of 500 and 1250 m/min. At the higher speed, the grindability of the 13 and 19% Cr alloys increased with the Cu content. The grindability of the 13% Cr alloy with 7% Cu was similar to that of CP Ti. Evaluation of the corrosion behavior in an artificial saliva revealed that the alloys are like many other titanium alloys within the normal intraoral oxidation potential. The wear resistance testing of these alloys also showed favorable results.

  7. Mechanical Properties of Cu-Cr-Nb Alloys

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    1997-01-01

    The chemical compositions of the alloys are listed. The alloying levels were near the values for stochiometric Cr2Nb. A slight excess of Cr was chosen for increased hydrogen embrittlement resistance. The microstructures of all Cu-Cr-Nb alloys were very similar. Two typical transmission electron microscope (TEM) micrographs are presented. The images show the presence of large mount of Cr2Nb precipitates in a nearly pure Cu matrix. The interactions between dislocations and precipitates are currently under investigations, but as the images demonstrates, the extremely fine (less then 15 nm) Cr2Nb are the primary strengtheners for the alloy.

  8. Structural and magnetic properties of Cu Ni Cr spinel oxides

    NASA Astrophysics Data System (ADS)

    Tovar, M.; Torabi, R.; Welker, C.; Fleischer, F.

    2006-11-01

    The compounds CuCr 2O 4 and NiCr 2O 4 crystallize at room temperature in a tetragonal distorted spinel structure, s.g. I4 1/amd, with axes ratio c/ a<1 and >1, respectively. The distortion is caused by the Jahn-Teller ions Cu 2+ and Ni 2+ which flatten or elongate their surrounding oxygen tetrahedron. CuCr 2O 4 and NiCr 2O 4 form a complete solid solution series Cu 1-xNi xCr 2O 4 where for 0.825< x<0.875 members with orthorhombic symmetry were found. Using neutron powder diffraction and thermal analysis methods several members of the solid solution series were investigated. On cooling, all samples showed a temperature-dependent crystallographic phase transition from cubic to tetragonal symmetry between 865 K (CuCr 2O 4) and 310 K (NiCr 2O 4). The phase Cu 0.15Ni 0.85Cr 2O 4 undergoes a second crystallographic transition to orthorhombic symmetry, space group Fddd, at T=300 K. The neutron diffraction experiments as well as SQUID measurements reveal magnetic ordering of the ions between 150 and 50 K which partially occurs as a two-step mechanism.

  9. 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.

  10. 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.

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

    SciTech Connect

    Youxian Wu; Baolin Deng

    2006-04-05

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

  12. Oriented Mn-doped CuO nanowire arrays.

    PubMed

    Han, Dongqiang; Wu, Zhaofeng; Wang, Zhihe; Yang, Shaoguang

    2016-04-01

    Using anodic aluminum oxide membranes as the nanoreactors and controller, oriented nanowire arrays of the diluted magnetic semiconductor Mn-doped CuO have been successfully fabricated using Mn(NO3)2 · 4H2O and Cu(NO3)2 · 3H2O as the starting materials. X-ray diffraction measurements showed that the as-prepared oriented nanowire arrays are of high purity. Scanning electron microscope and transmission electron microscope studies showed the nanowires are oriented, continuous and uniform with a diameter and length of about 170 nm and several tens of micrometers, respectively, and thus of a high aspect ratio. Low-temperature magnetic measurements showed the ferromagnetic property of the oriented Mn-doped CuO nanowire arrays with the critical temperature at around 80 K, which will endow them with great potential applications in spintronics in the future. PMID:26895391

  13. Oriented Mn-doped CuO nanowire arrays

    NASA Astrophysics Data System (ADS)

    Han, Dongqiang; Wu, Zhaofeng; Wang, Zhihe; Yang, Shaoguang

    2016-04-01

    Using anodic aluminum oxide membranes as the nanoreactors and controller, oriented nanowire arrays of the diluted magnetic semiconductor Mn-doped CuO have been successfully fabricated using Mn(NO3)2 · 4H2O and Cu(NO3)2 · 3H2O as the starting materials. X-ray diffraction measurements showed that the as-prepared oriented nanowire arrays are of high purity. Scanning electron microscope and transmission electron microscope studies showed the nanowires are oriented, continuous and uniform with a diameter and length of about 170 nm and several tens of micrometers, respectively, and thus of a high aspect ratio. Low-temperature magnetic measurements showed the ferromagnetic property of the oriented Mn-doped CuO nanowire arrays with the critical temperature at around 80 K, which will endow them with great potential applications in spintronics in the future.

  14. Interfacial Reactions of Sn-3.0Ag-0.5Cu Solder with Cu-Mn UBM During Aging

    NASA Astrophysics Data System (ADS)

    Tseng, Chien-Fu; Wang, Kai-Jheng; Duh, Jenq-Gong

    2010-12-01

    Cu under bump metallurgy (UBM) has been widely used in flip-chip technology. The major disadvantages of Cu UBM are fast consumption of copper, rapid growth of intermetallic compounds (IMCs), and easy formation of Kirkendall voids. In this study we added two different contents of Mn (2 at.% and 10 at.%) to Cu UBM by sputtering to modify the conventional Cu metallization. For the higher Mn concentration in the Cu-Mn UBM, a new Sn-rich phase formed between Cu6Sn5 and the Cu-Mn UBM, and cracks formed after aging. For the lower Mn concentration, growth of Cu3Sn and Kirkendall voids was significantly suppressed after thermal aging. Kinetic analysis and x-ray elemental mapping provided evidence that Mn diffusion into Cu3Sn slowed diffusion of Cu in the Cu3Sn layer. The Mn-enriched Cu3Sn layer may serve as a diffusion barrier to reduce the interfacial reaction rate and Kirkendall void formation. These results suggest that Cu-Mn UBM with low Mn concentration is beneficial in terms of retarding Cu pad consumption in solder joints.

  15. 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

  16. 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

    2015-01-01

    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

  17. Antiferromagnetic structure in tetragonal CuMnAs thin films

    NASA Astrophysics Data System (ADS)

    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.

    2015-11-01

    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.

  18. 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.

  19. 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).

  20. Spin polarization and exchange coupling of Cu and Mn atoms in paramagnetic CuMn diluted alloys induced by a Co layer

    SciTech Connect

    Abes, M.; Arena, D.; Atkinson, D.; Tanner, B.K.; Charlton, T.R.; Langridge, S.; Hase, T.P.A.; Ali, M.; Marrows, C.H.; Hickey, B.J.; Neudert, Al; Hicken, R.J.; Wilkins, S.B.; Mirone, A.; Lebegue, S.

    2010-11-09

    Using the surface, interface, and element specificity of x-ray resonant magnetic scattering in combination with x-ray magnetic circular dichroism, we have spatially resolved the magnetic spin polarization, and the associated interface proximity effect, in a Mn-based high-susceptibility material close to a ferromagnetic Co layer. We have measured the magnetic polarization of Mn and Cu3d electrons in paramagnetic CuMn alloy layers in [Co/Cu(x)/CuMn/Cu(x)]{sub 20} multilayer samples with varying copper layer thicknesses from x=0 to 25 {angstrom}. The size of the Mn and CuL{sub 2,3} edge dichroism shows a decrease in the Mn-induced polarization for increasing copper thickness indicating the dominant interfacial nature of the Cu and Mn spin polarization. The Mn polarization is much higher than that of Cu. Evidently, the Mn moment is a useful probe of the local spin density. Mn atoms appear to be coupled antiferromagnetically with the Co layer below x = 10 {angstrom} and ferromagnetically coupled above. In contrast, the interfacial Cu atoms remain ferromagnetically aligned to the Co layer for all thicknesses studied.

  1. 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

    2016-05-01

    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.

  2. 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)

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

    DOE PAGESBeta

    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 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

  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. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  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 Astrophysics Data System (ADS)

    Righter, K.

    2008-12-01

    oxygen fugacity. Preliminary results confirm that D(Ni) and D(Co) converge at pressures near 25-30 GPa and ~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. 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.

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

    DOE PAGESBeta

    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-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

  15. 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.

  16. 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'. PMID:27402936

  17. 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. PMID:26040736

  18. 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.

  19. 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.

  20. Ductile Chromium in Heavily Cold-Drawn Cu75Cr25 Alloy

    NASA Astrophysics Data System (ADS)

    Chang, Yanli; Zhou, Zhiming; Guo, Ziqin; Wang, Yaping

    2016-01-01

    Microstructure evolution, gas content, and properties of the heavily cold-drawn Cu75Cr25 alloy were studied. Results showed that the oxygen and nitrogen contents of Cu75Cr25 alloy prepared by vacuum induction melting in calcia crucibles were low, about 320 and 20 ppm, respectively. The Cu75Cr25 material with low gas content can be cold drawn to lines with diameter less than 0.1 mm, in which Cr phase displays thin and curving morphology. The coherent interface, forming between Cu(111) and Cr(110) during the heavily cold-drawing process, constrained Cr phase and greatly improved its deformability as well as increased the strength of the Cu-Cr alloy. The breaking strength and electrical conductivity of the Cu75Cr25 alloy were about 577 MPa and 60 pct IACS, respectively.

  1. Thermal fatigue damage of Cu-Cr-Zr alloys

    NASA Astrophysics Data System (ADS)

    Chatterjee, Arya; Mitra, R.; Chakraborty, A. K.; Rotti, C.; Ray, K. K.

    2013-11-01

    The primary aim of this investigation is to examine thermal fatigue damage (TFD) in Cu-Cr-Zr alloys used in High Heat Flux components of Tokamak and its subsystems. Thermal fatigue experiments have been carried out between 290 °C and 30 °C, which is analogous to the condition of service application on two Cu-Cr-Zr alloys having different aging treatments. The extents of TFD have been examined by standard measurements of electrical conductivity, lattice strain, residual stress and dynamic elastic modulus, supplemented by characterizations of microstructure and determination of hardness and tensile properties. The results lead to infer that the relative amounts of damage are different in the two alloys which are further dependent on their aging conditions; the reasons for the observed difference have been explained. The operative mechanisms of TFD are revealed to be as formation and subsequent coalescence of microvoids, and/or initiation and growth of microcracks.

  2. 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

    2016-07-01

    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.

  3. The resistance to cavitation erosion of CrMnN stainless steels

    SciTech Connect

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

    1998-12-01

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

  4. 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.

  5. Effect of mechanical activation on thermal and electrical conductivity of sintered Cu, Cr, and Cu/Cr composite powders

    NASA Astrophysics Data System (ADS)

    Rogachev, A. S.; Kuskov, K. V.; Moskovskikh, D. O.; Usenko, A. A.; Orlov, A. O.; Shkodich, N. F.; Alymov, M. I.; Mukasyan, A. S.

    2016-06-01

    The results of measurement of electric resistivity and thermal conductivity of materials obtained by spark plasma sintering from powders of Cu, Cr, and their mixtures in the range of 300-600 K are presented. It is shown that the grinding of powders in planetary mills results in a reasonably substantial change in the electric and thermal properties of materials: to increasing electric resistivity and decreasing thermal conductivity and temperature coefficients of electric resistivity. The possible causes of these effects are considered.

  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. 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.

  8. 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).

  9. 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.

  10. 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.

  11. 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

  12. High-temperature oxidation behavior of a wrought Ni-Cr-W-Mn-Si-La alloy

    SciTech Connect

    Tawancy, H.M.

    1996-04-01

    An investigation was carried out to study the kinetics and products of oxidation of a wrought Ni-Cr-W-Mn-Si-La alloy at temperatures in the range of 950 to 1150{degrees}C. Oxidation kinetics were evaluated from measurements of weight change, metal loss, and internal penetration. Analytical electron microscopy, scanning electron microscopy, electron probe microanalysis, and X-ray diffraction were used to characterize the scale microstructure. Initially, La was observed to segregate within a surface layer of about 5 {mu}m thick, which promoted selective oxidation of Cr and Mn. Oxidation kinetics were found to follow a parabolic-rate law with an activation energy of about 232 kJ/mol. During steady-state oxidation, the scale consisted of an inner adherent layer of {alpha}-Cr{sub 2}O{sub 3} modified by the presence of La and Si, and shielded by an outer layer of MnCr{sub 2}O{sub 4}. Most of the La was segregated to grain boundaries of the {alpha}-Cr{sub 2}O{sub 3} scale, however, Si was homogeneously distributed. It was concluded that the characteristic oxidation resistance of the alloy was related to the synergistic effects of Ni and Cr and to the effective minor additions of La, Si, and Mn; however, the useful life of the scale was limited by rupture and surface depletion in Cr, leading to accelerated internal oxidation.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. [XPS and UPS characterization for Cr and Mn in high-temperature oxide films of bulk nanocrystalline 304 stainless steel].

    PubMed

    Xu, Song-Ning; Wang, Sheng-Gang; Han, Hai-Bao; Sun, Nai-Kun

    2013-03-01

    The authors studied the binding energies of valence electrons of two oxide scales, the atomic percentages of Cr and Mn elements in two oxide films, the work function of two oxide films on bulk nanocrystalline 304 stainless steel (BN-SS304) and conventional polycrystalline 304 stainless steel (CP-SS304). BN-SS304 was prepared by severe rolling technique, and the two oxide films were formed in atmosphere at 900 degrees C for 24 hours oxidation on BN-SS304 and CP-SS304 surfaces. In the two oxide films, Cr and Mn elements exist in the forms of Cr3+, Cr0, Mn4+ and Mn0. The atomic percentage ratios of Cr+ / (Cr3+ + Cr0) and Mn4+ / (Mn4+ + Mn0) in the oxide film on BN-SS304 are lower than those in the oxide film on CP-SS304. The interactions of the two oxides and the valence electrons of elements are Mn-O, Cr-O,3d and 4s of Mn0 and Cr0. The binding energies of the valence electrons in the oxide film on BN-SS304 are larger than those in the oxide film on CP-SS304, the work function of the oxide film on BN-SS304 is 0.07 eV larger than that on CP-SS304. PMID:23705465

  19. Indirect mass determination for the neutron-deficient nuclides 44V, 48Mn, 52Co and 56Cu

    NASA Astrophysics Data System (ADS)

    Tu, X. L.; Litvinov, Yu. A.; Blaum, K.; Mei, B.; Sun, B. H.; Sun, Y.; Wang, M.; Xu, H. S.; Zhang, Y. H.

    2016-01-01

    Mass excess values for 44V, 52Co and 56Cu are derived indirectly using the mirror symmetry and known data from beta-delayed proton spectroscopy. The new mass excess obtained by using the energy conservation for 48Mn is - 29 303 (14) keV, which is an improvement by about an order of magnitude compared to the AME'12 value. Compared to previously known data, the new proton separation energy for 45Cr causes a ˜3.5 times smaller matter flow through the Casbnd Sc cycle during the rp-process. Obtained proton separation energies for 52Co and 56Cu are about 500 keV larger than the AME'12 values. If confirmed, this would affect photo disintegration rates of 52Co (γ, p)51Fe and 56Cu (γ, p)55Ni reactions during the rp-process in X-ray bursts.

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

    SciTech Connect

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

    2009-09-09

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

  1. 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.

  2. Characteristics of p-type transparent conductive CuCrO2 thin films

    NASA Astrophysics Data System (ADS)

    Yu, Ruei-Sung; Wu, Chung-Ming

    2013-10-01

    Cu-Cr-O films were prepared using reactive magnetron sputtering deposition followed by annealing at temperatures ranging from 550 to 625 °C in 25 °C increments. Correlations between the optoelectronic and microstructural properties of the p-type CuCrO2 films are discussed. The as-deposited film was amorphous; after annealing at 550 and 575 °C, films adopted mixed CuO and CuCr2O4 phases. Annealing at 600 °C led to the formation of a dominant phase of delafossite CuCrO2. The 625 °C-annealed film was single-phase CuCrO2 which had a bar- and polygonal-like mixed surface appearance, with a root mean square roughness of 17.7 nm. CuCrO2 is an intrinsic p-type semiconductor which exhibits electrical conductivity and transparency over the visible wavelength range. Two higher-energy subband transitions at 3.69 and 4.82 eV were observed in the band structure of CuCrO2. Point defects were the main reason source of hole carrier scattering in the material. The single-phase CuCrO2 film had the lowest resistivity of the films, 4.31 Ω cm, and had a direct band gap of 3.14 eV and light transmittance of 62% at 600 nm.

  3. 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.

  4. 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.

  5. Investigation of Modified Ni-Cr-Mn Base Alloys for SOFC Interconnect Applications

    SciTech Connect

    Yang, Z Gary; Singh, Prabhakar; Stevenson, Jeffry W.; Xia, Gordon

    2006-09-01

    Two Ni-Cr-W-Mn base alloys based on Haynes 230 were developed and evaluated against criteria relevant to SOFC interconnect applications, which included oxidation behavior under SOFC operating conditions, scale electrical conductivity, and thermal expansion. It was found that, similar to the ferritic stainless steel Crofer22 APU, additions of Mn led to the formation of a unique scale that was comprised of a M3O4 (M=Mn, Cr, Ni, …) spinel-rich top layer and Cr2O3-rich sub-layer. The modified alloys demonstrated reasonable oxidation resistance under SOFC operating conditions, though the Mn additions increased the scale growth rate and thus sacrificed to some extent the oxidation resistance of the base alloy (Haynes 230). The formation of a spinel-rich top layer improved the scale conductivity, especially during the early stages of oxidation, but the higher scale growth rate resulted in a higher rate of increase in the area-specific electrical resistance. Due to their FCC crystal structure, the Ni-Cr-W-Mn base alloys demonstrated a CTE that was higher than that of anode-supported cells and candidate ferritic stainless steels such as Crofer22 APU.

  6. 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).

  7. 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.

  8. 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).

  9. Dielectric function of the ferromagnetic semiconductor CdMnCrTe studied by using spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Hwang, Younghun; Um, Youngho

    2014-11-01

    We describe the pseudo-dielectric function of Cd1- x- y Mn x Cr y Te ferromagnetic semiconductor alloys by using spectroscopic ellipsometry in the 1.0 ~ 6.0 eV spectral range at room temperature. The ellipsometry data include structures that can be attributed to the effects of Cr concentration on the E 0, E 1, E 1 + Δ1, and E 2 critical points. Critical-point (CP) parameters were obtained by fitting standard critical point (SCP) model line shapes to the numerically-calculated second- energy derivatives of ɛ( ω) = ɛ 1( ω) + iɛ 2( ω). The E 0, E 1, E 1 + Δ1, and E 2 energies decreased with Cr content y; this phenomenon is related to the hybridization of the valence and the conduction bands in CdTe with the 3 d states of Mn and Cr.

  10. Vacuum Plasma Spray of Cu-8Cr-4Nb for Advanced Liquid-Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, F.; Elam, S.; Ellis, D.; Miller, H.; McKechnie, T.; Hickman, R.

    2001-01-01

    Vacuum plasma spray (VPS) formed Cu-8Cr-4Nb alloy, with low oxygen, exhibits higher strength at room and elevated temperature than material formed by extrusion. The VPS formed material exhibits slightly lower ductility than the extruded material. VPS forming of Cu-8Cr-4Nb can be used to produce near net structures with mechanical properties comparable to current extruded material.

  11. Cu Cr O nanocomposites: Synthesis and characterization as catalysts for solid state propellants

    NASA Astrophysics Data System (ADS)

    Li, Wei; Cheng, Hua

    2007-08-01

    In this article we present the synthesis of Cu-Cr-O nanocomposites via a citric acid (CA) complexing approach and the evaluation of the as-synthesized Cu-Cr-O nanocomposites as additives for the catalytic combustion of AP (ammonium perchlorate)-based solid state propellants. Techniques of thermo-gravimetric/differential thermal analyzer (TG-DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as scanning electron microscopy (SEM) have been employed to characterize the thermal decomposition procedure, crystal phase, micro-structural morphologies and grain size of the as-synthesized materials, respectively. The results show that well-crystallized Cu-Cr-O nanocomposites can be produced by using a temperature as low as 600 °C. Phase structure of the as-obtained Cu-Cr-O nanocomposites depends on the Cu/Cr molar ratio in the starting reactants. Addition of the as-synthesized Cu-Cr-O nanocomposites as catalysts enhances the burning rate as well as lowers the pressure exponent of the AP-based solid state propellants considerably. Noticeably, solid state propellants containing Cu-Cr-O nanocomposites with a Cu/Cr molar ratio of 0.7 exhibits the most stable combustion at all pressures.

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

    SciTech Connect

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

    1988-09-01

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

  13. 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.

  14. Thermal and structural characterization of Cu-Al-Mn-X (Ti, Ni) shape memory alloys

    NASA Astrophysics Data System (ADS)

    Canbay, C. Aksu; Genc, Z. Karagoz; Sekerci, M.

    2014-05-01

    In this study, the Cu-Al-Mn-X (X = Ni, Ti) shape memory alloys at the range of 10-12 at.% of aluminum and 4-5 at.% manganese were produced by arc melting. We have investigated the effects of the alloying elements on the transformation temperatures, and the structural and the magnetic properties of the quaternary Cu-Al-Mn-X (X = Ni, Ti) shape memory alloys. The evolution of the transformation temperatures was studied by differential scanning calorimetry with different heating and cooling rates. The characteristic transformation temperatures and the thermodynamic parameters were highly sensitive to variations in the aluminum and manganese content, and it was observed that the nickel addition into the Cu-Al-Mn system decreased the transformation temperature although Ti addition caused an increase in the transformation temperatures. The effect of the nickel and the titanium on the thermodynamic parameters such as enthalpy and entropy values was investigated. The structural changes of the samples were studied by X-ray diffraction measurements and by optical microscope observations at room temperature. It is evaluated that the element Ni has been completely soluble in the matrix, and the main phase of the Cu-Al-Mn-Ni sample is martensite, and due to the low solubility of the Ti, the Cu-Al-Mn-Ti sample has precipitates, and a martensite phase at room temperature. The magnetic properties of the Cu-Al-Mn, Cu-Al-Mn-Ni and Cu-Al-Mn-Ti samples were investigated, and the effect of the nickel and the titanium on the magnetic properties was studied.

  15. μSR investigation of a new diluted magnetic semiconductor Li(Zn,Mn,Cu)As with Mn and Cu codoping at the same Zn sites

    NASA Astrophysics Data System (ADS)

    Guo, S. L.; Zhao, Y.; Man, H. Y.; Ding, C.; Gong, X.; Zhi, G. X.; Fu, L. C.; Gu, Y. L.; Frandsen, B. A.; Liu, L.; Cheung, S. C.; Munsie, T. J.; Wilson, M. N.; Cai, Y. P.; Luke, G. M.; Uemura, Y. J.; Ning, F. L.

    2016-09-01

    We report the successful synthesis and characterization of a new type I–II–V bulk form diluted magnetic semiconductor (DMS) Li(Zn,Mn,Cu)As, in which charge and spin doping are decoupled via (Cu,Zn) and (Mn,Zn) substitution at the same Zn sites. Ferromagnetic transition temperature up to  ∼33 K has been observed with a coercive field  ∼40 Oe for the 12.5% doping level. μSR measurements confirmed that the magnetic volume fraction reaches nearly 100% at 2 K, and the mechanism responsible for the ferromagnetic interaction in this system is the same as other bulk form DMSs.

  16. {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.

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

    PubMed

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

    2015-04-01

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

  18. 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.

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

    SciTech Connect

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

    2008-01-01

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

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  2. 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

  3. Influence of oxygen partial pressure on the quasi-ternary system Cr-Mn-Ti oxide

    SciTech Connect

    Garcia-Rosales, C.; Schulze, H.A.; Naoumidis, A.; Nickel, H. . Research Centre Juelich)

    1993-11-01

    The quasi-ternary system Cr-Mn-Ti oxide was investigated at 1,000 C under oxygen partial pressures ranging from 0.21 bar to 10[sup [minus]21] bar (1 bar = 10[sup 5] Pa). X-ray diffraction analysis was used to identify phases and determine lattice parameters. The positions of phase boundaries as a function of oxygen partial pressure were measured using the emf method. The spinel MnCr[sub 2]O[sub 4] may be regarded as the most interesting compound in this system. Part of the chromium can be replaced by trivalent titanium at low oxygen partial pressures and by trivalent manganese at high pressures, and the formation of a limited solid solution with the spinel Mn[sub 2]TiO[sub 4] is possible in all cases. As a result, a coherent single-phase spinel region exists over the entire oxygen partial pressure range at 1,000 C.

  4. Sign reversal of magnetization in Mn substituted SmCrO3

    NASA Astrophysics Data System (ADS)

    Dash, Bibhuti B.; Ravi, S.

    2016-05-01

    Single phase samples of orthorhombic SmCr1-xMnxO3 compounds were prepared for x=0 to 0.50. Analysis of X-ray diffraction patterns shows a systematic increase in lattice parameters with increase in Mn concentration. The phenomenon of magnetization reversal is observed for x=0.10-0.30 samples with a maximum magnetic compensation temperature of 126 K. The mechanism of magnetization reversal is explained by considering the competition between the paramagnetic moments of Mn3+ and Sm3+ ions under the influence of negative internal field due to antiferromagnetically ordered Cr3+ ions and the canted ferromagnetic component of Cr3+ ions. For x≥0.40, the samples exhibit ferromagnetic like behavior.

  5. 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.

  6. Electronic, magnetic, elastic and thermodynamic properties of Cu2MnGa

    NASA Astrophysics Data System (ADS)

    Ghosh, Sukriti; Gupta, Dinesh C.

    2016-08-01

    The full-potential linearized augmented plane wave method in the stable Fm-3m phase has been implemented to investigate the structural, elastic, magnetic and electronic properties of Cu2MnGa. The optimized equilibrium lattice parameter in stable phase is found to be 5.9495 Å. By the spin resolved density of states calculations, we have shown that the exchange splitting due to Mn atom is the main reason of ferromagnetic behavior of Cu2MnGa. The absence of energy gap in both the spin channels predicts that the material is metallic. The total and partial density of states, elastic constants, Shear, Bulk and Young's moduli, Zener isotropy factor, Cauchy pressure, Pugh's ductility, Kleinman parameter and Poisson's ratio are reported for the first time for the alloy. Cauchy's pressure and Pugh's index of ductility label Cu2MnGa as ductile. Cu2MnGa is found to be ferromagnetic and anisotropic in nature. The quasi-harmonic approximations have been employed to study the pressure and temperature dependent thermodynamic properties of Cu2MnGa.

  7. Magnetic States in Ensemble of Ferromagnetic Nanoparticles in Cu-Mn-Al Alloy.

    PubMed

    Konoplyuk, S M; Kozlova, L E; Kokorin, V V; Perekos, A O; Kolomiets, O V

    2016-12-01

    Two Cu-Mn-Al samples of different compositions were studied: one exhibiting martensitic transformation, another without structural transition. X-ray diffraction and magnetic measurements demonstrate that different magnetic behaviors of alloys originate from different concentrations and sizes of ferromagnetic nanoparticles, which appear after solid solution decomposition.Estimation of magnetic moments of ferromagnetic nanoparticles from magnetization curves was performed using Langevin function and compared to those obtained from X-ray examination. Granular systems are known to show giant magnetoresistance. Therefore, magnetoresistance of Cu-Mn-Al melt-spun ribbons after different aging times was measured. The study has shown that increase in the concentration of Mn atoms and time of aging in Cu-Mn-Al alloy leads to an increase in the amount of precipitated phase appearing as ferromagnetic nanoparticles. PMID:26762264

  8. 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.

  9. 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.

  10. Self-Formed Barrier with Cu-Mn alloy Metallization and its Effects on Reliability

    SciTech Connect

    Koike, J.; Wada, M.; Usui, T.; Nasu, H.; Takahashi, S.; Shimizu, N.; Yoshimaru, M.; Shibata, H.

    2006-02-07

    Advancement of semiconductor devices requires the realization of an ultra-thin (less than 5 nm thick) diffusion barrier layer between Cu interconnect and insulating layers. Self-forming barrier layers have been considered as an alternative barrier structure to the conventional Ta/TaN barrier layers. The present work investigated the possibility of the self-forming barrier layer using Cu-Mn alloy thin films deposited directly on SiO2. After annealing at 450 deg. C for 30 min, an amorphous oxide layer of 3-4 nm in thickness was formed uniformly at the interface. The oxide formation was accompanied by complete expulsion of Mn atoms from the Cu-Mn alloy, leading to a drastic decrease in resistivity of the film. No interdiffusion was observed between Cu and SiO2, indicating an excellent diffusion-barrier property of the interface oxide.

  11. Coercivity enhancement in Mn-Al-Cu flakes produced by surfactant-assisted milling

    NASA Astrophysics Data System (ADS)

    Saravanan, P.; Hsu, Jen-Hwa; Vinod, V. T. P.; Černík, Miroslav; Kamat, S. V.

    2015-11-01

    We herein report the achievement of exceptionally high coercivity (Hc) values: 9.92 and 5.86 kOe at 5 and 300 K, respectively, for Mn55Al43Cu2 flakes produced by surfactant-assisted milling process without employing any heat-treatment. The use of surfactants such as oleic acid and oleylamine during milling yielded high-aspect ratio flakes for the Mn-Al-Cu alloy. Structural studies confirmed the presence of τ- and β-phases as the major constituents in the Mn-Al-Cu flakes. The observed Hc enhancement is due to the increase in anisotropy field and structural defects, which is hypothesized to originate from the domain-wall pinning as a consequence of precipitation of fine Cu-particles present at the grain boundaries.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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. PMID:19886654

  18. 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.

  19. CONSTITUTIVE BEHAVIOR OF AS-QUENCHED Al-Cu-Mn ALLOY

    NASA Astrophysics Data System (ADS)

    Yang, Xia-Wei; Zhu, Jing-Chuan; Nong, Zhi-Sheng; Ye, Mao; Lai, Zhong-Hong; Liu, Yong

    2013-07-01

    The hot flow stress of as-quenched Al-Cu-Mn alloy was modeled using the constitutive equations. The as-quenched Al-Cu-Mn alloy were treated with isothermal hot compression tests in the temperature range of 350-500°C, the strain rate range of 0.001-1 s-1. The hyperbolic sine equation was found to be appropriate for flow stress modeling and prediction. Based on the hyperbolic sine equation, a constitutive equation is a relation between 0.2 pct yield stress and deformation conditions (strain rate and deformation temperature) was established. The corresponding hot deformation activation energy (Q) for as-quenched Al-Cu-Mn alloy was determined to be 251.314 kJ/mol. Parameters of constitutive equation of as-quenched Al-Cu-Mn alloy were calculated at different small strains (≤ 0.01). The calculated flow stresses from the constitutive equation are in good agreement with the experimental results. Therefore, this constitutive equation can be used as an accurate temperature-stress model to solve the problems of quench distortion of Al-Cu-Mn alloy parts.

  20. Magnetic, structural and optical properties of Mn-based and Cr-based diluted magnetic semiconductors and alloys

    NASA Astrophysics Data System (ADS)

    Alsaad, A.

    2009-03-01

    We have implemented supercell approach by using local spin density functional theory for Mn-doped GaN, Mn-doped ScN and the linear muffin-tin orbital method to predict the structural and magnetic properties of these novel diluted magnetic semiconductors and their GaxMn1-xN and ScxMn1-xN alloys. The global energy minimum of MnN is obtained for zinc-blende structure. If the compound is compressed by 6 % the energy minimum corresponds to the NaCl structure in disagreement with the experimentally observed a slightly tetragonally distorted rocksalt structure, known as ? phase. The rocksalt structure of CrN at about 8 % lattice expansion becomes stable in the ferromagnetic (FM) state and has a global minimum energy at a lattice constant of 3.9 å. We have observed an isostructural phase transition for ScxMn1-xN alloys from zince-blende phase to hexagonal phase that occurs at a hydrostatic pressure of 17.5 GPa. Moreover, the structural and optical properties of single crystal CrN/ScN superlattices and Cr1-xScxN alloys are studied in details. We report an isostructural phase transition from wurtzite (w-CrN) to hexagonal (h-ScN) at a hydrostatic pressure of 21 GPa. We have also used first-principles methods to study the electronic, optical and magnetic properties of MnN and MnAs compounds in the hypothetical cubic zinc-blende phase, a phase in which the two MnN and MnAs binaries have the same local environment as that they have in GaMnN and GaMnAs alloys. We show that MnN exhibits antiferromagnetic (AFM) ground state and MnAs adopts ferromagnetic (FM) ground state.

  1. 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.

  2. 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.

  3. 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

    2016-03-01

    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. PMID:26419419

  4. An uncertain role for Cu(II) in stimulating Mn(II) oxidation by Leptothrix discophora SS-1.

    PubMed

    El Gheriany, Iman A; Bocioaga, Daniela; Hay, Anthony G; Ghiorse, William C; Shuler, Michael L; Lion, Leonard W

    2011-02-01

    In an effort to improve understanding of the role of Cu(II) in bacterial Mn(II) oxidation, a model Mn(II)-oxidizing bacterium, Leptothrix discophora SS-1, was grown in presence of toxic and non-toxic concentrations of Cu(II), Cd(II) and Mn(II). Mn(II)-oxidizing activity increased by 40% when cells were grown in the presence of 0.05 microM of Cu(II) and increased twofold at 0.18 microM Cu(II). Toxic levels of Cd(II) did not stimulate Mn(II) oxidizing activity, indicating that Mn(II) oxidation is not a response to metal toxicity. Stimulation by Cu(II) confirms the specific role of Cu(II) in Mn(II) oxidation. Comparison of transcript levels of the multicopper oxidase mofA gene in the presence and absence of added Cu(II) do not indicate a statistically significant change in mofA transcript levels in cultures supplemented with Cu(II). Thus, the exact role of Cu(II) in Mn(II) oxidation and its affect on mofA gene expression remain uncertain. PMID:21063867

  5. 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. PMID:23959149

  6. Tetragonal phase of epitaxial room-temperature antiferromagnet CuMnAs

    NASA Astrophysics Data System (ADS)

    Wadley, P.; Novák, V.; Campion, R. P.; Rinaldi, C.; Martí, X.; Reichlová, H.; Železný, 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.

    2013-08-01

    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.

  7. Effects of competing magnetic interactions on the electronic transport properties of CuCrSe{sub 2}

    SciTech Connect

    Tewari, Girish C.; Karppinen, Maarit; Rastogi, Ashok K.

    2013-02-15

    We have synthesized single-phase samples of the CuCrSe{sub 2} phase that exhibits hexagonal-rhombohedral layered crystal structure with space group R3m. Here we present a detailed study of electronic transport and magnetic properties of CuCrSe{sub 2}. We moreover investigate the heat capacity of CuCrSe{sub 2} in comparison to that of CuCrS{sub 2}. The electrical resistivity of CuCrSe{sub 2} shows metallic-like behavior down to 2 K, while the thermoelectric power is large around 100 {mu}V K{sup -1} at 300 K. A weak anomaly in resistivity and a rounded maximum in magnetic susceptibility are observed around 55 K. No sharp transition at 55 K is observed in the heat capacity of CuCrSe{sub 2}, rather a visible maximum is seen. At low temperatures from 2 to 14 K, the magnetic heat capacity follows T{sup 2}-dependence. We tentatively believe this behavior of CuCrSe{sub 2} to be due to competing magnetic interactions between intralayer Cr atoms. The ferromagnetic Cr-Se-Cr indirect exchange among intralayer Cr atoms is enhanced in the selenide compound (that is more metallic than the sulfide compound), and competes with the antiferromagnetic Cr-Cr direct interactions. The interlayer antiferromagnetic exchange through Cu atoms leads to magnetic ordering at low temperature at T{sub N}=55 K. - Graphical abstract: Comparison of magnetic properties of CuCrSe{sub 2} and CuCrS{sub 2} indicates a sharp cusp-like anomaly in magnetic susceptibility at the antiferromagnetic transition of CuCrS{sub 2} while the maximum of CuCrSe{sub 2} is well rounded. Magnetization is reversible after field-cooling (FC) and zero-field-cooling (ZFC) for both compounds. Highlights: Black-Right-Pointing-Pointer Layered CuCrSe{sub 2} can be synthesized in both fully and partially cation-ordered forms. Black-Right-Pointing-Pointer Contrary to previously believed insulating nature the cation-ordered phase is metallic. Black-Right-Pointing-Pointer Magnetic property of CuCrSe{sub 2} is somewhat different from

  8. 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.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  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. Reaction of aqueous Cu-Citrate with MnO2 birnessite: characterization of Mn dissolution, oxidation products and surface interactions.

    PubMed

    Jefferson, William A; Hu, Chengzhi; Liu, Huijuan; Qu, Jiuhui

    2015-01-01

    Citric acid, a widespread soil rhizosphere plant/microbe carboxylic acid exudate can easily form chelates with heavy metals, increasing their availability in the environment. When Cu(II) from algal control in water bodies or reservoirs and fungicides, such as the Bordeaux mixture, and citrate interact, solubilization through chelation is a possible outcome. Manganese (hydr)oxides represent a significant portion of the subsurface environment and can affect the fate and transport of chemical species through adsorption and oxidation. This study explores the possible interaction between MnO2 and Cu-Citrate under ambient oxic conditions. The calculated Mn(II) dissolution rates during the initial 1h of reaction followed the series Cu(II)>Cu-Citrate 1:0.5>Cu-Citrate 1:1(oxic)>Citrate>Cu-Citrate 1:1(Anoxic), reinforcing the central role of (complexed or un-complexed) Cu(II) during the initial surface-coordination instead of following the s-shaped auto-catalytic curves of Mn(II) dissolution in citrate solution. The use of capillary electrophoresis allowed the detection of an intermediate Cu(II)Acetonedicarboxylate complex and the oxidation products acetonedicarboxylate, acetoacetate, acetone and acetic acid. The mass balance analysis of Cu-Citrate 1:1 suggests the partial adsorption of Cu-Citrate(ads) and catalytic degradation of acetonedicarboxylate through a MnO2-Cu surface sorbed complex. Lastly, XPS analysis confirmed the MnO2 surface Cu(II) reduction along with an outer-hydration layer at the MnO2 interface, where electron transfer and aquo ligand exchange may lead to the oxidation of Cu-Citrate. PMID:25460741

  13. 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

  14. Regulation of Cu,Zn- and Mn-superoxide dismutase transcription in Saccharomyces cerevisiae.

    PubMed

    Galiazzo, F; Labbe-Bois, R

    1993-01-01

    The regulation of Cu,Zn- and Mn-superoxide dismutases (SOD) was investigated by Northern blotting and gene fusions of SOD1 and SOD2 promoters with the beta-galactosidase reporter gene. Cu,ZnSOD expression was increased 3-fold under glucose derepressing conditions, and decreased 4- to 6-fold by oxygen or heme deficiency. MnSOD expression was increased 5-fold by glucose derepression, and decreased 8- to 10-fold by anaerobiosis and 4- to 5-fold by heme deficiency. Induction by paraquat was modest, about 50% for SOD1 and 100% for SOD2; it was apparently independent of the respiratory chain function. PMID:8417979

  15. 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.

  16. μSR investigation of a new diluted magnetic semiconductor Li(Zn,Mn,Cu)As with Mn and Cu codoping at the same Zn sites.

    PubMed

    Guo, S L; Zhao, Y; Man, H Y; Ding, C; Gong, X; Zhi, G X; Fu, L C; Gu, Y L; Frandsen, B A; Liu, L; Cheung, S C; Munsie, T J; Wilson, M N; Cai, Y P; Luke, G M; Uemura, Y J; Ning, F L

    2016-09-14

    We report the successful synthesis and characterization of a new type I-II-V bulk form diluted magnetic semiconductor (DMS) Li(Zn,Mn,Cu)As, in which charge and spin doping are decoupled via (Cu,Zn) and (Mn,Zn) substitution at the same Zn sites. Ferromagnetic transition temperature up to  ∼33 K has been observed with a coercive field  ∼40 Oe for the 12.5% doping level. μSR measurements confirmed that the magnetic volume fraction reaches nearly 100% at 2 K, and the mechanism responsible for the ferromagnetic interaction in this system is the same as other bulk form DMSs. PMID:27401041

  17. 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.

  18. 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.

  19. Effects of Mn substitution on the structure and properties of chalcopyrite-type CuInSe{sub 2}

    SciTech Connect

    Yao Jinlei; Kline, Carly N.; Gu Hao; Yan Mi; Aitken, Jennifer A.

    2009-09-15

    Mn-doped CuInSe{sub 2} compounds (CuIn{sub 1-x}Mn{sub x}Se{sub 2}, x=0.0125-0.20 and Cu{sub 1-y}In{sub 1-y}Mn{sub 2y}Se{sub 2}, 2y=0.0125-0.60) were synthesized by high-temperature solid-state reactions. Single phase materials with chalcopyrite structure persist up to 0.10 and 0.20 doping for CuIn{sub 1-x}Mn{sub x}Se{sub 2} and Cu{sub 1-y}In{sub 1-y}Mn{sub 2y}Se{sub 2}, respectively. The chalcopyrite and sphalerite phases co-exist in the Cu{sub 1-y}In{sub 1-y}Mn{sub 2y}Se{sub 2} system for 2y=0.25-0.50. Attempts to introduce greater manganese content, x=0.15-0.20 for CuIn{sub 1-x}Mn{sub x}Se{sub 2} and 2y=0.60 for Cu{sub 1-y}In{sub 1-y}Mn{sub 2y}Se{sub 2}, result in partial phase segregation. For the single-phase samples, the lattice parameters of both systems increase linearly with manganese concentration and thus follow Vegard's law. The temperature of the chalcopyrite-sphalerite phase transition is decreased by manganese substitution for all single-phase samples. The bandgap of the materials remains around 0.9 eV. Additionally, the Mn-doped CuInSe{sub 2} compounds display paramagnetic behavior, whereas pure CuInSe{sub 2} is diamagnetic at 5-300 K. All the CuIn{sub 1-x}Mn{sub x}Se{sub 2} and Cu{sub 1-y}In{sub 1-y}Mn{sub 2y}Se{sub 2} compounds with chalcopyrite structure show antiferromagnetic coupling and measured effective magnetic moments up to 5.8 mu{sub B}/Mn. - Graphical abstract: The manganese solid solubility can reach up to 10% and 20% for CuIn{sub 1-x}Mn{sub x}Se{sub 2} and Cu{sub 1-y}In{sub 1-y}Mn{sub 2y}Se{sub 2}, respectively, while maintaining phase-pure, chalcopyrite-type materials. Lattice parameters increase linearly with increase manganese concentration suggesting that the manganese ions are distributed randomly on both the indium site and the copper and indium sites simultaneously.

  20. Removal of Cr(VI) from aqueous solutions by adsorption on MnO2.

    PubMed

    Gheju, Marius; Balcu, Ionel; Mosoarca, Giannin

    2016-06-01

    Adsorption of Cr(VI) on MnO2 was investigated with respect to effect of pH, temperature, ionic strength, initial Cr(VI) concentration, co-presence of different anions (HCO3(-), SO4(2-), H2PO4(-), NO3(-) and Cl(-)) and of low molecular weight natural organic materials (LMWNOM) (acetate, oxalate and citrate). The process was rapid during the first 3-5min, reaching equilibrium after one hour. Adsorption decreased with increasing pH, temperature and Cr(VI) initial concentration, and increased with increasing ionic strength. Co-presence of phosphate, sulfate, bicarbonate, citrate and oxalate hindered Cr(VI) adsorption, whereas nitrate, chloride and acetate did not exert any notable influence. The overall order of Cr(VI) adsorption suppression due to co-presence of anions and LMWNOM was H2PO4(-)>HCO3(-)>SO4(2-), and oxalate>citrate, respectively. Highest experimental equilibrium sorption capacity (0.83mgg(-1)) was obtained at 20°C and pH 5.9, while lowest (0.18mgg(-1)) was noticed in the co-presence of H2PO4(-), at 20°C and pH 6.9. Adsorption kinetics was successfully fitted by pseudo-second-order model. Mechanisms for both specific and non-specific adsorption are likely to be involved, while rate-controlling step involved both intra-particle and film diffusion processes. Cr(VI) was strongly bound to MnO2, which makes risks of its subsequent liberation into the environment to be low. PMID:26947189

  1. 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

    2016-06-01

    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. PMID:26921512

  2. 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.

  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. 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

    2015-01-01

    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

  5. 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.

  6. 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.

  7. Spin-polarised edge states in atomic Mn chains supported on Cu2N/Cu (100)

    NASA Astrophysics Data System (ADS)

    Choi, Deung-Jang; Robles, Roberto; Gauyacq, Jean-Pierre; Rubio-Verdú, Carmen; Lorente, Nicolás; Pascual, José Ignacio

    2016-06-01

    Scanning tunnelling microscopy and density functional theory studies of manganese chains adsorbed on Cu2N/Cu (100) reveal an unsuspected electronic edge state at ∼ 1 eV above the Fermi energy. This Tamm-like state is strongly localised to the terminal Mn atoms of the chain and fully spin polarised. However, no equivalence is found for occupied states, and the electronic structure at ∼   ‑1 eV is mainly spin unpolarised due to the extended p-states of the N atoms that mediate the coupling between the Mn atoms in the chain. The spin polarisation of the edge state is affected by the antiferromagnetic ordering of the chains leading to non-trivial consequences.

  8. Spin-polarised edge states in atomic Mn chains supported on Cu2N/Cu (100).

    PubMed

    Choi, Deung-Jang; Robles, Roberto; Gauyacq, Jean-Pierre; Rubio-Verdú, Carmen; Lorente, Nicolás; Ignacio Pascual, José

    2016-06-15

    Scanning tunnelling microscopy and density functional theory studies of manganese chains adsorbed on Cu2N/Cu (100) reveal an unsuspected electronic edge state at [Formula: see text] eV above the Fermi energy. This Tamm-like state is strongly localised to the terminal Mn atoms of the chain and fully spin polarised. However, no equivalence is found for occupied states, and the electronic structure at [Formula: see text]  -1 eV is mainly spin unpolarised due to the extended p-states of the N atoms that mediate the coupling between the Mn atoms in the chain. The spin polarisation of the edge state is affected by the antiferromagnetic ordering of the chains leading to non-trivial consequences. PMID:27158116

  9. 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.

  10. Stochastic jumps of magnetization in [Mn{(R/S)-pn}]2[Mn{(R/S)-pn}2(H2O)][Cr(CN)6]2 molecular magnet

    NASA Astrophysics Data System (ADS)

    Kirman, M. V.; Talantsev, A. D.; Koplak, O. V.; Morgunov, R. B.

    2015-03-01

    Series of stochastic jumps of the magnetic moment (up to five individual jumps) have been observed at the demagnetization of single crystals of [Mn{(R/S)-pn}]2[Mn{(R/S)-pn}2(H2O)][Cr(CN)6]2 molecular magnet in a narrow range of magnetic fields near the coercive force ( H c = 7.5 Oe). The magnetic field at which jumps of the magnetization arise decreases with an increase in the temperature.

  11. 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.

  12. 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

  13. 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.

  14. Luminescence Dynamics of Cr2+ in CdTe and Cd0.55Mn0.45Te

    NASA Astrophysics Data System (ADS)

    Bluiett, A.; Hommerich, U.; Seo, J. T.; Shah, R.; Trivedi, S. B.; Kutcher, S. W.; Chen, R. J.; Wang, C. C.; Zong, H.

    2001-04-01

    Cr^2+ in tetrahedrally coordinated CdTe and Cd_0.55Mn_0.45Te crystals are under investigation as potential host materials for tunable, mid-infrared (MIR) lasers. The small crystal field splitting of the free ion energy levels of Cr^2+ induces absorption (1900nm) and stokes shifted emission (2000nm-3000nm) bands in the MIR. Also, the relatively large ionic mass and tetrahedral environment of Cr^2+ in CdTe and Cd_0.55Mn_0.45Te have shown that the luminescence efficiency at room temperature is approximately 72100luminescence lifetime decreases rapidly, which suggest that the effects of nonradiative decay increases. The decay dynamics of Cr^2+ in CdTe and Cd_0.55Mn_0.45Te will be described with the model of Struck and Fonger for the non-radiative decay rate.

  15. Effect of hydrogen exposure on a Cu-8 Cr-4 Nb alloy

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Misra, Ajay K.; Dreshfield, Robert L.

    1993-01-01

    The advanced regeneratively cooled rocket thrust chamber may require new materials to achieve long life and improved performance. Current materials such as NARloy-Z (Cu-3 wt. percent Ag-0.5 wt. percent Zr), while highly conductive, do not have sufficient high temperature strength and creep resistance to meet the projected needs of advanced rocket motors. A Cu-8 at. percent Cr-4 at. percent Nb (Cu-8 Cr-4 Nb) alloy has been identified as a promising material for this application. However, hydrogen embrittlement is a concern given the presence of high pressure, high temperature hydrogen in regeneratively cooled rocket motors. Thermodynamic analysis of the reaction between Cr-rich Cr2Nb and H2 showed that there is a possibility of reaction at temperatures up to 323 K in a 35 MPa H2 environment. Above 323 K the pressure necessary to achieve reaction rapidly increased beyond the range experienced in rocket motors. Tensile specimens exposed in 34.5 MPa H2 at room temperatures and during cycling to 705 C did not show any degradation of properties. No evidence of reaction was observed for Cr2Nb precipitate observed on the fracture surfaces. Based on these results the Cu-8 Cr-4 Nb alloy was judged to be sufficiently stable for use in rocket motors.

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

    SciTech Connect

    Rawers, J.C.

    2008-05-01

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

  17. Incorporation, valence state, and electronic structure of Mn and Cr in bulk single crystal β-Ga2O3

    NASA Astrophysics Data System (ADS)

    Lovejoy, T. C.; Chen, Renyu; Yitamben, E. N.; Shutthanadan, V.; Heald, S. M.; Villora, E. G.; Shimamura, K.; Zheng, S.; Dunham, S. T.; Ohuchi, F. S.; Olmstead, M. A.

    2012-06-01

    Single crystals of transition metal (TM) doped β-Ga2O3, a wide gap semiconductor system of interest for transparent conductive oxide and diluted magnetic semiconductor applications, have been studied in the dilute, non-interacting limit (≤0.06 cation %). Based on optical absorption, particle induced x-ray emission, and Rutherford backscattering measurements, Mn does not incorporate as well as Cr, and Mn degrades the crystal quality. Using superconducting quantum interference device (SQuID) magnetometry, a Brillouin type paramagnetic magnetization is observed for Mn or Cr doped crystals with an effective number of Bohr magnetons per TM ion of 5.88 ± 0.1 or 3.95 ± 0.1, respectively. A trace ferromagnetic signal is consistent with a very small concentration of secondary phases in the Mn-doped crystal. The position of the edge in x-ray absorption near edge structure (XANES) measurements suggests that the Cr takes the 3+ valence, while a mixture of Mn2+ and Mn3+ are present; based on the absence of a prominent pre-edge feature in the XANES, both TM predominantly occupy an octahedral site in β-Ga2O3. Density functional theory (DFT) results, optical absorption and SQuID data are consistent with this assignment. While the Cr-doped crystal is conductive, the Mn-doped crystal is insulating, which is consistent with the Mn2+/Mn3+ mixed valence, assuming the Fermi level is pinned mid-gap at the Mn 2+/3+ transition level, which is predicted by DFT to be 1.8 eV above the valence band maximum.

  18. 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.

  19. 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.

  20. 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

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

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

  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. 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)

  5. 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.

  6. Explosive bonding of 316L to C18150 CuCrZr alloy for ITER applications.

    SciTech Connect

    Puskar, Joseph David; Butler, Don J.; Goods, Steven Howard; Brasher, Dave G.

    2010-10-01

    Recent developments in the ITER experimental fusion reactor require that a 316L stainless steel substructure be bonded to a precipitation strengthened CuCrZr heat sink alloy, C18150. This bond defines the cooling water pressure boundary. Given the importance of this interface, a variety of experiments with fusion welding and solid-state joining techniques have been performed. Analysis of the joints includes mechanical measurements of bond strength and microstructural analysis using optical and electron microscopy techniques. A particular emphasis was placed on the mechanical properties of the CuCrZr, since it undergoes additional thermal processing and cannot be solutionized and aged hardened per standard heat treatments. It was determined that the explosion bonding, of all the techniques examined, maximized the residual mechanical strength of the CuCrZr. The bonding parameters were optimized to minimize the amount of mixing and porosity at the interface. The details of these results and the optimization will be discussed.

  7. 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.

  8. Numerical exploration into the potential of tungsten reinforced CuCrZr matrix composites

    NASA Astrophysics Data System (ADS)

    Hohe, Jörg; Fliegener, Sascha; Findeisen, Claudio; Reiser, Jens; Widak, Verena; Rieth, Michael

    2016-03-01

    The present study provides a numerical investigation into the potential of tungsten reinforced CuCrZr materials in order to overcome their limited performance at higher temperatures. Metal matrix composites including (i) particle reinforced microstructures, (ii) short fiber reinforced microstructures with both randomly orientated and (iii) aligned fibers as well as (iv) laminates consisting of stacked tungsten and CuCrZr layers are considered. The numerical analysis is performed by means of an energy based homogenization procedure in conjunction with a finite element analysis of representative volume elements for the respective microstructures. The results of the screening analysis reveal a distinct improvement of the mechanical properties of CuCrZr materials by the tungsten reinforcements even for moderate tungsten volume fractions. In a comparison of the different microstructures, the ordered microstructures, i.e. laminates and the aligned short fiber reinforced composites in most cases outperform their disordered counterparts.

  9. 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

  10. 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.

  11. 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.

  12. 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

  13. On the strong impact of doping in the triangular antiferromagnet CuCrO 2

    NASA Astrophysics Data System (ADS)

    Maignan, A.; Martin, C.; Frésard, R.; Eyert, V.; Guilmeau, E.; Hébert, S.; Poienar, M.; Pelloquin, D.

    2009-06-01

    Electronic band structure calculations using the augmented spherical wave method have been performed for CuCrO 2. For this antiferromagnetic ( TN=24 K) semiconductor crystallizing in the delafossite structure, it is found that the valence band maximum is mainly due to the t 2g orbitals of Cr 3+ and that spin polarization is predicted with 3 μ per Cr 3+. The structural characterizations of CuCr 1- xMg xO 2 reveal a very limited range of Mg 2+ substitution for Cr 3+ in this series. As soon as x=0.02, a maximum of 1% Cr ions are substituted by Mg site is measured in the sample. This result is also consistent with the detection of Mg spinel impurities from X-ray diffraction for x=0.01. This explains the saturation of the Mg 2+ effect upon the electrical resistivity and thermoelectric power observed for x>0.01. Such a very weak solubility limit could also be responsible for the discrepancies found in the literature. Furthermore, the measurements made under magnetic field (magnetic susceptibility, electrical resistivity and Seebeck coefficient) support that the Cr 4+ "holes", created by the Mg 2+substitution, in the matrix of high spin Cr 3+ ( S=3/2) are responsible for the transport properties of these compounds.

  14. Characterization of a CuAlBe Alloy with Different Cr Contents

    NASA Astrophysics Data System (ADS)

    da M. Candido, Gemierson Valois; de A. Melo, Tadeu Antônio; De Albuquerque, Victor Hugo C.; Gomes, Rodinei Medeiros; de Lima, Severino Jackson G.; Tavares, João Manuel R. S.

    2012-11-01

    In this article, the use of chromium (Cr) as a grain refiner for a CuAlBe shape memory alloy is discussed. Alloys with 0.1, 0.2, 0.3, and 0.5 wt.% Cr were characterized by optical microscopy, scanning electron microscope, and x-ray diffraction. Also, the influence of the different percentages of Cr on the grain size and on the mechanical properties was analyzed through macro- and microscopic evaluations and by tensile and hardness tests, respectively. Finally, the phase transformation temperatures of the alloys were determined by thermal analysis using differential scanning calorimetry. The results showed that the higher the Cr content, the greater the grain refinement effect and lower the hardness. In addition, at room temperature the alloys with 0.1 and 0.2 wt.% Cr were austenitic, while the rest were martensitic. The tensile tests showed that the alloy with 0.2 wt.% Cr provided the best strain-stress performance. The conclusion was that the use of 0.2 wt.% Cr as a grain refiner improved the mechanical properties of the CuAlBe alloy; however, the same was not observed for the other Cr contents.

  15. Flux Pinning by Cr Nanoparticles in Cu_{0.5} Tl_{0.5} Ba2 Ca2 Cu3 O_{10-δ } Superconductor

    NASA Astrophysics Data System (ADS)

    Waqee-ur-Rehman, M.; Mumtaz, M.; Qasim, Irfan; Nadeem, K.

    2016-04-01

    Increase in flux pinning strength of Cu_{0.5} Tl_{0.5} Ba2 Ca2 Cu3 O_{10-δ } (CuTl-1223) superconductor has been observed after addition of Cr nanoparticles. We have thoroughly investigated the infield response of Cr nanoparticles-added CuTl-1223 superconductor in an external applied magnetic field in the range of 0-7 T. Solid-state reaction technique has been employed to synthesize (Cr)x -CuTl-1223; x = 0-1.00 wt% nanoparticle-superconductor composites. The flux pinning mechanism has been analyzed on the basis of thermally activated flux flow model in the presence of a small current (10 μ A). The increase in activation energy and decrease in transition width of CuTl-1223 superconducting phase show the enhancement in its flux pinning strength upon the addition of Cr nanoparticles.

  16. Flux Pinning by Cr Nanoparticles in Cu_{0.5}Tl_{0.5}Ba2Ca2Cu3O_{10-δ } Superconductor

    NASA Astrophysics Data System (ADS)

    Waqee-ur-Rehman, M.; Mumtaz, M.; Qasim, Irfan; Nadeem, K.

    2016-09-01

    Increase in flux pinning strength of Cu_{0.5}Tl_{0.5}Ba2Ca2Cu3O_{10-δ }(CuTl-1223) superconductor has been observed after addition of Cr nanoparticles. We have thoroughly investigated the infield response of Cr nanoparticles-added CuTl-1223 superconductor in an external applied magnetic field in the range of 0-7 T. Solid-state reaction technique has been employed to synthesize (Cr)x-CuTl-1223; x = 0-1.00 wt% nanoparticle-superconductor composites. The flux pinning mechanism has been analyzed on the basis of thermally activated flux flow model in the presence of a small current (10 μ A). The increase in activation energy and decrease in transition width of CuTl-1223 superconducting phase show the enhancement in its flux pinning strength upon the addition of Cr nanoparticles.

  17. High-pressure thermoluminescence and photoluminescence study of ZnS:Mn:Cu:Cl phosphor

    SciTech Connect

    Lang, J.M.; Dreger, Z.A.; Drickamer, H.G. , Urbana, Illinois 61801 )

    1992-02-15

    The effect of pressure has been studied on the thermoluminescence and photoluminescence of a well-characterized sample of ZnS:Mn:Cu:Cl. The thermoluminescence was particularly revealing. Initially two traps were present. As they increased in depth with increasing pressure new shallower traps appeared. The pressure dependence of four traps was established. By comparison with pressure measurements on ZnS doped only with Mn{sup +2} and only with Cu{sup +} and Cl{sup {minus}}, we established that the deepest trap is associated with defects introduced by Mn{sup +2}, while the two traps next lower in energy are associated with defects introduced by Cl{sup {minus}}. The shallowest trap could not be assigned to a specific defect. The photoluminescence emission (from the {sup 4}{ital T}{sub 1}, to the {sup 6}{ital A}{sub 1} energy level of Mn{sup +2}) shifted to lower energy at a rate identical to that previously reported for a less well-characterized ZnS:Mn sample. The shift could be described quantitatively in terms of changes in the ligand field parameters.

  18. 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.

  19. Mn1.4Co1.4Cu0.2O4 spinel protective coating on ferritic stainless steels for solid oxide fuel cell interconnect applications

    NASA Astrophysics Data System (ADS)

    Chen, Guoyi; Xin, Xianshuang; Luo, Ting; Liu, Leimin; Zhou, Yuchun; Yuan, Chun; Lin, Chucheng; Zhan, Zhongliang; Wang, Shaorong

    2015-03-01

    In an attempt to reduce the oxidation and Cr evaporation rates of solid oxide fuel cells (SOFCs), Mn1.4Co1.4Cu0.2O4 spinel coating is developed on the Crofer22 APU ferritic stainless steel substrate by a powder reduction technique. Doping of Cu into Mn-Co spinels improves electrical conductivity as well as thermal expansion match with the Crofer22 APU interconnect. Good adhesion between the coating and the alloy substrate is achieved by the reactive sintering process using the reduced powders. Long-term isothermal oxidation experiment and area specific resistance (ASR) measurement are investigated. The ASR is less than 4 mΩ cm2 even though the coated alloy undergoes oxidation at 800 °C for 530 h and four thermal cycles from 800 °C to room temperature. The Mn1.4Co1.4Cu0.2O4 spinel coatings demonstrate excellent anti-oxidation performance and long-term stability. It exhibits a promising prospect for the practical application of SOFC alloy interconnect.

  20. Measurement and analysis of radioactivity induced in CuCrZr by D?T neutrons

    NASA Astrophysics Data System (ADS)

    Eichin, R.; Adelhelm, C.; Blokhin, A. I.; Forrest, R. A.; Freiesleben, H.; Kovalchuk, V. D.; Markovskij, D. V.; Seidel, K.; Unholzer, S.

    2004-08-01

    CuCrZr is used in high heat flux components of ITER and other fusion reactor designs. A CuCrZr alloy of the European Fusion Technology Programme was irradiated with D-T neutrons, and the γ-activities of all nuclides which are relevant up to the recycling limit of the material were measured. The results were analysed with the European Activation System (versions EASY-2001 and EASY-2003). The calculated total activation property of the material was validated within 10%. The long-term radioactivity was estimated to be well below the hands-on limit with an uncertainty of 19%.

  1. [CrIII8MII6]12+ Coordination Cubes (MII=Cu, Co)**

    PubMed Central

    Sanz, Sergio; O'Connor, Helen M; Pineda, Eufemio Moreno; Pedersen, Kasper S; Nichol, Gary S; Mønsted, Ole; Weihe, Høgni; Piligkos, Stergios; McInnes, Eric J L; Lusby, Paul J; Brechin, Euan K

    2015-01-01

    [CrIII8MII6]12+ (MII=Cu, Co) coordination cubes were constructed from a simple [CrIIIL3] metalloligand and a “naked” MII salt. The flexibility in the design proffers the potential to tune the physical properties, as all the constituent parts of the cage can be changed without structural alteration. Computational techniques (known in theoretical nuclear physics as statistical spectroscopy) in tandem with EPR spectroscopy are used to interpret the magnetic behavior. PMID:25891167

  2. Effect of Cr and Cu addition on corrosion behavior of Ni-Ti alloys.

    PubMed

    Iijima, M; Endo, K; Ohno, H; Mizoguchi, I

    1998-03-01

    The corrosion behavior of three Ni-Ti alloys with compositions as commercial super-elastic orthodontic wires was investigated using polished plate specimens. Corrosion resistance was estimated by potentiodynamic polarization measurement in 0.9% NaCl and 1% lactic acid solutions and analysis of released metals by atomic absorption spectrophotometry. The influence of Cr and Cu addition on the structure of the surface oxide film was examined by X-ray photoelectron spectroscopy (XPS). Addition of 0.19 at% Cr had little effect on the structure of the oxide films and the corrosion resistance of the Ni-Ti alloys. For Ni-Ti-5Cu-0.3Cr alloy, the metallic Cu was enriched at the alloy/oxide film interface, resulting in increased susceptibility to pitting corrosion above +1000 mV. However, the passive current density and the amount of released Ni were not significantly increased by the addition of Cu. The study showed that small amounts of Cr and Cu added to change the super-elastic characteristics do not change the corrosion resistance of the Ni-Ti alloy freely immersed in simulated physiological environments. PMID:9663060

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  4. 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).

  5. 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. PMID:25623228

  6. 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.

  7. Revisiting the properties of delafossite CuCrO{sub 2}: A single crystal study

    SciTech Connect

    Poienar, Maria; Hardy, Vincent; Kundys, Bohdan; Singh, Kiran; Maignan, Antoine; Damay, Francoise; Martin, Christine

    2012-01-15

    Platelet-like single-crystals of delafossite CuCrO{sub 2} have been successfully grown and characterised by X-ray diffraction and pole figures, scanning electron and atomic force microscopy. Transport measurements reveal that the resistivity is highly anisotropic, with a ratio of about 35 at 300 K between the in- and out-of-plane directions, reflecting the layered crystal structure. The magnetization and specific heat data show that CuCrO{sub 2} undergoes a unique antiferromagnetic transition at T{sub N}=24.0 K, in contrast to a recent report on CuCrO{sub 2} single-crystals showing the existence of two magnetic transitions, T{sub N1}=24.2 K and T{sub N2}=23.6 K, depending on the orientation of the applied magnetic field along and perpendicular to c, respectively. - Graphical abstract: 3R-CuCrO{sub 2} platelet-like single crystals have been successfully grown by the flux method. As revealed by {chi}(T) and C(T) measurements, their properties are characterised by a unique antiferromagnetic transition at T{sub N}=24 K. Interestingly, despite a very small magnetic anisotropy, a large one is evidenced by the resistivity ratio, {rho}{sub c}/{rho}{sub ab}{approx}35, at 300 K. This suggests an easier charge hopping in the [CrO{sub 2}] planes rather than along (Cr-O-Cu) pathways, i.e. along c axis. Highlights: Black-Right-Pointing-Pointer R-CuCrO{sub 2} plate-like single crystals have been synthesised by the flux method. Black-Right-Pointing-Pointer Growth takes place layer-by-layer and some growth defects have been observed. Black-Right-Pointing-Pointer CuCrO{sub 2} single crystals exhibit a unique antiferromagnetic transition at T{sub N}=24 K. Black-Right-Pointing-Pointer Transport measurements reveal that the resistivity is highly anisotropic.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. Production and processing of Cu-Cr-Nb alloys

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Michal, Gary M.; Orth, Norman W.

    1990-01-01

    A new Cu-based alloy possessing high strength, high conductivity, and good stability at elevated temperatures was recently produced. This paper details the melting of the master alloys, production of rapidly solidified ribbon, and processing of the ribbon to sheet by hot pressing and hot rolling.

  14. 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.

  15. 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.

  16. ADSORPTION AND DESORPTION OF ZN, CU, AND CR BY SEDIMENTS FROM THE RAISIN RIVER (MICHIGAN)

    EPA Science Inventory

    Metal adsorption by Raisin River sediments in vitro depended linearly on soluble metal concentration to adsorption densities of 6,000-9,000 ug/g with 48 hr partition coefficients of approximately 50, 30, and 25 L/g for Cu, Cr, and Zn, respectively. artition coefficients computed ...

  17. 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

  18. 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. PMID:24381480

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

    PubMed

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

    2009-05-01

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

  20. The role of magnetism in the formation of the two-phase miscibility gap in β Cu-Al-Mn

    NASA Astrophysics Data System (ADS)

    Lanzini, Fernando; Alés, Alejandro

    2015-12-01

    A theoretical study of the ground state properties of alloys with compositions along the pseudobinary line Cu3Al-Cu2AlMn is presented. Cohesive energies, lattice parameters and magnetic moments of the two limiting compounds and three intermediate compositions are calculated by means of density functional theory. In order to evaluate the role of magnetism, both the spin-polarized (SP) and the non spin-polarized (NSP) cases have been considered. It is shown that magnetism plays a central role on the stabilization of the L21 crystal structure in Cu2AlMn, and in the formation of the miscibility gap in Cu3Al-Cu2AlMn. The considerable lattice mismatch between the end compounds can be attributed also to magnetic effects.

  1. The Supplementation of Yam Powder Products Can Give the Nutritional Benefits of the Antioxidant Mineral (Cu, Zn, Mn, Fe and Se) Intakes

    PubMed Central

    Shin, Mee-Young; Cho, Young-Eun; Park, Chana; Sohn, Ho-Yong; Lim, Jae-Hwan; Kwun, In-Sook

    2012-01-01

    Yam has been recognized having the beneficial effects for the prevention of various diseases, such as cancer, immunity, infection and obesity etc. There is increasing consideration to supplement the antioxidant nutrients to make up the lack of the antioxidant nutrient intakes. No study has been reported for the analysis of antioxidant mineral contents and comparison to dietary recommended intake for the sense of health promotion. In our study, we analyzed the contents of antioxidant trace elements (Zn, Mn, Fe, Cu and Se) and Cr contents in cultivated Korean yam powders for evaluation of nutrient intake aspects. We collected the commercial yam powders from six different cultivated areas in the South Korea and measured antioxidant minerals (Zn, Mn, Fe, Cu and Se) and Cr contents using trace element-free plasma spectrometer (ICP) or atomic absorption spectrometer (AAS) after dry-ashing and then wet-acid digestion. The accuracy of mineral analysis method was confirmed by the mineral analysis of standard reference material. Each analyzed element contents in yam were compared to dietary reference intakes of Koreans (KDRIs). The average levels of trace elements (Zn, Mn, Fe, Cu, Se and Cr) in yam powders were 18.3, 11.9, 36.0, 3.7, 1.9 and 1.27 μg/g yam powder, respectively. The intakes of Zn, Fe, Cu and Se of which KDRIs is determined, are accounted as being up to 23.8%, 55.6%, 32.5% and 236% recommended intake (RI) of KDRIs, if daily yam supplementation (50 g) of commercial instruction would be considered. The intake of Mn is about 25% adequate intake (AI) of KDRIs with the daily supplementation of yam powder. Most of mineral intakes from daily yam supplementation were with the range of non-detectable to <10% upper limit (UL) level, which is very much safe. The study results show that daily supplementation of Korean yam power is beneficial to provide the supplemental nutrient intake and also is safe, if the suggested dosage would be considered. PMID:24471100

  2. 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.

  3. 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.

  4. Semiconductor-to-metallic transition in Cu-substituted Ni-Mn ferrite

    NASA Astrophysics Data System (ADS)

    Ata-Allah, S. S.; Kaiser, M.

    2004-11-01

    The electrical properties of Cu-substituted Ni-Mn ferrite Ni1-xCuxMnyFe2-yO4 (with 0.0 ≤ x ≤ 1.0 and y = 0.6) are investigated by ac conductivity measurements in the frequency range 102-105 Hz and over the temperature range 300-730 K. The results obtained for these materials reveal a semiconductor-to-metallic transition as Cu content increases. All studied compositions exhibit a transition with a change in the slope of the conductivity versus temperature curve. This transition temperature is found to decrease linearly with increasing Cu concentration. Variations of dielectric permittivities ( and ) and dielectric loss tangent (tan δ) for the studied materials as a function of temperature and frequency are found to be strongly dependent on both Mn and Cu concentrations. The results for conductivity and dielectric parameters ( and ) and tan δ are explained on the basis of cation-anion-cation and cation-cation interactions over the octahedral sites in the spinel structure.

  5. 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.

  6. 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. PMID:26934114

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

    PubMed

    Gheju, M; Balcu, I; Vancea, C

    2016-04-01

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

  8. Interlayer thickness dependence of 90° exchange coupling in Co2MnAl/Cr/Co2MnAl epitaxial trilayer structures

    NASA Astrophysics Data System (ADS)

    Bosu, S.; Sakuraba, Y.; Saito, K.; Wang, H.; Mitani, S.; Takanashi, K.; You, C. Y.; Hono, K.

    2009-04-01

    The spacer layer thickness dependence of interlayer exchange coupling has been investigated in the fully epitaxial trilayers of the Co2MnAl (CMA)/Cr/CMA structure. A series of high-quality samples of CMA (20 nm)/Cr (tCr=0.3-8.1 nm)/CMA (10 nm) trilayers was prepared on a MgO substrate by ultrahigh vacuum compatible dc sputtering. Comparison of the results of the experiments and the simulations of magnetization curves revealed novel behavior, dominating the 90° coupling and the absence of 180° coupling. No clear oscillation, only a peak of the 90° coupling strength (J2˜-0.68 erg/cm2), was observed at tCr=1.2 nm.

  9. 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.

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

    DOE PAGESBeta

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

    2015-12-10

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

  11. 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

  12. Nanomechanical Behavior of CoCrFeMnNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Mridha, Sanghita; Das, Santanu; Aouadi, Samir; Mukherjee, Sundeep; Mishra, Rajiv S.

    2015-08-01

    The nanomechanical behavior of the Co20Cr20Fe20Mn20Ni20 high-entropy alloy was investigated in as-cast, rolled, annealed, and thin-film forms. Dislocation nucleation was studied by repeated indents at a low load for each of the different processing conditions. Distinct displacement bursts (pop in) were observed in the loading curve marked by incipient plasticity for all the samples. The as-cast and annealed samples showed pop ins for 100% of the indents, whereas the rolled and thin-film samples showed a much lower fraction of displacement bursts. This was explained by the high density of dislocations for the cold-worked and thin-film conditions. The strong depth dependence of hardness was explained by geometrically necessary dislocations. The nanomechanical behavior and twinned microstructure indicate low stacking-fault energy for this high-entropy alloy.

  13. Mechanical cycling effects at Fe-Mn-Si-Cr-Ni SMAs obtained by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Pricop, B.; Söyler, U.; Comčneci, R. I.; Özkal, B.; Bujoreanu, L. G.

    Specimens from Fe-Mn-Si-Cr-Ni SMA, obtained by powder metallurgy and compacted through hot rolling, were subjected to tensile loading-unloading cycles. The pseudoelastic parameters were determined based on recorded stress-strain curves, and their variation tendency with increasing the number of mechanical cycles was discussed. The gauges of tensile specimens were cut after mechanical cycling and were subjected to structural and dilatometric analysis. The structure was analyzed by XRD and SEM, aiming to reveal mechanical cycling effects. The thermomechanical response on heating, of mechanically cycled specimens, was recorded by dilatometry and revealed a tendency to enhance thermal expansion as an effect of increasing the number of cycles. The microstructural changes, induced by mechanical cycling, consisted in the stress induced formation of α' martensite.

  14. Formation of dislocations, precipitates and cavities in He-implanted Mn-Cr austenitic steels

    NASA Astrophysics Data System (ADS)

    Ruedl, E.; Valdrè, G.

    1991-03-01

    Solution-annealed discs of three Mn-Cr austenitic steels containing different amounts of C and N were uniformly implanted at 310 K with 1000 appm He corresponding to ~ 0.2 dpa. The samples were subsequently aged at temperatures from 923 to 1073 K for various times and, after electropolishing, examined by TEM, EDS and EELS. A study was made of the dislocation loops developing on aging and of the compositional changes in their neighbourhood. The formation and growth of precipitates and He-filled cavities was also investigated together with the elemental segregation to the cavity surfaces. It was found that the microstructural evolution in the three materials can take various forms depending on many parameters.

  15. Potential parent compound of superconductor: Sr 2CuM 2As 2O 2 (M = Mn, Fe)

    NASA Astrophysics Data System (ADS)

    Wang, Guangtao; Zhang, Minping; Zheng, Lihua; Yang, Zongxian

    2010-10-01

    The electronic structure of Sr 2CuMn 2As 2O 2 and Sr 2CuFe 2As 2O 2 are studied by the first-principle calculations. These compounds have a body-centered-tetragonal crystal structure that consists of the CuO 2 layers similar to those in the high- T cuprate superconductor, and intermetallic MAs (M = Mn, or Fe) layers similar to the FeAs layers in high- T pnictides. Such special structure makes them as interesting candidates for new type of superconductor since they have two types of superconducting layers. However, our calculations indicate that the states in the range from -2.0 eV to +2.0 eV are dominated by Mn-3d or Fe-3d states, while the states of Cu-3d are far away from the Fermi level (in the range from -3.0 eV to -1.0 eV). Such results are significantly different with the Cu-based superconductor, like La 2CuO 4, where the states around Fermi level are dominated by Cu-3d states. Besides, we find that the mean-field magnetic ground state is the checkerboard antiferromagnetic in Cu sublattice and the stripe antiferromagnetic in Fe (or Mn) sublattice.

  16. Synthetic, structural, spectroscopic and theoretical study of a Mn(III)-Cu(II) dimer containing a Jahn-Teller compressed Mn ion.

    PubMed

    Berg, Nelly; Hooper, Thomas N; Liu, Junjie; Beedle, Christopher C; Singh, Saurabh Kumar; Rajaraman, Gopalan; Piligkos, Stergios; Hill, Stephen; Brechin, Euan K; Jones, Leigh F

    2013-01-01

    The heterobimetallic complex [Cu(II)Mn(III)(L)(2)(py)(4)](ClO(4))·EtOH (1) built using the pro-ligand 2,2'-biphenol (LH(2)), contains a rare example of a Jahn-Teller compressed Mn(III) centre. Dc magnetic susceptibility measurements on 1 reveal a strong antiferromagnetic exchange between the Cu(II) and Mn(III) ions mediated through the phenolate O-atoms (J = -33.4 cm(-1)), with magnetisation measurements at low temperatures and high fields suggesting significant anisotropy. Simulations of high-field and high frequency powder EPR data suggest a single-ion anisotropy D(Mn(III)) = +4.45 cm(-1). DFT calculations also yield an antiferromagnetic exchange for 1, though the magnitude is overestimated (J(DFT) = -71 cm(-1)). Calculations reveal that the antiferromagnetic interaction essentially stems from the Mn(d(x(2)-y(2)))-Cu(d(x(2)-y(2))) interaction. The computed single-ion anisotropy and cluster anisotropy also correlates well with experiment. A larger cluster anisotropy for the S = 3/2 state compared to the single-ion anisotropy of Mn(III) is rationalised on the basis of orbital mixing and various contributions that arise due to the spin-orbit interaction. PMID:23108057

  17. A Prussian-blue type ferrimagnet Na[MnCr(CN)6]: single crystal structure and magnetic properties.

    PubMed

    Dong, Wen; Zhu, Li-Na; Song, Hai-Bin; Liao, Dai-Zheng; Jiang, Zong-Hui; Yan, Shi-Ping; Cheng, Peng; Gao, Song

    2004-04-19

    A novel Prussian-blue type ferrimagnet Na[MnCr(CN)(6)] has been prepared and characterized by single crystal X-ray analysis and magnetic measurements. The complex has a face-centered cubic lattice and shows ferrimagnetic ordering below 60 K. PMID:15074961

  18. Dielectric relaxation and magnetodielectric response in DyMn0.5Cr0.5O3

    NASA Astrophysics Data System (ADS)

    Yuan, B.; Yang, J.; Zuo, X. Z.; Kan, X. C.; Zu, L.; Zhu, X. B.; Dai, J. M.; Song, W. H.; Sun, Y. P.

    2015-09-01

    We investigate the structural, magnetic, and magnetodielectric properties of DyMn0.5Cr0.5O3. The sample can be indexed with an orthorhombic phase with B site disordered space group Pbnm. The valence state of both Mn and Cr ions are suggested to be +3 based on the results of x-ray photoelectron spectroscopy. Two thermally excited dielectric relaxation at temperatures TN2 < T< 300 K and large magnetodielectric effect (MDC = 20%-30%) due to the disordered arrangement of Mn3+/Cr3+ ions associated with electron hopping between them are observed. The absence of any noticeable magnetoresistance effect (MR < 0.5%) demonstrates that the observed magnetodielectric effect is an intrinsic behavior. These results suggest that DyMn0.5Cr0.5O3 is a magnetodielectric compound, whose dielectric properties are dependence of the applied magnetic field, which exhibits such effects near room temperature and holds great promise for future device applications.

  19. 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.

  20. 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.

  1. Thermal hysteresis of permeability and transport properties of Mn substituted Mg Cu Zn ferrites

    NASA Astrophysics Data System (ADS)

    Manjurul Haque, M.; Huq, M.; Hakim, M. A.

    2008-03-01

    Mn substituted Mg-Cu-Zn ferrites of composition Mg0.35Cu0.20Zn0.45O(Fe2-xMnx O3)0.97 have been prepared by the standard double sintering ceramic technique. X-ray diffraction patterns of the samples showed single phase cubic spinel structure without any detectable impurity phases. The lattice constant is found to increase linearly with increase in Mn3+ ion concentration obeying Vegard's law. The initial permeability (μi) of the Mg-Cu-Zn ferrites exhibits thermal hysteresis when the temperature is cycled from above the Curie temperature TC to below. The sharp decrease of μi at T = TC indicates that the samples have high homogeneity according to Globus et al. The Curie temperature TC of the studied ferrite system was determined from the μi-T curves where the Hopkinson type of effect at the TC has been observed with the manifestation of a sharp fall in permeability. The Curie temperature TC is found to increase with increasing Mn content. Dc electrical resistivity increases significantly with the increase in Mn content. The ac resistivity (ρac) and dielectric constant (ɛ') of the samples are found to decrease with increase in frequency, exhibiting normal ferrimagnetic behaviour. Dielectric relaxation peaks were observed for the frequency dependence of dielectric loss tangent curves. ɛ' increases as the temperature increases, which is the normal dielectric behaviour of the magnetic semiconductor ferrite. The observed variation of electrical and dielectric properties are explained on the basis of Fe2+/Fe3+ ionic concentration as well as the electronic hopping frequency between Fe2+ and Fe3+ ions in the present samples.

  2. 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.

  3. Adsorption and desorption of Zn, Cu, and Cr by sediments from the Raisin River (Michigan)

    SciTech Connect

    Young, T.C.; DePinto, J.V.; Kipp, T.W.

    1987-01-01

    Metal absorption by Raisin River sediments in vitro depended linearly on soluble metal concentration to adsorption densities of 6000-9000 ..mu..g/g with 48 hr partition coefficients of approximately 50, 30, and 25 L/g for Cu, Cr, and Zn, respectively. Partition coefficient computed from field data spanned a comparatively wider range of values in a manner consistent with the often reported adsorbent concentration effect, but other factors likely contributed, too. Desorption of Zn was complete and rapid in contrast to Cr, which was incomplete and much slower; Cu desorption was intermediate to Zn and Cr. A reversible-resistant equilibrium model could not describe the observations as Cu and Cr had not reached metastable desorption equilibria after 24 days. Metal desorption, however, could be described kinetically by distributing sorbed cations between either of two classes; rapidly desorbing and slowly desorbing cations. Sequential and simultaneous desorption models gave similar predictions. Aqueous chemical considerations suggested precipitated as well as adsorbed species could give rise to the observations, but available data did not permit adequate tests of this hypothesis. The extent to which kinetic constraints rather than irreversible reactions account for the desorption-resistant binding signifies a potentially greater metal mobility of bioavailability than would otherwise be assumed. 27 references, 5 figures, 4 tables.

  4. Adsorption and desorption of Zn, Cu, and Cr by sediments from the Raisi River (Michigan)

    SciTech Connect

    Young, T.C.; DePinto, J.V.; Kipp, T.W.

    1987-01-01

    Metal adsorption by Raisin River sediments in vitro depended linearly on soluble metal concentration to adsorption densities of 6,000-9,000 microg/g with 48 hr partition coefficients of approximately 50, 30, and 25 L/g for Cu, Cr, and Zn, respectively. Partition coefficients computed from field data spanned a comparatively wider range of values in a manner consistent with the often reported adsorbent concentration effect, but other factors likely contributed, too. Desorption of Zn was complete and rapid (24-48 hr) in contrast to Cr, which was incomplete and much slower; Cu desorption was intermediate to Zn and Cr. A reversible-resistant equilibrium model (DiToro et al. 1986) could not describe the observations as Cu and Cr had not reached metastable desorption equilibria after 24 days. Metal desorption, however, could be described kinetically by distributing sorbed cations between either of two classes; rapidly desorbing and slowly desorbing cations. Sequential and simultaneous desorption models gave similar predictions. Aqueous chemical considerations suggested precipitated as well as adsorbed species could give rise to the observations, but available data did not permit adequate tests of this hypothesis. The extent to which kinetic constraints rather than irreversible reactions account for the desorption-resistant binding signifies a potentially greater metal mobility or bioavailability than would otherwise be assumed.

  5. The effect of quaternary element on the thermodynamic parameters and structure of CuAlMn shape memory alloys

    NASA Astrophysics Data System (ADS)

    Aksu Canbay, C.; Karagoz, Z.

    2013-10-01

    In this study, the Cu-based shape memory alloys were produced by arc melting. We have investigated the effects of the alloying elements on the characteristic transformation temperatures, enthalpy, entropy values, and the structure of Cu-Al-Mn ternary system. The evolution of the transformation temperatures was studied by the differential scanning calorimetry. The characteristic transformation temperatures can be controlled by the variations in the aluminum and manganese content. Additionally, the effect of magnesium and iron on the transformation temperatures and thermodynamic parameters was investigated in the Cu-Al-Mn ternary system. The addition of the magnesium decreases the characteristic transformation temperatures of the Cu-Al-Mn system, but that of the iron increases. The structural changes of the samples were studied by X-ray diffraction measurements and optical microscope observations. Due to the low solubility of the magnesium, the magnesium addition into the Cu-Al-Mn system forms precipitates in the matrix. It is evaluated that the transformation parameters of the CuAlMn shape memory alloys can be controlled by the change of the alloying elements and the weight percentages of alloying elements.

  6. 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.

  7. Stabilization of As, Cr, Cu, Pb and Zn in soil using amendments--a review.

    PubMed

    Kumpiene, Jurate; Lagerkvist, Anders; Maurice, Christian

    2008-01-01

    The spread of contaminants in soil can be hindered by the soil stabilization technique. Contaminant immobilizing amendments decrease trace element leaching and their bioavailability by inducing various sorption processes: adsorption to mineral surfaces, formation of stable complexes with organic ligands, surface precipitation and ion exchange. Precipitation as salts and co-precipitation can also contribute to reducing contaminant mobility. The technique can be used in in situ and ex situ applications to reclaim and re-vegetate industrially devastated areas and mine-spoils, improve soil quality and reduce contaminant mobility by stabilizing agents and a beneficial use of industrial by-products. This study is an overview of data published during the last five years on the immobilization of one metalloid, As, and four heavy metals, Cr, Cu, Pb and Zn, in soils. The most extensively studied amendments for As immobilization are Fe containing materials. The immobilization of As occurs through adsorption on Fe oxides by replacing the surface hydroxyl groups with the As ions, as well as by the formation of amorphous Fe(III) arsenates and/or insoluble secondary oxidation minerals. Cr stabilization mainly deals with Cr reduction from its toxic and mobile hexavalent form Cr(VI) to stable in natural environments Cr(III). The reduction is accelerated in soil by the presence of organic matter and divalent iron. Clays, carbonates, phosphates and Fe oxides were the common amendments tested for Cu immobilization. The suggested mechanisms of Cu retention were precipitation of Cu carbonates and oxy-hydroxides, ion exchange and formation of ternary cation-anion complexes on the surface of Fe and Al oxy-hydroxides. Most of the studies on Pb stabilization were performed using various phosphorus-containing amendments, which reduce the Pb mobility by ionic exchange and precipitation of pyromorphite-type minerals. Zn can be successfully immobilized in soil by phosphorus amendments and clays

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

    DOE PAGESBeta

    Wu, Z.; Bei, H.

    2015-07-01

    Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with amore » composition of FeNiMnCr18 was successfully developed. This near-equiatomic FeNiMnCr18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.« less

  9. 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.

  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.