Sample records for ag fe ni

  1. Effect of NiO spin orientation on the magnetic anisotropy of the Fe film in epitaxially grown Fe/NiO/Ag(001) and Fe/NiO/MgO(001)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kim, W.; Jin, E.; Wu, J.

    Single crystalline Fe/NiO bilayers were epitaxially grown on Ag(001) and on MgO(001), and investigated by Low Energy Electron Diffraction (LEED), Magneto-Optic Kerr Effect (MOKE), and X-ray Magnetic Linear Dichroism (XMLD). We find that while the Fe film has an in-plane magnetization in both Fe/NiO/Ag(001) and Fe/NiO/MgO(001) systems, the NiO spin orientation changes from in-plane direction in Fe/NiO/Ag(001) to out-of-plane direction in Fe/NiO/MgO(001). These two different NiO spin orientations generate remarkable different effects that the NiO induced magnetic anisotropy in the Fe film is much greater in Fe/NiO/Ag(001) than in Fe/NiO/MgO(001). XMLD measurement shows that the much greater magnetic anisotropy inmore » Fe/NiO/Ag(001) is due to a 90{sup o}-coupling between the in-plane NiO spins and the in-plane Fe spins.« less

  2. Preparation, characterization, and antibacterial activity of NiFe2O4/PAMA/Ag-TiO2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Allafchian, Alireza; Jalali, Seyed Amir Hossein; Bahramian, Hamid; Ahmadvand, Hossein

    2016-04-01

    We have described a facile fabrication of silver deposited on the TiO2, Poly Acrylonitrile Co Maleic Anhydride (PAMA) polymer and nickel ferrite composite (NiFe2O4/PAMA/Ag-TiO2) through a three-step procedure. A pre-synthesized NiFe2O4 was first coated with PAMA polymer and then Ag-TiO2 was deposited on the surface of PAMA polymer shell. After the characterization of this three-component composite by various techniques, such as FTIR, XRD, FESEM, BET, TEM and VSM, it was impregnated in standard antibiotic discs. The antibacterial activity of NiFe2O4/PAMA/Ag-TiO2 nanocomposite was investigated against some gram positive and gram negative bacteria by employing disc diffusion assay and then compared with that of naked NiFe2O4, NiFe2O4/Ag, AgNPs and NiFe2O4/PAMA. The results demonstrated that the AgNPs, when embedded in TiO2 and combined with NiFe2O4/PAMA, became an excellent antibacterial agent. The NiFe2O4/PAMA/Ag-TiO2 nanocomposite could be readily separated from water solution after the disinfection process by applying an external magnetic field.

  3. Spin pumping and inverse Rashba-Edelstein effect in NiFe/Ag/Bi and NiFe/Ag/Sb

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Wei; Jungfleisch, Matthias B.; Jiang, Wanjun

    2015-03-20

    The Rashba effect is an interaction between the spin and the momentum of electrons induced by the spin-orbit coupling in surface or interface states. Here, we measured the inverse Rashba-Edelstein effect via spin pumping in Ag/Bi and Ag/Sb interfaces. The spin current is injected from the ferromagnetic resonance of a NiFe layer towards the Rashba interfaces, where it is further converted into a charge current. While using spin pumping theory, we quantify the conversion parameter of spin to charge current to be 0.11 ± 0.02 nm for Ag/Bi and a factor of ten smaller for Ag/Sb. Furthermore, the relative strengthmore » of the effect is in agreement with spectroscopic measurements and first principles calculations. The spin pumping experiment offers a straight-forward approach of using spin current as an efficient probe for detecting interface Rashba splitting.« less

  4. Containerless electromagnetic levitation melting of Cu-Fe and Ag-Ni alloys

    NASA Technical Reports Server (NTRS)

    Abbaschian, G. J.; Ethridge, E. C.

    1983-01-01

    The feasibility of producing silver or copper alloys containing finely dispersed nickel or iron particles, respectively, by utilizing containerless electromagnetic levitation casting techniques was investigated. A levitation coil was designed to successfully levitate and melt a variety of alloys including Nb-Ge, Cu-Fe, Fe-C, and Ag-Ni. Samples of 70 Cu-30 Fe and 80 Ag-20 Ni (atomic %), prepared by mechanical pressing of the constituent powders, were levitated and heated either to the solid plus liquid range of the alloys or to the fully liquid region. The samples were then solidified by passing helium gas into the bell jar or they were dropped into a quenching oil. The structure of the samples which were heated to the solid plus liquid range consists of uniform distribution of Fe or Ni particle in their respective matrices. A considerable amount of entrapped gas bubbles were contained. Upon heating for longer periods or to higher temperatures, the bubbles coalesced and burst, causing the samples to become fragmented and usually fall out of the coil.

  5. Spin pumping and inverse Rashba-Edelstein effect in NiFe/Ag/Bi and NiFe/Ag/Sb

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Wei, E-mail: zwei@anl.gov; Jungfleisch, Matthias B.; Jiang, Wanjun

    2015-05-07

    The Rashba effect is an interaction between the spin and the momentum of electrons induced by the spin-orbit coupling in surface or interface states. We measured the inverse Rashba-Edelstein effect via spin pumping in Ag/Bi and Ag/Sb interfaces. The spin current is injected from the ferromagnetic resonance of a NiFe layer towards the Rashba interfaces, where it is further converted into a charge current. Using spin pumping theory, we quantify the conversion parameter of spin to charge current to be 0.11 ± 0.02 nm for Ag/Bi and a factor of ten smaller for Ag/Sb. The relative strength of the effect is in agreementmore » with spectroscopic measurements and first principles calculations. We also vary the interlayer materials to study the voltage output in relation to the change of the effective spin mixing conductance. The spin pumping experiment offers a straight-forward approach of using spin current as an efficient probe for detecting interface Rashba splitting.« less

  6. Dependence of spin pumping and spin transfer torque upon Ni81Fe19 thickness in Ta/Ag /Ni 81Fe19/Ag/Co 2MnGe /Ag /Ta spin-valve structures

    NASA Astrophysics Data System (ADS)

    Durrant, C. J.; Shelford, L. R.; Valkass, R. A. J.; Hicken, R. J.; Figueroa, A. I.; Baker, A. A.; van der Laan, G.; Duffy, L. B.; Shafer, P.; Klewe, C.; Arenholz, E.; Cavill, S. A.; Childress, J. R.; Katine, J. A.

    2017-10-01

    Spin pumping has been studied within Ta / Ag / Ni81Fe19 (0-5 nm) / Ag (6 nm) / Co2MnGe (5 nm) / Ag / Ta large-area spin-valve structures, and the transverse spin current absorption of Ni81Fe19 sink layers of different thicknesses has been explored. In some circumstances, the spin current absorption can be inferred from the modification of the Co2MnGe source layer damping in vector network analyzer ferromagnetic resonance (VNA-FMR) experiments. However, the spin current absorption is more accurately determined from element-specific phase-resolved x-ray ferromagnetic resonance (XFMR) measurements that directly probe the spin transfer torque (STT) acting on the sink layer at the source layer resonance. Comparison with a macrospin model allows the real part of the effective spin mixing conductance to be extracted. We find that spin current absorption in the outer Ta layers has a significant impact, while sink layers with thicknesses of less than 0.6 nm are found to be discontinuous and superparamagnetic at room temperature, and lead to a noticeable increase of the source layer damping. For the thickest 5-nm sink layer, increased spin current absorption is found to coincide with a reduction of the zero frequency FMR linewidth that we attribute to improved interface quality. This study shows that the transverse spin current absorption does not follow a universal dependence upon sink layer thickness but instead the structural quality of the sink layer plays a crucial role.

  7. Dependence of spin pumping and spin transfer torque upon Ni 81 Fe 19 thickness in Ta / Ag / Ni 81 Fe 19 / Ag / Co 2 MnGe / Ag / Ta spin-valve structures

    DOE PAGES

    Durrant, C. J.; Shelford, L. R.; Valkass, R. A. J.; ...

    2017-10-18

    Spin pumping has been studied within Ta / Ag / Ni 81Fe 19 (0–5 nm) / Ag (6 nm) / Co 2MnGe (5 nm) / Ag / Ta large-area spin-valve structures, and the transverse spin current absorption of Ni 81Fe 19 sink layers of different thicknesses has been explored. In some circumstances, the spin current absorption can be inferred from the modification of the Co 2MnGe source layer damping in vector network analyzer ferromagnetic resonance (VNA-FMR) experiments. However, the spin current absorption is more accurately determined from element-specific phase-resolved x-ray ferromagnetic resonance (XFMR) measurements that directly probe the spin transfermore » torque (STT) acting on the sink layer at the source layer resonance. Comparison with a macrospin model allows the real part of the effective spin mixing conductance to be extracted. We find that spin current absorption in the outer Ta layers has a significant impact, while sink layers with thicknesses of less than 0.6 nm are found to be discontinuous and superparamagnetic at room temperature, and lead to a noticeable increase of the source layer damping. For the thickest 5-nm sink layer, increased spin current absorption is found to coincide with a reduction of the zero frequency FMR linewidth that we attribute to improved interface quality. Furthermore, this study shows that the transverse spin current absorption does not follow a universal dependence upon sink layer thickness but instead the structural quality of the sink layer plays a crucial role.« less

  8. Dependence of spin pumping and spin transfer torque upon Ni 81 Fe 19 thickness in Ta / Ag / Ni 81 Fe 19 / Ag / Co 2 MnGe / Ag / Ta spin-valve structures

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Durrant, C. J.; Shelford, L. R.; Valkass, R. A. J.

    Spin pumping has been studied within Ta / Ag / Ni 81Fe 19 (0–5 nm) / Ag (6 nm) / Co 2MnGe (5 nm) / Ag / Ta large-area spin-valve structures, and the transverse spin current absorption of Ni 81Fe 19 sink layers of different thicknesses has been explored. In some circumstances, the spin current absorption can be inferred from the modification of the Co 2MnGe source layer damping in vector network analyzer ferromagnetic resonance (VNA-FMR) experiments. However, the spin current absorption is more accurately determined from element-specific phase-resolved x-ray ferromagnetic resonance (XFMR) measurements that directly probe the spin transfermore » torque (STT) acting on the sink layer at the source layer resonance. Comparison with a macrospin model allows the real part of the effective spin mixing conductance to be extracted. We find that spin current absorption in the outer Ta layers has a significant impact, while sink layers with thicknesses of less than 0.6 nm are found to be discontinuous and superparamagnetic at room temperature, and lead to a noticeable increase of the source layer damping. For the thickest 5-nm sink layer, increased spin current absorption is found to coincide with a reduction of the zero frequency FMR linewidth that we attribute to improved interface quality. Furthermore, this study shows that the transverse spin current absorption does not follow a universal dependence upon sink layer thickness but instead the structural quality of the sink layer plays a crucial role.« less

  9. Synthesis and characterization of the NiFe2O4@TEOS-TPS@Ag nanocomposite and investigation of its antibacterial activity

    NASA Astrophysics Data System (ADS)

    Allafchian, Ali R.; Jalali, S. A. H.; Amiri, R.; Shahabadi, Sh.

    2016-11-01

    In this study, the NiFe2O4 was embedded in (3-mercaptopropyl) trimethoxysilane (TPS) and tetraethyl orthosilicate (TEOS) using the sol-gel method. These compounds were used as the support of Ag nanoparticles (Ag NPs). The NiFe2O4@TEOS-TPS@Ag nanocomposites were obtained with the development of bonding between the silver atoms of Ag NPs and the sulfur atoms of TPS molecule. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used for the characterization of the Ag nanocomposites. Also, the magnetic properties of these nanocomposites were studied by using a vibrating sample magnetometer (VSM) technique. The disk diffusion, minimum inhibition concentration (MIC) and minimum bactericidal concentrations (MBC) tests were used for the investigation of the antibacterial effect of this nanocomposite against bacterial strains. The synthesized nanocomposite presented high reusability and good antibacterial activity against gram-positive and gram-negative bacteria. Remarkably, this nanocomposite could be easily removed from the disinfected media by magnetic decantation.

  10. Study of structural phase transitions in quinary TiNi(MoFeAg)-based alloys

    NASA Astrophysics Data System (ADS)

    Gunther, Victor; Marchenko, Ekaterina; Chekalkin, Timofey; Baigonakova, Gulsharat; Kang, Ji-hoon; Kim, Ji-soon; Klopotov, Anatoliy

    2017-10-01

    The structural phase transitions of quinary Ti50Ni49.5-X Mo0.3Fe0.2Ag X (X  =  0, 0.1, 0.2, 0.5, 1.0, and 1.5 at%) alloys prepared by vacuum-induction melting were studied by means of the four-point-probe, x-ray diffraction (XRD), and optical microscopy methods after thermal cycling. The two-stage B2 ↔ R ↔ B19‧ reversible martensitic transformation (MT) took place in all the investigated samples. It is found that the substitution of Ag for Ni in the studied alloy when C Ag  =  0-0.5 at%, reduces the T R, M s, and M f characteristic points by 20-30 K, whereas they increase by 15-35 K when the Ag content was varied from 1.0 to 1.5 at% and the B2 ↔ R ↔ B19‧ MT was realized in the high-temperature area. XRD patterns of the studied alloys recorded at the ambient temperature detected the pure Ag phase as well as Ti2Ni precipitate with a small volume fraction (up to 5%) alongside with structural lines of B2, R, and B19‧ phases.

  11. Novel Fe3O4@SiO2@Ag@Ni trepang-like nanocomposites: High-efficiency and magnetic recyclable catalysts for organic dye degradation

    NASA Astrophysics Data System (ADS)

    Li, Chao; Sun, Jun-Jie; Chen, Duo; Han, Guang-Bing; Yu, Shu-Yun; Kang, Shi-Shou; Mei, Liang-Mo

    2016-08-01

    A facile step-by-step approach is developed for synthesizing the high-efficiency and magnetic recyclable Fe3O4@SiO2@Ag@Ni trepang-like nanocomposites. This method involves coating Fe2O3 nanorods with a uniform silica layer, reduction in 10% H2/Ar atmosphere to transform the Fe2O3 into magnetic Fe3O4, and finally depositing Ag@Ni core-shell nanoparticles on the L-lysine modified surface of Fe3O4@SiO2 nanorods. The fabricated nanocomposites are further characterized by x-ray diffraction, transmission electron microscopy, scanning electron microscope, Fourier transform infrared spectroscopy, and inductively coupled plasma mass spectroscopy. The Fe3O4@SiO2@Ag@Ni trepang-like nanocomposites exhibit remarkably higher catalytic efficiency than monometallic Fe3O4@SiO2@Ag nanocomposites toward the degradation of Rhodamine B (RhB) at room temperature, and maintain superior catalytic activity even after six cycles. In addition, these samples could be easily separated from the catalytic system by an external magnet and reused, which shows great potential applications in treating waste water. Project supported by the National Basic Research Program of China (Grant No. 2015CB921502), the National Natural Science Foundation of China (Grant Nos. 11474184 and 11174183), the 111 Project (Grant No. B13029), and the Fundamental Research Funds of Shandong University, China.

  12. Failure Mechanisms of SAC/Fe-Ni Solder Joints During Thermal Cycling

    NASA Astrophysics Data System (ADS)

    Gao, Li-Yin; Liu, Zhi-Quan; Li, Cai-Fu

    2017-08-01

    Thermal cycling tests have been conducted on Sn-Ag-Cu/Fe- xNi ( x = 73 wt.% or 45 wt.%) and Sn-Ag-Cu/Cu solder joints according to the Joint Electron Device Engineering Council industrial standard to study their interfacial reliability under thermal stress. The interfacial intermetallic compounds formed for solder joints on Cu, Fe-73Ni, and Fe-45Ni were 4.5 μm, 1.7 μm, and 1.4 μm thick, respectively, after 3000 cycles, demonstrating excellent diffusion barrier effect of Fe-Ni under bump metallization (UBM). Also, two deformation modes, viz. solder extrusion and fatigue crack formation, were observed by scanning electron microscopy and three-dimensional x-ray microscopy. Solder extrusion dominated for solder joints on Cu, while fatigue cracks dominated for solder joints on Fe-45Ni and both modes were detected for those on Fe-73Ni. Solder joints on Fe-Ni presented inferior reliability during thermal cycling compared with those on Cu, with characteristic lifetime of 3441 h, 3190 h, and 1247 h for Cu, Fe-73Ni, and Fe-45Ni UBM, respectively. This degradation of the interfacial reliability for solder joints on Fe-Ni is attributed to the mismatch in coefficient of thermal expansion (CTE) at interconnection level. The CTE mismatch at microstructure level was also analyzed by electron backscatter diffraction for clearer identification of recrystallization-related deformation mechanisms.

  13. Ferromagnetic resonance investigation in as-prepared NiFe/FeMn/NiFe trilayer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yuan, S. J.; Xu, K.; Yu, L. M.

    2007-06-01

    NiFe/FeMn/NiFe trilayer prepared by dc magnetron sputtering was systematically investigated by ferromagnetic resonance technique (FMR) at room temperature. For NiFe/FeMn/NiFe trilayer, there are two distinct resonance peaks both in in-plane and out-of-plane FMR spectra, which are attributed to the two NiFe layers, respectively. The isotropic in-plane resonance field shift is negative for the bottom NiFe layer, while positive for the top NiFe layer. And, such phenomena result from the negative interfacial perpendicular anisotropy at the bottom NiFe/FeMn interface and positive interfacial perpendicular anisotropy at the top FeMn/NiFe interface. The linewidth of the bottom NiFe layer is larger than that ofmore » the top NiFe layer, which might be related to the greater exchange coupling at the bottom NiFe/FeMn interface.« less

  14. Cu2O Photocathode for Low Bias Photoelectrochemical Water Splitting Enabled by NiFe-Layered Double Hydroxide Co-Catalyst

    PubMed Central

    Qi, Huan; Wolfe, Jonathan; Fichou, Denis; Chen, Zhong

    2016-01-01

    Layered double hydroxides (LDHs) are bimetallic hydroxides that currently attract considerable attention as co-catalysts in photoelectrochemical (PEC) systems in view of water splitting under solar light. A wide spectrum of LDHs can be easily prepared on demand by tuning their chemical composition and structural morphology. We describe here the electrochemical growth of NiFe-LDH overlayers on Cu2O electrodes and study their PEC behavior. By using the modified Cu2O/NiFe-LDH electrodes we observe a remarkable seven-fold increase of the photocurrent intensity under an applied voltage as low as −0.2 V vs Ag/AgCl. The origin of such a pronounced effect is the improved electron transfer towards the electrolyte brought by the NiFe-LDH overlayer due to an appropriate energy level alignment. Long-term photostability tests reveal that Cu2O/NiFe-LDH photocathodes show no photocurrent loss after 40 hours of operation under light at −0.2 V vs Ag/AgCl low bias condition. These improved performances make Cu2O/NiFe-LDH a suitable photocathode material for low voltage H2 production. Indeed, after 8 hours of H2 production under −0.2 V vs Ag/AgCl the PEC cell delivers a 78% faradaic efficiency. This unprecedented use of Cu2O/NiFe-LDH as an efficient photocathode opens new perspectives in view of low biasd or self-biased PEC water splitting under sunlight illumination. PMID:27487918

  15. The Effect of Metal Composition on Fe-Ni Partition Behavior between Olivine and FeNi-Metal, FeNi-Carbide, FeNi-Sulfide at Elevated Pressure

    NASA Technical Reports Server (NTRS)

    Holzheid, Astrid; Grove, Timothy L.

    2005-01-01

    Metal-olivine Fe-Ni exchange distribution coefficients were determined at 1500 C over the pressure range of 1 to 9 GPa for solid and liquid alloy compositions. The metal alloy composition was varied with respect to the Fe/Ni ratio and the amount of dissolved carbon and sulfur. The Fe/Ni ratio of the metal phase exercises an important control on the abundance of Ni in the olivine. The Ni abundance in the olivine decreases as the Fe/Ni ratio of the coexisting metal increases. The presence of carbon (up to approx. 3.5 wt.%) and sulfur (up to approx. 7.5 wt.%) in solution in the liquid Fe-Ni-metal phase has a minor effect on the partitioning of Fe and Ni between metal and olivine phases. No pressure dependence of the Fe-Ni-metal-olivine exchange behavior in carbon- and sulfur-free and carbon- and sulfur-containing systems was found within the investigated pressure range. To match the Ni abundance in terrestrial mantle olivine, assuming an equilibrium metal-olivine distribution, a sub-chondritic Fe/Ni-metal ratio that is a factor of 17 to 27 lower than the Fe/Ni ratios in estimated Earth core compositions would be required, implying higher Fe concentrations in the core forming metal phase. A simple metal-olivine equilibrium distribution does not seem to be feasible to explain the Ni abundances in the Earth's mantle. An equilibrium between metal and olivine does not exercise a control on the problem of Ni overabundance in the Earth's mantle. The experimental results do not contradict the presence of a magma ocean at the time of terrestrial core formation, if olivine was present in only minor amounts at the time of metal segregation.

  16. Viscosities of Fe Ni, Fe Co and Ni Co binary melts

    NASA Astrophysics Data System (ADS)

    Sato, Yuzuru; Sugisawa, Koji; Aoki, Daisuke; Yamamura, Tsutomu

    2005-02-01

    Viscosities of three binary molten alloys consisting of the iron group elements, Fe, Ni and Co, have been measured by using an oscillating cup viscometer over the entire composition range from liquidus temperatures up to 1600 °C with high precision and excellent reproducibility. The viscosities measured showed good Arrhenius linearity for all the compositions. The viscosities of Fe, Ni and Co as a function of temperature are as follows: \\eqalign{ & \\log \\eta={-}0.6074 + 2493/T\\qquad for\\quad Fe\\\\ & \\log \\eta={-}0.5695 + 2157/T\\qquad for\\quad Ni \\\\ & \\log \\eta={-}0.6620 + 2430/T\\qquad for\\quad Co.} The isothermal viscosities of Fe-Ni and Fe-Co binary melts increase monotonically with increasing Fe content. On the other hand, in Ni-Co binary melt, the isothermal viscosity decreases slightly and then increases with increasing Co. The activation energy of Fe-Co binary melt increased slightly on mixing, and those of Fe-Ni and Ni-Co melts decreased monotonically with increasing Ni content. The above behaviour is discussed based on the thermodynamic properties of the alloys.

  17. Enhancement of magnetoresistance by inserting thin NiAl layers at the interfaces in Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5}/Ag/Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5} current-perpendicular-to-plane pseudo spin valves

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jung, J. W.; Sakuraba, Y., E-mail: Sakuraba.Yuya@nims.go.jp; Sasaki, T. T.

    2016-03-07

    We have investigated the effects of insertion of a thin NiAl layer (≤0.63 nm) into a Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5} (CFGG)/Ag interface on the magnetoresistive properties in CFGG/Ag/CFGG current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo spin valves (PSVs). First-principles calculations of ballistic transmittance clarified that the interfacial band matching at the (001)-oriented NiAl/CFGG interface is better than that at the (001)-Ag/CFGG interface. The insertion of 0.21-nm-thick NiAl layers at the Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5}/Ag interfaces effectively improved the magnetoresistance (MR) output; the observed average and the highest MR ratio (ΔRA) are 62% (25 mΩ μm{sup 2}) and 77% (31 mΩ μm{sup 2}) atmore » room temperature, respectively, which are much higher than those without NiAl insertion. Microstructural analysis using scanning transmission electron microscopy confirmed the existence of thin NiAl layers at the Ag interfaces with only modest interdiffusion even after annealing at 550 °C. The improvement of the interfacial spin-dependent scattering by very thin NiAl insertion can be a predominant reason for the enhancement of the MR output.« less

  18. Morphological and Microstructural Evolution of Phosphorous-Rich Layer in SnAgCu/Ni-P UBM Solder Joint

    NASA Astrophysics Data System (ADS)

    Lin, Yung-Chi; Shih, Toung-Yi; Tien, Shih-Kang; Duh, Jenq-Gong

    2007-11-01

    Interfacial morphologies and microstructure of Sn-3Ag-0.5Cu/Ni-P under bump metallization (UBM) with various phosphorous contents were investigated by transmission electron microscope (TEM) and field emission electron probe microanalyzer (FE-EPMA). It was revealed that as the Ni-Sn-P compound was formed between the solder matrix and Ni-P UBM, the conventionally so-called phosphorous-rich (P-rich) layer was transformed to a series of layer compounds, including Ni3P, Ni12P5 and Ni2P. The relationship between Ni-Sn-P formation and evolution of P-rich layers was probed by electron microscopic characterization with the aid of the phase diagram of Ni-P. On the basis of the TEM micrograph, the selected area diffraction (SAD) pattern, and the FE-EPMA results, the detailed phase evolution of P-rich layers in the SnAgCu/Ni-P joint was revealed and proposed.

  19. The reactivity of Fe/Ni colloid stabilized by carboxymethylcellulose (CMC-Fe/Ni) toward chloroform.

    PubMed

    Jin, Xin; Li, Qun; Yang, Qi

    2018-05-16

    The use of stabilizers can prevent the reactivity loss of nanoparticles due to aggregation. In this study, carboxymethylcellulose (CMC) was selected as the stabilizer to synthesize a highly stable CMC-stabilized Fe/Ni colloid (CMC-Fe/Ni) via pre-aggregation stabilization. The reactivity of CMC-Fe/Ni was evaluated via the reaction of chloroform (CF) degradation. The effect of background solution which composition was affected by the preparation of Fe/Ni (Fe/Ni precursors, NaBH 4 dosage) and the addition of solute (common ions, sulfur compounds) on the reactivity of CMC-Fe/Ni was also investigated. Additionally, the dried CMC-Fe/Ni was used for characterization in terms of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The experimental results indicated that CMC stabilization greatly improved the reactivity of Fe/Ni bimetal and CF (10 mg/L) could be completely degraded by CMC-Fe/Ni (0.1 g/L) within 45 min. The use of different Fe/Ni precursors resulting in the variations of background solution seemed to have no obvious influence on the reactivity of CMC-Fe/Ni, whereas the dosage of NaBH 4 in background solution showed a negative correlation with the reactivity of CMC-Fe/Ni. Besides, the individual addition of external solutes into background solution all had an adverse effect on the reactivity of CMC-Fe/Ni, of which the poisoning effect of sulfides (Na 2 S, Na 2 S 2 O 4 ) was significant than common ions and sulfite.

  20. Phase Equilibria and Thermodynamic Descriptions of Ag-Ge and Ag-Ge-Ni Systems

    NASA Astrophysics Data System (ADS)

    Rajkumar, V. B.; Chen, Sinn-Wen

    2018-07-01

    Gibbs energy modeling of Ag-Ge and Ag-Ge-Ni systems was done using the calculation of the phase diagram method with associated data from this work and relevant literature information. In the Ag-Ge system, the solidus temperatures of Ag-rich alloys are measured using differential thermal analysis, and the energy of mixing for the FCC_A1 phase is calculated using the special quasi-random structures technique. The isothermal sections of the Ag-Ge-Ni system at 1023 K and 673 K are also experimentally determined. These data and findings in the relevant literature are used to model the Gibbs energy of the Ag-Ge and Ag-Ge- Ni systems. A reaction scheme and a liquidus projection of the Ag-Ge-Ni system are determined.

  1. Control of Surface Segregation in Bimetallic NiCr Nanoalloys Immersed in Ag Matrix

    PubMed Central

    Bohra, Murtaza; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Toulkeridou, Evropi; Diaz, Rosa E.; Bobo, Jean-François; Sowwan, Mukhles

    2016-01-01

    Cr-surface segregation is a main roadblock encumbering many magneto-biomedical applications of bimetallic M-Cr nanoalloys (where M = Fe, Co and Ni). To overcome this problem, we developed Ni95Cr5:Ag nanocomposite as a model system, consisting of non-interacting Ni95Cr5 nanoalloys (5 ± 1 nm) immersed in non-magnetic Ag matrix by controlled simultaneous co-sputtering of Ni95Cr5 and Ag. We employed Curie temperature (TC) as an indicator of phase purity check of these nanocomposites, which is estimated to be around the bulk Ni95Cr5 value of 320 K. This confirms prevention of Cr-segregation and also entails effective control of surface oxidation. Compared to Cr-segregated Ni95Cr5 nanoalloy films and nanoclusters, we did not observe any unwanted magnetic effects such as presence Cr-antiferromagnetic transition, large non-saturation, exchange bias behavior (if any) or uncompensated higher TC values. These nanocomposites films also lose their unique magnetic properties only at elevated temperatures beyond application requirements (≥800 K), either by showing Ni-type behavior or by a complete conversion into Ni/Cr-oxides in vacuum and air environment, respectively. PMID:26750659

  2. Ab initio Study of Ag-Based Fluoroperovskite AgMF3 (M = Co and Ni) Compounds

    NASA Astrophysics Data System (ADS)

    Mubarak, A. A.

    2018-01-01

    Ab initio calculations of Ag-based fluoroperovskite AgMF3 (M = Co and Ni) compounds are investigated using the full-potential linearized augmented plane wave method. Wien2k and BoltzTrap codes are used to calculate the different physical properties. The structural parameters of the present compounds are within reasonable agreement with previous calculations. This study shows that AgCoF3 and AgNiF3 are anisotropic, ductile, mechanically and thermodynamically stable compounds, where AgCoF3 is found to be stiffer and less compressible than AgNiF3. The spin-polarized electronic band structure illustrates that AgCoF3 is metallic, while AgNiF3 is a semiconductor with indirect (M-D) band gap energy of 0.43 eV. The bonding force between atoms is found to be mainly ionic with some covalent nature. The total magnetic moment of AgCoF3 (3.04 μ B) is found to be higher than that calculated for AgNiF3 (2.00 μ B). Using the magnetic susceptibility calculations, AgCoF3 is classified as antiferromagnetic, whereas AgNiF3 is a ferromagnetic compound. The calculated static refractive index of AgCoF3 (3.85) and AgNiF3 (3.60) is inversely proportional with the energy band gap. Suitable applications are predicted for AgCoF3 and AgNiF3 based on their absorption and reflection properties. Furthermore, beneficial thermoelectric applications are expected for the present compounds due to their large Seebeck coefficient ( S_{{{{AgCoF}}_{ 3} }} = 2.92 × 103 μ {V/K} {and} S_{{{{AgNiF}}3 }} = 2.84 × 103 μ {V/K} ) and their thermoelectric power factor with respect to relaxation time ( S2 σ /t_{{AgNiF3 }} = 1.11 × 109 {W/K}^{ 2} {and} S2 σ /t_{{AgNiF3 }} = 1.28 × 10^{11} {W/K}^{ 2} ).

  3. Two phase microstructure for Ag-Ni nanowires

    NASA Astrophysics Data System (ADS)

    Srivastava, Chandan; Rai, Rajesh Kumar

    2013-03-01

    In the present study, electrodeposition technique was used to produce Ag-Ni nanowires. Ag-Ni system shows extremely high bulk immiscibility. Nanowire morphology was achieved by employing an anodic alumina membrane having pores of ˜200 nm diameter. Microstructure of as-deposited wire was composed of nano-sized solid solution structured Ag-Ni nanoparticles embedded in a matrix of pure Ag phase. It is proposed that the two phase microstructure resulted from an initial formation of solid solution structured nanoparticles in the alumina template pore followed by nucleation of pure Ag phase over the particles which eventually grew to form the matrix phase.

  4. Cooling field and ion-beam bombardment effects on exchange bias behavior in NiFe/(Ni,Fe)O bilayers.

    PubMed

    Lin, K W; Wei, M R; Guo, J Y

    2009-03-01

    The dependence of the cooling field and the ion-beam bombardment on the exchange bias effects in NiFe/(Ni,Fe)O bilayers were investigated. The positive exchange bias was found in the zero-field-cooled (ZFC) process whereas a negative exchange bias occurred in the FC process. The increased exchange field, H(ex) with increasing (Ni,Fe)O thicknesses indicates the thicker the AF (Ni,Fe)O, the stronger the exchange coupling between the NiFe layer and the (Ni,Fe)O layer. In addition, the dependence of the H(ex) (ZFC vs. FC) on the (Ni,Fe)O thicknesses reflects the competition between the applied magnetic field and the (Ni,Fe)O surface layer exchange coupled to the NiFe layer. Further, an unusual oscillating exchange bias was observed in NiFe/(Ni,Fe)O bilayers that results from the surface of the (Ni,Fe)O layer being bombarded with different Ar-ion energies using End-Hall deposition voltages (V(EH)) from 0 to 150 V. The behavior of the H(ex) and the H(c) with the V(EH) is attributed to the surface spin reorientation that is due to moderate ion-beam bombardment effects on the surface of the (Ni,Fe)O layer. Whether the (Ni,Fe)O antiferromagnetic spins are coupled to the NiFe moments antiferromagnetically or ferromagnetically changes the sign of the exchange bias.

  5. Energy-converting [NiFe] hydrogenases: more than just H2 activation.

    PubMed

    Hedderich, Reiner; Forzi, Lucia

    2005-01-01

    The well-characterized [NiFe] hydrogenases have a key function in the H2 metabolism of various microorganisms. A subfamily of the [NiFe] hydrogenases with unique properties has recently been identified. The six conserved subunits that build the core of these membrane-bound hydrogenases share sequence similarity with subunits that form the catalytic core of energy-conserving NADH:quinone oxidoreductases (complex I). The physiological role of some of these hydrogenases is to catalyze the reduction of H+ with electrons derived from reduced ferredoxins or polyferredoxins. This exergonic reaction is coupled to energy conservation by means of electron-transport phosphorylation. Other members of this hydrogenase subfamily mainly function in providing the cell with reduced ferredoxin using H2 as electron donor in a reaction driven by reverse electron transport. These hydrogenases have therefore been designated as energy-converting [NiFe] hydrogenases. Copyright 2005 S. Karger AG, Basel.

  6. Effects of Ag addition on FePt L1{sub 0} ordering transition: A direct observation of ordering transition and Ag segregation in FePtAg alloy films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Lei; Yu, Youxing, E-mail: yuyouxing@buaa.edu.cn; Gao, Tenghua

    FePt and (FePt){sub 91.2}Ag{sub 8.8} alloy films were deposited by magnetron sputtering. The average coercivity of (FePt){sub 91.2}Ag{sub 8.8} films reaches 8.51 × 10{sup 5} A/m, which is 0.63 × 10{sup 5} A/m higher than that of the corresponding FePt films. Ag addition effectively promotes the FePt L1{sub 0} ordering transition at a relatively low annealing temperature of 400 °C. The promotion mechanism was investigated by using in situ high-resolution transmission electron microscopy (HRTEM) and ex situ X-ray absorption fine structure (XAFS). The concurrence of ordering transition and Ag segregation in FePtAg alloy films was first observed by using in situ heating HRTEM. The time-resolved evolution revealsmore » more details on the role of Ag addition in FePt low-temperature ordering. Ex situ XAFS results further confirm that Ag replaces Fe sites in the as-deposited films and segregates from FePt-Ag solid solution phase through annealing at elevated temperatures. The segregation of Ag atoms leaves vacancies in the grain. The vacancy formation is believed to accelerate the diffusion of Fe and Pt atoms, which is critical for the L1{sub 0} ordering transition.« less

  7. Structural features of [NiFeSe] and [NiFe] hydrogenases determining their different properties: a computational approach.

    PubMed

    Baltazar, Carla S A; Teixeira, Vitor H; Soares, Cláudio M

    2012-04-01

    Hydrogenases are metalloenzymes that catalyze the reversible reaction H(2)<->2H(+) + 2e(-), being potentially useful in H(2) production or oxidation. [NiFeSe] hydrogenases are a particularly interesting subgroup of the [NiFe] class that exhibit tolerance to O(2) inhibition and produce more H(2) than standard [NiFe] hydrogenases. However, the molecular determinants responsible for these properties remain unknown. Hydrophobic pathways for H(2) diffusion have been identified in [NiFe] hydrogenases, as have proton transfer pathways, but they have never been studied in [NiFeSe] hydrogenases. Our aim was, for the first time, to characterize the H(2) and proton pathways in a [NiFeSe] hydrogenase and compare them with those in a standard [NiFe] hydrogenase. We performed molecular dynamics simulations of H(2) diffusion in the [NiFeSe] hydrogenase from Desulfomicrobium baculatum and extended previous simulations of the [NiFe] hydrogenase from Desulfovibrio gigas (Teixeira et al. in Biophys J 91:2035-2045, 2006). The comparison showed that H(2) density near the active site is much higher in [NiFeSe] hydrogenase, which appears to have an alternative route for the access of H(2) to the active site. We have also determined a possible proton transfer pathway in the [NiFeSe] hydrogenase from D. baculatum using continuum electrostatics and Monte Carlo simulation and compared it with the proton pathway we found in the [NiFe] hydrogenase from D. gigas (Teixeira et al. in Proteins 70:1010-1022, 2008). The residues constituting both proton transfer pathways are considerably different, although in the same region of the protein. These results support the hypothesis that some of the special properties of [NiFeSe] hydrogenases could be related to differences in the H(2) and proton pathways. © SBIC 2012

  8. Heterobimetallic [NiFe] Complexes Containing Mixed CO/CN- Ligands: Analogs of the Active Site of the [NiFe] Hydrogenases.

    PubMed

    Perotto, Carlo U; Sodipo, Charlene L; Jones, Graham J; Tidey, Jeremiah P; Blake, Alexander J; Lewis, William; Davies, E Stephen; McMaster, Jonathan; Schröder, Martin

    2018-03-05

    The development of synthetic analogs of the active sites of [NiFe] hydrogenases remains challenging, and, in spite of the number of complexes featuring a [NiFe] center, those featuring CO and CN - ligands at the Fe center are under-represented. We report herein the synthesis of three bimetallic [NiFe] complexes [Ni( N 2 S 2 )Fe(CO) 2 (CN) 2 ], [Ni( S 4 )Fe(CO) 2 (CN) 2 ], and [Ni( N 2 S 3 )Fe(CO) 2 (CN) 2 ] that each contain a Ni center that bridges through two thiolato S donors to a {Fe(CO) 2 (CN) 2 } unit. X-ray crystallographic studies on [Ni( N 2 S 3 )Fe(CO) 2 (CN) 2 ], supported by DFT calculations, are consistent with a solid-state structure containing distinct molecules in the singlet ( S = 0) and triplet ( S = 1) states. Each cluster exhibits irreversible reduction processes between -1.45 and -1.67 V vs Fc + /Fc and [Ni( N 2 S 3 )Fe(CO) 2 (CN) 2 ] possesses a reversible oxidation process at 0.17 V vs Fc + /Fc. Spectroelectrochemical infrared (IR) and electron paramagnetic resonance (EPR) studies, supported by density functional theory (DFT) calculations, are consistent with a Ni III Fe II formulation for [Ni( N 2 S 3 )Fe(CO) 2 (CN) 2 ] + . The singly occupied molecular orbital (SOMO) in [Ni( N 2 S 3 )Fe(CO) 2 (CN) 2 ] + is based on Ni 3d z 2 and 3p S with the S contributions deriving principally from the apical S-donor. The nature of the SOMO corresponds to that proposed for the Ni-C state of the [NiFe] hydrogenases for which a Ni III Fe II formulation has also been proposed. A comparison of the experimental structures, and the electrochemical and spectroscopic properties of [Ni( N 2 S 3 )Fe(CO) 2 (CN) 2 ] and its [Ni( N 2 S 3 )] precursor, together with calculations on the oxidized [Ni( N 2 S 3 )Fe(CO) 2 (CN) 2 ] + and [Ni( N 2 S 3 )] + forms suggests that the binding of the {Fe(CO)(CN) 2 } unit to the {Ni(CysS) 4 } center at the active site of the [NiFe] hydrogenases suppresses thiolate-based oxidative chemistry involving the bridging thiolate S donors

  9. 3D Computer Models of T- x- y Diagrams, Forming the Fe-Ni-Co-FeS-NiS-CoS Subsystem

    NASA Astrophysics Data System (ADS)

    Lutsyk, V. I.; Vorob'eva, V. P.

    2017-12-01

    3D computer models of Fe-Ni-Co, Fe-Ni-FeS-NiS, Fe-Co-FeS-CoS, Ni-Co-NiS-CoS T- x- y diagrams have been designed. The geometric structure (35 surfaces, two-phase surface of the reaction type change, 17 phase regions) of the Fe-Ni-FeS-NiS T- x- y diagram is investigated in detail. The liquidus hypersurfaces prediction of the Fe-Ni-Co-FeS-NiS-CoS subsystem is represented.

  10. Modulated exchange bias in NiFe/CoO/α-Fe2O3 trilayers and NiFe/CoO bilayers

    NASA Astrophysics Data System (ADS)

    Li, X.; Lin, K.-W.; Yeh, W.-C.; Desautels, R. D.; van Lierop, J.; Pong, Philip W. T.

    2017-02-01

    While the exchange bias in ferromagnetic/antiferromagnetic (FM/AF) bilayer and FM1/AF/FM2 trilayer configurations has been widely investigated, the role of an AF2 layer in FM/AF1/AF2 trilayer configurations is still not well understood. In this work, the magnetic properties of NiFe/CoO, NiFe/α-Fe2O3 bilayers, and NiFe/CoO/α-Fe2O3 trilayer were studied comparatively. The microstructure and chemical composition were characterized. Temperature dependent magnetometry reveals increased irreversibility temperature in NiFe/CoO/α-Fe2O3 trilayer compared with NiFe/CoO bilayer. The magnetic hysteresis loops show that the exchange bias (Hex) and coercivity (Hc) depend strongly on the anisotropy of AF layer (CoO, α-Fe2O3 and CoO/α-Fe2O3). Our work shows that the AF1/AF2 interfacial interactions can be used effectively for tuning the exchange bias in FM/AF1/AF2 trilayers.

  11. Novel reactions of homodinuclear Ni2 complexes [Ni(RNPyS4)]2 with Fe3(CO)12 to give heterotrinuclear NiFe2 and mononuclear Fe complexes relevant to [NiFe]- and [Fe]-hydrogenases.

    PubMed

    Song, Li-Cheng; Cao, Meng; Wang, Yong-Xiang

    2015-04-21

    The homodinuclear complexes [Ni(RNPyS4)]2 (; RNPyS4 = 2,6-bis(2-mercaptophenylthiomethyl)-4-R-pyridine; R = H, MeO, Cl, Br, i-Pr) were found to be prepared by reactions of the in situ generated Li2[Ni(1,2-S2C6H4)2] with 2,6-bis[(tosyloxy)methyl]pyridine and its substituted derivatives 2,6-bis[(tosyloxy)methyl]-4-R-pyridine. Further reactions of with Fe3(CO)12 gave both heterotrinuclear complexes NiFe2(RNPyS4)(CO)5 () and mononuclear complexes Fe(RNPyS4)(CO) (), unexpectedly. Interestingly, complexes and could be regarded as models for the active sites of [NiFe]- and [Fe]-hydrogenases, respectively. All the prepared complexes were characterized by elemental analysis, spectroscopy, and particularly for some of them, by X-ray crystallography. In addition, the electrochemical properties of and as well as the electrocatalytic H2 production catalyzed by and were investigated by CV techniques.

  12. Fabrication of ordered Fe–Ni nitride film with equiatomic Fe/Ni ratio

    NASA Astrophysics Data System (ADS)

    Takata, Fumiya; Ito, Keita; Suemasu, Takashi

    2018-05-01

    We successfully grew a single-phase tetragonal FeNiN film with an equiatomic ratio of Fe, Ni, and N on a MgO(001) substrate by molecular beam epitaxy. We then demonstrated the formation of Fe2Ni2N films by extracting N atoms from the FeNiN film. These results suggested that Fe and Ni atoms in the Fe2Ni2N film were L10-ordered along the film plane direction because of the a-axis orientation growth of the FeNiN film on the MgO(001) substrate.

  13. A dithiolate-bridged (CN)2(CO)Fe-Ni complex reproducing the IR bands of [NiFe] hydrogenase.

    PubMed

    Tanino, Soichiro; Li, Zilong; Ohki, Yasuhiro; Tatsumi, Kazuyuki

    2009-03-16

    A dithiolate-bridged dinuclear Fe-Ni complex, which has the desired fac-(CN)(2)(CO) ligand set at iron, has been synthesized. Its CN/CO bands in the IR spectrum reproduce those of the Ni-A, Ni-B, and Ni-SU states, which indicate that these octahedral Fe(II) centers have similar electronic properties. This result verifies the assignment of a (CN)(2)(CO)Fe(II) moiety in the active site of [NiFe] hydrogenase.

  14. 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer spin valve component investigated by polarized neutron reflectometry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Callori, S. J., E-mail: sara.callori@ansto.gov.au; Bertinshaw, J.; Bragg Institute, Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234

    2014-07-21

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

  15. [FeFe]- and [NiFe]-hydrogenase diversity, mechanism, and maturation.

    PubMed

    Peters, John W; Schut, Gerrit J; Boyd, Eric S; Mulder, David W; Shepard, Eric M; Broderick, Joan B; King, Paul W; Adams, Michael W W

    2015-06-01

    The [FeFe]- and [NiFe]-hydrogenases catalyze the formal interconversion between hydrogen and protons and electrons, possess characteristic non-protein ligands at their catalytic sites and thus share common mechanistic features. Despite the similarities between these two types of hydrogenases, they clearly have distinct evolutionary origins and likely emerged from different selective pressures. [FeFe]-hydrogenases are widely distributed in fermentative anaerobic microorganisms and likely evolved under selective pressure to couple hydrogen production to the recycling of electron carriers that accumulate during anaerobic metabolism. In contrast, many [NiFe]-hydrogenases catalyze hydrogen oxidation as part of energy metabolism and were likely key enzymes in early life and arguably represent the predecessors of modern respiratory metabolism. Although the reversible combination of protons and electrons to generate hydrogen gas is the simplest of chemical reactions, the [FeFe]- and [NiFe]-hydrogenases have distinct mechanisms and differ in the fundamental chemistry associated with proton transfer and control of electron flow that also help to define catalytic bias. A unifying feature of these enzymes is that hydrogen activation itself has been restricted to one solution involving diatomic ligands (carbon monoxide and cyanide) bound to an Fe ion. On the other hand, and quite remarkably, the biosynthetic mechanisms to produce these ligands are exclusive to each type of enzyme. Furthermore, these mechanisms represent two independent solutions to the formation of complex bioinorganic active sites for catalyzing the simplest of chemical reactions, reversible hydrogen oxidation. As such, the [FeFe]- and [NiFe]-hydrogenases are arguably the most profound case of convergent evolution. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Controllable synthesis and enhanced microwave absorbing properties of Fe3O4/NiFe2O4/Ni heterostructure porous rods

    NASA Astrophysics Data System (ADS)

    Li, Yana; Wu, Tong; Jin, Keying; Qian, Yao; Qian, Naxin; Jiang, Kedan; Wu, Wenhua; Tong, Guoxiu

    2016-11-01

    We developed a coordinated self-assembly/precipitate transfer/sintering method that allows the controllable synthesis of Fe3O4/NiFe2O4/Ni heterostructure porous rods (HPRs). A series of characterizations confirms that changing [Ni2+] can effectively control the crystal size, internal strain, composition, textural characteristics, and properties of HPRs. Molar percentages of Ni and NiFe2O4 in HPRs increase with [Ni2+] in various Boltzmann function modes. Saturation magnetization Ms and coercivity Hc show U-shaped change trends because of crystal size, composition, and interface magnetic coupling. High magnetic loss is maintained after decorating NiFe2O4 and Ni on the surface of Fe3O4 PRs. Controlling the NiFe2O4 interface layers and Ni content can improve impedance matching and dielectric losses, thereby leading to lighter weight, stronger absorption, and broader absorption band of Fe3O4/NiFe2O4/Ni HPRs than Fe3O4 PRs. An optimum EM wave absorbing property was exhibited by Fe3O4/NiFe2O4/Ni HPRs formed at [Ni2+] = 0.05 M. The maximum reflection loss (RL) reaches -58.4 dB at 13.68 GHz, which corresponds to a 2.1 mm matching thickness. The absorbing bandwidth (RL ≤ -20 dB) reaches 14.4 GHz with the sample thickness at 1.6-2.4 and 2.8-10.0 mm. These excellent properties verify that Fe3O4/NiFe2O4/Ni HPRs are promising candidates for new and effective absorptive materials.

  17. Phase Decomposition in the Fe-rich Fe-Ni-S System from 900 Degrees C to 300 Degrees C--Application to Meteoritic Metal

    NASA Astrophysics Data System (ADS)

    Ma, L.; Williams, D. B.; Goldstein, J. I.

    1995-09-01

    phase forms in the Fe-Ni-S system at higher temperatures (500 degrees C) than in the Fe-Ni and Fe-Ni (P) systems (<400 degrees C) [4]. Because the tetrataenite phase forms in the Fe-Ni-S system at higher temperatures, the tetrataenite rim in chondrites should be much wider than that in other meteorites where phase growth is controlled by the presence of P. It is possible that the Ni distribution in the metal phases of chondrites is dictated by the g/FeS and g/FeS/g' tie-line variations rather than by a/g tie-lines in the case of iron or stony iron meteorites. References: [1] Holland-Duffield C. E. et al. (1991) Meteoritics, 26, 97-103. [2] Kullerud G. (1963) Carnegie Inst. Wash. Yearb., 62, 175-189. [3] Clark L. A. and Kullerud G. (1963) Econ. Geol., 58, 853-885. [4] Yang C. W. (1994) Ph.D. dissertation, Lehigh Univ.

  18. [NiFeSe]-hydrogenase chemistry.

    PubMed

    Wombwell, Claire; Caputo, Christine A; Reisner, Erwin

    2015-11-17

    The development of technology for the inexpensive generation of the renewable energy vector H2 through water splitting is of immediate economic, ecological, and humanitarian interest. Recent interest in hydrogenases has been fueled by their exceptionally high catalytic rates for H2 production at a marginal overpotential, which is presently only matched by the nonscalable noble metal platinum. The mechanistic understanding of hydrogenase function guides the design of synthetic catalysts, and selection of a suitable hydrogenase enables direct applications in electro- and photocatalysis. [FeFe]-hydrogenases display excellent H2 evolution activity, but they are irreversibly damaged upon exposure to O2, which currently prevents their use in full water splitting systems. O2-tolerant [NiFe]-hydrogenases are known, but they are typically strongly biased toward H2 oxidation, while H2 production by [NiFe]-hydrogenases is often product (H2) inhibited. [NiFeSe]-hydrogenases are a subclass of [NiFe]-hydrogenases with a selenocysteine residue coordinated to the active site nickel center in place of a cysteine. They exhibit a combination of unique properties that are highly advantageous for applications in water splitting compared with other hydrogenases. They display a high H2 evolution rate with marginal inhibition by H2 and tolerance to O2. [NiFeSe]-hydrogenases are therefore one of the most active molecular H2 evolution catalysts applicable in water splitting. Herein, we summarize our recent progress in exploring the unique chemistry of [NiFeSe]-hydrogenases through biomimetic model chemistry and the chemistry with [NiFeSe]-hydrogenases in semiartificial photosynthetic systems. We gain perspective from the structural, spectroscopic, and electrochemical properties of the [NiFeSe]-hydrogenases and compare them with the chemistry of synthetic models of this hydrogenase active site. Our synthetic models give insight into the effects on the electronic properties and reactivity of

  19. Fe Oxides on Ag Surfaces: Structure and Reactivity

    DOE PAGES

    Shipilin, M.; Lundgren, E.; Gustafson, J.; ...

    2016-09-09

    One layer thick iron oxide films are attractive from both applied and fundamental science perspectives. The structural and chemical properties of these systems can be tuned by changing the substrate, making them promising materials for heterogeneous catalysis. In the present work, we investigate the structure of FeO(111) monolayer films grown on Ag(100) and Ag(111) substrates by means of microscopy and diffraction techniques and compare it with the structure of FeO(111) grown on other substrates reported in literature. We also study the NO adsorption properties of FeO(111)/Ag(100) and FeO(111)/Ag(111) systems utilizing different spectroscopic techniques. Finally, we discuss similarities and differences inmore » the data obtained from adsorption experiments and compare it with previous results for FeO(111)/Pt(111).« less

  20. Fe Oxides on Ag Surfaces: Structure and Reactivity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shipilin, M.; Lundgren, E.; Gustafson, J.

    One layer thick iron oxide films are attractive from both applied and fundamental science perspectives. The structural and chemical properties of these systems can be tuned by changing the substrate, making them promising materials for heterogeneous catalysis. In the present work, we investigate the structure of FeO(111) monolayer films grown on Ag(100) and Ag(111) substrates by means of microscopy and diffraction techniques and compare it with the structure of FeO(111) grown on other substrates reported in literature. We also study the NO adsorption properties of FeO(111)/Ag(100) and FeO(111)/Ag(111) systems utilizing different spectroscopic techniques. Finally, we discuss similarities and differences inmore » the data obtained from adsorption experiments and compare it with previous results for FeO(111)/Pt(111).« less

  1. Local lattice distortion in NiCoCr, FeCoNiCr and FeCoNiCrMn concentrated alloys investigated by synchrotron X-ray diffraction

    DOE PAGES

    Tong, Yang; Jin, Ke; Bei, Hongbin; ...

    2018-05-26

    Severe lattice distortion is presumptively considered as a core effect of high-entropy alloys, but quantitative measurements are still missing. Here, we demonstrate that the lattice distortion in high-entropy alloys can be quantitatively analyzed based on pair distribution function obtained from synchrotron X-ray diffraction. By applying this method to equiatomic NiCoCr, FeCoNiCr and FeCoNiCrMn concentrated alloys, we found that the local lattice distortion in the NiCoCr (0.23%) and FeCoNiCrMn (0.24%) alloys are comparable while negligible in the FeCoNiCr alloy (0.04%). Furthermore, the origin of local lattice distortion in the NiCoCr and FeCoNiCrMn concentrated alloys was discussed.

  2. Local lattice distortion in NiCoCr, FeCoNiCr and FeCoNiCrMn concentrated alloys investigated by synchrotron X-ray diffraction

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tong, Yang; Jin, Ke; Bei, Hongbin

    Severe lattice distortion is presumptively considered as a core effect of high-entropy alloys, but quantitative measurements are still missing. Here, we demonstrate that the lattice distortion in high-entropy alloys can be quantitatively analyzed based on pair distribution function obtained from synchrotron X-ray diffraction. By applying this method to equiatomic NiCoCr, FeCoNiCr and FeCoNiCrMn concentrated alloys, we found that the local lattice distortion in the NiCoCr (0.23%) and FeCoNiCrMn (0.24%) alloys are comparable while negligible in the FeCoNiCr alloy (0.04%). Furthermore, the origin of local lattice distortion in the NiCoCr and FeCoNiCrMn concentrated alloys was discussed.

  3. Flexible bottom-emitting white organic light-emitting diodes with semitransparent Ni/Ag/Ni anode.

    PubMed

    Koo, Ja-Ryong; Lee, Seok Jae; Lee, Ho Won; Lee, Dong Hyung; Yang, Hyung Jin; Kim, Woo Young; Kim, Young Kwan

    2013-05-06

    We fabricated a flexible bottom-emitting white organic light-emitting diode (BEWOLED) with a structure of PET/Ni/Ag/Ni (3/6/3 nm)/ NPB (50 nm)/mCP (10 nm)/7% FIrpic:mCP (10 nm)/3% Ir(pq)(2) acac:TPBi (5 nm)/7% FIrpic:TPBi (5 nm)/TPBi (10 nm)/Liq (2 nm)/ Al (100 nm). To improve the performance of the BEWOLED, a multilayered metal stack anode of Ni/Ag/Ni treated with oxygen plasma for 60 sec was introduced into the OLED devices. The Ni/Ag/Ni anode effectively enhanced the probability of hole-electron recombination due to an efficient hole injection into and charge balance in an emitting layer. By comparing with a reference WOLED using ITO on glass, it is verified that the flexible BEWOLED showed a similar or better electroluminescence (EL) performance.

  4. Euhedral metallic-Fe-Ni grains in extraterrestrial samples

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1993-01-01

    Metallic Fe-Ni is rare in terrestrial rocks, being largely restricted to serpentinized peridotites and volcanic rocks that assimilated carbonaceous material. In contrast, metallic Fe-Ni is nearly ubiquitous among extraterrestrial samples (i.e., meteorites, lunar rocks, and interplanetary dust particles). Anhedral grains are common. For example, in eucrites and lunar basalts, most of the metallic Fe-Ni occurs interstitially between silicate grains and thus tends to have irregular morphologies. In many porphyritic chondrules, metallic Fe-Ni and troilite form rounded blebs in the mesostasis because their precursors were immiscible droplets. In metamorphosed ordinary chondrites, metallic Fe-Ni and troilite form coarse anhedral grains. Some of the metallic Fe-Ni and troilite grains has also been mobilized and injected into fractures in adjacent silicate grains where local shock-reheating temperatures reached the Fe-FeS eutectic (988 C). In interplanetary dust particles metallic Fe-Ni most commonly occurs along with sulfide as spheroids and fragments. Euhedral metallic Fe-Ni grains are extremely rare. Several conditions must be met before such grains can form: (1) grain growth must occur at free surfaces, restricting euhedral metallic Fe-Ni grains to systems that are igneous or undergoing vapor-deposition; (2) the metal (+/-) sulfide assemblage must have an appropriate bulk composition so that taenite is the liquidus phase in igneous systems or the stable condensate phase in vapor-deposition systems; and (3) metallic Fe-Ni grains must remain underformed during subsequent compaction, thermal metamorphism, and shock. Because of these restrictions, the occurrence of euhedral metallic Fe-Ni grains in an object can potentially provide important petrogenetic information. Despite its rarity, euhedral metallic Fe-Ni occurs in a wide variety of extraterrestrial materials. Some of these materials formed in the solar nebula; others formed on parent body surfaces by meteoroid

  5. Coexistence of unipolar and bipolar resistive switching behaviors in NiFe2O4 thin film devices by doping Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Hao, Aize; Ismail, Muhammad; He, Shuai; Huang, Wenhua; Qin, Ni; Bao, Dinghua

    2018-02-01

    The coexistence of unipolar and bipolar resistive switching (RS) behaviors of Ag-nanoparticles (Ag-NPs) doped NiFe2O4 (NFO) based memory devices was investigated. The switching voltages of required operations in the unipolar mode were smaller than those in the bipolar mode, while ON/OFF resistance levels of both modes were identical. Ag-NPs doped NFO based devices could switch between the unipolar and bipolar modes just by preferring the polarity of RESET voltage. Besides, the necessity of identical compliance current during the SET process of unipolar and bipolar modes provided an additional advantage of simplicity in device operation. Performance characteristics and cycle-to-cycle uniformity (>103 cycles) in unipolar operation were considerably better than those in bipolar mode (>102 cycles) at 25 °C. Moreover, good endurance (>600 cycles) at 200 °C was observed in unipolar mode and excellent nondestructive retention characteristics were obtained on memory cells at 125 °C and 200 °C. On the basis of temperature dependence of resistance at low resistance state, it was believed that physical origin of the RS mechanism involved the formation/rupture of the conducting paths consisting of oxygen vacancies and Ag atoms, considering Joule heating and electrochemical redox reaction effects for the unipolar and bipolar resistive switching behaviors. Our results demonstrate that 0.5% Ag-NPs doped nickel ferrites are promising resistive switching materials for resistive access memory applications.

  6. Fluorescence x-ray absorption fine structure studies of Fe-Ni-S and Fe-Ni-Si melts to 1600 K

    NASA Astrophysics Data System (ADS)

    Manghnani, M. H.; Hong, X.; Balogh, J.; Amulele, G.; Sekar, M.; Newville, M.

    2008-04-01

    We report NiK -edge fluorescence x-ray absorption fine structure spectra (XAFS) for Fe0.75Ni0.05S0.20 and Fe0.75Ni0.05Si0.20 ternary alloys from room temperature up to 1600 K. A high-temperature furnace designed for these studies incorporates two x-ray transparent windows and enables both a vertical orientation of the molten sample and a wide opening angle, so that XAFS can be measured in the fluorescence mode with a detector at 90° with respect to the incident x-ray beam. An analysis of the Ni XAFS data for these two alloys indicates different local structural environments for Ni in Fe0.75Ni0.05S0.20 and Fe0.75Ni0.05Si0.20 melts, with more Ni-Si coordination than Ni-S coordination persisting from room temperature through melting. These results suggest that light elements such as S and Si may impact the structural and chemical properties of Fe-Ni alloys with a composition similar to the earth’s core.

  7. High thermally stable Ni /Ag(Al) alloy contacts on p-GaN

    NASA Astrophysics Data System (ADS)

    Chou, C. H.; Lin, C. L.; Chuang, Y. C.; Bor, H. Y.; Liu, C. Y.

    2007-01-01

    Ag agglomeration was found to occur at Ni /Ag to p-GaN contacts after annealing at 500°C. This Ag agglomeration led to the poor thermal stability showed by the Ni /Ag contacts in relation to the reflectivity and electrical properties. However, after alloying with 10at.% Al by e-gun deposition, the Ni /Ag(Al) p-GaN contacts were found to effectively retard Ag agglomeration thereby greatly enhancing the thermal stability. Based on the x-ray photoelectron spectroscopy analysis, the authors believe that the key for the retardation of Ag agglomeration was the formation of ternary Al-Ni-O layer at p-GaN interface.

  8. High thermally stable Ni/Ag(Al) alloy contacts on p-GaN

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chou, C. H.; Lin, C. L.; Chuang, Y. C.

    2007-01-08

    Ag agglomeration was found to occur at Ni/Ag to p-GaN contacts after annealing at 500 degree sign C. This Ag agglomeration led to the poor thermal stability showed by the Ni/Ag contacts in relation to the reflectivity and electrical properties. However, after alloying with 10 at. % Al by e-gun deposition, the Ni/Ag(Al) p-GaN contacts were found to effectively retard Ag agglomeration thereby greatly enhancing the thermal stability. Based on the x-ray photoelectron spectroscopy analysis, the authors believe that the key for the retardation of Ag agglomeration was the formation of ternary Al-Ni-O layer at p-GaN interface.

  9. Air breathing cathodes for microbial fuel cell using Mn-, Fe-, Co- and Ni-containing platinum group metal-free catalysts

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kodali, Mounika; Santoro, Carlo; Serov, Alexey

    Here we discuss the oxygen reduction reaction (ORR) is one of the major factors that is limiting the overall performance output of microbial fuel cells (MFC). In this study, Platinum Group Metal-free (PGM-free) ORR catalysts based on Fe, Co, Ni, Mn and the same precursor (Aminoantipyrine, AAPyr) were synthesized using identical sacrificial support method (SSM). The catalysts were investigated for their electrochemical performance, and then integrated into an air-breathing cathode to be tested in “clean” environment and in a working microbial fuel cell (MFC). Their performances were also compared to activated carbon (AC) based cathode under similar conditions. Results showedmore » that the addition of Mn, Fe, Co and Ni to AAPyr increased the performances compared to AC. Fe-AAPyr showed the highest open circuit potential (OCP) that was 0.307 ± 0.001 V (vs. Ag/AgCl) and the highest electrocatalytic activity at pH 7.5. On the contrary, AC had an OCP of 0.203 ± 0.002 V (vs. Ag/AgCl) and had the lowest electrochemical activity. In MFC, Fe-AAPyr also had the highest output of 251 ± 2.3 μWcm –2, followed by Co-AAPyr with 196 ± 1.5 μWcm –2, Ni-AAPyr with 171 ± 3.6 μWcm –2, Mn-AAPyr with 160 ± 2.8 μWcm –2 and AC 129 ± 4.2 μWcm –2. The best performing catalyst (Fe-AAPyr) was then tested in MFC with increasing solution conductivity from 12.4 mScm –1 to 63.1 mScm –1. A maximum power density of 482 ± 5 μWcm –2 was obtained with increasing solution conductivity, which is one of the highest values reported in the field.« less

  10. Air breathing cathodes for microbial fuel cell using Mn-, Fe-, Co- and Ni-containing platinum group metal-free catalysts

    DOE PAGES

    Kodali, Mounika; Santoro, Carlo; Serov, Alexey; ...

    2017-02-07

    Here we discuss the oxygen reduction reaction (ORR) is one of the major factors that is limiting the overall performance output of microbial fuel cells (MFC). In this study, Platinum Group Metal-free (PGM-free) ORR catalysts based on Fe, Co, Ni, Mn and the same precursor (Aminoantipyrine, AAPyr) were synthesized using identical sacrificial support method (SSM). The catalysts were investigated for their electrochemical performance, and then integrated into an air-breathing cathode to be tested in “clean” environment and in a working microbial fuel cell (MFC). Their performances were also compared to activated carbon (AC) based cathode under similar conditions. Results showedmore » that the addition of Mn, Fe, Co and Ni to AAPyr increased the performances compared to AC. Fe-AAPyr showed the highest open circuit potential (OCP) that was 0.307 ± 0.001 V (vs. Ag/AgCl) and the highest electrocatalytic activity at pH 7.5. On the contrary, AC had an OCP of 0.203 ± 0.002 V (vs. Ag/AgCl) and had the lowest electrochemical activity. In MFC, Fe-AAPyr also had the highest output of 251 ± 2.3 μWcm –2, followed by Co-AAPyr with 196 ± 1.5 μWcm –2, Ni-AAPyr with 171 ± 3.6 μWcm –2, Mn-AAPyr with 160 ± 2.8 μWcm –2 and AC 129 ± 4.2 μWcm –2. The best performing catalyst (Fe-AAPyr) was then tested in MFC with increasing solution conductivity from 12.4 mScm –1 to 63.1 mScm –1. A maximum power density of 482 ± 5 μWcm –2 was obtained with increasing solution conductivity, which is one of the highest values reported in the field.« less

  11. Bimetallic NiFe2O4 synthesized via confined carburization in NiFe-MOFs for efficient oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Fang, Zhiqiang; Hao, Zhaomin; Dong, Qingsong; Cui, Yong

    2018-04-01

    Transition metal oxides that derived from metal-organic framework (MOF) precursor have intensively received attention because of their numerous electrochemical applications. Bimetallic Ni-Fe oxides have been rarely reported on the basis of MOF-related strategy. Herein, a bimetallic NiFe2O4 was successfully synthesized via confined carburization in NiFe-MOF precursors and characterized by XRD, XPS, SEM, and TEM. After conducting an investigation of oxygen evolution reaction (OER), the as-synthesized NiFe2O4 material exhibited good catalytic efficiency and high stability and durability in alkaline media. The as-synthesized NiFe2O4 material would promote the development of MOFs in non-noble-metal OER catalyst.

  12. Effect of Ni on Fe FeS phase relations at high pressure and high temperature

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Fei, Yingwei

    2008-04-01

    A series of melting experiments in the Fe-rich portion of the Fe-Ni-S system have been conducted at 19-23 GPa and 800-1100 °C. The solubility of S in the Fe-Ni solid alloy and the eutectic melting in the Fe-Ni-S system were determined as a function of Ni content. The maximum S solubility in the Fe-Ni alloy is 2.7 wt.% at 20 GPa and the eutectic temperature. The eutectic melting temperature in the Fe-Ni(5wt.%)-S system is ~ 1000 °C lower than the melting point of pure Fe at 20 GPa. We also found that Ni can substitute Fe in the Fe 3S structure to form (Fe,Ni) 3S solid solutions up to at least a Fe/Ni atomic ratio of 0.5. Similar to melting behavior in the Fe-FeS system, the eutectic melting relations in the Fe-Ni-S system could produce inner and outer cores with the right light element balance to account for the density difference between the solid inner core and the liquid outer core.

  13. Thermodynamic Modeling of Ag-Ni System Combining Experiments and Molecular Dynamic Simulation

    NASA Astrophysics Data System (ADS)

    Rajkumar, V. B.; Chen, Sinn-wen

    2017-04-01

    Ag-Ni is a simple and important system with immiscible liquids and (Ag,Ni) phases. Previously, this system has been thermodynamically modeled utilizing certain thermochemical and phase equilibria information based on conjecture. An attempt is made in this study to determine the missing information which are difficult to measure experimentally. The boundaries of the liquid miscibility gap at high temperatures are determined using a pyrometer. The temperature of the liquid ⇌ (Ag) + (Ni) eutectic reaction is measured using differential thermal analysis. Tie-lines of the Ag-Ni system at 1023 K and 1473 K are measured using a conventional metallurgical method. The enthalpy of mixing of the liquid at 1773 K and the (Ag,Ni) at 973 K is calculated by molecular dynamics simulation using a large-scale atomic/molecular massively parallel simulator. These results along with literature information are used to model the Gibbs energy of the liquid and (Ag,Ni) by a calculation of phase diagrams approach, and the Ag-Ni phase diagram is then calculated.

  14. Ag[Fe(CO)5]2(+) : a bare silver complex with Fe(CO)5 as a ligand.

    PubMed

    Malinowski, Przemysław J; Krossing, Ingo

    2014-12-01

    Attempts to prepare Fe(CO)5 (+) from Ag[Al(OR(F) )4 ] (R(F) =C(CF3 )3 ) and Fe(CO)5 in CH2 Cl2 yielded the first complex of a neutral metal carbonyl bound to a simple metal cation. The Ag[Fe(CO)5 ]2 (+) cation consists of two Fe(CO)5 molecules coordinating Ag(+) in an almost linear fashion. The ν(CO) modes are blue-shifted compared to Fe(CO)5 , with one band above 2143 cm(-1) indicating that back-bonding is heavily decreased in the Ag[Fe(CO)5 ]2 (+) cation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Control of the transition between Ni-C and Ni-SI(a) states by the redox state of the proximal Fe-S cluster in the catalytic cycle of [NiFe] hydrogenase.

    PubMed

    Tai, Hulin; Nishikawa, Koji; Suzuki, Masayuki; Higuchi, Yoshiki; Hirota, Shun

    2014-12-08

    [NiFe] hydrogenase catalyzes the reversible cleavage of H2. The electrons produced by the H2 cleavage pass through three Fe-S clusters in [NiFe] hydrogenase to its redox partner. It has been reported that the Ni-SI(a), Ni-C, and Ni-R states of [NiFe] hydrogenase are involved in the catalytic cycle, although the mechanism and regulation of the transition between the Ni-C and Ni-SI(a) states remain unrevealed. In this study, the FT-IR spectra under light irradiation at 138-198 K show that the Ni-L state of [NiFe] hydrogenase is an intermediate between the transition of the Ni-C and Ni-SI(a) states. The transition of the Ni-C state to the Ni-SI(a) state occurred when the proximal [Fe4S4]p(2+/+) cluster was oxidized, but not when it was reduced. These results show that the catalytic cycle of [NiFe] hydrogenase is controlled by the redox state of its [Fe4S4]p(2+/+) cluster, which may function as a gate for the electron flow from the NiFe active site to the redox partner. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Hierachical Ni@Fe2O3 superparticles through epitaxial growth of γ-Fe2O3 nanorods on in situ formed Ni nanoplates

    NASA Astrophysics Data System (ADS)

    Tahir, Muhammad Nawaz; Herzberger, Jana; Natalio, Filipe; Köhler, Oskar; Branscheid, Robert; Mugnaioli, Enrico; Ksenofontov, Vadim; Panthöfer, Martin; Kolb, Ute; Frey, Holger; Tremel, Wolfgang

    2016-05-01

    One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@γ-Fe2O3 superparticles containing Ni cores densely covered with highly oriented γ-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)2) and Fe(CO)5. Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mössbauer spectroscopy showed that selective and oriented growth of the γ-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 interface. The common orientation of the maghemite nanorods on the Ni core of the superparticles leads to a greatly enhanced magnetization. After functionalization with a catechol-functional polyethylene glycol (C-PEG) ligand the Ni@γ-Fe2O3 superparticles were dispersible in water.One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@γ-Fe2O3 superparticles containing Ni cores densely covered with highly oriented γ-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)2) and Fe(CO)5. Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mössbauer spectroscopy showed that selective and oriented growth of the γ-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 interface. The common orientation of the maghemite nanorods on the Ni core of the superparticles leads to a greatly enhanced magnetization. After functionalization with a catechol-functional polyethylene glycol (C-PEG) ligand the Ni@γ-Fe2O3 superparticles were dispersible in water. Electronic supplementary

  17. Battery Relevant Electrochemistry of Ag 7Fe 3(P 2O 7 ) 4 : Contrasting Contributions from the Redox Chemistries of Ag + and Fe 3+

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Yiman; Kirshenbaum, Kevin C.; Marschilok, Amy C.

    Ag 7Fe 3(P 2O 7 ) 4 is an example of an electrochemical displacement material which contains two different electrochemically active metal cations, where one cation (Ag +) forms metallic silver nanoparticles external to the crystals of Ag 7Fe 3(P 2O 7 ) 4 via an electrochemical reduction displacement reaction, while the other cation (Fe +3) is electrochemically reduced with the retention of iron cations within the anion structural framework concomitant with lithium insertion. These contrasting redox chemistries within one pure cathode material enable high rate capability and reversibility when Ag 7Fe 3(P 2O 7 ) 4 is employed asmore » cathode material in a lithium ion battery (LIB). Further, pyrophosphate materials are thermally and electrically stable, desirable attributes for cathode materials in LIBs. In this article, a bimetallic pyrophosphate material Ag 7Fe 3(P 2O 7 ) 4 is synthesized and confirmed to be a single phase by Rietveld refinement. Electrochemistry of Ag 7Fe 3(P 2O 7 ) 4 is reported for the first time in the context of lithium based batteries using cyclic voltammetry and galvanostatic discharge–charge cycling. The reduction displacement reaction and the lithium (de)insertion processes are investigated using ex situ X-ray absorption spectroscopy and X-ray diffraction of electrochemically reduced and oxidized Ag 7Fe 3(P 2O 7 ) 4. Ag 7Fe 3(P 2O 7 ) 4 exhibits good reversibility at the iron centers indicated by ~80% capacity retention over 100 cycles following the initial formation cycle and excellent rate capability exhibited by ~70% capacity retention upon a 4-fold increase in current.« less

  18. Battery Relevant Electrochemistry of Ag 7Fe 3(P 2O 7 ) 4 : Contrasting Contributions from the Redox Chemistries of Ag + and Fe 3+

    DOE PAGES

    Zhang, Yiman; Kirshenbaum, Kevin C.; Marschilok, Amy C.; ...

    2016-10-12

    Ag 7Fe 3(P 2O 7 ) 4 is an example of an electrochemical displacement material which contains two different electrochemically active metal cations, where one cation (Ag +) forms metallic silver nanoparticles external to the crystals of Ag 7Fe 3(P 2O 7 ) 4 via an electrochemical reduction displacement reaction, while the other cation (Fe +3) is electrochemically reduced with the retention of iron cations within the anion structural framework concomitant with lithium insertion. These contrasting redox chemistries within one pure cathode material enable high rate capability and reversibility when Ag 7Fe 3(P 2O 7 ) 4 is employed asmore » cathode material in a lithium ion battery (LIB). Further, pyrophosphate materials are thermally and electrically stable, desirable attributes for cathode materials in LIBs. In this article, a bimetallic pyrophosphate material Ag 7Fe 3(P 2O 7 ) 4 is synthesized and confirmed to be a single phase by Rietveld refinement. Electrochemistry of Ag 7Fe 3(P 2O 7 ) 4 is reported for the first time in the context of lithium based batteries using cyclic voltammetry and galvanostatic discharge–charge cycling. The reduction displacement reaction and the lithium (de)insertion processes are investigated using ex situ X-ray absorption spectroscopy and X-ray diffraction of electrochemically reduced and oxidized Ag 7Fe 3(P 2O 7 ) 4. Ag 7Fe 3(P 2O 7 ) 4 exhibits good reversibility at the iron centers indicated by ~80% capacity retention over 100 cycles following the initial formation cycle and excellent rate capability exhibited by ~70% capacity retention upon a 4-fold increase in current.« less

  19. The effect of Fe2NiO4 and Fe4NiO4Zn magnetic nanoparticles on anaerobic digestion activity.

    PubMed

    Chen, Jian Lin; Steele, Terry W J; Stuckey, David C

    2018-06-11

    Two types of magnetic nanoparticles (MNPs), i.e. Ni ferrite nanoparticles (Fe 2 NiO 4 ) and Ni Zn ferrite nanoparticles (Fe 4 NiO 4 Zn) containing the trace metals Ni and Fe, were added to the anaerobic digestion of synthetic municipal wastewater at concentrations between 1 and 100 mg Ni L -1 in order to compare their effects on biogas (methane) production and sludge activity. Using the production of methane over time as a measure, the assays revealed that anaerobic digestion was stimulated by the addition of 100 mg Ni L -1 in Fe 2 NiO 4 NPs, while it was inhibited by the addition of 1-100 mg Ni L -1 in Fe 4 NiO 4 Zn NPs. Especially at 100 mg Ni L -1 , Fe 4 NiO 4 Zn NPs resulted in a total inhibition of anaerobic digestion. The metabolic activity of the anaerobic sludge was tested using the resazurin reduction assay, and the assay clearly revealed the negative effect of Fe 4 NiO 4 Zn NPs and the positive effect of Fe 2 NiO 4 NPs. Re-feeding fresh synthetic medium reactivated the NPs added to the anaerobic sludge, except for the experiment with 100 mg Ni L -1 addition of Fe 4 NiO 4 Zn NPs. The findings in this present study indicate a possible new strategy for NPs design to enhance anaerobic digestion. Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.

  20. Tuning static and dynamic properties of FeGa/NiFe heterostructures

    NASA Astrophysics Data System (ADS)

    Rementer, Colin R.; Fitzell, Kevin; Xu, Qiang; Nordeen, Paul; Carman, Gregory P.; Wang, Yuanxun E.; Chang, Jane P.

    2017-06-01

    In this work, the frequency-dependent magnetic properties of sputtered Galfenol/Permalloy (Fe85Ga15/Ni81Fe19 or FeGa/NiFe) magnetic multilayers were examined to tailor their magnetic softness, loss at microwave frequencies, permeability, and magnetoelasticity, leveraging the magnetic softness and low loss of NiFe and the high saturation magnetostriction (λs) and magnetization (MS) of FeGa. The total volume of each material and their ratio were kept constant, and the number of alternating layers was increased (with decreasing individual layer thickness) to assess the role of increasing interfaces in these magnetic heterostructures. A systematic change was observed as the number of bilayers or interfaces increases: a seven-bilayer structure results in an 88% reduction in coercivity and a 55% reduction in ferromagnetic resonance linewidth at the X-band compared to a single phase FeGa film, while maintaining a high relative permeability of 700. The magnetostriction was slightly reduced by the addition of NiFe but was still maintained at up to 67% that of single phase FeGa. The tunability of these magnetic heterostructures makes them excellent candidates for RF magnetic applications requiring strong magnetoelastic coupling and low loss.

  1. Engineering of high performance supercapacitor electrode based on Fe-Ni/Fe{sub 2}O{sub 3}-NiO core/shell hybrid nanostructures

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Singh, Ashutosh K., E-mail: ashuvishen@gmail.com, E-mail: aksingh@bose.res.in; Mandal, Kalyan

    The present work reports on fabrication and supercapacitor applications of a core/shell Fe-Ni/Fe{sub 2}O{sub 3}-NiO hybrid nanostructures (HNs) electrode. The core/shell Fe-Ni/Fe{sub 2}O{sub 3}-NiO hybrid nanostructures have been fabricated through a two step method (nanowire fabrication and their controlled oxidation). The 1D hybrid nanostructure consists of highly porous shell layer (redox active materials NiO and Fe{sub 2}O{sub 3}) and the conductive core (FeNi nanowire). Thus, the highly porous shell layer allows facile electrolyte diffusion as well as faster redox reaction kinetics; whereas the conductive FeNi nanowire core provides the proficient express way for electrons to travel to the current collector,more » which helps in the superior electrochemical performance. The core/shell Fe-Ni/Fe{sub 2}O{sub 3}-NiO hybrid nanostructures electrode based supercapacitor shows very good electrochemical performances in terms of high specific capacitance nearly 1415 F g{sup −1} at a current density of 2.5 A g{sup −1}, excellent cycling stability and rate capability. The high quality electrochemical performance of core/shell hybrid nanostructures electrode shows its potential as an alternative electrode for forthcoming supercapacitor devices.« less

  2. Connecting [NiFe]- and [FeFe]-Hydrogenases: Mixed-Valence Nickel-Iron Dithiolates With Rotated Structures

    PubMed Central

    Schilter, David; Rauchfuss, Thomas B.; Stein, Matthias

    2012-01-01

    A series of mixed-valence iron-nickel dithiolates is described that exhibits structures similar to those of mixed-valence diiron dithiolates. Interaction of tricarbonyl salt [(dppe)Ni(pdt)Fe(CO)3]BF4 ([1]BF4, dppe = Ph2PCH2CH2PPh2, pdtH2 = HSCH2CH2CH2SH) with P-donor ligands (L) afforded the substituted derivatives [(dppe)Ni(pdt)Fe(CO)2L]BF4 incorporating L = PHCy2 ([1a]BF4), PPh(NEt2)2 ([1b]BF4), P(NMe2)3 ([1c]BF4), P(i-Pr)3 ([1d]BF4) and PCy3 ([1e]BF4). The related precursor [(dcpe)Ni(pdt)Fe(CO)3]BF4 ([2]BF4, dcpe = Cy2PCH2CH2PCy2) gave the more electron-rich family of compounds [(dcpe)Ni(pdt)Fe(CO)2L]BF4 for L = PPh2(2-pyridyl) ([2a]BF4), PPh3 ([2b]BF4) and PCy3 ([2c]BF4). For bulky and strongly basic monophosphorus ligands, the salts feature distorted Fe coordination geometries: crystallographic analyses of [1e]BF4 and [2c]BF4 showed they adopt ‘rotated’ Fe(I) centers, in which PCy3 occupies a basal site and one CO ligand partially bridges the Ni and Fe centers. Like the undistorted mixed-valence derivatives, the new class of complexes are described as Ni(II)Fe(I) (S = ½) systems according to EPR spectroscopy, although with attenuated 31P hyperfine interactions. DFT calculations using the BP86, B3LYP, and PBE0 exchange-correlation functionals agree with the structural and spectroscopic data, suggesting that the spin for [1e]+ is localized in a Fe(I)-centered d(z2) orbital, orthogonal to the Fe-P bond. The PCy3 complexes, rare examples of species featuring ‘rotated’ Fe centers, both structurally and spectroscopically resemble mixed-valence diiron dithiolates. Also reproducing the NiS2Fe core of the [NiFe]-H2ase active site, the hybrid models incorporate key features of the two major classes of H2ase. Furthermore, cyclic voltammetry experiments suggest that the highly basic phosphine ligands enable a second oxidation corresponding to the couple [(dxpe)Ni(pdt)Fe(CO)2L]+/2+. The resulting unsaturated 32e− dications represent the closest approach to

  3. Ag-nanoparticles-decorated NiO-nanoflakes grafted Ni-nanorod arrays stuck out of porous AAO as effective SERS substrates.

    PubMed

    Zhou, Qitao; Meng, Guowen; Huang, Qing; Zhu, Chuhong; Tang, Haibin; Qian, Yiwu; Chen, Bin; Chen, Bensong

    2014-02-28

    NiO-nanoflakes (NiO-NFs) grafted Ni-nanorod (Ni-NR) arrays stuck out of the porous anodic aluminum oxide (AAO) template are achieved by a combinatorial process of AAO-confined electrodeposition of Ni-NRs, selectively etching part of the AAO template to expose the Ni-NRs, wet-etching the exposed Ni-NRs in ammonia to obtain Ni(OH)2-NFs grafted onto the cone-shaped Ni-NRs, and annealing to transform Ni(OH)2-NFs in situ into NiO-NFs. By top-view sputtering, Ag-nanoparticles (Ag-NPs) are decorated on each NiO-NFs grafted Ni-NR (denoted as NiO-NFs@Ni-NR). The resultant Ag-NPs-decorated NiO-NFs@Ni-NR (denoted as Ag-NPs@NiO-NFs@Ni-NR) arrays exhibit not only strong surface-enhanced Raman scattering (SERS) activity but also reproducible SERS-signals over the whole array. It is demonstrated that the strong SERS-activity is mainly ascribed to the high density of sub-10 nm gaps (hot spots) between the neighboring Ag-NPs, the semiconducting NiO-NFs induced chemical enhancement effect, and the lightning rod effect of the cone-shaped Ni-NRs. The three-level hierarchical nanostructure arrays stuck out of the AAO template can be utilized to probe polychlorinated biphenyls (PCBs, a kind of global environmental hazard) with a concentration as low as 5 × 10(-6) M, showing promising potential in SERS-based rapid detection of organic environmental pollutants.

  4. High magnetic coercivity of FePt-Ag/MgO granular nanolayers

    NASA Astrophysics Data System (ADS)

    Roghani, R.; Sebt, S. A.; Khajehnezhad, A.

    2018-06-01

    L10-FePt ferromagnetic nanoparticles have a hight coercivity of Tesla order. Thus, these nanoparticles, with size of 10 to 15 nm and uniform surface distribution, are suitable in magnetic data storage technology with density of more than 1GB. In order to improve structural and magnetic properties of FePt nanoparticles, some elements and combinations have been added to compound. In this research, we show that due to the presence of the Ag, the phase transition temperature of FePt from fcc to L10-fct phase decreases. The presence of Ag as an additive in FePt-Ag nanocomposite, increases the magnetic coercivity. This nanocomposite, with 10% Ag, was deposited by magnetron sputtering on the MgO heat layer. VSM results of 10 nm nanoparticles show that coercivity has increased up to 1.4 T. XRD and FESEM results confirm that the size of the L10-FePt nanoparticles are 10 nm and their surface distribution are uniform. Ag gradually form nano scale clusters with separate lattice and FePt-Ag nanocomposite appears. The result of this process is emptiness of Ag position in FePt-fcc lattice. So, the mobility of Fe and Pt atoms in this lattice increases and it can be possible for them to move in lower temperature. This mechanism explain the effect of Ag on decreasing the transition temperature to fct-L10 phase, and hight coercivity of FePt nanoparticles.

  5. Tuning Surface Electronic Configuration of NiFe LDHs Nanosheets by Introducing Cation Vacancies (Fe or Ni) as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction.

    PubMed

    Wang, Yanyong; Qiao, Man; Li, Yafei; Wang, Shuangyin

    2018-04-01

    Intrinsically inferior electrocatalytic activity of NiFe layered double hydroxides (LDHs) nanosheets is considered as a limiting factor to inhibit the electrocatalytic properties for oxygen evolution reaction (OER). Proper defect engineering to tune the surface electronic configuration of electrocatalysts may significantly improve the intrinsic activity. In this work, the selective formation of cation vacancies in NiFe LDHs nanosheets is successfully realized. The as-synthesized NiFe LDHs-V Fe and NiFe LDHs-V Ni electrocatalysts show excellent activity for OER, mainly attributed to the introduction of rich iron or nickel vacancies in NiFe LDHs nanosheets, which efficiently tune the surface electronic structure increasing the adsorbing capacity of OER intermediates. Density functional theory (DFT) computational results also further indicate that the OER catalytic performance of NiFe LDHs can be pronouncedly improved by introducing Fe or Ni vacancies. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Tuning Ni-catalyzed CO 2 hydrogenation selectivity via Ni-ceria support interactions and Ni-Fe bimetallic formation

    DOE PAGES

    Winter, Lea R.; Gomez, Elaine; Yan, Binhang; ...

    2017-10-16

    CO 2 hydrogenation over Fe-modified Ni/CeO 2 catalysts was investigated in a batch reactor using time-resolved in situ FTIR spectroscopy. Low loading of Ni/CeO 2 was associated with high selectivity to CO over CH 4, while higher Ni loading improved CO 2 hydrogenation activity with a reduced CO selectivity. X-ray absorption near-edge structure (XANES) analysis revealed Ni to be metallic for all catalysts including the CO-selective low loading 0.5% Ni catalyst, suggesting that the selectivity trend is due to structural rather than oxidation state effects. The loading amount of 1.5% Ni was selected for co-impregnation with Fe, based on themore » significant shift in product selectivity towards CH 4 for that loading amount, in order to shift the selectivity towards CO while maintaining high activity. Temperature programmed reduction (TPR) results indicated bimetallic interactions between Ni and Fe, and XANES analysis showed that about 70% of Fe in the bimetallic catalysts was oxidized. The Ni-Fe catalysts demonstrated improved selectivity towards CO without significantly compromising activity, coupling the high activity of Ni catalysts and the high CO selectivity of Fe. The general trends in Ni loading and bimetallic modification should guide efforts to develop non-precious metal catalysts for the selective production of CO by CO 2 hydrogenation.« less

  7. Multiple resonance peaks of FeCo thin films with NiFe underlayer

    NASA Astrophysics Data System (ADS)

    Zhong, Xiaoxi; Soh, Wee Tee; Phuoc, Nguyen N.; Liu, Ying; Ong, C. K.

    2015-01-01

    Under zero external magnetic fields, single-layer FeCo thin films exhibit no ferromagnetic resonance (FMR) peaks, while multiple FMR peaks were obtained by growing FeCo thin films on NiFe underlayers with various thicknesses up to 50 nm. Comprehensive investigations of the dynamic magnetic properties and origin of the peaks were conducted through measurements of microwave permeability via a shorted microstrip perturbation technique. Through fitted values of saturation magnetization Ms, uniaxial anisotropy HKsta, and rotatable anisotropy HKrot extracted from the FMR experiments, it was found that two of the three resonance peaks originate from FeCo, and the third from NiFe. The two magnetic phases of FeCo grains are found to have different values of HKrot and explained by the exchange interaction between FeCo and NiFe grains.

  8. Ag@Ni core-shell nanowire network for robust transparent electrodes against oxidation and sulfurization.

    PubMed

    Eom, Hyeonjin; Lee, Jaemin; Pichitpajongkit, Aekachan; Amjadi, Morteza; Jeong, Jun-Ho; Lee, Eungsug; Lee, Jung-Yong; Park, Inkyu

    2014-10-29

    Silver nanowire (Ag NW) based transparent electrodes are inherently unstable to moist and chemically reactive environment. A remarkable stability improvement of the Ag NW network film against oxidizing and sulfurizing environment by local electrodeposition of Ni along Ag NWs is reported. The optical transmittance and electrical resistance of the Ni deposited Ag NW network film can be easily controlled by adjusting the morphology and thickness of the Ni shell layer. The electrical conductivity of the Ag NW network film is increased by the Ni coating via welding between Ag NWs as well as additional conductive area for the electron transport by electrodeposited Ni layer. Moreover, the chemical resistance of Ag NWs against oxidation and sulfurization can be dramatically enhanced by the Ni shell layer electrodeposited along the Ag NWs, which provides the physical barrier against chemical reaction and diffusion as well as the cathodic protection from galvanic corrosion. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Ni doped Fe3O4 magnetic nanoparticles.

    PubMed

    Larumbe, S; Gómez-Polo, C; Pérez-Landazábal, J I; García-Prieto, A; Alonso, J; Fdez-Gubieda, M L; Cordero, D; Gómez, J

    2012-03-01

    In this work, the effect of nickel doping on the structural and magnetic properties of Fe3O4 nanoparticles is analysed. Ni(x)Fe(3-x)O4 nanoparticles (x = 0, 0.04, 0.06 and 0.11) were obtained by chemical co-precipitation method, starting from a mixture of FeCl2 x 4H2O and Ni(AcO)2 x 4H2O salts. The analysis of the structure and composition of the synthesized nanoparticles confirms their nanometer size (main sizes around 10 nm) and the inclusion of the Ni atoms in the characteristic spinel structure of the magnetite Fe3O4 phase. In order to characterize in detail the structure of the samples, X-ray absorption (XANES) measurements were performed on the Ni and Fe K-edges. The results indicate the oxidation of the Ni atoms to the 2+ state and the location of the Ni2+ cations in the Fe2+ octahedral sites. With respect to the magnetic properties, the samples display the characteristic superparamagnetic behaviour, with anhysteretic magnetic response at room temperature. The estimated magnetic moment confirms the partial substitution of the Fe2+ cations by Ni2+ atoms in the octahedral sites of the spinel structure.

  10. Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi

    NASA Astrophysics Data System (ADS)

    Ang, Andrew Siao Ming; Berndt, Christopher C.; Sesso, Mitchell L.; Anupam, Ameey; S, Praveen; Kottada, Ravi Sankar; Murty, B. S.

    2015-02-01

    High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.

  11. Thermodynamic Optimization of the Ag-Bi-Cu-Ni Quaternary System: Part I, Binary Subsystems

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Cui, Senlin; Rao, Weifeng

    2018-07-01

    A comprehensive literature review and thermodynamic optimization of the phase diagrams and thermodynamic properties of the Ag-Bi, Ag-Cu, Ag-Ni, Bi-Cu, and Bi-Ni binary systems are presented. CALculation of PHAse Diagrams (CALPHAD)-type thermodynamic optimization was carried out to reproduce all available and reliable experimental phase equilibrium and thermodynamic data. The modified quasichemical model was used to model the liquid solution. The compound energy formalism was utilized to describe the Gibbs energies of all terminal solid solutions and intermetallic compounds. A self-consistent thermodynamic database for the Ag-Bi, Ag-Cu, Ag-Ni, Bi-Cu, and Bi-Ni binary subsystems of the Ag-Bi-Cu-Ni quaternary system was developed. This database can be used as a guide for research and development of lead-free solders.

  12. Thermodynamic Optimization of the Ag-Bi-Cu-Ni Quaternary System: Part I, Binary Subsystems

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Cui, Senlin; Rao, Weifeng

    2018-05-01

    A comprehensive literature review and thermodynamic optimization of the phase diagrams and thermodynamic properties of the Ag-Bi, Ag-Cu, Ag-Ni, Bi-Cu, and Bi-Ni binary systems are presented. CALculation of PHAse Diagrams (CALPHAD)-type thermodynamic optimization was carried out to reproduce all available and reliable experimental phase equilibrium and thermodynamic data. The modified quasichemical model was used to model the liquid solution. The compound energy formalism was utilized to describe the Gibbs energies of all terminal solid solutions and intermetallic compounds. A self-consistent thermodynamic database for the Ag-Bi, Ag-Cu, Ag-Ni, Bi-Cu, and Bi-Ni binary subsystems of the Ag-Bi-Cu-Ni quaternary system was developed. This database can be used as a guide for research and development of lead-free solders.

  13. Preparation and structure of Na2Ag5Fe3(P2O7)4 -Ag metal composite: Insights on electrochemistry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Yiman; Marschilok, Amy C.; Takeuchi, Esther S.

    ABSTRACT Ag 7Fe 3(P 2O 7) 4is a 3D structured material which has been recently studied as a possible cathode material for lithium batteries. Notably, Na 7Fe 3(P 2O 7) 4is reported to be a fast-ion conductor, yet poor electrical conductor. Here, partial replacement of Na +for Ag +yielded Na 2Ag 5Fe 3(P 2O 7) 4pyrophosphate framework where the formation of Ag metal is proposed to increase the intrinsic low electrical conductivity of this polyanion electrode. Specifically, the Ag 5Na 2Fe 3(P 2O 7) 4-Ag composite is synthesized via chemical reduction of Ag 7Fe 3(P 2O 7) 4using NaBH 4.more » The occupancy of Ag +and Na +in each site was determined via Rietveld analysis of the diffraction pattern. Electrochemistry of the Ag 5Na 2Fe 3(P 2O 7) 4-Ag metal composite was explored with voltammetry and galvanostatic charge/discharge cycling. The Ag 5Na 2Fe 3(P 2O 7) 4-Ag metal composite electrodes displayed good rate capability assisted by the presence of Ag metal from the chemical reduction and in-situ electrochemical formation of a Ag conductive network.« less

  14. Laboratory Studies of FeO and NiO Chemiluminescence

    NASA Astrophysics Data System (ADS)

    Kalogerakis, K. S.; Bartlett, N. C.; Copeland, R. A.; Slanger, T. G.

    2013-12-01

    Although the terrestrial nightglow spectrum has been studied for over a century, new identifications of spectral features continue to be made. Recently, FeO* continuum emissions in the mesosphere were identified by comparison of results from the OSIRIS spectrometer to existing laboratory spectra [1]. This discovery has sparked a renewal of interest in the reactions of meteoric metals with mesospheric gases [2,3], and has motivated the current study. We report laboratory-based chemiluminescence spectra from the reactions Fe + O3 and Ni + O3 produced under various conditions. Iron and nickel vapor was prepared in a vacuum cell using laser ablation at 248 and 800 nm in the presence of ozone. Emission spectra from FeO* and NiO* were recorded in the region of 450-700 nm using a commercial fiber-coupled spectrometer and compared to previous results using different methods. Knowledge of the excited-state production efficiency of Fe + O3 → FeO* + O2 and the analogous reaction with Ni is critical in modeling upper atmospheric dynamics of meteoric metal layers. The only relevant experimental study in the literature for iron oxide is from West and Broida [4], who reported a yield of approximately 2% at around 1 Torr, in stark contrast with the 100% efficiency used in relevant model calculations [5]. This work was supported by the National Science Foundation's Aeronomy Program under grant AGS-0637433. References 1. W.F.J. Evans, R.L. Gattinger, T.G. Slanger, D.V. Saran, D.A. Degenstein, and E.J. Llewellyn, Geophys. Res. Lett., 37, L22105 (2010). 2. D.V. Saran, T.G. Slanger, W. Feng, and J.M.C. Plane, J. Geophys. Res. 116, D12303 (2011). 3. R.L. Gattinger, W.F.J. Evans, and E.J. Llewellyn, Canadian Journal of Physics 89, 869 (2011). 4. J.B. West and H.P. Broida, J. Chem. Phys. 62, 2566 (1975 ). 5. C.S. Gardner, J.M.C. Plane, W.L. Pan, T. Vondrak, B.J. Murray, and X.Z. Chu, J. Geophys. Res. 110, D10302 (2005).

  15. Interplay between out-of-plane anisotropic L1{sub 1}-type CoPt and in-plane anisotropic NiFe layers in CoPt/NiFe exchange springs

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Saravanan, P.; Defence Metallurgical Research Laboratory, Hyderabad 500058; Hsu, Jen-Hwa, E-mail: jhhsu@phys.ntu.edu.tw

    2014-06-28

    Films of L1{sub 1}-type CoPt/NiFe exchange springs were grown with different NiFe (Permalloy) layer thickness (t{sub NiFe} = 0–10 nm). X-ray diffraction analysis reveals that the characteristic peak position of NiFe(111) is not affected by the CoPt-layer—confirming the absence of any inter-diffusion between the CoPt and NiFe layers. Magnetic studies indicate that the magnetization orientation of NiFe layer can be tuned through varying t{sub NiFe} and the perpendicular magnetic anisotropy of L1{sub 1}-type CoPt/NiFe films cannot sustain for t{sub NiFe} larger than 3.0 nm due to the existence of exchange interaction at the interface of L1{sub 1}-CoPt and NiFe layers. Magnetic force microscopy analysismore » on the as-grown samples shows the changes in morphology from maze-like domains with good contrast to hazy domains when t{sub NiFe} ≥ 3.0 nm. The three-dimensional micro-magnetic simulation results demonstrate that the magnetization orientation in NiFe layer is not uniform, which continuously increases from the interface to the top of NiFe layer. Furthermore, the tilt angle of the topmost NiFe layers can be changed over a very wide range from a small number to about 75° by varying t{sub NiFe} from 1 to 10 nm. It is worth noting that there is an abrupt change in the magnetization direction at the interface, for all the t{sub NiFe} investigated. The results of present study demonstrate that the tunable tilted exchange springs can be realized with L1{sub 1}-type CoPt/NiFe bilayers for future applications in three-axis magnetic sensors or advanced spintronic devices demanding inclined magnetic anisotropy.« less

  16. Thickness dependence of exchange anisotropy for (0 0 1) oriented Mn 89Pt 11/NiFe and Mn 80Ir 20/NiFe bilayers

    NASA Astrophysics Data System (ADS)

    Kume, T.; Yamato, T.; Kato, T.; Tsunashima, S.; Iwata, S.

    2007-03-01

    Antiferromagnetic layer thickness dependences of exchange anisotropy for (0 0 1) oriented Mn 89Pt 11 ( tAF nm)/Ni 80Fe 20 (5 nm) and Mn 80Ir 20 ( tAF nm)/Ni 80Fe 20 (5 nm) were investigated. For Mn 89Pt 11/NiFe, the exchange bias field appeared at tAF⩾5 nm. This critical thickness was found to be thicker than that of Mn 80Ir 20/NiFe ( tAF=3 nm). The thickness dependence of exchange bias field agreed well with that of 1-fold Fourier amplitude estimated from in-plane torque curves. The large coercivity of about 100 Oe was found for Mn 89Pt 11/NiFe at tAF=30 nm compared to that of Mn 80Ir 20/NiFe. The large coercivity in Mn 89Pt 11/NiFe bilayers seems to result from the large 4-fold anisotropy in their torque curve.

  17. Effect of Ag addition to L1{sub 0} FePt and L1{sub 0} FePd films grown by molecular beam epitaxy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tokuoka, Y.; Seto, Y.; Kato, T., E-mail: takeshik@nuee.nagoya-u.ac.jp

    2014-05-07

    L1{sub 0} ordered FePt-Ag (5 nm) and FePd-Ag (5 nm) films were grown on MgO (001) substrate at temperatures of 250–400 °C by using molecular beam epitaxy method, and their crystal and surface structures, perpendicular magnetic anisotropies and Curie temperatures were investigated. In the case of FePt-Ag, Ag addition with the amount of 10–20 at. % was effective to promote L1{sub 0} ordering and granular growth, resulting in the increase of the perpendicular magnetic anisotropy and coercivity of the FePt-Ag films. On the other hand, in the case of FePd-Ag, Ag addition changed the surface morphology from island to continuous film associated with themore » reductions of its coercivity and perpendicular anisotropy. The variations of lattice constants and Curie temperature with Ag addition were significantly different between FePt-Ag and FePd-Ag. For FePd-Ag, the c and a axes lattice spacings and Curie temperature gradually changed with increasing Ag content, while they unchanged for FePt-Ag. These results suggest the possibility of the formation of FePdAg alloy in FePd-Ag, while Ag segregation in FePt-Ag.« less

  18. Coercivity scaling in antidot lattices in Fe, Ni, and NiFe thin films

    NASA Astrophysics Data System (ADS)

    Gräfe, Joachim; Schütz, Gisela; Goering, Eberhard J.

    2016-12-01

    Antidot lattices can be used to artificially engineer magnetic properties in thin films, however, a conclusive model that describes the coercivity enhancement in this class of magnetic nano-structures has so far not been found. We prepared Fe, Ni, and NiFe thin films and patterned each with 21 square antidot lattices with different geometric parameters and measured their hysteretic behavior. On the basis of this extensive dataset we are able to provide a model that can describe both the coercivity scaling over a wide range of geometric lattice parameters and the influence of different materials.

  19. Thermoelastic properties of γ-Fe and γ- Fe64Ni36 alloys

    NASA Astrophysics Data System (ADS)

    Tsujino, N.; Nishihara, Y.; Nakajima, Y.; Takahashi, E.; Funakoshi, K.

    2009-12-01

    The Earth’s core consists mainly of Fe-Ni alloy. Therefore the physical property of Fe-Ni alloy is a key issue to understand the planetary core. At 1 bar, γ-Fe is known as Anti-Invar alloy which shows anomalously high thermal expansivity, while γ-Fe64Ni36 is as a typical Inver-alloy. In addition, previous studies on γ-Fe-Ni Invar-alloys reported an anomalous pressure dependence of compression behavior (e.g., Dubrovinsky et al., 2001, Nataf et al., 2006, Matsushita et al., 2008). However, these studies were conducted at limited pressure range (> 6 GPa) or low temperature (30-300 K) conditions to identify physical properties of those alloys in the planetary interior. Therefore, we performed pressure-volume-temperature (P-V-T) measurements on γ-Fe and γ-Fe-Ni alloys at a wide P-T range of 0-23 GPa and 773-1873 K using the SPEED- Mk.II kawai-type multi-anvil apparatus at the SPring-8 synchrotron facility. On the basis of 2-γ state model by Weiss (1963), the thermal expansivity of γ-Fe can be decreased significantly with pressure. Our data, however, show no anomalous variation in the thermal expansion coefficient relative to pressure up to 23 GPa. In addition, anomalous pressure dependence on volume of γ-Fe64Ni36 reported by Matsushita et al. (2008) was not observed. Fitting 3rd order Birch-Murnaghan EOS and Mie-Grüneisen-Debye EOS to the P-V-T data of γ-Fe yielded V 0 = 49.028 ± 0.027 Å 3 , K T 0 = 111.2 ± 1.8 GPa, K ’ T = 5.2 ± 0.2, γ 0 = 2.30 ± 0.04 and q = -0.09 ± 0.21 with the fixed value of θ 0 = 340 K. The P-V data of γ- Fe64Ni36 was fittied using the 3rd order Birch-Marnagan, which yields V 0 = 48.85 ± 0.06 Å 3 , K T 0 = 88.1 ± 3.4 GPa, and K ’ 0 = 8.6± 0.5 at 1273 K.

  20. Synthesis of FeCoNi nanoparticles by galvanostatic technique

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Budi, Setia, E-mail: setiabudi@unj.ac.id; Department of Chemistry, Faculty of Mathematics and Sciences, Universitas Negeri Jakarta, Jl. Pemuda No.10, Rawamangun, Jakarta 13220; Hafizah, Masayu Elita

    Soft magnetic nanoparticles of FeCoNi have been becoming interesting objects for many researchers due to its potential application in electronic devices. One of the most promising methods for material preparation is the electrodeposition which capable of growing nanoparticles alloy directly onto the substrate. In this paper, we report our electrodeposition studies on nanoparticles synthesis using galvanostatic electrodeposition technique. Chemical composition of the synthesized FeCoNi was successfully controlled through the adjustment of the applied currents. It is revealed that the content of each element, obtained from quantitative analysis using atomic absorption spectrometer (AAS), could be modified by the adjustment of currentmore » in which Fe and Co content decreased at larger applied currents, while Ni content increased. The nanoparticles of Co-rich FeCoNi and Ni-rich FeCoNi were obtained from sulphate electrolyte at the range of applied current investigated in this work. Broad diffracted peaks in the X-ray diffractograms indicated typical nanostructures of the solid solution of FeCoNi.« less

  1. Effect of NiFeCr seed and capping layers on exchange bias and planar Hall voltage response of NiFe/Au/IrMn trilayer structures

    NASA Astrophysics Data System (ADS)

    Talantsev, Artem; Elzwawy, Amir; Kim, CheolGi

    2018-05-01

    Thin films and cross junctions, based on NiFe/Au/IrMn structures, were grown on Ta and NiFeCr seed layers by magnetron sputtering. The effects of substitution of Ta with NiFeCr in seed and capping layers on an exchange bias field are studied. A threefold improvement of the exchange bias value in the structures, grown with NiFeCr seed and capping layers, is demonstrated. The reasons for this effect are discussed. Formation of clusters in the NiFeCr capping layer is proved by atomic force microscopy technique. Ta replacement on NiFeCr in the capping layer results in the enhancement of magnetoresistive response and a reduction of noise.

  2. Preparation, characterization and photocatalytic activity of visible-light-driven plasmonic Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Xiaojuan, E-mail: lixiaojuan@fzu.edu.cn; Tang, Duanlian; Tang, Fan

    2014-08-15

    Highlights: • A plasmonic Ag/AgBr/ZnFe{sub 2}O{sub 4} photocatalyst has been successfully synthesized. • Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposites exhibit high visible light photocatalytic activity. • Ag/AgBr/ZnFe{sub 2}O{sub 4} photocatalyst is stable and magnetically separable. - Abstract: A visible-light-driven plasmonic Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposite has been successfully synthesized via a deposition–precipitation and photoreduction through a novel one-pot process. X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy were employed to investigate the crystal structure, chemical composition, morphology, and optical properties of the as-prepared nanocomposites. The photocatalytic activities of the nanocomposites were evaluated by photodegradationmore » of Rhodamine B (RhB) and phenol under visible light. The results demonstrated that the obtained Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposites exhibited higher photocatalytic activity as compared to pure ZnFe{sub 2}O{sub 4}. In addition, the sample photoreduced for 20 min and calcined at 500 °C achieved the highest photocatalytic activity. Furthermore, the Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposite has high stability under visible light irradiation and could be conveniently separated by using an external magnetic field.« less

  3. NiFe nanoparticles: a soft magnetic material?

    PubMed

    Margeat, Olivier; Ciuculescu, Diana; Lecante, Pierre; Respaud, Marc; Amiens, Catherine; Chaudret, Bruno

    2007-03-01

    Polytetrahedral NiFe nanoparticles with diameters of (2.8+/-0.3) nm have been obtained by hydrogenation of Ni[(COD)(2)] (COD=1,5-cyclooctadiene) and Fe[{N(SiMe(3))(2)}(2)] at 150 degrees C using stearic acid and hexadecylamine as stabilizing ligands. The nanoparticles are superparamagnetic at room temperature and display a blocking temperature of 17.6 K. Their anisotropy (2.7x10(5)J m(-3)) is determined to be more than two orders of magnitude higher than that of the bulk NiFe alloy (10(3)J m(-3)) and is close to that determined for Fe nanoparticles of the same size. Still, they display a magnetization of (1.69+/-0.05) mu(B) per metallic atom, identical to that of the bulk NiFe alloy. Combining the results from X-ray absorption and Mössbauer studies, we evidence a progressive enrichment in iron atoms from the core to the surface of the nanoparticles. These results are discussed in relation to both size and chemical effects. They show the main role played by the enriched Fe surface on the magnetic properties and address the feasibility of soft magnetic materials at the nanoscale.

  4. Fe-Ni-bearing serpentines from the saprolite horizon of Caribbean Ni-laterite deposits: new insights from thermodynamic calculations

    NASA Astrophysics Data System (ADS)

    Villanova-de-Benavent, Cristina; Domènech, Cristina; Tauler, Esperança; Galí, Salvador; Tassara, Santiago; Proenza, Joaquín A.

    2017-10-01

    Fe-Ni-bearing serpentine from the saprolite horizon is the main Ni ores in hydrous silicate-type Ni laterites and formed by chemical weathering of partially serpentinized ultramafic rocks under tropical conditions. During lateritization, Mg, Si, and Ni are leached from the surface and transported downwards. Fe2+ is oxidized to Fe3+ and fixed as insoluble Fe-oxyhydroxides (mostly goethite) that incorporate Ni. This Ni is later leached from goethite and incorporated in secondary serpentine and garnierite. As a result, a serpentine-dominated saprolite horizon forms over the ultramafic protolith, overlapped by a Fe-oxyhydroxide-dominated limonite horizon. The serpentine from the protolith (serpentine I) is of hydrothermal origin and yields similar Ni (0.10-0.62 wt.% NiO) and lower Fe (mostly 1.37-5.81 wt.% FeO) concentrations than the primary olivine. In contrast, Fe-Ni-bearing serpentine from the saprolite (serpentine II) shows significantly higher and variable Fe and Ni contents, typically ranging from 2.23 to 15.59 wt.% Fe2O3 and from 1.30 to 7.67 wt.% NiO, suggesting that serpentine get enriched in Fe and Ni under supergene conditions. This study presents detailed mineralogical, textural, and chemical data on this serpentine II, as well as new insights by thermodynamic calculations assuming ideal solution between Fe-, Ni- and Mg-pure serpentines. The aim is to assess if at atmospheric pressure and temperature Fe-Ni-bearing serpentine can be formed by precipitation. Results indicate that the formation of serpentine II under atmospheric pressure and temperature is thermodynamically supported, and pH, Eh, and the equilibrium constant of the reaction are the parameters that affect the results more significantly.

  5. Nickel recovery from electronic waste II electrodeposition of Ni and Ni-Fe alloys from diluted sulfate solutions.

    PubMed

    Robotin, B; Ispas, A; Coman, V; Bund, A; Ilea, P

    2013-11-01

    This study focuses on the electrodeposition of Ni and Ni-Fe alloys from synthetic solutions similar to those obtained by the dissolution of electron gun (an electrical component of cathode ray tubes) waste. The influence of various parameters (pH, electrolyte composition, Ni(2+)/Fe(2+) ratio, current density) on the electrodeposition process was investigated. Scanning electron microscopy (SEM) and X-ray fluorescence analysis (XRFA) were used to provide information about the obtained deposits' thickness, morphology, and elemental composition. By controlling the experimental parameters, the composition of the Ni-Fe alloys can be tailored towards specific applications. Complementarily, the differences in the nucleation mechanisms for Ni, Fe and Ni-Fe deposition from sulfate solutions have been evaluated and discussed using cyclic voltammetry and potential step chronoamperometry. The obtained results suggest a progressive nucleation mechanism for Ni, while for Fe and Ni-Fe, the obtained data points are best fitted to an instantaneous nucleation model. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. Infrared Brazing of Ti50Ni50 Shape Memory Alloy and Inconel 600 Alloy with Two Ag-Cu-Ti Active Braze Alloys

    NASA Astrophysics Data System (ADS)

    Shiue, Ren-Kae; Wu, Shyi-Kaan; Yang, Sheng-Hao

    2017-02-01

    Infrared brazing of Ti50Ni50 SMA and Inconel 600 alloy using Cusil-ABA and Ticusil filler metals has been investigated. The joints were dominated by Ag-Cu eutectic with proeutectic Cu in the Cusil-ABA brazed joint and with proeutectic Ag in the Ticusil one. A continuous curved belt composed of a Ni3Ti layer and a (Cu x Ni1- x )2Ti layer formed in the brazed Ti50Ni50/Ticusil/Inconel 600 joint. On the Ti50Ni50 SMA side, an intermetallic layer of (Cu x Ni1- x )2Ti formed in all joints, with x values around 0.81 and 0.47. Layers of (Cu x Ni1- x )2Ti, Ni3Ti, and mixed Ni3Ti and Ni2Cr intermetallics were observed next to the Inconel 600 substrate in the brazed Ti50Ni50/Cusil-ABA/Inconel 600 joint. The maximum shear strengths of the joints using the Cusil-ABA filler metal and the Ticusil filler metal were 324 and 300 MPa, respectively. In the Cusil-ABA brazed joint, cracks with cleavage-dominated fracture propagated along the (Cu x Ni1- x )2Ti interfacial layer next to the Ti50Ni50 SMA substrate. In the Ticusil brazed joint, ductile dimple fracture occurred in the Ag-rich matrix near the Inconel 600 alloy substrate. The absence of a detrimental Ti-Fe-(Cu) layer on the Inconel 600 substrate side can effectively improve the shear strength of the joint.

  7. Template-grown NiFe/Cu/NiFe nanowires for spin transfer devices.

    PubMed

    Piraux, Luc; Renard, Krystel; Guillemet, Raphael; Matéfi-Tempfli, Stefan; Matéfi-Tempfli, Maria; Antohe, Vlad Andrei; Fusil, Stéphane; Bouzehouane, Karim; Cros, Vincent

    2007-09-01

    We have developed a new reliable method combining template synthesis and nanolithography-based contacting technique to elaborate current perpendicular-to-plane giant magnetoresistance spin valve nanowires, which are very promising for the exploration of electrical spin transfer phenomena. The method allows the electrical connection of one single nanowire in a large assembly of wires embedded in anodic porous alumina supported on Si substrate with diameters and periodicities to be controllable to a large extent. Both magnetic excitations and switching phenomena driven by a spin-polarized current were clearly demonstrated in our electrodeposited NiFe/Cu/ NiFe trilayer nanowires. This novel approach promises to be of strong interest for subsequent fabrication of phase-locked arrays of spin transfer nano-oscillators with increased output power for microwave applications.

  8. Effect of a CoFeB layer on the anisotropic magnetoresistance of Ta/CoFeB/MgO/NiFe/MgO/CoFeB/Ta films

    NASA Astrophysics Data System (ADS)

    Li, Minghua; Shi, Hui; Dong, Yuegang; Ding, Lei; Han, Gang; Zhang, Yao; Liu, Ye; Yu, Guanghua

    2017-10-01

    The anisotropic magnetoresistance (AMR) and magnetic properties of NiFe films can be remarkably enhanced via CoFeB layer. In the case of an ultrathin NiFe film having a Ta/CoFeB/MgO/NiFe/MgO/CoFeB/Ta structure, the CoFeB/MgO layers suppressed the formation of magnetic dead layers and the interdiffusions and interface reactions between the NiFe and Ta layers. The AMR reached a maximum value of 3.56% at 450 °C. More importantly, a single NiFe (1 1 1) peak can be formed resulting in higher AMR values for films having CoFeB layer. This enhanced AMR also originated from the significant specular reflection of electrons owing to the crystalline MgO layer, together with the sharp interfaces with the NiFe layer. These factors together resulted in higher AMR and improved magnetic properties.

  9. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy

    DOE PAGES

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; ...

    2015-08-10

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique ‘wagging’ mode involving H- motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)57Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe–CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)57Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)57Fe(CO)3]+ and DFT calculations, which collectively indicate amore » low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H- binding Ni more tightly than Fe. Lastly, the present methodology is also relevant to characterizing Fe–H moieties in other important natural and synthetic catalysts.« less

  10. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy

    PubMed Central

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B.; Gee, Leland B.; Scott, Aubrey D.; Yoda, Yoshitaka; Tanaka, Yoshihito; Lubitz, Wolfgang; Cramer, Stephen P.

    2015-01-01

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique ‘wagging' mode involving H− motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)57Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe–CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)57Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)57Fe(CO)3]+ and DFT calculations, which collectively indicate a low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H− binding Ni more tightly than Fe. The present methodology is also relevant to characterizing Fe–H moieties in other important natural and synthetic catalysts. PMID:26259066

  11. Growth Behavior of Intermetallic Compounds at SnAgCu/Ni and Cu Interfaces

    NASA Astrophysics Data System (ADS)

    Qi, Lihua; Huang, Jihua; Zhang, Hua; Zhao, Xingke; Wang, Haitao; Cheng, Donghai

    2010-02-01

    The growth behavior of reaction-formed intermetallic compounds (IMCs) at Sn3.5Ag0.5Cu/Ni and Cu interfaces under thermal-shear cycling conditions was investigated. The results show that the morphology of (Cu x Ni1- x )6Sn5 and Cu6Sn5 IMCs formed both at Sn3.5Ag0.5Cu/Ni and Cu interfaces gradually changed from scallop-like to chunk-like, and different IMC thicknesses developed with increasing thermal-shear cycling time. Furthermore, Cu6Sn5 IMC growth rate at the Sn3.5Ag0.5Cu/Cu interface was higher than that of (Cu x Ni1- x )6Sn5 IMC under thermal-shear cycling. Compared to isothermal aging, thermal-shear cycling led to only one Cu6Sn5 layer at the interface between SnAgCu solder and Cu substrate after 720 cycles. Moreover, Ag3Sn IMC was dispersed uniformly in the solder after reflow. The planar Ag3Sn formed near the interface changed remarkably and merged together to large platelets with increasing cycles. The mechanism of formation of Cu6Sn5, (Cu x Ni1- x )6Sn5 and Ag3Sn IMCs during thermal-shear cycling process was investigated.

  12. Nucleation and Growth of Tetrataenite (FeNi) in Meteorites

    NASA Astrophysics Data System (ADS)

    Goldstein, J. I.; Williams, D. B.; Zhang, J.

    1992-07-01

    The mineral tetrataenite (ordered FeNi) has been observed in chondrites, stony irons, and iron meteorites (1). FeNi is an equilibrium phase in the Fe-Ni phase diagram (Figure 1) and orders to tetrataenite at ~320 degrees C (2). The phase forms at temperatures at or below the eutectoid temperature (~400 degrees C) where taenite (gamma) transforms to kamacite (alpha) plus FeNi (gamma"). An understanding of the formation of tetrataenite can lead to a new method for determining cooling rates at low temperatures (<400 degrees C) for all types of meteorites. In a recent study of plessite in iron meteorites (3), two transformation sequences for the formation of tetrataenite were observed. In either sequence, during the cooling process, the taenite (gamma) phase initially undergoes a diffusionless transformation to a martensite (alpha, bcc) phase without a composition change. The martensite then decomposes either above or below the eutectoid temperature (~400 degrees C) during cooling or upon subsequent reheating. During martensite decomposition above the eutectoid, the taenite (gamma) phase nucleates by the reaction alpha(sub)2 ---> alpha + gamma and grows under volume diffusion control. The Ni composition of the taenite increases continuously following the equilibrium gamma/alpha + gamma boundary while the Ni composition of the kamacite matrix decreases following the alpha/alpha + gamma phase boundary (2), see Figure 1. Below the eutectoid temperature, the precipitate composition follows the equilibrium gamma"/alpha + gamma" boundary and reaches ~52 wt% Ni, the composition of FeNi, gamma". The kamacite (alpha) matrix composition approaches ~4 to 5 wt% Ni. The ordering transformation starts at ~320 degrees C forming the tetrataenite phase. During martensite decomposition below the eutectoid temperature, FeNi should form directly by the reaction alpha2 --> alpha + gamma" (FeNi). If this transformation sequence occurs, then the composition of kamacite and tetrataenite

  13. Synthetic Active Site Model of the [NiFeSe] Hydrogenase

    PubMed Central

    Wombwell, Claire; Reisner, Erwin

    2015-01-01

    A dinuclear synthetic model of the [NiFeSe] hydrogenase active site and a structural, spectroscopic and electrochemical analysis of this complex is reported. [NiFe(‘S2Se2’)(CO)3] (H2‘S2Se2’=1,2-bis(2-thiabutyl-3,3-dimethyl-4-selenol)benzene) has been synthesized by reacting the nickel selenolate complex [Ni(‘S2Se2’)] with [Fe(CO)3bda] (bda=benzylideneacetone). X-ray crystal structure analysis confirms that [NiFe(‘S2Se2’)(CO)3] mimics the key structural features of the enzyme active site, including a doubly bridged heterobimetallic nickel and iron center with a selenolate terminally coordinated to the nickel center. Comparison of [NiFe(‘S2Se2’)(CO)3] with the previously reported thiolate analogue [NiFe(‘S4’)(CO)3] (H2‘S4’=H2xbsms=1,2-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)benzene) showed that the selenolate groups in [NiFe(‘S2Se2’)(CO)3] give lower carbonyl stretching frequencies in the IR spectrum. Electrochemical studies of [NiFe(‘S2Se2’)(CO)3] and [NiFe(‘S4’)(CO)3] demonstrated that both complexes do not operate as homogenous H2 evolution catalysts, but are precursors to a solid deposit on an electrode surface for H2 evolution catalysis in organic and aqueous solution. PMID:25847470

  14. Tunable plasmonic properties of Ag-Fe nanoparticles

    NASA Astrophysics Data System (ADS)

    Bhatia, Pradeep; Verma, S. S.; Sinha, M. M.

    2018-05-01

    Compatibility problems with electronic processes, limited availability and the high cost of noble metals motivate towards the search of alternative materials to enhance the suitability and efficiency of plasmonic based devices. Alloy or coated bimetallic material configuration is an attractive way to engineer a system possessing tuneable plasmonic properties. Magneto-plasmonic nanoparticles (MPNPs) present the possibility to exhibit their tuneable magnetic and optical properties with extensive applications. We studied the optical properties of Ag-Fe alloy for different compositions. The Localised Surface Plasmon Resonance (LSPR) tunability of Agx-Fe1-x (x = 0.25, 0.50 and 0.75) alloy for nanospheres has been calculated by using Discrete Dipole Approximation (DDA) simulation technique. It is found that absorption and scattering efficiencies of Ag-Fe alloy are found in near ultra violet and visible region of electromagnetic spectrum. Large LSPR shift has been observed in absorption and scattering efficiencies peak for 40 nm and 80 nm size of nanospheres alloys. It is concluded that the LSPR can be tuned by changing nanoparticle size and the alloy composition. Results of the plasmonics properties for Ag-Fe alloy at wavelength 330-545nm (absorption) and 331-507nm (scattering) will open the avenues for new applications in optical imaging, biomedical fields particularly in (calorimetric)-DNA, pentose's, proteins (absorption) and plasmonic-enhanced spectroscopies/spectrometer devices (scattering) for determination of optical densities of cell cultures.

  15. Chemical Separation of Fe-Ni Particles after Impact

    NASA Astrophysics Data System (ADS)

    Miura, Y.; Fukuyama, S.; Kedves, M. A.; Yamori, A.; Okamoto, M.; Gucsik, A.

    Tiny grains of Fe-Ni system originated from planetesimals or meteoroids can remain under solid (or melt)-solid impact reactions even after impact process, probably together with high pressure form of Fe phase. Impact fragment with major Fe-Si (-Ni) system can be formed under vapor condition of impact reaction from terrestrial and artificial impact craters and spherules, and those with Ni-Cl (-S) system in composi- tion are formed under vapor condition of artificial impact experiments on the Barringer iron meteorite. These impact grains of Fe-bearing composition or high pressure form of iron-rich phases will be found probably on the asteroids in future exploration

  16. Enhanced photocatalytic performances and magnetic recovery capacity of visible-light-driven Z-scheme ZnFe2O4/AgBr/Ag photocatalyst

    NASA Astrophysics Data System (ADS)

    He, Jie; Cheng, Yahui; Wang, Tianzhao; Feng, Deqiang; Zheng, Lingcheng; Shao, Dawei; Wang, Weichao; Wang, Weihua; Lu, Feng; Dong, Hong; Zheng, Rongkun; Liu, Hui

    2018-05-01

    High efficiency, high stability and easy recovery are three key factors for practical photocatalysts. Z-scheme heterostructure is one of the most promising photocatalytic systems to meet all above requirements. However, efficient Z-scheme photocatalysts which could absorb visible light are still few and difficult to implement at present. In this work, the composite photocatalysts ZnFe2O4/AgBr/Ag were prepared through a two-step method. A ∼92% photodegradation rate on methyl orange was observed within 30 min under visible light, which is much better than that of individual ZnFe2O4 or AgBr/Ag. The stability was also greatly improved compared with AgBr/Ag. The increased performance is resulted from the suitable band alignment of ZnFe2O4 and AgBr, and it is defined as Z-scheme mechanism which was demonstrated by detecting active species and electrochemical impedance spectroscopy. Besides, ZnFe2O4/AgBr/Ag is ferromagnetic and can be recycled by magnet. These results show that ZnFe2O4/AgBr/Ag is a potential magnetically recyclable photocatalyst which can be driven by visible light.

  17. Electromigration effect upon the Sn-0.7 wt% Cu/Ni and Sn-3.5 wt% Ag/Ni interfacial reactions

    NASA Astrophysics Data System (ADS)

    Chen, Chih-ming; Chen, Sinn-wen

    2001-08-01

    This study investigates the effect of electromigration upon the interfacial reactions between the promising lead-free solders, Sn-Cu and Sn-Ag, with Ni substrate. Sandwich-type reaction couples, Sn-0.7 wt% Cu/Ni/Sn-0.7 wt% Cu and Sn-3.5 wt% Ag/Ni/Sn-3.5 wt% Ag, were reacted at 160, 180, and 200 °C for various lengths of time with and without the passage of electric currents. Without passage of electric currents through the couples, only one intermetallic compound Ni3Sn4 with ˜7 at. % Cu solubility was found at both interfaces of the Sn-0.7 wt% Cu/Ni couples. With the passage of an electric current of 500 A/cm2 density, the Cu6Sn5 phase was formed at the solder/Ni interface besides the Ni3Sn4 phase. Similar to those without the passage of electric currents, only the Ni3Sn4 phase was found at the Ni/solder interface. Directions of movement of electrons, Sn, and Cu atoms are the same at the solder/Ni interface, and the growth rates of the intermetallic layers were enhanced. At the Ni/solder interface, the electrons flow in the opposite direction of the Sn and Cu movement, and the growth rates of the intermetallic layers were retarded. Only the Ni3Sn4 phase was formed from the Sn-3.5 wt% Ag/Ni interfacial reaction with and without the passage of electric currents. Similar to the Sn-0.7 wt% Cu/Ni system, the movement of electrons enhances or retards the growth rates of the intermetallic layers at the solder/Ni and Ni/solder interfaces, respectively. Calculation results show the apparent effective charge za* decreases in magnitude with raising temperatures, which indicates the electromigration effect becomes insignificant at higher temperatures.

  18. Atomic-scale dynamics of edge dislocations in Ni and concentrated solid solution NiFe alloys

    DOE PAGES

    Zhao, Shijun; Osetsky, Yuri N.; Zhang, Yanwen; ...

    2017-01-19

    Single-phase concentrated solid solution alloys (CSAs), including high entropy alloys, exhibit excellent mechanical properties compared to conventional dilute alloys. However, the origin of this observation is not clear yet because the dislocation properties in CSAs are poorly understood. In this work, the mobility of a <110>{111} edge dislocation in pure Ni and equiatomic solid solution Ni 0.5Fe 0.5 (NiFe) is studied using molecular dynamics simulations with different empirical potentials. The threshold stress to initiate dislocation movement in NiFe is found to be much higher compared to pure Ni. The drag coefficient of the dislocation motion calculated from the linear regimemore » of dislocation velocities versus applied stress suggests that the movement of dislocations in NiFe is strongly damped compared to that in Ni. The present results indicate that the mobility of edge dislocations in fcc CSAs are controlled by the fluctuations in local stacking fault energy caused by the local variation of alloy composition.« less

  19. Synthetic Active Site Model of the [NiFeSe] Hydrogenase.

    PubMed

    Wombwell, Claire; Reisner, Erwin

    2015-05-26

    A dinuclear synthetic model of the [NiFeSe] hydrogenase active site and a structural, spectroscopic and electrochemical analysis of this complex is reported. [NiFe('S2Se2')(CO)3] (H2'S2Se2' = 1,2-bis(2-thiabutyl-3,3-dimethyl-4-selenol)benzene) has been synthesized by reacting the nickel selenolate complex [Ni('S2Se2')] with [Fe(CO)3bda] (bda = benzylideneacetone). X-ray crystal structure analysis confirms that [NiFe('S2Se2')(CO)3] mimics the key structural features of the enzyme active site, including a doubly bridged heterobimetallic nickel and iron center with a selenolate terminally coordinated to the nickel center. Comparison of [NiFe('S2Se2')(CO)3] with the previously reported thiolate analogue [NiFe('S4')(CO)3] (H2'S4' = H2xbsms = 1,2-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)benzene) showed that the selenolate groups in [NiFe('S2Se2')(CO)3] give lower carbonyl stretching frequencies in the IR spectrum. Electrochemical studies of [NiFe('S2Se2')(CO)3] and [NiFe('S4')(CO)3] demonstrated that both complexes do not operate as homogenous H2 evolution catalysts, but are precursors to a solid deposit on an electrode surface for H2 evolution catalysis in organic and aqueous solution. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

  20. Modulation of the electronic structure and the Ni–Fe distance in heterobimetallic models for the active site in [NiFe]hydrogenase

    PubMed Central

    Zhu, Wenfeng; Marr, Andrew C.; Wang, Qiang; Neese, Frank; Spencer, Douglas J. E.; Blake, Alexander J.; Cooke, Paul A.; Wilson, Claire; Schröder, Martin

    2005-01-01

    Reaction of the mononuclear Ni(II) thiolate complexes [Ni(L)] [L, L1, H2L1, bis(2-mercaptoethyl)-1,2-dimercaptoethane; L2, H2L2, N,N′-dimethyl-N,N′-bis(2-mercaptoethyl)-bis(aminoethyl)sulfide] with [FeCp(CO)2I] gives the dithiolate-bridged heterobimetallic species, [Ni(L1)FeCp(CO)]PF6, 1, and [Ni(L2)FeCp]I, 2, respectively. Binding of a Fe(CO)3 fragment via reaction of square-planar [Ni(pdt)(dppe)] (dppe, 1,2-diphenylphosphinoethane; pdt2–, 1,3-propanedithiolate) with Fe3(CO)12 or [Fe(CO)3(BDA)] (BDA, benzylidene acetone) affords diamagnetic [(dppe)Ni(μ-pdt)Fe(CO)3], 3, in which the Ni(II) center is bound tetrahedrally to two thiolate S-donors and to two P-donors. The complex [(dppe)Ni(μ-pdt)Fe(CO)3], 3, reacts in solution via rearrangement to afford [(OC)Ni(μ-dppe)(μ-pdt)Fe(CO)2], 4, in which one P-donor of dppe is bound to Ni and the other to Fe, and a CO ligand has transferred from Fe to Ni. Additionally, the syntheses of 3 and 4 afford the side products [(dppe)Ni(CO)2] and [(OC)3Fe(pdt)Fe(CO)3] together with the trinuclear species [(dppe)(CO)Fe(μ-CO)(μ-pdt)Fe(μ-pdt)Fe(CO)3], 5. Reaction of [Ni(pdt)(dppe)] with [FeCp(CO)2I] in CH2Cl2 affords two products [(dppe)Ni(μ-pdt)FeCp(CO)]PF6, 6, and [(dppe)Ni(pdt)(μ-I)Ni(dppe)]PF6, 7. The complexes 2, 3, and 4 show Ni–Fe distances of 2.539(4), 2.4666(6), and 2.4777(7) Å, respectively, with relatively acute dihedral angles of 79.5–81.8° for the Ni–S2-Fe bridge, thus mimicking the shortened Ni...Fe distance (2.5 Å) and the acute dihedral angle of the Ni–S2–Fe moiety observed in certain active forms of [NiFe]hydrogenase. The role of direct Ni–Fe bonding in these complexes is discussed and linked to electronic structure calculations on [(dppe)Ni(pdt)Fe(CO)3], 3, which confirm the presence of a bent Ni(dz2)-Fe(dz2) σ-bond in a singlet ground state. PMID:16352727

  1. Ag/AgO Nanoparticles Grown via Time Dependent Double Mechanism in a 2D Layered Ni-PCP and Their Antibacterial Efficacy

    NASA Astrophysics Data System (ADS)

    Agarwal, Rashmi A.; Gupta, Neeraj K.; Singh, Rajan; Nigam, Shivansh; Ateeq, Bushra

    2017-03-01

    A simple synthesis route for growth of Ag/AgO nanoparticles (NPs) in large quantitative yields with narrow size distribution from a functional, non-activated, Ni (II) based highly flexible porous coordination polymer (PCP) as a template has been demonstrated. This template is a stable storage media for the NPs larger than the pore diameters of the PCP. From EPR study it was concluded that NPs were synthesized via two mechanisms i.e. acid formation and the redox activity of the framework. Size range of Ag/AgO NPs is sensitive to choice of solvent and reaction time. Direct use of Ag/AgO@Ni-PCP shows influential growth inhibition towards Escherichia coli and the pathogen Salmonella typhimurium at extremely low concentrations. The pristine template shows no cytotoxic activity, even though it contains Ni nodes in the framework.

  2. Exploring the mechanism and kinetics of Fe-Cu-Ag trimetallic particles for p-nitrophenol reduction.

    PubMed

    Yuan, Yue; Yuan, Donghai; Zhang, Yunhong; Lai, Bo

    2017-11-01

    Preparation conditions of Fe-Cu-Ag trimetallic particles were optimized by single-factor and response surface methodology (RSM) batch experiments to obtain high-reactive Fe 0 -based materials for p-nitrophenol (PNP) removal. Under the optimal conditions (i.e., Fe 0 dosage of 34.86 g L -1 , theoretical Cu mass loading of 81.87 mg Cu/g Fe, theoretical Ag mass loading of 1.15 mg Ag/g Fe, and preparation temperature of 52.1 °C), the actual rate constant (k obs ) of PNP reduction in 5 min was 1.64 min -1 , which shows a good agreement between the model prediction (1.85 min -1 ) of RSM and the experimental data. Furthermore, the high reactivity of Fe 0 -based trimetals was mainly attributed to the plating order of transition metals (i.e., Ag and Cu). Furthermore, we propose a new theory that the pyramid trimetallic structure of Fe-Cu-Ag could improve the electron transport and create active sites with high electron density at the surface (Ag layer) that could enhance the generation of surface-bonded atomic hydrogen ([H] abs ) or the direct reduction of pollutant. Moreover, Fe-Cu-Ag trimetallic particles were characterized by SEM, EDS, and XPS, which also could confirm the proposed theory. In addition, the leached Cu 2+ (<10 μg L -1 ) and Ag + (below detection limits) in Fe-Cu-Ag system could be neglected completely, which suggests that Fe-Cu-Ag is reliable, safe, and environment friendly. Therefore, Fe-Cu-Ag trimetallic system would be promising for the removal of pollutants from industrial wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Magnetic analysis of a melt-spun Fe-dilute Cu60Ag35Fe5 alloy

    NASA Astrophysics Data System (ADS)

    Kondo, Shin-ichiro; Kaneko, Kazuhiro; Morimura, Takao; Nakashima, Hiromichi; Kobayashi, Shin-Taro; Michioka, Chishiro; Yoshimura, Kazuyoshi

    2015-04-01

    The magnetic properties of a melt-spun Fe-dilute Cu60Ag35Fe5 alloy are examined by X-ray diffraction, magnetic measurements, and transmission electron microscopy (TEM). The X-ray diffraction patterns show that the as-spun and annealed (773 K×36 ks) samples contain Cu and Ag phases and no Fe phases; thus, most Fe atoms are dispersed as clusters. Magnetic measurements indicate that the as-spun and annealed samples exhibit superparamagnetic behavior at 300 K, whereas ferromagnetic and superparamagnetic behaviors coexist at 4.2 K. The magnetic moments of small clusters at 300 K are determined by the nonlinear least squares method as 5148 and 4671 μB for as-spun and annealed samples, respectively, whereas those at 300 K are experimentally determined as 3500 and 3200 μB. This decrease in magnetic moments may imply the formation of anti-ferromagnetic coupling by annealing. TEM observation of the melt-spun sample suggests that there are three regions with different compositions: Cu-rich, Ag-rich, and Fe-rich with no precipitation in the matrix. In addition, these regions have obscure interfaces. The magnetic clusters are attributed to the Fe-rich regions.

  4. A model for the CO-inhibited form of [NiFe] hydrogenase: synthesis of (CO)3Fe(μ-StBu)3Ni{SC6H3-2,6-(mesityl)2} and reversible CO addition at the Ni site

    PubMed Central

    Ohki, Yasuhiro; Yasumura, Kazunari; Ando, Masaru; Shimokata, Satoko; Tatsumi, Kazuyuki

    2010-01-01

    A [NiFe] hydrogenase model compound having a distorted trigonal-pyramidal nickel center, (CO)3Fe(μ-StBu)3Ni(SDmp), 1 (Dmp = C6H3-2,6-(mesityl)2), was synthesized from the reaction of the tetranuclear Fe-Ni-Ni-Fe complex [(CO)3Fe(μ-StBu)3Ni]2(μ-Br)2, 2 with NaSDmp at -40 °C. The nickel site of complex 1 was found to add CO or CNtBu at -40 °C to give (CO)3Fe(StBu)(μ-StBu)2Ni(CO)(SDmp), 3, or (CO)3Fe(StBu)(μ-StBu)2Ni(CNtBu)(SDmp), 4, respectively. One of the CO bands of 3, appearing at 2055 cm-1 in the infrared spectrum, was assigned as the Ni-CO band, and this frequency is comparable to those observed for the CO-inhibited forms of [NiFe] hydrogenase. Like the CO-inhibited forms of [NiFe] hydrogenase, the coordination of CO at the nickel site of 1 is reversible, while the CNtBu adduct 4 is more robust. PMID:20147622

  5. Seedless synthesis and efficient recyclable catalytic activity of Ag@Fe nanocomposites towards methyl orange

    NASA Astrophysics Data System (ADS)

    Alzahrani, Salma Ahmed; Malik, Maqsood Ahmad; Al-Thabaiti, Shaeel Ahmed; Khan, Zaheer

    2018-03-01

    This work demonstrates a competitive reduction method of synthesis of nanomaterials. In this method along cetyltrimethylammonium bromide (CTAB), the reduction of Ag+ and Fe3+ ions is achieved by ascorbic acid-to-bimetallic Ag@Fe yellow-colored nanomaterials. The shape of UV-visible spectra and wavelengths absorbed of Ag@Fe can be tuned from ca. 290-600 nm by controlling [CTAB] and [Ag+]. The apparent first-order rate constants were calculated within the approximation of 6.1 × 10-3 s-1. The as-prepared Ag@Fe NPs have been found to be very important catalyst in terms of depredate methyl orange in vicinity of sodium borohydride (NaBH4), which exhibits excellent efficiency and re-usability in the prototypical reaction. The cmc of cationic surfactant CTAB has been determined by conductivity method under different experimental conditions. In the presence of CTAB, Ag+ and Fe3+ ions reduce to Ag@Fe core/shell nanoparticles, comprehend a change in wavelength and intensity of SRP band. The apparent first-order rate constant, activation energy, and turnover frequency for the methyl orange reduction catalyzed by Ag@Fe NPs were found to be 1.6 × 10-3 s-1, 58.2 kJ mol-1, and 1.1 × 10-3 s-1, respectively.

  6. Isotopic fractionation associated with [NiFe]- and [FeFe]-hydrogenases

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang, Hui; Gandhi, Hasand; Cornish, Adam J.

    2016-01-30

    Hydrogenases catalyze the reversible formation of H2 from electrons and protons with high efficiency. Understanding the relationships between H2 production, H2 uptake, and H2-H2O exchange can provide insight into the metabolism of microbial communities in which H2 is an essential component in energy cycling. In this manuscript, we used stable H isotopes (1H and 2H) to probe the isotope effects associated with three [FeFe]-hydrogenases and three [NiFe]-hydrogenases. All six hydrogenases displayed fractionation factors for H2 formation that were significantly less than 1, producing H2 that was severely depleted in 2H relative to the substrate, water. Consistent with differences in theirmore » active site structure, the fractionation factors for each class appear to cluster, with the three [NiFe]-hydrogenases (α = 0.27-0.40) generally having smaller values than the three [FeFe]-hydrogenases (α = 0.41-0.55). We also obtained isotopic fractionation factors associated with H2 uptake and H2-H2O exchange under conditions similar to those utilized for H2 production, providing us with a more complete picture of the three reactions catalyzed by hydrogenases. The fractionation factors determined in our studies can be used as signatures for different hydrogenases to probe their activity under different growth conditions and to ascertain which hydrogenases are most responsible for H2 production and/or uptake in complex microbial communities.« less

  7. Melting of Fe and Fe0.9Ni0.1 alloy at high pressures

    NASA Astrophysics Data System (ADS)

    Zhang, D.; Jackson, J. M.; Zhao, J.; Sturhahn, W.; Alp, E. E.; Hu, M. Y.; Toellner, T.

    2014-12-01

    Cosmochemical studies suggest that the cores of terrestrial planets are primarily composed of Fe alloyed with about 5 to 10 wt% Ni, plus some light elements (e.g., McDonough and Sun 1995). Thus, the high pressure melting curve of Fe0.9Ni0.1 is considered to be an important reference for characterizing the cores of terrestrial planets. We have determined the melting points of fcc-structured Fe and Fe0.9Ni0.1 up to 86 GPa using an in-situ method that monitors the atomic dynamics of the Fe atoms in the sample, synchrotron Mössbauer spectroscopy (Jackson et al. 2013). A laser heated diamond anvil cell is used to provide the high pressure-high temperature environmental conditions, and in-situ X-ray diffraction is used to constrain the pressure of the sample. To eliminate the influence of temperature fluctuations experienced by the sample on the determination of melting, we develop a Fast Temperature Readout (FasTeR) spectrometer. The FasTeR spectrometer features a fast reading rate (>100 Hz), a high sensitivity, a large dynamic range and a well-constrained focus. By combining the melting curve of fcc-structured Fe0.9Ni0.1 alloy determined in our study and the fcc-hcp phase boundary from Komabayashi et al. (2012), we calculate the fcc-hcp-liquid triple point of Fe0.9Ni0.1. Using this triple point and the thermophysical parameters from a nuclear resonant inelastic X-ray scattering study on hcp-Fe (Murphy et al. 2011), we compute the melting curve of hcp-structured Fe0.9Ni0.1. We will discuss our new experimental results with implications for the cores of Venus, Earth and Mars. Select references: McDonough & Sun (1995): The composition of the Earth. Chem. Geol. 120, 223-253. Jackson et al. (2013): Melting of compressed iron by monitoring atomic dynamics, EPSL, 362, 143-150. Komabayashi et al. (2012): In situ X-ray diffraction measurements of the fcc-hcp phase transition boundary of an Fe-Ni alloy in an internally heated diamond anvil cell, PCM, 39, 329-338. Murphy et al

  8. The prominent photoinduced voltage effect of as-prepared macroscopically long Ag core/Ni shell nanoheterojunctions.

    PubMed

    Sun, Jia-Lin; Zhao, Xingchen; Zhu, Jia-Lin

    2008-02-27

    Macroscopically long Ag core/Ni shell nanoheterojunctions have been well prepared by a dynamic growth approach. The structure characterized in detail by scanning electron microscopy reveals that the Ag nanowire bundles are wrapped in Ni nanoshields and form multicore coaxial cable frames. Notable photoinduced voltage with a fine repeatability, for irradiation with a laser, is exhibited compared with the case for bulk Ag pole/Ni shell heterojunctions and Ag nanowire bundle/bulk Ni heterojunctions. The prominent photoinduced voltage and the substantial metal nanoscale Ohmic interconnects provided by this kind of nanoheterojunction may have a wide range of applications in the future.

  9. Magnetic properties of Fe-doped NiO nanoparticles

    NASA Astrophysics Data System (ADS)

    Kurokawa, A.; Sakai, N.; Zhu, L.; Takeuchi, H.; Yano, S.; Yanoh, T.; Onuma, K.; Kondo, T.; Miike, K.; Miyasaka, T.; Ichiyanagi, Y.

    2013-08-01

    Ni1- x Fe x O ( x = 0, 0.05, 0.1) nanoparticles with several nanometers encapsulated with amorphous SiO2 were prepared by our novel preparation method. A NiO single phase structure was confirmed using the X-ray diffraction measurements. It is considered that Ni ions are replaced by Fe ions because it is observed that the lattice constant decreases. The temperature dependence behavior of the magnetization revealed that the blocking temperature, T B , shifted from 17 to 57 K as the amount of Fe ions increased, and that below T B , ferromagnetic behaviors were exhibited. The coercive force, H C , increased from 0.8 to 1.5 kOe as the amount of Fe ions increased.

  10. An advanced Ni-Fe layered double hydroxide electrocatalyst for water oxidation.

    PubMed

    Gong, Ming; Li, Yanguang; Wang, Hailiang; Liang, Yongye; Wu, Justin Z; Zhou, Jigang; Wang, Jian; Regier, Tom; Wei, Fei; Dai, Hongjie

    2013-06-12

    Highly active, durable, and cost-effective electrocatalysts for water oxidation to evolve oxygen gas hold a key to a range of renewable energy solutions, including water-splitting and rechargeable metal-air batteries. Here, we report the synthesis of ultrathin nickel-iron layered double hydroxide (NiFe-LDH) nanoplates on mildly oxidized multiwalled carbon nanotubes (CNTs). Incorporation of Fe into the nickel hydroxide induced the formation of NiFe-LDH. The crystalline NiFe-LDH phase in nanoplate form is found to be highly active for oxygen evolution reaction in alkaline solutions. For NiFe-LDH grown on a network of CNTs, the resulting NiFe-LDH/CNT complex exhibits higher electrocatalytic activity and stability for oxygen evolution than commercial precious metal Ir catalysts.

  11. Force Field Development and Molecular Dynamics of [NiFe] Hydrogenase

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Smith, Dayle MA; Xiong, Yijia; Straatsma, TP

    2012-05-09

    Classical molecular force-field parameters describing the structure and motion of metal clusters in [NiFe] hydrogenase enzymes can be used to compare the dynamics and thermodynamics of [NiFe] under different oxidation, protonation, and ligation circumstances. Using density functional theory (DFT) calculations of small model clusters representative of the active site and the proximal, medial, and distal Fe/S metal centers and their attached protein side chains, we have calculated classical force-field parameters for [NiFe] in reduced and oxidized states, including internal coordinates, force constants, and atom-centered charges. Derived force constants revealed that cysteinate ligands bound to the metal ions are more flexiblemore » in the Ni-B active site, which has a bridging hydroxide ligand, than in the Ni-C active site, which has a bridging hydride. Ten nanosecond all-atom, explicit-solvent MD simulations of [NiFe] hydrogenase in oxidized and reduced catalytic states established the stability of the derived force-field parameters in terms of C{alpha} and metal cluster fluctuations. Average active site structures from the protein MD simulations are consistent with [NiFe] structures from the Protein Data Bank, suggesting that the derived force-field parameters are transferrable to other hydrogenases beyond the structure used for testing. A comparison of experimental H{sub 2}-production rates demonstrated a relationship between cysteinate side chain rotation and activity, justifying the use of a fully dynamic model of [NiFe] metal cluster motion.« less

  12. Effects of two-temperature model on cascade evolution in Ni and NiFe

    DOE PAGES

    Samolyuk, German D.; Xue, Haizhou; Bei, Hongbin; ...

    2016-07-05

    We perform molecular dynamics simulations of Ni ion cascades in Ni and equiatomic NiFe under the following conditions: (a) classical molecular dynamics (MD) simulations without consideration of electronic energy loss, (b) classical MD simulations with the electronic stopping included, and (c) using the coupled two-temperature MD (2T-MD) model that incorporates both the electronic stopping and the electron-phonon interactions. Our results indicate that the electronic effects are more profound in the higher-energy cascades, and that the 2T-MD model results in a smaller amount of surviving damage and smaller defect clusters, while less damage is produced in NiFe than in Ni.

  13. Phase Equilibria of the Fe-Ni-Sn Ternary System at 270°C

    NASA Astrophysics Data System (ADS)

    Huang, Tzu-Ting; Lin, Shih-Wei; Chen, Chih-Ming; Chen, Pei Yu; Yen, Yee-Wen

    2016-12-01

    The Fe-42 wt.% Ni alloy, also known as a 42 invar alloy (Alloy 42), is used as a lead-frame material because its thermal expansion coefficient is much closer to Si substrate than Cu or Ni substrates. In order to enhance the wettability between the substrate and solder, the Sn layer was commonly electroplated onto the Alloy 42 surface. A clear understanding of the phase equilibria of the Fe-Ni-Sn ternary system is necessary to ensure solder-joint reliability between Sn and Fe-Ni alloys. To determine the isothermal section of the Fe-Ni-Sn ternary system at 270°C, 26 Fe-Ni-Sn alloys with different compositions were prepared. The experimental results confirmed the presence of the Fe3Ni and FeNi phases at 270°C. Meanwhile, it observed that the isothermal section of the Fe-Ni-Sn ternary system was composed of 11 single-phase regions, 19 two-phase regions and nine tie-triangles. Moreover, no ternary compounds were found in the Fe-Ni-Sn system at 270°C.

  14. Physical properties of FePt nanocomposite doped with Ag atoms: First-principles study

    NASA Astrophysics Data System (ADS)

    Jia, Yong-Fei; Shu, Xiao-Lin; Xie, Yong; Chen, Zi-Yu

    2014-07-01

    L10 FePt nanocomposite with high magnetocrystalline anisotropy energy has been extensively investigated in the fields of ultra-high density magnetic recording media. However, the order—disorder transition temperature of the nanocomposite is higher than 600 °C, which is a disadvantage for the use of the material due to the sustained growth of FePt grain under the temperature. To address the problem, addition of Ag atoms has been proposed, but the magnetic properties of the doped system are still unclear so far. Here in this paper, we use first-principles method to study the lattice parameters, formation energy, electronic structure, atomic magnetic moment and order—disorder transition temperature of L10 FePt with Ag atom doping. The results show that the formation energy of a Ag atom substituting for a Pt site is 1.309 eV, which is lower than that of substituting for an Fe site 1.346 eV. The formation energy of substituting for the two nearest Pt sites is 2.560 eV lower than that of substituting for the further sites 2.621 eV, which indicates that Ag dopants tend to segregate L10 FePt. The special quasirandom structures (SQSs) for the pure FePt and the FePt doped with two Ag atoms at the stable Pt sites show that the order—disorder transition temperatures are 1377 °C and 600 °C, respectively, suggesting that the transition temperature can be reduced with Ag atom, and therefore the FePt grain growth is suppressed. The saturation magnetizations of the pure FePt and the two Ag atoms doped FePt are 1083 emu/cc and 1062 emu/cc, respectively, indicating that the magnetic property of the doped system is almost unchanged.

  15. The growth of intermetallic compounds at Sn-Ag-Cu solder/Cu and Sn-Ag-Cu solder/Ni interfaces and the associated evolution of the solder microstructure

    NASA Astrophysics Data System (ADS)

    Zribi, A.; Clark, A.; Zavalij, L.; Borgesen, P.; Cotts, E. J.

    2001-09-01

    The evolution of intermetallics at and near SnAgCu/Cu and SnAgCu/Ni interfaces was examined, and compared to the behavior, near PbSn/metal and Sn/metal interfaces. Two different solder compositions were considered, Sn93.6Ag4.7Cu1.7 and Sn95.5Ag3.5Cu1.0 (Sn91.8Ag5.1 Cu3.1 and Sn94.35Ag3.8Cu1.85 in atomic percent). In both cases, phase formation and growth at interfaces with Cu were very similar to those commonly observed for eutectic SnPb solder. However, the evolution of intermetallics at SnAgCu/Ni interfaces proved much more complex. The presence of the Cu in the solder dramatically altered the phase selectivity at the solder/Ni interface and affected the growth kinetics of intermetallics. As long as sufficient Cu was available, it would combine with Ni and Sn to form (Cu,Ni)6)Sn5 which grew instead of the Ni3Sn4 usually observed in PbSn/Ni and Sn/Ni diffusion couples. This growing phase would, however, eventually consume essentially all of the available Cu in the solder. Because the mechanical properties of Sn-Ag-Cu alloys, depend upon the Cu content, this consumption can be expected to alter the mechanical properties of these Pb-free solderjoints. After depletion of the Cu from the solder, further annealing then gradually transformed the (Cu,Ni)6Sn5 phase into a (Ni,Cu)3Sn4 phase.

  16. Synthesis, characterization and some properties of mononuclear Ni and trinuclear NiFe2 complexes related to the active site of [NiFe]-hydrogenases.

    PubMed

    Song, Li-Cheng; Sun, Xiao-Jing; Zhao, Pei-Hua; Li, Jia-Peng; Song, Hai-Bin

    2012-08-07

    The [N(2)S(2)]-type ligand 1,2-(2-C(5)H(4)NCH(2)S)(2)C(6)H(4) (L) is prepared in 84% yield by a new method and its structure has been confirmed by X-ray crystallography. The new synthetic method involves sequential reaction of 1,2-phenylenedithiol with EtONa followed by treatment of the resulting disodium salt of 1,2-phenylenedithiol with in situ generated 2-(chloromethyl)pyridine from its HCl salt. Further treatment of ligand L with NiCl(2)·6H(2)O or NiI(2) affords the expected new mononuclear Ni complexes Ni[1,2-(2-C(5)H(4)NCH(2)S)(2)C(6)H(4)]Cl(2) (1) and Ni[1,2-(2-C(5)H(4)NCH(2)S)(2)C(6)H(4)]I(2) (3) in 87-88% yields, whereas reaction of L with NiBr(2) under similar conditions results in formation of the expected new mononuclear complex Ni[1,2-(2-C(5)H(4)NCH(2)S)(2)C(6)H(4)]Br(2) (2) and one unexpected new mononuclear complex Ni[1-(2-C(5)H(4)NCH(2)S)-2-(2-C(5)H(4)NCH(2)SC(6)H(4)S)C(6)H(4)]Br(2) (2*) in 82% and 5% yields, respectively. More interestingly, the ligand L-containing novel trinuclear NiFe(2) complex Ni{[1,2-(2-C(5)H(4)NCH(2)S)(2)C(6)H(4)}Fe(2)(CO)(6)(μ(3)-S)(2) (4) is found to be prepared by sequential reaction of (μ-S(2))Fe(2)(CO)(6) with Et(3)BHLi, followed by treatment of the resulting (μ-LiS)(2)Fe(2)(CO)(6) with mononuclear complex 1, 2, or 3 in 12-20% yields. The new complexes 1-4 and 2* are fully characterized by elemental analysis and various spectroscopies, and the crystal structures of 1, 2* and 3 as well as some electrochemical properties of 1-4 are also reported.

  17. One-pot fabrication of NiFe2O4 nanoparticles on α-Ni(OH)2 nanosheet for enhanced water oxidation

    NASA Astrophysics Data System (ADS)

    Chen, Hong; Yan, Junqing; Wu, Huan; Zhang, Yunxia; Liu, Shengzhong (Frank)

    2016-08-01

    Water splitting has been intensively investigated as a promising solution to resolve the future environmental and energy crises. The oxygen evolution reaction (OER) of the photo- and electric field-induced water splitting limits the development of other reactions, including hydrogen evolution reaction (HER). Fe, Ni and NiFe (hydro) oxide-based catalysts are generally acknowledged among the best candidates of OER catalysts for water splitting. Herein, we developed a one-pot simple hydrothermal process to assemble NiFe2O4 nanoparticles onto the α-Ni(OH)2 nanosheets. The first formed NiFe2O4 under high temperature and pressure environment induces and assists the α-Ni(OH)2 formation without any further additives, because the distance between the neighboring Ni atoms in the cubic NiFe2O4 is similar to that in the α-Ni(OH)2 {003} facets. We have synthesized a series of NiFe2O4/α-Ni(OH)2 compounds and find that the overpotential decreases with the increase of Ni(OH)2 content while the OER kinetics stays unchanged, suggesting that Ni(OH)2 plays a major role in overpotential while NiFe2O4 mainly affects the OER kinetics. The obtained NiFe2O4/α-Ni(OH)2 compounds is also found to be a promising co-catalyst for the photocatalytic water oxidation. In fact, it is even more active than the noble PtOx with acceptable stability for the oxygen generation.

  18. RGO modified Ni doped FeOOH for enhanced electrochemical and photoelectrochemical water oxidation

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaofan; Zhang, Bingyan; Liu, Shuangshuang; Kang, Hongwei; Kong, Weiqian; Zhang, Shouren; Shen, Yan; Yang, Baocheng

    2018-04-01

    Ni,Fe-based (oxy)hydroxides have been one of the most active catalysts for the oxygen evolution reaction. In this article, reduced graphene oxide supported Ni doped FeOOH (RGO/Ni:FeOOH) was prepared for electrochemical and photoelectrochemical (PEC) water oxidation. The RGO/Ni:FeOOH exhibited a lower over-potential (260 mV at 10 mA cm-2) and smaller Tafel slope (32.3 mV dec-1) than that of the FeOOH and Ni:FeOOH. Such significant enhancement is attributed to Ni doping and RGO, which reduce the over-potential, improve the conductivity and enlarge surface areas. Besides, RGO/Ni:FeOOH decorated the TiO2 nanorods (NRs) was also fabricated for photoelectrochemical (PEC) water oxidation, which exhibited a higher photocurrent density and lower onset potential than that of TiO2 NRs the bare under illumination due to the synergistic effect of RGO and Ni:FeOOH. These results demonstrate the RGO/Ni:FeOOH has great promising as a co-catalyst to improve the PEC performance.

  19. Diffusion, phase equilibria and partitioning experiments in the Ni-Fe-Ru system

    NASA Technical Reports Server (NTRS)

    Blum, Joel D.; Wasserburg, G. J.; Hutcheon, I. D.; Beckett, J. R.; Stolper, E. M.

    1989-01-01

    Results are presented on thin-film diffusion experiments designed to investigate phase equilibria in systems containing high concentrations of Pt-group elements, such as Ni-Fe-Ru-rich systems containing Pt, at temperatures of 1273, 1073, and 873 K. The rate of Ru diffusion in Ni was determined as a function of temperature, and, in addition, the degree of Pt and Ir partitioning between phases in a Ni-Fe-Ru-rich system and of V between phases in a Ni-Fe-O-rich system at 873 were determined. It was found that Pt preferentially partitions into the (gamma)Ni-Fe phase, whereas Ir prefers the (epsilon)Ru-Fe phase. V partitions strongly into Fe oxides relative to (gamma)Ni-Fe. These results have direct application to the origin and thermal history of the alloys rich in Pt-group elements in meteorites.

  20. Biomimetics of [NiFe]-Hydrogenase: Nickel- or Iron-Centered Proton Reduction Catalysis?

    PubMed

    Tang, Hao; Hall, Michael B

    2017-12-13

    The [NiFe] hydrogenase (H2ase) has been characterized in the Ni-R state with a hydride bridging between Fe and Ni but displaced toward the Ni. In nearly all of the synthetic Ni-R models reported so far, the hydride ligand is either displaced toward Fe, or terminally bound to Fe. Recently, a structural and functional [NiFe]-H2ase mimic ( Nat. Chem. 2016 , 8 , 1054 - 1060 ) was reported to produce H 2 catalytically via EECC mechanism through a Ni-centered hydride intermediate like the enzyme. Here, a comprehensive DFT study shows a much lower energy route via an E[ECEC] mechanism through an Fe-centered hydride intermediate. Although catalytic H 2 production occurs at the potential corresponding to the complex's second reduction, a third electron is needed to induce the second proton addition from the weak acid. The first two-electron reductions and a proton addition produce a semibridging hydride with a short Fe-H bond like other structured [NiFe]-biomimetics, but this species is not basic enough to add another proton from the weak acid without the third electron. The calculated mechanism provides insight into the origin of this structure in the enzyme.

  1. Quantum chemical approaches to [NiFe] hydrogenase.

    PubMed

    Vaissier, Valerie; Van Voorhis, Troy

    2017-05-09

    The mechanism by which [NiFe] hydrogenase catalyses the oxidation of molecular hydrogen is a significant yet challenging topic in bioinorganic chemistry. With far-reaching applications in renewable energy and carbon mitigation, significant effort has been invested in the study of these complexes. In particular, computational approaches offer a unique perspective on how this enzyme functions at an electronic and atomistic level. In this article, we discuss state-of-the art quantum chemical methods and how they have helped deepen our comprehension of [NiFe] hydrogenase. We outline the key strategies that can be used to compute the (i) geometry, (ii) electronic structure, (iii) thermodynamics and (iv) kinetic properties associated with the enzymatic activity of [NiFe] hydrogenase and other bioinorganic complexes. © 2017 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

  2. Point defect evolution in Ni, NiFe and NiCr alloys from atomistic simulations and irradiation experiments

    DOE PAGES

    Aidhy, Dilpuneet S.; Lu, Chenyang; Jin, Ke; ...

    2015-08-08

    Using molecular dynamics simulations, we elucidate irradiation-induced point defect evolution in fcc pure Ni, Ni 0.5Fe 0.5, and Ni 0.8Cr 0.2 solid solution alloys. We find that irradiation-induced interstitials form dislocation loops that are of 1/3 <111>{111}-type, consistent with our experimental results. While the loops are formed in all the three materials, the kinetics of formation is considerably slower in NiFe and NiCr than in pure Ni, indicating that defect migration barriers and extended defect formation energies could be higher in the alloys than pure Ni. As a result, while larger size clusters are formed in pure Ni, smaller andmore » more clusters are observed in the alloys. The vacancy diffusion occurs at relatively higher temperatures than interstitials, and their clustering leads to formation of stacking fault tetrahedra, also consistent with our experiments. The results also show that the surviving Frenkel pairs are composition-dependent and are largely Ni dominated.« less

  3. Photosensitivity of the Ni-A state of [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F with visible light

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Osuka, Hisao; Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5, Takayama-cho, Ikoma-shi, Nara 630-0192; Shomura, Yasuhito

    2013-01-04

    Highlights: Black-Right-Pointing-Pointer Ni-A state of [NiFe] hydrogenase showed light sensitivity. Black-Right-Pointing-Pointer New FT-IR bands were observed with light irradiation of the Ni-A state. Black-Right-Pointing-Pointer EPR g-values of the Ni-A state shifted upon light irradiation. Black-Right-Pointing-Pointer The light-induced state converted back to the Ni-A state under the dark condition. -- Abstract: [NiFe] hydrogenase catalyzes reversible oxidation of molecular hydrogen. Its active site is constructed of a hetero dinuclear Ni-Fe complex, and the oxidation state of the Ni ion changes according to the redox state of the enzyme. We found that the Ni-A state (an inactive unready, oxidized state) of [NiFe] hydrogenasemore » from Desulfovibrio vulgaris Miyazaki F (DvMF) is light sensitive and forms a new state (Ni-AL) with irradiation of visible light. The Fourier transform infrared (FT-IR) bands at 1956, 2084 and 2094 cm{sup -1} of the Ni-A state shifted to 1971, 2086 and 2098 cm{sup -1} in the Ni-AL state. The g-values of g{sub x} = 2.30, g{sub y} = 2.23 and g{sub z} = 2.01 for the signals in the electron paramagnetic resonance (EPR) spectrum of the Ni-A state at room temperature varied for -0.009, +0.012 and +0.010, respectively, upon light irradiation. The light-induced Ni-AL state converted back immediately to the Ni-A state under dark condition at room temperature. These results show that the coordination structure of the Fe site of the Ni-A state of [NiFe] hydrogenase is perturbed significantly by light irradiation with relatively small coordination change at the Ni site.« less

  4. Experimental determination of carbon solubility in Fe-Ni-S melts

    NASA Astrophysics Data System (ADS)

    Zhang, Zhou; Hastings, Patrick; Von der Handt, Anette; Hirschmann, Marc M.

    2018-03-01

    To investigate the effect of metal/sulfide and Ni/Fe ratio on the C storage capacity of sulfide melts, we determine carbon solubility in Fe-Ni-S melts with various (Fe + Ni)/S and Ni/Fe via graphite-saturated high-pressure experiments from 2-7 GPa and 1200-1600 °C. Consistent with previous results, C solubility is high (4-6 wt.%) in metal-rich sulfide melts and diminishes with increasing S content. Melts with near M/S = 1 (XS > 0.4) have <0.5 wt.% C in equilibrium with graphite. C solubility is diminished modestly with increased Ni/Fe ratio, but the effect is most pronounced for S-poor melts, and becomes negligible in near-monosulfide compositions. Immiscibility between S-rich and C-rich melts is observed in Ni-poor compositions, but above ∼18 wt.% Ni there is complete miscibility. Because mantle sulfide compositions are expected to have high Ni concentrations, sulfide-carbide immiscibility is unlikely in natural mantle melts. An empirical parameterization of C solubility in Ni-Fe-S melts as a function of S and Ni contents allows estimation of the C storage capacity of sulfide in the mantle. Importantly, as the metal/sulfide (M/S) ratio of the melt increases, C storage increases both because C solubility increases and because the mass fraction of melt is enhanced by addition of metal from surrounding silicates. Under comparatively oxidized conditions where melts are near M/S = 1, as prevails at <250 km depth, bulk C storage is <3 ppm. In the deeper, more reduced mantle where M/S increases, up to 200 ppm C in typical mantle with 200 ± 100 ppm S can be stored in Fe-Ni-S melts. Thus, metal-rich sulfide melts are the principal host of carbon in the deep upper mantle and below. Residual carbon is present either as diamond or, if conditions are highly reduced and total C concentrations are low, solid alloy.

  5. Effect of the spin-twist structure on the spin-wave dynamics in Fe{sub 55}Pt{sub 45}/Ni{sub 80}Fe{sub 20} exchange coupled bi-layers with varying Ni{sub 80}Fe{sub 20} thickness

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pal, Semanti; Barman, Saswati, E-mail: saswati@bose.res.in; Barman, Anjan, E-mail: abarman@bose.res.in

    2014-05-07

    We have investigated optically induced ultrafast magnetization dynamics of a series of Fe{sub 55}Pt{sub 45}/Ni{sub 80}Fe{sub 20} exchange spring bi-layers with varying Ni{sub 80}Fe{sub 20} thickness. Rich spin-wave spectra are observed; whose frequency shows a strong dependence on the Ni{sub 80}Fe{sub 20} layer thickness. Micromagnetic simulations based on a simplified magnetic microstructure were able to reproduce the experimental data qualitatively. The spin twist structure introduced in the Ni{sub 80}Fe{sub 20} layer gives rise to new modes in the composite system as opposed to the bare Ni{sub 80}Fe{sub 20} films.

  6. Self-Diffusion of small Ag and Ni islands on Ag(111) and Ni(111) using the self-learning kinetic Monte Carlo method

    NASA Astrophysics Data System (ADS)

    Islamuddin Shah, Syed; Nandipati, Giridhar; Kara, Abdelkader; Rahman, Talat S.

    2012-02-01

    We have applied a modified Self-Learning Kinetic Monte Carlo (SLKMC) method [1] to examine the self-diffusion of small Ag and Ni islands, containing up to 10 atom, on the (111) surface of the respective metal. The pattern recognition scheme in this new SLKMC method allows occupancy of the fcc, hcp and top sites on the fcc(111) surface and employs them to identify the local neighborhood around a central atom. Molecular static calculations with semi empirical interatomic potential and reliable techniques for saddle point search revealed several new diffusion mechanisms that contribute to the diffusion of small islands. For comparison we have also evaluated the diffusion characteristics of Cu clusters on Cu(111) and compared results with previous findings [2]. Our results show a linear increase in effective energy barriers scaling almost as 0.043, 0.051 and 0.064 eV/atom for the Cu/Cu(111), Ag/Ag(111), and Ni/Ni(111) systems, respectively. For all three systems, diffusion of small islands proceeds mainly through concerted motion, although several multiple and single atom processes also contribute. [1] Oleg Trushin et al. Phys. Rev. B 72, 115401 (2005) [2] Altaf Karim et al. Phys. Rev. B 73, 165411 (2006)

  7. Magnetic and conventional shape memory behavior of Mn-Ni-Sn and Mn-Ni-Sn(Fe) alloys

    NASA Astrophysics Data System (ADS)

    Turabi, A. S.; Lázpita, P.; Sasmaz, M.; Karaca, H. E.; Chernenko, V. A.

    2016-05-01

    Magnetic and conventional shape memory properties of Mn49Ni42Sn9(at.%) and Mn49Ni39Sn9Fe3(at.%) polycrystalline alloys exhibiting martensitic transformation from ferromagnetic austenite into weakly magnetic martensite are characterized under compressive stress and magnetic field. Magnetization difference between transforming phases drastically increases, while transformation temperature decreases with the addition of Fe. Both Mn49Ni42Sn9 and Mn49Ni39Sn9Fe3 alloys show remarkable superelastic and shape memory properties with recoverable strain of 4% and 3.5% under compression at room temperature, respectively. These characteristics can be counted as extraordinary among the polycrystalline NiMn-based magnetic shape memory alloys. Critical stress for phase transformation was increased by 34 MPa in Mn49Ni39Sn9Fe3 and 21 MPa in Mn49Ni42Sn9 at 9 T, which can be qualitatively understood in terms of thermodynamic Clausius-Clapeyron relationships and in the framework of the suggested physical concept of a volume magnetostress.

  8. DFT study on dry reforming of methane over Ni2Fe overlayer of Ni(1 1 1) surface

    NASA Astrophysics Data System (ADS)

    Xu, Li-li; Wen, Hong; Jin, Xin; Bing, Qi-ming; Liu, Jing-yao

    2018-06-01

    We reported the complete catalytic cycle of dry reforming of methane (DRM) on Ni2Fe overlayer of Ni(1 1 1) surface by periodic density functional theory (DFT) calculations. The pathways for dehydrogenation of CH4 and CO2 activation were located. Our results demonstrate that compared with pure Ni(1 1 1) surface, the introduction Fe into Ni increases the energy barrier of CH dissociation to carbon and hydrogen atoms, thereby suppressing coke deposition on the surface, while it promotes the H-induced CO2 activation pathway to form OH radical, and thus not only the surface oxygen but also OH are responsible for the oxidation of CHx (x = 0,1) on the Ni2Fe overlayer. The most favorable pathway of CH/C oxidation is found to be CH∗ + OH∗ → CHOH∗ → CHO∗ + H∗ → CO∗ + 2H∗, with the rate-limiting energy barrier of 1.12 eV. Furthermore, since Fe is oxidized partially to FeO leading to a partial dealloying under DRM conditions, we also studied the surface-carbon removal and the activity for the reforming of methane on the FeO ribbon supported Ni(1 1 1) (FeO/Ni) interface by DFT+U method. The surface C reacts with lattice oxygen of FeO to produce CO via a Mars-van Krevelen (MvK) mechanism, with a very lower energy barrier of 0.16 eV. The present results show that the introduction of Fe into Ni has a positive effect on the activity toward DRM and has an improved coke resistance.

  9. Local structure study of Fe dopants in Ni-deficit Ni 3Al alloys

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    V. N. Ivanovski; Umicevic, A.; Belosevic-Cavor, J.

    2015-08-24

    We found that the local electronic and magnetic structure, hyperfine interactions, and phase composition of polycrystalline Ni–deficient Ni 3-x FexAl (x = 0.18 and 0.36) were investigated by means of 57 Fe Mössbauer spectroscopy. The samples were characterized by X–ray diffraction and magnetization measurements. The ab initio calculations performed with the projector augmented wave method and the calculations of the energies of iron point defects were done to elucidate the electronic structure and site preference of Fe doped Ni 3 Al. Moreover, the value of calculated electric field gradient tensor V zz=1.6 10 21Vm -2 matches well with the resultsmore » of Mössbauer spectroscopy and indicates that the Fe atoms occupy Ni sites.« less

  10. Supergene neoformation of Pt-Ir-Fe-Ni alloys: multistage grains explain nugget formation in Ni-laterites

    NASA Astrophysics Data System (ADS)

    Aiglsperger, Thomas; Proenza, Joaquín A.; Font-Bardia, Mercè; Baurier-Aymat, Sandra; Galí, Salvador; Lewis, John F.; Longo, Francisco

    2017-10-01

    Ni-laterites from the Dominican Republic host rare but extremely platinum-group element (PGE)-rich chromitites (up to 17.5 ppm) without economic significance. These chromitites occur either included in saprolite (beneath the Mg discontinuity) or as `floating chromitites' within limonite (above the Mg discontinuity). Both chromitite types have similar iridium-group PGE (IPGE)-enriched chondrite normalized patterns; however, chromitites included in limonite show a pronounced positive Pt anomaly. Investigation of heavy mineral concentrates, obtained via hydroseparation techniques, led to the discovery of multistage PGE grains: (i) Os-Ru-Fe-(Ir) grains of porous appearance are overgrown by (ii) Ni-Fe-Ir and Ir-Fe-Ni-(Pt) phases which are overgrown by (iii) Pt-Ir-Fe-Ni mineral phases. Whereas Ir-dominated overgrowths prevail in chromitites from the saprolite, Pt-dominated overgrowths are observed within floating chromitites. The following formation model for multistage PGE grains is discussed: (i) hypogene platinum-group minerals (PGM) (e.g. laurite) are transformed to secondary PGM by desulphurization during serpentinization; (ii) at the stages of serpentinization and/or at the early stages of lateritization, Ir is mobilized and recrystallizes on porous surfaces of secondary PGM (serving as a natural catalyst) and (iii) at the late stages of lateritization, biogenic mediated neoformation (and accumulation) of Pt-Ir-Fe-Ni nanoparticles occurs. The evidence presented in this work demonstrates that in situ growth of Pt-Ir-Fe-Ni alloy nuggets of isometric symmetry is possible within Ni-laterites from the Dominican Republic.

  11. Phase relationships of the system Fe-Ni-S and structure of the high-pressure phase of (Fe1-xNix)3S2

    NASA Astrophysics Data System (ADS)

    Urakawa, Satoru; Kamuro, Ryota; Suzuki, Akio; Kikegawa, Takumi

    2018-04-01

    The phase relationships of the Fe-Ni-S system at 15 GPa were studied by high pressure quench experiments. The stability fields of (Fe,Ni)3S and (Fe,Ni)3S2 and the melting relationships of the Fe-Ni-S system were determined as a function of Ni content. The (Fe,Ni)3S solid solution is stable in the composition of Ni/(Fe + Ni) > 0.7 and melts incongruently into an Fe-Ni alloy + liquid. The (Fe,Ni)3S2 makes a complete solid solution and melts incongruently into (Fe,Ni)S + liquid, whose structure was determined to show Cmcm-orthorhombic symmetry by in situ synchrotron X-ray diffraction experiments. The eutectic contains about 30 at.% of S, and its temperature decreases with increasing Ni content with a rate of ∼5 K/at.% from 1175 K. The density of the Fe-FeS eutectic composition (Fe70S30) liquid is evaluated to be 6.93 ± 0.08 g/cm3 at 15 GPa and 1200 K based on the Clausius-Clapeyron relations and densities of subsolidus phases. The Fe-Ni-S liquids are a primary sulfur-bearing phase in the deep mantle with a reducing condition (250-660 km depth), and they would play a significant role in the carbon cycle as a carbon host as well as in the generation of diamond.

  12. Low-frequency creep in CoNiFe films.

    NASA Technical Reports Server (NTRS)

    Bartran, D. S.; Bourne, H. C., Jr.; Chow, L. G.

    1972-01-01

    Domain wall motion excited by slow rise-time, bipolar, hard-axis pulses in vacuum deposited CoNiFe films from 1500 to 2000 A thick is studied. The results are consistent with those of comparable NiFe films. Furthermore, the wall coercivity is found to be the most significant sample property correlated to the low-frequency creep properties of all the samples.

  13. Effects of Ni content on nanocrystalline Fe-Co-Ni ternary alloys synthesized by a chemical reduction method

    NASA Astrophysics Data System (ADS)

    Chokprasombat, Komkrich; Pinitsoontorn, Supree; Maensiri, Santi

    2016-05-01

    Magnetic properties of Fe-Co-Ni ternary alloys could be altered by changing of the particle size, elemental compositions, and crystalline structures. In this work, Fe50Co50-xNix nanoparticles (x=10, 20, 40, and 50) were prepared by the novel chemical reduction process. Hydrazine monohydrate was used as a reducing agent under the concentrated basic condition with the presence of poly(vinylpyrrolidone). We found that the nanoparticles were composed of Fe, Co and Ni with compositions according to the molar ratio of the metal sources. Interestingly, the particles were well-crystalline at the as-prepared state without post-annealing at high temperature. Increasing Ni content resulted in phase transformation from body centered cubic (bcc) to face centered cubic (fcc). For the fcc phase, the average particle size decreased when increased the Ni content; the Fe50Ni50 nanoparticles had the smallest average size with the narrowest size distribution. In additions, the particles exhibited ferromagnetic properties at room temperature with the coercivities higher than 300 Oe, and the saturation magnetiation decreased with increasing Ni content. These results suggest that the structural and magnetic properties of Fe-Co-Ni alloys could be adjusted by varying the Ni content.

  14. Characterization of NiFe oxyhydroxide electrocatalysts by integrated electronic structure calculations and spectroelectrochemistry.

    PubMed

    Goldsmith, Zachary K; Harshan, Aparna K; Gerken, James B; Vörös, Márton; Galli, Giulia; Stahl, Shannon S; Hammes-Schiffer, Sharon

    2017-03-21

    NiFe oxyhydroxide materials are highly active electrocatalysts for the oxygen evolution reaction (OER), an important process for carbon-neutral energy storage. Recent spectroscopic and computational studies increasingly support iron as the site of catalytic activity but differ with respect to the relevant iron redox state. A combination of hybrid periodic density functional theory calculations and spectroelectrochemical experiments elucidate the electronic structure and redox thermodynamics of Ni-only and mixed NiFe oxyhydroxide thin-film electrocatalysts. The UV/visible light absorbance of the Ni-only catalyst depends on the applied potential as metal ions in the film are oxidized before the onset of OER activity. In contrast, absorbance changes are negligible in a 25% Fe-doped catalyst up to the onset of OER activity. First-principles calculations of proton-coupled redox potentials and magnetizations reveal that the Ni-only system features oxidation of Ni 2+ to Ni 3+ , followed by oxidation to a mixed Ni 3+/4+ state at a potential coincident with the onset of OER activity. Calculations on the 25% Fe-doped system show the catalyst is redox inert before the onset of catalysis, which coincides with the formation of Fe 4+ and mixed Ni oxidation states. The calculations indicate that introduction of Fe dopants changes the character of the conduction band minimum from Ni-oxide in the Ni-only to predominantly Fe-oxide in the NiFe electrocatalyst. These findings provide a unified experimental and theoretical description of the electrochemical and optical properties of Ni and NiFe oxyhydroxide electrocatalysts and serve as an important benchmark for computational characterization of mixed-metal oxidation states in heterogeneous catalysts.

  15. Characterization of NiFe oxyhydroxide electrocatalysts by integrated electronic structure calculations and spectroelectrochemistry

    PubMed Central

    Goldsmith, Zachary K.; Harshan, Aparna K.; Gerken, James B.; Galli, Giulia; Stahl, Shannon S.

    2017-01-01

    NiFe oxyhydroxide materials are highly active electrocatalysts for the oxygen evolution reaction (OER), an important process for carbon-neutral energy storage. Recent spectroscopic and computational studies increasingly support iron as the site of catalytic activity but differ with respect to the relevant iron redox state. A combination of hybrid periodic density functional theory calculations and spectroelectrochemical experiments elucidate the electronic structure and redox thermodynamics of Ni-only and mixed NiFe oxyhydroxide thin-film electrocatalysts. The UV/visible light absorbance of the Ni-only catalyst depends on the applied potential as metal ions in the film are oxidized before the onset of OER activity. In contrast, absorbance changes are negligible in a 25% Fe-doped catalyst up to the onset of OER activity. First-principles calculations of proton-coupled redox potentials and magnetizations reveal that the Ni-only system features oxidation of Ni2+ to Ni3+, followed by oxidation to a mixed Ni3+/4+ state at a potential coincident with the onset of OER activity. Calculations on the 25% Fe-doped system show the catalyst is redox inert before the onset of catalysis, which coincides with the formation of Fe4+ and mixed Ni oxidation states. The calculations indicate that introduction of Fe dopants changes the character of the conduction band minimum from Ni-oxide in the Ni-only to predominantly Fe-oxide in the NiFe electrocatalyst. These findings provide a unified experimental and theoretical description of the electrochemical and optical properties of Ni and NiFe oxyhydroxide electrocatalysts and serve as an important benchmark for computational characterization of mixed-metal oxidation states in heterogeneous catalysts. PMID:28265083

  16. The Effect of (Ag, Ni, Zn)-Addition on the Thermoelectric Properties of Copper Aluminate

    PubMed Central

    Yanagiya, Shun-ichi; Van Nong, Ngo; Xu, Jianxiao; Pryds, Nini

    2010-01-01

    Polycrystalline bulk copper aluminate Cu1-x-yAgxByAlO2 with B = Ni or Zn were prepared by spark plasma sintering and subsequent thermal treatment. The influence of partial substitution of Ag, Ni and Zn for Cu-sites in CuAlO2 on the high temperature thermoelectric properties has been studied. The addition of Ag and Zn was found to enhance the formation of CuAlO2 phase and to increase the electrical conductivity. The addition of Ag or Ag and Ni on the other hand decreases the electrical conductivity. The highest power factor of 1.26 × 10-4 W/mK2 was obtained for the addition of Ag and Zn at 1,060 K, indicating a significant improvement compared with the non-doped CuAlO2 sample.

  17. Investigation of coercivity for electroplated Fe-Ni thick films

    NASA Astrophysics Data System (ADS)

    Yanai, T.; Eguchi, K.; Koda, K.; Kaji, J.; Aramaki, H.; Takashima, K.; Nakano, M.; Fukunaga, H.

    2018-05-01

    We have already reported Fe-Ni firms with good soft magnetic properties prepared by using an electroplating method. In our previous studies, we prepared the Fe-Ni films from citric-acid-based baths (CA-baths) and ammonium-chloride-based ones (AC-baths), and confirmed that the coercivity for the AC-baths was lower than that for the CA-baths. In the present study, we investigated reasons for the lower coercivity for the AC-baths to further improve the soft magnetic properties. From an observation of magnetic domains of the Fe22Ni78 films, we found that Fe22Ni78 film for AC-bath had a magnetic anisotropy in the width direction, and also found that the coercivity in the width direction was lower than the longitudinal one for the AC-bath. As an annealing for a stress relaxation in the films reduced the difference in the coercivity, we considered that the anisotropy is attributed to the magneto-elastic effect.

  18. The role of the non-magnetic material in spin pumping and magnetization dynamics in NiFe and CoFeB multilayer systems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ruiz-Calaforra, A., E-mail: ruiz@physik.uni-kl.de; Brächer, T.; Lauer, V.

    2015-04-28

    We present a study of the effective magnetization M{sub eff} and the effective damping parameter α{sub eff} by means of ferromagnetic resonance spectroscopy on the ferromagnetic (FM) materials Ni{sub 81}Fe{sub 19} (NiFe) and Co{sub 40}Fe{sub 40}B{sub 20} (CoFeB) in FM/Pt, FM/NM, and FM/NM/Pt systems with the non-magnetic (NM) materials Ru, Cr, Al, and MgO. Moreover, for NiFe layer systems, the influence of interface effects is studied by way of thickness dependent measurements of M{sub eff} and α{sub eff}. Additionally, spin pumping in NiFe/NM/Pt is investigated by means of inverse spin Hall effect (ISHE) measurements. We observe a large dependence ofmore » M{sub eff} and α{sub eff} of the NiFe films on the adjacent NM layer. While Cr and Al do not induce a large change in the magnetic properties, Ru, Pt, and MgO affect M{sub eff} and α{sub eff} in different degrees. In particular, NiFe/Ru and NiFe/Ru/Pt systems show a large perpendicular surface anisotropy and a significant enhancement of the damping. In contrast, the magnetic properties of CoFeB films do not have a large influence of the NM adjacent material and only CoFeB/Pt systems present an enhancement of α{sub eff}. However, this enhancement is much more pronounced in NiFe/Pt. By the introduction of the NM spacer material, this enhancement is reduced. Furthermore, a difference in symmetry between NiFe/NM/Pt and NiFe/NM systems in the output voltage signal from the ISHE measurements reveals the presence of spin pumping into the Pt layer in all-metallic NiFe/NM/Pt and NiFe/Pt systems.« less

  19. Crystallinity of Fe-Ni Sulfides in Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E.; Ohsumi, Kazumasa; Mikouchi, Takashi; Hagiya, Kenji; Le, Loan

    2008-01-01

    The main long-term goal of this research is to understand the physical conditions in the early solar nebula through the detailed characterization of a key class of mineral present in all primitive materials: Fe-Ni sulfides [1&2]. Fe-Ni sulfides can take dozens of structures, depending on the temperature of formation, as well as other physico-chemical factors which are imperfectly understood. Add to this the additional varying factor of Ni content, and we have a potentially sensitive cosmothermometer [3]. Unfortunately, this tool requires exact knowledge of the crystal structure of each grain being considered, and there have been few (none?) studies of the detailed structures of sulfides in chondritic materials. We report here on coordinated compositional and crystallographic investigation of Fe-Ni sulfides in diverse carbonaceous chondrites, initially Acfer 094 (the most primitive CM2 [4]) Tagish Lake (a unique type C2 [5]), a C1 lithology in Kaidun [6], Bali (oxidized CV3 [7]), and Efremovka (reduced CV3 [7]).

  20. Unusual reaction of [NiFe]-hydrogenases with cyanide.

    PubMed

    Hexter, Suzannah V; Chung, Min-Wen; Vincent, Kylie A; Armstrong, Fraser A

    2014-07-23

    Cyanide reacts rapidly with [NiFe]-hydrogenases (hydrogenase-1 and hydrogenase-2 from Escherichia coli) under mild oxidizing conditions, inhibiting the electrocatalytic oxidation of hydrogen as recorded by protein film electrochemistry. Electrochemical, EPR, and FTIR measurements show that the final enzyme product, formed within a second (even under 100% H2), is the resting state known as Ni-B, which contains a hydroxido-bridged species, Ni(III)-μ(OH)-Fe(II), at the active site. "Cyanide inhibition" is easily reversed because it is simply the reductive activation of Ni-B. This paper brings back into focus an observation originally made in the 1940s that cyanide inhibits microbial H2 oxidation and addresses the interesting mechanism by which cyanide promotes the formation of Ni-B. As a much stronger nucleophile than hydroxide, cyanide binds more rapidly and promotes oxidation of Ni(II) to Ni(III); however, it is quickly replaced by hydroxide which is a far superior bridging ligand.

  1. Cathodic Electrodeposition of Ni-Mo on Semiconducting NiFe2 O4 for Photoelectrochemical Hydrogen Evolution in Alkaline Media.

    PubMed

    Wijten, Jochem H J; Jong, Ronald P H; Mul, Guido; Weckhuysen, Bert M

    2018-04-25

    Photocathodes for hydrogen evolution from water were made by electrodeposition of Ni-Mo layers on NiFe 2 O 4 substrates, deposited by spin coating on F:SnO 2 -glass. Analysis confirmed the formation of two separate layers, without significant reduction of NiFe 2 O 4 . Bare NiFe 2 O 4 was found to be unstable under alkaline conditions during (photo)electrochemistry. To improve the stability significantly, the deposition of a bifunctional Ni-Mo layer through a facile electrodeposition process was performed and the composite electrodes showed stable operation for at least 1 h. Moreover, photocurrents up to -2.1 mA cm -2 at -0.3 V vs. RHE were obtained for Ni-Mo/NiFe 2 O 4 under ambient conditions, showing that the new combination functions as both a stabilizing and catalytic layer for the photoelectrochemical evolution of hydrogen. The photoelectrochemical response of these composite electrodes decreased with increasing NiFe 2 O 4 layer thickness. Transient absorption spectroscopy showed that the lifetime of excited states is short and on the ns timescale. An increase in lifetime was observed for NiFe 2 O 4 of large layer thickness, likely explained by decreasing the defect density in the primary layer(s), as a result of repetitive annealing at elevated temperature. The photoelectrochemical and transient absorption spectroscopy results indicated that a short charge carrier lifetime limits the performance of Ni-Mo/NiFe 2 O 4 photocathodes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    DOE PAGES

    Shao, Lin; Chen, Di; Wei, Chaochen; ...

    2014-10-01

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

  3. The thermal expansion of (Fe1-y Ni y )Si.

    PubMed

    Hunt, Simon A; Wann, Elizabeth T H; Dobson, David P; Vočadlo, Lindunka; Wood, Ian G

    2017-08-23

    We have measured the thermal expansion of (Fe 1-y Ni y )Si for y  =  0, 0.1 and 0.2, between 40 and 1273 K. Above ~700 K the unit-cell volumes of the samples decrease approximately linearly with increasing Ni content. Below ~200 K the unit-cell volume of FeSi falls to a value between that of (Fe 0.9 Ni 0.1 )Si and (Fe 0.8 Ni 0.2 )Si. We attribute this extra contraction of the FeSi, which is a narrow band-gap semiconductor, to the depopulation of the conduction band at low temperatures; in the two alloys the additional electrons introduced by the substitution of Ni lead to the conduction band always being populated. We have fit the unit-cell volume data with a Debye internal energy model of thermal expansion and an additional volume term, above 800 K, to take account of the volumetric changes associated with changes in the composition of the sample. Using the thermophysical parameters of the fit we have estimated the band gap in FeSi to be 21(1) meV and the unit-cell volume change in FeSi associated with the depopulation of the conduction band to be 0.066(35) Å 3 /unit-cell.

  4. High magnetization Fe-Co and Fe-Ni submicron and nanosize particles by thermal decomposition and hydrogen reduction

    NASA Astrophysics Data System (ADS)

    Cui, B. Z.; Marinescu, M.; Liu, J. F.

    2014-05-01

    This paper reports morphology, structure, and magnetic properties of air-stable soft magnetic FexCo100-x (x = 65, 50, and 34) and Fe50Ni50 (at. %) submicron and nanosize particles fabricated by template-free thermal decomposition of nitrates of Fe, Co, and Ni and subsequent hydrogen reduction. The particle compositions were tuned by modification of the precursor solution concentrations. The as-synthesized Fe-Co and Fe50Ni50 particles have body centered cubic and face centered cubic poly-nanocrystalline structures, respectively. The Fe-Co and Fe50Ni50 particles have particle sizes in the range of 28-200 nm and 70-480 nm, and average grain sizes of 16-29 nm and 20-24 nm, respectively. The particle and grain sizes were controlled by tuning particle composition, and the temperature and time of hydrogen reduction. Saturation magnetization Ms as high as 207-224 emu/g and intrinsic coercivity Hci of 59-228 Oe were obtained in the Fe-Co particles reduced at 550 °C for 90 min. Of special note, the Ms of 224 emu/g (˜2.3 T) obtained in the Fe65Co35 particles is among the highest values for Fe-Co particles reported so far. Ms of 135-137 emu/g and Hci of 59-111 Oe were obtained in the Fe50Ni50 particles reduced at 500 or 550 °C for 20 min.

  5. In situ growth of well-ordered NiFe-MOF-74 on Ni foam by Fe2+ induction as an efficient and stable electrocatalyst for water oxidation.

    PubMed

    Xing, Jiale; Guo, Kailu; Zou, Zehua; Cai, Minmin; Du, Jing; Xu, Cailing

    2018-06-06

    Well-ordered NiFe-MOF-74 is in situ grown on Ni foam by the induction of Fe2+ and directly used as an OER electrocatalyst. Benefited from the intrinsic open porous structure of MOF-74, the in situ formed MOF arrays and the synergistic effect of Ni and Fe, outstanding water oxidation activity is obtained in alkaline electrolytes with an overpotential of 223 mV at 10 mA cm-2.

  6. Characterization of NiFe oxyhydroxide electrocatalysts by integrated electronic structure calculations and spectroelectrochemistry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Goldsmith, Zachary K.; Harshan, Aparna K.; Gerken, James B.

    2017-03-06

    NiFe oxyhydroxide materials are highly active electrocatalysts for the oxygen evolution reaction (OER), an important process for carbon-neutral energy storage. Recent spectroscopic and computational studies increasingly support iron as the site of catalytic activity but differ with respect to the relevant iron redox state. A combination of hybrid periodic density functional theory calculations and spectroelectrochemical experiments elucidate the electronic structure and redox thermodynamics of Ni-only and mixed NiFe oxyhydroxide thin-film electrocatalysts. The UV/visible light absorbance of the Ni-only catalyst depends on the applied potential as metal ions in the film are oxidized before the onset of OER activity. In contrast,more » absorbance changes are negligible in a 25% Fe-doped catalyst up to the onset of OER activity. First-principles calculations of proton-coupled redox potentials and magnetizations reveal that the Ni-only system features oxidation of Ni2+ to Ni3+, followed by oxidation to a mixed Ni3+/4+ state at a potential coincident with the onset of OER activity. Calculations on the 25% Fedoped system show the catalyst is redox inert before the onset of catalysis, which coincides with the formation of Fe4+ and mixed Ni oxidation states. The calculations indicate that introduction of Fe dopants changes the character of the conduction band minimum from Ni-oxide in the Ni-only to predominantly Fe-oxide in the NiFe electrocatalyst. These findings provide a unified experimental and theoretical description of the electrochemical and optical properties of Ni and NiFe oxyhydroxide electrocatalysts and serve as an important benchmark for computational characterization of mixedmetal oxidation states in heterogeneous catalysts.« less

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  8. Magnetic anomalies in Fe-doped NiO nanoparticle

    NASA Astrophysics Data System (ADS)

    Pradeep, R.; Gandhi, A. C.; Tejabhiram, Y.; Mathar Sahib, I. K. Md; Shimura, Y.; Karmakar, L.; Das, D.; Wu, Sheng Yun; Hayakawa, Y.

    2017-09-01

    Undoped and iron-doped NiO nanoparticle were synthesized by standard hydrothermal method. A detailed study is carried out on the effect of dopant concentration on morphology, structural, resonance and magnetic properties of NiO nanoparticle by varying the Fe concentration from 0.01 to 0.10 M. The synchrotron-x-ray diffraction confirmed that no secondary phase was observed other than NiO. The x-ray photoelectron spectroscopy studies revealed that, Fe was primarily in the trivalent state, replacing the Ni2+ ion inside the octahedral crystal site of NiO. The Electron paramagnetic studies revealed the ferromagnetic cluster formation at high doping concentration (5 and 10%). The ZFC-FC curves displayed an average blocking temperature around 180 K due to particle size distribution. The anomalous behaviour of spontaneous exchange bias (H SEB) and magnetic remanence (M r) for all Fe-doped samples observed at 5 K showed an increase (0.1316-0.1384 emu g-1) in the moment of frozen spin (M p) as the dopant concentration increased. The role of frozen spin moment in spontaneous exchange bias behaviour was discussed.

  9. Mechanical Deformation Behavior of Sn-Ag-Cu Solders with Minor Addition of 0.05 wt.% Ni

    NASA Astrophysics Data System (ADS)

    Hammad, A. E.; El-Taher, A. M.

    2014-11-01

    The aim of the present work is to develop a comparative evaluation of the microstructural and mechanical deformation behavior of Sn-Ag-Cu (SAC) solders with the minor addition of 0.05 wt.% Ni. Test results showed that, by adding 0.05Ni element into SAC solders, generated mainly small rod-shaped (Cu,Ni)6Sn5 intermetallic compounds (IMCs) inside the β-Sn phase. Moreover, increasing the Ag content and adding Ni could result in the change of the shape and size of the IMC precipitate. Hence, a significant improvement is observed in the mechanical properties of SAC solders with increasing Ag content and Ni addition. On the other hand, the tensile results of Ni-doped SAC solders showed that both the yield stress and ultimate tensile strengths decrease with increasing temperature and with decreasing strain rate. This behavior was attributed to the competing effects of work hardening and dynamic recovery processes. The Sn-2.0Ag-0.5Cu-0.05Ni solder displayed the highest mechanical properties due to the formation of hard (Cu,Ni)6Sn5 IMCs. Based on the obtained stress exponents and activation energies, it is suggested that the dominant deformation mechanism in SAC (205)-, SAC (0505)- and SAC (0505)-0.05Ni solders is pipe diffusion, and lattice self-diffusion in SAC (205)-0.05Ni solder. In view of these results, the Sn-2.0Ag-0.5Cu-0.05Ni alloy is a more reliable solder alloy with improved properties compared with other solder alloys tested in the present work.

  10. NiFeCo/Cu superlattices with high magnetoresistive sensitivity and weak hysteresis

    NASA Astrophysics Data System (ADS)

    Bannikova, N. S.; Milyaev, M. A.; Naumova, L. I.; Krinitsina, T. P.; Patrakov, E. I.; Proglyado, V. V.; Chernyshova, T. A.; Ustinov, V. V.

    2016-10-01

    The microstructure and the magetoresistive characteristics of [NiFeCo/Cu]8 superlattices prepared by magnetron sputtering with various thickness of the buffer NiFeCr layer and exhibiting a giant magnetoresistive effect have been studied. It has been found that these nanostructures are formed with a strong or weak hysteresis depending on the structure (bcc or fcc) formed in the NiFeCr buffer layer. The method of the substantial decrease in the hysteresis loop width of the magnetoresistance by using the composite Ta/NiFeCr buffer layer has been suggested.

  11. Surface morphology, optical, and electrochromic properties of nanostructured nickel ferrite (NiFe2O4) prepared by sol-gel method: effects of Ni/Fe molar ratios

    NASA Astrophysics Data System (ADS)

    Bazhan, Z.; Ghodsi, F. E.; Mazloom, J.

    2016-05-01

    Nanostructured nickel ferrite (NF) was prepared by the sol-gel method and calcined at 500 °C for 2 h. The effect of Ni/Fe molar ratios (0, 10, 30, 50 %) on structural, morphological, compositional, optical, and magnetic properties of samples was investigated using analytical tools. XRD patterns indicated the presence of hematite phase in the pure and 10 % NF samples. The samples of 30 and 50 % Ni/Fe molar ratios showed the formation of nickel ferrite structure. Using AFM images, power spectrum density analysis were performed for Ni/Fe with different molar ratio. Also the effect of thickness on morphology of 30 % sample was studied. The fractal dimension increases by increasing the Ni/Fe molar ratio. Optical parameters were evaluated by theoretical approach, and compositional dependence of these parameters was discussed comprehensively. Band gap narrowing was observed in nickel ferrite thin films by increasing the nickel contents from 10 to 50 %. Magnetic analysis revealed that increasing nickel content improved the saturation magnetization. Electrochemical measurements indicated that NF thin films have higher total charge density rather than Fe2O3 thin films and the ion storage capacitance of NF thin films increased by increasing the Ni/Fe content.

  12. Electrochemical vs X-ray Spectroscopic Measurements of NiFe(CN)6 Crystals

    NASA Astrophysics Data System (ADS)

    Peecher, Benjamin; Hampton, Jennifer

    Pseudocapacitive materials like hexacyanoferrate have greater energy storage capabilities than standard capacitors while maintaining an ability to charge and discharge quickly. We modify the surface of an electrodeposited Ni thin film with a layer of hexacyanoferrate. Charging and discharging these modified films using cyclic voltammetry (CV) allows us to measure the electrochemically active Fe in the film. To determine how closely this resembles the full amount of Fe in the film, we measure the films' composition using particle-induced x-ray emission (PIXE). We also vary the amount of Ni deposited, both to compare the electrolysis value of charge deposited to the PIXE measurement of Ni in the film, and also to measure how varying the thickness of the Ni surface affects the presence of Fe in the film. Comparisons of the CV and PIXE measurements show agreement in Ni levels but disagreement in Fe levels. PIXE measurements of Fe in the film have positive correlation with Ni in the film. This correlation between PIXE measurements of Ni and Fe suggests that PIXE provides a reliable measure of Fe in the film. This implies that a variable proportion of total Fe in a given film is electrochemically active. This research was made possible by the Hope College Department of Physics Frissel Research Fund and the National Science Foundation under Grants RUI-DMR-1104725, MRI-CHE-0959282, and MRI/RUI-PHY-0319523.

  13. Nanoscale Fe/Ag particles activated persulfate: optimization using response surface methodology.

    PubMed

    Silveira, Jefferson E; Barreto-Rodrigues, Marcio; Cardoso, Tais O; Pliego, Gema; Munoz, Macarena; Zazo, Juan A; Casas, José A

    2017-05-01

    This work studied the bimetallic nanoparticles Fe-Ag (nZVI-Ag) activated persulfate (PS) in aqueous solution using response surface methodology. The Box-Behnken design (BBD) was employed to optimize three parameters (nZVI-Ag dose, reaction temperature, and PS concentration) using 4-chlorophenol (4-CP) as the target pollutant. The synthesis of nZVI-Ag particles was carried out through a reduction of FeCl 2 with NaBH 4 followed by reductive deposition of Ag. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area. The BBD was considered a satisfactory model to optimize the process. Confirmatory tests were carried out using predicted and experimental values under the optimal conditions (50 mg L -1 nZVI-Ag, 21 mM PS at 57 °C) and the complete removal of 4-CP achieved experimentally was successfully predicted by the model, whereas the mineralization degree predicted (90%) was slightly overestimated against the measured data (83%).

  14. Synergism between polyurethane and polydopamine in the synthesis of Ni-Fe alloy monoliths.

    PubMed

    Naresh Kumar, Thangavel; Sivabalan, Santhana; Chandrasekaran, Naveen; Phani, Kanala Lakshminarasimha

    2015-02-04

    Herein, we report the first synthesis of a light-weight macroporous 3-D alloy monolith of Ni-Fe/C using synergism between polydopamine (pDA) and polyurethane (pU); in situ formed polyurethane (pU) enables efficient mixing of pDA (carbon source) and Ni-FeOx resulting in Ni-Fe alloy monoliths at a temperature as low as ∼600 °C. The monolithic Ni-Fe/C exhibits enhanced oxygen evolution activity.

  15. An investigation of thin-film Ni-Fe oxide catalysts for the electrochemical evolution of oxygen.

    PubMed

    Louie, Mary W; Bell, Alexis T

    2013-08-21

    A detailed investigation has been carried out of the structure and electrochemical activity of electrodeposited Ni-Fe films for the oxygen evolution reaction (OER) in alkaline electrolytes. Ni-Fe films with a bulk and surface composition of 40% Fe exhibit OER activities that are roughly 2 orders of magnitude higher than that of a freshly deposited Ni film and about 3 orders of magnitude higher than that of an Fe film. The freshly deposited Ni film increases in activity by as much as 20-fold during exposure to the electrolyte (KOH); however, all films containing Fe are stable as deposited. The oxidation of Ni(OH)2 to NiOOH in Ni films occurs at potentials below the onset of the OER. Incorporation of Fe into the film increases the potential at which Ni(OH)2/NiOOH redox occurs and decreases the average oxidation state of Ni in NiOOH. The Tafel slope (40 mV dec(-1)) and reaction order in OH(-) (1) for the mixed Ni-Fe films (containing up to 95% Fe) are the same as those for aged Ni films. In situ Raman spectra acquired in 0.1 M KOH at OER potentials show two bands characteristic of NiOOH. The relative intensities of these bands vary with Fe content, indicating a change in the local environment of Ni-O. Similar changes in the relative intensities of the bands and an increase in OER activity are observed when pure Ni films are aged. These observations suggest that the OER is catalyzed by Ni in Ni-Fe films and that the presence of Fe alters the redox properties of Ni, causing a positive shift in the potential at which Ni(OH)2/NiOOH redox occurs, a decrease in the average oxidation state of the Ni sites, and a concurrent increase in the activity of Ni cations for the OER.

  16. Multiconfiguration Pair-Density Functional Theory and Complete Active Space Second Order Perturbation Theory. Bond Dissociation Energies of FeC, NiC, FeS, NiS, FeSe, and NiSe.

    PubMed

    Sharkas, Kamal; Gagliardi, Laura; Truhlar, Donald G

    2017-12-07

    We investigate the performance of multiconfiguration pair-density functional theory (MC-PDFT) and complete active space second-order perturbation theory for computing the bond dissociation energies of the diatomic molecules FeC, NiC, FeS, NiS, FeSe, and NiSe, for which accurate experimental data have become recently available [Matthew, D. J.; Tieu, E.; Morse, M. D. J. Chem. Phys. 2017, 146, 144310-144320]. We use three correlated participating orbital (CPO) schemes (nominal, moderate, and extended) to define the active spaces, and we consider both the complete active space (CAS) and the separated-pair (SP) schemes to specify the configurations included for a given active space. We found that the moderate SP-PDFT scheme with the tPBE on-top density functional has the smallest mean unsigned error (MUE) of the methods considered. This level of theory provides a balanced treatment of the static and dynamic correlation energies for the studied systems. This is encouraging because the method is low in cost even for much more complicated systems.

  17. Enhanced and broadband microwave absorption of flake-shaped Fe and FeNi composite with Ba ferrites

    NASA Astrophysics Data System (ADS)

    Li, Wangchang; Lv, Junjun; Zhou, Xiang; Zheng, Jingwu; Ying, Yao; Qiao, Liang; Yu, Jing; Che, Shenglei

    2017-03-01

    In order to achieve a broad bandwidth absorber at high frequency, the composites of M-type ferrite BaCo1.0Ti1.0Fe10O19 (BaM) with flaked carbonyl iron powders (CIP) and flaked Fe50Ni50 were prepared to optimize the surface impedance in broadband frequency, respectively. The diameter of the flaked carbonyl iron powders (CIP) and Fe50Ni50 is in the range of 5-10 μm and 10-20 μm and the thickness of the CIP and Fe50Ni50 is close to 200 nm and 400 nm, respectively. The complex permeability and permittivity show that the addition of BaM obviously reduces the values of real part of permittivity and imaginary part of the permeability which can enhance the matched-wave-impedance. The absorption bands less than -10 dB of CIP-BaM and FeNi-BaM absorber approach to 5.5 GHz (5.7-11.2 GHz) and 7 GHz (11-18 GHz) at 1.5 mm. However, the bands of CIP and FeNi are only 1.9 GHz (4.7-6.6 GHz) and 2.1 GHz (4.0-6.1 GHz). Hence, the electromagnetic match property is greatly improved by BaM ferrites, and this composite shows a broaden absorption band.

  18. Enhancing the magnetic anisotropy energy by tuning the contact areas of Ag and Ni at the Ag/Ni interface.

    PubMed

    Chow, Yu-Ting; Jiang, Bin-Han; Chang, Cheng-Hsun-Tony; Tsay, Jyh-Shen

    2018-01-17

    Modifying the interfacial conditions of magnetic layers by capping with overlayers can efficiently enhance the magnetic functionality of a material. However, the mechanisms responsible for this are closely related to the crystalline structure, compositional combinations, and interfacial quality, and are generally complex. In this contribution, we explored the use of Ag ultrathin overlayers on annealed . A method for preparing magnetic layers with different levels of enhanced magnetic anisotropy energy was developed. The method essentially involves simply modifying the contact area of the metallic/magnetic interface. A rougher interface results in a larger contact area between the Ag and Ni layers, resulting in an increase in magnetic anisotropy energy. Moreover, post-annealing treatments led to the segregation of Ni atoms, thus making the enhancement in the coercive force even more efficient. A model permits an understanding of the contact area and a strategy for enhancing the magnetic anisotropy energy and the coercive force was developed. Our approaches and the developed model promise to be helpful in terms of developing potential applications of ultrathin magnetic layers in the area of spintronics.

  19. Ag implantation-induced modification of Ni-Ti shape memory alloy thin films

    NASA Astrophysics Data System (ADS)

    Kumar, V.; Singhal, R.; Vishnoi, R.; Banerjee, M. K.; Sharma, M. C.; Asokan, K.; Kumar, M.

    2017-08-01

    Nanocrystalline thin films of Ni-Ti shape memory alloy are deposited on an Si substrate by the DC-magnetron co-sputtering technique and 120 keV Ag ions are implanted at different fluences. The thickness and composition of the pristine films are determined by Rutherford Backscattering Spectrometry (RBS). X-Ray diffraction (XRD), atomic force microscopy (AFM) and four-point probe resistivity methods have been used to study the structural, morphological and electrical transport properties. XRD analysis has revealed the existence of martensitic and austenite phases in the pristine film and also evidenced the structural changes in Ag-implanted Ni-Ti films at different fluences. AFM studies have revealed that surface roughness and grain size of Ni-Ti films have decreased with an increase in ion fluence. The modifications in the mechanical behaviour of implanted Ni-Ti films w.r.t pristine film is determined by using a Nano-indentation tester at room temperature. Higher hardness and the ratio of higher hardness (H) to elastic modulus (Er) are observed for the film implanted at an optimized fluence of 9 × 1015 ions/cm2. This improvement in mechanical behaviour could be understood in terms of grain refinement and dislocation induced by the Ag ion implantation in the Ni-Ti thin films.

  20. GeV ion irradiation of NiFe and NiCo: Insights from MD simulations and experiments

    DOE PAGES

    Leino, Aleksi A.; Samolyuk, German D.; Sachan, Ritesh; ...

    2018-03-31

    Concentrated solid solution alloys have attracted rapidly increasing attention due to their potential for designing materials with high tolerance to radiation damage. To tackle the effects of chemical complexity in defect dynamics and radiation response, we present in this paper a computational study on swift heavy ion induced effects in Ni and equiatomic Ni -based alloys (Ni 50Fe 50, Ni 50Co 50) using two-temperature molecular dynamics simulations (2T-MD). The electronic heat conductivity in the two-temperature equations is parameterized from the results of first principles electronic structure calculations. A bismuth ion (1.542 GeV) is selected and single impact simulations performed inmore » each target. We study the heat flow in the electronic subsystem and show that alloying Ni with Co or Fe reduces the heat dissipation from the impact by the electronic subsystem. Simulation results suggest no melting or residual damage in pure Ni while a cylindrical region melts along the ion propagation path in the alloys. In Ni 50Co 50 the damage consists of a dislocation loop structure (d = 2 nm) and isolated point defects, while in Ni 50Fe 50, a defect cluster (d = 4 nm) along the ion path is, in addition, formed. The simulation results are supported by atomic-level structural and defect characterizations in bismuth-irradiated Ni and Ni 50Fe 50. Finally, the significance of the 2T-MD model is demonstrated by comparing the results to those obtained with an instantaneous energy deposition model without consideration of e-ph interactions in pure Ni and by showing that it leads to a different qualitative behavior.« less

  1. GeV ion irradiation of NiFe and NiCo: Insights from MD simulations and experiments

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Leino, Aleksi A.; Samolyuk, German D.; Sachan, Ritesh

    Concentrated solid solution alloys have attracted rapidly increasing attention due to their potential for designing materials with high tolerance to radiation damage. To tackle the effects of chemical complexity in defect dynamics and radiation response, we present in this paper a computational study on swift heavy ion induced effects in Ni and equiatomic Ni -based alloys (Ni 50Fe 50, Ni 50Co 50) using two-temperature molecular dynamics simulations (2T-MD). The electronic heat conductivity in the two-temperature equations is parameterized from the results of first principles electronic structure calculations. A bismuth ion (1.542 GeV) is selected and single impact simulations performed inmore » each target. We study the heat flow in the electronic subsystem and show that alloying Ni with Co or Fe reduces the heat dissipation from the impact by the electronic subsystem. Simulation results suggest no melting or residual damage in pure Ni while a cylindrical region melts along the ion propagation path in the alloys. In Ni 50Co 50 the damage consists of a dislocation loop structure (d = 2 nm) and isolated point defects, while in Ni 50Fe 50, a defect cluster (d = 4 nm) along the ion path is, in addition, formed. The simulation results are supported by atomic-level structural and defect characterizations in bismuth-irradiated Ni and Ni 50Fe 50. Finally, the significance of the 2T-MD model is demonstrated by comparing the results to those obtained with an instantaneous energy deposition model without consideration of e-ph interactions in pure Ni and by showing that it leads to a different qualitative behavior.« less

  2. Effect of 120 MeV 28Si9+ ion irradiation on structural and magnetic properties of NiFe2O4 and Ni0.5Zn0.5Fe2O4

    NASA Astrophysics Data System (ADS)

    Sharma, R.; Raghuvanshi, S.; Satalkar, M.; Kane, S. N.; Tatarchuk, T. R.; Mazaleyrat, F.

    2018-05-01

    NiFe2O4, Ni0.5Zn0.5Fe2O4 samples were synthesized using sol-gel auto combustion method, and irradiated by using 120 MeV 28Si9+ ion with ion fluence of 1×1012 ions/cm2. Characterization of pristine, irradiated samples were done using X-Ray Diffraction (XRD), Field Emission Scanning Microscopy (FE-SEM), Energy Dispersive X-ray Analysis (EDAX) and Vibrating Sample Magnetometer (VSM). XRD validates the single phase nature of pristine, irradiated Ni- Zn nano ferrite except for Ni ferrite (pristine, irradiated) where secondary phases of α-Fe2O3 and Ni is observed. FE- SEM images of pristine Ni, Ni-Zn ferrite show inhomogeneous nano-range particle size distribution. Presence of diamagnetic ion (Zn2+) in NiFe2O4 increases oxygen positional parameter (u 4¯3m ), experimental, theoretical saturation magnetization (Msexp., Msth.), while decreases the grain size (Ds) and coercivity (Hc). With irradiation Msexp., Msth. increases but not much change are observed in Hc. New antistructure modeling for the pristine, irradiated Ni and Ni-Zn ferrite samples was used for describing the surface active centers.

  3. Hydrogen Activation by Biomimetic [NiFe]-Hydrogenase Model Containing Protected Cyanide Cofactors

    PubMed Central

    Manor, Brian C.; Rauchfuss, Thomas B.

    2013-01-01

    Described are experiments that allow incorporation of cyanide cofactors and hydride substrate into active site models [NiFe]-hydrogenases (H2ases). Complexes of the type (CO)2(CN)2Fe(pdt)Ni(dxpe), (dxpe = dppe, 1; dxpe = dcpe, 2) bind the Lewis acid B(C6F5)3 (BArF3) to give the adducts (CO)2(CNBArF3)2Fe(pdt)Ni(dxpe), (1(BArF3)2, 2(BArF3)2). Upon decarbonylation using amine oxides, these adducts react with H2 to give hydrido derivatives Et4N[(CO)(CNBArF3)2Fe(H)(pdt)Ni(dxpe)], (dxpe = dppe, Et4N[H3(BArF3)2]; dxpe = dcpe, Et4N[H4(BArF3)2]). Crystallographic analysis shows that Et4N[H3(BArF3)2] generally resembles the active site of the enzyme in the reduced, hydride-containing states (Ni-C/R). The Fe-H…Ni center is unsymmetrical with rFe-H = 1.51(3) and rNi-H = 1.71(3) Å. Both crystallographic and 19F NMR analysis show that the CNBArF3− ligands occupy basal and apical sites. Unlike cationic Ni-Fe hydrides, [H3(BArF3)2]− and [H4(BArF3)2]− oxidize at mild potentials, near the Fc+/0 couple. Electrochemical measurements indicate that in the presence of base, [H3(BArF3)2]− catalyzes the oxidation of H2. NMR evidence indicates dihydrogen bonding between these anionic hydrides and ammonium salts, which is relevant to the mechanism of hydrogenogenesis. In the case of Et4N[H3(BArF3)2], strong acids such as HCl induce H2 release to give the chloride Et4N[(CO)(CNBArF3)2Fe(pdt)(Cl)Ni(dppe)]. PMID:23899049

  4. Microplasma Jet Synthesis of Ni-Fe Oxide Films for Magnetic Exchange Bias and Electrocatalytic Studies

    NASA Astrophysics Data System (ADS)

    Pebley, Andrew Christian

    Ni-Fe oxides have received significant interest from the scientific community because they have attractive magnetic and electrochemical properties for use in next generation data storage and energy conversion technologies. For example, the NiFe2O4/NiO nanogranular system exhibits the exchange bias effect, a magnetic phenomenon occurring at the interface of a ferro- or ferrimagnet (FM or FiM) and an antiferromagnet (AFM), where the AFM acts to increase the magnetic hardness of the corresponding FM or FiM. Additionally, doping of NiO with Fe has resulted in remarkably high catalytic activities for water splitting, a potential clean energy alternative to fossil fuels. A key challenge in implementing these Ni-Fe oxides for magnetic and electrocatalytic applications is the ability to control film morphology, crystallinity, composition, chemical phase, and doping during synthesis. Moreover, how these physiochemical properties effect magnetic and electrochemical behavior in the Ni-Fe oxide system is not fully understood. This dissertation focuses on the development and use of a novel synthesis technique, known as microplasma (MP) jet-based deposition, for the fabrication of biphasic NiFe2O4 (FiM)/NiO (AFM) and Fe-doped NiO nanostructured films for fundamental studies of exchange bias and electrocatalysis, respectively. The goal of this work was to understand how MP operation and deposition conditions (e.g., precursor composition, flux, substrate temperature, and post-deposition heat treatment) influence Ni-Fe oxide growth and film microstructure. Specifically, the role of composition, phase fraction, grain size, temperature, and interfacial density on exchange bias phenomena in NiFe 2O4/NiO nanogranular films was investigated. MP jets were also used to realize metastable Fe-doped NiO films with high surface area to assess how doping affects the electrochemical properties of NiO for the oxygen evolution reaction (OER). Biphasic NiFe2O4/NiO films of different composition

  5. Damping studies in Ni-Mn-Ga-Fe/PU polymer composites

    NASA Astrophysics Data System (ADS)

    Saranya, C.; Kumar, S. Vinodh; Seenithurai, S.; Pandyan, R. Kodi; Munieswaran, P.; Mahendran, M.

    2015-06-01

    Ni-Mn-Ga-Fe/PU polymer composite is prepared to investigate the damping behavior by using an indigenous experimental setup. The excellent damping properties of Ni-Mn-Ga-Fe alloys bonded with polymer matrix makes possible to develop new damping materials which are effective, less expensive and easier than bulk Ni-Mn-Ga. At low frequency, the stress amplitude increases and then smoothly decreases on increasing the frequency.

  6. H+-induced irradiation damage resistance in Fe- and Ni-based metallic glass

    NASA Astrophysics Data System (ADS)

    Zhang, Hongran; Mei, Xianxiu; Zhang, Xiaonan; Li, Xiaona; Wang, Yingmin; Sun, Jianrong; Wang, Younian

    2016-05-01

    In this study, use of 40-keV H+ ion for irradiating metallic glass Fe80Si7.43B12.57 and Ni62Ta38 as well as metallic tungsten (W) at fluences of 1 × 1018 and 3 × 1018 ions/cm2, respectively, was investigated. At the fluence of 1 × 1018 ions/cm2, a crystalline layer appeared in metallic glass Fe80Si7.43B12.57, with α-Fe as the major crystalline phase, coupled with a little Fe2B, Fe3B, and metastable β-Mn-type phase. Fe80Si7.43B12.57 exhibited good soft magnetic properties after irradiation. At the fluence of 3 × 1018 ions/cm2, Ni62Ta38 was found to be amorphous-based, with a little μ-NiTa and Ni3Ta phases. No significant irradiation damage phenomenon appeared in metallic glasses Fe80Si7.43B12.57 and Ni62Ta38. Blistering, flaking, and other damage occurred on the surface of metallic W, and the root-mean-square (RMS) roughness increased with the increase of fluence. Metallic glass Ni62Ta38 exhibited better resistance to H+ irradiation than Fe80Si7.43B12.57, both of which were superior to the metallic W.

  7. Structural and magnetic characterization of Mn/NiFe bilayers with ion-beam-assisted deposition

    NASA Astrophysics Data System (ADS)

    Wu, Chun-Hsien; Zheng, Chao; Chiu, Chun-Cheng; Manna, Palash Kumar; van Lierop, Johan; Lin, Ko-Wei; Pong, Philip W. T.

    2018-01-01

    The exchange bias effect in ferromagnetic (FM)/antiferromagnetic (AF) bilayer structures has been widely investigated because its underlying principle is critical for spintronic applications. In this work, the effect of Ar+ beam bombardment on the microstructural and magnetic properties of the Mn/NiFe thin films was investigated. The in-situ Ar+ bombardment nontrivially promoted the Mn/NiFe intermixing and facilitated the formation of the FeMn phase, accompanied by a remarkable reduction of Mn and NiFe layer thickness. The enhanced Mn/NiFe intermixing greatly disordered the interfacial spins, inhibiting the interfacial exchange coupling and giving rise to a significant decrease of the exchange bias field (H ex). The facilitated Mn/NiFe intermixing effect also dramatically degraded the magnetocrystalline anisotropy of the NiFe crystallites, leading to a notable suppression of the coercivity (H c). These results indicate that both the exchange bias and coercivity of the Mn/NiFe bilayers can be directly affected by the in-situ Ar+ bombardment, offering an effective way to modify the magnetism of the exchange-bias systems.

  8. The Effect of Composition on Diffusion of Au in Fe and Fe-Ni Alloys

    NASA Astrophysics Data System (ADS)

    Johanesen, K. E.; Watson, H. C.; Fei, Y.

    2005-12-01

    Understanding siderophile element diffusion in Fe-Ni alloys will lead to tighter constraints on processes such as meteoritic body cooling rates, and inner core-outer core communication. Recent studies have determined the effect of temperature and pressure on diffusion in this system, but the effect of composition has not yet been explored adequately. The effect of Ni content on Au diffusion in an Fe-Ni system was explored for Fe-Ni alloys with concentrations of 0, 20, and 30 wt. % Ni. Diffusion couple experiments were conducted using a piston cylinder press at 1 GPa and temperatures ranging from 1150°C to 1400°C. Concentration profiles were measured by electron microprobe and were fitted to the linear diffusion solution for an semi-infinite diffusion couple to extract diffusion coefficients (D) using a non-linear least squares fit routine. As predicted, D increases with Ni content and also with temperature. The diffusivities ranged from 2.06×10-9 at 1150°C to 5.76×10-8 at 1350°C for 0 wt. % Ni; 5.17×10-9 at 1150° C to 1.93×10-7 at 1400°C for 20 wt. % Ni; and 2.41×10-8 at 1150°C to 2.13×10-7 at 1400°C for 30 wt. % Ni. As temperature increases, the effect of Ni on diffusion rates increases, implying a possible change in diffusion mechanism between 1250°C and 1300°C. Ni appears to have a negligible effect at lower temperatures, which would indicate that Ni may not need to be considered when modeling siderophile trace element diffusion rates in iron meteorites.

  9. Monodisperse core/shell Ni/FePt nanoparticles and their con-version to Ni/Pt to catalyze oxygen reduction

    DOE PAGES

    Zhang, Sen; Hao, Yizhou; Su, Dong; ...

    2014-10-28

    We report a size-controllable synthesis of monodisperse core/shell Ni/FePt nanoparticles (NPs) via a seed-mediated growth and their subsequent conversion to Ni/Pt NPs. Preventing surface oxidation of the Ni seeds is essential for the growth of uniform FePt shells. These Ni/FePt NPs have a thin (≈ 1 nm) FePt shell, and can be converted to Ni/Pt by acetic acid wash to yield active catalysts for oxygen reduction reaction (ORR). Tuning the core size allow for optimization of their electrocatalytic activity. The specific activity and mass activity of 4.2 nm/0.8 nm core/shell Ni/FePt reach 1.95 mA/cm² and 490 mA/mg Pt at 0.9more » V ( vs. reversible hydrogen electrode, RHE), which are much higher than those of benchmark commercial Pt catalyst (0.34 mA/cm² and 92 mA/mg Pt at 0.9 V). Our studies provide a robust approach to monodisperse core/shell NPs with non-precious metal core, making it possible to develop advanced NP catalysts with ultralow Pt content for ORR and many other heterogeneous reactions.« less

  10. Gamma ray irradiated AgFeO{sub 2} nanoparticles with enhanced gas sensor properties

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Xiuhua, E-mail: xhwang@mail.ahnu.edu.cn; Shi, Zhijie; Yao, Shangwu

    2014-11-15

    AgFeO{sub 2} nanoparticles were synthesized via a facile hydrothermal method and irradiated by various doses of gamma ray. The products were characterized with X-ray powder diffraction, UV–vis absorption spectrum and transmission electron microscope. The results revealed that the crystal structure, morphology and size of the samples remained unchanged after irradiation, while the intensity of UV–Vis spectra increased with irradiation dose increasing. In addition, gamma ray irradiation improved the performance of gas sensor based on the AgFeO{sub 2} nanoparticles including the optimum operating temperature and sensitivity, which might be ascribed to the generation of defects. - Graphical abstract: Gamma ray irradiationmore » improved the performance of gas sensor based on the AgFeO{sub 2} nanoparticles including sensitivity and optimum operating temperature, which might be ascribed to the generation of defects. - Highlights: • AgFeO{sub 2} nanoparticles were synthesized and irradiated with gamma ray. • AgFeO{sub 2} nanoparticles were employed to fabricate gas sensors to detect ethanol. • Gamma ray irradiation improved the sensitivity and optimum operating temperature.« less

  11. Microstructures responsible for the invar and permalloy effects in Fe-Ni alloys

    NASA Astrophysics Data System (ADS)

    Ustinovshchikov, Yu. I.; Shabanova, I. N.; Lomova, N. V.

    2015-05-01

    The experimental studies of Fe68Ni32 and Fe23Ni77 alloys by transmission electron microscopy and X-ray electron spectroscopy show that the ordering-separation phase transition in these alloys occurs in a temperature range near 600°C. At temperatures higher than the transition temperature, the ordering energy of the alloy is positive, and the structures contain clusters enriched in one of the components. After heat treatment at the temperatures where the invar effect in the Fe68Ni32 alloy is maximal, a modulated microstructure forms. Below the transition temperature, the ordering energy is negative, which provides a tendency to formation of chemical compounds. After aging at these temperatures (where the Fe23Ni77 alloy exhibits high permalloy properties), highly dispersed completely coherent particles of the FeNi3 phase with structure L12 precipitate in a solid solution.

  12. Purification and Characterization of [NiFe]-Hydrogenase of Shewanella oneidensis MR-1

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shi, Liang; Belchik, Sara M.; Plymale, Andrew E.

    2011-08-02

    The γ-proteobacterium Shewanella oneidensis MR-1 possesses a periplasmic [NiFe]-hydrogenase (MR-1 [NiFe]-H2ase) that was implicated in both H2 production and oxidation as well as technetium [Tc(VII)] reduction. To characterize the roles of MR-1 [NiFe]-H2ase in these proposed reactions, the genes encoding both subunits of MR-1 [NiFe]-H2ase were cloned into a protein expression vector. The resulting plasmid was transformed into a MR-1 mutant deficient in H2 formation. Expression of MR-1 [NiFe]-H2ase in trans restored the mutant’s ability to produce H2 at 37% of that for wild type. Following expression, MR-1 [NiFe]-H2ase was purified to near homogeneity. The purified MR-1 [NiFe]-H2ase could couplemore » H2 oxidation to reduction of Tc(VII) and methyl viologen directly. Change of the buffers used affected MR-1 [NiFe]-H2ase-mediated Tc(VII) but not methyl viologen reductions. Under the conditions tested, Tc(VII) reduction was complete in Tris buffer but not in HEPES buffer. The reduced Tc(IV) was soluble in Tris buffer but insoluble in HEPES buffer. Transmission electron microscopy analysis revealed that Tc(IV) precipitates formed in HEPES buffer were packed with crystallites. Although X-ray absorption near-edge spectroscopy measurements confirmed that the reduction products found in both buffers were Tc(IV), extended X-ray adsorption fine-structure measurements revealed that these products were very different. While the product in Tris buffer could not be determined, the Tc(IV) product in HEPES buffer was very similar to Tc(IV)O2•nH2O. These results shows for the first time that MR-1 [NiFe]-H2ase is a bidirectional enzyme that catalyzes both H2 formation and oxidation as well as Tc(VII) reduction directly by coupling H2 oxidation.« less

  13. Nickel-centred proton reduction catalysis in a model of [NiFe] hydrogenase

    NASA Astrophysics Data System (ADS)

    Brazzolotto, Deborah; Gennari, Marcello; Queyriaux, Nicolas; Simmons, Trevor R.; Pécaut, Jacques; Demeshko, Serhiy; Meyer, Franc; Orio, Maylis; Artero, Vincent; Duboc, Carole

    2016-11-01

    Hydrogen production through water splitting is one of the most promising solutions for the storage of renewable energy. [NiFe] hydrogenases are organometallic enzymes containing nickel and iron centres that catalyse hydrogen evolution with performances that rival those of platinum. These enzymes provide inspiration for the design of new molecular catalysts that do not require precious metals. However, all heterodinuclear NiFe models reported so far do not reproduce the Ni-centred reactivity found at the active site of [NiFe] hydrogenases. Here, we report a structural and functional NiFe mimic that displays reactivity at the Ni site. This is shown by the detection of two catalytic intermediates that reproduce structural and electronic features of the Ni-L and Ni-R states of the enzyme during catalytic turnover. Under electrocatalytic conditions, this mimic displays high rates for H2 evolution (second-order rate constant of 2.5 × 104 M-1 s-1 turnover frequency of 250 s-1 at 10 mM H+ concentration) from mildly acidic solutions.

  14. Nickel centred H+ reduction catalysis in a model of [NiFe] Hydrogenase

    PubMed Central

    Brazzolotto, Deborah; Gennari, Marcello; Queyriaux, Nicolas; Simmons, Trevor R.; Pécaut, Jacques; Demeshko, Serhiy; Meyer, Franc; Orio, Maylis; Artero, Vincent; Duboc, Carole

    2017-01-01

    Hydrogen production through water splitting is one of the most promising solutions for the storage of renewable energy. [NiFe] hydrogenases are organometallic enzymes containing nickel and iron centers that catalyze hydrogen evolution with performances that rival those of platinum. These enzymes provide inspiration for the design of new molecular catalysts that do not require precious metals. However, all heterodinuclear NiFe models reported so far do not reproduce the Ni-centered reactivity found at the active site of [NiFe] hydrogenases. Here we report a structural and functional NiFe mimic that displays reactivity at the Ni site. This is shown by the detection of two catalytic intermediates that reproduce structural and electronic features of the Ni-L and Ni-R states of the enzyme during catalytic turnover. Under electrocatalytic conditions, this mimic displays high rates for H2 evolution (second order rate constant of 2.5 104 M-1s-1; turnover frequency of 225 s-1 at 10 mM H+ concentration) from mildly acidic solutions. PMID:27768098

  15. Interactions of oxygen and ethylene with submonolayer Ag films supported on Ni(111).

    PubMed

    Rettew, Robert E; Meyer, Axel; Senanayake, Sanjaya D; Chen, Tsung-Liang; Petersburg, Cole; Ingo Flege, J; Falta, Jens; Alamgir, Faisal M

    2011-06-21

    We investigate the oxidation of, and the reaction of ethylene with, Ni(111) with and without sub-monolayer Ag adlayers as a function of temperature. The addition of Ag to Ni(111) is shown to enhance the activity towards the ethylene epoxidation reaction, and increase the temperature at which ethylene oxide is stable on the surface. We present a systematic study of the formation of chemisorbed oxygen on the Ag-Ni(111) surfaces and correlate the presence and absence of O(1-) and O(2-) surface species with the reactivity towards ethylene. By characterizing the samples with low-energy electron microscopy (LEEM) in combination with X-ray photoelectron spectroscopy (XPS), we have identified specific growth of silver on step-edge sites and successfully increased the temperature at which the produced ethylene oxide remains stable, a trait which is desirable for catalysis.

  16. Highly improved sensibility and selectivity ethanol sensor of mesoporous Fe-doped NiO nanowires

    NASA Astrophysics Data System (ADS)

    Li, X. Q.; Wei, J. Q.; Xu, J. C.; Jin, H. X.; Jin, D. F.; Peng, X. L.; Hong, B.; Li, J.; Yang, Y. T.; Ge, H. L.; Wang, Xinqing

    2017-12-01

    In this paper, nickel oxides (NiO) and iron (Fe)-doped NiO nanowires (NWs) with the various doping content (from 1 to 9 at%) were synthesized by using SBA-15 templates with the nanocasting method. All samples were synthesized in the same conditions and exhibited the same mesoporous-structures, uniform diameter, and defects. Mesoporous-structures with high surface area created more active sites for the adsorption of oxygen on the surface of all samples, resulting in the smaller surface resistance in air. The impurity energy levels from the donor Fe-doping provided electrons to neutralize the holes of p-type Fe-doped NiO NWs, which greatly enhanced the total resistance. The comparative gas-sensing study between NiO NWs and Fe-doped NiO NWs indicated that the high-valence donor Fe-doping obviously improved the ethanol sensitivity and selectivity for Fe-doped NiO NWs. And Ni0.94Fe0.06O1.03 NWs sensor presented the highest sensitivity of 14.30 toward ethanol gas at 320 °C for the high-valence metal-doping.

  17. Ag/α-Fe2O3 hollow microspheres: Preparation and application for hydrogen peroxide detection

    NASA Astrophysics Data System (ADS)

    Kang, Xinyuan; Wu, Zhiping; Liao, Fang; Zhang, Tingting; Guo, Tingting

    2015-09-01

    In this paper, we demonstrated a simple approach for preparing α-Fe2O3 hollow spheres by mixing ferric nitrate aqueous and glucose in 180 °C. The glucose was found to act as a soft template in the process of α-Fe2O3 hollow spheres formation. Ag/α-Fe2O3 hollow nanocomposite was obtained under UV irradiation without additional reducing agents or initiators. Synthesized Ag/α-Fe2O3 hollow composites exhibited remarkable catalytic performance toward H2O2 reduction. The electrocatalytic activity mechanism of Ag/α-Fe2O3/GCE were discussed toward the reduction of H2O2 in this paper.

  18. The importance of holes in aluminium tris-8-hydroxyquinoline (Alq{sub 3}) devices with Fe and NiFe contacts

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Hongtao; Desai, P.; Kreouzis, T.

    To study the dominant charge carrier polarity in aluminium tris-8-hydroxyquinoline (Alq{sub 3}) based spin valves, single Alq{sub 3} layer devices with NiFe, ITO, Fe, and aluminium electrodes were fabricated and characterised by Time of Flight (ToF) and Dark Injection (DI) techniques, yielding a lower hole mobility compared to electron mobility. We compare the mobility measured by DI for the dominant carrier injected from NiFe and Fe electrodes into Alq{sub 3}, to that of holes measured by ToF. This comparison leads us to conclude that the dominant charge carriers in Alq{sub 3} based spin valves with NiFe or Fe electrodes aremore » holes.« less

  19. Study of Sn and SnAgCu Solders Wetting Reaction on Ni/Pd/Au Substrates

    NASA Astrophysics Data System (ADS)

    Liu, C. Y.; Wei, Y. S.; Lin, E. J.; Hsu, Y. C.; Tang, Y. K.

    2016-12-01

    Wetting reactions of pure Sn and Sn-Ag-Cu solder balls on Au(100 Å and 1000 Å)/Pd(500 Å)/Ni substrates were investigated. The (Au, Pd)Sn4 phase formed in the initial interfacial reaction between pure Sn and Au(100 Å and 1000 Å)/Pd(500 Å)/Ni substrates. Then, the initially formed (Au, Pd)Sn4 compound layer either dissolved or spalled into the molten Sn solder with 3 s of reflowing. The exposed Ni under-layer reacted with Sn solder and formed an interfacial Ni3Sn4 compound. We did not observe spalling compound in the Sn-Ag-Cu case, either on the thin Au (100 Å) or the thick Au (1000 Å) substrates. This implies that the Cu content in the Sn-Ag-Cu solder can efficiently suppress the spalling effect and really stabilize the interfacial layer. Sn-Ag-Cu solder has a better wetting than that of the pure Sn solder, regardless of the Au thickness of the Au/Pd/Ni substrate. For both cases of pure Sn and Sn-Ag-Cu, the initial wetting (<3-s reflowing) on the thin Au (100 Å) substrate is better than that of the thick Au (1000 Å) substrate. Over 3-s reflowing, the wetting on the thicker Au layer (1000 Å) substrate becomes better than the wetting on the thinner Au layer (100 Å) substrate.

  20. Vancomycin-modified Fe3O4@SiO2@Ag microflowers as effective antimicrobial agents.

    PubMed

    Wang, Chongwen; Zhang, Kehan; Zhou, Zhe; Li, Qingjun; Shao, Liting; Hao, Rong Zhang; Xiao, Rui; Wang, Shengqi

    2017-01-01

    Nanomaterials combined with antibiotics exhibit synergistic effects and have gained increasing interest as promising antimicrobial agents. In this study, vancomycin-modified magnetic-based silver microflowers (Van/Fe 3 O 4 @SiO 2 @Ag microflowers) were rationally designed and prepared to achieve strong bactericidal ability, a wide antimicrobial spectrum, and good recyclability. High-performance Fe 3 O 4 @SiO 2 @Ag microflowers served as a multifunction-supporting matrix and exhibited sufficient magnetic response property due to their 200 nm Fe 3 O 4 core. The microflowers also possessed a highly branched flower-like Ag shell that provided a large surface area for effective Ag ion release and bacterial contact. The modified-vancomycin layer was effectively bound to the cell wall of bacteria to increase the permeability of the cell membrane and facilitate the entry of the Ag ions into the bacterium, resulting in cell death. As such, the fabricated Van/Fe 3 O 4 @SiO 2 @Ag microflowers were predicted to be an effective and environment-friendly antibacterial agent. This hypothesis was verified through sterilization of Gram-negative Escherichia coli and Gram-positive methicillin-resistant Staphylococcus aureus , with minimum inhibitory concentrations of 10 and 20 μg mL -1 , respectively. The microflowers also showed enhanced effect compared with bare Fe 3 O 4 @SiO 2 @Ag microflowers and free-form vancomycin, confirming the synergistic effects of the combination of the two components. Moreover, the antimicrobial effect was maintained at more than 90% after five cycling assays, indicating the high stability of the product. These findings reveal that Van/Fe 3 O 4 @SiO 2 @Ag microflowers exhibit promising applications in the antibacterial fields.

  1. Facile sonochemical synthesis of amorphous NiFe-(oxy)hydroxide nanoparticles as superior electrocatalysts for oxygen evolution reaction.

    PubMed

    Lee, Eunjik; Park, Ah-Hyeon; Park, Hyun-Uk; Kwon, Young-Uk

    2018-01-01

    In this work, we present facile synthesis of amorphous Ni/Fe mixed (oxy)hydroxide (NiFe(H)) nanoparticles (NPs) and their electrocatalytic performance for oxygen evolution reaction (OER) in alkaline media. a-NiFe(H) NPs have received lots of attention as OER electrocatalysts with many desirable properties. By using a simple sonochemical route, we prepared amorphous Ni and Fe-alkoxide (NiFe(A)) NPs whose composition can be controlled in the entire composition range (Ni 100-x Fe x , 0≤x≤1). These samples are composed of extremely small NiFe(A) NPs with Ni and Fe atoms homogeneously distributed. NiFe(A) NPs are readily converted into corresponding electrocatalytically active NiFe(H) NP by a simple electrochemical treatment. Electrochemical analysis data show that the OER activity of amorphous NiFe(H) samples follows the volcano-type trend when plotted against the Fe content. Ni 70 Fe 30 (H) sample showed the lowest overpotential of 292mV at 10mAcm -2 geo and the lowest Tafel slope of 30.4mVdec -1 , outperforming IrO x /C (326mV, 41.7mVdec -1 ). Our samples are highly durable based on the chronopotentiometry data at the current density of 10mAcm -2 geo for 2h which show that Ni 70 Fe 30 sample maintains the steady-state potential, contrary to the time-varying IrO x /C. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Effects of Fe concentration on the ion-irradiation induced defect evolution and hardening in Ni-Fe solid solution alloys

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jin, Ke; Guo, Wei; Lu, Chenyang

    Understanding alloying effects on the irradiation response of structural materials is pivotal in nuclear engineering. In order to systematically explore the effects of Fe concentration on the irradiation-induced defect evolution and hardening in face-centered cubic Ni-Fe binary solid solution alloys, single crystalline Ni-xFe (x = 0–60 at%) alloys have been grown and irradiated with 1.5 MeV Ni ions. The irradiations have been performed over a wide range of fluences from 3 × 10 13 to 3 × 10 16 cm -2 at room temperature. Ion channeling technique has shown reduced damage accumulation with increasing Fe concentration in the low fluencemore » regime, which is consistent to the results from molecular dynamic simulations. We did not observe any irradiation-induced compositional segregation in atom probe tomography within the detection limit, even in the samples irradiated with high fluence Ni ions. Transmission electron microscopy analyses have further demonstrated that the defect size significantly decreases with increasing Fe concentration, indicating a delay in defect evolution. Furthermore, irradiation induced hardening has been measured by nanoindentation tests. Ni and the Ni-Fe alloys have largely different initial hardness, but they all follow a similar trend for the increase of hardness as a function of irradiation fluence.« less

  3. Effects of Fe concentration on the ion-irradiation induced defect evolution and hardening in Ni-Fe solid solution alloys

    DOE PAGES

    Jin, Ke; Guo, Wei; Lu, Chenyang; ...

    2016-12-01

    Understanding alloying effects on the irradiation response of structural materials is pivotal in nuclear engineering. In order to systematically explore the effects of Fe concentration on the irradiation-induced defect evolution and hardening in face-centered cubic Ni-Fe binary solid solution alloys, single crystalline Ni-xFe (x = 0–60 at%) alloys have been grown and irradiated with 1.5 MeV Ni ions. The irradiations have been performed over a wide range of fluences from 3 × 10 13 to 3 × 10 16 cm -2 at room temperature. Ion channeling technique has shown reduced damage accumulation with increasing Fe concentration in the low fluencemore » regime, which is consistent to the results from molecular dynamic simulations. We did not observe any irradiation-induced compositional segregation in atom probe tomography within the detection limit, even in the samples irradiated with high fluence Ni ions. Transmission electron microscopy analyses have further demonstrated that the defect size significantly decreases with increasing Fe concentration, indicating a delay in defect evolution. Furthermore, irradiation induced hardening has been measured by nanoindentation tests. Ni and the Ni-Fe alloys have largely different initial hardness, but they all follow a similar trend for the increase of hardness as a function of irradiation fluence.« less

  4. Tri-functional Fe2O3-encased Ag-doped ZnO nanoframework: magnetically retrievable antimicrobial photocatalyst

    NASA Astrophysics Data System (ADS)

    Karunakaran, Chockalingam; Vinayagamoorthy, Pazhamalai

    2016-11-01

    Fe2O3-encased ZnO nanoframework was obtained by hydrothermal method and was doped with Ag through photoreduction process. Energy dispersive x-ray spectroscopy, transmission electron microscopy (TEM), high resolution TEM, selected area electron diffractometry, x-ray diffractometry and Raman spectroscopy were employed for the structural characterization of the synthesized material. While the charge transfer resistance of the prepared nanomaterial is larger than those of Fe2O3 and ZnO the coercivity of the nanocomposite is less than that of hydrothermally obtained Fe2O3 nanostructures. Although Fe2O3/Ag-ZnO exhibits weak visible light absorption its band gap energy does not differ from that of ZnO. The photoluminescence of the fabricated nanoframework is similar to that of ZnO. The radiative recombination of charge carriers is slightly slower in Fe2O3/Ag-ZnO than in ZnO. The synthesized Fe2O3-encased Ag-doped ZnO, under UV A light, exhibits sustainable photocatalytic activity to degrade dye and is magnetically recoverable. Also, the Fe2O3/Ag-ZnO nanocomposite disinfects bacteria effectively in absence of direct illumination.

  5. Synthesis and characterization of Fe3O4-SiO2-AgCl photocatalyst

    NASA Astrophysics Data System (ADS)

    Husni, H. N.; Mahmed, N.; Ngee, H. L.

    2016-07-01

    Magnetite-silica-silver chloride (Fe3O4-SiO2-AgCl) coreshell particles with AgCl crystallite size of 117 nm was prepared by a wet chemistry method at ambient temperature. The magnetite-core was synthesized by using iron (II) sulfate heptahydrate (FeSO4•7H2O) and iron (III) sulfate hydrate (Fe2(SO4)3) with ammonium hydroxide (NH4OH) as the precipitating agent. The silica-shell was synthesized by using a modified Stöber process. The silver ions (Ag+) was adsorbed onto the silica surface after Söber process, followed by the addition of Cl- and polyvinylpyrrolidone (PVP) for the formation of Fe3O4-SiO2-AgCl coreshell particles. The effectiveness of the synthesized photocatalyst was investigated by monitoring the degradation of the methylene blue (MB) under sunlight for five cycles. About 90 % of the MB solution can be degraded after 2 hours. The degradation of MB solution by the Fe3O4-SiO2-AgCl particles is highly efficient for first three cycles according to the MB concentration recorded by the UV-Visible spectroscopy (UV-Vis). Nevertheless, the synthesized particles could be a promising material for photocatalytic applications.

  6. Electric modulation of conduction in multiferroic Ni-doped GaFeO3 ceramics

    NASA Astrophysics Data System (ADS)

    Ghani, Awais; Yang, Sen; Rajput, S. S.; Ahmed, S.; Murtaza, Adil; Zhou, Chao; Yu, Zhonghai; Zhang, Yin; Song, Xiaoping; Ren, Xiaobing

    2018-06-01

    In this work, the effects of Ni substitution on the electrical leakage and multiferroic properties of GaFeO3 were examined. Structural analysis of grown ceramics using x-ray diffraction and Raman shows that all ceramics have pure phases with an orthorhombic structure and space group. Ni substitutions slightly modify lattice parameters and induce lattice distortion within the same crystalline structure. It is observed that with increasing Ni-content up to 0.10, the magnetic transition temperature () increases from 196 K to 407 K. Ni-doped samples showed better ferroelectric properties and a drastic reduction in leakage current (~three orders of magnitude) at room temperature. Enhanced characteristics behavior is observed for 10% Ni substitution (GaFe0.9Ni0.1O3) and higher substitution leads to deterioration of properties with a larger leakage current. It is proposed that the role of Ni substitution can reduce hopping between Fe+3 and Fe+2 as well as suppressing the oxygen vacancies. This work would open new possibilities for integrating polycrystalline GaFeO3 at room temperature for magnetoelectric applications.

  7. Effect of nickel on point defects diffusion in FeNi alloys

    DOE PAGES

    Anento, Napoleon; Serra, Anna; Osetsky, Yury N.

    2017-05-05

    Iron-Nickel alloys are perspective alloys as nuclear energy structural materials because of their good radiation damage tolerance and mechanical properties. Understanding of experimentally observed features such as the effect of Ni content to radiation defects evolution is essential for developing predictive models of radiation. Recently an atomic-scale modelling study has revealed one particular mechanism of Ni effect related to the reduced mobility of clusters of interstitial atoms in Fe-Ni alloys. In this paper we present results of the microsecond-scale molecular dynamics study of point defects, i.e. vacancies and self-interstitial atoms, diffusion in Fe-Ni alloys. It is found that the additionmore » of Ni atoms affects diffusion processes: diffusion of vacancies is enhanced in the presence of Ni, whereas diffusion of interstitials is reduced and these effects increase at high Ni concentration and low temperature. As a result, the role of Ni solutes in radiation damage evolution in Fe-Ni alloys is discussed.« less

  8. Electrochemical insights into the mechanism of NiFe membrane-bound hydrogenases

    PubMed Central

    Flanagan, Lindsey A.; Parkin, Alison

    2016-01-01

    Hydrogenases are enzymes of great biotechnological relevance because they catalyse the interconversion of H2, water (protons) and electricity using non-precious metal catalytic active sites. Electrochemical studies into the reactivity of NiFe membrane-bound hydrogenases (MBH) have provided a particularly detailed insight into the reactivity and mechanism of this group of enzymes. Significantly, the control centre for enabling O2 tolerance has been revealed as the electron-transfer relay of FeS clusters, rather than the NiFe bimetallic active site. The present review paper will discuss how electrochemistry results have complemented those obtained from structural and spectroscopic studies, to present a complete picture of our current understanding of NiFe MBH. PMID:26862221

  9. Molecular evolution of gas cavity in [NiFeSe] hydrogenases resurrected in silico

    NASA Astrophysics Data System (ADS)

    Tamura, Takashi; Tsunekawa, Naoki; Nemoto, Michiko; Inagaki, Kenji; Hirano, Toshiyuki; Sato, Fumitoshi

    2016-01-01

    Oxygen tolerance of selenium-containing [NiFeSe] hydrogenases (Hases) is attributable to the high reducing power of the selenocysteine residue, which sustains the bimetallic Ni-Fe catalytic center in the large subunit. Genes encoding [NiFeSe] Hases are inherited by few sulphate-reducing δ-proteobacteria globally distributed under various anoxic conditions. Ancestral sequences of [NiFeSe] Hases were elucidated and their three-dimensional structures were recreated in silico using homology modelling and molecular dynamic simulation, which suggested that deep gas channels gradually developed in [NiFeSe] Hases under absolute anaerobic conditions, whereas the enzyme remained as a sealed edifice under environmental conditions of a higher oxygen exposure risk. The development of a gas cavity appears to be driven by non-synonymous mutations, which cause subtle conformational changes locally and distantly, even including highly conserved sequence regions.

  10. Magneto-optical and catalytic properties of Fe3O4@HA@Ag magnetic nanocomposite

    NASA Astrophysics Data System (ADS)

    Amir, Md.; Güner, S.; Yıldız, A.; Baykal, A.

    2017-01-01

    Fe3O4@HA@Ag magnetic nanocomposites (MNCs) were successfully synthesized by the simple reflux method for the removal of azo dyes from the industrial aqueous media. Fe3O4@HA@AgMNCs exhibited high catalytic activity to reduce MB within 20 min from the waste water. The obtained materials were characterized by the means of different techniques. Powder X-ray diffraction (XRD) analysis confirmed the single-phase of Fe3O4 spinel structure. SEM and TEM analysis indicated that Fe3O4@HA@AgMNCs were nanoparticles like structure with small agglomeration. TG result showed that the products contained 9% of HA. The characteristic peaks of HA at 1601 cm-1 and 1703 cm-1 was observed by the means of FT-IR spectra of Fe3O4@HA@AgMNCs. The hysteresis (σ-H) curves revealed Fe3O4@HA@Ag MNCs exhibit a typical superparamagnetic characteristic with a saturation magnetization of 59.11 emu/g and measured magnetic moment is 2.45 μB. The average magnetic particle dimension (Dmag) is 13.25 nm. In accordance, the average crystallite and particle dimensions were obtained as 11.50 nm and 13.10 nm from XRD and TEM measurements, respectively. Magnetocrystalline anisotropy was offered as uniaxial and calculated effective anisotropy constant (Keff) is 2.96×105 Erg/g. The blocking temperature was estimated as 522 K. The size-dependent saturation magnetization suggests the existence of a magnetically dead layer as 0.793 nm for Fe3O4@HA@Ag MNCs. The UV-vis diffuse reflectance spectroscopy (DRS) and Kubelka-Munk theory were applied to determine the optical properties of powder samples. The direct optical energy band gap (Eg) values were estimated from Tauc plots between 1.62 eV and 2.12 eV.

  11. Fabrication and characterization of L10-ordered FeNi thin films

    NASA Astrophysics Data System (ADS)

    Takanashi, Koki; Mizuguchi, Masaki; Kojima, Takayuki; Tashiro, Takayuki

    2017-12-01

    L10-ordered FeNi, showing high uniaxial magnetic anisotropy (K u), is promising as a ‘rare metal-free’ high K u material. We have worked on L10-ordered FeNi thin films prepared by two methods: one is molecular beam epitaxy (MBE) with alternate deposition of Fe and Ni monatomic layers, and the other is sputtering with co-deposition or multilayer-deposition of Fe and Ni followed by rapid thermal annealing (RTA). For the MBE films prepared by alternate monatomic layer deposition (leading to the stoichiometric composition: Fe 50 at.%- Ni 50 at.%), a clear relationship between K u and the long-range order parameter S estimated by synchrotron x-ray diffraction (XRD) was found with maximum values of S  =  0.48 and K u  =  7.0  ×  106 erg cm-3. The composition dependence of K u was also investigated by deviating the thickness from monatomic layer, showing a maximum of 9.3  ×  106 erg cm-3 around 60 at.%Fe. In addition, the effect of Co addition to L10-ordered FeNi was investigated, suggesting that a small amount (<10 at.%) of Co substitution for Ni would enhance K u if S keeps the same. The experiments were in qualitatively good agreement with the first-principles calculations. The magnetic damping constant α was also measured to be approximately 0.01 irrespective of S, suggesting that L10-FeNi is a candidate material with high K u and low α. For the sputtered films with RTA, no major difference between co-deposition and multilayer-deposition was found: in both cases the formation of L10-ordered phase after RTA was definitely confirmed by XRD. Transmission electron microscopy observations indicated that nanometer-sized L10-ordered clusters were dispersed in a disordered phase, in contrast to that of MBE films showing the homogeneous formation of L10-ordered phase. The enhancement of coercivity (H c) and residual magnetization (M r/M s) was observed associated with the appearance of L10-ordered phase. The maxima of H c and M r/M s

  12. Phase relations of Fe Ni alloys at high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Mao, Wendy L.; Campbell, Andrew J.; Heinz, Dion L.; Shen, Guoyin

    2006-04-01

    Using a diamond anvil cell and double-sided laser-heating coupled with synchrotron X-ray diffraction, we determined phase relations for three compositions of Fe-rich FeNi alloys in situ at high pressure and high temperature. We studied Fe with 5, 15, and 20 wt.% Ni to 55, 62, and 72 GPa, respectively, at temperatures up to ˜3000 K. Ni stabilizes the face-centered cubic phase to lower temperatures and higher pressure, and this effect increases with increasing pressure. Extrapolation of our experimental results for Fe with 15 wt.% Ni suggests that the stable phase at inner core conditions is hexagonal close packed, although if the temperature at the inner core boundary is higher than ˜6400 K, a two phase outer region may also exist. Comparison to previous laser-heated diamond anvil cell studies demonstrates the importance of kinetics even at high temperatures.

  13. Negative tunneling magnetoresistance of Fe/MgO/NiO/Fe magnetic tunnel junction: Role of spin mixing and interface state

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Yan, X. H.; Guo, Y. D.; Xiao, Y.

    2017-08-01

    Motivated by a recent tunneling magnetoresistance (TMR) measurement in which the negative TMR is observed in MgO/NiO-based magnetic tunnel junctions (MTJs), we have performed systematic calculations of transmission, current, and TMR of Fe/MgO/NiO/Fe MTJ with different thicknesses of NiO and MgO layers based on noncollinear density functional theory and non-equilibrium Green's function theory. The calculations show that, as the thickness of NiO and MgO layers is small, the negative TMR can be obtained which is attributed to the spin mixing effect and interface state. However, in the thick MTJ, the spin-flipping scattering becomes weaker, and thus, the MTJs recover positive TMR. Based on our theoretical results, we believe that the interface state at Fe/NiO interface and the spin mixing effect induced by noncollinear interfacial magnetization will play important role in determining transmission and current of Fe/MgO/NiO/Fe MTJ. The results reported here will be important in understanding the electron tunneling in MTJ with the barrier made by transition metal oxide.

  14. A novel multifunctional NiTi/Ag hierarchical composite

    PubMed Central

    Hao, Shijie; Cui, Lishan; Jiang, Jiang; Guo, Fangmin; Xiao, Xianghui; Jiang, Daqiang; Yu, Cun; Chen, Zonghai; Zhou, Hua; Wang, Yandong; Liu, YuZi; Brown, Dennis E.; Ren, Yang

    2014-01-01

    Creating multifunctional materials is an eternal goal of mankind. As the properties of monolithic materials are necessary limited, one route to extending them is to create a composite by combining contrasting materials. The potential of this approach is neatly illustrated by the formation of nature materials where contrasting components are combined in sophisticated hierarchical designs. In this study, inspired by the hierarchical structure of the tendon, we fabricated a novel composite by subtly combining two contrasting components: NiTi shape-memory alloy and Ag. The composite exhibits simultaneously exceptional mechanical properties of high strength, good superelasticity and high mechanical damping, and remarkable functional properties of high electric conductivity, high visibility under fluoroscopy and excellent thermal-driven ability. All of these result from the effective-synergy between the NiTi and Ag components, and place the composite in a unique position in the properties chart of all known structural-functional materials providing new opportunities for innovative electrical, mechanical and biomedical applications. Furthermore, this work may open new avenues for designing and fabricating advanced multifunctional materials by subtly combining contrasting multi-components. PMID:24919945

  15. A novel polydentate ligand chromophore for simultaneously colorimetric detection of trace Ag + and Fe3 +

    NASA Astrophysics Data System (ADS)

    Yan, Zhengquan; Zhao, Qi; Wen, Meijun; Hu, Lei; Zhang, Xuezhong; You, Jinmao

    2017-11-01

    A novel polydentate ligand chromophore, 3,6-di-(N-ethyl-N-ethoxyl phenylazo) acridine (EEPA), was identified and synthesized. After its structure was characterized by FTIR, 1H NMR, mass spectra and element analyses, it was noted to find that there was a simultaneously colorimetric response to Ag+ and Fe3 + accompanying with different color changes, i.e., from brown to light purple for Ag+ and further to purple-red for Fe3 +, respectively. Their different action mechanisms, a 1:2 complex mode for EEPA-Ag+ and 1:1 for EEPA-Fe3 +, were investigated and confirmed by means of Job's plot and theoretical calculation. EEPA would be a potential colorimetric chemo-dosimeter for simultaneous detection of Ag+ and Fe3 + with the detection limits of 1.6 nmol·L- 1 and 69 nmol·L- 1, respectively.

  16. Vancomycin-modified Fe3O4@SiO2@Ag microflowers as effective antimicrobial agents

    PubMed Central

    Wang, Chongwen; Zhang, Kehan; Zhou, Zhe; Li, Qingjun; Shao, Liting; Hao, Rong Zhang; Xiao, Rui; Wang, Shengqi

    2017-01-01

    Nanomaterials combined with antibiotics exhibit synergistic effects and have gained increasing interest as promising antimicrobial agents. In this study, vancomycin-modified magnetic-based silver microflowers (Van/Fe3O4@SiO2@Ag microflowers) were rationally designed and prepared to achieve strong bactericidal ability, a wide antimicrobial spectrum, and good recyclability. High-performance Fe3O4@SiO2@Ag microflowers served as a multifunction-supporting matrix and exhibited sufficient magnetic response property due to their 200 nm Fe3O4 core. The microflowers also possessed a highly branched flower-like Ag shell that provided a large surface area for effective Ag ion release and bacterial contact. The modified-vancomycin layer was effectively bound to the cell wall of bacteria to increase the permeability of the cell membrane and facilitate the entry of the Ag ions into the bacterium, resulting in cell death. As such, the fabricated Van/Fe3O4@SiO2@Ag microflowers were predicted to be an effective and environment-friendly antibacterial agent. This hypothesis was verified through sterilization of Gram-negative Escherichia coli and Gram-positive methicillin-resistant Staphylococcus aureus, with minimum inhibitory concentrations of 10 and 20 μg mL−1, respectively. The microflowers also showed enhanced effect compared with bare Fe3O4@SiO2@Ag microflowers and free-form vancomycin, confirming the synergistic effects of the combination of the two components. Moreover, the antimicrobial effect was maintained at more than 90% after five cycling assays, indicating the high stability of the product. These findings reveal that Van/Fe3O4@SiO2@Ag microflowers exhibit promising applications in the antibacterial fields. PMID:28450783

  17. Interface perpendicular magnetic anisotropy in ultrathin Ta/NiFe/Pt layered structures

    NASA Astrophysics Data System (ADS)

    Hirayama, Shigeyuki; Kasai, Shinya; Mitani, Seiji

    2018-01-01

    Interface perpendicular magnetic anisotropy (PMA) in ultrathin Ta/NiFe/Pt layered structures was investigated through magnetization measurements. Ta/NiFe/Pt films with NiFe layer thickness (t) values of 2 nm or more showed typical in-plane magnetization curves, which was presumably due to the dominant contribution of the shape magnetic anisotropy. The thickness dependence of the saturation magnetization of the entire NiFe layer (M s) was well analyzed using the so-called dead-layer model, showing that the magnetically active part of the NiFe layer has saturation magnetization (M\\text{s}\\text{act}) independent of t and comparable to the bulk value. In the perpendicular direction, the saturation field H k was found to clearly decrease with decreasing t, while the effective field of shape magnetic anisotropy due to the active NiFe saturation magnetization M\\text{s}\\text{act} should be independent of t. These observations show that there exists interface PMA in the layered structures. The interface PMA energy density was determined to be ∼0.17 erg/cm2 using the dead-layer model. Motivated by the correlation observed between M s and H k, we also attempted to interpret the experimental results using an alternative approach beyond the dead-layer model; however, it gives only implications on the incomplete validity of the dead-layer model and no better understanding.

  18. Bulk synthesis of monodisperse magnetic FeNi3 nanopowders by flow levitation method.

    PubMed

    Chen, Shanjun; Chen, Yan; Kang, Xiaoli; Li, Song; Tian, Yonghong; Wu, Weidong; Tang, Yongjian

    2013-10-01

    In this work, a novel bulk synthesis method for monodisperse FeNi3 nanoparticles was developed by flow levitation method (FL). The Fe and Ni vapours ascending from the high temperature levitated droplet was condensed by cryogenic Ar gas under atmospheric pressure. X-ray diffraction was used to identify and characterize the crystal phase of prepared powders exhibiting a FeNi3 phase. The morphology and size of nanopowders were observed by transmission electron microscopy (TEM). The chemical composition of the nanoparticles was determined with energy dispersive spectrometer (EDS). The results indicated that the FeNi3 permalloy powders are nearly spherical-shaped with diameter about 50-200 nm. Measurement of the magnetic property of nanopowders by a superconducting quantum interference device (SQUID, Quantum Design MPMS-7) showed a symmetric hysteresis loop of ferromagnetic behavior with coercivity of 220 Oe and saturation magnetization of 107.17 emu/g, at 293 K. At 5 K, the obtained saturation magnetization of the sample was 102.16 emu/g. The production rate of FeNi3 nanoparticles was estimated to be about 6 g/h. This method has great potential in mass production of FeNi3 nannoparticles.

  19. Si-rich Fe-Ni grains in highly unequilibrated chondrites

    NASA Technical Reports Server (NTRS)

    Rambaldi, E. R.; Sears, D. W.; Wasson, J. T.

    1980-01-01

    Consideration is given to the Si contents of Fe-Ni grains in highly unequilibrated chondrites, which have undergone little metamorphosis and thus best preserve the record of processes in the solar nebula. Electron microprobe determinations of silicon content in grains of the Bishunpur chondrite are presented for the six Si-bearing Fe-Ni grains for which data could be obtained, five of which were found to be embedded in olivine chondrules. In addition, all grains are found to be Cr-rich, with Cr increased in concentration towards the grain edge, and to be encased in FeS shells which evidently preserved the Si that entered the FeNi at higher temperatures. A mechanism for the production of Si-bearing metal during the condensation of the cooling solar nebula is proposed which considers the metal to have condensed heterogeneously while the mafic silicates condensed homogeneously with amounts of required undercooling in the low-pressure regions where ordinary and carbonaceous chondrites formed, resulting in Si mole fractions of 0.003 at nebular pressures less than 0.000001 atm.

  20. Chemical synthesis of L10 Fe-Pt-Ni alloy nanoparticles

    NASA Astrophysics Data System (ADS)

    Deepchand, Vimal; Abel, Frank M.; Tzitzios, Vasileios; Hadjipanayis, George C.

    2018-05-01

    This work focuses on the study of the magnetic and structural properties of chemically synthesized FePt1-xNix nanoparticles, with Ni content x in the range 0.2-0.4. We report the effect of Ni substitution on the L10 structure, on both the as-synthesized and annealed nanoparticles. A decrease in nanoparticle size as well as in chemical order is observed with an increase in Ni content, for both the as-made and annealed nanoparticles. The results also show that the post annealing procedure at 700oC significantly enhanced the L10 ordering of the nanoparticles. Substitution of nickel leads to a decrease in coercivity from 14.9 kOe in FePt to 0.8 kOe for FePt0.6Ni0.4 alloy, while the magnetization at 3 T is increased from 48 emu/g to 88 emu/g.

  1. Thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys

    DOE PAGES

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-06-12

    Understanding the stability of precipitate phases in the Fe-rich Fe-Cr-Ni-Mo alloys is critical to the alloy design and application of Mo-containing Austenitic steels. Coupled with thermodynamic modeling, stability of the chi and Laves phases in two Fe-Cr-Ni-Mo alloys were investigated at 1000, 850 and 700 °C for different annealing time. The morphologies, compositions and crystal structures of the matrix and precipitate phases were carefully examined by Scanning Electron Microscopy, Electron Probe Microanalysis, X-ray diffraction and Transmission Electron Microscopy. The two key findings resulted from this work. One is that the chi phase is stable at high temperature and transformed intomore » the Laves phase at low temperature. The other is that both the chi and Laves phases have large solubilites of Cr, Mo and Ni, among which the Mo solubility has a major role on the relative stability of the precipitate phases. The developed thermodynamic models were then applied to evaluating the Mo effect on the stability of precipitate phases in AISI 316 and NF709 alloys.« less

  2. [3Fe-4S] to [4Fe-4S] cluster conversion in Desulfovibrio fructosovorans [NiFe] hydrogenase by site-directed mutagenesis.

    PubMed

    Rousset, M; Montet, Y; Guigliarelli, B; Forget, N; Asso, M; Bertrand, P; Fontecilla-Camps, J C; Hatchikian, E C

    1998-09-29

    The role of the high potential [3Fe-4S]1+,0 cluster of [NiFe] hydrogenase from Desulfovibrio species located halfway between the proximal and distal low potential [4Fe-4S]2+,1+ clusters has been investigated by using site-directed mutagenesis. Proline 238 of Desulfovibrio fructosovorans [NiFe] hydrogenase, which occupies the position of a potential ligand of the lacking fourth Fe-site of the [3Fe-4S] cluster, was replaced by a cysteine residue. The properties of the mutant enzyme were investigated in terms of enzymatic activity, EPR, and redox properties of the iron-sulfur centers and crystallographic structure. We have shown on the basis of both spectroscopic and x-ray crystallographic studies that the [3Fe-4S] cluster of D. fructosovorans hydrogenase was converted into a [4Fe-4S] center in the P238 mutant. The [3Fe-4S] to [4Fe-4S] cluster conversion resulted in a lowering of approximately 300 mV of the midpoint potential of the modified cluster, whereas no significant alteration of the spectroscopic and redox properties of the two native [4Fe-4S] clusters and the NiFe center occurred. The significant decrease of the midpoint potential of the intermediate Fe-S cluster had only a slight effect on the catalytic activity of the P238C mutant as compared with the wild-type enzyme. The implications of the results for the role of the high-potential [3Fe-4S] cluster in the intramolecular electron transfer pathway are discussed.

  3. [3Fe-4S] to [4Fe-4S] cluster conversion in Desulfovibrio fructosovorans [NiFe] hydrogenase by site-directed mutagenesis

    PubMed Central

    Rousset, Marc; Montet, Yael; Guigliarelli, Bruno; Forget, Nicole; Asso, Marcel; Bertrand, Patrick; Fontecilla-Camps, Juan C.; Hatchikian, E. Claude

    1998-01-01

    The role of the high potential [3Fe-4S]1+,0 cluster of [NiFe] hydrogenase from Desulfovibrio species located halfway between the proximal and distal low potential [4Fe-4S]2+,1+ clusters has been investigated by using site-directed mutagenesis. Proline 238 of Desulfovibrio fructosovorans [NiFe] hydrogenase, which occupies the position of a potential ligand of the lacking fourth Fe-site of the [3Fe-4S] cluster, was replaced by a cysteine residue. The properties of the mutant enzyme were investigated in terms of enzymatic activity, EPR, and redox properties of the iron-sulfur centers and crystallographic structure. We have shown on the basis of both spectroscopic and x-ray crystallographic studies that the [3Fe-4S] cluster of D. fructosovorans hydrogenase was converted into a [4Fe-4S] center in the P238 mutant. The [3Fe-4S] to [4Fe-4S] cluster conversion resulted in a lowering of approximately 300 mV of the midpoint potential of the modified cluster, whereas no significant alteration of the spectroscopic and redox properties of the two native [4Fe-4S] clusters and the NiFe center occurred. The significant decrease of the midpoint potential of the intermediate Fe-S cluster had only a slight effect on the catalytic activity of the P238C mutant as compared with the wild-type enzyme. The implications of the results for the role of the high-potential [3Fe-4S] cluster in the intramolecular electron transfer pathway are discussed. PMID:9751716

  4. Temperature of Earth's core constrained from melting of Fe and Fe0.9Ni0.1 at high pressures

    NASA Astrophysics Data System (ADS)

    Zhang, Dongzhou; Jackson, Jennifer M.; Zhao, Jiyong; Sturhahn, Wolfgang; Alp, E. Ercan; Hu, Michael Y.; Toellner, Thomas S.; Murphy, Caitlin A.; Prakapenka, Vitali B.

    2016-08-01

    The melting points of fcc- and hcp-structured Fe0.9Ni0.1 and Fe are measured up to 125 GPa using laser heated diamond anvil cells, synchrotron Mössbauer spectroscopy, and a recently developed fast temperature readout spectrometer. The onset of melting is detected by a characteristic drop in the time-integrated synchrotron Mössbauer signal which is sensitive to atomic motion. The thermal pressure experienced by the samples is constrained by X-ray diffraction measurements under high pressures and temperatures. The obtained best-fit melting curves of fcc-structured Fe and Fe0.9Ni0.1 fall within the wide region bounded by previous studies. We are able to derive the γ-ɛ-l triple point of Fe and the quasi triple point of Fe0.9Ni0.1 to be 110 ± 5GPa, 3345 ± 120K and 116 ± 5GPa, 3260 ± 120K, respectively. The measured melting temperatures of Fe at similar pressure are slightly higher than those of Fe0.9Ni0.1 while their one sigma uncertainties overlap. Using previously measured phonon density of states of hcp-Fe, we calculate melting curves of hcp-structured Fe and Fe0.9Ni0.1 using our (quasi) triple points as anchors. The extrapolated Fe0.9Ni0.1 melting curve provides an estimate for the upper bound of Earth's inner core-outer core boundary temperature of 5500 ± 200K. The temperature within the liquid outer core is then approximated with an adiabatic model, which constrains the upper bound of the temperature at the core side of the core-mantle boundary to be 4000 ± 200K. We discuss a potential melting point depression caused by light elements and the implications of the presented core-mantle boundary temperature bounds on phase relations in the lowermost part of the mantle.

  5. Temperature of Earth's core constrained from melting of Fe and Fe 0.9Ni 0.1 at high pressures

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Dongzhou; Jackson, Jennifer M.; Zhao, Jiyong

    The melting points of fcc- and hcp-structured Fe 0.9Ni 0.1 and Fe are measured up to 125 GPa using laser heated diamond anvil cells, synchrotron Mossbauer spectroscopy, and a recently developed fast temperature readout spectrometer. The onset of melting is detected by a characteristic drop in the time integrated synchrotron Mfissbauer signal which is sensitive to atomic motion. The thermal pressure experienced by the samples is constrained by X-ray diffraction measurements under high pressures and temperatures. The obtained best-fit melting curves of fcc-structured Fe and Fe 0.9Ni 0.1 fall within the wide region bounded by previous studies. We are ablemore » to derive the gamma-is an element of-1 triple point of Fe and the quasi triple point of Fe0.9Ni0.1 to be 110 ± 5 GPa, 3345 ± 120 K and 116 ± 5 GPa, 3260 ± 120 K, respectively. The measured melting temperatures of Fe at similar pressure are slightly higher than those of Fe 0.9Ni 0.1 while their one sigma uncertainties overlap. Using previously measured phonon density of states of hcp-Fe, we calculate melting curves of hcp-structured Fe and Fe 0.9Ni 0.1 using our (quasi) triple points as anchors. The extrapolated Fe 0.9Ni 0.1 melting curve provides an estimate for the upper bound of Earth's inner core-outer core boundary temperature of 5500 ± 200 K. The temperature within the liquid outer core is then approximated with an adiabatic model, which constrains the upper bound of the temperature at the core side of the core -mantle boundary to be 4000 ± 200 K. We discuss a potential melting point depression caused by light elements and the implications of the presented core -mantle boundary temperature bounds on phase relations in the lowermost part of the mantle.« less

  6. Embedded Ag/Ni Metal-Mesh with Low Surface Roughness As Transparent Conductive Electrode for Optoelectronic Applications.

    PubMed

    Chen, Xiaolian; Guo, Wenrui; Xie, Liming; Wei, Changting; Zhuang, Jinyong; Su, Wenming; Cui, Zheng

    2017-10-25

    Metal-mesh is one of the contenders to replace indium tin oxide (ITO) as transparent conductive electrodes (TCEs) for optoelectronic applications. However, considerable surface roughness accompanying metal-mesh type of transparent electrodes has been the root cause of electrical short-circuiting for optoelectronic devices, such as organic light-emitting diode (OLED) and organic photovoltaic (OPV). In this work, a novel approach to making metal-mesh TCE has been proposed that is based on hybrid printing of silver (Ag) nanoparticle ink and electroplating of nickel (Ni). By polishing back the electroplated Ni, an extremely smooth surface was achieved. The fabricated Ag/Ni metal-mesh TCE has a surface roughness of 0.17 nm, a low sheet resistance of 2.1 Ω/□, and a high transmittance of 88.6%. The figure of merit is 1450, which is 30 times better than ITO. In addition, the Ag/Ni metal-mesh TCE shows outstanding mechanical flexibility and environmental stability at high temperature and humidity. Using the polished Ag/Ni metal-mesh TCE, a flexible quantum dot light-emitting diode (QLED) was fabricated with an efficiency of 10.4 cd/A and 3.2 lm/W at 1000 cd/m 2 .

  7. Magnetic and Dielectric Property Studies in Fe- and NiFe-Based Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Sharma, Himani; Jain, Shubham; Raj, Pulugurtha Markondeya; Murali, K. P.; Tummala, Rao

    2015-10-01

    Metal-polymer composites were investigated for their microwave properties in the frequency range of 30-1000 MHz to assess their application as inductor cores and electromagnetic isolation shield structures. NiFe and Fe nanoparticles were dispersed in epoxy as nanocomposites, in different volume fractions. The permittivity, permeability, and loss tangents of the composites were measured with an impedance analyzer and correlated with the magnetic properties of the particle such as saturation magnetization and field anisotropy. Fe-epoxy showed lower magnetic permeability but improved frequency stability, compared to the NiFe-epoxy composites of the same volume loading. This is attributed to the differences in nanoparticle's structure such as effective metal core size and particle-porosity distribution in the polymer matrix. The dielectric properties of the nanocomposites were also characterized from 30 MHz to 1000 MHz. The instabilities in the dielectric constant and loss tangent were related to the interfacial polarization relaxation of the particles and the dielectric relaxation of the surface oxides.

  8. Facile one-step synthesis of Ag@Fe3O4 core-shell nanospheres for reproducible SERS substrates

    NASA Astrophysics Data System (ADS)

    Sun, Lijuan; He, Jiang; An, Songsong; Zhang, Junwei; Ren, Dong

    2013-08-01

    A facile approach has been developed to synthesize Ag@Fe3O4 core-shell nanospheres, in which the Ag nanoparticle core was well wrapped by a permeable Fe3O4 shell. An in situ reduction of AgNO3 and Fe(NO3)3 was the basis of this one-step method with ethylene glycol as the reducing agent. The as-obtained Ag@Fe3O4 nanospheres were a highly efficient surface-enhanced Raman scattering (SERS) substrate; high reproducibility, stability, and reusability were obtained by employing 4-aminothiophenol (4-ATP) and rhodamine 6G (R6G) as the Raman probe molecules. It was revealed that the SERS signals of 4-ATP and R6G on the Ag@Fe3O4 nanospheres were much stronger than those on the pure Ag nanoparticles, demonstrating that the magnetic enrichment procedures can improve SERS detection sensitivity efficiently. A highly efficient and recyclable SERS substrate was produced by the new model system that has potential applications in chemical and biomolecular assays.

  9. Collective magnetic response of inhomogeneous nanoisland FeNi films around the percolation transition

    NASA Astrophysics Data System (ADS)

    Kovaleva, Natalia N.; Bagdinov, Anton V.; Stupakov, Alexandr; Dejneka, Alexandr; Demikhov, Evgenii I.; Gorbatsevich, Alexandr A.; Pudonin, Fedor A.; Kugel, Kliment I.; Kusmartsev, Feodor V.

    2018-04-01

    By using superconducting quantum interference device (SQUID) magnetometry, we investigated anisotropic high-field ( H ≲ 7T) low-temperature (10 K) magnetization response of inhomogeneous nanoisland FeNi films grown by rf sputtering deposition on Sitall (TiO2) glass substrates. In the grown FeNi films, the FeNi layer nominal thickness varied from 0.6 to 2.5 nm, across the percolation transition at the d c ≃ 1.8 nm. We discovered that, beyond conventional spin-magnetism of Fe21Ni79 permalloy, the extracted out-of-plane magnetization response of the nanoisland FeNi films is not saturated in the range of investigated magnetic fields and exhibits paramagnetic-like behavior. We found that the anomalous out-of-plane magnetization response exhibits an escalating slope with increase in the nominal film thickness from 0.6 to 1.1 nm, however, it decreases with further increase in the film thickness, and then practically vanishes on approaching the FeNi film percolation threshold. At the same time, the in-plane response demonstrates saturation behavior above 1.5-2T, competing with anomalously large diamagnetic-like response, which becomes pronounced at high magnetic fields. It is possible that the supported-metal interaction leads to the creation of a thin charge-transfer (CT) layer and a Schottky barrier at the FeNi film/Sitall (TiO2) interface. Then, in the system with nanoscale circular domains, the observed anomalous paramagnetic-like magnetization response can be associated with a large orbital moment of the localized electrons. In addition, the inhomogeneous nanoisland FeNi films can possess spontaneous ordering of toroidal moments, which can be either of orbital or spin origin. The system with toroidal inhomogeneity can lead to anomalously strong diamagnetic-like response. The observed magnetization response is determined by the interplay between the paramagnetic- and diamagnetic-like contributions.

  10. Magnetic moment of {sup 104}Ag{sup m} and the hyperfine magnetic field of Ag in Fe using nuclear magnetic resonance on oriented nuclei

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Golovko, V. V.; Kraev, I. S.; Phalet, T.

    2010-05-15

    Nuclear magnetic resonance (NMR/ON) measurements with beta- and gamma-ray detection have been performed on oriented {sup 104}Ag{sup g,m} nuclei with the NICOLE {sup 3}He-{sup 4}He dilution refrigerator setup at ISOLDE/CERN. For {sup 104}Ag{sup g} (I{sup p}i=5{sup +}) the gamma-NMR/ON resonance signal was found at nu=266.70(5) MHz. Combining this result with the known magnetic moment for this isotope, the magnetic hyperfine field of Ag impurities in an Fe host at low temperature (<1 K) is found to be |B{sub hf}(AgFe)|=44.709(35) T. A detailed analysis of other relevant data available in the literature yields three more values for this hyperfine field. Averagingmore » all four values yields a new and precise value for the hyperfine field of Ag in Fe; that is, |B{sub hf}(AgFe)|=44.692(30) T. For {sup 104}Ag{sup m} (I{sup p}i=2{sup +}), the anisotropy of the beta particles provided the NMR/ON resonance signal at nu=627.7(4) MHz. Using the new value for the hyperfine field of Ag in Fe, this frequency corresponds to the magnetic moment mu({sup 104m}Ag)=+3.691(3) mu{sub N}, which is significantly more precise than previous results. The magnetic moments of the even-A {sup 102-110}Ag isotopes are discussed in view of the competition between the (pig{sub 9/2}){sub 7/2}{sup +-3}(nud{sub 5/2}nug{sub 7/2}){sub 5/2}{sup +} and the (pig{sub 9/2}){sub 9/2}{sup +-3}(nud{sub 5/2}nug{sub 7/2}){sub 5/2}{sup +} configurations. The magnetic moments of the ground and isomeric states of {sup 104}Ag can be explained by an almost complete mixing of these two configurations.« less

  11. Adsorption behavior of Fe atoms on a naphthalocyanine monolayer on Ag(111) surface

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yan, Ling -Hao; Wu, Rong -Ting; Bao, De -Liang

    2015-05-29

    Adsorption behavior of Fe atoms on a metal-free naphthalocyanine (H 2Nc) monolayer on Ag(111) surface at room temperature has been investigated using scanning tunneling microscopy combined with density functional theory (DFT) based calculations. We found that the Fe atoms adsorbed at the centers of H 2Nc molecules and formed Fe-H 2Nc complexes at low coverage. DFT calculations show that the configuration of Fe at the center of a molecule is the most stable site, in good agreement with the experimental observations. After an Fe-H 2Nc complex monolayer was formed, the extra Fe atoms self-assembled to Fe clusters of uniform sizemore » and adsorbed dispersively at the interstitial positions of Fe-H 2Nc complex monolayer. Furthermore, the H 2Nc monolayer grown on Ag(111) could be a good template to grow dispersed magnetic metal atoms and clusters at room temperature for further investigation of their magnetism-related properties.« less

  12. Simultaneous plate forming and hydriding of La(Fe, Si)13 magnetocaloric powders

    NASA Astrophysics Data System (ADS)

    Yang, Nannan; You, Caiyin; Tian, Na; Zhang, Yue; Leng, Haiyan; He, Jun

    2018-04-01

    In this work, we propose a way to simultaneously realize the plate forming and hydriding of La(Fe, Si)13 powders by mixing hydride MgNiYHx and solder powders Sn3.0Ag0.5Cu. Under the annealing of the green compact, the hydriding of La(Fe, Si)13 was realized through absorbing the released hydrogen from the metallic hydride MgNiYHx. The Curie temperature of La(Fe, Si)13 alloy increased from 213 K to 333 K and hysteresis reduced from 3.3 J/kg·K to 1.33 J/kg·K. Due to the bonding of Sn3.0Ag0.5Cu powders, the mechanical strength of the composite compact was highly improved in comparison to the compact of La(Fe, Si)13 powders alone.

  13. High-pressure and high-temperature phase diagram for Fe0.9Ni0.1-H alloy

    NASA Astrophysics Data System (ADS)

    Shibazaki, Yuki; Terasaki, Hidenori; Ohtani, Eiji; Tateyama, Ryuji; Nishida, Keisuke; Funakoshi, Ken-ichi; Higo, Yuji

    2014-03-01

    Planetary cores are considered to consist of an iron-nickel (Fe-Ni) alloy and light elements and hydrogen is one of plausible light elements in the core. Here we have performed in situ X-ray diffraction experiments on an Fe0.9Ni0.1-H system up to 15.1 GPa and 1673 K, and investigated the effect of Ni on phase relations of FeHx under high pressure and high temperature. The experimental system in the present work was oversaturated with hydrogen. We found a face-center-cubic (fcc) phase (with hydrogen concentration up to x∼1) and a body-center-cubic (bcc) phase (x < 0.1) as stable phases. The partial melting was observed below 6 GPa. We could not observe a double-hexagonal-close-packed (dhcp) phase because of limitations in pressure and temperature conditions. The stability field of each phase of Fe0.9Ni0.1Hx was almost same as that of FeHx. The solidus of Fe0.9Ni0.1Hx was 500-700 K lower than the melting curve of Fe and its liquidus was 400-600 K lower than that of Fe in the pressure range of this study. Both the solidus and liquidus of Fe0.9Ni0.1Hx were depressed at around 3.5 GPa, as was the solidus of FeHx. The hydrogen contents in fcc-Fe0.9Ni0.1Hx just below solidus were slightly lower than those of fcc-FeHx, which suggests that nickel is likely to prevent dissolution of hydrogen into iron. Due to the lower hydrogen solubilities in Fe0.9Ni0.1 compared to Fe, the solidus of Fe0.9Ni0.1Hx is about 100-150 K higher than that of FeHx.

  14. Magnetic x-ray linear dichroism of ultrathin Fe-Ni alloy films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schumann, F.O.; Willis, R.F.; Goodman, K.W.

    1997-04-01

    The authors have studied the magnetic structure of ultrathin Fe-Ni alloy films as a function of Fe concentration by measuring the linear dichroism of the 3p-core levels in angle-resolved photoemission spectroscopy. The alloy films, grown by molecular-beam epitaxy on Cu(001) surfaces, were fcc and approximately four monolayers thick. The intensity of the Fe dichroism varied with Fe concentration, with larger dichroisms at lower Fe concentrations. The implication of these results to an ultrathin film analogue of the bulk Invar effect in Fe-Ni alloys will be discussed. These measurements were performed at the Spectromicroscopy Facility (Beamline 7.0.1) of the Advanced Lightmore » Source.« less

  15. Sound velocity of liquid Fe-Ni-S at high pressure

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Saori I.; Nakajima, Yoichi; Hirose, Kei; Komabayashi, Tetsuya; Ozawa, Haruka; Tateno, Shigehiko; Kuwayama, Yasuhiro; Tsutsui, Satoshi; Baron, Alfred Q. R.

    2017-05-01

    The sound velocity of liquid Fe47Ni28S25 and Fe63Ni12S25 was measured up to 52 GPa/2480 K in externally resistance-heated and laser-heated diamond-anvil cells using high-resolution inelastic X-ray scattering. From these experimental data, we obtained the elastic parameters of liquid Fe47Ni28S25, KS0 = 96.1 ± 2.7 GPa and KS0' = 4.00 ± 0.13, where KS0 and KS0' are the adiabatic bulk modulus and its pressure derivative at 1 bar, when the density is fixed at ρ0 = 5.62 ± 0.09 g/cm3 for 1 bar and 2000 K. With these parameters, the sound velocity and density of liquid Fe47Ni28S25 were calculated to be 8.41 ± 0.17 km/s and 8.93 ± 0.19 to 9.10 ± 0.18 g/cm3, respectively, at the core mantle boundary conditions of 135 GPa and 3600-4300 K. These values are 9.4% higher and 17-18% lower than those of pure Fe, respectively. Extrapolation of measurements and comparison with seismological models suggest the presence of 5.8-7.5 wt % sulfur in the Earth's outer core if it is the only light element.

  16. Phase stability and magnetic behavior of FeCrCoNiGe high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Huang, Shuo; Vida, Ádám; Molnár, Dávid; Kádas, Krisztina; Varga, Lajos Károly; Holmström, Erik; Vitos, Levente

    2015-12-01

    We report an alternative FeCrCoNiGe magnetic material based on FeCrCoNi high-entropy alloy with Curie point far below the room temperature. Investigations are done using first-principles calculations and key experimental measurements. Results show that the equimolar FeCrCoNiGe system is decomposed into a mixture of face-centered cubic and body-centered cubic solid solution phases. The increased stability of the ferromagnetic order in the as-cast FeCrCoNiGe composite, with measured Curie temperature of 640 K, is explained using the exchange interactions.

  17. Preliminary Microstructural and Microscratch Results of Ni-Cr-Fe and Cr3C2-NiCr Coatings on Magnesium Substrate

    NASA Astrophysics Data System (ADS)

    Istrate, B.; Munteanu, C.; Lupescu, S.; Benchea, M.; Vizureanu, P.

    2017-06-01

    Thermal coatings have a large scale application in aerospace and automotive field, as barriers improving wear mechanical characteristics and corrosion resistance. In present research, there have been used two types of coatings, Ni-Cr-Fe, respectively Cr3C2-NiCr which were deposited on magnesium based alloys (pure magnesium and Mg-30Y master alloy). There have been investigated the microstructural aspects through scanning electronic microscopy and XRD analysis and also a series of mechanical characteristics through microscratch and indentation determinations. The results revealed the formation of some adherent layers resistant to the penetration of the metallic indenter, the coatings did not suffer major damages. Microstructural analysis highlighted the formation of Cr3C2, Cr7C3, Cr3Ni2, Cr7Ni3, FeNi3, Cr-Ni phases. Also, the apparent coefficient of friction for Ni-Cr-Fe coatings presents superior values than Cr3C2-NiCr coatings.

  18. Highly efficient and porous TiO2-coated Ag@Fe3O4@C-Au microspheres for degradation of organic pollutants

    NASA Astrophysics Data System (ADS)

    Shen, Mao; Chen, Suqing; Jia, Wenping; Fan, Guodong; Jin, Yanxian; Liang, Huading

    2016-12-01

    In this paper, we reported a novel hierarchical porous Ag@Fe3O4@C-Au@TiO2 core@shell microspheres with a highly photocatalytic activity and magnetically separable properties. The synthesis method is included of a Fe3O4 magnetic embedded Ag core (Ag@Fe3O4), an interlayer of carbon modified by PEI to form sufficient amounts of amine functional groups (Ag@Fe3O4@C-PEI), the grafting of Au nanoparticles on the surface of Ag@Fe3O4@C-PEI (Ag@Fe3O4@C-Au), and an ordered porous TiO2 structured shell. As an example of the applications, the photocatalytic activities of the samples were investigated by the reduction of Rhodamine B (RhB) under visible-light irradiation. The results show that the porous Ag@Fe3O4@C-Au@TiO2 core@shell microspheres display higher adsorption and photocatalytic activities compared to the pure porous TiO2 and Ag@Fe3O4@C@TiO2 microspheres, which are attributed to the local surface plasmon resonance (LSPR) by the Ag and Au nanoparticles and the high specific surface area.

  19. Nano-scaled Pt/Ag/Ni/Au contacts on p-type GaN for low contact resistance and high reflectivity.

    PubMed

    Kwon, Y W; Ju, I C; Kim, S K; Choi, Y S; Kim, M H; Yoo, S H; Kang, D H; Sung, H K; Shin, K; Ko, C G

    2011-07-01

    We synthesized the vertical-structured LED (VLED) using nano-scaled Pt between p-type GaN and Ag-based reflector. The metallization scheme on p-type GaN for high reflectance and low was the nano-scaled Pt/Ag/Ni/Au. Nano-scaled Pt (5 A) on Ag/Ni/Au exhibited reasonably high reflectance of 86.2% at the wavelength of 460 nm due to high transmittance of light through nano-scaled Pt (5 A) onto Ag layer. Ohmic behavior of contact metal, Pt/Ag/Ni/Au, to p-type GaN was achieved using surface treatments of p-type GaN prior to the deposition of contact metals and the specific contact resistance was observed with decreasing Pt thickness of 5 A, resulting in 1.5 x 10(-4) ohms cm2. Forward voltages of Pt (5 A)/Ag/Ni contact to p-type GaN showed 4.19 V with the current injection of 350 mA. Output voltages with various thickness of Pt showed the highest value at the smallest thickness of Pt due to its high transmittance of light onto Ag, leading to high reflectance. Our results propose that nano-scaled Pt/Ag/Ni could act as a promising contact metal to p-type GaN for improving the performance of VLEDs.

  20. Fabry-Perot magnonic ballistic coherent transport across ultrathin ferromagnetic lamellar bcc Ni nanostructures between Fe leads

    NASA Astrophysics Data System (ADS)

    Khater, A.; Saim, L.; Tigrine, R.; Ghader, D.

    2018-06-01

    We propose thermodynamically stable systems of ultrathin lamellar bcc Ni nanostructures between bcc Fe leads, sbnd Fe[Ni(n)]Fesbnd , based on the available literature for bcc Ni overlayers on Fe(001) surfaces, and establish the necessary criteria for their structural and ferromagnetic order, for thicknesses n ≤ 6 bcc Ni monatomic layers. The system is globally ferromagnetic. A theoretical model is presented to investigate and understand the ballistic coherent scattering of Fe spin-waves, incident from the leads, at the ferromagnetic bcc Ni nanostructure. The Nisbnd Ni and Nisbnd Fe exchange are computed using the Ising effective field theory (EFT), and the magnetic ground state of the system is constructed in the Heisenberg representation. We compute the spin-wave eigenmodes localized on the bcc Ni nanostructure, using the phase field matching theory (PFMT), illustrating the effects of symmetry breaking on the confinement of localized spin excitations. The reflection and transmission scattering properties of spin-waves incident from the Fe leads, across the embedded Ni nanostructures are investigated within the framework of the same PFMT methodology. A highly refined Fabry-Perot magnonic ballistic coherent transmission spectra is observed for these sbnd Fe[Ni(n)]Fesbnd systems.

  1. Evaporative segregation in 80% Ni-20% Cr and 60% Fe-40% Ni alloys

    NASA Technical Reports Server (NTRS)

    Gupta, K. P.; Mukherjee, J. L.; Li, C. H.

    1974-01-01

    An analytical approach is outlined to calculate the evaporative segregation behavior in metallic alloys. The theoretical predictions are based on a 'normal' evaporation model and have been examined for Fe-Ni and Ni-Cr alloys. A fairly good agreement has been found between the predicted values and the experimental results found in the literature.

  2. 57Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO2

    NASA Astrophysics Data System (ADS)

    Sobolev, A.; Rusakov, V.; Moskvin, A.; Gapochka, A.; Belik, A.; Glazkova, I.; Akulenko, A.; Demazeau, G.; Presniakov, I.

    2017-07-01

    We report new results of a 57Fe Mössbauer study of hyperfine magnetic interactions in the layered multiferroic 3R-AgFeO2 demonstrating two magnetic phase transitions at T N1 and T N2. The asymptotic value β *  ≈  0.34 for the critical exponent obtained from the temperature dependence of the hyperfine field H hf(T) at 57Fe the nuclei below T N1  ≈  14 K indicates that 3R-AgFeO2 shows quasi-3D critical behavior. The spectra just above T N1 (T N1  <  T  <  T  *  ≈  41 K) demonstrate a relaxation behavior due to critical spin fluctuations which indicates the occurrence of short-range correlations. At the intermediate temperature range, T N2  <  T  <  T N1, the 57Fe Mössbauer spectra are described in terms of collinear spin-density-waves (SDW) with the inclusion of many high-order harmonics, indicating that the real magnetic structure of the ferrite appears to be more complicated than a pure sinusoidally modulated SDW. Below T  <  T N2  ≈  9 K, the hyperfine field H hf reveals a large spatial anisotropy (ΔH anis  ≈  30 kOe) which is related with a local intra-cluster (FeO6) spin-dipole term that implies a conventional contribution of the polarized oxygen ions. We proposed a simple two-parametric formula to describe the dependence of H anis on the distortions of the (FeO6) clusters. Analysis of different mechanisms of spin and hyperfine interactions in 3R-AgFeO2 and its structural analogue CuFeO2 points to a specific role played by the topology of the exchange coupling and the oxygen polarization in the delafossite-like structures.

  3. Weldability of high toughness Fe-12% Ni alloys containing Ti, Al or Nb

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    Three exceptionally high-toughness Fe-12%Ni alloys designed for cryogenic service were welded using the GTA welding process. Evaluation of weldability included equivalent energy (KIed) fracture toughness tests, transverse-weld tensile tests at -196 and 25 C and weld crack sensitivity tests. The Fe-12%Ni-0.25%Ti alloy proved extremely weldable for cryogenic applications, having weld and HAZ properties comparable with those of the wrought base alloy. The Fe-12%Ni-0.5%Al had good weld properties only after the weld joint was heat treated. The Fe-12%Ni-0.25%Nb alloy was not considered weldable for cryogenic use because of its poor weld joint properties at -196 C and its susceptibility to hot cracking.

  4. The effect of Mn/Ni on thermodynamic properties of critical nucleus in Fe-Cu-Mn (Ni) ternary alloys

    DOE PAGES

    Li, Boyan; Zhang, Lei; Li, Chengliang; ...

    2018-04-18

    The aging- or radiation-induced hardening of Cu/Mn/Ni precipitates in Fe alloys is one of property degradation mechanisms in structural materials in nuclear reactors. Experiments show that aging or radiation leads the formation of Cu-rich precipitates, and the addition of Mn or Ni elements enhances the precipitation kinetics. In this study, the phase-field model coupled with the constrained string method have been applied to investigate the thermodynamic properties of critical nuclei such as the minimum energy path of Cu/Mn/Ni precipitation in Fe-Cu-Mn and Fe-Cu-Ni ternary alloys. The chemical free energies used in the model are taken from CALPHAD. The simulation resultsmore » show that the formation of Cu/Mn/Ni clusters needs to overcome an energy barrier, and the precipitate has a Core-Shell structure. The thermodynamic properties of the critical nucleus are influenced by temperature and Cu/Mn/Ni overall concentrations, which are in accordance with the simulation results as well as the experimental observations.« less

  5. The effect of Mn/Ni on thermodynamic properties of critical nucleus in Fe-Cu-Mn (Ni) ternary alloys

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Boyan; Zhang, Lei; Li, Chengliang

    The aging- or radiation-induced hardening of Cu/Mn/Ni precipitates in Fe alloys is one of property degradation mechanisms in structural materials in nuclear reactors. Experiments show that aging or radiation leads the formation of Cu-rich precipitates, and the addition of Mn or Ni elements enhances the precipitation kinetics. In this study, the phase-field model coupled with the constrained string method have been applied to investigate the thermodynamic properties of critical nuclei such as the minimum energy path of Cu/Mn/Ni precipitation in Fe-Cu-Mn and Fe-Cu-Ni ternary alloys. The chemical free energies used in the model are taken from CALPHAD. The simulation resultsmore » show that the formation of Cu/Mn/Ni clusters needs to overcome an energy barrier, and the precipitate has a Core-Shell structure. The thermodynamic properties of the critical nucleus are influenced by temperature and Cu/Mn/Ni overall concentrations, which are in accordance with the simulation results as well as the experimental observations.« less

  6. Development of flexible Ni80Fe20 magnetic nano-thin films

    NASA Astrophysics Data System (ADS)

    Vopson, M. M.; Naylor, J.; Saengow, T.; Rogers, E. G.; Lepadatu, S.; Fetisov, Y. K.

    2017-11-01

    Flexible magnetic Ni80Fe20 thin films with excellent adhesion, mechanical and magnetic properties have been fabricated using magnetron plasma deposition. We demonstrate that flexible Ni80Fe20 thin films maintain their non-flexible magnetic properties when the films are over 60 nm thick. However, when their thickness is reduced, the flexible thin films display significant increase in their magnetic coercive field compared to identical films coated on a solid Silicon substrate. For a 15 nm flexible Ni80Fe20 film coated onto 110 μm Polyvinylidene fluoride polymer substrate, we achieved a remarkable 355% increase in the magnetic coercive field relative to the same film deposited onto a Si substrate. Experimental evidence, backed by micro-magnetic modelling, indicates that the increase in the coercive fields is related to the larger roughness texture of the flexible substrates. This effect essentially transforms soft Ni80Fe20 permalloy thin films into medium/hard magnetic films allowing not only mechanical flexibility of the structure, but also fine tuning of their magnetic properties.

  7. Direct selenylation of mixed Ni/Fe metal-organic frameworks to NiFe-Se/C nanorods for overall water splitting

    NASA Astrophysics Data System (ADS)

    Xu, Bo; Yang, He; Yuan, Lincheng; Sun, Yiqiang; Chen, Zhiming; Li, Cuncheng

    2017-10-01

    Development of low-cost, highly active bifunctional catalyst for efficient overall water splitting based on earth-abundant metals is still a great challenging task. In this work, we report a NiFe-Se/C composite nanorod as efficient non-precious-metal electrochemical catalyst derived from direct selenylation of a mixed Ni/Fe metal-organic framework. The as-obtained catalyst requires low overpotential to drive 10 mA cm-2 for HER (160 mV) and OER (240 mV) in 1.0 M KOH, respectively, and its catalytic activity is maintained for at least 20 h. Moreover, water electrolysis using this catalyst achieves high water splitting current density of 10 mA cm-2 at cell voltage of 1.68 V.

  8. Structural, mechanical and magnetic study on galvanostatic electroplated nanocrystalline NiFeP thin films

    NASA Astrophysics Data System (ADS)

    Kalaivani, A.; Senguttuvan, G.; Kannan, R.

    2018-03-01

    Nickel based alloys has a huge applications in microelectronics and micro electromechanical systems owing to its superior soft magnetic properties. With the advantages of simplicity, cost-effectiveness and controllable patterning, electroplating processes has been chosen to fabricate thin films in our work. The soft magnetic NiFeP thin film was successfully deposited over the surface of copper plate through galvanostatic electroplating method by applying constant current density of 10 mA cm-2 for a deposition rate for half an hour. The properties of the deposited NiFeP thin films were analyzed by subjecting it into different physio-chemical characterization such as XRD, SEM, EDAX, AFM and VSM. XRD pattern confirms the formation of NiFeP particles and the structural analysis reveals that the NiFeP particles were uniformly deposited over the surface of copper substrate. The surface roughness analysis of the NiFeP films was done using AFM analysis. The magnetic studies and the hardness of the thin film were evaluated from the VSM and hardness test. The NiFeP thin films possess lower coercivity with higher magnetization value of 69. 36 × 10-3 and 431.92 Gauss.

  9. Acridine-based fluorescence chemosensors for selective sensing of Fe3+ and Ni2+ ions

    NASA Astrophysics Data System (ADS)

    Wang, Chaoyu; Fu, Jiaxin; Yao, Kun; Xue, Kun; Xu, Kuoxi; Pang, Xiaobin

    2018-06-01

    Two novel acridine-based fluorescence chemosensors (L1 and L2) were prepared and their metal ions sensing properties were investigated. L1 (L2) exhibited an excellent selective fluorescence response toward Fe3+ (Ni2+) and the stoichiometry ratio of L1-Fe3+ and L2-Ni2+ were 1:1. The detection limits of L1 and L2 were calculated by the fluorescence titration to be 4.13 μM and 1.52 μM, respectively, which were below the maximum permissive level of Fe3+ and Ni2+ ions in drinking water set by the EPA. The possible mechanism of the fluorescence detection of Fe3+ and Ni2+ had been proposed according to the analysis of Job's plot, IR spectra and ESI-MS. The determination of Fe3+ and Ni2+ ions in living cells had been applied successfully.

  10. Integration of Electrodeposited Ni-Fe in MEMS with Low-Temperature Deposition and Etch Processes

    PubMed Central

    Schiavone, Giuseppe; Murray, Jeremy; Perry, Richard; Mount, Andrew R.; Desmulliez, Marc P. Y.; Walton, Anthony J.

    2017-01-01

    This article presents a set of low-temperature deposition and etching processes for the integration of electrochemically deposited Ni-Fe alloys in complex magnetic microelectromechanical systems, as Ni-Fe is known to suffer from detrimental stress development when subjected to excessive thermal loads. A selective etch process is reported which enables the copper seed layer used for electrodeposition to be removed while preserving the integrity of Ni-Fe. In addition, a low temperature deposition and surface micromachining process is presented in which silicon dioxide and silicon nitride are used, respectively, as sacrificial material and structural dielectric. The sacrificial layer can be patterned and removed by wet buffered oxide etch or vapour HF etching. The reported methods limit the thermal budget and minimise the stress development in Ni-Fe. This combination of techniques represents an advance towards the reliable integration of Ni-Fe components in complex surface micromachined magnetic MEMS. PMID:28772683

  11. Mössbauer and XRD study of novel quaternary Sn-Fe-Co-Ni electroplated alloy

    NASA Astrophysics Data System (ADS)

    Kuzmann, E.; Sziráki, L.; Stichleutner, S.; Homonnay, Z.; Lak, G. B.; El-Sharif, M.; Chisholm, C. U.

    2017-11-01

    Constant current electrochemical deposition technique was used to obtain quaternary alloys of Sn-Fe-Co-Ni from a gluconate electrolyte, which to date have not been reported in the literature. For the characterization of electroplated alloys, 57Fe and 119Sn Conversion Electron Mössbauer Spectroscopy (CEMS), XRD and SEM/EDAX were used. XRD revealed the amorphous character of the novel Sn-Fe-Co-Ni electrodeposited alloys. 57Fe Mössbauer spectrum of quaternary deposit with composition of 37.0 at% Sn, 38.8 at% Fe, 16.8 at% Co and 7.4 at% Ni displayed a magnetically split sextet (B = 28.9T) with broad lines typical of iron bearing ferromagnetic amorphous alloys. Magnetically split 119Sn spectra reflecting a transferred hyperfine field (B = 2.3T) were also observed. New quaternary Sn-Fe-Co-Ni alloys were successfully prepared.

  12. Thermomechanical testing of FeNiCoTi shape memory alloy for active confinement of concrete

    NASA Astrophysics Data System (ADS)

    Chen, Qiwen; Andrawes, Bassem; Sehitoglu, Huseyin

    2014-05-01

    The thermomechanical properties of a new type of shape memory alloy (SMA), FeNiCoTi, are explored in this paper with the aim of examining the feasibility of using this new material as transverse reinforcement for concrete structures subjected to earthquake loading. One advantage of using FeNiCoTi alloy is its cost effectiveness compared to commonly studied NiTi alloy. Differential scanning calorimetry (DSC) tests are conducted to investigate the transformation temperatures of FeNiCoTi alloy under different heat treatment methods and prestrain schemes. First, a heat treatment method is established to produce FeNiCoTi alloy with wide thermal hysteresis that is pertinent to civil structural applications. Next, recovery stress tests are conducted to explore the effect of parameters including heating method, heating temperature, heating rate, heating protocol and prestrain level on the recovery stress. An optimum prestrain level is determined based on the recovery stress results. Moreover, cyclic tests are carried out to examine the cyclic response of FeNiCoTi alloy after stress recovery. Thermal cyclic tests are also carried out on the FeNiCoTi alloy to better understand the effect of temperature variation on the recovery stress. In addition, reheating of the FeNiCoTi alloy after deformation is conducted to examine the reusability of the material after being subjected to excessive deformation. Test results of the FeNiCoTi alloy indicate that this cost-effective SMA can potentially be a promising new material for civil structural applications.

  13. Sea-urchin-like Fe3O4@C@Ag particles: an efficient SERS substrate for detection of organic pollutants

    NASA Astrophysics Data System (ADS)

    Ye, Yingjie; Chen, Jin; Ding, Qianqian; Lin, Dongyue; Dong, Ronglu; Yang, Liangbao; Liu, Jinhuai

    2013-06-01

    Ag-coated sea-urchin-like Fe3O4@C core-shell particles can be synthesized by a facile one-step solvothermal method, followed by deposition of high-density Ag nanoparticles onto the carbon surface through an in situ growth process, respectively. The as-synthesized Ag-coated Fe3O4@C particles can be used as a surface-enhanced Raman scattering (SERS) substrate holding reproducible properties under an external magnetic force. The magnetic function of the particles allows concentrating the composite particles into small spatial regions, which can be exploited to decrease the amount of material per analysis while improving its SERS detection limit. In contrast to the traditional SERS substrates, the present Fe3O4@C@Ag particles hold the advantages of enrichment of organic pollutants for improving SERS detection limit and recycled utilization.Ag-coated sea-urchin-like Fe3O4@C core-shell particles can be synthesized by a facile one-step solvothermal method, followed by deposition of high-density Ag nanoparticles onto the carbon surface through an in situ growth process, respectively. The as-synthesized Ag-coated Fe3O4@C particles can be used as a surface-enhanced Raman scattering (SERS) substrate holding reproducible properties under an external magnetic force. The magnetic function of the particles allows concentrating the composite particles into small spatial regions, which can be exploited to decrease the amount of material per analysis while improving its SERS detection limit. In contrast to the traditional SERS substrates, the present Fe3O4@C@Ag particles hold the advantages of enrichment of organic pollutants for improving SERS detection limit and recycled utilization. Electronic supplementary information (ESI) available: Additional XRD patterns and SEM images of Fe3O4@C particles, SERS spectra of 4-ATP and 4-MPY using Fe3O4@C@Ag particles as the active substrates, magnetic behaviour of Fe3O4@C and Fe3O4@C@Ag particles. See DOI: 10.1039/c3nr01273e

  14. Cyclic voltammetric study of Co-Ni-Fe alloys electrodeposition in sulfate medium

    NASA Astrophysics Data System (ADS)

    Hanafi, I.; Daud, A. R.; Radiman, S.

    2013-11-01

    Electrochemical technique has been used to study the electrodeposition of cobalt, nickel, iron and Co-Ni-Fe alloy on indium tin oxide (ITO) coated glass substrate. To obtain the nucleation mechanism, cyclic voltammetry is used to characterize the Co-Ni-Fe system. The scanning rate effect on the deposition process was investigated. Deposition of single metal occurs at potential values more positive than that estimated stability potential. Based on the cyclic voltammetry results, the electrodeposition of cobalt, nickel, iron and Co-Ni-Fe alloy clearly show that the process of diffusion occurs is controlled by the typical nucleation mechanism.

  15. Antiferromagnetic layer thickness dependence of noncollinear uniaxial and unidirectional anisotropies in NiFe/FeMn/CoFe trilayers

    NASA Astrophysics Data System (ADS)

    Choi, Hyeok-Cheol; You, Chun-Yeol; Kim, Ki-Yeon; Lee, Jeong-Soo; Shim, Je-Ho; Kim, Dong-Hyun

    2010-06-01

    We have investigated the dependence of magnetic anisotropies of the exchange-biased NiFe/FeMn/CoFe trilayers on the antiferromagnetic (AF) layer thickness (tAF) by measuring in-plane angular-dependent ferromagnetic resonance fields. The resonance fields of NiFe and CoFe sublayers are shifted to lower and higher values compared to those of single unbiased ferromagnetic (F) layers, respectively, due to the interfacial exchange coupling when tAF≥2nm . In-plane angular dependence of resonance field reveals that uniaxial and unidirectional anisotropies coexist in the film plane, however, they are not collinear with each other. It is found that these peculiar noncollinear anisotropies significantly depend on tAF . The angle of misalignment displays a maximum around tAF=5nm and converges to zero when tAF is thicker than 10 nm. Contributions from thickness-dependent AF anisotropy and spin frustrations at both F/AF interfaces due to the structural imperfections should be accounted in order to understand the AF-layer thickness dependence of noncollinear magnetic anisotropies.

  16. NiO and Fe/Mn in Fo-rich olivines from OIB, MORB, and mantle peridotites

    NASA Astrophysics Data System (ADS)

    Li, H.; Baker, M.; Hofmann, A. E.; Clague, D.; Stolper, E.

    2006-12-01

    Olivines from mantle peridotites have a narrow range of NiO (0.36±0.03 [1σ] wt%), but NiO of olivines in basalts suggest NiO in mantle olivines is actually more variable: e.g., Hawaiian phenocrysts (Fo>90) have NiO >0.55%, and olivines from continental flood basalts can have >0.5% NiO. At the other end of the spectrum, some basaltic suites (e.g., Iceland, MORBs) have Fo>90 olivines with NiO >0.2%. Partial melting calculations on peridotites show it is difficult to generate liquids that crystallize Fo>90 olivines with >0.4% NiO without resorting to complex processes. Hypotheses to explain the variability of NiO in mantle-derived olivines include (1) reaction of peridotite with silica-rich melts of eclogite results in decreasing modal abundance of olivine and increasing NiO in olivine [1,2]; (2) magmas with NiO-rich olivines come from sources enriched in NiO due to a core-derived component [3]. [4] proposed that high Fe/Mn of Hawaiian vs. Icelandic and MORB lavas reflect a core-derived component in their sources. Possible core incorporation is poorly constrained but FeO and NiO are expected to increase by such processes, leading to correlations between NiO and Fe/Mn in mantle rocks with significant core-derived components. We present high-precision analyses of Fo-rich olivines from OIBs, MORBs, komatiites, and mantle peridotites, focusing on NiO contents and Fe/Mn ratios. Our goal is to test hypotheses to explain elevated NiO of Fo-rich olivines in basalts. Olivines are Fo85.1-93.4; more were analyzed, but we focused on this range to avoid complications due to decreasing NiO in olivine with crystallization. Errors (1σ) are 0.01 wt% in NiO and 1.5 in Fe/Mn (wt). Our data show several features: (1) NiO contents and Fe/Mn ratios of Fo>88 olivines are positively correlated, with the low end of the trend (NiO ~0.23%, Fe/Mn ~61) defined by MORB and Iceland and the high end of the trend (NiO ~0.55%, Fe/Mn ~80) by Reunion and Hawaii. Between these end points, there is a

  17. Structures and magnetic properties of Fe and Ni monoatomic chains encapsulated by an Au nanotube

    NASA Astrophysics Data System (ADS)

    Han, Zhi-Dong; Li, Xiu-Yan; Yang, Zhi; Liu, Rui-Ping; Liu, Shao-Ding; Zhang, Ying

    2012-11-01

    Structures and magnetic properties of transition metal (TM) Fe or Ni monoatomic chains (MACs) encapsulated by a Au (5, 5) nanotube (Fe@Au and Ni@Au) are investigated using the density functional theory (DFT). The calculated results show that both Fe@Au and Ni@Au prefer to adopt ferromagnetic (FM) orders as ground states. In particular, the Fe@Au keeps the magnetic properties of free-standing Fe MAC, indicating that this system may be viewed as a new candidate in electromagnetic devices.

  18. Dithiolato-bridged nickel-iron complexes as models for the active site of [NiFe]-hydrogenases.

    PubMed

    Song, Li-Cheng; Yang, Xi-Yue; Cao, Meng; Gao, Xiu-Yun; Liu, Bei-Bei; Zhu, Liang; Jiang, Feng

    2017-03-30

    The structural and functional modeling of the active site of [NiFe]-hydrogenases has been proved to be challenging to a great extent. Herein, we report the synthesis, structures, and some properties of the NiFe-based dicarbonyl, terminal hydride, and μ-hydroxo models for the active site of [NiFe]-hydrogenases.

  19. Forming a structure of the CoNiFe alloys by X-ray irradiation

    NASA Astrophysics Data System (ADS)

    Valko, Natalia; Kasperovich, Andrey; Koltunowicz, Tomasz N.

    The experimental data of electrodeposition kinetics researches and structure formation of ternary CoNiFe alloys deposited onto low-carbon steel 08kp in the presence of X-rays are presented. Relations of deposit rate, current efficiencies, element and phase compositions of CoNiFe coatings formed from sulfate baths with respect to cathode current densities (0.5-3A/dm2), electrolyte composition and irradiation were obtained. It is shown that, the CoNiFe coatings deposited by the electrochemical method involving exposure of the X-rays are characterized by more perfect morphology surfaces with less developed surface geometry than reference coatings. The effect of the X-ray irradiation on the electrodeposition of CoNiFe coatings promotes formatting of alloys with increased electropositive component and modified phase composition.

  20. Extraction of nickel from NiFe-LDH into Ni2P@NiFe hydroxide as a bifunctional electrocatalyst for efficient overall water splitting† †Electronic supplementary information (ESI) available: Experimental and computational details and additional data. See DOI: 10.1039/c7sc04569g

    PubMed Central

    Zhang, Fang-Shuai; Wang, Jia-Wei; Luo, Jun; Liu, Rui-Rui

    2017-01-01

    The development of highly efficient, low-cost and stable electrocatalysts for overall water splitting is highly desirable for the storage of intermittent solar energy and wind energy sources. Herein, we show for the first time that nickel can be extracted from NiFe-layered double hydroxide (NiFe-LDH) to generate an Ni2P@FePOx heterostructure. The Ni2P@FePOx heterostructure was converted to an Ni2P@NiFe hydroxide heterostructure (P-NiFe) during water splitting, which displays high electrocatalytic performance for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH solution, with an overpotential of 75 mV at 10 mA cm–2 for HER, and overpotentials of 205, 230 and 430 mV at 10, 100 and 1000 mA cm–2 for OER, respectively. Moreover, it could afford a stable current density of 10 mA cm–2 for overall water splitting at 1.51 V in 1.0 M KOH with long-term durability (100 h). This cell voltage is among the best reported values for bifunctional electrocatalysts. The results of theoretical calculations demonstrate that P-NiFe displays optimized adsorption energies for both HER and OER intermediates at the nickel active sites, thus dramatically enhancing its electrocatalytic activity. PMID:29675186

  1. Effect of Ag nanoparticle concentration on the electrical and ferroelectric properties of Ag/P(VDF-TrFE) composite films

    DOE PAGES

    Paik, Haemin; Choi, Yoon -Young; Hong, Seungbum; ...

    2015-09-04

    Here, we investigated the effect of the Ag nanoparticles on the ferroelectric and piezoelectric properties of Ag/poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) composite films. We found that the remanent polarization and direct piezoelectric coefficient increased up to 12.14 μC/cm 2 and 20.23 pC/N when the Ag concentration increased up to 0.005 volume percent (v%) and decreased down to 9.38 μC/cm 2 and 13.45 pC/N when it increased up to 0.01 v%. Further increase in Ag concentration resulted in precipitation of Ag phase and significant leakage current that hindered any meaningful measurement of the ferroelectric and piezoelectric properties. 46% increase of the remanent polarization valuemore » and 27% increase of the direct piezoelectric coefficient were observed in the film with the 0.005 v% of the Ag nanoparticles added without significant changes to the crystalline structure confirmed by both X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) experiments. The enhancements of both the ferroelectric and piezoelectric properties are attributed to the increase in the effective electric field induced by the reduction in the effective volume of P(VDF-TrFE) that results in more aligned dipoles.« less

  2. Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

    DOE PAGES

    Zhang, Chuan; Zhang, Fan; Diao, Haoyan; ...

    2016-07-19

    The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result,more » the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.« less

  3. Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Chuan; Zhang, Fan; Diao, Haoyan

    The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result,more » the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.« less

  4. Photoelectrochemical Water Splitting Properties of Ti-Ni-Si-O Nanostructures on Ti-Ni-Si Alloy

    PubMed Central

    Dong, Zhenbiao; Ning, Congqin

    2017-01-01

    Ti-Ni-Si-O nanostructures were successfully prepared on Ti-1Ni-5Si alloy foils via electrochemical anodization in ethylene glycol/glycerol solutions containing a small amount of water. The Ti-Ni-Si-O nanostructures were characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and diffuse reflectance absorption spectra. Furthermore, the photoelectrochemical water splitting properties of the Ti-Ni-Si-O nanostructure films were investigated. It was found that, after anodization, three different kinds of Ti-Ni-Si-O nanostructures formed in the α-Ti phase region, Ti2Ni phase region, and Ti5Si3 phase region of the alloy surface. Both the anatase and rutile phases of Ti-Ni-Si-O oxide appeared after annealing at 500 °C for 2 h. The photocurrent density obtained from the Ti-Ni-Si-O nanostructure photoanodes was 0.45 mA/cm2 at 0 V (vs. Ag/AgCl) in 1 M KOH solution. The above findings make it feasible to further explore excellent photoelectrochemical properties of the nanostructure-modified surface of Ti-Ni-Si ternary alloys. PMID:29088083

  5. Photoelectrochemical Water Splitting Properties of Ti-Ni-Si-O Nanostructures on Ti-Ni-Si Alloy.

    PubMed

    Li, Ting; Ding, Dongyan; Dong, Zhenbiao; Ning, Congqin

    2017-10-31

    Ti-Ni-Si-O nanostructures were successfully prepared on Ti-1Ni-5Si alloy foils via electrochemical anodization in ethylene glycol/glycerol solutions containing a small amount of water. The Ti-Ni-Si-O nanostructures were characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and diffuse reflectance absorption spectra. Furthermore, the photoelectrochemical water splitting properties of the Ti-Ni-Si-O nanostructure films were investigated. It was found that, after anodization, three different kinds of Ti-Ni-Si-O nanostructures formed in the α-Ti phase region, Ti₂Ni phase region, and Ti₅Si₃ phase region of the alloy surface. Both the anatase and rutile phases of Ti-Ni-Si-O oxide appeared after annealing at 500 °C for 2 h. The photocurrent density obtained from the Ti-Ni-Si-O nanostructure photoanodes was 0.45 mA/cm² at 0 V (vs. Ag/AgCl) in 1 M KOH solution. The above findings make it feasible to further explore excellent photoelectrochemical properties of the nanostructure-modified surface of Ti-Ni-Si ternary alloys.

  6. Microwave absorption property of the diatomite coated by Fe-CoNiP films

    NASA Astrophysics Data System (ADS)

    Yan, Zhenqiang; Cai, Jun; Xu, Yonggang; Zhang, Deyuan

    2015-08-01

    A bio-absorbent of Fe-CoNiP coated on the diatomite was fabricated by way of electroless plating of CoNiP and subsequent chemical vapor deposition of Fe. The surface morphology and composition of the above-mentioned diatomite particles at different stage were characterized with the scanning electron microscopy and the energy spectrum analysis respectively, and the results showed that the diatomite was successfully coated with CoNoP and Fe (carbony iron). The complex permittivity and permeability of composites filled with the bio-absorbent and paraffin was measured in frequency range of 2-18 GHz, and then the microwave reflection loss (RL) and the shielding effectiveness (SE) were calculated. The results showed that the permittivity and the permeability were both enlarged as Fe films were coated onto the CoNiP-coated diatomite, which was attributed to the excellent electromagnetic property of carbonyl irons. The composites made with the Fe-CoNiP diatomite had a better absorbing property (minimum RL -11.0 dB) as well as the shielding property (maximum SE 5.6 dB) at thickness 2 mm. It indicated the absorption property was mainly due to the attenuation on the microwave, and the Fe-CoNiP diatomite could be an effective absorbent with low-density.

  7. Photocatalytic degradation of gaseous toluene over hollow “spindle-like” α-Fe{sub 2}O{sub 3} loaded with Ag

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Hong; Department of Basic, Dalian Naval Academy, Dalian 116018; Zhao, Qidong

    2012-06-15

    Highlights: ► Hollow α-Fe{sub 2}O{sub 3} spindle-shaped microparticles were prepared for Ag support. ► The hollow α-Fe{sub 2}O{sub 3} and Ag/α-Fe{sub 2}O{sub 3} materials were used to degrade gaseous toluene. ► Complete degradation of toluene occurred on the Ag/α-Fe{sub 2}O{sub 3} surface. -- Abstract: In this work, hollow “spindle-like” α-Fe{sub 2}O{sub 3} nanoparticles were synthesized by a hydrothermal route. The Ag/α-Fe{sub 2}O{sub 3} catalyst was prepared based on the spindle-shaped α-Fe{sub 2}O{sub 3} with CTAB as the surfactant, which showed excellent photoelectric property and photocatalytic activity. The structural properties of these samples were systematically investigated by X-ray powder diffraction, scanningmore » electronic microscopy, transmission electronic microscopy, energy-dispersive X-ray spectra, and UV–Vis diffuse reflectance spectroscopy techniques. The photo-induced charge separation in the samples was demonstrated by surface photovoltage measurement. The photocatalytic performances of the Ag/α-Fe{sub 2}O{sub 3} and α-Fe{sub 2}O{sub 3} samples were comparatively studied in the degradation of toluene under xenon lamp irradiation by in situ FTIR spectroscopy. Benzaldehyde and benzoic acid species could be observed on the α-Fe{sub 2}O{sub 3} surface rather than Ag/α-Fe{sub 2}O{sub 3} surface. The results indicate that the Ag/α-Fe{sub 2}O{sub 3} sample exhibited higher photocatalytic efficiency.« less

  8. Evaluation and comparision of dc resistivity of NiZr x Co x Fe2-2x O4, Ni0.5Sn0.5Co x Mn x Fe2-2x O4, Mg1-x Ca x Ni y Fe2-y O4 and Mg1-x Ni x Co y Fe2-y O4 nanocrytalline materials

    NASA Astrophysics Data System (ADS)

    Ali, Rajjab; Gilani, Zaheer Abbas; Shahzad Shifa, Muhammad; Asghar, H. M. Noor Ul Huda Khan; Azhar Khan, Muhammad; Naeem Anjum, Muhammad; Nauman Usmani, Muhammad; Farooq Warsi, Muhammad; Khawaja, Imtiaz U.

    2017-11-01

    Four series nanocrystalline ferrites with nominal composition, NiZr x Co x Fe2-2x O4 (x  =  0.0, 0.2, 0.4, 0.6, 0.8) Ni0.5Sn0.5Co x Mn x Fe2-2x O4 (x  =  0.0, 0.2, 0.4, 0.6, 0.8), Mg1-x Ca x Ni y Fe2-y O4 (x  =  0.0, 0.2, 0.4, 0.6, 0.8; y  =  0, 04, 0.8, 1.2, 1.6) and Mg1-x Ni x Co y Fe2-y O4 (x,y  =  0.0, 0.2, 0.4, 0.6, 0.8) have been fabricated using the microemulsion synthesis route. The synthesized materials are investigated for dc electrical resistivity measurements. The variation of dc electrical resistivity of these materials has been explainedon the basis of hopping mechanism of both holes and electrons.

  9. MICROWAVE-ASSISTED SHAPE CONTROLLED BULK SYNTHESIS OF AG AND FE NANORODS IN POLY (ETHYLENE GLYCOL) SOLUTIONS

    EPA Science Inventory

    Bulk syntheses of silver (Ag) and iron (Fe) nanorods using poly (ethylene glycol), PEG, under microwave irradiation (MW) conditions are reported. Favorable conditions to make Ag nanorods were established and can be extended to make Fe nanorods with uniform size and shape. The nan...

  10. Catalysts for hydrogen evolution from the [NiFe] hydrogenase to the Ni2P(001) surface: the importance of ensemble effect.

    PubMed

    Liu, Ping; Rodriguez, José A

    2005-10-26

    Density functional theory (DFT) was employed to investigate the behavior of a series of catalysts used in the hydrogen evolution reaction (HER, 2H(+) + 2e(-) --> H(2)). The kinetics of the HER was studied on the [NiFe] hydrogenase, the [Ni(PS3*)(CO)](1)(-) and [Ni(PNP)(2)](2+) complexes, and surfaces such as Ni(111), Pt(111), or Ni(2)P(001). Our results show that the [NiFe] hydrogenase exhibits the highest activity toward the HER, followed by [Ni(PNP)(2)](2+) > Ni(2)P > [Ni(PS3*)(CO)](1)(-) > Pt > Ni in a decreasing sequence. The slow kinetics of the HER on the surfaces is due to the fact that the metal hollow sites bond hydrogen too strongly to allow the facile removal of H(2). In fact, the strong H-Ni interaction on Ni(2)P(001) can lead to poisoning of the highly active sites of the surface, which enhances the rate of the HER and makes it comparable to that of the [NiFe] hydrogenase. In contrast, the promotional effect of H-poisoning on the HER on Pt and Ni surfaces is relatively small. Our calculations suggest that among all of the systems investigated, Ni(2)P should be the best practical catalyst for the HER, combining the high thermostability of the surfaces and high catalytic activity of the [NiFe] hydrogenase. The good behavior of Ni(2)P(001) toward the HER is found to be associated with an ensemble effect, where the number of active Ni sites is decreased due to presence of P, which leads to moderate bonding of the intermediates and products with the surface. In addition, the P sites are not simple spectators and directly participate in the HER.

  11. Fusion of 48Ti+58Fe and 58Ni+54Fe below the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Stefanini, A. M.; Montagnoli, G.; Corradi, L.; Courtin, S.; Bourgin, D.; Fioretto, E.; Goasduff, A.; Grebosz, J.; Haas, F.; Mazzocco, M.; Mijatović, T.; Montanari, D.; Pagliaroli, M.; Parascandolo, C.; Scarlassara, F.; Strano, E.; Szilner, S.; Toniolo, N.; Torresi, D.

    2015-12-01

    Background: No data on the fusion excitation function of 48Ti+58Fe in the energy region near the Coulomb barrier existed prior to the present work, while fusion of 58Ni+54Fe was investigated in detail some years ago, down to very low energies, and clear evidence of fusion hindrance was noticed at relatively high cross sections. 48Ti and 58Fe are soft and have a low-lying quadrupole excitation lying at ≈800 -900 keV only. Instead, 58Ni and 54Fe have a closed shell (protons and neutrons, respectively) and are rather rigid. Purpose: We aim to investigate (1) the possible influence of the different structures of the involved nuclei on the fusion excitation functions far below the barrier and, in particular, (2) whether hindrance is observed in 48Ti+58Fe , and to compare the results with current coupled-channels models. Methods: 48Ti beams from the XTU Tandem accelerator of INFN-Laboratori Nazionali di Legnaro were used. The experimental setup was based on an electrostatic beam separator, and fusion-evaporation residues (ERs) were detected at very forward angles. Angular distributions of ERs were measured. Results: Fusion cross sections of 48Ti+58Fe have been obtained in a range of nearly six orders of magnitude around the Coulomb barrier, down to σ ≃2 μ b . The sub-barrier cross sections of 48Ti+58Fe are much larger than those of 58Ni+54Fe . Significant differences are also observed in the logarithmic derivatives and astrophysical S factors. No evidence of hindrance is observed, because coupled-channels calculations using a standard Woods-Saxon potential are able to reproduce the data in the whole measured energy range. Analogous calculations for 58Ni+54Fe predict clearly too large cross sections at low energies. The two fusion barrier distributions are wide and display a complex structure that is only qualitatively fit by calculations. Conclusions: It is pointed out that all these different trends originate from the dissimilar low-energy nuclear structures of

  12. Simultaneous enhancement of magnetic and mechanical properties in Ni-Mn-Sn alloy by Fe doping

    PubMed Central

    Tan, Changlong; Tai, Zhipeng; Zhang, Kun; Tian, Xiaohua; Cai, Wei

    2017-01-01

    Both magnetic-field-induced reverse martensitic transformation (MFIRMT) and mechanical properties are crucial for application of Ni-Mn-Sn magnetic shape memory alloys. Here, we demonstrate that substitution of Fe for Ni can simultaneously enhance the MFIRMT and mechanical properties of Ni-Mn-Sn, which are advantageous for its applications. The austenite in Ni44Fe6Mn39Sn11 shows the typical ferromagnetic magnetization with the highest saturation magnetization of 69 emu/g at 223 K. The result shows that an appropriate amount of Fe substitution can really enhance the ferromagnetism of Ni50Mn39Sn11 alloy in austenite, which directly leads to the enhancement of MFIRMT. Meanwhile, the mechanical property significantly improves with Fe doping. When there is 4 at.% Fe added, the compressive and maximum strain reach the maximum value (approximately 725.4 MPa and 9.3%). Furthermore, using first-principles calculations, we clarify the origin of Fe doping on martensitic transformation and magnetic properties. PMID:28230152

  13. Deep Drawing Behavior of CoCrFeMnNi High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

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

  14. Novel Chiral Magnetic Domain Wall Structure in Fe/Ni/Cu(001) Films

    NASA Astrophysics Data System (ADS)

    Chen, G.; Zhu, J.; Quesada, A.; Li, J.; N'Diaye, A. T.; Huo, Y.; Ma, T. P.; Chen, Y.; Kwon, H. Y.; Won, C.; Qiu, Z. Q.; Schmid, A. K.; Wu, Y. Z.

    2013-04-01

    Using spin-polarized low energy electron microscopy, we discovered a new type of domain wall structure in perpendicularly magnetized Fe/Ni bilayers grown epitaxially on Cu(100). Specifically, we observed unexpected Néel-type walls with fixed chirality in the magnetic stripe phase. Furthermore, we find that the chirality of the domain walls is determined by the film growth order with the chirality being right handed in Fe/Ni bilayers and left handed in Ni/Fe bilayers, suggesting that the underlying mechanism is the Dzyaloshinskii-Moriya interaction at the film interfaces. Our observations may open a new route to control chiral spin structures using interfacial engineering in transition metal heterostructures.

  15. Siderophile trace element diffusion in Fe-Ni alloys

    NASA Astrophysics Data System (ADS)

    Watson, Heather C.; Watson, E. Bruce

    2003-09-01

    Experiments were performed in a piston cylinder apparatus to characterize the diffusion behavior of the siderophile elements, Mo, Cu, Pd, Au, and Re in solid Fe-Ni alloy (90 wt.% Fe, 10 wt.% Ni). All experiments were conducted at 1 GPa and temperatures ranging from 1175 to 1400 °C. Activation energies of all elements fall between 270 kJ/mol (Cu) and 360 kJ/mol (Mo). Mo, Cu, Pd, and Au all show similar diffusivities at the same conditions, but the diffusivity of Re was consistently close to an order of magnitude lower. Initial experiments on other refractory elements (Os, Pt, and Ir) indicate that their diffusivities are close to or slightly lower than that of Re.

  16. Formation of Ni3Fe nanoparticles as studied using Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Parvathy, N. S.; Govindaraj, R.; Vinod, K.; Amarendra, G.

    2018-05-01

    Nickel and iron in the ratio of 3:1 have been taken and subjected to high energy ball milling and systematic post annealing treatments to obtain Ni3Fe. Structural and bulk magnetic properties have been deduced using XRD and magnetization studies, while the results of Mössbauer studies are used to deduce distinct 57Fe sites based on the hyperfine parameters. Formation of disordered Ni3Fe has been elucidated based on this study.

  17. Synthesis and characterization of T[Ni(CN){sub 4}].2pyz with T=Fe, Ni; pyz=pyrazine: Formation of T-pyz-Ni bridges

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lemus-Santana, A.A.; Rodriguez-Hernandez, J.; Institute of Materials Science and Technology, University of Havana

    2011-08-15

    The formation of T-pyz-Ni bridges (pyz=pyrazine) in the T[Ni(CN){sub 4}].2pyz series is known for T=Mn, Zn, Cd and Co but not with T=Fe, Ni. In this contribution the existence of such bridges also for T=Fe, Ni is discussed. The obtained pillared solids, T[Ni(CN){sub 4}].2pyz, were characterized from XRD, TG, UV-Vis, IR, Raman, Moessbauer and magnetic data. Their crystal structures were refined in the orthorhombic Pmna space group from XRD powder patterns. The structural behavior of these solids on cooling down to 77 K was also studied. In the 180-200 K temperature range the occurrence of a structural transition to amore » monoclinic structure (P2{sub 1}/c space group) was observed. No temperature induced spin transition was observed for Fe[Ni(CN){sub 4}].2pyz. The iron (II) was found to be in high spin electronic state and this configuration is preserved on cooling down to 2 K. The magnetic data indicate the occurrence of a low temperature weak anti-ferromagnetic interaction between T metal centers within the T[Ni(CN){sub 4}] layer. In the paramagnetic region for Ni[Ni(CN){sub 4}].2pyz, a reversible temperature induced spin transition for the inner Ni atom was detected. - Graphical abstract: Rippled sheets structure for the pillared solids T[Ni(CN){sub 4}].2pyz. The pyrazine molecule is found forming T-pyz-Ni bridges between neighboring layers. Highlights: > Pillared 2D solids. > Inorganic-organic solids. > Assembling of molecular blocks. > From 1D and 2D building blocks to 3D solids.« less

  18. Structural differences between the ready and unready oxidized states of [NiFe] hydrogenases.

    PubMed

    Volbeda, Anne; Martin, Lydie; Cavazza, Christine; Matho, Michaël; Faber, Bart W; Roseboom, Winfried; Albracht, Simon P J; Garcin, Elsa; Rousset, Marc; Fontecilla-Camps, Juan C

    2005-05-01

    [NiFe] hydrogenases catalyze the reversible heterolytic cleavage of molecular hydrogen. Several oxidized, inactive states of these enzymes are known that are distinguishable by their very different activation properties. So far, the structural basis for this difference has not been understood because of lack of relevant crystallographic data. Here, we present the crystal structure of the ready Ni-B state of Desulfovibrio fructosovorans [NiFe] hydrogenase and show it to have a putative mu-hydroxo Ni-Fe bridging ligand at the active site. On the other hand, a new, improved refinement procedure of the X-ray diffraction data obtained for putative unready Ni-A/Ni-SU states resulted in a more elongated electron density for the bridging ligand, suggesting that it is a diatomic species. The slow activation of the Ni-A state, compared with the rapid activation of the Ni-B state, is therefore proposed to result from the different chemical nature of the ligands in the two oxidized species. Our results along with very recent electrochemical studies suggest that the diatomic ligand could be hydro-peroxide.

  19. Method for measurement of diffusivity: Calorimetric studies of Fe/Ni multilayer thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, JX; Barmak, K

    2015-07-15

    A calorimetric method for the measurement of diffusivity in thin film multilayers is introduced and applied to the Fe Ni system. Using this method, the diffusivity in [Fe (25 nm)/Ni (25 nm)](20) multilayer thin films is measured as 4 x 10(-3)exp(-1.6 +/- 0.1 eV/ k(B)T) cm(2)/s, respectively. The diffusion mechanism in the multilayers and its relevance to laboratory synthesis of L1(0) ordered FeNi are discussed. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  20. A [NiFe]hydrogenase model that catalyses the release of hydrogen from formic acid.

    PubMed

    Nguyen, Nga T; Mori, Yuki; Matsumoto, Takahiro; Yatabe, Takeshi; Kabe, Ryota; Nakai, Hidetaka; Yoon, Ki-Seok; Ogo, Seiji

    2014-11-11

    We report the decomposition of formic acid to hydrogen and carbon dioxide, catalysed by a NiRu complex originally developed as a [NiFe]hydrogenase model. This is the first example of H2 evolution, catalysed by a [NiFe]hydrogenase model, which does not require additional energy.

  1. Efficient carbon dots/NiFe-layered double hydroxide/BiVO4 photoanodes for photoelectrochemical water splitting

    NASA Astrophysics Data System (ADS)

    Lv, Xiaowei; Xiao, Xin; Cao, Minglei; Bu, Yi; Wang, Chuanqing; Wang, Mingkui; Shen, Yan

    2018-05-01

    Modification of semiconductor photoanodes with oxygen evolution catalyst (OEC) is an effective approach for improving photoelectrochemical (PEC) water splitting efficiency. In the configuration, how to increase the activity of OEC is crucial to further improve PEC performance. Herein, a ternary photoanode system was designed to enhance PEC efficiency of photoelectrodes through introducing carbon dots (CDs), NiFe-layered double hydroxide (NiFe-LDH) nanosheets on BiVO4 particles. Systematic research shows that NiFe-LDH serves as an OEC which accelerates oxygen evolution kinetics, while the introduction of CDs can further reduce charge transfer resistance and overpotential for oxygen evolution. Under the synergistic effect of NiFe-LDH and CDs, the photocurrent and incident photon to current conversion efficiency (IPCE) of the resulting CDs/NiFe-LDH/BiVO4 photoanode is improved significantly than those of the NiFe-LDH/BiVO4 electrode. Consequently, such a ternary heterostructure could be an alternative way to further enhance PEC water splitting performance.

  2. Selective Internal Oxidation as a Mechanism for Intergranular Stress Corrosion Cracking of Ni-Cr-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Capell, Brent M.; Was, Gary S.

    2007-06-01

    The mechanism of selective internal oxidation (SIO) for intergranular stress corrosion cracking (IGSCC) of nickel-base alloys has been investigated through a series of experiments using high-purity alloys and a steam environment to control the formation of NiO on the surface. Five alloys (Ni-9Fe, Ni-5Cr, Ni-5Cr-9Fe, Ni-16Cr-9Fe, and Ni-30Cr-9Fe) were used to investigate oxidation and intergranular cracking behavior for hydrogen-to-water vapor partial pressure ratios (PPRs) between 0.001 and 0.9. The Ni-9Fe, Ni-5Cr, and Ni-5Cr-9Fe alloys formed a uniform Ni(OH)2 film at PPRs less than 0.09, and the higher chromium alloys formed chromium-rich oxide films over the entire PPR range studied. Corrosion coupon results show that grain boundary oxides extended for significant depths (>150 nm) below the sample surface for all but the highest Cr containing alloy. Constant extension rate tensile (CERT) test results showed that intergranular cracking varied with PPR and cracking was more pronounced at a PPR value where nonprotective Ni(OH)2 was able to form and a link between the nonprotective Ni(OH)2 film and the formation of grain boundary oxides is suggested. The observation of grain boundary oxides in stressed and unstressed samples as well as the influence of alloy content on IG cracking and oxidation support SIO as a mechanism for IGSCC.

  3. DFT calculations of strain and interface effects on electronic structures and magnetic properties of L10-FePt/Ag heterojunction of GMR applications

    NASA Astrophysics Data System (ADS)

    Pramchu, Sittichain; Jaroenjittichai, Atchara Punya; Laosiritaworn, Yongyut

    2018-03-01

    In this work, density functional theory (DFT) was employed to investigate the effect of strain and interface on electronic structures and magnetic properties of L10-FePt/Ag heterojunction. Two possible interface structures of L10-FePt(001)/Ag(001), that is, interface between Fe and Ag layers (Fe/Ag) and between Pt and Ag layers (Pt/Ag), were inspected. It was found that Pt/Ag interface is more stable than Fe/Ag interface due to its lower formation energy. Further, under the lattice mismatch induced tensile strain, the enhancement of magnetism for both Fe/Ag and Pt/Ag interface structures has been found to have progressed, though the magnetic moments of "interfacial" Fe and Pt atoms have been found to have decreased. To explain this further, the local density of states (LDOS) analysis suggests that interaction between Fe (Pt) and Ag near Fe/Ag (Pt/Ag) interface leads to spin symmetry breaking of the Ag atom and hence induces magnetism magnitude. In contrast, the magnetic moments of interfacial Fe and Pt atoms reduce because of the increase in the electronic states near the Fermi level of the minority-spin electrons. In addition, the significant enhancements of the LDOS near the Fermi levels of the minority-spin electrons signify the boosting of the transport properties of the minority-spin electrons and hence the spin-dependent electron transport at this ferromagnet/metal interface. From this work, it is expected that this clarification of the interfacial magnetism may inspire new innovation on how to improve spin-dependent electron transport for enhancing the giant magnetoresistance (GMR) ratio of potential GMR-based spintronic devices.

  4. The elastic properties and stability of fcc-Fe and fcc-FeNi alloys at inner-core conditions

    NASA Astrophysics Data System (ADS)

    Martorell, Benjamí; Brodholt, John; Wood, Ian G.; Vočadlo, Lidunka

    2015-07-01

    The agreement between shear wave velocities for the Earth's inner core observed from seismology with those derived from mineral physics is considerably worse than for any other region of the Earth. Furthermore, there is still debate as to the phase of iron present in the inner core, particularly when alloying with nickel and light elements is taken into account. To investigate the extent to which the mismatch between seismology and mineral physics is a function of either crystal structure and/or the amount of nickel present, we have used ab initio molecular dynamics simulations to calculate the elastic constants and seismic velocities (Vp and Vs) of face centred cubic (fcc) iron at Earth's inner core pressures (360 GPa) and at temperatures up to ˜7000 K. We find that Vp for fcc iron (fcc-Fe) is very similar to that for hexagonal close packed (hcp) iron at all temperatures. In contrast, Vs for fcc-Fe is significantly higher than in hcp-Fe, with the difference increasing with increasing temperature; the difference between Vs for the core (from seismology) and Vs for fcc-Fe exceeds 40 per cent. These results are consistent with previous work at lower temperatures. We have also investigated the effect of 6.5 and 13 atm% Ni in fcc-Fe. We find that Ni only slightly reduces Vp and Vs (e.g. by 2 per cent in Vs for 13 atm% Ni at 5500 K), and cannot account for the difference between the velocities observed in the core and those of pure fcc-Fe. We also tried to examine pre-melting behaviour in fcc-Fe, as reported in hcp-Fe by extending the study to very high temperatures (at which superheating may occur). However, we find that fcc-Fe spontaneously transforms to other hcp-like structures before melting; two hcp-like structures were found, both of hexagonal symmetry, which may most easily be regarded as being derived from an hcp crystal with stacking faults. That the structure did not transform to a true hcp phase is likely as a consequence of the limited size of the

  5. Characterization of Cu buffer layers for growth of L10-FeNi thin films

    NASA Astrophysics Data System (ADS)

    Mizuguchi, M.; Sekiya, S.; Takanashi, K.

    2010-05-01

    A Cu(001) layer was fabricated on a Au(001) layer to investigate the use of Cu as a buffer layer for growing L10-FeNi thin films. The epitaxial growth of a Cu buffer layer was observed using reflection high-energy electron diffraction. The flatness of the layer improved drastically with an increase in the substrate temperature although the layer was an alloy (AuCu3). An FeNi thin film was epitaxially grown on the AuCu3 buffer layer by alternate monatomic layer deposition and the formation of an L10-FeNi ordered alloy was expected. The AuCu3 buffer layer is thus a promising candidate material for the growth of L10-FeNi thin films.

  6. Novel synthesis of Ni-ferrite (NiFe{sub 2}O{sub 4}) electrode material for supercapacitor applications

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Venkatachalam, V.; Jayavel, R., E-mail: rjvel@annauniv.edu

    Novel nanocrystalline NiFe{sub 2}O{sub 4} has been synthesized through combustion route using citric acid as a fuel. Phase of the synthesized material was analyzed using powder X-ray diffraction. The XRD study revealed the formation of spinel phase cubic NiFe{sub 2}O{sub 4} with high crystallinity. The average crystallite size of NiFe{sub 2}O{sub 4} nanomaterial was calculated from scherrer equation. The electrochemical properties were realized by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. The electrode material shows a maximum specific capacitance of 454 F/g with pseudocapacitive behavior. High capacitance retention of electrode material over 1000 continuous charging-discharging cycles suggests its excellent electrochemicalmore » stability. The results revealed that the nickel ferrite electrode is a potential candidate for energy storage applications in supercapacitor.« less

  7. Characterization of Magnetic NiFe Nanoparticles with Controlled Bimetallic Composition

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Yan; Chi, Yanxiu; Shan, Shiyao

    2014-02-25

    The exploration of the magnetic properties of bimetallic alloy nanoparticles for various technological applications requires the ability to control the morphology, composition, and surface properties. In this report, we describe new findings of an investigation of the morphology and composition of NiFe alloy nanoparticles synthesized under controlled conditions. The controllability over the bimetallic composition has been demonstrated by the observation of an approximate linear relationship between the composition in the nanoparticles and in the synthetic feeding. The morphology of the NiFe nanoparticles is consistent with an fcc-type alloy, with the lattice strain increasing linearly with the iron content in themore » nanoparticles. The alloy nanoparticles exhibit remarkable resistance to air oxidation in comparison with Ni or Fe particles. The thermal stability and the magnetic properties of the as-synthesized alloy nanoparticles are shown to depend on the composition. The alloy nanoparticles have also be sown to display low saturation magnetization and coercivity values in comparison with the Ni nanoparticles, in line with the superparamagnetic characteristic. These findings have important implications for the design of stable and controllable magnetic nanoparticles for various technological applications.« less

  8. Synthesis and Magnetic Properties of Fe-Co-Ni/C Nanocomposites

    NASA Astrophysics Data System (ADS)

    Muratov, D. G.; Kozhitov, L. V.; Karpenkov, D. Yu.; Yakushko, E. V.; Korovin, E. Yu.; Vasil'ev, A. V.; Popkova, A. V.; Kazaryan, T. M.; Shadrinov, A. V.

    2018-03-01

    Nanoparticles of the Fe-Co-Ni ternary alloy, encapsulated in the carbon matrix of nanocomposites, have been synthesized, The structure, phase composition, and magnetic properties of the obtained materials have been determined with the help of diffractometry and magnetometry. It has been established that nanoparticles of the ternary alloy are formed due to solution of cobalt in the Fe-Ni alloy. The composition of the nanoparticles of the alloy depends on the mass percent ratio of the metas in the precursor. With growth of the iron content, nanoparticles of the ternary alloy with various composition are formed with FCC and BCC crystal lattice structure. As the synthesis temperature and relative iron content are increased, the magnetization of the Fe-Co-Ni/C nanocomposites increases from 26 to 157 A·m2/kg. The coercive force is determined by the synthesis temperature, the size of the nanoparticles, and the composition of the alloy, and its value varies from 330 to 43 Oe.

  9. Effect of annealing on magnetic properties of Ni80Fe20 permalloy nanoparticles prepared by polyol method.

    PubMed

    Qin, G W; Pei, W L; Ren, Y P; Shimada, Y; Endo, Y; Yamaguchi, M; Okamoto, S; Kitakami, O

    2011-12-01

    Ni80Fe20 permalloy nanoparticles with narrow size distribution and homogeneous composition have been prepared by the polyol processing at 180 degrees C for 2 h and their particle sizes can be tunable in the size range of 20-440 nm by proper addition of K2PtCI4 agent. X-ray diffraction results show that the NiFe nanoparticles are of face centered cubic structure. The addition of K2PtCl4 does not affect the composition of NiFe NPs but decreases the particle size remarkably. Both saturation magnetization and coercivity of the as-prepared NiFe nanoparticles decrease with decreasing particle size. Annealed at 280 degrees C, however, the saturation magnetization of various sized NiFe nanoparticles increases drastically and approaches to the bulk for the -440 nm NiFe particles, and a maximum coercivity (-270 Oe) happens at a critical size of -50 nm. The magnetic property dependency of these NiFe nanoparticles on annealing has been discussed by considering the surface chemistry.

  10. Phase evolution, mechanical and corrosion behavior of Fe(100-x) Ni(x) alloys synthesized by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Singh, Neera; Parkash, Om; Kumar, Devendra

    2018-03-01

    In the present investigation, Fe(100-x) Ni(x) alloys (x = 10, 20, 30, 40 and 50 wt%) were synthesized through the evolution of γ-taenite and α-kamacite phases by powder metallurgy route using commercially available Fe and Ni powders. Mechanically mixed powders of Fe and Ni were compacted at room temperature and sintered at three different temperatures 1000, 1200 and 1250 °C for 1 h. Both Ni concentration and sintering temperature have shown a strong impact on the phase formation, tribological and electrochemical behavior. Micro structural study has shown the formation of taenite (γ-Fe,Ni) and kamacite (α-Fe,Ni) phases in the sintered specimens. An increase in Ni fraction resulted in formation of more taenite which reduces hardness and wear resistance of specimens. Increasing the sintering temperature decreased the defect concentration with enhanced taenite formation, aiding to higher densification. Taenite formed completely in Fe50Ni50 after sintering at 1250 °C. Tribological test revealed the maximum wear resistance for Fe70Ni30 specimen due to the presence of both kamacite and taenite in significant proportions. The formation of taenite as well as the decrease in defect concentration improves the corrosion resistance of the specimens significantly in 1M HCl solution. A maximum corrosion protection efficiency of around ∼87% was achieved in acidic medium for Fe50Ni50, sintered at 1250 °C.

  11. Ternary NiFeX as soft biasing film in a magnetoresistive sensor

    NASA Astrophysics Data System (ADS)

    Chen, Mao-Min; Gharsallah, Neila; Gorman, Grace L.; Latimer, Jacquie

    1991-04-01

    The properties of NiFeX ternary films (X being Al, Au, Nb, Pd, Pt, Si, and Zr) have been studied for soft-film biasing of the magnetoresistive (MR) trilayer sensor. In general, the addition of the element X into the NiFe alloy film decreases the saturation magnetization Bs and magnetoresistance coefficient of the film, while increasing the film's electrical resistivity ρ. One of the desirable properties of a soft film for biasing is high sheet resistance for minimum current flow. A figure of merit Bsρ that takes into account both the rate of increase in Bs and the rate of decrease in ρ when adding X element was derived to compare the effectiveness of various X elements in reducing the current shunting through the soft-film layer. Using this criterion, NiFeNb and NiFeZr emerge as good soft-film materials having a maximum sheet resistance relative to the MR layer. Other critical properties such as magnetoresistance coefficient, magnetostriction, coercivity, and anisotropy field were also examined and are discussed in this paper.

  12. Thiolate-bridged dinuclear iron(tris-carbonyl)–nickel complexes relevant to the active site of [NiFe] hydrogenase

    PubMed Central

    Ohki, Yasuhiro; Yasumura, Kazunari; Kuge, Katsuaki; Tanino, Soichiro; Ando, Masaru; Li, Zilong; Tatsumi, Kazuyuki

    2008-01-01

    The reaction of NiBr2(EtOH)4 with a 1:2–3 mixture of FeBr2(CO)4 and Na(SPh) generated a linear trinuclear Fe–Ni–Fe cluster (CO)3Fe(μ-SPh)3Ni(μ-SPh)3Fe(CO)3, 1, whereas the analogous reaction system FeBr2(CO)4/Na(StBu)/NiBr2(EtOH)4 (1:2–3:1) gave rise to a linear tetranuclear Fe–Ni–Ni–Fe cluster [(CO)3Fe(μ-StBu)3Ni(μ-Br)]2, 2. By using this tetranuclear cluster 2 as the precursor, we have developed a new synthetic route to a series of thiolate-bridged dinuclear Fe(CO)3–Ni complexes, the structures of which mimic [NiFe] hydrogenase active sites. The reactions of 2 with SC(NMe2)2 (tmtu), Na{S(CH2)2SMe} and ortho-NaS(C6H4)SR (R = Me, tBu) led to isolation of (CO)3Fe(μ-StBu)3NiBr(tmtu), 3, (CO)3Fe(StBu)(μ-StBu)2Ni{S(CH2)2SMe}, 4, and (CO)3Fe(StBu)(μ-StBu)2Ni{S(C6H4)SR}, 5a (R = Me) and 5b (R = tBu), respectively. On the other hand, treatment of 2 with 2-methylthio-phenolate (ortho-O(C6H4)SMe) in methanol resulted in (CO)3Fe(μ-StBu)3Ni(MeOH){O(C6H4)SMe}, 6a. The methanol molecule bound to Ni is labile and is readily released under reduced pressure to afford (CO)3Fe(StBu)(μ-StBu)2Ni{O(C6H4)SMe}, 6b, and the coordination geometry of nickel changes from octahedral to square planar. Likewise, the reaction of 2 with NaOAc in methanol followed by crystallization from THF gave (CO)3Fe(μ-StBu)3Ni(THF)(OAc), 7. The dinuclear complexes, 3-7, are thermally unstable, and a key to their successful isolation is to carry out the reactions and manipulations at −40°C. PMID:18511566

  13. Synthesis of polycrystalline CoFe2O4 and NiFe2O4 powders by auto-combustion method using a novel amino-based gel

    NASA Astrophysics Data System (ADS)

    Jiang, Linwen; Yang, Shanshan; Zheng, Mengyao; Wu, Anhua; Chen, Hongbing

    2017-12-01

    Polycrystalline CoFe2O4/NiFe2O4 powders were prepared by auto-combustion method using a novel amino-based gel. The thermal evolution of gel precursors, as well as the microstructure, morphology and magnetic properties of as-synthesized powders were studied in detail. Energy dispersive x-ray spectroscopy indicated that the ratios of Ni:Fe was close to the theoretical value (Ni:Fe  =  1:2), suggesting high purity of synthesized NiFe2O4 powders. The saturated magnetization (M s) and residual magnetization (M r) of CoFe2O4 were highly dependent upon the annealed temperatures. The M s increased from 77.5 to 84.7 emu g-1, and M r increased from 37.7 emu g-1 to 42.5 emu g-1 by annealing from room temperature to 600 °C. The M s of NiFe2O4 was 38.7 emu g-1, much lower than that of CoFe2O4. The experimental results indicated that this auto-combustion method using amino-based gel was a suitable method for synthesizing high-quality CoFe2O4/NiFe2O4 powders.

  14. Highly Efficient, Low-Cost, and Magnetically Recoverable FePt⁻Ag Nanocatalysts: Towards Green Reduction of Organic Dyes.

    PubMed

    Liu, Yang; Zhang, Yuanyuan; Kou, Qiangwei; Chen, Yue; Sun, Yantao; Han, Donglai; Wang, Dandan; Lu, Ziyang; Chen, Lei; Yang, Jinghai; Xing, Scott Guozhong

    2018-05-14

    Nowadays, synthetic organic dyes and pigments discharged from numerous industries are causing unprecedentedly severe water environmental pollution, and conventional water treatment processes are hindered due to the corresponding sophisticated aromatic structures, hydrophilic nature, and high stability against light, temperature, etc. Herein, we report an efficient fabrication strategy to develop a new type of highly efficient, low-cost, and magnetically recoverable nanocatalyst, i.e., FePt⁻Ag nanocomposites, for the reduction of methyl orange (MO) and rhodamine B (RhB), by a facile seed deposition process. X-ray diffraction results elaborate that the as-synthesized FePt⁻Ag nanocomposites are pure disordered face-centered cubic phase. Transmission electron microscopy studies demonstrate that the amount of Ag seeds deposited onto the surfaces of FePt nanocrystals increases when increasing the additive amount of silver colloids. The linear correlation of the MO and RhB concentration versus reaction time catalyzed by FePt⁻Ag nanocatalysts is in line with pseudo-first-order kinetics. The reduction rate constants of MO and RhB increase with the increase of the amount of Ag seeds. FePt⁻Ag nanocomposites show good separation ability and reusability, and could be repeatedly applied for nearly complete reduction of MO and RhB for at least six successive cycles. Such cost-effective and recyclable nanocatalysts provide a new material family for use in environmental protection applications.

  15. Oxidation behaviour of Fe-Ni alloy nanoparticles synthesized by thermal plasma route

    NASA Astrophysics Data System (ADS)

    Ghodke, Neha; Kamble, Shalaka; Raut, Suyog; Puranik, Shridhar; Bhoraskar, S. V.; Rayaprol, Sudhindra; Mathe, V. L.

    2018-04-01

    Here we report synthesis of Fe-Ni nanoparticles using thermal plasma route. In thermal plasma, gas phase nucleation and growth at sufficiently higher temperature is observed. The synthesized Fe-Ni nanoparticles are examined by X-ray Diffraction, Raman Spectroscopy, Vibrating Sample Magnetometer and Thermo gravimetric Analysis. Formation of 16-21 nm sized Fe-Ni nanoparticles having surface oxidation show maximum value of magnetization of ˜107 emu/g. The sample synthesized at relatively low power (4kW) show presence of carbonaceous species whereas the high power (6 kW) synthesis does not depicts carbonaceous species. The presence of carbonaceous species protects oxidation of the nanoparticles significantly as evidenced from TGA data.

  16. s-process nucleosynthesis in massive stars: new results on {sup 60}Fe, {sup 62}Ni and {sup 64}Ni

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Domingo-Pardo, C.; Forschungszentrum Karlsruhe, Institut fuer Kernphysik, 76021 Karlsruhe; Dillmann, I.

    2009-01-28

    The s process synthesizes the elements between Fe and Sr in massive stars during two major evolutionary stages, convective core He burning and C shell burning. This scenario implies fascinating consequences for the chemical evolution of the star. For instance, the neutron capture rate at each isotope can have a big influence on the production of many of the subsequent higher mass isotopes. Correspondingly, one needs to know the (n,{gamma}) cross sections of the involved isotopes with high accuracy in order to determine the abundance pattern reliably and to obtain a consistent picture of this stage. This contribution gives anmore » overview on recent and future experiments for the Fe/Ni nucleosynthesis in massive stars. New results on {sup 60}Fe, {sup 62}Ni and {sup 64}Ni are reported. {sup 60}Fe is mostly produced during the short convective C shell burning phase, where peak densities of {approx}10{sup 11} cm{sup -3} are reached, prior to the SN explosion. The stellar (n,{gamma}) cross section of {sup 60}Fe could be measured with a 1 {mu}g sample obtained at PSI (Switzerland), which was sufficient for an activation measurement using the intense, quasi-stellar neutron field for a thermal energy of 25 keV at the Karlsruhe Van de Graaff accelerator. The FZK accelerator was also used for an activation of {sup 62}Ni, whereas in this case, the number of {sup 63}Ni nuclei produced were determined via accelerator mass spectroscopy at the Maier-Leibnitz-Laboratorium in Garching/Munich. The (n,{gamma}) cross section of {sup 64}Ni at a stellar temperature equivalent to 50 keV has been measured in a collaboration between FZK Karlsruhe and PTB Braunschweig. Finally, complementary time of flight measurements on the Fe and Ni isotopes over a broad energy range are planned at the white neutron source n lowbar TOF of CERN for the future campaign in 2009.« less

  17. Microstructures and Mechanical Properties of NiTiFeAlCu High-Entropy Alloys with Exceptional Nano-precipitates

    NASA Astrophysics Data System (ADS)

    Zhang, Yanqiu; Wang, Sibing; Jiang, Shuyong; Zhu, Xiaoming; Sun, Dong

    2017-01-01

    Three novel NiTiFeAlCu high-entropy alloys, which consist of nano-precipitates with face-centered cubic structure and matrix with body-centered cubic structure, were fabricated to investigate microstructures and mechanical properties. With the increase in Ni and Ti contents, the strength of NiTiFeAlCu alloy is enhanced, while the plasticity of NiTiFeAlCu alloy is lowered. Plenty of dislocations can be observed in the Ni32Ti32Fe12Al12Cu12 high-entropy alloy. The size of nano-precipitates decreases with the increase in Ni and Ti contents, while lattice distortion becomes more and more severe with the increase in Ni and Ti contents. The existence of nano-precipitates, dislocations and lattice distortion is responsible for the increase in the strength of NiTiFeAlCu alloy, but it has an adverse influence on the plasticity of NiTiFeAlCu alloy. Ni20Ti20Fe20Al20Cu20 alloy exhibits the substantial ability of plastic deformation and a characteristic of steady flow at 850 and 1000 °C. This phenomenon is attributed to a competition between the increase in the dislocation density induced by plastic strain and the decrease in the dislocation density due to the dynamic recrystallization.

  18. Defect energetics of concentrated solid-solution alloys from ab initio calculations: Ni 0.5 Co 0.5 , Ni 0.5 Fe 0.5 , Ni 0.8 Fe 0.2 and Ni 0.8 Cr 0.2

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhao, Shijun; Stocks, G. Malcolm; Zhang, Yanwen

    2016-01-01

    The distribution of migration energies of vacancies and interstitials in Ni 0.5Fe 0.5has a region of overlap, an indication of their comparable mobility compared to pure Ni (indicated by dotted line), which will greatly facilitate the recombination of Frenkel pairs.

  19. Nucleation of intragranular ferrite in Fe-Ni-P alloys

    NASA Astrophysics Data System (ADS)

    Narayan, C.; Goldstein, J. I.

    1984-05-01

    The nucleation of intragranular ferrite from austenite in Fe-Ni-P alloys was investigated in order to understand the development of the Widmanstätten pattern in iron meteorites. Alloys containing 5 to 10 wt pct Ni and 0 to 1 wt pct P were used to simulate iron meteorite compositions. In the isothermal and controlled cooling experiments the reaction path γ → α + γ serves only to nucleate ferrite along austenite grain boundaries. It is necessary for (FeNi)3P to be present within y grains in order to nucleate intragranular ferrite. The reaction path γ → γ + phosphide → α + γ + phosphide yields rod shaped ferrite nuclei that bear a near Kurdjumov-Sachs orientation relationship with the surrounding matrix. The precipitation of ferrite, both along grain boundaries and within the austenite grains, is suppressed in the absence of P.

  20. Metal insertion into NiFe-hydrogenases.

    PubMed

    Blokesch, M; Paschos, A; Theodoratou, E; Bauer, A; Hube, M; Huth, S; Böck, A

    2002-08-01

    The synthesis and the insertion of the metallocentre of NiFe-hydrogenases is a complex process, in which seven maturation enzymes plus ATP, GTP and carbamoyl phosphate are involved. The review summarizes what is known about the properties and activities of these auxiliary proteins, and postulates a pathway along which maturation may take place.

  1. Purification and Characterization of the [NiFe]-Hydrogenase of Shewanella oneidensis MR-1 ▿

    PubMed Central

    Shi, Liang; Belchik, Sara M.; Plymale, Andrew E.; Heald, Steve; Dohnalkova, Alice C.; Sybirna, Kateryna; Bottin, Hervé; Squier, Thomas C.; Zachara, John M.; Fredrickson, James K.

    2011-01-01

    Shewanella oneidensis MR-1 possesses a periplasmic [NiFe]-hydrogenase (MR-1 [NiFe]-H2ase) that has been implicated in H2 production and oxidation as well as technetium [Tc(VII)] reduction. To characterize the roles of MR-1 [NiFe]-H2ase in these proposed reactions, the genes encoding both subunits of MR-1 [NiFe]-H2ase were cloned and then expressed in an MR-1 mutant without hyaB and hydA genes. Expression of recombinant MR-1 [NiFe]-H2ase in trans restored the mutant's ability to produce H2 at 37% of that for the wild type. Following purification, MR-1 [NiFe]-H2ase coupled H2 oxidation to reduction of Tc(VII)O4− and methyl viologen. Change of the buffers used affected MR-1 [NiFe]-H2ase-mediated reduction of Tc(VII)O4− but not methyl viologen. Under the conditions tested, all Tc(VII)O4− used was reduced in Tris buffer, while in HEPES buffer, only 20% of Tc(VII)O4− was reduced. The reduced products were soluble in Tris buffer but insoluble in HEPES buffer. Transmission electron microscopy analysis revealed that Tc precipitates reduced in HEPES buffer were aggregates of crystallites with diameters of ∼5 nm. Measurements with X-ray absorption near-edge spectroscopy revealed that the reduction products were a mixture of Tc(IV) and Tc(V) in Tris buffer but only Tc(IV) in HEPES buffer. Measurements with extended X-ray adsorption fine structure showed that while the Tc bonding environment in Tris buffer could not be determined, the Tc(IV) product in HEPES buffer was very similar to Tc(IV)O2·nH2O, which was also the product of Tc(VII)O4− reduction by MR-1 cells. These results shows for the first time that MR-1 [NiFe]-H2ase catalyzes Tc(VII)O4− reduction directly by coupling to H2 oxidation. PMID:21724888

  2. Synthesis, characterization and low temperature electrical conductivity of Polyaniline/NiFe2O4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Prasanna, G. D.; Prasad, V. B.; Jayanna, H. S.

    2015-02-01

    Conducting polymer/ferrite nanocomposites with an organized structure provide a new functional hybrid between organic and inorganic materials. The most popular among the conductive polymers is the polyaniline (PANI) due to its wide application in different fields. In the present work nickel ferrite (NiFe2O4) nanoparticles were prepared by sol-gel citrate-nitrate method with an average size of 21.6nm. PANI/NiFe2O4 nanoparticles were synthesized by a simple general and inexpensive in-situ polymerization in the presence of NiFe2O4 nanoparticles. The effects of NiFe2O4 nanoparticles on the dc-electrical properties of polyaniline were investigated. The structural components in the nanocomposites were identified from Fourier Transform Infrared (FTIR) spectroscopy. The crystalline phase of nanocomposites was characterized by X-Ray Diffraction (XRD). The Scanning Electron Micrograph (SEM) reveals that there was some interaction between the NiFe2O4 particles and polyaniline and the nanocomposites are composed of polycrystalline ferrite nanoparticles and PANI. The dc conductivity of polyaniline/NiFe2O4 nanocomposites have been measured as a function of temperature in the range of 80K to 300K. It is observed that the room temperature conductivity cRT decreases with increase in the relative content of NiFe2O4. The experimental data reveals that the resistivity increases for all composites with decrease of temperature exhibiting semiconductor behaviour.

  3. Preferential diffusion in concentrated solid solution alloys: NiFe, NiCo and NiCoCr

    DOE PAGES

    Zhao, Shijun; Osetsky, Yuri; Zhang, Yanwen

    2017-02-13

    In single-phase concentrated solid-solution alloys (CSAs), including high entropy alloys (HEAs), remarkable mechanical properties are exhibited, as well as extraordinary corrosion and radiation resistance compared to pure metals and dilute alloys. But, the mechanisms responsible for these properties are unknown in many cases. In this work, we employ ab initio molecular dynamics based on density functional theory to study the diffusion of interstitial atoms in Ni and Ni-based face-centered cubic CSAs including NiFe, NiCo and NiCoCr. We model the defect trajectories over >100 ps and estimate tracer diffusion coefficients, correlation factors and activation energies. Furthermore, we found that the diffusionmore » mass transport in CSAs is not only slower than that in pure components, i.e. sluggish diffusion, but also chemically non-homogeneous. The results obtained here can be used in understanding and predicting the atomic segregation and phase separation in CSAs under irradiation conditions.« less

  4. Enhanced debromination of decabrominated diphenyl ether in aqueous solution by attapulgite supported Fe/Ni bimetallic nanoparticles: kinetics and pathways

    NASA Astrophysics Data System (ADS)

    Liu, Zongtang; Gu, Chenggang; Bian, Yongrong; Jiang, Xin; Sun, Yufeng; Fei, Zhenghao; Dai, Jingtao

    2017-08-01

    In this study, Fe/Ni bimetallic nanoparticles were supported on the attapulgite (A-Fe/Ni) to enhance the degradation reactivity of decabrominated diphenyl ether (BDE209) in aqueous solution. The Fe/Ni nanoparticles were well distributed on the attapulgite surface with an average diameter of 20-40 nm. The removal percentage of BDE209 by A-Fe/Ni was 1.59 times higher than Fe/Ni nanoparticles alone because attapulgite could act as supporting material to disperse Fe/Ni nanoparticles and prevent Fe/Ni nanoparticles from aggregation. The degradation kinetics for BDE209 debromination by A-Fe/Ni could be well described by a pseudo-first-order model, and the debromination rate constant of BDE209 increased with increasing the dosage of A-Fe/Ni, water/THF ratio, and decreasing the initial BDE209 concentration and solution pH. The degradation products were identified using a third-order polynomial regression equation between the experimental and reference gas chromatography relative retention times. Stepwise debromination from n-bromo-DE to (n  -  1)-bromo-DE was a possible pathway with bromines being substituted sequentially by hydrogen. The preferred elimination of bromines of BDE209 by A-Fe/Ni followed the debromination preference of para-Br  >  meta-Br  >  ortho-Br. The results provide evidences for understanding the debromination mechanism of polybrominated diphenyl ether by clay-supported Fe/Ni nanoparticles.

  5. Effect of silver thickness on structural, optical and morphological properties of nanocrystalline Ag/NiO thin films

    NASA Astrophysics Data System (ADS)

    Jalili, S.; Hajakbari, F.; Hojabri, A.

    2018-03-01

    Silver (Ag) nanolayers were deposited on nickel oxide (NiO) thin films by DC magnetron sputtering. The thickness of Ag layers was in range of 20-80 nm by variation of deposition time between 10 and 40 s. X-ray diffraction results showed that the crystalline properties of the Ag/NiO films improved by increasing the Ag film thickness. Also, atomic force microscopy and field emission scanning electron microscopy images demonstrated that the surface morphology of the films was highly affected by film thickness. The film thickness and the size of particles change by elevating the Ag deposition times. The composition of films was determined by Rutherford back scattering spectroscopy. The transmission of light was gradually reduced by augmentation of Ag films thickness. Furthermore; the optical band gap of the films was also calculated from the transmittance spectra.

  6. Preparation of surface plasmon resonance biosensor based on magnetic core/shell Fe3O4/SiO2 and Fe3O4/Ag/SiO2 nanoparticles.

    PubMed

    Wang, Liying; Sun, Ying; Wang, Jing; Wang, Jian; Yu, Aimin; Zhang, Hanqi; Song, Daqian

    2011-06-01

    In this paper, surface plasmon resonance biosensors based on magnetic core/shell Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were developed for immunoassay. With Fe(3)O(4) and Fe(3)O(4)/Ag nanoparticles being used as seeding materials, Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were formed by hydrolysis of tetraethyl orthosilicate. The aldehyde group functionalized magnetic nanoparticles provide organic functionality for bioconjugation. The products were characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), FTIR and UV-vis absorption spectrometry. The magnetic nanoparticles possess the unique superparamagnetism property, exceptional optical properties and good compatibilities, and could be used as immobilization matrix for goat anti-rabbit IgG. The magnetic nanoparticles can be easily immobilized on the surface of SPR biosensor chip by a magnetic pillar. The effects of Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles on the sensitivity of SPR biosensors were also investigated. As a result, the SPR biosensors based on Fe(3)O(4)/SiO(2) nanoparticles and Fe(3)O(4)/Ag/SiO(2) nanoparticles exhibit a response for rabbit IgG in the concentration range of 1.25-20.00 μg ml(-1) and 0.30-20.00 μg ml(-1), respectively. Copyright © 2011 Elsevier B.V. All rights reserved.

  7. Tuning the exchange bias in NiFe/Fe-oxide bilayers by way of different Fe-oxide based mixtures made with an ion-beam deposition technique.

    PubMed

    Lin, K W; Kol, P H; Guo, Z Y; Ouyang, H; van Lierop, J

    2007-01-01

    We have investigated the structural and magnetic properties of ion-beam deposited polycrystalline NiFe (25 nm)/Fe-oxide (35 nm) bilayers. A film prepared with an assist beam O2 to Ar gas ratio of 0% during deposition had a bottom layer that consisted of pure b.c.c. Fe (a = 2.87 A) whereas films prepared with 19%O2/Ar and 35%O2/Ar had either Fe3O4 (a = 8.47 angstroms) or alpha-Fe2O3 (a = 5.04 angstroms, c = 13.86 angstroms) bottom layers, respectively. Cross-sectional transmission electron microscopy revealed a smooth interface between the top nano-columnar NiFe and bottom nano-columnar Fe-oxide layer for all films. At room temperature, the observed coercivity (Hc approximately 25 Oe) for a film prepared with 19% O2/Ar indicates the existence of a magnetically hard ferrimagnetic Fe3O4 phase that is enhancing the plain NiFe (Hc approximately 2 Oe) by way of exchange coupling. A significant amount of exchange bias is observed below 50 K, and at 10 K the size of exchange bias hysteresis loops shift increases with increasing oxygen in the films. Furthermore, the strongest exchange coupling (H(ex) approximately 135 Oe at 10 K) is with alpha-Fe2O3 (35% O2/Ar) as the bottom film layer. This indicates that the pure antiferromagnetic phases work better than ferrimagnetic phases when in contact with ferromagnetic NiFe. H(ex) (T) is well described by an effective AF domain wall energy that creates an exchange field with a (1 - T/T(crit)) temperature dependence. Hc (T) exhibits three distinct regimes of constant temperature that may indicate the existence of different AF spin populations that couple to the FM layer at different temperatures.

  8. Syntheses, structures, and properties of trinuclear complexes [M(bpca)(2)(M'(hfac)(2))(2)], constructed with the complexed bridging ligand [M(bpca)(2)] [M, M' = Ni(II), Mn(II); Cu(II), Mn(II); Fe(II), Mn(II); Ni(II), Fe(II); and Fe(II), Fe(II); Hbpca = Bis(2-pyridylcarbonyl)amine, Hhfac = Hexafluoroacetylacetone].

    PubMed

    Kamiyama, Asako; Noguchi, Tomoko; Kajiwara, Takashi; Ito, Tasuku

    2002-02-11

    Five trinuclear complexes [M(bpca)(2)(M'(hfac)(2))(2)] (where MM'(2) = NiMn(2), CuMn(2), FeMn(2), NiFe(2), and FeFe(2); Hbpca = bis(2-pyridylcarbonyl)amine; and Hhfac = hexafluoroacetylacetone) were synthesized almost quantitatively by the reaction of [M(bpca)(2)] and [M'(hfac)(2)] in 1:2 molar ratio, and their structures and magnetic properties were investigated. Three complexes, with M' = Mn, crystallize in the same space group, Pna2(1), whereas two complexes, with M' = Fe, crystallize in P4(1), and complexes within each set are isostructural to one another. In all complexes, [M(bpca)(2)] acts as a bis-bidentate bridging ligand to form a linear trinuclear complex in which three metal ions are arranged in the manner M'-M-M'. The central metal ion is in a strong ligand field created by the N(6) donor set, and hence the Fe(II) in the [Fe(bpca)(2)] moiety is in a low-spin state. The terminal metal ions (M') are surrounded by O(6) donor sets with a moderate ligand field, which leads to the high-spin configuration of Fe(II). Three metal ions in all complexes are almost collinear, and metal-metal distances are ca. 5.5 A. The magnetic behavior of NiMn(2) and NiFe(2) shows a weak ferromagnetic interaction between the central Ni(II) ion and the terminal Mn(II) or Fe(II) ions. In these complexes, sigma-spin orbitals of the central Ni(II) ion and those of terminal metal ions have different symmetry about a 2-fold rotation axis through the Ni-N(amide)-M'(terminal) atoms, and this results in orthogonality between the neighboring sigma-spin orbitals and thus ferromagnetic interactions.

  9. FeCoNi coated glass fibers in composite sheets for electromagnetic absorption and shielding behaviors

    NASA Astrophysics Data System (ADS)

    Lee, Joonsik; Jung, Byung Mun; Lee, Sang Bok; Lee, Sang Kwan; Kim, Ki Hyeon

    2017-09-01

    To evaluate the electromagnetic (EM) absorption and shield of magnetic composite sheet, we prepared the FeCoNi coated glass fibers filled in composite sheet. The FeCoNi was coated by electroless plating on glass fiber as a filler. The coated FeCoNi found that consist of mixtures of bcc and fcc phase. The magnetization and coercivity of coated FeCoNi are about 110 emu/g and 57 Oe, respectively. The permittivity and permeability of the FeCoNi composite sheet were about 21 and 1, respectively. Power absorption increased 95% with the increment of frequency up to 10 GHz. Inter-decoupling of this composite sheet showed maximum 30 dB at around 5.3 GHz, which is comparable to that of a conductive Cu foil. Shielding effectiveness (SE) was measured by using rectangular waveguide method. SE of composite obtained about 37 dB at X-band frequency region.

  10. Fabrication and photocatalytic property of magnetic NiFe2O4/Cu2O composites

    NASA Astrophysics Data System (ADS)

    He, Zuming; Xia, Yongmei; Tang, Bin; Su, Jiangbin

    2017-09-01

    Magnetically separable NiFe2O4/Cu2O composites were successfully synthesized by a two-step method. The samples were characterized by XRD, XPS, SEM and VSM as well as their PL spectra and UV-vis adsorption spectra. The results showed that the NiFe2O4/Cu2O composites were composed of cubic-structured Cu2O and spinel-structured NiFe2O4, were able to absorb a large amount of visible light, exhibited excellent photocatalytic activity under simulated solar light irradiation and could be easily separated by an external magnetic field. The NiFe2O4/Cu2O composites exhibited higher photocatalytic performance than that of a single semiconductor. It was found that the prominently enhanced photocatalytic performance of NiFe2O4/Cu2O composites was ascribed to the effective separation of photo-generated electron-hole pairs and the effective generation of the hydroxyl radical •OH.

  11. Function and CO binding properties of the NiFe complex in carbon monoxide dehydrogenase from Clostridium thermoaceticum.

    PubMed

    Shin, W; Lindahl, P A

    1992-12-29

    Adding 1,10-phenanthroline to carbon monoxide dehydrogenase from Clostridium thermoaceticum results in the complete loss of the NiFeC EPR signal and the CO/acetyl-CoA exchange activity. Other EPR signals characteristic of the enzyme (the gav = 1.94 and gav = 1.86 signals) and the CO oxidation activity are completely unaffected by the 1,10-phenanthroline treatment. This indicates that there are two catalytic sites on the enzyme; the NiFe complex is required for catalyzing the exchange and acetyl-CoA synthase reactions, while some other site is responsible for CO oxidation. The strength of CO binding to the NiFe complex was examined by titrating dithionite-reduced enzyme with CO. During the titration, the NiFeC EPR signal developed to a final spin intensity of 0.23 spin/alpha beta. The resulting CO titration curve (NiFeC spins/alpha beta vs CO pha beta) was fitted using two reactions: binding of CO to the oxidized NiFe complex, and reduction of the CO-bound species to a form that exhibits the NiFeC signal. Best fits yielded apparent binding constants between 6000 and 14,000 M-1 (Kd = 70-165 microM). This sizable range is due to uncertainty whether CO binds to all or only a small fraction (approximately 23%) of the NiFe complexes. Reduction of the CO-bound NiFe complex is apparently required to activate it for catalysis. The electron used for this reduction originates from the CO oxidation site, suggesting that delivery of a low-potential electron to the CO-bound NiFe complex is the physiological function of the CO oxidation reaction catalyzed by this enzyme.

  12. Novel multifunctional NiFe2O4/ZnO hybrids for dye removal by adsorption, photocatalysis and magnetic separation

    NASA Astrophysics Data System (ADS)

    Zhu, Hua-Yue; Jiang, Ru; Fu, Yong-Qian; Li, Rong-Rong; Yao, Jun; Jiang, Sheng-Tao

    2016-04-01

    Novel multifunctional NiFe2O4/ZnO hybrids were prepared by a hydrothermal method and their physicochemical properties were characterized by XRD, SEM, TEM, TGA, VSM, BET and UV-vis DRS. The adsorption and photocatalytic performance of NiFe2O4/ZnO hybrids were systematically investigated using congo red as a model contaminant. With the introduction of NiFe2O4, NiFe2O4/ZnO hybrids can absorb the whole light from 300 nm to 700 nm. The adsorption capacity (221.73 mg g-1) of NiFe2O4/ZnO hybrids is higher than those of NiFe2O4, ZnO and mechanically mixed NiFe2O4/ZnO hybrids. The removal of congo red solution (20 mg L-1) by NiFe2O4/ZnO hybrids was about 94.55% under simulated solar light irradiation for 10 min. rad OH and h+ play important roles in the decolorization of congo red solution by NiFe2O4/ZnO hybrids under simulated solar light irradiation. The decolorization efficiency of congo red solution is 97.23% for the fifth time by NiFe2O4/ZnO hybrids under simulate solar light irradiation, indicating the high photostability and durability. NO3- and Cl- anions which are ubiquitous components in dye-containing wastewater have negligible influence on the effectiveness of NiFe2O4/ZnO hybrids. Moreover, the magnetic NiFe2O4/ZnO hybrids can be easily separated from the reacted solution by an external magnet.

  13. Structural and dielectric characteristics of double perovskite La2(NiFe)1/2MnO6

    NASA Astrophysics Data System (ADS)

    Nasir, Mohd.; Kandasami, Asokan; Sen, Somaditya

    2018-05-01

    Recently, La2NiMnO6 has drawn significant interest because large magnetic field induced changes in dielectric properties makes this compound a promising material for potential spintronic device applications. In the present study, the structural and dielectric characteristics of sol-gel prepared La2(Ni1/2Fe1/2)MnO6 double perovskite ceramics were evaluated. La2(Ni1/2Fe1/2)MnO6 was crystallized in the monoclinic P21/n structure with ordered Ni2+/Fe2+ and Mn4+ cations. A giant dielectric constant with relaxor-like behavior was observed, which was attributed to the dipolar effects arising from hopping between Ni2+/Fe2+ and Mn4+ ions.

  14. NiFe(C2O4)x as a heterogeneous Fenton catalyst for removal of methyl orange.

    PubMed

    Liu, Yucan; Zhang, Guangming; Chong, Shan; Zhang, Nan; Chang, Huazhen; Huang, Ting; Fang, Shunyan

    2017-05-01

    This paper studies a heterogeneous Fenton catalyst NiFe(C 2 O 4 ) x , which showed better catalytic activity than Ni(C 2 O 4 ) x and better re-usability than Fe(C 2 O 4 ) x . The methyl orange removal efficiency was 98% in heterogeneous Fenton system using NiFe(C 2 O 4 ) x . The prepared NiFe(C 2 O 4 ) x had a laminated shape and the size was in the range of 2-4 μm, and Ni was doped into catalyst's structure successfully. The NiFe(C 2 O 4 ) x had a synergistic effect of catalyst of 24.7 for methyl orange removal, and the dope of Ni significantly reduced the leaching of Fe by 77%. The reaction factors and kinetics were investigated. Under the optimal conditions, 0.4 g/L of catalyst dose and 10 mmol/L of hydrogen peroxide concentration, 98% of methyl orange was removed within 20 min. Analysis showed that hydroxyl radicals and superoxide radicals participated in the reaction. With NiFe(C 2 O 4 ) x catalyst, the suitable pH range for heterogeneous Fenton system was wide from 3 to 10. The catalyst showed good efficiency after five times re-use. NiFe(C 2 O 4 ) x provided great potential in treatment of refractory wastewater with excellent property. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Trichloroethene (TCE) hydrodechlorination by NiFe nanoparticles: Influence of aqueous anions on catalytic pathways.

    PubMed

    Han, Yanlai; Liu, Changjie; Horita, Juske; Yan, Weile

    2018-08-01

    Amending bulk and nanoscale zero-valent iron (ZVI) with catalytic metals significantly accelerates hydrodechlorination of groundwater contaminants such as trichloroethene (TCE). The bimetallic design benefits from a strong synergy between Ni and Fe in facilitating the production of active hydrogen for TCE reduction, and it is of research and practical interest to understand the impacts of common groundwater solutes on catalyst and ZVI functionality. In this study, TCE hydrodechlorination reaction was conducted using fresh NiFe bimetallic nanoparticles (NiFe BNPs) and those aged in chloride, sulfate, phosphate, and humic acid solutions with concurrent analysis of carbon fractionation of TCE and its daughter products. The apparent kinetics suggest that the reactivity of NiFe BNPs is relatively stable in pure water and chloride or humic acid solutions, in contrast to significant deactivation observed of PdFe bimetallic particles in similar media. Exposure to phosphate at greater than 0.1 mM led to a severe decrease in TCE reaction rate. The change in kinetic regimes from first to zeroth order with increasing phosphate concentration is consistent with consumption of reactive sites by phosphate. Despite severe kinetic effect, there is no significant shift in TCE 13 C bulk enrichment factor between the fresh and the phosphate-aged particles. Instead, pronounced retardation of TCE reaction by NiFe BNPs in deuterated water (D 2 O) points to the importance of hydrogen spillover in controlling TCE reduction rate by NiFe BNPs, and such process can be strongly affected by groundwater chemistry. Copyright © 2018 Elsevier Ltd. All rights reserved.

  16. Highly active and stable Ni-Fe bimetal prepared by ball milling for catalytic hydrodechlorination of 4-chlorophenol.

    PubMed

    Xu, Fuyuan; Deng, Shubo; Xu, Jie; Zhang, Wang; Wu, Min; Wang, Bin; Huang, Jun; Yu, Gang

    2012-04-17

    A novel Ni-Fe bimetal with high dechlorination activity for 4-chlorophenol (4-CP) was prepared by ball milling (BM) in this study. Increasing Ni content and milling time greatly enhanced the dechlorination activity, which was mainly attributed to the homogeneous distribution of Ni nanoparticles (50-100 nm) in bulk Fe visualized by scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) with image mapping. In comparison with the Ni-Fe bimetal prepared by a chemical solution deposition (CSD) process, the ball milled Ni-Fe bimetal possessed high dechlorination activity and stability before being used up. Dechlorination kinetics indicated that the dechlorination rates of 4-CP increased with increasing Ni-Fe dose but decreased with increasing solution pH. Solution pH had a significant effect on the dechlorination of 4-CP and the passivation of the Ni-Fe bimetal. The enhanced pH during the dechlorination process significantly accelerated the formation of passivating film on the bimetallic surface. The Ni-Fe bimetal at the dose of 60 g/L was reused 10 times without losing dechlorination activity for 4-CP at initial pH less than 6.0, but the gradual passivation was observed at initial pH above 7.0.

  17. First principles study of the magnetic properties and charge transfer of Ni-doped BiFeO3

    NASA Astrophysics Data System (ADS)

    Sun, Yuan; Sun, Zhenghao; Wei, Ren; Huang, Yuxin; Wang, Lili; Leng, Jing; Xiang, Peng; Lan, Min

    2018-03-01

    We present a first-principles study of electronic structures and magnetic properties in Ni-doped BiFeO3 using the density functional theory + U methods. The BiNixFe1-xO3 (x = 0.125, 0.25, 0.5) multiferroic ceramics represent ferromagnetic properties due to the ferrimagnetic order in Ni-O-Fe, and the magnetic moment rises with increase in Ni doping concentration agreeing well with experimental results. Ni atoms prefer to occupy the diagonal positions in the quasi-plane Ni-O-Fe eight-membered ring. Charge transfer from Bi 6s state to Ni 3d state through O 2p orbital lead to the 2+ oxidation state of Ni, indicating high Néel temperatures of BiNixFe1-xO3, and the electronic state of the system can be described as Bi4+xBi3+1-xNi2+xFe3+1-xO3. The spin polarization of Bi 6s state and O 2p state near the Fermi level contributes to the total magnetic moment. A spin-polarized acceptor level of about 0.4 eV constituted by Bi 6s state and O 2p state is found, which is responsible for the increase in leakage current of Ni-doped BiFeO3.

  18. Influence of Oxalate on Ni Fate during Fe(II)-Catalyzed Recrystallization of Hematite and Goethite.

    PubMed

    Flynn, Elaine D; Catalano, Jeffrey G

    2018-06-05

    During biogeochemical iron cycling at redox interfaces, dissolved Fe(II) induces the recrystallization of Fe(III) oxides. Oxalate and other organic acids promote dissolution of these minerals and may also induce recrystallization. These processes may redistribute trace metals among the mineral bulk, mineral surface, and aqueous solution. However, the impact of interactions among organic acids, dissolved Fe(II), and iron oxide minerals on trace metal fate in such systems is unclear. The present study thus explores the effect of oxalate on Ni release from and incorporation into hematite and goethite in the absence and presence of Fe(II). When Ni is initially structurally incorporated into the iron oxides, both oxalate and dissolved Fe(II) promote the release of Ni to aqueous solution. When both species are present, their effects on Ni release are synergistic at pH 7 but inhibitory at pH 4, indicating that cooperative and competitive interactions vary with pH. In contrast, oxalate suppresses Ni incorporation into goethite and hematite during Fe(II)-induced recrystallization, decreasing the proportion of Ni substituting in a mineral structure by up to 36%. These observations suggest that at redox interfaces oxalate largely enhances trace metal mobility. In such settings, oxalate, and likely other organic acids, may thus enhance micronutrient availability and inhibit contaminant sequestration.

  19. Research on microstructure properties of the TiC/Ni-Fe-Al coating prepared by laser cladding technology

    NASA Astrophysics Data System (ADS)

    Jiao, Junke; Xu, Zifa; Zan, Shaoping; Zhang, Wenwu; Sheng, Liyuan

    2017-10-01

    In this paper, the laser cladding method was used to preparation the TiC reinforced Ni-Fe-Al coating on the Ni base superalloy. The Ti/Ni-Fe-Al powder was preset on the Ni base superalloy and the powder layer thickness is 0.5mm. A fiber laser was used the melting Ti/Ni-Fe-Al powder in an inert gas environment. The shape of the cladding layer was tested using laser scanning confocal microscope (LSCM) under different cladding parameters such as the laser power, the melting velocity and the defocused amount. The microstructure, the micro-hardness was tested by LSCM, SEM, Vickers hardness tester. The test result showed that the TiC particles was distributed uniformly in the cladding layer and hardness of the cladding layer was improved from 180HV to 320HV compared with the Ni-Fe-Al cladding layer without TiC powder reinforced, and a metallurgical bonding was produced between the cladding layer and the base metal. The TiC powder could make the Ni-Fe-Al cladding layer grain refining, and the more TiC powder added in the Ni-Fe-Al powder, the smaller grain size was in the cladding layer.

  20. A study of the properties and microstructure of Ni 81Fe 19 ultrathin films with MgO

    NASA Astrophysics Data System (ADS)

    Li, Minghua; Han, Gan; Ding, Lei; Wang, Xiaocui; Liu, Yang; Feng, Chun; Wang, Haicheng; Yu, Guanghua

    2012-01-01

    The anisotropic magnetoresistance (AMR) of a Ta (5 nm)/MgO (3 nm)/Ni81Fe19 (10 nm)/MgO (2 nm)/Ta (3 nm) film with MgO-Nano Oxide Layer (NOL) increases dramatically from 1.05% to 3.24% compared with a Ta (5 nm)/Ni81Fe19 (10 nm)/Ta (3 nm) film without the MgO-NOL layer after annealing at 380 °C for 2 h. Although the MgO destroys the NiFe (1 1 1) texture, it enhances the specular electron scattering of the conduction electrons at the NOL interface and suppresses the interface reactions and diffusion at the Ta/NiFe and NiFe/Ta interfaces. The NiFe (1 1 1) texture was formed after the annealing, resulting in a higher AMR ratio. X-ray photoelectron spectroscope results show that Mg and Mg2+ were present in the MgOx films.

  1. Concerto catalysis--harmonising [NiFe]hydrogenase and NiRu model catalysts.

    PubMed

    Ichikawa, Koji; Nonaka, Kyoshiro; Matsumoto, Takahiro; Kure, Bunsho; Yoon, Ki-Seok; Higuchi, Yoshiki; Yagi, Tatsuhiko; Ogo, Seiji

    2010-03-28

    This communication reports the successful merging of the chemical properties of a natural [NiFe]hydrogenase (Desulfovibrio vulgaris Miyazaki F) and our previously reported [NiRu] hydrogenase-mimic. The catalytic activity of both the natural enzyme and the mimic is almost identical, with the exception of working pH ranges, and this allows us to use them simultaneously in the same reaction flask. In such a manner, isotope exchange between D(2) and H(2)O could be conducted over an extended pH range (about 2-10) in one pot under mild conditions at ambient temperature and pressure.

  2. Freestanding NiFe Oxyfluoride Holey Film with Ultrahigh Volumetric Capacitance for Flexible Asymmetric Supercapacitors.

    PubMed

    Liang, Kun; Marcus, Kyle; Yang, Zhenzhong; Zhou, Le; Pan, Hao; Bai, Yuanli; Du, Yingge; Engelhard, Mark H; Yang, Yang

    2018-01-01

    In this work, a freestanding NiFe oxyfluoride (NiFeOF) holey film is prepared by electrochemical deposition and anodic treatments. With the combination of good electrical conductivity and holey structure, the NiFeOF holey film offers superior electrochemical performance with maximum specific capacitance of 670 F cm -3 (134 mF cm -2 ), due to the following reasons: (i) The residual metal alloy framework can be used as the current collector to improve electrode conductivity. Moreover, the as-prepared freestanding NiFeOF holey film can be used as a supercapacitor electrode without reliance on binders and other additives. The residual metal alloy framework and binder-free electrode effectively reduce electrode resistance, thus improving electron transport. (ii) The highly interconnected holey structure and hierarchical pore distribution provide a high specific surface area to improve electron transport, enhancing rapid ion transport, and mitigating diffusion limitations throughout the holey film. (iii) The excellent mechanical characteristics facilitate flexibility and cyclability related performance. Additionally, the NiFeOF holey film presents exceptional electrochemical performance, showing that it is a promising alternative for small/microsize electronic devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Optimization of NiFe2O4/rGO composite electrode for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Li, Chen; Wang, Xia; Li, Shandong; Li, Qiang; Xu, Jie; Liu, Xiaomin; Liu, Changkun; Xu, Yuanhong; Liu, Jingquan; Li, Hongliang; Guo, Peizhi; Zhao, Xiu Song

    2017-09-01

    The combination of carbon compositing and the proper choice of binders in one system offer an effective strategy for improving electrode performance for lithium ion batteries (LIBs). Here, we focus on the optimization of reduced graphene oxide content in NiFe2O4/reduced graphene oxide (abbreviated to NiFe2O4/rGO) composites and the proper choice of binders to enhance the cycling stability of the NiFe2O4 electrode. The NiFe2O4/rGO composites were fabricated by a hydrothermal-annealing method, in which the mean size of spinel NiFe2O4 nanoparticles was approximately 20 nm. When tested as anode materials for LIBs, the NiFe2O4/rGO electrodes with carboxymethylcellulose (CMC) binder exhibited excellent lithium-storage performance including high reversible capacity, good cycling durability and high-rate capability. The capacity could be retained as high as 1105 mAh g-1 at a current density of 100 mA g-1 for over 50 cycles, even cycled at higher current density of 1000 mA g-1, a capacity of 800 mAh g-1can be obtained, whereas the electrode with the polyvinylidene fluoride (PVDF) binder suffered from rapid capacity decay under the same test conditions. As a result, the NiFe2O4/rGO composites with CMC binder electrode in this work are promising as anodes for high-performance LIBs, resulting from the synergistic effect of optimal graphene content and proper choice of binder.

  4. The role of Ag buffer layer in Fe islands growth on Ge (111) surfaces

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fu, Tsu-Yi, E-mail: phtifu@phy.ntnu.edu.tw; Wu, Jia-Yuan; Jhou, Ming-Kuan

    2015-05-07

    Sub-monolayer iron atoms were deposited at room temperature on Ge (111)-c(2 × 8) substrates with and without Ag buffer layers. The behavior of Fe islands growth was investigated by using scanning tunneling microscope (STM) after different annealing temperatures. STM images show that iron atoms will cause defects and holes on substrates at room temperature. As the annealing temperature rises, iron atoms pull out germanium to form various kinds of alloyed islands. However, the silver layer can protect the Ag/Ge(111)-(√3×√3) reconstruction from forming defects. The phase diagram shows that ring, dot, and triangular defects were only found on Ge (111)-c(2 × 8) substrates. The kindsmore » of islands found in Fe/Ge system are similar to Fe/Ag/Ge system. It indicates that Ge atoms were pulled out to form islands at high annealing temperatures whether there was a Ag layer or not. But a few differences in big pyramidal or strip islands show that the silver layer affects the development of islands by changing the surface symmetry and diffusion coefficient. The structure characters of various islands are also discussed.« less

  5. Giant magnetoresistance (GMR) behavior of electrodeposited NiFe/Cu multilayers: Dependence of non-magnetic and magnetic layer thicknesses

    NASA Astrophysics Data System (ADS)

    Kuru, Hilal; Kockar, Hakan; Alper, Mursel

    2017-12-01

    Giant magnetoresistance (GMR) behavior in electrodeposited NiFe/Cu multilayers was investigated as a function of non-magnetic (Cu) and ferromagnetic (NiFe) layer thicknesses, respectively. Prior to the GMR analysis, structural and magnetic analyses of the multilayers were also studied. The elemental analysis of the multilayers indicated that the Cu and Ni content in the multilayers increase with increasing Cu and NiFe layer thickness, respectively. The structural studies by X-ray diffraction revealed that all multilayers have face centred cubic structure with preferred (1 1 0) crystal orientation as their substrates. The magnetic properties studied with the vibrating sample magnetometer showed that the magnetizations of the samples are significantly affected by the layer thicknesses. Saturation magnetisation, Ms increases from 45 to 225 emu/cm3 with increasing NiFe layer thickness. The increase in the Ni content of the multilayers with a small Fe content causes an increase in the Ms. And, the coercivities ranging from 2 to 24 Oe are between the soft and hard magnetic properties. Also, the magnetic easy axis of the multilayers was found to be in the film plane. Magnetoresistance measurements showed that all multilayers exhibited the GMR behavior. The GMR magnitude increases with increasing Cu layer thickness and reaches its maximum value of 10% at the Cu layer thickness of 1 nm, then it decreases. And similarly, the GMR magnitude increases and reaches highest value of pure GMR (10%) for the NiFe layer thickness of 3 nm, and beyond this point GMR decreases with increasing NiFe layer thickness. Some small component of the anisotropic magnetoresistance was also observed at thin Cu and thick NiFe layer thicknesses. It is seen that the highest GMR values up to 10% were obtained in electrodeposited NiFe/Cu multilayers up to now. The structural, magnetic and magnetoresistance properties of the NiFe/Cu were reported via the variations of the thicknesses of Cu and NiFe

  6. A Threonine Stabilizes the NiC and NiR Catalytic Intermediates of [NiFe]-hydrogenase*

    PubMed Central

    Abou-Hamdan, Abbas; Ceccaldi, Pierre; Lebrette, Hugo; Gutiérrez-Sanz, Oscar; Richaud, Pierre; Cournac, Laurent; Guigliarelli, Bruno; De Lacey, Antonio L.; Léger, Christophe; Volbeda, Anne; Burlat, Bénédicte; Dementin, Sébastien

    2015-01-01

    The heterodimeric [NiFe] hydrogenase from Desulfovibrio fructosovorans catalyzes the reversible oxidation of H2 into protons and electrons. The catalytic intermediates have been attributed to forms of the active site (NiSI, NiR, and NiC) detected using spectroscopic methods under potentiometric but non-catalytic conditions. Here, we produced variants by replacing the conserved Thr-18 residue in the small subunit with Ser, Val, Gln, Gly, or Asp, and we analyzed the effects of these mutations on the kinetic (H2 oxidation, H2 production, and H/D exchange), spectroscopic (IR, EPR), and structural properties of the enzyme. The mutations disrupt the H-bond network in the crystals and have a strong effect on H2 oxidation and H2 production turnover rates. However, the absence of correlation between activity and rate of H/D exchange in the series of variants suggests that the alcoholic group of Thr-18 is not necessarily a proton relay. Instead, the correlation between H2 oxidation and production activity and the detection of the NiC species in reduced samples confirms that NiC is a catalytic intermediate and suggests that Thr-18 is important to stabilize the local protein structure of the active site ensuring fast NiSI-NiC-NiR interconversions during H2 oxidation/production. PMID:25666617

  7. A threonine stabilizes the NiC and NiR catalytic intermediates of [NiFe]-hydrogenase.

    PubMed

    Abou-Hamdan, Abbas; Ceccaldi, Pierre; Lebrette, Hugo; Gutiérrez-Sanz, Oscar; Richaud, Pierre; Cournac, Laurent; Guigliarelli, Bruno; De Lacey, Antonio L; Léger, Christophe; Volbeda, Anne; Burlat, Bénédicte; Dementin, Sébastien

    2015-03-27

    The heterodimeric [NiFe] hydrogenase from Desulfovibrio fructosovorans catalyzes the reversible oxidation of H2 into protons and electrons. The catalytic intermediates have been attributed to forms of the active site (NiSI, NiR, and NiC) detected using spectroscopic methods under potentiometric but non-catalytic conditions. Here, we produced variants by replacing the conserved Thr-18 residue in the small subunit with Ser, Val, Gln, Gly, or Asp, and we analyzed the effects of these mutations on the kinetic (H2 oxidation, H2 production, and H/D exchange), spectroscopic (IR, EPR), and structural properties of the enzyme. The mutations disrupt the H-bond network in the crystals and have a strong effect on H2 oxidation and H2 production turnover rates. However, the absence of correlation between activity and rate of H/D exchange in the series of variants suggests that the alcoholic group of Thr-18 is not necessarily a proton relay. Instead, the correlation between H2 oxidation and production activity and the detection of the NiC species in reduced samples confirms that NiC is a catalytic intermediate and suggests that Thr-18 is important to stabilize the local protein structure of the active site ensuring fast NiSI-NiC-NiR interconversions during H2 oxidation/production. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  8. Multilayer Ni/Fe thin films as oxygen evolution catalysts for solar fuel production

    NASA Astrophysics Data System (ADS)

    Biset-Peiró, M.; Murcia-López, S.; Fàbrega, C.; Morante, J. R.; Andreu, T.

    2017-03-01

    The slow kinetics and high overpotential of the oxygen evolution reaction is one of the main limiting factors to achieve the minimum required performances of the so-called photoelectrochemical water splitting systems. An oxygen evolution catalyst (OEC) becomes essential in order to perform this process with higher efficiency. Herein, we report the physical, optical and electrochemical characterization of multilayer Ni/Fe thin films as earth-abundant OEC, to avoid the use of platinum group metals (PGM). Uniform films of thicknesses ranging from 1 to 10 nm were fabricated by sequential and alternate thermal evaporation of Ni and Fe. It was found that the successive deposition allows the fabrication of a Ni terminated surface that does not need activation due to the Fe underlayer. The lowest overpotential achieved for NiFe was 370 mV at 10 mA cm-2 and a Tafel slope of 37 mV dec-1 with 1 nm thickness and 95% transmittance. Finally, NiFe OEC was implemented on top of Mo:BiVO4 photoanodes which resulted in a reduction of the open circuit potential of 0.2 V and up to five fold increase of the oxidation efficiency at 0.7 VRHE. The results presented facilitate the practical implementation of BiVO4 photoanodes in tandem configuration for bias free photoassisted water splitting.

  9. Note: Erosion of W-Ni-Fe and W-Cu alloy electrodes in repetitive spark gaps.

    PubMed

    Wu, Jiawei; Han, Ruoyu; Ding, Weidong; Qiu, Aici; Tang, Junping

    2018-02-01

    A pair of W-Ni-Fe and W-Cu electrodes were tested under 100 kA level pulsed currents for 10 000 shots, respectively. Surface roughness and morphology characteristics of the two pairs of electrodes were obtained and compared. Experimental results indicated cracks divided the W-Cu electrode surface to polygons while the W-Ni-Fe electrode surface remained as a whole with pits and protrusions. Accordingly, the surface roughness of W-Ni-Fe electrodes increased to ∼3 μm while that of W-Cu electrodes reached ∼7 μm at the end of the test. The results reveal that the W-Ni-Fe alloy has a better erosion resistance and potential to be further applied in spark gaps.

  10. Formation of NiFe2O4/Expanded Graphite Nanocomposites with Superior Lithium Storage Properties

    NASA Astrophysics Data System (ADS)

    Xiao, Yinglin; Zai, Jiantao; Tian, Bingbing; Qian, Xuefeng

    2017-07-01

    A NiFe2O4/expanded graphite (NiFe2O4/EG) nanocomposite was prepared via a simple and inexpensive synthesis method. Its lithium storage properties were studied with the goal of applying it as an anode in a lithium-ion battery. The obtained nanocomposite exhibited a good cycle performance, with a capacity of 601 mAh g-1 at a current of 1 A g-1 after 800 cycles. This good performance may be attributed to the enhanced electrical conductivity and layered structure of the EG. Its high mechanical strength could postpone the disintegration of the nanocomposite structure, efficiently accommodate volume changes in the NiFe2O4-based anodes, and alleviate aggregation of NiFe2O4 nanoparticles.

  11. Hydrogens detected by subatomic resolution protein crystallography in a [NiFe] hydrogenase.

    PubMed

    Ogata, Hideaki; Nishikawa, Koji; Lubitz, Wolfgang

    2015-04-23

    The enzyme hydrogenase reversibly converts dihydrogen to protons and electrons at a metal catalyst. The location of the abundant hydrogens is of key importance for understanding structure and function of the protein. However, in protein X-ray crystallography the detection of hydrogen atoms is one of the major problems, since they display only weak contributions to diffraction and the quality of the single crystals is often insufficient to obtain sub-ångström resolution. Here we report the crystal structure of a standard [NiFe] hydrogenase (∼91.3 kDa molecular mass) at 0.89 Å resolution. The strictly anoxically isolated hydrogenase has been obtained in a specific spectroscopic state, the active reduced Ni-R (subform Ni-R1) state. The high resolution, proper refinement strategy and careful modelling allow the positioning of a large part of the hydrogen atoms in the structure. This has led to the direct detection of the products of the heterolytic splitting of dihydrogen into a hydride (H(-)) bridging the Ni and Fe and a proton (H(+)) attached to the sulphur of a cysteine ligand. The Ni-H(-) and Fe-H(-) bond lengths are 1.58 Å and 1.78Å, respectively. Furthermore, we can assign the Fe-CO and Fe-CN(-) ligands at the active site, and can obtain the hydrogen-bond networks and the preferred proton transfer pathway in the hydrogenase. Our results demonstrate the precise comprehensive information available from ultra-high-resolution structures of proteins as an alternative to neutron diffraction and other methods such as NMR structural analysis.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  13. First-Principles Study on the Gilbert Damping Constants of Transition Metal Alloys, Fe--Ni and Fe--Pt Systems

    NASA Astrophysics Data System (ADS)

    Sakuma, Akimasa

    2012-08-01

    We adapt the tight-binding linear muffin-tin orbital (TB-LMTO) method to the torque-correlation model for the Gilbert damping constant α and perform the first-principles calculation for disordered transition metal alloys, Fe--Ni and Fe--Pt systems, within the framework of the CPA. Quantitatively, the calculated α values are about one-half of the experimental values, whereas the variations in the Fermi level dependence of α are much larger than these discrepancies. As expected, we confirm in the (Fe--Ni)1-XPtX and FePt systems that Pt atoms certainly enhance α owing to their large spin--orbit coupling. For the disordered alloys, we find that α decreases with increasing chemical degree of order in a wide range.

  14. Out-of-plane coercive field of Ni 80Fe 20 antidot arrays

    NASA Astrophysics Data System (ADS)

    Gao, Chunhong; Chen, Ke; Lü, Ling; Zhao, Jianwei; Chen, Peng

    2010-11-01

    The out-of-plane magnetic anisotropy and out-of-plane magnetization reversal process of nanoscale Ni 80Fe 20 antidot arrays deposited by magnetron sputtering technique on an anodic aluminum oxide (AAO) membrane are investigated. The angular dependence of out-of-plane remanent magnetization of Ni 80Fe 20 antidot arrays shows that the maximum remanence is in-plane and the squareness of the out-of-plane hysteresis loop follow a |cos θ| dependence. The angular dependence of out-of-plane coercivity of Ni 80Fe 20 antidot arrays shows that the maximum coercivity lies on the surface of a cone with its symmetric axis normal to the sample plane, which indicates a transition of magnetic reversal from curling to coherent rotation when changing the angle between the applied magnetic field and the sample plane.

  15. Crystallographic studies of [NiFe]-hydrogenase mutants: towards consensus structures for the elusive unready oxidized states.

    PubMed

    Volbeda, Anne; Martin, Lydie; Barbier, Elodie; Gutiérrez-Sanz, Oscar; De Lacey, Antonio L; Liebgott, Pierre-Pol; Dementin, Sébastien; Rousset, Marc; Fontecilla-Camps, Juan C

    2015-01-01

    Catalytically inactive oxidized O2-sensitive [NiFe]-hydrogenases are characterized by a mixture of the paramagnetic Ni-A and Ni-B states. Upon O2 exposure, enzymes in a partially reduced state preferentially form the unready Ni-A state. Because partial O2 reduction should generate a peroxide intermediate, this species was previously assigned to the elongated Ni-Fe bridging electron density observed for preparations of [NiFe]-hydrogenases known to contain the Ni-A state. However, this proposition has been challenged based on the stability of this state to UV light exposure and the possibility of generating it anaerobically under either chemical or electrochemical oxidizing conditions. Consequently, we have considered alternative structures for the Ni-A species including oxidation of thiolate ligands to either sulfenate or sulfenic acid. Here, we report both new and revised [NiFe]-hydrogenases structures and conclude, taking into account corresponding characterizations by Fourier transform infrared spectroscopy (FTIR), that the Ni-A species contains oxidized cysteine and bridging hydroxide ligands instead of the peroxide ligand we proposed earlier. Our analysis was rendered difficult by the typical formation of mixtures of unready oxidized states that, furthermore, can be reduced by X-ray induced photoelectrons. The present study could be carried out thanks to the use of Desulfovibrio fructosovorans [NiFe]-hydrogenase mutants with special properties. In addition to the Ni-A state, crystallographic results are also reported for two diamagnetic unready states, allowing the proposal of a revised oxidized inactive Ni-SU model and a new structure characterized by a persulfide ion that is assigned to an Ni-'Sox' species.

  16. Porous Ni-Fe alloys as anode support for intermediate temperature solid oxide fuel cells: I. Fabrication, redox and thermal behaviors

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Li, Kai; Jia, Lichao; Zhang, Qian; Jiang, San Ping; Chi, Bo; Pu, Jian; Jian, Li; Yan, Dong

    2015-03-01

    Porous Ni-Fe anode supports for intermediate solid oxide fuel cells are prepared by reducing the sintered NiO-(0-50 wt. %) Fe2O3 composites in H2, their microstructure, redox and thermal expansion/cycling characteristics are systematically investigated. The sintered NiO-Fe2O3 composites are consisted of NiO and NiFe2O4, and are fully reducible to porous metallic Ni-Fe alloys in H2 at temperatures between 600 and 750 °C. The porous structure contains pores in bimodal distribution with larger pores between the sintered particles and smaller ones inside the particles. The oxidation resistance of the Ni-Fe alloy anode supports at 600 and 750 °C is increased by the addition of Fe, their oxidation kinetics obeys a multistage parabolic law in the form of (Percentageweightgain /Specificsurfacearea) 2 =kp · t , where kp is the rate constant and t the oxidation time. The dimension of the Ni-Fe anode supports is slightly changed without disintegrating their structure, and Fe addition is beneficial to the redox stability. The TEC of the Ni-Fe alloy anode supports decreases with the increase of Fe content. The anode supports containing Fe is less stable in dimension during thermal cycles due to the continuous sintering, but the dimension change after thermal cycles is within 1%.

  17. SERS active Ag encapsulated Fe@SiO2 nanorods in electromagnetic wave absorption and crystal violet detection.

    PubMed

    Senapati, Samarpita; Srivastava, Suneel Kumar; Singh, Shiv Brat; Kulkarni, Ajit R

    2014-11-01

    The present work is focused on the preparation of Fe nanorods by the chemical reduction of FeCl3 (aq) using NaBH4 in the presence of glycerol as template followed by annealing of the product at 500°C in the presence of H2 gas flow. Subsequently, its surface has been modified by silica followed by silver nanoparticles to form silica coated Fe (Fe@SiO2) and Ag encapsulated Fe@SiO2 nanostructure employing the Stöber method and silver mirror reaction respectively. XRD pattern of the products confirmed the formation of bcc phase of iron and fcc phase of silver, though silica remained amorphous. FESEM images established the growth of iron nanorods from the annealed product and also formation of silica and silver coating on its surface. The appearance of the characteristics bands in FTIR confirmed the presence of SiO2 on the Fe surface. Magnetic measurements at room temperature indicated the ferromagnetic behavior of as prepared iron nanorods, Fe@SiO2 and silver encapsulated Fe@SiO2 nanostructures. All the samples exhibited strong microwave absorption property in the high frequency range (10GHz), though it is superior for Ag encapsulated Fe@SiO2 (-14.7dB) compared with Fe@SiO2 (-9.7dB) nanostructures of the same thickness. The synthesized Ag encapsulated Fe@SiO2 nanostructure also exhibited the SERS phenomena, which is useful in the detection of the carcinogenic dye crystal violet (CV) upto the concentration of 10(-10)M. All these findings clearly demonstrate that the Ag encapsulated Fe@SiO2 nanostructure could efficiently be used in the environmental remediation. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Micro/nanostructured porous Fe-Ni binary oxide and its enhanced arsenic adsorption performances.

    PubMed

    Liu, Shengwen; Kang, Shenghong; Wang, Guozhong; Zhao, Huijun; Cai, Weiping

    2015-11-15

    A simple method is presented to synthesize micro/nano-structured Fe-Ni binary oxides based on co-precipitation and subsequent calcination. It has been found that the Fe-Ni binary oxides are composed of the porous microsized aggregates built with nanoparticles. When the atomic ratio of Fe to Ni is 2 to 1 the binary oxide is the micro-scaled aggregates consisting of the ultrafine NiFe2O4 nanoparticles with 3-6nm in size, and shows porous structure with pore diameter of 3nm and a specific surface area of 245m(2)g(-1). Such material is of abundant surface functional groups and has exhibited high adsorption performance to As(III) and As(V). The kinetic adsorption can be described by pseudo-second order model and the isothermal adsorption is subject to Langmuir model. The maximum adsorption capacity on such Fe-Ni porous binary oxide is up to 168.6mgg(-1) and 90.1mgg(-1) for As(III) and As(V), respectively, which are much higher than the arsenic adsorption capacity for most commercial adsorbents. Such enhanced adsorption ability for this material is mainly attributed to its porous structure and high specific surface area as well as the abundant surface functional groups. Further experiments have revealed that the influence of the anions such as sulfate, carbonate, and phosphate, which commonly co-exist in water, on the arsenic adsorption is insignificant, exhibiting strong adsorption selectivity to arsenic. This micro/nano-structured porous Fe-Ni binary oxide is hence of good practicability to be used as a highly efficient adsorbent for arsenic removal from the real arsenic-contaminated waters. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Reversible [4Fe-3S] cluster morphing in an O(2)-tolerant [NiFe] hydrogenase.

    PubMed

    Frielingsdorf, Stefan; Fritsch, Johannes; Schmidt, Andrea; Hammer, Mathias; Löwenstein, Julia; Siebert, Elisabeth; Pelmenschikov, Vladimir; Jaenicke, Tina; Kalms, Jacqueline; Rippers, Yvonne; Lendzian, Friedhelm; Zebger, Ingo; Teutloff, Christian; Kaupp, Martin; Bittl, Robert; Hildebrandt, Peter; Friedrich, Bärbel; Lenz, Oliver; Scheerer, Patrick

    2014-05-01

    Hydrogenases catalyze the reversible oxidation of H(2) into protons and electrons and are usually readily inactivated by O(2). However, a subgroup of the [NiFe] hydrogenases, including the membrane-bound [NiFe] hydrogenase from Ralstonia eutropha, has evolved remarkable tolerance toward O(2) that enables their host organisms to utilize H(2) as an energy source at high O(2). This feature is crucially based on a unique six cysteine-coordinated [4Fe-3S] cluster located close to the catalytic center, whose properties were investigated in this study using a multidisciplinary approach. The [4Fe-3S] cluster undergoes redox-dependent reversible transformations, namely iron swapping between a sulfide and a peptide amide N. Moreover, our investigations unraveled the redox-dependent and reversible occurence of an oxygen ligand located at a different iron. This ligand is hydrogen bonded to a conserved histidine that is essential for H(2) oxidation at high O(2). We propose that these transformations, reminiscent of those of the P-cluster of nitrogenase, enable the consecutive transfer of two electrons within a physiological potential range.

  20. Mechanisms of radiation-induced segregation in CrFeCoNi-based single-phase concentrated solid solution alloys

    DOE PAGES

    He, Mo-Rigen; Wang, Shuai; Shi, Shi; ...

    2016-12-31

    Single-phase concentrated solid solution alloys have attracted wide interest due to their superior mechanical properties and enhanced radiation tolerance, which make them promising candidates for the structural applications in next-generation nuclear reactors. However, little has been understood about the intrinsic stability of their as-synthesized, high-entropy configurations against radiation damage. In this paper, we report the element segregation in CrFeCoNi, CrFeCoNiMn, and CrFeCoNiPd equiatomic alloys when subjected to 1250 kV electron irradiations at 400 °C up to a damage level of 1 displacement per atom. Cr/Fe/Mn/Pd can deplete and Co/Ni can accumulate at radiation-induced dislocation loops, while the actively segregating elementsmore » are alloy-specific. Moreover, electron-irradiated matrix of CrFeCoNiMn and CrFeCoNiPd shows L1 0 (NiMn)-type ordering decomposition and <001>-oriented spinodal decomposition between Co/Ni and Pd, respectively. Finally, these findings are rationalized based on the atomic size difference and enthalpy of mixing between the alloying elements, and identify a new important requirement to the design of radiation-tolerant alloys through modification of the composition.« less

  1. Electronic structure of Fe, Co, and Ni impurities in Pd

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    van Acker, J.F.; Weijs, P.W.J.; Fuggle, J.C.

    1988-11-15

    A photoemission study of the valence bands of the dilute alloys PdFe, PdCo, and PdNi is presented. We use the Cooper minimum effect to estimate the local density of states on the impurity site. The behavior of transition-metal impurities in a transition-metal matrix is shown to be very different from their behavior in s-p metals. Our conclusion is that the Fe and Co 3d states are mixed with states throughout the Pd 4d band, while the Ni contribution to the spectra is dominated by a peak of (minority) 3d states near the Fermi level.

  2. Prediction of the new efficient permanent magnet SmCoNiFe3

    NASA Astrophysics Data System (ADS)

    Söderlind, P.; Landa, A.; Locht, I. L. M.; Åberg, D.; Kvashnin, Y.; Pereiro, M.; Däne, M.; Turchi, P. E. A.; Antropov, V. P.; Eriksson, O.

    2017-09-01

    We propose a new efficient permanent magnet, SmCoNiFe3, which is a development of the well-known SmCo5 prototype. More modern neodymium magnets of the Nd-Fe-B type have an advantage over SmCo5 because of their greater maximum energy products due to their iron-rich stoichiometry. Our new magnet, however, removes most of this disadvantage of SmCo5 while preserving its superior high-temperature efficiency over the neodymium magnets. We show by means of first-principles electronic-structure calculations that SmCoNiFe3 has very favorable magnetic properties and could therefore potentially replace SmCo5 or Nd-Fe-B types in various applications.

  3. Prediction of the new efficient permanent magnet SmCoNiFe 3

    DOE PAGES

    Soderlind, P.; Landa, A.; Locht, I. L. M.; ...

    2017-09-14

    Here, we propose a new efficient permanent magnet, SmCoNiFe 3, which is a development of the well-known SmCo 5 prototype. More modern neodymium magnets of the Nd-Fe-B type have an advantage over SmCo 5 because of their greater maximum energy products due to their iron-rich stoichiometry. Our new magnet, however, removes most of this disadvantage of SmCo 5 while preserving its superior high-temperature efficiency over the neodymium magnets. We show by means of first-principles electronic-structure calculations that SmCoNiFe 3 has very favorable magnetic properties and could therefore potentially replace SmCo 5 or Nd-Fe-B types in various applications.

  4. Magnetic properties of mixed spinel BaTiO{sub 3}-NiFe{sub 2}O{sub 4} composites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sarkar, Babusona; Dalal, Biswajit; Dev Ashok, Vishal

    2014-03-28

    Solid solution of nickel ferrite (NiFe{sub 2}O{sub 4}) and barium titanate (BaTiO{sub 3}), (100-x)BaTiO{sub 3}–(x) NiFe{sub 2}O{sub 4} has been prepared by solid state reaction. Compressive strain is developed in NiFe{sub 2}O{sub 4} due to mutual structural interaction across the interface of NiFe{sub 2}O{sub 4} and BaTiO{sub 3} phases. Quantitative analysis of X-ray diffraction and X-ray photo electron spectrum suggest mixed spinel structure of NiFe{sub 2}O{sub 4}. A systematic study of composition dependence of composite indicates BaTiO{sub 3} causes a random distribution of Fe and Ni cations among octahedral and tetrahedral sites during non-equilibrium growth of NiFe{sub 2}O{sub 4}. Themore » degree of inversion decreases monotonically from 0.97 to 0.75 with increase of BaTiO{sub 3} content. Temperature dependence of magnetization has been analyzed by four sublattice model to describe complex magnetic exchange interactions in mixed spinel phase. Curie temperature and saturation magnetization decrease with increase of BaTiO{sub 3} concentration. Enhancement of strain and larger occupancy of Ni{sup 2+} at tetrahedral site increase coercivity up to 200 Oe. Magnetostructual coupling induced by BaTiO{sub 3} improves coercivity in NiFe{sub 2}O{sub 4}. An increase in the demagnetization and homogeneity in magnetization process in NiFe{sub 2}O{sub 4} is observed due to the interaction with diamagnetic BaTiO{sub 3}.« less

  5. Spin-polarized confined states in Ag films on Fe(110)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Moras, Paolo; Bihlmayer, G.; Vescovo, Elio

    Spin- and angle-resolved photoemission spectroscopy of thin Ag(111) films on ferromagnetic Fe(110) shows a series of spin-polarized peaks. These features derive from Ag sp-bands, which form quantum well states and resonances due to confinement by a spin-dependent interface potential barrier. The spin-up states are broader and located at higher binding energy than the corresponding spin-down states at Gamma, although the differences attenuate near the Fermi level. The spin-down states display multiple gap openings, which interrupt their parabolic-like dispersion. As a result, first-principles calculations attribute these findings to the symmetry- and spin-selective hybridization of the Ag states with the exchange-split bandsmore » of the substrate.« less

  6. Spin-polarized confined states in Ag films on Fe(110)

    DOE PAGES

    Moras, Paolo; Bihlmayer, G.; Vescovo, Elio; ...

    2017-11-16

    Spin- and angle-resolved photoemission spectroscopy of thin Ag(111) films on ferromagnetic Fe(110) shows a series of spin-polarized peaks. These features derive from Ag sp-bands, which form quantum well states and resonances due to confinement by a spin-dependent interface potential barrier. The spin-up states are broader and located at higher binding energy than the corresponding spin-down states at Gamma, although the differences attenuate near the Fermi level. The spin-down states display multiple gap openings, which interrupt their parabolic-like dispersion. As a result, first-principles calculations attribute these findings to the symmetry- and spin-selective hybridization of the Ag states with the exchange-split bandsmore » of the substrate.« less

  7. Contrast studies of the process optimization and characterization of shielding fabric by amorphous Ni-Fe-P and Ni-P alloy

    NASA Astrophysics Data System (ADS)

    Yao, Kai; Wu, Xueyan; An, Zhentao

    2017-01-01

    A flexible shielding fabric with dense uniform coating was prepared after electrical deposition of amorphous Ni-Fe-P and Ni-P alloy on copper-coated polyethylene terephthalate (PET) fabric. The effects of coating composition and the deposition rate were discussed by the current density, temperature and pH value. The morphology, composition, and structure of coating were analyzed by SEM, EDS, and XRD characterizations. The EMI shielding effectiveness and corrosion resistance were also tested. The results fabric possesses dense, smooth, and uniform coating, when the processing conditions are 60°C, pH=1.5, and current density =8.7A/dm2. The coating fabric consists of amorphous Ni-Fe-P alloy with 16.62% P (weight percent), which has excellent of corrosion resistance. By contrast the EMI shielding effectiveness of amorphous Ni-Fe-P was better than amorphous Ni-P. The EMI shielding effectiveness of this coated fabric achieves 69.20dB-80.30dB in a broad frequency range between 300 kHz˜1.5 GHz.

  8. Tannic Acid/Fe3+/Ag Nanofilm Exhibiting Superior Photodynamic and Physical Antibacterial Activity.

    PubMed

    Xu, Ziqiang; Wang, Xiuhua; Liu, Xiangmei; Cui, Zhenduo; Yang, Xianjin; Yeung, Kelvin Wai Kwok; Chung, Jonathan Chiyuen; Chu, Paul K; Wu, Shuilin

    2017-11-15

    Silver nanoparticles (AgNPs) enwrapped in the biologically safe tannic acid (TA)/Fe 3+ nanofilm are synthesized by an ultrafast, green, simple, and universal method. The physical antibacterial activity and photodynamic antibacterial therapy (PAT) efficacy of the TA/Fe 3+ /AgNPs nanofilm were investigated for the first time, which exhibited a strong physical antibacterial activity as well as great biocompatibility, through in vitro and in vivo studies. The results disclosed that this hybrid coating could possess high PAT capabilities upon irradiation under a visible light of 660 nm, which is longer than those of previously reported green and blue sensitization light, thus allowing deeper light penetration into biological tissues. Electron spin resonance (ESR) spectra proved that the PAT efficacy of the TA/Fe 3+ /AgNPs nanofilm was associated with the yields of singlet oxygen ( 1 O 2 ) under the irradiation of visible light (660 nm). A higher PAT efficiency of 100 and 94% against Escherichia coli and Staphylococcus aureus could be achieved within 20 min of illumination under 660 nm visible light, whereas the innate physical antibacterial activity of AgNPs could endow the implants with long-term prevention of bacterial infection. The mechanism of PAT may be associated with the formation of oxidative stress and oxidative damage to key biomolecules (proteins and lipids) in bacteria. Our results reveal that the synergistic action of both PAT and physical action of AgNPs in this hybrid nanofilm is an effective way to inactivate bacteria, with minimal side effects.

  9. Synthesis and characterization of bracelet-like magnetic nanorings consisting of Ag-Fe3O4 bi-component nanoparticles.

    PubMed

    Zhou, Shuai; Chen, Qianwang

    2011-09-14

    Stable bracelet-like magnetic nanorings, formed by Ag-Fe(3)O(4) nanoparticles with an average size around 40 nm, have been successfully prepared in large scale by means of reducing Ag(+) and Fe(3+) simultaneously under mild conditions. In the reaction, tiny grains of silver are used as seeds to prompt small Fe(3)O(4) nanoparticles to grow larger, which is essential to enhance the magnetic dipole-dipole interactions, while only superparamagnetic Fe(3)O(4) nanoparticles (about 10 nm in size) can be obtained in the absence of Ag seeds. The XRD, TEM, SAED and the EDS line scan data reveal that these nanoparticles are in the core-shell structure. These magnetic Ag-Fe(3)O(4) nanoparticles assembled into nanorings by magnetic dipole-dipole interactions with a diameter of 100-200 nm. The saturation magnetization of the nanorings is 39.5 emu g(-1) at room temperature. The MRI images indicate that these kind of nanorings have the potential application in diagnostics as a T(2) MRI contrast agent. This journal is © The Royal Society of Chemistry 2011

  10. Vacancy-mediated fcc/bcc phase separation in Fe 1-xNi x ultrathin films

    DOE PAGES

    Mentes, T. O.; Stojic, N.; Vescovo, E.; ...

    2016-08-01

    The phase separation occurring in Fe-Ni thin lms near the Invar composition is studied by using high resolution spectromicroscopy techniques and density functional theory calculations. Annealed at temperatures around 300 C, Fe 0.70Ni 0.30 lms on W(110) break into micron-sized bcc and fcc domains with compositions in agreement with the bulk Fe-Ni phase diagram. Ni is found to be the di using species in forming the chemical heterogeneity. The experimentally-determined energy barrier of 1.59 0.09 eV is identi ed as the vacancy formation energy via density functional theory calculations. Thus, the principal role of the surface in the phase separationmore » process is attributed to vacancy creation without interstitials.« less

  11. Interfacial exchange interactions and magnetism of Ni2MnAl /Fe bilayers

    NASA Astrophysics Data System (ADS)

    Yanes, R.; Simon, E.; Keller, S.; Nagyfalusi, B.; Khmelevsky, S.; Szunyogh, L.; Nowak, U.

    2017-08-01

    Based on multiscale calculations combining ab initio methods with spin dynamics simulations, we perform a detailed study of the magnetic behavior of Ni2MnAl /Fe bilayers. Our simulations show that such a bilayer exhibits a small exchange bias effect when the Ni2MnAl Heusler alloy is in a disordered B2 phase. Additionally, we present an effective way to control the magnetic structure of the Ni2MnAl antiferromagnet, in the pseudo-ordered B2-I as well as the disordered B2 phases, via a spin-flop coupling to the Fe layer.

  12. Metal elution from Ni- and Fe-based alloy reactors under hydrothermal conditions.

    PubMed

    Faisal, Muhammad; Quitain, Armando T; Urano, Shin-Ya; Daimon, Hiroyuki; Fujie, Koichi

    2004-05-20

    Elution of metals from Ni- and Fe-based alloy (i.e. Inconel 625 and SUS 316) under hydrothermal conditions was investigated. Results showed that metals could be eluted even in a short contact time. At subcritical conditions, a significant amount of Cr was extracted from SUS 316, while only traces of Ni, Fe, Mo, and Mn were eluted. In contrast, Ni was removed in significant amounts compared to Cr when Inconel 625 was tested. Several factors including temperature and contact time were found to affect elution behavior. The presence of air in the fluid even promoted elution under subcritical conditions.

  13. In Situ Characterization of Ni and Ni/Fe Thin Film Electrodes for Oxygen Evolution in Alkaline Media by a Raman-Coupled Scanning Electrochemical Microscope Setup.

    PubMed

    Steimecke, Matthias; Seiffarth, Gerda; Bron, Michael

    2017-10-17

    We present a spectroelectrochemical setup, in which Raman microscopy is combined with scanning electrochemical microscopy (SECM) in order to provide both spectroscopic and electrochemical information on the very same location of an electrode at the same time. The setup is applied to a subject of high academic and practical interest, namely, the oxygen evolution reaction at Ni and Ni/Fe electrodes. It comprises a transparent substrate electrode, onto which Ni and Ni/Fe thin films are deposited. An ultramicroelectrode (UME) is placed closely above the substrate to obtain electrochemical information, while a Raman microscope probes the same sample spot from below. To obtain information on oxygen evolution activity and structural changes, increasingly positive potentials from 0.1 up to 0.7 V vs Hg|HgO|1 M KOH were applied to the Ni/Fe-electrodes in 0.1 M KOH solution. Evolved oxygen is detected by reduction at a Pt UME, allowing for the determination of onset potentials, while the substrate current, which is recorded in parallel, is due to both overlapping oxygen evolution and the oxidation of Ni(OH) 2 to NiOOH. An optimum of 15% Fe in Ni/Fe films with respect to oxygen evolution activity was determined. At the same time, the potential-dependent formation of γ-NiOOH characterized by the Raman double band at 475 and 557 cm -1 allows for the conclusion that a certain amount of disorder introduced by Fe atoms is necessary to obtain high oxygen evolution reaction (OER) activity.

  14. Defect controlled magnetism in FeP/graphene/Ni(111)

    PubMed Central

    Bhandary, Sumanta; Eriksson, Olle; Sanyal, Biplab

    2013-01-01

    Spin switching of organometallic complexes by ferromagnetic surfaces is an important topic in the area of molecular nanospintronics. Moreover, graphene has been shown as a 2D surface for physisorption of molecular magnets and strain engineering on graphene can tune the spin state of an iron porphyrin (FeP) molecule from S = 1 to S = 2. Our ab initio density functional calculations suggest that a pristine graphene layer placed between a Ni(111) surface and FeP yields an extremely weak exchange interaction between FeP and Ni whereas the introduction of defects in graphene shows a variety of ferromagnetic and antiferromagnetic exchange interactions. Moreover, these defects control the easy axes of magnetization, strengths of magnetic anisotropy energies and spin-dipolar contributions. Our study suggests a new way of manipulating molecular magnetism by defects in graphene and hence has the potential to be explored in designing spin qubits to realize logic operations in molecular nanospintronics. PMID:24296980

  15. Low frequency creep in CoNiFe films

    NASA Technical Reports Server (NTRS)

    Bartran, D. S.; Bourne, H. C., Jr.; Chow, L. G.

    1972-01-01

    The results of an investigation of domain wall motion excited by slow rise-time, bipolar, hard-axis pulses in vacuum deposited CoNiFe films 1500A to 2000A thick are presented. The results are consistent with those of comparable NiFe films in spite of large differences in film properties. The present low frequency creep data together with previously published results in this and other laboratories can be accounted for by a model which requires that the wall structure change usually associated with low frequency creep be predominately a gyromagnetic process. The correctness of this model is reinforced by the observation that the wall coercive force, the planar wall mobility, and the occurrence of an abrupt wall structure change are the only properties closely correlated to the creep displacement characteristics of a planar wall in low dispersion films.

  16. Chromium Grain-boundary Segregation and Effect of Ion Beam Cleaning on Fe-Ni-Cr Alloys

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Saraf, Laxmikant V.

    2011-04-01

    The grain boundaries play important role to control the mechanical strength of ternary alloys. From spacecrafts to naval vessels to nuclear reactors, stress corrosion cracking, brittleness, oxidation mostly originates at the grain boundaries and cause long term structural stability problems in most of the metallic structures [1]. Fe-Ni-Cr based ternary metal alloys have been widely studied for more than fifty years [2, 3]. Despite of vast amount of research, chromium diffusion in stainless steel or other Ni-Fe-Cr based ternary alloys is still an open scientific problem with challenges in structural stability and corrosion resistance [4]. Particularly, austenite Fe-Ni-Cr is lookedmore » upon favorably in space and jet engine industry for their improved resistance to stress corrosion cracking [5]. In solid oxide fuel cells (SOFC), Ni-alloys are frequently used as interconnects and seals [6]. In this communication, simultaneous energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) mapping is utilized to study chemical and structural aspects of chromium segregation in Fe-Ni-Cr alloy. A focused Ga-ion beam is also utilized to study the effect of ion beam cleaning on EBSD image quality (IQ) and inverse pole figure (IPF) maps of Fe-Ni-Cr alloy.« less

  17. Evidence for Ni-56 yields Co-56 yields Fe-56 decay in type Ia supernovae

    NASA Technical Reports Server (NTRS)

    Kuchner, Marc J.; Kirshner, Robert P.; Pinto, Philip A.; Leibundgut, Bruno

    1994-01-01

    In the prevailing picture of Type Ia supernovae (SN Ia), their explosive burning produces Ni-56, and the radioactive decay chain Ni-56 yields Co-56 yields Fe-56 powers the subsequent emission. We test a central feature of this theory by measuring the relative strengths of a (Co III) emission feature near 5900 A and a (Fe III) emission feature near 4700 A. We measure 38 spectra from 13 SN Ia ranging from 48 to 310 days after maximum light. When we compare the observations with a simple multilevel calculation, we find that the observed Fe/Co flux ratio evolves as expected when the Fe-56/Co-56 abundance ratio follows from Ni-56 yields Co-56 yields Fe-56 decay. From this agreement, we conclude that the cobalt and iron atoms we observe through SN Ia emission lines are produced by the radioactive decay of Ni-56, just as predicted by a wide range of models for SN Ia explosions.

  18. Effect of Molybdenum on the Corrosion Behavior of High-Entropy Alloys CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 under Sodium Chloride Aqueous Conditions

    DOE PAGES

    Rodriguez, Alvaro A.; Tylczak, Joseph H.; Gao, Michael C.; ...

    2018-01-01

    The corrosion behavior of high-entropy alloys (HEAs) CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 was investigated in 3.5 wt. percent sodium chloride (NaCl) at 25°C by electrochemical methods. Their corrosion parameters were compared to those of HASTELLOY® C-276 (UNS N10276) and stainless steel 316L (UNS 31600) to assess the suitability of HEAs for potential industrial applications in NaCl simulating seawater type environments. The corrosion rates were calculated using corrosion current determined from electrochemical experiments for each of the alloys. In addition, potentiodynamic polarization measurements can indicate active, passive, and transpassive behavior of the metal as well as potential susceptibility to pittingmore » corrosion. Cyclic voltammetry (CV) can confirm the alloy susceptibility to pitting corrosion. Electrochemical impedance spectroscopy (EIS) elucidates the corrosion mechanism under studied conditions. The results of the electrochemical experiments and scanning electron microscopy (SEM) analyses of the corroded surfaces revealed general corrosion on alloy CoCrFeNi 2 Mo 0.25 and HASTELLOY C-276 and pitting corrosion on alloy CoCrFeNi 2 and stainless steel 316L.« less

  19. Effect of Molybdenum on the Corrosion Behavior of High-Entropy Alloys CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 under Sodium Chloride Aqueous Conditions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rodriguez, Alvaro A.; Tylczak, Joseph H.; Gao, Michael C.

    The corrosion behavior of high-entropy alloys (HEAs) CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 was investigated in 3.5 wt. percent sodium chloride (NaCl) at 25°C by electrochemical methods. Their corrosion parameters were compared to those of HASTELLOY® C-276 (UNS N10276) and stainless steel 316L (UNS 31600) to assess the suitability of HEAs for potential industrial applications in NaCl simulating seawater type environments. The corrosion rates were calculated using corrosion current determined from electrochemical experiments for each of the alloys. In addition, potentiodynamic polarization measurements can indicate active, passive, and transpassive behavior of the metal as well as potential susceptibility to pittingmore » corrosion. Cyclic voltammetry (CV) can confirm the alloy susceptibility to pitting corrosion. Electrochemical impedance spectroscopy (EIS) elucidates the corrosion mechanism under studied conditions. The results of the electrochemical experiments and scanning electron microscopy (SEM) analyses of the corroded surfaces revealed general corrosion on alloy CoCrFeNi 2 Mo 0.25 and HASTELLOY C-276 and pitting corrosion on alloy CoCrFeNi 2 and stainless steel 316L.« less

  20. The key role of biochar in the rapid removal of decabromodiphenyl ether from aqueous solution by biochar-supported Ni/Fe bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Yi, Yunqiang; Wu, Juan; Wei, Yufen; Fang, Zhanqiang; Tsang, Eric Pokeung

    2017-07-01

    Some problems exist in the current remediation of polybrominated diphenyl ethers (PBDEs) from aqueous solution by using iron-based nanoparticles. Our efforts have contributed to the synthesis of biochar-supported Ni/Fe bimetallic nanoparticle composites (BC@Ni/Fe). Under the optimum operating parameters of BC@Ni/Fe, the morphologic analysis revealed that biochar effectively solved the agglomeration of Ni/Fe nanoparticles and the removal efficiency of BDE209 obtained by BC@Ni/Fe (91.29%) was seven times higher than the sum of biochar (2.55%) and Ni/Fe (11.22%) in 10 min. The degradation products of BDE209 in the solution and absorbed on the BC@Ni/Fe were analyzed with gas chromatography-mass spectroscopy, which indicated that the degradation of BDE209 was mainly a process of stepwise debromination. Meanwhile, compared with Ni/Fe nanoparticles, the adsorption ability of the by-products of BDE209 by BC@Ni/Fe was greater, to a certain extent, which reduced the additional environmental burden. In addition, the concentration of nickle ion leaching from the Ni/Fe nanoparticles was 3.09 mg/L; conversely, the concentration of nickle leaching from BC@Ni/Fe was not detected. This excellent performance in our study indicates a possible means to enhance the reactivity and reduce the secondary risks of Ni/Fe nanoparticles.

  1. A matrix of heterobimetallic complexes for interrogation of hydrogen evolution reaction electrocatalysts† †Electronic supplementary information (ESI) available: Experimental, spectroscopic, additional electrochemical and computational details, X-ray crystallographic data (CIF) from the structure of the complexes [Ni–Fe]0, [Ni2–Fe2]2+, [Ni2–Fe]+, and computational coordinates are available. CCDC crystallographic data for the complexes [Ni–Fe]0, [Ni2–Fe2]2+ and [Ni2–Fe]+ were deposited in the Cambridge Crystallographic Data Centre. CCDC [Ni–Fe]0 (CCDC 1045461), [Ni2–Fe2]2+ (CCDC 1045460) and [Ni2–Fe]+ (CCDC 1565539). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc03378h

    PubMed Central

    Ghosh, Pokhraj; Ding, Shengda; Chupik, Rachel B.; Quiroz, Manuel; Hsieh, Chung-Hung; Bhuvanesh, Nattami; Hall, Michael B.

    2017-01-01

    Experimental and computational studies address key questions in a structure–function analysis of bioinspired electrocatalysts for the HER. Combinations of NiN2S2 or [(NO)Fe]N2S2 as donors to (η5-C5H5)Fe(CO)+ or [Fe(NO)2]+/0 generate a series of four bimetallics, gradually “softened” by increasing nitrosylation, from 0 to 3, by the non-innocent NO ligands. The nitrosylated NiFe complexes are isolated and structurally characterized in two redox levels, demonstrating required features of electrocatalysis. Computational modeling of experimental structures and likely transient intermediates that connect the electrochemical events find roles for electron delocalization by NO, as well as Fe–S bond dissociation that produce a terminal thiolate as pendant base well positioned to facilitate proton uptake and transfer. Dihydrogen formation is via proton/hydride coupling by internal S–H+···–H–Fe units of the “harder” bimetallic arrangements with more localized electron density, while softer units convert H–···H–via reductive elimination from two Fe–H deriving from the highly delocalized, doubly reduced [Fe2(NO)3]– derivative. Computational studies also account for the inactivity of a Ni2Fe complex resulting from entanglement of added H+ in a pinched –Sδ–···H+···δ–S– arrangement. PMID:29619175

  2. Magnetic and electrical characterization of nickel-rich NiFe thin films synthesized by atomic layer deposition and subsequent thermal reduction.

    PubMed

    Espejo, A P; Zierold, R; Gooth, J; Dendooven, J; Detavernier, C; Escrig, J; Nielsch, K

    2016-08-26

    Nickel-rich NiFe thin films (Ni92Fe8, Ni89Fe11 and Ni83Fe17) were prepared by combining atomic layer deposition (ALD) with a subsequent thermal reduction process. In order to obtain Ni x Fe1-x O y films, one ALD supercycle was performed according to the following sequence: m NiCp2/O3, with m = 1, 2 or 3, followed by one FeCp2/O3 cycle. The supercycle was repeated n times. The thermal reduction process in hydrogen atmosphere was investigated by in situ x-ray diffraction studies as a function of temperature. The metallic nickel iron alloy thin films were investigated and characterized with respect to crystallinity, morphology, resistivity, and magnetism. As proof-of-concept magnetic properties of an array of Ni83Fe17, close to the perfect Permalloy stoichiometry, nanotubes and an isolated tube were investigated.

  3. Magnetic and electrical characterization of nickel-rich NiFe thin films synthesized by atomic layer deposition and subsequent thermal reduction

    NASA Astrophysics Data System (ADS)

    Espejo, A. P.; Zierold, R.; Gooth, J.; Dendooven, J.; Detavernier, C.; Escrig, J.; Nielsch, K.

    2016-08-01

    Nickel-rich NiFe thin films (Ni92Fe8, Ni89Fe11 and Ni83Fe17) were prepared by combining atomic layer deposition (ALD) with a subsequent thermal reduction process. In order to obtain Ni x Fe1-x O y films, one ALD supercycle was performed according to the following sequence: m NiCp2/O3, with m = 1, 2 or 3, followed by one FeCp2/O3 cycle. The supercycle was repeated n times. The thermal reduction process in hydrogen atmosphere was investigated by in situ x-ray diffraction studies as a function of temperature. The metallic nickel iron alloy thin films were investigated and characterized with respect to crystallinity, morphology, resistivity, and magnetism. As proof-of-concept magnetic properties of an array of Ni83Fe17, close to the perfect Permalloy stoichiometry, nanotubes and an isolated tube were investigated.

  4. Investigating Planetesimal Evolution by Experiments with Fe-Ni Metallic Melts: Light Element Composition Effects on Trace Element Partitioning Behavior

    NASA Astrophysics Data System (ADS)

    Chabot, N. L.

    2017-12-01

    As planetesimals were heated up in the early Solar System, the formation of Fe-Ni metallic melts was a common occurrence. During planetesimal differentiation, the denser Fe-Ni metallic melts separated from the less dense silicate components, though some meteorites suggest that their parent bodies only experienced partial differentiation. If the Fe-Ni metallic melts did form a central metallic core, the core eventually crystallized to a solid, some of which we sample as iron meteorites. In all of these planetesimal evolution processes, the composition of the Fe-Ni metallic melt influenced the process and the resulting trace element chemical signatures. In particular, the metallic melt's "light element" composition, those elements present in the metallic melt in a significant concentration but with lower atomic masses than Fe, can strongly affect trace element partitioning. Experimental studies have provided critical data to determine the effects of light elements in Fe-Ni metallic melts on trace element partitioning behavior. Here I focus on combining numerous experimental results to identify trace elements that provide unique insight into constraining the light element composition of early Solar System Fe-Ni metallic melts. Experimental studies have been conducted at 1 atm in a variety of Fe-Ni systems to investigate the effects of light elements on trace element partitioning behavior. A frequent experimental examination of the effects of light elements in metallic systems involves producing run products with coexisting solid metal and liquid metal phases. Such solid-metal-liquid-metal experiments have been conducted in the Fe-Ni binary system as well as Fe-Ni systems with S, P, and C. Experiments with O-bearing or Si-bearing Fe-Ni metallic melts do not lend themselves to experiments with coexisting solid metal and liquid metal phases, due to the phase diagrams of these elements, but experiments with two immiscible Fe-Ni metallic melts have provided insight into

  5. Self-assembled NiFe2O4/carbon nanotubes sponge for enhanced glucose biosensing application

    NASA Astrophysics Data System (ADS)

    Li, Yingchun; Zhao, Minggang; Chen, Jing; Fan, Sisi; Liang, Jingjing; Ding, Longjiang; Chen, Shougang

    2016-01-01

    In this work, self-assembled NiFe2O4/carbon nanotubes (CNTs) sponge was prepared by ice-templating method. The device synergized the advantageous features of both the 3D porous nanostructure and the catalytic properties of CNTs with GOx and NiFe2O4 nanoparticles. The porous network construction of the NiFe2O4/CNTs sheets offered enlarged specific surface for GOx immobilization and opened channels for facilitating the electrons transport and reactants diffusion. With the help of the abnormal-valence elements Ni and Fe, double catalysis has happened and the enhanced glucose biosensing performance has been achieved. The fabricated glucose biosensor exhibited two large linear ranges (0-3.0 and 3.2-12.4 mM) and distinct sensitivities (84.1 and 24.6 μA mM-1 cm-2).

  6. Dendritic Ag-Fe nanocrystalline alloy synthesized by pulsed electrodeposition and its characterization

    NASA Astrophysics Data System (ADS)

    Santhi, Kalavathy; Revathy, T. A.; Narayanan, V.; Stephen, A.

    2014-10-01

    Synthesis of dendrite shaped Ag-Fe alloy nanomaterial by pulsed electrodeposition route was investigated. The alloy samples were deposited at different current densities from electrolytes of different compositions to study the influence of current density and bath composition on metal contents in the alloy, which was determined by ICP-OES analysis. The XRD studies were carried out to determine the structure of these samples. Magnetic characterization at room temperature and during heating was carried out to understand their magnetic behaviour and to confirm the inferences drawn from the XRD results. The XPS spectra proved the presence of Fe and Ag in the metallic form in the alloy samples. The FESEM and TEM micrographs were taken to view the surface morphology of the nanosized particles.

  7. Investigation on gas sensing properties of Ag doped BiFeO3

    NASA Astrophysics Data System (ADS)

    Bagwaiya, Toshi; Khade, Poonam; Reshi, Hilal Ahmad; Bhattacharya, Shovit; Shelke, Vilas; Kaur, Manmeet; Debnath, A. K.; Muthe, K. P.; Gadkari, S. C.

    2018-04-01

    Bismuth ferrite (BFO) and Ag substituted Bismuth ferrite with perovskite structure have been synthesized using sol-gel method and investigated for their gas sensing properties. Single phase and rhombohedral crystal structure of the samples were confirmed from XRD pattern. Oxidation state of the elements is confirmed using X-Ray Photoelectron Spectroscopy (XPS). Since Ag substituted Bismuth ferrite exhibited pronounced response to H2S gas as compared to other gases, H2S gas sensing properties of Bismuth ferrite (BFO) and Ag substituted Bismuth ferrite were investigated in detail. Bi0.9Ag0.1FeO3 (BAFO) exhibits enhanced sensitivity, quick response and selectivity towards H2S as compared to BFO.

  8. Enhanced photocatalytic activity of degrading short chain chlorinated paraffins over reduced graphene oxide/CoFe2O4/Ag nanocomposite.

    PubMed

    Chen, Xin; Zhao, Qidong; Li, Xinyong; Wang, Dong

    2016-10-01

    Short chain chlorinated paraffins have recently attracted great attention because of their environmental persistence and biological toxicity as an important organic pollutant. In this work, reduced graphene oxide/CoFe2O4/Ag (RGO/CoFe2O4/Ag) nanocomposite was prepared and employed for photocatalytic degradation of short chain chlorinated paraffins. The process of photocatalytic degradation of short chain chlorinated paraffins over RGO/CoFe2O4/Ag under visible light (λ>400nm) was investigated by in situ Fourier transform infrared spectroscopy and the related mechanisms were proposed. An apparent degradation ratio of 91.9% over RGO/CoFe2O4/Ag could be obtained under visible light illumination of 12h, while only about 21.7% was obtained with commercial P25 TiO2 under the same experimental conditions, which demonstrates that the RGO/CoFe2O4/Ag nanocomposite is a potential candidate for effective photocatalytic removal of short chain chlorinated paraffins. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. STRESS-INDUCED ASYMMETRIC MAGNETOIMPEDANCE EFFECT IN Ni80Fe20/Cu COMPOSITE WIRES

    NASA Astrophysics Data System (ADS)

    Lv, Wenxing; Li, Xin; Xie, Wenhui; Zhao, Qiang; Zhao, Zhenjie

    The magnetoimpedance effect of Ni80Fe20/Cu composited wires was experimentally investigated by varying the Ni80Fe20 coating thickness. An asymmetric MI behavior with a tunable linear region around zero magnetic field by altering the thickness of Ni80Fe20 layer was demonstrated. And the MI behavior was governed by the different anisotropy induced by the residual local stress in the multi-layer region. In addition, our investigation also suggested that the interactions between interface phase and outer phase of coating layer decreased with thickness, resulting in the domination of the asymmetric MI characteristic. For thickness of 485nm, the sensitivity was up to 225%/Oe from -2 Oe to 2 Oe, providing a promising candidate for linear sensor application.

  10. Electric-field tunable spin diode FMR in patterned PMN-PT/NiFe structures

    NASA Astrophysics Data System (ADS)

    Zietek, Slawomir; Ogrodnik, Piotr; Skowroński, Witold; Stobiecki, Feliks; van Dijken, Sebastiaan; Barnaś, Józef; Stobiecki, Tomasz

    2016-08-01

    Dynamic properties of NiFe thin films on PMN-PT piezoelectric substrate are investigated using the spin-diode method. Ferromagnetic resonance (FMR) spectra of microstrips with varying width are measured as a function of magnetic field and frequency. The FMR frequency is shown to depend on the electric field applied across the substrate, which induces strain in the NiFe layer. Electric field tunability of up to 100 MHz per 1 kV/cm is achieved. An analytical model based on total energy minimization and the Landau-Lifshitz-Gilbert equation, taking into account the magnetostriction effect, is used to explain the measured dynamics. Based on this model, conditions for optimal electric-field tunable spin diode FMR in patterned NiFe/PMN-PT structures are derived.

  11. Crystallization induced ordering of hard magnetic L1{sub 0} phase in melt-spun FeNi-based ribbons

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sato, Kazuhisa, E-mail: sato@uhvem.osaka-u.ac.jp; Sharma, Parmanand; Zhang, Yan

    2016-05-15

    The microstructure of newly developed hard magnetic Fe{sub 42}Ni{sub 41.3}Si{sub x}B{sub 12-x}P{sub 4}Cu{sub 0.7} (x = 2 to 8 at%) nanocrystalline alloy ribbons has been studied by transmission electron microscopy (TEM) and electron diffraction. A high-density polycrystalline grains, ∼30 nm in size, were formed in a ribbon after annealing at 673 K for 288 hours. Elemental mapping of the annealed specimen revealed the coexistence of three regions, Fe-rich, Ni-rich, and nearly equiatomic Fe-Ni, with areal fractions of 37%, 40%, and 23 %, respectively. The equiatomic L1{sub 0}-type ordered phase of FeNi was detected in between the Fe and Ni-rich phases.more » The presence of superlattice reflections in nanobeam electron diffraction patterns confirmed the formation of the hard magnetic L1{sub 0} phase beyond any doubt. The L1{sub 0} phase of FeNi was detected in alloys annealed in the temperature range of 673 to 813 K. The present results suggest that the order-disorder transition temperature of L1{sub 0} FeNi is higher than the previously reported value (593 K). The high diffusion rates of the constituent elements induced by the crystallization of an amorphous phase at relatively low temperature (∼673 K) are responsible for the development of atomic ordering in FeNi.« less

  12. Design of Novel Precipitate-Strengthened Al-Co-Cr-Fe-Nb-Ni High-Entropy Superalloys

    NASA Astrophysics Data System (ADS)

    Antonov, Stoichko; Detrois, Martin; Tin, Sammy

    2018-01-01

    A series of non-equiatomic Al-Co-Cr-Fe-Nb-Ni high-entropy alloys, with varying levels of Co, Nb and Fe, were investigated in an effort to obtain microstructures similar to conventional Ni-based superalloys. Elevated levels of Co were observed to significantly decrease the solvus temperature of the γ' precipitates. Both Nb and Co in excessive concentrations promoted the formation of Laves and NiAl phases that formed either during solidification and remained undissolved during homogenization or upon high-temperature aging. Lowering the content of Nb, Co, or Fe prevented the formation of the eutectic type Laves. In addition, lowering the Co content resulted in a higher number density and volume fraction of the γ' precipitates, while increasing the Fe content led to the destabilization of the γ' precipitates. Various aging treatments were performed which led to different size distributions of the strengthening phase. Results from the microstructural characterization and hardness property assessments of these high-entropy alloys were compared to a commercial, high-strength Ni-based superalloy RR1000. Potentially, precipitation-strengthened high-entropy alloys could find applications replacing Ni-based superalloys as structural materials in power generation applications.

  13. Reduced graphene oxide modified NiFe-calcinated layered double hydroxides for enhanced photocatalytic removal of methylene blue

    NASA Astrophysics Data System (ADS)

    Zhao, Guoqing; Li, Caifeng; Wu, Xia; Yu, Jingang; Jiang, Xinyu; Hu, Wenjihao; Jiao, Feipeng

    2018-03-01

    Calcined layered double hydroxides (CLDH) are one of the remarkable photocatalysts passionately studied for photodecolorization of organic dyes. NiFe-CLDH was successfully modified by reduced graphene oxide (RGO) through a facile in situ crystallization technique. The obtained RGO/NiFe-CLDH composites were fully characterized by powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FT-IR), and UV-vis diffuse reflectance spectroscopy (DRS). The results analysis indicated that RGO sheets could work as base course to prompt the growth of LDH crystallites and NiFe-LDH lamellar crystal promiscuously distributed on the sheets with a strong interplay between each other. The photocatalytic performance of RGO/NiFe-CLDH composites toward decolorization of methylene blue tightly depended on the mass fraction of RGO and calcinated temperature. At the RGO weight loading of 1%, calcination temperature of 500 °C, the photocatalytic degradation efficiency of RGO/NiFe-CLDH composites reached 93.0% within 5.0 h. The enhanced activity of RGO/NiFe-CLDH composites may be due to the concerted catalysis effect between two constituents of as-prepared composites.

  14. Easily Dispersible NiFe2O4/RGO Composite for Microwave Absorption Properties in the X-Band

    NASA Astrophysics Data System (ADS)

    Bateer, Buhe; Zhang, Jianjao; Zhang, Hongchen; Zhang, Xiaochen; Wang, Chunyan; Qi, Haiqun

    2018-01-01

    Composites with good dispersion and excellent microwave absorption properties have important applications. Therefore, an easily dispersible NiFe2O4/reduced graphene oxide (RGO) composite has been prepared conveniently through a simple hydrothermal method. Highly crystalline, small size (about 7 nm) monodispersed NiFe2O4 nanoparticles (NPs) are evenly distributed on the surface of RGO. The microwave absorbability revealed that the NiFe2O4/RGO composite exhibits excellent microwave absorption properties in the X-band (8-12 GHz), and the minimum reflection loss of the NiFe2O4/RGO composite is -27.7 dB at 9.2 GHz. The NiFe2O4/RGO composite has good dispersibility in nonpolar solvent, which facilitates the preparation of stable commercial microwave absorbing coatings. It can be a promising candidate for lightweight microwave absorption materials in many application fields.

  15. Physical Properties of NiFeCrCo-based High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Zaddach, Alexander Joseph

    Conventional alloy design has been based on improving the properties of a single base, or solvent, element through relatively small additions of other elements. More recently, research has been conducted on alloys that contain multiple principal elements, particularly multi-component equiatomic alloys. When such alloys form solid solution phases, they are termed "high-entropy alloys" (HEAs) due to their high configurational entropy. These alloys often have favorable properties compared to conventional dilute solution alloys, but their compositional complexity and relative novelty means that they remain difficult to design and their basic properties are often unknown. The motivation for this work is a detailed experimental exploration of some of the basic physical properties of NiFeCrCo-based alloys. NiFeCrCoMn was one of the first equiatomic HEAs developed. As the compositional space within this single system is extremely large, this work focuses primarily on equiatomic alloys and a limited subset of non-equiatomic alloys chosen for their specific properties. Several alloys are prepared using both conventional methods (arc melting) and nonequilibrium methods (mechanical alloying). Properties studied include stacking fault energy, bulk mechanical properties, single crystal elastic constants, and magnetic properties. The equiatomic NiFeCrCo and NiFeCrCoMn alloys were found to have a moderate to low stacking fault energy, 18 -- 30 mJ m-2. As they are single-phase, fcc alloys, they have high tensile ductility. Additionally, they also exhibit high work-hardening rates, resulting in high toughness. NiFeCrCo outperforms the 5-component equiatomic alloy in ductility and toughness. A 5-component alloy with higher Co content to reduce the stacking fault energy also performs well. The single crystal elastic constants were measured using nanoindentation modulus measurements of grains of known orientation. The measured elastic constants were consistent with those calculated

  16. Resonant photoemission study of pyrite-type NiS2, CoS2 and FeS2

    NASA Astrophysics Data System (ADS)

    Fujimori, A.; Mamiya, K.; Mizokawa, T.; Miyadai, T.; Sekiguchi, T.; Takahashi, H.; Môri, N.; Suga, S.

    1996-12-01

    The electronic structure of pyrite-type NiS2, CoS2, and FeS2 has been studied by photoemission spectroscopy. From resonant photoemission studies and configuration-interaction cluster-model analysis of the spectra, NiS2 is found to be a charge-transfer-type insulator, the band gap of which is formed between the occupied S 3p and the empty Ni 3d states. Cluster-model calculations indicate that the short Fe-S distance favors the low-spin (S=0) ground state in FeS2 compared to the high-spin FeS. Resonant photoemission results indicate a sign of electron correlation in the nonmagnetic semiconductor FeS2.

  17. Atomic scale study of ball milled Ni-Fe{sub 2}O{sub 3} using Mössbauer spectroscopy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yadav, Ravi Kumar; Govindaraj, R., E-mail: govind@igcar.gov.in; Vinod, K.

    Evolution of hyperfine fields at Fe atoms has been studied in a detailed manner in a mixture of Ni and α-Fe{sub 2}O{sub 3} subjected to high energy ball milling using Mossbauer spectroscopy. Mossbauer results indicate the dispersion of α-Fe{sub 2}O{sub 3} particles in Ni matrix in the as ball milled condition. Evolution of α-Fe{sub 2}O{sub 3} due to ball milling, reduction of the valence of associated Fe and possible interaction between the oxide particles with Ni in the matrix due to annealing treatments has been elucidated in the present study.

  18. Magnetic Mineralogy of Troilite-Inclusions and their Fe-Ni Host Alloys in IAB Iron Meteorites

    NASA Astrophysics Data System (ADS)

    Kontny, A. M.; Kramar, U.; Luecke, W.

    2011-12-01

    Iron-nickel meteorites often contain isolated, mostly rounded troilite nodules enclosed in a bulk of Fe-Ni alloy. As sulfur has a low solubility in metal, it is excluded from the crystallization of metal during cooling. Therefore troilite nodules are interpreted to be trapped droplets of residual sulfur-enriched melts. Microscopic examinations of the interface (mm-range) between troilite inclusions and Fe-Ni alloy yield clear mineralogical differences compared to the troilite inclusion. Such rims around troilite nodules seem to occur exclusively in Fe-Ni meteorites with slow cooling rates, and therefore might provide interesting clues on segregation, fractional crystallization and reequilibration processes between the Fe-Ni alloy and the sulfide phases. These interfaces however are also highly sensitive to terrestrial weathering. We present microscopic observations in combination with temperature-dependent magnetic susceptibility (k-T curves) in order to identify the magnetic mineralogy of the Morasko (Poland) and Coahuila (Mexico) meteorites, which both geochemically belong to the non-magmatic IAB or IIICD group. In the k-T curves both, rim and troilite nodule are characterized by Curie temperatures (TC) that can be related to magnetite, daubreelite (FeCr2O4), Fe-hydroxide and sometimes cohenite. Therefore the interface seems to be geochemically more similar to the troilite nodule than the Fe-Ni alloy. Optical microscopy in combination with the ferrofluid method revealed complex microstructures of intergrown magnetic (TC = 780-785 °C) and non-magnetic phases in the Fe-Ni alloy, which differ in their Ni-concentration. Towards the rim of the troilite nodule the concentration of magnetic cohenite ((Fe,Ni)3C) and especially schreibersite ((Fe,Ni)3P), which are both intergrown with the metal, increases. Cohenite is easily identified microscopically by a very characteristic stripe-like magnetic domain structure and it shows a TC at about 200 °C. The carbon-rich, dark

  19. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO 3 Fe 3Al, Co 3Al, and Ni 3Al based intermetallic phases

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO 3 Fe 3Al, Co 3Al and Ni 3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO 3 lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe 3Al and Co 3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.« less

  20. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO 3 Fe 3Al, Co 3Al, and Ni 3Al based intermetallic phases

    DOE PAGES

    Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

    2014-11-07

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO 3 Fe 3Al, Co 3Al and Ni 3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO 3 lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe 3Al and Co 3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.« less

  1. Magnetic Anisotropy and Chemical Order of Artificially Synthesized L10-Ordered FeNi Films on Au-Cu-Ni Buffer Layers

    NASA Astrophysics Data System (ADS)

    Kojima, Takayuki; Mizuguchi, Masaki; Koganezawa, Tomoyuki; Osaka, Keiichi; Kotsugi, Masato; Takanashi, Koki

    2012-01-01

    L10-FeNi films were grown by alternate monatomic layer deposition on Au-Cu-Ni buffer layers at several substrate temperatures (Ts), and the relation between the uniaxial magnetic anisotropy energy (Ku) and the long-range chemical order parameter (S) was investigated. A large Ku of (7.0 ±0.2) ×106 erg/cm3 and S of 0.48 ±0.05 were obtained. The value of Ku was larger than those reported previously for artificially synthesized FeNi films. It was first found that both Ku and S increased with Ts, and Ku was roughly proportional to S.

  2. Effect of Heat Treatment on Morphology of Fe-Rich Intermetallics in Hypereutectic Al-Si-Cu-Ni Alloy with 1.26 pct Fe

    NASA Astrophysics Data System (ADS)

    Sha, Meng; Wu, Shusen; Wan, Li; Lü, Shulin

    2013-12-01

    Cobalt is generally considered as the element that can neutralize the negative effects of iron in Al alloys, such as inducing fracture and failure for stress concentration. Nevertheless, Fe-rich intermetallics would be inclined to form coarse plate-like δ-Al4(Fe, Co, Ni)Si2 particles when the content of Fe was high, which could also cause inferior mechanical properties. The dissolution and transformation of δ-Al4(Fe, Co, Ni)Si2 phase in solution heat-treated samples of Al-20Si-1.85Cu-1.05Ni-1.26Fe-1.35Co alloy were studied using optical microscopy, image analysis, and scanning electron microscopy. The effects of solution heat treatment time ranging from 0 to 9 hours at 783.15 K (510 °C) on mechanical properties were also investigated. The coarse plate-like δ-Al4(Fe, Co, Ni)Si2 particles varied slowly through concurrent dissolution along widths and at the plate tips as solution treatment time increased, which could be explained from diffusion-induced grain boundary migration. Solution heat treatment also has an important influence on mechanical properties. The maximum ultimate tensile strength and yield strength after T6 treatment were 258 and 132 MPa, respectively, while the maximum hardness was 131 HB. Compared with those of the samples in the as-cast state, they increased by 53, 42, and 28 pct, respectively. Moreover, δ-Al4(Fe, Co, Ni)Si2 phase, which appears as a coarse plate-like particle in two dimensions, is actually a cuboid in three dimensions. The length of this cuboid is close to the width, while the height is much smaller.

  3. Revealing the Influence of Silver in Ni-Ag Catalysts on the Selectivity of Higher Olefin Synthesis from Stearic Acid

    NASA Astrophysics Data System (ADS)

    Danyushevsky, V. Ya.; Murzin, V. Yu.; Kuznetsov, P. S.; Shamsiev, R. S.; Katsman, E. A.; Khramov, E. V.; Zubavichus, Y. V.; Berenblyum, A. S.

    2018-01-01

    Results on the conversion of stearic acid to olefins over Ni-Ag/γ-Al2O3 catalysts are presented. XANES and EXAFS experiments in situ and DFT calculations were applied to reveal the structure of active sites therein. It is shown that the introduction of Ag to Ni catalysts leads to an increase in the olefin yield. After a reduction in hydrogen (350°C, 3 h) alumina-supported nanoparticles of nickel sulfides and metallic Ag are formed. The role of metal hydrides formed during the reaction is extensively discussed.

  4. Structural transitions and multiferroic properties of high Ni-doped BiFeO3

    NASA Astrophysics Data System (ADS)

    Betancourt-Cantera, L. G.; Bolarín-Miró, A. M.; Cortés-Escobedo, C. A.; Hernández-Cruz, L. E.; Sánchez-De Jesús, F.

    2018-06-01

    Nickel doped bismuth ferrite powders, BiFe1-x NixO3 (0 ≤ x ≤ 0.5), were synthesized by high-energy ball milling followed by an annealing at 700 °C. A detailed study about the substitution of Fe3+ by Ni2+ on the crystal structure and multiferroic properties is presented. The X-ray diffraction patterns reveal the formation of rhombohedral structure with small amounts of Bi2Fe4O9 as a secondary phase for x < 0.1. Also it is inferred the stabilization of a Bi25FeO40, sillenite phase, as the amount of Ni2+ substitution increases, reaching up 95.23% of sillenite for x = 0.5. The magnetic behavior indicates the frustration of the G-antiferromagnetic order typical of the un-doped BiFeO3, caused by the presence of small amounts of Ni2+ (x < 0.1) on the structure. The DC conductivity exhibited a little increment with increasing Ni content (up to x = 0.1). Although the conductivity increases, for nickel concentrations of 0.2-0.5, the bismuth ferrites doped with nickel retain their property of being an electrical insulating material. Behavior modifications of electrical conductivity, permittivity and dielectric loss versus frequency are related with crystal structure transformations, when nickel concentration is increased.

  5. Elastic moduli and thermal expansion coefficients of medium-entropy subsystems of the CrMnFeCoNi high-entropy alloy

    DOE PAGES

    Laplanche, Guillaume; Gadaud, P.; Barsch, C.; ...

    2018-02-23

    Elastic moduli of a set of equiatomic alloys (CrFeCoNi, CrCoNi, CrFeNi, FeCoNi, MnCoNi, MnFeNi, and CoNi), which are medium-entropy subsystems of the CrMnFeCoNi high-entropy alloy were determined as a function of temperature over the range 293 K–1000 K. Thermal expansion coefficients were determined for these alloys over the temperature range 100 K–673 K. All alloys were single-phase and had the face-centered cubic (FCC) crystal structure, except CrFeNi which is a two-phase alloy containing a small amount of body-centered cubic (BCC) precipitates in a FCC matrix. The temperature dependences of thermal expansion coefficients and elastic moduli obtained here are useful formore » quantifying fundamental aspects such as solid solution strengthening, and for structural analysis/design. Furthermore, using the above results, the yield strengths reported in literature for these alloys were normalized by their shear moduli to reveal the influence of shear modulus on solid solution strengthening.« less

  6. Elastic moduli and thermal expansion coefficients of medium-entropy subsystems of the CrMnFeCoNi high-entropy alloy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Laplanche, Guillaume; Gadaud, P.; Barsch, C.

    Elastic moduli of a set of equiatomic alloys (CrFeCoNi, CrCoNi, CrFeNi, FeCoNi, MnCoNi, MnFeNi, and CoNi), which are medium-entropy subsystems of the CrMnFeCoNi high-entropy alloy were determined as a function of temperature over the range 293 K–1000 K. Thermal expansion coefficients were determined for these alloys over the temperature range 100 K–673 K. All alloys were single-phase and had the face-centered cubic (FCC) crystal structure, except CrFeNi which is a two-phase alloy containing a small amount of body-centered cubic (BCC) precipitates in a FCC matrix. The temperature dependences of thermal expansion coefficients and elastic moduli obtained here are useful for quantifying fundamental aspects suchmore » as solid solution strengthening, and for structural analysis/design. Furthermore, using the above results, the yield strengths reported in literature for these alloys were normalized by their shear moduli to reveal the influence of shear modulus on solid solution strengthening.« less

  7. Electrodeposited Nanolaminated CoNiFe Cores for Ultracompact DC-DC Power Conversion

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kim, J; Kim, M; Herrault, F

    2015-09-01

    Laminated metallic alloy cores (i.e., alternating layers of thin film metallic alloy and insulating material) of appropriate lamination thickness enable suppression of eddy current losses at high frequencies. Magnetic cores comprised of many such laminations yield substantial overall magnetic volume, thereby enabling high-power operation. Previously, we reported nanolaminated permalloy (Ni-80 Fe-20) cores based on a sequential electrodeposition technique, demonstrating negligible eddy current losses at peak flux densities up to 0.5 T and operating at megahertz frequencies. This paper demonstrates improved performance of nanolaminated cores comprising tens to hundreds of layers of 300-500-nm-thick CoNiFe films that exhibit superior magnetic properties (e.g.,more » higher saturation flux density and lower coercivity) than permalloy. Nanolaminated CoNiFe cores can be operated up to a peak flux density of 0.9 T, demonstrating improved power handling capacity and exhibiting 30% reduced volumetric core loss, attributed to lowered hysteresis losses compared to the nanolaminated permalloy core of the same geometry. Operating these cores in a buck dc-dc power converter at a switching frequency of 1 MHz, the nanolaminated CoNiFe cores achieved a conversion efficiency exceeding 90% at output power levels up to 7 W, compared to an achieved permalloy core conversion efficiency below 86% at 6 W.« less

  8. Electric-field tunable spin diode FMR in patterned PMN-PT/NiFe structures

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ziętek, Slawomir, E-mail: zietek@agh.edu.pl; Skowroński, Witold; Stobiecki, Tomasz

    Dynamic properties of NiFe thin films on PMN-PT piezoelectric substrate are investigated using the spin-diode method. Ferromagnetic resonance (FMR) spectra of microstrips with varying width are measured as a function of magnetic field and frequency. The FMR frequency is shown to depend on the electric field applied across the substrate, which induces strain in the NiFe layer. Electric field tunability of up to 100 MHz per 1 kV/cm is achieved. An analytical model based on total energy minimization and the Landau-Lifshitz-Gilbert equation, taking into account the magnetostriction effect, is used to explain the measured dynamics. Based on this model, conditions formore » optimal electric-field tunable spin diode FMR in patterned NiFe/PMN-PT structures are derived.« less

  9. Modeling the active site of [NiFe] hydrogenases and the [NiFeu] subsite of the C-cluster of carbon monoxide dehydrogenases: low-spin iron(II) versus high-spin iron(II).

    PubMed

    Weber, Katharina; Erdem, Özlen F; Bill, Eckhard; Weyhermüller, Thomas; Lubitz, Wolfgang

    2014-06-16

    A series of four [S2Ni(μ-S)2FeCp*Cl] compounds with different tetradentate thiolate/thioether ligands bound to the Ni(II) ion is reported (Cp* = C5Me5). The {S2Ni(μ-S)2Fe} core of these compounds resembles structural features of the active site of [NiFe] hydrogenases. Detailed analyses of the electronic structures of these compounds by Mössbauer and electron paramagnetic resonance spectroscopy, magnetic measurements, and density functional theory calculations reveal the oxidation states Ni(II) low spin and Fe(II) high spin for the metal ions. The same electronic configurations have been suggested for the Cred1 state of the C-cluster [NiFeu] subsite in carbon monoxide dehydrogenases (CODH). The Ni-Fe distance of ∼3 Å excludes a metal-metal bond between nickel and iron, which is in agreement with the computational results. Electrochemical experiments show that iron is the redox active site in these complexes, performing a reversible one-electron oxidation. The four complexes are discussed with regard to their similarities and differences both to the [NiFe] hydrogenases and the C-cluster of Ni-containing CODH.

  10. Enhancement of electrochemical performance by simultaneous substitution of Ni and Mn with Fe in Ni-Mn spinel cathodes for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Kiziltas-Yavuz, Nilüfer; Yavuz, Murat; Indris, Sylvio; Bramnik, Natalia N.; Knapp, Michael; Dolotko, Oleksandr; Das, Bijoy; Ehrenberg, Helmut; Bhaskar, Aiswarya

    2016-09-01

    LiNi0.5-xFe2xMn1.5-xO4 (x = 0, 0.1, 0.15, 0.2) spinel cathode materials are synthesized using citric acid-assisted sol-gel method with final calcination temperature of 1000 °C. The structure and morphology of the materials are characterized by using synchrotron and neutron powder diffraction as well as scanning electron microscopy. Different from the parent LiNi0.5Mn1.5O4 (LNMO) material, the Fe-doped spinels do not contain a rock-salt type impurity phase. However, they contain additional layered (C2/m) and spinel Fe3O4 (Fd 3 bar m) phases in small amounts. The substitution of Fe into the spinel structure has been confirmed by Mössbauer spectroscopy. The Fe-doped spinels exhibit improved cycling stability (with a C/2 charge-discharge rate) and rate capability compared to the parent LNMO at room temperature in a voltage range 3.5-5.0 V. Among all these samples, the composition LiNi0.4Fe0.2Mn1.4O4 shows the best room temperature cycling stability (capacity retention of 92% after 300 cycles) as well as the highest initial discharge capacity (134 mAh g-1). The delivered capacities at high C-rates (especially at 10C and 20C) with respect to the capacity delivered at C/2 are higher for all Fe-doped samples compared to the parent LNMO. Furthermore, Fe-doping improves the thermal stability of the Ni-Mn spinels in the delithiated state.

  11. Insulating and metallic spin glass in Ni-doped K x Fe 2 - y Se 2 single crystals

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ryu, Hyejin; Abeykoon, Milinda; Wang, Kefeng

    2015-05-01

    Here in this paper, we report electron doping effects by Ni in K xFe 2- δ-y Ni ySe 2 (0.06 ≤ y ≤ 1.44) single-crystal alloys. A rich ground-state phase diagram is observed. A small amount of Ni (~4 %) suppressed superconductivity below 1.8 K, inducing insulating spin-glass magnetic ground state for higher Ni content. With further Ni substitution, metallic resistivity is restored. For high Ni concentration in the lattice the unit cell symmetry is high symmetry I4/mmm with no phase separation whereas both I4 / m + I4/mmm space groups were detected in the phase separated crystals when concentrationmore » of Ni< Fe. The absence of superconductivity coincides with the absence of crystalline Fe vacancy order.« less

  12. Structural and magnetic analysis of Cu, Co substituted NiFe2O4 thin films

    NASA Astrophysics Data System (ADS)

    Sharma, Hakikat; Bala, Kanchan; Negi, N. S.

    2016-05-01

    In the present work we prepared NiFe2O4, Ni0.95Cu0.05Fe2O4 and Ni0.94Cu0.05Co0.01 Fe2O4 thin films by metallo-organic decomposition method (MOD) using spin coating technique. The thin films were analyzed by X-ray diffractometer (XRD) and Atomic force microscope (AFM) for structural studies. The XRD patterns confirmed the ferrite phase of thin films. From AFM, we analyzed surface morphology, calculated grain size (GS) and root mean square roughness (RMSR). Room temperature magnetic properties were investigated by vibrating sample magnetometer (VSM).

  13. Spectroscopy and atomic physics of highly ionized Cr, Fe, and Ni for tokamak plasmas

    NASA Technical Reports Server (NTRS)

    Feldman, U.; Doschek, G. A.; Cheng, C.-C.; Bhatia, A. K.

    1980-01-01

    The paper considers the spectroscopy and atomic physics for some highly ionized Cr, Fe, and Ni ions produced in tokamak plasmas. Forbidden and intersystem wavelengths for Cr and Ni ions are extrapolated and interpolated using the known wavelengths for Fe lines identified in solar-flare plasmas. Tables of transition probabilities for the B I, C I, N I, O I, and F I isoelectronic sequences are presented, and collision strengths and transition probabilities for Cr, Fe, and Ni ions of the Be I sequence are given. Similarities of tokamak and solar spectra are discussed, and it is shown how the atomic data presented may be used to determine ion abundances and electron densities in low-density plasmas.

  14. Effects of environment on the release of Ni, Cr, Fe, and Co from new and recast Ni-Cr alloy.

    PubMed

    Oyar, Perihan; Can, Gülşen; Atakol, Orhan

    2014-07-01

    The addition of previously cast alloy to new alloy for economic reasons may increase the release of elements. The purpose of this study was to analyze the effects of the immersion period, immersion media, and addition of previously cast alloy to new alloy on the release of elements. Disk-shaped specimens were prepared from a Ni-Cr alloy (Ni: 61 wt%, Cr: 26 wt%, Mo: 11 wt%, Si: 1.5 wt%, Fe, Ce, Al, and Co <1 wt%) (Remanium CS; Dentaurum) with new alloy (group N) and 50% new/50% recast alloy (group R). After the immersion of the specimens in both NaCl (pH 4) and artificial saliva (pH 6.7) for 3, 7, 14, 30, and 60 days, the release of ions was determined by using atomic absorption spectrometry. Data were analyzed with a 3-way ANOVA (α=.001). The release of Ni was significantly affected by the immersion period, of Ni and Cr by the alloy and media (P<.01), and of Fe by the alloy (P<.01). Ion release from the recast alloy in artificial saliva was 109.71 for Ni, 6.49 for Cr, 223.22 for Fe, and 29.90 μg/L for Co. The release of Co in NaCl was below the detection limit in both groups. The release of Ni in NaCl and artificial saliva increased with the length of the immersion period in both groups. The release of Cr and Fe was higher in artificial saliva than in NaCl in group R, regardless of the immersion period. The release of Co in NaCl was below the detection limit in both groups. Copyright © 2014 The Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  15. Auger electron diffraction study of Fe 1- xNi x alloys epitaxially grown on Cu(100)

    NASA Astrophysics Data System (ADS)

    Martin, M. G.; Foy, E.; Chevrier, F.; Krill, G.; Asensio, M. C.

    1999-08-01

    We have combined Auger electron diffraction (AED), low-energy electron diffraction (LEED) and high-energy electron diffraction (RHEED) to examine the structure of Fe xNi 1- x alloys when the Fe content approaches 65%. At this concentration, the 'invar effect' takes place, so the magnetization falls to zero, and the thermal expansion coefficient is very small. The Fe xNi 1- x alloys, grown as metastable thin films by molecular-beam epitaxy on Cu(100) substrates, were studied as a function of the x stoichiometry. In contrast to the related bulk alloy compounds, we observe the collapse of the fcc-to-bcc structural transition in the Fe-rich films. Furthermore, the local atomic structure around Fe and Ni in the alloy has been simultaneously determined by the angular intensity distributions of Fe L 3VV (703 eV) and Ni L 3VV (848 eV) Auger electrons measured as a function of polar and azimuthal angles. For the films deposited at room temperature, we have confirmed the pseudomorphic growth morphology and the uniformity of the alloys.

  16. The synthesis and electronic structure of a novel [NiS4Fe2(CO)6] radical cluster: implications for the active site of the [NiFe] hydrogenases.

    PubMed

    Wang, Qiang; Barclay, J Elaine; Blake, Alexander J; Davies, E Stephen; Evans, David J; Marr, Andrew C; McInnes, Eric J L; McMaster, Jonathan; Wilson, Claire; Schröder, Martin

    2004-07-19

    A novel [NiS4Fe2(CO)6]cluster (1: 'S(4)'=(CH(3)C(6)H(3)S(2))(2)(CH(2))(3)) has been synthesised, structurally characterised and has been shown to undergo a chemically reversible reduction process at -1.31 V versus Fc(+)/Fc to generate the EPR-active monoanion 1(-). Multifrequency Q-, X- and S-band EPR spectra of (61)Ni-enriched 1(-) show a well-resolved quartet hyperfine splitting in the low-field region due to the interaction with a single (61)Ni (I=3/2) nucleus. Simulations of the EPR spectra require the introduction of a single angle of non-coincidence between g(1) and A(1), and g(3) and A(3) to reproduce all of the features in the S- and X-band spectra. This behaviour provides a rare example of the detection and measurement of non-coincidence effects from frozen-solution EPR spectra without the need for single-crystal measurements, and in which the S-band experiment is sensitive to the non-coincidence. An analysis of the EPR spectra of 1(-) reveals a 24 % Ni contribution to the SOMO in 1(-), supporting a delocalisation of the spin-density across the NiFe(2) cluster. This observation is supported by IR spectroscopic results which show that the CO stretching frequencies, nu(CO), shift to lower frequency by about 70 cm(-1) when 1 is reduced to 1(-). Density functional calculations provide a framework for the interpretation of the spectroscopic properties of 1(-) and suggest that the SOMO is delocalised over the whole cluster, but with little S-centre participation. This electronic structure contrasts with that of the Ni-A, -B, -C and -L forms of [NiFe] hydrogenase in which there is considerable S participation in the SOMO.

  17. A Comparative Study of the Microstructure, Mechanical Properties and Corrosion Resistance of Ni- or Fe- Based Composite Coatings by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Wan, M. Q.; Shi, J.; Lei, L.; Cui, Z. Y.; Wang, H. L.; Wang, X.

    2018-04-01

    Ni- and Fe-based composite coatings were laser cladded on 40Cr steel to improve the surface mechanical property and corrosion resistance, respectively. The microstructure and phase composition were analyzed by x-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) equipped with an energy-dispersive spectrometer (EDS). The micro-hardness, tribological properties and electrochemical corrosion behavior of the coatings were evaluated. The results show that the thickness of both the coatings is around 0.7 mm, the Ni-based coating is mainly composed of γ-(Ni, Fe), FeNi3, Ni31Si12, Ni3B, CrB and Cr7C3, and the Fe-based coating is mainly composed of austenite and (Fe, Cr)7C3. Micro-hardness of the Ni-based composite coating is about 960 HV0.3, much higher than that of Fe-based coating (357.4 HV0.3) and the 40Cr substrate (251 HV0.3). Meanwhile, the Ni-based composite coating possesses better wear resistance than the Fe-based coating validated by the worn appearance and the wear loss. Electrochemical results suggested that Ni-based coating exhibited better corrosion resistance than the Fe-based coating. The 40Cr substrate could be well protected by the Ni-based coating.

  18. Effect of tungsten (W) on structural and magnetic properties of electroplated NiFe thin films for MEMS applications

    NASA Astrophysics Data System (ADS)

    Kannan, R.; Devaki, P.; Premkumar, P. S.; Selvambikai, M.

    2018-04-01

    Electrodeposition of nanocrystalline NiFe and NiFeW thin films were carried out from ammonium citrate bath at a constant current density and controlled pH of 8 by varying the bath temperature from 40 °C to 70 °C. The surface morphology and chemical composition of the electrodeposited NiFe and NiFeW soft magnetic thin films were studied by using SEM and EDAX. The SEM micrographs of the films coated at higher electrodeposited bath temperature have no micro cracks and also the films have more uniform surface morphology. The existence of crystalline nature of the coated films were analysed by XRD. The presence of predominant peaks in x-ray diffraction pattern (compared with JCPDS data) reveal that the average crystalline size was in the order of few tens of nano meters. The magnetic properties such as coercivity, saturation magnetization and magnetic flux density have been calculated from vibrating sample magnetometer analysis. The VSM result shows that the NiFeW thin film synthesised at 70 °C exhibit the lower coercivity with higher saturation magnetization. The hardness and adhesion of the electroplated films have been investigated. Reasons for variation in magnetic properties and structural characteristics are also discussed. The electroplated NiFe and NiFeW thin films can be used for Micro Electro Mechanical System (MEMS) applications due to their excellent soft magnetic behaviour.

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gubbiotti, G., E-mail: gubbiotti@fisica.unipg.it; Tacchi, S.; Del Bianco, L.

    2015-05-07

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

  20. Antifungal activity of multifunctional Fe 3O 4-Ag nanocolloids

    NASA Astrophysics Data System (ADS)

    Chudasama, Bhupendra; Vala, Anjana K.; Andhariya, Nidhi; Upadhyay, R. V.; Mehta, R. V.

    2011-05-01

    In recent years, rapid increase has been observed in the population of microbes that are resistant to conventionally used antibiotics. Antifungal drug therapy is no exception and now resistance to many of the antifungal agents in use has emerged. Therefore, there is an inevitable and urgent medical need for antibiotics with novel antimicrobial mechanisms. Aspergillus glaucus is the potential cause of fatal brain infections and hypersensitivity pneumonitis in immunocompromised patients and leads to death despite aggressive multidrug antifungal therapy. In the present article, we describe the antifungal activity of multifunctional core-shell Fe 3O 4-Ag nanocolloids against A. glaucus isolates. Controlled experiments are also carried out with Ag nanocolloids in order to understand the role of core (Fe 3O 4) in the antifungal action. The minimum inhibitory concentration (MIC) of nanocolloids is determined by the micro-dilution method. MIC of A. glaucus is 2000 μg/mL. The result is quite promising and requires further investigations in order to develop a treatment methodology against this death causing fungus in immunocompromised patients.

  1. [Removal of AOX and Chroma in Biologically Treated Effluent of Chemical Dyestuff Wastewater with Nanoscale Ni/Fe].

    PubMed

    Shu, Xiao-ming; Xu, Can-can; Liu, Rui; Zhao, Yuan; Chen, Lü-jun

    2016-02-15

    Nanoscale Ni/Fe was applied to biologically treated effluent of chemical dyestuff wastewater. The removal rates of absorbable organic halogens (AOX) and chroma were investigated at different Ni loadings (0-5%), initial wastewater pH (4.1-10.0), Ni/Fe dosage (1-5 g x L(-1)) and reaction time (0.5-96 h). The results showed that the removal rates of AOX and chroma firstly increased and then decreased with the increase of the Ni loading, while continuously increased with the decrease of the initial wastewater pH and the increase of Ni/Fe dosage. The optimal condition was Ni loading of 1%, initial wastewater pH of 4.1 and Ni/Fe dosage of 3 g x L(-1), under which 29.2% of AOX and 79.6% of chroma were removed after 24 h reaction, and 50.6% of AOX and 80.7% of chroma were removed after 96 h reaction. GC-MS analysis revealed that toxicants such as chlorinated anilines, p-nitroaniline, 4-methoxy-2-nitroaniline and halogenated hydrocarbons were efficiently removed.

  2. Brazing Inconel 625 Using Two Ni/(Fe)-Based Amorphous Filler Foils

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Shiang; Shiue, Ren-Kae

    2012-07-01

    For MBF-51 filler, the brazed joint consists of interfacial grain boundary borides, coarse Nb6Ni16Si7, and Ni/Cr-rich matrix. In contrast, the VZ-2106 brazed joint is composed of interfacial Nb6Ni16Si7 precipitates as well as grain boundary borides, coarse Nb6Ni16Si7, and Ni/Cr/Fe-rich matrix. The maximum tensile strength of 443 MPa is obtained from the MBF-51 brazed specimen. The tensile strengths of VZ-2106 brazed joints are approximately 300 MPa. Both amorphous filler foils demonstrate potential in brazing IN-625 substrate.

  3. Ternary mixed metal Fe-doped NiCo2O4 nanowires as efficient electrocatalysts for oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Yan, Kai-Li; Shang, Xiao; Li, Zhen; Dong, Bin; Li, Xiao; Gao, Wen-Kun; Chi, Jing-Qi; Chai, Yong-Ming; Liu, Chen-Guang

    2017-09-01

    Designing mixed metal oxides with unique nanostructures as efficient electrocatalysts for water electrolysis has been an attractive approach for the storage of renewable energies. The ternary mixed metal spinel oxides FexNi1-xCo2O4 (x = 0, 0.1, 0.25, 0.5, 0.75, 0.9, 1) have been synthesized by a facile hydrothermal approach and calcination treatment using nickel foam as substrate. Fe/Ni ratios have been proved to affect the nanostructures of FexNi1-xCo2O, which imply different intrinsic activity for oxygen evolution reaction (OER). SEM images show that Fe0.5Ni0.5Co2O4 has the uniform nanowires morphology with about 30 nm of the diameter and 200-300 nm of the length. The OER measurements show that Fe0.5Ni0.5Co2O4 exhibits the better electrocatalytic performances with lower overpotential of 350 mV at J = 10 mA cm-2. In addition, the smaller Tafel slope of 27 mV dec-1 than other samples with different Fe/Ni ratios for Fe0.5Ni0.5Co2O4 is obtained. The improved OER activity of Fe0.5Ni0.5Co2O4 may be attributed to the synergistic effects from ternary mixed metals especially Fe-doping and the uniform nanowires supported on NF. Therefore, synthesizing Fe-doped multi-metal oxides with novel nanostructures may be a promising strategy for excellent OER electrocatalysts and it also provides a facile way for the fabrication of high-activity ternary mixed metal oxides electrocatalysts.

  4. Spectroscopic insights into the oxygen-tolerant membrane-associated [NiFe] hydrogenase of Ralstonia eutropha H16.

    PubMed

    Saggu, Miguel; Zebger, Ingo; Ludwig, Marcus; Lenz, Oliver; Friedrich, Bärbel; Hildebrandt, Peter; Lendzian, Friedhelm

    2009-06-12

    This study provides the first spectroscopic characterization of the membrane-bound oxygen-tolerant [NiFe] hydrogenase (MBH) from Ralstonia eutropha H16 in its natural environment, the cytoplasmic membrane. The H2-converting MBH is composed of a large subunit, harboring the [NiFe] active site, and a small subunit, capable in coordinating one [3Fe4S] and two [4Fe4S] clusters. The hydrogenase dimer is electronically connected to a membrane-integral cytochrome b. EPR and Fourier transform infrared spectroscopy revealed a strong similarity of the MBH active site with known [NiFe] centers from strictly anaerobic hydrogenases. Most redox states characteristic for anaerobic [NiFe] hydrogenases were identified except for one remarkable difference. The formation of the oxygen-inhibited Niu-A state was never observed. Furthermore, EPR data showed the presence of an additional paramagnetic center at high redox potential (+290 mV), which couples magnetically to the [3Fe4S] center and indicates a structural and/or redox modification at or near the proximal [4Fe4S] cluster. Additionally, significant differences regarding the magnetic coupling between the Nia-C state and [4Fe4S] clusters were observed in the reduced form of the MBH. The spectroscopic properties are discussed with regard to the unusual oxygen tolerance of this hydrogenase and in comparison with those of the solubilized, dimeric form of the MBH.

  5. [NiFe] hydrogenases: a common active site for hydrogen metabolism under diverse conditions.

    PubMed

    Shafaat, Hannah S; Rüdiger, Olaf; Ogata, Hideaki; Lubitz, Wolfgang

    2013-01-01

    Hydrogenase proteins catalyze the reversible conversion of molecular hydrogen to protons and electrons. The most abundant hydrogenases contain a [NiFe] active site; these proteins are generally biased towards hydrogen oxidation activity and are reversibly inhibited by oxygen. However, there are [NiFe] hydrogenase that exhibit unique properties, including aerobic hydrogen oxidation and preferential hydrogen production activity; these proteins are highly relevant in the context of biotechnological devices. This review describes four classes of these "nonstandard" [NiFe] hydrogenases and discusses the electrochemical, spectroscopic, and structural studies that have been used to understand the mechanisms behind this exceptional behavior. A revised classification protocol is suggested in the conclusions, particularly with respect to the term "oxygen-tolerance". This article is part of a special issue entitled: metals in bioenergetics and biomimetics systems. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Microstructure, AC impedance and DC electrical conductivity characteristics of NiFe2-xGdxO4 (x = 0, 0.05 and 0.075)

    NASA Astrophysics Data System (ADS)

    Kamala Bharathi, K.; Markandeyulu, G.; Ramana, C. V.

    2012-03-01

    The structure and electrical characteristics of Gd doped Ni ferrite materials, namely NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4, are reported to demonstrate their improved electrical properties compared to that of pure NiFe2O4. NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds crystallize in the cubic inverse spinel phase with a very small amount of GdFeO3 additional phase while pure NiFe2O4 crystallize in inverse spinel phase without any impurity phase. The back scattered electron imaging analysis indicate the primary and secondary formation in NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds. Atomic force microscopy measurements indicate that the bulk grains are ˜2-5 micron size while the grain boundaries are thin compared to bulk grains. Impedance spectroscopic analysis at different temperature indicates the different relaxation mechanisms and their variation with temperature, bulk grain and grain-boundary contributions to the electrical conductivity (Rg) and capacitance (Cg) of these materials. The conductivity in pure NiFeO4 is found to be predominantly due to intrinsic bulk contribution (Rg=213 kΩ and Cg=4.5 x 10-8 F). In the case of NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds, grain and grain-boundary contributions to the conductivity are clearly observed. The DC conductivity values (at 300 K) of NiFe2O4, NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds are found to be 1.06 x 10-7 Ω-1 cm-1, 5.73 x 10-8 Ω-1 cm-1 and 1.28 x 10-8 Ω-1 cm-1 respectively.

  7. Room-temperature ferromagnetic transitions and the temperature dependence of magnetic behaviors in FeCoNiCr-based high-entropy alloys

    NASA Astrophysics Data System (ADS)

    Na, Suok-Min; Yoo, Jin-Hyeong; Lambert, Paul K.; Jones, Nicholas J.

    2018-05-01

    High-entropy alloys (HEAs) containing multiple principle alloying elements exhibit unique properties so they are currently receiving great attention for developing innovative alloy designs. In FeCoNi-based HEAs, magnetic behaviors strongly depend on the addition of alloying elements, usually accompanied by structural changes. In this work, the effect of non-magnetic components on the ferromagnetic transition and magnetic behaviors in equiatomic FeCoNiCrX (X=Al, Ga, Mn and Sn) HEAs was investigated. Alloy ingots of nominal compositions of HEAs were prepared by arc melting and the button ingots were cut into discs for magnetic measurements as functions of magnetic field and temperature. The HEAs of FeCoNiCrMn and FeCoNiCrSn show typical paramagnetic behaviors, composed of solid solution FCC matrix, while the additions of Ga and Al in FeCoNiCr exhibit ferromagnetic behaviors, along with the coexistence of FCC and BCC phases due to spinodal decomposition. The partial phase transition in both HEAs with the additions of Ga and Al would enhance ferromagnetic properties due to the addition of the BCC phase. The saturation magnetization for the base alloy FeCoNiCr is 0.5 emu/g at the applied field of 20 kOe (TC = 104 K). For the HEAs of FeCoNiCrGa and FeCoNiCrAl, the saturation magnetization significantly increased to 38 emu/g (TC = 703 K) and 25 emu/g (TC = 277 K), respectively. To evaluate the possibility of solid solution FCC and BCC phases in FeCoNiCr-type HEAs, we introduced a parameter of valence electron concentration (VEC). The proposed rule for solid solution formation by the VEC was matched with FeCoNiCr-type HEAs.

  8. Electrodeposition of amorphous Ni P coatings onto Nd Fe B permanent magnet substrates

    NASA Astrophysics Data System (ADS)

    Ma, C. B.; Cao, F. H.; Zhang, Z.; Zhang, J. Q.

    2006-12-01

    Decorative and protective Ni-P amorphous coatings were electroplated onto NdFeB permanent magnet from an ortho-phosphorous acid contained bath. The influences of the main electroplating technological parameters including current density, bath pH, bath temperature and H3PO3 on the structure and chemical composition of Ni-P coatings were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques in conjunction with X-ray diffraction (XRD), scanning transmission electron microscopy (SEM) and X-ray energy-dispersive spectrometry (EDX). The optimized amorphous Ni-P coated NdFeB can stand for ca. 180 h against neutral 3.0 wt.% NaCl salt spray without any pitting corrosion. Meanwhile, the results also showed that large phosphorous content is the precondition for Ni-P coatings to possess the amorphous structure, but too much high phosphorous content can damage the amorphous structure due to the separation of superfluous P from Ni2P/Ni3P and the resultant formation of multi-phase coatings (such as Ni2P-P).

  9. Significant enhancement in photocatalytic performance of Ni doped BiFeO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Nadeem, M.; Khan, Wasi; Khan, Shakeel; Shoeb, Mohd; Husain, Shahid; Mobin, Mohammad

    2018-06-01

    In the present work, we have investigated the effect of Ni doping on the microstructure and photocatalytic properties of BiFeO3 samples. All the compositions of BiFe1‑xNixO3 (0 ≤ x ≤ 0.07) have been synthesized via cost effective ethylene glycol based sol-gel method. The Rietveld refinement of the XRD data revealed rhombohedral crystal structure with R3c space group. The FTIR spectroscopy confirms the formation of BiFeO3 compound. UV–visible DRS result affirmed that the band gap of the samples can be tuned towards visible range by the Ni substitution. The photoluminescence spectra indicate lower intensity with the Ni content, signify reduction in recombination rate of the electron-hole pairs. The photocatalytic response of the nanoparticles was examined for the degradation of methylene blue (MB) dye under visible light irradiation and the highest photocatalytic response was observed for 7% Ni doped sample. Therefore, the observed results suggest potential application of the synthesized nanoparticles for wastewater treatment purpose.

  10. Ag/α-Fe{sub 2}O{sub 3} hollow microspheres: Preparation and application for hydrogen peroxide detection

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kang, Xinyuan; Wu, Zhiping; Liao, Fang, E-mail: liaozhang2003@163.com

    2015-09-15

    In this paper, we demonstrated a simple approach for preparing α-Fe{sub 2}O{sub 3} hollow spheres by mixing ferric nitrate aqueous and glucose in 180 °C. The glucose was found to act as a soft template in the process of α-Fe{sub 2}O{sub 3} hollow spheres formation. Ag/α-Fe{sub 2}O{sub 3} hollow nanocomposite was obtained under UV irradiation without additional reducing agents or initiators. Synthesized Ag/α-Fe{sub 2}O{sub 3} hollow composites exhibited remarkable catalytic performance toward H{sub 2}O{sub 2} reduction. The electrocatalytic activity mechanism of Ag/α-Fe{sub 2}O{sub 3}/GCE were discussed toward the reduction of H{sub 2}O{sub 2} in this paper. - Graphical abstract: Glucosemore » is carbonized as carbon balls in the 180 °C hydrothermal carbonization process, which plays a role of a soft template. Carbon spherical shell is rich in many hydroxyls, which have good hydrophilicity and surface reactivity. When Fe(NO{sub 3}){sub 3} is added to the aqueous solution of Glucose, the hydrophilic -OH will adsorb Fe{sup 3+} to form coordination compound by coordination bond. α-FeOOH is formed on the surface of carbon balls by hydrothermal reaction. After calcination at 500 °C, carbon spheres react with oxygen to form carbon dioxide, which disappears in the air. Meanwhile α-FeOOH is calcined to form α-Fe{sub 2}O{sub 3} hollow spheres.« less

  11. Heterologous Expression of the Desulfovibrio gigas [NiFe] Hydrogenase in Desulfovibrio fructosovorans MR400

    PubMed Central

    Rousset, Marc; Magro, Valérie; Forget, Nicole; Guigliarelli, Bruno; Belaich, Jean-Pierre; Hatchikian, E. Claude

    1998-01-01

    The ability of Desulfovibrio fructosovorans MR400 ΔhynABC to express the heterologous cloned [NiFe] hydrogenase of Desulfovibrio gigas was investigated. The [NiFe] hydrogenase operon from D. gigas, hynABCD, was cloned, sequenced, and introduced into D. fructosovorans MR400. A portion of the recombinant heterologous [NiFe] hydrogenase was totally matured, exhibiting catalytic and spectroscopic properties identical to those of the native D. gigas protein. A chimeric operon containing hynAB from D. gigas and hynC from D. fructosovorans placed under the control of the D. fructosovorans hynAp promoter was constructed and expressed in D. fructosovorans MR400. Under these conditions, the same level of activity was obtained as with the D. gigas hydrogenase operon. PMID:9733707

  12. Heterologous expression of the Desulfovibrio gigas [NiFe] hydrogenase in Desulfovibrio fructosovorans MR400.

    PubMed

    Rousset, M; Magro, V; Forget, N; Guigliarelli, B; Belaich, J P; Hatchikian, E C

    1998-09-01

    The ability of Desulfovibrio fructosovorans MR400 DeltahynABC to express the heterologous cloned [NiFe] hydrogenase of Desulfovibrio gigas was investigated. The [NiFe] hydrogenase operon from D. gigas, hynABCD, was cloned, sequenced, and introduced into D. fructosovorans MR400. A portion of the recombinant heterologous [NiFe] hydrogenase was totally matured, exhibiting catalytic and spectroscopic properties identical to those of the native D. gigas protein. A chimeric operon containing hynAB from D. gigas and hynC from D. fructosovorans placed under the control of the D. fructosovorans hynAp promoter was constructed and expressed in D. fructosovorans MR400. Under these conditions, the same level of activity was obtained as with the D. gigas hydrogenase operon.

  13. Fe-Ni metal in primitive chondrites: Indicators of classification and metamorphic conditions for ordinary and CO chondrites

    USGS Publications Warehouse

    Kimura, M.; Grossman, J.N.; Weisberg, M.K.

    2008-01-01

    We report the results of our petrological and mineralogical study of Fe-Ni metal in type 3 ordinary and CO chondrites, and the ungrouped carbonaceous chondrite Acfer 094. Fe-Ni metal in ordinary and CO chondrites occurs in chondrule interiors, on chondrule surfaces, and as isolated grains in the matrix. Isolated Ni-rich metal in chondrites of petrologic type lower than type 3.10 is enriched in Co relative to the kamacite in chondrules. However, Ni-rich metal in type 3.15-3.9 chondrites always contains less Co than does kamacite. Fe-Ni metal grains in chondrules in Semarkona typically show plessitic intergrowths consisting of submicrometer kamacite and Ni-rich regions. Metal in other type 3 chondrites is composed of fine- to coarse-grained aggregates of kamacite and Ni-rich metal, resulting from metamorphism in the parent body. We found that the number density of Ni-rich grains in metal (number of Ni-rich grains per unit area of metal) in chondrules systematically decreases with increasing petrologic type. Thus, Fe-Ni metal is a highly sensitive recorder of metamorphism in ordinary and carbonaceous chondrites, and can be used to distinguish petrologic type and identify the least thermally metamorphosed chondrites. Among the known ordinary and CO chondrites, Semarkona is the most primitive. The range of metamorphic temperatures were similar for type 3 ordinary and CO chondrites, despite them having different parent bodies. Most Fe-Ni metal in Acfer 094 is martensite, and it preserves primary features. The degree of metamorphism is lower in Acfer 094, a true type 3.00 chondrite, than in Semarkona, which should be reclassified as type 3.01. ?? The Meteoritical Society, 2008.

  14. Composition gradient, structure, stress, roughness and magnetic properties of 5-500 nm thin NiFe films obtained by electrodeposition

    NASA Astrophysics Data System (ADS)

    Gong, Jie; Riemer, Steve; Kautzky, Michael; Tabakovic, Ibro

    2016-01-01

    The composition gradients of 5-500 nm thin NiFe films on Cu and NiP substrates obtained by electrodeposition in stirred plating solutions at pH 3.0 on 8 in wafers were studied. It was found that the average elemental composition of the NiFe changes during electrodeposition with steep downturns of Fe-content, from 58 to 50 wt% Fe, in composition gradient zone near the substrate interface in the thickness range 5-250 nm depending on the electrode substrate (Cu and NiP). The increase of Fe-content in the composition gradient zone is accompanied by the increase of coercivity, Hc, magnetic flux saturation, Bs, saturation magnetostriction, λs, increase of dimensionless roughness, ρrms, and change of stress, σ. The coercivity (easy and hard axis) follows the Neel's relation Hc=ct-n (t is thickness and c is a constant). The mechanisms related to the change of coercivity of the NiFe films deposited on different substrates (Cu and NiP) are discussed in terms of material properties of these films.

  15. Lightweight NiFe2O4 with controllable 3D network structure and enhanced microwave absorbing properties

    NASA Astrophysics Data System (ADS)

    Wang, Fen; Wang, Xing; Zhu, Jianfeng; Yang, Haibo; Kong, Xingang; Liu, Xiao

    2016-11-01

    3D network structure NiFe2O4 was successfully synthesized by a templated salt precipitation method using PMMA colloid crystal as templates. The morphology, phase composition and microwave absorbing properties of as-prepared samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), vector network analyzer (VNA), and so on. The results revealed that the 3D network structure was configurated with smooth spherical walls composed of NiFe2O4 nanocrystals and their pore diameters being in the range of 80-250 nm. The microwave absorption properties of the 3D network structure NiFe2O4 were crucially determined by the special structure. The synergy of intrinsic magnetic loss of magnetic NiFe2O4 and the interfacial polarization enhanced by 3D network structure and the interaction of multiple mechanisms endowed the sample with the feature of strong absorption, broad bandwidth and lightweight. There is more than one valley in the reflection loss curves and the maximum reflection loss is 27.5 dB with a bandwidth of 4 GHz. Moreover, the 3D network structure NiFe2O4 show a greater reflection loss with the same thickness comparing to the ordinary NiFe2O4 nanoparticles, which could achieve the feature of lightweight of the microwave absorbing materials.

  16. Lightweight NiFe2O4 with controllable 3D network structure and enhanced microwave absorbing properties

    PubMed Central

    Wang, Fen; Wang, Xing; Zhu, Jianfeng; Yang, Haibo; Kong, Xingang; Liu, Xiao

    2016-01-01

    3D network structure NiFe2O4 was successfully synthesized by a templated salt precipitation method using PMMA colloid crystal as templates. The morphology, phase composition and microwave absorbing properties of as-prepared samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), vector network analyzer (VNA), and so on. The results revealed that the 3D network structure was configurated with smooth spherical walls composed of NiFe2O4 nanocrystals and their pore diameters being in the range of 80–250 nm. The microwave absorption properties of the 3D network structure NiFe2O4 were crucially determined by the special structure. The synergy of intrinsic magnetic loss of magnetic NiFe2O4 and the interfacial polarization enhanced by 3D network structure and the interaction of multiple mechanisms endowed the sample with the feature of strong absorption, broad bandwidth and lightweight. There is more than one valley in the reflection loss curves and the maximum reflection loss is 27.5 dB with a bandwidth of 4 GHz. Moreover, the 3D network structure NiFe2O4 show a greater reflection loss with the same thickness comparing to the ordinary NiFe2O4 nanoparticles, which could achieve the feature of lightweight of the microwave absorbing materials. PMID:27897209

  17. Half-metallic ferromagnetism in Fe, Co and Ni doped BaS: First principles calculations

    NASA Astrophysics Data System (ADS)

    Maurya, Savita; Sharma, Ramesh; Bhamu, K. C.

    2018-04-01

    The first principle investigation of structural, electronic, magnetic and optical properties of Ba1-xTMxS (x = 0.25) have been done using FPLAW method within the density functional theory (DFT) using generalized gradient approximation (GGA) for exchange correlation potential using two different functionals which are the PBE-sol and the modified Becke and Johnson local (spin) density approximation (mBJLDA). It was found that mBJLDA functional offer better account for the electronic structure of the Fe, Co and Ni-doped BaS. It was also observed that Fe/Co/Ni d, S p and Ba d states play a major role in determining the electronic properties of this alloy system. Investigation results shows that Ba0.75(Fe/Co/Ni)0.25S is ferromagnetic with magnetic moment of 3.72 µB, 2.73908 µB and 1.74324 µB at Fe, Co and Ni sites respectively. Complex dielectric constant ɛ(ω) and normal incidence reflectivity R(ω) are also been investigate for broad range of photon energies. These results are compared with the some reported existing experimental values.

  18. Highly Reflective Nonalloyed Ni/Ag/Pt Contact to Mg-Si Codoped p-GaN for Enhanced Efficiency of Light-Emitting Diodes.

    PubMed

    Oh, Munsik; Kim, Hyunsoo

    2015-10-01

    The authors report enhanced efficiency of GaN-based light-emitting diodes (LEDs) fabricated with highly reflective nonalloyed Ni/Ag/Pt contact. The Ni/Ag/Pt contact formed on the Mg-Si codoped p-GaN produced the low specific contact resistance of 7.9 x 10(-4) Ωcm2 under as-deposited condition, which is comparable to the reference reflector (annealed at 500 °C for 1 min in oxygen ambient). Current-voltage-temperature measurements and the secondary ion mass spectroscopy revealed that the ohmic mechanism of the nonalloyed Ni/Ag/Pt contact is due to the more generated deep-level states associated with Mg-Si codoping, which act as the efficient hopping centers for the carrier transport at the contact/p-GaN interface. Due to the absence of interfacial reaction, the nonalloyed Ni/Ag/Pt contact showed much higher optical reflectivity (93.4% at 450 nm) as compared to the annealed sample (57.7%), resulting in a 40.5% brighter light output power as compared to the reference LEDs.

  19. Low-cost Fe--Ni--Cr alloys for high temperature valve applications

    DOEpatents

    Muralidharan, Govindarajan

    2017-03-28

    An Fe--Ni--Cr alloy is composed essentially of, in terms of weight percent: 1 to 3.5 Al, up to 2 Co, 15 to 19.5 Cr, up to 2 Cu, 23 to 40 Fe, up to 0.3 Hf, up to 4 Mn, 0.15 to 2 Mo, up to 0.15 Si, up to 1.05 Ta, 2.8 to 4.3 Ti, up to 0.5 W, up to 0.06 Zr, 0.02 to 0.15 C, 0.0001 to 0.007 N, balance Ni, wherein, in terms of atomic percent: 6.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.10, 0.33.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.065, 4.ltoreq.(Fe+Cr)/(Al+Ti+Zr+Hf+Ta).ltoreq.10, the alloy being essentially free of Nb and V.

  20. Influence of media with different acidity on structure of FeNi nanotubes

    NASA Astrophysics Data System (ADS)

    Shumskaya, Alena; Kaniukov, Egor; Kutuzau, Maksim; Bundyukova, Victoria; Tulebayeva, Dinara; Kozlovskiy, Artem; Borgekov, Daryn; Kenzhina, Inesh; Zdorovets, Maxim

    2018-04-01

    A detailed analysis of the structure features of FeNi nanotubes exposed at environment with different acidity is carried out. It is demonstrated that the exposure of the nanostructures in the environment with high acidity causes the structure deformation, leading to sharply increasing of the presents of oxide phases and partial amorphization of nanotubes walls that determined the rate of FeNi nanotubes destruction. It was established that the evolution of the crystal structure parameters concerned with appearance of oxide phases and with formation of disorder regions as a result of oxidation processes.

  1. Surface Electrochemical Modification of a Nickel Substrate to Prepare a NiFe-based Electrode for Water Oxidation.

    PubMed

    Guo, Dingyi; Qi, Jing; Zhang, Wei; Cao, Rui

    2017-01-20

    The slow kinetics of water oxidation greatly jeopardizes the efficiency of water electrolysis for H 2 production. Developing highly active water oxidation electrodes with affordable fabrication costs is thus of great importance. Herein, a Ni II Fe III surface species on Ni metal substrate was generated by electrochemical modification of Ni in a ferrous solution by a fast, simple, and cost-effective procedure. In the prepared Ni II Fe III catalyst film, Fe III was incorporated uniformly through controlled oxidation of Fe II cations on the electrode surface. The catalytically active Ni II originated from the Ni foam substrate, which ensured the close contact between the catalyst and the support toward improved charge-transfer efficiency. The as-prepared electrode exhibited high activity and long-term stability for electrocatalytic water oxidation. The overpotentials required to reach water oxidation current densities of 50, 100, and 500 mA cm -2 are 276, 290, and 329 mV, respectively. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Proton Transfer in the Catalytic Cycle of [NiFe] Hydrogenases: Insight from Vibrational Spectroscopy

    PubMed Central

    2017-01-01

    Catalysis of H2 production and oxidation reactions is critical in renewable energy systems based around H2 as a clean fuel, but the present reliance on platinum-based catalysts is not sustainable. In nature, H2 is oxidized at minimal overpotential and high turnover frequencies at [NiFe] catalytic sites in hydrogenase enzymes. Although an outline mechanism has been established for the [NiFe] hydrogenases involving heterolytic cleavage of H2 followed by a first and then second transfer of a proton and electron away from the active site, details remain vague concerning how the proton transfers are facilitated by the protein environment close to the active site. Furthermore, although [NiFe] hydrogenases from different organisms or cellular environments share a common active site, they exhibit a broad range of catalytic characteristics indicating the importance of subtle changes in the surrounding protein in controlling their behavior. Here we review recent time-resolved infrared (IR) spectroscopic studies and IR spectroelectrochemical studies carried out in situ during electrocatalytic turnover. Additionally, we re-evaluate the significant body of IR spectroscopic data on hydrogenase active site states determined through more conventional solution studies, in order to highlight mechanistic steps that seem to apply generally across the [NiFe] hydrogenases, as well as steps which so far seem limited to specific groups of these enzymes. This analysis is intended to help focus attention on the key open questions where further work is needed to assess important aspects of proton and electron transfer in the mechanism of [NiFe] hydrogenases. PMID:28413691

  3. Room temperature spin valve effect in NiFe/WS₂/Co junctions.

    PubMed

    Iqbal, Muhammad Zahir; Iqbal, Muhammad Waqas; Siddique, Salma; Khan, Muhammad Farooq; Ramay, Shahid Mahmood

    2016-02-12

    The two-dimensional (2D) layered electronic materials of transition metal dichalcogenides (TMDCs) have been recently proposed as an emerging canddiate for spintronic applications. Here, we report the exfoliated single layer WS2-intelayer based spin valve effect in NiFe/WS2/Co junction from room temperature to 4.2 K. The ratio of relative magnetoresistance in spin valve effect increases from 0.18% at room temperature to 0.47% at 4.2 K. We observed that the junction resistance decreases monotonically as temperature is lowered. These results revealed that semiconducting WS2 thin film works as a metallic conducting interlayer between NiFe and Co electrodes.

  4. Electronic and magnetic properties of Fe-, Co-, and Ni-decorated BC3: A first-principles study

    NASA Astrophysics Data System (ADS)

    Zhu, Jingzhong; Zhao, Yinchang; Zulfiqar, Muhammad; Zeng, Shuming; Ni, Jun

    2018-05-01

    The electronic and magnetic properties of Fe-, Co-, and Ni-decorated two dimensional (2D) BC3 are systematically investigated by first-principles calculations. We find that the Fe, Co, and Ni atoms can be strongly adsorbed on the hollow sites of 2D BC3. Fe and Co adatoms are more stable when adsorbed on the hollow sites of the carbon rings in the 2D BC3, while the hollow sites of boron-carbon rings in the 2D BC3 are the most stable sites for the adsorption of Ni adatoms. These proposed metal-BC3 complexes exhibit interesting electronic and magnetic behaviors. In particular, the Fe-BC3 and Co-BC3 complexes are metals with magnetic ground states , while the Ni-BC3 complex behaves as a nonmagnetic semiconductor with a direct bandgap. Furthermore, our magnetic analysis reveals that induced magnetism in the Fe-BC3 and Co-BC3 complexes arises from their local magnetic moments. Functionalization of 2D BC3 through these metal-adatom adsorption appears to be a promising way to extend its applications.

  5. Complex magnetic structure of clusters and chains of Ni and Fe on Pt(111)

    PubMed Central

    Bezerra-Neto, Manoel M.; Ribeiro, Marcelo S.; Sanyal, Biplab; Bergman, Anders; Muniz, Roberto B.; Eriksson, Olle; Klautau, Angela B.

    2013-01-01

    We present an approach to control the magnetic structure of adatoms adsorbed on a substrate having a high magnetic susceptibility. Using finite Ni-Pt and Fe-Pt nanowires and nanostructures on Pt(111) surfaces, our ab initio results show that it is possible to tune the exchange interaction and magnetic configuration of magnetic adatoms (Fe or Ni) by introducing different numbers of Pt atoms to link them, or by including edge effects. The exchange interaction between Ni (or Fe) adatoms on Pt(111) can be considerably increased by introducing Pt chains to link them. The magnetic ordering can be regulated allowing for ferromagnetic or antiferromagnetic configurations. Noncollinear magnetic alignments can also be stabilized by changing the number of Pt-mediated atoms. An Fe-Pt triangularly-shaped nanostructure adsorbed on Pt(111) shows the most complex magnetic structure of the systems considered here: a spin-spiral type of magnetic order that changes its propagation direction at the triangle vertices. PMID:24165828

  6. A facile route to the synthesis of magnetically separable BiOBr/NiFe2O4 composites with enhanced photocatalytic performance

    NASA Astrophysics Data System (ADS)

    Li, Xiaowei; Wang, Li; Zhang, Lei; Zhuo, Shuping

    2017-10-01

    Novel magnetically separable BiOBr/NiFe2O4 composite photocatalysts with different mass ratios were fabricated through a facile hydrothermal treatment. The phases, morphologies and photophysical properties of the as-obtained samples were characterized by X-ray diffraction (XRD), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microcopy (TEM) and diffuse reflection spectroscopy (DRS). Their visible light photocatalytic performances were examined by degradation of methylene blue (MB) and phenol. Compared with bare BiOBr and NiFe2O4, all heterostructured BiOBr/NiFe2O4 nanocomposites exhibited significantly enhanced photocatalytic efficiency. The BiOBr/NiFe2O4-20% composite showed the highest photodegradation capacity, which was about 3.2 and 22.4 times greater than that of individual BiOBr and NiFe2O4, respectively. The degradation efficiency of BiOBr/NiFe2O4-20% in the degradation of MB dye hardly changed after five cycles, signifying that the BiOBr/NiFe2O4-20% photocatalyst had excellent recyclability. In addition, BiOBr/NiFe2O4 composite photocatalysts could be easily separated from contaminant solution by using a magnet and recycled, exhibiting great potential for application in the fields of environmental purification of organic pollutants and wastewater treatment. In the light of experimental results, we proposed a photocatalytic mechanism which confirmed that the enhancement of photocatalytic performance for BiOBr/NiFe2O4 composites was mainly ascribed to the efficient separation of photo-induced charges resulting from the well-known "heterostructure effect" between NiFe2O4 nanorods and BiOBr nanosheets.

  7. Intermixing enables strong exchange coupling in nanocomposites: Magnetism through the interfacial ferrite in γ -Fe2O3/NiO

    NASA Astrophysics Data System (ADS)

    Skoropata, E.; Su, T. T.; Ouyang, H.; Freeland, J. W.; van Lierop, J.

    2017-07-01

    γ -Fe2O3 particles, surface modified with NiO crystallites, form a unique nanocomposite that points to how to tune strong interfacial exchange coupling. We find that Ni2 + migrates into the octahedral sites of the γ -Fe2O3 nanoparticle surface, and this NiFe2O4 -like layer permits effective magnetic coupling of Ni and Fe sites that strengthens the interface exchange. A large increase in coercivity coinciding with a loss of exchange bias is achieved by this strong interfacial coupling that results in a Ni2 + moment reversal in the NiO with the γ -Fe2O3 . This work reveals the importance of intermixing in, and possibility to use, such an exchange coupling regime to alter substantially the coercivity and hence control an important property of exchange-coupled nanocomposite magnets.

  8. Phase Evolution and Properties of Al2CrFeNiMo x High-Entropy Alloys Coatings by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Jiang, Li; Jiang, Hui; Pan, Xuemin; Cao, Zhiqiang; Deng, Dewei; Wang, Tongmin; Li, Tingju

    2015-10-01

    A series of Al2CrFeNiMo x ( x = 0 to 2.0 at.%) high-entropy alloys coatings was synthesized on stainless steel by laser cladding. The effect of Mo content on the microstructures and mechanical properties of Al2CrFeNiMo x coatings was studied. The results show that the laser clad layer consists of the cladding zone, bonding zone, and heat-affected zone. The Al2CrFeNiMo x coatings are composed of two simple body-center cubic phases and the cladding zone is mainly composed of equiaxed grains. When the content of Mo reaches 2 at.%, a eutectic structure is found in the interdendritic regions. The surface microhardness of the Al2CrFeNiMo2 coating is 678 HV, which is about three times higher than that of the substrate (243 HV). Compared with stainless steel, the wear resistance of the coatings has been improved greatly. The wear mass loss of the Al2CrFeNiMo alloy is 9.8 mg, which is much less than that of the substrate (18.9 mg) and its wear scar width is the lowest among the Al2CrFeNiMo x coatings, indicating that the wear resistance of the Al2CrFeNiMo is the best.

  9. Highly-active oxygen evolution electrocatalyzed by an Fe-doped NiCr2O4 nanoparticle film.

    PubMed

    Zhao, Jinxiu; Li, Xianghong; Cui, Guanwei; Sun, Xuping

    2018-05-11

    Alkaline water splitting offers a simple method for the mass production of hydrogen but suffers from the sluggish kinetics of the anodic oxygen evolution reaction (OER). Here, we report on the development of an Fe-doped NiCr2O4 nanoparticle film on Ni foam (Fe-NiCr2O4/NF) as a non-noble-metal OER electrocatalyst with superior catalytic activity at alkaline pH. Such Fe-NiCr2O4/NF demands overpotentials as low as 228 and 318 mV to drive current densities of 20 and 500 mA cm-2, respectively, in 1.0 M KOH. Notably, it also shows strong long-term electrochemical durability with its activity being retained for at least 60 h.

  10. Magnetic resonance of the NiFe2O4 nanoparticles in the gigahertz range

    PubMed Central

    2013-01-01

    We report an adjustable magnetic resonance frequency from 1.45 to 2.54 GHz for NiFe2O4 nanoparticles which were prepared by a sol–gel process. X-ray diffraction and scanning electron microscopy results indicate that the samples are polycrystalline nanoparticles, and the size of the particles increases obviously with the thermal treatment temperature. The consequence of the surface composition suggests that the oxygen defects are present in the nanoparticle surface, and this surface magnetic state can show a strong surface anisotropy. With decreasing size of the particle, the surface magnetic effect is predominant, resulting in an increase of resonance frequency for NiFe2O4 nanoparticles. This finding provides a new route for NiFe2O4 materials that can be used in the gigahertz range. PMID:24083340

  11. Real-time wetting dynamics and interfacial chemistry in low-melting 57Bi-42Sn-1Ag solder paste on Ni-Au

    NASA Astrophysics Data System (ADS)

    Bozack, M. J.

    2004-11-01

    We report the observation of real-time, in situ, wetting and spreading dynamics for 57Bi-42Sn-1Ag solder paste on Ni-Au surfaces during melting in a scanning electron microscope. The 57Bi-42Sn-1Ag is a low melting (139 °C) Pb-free eutectic alloy currently under consideration by automobile manufacturers for use in instrument displays. We find that, while there is excellent wetting of 57Bi-42Sn-1Ag solder paste on Ni-Au, there is almost no spreading. A large amount of Bi segregates to the surface of 57Bi-42Sn-1Ag solder balls during the sintering process. At melting, excessive flux outgassing and pooling are observed, several melted solder balls float on top of the flux, and substantial elemental segregation occurs during the first minutes of wetting. Neither Ni nor Au fully intermixes throughout the alloy at the interface within seconds of wetting. Bi does not move outward with the expanding alloy front. This combination of detrimental effects forms voids in the solder paste, contributes to low reliability of solder joints, and complicates the materials science at the solder-substrate interface as shown by Auger electron spectroscopy. Reliability work in progress (3000 cycles) shows that 57Bi-42Sn-1Ag on Ni-Au is less reliable than eutectic Sn-37Pb on Ni-Au for 2512 chip resistors cycled from -40 to 125 °C.

  12. An S-Oxygenated [NiFe] Complex Modelling Sulfenate Intermediates of an O2 -Tolerant Hydrogenase.

    PubMed

    Lindenmaier, Nils J; Wahlefeld, Stefan; Bill, Eckhard; Szilvási, Tibor; Eberle, Christopher; Yao, Shenglai; Hildebrandt, Peter; Horch, Marius; Zebger, Ingo; Driess, Matthias

    2017-02-13

    To understand the molecular details of O 2 -tolerant hydrogen cycling by a soluble NAD + -reducing [NiFe] hydrogenase, we herein present the first bioinspired heterobimetallic S-oxygenated [NiFe] complex as a structural and vibrational spectroscopic model for the oxygen-inhibited [NiFe] active site. This compound and its non-S-oxygenated congener were fully characterized, and their electronic structures were elucidated in a combined experimental and theoretical study with emphasis on the bridging sulfenato moiety. Based on the vibrational spectroscopic properties of these complexes, we also propose novel strategies for exploring S-oxygenated intermediates in hydrogenases and similar enzymes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Interfacial reactions and compound formation of Sn-Ag-Cu solders by mechanical alloying on electroless Ni-P/Cu under bump metallization

    NASA Astrophysics Data System (ADS)

    Kao, Szu-Tsung; Duh, Jenq-Gong

    2005-08-01

    Electroless Ni-P under bump metallization (UBM) has been widely used in electronic interconnections due to the good diffusion barrier between Cu and solder. In this study, the mechanical alloying (MA) process was applied to produce the SnAgCu lead-free solder pastes. Solder joints after annealing at 240°C for 15 min were employed to investigate the evolution of interfacial reaction between electroless Ni-P/Cu UBM and SnAgCu solder with various Cu concentrations ranging from 0.2 to 1.0 wt.%. After detailed quantitative analysis with an electron probe microanalyzer, the effect of Cu content on the formation of intermetallic compounds (IMCs) at SnAgCu solder/electroless Ni-P interface was evaluated. When the Cu concentration in the solder was 0.2 wt.%, only one (Ni, Cu)3Sn4 layer was observed at the solder/electroless Ni-P interface. As the Cu content increased to 0.5 wt.%, (Cu, Ni)6Sn5 formed along with (Ni, Cu)3Sn4. However, only one (Cu, Ni)6Sn5 layer was revealed, if the Cu content was up to 1 wt.%. With the aid of microstructure evolution, quantitative analysis, and elemental distribution by x-ray color mapping, the presence of the Ni-Sn-P phase and P-rich layer was evidenced.

  14. Orientation dependence of elastic and piezomagnetic properties in NiFe2O4

    NASA Astrophysics Data System (ADS)

    Jian, Gang; Xue, Fei; Zhang, Chen; Yan, Chao; Zhao, Ning; Wong, C. P.

    2017-11-01

    In this paper, the crystal orientation dependence of the elastic and piezomagnetic properties have been calculated for nickel ferrite (NiFe2O4) in three-dimensional space by means of coordinate transformations. The maximum elastic compliances s11‧, s12‧ and piezomagnetic constants q31‧, q33‧ along specific orientations have been determined based on experimental data of NiFe2O4 and original matrices for m3m point group. The piezomagnetic constants q31‧ and q33‧ show highly dependence on crystal orientation compared with elastic compliances s11‧, s12‧, meanwhile permittivity μ33‧ is a constant. The max s11‧ and s12‧ can be obtained along directions [n k l] (n·k = 0, l ≠ 0) and [n k l] (n·k·l = 0), respectively. The max q31‧ and max q33‧ lie along [0 0 1] and [1 1 1] axes, respectively, NiFe2O4||[1 1 1] axis can produce large q31‧ and q33‧ at the same time. The result suggests that by adopting the optimal directions, the elastic and piezomagnetic properties of the devices made from NiFe2O4 can be precisely modulated.

  15. NiFe layered double hydroxide/reduced graphene oxide nanohybrid as an efficient bifunctional electrocatalyst for oxygen evolution and reduction reactions

    NASA Astrophysics Data System (ADS)

    Zhan, Tianrong; Zhang, Yumei; Liu, Xiaolin; Lu, SiSi; Hou, Wanguo

    2016-11-01

    Highly active and low-cost bifunctional electrocatalysts for oxygen evolution and reduction reactions (OER and ORR) hold a heart position for the renewable energy technologies such as metal-air batteries and fuel cells. Here, we reported the synthesis of NiFe layered double hydroxide/reduced graphene oxide (NiFe-LDH/rGO) nanohybrid via the facile solvothermal method followed by chemical reduction. The template role of surfactant and the hybridization of rGO supplied the NiFe-LDH/rGO catalyst with a porous nanostructure and an enhanced conductivity, favoring both mass transport and charge communication of electrocatalytic reactions. The NiFe-LDH/rGO composite not only displayed highly efficient OER activity in alkaline solution with a low onset overpotential of 240 mV, but also only needed an overpotential of 250 mV to reach the 10 mA cm-2 current density. The NiFe-LDH/rGO nanohybrid also offered excellent ORR catalytic activity with onset potential at 0.796 V in alkaline media. The rotating-disk and rotating-ring-disk electrodes both revealed that the ORR on NiFe-LDH/rGO mainly involved a direct four-electron reaction pathways accompanying part of the two-electron process. The excellent bifunctional activity of the NiFe-LDH/rGO nanohybrid could be attributed to the synergistic effects of rGO and NiFe-LDH components due to the strongly coupled interactions.

  16. Study of Metal-NH[subscript 3] Interfaces (Metal= Cu, Ni, Ag) Using Potentiostatic Curves

    ERIC Educational Resources Information Center

    Nunes, Nelson; Martins, Angela; Leitao, Ruben Elvas

    2007-01-01

    Experiment is conducted to determine the kinetic parameters of metal-solution interfaces. During the experiment the kinetic parameters for the interfaces Cu-NH[subscript 3], Ag-NH[subscript 3] and Ni-NH[subscript 3] is easily determined.

  17. High Ms Fe16N2 thin film with Ag under layer on GaAs substrate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Allard Jr, Lawrence Frederick

    2016-01-01

    (001) textured Fe16N2 thin film with Ag under layer is successfully grown on GaAs substrate using a facing target sputtering (FTS) system. After post annealing, chemically ordered Fe16N2 phase is formed and detected by X-ray diffraction (XRD). High saturation magnetization (Ms) is measured by a vibrating sample magnetometer (VSM). In comparison with Fe16N2 with Ag under layer on MgO substrate and Fe16N2 with Fe under layer on GaAs substrate, the current layer structure shows a higher Ms value, with a magnetically softer feature in contrast to the above cases. In addition, X-ray photoelectron spectroscopy (XPS) is performed to characterize themore » binding energy of N atoms. To verify the role of strain that the FeN layer experiences in the above three structures, Grazing Incidence X-ray Diffraction (GIXRD) is conducted to reveal a large in-plane lattice constant due to the in-plane biaxial tensile strain. INTRODUCTION« less

  18. Modifying exchange-spring behavior of CoPt/NiFe bilayer by inserting a Pt or Ru spacer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hsu, Jen-Hwa, E-mail: jhhsu@phys.ntu.edu.tw; Tsai, C. L.; Lee, C.-M.

    2015-05-07

    We herein explore the possibility of obtaining tunable tilted magnetic anisotropy in ordered-CoPt (5 nm)/NiFe(t{sub NiFe}) bilayers through modifying their exchange spring behavior by inserting Pt and Ru-spacers. The tuning process of tilt angle magnetization of NiFe-layer was systematically investigated by varying the Pt or Ru thickness (t{sub Pt} or t{sub Ru}) from 0 to 8 nm at different thicknesses of NiFe (t{sub NiFe} = 1.5, 4.0, and 6.0 nm). Polar magneto-optic Kerr effect (p-MOKE) studies reveal that the bilayers grown in absence of spacers exhibit almost a rectangular hysteresis loop. With the insertion of Pt-spacer, the loop becomes more and more tilted as t{submore » Pt} increases; whereas, in the case of Ru-spacer, the nature of the loops is not simply changing in one direction. The estimated SQR{sub ⊥} (= θ{sub r}/θ{sub s}) values from the p-MOKE loops are found to monotonically decrease with increasing t{sub Pt} when t{sub Pt} ≦ 4 nm. In contrast, in the case of Ru-spacer, an oscillatory behavior for the SQR{sub ⊥} values is apparent when t{sub Ru} ≦ 4 nm. As a result, an oscillatory tilted angle of NiFe spin configuration was obtained in the case of Ru-spacer; while a decoupling effect was prominent for the Pt-spacer. The results of present study reveal that the insertion of Pt and Ru-spacers as an appropriate means for realizing tunable tilted magnetic anisotropy in the CoPt/NiFe exchange springs.« less

  19. NiFe-Layered Double Hydroxide Nanosheet Arrays Supported on Carbon Cloth for Highly Sensitive Detection of Nitrite.

    PubMed

    Ma, Yue; Wang, Yongchuang; Xie, Donghua; Gu, Yue; Zhang, Haimin; Wang, Guozhong; Zhang, Yunxia; Zhao, Huijun; Wong, Po Keung

    2018-02-21

    Excessive uptake of nitrite has been proven to be detrimental to the ecological system and human health. Hence, there is a rising requirement for constructing effective electrochemical sensors to precisely monitor the level of nitrite. In this work, NiFe-layered double hydroxide nanosheet arrays (NiFe-LDH NSAs) have been successfully fabricated on a carbon cloth (CC) substrate via a facile one-pot hydrothermal route. By integrating the collective merits of macroporous CC and NiFe-LDH NSAs such as superior electrical conductivity, striking synergistic effect between the dual active components, enlarged electrochemically active surface area, unique three-dimensional hierarchical porous network characteristics, and fast charge transport and ion diffusion, the proposed NiFe-LDH NSAs/CC architecture can be served as a self-supporting sensor toward nitrite detection. As a consequence, the resulting NiFe-LDH NSAs/CC electrode demonstrates superior nitrite sensing characteristics, accompanied by broad linear range (5-1000 μM), quick response rate (ca. 3 s), ultralow detection limit (0.02 μM), and high sensitivity (803.6 μA·mM -1 ·cm -2 ). Meanwhile, the electrochemical sensor possesses timeless stability, good reproducibility, and strong anti-interference feature. Importantly, the resulting sensor can determine nitrite level in tap and lake water with high recoveries, suggesting its feasibility for practical applications. These findings show that the obtained NiFe-LDH NSAs/CC electrode holds great prospect in highly sensitive and specific detection of nitrite.

  20. Enhanced methane steam reforming activity and electrochemical performance of Ni0.9Fe0.1-supported solid oxide fuel cells with infiltrated Ni-TiO2 particles

    PubMed Central

    Li, Kai; Jia, Lichao; Wang, Xin; Pu, Jian; Chi, Bo; Li, Jian

    2016-01-01

    Ni0.9Fe0.1 alloy-supported solid oxide fuel cells with NiTiO3 (NTO) infiltrated into the cell support from 0 to 4 wt.% are prepared and investigated for CH4 steam reforming activity and electrochemical performance. The infiltrated NiTiO3 is reduced to TiO2-supported Ni particles in H2 at 650 °C. The reforming activity of the Ni0.9Fe0.1-support is increased by the presence of the TiO2-supported Ni particles; 3 wt.% is the optimal value of the added NTO, corresponding to the highest reforming activity, resistance to carbon deposition and electrochemical performance of the cell. Fueled wet CH4 at 100 mL min−1, the cell with 3 wt.% of NTO demonstrates a peak power density of 1.20 W cm−2 and a high limiting current density of 2.83 A cm−2 at 650 °C. It performs steadily for 96 h at 0.4 A cm−2 without the presence of deposited carbon in the Ni0.9Fe0.1-support and functional anode. Five polarization processes are identified by deconvoluting and data-fitting the electrochemical impedance spectra of the cells under the testing conditions; and the addition of TiO2-supported Ni particles into the Ni0.9Fe0.1-support reduces the polarization resistance of the processes ascribed to CH4 steam reforming and gas diffusion in the Ni0.9Fe0.1-support and functional anode. PMID:27775092

  1. Phase relations in the Fe-Ni-Cr-S system and the sulfidation of an austenitic stainless steel

    NASA Technical Reports Server (NTRS)

    Jacob, K. T.; Rao, D. B.; Nelson, H. G.

    1977-01-01

    The stability fields of various sulfide phases that form on Fe-Cr, Fe-Ni, Ni-Cr and Fe-Cr-Ni alloys were developed as a function of temperature and the partial pressure of sulfur. The calculated stability fields in the ternary system were displayed on plots of log P sub S sub 2 versus the conjugate extensive variable which provides a better framework for following the sulfidation of Fe-Cr-Ni alloys at high temperatures. Experimental and estimated thermodynamic data were used in developing the sulfur potential diagrams. Current models and correlations were employed to estimate the unknown thermodynamic behavior of solid solutions of sulfides and to supplement the incomplete phase diagram data of geophysical literature. These constructed stability field diagrams were in excellent agreement with the sulfide phases and compositions determined during a sulfidation experiment.

  2. Negative Thermal Expansion over a Wide Temperature Range in Fe-doped MnNiGe Composites

    NASA Astrophysics Data System (ADS)

    Zhao, Wenjun; Sun, Ying; Liu, Yufei; Shi, Kewen; Lu, Huiqing; Song, Ping; Wang, Lei; Han, Huimin; Yuan, Xiuliang; Wang, Cong

    2018-02-01

    Fe-doped MnNiGe alloys were successfully synthesized by solid-state reaction. Giant negative thermal expansion (NTE) behaviors with the coefficients of thermal expansion (CTE) of -285.23×10-6 K-1 (192-305 K) and -1167.09×10-6 K-1 (246-305 K) have been obtained in Mn0.90Fe0.10NiGe and MnNi0.90Fe0.10Ge, respectively. Furthermore, these materials were combined with Cu in order to control the NTE properties. The results indicate that the absolute value of CTE gradually decreases with increasing Cu contents. In Mn0.92Fe0.08NiGe/x%Cu, the CTE gradually changes from -64.92×10-6 K-1 (125-274 K) to -4.73×10-6 K-1 (173-229 K) with increasing value of x from 15 to 70. The magnetic measurements reveal that the NTE behaviors in this work are strongly correlated with the process of the magnetic phase transition and the introduction of Fe atoms could also change the spiral anti-ferromagnetic (s-AFM) state into ferromagnetic (FM) state at low temperature. Our study launches a new candidate for controlling thermal expansion properties of metal matrix materials which could have potential application in variable temperature environment.

  3. Structural, magnetic, dielectric, and electrical properties of NiFe2O4 spinel ferrite nanoparticles prepared by honey-mediated sol-gel combustion

    NASA Astrophysics Data System (ADS)

    Yadav, Raghvendra Singh; Kuřitka, Ivo; Vilcakova, Jarmila; Havlica, Jaromir; Masilko, Jiri; Kalina, Lukas; Tkacz, Jakub; Enev, Vojtěch; Hajdúchová, Miroslava

    2017-08-01

    In this study, NiFe2O4 nanoparticles were synthesized using a honey-mediated sol-gel combustion method. The synthesized nanoparticles and samples annealed at 800 °C and 1100 °C were characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM). XRD and Raman spectroscopy confirmed the formation of a cubic spinel ferrite structure. FE-SEM demonstrated the octahedral morphology of the NiFe2O4 spinel ferrite nanoparticles with sizes ranging from 10 to 70 nm. Quantitative analysis based on XPS suggested a mixed spinel structure comprising NiFe2O4 nanoparticles. XPS analysis determined occupation formulae of (Ni0.212+ Fe0.443+)[Ni0.792+ Fe1.563+]O4 and (Ni0.232+ Fe0.503+)[Ni0.772+ Fe1.503+]O4, for the as-prepared NiFe2O4 nanoparticles and those annealed at 1100 °C, respectively. Magnetic measurements showed that the saturation magnetization increased with the crystallite size from 32.3 emu/g (20 nm) to 49.9 emu/g (163 nm), whereas the coercivity decreased with the crystallite size from 162 Oe (20 nm) to 47 Oe (163 nm). Furthermore, the dielectric constant, dielectric loss tangent, and AC conductivity of the NiFe2O4 nanoparticles were dependent on the frequency (1-107 Hz) and grain size. The influence of the grain size was also observed by modulus spectroscopy based on the Cole-Cole plot.

  4. A novel green synthesis of Fe3O4-Ag core shell recyclable nanoparticles using Vitis vinifera stem extract and its enhanced antibacterial performance

    NASA Astrophysics Data System (ADS)

    Venkateswarlu, Sada; Natesh Kumar, B.; Prathima, B.; Anitha, K.; Jyothi, N. V. V.

    2015-01-01

    We described a novel and eco-friendly method for preparing Fe3O4-Ag core shell nanoparticles (CSNPs) with high magnetism and potent antibacterial activity. The Fe3O4-Ag CSNPs were obtained using waste material of Vitis vinifera (grape) stem extract as the green solvent, reducing and capping agent. The result recorded from X-ray powder diffraction (XRD), UV-vis spectrum, energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR) supports the biosynthesis and characterization of Fe3O4-Ag CSNPs. From transmission electron microscopy (TEM) the size of the Fe3O4-Ag nanoparticles was measured below 50 nm; high-resolution TEM (HRTEM) indicates the core shell structure; and selected area electron diffraction (SAED) has revealed polycrystalline nature. Vibrating sample magnetometer (VSM) shows the ferromagnetic nature of Fe3O4-Ag CSNPs at room temperature with saturation magnetization of 15.74 emu/g. Further, these biogenic nanoparticles were highly hazardous to microorganisms. The antibacterial activity of biogenic Fe3O4-Ag CSNPs showed potent inhibitory activity against both Gram-positive and Gram-negative pathogens. These nanoparticles may also be reusable because of its excellent ferromagnetic property.

  5. The annealing temperature dependences of microstructures and magnetic properties in electro-chemical deposited CoNiFe thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Suharyadi, Edi, E-mail: esuharyadi@ugm.ac.id; Riyanto, Agus; Abraha, Kamsul

    2016-04-19

    CoNiFe thin films with various compositions had been successfully fabricated using electro-chemical deposition method. The crystal structure of Co{sub 65}Ni{sub 15}Fe{sub 20}, Co{sub 62}Ni{sub 15}Fe{sub 23}, and Co{sub 55}Ni{sub 15}Fe{sub 30} thin films was fcc, bcc-fcc mix, and bcc, respectively. The difference crystal structure results the difference in magnetic properties. The saturation magnetic flux density (Bs) of Co{sub 65}Ni{sub 15}Fe{sub 20}, Co{sub 62}Ni{sub 15}Fe{sub 23}, and Co{sub 55}Ni{sub 15}Fe{sub 30} thin films was 1.89 T, 1.93 T, and 2.05 T, respectively. An optimal annealing temperature was determined for controlling the microstructure and magnetic properties of CoNiFe thin films. Depending onmore » annealing temperature, the ratio of bcc and fcc structure varied without changing the film composition. By annealing at temperature of T ≥ 350°C, the intensity ratio of X-ray diffraction peaks for bcc(110) to fcc(111) increased. The increase of phase ratio of bcc(110) to fcc(111) caused the increase of Bs, from 1.89 T to 1.95 T. Coercivity (Hc) also increased after annealing, from 2.6 Oe to 18.6 Oe for fcc phase thin films, from 2.0 Oe to 12.0 Oe for fcc-bcc mix phase thin films, and 7.8 Oe to 8 Oe for bcc phase thin films. The changing crystal structures during annealing process indicated that the thermal treatment at high temperature cause the changing crystallinity and atomic displacement. The TEM bright-field images with corresponding selected-area electron diffraction (SAED) patterns showed that there are strongly effects of thermal annealing on the size of fcc and bcc phase crystalline grain as described by size of individual spot and discontinuous rings. The size of crystalline grains increased by thermal annealing. The evolution of bcc and fcc structures of CoNiFe during annealing is though to be responsible for the change of magnetic properties.« less

  6. Theoretical investigation of aerobic and anaerobic oxidative inactivation of the [NiFe]-hydrogenase active site.

    PubMed

    Breglia, Raffaella; Greco, Claudio; Fantucci, Piercarlo; De Gioia, Luca; Bruschi, Maurizio

    2018-01-17

    The extraordinary capability of [NiFe]-hydrogenases to catalyse the reversible interconversion of protons and electrons into dihydrogen (H 2 ) has stimulated numerous experimental and theoretical studies addressing the direct utilization of these enzymes in H 2 production processes. Unfortunately, the introduction of these natural H 2 -catalysts in biotechnological applications is limited by their inhibition under oxidising (aerobic and anaerobic) conditions. With the aim of contributing to overcome this limitation, we studied the oxidative inactivation mechanism of [NiFe]-hydrogenases by performing Density Functional Theory (DFT) calculations on a very large model of their active site in which all the amino acids forming the first and second coordination spheres of the NiFe cluster have been explicitly included. We identified an O 2 molecule and two H 2 O molecules as sources of the two oxygen atoms that are inserted at the active site of the inactive forms of the enzyme (Ni-A and Ni-B) under aerobic and anaerobic conditions, respectively. Furthermore, our results support the experimental evidence that the Ni-A-to-Ni-B ratio strongly depends on the number of reducing equivalents available for the process and on the oxidizing conditions under which the reaction takes place.

  7. The Effects of Strain-Annealing on Tuning Permeability and Lowering Losses in Fe-Ni-Based Metal Amorphous Nanocomposites

    DOE PAGES

    Aronhime, Natan; DeGeorge, Vincent; Keylin, Vladimir; ...

    2017-07-25

    Here, Fe-Ni-based metal amorphous nanocomposites with a range of compositions (Fe 100–xNi x) 80Nb 4Si 2B 14 (30 ≤ x ≤ 70) are investigated for motor and transformer applications, where it is beneficial to have tunable permeability. It is shown that strain annealing offers an effective method for tuning permeability in these alloys. For an Fe-rich alloy, permeability increased from 4000 to 16,000 with a positive magnetostriction. In a Ni-rich alloy, permeability decreased from 290 to 40 with a negative magnetostriction. Significant elongations (above 60%) are observed during strain annealing at high stress. Crystallization products have been determined in allmore » alloys heated to 480°C. γ-FeNi is formed in all alloys, while (Fe 30Ni 70) 80Nb 4Si 2B 14 also undergoes secondary crystallization at temperatures of approximately 480°C to form a phase with the Cr 23C 6-type structure and a likely composition of Fe 21Nb 2B 6. Toroidal losses have been measured for (Fe 70Ni 30) 80Nb 4Si y B 16–y (0 ≤ y ≤ 3) at various annealing temperatures. At an induction of 1 T and frequency of 400 Hz and 1 kHz, the toroidal losses obtained are W 1.0T, 400 Hz = 0.9 W/kg and W 1.0T, 1 kHz = 2.3 W/kg, respectively. These losses are lower than losses recently reported for state of the art 3.0% and 6.5% silicon steels, a Metglas Fe-based amorphous alloy, and some Fe-based nanocomposites.« less

  8. The Effects of Strain-Annealing on Tuning Permeability and Lowering Losses in Fe-Ni-Based Metal Amorphous Nanocomposites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aronhime, Natan; DeGeorge, Vincent; Keylin, Vladimir

    Here, Fe-Ni-based metal amorphous nanocomposites with a range of compositions (Fe 100–xNi x) 80Nb 4Si 2B 14 (30 ≤ x ≤ 70) are investigated for motor and transformer applications, where it is beneficial to have tunable permeability. It is shown that strain annealing offers an effective method for tuning permeability in these alloys. For an Fe-rich alloy, permeability increased from 4000 to 16,000 with a positive magnetostriction. In a Ni-rich alloy, permeability decreased from 290 to 40 with a negative magnetostriction. Significant elongations (above 60%) are observed during strain annealing at high stress. Crystallization products have been determined in allmore » alloys heated to 480°C. γ-FeNi is formed in all alloys, while (Fe 30Ni 70) 80Nb 4Si 2B 14 also undergoes secondary crystallization at temperatures of approximately 480°C to form a phase with the Cr 23C 6-type structure and a likely composition of Fe 21Nb 2B 6. Toroidal losses have been measured for (Fe 70Ni 30) 80Nb 4Si y B 16–y (0 ≤ y ≤ 3) at various annealing temperatures. At an induction of 1 T and frequency of 400 Hz and 1 kHz, the toroidal losses obtained are W 1.0T, 400 Hz = 0.9 W/kg and W 1.0T, 1 kHz = 2.3 W/kg, respectively. These losses are lower than losses recently reported for state of the art 3.0% and 6.5% silicon steels, a Metglas Fe-based amorphous alloy, and some Fe-based nanocomposites.« less

  9. The Effects of Strain-Annealing on Tuning Permeability and Lowering Losses in Fe-Ni-Based Metal Amorphous Nanocomposites

    NASA Astrophysics Data System (ADS)

    Aronhime, Natan; DeGeorge, Vincent; Keylin, Vladimir; Ohodnicki, Paul; McHenry, Michael E.

    2017-11-01

    Fe-Ni-based metal amorphous nanocomposites with a range of compositions (Fe100- x Ni x )80Nb4Si2B14 (30 ≤ x ≤ 70) are investigated for motor and transformer applications, where it is beneficial to have tunable permeability. It is shown that strain annealing offers an effective method for tuning permeability in these alloys. For an Fe-rich alloy, permeability increased from 4000 to 16,000 with a positive magnetostriction. In a Ni-rich alloy, permeability decreased from 290 to 40 with a negative magnetostriction. Significant elongations (above 60%) are observed during strain annealing at high stress. Crystallization products have been determined in all alloys heated to 480°C. γ-FeNi is formed in all alloys, while (Fe30Ni70)80Nb4Si2B14 also undergoes secondary crystallization at temperatures of approximately 480°C to form a phase with the Cr23C6-type structure and a likely composition of Fe21Nb2B6. Toroidal losses have been measured for (Fe70Ni30)80Nb4Si y B16- y (0 ≤ y ≤ 3) at various annealing temperatures. At an induction of 1 T and frequency of 400 Hz and 1 kHz, the toroidal losses obtained are W1.0T, 400 Hz = 0.9 W/kg and W1.0T, 1 kHz = 2.3 W/kg, respectively. These losses are lower than losses recently reported for state of the art 3.0% and 6.5% silicon steels, a Metglas Fe-based amorphous alloy, and some Fe-based nanocomposites.

  10. on the High-Temperature Performance of Ni-Based Welding Material NiCrFe-7

    NASA Astrophysics Data System (ADS)

    Mo, Wenlin; Lu, Shanping; Li, Dianzhong; Li, Yiyi

    2014-10-01

    The effects of M 23C6 ( M = Cr, Fe) on the high-temperature performance of the NiCrFe-7 welding rods and weld metals were studied by high-temperature tensile tests and microstructure analysis. M 23C6 at the grain boundaries (GBs) has a cube-on-cube coherence with one grain in the NiCrFe-7 weld metals, and the adjacent M 23C6 has the coherence relationship with the same grain. The grain with a coherent M 23C6 has a Cr-depletion region. The number and size of M 23C6 particles can be adjusted by heat treatment and alloying. There are two temperatures [ T E1: 923 K to 1083 K (650 °C to 810 °C) and T E2: 1143 K to 1203 K (870 °C to 930 °C)] at which the GBs and grains of the NiCrFe-7 welding rod have equal strength during the high-temperature tensile test. When the temperatures are between T E1 and T E2, the strength of the GBs is lower than that of the grains, and the tensile fractures are intergranular. When the temperatures are below T E1 or over T E2, the strength of the GBs is higher than that of the grains, and the tensile fractures are dimples. M 23C6 precipitates at the GBs, which deteriorates the ductility of the welding rods at temperature between T E1 and T E2. M 23C6 aggravates ductility-dip-cracking (DDC) in the weld metals. The addition of Nb and Ti can form MX ( M = Ti, Nb, X = C, N), fix C in grain, decrease the initial precipitation temperature of M 23C6, and mitigate the precipitation of M 23C6, which is helpful for minimizing DDC in the weld.

  11. Surface Properties of a Nanocrystalline Fe-Ni-Nb-B Alloy After Neutron Irradiation

    NASA Astrophysics Data System (ADS)

    Pavùk, Milan; Sitek, Jozef; Sedlačková, Katarína

    2014-09-01

    The effect of neutron radiation on the surface properties of the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy was studied. Firstly, amorphous (Fe0.25Ni0.75)81Nb7B12 ribbon was brought by controlled annealing to the nanocrystalline state. After annealing, the samples of the nanocrystalline ribbon were irradiated in a nuclear reactor with neutron fluences of 1×1016cm-2 and 1 × 1017cm-2 . By utilizing the magnetic force microscopy (MFM), topography and a magnetic domain structure were recorded at the surface of the ribbon-shaped samples before and after irradiation with neutrons. The results indicate that in terms of surface the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy is radiation-resistant up to a neutron fluence of 1 × 1017cm-2 . The changes in topography observed for both irradiated samples are discussed

  12. Fabrication and characterization of He-charged ODS-FeCrNi films deposited by a radio-frequency plasma magnetron sputtering technique

    NASA Astrophysics Data System (ADS)

    Song, Liang; Wang, Xianping; Wang, Le; Zhang, Ying; Liu, Wang; Jiang, Weibing; Zhang, Tao; Fang, Qianfeng; Liu, Changsong

    2017-04-01

    He-charged oxide dispersion strengthened (ODS) FeCrNi films were prepared by a radio-frequency (RF) plasma magnetron sputtering method in a He and Ar mixed atmosphere at 150 °C. As a comparison, He-charged FeCrNi films were also fabricated at the same conditions through direct current (DC) plasma magnetron sputtering. The doping of He atoms and Y2O3 in the FeCrNi films was realized by the high backscattered rate of He ions and Y2O3/FeCrNi composite target sputtering method, respectively. Inductive coupled plasma (ICP) and x-ray photoelectron spectroscopy (XPS) analysis confirmed the existence of Y2O3 in FeCrNi films, and Y2O3 content hardly changed with sputtering He/Ar ratio. Cross-sectional scanning electron microscopy (SEM) shows that the FeCrNi films were composed of dense columnar nanocrystallines and the thickness of the films was obviously dependent on He/Ar ratio. Nanoindentation measurements revealed that the FeCrNi films fabricated through DC/RF plasma magnetron sputtering methods exhibited similar hardness values at each He/Ar ratio, while the dispersion of Y2O3 apparently increased the hardness of the films. Elastic recoil detection (ERD) showed that DC/RF magnetron sputtered FeCrNi films contained similar He amounts (˜17 at.%). Compared with the minimal change of He level with depth in DC-sputtered films, the He amount decreases gradually in depth in the RF-sputtered films. The Y2O3-doped FeCrNi films were shown to exhibit much smaller amounts of He owing to the lower backscattering possibility of Y2O3 and the inhibition effect of nano-sized Y2O3 particles on the He element.

  13. Enhanced photocatalytic activity and characterization of magnetic Ag/BiOI/ZnFe2O4 composites for Hg0 removal under fluorescent light irradiation

    NASA Astrophysics Data System (ADS)

    Li, Chengwei; Zhang, Anchao; Zhang, Lixiang; Song, Jun; Su, Sheng; Sun, Zhijun; Xiang, Jun

    2018-03-01

    A series of magnetic Ag/BiOI/ZnFe2O4 hybrids synthesized via hydrothermal process, subsequent deposition-precipitation and photoreduction method were employed to remove elemental mercury (Hg0) under fluorescent light irradiation. The effects of Ag content, fluorescent light irradiation, reaction temperature, pH value, flue gas composition, anions and photocatalyst dosage on Hg0 removal were investigated in detail. The as-synthesized photocatalysts were characterized using N2 adsorption-desorption, XRD, SEM, TEM, HRTEM, XPS, VSM, DRS, ESR, PL and photocurrent response. The results showed that the ternary Ag/BiOI/ZnFe2O4 hybrids possessed enhanced visible-light-responsive photocatalytic performances for Hg0 removal. Ag/BiOI/ZnFe2O4 photocatalyst could be easily recovered from the reaction solution by an extra magnet and was stable in the process of Hg0 removal. Lower content of Ag was highly dispersed on the surface of BiOI/ZnFe2O4, while higher content of Ag would result in some aggregations and/or the blockages of micropore. In comparison to BiOI/ZnFe2O4, Ag deposited BiOI/ZnFe2O4 material showed lower recombination rate of electron-hole pairs. The superior Hg0 oxidation removal could correspond to good match of BiOI and ZnFe2O4, excellent fluidity and surface plasmon resonance effect of Ag0 nanoparticles, which led to higher separation efficiency of photogenerated electrons and holes, thereby enhancing the hybrids' photocatalytic activity.

  14. Reactions of laser-ablated Fe, Co, and Ni with NO: Infrared spectra and density functional calculations of MNO{sup +} and M(NO){sub x} (M = Fe, Co, x = 1--3; M = Ni, x = 1,2), and M(NO){sub x}{sup {minus}} (M = Co, Ni; x = 1,2)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhou, M.; Andrews, L.

    2000-05-04

    Laser-ablated iron, cobalt, and nickel atoms, cations, and electrons have been reacted with NO molecules during condensation in excess neon and argon. The end-on bonded Fe(NO){sub 1-3}, Co(NO){sub 1-3}, and Ni(NO){sub 1-2} nitrosyls and side-bonded Fe-({eta}{sup 2}-NO), Co-({eta}{sup 2}-NO), and Ni-({eta}{sup 2}-NO) species are formed during sample deposition or on annealing. The FeNO{sup +}, CoNO{sup +}, and NiNO{sup +} mononitrosyl cations are also produced via metal cation reactions with NO. Evidence is also presented for the Ni(NO){sub 1,2}{sup {minus}} and Co(NO){sub 1,2}{sup {minus}} anions. The product absorptions are identified by isotopic substitution ({sup 15}N{sup 16}O, {sup 15}N{sup 18}O, and mixtures),more » electron trapping with added CCl{sub 4}, and density functional calculations of isotopic frequencies. This work provides the first vibrational spectroscopic characterization of Fe, Co, and Ni nitrosyl cations and anions.« less

  15. Preparation and magnetic properties of cylindrical NiFe films and antidot arrays.

    PubMed

    Sanz, R; Navas, D; Vazquez, M; Hernández-Vélez, M; Ross, C A

    2010-10-01

    Continuous NiFe (Permalloy) cylindrical films and arrays of cylindrical NiFe antidots 7 nm thick have been prepared by sputtering onto cylindrical aluminum wires and onto wires anodized to form a porous anodic alumina layer. The antidots are arranged in a close-packed pattern determined by the hexagonal pore arrangement in the porous alumina, with period 103 nm and diameter 42 nm. Hysteresis loops were measured at different angles with respect to the cylinder axis and indicate an easy plane normal to the radius of the wire. The antidots enhance the coercivity compared to the continuous cylindrical film.

  16. Synthesis of 3D porous ferromagnetic NiFe2O4 and using as novel adsorbent to treat wastewater.

    PubMed

    Hou, Xiangyu; Feng, Jing; Liu, Xiaohan; Ren, Yueming; Fan, Zhuangjun; Wei, Tong; Meng, Jian; Zhang, Milin

    2011-10-15

    Three dimensions (3D) porous NiFe(2)O(4) is synthesized by a sol-gel method using egg white. The obtained NiFe(2)O(4) shows both good ferromagnetic properties and high adsorption capacity. The porous NiFe(2)O(4) shows good adsorption properties for organic dyes (Methylene Blue (138.50 mg/g), Fuchsine Red (14.61 mg/g), Methyl Violet (19.06 mg/g)) and heavy metal ions (Cu (II) (55.83 mg/g), Cr (VI) (36.95 mg/g) and Ni (II) (37.02 mg/g)) due to its 3D interconnected porous structure. The maximum adsorption of Methylene Blue (MB) fit the pseudo-second-order model and Langmuir isotherm equation well. More interestingly, the ferromagnetic NiFe(2)O(4) can be separated under a magnetic field conveniently and keeps high removal efficiency (>97%) during seven reusable cycles. These results suggest that the porous NiFe(2)O(4) is a promising favorable and reusable adsorbent. Copyright © 2011 Elsevier Inc. All rights reserved.

  17. High-precision QEC values of superallowed 0+ → 0+β-emitters 46Cr, 50Fe and 54Ni

    NASA Astrophysics Data System (ADS)

    Zhang, P.; Xu, X.; Shuai, P.; Chen, R. J.; Yan, X. L.; Zhang, Y. H.; Wang, M.; Litvinov, Yu. A.; Blaum, K.; Xu, H. S.; Bao, T.; Chen, X. C.; Chen, H.; Fu, C. Y.; He, J. J.; Kubono, S.; Lam, Y. H.; Liu, D. W.; Mao, R. S.; Ma, X. W.; Sun, M. Z.; Tu, X. L.; Xing, Y. M.; Yang, J. C.; Yuan, Y. J.; Zeng, Q.; Zhou, X.; Zhou, X. H.; Zhan, W. L.; Litvinov, S.; Audi, G.; Uesaka, T.; Yamaguchi, Y.; Yamaguchi, T.; Ozawa, A.; Sun, B. H.; Sun, Y.; Xu, F. R.

    2017-04-01

    Short-lived 46Cr, 50Fe and 54Ni were studied by isochronous mass spectrometry at the HIRFL-CSR facility in Lanzhou. The measured precision mass excesses (ME) of 46Cr, 50Fe and 54Ni are - 29471 (11) keV, - 34477 (6) keV and - 39278 (4) keV, respectively. The superallowed 0+ →0+β-decay Q values were derived to be QEC (46Cr) = 7604 (11) keV, QEC (50Fe) = 8150 (6) keV and QEC (54Ni) = 8731 (4) keV. The values for 50Fe and 54Ni are by one order of magnitude more precise than the adopted literature values. By combining the existing half-lives and branching ratios, we obtained the corrected Ft values to be Ft (50Fe) = 3103 (70) s and Ft (54Ni) = 3076 (50) s. The main contribution to the Ft uncertainties is now due to β-decay branching ratios, still, more high-precision measurements of the half-lives, the masses, and especially the branching ratios are needed in order to satisfy the requirements for a stringent CVC test.

  18. The influence of an MgO nanolayer on the planar Hall effect in NiFe films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Minghua, E-mail: mhli@ustb.edu.cn; Department of Electrical Engineering, University of California, Los Angeles, California 90095; Zhao, Zhiduo

    2015-03-28

    The Planar Hall Effect (PHE) in NiFe films was studied using MgO as the buffer and capping layer to reduce the shunt effect. The thermal annealing was found to be effective in increasing the sensitivity. The sensitivity of the magnetic field reached as high as 865 V/AT in a MgO (3 nm)/NiFe (5 nm)/MgO(3 nm)/Ta(3 nm) structure after annealing at 500 °C for 2 h, which is close to the sensitivity of semiconductor Hall Effect (HE) sensors. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) were used to study the sample. The results show that the top crystallization of MgO and NiFemore » (111) texture were improved by proper annealing. The smooth and clear bottom MgO/NiFe and top NiFe/MgO interface is evident from our data. In addition, the shunt current of Ta was decreased. These combined factors facilitate the improvement of the sensitivity of the magnetic field.« less

  19. Low-cost, high-strength Fe--Ni--Cr alloys for high temperature exhaust valve application

    DOEpatents

    Muralidharan, Govindarajan

    2017-09-05

    An Fe--Ni--Cr alloy is composed essentially of, in terms of wt. %: 2.4 to 3.7 Al, up to 1.05 Co, 14.8 to 15.9 Cr, 25 to 36 Fe, up to 1.2 Hf, up to 4 Mn, up to 0.6 Mo, up to 2.2 Nb, up to 1.05 Ta, 1.9 to 3.6 Ti, up to 0.08 W, up to 0.03 Zr, 0.18 to 0.27 C, up to 0.0015 N, balance Ni, wherein, in terms of atomic percent: 8.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.11.5, 0.53.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.65, and 0.16.ltoreq.Cr/(Fe+Ni+Cr+Mn).ltoreq.0.21, the alloy being essentially free of Cu, Si, and V.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  1. Heat treatment of NiCrFe alloy to optimize resistance to intergrannular stress corrosion

    DOEpatents

    Steeves, Arthur F.; Bibb, Albert E.

    1984-01-01

    A process of producing a NiCrFe alloy having a high resistance to stress corrosion cracking comprising heating a NiCrFe alloy to a temperature sufficient to enable the carbon present in the alloy body in the form of carbide deposits to enter into solution, rapidly cool the alloy body, and heat the cooled body to a temperature between 1100.degree. to 1500.degree. F. for about 1 to 30 hours.

  2. Electrical characteristics for Sn-Ag-Cu solder bump with Ti/Ni/Cu under-bump metallization after temperature cycling tests

    NASA Astrophysics Data System (ADS)

    Shih, T. I.; Lin, Y. C.; Duh, J. G.; Hsu, Tom

    2006-10-01

    Lead-free solder bumps have been widely used in current flip-chip technology (FCT) due to environmental issues. Solder joints after temperature cycling tests were employed to investigate the interfacial reaction between the Ti/Ni/Cu under-bump metallization and Sn-Ag-Cu solders. The interfacial morphology and quantitative analysis of the intermetallic compounds (IMCs) were obtained by electron probe microanalysis (EPMA) and field emission electron probe microanalysis (FE-EPMA). Various types of IMCs such as (Cu1-x,Agx)6Sn5, (Cu1-y,Agy)3Sn, and (Ag1-z,Cuz)3Sn were observed. In addition to conventional I-V measurements by a special sample preparation technique, a scanning electron microscope (SEM) internal probing system was introduced to evaluate the electrical characteristics in the IMCs after various test conditions. The electrical data would be correlated to microstructural evolution due to the interfacial reaction between the solder and under-bump metallurgy (UBM). This study demonstrated the successful employment of an internal nanoprobing approach, which would help further understanding of the electrical behavior within an IMC layer in the solder/UBM assembly.

  3. Enhanced thermal stability of Cu alloy films by strong interaction between Ni and Zr (or Fe)

    NASA Astrophysics Data System (ADS)

    Zheng, Yuehong; Li, Xiaona; Cheng, Xiaotian; Li, Zhuming; Liu, Yubo; Dong, Chuang

    2018-04-01

    Low resistivity, phase stability and nonreactivity with surrounding dielectrics are the key to the application of Cu to ultra-large-scale integrated circuits. Here, a stable solid solution cluster model was introduced to design the composition of barrierless Cu-Ni-Zr (or Fe) seed layers. The third elements Fe and Zr were dissolved into Cu via a second element Ni, which is soluble in both Cu and Zr (or Fe). The films were prepared by magnetron sputtering on the single-crystal p-Si (1 0 0) wafers. Since the diffusion characteristics of the alloying elements are different, the effects of the strong interaction between Ni and Zr (or Fe) on the film’s stability and resistivity were studied. The results showed that a proper addition of Zr-Ni (Zr/Ni  ⩽  0.6/12) into Cu could form a large negative lattice distortion, which inhibits Cu-Si interdiffusion and enhances the stability of Cu film. When Fe-Ni was co-added into Cu, the lattice distortion of Cu reached a lower value, 0.0029 Å  ⩽  |Δa|  ⩽  0.0046 Å, and the films showed poor stability. Therefore, when the model is applied to the composition design of the films, the strong interaction between the elements and the addition ratio should be taken into consideration.

  4. Spinel FeCo2S4 nanoflower arrays grown on Ni foam as novel binder-free electrodes for long-cycle-life supercapacitors

    NASA Astrophysics Data System (ADS)

    Deng, Cuifen; Yang, Lishan; Yang, Chunming; Shen, Ping; Zhao, Liping; Wang, Zhiyu; Wang, Chunhui; Li, Junhua; Qian, Dong

    2018-01-01

    Spinel FeCo2S4 nanoflower arrays grown on Ni foam (FeCo2S4@Ni) have been successfully fabricated via a facile hydrothermal sulfurization of the corresponding FeCo2O4 precursor. The results of X-ray diffraction and X-ray photoelectron spectroscopy characterizations affirm that partial Co2+/Co3+ ions in Co3S4 have been substituted by Fe2+/Fe3+ ions to form FeCo2S4. The obtained FeCo2S4@Ni exhibits an ultrahigh specific capacitance (1644.07 mF cm-2 at 50 mA cm-2) and a supreme cycling stability (∼100% after 10,000 cycles at 50 mA cm-2) as binder-free electrodes for supercapacitors. The cycling stability of the fabricated product is the highest among the documented ternary metallic sulfides so far. The excellent supercapacitive performance of FeCo2S4@Ni emanates from the unique architectures of Fe2Co2S4 nanoflower arrays constituted by ultrathin nanoflakes, three-dimensional porous and conductive Ni foam, and solid skeleton of Ni foam for robust connections to the Fe2Co2S4.

  5. Synthesis and characterization of NiFe{sub 2}O{sub 4}–Pd magnetically recyclable catalyst for hydrogenation reaction

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Karaoğlu, E., E-mail: ekaraoglu@fatih.edu.tr; Özel, U.; Caner, C.

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► Novel superparamagnetic NiFe{sub 2}O{sub 4}–Pd magnetically recyclable catalyst was fabricated through co-precipitation. ► It could be reused several times without significant loss in catalytic activity for hydrogenation reaction. ► No further modification of the NiFe{sub 2}O{sub 4}–Pd magnetically recyclable catalyst is necessary for utilization as catalyst. -- Abstract: Herein we report the fabrication and characterization magnetically recyclable catalysts of NiFe{sub 2}O{sub 4}–Pd nanocomposite as highly effective catalysts for reduction reactions in liquid phase. The reduction Pd{sup 2+} was accomplished with polyethylene glycol 400 (PEG-400) instead of sodium borohydride (NaBH{sub 4}) and NiFe{sub 2}O{sub 4}more » nanoparticles was prepared by sonochemically using FeCI{sub 3}·6H{sub 2}O and NiCl{sub 2}. The chemical characterization of the product was done with X-ray diffractometry, Infrared spectroscopy, transmission electron microscopy, UV–Vis spectroscopy, thermal gravimetry and inductively coupled plasma. Thus formed NiFe{sub 2}O{sub 4}–Pd MRCs showed a very high activity in reduction reactions of 4-nitro aniline and 1,3-dinitrobenzene in liquid phase. It was found out that the catalytic activity of NiFe{sub 2}O{sub 4}–Pd MRCs on the reduction of 4-nitro aniline and 1,3-dinitrobenzene in liquid phase are between 99–93% and 98–93%, respectively. Magnetic character of this system allowed recovery and multiple use without significant loss of its catalytic activity. It is found that NiFe{sub 2}O{sub 4}–Pd MRCs showed very efficient catalytic activity and multiple usability.« less

  6. Coupled, Simultaneous Displacement and Dealloying Reactions into Fe-Ni-Co Nanowires for Thinning Nanowire Segments.

    PubMed

    Geng, Xiaohua; Podlaha, Elizabeth J

    2016-12-14

    A new methodology is reported to shape template-assisted electrodeposition of Fe-rich, Fe-Ni-Co nanowires to have a thin nanowire segment using a coupled displacement reaction with a more noble elemental ion, Cu(II), and at the same time dealloying predominantly Fe from Fe-Ni-Co by the reduction of protons (H + ), followed by a subsequent etching step. The displacement/dealloyed layer was sandwiched between two trilayers of Fe-Ni-Co to facilitate the characterization of the reaction front, or penetration length. The penetration length region was found to be a function of the ratio of proton and Cu(II) concentration, and a ratio of 0.5 was found to provide the largest penetration rate, and hence the larger thinned length of the nanowire. Altering the etching time affected the diameter of the thinned region. This methodology presents a new way to thin nanowire segments connected to larger nanowire sections and also introduces a way to study the propagation of a reaction front into a nanowire.

  7. Modification of the magnetization dynamics of a NiFe nanodot due to thermal spin injection

    NASA Astrophysics Data System (ADS)

    Asam, Nagarjuna; Yamanoi, Kazuto; Kimura, Takashi

    2018-06-01

    An array of NiFe nanodots has been prepared on a Cu/CoFeAl film. Since a thermal spin current is expected to be excited owing to a large spin-dependent Seebeck coefficient for the CoFeAl, we investigate the magnetization dynamics of the NiFe dots under the temperature gradient along the vertical direction. By using vector network analyzer measurements, we have demonstrated that the temperature gradient produces modulations of the frequency of ferromagnetic resonance and the linewidth of the resonance spectra. The observed parabolic dependences are well explained by the damping-like and field-like components of spin transfer torque.

  8. The membrane-bound [NiFe]-hydrogenase (Ech) from Methanosarcina barkeri: unusual properties of the iron-sulphur clusters.

    PubMed

    Kurkin, Sergei; Meuer, Jörn; Koch, Jürgen; Hedderich, Reiner; Albracht, Simon P J

    2002-12-01

    The purified membrane-bound [NiFe]-hydrogenase from Methanosarcina barkeri was studied with electron paramagnetic resonance (EPR) focusing on the properties of the iron-sulphur clusters. The EPR spectra showed signals from three different [4Fe-4S] clusters. Two of the clusters could be reduced under 101 kPa of H2, whereas the third cluster was only partially reduced. Magnetic interaction of one of the clusters with an unpaired electron localized on the Ni-Fe site indicated that this was the proximal cluster as found in all [NiFe]-hydrogenases. Hence, this cluster was assigned to be located in the EchC subunit. The other two clusters could therefore be assigned to be bound to the EchF subunit, which has two conserved four-Cys motifs for the binding of a [4Fe-4S] cluster. Redox titrations at different pH values demonstrated that the proximal cluster and one of the clusters in the EchF subunit had a pH-dependent midpoint potential. The possible relevance of these properties for the function of this proton-pumping [NiFe]-hydrogenase is discussed.

  9. Observation of a thermally enhanced magnetoresistance in NiFe

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cao, Y.; Feng, C., E-mail: fengchun@ustb.edu.cn, E-mail: ghyu@mater.ustb.edu.cn; Liu, D. X.

    2016-04-15

    A thermally enhanced magnetoresistance (ThMR) was designed and obtained by simultaneously applying charge and heat currents to a NiFe thin film. From the measurement we observed that the magnetoresistance value was as high as -22600% when the input charge current and applied temperature gradient was 0.966 μA and 2.5 °C/mm, respectively. This ThMR can be controllable by adjusting the relative values of the input charge and heat currents. On increasing the input charge current from 0.85 to 1.05 μA by fixing the temperature gradient at 2.5 °C/mm, the ThMR first increased from 9% to 183% and then decreased from -259%more » to -13%, at intervals of ∼0.96 μA. This can be explained by the spin-dependent transport phenomenon i.e., scattering induced sign difference between magnetoresistance and magnetothermopower in NiFe.« less

  10. The Effect of Mo Particles Addition in Ag-Cu-Ti Filler Alloy on Ti(C,N)-Based Cermet/45 Steel-Brazed Joints

    NASA Astrophysics Data System (ADS)

    He, Hu; Du, Xueming; Huang, Xiaokai; Xu, Weijian; Yao, Zhenhua

    2018-05-01

    Reliable brazing of Ti(C,N)-based cermet and 45 steel was successfully achieved by using the Mo-particle-reinforced Ag-Cu-Ti composite filler. The effects of Mo content on the interfacial microstructure and mechanical properties of Ti(C,N)-based cermet/45 steel joints were analyzed. The results showed that the joint microstructure was primarily composed of Ni3Ti+Cu3Ti2, Ag(s,s)+Cu(s.s), CuTi+Mo, Ti-based solid solution, and FeTi+Fe2Ti. With the increase in Mo content in filler, the thickness of the Ni3Ti+Cu3Ti2 layer adjacent to the Ti(C,N)-based cermet decreases, while more blocky Ti-Cu intermetallic were observed in the brazing seam. The shear strength of the joint could be significantly improved by adding suitable amounts of Mo into the Ag-Cu-Ti filler, and the peak value of 263 MPa was achieved when the alloys were brazed with Ag-Cu-Ti+8wt.%Mo composite filler at 920 °C for 20 min.

  11. Defect energetics of concentrated solid-solution alloys from ab initio calculations: Ni0.5Co0.5, Ni0.5Fe0.5, Ni0.8Fe0.2 and Ni0.8Cr0.2.

    PubMed

    Zhao, Shijun; Stocks, G Malcolm; Zhang, Yanwen

    2016-09-14

    It has been shown that concentrated solid solution alloys possess unusual electronic, magnetic, transport, mechanical and radiation-resistant properties that are directly related to underlying chemical complexity. Because every atom experiences a different local atomic environment, the formation and migration energies of vacancies and interstitials in these alloys exhibit a distribution, rather than a single value as in a pure metal or dilute alloy. Using ab initio calculations based on density functional theory and special quasirandom structures, we have characterized the distribution of defect formation energy and migration barrier in four Ni-based solid-solution alloys: Ni0.5Co0.5, Ni0.5Fe0.5, Ni0.8Fe0.2, and Ni0.8Cr0.2. As defect formation energies in finite-size models depend sensitively on the elemental chemical potential, we have developed a computationally efficient method for determining it which takes into account the global composition and the local short-range order. In addition we have compared the results of our ab initio calculations to those obtained from available embedded atom method (EAM) potentials. Our results indicate that the defect formation and migration energies are closely related to the specific atoms in the structure, which further determines the elemental diffusion properties. Different EAM potentials yield different features of defect energetics in concentrated alloys, pointing to the need for additional potential development efforts in order to allow spatial and temporal scale-up of defect and simulations, beyond those accessible to ab initio methods.

  12. Helium accumulation and bubble formation in FeCoNiCr alloy under high fluence He+ implantation

    NASA Astrophysics Data System (ADS)

    Chen, Da; Tong, Y.; Li, H.; Wang, J.; Zhao, Y. L.; Hu, Alice; Kai, J. J.

    2018-04-01

    Face-centered cubic (FCC) high-entropy alloys (HEA), as emerging alloys with equal-molar or near equal-molar constituents, show a promising radiation damage resistance under heavy ion bombardment, making them potential for structural material application in next-generation nuclear reactors, but the accumulation of light helium ions, a product of nuclear fission reaction, has not been studied. The present work experimentally studied the helium accumulation and bubble formation at implantation temperatures of 523 K, 573 K and 673 K in a homogenized FCC FeCoNiCr HEA, a HEA showing excellent radiation damage resistance under heavy ion irradiation. The size and population density of helium bubbles in FeCoNiCr samples were quantitatively analyzed through transmission electron microscopy (TEM), and the helium content existing in bubbles were estimated from a high-pressure Equation of State (EOS). We found that the helium diffusion in such condition was dominated by the self-interstitial/He replacement mechanism, and the corresponding activation energy in FeCoNiCr is comparable with the vacancy migration energy in Ni and austenitic stainless steel but only 14.3%, 31.4% and 51.4% of the accumulated helium precipitated into helium bubbles at 523 K, 573 K and 673 K, respectively, smaller than the pure Ni case. Importantly, the small bubble size suggested that FeCoNiCr HEA has a high resistance of helium bubble formation compared with Ni and steels.

  13. Sol-gel NiFe2O4 nanoparticles: Effect of the silica coating

    NASA Astrophysics Data System (ADS)

    Larumbe, S.; Pérez-Landazábal, J. I.; Pastor, J. M.; Gómez-Polo, C.

    2012-05-01

    NiFe2O4 and NiFe2O4-SiO2 nanoparticles were synthesized by a sol-gel method using citric acid as fuel, giving rise its combustion to the crystallization of the spinel phase. Different synthesis conditions were analyzed with the aim of obtaining stoichiometric NiFe2O4 nanoparticles. The spinel structure in the calcined nanoparticles (400 °C, 2 h) was evaluated by x-ray diffraction. Their nanometer size (mean diameters around 10-15 nm) was confirmed through electron microscopy (field emission scanning electron microscopy and transmission electron microscopy). Rietveld refinement indicates the existence of a small percentage of NiO and Fe3O4 phases and a certain degree of structural disorder. The main effect of the silica coating is to enhance the disorder effects and prevent the crystalline growth after post-annealing treatments. Due to the small particle size, the nanoparticles display characteristic superparamagnetic behaviour and surface effects associated to a spin-glass like state: i.e., reduction in the saturation magnetization values and splitting of the zero field cooled (ZFC)-field cooled (FC) high field magnetization curves. The fitting of the field dependence of the ZFC-FC irreversibility temperatures to the Almeida—Thouless equation confirms the spin-glass nature of the detected magnetic phenomena. Exchange bias effects (shifts in the FC hysteresis loops) detected below the estimated freezing temperature support the spin-glass nature of the spin disorder effects.

  14. Disclosure of key stereoelectronic factors for efficient H2 binding and cleavage in the active site of [NiFe]-hydrogenases.

    PubMed

    Bruschi, Maurizio; Tiberti, Matteo; Guerra, Alessandro; De Gioia, Luca

    2014-02-05

    A comparative analysis of a series of DFT models of [NiFe]-hydrogenases, ranging from minimal NiFe clusters to very large systems including both the first and second coordination sphere of the bimetallic cofactor, was carried out with the aim of unraveling which stereoelectronic properties of the active site of [NiFe]-hydrogenases are crucial for efficient H2 binding and cleavage. H2 binding to the Ni-SIa redox state is energetically favored (by 4.0 kcal mol(-1)) only when H2 binds to Ni, the NiFe metal cluster is in a low spin state, and the Ni cysteine ligands have a peculiar seesaw coordination geometry, which in the enzyme is stabilized by the protein environment. The influence of the Ni coordination geometry on the H2 binding affinity was then quantitatively evaluated and rationalized analyzing frontier molecular orbitals and populations. Several plausible reaction pathways leading to H2 cleavage were also studied. It turned out that a two-step pathway, where H2 cleavage takes place on the Ni-SIa redox state of the enzyme, is characterized by very low reaction barriers and favorable reaction energies. More importantly, the seesaw coordination geometry of Ni was found to be a key feature for facile H2 cleavage. The discovery of the crucial influence of the Ni coordination geometry on H2 binding and activation in the active site of [NiFe]-hydrogenases could be exploited in the design of novel biomimetic synthetic catalysts.

  15. Effects of post-deposition magnetic field annealing on magnetic properties of NiO/Co90Fe10 bilayers

    NASA Astrophysics Data System (ADS)

    Zheng, Chao; Su, Shan; Chiu, Chun-Cheng; Skoropata, Elizabeth; Desautels, Ryan D.; van Lierop, Johan; Lin, Ko-Wei; Pong, Philip W. T.

    2018-01-01

    The ferromagnetic (FM)/antiferromagnetic (AF) bilayer structures have drawn intensive attention because of their wide applications in modern spintronic devices. While abundant published works have been reported on the interface effects of the FM/AF bilayers caused by the magnetic field annealing (MFA) process, the volume effects caused by the MFA treatment have been rarely considered. In this work, the microstructural and magnetic properties of the NiO/CoFe bilayers with various CoFe thicknesses were investigated under different annealing temperatures. At high annealing temperature, the interlayer mixing and exchange coupling between NiO and CoFe layers were promoted and consequently the interface effects were facilitated. The interfacial oxides acted as pinning centers and randomly pinned the FM domains, leading to an increase of coercivity and a considerable degradation of uniaxial anisotropy. The increase of coercivity was also contributed by the enhancement of the interfacial exchange coupling between the NiO and CoFe layers after MFA. As the CoFe thickness increased, the volume effects tended to dominate over the interface effects, resulting in the preservation the uniaxially anisotropic features of CoFe. These results indicate that both the coercivity and anisotropic features of the NiO/CoFe bilayers can be directly affected by the MFA process, opening up the possibility of modifying the magnetism in the NiO/CoFe bilayers and offering an effective way to improve the performance of modern spintronic devices.

  16. High-performance NiO/Ag/NiO transparent electrodes for flexible organic photovoltaic cells.

    PubMed

    Xue, Zhichao; Liu, Xingyuan; Zhang, Nan; Chen, Hong; Zheng, Xuanming; Wang, Haiyu; Guo, Xiaoyang

    2014-09-24

    Transparent electrodes with a dielectric-metal-dielectric (DMD) structure can be implemented in a simple manufacturing process and have good optical and electrical properties. In this study, nickel oxide (NiO) is introduced into the DMD structure as a more appropriate dielectric material that has a high conduction band for electron blocking and a low valence band for efficient hole transport. The indium-free NiO/Ag/NiO (NAN) transparent electrode exhibits an adjustable high transmittance of ∼82% combined with a low sheet resistance of ∼7.6 Ω·s·q(-1) and a work function of 5.3 eV after UVO treatment. The NAN electrode shows excellent surface morphology and good thermal, humidity, and environmental stabilities. Only a small change in sheet resistance can be found after NAN electrode is preserved in air for 1 year. The power conversion efficiencies of organic photovoltaic cells with NAN electrodes deposited on glass and polyethylene terephthalate (PET) substrates are 6.07 and 5.55%, respectively, which are competitive with those of indium tin oxide (ITO)-based devices. Good photoelectric properties, the low-cost material, and the room-temperature deposition process imply that NAN electrode is a striking candidate for low-cost and flexible transparent electrode for efficient flexible optoelectronic devices.

  17. Static compression of Fe 0.83Ni 0.09Si 0.08 alloy to 374 GPa and Fe 0.93Si 0.07 alloy to 252 GPa: Implications for the Earth's inner core

    NASA Astrophysics Data System (ADS)

    Asanuma, Hidetoshi; Ohtani, Eiji; Sakai, Takeshi; Terasaki, Hidenori; Kamada, Seiji; Hirao, Naohisa; Ohishi, Yasuo

    2011-10-01

    The pressure-volume equations of state of iron-nickel-silicon alloy Fe 0.83Ni 0.09Si 0.08 (Fe-9.8 wt.% Ni-4.0 wt.% Si) and iron-silicon alloy Fe 0.93Si 0.07 (Fe-3.4 wt.% Si) have been investigated up to 374 GPa and 252 GPa, respectively. The present compression data covered pressures of the Earth's core. We confirmed that both Fe 0.83Ni 0.09Si 0.08 and Fe 0.93Si 0.07 alloys remain in the hexagonal close packed structure at all pressures studied. We obtained the density of these alloys at the pressure of the inner core boundary (ICB), 330 GPa at 300 K by fitting the compression data to the third order Birch-Murnaghan equation of state. Using these density values combined with the previous data for hcp-Fe, hcp-Fe 0.8Ni 0.2, and hcp-Fe 0.84Si 0.16 alloys and comparing with the density of the PREM inner core, we estimated the Ni and Si contents of the inner core. The Si content of the inner core estimated here is slightly greater than that estimated previously based on the sound velocity measurement of the hcp-Fe-Ni-Si alloy at high pressure.

  18. hypD as a Marker for [NiFe]-Hydrogenases in Microbial Communities of Surface Waters

    PubMed Central

    Beimgraben, Christian; Gutekunst, Kirstin; Opitz, Friederike

    2014-01-01

    Hydrogen is an important trace gas in the atmosphere. Soil microorganisms are known to be an important part of the biogeochemical H2 cycle, contributing 80 to 90% of the annual hydrogen uptake. Different aquatic ecosystems act as either sources or sinks of hydrogen, but the contribution of their microbial communities is unknown. [NiFe]-hydrogenases are the best candidates for hydrogen turnover in these environments since they are able to cope with oxygen. As they lack sufficiently conserved sequence motifs, reliable markers for these enzymes are missing, and consequently, little is known about their environmental distribution. We analyzed the essential maturation genes of [NiFe]-hydrogenases, including their frequency of horizontal gene transfer, and found hypD to be an applicable marker for the detection of the different known hydrogenase groups. Investigation of two freshwater lakes showed that [NiFe]-hydrogenases occur in many prokaryotic orders. We found that the respective hypD genes cooccur with oxygen-tolerant [NiFe]-hydrogenases (groups 1 and 5) mainly of Actinobacteria, Acidobacteria, and Burkholderiales; cyanobacterial uptake hydrogenases (group 2a) of cyanobacteria; H2-sensing hydrogenases (group 2b) of Burkholderiales, Rhizobiales, and Rhodobacterales; and two groups of multimeric soluble hydrogenases (groups 3b and 3d) of Legionellales and cyanobacteria. These findings support and expand a previous analysis of metagenomic data (M. Barz et al., PLoS One 5:e13846, 2010, http://dx.doi.org/10.1371/journal.pone.0013846) and further identify [NiFe]-hydrogenases that could be involved in hydrogen cycling in aquatic surface waters. PMID:24727276

  19. Graphene-supported Ag-based core-shell nanoparticles for hydrogen generation in hydrolysis of ammonia borane and methylamine borane.

    PubMed

    Yang, Lan; Luo, Wei; Cheng, Gongzhen

    2013-08-28

    Well-dispersed magnetically recyclable core-shell Ag@M (M = Co, Ni, Fe) nanoparticles (NPs) supported on graphene have been synthesized via a facile in situ one-step procedure, using methylamine borane (MeAB) as a reducing agent under ambient condition. Their catalytic activity toward hydrolysis of ammonia borane (AB) were studied. Although the Ag@Fe/graphene NPs are almost inactive, the as-prepared Ag@Co/graphene NPs are the most reactive catalysts, followed by Ag@Ni/graphene NPs. Compared with AB and NaBH4, the as-synthesized Ag@Co/graphene catalysts which reduced by MeAB exert the highest catalytic activity. Additionally, the Ag@Co NPs supported on graphene exhibit higher catalytic activity than the catalysts with other conventional supports, such as the SiO2, carbon black, and γ-Al2O3. The as-synthesized Ag@Co/graphene NPs exert satisfied catalytic activity, with the turnover frequency (TOF) value of 102.4 (mol H2 min(-1) (mol Ag)(-1)), and the activation energy Ea value of 20.03 kJ/mol. Furthermore, the as-synthesized Ag@Co/graphene NPs show good recyclability and magnetically reusability for the hydrolytic dehydrogenation of AB and MeAB, which make the practical reusing application of the catalysts more convenient. Moreover, this simple synthetic method indicates that MeAB could be used as not only a potential hydrogen storage material but also an efficient reducing agent. It can be easily extended to facile preparation of other graphene supported metal NPs.

  20. The solid solution K3.84Ni0.78Fe3.19(PO4)5

    PubMed Central

    Strutynska, Nataliia Yu.; Ogorodnyk, Ivan V.; Livitska, Oksana V.; Baumer, Vyacheslav N.; Slobodyanik, Nikolay S.

    2014-01-01

    The title compound, tetra­potassium tetra­[nickel(II)/iron(III)] penta­kis­(orthophosphate), K3.84Ni0.78Fe3.19(PO4)5, has been obtained from a flux. The structure is isotypic with that of K4MgFe3(PO4)5. The three-dimensional framework is built up from (Ni/Fe)O5 trigonal bipyramids with a mixed Fe:Ni occupancy of 0.799 (8):0.196 (10) and isolated PO4 tetra­hedra, one of which is on a general position and one of which has -4.. site symmetry. Two K+ cations are statistically occupied and are distributed over two positions in hexa­gonally shaped channels that run parallel to [001]. One K+ cation [occupancy 0.73 (3)] is surrounded by nine O atoms, while the other K+ cation [occupancy 0.23 (3)] is surrounded by eight O atoms. PMID:25161510

  1. Crystallization and preliminary X-ray analysis of the NAD+-reducing [NiFe] hydrogenase from Hydrogenophilus thermoluteolus TH-1

    PubMed Central

    Taketa, Midori; Nakagawa, Hanae; Habukawa, Mao; Osuka, Hisao; Kihira, Kiyohito; Komori, Hirofumi; Shibata, Naoki; Ishii, Masaharu; Igarashi, Yasuo; Nishihara, Hirofumi; Yoon, Ki-Seok; Ogo, Seiji; Shomura, Yasuhito; Higuchi, Yoshiki

    2015-01-01

    NAD+-reducing [NiFe] hydrogenases catalyze the oxidoreduction of dihydrogen concomitant with the interconversion of NAD+ and NADH. Here, the isolation, purification and crystallization of the NAD+-reducing [NiFe] hydrogenase from Hydrogenophilus thermoluteolus TH-1 are reported. Crystals of the NAD+-reducing [NiFe] hydrogenase were obtained within one week from a solution containing polyethylene glycol using the sitting-drop vapour-diffusion method and micro-seeding. The crystal diffracted to 2.58 Å resolution and belonged to space group C2, with unit-cell parameters a = 131.43, b = 189.71, c = 124.59 Å, β = 109.42°. Assuming the presence of two NAD+-reducing [NiFe] hydrogenase molecules in the asymmetric unit, V M was calculated to be 2.2 Å3  Da−1, which corresponds to a solvent content of 43%. Initial phases were determined by the single-wavelength anomalous dispersion method using the anomalous signal from the Fe atoms. PMID:25615977

  2. Rocking-beam spectrum images and ALCHEMI of Ni{sub 50}Al{sub 40}Fe{sub 10}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Anderson, I.M.; Bentley, J.

    1997-04-01

    A rocking-beam energy-dispersive X-ray (EDX) spectrum image was acquired near the [035] zone axis of a B2-ordered alloy of composition Ni{sub 50}Al{sub 40}Fe{sub 10}. Images comparable to those acquired by Rossouw et al. were formed a posteriori by integrating the X-ray intensities in windows enclosing the Al-K, Fe-K{sub {alpha}}, and Ni-K{sub {alpha}} characteristic X-ray peaks for each pixel of the spectrum image. These images are shown along with a bright-field transmission channeling pattern (TCP), which records the signal from the bright-field STEM detector as the incident beam direction is varied with the beam-tilt coils, and an EDX spectrum from onemore » pixel of the image. The range of orientations from which the spectrum image was acquired is indicated by the square superimposed on the TCP. ALCHEMI (atom-location by channeling-enhanced microanalysis) was performed on a subset of the spectrum image using standard methods. Spectra from a series of {approximately}30 pixels along lines parallel to the (200) band were summed at each of 31 orientations relative to the band in the range 0 {le} {theta}/{theta}{sub 200} {le} 2.3. Characteristic X-ray intensities of the K-shell X-rays of Ni, Fe, and Al were extracted from the 31 summed spectra with the simplex fitting procedure of the DTSA spectral analysis software. The fraction of Fe on the `Ni`-site from this analysis, p{sub Fe`Ni`} = 23.8 {+-} 2.1%, is in excellent agreement with p{sub Fe`Ni`} = 23.7 {+-} 0.9%, which was determined by an analysis of a series of ten spectra acquired at orientations of the crystal carefully chosen so that the contributions of nonsystematic reflections are negligible.« less

  3. Low operational current spin Hall nano-oscillators based on NiFe/W bilayers

    NASA Astrophysics Data System (ADS)

    Mazraati, Hamid; Chung, Sunjae; Houshang, Afshin; Dvornik, Mykola; Piazza, Luca; Qejvanaj, Fatjon; Jiang, Sheng; Le, Tuan Q.; Weissenrieder, Jonas; Åkerman, Johan

    2016-12-01

    We demonstrate highly efficient spin Hall nano-oscillators (SHNOs) based on NiFe/β-W bilayers. Thanks to the very high spin Hall angle of β-W, we achieve more than a 60% reduction in the auto-oscillation threshold current compared to NiFe/Pt bilayers. The structural, electrical, and magnetic properties of the bilayers, as well as the microwave signal generation properties of the SHNOs, have been studied in detail. Our results provide a promising path for the realization of low-current SHNO microwave devices with highly efficient spin-orbit torque from β-W.

  4. AcsF Catalyzes the ATP-dependent Insertion of Nickel into the Ni,Ni-[4Fe4S] Cluster of Acetyl-CoA Synthase*

    PubMed Central

    Gregg, Christina M.; Goetzl, Sebastian; Jeoung, Jae-Hun

    2016-01-01

    Acetyl-CoA synthase (ACS) catalyzes the reversible condensation of CO, CoA, and a methyl-cation to form acetyl-CoA at a unique Ni,Ni-[4Fe4S] cluster (the A-cluster). However, it was unknown which proteins support the assembly of the A-cluster. We analyzed the product of a gene from the cluster containing the ACS gene, cooC2 from Carboxydothermus hydrogenoformans, named AcsFCh, and showed that it acts as a maturation factor of ACS. AcsFCh and inactive ACS form a stable 2:1 complex that binds two nickel ions with higher affinity than the individual components. The nickel-bound ACS-AcsFCh complex remains inactive until MgATP is added, thereby converting inactive to active ACS. AcsFCh is a MinD-type ATPase and belongs to the CooC protein family, which can be divided into homologous subgroups. We propose that proteins of one subgroup are responsible for assembling the Ni,Ni-[4Fe4S] cluster of ACS, whereas proteins of a second subgroup mature the [Ni4Fe4S] cluster of carbon monoxide dehydrogenases. PMID:27382049

  5. Ni@Fe2O3 heterodimers: controlled synthesis and magnetically recyclable catalytic application for dehalogenation reactions

    NASA Astrophysics Data System (ADS)

    Nakhjavan, Bahar; Tahir, Muhammad Nawaz; Natalio, Filipe; Panthöfer, Martin; Gao, Haitao; Dietzsch, Michael; Andre, Rute; Gasi, Teuta; Ksenofontov, Vadim; Branscheid, Robert; Kolb, Ute; Tremel, Wolfgang

    2012-07-01

    Ni@Fe2O3 heterodimer nanoparticles (NPs) were synthesized by thermal decomposition of organometallic reactants. After functionalization, these Ni@Fe2O3 heterodimers became water soluble. The pristine heterodimeric NPs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mössbauer spectroscopy and magnetic susceptibility measurements. A special advantage of the heterodimers lies in the fact that nanodomains of different composition can be used as catalysts for the removal of environmentally hazardous halogenated pollutants.Ni@Fe2O3 heterodimer nanoparticles (NPs) were synthesized by thermal decomposition of organometallic reactants. After functionalization, these Ni@Fe2O3 heterodimers became water soluble. The pristine heterodimeric NPs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mössbauer spectroscopy and magnetic susceptibility measurements. A special advantage of the heterodimers lies in the fact that nanodomains of different composition can be used as catalysts for the removal of environmentally hazardous halogenated pollutants. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr12121b

  6. Optimizing Heat Treatment Process of Fe-13Cr-3Mo-3Ni Martensitic Stainless of Steel

    NASA Astrophysics Data System (ADS)

    Anwar, M. S.; Prifiharni, S.; Mabruri, E.

    2017-05-01

    The Fe-13Cr-3Mo-3Ni stainless steels are modified into martensitic stainless steels for steam turbine blades application. The working temperature of steam turbine was around 600 - 700 °C. The improvement properties of turbine blade material is necessary to maintain steam turbine work. The previous research revealed that it has corrosion resistance of Fe-13Cr-3Mo-3Ni which is better than 13Cr stainless steels in the chloride environment. In this work, the effect of heat treatment on microstructure and hardness of Fe-13Cr-3Mo-3Ni stainless steels has been studied. The steel was prepared by induction melting followed by hot forging. The steels were austenitized at 1000, 1050, and 1100 °C for 1 hour and were tempered at 600, 650, and 700 °C for 1 hour. The steels were then subjected to metallographic observation and hardness test of Rockwell C. The optimal heat treatment of Fe-13Cr-3Mo-3Ni was carried out austenitized in 1050 °C and tempered in 600 - 700 °C.

  7. Hydrogen vibrations in austenitic fcc Fe-Cr-Mn-Ni steels

    NASA Astrophysics Data System (ADS)

    Danilkin, S. A.; Fuess, H.; Wipf, H.; Ivanov, A.; Gavriljuk, V. G.; Delafosse, D.; Magnin, T.

    2003-07-01

    By neutron spectroscopy, we studied vibrations of H interstitials in two austenitic fcc steels (Fe0.55Cr0.20Mn0.10Ni0.15 and Fe0.54Cr0.27Ni0.19) doped with 0.37 and 0.33 at% H. The band modes, in which H vibrates with its metal neighbours, cause a weak intensity in the energy range of the acoustic vibrations of the H-free steels. The energies of the fundamental and the twofold local-mode excitations, in which H vibrates against its metal neighbours, were ~ 130 and ~ 260 meV, respectively. The respective peaks in the spectra were broadened because the metal neighbours of H, and thus its vibrational energies, vary from interstitial site to interstitial site. The above energy values support an H occupation of octahedral interstitial sites.

  8. Negative Thermal Expansion over a Wide Temperature Range in Fe-Doped MnNiGe Composites

    PubMed Central

    Zhao, Wenjun; Sun, Ying; Liu, Yufei; Shi, Kewen; Lu, Huiqing; Song, Ping; Wang, Lei; Han, Huimin; Yuan, Xiuliang; Wang, Cong

    2018-01-01

    Fe-doped MnNiGe alloys were successfully synthesized by solid-state reaction. Giant negative thermal expansion (NTE) behaviors with the coefficients of thermal expansion (CTE) of −285.23 × 10−6 K−1 (192–305 K) and −1167.09 × 10−6 K−1 (246–305 K) have been obtained in Mn0.90Fe0.10NiGe and MnNi0.90Fe0.10Ge, respectively. Furthermore, these materials were combined with Cu in order to control the NTE properties. The results indicate that the absolute value of CTE gradually decreases with increasing Cu contents. In Mn0.92Fe0.08NiGe/x%Cu, the CTE gradually changes from −64.92 × 10−6 K−1 (125–274 K) to −4.73 × 10−6 K−1 (173–229 K) with increasing value of x from 15 to 70. The magnetic measurements reveal that the NTE behaviors in this work are strongly correlated with the process of the magnetic phase transition and the introduction of Fe atoms could also change the spiral anti-ferromagnetic (s-AFM) state into ferromagnetic (FM) state at low temperature. Our study launches a new candidate for controlling thermal expansion properties of metal matrix materials which could have potential application in variable temperature environment. PMID:29468152

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  10. New series of triple molybdates AgA{sub 3}R(MoO{sub 4}){sub 5} (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) with framework structures and mobile silver ion sublattices

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kotova, Irina Yu.; Buryat State University, Smolin St. 24a, Ulan-Ude 670000, Buryat Republic; Solodovnikov, Sergey F.

    Triple molybdates AgA{sub 3}R(MoO{sub 4}){sub 5} (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg{sub 3}In(MoO{sub 4}){sub 5} type were synthesized and single crystals of AgMg{sub 3}R(MoO{sub 4}){sub 5} (R=Cr, Fe) were grown. In their structures, the MoO{sub 4} tetrahedra, pairs and trimers of edge-shared (Mg, R)O{sub 6} octahedra are connected by common vertices to form a 3D framework. Large framework cavities involve Ag{sup +} cations disordered on three nearby positions with CN=3+1 or 4+1. Alternating (Mg, R)O{sub 6} octahedra and MoO{sub 4} tetrahedra in the framework form quadrangular windows penetrable for Ag{sup +} at elevated temperatures.more » Above 653–673 K, the newly obtained molybdates demonstrate abrupt reduction of the activation energy to 0.4–0.6 eV. At 773 K, AgMg{sub 3}Al(MoO{sub 4}){sub 5} shows electric conductivity 2.5·10{sup −2} S/cm and E{sub a}=0.39 eV compatible with characteristics of the best ionic conductors of the NASICON type. - Graphical abstract: Triple molybdates AgA{sub 3}R(MoO{sub 4}){sub 5} (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg{sub 3}In(MoO{sub 4}){sub 5} type were synthesized, AgMg{sub 3}R(MoO{sub 4}){sub 5} (R=Cr, Fe) were structurally characterized, ion-conductive properties of AgMg{sub 3}Al(MoO{sub 4}){sub 5} were measured. Display Omitted - Highlights: • Triple molybdates AgA{sub 3}R(MoO{sub 4}){sub 5} (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg{sub 3}In(MoO{sub 4}){sub 5} type were synthesized. • Single crystals of AgMg{sub 3}R(MoO{sub 4}){sub 5} (R=Cr, Fe) were grown and their crystal structures were determined. • Disordering Ag{sup +} ions and penetrable framework structures of AgMg{sub 3}R(MoO{sub 4}){sub 5} (R=Cr, Fe) suggest 2D-character of silver-ion mobility. • Measured ion-conductive properties of AgMg{sub 3}Al(MoO{sub 4}){sub 5} are compatible with characteristics of the best ionic conductors of the NASICON type.« less

  11. Interfacial characteristics and multiferroic properties of ion-doped BiFeO3/NiFe2O4 thin films

    NASA Astrophysics Data System (ADS)

    Guo, Meiyou; Tan, Guoqiang; Zheng, Yujuan; Liu, Wenlong; Ren, Huijun; Xia, Ao

    2017-05-01

    Multi-ion doped BiFeO3/NiFe2O4 bilayered thin films were successfully prepared on fluorine-doped SnO2/glass (SnO2:F) substrates by sol-gel method. The crystalline structure, leakage current, interfacial characteristics, and multiferroic properties were investigated in detail. The results of Rietveld refinement showed that the structure of BSrSFMC layer is transformed from rhombohedral to tetragonal structure by the means of ion-doping. The difference of leakage current density of the BSrSFMC/NiFe2O4 (NFO) bilayered films of the -40 V to 40 V and 40 V to -40 V are 0.32 × 10-5 and 1.13 × 10-5 A/cm2, respectively. It was observed that there are obvious interface effects between BSrSFMC and NFO layers, which will cause the accumulation of space charges and the establishment of built-in internal electric field (EI) at the interface. Therefore, different EI directions will affect the dipoles reversal and migration of carriers in the BSrSFMC layer, which will result in different values of transient current with the same applied voltage in the opposite directions. The larger coercive field (Ec ˜ 750 kV/cm) of BSrSFMC/NFO film indicated that there is a tensile stress at the interface between BSrSFMC and NFO layers, making the polarization difficult. These results showed that the above interesting phenomena of the J-V are closely related to the interface effects between the layer of BiFeO3 and NiFe2O4.

  12. Thermoelectric power study of Ag 7C 6H 14NI 8 material

    NASA Astrophysics Data System (ADS)

    Khalifa, M. M.; EL-Mashri, S. M.; Avasthi, M. N.

    2002-08-01

    Thermoelectric power of the material Ag 7C 6H 14NI 8 has been studied for the first time in the temperature range 20-l00°C. Thermopower versus 1/ T plot comes out to be a straight line and can be represented by the equation -θ=0.15 {10 3}/{T}+0.06 for the material. Heat of transport of Ag + ion in the material is very nearly equal to the activation energy. The work points towards the correctness of the Rice and Roth model. It also shows that the material is ordered.

  13. Facile synthesis of mesoporous NiFe2O4/CNTs nanocomposite cathode material for high performance asymmetric pseudocapacitors

    NASA Astrophysics Data System (ADS)

    Kumar, Nagesh; Kumar, Amit; Huang, Guan-Min; Wu, Wen-Wei; Tseng, Tseung Yuen

    2018-03-01

    Morphology and synergistic effect of constituents are the two very important factors that greatly influence the physical, chemical and electrochemical properties of a composite material. In the present work, we report the enhanced electrochemical performance of mesoporous NiFe2O4 and multiwall carbon nanotubes (MWCNTs) nanocomposites synthesized via hexamethylene tetramine (HMT) assisted one-pot hydrothermal approach. The synthesized cubic phase spinel NiFe2O4 nanomaterial possesses high specific surface area (148 m2g-1) with narrow mesopore size distribution. The effect of MWCNTs addition on the electrochemical performance of nanocomposite has been probed thoroughly in a normal three electrode configuration using 2 M KOH electrolyte at room temperature. Experimental results show that the addition of mere 5 mg MWCNTs into fixed NiFe2O4 precursors amount enhances the specific capacitance up to 1291 F g-1 at 1 A g-1, which is the highest reported value for NiFe2O4 nanocomposites so far. NiFe2O4/CNT nanocomposite exhibits small relaxation time constant (1.5 ms), good rate capability and capacitance retention of 81% over 500 charge-discharge cycles. This excellent performance can be assigned to high surface area, mesoporous structure of NiFe2O4 and conducting network formed by MWCNTs in the composite. Further, to evaluate the device performance of the composite, an asymmetric pseudocapacitor has been designed using NiFe2O4/CNT nanocomposite as a positive and N-doped graphene as a negative electrode material, respectively. Our designed asymmetric pseudocapacitor gives maximum energy density of 23 W h kg-1 at power density of 872 W kg-1. These promising results assert the potential of synthesized nanocomposite in the development of efficient practical high-capacitive energy storage devices.

  14. First-principles investigation of diffusion and defect properties of Fe and Ni in Cr2O3

    NASA Astrophysics Data System (ADS)

    Rak, Zs.; Brenner, D. W.

    2018-04-01

    Diffusion of Fe and Ni and the energetics of Fe- and Ni-related defects in chromium oxide (α-Cr2O3) are investigated using first-principles Density Functional Theory calculations in combination with the climbing-image nudged elastic band method. The orientations of the spin magnetic moments of the migrating ions are taken into account and their effects on migration barriers are examined. Several possible diffusion pathways were explored through interstitial and vacancy mechanisms, and it was found that the principal mode of ion transport in Cr2O3 is via vacancies. Both interstitial- and vacancy-mediated diffusions are anisotropic, with diffusion being faster in the z-direction. The energetics of defect formation indicates that the Ni-related defects are less stable than the Fe-related ones. This is consistent with Ni-diffusion being faster than Fe-diffusion. The results are compared with previous theoretical and experimental data and possible implications in corrosion control are discussed.

  15. Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3−δ} (Me = Fe, Mn)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Niwa, Eiki, E-mail: e-niwa@phys.chs.nihon-u.ac.jp; Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550; Maeda, Hiroki

    Graphical abstract: Compositional dependence of (a) electrical conductivity and (b) E{sub a} for hopping conduction of LaNi{sub x}Me{sub 1−x}O{sub 3} (Me = Fe, Mn). - Highlights: • Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3} (Me = Fe, Mn) was investigated. • Hopping conduction model could be applied for conductivity of both specimens. • The difference of E{sub a} due to that of energy level of Fe and Mn was observed. • Hole concentration estimated by iodimetry increases with increasing Ni content. - Abstract: Electrical conduction mechanism of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} expected as Sr-freemore » new cathode material for solid oxide fuel cells was analyzed. Electrical conduction behaviors of both specimens could be well fitted by small polaron hopping conduction model. The electrical conductivity of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} increased with increasing Ni content, showing agreement with decrease of activation energy for hopping conduction. The decrease of electrical conductivity and increase of activation energy of LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} were observed with increasing Ni content for 0.0 ≤ x ≤ 0.4. Further Ni substitution increased electrical conductivity and decreased activation energy for 0.4 ≤ x ≤ 0.6. It was revealed using iodometry that the difference of hole carrier density between LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} was small. It was suspected that the origin of the difference of electrical conduction behavior of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1-x}O{sub 3+δ} was difference of energy level of e{sub g} band composed of Fe 3d or Mn 3d orbitals and their overlapping quantity with O 2p and Ni 3d band.« less

  16. Siderophile Element Partitioning between Cohenite and Liquid in Fe-Ni-S-C System and Implications for Geochemistry of Planetary Cores and Mantles

    NASA Astrophysics Data System (ADS)

    Buono, A. S.; Dasgupta, R.; Walker, D.

    2011-12-01

    Secular cooling of terrestrial planets is known to cause crystallization of a solid inner core from metallic liquid core. Fractionation of light and siderophile elements is important during such crystallization for evolution of outer core and possible core-mantle interaction. Thus far studies focused on a pure Fe inner core in simple binary systems but the effects of possible formation of a carbide inner core component on siderophile element partitioning in a multi-component system has yet to be looked at in detail. We investigated the effects of pressure and S content on partition coefficients (D) between cohenite and liquid in the Fe-Ni-S-C system. Multi-anvil experiments were performed at 3 and 6 GPa at 1150 °C, in an Fe-rich mix containing a constant C and Ni to which S contents of 0, 5, and 14 wt.% were added. All the mixes were doped with W, Re, Os, Pt, and Co. Samples were imaged and analyzed for Fe, Ni, S, and C using an EPMA. Fe, Ni, and trace elements were analyzed using a LA-ICP-MS. All the experiments produced cohenite and Fe-Ni-C±S liquid. Compared to solid-Fe/melt Ds [1-2], cohenite/melt Ds are lower for all elements except W. The light element (S+C) content of the liquid is the dominant controlling factor in siderophile element partitioning between cohenite and liquid as it is between crystalline Fe and liquid. In the cohenite-metallic melt experiments, D Ni decreases as S+C increases. Ni is excluded from the crystallizing solid if the solid is cohenite. We also find that in the Fe-Ni-S-C system, cohenite is stabilized to higher P than in the Fe-S-C system [3-5]. Similar to the Fe-metallic liquid systems the non-metal avoidance model [6] is applicable to the Fe3C-metallic liquid system studied here. Our study has implications for both the cores of smaller planets and the mantles of larger planets. If inner core forms a cohenite layer we would predict that depletions in the outer core will be less than they might be for Fe metal crystallization. For

  17. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO{sub 3} Fe{sub 3}Al, Co{sub 3}Al, and Ni{sub 3}Al based intermetallic phases

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Samolyuk, G. D.; Stocks, G. M.; Újfalussy, B.

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co, and Ti within the AlNi-based matrix phase. In this paper, we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO{sub 3} Fe{sub 3}Al, Co{sub 3}Al, and Ni{sub 3}Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which correspond to experimental situation, Ti and Fe are found to occupy the α sites, while Co and Ni prefer the γ sites of the DO{sub 3} lattice. An important finding is that the magnetic moments of transition metals in Fe{sub 3}Al and Co{sub 3}Al are ordered ferromagnetically, whereas the Ni{sub 3}Al were found to be nonmagnetic unless the Fe or Co is added as a ternary element.« less

  18. A facile method to synthesize boron-doped Ni/Fe alloy nano-chains as electrocatalyst for water oxidation

    NASA Astrophysics Data System (ADS)

    Yang, Yisu; Zhuang, Linzhou; Lin, Rijia; Li, Mengran; Xu, Xiaoyong; Rufford, Thomas E.; Zhu, Zhonghua

    2017-05-01

    We report a novel magnetic field assisted chemical reduction method for the synthesis of boron-doped Ni/Fe nano-chains as promising catalysts for the oxygen evolution reaction (OER). The boron-doped Ni/Fe nano-chains were synthesised in a one step process at room temperature using NaBH4 as a reducing agent. The addition of boron reduced the magnetic moment of the intermediate synthesis products and produced nano-chains with a high specific surface area of 73.4 m2 g-1. The boron-doped Ni/Fe nano-chains exhibited catalytic performance superior to state-of-the-art Ba0.5Sr0.5Co0.8Fe0.2O3-δ perovskite and RuO2 noble metal oxide catalysts. The mass normalized activity of the boron-doped Ni/Fe nano-chains measured at an overpotential of 0.35 V was 64.0 A g-1, with a Tafel slope of only 40 mV dec-1. The excellent performance of the boron-doped Ni/Fe nano-chains can be attributed to the uniform elemental distribution and highly amorphous structure of the B-doped nano-chains. These results provide new insights into the effect of doping transition-metal based OER catalysts with non-metallic elements. The study demonstrates a facile approach to prepare transition metal nano-chains using magnetic field assisted chemical reduction method as cheap and highly active catalysts for electrochemical water oxidation.

  19. Microwave hydrothermal-assisted preparation of novel spinel-NiFe2O4/natural mineral composites as microwave catalysts for degradation of aquatic organic pollutants.

    PubMed

    Shen, Manli; Fu, Lu; Tang, Jianhua; Liu, Mingyu; Song, Youtao; Tian, Fangyuan; Zhao, Zhigang; Zhang, Zhaohong; Dionysiou, Dionysios D

    2018-05-15

    In this study, novel spinel-NiFe 2 O 4 /natural mineral (sepiolite, diatomite and kaolinite) composites were developed using microwave (MW) hydrothermal method, and applied in MW-induced catalytic degradation (NiFe 2 O 4 /natural mineral/MW) of organic pollutants such as sodium dodecyl benzene sulfonate (SDBS), azo fuchsine (AF), methyl parathion (MP), and crystal violet (CVL) in solution. Catalytic activities of three NiFe 2 O 4 /natural mineral composites were compared. The effects of material synthesis process parameters such as molar ratios of NiFe 2 O 4 and natural mineral, and pH of precursor solutions for synthesizing catalysts, and degradation parameters such as MW irradiation time and catalyst reuse cycles were also investigated. The principle on NiFe 2 O 4 /natural mineral/MW degradation was provided. The results reveal that organic pollutants in wastewater can be removed completely using NiFe 2 O 4 /natural mineral/MW within minutes. NiFe 2 O 4 /sepiolite shows higher catalytic activity than the others. The calculated degradation rate constants are 1.865, 0.672, 0.472, and 0.329 min -1 for SDBS, AF, MP, and CVL, respectively, using NiFe 2 O 4 /sepiolite/MW system. The performance of NiFe 2 O 4 /natural mineral can be maintained for three reuse cycles. Active species OH, O 2 - , and h + play main roles in NiFe 2 O 4 /sepiolite/MW degradation. Hence, NiFe 2 O 4 /sepiolite/MW technology with rapid and cost-effective degradation, magnetic separation, and no secondary pollution, demonstrates to be promising in treating organic contaminants in wastewater. Copyright © 2018 Elsevier B.V. All rights reserved.

  20. Dependence of phase configurations, microstructures and magnetic properties of iron-nickel (Fe-Ni) alloy nanoribbons on deoxidization temperature in hydrogen

    NASA Astrophysics Data System (ADS)

    Jing, Panpan; Liu, Mengting; Pu, Yongping; Cui, Yongfei; Wang, Zhuo; Wang, Jianbo; Liu, Qingfang

    2016-11-01

    Iron-nickel (Fe-Ni) alloy nanoribbons were reported for the first time by deoxidizing NiFe2O4 nanoribbons, which were synthesized through a handy route of electrospinning followed by air-annealing at 450 °C, in hydrogen (H2) at different temperatures. It was demonstrated that the phase configurations, microstructures and magnetic properties of the as-deoxidized samples closely depended upon the deoxidization temperature. The spinel NiFe2O4 ferrite of the precursor nanoribbons were firstly deoxidized into the body-centered cubic (bcc) Fe-Ni alloy and then transformed into the face-centered cubic (fcc) Fe-Ni alloy of the deoxidized samples with the temperature increasing. When the deoxidization temperature was in the range of 300 ~ 500 °C, although each sample possessed its respective morphology feature, all of them completely reserved the ribbon-like structures. When it was further increased to 600 °C, the nanoribbons were evolved completely into the fcc Fe-Ni alloy nanochains. Additionally, all samples exhibited typical ferromagnetism. The saturation magnetization (Ms) firstly increased, then decreased, and finally increased with increasing the deoxidization temperature, while the coercivity (Hc) decreased monotonously firstly and then basically stayed unchanged. The largest Ms (~145.7 emu·g-1) and the moderate Hc (~132 Oe) were obtained for the Fe-Ni alloy nanoribbons with a mixed configuration of bcc and fcc phases.

  1. Dependence of phase configurations, microstructures and magnetic properties of iron-nickel (Fe-Ni) alloy nanoribbons on deoxidization temperature in hydrogen.

    PubMed

    Jing, Panpan; Liu, Mengting; Pu, Yongping; Cui, Yongfei; Wang, Zhuo; Wang, Jianbo; Liu, Qingfang

    2016-11-23

    Iron-nickel (Fe-Ni) alloy nanoribbons were reported for the first time by deoxidizing NiFe 2 O 4 nanoribbons, which were synthesized through a handy route of electrospinning followed by air-annealing at 450 °C, in hydrogen (H 2 ) at different temperatures. It was demonstrated that the phase configurations, microstructures and magnetic properties of the as-deoxidized samples closely depended upon the deoxidization temperature. The spinel NiFe 2 O 4 ferrite of the precursor nanoribbons were firstly deoxidized into the body-centered cubic (bcc) Fe-Ni alloy and then transformed into the face-centered cubic (fcc) Fe-Ni alloy of the deoxidized samples with the temperature increasing. When the deoxidization temperature was in the range of 300 ~ 500 °C, although each sample possessed its respective morphology feature, all of them completely reserved the ribbon-like structures. When it was further increased to 600 °C, the nanoribbons were evolved completely into the fcc Fe-Ni alloy nanochains. Additionally, all samples exhibited typical ferromagnetism. The saturation magnetization (M s ) firstly increased, then decreased, and finally increased with increasing the deoxidization temperature, while the coercivity (H c ) decreased monotonously firstly and then basically stayed unchanged. The largest M s (~145.7 emu·g -1 ) and the moderate H c (~132 Oe) were obtained for the Fe-Ni alloy nanoribbons with a mixed configuration of bcc and fcc phases.

  2. Preparation of a γ-Fe2 O3 /Ag nanowire coaxial nanocable for high-performance lithium-ion batteries.

    PubMed

    Geng, Hongbo; Ge, Danhua; Lu, Shuanglong; Wang, Jiaqing; Ye, Zhengmao; Yang, Yonggang; Zheng, Junwei; Gu, Hongwei

    2015-07-27

    In this study, we report the design and synthesis of a silver nanowire-γ-Fe2 O3 coaxial nanocable architecture (Ag NWs@γ-Fe2 O3 nanocable) through mild oxidation of [Fe(CO)5 ] on the surface of silver nanowires followed by a calcination process. After optimization of the structural design, the Ag NWs@γ-Fe2 O3 nanocable could deliver superior lithium storage performance in terms of high reversible capacity, good rate performance, and excellent stability, such as a high reversible capacity of about 890 mA h g(-1) after 60 cycles at a current rate of 0.1 C (1.0 C=1005 mA g(-1) ). The reversible capacity remains as high as about 550 mA h g(-1) even at a high current rate of 2.0 C. This dramatic performance is mainly attributed to the smart coaxial design, which can not only alleviate the large volume change and prevent the aggregation of γ-Fe2 O3 nanoparticles, but also enables good conductivity and thus enhances fast charge transfer. The unique structural features of the Ag NWs@γ-Fe2 O3 nanocable represent a promising anode material in lithium-ion battery applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Modifications of the structure and magnetic properties of ceramic YCrO3 with Fe/Ni doping

    NASA Astrophysics Data System (ADS)

    Mall, Ashish Kumar; Garg, Ashish; Gupta, Rajeev

    2017-07-01

    In this manuscript, we have investigated the effect of Fe and Ni doping on the structure and magnetic properties of YCr1-x M x O3 ceramics (M  =  Fe, Ni and x  =  0, 0.1). X-ray diffraction analysis of the samples accompanied with, Rietveld refinement suggested no change in the structure upon doping, with structure of the samples being orthorhombic (space group: Pnma). Raman spectroscopic analysis of the samples revealed that doping induced disorder leads to broadening of the certain Raman modes of the system. While, both B 3g(5) and B 1g(3) modes are broadened in Ni and Fe doped samples, in addition Fe doped samples also show broadening of B 1g(4) mode. In doped samples a new mode, A 1g(3) appears due to the induced lattice disorder. Temperature dependent magnetic measurements suggested a negative value of Curie-Weiss temperature (θ cw) indicating that all the samples are antiferromagnetic. However, the Neel temperature (T N) increased for Fe doping and decreased with Ni doping. These changes in the Neel temperature upon doping can be correlated to the changes in the nearest neighbor and next nearest neighbor exchange interactions.

  4. NiFe (Oxy) Hydroxides Derived from NiFe Disulfides as an Efficient Oxygen Evolution Catalyst for Rechargeable Zn-Air Batteries: The Effect of Surface S Residues.

    PubMed

    Wang, Tanyuan; Nam, Gyutae; Jin, Yue; Wang, Xingyu; Ren, Pengju; Kim, Min Gyu; Liang, Jiashun; Wen, Xiaodong; Jang, Haeseong; Han, Jiantao; Huang, Yunhui; Li, Qing; Cho, Jaephil

    2018-05-21

    A facile H 2 O 2 oxidation treatment to tune the properties of metal disulfides for oxygen evolution reaction (OER) activity enhancement is introduced. With this method, the degree of oxidation can be readily controlled and the effect of surface S residues in the resulted metal (oxy)hydroxides for the OER is revealed for the first time. The developed NiFe (oxy)hydroxide catalyst with residual S demonstrates an extraordinarily low OER overpotential of 190 mV at the current density of 10 mA cm -2 after coupling with carbon nanotubes, and outstanding performance in Zn-air battery tests. Theoretical calculation suggests that the surface S residues can significantly reduce the adsorption free energy difference between O* and OH* intermediates on the Fe sites, which should account for the high OER activity of NiFe (oxy)hydroxide catalysts. This work provides significant insight regarding the effect of surface heteroatom residues in OER electrocatalysis and offers a new strategy to design high-performance and cost-efficient OER catalysts. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Structure and properties of electrodeposited nanocrystalline Ni and Ni-Fe alloy continuous foils

    NASA Astrophysics Data System (ADS)

    Giallonardo, Jason Derek

    This research work presents the first comprehensive study on nanocrystalline materials produced in bulk quantities using a novel continuous electrodeposition process. A series of nanocrystalline Ni and Ni-Fe alloy continuous foils were produced and an intensive investigation into their structure and various properties was carried out. High-resolution transmission electron microscopy (HR-TEM) revealed the presence of local strain at high and low angle, and twin boundaries. The cause for these local strains was explained based on the interpretation of non-equilibrium grain boundary structures that result when conditions of compatibility are not satisfied. HR-TEM also revealed the presence of twin faults of the growth type, or "growth faults", which increased in density with the addition of Fe. This observation was found to be consistent with a corresponding increase in the growth fault probabilities determined quantitatively using X-ray diffraction (XRD) pattern analysis. Hardness and Young's modulus were measured by nanoindentation. Hardness followed the regular Hall-Petch behaviour down to a grain size of 20 nm after which an inverse trend was observed. Young's modulus was slightly reduced at grain sizes less than 20 nm and found to be affected by texture. Microstrain based on XRD line broadening was measured for these materials and found to increase primarily with a decrease in grain size or an increase in intercrystal defect density (i.e., grain boundaries and triple junctions). This microstrain is associated with the local strains observed at grain boundaries in the HR-TEM image analysis. A contribution to microstrain from the presence of growth faults in the nanocrystalline Ni-Fe alloys was also noted. The macrostresses for these materials were determined from strain measurements using a two-dimensional XRD technique. At grain sizes less than 20 nm, there was a sharp increase in compressive macrostresses which was also owed to the corresponding increase in

  6. Study of NiFe2O4 nanoparticles using Mössbauer spectroscopy with a high velocity resolution

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Ushakov, M. V.; Senthilkumar, B.; Selvan, R. Kalai; Sanjeeviraja, C.; Felner, I.; Semionkin, V. A.

    2013-04-01

    The nanocrystalline NiFe2O4 particles prepared by solution combustion synthesis technique using different fuels such as ethylene-diamine-tetra-acetic acid (NA sample) and urea (NB sample) were studied using magnetic measurement and 57Fe Mössbauer spectroscopy with a high velocity resolution. The temperature dependence of magnetization is different for the two samples. Mössbauer spectra demonstrate the necessity to use more than two magnetic sextets, usually used to fit the NiFe2O4 nanoparticles spectra. Evaluation of the different local microenvironments for Fe in both tetrahedral (A) and octahedral (B) sites, caused by different Ni2 + occupation of octahedral sites, demonstrates at least five different local microenvironments for both A and B sites. Therefore, the Mössbauer spectra were fitted by using ten magnetic sextets which are related to the spread 57Fe location in octahedral and tetrahedral sites.

  7. Chitosan film loaded with silver nanoparticles-sorbent for solid phase extraction of Al(III), Cd(II), Cu(II), Co(II), Fe(III), Ni(II), Pb(II) and Zn(II).

    PubMed

    Djerahov, Lubomir; Vasileva, Penka; Karadjova, Irina; Kurakalva, Rama Mohan; Aradhi, Keshav Krishna

    2016-08-20

    The present study describes the ecofriendly method for the preparation of chitosan film loaded with silver nanoparticles (CS-AgNPs) and application of this film as efficient sorbent for separation and enrichment of Al(III), Cd(II), Cu(II), Co(II), Fe(III), Ni(II), Pb(II) and Zn(II). The stable CS-AgNPs colloid was prepared by dispersing the AgNPs sol in chitosan solution at appropriate ratio and further used to obtain a cast film with very good stability under storage and good mechanical strength for easy handling in aqueous medium. The incorporation of AgNPs in the structure of CS film and interaction between the polymer matrix and nanoparticles were confirmed by UV-vis and FTIR spectroscopy. The homogeneously embedded AgNPs (average diameter 29nm, TEM analysis) were clearly observed throughout the film by SEM. The CS-AgNPs nanocomposite film shows high sorption activity toward trace metals under optimized chemical conditions. The results suggest that the CS-AgNPs nanocomposite film can be feasibly used as a novel sorbent material for solid-phase extraction of metal pollutants from surface waters. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Sorption, desorption, and speciation of Cd, Ni, and Fe by four calcareous soils as affected by pH.

    PubMed

    Tahervand, Samaneh; Jalali, Mohsen

    2016-06-01

    The sorption, desorption, and speciation of cadmium (Cd), nickel (Ni), and iron (Fe) in four calcareous soils were investigated at the pH range of 2-9. The results indicated that sorption of Fe by four soils was higher than 80 % at pH 2, while in the case of Cd and Ni was less than 30 %. The most common sequence of metal sorption at pH 2-9 for four soils was in the order of Fe ≫ Ni > Cd. Cadmium and Ni sorption as a function of pH showed the predictable trend of increasing metal sorption with increase in equilibrium pH, while the Fe sorption trend was different and characterized by three phases. With regard to the order of Cd, Ni, and Fe sorption on soils, Cd and Ni showed high affinity for organic matter (OM), whereas Fe had high tendency for calcium carbonate (CaCO3). Results of metal desorption using 0.01 M NaCl demonstrated that metal sorption on soils containing high amounts of CaCO3 was less reversible in comparison to soils containing high OM. In general, Cd and Ni desorption curves were characterized by three phases; (1) the greatest desorption at pH 2, (2) the low desorption at pH 3-7, and (3) the least desorption at pH > 7. The MINTEQ speciation solubility program showed that the percentage of free metals declined markedly with increase of pH, while the percentage of carbonate and hydroxyl species increased. Furthermore, MINTEQ predicted that saturation index (SI) of metals increased with increasing pH.

  9. Thermodynamic modeling and experimental validation of the Fe-Al-Ni-Cr-Mo alloy system

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Teng, Zhenke; Zhang, F; Miller, Michael K

    2012-01-01

    NiAl-type precipitate-strengthened ferritic steels have been known as potential materials for the steam turbine applications. In this study, thermodynamic descriptions of the B2-NiAl type nano-scaled precipitates and body-centered-cubic (BCC) Fe matrix phase for four alloys based on the Fe-Al-Ni-Cr-Mo system were developed as a function of the alloy composition at the aging temperature. The calculated phase structure, composition, and volume fraction were validated by the experimental investigations using synchrotron X-ray diffraction and atom probe tomography. With the ability to accurately predict the key microstructural features related to the mechanical properties in a given alloy system, the established thermodynamic model inmore » the current study may significantly accelerate the alloy design process of the NiAl-strengthened ferritic steels.« less

  10. Anomalous fast diffusion in Cu-NiFe nanolaminates.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jankowski, Alan F.

    2017-09-01

    For this work, the decomposition of the one-dimensional composition wave in Cu-NiFe nanolaminate structures is examined using x-ray diffraction to assess the kinetics of phase decomposition. The anomalously high diffusivity value found for long-term aging at room temperature is attributed to the inherent nanostructure that features paths for short-circuit diffusion in nanolaminates as attributed to interlayer grain boundaries.

  11. On the ortho-positronium quenching reactions promoted by Fe(II), Fe(III), Co(III), Ni(II), Zn(II) and Cd(II) cyanocomplexes

    NASA Astrophysics Data System (ADS)

    Fantola Lazzarini, Anna L.; Lazzarini, Ennio

    The o-Ps quenching reactions promoted in aqueous solutions by the following six cyanocomplexes: [Fe(CN) 6] 4-; [Co(CN) 6] 3-; [Zn(CN) 4] 2-; [Cd(CN) 6] 2-; [Fe(CN) 6] 3-; [Ni(CN) 4] 2- were investigated. The first four reactions probably consist in o-Ps addition across the CN bond, their rate constants at room temperature, Tr, being ⩽(0.04±0.02) × 10 9 M -1 s -1, i.e. almost at the limit of experimental errors. The rate constant of the fifth reaction, in o-Ps oxydation, at Tr is (20.3±0.4) × 10 9 M -1 s -1. The [Ni(CN) 4] 2-k value at Tr, is (0.27±0.01) × 10 9 M -1 s -1, i.e. 100 times less than the rate constants of o-Ps oxydation, but 10 times larger than those of the o-Ps addition across the CN bond. The [Ni(CN) 4] 2- reaction probably results in formation of the following positronido complex: [Ni(CN) 4Ps] 2-. However, it is worth noting that the existence of such a complex is only indirectly deduced. In fact it arises from comparison of the [Ni(CN) 4] 2- rate constant with those of the Fe(II), Zn(II), Cd(II), and Co(III) cyanocomplexes, which, like the Ni(II) cyanocomplex, do not promote o-Ps oxydation or spin exchange reactions.

  12. Intra- and inter-atomic optical transitions of Fe, Co, and Ni ferrocyanides studied using first-principles many-electron calculations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Watanabe, Shinta, E-mail: s-watanabe@nucl.nagoya-u.ac.jp, E-mail: j-onoe@nucl.nagoya-u.ac.jp; Sawada, Yuki; Nakaya, Masato

    We have investigated the electronic structures and optical properties of Fe, Co, and Ni ferrocyanide nanoparticles using first-principles relativistic many-electron calculations. The overall features of the theoretical absorption spectra for Fe, Ni, and Co ferrocyanides calculated using a first-principles many-electron method well reproduced the experimental one. The origins of the experimental absorption spectra were clarified by performing a configuration analysis based on the many-electron wave functions. For Fe ferrocyanide, the experimental absorption peaks originated from not only the charge-transfer transitions from Fe{sup 2+} to Fe{sup 3+} but also the 3d-3d intra-transitions of Fe{sup 3+} ions. In addition, the spin crossovermore » transition of Fe{sup 3+} predicted by the many-electron calculations was about 0.24 eV. For Co ferrocyanide, the experimental absorption peaks were mainly attributed to the 3d-3d intra-transitions of Fe{sup 2+} ions. In contrast to the Fe and Co ferrocyanides, Ni ferrocyanide showed that the absorption peaks originated from the 3d-3d intra-transitions of Ni{sup 3+} ions in a low-energy region, while from both the 3d-3d intra-transitions of Fe{sup 2+} ions and the charge-transfer transitions from Fe{sup 2+} to Ni{sup 3+} in a high-energy region. These results were quite different from those of density-functional theory (DFT) calculations. The discrepancy between the results of DFT calculations and those of many-electron calculations suggested that the intra- and inter-atomic transitions of transition metal ions are significantly affected by the many-body effects of strongly correlated 3d electrons.« less

  13. Improvement of the magnetic moment of NiZn ferrites induced by substitution of Nd3+ ions for Fe3+ ions

    NASA Astrophysics Data System (ADS)

    Wu, Xuehang; Chen, Wen; Wu, Wenwei; Wu, Juan; Wang, Qing

    2018-05-01

    Four types of Ni-Zn based ferrites materials having the general formula Ni0.5Zn0.5NdxFe2-xO4 (0.0 ≤ x ≤ 0.12) have been successfully synthesized by calcining oxalates in air and the influence of Nd content on the structure and magnetic properties of Ni0.5Zn0.5NdxFe2-xO4 is studied. X-ray diffraction examination confirms that a high-crystallized Ni0.5Zn0.5NdxFe2-xO4 with cubic spinel structure is obtained when the precursor is calcined at 1000 °C in air for 2 h. The substitutions of Nd3+ ions for partial Fe3+ ions do not change the spinel crystalline structure of MFe2O4. The incorporation of Nd3+ ions in place of Fe3+ ions in Ni-Zn ferrites increases the average crystallite size. Specific saturation magnetization decreases with increase in Nd content. This is because Nd3+ ions with smaller magnetic moment preferentially fill the octahedral sites. In addition, antiferromagnetic FeNdO3 increases with increase in Nd content. In this study, Ni0.5Zn0.5Nd0.08Fe1.92O4, calcined at 1000 °C, exhibits the highest magnetic moment (4.2954 μB) and the lowest coercivity (28.82 Oe).

  14. Reduction of Ag{sup I}, Au{sup III}, Cu{sup II}, and Hg{sup II} by Fe{sup II}/Fe{sup III} hydroxysulfate green rust.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    O'Loughlin, E. J.; Kelly, S. D.; Kemner, K. M.

    Green rusts are mixed Fe{sup II}/Fe{sup III} hydroxides that are found in many suboxic environments where they are believed to play a central role in the biogeochemical cycling of iron. X-ray absorption fine structure analysis of hydroxysulfate green rust suspensions spiked with aqueous solutions of AgCH{sub 3}COO, AuCl{sub n}(OH){sub 4-n}, CuCl{sub 2}, or HgCl{sub 2} showed that Ag{sup I}, Au{sup III}, Cu{sup II}, and Hg{sup II} were readily reduced to Ag{sup 0}, Au{sup 0}, Cu{sup 0}, and Hg{sup 0}. Imaging of the resulting solids from the Ag{sup I}-, Au{sup III}-, and Cu{sup II}-amended green rust suspensions by transmission electron microscopymore » indicated the formation of submicron-sized particles of Ag{sup 0}, Au{sup 0}, and Cu{sup 0}. The facile reduction of Ag{sup I}, Au{sup III}, Cu{sup II}, and Hg{sup II} to Ag{sup 0}, Au{sup 0}, Cu{sup 0}, and Hg{sup 0}, respectively, by green rust suggests that the presence of green rusts in suboxic soils and sediments can have a significant impact on the biogeochemistry of silver, gold, copper, and mercury, particularly with respect to their mobility.« less

  15. The effect of intermetallic compound morphology on Cu diffusion in Sn-Ag and Sn-Pb solder bump on the Ni/Cu Under-bump metallization

    NASA Astrophysics Data System (ADS)

    Jang, Guh-Yaw; Duh, Jenq-Gong

    2005-01-01

    The eutectic Sn-Ag solder alloy is one of the candidates for the Pb-free solder, and Sn-Pb solder alloys are still widely used in today’s electronic packages. In this tudy, the interfacial reaction in the eutectic Sn-Ag and Sn-Pb solder joints was investigated with an assembly of a solder/Ni/Cu/Ti/Si3N4/Si multilayer structures. In the Sn-3.5Ag solder joints reflowed at 260°C, only the (Ni1-x,Cux)3Sn4 intermetallic compound (IMC) formed at the solder/Ni interface. For the Sn-37Pb solder reflowed at 225°C for one to ten cycles, only the (Ni1-x,Cux)3Sn4 IMC formed between the solder and the Ni/Cu under-bump metallization (UBM). Nevertheless, the (Cu1-y,Niy)6Sn5 IMC was observed in joints reflowed at 245°C after five cycles and at 265°C after three cycles. With the aid of microstructure evolution, quantitative analysis, and elemental distribution between the solder and Ni/Cu UBM, it was revealed that Cu content in the solder near the solder/IMC interface played an important role in the formation of the (Cu1-y,Niy)6Sn5 IMC. In addition, the diffusion behavior of Cu in eutectic Sn-Ag and Sn-Pb solders with the Ni/Cu UBM were probed and discussed. The atomic flux of Cu diffused through Ni was evaluated by detailed quantitative analysis in an electron probe microanalyzer (EPMA). During reflow, the atomic flux of Cu was on the order of 1016-1017 atoms/cm2sec in both the eutectic Sn-Ag and Sn-Pb systems.

  16. Removal of Crystal Violet by Using Reduced-Graphene-Oxide-Supported Bimetallic Fe/Ni Nanoparticles (rGO/Fe/Ni): Application of Artificial Intelligence Modeling for the Optimization Process

    PubMed Central

    Ruan, Wenqian; Qi, Jimei; Hou, Yu; Cao, Rensheng; Wei, Xionghui

    2018-01-01

    Reduced-graphene-oxide-supported bimetallic Fe/Ni nanoparticles were synthesized in this study for the removal of crystal violet (CV) dye from aqueous solutions. This material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), Raman spectroscopy, N2-sorption, and X-ray photoelectron spectroscopy (XPS). The influence of independent parameters (namely, initial dye concentration, initial pH, contact time, and temperature) on the removal efficiency were investigated via Box–Behnken design (BBD). Artificial intelligence (i.e., artificial neural network, genetic algorithm, and particle swarm optimization) was used to optimize and predict the optimum conditions and obtain the maximum removal efficiency. The zero point of charge (pHZPC) of rGO/Fe/Ni composites was determined by using the salt addition method. The experimental equilibrium data were fitted well to the Freundlich model for the evaluation of the actual behavior of CV adsorption, and the maximum adsorption capacity was estimated as 2000.00 mg/g. The kinetic study discloses that the adsorption processes can be satisfactorily described by the pseudo-second-order model. The values of Gibbs free energy change (ΔG0), entropy change (ΔS0), and enthalpy change (ΔH0) demonstrate the spontaneous and endothermic nature of the adsorption of CV onto rGO/Fe/Ni composites. PMID:29789483

  17. Removal of Crystal Violet by Using Reduced-Graphene-Oxide-Supported Bimetallic Fe/Ni Nanoparticles (rGO/Fe/Ni): Application of Artificial Intelligence Modeling for the Optimization Process.

    PubMed

    Ruan, Wenqian; Hu, Jiwei; Qi, Jimei; Hou, Yu; Cao, Rensheng; Wei, Xionghui

    2018-05-22

    Reduced-graphene-oxide-supported bimetallic Fe/Ni nanoparticles were synthesized in this study for the removal of crystal violet (CV) dye from aqueous solutions. This material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), Raman spectroscopy, N₂-sorption, and X-ray photoelectron spectroscopy (XPS). The influence of independent parameters (namely, initial dye concentration, initial pH, contact time, and temperature) on the removal efficiency were investigated via Box⁻Behnken design (BBD). Artificial intelligence (i.e., artificial neural network, genetic algorithm, and particle swarm optimization) was used to optimize and predict the optimum conditions and obtain the maximum removal efficiency. The zero point of charge (pH ZPC ) of rGO/Fe/Ni composites was determined by using the salt addition method. The experimental equilibrium data were fitted well to the Freundlich model for the evaluation of the actual behavior of CV adsorption, and the maximum adsorption capacity was estimated as 2000.00 mg/g. The kinetic study discloses that the adsorption processes can be satisfactorily described by the pseudo-second-order model. The values of Gibbs free energy change (Δ G ⁰), entropy change (Δ S ⁰), and enthalpy change (Δ H ⁰) demonstrate the spontaneous and endothermic nature of the adsorption of CV onto rGO/Fe/Ni composites.

  18. Magnetic properties of the CrMnFeCoNi high-entropy alloy

    DOE PAGES

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

    2017-07-28

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

  19. Heat treatment of NiCrFe alloy 600 to optimize resistance to intergranular stress corrosion

    DOEpatents

    Steeves, A.F.; Bibb, A.E.

    A process of producing a NiCrFe alloy having a high resistance to stress corrosion cracking comprises heating a NiCrFe alloy to a temperature sufficient to enable the carbon present in the alloy body in the form of carbide deposits to enter into solution, rapidly cooling the alloy body, and heating the cooled body to a temperature between 1100 to 1500/sup 0/F for about 1 to 30 hours.

  20. Hierarchical 3D NiFe2O4@MnO2 core-shell nanosheet arrays on Ni foam for high-performance asymmetric supercapacitors.

    PubMed

    Zhang, Xinyang; Zhang, Ziqing; Sun, Shuanggan; Sun, Qiushi; Liu, Xiaoyang

    2018-02-13

    Hierarchical NiFe 2 O 4 @MnO 2 core-shell nanosheet arrays (NSAs) were synthesized on Ni foam as an integrated electrode for supercapacitors, using a facile two-step hydrothermal method followed by calcination treatment. The NiFe 2 O 4 nanosheets were designed as the core and ultrathin MnO 2 nanoflakes as the shell, creating a unique three-dimensional (3D) hierarchical electrode on Ni foam. The composite electrode exhibited remarkable electrochemical performance with a high specific capacitance of 1391 F g -1 at a current density of 2 mA cm -2 and long cycling stability at a high current density of 10 mA cm -2 (only 11.4% loss after 3000 cycles). Additionally, an asymmetric supercapacitor (ASC) device was fabricated with a NiFe 2 O 4 @MnO 2 composite as the positive electrode material and activated carbon (AC) as the negative one. The ASC device exhibited a high energy density (45.2 W h kg -1 ) at a power density of 174 W kg -1 , and an excellent cycling stability over 3000 cycles with 92.5% capacitance retention. The remarkable electrochemical performance demonstrated its great potential as a promising candidate for high-performance supercapacitors.