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Sample records for level suitei ni

  1. On the Metastable Level in Ni-like Ions

    SciTech Connect

    Trabert, E; Beiersdorfer, P; Brown, G V; Terracol, S; Safronova, U I

    2004-09-14

    The lowest excited level in Ni-like ions, 3d{sup 9}4s {sup 3}D{sub 3}, decays only via a magnetic octupole (M3) decay. They present calculated values of transition wavelengths and rates for ions with 30 {le} Z {le} 100. They have observed this line in Xe{sup 26+}, using the Livermore EBIT-I electron beam ion trap and a microcalorimeter, as well as a high-resolution flat-field grating spectrometer.

  2. El Niño, La Niña, and the global sea level budget

    NASA Astrophysics Data System (ADS)

    Piecuch, Christopher G.; Quinn, Katherine J.

    2016-11-01

    Previous studies show that nonseasonal variations in global-mean sea level (GMSL) are significantly correlated with El Niño-Southern Oscillation (ENSO). However, it has remained unclear to what extent these ENSO-related GMSL fluctuations correspond to steric (i.e., density) or barystatic (mass) effects. Here we diagnose the GMSL budget for ENSO events observationally using data from profiling floats, satellite gravimetry, and radar altimetry during 2005-2015. Steric and barystatic effects make comparable contributions to the GMSL budget during ENSO, in contrast to previous interpretations based largely on hydrological models, which emphasize the barystatic component. The steric contributions reflect changes in global ocean heat content, centered on the Pacific. Distributions of ocean heat storage in the Pacific arise from a mix of diabatic and adiabatic effects. Results have implications for understanding the surface warming slowdown and demonstrate the usefulness of the Global Ocean Observing System for constraining Earth's hydrological cycle and radiation imbalance.

  3. Imprint of the El Niño Modoki on decadal sea level changes

    NASA Astrophysics Data System (ADS)

    Behera, Swadhin; Yamagata, Toshio

    2010-12-01

    Decadal variation in sea level is shown to manifest as higher than normal sea level in the central Pacific flanked by lower than normal sea level on either side of the basin during the early 21st century. This abnormal condition is evidently aided by frequent occurrences of El Niño Modoki events and associated wind convergence to the dateline during 2000-2004. The sea level rise in central Pacific succeeded a phase of lower than normal sea level associated with La Niña Modoki events toward the end of 20th century. A correlation analysis confirms the dominant influence of El Niño/La Niña Modoki on the sea level rise in the central Pacific as compared to that of the El Niño/La Niña. This influence can even be seen in remote regions such as the coasts of California and Mauritius through atmospheric teleconnections.

  4. Evaluation of damage induced by high irradiation levels on α-Ni-Ni3Si eutectic structure

    NASA Astrophysics Data System (ADS)

    Camacho Olguin, Carlos Alberto; Garcia-Borquez, Arturo; González-Rodríguez, Carlos Alberto; Loran-Juanico, Jose Antonio; Cruz-Mejía, Hector

    2015-06-01

    to 380 dpa at 650°C in a Tandetron linear accelerator. The level of irradiation dose was chosen similar to the irradiation conditions of the next-generation nuclear reactors. The theoretical maximum depth of the DII (maximum depth of damage (MDD)) was calculated as 1.35 µm using the SRIM-2013 program; the laminar microstructure of the eutectic was simulated using the lattice parameters of the eutectic before irradiation. The experimental MDD was 1.47 µm, as determined through transmission electron microscope (TEM) images and the DII was characterized using µX-ray diffraction and TEM. The elimination of cubic phase of the intermetallic Ni3Si, the suppression of lamellae of the α-Ni phase, the generation of dislocation loops and lines, all of these changes generated by the irradiation are clear evidences that the DII was severe. Based on theoretical and experimental evidence, we propose that the amount of phases, alternate of lamellae with different chemical concentrations of silicon and lamellae spatial distribution have a direct relation with the severe evolution of the DII.

  5. An interhemispheric tropical sea level seesaw due to El Niño Taimasa

    NASA Astrophysics Data System (ADS)

    Widlansky, M. J.; Timmermann, A.; McGregor, S.; Stuecker, M. F.; Cai, W.

    2013-12-01

    During strong El Niño events, sea level drops around some tropical western Pacific islands by up to 20-30 cm. Such extreme events (referred to as ';taimasa' in Samoa) expose shallow reefs, thereby damaging associated coastal ecosystems and contributing to the formation of ';flat topped coral heads' often referred to as microatolls. We show that during the termination of strong El Niño events, a southward movement of weak trade winds and development of an anomalous anticyclone in the Philippine Sea force an interhemispheric sea level seesaw in the tropical Pacific which enhances and prolongs extreme low sea levels in the southwestern Pacific. Spectral features, in addition to wind forced linear shallow water ocean model experiments, identify an interaction between El Niño and the annual cycle as the main cause of these sea level anomalies. Given the well established seasonal prediction skill for El Niño events and their seasonally paced termination, our analysis suggests that long-duration extreme sea level drops may also be highly predictable.

  6. Deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase-epitaxy n-GaAs

    NASA Technical Reports Server (NTRS)

    Partin, D. L.; Chen, J. W.; Milnes, A. G.; Vassamillet, L. F.

    1979-01-01

    The paper presents deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase epitaxy n-GaAs. Nickel diffused into VPE n-GaAs reduces the hole diffusion length L sub p from 4.3 to 1.1 microns. Deep-level transient spectroscopy was used to identify energy levels in Ni-diffused GaAs; the as-grown VPE GaAs contains traces of these levels and an electron trap. Ni diffusion reduces the concentration of this level by an amount that matches the increase in concentration of each of the two Ni-related levels. A technique for measuring minority-carrier capture cross sections was developed, which indicates that L sub p in Ni-diffused VPE n-GaAs is controlled by the E sub c - 0.39 eV defect level.

  7. Levels of nickel and other potentially allergenic metals in Ni-tested commercial body creams.

    PubMed

    Bocca, B; Forte, G; Petrucci, F; Cristaudo, A

    2007-09-03

    It is extensively well-known that Ni and other metals occurring as impurities in cosmetic products might give rise to contact dermatitis in subjects with pre-existing allergy. The present study on the content of 13 metals (Cd, Co, Cr, Cu, Hg, Ir, Mn, Ni, Pb, Pd, Pt, Rh, and V) in moisturizing creams, labelled as "Ni-tested" (i.e., Ni content <100 ng g(-1)) and available on the Italian market, provides a basis for assessing their safety for consumers. Quantification of metals was performed by sector field inductively coupled plasma mass spectrometry after microwave-assisted acid digestion of products. The developed method had limits of quantification less than 0.8 ng g(-1) for all the elements; recovery was in the interval 88% (Cd, Co) to 110% (Hg), and precision was always under 7%. Nickel was present in all the products with levels between 17.5 and 153 ng g(-1); three skin creams were slightly above the concentration reported on the label. The other elements were at levels below 1 microg g(-1). The highest concentrations, in ng g(-1), of Co, Cr, Cu, and Mn were 222, 303, 51.2, and 59.9, respectively. Mean Cd, Pb, and V were below 5 ng g(-1), while Hg was absent in all the samples. Among the new emergent allergens, Ir and Rh were in traces or even undetectable, while Pt had levels of 2.65 and 6.28 ng g(-1) in two creams and Pd was equal to 1.07 ng g(-1) in one product. The overall results are below the sensitizing limit proposed for consumer products and, thus, probably have no significant toxicological effects. Nevertheless, some creams presented amounts of Co and Cr comparable to those of Ni and therefore they have to be monitored in consideration of their cross-reactivity as well.

  8. Strong Deep-Level-Emission Photoluminescence in NiO Nanoparticles.

    PubMed

    Gandhi, Ashish Chhaganlal; Wu, Sheng Yun

    2017-08-22

    Nickel oxide is one of the highly promising semiconducting materials, but its large band gap (3.7 to 4 eV) limits its use in practical applications. Here we report the effect of nickel/oxygen vacancies and interstitial defects on the near-band-edge (NBE) and deep-level-emission (DLE) in various sizes of nickel oxide (NiO) nanoparticles. The ultraviolet (UV) emission originated from excitonic recombination corresponding near-band-edge (NBE) transition of NiO, while deep-level-emission (DLE) in the visible region due to various structural defects such as oxygen vacancies and interstitial defects. We found that the NiO nanoparticles exhibit a strong green band emission around ~2.37 eV in all samples, covering 80% integrated intensity of PL spectra. This apparently anomalous phenomenon is attributed to photogenerated holes trapped in the deep level oxygen vacancy recombining with the electrons trapped in a shallow level located just below the conducting band.

  9. Shapes and structures in the neighborhood of 68Ni: levels in 69Cu

    NASA Astrophysics Data System (ADS)

    Walters, William

    2014-03-01

    The study of the level structure of 68Ni40 during the last 15 years has been intense, fueled by the presence of two excited 0+ levels and a single excited 2+ level below 2.6 MeV. Recently, Tsunoda et al., have performed a series of calculations that indicate spherical, oblate, and prolate shapes for the ground, first excited 0+ level at 1604 keV, and second excited 0+ level at 2511 keV. [Y. Tsunoda, T. Otsuka, N. Shimizu, M. Honma, and Y. Utsuno, arXiv:1309.5851v1] One approach to gaining additional insight into these ideas is to examine the structure of 69Cu40 that has a single proton coupled to 68Ni. In this presentation, new levels and transitions will be presented for 69Cu40.42 and discussed in the context of these three proposed shapes. Excited states in these nuclei were populated through multinucleon-transfer reactions using beams provided by the ATLAS facility at Argonne National Laboratory and studied with Gammasphere. From these data, an estimate of the barrier height separating the oblate and prolate shapes will be deduced. This work was supported in part by the US DoE under DEFG02- 94-ER40834 & DE-AC02-06CH11357.

  10. Energy levels and radiative rates for transitions in Fe V, Co VI and Ni VII

    NASA Astrophysics Data System (ADS)

    Aggarwal, K. M.; Bogdanovich, P.; Keenan, F. P.; Kisielius, R.

    2017-03-01

    Energy levels, Landé g-factors and radiative lifetimes are reported for the lowest 182 levels of the 3d4, 3d34s and 3d34p configurations of Fe V, Co VI and Ni VII. Additionally, radiative rates (A-values) have been calculated for the E1, E2 and M1 transitions among these levels. The calculations have been performed in a quasi-relativistic approach (QR) with a very large configuration interaction (CI) wavefunction expansion, which has been found to be necessary for these ions. Our calculated energies for all ions are in excellent agreement with the available measurements, for most levels. Discrepancies among various calculations for the radiative rates of E1 transitions in Fe V are up to a factor of two for stronger transitions (f ≥ 0.1), and larger (over an order of magnitude) for weaker ones. The reasons for these discrepancies have been discussed and mainly are due to the differing amount of CI and methodologies adopted. However, there are no appreciable discrepancies in similar data for M1 and E2 transitions, or the g-factors for the levels of Fe V, the only ion for which comparisons are feasible.

  11. Linking a sea level pressure anomaly dipole over North America to the central Pacific El Niño

    NASA Astrophysics Data System (ADS)

    Ding, Ruiqiang; Li, Jianping; Tseng, Yu-heng; Sun, Cheng; Zheng, Fei

    2017-08-01

    This study demonstrates the close connection between the north-south dipole pattern of sea level pressure anomalies over northeastern North America to the western tropical North Atlantic, referred to as the North American dipole (NAD), and the central Pacific (CP)-type El Niño a year later. In contrast to other ENSO precursors, such as the North Pacific Oscillation (NPO) and Pacific-North America (PNA) pattern, the NAD appears more closely related to the CP-type El Niño than to the eastern Pacific (EP)-type El Niño, indicating that the NAD may serve as a unique precursor for the CP El Niño. The wintertime NAD induces sea surface temperature anomalies in the northern tropical Atlantic (NTA), which subsequently play an important role in developing the CP El Niño-like pattern in the tropical Pacific over the course of the following year. It appears that the NAD influence on CP El Niño involves air-sea interaction over several major basins, including the subtropical/tropical Pacific and the NTA. Additional analysis indicates that the correlation of either the NAD index or the NPO index with the CP El Niño state a year later depends on the status of the other index. When the wintertime NAD index is of the opposite sign to the simultaneous NPO index, the correlation of the NAD or NPO index with the Niño4 index becomes much weaker.

  12. Linking a sea level pressure anomaly dipole over North America to the central Pacific El Niño

    NASA Astrophysics Data System (ADS)

    Ding, Ruiqiang; Li, Jianping; Tseng, Yu-heng; Sun, Cheng; Zheng, Fei

    2016-10-01

    This study demonstrates the close connection between the north-south dipole pattern of sea level pressure anomalies over northeastern North America to the western tropical North Atlantic, referred to as the North American dipole (NAD), and the central Pacific (CP)-type El Niño a year later. In contrast to other ENSO precursors, such as the North Pacific Oscillation (NPO) and Pacific-North America (PNA) pattern, the NAD appears more closely related to the CP-type El Niño than to the eastern Pacific (EP)-type El Niño, indicating that the NAD may serve as a unique precursor for the CP El Niño. The wintertime NAD induces sea surface temperature anomalies in the northern tropical Atlantic (NTA), which subsequently play an important role in developing the CP El Niño-like pattern in the tropical Pacific over the course of the following year. It appears that the NAD influence on CP El Niño involves air-sea interaction over several major basins, including the subtropical/tropical Pacific and the NTA. Additional analysis indicates that the correlation of either the NAD index or the NPO index with the CP El Niño state a year later depends on the status of the other index. When the wintertime NAD index is of the opposite sign to the simultaneous NPO index, the correlation of the NAD or NPO index with the Niño4 index becomes much weaker.

  13. Corticosterone levels predict survival probabilities of Galápagos marine iguanas during El Niño events

    PubMed Central

    Romero, L. Michael; Wikelski, Martin

    2001-01-01

    Plasma levels of corticosterone are often used as a measure of “stress” in wild animal populations. However, we lack conclusive evidence that different stress levels reflect different survival probabilities between populations. Galápagos marine iguanas offer an ideal test case because island populations are affected differently by recurring El Niño famine events, and population-level survival can be quantified by counting iguanas locally. We surveyed corticosterone levels in six populations during the 1998 El Niño famine and the 1999 La Niña feast period. Iguanas had higher baseline and handling stress-induced corticosterone concentrations during famine than feast conditions. Corticosterone levels differed between islands and predicted survival through an El Niño period. However, among individuals, baseline corticosterone was only elevated when body condition dropped below a critical threshold. Thus, the population-level corticosterone response was variable but nevertheless predicted overall population health. Our results lend support to the use of corticosterone as a rapid quantitative predictor of survival in wild animal populations. PMID:11416210

  14. Ab initio calculations of energy levels, transition rates and lifetimes in Ni xii

    NASA Astrophysics Data System (ADS)

    Bilal, M.; Beerwerth, R.; Volotka, A. V.; Fritzsche, S.

    2017-08-01

    We report large-scale multi-configuration Dirac-Hartree-Fock calculations and relativistic configuration interaction calculations for allowed E1 and forbidden transitions (M1, E2, M2) among the fine structure levels of the 3s23p5, 3s3p6 and 3s23p43d configurations for Ni xii. In our systematically enlarged wave functions, we incorporated the effects of relativity, all important electron correlations and rearrangement of the bound electron density within two different computational models. We compare our calculated energies for the fine structure levels with previous calculations and experiments. We validate all the tentative experimental lines recently identified by Del Zanna & Badnell with one exception. We discuss the consistency of our transition rates in comparison to semi-empirical predictions. We present ab initio lifetime values by taking into account all allowed E1 and forbidden transitions (M1, E2, M2) rates among lowest 31 levels. Our results for lifetime values are better than previously reported ab initio and semi-empirical values as compared to available experiments, thus, providing reliable predictions in the prospects of future experiments.

  15. Low-level measurement of 63Ni by means of accelerator mass spectrometry

    NASA Astrophysics Data System (ADS)

    Rugel, G.; Arazi, A.; Carroll, K. L.; Faestermann, T.; Knie, K.; Korschinek, G.; Marchetti, A. A.; Martinelli, R. E.; McAninch, J. E.; Rühm, W.; Straume, T.; Wallner, A.; Wallner, C.

    2004-08-01

    The radionuclide 63Ni (T1/2=100.1 a) has been proposed as a fluence monitor for fast neutrons in copper samples from Hiroshima. Accelerator mass spectrometry (AMS) represents a powerful tool for the detection of this radionuclide, provided the isobaric interference of 63Cu can be sufficiently suppressed. In this paper, we report the first results from a study on the 63Cu background observed in different sets of control samples, and in a 127-year-old environmental copper sample which was directly exposed to cosmic radiation for about 80 years. The 63Ni/Ni ratios measured in the blank samples range up to about 2 × 10-13 corresponding to concentrations of a few times 10463Ni atoms/g Cu. These results provide information on the overall background of the applied methodology and, thus, on the possible sensitivity of 63Ni measurements in copper samples by means of AMS. In the environmental sample, a 63Ni concentration of (1.0 ± 0.3) × 10563Ni atoms/g Cu was observed which is not significantly different from the results obtained on commercially available copper material. A similar concentration would be expected in a copper sample located 1300 m from the hypocenter of the Hiroshima atomic bomb.

  16. Intensity and Energy Level Analysis of the Vacuum Ultraviolet Spectrum of Four Times Ionize Nickel (Ni V)

    NASA Astrophysics Data System (ADS)

    Ward, Jacob Wolfgang; Nave, Gillian

    2016-01-01

    Recent measurements of four times ionized iron and nickel (Fe V & Ni V) wavelengths in the vacuum ultraviolet (VUV) have been taken using the National Institute for Standards and Technology (NIST) Normal Incidence Vacuum Spectrograph (NIVS) with a sliding spark light source with invar electrodes. The wavelengths observed in those measurements make use of high resolution photographic plates with the majority of observed lines having uncertainties of approximately 3mÅ. In addition to observations made with photographic plates, the same wavelength region was observed with phosphor image plates, which have been demonstrated to be accurate as a method of intensity calibration when used with a deuterium light source. This work will evaluate the use of phosphor image plates and deuterium lamps as an intensity calibration method for the Ni V spectrum in the 1200-1600Å region of the VUV. Additionally, by pairing the observed wavelengths of Ni V with accurate line intensities, it is possible to create an energy level optimization for Ni V providing high accuracy Ritz wavelengths. This process has previously been applied to Fe V and produced Ritz wavelengths that agreed with the above experimental observations.

  17. Nonlocal Screening Effects on the Ni 2p Core Level Photoemission of the Linear-Chain Nickelate Y2BaNiO5

    NASA Astrophysics Data System (ADS)

    Okada, Kozo; Takeuchi, Yurika

    2017-06-01

    The Ni 2p X-ray photoemission spectrum (Ni 2p XPS) of the linear-chain nickelate Y2BaNiO5 is calculated by a Ni5O26 cluster model, adopting the numerically-exact diagonalization method based on the Lanczos algorithm. Particular attention is paid to how the Ni 2p core-hole charge is screened by the Ni 3d-O 2p valence electron system. The result shows that the leading d9L peak of the Ni 2p XPS has two components, as in the case of the Ni 2p XPS of NiO, where L denotes a ligand hole. The hole distribution analysis shows the importance of "nonlocal screening" that the Ni 3d holes apart from the core-hole site actively participate in the core-hole screening, and it also shows that the "local screening" is realized in the lowest-energy final state. The calculated spectrum of Y2BaNiO5 well reproduces that obtained experimentally.

  18. ALCHEMI of Fe-doped B2-ordered NiAl alloys with different doping levels

    SciTech Connect

    Anderson, I.M.; Bentley, J.; Duncan, A.J.

    1994-09-01

    The ALCHEMI technique yields exact expressions for best-fit parameters in terms of ionization localization constants and site distributions of 3 elements distributed over two sublattices. In this paper, a graphical plotting technique is applied to Fe-doped NiAl B2-ordered alloys Ni{sub 0.5-x}Fe{sub x}Al{sub 0.5}, with x=0.02 or 0.10. The thin foil samples were examined in an electron microscope with an x-ray spectrometer.

  19. Relativistic MR-MP calculations of the energy levels and transition probabilities in Ni- to Kr-like Pt ions

    SciTech Connect

    Santana, Juan A.; Ishikawa, Yasuyuki; Träbert, Elmar

    2014-01-15

    Ni- to Kr-like Pt ions have been studied by relativistic multi-reference Møller–Plesset many-body perturbation theory calculations. Energy levels and lifetimes of low-lying excited states within the n=4 complex are reported for each ion. Wavelengths and transition probabilities for the strongest electric-dipole transitions are compared with available experimental data. Synthetic radiative spectra are shown for various wavelength regions.

  20. High-level ab initio predictions for the ionization energy, bond dissociation energies, and heats of formation of nickel carbide (NiC) and its cation (NiC+).

    PubMed

    Lau, Kai-Chung; Chang, Yih Chung; Shi, Xiaoyu; Ng, C Y

    2010-09-21

    The ionization energy (IE) of NiC and the 0 K bond dissociation energies (D(0)) and heats of formation at 0 K (ΔH(o)(f0)) and 298 K (ΔH(o)(f298)) for NiC and NiC(+) are predicted by the wavefunction based CCSDTQ(Full)/CBS approach and the multireference configuration interaction (MRCI) method with Davidson correction (MRCI+Q). The CCSDTQ(Full)/CBS calculations presented here involve the approximation to the complete basis set (CBS) limit at the coupled cluster level up to full quadruple excitations along with the zero-point vibrational energy (ZPVE), high-order correlation, core-valence electronic (CV), spin-orbit coupling (SO), and scalar relativistic effect (SR) corrections. The present calculations provide the correct symmetry predictions for the ground states of NiC and NiC(+) to be (1)∑(+) and (2)∑(+), respectively. The CCSDTQ(Full)/CBS IE(NiC)=8.356 eV is found to compare favorably with the experimental IE value of 8.372 05±0.000 06 eV. The predicted IE(NiC) value at the MRCI+Q/cc-pwCV5Z level, including the ZPVE, SO, and SR effects is 8.00 eV, which is 0.37 eV lower than the experimental value. This work together with the previous experimental and theoretical investigations supports the conclusion that the CCSDTQ(Full)/CBS method is capable of providing reliable IE predictions for 3d-transition metal carbides, such as FeC and NiC. Furthermore, the CCSDTQ(Full)/CBS calculations give the prediction of D(0)(Ni-C)-D(0)(Ni(+)-C)=0.688 eV, which is also consistent with the experimental determination of 0.732 21±0.000 06 eV, whereas the MRCI+Q calculations (with relativistic and CV effects) predict a significantly lower value of 0.39 eV for D(0)(Ni-C)-D(0)(Ni(+)-C). The analysis of the correction terms shows that the CV and valence-valence electronic correlations beyond CCSD(T) wavefunction and the relativistic effect make significant contributions to the calculated thermochemical properties of NiC/NiC(+). For the experimental D(0) and ΔH(o)(f0) values of

  1. A method to detect low-level 63Ni activity for estimating fast neutron fluence from the Hiroshima atomic bomb.

    PubMed

    Ito, Y; Shibata, T; Imamura, M; Shibata, S; Nogawa, N; Uwamino, Y; Shizuma, K

    1999-06-01

    The Hiroshima and Nagasaki atomic bombs resulted in the worst reported exposure of radiation to the human body. The data of survivors have provided the basis for the risk estimation for ionizing radiation, and thus are widely used as the basis of radiation safety. In this report we have studied a new method to detect the low-level 63Ni activity in copper samples in order to estimate the fast neutron fluence from the Hiroshima atomic bomb. Only 0.8 x 10(-3) Bq g(-1) of 63Ni is expected to be produced by the atomic bomb in a copper sample with the 63Cu(n, p)63Ni reaction at a distance of 500 m from the hypocenter. Our method has the required level of sensitivity for determination of the fast neutron fluence out to distances of at least 500 m, and perhaps as far as 1,000 m. We have already investigated and collected some bomb-irradiated copper samples for further study.

  2. Radiative data for highly excited 3d84d levels in Ni II from laboratory measurements and atomic calculations

    NASA Astrophysics Data System (ADS)

    Hartman, H.; Engström, L.; Lundberg, H.; Nilsson, H.; Quinet, P.; Fivet, V.; Palmeri, P.; Malcheva, G.; Blagoev, K.

    2017-04-01

    Aims: This work reports new experimental radiative lifetimes and calculated oscillator strengths for transitions from 3d84d levels of astrophysical interest in singly ionized nickel. Methods: Radiative lifetimes of seven high-lying levels of even parity in Ni II (98 400-100 600 cm-1) have been measured using the time-resolved laser-induced fluorescence method. Two-step photon excitation of ions produced by laser ablation has been utilized to populate the levels. Theoretical calculations of the radiative lifetimes of the measured levels and transition probabilities from these levels are reported. The calculations have been performed using a pseudo-relativistic Hartree-Fock method, taking into account core polarization effects. Results: A new set of transition probabilities and oscillator strengths has been deduced for 477 Ni II transitions of astrophysical interest in the spectral range 194-520 nm depopulating even parity 3d84d levels. The new calculated gf-values are, on the average, about 20% higher than a previous calculation and yield lifetimes within 5% of the experimental values.

  3. Investigating the atomic level influencing factors of glass forming ability in NiAl and CuZr metallic glasses

    SciTech Connect

    Sedighi, Sina; Kirk, Donald Walter; Singh, Chandra Veer Thorpe, Steven John

    2015-09-21

    Bulk metallic glasses are a relatively new class of amorphous metal alloy which possess unique mechanical and magnetic properties. The specific concentrations and combinations of alloy elements needed to prevent crystallization during melt quenching remains poorly understood. A correlation between atomic properties that can explain some of the previously identified glass forming ability (GFA) anomalies of the NiAl and CuZr systems has been identified, with these findings likely extensible to other transition metal–transition metal and transition metal–metalloid (TM–M) alloy classes as a whole. In this work, molecular dynamics simulation methods are utilized to study thermodynamic, kinetic, and structural properties of equiatomic CuZr and NiAl metallic glasses in an attempt to further understand the underlying connections between glass forming ability, nature of atomic level bonding, short and medium range ordering, and the evolution of structure and relaxation properties in the disordered phase. The anomalous breakdown of the fragility parameter as a useful GFA indicator in TM–M alloy systems is addressed through an in-depth investigation of bulk stiffness properties and the evolution of (pseudo)Gruneisen parameters over the quench domain, with the efficacy of other common glass forming ability indicators similarly being analyzed through direct computation in respective CuZr and NiAl systems. Comparison of fractional liquid-crystal density differences in the two systems revealed 2-3 times higher values for the NiAl system, providing further support for its efficacy as a general purpose GFA indicator.

  4. Investigating the atomic level influencing factors of glass forming ability in NiAl and CuZr metallic glasses.

    PubMed

    Sedighi, Sina; Kirk, Donald Walter; Singh, Chandra Veer; Thorpe, Steven John

    2015-09-21

    Bulk metallic glasses are a relatively new class of amorphous metal alloy which possess unique mechanical and magnetic properties. The specific concentrations and combinations of alloy elements needed to prevent crystallization during melt quenching remains poorly understood. A correlation between atomic properties that can explain some of the previously identified glass forming ability (GFA) anomalies of the NiAl and CuZr systems has been identified, with these findings likely extensible to other transition metal-transition metal and transition metal-metalloid (TM-M) alloy classes as a whole. In this work, molecular dynamics simulation methods are utilized to study thermodynamic, kinetic, and structural properties of equiatomic CuZr and NiAl metallic glasses in an attempt to further understand the underlying connections between glass forming ability, nature of atomic level bonding, short and medium range ordering, and the evolution of structure and relaxation properties in the disordered phase. The anomalous breakdown of the fragility parameter as a useful GFA indicator in TM-M alloy systems is addressed through an in-depth investigation of bulk stiffness properties and the evolution of (pseudo)Gruneisen parameters over the quench domain, with the efficacy of other common glass forming ability indicators similarly being analyzed through direct computation in respective CuZr and NiAl systems. Comparison of fractional liquid-crystal density differences in the two systems revealed 2-3 times higher values for the NiAl system, providing further support for its efficacy as a general purpose GFA indicator.

  5. High-level ab initio predictions for the ionization energy, bond dissociation energies, and heats of formation of nickel carbide (NiC) and its cation (NiC+)

    NASA Astrophysics Data System (ADS)

    Lau, Kai-Chung; Chang, Yih Chung; Shi, Xiaoyu; Ng, C. Y.

    2010-09-01

    The ionization energy (IE) of NiC and the 0 K bond dissociation energies (D0) and heats of formation at 0 K (ΔHof0) and 298 K (ΔHof298) for NiC and NiC+ are predicted by the wavefunction based CCSDTQ(Full)/CBS approach and the multireference configuration interaction (MRCI) method with Davidson correction (MRCI+Q). The CCSDTQ(Full)/CBS calculations presented here involve the approximation to the complete basis set (CBS) limit at the coupled cluster level up to full quadruple excitations along with the zero-point vibrational energy (ZPVE), high-order correlation, core-valence electronic (CV), spin-orbit coupling (SO), and scalar relativistic effect (SR) corrections. The present calculations provide the correct symmetry predictions for the ground states of NiC and NiC+ to be ∑1+ and ∑2+, respectively. The CCSDTQ(Full)/CBS IE(NiC)=8.356 eV is found to compare favorably with the experimental IE value of 8.372 05±0.000 06 eV. The predicted IE(NiC) value at the MRCI+Q/cc-pwCV5Z level, including the ZPVE, SO, and SR effects is 8.00 eV, which is 0.37 eV lower than the experimental value. This work together with the previous experimental and theoretical investigations supports the conclusion that the CCSDTQ(Full)/CBS method is capable of providing reliable IE predictions for 3d-transition metal carbides, such as FeC and NiC. Furthermore, the CCSDTQ(Full)/CBS calculations give the prediction of D0(NiC)-D0(Ni+C)=0.688 eV, which is also consistent with the experimental determination of 0.732 21±0.000 06 eV, whereas the MRCI+Q calculations (with relativistic and CV effects) predict a significantly lower value of 0.39 eV for D0(NiC)-D0(Ni+C). The analysis of the correction terms shows that the CV and valence-valence electronic correlations beyond CCSD(T) wavefunction and the relativistic effect make significant contributions to the calculated thermochemical properties of NiC/NiC+. For the experimental D0 and ΔHof0 values of NiC/NiC+, which are not known

  6. Microstructures of La 1.85Sr 0.15CuO 4 doped with Ni at high doping level

    NASA Astrophysics Data System (ADS)

    Wu, X. S.; Jiang, S. S.; Pan, F. M.; Lin, J.; Xu, N.; Mao Zhiqiang; Xu Gaoji; Zhang Yuheng

    1996-02-01

    Ceramic superconductors of La 1.85Sr 0.15Cu 1- yNi yO 4 with 0.00 ≤ y ≤ 0.50 were synthesized. There is no impurity phase detected in the entire Ni doped region. The structure of these Ni-doped samples was characterized by X-ray diffraction studies. The atomic structural parameters were obtained by Rietveld refinements for the Ni-doped samples with y ≤ 0.50. Some meaningful bond distances were determined according to the refined results. According to the variations of some bond distances with y, the whole doping range could be divided into two regions: low doping level (LDL) and high doping level (HDL). The bond length between the two apical oxygen atoms in the CuO 6 octahedra for the Ni-doped samples increased with increasing content of Ni in the LDL, and decreased in the HDL. The average bond distance of LaO was not changed in the whole doping region. The metal-insulator transition was also observed in this Ni-doped system.

  7. Performance of the Prognocean Plus system during the El Niño 2015/2016: predictions of sea level anomalies as tools for forecasting El Niño

    NASA Astrophysics Data System (ADS)

    Świerczyńska-Chlaściak, Małgorzata; Niedzielski, Tomasz; Miziński, Bartłomiej

    2017-04-01

    The aim of this paper is to present the performance of the Prognocean Plus system, which produces long-term predictions of sea level anomalies, during the El Niño 2015/2016. The main objective of work is to identify such ocean areas in which long-term forecasts of sea level anomalies during El Niño 2015/2016 reveal a considerable accuracy. At present, the system produces prognoses using four data-based models and their combinations: polynomial-harmonic model, autoregressive model, threshold autoregressive model and multivariate autoregressive model. The system offers weekly forecasts, with lead time up to 12 weeks. Several statistics that describe the efficiency of the available prediction models in four seasons used for estimating Oceanic Niño index (ONI) are calculated. The accuracies/skills of the predicting models were computed in the specific locations in the equatorial Pacific, namely the geometrically-determined central points of all Niño regions. For the said locations, we focused on the forecasts which targeted at the local maximum of sea level, driven by the El Niño 2015/2016. As a result, a series of the "spaghetti" graphs (for each point, season and model) as well as plots presenting the prognostic performance of every model - for all lead times, seasons and locations - were created. It is found that the Prognocean Plus system has a potential to become a new solution which may enhance the diagnostic discussions on the El Niño development. The forecasts produced by the threshold autoregressive model, for lead times of 5-6 weeks and 9 weeks, within the Niño1+2 region for the November-to-January (NDJ) season anticipated the culmination of the El Niño 2015/2016. The longest forecasts (8-12 weeks) were found to be the most accurate in the phase of transition from El Niño to normal conditions (the multivariate autoregressive model, central point of Niño1+2 region, the December-to-February season). The study was conducted to verify the ability and

  8. Fermi Level shifting, Charge Transfer and Induced Magnetic Coupling at La0.7Ca0.3MnO3/LaNiO3 Interface

    PubMed Central

    Ning, Xingkun; Wang, Zhanjie; Zhang, Zhidong

    2015-01-01

    A large magnetic coupling has been observed at the La0.7Ca0.3MnO3/LaNiO3 (LCMO/LNO) interface. The x-ray photoelectron spectroscopy (XPS) study results show that Fermi level continuously shifted across the LCMO/LNO interface in the interface region. In addition, the charge transfer between Mn and Ni ions of the type Mn3+ − Ni3+ → Mn4+ − Ni2+ with the oxygen vacancies are observed in the interface region. The intrinsic interfacial charge transfer can give rise to itinerant electrons, which results in a “shoulder feature” observed at the low binding energy in the Mn 2p core level spectra. Meanwhile, the orbital reconstruction can be mapped according to the Fermi level position and the charge transfer mode. It can be considered that the ferromagnetic interaction between Ni2+ and Mn4+ gives rise to magnetic regions that pin the ferromagnetic LCMO and cause magnetic coupling at the LCMO/LNO interface. PMID:25676088

  9. Determination of contamination levels of Pb, Cd, Cu, Ni, and Mn caused by former lead mining gallery.

    PubMed

    Bakırdere, Sezgin; Bölücek, Cemal; Yaman, Mehmet

    2016-03-01

    In the present study, levels of metal contamination caused by former lead mining area were figured out. For this purpose, Pb, Cd, Cu, Ni, and Mn were determined not only in sediment samples taken from different places of the mining area but also in some plants taken around the mining place. In the digestion of plant samples, dry ashing procedure was applied. Flame atomic absorption spectrophotometer (FAAS) was used in the determination of analytes of interest. All the parameters in digestion and detection procedures were optimized to obtain efficient digestion and high sensitivities for analytes. Standard addition and direct calibration methods were applied to find whether there was any matrix interference to affect the determination of analytes. Mn concentration was found to be the highest for each sample analyzed. Lead concentration was found to be between 41 and 249 mg/kg in soil/sediment samples and between 2.2 and 1003 mg/kg in plant samples. The highest contamination levels for all of the analytes with the exception of Cd were found in current sediment sample.

  10. Sunspots, El Niño, and the levels of Lake Victoria, East Africa

    NASA Astrophysics Data System (ADS)

    Stager, J. Curt; Ruzmaikin, Alexander; Conway, Declan; Verburg, Piet; Mason, Peter J.

    2007-08-01

    An association of high sunspot numbers with rises in the level of Lake Victoria, East Africa, has been the focus of many investigations and vigorous debate during the last century. In this paper, we show that peaks in the ~11-year sunspot cycle were accompanied by Victoria level maxima throughout the 20th century, due to the occurrence of positive rainfall anomalies ~1 year before solar maxima. Similar patterns also occurred in at least five other East African lakes, which indicates that these sunspot-rainfall relationships were broadly regional in scale. Although irradiance fluctuations associated with the sunspot cycle are weak, their effects on tropical rainfall could be amplified through interactions with sea surface temperatures and atmospheric circulation systems, including ENSO. If this Sun-rainfall relationship persists in the future, then sunspot cycles can be used for long-term prediction of precipitation anomalies and associated outbreaks of insect-borne disease in much of East Africa. In that case, unusually wet rainy seasons and Rift Valley Fever epidemics should occur a year or so before the next solar maximum, which is expected to occur in 2011-2012 AD.

  11. Assessment of Ni, Cu, Zn and Pb levels in beach and dune sands from Havana resorts, Cuba.

    PubMed

    Díaz Rizo, Oscar; Buzón González, Fran; Arado López, Juana O

    2015-11-15

    Concentrations of nickel (Ni), copper (Cu), zinc (Zn) and lead (Pb) in beach and dune sands from thirteen Havana (Cuba) resorts were estimated by X-ray fluorescence analysis. Determined mean metal contents (in mg·kg(-1)) in beach sand samples were 28±12 for Ni, 35±12 for Cu, 31±11 for Zn and 6.0±1.8 for Pb, while for dune sands were 30±15, 38±22, 37±15 and 6.8±2.9, respectively. Metal-to-iron normalization shows moderately severe and severe enrichment by Cu. The comparison with sediment quality guidelines shows that dune sands from various resorts must be considered as heavily polluted by Cu and Ni. Almost in every resort, the Ni and Cu contents exceed their corresponding TEL values and, in some resorts, the Ni PEL value. The comparison with a Havana topsoil study indicates the possible Ni and Cu natural origin. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Correction: BTI-Tnao38, a new cell line derived from Trichoplusia ni, is permissive for AcMNPV infection and produces high levels of recombinant proteins.

    PubMed

    Hashimoto, Yoshi; Zhang, Sheng; Zhang, Shiying; Chen, Yun-Ru; Blissard, Gary W

    2012-04-24

    After publication we discovered an error in the identification of the origin of the cell line reported in our article in BMC Biotechnology (2010, 10:50), entitled "Ao38, a new cell line from eggs of the black witch moth, Ascalapha odorata (Lepidoptera: Noctuidae), is permissive for AcMNPV infection and produces high levels of recombinant proteins". Upon analysis of primary A. odorata cultures, we found that they were contaminated with cells of Trichoplusia ni origin. The origin of the Ao38 cell line was determined as T. ni using three marker genes and the Ao38 cell line was renamed BTI-Tnao38. References to the origin of the cell line as Ascalapha odorata should be replaced with "a cell line of Trichoplusia ni origin". The absence of TNCL virus detection in the BTI-Tnao38 (Ao38) cell line was confirmed using a highly sensitive RT-PCR protocol capable of detecting TNCL virus RNA at approximately 0.018 copies/cell. Because of these observations, we have revised the title of the original article to "Correction: BTI-Tnao38, a new cell line derived from Trichoplusia ni, is permissive for AcMNPV infection and produces high levels of recombinant proteins" and two additional authors were added to reflect their contributions to the analysis of this cell line.

  13. Ferromagnetic contact between Ni and MoX2 (X  =  S, Se, or Te) with Fermi-level pinning

    NASA Astrophysics Data System (ADS)

    Min, Kyung-Ah; Cha, Janghwan; Cho, Kyeongjae; Hong, Suklyun

    2017-06-01

    Recently, two-dimensional (2D) layered materials have drawn much attention due to their unique atomic and electronic properties. Among 2D layered materials, transition metal dichalcogenides (TMDs) display metallic or semiconducting properties depending on the structural phase. In particular, MoS2, which is one such TMD, has the most stable structure in the trigonal prismatic phase with a sizable band gap of about 1.8 eV. To utilize this semiconducting property and take advantage of the nature of metal-MoS2 contacts, many efforts have been made to employ MoS2 in electronic devices such as field-effect transistors. Despite various studies of metal-MoS2 contacts, however, understanding of the contact behavior between ferromagnetic metals and MoS2 is insufficient. Additionally, we need to understand the contact nature between metals and various TMDs for various applications. Here, we report on ferromagnetic contacts between Ni(1 1 1) and MoX2 (X  =  S, Se, or Te) with first-principles calculations. In particular, we study the different electronic and spin properties at Ni-MoX2 interfaces, depending on the type of chalcogen atoms. Our calculations show that the Fermi level is not simply aligned by the work function difference between Ni(1 1 1) and MoX2, representing the Fermi-level pinning occurring at metal-semiconductor interfaces, and that Schottky barrier types are varied depending on MoX2. Interestingly, spin splitting occurs at the conduction band offset or valence band offset, depending on the X type in the MoX2, and a spin magnetic moment is induced on MoX2 by Ni(1 1 1) due to the ferromagnetic nature of Ni.

  14. Coral mortality induced by the 2015-2016 El-Niño in Indonesia: the effect of rapid sea level fall

    NASA Astrophysics Data System (ADS)

    Elvan Ampou, Eghbert; Johan, Ofri; Menkes, Christophe E.; Niño, Fernando; Birol, Florence; Ouillon, Sylvain; Andréfouët, Serge

    2017-02-01

    The 2015-2016 El-Niño and related ocean warming has generated significant coral bleaching and mortality worldwide. In Indonesia, the first signs of bleaching were reported in April 2016. However, this El Niño has impacted Indonesian coral reefs since 2015 through a different process than temperature-induced bleaching. In September 2015, altimetry data show that sea level was at its lowest in the past 12 years, affecting corals living in the bathymetric range exposed to unusual emersion. In March 2016, Bunaken Island (North Sulawesi) displayed up to 85 % mortality on reef flats dominated by Porites, Heliopora and Goniastrea corals with differential mortality rates by coral genus. Almost all reef flats showed evidence of mortality, representing 30 % of Bunaken reefs. For reef flat communities which were living at a depth close to the pre-El Niño mean low sea level, the fall induced substantial mortality likely by higher daily aerial exposure, at least during low tide periods. Altimetry data were used to map sea level fall throughout Indonesia, suggesting that similar mortality could be widespread for shallow reef flat communities, which accounts for a vast percent of the total extent of coral reefs in Indonesia. The altimetry historical records also suggest that such an event was not unique in the past two decades, therefore rapid sea level fall could be more important in the dynamics and resilience of Indonesian reef flat communities than previously thought. The clear link between mortality and sea level fall also calls for a refinement of the hierarchy of El Niño impacts and their consequences on coral reefs.

  15. Metallothionein-Like Proteins and Energy Reserve Levels after Ni and Pb Exposure in the Pacific White Prawn Penaeus vannamei

    PubMed Central

    Nunez-Nogueira, Gabriel; Mouneyrac, Catherine; Muntz, Alice; Fernandez-Bringas, Laura

    2010-01-01

    This study analyzed the changes in metallothionein-like proteins (MTLPs) and Energy Reserves (ERs) in hepatopancreas and abdominal muscle of the white prawn Penaeus vannamei. Realistic metal concentration exposure for 10 days to Ni and Pb in solution revealed that juvenile prawns partially induce MTLP in hepatopancreas after Pb exposure. Ni was distributed equally between soluble and insoluble fractions, while Pb was present only in the insoluble fraction, suggesting different detoxification strategy. No changes in lipids and glycogen concentration were detected under these experimental conditions in both tissues analyzed. MTLP could not be considered as a suitable indicator for lead exposure in hepatopancreas. PMID:20862200

  16. Metallothionein-Like Proteins and Energy Reserve Levels after Ni and Pb Exposure in the Pacific White Prawn Penaeus vannamei.

    PubMed

    Nunez-Nogueira, Gabriel; Mouneyrac, Catherine; Muntz, Alice; Fernandez-Bringas, Laura

    2010-01-01

    This study analyzed the changes in metallothionein-like proteins (MTLPs) and Energy Reserves (ERs) in hepatopancreas and abdominal muscle of the white prawn Penaeus vannamei. Realistic metal concentration exposure for 10 days to Ni and Pb in solution revealed that juvenile prawns partially induce MTLP in hepatopancreas after Pb exposure. Ni was distributed equally between soluble and insoluble fractions, while Pb was present only in the insoluble fraction, suggesting different detoxification strategy. No changes in lipids and glycogen concentration were detected under these experimental conditions in both tissues analyzed. MTLP could not be considered as a suitable indicator for lead exposure in hepatopancreas.

  17. Comparative evaluation of pentraxin 3 levels in GCF during canine retraction with active tieback and NiTi coil spring: An in vivo study

    PubMed Central

    Patel, Pratik; Shanthraj, Ravi; Bhagyalakshmi, A; Garg, Nekta; Vallakati, Anisha

    2016-01-01

    Objectives: To compare the levels of pentraxin 3 (PTX-3) in gingival crevicular fluid (GCF) in patients undergoing orthodontic canine retraction with active tieback and nickel titanium (NiTi) coil spring. Materials and Methods: Fifteen patients of the age group 15–25 years with first premolar extraction undergoing canine retraction were selected. One month after placement of 0.019” × 0.025” stainless steel wire, canine retraction was started with active tieback (150 g force) on upper right quadrant and NiTi coil spring (150 g force) on upper left quadrant. GCF samples were collected 1 h before commencement of canine retraction and thereafter at intervals of 1 h, 1 day, 1 week, and 2 weeks after application of force. The collected GCF was eluted from the microcapillary pipette in 100 μl phosphate-buffered saline (pH 5–7.2). The samples were analyzed for PTX-3 levels by the ELISA technique. Results: The mean levels of PTX-3 at 1 h before canine retraction (baseline) was 1.30 ± 0.22 ng/ml and at 1 h 1.66 ± 0.33 ng/ml, 1 day 2.65 ± 0.09 ng/ml, 1 week 1.96 ± 0.15 ng/ml, and 2 weeks 1.37 ± 0.18 ng/ml in active tieback group. The mean levels of PTX-3 at 1 h before canine retraction was 1.32 ± 0.30 ng/ml, and at 1 h 1.71 ± 0.39 ng/ml, 1 day 2.78 ± 0.12 ng/ml, 1 week 2.52 ± 0.18 ng/ml, and 2 weeks 2.12 ± 0.17 ng/ml in NiTi coil spring group. A significant difference of P < 0.001 was found in PTX-3 levels in GCF during canine retraction between active tieback and NiTi coil spring at 1 day, 1 week, and 2 weeks. Conclusion: The results showed that PTX-3 levels increased from 1 h after application of orthodontic force and reached peak at 1 day, followed by a gradual decrease at 1 week and 2 weeks in both active tie back and NiTi coil spring groups. PMID:27127751

  18. Blood glucose and insulin levels, thyroid function, and serology in Ménière's disease, recurrent vestibulopathy, and psychogenic vertigo.

    PubMed

    Charles, D A; Barber, H O; Hope-Gill, H F

    1979-08-01

    Nineteen patients with unilateral Ménière's disease, 20 with psychogenic dizziness, and 20 with recurrent vestibulopathy (diagnostic criteria in text of paper) were found to have normal five hour glucose tolerance tests, serum thyroxine and effective thyroid indices, and serologic tests for syphilis. Hypothyroidism and hypoglycemia were absent in all groups. An unexplained finding of each diagnostic group was significant increase of fasting blood glucose and insulin levels, and elevated insulin:glucose ratios, compared to a control group. There appears to be no diagnostic indication for performing these chemical and serologic studies in patients with unilateral Ménière's disease, psychogenic vertigo, or recurrent vestibulopathy. Reasons are given to support the view that recurrent vestibulopathy may be a specific vestibular disturbance.

  19. Energy Level Alignment in PCDTBT:PC70BM Solar Cells: Solution Processed NiOx for Improved Hole Collection and Efficiency

    SciTech Connect

    Ratcliff, E. L.; Meyer, J.; Steirer, K. X.; Armstrong, N. R.; Olson, D.; Kahn, A.

    2012-05-01

    Solution-based NiO{sub x} outperforms PEDOT:PSS in device performance and stability when used as a hole-collection layer in bulk-heterojunction (BHJ) solar cells formed with poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) and PC70BM. The origin of the enhancement is clarified by studying the interfacial energy level alignment between PCDTBT or the 1:4 blended heterojunctions and PEDOT:PSS or NiO{sub x} using ultraviolet and inverse photoemission spectroscopies. The 1.6 eV electronic gap of PEDOT:PSS and energy level alignment with the BHJ result in poor hole selectivity of PEDOT:PSS and allows electron recombination at the PEDOT:PSS/BHJ interface. Conversely, the large band gap (3.7 eV) of NiO{sub x} and interfacial dipole (0.6 eV) with the organic active layer leads to a hole-selective interface. This interfacial dipole yields enhanced electron blocking properties by increasing the barrier to electron injection. The presence of such a strong dipole is predicted to further promote hole collection from the organic layer into the oxide, resulting in increased fill factor and short circuit current. An overall decrease in recombination is manifested in an increase in open circuit voltage and power conversion efficiency of the device on NiO{sub x} versus PEDOT:PSS interlayers.

  20. Chemical bonding and charge redistribution - Valence band and core level correlations for the Ni/Si, Pd/Si, and Pt/Si systems

    NASA Technical Reports Server (NTRS)

    Grunthaner, P. J.; Grunthaner, F. J.; Madhukar, A.

    1982-01-01

    Via a systematic study of the correlation between the core and valence level X-ray photoemission spectra, the nature of the chemical bonding and charge redistribution for bulk transition metal silicides has been examined. Particular emphasis is placed on Pt2Si and PtSi. It is observed that the strength of the metal (d)-silicon (p) interaction increases in the order Ni2Si, Pd2Si, Pt2Si. It is also observed that both the metal and silicon core lines shift to higher binding energy as the silicides are formed. The notion of charge redistribution for metallic bonds is invoked to explain these data.

  1. Chemical bonding and charge redistribution - Valence band and core level correlations for the Ni/Si, Pd/Si, and Pt/Si systems

    NASA Technical Reports Server (NTRS)

    Grunthaner, P. J.; Grunthaner, F. J.; Madhukar, A.

    1982-01-01

    Via a systematic study of the correlation between the core and valence level X-ray photoemission spectra, the nature of the chemical bonding and charge redistribution for bulk transition metal silicides has been examined. Particular emphasis is placed on Pt2Si and PtSi. It is observed that the strength of the metal (d)-silicon (p) interaction increases in the order Ni2Si, Pd2Si, Pt2Si. It is also observed that both the metal and silicon core lines shift to higher binding energy as the silicides are formed. The notion of charge redistribution for metallic bonds is invoked to explain these data.

  2. {sup 64}Cu levels from the {sup 62 }Ni({sup 3}He,p) reaction at 18 MeV

    SciTech Connect

    Basak, A.K. |; Basher, M.A.; Mondal, A.S.; Uddin, M.A.; Bhattacherjee, S.; Husain, A.; Das, S.K.; Haque, M.; Sen Gupta, H.M.

    1997-10-01

    The ({sup 3}He,p) reaction has been studied on {sup 62}Ni using a beam of 18 MeV {sup 3}He particles. Angular distributions of the outgoing protons have been measured for 65 levels including the new levels at 2.323, 3.231, 5.043, and 7.339 MeV and the analog states at 6.821 MeV (0{sup + };4) and 8.188 MeV (2{sup +};4) in the angular range {theta}{sub lab}=5{degree}{endash}80 {degree}. Data have been analyzed in terms of the distorted-wave Born approximation (DWBA). The L transfers have been obtained, J{sup {pi}} limits have been assigned, and the normalization constant has been deduced for several low-lying states. {copyright} {ital 1997} {ital The American Physical Society}

  3. [Levels of dissatisfaction of external users of the Instituto Nacional de Salud del Niño (National Institute of Child Health) in Lima, Peru].

    PubMed

    Shimabuku, Roberto; Huicho, Luis; Fernández, Danitza; Nakachi, Graciela; Maldonado, Ruth; Barrientos, Armando

    2012-01-01

    To determine the changes in the levels of dissatisfaction of the external users of the Instituto Nacional de Salud del Niño, in Lima, Peru. Observational study based on a software to evaluate surveys completed by health care users (Software de Evaluación de Encuestas de Usuarios en Salud - SEEUS). The population consisted of every person accompanying external users to outpatient visits, inpatient visits or emergency treatment in the years 2008, 2009 and 2010. To calculate the sample size, last year's proportion of users dissatisfied with each service was used, with an estimated error of 5% at a 95% confidence level. A sample of 2051 people was obtained, which revealed a decreasing trend in the levels of dissatisfaction with outpatient visits, and an increased dissatisfaction in the medical capabilities dimension for hospitalization and emergency services. In addition, a dissatisfaction index lower than 0.20 was registered in the medical capabilities dimension for outpatient visits. In contrast, the highest dissatisfaction indexes were registered in the hygiene dimension for 2009 (0.25) and 2010 (0.25), and in the others dimension for emergency services in 2009 (0.25). The dimensions showing an increase in the dissatisfaction index were tangible aspects, hygiene and others for hospitalization and emergency services. On the other hand, the medical capabilities dimension for outpatient visits showed a decrease in the level of dissatisfaction over the evaluated period.

  4. Extended calculations of level and transition properties in the nitrogen isoelectronic sequence: Cr XVIII, Fe XX, Ni XXII, and Zn XXIV

    NASA Astrophysics Data System (ADS)

    Radžiūtė, L.; Ekman, J.; Jönsson, P.; Gaigalas, G.

    2015-10-01

    Extensive multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations and relativistic configuration interaction (RCI) calculations are performed for 272 states of the 2s22p3, 2s2p4, 2p5, 2s22p23l, 2s2p33l, and 2p43l (l = 0,1,2) configurations in the nitrogen-like ions Cr XVIII, Fe XX, Ni XXII, and Zn XXIV. Valence, core-valence, and core-core electron correlation effects are accounted for through large configuration state function expansions. Calculated energy levels are compared with data from other calculations and with experimental data from the NIST database. Landé gJ-factors; hyperfine structures; isotope shifts; and radiative electric dipole (E1), electric quadrupole (E2), and magnetic dipole (M1) transition rates are given for all ions. The accuracy of the calculated energy levels is high enough to facilitate identification of observed spectral lines involving the 2l43l' configurations, for which experimental data are largely missing. Tables 5-21 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/582/A61

  5. The influence of aging on critical transformation stress levels and martensite start temperatures in NiTi. Part 2: Discussion of experimental results

    SciTech Connect

    Gall, K.; Sehitoglu, H.; Chumlyakov, Y.I.; Kireeva, I.V.; Maier, H.J.

    1999-01-01

    An experimental study was performed to determine the effect of aging on martensitic transformations in NiTi. Polycrystalline and single crystal NiTi ([100], [110], and [111] orientations) were both considered. Stress-induced transformations in single crystals of the [110] and [111] orientations. Solutionized and over-aged single crystals exhibited a strong orientation dependence of the critical stress required to trigger the transformation, {sigma}{sub cr}. The Schmid law was able to accurately predict the orientation dependence of {sigma}{sub cr} in the solutionized and over-aged single crystals. Peak-aged single crystals demonstrated a much weaker orientation dependence of {sigma}{sub cr} and in general, the Schmid law was not obeyed. By considering the local stress fields outside of the semi-coherent precipitates, the decrease in the orientation dependence of {sigma}{sub cr} was accounted for. The martensite start temperatures, M{sub s}, in aged single crystal and polycrystalline NiTi were much higher than in solutionized samples. In peak-aged NiTi the increase was primarily attributed to the local stress fields outside the coherent precipitates which create preferential nucleation sites for the martensite. In the over-aged NiTi the increase in M{sub s} was primarily attributed to the decrease in the average Ni concentration of the matrix surrounding the coarsened precipitates.

  6. Effect of magnetic ordering of Dy2BaNiO5 on the crystal-field levels of dysprosium: optical spectroscopy of f-f transitions

    NASA Astrophysics Data System (ADS)

    Galkin, A. S.; Klimin, S. A.

    2016-12-01

    Optical transmission spectroscopy study of the Haldane magnet Dy2BaNiO5 was performed in the region of f-f transitions of the Dy3+ ion in a wide range of temperatures (5-300 K). At temperatures lower than TN (59 K), Kramers doublets of the rare-earth ion split. Spectroscopic data obtained were used to calculate the Schottky-type anomaly in the temperature dependence of the magnetic susceptibility of Dy2BaNiO5 and to model the experimental data available in literature. Anomalous behavior of crystal-field energies of the Dy3+ ion was attributed to the magnetoelectric interactions.

  7. Charge-separation enhancement in inverted polymer solar cells by molecular-level triple heterojunction: NiO-np:P3HT:PCBM.

    PubMed

    Pradeep, U W; Villani, M; Calestani, D; Cristofolini, L; Iannotta, S; Zappettini, A; Coppedè, N

    2017-01-20

    Hole collection and transport are crucial physical processes in bulk-heterojunction (BHJ) solar cells, which represent major bottlenecks due to their limitations in power conversion efficiency (PCE). Hence, a more efficient alternative is needed to accept and transport holes to the collection electrode in BHJ solar cells. Here, we bring both electron and hole collection centres close to the point of exciton generation by infiltrating P3HT poly(3-hexylthiophene):PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) blend into a highly porous interconnected p-type NiO-nanoparticle (NiO-np) network, through solvent-assisted grafting. In this study, a hybrid polymer solar cell is demonstrated with a P3HT:PCBM:NiO-np triple-heterojunction active layer which showed greatly improved rectification behaviour, long electron lifetime and generated higher PCE of 4% under AM 1.5 solar illumination with a 75% increase in PCE with respect to the P3HT:PCBM device. The optimum NiO-np amount and active-layer thickness were found to be 2% and 250 nm, respectively.

  8. Charge-separation enhancement in inverted polymer solar cells by molecular-level triple heterojunction: NiO-np:P3HT:PCBM

    NASA Astrophysics Data System (ADS)

    Pradeep, U. W.; Villani, M.; Calestani, D.; Cristofolini, L.; Iannotta, S.; Zappettini, A.; Coppedè, N.

    2017-01-01

    Hole collection and transport are crucial physical processes in bulk-heterojunction (BHJ) solar cells, which represent major bottlenecks due to their limitations in power conversion efficiency (PCE). Hence, a more efficient alternative is needed to accept and transport holes to the collection electrode in BHJ solar cells. Here, we bring both electron and hole collection centres close to the point of exciton generation by infiltrating P3HT poly(3-hexylthiophene):PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) blend into a highly porous interconnected p-type NiO-nanoparticle (NiO-np) network, through solvent-assisted grafting. In this study, a hybrid polymer solar cell is demonstrated with a P3HT:PCBM:NiO-np triple-heterojunction active layer which showed greatly improved rectification behaviour, long electron lifetime and generated higher PCE of 4% under AM 1.5 solar illumination with a 75% increase in PCE with respect to the P3HT:PCBM device. The optimum NiO-np amount and active-layer thickness were found to be 2% and 250 nm, respectively.

  9. The impact of Ni on the physiology of a Mediterranean Ni-hyperaccumulating plant.

    PubMed

    Roccotiello, Enrica; Serrano, Helena Cristina; Mariotti, Mauro Giorgio; Branquinho, Cristina

    2016-06-01

    High nickel (Ni) levels exert toxic effects on plant growth and plant water content, thus affecting photosynthesis. In a pot experiment, we investigated the effect of the Ni concentration on the physiological characteristics of the Ni hyperaccumulator Alyssoides utriculata when grown on a vermiculite substrate in the presence of different external Ni concentrations (0-500 mg Ni L(-1)). The results showed that the Ni concentration was higher in leaves than in roots, as evidenced by a translocation factor = 3 and a bioconcentration factor = 10. At the highest concentration tested (500 mg Ni L(-1)), A. utriculata accumulated 1100 mg Ni per kilogram in its leaves, without an effects on its biomass. Plant water content increased significantly with Ni accumulation. Ni treatment did not, or only slightly, affected chlorophyll fluorescence parameters. The photosynthetic efficiency (FV/FM) of A. utriculata was stable between Ni treatments (always ≥ 0.8) and the photosynthetic performance of the plant under Ni stress remained high (performance index = 1.5). These findings support that A. utriculata has several mechanisms to avoid severe damage to its photosynthetic apparatus, confirming the tolerance of this species to Ni under hyperaccumulation.

  10. Structure of the near-surface layer of NiTi on the meso- and microscale levels after ion-beam surface treatment

    SciTech Connect

    Meisner, L. L. Meisner, S. N.; Poletika, T. M. Girsova, S. L.; Tverdichlebova, A. V.; Shulepov, I. A.

    2014-11-14

    Using the EBSD, SEM and TEM methods, the structure of surface layer of polycrystalline NiTi alloy samples was examined after the modification of material surface by the pulsed action of mean-energy silicon ion beam. It was found that the ion beam treatment would cause grain fragmentation of the near-surface layer to a depth 5÷50 μm; a higher extent of fragmentation was observed in grains whose close-packed planes were oriented approximately in the same direction as the ion beam was. The effect of high-intensity ion beam treatment on the anisotropic behavior of polycrystalline NiTi alloy and the mechanisms involved were also examined.

  11. Sterics level the rates of proton transfer to [Ni(XPh){PhP(CH₂CH₂PPh₂)₂}]⁺ (X = O, S or Se).

    PubMed

    Alwaaly, Ahmed; Henderson, Richard A

    2014-09-04

    Rates of proton transfers between lutH(+) (lut = 2,6-dimethylpyridine) and [Ni(XPh)(PhP{CH2CH2PPh2}2)](+) (X = O, S or Se) are slow and show little variation (k(O) : k(S) : k(Se) = 1 : 12 : 9). This unusual behaviour is a consequence of sterics affecting the optimal interaction between the reactants prior to proton transfer.

  12. The dependence of helium generation rate on nickel content of Fe-Cr-Ni alloys irradiated at high dpa levels in fast reactors

    SciTech Connect

    Garner, F.A.; Oliver, B.M.; Greenwood, L.R.

    1997-04-01

    With a few exceptions in the literature, it is generally accepted that it is nickel in Fe-Cr-Ni alloys that produces most of the transmutant helium and that the helium generation rate should scale linearly with the nickel content. Surprisingly, this assumption is based only on irradiations of pure nickel and has never been tested in an alloy series. There have also been no extensive tests of the predictions for helium production in alloys in various fast reactors spectra.

  13. The smart 2-(2-fluorobenzoyl)-N-(2-methoxyphenyl)hydrazinecarbothioamide functionalized as Ni(II) sensor in micromolar concentration level and its application in live cell imaging.

    PubMed

    Saleem, Muhammad; Ali, Anser; Choi, Chang-Shik; Park, Bong Joo; Choi, Eun Ha; Lee, Ki Hwan

    2014-07-01

    In recent years, fluorescent probes for the detection of environmentally and biologically important metal cations have received extensive attention for designing and development of fluorescent chemosensors. Herein, we report the photophysical results of 2-(2-fluorobenzoyl)-N-(2-methoxyphenyl) hydrazinecarbothioamide (4) functionalized as Ni (II) sensor in micromolar concentration level. Through fluorescence titration at 488 nm, we were confirmed that ligand 4 showed the remarkable emission by complexation between 4 and Ni (II) while it appeared no emission in case of the competitive ions (Cr(3+), Fe(2+), Co(2+), Ba(2+), Cu(2+), Ca(2+), Na(+), K(+), Cu(+), Cs(+)). Furthermore, ligand 4 exhibited no toxicity with precise cell permeability toward normal living cells using L929 cell lines in bio imaging experiment investigated through confocal fluorescence microscope. The non-toxic behavior of ligand 4 (assessed by MTT assay) and its ability to track the Ni(2+) in living cells suggest its possibility to use in biological system as nickel sensor.

  14. Leveling

    USGS Publications Warehouse

    1966-01-01

    Geodetic leveling by the U.S. Geological Survey provides a framework of accurate elevations for topographic mapping. Elevations are referred to the Sea Level Datum of 1929. Lines of leveling may be run either with automatic or with precise spirit levels, by either the center-wire or the three-wire method. For future use, the surveys are monumented with bench marks, using standard metal tablets or other marking devices. The elevations are adjusted by least squares or other suitable method and are published in lists of control.

  15. Measurements of labile Cd, Cu, Ni, Pb, and Zn levels at a northeastern Brazilian coastal area under the influence of oil production with diffusive gradients in thin films technique (DGT).

    PubMed

    de Souza, João M; Menegário, Amauri A; de Araújo Júnior, Marcus A G; Francioni, Eleine

    2014-12-01

    In this work, the ability of the diffusive gradients in thin films technique (DGT) was evaluated for monitoring the concentrations, and estimating the availability, of metals at a northeastern Brazilian coastal area under the influence of oil production. Three sites with an average distance between 0m (EM-1), 100 m (EM-2), and 1,000 m (EM-3) of a submarine outfall-I (Guamaré-RN, Brazil) and another site (GA-1) with an average distance of 12,000 m east of Outfall I, near the city of Galinhos, were studied. DGT units were deployed at the same sites in three campaigns from July, 2010 to June, 2011. Effects on the accuracy of analytical results regarding the deployment time, gel porosity, and thickness were evaluated. There was no difference between the measurements obtained with two sets of DGT devices, those assembled with open or restrictive pore gel, respectively, showing that organic metallic species are not present near the submarine outlet. After 21 day deployments in a region (near Submarine Outfall I) that receives produced waters that have been treated, there was evidence of biofilm formation on DGT membranes. However, it was demonstrated that the biofilm interference with DGT measurements was negligible. Data found in this work show that total concentrations of Cd, Cu, Pb, Ni, and Zn in seawater samples collected at sites GA-1 and EM-1 in two campaigns were below 0.33, 1.67, 0.47, 0.70, 2.86 ng mL(-1) respectively. For the first time, labile levels of Cd, Cu, Pb, Ni, and Zn in an area under the influence of oil production were determined. DGT measurements allowed the verification of the effects of temporal variation on levels of Zn and Ni. There were no effects of spatial variations on levels of Cd, Cu, Ni, Pb, and Zn at the four studied sites, suggesting no contamination of these metals at the northeastern Brazilian coastal area investigated in this work. Copyright © 2014. Published by Elsevier B.V.

  16. A study of angle-resolved photoemission extended fine structure as applied to the Ni 3p, Cu 3s, and Cu 3p core levels of the respective clean (111) surfaces

    SciTech Connect

    Huff, W.R.A.; Moler, E.J.; Kellar, S.A.

    1997-04-01

    The first non-s initial state angle-resolved photoemission extended fine structure (ARPEFS) study of clean surfaces for the purpose of further understanding the technique is reported. The surface structure sensitivity of ARPEFS applied to clean surfaces and to arbitrary initial states is studied using normal photoemission data taken from the Ni 3p core levels of a Ni(111) single crystal and the Cu 3s and the Cu 3p core-levels of a Cu(111) single crystal. The Fourier transforms of these clean surface data are dominated by backscattering. Unlike the s initial state data, the p initial state data show a peak in the Fourier transform corresponding to in-plane scattering from the six nearest-neighbors to the emitter. Evidence was seen for single-scattering events from in the same plane as the emitters and double-scattering events. Using a newly developed, multiple-scattering calculation program, ARPEFS data from clean surfaces and from p initial states can be modeled to high precision. Although there are many layers of emitters when measuring photoemission from a clean surface, test calculations show that the ARPEFS signal is dominated by photoemission from atoms in the first two crystal layers. Thus, ARPEFS applied to clean surfaces is sensitive to surface reconstruction. The known contraction of the first two Cu(111) layers is confirmed. The best-fit calculation for clean Ni(111) indicates an expansion of the first two layers. To better understand the ARPEFS technique, the authors studied s and non-s initial state photoemission from clean metal surfaces.

  17. Enhanced cycle performance of a Na/NiCl2 battery based on Ni particles encapsulated with Ni3S2 layer

    NASA Astrophysics Data System (ADS)

    Ao, Xin; Wen, Zhaoyin; Hu, Yingying; Wu, Tian; Wu, Xiangwei; He, Qiming

    2017-02-01

    Nickel particles with different contents of Ni3S2 surface layer were prepared for their application as cathode materials in Na/NiCl2 batteries. The surface modification of nickel particles is found to prevent their growth and battery degradation during cycling. The optimum level of surface modification was determined by electrochemical tests and morphology characterization. Excessive Ni3S2 layer seems to cause particle aggregation resulting in low reversible capacity. The capacity of the cell with optimum level of Ni3S2 surface modification layer after 50 cycles is about 4 times greater than that without Ni3S2 surface modification layer.

  18. Effects of Ni content on the shape memory properties and microstructure of Ni-rich NiTi-20Hf alloys

    NASA Astrophysics Data System (ADS)

    Saghaian, S. M.; Karaca, H. E.; Tobe, H.; Pons, J.; Santamarta, R.; Chumlyakov, Y. I.; Noebe, R. D.

    2016-09-01

    Shape memory properties and microstructure of four Ni-rich NiTiHf alloys (Ni50.3Ti29.7Hf20, Ni50.7Ti29.3Hf20, Ni51.2Ti28.8Hf20, and Ni52Ti28Hf20 (at.%)) were systematically characterized in the furnace cooled condition. H-phase precipitates were formed during furnace cooling in compositions with greater than 50.3Ni and the driving force for nucleation increased with Ni content. Alloy strength increased while recoverable strain decreased with increasing Ni content due to changes in precipitate characteristics. When the precipitates were small (˜5-15 nm), they were readily absorbed by martensite plates, which resulted in maximum recoverable strain of 2% in Ni50.7Ti29.3Hf20. With increasing Ni content, the size (>100 nm) and volume fraction of precipitates increased and the growth of martensite plates was constrained between the precipitates when the Ni concentration was greater than 50.7 at.%. Near perfect dimensional stability with negligible irrecoverable strain was observed at stress levels as high as 2 GPa in the Ni52Ti28Hf20 alloy, though the recoverable strain was rather small. In general, strong local stress fields were created at precipitate/matrix interphases, which lead to high stored elastic energy during the martensitic transformation.

  19. Ion irradiation induced defect evolution in Ni and Ni-based FCC equiatomic binary alloys

    SciTech Connect

    Jin, Ke; Zhang, Yanwen; Bei, Hongbin

    2016-01-01

    In order to explore the chemical effects on radiation response of alloys with multi-principal elements, defect evolution under Au ion irradiation was investigated in the elemental Ni, equiatomic NiCo and NiFe alloys. Single crystals were successfully grown in an optical floating zone furnace and their (100) surfaces were irradiated with 3 MeV Au ions at fluences ranging from 1 × 1013 to 5 × 1015 ions cm–2 at room temperature. The irradiation-induced defect evolution was analyzed by using ion channeling technique. Experiment shows that NiFe is more irradiation-resistant than NiCo and pure Ni at low fluences. With continuously increasing the ion fluences, damage level is eventually saturated for all materials but at different dose levels. The saturation level in pure Ni appears at relatively lower irradiation fluence than the alloys, suggesting that damage accumulation slows down in the alloys. Here, under high-fluence irradiations, pure Ni has wider damage ranges than the alloys, indicating that defects in pure Ni have high mobility.

  20. Ion irradiation induced defect evolution in Ni and Ni-based FCC equiatomic binary alloys

    DOE PAGES

    Jin, Ke; Zhang, Yanwen; Bei, Hongbin

    2016-01-01

    In order to explore the chemical effects on radiation response of alloys with multi-principal elements, defect evolution under Au ion irradiation was investigated in the elemental Ni, equiatomic NiCo and NiFe alloys. Single crystals were successfully grown in an optical floating zone furnace and their (100) surfaces were irradiated with 3 MeV Au ions at fluences ranging from 1 × 1013 to 5 × 1015 ions cm–2 at room temperature. The irradiation-induced defect evolution was analyzed by using ion channeling technique. Experiment shows that NiFe is more irradiation-resistant than NiCo and pure Ni at low fluences. With continuously increasing themore » ion fluences, damage level is eventually saturated for all materials but at different dose levels. The saturation level in pure Ni appears at relatively lower irradiation fluence than the alloys, suggesting that damage accumulation slows down in the alloys. Here, under high-fluence irradiations, pure Ni has wider damage ranges than the alloys, indicating that defects in pure Ni have high mobility.« less

  1. Ion irradiation induced defect evolution in Ni and Ni-based FCC equiatomic binary alloys

    NASA Astrophysics Data System (ADS)

    Jin, K.; Bei, H.; Zhang, Y.

    2016-04-01

    In order to explore the chemical effects on radiation response of alloys with multi-principal elements, defect evolution under Au ion irradiation was investigated in the elemental Ni, equiatomic NiCo and NiFe alloys. Single crystals were successfully grown in an optical floating zone furnace and their (100) surfaces were irradiated with 3 MeV Au ions at fluences ranging from 1 × 1013 to 5 × 1015 ions cm-2 at room temperature. The irradiation-induced defect evolution was analyzed by using ion channeling technique. Experiment shows that NiFe is more irradiation-resistant than NiCo and pure Ni at low fluences. With continuously increasing the ion fluences, damage level is eventually saturated for all materials but at different dose levels. The saturation level in pure Ni appears at relatively lower irradiation fluence than the alloys, suggesting that damage accumulation slows down in the alloys. Under high-fluence irradiations, pure Ni has wider damage ranges than the alloys, indicating that defects in pure Ni have high mobility.

  2. Monoligated monovalent Ni: the 3d(Ni)9 manifold of states of NiCu and comparison to the 3d9 States of AlNi, NiH, NiCl, and NiF.

    PubMed

    Rothschopf, Gretchen K; Morse, Michael D

    2005-12-22

    A dispersed fluorescence investigation of the low-lying electronic states of NiCu has allowed the observation of four out of the five states that derive from the 3d(Ni)9 3d(Cu)10 sigma2 manifold. Vibrational levels of the ground X2delta(5/2) state corresponding to v = 0-11 are observed and are fit to provide omega(e) = 275.93 +/- 1.06 cm(-1) and omega(e)x(e) = 1.44 +/- 0.11 cm(-1). The v = 0 levels of the higher lying states deriving from the 3d(Ni)9 3d(Cu)10 sigma2 manifold are located at 912, 1466, and 1734 cm(-1), and these states are assigned to omega values of 3/2, 1/2, and 3/2, respectively. The last of these assignments is based on selection rules and is unequivocal; the first two are based on a comparison to ab initio and ligand field calculations and could conceivably be in error. It is also possible that the v = 0 level of the state found at 912 cm(-1) is not observed, so that T0 for the lowest excited state actually lies near 658 cm(-1). These results are modeled using a matrix Hamiltonian based on the existence of a ground manifold of states deriving from the 3d9 configuration on nickel. This matrix Hamiltonian is also applied to the spectroscopically well-known molecules AlNi, NiH, NiCl, and NiF. The term energies of the 2sigma+, 2pi, and 2delta states of these molecules, which all derive from a 3d9 configuration on the nickel atom, display a clear and understandable trend as a function of the electronegativity of the ligands.

  3. Comparative study of the dissociation energies of Ni2 and Ni2(+)

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Langhoff, Stephen R.

    1992-01-01

    Computations at the internally contracted averaged coupled-pair-functional level of theory yield a dissociation energy (Do) for Ni2(+) that is 0.17 eV larger than that of Ni2. This finding is consistent with the collision-induced dissociation experiments of Lian, Su, and Armentrout, but rules out the results from the resonant two-photon dissociation experiments of Lessen and Brucat, which predict that the Do value of Ni2(+) is about 1 eV larger than that of Ni2.

  4. Charge ordering in Ni1+/Ni2+ nickelates: La4Ni3O8 and La3Ni2O6

    DOE PAGES

    Botana, Antia S.; Pardo, Victor; Pickett, Warren E.; ...

    2016-08-09

    Ab initio calculations allow us to establish a close connection between the Ruddlesden-Popper layered nickelates and cuprates not only in terms of filling of d levels (close to d9) but also because they show Ni1+(S = 1/2)/Ni2+(S = 0) stripe ordering. We obtained the insulating charge-ordered ground state from a combination of structural distortions and magnetic order. The Ni2+ ions are in a low-spin configuration (S = 0) yielding an antiferromagnetic arrangement of Ni1+ S = 1/2 ions like the long-sought spin-1/2 antiferromagnetic insulator analog of the cuprate parent materials. Furthermore, the analogy extends further with the main contribution to the bands near the Fermi energy coming from hybridized Ni dmore » $$_x$$2-$$_y$$2 and O $p$ states.« less

  5. The effect of two types of El Niño on the southerly low-level jets in North America

    Treesearch

    Lejiang Yu; Shiyuan Zhong; Warren E. Heilman; Xindi Bian

    2016-01-01

    Low-level jets (LLJs) are frequent weather phenomena in many regions of North America and have profound impacts on precipitation and wind energy. We used a 31 year (1979-2010) three-hourly reanalysis data set to examine the teleconnection between southerly LLJ activity in North America and the two dominant patterns of the equatorial Pacific Ocean sea surface...

  6. Impact of the silicon substrate resistivity and growth condition on the deep levels in Ni-Au/AlN/Si MIS Capacitors

    NASA Astrophysics Data System (ADS)

    Wang, Chong; Simoen, Eddy; Zhao, Ming; Li, Wei

    2017-10-01

    Deep levels formed under different growth conditions of a 200 nm AlN buffer layer on B-doped Czochralski Si(111) substrates with different resistivity were investigated by deep-level transient spectroscopy (DLTS) on metal-insulator-semiconductor capacitors. Growth-temperature-dependent Al diffusion in the Si substrate was derived from the free carrier density obtained by capacitance-voltage measurement on samples grown on p- substrates. The DLTS spectra revealed a high concentration of point and extended defects in the p- and p+ silicon substrates, respectively. This indicated a difference in the electrically active defects in the silicon substrate close to the AlN/Si interface, depending on the B doping concentration.

  7. Results of a multi-level intervention to prevent and control childhood obesity among Latino children: the Aventuras Para Niños Study.

    PubMed

    Crespo, Noe C; Elder, John P; Ayala, Guadalupe X; Slymen, Donald J; Campbell, Nadia R; Sallis, James F; McKenzie, Thomas L; Baquero, Barbara; Arredondo, Elva M

    2012-02-01

    Community-based interventions are needed to reduce the burden of childhood obesity. To evaluate the impact of a multi-level promotora-based (Community Health Advisor) intervention to promote healthy eating and physical activity and prevent excess weight gain among Latino children. Thirteen elementary schools were randomized to one of four intervention conditions: individual/family level (Family-only), school/community level (Community-only), combined (Family + Community), or a measurement-only condition. Participants were 808 Latino parents and their children enrolled in kindergarten through 2(nd) grade. Measures included parent and child body mass index (BMI) and a self-administered parent survey that assessed several parent and child behaviors. There were no significant intervention effects on children's BMI z-score. The family intervention changed several obesity-related child behaviors (e.g., fruit/vegetable consumption) and these were mediated by changes in parenting variables (e.g., parent monitoring). A promotora-based behavioral intervention was efficacious at changing parental factors and child obesity-related health behaviors.

  8. Results of a Multi-level Intervention to Prevent and Control Childhood Obesity among Latino Children: The Aventuras Para Niños Study

    PubMed Central

    Crespo, Noe C.; Elder, John P.; Ayala, Guadalupe X.; Campbell, Nadia R.; Arredondo, Elva M.; Slymen, Donald J.; Baquero, Barbara; Sallis, James F.; McKenzie, Thomas L.

    2014-01-01

    Background Community-based behavioral interventions are needed to reduce the burden of childhood obesity. Purpose This study evaluated the impact of a multi-level promotora-based (Community Health Advisor) intervention to promote healthy eating and physical activity (PA) and prevent excess weight gain among Latino children. Methods Thirteen elementary schools were randomized to one of four intervention conditions: individual and family level (Fam-only), school and community level (Comm-only), combined Fam+Comm intervention, or a measurement-only condition. Participants were 808 Latino parents and their children enrolled in kindergarten through 2nd grade. Measures included parent and child BMI and a self-administered parent survey that assessed several parent and child behaviors. Results There were no intervention effects on children's BMI z-score. The Fam-only and Fam+Comm interventions changed several obesity-related child behaviors and these were mediated by changes in parenting variables. Discussion A promotora-based behavioral intervention was efficacious at changing parental factors and child obesity-related health behaviors. PMID:22215470

  9. Contribution of continental water to sea level variations during the 1997-1998 El Niño-Southern Oscillation event: Comparison between Atmospheric Model Intercomparison Project simulations and TOPEX/Poseidon satellite data

    NASA Astrophysics Data System (ADS)

    Ngo-Duc, T.; Laval, K.; Polcher, J.; Cazenave, A.

    2005-05-01

    Satellite altimetry from TOPEX/Poseidon (T/P) is used to estimate the variation of the global sea level. This signal, once corrected for steric effects, reflects water mass exchange with the atmosphere and land reservoirs (mainly ice caps, soils and snowpack). It can thus be used to test the capacity of general circulations models (GCMs) to estimate change in land water storage. In this study, we compare the land hydrology contribution to global mean sea level variations during the major 1997-1998 El Niño-Southern Oscillation event from two data sets: (1) the results of the Organizing Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE) land surface scheme, developed at the Institute Pierre Simon Laplace, coupled to the Laboratoire de Météorologie Dynamique Atmospheric General Circulation Model (LMD AGCM) and (2) the T/P-based estimates. We show that the seasonal variation of the continental water storage is well represented in the model. The drastic amplitude change between the two contrasted years, 1997 and 1998, observed from satellite altimetry, is also simulated. We analyze the role of each component of simulated water fluxes (precipitation, evaporation, and runoff) in determining the range of annual continental water mass variation and its interannual variability. The difference between the two years, 1997 and 1998, is, for an essential part, due to land precipitation in the 20°N-20°S domain. This analysis emphasizes the important role of tropical regions in interannual variability of climate.

  10. Nuclear Magnetic Resonance Reveals Disordered Level-Crossing Physics in the Bose-Glass Regime of the Br-Doped Ni (Cl1 -xBrx )2-4 SC (NH2 )2 Compound at a High Magnetic Field

    NASA Astrophysics Data System (ADS)

    Orlova, Anna; Blinder, Rémi; Kermarrec, Edwin; Dupont, Maxime; Laflorencie, Nicolas; Capponi, Sylvain; Mayaffre, Hadrien; Berthier, Claude; Paduan-Filho, Armando; Horvatić, Mladen

    2017-02-01

    By measuring the nuclear magnetic resonance (NMR) T1-1 relaxation rate in the Br (bond) doped DTN compound, Ni (Cl1 -xBrx )2-4 SC (NH2 )2(DTN X ) , we show that the low-energy spin dynamics of its high magnetic field "Bose-glass" regime is dominated by a strong peak of spin fluctuations found at the nearly doping-independent position H*≅13.6 T . From its temperature and field dependence, we conclude that this corresponds to a level crossing of the energy levels related to the doping-induced impurity states. Observation of the local NMR signal from the spin adjacent to the doped Br allowed us to fully characterize this impurity state. We have thus quantified a microscopic theoretical model that paves the way to better understanding of the Bose-glass physics in DTN X , as revealed in the related theoretical study [M. Dupont, S. Capponi, and N. Laflorencie, Phys. Rev. Lett. 118, 067204 (2017)., 10.1103/PhysRevLett.118.067204].

  11. In situ NiTi/Nb(Ti) composite

    SciTech Connect

    Jiang, Daqiang Cui, Lishan; Jiang, Jiang; Zheng, Yanjun

    2013-12-15

    Graphical abstract: - Highlights: • In situ NiTi/Nb(Ti) composites were fabricated. • The transformation temperature was affected by the mixing Ti:Ni atomic ratios. • The NiTi component became micron-scale lamella after forging and rolling. • The composite exhibited high strength and high damping capacity. - Abstract: This paper reports on the creation of a series of in situ NiTi/Nb(Ti) composites with controllable transformation temperatures based on the pseudo-binary hypereutectic transformation of NiTi–Nb system. The composite constituent morphology was controlled by forging and rolling. It is found that the thickness of the NiTi lamella in the composite reached micron level after the hot-forging and cold-rolling. The NiTi/Nb(Ti) composite exhibited high damping capacity as well as high yield strength.

  12. Water dissociation on Ni(100), Ni(110), and Ni(111) surfaces: Reaction path approach to mode selectivity

    DOE PAGES

    Seenivasan, H.; Jackson, Bret; Tiwari, Ashwani K.

    2017-02-17

    We performed a comparative study of mode-selectivity of water dissociation on Ni(100), Ni(110), and Ni(111) surfaces at the same level of theory using a fully quantum approach based on the reaction path Hamiltonian. Calculations show that the barrier to water dissociation on the Ni(110) surface is significantly lower compared to its close-packed counterparts. Transition states for this reaction on all three surfaces involve the elongation of one of the O–H bonds. Furthermore, a significant decrease in the symmetric stretching and bending mode frequencies near the transition state is observed in all three cases and in the vibrational adiabatic approximation, excitationmore » of these softened modes results in a significant enhancement in reactivity. Inclusion of non-adiabatic couplings between modes results in the asymmetric stretching mode showing a similar enhancement of reactivity as the symmetric stretching mode. Dissociation probabilities calculated at a surface temperature of 300 K showed higher reactivity at lower collision energies compared to that of the static surface case, underlining the importance of lattice motion in enhancing reactivity. Mode selective behavior is similar on all the surfaces. Molecules with one-quantum of vibrational excitation in the symmetric stretch, at lower energies (up to 0.45 eV), are more reactive on Ni(110) than the Ni(100) and Ni(111) surfaces. But, the dissociation probabilities approach saturation on all the surfaces at higher incident energy values. Ultimately, Ni(110) is found to be highly reactive toward water dissociation among the low-index nickel surfaces owing to a low reaction barrier resulting from the openness and corrugation of the surface. These results show that the mode-selective behavior does not vary with different crystal facets of Ni qualitatively, but there is a significant quantitative effect.« less

  13. Water dissociation on Ni(100), Ni(110), and Ni(111) surfaces: Reaction path approach to mode selectivity

    NASA Astrophysics Data System (ADS)

    Seenivasan, H.; Jackson, Bret; Tiwari, Ashwani K.

    2017-02-01

    A comparative study of mode-selectivity of water dissociation on Ni(100), Ni(110), and Ni(111) surfaces is performed at the same level of theory using a fully quantum approach based on the reaction path Hamiltonian. Calculations show that the barrier to water dissociation on the Ni(110) surface is significantly lower compared to its close-packed counterparts. Transition states for this reaction on all three surfaces involve the elongation of one of the O-H bonds. A significant decrease in the symmetric stretching and bending mode frequencies near the transition state is observed in all three cases and in the vibrational adiabatic approximation, excitation of these softened modes results in a significant enhancement in reactivity. Inclusion of non-adiabatic couplings between modes results in the asymmetric stretching mode showing a similar enhancement of reactivity as the symmetric stretching mode. Dissociation probabilities calculated at a surface temperature of 300 K showed higher reactivity at lower collision energies compared to that of the static surface case, underlining the importance of lattice motion in enhancing reactivity. Mode selective behavior is similar on all the surfaces. Molecules with one-quantum of vibrational excitation in the symmetric stretch, at lower energies (up to ˜0.45 eV), are more reactive on Ni(110) than the Ni(100) and Ni(111) surfaces. However, the dissociation probabilities approach saturation on all the surfaces at higher incident energy values. Overall, Ni(110) is found to be highly reactive toward water dissociation among the low-index nickel surfaces owing to a low reaction barrier resulting from the openness and corrugation of the surface. These results show that the mode-selective behavior does not vary with different crystal facets of Ni qualitatively, but there is a significant quantitative effect.

  14. Effects of a Multi-Pronged Intervention on Children’s Activity Levels at Recess: The Aventuras para Niños Study12

    PubMed Central

    Elder, John P.; McKenzie, Thomas L.; Arredondo, Elva M.; Crespo, Noe C.; Ayala, Guadalupe X.

    2011-01-01

    Latino children spend more time in sedentary activities than other American children, and only ~1 in 5 Latino children in public elementary and middle schools meet all 6 fitness standards in statewide fitness testing. Schools that facilitate physical activity (PA) by maintaining playgrounds and providing physical education classes have children who are more active and less overweight. The aims of the present study were to examine the extent to which several social and physical environmental changes in school settings resulted in observed changes in area characteristics and children’s activity levels during recess. Thirteen elementary schools serving predominately Mexican American children were randomized into control or activity and nutrition environmental intervention conditions. Playgrounds and activities were restructured in 6 intervention schools to promote more PA. After 1 y, there were no overall statistical differences between treatment groups in PA or sedentary behavior in these settings and results did not differ by gender. Changing the social and physical environments to promote children’s moderate-to-vigorous PA is important to the design of active and healthy recess environments. The present results are not conclusive as to the link between these interventions and actual behavior, but show sufficient promise for further population and setting specific research. PMID:22332049

  15. Spectroscopic investigation of Ni speciation in hardened cement paste.

    PubMed

    Vespa, M; Dähn, R; Grolimund, D; Wieland, E; Scheidegger, A M

    2006-04-01

    Cement-based materials play an important role in multi-barrier concepts developed worldwide for the safe disposal of hazardous and radioactive wastes. Cement is used to condition and stabilize the waste materials and to construct the engineered barrier systems (container, backfill, and liner materials) of repositories for radioactive waste. In this study, Ni uptake by hardened cement paste has been investigated with the aim of improving our understanding of the immobilization process of heavy metals in cement on the molecular level. X-ray absorption spectroscopy (XAS) coupled with diffuse reflectance spectroscopy (DRS) techniques were used to determine the local environment of Ni in cement systems. The Ni-doped samples were prepared at two different water/cement ratios (0.4, 1.3) and different hydration times (1 hour to 1 year) using a sulfate-resisting Portland cement. The metal loadings and the metal salts added to the system were varied (50 up to 5000 mg/kg; NO3(-), SO4(2-), Cl-). The XAS study showed that for all investigated systems Ni(ll) is predominantly immobilized in a layered double hydroxide (LDH) phase, which was corroborated by DRS measurements. Only a minor extent of Ni(ll) precipitates as Ni-hydroxides (alpha-Ni(OH)2 and beta-Ni(OH)2). This finding suggests that Ni-Al LDH, rather than Ni-hydroxides, is the solubility-limiting phase in the Ni-doped cement system.

  16. Overall Photocatalytic Water Splitting with NiOx-SrTiO3 – A Revised Mechanism

    SciTech Connect

    Townsend, Troy K.; Browning, Nigel D.; Osterloh, Frank

    2012-11-01

    NiOx (0 < x < 1) modified SrTiO3 (STO) is one of the best studied photocatalyst for overall water splitting under UV light. The established mechanism for this and many other NiOx containing catalysts assumes water oxidation to occur at the early transition metal oxide and water reduction at NiOx. Here we show that NiOx-STO is more likely a three component Ni-STO-NiO catalyst, in which STO absorbs the light, Ni reduces protons, and NiO oxidizes water. This interpretation is based on systematic H2/O2 evolution tests of appropriately varied catalyst compositions using oxidized, chemically and photochemically added nickel and NiO nanoparticle cocatalysts. Surface photovoltage (SPV) measurements reveal that Ni(0) serves as an electron trap (site for water reduction) and that NiO serves as a hole trap (site for water oxidation). Electrochemical measurements show that the overpotential for water oxidation correlates with NiO content, whereas the water reduction overpotential depends on Ni content. Photodeposition experiments with NiCl2 and H2PtCl6 on NiO-STO show that electrons are available on the STO surface, not on the NiO particles. Based on photoelectrochemistry, both NiO and Ni particles suppress the Fermi level in STO, but the effect of this shift on catalytic activity is not clear. Overall, the results suggest a revised role for NiO in NiOx-STO and in many other nickel-containing water splitting systems, including NiOx-La:KTaO3, and many layered perovskites.

  17. Granger causality from changes in level of atmospheric CO2 to global surface temperature and the El Niño-Southern Oscillation, and a candidate mechanism in global photosynthesis

    NASA Astrophysics Data System (ADS)

    Leggett, L. M. W.; Ball, D. A.

    2015-10-01

    A significant difference, now of some 16 years' duration, has been shown to exist between the observed global surface temperature trend and that expected from the majority of climate simulations. For its own sake, and to enable better climate prediction for policy use, the reasons behind this mismatch need to be better understood. While an increasing number of possible causes have been proposed, the candidate causes have not yet converged. With this background, this paper reinvestigates the relationship between change in the level of CO2 and two of the major climate variables, atmospheric temperature and the El Niño-Southern Oscillation (ENSO). Using time-series analysis in the form of dynamic regression modelling with autocorrelation correction, it is shown that first-difference CO2 leads temperature and that there is a highly statistically significant correlation between first-difference CO2 and temperature. Further, a correlation is found for second-difference CO2 with the Southern Oscillation Index, the atmospheric-pressure component of ENSO. This paper also shows that both these correlations display Granger causality. It is shown that the first-difference CO2 and temperature model shows no trend mismatch in recent years. These results may contribute to the prediction of future trends for global temperature and ENSO. Interannual variability in the growth rate of atmospheric CO2 is standardly attributed to variability in the carbon sink capacity of the terrestrial biosphere. The terrestrial biosphere carbon sink is created by the difference between photosynthesis and respiration (net primary productivity): a major way of measuring global terrestrial photosynthesis is by means of satellite measurements of vegetation reflectance, such as the Normalized Difference Vegetation Index (NDVI). In a preliminary analysis, this study finds a close correlation between an increasing NDVI and the increasing climate model/temperature mismatch (as quantified by the difference

  18. The first principle study of Ni2ScGa and Ni2TiGa

    NASA Astrophysics Data System (ADS)

    Özduran, Mustafa; Turgut, Kemal; Arikan, Nihat; Iyigör, Ahmet; Candan, Abdullah

    2014-10-01

    We computed the electronic structure, elastic moduli, vibrational properties, and Ni2TiGa and Ni2ScGa alloys in the cubic L21 structure. The obtained equilibrium lattice constants of these alloys are in good agreement with available data. In cubic systems, there are three independent elastic constants, namely C11, C12 and C44. We calculated elastic constants in L21 structure for Ni2TiGa and Ni2ScGa using the energy-strain method. The electronic band structure, total and partial density of states for these alloys were investigated within density functional theory using the plane-wave pseudopotential method implemented in Quantum-Espresso program package. From band structure, total and projected density of states, we observed metallic characters of these compounds. The electronic calculation indicate that the predominant contributions of the density of states at Fermi level come from the Ni 3d states and Sc 3d states for Ni2TiGa, Ni 3d states and Sc 3d states for Ni2ScGa. The computed density of states at Fermi energy are 2.22 states/eV Cell for Ni2TiGa, 0.76 states/eV Cell for Ni2ScGa. The vibrational properties were obtained using a linear response in the framework at the density functional perturbation theory. For the alloys, the results show that the L21 phase is unstable since the phonon calculations have imagine modes.

  19. Effects of Cycling Conditions of Active Material From Discharged Ni Positive Plates Studied by Inelastic Neutron Scattering Spectroscopy

    NASA Technical Reports Server (NTRS)

    Eckert, Juergen; Varma, Ravi; Diebolt, Lisa; Reid, Margaret

    1998-01-01

    The objectives of this presentation are: identify atomic-level signatures of electrochemical activity of the active material on the Ni positive plates of Ni-H2 batteries, relate finding to cycling conditions and histories, and develop INS spectroscopy as a non-destructive testing technique for the evaluation of Ni-positive plates of Ni-H2 batteries.

  20. Magnetic properties of Ni and Cu-Ni nanoparticles

    NASA Astrophysics Data System (ADS)

    Ganga, B. G.; Santhosh, P. N.; Thomas, P. John

    2012-06-01

    Ni and Cu-Ni nanoparticles were prepared by solution phase method and crystal phase was identified by XRD. SEM and EDX were used to analyze morphology and elemental composition of nanoparticles. Magnetic measurements indicate that Ni nanoparticles are superparamagnetic at room temperature and blocking temperature is around 103 K. Ferromagnetism is observed in the case of Cu-Ni nanoparticles with decrease in magnetization compared to Ni nanoparticles.

  1. Measurement of {sup 63}Ni and {sup 59}Ni by accelerator mass spectrometry using characteristic projectile x-rays

    SciTech Connect

    McAninch, J.E.; Hainsworth, L.J.; Marchetti, A.A.

    1996-05-01

    The long-lived isotopes of nickel ({sup 59}Ni, {sup 63}Ni) have current and potential use in a number of applications including cosmic radiation studies, biomedical tracing, characterization of low-level radioactive wastes, and neutron dosimetry. Methods are being developed at LLNL for the routine detection of these isotopes by AMS. One intended application is in Hiroshima dosimetry. The reaction {sup 63}Cu(n,p){sup 63}Ni has been identified as one of a small number of reactions which might be used for the direct determination of the fast neutron fluence emitted by the Hiroshima bomb. AMS measurement of {sup 63}Ni(t{sub 1/2} = 100 y) requires the chemical removal of {sup 63}Cu, which is a stable isobar of {sup 63}Ni. Following the electrochemical separation of Ni from gram-sized copper samples, the Cu concentration is further lowered to < 2 x 10{sup -8} (Cu/Ni) using the reaction of Ni with carbon monoxide to form the gas Ni(CO){sub 4}. The Ni(CO){sub 4} is thermally decomposed directly in sample holders for measurement by AMS. After analysis in the AMS spectrometer, the ions are identified using characteristic projectile x-rays, allowing further rejection of remaining {sup 63}Cu. In a demonstration experiment, {sup 63}Ni was measured in Cu wires (2-20 g) which had been exposed to neutrons from a {sup 252}Cf source. We successfully measured {sup 63}Ni at levels necessary for the measurement of Cu samples exposed near the Hiroshima hypocenter. For the demonstration samples, the Cu content was chemically reduced by a factor of 10{sup 12} with quantitative retention of {sup 63}Ni. Detection sensitivity (3{sigma}) was {approximately}20 fg {sup 63}Ni in 1 mg Ni carrier ({sup 63}Ni/Ni {approx} 2 x 10{sup -11}). Significant improvements in sensitivity are expected with planned incremental changes in the methods. Preliminary results indicate that a similar sensitivity is achievable for {sup 59}Ni (t{sub 1/2} = 10{sup 5} y).

  2. A theoretical study of CH x chemisorption on the Ni(100) and Ni(111) surfaces

    NASA Astrophysics Data System (ADS)

    Siegbahn, Per E. M.; Panas, Itai

    1990-12-01

    Cluster model calculations have been performed for CH x, x = 0-3, chemisorbed on Ni(100) and Ni(111). The predicted chemisorption energies, at the present level of theory, based on bond-prepared clusters for Ni(100) are for carbon 150 kcal/mol, for CH 136 kcal/mol, for CH 2 91 kcal/mol and for CH 3 46 kcal/mol. The corresponding energies for Ni(111) are for CH 120 kcal/mol, for CH 2 88 cal/mol and for CH 3 49 kcal/mol. These chemisorption energies lead to similar stabilities for all CH x fragments on both Ni(100) and Ni(111). Large basis sets and multi-reference correlation treatments are found to be very important in particular for the multiply bonded species. The vibrational C-H stretching frequencies predicted for CH x on Ni(111) are for CH 3054 cm -1 (2980 cm -1), for CH 2 3204 cm -1 and for CH 3 2709 cm -1 (2680 cm -1), where the available experimental values are given in parent The predicted ionization spectra of adsorbed CH x are also in general agreement with experimental findings.

  3. Radiation damage buildup and dislocation evolution in Ni and equiatomic multicomponent Ni-based alloys

    NASA Astrophysics Data System (ADS)

    Levo, E.; Granberg, F.; Fridlund, C.; Nordlund, K.; Djurabekova, F.

    2017-07-01

    Single-phase multicomponent alloys of equal atomic concentrations (;equiatomic;) have proven to exhibit promising mechanical and corrosion resistance properties, that are sought after in materials intended for use in hazardous environments like next-generation nuclear reactors. In this article, we investigate the damage production and dislocation mobility by simulating irradiation of elemental Ni and the alloys NiCo, NiCoCr, NiCoFe and NiFe, to assess the effect of elemental composition. We compare the defect production and the evolution of dislocation networks in the simulation cells of two different sizes, for all five studied materials. We find that the trends in defect evolution are in good agreement between the different cell sizes. The damage is generally reduced with increased alloy complexity, and the dislocation evolution is specific to each material, depending on its complexity. We show that increasing complexity of the alloys does not always lead to decreased susceptibility to damage accumulation under irradiation. We show that, for instance, the NiCo alloy behaves very similarly to Ni, while presence of Fe or Cr in the alloy even as a third component reduces the saturated level of damage substantially. Moreover, we linked the defect evolution with the dislocation transformations in the alloys. Sudden drops in defect number and large defect fluctuations from the continuous irradiation can be explained from the dislocation activity.

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

    NASA Astrophysics Data System (ADS)

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

    1996-06-01

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

  5. NiW and NiRu Bimetallic Catalysts for Ethylene Steam Reforming: Alternative Mechanisms for Sulfur Resistance

    SciTech Connect

    Rangan, M.; Yung, M. M.; Medlin, J. W.

    2012-06-01

    Previous investigations of Ni-based catalysts for the steam reforming of hydrocarbons have indicated that the addition of a second metal can reduce the effects of sulfur poisoning. Two systems that have previously shown promise for such applications, NiW and NiRu, are considered here for the steam reforming of ethylene, a key component of biomass derived tars. Monometallic and bimetallic Al{sub 2}O{sub 3}-supported Ni and W catalysts were employed for ethylene steam reforming in the presence and absence of sulfur. The NiW catalysts were less active than Ni in the absence of sulfur, but were more active in the presence of 50 ppm H{sub 2}S. The mechanism for the W-induced improvements in sulfur resistance appears to be different from that for Ru in NiRu. To probe reasons for the sulfur resistance of NiRu, the adsorption of S and C{sub 2}H{sub 4} on several bimetallic NiRu alloy surfaces ranging from 11 to 33 % Ru was studied using density functional theory (DFT). The DFT studies reveal that sulfur adsorption is generally favored on hollow sites containing Ru. Ethylene preferentially adsorbs atop the Ru atom in all the NiRu (111) alloys investigated. By comparing trends across the various bimetallic models considered, sulfur adsorption was observed to be correlated with the density of occupied states near the Fermi level while C{sub 2}H{sub 4} adsorption was correlated with the number of unoccupied states in the d-band. The diverging mechanisms for S and C{sub 2}H{sub 4} adsorption allow for bimetallic surfaces such as NiRu that enhance ethylene binding without accompanying increases in sulfur binding energy. In contrast, bimetallics such as NiSn and NiW appear to decrease the affinity of the surface for both the reagent and the poison.

  6. Surface Modification of NiTi Alloy via Cathodic Plasma Electrolytic Deposition and its Effect on Ni Ion Release and Osteoblast Behaviors

    NASA Astrophysics Data System (ADS)

    Yan, Ying; Cai, Kaiyong; Yang, Weihu; Liu, Peng

    2013-07-01

    To reduce Ni ion release and improve biocompatibility of NiTi alloy, the cathodic plasma electrolytic deposition (CPED) technique was used to fabricate ceramic coating onto a NiTi alloy surface. The formation of a coating with a rough and micro-textured surface was confirmed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, respectively. An inductively coupled plasma mass spectrometry test showed that the formed coating significantly reduced the release of Ni ions from the NiTi alloy in simulated body fluid. The influence of CPED treated NiTi substrates on the biological behaviors of osteoblasts, including cell adhesion, cell viability, and osteogenic differentiation function (alkaline phosphatase), was investigated in vitro. Immunofluorescence staining of nuclei revealed that the CPED treated NiTi alloy was favorable for cell growth. Osteoblasts on CPED modified NiTi alloy showed greater cell viability than those for the native NiTi substrate after 4 and 7 days cultures. More importantly, osteoblasts cultured onto a modified NiTi sample displayed significantly higher differentiation levels of alkaline phosphatase. The results suggested that surface functionalization of NiTi alloy with ceramic coating via the CPED technique was beneficial for cell proliferation and differentiation. The approach presented here is useful for NiTi implants to enhance bone osseointegration and reduce Ni ion release in vitro.

  7. Resistance to sulfur poisoning of Ni-based alloy with coinage (IB) metals

    NASA Astrophysics Data System (ADS)

    Xu, Xiaopei; Zhang, Yanxing; Yang, Zongxian

    2015-12-01

    The poisoning effects of S atom on the (1 0 0), (1 1 0) and (1 1 1) metal surfaces of pure Ni and Ni-based alloy with IB (coinage) metals (Cu, Ag, Au) are systematically studied. The effects of IB metal dopants on the S poisoning features are analyzed combining the density functional theory (DFT) results with thermodynamics data using the ab initio atomistic thermodynamic method. It is found that introducing IB doping metals into Ni surface can shift the d-band center downward from the Fermi level and weaken the adsorption of S on the (1 0 0) and (1 1 0) surfaces, and the S tolerance ability increases in the order of Ni, Cu/Ni, Ag/Ni and Au/Ni. Nevertheless, on the (1 1 1) surface, the S tolerance ability increases in the order of Ag/Ni (or Cu/Ni), Ni, and Au/Ni. When we increase the coverage of the IB metal dopants, we found that not only Au, but Cu and Ag can increase its S tolerance. We therefore propose that alloying can increase its S tolerance and alloying with Au would be a better way to increase the resistance to sulfur poisoning of the Ni anode as compared with the pure Ni and the Ag- or, Cu-doped Ni materials.

  8. Oxygen vacancies and ordering of d-levels control voltage suppression in oxide cathodes: the case of spinel LiNi0.5Mn1.5O4-δ

    SciTech Connect

    Sushko, Petr V.; Rosso, Kevin M.; Zhang, Jiguang; Liu, Jun; Sushko, Maria L.

    2013-06-19

    Spinel Li-Mn rich oxides form one of the most promising classes of high voltage cathode materials for next generation Li-ion batteries for electric vehicle applications. Our simulations for spinel LiNi0.5Mn1.5O4 (LNMO) show that neutral oxygen vacancies promote formation of Ni-rich regions, which are negatively charged with respect to the lattice. This makes the electrons associated with these vacancies to localize on Mn3+ eg states of two types: shallow states in the Ni-rich regions and deep states in the Ni-poor regions. The positive electrostatic potential produced by the oxygen vacancies and the existence of the shallow and deep Mn3+ states result in appearance of the low-voltage region at high Li content and high-voltage region at low Li content. This is consistent with characteristic changes in the voltage capacity curves observed experimentally during electrochemical cycling. We propose that doping LNMO with judiciously selected cations can help to remedy voltage suppression effects. This approach may also be used to enhance the electrochemical stability of Li-Mn rich oxides, which tend to experience continuous voltage fade.

  9. Electronic, magnetic and Fermi properties investigates on quaternary Heusler NiCoCrAl, NiCoCrGa and NiFeCrGa

    NASA Astrophysics Data System (ADS)

    Wei, Xiao-Ping; Zhang, Ya-Ling; Chu, Yan-Dong; Sun, Xiao-Wei; Sun, Ting; Guo, Peng; Deng, Jian-Bo

    2015-07-01

    Using the full-potential local-orbital minimum-basis method within the framework of density functional theory, we study the electronic, magnetic and Fermi properties of three quaternary Heusler compounds: NiCoCrAl, NiCoCrGa and NiFeCrGa. Results identify that these compounds are half-metallic ferromagnets with integer spin magnetic moment, and their spin moments follow the Slater-Pauling rule. Accordingly, the origin of gap and magnetic moment are also discussed. In addition, the Fermi surface is further plotted to explore the behavior of electronic states in the vicinity of Fermi level for these compounds. Finally, we argue the influence of tetragonal deformation on electronic and magnetic properties. Meanwhile, the possible L21 disorder is also discussed for NiCoCrAl and NiCoCrGa.

  10. Thermal expansion behavior of NiSi/NiSi2

    NASA Technical Reports Server (NTRS)

    Wilson, D. F.; Cavin, O. B.

    1992-01-01

    The thermal expansion of NiSi/NiSi2 for a range of temperatures from 293 to 1223 K was determined using high-temperature X-ray diffraction. While a linear relation with temperature was found for the lattice parameter of NiSi2, third-order relationships were found for the three lattice parameters of NiSi, with one of the parameters showing a decrease with increasing temperature. The volumetric expansion of both materials exhibited linear relationships.

  11. Low-lying excitations in 72Ni

    NASA Astrophysics Data System (ADS)

    Morales, A. I.; Benzoni, G.; Watanabe, H.; Nishimura, S.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y.; Lorusso, G.; Patel, Z.; Rice, S.; Sinclair, L.; Söderström, P.-A.; Sumikama, T.; Wu, J.; Xu, Z. Y.; Yagi, A.; Yokoyama, R.; Baba, H.; Avigo, R.; Bello Garrote, F. L.; Blasi, N.; Bracco, A.; Camera, F.; Ceruti, S.; Crespi, F. C. L.; de Angelis, G.; Delattre, M.-C.; Dombradi, Zs.; Gottardo, A.; Isobe, T.; Kojouharov, I.; Kurz, N.; Kuti, I.; Matsui, K.; Melon, B.; Mengoni, D.; Miyazaki, T.; Modamio-Hoyborg, V.; Momiyama, S.; Napoli, D. R.; Niikura, M.; Orlandi, R.; Sakurai, H.; Sahin, E.; Sohler, D.; Shaffner, H.; Taniuchi, R.; Taprogge, J.; Vajta, Zs.; Valiente-Dobón, J. J.; Wieland, O.; Yalcinkaya, M.

    2016-03-01

    Low-lying excited states in 72Ni have been investigated in an in-flight fission experiment at the RIBF facility of the RIKEN Nishina Center. The combination of the state-of-the-art BigRIPS and EURICA setups has allowed for a very accurate study of the β decay from 72Co to 72Ni, and has provided first experimental information on the decay sequence 72Fe→72Co→72Ni and on the delayed neutron-emission branch 73Co→72Ni . Accordingly, we report nearly 60 previously unobserved γ transitions which deexcite 21 new levels in 72Ni. Evidence for the location of the so-sought-after (42+) ,(62+) , and (81+) seniority states is provided. As well, the existence of a low-spin β -decaying isomer in odd-odd neutron-rich Co isotopes is confirmed for mass A =72 . The new experimental information is compared to simple shell-model calculations including only neutron excitations across the f p g shells. It is shown that, in general, the calculations reproduce well the observed states.

  12. Ni cycling in mangrove sediments from New Caledonia

    NASA Astrophysics Data System (ADS)

    Noël, Vincent; Morin, Guillaume; Juillot, Farid; Marchand, Cyril; Brest, Jessica; Bargar, John R.; Muñoz, Manuel; Marakovic, Grégory; Ardo, Sandy; Brown, Gordon E.

    2015-11-01

    Covering more than 70% of tropical and subtropical coastlines, mangrove intertidal forests are well known to accumulate potentially toxic trace metals in their sediments, and thus are generally considered to play a protective role in marine and lagoon ecosystems. However, the chemical forms of these trace metals in mangrove sediments are still not well known, even though their molecular-level speciation controls their long-term behavior. Here we report the vertical and lateral changes in the chemical forms of nickel, which accumulates massively in mangrove sediments downstream from lateritized ultramafic deposits from New Caledonia, where one of nature's largest accumulations of nickel occurs. To accomplish this we used Ni K-edge Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy data in combination with microscale chemical analyses using Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy (SEM-EDXS). After Principal Component and Target Transform analyses (PCA-TT), the EXAFS data of the mangrove sediments were reliably least-squares fitted by linear combination of 3-components chosen from a large model compound spectral database including synthetic and natural Ni-bearing sulfides, clay minerals, oxyhydroxides, and organic complexes. Our results show that in the inland salt flat Ni is hosted in minerals inherited from the eroded lateritic materials, i.e. Ni-poor serpentine (44-58%), Ni-rich talc (20-31%), and Ni-goethite (18-24%). In contrast, in the hydromorphic sediments beneath the vegetated Avicennia and Rhizophora stands, a large fraction of Ni is partly redistributed into a neoformed smectite pool (20-69% of Ni-montmorillonite), and Ni speciation significantly changes with depth in the sediment. Indeed, Ni-rich talc (25-56%) and Ni-goethite (15-23%) disappear below ∼15 cm depth in the sediment and are replaced by Ni-sorbed pyrite (23-52%) in redox-active intermediate depth layers and by pyrite (34-55%) in the deepest

  13. Microstructure of the Native Oxide Layer on Ni and Cr-doped Ni Nanoparticles

    SciTech Connect

    Wang, Chong M.; Baer, Donald R.; Bruemmer, Stephen M.; Engelhard, Mark H.; Bowden, Mark E.; Sundararajan, J. A.; Qiang, You

    2011-10-01

    Metallic or alloy nanoparticles exposed to air at room temperature will be instantaneously oxidized and covered by an oxide layer. However, for most cases, the true structural nature of the oxide layer formed at this stage is hard to determine. In this paper, we report the structure, morphology, and electronic structure (the density of state of both valence and conduction bands measured by a combination of XPS and EELS) of pure Ni and Cr-doped Ni nanoparticles synthesized using a cluster deposition process. Structural characterization carried out at the atomic level using aberration corrected high resolution transmission electron microscopy (HRTEM) in combination with electron and x-ray diffractions reveals that both pure Ni and Cr-doped Ni particles exposed to air at room temperature similarly possesses a core-shell structure of metal core covered by an oxide layer of typically 1.6 nm in thickness. There exists a critical size of ~ 6 nm, below which the particle is fully oxidized. The oxide particle corresponds to the rock-salt structured NiO and is faceted on the (001) planes. XPS of O-1s shows a strong peak that is attributed to (OH)-, which in combination with the atomic level HRTEM imaging indicates that the very top layer of the oxide is hydrolyzed as Ni(OH)2. Chemical composition analysis using EDS, EELS, and XPS indicates that the Cr dopant at the level of ~ 5at% forms solid solution with the Ni lattice. The Cr shows no segregation on the surface or preferential oxidation during the initial oxidation.

  14. Ni-Co laterite deposits

    USGS Publications Warehouse

    Marsh, Erin E.; Anderson, Eric D.

    2011-01-01

    Nickel-cobalt (Ni-Co) laterite deposits are an important source of nickel (Ni). Currently, there is a decline in magmatic Ni-bearing sulfide lode deposit resources. New efforts to develop an alternative source of Ni, particularly with improved metallurgy processes, make the Ni-Co laterites an important exploration target in anticipation of the future demand for Ni. This deposit model provides a general description of the geology and mineralogy of Ni-Co laterite deposits, and contains discussion of the influences of climate, geomorphology (relief), drainage, tectonism, structure, and protolith on the development of favorable weathering profiles. This model of Ni-Co laterite deposits represents part of the U.S. Geological Survey Mineral Resources Program's effort to update the existing models to be used for an upcoming national mineral resource assessment.

  15. Synthesis and cyclic oxidation behavior of a (Ni, Pt) Al coating on a desulfurized Ni-base superalloy

    SciTech Connect

    Zhang, Y.; Lee, W.Y.; Haynes, J.A.; Wright, I.G.; Pint, B.A.; Cooley, K.M.; Liaw, P.K.

    1999-10-01

    The influences of sulfur impurities and Pt incorporation on the scale adhesion behavior of aluminide coatings were studied and compared. Low-sulfur NiAl coatings were prepared on a desulfurized, yttrium-free, single-crystal Ni-based superalloy by a modified version of a conventional aluminizing procedure based on chemical vapor deposition. The sulfur level in the resulting NiAl coatings was measured to be less than {approximately}0.5 ppmw by glow-discharge mass spectroscopy. Platinum-modified aluminide coatings were synthesized by first electroplating a thin layer of Pt({approximately}7 {micro}m) on the superalloy, followed by the same low-sulfur aluminizing procedure. The measured sulfur content in the (Ni,Pt)Al coating was substantially higher than that of the low-sulfur NiAl coating due to contamination during the Pt electroplating process. A very adherent {alpha}-Al{sub 2}O{sub 3} scale formed on the grain surfaces of the low-sulfur NiAl coating during cyclic oxidation testing at 1,150 C, but scale spallation eventually occurred over many of the NiAl grain boundaries. In contrast, despite the higher level of sulfur in the (NI,Pt)Al coating, a very adherent scale was formed over both the coating grain surfaces and grain boundaries during thermal cycling. These results suggest that Pt additions can mitigate the detrimental influence of sulfur on scale adhesion.

  16. Transmutation-induced embrittlement of V-Ti-Ni and V-Ni alloys in HFIR

    SciTech Connect

    Ohnuki, S.; Takahashi, H.; Garner, F.A.; Pawel, J.E.

    1996-04-01

    Vanadium, V-1Ni, V-10Ti and V-10Ti-1Ni (at %) were irradiated in HFIR to doses ranging from 18 to 30 dpa and temperatures between 300 and 600C. Since the irradiation was conducted in a highly thermalized neutron spectrum without shielding against thermal neutrons, significant levels of chromium (15-22%) were formed by transmutation. The addition of such large chromium levels strongly elevated the ductile to brittle transition temperature. At higher irradiation temperatures radiation-induced segregation of transmutant Cr and solute Ti at specimen surfaces leads to strong increases in the density of the alloy.

  17. Nickel and Manganese Accumulation, Interaction and Localization in Leaves of the Ni Hyperaccumulators Alyssum murale and Alyssum corsicum

    USDA-ARS?s Scientific Manuscript database

    The genus Alyssum contains >50 Ni hyperaccumulator species; many can achieve 3% Ni in dry leaf. In soils with normal Mn levels, Alyssum trichome bases were observed previously to accumulate Ni and Mn to high levels. Here we report concentration and localization patterns in A. murale and A. corsicum...

  18. Electronic and optical properties of antiferromagnetic iron doped NiO - A first principles study

    NASA Astrophysics Data System (ADS)

    Petersen, John E.; Twagirayezu, Fidele; Scolfaro, Luisa M.; Borges, Pablo D.; Geerts, Wilhelmus J.

    2017-05-01

    Antiferromagnetic NiO is a candidate for next generation high-speed and scaled RRAM devices. Here, electronic and optical properties of antiferromagnetic NiO: Fe 25% in the rock salt structure are studied and compared to intrinsic NiO. From density of states and complex dielectric function analysis, the first optical transition is found to be at lower frequency than intrinsic NiO due to an Fe impurity level being the valence band maximum. The resulting effects on refractive index, reflectivity, absorption, optical conductivity and loss function for Fe-doped NiO are compared to those of intrinsic NiO, and notable differences are analyzed. The electronic component of the static dielectric constant of NiO: Fe 25% is calculated to be about 2% less than that of intrinsic NiO.

  19. Structural and oxidation properties of CoNi nanowires

    NASA Astrophysics Data System (ADS)

    Aguilera-Granja, Faustino; Montejano-Carrizales, Juan Martin; Vogel, Eugenio E.

    2016-06-01

    Nanocylinders made out of CoNi alloys offer interesting properties which are dependent on the proportion of the constituent elements, the preparation methods and the thermal history of the sample. In the present paper we calculate the structural and electronic properties of Co1- x Ni x alloys at subnanoscopic level. SIESTA program is used to relax the structures following standard protocols. Relative positions of the minority atoms (Ni) are varied aiming to find the lowest energy configurations. It is found that Ni atoms minimize energy at surface positions mainly at the ends of the cylinders. The implications of this result in the magnetic properties of the systems are discussed. The work is continued to study the oxidation properties of the different possible surface compositions. It is found that surfaces of Ni are more resistant to oxidation than Co ones. The combination of the two previous results can lead to cylinders with high magnetic coercivity and relatively high resistance to oxidation.

  20. The oxidation of Ni-rich Ni-Al intermetallics

    NASA Technical Reports Server (NTRS)

    Doychak, Joseph; Smialek, James L.; Barrett, Charles A.

    1988-01-01

    The oxidation of Ni-Al intermetallic alloys in the beta-NiAl phase field and in the two phase beta-NiAl/gamma'-Ni3Al phase field has been studied between 1000 and 1400 C. The stoichiometric beta-NiAl alloy doped with Zr was superior to other alloy compositions under cyclic and isothermal oxidation. The isothermal growth rates did not increase monotonically as the alloy Al content was decreased. The characteristically ridged alpha-Al2O3 scale morphology, consisting of cells of thin, textured oxide with thick growth ridges at cell boundaries, forms on oxidized beta-NiAl alloys. The correlation of scale features with isothermal growth rates indicates a predominant grain boundary diffusion growth mechanism. The 1200 C cyclic oxidation resistance decreases near the lower end of the beta-NiAl phase field.

  1. Bulk Migration of Ni/NiO in Ni-YSZ during Reducing Conditions

    SciTech Connect

    Saraf, Laxmikant V.; Baer, Donald R.; Lea, Alan S.; Zhu, Zihua; Strohm, James J.; Sitzman, S. D.; King, David L.

    2010-02-09

    Understanding the migration of Ni/NiO in Ni-YSZ can potentially help to design a better solid oxide fuel cell (SOFC) anode. We have observed that extensive hydrogen reduction and methane steam reforming of Ni-YSZ caused bulk migration of Ni/NiO to at least ~ 5 µm deeper from the Ni-YSZ surface. No significant bulk migration effects were detected after simple thermal treatments in non-reducing/non-reforming environment. Surface analysis of a single zirconia grain in the first 10-20 nm region from annealed, hydrogen reduced and methane steam reformed Ni-YSZ shows Ni-enriched surface supporting earlier claims of Ni exsolution. 3D-EBSD analysis of thermally treated sample before exposing it to reducing and reforming environment indicated mixed NiO/YSZ phase with some porosity and random grain orientation. The surface analysis and mapping were carried out using ToF-SIMS and AES whereas EDS maps on FIB sliced areas on Ni-YSZ were utilized for the bulk analysis. The results provide additional information related to complex reactions occurring in SOFC during internal reforming conditions.

  2. Microstructure of the native oxide layer on Ni and Cr-doped Ni nanoparticles.

    PubMed

    Wang, Chong-Min; Baer, Donald R; Bruemmer, Stephen M; Engelhard, Mark H; Bowden, Mark E; Sundararajan, Jennifer A; Qiang, You

    2011-10-01

    Most metallic nanoparticles exposed to air at room temperature will be instantaneously oxidized and covered by an oxide layer. In most cases the true structural nature of the oxide layer formed at this stage is hard to determine. As shown previously for Fe and other nanoparticles, the nature of the oxides form on the particles can vary with particle size and nature of the oxidation process. In this paper, we report the morphology and structural features of the native oxide layer on pure Ni and Cr-doped Ni nanoparticles synthesized using a cluster deposition process. Structural characterization carried out at the atomic level using aberration corrected high resolution transmission electron microscopy (HRTEM) in combination with electron and X-ray diffractions reveals that both pure Ni and Cr-doped Ni particles exposed to air at room temperature similarly possesses a core-shell structure of metal core covered by an oxide layer of typically 1.6 nm in thickness. There exists a critical size of approximately 6 nm, below which the particle is fully oxidized. The oxide particle corresponds to the rock-salt structured NiO and is faceted on the (001) planes. XPS of O-1s shows a strong peak that is attributed to (OH)-, which in combination with the atomic level HRTEM imaging indicates that the very top layer of the oxide is hydrolyzed.

  3. Cu-Ni core-shell nanoparticles: structure, stability, electronic, and magnetic properties: a spin-polarized density functional study

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Wang, Xinyan; Liu, Jianlan; Yang, Yanhui

    2017-02-01

    Bimetallic core-shell nanoparticles (CSNPs) have attracted great interest not only because of their superior stability, selectivity, and catalytic activity but also due to their tunable properties achieved by changing the morphology, sequence, and sizes of both core and shell. In this study, the structure, stability, charge transfer, electronic, and magnetic properties of 13-atom and 55-atom Cu and Cu-Ni CSNPs were investigated using the density functional theory (DFT) calculations. The results show that Ni@Cu CSNPs with a Cu surface shell are more energetically favorable than Cu@Ni CSNPs with a Ni surface shell. Interestingly, three-shell Ni@Cu12@Ni42 is more stable than two-shell Cu13@Ni42, while two-shell Ni13@Cu42 is more stable than three-shell Cu@Ni12@Cu42. Analysis of Bader charge illustrates that the charge transfer increases from Cu core to Ni shell in Cu@Ni NPs, while it decreases from Ni core to Cu shell in Ni@Cu NPs. Furthermore, the charge transfer results that d-band states have larger shift toward the Fermi level for the Ni@Cu CSNPs with Cu surface shell, while the Cu@Ni CSNPs with Ni surface shell have similar d-band state curves and d-band centers with the monometallic Ni NPs. In addition, the Cu-Ni CSNPs possess higher magnetic moment when the Ni atoms aggregated at core region of CSNPs, while having lower magnetic moment when the Ni atoms segregate on surface region. The change of the Cu atom location in CSNPs has a weak effect on the total magnetic moment. Our findings provide useful insights for the design of bimetallic core-shell catalysts.

  4. Shape memory behavior of single crystal and polycrystalline Ni-rich NiTiHf high temperature shape memory alloys

    NASA Astrophysics Data System (ADS)

    Saghaian, Sayed M.

    NiTiHf shape memory alloys have been receiving considerable attention for high temperature and high strength applications since they could have transformation temperatures above 100 °C, shape memory effect under high stress (above 500 MPa) and superelasticity at high temperatures. Moreover, their shape memory properties can be tailored by microstructural engineering. However, NiTiHf alloys have some drawbacks such as low ductility and high work hardening in stress induced martensite transformation region. In order to overcome these limitations, studies have been focused on microstructural engineering by aging, alloying and processing. Shape memory properties and microstructure of four Ni-rich NiTiHf alloys (Ni50.3Ti29.7Hf20, Ni50.7Ti 29.3Hf20, Ni51.2Ti28.8Hf20, and Ni52Ti28Hf20 (at. %)) were systematically characterized in the furnace cooled condition. H-phase precipitates were formed during furnace cooling in compositions with greater than 50.3Ni and the driving force for nucleation increased with Ni content. Alloy strength increased while recoverable strain decreased with increasing Ni content due to changes in precipitate characteristics. The effects of the heat treatments on the transformation characteristics and microstructure of the Ni-rich NiTiHf shape memory alloys have been investigated. Transformation temperatures are found to be highly annealing temperature dependent. Generation of nanosize precipitates (˜20 nm in size) after three hours aging at 450 °C and 550 °C improved the strength of the material, resulting in a near perfect dimensional stability under high stress levels (> 1500 MPa) with a work output of 20-30 J cm- 3. Superelastic behavior with 4% recoverable strain was demonstrated at low and high temperatures where stress could reach to a maximum value of more than 2 GPa after three hours aging at 450 and 550 °C for alloys with Ni great than 50.3 at. %. Shape memory properties of polycrystalline Ni50.3Ti29.7 Hf20 alloys were studied via

  5. Magnetic Properties of FeNi-Based Thin Film Materials with Different Additives

    PubMed Central

    Liang, Cai; Gooneratne, Chinthaka P.; Wang, Qing Xiao; Liu, Yang; Gianchandani, Yogesh; Kosel, Jurgen

    2014-01-01

    This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials attractive for sensor applications. Our findings show that FeNi deposited with Mo or Al yields magnetically soft materials and that depositing with B further increases the softness. The out-of-plane magnetic anisotropy of FeNi thin films is reduced by depositing with Al and completely removed by depositing with B. The effect of depositing with Mo is dependent on the Mo concentration. The coercivity of FeNiMo and FeNiAl is reduced to less than a half of that of FeNi, and a value as low as 40 A/m is obtained for FeNiB. The surfaces of the obtained FeNiMo, FeNiAl and FeNiB thin films reveal very different morphologies. The surface of FeNiMo shows nano-cracks, while the FeNiAl films show large clusters and fewer nano-cracks. When FeNi is deposited with B, a very smooth morphology is obtained. The crystal structure of FeNiMo strongly depends on the depositant concentration and changes into an amorphous structure at a higher Mo level. FeNiAl thin films remain polycrystalline, even at a very high concentration of Al, and FeNiB films are amorphous, even at a very low concentration of B. PMID:25587418

  6. Magnetic Properties of FeNi-Based Thin Film Materials with Different Additives.

    PubMed

    Liang, Cai; Gooneratne, Chinthaka P; Wang, Qing Xiao; Liu, Yang; Gianchandani, Yogesh; Kosel, Jurgen

    2014-09-01

    This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials attractive for sensor applications. Our findings show that FeNi deposited with Mo or Al yields magnetically soft materials and that depositing with B further increases the softness. The out-of-plane magnetic anisotropy of FeNi thin films is reduced by depositing with Al and completely removed by depositing with B. The effect of depositing with Mo is dependent on the Mo concentration. The coercivity of FeNiMo and FeNiAl is reduced to less than a half of that of FeNi, and a value as low as 40 A/m is obtained for FeNiB. The surfaces of the obtained FeNiMo, FeNiAl and FeNiB thin films reveal very different morphologies. The surface of FeNiMo shows nano-cracks, while the FeNiAl films show large clusters and fewer nano-cracks. When FeNi is deposited with B, a very smooth morphology is obtained. The crystal structure of FeNiMo strongly depends on the depositant concentration and changes into an amorphous structure at a higher Mo level. FeNiAl thin films remain polycrystalline, even at a very high concentration of Al, and FeNiB films are amorphous, even at a very low concentration of B.

  7. ZnNi data

    DTIC Science & Technology

    2014-11-01

    carried out HE testing and passed, so that issue is resolved Concern over dezincification Keith Legg 847-680-9420 klegg@rowantechnology.com http...of the Zn-Ni plating 417 SCMS /GUEA, BR&T and ES3 are currently reviewing past industry de-zincification studies  Initial findings show that the...corrosion electro- potential is consistent throughout the corrosion process 417 SCMS /GUEA, BR&T and ES3 will identify any addition testing that

  8. Oxygen impurity effects at metal/silicide interfaces - Formation of silicon oxide and suboxides in the Ni/Si system

    NASA Technical Reports Server (NTRS)

    Grunthaner, P. J.; Grunthaner, F. J.; Scott, D. M.; Nicolet, M.-A.; Mayer, J. W.

    1981-01-01

    The effect of implanted oxygen impurities on the Ni/Ni2Si interface is investigated using X-ray photoelectron spectroscopy, He-4(+) backscattering and O(d, alpha)-16 N-14 nuclear reactions. Oxygen dosages corresponding to concentrations of 1, 2, and 3 atomic percent were implanted into Ni films evaporated on Si substrates. The oxygen, nickel, and silicon core lines were monitored as a function of time during in situ growth of the Ni silicide to determine the chemical nature of the diffusion barrier which forms in the presence of oxygen impurities. Analysis of the Ni, Si, and O core levels demonstrates that the formation of SiO2 is responsible for the Ni diffusion barrier rather than Ni oxide or mixed oxides, such as Ni2SiO4. It is determined that 2.2 x 10 to the 16th O/qu cm is sufficient to prevent Ni diffusion under UHV annealing conditions.

  9. Electronic structure of cyclohexane on Ni(111)

    NASA Astrophysics Data System (ADS)

    Huber, W.; Zebisch, P.; Bornemann, T.; Steinrück, H.-P.

    1990-12-01

    Mono- and multilayers of cyclohexane adsorbed on a Ni(111) surface have been studied by angle resolved UV photoelectron spectroscopy (ARUPS) using linearly polarized synchrotron radiation, temperature programmed desorption (TPD) and low energy electron diffraction (LEED). Cyclohexane is molecularly adsorbed on Ni(111) at temperatures below 200 K and desorbs without dehydrogenation. Desorption from the first layer exhibits zeroth-order desorption behavior indicative of desorption from two-dimensional islands. The first layer exhibits a well ordered ( 7 × 7)R19.1° LEED structure starting at coverages of 0.04 ML up to the saturation coverage of 0.143 ML, also indicative of island formation. For cyclohexane in the first layer the binding energies of the various molecular levels are, apart from an overall shift to smaller values by 0.7 eV, within ± 0.1 eV identical to those of condensed cyclohexane. This absence of chemical shifts indicates that there is only very weak (if any) chemical interaction between cyclohexane and the Ni(111) surface. From the normal emission ARUPS spectra and symmetry selection rules we conclude that the symmetry of cyclohexane adsorbed on Ni(111) is lower than C 3v. This is attributed to a slightly inclined adsorption geometry with intramolecular C 3v symmetry of the adsorbed molecules.

  10. The first principle study of Ni{sub 2}ScGa and Ni{sub 2}TiGa

    SciTech Connect

    Özduran, Mustafa; Turgut, Kemal; Arikan, Nihat; İyigör, Ahmet; Candan, Abdullah

    2014-10-06

    We computed the electronic structure, elastic moduli, vibrational properties, and Ni{sub 2}TiGa and Ni{sub 2}ScGa alloys in the cubic L2{sub 1} structure. The obtained equilibrium lattice constants of these alloys are in good agreement with available data. In cubic systems, there are three independent elastic constants, namely C{sub 11}, C{sub 12} and C{sub 44}. We calculated elastic constants in L2{sub 1} structure for Ni{sub 2}TiGa and Ni{sub 2}ScGa using the energy-strain method. The electronic band structure, total and partial density of states for these alloys were investigated within density functional theory using the plane-wave pseudopotential method implemented in Quantum-Espresso program package. From band structure, total and projected density of states, we observed metallic characters of these compounds. The electronic calculation indicate that the predominant contributions of the density of states at Fermi level come from the Ni 3d states and Sc 3d states for Ni{sub 2}TiGa, Ni 3d states and Sc 3d states for Ni{sub 2}ScGa. The computed density of states at Fermi energy are 2.22 states/eV Cell for Ni{sub 2}TiGa, 0.76 states/eV Cell for Ni{sub 2}ScGa. The vibrational properties were obtained using a linear response in the framework at the density functional perturbation theory. For the alloys, the results show that the L2{sub 1} phase is unstable since the phonon calculations have imagine modes.

  11. Gamow-Teller decays near 78Ni

    NASA Astrophysics Data System (ADS)

    Grzywacz, Robert; Alshudifat, Mohammad; Madurga, Miguel; Rykaczewski, Krzysztof; Gross, Carl

    2015-10-01

    Decays of neutron-rich nuclei close to 78Ni such as 82,83Zn and 82,83Ga produced in proton-induced fission of 238U were studied at the Holifield Radioactive Ion Beam Facility. New gamma-ray transitions were identified and level schemes, which include states at high excitation energies were constructed. The high energy levels were populated through allowed Gamow-Teller decays of the 78Ni components of the wave function, and were interpreted with new shell model calculations. This work is supported in part under US DOE Grants DE-AC05-00OR22725, DE-FG02-96ER40983, DE-AC05-06OR23100, and DE-FG05-88ER40407, DE-FG52-08NA28552; in part by the Polish Ministry of Science and Higher Education, Grant No. 2011/01/B/ST2/02476.

  12. LaBaNiO4: a Fermi glass

    NASA Astrophysics Data System (ADS)

    Schilling, A.; Dell'Amore, R.; Karpinski, J.; Bukowski, Z.; Medarde, M.; Pomjakushina, E.; Müller, K. A.

    2009-01-01

    Polycrystalline samples of LaSr1-xBaxNiO4 show a crossover from a state with metallic transport properties for x = 0 to an insulating state as x\\to 1 . The end member LaBaNiO4 with a nominal nickel Ni 3d7 configuration might therefore be regarded as a candidate for an antiferromagnetic insulator. However, we do not observe any magnetic ordering in LaBaNiO4 down to 1.5 K, and despite its insulating transport properties several other physical properties of LaBaNiO4 resemble those of metallic LaSrNiO4. Based on an analysis of electrical and thermal-conductivity data as well as magnetic-susceptibility and low-temperature specific-heat measurements, we suggest that LaBaNiO4 is a Fermi glass with a finite electron density of states at the Fermi level but these states are localized.

  13. A New Polycrystalline Co-Ni Superalloy

    NASA Astrophysics Data System (ADS)

    Knop, M.; Mulvey, P.; Ismail, F.; Radecka, A.; Rahman, K. M.; Lindley, T. C.; Shollock, B. A.; Hardy, M. C.; Moody, M. P.; Martin, T. L.; Bagot, P. A. J.; Dye, D.

    2014-12-01

    In 2006, a new-ordered L12 phase, Co3(Al,W), was discovered that can form coherently in a face-centered cubic (fcc) A1 Co matrix. Since then, a community has developed that is attempting to take these alloys forward into practical applications in gas turbines. A new candidate polycrystalline Co-Ni γ/ γ' superalloy, V208C, is presented that has the nominal composition 36Co-35Ni-15Cr-10Al-3W-1Ta (at.%). The alloy was produced by conventional powder metallurgy superalloy methods. After forging, a γ' fraction of ~56% and a secondary γ' size of 88 nm were obtained, with a grain size of 2.5 μm. The solvus temperature was 1000°C. The density was found to be 8.52 g cm-3, which is similar to existing Ni alloys with this level of γ'. The alloy showed the flow stress anomaly and a yield strength of 920 MPa at room temperature and 820 MPa at 800°C, similar to that of Mar-M247. These values are significantly higher than those found for either conventional solution and carbide-strengthened Co alloys or the γ/ γ' Co superalloys presented in the literature thus far. The oxidation resistance, with a mass gain of 0.08 mg cm-2 in 100 h at 800°C, is also comparable with that of existing high-temperature Ni superalloys. These results suggest that Co-based and Co-Ni superalloys may hold some promise for the future in gas turbine applications.

  14. Imaging Chemical Aggregation of Ni/NiO Particles from Reduced NiO-YSZ

    SciTech Connect

    Saraf, Laxmikant V.

    2011-07-20

    Energy dispersive X-ray spectroscopy (EDS) mapping of nickel oxide yttria-stabilized zirconia (NiO-YSZ) was carried out after various hydrogen reducing and methane steam reforming conditions. Nickel aggregation was visualized after methane steam reforming by correlating Ni K{sub {alpha}} map with scanning transmission electron microscopy (STEM) images. From the reduced O K{sub {alpha}} intensities in the Ni K{sub {alpha}} dominated regions after methane steam reforming, NiO reduction in to Ni can be interpreted. From correlation between Zr K{sub {alpha}} and O K{sub {alpha}} maps, high stability of YSZ was also realized. Examples of NiO-YSZ overlapped particles are considered to discuss chemical imaging of a single particle.

  15. Chelator-buffered nutrient solution is ineffective in extracting Ni from seeds of Alyssum.

    PubMed

    Centofanti, Tiziana; Tappero, Ryan V; Davis, Allen P; Chaney, Rufus L

    2011-01-01

    Hyperaccumulator species of the genera Alyssum can accumulate 100 times more Ni than normal crops and are therefore used for phytomining and phytoextraction of nickel contaminated soils. Basic studies on the physiology and metal uptake mechanisms of these plants are needed to increase efficiency and uptake capacity of Nickel (Ni) by hyperaccumulators. Recent attempts to disclose if those hyperaccumulator species require higher Ni level than normal plants failed because of the high Ni content in the seeds (7000-9000 microg g(-1)). In this study, we attempted to use chelator buffered nutrient solution to deplete Ni from the seed/seed coat and to obtain low Ni seedlings of Alyssum cultivars to be used in physiology studies. HEDTA-buffered nutrient solution did not deplete Ni from the seeds, perhaps because Ni was mainly localized within the seedling embryonic tissues with greatest Ni enrichment in the cotyledons and hypocotyls. We could not observe any positive correlation between seed fitness and germination capacity with seed Ni content. Investigation of nickel localization in Alyssum seeds using synchrotron X-ray microfluorescence (micro-SXRF) showed that nickel is localized in the embryonic tissues with greatest Ni enrichment observed in the cotyledons and hypocotyl.

  16. Coherent nuclear resonant scattering by {sup 61}Ni using the nuclear lighthouse effect

    SciTech Connect

    Roth, T.; Leupold, O.; Wille, H.-C.; Rueffer, R.; Quast, K.W.; Burkel, E.; Roehlsberger, R.

    2005-04-01

    We have observed coherent nuclear resonant scattering of synchrotron radiation from the 67.41-keV level of {sup 61}Ni. The time evolution of the forward scattering signal was recorded by employing the nuclear lighthouse effect. This method is used to investigate Moessbauer isotopes in a coherent scattering process with synchrotron radiation at high transition energies. The decay of the excited ensemble of nuclei in Ni metal shows quantum beats that allowed the determination of the magnetic hyperfine field at the {sup 61}Ni nucleus. Moreover, we determined the lifetime of the 67.41-keV level of {sup 61}Ni to be 7.4(1) ns.

  17. Reactive Ni/Ti nanolaminates

    SciTech Connect

    Adams, D. P.; Bai, M. M.; Rodriguez, M. A.; McDonald, J. P.; Jones, E. Jr.; Brewer, L.; Moore, J. J.

    2009-11-01

    Nickel/titanium nanolaminates fabricated by sputter deposition exhibited rapid, high-temperature synthesis. When heated locally, self-sustained reactions were produced in freestanding Ni/Ti multilayer foils characterized by average propagation speeds between approx0.1 and 1.4 m/s. The speed of a propagating reaction front was affected by total foil thickness and bilayer thickness (layer periodicity). In contrast to previous work with compacted Ni-Ti powders, no preheating of Ni/Ti foils was required to maintain self-propagating reactions. High-temperature synthesis was also stimulated by rapid global heating demonstrating low ignition temperatures (T{sub ig})approx300-400 deg. C for nanolaminates. Ignition temperature was influenced by bilayer thickness with more coarse laminate designs exhibiting increased T{sub ig}. Foils reacted in a vacuum apparatus developed either as single-phase B2 cubic NiTi (austenite) or as a mixed-phase structure that was composed of monoclinic B19{sup '} NiTi (martensite), hexagonal NiTi{sub 2}, and B2 NiTi. Single-phase, cubic B2 NiTi generally formed when the initial bilayer thickness was made small.

  18. 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.

  19. Probing spin accumulation in Ni/Au/Ni single-electron transistors with efficient spin injection and detection electrodes.

    PubMed

    Liu, R S; Pettersson, H; Michalak, L; Canali, C M; Samuelson, L

    2007-01-01

    We have investigated spin accumulation in Ni/Au/Ni single-electron transistors assembled by atomic force microscopy. The fabrication technique is unique in that unconventional hybrid devices can be realized with unprecedented control, including real-time tunable tunnel resistances. A grid of Au disks, 30 nm in diameter and 30 nm thick, is prepared on a SiO2 surface by conventional e-beam writing. Subsequently, 30 nm thick ferromagnetic Ni source, drain, and side-gate electrodes are formed in similar process steps. The width and length of the source and drain electrodes were different to exhibit different coercive switching fields. Tunnel barriers of NiO are realized by sequential Ar and O2 plasma treatment. By use of an atomic force microscope with specially designed software, a single nonmagnetic Au nanodisk is positioned into the 25 nm gap between the source and drain electrodes. The resistance of the device is monitored in real time while the Au disk is manipulated step-by-step with angstrom-level precision. Transport measurements in magnetic field at 1.7 K reveal no clear spin accumulation in the device, which can be attributed to fast spin relaxation in the Au disk. From numerical simulations using the rate-equation approach of orthodox Coulomb blockade theory, we can put an upper bound of a few nanoseconds on the spin-relaxation time for electrons in the Au disk. To confirm the magnetic switching characteristics and spin injection efficiency of the Ni electrodes, we fabricated a test structure consisting of a Ni/NiO/Ni magnetic tunnel junction with asymmetric dimensions of the electrodes similar to those of the single-electron transistors. Magnetoresistance measurements on the test device exhibited clear signs of magnetic reversal and a maximum tunneling magnetoresistance of 10%, from which we deduced a spin polarization of about 22% in the Ni electrodes.

  20. Atomic diffusion in liquid Ni, NiP, PdNiP, and PdNiCuP alloys

    SciTech Connect

    Chathoth, S. Mavila; Meyer, A.; Koza, M.M.; Juranyi, F.

    2004-11-22

    We investigated the self-diffusion of Ni in liquid Ni, Ni{sub 80}P{sub 20}, Pd{sub 40}Ni{sub 40}P{sub 20}, and Pd{sub 43}Ni{sub 10}Cu{sub 27}P{sub 20} at temperatures up to 1795 K with incoherent, quasielastic neutron scattering. Values of measured self-diffusion coefficients vary over the accessible temperature ranges as a function of composition only within 10%. Although mixing has a drastic effect on the liquidus temperature and the undercooling capabilities, a relation between these properties and the atomic diffusion in the liquid is not observed. Apparently, diffusive motion is governed by the packing fraction of the atoms, that is very similar in these dense liquids.

  1. Comparison of benzene adsorption on Ni(111) and Ni(100)

    SciTech Connect

    Myers, A.K.; Schoofs, G.R.; Benziger, J.B.

    1987-04-23

    The adsorption of benzene on the Ni(100) and the Ni(111) crystal faces was compared in order to investigate the effect of crystallographic orientation on the interaction of benzene with nickel. Temperature programmed reaction (TPR) was used to characterize adsorption bond strengths and determine product distributions. Benzene was found to adsorb 44 kJ/mol less strongly on the Ni(111) plane than on the Ni(100) surface. Di-hydrogen evolution formed after decomposition of benzene was similar for both surfaces. Benzene chemisorption was modeled by using extended Hueckel theory (EHT), a semiempirical molecular orbital method. The calculations predict bonding of benzene over a threefold hollow site on Ni(111). Multicenter bonding of the benzene carbon atoms with the nickel atoms is indicated by the calculations. The binding strength of benzene is controlled by the degree of overlap of the carbon ..pi.. orbitals with the nickel atom orbitals. Benzene binds more strongly to the Ni(100) surface because the carbon ..pi.. orbitals can overlap with four nickel atoms on the fourfold hollow site, whereas on Ni(111) the carbon atoms are closely associated with only three nickel atoms on the threefold hollow site.

  2. Effect of major cations (Ca2+, Mg2+, Na+, K+) and anions (SO4(2-), Cl- , NO3-) on Ni accumulation and toxicity in aquatic plant (Lemna minor L.): implications For Ni risk assessment.

    PubMed

    Gopalapillai, Yamini; Hale, Beverley; Vigneault, Bernard

    2013-04-01

    The effect of major cation activity (Ca(2+) , Mg(2+) , Na(+) , K(+) ) on Ni toxicity, with dose expressed as exposure (total dissolved Ni concentration NiTot ) or free Ni ion activity (in solution Ni(2+) ), or as tissue residue (Ni concentration in plant tissue NiTiss ) to the aquatic plant Lemna minor L. was examined. In addition, Ni accumulation kinetics was explored to provide mechanistic insight into current approaches of toxicity modeling, such as the tissue residue approach and the biotic ligand model (BLM), and the implications for plant Ni risk assessment. Major cations did not inhibit Ni accumulation via competitive inhibition as expected by the BLM framework. For example, Ca(2+) and Mg(2+) (sulfate as counter-anion) had an anticompetitive effect on Ni accumulation, suggesting that Ca or Mg forms a ternary complex with Ni-biotic ligand. The counter-anion of the added Ca (sulfate, chloride, or nitrate) affected plant response (percentage of root growth inhibition) to Ni. Generally, sulfate and chloride influenced plant response while nitrate did not, even when compared within the same range of Ca(2+) , which suggests that the anion dominated the observed plant response. Overall, although an effect of major cations on Ni toxicity to L. minor L. was observed at a physiological level, Ni(2+) or NiTot alone modeled plant response, generally within a span of twofold, over a wide range of water chemistry. Thus, consideration of major cation competition for improving Ni toxicity predictions in risk assessment for aquatic plants may not be necessary. Copyright © 2013 SETAC.

  3. NiH2 Battery Reconditioning for LEO Applications

    NASA Technical Reports Server (NTRS)

    Armantrout, J. D.; Hafen, D. P.

    1997-01-01

    This paper summarizes reasons for and benefits of reconditioning nickel-hydrogen (NiH2) batteries used for Low Earth Orbit (LEO) applications. NiH2 battery cells do not have the classic discharge voltage problems more commonly associated with nickel-cadmium (NiCd) cells. This is due, in part, to use of hydrogen electrodes in place of cadmium electrodes. The nickel electrode, however, does have a similar discharge voltage signature for both cell designs. This can have an impact on LEO applications where peak loads at higher relative depths of discharge can impact operations. Periodic reconditioning provides information which can be used for analyzing long term performance trends to predict usable capacity to a specified voltage level. The reconditioning process described herein involves discharging NiH2 batteries at C/20 rates or less, to an average cell voltage of 1.0 volts or less. Recharge is performed at nominal C/5 rates to specified voltage/temperature (V/T) charge levels selected to restore required capacity with minimal overcharge. Reconditioning is a process of restoring reserve capacity lost on cycling, which is commonly called the memory effect in NiCd cells. This effect is characterized by decreases in the discharge voltage curve with operational life and cycling. The end effect of reconditioning NiH2 cells may be hidden in the versatility, of that design over the NiCd cell design and its associated negative electrode fading problem. The process of deep discharge at lower rates by way of reconditioning tends to redistribute electrolyte and water in the NiH2 cell electrode stack, while improving utilization and charge efficiency. NiH2 battery reconditioning effects on life are considered beneficial and may, in fact. extend life based on NiCd experience. In any case, usable capacity data obtained from reconditioning is required for performance evaluation and trend analysis. Characterization and life tests have provided the historical data base used to

  4. Constructing Multifunctional Metallic Ni Interface Layers in the g-C3N4 Nanosheets/Amorphous NiS Heterojunctions for Efficient Photocatalytic H2 Generation.

    PubMed

    Wen, Jiuqing; Xie, Jun; Zhang, Hongdan; Zhang, Aiping; Liu, Yingju; Chen, Xiaobo; Li, Xin

    2017-04-26

    The construction of exceptionally robust and high-quality semiconductor-cocatalyst heterojunctions remains a grand challenge toward highly efficient and durable solar-to-fuel conversion. Herein, novel graphitic carbon nitride (g-C3N4) nanosheets decorated with multifunctional metallic Ni interface layers and amorphous NiS cocatalysts were fabricated via a facile three-step process: the loading of Ni(OH)2 nanosheets, high-temperature H2 reduction, and further deposition of amorphous NiS nanosheets. The results demonstrated that both robust metallic Ni interface layers and amorphous NiS can be utilized as electron cocatalysts to markedly boost the visible-light H2 evolution over g-C3N4 semiconductor. The optimized g-C3N4-based photocatalyst containing 0.5 wt % Ni and 1.0 wt % NiS presented the highest hydrogen evolution of 515 μmol g(-1) h(-1), which was about 2.8 and 4.6 times as much as those obtained on binary g-C3N4-1.0%NiS and g-C3N4-0.5%Ni, respectively. Apparently, the metallic Ni interface layers play multifunctional roles in enhancing the visible-light H2 evolution, which could first collect the photogenerated electrons from g-C3N4, and then accelerate the surface H2-evolution reaction kinetics over amorphous NiS cocatalysts. More interestingly, the synergetic effects of metallic Ni and amorphous NiS dual-layer electron cocatalysts could also improve the TEOA-oxidation capacity through upshifting the VB levels of g-C3N4. Comparatively speaking, the multifunctional metallic Ni layers are dominantly favorable for separating and transferring photoexcited charge carriers from g-C3N4 to amorphous NiS cocatalysts owing to the formation of Schottky junctions, whereas the amorphous NiS nanosheets are mainly advantageous for decreasing the thermodynamic overpotentials for surface H2-evolution reactions. It is hoped that the implantation of multifunctional metallic interface layers can provide a versatile approach to enhance the photocatalytic H2 generation over

  5. Dirac R-matrix calculations of photoionization cross sections of Ni XII and atomic structure data of Ni XIII

    NASA Astrophysics Data System (ADS)

    Nazir, R. T.; Bari, M. A.; Bilal, M.; Sardar, S.; Nasim, M. H.; Salahuddin, M.

    2017-02-01

    We performed R-matrix calculations for photoionization cross sections of the two ground state configuration 3s23p5 (^2P^o3/2,1/2) levels and 12 excited states of Ni XII using relativistic Dirac Atomic R-matrix Codes (DARC) across the photon energy range between the ionizations thresholds of the corresponding states and well above the thresholds of the last level of the Ni XIII target ion. Generally, a good agreement is obtained between our results and the earlier theoretical photoionization cross sections. Moreover, we have used two independent fully relativistic GRASP and FAC codes to calculate fine-structure energy levels, wavelengths, oscillator strengths, transitions rates among the lowest 48 levels belonging to the configuration (3s23p4, 3s3p5, 3p6, 3s23p33d) in Ni XIII. Additionally, radiative lifetimes of all the excited states of Ni XIII are presented. Our results of the atomic structure of Ni XIII show good agreement with other theoretical and experimental results available in the literature. A good agreement is found between our calculated lifetimes and the experimental ones. Our present results are useful for plasma diagnostic of fusion and astrophysical plasmas.

  6. Investigation of microstructure, electrical and photoluminescence behaviour of Ni-doped Zn0.96Mn0.04O nanoparticles: Effect of Ni concentration

    NASA Astrophysics Data System (ADS)

    Rajakarthikeyan, R. K.; Muthukumaran, S.

    2017-07-01

    ZnO, Zn0.96Mn0.04O and Ni-doped Zn0.96Mn0.04O nanoparticles with different Ni concentrations (0%, 2% and 4%) have been synthesized successfully by sol-gel method. The effects of Ni doping on the structural and optical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy and photoluminescence (PL) spectroscopy. The XRD pattern confirmed the existence of single phase wurtzite-like hexagonal structure throughout the Ni concentrations without any additional phases. The substitution of Ni created the lattice distortion due to the disparity of ionic radius between Zn and Ni which reduced the crystallite size. The microscopic images showed that the size of ZnO nanoparticles reduced by Ni-doping while the shape remains almost spherical/hexagonal type. The electrical conductivity found to be maximum at Ni = 2% due to the availability of more charge carriers generated by Ni. The decrease of electrical conductivity at higher doping (Ni = 4%) is due to the fact that the generation of more defects. The enhanced band gap from 3.73 eV (Ni = 0%) to 3.79 eV (Ni = 4%) by the addition of Ni explained by Burstein-Moss effect. The change in infra-red (IR) intensity and full width at half maximum (FWHM) corresponding to the frequency around defect states were caused by the difference in the bond lengths that occurs when Ni ion replaces Zn ion. The observed blue band emission from 474 nm to 481 nm is due to a radiative transition of an electron from the deep donar level of Zni to an acceptor level of neutral VZn and the origin of green band may be due to oxygen vacancies and intrinsic defects. The tuning of the band gap and the visible emission bands by Ni doping concluded that Ni-doped Zn0.96Mn0.04O is suitable for various nano-photo-electronics applications.

  7. Three-dimensional phase field simulation of the morphology and growth kinetics of Ni4Ti3 precipitates in a NiTi alloy

    NASA Astrophysics Data System (ADS)

    Ke, C. B.; Cao, S.; Zhang, X. P.

    2014-07-01

    A three-dimensional phase field model is applied to study the morphology and growth kinetics of Ni4Ti3 precipitates, as well as the Ni concentration distribution feature, during the aging of a NiTi alloy. The model can reproduce well the multiple-variants morphology of Ni4Ti3 precipitates. The diameter-to-thickness ratio of lenticular Ni4Ti3 precipitates in the equilibrium shape is 4.2. Simulation results show that the Ni depletion region near the face of Ni4Ti3 precipitates is broader than that near the edge of the precipitates, and both the depletion level of Ni concentration and the length of the Ni depletion region adjacent to the precipitates increase with the aging time. The growth of the precipitate diameter and thickness can be described by the power-law fitting equation, with growth exponent m = 0.47 for the diameter and m = 0.46 for the thickness, which are in good agreement with those obtained in previous experimental and analytical studies.

  8. The influence of Ni(II) on brushite structure stabilization

    NASA Astrophysics Data System (ADS)

    Guerra-López, J. R.; Güida, J. A.; Ramos, M. A.; Punte, G.

    2017-06-01

    Brushite samples doped with Ni(II) in different concentrations, from 5% to 20%, were prepared in aqueous solution at pH = 7 and at two temperatures: 25 and 37 °C. The solid samples were characterized by chemical analysis, infrared spectroscopy (FTIR) and x-ray powder diffraction (XRPD). Chemical analysis has shown Ni(II) almost complete incorporation to the solid phase up to 15%. X-ray diffraction patterns have allowed to identify brushite phase with almost no modification of the line breadth and only small shifts of lines positions with increasing Ni(II) incorporation up to 15%. For larger Ni(II) concentration, in solution, a mixture of phases has been detected. Infrared spectra have supported diffraction results. For Ni(II) 20% and over the characteristic bands of HPO42- anions tend to vanish, and the typical shaped PO43- bands are observed. These results have allowed to establish that the presence of low levels of Ni in the synthetic process not only helps brushite formation; but, also prevents brushite from apatite conversion and, in addition, preserves brushite crystallinity. According to these findings, it is possible to propose that nickel traces present in the urinary system might be a trigger to brushite stone formation and/or growth, rather than the expected brushite conversion to hydroxyapatite. This outcome would explain the recurrent detection of difficult to treat brushite stones, observed in the last three decades.

  9. NiTi superelasticity via atomistic simulations

    NASA Astrophysics Data System (ADS)

    Chowdhury, Piyas; Ren, Guowu; Sehitoglu, Huseyin

    2015-12-01

    The NiTi shape memory alloys (SMAs) are promising candidates for the next-generation multifunctional materials. These materials are superelastic i.e. they can fully recover their original shape even after fairly large inelastic deformations once the mechanical forces are removed. The superelasticity reportedly stems from atomic scale crystal transformations. However, very few computer simulations have emerged, elucidating the transformation mechanisms at the discrete lattice level, which underlie the extraordinary strain recoverability. Here, we conduct breakthrough molecular dynamics modelling on the superelastic behaviour of the NiTi single crystals, and unravel the atomistic genesis thereof. The deformation recovery is clearly traced to the reversible transformation between austenite and martensite crystals through simulations. We examine the mechanistic origin of the tension-compression asymmetries and the effects of pressure/temperature/strain rate variation isolatedly. Hence, this work essentially brings a new dimension to probing the NiTi performance based on the mesoscale physics under more complicated thermo-mechanical loading scenarios.

  10. Synthesis and electrochemical behavior of nanostructured cauliflower-shape Co-Ni/Co-Ni oxides composites

    SciTech Connect

    Gupta, Vinay Kawaguchi, Toshikazu; Miura, Norio

    2009-01-08

    Nanostructured Co-Ni/Co-Ni oxides were electrochemically deposited onto stainless steel electrode by electrochemical method and characterized for their structural and supercapacitive properties. The SEM images indicated that the obtained Co-Ni/Co-Ni oxides had cauliflower-type nanostructure. The X-ray diffraction pattern showed the formation of Co{sub 3}O{sub 4}, NiO, Co and Ni. The EDX elemental mapping images indicated that Ni, Co and O are distributed uniformly. The deposited Co-Ni/Co-Ni oxides showed good supercapacitive characteristics with a specific capacitance of 331 F/g at 1 mA/cm{sup 2} current density in 1 M KOH electrolyte. A mechanism of the formation of cauliflower-shape Co-Ni/Co-Ni oxides was proposed. A variety of promising applications in the fields such as energy storage devices and sensors can be envisioned from Co-Ni/Co-Ni oxides.

  11. Domain Structures and Anisotropy in Exchange-coupled [Co/Pd]-NiFe and [Co/Ni]-NiFe Multilayers

    NASA Astrophysics Data System (ADS)

    Tryputen, Larysa; Chung, Sunjae; Mohseni, Majid; Nguyen, T. N. Anh; Åkerman, Johan; Guo, Feng; McMichael, Robert D.; Ross, Caroline A.

    2014-03-01

    Exchange-coupled multilayers [Co/Pd]5-/NiFe and [Co/Ni]4-NiFe with strong perpendicular magnetic anisotropy have been proposed to use in spin-torque switching and oscillators devices with tilted fixed and free layer to improve their functional performance. We present an experimental study of the magnetization behavior of [Co/Pd]5-/NiFe and [Co/Ni]4-NiFe multilayers measured using magnetometry, magnetic force microscopy (MFM) and ferromagnetic resonance (FMR) as a function of the thickness of the top NiFe layer. We varied the thickness of the NiFe layer in [Co/Pd]5-NiFe (t), t = 0 - 80 nm and [Co/Ni]4-NiFe (t), t = 0.5 - 2.5 nm in order to study the interplay between perpendicular magnetization of the Co/Pd or Co/Ni multilayers and in-plane magnetization of the NiFe. Our magnetometry and FMR data suggest that the [Co/Ni]4/NiFe multilayer behaves like a homogeneous ferromagnetic film with anisotropy that reorients towards in-plane as the NiFe thickness increases, whereas the [Co/Pd]5/NiFe multilayer reveals more complex behavior in which the [Co/Pd] layer retains out-of-plane anisotropy while the magnetization of NiFe layer tilts in-plane with increasing thickness. MFM showed that domains with ~0.1 +/-m size were visible in [Co/Pd]-/NiFe with NiFe thickness of 20-80 nm. Multilayers were patterned into sub-100 nm dots using ion beam etching and their magnetization behavior are compared with unpatterned films.

  12. Solvotermal synthesis of NiO, Ni and NiS nanoparticles.

    PubMed

    Gutierrez, Angel; Perpiñán, M Felisa; Sánchez, Ana E; Torralba, M Carmen

    2013-01-01

    Nanoparticles of NiO, Ni or NiS have been obtained by solvothermal decomposition of different molecular precursors. The influence of several parameters, such as temperature, reaction time, solvent or capping agent used, in the nature and size of the obtained nanoparticle has been studied. The characterization by XRD and TEM techniques indicates that the nanoparticles of NiO exhibit average sizes of 3-8 nm, while those of Ni are in the 30-40 nm range. This difference in size has been attributed to the presence of molecules of the capping agent (n-octylamine or oleic acid) that surround the NiO nanoparticles but were not present in the nickel ones. The capping agent is, thus, preventing the aggregation of the smallest nanoparticles. The use of either a S-donor capping agent (4-mercaptopyridine) or a precursor having S-donor ligands (diethyldithiocarbamate) have led to the formation of NiS with average sizes around 35 nm. The magnetic properties of the nanoparticles have been studied, showing superparamagnetism and magnetic hysteresis below the blocking temperature, which, in time, is dependent of the particle size.

  13. The effects of alloy purity on the mechanical behavior of soft oriented NiAl single crystals

    NASA Technical Reports Server (NTRS)

    Weaver, M. L.; Kaufman, M. J.; Noebe, R. D.

    1993-01-01

    Preliminary results of the effects of alloy purity on the mechanical properties of NiAl single crystals are presented. Two stoichiometric NiAl single crystals with different impurity contents were studied. It is concluded that reductions in the interstitial and substitutional levels cause reduced yield strengths in NiAl. Heat treatment also results in reduced yield and flow stresses in both CP-NiAl and Hp-NiAl which are considered to be due to a reduction in the concentration of thermal vacancies due to vacancy coalescence during heat treatment.

  14. Neutron-capture rates for explosive nucleosynthesis: the case of 68Ni(n, γ)69Ni

    NASA Astrophysics Data System (ADS)

    Spyrou, A.; Larsen, A. C.; Liddick, S. N.; Naqvi, F.; Crider, B. P.; Dombos, A. C.; Guttormsen, M.; Bleuel, D. L.; Couture, A.; Crespo Campo, L.; Lewis, R.; Mosby, S.; Mumpower, M. R.; Perdikakis, G.; Prokop, C. J.; Quinn, S. J.; Renstrøm, T.; Siem, S.; Surman, R.

    2017-04-01

    Neutron-capture reactions play an important role in heavy element nucleosynthesis, since they are the driving force for the two processes that create the vast majority of the heavy elements. When a neutron capture occurs on a short-lived nucleus, it is extremely challenging to study the reaction directly and therefore the use of indirect techniques is essential. The present work reports on such an indirect measurement that provides strong constraints on the 68Ni(n, γ)69Ni reaction rate. This is done by populating the compound nucleus 69Ni via the β decay of 69Co and measuring the γ-ray deexcitation of excited states in 69Ni. The β-Oslo method was used to extract the γ-ray strength function and the nuclear level density. In addition the half-life of 69Co was extracted and found to be in agreement with previous literature values. Before the present results, the 68Ni(n, γ)69Ni reaction was unconstrained and the purely theoretical reaction rate was highly uncertain. The new uncertainty on the reaction rate based on the present experiment (variation between upper and lower limit) is approximately a factor of 3. The commonly used reaction libraries JINA-REACLIB and BRUSLIB are in relatively good agreement with the experimental rate. The impact of the new rate on weak r-process calculations is discussed.

  15. Shape coexistence in 68Ni

    NASA Astrophysics Data System (ADS)

    Suchyta, S.; Liddick, S.; Bennet, M.; Larson, N.; Prokop, C.; Quinn, S.; Spyrou, A.; Chemey, A.; Simon, A.; Otsuka, T.; Tsunoda, Y.; Shimizu, N.; Honma, M.; Utsuno, Y.; Tripath, V.; Vonmoss, J.

    2013-10-01

    68 Ni has been a focus of recent work aiming to understand the apparent rapid development of collectivity along neutron-rich N = 40 nuclei, but despite many studies, is not entirely understood. The decay of the first excited 0+ state in 68Ni was investigated at the NSCL. Ions of 68Co were implanted into a planar germanium double-sided strip detector (GeDSSD). The beta decay of 68Co populated the first excited 0+ state in 68Ni and within hundreds of nanoseconds the decay of the first excited 0+ state was measured in the GeDSSD. Both the energy of the first excited 0+ state and the electric monopole transition strength from the first excited 0+ state were precisely determined. Comparisons to Monte Carlo Shell Model calculations suggest shape coexistence between spherical ground and oblate first excited 0+ states in 68Ni. The experimental results and theoretical interpretation will be presented.

  16. Microstructure, mechanical properties and superelasticity of biomedical porous NiTi alloy prepared by microwave sintering.

    PubMed

    Xu, J L; Bao, L Z; Liu, A H; Jin, X J; Tong, Y X; Luo, J M; Zhong, Z C; Zheng, Y F

    2015-01-01

    Porous NiTi alloys were prepared by microwave sintering using ammonium hydrogen carbonate (NH4HCO3) as the space holder agent to adjust the porosity in the range of 22-62%. The effects of porosities on the microstructure, hardness, compressive strength, bending strength, elastic modulus, phase transformation temperature and superelasticity of the porous NiTi alloys were investigated. The results showed that the porosities and average pore sizes of the porous NiTi alloys increased with increasing the contents of NH4HCO3. The porous NiTi alloys consisted of nearly single NiTi phase, with a very small amount of two secondary phases (Ni3Ti, NiTi2) when the porosities are lower than 50%. The amount of Ni3Ti and NiTi2 phases increased with further increasing of the porosity proportion. The porosities had few effects on the phase transformation temperatures of the porous NiTi alloys. By increasing the porosities, all of the hardness, compressive strength, elastic modulus, bending strength and superelasticity of the porous NiTi alloys decreased. However, the compressive strength and bending strength were higher or close to those of natural bone and the elastic modulus was close to the natural bone. The superelastic recovery strain of the trained porous NiTi alloys could reach between 3.1 and 4.7% at the pre-strain of 5%, even if the porosity was up to 62%. Moreover, partial shape memory effect was observed for all porosity levels under the experiment conditions. Therefore, the microwave sintered porous NiTi alloys could be a promising candidate for bone implant. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Fate of half-metallicity near interfaces: the case of NiMnSb/MgO and NiMnSi/MgO.

    PubMed

    Zhang, Rui-Jing; Eckern, Ulrich; Schwingenschlögl, Udo

    2014-08-27

    The electronic and magnetic properties of the interfaces between the half-metallic Heusler alloys NiMnSb, NiMnSi, and MgO have been investigated using first-principles density-functional calculations with projector augmented wave potentials generated in the generalized gradient approximation. In the case of the NiMnSb/MgO (100) interface, the half-metallicity is lost, whereas the MnSb/MgO contact in the NiMnSb/MgO (100) interface maintains a substantial degree of spin polarization at the Fermi level (∼60%). Remarkably, the NiMnSi/MgO (111) interface shows 100% spin polarization at the Fermi level, despite considerable distortions at the interface, as well as rather short Si/O bonds after full structural optimization. This behavior markedly distinguishes NiMnSi/MgO (111) from the corresponding NiMnSb/CdS and NiMnSb/InP interfaces.

  18. Density functional theory study on the interactions between Ni(n) (n = 1,..., 6) and methylamine or acetic acid.

    PubMed

    Wei, Fadong; Liu, Wei; Lv, Gang; Jiang, Hui; Wang, Xuemei

    2013-06-01

    The interactions between methylamine or acetic acid with the Ni(n) (n = 1,...,6) in triplet clusters were examined at the B3LYP/6-31G(d, p) and LANL2TZ+ level. The structural stability, interacting strength and the charge transferring properties of the different interacting complexes were studied. The stable distance between the Ni(1) and the nitrogen or oxygen is about 2.00 or 1.95 angstroms for the Ni(n)-CH3NH2 or Ni(n)-CH3COOH, respectively. The results indicate that the interacting energy is -27.385 approximatley -134.269 and -18.379 approximately -55.136 kJ/mol for the Ni(n)-CH3NH2 and Ni(n)-CH3COOH, respectively. The effective electron transfer processes for the Ni(n)-CH3NH2 or Ni(n)-CH3COOH is from the lone pair of the nitrogen to the lone pair anti-bonding orbital of the Ni(1) or from the oxygen lone pair to the sigma antibonding orbitals of Ni(1)-Ni and the sigma anti-bonding orbital of the Ni(1) lone pair, respectively.

  19. Abnormal Intermetallic Compound Evolution in Ni/Sn/Ni and Ni/Sn-9Zn/Ni Micro Solder Joints Under Thermomigration

    NASA Astrophysics Data System (ADS)

    Zhao, N.; Deng, J. F.; Zhong, Y.; Huang, M. L.; Ma, H. T.

    2017-04-01

    Interfacial reactions in Ni/Sn/Ni and Ni/Sn-9Zn/Ni micro solder joints during thermomigration (TM) have been studied by reflowing solder joints on a hot plate. Asymmetrical growth and transformation of interfacial intermetallic compounds (IMCs) were clearly observed. The growth of the Ni3Sn4 IMC in the Ni/Sn/Ni solder joints was always fast at the cold end and relatively slow at the hot end. Only asymmetrical growth of the Ni5Zn21 IMC in the Ni/Sn-9Zn/Ni solder joints occurred at the beginning because Zn was the dominant TM species; however, asymmetrical transformation of the Ni5Zn21 IMC also occurred under the combined effect of Zn depletion and Ni dissolution and migration, resulting in formation of a thin τ-phase layer at the hot end and a thick τ-phase/Ni5Zn21/τ-phase sandwich structure at the cold end. TM of Ni and Zn atoms was identified towards the cold end, being responsible for the abnormal IMC evolution. Addition of Zn was found to slow the TM-induced IMC growth and Ni dissolution.

  20. Measurement of 59Ni and 63Ni by accelerator mass spectrometry at CIAE

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoming; He, Ming; Ruan, Xiangdong; Xu, Yongning; Shen, Hongtao; Du, Liang; Xiao, Caijin; Dong, Kejun; Jiang, Shan; Yang, Xuran; Lan, Xiaoxi; Wu, Shaoyong; Zhao, Qingzhang; Cai, Li; Pang, Fangfang

    2015-10-01

    The long lived isotopes 59Ni and 63Ni can be used in many areas such as radioactive waste management, neutron dosimetry, cosmic radiation study, and so on. Based on the large accelerator and a big Q3D magnetic spectrometer, the measurement method for 59Ni and 63Ni is under development at the AMS facility at China Institute of Atomic Energy (CIAE). By using the ΔE-Q3D technique with the Q3D magnetic spectrometer, the isobaric interferences were greatly reduced in the measurements of 59Ni and 63Ni. A four anode gas ionization chamber was then used to further identify isobars. With these techniques, the abundance sensitivities of 59Ni and 63Ni measurements are determined as 59Ni/Ni = 1 × 10-13 and 63Ni/Ni = 2 × 10-12, respectively.

  1. Interaction of Nickel and Manganese in Accumulation and Localization in Leaves of the Ni Hyperaccumulators Alyssum murale and Alyssum corsicum

    SciTech Connect

    Broadhurst, C.; Tappero, R; Maugel, T; Erbe, E; Sparks, D; Chaney, R

    2009-01-01

    The genus Alyssum contains >50 Ni hyperaccumulator species; many can achieve >2.5% Ni in dry leaf. In soils with normal Mn levels, Alyssum trichome bases were previously observed to accumulate Ni and Mn to high levels. Here we report concentration and localization patterns in A. murale and A. corsicum grown in soils with nonphytotoxic factorial additions of Ni and Mn salts. Four leaf type subsets based on size and age accumulated Ni and Mn similarly. The greatest Mn accumulation (10 times control) was observed in A. corsicum with 40 mmol Mn kg-1 and 40 mmol Ni kg-1 added to potting soil. Whole leaf Ni concentrations decreased as Mn increased. Synchrotron X-ray fluorescence mapping of whole fresh leaves showed localized in distinct high-concentration Mn spots associated with trichomes, Ni and Mn distributions were strongly spatially correlated. Standard X-ray fluorescence point analysis/mapping of cryofractured and freeze-dried samples found that Ni and Mn were co-located and strongly concentrated only in trichome bases and in cells adjacent to trichomes. Nickel concentration was also strongly spatially correlated with sulfur. Results indicate that maximum Ni phytoextraction by Alyssum may be reduced in soils with higher phytoavailable Mn, and suggest that Ni hyperaccumulation in Alyssum species may have developed from a Mn handling system.

  2. Accessing Ni(III)-thiolate versus Ni(II)-thiyl bonding in a family of Ni-N2S2 synthetic models of NiSOD.

    PubMed

    Broering, Ellen P; Dillon, Stephanie; Gale, Eric M; Steiner, Ramsey A; Telser, Joshua; Brunold, Thomas C; Harrop, Todd C

    2015-04-20

    Superoxide dismutase (SOD) catalyzes the disproportionation of superoxide (O2(• -)) into H2O2 and O2(g) by toggling through different oxidation states of a first-row transition metal ion at its active site. Ni-containing SODs (NiSODs) are a distinct class of this family of metalloenzymes due to the unusual coordination sphere that is comprised of mixed N/S-ligands from peptide-N and cysteine-S donor atoms. A central goal of our research is to understand the factors that govern reactive oxygen species (ROS) stability of the Ni-S(Cys) bond in NiSOD utilizing a synthetic model approach. In light of the reactivity of metal-coordinated thiolates to ROS, several hypotheses have been proffered and include the coordination of His1-Nδ to the Ni(II) and Ni(III) forms of NiSOD, as well as hydrogen bonding or full protonation of a coordinated S(Cys). In this work, we present NiSOD analogues of the general formula [Ni(N2S)(SR')](-), providing a variable location (SR' = aryl thiolate) in the N2S2 basal plane coordination sphere where we have introduced o-amino and/or electron-withdrawing groups to intercept an oxidized Ni species. The synthesis, structure, and properties of the NiSOD model complexes (Et4N)[Ni(nmp)(SPh-o-NH2)] (2), (Et4N)[Ni(nmp)(SPh-o-NH2-p-CF3)] (3), (Et4N)[Ni(nmp)(SPh-p-NH2)] (4), and (Et4N)[Ni(nmp)(SPh-p-CF3)] (5) (nmp(2-) = dianion of N-(2-mercaptoethyl)picolinamide) are reported. NiSOD model complexes with amino groups positioned ortho to the aryl-S in SR' (2 and 3) afford oxidized species (2(ox) and 3(ox)) that are best described as a resonance hybrid between Ni(III)-SR and Ni(II)-(•)SR based on ultraviolet-visible (UV-vis), magnetic circular dichroism (MCD), and electron paramagnetic resonance (EPR) spectroscopies, as well as density functional theory (DFT) calculations. The results presented here, demonstrating the high percentage of S(3p) character in the highest occupied molecular orbital (HOMO) of the four-coordinate reduced form of NiSOD (Ni

  3. Low salinity enhances NI-mediated oxidative stress and sub-lethal toxicity to the green shore crab (Carcinus maenas).

    PubMed

    Blewett, Tamzin A; Wood, Chris M

    2015-12-01

    Nickel (Ni) is a metal of environmental concern, known to cause toxicity to freshwater organisms by impairing ionoregulation and/or respiratory gas exchange, and by inducing oxidative stress. However, little is known regarding how nickel toxicity is influenced by salinity. In the current study we investigated the salinity-dependence and mechanisms of sub-lethal Ni toxicity in a euryhaline crab (Carcinus maenas). Crabs were acclimated to three experimental salinities--20, 60 and 100% seawater (SW)--and exposed to 3mg/L Ni for 24h or 96 h. Tissues were dissected for analysis of Ni accumulation, gills were taken for oxidative stress analysis (catalase activity and protein carbonyl content), haemolymph ions were analysed for ionoregulatory disturbance, and oxygen consumption was determined in exercised crabs after 96 h of Ni exposure. Total Ni accumulation was strongly dependant on salinity, with crabs from 20% SW displaying the highest tissue Ni burdens after both 24 and 96-h exposures. After 96 h of exposure, the highest accumulation of Ni occurred in the posterior (ionoregulatory) gills at the lowest salinity, 20% SW. Posterior gill 8 exhibited elevated protein carbonyl levels and decreased catalase activity after Ni exposure, but only in 20% SW. Similarly, decreased levels of haemolymph Mg and K and an increased level of Ca were recorded but only in crabs exposed to Ni for 96 h in 20% SW. Oxygen consumption after exercise was also inhibited in crabs exposed to Ni in 20% SW. These data show for the first time the simultaneous presence of all three modes of sub-lethal Ni toxicity in exposed animals, and indicate a strong salinity dependence of sub-lethal Ni toxicity to the euryhaline crab, C. maenas, a pattern that corresponded to tissue Ni accumulation.

  4. Isolation and characterization of Ni mobilizing PGPB from serpentine soils and their potential in promoting plant growth and Ni accumulation by Brassica spp.

    PubMed

    Ma, Ying; Rajkumar, Mani; Freitas, Helena

    2009-05-01

    The study was undertaken to assess the effects of Ni mobilizing bacteria on the plant growth and the uptake of Ni by Brassica juncea and Brassica oxyrrhina. Among a collection of Ni resistant bacterial strains isolated from the non-rhizosphere and rhizosphere soils of Alyssum serpyllifolium and Astragalus incanus at a serpentine site in Bragança, north-east of Portugal, nine strains were selected based on their ability to solubilize Ni in soil. Further assessment on plant growth-promoting parameters revealed the intrinsic ability of the Ni mobilizing strains to produce indole-3-acetic acid (IAA), siderophores, utilize 1-aminocyclopropane-1-carboxylic acid (ACC) as the sole N source and solubilize insoluble phosphate. All of the strains tested positive for IAA production and phosphate solubilization. In addition, all the strains, except SRS5 exhibited significant levels of siderophore production. Besides, five isolates showed positive for ACC deaminase activity. In pot experiments, inoculation of plants with Ni mobilizing strains increased the biomass of both B. juncea and B. oxyrrhina. Among the strains, Pseudomonas sp. SRI2, Psychrobacter sp. SRS8 and Bacillus sp. SN9 showed maximum increase in the biomass of the test plants. In addition, the strain SN9 significantly increased the Ni concentration in the root and shoot tissues of B. juncea and B. oxyrrhina. Further, a significantly positive correlation was observed between the bacterial Ni mobilization in soil and the total Ni uptake in both plant species. The findings, therefore, revealed that inoculation of Ni mobilizing plant growth-promoting bacterial strain SN9 increases the efficiency of phytoextraction directly by enhancing Ni accumulation in plant tissues and indirectly by promoting the shoot and root biomass of B. juncea and B. oxyrrhina.

  5. Spatiotemporal change of intraseasonal oscillation intensity over the tropical Indo-Pacific Ocean associated with El Niño and La Niña events

    NASA Astrophysics Data System (ADS)

    Wu, Renguang; Song, Lei

    2017-04-01

    The present study analyzes the intraseasonal oscillation (ISO) intensity change over the tropical Indo-Pacific associated with the El Niño-Southern Oscillation (ENSO) and compares the intensity change between El Niño and La Niña years and between the 10-20-day and 30-60-day ISOs. The ISO intensity change tends to be opposite between El Niño and La Niña years in the developing and mature phases. The intensity change features a contrast between the tropical southeastern Indian Ocean and the tropical western North Pacific (WNP) in the developing phases and between the Maritime Continent and the tropical central Pacific in the mature phase. In the decaying phases, the intensity change shows notable differences between El Niño and La Niña events and between fast and slow decaying El Niño events. Large intensity change is observed over the tropical WNP in the developing summer, over the tropical southeastern Indian Ocean in the developing fall, and over the tropical WNP in the fast decaying El Niño summer due to a combined effect of vertical shear, vertical motion, and lower-level moisture. In the ENSO developing summer and in the El Niño decaying summer, the 10-20-day ISO intensity change displays a northwest-southeast tilted distribution over the tropical WNP, whereas the large 30-60-day ISO intensity change is confined to the off-equatorial WNP. In the La Niña decaying summer, the 30-60-day ISO intensity change features a large zonal contrast across the Philippines, whereas the 10-20-day ISO intensity anomaly is characterized by a north-south contrast over the tropical WNP.

  6. Magnetic properties and electronic structure of Mn-Ni-Ga magnetic shape memory alloys.

    PubMed

    D'Souza, Sunil Wilfred; Roy, Tufan; Barman, Sudipta Roy; Chakrabarti, Aparna

    2014-12-17

    Influence of disorder, antisite defects, martensite transition and compositional variation on the magnetic properties and electronic structure of Mn(2)NiGa and Mn(1+x)Ni(2-x)Ga magnetic shape memory alloys have been studied by using full potential spin-polarized scalar relativistic Korringa-Kohn-Rostocker (FP-SPRKKR) method. Mn(2)NiGa is ferrimagnetic and its total spin moment increases when disorder in the occupancy of MnNi (Mn atom in Ni position) is considered. The moment further increases when Mn-Ga antisite defect [1] is included in the calculation. A reasonable estimate of TC for Mn(2)NiGa is obtained from the exchange parameters for the disordered structure. Disorder influences the electronic structure of Mn(2)NiGa through overall broadening of the density of states and a decrease in the exchange splitting. Inclusion of antisite defects marginally broaden the minority spin partial DOS (PDOS), while the majority spin PDOS is hardly affected. For Mn(1+x)Ni(2-x)Ga where 1 ⩾ x ⩾ 0, as x decreases, Mn(Mn) moment increases while Mn(Ni) moment decreases in both austenite and martensite phases. For x ⩾ 0.25, the total moment of the martensite phase is smaller compared to the austenite phase, which indicates possible occurrence of inverse magnetocaloric effect. We find that the redistribution of Ni 3d- Mn(Ni) 3d minority spin electron states close to the Fermi level is primarily responsible for the stability of the martensite phase in Mn-Ni-Ga.

  7. Schottky diode behaviour with excellent photoresponse in NiO/FTO heterostructure

    NASA Astrophysics Data System (ADS)

    Saha, B.; Sarkar, K.; Bera, A.; Deb, K.; Thapa, R.

    2017-10-01

    Delocalization of charge carriers through formation of native defects in NiO, to achieve a good metal oxide hole transport layer was attemted in this work and thus a heterojunction of p-type NiO and n-type FTO have been prepared through sol-gel process on FTO coated glass substrate. The synthesis process was stimulated by imparting large number of OH- sites during nucleation of Ni(OH)2 on FTO, so that during oxidation through annealing Ni vacancies are introduced. The structural properties as observed from X-ray diffraction measurement indicate formation of well crystalline NiO nanoparticles. Uniform distribution of NiO nanoparticles has been observed in the images obtained from scanning electron microscope. The occurrence of p-type conductivity in the NiO film was stimulated through the formation of delocalized defect carriers originated from crystal defects like vacancies or interstitials in the lattice. Ni vacancy creates shallow levels with respect to the valance band maxima and they readily produce holes. Thus a native p-type conductivity of NiO originates from Ni vacancies. NiO was thus obtained as an auspicious hole transport medium, which creates an expedient heterojunction at the interface with FTO. Excellent rectifying behavior was observed in the electrical J-V plot obtained from the prepared heterojunction. The results are explained from the band energy diagram of the NiO/FTO heterojunction. Remarkable photoresponse has been observed in the reverse characteristics of the heterojunction caused by photon generated electron hole pairs.

  8. Static atomic displacements in Ni-rich Ni-Al

    NASA Astrophysics Data System (ADS)

    Schönfeld, B.; Kostorz, G.; Celino, M.; Rosato, V.

    2001-05-01

    Short-range order and static atomic displacement parameters, previously determined from diffuse neutron scattering for Ni-8.9 at.% Al equilibrated at 775 K and quenched to room temperature, were used to study lattice relaxation effects in molecular-dynamics simulations. An occupation of average lattice sites with Ni and Al atoms compatible with the short-range ordered state was taken as the starting situation. Displacement parameters obtained from the relaxation simulations and from diffuse neutron scattering show general similarity in magnitude and dependence on distance. Also, the species dependence of the displacement parameters known from diffuse X-ray scattering investigations is reproduced in magnitude.

  9. Synthesis and Characterization of Pure Ni and Ni-Sn Intermetallic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Yakymovych, A.; Ipser, H.

    2017-02-01

    The present research focused on the synthesis of Ni and Ni-Sn nanoparticles via a chemical reduction method using hydrazine hydrate. The syntheses were performed applying highly purified water or diethylene glycol as solvent. The produced nanoparticles were characterized by scanning electron microscopy and powder X-ray diffraction. The as-synthesized Ni-Sn nanoparticles with nominal starting ratios Ni:Sn = 3:1, 3:2, and 3:4 consisted of different amounts of pure Ni and a low-temperature Ni3Sn2 phase. It was found that all synthesized nanopowders had a spherical shape with the largest average size for pure Ni and decreasing size for particles containing Sn. X-ray diffraction showed that all synthesized nanoparticles contained Ni and a low-temperature Ni3Sn2 phase independent of the initial molar ratio; while Ni3Sn and Ni3Sn4 could not be detected.

  10. Hubble Space Telescope NiH2 six battery test

    NASA Technical Reports Server (NTRS)

    Whitt, Thomas H.; Lanier, J. Roy

    1991-01-01

    The primary objectives of the test are: (1) to get a better understanding of the operating characteristics of the NiH2 batteries in the Hubble Space Telescope (HST) Electric Power Subsystem (EPS) by simulating every aspect of the expected operating environment; (2) to determine the optimum charge level and charge scheme for the NiH2 batteries in the HST EPS; (3) to predict the performance of the actual HST EPS; (4) to observe the aging characteristics of the batteries; and (5) to test different EPS anomalies before experiencing the anomalies on the actual HST.

  11. Hubble Space Telescope NiH2 six battery test

    NASA Technical Reports Server (NTRS)

    Whitt, Thomas H.; Lanier, J. Roy

    1991-01-01

    The primary objectives of the test are: (1) to get a better understanding of the operating characteristics of the NiH2 batteries in the Hubble Space Telescope (HST) Electric Power Subsystem (EPS) by simulating every aspect of the expected operating environment; (2) to determine the optimum charge level and charge scheme for the NiH2 batteries in the HST EPS; (3) to predict the performance of the actual HST EPS; (4) to observe the aging characteristics of the batteries; and (5) to test different EPS anomalies before experiencing the anomalies on the actual HST.

  12. Ferromagnetism in antiferromagnetic NiO-based thin films

    NASA Astrophysics Data System (ADS)

    Lin, Yuan-Hua; Zhan, Bin; Nan, Ce-Wen; Zhao, Rongjuan; Xu, Xiang; Kobayashi, M.

    2011-08-01

    Polycrystalline NiO-based thin films with Li or/and transition metal ions (V, Cr, Mn, Fe, Co, Cu, Zn) doping have been prepared by a sol-gel spin-coating method. Magnetization measurements reveal that V-, Fe-, and Mn-doped NiO thin films show obvious room-temperature ferromagnetic behaviors and ferromagnetic properties can be enhanced by the Li co-doping. Microstructure and X-ray core-level photoemission spectra analysis indicate that the ferromagnetism was not from the impurity TM metal cluster and may be ascribed to double exchange coupling effects via Li-induced holes.

  13. Preparation and property of duplex Ni-B-TiO2/Ni nano-composite coatings

    NASA Astrophysics Data System (ADS)

    Wang, Shu-Jen; Wang, Yuxin; Shu, Xin; Tay, Seeleng; Gao, Wei; Shakoor, R. A.; Kahraman, Ramazan

    2015-03-01

    The duplex Nickel-Boron-Titania/Nickel (Ni-B-TiO2/Ni) coatings were deposited on mild steel by using two baths with Ni as the inner layer. TiO2 nanoparticles were incorporated into the Ni-B coatings as the outer layer by using solid particle mixing method. The microstructure, morphology and corrosion resistance of the duplex Ni-B-TiO2/Ni nanocomposite coatings were systemically investigated. The results show that the duplex interface was uniform and the adhesion between two layers was very good. The microhardness of duplex Ni-B-TiO2/Ni coating was much higher than the Ni coating due to the outer layer of Ni-B-TiO2 coating. The corrosion resistance of the duplex Ni-B-TiO2/Ni coating was also significantly improved comparing with single Ni-B coating. The Ni-B-10 g/L TiO2/Ni coating was found to have the best corrosion resistance among these duplex coatings. This type of duplex Ni-B-TiO2/Ni coating, with high hardness and good corrosion resistance properties, should be able to find broad applications under adverse environmental conditions.

  14. Effect of the Ar-Ni(s) potential on the cross section for Ar+CH4/Ni{111} collision-induced desorption and the need for a more accurate CH4/Ni{111} potential

    NASA Astrophysics Data System (ADS)

    Sun, Lipeng; Peterson, Kirk A.; Alexeev, Yuri; Windus, Theresa; Kindt, James; Hase, William L.

    2005-01-01

    In a previous paper [L. Sun, P. de Sainte Claire, O. Meroueh, and W. L Hase, J. Chem. Phys. 114, 535 (2001)], a classical trajectory simulation was reported of CH4 desorption from Ni{111} by Ar-atom collisions. At an incident angle θi of 60° (with respect to the surface normal), the calculated collision-induced desorption (CID) cross sections are in excellent agreement with experiment. However, for smaller incident angles the calculated cross sections are larger than the experimental values and for normal collisions, θi=0°, the calculated cross sections are approximately a factor of 2 larger. This trajectory study used an analytic function for the Ar+Ni(s) intermolecular potential which gives an Ar-Ni{111} potential energy minimum which is an order of magnitude too deep. In the work reported here, the previous trajectory study is repeated with an Ar+Ni(s) analytic intermolecular potential which gives an accurate Ar-Ni{111} potential energy minimum and also has a different surface corrugation than the previous potential. Though there are significant differences between the two Ar+Ni(s) analytic potentials, they have no important effects on the CID dynamics and the cross sections reported here are nearly identical to the previous values. Zero-point energy motions of the surface and the CH4-Ni(s) intermolecular modes are considered in the simulation and they are found to have a negligible effect on the CID cross sections. Calculations of the intermolecular potential between CH4 and a Ni atom, at various levels of theory, suggest that there are substantial approximations in the ab initio calculation used to develop the CH4+Ni{111} potential. The implication is that the differences between the trajectory and experimental CID cross sections may arise from an inaccurate CH4+Ni{111} potential used in the trajectory simulation.

  15. Shape coexistence in Ni68

    NASA Astrophysics Data System (ADS)

    Suchyta, S.; Liddick, S. N.; Tsunoda, Y.; Otsuka, T.; Bennett, M. B.; Chemey, A.; Honma, M.; Larson, N.; Prokop, C. J.; Quinn, S. J.; Shimizu, N.; Simon, A.; Spyrou, A.; Tripathi, V.; Utsuno, Y.; VonMoss, J. M.

    2014-02-01

    The internal-conversion and internal-pair-production decays of the first excited 0+ state in Ni68 are studied following the β decay of Co68. A novel experimental technique, in which the ions of Co68 were implanted into a planar germanium double-sided strip detector and which required digital pulse processing, is developed. The values for the energy of the first excited 0+ state and the electric monopole transition strength from the first excited 0+ state to the ground state in Ni68 are determined to be 1605(3) keV and 7.6(4)×10-3, respectively. Comparisons of the experimental results to Monte Carlo shell-model calculations suggest the coexistence between a spherical ground state and an oblate first excited 0+ state in Ni68.

  16. Nuclear Magnetic Resonance Reveals Disordered Level-Crossing Physics in the Bose-Glass Regime of the Br-Doped Ni(Cl_{1-x}Br_{x})_{2}-4SC(NH_{2})_{2} Compound at a High Magnetic Field.

    PubMed

    Orlova, Anna; Blinder, Rémi; Kermarrec, Edwin; Dupont, Maxime; Laflorencie, Nicolas; Capponi, Sylvain; Mayaffre, Hadrien; Berthier, Claude; Paduan-Filho, Armando; Horvatić, Mladen

    2017-02-10

    By measuring the nuclear magnetic resonance (NMR) T_{1}^{-1} relaxation rate in the Br (bond) doped DTN compound, Ni(Cl_{1-x}Br_{x})_{2}-4SC(NH_{2})_{2}(DTNX), we show that the low-energy spin dynamics of its high magnetic field "Bose-glass" regime is dominated by a strong peak of spin fluctuations found at the nearly doping-independent position H^{*}≅13.6  T. From its temperature and field dependence, we conclude that this corresponds to a level crossing of the energy levels related to the doping-induced impurity states. Observation of the local NMR signal from the spin adjacent to the doped Br allowed us to fully characterize this impurity state. We have thus quantified a microscopic theoretical model that paves the way to better understanding of the Bose-glass physics in DTNX, as revealed in the related theoretical study [M. Dupont, S. Capponi, and N. Laflorencie, Phys. Rev. Lett. 118, 067204 (2017).PRLTAO0031-900710.1103/PhysRevLett.118.067204].

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  18. Relativistic R-Matrix Close-Coupling Calculations for Photoionization of Si-Like Ni XV

    NASA Astrophysics Data System (ADS)

    Singh, Jagjit; Jha, A. K. S.; Mohan, Man

    2010-02-01

    We present relativistic close-coupling photoionization calculations of Ni XV using the Breit-Pauli R-matrix method to obtain photoionization cross section of Ni XV from the ground state 3s 23p 2(3 P 0) and the lowest four 3s 23p 2 (3 P 1,2, 1 D 2, 1 S 0) excited states. A multiconfiguration eigenfunction expansion of the core Ni XVI is employed with configurations 3s 23p, 3s3p 2, 3s 23d, 3p 3, 3s3p3d, 3p 23d, 3s3d 2, 3p3d 2. We have included the lowest 40 target level states of Ni XVI in the photoionization calculations of Ni XV. Cross sections are determined by the Rydberg series of autoionizing resonances converging to several ionic states of Ni XVI. In our calculations, we have taken into account all the important physical effects such as exchange, channel coupling, and short-range correlation. Further, relativistic effects are incorporated by including mass correction, Darwin term, and spin-orbit interaction terms. The present calculations using the lowest 40 target levels of Ni XVI are presented for the first time and can be useful for modeling the ionization balance of Ni XV in laboratory and astrophysical plasmas.

  19. RELATIVISTIC R-MATRIX CLOSE-COUPLING CALCULATIONS FOR PHOTOIONIZATION OF Si-LIKE Ni XV

    SciTech Connect

    Singh, Jagjit; Jha, A. K. S.; Mohan, Man

    2010-02-01

    We present relativistic close-coupling photoionization calculations of Ni XV using the Breit-Pauli R-matrix method to obtain photoionization cross section of Ni XV from the ground state 3s {sup 2}3p {sup 2}({sup 3} P {sub 0}) and the lowest four 3s {sup 2}3p {sup 2} ({sup 3} P {sub 1,2}, {sup 1} D {sub 2}, {sup 1} S {sub 0}) excited states. A multiconfiguration eigenfunction expansion of the core Ni XVI is employed with configurations 3s {sup 2}3p, 3s3p {sup 2}, 3s {sup 2}3d, 3p {sup 3}, 3s3p3d, 3p {sup 2}3d, 3s3d {sup 2}, 3p3d {sup 2}. We have included the lowest 40 target level states of Ni XVI in the photoionization calculations of Ni XV. Cross sections are determined by the Rydberg series of autoionizing resonances converging to several ionic states of Ni XVI. In our calculations, we have taken into account all the important physical effects such as exchange, channel coupling, and short-range correlation. Further, relativistic effects are incorporated by including mass correction, Darwin term, and spin-orbit interaction terms. The present calculations using the lowest 40 target levels of Ni XVI are presented for the first time and can be useful for modeling the ionization balance of Ni XV in laboratory and astrophysical plasmas.

  20. Informatics competencies for nurses at four levels of practice.

    PubMed

    Staggers, N; Gassert, C A; Curran, C

    2001-10-01

    Valid and comprehensive nursing informatics (NI) competencies currently are lacking. Meanwhile, nursing leaders are emphasizing the need to include NI in nursing curricula, as well as within the roles of practicing nurses in all settings. This article presents the initial work of a team of NI experts toward development of a valid and reliable set of NI competencies. Previous work primarily has focused on computer-related skills, rather than examining a broad definition of informatics competencies. For this current work, NI competencies encompass all skills, not only computer-related skills, as well as knowledge and attitudes needed by nurses. The first two authors created a database of NI competencies from the existing literature. A larger panel of NI experts then affirmed, modified, added, or deleted competencies from this database. Competencies were placed into four distinct skill levels. Definitions of each skill level and an initial master list of competencies are provided.

  1. Thermal modeling of NiH2 batteries

    NASA Technical Reports Server (NTRS)

    Ponthus, Agnes-Marie; Alexandre, Alain

    1994-01-01

    The following are discussed: NiH2 battery mission and environment; NiH2 cell heat dissipation; Nodal software; model development general philosophy; NiH2 battery model development; and NiH2 experimental developments.

  2. Dominating Role of Ni(0) on the Interface of Ni/NiO for Enhanced Hydrogen Evolution Reaction.

    PubMed

    Wang, Jing; Mao, Shanjun; Liu, Zeyan; Wei, Zhongzhe; Wang, Haiyan; Chen, Yiqing; Wang, Yong

    2017-03-01

    The research of a robust catalytic system based on single NiOx electrocatalyst for hydrogen evolution reaction (HER) remains a huge challenge. Particularly, the factors that dominate the catalytic properties of NiOx-based hybrids for HER have not been clearly demonstrated. Herein, a convenient protocol for the fabrication of NiOx@bamboo-like carbon nanotube hybrids (NiOx@BCNTs) is designed. The hybrids exhibit superb catalytic ability and considerable durability in alkaline solution. A benchmark HER current density of 10 mA cm(-2) has been achieved at an overpotential of ∼79 mV. In combination with the experimental results and density functional theory (DFT) calculations, this for the first time definitely validates that the inherent high Ni(0) ratio and the Ni(0) on the interface of Ni/NiO play a vital role in the outstanding catalytic performance. Especially, the Ni(0) on the interface of Ni/NiO performs superior activity for water splitting compared with that of bulk Ni(0). These conclusions provide guidance for the rational design of the future non-noble metallic catalysts.

  3. Comprehensive theoretical studies on the low-lying electronic states of NiF, NiCl, NiBr, and NiI.

    PubMed

    Zou, Wenli; Liu, Wenjian

    2006-04-21

    The low-lying electronic states of the nickel monohalides, i.e., NiF, NiCl, NiBr, and NiI, are investigated by using multireference second-order perturbation theory with relativistic effects taken into account. For the energetically lowest 11 lambda-S states and 26 omega states there into, the potential energy curves and corresponding spectroscopic constants (vertical and adiabatic excitation energies, equilibrium bond lengths, vibrational frequencies, and rotational constants) are reported. The calculated results are grossly in very good agreement with those solid experimental data. In particular, the ground state of NiI is shown to be different from those of NiF, NiCl, and NiBr, being in line with the recent experimental observation. Detailed analyses are provided on those states that either have not been assigned or have been incorrectly assigned by previous experiments.

  4. El Niño/La Niña shelf edge flow and Australian western rock lobsters

    NASA Astrophysics Data System (ADS)

    Clarke, A. J.; Li, J.

    2004-06-01

    Due to the leak in the gappy western equatorial Pacific, sea level (SL) is highly correlated with El Niño all along the western Australian coast. According to standard theory, this coastal interannual (IA) signal should propagate westward as Rossby waves with large zonal scale. High-resolution satellite SL estimates show that along the shelf edge south of 23°S the IA SL signal does not have the expected large spatial scale as it decreases rapidly seaward from the shelf edge. The drop in IA SL amplitude coincides with the mean position of the Leeuwin Current (LC). Theory shows how a nearly meridional mean flow, as in the case of the LC, can induce this fall in IA signal amplitude. The associated IA shelf-edge flow tends to strengthen the LC during La Niña, weaken it during El Niño and may profoundly affect the recruitment of the western rock lobster.

  5. Density functional theory study of the interfacial properties of Ni/Ni3Si eutectic alloy

    NASA Astrophysics Data System (ADS)

    Zhao, Yuhong; Wen, Zhiqin; Hou, Hua; Guo, Wei; Han, Peide

    2014-06-01

    In order to clarify the heterogeneous nucleation potential of α-Ni grains on Ni3Si particles in Ni-Ni3Si eutectic alloy, the work of adhesion (Wad), fracture toughness (G), interfacial energy (γi), and electronic structure of the index (0 0 1), (1 1 0) and (1 1 1) Ni/Ni3Si interfaces with two different cohesive manners are investigated using first-principles method based on density functional theory. Results indicate that the center site stacking sequence (OM) is preferable to continue the natural stacking sequence of bulk Ni and Ni3Si. Since OM stacking interfaces have larger Wad, G and γi than that of the top site stacking (OT) interfaces. The Ni/Ni3Si (1 1 0) interface with OM stacking has the best mechanical properties. Therefore, the formation of this interface can improve the stability, ductility and fracture toughness of Ni-Ni3Si eutectic alloy. The calculated interfacial energy of Ni/Ni3Si (0 0 1), (1 1 0) and (1 1 1) interfaces with OM stacking proves the excellent nucleation potency of Ni3Si particles for α-Ni phase from thermodynamic considerations. Besides, the electronic structure and chemical bonding of (1 1 0) interface with OM stacking are also discussed.

  6. Chemical reactivity of Ni-Rh nanowires.

    PubMed

    Schoiswohl, J; Mittendorfer, F; Surnev, S; Ramsey, M G; Andersen, J N; Netzer, F P

    2006-09-22

    The properties of bimetallic Ni-Rh nanowires, fabricated by decorating the steps of vicinal Rh(111) surfaces by stripes of self-assembled Ni adatoms, have been probed by STM, photoemission, and ab initio density functional theory calculations. These Ni-Rh nanowires have specific electronic properties that lead to a significantly enhanced chemical reactivity towards oxygen. As a result, the Ni-Rh nanowires can be oxidized exclusively, generating novel quasi-one-dimensional oxide structures.

  7. On the similarity of the bonding in NiS and NiO

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.

    1985-01-01

    The bonding in NiS is found to be quite similar to that in NiO, having an ionic contribution arising from the donation of the Ni 4s electron to the S atom and a covalent component arising from bonds between the Ni 3d and the S 3p. The one-electron d bonds are found to be of equal strength for NiO and NiS, but the two-electron d bonds are weaker for NiS.

  8. On the similarity of the bonding in NiS and NiO

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.

    1985-01-01

    The bonding in NiS is found to be quite similar to that in NiO, having an ionic contribution arising from the donation of the Ni 4s electron to the S atom and a covalent component arising from bonds between the Ni 3d and the S 3p. The one-electron d bonds are found to be of equal strength for NiO and NiS, but the two-electron d bonds are weaker for NiS.

  9. Hierarchical hollow urchin-like NiCo2O4 nanomaterial as electrocatalyst for oxygen evolution reaction in alkaline medium

    NASA Astrophysics Data System (ADS)

    Wang, Juan; Qiu, Tian; Chen, Xu; Lu, Yanluo; Yang, Wensheng

    2014-12-01

    Hierarchical hollow urchins of NiCo2O4 (HU-NiCo2O4) were synthesized by a hard templating method followed by thermal decomposition. The structure consists of three levels of hierarchy i.e., zero-dimensional nanoparticle with a diameter of about 6 nm, one-dimensional chain, and three-dimensional hollow urchin, respectively. Nanoparticle aggregates of NiCo2O4 (NA-NiCo2O4) were also synthesized by the same procedure in the absence of the hard template. Relative to NA-NiCo2O4, HU-NiCo2O4 features a well-connected three-dimensional porous structure, which is beneficial for diffusion of oxygen. Consequently, HU-NiCo2O4 displayed superior electrocatalytic activity towards oxygen evolution processes with lower overpotential, higher current density, and higher stability than NA-NiCo2O4.

  10. Direct Experimental Probe of the Ni(II)/Ni(III)/Ni(IV) Redox Evolution in LiNi0.5Mn1.5O4 Electrodes

    DOE PAGES

    Qiao, Ruimin; Wray, L. Andrew; Kim, Jung -Hyun; ...

    2015-11-11

    The LiNi0.5Mn1.5O4 spinel is an appealing cathode material for next generation rechargeable Li-ion batteries due to its high operating voltage of ~4.7 V (vs Li/Li+). Although it is widely believed that the full range of electrochemical cycling involves the redox of Ni(II)/(IV), it has not been experimentally clarified whether Ni(III) exists as the intermediate state or a double-electron transfer takes place. Here, combined with theoretical calculations, we show unambiguous spectroscopic evidence of the Ni(III) state when the LiNi0.5Mn1.5O4 electrode is half charged. This provides a direct verification of single-electron-transfer reactions in LiNi0.5Mn1.5O4 upon cycling, namely, from Ni(II) to Ni(III), thenmore » to Ni(IV). Additionally, by virtue of its surface sensitivity, soft X-ray absorption spectroscopy also reveals the electrochemically inactive Ni2+ and Mn2+ phases on the electrode surface. Our work provides the long-awaited clarification of the single-electron transfer mechanism in LiNi0.5Mn1.5O4 electrodes. Furthermore, the experimental results serve as a benchmark for further spectroscopic characterizations of Ni-based battery electrodes.« less

  11. Reaction of amorphous Ni-W and Ni-N-W films with substrate silicon

    NASA Technical Reports Server (NTRS)

    Zhu, M. F.; Suni, I.; Nicolet, M.-A.; Sands, T.

    1984-01-01

    Wiley et al. (1982) have studied sputtered amorphous films of Nb-Ni, Mo-Ni, Si-W, and Si-Mo. Kung et al. (1984) have found that amorphous Ni-Mo films as diffusion barriers between multilayer metallizations on silicon demonstrate good electrical and thermal stability. In the present investigation, the Ni-W system was selected because it is similar to the Ni-Mo system. However, W has a higher silicide formation temperature than Mo. Attention is given to aspects of sample preparation, sample characterization, the interaction between amorphous Ni-W films and Si, the crystallization of amorphous Ni(36)W(64) films on SiO2, amorphous Ni-N-W films, silicide formation and phase separation, and the crystallization of amorphous Ni(36)W(64) and Ni(30)N(21)W(49) layers.

  12. Atomic data for astrophysics: Ni XI

    NASA Astrophysics Data System (ADS)

    Del Zanna, G.; Storey, P. J.; Badnell, N. R.

    2014-06-01

    We present a new large-scale R-matrix scattering calculation for electron collisional excitation of Ni xi, carried out with the intermediate-coupling frame transformation method. The target includes all the main configurations up to n = 4, and is a significant improvement over earlier R-matrix (only three n = 3 configurations) and distorted-wave (DW) calculations. We find significant enhancements in the collision strengths of many of the strong transitions to the n = 3,4 levels. They are due to the resonances that arise within the present large-scale target. This results in significant increases in the predicted intensities of the UV and visible forbidden lines within the 3s23p53d configuration, the strong EUV lines that result from the decays of the 3s23p53d levels to the ground state, and the decays from the n = 4 levels, which are visible in the soft X-rays. We find good agreement between predicted and observed line intensities in the EUV. With the present atomic data, lines from Ni xi can reliably be used for plasma diagnostics. We also revise some level energies and suggest a few new possible identifications. The full dataset (energies, transition probabilities and rates) are only available in electronic form at our APAP website (http://www.apap-network.org) as well as at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/566/A123

  13. Stability of NiTi-Pd and NiTi-Hf high temperature shape memory alloys

    SciTech Connect

    Zhu, Y.R.; Pu, Z.J.; Li, C.; Wu, K.H.

    1994-09-28

    The thermal cycling tests and high temperature aging tests were performed to characterize the stability of NiTi-Pd and NiTi-Hf high temperature shape memory alloys. These alloys have better stability than NiTi during thermal cycling. In addition, it also found that the NiTi-Pd and NiTi-Hf alloy have a very good stability in high temperature aging.

  14. Electrical and thermal transport in CeNi and LaNi

    NASA Astrophysics Data System (ADS)

    Rudajevová, Alexandra; Vasylyev, Denis; Musil, Ondřej

    2006-05-01

    We have measured the electrical resistivity and thermal conductivity of CeNi, LaNi and La 0.15Ce 0.85Ni in the temperature range 4-400 K simultaneously on the same specimen using the TTO option in PPMS (Quantum Design) facility. Anomalous behaviour of the resistivity and the Lorenz number for CeNi and La 0.15Ce 0.85Ni can be attributed to valence fluctuations.

  15. Early ⁵⁶Ni decay gamma rays from SN2014J suggest an unusual explosion.

    PubMed

    Diehl, Roland; Siegert, Thomas; Hillebrandt, Wolfgang; Grebenev, Sergei A; Greiner, Jochen; Krause, Martin; Kromer, Markus; Maeda, Keiichi; Röpke, Friedrich; Taubenberger, Stefan

    2014-09-05

    Type Ia supernovae result from binary systems that include a carbon-oxygen white dwarf, and these thermonuclear explosions typically produce 0.5 solar mass of radioactive (56)Ni. The (56)Ni is commonly believed to be buried deeply in the expanding supernova cloud. In SN2014J, we detected the lines at 158 and 812 kiloelectron volts from (56)Ni decay (time ~8.8 days) earlier than the expected several-week time scale, only ~20 days after the explosion and with flux levels corresponding to roughly 10% of the total expected amount of (56)Ni. Some mechanism must break the spherical symmetry of the supernova and at the same time create a major amount of (56)Ni at the outskirts. A plausible explanation is that a belt of helium from the companion star is accreted by the white dwarf, where this material explodes and then triggers the supernova event.

  16. Metal/silicon interface formation - The Ni/Si and Pd/Si systems

    NASA Technical Reports Server (NTRS)

    Grunthaner, P. J.; Grunthaner, F. J.; Madhukar, A.; Mayer, J. W.

    1981-01-01

    The valence level spectra of the Ni/Si and Pd/Si systems have been investigated using high resolution X-ray photoelectron spectroscopy. Temperature dependence studies for Ni deposited on thin thermal SiO2 demonstrate the importance of metal aggregation effects in the interpretation of binding energies as chemical shifts. Temperature studies for the Ni/Si system indicate that substantial chemical interaction occurs at the interface at temperatures as low as 100 K. These studies also show the presence of Ni in interstitial voids in the Si near the interface. A comparative study of the core and valence band features for the Ni and Pd silicides provides many valuable insights and a self-consistent picture of the attendent valence charge redistribution and its influence on the observed chemical shifts.

  17. Thermal Stability of Cu/NiSi-Contacted p+n Shallow Junction

    NASA Astrophysics Data System (ADS)

    Wang, Chao-Chun; Lin, Hsin-Hung; Chen, Mao-Chieh

    2004-09-01

    The thermal stability of Cu/NiSi-contacted p+n shallow junction diodes was investigated with respect to their electrical characteristics and metallurgical reactions. The TaN/Cu/NiSi/p+n junction diode remained intact after 30 min thermal annealing at temperatures of up to 350°C. Upon annealing at 375°C, a marked increase in reverse bias leakage current occurred, and secondary ion mass spectrometry (SIMS) analysis indicated that Cu started to penetrate into the NiSi-contacted shallow junction region. After a higher temperature annealing at 425°C, a Cu3Si phase was formed. The failure of the TaN/Cu/NiSi/p+n junction diodes is attributed to the penetration of Cu through the NiSi layer into the junction region, leading to junction degradation by introducing deep-level trap states and the eventual formation of Cu3Si.

  18. Nuclear structure in the neutron-rich doubly magic sup 78 Ni region

    SciTech Connect

    Hill, J.C.; Wohn, F.K.; Winger, J.A.; Warburton, E.K.; Gill, R.L.; Schuhmann, R.B.; Brookhaven National Lab., Upton, NY; Clark Univ., Worcester, MA )

    1989-01-01

    The magic numbers Z=28 and N=50 imply that very neutron-rich {sup 78}Ni, which has not yet been observed, is doubly magic. The {sup 78}Ni region was investigated by studying the N=50 isotones and neutron-rich Zn isotopes. Results on the level structure of {sup 83}As, {sup 74}Zn, and {sup 76}Zn populated in the decays of {sup 83}Ge, {sup 74}Cu, and {sup 76}Cu are presented. The parent nuclides were produced and mass separated using the TRISTAN facility on-line to the High-Flux Beam Reactor at Brookhaven. The systematics of the N=50 isotones and even-A Zn isotopes are discussed and compared with shell-model calculations involving active nucleons outside of a {sup 78}Ni and {sup 66}Ni core, respectively. The extent to which the {sup 78}Ni region can be considered doubly magic is assessed. 43 refs., 7 figs.

  19. Water-Gas Shift and CO Methanation Reactions over Ni-CeO2(111) Catalysts

    SciTech Connect

    Senanayake, Sanjaya D; Evans, Jaime; Agnoli, Stefano; Barrio, Laura; Chen, Tsung-Liang; Hrbek, Jan; Radriguez, Jose

    2011-01-01

    X-ray and ultraviolet photoelectron spectroscopies were used to study the interaction of Ni atoms with CeO2(111) surfaces. Upon adsorption on CeO2(111) at 300 K, nickel remains in a metallic state. Heating to elevated temperatures (500 800 K) leads to partial reduction of the ceria substrate with the formation of Ni2? species that exists as NiO and/or Ce1-xNixO2-y. Interactions of nickel with the oxide substrate significantly reduce the density of occupied Ni 3d states near the Fermi level. The results of core-level photoemission and near-edge X-ray absorption fine structure point to weakly bound CO species on CeO2(111) which are clearly distinguishable from the formation of chemisorbed carbonates. In the presence of Ni, a stronger interaction is observed with chemisorption of CO on the admetal. When the Ni is in contact with Ce?3 cations, CO dissociates on the surface at 300 K forming NiCx compounds that may be involved in the formation of CH4 at higher temperatures. At medium and large Ni coverages ([0.3 ML), the Ni/CeO2(111) surfaces are able to catalyze the production of methane from CO and H2, with an activity slightly higher than that of Ni(100) or Ni(111). On the other hand, at small coverages of Ni (\\0.3 ML), the Ni/CeO2(111) surfaces exhibit a very low activity for CO methanation but are very good catalysts for the water gas shift reaction.

  20. Kinetics of Ni2Si growth from pure Ni and Ni(V) films on (111) and (100) Si

    NASA Astrophysics Data System (ADS)

    Harith, M. A.; Zhang, J. P.; Campisano, S. U.; Klaar, H.-J.

    1987-01-01

    The kinetics of Ni2Si growth from pure Ni and from Ni0.93V0.07 films on (111) and (100) silicon has been studied by the combination of He+ backscattering, x-ray diffraction, Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) techniques. The activation energies are 1.5 and 1.0 eV for pure Ni and Ni(V) films, respectively while the pre-exponential factors in Ni(V) are 4 5 orders of magnitude smaller than in the pure Ni case. The variations in the measured rates are related to the different grain size of the growing suicide layers. The vanadium is rejected from the silicide layer and piles up at the metalsilicide interface.

  1. Kinetics of Ni Sorption in Soils: Roles of Soil Organic Matter and Ni Precipitation

    SciTech Connect

    Shi, Zhenqing; Peltier, Edward; Sparks, Donald L.

    2012-12-10

    The kinetics of Ni sorption to two Delaware agricultural soils were studied to quantitatively assess the relative importance of Ni adsorption on soil organic matter (SOM) and the formation of Ni layered double hydroxide (Ni-LDH) precipitates using both experimental studies and kinetic modeling. Batch sorption kinetic experiments were conducted with both soils at pH 6.0, 7.0, and 7.5 from 24 h up to 1 month. Time-resolved Ni speciation in soils was determined by X-ray absorption spectroscopy (XAS) during the kinetic experiments. A kinetics model was developed to describe Ni kinetic reactions under various reaction conditions and time scales, which integrated Ni adsorption on SOM with Ni-LDH precipitation in soils. The soil Ni speciation (adsorbed phases and Ni-LDH) calculated using the kinetics model was consistent with that obtained through XAS analysis during the sorption processes. Under our experimental conditions, both modeling and XAS results demonstrated that Ni adsorption on SOM was dominant in the short term and the formation of Ni-LDH precipitates accounted for the long-term Ni sequestration in soils, and, more interestingly, that the adsorbed Ni may slowly transfer to Ni-LDH phases with longer reaction times.

  2. Synthesis and catalytic performance of SiO2@Ni and hollow Ni microspheres

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Liu, Yanhua; Shi, Xueting; Yu, Zhengyang; Feng, Libang

    2016-11-01

    Nickel (Ni) catalyst has been widely used in catalytic reducing reactions such as catalytic hydrogenation of organic compounds and catalytic reduction of organic dyes. However, the catalytic efficiency of pure Ni is low. In order to improve the catalytic performance, Ni nanoparticle-loaded microspheres can be developed. In this study, we have prepared Ni nanoparticle-loaded microspheres (SiO2@Ni) and hollow Ni microspheres using two-step method. SiO2@Ni microspheres with raspberry-like morphology and core-shell structure are synthesized successfully using SiO2 microsphere as a template and Ni2+ ions are adsorbed onto SiO2 surfaces via electrostatic interaction and then reduced and deposited on surfaces of SiO2 microspheres. Next, the SiO2 cores are removed by NaOH etching and the hollow Ni microspheres are prepared. The NaOH etching time does no have much influence on the crystal structure, shape, and surface morphology of SiO2@Ni; however, it can change the phase composition evidently. The hollow Ni microspheres are obtained when the NaOH etching time reaches 10 h and above. The as-synthesized SiO2@Ni microspheres exhibit much higher catalytic performance than the hollow Ni microspheres and pure Ni nanoparticles in the catalytic reduction of methylene blue. Meanwhile, the SiO2@Ni catalyst has high stability and hence it can be recycled for reuse.

  3. Kinetics of Ni sorption in soils: roles of soil organic matter and Ni precipitation.

    PubMed

    Shi, Zhenqing; Peltier, Edward; Sparks, Donald L

    2012-02-21

    The kinetics of Ni sorption to two Delaware agricultural soils were studied to quantitatively assess the relative importance of Ni adsorption on soil organic matter (SOM) and the formation of Ni layered double hydroxide (Ni-LDH) precipitates using both experimental studies and kinetic modeling. Batch sorption kinetic experiments were conducted with both soils at pH 6.0, 7.0, and 7.5 from 24 h up to 1 month. Time-resolved Ni speciation in soils was determined by X-ray absorption spectroscopy (XAS) during the kinetic experiments. A kinetics model was developed to describe Ni kinetic reactions under various reaction conditions and time scales, which integrated Ni adsorption on SOM with Ni-LDH precipitation in soils. The soil Ni speciation (adsorbed phases and Ni-LDH) calculated using the kinetics model was consistent with that obtained through XAS analysis during the sorption processes. Under our experimental conditions, both modeling and XAS results demonstrated that Ni adsorption on SOM was dominant in the short term and the formation of Ni-LDH precipitates accounted for the long-term Ni sequestration in soils, and, more interestingly, that the adsorbed Ni may slowly transfer to Ni-LDH phases with longer reaction times.

  4. A Thermally Stable NiZn/Ta/Ni Scheme to Replace AuBe/Au Contacts in High-Efficiency AlGaInP-Based Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Kim, Dae-Hyun; Park, Jae-Seong; Kang, Daesung; Seong, Tae-Yeon

    2017-08-01

    We developed NiZn/(Ta/)Ni ohmic contacts to replace expensive AuBe/Au contacts commonly used in high-efficiency AlGaInP-based light-emitting diodes (LEDs), and compared the electrical properties of the two contact types. Unlike the AuBe/Au (130 nm/100 nm) contact, the NiZn/Ta/Ni (130 nm/20 nm/100 nm) contact shows improved electrical properties after being annealed at 500°C, with a contact resistivity of 5.2 × 10-6 Ω cm2. LEDs with the NiZn/Ta/Ni contact exhibited a 4.4% higher output power (at 250 mW) than LEDs with the AuBe/Au contact. In contrast to the trend for the AuBe/Au contact, the Ga 2 p core level for the NiZn/Ta/Ni contact shifted toward lower binding energies after being annealed at 500°C. Auger electron spectroscopy (AES) depth profiles showed that annealing the AuBe/Au samples caused the outdiffusion of both Be and P atoms into the metal contact, whereas in the NiZn/Ta/Ni samples, Zn atoms indiffused into the GaP layer. The annealing-induced electrical degradation and ohmic contact formation mechanisms are described and discussed on the basis of the results of x-ray photoemission spectroscopy and AES.

  5. A Thermally Stable NiZn/Ta/Ni Scheme to Replace AuBe/Au Contacts in High-Efficiency AlGaInP-Based Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Kim, Dae-Hyun; Park, Jae-Seong; Kang, Daesung; Seong, Tae-Yeon

    2017-03-01

    We developed NiZn/(Ta/)Ni ohmic contacts to replace expensive AuBe/Au contacts commonly used in high-efficiency AlGaInP-based light-emitting diodes (LEDs), and compared the electrical properties of the two contact types. Unlike the AuBe/Au (130 nm/100 nm) contact, the NiZn/Ta/Ni (130 nm/20 nm/100 nm) contact shows improved electrical properties after being annealed at 500°C, with a contact resistivity of 5.2 × 10-6 Ω cm2. LEDs with the NiZn/Ta/Ni contact exhibited a 4.4% higher output power (at 250 mW) than LEDs with the AuBe/Au contact. In contrast to the trend for the AuBe/Au contact, the Ga 2p core level for the NiZn/Ta/Ni contact shifted toward lower binding energies after being annealed at 500°C. Auger electron spectroscopy (AES) depth profiles showed that annealing the AuBe/Au samples caused the outdiffusion of both Be and P atoms into the metal contact, whereas in the NiZn/Ta/Ni samples, Zn atoms indiffused into the GaP layer. The annealing-induced electrical degradation and ohmic contact formation mechanisms are described and discussed on the basis of the results of x-ray photoemission spectroscopy and AES.

  6. NiAl-Base Composite Containing High Volume Fraction of AIN Particulate for Advanced Engines

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.; Whittenberger, J. D.; Lowell, C. E.; Garg, A.

    1995-01-01

    Cryomilling of prealloyed NiAl containing 53 at. % AJ was carried out to achieve high nitrogen levels. The consolidation of cryomilled powder by extrusion or hot pressing/ hot isostatic pressing resulted in a fully dense NiAl-base composite containing 30 vol. % of inhomogeneously distributed, nanosized AIN particulate. The NiAl-30AIN composite exhibited the highest compression yield strengths at all temperatures between 300 and 1300 K as compared with other compositions of NiAl-AIN composite. The NiAl-30AIN specimens tested under compressive creep loading between 1300 and 1500 K also exhibited the highest creep resistance with very little surface oxidation indicating also their superior elevated temperature oxidation resistance. In the high stress exponent regime, the strength is proportional to the square root of the AIN content and in the low stress exponent regime, the influence of AIN content on strength appears to be less dramatic. The specific creep strength of this material at 1300 K is superior to a first generation Ni-base single crystal superalloy. The improvements in elevated temperature creep strength and oxidation resistance have been achieved without sacrificing the room temperature fracture toughness of the NiAl-base material. Based on its attractive combination of properties, the NiAl-30AIN composite is a potential candidate for advanced engine applications,

  7. Spin Glass Statics and Dynamics in the Disordered Stacked Quantum Ferromagnet LiNiO2

    NASA Astrophysics Data System (ADS)

    Clancy, J. P.; Gaulin, B. D.; Dunsiger, S. R.; Haravifard, S.; Copley, J. R. D.; Qiu, Y.

    2006-03-01

    We have performed time-of-flight neutron scattering measurements on polycrystalline LiNiO2 using the Disk Chopper Spectrometer at the NIST Center for Neutron Research. Similar measurements performed on its sister compound, NaNiO2, show a simple magnetic structure below Tn˜22K consisting of ferromagnetic sheets of s=1/2 moments stacked in an antiferromagnetic (AF) fashion [1]. Our measurements on LiNiO2 illustrate the absence of magnetic order down to 1.7K. Further they provide direct evidence for a spin glass transition at 9K through a narrowing of the inelastic magnetic scattering on approaching Tg from above, along with a concomitant increase in the elastic magnetic scattering, indicative of frozen disordered moments. The inelastic magnetic scattering in LiNiO2 resembles that in NaNiO2 above Tn, suggesting that the low Q spin response is due to short-lived spin wave modes below the lowest Q AF ordering wavevector. This reinforces the picture that the simple stacked ferromagnetic ordered state displayed by NaNiO2 is precluded by mixing between the Li and Ni sublattices, which occurs in LiNiO2 at the 1-3% level. [1] M.J. Lewis et al., PRB 72, 014408 (2005).

  8. Ultra-separation of nickel from copper metal for the measurement of 63Ni by AMS

    NASA Astrophysics Data System (ADS)

    Marchetti, A. A.; Hainsworth, L. J.; McAninch, J. E.; Leivers, M. R.; Jones, P. R.; Proctor, I. D.; Straume, T.

    1997-03-01

    Measurements of 63Ni (t{1}/{2} = 100 yr) produced by the reaction 63Cu(n,p)63Ni could be used in the assessment of fast-neutron fluence from the Hiroshima atomic bomb. Such measurements would add new information to help resolve the current discrepancy between measured thermal neutron activation values and those calculated with the DS86 dosimetry system. It has been estimated that the 63Ni production at 5 m from the hypocenter was (1.4 ± 0.1) × 107 atoms/g Cu. Because of its sensitivity, accelerator mass spectrometry (AMS) is ideal for measurements at this low level. However, 63Ni has to be separated from large amounts of stable atomic isobar 63Cu (69% of pure Cu). In this study, a procedure is presented for the electrochemical separation of ultra-low amounts of Ni from Cu. The method was developed using samples of electrical Cu wire that were irradiated with fission neutrons from a 252Cf source. The wire samples were electrochemically dissolved in a solution containing 1 mg of Ni carrier. The Cu was selectively deposited on a cathode at controlled potential. Measurements of total Ni after electroseparation indicate ˜ 100% carrier recovery. To prevent Cu contamination, AMS targets were prepared by nickel carbonyl generation. The AMS results show a successful quantitative separation of ˜ 107 atoms of 63Ni from 2-20 g samples of Cu.

  9. Structural evaluation and nonlinear optical properties of Ni/NiO, Ni/NiCo2O4 and Co/Co3O4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Rahulan, K. Mani; Padmanathan, N.; Philip, Reji; Balamurugan, S.; Kanakam, Charles C.

    2013-10-01

    Nanocomposites of Ni/NiO, Ni/NiCo2O4 and Co/Co3O4 have been synthesized by a chemical reduction technique. X-ray diffraction (XRD) and transmission electron microscopy (TEM) images confirm the mixed composite nature of the sample and uniform particle size of approximately 13 nm. Formation of Ni/NiCo3O4 solid solution or NiCo2O4 spinel phase in the mixed composite is confirmed by energy dispersive X-ray (EDX) spectrum. Magnetic hysteresis (M-H) curves of the nanocomposites show excellent ferromagnetic (FM) nature at room temperature. Nonlinear optical transmission of the nanocomposites is measured using the open aperture Z-scan technique employing 7 nanosecond laser pulses at 532 nm. Experimental results show that NiO/NiO-Co3O4/Co3O4 nanocomposites exhibit good optical limiting performance. From the measurements and numerical fitting of the data to theory, it is found that nonlinear absorption has contributions from excited state absorption and two-photon absorption. Optical limiting is enhanced in Co3O4 and Ni/NiCo2O4 in which the Co3O4 content has a larger volume ratio.

  10. Hydrogen effects on the electronic and microstructural properties of Ce, Ni, and CeNi 2 intermetallic compound

    NASA Astrophysics Data System (ADS)

    Roustila, A.; Severac, C.; Chêne, J.; Percheron-Guégan, A.

    1994-05-01

    The electronic properties and the microstructure associated with room temperature (RT) cathodic charging of Ce, Ni, and CeNi 2 massive specimens have been investigated by XPS analysis and microscopic observations. The use of a cooling stage allows us to study the hydride formed by cathodic charging on the nickel surface and to evidence by XPS the hydrogen induced filling of the 3d band in nickel. A thin hydride layer (CeH 2.53) is readily formed at RT on Ce. In spite of a hydrogen induced lowering of the valence band intensity, conduction states at EF are present in this hydride. The XPS spectra of the Ce 3d and 4d core levels also demonstrate the existence of a hybridization effect of the 4f electrons with those of the conduction band which raises the intensity of the f 0 and f 2 satellites. Needle-shaped hydride precipitates are observed at the very beginning stage of the cathodic charging of CeNi 2; they are readily replaced by an amorphous CeNi 2H 4 hydride. The hydrogenated surface exhibits a metal-hydrogen band at 6 eV below EF; the presence of hydrogen also increases the relative intensity of the f 0 and f 2 satellites in the 3d and 4d core levels.

  11. California Niño/Niña

    PubMed Central

    Yuan, Chaoxia; Yamagata, Toshio

    2014-01-01

    The present study shows the existence of intrinsic coastal air-sea coupled phenomenon in the coastal ocean off Baja California and California in boreal summer for the first time. It contributes significantly to the interannual sea surface temperature (SST) anomalies there. An initial decrease/increase in the equatorward alongshore surface winds weakens/strengthens the coastal upwelling and raises/lowers the coastal SSTs through oceanic mixed-layer processes. The resultant coastal warming/cooling, in turn, heats/cools the overlying atmosphere anomalously, decreases/increases the atmospheric pressure in the lower troposphere, generates an anomalous cross-shore pressure gradient, and thus reinforces or maintains the alongshore surface wind anomalies. The regional air-sea coupled phenomenon seems to be analogous to the well-known El Niño/Southern Oscillation (ENSO) in the tropical Pacific but with much smaller time and space scales, and may be referred to as California Niño/Niña in its intrinsic sense. PMID:24763062

  12. California Niño/Niña.

    PubMed

    Yuan, Chaoxia; Yamagata, Toshio

    2014-04-25

    The present study shows the existence of intrinsic coastal air-sea coupled phenomenon in the coastal ocean off Baja California and California in boreal summer for the first time. It contributes significantly to the interannual sea surface temperature (SST) anomalies there. An initial decrease/increase in the equatorward alongshore surface winds weakens/strengthens the coastal upwelling and raises/lowers the coastal SSTs through oceanic mixed-layer processes. The resultant coastal warming/cooling, in turn, heats/cools the overlying atmosphere anomalously, decreases/increases the atmospheric pressure in the lower troposphere, generates an anomalous cross-shore pressure gradient, and thus reinforces or maintains the alongshore surface wind anomalies. The regional air-sea coupled phenomenon seems to be analogous to the well-known El Niño/Southern Oscillation (ENSO) in the tropical Pacific but with much smaller time and space scales, and may be referred to as California Niño/Niña in its intrinsic sense.

  13. Corrosion behavior of Ni/sup +/-ion irradiated NiTi alloys

    SciTech Connect

    Wang, R.; Brimhall, J.L.

    1983-11-01

    Corrosion behavior of Ni/sup +/-irradiated NiTi alloys was studied in chloride solutions, together with unirradiated NiTi material with different surface conditions. Ion irradiation with either 2.5 or 5 MeV Ni/sup +/ ions transformed the NiTi surface into an amorphous layer up to 1.5 micrometers thick. Studies of corrosion potential vs time and polarization behavior indicated a small enhancement of the passivation for the Ni/sup +/-irradiated NiTi over the unirradiated NiTi. The unirradiated NiTi with a mechanically polished, course surface was susceptible to pitting and crevice corrosion attack in 1 N HCl solution. The homogeneous amorphous structure in the irradiated alloy retarded this type of localized corrosion.

  14. Synthesis and magnetic studies of Ni/NiO core/shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Rinsha, C.; Anumol, C. N.; Chithra, M.; Sahu, B. N.; Sahoo, Subasa C.

    2015-06-01

    Ni/NiO core/shell nanoparticles were synthesized by chemical reduction method followed by oxidation by two different methods; (a) in air and (b) in microwave oven. Structural studies showed that the thickness of NiO shell on Ni core is less in air oxidized sample than the microwave oxidized samples which were supported by the magnetic studies. The samples prepared by air oxidation showed positive exchange biasing where as the samples prepared by microwave oxidation showed negative exchange biasing. Our study also showed that the thickness of the antiferromagnetic NiO is responsible for the different types of magnetic interactions at the interfaces between antiferromagnetic NiO and ferromagnetic Ni in Ni/NiO core/shell nanoparticles.

  15. Superelasticity and compression behavior of porous TiNi alloys produced using Mg spacers.

    PubMed

    Aydoğmuş, Tarık; Bor, Sakir

    2012-11-01

    In the scope of the present study, Ni-rich TiNi (Ti-50.6 at %Ni) foams with porosities in the range 38-59% were produced by space holder technique using spherical magnesium powders as space formers. Single phase porous TiNi alloys produced with spherical pores were subjected to loading-unloading cycles in compression up to 250 MPa stress levels at different temperatures in as-processed and aged conditions. It has been observed that strength, elastic modulus and critical stress for inducing martensite decrease with increasing porosity. Partial superelasticity was observed for all porosity levels at different test temperatures and conditions employed. Irrecoverable strain was found to decrease with pre-straining and with increasing test temperature. Unlike in bulk TiNi alloys a constant stress plateau has not been observed during the compression testing of porous TiNi alloys. Instead linear superelasticity with a quite steep slope allowing 5% applied strain to be recovered after pre-straining or aging was observed. Even at test temperatures higher than austenite finish temperature in as-sintered and aged condition, strain applied could not be recovered fully due to martensite stabilization resulting from heavy deformation of macro-pore walls and sintering necks. TiNi foams produced with porosities in the range of 38-51% meet the main requirements of biomaterials in terms of mechanical properties for use as bone implant.

  16. Mechanical Properties of NiTi-Based Foam with High Porosity for Implant Applications

    NASA Astrophysics Data System (ADS)

    Qiu, Ying; Yu, Hao; Young, Marcus L.

    2015-11-01

    In order to better understand NiTi-based shape memory alloy foams for implant applications, Ni40Ti50Cu10 foams were heat treated and then deformed under incremental and cyclic compression loading. After heat treatment, the microstructure consists of a (Ni,Cu)Ti matrix with small (Ni,Cu)4Ti3 precipitates and a large Ti2(Ni,Cu) secondary phase. The heat-treated Ni40Ti50Cu10 foam exhibits a two-step transformation, involving B19' → B19 and B19 → B2 on heating and B2 → B19 and B19 → B19' on cooling, respectively. One Ni40Ti50Cu10 foam was compression loaded for 10 cycles at each subsequent strain level, i.e., 1, 2, 3, 4, 5, and 6 % strain. In each set of compressive stress-strain loops, the maximum stress level decreases due to plastic damage accumulation and/or retention of transformed martensite. Cross-sectional images from micro-computed tomography were collected during compression loading, which shows very uniform deformation without severe structural damage even up to 5 % strain. Localized deformation is visible at 6 % strain.

  17. Final Viking NiCd battery conditioning

    SciTech Connect

    Britting, A.

    1983-08-01

    The Viking Lander Monitor Mission (VLMM) is well beyond its planned 90-day landed Mars mission. It has been an established NASA goal to maintain an American presence on Mars for as long as possible. With healthy subsystems, the mission could conceivably last until December 5, 1994. At that time the radioisotope thermoelectric generator (RTG) power source output power would be marginal for support of the system electrical loads and for battery maintenance. The antenna pointing coefficients will also expire at that time, resulting in telecommunication system shutdown. Recently three of the four, 8 ampere-hour (AH) nickel-cadmium (NiCd) batteries onboard Viking Lander 1 (VL-1) have indicated signs of significant loss of energy storage capacity. An intensive program of deep-discharge battery reconditioning was begun in January 1982 in an attempt to return the batteries to levels of capacity approaching early mission values.

  18. Nanostructurization of Fe-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Danilhenko, Vitaliy E.

    2017-03-01

    Data about an effect of cyclic γ-α-γ martensitic transformations on the structure state of reverted austenite Fe-31.7 wt.% Ni-0.06 wt.% C alloy are presented. The effect of multiple direct γ-α and reverse α-γ martensitic transformations on fragmentation of austenitic grains has been investigated by electron microscopy and X-ray diffraction methods. An ultrafine structure has been formed by nanofragmentation inside the initial austenite grains due to the successive misorientation of their crystal lattice. Austenite was nanofragmented as a result of multiple γ-α-γ martensitic transformations. Slow heating of the nanofragmented alloy at a rate below 2 °C/s results in nanograin refinement of the structure by multiplication of the reverted γ-phase orientations. The conditions of structure refinement up to ultrafine and nanocrystalline levels as a result of both shear and diffusion mechanisms of reverse α-γ transformation are determined.

  19. Can Ni phosphides become viable hydroprocessing catalysts?

    SciTech Connect

    Soled, S.; Miseo, S.; Baumgartner, J.; Guzman, J.; Bolin, T.; Meyer, R.

    2015-05-15

    We prepared higher surface area nickel phosphides than are normally found by reducing nickel phosphate. To do this, we hydrothermally synthesized Ni hydroxy phosphite precursors with low levels of molybdenum substitution. The molybdenum substitution increases the surface area of these precursors. During pretreatment in a sulfiding atmosphere (such as H2S/H2) dispersed islands of MoS2 segregate from the precursor and provide a pathway for H2 dissociation that allows reduction of the phosphite precursor to nickel phosphide at substantially lower temperatures than in the absence of MoS2. The results reported here show that to create nickel phosphides with comparable activity to conventional supported sulfide catalysts, one would have to synthesize the phosphide with surface areas exceeding 400 m2/g (i.e. with nanoparticles less than 30 Å in lateral dimension).

  20. Ni/TiO2 Ultraviolet Detector

    NASA Astrophysics Data System (ADS)

    Mohamadzade Lajvardi, Mehdi; Jahangiri, Mojtaba

    2016-03-01

    The fabrication technology of solid-state photon detectors based on semiconductors other than silicon is yet to mature, but their recent progress opens new possibilities. Such devices are especially attractive for ultraviolet radiation level measurements because semiconductor materials with band gaps larger than 3.0 eV can be used as “visible-blind” detectors, the operation of which do not require using visible light filters. Here, fabrication and characterization of a UV detector based on nickel/titanium dioxide Schottky junction is reported. The operation of the device is described based on the photoelectric mechanism taking place in the carrier- depleted oxide adjacent to the Ni layer. Simplicity of fabrication, cost-effectiveness and fast response are the positive features of the device. These features of the device are compared with those of the previously reported Ag/TiO2 UV detectors.

  1. Crystallographic, magnetic, and electronic structures of ferromagnetic shape memory alloys Ni2XGa (X=Mn,Fe,Co) from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Bai, J.; Raulot, J. M.; Zhang, Y. D.; Esling, C.; Zhao, X.; Zuo, L.

    2011-01-01

    The crystallographic, magnetic and electronic structures of the ferromagnetic shape memory alloys Ni2XGa (X=Mn, Fe, and Co), are systematically investigated by means of the first-principles calculations within the framework of density functional theory using the VIENNA AB INITIO SOFTWARE PACKAGE. The lattice parameters of both austenitic and martensitic phases in Ni2MnGa have been calculated. The formation energies of the cubic phase of Ni2XGa are estimated, and show a destabilization tendency if Mn atom is substituted by Fe or Co. From Ni2MnGa to Ni2CoGa, the down spin total density of states (DOS) at Fermi level is gradually increasing, whereas that of the up spin part remains almost unchanged. This is the main origin of the difference of the magnetic moment in these alloys. The partial DOS is dominated by the Ni and Mn 3d states in the bonding region below EF. There are two bond types existing in Ni2XGa: one is between neighboring Ni atoms in Ni2MnGa; the other is between Ni and X atoms in Ni2FeGa and Ni2CoGa alloys.

  2. Crystallographic, magnetic, and electronic structures of ferromagnetic shape memory alloys Ni{sub 2}XGa (X=Mn,Fe,Co) from first-principles calculations

    SciTech Connect

    Bai, J.; Raulot, J. M.; Zhang, Y. D.; Esling, C.; Zhao, X.; Zuo, L.

    2011-01-01

    The crystallographic, magnetic and electronic structures of the ferromagnetic shape memory alloys Ni{sub 2}XGa (X=Mn, Fe, and Co), are systematically investigated by means of the first-principles calculations within the framework of density functional theory using the VIENNA AB INITIO SOFTWARE PACKAGE. The lattice parameters of both austenitic and martensitic phases in Ni{sub 2}MnGa have been calculated. The formation energies of the cubic phase of Ni{sub 2}XGa are estimated, and show a destabilization tendency if Mn atom is substituted by Fe or Co. From Ni{sub 2}MnGa to Ni{sub 2}CoGa, the down spin total density of states (DOS) at Fermi level is gradually increasing, whereas that of the up spin part remains almost unchanged. This is the main origin of the difference of the magnetic moment in these alloys. The partial DOS is dominated by the Ni and Mn 3d states in the bonding region below E{sub F}. There are two bond types existing in Ni{sub 2}XGa: one is between neighboring Ni atoms in Ni{sub 2}MnGa; the other is between Ni and X atoms in Ni{sub 2}FeGa and Ni{sub 2}CoGa alloys.

  3. Processing and Mechanical Properties of Directionally Solidified NiAl/NiAlTa Alloys

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1994-01-01

    Promising creep strengths were found for a directionally solidified NiAl-NiAlTa alloy when compared to other NiAl based intermetallics. The directionally solidified alloy had an off-eutectic composition that resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The room temperature toughness of the two phase alloy was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa. Alloying additions that may improve the room temperature toughness by producing multiphase alloys are discussed.

  4. B-Ni-Ti (164)

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 2 http://dx.doi.org/10.1007/97.etType="URL"/> 'Systems from B-Be-Fe to Co-W-Zr' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'B-Ni-Ti (164)' with the content:

  5. Al-La-Ni (069)

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 1 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Al-La-Ni (069)' with the content:

  6. Measured Activities of Al and Ni in gamma-(Ni) and gamma'-(Ni)3Al in the Ni-Al-Pt System

    NASA Technical Reports Server (NTRS)

    Copland, Evan

    2007-01-01

    Adding Pt to Ni-Al coatings is critical to achieving the required oxidation protection of Ni-based superalloys, but the nature of the Pt effect remains unresolved. This research provides a fundamental part of the answer by measuring the influence of Pt on the activities of Al and Ni in gamma-(Ni), gamma prime-(Ni)3Al and liquid in the Ni-Al-Pt system. Measurements have been made at 25 compositions in the Ni-rich corner over the temperature range, T = 1400-1750 K, by the vapor pressure technique with a multiple effusion-cell mass spectrometer (multi-cell KEMS). These measurements clearly show adding Pt (for X(sub Pt) less than 0.25) decreases a(Al) while increasing a(Ni). This solution behavior supports the idea that Pt increases Al transport to an alloy / Al2O3 interface and also limits the interaction between the coating and substrate alloys in the gamma-(Ni) + gamma prime-(Ni)3Al region. This presentation will review the progress of this study.

  7. 58Ni: an unpaired band crossing at new heights of angular momentum for rotating nuclei.

    PubMed

    Rudolph, D; Carlsson, B G; Ragnarsson, I; Aberg, S; Andreoiu, C; Bentley, M A; Carpenter, M P; Charity, R J; Clark, R M; Cromaz, M; Ekman, J; Fahlander, C; Fallon, P; Ideguchi, E; Macchiavelli, A O; Mineva, M N; Reviol, W; Sarantites, D G; Seweryniak, D; Williams, S J

    2006-03-10

    High-spin states in 58Ni have been investigated by means of the fusion-evaporation reaction 28Si(32S, 2p)58Ni at 130 MeV beam energy. Discrete-energy levels are observed in 58Ni at record-breaking 42 MeV excitation energy and angular momenta in excess of 30h. The states form regular rotational bands with unprecedented high rotational frequencies. A comparison with configuration dependent cranked Nilsson-Strutinsky calculations reveals an exceptional two-band crossing scenario, the interaction strength of which is strongly shape dependent.

  8. Cytosolic Ni(II) Sensor in Cyanobacterium

    PubMed Central

    Foster, Andrew W.; Patterson, Carl J.; Pernil, Rafael; Hess, Corinna R.; Robinson, Nigel J.

    2012-01-01

    Efflux of surplus Ni(II) across the outer and inner membranes of Synechocystis PCC 6803 is mediated by the Nrs system under the control of a sensor of periplasmic Ni(II), NrsS. Here, we show that the product of ORF sll0176, which encodes a CsoR/RcnR-like protein now designated InrS (for internal nickel-responsive sensor), represses nrsD (NrsD is deduced to efflux Ni(II) across the inner membrane) from a cryptic promoter between the final two ORFs in the nrs operon. Transcripts initiated from the newly identified nrsD promoter accumulate in response to nickel or cobalt but not copper, and recombinant InrS forms specific, Ni(II)-inhibited complexes with the nrsD promoter region. Metal-dependent difference spectra of Ni(II)- and Cu(I)-InrS are similar to Cu(I)-sensing CsoR and dissimilar to Ni(II)/Co(II)-sensing RcnR, consistent with factors beyond the primary coordination sphere switching metal selectivity. Competition with chelators mag-fura-2, nitrilotriacetic acid, EDTA, and EGTA estimate KD Ni(II) for the tightest site of InrS as 2.05 (±1.5) × 10−14 m, and weaker KD Ni(II) for the cells' metal sensors of other types: Zn(II) co-repressor Zur, Co(II) activator CoaR, and Zn(II) derepressor ZiaR. Ni(II) transfer to InrS occurs upon addition to Ni(II) forms of each other sensor. InrS binds Ni(II) sufficiently tightly to derepress Ni(II) export at concentrations below KD Ni(II) of the other sensors. PMID:22356910

  9. Charge optimized many-body (COMB) potential for dynamical simulation of Ni-Al phases

    NASA Astrophysics Data System (ADS)

    Kumar, Aakash; Chernatynskiy, Aleksandr; Liang, Tao; Choudhary, Kamal; Noordhoek, Mark J.; Cheng, Yu-Ting; Phillpot, Simon R.; Sinnott, Susan B.

    2015-08-01

    An interatomic potential for the Ni-Al system is presented within the third-generation charge optimized many-body (COMB3) formalism. The potential has been optimized for Ni3Al, or the γ‧ phase in Ni-based superalloys. The formation energies predicted for other Ni-Al phases are in reasonable agreement with first-principles results. The potential further predicts good mechanical properties for Ni3Al, which includes the values of the complex stacking fault (CSF) and the anti-phase boundary (APB) energies for the (1 1 1) and (1 0 0) planes. It is also used to investigate dislocation propagation across the Ni3Al (1 1 0)-Ni (1 1 0) interface, and the results are consistent with simulation results reported in the literature. The potential is further used in combination with a recent COMB3 potential for Al2O3 to investigate the Ni3Al (1 1 1)-Al2O3 (0 0 01) interface, which has not been modeled previously at the classical atomistic level due to the lack of a reactive potential to describe both Ni3Al and Al2O3 as well as interactions between them. The calculated work of adhesion for this interface is predicted to be 1.85 J m-2, which is in agreement with available experimental data. The predicted interlayer distance is further consistent with the available first-principles results for Ni (1 1 1)-Al2O3 (0 0 0 1).

  10. Enhanced endothelial cell density on NiTi surfaces with sub-micron to nanometer roughness.

    PubMed

    Samaroo, Harry D; Lu, Jing; Webster, Thomas J

    2008-01-01

    The shape memory effect and superelastic properties of NiTi (or Nitinol, a nickel-titanium alloy) have already attracted much attention for various biomedical applications (such as vascular stents, orthodontic wires, orthopedic implants, etc). However, for vascular stents, conventional approaches have required coating NiTi with anti-thrombogenic or antiinflammatory drug-eluting polymers which as of late have proven problematic for healing atherosclerotic blood vessels. Instead of focusing on the use of drug-eluting anti-thrombogenic or anti-inflammatory proteins, this study focused on promoting the formation of a natural antithrombogenic and anti-inflammatory surface on metallic stents: the endothelium. In this study, we synthesized various NiTi substrates with different micron to nanometer surface roughness by using dissimilar dimensions of constituent NiTi powder. Endothelial cell adhesion on these compacts was compared with conventional commercially pure (cp) titanium (Ti) samples. The results after 5 hrs showed that endothelial cells adhered much better on fine grain (< 60 microm) compared with coarse grain NiTi compacts (< 100 microm). Coarse grain NiTi compacts and conventional Ti promoted similar levels of endothelial cell adhesion. In addition, cells proliferated more after 5 days on NiTi with greater sub-micron and nanoscale surface roughness compared with coarse grain NiTi. In this manner, this study emphasized the positive pole that NiTi with sub-micron to nanometer surface features can play in promoting a natural anti-thrombogenic and anti-inflammatory surface (the endothelium) on a vascular stent and, thus, suggests that more studies should be conducted on NiTi with sub-micron to nanometer surface features.

  11. Enhanced endothelial cell density on NiTi surfaces with sub-micron to nanometer roughness

    PubMed Central

    Samaroo, Harry D; Lu, Jing; Webster, Thomas J

    2008-01-01

    The shape memory effect and superelastic properties of NiTi (or Nitinol, a nickel-titanium alloy) have already attracted much attention for various biomedical applications (such as vascular stents, orthodontic wires, orthopedic implants, etc). However, for vascular stents, conventional approaches have required coating NiTi with anti-thrombogenic or anti-inflammatory drug-eluting polymers which as of late have proven problematic for healing atherosclerotic blood vessels. Instead of focusing on the use of drug-eluting anti-thrombogenic or anti-inflammatory proteins, this study focused on promoting the formation of a natural anti-thrombogenic and anti-inflammatory surface on metallic stents: the endothelium. In this study, we synthesized various NiTi substrates with different micron to nanometer surface roughness by using dissimilar dimensions of constituent NiTi powder. Endothelial cell adhesion on these compacts was compared with conventional commercially pure (cp) titanium (Ti) samples. The results after 5 hrs showed that endothelial cells adhered much better on fine grain (<60 μm) compared with coarse grain NiTi compacts (<100 μm). Coarse grain NiTi compacts and conventional Ti promoted similar levels of endothelial cell adhesion. In addition, cells proliferated more after 5 days on NiTi with greater sub-micron and nanoscale surface roughness compared with coarse grain NiTi. In this manner, this study emphasized the positive pole that NiTi with sub-micron to nanometer surface features can play in promoting a natural anti-thrombogenic and anti-inflammatory surface (the endothelium) on a vascular stent and, thus, suggests that more studies should be conducted on NiTi with sub-micron to nanometer surface features. PMID:18488418

  12. Development of FeNiMoB thin film materials for microfabricated magnetoelastic sensors

    SciTech Connect

    Liang Cai; Gooneratne, Chinthaka; Cha, Dongkyu; Chen Long; Kosel, Jurgen; Gianchandani, Yogesh

    2012-12-01

    Metglas{sup TM} 2826MB foils of 25-30 {mu}m thickness with the composition of Fe{sub 40}Ni{sub 38}Mo{sub 4}B{sub 18} have been used for magnetoelastic sensors in various applications over many years. This work is directed at the investigation of {approx}3 {mu}m thick iron-nickel-molybdenum-boron (FeNiMoB) thin films that are intended for integrated microsystems. The films are deposited on Si substrate by co-sputtering of iron-nickel (FeNi), molybdenum (Mo), and boron (B) targets. The results show that dopants of Mo and B can significantly change the microstructure and magnetic properties of FeNi materials. When FeNi is doped with only Mo its crystal structure changes from polycrystalline to amorphous with the increase of dopant concentration; the transition point is found at about 10 at. % of Mo content. A significant change in anisotropic magnetic properties of FeNi is also observed as the Mo dopant level increases. The coercivity of FeNi films doped with Mo decreases to a value less than one third of the value without dopant. Doping the FeNi with B together with Mo considerably decreases the value of coercivity and the out-of-plane magnetic anisotropy properties, and it also greatly changes the microstructure of the material. In addition, doping B to FeNiMo remarkably reduces the remanence of the material. The film material that is fabricated using an optimized process is magnetically as soft as amorphous Metglas{sup TM} 2826MB with a coercivity of less than 40 Am{sup -1}. The findings of this study provide us a better understanding of the effects of the compositions and microstructure of FeNiMoB thin film materials on their magnetic properties.

  13. Nickel segregation to grain boundaries in Ni sub 3 Al alloys

    SciTech Connect

    Subramanian, R.; Robertson, I.M.; Birnbaum, H.K. )

    1991-12-01

    This paper reports that a considerable research effort has been undertaken to understand the improved ductility of hypo-stoichiometric Ni{sub 3} Al containing B relative to stoichiometric and hyper-stoichiometric alloys. A variety of techniques have shown that in ductile alloys, the level of B at the grain boundary is significantly higher than in the matrix and that the B exhibits equilibrium segregation over distances of the order of 1 nm from the boundaries. The concentration of nickel at the boundaries is less certain. Some measurements have shown somewhat enhanced Ni concentrations within 1 nm of the grain boundaries and correlations between B and Ni segregation, while in others a small amount of Ni segregation was observed but with no correlation to B segregation, and on others no Ni segregation was observed. Baker et al. report the formation of a second phase extending for distances of about 20 nm from the boundaries and having very high Ni concentrations in hypo-stoichiometric Ni{sub 3}Al containing B. These different results may reflect the different material preparation and annealing procedures that have been used. Horton and Liu have shown that the presence of the Ni-rich second phase was not necessary for the ductility of Ni{sub 3}Al. It has been suggested that a disordered fcc layer may exist at B enriched grain boundaries, and that this disorder may enhance Ni{sub 3}Al ductility by making it easier for dislocation to be transmitted through the grain boundaries.

  14. Development of FeNiMoB thin film materials for microfabricated magnetoelastic sensors

    NASA Astrophysics Data System (ADS)

    Liang, Cai; Gooneratne, Chinthaka; Cha, Dongkyu; Chen, Long; Gianchandani, Yogesh; Kosel, Jurgen

    2012-12-01

    MetglasTM 2826MB foils of 25-30 μm thickness with the composition of Fe40Ni38Mo4B18 have been used for magnetoelastic sensors in various applications over many years. This work is directed at the investigation of ˜3 μm thick iron-nickel-molybdenum-boron (FeNiMoB) thin films that are intended for integrated microsystems. The films are deposited on Si substrate by co-sputtering of iron-nickel (FeNi), molybdenum (Mo), and boron (B) targets. The results show that dopants of Mo and B can significantly change the microstructure and magnetic properties of FeNi materials. When FeNi is doped with only Mo its crystal structure changes from polycrystalline to amorphous with the increase of dopant concentration; the transition point is found at about 10 at. % of Mo content. A significant change in anisotropic magnetic properties of FeNi is also observed as the Mo dopant level increases. The coercivity of FeNi films doped with Mo decreases to a value less than one third of the value without dopant. Doping the FeNi with B together with Mo considerably decreases the value of coercivity and the out-of-plane magnetic anisotropy properties, and it also greatly changes the microstructure of the material. In addition, doping B to FeNiMo remarkably reduces the remanence of the material. The film material that is fabricated using an optimized process is magnetically as soft as amorphous MetglasTM 2826MB with a coercivity of less than 40 Am-1. The findings of this study provide us a better understanding of the effects of the compositions and microstructure of FeNiMoB thin film materials on their magnetic properties.

  15. Enhanced room temperature ferromagnetism in Ni doped SnO2 nanoparticles: A comprehensive study

    NASA Astrophysics Data System (ADS)

    Ahmed, Ateeq; Ali, T.; Naseem Siddique, M.; Ahmad, Abid; Tripathi, P.

    2017-08-01

    We emphasized on a detailed investigation of the structural, optical, and magnetic properties of pure and Ni-doped SnO2 nanoparticles (NPs) synthesized by a sol-gel process. An extensive structural study has been carried out using various characterization techniques. The X-ray Diffraction (XRD) spectra show the formation of the single phase tetragonal structure of pure and Ni-doped SnO2 NPs without any noticeable impurity phase such as NiO. XRD results indicate that the crystallite size of SnO2 is found to be decreased with Ni doping, which has also been confirmed by the Field Emission Scanning Electron Microscopy study. X-ray Photoelectron Spectroscopy (XPS) measurements displayed a clear sign for Ni2+ ions occupying the lattice sites of Sn4+ in the SnO2 host which also gives clear evidence for the formation of single phase Sn1-xNixO2 NPs. The optical analysis shows a significant decrease in the energy gap of SnO2, i.e., (from 3.71 eV to 3.28 eV) as Ni concentration increases which may be correlated with the core level valence band XPS analysis. Photoluminescence studies show that Ni doping creates oxygen vacancies due to dissimilar ionic radii of Ni2+ and Sn4+. Superconducting quantum interference device measurements revealed that the Ni doped SnO2 NPs exhibit strong ferromagnetic behavior at room temperature and this analysis has been well fitted with a simple relationship to find out magnetic parameters proposed by Stearns and Cheng et al. Hence, our results demonstrate that Ni-doping has strong impact on the structural, optical, and magnetic properties.

  16. Ultrafast Alkaline Ni/Zn Battery Based on Ni-Foam-Supported Ni3S2 Nanosheets.

    PubMed

    Hu, Pu; Wang, Tianshi; Zhao, Jingwen; Zhang, Chuanjian; Ma, Jun; Du, Huiping; Wang, Xiaogang; Cui, Guanglei

    2015-12-09

    Self-supported Ni3S2 ultrathin nanosheets were in situ formed by direct sulfurization of commercially available nickel foam using thioacetamide as sulfur source under hydrothermal process. The morphology and structure of the as-obtained sample were analyzed by using XRD, XPS, SEM, and TEM, revealing that an ultrathin nanosheets Ni3S2 were grown on the surface of Ni form. The as-obtained Ni3S2/Ni composite with uniform architecture was used as cathode material for alkaline Ni/Zn battery, which delivered high capacity of 125 mAh g(-1) after 100 cycles with no obvious capacity fading, extraordinary rate capability (68 mAh g(-1) at the current density of 5.0 A g(-1)), and high operating voltage (1.75 V).

  17. Magnetic Properties of Grain Boundaries of Nanocrystalline Ni and of Ni Precipitates in Nanocrystalline NiCu Alloys

    NASA Astrophysics Data System (ADS)

    Wolf, H.; Guan, Z.; Li, X.; Wichert, Th.

    2001-11-01

    Perturbed γγ-angular correlation spectroscopy (PAC) was used to investigate nanocrystalline Ni and NiCu alloys, which are prepared by pulsed electrodeposition (PED). Using diffusion for doping nanocrystalline Ni with 111In four different ordered grain boundary structures are observed, which are characterized by unique electric field gradients. The incorporation of 111In on substitutional bulk sites of Ni is caused by moving grain boundaries below 1000 K and by volume diffusion above 1000 K. The nanocrystalline NiCu alloys prepared by PED are microscopically inhomogeneous as observed by PAC. In contrast, this inhomogeneity cannot be detected by X-ray diffraction. The influence of the temperature of the electrolyte, the current density during deposition, and the optional addition of saccharin to the electrolyte on the homogeneity of nanocrystalline NiCu alloys was investigated.

  18. Ni-based nanoalloys: Towards thermally stable highly magnetic materials

    SciTech Connect

    Palagin, Dennis Doye, Jonathan P. K.

    2014-12-07

    Molecular dynamics simulations and density functional theory calculations have been used to demonstrate the possibility of preserving high spin states of the magnetic cores within Ni-based core-shell bimetallic nanoalloys over a wide range of temperatures. We show that, unlike the case of Ni–Al clusters, Ni–Ag clusters preserve high spin states (up to 8 μ{sub B} in case of Ni{sub 13}Ag{sub 32} cluster) due to small hybridization between the electronic levels of two species. Intriguingly, such clusters are also able to maintain geometrical and electronic integrity of their cores at temperatures up to 1000 K (e.g., for Ni{sub 7}Ag{sub 27} cluster). Furthermore, we also show the possibility of creating ordered arrays of such magnetic clusters on a suitable support by soft-landing pre-formed clusters on the surface, without introducing much disturbance in geometrical and electronic structure of the cluster. We illustrate this approach with the example of Ni{sub 13}Ag{sub 38} clusters adsorbed on the Si(111)–(7×7) surface, which, having two distinctive halves to the unit cell, acts as a selective template for cluster deposition.

  19. Shell Evolution towards 78Ni: Low-Lying States in 77Cu

    NASA Astrophysics Data System (ADS)

    Sahin, E.; Bello Garrote, F. L.; Tsunoda, Y.; Otsuka, T.; de Angelis, G.; Görgen, A.; Niikura, M.; Nishimura, S.; Xu, Z. Y.; Baba, H.; Browne, F.; Delattre, M.-C.; Doornenbal, P.; Franchoo, S.; Gey, G.; Hadyńska-KlÈ©k, K.; Isobe, T.; John, P. R.; Jung, H. S.; Kojouharov, I.; Kubo, T.; Kurz, N.; Li, Z.; Lorusso, G.; Matea, I.; Matsui, K.; Mengoni, D.; Morfouace, P.; Napoli, D. R.; Naqvi, F.; Nishibata, H.; Odahara, A.; Sakurai, H.; Schaffner, H.; Söderström, P.-A.; Sohler, D.; Stefan, I. G.; Sumikama, T.; Suzuki, D.; Taniuchi, R.; Taprogge, J.; Vajta, Z.; Watanabe, H.; Werner, V.; Wu, J.; Yagi, A.; Yalcinkaya, M.; Yoshinaga, K.

    2017-06-01

    The level structure of the neutron-rich 77Cu nucleus is investigated through β -delayed γ -ray spectroscopy at the Radioactive Isotope Beam Factory of the RIKEN Nishina Center. Ions of 77Ni are produced by in-flight fission, separated and identified in the BigRIPS fragment separator, and implanted in the WAS3ABi silicon detector array, surrounded by Ge cluster detectors of the EURICA array. A large number of excited states in 77Cu are identified for the first time by correlating γ rays with the β decay of 77Ni, and a level scheme is constructed by utilizing their coincidence relationships. The good agreement between large-scale Monte Carlo shell model calculations and experimental results allows for the evaluation of the single-particle structure near 78Ni and suggests a single-particle nature for both the 5 /21- and 3 /21- states in 77Cu, leading to doubly magic 78Ni.

  20. Solidification Behavior in Newly Designed Ni-Rich Ni-Ti-Based Alloys

    NASA Astrophysics Data System (ADS)

    Samal, Sumanta; Biswas, Krishanu; Phanikumar, Gandham

    2016-12-01

    The present investigation reports phase and microstructure evolution during solidification of novel Ni-rich Ni-Ti-based alloys, Ni60Ti40, Ni50Cu10Ti40, Ni48Cu10Co2Ti40, and Ni48Cu10Co2Ti38Ta2 during suction casting. The design philosophy of the multicomponent alloys involves judicious selection of alloying elements such as Cu, Co, and Ta in the near Ni60Ti40 eutectic alloy by replacing both Ni and Ti so that phase mixture in the microstructure remains the same from the binary to quinary alloy. The basic objective is to study the effect of addition of Cu, Co, and Ta on the phase evolution and transformation in the Ni-rich Ni-Ti-based alloys. The detailed electron microscopic studies on these suction cast alloys reveal the presence of ultrafine eutectic lamellae between NiTi and Ni3Ti phases along with dendritic NiTi and Ti2Ni phases. It has also been observed that in the binary (Ni60Ti40) alloy, the ordered NiTi (B2) phase transforms to trigonal (R) phase followed by NiTi martensitic phase (M-phase), i.e., B2 → R-phase → M-phase during solid-state cooling. However, the addition of alloying elements such as Cu, Co to the binary (Ni60Ti40) alloy suppresses the martensitic transformation of the ordered NiTi (B2) dendrite. Thus, in the ternary and quaternary alloys, the ordered NiTi (B2) phase is transformed to only trigonal (R) phase, i.e., B2 → R-phase. The secondary precipitate of Ti2Ni has been observed in all of the studied alloys. Interestingly, Ni48Cu10Co2Ti38Ta2 quinary alloy shows the disordered nature of NiTi dendrites. The experimentally observed solidification path is in good agreement with Gulliver-Scheil simulated path for binary alloy, whereas simulated solidification path deviates from the experimental results in case of ternary, quaternary, and quinary alloys.

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

    SciTech Connect

    Aidhy, Dilpuneet S.; Lu, Chenyang; Jin, Ke; Bei, Hongbin; Zhang, Yanwen; Wang, Lumin; Weber, William J.

    2015-08-08

    Using molecular dynamics simulations, we elucidate irradiation-induced point defect evolution in fcc pure Ni, Ni0.5Fe0.5, and Ni0.8Cr0.2 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 and 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.

  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, Ni0.5Fe0.5, and Ni0.8Cr0.2 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 and more clusters are observedmore » 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. 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

  4. 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.

  5. Grain boundary segregation of Ni in W

    SciTech Connect

    Nieh, T.G.

    1984-11-01

    The compatibility between Ni and W is an important consideration in a number of structural applications involving tungsten alloys. Here, results of an experimental study using Auger electron spectroscopy are presented which provide direct evidence of grain boundary segregation of Ni in W. It is also demonstrated that the segregation of nickel results in a severe embrittlement of tungsten filaments. Also, the activation energy for grain boundary diffusion of Ni in W has been calculated to be 358 kJ/mol, almost identical to the activation energy for recrystallization of dilute W-Ni alloys. This suggests that grain boundary diffusion of Ni may govern the recrystallization processes in dilute W-Ni alloys. 11 references.

  6. Electroless Plated Co-Ni-P-B/Ni Foam Catalyst for Hydrogen Generation from Sodium Borohydride.

    PubMed

    Park, Daeil; Kim, Taegyu

    2016-02-01

    Co-Ni-P-B catalyst supported on Ni foam was prepared using electroless plating for hydrogen generation from an alkaline NaBH4 solution. Co-B, Co-P-B, and Co-Ni-B were prepared for comparison. Surface morphology of catalyst/Ni foams were observed using SEM analysis. The Co- Ni-P-B/Ni foam catalyst showed the superior performance on hydrogen generation rate due to the uniform formation of catalyst particles on the surface of Ni foam. Characteristics of hydrogen generation rate on the Co-N-P-B/Ni foam catalyst were investigated at the variety of NaBH4 and NaOH concentrations. The hydrogen generation rate increased with decreasing NaBH4 concentration, while increasing NaOH concentration. Durability test was performed, resulting in the stable hydrogen generation for 6 hours.

  7. An advanced Ni-Cd battery cell design

    NASA Technical Reports Server (NTRS)

    Miller, L.

    1986-01-01

    The evolution of an advanced Ni-Cd space battery cell design continues to prove very promising. High oxygen/hydrogen gas recombination rates (currently up to a C/5 charge rate) and increased electrolyte activation level tolerance (currently up to 5.6 grams Ah of positive capacity) were demonstrated by test. A superior performance, extended life battery cell offering advantages should soon be available for mission applications

  8. NiF2 Cathodes For Rechargeable Na Batteries

    NASA Technical Reports Server (NTRS)

    Bugga, Ratnakumar V.; Distefano, Salvador; Halpert, Gerald

    1992-01-01

    Use of NiF2 cathodes in medium-to-high-temperature rechargeable sodium batteries increases energy and power densities by 25 to 30 percent without detracting from potential advantage of safety this type of sodium battery offers over sodium batteries having sulfur cathodes. High-energy-density sodium batteries with metal fluoride cathodes used in electric vehicles and for leveling loads on powerlines.

  9. Composite Ni/NiO-Cr2O3 Catalyst for Alkaline Hydrogen Evolution Reaction

    SciTech Connect

    Bates, MK; Jia, QY; Ramaswamy, N; Allen, RJ; Mukerjee, S

    2015-03-12

    We report a Ni-Cr/C electrocatalyst with unpreeedented massactivity for the hydrogen evolution reaction (HER). in alkaline electrolyte. The HER Oietics of numerous binary and ternary Ni-alloys and composite Ni/metal-euride/C samples were evaluated in aquebus 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni-Cr materials which exhibit metallic Ni as well as NiOx and Cr2O3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to munerous binary dor ternary Ni-alloys, inCluding Ni Mg materials. It is likely that at adjacent Ni/NiOx sites, the oxide acts as a sink for OHads, while the metallic Ni acts as a, sink for the H-ads, intermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiO content and that the Cr2O3 appears to stabilize the composite NiO component-under HER conditions (where NiOx would typically be reduced to metallic Ni-0). Furthermore, in contrast to Pt, the Ni(O-x)/Cr2O3 catalyst appears resistant to poisoning by the anion.exchange ionomer (AEI), a serloua consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a: detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI.

  10. Ni clay neoformation on montmorillonite surface.

    PubMed

    Dähn, R; Scheidegger, A; Manceau, A; Schlegel, M; Baeyens, B; Bradbury, M H

    2001-03-01

    Polarized extended X-ray absorption fine structure spectroscopy (P-EXAFS) was used to study the sorption mechanism of Ni on the aluminous hydrous silicate montmorillonite at high ionic strength (0.3 M NaClO4), pH 8 and a Ni concentration of 0.66 mM. Highly textured self-supporting clay films were obtained by slowly filtrating a clay suspension after a reaction time of 14 days. P-EXAFS results indicate that sorbed Ni has a Ni clay-like structural environment with the same crystallographic orientation as montmorillonite layers.

  11. Morphology controlled synthesis of 2-D Ni-Ni3S2 and Ni3S2 nanostructures on Ni foam towards oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Chaudhari, Nitin Kaduba; Oh, Aram; Sa, Young Jin; Jin, Haneul; Baik, Hionsuck; Kim, Sang Gu; Lee, Suk Joong; Joo, Sang Hoon; Lee, Kwangyeol

    2017-03-01

    Catalysts for oxygen evolution reactions (OER) are at the heart of key renewable energy technologies, and development of non-precious metal catalysts with high activity and stability remain a great challenge in this field. Among various material candidates, metal sulfides are receiving increasing attention. While morphology-dependent catalytic performances are well established in noble metal-based catalysts, relatively little is known for the morphology‒catalytic performance relationship in metal sulfide catalysts. In this study, uniform spider web-like Ni nanosheets-Ni3S2 and honeycomb-like Ni3S2 structures are deposited on nickel foam (Ni3S2/NF) by a facile one-step hydrothermal synthetic route. When used as an oxygen evolution electrode, the spider web-like Ni-Ni3S2/NF with the large exposed surface area shown excellent catalytic activity and stability with an overpotential of 310 mV to achieve at 10 mA/cm2 and a Tafel slope of 63 mV/dec in alkaline media, which is superior to the honeycomb-like structure without Ni nanosheet. The low Tafel slope of the spider web-like Ni-Ni3S2/NF represents one of the best OER kinetics among nickel sulfide-based OER catalysts. The results point to the fact that performance of the metal sulfide electrocatalysts might be fine-tuned and optimized with morphological controls.

  12. The effects of deposition parameters on surface morphology and crystallographic orientation of electroless Ni-B coatings

    NASA Astrophysics Data System (ADS)

    Bulbul, Ferhat

    2011-02-01

    Electroless Ni-B coatings were deposited on AISI 304 stainless steels by electroless deposition method, which was performed for nine different test conditions at various levels of temperature, concentration of NaBH4, concentration of NiCl2, and time, using the Taguchi L9(34) experimental method. The effects of deposition parameters on the crystallographic orientation of electroless Ni-B coatings were investigated using SEM and XRD equipment. SEM analysis revealed that the Ni-B coatings developed six types (pea-like, maize-like, primary nodular, blackberry-like or grapes-like, broccoli-like, and cauliflower-like) of morphological structures depending on the deposition parameters. XRD results also showed that these structures exhibited different levels of amorphous character. The concentration of NaBH4 had the most dominant effect on the morphological and crystallographic development of electroless Ni-B coatings.

  13. (001) Oriented piezoelectric films prepared by chemical solution deposition on Ni foils

    SciTech Connect

    Yeo, Hong Goo Trolier-McKinstry, Susan

    2014-07-07

    Flexible metal foil substrates are useful in some microelectromechanical systems applications including wearable piezoelectric sensors or energy harvesters based on Pb(Zr,Ti)O₃ (PZT) thin films. Full utilization of the potential of piezoelectrics on metal foils requires control of the film crystallographic texture. In this study, (001) oriented PZT thin films were grown by chemical solution deposition (CSD) on Ni foil and Si substrates. Ni foils were passivated using HfO₂ grown by atomic layer deposition in order to suppress substrate oxidation during subsequent thermal treatment. To obtain the desired orientation of PZT film, strongly (100) oriented LaNiO₃ films were integrated by CSD on the HfO₂ coated substrates. A high level of (001) LaNiO₃ and PZT film orientation were confirmed by X-ray diffraction patterns. Before poling, the low field dielectric permittivity and loss tangents of (001) oriented PZT films on Ni are near 780 and 0.04 at 1 kHz; the permittivity drops significantly on poling due to in-plane to out-of-plane domain switching. (001) oriented PZT film on Ni displayed a well-saturated hysteresis loop with a large remanent polarization ~36 μC/cm², while (100) oriented PZT on Si showed slanted P-E hysteresis loops with much lower remanent polarizations. The |e{sub 31,f}| piezoelectric coefficient was around 10.6 C/m² for hot-poled (001) oriented PZT film on Ni.

  14. Biopsy applications of Ti50Ni41Cu9 shape memory films for wireless capsule endoscope

    NASA Astrophysics Data System (ADS)

    Du, Hejun; Fu, Yongqing; Zhang, S.; Luo, Jack K.; Flewitt, Andrew J.; Milne, William I.

    2004-02-01

    Wireless capsule endoscopy (WCE) is a new technology to evaluate the patient with obscure gastrointestinal bleeding. However, there is still some deficiency existing in the current WCE, for example, lack of ability to biopsy and precisely locate the pathology. This study aimed to prepare and characterize TiNiCu shape memory alloy thin films for developing microgripper for biopsy (tissue sampling and tagging) applications. Ti50Ni41Cu9 thin films were prepared by co-sputtering of TiNi and Cu targets, and their transformation temperatures were slightly above that of human body. Results from differential scanning calorimetry, in-situ X-ray diffraction, curvature and electrical resistance measurement revealed clearly martensitic transformation of the deposited TiNiCu films upon heating and cooling. The biocompatibility of the TiNiCu films in the simulated gastric and intestinal solutions was also studied. Results showed the release of Ni and Cu ions is much less than the toxic level and the film did not lose shape memory effect even after 10-day immersion in the simulated solutions. TiNiCu/Si micro-cantilevers with and without electrodes were fabricated using the conventional micromachining methods and apparent shape memory effect upon heating and cooling was demonstrated.

  15. Observations and modeling of San Diego beaches during El Niño

    NASA Astrophysics Data System (ADS)

    Doria, André; Guza, R. T.; O'Reilly, William C.; Yates, M. L.

    2016-08-01

    Subaerial sand levels were observed at five southern California beaches for 16 years, including notable El Niños in 1997-98 and 2009-10. An existing, empirical shoreline equilibrium model, driven with wave conditions estimated using a regional buoy network, simulates well the seasonal changes in subaerial beach width (e.g. the cross-shore location of the MSL contour) during non-El Niño years, similar to previous results with a 5-year time series lacking an El Niño winter. The existing model correctly identifies the 1997-98 El Niño winter conditions as more erosive than 2009-10, but overestimates shoreline erosion during both El Niños. The good skill of the existing equilibrium model in typical conditions does not necessarily extrapolate to extreme erosion on these beaches where a few meters thick sand layer often overlies more resistant layers. The modest over-prediction of the 2009-10 El Niño is reduced by gradually decreasing the model mobility of highly eroded shorelines (simulating cobbles, kelp wrack, shell hash, or other stabilizing layers). Over prediction during the more severe 1997-98 El Niño is corrected by stopping model erosion when resilient surfaces (identified with aerial imagery) are reached. The trained model provides a computationally simple (e.g. nonlinear first order differential equation) representation of the observed relationship between incident waves and shoreline change.

  16. Hydrogen diffusivity in boron-doped polycrystalline Ni[sub 3]Al

    SciTech Connect

    Wan, X.J.; Zhu, J.H.; Jing, K.L. ); Liu, C.T. . Metals and Ceramics Div.)

    1994-09-15

    Recent studies have shown that Ni[sub 3]Al, like many other ordered intermetallics, exhibit severe environmental embrittlement in air at ambient temperatures. Polycrystalline Ni[sub 3]Al shows a tensile ductility as high as 23% when tested in ultra-high vacuum at room temperature, whereas the same alloy exhibits a low ductility of only 3% in laboratory air. The loss in ductility is due to air moisture, which reacts with aluminum and generates atomic hydrogen at crack tips. These results clearly indicate that the grain boundaries in Ni[sub 3]Al are not brittle at all, and that moisture-induced hydrogen causes severe embrittlement. It has been known for 15 years that additions of boron in ppm levels suppress brittle grain-boundary fracture and dramatically improve the tensile ductility of polycrystalline Ni[sub 3]Al. The ductilizing effect of boron, however, is still not well understood at present. Several researchers have suggested that boron strongly segregates to Ni[sub 3]Al grain boundaries and reduces hydrogen penetration along these boundaries. Nevertheless, there is a lack of critical experimental data to support this mechanism. The objective of this work is to provide an experimental evidence that the doping of boron in Ni[sub 3]Al substantially reduces the hydrogen diffusivity at the grain boundaries, thereby suppressing moisture-induced hydrogen embrittlement in Ni[sub 3]Al doped with sufficient amounts of boron.

  17. CH4–CO2 reforming over Ni-substituted barium hexaaluminate catalysts

    SciTech Connect

    Gardner, Todd H.; Spivey, James J.; Kugler, Edwin L.; Pakhare, Devendra

    2013-03-01

    A series of Ni-substituted barium hexaaluminate catalysts, Ba{sub 0.75}Ni{sub y}Al{sub 12-y}O{sub 19-δ} (y = 0.4, 0.6 and 1.0), were tested for CO{sub 2} reforming of CH{sub 4} at temperatures between 200 and 900 °C. Temperature programmed surface reaction results show that the reaction lights-off in a temperature range between 448 and 503 °C with a consistent decrease in light-off temperature with increasing Ni substitution. Isothermal runs performed at 900 °C show near equilibrium conversion and stable product concentrations for 18 h on all catalysts. Temperature programmed oxidation of the used catalysts show that the amount of carbon deposited on the catalyst increases with Ni substitution. High resolution XRD of the used Ba{sub 0.75}Ni{sub 0.4}Al{sub 11.6}O{sub 19-δ} catalyst shows a statistically significant contraction of the unit cell which is the result of NiO reduction from the lattice. XRD of the used catalyst also confirms the presence of graphitic carbon. XPS and ICP measurements of the as prepared catalysts show that lower levels of Ni substitution result in an increasing proportion of Ba at the surface.

  18. A prefilter for mitigating PH 3 contamination of a Ni-YSZ anode

    NASA Astrophysics Data System (ADS)

    Xu, Chunchuan; Zondlo, John W.; Sabolsky, Edward M.

    Ni-YSZ is used as the anode of a solid oxide fuel cell (SOFC) because it has excellent electrochemical performance for operation with coal-derived syngas. However, trace impurities, PH 3 H 2S AsH 3, and Sb in coal-syngas can cause SOFC degradation. Described here is a means of removing PH 3 impurity from syngas by using a Ni-based prefilter. In one test, a thin Ni-based filter was set upstream of a Ni-YSZ anode-supported SOFC. The SOFC was exposed to syngas with PH 3 under a constant current load at 800 °C. The filter decreased 20 ppm PH 3 in the feed to a level which did not degrade the SOFC for over 400 h until the filter became saturated. In another test, both H 2S and PH 3 were co-fed to the cell with Ni-based and Fe/Ni-based filters. The interaction between these two impurities did not significantly impact the filter performance with respect to PH 3 removal for both filter formulations. The cell performance was evaluated by current-voltage measurements and impedance spectroscopy. Post-mortem analyses of the cell and filter were performed by means of XRD, SEM/EDS and XPS. With proper filter design, the Ni-YSZ SOFC can operate on contaminated coal-syngas without degradation over a prescribed period of time.

  19. Kinetic tendencies of thermal transformations in nanosized Ni-MoO3 systems

    NASA Astrophysics Data System (ADS)

    Surovoi, E. P.; Bin, S. V.

    2017-02-01

    The transformations in nanosized Ni-MoO3 systems were studied by optical spectroscopy, microscopy, and gravimetry depending on the thickness of the Ni ( d = 1-40 nm) and MoO3 ( d = 3-50 nm) films, temperature (473-773 K), and thermal treatment time. The contact potential difference was measured for Ni and MoO3 films; photovoltage, for Ni-MoO3 systems. An energy band diagram of the Ni-MoO3 systems was constructed. A model of the thermal transformation of MoO3 films in Ni-MoO3 systems was suggested, which involves a redistribution of equilibrium charge carriers at the contact, formation of a [(Va)++e] center during the preparation of the MoO3 film, the transformation of this center into an [e(Va)++e] center during the formation of Ni-MoO3 systems, and the thermal transition of an electron to the level of the [(Va)++e] center to form an [e(Va)++e] center.

  20. Ordering and Spin Waves in NaNiO2: A Stacked Quantum Ferromagnet

    NASA Astrophysics Data System (ADS)

    Lewis, M. J.; Gaulin, B. D.; Dabkowska, H. A.; Qui, Y.; Copley, J. R. D.

    2004-03-01

    We have carried out time-of-flight neutron scattering measurements on NaNiO2 using the DCS spectrometer at the NIST Center for Neutron Research. NaNiO2 is made up of alternating triangular layers of NiO and NaO stacked along the c-direction. The conventional picture of the magnetism in this material has it arsing from s=1/2 moments originating from the Ni^3+ oxidation state. Our measurements reveal magnetic Bragg peaks and spin waves characteristic of strongly correlated s=1/2 magnetic moments arranged in ferromagnetic sheets and stacked in an antferromagnetic fashion. This structure lends itself very naturally to stacking sequence frustration in the presence of mixing of the Ni and alkali metal sublattice, a form of disorder known to occur at the 1-3% level in its isostructural sister compound LiNiO_2. We argue that these measurements provide a natural explanation for the enigmatic spin glass state observed in LiNiO_2, which has been a subject of speculation for nearly 20 years.

  1. New low-energy 0+ state and shape coexistence in 70Ni

    NASA Astrophysics Data System (ADS)

    Prokop, C. J.; Crider, B. P.; Liddick, S. N.; Ayangeakaa, A. D.; Carpenter, M. P.; Carroll, J. J.; Chen, J.; Chiara, C. J.; David, H. M.; Dombos, A. C.; Go, S.; Harker, J.; Janssens, R. V. F.; Larson, N.; Lauritsen, T.; Lewis, R.; Quinn, S. J.; Recchia, F.; Seweryniak, D.; Spyrou, A.; Suchyta, S.; Walters, W. B.; Zhu, S.

    2015-12-01

    In recent models, the neutron-rich Ni isotopes around N =40 are predicted to exhibit multiple low-energy excited 0+ states attributed to neutron and proton excitations across both the N =40 and Z =28 shell gaps. In 68Ni, the three observed 0+ states have been interpreted in terms of triple shape coexistence between spherical, oblate, and prolate deformed shapes. In the present work a new (02+) state at an energy of 1567 keV has been discovered in 70Ni by using β -delayed, γ -ray spectroscopy following the decay of 70Co. The precipitous drop in the energy of the prolate-deformed 0+ level between 68Ni and 70Ni with the addition of two neutrons compares favorably with results of Monte Carlo shell-model calculations carried out in the large f p g9 /2d5 /2 model space, which predict a 02+ state at 1525 keV in 70Ni. The result extends the shape-coexistence picture in the region to 70Ni and confirms the importance of the role of the tensor component of the monopole interaction in describing the structure of neutron-rich nuclei.

  2. Joining of Ni-TiC FGM and Ni-Al Intermetallics by Centrifugal Combustion Synthesis

    SciTech Connect

    Ohmi, Tatsuya; Matsuura, Kiyotaka; Iguchi, Manabu; Mizuma, Kiminori

    2008-02-15

    A centrifugal combustion synthesis (CCS) process has been investigated to join a Ni-Al intermetallic compound and a Ni-TiC cermet. The cermet, a tubular graphite mold, and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. When the combustion synthesis reaction was induced in the centrifugal force field, a synthesized molten Ni-Al alloy flowed into the graphite mold and joined to the cermet. The soundness of the joint interface depended on the volume percentage of TiC phase in the cermet. A lot of defects were formed near the interface between the Ni-TiC cermet and the cast Ni-Al alloy when the volume percentage of TiC was 50% or higher. For this kind of cermet system, using a functionally graded cermet such as Ni-10 vol.%TiC/Ni-25 vol.%TiC/Ni-50 vol.%TiC overcame this difficulty. The four-point bending strength of the joined specimen consisting of the three-layered FGM cermet and cast Ni-29 mol%Al alloy was 1010 MPa which is close to the result for a Ni-29 mol%Al alloy specimen.

  3. Ni cluster formation in low temperature annealed Ni50.6Ti49.4

    NASA Astrophysics Data System (ADS)

    Pourbabak, Saeid; Wang, Xiebin; van Dyck, Dirk; Verlinden, Bert; Schryvers, Dominique

    Various low temperature treatments of Ni50.6Ti49.4 have shown an unexpected effect on the martensitic start temperature. Periodic diffuse intensity distributions in reciprocal space indicate the formation of short pure Ni strings along the <111> directions in the B2 ordered lattice, precursing the formation of Ni4Ti3 precipitates formed at higher annealing temperatures.

  4. Internal-nitriding behavior of Ni-V and Ni-3Nb alloys

    SciTech Connect

    Allen, A.T.; Douglass, D.L.

    1999-02-01

    Ni-2V, Ni-5V, Ni-12V, and Ni-3Nb alloys (w/o) were nitrided in 10 v/o NH{sub 3} (bal H{sub 2}) over the range of 700--1000 C. The growth rates of the reaction zones followed parabolic behavior for all of the alloys from 700 to 900 C. At 1000 C, Ni-2V and Ni-3Nb formed nitride scales, whereas Ni-5V and Ni-12V formed internal-nitride zones. Nitridation rates decreased with increasing vanadium content for the Ni-V alloys. VN precipitated in the Ni-V alloys and NbN precipitated in Ni-3Nb for all exposure conditions in which internal nitridation occurred. The precipitate morphology changed with temperature and distance from the gas-metal surface. The VN and NbN precipitates were generally small and spheroidal near the surface, increasing in size with distance and temperature. The NbN precipitates became Widmanstaetten at higher temperatures and/or increasing distance within the nitrided zone. The solubility of nitrogen in pure Ni was determined and found to decrease with increasing temperature from 700 to 1000 C. Expressions for the diffusion coefficient of nitrogen in nickel were determined from the measured permeabilities of each alloy and the nitrogen solubilities in nickel.

  5. Effect of air annealing on structural and magnetic properties of Ni/NiO nanoparticles

    NASA Astrophysics Data System (ADS)

    Nadeem, K.; Ullah, Asmat; Mushtaq, M.; Kamran, M.; Hussain, S. S.; Mumtaz, M.

    2016-11-01

    We reported systematic study on structural and magnetic properties of nickel/nickel oxide (Ni/NiO) nanoparticles annealed under air atmosphere at different temperatures in the range 400-800 °C. The XRD spectra revealed two phases such as Ni and NiO. The average crystallite size increases with increasing annealing temperature. A phase diagram was developed between two phases versus annealing temperature using XRD analysis. At lower annealing temperatures, Ni phase is dominant which does not easily undergo oxidation to form NiO. The NiO phase increases with increasing annealing temperature. FTIR spectroscopy revealed an increase in the NiO phase content at higher annealing temperature, which is in agreement with the XRD analysis. SEM images showed that nanoparticles are well separated at lower annealing temperatures but get agglomerated at higher annealing temperatures. The ferromagnetic (FM) Ni phase content and saturation magnetization (Ms) showed nearly the same trend with increasing annealing temperature. The nanoparticles annealed at 500 °C and 800 °C revealed highest and lowest Ms values, respectively, which is in accordance with the XRD phase diagram. Coercivity showed an overall decreasing trend with increasing annealing temperature due to decreased concentration of FM Ni phase and increasing average crystallite size. All these measurements indicate that the structural and magnetic properties of Ni/NiO nanoparticles are strongly influenced by the annealing temperature.

  6. Porous NiTi shape memory alloys produced by SHS: microstructure and biocompatibility in comparison with Ti2Ni and TiNi3.

    PubMed

    Bassani, Paola; Panseri, Silvia; Ruffini, Andrea; Montesi, Monica; Ghetti, Martina; Zanotti, Claudio; Tampieri, Anna; Tuissi, Ausonio

    2014-10-01

    Shape memory alloys based on NiTi have found their main applications in manufacturing of new biomedical devices mainly in surgery tools, stents and orthopedics. Porous NiTi can exhibit an engineering elastic modulus comparable to that of cortical bone (12-17 GPa). This condition, combined with proper pore size, allows good osteointegration. Open cells porous NiTi was produced by self propagating high temperature synthesis (SHS), starting from Ni and Ti mixed powders. The main NiTi phase is formed during SHS together with other Ni-Ti compounds. The biocompatibility of such material was investigated by single culture experiment and ionic release on small specimen. In particular, NiTi and porous NiTi were evaluated together with elemental Ti and Ni reference metals and the two intermetallic TiNi3, Ti2Ni phases. This approach permitted to clearly identify the influence of secondary phases in porous NiTi materials and relation with Ni-ion release. The results indicated, apart the well-known high toxicity of Ni, also toxicity of TiNi3, whilst phases with higher Ti content showed high biocompatibility. A slightly reduced biocompatibility of porous NiTi was ascribed to combined effect of TiNi3 presence and topography that requires higher effort for the cells to adapt to the surface.

  7. Durability of Ni anodes during reoxidation cycles

    NASA Astrophysics Data System (ADS)

    Ettler, M.; Timmermann, H.; Malzbender, J.; Weber, A.; Menzler, N. H.

    Anodes manufactured from NiO- and yttria-stabilized zirconia (Y 2O 3 doped ZrO 2, YSZ) powders are today's state of the art for solid oxide fuel cells (SOFCs) because they are easy to manufacture and have high performance in both anode-supported and electrolyte-supported cells. However, such cells can show significant degradation or fail completely if nickel is reoxidized during high-temperature operation even though it can be reduced again. Tests with stacks and systems have shown that system shutdown procedures, accidental air entry due to component failure or controlled air feed to the anode side as a result of operational necessities may occur and result in the reoxidation of the metallic nickel. This reoxidation is not only associated with a volume expansion, but also with significant structural changes in the anode microstructure, generating stresses in the anode itself, as well as in the electrolyte. These stresses can exceed the stability of the components, potentially promoting crack growth, which leads to degradation of the SOFC or complete failure. This problem has been addressed by a number of contributions in the literature over the last decade, but interest is increasing, particularly because SOFC systems are being discussed for transport and mobile applications requiring new system specifications. The most critical problem to be overcome is the tolerance of a large number of intentional redox cycles due to system requirements during operating lifetime. This article gives an overview of the various approaches to the redox problem by summarizing many of the contributions, starting with a basic understanding of the underlying physicochemical processes of Ni reduction and oxidation and ending at stack-level results, leading finally to their combination with recent findings. It aims to elaborate reliable results and open questions on this topic considering the mechanical and electrochemical aspects of the problem.

  8. Different Effect of Co on the Formation of Topologically Close-Packed Phases in Ni-Cr-Mo and Ni-Cr-Re Alloys

    NASA Astrophysics Data System (ADS)

    Shi, Qianying; An, Ning; Huo, Jiajie; Ding, Xianfei; Zheng, Yunrong; Feng, Qiang

    2017-09-01

    In current study, two sets of Ni-based alloys (Ni-Cr-Mo and Ni-Cr-Re series) containing 0 to 15 at. pct of Co addition were investigated to understand the formation behavior of TCP phases. Significant difference on the formation behavior of TCP phases and corresponding Co effect was found in two series alloys. TCP precipitates (P and µ phase) were observed in both grain interiors and boundaries in Ni-Cr-Mo series alloys. Higher levels of Co addition increased the supersaturation of Mo in the γ matrix, which explained that Co addition promoted µ phase formation. In contrast, the TCP precipitates (σ phase) formed by the manner of discontinuous precipitation transformation in the grain boundaries in Ni-Cr-Re series alloys. More Co additions suppressed the formation of σ phase, which was mainly attributed to the decreased supersaturation of Re in thermodynamically metastable γ matrix. The information obtained from simplified alloy systems in this study is helpful for the design of multicomponent Ni-based superalloys.

  9. Corals record long-term Leeuwin current variability including Ningaloo Niño/Niña since 1795.

    PubMed

    Zinke, J; Rountrey, A; Feng, M; Xie, S-P; Dissard, D; Rankenburg, K; Lough, J M; McCulloch, M T

    2014-04-01

    Variability of the Leeuwin current (LC) off Western Australia is a footprint of interannual and decadal climate variations in the tropical Indo-Pacific. La Niña events often result in a strengthened LC, high coastal sea levels and unusually warm sea surface temperatures (SSTs), termed Ningaloo Niño. The rarity of such extreme events and the response of the southeastern Indian Ocean to regional and remote climate forcing are poorly understood owing to the lack of long-term records. Here we use well-replicated coral SST records from within the path of the LC, together with a reconstruction of the El Niño-Southern Oscillation to hindcast historical SST and LC strength from 1795 to 2010. We show that interannual and decadal variations in SST and LC strength characterized the past 215 years and that the most extreme sea level and SST anomalies occurred post 1980. These recent events were unprecedented in severity and are likely aided by accelerated global ocean warming and sea-level rise.

  10. Corals record long-term Leeuwin current variability including Ningaloo Niño/Niña since 1795

    PubMed Central

    Zinke, J.; Rountrey, A.; Feng, M.; Xie, S.-P.; Dissard, D.; Rankenburg, K.; Lough, J.M.; McCulloch, M.T.

    2014-01-01

    Variability of the Leeuwin current (LC) off Western Australia is a footprint of interannual and decadal climate variations in the tropical Indo-Pacific. La Niña events often result in a strengthened LC, high coastal sea levels and unusually warm sea surface temperatures (SSTs), termed Ningaloo Niño. The rarity of such extreme events and the response of the southeastern Indian Ocean to regional and remote climate forcing are poorly understood owing to the lack of long-term records. Here we use well-replicated coral SST records from within the path of the LC, together with a reconstruction of the El Niño-Southern Oscillation to hindcast historical SST and LC strength from 1795 to 2010. We show that interannual and decadal variations in SST and LC strength characterized the past 215 years and that the most extreme sea level and SST anomalies occurred post 1980. These recent events were unprecedented in severity and are likely aided by accelerated global ocean warming and sea-level rise. PMID:24686736

  11. 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.

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

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.

    1973-01-01

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

  13. Nickel dispersion and enrichment at the bottom of the regolith: formation of pimelite target-like ores in rock block joints (Koniambo Ni deposit, New Caledonia)

    NASA Astrophysics Data System (ADS)

    Cathelineau, Michel; Quesnel, Benoît; Gautier, Pierre; Boulvais, Philippe; Couteau, Clément; Drouillet, Maxime

    2016-02-01

    In New Caledonian Ni deposits, the richest Ni silicate ores occur in fractures within the bedrock and saprolite, generally several tens of meters to hundred meters below the present-day surface. Fracture-related Ni silicate ore accounts for high Ni grades, at least a few weight percent above the average exploited grade (2.5 %). These Ni-rich veins are affected by active dissolution-precipitation processes at the level of the water table. Ni in solution is precipitated as silicates in thin layer cementing joints. This mineralization is characterized by chemical and mineralogical concentric zoning with an outer green rim around an inner white zone composed, from the edge to the centre of the block, (i) a highly oxidized and altered zone, (ii) a green pure Ni-rich pimelite zone, (iii) a zone (limited to a few centimetres) with a mixture of Ni-poor kerolite and Ni-rich pimelite and intermediate colours and (iv) a large white Mg-kerolite mineralization zone. This study proposes that the concentric zonation results from evapo-precipitation process related to alternate periods of hydration and drying, induced by water table movements. This extensive dispersion of Ni in concentrically zoned ores can partly explain the rather monotonous Ni grade of the bulk exploitation at the base of the regolith with values between 2 and 3 wt%.

  14. Bioavailability and trophic transfer of sediment-bound Ni and U in a southeastern wetland system.

    PubMed

    Punshon, T; Gaines, K F; Jenkins Jr, R A

    2003-01-01

    Elemental composition of soil, herbaceous and woody plant species, and the muscle and liver tissue of two common small mammal species were determined in a wetland ecosystem contaminated with Ni and U from nuclear target processing activities at the Savannah River Site, Aiken, SC. Species studied were black willow ( Salix nigra L.), rushes ( Juncus effusus L.), marsh rice rat ( Oryzomys palustris), and cotton rat ( Sigmodon hispidus). Two mature trees were sampled around the perimeter of the former de facto settling basin, and transect lines sampling rushes and trapping small mammals were laid across the wetland area, close to a wooden spillway that previously enclosed the pond. Ni and U concentrations were elevated to contaminant levels; with a total concentration of 1,065 (+/- 54) mg kg(-1) U and 526.7 (+/-18.3) mg kg(-1) Ni within the soil. Transfer of contaminants into woody and herbaceous plant tissues was higher for Ni than for U, which appeared to remain bound to the outside of root tissues, with very little (0.03 +/- 0.001 mg kg(-1)) U detectable within the leaf tissues. This indicated a lower bioavailability of U than the cocontaminant Ni. Trees sampled from the drier margins of the pond area contained more Ni within their leaf tissues than the rushes sampled from the wetter floodplain area, with leaf tissues concentrations of Ni of approximately 75.5 (+/- 3.6) mg kg(-1) Ni. Ni concentrations were also elevated in small mammal tissues. Transfer factors of contaminants indicated that U bioavailability is negligable in this wetland ecosystem.

  15. Where is La Niña?

    NASA Image and Video Library

    2003-07-14

    Since the weak El Niño event of last winter, the equatorial Pacific has cooled and oceanographers have been on a La Niña watch. Thus far, equatorial waters have seesawed between cooling and the present slight warming.

  16. Who is El Niño?

    NASA Astrophysics Data System (ADS)

    Philander, S. George

    It is a curious story, about a phenomenon we first welcomed as a blessing but now view with dismay, if not horror [Philander, 1998]. We named it El Niño for the child Jesus, provided it with relatives—La Niña and ENSO—and are devoting innumerable studies to the description and idealization of this family. These scriptures provide such a broad spectrum of historical, cultural, and scientific perspectives that there is now confusion about the identity of El Niño. Trenberth [1997] summarizes the situation as follows.The atmospheric component tied to El Niño is termed the “Southern Oscillation.” Scientists often call the phenomenon where the atmosphere and ocean collaborate ENSO, short for El Niño-Southern Oscillation. El Niño then corresponds to the warm phase of ENSO. The opposite “La Niña” (“the girl” in Spanish) phase consists of a basinwide cooling of the tropical Pacific and thus the cold phase of ENSO. However, for the public, the term for the whole phenomenon is “El Niño.”

  17. AF Ni-Cd cell qualification program

    NASA Technical Reports Server (NTRS)

    Hall, Steve; Brown, Harry; Collins, G.; Hwang, Warren

    1994-01-01

    The present status of the USAF NiCd cell qualification program, which is underway at the Naval Surface Warfare Center-Crane Division, is summarized. The following topics are discussed: overview; background; purpose; stress tests; results for super Ni-Cd; results for SAFT cells; GPS stress test; GPS simulated orbit; and results for gates cells. The discussion is presented in viewgraph format.

  18. Diel nitrogen fixation pattern of Trichodesmium: the interactive control of light and Ni

    PubMed Central

    Rodriguez, Irene B.; Ho, Tung-Yuan

    2014-01-01

    Trichodesmium, a nonheterocystous cyanobacterium widely abundant in the surface water of the tropical and subtropical ocean, fixes dinitrogen under high light conditions while concurrently undergoing photosynthesis. The new production considerably influences the cycling of nitrogen and carbon in the ocean. Here, we investigated how light intensity and nickel (Ni) availability interplay to control daily rates and diel patterns of N2 fixation in Trichodesmium. We found that increasing Ni concentration increased N2 fixation rates by up to 30-fold in the high light treatment. Cultures subjected to high Ni and light levels fixed nitrogen throughout most of the 24 H light:dark regime with the highest rate coinciding with the end of the 12 H light period. Our study demonstrates the importance of Ni on nitrogen fixation rates for Trichodesmium under high light conditions. PMID:24658259

  19. Diel nitrogen fixation pattern of Trichodesmium: the interactive control of light and Ni

    NASA Astrophysics Data System (ADS)

    Rodriguez, Irene B.; Ho, Tung-Yuan

    2014-03-01

    Trichodesmium, a nonheterocystous cyanobacterium widely abundant in the surface water of the tropical and subtropical ocean, fixes dinitrogen under high light conditions while concurrently undergoing photosynthesis. The new production considerably influences the cycling of nitrogen and carbon in the ocean. Here, we investigated how light intensity and nickel (Ni) availability interplay to control daily rates and diel patterns of N2 fixation in Trichodesmium. We found that increasing Ni concentration increased N2 fixation rates by up to 30-fold in the high light treatment. Cultures subjected to high Ni and light levels fixed nitrogen throughout most of the 24 H light:dark regime with the highest rate coinciding with the end of the 12 H light period. Our study demonstrates the importance of Ni on nitrogen fixation rates for Trichodesmium under high light conditions.

  20. Effects of added Zn, Ni and Cd on desert shrubs grown in desert soil

    SciTech Connect

    Patel, P.M.; Wallace, A.; Romney, E.M.; Alexander, G.V.

    1980-01-01

    Desert shrubs - Ambrosia dumosa, Lycium andersonii, Larrea tridenata, and Ephedra nevadensis wre grown in a glasshouse in desert (calcarous) soil with different levels of added Zn, Ni, and Cd. The objective was to study effects of the metals on growth and yield and uptake and translocation of metals in desert plant species which are common in the Mojave Desert (areas of Nevada and southeast California). Zinc and Cd considerably decreased yields of all four species. Yields of E. nevadensis were increased by Ni at 250 and 500 mg/kg applied to desert soil. Ephedra nevadensis was more tolerant of Ni than were the other three desert shrubs. Some interactions were observed among various elements: manganese concentration was increased in shrubs by Zn. Particularly, application of Ni reduced the concentrations of Zn and Mn over the control.

  1. Hydrogen Sensing with Ni-Doped TiO2 Nanotubes

    PubMed Central

    Li, Zhaohui; Ding, Dongyan; Liu, Qiang; Ning, Congqin

    2013-01-01

    Doping with other elements is one of the efficient ways to modify the physical and chemical properties of TiO2 nanomaterials. In the present work, Ni-doped TiO2 nanotubes were fabricated through anodic oxidation of NiTi alloy and further annealing treatment. The hydrogen sensing properties of the nanotube sensor were investigated. It was found that the Ni-doped TiO2 nanotubes were sensitive to an atmosphere of 1,000 ppm hydrogen, showing a good response at both room temperature and elevated temperatures. A First-Principle simulation revealed that, in comparison with pure anatase TiO2 oxide, Ni doping in the TiO2 oxide could result in a decreased bandgap. When the oxide sensor adsorbed a certain amount of hydrogen the bandgap increased and the acceptor impurity levels was generated, which resulted in a change of the sensor resistance. PMID:23881124

  2. Preparation and characterization of Ni-P/Ni3.1B composite alloy coatings

    NASA Astrophysics Data System (ADS)

    Wang, Yurong; He, Jiawei; Wang, Wenchang; Shi, Jianhua; Mitsuzaki, Naotoshi; Chen, Zhidong

    2014-02-01

    The preparation of Ni-P/Ni3.1B composite alloy coating on the surface of copper was achieved by co-deposition of Ni3.1B nanoparticles with Ni-P coating during electroless plating. Ni-P-B alloy coating was obtained by heat-treating the as-plated Ni-P/Ni3.1B composite coating. The effect of the concentration of sodium alginate, borax, thiourea, Ni3.1B, temperature, and pH value on the deposition rate and B content were investigated and determined to be: 30 g L-1, 10 g L-1, 2 mg L-1, 20 mg L-1, 70 °C and 9.0 , respectively. Sodium alginate and thiourea were played as surfactant for coating Ni3.1B nanoparticles and stabilizer for the plating bath, respectively. Ni-P/Ni3.1B composite coating had good performance such as corrosion resistance and solderability.

  3. Water dissociation on Ni(100) and Ni(111): Effect of surface temperature on reactivity

    SciTech Connect

    Seenivasan, H.; Tiwari, Ashwani K.

    2013-11-07

    Water adsorption and dissociation on Ni(100) and Ni(111) surfaces are studied using density functional theory calculations. Water adsorbs on top site on both the surfaces, while H and OH adsorb on four fold hollow and three fold hollow (fcc) sites on Ni(100) and Ni(111), respectively. Transition states (TS) on both surfaces are identified using climbing image-nudged elastic band method. It is found that the barrier to dissociation on Ni(100) surface is slightly lower than that on Ni(111) surface. Dissociation on both the surfaces is exothermic, while the exothermicity on Ni(100) is large. To study the effect of lattice motion on the energy barrier, TS calculations are performed for various values of Q (lattice atom coordinate along the surface normal) and the change in the barrier height and position is determined. Calculations show that the energy barrier to reaction decreases with increasing Q and increases with decreasing Q on both the surfaces. Dissociation probability values at different surface temperatures are computed using semi-classical approximation. Results show that the influence of surface temperature on dissociation probability on the Ni(100) is significantly larger compared to that of Ni(111). Moreover, on Ni(100), a dramatic shift in energy barrier to lower incident energy values is observed with increasing surface temperature, while the shift is smaller in the case of Ni(111)

  4. Analyzing the magnetic profile in NiFe/NiO bilayers

    NASA Astrophysics Data System (ADS)

    Tafur, Miguel; Nascimento, V. P.; Alayo, W.; Xing, Y. T.; Baggio-Saitovitch, E.

    2017-04-01

    The magnetic profile of the Si(100)/NiO(35 nm)/NiFe(10 nm)/Ta(1 nm) sample has been obtained by X-ray absorption spectroscopy (XAS) and the X-ray magnetic circular dichroism (XMCD). Two experimental procedures were used. In the procedure 1, the magnetic depth profile has been determines using samples deposited with different NiFe thicknesses, Si(100)/NiO(35 nm)/NiFe(t)/Ta(1 nm), t = 1 , 3 , 5 , 7 , 10 nm . In procedure 2, the sample (NiFe=10 nm), was thinned by several in situ sputtering cycles with Ar+ ions, followed by XAS and XMCD analysis. In both procedures, the calculated magnetic moments values tend to decrease close to interface with the NiO antiferromagnetic (AF) layer, however, this decreasement is more evidenced in the sputtered sample. There is no charge transfer between Ni and Fe in the inner part of the NiFe layer, a reduction of the morb /mspineff has been found at the NiFe/NiO interface. Procedure 1 emerged as the most indicated to analyse the interface region.

  5. Reaction of amorphous Ni-W and Ni-N-W films with substrate silicon

    SciTech Connect

    Zhu, M.F.; Suni, I.; Nicolet, M.; Sands, T.

    1984-11-15

    Amorphous films of Ni-W and Ni-N-W were deposited on single-crystal silicon with discharge gases of Ar or Ar+N/sub 2/ by rf cosputtering of Ni and W. The reaction of these Ni-W and Ni-N-W films with the Si substrate were studied in the temperature range of 450--750 /sup 0/C by a combination of backscattering spectrometry, x-ray diffraction, cross-sectional transmission electron microscopy, and resistivity measurements. Films with composition Ni/sub 36/W/sub 64/ are stable below 500 /sup 0/C. NiSi and NiSi/sub 2/ form at 500 /sup 0/C, and WSi/sub 2/ forms rapidly in the temperature range of 625--650 /sup 0/C. The nickel silicide forms adjacent to and within the silicon, while the outer layer becomes a mixture of WSi/sub 2/ and NiSi/sub 2/. The morphologies of the reacted layers are revealed by cross-sectional transmission electron microscopy. The crystallization temperature of amorphous Ni/sub 36/W/sub 64/ films on SiO/sub 2/ is near 650 /sup 0/C also. Adding nitrogen to form amorphous Ni/sub 30/N/sub 21/W/sub 49/ films lowers the crystallization temperature, but raises the reaction temperature with Si to 750 /sup 0/C.

  6. Water dissociation on Ni(100) and Ni(111): effect of surface temperature on reactivity.

    PubMed

    Seenivasan, H; Tiwari, Ashwani K

    2013-11-07

    Water adsorption and dissociation on Ni(100) and Ni(111) surfaces are studied using density functional theory calculations. Water adsorbs on top site on both the surfaces, while H and OH adsorb on four fold hollow and three fold hollow (fcc) sites on Ni(100) and Ni(111), respectively. Transition states (TS) on both surfaces are identified using climbing image-nudged elastic band method. It is found that the barrier to dissociation on Ni(100) surface is slightly lower than that on Ni(111) surface. Dissociation on both the surfaces is exothermic, while the exothermicity on Ni(100) is large. To study the effect of lattice motion on the energy barrier, TS calculations are performed for various values of Q (lattice atom coordinate along the surface normal) and the change in the barrier height and position is determined. Calculations show that the energy barrier to reaction decreases with increasing Q and increases with decreasing Q on both the surfaces. Dissociation probability values at different surface temperatures are computed using semi-classical approximation. Results show that the influence of surface temperature on dissociation probability on the Ni(100) is significantly larger compared to that of Ni(111). Moreover, on Ni(100), a dramatic shift in energy barrier to lower incident energy values is observed with increasing surface temperature, while the shift is smaller in the case of Ni(111).

  7. Thermodynamic Assessment of the Bi-Ni and Bi-Ni-X (X = Ag, Cu) Systems

    NASA Astrophysics Data System (ADS)

    Liu, Yuling; Liu, Shuhong; Zhang, Cong; Lu, Xingxu; Chen, Chong; Du, Yong; Živković, Dragana

    2016-02-01

    The Bi-Ni system was reassessed by means of the calculation of phase diagrams (CALPHAD) method by considering the latest published experimental data. To maintain the compatibility in higher-order systems, the excess Gibbs energy of the solution phases was modeled with the Redlich-Kister polynomials, and a three-sublattice model, (Bi)0.3334(Ni,Va)0.3333(Va,Ni)0.3333, was used to describe the intermetallic compound BiNi with NiAs-type crystal structure. Compared with the previous thermodynamic description for the Bi-Ni system, noticeable improvements are achieved in the present work. The current thermodynamic parameters can well reproduce the newly published experimental data on thermodynamic properties. Based on the newly obtained parameters for the Bi-Ni system, as well as the thermodynamic descriptions for the Bi-Ag, Ni-Ag, Bi-Cu, and Ni-Cu systems in literature, a thermodynamic database of the Bi-Ni-Ag and Bi-Ni-Cu ternary systems was established by considering the available experimental data. The calculated phase equilibria in these ternary systems are in satisfactory agreement with experimental observations.

  8. Predictability of the Ningaloo Niño/Niña.

    PubMed

    Doi, Takeshi; Behera, Swadhin K; Yamagata, Toshio

    2013-10-08

    The seasonal prediction of the coastal oceanic warm event off West Australia, recently named the Ningaloo Niño, is explored by use of a state-of-the-art ocean-atmosphere coupled general circulation model. The Ningaloo Niño/Niña, which generally matures in austral summer, is found to be predictable two seasons ahead. In particular, the unprecedented extreme warm event in February 2011 was successfully predicted 9 months in advance. The successful prediction of the Ningaloo Niño is mainly due to the high prediction skill of La Niña in the Pacific. However, the model deficiency to underestimate its early evolution and peak amplitude needs to be improved. Since the Ningaloo Niño/Niña has potential impacts on regional societies and industries through extreme events, the present success of its prediction may encourage development of its early warning system.

  9. Self-oxidized NiO on cube-textured Ni for YBCO coated superconductor

    NASA Astrophysics Data System (ADS)

    Wang, Rong-Ping; Wang, Huan-Hua; Zhou, Yue-Liang; Pan, Shao-Hua; Liu, Chun-Fang; Wu, Xuan; Liu, Dan-Ming; Zhang, Ping-Xiang; Zhou, Lian

    2000-10-01

    In this paper, we report a self-oxidation approach to obtain NiO on the surface of Ni substrates. Under optimal oxidizing conditions, high-textured NiO layers on the surface of Ni substrates were obtained. Detailed pole figure (PF) measurements show an improvement in the full width at half maximum of NiO layers compared with that of Ni substrate. Orientation distribution function calculated from two PFs shows that the best cubic texture of NiO can be formed at 680°C in 5 Pa oxygen. A grain size less than 1 μm is evident from scanning electron microscopy observation. Some possible ways were proposed to improve surface quality. The self-oxidation approach provides a potential to prepare high- Jc YBCO films on a large scale.

  10. Nanoscale structural heterogeneity in Ni-rich half-Heusler TiNiSn

    SciTech Connect

    Douglas, Jason E. Pollock, Tresa M.; Chater, Philip A.; Brown, Craig M.; Seshadri, Ram

    2014-10-28

    The structural implications of excess Ni in the TiNiSn half-Heusler compound are examined through a combination of synchrotron x-ray and neutron scattering studies, in conjunction with first principles density functional theory calculations on supercells. Despite the phase diagram suggesting that TiNiSn is a line compound with no solid solution, for small x in TiNi{sub 1+x}Sn there is indeed an appearance—from careful analysis of the scattering—of some solubility, with the excess Ni occupying the interstitial tetrahedral site in the half-Heusler structure. The analysis performed here would point to the excess Ni not being statistically distributed, but rather occurring as coherent nanoclusters. First principles calculations of energetics, carried out using supercells, support a scenario of Ni interstitials clustering, rather than a statistical distribution.

  11. Prolidase-Associated Trace Elements (Mn, Zn, Co, and Ni) in the Patients with Parkinson's Disease.

    PubMed

    Verma, Akhilesh Kumar; Keshari, Anand Kumar; Raj, Janak; Kumari, Renu; Kumar, Tarun; Sharma, Vivek; Singh, Tej Bali; Srivastava, Shalabh; Srivastava, Ragini

    2016-05-01

    Micronutrients and trace elements have been identified to play an important role in the development of Parkinson's disease (PD). In our previous study, we observed that prolidase activity is associated with oxidative stress and progression of PD. In present study, we aimed to study the association of prolidase-associated trace elements, such as Co, Mn, Ni, and Zn in the plasma of patients with PD by inductively coupled plasma spectrometry. Plasma levels of Co, Mn, and Ni were significantly increased, whereas plasma levels of Zn was significantly decreased (all P < 0.05) in the patients with PD than healthy controls. Plasma prolidase activity was not correlated to its associated trace elements in PD. A positive, linear, and significant correlation was observed between age and Co, and Mn, and Ni while negative and non-significant between age and status of Zn in the patients. Co, Mn, and Ni were continually elevated with increase in age as well as duration of disease in the patients with PD, whereas status of Zn was continually decreased. Thus, the study concluded that trace elements Co, Ni, and Mn status were increased and Zn status was decreased in the plasma of patients with PD. It is also concluded that elevated Co, Mn, and Ni has been associated with progression of Parkinson's disease.

  12. Hydrogen enhanced crack growth in 18 Ni maraging steels

    NASA Technical Reports Server (NTRS)

    Hudak, S. J., Jr.; Wei, R. P.

    1976-01-01

    The kinetics of sustained-load subcritical crack growth for 18 Ni maraging steels in high-purity hydrogen are examined using the crack-tip stress intensity factor K as a measure of crack driving force. Crack growth rate as a function of stress intensity exhibited a clearly defined K-independent stage (Stage II). Crack growth rates in an 18 Ni (grade 250) maraging steel are examined for temperatures from -6 to +100 C. A critical temperature was observed above which crack growth rates became diminishingly small. At lower temperatures the activation energy for Stage II crack growth was found to be 16.7 plus or minus 3.3 kJ/mole. Temperature and hydrogen partial pressure are shown to interact in a complex manner to determine the apparent Kth (stress intensity level below which no observable crack growth occurs) and the crack growth behavior. Comparison of results on '250' and '300' grades of 18 Ni maraging steel indicate a significant influence of alloy composition and/or strength level on the crack growth behavior.

  13. Analogous Intruder Behavior Near Ni, Sn, and Pb

    SciTech Connect

    Liddick, S. N.; Walters, W. B.; Chiara, C. J.; Janssens, R. V. F.; Abromeit, B.; Ayres, A.; Bey, A.; Bingham, C. R.; Carpenter, M. P.; Cartegni, L.; Hoffman, C. R.; Kondev, F. G.; Seweryniak, D.; Zhu, S.

    2015-08-25

    Near shell closures, the presence of unexpected states at lowenergies provides a critical test of our understanding of the atomic nucleus. New measurements for the N = 42 isotones Co-69(27) and Cu-71(29), along with recent data and calculations in the Ni isotopes, establish a full set of complementary, deformed, intruder states astride the closed-shell Ni-28 isotopes. Nuclei with a one-proton hole or one-proton particle adjacent to Z = 28 were populated in beta-decay experiments and in multinucleon transfer reactions. A beta-decaying isomer, with a 750(250)-ms half-life, has been identified in Co-69(27)42. It likely has low spin and accompanies the previously established 7/2(-) state. Complementary data for the levels of isotonic Cu-71(29)42 support the presence of a deformed, Delta J = 1 band built on the proton intruder 7/2(-) level at 981 keV. These data, together with recent studies of lower-mass Co and Cu isotopes and extensive work near Ni-68, support the view that intruder states based on particle-hole excitations accompany all closed proton shells with Z >= 28.

  14. Capture of Hydrogen Using ZrNi

    NASA Technical Reports Server (NTRS)

    Patton, Lisa; Wales, Joshua; Lynch, David; Parrish, Clyde

    2005-01-01

    Water, as ice, is thought to reside in craters at the lunar poles along with CH4 and H2 . A proposed robotic mission for 2012 will utilize metal/metal hydrides for H2 recovery. Specifications are 99% capture of H2 initially at 5 bar and 100C (or greater), and degassing completely at 300C. Of 47-systems examined using the van't Hoff equation, 4 systems, Mg/MgH2, Mg2Ni/Mg2NiH4, ZrNi/ZrNiH2.8, and Pd/PdH0.77, were considered likely candidates for further examination. It is essential, when selecting a system, to also examine questions regarding activation, kinetics, cyclic stability, and gas impurity effects. After considering those issues, ZrN1 was selected as the most promising candidate, as it is easily activated and rapidly forms ZrNiH 2.8 . In addition, it resists oxide poisoning by CO2, and H2O, while some oxidation by O2 is recommended for improved activation . The presence of hydrogen in the as received Zr-Ni alloy from Alfa Aesar posed additional technical problems. X-ray diffraction of the Zr-Ni powder (-325 mesh), with a Zr:Ni wt% ratio of 70:30, was found to consist of ZrH2, ZrNiH2.8, and ZrNi. ZrH2 in the alloy presented the risk that after degassing that both Zr and ZrNi would be present, and thus lead to erroneous results regarding the reactivity of ZrNi with H2 . Fortunately, ZrH2 is a highly stable hydride that does not degas H2 to any significant extent at temperatures below 300C. Based on equilibrium calculations for the decomposition of ZrH2, only 1 millionth of the hydride decomposed at 300C under a N2 atmosphere flowing at 25 ccm for 64 hours, the longest time for pretreatment employed in the investigation. It was possible, from the X-ray results and knowledge of the Zr:Ni ratio, to compute the composition of a pretreated specimen as being 76 wt% ZrNi and the balance ZrH2.

  15. NiAl alloys for structural uses

    NASA Technical Reports Server (NTRS)

    Koss, D. A.

    1991-01-01

    Alloys based on the intermetallic compound NiAl are of technological interest as high temperature structural alloys. These alloys possess a relatively low density, high melting temperature, good thermal conductivity, and (usually) good oxidation resistance. However, NiAl and NiAl-base alloys suffer from poor fracture resistance at low temperatures as well as inadequate creep strength at elevated temperatures. This research program explored macroalloying additions to NiAl-base alloys in order to identify possible alloying and processing routes which promote both low temperature fracture toughness and high temperature strength. Initial results from the study examined the additions of Fe, Co, and Hf on the microstructure, deformation, and fracture resistance of NiAl-based alloys. Of significance were the observations that the presence of the gamma-prime phase, based on Ni3Al, could enhance the fracture resistance if the gamma-prime were present as a continuous grain boundary film or 'necklace'; and the Ni-35Al-20Fe alloy was ductile in ribbon form despite a microstructure consisting solely of the B2 beta phase based on NiAl. The ductility inherent in the Ni-35Al-20Fe alloy was explored further in subsequent studies. Those results confirm the presence of ductility in the Ni-35Al-20Fe alloy after rapid cooling from 750 - 1000 C. However exposure at 550 C caused embrittlement; this was associated with an age-hardening reaction caused by the formation of Fe-rich precipitates. In contrast, to the Ni-35Al-20Fe alloy, exploratory research indicated that compositions in the range of Ni-35Al-12Fe retain the ordered B2 structure of NiAl, are ductile, and do not age-harden or embrittle after thermal exposure. Thus, our recent efforts have focused on the behavior of the Ni-35Al-12Fe alloy. A second parallel effort initiated in this program was to use an alternate processing technique, mechanical alloying, to improve the properties of NiAl-alloys. Mechanical alloying in the

  16. Tensile deformation of NiTi wires.

    PubMed

    Gall, Ken; Tyber, Jeff; Brice, Valerie; Frick, Carl P; Maier, Hans J; Morgan, Neil

    2005-12-15

    We examine the structure and properties of cold drawn Ti-50.1 at % Ni and Ti-50.9 at % Ni shape memory alloy wires. Wires with both compositions possess a strong <111> fiber texture in the wire drawing direction, a grain size on the order of micrometers, and a high dislocation density. The more Ni rich wires contain fine second phase precipitates, while the wires with lower Ni content are relatively free of precipitates. The wire stress-strain response depends strongly on composition through operant deformation mechanisms, and cannot be explained based solely on measured differences in the transformation temperatures. We provide fundamental connections between the material structure, deformation mechanisms, and resulting stress-strain responses. The results help clarify some inconsistencies and common misconceptions in the literature. Ramifications on materials selection and design for emerging biomedical applications of NiTi shape memory alloys are discussed.

  17. A dinuclear Ni(II) complex with two types of intramolecular magnetic couplings: Ni(II)-Ni(II) and Ni(II)-TTF*+.

    PubMed

    Liu, Shi-Xia; Ambrus, Christina; Dolder, Stefan; Neels, Antonia; Decurtins, Silvio

    2006-11-27

    A dinuclear Ni(II) complex involving tetrathiafulvalene (TTF) radicals as ligands has been prepared and characterized, [Ni2(mu-Cl)2(L*+)2(I3)4(I2)3.(H2O)2.(C4H8O)3 (1), L = 4,5-bis(2-pyridylmethylsulfanyl)-4',5'-ethylenedithiotetrathiafulvalene. There are two types of intramolecular magnetic exchange interactions, namely one ferromagnetic Ni(II)-Ni(II) and one antiferromagnetic Ni(II)-TTF*+. This study is new in the respect of revealing a magnetic exchange interaction between a TTF*+ radical and a paramagnetic transition metal ion. This is due to the fact of a direct binding of the transition metal ion to the skeleton of the TTF*+ radical.

  18. Deformations and magnetic rotations in the Ni60 nucleus

    NASA Astrophysics Data System (ADS)

    Torres, D. A.; Cristancho, F.; Andersson, L.-L.; Johansson, E. K.; Rudolph, D.; Fahlander, C.; Ekman, J.; Du Rietz, R.; Andreoiu, C.; Carpenter, M. P.; Seweryniak, D.; Zhu, S.; Charity, R. J.; Chiara, C. J.; Hoel, C.; Pechenaya, O. L.; Reviol, W.; Sarantites, D. G.; Sobotka, L. G.; Baktash, C.; Yu, C.-H.; Carlsson, B. G.; Ragnarsson, I.

    2008-11-01

    Data from three experiments using the heavy-ion fusion evaporation-reaction 36Ar+28Si have been combined to study high-spin states in the residual nucleus Ni60, which is populated via the evaporation of four protons from the compound nucleus Ge64. The GAMMASPHERE array was used for all the experiments in conjunction with a 4π charged-particle detector arrays (MICROBALL, LUWUSIA) and neutron detectors (NEUTRON SHELL) to allow for the detection of γ rays in coincidence with the evaporated particles. An extended Ni60 level scheme is presented, comprising more than 270γ-ray transitions and 110 excited states. Their spins and parities have been assigned via directional correlations of γ rays emitted from oriented states. Spherical shell-model calculations in the fp-shell characterize some of the low-spin states, while the experimental results of the rotational bands are analyzed with configuration-dependent cranked Nilsson-Strutinsky calculations.

  19. Catalytic dry reforming of methane over ni-substituted hexaaluminates

    SciTech Connect

    Gardner, T; Kugler, E; Spivey, J

    2012-01-01

    CO2 re-use as an oxidant at point emission sources represents a potentially viable option to reducing CO2 footprint. CO2-CH4 reforming performance for a series of Ba0.75NiyAl12-yO19-(y = 0.2, 0.4, 0.6, 0.8 and 1.0) catalysts are examined over the temperature range 200 to 900 °C. The catalysts exhibit unique CO2 adsorption characteristics that are directly related to surface bascity and the extent of Ni-substitution. The systematic study of the Ni substitution level on both structural and catalytic effects indicates that the segregation of Ba at the surface produces an effect on surface basicity and carbon deposition. The relationship between catalyst activity and structure is characterized by EXAFS, XRD, XPS and TPR1,2.

  20. The Ni-rich part of the Al–Ge–Ni phase diagram

    PubMed Central

    Jandl, Isabella; Reichmann, Thomas L.; Richter, Klaus W.

    2013-01-01

    The Ni-rich part of the ternary system Al–Ge–Ni (xNi > 50 at.%) was investigated by means of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM). The two isothermal sections at 550 °C and 700 °C were determined. Within these two sections a new ternary phase, designated as τ4, AlyGe9−yNi13±x (hP66, Ga3Ge6Ni13-type) was detected and investigated by single crystal X-ray diffraction. Another ternary low temperature phase, τ5, was found only in the isothermal section at 550 °C around the composition AlGeNi4. This compound was found to crystallise in the Co2Si type structure (oP12, Pnma). The structure was identified by Rietveld refinement of powder data. The NiAs type (B8) phase based on binary Ge3Ni5 revealed an extended solid solubility of Al and the two isotypic compounds AlNi3 and GeNi3 form a complete solid solution. Based on DTA results, six vertical sections at 55, 60, 70, 75 and 80 at.% Ni and at a constant Al:Ni ratio of 1:3 were constructed. Furthermore, the liquidus surface projection and the reaction scheme (Scheil diagram) were completed by combining our results with previous results from the Ni-poor part of the phase diagram. Six invariant ternary reactions were identified in the Ni-rich part of the system. PMID:27087754

  1. Atomic data for astrophysics: Ni XII

    NASA Astrophysics Data System (ADS)

    Del Zanna, G.; Badnell, N. R.

    2016-01-01

    We present new large-scale R-matrix (up to n = 4) scattering calculations for the electron collisional excitation of Cl-like Ni xii. We used the intermediate-coupling frame transformation method. We compare predicted and observed line intensities using laboratory and solar spectra, finding good agreement for all the main soft X-ray lines. With the exception of the three strongest transitions, large discrepancies with previous estimates are found, especially for the decays from the lowest 3s2 3p4 3d levels. This includes the forbidden UV lines. The atomic data for the n = 4 levels are the first to be calculated. We revise previous experimental energies, and suggest several new identifications. We point out the uncertainty in the wavelength of the 3s2 3p52P1/2-3s2 3p4 3d 2D3/2 transition, which is important for density diagnostics. The full dataset is available at our APAP website (http://www.apapnetwork.org) and at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/585/A118

  2. Creep Properties of NiAl-1Hf Single Crystals Re-Investigated

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Locci, Ivan E.; Darolia, Ram; Bowman, Randy R.

    2000-01-01

    NiAl-1Hf single crystals have been shown to be quite strong at 1027 C, with strength levels approaching those of advanced Ni-based superalloys. Initial testing, however, indicated that the properties might not be reproducible. Study of the 1027 C creep behavior of four different NiAl-1Hf single-crystal ingots subjected to several different heat treatments indicated that strength lies in a narrow band. Thus, we concluded that the mechanical properties are reproducible. Recent investigations of the intermetallic NiAl have confirmed that minor alloying additions combined with single-crystal growth technology can produce elevated temperature strength levels approaching those of Ni-based superalloys. For example, General Electric alloy AFN 12 {Ni-48.5(at.%) Al-0.5Hf-1Ti-0.05Ga} has a creep rupture strength equivalent to Rene 80 combined with a approximately 30-percent lower density, a fourfold improvement in thermal conductivity, and the ability to form a self-protective alumina scale in aggressive environments. Although the compositions of strong NiAl single crystals are relatively simple, the microstructures are complex and vary with the heat treatment and with small ingot-toingot variations in the alloy chemistry. In addition, initial testing suggested a strong dependence between microstructure and creep strength. If these observations were true, the ability to utilize NiAl single-crystal rotating components in turbine machinery could be severely limited. To investigate the possible limitations in the creep response of high-strength NiAl single crystals, the NASA Glenn Research Center at Lewis Field initiated an in depth investigation of the effect of heat treatment on the microstructure and subsequent 1027 C creep behavior of [001]-oriented NiAl-1Hf with a nominal chemistry of Ni-47.5Al-1Hf-0.5Si. This alloy was selected since four ingots, grown over a number of years and possessing slightly different compositions, were available for study. Specimens taken from the

  3. Observations of Low-Lying Electronic States of NiD, and Multi-Isotope Analysis

    NASA Astrophysics Data System (ADS)

    Abbasi, Mahdi; Shayesteh, Alireza; Crozet, Patrick; Ross, Amanda J.

    2017-06-01

    Resolved laser induced fluorescence spectra of NiD, recorded at Doppler resolution between 11500 and 18000 {cm^{-1}}, have defined some 200 term energies in two of the three strongly-interacting, low-lying ({X ^2Δ}, {W ^2Π} and {V ^2Σ^+}) states of NiD associated with an Ni{^+(3d^9})-D^- configuration. Our observations span v = 0 - 5 in the lowest spin-orbit component of the ground state, {X_1 ^2Δ_{5/2} }, v = 0 - 3 in {X_2 ^2Δ_{3/2} } and v = 0 - 1 in {W_1 ^2Π_{3/2} }, the lower component of the {W ^2Π } state. Spin-orbit and rotation-electronic interactions are strong in NiD. Large parity splittings are seen, due to interactions with the unobserved ^2Σ^+ state. We have attempted a global, multi-isotope fit to reproduce observed term energies up to 6000 {cm^{-1}} in NiD and ^{58,60,62}NiH, in an extension of the `Supermultiplet' model proposed by Gray and co-workers, because fits with NiD term energies alone failed to converge to sensible solutions. Dunham-type parameters have been used to represent the unperturbed X ^2Δ, W ^2Π and V ^2Σ^+ states, with off-diagonal matrix elements (treating spin-orbit, L- and S-uncoupling effects) based on Ni^+ atomic properties. Some electronic Born-Oppenheimer breakdown terms were included in the model. The spectra show emission from several excited states close to the unique level populated by the single-mode laser. Bands of collisionally-induced fluorescence identify three levels (A (Ω = 5/2) v = 1, E (Ω = 3/2) v = 1 and I (Ω = 3/2) v = 0) that have not been reported before. Gray, Li, Nelis, and Field, {J. Chem. Phys. 95, 7164 (1991)

  4. Hole-states of 55Ni from (p,d) transfer reactions

    NASA Astrophysics Data System (ADS)

    Tsang, Betty; Sanetullaev, Alisher; Lynch, William; Lee, Jenny; Bazin, Daniel; Chan, K. P.; Coupland, Daniel; Henzl, Vlad; Henzlova, Daniela; Kilburn, Micha; Rogers, Andrew; Sun, Z. Y.; Youngs, Michael; Charity, Robert; Sobotka, Lee; Famiano, Michael; Hudan, Sylvie; Shapira, Daniel; Peters, W. A.; Barbieri, C.; Hjorth-Jensen, M.; Horoi, M.; Otsuka, T.; Suzuki, T.; Utsuno, Y.

    2014-09-01

    Spectroscopic information has been extracted on the hole-states of 55Ni. Using the 1H(56Ni,d)55Ni transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f7/2, p3/2 and the s1/2 hole-states of 55Ni. These new data provide a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. Most shell models describe the ground state and the first p3/2 excited state very well. However, most models have difficulties describing the deep hole state in the sd orbits. In this talk, we will compare the experimental energy levels and spectroscopic factors to state of the art shell model calculations. Spectroscopic information has been extracted on the hole-states of 55Ni. Using the 1H(56Ni,d)55Ni transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f7/2, p3/2 and the s1/2 hole-states of 55Ni. These new data provide a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. Most shell models describe the ground state and the first p3/2 excited state very well. However, most models have difficulties describing the deep hole state in the sd orbits. In this talk, we will compare the experimental energy levels and spectroscopic factors to state of the art shell model calculations. PHY-1102511.

  5. Preferred orientation relationships with large misfit interfaces between Ni{sub 3}Sn{sub 4} and Ni in reactive wetting of eutectic SnPb on Ni

    SciTech Connect

    Suh, J. O.; Tu, K. N.; Wu, Albert T.; Tamura, N.

    2011-06-15

    Ni{sub 3}Sn{sub 4} grains were formed on Ni by reactive wetting between molten eutectic SnPb and thermally annealed Ni foil. Using synchrotron white beam micro x-ray diffraction analysis, two kinds of preferred orientation relationships between Ni{sub 3}Sn{sub 4} and Ni were found. The existence of preferred orientation with large interfacial misfit is suggested as a general mechanism of intermetallic compound formation in reactive solder wetting on metals.

  6. TOPEX/El Niño Watch - La Niña Barely Has a Pulse, June 18, 1999

    NASA Image and Video Library

    1999-08-23

    Lingering just a month ago in the eastern Pacific Ocean, the La Niña phenomenon, with its large volume of chilly water, barely has a pulse this month, according to new satellite data from NASA U.S.-French TOPEX/Poseidon mission. The data, taken during a 10-day cycle of data collection ending June 18, show that the equatorial Pacific Ocean is warming up and returning to normal (green) as La Niña all but vanishes. The warming trend is most apparent in the equatorial Pacific Ocean, where only a few patches of cooler, low sea levels (seen in blue and purple) remain. The blue areas are between 5 and 13 centimeters (2 and 5 inches) below normal, whereas the purple areas range from 14 to 18 centimeters (6 to 7 inches) below normal. Like its counterpart, El Niño, a La Niña condition will influence global climate and weather until it has completely subsided. As summer begins in the northern hemisphere, lower-than-normal sea surface levels and cool ocean temperatures persist in the northeastern Gulf of Alaska and along the western coast of North America. In contrast, the trend is the opposite over most of the Pacific, where above-normal sea surface heights and warmer ocean temperatures (indicated by the red and white areas) appear to be increasing and dominating the overall Pacific Ocean. Red areas are about 10 centimeters (4 inches) above normal; white areas show the sea surface height is between 14 and 32 centimeters (6 and 13 inches) above normal. Scientists are not ready to administer last rites to La Niña, though. In the last 12 months, the pool of unusually cold water in the Pacific has shrunk (warmed) several times before cooling (expanding) again. This summer's altimeter data will help them determine whether La Niña has truly dissipated or whether they will see another resurgence of cool water in the Pacific. http://photojournal.jpl.nasa.gov/catalog/PIA01586

  7. Intermixing in Cu/Ni multilayers induced by cold rolling

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Perepezko, J. H.; Larson, D.; Reinhard, D.

    2015-04-01

    Repeated cold rolling was performed on multilayers of Cu60/Ni40 and Cu40/Ni60 foil arrays to study the details of driven atomic scale interfacial mixing. With increasing deformation, there is a significant layer refinement down to the nm level that leads to the formation of a solid solution phase from the elemental end members. Intriguingly, the composition of the solid solution is revealed by an oscillation in the composition profile across the multilayers, which is different from the smoothly varying profile due to thermally activated diffusion. During the reaction, Cu mixed into Ni preferentially compared to Ni mixing into Cu, which is also in contrast to the thermal diffusion behavior. This is confirmed by observations from X-ray diffraction, electron energy loss spectrum and atom probe tomography. The diffusion coefficient induced by cold rolling is estimated as 1.7 × 10-17 m2/s, which cannot be attributed to any thermal effect. The effective temperature due to the deformation induced mixing is estimated as 1093 K and an intrinsic diffusivity db, which quantifies the tendency towards equilibrium in the absence of thermal diffusion, is estimated as 6.38 × 10-18 m2/s. The fraction of the solid solution phase formed is illustrated by examining the layer thickness distribution and is described by using an error function representation. The evolution of mixing in the solid solution phase is described by a simplified sinusoid model, in which the amplitude decays with increased deformation level. The promoted diffusion coefficient could be related to the effective temperature concept, but the establishment of an oscillation in the composition profile is a characteristic behavior that develops due to deformation.

  8. Intermixing in Cu/Ni multilayers induced by cold rolling

    SciTech Connect

    Wang, Z.; Perepezko, J. H.; Larson, D.; Reinhard, D.

    2015-04-28

    Repeated cold rolling was performed on multilayers of Cu60/Ni40 and Cu40/Ni60 foil arrays to study the details of driven atomic scale interfacial mixing. With increasing deformation, there is a significant layer refinement down to the nm level that leads to the formation of a solid solution phase from the elemental end members. Intriguingly, the composition of the solid solution is revealed by an oscillation in the composition profile across the multilayers, which is different from the smoothly varying profile due to thermally activated diffusion. During the reaction, Cu mixed into Ni preferentially compared to Ni mixing into Cu, which is also in contrast to the thermal diffusion behavior. This is confirmed by observations from X-ray diffraction, electron energy loss spectrum and atom probe tomography. The diffusion coefficient induced by cold rolling is estimated as 1.7 × 10{sup −17} m{sup 2}/s, which cannot be attributed to any thermal effect. The effective temperature due to the deformation induced mixing is estimated as 1093 K and an intrinsic diffusivity d{sub b}, which quantifies the tendency towards equilibrium in the absence of thermal diffusion, is estimated as 6.38 × 10{sup −18} m{sup 2}/s. The fraction of the solid solution phase formed is illustrated by examining the layer thickness distribution and is described by using an error function representation. The evolution of mixing in the solid solution phase is described by a simplified sinusoid model, in which the amplitude decays with increased deformation level. The promoted diffusion coefficient could be related to the effective temperature concept, but the establishment of an oscillation in the composition profile is a characteristic behavior that develops due to deformation.

  9. Robust half-metallicity of hexagonal SrNiO{sub 3}

    SciTech Connect

    Chen, Gao-Yuan; Ma, Chun-Lan; Chen, Da; Zhu, Yan

    2016-01-15

    In the rich panorama of the electronic and magnetic properties of 3d transition metal oxides SrMO{sub 3} (M=Ti, V, Cr, Mn, Fe, Co, Ni, Cu), one member (SrNiO{sub 3}) is missing. In this paper we use GGA+U method based on density functional theory to examine its properties. It is found that SrNiO{sub 3} is a ferromagnetic half-metal. The charge density map shows a high degree of ionic bonding between Sr and other atoms. Meanwhile, a covalent-bonding Ni–O–Ni–O–Ni chain is observed. The spin density contour of SrNiO{sub 3} further indicates that the magnetic interaction between Ni atoms mediated by O is semicovalent exchange. The density of states are examined to explore the unusual indirect magnetic-exchange mechanism. Corresponding to the total energies results, a robust half-metallic character is observed, suggesting a promising giant magneto-optical Kerr property of the material. The partial density of states are further examined to explore the origin of ferromagnetic half-metallicity. The O atoms are observed to have larger contribution at fermi level than Ni atoms to the spin-polarized states, demonstrating that O atoms play a critical role in ferromagnetic half-metallicity of SrNiO{sub 3}. Hydrostatic pressure effect is examined to evaluate how robust the half-metallic ferromagnetism is. - Graphical abstract: (a) The total energy as a function of the lattice constant a for hexagonal SrNiO3 with various magnetic phases. (b) The total electronic density of states for hexagonal SrNiO{sub 3} with FM configuration from GGA+U calculations. (c) Total electron-density distribution in the (110) plane. The colors gradually change from cyan (through pink) to yellow corresponding to charge density value from 0 to 4.0. (d) The magnetization density map in the (110) plane. The colors range from blue (through green) to red corresponding to magnetization density value from −0.15 to 0.45. Black and white contours stand for positive and negative values, respectively

  10. Ni speciation in tea infusions by monolithic chromatography--ICP-MS and Q-TOF-MS.

    PubMed

    Ščančar, Janez; Zuliani, Tea; Žigon, Dušan; Milačič, Radmila

    2013-02-01

    For humans, Ni is not considered to be an essential trace element. Its compounds, at levels present in foodstuffs and drinks, are generally considered to be safe for consumption, but for individuals who already suffer from contact allergy to Ni and may be subject to develop systemic reactions from its dietary ingestion, dietary exposure to Ni must be kept under control. Being the second most popular beverage, tea is a potential source of dietary Ni. Present knowledge on its speciation in tea infusions is poor. Therefore, complete speciation analysis, consisting of separation by liquid chromatography using a weak CIM DEAE-1 monolithic column, "on-line" detection by inductively coupled plasma mass spectrometry (ICP-MS) and "off-line" identification of ligands by hybrid quadrupole time-of-flight mass spectrometry (Q-TOF MS), was implemented for the first time to study Ni speciation in tea infusions. Total concentrations of Ni in dry leaves of white, green, oolong and black tea (Camellia sinensis) and flowers of herbal chamomile (Matricaria chamomilla) and hibiscus (Hibiscus sabdariffa) tea were determined after microwave digestion by ICP-MS. They lay between 1.21 and 14.4 mg kg(-1). Good agreement between the determined and the certified values of the Ni content in the standard reference material SRM 1573a tomato leaves confirmed the accuracy of the total Ni determination. During the infusion process, up to 85 % of Ni was extracted from tea leaves or flowers. Separation of Ni species was completed in 10 min by applying aqueous linear gradient elution with 0.6 mol L(-1) NH(4)NO(3). Ni was found to be present in the chromatographic fraction in which quinic acid was identified by Q-TOF in all the tea infusions analysed, which had pH values between 5.6 and 6.0. The only exception was the infusion of hibiscus tea with a pH of 2.7, where results of speciation analysis showed that Ni is present in its divalent ionic form.

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

    NASA Astrophysics Data System (ADS)

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

    1999-04-01

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

  12. Mean flow-storm track relationship and Rossby wave breaking in two types of El-Niño

    NASA Astrophysics Data System (ADS)

    Liu, Chengji; Ren, Xuejuan; Yang, Xiuqun

    2014-01-01

    The features of large-scale circulation, storm tracks and the dynamical relationship between them were examined by investigating Rossby wave breaking (RWB) processes associated with Eastern Pacific (EP) and Central Pacific (CP) El-Niño. During EP El-Niño, the geopotential height anomaly at 500 hPa (Z500) exhibits a Pacific-North America (PNA) pattern. During CP El-Niño, the Z500 anomaly shows a north positive-south negative pattern over the North Pacific. The anomalous distributions of baroclinicity and storm track are consistent with those of upper-level zonal wind for both EP and CP El-Niño, suggesting impacts of mean flow on storm track variability. Anticyclonic wave breaking (AWB) occurs less frequently in EP El-Niño years, while cyclonic wave breaking (CWB) occurs more frequently in CP El-Niño years over the North Pacific sector. Outside the North Pacific, more CWB events occur over North America during EP El-Niño. When AWB events occur less frequently over the North Pacific during EP El-Niño, Z500 decreases locally and the zonal wind is strengthened (weakened) to the south (north). This is because AWB events reflect a monopole high anomaly at the centroid of breaking events. When CWB events occur more frequently over the North Pacific under CP El-Niño conditions, and over North America under EP El-Niño condition, Z500 increases (decreases) to the northeast (southwest), since CWB events are related to a northeast-southwest dipole Z500 anomaly. The anomalous RWB events act to invigorate and reinforce the circulation anomalies over the North Pacific-North America region linked with the two types of El-Niño.

  13. Effect of curvature on the structural and magnetic properties of Ni film deposited on self-assembled nanospheres

    NASA Astrophysics Data System (ADS)

    Sharma, A.; Tripathi, S.; Gupta, Dileep; Halder, N.; Tripathi, J.

    2016-05-01

    Important experimental findings and their impact on physical properties of Ni thin film are presented with the focus on structural and magnetic property investigations. For this purpose, Ni film (40 nm) was deposited on polystyrene nanospheres (PS, diameter 800 nm) using electron beam evaporation technique simultaneously with a similar reference film on plane Si substrate. The structural properties of the films measured using XRD technique show nanocrystalline growth of Ni on both size PS spheres with an average grain size of ˜ 78 nm, while high crystallinity was observed in the film deposited onto plane Si substrate. A lower coercivity (9 mT) was observed in the Ni/(800 nm) PS as compared to the film deposited on 530 nm PS (23 mT) (our earlier study) and Ni/Si (20 mT). The observed changes in structural and magnetic properties are attributed to the curvature induced modifications at atomic level.

  14. NiCd battery electrodes

    NASA Technical Reports Server (NTRS)

    Holleck, G.; Turchan, M.; Hopkins, J.

    1972-01-01

    The objective of this research program was to develop and evaluate electrodes for a negative limited nickel-cadmium cell and to prove its feasibility. The program consisted of three phases: (1) the development of cadmium electrodes with high hydrogen overvoltage characteristics, (2) the testing of positive and negative plates, and (3) the fabrication and testing of complete negative limited NiCd cells. The following electrode structures were manufactured and their physical and electrochemical characteristics were evaluated: (1) silver sinter-based Cd electrodes, (2) Teflon-bonded Cd electrodes, (3) electrodeposited Cd sponge, and (4) Cd-sinter structures. All cadmium electrode structures showed a sharp increase in potential at the end of charge, with the advent of hydrogen evolution occurring at approximately -1.3 V versus Hg/HgO. The hydrogen advent potentials on pure cadmium structures were 50 to 70 mV more cathodic than those of their silver-containing counterparts.

  15. Stability of Ni-yttria stabilized zirconia anodes based on Ni-impregnation

    NASA Astrophysics Data System (ADS)

    Klemensø, Trine; Thydén, Karl; Chen, Ming; Wang, Hsiang-Jen

    Sintering of Ni is a key stability issue for Ni-YSZ anodes, and especially infiltration based electrodes. The potential of MgO, Al 2O 3, TiO 2, CeO 2 and Ce 0.90Gd 0.10O 1.95 (CGO10) as sintering inhibitors was investigated for infiltrated Ni based anode structures. The structures were prepared from tape cast porous YSZ layers that were impregnated with Ni to form an electronic percolating phase. The Ni-YSZ structure was subsequently impregnated with the inhibitor candidate, and the stability of the structure was evaluated from conductivity measurements. Lower conductivity degradation rates were observed for samples infiltrated with the inhibitor candidates, and the best inhibitor effect was seen with higher loadings of CGO10, and CeO 2 showed similar potential. The degradation in conductivity was not visibly reflected in the microstructure as Ni coarsening in any of the cases. An adverse effect of MgO, TiO 2 and Al 2O 3 was reduced conductivity, possibly due to reaction with Ni and the formation of higher resistive phases. The Ni-infiltrated anodes were shown to have better initial electrochemical performance at 650 °C than conventionally produced Ni-YSZ anodes, but still very poor stability, and further improvement of the inhibitor approach is necessary before applying the Ni-infiltrated anodes in SOFCs.

  16. Nonenzymatic Glucose Sensor Based on In Situ Reduction of Ni/NiO-Graphene Nanocomposite

    PubMed Central

    Zhang, Xiaohui; Zhang, Zheng; Liao, Qingliang; Liu, Shuo; Kang, Zhuo; Zhang, Yue

    2016-01-01

    Ni/NiO nanoflower modified reduced graphene oxide (rGO) nanocomposite (Ni/NiO-rGO) was introduced to screen printed electrode (SPE) for the construction of a nonenzymatic electrochemical glucose biosensor. The Ni/NiO-rGO nanocomposite was synthesized by an in situ reduction process. Graphene oxide (GO) hybrid Nafion sheets first chemical adsorbed Ni ions and assembled on the SPE. Subsequently, GO and Ni ions were reduced by hydrazine hydrate. The electrochemical properties of such a Ni/NiO-rGO modified SPE were carefully investigated. It showed a high activity for electrocatalytic oxidation of glucose in alkaline medium. The proposed nonenzymatic sensor can be utilized for quantification of glucose with a wide linear range from 29.9 μM to 6.44 mM (R = 0.9937) with a low detection limit of 1.8 μM (S/N = 3) and a high sensitivity of 1997 μA/mM∙cm−2. It also exhibited good reproducibility as well as high selectivity. PMID:27792199

  17. Theoretical study of the Pb adsorption on Ni, Cr, Fe surfaces and on Ni based alloys

    NASA Astrophysics Data System (ADS)

    Bonnet, Marie-Laure; Costa, Dominique; Protopopoff, Elie; Marcus, Philippe

    2017-12-01

    Adsorption of Pb atoms on the Ni(111), Ni(100), Fe(110), and Cr(110) metallic surfaces was studied theoretically within an ab initio density functional theory approach (DFT). (√3 × √3)R30° super structures for Ni(111), and (2 × 2) for the other surfaces, corresponding to the saturation state, were considered. The preferred adsorption sites are found to be ternary sites for Ni(111), Fe(110), Cr(110) and quaternary sites for Ni(100). Adsorption on Fe and Cr is less exothermic than on Ni, by 0.16 and 0.33 eV/mol respectively. Adsorption on model surfaces of Ni based alloys was also investigated. It was found that the energy of adsorption depends mostly on the chemical composition of the ternary site, and can be described by a linear combination of the energies of adsorption on the pure metals. The nature of the second nearest neighbour of the adsorbed Pb atom has no significant influence on the adsorption energy. Average energies of adsorption were calculated in two cases: the limit of low coverage, and the saturation. The energies of adsorption of Pb at saturation on nickel base alloy surface representative of alloy 600 (Ni-15Cr-8Fe) and alloy 690 (Ni-30Cr-8Fe) were calculated to be 0.07 and 0.11 eV lower than on pure Ni respectively.

  18. Ni 3+ adsorbate dynamics on a NiO(0 0 1) surface

    NASA Astrophysics Data System (ADS)

    Karakasidis, Theodoros E.; Vamvakopoulos, E.

    2006-05-01

    We present results concerning the dynamical behavior of a Ni 3+ adsorbate on a NiO(0 0 1) surface obtained by molecular dynamics simulations. In a first place, we examined at low temperature the position of the Ni 3+ ion as an adatom on the surface and the corresponding modification of its local environment as reflected on the pair-wise radial distribution function. The calculation of the vibrational properties of the adatom by means of the phonon local density of states (LDOS) shows that there is an anisotropic behavior both in the two principal in-plane directions as well as in the direction normal to the surface in accordance with the structural results. We compare the phonon LDOS of the Ni 3+ adatom with the corresponding results for the Ni 2+ adatom and the Ni 2+ surface cations. Static energetic calculations are indicative that the exchange of the Ni 3+ ion with a surface Ni 2+ ion could be favorable. Such a behavior is confirmed by results observed at temperatures higher than 700 K where the Ni 3+ adsorbate is located on a substitutional position on the surface and not on adatom position. The exchange takes place through simple or double exchange mechanisms. The structural and dynamical behavior of the Ni 3+ ion at the substitution position was investigated in the temperature range 700-2000 K through the calculation of the pair distribution function, the relaxed interlayer relative position (RIRP), mean-square displacements (MSDs) and phonon LDOS. Results show that in comparison with the Ni 2+ surface ions the Ni 3+ ion at substitution position is more tightly bound especially in the direction normal to the surface as is indicated by the local structure and the contraction it presents as well as its phonon LDOS. As temperature increases the binding of the Ni 3+ ion becomes less important as reflected on the physical properties mentioned above.

  19. Composite Ni/NiO-Cr2O3 Catalyst for Alkaline Hydrogen Evolution Reaction

    PubMed Central

    Bates, Michael K.; Jia, Qingying; Ramaswamy, Nagappan; Allen, Robert J.; Mukerjee, Sanjeev

    2015-01-01

    We report a Ni–Cr/C electrocatalyst with unprecedented mass-activity for the hydrogen evolution reaction (HER) in alkaline electrolyte. The HER kinetics of numerous binary and ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni–Cr materials which exhibit metallic Ni as well as NiOx and Cr2O3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to numerous binary and ternary Ni-alloys, including Ni–Mo materials. It is likely that at adjacent Ni/NiOx sites, the oxide acts as a sink for OHads, while the metallic Ni acts as a sink for the Hads intermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiOx content and that the Cr2O3 appears to stabilize the composite NiOx component under HER conditions (where NiOx would typically be reduced to metallic Ni0). Furthermore, in contrast to Pt, the Ni(Ox)/Cr2O3 catalyst appears resistant to poisoning by the anion exchange ionomer (AEI), a serious consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI. PMID:26191118

  20. High Temperature Oxidation Behavior of gamma-Ni+gamma'-Ni3Al Alloys and Coatings Modified with Pt and Reactive Elements

    SciTech Connect

    Mu, Nan

    2007-12-01

    temperatures (~970 C) in the very early stage of oxidation. It was also inferred that Pt enhances the diffusive flux of aluminum from the substrate to the scale/alloy interface. Relatively low levels of hafnium addition to Pt-free γ'-Ni3Al increased the extent of external NiO formation due to non-protective HfO2 formation. Accordingly, this effect intensified with increasing Hf content from 0.2 to 0.5 at.%.

  1. Mechanisms of radiation-induced segregation in CrFeCoNi-based single-phase concentrated solid solution alloys

    SciTech Connect

    He, Mo-Rigen; Wang, Shuai; Shi, Shi; Jin, Ke; Bei, Hongbin; Yasuda, Kazuhiro; Matsumura, Syo; Higashida, Kenji; Robertson, Ian M.

    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 elements are alloy-specific. Moreover, electron-irradiated matrix of CrFeCoNiMn and CrFeCoNiPd shows L10 (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.

  2. 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 L10 (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

  3. A comparative study of humidity sensing and photocatalytic applications of pure and nickel (Ni)-doped WO3 thin films

    NASA Astrophysics Data System (ADS)

    Ramkumar, S.; Rajarajan, G.

    2017-06-01

    Nanocrystalline of pristine and nickel (Ni)-doped tungsten trioxide (WO3) thin films was deposited by chemical bath deposition method. The concentrations of Ni ions were varied from 0 to 10 wt%. In order to improve the crystallinity of the films were annealed at 600 °C for 2 h in the ambient atmosphere. X-ray diffraction results reveal that the WO3 doped with nickel crystallizes in monoclinic structure and the results are in good agreement with the standard JCPDS data (card no: 83-0951). AFM micrographs reveal that average grain size of about 27-39 nm for pure and Ni-doped WO3 thin films. In addition, the band gap of the Ni-doped WO3 nanostructures is facilely tunable by controlling the Ni contents. The humidity sensor setup was fabricated and measured for pure and Ni-doped WO3 thin film sensor with various level of RH (10-90%). The Ni-doped WO3 sensor showed fast response and high sensitivity than pure WO3. The photocatalytic activities of the films were evaluated by degradation of methyl orange, methylene blue and phenol in an aqueous solution under visible light irradiation. The photocatalytic activity of WO3 nanostructures could be remarkably enhanced by doping the Ni impurity.

  4. Facile Synthesis of Vanadium-Doped Ni3S2 Nanowire Arrays as Active Electrocatalyst for Hydrogen Evolution Reaction.

    PubMed

    Qu, Yuanju; Yang, Mingyang; Chai, Jianwei; Tang, Zhe; Shao, Mengmeng; Kwok, Chi Tat; Yang, Ming; Wang, Zhenyu; Chua, Daniel; Wang, Shijie; Lu, Zhouguang; Pan, Hui

    2017-02-22

    Ni3S2 nanowire arrays doped with vanadium(V) are directly grown on nickel foam by a facile one-step hydrothermal method. It is found that the doping can promote the formation of Ni3S2 nanowires at a low temperature. The doped nanowires show excellent electrocatalytic performance toward hydrogen evolution reaction (HER), and outperform pure Ni3S2 and other Ni3S2-based compounds. The stability test shows that the performance of V-doped Ni3S2 nanowires is improved and stabilized after thousands of linear sweep voltammetry test. The onset potential of V-doped Ni3S2 nanowire can be as low as 39 mV, which is comparable to platinum. The nanowire has an overpotential of 68 mV at 10 mA cm(-2), a relatively low Tafel slope of 112 mV dec(-1), good stability and high Faradaic efficiency. First-principles calculations show that the V-doping in Ni3S2 extremely enhances the free carrier density near the Fermi level, resulting in much improved catalytic activities. We expect that the doping can be an effective way to enhance the catalytic performance of metal disulfides in hydrogen evolution reaction and V-doped Ni3S2 nanowire is one of the most promising electrocatalysts for hydrogen production.

  5. Effect of thermomechanical pre-treatment on short- and long-term Ni release from biomedical NiTi.

    PubMed

    Freiberg, Katharina E; Bremer-Streck, Sibylle; Kiehntopf, Michael; Rettenmayr, Markus; Undisz, Andreas

    2014-05-01

    The effect of annealing and deformation on short-term (21days) and long-term (8months) Ni release from biomedical NiTi wires is studied. The deformation of annealed NiTi wires causes cracking and flaking of the surface oxide layer. Flaking of oxide particles does not uncover the Ni-rich layer underneath the surface oxide layer, since at sites where flaking occurs, a thin (∼25nm) layer of oxide remains on top of this Ni-rich layer. The number of cracks in the oxide and Ni-rich layer, respectively, increases with deformation, and intercrystalline crack propagation into the Ni-rich layer and the NiTi bulk is observed. In plastically deformed wires, the cracks may remain opened, providing access of immersion liquid to these zones. Characteristics and quantity of short-term Ni release are significantly affected by the pre-deformation, resulting in an up to 2 times higher total Ni release within the first 21days of deformed compared to annealed wires. Pre-deformation does not significantly influence long-term Ni release; all annealed and deformed samples exhibit similar long-term Ni release rates. The source of Ni during short-term release is the Ni contained in the surface zone of the oxide layer. For high pre-deformation, the Ni-rich layer is a second source for Ni. This second source is also the cause for Ni release in long-term immersion experiments.

  6. Characterization of Ternary NiTiPt High-Temperature Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

    Rios, Orlando; Noebe, Ronald; Biles, Tiffany; Garg, Anita; Palczer, Anna; Scheiman, Daniel; Seifert, Hans Jurgen; Kaufman, Michael

    2005-01-01

    Pt additions substituted for Ni in NiTi alloys are known to increase the transformation temperature of the alloy but only at fairly high Pt levels. However, until now only ternary compositions with a very specific stoichiometry, Ni50-xPtxTi50, have been investigated and then only to very limited extent. In order to learn about this potential high-temperature shape memory alloy system, a series of over twenty alloys along and on either side of a line of constant stoichiometry between NiTi and TiPt were arc melted, homogenized, and characterized in terms of their microstructure, transformation temperatures, and hardness. The resulting microstructures were examined by scanning electron microscopy and the phase compositions quantified by energy dispersive spectroscopy."Stoichiometric" compositions along a line of constant stoichiometry between NiTi to TiPt were essentially single phase but by any deviations from a stoichiometry of (Ni,Pt)50Ti50 resulted in the presence of at least two different intermetallic phases, depending on the overall composition of the alloy. Essentially all alloys, whether single or two-phase, still under went a martensitic transformation. It was found that the transformation temperatures were depressed with initial Pt additions but at levels greater than 10 at.% the transformation temperature increased linearly with Pt content. Also, the transformation temperatures were relatively insensitive to alloy stoichiometry within the range of alloys examined. Finally, the dependence of hardness on Pt content for a series of Ni50-xPtxTi50 alloys showed solution softening at low Pt levels, while hardening was observed in ternary alloys containing more than about 10 at.% Pt. On either side of these "stoichiometric" compositions, hardness was also found to increase significantly.

  7. Precipitation Producing Synoptic-Scale Flow and El Niño-Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Svoma, B. M.

    2014-12-01

    The differences in winter synoptic-scale flow during precipitation events between phases of El Niño-Southern Oscillation are established for the coastal southwest United States. Principal component analysis in T-mode with Varimax rotation was performed on fields of 500-hPa, 700-hPa, and 850-hPa geopotential height and specific humidity (from the North American Regional Reanalysis) during days with precipitation. These precipitation days were grouped through a k-means cluster analysis of the loadings on the extracted components from all atmospheric variables. Eight clusters were ultimately analyzed based on separation and cohesion statistics. Analyses of cluster membership and cluster composite maps reveal synoptic-scale patterns that are most common during particular phases of ENSO. Distinctly El Niño patterns are charactized by a broad offshore upper level trough with relatively moist low-level onshore flow. Distinctly La Niña patterns display a deep southwest-northeast oriented trough over the western United States with drier low-level onshore flow. Analysis of 250-hPa potential vorticity suggests that the La Niña (El Niño) patterns are linked to anticyclonic (cyclonic) baroclinic wave breaking events. This agrees with a recent line of investigations which find anticyclonic (cyclonic) wave breaking in the Pacific North American region to be more common during La Niña (El Niño) events. Knowledge of interannual variability in winter precipitation event characteristics can improve seasonal runoff forecasts and advance understanding of interdecadal variability and the effects of climate change in the western United States.

  8. Nickel Release, ROS Generation and Toxicity of Ni and NiO Micro- and Nanoparticles

    PubMed Central

    Hedberg, Jonas; Di Bucchianico, Sebastiano; Möller, Lennart; Odnevall Wallinder, Inger; Elihn, Karine; Karlsson, Hanna L.

    2016-01-01

    Occupational exposure to airborne nickel is associated with an elevated risk for respiratory tract diseases including lung cancer. Therefore, the increased production of Ni-containing nanoparticles necessitates a thorough assessment of their physical, chemical, as well as toxicological properties. The aim of this study was to investigate and compare the characteristics of nickel metal (Ni) and nickel oxide (NiO) particles with a focus on Ni release, reactive oxygen species (ROS) generation, cellular uptake, cytotoxicity and genotoxicity. Four Ni-containing particles of both nano-size (Ni-n and NiO-n) and micron-size (Ni-m1 and Ni-m2) were tested. The released amount of Ni in solution was notably higher in artificial lysosomal fluid (e.g. 80–100 wt% for metallic Ni) than in cell medium after 24h (ca. 1–3 wt% for all particles). Each of the particles was taken up by the cells within 4 h and they remained in the cells to a high extent after 24 h post-incubation. Thus, the high dissolution in ALF appeared not to reflect the particle dissolution in the cells. Ni-m1 showed the most pronounced effect on cell viability after 48 h (alamar blue assay) whereas all particles showed increased cytotoxicity in the highest doses (20–40 μg cm2) when assessed by colony forming efficiency (CFE). Interestingly an increased CFE, suggesting higher proliferation, was observed for all particles in low doses (0.1 or 1 μg cm-2). Ni-m1 and NiO-n were the most potent in causing acellular ROS and DNA damage. However, no intracellular ROS was detected for any of the particles. Taken together, micron-sized Ni (Ni-m1) was more reactive and toxic compared to the nano-sized Ni. Furthermore, this study underlines that the low dose effect in terms of increased proliferation observed for all particles should be further investigated in future studies. PMID:27434640

  9. Accessing Ni(III)-Thiolate Versus Ni(II)-Thiyl Bonding in a Family of Ni–N2S2 Synthetic Models of NiSOD

    PubMed Central

    Broering, Ellen P.; Dillon, Stephanie; Gale, Eric M.; Steiner, Ramsey A.; Telser, Joshua; Brunold, Thomas C.; Harrop, Todd C.

    2015-01-01

    Superoxide dismutase (SOD) catalyzes the disproportionation of superoxide (O2• −) into H2O2 and O2(g) by toggling through different oxidation states of a first-row transition metal ion at its active site. Ni-containing SODs (NiSODs) are a distinct class of this family of metalloenzymes due to the unusual coordination sphere that is comprised of mixed N/S-ligands from peptide-N and cysteine-S donor atoms. A central goal of our research is to understand the factors that govern reactive oxygen species (ROS) stability of the Ni–S(Cys) bond in NiSOD utilizing a synthetic model approach. In light of the reactivity of metal-coordinated thiolates to ROS, several hypotheses have been proffered and include the coordination of His1-Nδ to the Ni(II) and Ni(III) forms of NiSOD, as well as hydrogen bonding or full protonation of a coordinated S(Cys). In this work, we present NiSOD analogues of the general formula [Ni(N2S)(SR′)]−, providing a variable location (SR′ = aryl thiolate) in the N2S2 basal plane coordination sphere where we have introduced o-amino and/or electron-withdrawing groups to intercept an oxidized Ni species. The synthesis, structure, and properties of the NiSOD model complexes (Et4N)[Ni(nmp)(SPh-o-NH2)] (2), (Et4N)[Ni(nmp)(SPh-o-NH2-p-CF3)] (3), (Et4N)[Ni(nmp)(SPh-p-NH2)] (4), and (Et4N)[Ni(nmp)(SPh-p-CF3)] (5) (nmp2− = dianion of N-(2-mercaptoethyl)picolinamide) are reported. NiSOD model complexes with amino groups positioned ortho to the aryl-S in SR′ (2 and 3) afford oxidized species (2ox and 3ox) that are best described as a resonance hybrid between Ni(III)-SR and Ni(II)-•SR based on ultraviolet–visible (UV-vis), magnetic circular dichroism (MCD), and electron paramagnetic resonance (EPR) spectroscopies, as well as density functional theory (DFT) calculations. The results presented here, demonstrating the high percentage of S(3p) character in the highest occupied molecular orbital (HOMO) of the four-coordinate reduced form of NiSOD (Ni

  10. Ni nanoparticles prepared by simple chemical method for the synthesis of Ni/NiO-multi-layered graphene by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Ali, Mokhtar; Remalli, Nagarjuna; Gedela, Venkataramana; Padya, Balaji; Jain, Pawan Kumar; Al-Fatesh, Ahmed; Rana, Usman Ali; Srikanth, Vadali V. S. S.

    2017-02-01

    A new chemical method was used to obtain a high yield of nickel nanoparticles (Ni-NPs). The effect of solvent (distilled water, ethylene glycol, and ethanol) and surfactant (oleic acid and polyvinyl pyrrolidinone) on the morphology and crystallinity of the synthesized Ni-NPs has been investigated. The experimental results revealed that among the solvents mentioned above, ethanol gives the best results in terms of complete reduction, controlled morphology and size distribution of Ni-NPs. The surfactants played an important role in impeding the agglomeration and surface oxidation of Ni-NPs. The surfactants also affected the morphology of the Ni-NPs. The synthesized Ni-NPs are found to be quite stable in air. The best of the synthesized Ni-NPs were effectively used as catalysts for the synthesis of Ni/NiO-multi-layered graphene using catalytic chemical vapor deposition technique.

  11. Ni{sub 3}Al aluminide alloys

    SciTech Connect

    Liu, C.T.

    1993-10-01

    This paper provides a brief review of the recent progress in research and development of Ni{sub 3}Al and its alloys. Emphasis has been placed on understanding low ductility and brittle fracture of Ni{sub 3}Al alloys at ambient and elevated temperatures. Recent studies have resulted in identifying both intrinsic and extrinsic factors governing the fracture behavior of Ni{sub 3}Al alloys. Parallel efforts on alloy design using physical metallurgy principles have led to properties for structural use. Industrial interest in these alloys is high, and examples of industrial involvement in processing and utilization of these alloys are briefly mentioned.

  12. Momentum microscopy of the layered semiconductor TiS2 and Ni intercalated Ni1/3TiS2

    NASA Astrophysics Data System (ADS)

    Suga, Shigemasa; Tusche, Christian; Matsushita, Yu-ichiro; Ellguth, Martin; Irizawa, Akinori; Kirschner, Jürgen

    2015-08-01

    The detailed electronic structure of a layered semiconductor 1T-TiS2 and its modification in Ni-intercalated Ni1/3TiS2 were studied beyond the full surface Brillouin zone by use of a momentum microscope and He-I light source on their in-situ cleaved surfaces. Clear dispersions associated with the electron Fermi surface (FS) pockets induced by the self-intercalated Ti in non-doped 1T-TiS2 around the M points, as well as the hole FS pocket induced by the surface Ni in Ni1/3TiS2 around the Γ point, were confirmed in the observed high-resolution EB(kx, ky) band cross sections. A bird’s eye view of the two-dimensional band dispersions EB(kx, ky) clarified many complex band dispersions. The experimental results are compared with first-principles band calculations performed for the bulk as well as the one monolayer (ML)-TiS2 and surface-1ML-Ni1/3TiS2. The characteristic changes of the band dispersions near the Fermi level (EF) are ascribed to the contribution of the 3d states of the surface Ni atoms with the C3v symmetry in contrast to the ‘D3d’ symmetry of the intercalated Ni. The importance of experimental studies of band dispersions in the full Brillouin zone is demonstrated, showing the high potential of momentum microscopy.

  13. Fine Structure in Multi-Phase Zr8Ni21-Zr7Ni10-Zr2Ni7 Alloy Revealed by Transmission Electron Microscope

    PubMed Central

    Shen, Haoting; Bendersky, Leonid A.; Young, Kwo; Nei, Jean

    2015-01-01

    The microstructure of an annealed alloy with a Zr8Ni21 composition was studied by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of three phases, Zr8Ni21, Zr2Ni7, and Zr7Ni10, was confirmed by SEM/X-ray energy dispersive spectroscopy compositional mapping and TEM electron diffraction. Distribution of the phases and their morphology can be linked to a multi-phase structure formed by a sequence of reactions: (1) L → Zr2Ni7 + L’; (2) peritectic Zr2Ni7 + L’ → Zr2Ni7 + Zr8Ni21 + L”; (3) eutectic L” → Zr8Ni21 + Zr7Ni10. The effect of annealing at 960 °C, which was intended to convert a cast structure into a single-phase Zr8Ni21 structure, was only moderate and the resulting alloy was still multi-phased. TEM and crystallographic analysis of the Zr2Ni7 phase show a high density of planar (001) defects that were explained as low-energy boundaries between rotational variants and stacking faults. The crystallographic features arise from the pseudo-hexagonal structure of Zr2Ni7. This highly defective Zr2Ni7 phase was identified as the source of the broad X-ray diffraction peaks at around 38.4° and 44.6° when a Cu-K was used as the radiation source. PMID:28793460

  14. Diversity, Function and Evolution of Genes Coding for Putative Ni-Containing Superoxide Dismutases

    SciTech Connect

    Dupont,C.; Neupane, K.; Shearer, J.; Palenik, B.

    2008-01-01

    We examined the phylogenetic distribution, functionality and evolution of the sodN gene family, which has been shown to code for a unique Ni-containing isoform of superoxide dismutase (Ni-SOD) in Streptomyces. Many of the putative sodN sequences retrieved from public domain genomic and metagenomic databases are quite divergent from structurally and functionally characterized Ni-SOD. Structural bioinformatics studies verified that the divergent members of the sodN protein family code for similar three-dimensional structures and identified evolutionarily conserved amino acid residues. Structural and biochemical studies of the N-terminus 'Ni-hook' motif coded for by the putative sodN sequences confirmed both Ni (II) ligating and superoxide dismutase activity. Both environmental and organismal genomes expanded the previously noted phylogenetic distribution of sodN, and the sequences form four well-separated clusters, with multiple subclusters. The phylogenetic distribution of sodN suggests that the gene has been acquired via horizontal gene transfer by numerous organisms of diverse phylogenetic background, including both Eukaryotes and Prokaryotes. The presence of sodN correlates with the genomic absence of the gene coding for Fe-SOD, a structurally and evolutionarily distinct isoform of SOD. Given the low levels of Fe found in the marine environment from where many sequences were attained, we suggest that the replacement of Fe-SOD with Ni-SOD may be an evolutionary adaptation to reduce iron requirements.

  15. Late time optical spectra from the /sup 56/Ni model for Type I supernovae

    SciTech Connect

    Axelrod, T.S.

    1980-07-01

    The hypothesis that the optical luminosity of Type I supernovae results from the radioactive decay of /sup 56/Ni synthesized and ejected by the explosion has been investigated by numerical simulation of the optical spectrum resulting from a homologously expanding shell composed initially of pure /sup 56/Ni core. This model, which neglects the effects of material external to the /sup 56/Ni core, is expected to provide a reasonable representation of the supernova at late times when the star is nearly transparent to optical photons. The numerical simulation determines the temperature, ionization state, and non-LTE level populations which result from energy deposition by the radioactive decay products of /sup 56/Ni and /sup 56/Co. The optical spectrum includes the effects of both allowed and forbidden lines. The optical spectra resulting from the simulation are found to be sensitive to the mass and ejection velocity of the /sup 56/Ni shell. A range of these parameters has been found which results in good agreement with the observed spectra of SN1972e over a considerable range of time. In particular, evidence for the expected decaying abundance of /sup 56/Co has been found in the spectra of SN1972e. These results are used to assess the validity of the /sup 56/Ni model and set limits on the mass and explosion mechanism of the Type I progenitor. The possibilities for improvement of the numerical model are discussed and future atomic data requirements defined.

  16. decay of 71,73Co: Probing single-particle states approaching doubly magic 78Ni

    SciTech Connect

    Rajabali, M. M.; Grzywacz, R.; Liddick, Sean; Mazzocchi, C.; Batchelder, Jon Charles; Baumann, T.; Bingham, C. R.; Darby, Iain; Ginter, T. N.; Ilyushkin, S.; Karny, M.; Krolas, W; Mantica, P. F.; Miernik, K.; Pfutzner, Marek; Rykaczewski, Krzysztof Piotr; Weisshaar, D.; Winger, J. A.

    2012-01-01

    Low-energy excited states in 71,73Ni populated via the decay of 71,73Co were investigated in an experiment performed at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU). Detailed analysis led to the construction of level schemes of 71,73Ni, which are interpreted using systematics and analyzed using shell-model calculations. The 5/2 states attributed to the the f5/2 orbital and positive-parity 5/2+ and 7/2+ states from the g9/2 orbital have been identified in both 71,73Ni. In 71Ni the location of a 1/2 -decaying isomer is proposed, and limits are suggested as to the location of the isomer in 73Ni. The location of positive-parity cluster states are also identified in 71,73Ni. Beta-delayed neutron branching ratios obtained from this data are given for both 71,73Co. DOI: 10.1103/PhysRevC.85.034326 PACS number(s): 23.40. s, 21.10.Pc, 21.60.Cs, 27.50.+

  17. Alloying effects on mechanical and metallurgical properties of NiAl

    SciTech Connect

    Liu, C.T.; Horton, J.A.; Lee, E.H.; George, E.P.

    1993-06-01

    Alloying effects were investigated in near-stoichiometric NiAl for improving its mechanical and metallurgical properties. Ternary additions of 19 elements at levels up to 10 at. % were added to NiAl; among them, molybdenum is found to be most effective in improving the room-temperature ductility and high-temperature strength. Alloying with 1.0 {plus_minus} 0.6% molybdenum almost doubles the room-temperature tensile ductility of NiAl and triples its yield strength at 1000C. The creep properties of molybdenum-modified NiAl alloys can be dramatically improved by alloying with up to 1% of niobium or tantalum. Because of the low solubilities of molybdenum and niobium in NiAl, the beneficial effects mainly come from precipitation hardening. Fine and coarse precipitates are revealed by both transmission electron microscopy (TEM) and electron microprobe analyses. Molybdenum-containing alloys possess excellent oxidation resistance and can be fabricated into rod stock by hot extrusion at 900 to 1050C. This study of alloying effects provides a critical input for the alloy design of ductile and strong NiAl aluminide alloys for high-temperature structural applications.

  18. Investigation of the shock-induced chemical reaction (SICR) in Ni + Al nanoparticle mixtures.

    PubMed

    Xiong, Yongnan; Xiao, Shifang; Deng, Huiqiu; Zhu, Wenjun; Hu, Wangyu

    2017-07-21

    Molecular dynamics (MD) simulations are used to investigate the shock-compression response of Ni + Al spherical nanoparticles arranged in a NaCl-like structure. The deformation and reaction characteristics are studied from the particle level to the atomic scale at various piston velocities. Shock-induced chemical reactions (SICRs) occur during non-equilibrium processes, accompanied by a sharp rise in temperature and rapid mixing of atoms. The preferentially deformed Al particles form a high-speed mass flow relative to the Ni at the shock front, which impinges on the Ni particles, and mixing of Ni and Al atoms occurs immediately at the interface. The particle velocity dispersion (PVD) that appears at the shock front has important implications for the initiation of shock-induced chemical reactions. We show that dislocations are mainly generated at the beginning of particle deformation or at the shock front, and do not directly affect the occurrence of SICRs. The intimate contact of the molten Al and the amorphous Ni is found to be critical to the subsequent reactions for the extensive mixing of Ni and Al. We conclude that the mechanisms of SICRs involve mechanochemical processes near the shock front and subsequent interdiffusion processes.

  19. Synthesis, microstructure and magnetic properties of Ni-Zn ferrites

    NASA Astrophysics Data System (ADS)

    Costa, A. C. F. M.; Tortella, E.; Morelli, M. R.; Kiminami, R. H. G. A.

    2003-01-01

    Ni-Zn ferrite powders with a nominal composition of Ni 0.5Zn 0.5Fe 2O 4 were prepared by combustion synthesis, using urea as fuel. The large quantity of gas that developed inhibited particle aggregation and yielded soft powders suitable for dispersion and use. The as-prepared combustion products, helium pycnometer and BET, which were characterized by XRD, showed a high specific surface area (44.26 m 2/g) and a very small particle and crystalline phase with atomic level homogeneity. The samples were uniaxially compacted by dry pressing and sintered at 1100°C, 1200°C, 1300°C and 1400°C for 2 h. The samples were characterized by bulk density, SEM, and B- H loop measurements. Optimum properties were obtained for samples sintered at 1200°C. The Ni-Zn ferrite presented a uniform microstructure with small grain size (2.0 μm), high density (95% TD) and significant hysteresis parameter values.

  20. The Otto thermodynamic cycle using the magnetic molecule Ni2

    NASA Astrophysics Data System (ADS)

    Hübner, Wolfgang; Dong, Chuanding; Lefkidis, Georgios

    2012-02-01

    In order to design realistic molecular heat engines, the study of quantum thermodynamics is essential since classical thermodynamics does not apply in this extreme miniaturization limit [1,2]. Realizing a thermodynamic cycle on an existing magnetic molecule embodies a novel and unique approach to understand and exploit the thermodynamic properties of spin at the molecular level.Here we propose an Otto cycle in the Ni2 dimer based on a fully ab-initio calculation of the electronic states and the perturbative inclusion of spin-orbit coupling. A laser pulse, described by the time-dependent Schr"odinger equation, is used to heat the Ni2 dimer. The pulse not only excites the electrons to higher, many-body electronic states, but also influences the spin of the system due to spin-orbit coupling. Using a low-temperature thermal bath the system is cooled back to the ground state. The adiabatic work exchange between the Ni2 and the environment is described by the quasi-static expansion or compression of the bond length of the dimer. The calculated efficiency of the cycle is up to 34%.[1] T. D. Kieu, Phys. Rev. Lett. 93 140403 (2004)[2] H. T. Quan, Phys. Rev. E 79 041129 (2009)[3] T. Zhang et al., Phys. Rev. A 75 062102 (2007)

  1. Joint effect of ferromagnetic and non-ferromagnetic cations for adjusting room temperature ferromagnetism of highly luminescent CuNiInS quaternary nanocrystals

    NASA Astrophysics Data System (ADS)

    Shen, Jin; Wang, Chunlei; Xu, Shuhong; Lv, Changgui; Zhang, Ruohu; Cui, Yiping

    2017-01-01

    In this work, highly luminescent quaternary CuNiInS nanocrystals (NCs) are put forward as a good prototype for investigating defect-induced room temperature ferromagnetism. A ferromagnetic Ni cation can preserve the strong luminescence of NCs without introducing intermediate energy levels in the center of the forbidden band. The strong luminescence of NCs is used as an indicator for monitoring the concentration of vacancy defects inside them, facilitating the investigation of the origin of room temperature ferromagnetism in CuNiInS NCs. Our results reveal that the patching of Cu vacancies ({{{{V}}}{{Cu}}}-) with Ni will result in bound magnetic polarons composed of both {{{{V}}}{{Cu}}}- and a substitution of Cu by Ni ({{{{Ni}}}{{Cu}}}+), giving rise to the room temperature ferromagnetism of CuNiInS NCs. Either the ferromagnetic Ni or the non-ferromagnetic Cu cation can tune the magnetism of CuNiInS NCs because of the change of bound magnetic polaron concentration at the altered concentration ratio of {{{{V}}}{{Cu}}}- and {{{{Ni}}}{{Cu}}}+.

  2. Research of surface-oxidation epitaxy of NiO films on cube textured Ni tapes

    NASA Astrophysics Data System (ADS)

    Shi, D. Q.; Ionescu, M.; McKinnon, J.; Chen, W. M.; Dou, S. X.

    2002-05-01

    Thin films of NiO were fabricated in air by surface-oxidation epitaxy (SOE) on biaxially-textured Ni substrate, for use as buffer layers for YBCO coated conductors. The surface-oxidation conditions such as the temperature and the reaction time, as well as the cooling rate, play a determining role in the process of epitaxial growth of the NiO layer. A continuous, biaxially-aligned textured NiO layer, was obtained for a 10 min oxidation in air at 1120 °C, and a cooling rate of 150 K/h. The roughness of the NiO layer is mostly controlled by a coarsening of some NiO grains.

  3. Triclinic Ni[sub 2]Al phase in 63. 1 atomic percent NiAl

    SciTech Connect

    Murthy, A.S.; Goo, E. . Dept. of Materials Science and Engineering)

    1994-01-01

    Transmission electron microscopy (TEM) studies on the 63.1 at pct NiAl specimens aged in the L1[sub 0] phase indicate the presence of localized regions consisting of very high-density twins along with precipitates of Ni[sub 2]Al stoichiometry. In regions representative of the 7R phase, it is observed that the ordered Ni[sub 2]Al phase exists in lattice correspondence with the 7R phase. Based on the electron-diffraction results, the crystal structure of this Ni[sub 2]Al phase is determined to be triclinic, belonging to the space group P[bar 1]. This new Ni[sub 2]Al phase alternatively may be viewed as a periodically microtwinned monoclinic Ni[sub 2]Al phase, existing in coherence with the matrix L1[sub 0] phase that is also periodically microtwinned.

  4. Synthesis of Ni-poor NiO nanoparticles for p-DSSC applications

    NASA Astrophysics Data System (ADS)

    Polteau, Baptiste; Tessier, Franck; Cheviré, François; Cario, Laurent; Odobel, Fabrice; Jobic, Stéphane

    2016-04-01

    To improve the performances of p-Dye Sensitized Solar Cell (p-DSSC) for the future, the synthesis of modified p-type nickel oxide semiconductor, commonly used as photocathode in such devices, was initiated with Ni3O2(OH)4 as precursor. This specific nickel oxyhydroxide was first characterized by X-ray photo-electron spectroscopy and magnetic susceptibility measurements. Then its thermal decomposition was thoroughly studied in order to control the particles size of the as-prepared NiO nanopowders. Low temperature decomposition in air of this precursor allows the formation of Ni1-xO nanoparticles with a large amount of Ni vacancies and specific surface areas up to 250 m2 g-1. Its ammonolysis at 250 °C leads to nanostructured N-doped NiO (NiO:N) materials.

  5. Multi-stage martensitic transformation in Ni-rich NiTi shape memory alloys

    NASA Astrophysics Data System (ADS)

    Wang, Xiebin; Verlinden, Bert; Kustov, Sergey

    Precipitation hardening is an effective way to improve the functional stability of NiTi shape memory alloys. The precipitates, mainly Ni4Ti3, could be introduced by aging treatment in Ni-rich NiTi alloys. However, the presence of Ni4Ti3 precipitates could disturb the transformation behavior, resulting in the multi-stage martensitic transformation (MMT). With the presence of MMT, it is difficult to control the transformation behavior, and thus limits the applicability of NiTi alloys. In this work, previous efforts on explaining the observed MMT are summarized. The difficulties in developing a unified explanation are discussed, and a possible way to avoid the MMT is proposed.

  6. NiCo-lead zirconium titanate-NiCo trilayered magnetoelectric composites prepared by electroless deposition

    SciTech Connect

    Zhou, M. H.; Wang, Y. G.; Bi, K.; Fan, H. P.; Zhao, Z. S.

    2015-04-15

    The NiCo layers with various Ni/Co atomic ratio have been successfully electroless deposited on PZT layers by varying the bath composition. As the cobalt atomic ratio in the deposited layer increases from 17.2 to 54.8 wt%, the magnetostrictive coefficient decreases. The magnetoelectric effect depends strongly on the magnetostrictive properties of magnetostrictive phase. The magnetoelectric coefficient of NiCo/PZT/NiCo trilayers increases with Ni/Co atomic ratio of the deposited NiCo layers increasing from 45:55 to 83:17. A maximum ME voltage coefficient of α{sub E,31} = 2.8 V ⋅ cm{sup −1} ⋅ Oe{sup −1} is obtained at a frequency of about 88 kHz, which makes these trilayers suitable for applications in actuators, transducers and sensors.

  7. Nonprotective Alumina Growth in Sulfur-Doped NiAl(Zr)

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    2000-01-01

    The 1200 C oxidation behavior of NiAl was examined at various levels of sulfur and zirconium dopants to test the possibility of a critical S/Zr ratio required for adhesion. Cyclic furnace testing for 200 1 -hr cycles and interrupted testing for 500 hr were used as screening tests. Pure NiAl and NiAl(Zr) with 0. 14 at.% Zr were chosen as model base compositions; they exhibited normal, slow-growing scales (3 Mg/sq cm) with excellent adhesion for the Zr-doped alloys. NiAl with about 120 ppma S exhibited a substantial weight loss (-20 Mg/sq cm) in cyclic tests and a very large weight gain (+60 Mg/sq cm) in interrupted tests. The major surface phase remained as alpha -Al2O3. Sulfur doping the NiAl(Zr) alloy caused massive weight gains of 80 - 100 Mg/sq cm, swelling, cracking, and nearly complete conversion into NiAl2O4, and alpha- Al2O3. The initial objective of determining critical S/Zr ratios for adhesion was therefore unattainable. Initiation of the catastrophic attack was examined after a 10 hr exposure, revealing a few sites of broad, raised, and cracked ridges. In cross-section, the ridges appeared as modular intrusions, with a complex, fractal, oxide-metal interface. They were primarily alumina (with occasional entrapped islands of NiAl2O4 or pure Ni metal). They possessed a unique microstructure consisting of 0.3 microns lamellae, separated by 0.1 microns open channels. This allowed for rapid growth controlled by gaseous diffusion. The microstructure is discussed in terms of SO2 evolution and a sulfur-driven de-passivation process.

  8. Crystallographic Orientation Effect on Electromigration in Ni-Sn Microbump

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Ting; Chen, Chih-Hao; Chakroborty, Subhendu; Wu, Albert T.

    2017-09-01

    This article addresses the reliability challenges regarding electromigration in developing three-dimensional integrated circuits (3D-ICs). The line-type sandwich structure of Ni/Sn3.5Ag(15 μm)/Ni was used to simulate microbumps to examine the reliability of electromigration in 3D-IC technology. The solder strip of Ni/Sn3.5Ag(15 μm)/Ni was stressed with a current density of 1.0 × 104 A/cm2 at 150°C. The current stressing enhanced the reaction between the solder and Ni to form Ni3Sn4, which occupied the entire joint and transformed into a Ni/Ni3Sn4/Ni structure when the solder was completely consumed. Electron backscatter diffraction was used to analyze the crystallographic characteristics of Sn and Ni3Sn4 as related to the electromigration effect. The results indicated that the crystallographic orientation of Sn plays a significant role in the Ni/Sn3.5Ag/Ni, whereas the orientation of Ni3Sn4 is the dominant factor of diffusion behavior in the Ni/Ni3Sn4/Ni.

  9. Crystallographic Orientation Effect on Electromigration in Ni-Sn Microbump

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Ting; Chen, Chih-Hao; Chakroborty, Subhendu; Wu, Albert T.

    2017-07-01

    This article addresses the reliability challenges regarding electromigration in developing three-dimensional integrated circuits (3D-ICs). The line-type sandwich structure of Ni/Sn3.5Ag(15 μm)/Ni was used to simulate microbumps to examine the reliability of electromigration in 3D-IC technology. The solder strip of Ni/Sn3.5Ag(15 μm)/Ni was stressed with a current density of 1.0 × 104 A/cm2 at 150°C. The current stressing enhanced the reaction between the solder and Ni to form Ni3Sn4, which occupied the entire joint and transformed into a Ni/Ni3Sn4/Ni structure when the solder was completely consumed. Electron backscatter diffraction was used to analyze the crystallographic characteristics of Sn and Ni3Sn4 as related to the electromigration effect. The results indicated that the crystallographic orientation of Sn plays a significant role in the Ni/Sn3.5Ag/Ni, whereas the orientation of Ni3Sn4 is the dominant factor of diffusion behavior in the Ni/Ni3Sn4/Ni.

  10. Binomial level densities

    NASA Astrophysics Data System (ADS)

    Zuker, A. P.

    2001-08-01

    It is shown that nuclear level densities in a finite space are described by a continuous binomial function, determined by the first three moments of the Hamiltonian, and the dimensionality of the underlying vector space. Experimental values for 55Mn, 56Fe, and 60Ni are very well reproduced by the binomial form, which turns out to be almost perfectly approximated by Bethe's formula with backshift. A proof is given for which binomial densities reproduce the low moments of Hamiltonians of any rank: A strong form of the famous central limit result of Mon and French. Conditions under which the proof may be extended to the full spectrum are examined.

  11. Atomic data for astrophysics: Ni XV

    NASA Astrophysics Data System (ADS)

    Del Zanna, G.; Storey, P. J.; Mason, H. E.

    2014-07-01

    We present the first R-matrix scattering calculation for electron collisional excitation of Ni xv. The large-scale target includes configurations up to n = 4. The calculations were carried out using the intermediate-coupling frame transformation method. Significant enhancements in the collision strengths, compared to previous distorted-wave (DW) calculations, are found for several cases, in particular the forbidden lines within the ground configuration and the 3s2 3p 4s levels. We provide a complete set of rates and a list of strongest lines that are observable in astrophysical plasmas. Previous identifications are reviewed, and a few new ones suggested. The new data can be used to accurately measure electron densities for high-temperature (3 MK) plasmas, and the nickel abundance. The full dataset (energies, transition probabilities and rates) is available from our APAP website http://www.apap-network.org, and also at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/567/A18

  12. National Low-Level Waste Management Program Radionuclide Report Series. Volume 10, Nickel-63

    SciTech Connect

    Carboneau, M.L.; Adams, J.P.

    1995-02-01

    This report outlines the basic radiological, chemical, and physical characteristics of nickel-63 ({sup 63}Ni) and examines how these characteristics affect the behavior of {sup 63}Ni in various environmental media, such as soils, groundwater, plants, animals, the atmosphere, and the human body. Discussions also include methods of {sup 63}Ni production, waste types, and waste forms that contain {sup 63}Ni. The primary source of {sup 63}Ni in the environment has been low-level radioactive waste material generated as a result of neutron activation of stable {sup 62}Ni that is present in the structural components of nuclear reactor vessels. {sup 63}Ni enters the environment from the dismantling activities associated with nuclear reactor decommissioning. However, small amounts of {sup 63}Ni have been detected in the environment following the testing of thermonuclear weapons in the South Pacific. Concentrations as high as 2.7 Bq{sup a} per gram of sample (or equivalently 0.0022 parts per billion) were observed on Bikini Atoll (May 1954). {sup 63}Ni was not created as a fission product species (e.g., from {sup 235}U or {sup 239}Pu fissions), but instead was produced as a result of neutron capture in {sup 63}Ni, a common nickel isotope present in the stainless steel components of nuclear weapons (e.g., stainless-304 contains {approximately}9% total Ni or {approximately}0.3% {sup 63}Ni).

  13. Growth of nanotubular oxide layer on Ti-Ni alloys with different Ni contents

    NASA Astrophysics Data System (ADS)

    Kim, Min-Su; Tsuchiya, Hiroaki; Fujimoto, Shinji

    2016-04-01

    Anodization of near-equiatomic Ti-Ni alloys was performed in an ethylene glycol based electrolyte under various conditions in order to investigate the effects of crystal structure and chemical composition of the Ti-Ni alloy on the morphology of the resulting oxide layers. X-ray diffraction patterns revealed that Ti-Ni substrates with Ni content lower than 50.0 at.% were in the martensitic phase, while substrates with Ni content higher than 50.0 at.% were in the austenitic phase. Oxide layers formed at 20 or 35 V for 5 min exhibited no distinct nanotubular structures; however, at 50 V, nanotubular oxide layers were formed. After anodization at 50 V for 20 min, the growth of an irregular-shaped porous layer underneath the nanotubular oxide layer was observed for Ti-Ni alloys with Ni content lower than 52.2 at.%, whereas the oxide layer consisted of only irregular-shaped porous structures for the Ti-52.5 at.% Ni alloy. Further anodization resulted in the formation of irregular-shaped porous oxide layers on all Ti-Ni alloys examined. Energy-dispersive X-ray analysis indicated that this morphological transition is related to Ni accumulation in the vicinity of the interface between the bottoms of the oxide layers and the surfaces of the substrate alloys. Therefore, nanotubular oxide layers cannot be grown, and instead irregular-shaped porous oxide layers are formed underneath the nanotubular layers. These results indicate that the morphology of anodic oxide layers formed on the near-equiatomic Ti-Ni alloys is not affected by their crystal structure, but by Ni content and anodization time.

  14. Pt redistribution during Ni(Pt) silicide formation

    SciTech Connect

    Demeulemeester, J.; Smeets, D.; Vantomme, A.; Van Bockstael, C.; Detavernier, C.; Comrie, C. M.; Barradas, N. P.; Vieira, A.

    2008-12-29

    We report on a real-time Rutherford backscattering spectrometry study of the erratic redistribution of Pt during Ni silicide formation in a solid phase reaction. The inhomogeneous Pt redistribution in Ni(Pt)Si films is a consequence of the low solubility of Pt in Ni{sub 2}Si compared to NiSi and the limited mobility of Pt in NiSi. Pt further acts as a diffusion barrier and resides in the Ni{sub 2}Si grain boundaries, significantly slowing down the Ni{sub 2}Si and NiSi growth kinetics. Moreover, the observed incorporation of a large amount of Pt in the NiSi seeds indicates that Pt plays a major role in selecting the crystallographic orientation of these seeds and thus in the texture of the resulting Ni{sub 1-x}Pt{sub x}Si film.

  15. Catalytic modification of Ni-Sm-doped ceria anodes with copper for direct utilization of dry methane in low-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Wang, Zhicheng; Weng, Wenjian; Cheng, Kui; Du, Piyi; Shen, Ge; Han, Gaorong

    2008-05-01

    A Cu/Ni/Sm-doped ceria (SDC) anode has been designed for direct utilization of dry methane in low-temperature anode-supported solid oxide fuel cells. The anode is prepared by the impregnation method, whereby a small amount of Cu is incorporated into the previously prepared Ni/SDC porous matrix. After reduction, Cu nanoparticles adhere to and are uniformly distributed on the surface of the Ni/SDC matrix. For the resulting Cu/Ni/SDC anode-supported cell, maximum power density of 317 mW cm-2 is achieved at 600 °C. The power density shows only ∼2% loss after 12-h operation. The results demonstrate that the Cu/Ni/SDC anode effectively suppresses carbon deposition by decreasing the Ni surface area available and the level of carbon monoxide disproportionation. This combination of effects results in very low-power density loss over the operating time.

  16. Ab initio study of W-Al-Co-Ni : An approximant of the decagonal Al-Co-Ni quasicrystal

    NASA Astrophysics Data System (ADS)

    Hassdenteufel, Kai H.; Oganov, Artem R.; Katrych, Sergiy; Steurer, Walter

    2007-04-01

    We have performed ab initio simulations of binary and ternary periodic model structures based on the W phase in order to investigate chemical bonding, its response to pressure, and structural relaxations accompanying the substitution of Co by Ni. Our results support previous conclusions that the maximization of Al-Co and Ni-Ni interactions is favorable for reaching the lowest-energy state. The valence electron localization function (ELF) indicates partially covalent bonding supporting the formation of energetically favorable atomic clusters. The existence of a pseudogap in the calculated electronic density of states close to the Fermi level suggests electronic stabilization according to the Hume-Rothery-type mechanism. High-pressure simulations of binary W-(Al,Co) up to 90GPa reveal increasing puckering of the atomic layers perpendicular to the pseudotenfold b axis. Furthermore, the basic pentagonal columnar clusters become distorted, leading to shorter distances between neighboring Co atoms. The structural changes in the vicinity of the distorted clusters point to local changes in the chemical bonding as reflected in the valence ELF.

  17. Pressure dependence on the remanent magnetization of Fe-Ni alloys and Ni metal

    NASA Astrophysics Data System (ADS)

    Wei, Qingguo; Gilder, Stuart Alan; Maier, Bernd

    2014-10-01

    We measured the acquisition of magnetic remanence of iron-nickel alloys (Fe64Ni36, Fe58Ni42, and Fe50Ni50) and pure Ni under pressures up to 23 GPa at room temperature. Magnetization decreases markedly for Fe64Ni36 between 5 and 7 GPa yet remains ferromagnetic until at least 16 GPa. Magnetization rises by a factor of 2-3 for the other compositions during compression to the highest applied pressures. Immediately upon decompression, magnetic remanence increases for all Fe-Ni alloys while magnetic coercivity remains fairly constant at relatively low values (5-20 mT). The amount of magnetization gained upon complete decompression correlates with the maximum pressure experienced by the sample. Martensitic effects best explain the increase in remanence rather than grain-size reduction, as the creation of single domain sized grains would raise the coercivity. The magnetic remanence of low Ni Invar alloys increases faster with pressure than for other body-centered-cubic compositions due to the higher magnetostriction of the low Ni Invar metals. Thermal demagnetization spectra of Fe64Ni36 measured after pressure release broaden as a function of peak pressure, with a systematic decrease in Curie temperature. Irreversible strain accumulation from the martensitic transition likely explains the broadening of the Curie temperature spectra, consistent with our x-ray diffraction analyses.

  18. Modeling and simulation of NiO dissolution and Ni deposition in molten carbonate fuel cells

    SciTech Connect

    Nam, Suk Woo; Choi, Hyung-Joon; Lim, Tae Hoon

    1996-12-31

    Dissolution of NiO cathode into the electrolyte matrix is an important phenomena limiting the lifetime of molten carbonate fuel cell (MCFC). The dissolved nickel diffuses into the matrix and is reduced by dissolved hydrogen leading to the formation of metallic nickel films in the pores of the matrix. The growth of Ni films in the electrolyte matrix during the continuous cell operation results eventually in shorting between cathode and anode. Various mathematical and empirical models have been developed to describe the NiO dissolution and Ni deposition processes, and these models have some success in estimating the lifetime of MCFC by correlating the amount of Ni deposited in the matrix with shorting time. Since the exact mechanism of Ni deposition was not well understood, deposition reaction was assumed to be very fast in most of the models and the Ni deposition region was limited around a point in the matrix. In fact, formation of Ni films takes place in a rather broad region in the matrix, the location and thickness of the film depending on operating conditions as well as matrix properties. In this study, we assumed simple reaction kinetics for Ni deposition and developed a mathematical model to get the distribution of nickel in the matrix.

  19. Anodic vacuum arc developed nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples

    SciTech Connect

    Mukherjee, S. K.; Sinha, M. K.; Pathak, B.; Rout, S. K.; Barhai, P. K.

    2009-12-01

    This paper deals with the development of nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples (TFTCs) by using ion-assisted anodic vacuum arc deposition technique. The crystallographic structure and surface morphology of individual layer films have been studied by x-ray diffraction and scanning electron microscopy, respectively. The resistivity, temperature coefficient of resistance, and thermoelectric power of as deposited and annealed films have been measured. The observed departure of these transport parameters from their respective bulk values can be understood in terms of intrinsic scattering due to enhanced crystallite boundaries. From the measured values of thermoelectric power and the corresponding temperature coefficient of resistance of annealed Cu, Ni, and Fe films, the calculated values of log derivative of the mean free path of conduction electrons at the Fermi surface with respect to energy (U) are found to be -0.51, 3.22, and -8.39, respectively. The thermoelectric response of annealed Cu-Ni and Fe-Ni TFTCs has been studied up to a maximum temperature difference of 300 deg. C. Reproducibility of TFTCs has been examined in terms of the standard deviation in thermoelectric response of 16 test samples for each pair. Cu-Ni and Fe-Ni TFTCs agree well with their wire thermocouple equivalents. The thermoelectric power values of Cu-Ni and Fe-Ni TFTCs at 300 deg. C are found to be 0.0178 and 0.0279 mV/ deg. C, respectively.

  20. Anodic vacuum arc developed nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples

    NASA Astrophysics Data System (ADS)

    Mukherjee, S. K.; Sinha, M. K.; Pathak, B.; Rout, S. K.; Barhai, P. K.

    2009-12-01

    This paper deals with the development of nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples (TFTCs) by using ion-assisted anodic vacuum arc deposition technique. The crystallographic structure and surface morphology of individual layer films have been studied by x-ray diffraction and scanning electron microscopy, respectively. The resistivity, temperature coefficient of resistance, and thermoelectric power of as deposited and annealed films have been measured. The observed departure of these transport parameters from their respective bulk values can be understood in terms of intrinsic scattering due to enhanced crystallite boundaries. From the measured values of thermoelectric power and the corresponding temperature coefficient of resistance of annealed Cu, Ni, and Fe films, the calculated values of log derivative of the mean free path of conduction electrons at the Fermi surface with respect to energy (U) are found to be -0.51, 3.22, and -8.39, respectively. The thermoelectric response of annealed Cu-Ni and Fe-Ni TFTCs has been studied up to a maximum temperature difference of 300°C. Reproducibility of TFTCs has been examined in terms of the standard deviation in thermoelectric response of 16 test samples for each pair. Cu-Ni and Fe-Ni TFTCs agree well with their wire thermocouple equivalents. The thermoelectric power values of Cu-Ni and Fe-Ni TFTCs at 300°C are found to be 0.0178 and 0.0279mV/°C, respectively.

  1. Directional Solidification and Mechanical Properties of NiAl-NiAlTa Alloys

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Chen, X. F.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1995-01-01

    Directional solidification of eutectic alloys is a promising technique for producing in-situ composite materials exhibiting a balance of properties. Consequently, the microstructure, creep strength and fracture toughness of directionally solidified NiAl-NiAlTa alloys were investigated. Directional solidification was performed by containerless processing techniques to minimize alloy contamination. The eutectic composition was found to be NiAl-15.5 at% Ta and well-aligned microstructures were produced at this composition. A near-eutectic alloy of NiAl-14.5Ta was also investigated. Directional solidification of the near-eutectic composition resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The off-eutectic alloy exhibited promising compressive creep strengths compared to other NiAl-based intermetallics, while preliminary testing indicated that the eutectic alloy was competitive with Ni-base single crystal superalloys. The room temperature toughness of these two-phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa.

  2. Thickness and ordering temperature of surface NiO/Ni systems

    SciTech Connect

    Shih, Ying-Ta; Su, Chien-Yu; Tsai, Chung-Wei; Pan, Wei

    2014-02-15

    We estimate the thickness and ordering temperature of an antiferromagnetic and passivation surface oxide through exchange bias coupling. The surface NiO, which is generated through the exposure of a Ni/Cu(001) surface to oxygen, is taken as a model system on which to perform the estimation. Since no exchange bias is found in the surface NiO/Ni/Cu(001), we have built a sandwich structure of NiO/n ML Ni/10 ML Co/Cu(001) to measure the n dependence of exchange bias. With n ⩽ 2, a large exchange bias field is found above 300 K, which could be due to the direct contact between the oxides and the Co layer. With 3 ⩽ n ⩽ 6, a smaller exchange bias field is found with a blocking temperature of 190 K. This implies that the thickness of NiO is, at most, 3 ML. Discovering the thickness and ordering temperature of the surface NiO provides us to explore the potential applications by using surface NiO.

  3. Electron Probe Microanalysis of Ni Silicides Using Ni-L X-Ray Lines.

    PubMed

    Llovet, Xavier; Pinard, Philippe T; Heikinheimo, Erkki; Louhenkilpi, Seppo; Richter, Silvia

    2016-12-01

    We report electron probe microanalysis measurements on nickel silicides, Ni5Si2, Ni2Si, Ni3Si2, and NiSi, which were done in order to investigate anomalies that affect the analysis of such materials by using the Ni L3-M4,5 line (Lα). Possible sources of systematic discrepancies between experimental data and theoretical predictions of Ni L3-M4,5 k-ratios are examined, and special attention is paid to dependence of the Ni L3-M4,5 k-ratios on mass-attenuation coefficients and partial fluorescence yields. Self-absorption X-ray spectra and empirical mass-attenuation coefficients were obtained for the considered materials from X-ray emission spectra and relative X-ray intensity measurements, respectively. It is shown that calculated k-ratios with empirical mass attenuation coefficients and modified partial fluorescence yields give better agreement with experimental data, except at very low accelerating voltages. Alternatively, satisfactory agreement is also achieved by using the Ni L3-M1 line (Lℓ) instead of the Ni L3-M4,5 line.

  4. Metal-insulator transition in Au-NiO-Ni dual Schottky nanojunctions.

    PubMed

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

    2009-11-11

    Ni nanowire arrays were fabricated through electrochemical deposition on a template. After a nanoscale NiO layer was formed on the top of the nanowires, a layer of Au paint was coated on the top of the nanowire arrays to construct Au-NiO-Ni dual Schottky nanojunctions, and the structure was characterized at different scales. Within a small range of voltages, extraordinary current jumps were observed at room temperature and at 77 K. The resistance switch effect can be repeated at room temperature, while switching is irreversible at low temperature. The significant change in resistance of the samples does not require doping and may find future applications.

  5. Layering and temperature-dependent magnetization and anisotropy of naturally produced Ni/NiO multilayers

    SciTech Connect

    Pappas, S. D.; Trachylis, D.; Velgakis, M. J.; Kapaklis, V.; Joensson, P. E.; Papaioannou, E. Th.; Delimitis, A.; Poulopoulos, P.; Fumagalli, P.; Politis, C.

    2012-09-01

    Ni/NiO multilayers were grown by magnetron sputtering at room temperature, with the aid of the natural oxidation procedure. That is, at the end of the deposition of each single Ni layer, air is let to flow into the vacuum chamber through a leak valve. Then, a very thin NiO layer ({approx}1.2 nm) is formed. Simulated x-ray reflectivity patterns reveal that layering is excellent for individual Ni-layer thickness larger than 2.5 nm, which is attributed to the intercalation of amorphous NiO between the polycrystalline Ni layers. The magnetization of the films, measured at temperatures 5-300 K, has almost bulk-like value, whereas the films exhibit a trend to perpendicular magnetic anisotropy (PMA) with an unusual significant positive interface anisotropy contribution, which presents a weak temperature dependence. The power-law behavior of the multilayers indicates a non-negligible contribution of higher order anisotropies in the uniaxial anisotropy. Bloch-law fittings for the temperature dependence of the magnetization in the spin-wave regime show that the magnetization in the multilayers decreases faster as a function of temperature than the one of bulk Ni. Finally, when the individual Ni-layer thickness decreases below 2 nm, the multilayer stacking vanishes, resulting in a dramatic decrease of the interface magnetic anisotropy and consequently in a decrease of the perpendicular magnetic anisotropy.

  6. Significant reduction in NiO band gap upon formation of Lix Ni1-x O alloys: applications to solar energy conversion.

    PubMed

    Alidoust, Nima; Toroker, Maytal Caspary; Keith, John A; Carter, Emily A

    2014-01-01

    Long-term sustainable solar energy conversion relies on identifying economical and versatile semiconductor materials with appropriate band structures for photovoltaic and photocatalytic applications (e.g., band gaps of ∼ 1.5-2.0 eV). Nickel oxide (NiO) is an inexpensive yet highly promising candidate. Its charge-transfer character may lead to longer carrier lifetimes needed for higher efficiencies, and its conduction band edge is suitable for driving hydrogen evolution via water-splitting. However, NiO's large band gap (∼ 4 eV) severely limits its use in practical applications. Our first-principles quantum mechanics calculations show band gaps dramatically decrease to ∼ 2.0 eV when NiO is alloyed with Li2O. We show that Lix Ni1-x O alloys (with x=0.125 and 0.25) are p-type semiconductors, contain states with no impurity levels in the gap and maintain NiO's desirable charge-transfer character. Lastly, we show that the alloys have potential for photoelectrochemical applications, with band edges well-placed for photocatalytic hydrogen production and CO2 reduction, as well as in tandem dye-sensitized solar cells as a photocathode. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Unusual high-spin Fe5 +-Ni3 + state and strong ferromagnetism in the mixed perovskite SrFe0.5Ni0.5O3

    NASA Astrophysics Data System (ADS)

    Fan, Fengren; Li, Zhengwei; Zhao, Zhen; Yang, Ke; Wu, Hua

    2016-12-01

    The charge-spin-orbital state plays a vital role in correlated oxides with mixed transition-metal elements, and it is often a matter of debate. Here, we address this issue for the newly synthesized unusual high-valence perovskite SrFe1 -xNixO3 , using an analysis of crystal-field level diagrams, density functional calculations, and Monte Carlo simulations. We have identified the formal high-spin Fe5 +(t2g 3, S =3 /2 ) and high-spin Ni3 +(t2g 5eg2 , S =3 /2 ) state for SrFe0.5Ni0.5O3 , rather than the previously suggested high-spin Fe4 +(t2g 3eg1, S =2 ) and low-spin Ni4 + (t2g 6, S =0 ) state. Moreover, our model and the present results well explain the observed small lattice variation of SrFe1 -xNixO3 (0 ≤x ≤0.5 ) and the above room temperature ferromagnetic order in SrFe0.5Ni0.5O3 regardless of a Fe-Ni atomic order or disorder.

  8. Graphene Growth and Defects on Ni(111)

    NASA Astrophysics Data System (ADS)

    Batzill, Matthias; Lahiri, Jayeeta

    2011-03-01

    Using scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES) we have investigated the growth of graphene on Ni(111) surfaces by carbon segregation from the bulk. We reveal two distinct growth modes for graphene growth. Between 480 and 650 C graphene forms on clean Ni(111) and below 480 C graphene grows by an in-plane conversion of a surface carbide phase. This is the first time that graphene formation is observed by transformation of a surface carbide. STM indicates that a lattice-matched, one-dimensional in-plane domain boundary between graphene and the carbide forms and graphene grows by replacing Ni-atoms with carbon at this interface. In addition to the growth of graphene we will also briefly discuss atomic-scale defects that can be synthesized in Ni-supported graphene. In particular we emphasize the formation of an extended line-defect with metallic properties.

  9. Atomic Data and Spectral Line Intensities for Ni XXI

    NASA Technical Reports Server (NTRS)

    Bhatia, A. K.; Landi, E.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Electron impact collision strengths, energy levels, oscillator strengths and spontaneous radiative decay rates are calculated for Ni XXI. The configurations used are 2s(sup 2)2p(sup 4), 2s2p(sup 5), 2p(sup 6), 2s(sup 2)2p(sup 3)3s, and 2s(sup 2)3p(sup 3)3d giving rise to 58 fine-structure levels in intermediate coupling. Collision strengths are calculated at five incident energies, 85, 170, 255, 340, and 425 Ry. Excitation rate coefficients are calculated by assuming a Maxwellian electron velocity distribution at an electron temperature of log T(sub e)(K)=6.9, corresponding to maximum abundance of Ni XXI. Using the excitation rate coefficients and the radiative transition rates, statistical equilibrium equations for level populations are solved at electron densities 10(exp 8)-10(exp 14) per cubic centimeter. Relative spectral line intensities are calculated. Proton excitation rates between the lowest three levels have been included in the statistical equilibrium equations. The predicted intensity ratios are compared with available observations.

  10. Atomic Data and Spectral Line Intensities for Ni XV

    NASA Technical Reports Server (NTRS)

    Landi, E.; Bhatia, A. K.

    2011-01-01

    Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for Ni XV.Weinclude in the calculations the 9 lowest configurations, corresponding to 126 fine structure levels: 3s23p2, 3s3p3, 3s23p3d, 3p4, 3s3p23d, and 3s2 3p4l with l =, s, p, d, f. Collision strengths are calculated at five incident energies for all transitions: 7.8, 18.5, 33.5, 53.5, and 80.2 Ry above the threshold of each transition. An additional energy, very close to the transition threshold, has been added, whose value is between 0.004 and 0.28 Ry depending on the levels involved. Calculations have been carried out using the Flexible Atomic Code and the distorted-wave approximation. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates calculated in the present work, statistical equilibrium equations for level populations are solved at electron densities covering the 10(exp 8)-10(exp 14)/cu cm range and at an electron temperature of log T(sub e)(K) = 6.4, corresponding to the maximum abundance of Ni XV. Spectral line intensities are calculated, and their diagnostic relevance is discussed. This dataset will be made available in the next version of the CHIANTI database.

  11. Atomic Data and Spectral Line Intensities for Ni XV

    NASA Technical Reports Server (NTRS)

    Landi, E.; Bhatia, A. K.

    2011-01-01

    Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for Ni XV.Weinclude in the calculations the 9 lowest configurations, corresponding to 126 fine structure levels: 3s23p2, 3s3p3, 3s23p3d, 3p4, 3s3p23d, and 3s2 3p4l with l =, s, p, d, f. Collision strengths are calculated at five incident energies for all transitions: 7.8, 18.5, 33.5, 53.5, and 80.2 Ry above the threshold of each transition. An additional energy, very close to the transition threshold, has been added, whose value is between 0.004 and 0.28 Ry depending on the levels involved. Calculations have been carried out using the Flexible Atomic Code and the distorted-wave approximation. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates calculated in the present work, statistical equilibrium equations for level populations are solved at electron densities covering the 10(exp 8)-10(exp 14)/cu cm range and at an electron temperature of log T(sub e)(K) = 6.4, corresponding to the maximum abundance of Ni XV. Spectral line intensities are calculated, and their diagnostic relevance is discussed. This dataset will be made available in the next version of the CHIANTI database.

  12. Liquidus Projections of Sn-Co-Ni and Sn-Rich Sn-Ag-Co-Ni Systems

    NASA Astrophysics Data System (ADS)

    Chen, Sinn-wen; Chen, Tung-Kai; Hsu, Chia-ming; Chang, Jui-shen; Pan, Kevin

    2014-07-01

    Alloys based on Sn and Sn-Ag are commonly used as Pb-free solders, and Ni is frequently used in barrier layers. Co has been studied as a possible alloying element in both solders and barrier layers. Thus, the Sn-Co-Ni and Sn-Ag-Co-Ni alloy systems are important for electronic soldering. Forty-nine Sn-Co-Ni alloys and 24 Sn-rich Sn-Ag-Co-Ni alloys were prepared. The primary solidification phases of these as-cast alloys were determined, and based on these results and the available phase diagrams of the constituent systems, the liquidus projections of Sn-Co-Ni ternary and Sn-Ag-Co-Ni quaternary systems at 90 at.% and 95 at.% Sn were determined. In the Sn-Co-Ni system, no ternary compound was found; (Ni,Co)3Sn2 and (Ni,Co) are continuous solid solutions, and there are eight kinds of primary solidification phases: Sn, CoSn3, CoSn2, CoSn, (Ni,Co)3Sn2, (Ni,Co), Ni3Sn, and Ni3Sn4. In the 90 at.% and 95 at.% Sn isoplethal sections of the Sn-Ag-Co-Ni liquidus projection, the primary solidification phases are CoSn2, CoSn, Ni3Sn4, and Ag3Sn.

  13. Increasing foliar Zn:Ni or Cu:Ni concentration ratios increase severity of nickel deficiency symptoms

    USDA-ARS?s Scientific Manuscript database

    The influence of essential micronutrients on the endogenous bioavailability of Ni is unknown. This study examines the linkage between Ni deficiency and endogenous foliar concentration of Ni, Zn, and Cu. It was hypothesized that expression of morphological symptoms of Ni deficiency by pecan [Carya i...

  14. Long-term monitoring of airborne nickel (Ni) pollution in association with some potential source processes in the urban environment.

    PubMed

    Kim, Ki-Hyun; Shon, Zang-Ho; Mauulida, Puteri T; Song, Sang-Keun

    2014-09-01

    The environmental behavior and pollution status of nickel (Ni) were investigated in seven major cities in Korea over a 13-year time span (1998-2010). The mean concentrations of Ni measured during the whole study period fell within the range of 3.71 (Gwangju: GJ) to 12.6ngm(-3) (Incheon: IC). Although Ni values showed a good comparability in a relatively large spatial scale, its values in most cities (6 out of 7) were subject to moderate reductions over the study period. To assess the effect of major sources on the long-term distribution of Ni, the relationship between their concentrations and the potent source processes like non-road transportation sources (e.g., ship and aircraft emissions) were examined from some cities with port and airport facilities. The potential impact of long-range transport of Asian dust particles in controlling Ni levels was also evaluated. The overall results suggest that the Ni levels were subject to gradual reductions over the study period irrespective of changes in such localized non-road source activities. The pollution of Ni at all the study sites was maintained well below the international threshold (Directive 2004/107/EC) value of 20ngm(-3).

  15. Magnetic Properties of ni Nanowires Grown in Mesoporous Silicon Templates

    NASA Astrophysics Data System (ADS)

    Dolgiy, A. L.; Redko, S. V.; Yanushkevich, K. I.

    2013-05-01

    Magnetic properties of Ni nanowires electrochemically deposited into pores of mesoporous silicon template under the stationary galvanostatic regime were investigated by measuring the temperature dependence (77-700 K) of the specific magnetization σ. The measured σ values were lower with respect to that of bulk Ni. The Curie temperature, TC, derived from σ(T) for low deposition times of Ni was less (575 K) than that for bulk Ni (630 K). This is caused by dimensional effects of Ni nanoparticles.

  16. Domain structure and magnetization process of a giant magnetoimpedance geometry FeNi/Cu/FeNi(Cu)FeNi/Cu/FeNi sensitive element

    NASA Astrophysics Data System (ADS)

    Kurlyandskaya, G. V.; Elbaile, L.; Alves, F.; Ahamada, B.; Barrué, R.; Svalov, A. V.; Vas'kovskiy, V. O.

    2004-09-01

    The magnetization process and the magnetic domains of the FeNi (100 nm)/Cu (2.5 nm)/FeNi (100 nm)/Cu (480 nm)/FeNi (100 nm)/Cu (2.5 nm)/FeNi (100 nm) structure were studied. This geometry consists of two FeNi/Cu/FeNi trilayers with a thick in the direction perpendicular to the plane of the sensitive element and narrow in the direction of the flowing current Cu electrode in the centre. Ferromagnet/conductor/ferromagnet is the typical geometry of magnetoimpedance thin-film-based sensitive elements used to detect small magnetic fields. Multilayered structures were prepared by rf-sputtering in a magnetic field of 100 Oe applied perpendicular to the Cu electrode in order to induce transverse magnetic anisotropy. The magnetic measurements and magnetic domain structure observations were made in magnetic fields applied one at a time parallel or perpendicular to the Cu electrode. Different magnetization processes with non-homogeneous rotations in the first case and dominant multiple nucleation and merging of domains in the second one were observed.

  17. Distribution patterns of the metal pollutants Cd and Ni in soybean seeds

    NASA Astrophysics Data System (ADS)

    Malan, H. L.; Mesjasz-Przybylowicz, J.; Przybylowicz, W. J.; Farrant, J. M.; Linder, P. W.

    2012-02-01

    Soybean ( Glycine max) plants were grown to maturity in nutrient solution, amended with either Cd or Ni. The distribution of these metals in mature seeds was examined with micro-PIXE. The levels of Cd were too low for mapping and only average concentrations from selected regions could be obtained. Cd was localised mainly in the seed coat and cotyledons, with very little in the embryo axis. Levels of Ni were high enough to obtain the distribution maps. This metal was mainly concentrated in the axis, particularly in the apical meristem and cortex, and least in the cotyledons. Localisation of Ni within different tissues of the embryo was facilitated by mapping of Ca which is present in the cell walls of plants. This enabled the different plant tissues of the seed embryo to be identified. Micro-PIXE is a valuable tool for localising the distribution of metal pollutants in plant tissue.

  18. A lucrative technique to reduce Ni toxicity in Raphanus sativus plant by phosphate amendment: Special reference to plant metabolism.

    PubMed

    Singh, Anita; Prasad, Sheo Mohan

    2015-09-01

    Nickel (Ni) contamination is one of the serious environmental problems. It creates hazard in soil environment and also in crop quality. In the present study, response of Raphanus sativus (radish) to Ni (50mgkg(-1) soil) under different concentrations (100, 200, 500 and 1000 DAPmgkg(-1) soil) of phosphate as soil amendment was investigated after 40 days of growth. Ni-treated plants without amendment showed reduction in their growth as a result of appreciable decrease in the photosynthetic activity. Under this treatment, Ni accumulation significantly enhanced lipid peroxidation and level of oxidants showing oxidative stress and it was also associated with decrease in the activities of antioxidative enzymes except super oxide dismutase (SOD). Application of phosphate in Ni contaminated soil resulted into significant improvement in plant growth. Under phosphate amendment, the status of oxidative biomarkers: SOR, TBARS and H2O2 were under control by the higher activity of antioxidants: APX, CAT, POD, GST and DHAR compared to Ni contaminated soil without amendment. Principal component analysis (PCA) was performed to show the significant changes in biochemical traits under control and phosphate amendment. The values of PS II transient kinetics: Phi-E0, Psi-0 and PIABS increased and values of energy fluxes: ABC/RC, Tro/RC, Eto/RC and Dio/RC decreased in plants grown in Ni contaminated soil under phosphate amendment as compared to without amendment. Among all doses of phosphate amendment soil amended at 500mg DAPkg(-)(1) soil the yield of plant was the highest and Ni accumulation was the lowest. As compared to plants grown in Ni treated soil without amendment the yield of plant at 500mg DAPkg(-1) soil showed about 70% increment and the reduction in Ni accumulation was 63% in shoot and 64% in root. Because of these beneficial effects this technique can be easily applied at metal contaminated agricultural fields to reduce food chain contamination and to improve food quality.

  19. Methanethiol decomposition on Ni(100)

    SciTech Connect

    Castro, M.E.; Ahkter, S.; Golchet, A.; White, J.M. ); Sahin, T. )

    1991-01-01

    Static secondary ion mass spectroscopy (SSIMS), temperature programmed desorption (TPD), and Auger electron spectroscopy (AES) were used under ultrahigh vacuum conditions to study the decomposition of CH{sub 3}SH on Ni(100). Only methane, hydrogen, and the parent molecule are observed in TPD. Complete decomposition to C(a), S(a) and desorbing H{sub 2} is the preferred reaction pathway for low exposures, while desorption of methane is observed at higher coverages. Preadsorbed hydrogen promoted methane desorption. Upon adsorption, and for low coverages, SSIMS evidence indicates S-H bond cleavage into CH{sub 3}S and surface hydrogen. S-H bond cleavage is inhibited for high coverages. The TP-SSIMS data are consistent with an activated C-S bond cleavage in CH{sub 3}S, with an activation energy of 8.81 kcal/mol and preexponential factor of 10{sup 6.5}s{sup {minus}1}. The low preexponential factor is taken as indicating a complex decomposition pathway. A mechanism consistent with the observed data is discussed.

  20. Oxygen-induced changes in electron-energy-loss spectra for Al, Be and Ni. [Al; Be; Ni

    SciTech Connect

    Madden, H.H.; Landers, R.; Kleiman, G.G. , 13081-970 Campinas, Sao Paulo, Brasil); Zehner, D.M. )

    1999-09-01

    Electron-energy-loss spectroscopy (EELS) data are presented to illustrate line shape changes that occur as a result of oxygen interaction with metal surfaces. The metals were aluminum, beryllium and nickel. Core-level EELS data were taken for excitations from Al(2p), Be(1s), Ni(3p/3s) and O(1s) levels to the conduction band (CB) density of states (DOS) of the materials. The primary beam energies for the spectra were 300, 450, 300, and 1135 eV, respectively. The data are presented in both the (as measured) first-derivative and the integral forms. The integral spectra were corrected for coherent background losses and analyzed for CB DOS information. These spectra were found to be in qualitative agreement with published experimental and theoretical studies of these materials. One peak in the spectra for Al oxide is analyzed for its correlation with excitonic screening of the Al(2p) core hole. Similar evidence for exciton formation is found in the Ni(3p) spectra for Ni oxide. Data are also presented showing oxygen-induced changes in the lower-loss-energy EELS curves that, in the pure metal, are dominated by plasmon-loss and interband-transition signals. Single-scattering loss profiles in the integral form of the data were calculated using a procedure of Tougaard and Chorkendorff [S. Tougaard and I. Chorkendorff, Phys. Rev. B. [bold 35], 6570 (1987)]. For all three oxides these profiles are dominated by a feature with a loss energy of around 20[endash]25 eV. Although this feature has been ascribed by other researchers as due to bulk plasmon losses in the oxide, an alternative explanation is that the feature is simply due to O(2s)-to-CB-level excitations. An even stronger feature is found at 7 eV loss energy for Ni oxide. Speculation is given as to its source. The line shapes in both the core-level and noncore-level spectra can also be used simply as [open quotes]fingerprints[close quotes] of the surface chemistry of the materials. Our data were taken using commercially

  1. The molecular mechanism for effects of TiN coating on NiTi alloy on endothelial cell function.

    PubMed

    Yang, Dayun; Lü, Xiaoying; Hong, Ying; Xi, Tingfei; Zhang, Deyuan

    2014-08-01

    The aim of this study is to systematically investigate the molecular mechanism of different effects of nickel titanium (NiTi) alloy surface and titanium nitride (TiN) coating on endothelial cell function. Release of nickel (Ni) ion from bare and TiN-coated NiTi alloys and proliferation of endothelial cells on the two materials were evaluated, and then influence of the two materials on cellular protein expression profiles was investigated by proteomic technology. Subsequently, proteomic data were analyzed with bioinformatics analyses and further validated using a series of biological experiments. Results showed that although the two materials did not affect cell proliferation, the Ni ions released from bare NiTi alloy generated inhibition on pathways associated with actin cytoskeleton, focal adhesion, energy metabolism, inflammation, and amino acid metabolism. In comparison, TiN coating not only effectively prevented release of Ni ions from NiTi alloy, but also promoted actin cytoskeleton and focal adhesion formation, increased energy metabolism, enhanced regulation of inflammation, and promoted amino acid metabolism. Furthermore, the two processes, "the initial mediation of adsorbed serum protein layer to endothelial cell adhesion and growth on the two materials" from our previous study, and "the following action of the two materials on cellular protein expression profile", were linked up and comprehensively analyzed. It was found that in stage of cell adhesion (within 4 h), release of Ni ions from bare NiTi alloy was very low, and the activation of adsorbed proteins to cell adhesion and growth related biological pathways (such as regulation of actin cytoskeleton, and focal adhesion pathways) was almost as same as TiN-coated NiTi alloy. This indicated that the released Ni ions did not affect the mediation of adsorbed proteins to endothelial cell adhesion. However, in stage of cell growth and proliferation, the release of Ni ions from bare NiTi alloy increased with

  2. Toxicity assessment and selective leaching characteristics of Cu-Al-Ni shape memory alloys in biomaterials applications.

    PubMed

    Chang, Shih-Hang; Chen, Bor-Yann; Lin, Jin-Xiang

    2016-04-06

    Cu-Al-Ni shape memory alloys (SMAs) possess two-way shape memory effects, superelasticity, and damping capacity. Nonetheless, Cu-Al-Ni SMAs remain promising candidates for use in biomedical applications, as they are more economical and machinable than other SMAs. Ensuring the biocompatibility of Cu-Al-Ni SMAs is crucial to their development for biomedical applications. Therefore, this study aimed to assess the toxicity of Cu-Al-Ni SMAs using a Probit dose-response model and augmented simplex design. In this study, the effects of Cu2+, Al3+ and Ni2+ metal ions on bacteria (Escherichia coli DH5α) using Probit dose-response analysis and augmented simplex design to assess the actual toxicity of the Cu-Al-Ni SMAs. Extraction and repetition of Escherichia coli DH5α solutions with high Cu2+ ion concentrations and 30-hour incubation demonstrated that Escherichia coli DH5α was able to alter its growth mechanisms in response to toxins. Metal ions leached from Cu-Al-Ni SMAs appeared in a multitude of compositions with varying degrees of toxicity, and those appearing close to a saddle region identified in the contour plot of the augmented simplex model were identified as candidates for elevated toxicity levels. When the Cu-13.5Al-4Ni SMA plate was immersed in Ringer's solution, the selective leaching rate of Ni2+ ions far exceeded that of Cu2+ and Al3+. The number of Cu2+, Al3+ and Ni2+ ions leached from Cu-Al-Ni SMAs increased with immersion time; however, at higher ratios, toxicity interactions among the metal ions had the effect of gradually reducing overall toxicity levels with regard to Escherichia coli DH5α. The quantities of Cu2+, Al3+ and Ni2+ ions leached from the Cu-13.5Al-4Ni SMA plate increased with immersion time, the toxicity interactions associated with these compositions reduced the actual toxicity to Escherichia coli DH5α.

  3. Improvement of Ni phytostabilization by inoculation of Ni resistant Bacillus megaterium SR28C.

    PubMed

    Rajkumar, Mani; Ma, Ying; Freitas, Helena

    2013-10-15

    The use of metal tolerant plants for the phytostabilization of metal contaminated soil is an area of extensive research and development. In this study the effects of inoculation of Ni-resistant bacterial strains on phytostabilization potential of various plants, including Brassica juncea, Luffa cylindrica and Sorghum halepense, were studied. A Ni-resistant bacterial strain SR28C was isolated from a nickel rich serpentine soil and identified as Bacillus megaterium based on the morphological features, biochemical characteristics and partial 16S rDNA sequence analysis. The strain SR28C tolerated concentrations up to 1200 mg Ni L(-1) on a Luria-Bertani (LB) agar medium. Besides, it showed high degree of resistance to various metals (Cu, Zn, Cd, Pb and Cr) and antibiotics (ampicillin, tetracycline, streptomycin, chloramphenicol, penicillin and kanamycin) tested. In addition, the strain bound considerable amounts of Ni in their resting cells. Besides, the strain exhibited the plant growth promoting traits, such as solubilization of phosphate and production of indole-3-acetic acid (IAA) in modified Pikovskayas medium and LB medium, respectively in the absence and presence of Ni. Considering such potential, the effects of SR28C on the growth and Ni accumulation of B. juncea, L. cylindrica and S. halepense, were assessed with different concentrations of Ni in soil. Inoculation of SR28C stimulated the biomass of the test plants grown in both Ni contaminated and non-contaminated soils. Further, SR28C alleviated the detrimental effects of Ni by reducing its uptake and translocation to the plants. This study suggested that the PGPB inoculant due to its intrinsic abilities of growth promotion and attenuation of the toxic effects of Ni could be exploited for phytostabilization of Ni contaminated site. © 2013 Elsevier Ltd. All rights reserved.

  4. Imaging of electrical response of NiOx under controlled environment with sub-25-nm resolution

    DOE PAGES

    Jacobs, Christopher B.; Ievlev, Anton V.; Collins, Liam F.; ...

    2016-07-19

    The spatially resolved electrical response of rf-sputtered polycrystalline NiOx films composed of 40 nm crystallites was investigated under different relative humidity levels (RH). The topological and electrical properties (surface potential and resistance) were characterized using Kelvin probe force microscopy (KPFM) and conductive scanning probe microscopy at 0%, 50%, and 80% relative humidity with sub 25nm resolution. The surface potential of NiOx decreased by about 180 mV and resistance decreased in a nonlinear fashion by about 2 G when relative humidity was increased from 0% to 80%. The dimensionality of surface features obtained through autocorrelation analysis of topological, surface potential andmore » resistance maps increased linearly with increased relative humidity as water was adsorbed onto the film surface. Spatially resolved surface potential and resistance of the NiOx films were found to be heterogeneous, with distinct features that grew in size from about 60 nm to 175 nm between 0% and 80% RH levels, respectively. Here, we find that the changes in the heterogeneous character of the NiO films are consistent through the topological, surface potential, and resistance measurements, suggesting that the nanoscale surface potential and resistance properties converge with the mesoscale properties as water is adsorbed onto the NiOx film.« less

  5. Electron phonon coupling in Ni-based binary alloys with application to displacement cascade modeling

    DOE PAGES

    Samolyuk, German D.; Stocks, George Malcolm; Stoller, Roger E.

    2016-04-01

    Energy transfer between lattice atoms and electrons is an important channel of energy dissipation during displacement cascade evolution in irradiated materials. On the assumption of small atomic displacements, the intensity of this transfer is controlled by the strength of electron–phonon (el–ph) coupling. The el–ph coupling in concentrated Ni-based alloys was calculated using electronic structure results obtained within the coherent potential approximation. It was found that Ni0.5Fe0.5, Ni0.5Co0.5 and Ni0.5Pd0.5 are ordered ferromagnetically, whereas Ni0.5Cr0.5 is nonmagnetic. Since the magnetism in these alloys has a Stoner-type origin, the magnetic ordering is accompanied by a decrease of electronic density of states atmore » the Fermi level, which in turn reduces the el–ph coupling. Thus, the el–ph coupling values for all alloys are approximately 50% smaller in the magnetic state than for the same alloy in a nonmagnetic state. As the temperature increases, the calculated coupling initially increases. After passing the Curie temperature, the coupling decreases. The rate of decrease is controlled by the shape of the density of states above the Fermi level. Introducing a two-temperature model based on these parameters in 10 keV molecular dynamics cascade simulation increases defect production by 10–20% in the alloys under consideration.« less

  6. Phase Offsets in the Critical-Current Oscillations of Josephson Junctions Based on Ni and Ni-(Ni81Fe19)xNby Barriers

    NASA Astrophysics Data System (ADS)

    Baek, B.; Schneider, M. L.; Pufall, M. R.; Rippard, W. H.

    2017-06-01

    We measure and compare the critical-current oscillation characteristics of Josephson junctions as a function of Ni thickness in different barrier structures. The characteristics dependent on the relative Ni thickness, such as the presence of nodes and the oscillation period, are consistent with a conventional, clean-limit magnetic Josephson-junction model. However, the oscillation phases have different offsets in the Ni thickness between single Ni and Ni - (Ni81Fe19)xNby -based barriers, which cannot be explained by the bulk exchange field effect alone. This effect does not originate from the ferromagnetism in (Ni81Fe19)xNby nor is it cumulative with an additional (Ni81Fe19)xNby layer. Our results present clear evidence that a nonmagnetic layer can affect the superconducting spin phase across the junction as strongly as the conventional exchange field effect.

  7. Processing condition for the development of cube texture in Ni and Ni alloy tapes fabricated by powder metallurgy process

    NASA Astrophysics Data System (ADS)

    Ji, Bong Ki; Lee, Dong-Wook; Kim, Min-Woo; Jun, Byung-Hyuk; Park, Pyeong Yeal; Jung, Kyu-Dong; Kim, Chan-Joong

    2004-10-01

    Bi-axially textured Ni, Ni-W (1, 3 and 5 at.%) and Ni-Cu alloy tapes for YBCO coated conductors were fabricated by powder metallurgy process including powder compaction, cold isostatic pressing, cold rolling and recrystallization heat treatment. The rod-like Ni and Ni alloy compacts were sintered at 1100 °C for 6 h in 96% Ar-4% H 2 atmosphere. The sintered Ni and Ni-W rods were successfully cold-rolled into thin tapes of 80-100 μm thickness with 5% reduction at each path, but the Ni-Cu alloy rods with Cu content less than 20 at.% were made into tapes. The Ni and Ni alloy tapes were heat-treated at 800-1200 °C for the development of cube texture. The good (2 0 0) texture was obtained for both Ni and Ni-W alloy tapes, while it was obtained only for the Ni-Cu tapes with low Cu contents. The W and Cu addition to Ni improved the mechanical properties by solid solution hardening. Critical current density ( Jc) of YBCO film deposited on the CeO 2/YSZ/CeO 2(CYC)/Ni template was 0.25 MA/cm 2 at 77 K and self-field.

  8. Synthesis and characterizations of Ni-NiO nanoparticles on PDDA-modified graphene for oxygen reduction reaction

    PubMed Central

    2014-01-01

    We are presenting our recent research results about the Ni-NiO nanoparticles on poly-(diallyldimethylammonium chloride)-modified graphene sheet (Ni-NiO/PDDA-G) nanocomposites prepared by the hydrothermal method at 90°C for 24 h. The Ni-NiO nanoparticles on PDDA-modified graphene sheets are measured by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and selected area electron diffraction (SAED) pattern for exploring the structural evidence to apply in the electrochemical catalysts. The size of Ni-NiO nanoparticles is around 5 nm based on TEM observations. The X-ray diffraction (XRD) results show the Ni in the (012), (110), (110), (200), and (220) crystalline orientations, respectively. Moreover, the crystalline peaks of NiO are found in (111) and (220). The thermal gravimetric analysis (TGA) result represents the loading content of the Ni metal which is about 34.82 wt%. The electron spectroscopy for chemical analysis/X-ray photoelectron spectroscopy (ESCA/XPS) reveals the Ni0 to NiII ratio in metal phase. The electrochemical studies with Ni-NiO/PDDA-G in 0.5 M aqueous H2SO4 were studied for oxygen reduction reaction (ORR). PMID:25246863

  9. Peculiarities of thermoelectric half-Heusler phase formation in Gd-Ni-Sb and Lu-Ni-Sb ternary systems

    NASA Astrophysics Data System (ADS)

    Romaka, V. V.; Romaka, L.; Horyn, A.; Rogl, P.; Stadnyk, Yu; Melnychenko, N.; Orlovskyy, M.; Krayovskyy, V.

    2016-07-01

    The phase equilibria in the Gd-Ni-Sb and Lu-Ni-Sb ternary systems were studied at 873 K by X-ray and metallographic analyses in the whole concentration range. The interaction of the elements in the Gd-Ni-Sb system results the formation of five ternary compounds at investigated temperature: Gd5Ni2Sb (Mo5SiB2-type), Gd5NiSb2 (Yb5Sb3-type), GdNiSb (MgAgAs-type), Gd3Ni6Sb5 (Y3Ni6Sb5-type), and GdNi0.72Sb2 (HfCuSi2-type). At investigated temperature the Lu-Ni-Sb system is characterized by formation of the LuNiSb (MgAgAs-type), Lu5Ni2Sb (Mo5SiB2-type), and Lu5Ni0.56Sb2.44 (Yb5Sb3-type) compounds. The disordering in the crystal structure of half-Heusler GdNiSb and LuNiSb was revealed by EPMA and studied by means of Rietveld refinement and DFT modeling. The performed electronic structure calculations are in good agreement with electrical transport property studies.

  10. Generation of free radicals from lipid hydroperoxides by Ni2+ in the presence of oligopeptides.

    PubMed

    Shi, X; Dalal, N S; Kasprzak, K S

    1992-11-15

    The generation of free radicals from lipid hydroperoxides by Ni2+ in the presence of several oligopeptides was investigated by electron spin resonance (ESR) utilizing 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trap. Incubation of Ni2+ with cumene hydroperoxide or t-butyl hydroperoxide did not generate any detectable free radical. In the presence of glycylglycylhistidine (GlyGlyHis), however, Ni2+ generated cumene peroxyl (ROO.) radical from cumene hydroperoxide, with the free radical generation reaching its saturation level within about 3 min. The reaction was first order with respect to both cumene hydroperoxide and Ni2+. Similar results were obtained using t-butyl hydroperoxide, but the yield of t-butyl peroxyl radical generation was about 7-fold lower. Other histidine-containing oligopeptides such as beta-alanyl-L-histidine (carnosine), gamma-aminobutyryl-L-histidine (homocarnosine), and beta-alanyl-3-methyl-L-histidine (anserine) caused the generation of both cumene alkyl (R.) and cumene alkoxyl (RO.) radicals in the reaction of Ni2+ with cumene hydroperoxide. Similar results were obtained using t-butyl hydroperoxide. Glutathione also caused generation of R. and RO. radicals in the reaction of Ni2+ with cumene hydroperoxide but the yield was approximately 25-fold greater than that produced by the histidine-containing peptides, except GlyGlyHis. The ratio of DMPO/R. and DMPO/RO. produced with glutathione and cumene hydroperoxide was approximately 3:1. Essentially the same results were obtained using t-butyl hydroperoxide except that the ratio of DMPO/R. to DMPO/RO. was approximately 1:1. The free radical generation from cumene hydroperoxide reached its saturation level almost instantaneously while in the case of t-butyl hydroperoxide, the saturation level was reached in about 3 min. In the presence of oxidized glutathione, the Ni2+/cumene hydroperoxide system caused DMPO/.OH generation from DMPO without forming free hydroxyl radical. Since glutathione

  11. Ocular vestibular evoked myogenic potentials in response to air-conducted sound in Ménière's disease.

    PubMed

    Winters, Stephanie M; Campschroer, Thijs; Grolman, Wilko; Klis, Sjaak F L

    2011-10-01

    Currently, Ménière's disease is predominantly diagnosed through clinical criteria. Additional standard vestibular testing, such as nystagmography, can show variable responses. In the last decade, the cervical vestibular evoked myogenic potential (VEMP) has shown to be of additive value in diagnosing Ménière's disease. In this study, the results of the ocular VEMP (oVEMP) in response to air-conducted sound will be discussed. To evaluate possible changes of the oVEMP in a large group (n = 37) of patients with Ménière's disease. In 55 subjects without Ménière's disease and 37 patients with Ménière's disease, oVEMPs in response to air-conducted sound stimulation (tone-burst, 500 Hz; maximum stimulus level, 120 dB sound pressure level) were studied. Recording was performed in upgaze with surface electrodes underneath both eyes. The burden of the test was scored by all subjects on a visual analogue scale. In patients with Ménière's disease the response rates are lower, the oVEMP amplitudes are smaller, and thresholds are higher than in subjects without Ménière's disease. This effect is observed in both ears of patients with Ménière's disease. The affected ear is more altered than the clinically unaffected ear. The air-conducted oVEMP can be a relevant addition to the current diagnostic workup of patients with possible Ménière's disease. A lower response rate, smaller amplitude, and higher threshold of the oVEMP indicate the pathologic disease in this population.

  12. Atomic Data and Spectral Line Intensities for NI XVII

    NASA Technical Reports Server (NTRS)

    Bhatia, A. K.; Landi, E.

    2011-01-01

    Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for Ni XVII. We include in the calculations the 23 lowest configurations, corresponding to 159 fine-structure levels: 3l3l', 3l4l0'' , and 3s5l0''' , with l,l' = s,p,d, l'' = s,p,d, f, and l''' = s,p,d. Collision strengths are calculated at five incident energies for all transitions at varying energies above the threshold of each transition. One additional energy, very close to the threshold of each transition, has also been included. Calculations have been carried out using the Flexible Atomic Code in the distorted wave approximation. Additional calculations have been performed with the University College London suite of codes for comparison. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates of the present work, statistical equilibrium equations for level populations are solved at electron densities covering the range of 10(exp 8) - 10(exp 14) / cubic cm and at an electron temperature of logT(sub e)e(K) = 6.5, corresponding to the maximum abundance of Ni XVII. Spectral line intensities are calculated, and their diagnostic relevance is discussed. This dataset will be made available in the next version of the CHIANTI database

  13. Electronic circuits having NiAl and Ni.sub.3 Al substrates

    DOEpatents

    Deevi, Seetharama C.; Sikka, Vinod K.

    1999-01-01

    An electronic circuit component having improved mechanical properties and thermal conductivity comprises NiAl and/or Ni.sub.3 Al, upon which an alumina layer is formed prior to applying the conductive elements. Additional layers of copper-aluminum alloy or copper further improve mechanical strength and thermal conductivity.

  14. 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.

  15. Enhanced Electrocatalytic Activity for Water Splitting on NiO/Ni/Carbon Fiber Paper.

    PubMed

    Zhang, Ruoyu; Wei, Hehe; Si, Wenjie; Ou, Gang; Zhao, Chunsong; Song, Mingjun; Zhang, Cheng; Wu, Hui

    2016-12-28

    Large-scale growth of low-cost, efficient, and durable non-noble metal-based electrocatalysts for water splitting is crucial for future renewable energy systems. Atomic layer deposition (ALD) provides a promising route for depositing uniform thin coatings of electrocatalysts, which are useful in many technologies, including the splitting of water. In this communication, we report the growth of a NiO/Ni catalyst directly on carbon fiber paper by atomic layer deposition and report subsequent reduction and oxidation annealing treatments. The 10-20 nm NiO/Ni nanoparticle catalysts can reach a current density of 10 mA·cm(-2) at an overpotential of 189 mV for hydrogen evolution reactions and 257 mV for oxygen evolution reactions with high stability. We further successfully achieved a water splitting current density of 10 mA·cm(-2) at 1.78 V using a typical NiO/Ni coated carbon fiber paper two-electrode setup. The results suggest that nanoparticulate NiO/Ni is an active, stable, and noble-metal-free electrocatalyst, which facilitates a method for future water splitting applications.

  16. 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.

  17. Adios El Niño, Hello La Niña?

    NASA Image and Video Library

    2010-06-22

    This image from NASA European Ocean Surface Topography Mission/Jason-2 shows that the moderate El Niño of the past year has officially bowed out, leaving his cool sibling, La Niña, poised to potentially take the equatorial stage.

  18. Orbital and spin physics in LiNiO2 and NaNiO2

    NASA Astrophysics Data System (ADS)

    Reitsma, Albert J. W.; Feiner, Louis Felix; Oles, Andrzej M.

    2005-05-01

    We derive a spin-orbital Hamiltonian for a triangular lattice of eg orbital degenerate (Ni3+) transition-metal ions interacting via 90° superexchange involving (O2-) anions, taking into account the onsite Coulomb interactions on both the anions and the transition metal ions. The derived interactions in the spin-orbital model are strongly frustrated, with the strongest orbital interactions selecting different orbitals for pairs of Ni ions along the three different lattice directions. In the orbital-ordered phase, favoured in mean field theory, the spin-orbital interaction can play an important role by breaking the U(1) symmetry generated by the much stronger orbital interaction and restoring the three-fold symmetry of the lattice. As a result, the effective magnetic exchange is non-uniform and includes both ferromagnetic and antiferromagnetic spin interactions. Since ferromagnetic interactions still dominate, this offers yet insufficient explanation for the absence of magnetic order and the low-temperature behaviour of the magnetic susceptibility of stoichiometric LiNiO2. The scenario proposed to explain the observed difference in the physical properties of LiNiO2 and NaNiO2 includes small covalency of Ni-O-Li-O-Ni bonds inducing weaker interplane superexchange in LiNiO2, insufficient to stabilize orbital long-range order in the presence of stronger intraplane competition between superexchange and Jahn-Teller coupling.

  19. Eutectic superalloys strengthened by delta Ni3Cb lamellae, and gamma prime, Ni3Al precipitates.

    NASA Technical Reports Server (NTRS)

    Lemkey, F. D.; Thompson, E. R.

    1972-01-01

    Bivariant eutectic alloys, located on a liquidus surface within the Ni-Cb-Cr-Al quaternary, were identified which permitted the production of aligned delta Ni3Cb lamellae within a nichrome matrix containing the fcc precipitate gamma prime Ni3Al. The volume fraction of delta and gamma prime could be varied significantly by compositional changes. After directional solidification certain alloys possessed improved ductility and corrosion resistance with respect to the Ni3Al-Ni3Cb eutectic, while their values of tensile and creep strength approached or exceeded those for the Ni3Al-Ni3Cb pseudobinary system. The mechanical properties of the directionally solidified alloy, Ni-19.7 wt % Cb-6.0 wt % Cr-2.5 wt % Al, were evaluated. Its longitudinal strength in tension and creep was found to be superior to all advanced nickel base superalloys. It is thus demonstrated that useful properties for gas turbine airfoil applications can be achieved by reinforcing a strong and tough gamma nichrome matrix containing precipitated gamma prime by a strong lamellar intermetallic compound having greater strength at elevated temperature.

  20. 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

  1. Ba-filled Ni-Sb-Sn based skutterudites with anomalously high lattice thermal conductivity.

    PubMed

    Paschinger, W; Rogl, G; Grytsiv, A; Michor, H; Heinrich, P R; Müller, H; Puchegger, S; Klobes, B; Hermann, R P; Reinecker, M; Eisenmenger-Sitter, Ch; Broz, P; Bauer, E; Giester, G; Zehetbauer, M; Rogl, P F

    2016-07-05

    Novel filled skutterudites BayNi4Sb12-xSnx (ymax = 0.93) have been prepared by arc melting followed by annealing at 250, 350 and 450 °C up to 30 days in vacuum-sealed quartz vials. Extension of the homogeneity region, solidus temperatures and structural investigations were performed for the skutterudite phase in the ternary Ni-Sn-Sb and in the quaternary Ba-Ni-Sb-Sn systems. Phase equilibria in the Ni-Sn-Sb system at 450 °C were established by means of Electron Probe Microanalysis (EPMA) and X-ray Powder Diffraction (XPD). With rather small cages Ni4(Sb,Sn)12, the Ba-Ni-Sn-Sb skutterudite system is perfectly suited to study the influence of filler atoms on the phonon thermal conductivity. Single-phase samples with the composition Ni4Sb8.2Sn3.8, Ba0.42Ni4Sb8.2Sn3.8 and Ba0.92Ni4Sb6.7Sn5.3 were used to measure their physical properties, i.e. temperature dependent electrical resistivity, Seebeck coefficient and thermal conductivity. The resistivity data demonstrate a crossover from metallic to semiconducting behaviour. The corresponding gap width was extracted from the maxima in the Seebeck coefficient data as a function of temperature. Single crystal X-ray structure analyses at 100, 200 and 300 K revealed the thermal expansion coefficients as well as Einstein and Debye temperatures for Ba0.73Ni4Sb8.1Sn3.9 and Ba0.95Ni4Sb6.1Sn5.9. These data were in accordance with the Debye temperatures obtained from the specific heat (4.4 K < T < 140 K) and Mössbauer spectroscopy (10 K < T < 290 K). Rather small atom displacement parameters for the Ba filler atoms indicate a severe reduction in the "rattling behaviour" consistent with the high levels of lattice thermal conductivity. The elastic moduli, collected from Resonant Ultrasonic Spectroscopy ranged from 100 GPa for Ni4Sb8.2Sn3.8 to 116 GPa for Ba0.92Ni4Sb6.7Sn5.3. The thermal expansion coefficients were 11.8 × 10(-6) K(-1) for Ni4Sb8.2Sn3.8 and 13.8 × 10(-6) K(-1) for Ba0.92Ni4Sb6.7Sn5.3. The room temperature Vickers

  2. Hydride reactivity of Ni(II)-X-Ni(II) entities: mixed-valent hydrido complexes and reversible metal reduction.

    PubMed

    Gehring, Henrike; Metzinger, Ramona; Herwig, Christian; Intemann, Julia; Harder, Sjoerd; Limberg, Christian

    2013-01-28

    After the lithiation of PYR-H(2) (PYR(2-) =[{NC(Me)C(H)C(Me)NC(6)H(3)(iPr)(2)}(2)(C(5)H(3)N)](2-)), which is the precursor of an expanded β-diketiminato ligand system with two binding pockets, its reaction with [NiBr(2) (dme)] led to a dinuclear nickel(II)-bromide complex, [(PYR)Ni(μ-Br)NiBr] (1). The bridging bromide ligand could be selectively exchanged for a thiolate ligand to yield [(PYR)Ni(μ-SEt)NiBr] (3). In an attempt to introduce hydride ligands, both compounds were treated with KHBEt(3). This treatment afforded [(PYR)Ni(μ-H)Ni] (2), which is a mixed valent Ni(I)-μ-H-Ni(II) complex, and [(PYR-H)Ni(μ-SEt)Ni] (4), in which two tricoordinated Ni(I) moieties are strongly antiferromagnetically coupled. Compound 4 is the product of an initial salt metathesis, followed by an intramolecular redox process that separates the original hydride ligand into two electrons, which reduce the metal centres, and a proton, which is trapped by one of the binding pockets, thereby converting it into an olefin ligand on one of the Ni(I) centres. The addition of a mild acid to complex 4 leads to the elimination of H(2) and the formation of a Ni(II)Ni(II) compound, [(PYR)Ni(μ-SEt)NiOTf] (5), so that the original Ni(II) (μ-SEt)Ni(II) X core of compound 3 is restored. All of these compounds were fully characterized, including by X-ray diffraction, and their molecular structures, as well as their formation processes, are discussed.

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

    SciTech Connect

    Osuka, Hisao; Shomura, Yasuhito; Komori, Hirofumi; Shibata, Naoki; Nagao, Satoshi; Higuchi, Yoshiki; Hirota, Shun

    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] hydrogenase 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.

  4. Exchange coupling and noncollinear magnetic states in Ni/Fen/Ni(1 0 0) multilayers

    NASA Astrophysics Data System (ADS)

    Malonda-Boungou, B. R.; Stojić, N.; Binggeli, N.; M'Passi-Mabiala, B.

    2015-01-01

    The Ni interlayer exchange coupling (IEC) and the atomic-scale magnetic configurations in fcc Ni /Fen /Ni (1 0 0) multilayers, with ultrathin Fe spacers, are investigated using first-principles density-functional theory including the noncollinear spin formalism. The trends with changing Fe thickness (n) between 3 and 5 monolayers (MLs) are examined. For n = 3 and 4 MLs, we find the ground state to display antiferromagnetic IEC between the Ni films, while for the 5-ML Fe spacer, the IEC changes into ferromagnetic. Upon reversal of the magnetization alignment, from antiparallel to parallel, between the Ni films with 3- and 4-ML thick Fe spacer, we find noncollinear magnetic configurations in the Fe layer as the lowest-energy states, which are related to the magnetic instability towards noncollinear solutions in bulk γ -Fe.

  5. 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.

  6. Fabrication and Characterization of Ni-P-CoNiCrAlY Composite Coatings

    NASA Astrophysics Data System (ADS)

    Heydari, H.; Monirvaghefi, S. M.; Hadipour, Ali

    2017-03-01

    In this study, Ni-P-CoNiCrAlY composite coatings were deposited on 310 stainless steel. The surface morphology and cross-sectional observations were carried out using scanning electron microscopy and optical microscopy. The high-temperature corrosion of all coatings was evaluated by cyclic oxidation method. According to the results, the amounts of CoNiCrAlY particles co-deposited in all samples coated at pH = 4.7 were higher than that of those produced at pH = 6.7. Also, the surface roughness of all composite coatings coated at pH = 6.7 is lower than the coatings produced at pH = 4.7. The Ni-P-(3 g/l) CoNiCrAlY deposit produced at pH = 6.7 had the best corrosion resistance among other coatings.

  7. Synthesis and tuning the exchange bias in Ni-NiO nanoparticulate systems

    NASA Astrophysics Data System (ADS)

    Sharma, S. K.; Vargas, J. M.; Knobel, M.; Pirota, K. R.; Meneses, C. T.; Kumar, Shalendra; Lee, C. G.; Pagliuso, P. G.; Rettori, Carlos

    2010-05-01

    We report studies on exchange bias effects in Ni-NiO nanoparticles with different particle diameters/distributions and concentration of metallic nickel, which vary from 0% to 32%. The exchange bias field, Hex, depends strongly upon both particle size and the concentration of metallic Ni, being maximum (˜2.2 kOe) at 5 K for the sample with almost negligible concentration of metallic Ni, whereas the corresponding value for the sample with highest concentration of metallic Ni (˜32±5.0%) is about 0.07 kOe. The structural features of the samples have been investigated thoroughly by using the Reitveld refinement of x-ray diffraction data and high resolution transmission electron microscopy, where as the magnetic properties using superconducting quantum interference device magnetometer.

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

    SciTech Connect

    Samolyuk, German D.; Xue, Haizhou; Bei, Hongbin; Weber, William J.

    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.

  9. Improvement of thermoelectric properties for half-Heusler TiNiSn by interstitial Ni defects

    SciTech Connect

    Hazama, Hirofumi; Matsubara, Masato; Asahi, Ryoji; Takeuchi, Tsunehiro

    2011-09-15

    We have synthesized off-stoichiometric Ti-Ni-Sn half-Heusler thermoelectrics in order to investigate the relation between randomly distributed defects and thermoelectric properties. A small change in the composition of Ti-Ni-Sn causes a remarkable change in the thermal conductivity. An excess content of Ni realizes a low thermal conductivity of 2.93 W/mK at room temperature while keeping a high power factor. The low thermal conductivity originates in the defects generated by an excess content of Ni. To investigate the detailed defect structure, we have performed first-principles calculations and compared with x ray photoemission spectroscopy measurement. Based on these analyses, we conclude that the excess Ni atoms randomly occupy the vacant sites in the half-Heusler structure, which play as phonon scattering centers, resulting in significant improvement of the figure of merit without any substitutions of expensive heavy elements, such as Zr and Hf.

  10. Fabrication and Characterization of Ni-P-CoNiCrAlY Composite Coatings

    NASA Astrophysics Data System (ADS)

    Heydari, H.; Monirvaghefi, S. M.; Hadipour, Ali

    2017-02-01

    In this study, Ni-P-CoNiCrAlY composite coatings were deposited on 310 stainless steel. The surface morphology and cross-sectional observations were carried out using scanning electron microscopy and optical microscopy. The high-temperature corrosion of all coatings was evaluated by cyclic oxidation method. According to the results, the amounts of CoNiCrAlY particles co-deposited in all samples coated at pH = 4.7 were higher than that of those produced at pH = 6.7. Also, the surface roughness of all composite coatings coated at pH = 6.7 is lower than the coatings produced at pH = 4.7. The Ni-P-(3 g/l) CoNiCrAlY deposit produced at pH = 6.7 had the best corrosion resistance among other coatings.

  11. Influence of He-ion irradiation on thin NiMn/FeNi exchange bias films

    NASA Astrophysics Data System (ADS)

    Cantelli, V.; von Borany, J.; Grenzer, J.; Fassbender, J.; Kaltofen, R.; Schumann, J.

    2006-04-01

    Using synchrotron x-ray diffraction and reflectivity, we studied the transition from the paramagnetic NiMn phase to the chemically ordered, antiferromagnetic L10 phase of NiMn/Fe19Ni81 thin films deposited on a Si/SiO2 substrate as a function of the annealing temperature. The transformation to a dominating L10-ordered NiMn film takes place between 300 and 400 °C irrespective of the irradiation. This is also consistent with magnetization reversal measurements of the corresponding permalloy layers. The benefit of the ion irradiation is a reduction of the mosaicity for both the NiMn and the permalloy film, and a smoothening of internal interfaces.

  12. Influence of He-ion irradiation on thin NiMn/FeNi exchange bias films

    SciTech Connect

    Cantelli, V.; Borany, J. von; Grenzer, J.; Fassbender, J.; Kaltofen, R.; Schumann, J.

    2006-04-15

    Using synchrotron x-ray diffraction and reflectivity, we studied the transition from the paramagnetic NiMn phase to the chemically ordered, antiferromagnetic L1{sub 0} phase of NiMn/Fe{sub 19}Ni{sub 81} thin films deposited on a Si/SiO{sub 2} substrate as a function of the annealing temperature. The transformation to a dominating L1{sub 0}-ordered NiMn film takes place between 300 and 400 deg. C irrespective of the irradiation. This is also consistent with magnetization reversal measurements of the corresponding permalloy layers. The benefit of the ion irradiation is a reduction of the mosaicity for both the NiMn and the permalloy film, and a smoothening of internal interfaces.

  13. Innovative materials: the NiTi alloys in orthodontics.

    PubMed

    Airoldi, G; Riva, G

    1996-01-01

    Since ten years the NiTi alloys have gained an ever increasing place in orthodontic practice: that is due to their peculiar mechanical properties ascribed to a martensitic thermoelastic transformation which can be thermally or, in a proper temperature range, stress-induced. In the last case, when martensite is stress-induced at body temperature, the stress-strain behaviour is pseudoelastic with large deformations gained or recovered at constant stress, respectively in direct/reverse transformation: this behaviour exploited in orthodontics allowed to overcome the drawbacks intrinsic to the use of conventional alloys as stainless steel or Co-Mo alloys, where small displacements can be achieved at decreasing loads. From the phase state diagram of NiTi alloys it appears that at body temperature they are stable, but out of equilibrium: thermal treatments at intermediate temperatures can therefore modify the equilibrium state and as a consequence the transformation temperatures respect to body temperature. That allows to modify the recovery stress level according to the requirements of practice and thus disclosing new roads: the capability to foresee NiTi archwires pre-programmed in different sections, with a personalized scheme. Attention has not currently been paid to the modifications in the recovery stress induced by a temperature change inside the oral cavity. Recent results have shown that the thermal changes in the oral cavity induced by cold/hot liquid intake can considerably modify the stress level to which the dentition is exposed: though confined to the time extent connected with drinking, similar effects can be expected also for meals intake and should be taken into account for a correct procedure.

  14. Nanoscale η-NiSi formation via ion irradiation of Si/Ni/Si

    NASA Astrophysics Data System (ADS)

    Banu, Nasrin; Satpati, Biswarup; Bhukta, Anjan; Dev, B. N.

    2017-01-01

    Nickel monosilicide (NiSi) has emerged as an excellent material of choice for source-drain contact applications below 45 nm node complementary metal-oxide-semiconductor technology. We have investigated the formation of nanoscale NiSi by ion irradiation of Si (˜5 nm)/Ni(˜15 nm)/Si, grown in an ultrahigh vacuum environment. Irradiation was carried out at room temperature with 1 MeV Si+ ions. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed for analysis. With increasing ion fluence, ion beam mixing occurs and more and more Si is incorporated into the Ni layer, and this layer gets amorphized. At an even higher fluence, a recrystallized uniform nickel monosilicide (η-NiSi) layer is formed. Several planar spacings of different Miller indices of η-NiSi have been observed in XRD and TEM. Additionally, an interesting amorphization and recrystallization behavior has been observed in the substrate Si with increasing ion fluence. To our knowledge, this has never been observed in ion irradiation of bare Si in decades of work in this area. This kind of amorphization/recrystallization in Si is apparently Ni-induced. Irradiation displaces Ni and produces a distribution of Ni in amorphized Si. Irradiation at a higher fluence produces two recrystallized Si bands in amorphous Si with concomitant accumulation of Ni at the amorphous/crystalline interfaces. On a further increase in irradiation fluence, the recrystallized Si bands again pass through amorphization and recrystallization. The total thickness of recrystallized, as well as amorphous Si, shows an oscillatory behavior as a function of ion fluence.

  15. Oxide Scales Formed on NiTi and NiPtTi Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Garg, Anita; Rogers, Richard B.; Noebe, Ronald D.

    2011-01-01

    Ni-49Ti and Ni-30Pt-50Ti (at.%) shape memory alloys were oxidized isothermally in air over the temperature range of 500 to 900 C. The microstructure, composition, and phase content of the scales were studied by SEM, EDS, XRD, and metallography. Extensive plan view SEM/EDS identified various features of intact or spalled scale surfaces. The outer surface of the scale was a relatively pure TiO2 rutile structure, typified by a distinct highly striated and faceted crystal morphology. Crystal size increased significantly with temperature. Spalled regions exhibited some porosity and less distinct features. More detailed information was obtained by correlation of SEM/EDS studies of 700 C/100 hr cross-sections with XRD analyses of serial or taper-polishing of plan surfaces. Overall, multiple layers exhibited graded mixtures of NiO, TiO2, NiTiO3, Ni(Ti) or Pt(Ni,Ti) metal dispersoids, Ni3Ti or Pt3Ti depletion zones, and substrate, in that order. The NiTi alloy contained a 3 at.% Fe impurity that appeared in embedded localized Fe-Ti-rich oxides, while the NiPtTi alloy contained a 2 v/o dispersion of TiC that appeared in lower layers. The oxidation kinetics of both alloys (in a previous report) indicated parabolic growth and an activation energy (250 kJ/mole) near those reported in other Ti and NiTi studies. This is generally consistent with TiO2 existing as the primary scale constituent, as described here.

  16. Structural and magnetic properties of Ni-Zn and Ni-Zn-Co ferrites

    NASA Astrophysics Data System (ADS)

    Knyazev, A. V.; Zakharchuk, I.; Lähderanta, E.; Baidakov, K. V.; Knyazeva, S. S.; Ladenkov, I. V.

    2017-08-01

    Ni-Zn and Ni-Zn-Co ferrite powders with nominal compositions Ni0.5Zn0.5Fe2O4 and Ni0.5Zn0.3Co0.2Fe2O4 were prepared by the solid-state reaction synthesis with periodic regrinding during the calcination at 1073 K. The structure of Ni0.5Zn0.5Fe2O4 and Ni0.5Zn0.3Co0.2Fe2O4 was refined assuming space group F d-3m. Scanning electron microscopy revealed the average sizes of the crystalline ferrite particles are 130-630 nm for Ni0.5Zn0.5Fe2O4 and 140-350 nm for Ni0.5Zn0.3Co0.2Fe2O4. The room temperature saturation magnetizations are 59.7 emu/g for Ni0.5Zn0.5Fe2O4 and 57.1 emu/g for Ni0.5Zn0.3Co0.2Fe2O4. The coercivity of the samples is found to be much larger than that of bulk ferrites and increases with Co introduction. The Curie temperature tends to increase upon Zn substitution by Co, as well. The temperature dependences of magnetization measured using zero-field cooled and field cooled protocols exhibit large spin frustration and spin-glass-like behavior.

  17. Tuning the magnetic properties of multisegmented Ni/Cu electrodeposited nanowires with controllable Ni lengths.

    PubMed

    Susano, M; Proenca, M P; Moraes, S; Sousa, C T; Araújo, J P

    2016-08-19

    The fabrication of segmented Ni/Cu nanowires (NWs), with tunable structural and magnetic properties, is reported. A potentiostatic electrodeposition method with a single electrolytic bath has been used to fabricate multisegmented Ni/Cu NWs inside a highly hexagonally ordered anodic nanoporous alumina membrane, with diameters of 50 nm and Ni segment lengths (L Ni) tuned from 10 nm up to 140 nm. The x-ray diffraction results evidenced a strong dependence of the Ni NWs crystallographic face-centered-cubic (fcc) texture along the [220] direction on the aspect ratio of the NWs. The magnetic behavior of the multisegmented Ni/Cu NW arrays, as a function of the magnetic field and temperature, is also studied and correlated with their structural and morphological properties. Micromagnetic simulations, together with the experimental results, showed a dominant antiferromagnetic coupling between Ni segments along the wire length for small low aspect-ratio magnetic segments. When increasing the Ni segments' length, the magnetic interactions between these along the wire became stronger, favouring a ferromagnetic coupling. The Curie temperature of the NWs was also found to strongly depend on the Ni magnetic segment length. Particularly the Curie temperature was found to be reduced 75 K for the 20 nm Ni segments, following the finite-size scaling relation with ξ 0 = 8.1 Å and γ = 0.48. These results emphasize the advantages of using a template assisted method to electrodeposit multilayer NWs, as it allows an easy tailor of the respective morphological, chemical, structural and magnetic properties.

  18. Direct Observation of Charge Order in Triangular Metallic AgNiO2 by Single-Crystal Resonant X-Ray Scattering

    NASA Astrophysics Data System (ADS)

    Pascut, G. L.; Coldea, R.; Radaelli, P. G.; Bombardi, A.; Beutier, G.; Mazin, I. I.; Johannes, M. D.; Jansen, M.

    2011-04-01

    We report resonant x-ray scattering measurements on a single crystal of the orbitally degenerate triangular metallic antiferromagnet 2H-AgNiO2 to probe the spontaneous transition to a triple-cell superstructure at temperatures below TS=365K. We observe a strong resonant enhancement of the supercell reflections through the Ni K edge. The empirically extracted K-edge shift between the crystallographically distinct Ni sites of 2.5(3) eV is much larger than the value expected from the shift in final states, and implies a core-level shift of ˜1eV, thus providing direct evidence for the onset of spontaneous honeycomb charge order in the triangular Ni layers. We also provide band-structure calculations that explain quantitatively the observed edge shifts in terms of changes in the Ni electronic energy levels due to charge order and hybridization with the surrounding oxygens.

  19. Evolution of cavity microstructure in ion-irradiated 316 SS and Fe-20Ni-15Cr alloy. [Fe-20Ni-15Cr

    SciTech Connect

    Kohyama, A.; Loomis, B.; Ayrault, G.; Igata, N.

    1984-04-01

    The effect of helium implantation schedule on the evolution of the cavity microstructure in 316 SS and Fe-20Ni-15Cr alloy during heavy-ion irradiation was investigated for damage levels up to 100 dpa with three helium injection schedules, i.e., 15 appm He/dpa, 50 appm He/dpa and 15 appm He preinjected prior to Ni/sup +/ ion irradiation. In the case of the dual-ion irradiated specimens, there was a trend towards a saturation of the swelling with increasing damage level that was closely related to the saturation and subsequent decrease of the number density of the small cavities (<8 nm diameter for 316 SS and <4 nm for Fe-20Ni-15Cr) and the dislocation density. The bi-model cavity size distribution that was determined for the Fe-20Ni-15Cr alloy at 40 dpa changed to uni-modal distribution at 65 and 100 dpa. Radiation-induced segregation was high and this was related to the saturation tendency for the swelling.

  20. High performance p-type NiO{sub x} thin-film transistor by Sn doping

    SciTech Connect

    Lin, Tengda; Li, Xiuling; Jang, Jin

    2016-06-06

    Major obstacles towards power efficient complementary electronics employing oxide thin-film transistors (TFTs) lie in the lack of equivalent well performing p-channel devices. Here, we report a significant performance enhancement of solution-processed p-type nickel oxide (NiO{sub x}) TFTs by introducing Sn dopant. The Sn-doped NiO{sub x} (Sn-NiO{sub x}) TFTs annealed at 280 °C demonstrate substantially improved electrical performances with the increase in the on/off current ratio (I{sub on}/I{sub off}) by ∼100 times, field-effect mobility (μ{sub lin}) by ∼3 times, and the decrease in subthreshold swing by half, comparing with those of pristine NiO{sub x} TFTs. X-ray photoelectron spectroscopy and X-ray diffraction results confirm that Sn atoms tend to substitute Ni sites and induce more amorphous phase. A decrease in density of states in the gap of NiO{sub x} by Sn doping and the shift of Fermi level (E{sub F}) into the midgap lead to the improvements of TFT performances. As a result, Sn-NiO{sub x} can be a promising material for the next-generation, oxide-based electronics.

  1. Detailed spatiotemporal impacts of El Niño on phytoplankton biomass in the South China Sea

    NASA Astrophysics Data System (ADS)

    Siswanto, Eko; Ye, Haijun; Yamazaki, Dai; Tang, DanLing

    2017-04-01

    The lagging and leading correlations among satellite observations, reanalyzed biogeophysical data, and the Nino3.4 El Niño index were investigated to reveal the impacts of El Niño on the phytoplankton biomass (chlorophyll a [Chl a]) in the South China Sea (SCS), in an attempt to identify the probable responsible factors in greater spatiotemporal detail. A basin-scale high Chl a concentration during the developing phase of El Niño changed to basin-scale low Chl a during the weakening phase. Cyclonic wind circulation in the northern basin, increased wind speed in the southern basin, and strengthened upwelling off the Vietnamese coast likely caused a basin-scale nutrient increase during the developing phase of an El Niño event; the opposite conditions led to low nutrient levels during the weakening phase. Decreases in Chl a east of the Vietnamese coast and northwest of Borneo Island were due to decreases in nutrients supplied by rivers. These spatiotemporal changes are considered biogeophysical responses to a variety of types of El Niño. Regardless of the El Niño type, reanalyzing biogeophysical data sets during central Pacific warming separately from those during eastern Pacific warming is recommended for a more robust understanding of the detailed spatiotemporal impacts of different El Niño types on the biogeophysical environment of the SCS.

  2. Electro-codeposition of Ni-SiO2 nanocomposite coatings from deep eutectic solvent with improved corrosion resistance

    NASA Astrophysics Data System (ADS)

    Li, Ruiqian; Hou, Yuanyuan; Liang, Jun

    2016-03-01

    Electro-codeposition of nano-sized SiO2 particles into the metal matrix in aqueous solution is generally difficult. In this paper, the nano-sized SiO2 particles were successfully codeposited in the Ni matrix from a choline chloride (ChCl)/ethylene glycol (EG) based deep eutectic solvent (DES) by pulse electro-codeposition. The effects of nano-sized SiO2 particles on electrochemical behaviour of Ni(II) were investigated. The microstructure, composition and corrosion resistance of pure Ni and Ni-SiO2 nanocomposite coatings were explored. Results showed that the SiO2 nanoparticles exhibited excellent dispersion stability in ChCl:2EG DES without any stabilizing additives and the presence of SiO2 nanoparticles have significant effects on the nucleation mechanism of Ni. The maximum content of SiO2 nanoparticles in composite coatings can achieve 4.69 wt.%, which closes to the level of co-deposition micro-sized SiO2 particles from aqueous solution. The Ni-SiO2 nanocomposite coatings exhibit much better corrosion resistance than pure Ni coating, and the corrosion resistance performance increases with increasing SiO2 content in the composite coatings.

  3. Transport properties and metal-insulator transition in oxygen deficient LaNiO3: a density functional theory study

    NASA Astrophysics Data System (ADS)

    Misra, D.; Kundu, T. K.

    2016-09-01

    Density functional theory with appropriate functional has been employed to investigate the metal to insulator transition in oxygen deficient LaNiO3-x (x = 0.0, 0.25, 0.5, 1.0) compounds. While the metallic nature of LaNiO3 is characterized by the low temperature Fermi liquid behavior of resistivity and a finite density of states at the Fermi level, the density of states and the transport properties clearly identify LaNiO2.75 as a semiconductor, and LaNiO2.5 as an insulator, which is followed by another insulator to semiconductor transition with further increase of x to ‘1’ in LaNiO2. This oxygen vacancy controlled metal to insulator transition is explained on the basis of non-adiabatic polaronic transport. From the covalency metric calculation of the chemical bonding and the Bader charge transfer analysis, this metal to insulator transition is attributed to the enhanced covalent part in the chemical bonding and reduced charge transfer from Ni to O atoms in LaNiO3-x compounds.

  4. Geometry and electronic structure of (CO)3NiCH2. A model transition-metal carbene

    SciTech Connect

    Spangler, Dale; Wendoloski, John J.; Dupuis, Michel; Chen, Maynard M. L.; Schaefer, III, Henry F.

    1981-07-01

    The first application of nonempirical molecular electronic structure theory to a realistic transition metal carbene complex is reported. The system chosen was (CO)3NiCH2, methylene (tricarbonyl) nickel(0). All studies were performed at the self-consistent-field (SCF) level. A large and flexibly contracted basis set was chosen, labeled Ni(15s 11p 6d/11s 8p 3d); C,O(9s 5p/4s 2p); H(5s/3s). In addition, the importance of methylene carbon d functions was investigated. The critical predicted equilibrium geometrical parameters were R [Ni-C (methylene)] = 1.83 Å, θ(HCH)=108°. The sixfold barrier to rotation about the Ni-C (methylene) axis is small, ~0.2 kcal. The electronic structure of (CO)3NiCH2 is discussed and compared with those of the "naked" complex NiCH2 and the stable Ni(CO)4 molecule.

  5. Effects of the 1997–1998 El Niño Episode on Community Rates of Diarrhea

    PubMed Central

    Bennett, Adam; Epstein, Leonardo D.; Gilman, Robert H.; Cama, Vitaliano; Bern, Caryn; Cabrera, Lilia; Lescano, Andres G.; Patz, Jonathan; Carcamo, Cesar; Sterling, Charles R.

    2012-01-01

    Objectives. To improve our understanding of climate variability and diarrheal disease at the community level and inform predictions for future climate change scenarios, we examined whether the El Niño climate pattern is associated with increased rates of diarrhea among Peruvian children. Methods. We analyzed daily surveillance data for 367 children aged 0 to 12 years from 2 cohorts in a peri-urban shantytown in Lima, Peru, 1995 through 1998. We stratified diarrheal incidence by 6-month age categories, season, and El Niño, and modeled between-subject heterogeneity with random effects Poisson models. Results. Spring diarrheal incidence increased by 55% during El Niño compared with before El Niño. This increase was most acute among children older than 60 months, for whom the risk of a diarrheal episode during the El Niño spring was nearly 100% greater (relative risk = 1.96; 95% confidence interval = 1.24, 3.09). Conclusions. El Niño–associated climate variability affects community rates of diarrhea, particularly during the cooler seasons and among older children. Public health officials should develop preventive strategies for future El Niño episodes to mitigate the increased risk of diarrheal disease in vulnerable communities. PMID:22594750

  6. Effects of the 1997-1998 El Niño episode on community rates of diarrhea.

    PubMed

    Bennett, Adam; Epstein, Leonardo D; Gilman, Robert H; Cama, Vitaliano; Bern, Caryn; Cabrera, Lilia; Lescano, Andres G; Patz, Jonathan; Carcamo, Cesar; Sterling, Charles R; Checkley, William

    2012-07-01

    To improve our understanding of climate variability and diarrheal disease at the community level and inform predictions for future climate change scenarios, we examined whether the El Niño climate pattern is associated with increased rates of diarrhea among Peruvian children. We analyzed daily surveillance data for 367 children aged 0 to 12 years from 2 cohorts in a peri-urban shantytown in Lima, Peru, 1995 through 1998. We stratified diarrheal incidence by 6-month age categories, season, and El Niño, and modeled between-subject heterogeneity with random effects Poisson models. Spring diarrheal incidence increased by 55% during El Niño compared with before El Niño. This increase was most acute among children older than 60 months, for whom the risk of a diarrheal episode during the El Niño spring was nearly 100% greater (relative risk=1.96; 95% confidence interval=1.24, 3.09). El Niño-associated climate variability affects community rates of diarrhea, particularly during the cooler seasons and among older children. Public health officials should develop preventive strategies for future El Niño episodes to mitigate the increased risk of diarrheal disease in vulnerable communities.

  7. The effect of platinum on diffusion kinetics in beta-NiAl: implications for thermal barrier coating lifetimes.

    PubMed

    Marino, Kristen A; Carter, Emily A

    2009-01-12

    Platinum is added to thermal barrier coatings (TBCs) as it is observed empirically to extend their lifetime, but the mechanism by which Pt acts is unknown. Since Pt has been proposed to alter diffusivities in NiAl, a key component of TBCs, we use first-principles quantum mechanics calculations to investigate atomic level diffusion mechanisms. Here, we examine the effect of Pt on five previously proposed mechanisms for Ni diffusion in NiAl: next-nearest-neighbor jumps, the triple defect mechanism, and three variants of the six jump cycle. We predict that Pt increases the rate of Ni diffusion by stabilizing point defects and defect clusters that are diffusion intermediates. Previously, we predicted the triple defect mechanism to be a dominant Ni diffusion mechanism; it simultaneously results in long-range Al diffusion in the opposite direction. Since Pt increases the rate of Ni diffusion, it also increases Al diffusion in NiAl, which may be key to extending the coating lifetime.

  8. The Influence of Cu on Metastable NiSn4 in Sn-3.5Ag- xCu/ENIG Joints

    NASA Astrophysics Data System (ADS)

    Belyakov, S. A.; Gourlay, C. M.

    2016-01-01

    We have investigated the effect of small amounts of Cu on suppression of metastable βSn-NiSn4 eutectic growth in solder joints between Sn-3.5Ag- xCu solders and Ni-based substrates. For Sn-3.5Ag/electroless nickel immersion gold (ENIG) and Sn-3.5Ag/Ni solder joints we showed that the eutectic mixture contains βSn, Ag3Sn, and metastable NiSn4. It was found that addition of only 0.005 wt.% Cu to Sn-3.5Ag- xCu/ENIG or Sn-3.5Ag- xCu/Ni joints promoted formation of a stable βSn-Ni3Sn4 eutectic and that both Ni3Sn4 and NiSn4 occur in the eutectic at this Cu level. We also showed that for complete prevention of formation of metastable NiSn4 during eutectic solidification of the solder joint, addition of at least 0.3 wt.% Cu was required.

  9. Preparation and electrical properties of Ca-doped La(2)NiO(4+δ) cathode materials for IT-SOFC.

    PubMed

    Shen, Yongna; Zhao, Hailei; Liu, Xiaotong; Xu, Nansheng

    2010-12-07

    Ca-doped La(2)NiO(4+δ) is synthesized via the nitrate-citrate route. The effects of Ca substitution for La on the sinterability, lattice structure and electrical properties of La(2)NiO(4+δ) are investigated. Ca-doping is unfavorable for the densification process of La(2-x)Ca(x)NiO(4+δ) materials. The introduction of Ca leads to the elongation of the La-O(2) bond length, which provides more space for the migration of oxygen ion in La(2)O(2) rock salt layers. The substitution of Ca increases remarkably the electronic conductivity of La(2-x)Ca(x)NiO(4+δ). With increasing Ca-doping level, both the excess oxygen concentration and the activation energy of oxygen ion migration decrease, resulting in an optimization where a highest ionic conductivity is presented. Ca-doping is charge compensated by the oxidation of Ni(2+) to Ni(3+) and the desorption of excess oxygen. The substitution of Ca enhances the structural stability of La(2)NiO(4+δ) material at high temperatures and renders the material a good thermal cycleability. La(1.7)Ca(0.3)NiO(4+δ) exhibits an excellent chemical compatibility with CGO electrolyte. La(2-x)Ca(x)NiO(4+δ) is a promising cathode alternative for solid oxide fuel cells.

  10. An Electrochemical, Microtopographical and Ambient Pressure X-Ray Photoelectron Spectroscopic Investigation of Si/TiO2/Ni/Electrolyte Interfaces

    DOE PAGES

    Lichterman, Michael F.; Richter, Matthias H.; Hu, Shu; ...

    2015-12-05

    The electrical and spectroscopic properties of the TiO2/Ni protection layer system, which enables stabilization of otherwise corroding photoanodes, have been investigated in contact with electrolyte solutions by scanning-probe microscopy, electrochemistry and in-situ ambient pressure X-ray photoelectron spectroscopy (AP-XPS). Specifically, the energy-band relations of the p+-Si/ALD-TiO2/Ni interface have been determined for a selected range of Ni thicknesses. AP-XPS measurements using tender X-rays were performed in a three-electrode electrochemical arrangement under potentiostatic control to obtain information from the semiconductor near-surface region, the electrochemical double layer (ECDL) and the electrolyte beyond the ECDL. The degree of conductivity depended on the chemical state ofmore » the Ni on the TiO2 surface. At low loadings of Ni, the Ni was present primarily as an oxide layer and the samples were not conductive, although the TiO2 XPS core levels nonetheless displayed behavior indicative of a metal-electrolyte junction. In contrast, as the Ni thickness increased, the Ni phase was primarily metallic and the electrochemical behavior became highly conductive, with the AP-XPS data indicative of a metal-electrolyte junction. Electrochemical and microtopographical methods have been employed to better define the nature of the TiO2/Ni electrodes and to contextualize the AP-XPS results.« less

  11. An Electrochemical, Microtopographical and Ambient Pressure X-Ray Photoelectron Spectroscopic Investigation of Si/TiO2/Ni/Electrolyte Interfaces

    SciTech Connect

    Lichterman, Michael F.; Richter, Matthias H.; Hu, Shu; Crumlin, Ethan J.; Axnanda, Stephanus; Favaro, Marco; Drisdell, Walter; Hussain, Zahid; Brunschwig, Bruce S.; Lewis, Nathan S.; Liu, Zhi; Lewerenz, Hans-Joachim

    2015-12-05

    The electrical and spectroscopic properties of the TiO2/Ni protection layer system, which enables stabilization of otherwise corroding photoanodes, have been investigated in contact with electrolyte solutions by scanning-probe microscopy, electrochemistry and in-situ ambient pressure X-ray photoelectron spectroscopy (AP-XPS). Specifically, the energy-band relations of the p+-Si/ALD-TiO2/Ni interface have been determined for a selected range of Ni thicknesses. AP-XPS measurements using tender X-rays were performed in a three-electrode electrochemical arrangement under potentiostatic control to obtain information from the semiconductor near-surface region, the electrochemical double layer (ECDL) and the electrolyte beyond the ECDL. The degree of conductivity depended on the chemical state of the Ni on the TiO2 surface. At low loadings of Ni, the Ni was present primarily as an oxide layer and the samples were not conductive, although the TiO2 XPS core levels nonetheless displayed behavior indicative of a metal-electrolyte junction. In contrast, as the Ni thickness increased, the Ni phase was primarily metallic and the electrochemical behavior became highly conductive, with the AP-XPS data indicative of a metal-electrolyte junction. Electrochemical and microtopographical methods have been employed to better define the nature of the TiO2/Ni electrodes and to contextualize the AP-XPS results.

  12. Generalized melting criterion for amorphization. [NiZr, NiZr[sub 2], NiTi, FeTi

    SciTech Connect

    Devanathan, R. Northwestern Univ., Evanston, IL . Dept. of Materials Science and Engineering); Lam, N.Q.; Okamoto, P.R. ); Meshii, M. . Dept. of Materials Science and Engineering)

    1992-12-01

    We present a thermodynamic model of solid-state amorphization based on a generalization of the well-known Lindemann criterion. The original Lindemann criterion proposes that melting occurs when the root-mean-square amplitude of thermal displacement exceeds a critical value. This criterion can be generalized to include solid-state amorphization by taking into account the static displacements. In an effort to verify the generalized melting criterion, we have performed molecular dynamics simulations of radiation-induced amorphization in NiZr, NiZr[sub 2], NiTi and FeTi using embedded-atom potentials. The average shear elastic constant G was calculated as a function of the total mean-square atomic displacement following random atom-exchanges and introduction of Frenkel pairs. Results provide strong support for the generalized melting criterion.

  13. {001} Oriented piezoelectric films prepared by chemical solution deposition on Ni foils

    NASA Astrophysics Data System (ADS)

    Yeo, Hong Goo; Trolier-McKinstry, Susan

    2014-07-01

    Flexible metal foil substrates are useful in some microelectromechanical systems applications including wearable piezoelectric sensors or energy harvesters based on Pb(Zr,Ti)O3 (PZT) thin films. Full utilization of the potential of piezoelectrics on metal foils requires control of the film crystallographic texture. In this study, {001} oriented PZT thin films were grown by chemical solution deposition (CSD) on Ni foil and Si substrates. Ni foils were passivated using HfO2 grown by atomic layer deposition in order to suppress substrate oxidation during subsequent thermal treatment. To obtain the desired orientation of PZT film, strongly (100) oriented LaNiO3 films were integrated by CSD on the HfO2 coated substrates. A high level of {001} LaNiO3 and PZT film orientation were confirmed by X-ray diffraction patterns. Before poling, the low field dielectric permittivity and loss tangents of (001) oriented PZT films on Ni are near 780 and 0.04 at 1 kHz; the permittivity drops significantly on poling due to in-plane to out-of-plane domain switching. (001) oriented PZT film on Ni displayed a well-saturated hysteresis loop with a large remanent polarization ˜36 μC/cm2, while (100) oriented PZT on Si showed slanted P-E hysteresis loops with much lower remanent polarizations. The |e31,f| piezoelectric coefficient was around 10.6 C/m2 for hot-poled (001) oriented PZT film on Ni.

  14. Crystal growth, electronic structure, and properties of Ni-substituted FeGa{sub 3}

    SciTech Connect

    Likhanov, Maxim S.; Verchenko, Valeriy Yu.; Bykov, Mikhail A.; Tsirlin, Alexander A.; Gippius, Andrei A.; Berthebaud, David; Maignan, Antoine

    2016-04-15

    Crystals of the Fe{sub 1−x}Ni{sub x}Ga{sub 3} limited solid solution (x<0.045) have been grown from gallium flux. We have explored the electronic structure as well as magnetic and thermoelectric properties of Fe{sub 0.975}Ni{sub 0.025}Ga{sub 3} in comparison with Fe{sub 0.95}Co{sub 0.05}Ga{sub 3}, following the rigid band approach and assuming that one Ni atom donates twice the number of electrons as one Co atom. However, important differences between the Co- and Ni-doped compounds are found below 620 K, which is the temperature of the metal-to-insulator transition for both compounds. We have found that Fe{sub 0.975}Ni{sub 0.025}Ga{sub 3} displays lower degree of spatial inhomogeneity on the local level and exhibits diamagnetic behavior with a broad shallow minimum in the magnetic susceptibility near 35 K, in sharp contrast with the Curie–Weiss paramagnetism of Fe{sub 0.95}Co{sub 0.05}Ga{sub 3}. Transport measurements have shown the maximum of the thermoelectric figure-of-merit ZT of 0.09 and 0.14 at 620 K for Fe{sub 0.975}Ni{sub 0.025}Ga{sub 3} and Fe{sub 0.95}Co{sub 0.05}Ga{sub 3}, respectively. - Graphical abstract: Crystals of Ni-substituted FeGa{sub 3} up to 8 mm long were grown from gallium flux (see Figure for the temperature profile and crystal shape) that allowed studying magnetic and thermoelectric properties of the title solid solution.

  15. Novel Electronic Behavior Driving NdNiO3 Metal-Insulator Transition.

    PubMed

    Upton, M H; Choi, Yongseong; Park, Hyowon; Liu, Jian; Meyers, D; Chakhalian, J; Middey, S; Kim, Jong-Woo; Ryan, Philip J

    2015-07-17

    We present evidence that the metal-insulator transition (MIT) in a tensile-strained NdNiO3 (NNO) film is facilitated by a redistribution of electronic density and that it neither requires Ni charge disproportionation nor a symmetry change [U. Staub et al., Phys. Rev. Lett. 88, 126402 (2002); R. Jaramillo et al., Nat. Phys. 10, 304 (2014)]. Given that epitaxial tensile strain in thin NNO films induces preferential occupancy of the e(g) d(x(2)-y(2)) orbital we propose that the larger transfer integral of this orbital state with the O 2p orbital state mediates a redistribution of electronic density from the Ni atom. A decrease in the Ni d(x(2)-y(2)) orbital occupation is directly observed by resonant inelastic x-ray scattering below the MIT temperature. Furthermore, an increase in the Nd charge occupancy is measured by x-ray absorption at the Nd L(3) edge. Both spin-orbit coupling and crystal field effects combine to break the degeneracy of the Nd 5d states, shifting the energy of the Nd e(g) d(x(2)-y(2)) orbit towards the Fermi level, allowing the A site to become an active acceptor during the MIT. This work identifies the relocation of electrons from the Ni 3d to the Nd 5d orbitals across the MIT. We propose that the insulating gap opens between the Ni 3d and O 2p states, resulting from Ni 3d electron localization. The transition seems to be neither a purely Mott-Hubbard transition nor a simple charge transfer.

  16. Novel Electronic Behavior Driving NdNiO3 Metal-Insulator Transition

    NASA Astrophysics Data System (ADS)

    Upton, M. H.; Choi, Yongseong; Park, Hyowon; Liu, Jian; Meyers, D.; Chakhalian, J.; Middey, S.; Kim, Jong-Woo; Ryan, Philip J.

    2015-07-01

    We present evidence that the metal-insulator transition (MIT) in a tensile-strained NdNiO3 (NNO) film is facilitated by a redistribution of electronic density and that it neither requires Ni charge disproportionation nor a symmetry change [U. Staub et al., Phys. Rev. Lett. 88, 126402 (2002); R. Jaramillo et al., Nat. Phys. 10, 304 (2014)]. Given that epitaxial tensile strain in thin NNO films induces preferential occupancy of the eg dx2-y2 orbital we propose that the larger transfer integral of this orbital state with the O 2 p orbital state mediates a redistribution of electronic density from the Ni atom. A decrease in the Ni dx2-y2 orbital occupation is directly observed by resonant inelastic x-ray scattering below the MIT temperature. Furthermore, an increase in the Nd charge occupancy is measured by x-ray absorption at the Nd L3 edge. Both spin-orbit coupling and crystal field effects combine to break the degeneracy of the Nd 5 d states, shifting the energy of the Nd eg dx2-y2 orbit towards the Fermi level, allowing the A site to become an active acceptor during the MIT. This work identifies the relocation of electrons from the Ni 3 d to the Nd 5 d orbitals across the MIT. We propose that the insulating gap opens between the Ni 3 d and O 2 p states, resulting from Ni 3 d electron localization. The transition seems to be neither a purely Mott-Hubbard transition nor a simple charge transfer.

  17. Ultrafine NiO particles induce cytotoxicity in vitro by cellular uptake and subsequent Ni(II) release.

    PubMed

    Horie, Masanori; Nishio, Keiko; Fujita, Katsuhide; Kato, Haruhisa; Nakamura, Ayako; Kinugasa, Shinichi; Endoh, Shigehisa; Miyauchi, Arisa; Yamamoto, Kazuhiro; Murayama, Hideki; Niki, Etsuo; Iwahashi, Hitoshi; Yoshida, Yasukazu; Nakanishi, Junko

    2009-08-01

    Nickel oxide (NiO) is one of the important industrial materials used in electronic substrates and for ceramic engineering. Advancements in industrial technology have enabled the manufacture of ultrafine NiO particles. On the other hand, it is well-known that nickel compounds exert toxic effects. The toxicity of nickel compounds is mainly caused by nickel ions (Ni(2+)). However, the ion release properties of ultrafine NiO particles are still unclear. In the present study, the influences of ultrafine NiO particles on cell viability were examined in vitro to obtain fundamental data for the biological effects of ultrafine green NiO and ultrafine black NiO. Ultrafine NiO particles showed higher cytotoxicities toward human keratinocyte HaCaT cells and human lung carcinoma A549 cells than fine NiO particles and also showed higher solubilities in culture medium (Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum) than fine NiO particles. In particular, the concentration of Ni(2+) released into the culture medium by ultrafine green NiO was 150-fold higher than that released by fine green NiO. The concentrations of Ni(2+) released by both types of NiO particles in an aqueous solution containing amino acids were remarkably higher than those released by NiO particles in water. Moreover, we prepared a uniform and stable dispersion of ultrafine black NiO in culture medium and examined its influence on cell viability in comparison with that of NiCl(2), a soluble nickel compound. A medium exchange after 6 h of exposure resulted in a loss of cytotoxicity in the cells exposed to NiCl(2), whereas cytotoxicity was retained in the cells exposed to NiO. Transmission electron microscope observations revealed uptake of both ultrafine and fine NiO particles into HaCaT cells. Taken together, the present results suggest that the intracellular Ni(2+) release could be an important factor that determines the cytotoxicity of NiO. Ultrafine NiO is more cytotoxic than fine

  18. A new Ni12 cluster based on polyoxometalate ligands.

    PubMed

    Zhang, Hong-Mei; Li, Yang-Guang; Lu, Ying; Clérac, Rodolphe; Zhang, Zhi-Ming; Wu, Qiong; Feng, Xiao-Jia; Wang, En-Bo

    2009-12-07

    A new Ni(12) cluster based on polyoxometalate ligands [Ni(12)(OH)(9)WO(4)(W(7)O(26)(OH))(PW(9)O(34))(3)](25-) (1) has been assembled in aqueous solution containing [PW(9)O(34)](9-), WO(4)(2-), and NiCl(2) x 6 H(2)O. The Ni(12) core in 1 shows a unique three-petal flower-shaped structure composed of three Ni(4) cubane units. Magnetic investigation indicates the presence of dominantly ferromagnetic interactions within the Ni(12) core.

  19. Microstructure and martensitic transformation of Ni-Ti-Pr alloys

    NASA Astrophysics Data System (ADS)

    Zhao, Chunwang; Zhao, Shilei; Jin, Yongjun; Guo, Shaoqiang; Hou, Qingyu

    2017-09-01

    The effect of Pr addition on the microstructure and martensitic transformation behavior of Ni50Ti50- x Pr x ( x = 0, 0.1, 0.3, 0.5, 0.7, 0.9) alloys were investigated experimentally. Results show that the microstructures of Ni-Ti-Pr alloys consist of the NiTi matrix and the NiPr precipitate with the Ti solute. The martensitic transformation start temperature decreases gradually with the increase in Pr fraction. The stress around NiPr precipitates is responsible for the decrease in martensitic transformation temperature with the increase in Pr fraction in Ni-Ti-Pr alloys.

  20. Coexistence of ferromagnetism and superconductivity in Ni/Bi bilayers.

    PubMed

    LeClair, P; Moodera, J S; Philip, J; Heiman, D

    2005-01-28

    In spite of a lack of superconductivity in bulk crystalline Bi, thin film Bi deposited on thin Ni underlayers are strong-coupled superconductors below approximately 4 K. We unambiguously demonstrate that by tuning the Ni thickness the competition between ferromagnetism and superconductivity in the Ni/Bi can be tailored. For a narrow range of Ni thicknesses, the coexistence of both a superconducting energy gap and conduction electron spin polarization are visible within the Ni side of the Ni/Bi bilayers, independent of any particular theoretical model. We believe that this represents one of the clearest observations of superconductivity and ferromagnetism coexisting.

  1. Larger Pacific Climate Event Helps Current La Niña Linger

    NASA Image and Video Library

    2008-04-22

    One of the strongest La Niñas in many years is slowly weakening but continues to blanket the Pacific Ocean near the equator, as shown by new sea-level height data collected by NASA U.S.-French Jason oceanographic satellite.

  2. Radiation-Induced Glass Transition and Structural Fluctuation in NiTi Metallic Glass System

    SciTech Connect

    Watanabe, Seiichi

    2006-05-05

    We report an evidence of fluctuation during amorphization in NiTi ordered intermetallic compounds under electron irradiation, using an in situ observation technique with a high resolution High Voltage Electron Microscope (HVEM). Molecular dynamics calculation, which is executed to simulate atomic-level electron micrographic images, also revealed the similar fluctuation trend.

  3. Local superconducting density of States of ErNi2B2C.

    PubMed

    Crespo, M; Suderow, H; Vieira, S; Bud'ko, S; Canfield, P C

    2006-01-20

    We present local tunneling microscopy and spectroscopy measurements at low temperatures in single crystalline samples of the magnetic superconductor ErNi2B2C . The electronic local density of states shows a striking departure from s-wave BCS theory with a finite value at the Fermi level, which amounts to half of the normal phase density of states.

  4. El Ni?o Pumping Up, Warm Kelvin Wave Surges Toward South America

    NASA Image and Video Library

    2009-11-12

    ElNi?o is experiencing a late-fall resurgence. Sea-level height data from the NASA/European Ocean Surface Topography Mission/Jason-2 oceanography satellite show the equatorial Pacific has triggered a wave of warm water, known as a Kelvin wave.

  5. Comparison in the Oxidation and Corrosion Behavior of Aluminum and Alumina-Reinforced Ni/Ni-Co Alloy Coatings

    NASA Astrophysics Data System (ADS)

    Srivastava, Meenu; Balaraju, J. N.; Ravisankar, B.; Grips, V. K. William

    2013-02-01

    In this study, a comparison in the oxidation and corrosion behavior of Ni/Ni-Co aluminum and alumina-reinforced electrodeposited composites has been made. The developed coatings were characterized for the morphology, structure, microhardness, oxidation, and corrosion resistance. It was found that the incorporation of Al particles in NiCo matrix is higher (9 wt pct) compared to Ni matrix (1 wt pct). In the case of aluminum oxide particles, about 5 and 7 wt pct had been obtained in Ni and NiCo matrices respectively. The difference in the surface morphology was observed with respect to metallic (Al) and inert ceramic (Al2O3) particle incorporation. X-ray diffraction studies showed the presence of predominant Ni (200) reflection in the coatings. Also, peaks corresponding to Al and Al2O3 particles were present. The Ni/NiCo-Al coatings exhibited higher microhardness values at 1273 K (1000 °C) compared to alumina-reinforced coatings, indicating better thermal stability of the former coatings. The NiAl coating showed one and two orders of magnitude improved oxidation resistance compared to NiCoAl and Ni/NiCo-Al2O3 coatings, respectively. It was observed that the Ni-Al composite coating exhibited poor corrosion resistance in 3.5 pct NaCl solution compared to the other coatings studied.

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

    PubMed

    Osuka, Hisao; Shomura, Yasuhito; Komori, Hirofumi; Shibata, Naoki; Nagao, Satoshi; Higuchi, Yoshiki; Hirota, Shun

    2013-01-04

    [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] hydrogenase 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(-1) of the Ni-A state shifted to 1971, 2086 and 2098 cm(-1) in the Ni-AL state. The g-values of g(x)=2.30, g(y)=2.23 and g(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.

  7. Modeling, Simulation, Additive Manufacturing, and Experimental Evaluation of Solid and Porous NiTi

    NASA Astrophysics Data System (ADS)

    Taheri Andani, Mohsen

    In recent years, shape memory alloys (SMAs) have entered a wide range of engineering applications in fields such as aerospace and medical applications. Nickel-titanium (NiTi) is the most commonly used SMAs due to its excellent functional characteristics (shape memory effect and superelasticity behavior). These properties are based on a solid-solid phase transformation between martensite and austenite. Beside these two characteristics, low stiffness, biocompatibility and corrosion properties of NiTi make it an attractive candidate for biomedical applications (e.g., bone plates, bone screws, and vascular stents). It is well know that manufacturing and processing of NiTi is very challenging. The functional properties of NiTi are significantly affected by the impurity level and due to the high titanium content, NiTi are highly reactive. Therefore, high temperature processed parts through methods such as melting and casting which result in increased impurity levels have inadequate structural and functional properties. Furthermore, high ductility and elasticity of NiTi, adhesion, work hardening and spring back effects make machining quite challenging. These unfavorable effects for machining cause significant tool wear along with decreasing the quality of work piece. Recently, additive manufacturing (AM) has gained significant attention for manufacturing NiTi. Since AM can create a part directly from CAD data, it is predicted that AM can overcome most of the manufacturing difficulties. This technique provides the possibility of fabricating highly complex parts, which cannot be processed by any other methods. Curved holes, designed porosity, and lattice like structures are some examples of mentioned complex parts. This work investigates manufacturing superelastic NiTi by selective laser melting (SLM) technique (using PXM by Phenix/3D Systems). An extended experimental study is conducted on the effect of subsequent heat treatments with different aging conditions on phase

  8. Initial surface silicidation on Ni(110)

    NASA Astrophysics Data System (ADS)

    Fukuda, T.; Kishida, I.; Umezawa, K.

    2017-05-01

    Initial silicide formation on a Ni(110) surface was studied by scanning tunneling microscopy (STM) in an ultrahigh vacuum. Less than 0.5 ML of Si deposition initiated a Si-Ni mixed layer by displacing substrate Ni, and dark sites were formed in the STM images. A 0.5 ML-Si deposited surface showed that Si and Ni were alternately aligned in a close-packed [ 1 1 bar 0 ] row whereas Si pairs aligned along the [ 001 ] direction forming p(1×2), obliquely aligned forming c(2×2), or even straightly-and-obliquely aligned forming c(4×2) superstructures. A first-principles total energy calculation showed that the p(1×2) and c(4×2) structures had almost the same energy while the c(2×2) structure gave 13 meV/1×1 higher energy. Because a Si-Si bond in the close-packed [ 1 1 bar 0 ] row is energetically unfavorable, Si deposition of more than 0.5 ML did not further replace the substrate Ni, but silicide islands were nucleated along with a trench structure.

  9. Oxidation of CoCrFeMnNi High Entropy Alloys

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  10. Exchange bias beyond the superparamagnetic blocking temperature of the antiferromagnet in a Ni-NiO nanoparticulate system

    NASA Astrophysics Data System (ADS)

    Roy, Aparna; De Toro, J. A.; Amaral, V. S.; Muniz, P.; Riveiro, J. M.; Ferreira, J. M. F.

    2014-02-01

    We report magnetic and exchange bias studies on Ni-NiO nanoparticulate systems synthesized by a two-step process, namely, chemical reduction of a Ni salt followed by air annealing of the dried precipitate in the temperature range 400-550 °C. Size of Ni and NiO crystallites as estimated from X-ray diffraction line broadening ranges between 10.5-13.5 nm and 2.3-4 nm, respectively. The magneto-thermal plots (M-T) of these bi-magnetic samples show a well developed peak in the vicinity of 130 K. This has been identified as the superparamagnetic blocking temperature "TB" of NiO. Interestingly, all samples exhibit exchange bias even above their respective NiO blocking temperatures, right up to 300 K, the maximum temperature of measurement. This is in contrast to previous reports since exchange bias requires the antiferromagnetic NiO to have a stable direction of its moment in order to pin the ferromagnet (Ni) magnetization, whereas such stability is unlikely above TB since the NiO is superparamagnetic, its moment flipping under thermal activation. Our observation is elucidated by taking into account the core-shell morphology of the Ni-NiO nanoparticles whereby clustering of some of these nanoparticles connects their NiO shells to form extended continuous regions of NiO, which because of their large size remain blocked at T > TB, with thermally stable spins capable of pinning the Ni cores and giving rise to exchange bias. The investigated samples may thus be envisaged as being constituted of both isolated core-shell Ni-NiO nanoparticles as well as clustered ones, with TB denoting the blocking temperature of the NiO shell of the isolated particles.

  11. Exchange bias beyond the superparamagnetic blocking temperature of the antiferromagnet in a Ni-NiO nanoparticulate system

    SciTech Connect

    Roy, Aparna E-mail: aparnaroy15@gmail.com; Ferreira, J. M. F.; De Toro, J. A.; Muniz, P.; Riveiro, J. M.; Amaral, V. S.

    2014-02-21

    We report magnetic and exchange bias studies on Ni-NiO nanoparticulate systems synthesized by a two-step process, namely, chemical reduction of a Ni salt followed by air annealing of the dried precipitate in the temperature range 400–550 °C. Size of Ni and NiO crystallites as estimated from X–ray diffraction line broadening ranges between 10.5–13.5 nm and 2.3–4 nm, respectively. The magneto-thermal plots (M-T) of these bi-magnetic samples show a well developed peak in the vicinity of 130 K. This has been identified as the superparamagnetic blocking temperature “T{sub B}” of NiO. Interestingly, all samples exhibit exchange bias even above their respective NiO blocking temperatures, right up to 300 K, the maximum temperature of measurement. This is in contrast to previous reports since exchange bias requires the antiferromagnetic NiO to have a stable direction of its moment in order to pin the ferromagnet (Ni) magnetization, whereas such stability is unlikely above T{sub B} since the NiO is superparamagnetic, its moment flipping under thermal activation. Our observation is elucidated by taking into account the core-shell morphology of the Ni-NiO nanoparticles whereby clustering of some of these nanoparticles connects their NiO shells to form extended continuous regions of NiO, which because of their large size remain blocked at T > T{sub B}, with thermally stable spins capable of pinning the Ni cores and giving rise to exchange bias. The investigated samples may thus be envisaged as being constituted of both isolated core-shell Ni-NiO nanoparticles as well as clustered ones, with T{sub B} denoting the blocking temperature of the NiO shell of the isolated particles.

  12. Surface electronic structure of polar NiO thin film grown on Ag(111)

    SciTech Connect

    Das, Jayanta; Menon, Krishnakumar S. R.

    2015-06-24

    The growth and structure of NiO thin films on top of Ag(111) substrate were studied where the formation of faceted surface was confirmed by Low Energy Electron Diffraction. The electronic structure of polar NiO(111) surface has been probed using photoemission techniques. The core energy levels and the valence band electronic structure were excited by x-ray and ultraviolet photons respectively. The modifications in physical structure and valence band electronic structure of the film under vacuum annealing have also been enlightened.

  13. Correlation Between Surface Chemistry and Electrocatalytic Properties of Monodisperse Pt(x)Ni(1-x) Nanoparticles

    SciTech Connect

    Wang, Chao; Chi, Miaofang; Wang, Guofeng; Van der Vliet, Dennis; Li, Dongguo; More, Karren Leslie; Wang, Hsien-Hua; Schlueter, John; Markovic, Nenad; Stamenkovic, Vojislav

    2011-01-01

    Monodisperse and homogeneous Pt{sub x}Ni{sub 1-x} alloy nanoparticles of various compositions are synthesized via an organic solution approach in order to reveal the correlation between surface chemistry and their electrocatalytic properties. Atomic-level microscopic analysis of the compositional profile and modeling of nanoparticle structure are combined to follow the dependence of Ni dissolution on the initial alloy composition and formation of the Pt-skeleton nanostructures. The developed approach and acquired knowledge about surface structure-property correlation can be further generalized and applied towards the design of advanced functional nanomaterials.

  14. Neutron cross section covariances in the resonance region: 52Cr, 56Fe, 58Ni

    SciTech Connect

    Oblozinsky, P.; Cho, Y.-S.; Mattoon, C.M.; Mughabghab, S.F.

    2010-08-03

    We evaluated covariances for neutron capture and elastic scattering cross sections on major structural materials, {sup 52}Cr, {sup 56}Fe and {sup 58}Ni, in the resonance region which extends beyond 800 keV for each of them. Use was made of the recently developed covariance formalism based on kernel approximation along with data in the Atlas of Neutron Resonances. The data of most interest for AFCI applications, elastic scattering cross section uncertainties at energies above about few hundred keV, are on the level of about 12% for {sup 52}Cr, 7-8% for {sup 56}Fe and 5-6% for {sup 58}Ni.

  15. Dislocation dynamics in Ni{sub 3}Al: Experiments and computations

    SciTech Connect

    Bhate, N.; Kumar, S.; Phillips, R.; Clifton, R.J.

    1999-07-01

    A modified electrolytic etchant has been successfully used to observe dislocation etch-pits on {l{underscore}brace}100{r{underscore}brace} surfaces of single crystal Ni{sub 3}Al containing Hf and B additions. Four-point bending tests have been used to obtain the dependence of dislocation velocity on resolved shear stress at room temperature. A comparison with earlier studies reveal that the rate of change of dislocation velocity with resolved shear stress, to a first approximation, is independent of alloying. Atomic level simulations have been performed using the embedded atom method (EAM) to study dislocation core structures and frictional stress in Ni{sub 3}Al.

  16. Orbital-Specific observation of O2p and Ni3d electrons in LiNi0.5Mn0.5O2, a cathode material for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Satou, Yoshinori; Komine, Shigeki; Shimizu, Sumera

    2017-09-01

    Cathode materials for lithium-ion batteries containing Ni2+ have attracted much interest because of their high theoretical capacity. However, the precise electronic structures of these cathode materials have not yet been clearly observed, especially the energy positions of the O2p and Ni3d orbitals and the shape of the density of states. The aim of this study was to investigate the relative energy positions and shape of the density of states of O2p and Ni3d for LiNi0.5Mn0.5O2 experimentally. We cleaved a LiNi0.5Mn0.5O2 pellet in an Ar-filled glove box and performed synchrotron ultraviolet photoelectron spectroscopy for different photon energies, which enabled us to investigate the relative cross-section intensity of O2p and Ni3d. As a result, the valence-band structure was determined. We found that O2p electrons are itinerant and exist in the vicinity of the Fermi energy more than Ni3d electrons. Ni3d electrons are more localized and spread mainly from 1.2-1.5 eV below the Fermi energy. To validate the electronic structure, we measured the synchrotron O K-edge X-ray absorption fine structure of electrochemically lithium-extracted LiNi0.5Mn0.5O2. The electronic structure demonstrated that ligand holes in the oxygen atoms form below the Fermi level during the initial stage of Li extraction and that the formation rate of the holes decreases with Li extraction.

  17. Cyclic creep and fatigue of TD-NiCr (thoria-dispersion-strengthened nickel-chromium), TD-Ni, and NiCr sheet at 1200 C

    NASA Technical Reports Server (NTRS)

    Hirschberg, M. H.; Spera, D. A.; Klima, S. J.

    1972-01-01

    The resistance of thin TD-NiCr sheet to cyclic deformation was compared with that of TD-Ni and a conventional nickel-chromium alloy. Strains were determined by a calibration technique which combines room-temperature strain gage and deflection measurements with high-temperature deflection measurements. Analyses of the cyclic tests using measured tensile and creep-rupture data indicated that the TD-NiCr and NiCr alloy specimens failed by a cyclic creep mechanism. The TD-Ni specimens, on the other hand, failed by a fatigue mechanism.

  18. First-principles studies of Ni-Ta intermetallic compounds

    SciTech Connect

    Zhou Yi; Wen Bin; Ma Yunqing; Melnik, Roderick; Liu Xingjun

    2012-03-15

    The structural properties, heats of formation, elastic properties, and electronic structures of Ni-Ta intermetallic compounds are investigated in detail based on density functional theory. Our results indicate that all Ni-Ta intermetallic compounds calculated here are mechanically stable except for P21/m-Ni{sub 3}Ta and hc-NiTa{sub 2}. Furthermore, we found that Pmmn-Ni{sub 3}Ta is the ground state stable phase of Ni{sub 3}Ta polymorphs. The polycrystalline elastic modulus has been deduced by using the Voigt-Reuss-Hill approximation. All Ni-Ta intermetallic compounds in our study, except for NiTa, are ductile materials by corresponding G/K values and poisson's ratio. The calculated heats of formation demonstrated that Ni{sub 2}Ta are thermodynamically unstable. Our results also indicated that all Ni-Ta intermetallic compounds analyzed here are conductors. The density of state demonstrated the structure stability increases with the Ta concentration. - Graphical abstract: Mechanical properties and formation heats of Ni-Ta intermetallic compounds are discussed in detail in this paper. Highlights: Black-Right-Pointing-Pointer Ni-Ta intermetallic compounds are investigated by first principle calculations. Black-Right-Pointing-Pointer P21/m-Ni{sub 3}Ta and hc-NiTa{sub 2} are mechanically unstable phases. Black-Right-Pointing-Pointer Pmmn-Ni{sub 3}Ta is ground stable phase of Ni{sub 3}Ta polymorphs. Black-Right-Pointing-Pointer All Ni-Ta intermetallic compounds are conducting materials.

  19. Ternary Ni-Co-F Nanocrystals Based Supercapacitors.

    PubMed

    Li, Xudong; Ding, Rui; Shi, Wei; Xu, Qilei; Liu, Enhui

    2017-03-14

    The ternary nickel cobalt fluorides (Ni-Co-F) nanocrystals have been solvothermally constructed for supercapacitors' positive electrode materials. The optimal Ni-Co-F (Ni/Co=2:1) has showed lightly chemical shifts in the X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) compared with the bare Ni-F and Co-F. The Ni-Co-F (Ni/Co=2:1) has demonstrated typical square nanocrystal morphology together with mesoporous surface structure from transmission electron microscopy (TEM) observations and nitrogen sorption measurements. Due to the stronger synergistic effect of Ni and Co redox species originated from the richer Ni, Co surface electroactive sites, the Ni-Co-F (Ni/Co=2:1) has showed superior performances of specific capacitance, rate capability and charge transfer kinetics (564 F g-1 at 1 A g-1, 418 F g-1 at 16 A g-1, 449 Ω) than all the other Ni-Co-F candidates, moreover, the activated carbon (AC)//Ni-Co-F (Ni/Co=2:1) asymmetric capacitor designed through the charge-balance has delivered superior energy and power densities (18.4 Wh kg-1, 6.64 kW kg-1) together with longer cycle life (77% retention after 10,000 cycles at 4 A g-1).

  20. Nanoindentation of NiAl and Ni3Al crystals on (100), (110), and (111) surfaces: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Seymour, Richard; Hemeryck, Anne; Nomura, Ken-ichi; Wang, Weiqiang; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

    2014-04-01

    Molecular dynamics simulations were performed to study the nanoindentation of NiAl and Ni3Al crystals on three surfaces: (100), (110), and (111). The calculated load-displacement curves show discrete drops at certain indentation depths, indicating dislocation bursts during indentation. The hardness values for the two materials were found to depend significantly on the indented crystallographic plane: the (100) surface is the softest for NiAl and the hardest for Ni3Al. We also found distinctive deformation activities in the subsurface region in Ni3Al crystals, while dislocation loops propagate deep into the substrate in NiAl systems.

  1. Crystalline/amorphous Ni/NiO core/shell nanosheets as highly active electrocatalysts for hydrogen evolution reaction

    NASA Astrophysics Data System (ADS)

    Yan, Xiaodong; Tian, Lihong; Chen, Xiaobo

    2015-12-01

    Novel crystalline/amorphous core/shell Ni/NiO nanosheets have shown a high electrocatalytic activity in hydrogen evolution reaction (HER). In 1 M KOH, they display an HER current of 5 mA cm-2 at an overpotential of 110 mV with a good stability. It is proposed that their excellent HER performance is achieved through the synergistic effect between the Ni core and the amorphous NiO shell, where the Ni core can reduce the resistance and the amorphous NiO shell can accelerate both Volmer and Heyrovsky processes to drive HER at low overpotentials.

  2. Microstructure evolution of electroless Ni P and Ni Cu P deposits on Cu in the presence of additives

    NASA Astrophysics Data System (ADS)

    Lin, Kwang-Lung; Chang, Yu-Lan; Huang, Chiao-Chan; Li, Fang-I.; Hsu, Jen-Che

    2001-09-01

    The microstructures of electroless Ni-P and Ni-Cu-P deposits were investigated in the presence of thiourea and saccharin with AFM. The phosphorus contents and crystallinity of the deposits were investigated. Saccharin was found to refine the nodular structure of the Ni-Cu-P deposit, while not affecting the P% of the Ni-P and Ni-Cu-P deposits. On the other hand, thiourea was found to affect the P% and surface roughness of the Ni-P deposit. Thiourea does not exhibit nodular refining effect on the deposit.

  3. The acceleration intermediate phase (NiS and Ni3S2) evolution by nanocrystallization in Li/NiS2 thermal batteries with high specific capacity

    NASA Astrophysics Data System (ADS)

    Jin, Chuanyu; Zhou, Lingping; Fu, Licai; Zhu, Jiajun; Li, Deyi; Yang, Wulin

    2017-06-01

    The intermediate phase of NiS2 is thought to be a bottleneck currently to improve the overall performance of Li/NiS2 thermal batteries because of its low conductivity and close formation enthalpy between NiS2 and the intermediate phase (NiS, Ni3S2, etc). For improving the discharge performances of Li/NiS2 thermal batteries, the nano NiS2 with an average size of 85 ± 5 nm is designated as a cathode material. The electrochemical measurements show that the specific capacity of nano NiS2 cathode is higher than micro NiS2. The nano NiS2 cathode exhibits excellent electrochemical performances with high specific capacities of 794 and 654 mAh g-1 at current density of 0.1 and 0.5 A cm-2 under a cut-off voltage of 0.5 V, respectively. These results show that the rapid intermediate phase evolution from the nanocrystallization can obviously enhance use efficiency of NiS2 and improve discharge performances of thermal batteries.

  4. Mechanical properties of CuNi films

    SciTech Connect

    Brueckner, W.; Macionczyk, F.; Reiss, G. |

    1997-05-01

    CuNi alloys are widely used for precision resistors and thermocouples. Recently, they have been applied to low resistance thin film components. The mechanical properties of resistive CuNi films sputtered on both silicon wafers and flexible Kapton foils are important for reliability and lifetime of resistors. Studies of stress-temperature dependence and stress relaxation, stress-strain measurements and scanning scratch tests were performed to investigate film stresses, elastic properties, plastic flow, stress for crack initiation and film adhesion. The growth and annealing stresses were found to be tensile and can be seen as the reason for resistance degradation by stress relaxation due to plastic flow. The strains for crack initiation of 0.2% to 0.7% depending on film thickness and annealing restrict the application in resistors on flexible substrates. The film adhesion can be improved by a NiCr base-layer.

  5. Enhancement of perpendicular magnetic anisotropy by compressive strain in alternately layered FeNi thin films.

    PubMed

    Sakamaki, M; Amemiya, K

    2014-04-23

    The effect of the lattice strain on magnetic anisotropy of alternately layered FeNi ultrathin films grown on a substrate, Cu(tCu = 0-70 ML)/Ni(48)Cu(52)(124 ML)/Cu(0 0 1) single crystal, is systematically studied by means of in situ x-ray magnetic circular dichroism (XMCD) and reflection high-energy electron diffraction (RHEED) analyses. To investigate the magnetic anisotropy of the FeNi layer itself, a non-magnetic substrate is adopted. From the RHEED analysis, the in-plane lattice constant, ain, of the substrate is found to shrink by 0.8% and 0.5% at tCu = 0 and 10 ML as compared to that of bulk Cu, respectively. Fe L-edge XMCD analysis is performed for n ML FeNi films grown on various ain, and perpendicular magnetic anisotropy (PMA) is observed at n = 3 and 5, whereas the film with n = 7 shows in-plane magnetic anisotropy. Moreover, it is found that PMA is enhanced with decreasing ain, in the case where a Cu spacer layer is inserted. We suppose that magnetic anisotropy in the FeNi films is mainly carried by Fe, and the delocalization of the in-plane orbitals near the Fermi level increases the perpendicular orbital magnetic moment, which leads to the enhancement of PMA.

  6. South-coast cyclone in Japan during El Niño-caused warm winters

    NASA Astrophysics Data System (ADS)

    Ueda, Hiroaki; Amagai, Yuusuke; Hayasaki, Masamitsu

    2017-05-01

    La Niña conditions during boreal winter sometimes brings excessive snowfall in Japan, especially on the East Sea/Sea of Japan coastal and mountain areas through intensified northwesterly cold winds caused by La-Niña related atmospheric teleconnection. Meanwhile, snowfall events also increase in the Pacific coast area of Japan during the El Niño state due to extratropical cyclones passing along the south coast of Japan (hereafter referred to as South-coast cyclone). In the present study, we investigated year-to-year snowfall/rainfall variations based on meteorological station data and cyclone tracks identified by using the Japanese 55-year Reanalysis. The result clearly indicates increase of the South-coast cyclone during El Niño-developing winters, which is consistent with excessive snow-fall in the northern part of the Pacific coast. Strong subtropical jet hampers cyclogenesis due to less vertical interaction through the trapping of upper-level eddies. During El Niño-developing winters, the subtropical jet is weakened over East Asia, indicating dynamic linkage to increased cyclone frequency. In addition to this, both the deepening of the upper-tropospheric trough over East Asia and anomalous low-tropospheric northwest anticyclones extending from the Philippines toward Japan are also consistent with the enhancement of cyclogenesis over the East China Sea as well as warm winter in Japan.

  7. Recent enhancement of central Pacific El Niño variability relative to last eight centuries

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Cobb, Kim M.; Song, Huiming; Li, Qiang; Li, Ching-Yao; Nakatsuka, Takeshi; An, Zhisheng; Zhou, Weijian; Cai, Qiufang; Li, Jinbao; Leavitt, Steven W.; Sun, Changfeng; Mei, Ruochen; Shen, Chuan-Chou; Chan, Ming-Hsun; Sun, Junyan; Yan, Libin; Lei, Ying; Ma, Yongyong; Li, Xuxiang; Chen, Deliang; Linderholm, Hans W.

    2017-05-01

    The far-reaching impacts of central Pacific El Niño events on global climate differ appreciably from those associated with eastern Pacific El Niño events. Central Pacific El Niño events may become more frequent in coming decades as atmospheric greenhouse gas concentrations rise, but the instrumental record of central Pacific sea-surface temperatures is too short to detect potential trends. Here we present an annually resolved reconstruction of NIÑO4 sea-surface temperature, located in the central equatorial Pacific, based on oxygen isotopic time series from Taiwan tree cellulose that span from 1190 AD to 2007 AD. Our reconstruction indicates that relatively warm Niño4 sea-surface temperature values over the late twentieth century are accompanied by higher levels of interannual variability than observed in other intervals of the 818-year-long reconstruction. Our results imply that anthropogenic greenhouse forcing may be driving an increase in central Pacific El Niño-Southern Oscillation variability and/or its hydrological impacts, consistent with recent modelling studies.

  8. Improved resistive switching characteristics in Ni/SiNx/p++-Si devices by tuning x

    NASA Astrophysics Data System (ADS)

    Kim, Sungjun; Chang, Yao-Feng; Kim, Min-Hwi; Park, Byung-Gook

    2017-07-01

    This letter studies the effect of the negative-set on the resistive switching performances of CMOS-compatible Ni/SiNx/p++-Si resistive memory devices by simply tuning x. A Ni/SiN1.07/p++-Si device showed lower power switching (20 μW) and better endurance cycles (103) compared to a Ni/SiN0.82/p++-Si device because of the improved negative set behavior and initially lower set and reset currents. In addition, we achieved fast switching speed for set (200 ns) and reset (100 ns) processes in the Ni/SiN1.07/p++-Si device. For the Ni/SiN1.07/p++-Si device, fine adjustment of resistance values is attainable by varying the pulse amplitude and width due to the gradual reset switching characteristics. The barrier-height-dependent conduction model is proposed to explain the change in the current level with the x value.

  9. Ni(II) affects ubiquitination of core histones H2B and H2A.

    PubMed

    Karaczyn, Aldona A; Golebiowski, Filip; Kasprzak, Kazimierz S

    2006-10-15

    The molecular mechanisms of nickel-induced malignant cell transformation include effects altering the structure and covalent modifications of core histones. Previously, we found that exposure of cells to Ni(II) resulted in truncation of histones H2A and H2B and thus elimination of some modification sites. Here, we investigated the effect of Ni(II) on one such modification, ubiquitination, of histones H2B and H2A in nuclei of cultured 1HAEo- and HPL1D human lung cells. After 1-5 days of exposure, Ni(II) up to 0.25 mM stimulated mono-ubiquitination of both histones, while at higher concentrations a suppression was found. Di-ubiquitination of H2A was not affected except for a drop after 5 days at 0.5 mM Ni(II). The decrease in mono-ubiquitination coincided with the appearance of truncated H2B that lacks the K120 ubiquitination site. However, prevention of truncation did not avert the decrease of H2B ubiquitination, indicating mechanistic independence of these effects. The changes in H2B ubiquitination did not fully coincide with concurrent changes in the nuclear levels of the ubiquitin-conjugating enzymes Rad6 and UbcH6. Overall, our results suggest that dysregulation of H2B ubiquitination is a part of Ni(II) adverse effects on gene expression and DNA repair which may assist in cell transformation.

  10. Atomic Structure of Pt3Ni Nanoframe Electrocatalysts by in Situ X-ray Absorption Spectroscopy.

    PubMed

    Becknell, Nigel; Kang, Yijin; Chen, Chen; Resasco, Joaquin; Kornienko, Nikolay; Guo, Jinghua; Markovic, Nenad M; Somorjai, Gabor A; Stamenkovic, Vojislav R; Yang, Peidong

    2015-12-23

    Understanding the atomic structure of a catalyst is crucial to exposing the source of its performance characteristics. It is highly unlikely that a catalyst remains the same under reaction conditions when compared to as-synthesized. Hence, the ideal experiment to study the catalyst structure should be performed in situ. Here, we use X-ray absorption spectroscopy (XAS) as an in situ technique to study Pt3Ni nanoframe particles which have been proven to be an excellent electrocatalyst for the oxygen reduction reaction (ORR). The surface characteristics of the nanoframes were probed through electrochemical hydrogen underpotential deposition and carbon monoxide electrooxidation, which showed that nanoframe surfaces with different structure exhibit varying levels of binding strength to adsorbate molecules. It is well-known that Pt-skin formation on Pt-Ni catalysts will enhance ORR activity by weakening the binding energy between the surface and adsorbates. Ex situ and in situ XAS results reveal that nanoframes which bind adsorbates more strongly have a rougher Pt surface caused by insufficient segregation of Pt to the surface and consequent Ni dissolution. In contrast, nanoframes which exhibit extremely high ORR activity simultaneously demonstrate more significant segregation of Pt over Ni-rich subsurface layers, allowing better formation of the critical Pt-skin. This work demonstrates that the high ORR activity of the Pt3Ni hollow nanoframes depends on successful formation of the Pt-skin surface structure.

  11. Microstructures and martensitic transformation behavior of superelastic Ti-Ni-Ag scaffolds

    SciTech Connect

    Li, Shuanglei; Kim, Eun-soo; Kim, Yeon-wook; Nam, Tae-hyun

    2016-10-15

    Highlights: • The B2-R-B19′ transformation occurred in 49Ti-50.3Ni-0.7Ag alloy fibers. • Annealing treated alloy fibers showed superelastic recovery ratio of 93%. • Ageing treated scaffold had an elastic modulus of 0.67 GPa. • Ageing treated scaffold exhibited good superelasticity at human body temperature. - Abstract: Ti-Ni-Ag scaffolds were prepared by sintering rapidly solidified alloy fibers. Microstructures and transformation behaviors of alloy fibers and scaffolds were investigated by means of electron probe micro-analyzer (EPMA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The B2-R-B19′ transformation occurs in alloy fibers. The alloy fibers have good superelasticity with superelastic recovery ratio of 93% after annealing heat treatment. The as-sintered Ti-Ni-Ag scaffolds possess three-dimensional and interconnected pores and have the porosity level of 80%. The heat treated Ti-Ni-Ag scaffolds not only have an elastic modulus of 0.67 GPa, which match well with that of cancellous bone, but also show excellent superelasticity at human body temperature. In terms of the mechanical properties, the Ti-Ni-Ag scaffolds in this study can meet the main requirements of bone scaffold for the purpose of bone replacement applications.

  12. Ni-doped TiO2 nanotubes for wide-range hydrogen sensing

    PubMed Central

    2014-01-01

    Doping of titania nanotubes is one of the efficient way to obtain improved physical and chemical properties. Through electrochemical anodization and annealing treatment, Ni-doped TiO2 nanotube arrays were fabricated and their hydrogen sensing performance was investigated. The nanotube sensor demonstrated a good sensitivity for wide-range detection of both dilute and high-concentration hydrogen atmospheres ranging from 50 ppm to 2% H2. A temperature-dependent sensing from 25°C to 200°C was also found. Based on the experimental measurements and first-principles calculations, the electronic structure and hydrogen sensing properties of the Ni-doped TiO2 with an anatase structure were also investigated. It reveals that Ni substitution of the Ti sites could induce significant inversion of the conductivity type and effective reduction of the bandgap of anatase oxide. The calculations also reveal that the resistance change for Ni-doped anatase TiO2 with/without hydrogen absorption was closely related to the bandgap especially the Ni-induced impurity level. PMID:24624981

  13. Crystal growth, electronic structure, and properties of Ni-substituted FeGa3

    NASA Astrophysics Data System (ADS)

    Likhanov, Maxim S.; Verchenko, Valeriy Yu.; Bykov, Mikhail A.; Tsirlin, Alexander A.; Gippius, Andrei A.; Berthebaud, David; Maignan, Antoine; Shevelkov, Andrei V.

    2016-04-01

    Crystals of the Fe1-xNixGa3 limited solid solution (x<0.045) have been grown from gallium flux. We have explored the electronic structure as well as magnetic and thermoelectric properties of Fe0.975Ni0.025Ga3 in comparison with Fe0.95Co0.05Ga3, following the rigid band approach and assuming that one Ni atom donates twice the number of electrons as one Co atom. However, important differences between the Co- and Ni-doped compounds are found below 620 K, which is the temperature of the metal-to-insulator transition for both compounds. We have found that Fe0.975Ni0.025Ga3 displays lower degree of spatial inhomogeneity on the local level and exhibits diamagnetic behavior with a broad shallow minimum in the magnetic susceptibility near 35 K, in sharp contrast with the Curie-Weiss paramagnetism of Fe0.95Co0.05Ga3. Transport measurements have shown the maximum of the thermoelectric figure-of-merit ZT of 0.09 and 0.14 at 620 K for Fe0.975Ni0.025Ga3 and Fe0.95Co0.05Ga3, respectively.

  14. Recent enhancement of central Pacific El Niño variability relative to last eight centuries.

    PubMed

    Liu, Yu; Cobb, Kim M; Song, Huiming; Li, Qiang; Li, Ching-Yao; Nakatsuka, Takeshi; An, Zhisheng; Zhou, Weijian; Cai, Qiufang; Li, Jinbao; Leavitt, Steven W; Sun, Changfeng; Mei, Ruochen; Shen, Chuan-Chou; Chan, Ming-Hsun; Sun, Junyan; Yan, Libin; Lei, Ying; Ma, Yongyong; Li, Xuxiang; Chen, Deliang; Linderholm, Hans W

    2017-05-30

    The far-reaching impacts of central Pacific El Niño events on global climate differ appreciably from those associated with eastern Pacific El Niño events. Central Pacific El Niño events may become more frequent in coming decades as atmospheric greenhouse gas concentrations rise, but the instrumental record of central Pacific sea-surface temperatures is too short to detect potential trends. Here we present an annually resolved reconstruction of NIÑO4 sea-surface temperature, located in the central equatorial Pacific, based on oxygen isotopic time series from Taiwan tree cellulose that span from 1190 AD to 2007 AD. Our reconstruction indicates that relatively warm Niño4 sea-surface temperature values over the late twentieth century are accompanied by higher levels of interannual variability than observed in other intervals of the 818-year-long reconstruction. Our results imply that anthropogenic greenhouse forcing may be driving an increase in central Pacific El Niño-Southern Oscillation variability and/or its hydrological impacts, consistent with recent modelling studies.

  15. Fully gapped superconductivity in Ni-pnictide superconductors BaNi2As2 and SrNi2P2

    NASA Astrophysics Data System (ADS)

    Kurita, N.; Ronning, F.; Miclea, C. F.; Tokiwa, Y.; Bauer, E. D.; Subedi, A.; Singh, D. J.; Sakai, H.; Thompson, J. D.; Movshovich, R.

    2011-01-01

    We have performed low-temperature specific heat C and thermal conductivity κ measurements on the Ni-pnictide superconductors BaNi2As2 (Tc = 0.7K) and SrNi2P2 (Tc = 1.4K). The temperature dependences C(T) and κ(T) of the two compounds are similar to the results of a number of s-wave superconductors. Furthermore, the concave field responses of the residual κ for BaNi2As2 rules out the presence of nodes on the Fermi surfaces. We postulate that fully gapped superconductivity could be universal for Ni-pnictide superconductors. Specific heat data on Ba0.6La0.4Ni2As2 shows a mild suppression of Tc and Hc2 relative to BaNi2As2.

  16. Shubnikov-de Haas oscillations in the Kondo semimetal CeNiSn

    NASA Astrophysics Data System (ADS)

    Terashima, Taichi; Terakura, Chieko; Uji, Shinya; Aoki, Haruyoshi; Echizen, Yuji; Takabatake, Toshiro

    2001-03-01

    The title compound CeNiSn was once classified as a Kondo insulator. However, recent studies have suggested that the energy gap opening in CeNiSn is a pseudogap with a finite density of states at the Fermi level (see, for example, Refs. 1-3). In the present work, we succeeded in observing Shubnikov-de Haas oscillations in low-temperature magnetoresistance, and thus directly proved that CeNiSn is a semimetal rather than a semiconductor. We discuss experimental results in terms of a hybridization gap picture. References 1. G. Nakamoto et al., J. Phys. Soc. Jpn. 64, 4834 (1995). 2. K. Nakamura et al., Phys. Rev. B 53, 6385 (1996). 3. K. Izawa et al., J. Phys. Soc. Jpn. 65, 3119 (1996).

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

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

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

  18. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approx. 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  19. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33 Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approximately 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  20. Calculated electric dipole moment of NiH X2Delta

    NASA Technical Reports Server (NTRS)

    Walch, S.; Bauschlicher, C. W., Jr.; Langhoff, S. R.

    1985-01-01

    A calculated dipole moment of 2.39 D at R sub e = 2.79 a sub 0 is reported, obtained from complete active space SCF/configuration interaction calculations plus one natural orbital iteration. The calculation is in good agreement with the experimental value of 2.4 + or - 0.1 D measured for the lowest vibrational level. In agreement with Gray et al. (1985), it is found that the dipole moment is strongly correlated with the 3d electron population; the good agreement with experiment thus provides verification of the mixed state model of NiH. It is concluded that the electric dipole moment of NiH is a sensitive test of the quality of the NiH wave function.

  1. Ab initio study of optical and vibrational properties of Ni3C

    NASA Astrophysics Data System (ADS)

    Golivand, Mohammad Bagher; Boochani, Arash; Akhtar, Arsalan; Torkashvand, Maryam; Karimian, Nashmyl

    2017-01-01

    The structural, electronic, optical and vibrational properties of Ni3C have been studied by density functional theory (DFT) framework with first-principles study. The obtained structural parameters are in good agreement with other works. The electronic study demonstrates metallic behavior of Ni3C since it has no energy gap at Fermi level. The optical parameters such as real and imaginary dielectric functions, loss function, conductivity, reflection, refraction indexes and absorption coefficients are studied. The phonon investigations confirm that the Ni3C bulk is dynamically stable and carbon has a major role in optical spectrum of the material at infrared region. Finally, the T3 behavior of Cv at low temperatures is obtained, as expected.

  2. Dirac R-matrix calculations of photoionization cross-sections of Ni XIII

    NASA Astrophysics Data System (ADS)

    Sardar, S.; Bilal, M.; Bari, M. A.; Nazir, R. T.; Hannan, A.; Salahuddin, M.; Nasim, M. H.

    2016-05-01

    In this paper, we report total photoionization cross-sections of Ni XIII in the ground state (3P2) and four excited states (3P1,0, 1D2, 1S0) for the first time over the photon energy range 380-480 eV. The target wavefunctions are constructed with fully relativistic atomic structure GRASP code. Our calculated energy levels and oscillator strengths of core ion Ni XIV agree well with available experimental and theoretical results. The ionization threshold value of ground state of Ni XIII is found to be more closer to the experimental ionization energy and improved over the previous calculations. The photoionization cross-sections are calculated using the fully relativistic DARC code with an appropriate energy step of 0.01 eV to delineate the resonance structures. The calculated ionization cross-sections are important for the modelling of features of photoionized plasmas and for stellar opacities.

  3. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting

    DOE PAGES

    Gong, Ming; Zhou, Wu; Kenney, Michael James; ...

    2015-08-24

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2O3-blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20more » mA cm–2 at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. Thus, the non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells.« less

  4. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting.

    PubMed

    Gong, Ming; Zhou, Wu; Kenney, Michael James; Kapusta, Rich; Cowley, Sam; Wu, Yingpeng; Lu, Bingan; Lin, Meng-Chang; Wang, Di-Yan; Yang, Jiang; Hwang, Bing-Joe; Dai, Hongjie

    2015-10-05

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2 O3 -blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2 O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2 O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20 mA cm(-2) at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. The non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells.

  5. Easy access to Ni3N- and Ni-carbon nanocomposite catalysts.

    PubMed

    Clavel, Guylhaine; Molinari, Valerio; Kraupner, Alexander; Giordano, Cristina

    2014-07-14

    In the search for alternative materials to current expensive catalysts, Ni has been addressed as one of the most promising and, on this trail, its corresponding nitride. However, nickel nitride is a thermally unstable compound, and therefore not easy to prepare especially as nanoparticles. In the present work, a sol-gel-based process (the urea glass route) is applied to prepare well-defined and homogeneous Ni3N and Ni nanoparticles. In both cases, the prepared crystalline nanoparticles (∼25 nm) are dispersed in a carbon matrix forming interesting Ni3N- and Ni-based composites. These nanocomposites were characterised by means of several techniques, such as XRD, HR-TEM, EELS, and the reaction mechanism was investigated by TGA and IR and herein discussed. The catalytic activity of Ni3N is investigated for the first time, to the best of our knowledge, for hydrogenation reactions involving H2, and here compared to the one of Ni. Both materials show good catalytic activities but, interestingly, give a different selectivity between different functional groups (namely, nitro, alkene and nitrile groups).

  6. Atomistic structure of the coherent Ni/Ni[sub 3]Al interface

    SciTech Connect

    Farkas, D. . Dept. of Materials Science and Engineering); Campos, M.F. de; Souze, R.M. de; Goldenstein, H. . Dept. de Metalurgia)

    1994-02-01

    Most Ni-based superalloys are strengthened by the presence of coherent precipitates of an ordered fcc bases phase, known as [gamma][prime]. This phase is basically Ni[sub 3]Al. The precipitates are coherent up to a certain size and they present a cubic shape with faces oriented in the (100) planes of both matrix and precipitate. The detailed atomistic structure of this interface has not been studied. Interest in the use of ordered intermetallic compounds as possible structural materials has resulted in a large amount of work in Ni[sub 3]Al and in particular, the development of interatomic potentials for the Ni-Al system using the embedded atom technique. These potentials have been employed in the simulation of a variety of defects in Ni[sub 3]Al, including dislocation cores, grain boundaries and free surfaces. However, there is no simulation of the Ni/Ni[sub 3]Al interface structure using the embedded atom method. The objective of the present work is to carry out such a simulation. Besides the practical importance of the interface in superalloys, it is the simplest type of interface that can be modeled and it is a good starting point for interface work using the embedded atom technique.

  7. Ni3Si2 nanowires grown in situ on Ni foam for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Jiang, Yizhe; Li, Zhihui; Li, Beibei; Zhang, Jinying; Niu, Chunming

    2016-07-01

    Ni3Si2 nanowires and nanoawls have grown in situ on the surface of Ni foams by a controlled low pressure chemical vapor deposition process. Structural characterization shows that the individual Ni3Si2 nanowire is single crystal covered with a thin layer (1-2 nm) of SiO2 with a diameter of ∼20-30 nm and length of ten's micrometers. Individual nanoawl with a circular cone shape is polycrystalline. Both Ni3Si2 nanowire and nanoawl samples are evaluated as potential electrode materials for supercapacitors. The nanowire electrode delivers a very high specific capacitance and excellent rate capability. A specific capacitance of 760 F g-1 is measured at current density of 0.5 A g-1, which decreases to 518 F g-1 when the current density increases to 10 A g-1. The capacitance is dominated by pseudocapacitance with a mechanism similar to that of NiO or Ni(OH)2 widely studied in the literature. An asymmetric supercapacitor fabricated by pairing Ni3Si2 nanowire electrode with an activated carbon electrode exhibits energy densities of 17.5 Wh kg-1 and 8.8 Wh kg-1 at power densites of 301 W kg-1 and 3000 W kg-1.

  8. Reactive transport model and apparent Kd of Ni in the near field of a HLW repository in granite

    NASA Astrophysics Data System (ADS)

    Lu, Chuanhe; Samper, Javier; Luis Cormenzana, José; Ma, Hongyun; Montenegro, Luis; Ángel Cuñado, Miguel

    2012-12-01

    Current performance assessment models for radionuclide migration through the near field of high-level radioactive waste repositories often rely on the assumption of a constant Kd for sorption. The validity of such assumption is evaluated here with a reactive transport model for Ni2+ in the near field of a repository in granite. Model results show that Ni2+ sorbs mainly by surface complexation on weak sorption sites. The apparent Kd of Ni2+, Kda, depends on the concentration of dissolved Ni and pH and is constant only when the concentration of dissolved Ni is smaller than 10-6 mol/L. The results of the sensitivity runs show that Kda is sensitive to the water flux at the bentonite-granite interface, the effective diffusion of the bentonite and the concentration of weak sorption sites of the bentonite. The competition of other nuclides such as Cs+ on Ni2+ sorption is not important. Corrosion products, however, affect significantly the sorption of Ni2+ on the bentonite. The model with a constant Kd does not reproduce the release rates of Ni2+ from the bentonite into the granite. A model with a variable Kd which depends on the concentration of dissolved Ni2+ and pH may provide an acceptable surrogate of the multicomponent reactive transport model for the conditions of the repository considered in our model. Simulations using the Kd-approach were performed with GoldSim based on the interpolation in the pH and concentration table, while the reactive transport model simulations were performed with CORE2D which incorporates multisite surface complexation.

  9. The Influence of El Niño and La Niña on Winter Climate Conditions at 138 Ski Resorts in Western North America

    NASA Astrophysics Data System (ADS)

    Pidwirny, M. J.; Mei Turney, A.

    2014-12-01

    This research examines the effect El Niño and La Niña have on the climate conditions of 138 ski resorts in western North America. Using ClimateWNA, monthly values for snowfall and degree days < 0°C (a measure of winter season coldness) were generated for the mid-slope elevation of the resorts for the primary ski season months of December, January, February, and March. From this data, composite values were computed by summing the four months analyzed for each of the two variables, with the December value coming from the previous year. Regression analysis was used to see if a relationship exists between the two climate variables and a summed composite of the monthly Southern Oscillation Index (SOI) for the same four months. Correlation coefficients were determined by regressing the observations for the time period 1935 to 2012. The correlation coefficients were then mapped using ARCGIS to display possible spatial patterns across the study area. Different map symbols were used to identify whether the correlation coefficient was positive or negative, and whether it fell within four levels of statistical significance: P ≥ 0.01, P < 0.01, P < 0.001, and P < 0.0001. Correlation coefficients with probability values equal to P ≥ 0.01 were considered not significant on the map. For the variable degree days < 0°C, resorts located in British Columbia, Alberta, Washington, and coastal south Oregon generally had warmer than usual winters during El Niño events and colder winters when SOI values suggested the occurrence of La Niña. A single resort, Ski Apache in New Mexico showed the opposite trend. Snowfall was found to be higher during La Niña events and lower with El Niño events for a number of resorts above 42° N latitude. Further, the strength of these correlations generally decreased with distance from the coast. Resorts in New Mexico and Arizona generally had more snowfall with El Niño and less snowfall with La Niña.

  10. Zn,Ni ferrite/NiO nanocomposite powder obtained from acetylacetonato complexes

    NASA Astrophysics Data System (ADS)

    Vucinic-Vasic, M.; Antic, B.; Kremenovic, A.; Nikolic, A. S.; Stoiljkovic, M.; Bibic, N.; Spasojevic, V.; Colomban, Ph

    2006-10-01

    The results on the synthesis, microstructure, structure and DC magnetization studies of nanocomposite Zn,Ni ferrite/NiO powder obtained by thermal decomposition of acetylacetonato complexes are reported in this paper. According to the results obtained by inductively coupled plasma optical emission spectroscopy (ICP-OES) element analysis and multiphase Rietveld refinement, the three samples made are composed of spinel-ferrite (86.7% 96.7%) and NiO (3.3% 13.3%) phases. The compositions of the spinel-ferrite (SP) phase in the investigated samples, S1 S3, are Zn0.72Ni0.24Fe1.98O4, Zn0.56Ni0.29Fe2.07O4 and Zn0.40Ni0.40Fe2.10O4, respectively. Due to the cation deficiency in spinels, created vacancies induce a partial change in the cation valence, \\mathrm {Ni^{2+}} \\to \\mathrm {Ni^{3+}} . The vacancy distribution is found to be random at 8a and 16d cation sites, except in sample S3, where all vacancies are over octahedral sites. The x-ray line broadening due to crystallite size effect is found to be isotropic for all spinels, while the x-ray line broadening due to the strain effect is anisotropic. A correlation between the Zn2+ occupancy of the tetrahedral site and the 650 cm-1 Raman peak intensities is shown. The observed coercivity decrease and shift in hysteresis loop in the samples are caused by the interaction between spinel and NiO phase. The results of M(H) measurements point to the properties of an ensemble of interacting nanoparticles. High saturation magnetization values and superparamagnetic behaviour at room temperature point to the technological significance of the title compounds.

  11. Opposing forces of aerosol cooling and El Niño drive coral bleaching on Caribbean reefs

    PubMed Central

    Gill, Jennifer A.; Watkinson, Andrew R.; McWilliams, John P.; Côté, Isabelle M.

    2006-01-01

    Bleaching of corals as a result of elevated sea surface temperatures (SST) is rapidly becoming a primary source of stress for reefs globally; the scale and extent of this threat will depend on how the drivers of SST interact to influence bleaching patterns. We demonstrate how the opposing forces of the El Niño–Southern Oscillation (ENSO) and levels of atmospheric aerosols drive regional-scale patterns of coral bleaching across the Caribbean. When aerosol levels are low, bleaching is largely determined by El Niño strength, but high aerosol levels mitigate the effects of a severe El Niño. High aerosol levels, resulting principally from recent volcanic activity, have thus protected Caribbean reefs from more frequent widespread bleaching events but cannot be relied on to provide similar protection in the future. PMID:17116861

  12. Ni Foam-Ni3 S2 @Ni(OH)2 -Graphene Sandwich Structure Electrode Materials: Facile Synthesis and High Supercapacitor Performance.

    PubMed

    Wang, Xiaobing; Hu, Jiangjiang; Su, Yichang; Hao, Jin; Liu, Fanggang; Han, Shuang; An, Jian; Lian, Jianshe

    2017-03-23

    A novel Ni foam-Ni3 S2 @Ni(OH)2 -graphene sandwich-structured electrode (NF-NN-G) with high areal mass loading (8.33 mg cm(-2) ) has been developed by sulfidation and hydrolysis reactions. The conductivity of Ni3 S2 and Ni(OH)2 were both improved. The upper layer of Ni(OH)2 , covered with a thin graphene film, is formed in situ from the surface of the lower layer of Ni3 S2 , whereas the Ni3 S2 grown on Ni foam substrate mainly acts as a rough support bridging the Ni(OH)2 and Ni foam. The graphene stabilized the Ni(OH)2 and the electrochemical properties were effectively enhanced. The as-synthesized NF-NN-G-5mg electrode shows a high specific capacitance (2258 F g(-1) at 1 A g(-1) or 18.81 F cm(-2) at 8.33 mA cm(-2) ) and an outstanding rate property (1010 F g(-1) at 20 Ag(-1) or 8.413 F cm(-2) at 166.6 mA cm(-2) ). This result is around double the capacitance achieved in previous research on Ni3 S2 @Ni(OH)2 /3DGN composites (3DGN=three-dimensional graphene network). In addition, the as-fabricated NF-NN-G-5mg composite electrode has an excellent cycle life with no capacitance loss after 3000 cycles, indicating a potential application as an efficient electrode. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Atomic Data and Spectral Line Intensities for Ni XI

    NASA Technical Reports Server (NTRS)

    Bhatia, A. K.; Landi, E.

    2010-01-01

    Electron impact collision strengths, energy levels, oscillator strengths and spontaneous radiative decay rates are calculated for Ni XI. We include in the calculations the 10 lowest configurations, corresponding to 164 fine structure levels: 3s(sup 2)3p(sup 6), 3s(sup 2)3p(sup 5)3d, 3s(sup 2)3p(sup 4)3d(sup 2), 3s3p(sup 6)3d, 3s(sup 2)3p(sup 5)4l and 3s3p6 4l with l =.s, p, d. Collision strengths are calculated at five incident energies for all transitions: 7.1, 16.8, 30.2, 48.7 and 74.1 Ry above the threshold of each transition. An additional energy, very close to the transition threshold, has been added, whose value is between 0.06 Ry and 0.25 Ry depending on the lower level. Calculations have been carried out using the Flexible Atomic Code and the distorted wave approximation. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates of the present work, combined with Close Coupling collision excitation rate coefficient available in the literature for the lowest 17 levels, statistical equilibrium equations for level populations are solved at electron densities covering the 10(exp 8)-10(exp 14) cu cm range and at an electron temperature of logT(sub c)(K)=6.1, corresponding to the maximum abundance of Ni XI. Spectral line intensities are calculated, and their diagnostic relevance is discussed. This dataset will be made available in the next version of the CHIANTI database.

  14. Selective laser ionisation of radionuclide 63Ni

    NASA Astrophysics Data System (ADS)

    Tsvetkov, G. O.; D'yachkov, A. B.; Gorkunov, A. A.; Labozin, A. V.; Mironov, S. M.; Firsov, V. A.; Panchenko, V. Ya.

    2017-02-01

    We report a search for a scheme of selective laser stepwise ionisation of radionuclide 63Ni by radiation of a dye laser pumped by a copper vapour laser. A three-stage scheme is found with ionisation through an autoionising state (AIS): 3d 84s2 3F4(E = 0) → 3d 94p 1Fo3(31030.99 cm-1) → 3d 94d 2[7/2]4(49322.56 cm-1) → AIS(67707.61 cm-1) which, by employing saturated radiation intensities provides the ionisation selectivity of above 1200 for 63Ni.

  15. NiCo₂O₄-Based Supercapacitor Nanomaterials.

    PubMed

    Wang, Chenggang; Zhou, E; He, Weidong; Deng, Xiaolong; Huang, Jinzhao; Ding, Meng; Wei, Xianqi; Liu, Xiaojing; Xu, Xijin

    2017-02-15

    In recent years, the research on supercapacitors has ushered in an explosive growth, which mainly focuses on seeking nano-/micro-materials with high energy and power densities. Herein, this review will be arranged from three aspects. We will summarize the controllable architectures of spinel NiCo₂O₄ fabricated by various approaches. Then, we introduce their performances as supercapacitors due to their excellent electrochemical performance, including superior electronic conductivity and electrochemical activity, together with the low cost and environmental friendliness. Finally, the review will be concluded with the perspectives on the future development of spinel NiCo₂O₄ utilized as the supercapacitor electrodes.

  16. Ionizing Radiation Effects in Ni Nanotubes

    NASA Astrophysics Data System (ADS)

    Shlimas, D.; Kozlovsky, A.; Shumskaya, A.; Kaniukov, E.; Ibragimova, M.; Zdorovets, M.; Kadyrzhanov, K.

    2017-01-01

    Polycrystalline nickel nanotubes with diameter of 380 nm and wall thickness 95 nm were synthesized by electrochemical method using PET track-etched membranes with thickness of 12 μm. A comprehensive study of the structural, morphological and electrical characteristics of Ni nanotubes irradiated with C+13 ions with energy 1.75 MeV/nucleon and fluence ranging from 109 to 5 × 1011 cm-2 was carried out. The ability of modification of structural parameters such as lattice parameter and the average size of crystallites and conductivity of Ni nanotubes by irradiation was shown.

  17. Biological and chemical consequences of the 1997 1998 El Niño in central California waters

    NASA Astrophysics Data System (ADS)

    Chavez, F. P.; Pennington, J. T.; Castro, C. G.; Ryan, J. P.; Michisaki, R. P.; Schlining, B.; Walz, P.; Buck, K. R.; McFadyen, A.; Collins, C. A.

    2002-09-01

    The physical, chemical and biological perturbations in central California waters associated with the strong 1997-1998 El Niño are described and explained on the basis of time series collected from ships, moorings, tide gauges and satellites. The evolution of El Niño off California closely followed the pattern observed in the tropical Pacific. In June 1997 an anomalous influx of warm southerly waters, with weak signatures on coastal sea level and thermocline depth, marked the onset of El Niño in central California. The timing was consistent with propagation from the tropics via the equatorial and coastal wave-guide. By late 1997, the classical stratified ocean condition with a deep thermocline, high sea level, and warm sea surface temperature (SST) commonly associated with El Niño dominated the coastal zone. During the first half of 1998 the core of the California Current, which is normally detected several hundred kilometers from shore as a river of low salinity, low nutrient water, was hugging the coast. High nutrient, productive waters that occur in a north-south band from the coast to approximately 200 km offshore during cool years disappeared during El Niño. The nitrate in surface waters was less than 20% of normal and new production was reduced by close to 70%. The La Niña recovery phase began in the fall of 1998 when SSTs dropped below normal, and ocean productivity rebounded to higher than normal levels. The reduction in coastal California primary productivity associated with El Niño was estimated to be 50 million metric tons of carbon (5× 1013 g C). This reduction certainly had deleterious effects on zooplankton, fish, and marine mammals. The 1992-1993 El Niño was more moderate than the 1997-1998 event, but because its duration was longer, its overall chemical and biological impact may have been comparable. How strongly the ecosystem responds to El Niño appears related to the longer-term background climatic state of the Pacific Ocean. The 1982

  18. Accelerator mass spectrometry of 63Ni using a gas-filled magnet at the Munich Tandem Laboratory

    NASA Astrophysics Data System (ADS)

    Rugel, G.; Faestermann, T.; Knie, K.; Korschinek, G.; Marchetti, A. A.; McAninch, J. E.; Rühm, W.; Straume, T.; Wallner, C.

    2000-10-01

    The detection of 63Ni ( T1/2=100.1 yr) by means of accelerator mass spectrometry (AMS) using a gas-filled magnet (GFM) is described. The experimental setup includes a dedicated ion source, a 14 MV MP tandem, a GFM and a multi-anode ionization chamber. First results indicate a background level of 63Ni/Ni ratios as low as 2×10 -14. This sensitivity will allow - for the first time ever - to detect 63Ni induced by fast neutrons in copper samples from Hiroshima and Nagasaki, even for distances beyond 1500 m from the hypocenters. Thus, it will be possible to reconstruct experimentally the neutron doses of the A-bomb survivors from Hiroshima and Nagasaki.

  19. Temperature independent Seebeck coefficient through quantum confinement modulation in amorphous Nb-O/Ni-Ta-O multilayers

    NASA Astrophysics Data System (ADS)

    Music, Denis; Hunold, Oliver; Coultas, Sarah; Roberts, Adam

    2017-05-01

    Employing a correlative experimental and theoretical methodology, we have investigated amorphous monoxide Nb-O/Ni-Ta-O multilayers. It is feasible to obtain a temperature independent Seebeck coefficient up to 500 °C for these metallic-like conductors, attaining -25 μV K-1. While Nb and Ta strongly interact with O, Ni experiences the metallic and monoxide-like bonding. We observe a 3 eV wide region below the Fermi level convoluted through several first nearest neighbor Ni - Ni and second nearest neighbor Nb - Nb interactions resulting in many confined states. It can be proposed that by increasing temperature these modulated quantum states gradually become thermally accessible eradicating the temperature dependence of the Seebeck coefficient.

  20. Influence of Al grain boundaries segregations and La-doping on embrittlement of intermetallic NiAl

    NASA Astrophysics Data System (ADS)

    Kovalev, Anatoly I.; Wainstein, Dmitry L.; Rashkovskiy, Alexander Yu.

    2015-11-01

    The microscopic nature of intergranular fracture of NiAl was experimentally investigated by the set of electron spectroscopy techniques. The paper demonstrates that embrittlement of NiAl intermetallic compound is caused by ordering of atomic structure that leads to formation of structural aluminum segregations at grain boundaries (GB). Such segregations contain high number of brittle covalent interatomic bonds. The alloying by La increases the ductility of material avoiding Al GB enrichment and disordering GB atomic structure. The influence of La alloying on NiAl mechanical properties was investigated. GB chemical composition, atomic and electronic structure transformations after La doping were investigated by AES, XPS and EELFS techniques. To qualify the interatomic bonds metallicity the Fermi level (EF) position and electrons density (neff) in conduction band were determined in both undoped and doped NiAl. Basing on experimental results the physical model of GB brittleness formation was proposed.

  1. Extraction of Ni(II) on micro crystalline naphthalene modified with organic-solution-processable functionalized nano graphene

    NASA Astrophysics Data System (ADS)

    Moghimi, Ali

    2014-07-01

    A novel and selective method for the fast determination of trace amounts of Ni(II) ions in water samples is described. Method has been developed for preconcentration of Ni on organic-solution-processable functionalized-nano graphene (SPFGraphene) adsorbent in the pH range 5.0-10.0, prior to its spectrophotometric determination, based on the oxidation of bromopyrogallol red at λ = 517 nm. This method makes it possible to quantitize Ni in the range of 4.2 × 10-9 to 2.3 × 10-5 M, with a detection limit ( S/N = 3) of 1.42 × 10-9 M. This procedure has been successfully applied to determine the ultra trace levels of Ni in the environmental samples, free from the interference of some diverse ions. The precision, expressed as relative standard deviation of three measurements is better than 3.0%.

  2. Exchange bias in finite sized NiO nanoparticles with Ni clusters

    NASA Astrophysics Data System (ADS)

    Gandhi, Ashish Chhaganlal; Lin, Jauyn Grace

    2017-02-01

    Structural and magnetic properties of finite sized NiO nanoparticles are investigated with synchrotron X-ray diffraction (XRD), transmission electron microscopy, magnetometer and ferromagnetic resonance (FMR) spectroscopy. A minor Ni phase is detected with synchrotron XRD, attributed to the oxygen defects in the NiO core. A considerable exchange bias of 100 Oe is observed at 50 K and it drops abruptly and vanishes above 150 K, in association with the reduction of frozen spins. FMR data indicate a strong interaction between ferromagnetic (FM) and antiferromagnetic (AFM) phases below 150 K, consistent with the picture of isolated FM clusters in AFM matrix.

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

    SciTech Connect

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

    2009-03-08

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

  4. Tensile strength of thermomechanically processed Cu-9Ni-6Sn alloys

    SciTech Connect

    Rhu, J.C.; Kim, S.S.; Jung, Y.C.; Han, S.Z.; Kim, C.J.

    1999-10-01

    The tensile properties of Cu-9Ni-6Sn alloys with different swaging amounts of 64, 77, and 95 pct, either solutionized and aged (S/A), were examined as a function of aging time. It was found that the aging response of Cu-9Ni-6Sn alloys varied greatly depending on the prior solution heat treatment before aging and/or different swaging amounts. The swaged S/A Cu-9Ni-6Sn alloys showed a multistage increase in tensile strength with respect to aging time, probably due to the sequential occurrence of spinodal decomposition, formation of metastable {gamma}{center{underscore}dot} precipitates, and recrystallization. The effect of different swaging amounts, ranging from 64 to 95 pct, was minimal on the aging response of S/A specimens. The prior cold working, however, appeared to favor the spinodal strengthening, comparing unswaged and swaged S/A Cu-9Ni-6Sn alloys. In 95 pct swaged D/A Cu-9Ni-6Sn alloys, the level of hardening was much less sensitive to aging time. A complex interaction between the reduction in dislocation density, the formation of equilibrium precipitates, and the reduction of Sn content in the Sn-rich segregates during an aging process is believed to be responsible for such a lean sensitivity. The increases in tensile strength of 64 and 77 pct swaged D/A Cu-9Ni-6Sn alloys were found to be much steeper than that in the 95 pct counterparts in the early and intermediate stages of aging, which is believed to be related to the relative contribution from work hardening and precipitation hardening to the strength level of D/A specimens.

  5. Perpendicularly magnetized spin filtering Cu/Ni multilayers

    SciTech Connect

    Shirahata, Yasuhiro; Wada, Eiji; Itoh, Mitsuru; Taniyama, Tomoyasu

    2014-01-20

    Spin filtering at perpendicular magnetized Cu/Ni multilayer/GaAs(001) interfaces is demonstrated at remanence using optical spin orientation method. [Cu(9 nm)/Ni(t{sub Ni} nm)]{sub n} multilayers are found to show a crossover from the in-plane to out-of-plane magnetic anisotropy at the Cu/Ni bilayer repetition n = 4 and the Ni layer thickness t{sub Ni} = 3. For a perpendicularly magnetized Cu/Ni multilayer/n-GaAs(001) interface, circular polarization dependent photocurrent shows a clear hysteretic behavior under optical spin orientation conditions as a function of magnetic field out-of-plane while the bias dependence exhibits a substantial peak at a forward bias, verifying that Cu/Ni multilayers work as an efficient spin filter in the remanent state.

  6. Structural study of radiolytic catalysts Ni-Ce/Al2O3 and Ni-Pt/Al2O3

    NASA Astrophysics Data System (ADS)

    Seridi, F.; Chettibi, S.; Keghouche, N.; Beaunier, P.; Belloni, J.

    2017-01-01

    Ni-Ce and Ni-Pt bimetallic catalysts supported over α-Al2O3 are synthesized by using co-impregnation method, and then reduced, each via radiolytic process or thermal H2-treatment. For Ni-Ce/Al2O3, the structural study reveals that Ce is alloyed with Ni as Ce2Ni7 nanoparticles in the radiation-reduced catalysts, while it segregates to the surface in the form of CeO2 in the H2-reduced catalysts. For Ni-Pt/Al2O3 radiolytic catalysts, Ni, Pt, NiPt and Ni3Pt nanoparticles, which size is 3.5 nm, are observed. When the radiation-reduced samples are tested in the benzene hydrogenation, they both display high conversion rate. However, the Ni-Pt/Al2O3 is more efficient than Ni-Ce/Al2O3. The performance of the catalysts is correlated with the high dispersion of the metal and the presence of intermetallic Ni-Pt and Ni-Ce phases. It is compared to that of other radiolytic monometallic/oxide catalysts of the literature.

  7. Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3−δ} (Me = Fe, Mn)

    SciTech Connect

    Niwa, Eiki; Maeda, Hiroki; Uematsu, Chie; Hashimoto, Takuya

    2015-10-15

    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-free 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.

  8. Amplification of El Niño by cloud longwave coupling to atmospheric circulation

    NASA Astrophysics Data System (ADS)

    Rädel, Gaby; Mauritsen, Thorsten; Stevens, Bjorn; Dommenget, Dietmar; Matei, Daniela; Bellomo, Katinka; Clement, Amy

    2016-02-01

    The El Niño/Southern Oscillation (ENSO) is the dominant mode of inter-annual variability, with major impacts on social and ecological systems through its influence on extreme weather, droughts and floods. The ability to forecast El Niño, as well as anticipate how it may change with warming, requires an understanding of the underlying physical mechanisms that drive it. Among these, the role of atmospheric processes remains poorly understood. Here we present numerical experiments with an Earth system model, with and without coupling of cloud radiative effects to the circulation, suggesting that clouds enhance ENSO variability by a factor of two or more. Clouds induce heating in the mid and upper troposphere associated with enhanced high-level cloudiness over the El Niño region, and low-level clouds cool the lower troposphere in the surrounding regions. Together, these effects enhance the coupling of the atmospheric circulation to El Niño surface temperature anomalies, and thus strengthen the positive Bjerknes feedback mechanism between west Pacific zonal wind stress and sea surface temperature gradients. Behaviour consistent with the proposed mechanism is robustly represented in other global climate models and in satellite observations. The mechanism suggests that the response of ENSO amplitude to climate change will in part be determined by a balance between increasing cloud longwave feedback and a possible reduction in the area covered by upper-level clouds.

  9. Amplification of El Niño by cloud longwave coupling to atmospheric circulation

    NASA Astrophysics Data System (ADS)

    Raedel, Gaby; Mauritsen, Thorsten; Stevens, Bjorn; Dommenget, Dietmar; Matei, Daniela; Bellomo, Katinka; Clement, Amy

    2016-04-01

    The El Niño/Southern Oscillation(ENSO) is the dominant mode of inter-annual variability, with major impacts on social and ecological systems through its influence on extreme weather, droughts and floods. The ability to forecast El Niño, as well as anticipate how it may change with warming, requires an understanding of the underlying physical mechanisms that drive it. Among these, the role of atmospheric processes remains poorly understood. Here we present numerical experiments with an Earth system model, with and without coupling of cloud radiative effects to the circulation, suggesting that clouds enhance ENSO variability by a factor of two or more. Clouds induce heating in the mid and upper troposphere associated with enhanced high-level cloudiness over the El Niño region, and low-level clouds cool the lower troposphere in the surrounding regions. Together, these effects enhance the coupling of the atmospheric circulation to El Niño surface temperature anomalies, and thus strengthen the positive Bjerknes feedback mechanism between west Pacific zonal wind stress and sea surface temperature gradients. Behaviour consistent with the proposed mechanisms robustly represented in other global climate models and in satellite observations. The mechanism suggests that the response of ENSO amplitude to climate change will in part be determined by a balance between increasing cloud long wave feedback and a possible reduction in the area covered by upper-level clouds.

  10. Electrical properties and stoichiometry in La 2NiO 4

    NASA Astrophysics Data System (ADS)

    Sayer, M.; Odier, P.

    1987-03-01

    The electrical properties of La 2NiO 4 have been studied with respect to the stoichiometry of the material. The conductivity of reduced compositions has been measured between 20 and 1000 K and compared to that of the air-prepared ones. Nonstoichiometry is present in both cases and produces disorder leading to Anderson localization and to the definition of a mobility edge in the σx2- y2 itinerant band. Air-prepared compounds contain in addition a large number of Ni 3+ states which may overlap the itinerant σx2- y2 band. For reduced materials containing small amounts of Ni 3+, the electrical properties can be described below 200 K by a hopping conductivity at the Fermi level within a sharply peaked density of states. The results are well described within the frame of the Mott theory of variable range hopping. Above 200 K highly reduced materials exhibit direct excitation of holes from Ni 3+ states to the mobility edge in the itinerant band. Under conditions appropriate to air-prepared materials, the Fermi level is shifted toward the itinerant band and a major contribution to the conductivity arises from hopping at the Fermi level. At high temperature a progressive excitation of carriers from the localized states is anticipated with an eventual exhaustion region. This last assumption is corroborated with a shift of the conductivity maximum to higher temperature for increasingly reduced materials.

  11. Anomalous self-reduction of layered double hydroxide (LDH): from α-Ni(OH)2 to hexagonal close packing (HCP) Ni/NiO by annealing without a reductant.

    PubMed

    Ge, X; Gu, C D; Wang, X L; Tu, J P

    2015-01-21

    The traditional concept that nickel layered double hydroxide (Ni LDH, also known as α-Ni(OH)2) converts to NiO after annealing has been taken without doubt and utilized to fabricate NiO for years. This work reports that an anomalous self-reduction phenomenon can occur for Ni LDH synthesized from an ionic liquid system.

  12. Asymmetry in summertime atmospheric circulation anomalies over the northwest Pacific during decaying phase of El Niño and La Niña

    NASA Astrophysics Data System (ADS)

    Tao, Weichen; Huang, Gang; Wu, Renguang; Hu, Kaiming; Wang, Pengfei; Chen, Dong

    2017-09-01

    The present study has revealed the asymmetric characteristics of summertime atmospheric circulation anomalies over the Indo-Pacific for El Niño and La Niña, as well as the possible mechanism. During the summer when El Niño has dissipated, there are basin-wide warming over the tropical Indian Ocean (TIO) and cooling over the equatorial central and eastern Pacific (CEP). The northwest Pacific (NWP) anticyclone is maintained by a combined effect of the TIO warming and equatorial CEP cooling. The impact of TIO warming is via the Kelvin wave-induced divergence mechanism, and the effect of CEP cooling is by stimulating a Rossby wave response to its northwest. Correspondingly, there are lower (upper) level convergence (divergence) over the TIO and divergence (convergence) over the NWP. The tropical atmospheric waves and large-scale circulation anomalies could couple together and maintain the anticyclone. However, for La Niña, there are easterly wind anomalies over the equatorial western Pacific, and the anomalous NWP cyclone (NWPC) is weak and shifts northwestward, which are largely different from El Niño. The equatorial CEP cooling plays a dominant role in the maintenance of NWPC. The negative rainfall anomalies induced by CEP cooling force the anticyclonic wind anomalies over the WP as a Rossby wave response, which further cause the lower (upper) level convergence (divergence) over the MC and NWP. The resultant convergence leads to the enhanced convection there, inducing the NWPC as a Rossby wave response. Besides, the equatorial easterly wind anomalies trigger the upwelling oceanic Kelvin wave and maintain the CEP cooling as the Bjerknes feedback.

  13. NiCl2-down-regulated antioxidant enzyme mRNA expression causes oxidative damage in the broiler(')s kidney.

    PubMed

    Guo, Hongrui; Wu, Bangyuan; Cui, Hengmin; Peng, Xi; Fang, Jing; Zuo, Zhicai; Deng, Junliang; Wang, Xun; Deng, Jie; Yin, Shuang; Li, Jian; Tang, Kun

    2014-12-01

    The kidney serves as a major organ of nickel (Ni) excretion and is a target organ for acute Ni toxicity due to Ni accumulation. There are no studies on the Ni or Ni compound-regulated antioxidant enzyme mRNA expression in animals and human beings at present. This study was conducted to investigate the pathway of nickel chloride (NiCl2)-caused renal oxidative damage by the methods of biochemistry, quantitative real-time polymerase chain reaction, and enzyme-linked immunosorbent assay. Two hundred and eighty one-day-old broilers were randomly divided into four groups and fed on a control diet and three experimental diets supplemented with 300, 600, and 900 mg/kg of NiCl2 for 42 days. Dietary NiCl2 elevated the malondialdehyde (MDA), nitric oxide (NO), 8-hydroxy-2'-deoxyguanosine (8-OHdG) contents, and reduced the ability to inhibit hydroxy radical in the NiCl2-treated groups. Also, the renal inducible nitric oxide synthase (iNOS) activity and mRNA expression levels were increased. The total antioxidant (T-AOC) and activities of antioxidant enzymes including copper zinc superoxide dismutase (CuZn-SOD), manganese superoxide dismutase (Mn-SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), and glutathione-s-transferase (GST) were decreased, and the glutathione (GSH) contents as well were decreased in the kidney. Concurrently, the renal CuZn-SOD, Mn-SOD, CAT, GSH-Px, GST, and GR mRNA expression levels were decreased. The above-mentioned results showed that dietary NiCl2 in excess of 300 mg/kg caused renal oxidative damage by reducing mRNA expression levels and activities of antioxidant enzymes, and then enhancing free radicals generation, lipid peroxidation, and DNA oxidation.

  14. NiO Nanofibers as a Candidate for a Nanophotocathode

    PubMed Central

    Macdonald, Thomas J.; Xu, Jie; Elmas, Sait; Mange, Yatin J.; Skinner, William M.; Xu, Haolan; Nann, Thomas

    2014-01-01

    p-type NiO nanofibers have been synthesized from a simple electrospinning and sintering procedure. For the first time, p-type nanofibers have been electrospun onto a conductive fluorine doped tin oxide (FTO) surface. The properties of the NiO nanofibers have been directly compared to that of bulk NiO nanopowder. We have observed a p-type photocurrent for a NiO photocathode fabricated on an FTO substrate.

  15. Ternary system Er-Ni-In at T=870 K

    SciTech Connect

    Dzevenko, M.; Tyvanchuk, Yu.; Bratash, L.; Zaremba, V.; Havela, L.; Kalychak, Ya.

    2011-10-15

    Isothermal section of the Er-Ni-In system at T=870 K was constructed by means of X-ray powder diffraction and EDX-analyses. Nine ternary compounds, namely ErNi{sub 9}In{sub 2} (YNi{sub 9}In{sub 2}-type), Er{sub 1-1.22}Ni{sub 4}In{sub 1-0.78} (MgCu{sub 4}Sn-type), Er{sub 10}Ni{sub 9.07}In{sub 20} (Ho{sub 10}Ni{sub 9}In{sub 20}-type), ErNi{sub 1-0.60}In{sub 1-1.40} (ZrNiAl-type), Er{sub 2}Ni{sub 2}In (Mn{sub 2}AlB{sub 2}-type), Er{sub 2}Ni{sub 1.78}In (Mo{sub 2}FeB{sub 2}-type), Er{sub 5}Ni{sub 2}In{sub 4} (Lu{sub 5}Ni{sub 2}In{sub 4}-type), Er{sub 5}Ni{sub 2}In (Mo{sub 5}SiB{sub 2}-type), and Er{sub 13.53}Ni{sub 3.14}In{sub 3.33} (Lu{sub 14}Co{sub 2}In{sub 3}-type), exist in the Er-Ni-In system at this temperature. The substitution of Ni for In was observed for ErNi{sub 1-0.60}In{sub 1-1.40} and In for Er in the case of related compounds ErNi{sub 2} and ErNi{sub 4}In. Er can enter NiIn (CoSn-type) leading to including-substitution type of compound Er{sub 0-0.12}NiIn{sub 1-0.89}. Basic magnetic properties of the Er{sub 0.04}NiIn{sub 0.97}, ErNi{sub 2}, Er{sub 0.9}Ni{sub 2}In{sub 0.1}, and ErNi{sub 4}In phases were inspected. Electrical-resistivity studies were performed on the ErNiIn, ErNi{sub 0.9}In{sub 1.1}, and ErNi{sub 4}In phases. - Graphical Abstract: Phase relations in the ternary system Er-Ni-In have been established for the isothermal section at T=870 K based on X-ray phase and EDX-analyses. Nine ternary compounds were observed. Highlights: > Isothermal section of Er-Ni-In system at T=870 K was constructed. > Nine ternary compounds were detected. > Basic magnetic properties of Er{sub 0.04}NiIn{sub 0.97} and ErNi{sub 4}In phases were inspected.

  16. (001) 3C SiC/Ni contact interface: In situ XPS observation of annealing induced Ni2Si formation and the resulting barrier height changes

    NASA Astrophysics Data System (ADS)

    Tengeler, Sven; Kaiser, Bernhard; Chaussende, Didier; Jaegermann, Wolfram

    2017-04-01

    The electronic states of the (001) 3C SiC/Ni interface prior and post annealing are investigated via an in situ XPS interface experiment, allowing direct observation of the induced band bending and the transformation from Schottky to ohmic behaviour for the first time. A single domain (001) 3C SiC sample was prepared via wet chemical etching. Nickel was deposited on the sample in multiple in situ deposition steps via RF sputtering, allowing observation of the 3C SiC/Ni interface formation. Over the course of the experiments, an upward band bending of 0.35 eV was observed, along with defect induced Fermi level pinning. This indicates a Schottky type contact behaviour with a barrier height of 0.41 eV. The subsequent annealing at 850 °C for 5 min resulted in the formation of a