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Sample records for elements nb ta

  1. Niobium Nb and tantalum Ta

    International Nuclear Information System (INIS)

    Busev, A.I.; Tiptsova, V.G.; Ivanov, V.M.

    1978-01-01

    The basic methods for determining niobium and tantalum in various objects are described. Nb and Ta are separated with the aid of N-benzoyl-N-phenylhydroxylamine by precipitating Nb(5) from a tartaric acid solution with subsequent precipitation of Ta from the filtrate. The gravimetric determination of Nb and Ta in steels is based on their quantitative separation from a diluted solution by way of hydrolysis with subsequent after-precipitation with phenylarsonic acid (in the absence of W). The gravimetric determination of Nb in the presence of W is carried out with the aid of Cupferron. To determine Nb in its carbide, Nb(5) reduced to Nb(3) is titrated with a solution of K 2 Cr 2 O 7 in the presence of phenyl-anthranilic acid. The photometric determination of Nb in tungsten-containing steels and in ores containing Ti, W, Mo and Cr is based on the rhodanide method. Nb is determined in alloys with Zr and Ti photometrically with the aid of 4-(2-pyridylazo)-resorcin and in alloyed steels with the aid of benzhydroxamic acid. The latter complex is extracted with chloroform. This method is used to determine Nb in rocks. The photometric determination of Ta in TiCl 4 is carried out with the aid of pyrogallol, in commercial niobium with the aid of methyl violet, and in steel with the aid of 4-(-pyridylazo)-resorcin. Also described is the polarographic determination of Nb in tantalum pentoxide

  2. Solution chemistry of element 105. Pt. III. Hydrolysis and complex formation of Nb, Ta, Db and Pa in HF and HBr solutions

    International Nuclear Information System (INIS)

    Pershina, V.; Bastug, T.

    1999-01-01

    Calculations of the electronic structure of MF 6 - and MBr 6 - complexes of Nb, Ta, Pa and element 105, Db, formed in HF and HBr solutions have been performed using the Dirac-Slater Discrete Variational method. On the basis of results of these calculations, relative values of the free energy change of reactions of complex formation have been determined. The order of the complex formation for both acids is shown to be Pa >> Nb > Db > Ta. Such a sequence is defined by a predominant electrostatic energy of the metal-ligand interaction. The hydrolysis of compounds, as a reverse process, proved to change as Ta > Db > Nb >> Pa. Using the theory of metal extraction by anion exchange, the following trend in the extraction of the anionic species from both the HF and HBr aqueous solutions has been predicted: Pa >> Nb ≥ Db > Ta. The strength of the ML 6 - complexes is shown to decrease from MF 6 , to MCl 6 and further to MBr 6 - which is reflected by shifting the complex formation process to the area of higher acid concentrations. (orig.)

  3. Tritium diffusion in V, Nb and Ta

    International Nuclear Information System (INIS)

    Qi, Z.; Voelkl, J.; Laesser, R.; Wenzl, H.

    1983-01-01

    Gorsky-effect measurements of the diffusion coefficient of tritium (T) in V, Nb and Ta are reported. The measurements were performed at small T concentrations (less than about 1.4 at%), and in the temperature range from -140 0 C to 100 0 C. Comparison with results obtained for H and D shows an increase of the activation energy with increasing isotopic mass. For Nb and Ta, the pre-exponential factors are identical for all the isotopes, whereas for V this factor is appreciably larger for T than for H and D. The reduction of the relaxation strength in the presence of precipitation allows a rough determination of the solubility limit, which is found to be isotope independent for Nb and Ta. In V, the solubility limit for T is shifted slightly to lower temperatures. The H, D or T induced lattice expansion calculated from the relaxation strength shows no dependence on isotopic mass. (author)

  4. Supporting data for senary refractory high-entropy alloy CrxMoNbTaVW

    Directory of Open Access Journals (Sweden)

    B. Zhang

    2015-12-01

    Full Text Available This data article is related to the research paper entitled “senary refractory high-entropy alloy CrxMoNbTaVW [1]”. In this data article, the pseudo-binary Cr-MoNbTaVW phase diagram is presented to show the impact of Cr content to the senary Cr-MoNbTaVW alloy system; the sub-lattice site fractions are presented to show the disordered property of the Cr-MoNbTaVW BCC structures; the equilibrium and Scheil solidification results with the actual sample elemental compositions are presented to show the thermodynamic information of the melted/solidified CrxMoNbTaVW samples; and the raw EDS scan data of the arc-melted CrxMoNbTaVW samples are also provided.

  5. Behaviour at the indicator scale of the elements Zr, Hf and 104, Nb,Ta and Pa (105) in very complexation media; Comportement a l`echelle des indicateurs des elements Zr, Hf, et 104, Nb, Ta, et Pa (105) en milieux tres complexants

    Energy Technology Data Exchange (ETDEWEB)

    Monroy Guzman, F. [Institut de Physique Nucleaire, CNRS - IN2P3 Universite Paris Sud, 91406 Orsay Cedex (France)

    1997-12-31

    In order to determine the chemical properties of the trans-actinide elements of Z = 104 and 105 in aqueous solutions we studied their behaviour to ion exchange resin in different complex media. Due to the very short lifetimes (some tens of seconds) et to the low yield of these elements (a few atoms per irradiation hour) only very fast radiochemical techniques can be used. These severe constraints impose comparative studies of these elements with their most likely homologues to be carried out. The corresponding homologues were the elements of group 4 (Zr and Hf) for the element 104 and the elements of group 5 (Nb and Ta) and also Pa for the element 105. The complexation properties of the elements at indicator scale were determined in the media of HF, NH{sub 4}/HClO{sub 4}, NH{sub 4}SCN/HClO{sub 4}, NH{sub 4}SCN/HF and HCl/HF by ion exchange chromatography. The studies in fluorides media allowed us to identify the complexes in solution and to explain the shape of the experimentally observed sorption curves. The decrease of sorption for higher acid concentration in case of HF/HCl medium was interpreted by formation of chloro-fluoro-complexes. In case of the mixture NH{sub 4}SCN/HF, the particularly pronounced anti-synergic effects were observed and discussed. At the same time studies of the Hf and Ta short-lived isotopes were carried out by means of the RACHEL facility operating by the Orsay Tandem accelerator. These realistic simulations allowed optimization of different production, transportation and separation stages of the trans-actinide elements. The two experiments of 104 element production showed that this element forms in HF very stable anionic complexes similarly to its homologues Zr and Hf. (authors). 181 refs.

  6. A concise guide for the determination of less-studied technology-critical elements (Nb, Ta, Ga, In, Ge, Te) by inductively coupled plasma mass spectrometry in environmental samples

    Science.gov (United States)

    Filella, Montserrat; Rodushkin, Ilia

    2018-03-01

    There is an increasing demand for analytical techniques able to measure so-called 'technology-critical elements', a set of chemical elements increasingly used in technological applications, in environmental matrices. Nowadays, inductively coupled plasma-mass spectrometry (ICP-MS) has become the technique of choice for measuring trace element concentrations. However, its application is often less straightforward than often assumed. The hints and drawbacks of ICP-MS application to the measurement of a set of less-studied technology-critical elements (Nb, Ta, Ga, In, Ge and Te) is discussed here and concise guidelines given.

  7. High-pressure phases of Weyl semimetals NbP, NbAs, TaP, and TaAs

    Science.gov (United States)

    Guo, ZhaoPeng; Lu, PengChao; Chen, Tong; Wu, JueFei; Sun, Jian; Xing, DingYu

    2018-03-01

    In this study, we used the crystal structure search method and first-principles calculations to systematically explore the highpressure phase diagrams of the TaAs family (NbP, NbAs, TaP, and TaAs). Our calculation results show that NbAs and TaAs have similar phase diagrams, the same structural phase transition sequence I41 md→ P6¯ m2→ P21/ c→ Pm3¯ m, and slightly different transition pressures. The phase transition sequence of NbP and TaP differs somewhat from that of NbAs and TaAs, in which new structures emerge, such as the Cmcm structure in NbP and the Pmmn structure in TaP. Interestingly, we found that in the electronic structure of the high-pressure phase P6¯ m2-NbAs, there are coexistingWeyl points and triple degenerate points, similar to those found in high-pressure P6¯ m2-TaAs.

  8. Differential Nb-Ta diffusion in rutile: disequilibrium formation of the continental crust

    Science.gov (United States)

    Marschall, H. R.; Dohmen, R.; Ludwig, T.

    2012-12-01

    Models for the differentiation of the crust-mantle system are guided by elemental abundances in these reservoirs. Elements are fractionated between coexisting phases during partial melting, and geochemical models have mostly been based on the assumption that trace-element equilibrium is established between the partial melts and the restitic minerals. Based on this assumption, experimentally determined mineral/melt element partition coefficients have been used to model the effects of crust-mantle differentiation. The element pair niobium and tantalum has been key for the distinction of different melting regimes involved in crustal differentiation, but equilibrium partition models have largely failed to reproduce the observed Nb/Ta patterns. Here we demonstrate that Nb and Ta are significantly fractionated kinetically by diffusion, and that Nb/Ta systematics of partial melts and restites will likely be influenced by kinetic factors. We employed two different experimental setups to determine diffusivities of Nb and Ta in rutile: (1) Thin film diffusion couples prepared by PLD [1] were annealed in gas mixing furnaces between 850 and \\unit{1150}{ȩlsius}. The resulting diffusion profiles were analysed by SIMS in depth profiling mode. (2) Rutile single crystals were placed in rutile-saturated Nb-Ta-doped basaltic melt at \\unit{1250}{ȩlsius} and lateral diffusion profiles were analysed by EPMA. Both sets of experiments demonstrate consistently and unequivocally that diffusion coefficients in rutile of Nb are 3 to 5 (!) times higher than those of Ta for the entire temperature range. The significantly higher mobility of Nb compared to Ta in rutile has direct consequences for their liquid-rock fractionation during partial melting events. We conclude that trace-element equilibrium cannot be expected for the natural range of grain sizes of rutile (the dominant mineral host of Nb and Ta in high-grade rocks) and the temperatures and time scales involved in partial melting of

  9. Method of treating Ti--Nb--Zr--Ta superconducting alloys

    International Nuclear Information System (INIS)

    Horiuchi, T.; Monju, Y.; Tatara, I.; Nagai, N.; Hisata, M.; Matsumoto, K.

    1975-01-01

    A superconducting alloy is formulated from 10 to 50 at. percent Ti, 20 to 50 at. percent Nb, 10 to 40 at. percent Zr, and 5 to 12 at. percent Ta. A Ti--Nb--Zr--Ta superconducting alloy with a fine, non-homogeneous structure is obtained by forming a β solid solution of Ti--Nb--Zr--Ta alloy by heating to a temperature within the β solid solution range, cooling, and then cold working the heated alloy. The cold worked alloy is heated to a temperature within the (β' + β'') alloy to maintain the peritectoid structure, cold worked, then heated to a temperature within the eutectoid range to form a multiphase alloy structure and then cooled and finally cold worked. (U.S.)

  10. Superelastic and shape memory properties of TixNb3Zr2Ta alloys.

    Science.gov (United States)

    Zhu, Yongfeng; Wang, Liqiang; Wang, Minmin; Liu, Zhongtang; Qin, Jining; Zhang, Di; Lu, Weijie

    2012-08-01

    The microstructure and phase constitutions of TixNb3Zr2Ta alloys (x=35, 31, 27, 23) (wt%) were studied. With a lower niobium content the grain size of β phase in TixNb3Zr2Ta alloys increased significantly, and the TixNb3Zr2Ta system was more likely to form α″ phase and even α phase. Tensile tests showed that UTS of TixNb3Zr2Ta alloys improved as the Nb content was decreased. Cyclic loading-unloading tensile tests were carried on TixNb3Zr2Ta alloys. Ti23Nb3Zr2Ta and Ti27Nb3Zr2Ta alloys featured the best superelasticity among the alloys studied. The pseudoelastic strain ratio of Ti35Nb3Zr2Ta alloy decreased a lot as the cycle number increased. Ti31Nb3Zr2Ta alloy showed only minimum superelasticity. This is because Ti23Nb3Zr2Ta and Ti27Nb3Zr2Ta alloys had higher yield strength than Ti31Nb3Zr2Ta did, which allowed martensite phase to be induced. On the contrary, Ti31Nb3Zr2Ta alloy exhibited better shape memory property than Ti27Nb3Zr2Ta, Ti23Nb3Zr2Ta and Ti35Nb3Zr2Ta titanium alloys. β phase, α phase and α″ phase were found in Ti23Nb3Zr2Ta alloy by TEM observation. The dislocation density of α phase was much lower than that of β phase due to their crystal structure difference. This may explained why Ti23Nb3Zr2Ta with α phase possessed higher tensile strength. The incomplete shape recovery of Ti23Nb3Zr2Ta alloy after unloading resulted from two sources. Plastic deformation occurred in β phase, α phase and even α″ phase under dislocation slip mechanism, and incomplete decomposition of α″ martensitic phase resulted in unrecovered strain as well. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. Microstructure, mechanical behavior and biocompatibility of powder metallurgy Nb-Ti-Ta alloys as biomedical material.

    Science.gov (United States)

    Liu, Jue; Chang, Lin; Liu, Hairong; Li, Yongsheng; Yang, Hailin; Ruan, Jianming

    2017-02-01

    Microstructures, mechanical properties, apatite-forming ability and in vitro experiments were studied for Nb-25Ti-xTa (x=10, 15, 20, 25, 35at.%) alloys fabricated by powder metallurgy. It is confirmed that the alloys could achieve a relative density over 80%. Meanwhile, the increase in Ta content enhances the tensile strength, elastic modulus and hardness of the as-sintered alloys. When increasing the sintering temperatures, the microstructure became more homogeneous for β phase, resulting in a decrease in the modulus and strength. Moreover, the alloys showed a good biocompatibility due to the absence of cytotoxic elements, and were suitable for apatite formation and cell adhesion. In conclusion, Nb-25Ti-xTa alloys are potentially useful in biomedical applications with their mechanical and biological properties being evaluated in this work. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Comparison of the costs of superconducting accelerator dipoles using NbTi, Nb3Sn and NbTiTa

    International Nuclear Information System (INIS)

    Hassenzahl, W.

    1981-03-01

    The present study, which is based on the assumption that future, high-energy accelerators will use superconductors, is a comparison of the costs of 5 to 12 Tesla NbTi, Nb 3 S/sub n/, and NbTiTa accelerator magnets operating at 4.2 K or 1.8 K. The object of this evaluation is not to determine the actual cost of future accelerators, rather, its purpose is to provide some rationale for research on the next generation of superconducting accelerator magnets. Thus, though the actual costs of accelerator magnets may be different from those given here, the comparisons are valid

  13. Correlation between hardness and stress in Al-(Nb, Mo, Ta) thin films

    Energy Technology Data Exchange (ETDEWEB)

    Car, T., E-mail: car@irb.h [Rudjer Boskovic Institute, Division of Materials Science, Bijenicka cesta 54, 10000 Zagreb, P.O.B. 1016 (Croatia); Radic, N. [Rudjer Boskovic Institute, Division of Materials Science, Bijenicka cesta 54, 10000 Zagreb, P.O.B. 1016 (Croatia); Panjan, P.; Cekada, M. [Jozef Stefan Institute, Ljubljana (Slovenia); Tonejc, A. [Department of Physics, Bijenicka cesta 32, 10000 Zagreb, P.O.B. 331 (Croatia)

    2009-06-30

    The thin films of Al{sub x}Nb{sub 1-x} (95 {>=} x {>=} 20), Al{sub x}Mo{sub x} (90 {>=} x {>=} 20) and Al{sub x}Ta{sub 1-x} (95 {>=} x {>=} 20) were prepared by magnetron codeposition at room temperature. The average film thickness was from 325 to 400 nm, depending on the film composition. The structure of the as-deposited films was examined by the X-ray diffraction. The stress of the films was determined from the substrate deformation by the profilometer, and the microhardness (load 2 mN) was examined by the micro- and nano-hardness device. For the purpose of the examination of the hardness, the samples were deposited onto the sapphire wafers, while the examination of the film stress, was performed by using thin glass substrates. For all the Al-(Nb, Mo, Ta) alloy compositions, the microhardness is predominantly under the influence of the harder element, and monotonically decreases with the increase of the aluminum content. However, the microhardness of the amorphous AlTa films was higher than the bulk value of a harder element (Ta) in the alloy. A simple empirical linear relationship between the Vickers hardness, the bulk value hardness of the transition metal (harder element) and the elastic energy fraction of the identation deformation, was established. The elastic energy fraction in the microhardness is also linearly correlated with the stress in films.

  14. MoNbTaV Medium-Entropy Alloy

    Directory of Open Access Journals (Sweden)

    Hongwei Yao

    2016-05-01

    Full Text Available Guided by CALPHAD (Calculation of Phase Diagrams modeling, the refractory medium-entropy alloy MoNbTaV was synthesized by vacuum arc melting under a high-purity argon atmosphere. A body-centered cubic solid solution phase was experimentally confirmed in the as-cast ingot using X-ray diffraction and scanning electron microscopy. The measured lattice parameter of the alloy (3.208 Å obeys the rule of mixtures (ROM, but the Vickers microhardness (4.95 GPa and the yield strength (1.5 GPa are about 4.5 and 4.6 times those estimated from the ROM, respectively. Using a simple model on solid solution strengthening predicts a yield strength of approximately 1.5 GPa. Thermodynamic analysis shows that the total entropy of the alloy is more than three times the configurational entropy at room temperature, and the entropy of mixing exhibits a small negative departure from ideal mixing.

  15. (Nb,Ta,Ti) 3Sn multifilamentary wires using Osprey bronze with high tin content and NbTa/NbTi composite filaments

    Science.gov (United States)

    Abächerli, V.; Uglietti, D.; Seeber, B.; Flükiger, R.

    2002-08-01

    Several (Nb,Ta,Ti) 3Sn multifilamentary wires with different Ti contents (up to 0.6 wt.%), but identical configuration have been processed using the bronze route and NbTa/NbTi composite filaments. The wires were manufactured by a sequence of three extrusion steps using a Cu 15.4 Sn Osprey bronze as matrix. The wires of 1.06 mm diameter with 14641 filaments of 4.4 μm size were reacted by various heat treatments, ranging from 600 to 730 °C. Critical current density ( Jc) measurements on samples in a coil geometry have been performed up to 17 T at 4.2 K, yielding to 195 A mm -2 at 17 T. Upper critical magnetic fields ( Bc2) up to 28.2 T were estimated by Kramer extrapolation. The variation of the critical temperature ( Tc) as well as of the n factor were determined. The effect of various Ti contents was analyzed with respect to the various superconducting parameters, especially in view of applications at fields >20 T.

  16. Anion exchange behaviour of Zr, Hf, Nb, Ta and Pa as homologues of RF and Db in fluoride medium

    Energy Technology Data Exchange (ETDEWEB)

    Monroy G, F. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Trubert, D.; Brillard, L.; Hussonnois, M.; Constantinescu, O.; Le Naour, C., E-mail: fabiola.monroy@inin.gob.m [Institut de Physique Nucleaire, F-91406 Orsay, France (France)

    2010-07-01

    Studies of the chemical property of trans actinide elements are very difficult due to their short half-lives and extremely small production yields. However it is still possible to obtain considerable information about their chemical properties, such as the most stable oxidation states in aqueous solution, complexing ability, etc., comparing their behaviour with their lighter homologous in the periodic table. In order to obtain a better knowledge of the behaviour of rutherfordium, RF (element 104), dub nium, Db (element 105) in HF medium, the sorption properties of Zr, Hf, Nb, Ta an Pa, homologues of RF and Db, were studied in NH{sub 4}F/HClO{sub 4} medium in this work. Stability constants of the fluoride complexes of these elements were experimentally obtained from K{sub d} obtained at different F{sup -} and H{sup +} concentrations. The anionic complexes: [Zr(Hf)F{sub 5}]{sup -}, [Zr(Hf)F{sub 6}]{sup 2-}, [Zr(Hf)F{sub 7}]{sup 3-}, [Ta(Pa)F{sub 6}]{sup -}, [Ta(Pa)F{sub 7}]{sup 2-}, [Ta(Pa)F{sub 8}]{sup 3-}, [NbOF{sub 4}]{sup -} and [NbOF{sub 5}]{sup 2-} are present as predominant species in the HF range over investigation. (Author)

  17. Anion exchange behaviour of Zr, Hf, Nb, Ta and Pa as homologues of RF and Db in fluoride medium

    International Nuclear Information System (INIS)

    Monroy G, F.; Trubert, D.; Brillard, L.; Hussonnois, M.; Constantinescu, O.; Le Naour, C.

    2010-01-01

    Studies of the chemical property of trans actinide elements are very difficult due to their short half-lives and extremely small production yields. However it is still possible to obtain considerable information about their chemical properties, such as the most stable oxidation states in aqueous solution, complexing ability, etc., comparing their behaviour with their lighter homologous in the periodic table. In order to obtain a better knowledge of the behaviour of rutherfordium, RF (element 104), dub nium, Db (element 105) in HF medium, the sorption properties of Zr, Hf, Nb, Ta an Pa, homologues of RF and Db, were studied in NH 4 F/HClO 4 medium in this work. Stability constants of the fluoride complexes of these elements were experimentally obtained from K d obtained at different F - and H + concentrations. The anionic complexes: [Zr(Hf)F 5 ] - , [Zr(Hf)F 6 ] 2- , [Zr(Hf)F 7 ] 3- , [Ta(Pa)F 6 ] - , [Ta(Pa)F 7 ] 2- , [Ta(Pa)F 8 ] 3- , [NbOF 4 ] - and [NbOF 5 ] 2- are present as predominant species in the HF range over investigation. (Author)

  18. Petrochemical Characteristics and Age of Rare Metal (Ta-Nb Mineralization in Precambrian Pegmatites, Komu, Nigeria

    Directory of Open Access Journals (Sweden)

    A. OLUGBENGA

    2010-06-01

    Full Text Available The Precambrian pegmatites of Komu area intrude semi discordantly older rock types, such as biotite gneiss, amphibolites and pelitic schists. The pegmatites occur as near flat lying bodies. This study aims at elucidating the geological setting, petrography, geochemical features and age of mineralization of these pegmatite bodies, with a view to classifying them and knowing their economic potential. The petrographic analysis shows that the pegmatite samples contain mainly quartz (35%, plagioclase (15%, microcline (10% and muscovite (12% with accessories like tourmaline, tantalum, niobium and illmeno-rutiles. Geochemical analysis of the muscovites extracted from pegmatites show that these rocks are enriched in silica (>60% and Al2O3 (>12% and depleted in Fe2O3, MgO and TiO2. Trace element analysis shows that the pegmatites contain rare metals with moderately high Ta, Nb, Sn, Rb, Li and Cs values and depleted in Ti, Ba and Zr. Elemental ratios indicate low ratios of K/Cs, Th/U and K/Rb. Variation plots of Ta/(Ta+Nb versus Mn/ (Mn+Fe show that the pegmatites plot in the complex (beryl subtype field. The Na/K versus Sn, Nb, Rb variation plots show that the pegmatites of Komu area are mineralized and compare favourably with those of other mineralized pegma-tite areas like Egbe and Ijero in southwestern Nigeria. The variation plots of Ta versus K/Cs, and Ta/W versus Cs, also confirm rare metal mineralization of Komu pegmatites, which plot over the mineralized line of Beus and Gordiyenko. The K/Rb versus Rb, Cs and Sn plots indicate low K/Rb ratios indicating moderate differentiation. The Rare Earth Elements (REE show high heavy REE values and lower light REE values with prominent positive Ce anomaly and negative Eu anomaly from normalized chondrite plots. K/Ar dating of the age of mineralization of muscovites extracted from the pegmatite yielded late Pan-African ages between 502.8±13Ma and 514.5±13.2Ma. This period represents the cooling ages of the

  19. Superconductivity and specific heat measurements in V--Nb--Ta ternary alloys

    International Nuclear Information System (INIS)

    Wang, R.Y.P.

    1977-01-01

    The correlation between the superconducting transition temperature T/sub c/ with electronic specific heat coefficient γ and Debye temperature theta/sub D/ in some isoelectronic ternary V--Nb--Ta alloys is investigated. It has been known that the variation of theta/sub D/ with concentration in both V--Nb and V--Ta systems is clearly of the same curvature as that of T/sub c/ and γ. In Ta--Nb alloys, however, over most of the concentration range theta/sub D/ seems to have a slight negative curvature while T/sub c/ and γ curve upwards. (But beyond approx. 80 at. % Nb theta/sub D/ rises rapidly to the pure Nb value.) By choosing alloys along a line connecting Ta and V 25 --Nb 75 which is close to the Nb--Ta side of the Gibb's triangle the extent to which the Nb--Ta type of behavior persists in this ternary system can be estimated. A model proposed by Miedema that takes into account the variation of properties caused by possible charge transfer among constituent atoms in an alloy has been found to apply almost quantitatively for nearly all binary alloy systems whose experimental data are available, including those for which Hopfield's method fails. A previous test of the extension of Miedema's empirical model into ternary alloys shows qualitatively correct behavior for intra-row Zr/sub x/Nb/sub 1-2x/Mo/sub x/ alloys. The good agreement between the predicted values of γ and T/sub c/ and the experimental values in the inter-row ternary V--Nb--Ta system studied here gives another and better test of the application of Miedema's model

  20. Mesoporous (Ta, Nb3W7 Modified with Stearic Acid Used as Solid Acids for Esterification

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    Fei Chang

    2017-01-01

    Full Text Available Mesoporous solid acids Ta3W7 and Nb3W7 were prepared from TaCl5 and NbCl5 with WCl6 in the presence of stearic acid (SA via a sol-gel method, respectively. For comparison, mesoporous Ta3W7-P123 mixed oxides and mesoporous Nb3W7-P123 mixed oxides were synthesized in the same way. The catalysts were characterized through TGA, XRD, SEM, TEM, BET, and NH3-TPD. Experimental results showed that Ta3W7-SA and Nb3W7-SA exhibited several advantages such as higher activity, shorter preparation period, lower cost, stronger acid sites, and higher surface area, which had potential to be used as mesoporous heterogeneous catalysts in biodiesel production.

  1. Fabrication of Nb and Ta/Al/AlO{sub x}/Al/Nb tunneling junction X-ray detectors: a list of problems

    Energy Technology Data Exchange (ETDEWEB)

    Nussbaumer, T. [Paul-Scherrer Inst., Villigen (Switzerland). Solid State Div.; Finkbeiner, F. [Paul-Scherrer Inst., Villigen (Switzerland). Solid State Div.; Lerch, P. [Paul-Scherrer Inst., Villigen (Switzerland). Solid State Div.; Zehnder, A. [Paul-Scherrer Inst., Villigen (Switzerland). Solid State Div.; Ott, H.R. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Lab. fuer Festkoerperphysik

    1996-02-11

    A whole wafer fabrication procedure using selective etching of refractory materials to produce Nb- or Ta/Al/AlO{sub x}Al/Nb tunneling X-ray detectors is discussed. Fabrication aspects and preliminary results are presented. (orig.).

  2. Influence of Ta and Ti Doping on the High Field Performance of (Nb, Ta, Ti)3Sn Multifilamentary Wires based on Osprey Bronze with High Tin Content

    Science.gov (United States)

    Abächerli, V.; Uglietti, D.; Lezza, P.; Seeber, B.; Flükiger, R.; Cantoni, M.; Buffat, P.-A.

    2006-06-01

    Ta and Ti are the most widely used additions for technical Nb3Sn multifilamentary superconductors. These elements are known to influence grain growth, grain morphology and chemical composition in the A15 layer, hence the current carrying properties of the wires over a wide magnetic field range. So far only few studies tried to compare systematically Ta and Ti doped and undoped Nb3Sn wires in the frame of the same work, down to a nanometric scale. We present an investigation on several multifilamentary (Nb, Ta, Ti)3Sn bronze route wires, fabricated at a laboratory scale, with various amounts of additives. The wires consist of fine filaments embedded in a Cu-Sn or Cu-Sn-Ti Osprey bronze with > 15 wt.% Sn and an external Cu stabilization. Microstructural observations are compared with the results of Jc and n values measured up to 21 T at 4.2 and 2.2 K, and for longitudinal strains up to 0.5%. Non-Cu Jc values up to 300 Amm-2 and n values up to 50 at 17 T and 4.2 K show clearly that wires with Ti addition to the bronze have a better performance with respect to wires with Ti additions to the filaments.

  3. Isoelectronic substitutions and aluminium alloying in the Ta-Nb-Hf-Zr-Ti high-entropy alloy superconductor

    Science.gov (United States)

    von Rohr, Fabian O.; Cava, Robert J.

    2018-03-01

    High-entropy alloys (HEAs) are a new class of materials constructed from multiple principal elements statistically arranged on simple crystallographic lattices. Due to the large amount of disorder present, they are excellent model systems for investigating the properties of materials intermediate between crystalline and amorphous states. Here we report the effects of systematic isoelectronic replacements, using Mo-Y, Mo-Sc, and Cr-Sc mixtures, for the valence electron count 4 and 5 elements in the body-centered cubic (BCC) Ta-Nb-Zr-Hf-Ti high-entropy alloy (HEA) superconductor. We find that the superconducting transition temperature Tc strongly depends on the elemental makeup of the alloy, and not exclusively its electron count. The replacement of niobium or tantalum by an isoelectronic mixture lowers the transition temperature by more than 60%, while the isoelectronic replacement of hafnium, zirconium, or titanium has a limited impact on Tc. We further explore the alloying of aluminium into the nearly optimal electron count [TaNb] 0.67(ZrHfTi) 0.33 HEA superconductor. The electron count dependence of the superconducting Tc for (HEA)Al x is found to be more crystallinelike than for the [TaNb] 1 -x(ZrHfTi) x HEA solid solution. For an aluminum content of x =0.4 the high-entropy stabilization of the simple BCC lattice breaks down. This material crystallizes in the tetragonal β -uranium structure type and superconductivity is not observed above 1.8 K.

  4. Phase diagrams for pseudo-binary carbide systems TiC-NbC, TiC-TaC, ZrC-NbC, ZrC-TaC and HfC-TaC

    International Nuclear Information System (INIS)

    Gusev, A.I.

    1985-01-01

    Parameters of interaction and energy of mutual exchange in the liquid and solid phases of pseudobinary TiC-NbC, TiC-TaC, ZrC-NbC, ZrC-TaC, HfC-TaC systems are calculated with account of dependence on composition and temperature. Positions of liquidus-solidus phase boundaries on the phase diagrams of the mentioned systems are calculated on the basis of the determined mutual exchange energies in approximati.on of subregular solutions. The existance of latent decomposition ranges in the solid phase on the phase diagrams of the investgated systems is established

  5. Photoluminescent properties of Pr3+ doped YTiAO6 (A= Nb&Ta) euxenite compounds

    Science.gov (United States)

    Venugopal, Meenu; Kumar, H. Padma

    2018-04-01

    Pr3+ doped YTiAO6 (A = Nb and Ta) compounds were prepared by conventional solid state ceramic route. X - ray diffraction studies of the samples confirmed the euxenite orthorhombic phase formation. Effect of Pr3+ doping on the optical and luminescence properties of YTiAO6 (A = Nb and Ta) were studied. The strong absorption in the UV region are due to the absorption by the host YTiAO6 (A = Nb and Ta) and all other peaks can be attributed to that of Pr3+. Host emission peaks are observed around 485 nm and 460 nm in all samples. The red emission observed at 614 nm in the doped samples corresponds to the 1D2 to 3H4 transition of Pr3+ ion. CIE colour coordinates and chromaticity values were also discussed.

  6. Wear resistance of laser-deposited boride reinforced Ti-Nb-Zr-Ta alloy composites for orthopedic implants

    International Nuclear Information System (INIS)

    Samuel, Sonia; Nag, Soumya; Scharf, Thomas W.; Banerjee, Rajarshi

    2008-01-01

    The inherently poor wear resistance of titanium alloys limits their application as femoral heads in femoral (hip) implants. Reinforcing the soft matrix of titanium alloys (including new generation β-Ti alloys) with hard ceramic precipitates such as borides offers the possibility of substantially enhancing the wear resistance of these composites. The present study discusses the microstructure and wear resistance of laser-deposited boride reinforced composites based on Ti-Nb-Zr-Ta alloys. These composites have been deposited using the LENS TM process from a blend of elemental Ti, Nb, Zr, Ta, and boron powders and consist of complex borides dispersed in a matrix of β-Ti. The wear resistance of these composites has been compared with that of Ti-6Al-4V ELI, the current material of choice for orthopedic femoral implants, against two types of counterfaces, hard Si 3 N 4 and softer SS440C stainless steel. Results suggest a substantial improvement in the wear resistance of the boride reinforced Ti-Nb-Zr-Ta alloys as compared with Ti-6Al-4V ELI against the softer counterface of SS440. The presence of an oxide layer on the surface of these alloys and composites also appears to have a substantial effect in terms of enhanced wear resistance

  7. Corrosion resistance and in vitro response of a novel Ti35Nb2Ta3Zr alloy with a low Young's modulus.

    Science.gov (United States)

    Guo, Yongyuan; Chen, Desheng; Lu, Weijie; Jia, Yuhua; Wang, Liqiang; Zhang, Xianlong

    2013-10-01

    β type titanium alloys have attracted much attention in the biomedical field because they consist of non-cytotoxic elements, show high corrosion resistance, and are biologically compatible. In this study, a novel β type titanium alloy (Ti35Nb3Zr2Ta) with a Young's modulus of 48 GPa was fabricated and the alloy's corrosion resistance and in vitro response were determined. The results indicate that the novel alloy exhibits comparable corrosion resistance when compared with Ti6Al4V, but in vitro experiments show that osteoblasts attach, spread, proliferate, and differentiate better on Ti35Nb2Ta3Zr than on Ti6Al4V. The high corrosion resistance and satisfactory biocompatibility make the novel Ti35Nb3Zr2Ta alloy a promising biomaterial for surgical implants.

  8. Effect of Cu, Nb and Ta addition on the structural and magnetic properties of amorphous Fe-Si-B alloys

    International Nuclear Information System (INIS)

    Gupta, A.; Kane, S.N.; Bhagat, N.; Kulik, T.

    2003-01-01

    The effect of successive additions of Cu, Nb and Ta in amorphous Fe 77.5 Si 13.5 B 9 has been studied using X-ray diffraction and Moessbauer spectroscopy. Addition of Nb/Ta results in an increased near-neighbor distance as well as a decrease in topological order in the system. On the other hand, Cu addition results in a significant increase in the topological order. Addition of Cu does not significantly change the average hyperfine field, whereas, addition of Nb/Ta decreases the hyperfine field. Nb and Ta addition results in appearance of an additional hump in B hf around 13 T due to Fe atoms with Nb/Ta near neighbors. Thermal annealing of the specimens at 390 deg. C results in changes in the short-range order, which are mainly chemical in nature

  9. Acoustic wave propagation in Ni3 R (R= Mo, Nb, Ta) compounds

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 76; Issue 4. Acoustic wave propagation in Ni3 ( = Mo, Nb, Ta) compounds. Pramod Kumar Yadawa ... Author Affiliations. Pramod Kumar Yadawa1. Department of Applied Physics, AMITY School of Engineering and Technology, Bijwasan, New Delhi 110 061, India ...

  10. Acoustic wave propagation in Ni3 R (R = Mo, Nb, Ta) compounds

    Indian Academy of Sciences (India)

    Department of Applied Physics, AMITY School of Engineering and Technology, Bijwasan,. New Delhi 110 061, India. E-mail: pkyadawa@aset.amity.edu ... In the present investigation, ultrasonic properties like orientation-dependent sound veloc- ities and second-order elastic constants for the Ni3Mo, Ni3Nb and Ni3Ta ...

  11. Effect of ternary alloying elements on microstructure and superelastictity of Ti-Nb alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, D.C.; Mao, Y.F.; Li, Y.L.; Li, J.J.; Yuan, M. [Key Laboratory of Low Di-mensional Materials and Application Technology of Ministry of Education, Xiangtan University, Xiangtan, Hunan 411105 (China); Faculty of Material and Optical-Electronic Physics, Xiangtan University, Xiangtan, Hunan 411105 (China); Lin, J.G., E-mail: lin_j_g@xtu.edu.cn [Key Laboratory of Low Di-mensional Materials and Application Technology of Ministry of Education, Xiangtan University, Xiangtan, Hunan 411105 (China); Faculty of Material and Optical-Electronic Physics, Xiangtan University, Xiangtan, Hunan 411105 (China)

    2013-01-01

    The effect of ternary alloying elements (X=Ta, Fe, Zr, Mo, Sn and Si) on the microstructure, the mechanical properties and the superelasticity of Ti--22Nb-X alloys were investigated. The 1% addition of a ternary alloying element (X=Ta, Fe, Zr, Mo, Sn and Si) has a slight influence on the microstructure of the Ti-22Nb alloy. All the alloys after solution-treatment at 1073 K for 1.8 ks contain {beta} and {alpha} Double-Prime phases. The elements of Sn, Si, Fe and Ta with a high number of valence electrons or a small atomic size have a strong solid-solution strengthening effect to the {beta} phases in the alloys and the alloys with high Md{sup Macron} and low Bo{sup Macron} exhibit low elastic moduli. All the alloying elements improve the superelasticity of Ti-22Nb-X alloys. The elements, Fe, Mo, Sn and Si, which are with a high number of valence electrons and a small atomic size, strongly increase {sigma}{sub SIM} of the Ti-22Nb alloy.

  12. Color tone and interfacial microstructure of white oxide layer on commercially pure Ti and Ti-Nb-Ta-Zr alloys

    Science.gov (United States)

    Miura-Fujiwara, Eri; Mizushima, Keisuke; Watanabe, Yoshimi; Kasuga, Toshihiro; Niinomi, Mitsuo

    2014-11-01

    In this study, the relationships among oxidation condition, color tone, and the cross-sectional microstructure of the oxide layer on commercially pure (CP) Ti and Ti-36Nb-2Ta-3Zr-0.3O were investigated. “White metals” are ideal metallic materials having a white color with sufficient strength and ductility like a metal. Such materials have long been sought for in dentistry. We have found that the specific biomedical Ti alloys, such as CP Ti, Ti-36Nb-2Ta-3Zr-0.3O, and Ti-29Nb-13Ta-4.6Zr, form a bright yellowish-white oxide layer after a particular oxidation heat treatment. The brightness L* and yellowness +b* of the oxide layer on CP Ti and Ti-36Nb-2Ta-3Zr-0.3O increased with heating time and temperature. Microstructural observations indicated that the oxide layer on Ti-29Nb-13Ta-4.6Zr and Ti-36Nb-2Ta-3Zr-0.3O was dense and firm, whereas a piecrust-like layer was formed on CP Ti. The results obtained in this study suggest that oxide layer coating on Ti-36Nb-2Ta-3Zr-0.3O is an excellent technique for dental applications.

  13. Loparite, a rare-earth ore (Ce, Na, Sr, Ca)(Ti, Nb, Ta, Fe+3)O3

    Science.gov (United States)

    Hedrick, James B.; Sinha, Shyama P.; Kosynkin, Valery D.

    1997-01-01

    The mineral loparite (Ce, NA, Sr, Ca)(Ti, Nb, Ta, Fe+3)O3 is the principal ore of the light-group rare-earth elements (LREE) in Russia. The complex oxide has a perovskite (ABO3) structure with coupled substitutions, polymorphism, defect chemistry and a tendency to become metamict. The A site generally contains weakly bonded, easily exchanged cations of the LREE, Na and Ca. The B site generally contains smaller, highly charged cations of Ti, Nb or Fe+3. Mine production is from Russia's Kola Peninsula. Ore is beneficiated to produce a 95% loparite concentrate containing 30% rare-earth oxides. Loparite concentrate is refined by either a chlorination process or acid decomposition process to recover rare-earths, titanium, niobium and tantalum. Rare-earths are separated by solvent extraction and selective precipitation/dissolution. The concentrate is processed at plants in Russia, Estonia and Kazakstan.

  14. Mesoporous Nb and Ta Oxides: Synthesis, Characterization and Applications in Heterogeneous Acid Catalysis

    Science.gov (United States)

    Rao, Yuxiang Tony

    In this work, a series of mesoporous Niobium and Tantalum oxides with different pore sizes (C6, C12, C18 , ranging from 12A to 30 A) were synthesized using the ligand-assisted templating approach and investigated for their activities in a wide range of catalytic applications including benzylation, alkylation and isomerization. The as-synthesized mesoporous materials were characterized by nitrogen adsorption, powder X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), and solid-state Nuclear magnetic resonance (NMR) techniques. In order to probe into the structural and coordination geometry of mesoporous Nb oxide and in efforts to make meaningful comparisons of mesoporous niobia prepared by the amine-templating method with the corresponding bulk sol-gel prepared Nb2O5 phase, 17O magic-angle-spinning solid-state NMR studies were conducted. The results showed a very high local order in the mesoporous sample. The oxygen atoms are coordinated only as ONb 2 in contrast with bulk phases in which the oxygen atoms are always present in a mixture of ONb2 and ONb3 coordination environments. To enhance their surface acidities and thus improve their performance as solid acid catalysts in the acid-catalyzed reactions mentioned above, pure mesoporous Nb and Ta oxides were further treated with 1M sulfuric acid or phosphoric acid. Their surface acidities before and after acid treatment were measured by Fourier transform infraRed (FT IR), amine titration and temperature programmed desorption of ammonia (NH3-TPD). Results obtained in this study showed that sulfated mesoporous Nb and Ta oxides materials possess relative high surface areas (up to 612 m 2/g) and amorphous wormhole structure. These mesoporous structures are thus quite stable to acid treatment. It was also found that Bronsted (1540 cm-1) and Lewis (1450 cm-1) acid sites coexist in a roughly 50:50 mixture

  15. High-temperature phases of NaNbO3 and NaTaO3.

    Science.gov (United States)

    Darlington; Knight

    1999-02-01

    The high-temperature phases of the perovskites sodium niobate, NaNbO(3), and sodium tantalate, NaTaO(3), have been re-examined using the high-resolution powder diffractometer HRPD at the ISIS neutron spallation source; the two materials show the same sequence of phases with tilted octahedra. Diffraction patterns were measured every 5 K allowing structural changes with temperature within a single phase to be determined for the first time. Previous structure determinations within one phase had been performed at a single temperature only. The octahedra are tilted about pseudocubic directions and are also deformed; the magnitude of the deformation is shown to be proportional to the square of the angle of tilt as expected from a phenomenological theory applied to such transitions. The structures of NaNbO(3) between 753 and 793 K and of NaTaO(3) below 758 K are not as reported in the literature.

  16. Electric field gradient at the Nb3M(M = Al, In, Si, Ge, Sn) and T3Al (T = Ti, Zr, Hf, V, Nb, Ta) alloys by perturbed angular correlation method

    International Nuclear Information System (INIS)

    Junqueira, Astrogildo de Carvalho

    1999-01-01

    The electric field gradient (efg) at the Nb site in the intermetallic compounds Nb 3 M (M = Al, Si, Ge, Sn) and at the T site in the intermetallic compounds T 3 Al (T = Ti, Zr, Hf, V, Nb, Ta) was measured by Perturbed Angular Correlation (PAC) method using the well known gamma-gamma cascade of 133-482 keV in 181 Ta from the β - decay of 181 Hf. The compounds were prepared by arc melting the constituent elements under argon atmosphere along with radioactive 181 Hf substituting approximately 0.1 atomic percent of Nb and T elements. The PAC measurements were carried out at 295 K for all compounds and the efg was obtained for each alloy. The results for the efg in the T 3 Al compounds showed a strong correlation with the number of conduction electrons, while for the Nbs M compounds the efg behavior is influenced mainly by the p electrons of the M elements. The so-called universal correlation between the electronic and lattice contribution for the efg in metals was not verified in this work for all studied compounds. Measurements of the quadrupole frequency in the range of 100 to 1210 K for the Nb 3 Al compound showed a linear behaviour with the temperature. Superconducting properties of this alloys may probably be related with this observed behaviour. The efg results are compared to those reported for other binary alloys and discussed with the help of ab-initio methods. (author)

  17. Resistivity of Weyl semimetals NbP and TaP under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Einaga, M.; Shimizu, K. [KYOKUGEN, Graduate School of Engineering Science, Osaka University, Toyonaka (Japan); Hu, J.; Mao, Z.Q. [Department of Physics and Engineering Physics, Tulane University, New Orleans, LA (United States); Politano, A. [Fondazione Istituto Italiano di Tecnologia, Graphene Labs, Genova (Italy)

    2017-08-15

    The resistivity of Weyl semimetals NbP and TaP has been investigated as a function of pressure and temperature. The behaviour of the resistivity as a function of pressure and temperature is closely correlated to the location of the Weyl points compared to the Fermi energy. The rapid increase of the resistivity in TaP and NbP under the application of 4.5 and 8.0 GPa is related with the shift of Weyl points, which affords a finite density of states near the Fermi energy. Specifically, we find that under pressure the Weyl points are situated above the Fermi energy. As regards the temperature behaviour, we detect a nonmonotonous behaviour of resistivity in TaP at 8.7 and 9.8 GPa as a function of temperature, whereas in the case of NbP the behaviour is more complicate. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Mechanical properties and microstructure of Ti-35.5Nb-5.7Ta beta alloy.

    Science.gov (United States)

    Bartakova, S; Prachar, P; Dvorak, I; Hruby, V; Vanek, J; Pospichal, M; Svoboda, E; Martikan, A; Konecna, H; Sedlak, I

    2015-01-01

    Titanium and titanium alloys represent generally accepted metallic biomaterials for clinical dentistry and dental implantology. In this paper, we present a Ti-35.5Nb-5.7Ta alloy with a special respect to its microstructure and mechanical characteristics, such as Young modulus of elasticity. Three thermal treatments differing in temperature and time of annealing were used during the Ti-35.5Nb-5.7Ta processing in order to evaluate the effects of ageing, melting annealing, and annealing on mechanical characteristics and microstructure. Using microscopy, the alloy was analyzed and the differences in shares of beta phase grains, alpha particles and precipitates evaluated. The three thermal treatments were evaluated also from technological point of view. The following thermal treatment was found optimal for the Ti-35.5Nb-5.7Ta alloy: melting annealing at 800 °C for 0.5 hour followed by a cold swaging with a 52-79 % deformation, and final hardening at 500 °C for 2 hours in water(Tab. 2, Fig. 3, Ref. 24).

  19. MRI-compatible Nb-60Ta-2Zr alloy for vascular stents: Electrochemical corrosion behavior in simulated plasma solution.

    Science.gov (United States)

    Li, Hui-Zhe; Zhao, Xu; Xu, Jian

    2015-11-01

    Using revised simulated body fluid (r-SBF), the electrochemical corrosion behavior of an Nb-60Ta-2Zr alloy for MRI compatible vascular stents was characterized in vitro. As indicated by XPS analysis, the surface passive oxide film of approximately 1.3nm thickness was identified as a mixture of Nb2O5, Ta2O5 and ZrO2 after immersion in the r-SBF. The Nb-60Ta-2Zr alloy manifests a low corrosion rate and high polarization resistance similar to pure Nb and Ta, as shown by the potentiodynamic polarization curves and EIS. Unlike 316L stainless steel and the L605 Co-Cr alloy, no localized corrosion has been detected. Semiconducting property of passive film on the Nb-60Ta-2Zr alloy was identified as the n-type, with growth mechanism of high-field controlled growth. The excellent corrosion resistance in simulated human blood enviroment renders the Nb-60Ta-2Zr alloy promising as stent candidate material. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Corrosion resistance and in vitro response of laser-deposited Ti-Nb-Zr-Ta alloys for orthopedic implant applications.

    Science.gov (United States)

    Samuel, Sonia; Nag, Soumya; Nasrazadani, Seifollah; Ukirde, Vaishali; El Bouanani, Mohamed; Mohandas, Arunesh; Nguyen, Kytai; Banerjee, Rajarshi

    2010-09-15

    While direct metal deposition of metallic powders, via laser deposition, to form near-net shape orthopedic implants is an upcoming and highly promising technology, the corrosion resistance and biocompatibility of such novel metallic biomaterials is relatively unknown and warrants careful investigation. This article presents the results of some initial studies on the corrosion resistance and in vitro response of laser-deposited Ti-Nb-Zr-Ta alloys. These new generation beta titanium alloys are promising due to their low elastic modulus as well as due the fact that they comprise of completely biocompatible alloying elements. The results indicate that the corrosion resistance of these laser-deposited alloys is comparable and in some cases even better than the currently used commercially-pure (CP) titanium (Grade 2) and Ti-6Al-4V ELI alloys. The in vitro studies indicate that the Ti-Nb-Zr-Ta alloys exhibit comparable cell proliferation but enhanced cell differentiation properties as compared with Ti-6Al-4V ELI. (c) 2010 Wiley Periodicals, Inc.

  1. Heat treatment processes and mechanical properties of new {beta}-type biomedical Ti-29Nb-13Ta-4.6Zr alloy; Seitaiyo {beta}gata Ti-29Nb-13Ta-4.6Zr gokin no netsushori process to rikigakuteki seishitsu

    Energy Technology Data Exchange (ETDEWEB)

    Kuroda, D.; Niimori, M. [Toyohashi University, Aichi (Japan); Fukui, H.; Hasegawa, J. [Aichi-Gakuin University, Aichi (Japan). School of Denstistry; Suzuki, A. [Daido Steel Co. Ltd., Nagoya (Japan)

    2000-09-01

    Practical size ingot of new 3-type titanium alloy, Ti-29Nb-13Ta-4.6Zr, which was composed of non-toxic elements of Nb, Ta and Zr, with lower modulus of elasticity, high strength and excellent biocompatibility was tried to be fabricated, Then the heat treatment processes of the alloy, which gave a good balance of strength, ductility and modulus of elasticity, were investigated in this study. Practical size ingot of Ti-29Nb-13Ta-4.6Zr with a weight of 17kg has been successfully fabricated. The distribution of alloying elements was homogeneous through the ingot. The practical size ingot can be easily hot forged and cold rolled by a total reduction of 98%. Ti-29Nb-13Ta-4.6Zr which was aged after cold rolling indicates higher strength and lower elongation as compared with those of the alloy aged after solution treatment. In the aging temperature range between 598K and 648K, the alloy indicates relatively higher strength and lower elongation. The precipitation of {omega} phase increases tensile strength and decreases elongation in the alloy aged between 598K and 643K after solution treatment. In the aging temperature above 673K, the precipitation of a phase increases tensile strength and elongation in the alloy aged after solution treatment. New alloy has excellent strength ductility relationship when aging temperature was above 673K. (author)

  2. Mechanical and corrosion resistance of a new nanostructured Ti-Zr-Ta-Nb alloy.

    Science.gov (United States)

    Raducanu, D; Vasilescu, E; Cojocaru, V D; Cinca, I; Drob, P; Vasilescu, C; Drob, S I

    2011-10-01

    In this work, a multi-elementary Ti-10Zr-5Nb-5Ta alloy, with non-toxic alloying elements, was used to develop an accumulative roll bonding, ARB-type procedure in order to improve its structural and mechanical properties. The alloy was obtained by cold crucible semi-levitation melting technique and then was ARB deformed following a special route. After three ARB cycles, the total deformation degree per layer is about 86%; the calculated medium layer thickness is about 13 μm. The ARB processed alloy has a low Young's modulus of 46 GPa, a value very close to the value of the natural cortical bone (about 20 GPa). Data concerning ultimate tensile strength obtained for ARB processed alloy is rather high, suitable to be used as a material for bone substitute. Hardness of the ARB processed alloy is higher than that of the as-cast alloy, ensuring a better behaviour as a implant material. The tensile curve for the as-cast alloy shows an elastoplastic behaviour with a quite linear elastic behaviour and the tensile curve for the ARB processed alloy is quite similar with a strain-hardening elastoplastic body. Corrosion behaviour of the studied alloy revealed the improvement of the main electrochemical parameters, as a result of the positive influence of ARB processing. Lower corrosion and ion release rates for the ARB processed alloy than for the as-cast alloy, due to the favourable effect of ARB thermo-mechanical processing were obtained. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. High-temperature oxidation behaviour of novel Co-Al-W-Ta-B-(Mo, Hf, Nb alloys with a coherent γ/γ'–dominant microstructure

    Directory of Open Access Journals (Sweden)

    Fei Zhong

    2016-12-01

    Full Text Available In this work, 2 at% Mo, 2 at% Nb and 2 at% Hf were substituted for the same amount of W into a Co-9Al-9W-2Ta-0.02B alloy (hereafter referred as to 2Mo, 2Nb and 2Hf alloys, respectively, while the original alloy is denoted as 0Me alloy. The effect of the Mo, Hf and Nb additions on the isothermal oxidation resistance, oxide scale evolution and failure mechanism, of the Co-9Al-9W-2Ta-0.02B alloy when exposed at 800 °C and 900 °C for 100 h was investigated. It was found the Mo, Hf and Nb additions degraded the oxidation resistance of the Co-9Al-9W-2Ta-0.02B alloy, while the 2Mo alloy always displayed the poorest oxidation resistance, resulted from heavy spallation of the oxide scale. An oxide scale composed of an outer Co3O4+CoO layer, a middle complex oxide layer enriched with Al, W and Ta, and a γ/needle-like Co3W zone adhering to the γ/γ' substrate was gradually formed; moreover, a continuous or discontinuous Al2O3 layer and dispersive Al2O3 dots or slices were observed within the γ/needle-like Co3W zone, depending on the oxidation temperature and added elements (Mo, Hf and Nb. The formation of volatile MoO3 in the oxide scale of the 2Mo alloy enhance the exfoliation of the oxide products, resulting in severe spallation and poor oxidation resistance.

  4. The Structure and Magnetic Properties of Pr 3MO7 with M = Nb, Ta, and Sb

    Science.gov (United States)

    Vente, J. F.; Helmholdt, R. B.; IJdo, D. J. W.

    1994-01-01

    The crystal structure of the fluorite-related praseodymium compounds with the composition Pr 3MO7, M = Nb, Ta, and Sb, have been determined using Rietveld refinement from X-ray and neutron powder diffraction data at 293 and 4 K. The structure described is orthorhombic with space group Cmcm (No. 63). It is a superstructure of the cubic fluorite structure with unit cell parameters a orth ≈ 2a c, b orth ≈ c orth ≈ a c2, as in La 3NbO 7. This structure consists of chains of corner linked MO 6 octahedra parallel with the c-axis. The magnetic susceptibility was measured between 4 and 300 K. The compounds obey the Curie-Weiss law including a Van Vleck temperature independent term. Pr 3SbO 7 shows a small deviation from this law below 25 K.

  5. Long Periodic Helimagnetic Ordering in CrM 3S6 (M = Nb and Ta)

    Science.gov (United States)

    Kousaka, Y.; Ogura, T.; Zhang, J.; Miao, P.; Lee, S.; Torii, S.; Kamiyama, T.; Campo, J.; Inoue, K.; Akimitsu, J.

    2016-09-01

    We report long periodic chiral helimagnetic orderings in ferromagnetic inorganic compounds CrM 3S6 (M = Nb and Ta) with a chiral space group of P6322. Magnetization in polycrystalline samples and high resolution powder neutron diffraction were measured. Our powder neutron diffraction measurements in CrM 3S6 successfully separated nuclear and magnetic satellite peaks, having the period of hundreds of angstroms along the c— axis. Therefore, we propose that the magnetic ordering in ferromagnetic CrM3S6 is not ferromagnetic, but long periodic chiral helimagnetic ordering.

  6. Effect of electron count and chemical complexity in the Ta-Nb-Hf-Zr-Ti high-entropy alloy superconductor.

    Science.gov (United States)

    von Rohr, Fabian; Winiarski, Michał J; Tao, Jing; Klimczuk, Tomasz; Cava, Robert Joseph

    2016-11-15

    High-entropy alloys are made from random mixtures of principal elements on simple lattices, stabilized by a high mixing entropy. The recently discovered body-centered cubic (BCC) Ta-Nb-Hf-Zr-Ti high-entropy alloy superconductor appears to display properties of both simple crystalline intermetallics and amorphous materials; e.g., it has a well-defined superconducting transition along with an exceptional robustness against disorder. Here we show that the valence electron count dependence of the superconducting transition temperature in the high-entropy alloy falls between those of analogous simple solid solutions and amorphous materials and test the effect of alloy complexity on the superconductivity. We propose high-entropy alloys as excellent intermediate systems for studying superconductivity as it evolves between crystalline and amorphous materials.

  7. Study of transformation behavior in a Ti-4.4 Ta-1.9 Nb alloy

    International Nuclear Information System (INIS)

    Mythili, R.; Paul, V. Thomas; Saroja, S.; Vijayalakshmi, M.; Raghunathan, V.S.

    2005-01-01

    An alloy of composition Ti-4.4 wt.% Ta-1.9 wt.% Nb is being developed as a structural material for corrosion applications, as titanium and its alloys possess excellent corrosion resistance in many oxidizing media. The primary physical metallurgy database for the Ti-4.4 wt.% Ta-1.9 wt.% Nb alloy is being presented for the first time. Determination of the β transus, M s temperature and classification of the alloy have been carried out, employing a variety of microscopy techniques, X-ray diffraction (XRD), micro-hardness and differential scanning calorimetry (DSC). The β transition temperature or β transus determined using different experimental techniques was found to agree very well with evaluations based on empirical calculations. Based on chemistry and observed room temperature microstructure, the alloy has been classified as an α + β titanium alloy. The high temperature β transforms to either α' or α + β by a martensitic or Widmanstatten transformation. The mechanisms of transformation of β under different conditions and characteristics of different types of α have been studied and discussed in this paper

  8. High-temperature phases of NaNbO3 and NaTaO3

    International Nuclear Information System (INIS)

    Darlington, C.N.W.

    1999-01-01

    The high-temperature phases of the perovskites sodium niobate, NaNbO 3 , and sodium tantalate, NaTaO 3 , have been re-examined using the high-resolution powder diffractometer HRPD at the ISIS neutron spallation source; the two materials show the same sequence of phases with tilted octahedra. Diffraction patterns were measured every 5 K allowing structural changes with temperature within a single phase to be determined for the first time. Previous structure determinations within one phase had been performed at a single temperature only. The octahedra are tilted about pseudocubic left angle 100 right angle directions and are also deformed; the magnitude of the deformation is shown to be proportional to the square of the angle of tilt as expected from a phenomenological theory applied to such transitions. The structures of NaNbO 3 between 753 and 793 K and of NaTaO 3 below 758 K are not as reported in the literature. (orig.)

  9. Cytotoxicity of Group 5 Transition Metal Ditellurides (MTe2; M=V, Nb, Ta).

    Science.gov (United States)

    Chia, Hui Ling; Latiff, Naziah Mohamad; Sofer, Zdenĕk; Pumera, Martin

    2018-01-02

    Much research effort has been put in to study layered compounds with transition metal dichalcogenides (TMDs) being one of the most studied compounds. Due to their extraordinary properties such as excellent electrochemical properties, tuneable band gaps, and low shear resistance due to weak van der Waals interactions between layers, TMDs have been found to have wide applications such as electrocatalysts for hydrogen evolution reactions, supercapacitors, biosensors, field-effect transistors (FETs), photovoltaics, and lubricant additives. In very recent years, Group 5 transition metal ditellurides have received an immense amount of research attention. However to date, little has been known of the potential toxicities posed by these materials. As such, we conducted the cytotoxicity study by incubating various concentrations of the Group 5 transition metal ditellurides (MTe 2 ; M=V, Nb, Ta) with human lung carcinoma epithelial A549 cells for 24 hours and the remaining cell viabilities after treatment was measured. Our findings indicate that VTe 2 is highly toxic whereas NbTe 2 and TaTe 2 are deemed to exhibit mild toxicities. This study constitutes an exemplary first step towards the understanding of the Group 5 transition metal ditellurides' toxicity effects in preparation for their possible future commercialisation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Bone bonding bioactivity of Ti metal and Ti-Zr-Nb-Ta alloys with Ca ions incorporated on their surfaces by simple chemical and heat treatments.

    Science.gov (United States)

    Fukuda, A; Takemoto, M; Saito, T; Fujibayashi, S; Neo, M; Yamaguchi, S; Kizuki, T; Matsushita, T; Niinomi, M; Kokubo, T; Nakamura, T

    2011-03-01

    Ti15Zr4Nb4Ta and Ti29Nb13Ta4.6Zr, which do not contain the potentially cytotoxic elements V and Al, represent a new generation of alloys with improved corrosion resistance, mechanical properties, and cytocompatibility. Recently it has become possible for the apatite forming ability of these alloys to be ascertained by treatment with alkali, CaCl2, heat, and water (ACaHW). In order to confirm the actual in vivo bioactivity of commercially pure titanium (cp-Ti) and these alloys after subjecting them to ACaHW treatment at different temperatures, the bone bonding strength of implants made from these materials was evaluated. The failure load between implant and bone was measured for treated and untreated plates at 4, 8, 16, and 26 weeks after implantation in rabbit tibia. The untreated implants showed almost no bonding, whereas all treated implants showed successful bonding by 4 weeks, and the failure load subsequently increased with time. This suggests that a simple and economical ACaHW treatment could successfully be used to impart bone bonding bioactivity to Ti metal and Ti-Zr-Nb-Ta alloys in vivo. In particular, implants heat treated at 700 °C exhibited significantly greater bone bonding strength, as well as augmented in vitro apatite formation, in comparison with those treated at 600 °C. Thus, with this improved bioactive treatment process these advantageous Ti-Zr-Nb-Ta alloys can serve as useful candidates for orthopedic devices. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  11. Are lithium niobate (LiNbO{sub 3}) and lithium tantalate (LiTaO{sub 3}) ferroelectrics bioactive?

    Energy Technology Data Exchange (ETDEWEB)

    Vilarinho, Paula Maria, E-mail: paula.vilarinho@ua.pt; Barroca, Nathalie; Zlotnik, Sebastian; Félix, Pedro; Fernandes, Maria Helena

    2014-06-01

    The use of functional materials, such as ferroelectrics, as platforms for tissue growth in situ or ex situ, is new and holds great promise. But the usage of materials in any bioapplication requires information on biocompatibility and desirably on bioactive behavior when bone tissue engineering is envisaged. Both requirements are currently unknown for many ferroelectrics. Herein the bioactivity of LiNbO{sub 3} and LiTaO{sub 3} is reported. The formation of apatite-like structures on the surface of LiNbO{sub 3} and LiTaO{sub 3} powders after immersion in simulated body fluid (SBF) for different soaking periods indicates their bioactive potential. The mechanism of apatite formation is suggested. In addition, the significant release of lithium ions from the ferroelectric powders in the very first minutes of soaking in SBF is examined and ways to overcome this likely hurdle addressed. - Highlights: • LiNbO{sub 3} and LiTaO{sub 3} are bioactive ferroelectrics. • Cauliflower apatite type structures indicative of in-vitro bioactivity of LiNbO{sub 3} and LiTaO{sub 3.} • Negative surface charges anchor Ca{sup 2+} to which PO{sub 4}{sup 3−} attracts forming apatite structure nuclei. • Use of ferroelectrics as platforms for tissue growth in situ or ex situ is new and holds great promise.

  12. Solid electrolytes Sr(Ba)6Nb(Ta)2O11 with structural disordering of oxygen sublattice

    International Nuclear Information System (INIS)

    Nejman, A.Ya.; Podkorytov, A.L.; Yurkovskaya, N.Yu.; Zhukovskij, V.M.

    1986-01-01

    Electric conductivity at alternating and direct current and ratio of ionic component of conductivity in M 2 O-M 2 5 O 5 systems (M 2 -Sr, Ba; M 5 -Nb, Ta) are measured. High ionic conductivity of M 6 2 M 2 5 O 11 compounds is shown to be conducted by structural disordering of oxygen sublattice

  13. Study on ( n,t) Reactions of Zr, Nb and Ta Nuclei

    Science.gov (United States)

    Tel, E.; Yiğit, M.; Tanır, G.

    2012-04-01

    The world faces serious energy shortages in the near future. To meet the world energy demand, the nuclear fusion with safety, environmentally acceptability and economic is the best suited. Fusion is attractive as an energy source because of the virtually inexhaustible supply of fuel, the promise of minimal adverse environmental impact, and its inherent safety. Fusion will not produce CO2 or SO2 and thus will not contribute to global warming or acid rain. Furthermore, there are not radioactive nuclear waste problems in the fusion reactors. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. Because, tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. And also, the success of fusion power system is dependent on performance of the first wall, blanket or divertor systems. So, the performance of structural materials for fusion power systems, understanding nuclear properties systematic and working out of ( n,t) reaction cross sections are very important. Zirconium (Zr), Niobium (Nb) and Tantal (Ta) containing alloys are important structural materials for fusion reactors, accelerator-driven systems, and many other fields. In this study, ( n,t) reactions for some structural fusion materials such as 88,90,92,94,96Zr, 93,94,95Nb and 179,181Ta have been investigated. The calculated results are discussed andcompared with the experimental data taken from the literature.

  14. Osseointegration behavior of novel Ti-Nb-Zr-Ta-Si alloy for dental implants: an in vivo study.

    Science.gov (United States)

    Wang, Xiaona; Meng, Xing; Chu, Shunli; Xiang, Xingchen; Liu, Zhenzhen; Zhao, Jinghui; Zhou, Yanmin

    2016-09-01

    This study aimed to evaluate the effects of Ti-Nb-Zr-Ta-Si alloy implants on mineral apposition rate and new BIC contact in rabbits. Twelve Ti-Nb-Zr-Ta-Si alloy implants were fabricated and placed into the right femur sites in six rabbits, and commercially pure titanium implants were used as controls in the left femur. Tetracycline and alizarin red were administered 3 weeks and 1 week before euthanization, respectively. At 4 weeks and 8 weeks after implantation, animals were euthanized, respectively. Surface characterization and implant-bone contact surface analysis were performed by using a scanning electron microscope and an energy dispersive X-ray detector. Mineral apposition rate was evaluated using a confocal laser scanning microscope. Toluidine blue staining was performed on undecalcified sections for histology and histomorphology evaluation. Scanning electron microscope and histomorphology observation revealed a direct contact between implants and bone of all groups. After a healing period of 4 weeks, Ti-Nb-Zr-Ta-Si alloy implants showed significantly higher mineral apposition rate compared to commercially pure titanium implants (P implants and commercially pure titanium implants (P > 0.05) at 8 weeks. No significant difference of bone-to-implant contact was observed between Ti-Nb-Zr-Ta-Si alloy implants and commercially pure titanium implants implants after a healing period of 4 weeks and 8 weeks. This study showed that Ti-Nb-Zr-Ta-Si alloy implants could establish a close direct contact comparedto commercially pure titanium implants implants, improved mineral matrix apposition rate, and may someday be an alternative as a material for dental implants.

  15. Experimental Evidence for Linear Metal-Azide Coordination: The Binary Group 5 Azides [Nb(N3)5], [Ta(N3)5], [Nb(N3)6], and [Ta(N3)6], and 1:1 Acetonitrile Adducts [Nb(N3)5(CH3CN)] and (Ta(N3)5(CH3CN))

    Science.gov (United States)

    2006-03-20

    significantly longer than the equatorial ones, as expected from VSEPR argu- ments.[29] In contrast, the axial M-N-N arrangements in [Nb(N3)5] and [Ta(N3)5...Int. Ed. 2000, 39, 2108. [29] a) R. J. Gillespie, I. Hargittai, The VSEPR Model of Molecular Geometry, Allyn and Bacon, Needham Heights, MA, 1991; b

  16. Experimental Evidence for Linear Metal-Azide Bonds. The Binary Group 5 Azides Nb(N3)5, Ta(N3)5, [Nb(N3)6]- and [Ta(N3)6]-, and 1:1 Adducts of Nb(N3)5 and [Ta(N3)5 with CH3CN] (POSTPRINT)

    Science.gov (United States)

    2006-04-27

    the equatorial ones, as expected from VSEPR argu- ments.[29] In contrast, the axial M-N-N arrangements in [Nb(N3)5] and [Ta(N3)5] are calculated to be...2108. [29] a) R. J. Gillespie, I. Hargittai, The VSEPR Model of Molecular Geometry, Allyn and Bacon, Needham Heights, MA, 1991; b) R. J. Gillespie, P

  17. Visible light-induced electronic structure modulation of Nb- and Ta-doped α-Fe2O3 nanorods for effective photoelectrochemical water splitting

    Science.gov (United States)

    Chang, Han-Wei; Fu, Yanming; Lee, Wan-Yi; Lu, Ying-Rui; Huang, Yu-Cheng; Chen, Jeng-Lung; Chen, Chi-Liang; Chou, Wu Ching; Chen, Jin-Ming; Lee, Jyh-Fu; Shen, Shaohua; Dong, Chung-Li

    2018-02-01

    The photoelectrochemical (PEC) water splitting activity of Nb and Ta-doped hematite (α-Fe2O3) nanorods was investigated with reference to electronic structures by in situ synchrotron x-ray absorption spectroscopy (XAS). Current density-potential measurements demonstrate that the PEC activity of α-Fe2O3 nanorods depends strongly on the species and concentrations of dopants. The doping of α-Fe2O3 nanorods with a low level of Nb or Ta can improve their electrical conductivity and thereby facilitate charge transport and reduced electron-hole recombination therein. The photoconversion effects of Nb and Ta-doped α-Fe2O3 by in situ XAS in the dark and under illumination revealed opposite evolutions of the spectral intensities of the Fe L-edge and Nb/Ta L-edge, indicating that charge transfer and a conduction pathway are involved in the photoconversion. Analytic in situ XAS results reveal that the α-Fe2O3 that is doped with a low level of Nb has a greater photoconversion efficiency than that doped with Ta because Nb sites are more active than Ta sites in α-Fe2O3. The correlation between PEC activity and the electronic structure of Nb/Ta-doped α-Fe2O3 is examined in detail using in situ XAS and helps to elucidate the mechanism of PEC water splitting in terms of the electronic structure.

  18. Pressure-induced superconductivity in the semiconducting metal-cluster compounds Ga(Ta,Nb) sub 4 (Se,S) sub 8

    CERN Document Server

    Ni Bing Fa

    2002-01-01

    The effect of pressure on the electronic and structural properties of GaNb sub 4 Se sub 8 , GaNb sub 4 S sub 8 and GaTa sub 4 Se sub 8 has been investigated. Measurements of the magnetic susceptibility and electrical resistance at ambient pressure showed anomalies at low temperatures (GaNb sub 4 Se sub 8 and GaNb sub 4 S sub 8 : 35 K; GaTa sub 4 Se sub 8 : 55 K). These are suggested to be related to a structural distortion of a lower symmetry which results in a change of the population of spin states. The analysis of the temperature dependence of the electrical resistance as a function of increasing pressure shows a transition from semiconducting to metallic behavior in GaNb sub 4 Se sub 8 (p>22.5 GPa) and in GaTa sub 4 Se sub 8 (p>13 GPa) but not in GaNb sub 4 S sub 8 up to p=31 GPa. This has been explained to be due to stronger localized Nb(4d)-states (larger energy gap) than in GaNb sub 4 Se sub 8 and Ta(5d)-states in GaTa sub 4 Se sub 8. Most interesting is the observation of a pressure-induced supercondu...

  19. Dirac cone in two dimensional bilayer graphene by intercalation with V, Nb, and Ta transition metals

    Science.gov (United States)

    Pakhira, Srimanta; Lucht, Kevin P.; Mendoza-Cortes, Jose L.

    2018-02-01

    Bilayer graphene (BLG) is a semiconductor whose band gap and properties can be tuned by various methods such as doping or applying gate voltage. Here, we show how to tune electronic properties of BLG by intercalation of transition metal (TM) atoms between two monolayer graphene (MLG) using a novel dispersion-corrected first-principle density functional theory (DFT) approach. We intercalated V, Nb, and Ta atoms between two MLG. We found that the symmetry, the spin, and the concentration of TM atoms in BLG-intercalated materials are the important parameters to control and to obtain a Dirac cone in their band structures. Our study reveals that the BLG intercalated with one vanadium (V) atom, BLG-1V, has a Dirac cone at the K-point. In all the cases, the present DFT calculations show that the 2pz sub-shells of C atoms in graphene and the 3dyz sub-shells of the TM atoms provide the electron density near the Fermi energy level (EF) which controls the material properties. Thus, we show that out-of-plane atoms can influence in-plane electronic densities in BLG and enumerate the conditions necessary to control the Dirac point. This study offers insight into the physical properties of 2D BLG intercalated materials and presents a new strategy for controlling the electronic properties of BLG through TM intercalation by varying the concentration and spin arrangement of the metals resulting in various conducting properties, which include: metal, semi-metal and semiconducting states.

  20. Electronic parameters of Sr2M2O7 (M = V, Nb, Ta) and Sr-O chemical bonding

    DEFF Research Database (Denmark)

    Atuchin, Victor V.; Grivel, Jean-Claude; Zhang, Zhaoming

    2010-01-01

    on the formation of the Sr-O bonds. The chemical bonding effects were considered on the basis of our XPS results for Sr2Nb2O7 and Sr2Ta2O7 and the previously published structural and XPS data for other Sr-oxide compounds. A new empirical relationship between Δ(O-Sr) and L(Sr-O) was obtained. Possible applications...

  1. Al-, Nb-, and Ta-based perfluoroaryloxide anions as cocatalysts for metallocene-mediated Ziegler-Natta olefin polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Y.; Metz, M.V.; Stern, C.L.; Marks, T.J.

    2000-05-01

    Perfluoroaryloxide salts of the formula Ph{sub 3}C{sup +}-Al(OC{sub 6}F{sub 5}){sub 4}{sup {minus}} and Ph{sub 3}C{sup +}M(OC{sub 6}F{sub 5}){sub 6}{sup {minus}} (M = Nb, Ta) have been synthesized and characterized. In combination with sterically encumbered zirconocene dimethyl complexes, they yield active ethylene polymerization catalysts.

  2. Tetrahydrometalate species VH(2)(H(2)), NbH(4), and TaH(4): matrix infrared spectra and quantum chemical calculations.

    Science.gov (United States)

    Wang, Xuefeng; Andrews, Lester

    2011-12-15

    Laser ablated V, Nb, and Ta atoms react with molecular hydrogen in excess neon at 4 K to give vanadium, niobium, and tantalum dihydrides that further react with H(2) to form VH(2)(H(2)), NbH(4), and TaH(4). The reaction products are identified by deuterium and deuterium hydride isotopic substitution. DFT and CCSD theoretical calculations are used to predict energies, geometries, and vibrational frequencies for these novel metal hydrides complex and molecules. The vanadium dihydride hydrogen complex, VH(2)(H(2)), is identified, while the niobium and tantalum tetrahydrides, NbH(4) and TaH(4,) with D(2d) symmetry structures are confirmed. Reactions of group 5 metal atoms with H(2) condensing in solid hydrogen gave VH(2)(H(2)) and the higher tetrahydride-hydrogen complexes NbH(4)(H(2))(4) and TaH(4)(H(2))(4).

  3. TiZrNbTaMo high-entropy alloy designed for orthopedic implants: As-cast microstructure and mechanical properties.

    Science.gov (United States)

    Wang, Shao-Ping; Xu, Jian

    2017-04-01

    Combining the high-entropy alloy (HEA) concept with property requirement for orthopedic implants, we designed a Ti 20 Zr 20 Nb 20 Ta 20 Mo 20 equiatomic HEA. The arc-melted microstructures, compressive properties and potentiodynamic polarization behavior in phosphate buffer solution (PBS) were studied in detail. It was revealed that the as-cast TiZrNbTaMo HEA consisted of dual phases with bcc structure, major bcc1 and minor bcc2 phases with the lattice parameters of 0.3310nm and 0.3379nm, respectively. As confirmed by nanoindentation tests, the bcc1 phase is somewhat harder and stiffer than the bcc2 phase. The TiZrNbTaMo HEA exhibited Young's modulus of 153GPa, Vickers microhardness of 4.9GPa, compressive yield strength of σ y =1390MPa and apparent plastic strain of ε p ≈6% prior to failure. Moreover, the TiZrNbTaMo HEA manifested excellent corrosion resistance in PBS, comparable to the Ti6Al4V alloy, and pitting resistance remarkably superior to the 316L SS and CoCrMo alloys. These preliminary advantages of the TiZrNbTaMo HEA over the current orthopedic implant metals in mechanical properties and corrosion resistance offer an opportunity to explore new orthopedic-implant alloys based on the TiZrNbTaMo concentrated composition. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Experimental Evidence for Linear Metal-Azide Bonds. The Binary Group 5 Azides Nb(N3)5, Ta(N3)5, [Nb(N3)6]- and [Ta(N3)6]-, and 1:1 Adducts of Nb(N3)5 and Ta(N3)5 with CH3CN

    Science.gov (United States)

    2005-04-27

    bonds are significantly longer than the equatorial ones, as expected from VSEPR arguments.[29] In contrast, the axial M-N-N bonds in Nb(N3)5 and Ta...Klapötke, H. Nöth, T. Schütt, M. Warchhold, Angew. Chem. Int. Ed. 2000, 39, 2108. [29] (a) R. J. Gillespie, I. Hargittai, The VSEPR Model of

  5. Experimental Evidence for Linear Metal-Azide Bonds. The Binary Group 5 Azides Nb(N3)5, Ta(N3)5, [Nb(N3)6]- and [Ta(N3)6]-, and 1:1 Adducts of Nb(N3)5 and Ta(N3)5 with CH3CN (PREPRINT)

    Science.gov (United States)

    2006-03-20

    than the equatorial ones, as expected from VSEPR arguments.[29] In contrast, the axial M-N-N bonds in Nb(N3)5 and Ta(N3)5 are calculated to be almost...Angew. Chem. Int. Ed. 2000, 39, 2108. [29] (a) R. J. Gillespie, I. Hargittai, The VSEPR Model of Molecular Geometry, Allyn and Bacon, A Division of

  6. Electrodeposited ultrafine NbOx, ZrOx, and TaO x nanoparticles on carbon black supports for oxygen reduction electrocatalysts in acidic media

    KAUST Repository

    Seo, Jeongsuk

    2013-09-06

    A remarkable electrocatalytic activity was obtained for the oxygen reduction reaction (ORR) in acidic solutions on ultrafine nano-oxide catalysts based on group IV or V elements. By potentiostatic electrodepostion in nonaqueous solutions at 298 K followed by heat treatment in H2 gas, highly dispersed fine nanoparticles of NbOx, ZrOx, and TaOx with sizes of less than 5 nm were prepared and deposited on carbon black (CB) loaded electrodes. These oxide nanoparticles showed high catalytic activities with high onset potentials of 0.96 VRHE (NbOx), 1.02 VRHE (ZrOx), and 0.93 V RHE (TaOx) for the ORR. Owing to the high chemical stability of group IV and V oxides, the catalysts were very stable during the ORR in acidic solutions. Surface characterization and chemical identification were performed using scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). All results clearly indicate the formation of nano-oxide electrocatalysts that show an outstanding ORR performance, whereas the bulk oxides are not active because of the absence of electronic conductivity. The present work demonstrates potential candidates for highly stable, non-noble-metal cathode catalysts for polymer electrolyte fuel cells (PEFCs), where the catalysts are exposed to highly acidic and oxidizing conditions. © 2013 American Chemical Society.

  7. Structure and magnetic properties of NdFeB thin films with Cr, Mo, Nb, Ta, Ti, and V buffer layers

    International Nuclear Information System (INIS)

    Jiang, H.; O'Shea, M.J.

    2000-01-01

    Layers of NdFeB of the form A(20 nm)/NdFeB(d nm)/A(20 nm) where A represents Cr, Mo, Nb, Ta, Ti, V were prepared on a silicon substrate by magnetron sputtering. The purpose is to determine how (i) the chosen buffer layer and (ii) NdFeB layer thickness d (especially d 2 Fe 14 B with no preferred crystalline orientation. Our highest coercivities occur for buffer layer elements from row five of the periodic table, 20 kOe (1600 kA/m) in a Nb buffered sample with d of 180 nm and 17 kOe (1350 kA/m) in a Mo buffered sample with d of 180 nm. Buffer layers from row four (Ti, V, and Cr) and row six (Ta) all give lower coercivities. Our largest energy product, 10.3 MG-Oe (82 kJ/m 3 ), is obtained for the Mo buffered sample. Average Nd 2 Fe 14 B crystallite size for this sample is 27 nm. Only the Cr and Ti buffered films show a large coercivity (≥2 kOe) for d of 54 nm with the Cr films showing the highest coercivity, 2.7 kOe (215 kA/m). In films subjected to a rapid thermal anneal (anneal time 30 s) we find that both the coercivity and energy product are larger than in samples subjected to a 20 min anneal. In our Nb buffered systems we obtain coercivities as high as 26.3 kOe (2090 kA/m) after a rapid thermal anneal

  8. Crystal structure and X-ray photoemission spectroscopic study of A{sub 2}LaMO{sub 6} [A=Ba, Ca; M=Nb, Ta

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Alo, E-mail: alo_dutta@yahoo.com [Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India); Saha, Sujoy [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Kumari, Premlata [Department of Chemistry, Government P.G. College, Lansdowne, Pauri-Garhwal 246139 (India); Sinha, T.P. [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Shannigrahi, Santiranjan [Institute of Materials Research and Engineering, Agency for Science Technology and Research, 3 Research Link, Singapore 117602 (Singapore)

    2015-09-15

    The X-ray photoemission spectroscopic (XPS) study of the double perovskite oxides A{sub 2}LaMO{sub 6} [A=Ba, Ca; M=Nb, Ta] synthesized by the solid-state reaction technique has been carried out to investigate the nature of the chemical state of the constituent ions and the bonding between them. The Rietveld refinement of the X-ray diffraction patterns suggests the monoclinic crystal structure of all the materials at room temperature. The negative and positive chemical shifts of the core level XPS spectrum of O-1s and Nb-3d{sub 3/2}/Ta-4f{sub 5/2} respectively suggest the covalent bonding between Nb/Ta cations and O ion. The change of the bonding strength between the anion and the cations from one material to another has been analyzed. The vibrational property of the materials is investigated using the room temperature Raman spectra. A large covalency of Ta-based compound than Nb compound is confirmed from the relative shifting of the Raman modes of the materials. - Graphical abstract: Crystal structure of two perovskite oxides CLN and CLT is investigated. XPS study confirms the two different co-ordination environments of Ca and covalent bonding between B-site cations and O-ion. - Highlights: • Ordered perovskite structure obtained by Rietveld refinement of XRD patterns. • Study of nature of chemical bonding by X-ray photoemission spectroscopy. • Opposite chemical shift of d-states of Nb/Ta with respect to O. • Covalent bonding between d-states of Nb/Ta and O. • Relative Raman shifts of CLN and CLT substantiate the more covalent character of Ta than Nb.

  9. Source and fractionation controls on subduction-related plutons and dike swarms in southern Patagonia (Torres del Paine area) and the low Nb/Ta of upper crustal igneous rocks

    Science.gov (United States)

    Müntener, Othmar; Ewing, Tanya; Baumgartner, Lukas P.; Manzini, Mélina; Roux, Thibaud; Pellaud, Pierre; Allemann, Luc

    2018-05-01

    The subduction system in southern Patagonia provides direct evidence for the variability of the position of an active continental arc with respect to the subducting plate through time, but the consequences on the arc magmatic record are less well studied. Here we present a geochemical and geochronological study on small plutons and dykes from the upper crust of the southern Patagonian Andes at 51°S, which formed as a result of the subduction of the Nazca and Antarctic plates beneath the South American continent. In situ U-Pb geochronology on zircons and bulk rock geochemical data of plutonic and dyke rocks are used to constrain the magmatic evolution of the retro-arc over the last 30 Ma. We demonstrate that these combined U-Pb and geochemical data for magmatic rocks track the temporal and spatial migration of the active arc, and associated retro-arc magmatism. Our dataset indicates that the rear-arc area is characterized by small volumes of alkaline basaltic magmas at 29-30 Ma that are characterized by low La/Nb and Th/Nb ratios with negligible arc signatures. Subsequent progressive eastward migration of the active arc culminated with the emplacement of calc-alkaline plutons and dikes 17-16 Ma with elevated La/Nb and Th/Nb ratios and typical subduction signatures constraining the easternmost position of the southern Patagonian batholith at that time. Geochemical data on the post-16 Ma igneous rocks including the Torres del Paine laccolith indicate an evolution to transitional K-rich calc-alkaline magmatism at 12.5 ± 0.2 Ma. We show that trace element ratios such as Nb/Ta and Dy/Yb systematically decrease with increasing SiO2, for both the 17-16 Ma calc-alkaline and the 12-13 Ma K-rich transitional magmatism. In contrast, Th/Nb and La/Nb monitor the changes in the source composition of these magmas. We suggest that the transition from the common calc-alkaline to K-rich transitional magmatism involves a change in the source component, while the trace element ratios

  10. Micro-nanocomposites Al2O3/ NbC/ WC and Al2O3/ NbC/ TaC

    International Nuclear Information System (INIS)

    Santos, Thais da Silva

    2014-01-01

    Alumina based ceramics belong to a class of materials designated as structural, which are widely used in cutting tools. Although alumina has good properties for application as a structural ceramics, composites with different additives have been produced with the aim of improving its fracture toughness and mechanical strength. New studies point out micro-nanocomposites, wherein the addition of micrometric particles should enhance mechanical strength, and nano-sized particles enhance fracture toughness. In this work, alumina based micro nanocomposites were obtained by including nano-sized NbC and micrometer WC particles at 2:1, 6:4, 10:5 and 15:10 vol% proportions, and also with the inclusion of nano-sized NbC and micrometer TaC particles at 2:1 vol% proportion. For the study of densification, micro-nanocomposites were sintered in a dilatometer with a heating rate of 20°C/min until a temperature of 1800°C in argon atmosphere. Based on the dilatometry results, specimens were sintered in a resistive graphite furnace under argon atmosphere between 1500°C and 1700°C by holding the sintering temperature for 30 minutes. Densities, crystalline phases, hardness and tenacity were determined, and micro-nanocomposites microstructures were analyzed. The samples Al 2 O 3 : NbC: TaC sintered at 1700 ° C achieved the greater apparent density (~ 95% TD) and the sample sintered at 1600 ° C showed homogeneous microstructure and increased hardness value (15.8 GPa) compared to the pure alumina . The compositions with 3% inclusions are the most promising for future applications. (author)

  11. Fission of Al, Ti, Co, Zr, Nb, Ag, In, Nd, Sm, and Ta nuclei induced by 0.8-1.8 GeV photons

    International Nuclear Information System (INIS)

    Lima, D.A. de; Martins, J.B.; Tavares, O.A.P.

    1989-01-01

    Samples of Al, Ti, Co, Zr, Nb, Ag, In, Nd, Sm, and Ta elements in contact with solid state nuclear track detectors were exposed to 0.8-1.8 GeV bremsstrahlung beams at the 2.5-GeV Electron Synchrotron of the Bonn University. The detectors were processed to produce visible fission tracks for track analysis with optical microscopes. Absolute mean cross section per photon and fissility were evaluated. Results are discussed and compared with other photofission data as well as with estimates from the current fission models. A broad minimum found for nuclear fissility of 10 -4 -10 -3 covering the range 15 approx Z 2 /A approx 25 seems to confirm the predictions from the models. For Al and Ti nuclei the probability of fission amounts to approx 10 -1 . (author) [pt

  12. Determination of superstructures and magnetic structures in the system (Fe,Mn)(Nb,Ta)2O6 with elastic neutron scattering experiments

    International Nuclear Information System (INIS)

    Klein, S.

    1976-01-01

    The aim of this work was to study the magnetic structures of the Trirutil FeTa 2 O 6 and the Columbit MnTa 2 O 6 . A further question was the influence of the nonmagnetic positive Ions on the developing magnetic structure. One example is the mixed-crystal series Mn(Nb,Ta) 2 O 6 . The different magnetic structures of FeNb 2 O 6 and MnNb 2 O 6 , having the same chemical structure, causes the existence of a transition region between these two magnetic structures. Neutron diffration is a well-suited method to investigate the character of these concentration-dependent phase tansitions. All experiments have been performed with elastic neutrons, and a new set-up for measurrement of low temperatures has been used. For the evaluaion of these data two computer programs are developed. (orig./HPOE) [de

  13. Magnetic torque study of Weyl semimetal compounds TaP and NbP up to 45 Tesla

    Science.gov (United States)

    Li, Gang; Asaba, Tomoya; Tinsman, Colin; Yu, Fan; Lawson, Benjamin; Chen, Yulin; Li, Lu

    Weyl semimetal is a recently proposed new state in condensed matter physics, in which the bulk bands could have three dimensional linear dispersion but the degeneracy at the cross point is lifted into a pair of Weyl points with opposite chirality. Among the predicted candidates, Tantalum monophorspide (TaP) and Niobium monophorspide (NbP) have the simplest composition and do not require extrinsic tuning. Photoemission data is accumulating and the unique Fermi-arc surface state is observed. Magnetotransport experiments has shown highly anisotropic magnetoresistance and quantum oscillations has been observed. Because both linear dispersive bands and conventional bands exist in these materials, a detailed study of the electronic strucuture of the bulk is highly desirable. We use torque magnetometry to study quantum oscillations of TaP and NbP down to 300 mK, and up to 45 Tesla, with focus on the angular dependence of oscillation frequencies. Our comparison shows clear difference in geometry of different bulk bands in these materials. Besides, a discussion will be made on high field torque data since 45 Tesla is high enough to push several of the bands into quantum limit.

  14. Porous Nb-Ti-Ta alloy scaffolds for bone tissue engineering: Fabrication, mechanical properties and in vitro/vivo biocompatibility.

    Science.gov (United States)

    Liu, Jue; Ruan, Jianming; Chang, Lin; Yang, Hailin; Ruan, Wei

    2017-09-01

    Porous Nb-Ti-Ta (at.%) alloys with the pore size of 100-600μm and the porosity of 50%-80% were fabricated by the combination of the sponge impregnation technique and sintering method. The results revealed that the pores were well connected with three-dimensional (3D) network structure, which showed morphological similarity to the anisotropic porous structure of human bones. The results also showed that the alloys could provide the compressive Young's modulus of 0.11±0.01GPa to 2.08±0.09GPa and the strength of 17.45±2.76MPa to 121.67±1.76MPa at different level of porosity, indicating that the mechanical properties of the alloys are similar to those of human bones. Pore structure on the compressive properties was also discussed on the basis of the deformation mode. The relationship between compressive properties and porosity was well consistent with the Gibson-Ashby model. The mechanical properties could be tailored to match different requirements of the human bones. Moreover, the alloys had good biocompatibility due to the porous structure with higher surface, which were suitable for apatite formation and cell adhesion. In conclusion, the porous Nb-Ti-Ta alloy is potentially useful in the hard tissue implants for the appropriate mechanical properties as well as the good biocompatible properties. Copyright © 2017. Published by Elsevier B.V.

  15. In situ resistance measurements of bronze process Nb-Sn-Cu-Ta multifilamentary composite conductors during reactive diffusion

    International Nuclear Information System (INIS)

    Tan, K S; Hopkins, S C; Glowacki, B A; Majoros, M; Astill, D

    2004-01-01

    The conditions under which the Nb 3 Sn intermetallic layer is formed by solid-state reactive diffusion processes in bronze process multifilamentary conductors greatly influence the performance of the conductors. By convention, isothermal heat treatment is used and often causes non-uniformity of A15 layers formed across the wire. Therefore, characterization and optimization of the conductor during the reactive diffusion processes is crucial in order to improve the overall conductor's performance. In this paper, a different characterization approach and perhaps an optimization technique is presented, namely in situ resistance measurement by an alternating current (AC) method. By treating the components of such multifilamentary wires as a set of parallel resistors, the resistances of the components may be combined using the usual rules for resistors in parallel. The results show that the resistivity of the entire wire changes significantly during the reactive diffusion processes. The development of the Nb 3 Sn layer in bronze process Nb-Sn-Cu-Ta multifilamentary wires at different stages of the reactive diffusion processes has been monitored using measured resistivity changes, and correlated with results from DTA, ACS, SEM and EDS

  16. Magnetic resonance as a local probe for linear bands in the Weyl semimetals NbP and TaP

    Energy Technology Data Exchange (ETDEWEB)

    Baenitz, Michael; Yasuoka, Hiroshi; Majumder, Mayukh; Shekhar, Chandra; Yan, Binghai; Felser, Claudia; Schmidt, Marcus [MPI for Chemical Physics of Solids, Dresden (Germany)

    2016-07-01

    Some compensated d-electron semimetals, for example the monophosphites NbP and TaP, with non centrosymmetric structure and with sizable spin orbit coupling (SOC) form a new class of material: the Weyl semimetals (WSM). A unique linear crossing of valence- and conduction- band in a single point in reciprocal space defines the so called Weyl point where the fermion mass vanishes theoretically. In real materials the Fermi level E{sub F} does not exactly match the Weyl node and as a consequence residual very light fermions are found. Due to the SOC these Weyl fermions have a chirality (handedness) on their linear dispersive (E ∝k) bands and frequently a linear density of states (DOS) at the Fermi level E{sub F}. We use NMR as a probe for this linear d- electron bands. The shift provides the s- and d- electron contributions to the DOS at E{sub F}, whereas the spin lattice relaxation is governed by low energy excitations around E{sub F}. {sup 31}P (I = 1/2) - Fourier - transform - and {sup 95}Nb (I = 9/2) - broadline - sweep - NMR studies are performed. We investigated powder samples as well as single crystals on both systems. The angular dependence of the {sup 95}Nb- and {sup 31}P - NMR lines is discussed.

  17. Electric properties of textured (K0.44Na0.52Li0.04)(Nb0.86Ta0 ...

    Indian Academy of Sciences (India)

    Abstract. Textured (K0.44Na0.52Li0.04) (Nb0.86Ta0.10Sb0.04)O3 thick film was fabricated by the screen printing method with plate-like NaNbO3 particles as template. Thick film with 75% grain orientation was prepared. Rem- nant polarization and coercive field observed from the P–E loops of textured thick film were 3.6 μC ...

  18. Phase Composition of a CrMo0.5NbTa0.5TiZr High Entropy Alloy: Comparison of Experimental and Simulated Data

    OpenAIRE

    Fan Zhang; Oleg N. Senkov; Jonathan D. Miller

    2013-01-01

    Microstructure and phase composition of a CrMo0.5NbTa0.5TiZr high entropy alloy were studied in the as-solidified and heat treated conditions. In the as-solidified condition, the alloy consisted of two disordered BCC phases and an ordered cubic Laves phase. The BCC1 phase solidified in the form of dendrites enriched with Mo, Ta and Nb, and its volume fraction was 42%. The BCC2 and Laves phases solidified by the eutectic-type reaction, and their volume fractions were 27% and 31%, respectively....

  19. Neutron diffraction study on formation and structure of Dsub(x)TaS2 and Hsub(x)NbS2

    International Nuclear Information System (INIS)

    Riekel, C.; Reznik, H.G.; Schoellhorn, R.; Wright, C.J.

    1978-09-01

    Cathodic reduction of 2H-TaS 2 in D 2 SO 4 was investigated by transient neutron powder diffractometry. Deuterium was found to enter the lattice in a regular way. The structural model proposed implies a strong Ta-D bond. Single crystal neutron diffraction data on Hsub(0.76)NbS 2 confirm the position of hydrogen in a three center metal bond inside the dichalcogenide layers. Structural data are in accordance with inelastic neutron scattering data. (author)

  20. Characterization of the Microstructure of the Compositionally Complex Alloy Al1Mo0.5Nb1Ta0.5Ti1Zr1 (Postprint)

    Science.gov (United States)

    2016-05-01

    grain boundaries of the Al1Mo0.5Nb1Ta0.5Ti1Zr1 sample. EBSD inverse pole figure (IPF) maps overlaid with image quality ( IQ ) micrographs, shown in Fig. 1...tomographic recon- structions using the STEM-HAADF and the Ta and Zr XEDS spectral im- ages are shown in Fig. 4. Themorphology of the disordered bcc phase

  1. Influence of oxygen on omega phase stability in the Ti-29Nb-13Ta-4.6Zr alloy

    International Nuclear Information System (INIS)

    Niinomi, Mitsuo; Nakai, Masaaki; Hendrickson, Mandana; Nandwana, Peeyush; Alam, Talukder; Choudhuri, Deep; Banerjee, Rajarshi

    2016-01-01

    The effect of oxygen on stability of isothermal omega precipitates in Ti-29Nb-13Ta-4.6Zr was examined using X-ray powder diffraction, transmission electron microscopy, and atom probe tomography. Two alloys with 0.1 and 0.4 mass% oxygen were subjected to single step, and two-step annealing heat-treatments to respectively promote omega and alpha formation. After second step annealing, large volume fraction of omega precipitates was retained in 0.4 mass% O alloy while mainly alpha phase was observed in TNTZ-0.1O. The enhanced stability of omega in the higher oxygen containing TNTZ alloys questions the conventionally accepted understanding that oxygen destabilizes the omega phase in titanium alloys.

  2. First principles study of structural, vibrational and electronic properties of graphene-like MX2 (M=Mo, Nb, W, Ta; X=S, Se, Te) monolayers

    International Nuclear Information System (INIS)

    Ding Yi; Wang Yanli; Ni Jun; Shi Lin; Shi Siqi; Tang Weihua

    2011-01-01

    Using first principles calculations, we investigate the structural, vibrational and electronic structures of the monolayer graphene-like transition-metal dichalcogenide (MX 2 ) sheets. We find the lattice parameters and stabilities of the MX 2 sheets are mainly determined by the chalcogen atoms, while the electronic properties depend on the metal atoms. The NbS 2 and TaS 2 sheets have comparable energetic stabilities to the synthesized MoS 2 and WS 2 ones. The molybdenum and tungsten dichalcogenide (MoX 2 and WX 2 ) sheets have similar lattice parameters, vibrational modes, and electronic structures. These analogies also exist between the niobium and tantalum dichalcogenide (NbX 2 and TaX 2 ) sheets. However, the NbX 2 and TaX 2 sheets are metals, while the MoX 2 and WX 2 ones are semiconductors with direct-band gaps. When the Nb and Ta atoms are doped into the MoS 2 and WS 2 sheets, a semiconductor-to-metal transition occurs. Comparing to the bulk compounds, these monolayer sheets have similar structural parameters and properties, but their vibrational and electronic properties are varied and have special characteristics. Our results suggest that the graphene-like MX 2 sheets have potential applications in nano-electronics and nano-devices.

  3. Development of Low Cost Membranes (Ta, Nb & Cellulose Acetate) for H2/CO2 Separation in WGS Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Seetala, Naidu [Grambling State Univ., LA (United States); Siriwardane, Upali [Louisiana Tech Univ., Ruston, LA (United States)

    2011-12-15

    The main aim of this work is to synthesize low temperature bimetallic nanocatalysts for Water Gas Shift reaction (WGS) for hydrogen production from CO and steam mixture; and develop low-cost metal (Nb/Ta)/ceramic membranes for H2 separation and Cellulose Acetate membranes for CO2 separation. .

  4. Ab initio study of structural, elastic, and vibrational properties of transition-metal disilicides NbSi2 and TaSi2 in hexagonal C40 structure

    Science.gov (United States)

    Ertürk, Esra; Gürel, Tanju

    2018-05-01

    We present an ab initio study of structural, elastic and vibrational properties of transition-metal disilicides NbSi2 and TaSi2. The calculations have been carried out within the density-functional theory and linear-response formalism using norm-conserving pseudopotentials and a plane-wave basis. The calculated lattice parameters, bulk moduli, and elastic constants agree well with previous theoretical and experimental results. The calculated phonon frequencies at the Brillouin zone center are in good agreement with the reported Raman spectra and provide reference values for the future infrared and neutron phonon measurements. Phonon dispersion relations, mode Grüneisen parameters, and total and partial phonon density of states are also discussed. Mode Grüneisen parameters of NbSi2 and TaSi2 at Brillouin zone center show similar trends and all values are found to be positive. From phonon dispersion relations and phonon density of states, we have found a gap around 200 cm-1 for TaSi2, where the frequencies below this gap mainly belong to Ta vibrations and frequencies above the gap is mainly related with Si vibrations. In the case of NbSi2, there is no such gap and both Nb and Si atoms contribute to the phonon density of states in an energy range of 150-270 cm-1.

  5. Fractionation of Li, Be, Ga, Nb, Ta, In, Sn, Sb, W and Bi in the peraluminous Early Permian Variscan granites of the Cornubian Batholith: Precursor processes to magmatic-hydrothermal mineralisation

    Science.gov (United States)

    Simons, Beth; Andersen, Jens C. Ø.; Shail, Robin K.; Jenner, Frances E.

    2017-05-01

    The Early Permian Variscan Cornubian Batholith is a peraluminous, composite pluton intruded into Devonian and Carboniferous metamorphosed sedimentary and volcanic rocks. Within the batholith there are: G1 (two-mica), G2 (muscovite), G3 (biotite), G4 (tourmaline) and G5 (topaz) granites. G1-G2 and G3-G4 are derived from greywacke sources and linked through fractionation of assemblages dominated by feldspars and biotite, with minor mantle involvement in G3. G5 formed though flux-induced biotite-dominate melting in the lower crust during granulite facies metamorphism. Fractionation enriched G2 granites in Li (average 315 ppm), Be (12 ppm), Ta (4.4 ppm), In (74 ppb), Sn (18 ppm) and W (12 ppm) relative to crustal abundances and G1 granites. Gallium (24 ppm), Nb (16 ppm) and Bi (0.46 ppm) are not significantly enriched during fractionation, implying they are more compatible in the fractionating assemblage. Sb (0.16 ppm) is depleted in G1-G2 relative to the average upper and lower continental crust. Muscovite, a late-stage magmatic/subsolidus mineral, is the major host of Li, Nb, In, Sn and W in G2 granites. G2 granites are spatially associated with W-Sn greisen mineralisation. Fractionation within the younger G3-G4 granite system enriched Li (average 364 ppm), Ga (28 ppm), In (80 ppb), Sn (14 ppm), Nb (27 ppm), Ta (4.6 ppm), W (6.3 ppm) and Bi (0.61 ppm) in the G4 granites with retention of Be in G3 granites due to partitioning of Be into cordierite during fractionation. The distribution of Nb and Ta is controlled by accessory phases such as rutile within the G4 granites, facilitated by high F and lowering the melt temperature, leading to disseminated Nb and Ta mineralisation. Lithium, In, Sn and W are hosted in biotite micas which may prove favourable for breakdown on ingress of hydrothermal fluids. Higher degrees of scattering on trace element plots may be attributable to fluid-rock interactions or variability within the magma chamber. The G3-G4 system is more boron

  6. Quaternary germanides RE{sub 3}TRh{sub 4}Ge{sub 4} (RE = Ce, Pr, Nd; T = Nb, Ta) - a new coloring variant of the aristotype AlB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Rolf-Dieter; Vosswinkel, Daniel; Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Matar, Samir F. [CNRS, Universite de Bordeaux, ICMCB, UPR 9048, 33600 Pessac (France)

    2016-09-15

    The quaternary germanides RE{sub 3}TRh{sub 4}Ge{sub 4} (RE = Ce, Pr, Nd; T = Nb, Ta) were synthesized from the elements by arc-melting and subsequent annealing in a muffle furnace. The structure of Ce{sub 3}TaRh{sub 4}Ge{sub 4} was refined from single-crystal X-ray diffractometer data: new type, Pbam, a = 719.9(2), b = 1495.0(3), c = 431.61(8), wR{sub 2} = 0.0678, 1004 F{sup 2} values, and 40 variables. Isotypy of the remaining phases was evident from X-ray powder patterns. Ce{sub 3}TaRh{sub 4}Ge{sub 4} is a new superstructure variant of the aristotype AlB{sub 2} with an ordering of cerium and tantalum on the aluminum site, whereas the honey-comb network is built up by a 1:1 ordering of rhodium and germanium. This crystal-chemical relationship is discussed based on a group-subgroup scheme. The distinctly different size of tantalum and cerium leads to a pronounced puckering of the [Rh{sub 4}Ge{sub 4}] network, which shows the shortest interatomic distances (253-271 pm Rh-Ge) within the Ce{sub 3}TaRh{sub 4}Ge{sub 4} structure. Another remarkable structural feature concerns the tantalum coordination with six shorter Ta-Rh bonds (265-266 pm) and six longer Ta-Ge bonds (294-295 pm). The [Rh{sub 4}Ge{sub 4}] network fully separates the tantalum and cerium atoms (Ce-Ce > 387 pm, Ta-Ta > 431 pm, and Ce-Ta > 359 pm). The electronic density of states DOS from DFT calculations show metallic behavior with large contributions of localized Ce 4f as well as itinerant ones from all constituents at the Fermi level but no significant magnetic polarization on Ce could be identified. The bonding characteristics described based on overlap populations illustrate further the crystal chemistry observations of the different coordination of Ce1 and Ce2 in Ce{sub 3}TaRh{sub 4}Ge{sub 4}. The Rh-Ge interactions within the network are highlighted as dominant. The bonding magnitudes follow the interatomic distances and identify differences of Ta bonding vs. Ce1/Ce2 bonding with the Rh and Ge

  7. Analysis of sodium metal by X-ray fluorescence spectrometry (I). Determination of Hf, Mo, Nb, Ta, Ti, V and Zr

    International Nuclear Information System (INIS)

    Diaz-Guerra, J. P.

    1981-01-01

    A method allowing the determination of trace quantities of Hf, Mo, Nb, Ta, Ti, Vi and Zr in sodium metal previous transformation into Na 2 S0 4 is described. The enrichment of the impurities is performed through a coprecipitation technique in sulfuric medium by using Fe 3 + as a collector and cupferron or phenyfluorone as the precipitating reagent. The matrix influence and the best concentration of the collector (10/μ/ml), adequate pH (1,3 or 4, respectively) and optimum filter type (Millipore BSWP02500 or BDWP04700, respectively) have been studied, as well as the precipitation recoveries corresponding to the reagent above. It has been demonstrated the batter efficiency of the cupferron for determining all the Impurities. Detection limits range from 0.01 to 0.2 ppm., depending on the element, for samples 4 g in weight. An automatic spectrometer attached to a 16 K minicomputer and X-ray tube with a gold anode (2250-2700 W) are used. The Interferences between the lines ZrKα (2 n d order) - HfLα and TiKβ - VK α have been studied and the respective correction coefficients have been deduced. (Author) 8 refs

  8. Binary and tertiary reaction cross-sections of V, Cr, Mn, Fe, Ni, Cu, Zr, Nb, Mo, Ta, W, Pt and their isotopes

    International Nuclear Information System (INIS)

    Garg, S.B.

    1982-01-01

    Neutron induced binary and tertiary reaction cross-sections have been evaluated for V, Cr, Mn, Fe, Ni, Cu, Zr, Nb, Mo, Ta, W, Pt and their isotopes in the 'energy range 0.5 MeV to 20 MeV using the nuclear statistical empirical model. The reactions considered are (n,n'), (n,2n), (n,3n), (n,p), (n,d), (n,t), (n, 3 He), (n,α), (n,np), (n,nd), (n,nt), (n,n 3 He), (n,nα), (n,pn), (n,2p), (n,ν), (n,αp), (n,dn) and (n,pα). Most of the above mentioned elements are used as structural materials in nuclear reactors and the measured cross-section data for the above listed reactions are seldom available for the radiation damage and safety analysis. With a view to providing these data, this nuclear model based evaluation has been undertaken. The associated uncertainties in the cross-sections and their fission averages have also been evaluated. (author)

  9. Spectrophotometric determination of traces of Ti, Zr, Hf, Nb, Ta and V after selective separation with B.P.H.A. - Application to uranium compounds

    International Nuclear Information System (INIS)

    Lamarque, Gerard

    1971-08-01

    The extraction of traces of Ti, Zr, Hf, Nb and Ta using 0.1 per cent, 0. 2 per cent and 0.5 per cent HCl-N-benzoylphenyl-hydroxylamine in benzene was investigated. A further extraction with HCl-HF allowed the concentration of each component to be obtained by spectrophotometric means. The proposed techniques, which are simple and selective, applied to uranium solutions enabled the detection down to 0.15 ppm Ti, 0.08 ppm Zr, 0.12 ppm Hf, 0.05 ppm Nb and 0.15 ppm Ta with two 5 gram uranium test samples. A further 4 gram test sample enabled V to be detected down to 0. 25 ppm [fr

  10. Effects of shot-peening and atmospheric-pressure plasma on aesthetic improvement of Ti-Nb-Ta-Zr alloy for dental applications

    Science.gov (United States)

    Miura-Fujiwara, Eri; Suzuki, Yuu; Ito, Michiko; Yamada, Motoko; Matsutake, Sinpei; Takashima, Seigo; Sato, Hisashi; Watanabe, Yoshimi

    2018-01-01

    Ti and Ti alloys are widely used for biomedical applications such as artificial joints and dental devices because of their good mechanical properties and biochemical compatibility. However, dental devices made of Ti and Ti alloys do not have the same color as teeth, so they are inferior to ceramics and polymers in terms of aesthetic properties. In a previous study, Ti-29Nb-13Ta-4.6Zr was coated with a white Ti oxide layer by heat treatment to improve its aesthetic properties. Shot-peening is a severe plastic deformation process and can introduce a large shear strain on the peened surface. In this study, the effects of shot-peening and atmospheric-pressure plasma on Ti-29Nb-13Ta-4.6Zr were investigated to form a white layer on the surface for dental applications.

  11. Increasing strength of a biomedical Ti-Nb-Ta-Zr alloy by alloying with Fe, Si and O.

    Science.gov (United States)

    Stráský, Josef; Harcuba, Petr; Václavová, Kristína; Horváth, Klaudia; Landa, Michal; Srba, Ondřej; Janeček, Miloš

    2017-07-01

    Low-modulus biomedical beta titanium alloys often suffer from low strength which limits their use as load-bearing orthopaedic implants. In this study, twelve different Ti-Nb-Zr-Ta based alloys alloyed with Fe, Si and O additions were prepared by arc melting and hot forging. The lowest elastic modulus (65GPa) was achieved in the benchmark TNTZ alloy consisting only of pure β phase with low stability due to the 'proximity' to the β to α'' martensitic transformation. Alloying by Fe and O significantly increased elastic modulus, which correlates with the electrons per atom ratio (e/a). Sufficient amount of Fe/O leads to increased yield stress, increased elongation to fracture and also to work hardening during deformation. A 20% increase in strength and a 20% decrease in the elastic modulus when compared to the common Ti-6Al-4V alloy was achieved in TNTZ-Fe-Si-O alloys, which proved to be suitable for biomedical use due to their favorable mechanical properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Development of the dislocation arrangement in high-purity Nb-34 at% Ta alloy single crystals deformed in tension

    International Nuclear Information System (INIS)

    Wasserbaech, W.

    1995-01-01

    The deformation behaviour and the dislocation arrangement of high-purity Nb-34 at% Ta alloy single crystals after tensile deformation at 330 K into different stages are studied by slip-line observations, Laue X-ray back-reflection, X-ray topography, and transmission electron microscopy (TEM). In stage I of the work-hardening curve, the dislocation arrangement consists predominantly of primary dislocations, which are clustered into bundles in the form of braids. Fine slip traces on the surface of the specimens show that the slip proceeds homogeneously in the whole volume of the crystal. Stage II, which is a characteristic property of f.c.c. metals, is missing. Instead, the experimental findings suggest that a gradual transition occurs from stage I into stage III. The transition region is characterized by a pronounced formation of dislocation sheets approximately parallel to the primary slip plane. The dislocation sheets are crossed grids of primary and secondary dislocations and occur in pairs. The secondary slip necessary for the formation of the dislocation sheets is found to occur in the direction favoured by the applied shear stress. In spite of the different dislocation arrangements, the slip processes in stage I and stage III seem to be essentially the same. In both cases the macroscopic slip proceeds by glide of primary dislocations over large slip distances, whereby the plane that carries the maximum resolved shear stress (MRSS) is the active macroscopic slip plane. (orig.)

  13. Influence of Heat Treatment and UV Irradiation on the Wettability of Ti35Nb10Ta Nanotubes

    Directory of Open Access Journals (Sweden)

    Joan Lario

    2018-01-01

    Full Text Available The implant osseointegration rate depends on the surface’s topography and chemical composition. There is a growing interest in the anodic oxidation process to obtain an oxide layer with a nanotube morphology on beta titanium alloys. This surface treatment presents large surface area, nanoscale rugosity and electrochemical properties that may increase the biocompatibility and osseointegration rate in titanium implants. In this work, an anodic oxidation process was used to modify the surface on the Ti35Nb10Ta alloy to obtain a titanium nanotubes topography. The work focused on analyzing the influence of some variables (voltage, heat treatment and ultraviolet irradiation on the wettability performance of a titanium alloy. The morphology of the nanotubes surfaces was studied by Field Emission Scanning Electron Microscopy (FESEM, and surface composition was analyzed by Energy Dispersive Spectroscopy (EDS. The measurement of contact angle for the TiO2 nanotube surfaces was measured by a video contact angle system. The surface with the non photoinduced nanotubes presented the largest contact angles. The post-heat treatment lowered the F/Ti ratio in the nanotubes and decreased the contact angle. Ultraviolet (UV irradiation of the TiO2 nanotubes decrease the water contact angle.

  14. Estudio de las soluciones de los ferroeléctricos LiNbO3 y LiTaO3

    Directory of Open Access Journals (Sweden)

    Villafuerte Castrejón, M. E.

    2002-06-01

    Full Text Available Ceramic compounds LiNbO3 and LiTaO3 have been widely studied in the last years due to their interesting optical and electrical properties (piezoelectricity, piroelectricity, ferroelectricity. For this reason these materials are regarded excellent candidates for technological applications. An important characteristic of these compounds is the facility to form solid solution series, a large number of cations can be accommodated in the lattice and thus different optical and electrical properties have been obtained. In this work a review of LiNbO3 and LiTaO3 solid solutions is presented, the formation mechanisms, cation sites in the unitcell and some of the most representative properties are also included.Los compuestos cerámicos LiNbO3 y LiTaO3 han sido estudiados considerablemente en los últimos años, debido a las interesantes propiedades ópticas y eléctricas (piezoelectricidad, piroelectricidad, ferroelectricidad que presentan. Por estas razones estos materiales se consideran excelentes candidatos para un gran número de aplicaciones tecnológicas. Una característica importante de estos compuestos, es la facilidad con la que forman series de soluciones sólidas, incorporando diferentes cationes en sus redes. Se han obtenido series de soluciones sólidas con cationes de diferente tamaño y diferente carga con la consiguiente variación de las propiedades eléctricas y ópticas. En este trabajo se presenta un resumen de los estudios de las soluciones sólidas de LiNbO3 y LiTaO3, los mecanismos de formación y los sitios que ocupan los cationes en la celda unidad, así como algunas de sus propiedades físicas más representativas.

  15. Characterization, electrical transport and magnetic properties of the rare earth misfit layer compounds (TbS)(1.21)NbS2, (TbS)(1.20)TaS2, (DyS)(1.22)NbS2 and (DyS)(1.21)TaS2

    NARCIS (Netherlands)

    Zhou, W.Y.; Meetsma, A.; deBoer, J.L.; Wiegers, G.A

    1996-01-01

    X-ray powder and single-crystal X-ray diffraction of the title compounds showed that they are planar intergrowth compounds, built of alternating sandwiches TS2 (T=Nb, Ta) and double layers LnS (Ln=Tb, Dy), present in three orientational variants related by rotations of 120 degrees around the c axis

  16. The effect of microstructure and temperature on the oxidation behavior of two-phase Cr-Cr2X (X=Nb,Ta) alloys

    International Nuclear Information System (INIS)

    Brady, M.P.; Tortorelli, P.F.

    1998-01-01

    The oxidation behavior of Cr(X) solid solution (Cr ss ) and Cr 2 X Laves phases (X = Nb, Ta) was studied individually and in combination at 950--1,100 C in air. The Cr ss phase was significantly more oxidation resistant than the Cr 2 X Laves phase. At 950 C, two-phase alloys of Cr-Cr 2 Nb and Cr-Cr 2 Ta exhibited in-situ internal oxidation, in which remnants of the Cr 2 X Laves phase were incorporated into a growing chromia scale. At 1,100 C, the Cr-Cr 2 Nb alloys continued to exhibit in-situ internal oxidation, which resulted in extensive O/N penetration into the alloy ahead of the alloy-scale interface and catastrophic failure during cyclic oxidation. IN contrast, the Cr-Cr 2 Ta alloys exhibited a transition to selective Cr oxidation and the formation of a continuous chromia scale. The oxidation mechanism is interpreted in terms of multiphase oxidation theory

  17. Phase Composition of a CrMo0.5NbTa0.5TiZr High Entropy Alloy: Comparison of Experimental and Simulated Data

    Directory of Open Access Journals (Sweden)

    Fan Zhang

    2013-09-01

    Full Text Available Microstructure and phase composition of a CrMo0.5NbTa0.5TiZr high entropy alloy were studied in the as-solidified and heat treated conditions. In the as-solidified condition, the alloy consisted of two disordered BCC phases and an ordered cubic Laves phase. The BCC1 phase solidified in the form of dendrites enriched with Mo, Ta and Nb, and its volume fraction was 42%. The BCC2 and Laves phases solidified by the eutectic-type reaction, and their volume fractions were 27% and 31%, respectively. The BCC2 phase was enriched with Ti and Zr and the Laves phase was heavily enriched with Cr. After hot isostatic pressing at 1450 °C for 3 h, the BCC1 dendrites coagulated into round-shaped particles and their volume fraction increased to 67%. The volume fractions of the BCC2 and Laves phases decreased to 16% and 17%, respectively. After subsequent annealing at 1000 °C for 100 h, submicron-sized Laves particles precipitated inside the BCC1 phase, and the alloy consisted of 52% BCC1, 16% BCC2 and 32% Laves phases. Solidification and phase equilibrium simulations were conducted for the CrMo0.5NbTa0.5TiZr alloy using a thermodynamic database developed by CompuTherm LLC. Some discrepancies were found between the calculated and experimental results and the reasons for these discrepancies were discussed.

  18. HNbO3 and HTaO3: new cubic perovskites prepared from LiNbO3 and LiTaO3 via ion exchange

    International Nuclear Information System (INIS)

    Rice, C.E.; Jackel, J.L.

    1982-01-01

    The synthesis of HNbO 3 and HTaO 3 from LiNbO 3 via ion exchange in hot aqueous acid solutions is reported. This reaction is accompanied by a topotactic structural transformation from the rhombohedral LiNbO 3 structure to the cubic perovskite structure; cell constants are a = 3.822(1) angstrom for HNbO 3 and 3.810(2) angstrom for HTaO 3 . These new compounds have been characterized by powder X-ray diffraction, thermogravimetric analysis, and solid-state NMR. They are electronic insulators and have low ionic conductivity. Evidence of partially proton-exchange phases Li/sub 1-x/H/sub x/MO 3 was also seen. The possible significance of this ion exchange reaction for devices using LiNbO 3 or LiTaO 3 is discussed

  19. The influence of Ta on the solidification microstructure and segregation behavior of γ(Ni)/γ′(Ni3Al)–δ(Ni3Nb) eutectic Ni-base superalloys

    International Nuclear Information System (INIS)

    Xie, M.; Helmink, R.; Tin, S.

    2013-01-01

    Highlights: ► Ta and Nb have a nominally identical influence on equilibrium δ volume fraction. ► Ta and Nb impact the sequence and segregation differently during solidification. ► Microstructure varies with both overall Ta + Nb level and Ta/Nb ratio. ► Pandat (PanNi7) is unable to predict trends quantitatively in this system. -- Abstract: Polycrystalline γ/γ′–δ eutectic Ni-base superalloys based on the Ni–Al–Nb alloy system were recently demonstrated to possess excellent high temperature strength and creep resistance. Investigations aimed to establish the fundamental relationships between alloy chemistry, solidification behavior and cast microstructure in these novel Ni–Al–Nb γ/γ′–δ alloy systems are currently underway. This particular study is focused on understanding the influence of Ta additions on the solidification sequence, phase volume fraction, distribution coefficient and solid state partitioning parameter of this eutectic alloy system by systematically investigating a series of experimental alloys with nominally constant overall levels of Ta + Nb content but varying Ta/Nb ratios. Although many of the tendencies observed in these multi-component γ/γ′–δ eutectic alloys are in agreement with trends observed in lower order model alloy systems, Ta additions were found to significantly modify solidification characteristics of the alloys. The experimental observations were also used to critically assess the predictive capability of thermodynamic database calculations. Despite the qualitative agreement observed between the experimental results and predictions for relatively simple quaternary and quinary model alloys, comparison of the results for higher order, multi-component γ/γ′–δ eutectic alloys reveals notable differences

  20. Analysis of sodium metal by X-ray fluorescence spectrometry (I). Determination of Hf, Mo, Nb, Ta, Ti, V and Zr; Analisis de sodio metal por espectrometria de fluorescencia de rayos X. Determinacion de Hf, Mo, Nb, Ta, Ti, V y Zr

    Energy Technology Data Exchange (ETDEWEB)

    Diaz-Guerra, J. P.

    1981-07-01

    A method allowing the determination of trace quantities of Hf, Mo, Nb, Ta, Ti, Vi and Zr in sodium metal previous transformation into Na{sub 2}S0{sub 4} is described. The enrichment of the impurities is performed through a coprecipitation technique in sulfuric medium by using Fe{sup 3}+ as a collector and cupferron or phenyfluorone as the precipitating reagent. The matrix influence and the best concentration of the collector (10/{mu}/ml), adequate pH (1,3 or 4, respectively) and optimum filter type (Millipore BSWP02500 or BDWP04700, respectively) have been studied, as well as the precipitation recoveries corresponding to the reagent above. It has been demonstrated the batter efficiency of the cupferron for determining all the Impurities. Detection limits range from 0.01 to 0.2 ppm., depending on the element, for samples 4 g in weight. An automatic spectrometer attached to a 16 K minicomputer and X-ray tube with a gold anode (2250-2700 W) are used. The Interferences between the lines ZrK{alpha} (2{sup n}d order) - HfL{alpha} and TiK{beta} - VK {alpha} have been studied and the respective correction coefficients have been deduced. (Author) 8 refs.

  1. Influence of the B-site ordering on the magnetic properties of the new La3Co2MO9 double perovskites with M = Nb or Ta

    International Nuclear Information System (INIS)

    Fuertes, V.C.; Blanco, M.C.; Franco, D.G.; De Paoli, J.M.; Sanchez, R.D.; Carbonio, R.E.

    2011-01-01

    Double perovskites La 3 Co 2 NbO 9 and La 3 Co 2 TaO 9 have been prepared by both solid state and sol-gel synthesis. The crystal structures have been studied from X-ray and neutron powder diffraction data. Rietveld refinements show that the crystal structure is monoclinic (P2 1 /n), with different degrees of ordering of B' and B'' cations, with octahedra tilted according to the Glazer notation a - b - c + . Occupancy refinements show that the solid state materials are more B-site ordered than the sol-gel ones. Magnetization measurements show that these perovskites show two magnetic contributions, one with spontaneous magnetization and other with linear behaviour with the magnetic field associated to antiferromagnetic correlations. In the samples synthesized by solid state the spontaneous magnetization is more important than those synthesized by the sol-gel and present T C of 62 K for Nb and 72 K for Ta. On the other hand, materials prepared by sol-gel have T C 20 K for Nb and 40 K for Ta, respectively and major presence of the antiferromagnetic contribution. The competition between these magnetic behaviours is interpreted, by a microscopic point of view, as to be due to the different degrees of Co 2+ ions disorder on the B site of the double perovskite structure. This disorder affects the ratio between the antiferromagnetic Co 2+ -O-Co 2+ and the ferromagnetic Co 2+ -O-M 5+ -O-Co 2+ couplings proposed for the system.

  2. Electrochemical characterization of pulsed layer deposited hydroxyapatite-zirconia layers on Ti-21Nb-15Ta-6Zr alloy for biomedical application

    Energy Technology Data Exchange (ETDEWEB)

    Izquierdo, Javier [Department of Chemistry, Universidad de La Laguna, P.O. Box 456, E-38200 La Laguna, Tenerife (Spain); Bolat, Georgiana [“Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering and Environmental Protection, 73 Prof. Dr. Doc. D. Mangeron Street, 700050 Iasi (Romania); Cimpoesu, Nicanor [“Gheorghe Asachi” Technical University of Iasi, Faculty of Materials Science, 61-63 Prof. Dr. Doc. D. Mangeron Street, 700050 Iasi (Romania); Trinca, Lucia Carmen [Science Department, University of Agricultural Sciences and Veterinary Medicine, M. Sadoveanu Alley 3, 700490 Iasi (Romania); Mareci, Daniel, E-mail: danmareci@yahoo.com [“Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering and Environmental Protection, 73 Prof. Dr. Doc. D. Mangeron Street, 700050 Iasi (Romania); Souto, Ricardo Manuel, E-mail: rsouto@ull.es [Department of Chemistry, Universidad de La Laguna, P.O. Box 456, E-38200 La Laguna, Tenerife (Spain); Institute of Material Science and Nanotechnology, Universidad de La Laguna, E-38200 La Laguna, Tenerife (Spain)

    2016-11-01

    Highlights: • New quarternary Ti-based alloy for biomaterial application. • Combined hydroxyapatite-zirconia coating produced by pulsed laser deposition. • Porous layer formed on the coated alloy blocks electron transfer reactions. • Electrochemical behaviour consistent with passive film with duplex structure. • HA–ZrO{sub 2} coated Ti-21Nb-15Ta-6Zr exhibits high potential for osseointegration. - Abstract: A new titanium base Ti-21Nb-15Ta-6Zr alloy covered with hydroxyapatite-zirconia (HA–ZrO{sub 2}) by pulsed laser deposition (PLD) technique was characterized regarding its corrosion resistance in simulated physiological Ringer’s solution at 37 °C. For the sake of comparison, Ti-6Al-4V standard implant alloy, with and without hydroxyapatite-zirconia coating, was also characterized. Multiscale electrochemical analysis using both conventional averaging electrochemical techniques, namely electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization, and spatially-resolved microelectrochemical techniques (scanning electrochemical microscopy, SECM) were used to investigate the electrochemical behaviour of the materials. In addition, scanning electron microscopy evidenced that no relevant surface morphology changes occurred on the materials upon immersion in the simulated physiological solution, despite variations in their electrochemical behaviour. Although uncoated metals appear to show better performances during conventional corrosion tests, the response is still quite similar for the HA–ZrO{sub 2} coated materials while providing superior resistance towards electron transfer due to the formation of a more dense film on the surface, thus effectively behaving as a passive material. It is believed corrosion of the HA–ZrO{sub 2} coated Ti-21Nb-15Ta-6Zr alloy will have negligible effect upon biochemical and cellular events at the bone-implant interface and could facilitate osseointegration.

  3. Development of NbN Josephson junctions with Ta{sub x}N semi-metal barrier; application to RSFQ circuits; Etude et realisation de jonction Josephson en NbN a barriere semi-metallique en Ta{sub x}N; application aux circuits logiques RSFQ

    Energy Technology Data Exchange (ETDEWEB)

    Setzu, R

    2007-11-15

    This thesis research, brought to the development and optimization of SNS (Superconductor / Normal Metal / Superconductor) Josephson junctions with NbN electrodes and a high resistivity Ta{sub x}N barrier. We were able to point out Josephson oscillations for frequencies above 1 THz and operation temperatures up to 10 K, which constituted the original goal of the project. This property makes these junctions unique and well adapted for realizing ultra-fast RSFQ (Rapid Single Flux Quantum) logic circuits suitable for spatial telecommunications. We showed a good reproducibility of Ta{sub x}N film properties as a function of the sputtering parameters. The NbN/Ta{sub x}N/NbN tri-layers exhibit high critical temperature (16 K). The junctions showed a clear dependence of the R{sub n}I{sub c} product as a function of the partial nitrogen pressure inside the reactive plasma; the R{sub n}I{sub c} is the product between the junction critical current and its normal resistance, and indicates the upper limit Josephson frequency. We have also obtained some really high R{sub n}I{sub c} products, up to 3.74 mV at 4.2 K for critical current densities of about 15 kA/cm{sup 2}. Junctions show the expected Josephson behaviors, respectively Fraunhofer diffraction and Shapiro steps. up to 14 K. This allows expecting good circuit operations in a relaxed cryogenics environment (with respect to the niobium circuits limited at 4.2 K). The junctions appear to be self-shunted. The SNOP junctions J{sub c}-temperature dependence has been fitted by using the long SNS junction model in the dirty limit, which gives a normal metal coherence length of about 3.8 nm at 4.2 K. We have finally studied a multilayer fabrication process, including a common ground plane and bias resistors, suitable for RSFQ logic basic circuits. To conclude we have been able to show the performance superiority of NbN/Ta{sub x}N/NbN junctions over the actual niobium junctions, as well as their interest for realizing compact

  4. Structure and mechanical properties of a two-layered material produced by the E-beam surfacing of Ta and Nb on the titanium base after multiple rolling

    Science.gov (United States)

    Bataev, V. A.; Golkovski, M. G.; Samoylenko, V. V.; Ruktuev, A. A.; Polyakov, I. A.; Kuksanov, N. K.

    2018-04-01

    The study has been conducted in line with the current approach to investigation of materials obtained by considerably deep surface alloying of the titanium substrate with Ta, Nb, and Zr. The thickness of the resulting alloyed layer was equal to 2 mm. The coating was formed through weld deposition of a powder with the use of a high-voltage electron beam in the air. It has been lately demonstrated that manufactured such a way alloyed layers possess corrosion resistance which is significantly higher than the resistance of titanium substrates. It has already been shown that such two-layered materials are weldable. The study objective is to investigate the feasibility of rolling for necking the sheets with the Ti-Ta-Nb anticorrosion coating with further fourfold decrease in their thickness. The research is also aimed at investigation of the material properties after rolling. Anticorrosion layers were formed both on CP-titanium and on VT14 (Ti-4Al-3Mo-1 V) durable titanium alloy. The results of chemical composition determination, structure examination, X-ray phase analysis and mechanical properties observations (including bending properties of the alloyed layers) are presented in the paper. The combination of welding, rolling, and bending enables the manufacture of corrosion-resistant vessels and process pipes which are made from the developed material and find technological application.

  5. Shapes of isolated domains and field induced evolution of regular and random 2D domain structures in LiNbO3 and LiTaO3

    International Nuclear Information System (INIS)

    Chernykh, A.; Shur, V.; Nikolaeva, E.; Shishkin, E.; Shur, A.; Terabe, K.; Kurimura, S.; Kitamura, K.; Gallo, K.

    2005-01-01

    The variety of the shapes of isolated domains, revealed in congruent and stoichiometric LiTaO 3 and LiNbO 3 by chemical etching and visualized by optical and scanning probe microscopy, was obtained by computer simulation. The kinetic nature of the domain shape was clearly demonstrated. The kinetics of domain structure with the dominance of the growth of the steps formed at the domain walls as a result of domain merging was investigated experimentally in slightly distorted artificial regular two-dimensional (2D) hexagonal domain structure and random natural one. The artificial structure has been realized in congruent LiNbO 3 by 2D electrode pattern produced by photolithography. The polarization reversal in congruent LiTaO 3 was investigated as an example of natural domain growth limited by merging. The switching process defined by domain merging was studied by computer simulation. The crucial dependence of the switching kinetics on the nuclei concentration has been revealed

  6. Characterization and corrosion resistance of anodic electrodeposited titanium oxide/phosphate films on Ti-20Nb-10Zr-5Ta bioalloy

    Energy Technology Data Exchange (ETDEWEB)

    Popa, Monica; Vasilescu, Cora; Drob, Silviu I.; Osiceanu, Petre; Anastasescu, Mihai; Calderon-Moreno, Jose M., E-mail: josecalderonmoreno@yahoo.com [Institute of Physical Chemistry ' Ilie Murgulescu' of the Romanian Academy, Bucharest (Romania)

    2013-07-15

    In this work, the anodic galvanostatic electrodeposition of an oxidation film containing phosphates on Ti-20Nb-10Zr-5Ta alloy from orthophosphoric acid solution is presented. Its composition was determined by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman micro-spectroscopy, and its topography by atomic force microscopy (AFM). The corrosion resistance of the coated alloy in simulated human fluid (by linear polarization method and monitoring of open circuit potentials, corresponding open circuit potential gradients) as well as the characterization of the coating (by Raman spectroscopy and depth profile X-ray photoelectron spectroscopy (XPS)) deposited in a period of 300 h soaking in simulated human body fluid were studied. The electrodeposited film was composed of amorphous titanium dioxide and contained phosphate groups. The corrosion resistance of the coated Ti-20Nb-10Zr-5Ta alloy in neutral and alkaline Ringer's solutions was higher than that of the bare alloy due to the protective properties of the electrodeposited film. The corrosion parameters improved over time as result of the thickening of the surface film by the deposition from the physiological solution. The deposited coating presented a variable composition in depth: at the deeper layer nucleated nanocrystalline hydroxyapatite and at the outer layer amorphous calcium phosphate. (author)

  7. Ab-initio study of the stability of the D8{sub m}-Nb{sub 5}Sn{sub 2}Ga and D8{sub m}-Ta{sub 5}SnGa{sub 2} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Colinet, Catherine, E-mail: ccolinet@simap.grenoble-inp.fr [Science et Ingénierie des Matériaux et Procédés, Grenoble INP, UJF, CNRS, 38402 Saint Martin d’Hères Cedex (France); Tedenac, Jean-Claude [Institut de Chimie Moléculaire et des Matériaux I.C.G., UMR-CNRS 5253, Université Montpellier II, Place E. Bataillon, 34095 Montpellier Cedex 5 (France)

    2015-03-15

    Graphical abstract: Thermodynamic data along the sections Ta{sub 5}Sn{sub 3}–Ta{sub 5}Ga{sub 3} at low and high temperature. - Highlights: • First principles calculations were performed along sections V{sub 5}Sn{sub 3}–V{sub 5}Ga{sub 3}, Nb{sub 5}Sn{sub 3}–Nb{sub 5}Ga{sub 3}, and Ta{sub 5}Sn{sub 3}–Ta{sub 5}Ga{sub 3}. • The ternary compound D8{sub m}-Nb{sub 5}Sn{sub 2}Ga is stable. • The phase D8{sub m}-Ta{sub 5}SnGa{sub 2} is stable in the D8{sub m} structure. • In this phase, the Sn and Ga atoms share the 8h sites. - Abstract: First principles calculations have been performed in the T–Sn–Ga (T = V, Nb, Ta) systems along the section x{sub T} = 0.625. The enthalpies of formation of the binary and ternary D8{sub m}, D8{sub 1}, and D8{sub 8} structures have been calculated. In the V–Sn–Ga system, no ternary structure is stable in the section. In the Nb–Sn–Ga system, the ternary compound D8{sub m}-Nb{sub 5}Sn{sub 2}Ga is stable. In the Ta–Sn–Ga system, a combination of the ab-initio calculations and Gibbs energy calculations using the sublattice model allows the show that the phase D8{sub m}-Ta{sub 5}(Sn,Ga){sub 2}Ga with a mixed occupancy of the 8h sites of the structure by Ga and Sn atoms is stable at high temperature due to the configurational entropy. These results are in agreement with the experimental determinations previously published in the literature.

  8. Durability of adhesive bonds to uranium alloys, tungsten, tantalum, and thorium. [U--Nb; Ta--10 percent W

    Energy Technology Data Exchange (ETDEWEB)

    Childress, F. G.

    1975-06-14

    Long-term durability of epoxy bonds to alloys of uranium (U-Nb and Mulberry), nickel-plated uranium, thorium, tungsten, tantalum, tantalum--10 percent tungsten, and aluminum was evaluated. Significant strengths remain after ten years of aging; however, there is some evidence of bond deterioration with uranium alloys and thorium stored in ambient laboratory air.

  9. Role of the (Ta/Nb)O{sub x}/Al{sub 2}O{sub 3} interface on the flatband voltage shift for Al{sub 2}O{sub 3}/(Ta/Nb)O{sub x}/Al{sub 2}O{sub 3} multilayer charge trap capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Nabatame, Toshihide, E-mail: NABATAME.Toshihide@nims.go.jp [MANA Foundry and Nano-Electronics Materials Unit, International Center for Materials Nanoarchitectonics, National Institute for Materials Science (WPI-MANA), 1-1 Namiki, Tsukuba 305-0044, Japan and CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 322-0012 (Japan); Ohi, Akihiko [MANA Foundry, International Center for Materials Nanoarchitectonics, National Institute for Materials Science (WPI-MANA), 1-1 Namiki, Tsukuba 305-0044 (Japan); Ito, Kazuhiro; Takahashi, Makoto [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Chikyo, Toyohiro [Nano-Electronics Materials Unit, International Center for Materials Nanoarchitectonics, National Institute for Materials Science (WPI-MANA), 1-1 Namiki, Tsukuba 305-0044 (Japan)

    2015-01-15

    The authors studied the characteristics of Si/Al{sub 2}O{sub 3}/(Ta/Nb)O{sub x}/Al{sub 2}O{sub 3}/SiO{sub 2}/Pt charge trap capacitors fabricated by atomic layer deposition and postmetallization annealing at 400 °C. Al{sub 2}O{sub 3} and (Ta/Nb)O{sub x} films are amorphous and have negligible fixed charges. In program mode, a flatband voltage (V{sub fb}) drastically shifts toward the positive direction at a short program time of 10{sup −4} s. A large V{sub fb} shift of approximately 4 V arises after programming at 1 mC/cm{sup 2} because there is a large difference in the conduction band offset between the (Ta/Nb)O{sub x}-charge trapping layer (TNO-CTL) and the Al{sub 2}O{sub 3}-blocking layer (AlO-BL) (1.8 eV). In the retention mode, most of the trapped electrons in the TNO-CTL transfers across the Al{sub 2}O{sub 3}-tunneling layer (AlO-TL) rather than the AlO-BL. The thickness of the AlO-TL affects the V{sub fb} shift degradation behavior in the retention mode. The injected electrons are dominantly located at the TNO-CTL/ALO-BL interface, determined from the thickness dependence of the TNO-CTL on the V{sub fb} shift.

  10. Tight-binding calculations of structural energetics of transition metal-carbides. [TiC; ZrC; HfC; VC; NbC; TaC

    Energy Technology Data Exchange (ETDEWEB)

    Le, D.H.; Colinet, C.; Pasturel, A. (Lab. de Thermodynamique et Physico-Chimie Metallurgiques, ENSEEG, 38 - Saint-Martin-d' Heres (France))

    1991-05-01

    A tight-binding recursion method is used to study the electronic and cohesive properties of stoichiometric and substoichiometric transition metal-carbides crystallizing with the NaCl structure. The electronic structure is analyzed in terms of a p-d interaction between the p orbitals of C and the d orbitals of the transition metal. Concerning the cohesive properties of these compounds, we have calculated the energies of formation of stoichiometric (Ti, Zr, Hf, V, Nb, Ta)-C compounds and compared with the experimental values. We have also studied the stability of vacancy-ordered compounds with a vacancy concentration of 50% on the carbon sublattice, i.e. M{sub 2}C compounds. (orig.).

  11. Thermally induced A'-A site exchange in novel layered perovskites Ag2[Ca1.5M3O10] (M = Nb, Ta).

    Science.gov (United States)

    Bhuvanesh, Nattamai S P; Woodward, Patrick M

    2002-12-04

    We have synthesized and characterized new layered perovskites Ag2[A1.5M3O10] (A = Ca, M = Nb, Ta), from their lithium analogues, by soft-chemical ion exchange. These oxides show topotactic irreversible thermally induced A'-A site exchange, resulting in Ag1.1Ca0.9[Ca0.6Ag0.9M3O10], conferred from our high-temperature X-ray and ionic conductivity studies. The latter phases are the first compounds where Ag+ ions reside in both A' and A sites in layered perovskites. The absence of similar phase transition for A = Sr suggests that these transitions strongly depend on the size, charge, and the coordination preference of A' and A cations. This result provides a new synthetic tool for modifying the occupation of the 12-coordinate A site of layered perovskites using soft chemical routes.

  12. Transition metal carbides (WC, Mo2C, TaC, NbC) as potential electrocatalysts for the hydrogen evolution reaction (HER) at medium temperatures

    DEFF Research Database (Denmark)

    Meyer, Simon; Nikiforov, Aleksey V.; Petrushina, Irina M.

    2015-01-01

    used as electrodes and allowed the measurement of the intrinsic catalytic properties of different transition metal carbides in direct comparison to Pt at 260 degrees C. Under these conditions, the activity in the hydrogen evolution reaction (HER) followed the order WC > Pt approximate to MO2C > Nb...... at medium temperatures (200-400 degrees C). By introducing a new setup which makes use of molten KH2PO4 as electrolyte, a model system for solid acid membrane electrolyser cells was obtained. Metal carbide coated wires prepared by a two-step oxidation carburization reaction of the metal wire surfaces were......C > TaC. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved....

  13. First-principles investigation of the stability of MN and CrMN precipitates under coherency strains in α-Fe (M = V, Nb, Ta)

    Science.gov (United States)

    Fors, Dan H. R.; Wahnström, Göran

    2011-06-01

    We perform a systematic ab initio study of the interface energetics of thin coherent rocksalt (nacl) structured MN and tetragonal CrMN films in bcc Fe (M = V, Nb, Ta), motivated by the vital role of MN and CrMN precipitates for the long-term creep resistance in 9%-12%Cr steels. The similarities and differences in the work of separations and the elastic costs for the coherency strains are identified, and the possibility for formation of coherent films are discussed. Our findings provide valuable information of the interface energetics, which in continuation can be combined with thermodynamical modeling to obtain a better understanding of the initial nucleation stage of the MN and CrMN precipitates, and their influence on the long-term microstructural evolution in 9%-12%Cr steels.

  14. Leakage current behavior in lead-free ferroelectric (K,Na)NbO3-LiTaO3-LiSbO3 thin films

    Science.gov (United States)

    Abazari, M.; Safari, A.

    2010-12-01

    Conduction mechanisms in epitaxial (001)-oriented pure and 1 mol % Mn-doped (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.1,Sb0.06)O3 (KNN-LT-LS) thin films on SrTiO3 substrate were investigated. Temperature dependence of leakage current density was measured as a function of applied electric field in the range of 200-380 K. It was shown that the different transport mechanisms dominate in pure and Mn-doped thin films. In pure (KNN-LT-LS) thin films, Poole-Frenkel emission was found to be responsible for the leakage, while Schottky emission was the dominant mechanism in Mn-doped thin films at higher electric fields. This is a remarkable yet clear indication of effect of 1 mol % Mn on the resistive behavior of such thin films.

  15. A new type of Nb (Ta)-Zr(Hf)-REE-Ga polymetallic deposit in the late Permian coal-bearing strata, eastern Yunnan, southwestern China: Possible economic significance and genetic implications

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Shifeng; Wang, Xibo; Luo, Yangbing; Song, Zhentao; Ren, Deyi [State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Beijing 100083 (China); Zhou, Yiping; Zhang, Mingquan; Wang, Jumin; Song, Xiaolin; Yang, Zong [Yunnan Institute of Coal Geology Prospection, Kunming 650218 (China); Jiang, Yaofa [Xuzhou Institute of Architectural Technology, Xuzhou 221116 (China)

    2010-07-01

    This paper describes a new type of Nb(Ta)-Zr(Hf)-REE-Ga polymetallic deposit of volcanic origin in the late Permian coal-bearing strata of eastern Yunnan, southwestern China. Well logging data (especially natural gamma-ray), geochemical data (high concentrations of Nb, Ta, Zr, Hf, REE, and Ga) and mineralogical compositions (Nb(Ta)-, Zr(Hf)-, or REE-bearing minerals rarely observed), together with the volcanic lithological characteristics indicate that there are thick (1-10 m, mostly 2-5 m) ore beds in the lower Xuanwei Formation (late Permian) in eastern Yunann of southwestern China. The ore beds are highly enriched in (Nb,Ta){sub 2}O{sub 5} (302-627 ppm), (Zr,Hf)O{sub 2} (3805-8468 ppm), REE (oxides of La-Lu + Y) (1216-1358 ppm), and Ga (52.4-81.3 ppm). The ore beds are mainly composed of quartz, mixed-layer illite-smectite, kaolinite, berthierine, and albite. Four types of ore beds in the study area were identified, namely, clay altered volcanic ash, tuffaceous clay, tuff, and volcanic breccia. Preliminary studies suggest that the high concentrations of otherwise rare metals were mainly derived from the alkalic pyroclastic rocks. The modes of occurrence, spatial distribution, and enrichment mechanism of the rare metals, however, require further study. (author)

  16. Role of Boron Element on the Electronic Properties of α-Nb5Si3: A First-Principle Study

    Science.gov (United States)

    Pan, Yong; Lin, Yuanhua

    2018-03-01

    Transition metal silicides (TMSis) are attracting increasing interest from the microelectronics and nanoelectronic industries. In this paper, we use the first-principles method to investigate the B-doped mechanism and the influence of B on the electronic properties of α-Nb5Si3. The calculated results show that B-doped Nb5Si3 is thermodynamically stable at the ground state. The calculated electronic structure shows that the thermodynamically stable B-doped Nb5Si3 is attributed to the 3D-network B-Si bonds and B-Nb bond. In particular, B element prefers to occupy B -IT4 site in comparison to other sites. Moreover, the calculated band structure indicates that Nb5Si3 exhibits metallic behavior at the ground state. We find that B-doping can improve charge overlap between conduction band and the valence band, which effectively improves the electronic properties of Nb5Si3.

  17. Beneficial effect of Cu on Ti-Nb-Ta-Zr sputtered uniform/adhesive gum films accelerating bacterial inactivation under indoor visible light.

    Science.gov (United States)

    Alhussein, Akram; Achache, Sofiane; Deturche, Regis; Sanchette, Frederic; Pulgarin, Cesar; Kiwi, John; Rtimi, Sami

    2017-04-01

    This article presents the evidence for the significant effect of copper accelerating the bacterial inactivation on Ti-Nb-Ta-Zr (TNTZ) sputtered films on glass up to a Cu content of 8.3 at.%. These films were deposited by dc magnetron co-sputtering of an alloy target Ti-23Nb-0.7Ta-2Zr (at.%) and a Cu target. The fastest bacterial inactivation of E. coli on this later TNTZ-Cu surface proceeded within ∼75min. The films deposited by magnetron sputtering are chemically homogenous. The film roughness evaluated by atomic force spectroscopy (AFM) on the TNTZ-Cu 8.3 at.% Cu sample presented an RMS-value of 20.1nm being the highest RMS of any Cu-sputtered TNTZ sample. The implication of the RMS value found for this sample leading to the fastest interfacial bacterial inactivation kinetics is also discussed. Values for the Young's modulus and hardness are reported for the TNTZ films in the presence of various Cu-contents. Evaluation of the bacterial inactivation kinetics of E. coli under low intensity actinic hospital light and in the dark was carried out. The stable repetitive bacterial inactivation was consistent with the extremely low Cu-ion release from the samples of 0.4 ppb. Evidence is presented by the bacterial inactivation dependence on the applied light intensity for the intervention of Cu as semiconductor CuO during the bacterial inactivation at the TNTZ-Cu interface. The mechanism of CuO-intervention under light is suggested based on the pH/and potential changes registered during bacterial disinfection. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Evaluation of structure, dielectric and electrical properties of (Li/Ta/Sb modified (Na, K NbO3 lead-free ceramics with excess Na concentration

    Directory of Open Access Journals (Sweden)

    Md. Kashif Shamim

    2017-12-01

    Full Text Available Polycrystalline perovskite structured (Li0.04 (Na0.54+x K0.460.96 (Nb0.81Ta0.15 Sb0.04 O3 ceramics with x=0.00, 0.005 and 0.01 mole excess Na concentration were prepared by solid state sintering method. The present study relates the role of excess Na addition with the stoichiometry, density, structure, dielectric and ferroelectric properties of the samples. X-ray diffraction (XRD pattern exhibits single phase orthorhombic structure. The characteristic Raman modes were observed due to translational modes of cations and vibrational modes of NbO6 octahedra and no structural phase transition were observed. This confirms the formation of single phase perovskite structure and is consistent with XRD results. The dielectric permittivity increases about two times, while dielectric loss decreases by four times for x=0.01 composition. The electrical measurements carried by Complex Impedance spectroscopic analysis suggest negative temperature coefficient of resistance (NTCR behavior.

  19. Nano-nitride cathode catalysts of Ti, Ta, and Nb for polymer electrolyte fuel cells: Temperature-programmed desorption investigation of molecularly adsorbed oxygen at low temperature

    KAUST Repository

    Ohnishi, Ryohji

    2013-01-10

    TiN, NbN, TaN, and Ta3N5 nanoparticles synthesized using mesoporous graphitic (mpg)-C3N4 templates were investigated for the oxygen reduction reaction (ORR) as cathode catalysts for polymer electrolyte fuel cells. The temperature-programmed desorption (TPD) of molecularly adsorbed O2 at 120-170 K from these nanoparticles was examined, and the resulting amount and temperature of desorption were key factors determining the ORR activity. The size-dependent TiN nanoparticles (5-8 and 100 nm) were then examined. With decreasing particle size, the density of molecularly adsorbed O2 per unit of surface area increased, indicating that a decrease in particle size increases the number of active sites. It is hard to determine the electrochemical active surface area for nonmetal electrocatalysts (such as oxides or nitrides), because of the absence of proton adsorption/desorption peaks in the voltammograms. In this study, O2-TPD for molecularly adsorbed O2 at low temperature demonstrated that the amount and strength of adsorbed O2 were key factors determining the ORR activity. The properties of molecularly adsorbed O2 on cathode catalysts are discussed against the ORR activity. © 2012 American Chemical Society.

  20. Microstructural evolution of Ti-10Nb and Ti-15Nb alloys produced by the blended elemental technique

    International Nuclear Information System (INIS)

    Martins, G.V.; Souza, J.V.C.; Machado, J.P.B.; Silva, C.R.M.; Henriques, V.A.R.

    2009-01-01

    Alfa/beta titanium alloys have been intensely used for aerospace and biomedical applications. Production of powder metallurgy titanium alloys components may lead to a reduction in the cost of parts, compared to those produced by conventional cast and wrought (ingot metallurgy) processes, because additional working operations (machining, turning, milling, etc.) and material waste can be avoided. In this work, samples of Ti- 10, 15Nb (weight%) alloys were obtained by the blended elemental technique using hydride-de hydride (HDH) powders as raw material, followed by uniaxial and cold isostatic pressing with subsequent densification by sintering carried out in the range 900-1500 deg C. These alloys were characterized by X-ray diffractometry for phase composition, scanning electron microscopy for microstructure, Vickers indentation for hardness, Archimedes method for specific mass and resonance ultrasound device for elastic modulus. For the samples sintered at 1500 deg C it was identified α and β phases. It was observed the influence of the sintering temperatures on the final microstructure. With increasing sintering temperature, microstructure homogenization of the alloy takes place and at 1500 deg C this process is complete. The same behavior is observed for densification. Comparing to the Ti6Al4V alloy properties, these alloys hardness (sintered at 1500 deg C) are near and elastic modulus are 18% less. (author)

  1. Microstructural comparison between Nb- and Ta-systems in Li{sub 1+x−y}M{sub 1−x−3y}Ti{sub x+4y}O{sub 3} (M = Nb{sup 5+}, Ta{sup 5+}) solid solution with superstructure

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, Hiromi, E-mail: hiromi@crfc.tut.ac.jp [Cooperative Research Facility Center, Toyohashi University of Technology, Toyohashi 441-8580 (Japan); Department of Environmental and Life Sciences, Toyohashi University of Technology, Toyohashi 441-8580 (Japan); Suehiro, Shiho; Furuya, Syohei [Department of Environmental and Life Sciences, Toyohashi University of Technology, Toyohashi 441-8580 (Japan); Fukuda, Koichiro [Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

    2015-01-05

    Highlights: • The composition range of superstructure formed by self-organization was clarified. • The detailed microstructures were analyzed using SEM, XRD and TEM. • The microstructural difference between LNT and LTT was determined. • The superstructure’s formation speed, period and area were controlled by Ti content. - Abstract: We successfully synthesized Li{sub 1+x−y}M{sub 1−x−3y}Ti{sub x+4y}O{sub 3} solid solutions (M = Nb or Ta, LMT, 0.07 ⩽ x ⩽ 0.33, 0 ⩽ y ⩽ 0.175) that have a superstructure, using a conventional electric furnace. The synthesizing time depended on the Ti content, and annealing was repeated for 24–264 h until a homogeneous structure was formed by the insertion of periodical intergrowth layers. We characterized the LMT solid solutions, from micro-scale to nano-scale, using X-ray diffraction, a scanning electron microscope, and a transmission electron microscope. The period of the intergrowth layer was controlled by the Ti content. LNT’s period of the intergrowth layer was narrower than that of LTT in the real lattice when the Ti content was the same. The narrowest interplanar distance (1.82 nm) of the intergrowth layer was formed in Li{sub 0.935}Ta{sub 0.365}Ti{sub 0.810}O{sub 3}. The widest distance (14.3 nm) appeared in Li{sub 1.11}Nb{sub 0.89}Ti{sub 0.11}O{sub 3}, but no such wide period formed in the Ta-system.

  2. Critical thickness for Nb nanofilm on sapphire substrate: a critical analysis using finite element method

    International Nuclear Information System (INIS)

    Kumar, Arun; Subramaniam, Anandh

    2009-01-01

    Full text: On growth beyond critical thickness, interfacial misfit dislocations partially relax the misfit strains, in epitaxially grown nanofilms. In this study the stress state and growth of nanofilms is simulated using Finite Element Method (FEM); by imposing stress-free strains, corresponding to the lattice mismatch between Nb nanofilm and Sapphire substrate. On growth of the Nb nanofilm, a triangular network of edge misfit dislocations nucleates at the (0001) Al2ο3 || (111) Nb , interface. Using a combined simulation of a coherently strained nanofilm and an edge dislocation, the equilibrium criterion for the nucleation of an edge dislocation is determined. Theoretical analyses in literature use only the component of the Burger's vector parallel to the interface, which is an erroneous description of the stress state and energetics of the system. In this investigation the full interfacial edge dislocation is simulated using standard commercially available software and comparisons are made with results available in literature to bring out the utility of the methodology

  3. Effect of ternary alloying elements on microstructure and mechanical property of Nb-Si based refractory intermetallic alloy

    International Nuclear Information System (INIS)

    Kim, W.Y.; Kim, H.S.; Kim, S.K.; Ra, T.Y.; Kim, M.S.

    2005-01-01

    Microstructure and mechanical property at room temperature and at 1773 K of Nb-Si based refractory intermetallic alloys were investigated in terms of compression and fracture toughness test. Mo and V were chosen as ternary alloying elements because of their high melting points, atomic sizes smaller than Nb. Both ternary alloying elements were found to have a significant role in modifying the microstructure from dispersed structure to eutectic-like structure in Nb solid solution/Nb 5 Si 3 intermetallic composites. The 0.2% offset yield strength at room temperature increased with increasing content of ternary elements in Nb solid solution and volume fraction of Nb 5 Si 3 . At 1773 K, Mo addition has a positive role in increasing the yield strength. On the other hand, V addition has a role in decreasing the yield strength. The fracture toughness of ternary alloys was superior to binary alloys. Details will be discussed in correlation with ternary alloying, volume fraction of constituent phase, and the microstructure. (orig.)

  4. The influence of heat treatment and role of boron on sliding wear behaviour of β-type Ti-35Nb-7.2Zr-5.7Ta alloy in dry condition and in simulated body fluids.

    Science.gov (United States)

    Majumdar, P; Singh, S B; Chakraborty, M

    2011-04-01

    The wear behaviour of heat-treated Ti-35Nb-7.2Zr-5.7Ta (TNZT) and Ti-35Nb-7.2Zr-5.7Ta-0.5B (TNZTB) alloys (all compositions are in wt%) was investigated in dry condition and in simulated body fluids. It has been found that there is no straightforward relationship between the wear rate and the microstructure. The hardness has no appreciable effect on the wear behaviour of these alloys. The presence of boron in the TNZT alloy deteriorates its wear properties. The wear rate of TNZT and TNZTB alloys in various media increases in the following sequence: dry condition < Hank's solution < bovine serum. Copyright © 2010 Elsevier Ltd. All rights reserved.

  5. Microstructure and Properties of a Refractory NbCrMo0.5Ta0.5TiZr Alloy (Postprint)

    Science.gov (United States)

    2014-04-01

    in this phase is nly slightly lower of the average alloy composition. In spite of the educed amount of the BCC-forming elements in the BCC2 phase...distribution unlimited. 3 cience B r g t s b T M B i d F B p b B r t c t T p p m m t 1 o i P s d 4 a c H B 1 o [ [ [ [ 20 O.N. Senkov, C.F. Woodward...Zr and Ti and educed amounts of Cr, Mo and Ta relative to the BCC1 phase of he large primary particles. The composition of these particles is lose to

  6. (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 ferroelectric ceramics.

    Science.gov (United States)

    Safari, Ahmad; Abazari, Maryam; Kerman, Kian; Marandian-Hagh, Nader; Akdoğan, E Koray

    2009-08-01

    Recent progress in (K0.44, Na0.52, Li0.04)O3-based ceramics (KNN) with special emphasis on(K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 (KNN-LT-LS) is reviewed concisely. The base KNN and its compositional derivatives are analyzed in terms of dopant-property relationships, which are then extended to the ternary derivatives. The effects of processing conditions such as humidity, precursor purity, and oxygen partial pressure during sintering are elaborated on from a phenomenological perspective. It is also shown that the spontaneous polarization is sensitive to the processing route chosen for synthesis (mixed oxide versus perovskite routes). Special attention is devoted to the discussion of the morphotropic phase boundary (MPB) dilemma in the KNN-LT-LS system, where it is shown that the origin of high piezoelectric activity is actually due to a polymorphic transition at room temperature. It is shown that prototype transducers based on pure and 1 mol% Ba2+ doped KNN-LT-LS exhibit performance metrics comparable to those fabricated using PZT-5H. Overall, KNNLT- LS ceramics show great promise for lead-free applications, although issues such as temperature dependence of properties and strong sensitivity to processing conditions remain as the 2 major challenges.

  7. Nonsymmorphic-symmetry-protected hourglass Dirac loop, nodal line, and Dirac point in bulk and monolayer X3SiTe6 (X = Ta, Nb)

    Science.gov (United States)

    Li, Si; Liu, Ying; Wang, Shan-Shan; Yu, Zhi-Ming; Guan, Shan; Sheng, Xian-Lei; Yao, Yugui; Yang, Shengyuan A.

    2018-01-01

    Nonsymmorphic space group symmetries can generate exotic band crossings in topological metals and semimetals. Here, based on symmetry analysis and first-principles calculations, we reveal rich band-crossing features in the existing layered compounds Ta3SiTe6 and Nb3SiTe6 , enabled by nonsymmorphic symmetries. We show that in the absence of spin-orbit coupling (SOC), these three-dimensional (3D) bulk materials possess accidental Dirac loops and essential fourfold nodal lines. In the presence of SOC, there emerges an hourglass Dirac loop—a fourfold degenerate nodal loop, on which each point is a neck point of an hourglass-type dispersion. We show that this interesting type of band crossing is protected and dictated by the nonsymmorphic space group symmetries and it gives rise to drumheadlike surface states. Furthermore, we also investigate these materials in the monolayer form. We show that these two-dimensional (2D) monolayers host nodal lines in the absence of SOC and the nodal lines transform to essential spin-orbit Dirac points when SOC is included. Our work suggests a realistic material platform for exploring the fascinating physics associated with nonsymmorphic band crossings in both 3D and 2D systems.

  8. Structures and solid solution mechanisms of pyrochlore phases in the systems Bi2O3-ZnO-(Nb, Ta)2O5

    International Nuclear Information System (INIS)

    Tan, K.B.; Khaw, C.C.; Lee, C.K.; Zainal, Z.; Miles, G.C.

    2010-01-01

    Research highlights: → Combined XRD and ND Rietveld structural refinement of pyrochlores. → Structures and solid solution mechanisms of Bi-pyrochlores. → Bi and Zn displaced off-centre to different 96g A-site positions. → Summary of composition-structure-property of Bi-pyrochlores. - Abstract: The crystal structures of two pyrochlore phases have been determined by Rietveld refinement of combined X-ray and neutron powder diffraction data. These are stoichiometric, Bi 1.5 ZnTa 1.5 O 7 and non-stoichiometric Bi 1.56 Zn 0.92 Nb 1.44 O 6.86 . In both structures, Zn is distributed over A- and B-sites; Bi and Zn are displaced off-centre, to different 96g A-site positions; of the three sets of oxygen positions, O(1) are full, O(2) contain vacancies and O(3) contain a small number of oxygen, again in both cases. Comparisons between these structures, those of related Sb analogues and literature reports are made.

  9. Improvement of adhesive strength of segmented polyurethane on Ti-29Nb-13Ta-4.6Zr alloy through H₂O₂ treatment for biomedical applications.

    Science.gov (United States)

    Hieda, Junko; Niinomi, Mitsuo; Nakai, Masaaki; Kamura, Hiroyuki; Tsutsumi, Harumi; Hanawa, Takao

    2013-07-01

    The number of hydroxyl groups on a Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy surface was controlled through H₂O₂ treatment for further improvement of the adhesive strength and durability against water of TNTZ/silane layers (SILs)/segmented polyurethane (SPU) composites. The effect of the terminal functional groups on the adhesive strength of SPU on TNTZ, and the adhesiveness of SPU on TNTZ against water was investigated. Three types of silane-coupling agents were used to bind TNTZ and SPU: methacryloxypropyltrimethoxysilane (γ-MPTS), aminopropyltriethoxysilane (APS), and mercaptopropyltrimethoxysilane (γ-MPS). The adhesive strength of each composite was evaluated by shear bonding tests. The number of hydroxyl groups increases with an increase in treatment time at a H₂O₂ concentration of 5% (v/v). On the other hand, an increase from 5% (v/v) to 30% (v/v) in H₂O₂ concentration leads to a decrease in the number of hydroxyl groups on the TNTZ surface because at higher H₂O₂ concentrations, the reaction that consumes the hydroxyl groups is dominant. The shear bonding strength is doubled compared with the untreated TNTZ/SIL/SPU interface. Although the shear bonding strength decreases after immersion in water for 30 days when APS and γ-MPS are used, TNTZ/γ-MPTS/SPU composites exhibit good durability to water and maintain an equivalent shear bonding strength before immersion in water. Copyright © 2013 Wiley Periodicals, Inc.

  10. Development of thermo-mechanical processing for fabricating highly durable β-type Ti-Nb-Ta-Zr rod for use in spinal fixation devices.

    Science.gov (United States)

    Narita, Kengo; Niinomi, Mitsuo; Nakai, Masaaki; Hieda, Junko; Oribe, Kazuya

    2012-05-01

    The mechanical strength of a beta titanium alloy such as Ti-Nb-Ta-Zr alloy (TNTZ) can be improved significantly by thermo-mechanical treatment. In this study, TNTZ was subjected to solution treatment, cold caliber rolling, and cold swaging before aging treatment to form a rod for spinal fixation. The {110}(β) are aligned parallel to the cross-section with two strong peaks approximately 180° apart, facing one another, in the TNTZ rods subjected to cold caliber rolling and six strong peaks at approximately 60° intervals, facing one another, in the TNTZ rods subjected to cold swaging. Therefore, the TNTZ rods subjected to cold swaging have a more uniform structure than those subjected to cold caliber rolling. The orientation relationship between the α and β phases is different. A [110](β)//[121](α), (112)(β)//(210)(α) orientation relationship is observed in the TNTZ rods subjected to aging treatment at 723 K after solution treatment and cold caliber rolling. On the other hand, a [110](β)//[001](α), (112)(β)//(200)(α) orientation relationship is observed in TNTZ rod subjected to aging treatment at 723 K after cold swaging. A high 0.2% proof stress of about 1200 MPa, high elongation of 18%, and high fatigue strength of 950 MPa indicate that aging treatment at 723 K after cold swaging is the optimal thermo-mechanical process for a TNTZ rod. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. Microstructure evolution and mechanical properties of a Ti-35Nb-3Zr-2Ta biomedical alloy processed by equal channel angular pressing (ECAP).

    Science.gov (United States)

    Lin, Zhengjie; Wang, Liqiang; Xue, Xiaobing; Lu, Weijie; Qin, Jining; Zhang, Di

    2013-12-01

    In this paper, an equal channel angular pressing method is employed to refine grains and enhance mechanical properties of a new β Ti-35Nb-3Zr-2Ta biomedical alloy. After the 4th pass, the ultrafine equiaxed grains of approximately 300 nm and 600 nm are obtained at pressing temperatures of 500 and 600°C respectively. The SEM images of billets pressed at 500°C reveal the evolution of shear bands and finally at the 4th pass intersectant networks of shear bands, involving initial band propagation and new band broadening, are formed with the purpose of accommodating large plastic strain. Furthermore, a unique herringbone microstructure of twinned martensitic variants is observed in TEM images. The results of microhardness measurements and uniaxial tensile tests show a significant improvement in microhardness and tensile strength from 534 MPa to 765 MPa, while keeping a good level of ductility (~16%) and low elastic modulus (~59 GPa). The maximum superelastic strain of 1.4% and maximum recovered strain of 2.7% are obtained in the billets pressed at 500°C via the 4th pass, which exhibits an excellent superelastic behavior. Meanwhile, the effects of different accumulative deformations and pressing temperatures on superelasticity of the ECAP-processed alloys are investigated. © 2013. Published by Elsevier B.V. All rights reserved.

  12. Influence of cold rolling and ageing treatment on microstructure and mechanical properties of Ti-30Nb-5Ta-6Zr alloy.

    Science.gov (United States)

    Wang, Yu; Zhao, Juan; Dai, Shijuan; Chen, Feng; Yu, Xinquan; Zhang, Youfa

    2013-11-01

    In this study, the relationship between deformation mechanism and rolling reductions was investigated, and the effects of deformation reductions on the microstructure and mechanical properties of the alloys both cold rolled and aged were revealed. It was found that the equiaxed β grains of the Ti-30Nb-5Ta-6Zr alloy have elongated gradually with increasing the deformation reduction. The deformation mechanism of dislocation slipping, deformed twins and SIM α″ phase appeared in the alloy deformed by 23% and 66%. The type of twins of the alloy deformed by 23% and 66% are {112}〈111〉 and {332}〈113〉 respectively. When the reduction was up to 85%, dislocation slipping was the main mode of deformation accompanying with SIM α″ phase occurred. With increasing deformation reduction, the average size of lenticular precipitation α phase decreased gradually. The strength of cold rolled and aged samples increased with increasing deformation reduction, while elastic modulus decreased. Due to the precipitation α phase, the elastic modulus of aged samples was higher than cold rolled. © 2013 Elsevier Ltd. All rights reserved.

  13. Enhanced second harmonic generation and photoluminescence in Pr-doped LiNb0.5Ta0.5O3 nanocrystals embedded in a borate based glass

    Science.gov (United States)

    Jaschin, P. W.; Varma, K. B. R.

    2017-08-01

    Non-linear optical properties and photoluminescence exhibited by Pr-doped LiNb0.5Ta0.5O3 nanocrystals embedded in a borate based glass are presented here. The glasses of composition 1.5Li2O-2B2O3-0.5Nb2O5-0.5Ta2O5:xPr6O11 (x = 0.0025, 0.005, and 0.01) were synthesized via the conventional melt-quenching technique, and the nanocrystal growth was induced by subjecting the as-quenched glasses to heat treatment between 530 and 560 °C for 3 h. Coalesced nanocrystals of sizes in the 20-38 nm range, resulting in the formation of dendritic spherulites, were obtained from the isothermal heat treatment. Effect of doping on the structural units of LiNb0.5Ta0.5O3 lattice was analysed by Raman studies, which indicated that Pr ions occupied Li+ vacancies or Nb/Ta antisites. A strong red emission at 620 nm, due to 1D2 → 3H4 electronic transition of Pr3+ ions, was observed upon excitation by a 450 nm radiation. The maximum intensity was exhibited by the composition corresponding to Pr-doping level, x = 0.005, while the crystallization had a pronounced effect on the intensity of the red output. A non-linear optical coefficient as high as 0.77 pm/V (twice that of d36 of potassium dihydrogen phosphate single crystal) was obtained from the bulk glass-nanocrystal composites of the composition in which x = 0.0025.

  14. Fundamental simulations of transverse load effects on Nb3Sn strands using finite element analysis

    Science.gov (United States)

    Wang, T.; Chiesa, L.; Takayasu, M.

    2012-06-01

    A 2D finite element elasto-plastic analysis with various property values of the materials in composite Nb3Sn wires has been conducted to simulate the transverse compression effect on a single strand and a 3-strand cable as basic elements of a Cable-in-Conduit Conductor (CICC). The simulation results have been compared with previously reported experimental results. A parametric study of the stress-strain characteristics of copper at 4 K was considered. The simulation results showed that wire and cable deformations due to the transverse load are very sensitive to the elasto-plastic material properties of copper and bronze. In a triplet it is found that the strain distributions inside the superconducting strand are very different along its axis, that is, for a configuration in which two strands lined in parallel to the transverse load direction shows much higher internal strain than other configurations under the same transverse load. The simulation results agree with the reported experimental results indicating a low Young's modulus for Nb3Sn wires under transverse compression. The simulation also supports the reported contact mechanics model for critical current degradation.

  15. Effect of MnO doping on the structure, microstructure and electrical properties of the (K,Na,Li)(Nb,Ta,Sb)O{sub 3} lead-free piezoceramics

    Energy Technology Data Exchange (ETDEWEB)

    Rubio-Marcos, F., E-mail: fernando.rubio-marcos@unilim.fr [Laboratoire de Science des Procedes Ceramiques et de Traitements de Surface, UMR 6638 CNRS, Universite de Limoges, Centre Europeen de la Ceramique, 12, rue Atlantis, 87068 Limoges Cedex (France); Marchet, P. [Laboratoire de Science des Procedes Ceramiques et de Traitements de Surface, UMR 6638 CNRS, Universite de Limoges, Centre Europeen de la Ceramique, 12, rue Atlantis, 87068 Limoges Cedex (France); Vendrell, X. [Grup de Quimica de l' Estat Solid, Departament de Quimica Inorganica, Universitat de Barcelona, 08028 Barcelona (Spain); Romero, J.J. [Electroceramic Department, Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain); Remondiere, F. [Laboratoire de Science des Procedes Ceramiques et de Traitements de Surface, UMR 6638 CNRS, Universite de Limoges, Centre Europeen de la Ceramique, 12, rue Atlantis, 87068 Limoges Cedex (France); Mestres, L. [Grup de Quimica de l' Estat Solid, Departament de Quimica Inorganica, Universitat de Barcelona, 08028 Barcelona (Spain); Fernandez, J.F. [Electroceramic Department, Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain)

    2011-09-01

    Highlights: {center_dot} MnO doping effects on structure and properties of (K,Na,Li)(Nb,Ta,Sb)O{sub 3} piezoceramics. {center_dot} The structure changes towards an orthorhombic symmetry for higher MnO concentrations. {center_dot} High doping levels induce a tetragonal tungsten-bronze secondary phase. {center_dot} Mn{sup 2+} doping modifies the phase transition temperature and the piezoelectric properties. {center_dot} Manganese doping increases the mechanical quality factor Q{sub m}. - Abstract: Mn{sup 2+}-doped (K,Na,Li)(Nb,Ta,Sb)O{sub 3} lead-free piezoelectric ceramics have been prepared by a conventional sintering technique. The effects of Mn{sup 2+} doping on the phase structure, microstructure and ferro-piezoelectric properties of the ceramics have been evaluated. MnO doping modifies the (K,Na,Li)(Nb,Ta,Sb)O{sub 3} structure, giving rise to the appearance of a TTB-like secondary phase and to changes on the orthorhombic to tetragonal phase transition temperature. The modification of this temperature induces a reduction of the piezoelectric constants, which is accompanied by an increase on the mechanical quality factor. Mn{sup 2+} ions incorporate into the perovskite structure in different off ways depending on their concentration.

  16. Novel elastic, lattice dynamics and thermodynamic properties of metallic single-layer transition metal phosphides: 2H-M 2P (Mo2P, W2P, Nb2P and Ta2P)

    Science.gov (United States)

    Yin, Jiuren; Wu, Bozhao; Wang, Yanggang; Li, Zhimi; Yao, Yuanpeng; Jiang, Yong; Ding, Yanhuai; Xu, Fu; Zhang, Ping

    2018-04-01

    Recently, there has been a surge of interest in the research of two-dimensional (2D) phosphides due to their unique physical properties and wide applications. Transition metal phosphides 2H-M 2Ps (Mo2P, W2P, Nb2P and Ta2P) show considerable catalytic activity and energy storage potential. However, the electronic structure and mechanical properties of 2D 2H-M 2Ps are still unrevealed. Here, first-principles calculations are employed to investigate the lattice dynamics, elasticity and thermodynamic properties of 2H-M 2Ps. Results show that M 2Ps with lower stiffness exhibit remarkable lateral deformation under unidirectional loads. Due to the largest average Grüneisen parameter, single-layer Nb2P has the strongest anharmonic vibrations, resulting in the highest thermal expansion coefficient. The lattice thermal conductivities of Ta2P, W2P and Nb2P contradict classical theory, which would predict a smaller thermal conductivity due to the much heavier atom mass. Moreover, the calculations also demonstrate that the thermal conductivity of Ta2P is the highest as well as the lowest thermal expansion, owing to its weak anharmonic phonon scattering and the lowest average Grüneisen parameter. The insight provided by this study may be useful for future experimental and theoretical studies concerning 2D transition metal phosphide materials.

  17. Electrochemical Stability of Li{sub 6.5}La{sub 3}Zr{sub 1.5}M{sub 0.5}O{sub 12} (M = Nb or Ta) against Metallic Lithium

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yunsung [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI (United States); Yoo, Aeri [Department of Advanced Materials Engineering, Korea Polytechnic University, Siheung (Korea, Republic of); Schmidt, Robert; Sharafi, Asma [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI (United States); Lee, Heechul [Department of Advanced Materials Engineering, Korea Polytechnic University, Siheung (Korea, Republic of); Wolfenstine, Jeff [Army Research Laboratory, RDRL-SED-C, Adelphi, MD (United States); Sakamoto, Jeff, E-mail: jeffsaka@umich.edu [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI (United States)

    2016-05-20

    The electrochemical stability of Li{sub 6.5}La{sub 3}Zr{sub 1.5}Nb{sub 0.5}O{sub 12} (LLZNO) and Li{sub 6.5}La{sub 3}Zr{sub 1.5}Ta{sub 0.5}O{sub 12} (LLZTO) against metallic Li was studied using direct current (DC) and electrochemical impedance spectroscopy (EIS). Dense polycrystalline LLZNO (ρ = 97%) and LLZTO (ρ = 92%) were made using sol–gel synthesis and rapid induction hot-pressing at 1100°C and 15.8 MPa. During DC cycling tests at room temperature (± 0.01 mA/cm{sup 2} for 36 cycles), LLZNO exhibited an increase in Li–LLZNO interface resistance and eventually short-circuiting while the LLZTO was stable. After DC cycling, LLZNO appeared severely discolored while the LLZTO did not change in appearance. We believe the increase in Li–LLZNO interfacial resistance and discoloration are due to reduction of Nb{sup 5+} to Nb{sup 4+}. The negligible change in interfacial resistance and no color change in LLZTO suggest that Ta{sup 5+} may be more stable against reduction than Nb{sup 5+} in cubic garnet versus Li during cycling.

  18. Formation of Fe-Nb-X (X=Zr, Ti) amorphous alloys from pure metal elements by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Zhiyu [National Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640 (China); Tang Cuiyong, E-mail: hnrtcy@163.com [National Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640 (China); Ngai, Tungwai Leo; Yang Chao; Li Yuanyuan [National Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640 (China)

    2012-01-15

    Fe-based amorphous powders of Fe{sub 56}Nb{sub 6}Zr{sub 38} and Fe{sub 60}Nb{sub 6}Ti{sub 34} based on binary eutectic were prepared by mechanical alloying starting from mixtures of pure metal powders. The amorphization behavior and thermal stability were examined by x-ray diffraction, scanning electron microscopy, transmission electron microscopy and differential scanning calorimetry. Results show that Fe{sub 56}Nb{sub 6}Zr{sub 38} alloy has a better glass forming ability and a relatively lower thermal stability comparing with Fe{sub 60}Nb{sub 6}Ti{sub 34} alloy. The prepared amorphous powders have homogeneous element distribution and no obvious contaminants coming from mechanical alloying. The synthesized amorphous powders offer the potential for consolidation to full density with desirable mechanical properties through the powder metallurgy methods.

  19. Technology development and commercial production of current-carrying elements on the basis of Nb3Sn superconductor

    International Nuclear Information System (INIS)

    Nikulin, A.D.; Shikov, A.K.; Davydov, I.I.

    1995-01-01

    A description of a current carrying element intended for Tokamak-15 magnetic system is presented. The element is produced from multicore wires with superconducting Nb 3 Sn cores and calculated for 8.5 kA critical current in magnetic field of 8 T. Main processing procedures of its manufacturing are shown. Extrusion conditions needed for production of composite bronze-niobium rods and multicore wire 1.5 mm in diameter with 14641 niobium cores are determined. Heat treatment used results in formation of Nb 3 Sn intermetallics and assures maximal current-carrying capacity of 910-920 A in 8 T magnetic field. 15 refs., 9 figs

  20. Promotion effect of nanosized Pt, RuO2 and NiOx loading on visible light-driven photocatalysts K4Ce2M10O30 (M=Ta, Nb for hydrogen evolution from water decomposition

    Directory of Open Access Journals (Sweden)

    Mengkui Tian et al

    2007-01-01

    Full Text Available Metal oxide photocatalysts K4Ce2M10O30 (M=Ta, Nb capable of responding to visible light were synthesized by conventional high temperature solid-state reaction. The photocatalysts have an appropriate band gap energy ca. 1.8–2.3 eV and excellent chemical potential level to evolve H2 from aqueous solutions containing a sacrificial electron donor (Na2SO3 under visible light irradiation (λ>420 nm without any co-catalyst. When they were loading with Pt, RuO2 and NiOx, the activities for evolving H2 were prompted markedly. By SEM and TEM investigations, it can be seen that these loading metal and metal oxides are dispersed on the surface of photocatalysts K4Ce2M10O30 (M=Ta, Nb in diameter of about 10–30 nm particles, especially the NiOx loading even formed double layered structure with metal nickel (Ni and metal oxide (NiO. The reasons for the increasing activities after these loading may be attributable to facilitate electron migrating from the conduction band of K4Ce2M10O30 (M=Ta, Nb to the Pt, RuO2 and NiOx nanoparticles, which function as H2 production sites on the surface of catalysts. The same phenomenon appears on the solid solution K4Ce2Ta10−xNbxO30 (x=0–10 with loading RuO2.

  1. Origin of magnetoelectric effect in Co4Nb2O9 and Co4Ta2O9 : The lessons learned from the comparison of first-principles-based theoretical models and experimental data

    Science.gov (United States)

    Solovyev, I. V.; Kolodiazhnyi, T. V.

    2016-09-01

    We report results of joint experimental and theoretical studies on magnetoelectric (ME) compounds Co4Nb2O9 and Co4Ta2O9 . On the experimental side, we present results of the magnetization and dielectric permittivity measurements in the magnetic field. On the theoretical side, we construct the low-energy Hubbard-type model for the magnetically active Co 3 d bands in the Wannier basis, using the input of the first-principles electronic structure calculations, solve this model in the mean-field Hartree-Fock approximation, and evaluate the electric polarization in terms of the Berry phase theory. Both experimental and theoretical results suggest that Co4Ta2O9 is magnetically softer than Co4Nb2O9 . Therefore, it is reasonable to expect that the antiferromagnetic structure of Co4Ta2O9 can be easier deformed by the external magnetic field, yielding larger polarization. This trend is indeed reproduced by our theoretical calculations, but does not seem to be consistent with the experimental behavior of the polarization and dielectric permittivity. Thus, we suggest that there should be a hidden mechanism controlling the ME coupling in these compounds, probably related to the magnetic striction or a spontaneous change of the magnetic structure, which breaks the inversion symmetry. Furthermore, we argue that unlike in other ME systems (e.g., Cr2O3 ), in Co4Nb2O9 and Co4Ta2O9 there are two crystallographic sublattices, which contribute to the ME effect. These contributions are found to be of the opposite sign and tend to compensate each other. The latter mechanism can be also used to control and reverse the electric polarization in these compounds.

  2. Structural and magnetic study of Yb3+ in the perovskites Sr2YbMO6 (M=Nb, Ta, Sb)

    International Nuclear Information System (INIS)

    Coomer, Fiona C.; Campbell, John; Giordano, Nico; Collins, Oonagh M.; Cussen, Edmund J.

    2015-01-01

    The compounds Sr 2 YbNbO 6 , Sr 2 YbTaO 6 and Sr 2 YbSbO 6 have been prepared using solid state methods by heating pelleted reagents in air at temperatures up to 1400 °C. Rietveld refinement against room temperature neutron powder diffraction data show that all three compounds crystallise with a cation-ordered variant of the perovskite structure in the P2 1 /n space group. Complete cation ordering occurs between M 5+ and Yb 3+ over two octahedrally-coordinated sites in the structure and all compounds are stoichiometric in oxygen. The Sb–O bond lengths are similar to related perovskite compounds but differ slightly from those indicated by bond valence sums. Magnetic susceptibility data resemble Curie–Weiss paramagnetic behaviour, but can be better understood as arising from the effect of the octahedral crystal field on the 2 F 5/2 ground state of Yb 3+ leading to a temperature dependent magnetic moment on this ion below 100 K. - Graphical abstract: The magnetic susceptibility of the face-centred cubic Yb 3+ lattice is dominated by the temperature dependent single-ion moment below 100 K. - Highlights: • Cation-ordered perovskites are studied using neutron diffraction and magnetometry. • Yb 3+ cations form a pseudo face centred cubic lattice in a distorted structure. • Sb 5+ cation is slightly overbonded as observed in related perovskites. • Crystal field splitting of 4f 13 Yb 3+ giving a temperature dependent moment. • Magnetic susceptibility reproduces theoretical predictions below 100 K

  3. Structural and mechanical properties of lanthanide doped La1/3Nb0.8Ta0.2O3 thin films prepared by sol-gel method

    Science.gov (United States)

    Brunckova, Helena; Medvecky, Lubomir; Kovalcikova, Alexandra; Fides, Martin; Mudra, Erika; Durisin, Juraj; Skvarla, Jiri; Kanuchova, Maria

    2017-04-01

    Transparent Eu and Nd doped lanthanum niobate tantalate La1/3Nb0.8Ta0.2O3 (LNT) thin films (˜150 nm) were prepared by sol-gel/spin-coating process on Pt/SiO2/Si substrates and annealing at 1100 °C. The x-ray diffraction analysis of films confirmed formation of the perovskite La1/3NbO3 and La1/3TaO3 phases with traces of pyrochlore LaNbO4. Eu and Nd doped LNT films were smoother with roughness 17.1 and 25.4 nm in comparison with LNT (43.3 nm). In all films was observed heterogeneous microstructure with the perovskite spherical and pyrochlore needle-like particles. The mechanical properties of films were characterized for the first time by conventional and continuous stiffness (CSM) nanoindentation. The Eu and Nd doped LNT film modulus (E) and hardness (H) were higher than LNT (˜99.8 and 4.4 GPa) determined by conventional nanoindentation. It was measured the significant effect of substrate on properties of Eu or Nd films (H ˜ 5.9 or 4.9 GPa and E ˜ 107.3 or 104.1 GPa) by CSM nanoindentation.

  4. Estudio teórico de las propiedades elásticas de los minerales Cu3TMSe4 (TM = V, Nb, Ta por medio de cálculos atomísticos de primeros principios Theoretical study of the elastic properties of the minerals Cu3TMSe4 (TM = V, Nb, Ta by means of atomistic first-principles calculations

    Directory of Open Access Journals (Sweden)

    Carlos Mario Ruiz

    2011-06-01

    Full Text Available Las propiedades elásticas de la familia de los minerales isoestructurales Cu3VSe4, Cu3NbSe4 y Cu3TaSe4 han sido calculadas por primera vez usandoel estado del arte en cálculos atomísticos de primeros-principios, utilizandola Teoría de los Funcionales de la Densidad y la Aproximación del Gradiente Generalizado para el funcional de la energía de intercambio-correlación. Laspropiedades elásticas calculadas son el módulo volumétrico (B, las constantes elásticas (c11, c12 y c44, el factor de anisotropía de Zener (A, el módulo de cizalladura isotrópico (G, el módulo de Young (Y, y la razón de Poisson(ν. A través de estas cantidades también hemos calculado otras propiedades termodinámicas tales como la velocidad promedio del sonido transversal (st y longitudinal (sl y la temperatura de Debye (ΘD. Los valores calculados de B, c11, c12 y c44, G, Y , y ν nos llevan a la conclusión que estos compuestosson compresibles, frágiles y quebradizos.The elastic properties of the family of isostructural minerals Cu3VSe4, Cu3NbSe4 and Cu3TaSe4 have been calculated for the first time using the state of the art in first-principles atomistic calculations, using Density Functional Theory and the Generalized Gradient Approximation for the exchangecorrelation energy functional. The elastic properties calculated are bulk modulus (B, the elastic constants (c11, c12 and c44, the Zener anisotropy factor (A, the isotropic shear modulus (G, the Young modulus (Y , and the Poisson ratio (. By means of these quantities we also computed other thermodynamic properties such as the average transversal (st and longitudinal (sl sound velocities and the Debye temperature (D. The calculated values of B, c11, c12 and c44, G, Y and lead us to the conclusion that these compounds are compressible, fragile and brittle.

  5. Validation of Finite-Element Models of Persistent-Current Effects in Nb3Sn Accelerator Magnets

    International Nuclear Information System (INIS)

    Wang, X.; Ambrosio, G.; Chlachidze, G.; Collings, E. W.; Dietderich, D. R.; DiMarco, J.; Felice, H.; Ghosh, A. K.; Godeke, A.; Gourlay, S. A.; Marchevsky, M.; Prestemon, S. O.; Sabbi, G.; Sumption, M. D.; Velev, G. V.; Xu, X.; Zlobin, A. V.

    2015-01-01

    Persistent magnetization currents are induced in superconducting filaments during the current ramping in magnets. The resulting perturbation to the design magnetic field leads to field quality degradation, in particular at low field where the effect is stronger relative to the main field. The effects observed in NbTi accelerator magnets were reproduced well with the critical-state model. However, this approach becomes less accurate for the calculation of the persistent-current effects observed in Nb 3 Sn accelerator magnets. Here a finite-element method based on the measured strand magnetization is validated against three state-of-art Nb3Sn accelerator magnets featuring different subelement diameters, critical currents, magnet designs and measurement temperatures. The temperature dependence of the persistent-current effects is reproduced. Based on the validated model, the impact of conductor design on the persistent current effects is discussed. The performance, limitations and possible improvements of the approach are also discussed

  6. Differing reactivities of (trimpsi)M(CO)(2)(NO) complexes [M = V, Nb, Ta; trimpsi = (t)BuSi(CH(2)PMe(2))(3)] with halogens and halogen sources.

    Science.gov (United States)

    Hayton, Trevor W; Legzdins, Peter; Patrick, Brian O

    2002-10-21

    Treatment of (trimpsi)V(CO)(2)(NO) (trimpsi = (t)BuSi(CH(2)PMe(2))(3)) with 1 equiv of PhICl(2) or C(2)Cl(6) or 2 equiv of AgCl affords (trimpsi)V(NO)Cl(2) (1) in moderate yields. Likewise, (trimpsi)V(NO)Br(2) (2) and (trimpsi)V(NO)I(2) (3) are formed by the reactions of (trimpsi)V(CO)(2)(NO) with Br(2) and I(2), respectively. The complexes (trimpsi)M(NO)I(2)(PMe(3)) (M = Nb, 4; Ta, 5) can be isolated in moderate to low yields when the (trimpsi)M(CO)(2)(NO) compounds are sequentially treated with 1 equiv of I(2) and excess PMe(3). The reaction of (trimpsi)V(CO)(2)(NO) with 2 equiv of ClNO forms 1 in low yield, but the reactions of (trimpsi)M(CO)(2)(NO) (M = Nb, Ta) with 1 equiv of ClNO generate (trimpsi)M(NO)(2)Cl (M = Nb, 6; Ta, 7). Complexes 6 and 7 are thermally unstable and decompose quickly at room temperature; consequently, they have been characterized solely by IR and (31)P[(1)H] NMR spectroscopies. All other new complexes have been fully characterized by standard methods, and the solid-state molecular structures of 1.3CH(2)Cl(2), 4.(3/4)CH(2)Cl(2), and 5.THF have been established by single-crystal X-ray diffraction analyses. A convenient method of generating Cl(15)NO has also been developed during the course of these investigations.

  7. A new approach for precise measurements of keV neutron capture cross sections: The examples of 93Nb, 103Rh, and 181Ta

    International Nuclear Information System (INIS)

    Wisshak, K.; Voss, F.; Kaeppeler, F.; Reffo, G.

    1990-04-01

    A new experimental method has been implemented for precise measurements of neutron capture cross sections in the energy range from 3 to 200 keV. Neutrons are produced via the 7 Li(p,n) 7 Be reaction using a pulsed 3 MV Van de Graaff accelerator. The neutron energy is determined by the time of flight technique using flight paths of less than 1 m. Capture events are detected with the Karlsruhe 4π Barium Fluoride Detector. This detector is characterized by a resolution in gamma-ray energy of 14% at 662 keV and 7% at 2.5 MeV, a time resolution of 500 ps, and a peak efficiency of 90% at 1 MeV. Capture events are registered with ≅ 95% probability above a gamma-ray threshold of 2.5 MeV. The combined effect of the relatively short primary flight path, the 10 cm inner radius of the detector sphere, and of the low capture cross section of BaF 2 allows to discriminate the main background due to capture of sample scattered neutrons in the scintillator via time of flight, leaving part of the neutron energy range completely undisturbed. The high efficiency and good energy resolution for capture gamma-rays yields a further reduction of this background by using only the relevant energy channels for data evaluation. In the first measurements with the new detector, the neutron capture cross sections of 93 Nb, 103 Rh, and 181 Ta were determined in the energy range from 3 to 200 keV relative to gold as a standard. The cross section ratios could be determined with overall systematic uncertainties of 0.7 to 0.8%; statistical uncertainties were less than 1% in the energy range from 20 to 100 keV, if the data are combined in 20 keV wide bins. The necessary sample masses were of the order of one gram. Further improvements with respect to sensitivity and accuracy are discussed. (orig.) [de

  8. Estudo do calor específico de compostos Heusler paramagnéticos, da série do níquel Ni 2 Tal, onde T=Ti, Zr, Hf, V, Nb e Ta

    OpenAIRE

    Fabio Saraiva da Rocha

    1997-01-01

    Neste trabalho apresentamos os resultados experimentais da medida do calor específico dos compostos Heusler da série Ni2TA1, onde T =Ti, Zr,Hf,V,Nb, Ta. Estas medidas foram feitas utilizando-se um calorímetro adiabático que atua na faixa de 1,84 K a 10,3 K e visaram o estudo da estrutura elêtrônica dos compostos em termos da densidade de estados eletrônicos à nível de Fermi, bem como da dinâmica da rede cristalina, com o uso dos modelos de Debye e de Einstein para o calor específico. Apresent...

  9. Heterogeneous structure and mechanical hardness of biomedical β-type Ti-29Nb-13Ta-4.6Zr subjected to high-pressure torsion.

    Science.gov (United States)

    Yilmazer, H; Niinomi, M; Nakai, M; Hieda, J; Todaka, Y; Akahori, T; Miyazaki, T

    2012-06-01

    A novel β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), has been developed as a candidate for biomedical applications. TNTZ exhibits non-toxicity and a low Young's modulus close to that of bone (10-30 GPa). Such a low Young's modulus of this alloy is achieved by comprising a single metastable β phase. Greater mechanical biocompatibility, which implies higher mechanical strength and hardness while maintaining a low Young's modulus, has been aimed for TNTZ. Therefore, strengthening by grain refinement and increasing dislocation density is expected to provide TNTZ high mechanical strength while keeping a low Young's modulus because they keep the original β phase. In this case, high-pressure torsion (HPT) processing is one of the effective ways to obtain these properties simultaneously in TNTZ. Thus, in this study, the effect of HPT processing on the microstructure and mechanical hardness of TNTZ was systematically investigated at rotation numbers (N) of 1 to 20 under a pressure of around 1.25 GPa at room temperature. On the cross sections of TNTZ subjected to HPT processing (TNTZ(HPT)) after cold rolling (TNTZ(CR)) at any rotation number, a heterogeneous microstructure consisting of a matrix and a non-etched band, which is not corroded by etching solution, can be observed. The thickness of non-etched band increases as rotation number and distance from specimen center increase. Both matrix and non-etched band comprise a single β phase, but their grain geometries are different each other. Equiaxed grains and elongated grains are observed in the matrix and the non-etched band, respectively. The equiaxed grain diameter, which is ranged from 155 nm to 44 nm, in the matrix decreases with increasing rotation number. Contrastingly, the elongated grains with a length of around 300 nm and a width of 30 nm, which are nearly constant with rotation number, are observed in the non-etched band. The mechanical hardness of TNTZ(HPT) is consistently much higher than that of

  10. NEAR-ABSOLUTE EQUATIONS OF STATE OF DIAMOND, Ag, Al, Au, Cu, Mo, Nb, Pt, Ta, AND W FOR QUASI-HYDROSTATIC CONDITIONS

    Directory of Open Access Journals (Sweden)

    Peter I. Dorogokupets

    2012-01-01

    Full Text Available Using the modified formalism of [Dorogokupets, Oganov, 2005, 2007], equations of state are developed for diamond, Ag, Al, Au, Cu, Mo, Nb, Pt, Ta, and W by simultaneous optimization of shock-wave data, ultrasonic, X-ray, dilatometric and thermochemical measurements in the temperature range from ~100 K to the melting temperature and pressures up to several Mbar, depending on the substance. The room-temperature isotherm is given in two forms: (1 the equation from [Holzapfel, 2001, 2010] which is the interpolation between the low pressure (x≥1 and the pressure at infinite compression (x=0; it corresponds to the Thomas-Fermi model, and (2 the equation from [Vinet et al., 1987]. The volume dependence of the Grüneisen parameter is calculated according to equations from [Zharkov, Kalinin, 1971; Burakovsky, Preston, 2004] with adjustable parameters, t and δ. The room-temperature isotherm and the pressure on the Hugoniot adiabat are determined by three parameters, K', t and δ, and K0 is calculated from ultrasonic measurements. In our study, reasonably accurate descriptions of all of the basic thermodynamic functions of metals are derived from a simple equation of state with a minimal set of adjustable parameters.The pressure calculated from room-temperature isotherms can be correlated with a shift of the ruby R1 line. Simultaneous measurements of the shift and unit cell parameters of metals are conducted in mediums containing helium [Dewaele et al., 2004b; 2008; Takemura, Dewaele, 2008; Takemura, Singh, 2006], hydrogen [Chijioke et al., 2005] and argon [Tang et al., 2010]. According to [Takemura, 2001], the helium medium in diamond anvil cells provides for quasi-hydrostatic conditions; therefore, the ruby pressure scale, that is calibrated for the ten substances, can be considered close to equilibrium or almost absolute. The ruby pressure scale is given as P(GPa=1870⋅Δλ/λ0⋅(1+6⋅Δλ/λ0. The room-temperature isotherms corrected with regard

  11. Promising Ta-Ti-Zr-Si metallic glass coating without cytotoxic elements for bio-implant applications

    Science.gov (United States)

    Lai, J. J.; Lin, Y. S.; Chang, C. H.; Wei, T. Y.; Huang, J. C.; Liao, Z. X.; Lin, C. H.; Chen, C. H.

    2018-01-01

    Tantalum (Ta) is considered as one of the most promising metal due to its high corrosion resistance, excellent biocompatibility and cell adhesion/in-growth capabilities. Although there are some researches exploring the biomedical aspects of Ta and Ta based alloys, systematic characterizations of newly developed Ta-based metallic glasses in bio-implant applications is still lacking. This study employs sputtering approach to produced thin-film Ti-based metallic glasses due to the high melting temperature of Ta (3020 °C). Two fully amorphous Ta-based metallic glasses composed of Ta57Ti17Zr15Si11 and Ta75Ti10Zr8Si7 are produced and experimentally characterized in terms of their mechanical properties, bio-corrosion properties, surface hydrophilic characteristics, and in-vitro cell viability and cells attachment tests. Compare to conventional pure Ti and Ta metals, the developed Ta-based metallic glasses exhibit higher hardness and lower modulus which are better match to the mechanical properties of bone. MTS assay results show that Ta-based metallic glasses show comparable cell viability and cell attachment rate compared to that of pure Ti and Ta surface in a 72 h in-vitro test.

  12. Dielectric, ferroelectrics properties and impedance spectroscopy analysis of the [(Na0.535K0.4800.966Li0.058](Nb0.90Ta0.10O3-based lead-free ceramics

    Directory of Open Access Journals (Sweden)

    M. Saidi

    2015-03-01

    Full Text Available Polycrystalline of [(Na0.535K0.4800.966Li0.058](Nb0.90Ta0.10O3 samples were prepared using the high-temperature solid-state reaction technique. X-ray diffraction (XRD analysis indicates the formation of a single-phase with orthorhombic structure. AC impedance plots were used as tool to analyze the electrical behavior of the sample as a function of frequency at different temperatures. The AC impedance studies revealed the presence of grain effect, from 425°C onwards. Complex impedance analysis indicated non-Debye type dielectric relaxation. The Nyquist plot showed the negative temperature coefficient of resistance (NTCR characteristic of NKLNT. The AC conductivity results were used to correlate with the barrier hopping (CBH model to evaluate the binding energy (Wm, the minimum hopping distance (Rmin, the density of states at Fermi level (N(Ef, and the activation energy of the compound.

  13. Nickel Alloy, Corrosion and Heat-Resistant, Sheet, Strip, and Plate 72Ni - 15.5Cr - 0.95 (Cb (Nb) + Ta) - 2.5Ti - 0.70Al - 7.0Fe Consumable Electrode, Remelted or Vacuum Induction Melted, Solution Heat Treated, Precipitation-Hardenable

    CERN Document Server

    SAE Aerospace Standards. London

    2012-01-01

    Nickel Alloy, Corrosion and Heat-Resistant, Sheet, Strip, and Plate 72Ni - 15.5Cr - 0.95 (Cb (Nb) + Ta) - 2.5Ti - 0.70Al - 7.0Fe Consumable Electrode, Remelted or Vacuum Induction Melted, Solution Heat Treated, Precipitation-Hardenable

  14. Mechanical behavior and microstructure of Ti{sub 20}Hf{sub 20}Zr{sub 20}Ta{sub 20}Nb{sub 20} high-entropy alloy loaded under quasi-static and dynamic compression conditions

    Energy Technology Data Exchange (ETDEWEB)

    Dirras, G., E-mail: dirras@univ-paris13.fr [Université Paris 13, Sorbonne Paris Cité, LSPM-CNRS, UPR 3407, 99 avenue JB Clément, 93430 Villetaneuse (France); Couque, H. [Nexter-munitions, 7 Route de Guerry, 18200 Bourges (France); Lilensten, L. [Université Paris Est, ICMPE (UMR 7182), CNRS, UPEC, 94320 Thiais (France); Heczel, A. [Department of Materials Physics, Eötvös Loránd University, Budapest, P.O.B. 32, H-1518 (Hungary); Tingaud, D. [Université Paris 13, Sorbonne Paris Cité, LSPM-CNRS, UPR 3407, 99 avenue JB Clément, 93430 Villetaneuse (France); Couzinié, J.-P.; Perrière, L. [Université Paris Est, ICMPE (UMR 7182), CNRS, UPEC, 94320 Thiais (France); Gubicza, J. [Department of Materials Physics, Eötvös Loránd University, Budapest, P.O.B. 32, H-1518 (Hungary); Guillot, I. [Université Paris Est, ICMPE (UMR 7182), CNRS, UPEC, 94320 Thiais (France)

    2016-01-15

    The microstructure and the mechanical behavior of equimolar Ti{sub 20}Hf{sub 20}Zr{sub 20}Ta{sub 20}Nb{sub 20} high-entropy alloy in a wide range of initial strain rates between ~ 10{sup −3} s{sup −1} and ~ 3.4 × 10{sup 3} s{sup −1} were studied. A significant increment in the yield strength with increasing strain rate was observed. The yield strength at ~ 3.4 × 10{sup 3} s{sup −1} was about 40% higher than that measured at ~ 10{sup −3} s{sup −1}. Analysis by electron backscatter diffraction shows that in the low strain rate regime (up to ~ 10 s{sup −1}) the deformation occurs mainly in evenly distributed bands, while in the dynamic regime the deformation is strongly localized in macroscopic shear bands accompanied by softening even after the onset of yielding. The Kernel Average Misorientation technique reveals a high level of lattice rotation within these bands that also carries intense shear. In addition, X-ray diffraction line profile analysis indicates that the sharp increase in the flow stress is mostly related to an increase of the dislocation density. - Highlights: • Strain rate effect on the plastic behavior of Ti{sub 20}Hf{sub 20}Zr{sub 20}Ta{sub 20}Nb{sub 20} HEA was studied. • Low strain rate regime was characterized by a continuous hardening. • At high strain rates softening occurred shortly after the onset of yielding. • Intense strain localization in shear bands occurred in the high strain rate regime. • High dislocation density explained the upturn of flow stress at high strain rates.

  15. Microstructural investigation of plastically deformed Ti{sub 20}Zr{sub 20}Hf{sub 20}Nb{sub 20}Ta{sub 20} high entropy alloy by X-ray diffraction and transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dirras, G., E-mail: dirras@univ-paris13.fr [Université Paris 13, Sorbonne Paris Cité, LSPM (UPR 3407) CNRS, 99 avenue JB Clément, 93430 Villetaneuse (France); Gubicza, J.; Heczel, A. [Department of Materials Physics, Eötvös Loránd University, Budapest, P.O. Box 32, H-1518 (Hungary); Lilensten, L.; Couzinié, J.-P.; Perrière, L.; Guillot, I. [Université Paris Est, ICMPE (UMR 7182), CNRS, UPEC, 94320 Thiais (France); Hocini, A. [Université Paris 13, Sorbonne Paris Cité, LSPM (UPR 3407) CNRS, 99 avenue JB Clément, 93430 Villetaneuse (France)

    2015-10-15

    The microstructure evolution in body-centered cubic (bcc) Ti{sub 20}Zr{sub 20}Hf{sub 20}Nb{sub 20}Ta{sub 20} high entropy alloy during quasi-static compression test was studied by X-ray line profile analysis (XLPA) and transmission electron microscopy (TEM). The average lattice constant and other important parameters of the microstructure such as the mean crystallite size, the dislocation density and the edge/screw character of dislocations were determined by XLPA. The elastic anisotropy factor required for XLPA procedure was determined by nanoindentation. XLPA shows that the crystallite size decreased while the dislocation density increased with strain during compression, and their values reached about 39 nm and 15 × 10{sup 14} m{sup −2}, respectively, at a plastic strain of ~ 20%. It was revealed that with increasing strain the dislocation character became more screw. This can be explained by the reduced mobility of screw dislocations compared to edge dislocations in bcc structures. These observations are in line with TEM investigations. The development of dislocation density during compression was related to the yield strength evolution. - Highlights: • Ti{sub 20}Zr{sub 20}Hf{sub 20}Nb{sub 20}Ta{sub 20} high entropy alloy was processed by arc-melting. • The mechanical was evaluated by RT compression test. • The microstructure evolution was studied by XLPA and TEM. • With increasing strain the dislocation character became more screw. • The yield strength was related to the development of the dislocation density.

  16. Screened coulomb hybrid DFT investigation of band gap and optical absorption predictions of CuVO3, CuNbO3 and Cu 5Ta11O30 materials

    KAUST Repository

    Harb, Moussab

    2014-01-01

    We present a joint theoretical and experimental investigation of the optoelectronic properties of CuVO3, CuNbO3 and Cu 5Ta11O30 materials for potential photocatalytic and solar cell applications. In addition to the experimental results obtained by powder X-ray diffraction and UV-Vis spectroscopy of the materials synthesized under flowing N2 gas at atmospheric pressure via solid-state reactions, the electronic structure and the UV-Vis optical absorption coefficient of these compounds are predicted with high accuracy using advanced first-principles quantum methods based on DFT (including the perturbation theory approach DFPT) within the screened coulomb hybrid HSE06 exchange-correlation formalism. The calculated density of states are found to be in agreement with the UV-Vis diffuse reflectance spectra, predicting a small indirect band gap of 1.4 eV for CuVO3, a direct band gap of 2.6 eV for CuNbO3, and an indirect (direct) band gap of 2.1 (2.6) eV for Cu5Ta 11O30. It is confirmed that the Cu(i)-based multi-metal oxides possess a strong contribution of filled Cu(i) states in the valence band and of empty d0 metal states in the conduction band. Interestingly, CuVO3 with its predicted small indirect band gap of 1.4 eV shows the highest absorption coefficient in the visible range with a broad absorption edge extending to 886 nm. This novel result offers a great opportunity for this material to be an excellent candidate for solar cell applications. © the Partner Organisations 2014.

  17. Influencia de las adiciones de TaC y NbC en las propiedades de los aceros rápidos pulvimetalúrgicos M3/2

    Directory of Open Access Journals (Sweden)

    Gordo, E.

    2002-04-01

    Full Text Available Metal matrix composites based on M3/2 high speed steel and reinforced with different percentages of NbC and TaC were manufactured following a conventional powder metallurgy route: mixing, compacting and sintering. Graphite, to compensate carbon losses during sintering, and copper-phosphorous, to promote liquid phase sintering, were added to M3/2 powders to constitute the base material. Carbide and base material powders were dry mixed and uniaxially compacted at 700 MPa. After this, vacuum sintering was carried out at two temperatures: 1190 °C and 1230 °C. The mechanical properties and wear behaviour of all sintered materials were examined, and their characterisation was completed with a broad microstructural study

    Este trabajo plantea la fabricación de materiales compuestos de matriz metálica, basados en el acero rápido M3/2 y reforzados con distintas cantidades de NbC y TaC, mediante técnicas convencionales pulvimetalúrgicas (P/M: mezcla, compactación y sinterización. Al acero rápido se añadió grafito para compensar las pérdidas de carbono durante la sinterización y cupro-fósforo para promover sinterización en fase líquida, constituyendo esta mezcla el material base. Los polvos de carburos y de material base fueron mezclados en seco y compactados uniaxialmente a 700 MPa. Tras esta etapa, se realizó la sinterización en vacío a dos temperaturas: 1.190 °C y 1.230 °C. Todos los materiales sinterizados fueron caracterizados mediante el estudio de las propiedades mecánicas, el comportamiento a desgaste y un amplio análisis microestructural.

  18. Phase transitions and optical characterization of lead-free piezoelectric (K0.5Na0.5)0.96Li0.04(Nb 0.8Ta0.2)O3 thin films

    KAUST Repository

    Yao, Yingbang

    2013-06-01

    Lead-free piezoelectric thin films, (K0.5Na0.5) 0.96Li0.04(Nb0.8Ta0.2)O 3, were epitaxially grown on MgO(001) and Nb-doped SrTiO 3(001) substrates using pulsed laser deposition. The optimum deposition temperature was found to be 600 C. Two types of in-plane orientations were observed in the films depending on the substrates used. The transmittance and photoluminescence spectra as well as the dielectric and ferroelectric properties of the films were measured. The measured band-gap energy was found to be decreased with the deposition temperature. The dielectric constant decreased from 550 to 300 as the frequency increased from 100 Hz to 1 MHz. The measured remnant polarization and coercive field were 4 μC/cm2 and 68 kV/cm, respectively. The phase transitions of the films were studied by Raman spectroscopy. Two distinct anomalies originating from the cubic-to-tetragonal (TC-T ~ 300 C) and tetragonal-to-orthorhombic (TT-O ~ 120 C) phase transitions were observed. Our results show that Raman spectroscopy is a powerful tool in identifying the phase transitions in ferroelectric thin films. © 2013 Elsevier B.V.

  19. Anion photoelectron spectroscopy of germanium and tin clusters containing a transition- or lanthanide-metal atom; MGe(n)- (n = 8-20) and MSn(n)- (n = 15-17) (M = Sc-V, Y-Nb, and Lu-Ta).

    Science.gov (United States)

    Atobe, Junko; Koyasu, Kiichirou; Furuse, Shunsuke; Nakajima, Atsushi

    2012-07-14

    The electronic properties of germanium and tin clusters containing a transition- or lanthanide-metal atom from group 3, 4, or 5, MGe(n) (M = Sc, Ti, V, Y, Zr, Nb, Lu, Hf, and Ta) and MSn(n) (M = Sc, Ti, Y. Zr, and Hf), were investigated by anion photoelectron spectroscopy at 213 nm. In the case of the group 3 elements Sc, Y, and Lu, the threshold energy of electron detachment of MGe(n)(-) exhibits local maxima at n = 10 and 16, while in the case of the group 4 elements Ti, Zr, and Hf, it exhibits a local minimum only at n = 16, associated with the presence of a small bump in the spectrum. A similar behavior is observed for MSn(n)(-) around n = 16, and these electronic characteristics of MGe(n) and MSn(n) are closely related to those of MSi(n). Compared to MSi(n), however, the larger cavity size of a Ge(n) cage allows metal atom encapsulation at a smaller size n. A cooperative effect between the electronic and geometric structures of clusters with a large cavity of Ge(16) or Sn(16) is discussed together with the results of experiments that probe their geometric stability via their reactivity to H(2)O adsorption.

  20. Basic research for alloy design of Nb-base alloys as ultra high temperature structural materials; Chokoon kozoyo niobuki gokin no gokin sekkei no tame no kisoteki kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Miura, E. [Tohoku University, Sendai (Japan); Yoshimi, K.; Hanada, S. [Tohoku Univ., Sendai (Japan). Research Inst. for Iron, Steel and Other Metals

    1997-02-01

    This paper describes an influence of additional elements on the high temperature deformation behavior of Nb-base solid solution alloys. Highly concentrated solid solution single crystals of Nb-Ta and Nb-Mo alloys were prepared. Compression test and strain rate sudden change test were conducted in the vacuum at temperatures ranging from 77 to 1773 K, to determine the strain rate sensitivity index. Yield stress of the Nb-Ta alloy was similar to that of Nb alloy at temperatures over 0.3{times}T{sub M}, where T{sub M} is fusing point of Nb. While, the yield stress increased with increasing the impurity oxygen concentration at temperatures below 0.3{times}T{sub M}. The yield stress became much higher than that of Nb alloy. The strain rate sensitivity index showed positive values in the whole temperature range. On the other hand, the yield stress of Nb-Mo alloy was higher than that of Nb alloy in the whole temperature range, and increased with increasing the Mo concentration. The strain rate sensitivity index showed negative values at the temperature range from 0.3{times}T{sub M} to 0.4{times}T{sub M}. It was found that serration occurred often for Nb-40Mo alloys. 1 ref., 4 figs., 1 tab.

  1. Ab initio study of the energy loss near sulfur K and L2,3 edges of layered MS2 (M=Ta, Nb and V) in trigonal prismatic and octahedral structures.

    Science.gov (United States)

    Dadsetani, Mehrdad; Nouri, Tahereh; Nejatipour, Hajar

    2017-07-01

    This study set out to calculate the full-potential linearized augmented plane wave (FPLAPW)-based energy loss near sulfur K and L 2,3 edge structures of group V layered transition metal disulfides MS 2 (M=Ta, Nb, and V) in octahedral (1T) as well as trigonal prismatic (2H) structures. The calculations showed that, consistent with other calculations, all the studied materials were metallic due to the partially filled d bands in their configurations. Furthermore, the calculated ELNES spectra revealed a good agreement with the available experimental XANES analogues. The d-like and p-like transitions of M and sulfur atoms were the dominant electron transitions in K edge spectra. Spectrum characteristics of the sulfur L 2,3 edge of ELNES indicated the transition of sulfur-p electrons to the unoccupied s or d states. These spectra reflect the electronic band structures of materials, as well. As the focus shifts from bulk to monolayer, substrate hybridization becomes stronger. In 2H phases, the dominant peaks of sulfur K edge spectra originate from unoccupied d bands. Further, the broad peaks at higher energy ranges are due to the transitions to sulfur p hybridized with M-s and p states. For energies below 7eV, M-d state is the target state of most of the transitions in both 1T and 2H phases. For above 10eV energies, however, sulfur-d is the target state. Moreover, density of states of sulfur-p (d) is very similar in shape to that of sulfur K (L 2,3 ) edges spectra. For the sulfur L 2,3 edges, from 2H-TaS 2 to 2H-VS 2 and also from bulk to monolayer, the number of transitions to M-d state increases. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. In situ elaboration of a binary Ti–26Nb alloy by selective laser melting of elemental titanium and niobium mixed powders

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, M. [Laboratoire d' Etude des Microstructures et de Mécanique des Matériaux LEM3 (UMR CNRS 7239), Université de Lorraine, Ile de Saulcy, F-57045 Metz (France); Joguet, D. [Laboratoire d' Etudes et de Recherches sur les Matériaux, les Procédés et les Surfaces LERMPS, Université de Technologie de Belfort Montbéliard, Sevenans, 90010 Belfort (France); Robin, G. [Laboratoire d' Etude des Microstructures et de Mécanique des Matériaux LEM3 (UMR CNRS 7239), Université de Lorraine, Ile de Saulcy, F-57045 Metz (France); Peltier, L. [Laboratoire d' Etude des Microstructures et de Mécanique des Matériaux LEM3 (UMR CNRS 7239), Ecole Nationale Supérieure d' Arts et Métiers, F-57078 Metz (France); Laheurte, P. [Laboratoire d' Etude des Microstructures et de Mécanique des Matériaux LEM3 (UMR CNRS 7239), Université de Lorraine, Ile de Saulcy, F-57045 Metz (France)

    2016-05-01

    Ti–Nb alloys are excellent candidates for biomedical applications such as implantology and joint replacement because of their very low elastic modulus, their excellent biocompatibility and their high strength. A low elastic modulus, close to that of the cortical bone minimizes the stress shielding effect that appears subsequent to the insertion of an implant. The objective of this study is to investigate the microstructural and mechanical properties of a Ti–Nb alloy elaborated by selective laser melting on powder bed of a mixture of Ti and Nb elemental powders (26 at.%). The influence of operating parameters on porosity of manufactured samples and on efficacy of dissolving Nb particles in Ti was studied. The results obtained by optical microscopy, SEM analysis and X-ray microtomography show that the laser energy has a significant effect on the compactness and homogeneity of the manufactured parts. Homogeneous and compact samples were obtained for high energy levels. Microstructure of these samples has been further characterized. Their mechanical properties were assessed by ultrasonic measures and the Young's modulus found is close to that of classically elaborated Ti–26Nb ingot. - Highlights: • Biomimetic implants can be provided from additive manufacturing with Ti–Nb. • We made parts in a Ti–Nb alloy elaborated in situ from a mixture of elemental powders. • Process parameters have a significant impact on homogeneity and compactness. • Non-columnar elongated beta-grains are stacked with an orientation {001}<100 >. • Low Young's modulus is achieved by this texture.

  3. Development of Nb3Sn multi-filamentary wires superior in mass productivity

    International Nuclear Information System (INIS)

    Nakagawa, Kazuhiko; Ohata, Katsumi; Miyashita, Katsumi; Nakada, Yasushi

    2015-01-01

    We have developed superconducting wire about bronze route Nb 3 Sn and internal tin processed Nb 3 Sn. SH Copper Products Ltd. manufactures bronze route Nb 3 Sn superconducting strands for ITER-TF coils under a contract with the Japan Atomic Energy Agency (JAEA). The Nb 3 Sn strands which are composed of Nb-1 wt%Ta filaments and Cu-15.5 wt%-0.3 wt%Ti bronze have good workability and high performance. More than 850 A/mm 2 of non Cu J c at 12 T can be stably obtained using two-stage heat treatment technique. The internal-tin technique is an excellent method for fabricating Nb 3 Sn superconducting wire with a high critical current density. We have developed a new type of internal-tin Nb 3 Sn wire in which the multi-filamentary wire is fabricated by combining mono-filamentary Nb elements and mono-filamentary Sn elements. The simple fabrication process will enable the fabrication cost of the wires to be reduced. (author)

  4. Structural and piezoelectric properties of aged 1-mol% Li2O-excess (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 ceramics

    International Nuclear Information System (INIS)

    Moon, Sang-Ho; Yun, Seok-Woo; Ham, Yong-Su; Lee, Young-Hie; Nam, Song-Min; Koh, Jung-Hyuk; Jeong, Soon-Jong; Kim, Min-Soo

    2010-01-01

    One (1)-mol% Li 2 O-excess (Na 0.51 K 0.47 Li 0.02 )(Nb 0.8 Ta 0.2 )O 3 lead-free piezoelectric ceramics were aged under different unipolar electric fields. Unipolar electric fields of 3, 5, and 7 kV/cm were applied to the specimens to accelerate the electric aging behavior. By employing a unipolar electric field for the piezoelectric actuators, we were able to remove undesirable heating problem from the relaxation current in the ferroelectric domain motions. To accelerate the aging test, we used an applied electric fields with a frequency of 910 Hz. To earn enough time for charging and discharging, we used an accurate time constant for the equivalent model for the piezoelectric actuators. X-ray diffraction analyses were carried out to determine the structural aging behavior of the poled piezoelectric specimens. As the piezoelectric specimens were exposed to high electric fields for aging tests, the actuators lost their tetragonality and took on a pseudo-cubic structure. The cycling dependent piezoelectric coefficient and electromechnical coupling coefficient followed a stretched exponential law as aging process.

  5. Scanning tunneling microscopy study of nano-structured polyatom-substituted H4PW11M1O40 Keggin and H7P2W17M1O62 (M = Nb, Ta) Wells-Dawson heteropolyacid catalysts.

    Science.gov (United States)

    Choi, Jung Ho; Park, Dong Ryul; Park, Sunyoung; Song, In Kyu

    2012-07-01

    Polyatom-substituted H4PW11M1O40 Keggin and H7P2W17M1O62 (M = Nb, Ta) Wells-Dawson heteropolyacid (HPA) catalysts were investigated by scanning tunneling microscopy (STM) and tunneling spectroscopy to elucidate their redox property and oxidation catalysis. STM images clearly showed that HPAs formed nano-structured monolayer arrays on graphite surface. In tunneling spectroscopy, HPAs exhibited a distinctive current-voltage behavior called negative differential resistance (NDR). NDR peak voltage of the HPAs was then correlated with reduction potential determined by electrochemical method in solution. NDR peak voltage of the HPAs appeared at less negative voltage with increasing reduction potential. Vapor-phase oxidative dehydrogenation of isobutyraldehyde to methacrolein was also carried out as a model reaction to probe oxidation catalysis of the HPAs. NDR peak voltage of the HPAs appeared at less negative voltage with increasing yield for methacrolein. NDR peak voltage could be utilized as a correlating parameter for the reduction potential and as a probe of oxidation catalysis in the oxidative dehydrogenation of isobutyraldehyde.

  6. Synthesis, structure, and electrical conductivity of A'[A(sub 2)B(sub 3)O(sub 10)] (A'=Rb, Cs A=Sr, Ba; B=Nb, Ta)

    International Nuclear Information System (INIS)

    Thangadurai, Venkataraman; Schmid-Beurmann, Peter; Weppner, Werner

    2001-01-01

    New members of Dion-Jacobson (D-J)-type layered perovskites of the general formula A'[A(sub 2)B(sub 3)O(sub 10)] (A'=Rb, Cs; A=Sr, Ba; B=Nb, Ta) were prepared by solid-state reactions between the metal oxides, nitrates, and carbonates under specific conditions. The crystal structures were determined using powder X-ray diffraction data in combination with Rietveld analysis. The c-axis lattice parameter increases as the size of the alkaline earth ion increases. Both Sr and Ba compounds crystallize in a tetragonal cell, while the corresponding Ca compounds crystallize in an orthorhombic cell. The electrical conductivity of the layered perovskites was determined using AC impedance analysis and DC methods. Among the compounds with the same alkali ion and different alkaline earth ions, the Ca compound exhibits a higher electrical conductivity than the corresponding Sr and Ba compounds. DC measurements reveal that the layered perovskites exhibit both ionic and electronic conduction

  7. A Study on Thermal Properties and α( hcp) → β( bcc) Phase Transformation Energetics in Ti-5 mass% Ta-1.8 mass% Nb Alloy Using Inverse Drop Calorimetry

    Science.gov (United States)

    Behera, Madhusmita; Raju, S.; Jeyaganesh, B.; Mythili, R.; Saroja, S.

    2010-12-01

    Accurate measurements of enthalpy increment ( H T - H 298.15) values have been made on a Ti-5 mass% Ta-1.8 mass% Nb alloy using the inverse drop calorimetry technique in the temperature range from 463 K to 1457 K. The measured enthalpy increment values show a steady increase with temperature in both α- hcp and β- bcc solid solution regions. It is found that both the onset as well the completion of the α → β phase change are demonstrated by a marked deviation of the enthalpy increment behavior from the otherwise smooth variation encountered in the respective low-temperature α- and high-temperature β-phase domains. The transformation start ( T s) and finish ( T f) temperatures of the α → β phase change are found to be (1072±10) K and (1156±10) K, respectively. In the actual α → β phase transformation region, the variation of the enthalpy with the progress of transformation is found to follow a sigmoidal shape which is in line with the diffusive nature of the phase transformation. An estimation of the total enthalpy change associated with the α → β phase transformation (Δ° H tr) has been made by assuming a simple diffusion limited kinetic model for the phase change. The net enthalpy change for the α → β transformation is found to be 76 J · g-1. The measured temperature variation of the enthalpy increment in both α- and β-phase regimes are fitted to simple analytical functional forms to obtain temperature-dependent estimates of the specific heat, C P . The total specific heat change associated with the α → β phase transformation {Δ^{circ}{CP^{α}}^{→{β}}} is estimated to be 904 J · kg-1 · K-1.

  8. Structures and magnetic properties of double perovskites A2LnMO6 and 6H-perovskites Ba3LnRu2O9 (A=Sr, Ba; Ln=Y, lanthanides; M=Nb, Ta, Ru)

    International Nuclear Information System (INIS)

    Hinatsu, Yukio; Doi, Yoshihiro

    2003-01-01

    This account describes the synthesis, crystal structures and magnetic properties of double perovskites A 2 LnMO 6 and 6H-perovskites Ba 3 LnRu 2 O 9 (A=Sr, Ba; Ln=Y, lanthanides; M=Nb, Ta, Ru). The double perovskites A 2 LnMO 6 have two kinds of cations, Ln and M, in the B site of the perovskite ABO 3 . These cations adopt the alternative ordered arrangement. Measurements of the magnetic susceptibility, specific heat, and powder neutron diffraction showed that all of the A 2 LnRuO 6 compounds exhibited an antiferromagnetic transition at low temperatures and a complex temperature dependence of the magnetic susceptibility below their transition temperatures. In these compounds, the magnetic interaction between the Ln (4f electrons) and Ru (4d electrons) ions via the Ln-O-Ru pathway contributes greatly to their magnetic cooperative phenomena. The structural and magnetic studies for the 6H-perovskites Ba 3 LnRu 2 O 9 show that the Ln cations occupy the corner-sharing octahedra (LnO 6 octahedron) and the Ru cations occupy the face-sharing octahedra (Ru 2 O 9 dimer). The Ba 3 LnRu 2 O 9 compounds show a characteristic temperature-dependence of the magnetic susceptibilities, that is, a broad maximum at temperatures above 135 K and a magnetic transition at 5-15 K. These magnetic properties mainly reflect two kinds of the magnetic interactions: the interaction between Ln and Ru ions and that between Ru ions in the Ru 2 O 9 dimer. (author)

  9. Effects of SrTiO3 on dielectric and piezoelectric properties of K0.48Na0.48Li0.04Nb0.96Ta0.04O3-based piezoceramics

    International Nuclear Information System (INIS)

    Bafandeh, Mohammad Reza; Abbasi, Mohammad Hasan; Saidi, Ali; Lee, Jae-Shin

    2013-01-01

    Highlights: ► Sodium potassium niobate based piezoceramics modified with SrTiO 3 (ST) were prepared. ► Crystal structure, microstructure and dielectric properties of ceramics were investigated. ► Addition of ST more than 3 mol% changed ferroelectric behavior from normal to relaxor. ► Coexistence of two structures in ceramic with 1 mol% ST enhanced piezoelectric constant. - Abstract: In this study, (100 − x) K 0.48 Na 0.48 Li 0.04 Nb 0.96 Ta 0.04 O 3 − xSrTiO 3 (0 ≤ x ≤ 10) ceramics were fabricated via normal sintering of synthesized powder by using solid state reaction. All ceramics revealed pure perovskite structure, indicating formation of solid solution between KNNLT and ST up to 10%. With increasing x, the crystal structure of ceramics changed from orthorhombic to tetragonal and finally pseudocubic symmetry when x = 10. Ceramic containing 1% ST had orthorhombic and tetragonal symmetries, simultaneously. Investigation of the variation of dielectric constant of ceramics versus temperature revealed that for ceramic with x = 1, polymorphic phase transition (PPT) temperature between orthorhombic and tetragonal is less than room temperature. Thus coexistence of two different structures in this ceramic is due to vicinity of its composition to morphotropic phase boundary (MPB). As a result, the maximum piezoelectric constant was measured for this ceramic. Ceramics containing 5 and 7.5% ST tend to appear relaxor ferroelectric behavior which is because of chemical inhomogeneities in both A- and B-sites of the ABO 3 perovskite structure.

  10. Nb2O5

    Indian Academy of Sciences (India)

    Unknown

    Abstract. MgNb2–xTaxO6 (0 ≤ x ≤ 2) phases can be obtained as the major phase. (75 to 90%) by solid state reactions starting from oxides. These oxides crystallize in the orthorhombic columbite structure till x = 1⋅75 and the tetragonal trirutile structure for MgTa2O6 (x = 2⋅0). For all the compositions there exist secondary.

  11. In situ elaboration of a binary Ti-26Nb alloy by selective laser melting of elemental titanium and niobium mixed powders.

    Science.gov (United States)

    Fischer, M; Joguet, D; Robin, G; Peltier, L; Laheurte, P

    2016-05-01

    Ti-Nb alloys are excellent candidates for biomedical applications such as implantology and joint replacement because of their very low elastic modulus, their excellent biocompatibility and their high strength. A low elastic modulus, close to that of the cortical bone minimizes the stress shielding effect that appears subsequent to the insertion of an implant. The objective of this study is to investigate the microstructural and mechanical properties of a Ti-Nb alloy elaborated by selective laser melting on powder bed of a mixture of Ti and Nb elemental powders (26 at.%). The influence of operating parameters on porosity of manufactured samples and on efficacy of dissolving Nb particles in Ti was studied. The results obtained by optical microscopy, SEM analysis and X-ray microtomography show that the laser energy has a significant effect on the compactness and homogeneity of the manufactured parts. Homogeneous and compact samples were obtained for high energy levels. Microstructure of these samples has been further characterized. Their mechanical properties were assessed by ultrasonic measures and the Young's modulus found is close to that of classically elaborated Ti-26 Nbingot. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. 182Ta determination in biological materials

    International Nuclear Information System (INIS)

    Holgye, Z.

    1976-01-01

    A sensitive and selective method of 182 Ta determination in the urine and feces was elaborated. 182 Ta is separated from a partly mineralized urine and from mineralized feces by precipitation in form of tantalum phosphate following the addition of the tantalum carrier. 182 Ta is separated from interfering radionuclides especially 95 Zr and 95 Nb, by extraction with methyl isobutyl ketone. Rare earths and other radionuclides are then removed by coprecipitation with LaF 3 . The sensitivity of the methods is within pCi units for 182 Ta/l urine or 24-hour feces. (author)

  13. SÍNTESIS Y CARACTERIZACIÓN ESTRUCTURAL DE LAS ALEACIONES (CuInTe21-x (Cu3-MT-Te4x (MT: Nb, Ta con x = 1/10, 1/5, 1/3, 1/2 y 2/3 // SYNTHESIS AND STRUCTURAL CHARATERIZATION OF THE ALLOYS (CuInTe21-x (Cu3-MT-Te4 x (MT: Nb, Ta with x = 1/10, 1/5, 1/3, 1/2 y 2/3

    Directory of Open Access Journals (Sweden)

    Menjamín Salas

    2017-06-01

    Full Text Available En este trabajo se reporta la caracterización de las aleaciones (CuInTe21-x (Cu3-MT-Te4x (MT: Nb, Ta y x = 1/10, 1/5, 1/3, 1/2 y 2/3, utilizando las técnicas de Microscopia Electrónica de Barrido (MEB, Difracción de Rayos-X (DRX y Análisis Térmico Diferencial (ATD. Estas aleaciones fueron preparadas por la técnica de fusión y recocido cumpliendo con la regla de Grimm-Sommerfeld. El trabajo se apoya en los termogramas de los compuestos CuInTe2 y Cu3NbTe4 que fueron medidos con anterioridad e incorporados en los diagramas de fases para el sistema (CuInTe21-x (Cu3-MT-Te4x en x = 0 y x = 1; con la intensión de obtener la mejor información de las fases desde x=0 a x=1. En estos diagramas de fases de la familia de aleaciones, obtuvimos en los rangos de concentraciones, las siguientes fases: en 0 < x < 0.1, la fase tipo calcopirita, para 0 < x < 0.9 una zona de dos fases, calcopirita más sulvanita y para 0.9 < x < 1, la fase sulvanita. La solubilidad de la fase sulvanita Cu3NbTe4 en la calcopirita es de aproximadamente 10 % al igual que la solubilidad de la fase CuInTe2 en la sulvanita. Esta poca solubilidad entre la familia de la calcopirita y los metales de transición Nb y Ta hizo imposible aumentar la brecha de energía. /// In this work we reported the characterization of the (CuInTe21-x (Cu3-BV- Te4x (BV: Nb, Ta y x = 1/10, 1/5, 1/3, 1/2 y 2/3, alloys system using the techniques Scanning Electron Microscope (SEM, X- Ray Diffraction (XRD and Differential Thermal Analysis (DTA. Alloys system was prepared by fusion and annealing direct fulfilling the rule of Grimm-Sommerfeld. The work is based on the thermograms of the CuInTe2 and Cu3NbTe4 compounds that were previously measured and incorporated in the phase diagrams for the system (CuInTe21-x (Cu3-MT-Te4 at x = 0 and x = 1; with the intention of obtaining the best information of the phases from x = 0 to x = 1. In these phase diagrams of the alloy family, we obtained in the concentration

  14. (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3 thick film prepared ...

    Indian Academy of Sciences (India)

    2Functional Materials Research Laboratory, Tongji University, Shanghai 200092, China ... Fang Fu et al. Figure 1. SEM image of plate-like (a) Bi2.5Na2.5Nb4O15 particles and (b) NaNbO3 particles. NaNbO3 particles have a thickness of about 1 μm and a ..... [13] Fu F, Shen B and Zhai J W 2011 J. Alloys Compd. 509 7130.

  15. Improvement of ferroelectric properties by heat treating SrBi sub 2 (Ta sub 1 sub - sub x Nb sub x) sub 2 O sub 9 /Bi sub 2 O sub 3 /SrBi sub 2 (Ta sub 1 sub - sub x Nb sub x) sub 2 O sub 9 heterostructure

    CERN Document Server

    Park, Y B; Jung, H J; Park, J W

    1998-01-01

    Ferroelectric properties of SrBi sub 2 TaNnO sub 9 (SBTN) thin films were changed in terms of the amount of Bi content in SBTN. We suggested that the addition of excess Bi in the films could be accomplished by heat treating SBTN/Bi sub 2 O sub 3 /SBTN heterostructure fabricated by r.f. magnetron sputtering method. excess Bi composition was controlled by changing the thickness of the sandwiched Bi sub 2 O sub 3 in SBTN/Bi sub 2 O sub 3 /SBTN heterostructure from 50 A to 400 A. As the thickness of Bi sub 2 O sub 3 films were increased from 0 to 100 A, the grain grew faster and the ferroelectric properties were improved. On the other hand, when the thickness of Bi sub 2 O sub 3 films was greater than 400 A, a Bi sub 2 Pt phase appeared as a second phase, which led to poor ferroelectric properties. The maximum remanent polarization (2Pr) and good coercive field (Ec) were obtained for the SBTN/Bi sub 2 O sub 3 (100A)/SBTN films. In this case, 2Pr and Ec were 14.75 mu C/cm sup 2 and 53.4kV/cm, respectively.

  16. Chemistry of rare elements

    International Nuclear Information System (INIS)

    Tananaev, I.V.

    1988-01-01

    The main directions of the research in the field of rare element chemistry (mainly rare earths, as well as In, U, Th, V, Nb, Ta, Mo, W) carried out for the recent decade in the laboratory of chemistry of rare elements and inorganic polymers of the USSR Academy of Sciences Institute, of General and Inorganic Chemistry (IGIC) are reviewed. The research of synthesis, structure and properties of rare earth phosphites, phoshates, arsenates, selenates, selenites and borates, as well as rare earth compounds with mixed oxide anions is of great importance. The fields of practical application of these compounds in view of their unique properties are noted

  17. Redetermination of tantalum pentabromide, (TaBr52

    Directory of Open Access Journals (Sweden)

    Katja Habermehl

    2010-09-01

    Full Text Available Crystals of di-μ-bromido-bis[tetrabromidotantalum(V], (TaBr52, were obtained by recrystallization at 773 K. A first crystal structure study of (TaBr52 was reported by Rolsten [J. Am. Chem. Soc. (1958, 80, 2952–2953], who analysed the powder diffraction pattern and came to the conclusion that it crystallizes isotypically with (NbBr52 in a primitive orthorhombic cell. These findings are not in agreement with our current results of a monoclinic C-centred structure. (TaBr52 is isotypic with α-(NbCl52. The crystal structure contains [TaBr6] octahedra sharing common edges forming [TaBr5]2 dimers. Two crystallographically independent dimers with symmetries m and 2/m and Ta...Ta distances of 4.1574 (11 and 4.1551 (15 Å, respectively, are present in the structure.

  18. Development of Ti-12Mo-3Nb alloy for biomedical application; Desenvolvimento da liga Ti-12Mo-3Nb para aplicacao biomedica

    Energy Technology Data Exchange (ETDEWEB)

    Panaino, J.V.P.; Gabriel, S.B., E-mail: josevicentepanaino@hotmail.co [Centro Universidade de Volta Redonda (UNIFOA), RJ (Brazil); Mei, P. [Universidade Estadual de Campinas (DEMa/UNICAMP), SP (Brazil). Dept. de Materiais; Brum, M.V. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Programa de Engenharia Metalurgica e de Materiais; Nunes, C.A. [Universidade de Sao Paulo (EEL/USP), Lorena, SP (Brazil). Escola de Engenharia

    2010-07-01

    The titanium alloys are quite satisfactory for biomedical applications due to their physical, mechanical and biological properties. Recent studies focuses on the development of beta type titanium alloys, composed of toxic elements (Nb, Mo, Ta ,...), because they have more advantages than alpha and alpha + beta (Ti- 6Al-4V) alloys such as lower modulus of elasticity, better plasticity and, moreover, the process variables can be controlled to produce selected results. This project focused on the development and characterization of Ti-12Mo-3Nb alloy in the condition 'as cast' and after thermomechanical treatment. The material was characterized in different conditions by X-ray diffraction, optical microscopy, microhardness measurements and elasticity modulus. The results showed that the forged Ti-12Mo-3Nb alloy showed the best combination of properties, being a promising candidate for use as implant. (author)

  19. Light-weight steels based on iron-aluminium - influence of micro alloying elements (B, Ti, Nb) on microstructures, textures and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Bruex, U.; Frommeyer, G. [Dept. of Materials Technology, Max-Planck-Inst. fuer Eisenforschung GmbH, Duesseldorf (Germany); Jimenez, J. [Centro Nacional de Investigaciones Metalurgicas (C.S.I.C.), Madrid (Spain)

    2002-12-01

    The influence of the micro alloying elements B, Ti and Nb on the recrystallization texture and mechanical properties of iron aluminium light-weight steels, particularly with reference to their improved deep drawing properties was investigated. Depending on the combination of the alloying elements the microstructures of the investigated micro alloyed Fe-6Al steels are influenced by grain refinement. Likewise, variable combinations of micro alloying elements differently affect the texture. Generally, the mechanical properties are improved. However, small amounts of B, Ti and Nb cause superior deep drawing and stretch forming properties of these iron aluminium light-weight steels. The microstructures of various micro alloyed cold rolled Fe-6Al steel sheets were evaluated by optical microscopy, scanning electron microscopy (SEM) inclusively EDAX and X-ray diffraction. Texture measurements were performed using a goniometer with a closed Eulerian cradle and analysed by ODF calculations. Tensile tests were carried out at room temperature and 200 C, respectively. The deep drawing behaviour was determined by performing cupping tests and digitalised strain analysis. (orig.)

  20. Development of Ti-12Mo-3Nb alloy for biomedical application

    International Nuclear Information System (INIS)

    Panaino, J.V.P.; Gabriel, S.B.; Mei, P.; Brum, M.V.; Nunes, C.A.

    2010-01-01

    The titanium alloys are quite satisfactory for biomedical applications due to their physical, mechanical and biological properties. Recent studies focuses on the development of beta type titanium alloys, composed of toxic elements (Nb, Mo, Ta ,...), because they have more advantages than alpha and alpha + beta (Ti- 6Al-4V) alloys such as lower modulus of elasticity, better plasticity and, moreover, the process variables can be controlled to produce selected results. This project focused on the development and characterization of Ti-12Mo-3Nb alloy in the condition 'as cast' and after thermomechanical treatment. The material was characterized in different conditions by X-ray diffraction, optical microscopy, microhardness measurements and elasticity modulus. The results showed that the forged Ti-12Mo-3Nb alloy showed the best combination of properties, being a promising candidate for use as implant. (author)

  1. Effect of microalloying elements (Nb, V and Ti) on the hot flow behavior of high-Mn austenitic twinning induced plasticity (TWIP) steel

    International Nuclear Information System (INIS)

    Reyes-Calderón, F.; Mejía, I.; Boulaajaj, A.; Cabrera, J.M.

    2013-01-01

    This research work studies the effect of microalloying elements such as Nb, V and Ti on the hot flow behavior of high-Mn austenitic TWIP steel. For this purpose, isothermal uniaxial hot compression tests were carried out at three temperatures (900, 1000 and 1100 °C) and four constant strain rates (10 −1 , 10 −2 , 10 −3 and 10 −4 s −1 ). Experimental results revealed that hot flow curves of microalloyed TWIP steels show single peak curves for all test conditions. Results are discussed in terms of the peak stress (σ p ) and peak strain (ε p ) and its dependence on the strain rate (ε) and temperature. The addition of microalloying elements such as Nb, V and Ti in TWIP steels generates a slight increase in the σ p value, and Ti microalloyed TWIP steel exhibits the highest σ p value. Hot deformed microstructures were analyzed by the Electron Back-Scattering Diffraction Technique (EBSD). The most important results of the austenitic recrystallized grain refinement were obtained for V and Ti microalloyed TWIP steels.

  2. Implications of heavy-ion-induced satellite x-ray emission. II. Production of K and L x rays by 0. 9 to 2. 6 MeV/u Ar ions in thick targets of V, Cu, Nb, Ta, and Pt

    Energy Technology Data Exchange (ETDEWEB)

    O' Kelley, G.D.; Auble, R.L.; Hulett, L.D.; Kim, H.J.; Milner, W.T.; Raman, S.; Shaha, O.; Vane, C.R.; Young, J.P.; Lapicki, G.

    1983-01-01

    Cross sections are reported for x-ray production in targets of /sup 23/V, /sup 29/Cu, /sup 41/Nb, /sup 73/Ta, and /sup 78/Pt by /sup 40/Ar ions of 36.0, 56.4, 76.6, and 103 MeV. Because the targets were relatively thick, approx. 1 mg/cm/sup 2/, the data were corrected, using a novel approach, for projectile energy loss and x-ray attenuation in the targets. The cross sections so analyzed are compared with the predictions of the first Born approximation as well as with those of a more extensive treatment which includes energy loss, Coulomb deflection, perturbed stationary-state, and relativistic effects. The significant discrepancies between the data and this latter theory are atrributed primarily to the influence of multiple ionization on the x-ray emission probabilities.

  3. Phase development, densification and dielectric properties of (0.95-xNa0.5K0.5NbO3 - 0.05LiTaO3 - x LiSbO3 lead-free piezoelectric ceramics

    Directory of Open Access Journals (Sweden)

    Pornsuda Bomlai

    2008-08-01

    Full Text Available Lead-free piezoelectric ceramics in the system (0.95-x Na0.5K0.5NbO3 - 0.05LiTaO3 - x LiSbO3, x = 0-0.1, were synthesized by a reaction-sintering method. The effects of the content of LiSbO3, and the sintering temperature on phase-development, microstructure and dielectric properties of the samples were investigated. Additions of LiSbO3 produced a change in crystal system from orthorhombic to tetragonal. The additive reduced the temperature at which secondary recrystallisation occurred, and also affected average grain size and dielectric constant. A sintering temperature of 1050oC (for 2 h was the optimum for this system in order to achieve a high density and high dielectric constant. A maximum dielectric constant of 1510 was recorded for the x = 0.04 composition.

  4. Effects of background oxygen pressure on dielectric and ferroelectric properties of epitaxial (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films on SrTiO3

    Science.gov (United States)

    Abazari, M.; Akdoǧan, E. K.; Safari, A.

    2008-11-01

    Oxygen partial pressure (PO_2) in pulsed laser deposition significantly influences the composition, microstructure, and electrical properties of epitaxial misfit strain-relieved 450nm ⟨001⟩ oriented epitaxial (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films on SrRuO3 coated SrTiO3. Films deposited at 400mTorr exhibit high remnant and saturated polarization of 7.5 and 16.5μC /cm2, respectively, which is ˜100% increase over the ones grown at 100mTorr. The dielectric constant linearly increases from 220 to 450 with increasing PO2. The observed changes in surface morphology of the films and their properties are shown to be due to the suppression of volatile A-site cation loss.

  5. Effect of manganese doping on remnant polarization and leakage current in (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 epitaxial thin films on SrTiO3

    Science.gov (United States)

    Abazari, M.; Akdoǧan, E. K.; Safari, A.

    2008-05-01

    Single phase, epitaxial, ⟨001⟩ oriented, undoped and 1mol% Mn-doped (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films of 400nm thickness were synthesized on SrRuO3 coated SrTiO3. Such films exhibit well saturated hysteresis loops and have a spontaneous polarization (Ps) of 10μC /cm2, which is a 150% higher over the Ps of the undoped composition. The coercive field of 1mol% Mn doped films is 13kV/cm. Mn-doping results in three orders of magnitude decrease in leakage current above 50kV/cm electric field, which we attribute to the suppression of intrinsic p-type conductivity of undoped films by Mn donors.

  6. Development and Implementation of a Transport Method for the Transport and Reaction Simulation Engine (TaRSE) based on the Godunov-Mixed Finite Element Method

    Science.gov (United States)

    James, Andrew I.; Jawitz, James W.; Munoz-Carpena, Rafael

    2009-01-01

    A model to simulate transport of materials in surface water and ground water has been developed to numerically approximate solutions to the advection-dispersion equation. This model, known as the Transport and Reaction Simulation Engine (TaRSE), uses an algorithm that incorporates a time-splitting technique where the advective part of the equation is solved separately from the dispersive part. An explicit finite-volume Godunov method is used to approximate the advective part, while a mixed-finite element technique is used to approximate the dispersive part. The dispersive part uses an implicit discretization, which allows it to run stably with a larger time step than the explicit advective step. The potential exists to develop algorithms that run several advective steps, and then one dispersive step that encompasses the time interval of the advective steps. Because the dispersive step is computationally most expensive, schemes can be implemented that are more computationally efficient than non-time-split algorithms. This technique enables scientists to solve problems with high grid Peclet numbers, such as transport problems with sharp solute fronts, without spurious oscillations in the numerical approximation to the solution and with virtually no artificial diffusion.

  7. 179Ta and 180Ta structure by transfer reactions

    International Nuclear Information System (INIS)

    Warde, Elias.

    1979-01-01

    Transfer reactions (α,t); ( 3 He,d); (p,t) and (p,d) have been used to study the nuclear spectroscopy of 179 Ta and 180 Ta. In 179 Ta, 5/2 - and 9/2 - states of the 1/2(541) configuration have been identified. The core-quasiproton interaction has to be taken into account in order to explain the two-nucleon transfer intensities in the 181 Ta(p,t) 179 Ta reaction. A level scheme has been proposed for 180 Ta for the first time. Especially the ground state is identified with the (1 + ,1) level of the [7/2 + (404)sub(p), 9/2 + (624)sub(n)] configuration and spin (9 - ,9) of the configuration [9/2 - (514)sub(p), 9/2 + (624)sub(n)] has been assigned to the long-lived isomer. From the observed configurations in 180 Ta, the matrix elements of the effective residual interaction vsub(np) have been deduced and compared to theoretical predictions [fr

  8. Team one (GA/MCA) effort of the DOE 12 Tesla Coil Development Program. 12 Tesla ETF toroidal field coil helium bath cooled NbTi alloy concept

    International Nuclear Information System (INIS)

    1980-07-01

    This report presents the conceptual design of an ETF compatible toroidal field coil, employing helium bath cooled NbTi alloy conductor. The ten TF-coil array generates a peak field of 11-1/2 tesla at 2.87 m radius, corresponding to a major axis field of 6.1 tesla. The 10 kA conductor is an uninsulated, unsoldered Rutherford cable, employing NbTiTa ally as developed in Phase I of this effort. The conductor is encased within a four element frame of stainless steel strips to provide hoop and bearing load support

  9. X-ray detection with Nb/Al/AlO{sub x}/Al/Nb tunneling junctions

    Energy Technology Data Exchange (ETDEWEB)

    Nussbaumer, T.; Finkbeiner, F.; Weber, K.J.; Lerch, P.; Zehnder, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Ott, H.R. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1996-10-01

    A whole wafer fabrication procedure using selective etching of refractory materials to produce Nb- or Ta/Al/AlO{sub x}/Al/Nb tunneling detectors is discussed. Fabrication aspects and preliminary results are presented. (author) 2 figs., 5 refs.

  10. Study of corrosion kinetics of fuel element tubes from calcium-thermal zirconium alloy Zr1Nb in water at 350 degree C and in vapour at 400 and 500 degree C

    International Nuclear Information System (INIS)

    Petel'guzov, I.A.

    2002-01-01

    In the report brought results of corrosion process studies in water medium of pipe samples for fuel element shells from Zr1Nb alloy (earlier KTZ-110),made from the calcium-thermal zirconium alloys developed in the Ukraine of technology and,for the comparison,samples of pipes from the staff alloy E110, applicable in fuel elements acting reactors of type WWER. Tests were conducted under the working temperature of fuel shells in the reactor (350 degree C) in during of 14000 hours and under increased temperatures (400 degree C) within a time acordinly 4000 hours. Samples from the alloy Zr1Nb had more high contents of oxygen (before 0,12%...0,16%), than staff alloy Eh110 (0,08%O). Studies have shown sufficiently high corrosion stability of experimental alloy Zr1Nb, close to stability of alloy E110.Discovered signs of corrosion 'breakway' or 'transition' on kinetic corrosion curves of Zr1Nb alloys and E110 alloy, characterisating zircaloy type of alloy. Considered mechanism of influence of oxygen on the corrosion process of zirconium alloys with the additive a niobium

  11. Observation of Element-Specific Energy-Filtered X-Ray Photoemission Electron Microscopy Images of Au on Ta Using a Wien Filter Type Energy Analyzer

    Science.gov (United States)

    Yasufuku, Hideyuki; Ohminami, Yusuke; Tsutsumi, Tetsuya; Niimi, Hironobu; Matsudaira, Nobuaki; Asakura, Kiyotaka; Kato, Makoto; Sakai, Yuji; Kitajima, Yoshinori; Iwasawa, Yasuhiro

    2004-11-01

    We have shown the possibility of a Wien filter as an energy analyzer for the energy-filtered X-ray photoemission electron microscopy (EXPEEM) by obtaining images of Au islands on a Ta substrate using an inner shell photoelectron excited by an X-ray with a photon energy of 2300 eV. When the photoelectron with kinetic energy of nearly 0 eV was selected, brighter Au islands were observed. When the kinetic energies of photoelectrons passing the Wien filter are set at those of Au 3d5/2 and Ta 3p3/2 photoelectrons, the Au and Ta regions appeared brighter, respectively, indicating that the chemical imaging was successful using a high energy X-ray and a Wien filter energy analyzer.

  12. Measurement of neutron activation cross-sections for elements Co, Ni, Y, Nb, Tm and Au between 12 and 20 MeV

    International Nuclear Information System (INIS)

    Iwasaki, S.; Matsuyama, S.; Ohkubo, T.; Fukuda, H.; Sakuma, M.; Kitamura, M.; Odano, N.

    1995-01-01

    Neutron activation cross-sections for cobalt, nickel, yttrium, niobium, thulium and gold have been measured in the neutron energies from 12 to 20 MeV with the reference cross section of NEA 93 Nb(n,2n) 92m Nb at Tohoku Dynamitron Facility. (author)

  13. Quench tests of Nb3Al small racetrack magnets

    International Nuclear Information System (INIS)

    Yamada, R.; Kikuchi, A.; Tartaglia, Michael Albert; Ambrosio, G.; Andreev, N.; Barzi, E.; Carcagno, R.; Feher, S.; Kashikhin, V.V.; Kotelnikov, S.; Lamm, Michael J.; Fermilab; NIMC, Tsukuba; KEK, Tsukuba

    2007-01-01

    Two Cu stabilized Nb3Al strands, F1 (Nb matrixed) and F3 (Ta matrixed), have been made at NIMS and their Rutherford cables were made at Fermilab in collaboration with NIMS. A Small Race-track magnet using F1 Rutherford cable, the first Nb3Al dipole magnet in the world, was constructed and tested to full current at Fermilab. This magnet was tested extensively to full short sample data and its quench characteristics were studied and reported. The 3-D magnetic field calculation was done with ANSYS to find the peak field. The quench characteristics of the magnet are explained with the characteristics of the Nb3Al strand and Rutherford cable. The other Small Race-track magnet using Ta matrixed F3 strand was constructed and will be tested in the near future. The advantages and disadvantages of these Nb3Al cables are discussed

  14. Experimental partitioning of Zr, Ti, and Nb between silicate liquid and a complex noble metal alloy and the partitioning of Ti between perovskite and platinum metal

    Science.gov (United States)

    Jurewicz, Stephen R.; Jones, John H.

    1993-01-01

    El Goresy et al.'s observation of Nb, Zr, and Ta in refractory platinum metal nuggets (RPMN's) from Ca-Al-rich inclusions (CAI's) in the Allende meteorite led them to propose that these lithophile elements alloyed in the metallic state with noble metals in the early solar nebula. However, Grossman pointed out that the thermodynamic stability of Zr in the oxide phase is vastly greater than metallic Zr at estimated solar nebula conditions. Jones and Burnett suggested this discrepancy may be explained by the very non-ideal behavior of some lithophile transition elements in noble metal solutions and/or intermetallic compounds. Subsequently, Fegley and Kornacki used thermodynamic data taken from the literature to predict the stability of several of these intermetallic compounds at estimated solar nebula conditions. Palme and Schmitt and Treiman et al. conducted experiments to quantify the partitioning behavior of certain lithophile elements between silicate liquid and Pt-metal. Although their results were somewhat variable, they did suggest that Zr partition coefficients were too small to explain the observed 'percent' levels in some RPMN's. Palme and Schmitt also observed large partition coefficients for Nb and Ta. No intermetallic phases were identified. Following the work of Treiman et al., Jurewicz and Jones performed experiments to examine Zr, Nb, and Ti partitioning near solar nebula conditions. Their results showed that Zr, Nb, and Ti all have an affinity for the platinum metal, with Nb and Ti having a very strong preference for the metal. The intermetallic phases (Zr,Fe)Pt3, (Nb,Fe)Pt3, and (Ti,Fe)Pt3 were identified. Curiously, although both experiments and calculations indicate that Ti should partition strongly into Pt-metal (possibly as TiPt3), no Ti has ever been observed in any RPMN's. Fegley and Kornacki also noticed this discrepancy and hypothesized that the Ti was stabilized in perovskite which is a common phase in Allende CAI's.

  15. Superconductivity in the Nb-Ru-Ge σ phase

    Science.gov (United States)

    Carnicom, Elizabeth M.; Xie, Weiwei; Sobczak, Zuzanna; Kong, Tai; Klimczuk, Tomasz; Cava, R. J.

    2017-12-01

    We show that the previously unreported ternary σ -phase material N b20.4R u5.7G e3.9 (N b0.68R u0.19G e0.13 ) is a superconductor with a critical temperature of 2.2 K. Temperature-dependent magnetic susceptibility, resistance, and specific-heat measurements were used to characterize the superconducting transition. The Sommerfeld constant γ for N b20.4R u5.7G e3.9 is 91 mJ mol f .u .-1K-2 (˜3 mJ mol ato m-1K-2 ) and the specific-heat anomaly at the superconducting transition, Δ C /γ Tc , is approximately 1.38. The zero-temperature upper critical field [μ0H c2(0 ) ] was estimated to be 2 T by resistance data. Field-dependent magnetization data analysis estimated μ0H c1(0 ) to be 5.5 mT. Thus, the characterization shows N b20.4R u5.7G e3.9 to be a type-II BCS superconductor. This material appears to be the first reported ternary phase in the Nb-Ru-Ge system, and the fact that there are no previously reported binary Nb-Ru, Nb-Ge, or Ru-Ge σ phases shows that all three elements are necessary to stabilize the material. An analogous σ phase in the Ta-Ru-Ge system did not display superconductivity above 1.7 K, which suggests that electron count cannot govern the superconductivity observed. Preliminary characterization of a possible superconducting σ phase in the Nb-Ru-Ga system is also reported.

  16. Structures and magnetic properties of double perovskites A sub 2 LnMO sub 6 and 6H-perovskites Ba sub 3 LnRu sub 2 O sub 9 (A=Sr, Ba; Ln=Y, lanthanides; M=Nb, Ta, Ru)

    CERN Document Server

    Hinatsu, Y

    2003-01-01

    This account describes the synthesis, crystal structures and magnetic properties of double perovskites A sub 2 LnMO sub 6 and 6H-perovskites Ba sub 3 LnRu sub 2 O sub 9 (A=Sr, Ba; Ln=Y, lanthanides; M=Nb, Ta, Ru). The double perovskites A sub 2 LnMO sub 6 have two kinds of cations, Ln and M, in the B site of the perovskite ABO sub 3. These cations adopt the alternative ordered arrangement. Measurements of the magnetic susceptibility, specific heat, and powder neutron diffraction showed that all of the A sub 2 LnRuO sub 6 compounds exhibited an antiferromagnetic transition at low temperatures and a complex temperature dependence of the magnetic susceptibility below their transition temperatures. In these compounds, the magnetic interaction between the Ln (4f electrons) and Ru (4d electrons) ions via the Ln-O-Ru pathway contributes greatly to their magnetic cooperative phenomena. The structural and magnetic studies for the 6H-perovskites Ba sub 3 LnRu sub 2 O sub 9 show that the Ln cations occupy the corner-sha...

  17. Effect of ZnO-B2O3 addition on the dielectric and the piezoelectric properties of lead-free (Na0.525K0.443Li0.037)(Nb0.883Sb0.08Ta0.037)O3 ceramics

    Science.gov (United States)

    Kim, You-Seok; Yoo, Ju-Hyun

    2014-12-01

    (Na0.525K0.443Li0.037)(Nb0.883Sb0.08Ta0.037)O3 + x wt% ZnO-B2O3 (NKLNST + x ZnO-B2O3) lead-free piezoelectric ceramics were prepared via a conventional solid-state reaction for various values of x = {0, 0.3, 0.6, 0.9, 1.2}; then, the dielectric and the piezoelectric properties of these ceramics were investigated. A pure perovskite structure and a small secondary phase were observed in the X-ray diffraction patterns. For the 0.3-wt% ZnO-B2O3 specimen, a density of ρ = 4.537 g/cm3, an electromechanical coupling factor of k P = 0.432, a mechanical quality factor of Q m = 96, and piezoelectric constant of d 33 = 209 pC/N were found to be optimal. These results indicate that the material with this composition is a promising candidate for use in a lead-free piezoelectric device.

  18. Web TA Production (WebTA)

    Data.gov (United States)

    US Agency for International Development — WebTA is a web-based time and attendance system that supports USAID payroll administration functions, and is designed to capture hours worked, leave used and...

  19. A Study on the Evaluation of the Cytotoxicity of Al2O3, Nb2O5, Ta2O5, TiO2 and ZrO2

    OpenAIRE

    AlO, A Study on the Evaluation of the Cytotox

    2004-01-01

    Nearly all metals used in implants are pure or alloys composed of transition elements forming spontaneously passive layers on the surface in electrolytes in a wide pH region. The biocompatibility of these metals used in implants is tested before surgical implantation. Determining the biocompatibility of these metals is implemented firstly by the testing of their cytotoxicity. The first step consists of evaluating the cell morphology and proliferation. In this study, glass slices we...

  20. Piezoelectric properties and diffusion phase transition around PPT of La-doped (Na{sub 0.52}K{sub 0.44}Li{sub 0.04}) Nb{sub 0.8}Ta{sub 0.2}O{sub 3} lead-free piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Wenlong, E-mail: yangwenlong1983@163.com; Wang, Li; Li, Haidong; Han, Junsheng; Xiu, Hanjiang; Zhou, Zhongxiang

    2016-10-01

    Lead-free ceramics (Na{sub 0.52}K{sub 0.44}Li{sub 0.04}){sub 1−3x}La{sub x}Nb{sub 0.8}Ta{sub 0.2}O{sub 3} (KNLNT-Lax, x=0.00, 0.25, 0.5, 0.75, 1.00, 1.25 mol%) as non-polluting materials were prepared by solid state reaction method. The structure, piezoelectric proprieties and temperature stability of KNLNT ceramic with different La doping concentrations were investigated. The results show a transition from orthorhombic-tetragonal mix phase to tetragonal single phase with the variation of La{sup 3+} concentrations. The SEM micrographs of surface and fractured surface show a dense microstructure with few micropores. The La-doped KNLTN ceramic will be an alternative candidate contributes to excellent piezoelectric properties, which are found in the 0.75 mol% La-doped KNLNT ceramics, with d{sub 33}=215pC/N, k{sub p}=42.8%and Q{sub m}=89. It has been remarkably improved that the temperature stability of KNLTN-Lax piezoelectric properties at room temperature, and the dielectric relaxation can be observed obviously. The mechanism of La doping was analyzed in terms of valence compensation and polymorphic phase transition (PPT) diffusion. The orthorhombic-tetragonal phase transition around room temperature and the relaxation transition were considered contributing to the excellent piezoelectric performance and improved temperature stability of La{sup 3+}-doped KNLTN.

  1. Nb-Based Nb-Al-Fe Alloys: Solidification Behavior and High-Temperature Phase Equilibria

    Science.gov (United States)

    Stein, Frank; Philips, Noah

    2018-03-01

    High-melting Nb-based alloys hold significant promise for the development of novel high-temperature materials for structural applications. In order to understand the effect of alloying elements Al and Fe, the Nb-rich part of the ternary Nb-Al-Fe system was investigated. A series of Nb-rich ternary alloys were synthesized from high-purity Nb, Al, and Fe metals by arc melting. Solidification paths were identified and the liquidus surface of the Nb corner of the ternary system was established by analysis of the as-melted microstructures and thermal analysis. Complementary analysis of heat-treated samples yielded isothermal sections at 1723 K and 1873 K (1450 °C and 1600 °C).

  2. A back-arc setting for mafic rocks of the Honeysuckle Beds, southeastern N.S.W.: the use of trace and rare earth element abundances determined by INAA

    Energy Technology Data Exchange (ETDEWEB)

    Dadd, K.A. [University of Technology, Sydney, NSW (Australia)

    1993-12-31

    Major, trace and rare earth elements abundance in mafic rocks of the Honeysuckle Beds was determined by x-ray fluorescence and neutron activation analysis . A comparison with typical mid-ocean ridge basalt compositions reveals an enrichment in light rare earths elements (Ba, Rb, and Th) and depletion in Nb, Ta and Ti, consistent with modifications of the source by subduction-related fluids. 9 refs., 6 figs.

  3. Depth dependant element analysis of PbMg1/3Nb2/3O3 using muonic x-rays

    Science.gov (United States)

    Brown, K. L.; Stockdale, C. P. J.; Luo, H.; Zhao, X.; Li, J.-F.; Viehland, D.; Xu, G.; Gehring, P. M.; Ishida, K.; Hillier, A. D.; Stock, C.

    2018-03-01

    The relaxor PbMg1/3Nb2/3O3 (PMN) has received attention due to its potential applications as a piezoelectric when doped with PbTiO3 (PT). Previous results have found that there are two phases existing in the system, one linked to the near-surface regions of the sample, the other in the bulk. However, the exact origin of these two phases is unclear. In this paper, depth dependant analysis results from negative muon implantation experiments are presented. It is shown that the Pb content is constant throughout all depths probed in the sample, but the Mg and Nb content changes in the near-surface region below 100 μm. At an implantation depth of 60 μm, it is found that there is a 25% increase in Mg content, with a simultaneous 5% decrease in Nb content in order to maintain charge neutrality. These results show that the previously observed skin effects in PMN are due to a change in concentration and unit cell.

  4. Chemical and nuclear properties of lawrencium (element 103) and hahnium (element 105)

    International Nuclear Information System (INIS)

    Henderson, R.A.

    1990-01-01

    The chemical and nuclear properties of Lr and Ha have been studied, using 3-minute 260 Lr and 35-second 262 Ha. The crystal ionic radius of Lr 3+ was determined by comparing its elution position from a cation-exchange resin column with those of lanthanide elements having known ionic radii. Comparisons are made to the ionic radii of the heavy actinides, Am 3+ through Es 3+ , obtained by x-ray diffraction methods, and to Md 3+ and Fm 3+ which were determined in the same manner as Lr 3+ . The hydration enthalpy of -3622 kJ/mol was calculated from the crystal ionic radius using an empirical form of the Born equation. Comparisons to the spacings between the ionic radii of the heaviest members of the lanthanide series show that the 2Z spacing between Lr 3+ and Md 3+ is anomalously small, as the ionic radius of Lr 3+ of 0.0886 nm is significantly smaller than had been expected. The chemical properties of Ha were determined relative to the lighter homologs in group 5, Nb and Ta. Group 4 and group 5 tracer activities, as well as Ha, were absorbed onto glass surfaces as a first step toward the determination of the chemical properties of Ha. Ha was found to adsorb on surfaces, a chemical property unique to the group 5 elements, and as such demonstrates that Ha has the chemical properties of a group 5 element. A solvent extraction procedure was adapted for use as a micro-scale chemical procedure to examine whether or not Ha displays eka-Ta-like chemical under conditions where Ta will be extracted into the organic phase and Nb will not. Under the conditions of this experiment Ha did not extract, and does not show eka-Ta-like chemical properties

  5. Application of paper chromatography to the determination of some elements in minerals and rocks

    International Nuclear Information System (INIS)

    Agrinier, H.

    1964-11-01

    This publication describes our work in applying paper chromatography to the fields of mineralogy and geology. We have studied the separation and determination of the following elements: Nb, Ta, Ti, Co, Cu, Mn, Sn, Ge, As, Sb, Bi, U, Th, Be, Au, Pb, Zn, V and Mo. The development of separation methods for these various elements has led us to solve many interference problems. These methods make it possible to separate and measure mineral components. They also enable us to search for trace elements in ores, rocks soils and carbonaceous materials. Finally let us point out that this technique may equally be used for analysis in very radioactive environment. (author) [fr

  6. Modeling of high entropy alloys of refractory elements

    Energy Technology Data Exchange (ETDEWEB)

    Grosso, M.F. del, E-mail: delgrosso@tandar.cnea.gov.ar [Gcia. Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499, (B1650KNA), San Martin (Argentina); GCMM, UTN, FRG Pacheco, Av. H. Yrigoyen 288, Gral. Pacheco (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, CONICET (Argentina); Bozzolo, G. [Loyola University Maryland, 4501 N. Charles St., Baltimore, MD 21210 (United States); Mosca, H.O. [Gcia. Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499, (B1650KNA), San Martin (Argentina); GCMM, UTN, FRG Pacheco, Av. H. Yrigoyen 288, Gral. Pacheco (Argentina)

    2012-08-15

    Reverting the traditional process of developing new alloys based on one or two single elements with minority additions, the study of high entropy alloys (HEA) (equimolar combinations of many elements) has become a relevant and interesting new field of research due to their tendency to form solid solutions with particular properties in the absence of intermetallic phases. Theoretical or modeling studies at the atomic level on specific HEA, describing the formation, structure, and properties of these alloys are limited due to the large number of constituents involved. In this work we focus on HEA with refractory elements showing atomistic modeling results for W-Nb-Mo-Ta and W-Nb-Mo-Ta-V HEA, for which experimental background exists. An atomistic modeling approach is applied for the determination of the role of each element and identification of the interactions and features responsible for the transition to the high entropy regime. Results for equimolar alloys of 4 and 5 refractory elements, for which experimental results exist, are shown. A straightforward algorithm is introduced to interpret the transition to the high entropy regime.

  7. Effect of Nb on the Microstructure, Mechanical Properties, Corrosion Behavior, and Cytotoxicity of Ti-Nb Alloys

    Directory of Open Access Journals (Sweden)

    Mi-Kyung Han

    2015-09-01

    Full Text Available In this paper, the effects of Nb addition (5–20 wt % on the microstructure, mechanical properties, corrosion behavior, and cytotoxicity of Ti-Nb alloys were investigated with the aim of understanding the relationship between phase/microstructure and various properties of Ti-xNb alloys. Phase/microstructure was analyzed using X-ray diffraction (XRD, SEM, and TEM. The results indicated that the Ti-xNb alloys (x = 10, 15, and 20 wt % were mainly composed of α + β phases with precipitation of the isothermal ω phase. The volume percentage of the ω phase increased with increasing Nb content. We also investigated the effects of the alloying element Nb on the mechanical properties (including Vickers hardness and elastic modulus, oxidation protection ability, and corrosion behavior of Ti-xNb binary alloys. The mechanical properties and corrosion behavior of Ti-xNb alloys were found to be sensitive to Nb content. These experimental results indicated that the addition of Nb contributed to the hardening of cp-Ti and to the improvement of its oxidation resistance. Electrochemical experiments showed that the Ti-xNb alloys exhibited superior corrosion resistance to that of cp-Ti. The cytotoxicities of the Ti-xNb alloys were similar to that of pure titanium.

  8. Effect of Nb on the Microstructure, Mechanical Properties, Corrosion Behavior, and Cytotoxicity of Ti-Nb Alloys.

    Science.gov (United States)

    Han, Mi-Kyung; Kim, Jai-Youl; Hwang, Moon-Jin; Song, Ho-Jun; Park, Yeong-Joon

    2015-09-09

    In this paper, the effects of Nb addition (5-20 wt %) on the microstructure, mechanical properties, corrosion behavior, and cytotoxicity of Ti-Nb alloys were investigated with the aim of understanding the relationship between phase/microstructure and various properties of Ti-xNb alloys. Phase/microstructure was analyzed using X-ray diffraction (XRD), SEM, and TEM. The results indicated that the Ti-xNb alloys (x = 10, 15, and 20 wt %) were mainly composed of α + β phases with precipitation of the isothermal ω phase. The volume percentage of the ω phase increased with increasing Nb content. We also investigated the effects of the alloying element Nb on the mechanical properties (including Vickers hardness and elastic modulus), oxidation protection ability, and corrosion behavior of Ti-xNb binary alloys. The mechanical properties and corrosion behavior of Ti-xNb alloys were found to be sensitive to Nb content. These experimental results indicated that the addition of Nb contributed to the hardening of cp-Ti and to the improvement of its oxidation resistance. Electrochemical experiments showed that the Ti-xNb alloys exhibited superior corrosion resistance to that of cp-Ti. The cytotoxicities of the Ti-xNb alloys were similar to that of pure titanium.

  9. Nonlinear behavior of structural and luminescent properties in Gd(NbxTa1-x)O4 mixed crystals

    Science.gov (United States)

    Voloshyna, Olesia; Sidletskiy, Oleg; Spassky, Dmitry; Gerasymov, Iaroslav; Romet, Ivo; Belsky, Andrey

    2018-02-01

    Ceramic samples of gadolinium tantalo-niobate mixed crystals were obtained by the solid-state technique. The dependence of luminescence properties on the Nb/Ta ratio in the Gd(NbxTa1-x)O4 system is studied in the 5-450 K temperature range, including thermostimulated luminescence curves in the series of solid solutions. The relation of nonlinear behavior of light output with x variation to non-homogeneous distribution of Nb and Ta in solid solutions is discussed.

  10. Submicron area NbN/MgO/NbN tunnel junctions for SIS mixer applications

    Science.gov (United States)

    Leduc, H. G.; Judas, A.; Cypher, S. R.; Bumble, B.; Hunt, B. D.

    1991-01-01

    The development of submicron area mixer elements for operation in the submillimeter wave range is discussed. High-current-density NbN/MgO/NbN tunnel junctions with areas down to 0.1 sq microns have been fabricated in both planar and edge geometries. The planar junctions were fabricated from in situ deposited trilayers using electron-beam lithography to pattern submicron area mesas. Modifications of fabrication techniques used in larger-area NbN tunnel junctions are required and are discussed. The NbN/MgO/NbN edge junction process using sapphire substrates has been transferred to technologically important quartz substrates using MgO buffer layers to minimize substrate interactions. The two junction geometries are compared and contrasted in the context of submillimeter wave mixer applications.

  11. The application of proton induced x-ray emission to the element analysis of thick obsidian samples

    International Nuclear Information System (INIS)

    Duerden, P.; Cohen, D.; Clayton, E.

    1979-11-01

    The proton induced X-ray emission (PIXE) technique has been applied to the analysis of element concentrations in obsidian source samples. No target preparation other than washing and the selection of a flat surface was undertaken. Thick target yields have been calculated and element concentrations derived from the detected X-ray spectra; concentrations are given for K, Ca, Ti, V, Mn, Fe, Ga, As, Rb, Sr, Y, Zr, Nb, Ta, and Pb. A pinhole filter is described which enables a single measurement of about 5 minutes' duration to give element concentration data over an X-ray energy range 3-20 keV

  12. Formation of titanium dioxide nanotubes on Ti–30Nb–xTa alloys by anodizing

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eun-Sil [Department of Dental Materials and Research Center of Nano-Interface Activation for Biomaterials, School of Dentistry, Chosun University, Gwangju (Korea, Republic of); Jeong, Yong-Hoon [Department of Dental Materials and Research Center of Nano-Interface Activation for Biomaterials, School of Dentistry, Chosun University, Gwangju (Korea, Republic of); Biomechanics and Tissue Engineering Laboratory, Division of Orthodontics, College of Dentistry, The Ohio State University, Columbus, OH (United States); Choe, Han-Cheol, E-mail: hcchoe@chosun.ac.kr [Department of Dental Materials and Research Center of Nano-Interface Activation for Biomaterials, School of Dentistry, Chosun University, Gwangju (Korea, Republic of); Brantley, William A. [Division of Restorative, Prosthetic and Primary Care Dentistry, College of Dentistry, The Ohio State University, Columbus, OH (United States)

    2013-12-31

    The goal of this study was to investigate the formation of titanium dioxide nanotubes on the surface of cast Ti–30Nb–xTa alloys by anodizing. The anodization technique for creating the nanotubes utilized a potentiostat and an electrolyte containing 1 M H{sub 3}PO{sub 4} with 0.8 wt.% NaF. The grain size of the Ti–30Nb–xTa alloys increased as the Ta content increased. Using X-ray diffraction, for the Ti–30Nb alloy the main peaks were identified as α″ martensite with strong peaks of β phase. The phases in the Ti–30Nb–xTa alloys changed from a duplex (α″ + β) microstructure to solely β phase with increasing Ta content. The nanotubes that formed on the surface of the Ti–30Nb–xTa alloys were amorphous TiO{sub 2} without an evidence of the crystalline anatase or rutile forms of TiO{sub 2}. Scanning electron microscopy revealed that the average diameters of the small and large nanotubes on the Ti–30Nb alloy not containing Ta were approximately 100 nm and 400 nm, respectively, whereas the small and large nanotubes on the alloy had diameters of approximately 85 nm and 300 nm, respectively. As the Ta content increased from 0 to 15 wt.%, the average lengths of the nanotubes increased from 2 μm to 3.5 μm. Energy-dispersive X-ray spectroscopy indicated that the nanotubes were principally composed of Ti, Nb, Ta, O and F. Contact angle measurements showed that the nanotube surface had good wettability by water droplets. - Highlights: • TiO{sub 2} nanotube layers on anodized Ti-30Nb-xTa alloys have been investigated. • Nanotube surface had an amorphous structure without heat treatment. • Nanotube diameter of Ti-30Nb-xTa decreased, whereas tube layer increased with Ta content. • The nanotube surface exhibited the low contact angle and good wettability.

  13. A novel modeling to predict the critical current behavior of Nb3Sn PIT strand under transverse load based on a scaling law and Finite Element Analysis

    CERN Document Server

    Wang, Tiening; Takayasu, Makoto; Bordini, Bernardo

    2014-01-01

    Superconducting Nb3Sn Powder-In-Tube (PIT) strands could be used for the superconducting magnets of the next generation Large Hadron Collider. The strands are cabled into the typical flat Rutherford cable configuration. During the assembly of a magnet and its operation the strands experience not only longitudinal but also transverse load due to the pre-compression applied during the assembly and the Lorentz load felt when the magnets are energized. To properly design the magnets and guarantee their safe operation, mechanical load effects on the strand superconducting properties are studied extensively; particularly, many scaling laws based on tensile load experiments have been established to predict the critical current dependence on strain. However, the dependence of the superconducting properties on transverse load has not been extensively studied so far. One of the reasons is that transverse loading experiments are difficult to conduct due to the small diameter of the strand (about 1 mm) and the data curre...

  14. The stability of thermodynamically metastable phases in a Zr-Sn-Nb-Mo alloy: Effects of alloying elements, morphology and applied stress/strain

    Science.gov (United States)

    Yu, Hongbing; Yao, Zhongwen; Daymond, Mark R.

    2017-09-01

    In this paper, a dual phase Zr-Sn-Nb-Mb alloy was studied with TEM after thermal treatment and high-temperature tensile deformation. Plate and pressure tube material, manufactured through different processing routes, were used in this study. The overall average concentrations of Mo and Nb in the β phase are higher in the pressure tube than in the plate. It was revealed that these concentrations have significant effects on the subsequent stability of the β and ω phases as well as on the precipitation behavior of the α phase from the β phase. That is, the higher the concentrations, the more stable the β and ω phases are, and hence there is a reduced tendency for precipitation of α phase. Aging treatments cause the transformation of athermal ω to isothermal ω, as expected. The most striking finding is the product of the decomposition of the isothermal ω particles during aging treatment is determined as not being α phase, even though the structure of it is, as-yet, not fully determined. The non-uniform morphology of the β grains in the plate material provides us a unique opportunity to investigate the effects of morphology on the aging response of the β phase. It was found that thin β filaments suppress the precipitation of isothermal ω particles but enhance the precipitation of α phase at α/β interfaces. The effect of the Burgers orientation relationship between α and β grains on the precipitation of the α phase at the α/β interface is discussed. Applied high-temperature stress/strain has been found to enhance the decomposition of isothermal ω phase but suppress α precipitation inside the β grains. The suppression of α precipitation by applied stress/strain is discussed in terms of the ω assisted α precipitation. Implications of these findings for the in-service application of the alloy are discussed.

  15. Structures of the three homoeologous loci of wheat benzoxazinone biosynthetic genes TaBx3 and TaBx4 and characterization of their promoter sequences.

    Science.gov (United States)

    Nomura, Taiji; Nasuda, Shuhei; Kawaura, Kanako; Ogihara, Yasunari; Kato, Nobuhiko; Sato, Fumihiko; Kojima, Toshio; Toyoda, Atsushi; Iwamura, Hajime; Endo, Takashi R

    2008-02-01

    Common wheat (2n=6x=42, genome formula AABBDD) accumulates benzoxazinones (Bxs) as defensive compounds. There are five Bx biosynthetic genes (TaBx1-TaBx5), and their homoeologous alleles are located on all three homoeologous chromosomes of the A, B and D genomes. Here the molecular structures of the TaBx3 and TaBx4 loci, both of which are located on chromosomes 5A, 5B and 5D, were revealed by sequencing transformation-competent artificial chromosome (TAC) clones. In all homoeologous chromosomes, TaBx3 existed downstream of TaBx4 in a tail-to-head manner, and the two genes were separated from each other by 9.0 kb in 5A, 7.3 kb in 5B and 11.3 kb in 5D. Among the three homoeologs of TaBx3 and TaBx4, the promoter sequences were less conserved than the coding sequences. The promoter sequences of TaBx3 and TaBx4 were highly similar to those of their respective orthologs in the diploid progenitors of common wheat, but were not similar to those of the maize orthologs. Sequence similarity was found between the TaBx3 and TaBx4 coding sequences, but not between their promoter sequences despite their similar transcription pattern at the seedling stage. Some putative cis-elements were found to be shared by all TaBx3 and TaBx4 promoter regions. These results imply that stage-specific transcription of TaBx3 and TaBx4 is not controlled by global sequence similarity of their promoters but by some essential cis-elements. The promoter activity measured by transient assays in wheat protoplasts was similar among the three homoeologs of TaBx3 and TaBx4 in spite of their differential transcript levels in wheat seedlings.

  16. Social shaping of technology in TA and HTA

    DEFF Research Database (Denmark)

    Clausen, Christian; Yoshinaka, Yutaka

    2004-01-01

    The paper discusses how the social shaping of technology (SST) approach may be useful in understanding the role played by technology assessment within the context of technological development and change. It is proposed that an SST perspective on TA (or HTA) yields particular insight, regardless...... of whether or not the TA activity bases itself on a social shaping understanding of technology. This is because SST addresses the socially negotiated character of technological development, where TA itself may be construed as an element influencing the process of such negotiation. At the same time, TA...... is a construction, that is, itself a product of negotiations involving social actors. Thus, an understanding that TA is socially shaped, and is involved in the shaping of technology, opens up for a perspective on TA as both entailing constraints and enablements within the context of the particular agenda...

  17. Formation of elements of integrated acousto-optic cell based on LiNbO3 films by methods of nanotechnology

    International Nuclear Information System (INIS)

    Ageev, O A; Zamburg, E G; Kolomiytsev, A S; Suchkov, D O; Shipulin, I A; Shumov, A V

    2015-01-01

    In the experiments we defined modes, and developed the technology of formation of elements of input-output laser emission and microlens of integrated acousto-optic cell by Pulsed Laser Deposition and Focused Ion Beams by using nanotechnology cluster complex, allowing controlled creation of elements in a single process cycle. (paper)

  18. Diffusion of Nb in Fe and in some Fe alloys

    International Nuclear Information System (INIS)

    Kurokawa, S.; Ruzzante, J.E.; Hey, A.M.; Dyment, F.

    1981-01-01

    Diffusion data of microalloying elements such as Nb, V, Ti, are required when analysing the transformation and recrystallization behaviour of HSLA steels in order to optimize grain refinement and precipitation hardening. The diffusion behaviour of Nb in pure Fe, Fe 1.5 Mn, Fe 0.6 Si and Fe 1.5 Mn 0.6 Si has been measured between 1080 and 1200 0 C. Results indicate that Si increases Nb diffusivity while Mn decreases it. The sequence of diffusion coeficients values is: D sup(Nb) sub(Fe 1.5 Mn) [pt

  19. Effect of ZnO-B{sub 2}O{sub 3} addition on the dielectric and the piezoelectric properties of lead-free (Na{sub 0.525}K{sub 0.443}Li{sub 0.037})(Nb{sub 0.883}Sb{sub 0.08}Ta{sub 0.037})O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, You-Seok; Yoo, Ju-Hyun [Semyung University, Jecheon (Korea, Republic of)

    2014-12-15

    (Na{sub 0.525}K{sub 0.443}Li{sub 0.037})(Nb{sub 0.883}Sb{sub 0.08}Ta{sub 0.037})O{sub 3} + x wt% ZnO-B{sub 2}O{sub 3} (NKLNST + x ZnO-B{sub 2}O{sub 3}) lead-free piezoelectric ceramics were prepared via a conventional solid-state reaction for various values of x = 0, 0.3, 0.6, 0.9, 1.2; then, the dielectric and the piezoelectric properties of these ceramics were investigated. A pure perovskite structure and a small secondary phase were observed in the X-ray diffraction patterns. For the 0.3-wt% ZnO-B{sub 2}O{sub 3} specimen, a density of ρ = 4.537 g/cm{sup 3}, an electromechanical coupling factor of k{sub P} = 0.432, a mechanical quality factor of Q{sub m} = 96, and piezoelectric constant of d{sub 33} = 209 pC/N were found to be optimal. These results indicate that the material with this composition is a promising candidate for use in a lead-free piezoelectric device.

  20. A model for Nb-Zr-REE-Ga enrichment in Lopingian altered alkaline volcanic ashes: Key evidence of H-O isotopes

    Science.gov (United States)

    Dai, Shifeng; Nechaev, Victor P.; Chekryzhov, Igor Yu.; Zhao, Lixin; Vysotskiy, Sergei V.; Graham, Ian; Ward, Colin R.; Ignatiev, Alexander V.; Velivetskaya, Tatyana A.; Zhao, Lei; French, David; Hower, James C.

    2018-03-01

    Clay-altered volcanic ash with highly-elevated concentrations of Nb(Ta), Zr(Hf), rare earth elements (REE), and Ga, is a new type of critical metal deposit with high commercial prospects that has been discovered in Yunnan Province, southwest China. Previous studies showed that the volcanic ashes had been subjected to hydrothermal fluids, the nature of which, however, is not clear. Here we show that the volcanic ashes were originated from alkaline magmatism, followed by a continuous hydrothermal-weathering process. Heated meteoric waters, which were sourced from acidic rains and mixed with CO2 from degassing of the Emeishan plume, have caused partial, but widespread, acidic leaching of Nb, Ta, Zr, Hf, REE, and Ga into ground water and residual enrichment of these elements, along with Al and Ti, in the deeply altered rocks. Subsequent alteration occurring under cooler, neutral or alkaline conditions, caused by water-rock interaction, resulted in precipitation of the leached critical metals in the deposit. Polymetallic mineralization of similar origin may be found in other continental regions subjected to explosive alkaline volcanism associated with deep weathering in humid conditions.

  1. Texture in state-of-the-art Nb3Sn multifilamentary superconducting wires

    CERN Document Server

    Scheuerlein, C; Alknes, P; Jimenez, N; Bordini, B; Ballarino, A; Di Michiel, M; Thilly, L; Besara, T; Siegrist, T

    2014-01-01

    The texture of Nb3Sn in recent multifilamentary composite wires has been studied by neutron diffraction, synchrotron x-ray diffraction and electron backscatter diffraction. In powder-in-tube (PIT) type superconductors the Nb precursor filaments exhibit a strong 〈110〉 fiber texture as a consequence of the severe cold drawing process, and a 〈110〉 texture is also observed in the Nb3Sn. In the Nb–Ta precursor of the restacked rod process (RRP) strand there is an additional texture component, and in both Ta-alloyed and Ti-alloyed RRP type conductors the Nb3Sn grains grow with a preferential 〈100〉 orientation.

  2. Creep behavior of Ti3Al-Nb intermetallic alloys

    International Nuclear Information System (INIS)

    Yu, T.H.; Yue, W.J.; Koo, C.H.

    1997-01-01

    It is well known that Ti 3 Al-Nb alloys are potential materials for aerospace applications. The creep property is an important consideration when materials are used at high temperature. In this article, the effect of microstructure of Ti-25Al-10Nb alloy on the creep property was investigated, and the creep property of Ti-25Al-10Nb alloy modified by small addition of silicon 0.2 at.% or carbon 0.1 at.% was observed. The alloy with the addition of molybdenum to replace part of niobium 2 at.% was also studied. The experimental results show that the furnace-cooled Ti-25Al-10Nb alloy has superior creep resistance to the air-cooled Ti-25Al-10Nb alloy at 200 MPa, but exhibits poor creep resistance at 250 MPa or above. Small addition of silicon to the Ti-25Al-10Nb alloy may increase creep resistance. Small addition of carbon to the Ti-25Al-10Nb alloy may reduce creep resistance but raise rupture strain. Molybdenum is the most effective alloying element to increase creep resistance for the Ti-25Al-10Nb alloy. The creep mechanism of Ti-25Al-10Nb alloy is governed by dislocation climb. (orig.)

  3. Application of paper chromatography to the determination of some elements in minerals and rocks; Application de la chromatographie sur papier a la determination de certains elements dans les mineraux et les roches

    Energy Technology Data Exchange (ETDEWEB)

    Agrinier, H. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1964-11-01

    This publication describes our work in applying paper chromatography to the fields of mineralogy and geology. We have studied the separation and determination of the following elements: Nb, Ta, Ti, Co, Cu, Mn, Sn, Ge, As, Sb, Bi, U, Th, Be, Au, Pb, Zn, V and Mo. The development of separation methods for these various elements has led us to solve many interference problems. These methods make it possible to separate and measure mineral components. They also enable us to search for trace elements in ores, rocks soils and carbonaceous materials. Finally let us point out that this technique may equally be used for analysis in very radioactive environment. (author) [French] Dans cette etude, nous etendons le champ d'application de la chromatographie sur papier aux domaines de la mineralogie et de la geologie. Nous avons etudie la separation et la determination des elements suivants: Nb, Ta, Ti, Co, Cu, Mn, Sn, Ge, As, Sb, Bi, U, Th, Be, Au, Pb, Zn, V et Mo. La mise au point des methodes de separation concernant ces differents elements nous a amenes a resoudre de nombreux problemes d'interference. Ces methodes permettent la separation et le dosage des constituants des mineraux, ainsi que la recherche d'elements en traces dans les minerais, les roches, les sols et les materiaux carbonnes. Signalons pour terminer que cette technique peut egalement trouver son utilisation dans le domaine de l'analyse en milieu tres radio-actif. (auteur)

  4. Investigation of TaC–TaB2 ceramic composites

    Indian Academy of Sciences (India)

    2.2 Spark plasma sintering. Spark plasma sintering (SPS) was utilized to consolidate. TaC–B4C and TaC–TaB2 powders. SPS was carried out in. Argon atmosphere at 1900 to 2100◦C. The heating rate of. 100◦C min−1 was adopted to reach the maximum temper- ature with a hold time of 10 min. SPS was carried out at.

  5. In-Situ Neutron Diffraction Under Tensile Loading of Powder-in-Tube Cu/Nb3Sn Composite Wires Effect of Reaction Heat Treatment on Texture, Internal Stress State and Load Transfer

    CERN Document Server

    Scheuerlein, C; Thilly, L

    2007-01-01

    The strain induced degradation of Nb3Sn superconductors can hamper the performance of high field magnets. We report elastic strain measurements in the different phases of entire non-heat treated and fully reacted Nb3Sn composite strands as a function of uniaxial stress during in-situ deformation under neutron beam. After the reaction heat treatment the Cu matrix loses entirely its load carrying capability and the applied stress is transferred to the remaining Nb-Ta alloy and to the brittle (Nb-Ta)3Sn phase, which exhibits a preferential grain orientation parallel to the strand axis.

  6. On-line gas chromatographic studies of rutherfordium (Element 104), hahnium (Element 105), and homologs

    International Nuclear Information System (INIS)

    Kadkhodayan, B.

    1993-05-01

    Gas-phase isothermal chromatogaphy is a method by which volatile compounds of different chemical elements can be separated according to their volatilities. The technique, coupled with theoretical modeling of the processes occurring in the chromatogaphy column, provides accurate determination of thermodynamic properties (e.g., adsorption enthalpies) for compounds of elements, such as the transactinides, which can only be produced on an atom-at-a-time basis. In addition, the chemical selectivity of the isothermal chromatogaphy technique provides the decontamination from interfering activities necessary for the determination of the nuclear decay properties of isotopes of the transactinide elements. Volatility measurements were performed on chloride species of Rf and its group 4 homologs, Zr and Hf, as well as Ha and its group 5 homologs, Nb and Ta. Adsorption enthalpies were calculated for all species using a Monte Carlo code simulation based on a microscopic model for gas thermochromatography in open columns with laminar flow of the carrier gas. Preliminary results are presented for Zr- and Nb-bromides

  7. The potential capacities of Ta'ziyeh in Modern Imagism

    Directory of Open Access Journals (Sweden)

    A.M Nedai

    2009-03-01

    Full Text Available Ta'ziyeh as the most important method in religious and ritual theatre in Iran has many capabilities which can be used in modern visualization. The only element in this theatre which has been studied is distancing in performance styles. But by studying the existent versions of Ta'ziyehs, there are other elements for recognition and use, which has not still been studied. The relationship between religious and ritual theatre with Ta'ziyeh and also their main themes helps to identify these elements and their capabilities. Meanwhile, the presence of music as an expressive and performing element provides a basis which can be used in finding a new manner of expression in visual/dramatic works (such as music videos. Studying on such elements as time-place interlace, character replacement, functions of music, and their effects on audiences, shows that Ta'ziyeh has specific capabilities in visualization (even in Cinema and Media. This article, through capitalizing on this subject and introducing one paradigm (Moses and poor Pilgrim, and comparing two versions of it, tries to represent these capabilities, and illuminates Ta'ziyeh's abilities for modern (and even postmodern visualization.

  8. Comparison of ASME Code NB-3200 and NB-3600 results for fatigue analysis of B31.1 branch nozzles

    International Nuclear Information System (INIS)

    Nitzel, M.E.; Ware, A.G.; Morton, D.K.

    1996-01-01

    Fatigue analyses wre conducted on two reactor coolant system branch nozzles in an operating PWR designed to the B31.1 Code, for which no explicit fatigue analysis was required by the licensing basis. These analyses were performed as part of resolving issues connected with NRC's Fatigue Action Plan to determine if the cumulative usage factor (CUF) for these nozzles, using the 1992 ASME Code and representative PWR transients, were comparable to nozzles designed and analyzed to the ASME Code. Both NB-3200 and NB-3600 ASME Code methods were used. NB-3200 analyses included the development of finite element models for each nozzle. Although detailed thermal transients were not available for the plant analyzed, representative transients from similar PWRs were applied in each method. CUFs calculated using NB-3200 methods were significantly less than using NB-3600. The paper points out differences in analysis methods and highlights difficulties and unknowns in performing more detailed analyses to reduce conservative assumptions

  9. Fabrication, characterization and in vitro biocompatibility evaluation of porous Ta–Nb alloy for bone tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Huifeng; Li, Jing; Yang, Hailin; Liu, Chao; Ruan, Jianming, E-mail: jianming@csu.edu.cn

    2014-07-01

    Porous Ta–Nb alloys were fabricated using the sponge impregnation technique and the powder metallurgy technique (P/M) in combination. All porous Ta–Nb alloys displayed interconnected open cell structures with porosities around 64% and pore sizes in the range of 300–500 μm. No carbide, oxide, or intermetallic-related phases were detected by the X-ray diffraction (XRD). Porous Ta–Nb alloys displayed sintering neck growth, smoother surface of the particles and more shrinkage of the micropores, with Nb contents increasing from 5% to 15%. The compressive strength and Young's modulus of the Ta–Nb alloys agreed well with the requirements of trabecular bone. The normalized compressive plateau stress and Young's modulus increased from 52.27 MPa to 85.43 MPa and from 1.850 GPa to 2.540 GPa, respectively, with Nb contents increasing from 5% to 15%. Porous Ta–Nb alloys had no cytotoxicity and possessed the excellent biocompatibility similar to porous Ta scaffolds. - Highlights: • Porous Ta–Nb alloys were prepared as a novel biomaterial for the first time. • Excellent mechanical properties of the porous Ta–Nb alloy were obtained. • The mechanical properties can be tailored by adjusting the Nb content. • The excellent in vitro biocompatibility of porous Ta–Nb alloys was shown.

  10. Creep oceli L360NB za normálních teplot

    Czech Academy of Sciences Publication Activity Database

    Gajdoš, Lubomír; Šperl, Martin; Náprstek, Jiří; Pavelková, M.

    2016-01-01

    Roč. 96, 9/10 (2016), s. 202-211 ISSN 0032-1761 R&D Projects: GA TA ČR(CZ) TE02000162 Institutional support: RVO:68378297 Keywords : L360NB steel * creep deformation * normal temperatures Subject RIV: JL - Materials Fatigue, Friction Mechanics

  11. Mineral potential for incompatible element deposits hosted in pegmatites, alkaline rocks, and carbonatites in the Islamic Republic of Mauritania (phase V, deliverable 87): Chapter Q in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    Science.gov (United States)

    Taylor, Cliff D.; Giles, Stuart A.

    2015-01-01

    Review of PRISM-I documents and the National inventory of mineral occurrences suggests that resources of U, Th, Nb, Ta, Be, rare earth elements (REEs) and fluorite are known in Mauritania and have been exploited in the past at the Bou Naga alkaline complex. Several different deposit types are indicated by the available data. Pegmatitic veins are recorded in several areas of the Archean and Paleoproterozoic portions of the Rgueïbat Shield and are prospective for resources of Li, Be, Nb, Ta, U, Th, and REEs. Over 150 beryl pegmatites are known in the Khnefissat and Inkebden areas of the Chami greenstone belt, and additional concentrations of pegmatites are known in the Guelb Nich Sud area of the Sebkhet Nich greenstone belt and in the northeastern part of the Amsaga Complex. Due to the small size of these deposits, they are unlikely to be economic unless additional value can be gained by processing contained minerals for their industrial uses.

  12. Er{sup 3+} diffusion in LiTaO{sub 3} crystal

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, De-Long, E-mail: dlzhang@tju.edu.cn [Department of Opto-electronics and Information Engineering, School of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072 (China); Key Laboratory of Optoelectronic Information Technology (Ministry of Education), Tianjin University, Tianjin 300072 (China); Department of Electronic Engineering and State Key Laboratory of Millimeter Waves, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong (China); Zhang, Qun; Wong, Wing-Han [Department of Opto-electronics and Information Engineering, School of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072 (China); Key Laboratory of Optoelectronic Information Technology (Ministry of Education), Tianjin University, Tianjin 300072 (China); Department of Electronic Engineering and State Key Laboratory of Millimeter Waves, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong (China); Pun, Edwin Yue-Bun [Department of Electronic Engineering and State Key Laboratory of Millimeter Waves, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong (China)

    2015-12-01

    Graphical abstract: Diffusion characteristics of Er{sup 3+} in LiTaO{sub 3} crystal were studied in a wide temperature range from 1000 to 1500 °C. The study shows that Er{sup 3+} doping has little effect on the LiTaO{sub 3} index. Li{sub 2}O out-diffusion is slight for a lower temperature while is moderate for a high temperature. The diffusion can be described by Fick's law of diffusion with a constant Er{sup 3+} diffusivity. Some characteristic diffusion parameters including diffusion constant, activation energy, solubility constant and heat of solution were obtained. In comparison with the case of LiNbO{sub 3}, Er{sup 3+} diffusion in LiTaO{sub 3} is at least two orders slower and Er{sup 3+} solubility in LiTaO{sub 3} is measurably lower. - Highlights: • Diffusion characteristics of Er{sup 3+} in LiTaO{sub 3} crystal were studied. • Diffusion constant is (1.05 ± 0.2) × 10{sup 10} μm{sup 2}/h and activation energy is 3.9 ± 0.04 eV. • Solubility constant is (9.12 ± 1.3) × 10{sup 24} cm{sup −3} and heat of solution is 1.33 ± 0.02 eV. • Er{sup 3+} diffusion in LiTaO{sub 3} is at least two orders slower than in LiNbO{sub 3}. • Er{sup 3+} solubility in LiTaO{sub 3} is measurably lower than in LiNbO{sub 3}. - Abstract: Some Er{sup 3+}-doped LiTaO{sub 3} plates were prepared by in-diffusion of Er-metal film locally coated onto congruent Z-cut substrate in air at a wide temperature range from 1000 to 1500 °C. After diffusion, Er{sup 3+}-doping effect on LiTaO{sub 3} refractive index and Li{sub 2}O out-diffusion arising from Er{sup 3+} in-diffusion were studied at first. Refractive indices at the doped and undoped surface parts were measured by prism coupling technique and the surface composition was estimated. The results show that Er{sup 3+} dopant has small contribution to the LiTaO{sub 3} index. Li{sub 2}O out-diffusion is slight (Li{sub 2}O content loss <0.3 mol%) for the temperature below 1300 °C while is moderate (Li{sub 2}O content loss

  13. Extreme trace elements fractionation in Cenozoic nephelinites and phonolites from the Moroccan Anti-Atlas (Eastern Saghro)

    Science.gov (United States)

    Berger, Julien; Ennih, Nasser; Liégeois, Jean-Paul

    2014-12-01

    Nephelinites and phonolites from the Moroccan Anti-Atlas form a cogenetic series of volcanic rocks linked by a fractional crystallization process and showing continuous evolutionary trends for trace-elements. According to partial melting calculations, minor element data in olivine and review of published experimental studies, the most primitive nephelinites are low degree (~ 2%) partial melts from a carbonated LREE-rich spinel lherzolite. Sr-Nd-Pb isotopic compositions indicate the participation of both DM and HIMU end-members in the mantle source of nephelinites; the HIMU component is here interpreted as a relic of the shallow metasomatized Pan-African mantle. The phonolites show similar isotopic composition except for slightly more radiogenic Sr isotopic values. Fractional crystallization calculations were performed using trace-element mineral/bulk rock coefficients determined with new LA-ICP-MS data on minerals together with published equilibrium partition coefficients. The decrease of LREE, Sr and Ba with increasing differentiation is explained by fractionation of large amounts of apatite. Th, Nb and Zr display a behavior of very incompatible elements, reaching extreme concentration in most differentiated phonolites. Ta, Hf and MREE by contrast are characterized by a moderately incompatible to compatible behavior during differentiation. Fractionation of small amount of titanite, in which Ta, Hf and MREE are highly compatible compared to Nb, Zr and LREE (DNb/DTa: 2, DZr/DHf: 1.5 for titanite/phonolite ratios), explains the observed increase in Nb/Ta and Zr/Hf ratios with increasing silica content, from 18 and 40 in nephelinites to 70 and 80 in phonolites, respectively. Clinopyroxene also contributed to the fractionation of Hf from Zr in the very first steps of crystallization. The low values of Nb/Ta and Zr/Hf ratios observed in the two most differentiated Si-rich phonolites are probably a consequence of late stage segregation of volatile-rich agpaitic

  14. Institutional Interpretation of Participatory TA

    DEFF Research Database (Denmark)

    Nielsen, Rasmus Øjvind

    2014-01-01

    This article discusses why and how the history and the current state of participatory technology assessment (referred to as pTA; not to be confuse with PTA, which stands for parliamentary TA), especially in Denmark, may be understood in terms of institutionalization. The core argument is that whi...... of developing the framework, however, will be to serve as a conceptual resource for the long-term strategic outlooks of organizational entrepreneurs working to establish or continue pTA practices within STI policy-making....

  15. Ta-Tsing-Leu-Lee

    OpenAIRE

    Staunton, George Thomas

    2017-01-01

    Anastatic reprint of Ta-Tsing-Leu-Lee o Sia Leggi Fondamentali del Codice Penale della China, stampato e promulgato a Pekin coll’autorità di tutti gl’Imperatori Ta-Tsing, della presente dinastìa. Tradotto dal chinese da Giorgio Tommaso Staunton, membro della Società reale di Londra […] Versione italiana […] 3 vols. (Milano: dalla Stamperia di Giovanni Silvestri agli Scalini del Duomo n° 994, 1812), Italian translation of George Thomas Staunton, Ta Tsing Leu Lee; Being the Funda...

  16. Magnetotransport of single crystalline NbAs

    International Nuclear Information System (INIS)

    Ghimire, N J; Luo, Yongkang; Neupane, M; Williams, D J; Bauer, E D; Ronning, F

    2015-01-01

    We report transport measurement in zero and applied magnetic field on a single crystal of NbAs. Transverse and longitudinal magnetoresistance in the plane of this tetragonal structure does not saturate up to 9 T. In the transverse configuration (H ∥ c, I ⊥ c) it is 230 000% at 2 K. The Hall coefficient changes sign from hole-like at room temperature to electron-like below ∼150 K. The electron carrier density and mobility calculated at 2 K based on a single band approximation are 1.8 × 10 19  cm −3 and 3.5 × 10 5  cm 2  Vs −1 , respectively. These values are similar to reported values for TaAs and NbP, and further emphasize that this class of noncentrosymmetric, transition-metal monopnictides is a promising family to explore the properties of Weyl semimetals and the consequences of their novel electronic structure. (fast track communication)

  17. Effect of Nb aggregates on Zr2Fe

    International Nuclear Information System (INIS)

    Ramos, Cinthia P.

    2001-01-01

    The binary Zr-Fe phase diagram revision, performed by Arias et al., accepted the intermetallic Zr 2 Fe crystalline structure as tetragonal and determined that the presence of a third element like oxygen, nitrogen or carbon, stabilizes a cubic phase. Nevitt et al. studying Ti, Zr and Hf alloys with transition metals as second or third element and ternary systems with oxygen as third element, systematized the occurrence of phases with a cubic Ti 2 Ni type crystalline structure. From previous studies in the Zr-Nb-Fe system, it is an agreed fact that Nb presence in the Zr 2 Fe intermetallic stabilizes a cubic Ti 2 Ni type phase. The purpose of the present work is to determine the stability range of the Zr 2 Fe intermetallic with Nb contents, the existence range of the ternary cubic Ti 2 Ni type phase (designated Λ) and the corresponding two-phase region. We analyze as cast and heat treated (800 C degrees) Zr-Nb-Fe alloys with 35 atomic % Fe and Nb contents between 0.5 and 15 atomic %. The determination and characterization of the phases is made by optical and scanning electron microscopy, X-ray diffraction microprobe analysis and Moessbauer Spectroscopy. Joining these techniques together it is found, among many other things, that the Zr 2 Fe phase would accept up to around 0.5 atomic % Nb in solution and that the two-phase region Zr 2 Fe+Λ would be stable in the (0.5 - 3.5) Nb atomic % range. It is proposed as well a 800 C degrees section of the ternary (Zr-Nb-Fe) in the studied region. (author) [es

  18. Analysis of Nb3Sn surface layers for superconducting radio frequency cavity applications

    International Nuclear Information System (INIS)

    Becker, Chaoyue; Posen, Sam; Hall, Daniel Leslie; Groll, Nickolas; Proslier, Thomas; Cook, Russell; Schlepütz, Christian M.; Liepe, Matthias; Pellin, Michael; Zasadzinski, John

    2015-01-01

    We present an analysis of Nb 3 Sn surface layers grown on a bulk Niobium (Nb) coupon prepared at the same time and by the same vapor diffusion process used to make Nb 3 Sn coatings on 1.3 GHz Nb cavities. Tunneling spectroscopy reveals a well-developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 ± 0.4 meV and superconducting critical temperatures (T c ) up to 16.3 K. Scanning transmission electron microscopy performed on cross sections of the sample's surface region shows an ∼2 μm thick Nb 3 Sn surface layer. The elemental composition map exhibits a Nb:Sn ratio of 3:1 and reveals the presence of buried sub-stoichiometric regions that have a ratio of 5:1. Synchrotron x-ray diffraction experiments indicate a polycrystalline Nb 3 Sn film and confirm the presence of Nb rich regions that occupy about a third of the coating volume. These low T c regions could play an important role in the dissipation mechanisms occurring during RF tests of Nb 3 Sn-coated Nb cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators

  19. Effect of Nb addition on the terminal solid solubility of hydrogen for Zr and Zircaloy-4

    International Nuclear Information System (INIS)

    Ito, Masato; Ko, Kazuhira; Muta, Hiroaki; Uno, Masayoshi; Yamanaka, Shinsuke

    2007-01-01

    The terminal solid solubility of hydrogen (TSS) for pure Zr, Zr-Nb binary alloys with different Nb concentrations, and Nb added Zircaloy-4 was examined from the view point of the integrity of new-type nuclear fuel cladding. These alloys were hydrogenated by a modified UHV Sieverts' apparatus at 973 K. The hydrogen concentration and the hydride dissolution temperature of specimen were measured by using a hydrogen analyzer and a differential scanning calorimeter (DSC), respectively, and then the terminal solid solubility of hydrogen was determined. The TSS of the α single-phase Zr-0.3Nb (Zr-0.3 wt.% Nb) specimen appeared to be almost same as that of pure Zr. On the contrary, the TSS of the Zr-1.0Nb and Zr-2.5Nb alloys, which were α + β biphasic specimens, were larger than that of pure Zr and slightly increased with Nb concentration. The increment of TSS by Nb addition was slightly larger than that by the traditional additive elements of Sn, Ni, and Cr in Zircaloys. The Nb added Zircaloy-4 had higher TSS than the Zircaloy-2 and -4, which was attributed to the further additive effect by βZr precipitation in Zircaloy besides the traditional additive element effects

  20. Heat capacity measurement on Sr2Nb2O7 using DSC

    International Nuclear Information System (INIS)

    Samui, Pradeep; Singh, Brij Mohan; Agarwal, Renu

    2016-01-01

    Fission products, strontium and niobium form ternary oxides compounds in an operating nuclear reactor with oxide fuels under certain oxygen potential. Evaluations of thermodynamic functions of these ternary oxides are therefore important for assessment of fission product interactions and modeling of fuel. Furthermore, thermodynamic data of these oxides are also of relevance because of computation of phase diagram and phase stability of pseudo-ternary systems BaO-SrO-Nb 2 O 5 , SrO-Nb 2 O 5 -TaO 5 etc. in which some of the compounds are potential candidate materials for microwave ceramics with high dielectric constant, electro-optic, pyroelectric and piezoelectric devices. The system Sr-Nb-O contains many ternary oxides out of which we have measured heat capacity for the compound Sr 2 Nb 2 O 7 in the present study

  1. Refining U-Zr-Nb alloys by remelting

    International Nuclear Information System (INIS)

    Aguiar, B.M.; Kniess, C.T.; Riella, H.G.; Ferraz, W.B.

    2011-01-01

    The high density U-Zr-Nb and U-Nb uranium-based alloys can be employed as nuclear fuel in a PWR reactor due to their high density and nuclear properties. These alloys can stabilize the gamma phase, however, according to TTT diagrams, at the working temperature of a PWR reactor, all gamma phase transforms to α'' phase in a few hours. To avoid this kind of transformation during the nuclear reactor operation, the U-Zr-Nb alloy and U-Nn are used in α'' phase. The stability of α'' phase depends on the alloy composition and cooling rate. The alloy homogenization has to be very effective to eliminate precipitates rich in Zr and Nb to avoid changes in the alloying elements contents in the matrix. The homogenization was obtained by remelting the alloy and keeping it in the liquid state for enough time to promote floating of the precipitates (usually carbides, less dense) and leaving the matrix free of precipitates. However, this floating by density difference may result in segregation between the alloying elements (Nb and Zr, at the top) and uranium (at the bottom). The homogenized alloys were characterized in terms of metallographic techniques, optical microscopy, scanning electronic microscopy, EDS and X-ray diffraction. In this paper, it is shown that the contents of Zr and Nb at the bottom and at the top of the matrix are constant. (author)

  2. Microscale 1-3-Type (Na,K)NbO(3)-Based Pb-Free Piezocomposites for High-Frequency Ultrasonic Transducer Applications.

    Science.gov (United States)

    Shen, Zong-Yang; Li, Jing-Feng; Chen, Ruimin; Zhou, Qifa; Shung, K Kirk

    2011-05-01

    Fine-grained Pb-free (Na(0.535)K(0.485))(0.95)Li(0.05)(Nb(0.8)Ta(0.2))O(3) (NKLNT) piezoceramics prepared by spark plasma sintering (SPS) technique was used to fabricate NKLNT/epoxy 1-3 composites with a modified dice-fill method. Because of its good machinability, SPSed NKLNT ceramic rods could be miniaturized to a lateral width of 50 µm. After lapping down to 56 µm in thickness, the composite was used to fabricate an ultrasonic transducer as the active piezoelectric element. This composite transducer showed a bandwidth at -6 dB nearly 90%at a center frequency of 29 MHz, demonstrating that this Pb-free composite thick film is very promising for the fabrication of high-frequency ultrasonic transducers in medical imaging applications.

  3. Alloying effects on the high-temperature oxidation resistance of Cr-Cr{sub 2}Nb

    Energy Technology Data Exchange (ETDEWEB)

    Tortorelli, P.F.; DeVan, J.H.

    1994-09-01

    Alloying effects on the high-temperature oxidation resistance of Cr-Cr{sub 2}Nb were examined on the basis of isothermal exposures to air at 950 C. Additions of either Re and Al or Fe, Ni, and Al had relatively little effect on weight gains relative to the Cr-6% Nb binary alloy. One alloying element that improved the mechanical behavior of Cr-Cr{sub 2}Nb alloys substantially increased the oxidation rates and spallation susceptibilities of Cr-6 and -12% Nb alloys. However, the addition of another element completely offset these deleterious effects. The presence of this latter element resulted in the best overall oxidation behavior (in terms of both weight gains and spallation tendencies) of all Cr-Cr{sub 2}Nb compositions. Its beneficial effect can be attributed to improvement in the oxidation resistance of the Cr-rich phase.

  4. The cyclic oxidation resistance at 1200 C of Beta-NiAl, FeAl, and CoAl alloys with selected third element additions

    International Nuclear Information System (INIS)

    Barrett, C.A.; Titran, R.H.

    1992-04-01

    The intermetallic compounds Beta-NiAl, FeAl, and CoAl were tested in cyclic oxidation with selected third element alloy additions. Tests in static air for 200 1-hr cycles at 1200 C indicated by specific weight change/time data and x-ray diffraction analysis that the 5 at percent alloy additions did not significantly improve the oxidation resistance over the alumina forming baseline alloys without the additions. Many of the alloy additions were actually deleterious. Ta and Nb were the only alloy additions that actually altered the nature of the oxide(s) formed and still maintained the oxidation resistance of the protective alumina scale

  5. Effects of helium and deuterium irradiation on SPS sintered W–Ta composites at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Mateus, R., E-mail: rmateus@ipfn.ist.utl.pt [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Dias, M. [ITN, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém (Portugal); Lopes, J. [ITN, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém (Portugal); ISEL, Instituto Superior de Engenharia de Lisboa, Rua Conselheiro Emídio Navarro, 1, 1959-007 Lisboa (Portugal); Rocha, J.; Catarino, N.; Franco, N. [ITN, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém (Portugal); Livramento, V. [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); LNEG, Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 1649-038 Lisboa (Portugal); and others

    2013-11-15

    Energetic He{sup +} and D{sup +} ions were implanted into different W–Ta composites in order to investigate their stability under helium and deuterium irradiation. The results were compared with morphological and chemical modifications arising from exposure of pure W and Ta. Special attention was given to tantalum hydride (Ta{sub 2}H) formation due to its implications for tritium inventory. Three W–Ta composites with 10 and 20 at.% Ta were prepared from elemental W powder and Ta fibre or powder through low-energy ball milling in argon atmosphere. Spark plasma sintering (SPS) was used as the consolidation process in the temperature range from 1473 to 1873 K. The results obtained from pure elemental samples and composites are similar. However, Ta{sub 2}H is easily formed in pure Ta by using a pre-implantation stage of He{sup +}, whereas in W–Ta composites the same reaction is clearly reduced, and it can be inhibited by controlling the sintering temperature.

  6. Effect of Ni interlayer on diffusion bonding of a W alloy and a Ta alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jian; Liu, Ruxia; Wei, Qinqin; Luo, Guoqiang; Shen, Qiang; Zhang, Lianmeng [Wuhan Univ. of Technology (China). The State Key Lab. of Advanced Technology for Materials Synthesis and Processing

    2017-11-01

    The combination of W and Ta is expected to be highly beneficial for many applications from aerospace, weapons, military and nuclear industry. In this paper, W and Ta alloys were successfully diffusion bonded with Ni interlayer. The process of the formation of W/Ni/Ta diffusion bonded joints was investigated by means of scanning electron microscopy, X-ray diffraction system, electron probe micro-analyzer, energy dispersive spectrometry and shear strength measurement. The results show that the shear strength increases when the bonding temperature increases and exhibits a maximum value of 244 MPa at 930 C. The bonding of W/Ni can be attributed to the bonding of Ni to tungsten grains and the bonding of Ni to a Ni-Fe-binder mainly by elemental diffusion. The fracture takes place in the Ni/Ta interface and Ni{sub 3}Ta and Ni{sub 2}Ta intermetallic compounds are formed on the fracture surfaces.

  7. Core level photoemission spectroscopy and chemical bonding in Sr2Ta2O7

    DEFF Research Database (Denmark)

    Atuchin, V. V.; Grivel, Jean-Claude; Zhang, Z. M.

    2009-01-01

    Electronic parameters of constituent element core levels of strontium pyrotantalate (Sr2Ta2O7) were measured with X-ray photoelectron spectroscopy (XPS). The Sr2Ta2O7 powder sample was synthesized using standard solid state method. The valence electron transfer on the formation of the Sr-O and Ta......-O bonds was characterized by the binding energy differences between the O 1s and cation core levels, Delta(O-Sr) = BE(O 1s) - BE(Sr 3d(5/2)) and Delta(O-Ta) = BE(O 1s) - BE(Ta 4f(7/2)). The chemical bonding effects were considered on the basis of our XPS results for Sr2Ta2O7 and earlier published...

  8. Alloy Design and Property Evaluation of Ti-Mo-Nb-Sn Alloy for ...

    African Journals Online (AJOL)

    Ti-Mo alloy containing Nb and Sn were arc melted and composition analyzed by EDX. The XRD analysis indicates that the crystal structure and mechanical properties are sensitive to Sn concentration. A combination of Sn and Nb elements in synergy hindered formation athermal w phase and significantly enhanced b phase ...

  9. Binuclear metallocenes of elements at the beginning of the transition series: The first heterometallic complex (n5:n5-C10H8)(n-CpTi)(n-CpNb)(u-H)2

    International Nuclear Information System (INIS)

    Demenovskii, D.A.; Nifant'er, I.E.; Zagorevskii, D.V.

    1986-01-01

    The authors synthesized the first mixed bis-metallocene complex (I) containing titanium and niobium. This complex was synthesized by the combined reduction of a mixture of metallocene dihalides as well as by the reaction of Cp 2 TiCl with lithium derivative. The yield of (I) in the first reaction was about 40% while it was more than 90% in the second. Complex (II), Cp 2 NbH 2 Li, is a new, convenient synthetic reagent readily formed in the crystalline state in the metallation of Cp 2 NbH 3 by butyllithium in toluene. The mass spectrum of (I) at 9-V ionizing potential shows a strong peak for only the molecular ion m/z 401 (for the ion with Ti 48); extensive dehydrogenation of the molecular ion occurs upon increasing the ionizing electron energy

  10. Spectroscopic study of the charge density wave order in 2H[ -TaS2

    Science.gov (United States)

    Zhao, J.; Wijayaratne, K.; Malliakas, C. D.; Kanatzidis, M. G.; Chung, D. Y.; Gu, G.; Chatterjee, U.

    2017-09-01

    We conduct Angle Resolved Photoemission Spectroscopy (ARPES) investigation on 2H-TaS2, a prototypical incommensurate Charge Density Wave (CDW) material. A comparative study of the low-energy electronic structures of 2H-TaS2 and two other related compounds, 2H-TaSe2 and 2H-NbSe2, identifies several generic features of their CDW orders. Firstly, Fermi surface (FS) nesting alone doesn't seem to give rise to the CDW instability in these compounds. Secondly, partial gapping of the underlying FS surface in the CDW state is common to each of these materials. Finally, the CDW energy gap, unlike the energy gap in a superconductor, is not symmetric with respect to the chemical potential.

  11. Investigation of TaC–TaB2 ceramic composites

    Indian Academy of Sciences (India)

    mance materials for applications in extremely harsh envi- ronments, such as propulsion systems for future hypersonic vehicles [2–5]. Tantalum carbide ceramics are difficult to densify because of the rapid grain growth of TaCy [6–8], which leads to entrapped porosity. One of the methods to inhibit grain growth is by reductive ...

  12. Investigation of TaC–TaB2 ceramic composites

    Indian Academy of Sciences (India)

    C and applied pressure of 30 MPa. TaC and 2–3 wt% B4C were used as starting powders. Densification process, phase evolution, microstructure and the mechanical properties of the composites were investigated. The results indicated that the ...

  13. Effect of Nb on magnetic and mechanical properties of TbDyFe alloys

    Science.gov (United States)

    Wang, Naijuan; Liu, Yuan; Zhang, Huawei; Chen, Xiang; Li, Yanxiang

    2018-03-01

    The intrinsic brittleness in giant magnetostrictive material TbDyFe alloy has devastating influence on the machinability and properties of the alloy, thus affecting its applications. The purpose of this paper is to study the mechanical properties of the TbDyFe alloy by alloying with Nb element. The samples (Tb0.3Dy0.7)xFe2xNby (y = 0, 0.01, 0.04, 0.07, 0.1; 3x + y = 1) were melted in an arc melting furnace under high purity argon atmosphere. The microstructure, magnetostrictive properties and mechanical performance of the alloys were studied systematically. The results showed that NbFe2 phases were observed in the alloys with the addition of Nb. Moreover, both the NbFe2 phases and rare earth (RE)-rich phases were increased with the increasing of Nb element. The mechanical properties results revealed that the fracture toughness of the alloy with the addition of Nb enhanced 1.5-5 times of the Nb-free alloy. Both the NbFe2 phase and the RE-rich phase had the ability to prevent crack propagation, so that they can strengthen the REFe2 body. However, NbFe2 phase is a paramagnetic phase, which can reduce the magnetostrictive properties of the alloy by excessive precipitation.

  14. Immiscible silicate liquids at high pressure: the influence of melt structure on elemental partitioning

    Energy Technology Data Exchange (ETDEWEB)

    Vicenzi, E. [Princeton Materials Laboratory, Princeton, NJ (United States); Green, T.H. [Macquarie Univ., North Ryde, NSW (Australia); Sie, S.H. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience

    1993-12-31

    Micro-PIXE analyses have been applied to study partitioning of trace elements between immiscible silicate melts stabilised at 0.5 and 1.0 GPa over a temperature range of 1160-1240 deg C in the system SiO{sub 2}-FeO-Al{sub 2}0{sub 3}-K{sub 2}0 (+P{sub 2}0{sub 5}). The system was doped with a suite of trace elements of geochemical interest: Rb, Ba, Pb, Sr, La, Ce, Sm, Ho, Y, Lu, Th, U, Zr, Hf, Nb and Ta at approximately 200 ppm level for all elements except for the REE`s, Ba and Ta (600-1200 ppm). Trace element partitioning was found to be a complex function of cation field strength (charge/radius{sup 2}). Although field strength is important in determining the nature and degree of partitioning, the authors emphasised that it is only one component of the underlying mechanism for the way in which elements distribute themselves between two silicate liquids. 8 refs., 2 figs.

  15. Growth and characterization of lead-free (K,Na)NbO3-based piezoelectric single crystals

    International Nuclear Information System (INIS)

    Liu, Hairui

    2016-01-01

    ) For individual elements, segregation coefficients highly rely on the initial concentration in the liquid solution. The systematic discussion in this work contributes to future composition design in KNN-based crystals. (ii) A competition between elements occupied on the same lattice site was found. (iii) The very low Li segregation coefficient in the KNN matrix is importantly responsible for the occurrence of a secondary phase with the tetragonal tungsten bronze structure. (iv) The observed optically-cloudy regions in as-grown KNN-based single crystals decrease the electrical response and can be reduced by thermal treatment with slow cooling. In the second part of the thesis we used three approaches to enhance the piezoelectric and ferroelectric behavior of KNN-based single crystals, which is shown in Chapter 5. Chemical substitution with Ta or Sb ions indicates that enhanced electromechanical response is achieved when the orthorhombic-tetragonal phase transition temperature is in the proximity of room temperature, as previously reported for polycrystalline ceramics. Thermal treatment in pure O 2 atmosphere resulted in a twofold increase of the piezoelectric coefficient and ferroelectric parameters (maximum and remanent polarization) of a (K,Na,Li)(Ta,Nb,Sb)O 3 single crystal. The up-to-date highest room-temperature piezoelectric coefficient in annealed KNN-based single crystals of 732 pC/N was obtained, which is attributed to the lower defect concentration after the thermal treatment. The third approach, doping with a small amount of transition metal Mn ions in (K,Na,Li)(Ta,Nb)O 3 single crystals, is also presented. Orientation dependence of electromechanical properties in Chapter 6 indicates that high maximum polarization, remanent polarization, coercive field, maximum strain, and negative strain were observed when the electric field was applied along one of the spontaneous polarization vectors in both tetragonal and orthorhombic phases. This is related to the effect

  16. A note on chemical composition and origin of ferromanganese oxide coated and uncoated pumice samples from central Indian Ocean basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Parthiban, G.; Moraes, C.; Rajalakshmi, R.; Lekshmi, S.; Athira, S.; JaiSankar, S.

    other suggesting a same source. Tectonomagmatic discrimination diagrams (Nb vs Y: Yb vs. Ta), triangular plot (TiO2-Y) and High Field Strength Element ratios (La/Ta-25; Ta/Hf-0.2; Nb/Ta-9; Zr/Nb-22 and Ba/Ta-1084) indicate volcanic arc origin...

  17. TA-55 change control manual

    International Nuclear Information System (INIS)

    Blum, T.W.; Selvage, R.D.; Courtney, K.H.

    1997-11-01

    This manual is the guide for initiating change at the Plutonium Facility, which handles the processing of plutonium as well as research on plutonium metallurgy. It describes the change and work control processes employed at TA-55 to ensure that all proposed changes are properly identified, reviewed, approved, implemented, tested, and documented so that operations are maintained within the approved safety envelope. All Laboratory groups, their contractors, and subcontractors doing work at TA-55 follow requirements set forth herein. This manual applies to all new and modified processes and experiments inside the TA-55 Plutonium Facility; general plant project (GPP) and line item funded construction projects at TA-55; temporary and permanent changes that directly or indirectly affect structures, systems, or components (SSCs) as described in the safety analysis, including Facility Control System (FCS) software; and major modifications to procedures. This manual does not apply to maintenance performed on process equipment or facility SSCs or the replacement of SSCs or equipment with documented approved equivalents

  18. TA-55 change control manual

    Energy Technology Data Exchange (ETDEWEB)

    Blum, T.W.; Selvage, R.D.; Courtney, K.H.

    1997-11-01

    This manual is the guide for initiating change at the Plutonium Facility, which handles the processing of plutonium as well as research on plutonium metallurgy. It describes the change and work control processes employed at TA-55 to ensure that all proposed changes are properly identified, reviewed, approved, implemented, tested, and documented so that operations are maintained within the approved safety envelope. All Laboratory groups, their contractors, and subcontractors doing work at TA-55 follow requirements set forth herein. This manual applies to all new and modified processes and experiments inside the TA-55 Plutonium Facility; general plant project (GPP) and line item funded construction projects at TA-55; temporary and permanent changes that directly or indirectly affect structures, systems, or components (SSCs) as described in the safety analysis, including Facility Control System (FCS) software; and major modifications to procedures. This manual does not apply to maintenance performed on process equipment or facility SSCs or the replacement of SSCs or equipment with documented approved equivalents.

  19. Observation of A15 phase transformation in RHQ-Nb3Al wire by neutron diffraction at high-temperature

    International Nuclear Information System (INIS)

    Jin Xinzhe; Nakamoto, Tatsushi; Harjo, Stefanus; Ito, Takayoshi; Ogitsu, Toru; Tsuchiya, Kiyosumi; Yamamoto, Akira; Kikuchi, Akihiro; Takeuchi, Takao; Hemmi, Tsutomu

    2012-01-01

    Highlights: ► A15 phase transition from solid solution occurred within 5 min in RHQ-Nb 3 Al wire. ► The holding duration of 9 h at 800 °C was found to optimize growth of the A15 phase. ► The residual strain in the Nb 3 Al filaments appeared between 200 and 300 °C. ► An isotropic tensile strain of 0.07% was found in the Nb 3 Al at room temperature. ► The tensile effect of the Nb/Ta matrix was dominant in the RHQ-Nb3Al wire. - Abstract: Nb 3 Al superconducting wires produced by rapid heating and quenching (RHQ) method have been developed for application to high field accelerator magnet. In an A15-type superconductor, it is known that residual strain in the superconducting phase induced by thermal contraction after heat treatment influences superconducting properties such as the critical current density. After RHQ treatment, a solid solution of NbAl y with a bcc structure was formed from a jelly-roll of Nb and Al sheets in the wire. To observe the A15 phase transition in the NbAl y and to clarify the mechanism of residual strain generation in the RHQ-Nb 3 Al wire, neutron diffraction measurements were carried out on the J-PARC “TAKUMI” between room-temperature and 800 °C, in which the Nb 3 Al superconducting phase is formed. Here, we report measurements on an RHQ-Nb 3 Al wire with an Nb/Ta composite matrix, using single-peak analysis and multi-peak analysis for peak intensity fitting and peak position fitting, respectively. The phase transition to the A15 was found to occur within a short period about 5 min while the temperature was increasing from 735 to 800 °C. Along the axial direction of the wire, growth of the A15 phase was found to be optimized using a subsequent holding process of 9 h at 800 °C. Following cooling to room temperature, the Nb 3 Al filaments in the wire exhibited an isotropic tensile residual strain of about 0.07%.

  20. Effect of alloying on the properties of the Nb3Sn compound

    International Nuclear Information System (INIS)

    Efimov, Yu.V.; Mikhajlov, B.P.; Moroz, E.A.

    1979-01-01

    The effect of some alloying elements upon the structure and the superconducting properties of Nb 3 Sn was studied. The superconductivity transition point was determined from the variation of the magnetic susceptibility at temperatures above 4.2 K +-0.1K. The alloying of Nb 3 Sn by vanadium, molybdenum, titanium, zirconium, scandium, sodium silicon, tin, copper, carbon or oxygen was found to lower the superconductivity transition point. The drop in Tsub(k) correlates with the maximum solubility of the alloying element. Small additions of aluminium, gallium, germanium or indium give raise to Tsub(k) of Nb 3 Sn. Elements, poorly soluble in Nb 3 Sn (yttrium, scandium, copper) raise the critical current of the coats, whereas elements with a high solubility in this compound, lower the critical current

  1. Proximity phenomena in double-barrier structure NbZr/NbOx/Al/AlOy/NbZr

    International Nuclear Information System (INIS)

    Plecenik, A.; Gasi, S.; Zuzcak, M.; Benacka, S.

    1999-01-01

    A tunneling structures NbZr/NbO x /Al/AlO y /NbZr with a thin barrier in the NbZr/NbO x /Al junction and 4 to 6-nm-thick Al interlayer were prepared and studied experimentally. A proximity effect between NbZr and Al through NbO x barrier has been observed. An electrical voltage was generated in the NbO x barrier and a coexistence of the proximity effect and applied voltage in the junction NbZr/NbO x /Al has been observed. This experiment could be described on the basis of a model for coherent charge transport in superconducting/normal proximity structures

  2. Anion-exchange Studies of Radioactive Trace Elements in Sulphuric Acid Solutions

    International Nuclear Information System (INIS)

    Samsahl, K.

    1963-01-01

    As part of a chemical group separation procedure used as a pretreatment in gamma spectrometric analysis, a study has been made of the adsorption from sulphuric acid solutions on strongly basic anion exchange resins, prepared in the hydroxide and the sulphate forms, of trace activities of Na, P, K, Ca, Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Zr, Nb, Mo, Tc, Ag, Cd, In, Cs, Ba, La, Ce, Hf, Ta, W, Ir, Pa and Np. Besides adsorbing some of the trace elements in the solution, the anion exchange resin in the hydroxide form will neutralize the bulk of the sulphuric acid. This makes possible the subsequent sequential separation of chloride complexes on short anion-exchange columns by a stepwise increasing of the HCl concentration of the solution. On the basis of the results obtained in the present and earlier experiments, a new improved chemical group-separation procedure for mixtures of radioactive trace elements is outlined

  3. Coprecipitation synthesis and negative thermal expansion of NbVO5.

    Science.gov (United States)

    Wang, Jinrui; Deng, Jinxia; Yu, Ranbo; Chen, Jun; Xing, Xianran

    2011-04-07

    We develop a coprecipitation synthesis route to prepare NbVO(5) with simple oxide Nb(2)O(5) and NH(4)VO(3) as starting materials. No metal alkoxide or organometallic substance was used in the process. Nano-crystal NbVO(5) was obtained by calcination of the coprecipitates at 550 °C for 2 h. DSC/TG and XRD investigations indicate that the target compound NbVO(5) is completely formed up to 504.5 °C and is thermally stable below 658 °C. Rietveld XRD refinements give an orthorhombic structure with space group Pnma and lattice parameters, a=11.8453(2), b=5.5126(3) and c=6.9212(2) Å, respectively. In particular, HTXRD determinations show a negative thermal expansion in NbVO(5) with a TEC of -6.63 × 10(-6) °C(-1) in the temperature range of RT-600 °C. This fact is ascribed to the tilting of NbO(6) octahedra and VO(4) tetrahedra in the flexible framework structure. The present synthesis route is facile and easy to be extended to prepare analogues such as TaVO(5), etc. © The Royal Society of Chemistry 2011

  4. X-ray attenuation around K-edge of Zr, Nb, Mo and Pd: A ...

    Indian Academy of Sciences (India)

    Abstract. Mass attenuation coefficients (µ/ρ) for Zr, Nb, Mo and Pd elements around their K-edges are measured at 14 energies in the range 15.744–28.564 keV using secondary excitation from thin Zr, Nb, Mo, Rh, Pd, Cd and Sn foils. The measurements were carried out at the Kα and Kβ energy values of the target elements ...

  5. In situ synthesis of NiAl–NbB2 composite powder through combustion synthesis

    International Nuclear Information System (INIS)

    Shokati, Ali Akbar; Parvin, Nader; Sabzianpour, Naser; Shokati, Mohammad; Hemmati, Ali

    2013-01-01

    Highlights: ► A Novel NiAl matrix composite powder with 0–40 wt.% NbB 2 was synthesized. ► Composite powders were synthesized by thermal explosion reaction of Ni–Al–Nb–B system. ► Microhardness of NiAl considerably increased with raising NbB 2 content. ► Synthesized composite powders is a good candidate as precursor for thermal barrier application. - Abstract: Synthesis of a novel NiAl matrix composite powder reinforced with 0–40 wt.% NbB 2 by combustion synthesis in thermal explosion mode was investigated. The elemental powders of Ni, Al, Nb, and amorphous boron were used as starting material. For all compositions final products consisted of only the NiAl and NbB 2 phases. Coarser NbB 2 with a relatively uniform distribution in NiAl matrix was formed with rising NbB 2 content. Microhardness of NiAl considerably increased from 377 ± 13 HV 0.05 to 866 ± 81 HV 0.05 for NiAl with 40 wt.% NbB 2 . High microhardness, proper size and distribution of NbB 2 in NiAl matrix make it a good candidate as precursor for thermal spray application.

  6. Influences of Pr and Ta doping concentration on the characteristic features of FTO thin film deposited by spray pyrolysis

    International Nuclear Information System (INIS)

    Turgut, Güven; Koçyiğit, Adem; Sönmez, Erdal

    2015-01-01

    The Pr and Ta separately doped FTO (10 at.% F incorporated SnO 2 ) films are fabricated via spray pyrolysis. The microstructural, topographic, optical, and electrical features of fluorine-doped TO (FTO) films are investigated as functions of Pr and Ta dopant concentrations. The x-ray diffraction (XRD) measurements reveal that all deposited films show polycrystalline tin oxide crystal property. FTO film has (200) preferential orientation, but this orientation changes to (211) direction with Pr and Ta doping ratio increasing. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses show that all films have uniform and homogenous nanoparticle distributions. Furthermore, morphologies of the films depend on the ratio between Pr and Ta dopants. From ultraviolet-visible (UV-Vis) spectrophotometer measurements, it is shown that the transmittance value of FTO film decreases with Pr and Ta doping elements increasing. The band gap value of FTO film increases only at 1 at.% Ta doping level, it drops off with Pr and Ta doping ratio increasing at other doped FTO films. The electrical measurements indicate that the sheet resistance value of FTO film initially decreases with Pr and Ta doping ratio decreasing and then it increases with Pr and Ta doping ratio increasing. The highest value of figure of merit is obtained for 1 at.% Ta- and Pr-doped FTO film. These results suggest that Pr- and Ta-doped FTO films may be appealing candidates for TCO applications. (paper)

  7. Utilization of Neutron Activation Analysis for geochemical study of major and trace elements in Bouregreg river basin (Morocco)

    International Nuclear Information System (INIS)

    Bounouira, H.; Bounakhla, M.; Embarch, K.; Choukri, A.; Cherkaoui, R.; Gaudry, A.; Treuil, M.; Chakiri, S.

    2010-01-01

    The Bouregreg river basin is located in the moroccan central massif which consists mainly of palaeozoic formations that were subject to the Hercynian orogeny. This study documents the backround geochemistry and hydrochemistry of the Bouregreg river basin, focusing on the distribution of major and trace elements, Rock samples were collected at 9 locations along the bouregreg river and its tributaries in the winter of 2005. Major (Al, fe, Mn, Na, K and Ti) and trace (Rb, Cs, Sr, Sc, Ba, Cr, V, Co, Ni, Zn, As, Sb, La, Ce, Nd, Sm, Tb, Dy, Yb, Lu, Hf, Ta, Mo, Th and U) elements were anlysed using instrumental Neutron Activation Analysis (INAA). Data show that most of the geochemistry and hydrochemistry are related to regional and local geology. the geochemical heritage of geological environment in the Bouregreg river basin is very important, that results from the more compatible behaviour and the inertia of some elements during the weathering (3d transition elements (Co, Ni, Cr,...), interne transition elements f (lanthanides, Zr, Hf, Nb, Ta,...)). The geochemical homogeneity of the basin shows also heritage during the crustal accretion (magmatism-metamorphism-sedimention) and the typology of this continental area is the same that the Upper Continental Crust (UCC). Some anomalously high heavy metal analyses, particulary for As and Sb, may be related to anthropogenic activities

  8. A 345 GHZ WAVE-GUIDE MIXER USING AN ARRAY OF 4 NB-AL-AL2O3-NB SIS JUNCTIONS

    NARCIS (Netherlands)

    HONINGH, CE; DIERICHS, MMTM; SCHAEFFER, HHA; KLAPWIJK, TM; DEGRAAUW, T

    1991-01-01

    An array of four Nb-Al-Al2O3-Nb sis junctions in series is used as the mixing element in a waveguide mixer at 345 GHz. The area of one junction is 4-mu-m2 and its normal state resistance is about 12-OMEGA, yielding at 345 GHz, omega-RC approximately 5. The receiver noise temperature below 550 K is

  9. Mineralogy and Trace Element Chemistry of Ferberite/Reinite from Tungsten Deposits in Central Rwanda

    Directory of Open Access Journals (Sweden)

    Philippe Muchez

    2013-04-01

    Full Text Available Tungsten mineralization in hydrothermal quartz veins from the Nyakabingo,Gifurwe and Bugarama deposits in central Rwanda occurs as the iron-rich endmember ofthe wolframite solid solution series (ferberite and in the particular form of reinite, whichrepresents a pseudomorph of ferberite after scheelite. Primary ferberite, reinite and latesecondary ferberite are characterized by their trace element chemistry and rare earthelement patterns. The replacement of scheelite by ferberite is also documented in the traceelement composition. Primary ferberite shows high Mg, Zn, Sc, V, Nb, In and Snconcentrations, but very low Ca, Pb, Sr and Ba contents. Reinite and late secondaryferberite display an uncommon trace element composition containing high concentrationsof Ca, Pb, Sr, Ba, As and Ga, but very low levels in Sn, Zr, Hf, In, Ti, Sc, Nb, Ta, Mg andZn. Late secondary ferberite replacing primary ferberite is characterized by additionalenrichments in Bi, Pb, As and Sb. The rare earth element patterns of reinite and secondaryferberite are also similar to hydrothermal scheelite. The formation of the tungsten depositsin central Rwanda is interpreted to be epigenetic in origin, and the hydrothermalmineralizing fluids are related to the intrusion of the G4-granites.

  10. Effects of differential thermal contraction between the matrix and the filaments in mono- and multifilamentary Nb3Sn on the superconducting critical temperature

    International Nuclear Information System (INIS)

    Aihara, K.; Suenage, M.; Luhman, T.

    1979-01-01

    The strain on Nb 3 Sn due to the differential thermal contraction between the matrix (Cu, bronze) and the filaments (Nb, Nb 3 Sn, Ta) of a superconducting wire is known to decrease the superconducting critical temperature T/sub c/. In order to study the effects of heat treatment conditions and filament size on the degradation of T/sub c/ by the strain. T/sub c/ for monofilamentary wires [(Nb 3 Sn and bronze in Ta) in Cu matrix, and (bronze in Nb tubings) in Cu matrix] were measured for heat-treating periods in of 1 to 120 h at 725 0 C. Several observations were made regarding the effects on T/sub c/ of thermal contraction strains from various components of the conductors. The influence of a Cu matrix on T/sub c/ was small (approx. 0.2 K). When the bronze matrix was inside Nb tubing the degradation of T/sub c/ due to strains was substantially larger than when the Nb filaments were in a bronze. Wires with smaller filament diameters achieved a maximum T/sub c/ in shorter heat treatment times than those with larger filaments. These results are discussed in terms of the critical currents of these wires under applied tensile strains

  11. Thermal stability of nano structured iron powder as a function of amount and nature of reinforcement (Nb or NbC); Estudio de la estabilidad termica de polvo de hierro nanoestructurado en funcion del tipo de refuerzo (Nb, NbC) y de su contenido

    Energy Technology Data Exchange (ETDEWEB)

    Fuentes-Pacheco, L.; Campos, M.; Torralba, J. M.

    2011-07-01

    In structural steels, an effective strategy to succeed in increasing both strength and toughness is the grain refining, like in microalloyed steels. To delay or even inhibit the grain growth there are two basic mechanisms: particle pinning and solute drag. The effect of the presence of small particles of NbC to inhibit the austenitic grain growth is well known. However, it is not so clear which mechanism will be more effective to delay ferritic grain growth. In order to confirm it, nano structured iron powders reinforced with Nb and NbC have been prepared by mechanical alloying. The main objective of this work is, therefore, to study the thermal stability of the nano structured powder as a function of the reinforce type (elemental Nb or NbC) and its content. (Author) 19 refs.

  12. Mg:Nb films produced by pulsed laser deposition for hydrogen storage

    Energy Technology Data Exchange (ETDEWEB)

    Mosaner, Paolo; Bazzanella, Nicola; Bonelli, Marco; Checchetto, Riccardo; Miotello, Antonio

    2004-04-25

    Magnesium thin films with controlled Nb content (Mg:Nb) were deposited by pulsed laser deposition (PLD) in a single step process using a composite target consisting on separate zones of matrix (Mg) and alloying element (Nb). Scanning electron microscopy (SEM) analysis showed a double structure of the thin film samples consisting on a homogeneous thin film {approx}1 {mu}m thick and large Mg:Nb spheres with dimensions ranging from {approx}1 {mu}m for energy density of the laser pulse lower than 10 J/cm{sup 2} to {approx}10 {mu}m for higher energy, 30-40 J/cm{sup 2}. The crystalline structure of the deposited samples consisted of (0 0 1) oriented Mg layers with Nb atomically dispersed in the Mg structure or in form of nanoclusters. A preliminary test on the hydrogen absorption capacity of the PLD deposited samples was carried out by thermal desorption spectroscopy (TDS)

  13. Determination of the transition to the high entropy regime for alloys of refractory elements

    Energy Technology Data Exchange (ETDEWEB)

    Grosso, Mariela F. del [Gerencia de Investigacion y Aplicaciones, Comision Nacional de Energia Atomica, Av. Gral. Paz 1499 (B1650KNA), San Martin (Argentina); CONICET, Buenos Aires (Argentina); Grupo de Caracterizacion y Modelizacion de Materiales, UTN, FRGP, H. Yrigoyen 288, (B1617FRG) Gral. Pacheco (Argentina); Bozzolo, Guillermo, E-mail: guille_bozzolo@yahoo.com [Loyola University Maryland, 4501 N. Charles St., Baltimore, MD 21210 (United States); Mosca, Hugo O. [Gerencia de Investigacion y Aplicaciones, Comision Nacional de Energia Atomica, Av. Gral. Paz 1499 (B1650KNA), San Martin (Argentina); Grupo de Caracterizacion y Modelizacion de Materiales, UTN, FRGP, H. Yrigoyen 288, (B1617FRG) Gral. Pacheco (Argentina)

    2012-09-05

    Highlights: Black-Right-Pointing-Pointer Atomistic modeling using a quantum approximate method for the energetics. Black-Right-Pointing-Pointer Modeling of the phase structure of high entropy alloys of refractory elements. Black-Right-Pointing-Pointer Comparison of modeled structure with experimental results for five-element alloys. Black-Right-Pointing-Pointer Determination of bulk properties of transitional chains from 4 to 5 element alloys. Black-Right-Pointing-Pointer Introduction of an algorithm to aid in the design of high entropy alloys. - Abstract: The development of high entropy alloys is currently limited to experimental work aimed at the determination of specific compositions that exhibit particular properties. The main feature of these alloys is their particular phase structure, which tends to be a continuous solid solution in spite of the large number of constituents which would otherwise form a large number of intermetallic phases. While it is known that equimolar concentrations and large number of elements are two necessary conditions for achieving high entropy behavior, not much is known regarding the transition to this regime in the presence of specific elements. Such knowledge would be useful when determining alloy compositions, as it would set boundaries for the necessary concentrations of each element in experimental situations. In this work, results of a computational modeling effort are presented, where a recently developed 5-element high entropy alloy of refractory elements is used as the foundation needed to examine such transition and determine the necessary lower bounds for the concentration of each element. Details of the phase structure of the quaternary combinations of W, Nb, Mo, Ta and V as they evolve upon the addition of a fifth element are discussed. The results are compared to the experimental case for the case of V added to W-Nb-Mo-Ta. Using these examples as a reference, the concept of critical concentrations for each element

  14. Irradiation resistance, microstructure and mechanical properties of nanostructured (TiZrHfVNbTa)N coatings

    Energy Technology Data Exchange (ETDEWEB)

    Pogrebnjak, Alexander D. [Sumy State University, Sumy (Ukraine); Institute of Transport, Combustion Engines and Ecology, Lublin University of Technology, 20-618 Lublin (Poland); Yakushchenko, Ivan V.; Bondar, Oleksandr V. [Sumy State University, Sumy (Ukraine); Beresnev, Vyacheslav M. [Karazin National University, Kharkiv (Ukraine); Oyoshi, Keiji [National Institute for Material Science (NIMS), Tsukuba (Japan); Ivasishin, Orest M. [V. Kurdyumov Institute for Metal Physics, NAS of Ukraine, Kiev (Ukraine); Amekura, Hiroshi; Takeda, Yoshihiko [National Institute for Material Science (NIMS), Tsukuba (Japan); Opielak, Marek, E-mail: m.opielak@pollub.pl [Institute of Transport, Combustion Engines and Ecology, Lublin University of Technology, 20-618 Lublin (Poland); Kozak, Czeslaw [Department of Electrical Devices and High Voltage Technology, Lublin University of Technology, 20-618 Lublin (Poland)

    2016-09-15

    Nitrides of high-entropy alloys (TiHfZrNbVTa)N were fabricated using cathodic-vacuum-arc-vapor-deposition method. Morphology and topology of the surface of the coatings, roughness, elemental and phase composition, microstructure and mechanical properties were investigated. Dependence of deposition parameters on surface morphology and elemental composition was demonstrated. Influence of the heavy negative charged Au{sup −} ions implantation on phase structure, microstructure and hardness of nitride (TiHfZrNbVTa)N coatings was investigated. - Highlights: • (TiHfZrNbVTa)N fabricated using cathodic-vacuum-arc-vapor-deposition method. • Roughness, elemental and phase composition, microstructure and mechanical properties. • Influence of the heavy negative charged Au- ions implantation on mechanical properties.

  15. Copper diffusion in TaN-based thin layers

    Energy Technology Data Exchange (ETDEWEB)

    Nazon, J. [Universite Montpellier II, Institut Charles Gerhardt, UMR 5253 CNRS-UM2-ENSCM-UM1, cc 1504, 34095 Montpellier Cedex 5 (France); Fraisse, B. [Laboratoire Structure, Proprietes et Modelisation des Solides (UMR 8580), Ecole Centrale de Paris, Grande Voie des Vignes, 92295 Chatenay-Malabry Cedex (France); Sarradin, J. [Universite Montpellier II, Institut Charles Gerhardt, UMR 5253 CNRS-UM2-ENSCM-UM1, cc 1504, 34095 Montpellier Cedex 5 (France); Fries, S.G. [SGF Scientific Consultancy, Arndt str.9, D-52064 Aachen (Germany); Tedenac, J.C. [Universite Montpellier II, Institut Charles Gerhardt, UMR 5253 CNRS-UM2-ENSCM-UM1, cc 1504, 34095 Montpellier Cedex 5 (France); Frety, N. [Universite Montpellier II, Institut Charles Gerhardt, UMR 5253 CNRS-UM2-ENSCM-UM1, cc 1504, 34095 Montpellier Cedex 5 (France)], E-mail: Nicole.Frety@univ-montp2.fr

    2008-07-15

    The diffusion of Cu through TaN-based thin layers into a Si substrate has been studied. The barrier efficiency of TaN/Ta/TaN multilayers of 150 nm in thickness has been investigated and is compared with that of TaN single layers. Thermal stabilities of these TaN-based thin layers against Cu diffusion were determined from in situ X-ray diffraction experiments, conducted in the temperature range of 773-973 K. The TaN/Ta/TaN barrier appeared to be more efficient in preventing Cu diffusion than the TaN single layer.

  16. Design and mechanical characterization of a Zr-Nb-O-P alloy

    International Nuclear Information System (INIS)

    Lee, Jong Min; Hong, Sun Ig

    2011-01-01

    Highlights: → In commercial Zr-Nb alloys, Sn was removed for improved corrosion resistance at the expense of strength. → The addition of sulphur was found to enhance the mechanical strength and corrosion resistance. → Phosphorous and sulphur have the similar electronic structure, atomic radius and electronegativity. → The strength was enhanced by increasing Nb (to 1.5%) and oxygen (to 1600 ppm) and adding phosphorous. → Zr-1.5Nb-O-P alloys were found to have excellent mechanical properties. -- Abstract: In this study, Sn-free Zr-1.5Nb-O-P alloys were manufactured and their mechanical properties were characterized. The ultimate tensile strength (UTS) of cold rolled Zr-1.5Nb-O-P alloy with 160 ppm phosphorous (680 MPa) were close to that of a commercially available Zr-1Nb-1Sn-0.1Fe alloy (720 MPa), achieving a good mechanical strength without the addition of Sn, an effective solution strengthening element. The UTS of recrystallized Zr-1.5Nb-O-P alloy with 160 ppm phosphorous (533 MPa) was far greater than that of a commercially available Zr-1Nb-O (323 MPa) because of the strengthening due to higher Nb and oxygen content combined with phosphorous strengthening. The activation volumes for the cold rolled Zr-1.5Nb-P alloys were not much different from those of annealed Zr-1.5Nb-P alloys despite the higher dislocation density in the cold rolled alloys. Insensitivity of the activation volume to the dislocation density and the decrease of the activation volume with the addition of phosphorous support the suggestion linking the activation volume with the activated bulge of dislocations limited by segregation of oxygen and phosphorous atoms.

  17. Corrosion Characteristics of Ti-xTa Alloys with Ta contents

    International Nuclear Information System (INIS)

    Kim, H. J.; Choe, H. C.

    2013-01-01

    The purpose of this study was to investigate corrosion characteristics of Ti-xTa alloys with Ta contents. Ti-xTa alloys used as samples (x=30, 40%) were arc-melted under argon atmosphere of 99.9% purity. Ti-xTa alloys were homogenized for 12hr at 1000 .deg. C and then water quenched. The surface characteristics of Ti-xTa alloys were investigated using optical microscopy (OM) and X-ray diffractometer (XRD). The anodic corrosion behaviors of the specimens were examined through potentiodynamic, potentiostatic and galvanostatic test in 0.9 % NaCl solution at 36.5 ± 1 .deg. C. After corrosion test, the surface characteristics of Ti-xTa alloys were investigated using OM. The microstructure of Ti-Ta alloy showed the beta structure with Ta content. The corrosion resistance of Ti alloy was improved by increasing Ta content and the corrosion morphology of Ti-Ta alloy showed that the site attacked by chloride ion decreased from the active to passive region with Ta content. Potential of Ti-40Ta alloy increased as time increased, whereas, current density of Ti-40Ta alloy decreased as time increased compared to Ti-30 alloy

  18. Distribution of incompatible trace elements between the constituents of spinel peridotite xenoliths: ICP-MS data from the East African rift

    Science.gov (United States)

    Bedini, R. M.; Bodinier, J.-L.

    1999-11-01

    To constrain the geochemical models of the lithospheric mantle, we have carried out a detailed study of the distribution of incompatible trace elements between the various constituents of spinel peridotites. Predominant and accessory minerals were separated in 12 mantle xenoliths from Mega (East African Rift, Sidamo region, SE Ethiopia). The samples range in composition from cpx-rich lherzolites to refractory harzburgites and are devoid of modal metasomatism, except for minor amount of apatite in some of them. Their trace element concentration encompasses almost the whole range reported in the literature for basalt-born xenoliths. Mineral separates (ol, opx, cpx, spinel and apatite) and their leachates were analyzed by ICP-MS, for rare earth elements (REE) and several incompatible trace elements (Rb, Sr, Ba, Zr, Hf, Nb, Ta, Th, U, and Ti). Spinel surfaces were investigated by SEM and EPMA to determine the composition of the attached micro-phases. Mass-balance inversion shows that the trace element composition of whole rocks is controlled by five distinct components: 1). the silicate minerals which account for the total HREE abundance, and 50-90% of LREE, Sr, and Zr-Hf, in the apatite-free peridotites; 2). the mineral-hosted fluid inclusions which play a significant role for Rb (20-25%), and to a lesser degree for the other LILEs; 3). a pervasive grain-boundary component selectively enriched in highly incompatible elements, which contributes 25-90% of the whole-rock budget for Ba, Th and U, and 10-50% for Nb and LREE, in the apatite-free samples; 4). thin reaction layers (<10 μm thick) coating the surfaces of spinel grains and mainly composed of Ti-oxides and phlogopite. They are the predominant repository of Nb-Ta (45-60%) and Rb-Ba (30-80%) in all the studied xenoliths; 5). apatite which largely predominates the budget of Th, U, Sr and LREE (25-75%) in the samples containing this mineral. Compared to the other peridotite constituents, fluid-derived inclusions in

  19. Sulfide Melts and Chalcophile Element Behavior in High Temperature Systems

    Science.gov (United States)

    Wood, B. J.; Kiseeva, K.

    2016-12-01

    We recently found that partition coefficients (Di) of many weakly and moderately chalcophile elements (e.g., Cd, Zn, Co, Cr, Pb, Sb, In) between sulfide and silicate melts are simple functions of the FeO content of the silicate liquid: logDi A-Blog[FeO] where [FeO] is the FeO concentration in the silicate, A and B are constants and the latter is related to the valency of the element of interest. In contrast, some strongly chalcophile (e.g Cu, Ni, Ag) and lithophile elements (e.g Mn) show marked deviations from linearity on a plot of logDi vs log[FeO]. More recent experiments show that linear behavior is confined to elements whose affinities for S and O are similar to those of Fe. In the case of elements more strongly lithophile than Fe (Ti, U, REE, Zr, Nb, Ta, Mn) a plot of logDi versus log[FeO] describes a U-shape with the element partitioning strongly into the sulfide at very low FeO and again at very high FeO content of the silicate melt. In contrast, strongly chalcophile elements (Cu, Ni, Ag) describe an n-shape on the plot of logD vs log[FeO]. The result is that lithophile elements such as Nb become more "chalcophile" than Cu at very low and very high FeO contents of the silicate melt. The reasons for this surprising behavior are firstly that, at very low FeO contents the silicate melt dissolves substantial amounts of sulfur, which drives down the activity of FeO and, from mass-action "pulls" the lihophile element into the sulfide. At high FeO contents of the silicate the sulfide itself starts to dissolve substantial amounts of oxygen and lithophile elements follow the oxygen into the sulfide. Given the principles which we have established, we are able to describe the patterns of chalcophile element behavior during partial melting and fractional crystallisation on Earth and also on bodies such as Mercury and Mars which are, respectively, strongly reduced relative to Earth and more oxidised than Earth.

  20. Mechanism of decomposition of transition element organometallic compounds and role of intermediate particles in catalySis

    International Nuclear Information System (INIS)

    Dolgoplosk, B.A.

    1983-01-01

    Ways of decomposition of transition element organometallic compounds (Mo, W, Ta, Re, Pt, Pd, Rh, Cr, Nd, Y, Nb) during formation are considered. α-decomposition followed by formas tion of carbene and carbyne particles is characteristic for methyl, benzyl, trimethylsilylmethyl and neophilous derivatives. The decomposition proceed without layers of radial stages. Mechanism of chain process of metathesis of olefins and cycloolefins under effect of carbene complexes of transition metals is considered. On the base of representatives on primary formation of organometallic compounds at oxidizing joining of hydrocarbons to zero valent metals, the sUpposition is made on chemical natUre of elemental acts in the reactions of hydrogenolysis, isomerization of carbon frame, dehydrogenation and hydrogenation of the hydrocarbons

  1. NB market update

    International Nuclear Information System (INIS)

    Marshall, W. K.

    2004-01-01

    the NB market to the maritime area market. tabs., figs

  2. Perovskite, reaction product of a harzburgite with Jurassic– Cretaceous accretionary wedge fluids (Western Carpathians, Slovakia: evidence from the whole-rock and mineral trace element data

    Directory of Open Access Journals (Sweden)

    Putiš Marián

    2016-04-01

    Full Text Available Perovskite (Prv was discovered in an abyssal harzburgite from a “mélange” type blueschist-bearing accretionary wedge of the Western Carpathians (Meliata Unit, Slovakia. Perovskite-1 formation in serpentinized orthopyroxene may be simplified by the mass-balance reaction: Ca2Si2O6 (Ca-pyroxene-member+2Fe2TiO4 (ulvöspinel molecule in spinel+2H2O+O2=2CaTiO3 (Prv+2SiO2+4FeOOH (goethite. Perovskite-2 occurs in a chlorite-rich blackwall zone separating serpentinite and rodingite veins, and in rodingite veins alone. The bulk-rock trace-element patterns suggest negligible differences from visually and microscopically less (“core” to strongly serpentinized harzburgite due to serpentinization and rodingitization: an enrichment in LREE(La,Ce, Cs, ±Ba, U, Nb, Pb, As, Sb, ±Nd and Li in comparison with HREE, Rb and Sr. The U/Pb perovskite ages at ~135 Ma are interpreted to record the interaction of metamorphic fluids with harzburgite blocks in the Neotethyan Meliatic accretionary wedge. Our LA-ICP-MS mineral study provides a complex view on trace element behaviour during the two stages of rodingitization connected with Prv genesis. The positive anomalies of Cs, U, Ta, Pb, As, Sb, Pr and Nd in Cpx, Opx and Ol are combined with the negative anomalies of Rb, Ba, Th, Nb and Sr in these minerals. The similar positive anomalies of Cs, U, Ta, ±Be, As, Sb found in typical serpentinization and rodingitization minerals, with variable contents of La, Ce and Nd, and negative anomalies of Rb, Ba, Th, Nb and Sr suggest involvement of crustal fluids during MP-LP/LT accretionary wedge metamorphism. LA-ICP-MS study revealed strong depletion in LREE from Prv-1 to Prv-2, and a typically negative Eu (and Ti anomaly for Prv-1, while a positive Eu (and Ti anomaly for Prv-2. Our multi-element diagram depicts enrichment in U, Nb, La, Ce, As, Sb, Pr, Nd and decreased Rb, Ba, Th, Ta, Pb, Sr, Zr in both Prv generations. In general, both Prv generations are very close to the

  3. Novel Method for Making Biomedical Segregation-Free Ti-30Ta Alloy Spherical Powder for Additive Manufacturing

    Science.gov (United States)

    Xia, Yang; Fang, Zhigang Zak; Sun, Pei; Zhang, Ying; Zhu, Jun

    2018-01-01

    Ti-Ta alloys offer a good combination of high strength and low modulus among Ti-based alloys, and are ideal for biomedical applications. However, making Ti-Ta alloys has always been challenging because they tend to suffer from compositional segregation during melting due to the large difference between the melting points of Ti and Ta. This article describes a novel process for making spherical Ti-30Ta alloy powder through a unique powder metallurgy technique, namely the granulation-sintering-deoxygenation process. The results indicate that the compositional segregation problem can be overcome using this process technology. Combined with use of a deoxygenation process, the critical interstitial element, oxygen, can be controlled to < 400 ppm for powder with particle size < 75 µm. The destabilization effect of Ta on Ti-O solid solutions, and the resulting improved deoxygenation process for Ti-Ta, are discussed, as well as the phase composition and microstructure of the powders.

  4. Novel Method for Making Biomedical Segregation-Free Ti-30Ta Alloy Spherical Powder for Additive Manufacturing

    Science.gov (United States)

    Xia, Yang; Fang, Zhigang Zak; Sun, Pei; Zhang, Ying; Zhu, Jun

    2018-03-01

    Ti-Ta alloys offer a good combination of high strength and low modulus among Ti-based alloys, and are ideal for biomedical applications. However, making Ti-Ta alloys has always been challenging because they tend to suffer from compositional segregation during melting due to the large difference between the melting points of Ti and Ta. This article describes a novel process for making spherical Ti-30Ta alloy powder through a unique powder metallurgy technique, namely the granulation-sintering-deoxygenation process. The results indicate that the compositional segregation problem can be overcome using this process technology. Combined with use of a deoxygenation process, the critical interstitial element, oxygen, can be controlled to < 400 ppm for powder with particle size < 75 µm. The destabilization effect of Ta on Ti-O solid solutions, and the resulting improved deoxygenation process for Ti-Ta, are discussed, as well as the phase composition and microstructure of the powders.

  5. A Ta-rich low-P peraluminous granite: the Rechla cupola (Hoggar, Algeria) and associated pegmatites, the result of extreme fractionation of a A2-type magma.

    Science.gov (United States)

    Kesraoui, M.; Marignac, C.; Hamis, A.; Cuney, M.

    2012-04-01

    pronounced <0 Eu anomaly. Geochemical modelling shows that the main Rechla magma is likely the fractionated product of this already differentiated magma, mainly involving quartz and Kfs. The pegmatite rim is interpreted as the result of the sequential crystallization of a Rechla-type melt, with late individualisation of a Fe-rich magmatic-hydrothermal phase responsible for the quartz-zinnwaldite assemblage, leaving a strongly Be-enriched residual liquid (the fine-grained granite). As demonstrated by the Rechla occurrence, Ta concentration at levels similar to those in Beauvoir-type high-P peraluminous granites may be reached in the low-P low-Ta A2 suites, provided that extreme fractionation processes are established. Azzouni-Sekkal, A., Boissonnas, J. (1993). Une province magmatique de transition du calco-alcalin à l'alcalin : les granitoïdes pan-africains à structure annulaire de la chaîne pharusienne du Hoggar (Algérie). Bulletin Société Géologique France 164, 597-608. Linnen, R.L., Cuney, M. (2005). Granite-related rare-element deposits and experimental constraints on Ta-Nb-W-Sn-Zr-Hf mineralization. In: RL Linnen, IM Samson (eds), Rare-element geochemistry and mineral deposits, Geological Association of Canada (GAC) Short Course Notes 17, pp. 45-67.

  6. Neutron diffraction study on the mechanism of the topotactic reduction of 2HTaS 2 electrodes

    Science.gov (United States)

    Riekel, C.; Reznik, H. G.; Schöllhorn, R.

    1980-09-01

    The dynamic investigation by neutron diffraction of the topotactic reduction of 2HTaS 2 electrodes in {K+}/{D2O} electrolyte to the ionic layered hydrate K +0.5(D 2O) 0.5[TaS 2] 0.5- is shown to proceed via third-stage K +x(D 2O) y[TaS 2] 3x- , second-stage K +x(D 2O) y [TaS 2] 2x- , and first-stage K +x(D 2O) y[TaS 2] x- intermediates. A comparative study by X-ray diffraction on the cathodic intercalation of 2HTaS 2 and 2HNbS 2 electrodes with hydrated main group and transition metal ions reveals analogous behavior; the formation of higher-stage intermediates is supposedly correlated with stable electronic layer states. Influence of kinetic factors is observed for larger guest cations such as transition metal complexes and organic ions. CdI 2-type host lattices with an octahedral environment of intralayer cations shown different reaction pathways, although the occurrence of intermediate states (at least in the nucleation phase) can be demonstrated. It is concluded that the presence of ordered intermediate states is a general phenomenon in topotactic electrode processes of layered dichalcogenides.

  7. Alteration of Eudialyte and implications for the REE, ZR, and NB resources of the layered Kakortokites in the ILÍMAUSSAQ intrusion, South West Greenland

    DEFF Research Database (Denmark)

    Borst, Anouk Margaretha; Waight, Tod Earle; Smit, Matthijs Arjen

    2014-01-01

    The layered kakortokites in the southern part of the Ilímaussaq Intrusion are of great economic interest due to their high concentrations of REE, Zr, Nb and Ta. The prospective metals are largely contained in eudialyte, a complex sodium‐zirconosilicate and one of the major cumulus phases. Eudialyte...

  8. Alteration of Eudialyte and implications for the REE, ZR, and NB resources of the layered Kakortokites in the ILÍMAUSSAQ intrusion, South West Greenland

    DEFF Research Database (Denmark)

    Borst, Anouk Margaretha; Waight, Tod Earle; Smit, Matthijs Arjen

    2014-01-01

    The layered kakortokites in the southern part of the Ilímaussaq Intrusion are of great economic interest due to their high concentrations of REE, Zr, Nb and Ta. The prospective metals are largely contained in eudialyte, a complex sodium‐zirconosilicate and one of the major cumulus phases. Eudialy...

  9. Magneto-optic measurements of the Weyl semimetal NbAs

    Science.gov (United States)

    Armstrong, Nathan; Shao, Yinming; Yuan, Zhujun; Jia, Shuang; Basov, D. N.; Timusk, Thomas

    NbAs is among the newly discovered Weyl semimetals that are of great interest because they have the potential to confirm the chiral anomaly predicted by particle physics. It has been theorized that two separated Weyl nodes of opposite chirality can have a chiral current flow between them with the application electric and magnetic fields parallel to the displacement of the nodes. Indeed, magnetoresistance measurements on TaAs and NbAs found a negative magnetoresistance with these fields. ARPES and band structure calculations show that NbAs has two different groups of Weyl nodes with all the node splittings in kx -ky planes. In addition to the Weyl nodes there are other trivial bands that create Fermi pockets elsewhere in the BZ that are also observed in reflectance measurements. We will present magneto-optics results from far infrared optical data of NbAs in Voigt geometry up to 8 Tesla. In the far infrared at large fields there are two strong features that show an 11% and 3% change of reflectance in field at 60 and 480 cm-1 , respectively. We evaluate these data with comparison to the above mentioned band structure of NbAs.

  10. Low Cycle Fatigue Behavior Zr-Sn-Nb Slice Alloy at Elevated Temperature

    International Nuclear Information System (INIS)

    Huang Xuewei; Cai Lixun; Bao Chen; Tan Jun

    2010-01-01

    A series of low cycle fatigue tests were carried out on small funnel-like slice-specimens of Zr-Sn-Nb alloy at room temperature and 500 degree C. Based on the local uniaxial strain of small funnel-like specimens, the fatigue damage equivalent hypothesis was given. Through finite element analysis, the strain conversion model for funnel-like specimens from uniaxial testing strain to local uniaxial strain was established,besides, the validity of finite element analysis was checked by the test results; with the results of test, Manson-Conffin model for Zr-Sn-Nb alloy strain fatigue life estimation was presented. The results show that, Zr-Sn-Nb alloy exhibits cyclic stability; elevated temperature shorten the fatigue life of Zr-Sn-Nb alloy seriously and temperature effect impairs gradually with the increase of strain amplitude. (authors)

  11. Examining metallic glass formation in LaCe:Nb by ion implantation

    Directory of Open Access Journals (Sweden)

    Sisson Richard

    2017-01-01

    Full Text Available In order to combine niobium (Nb with lanthanum (La and cerium (Ce, Nb ions were deposited within a thin film of these two elements. According to the Hume-Rothery rules, these elements cannot be combined into a traditional crystalline metallic solid. The creation of an amorphous metallic glass consisting of Nb, La, and Ce is then investigated. Amorphous metallic glasses are traditionally made using fast cooling of a solution of molten metals. In this paper, we show the results of an experiment carried out to form a metallic glass by implanting 9 MeV Nb 3+ atoms into a thin film of La and Ce. Prior to implantation, the ion volume distribution is calculated by Monte Carlo simulation using the SRIM tool suite. Using multiple methods of electron microscopy and material characterization, small quantities of amorphous metallic glass are indeed identified.

  12. Orbital selectivity causing anisotropy and particle-hole asymmetry in the charge density wave gap of 2H-TaS2

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, J.; Wijayaratne, K.; Butler, A.; Yang, J.; Malliakas, C. D.; Chung, D. Y.; Louca, D.; Kanatzidis, M. G.; van Wezel, J.; Chatterjee, U.

    2017-09-05

    We report an in-depth angle-resolved photoemission spectroscopy study on 2H-TaS2, a canonical incommensurate charge density wave (CDW) system. This study demonstrates that just as in related incommensurate CDW systems, 2H-TaSe2 and 2H-NbSe2, the energy gap (triangle(CDW)) of 2H-TaS2 is localized along the K-centered Fermi surface barrels and is particle-hole asymmetric. The persistence of triangle(CDW) even at temperatures higher than the CDW transition temperature T-CDW in 2H-TaS2, reflects the similar pseudogap behavior observed previously in 2H-TaSe2 and 2H-NbSe2. However, in sharp contrast to 2H-NbSe2, where triangle(CDW) is nonzero only in the vicinity of a few "hot spots" on the innerK-centered Fermi surface barrels, triangle(CDW) in 2H-TaS2 is nonzero along the entirety of both K-centered Fermi surface barrels. Based on a tight-binding model, we attribute this dichotomy in the momentum dependence and the Fermi surface specificity of triangle(CDW) between otherwise similar CDW compounds to the different orbital orientations of their electronic states that participate in the CDW pairing. Our results suggest that the orbital selectivity plays a critical role in the description of incommensurate CDW materials.

  13. Growth mechanism, distribution characteristics and reinforcing behavior of (Ti, Nb)C particle in laser cladded Fe-based composite coating

    International Nuclear Information System (INIS)

    Li, Qingtang; Lei, Yongping; Fu, Hanguang

    2014-01-01

    Highlights: • Reinforced (Ti, Nb)Cp can be synthesized in the molten pool during laser cladding. • Formation mechanism of (Ti, Nb)Cp are impacted by Ti/Nb atomic ratio. • Appropriate Ti element can improve the precipitation of carbide particle. • Excess Ti weakens this effect above-mentioned. • The wear resistance of the coating was improved when Ti/Nb = 1. - Abstract: Over the past decade, researchers have demonstrated much interest in laser cladded metal matrix composite coatings for its good wear resistance, corrosion resistance, and high temperature properties. In this paper, in-situ (Ti, Nb)C particle reinforced Fe-based composite coatings were produced by laser cladding. The effects of Ti/Nb(atomic ratio) in the cladding powder on the formation mechanism and distribution characteristics of multiple particle were investigated. The results showed that when Ti/Nb > 1, Ti had a stronger ability to bond with C compared with Nb. (Ti, Nb)C multiple particles with TiC core formed in the molten pool. With the decrease of Ti/Nb, core-shell structure disappeared, the structure of particle got close to that of NbC gradually. It is found that the amount, area ratio and distribution of the reinforced particle in the coating containing Ti and Nb elements were improved, compared with these in the coating containing equal Nb element. When Ti/Nb = 1, the effects above-mentioned is most prominent, and the wear resistance of the coating is promoted obviously

  14. TA-55 and Sigma Overview

    Energy Technology Data Exchange (ETDEWEB)

    Spearing, Dane Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Safeguards Science and Technology Group (NEN-1)

    2016-11-29

    These are slides from a facility overview presentation for visiting agencies to Los Alamos National Laboratory (LANL). The TA-55 Plutonium Facility (PF-4) is discussed in detail. PF-4 is a unique resource for US plutonium programs. The basic design is flexible and has adapted to changing national needs. It is a robust facility with strong safety and security implementation. It supports a variety of national programs. It will continue for many years into the future. Sigma is then discussed in detail, which handles everything from hydrogen to uranium. It has been in long term service to the Nation (nearly 60 years). It has a flexible authorization basis to handle almost the entire periodic table. It has a wide breadth of prototyping and characterization capabilities. It has integrated program and line management.

  15. Project Ta-Kos Outreach. Final Report.

    Science.gov (United States)

    Askew, Linda; Husted, Tony; Faris, Cindy

    This final report describes activities and accomplishments of Project Ta-Kos Outreach, a 3-year program to provide consultation and site-specific training for families, educators, and health care providers. Project Ta-kos, through its curriculum and training approach, was designed to increase the probability that children, ages birth through eight…

  16. Subsolidus phase relations of the SrO-Ta2O5-CuO system at 900 °C in air

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude

    2009-01-01

    The subsolidus phase relations of the SrO–Ta2O5–CuO system were investigated in air. The samples were equilibrated at 900 °C. The ternary oxide Sr3Ta2CuO9 compound is stable under these conditions. This phase presents a solid solution range, its actual composition being Sr3Ta2−xCu1+xO9+δ with 0.......0 ≤ x ≤ 0.2. Up to about 5 at.% Cu can be incorporated in the Sr3−xTa1+xO5.5+δ phase. Similarities with the SrO–Nb2O5–CuO system are discussed....

  17. NMR-ON of 182Ta and 183Ta in Fe

    International Nuclear Information System (INIS)

    Allsop, A.L.; Chaplin, D.H.; Murray, D.W.; Stone, N.J.

    1980-01-01

    Nuclear magnetic resonance has been observed on radioactive 182 Ta and 183 Ta oriented at low temperature in an Fe host, by detection of the change in spatial anisotropy of γ-rays emitted during nuclear decay. By measuring the resonant frequencies of 183 Ta in four different applied magnetic fields the nuclear magnetic moment and hyperfine field have been deduced. These are: vertical stroke μ( 183 Ta;I = 7/2) = 2.28(3)μsub(N) and Bsub(h)sub(f)(TaFe at 0 K) = -67.2(1.3)T. The sin of the ground state of 182 Ta has been determined as I = 3 by comparing resonance results with those obtained in a thermal equilibrium nuclear orientation study. The ratio of the resonant frequencies observed for 182 Ta and 183 Ta at one applied field value yields a magnetic moment for the former of vertical stroke μ( 182 Ta;I = 3) vertical stroke = 2.91(3)μsub(N). The spin lattice relaxation time for 183 TaFe (0.12 at% Ta) at 18 mK in an applied field of 0.5 T has been found to be 40(10)s. (orig.)

  18. Stoichiometry behavior of TaN, TaCN and TaC thin films produced by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Vargas, M. [Centro de Nanociencia y Nanotecnología, Universidad Nacional Autónoma de México, A.P. 2681, C.P. 22860, Ensenada, B.C. (Mexico); Castillo, H.A. [Centro de Enseñanza Técnica y Superior, CETYS Universidad, Campus Tijuana, Tijuana, B.C. (Mexico); Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [Universidad Nacional de Colombia Sede Medellín Colombia, Facultad de Minas, Manizales (Colombia); De La Cruz, W. [Centro de Nanociencia y Nanotecnología, Universidad Nacional Autónoma de México, A.P. 2681, C.P. 22860, Ensenada, B.C. (Mexico)

    2013-08-15

    Thin films were synthesized in a magnetron sputtering system using a target of Ta with 99.99% purity and silicon substrates (1 1 1). The gases used for the film growth were (Ar + N{sub 2}), (Ar + CH{sub 4} + N{sub 2}) and (Ar + CH{sub 4}) mixtures for TaN, TaCN and TaC, respectively. The substrate temperature increased from room temperature to 500 °C. The chemical composition and bonding configuration were examined using X-ray photoelectron spectroscopy (XPS), revealing Ta-N, Ta-C-N, Ta-C and C-C bonds. Moreover, the crystallographic structure was analyzed using X-ray diffraction (XRD), indicating the presence of (1 1 1) and (2 0 0) planes belonging to a face-centered cubic structure. The stoichiometry variation dependence on the CH{sub 4} and N{sub 2} flow was analyzed, and the influence of the substrate temperature on the coatings was investigated. Finally, scanning electron microscopy (SEM) was used to determine the evolution on the grain formation in the coatings as the substrate temperature increased.

  19. Paramagnetic Meissner effect in Nb

    International Nuclear Information System (INIS)

    Kostic, P.; Veal, B.; Paulikas, A.P.; Welp, U.; Todt, V.R.; Gu, C.; Geiser, U.; Williams, J.M.; Carlson, K.D.; Klemm, R.A.

    1996-01-01

    The paramagnetic Meissner effect (PME), or Wohlleben effect, in which the field-cooled magnetization of superconducting samples is paramagnetic below T c , has been reported to occur in some samples of a variety of high-T c cuprate superconductors. It has been proposed that the effect arose in granular hole-doped cuprates from current loops with π phase shifts of the superconducting order parameter at some grain-boundary junctions. It is argued that such behavior would be expected to occur in a d-wave superconductor, but not in a conventional s-wave superconductor. To test this hypothesis, we have searched for the occurrence of the effect in Nb, and have confirmed a recent report by Minhaj et al. of its occurrence in some Nb samples. For these studies, the effects of stray fields and field gradients in the measurement volume of the superconducting quantum interference device magnetometer have been carefully considered to rule out the possibility that measurement artifacts might be responsible for the apparent paramagnetic behavior in Nb. The M(T) and M(H) curves obtained in Nb samples that show the PME also show remarkably strong resemblance to those curves reported for the cuprate materials exhibiting the PME. Evidence is presented that the effect arises from inhomogeneously trapped flux, and is strongly influenced by sample geometry and surface effects. These results suggest that, for the effect to be observable, T c on the sample surface must be different from the bulk T c . The occurrence of the PME in Nb strongly suggests that the observation of this effect is unrelated to d-wave superconductivity. copyright 1996 The American Physical Society

  20. Nonequilibrium synthesis of NbAl3 and Nb-Al-V alloys by laser cladding. I - Microstructure evolution

    Science.gov (United States)

    Sircar, S.; Chattopadhyay, K.; Mazumder, J.

    1992-01-01

    The evolution of the microstructure in NbAl3 synthesized by a laser cladding technique (a rapid solidification process, with cooling rates up to 10 exp 6 C/sec) is investigated, and the phases are identified using convergent beam electron diffraction. Two new metastable phases were identified and characterized in detail. The effect of adding V on the final microstructure was also investigated, and the various phase chemistries and the partitioning of different elements into different phases were studied.

  1. Ion-Exchange Reaction Of A-Site In A2Ta2O6 Pyrochlore Crystal Structure

    Directory of Open Access Journals (Sweden)

    Matsunami M.

    2015-06-01

    Full Text Available Na+ or K+ ion rechargeable battery is started to garner attention recently in Place of Li+ ion cell. It is important that A+ site ion can move in and out the positive-electrode materials. When K2Ta2O6 powder had a pyrochlore structure was only dipped into NaOH aqueous solution at room temperature, Na2Ta2O6 was obtained. K2Ta2O6 was fabricated from a tantalum sheet by a hydrothermal synthesize with KOH aqueous solution. When Na2Ta2O6 was dipped into KOH aqueous solution, K2Ta2O6 was obtained again. If KTaO3 had a perovskite structure was dipped, Ion-exchange was not observed by XRD. Because a lattice constant of pyrochlore structure of K-Ta-O system is bigger than perovskite, K+ or Na+ ion could shinny through and exchange between Ta5+ and O2− ion site in a pyrochlore structure. K+ or Na+ ion exchange of A2Ta2O6 pyrochlore had reversibility. Therefore, A2Ta2O6 had a pyrochlore structure can be expected such as Na+ ion rechargeable battery element.

  2. The diffusion of H and D in Nb and Ta at low temperatures

    International Nuclear Information System (INIS)

    Engelhard, J.

    1978-01-01

    The mobility of hydrogen and deuterium in niobium and tantalum has been studied by quenching to 4.2 K and annealing between 10 K and 100 K. The concentration of quenched hydrogen has been computed from the resistivity increase after quenching. The decrease of the residual resistivity during annealing is interpreted by the trapping of hydrogen and by the formation of precipitations. By the variation of the hydrogen concentration and the impurity content, the annealing stage corresponding to the intrinsic diffusion of the hydrogen has been identified. Diffusion coefficients and activation energies for H and D diffusion in niobium and tantalum were determined. (orig./GSCH)

  3. Acoustic wave propagation in Ni3 R (R = Mo, Nb, Ta) compounds

    Indian Academy of Sciences (India)

    tile and stable, and contains few defects in the crystal structure in comparison to other compounds. 4. Conclusions. Based on the above discussion it is worthwhile to state that. • Present method to evaluate second-order elastic constants involving many- body interaction potential for hexagonal wurtzite crystal structured ...

  4. A coprecipitation technique to prepare NaNbO3 and NaTaO3

    Indian Academy of Sciences (India)

    Unknown

    both sodium hydroxide and niobium (or tantalum) fluoride. Then, aqueous solution of ammonium carbonate and am- monium hydroxide was added with constant stirring to the above solution mixture to reach pH ~ 9 to ensure com- plete precipitation of sodium carbonate and niobium (or tantalum) hydroxide. The precipitate ...

  5. Acoustic wave propagation in Ni3 R (R= Mo, Nb, Ta) compounds

    Indian Academy of Sciences (India)

    The velocities 1 and 2 have minima and maxima respectively at 45° with the unique axis of the crystal, while 3 increases with respect to angle with the unique axis of the crystal. The inconsistent behaviour of angle-dependent velocities is associated with the action of second-order elastic constants. Debye average ...

  6. A coprecipitation technique to prepare NaNbO3 and NaTaO3

    Indian Academy of Sciences (India)

    Unknown

    (V) oxide, tantalum(V) oxide, sodium hydroxide, ethyl alcohol, am- monium carbonate and standard ammonia solution were used and all the starting materials were of AR grade. (Loba chemie). A stoichiometric amount of NaOH was dissolved ...

  7. Development of NbN Josephson junctions with TaxN semi-metal barrier; application to RSFQ circuits

    International Nuclear Information System (INIS)

    Setzu, R.

    2007-11-01

    This thesis research, brought to the development and optimization of SNS (Superconductor / Normal Metal / Superconductor) Josephson junctions with NbN electrodes and a high resistivity Ta x N barrier. We were able to point out Josephson oscillations for frequencies above 1 THz and operation temperatures up to 10 K, which constituted the original goal of the project. This property makes these junctions unique and well adapted for realizing ultra-fast RSFQ (Rapid Single Flux Quantum) logic circuits suitable for spatial telecommunications. We showed a good reproducibility of Ta x N film properties as a function of the sputtering parameters. The NbN/Ta x N/NbN tri-layers exhibit high critical temperature (16 K). The junctions showed a clear dependence of the R n I c product as a function of the partial nitrogen pressure inside the reactive plasma; the R n I c is the product between the junction critical current and its normal resistance, and indicates the upper limit Josephson frequency. We have also obtained some really high R n I c products, up to 3.74 mV at 4.2 K for critical current densities of about 15 kA/cm 2 . Junctions show the expected Josephson behaviors, respectively Fraunhofer diffraction and Shapiro steps. up to 14 K. This allows expecting good circuit operations in a relaxed cryogenics environment (with respect to the niobium circuits limited at 4.2 K). The junctions appear to be self-shunted. The SNOP junctions J c -temperature dependence has been fitted by using the long SNS junction model in the dirty limit, which gives a normal metal coherence length of about 3.8 nm at 4.2 K. We have finally studied a multilayer fabrication process, including a common ground plane and bias resistors, suitable for RSFQ logic basic circuits. To conclude we have been able to show the performance superiority of NbN/Ta x N/NbN junctions over the actual niobium junctions, as well as their interest for realizing compact RSFQ logic circuits. In fact these junctions do not

  8. Safety assessment for TA-48 radiochemical operations

    International Nuclear Information System (INIS)

    1994-08-01

    The purpose of this report is to document an assessment performed to evaluate the safety of the radiochemical operations conducted at the Los Alamos National Laboratory operations area designated as TA-48. This Safety Assessment for the TA-48 radiochemical operations was prepared to fulfill the requirements of US Department of Energy (DOE) Order 5481.1B, ''Safety Analysis and Review System.'' The area designated as TA-48 is operated by the Chemical Science and Technology (CST) Division and is involved with radiochemical operations associated with nuclear weapons testing, evaluation of samples collected from a variety of environmental sources, and nuclear medicine activities. This report documents a systematic evaluation of the hazards associated with the radiochemical operations that are conducted at TA-48. The accident analyses are limited to evaluation of the expected consequences associated with a few bounding accident scenarios that are selected as part of the hazard analysis. Section 2 of this report presents an executive summary and conclusions, Section 3 presents pertinent information concerning the TA-48 site and surrounding area, Section 4 presents a description of the TA-48 radiochemical operations, and Section 5 presents a description of the individual facilities. Section 6 of the report presents an evaluation of the hazards that are associated with the TA-48 operations and Section 7 presents a detailed analysis of selected accident scenarios

  9. Field investigations of soils at TA-19, TA-26, TA-73 and TA-0, SWMU aggregate 0-D and 016

    International Nuclear Information System (INIS)

    McFadden, L.D.

    1995-01-01

    Field based investigations of the general soil-geomorphic characteristics were carried out at TA-19, -26, -73, -0, Aggregate 0-D and -016 in order to provide information for utilization in ongoing and anticipated LANL ERP (Environmental Restoration Project) activities at these sites. These investigations show that soils exhibiting diverse morphologic character, varying ages, and relations to landforms characterize these sites. A review of recent and ongoing soils studies also shows that soil textural, chemical, and mineralogical characteristics may profoundly influence the migration and/or retardation of a variety of potential contaminants initially placed in direct contact with soils, or that encounter soils during subsurface percolation or discharge. Soil-geomorphic relations also provide important insights into recent site erosion, deposition or other surficial processes that must, be considered as part of environmental assessment of a given site and remediation; and, the planned geomorphic mapping activities at each site, as well as other associated activities (e.g, geophysical survey, site sampling) are accordingly appropriate and necessary with respect to identification of significant soil relations at each site. Specific and general recommendations in consideration of important findings regarding the possible impacts of soil development of the nature of contaminant behavior at various sites are provided to help guide sampling and analysis activities during ERP investigations outlined in the RFI Work Plan for Operational Unit-1071

  10. Comparative study of the magnetic properties of La3Ni2B‧O9 for B‧ = Nb, Taor Sb

    Science.gov (United States)

    Chin, Chun-Mann; Battle, Peter D.; Blundell, Stephen J.; Hunter, Emily; Lang, Franz; Hendrickx, Mylène; Paria Sena, Robert; Hadermann, Joke

    2018-02-01

    Polycrystalline samples of La3Ni2NbO9 and La3Ni2TaO9 have been characterised by X-ray and neutron diffraction, electron microscopy, magnetometry and muon spin relaxation (μSR); the latter technique was also applied to La3Ni2SbO9. On the length scale of a neutron diffraction experiment, the six-coordinate sites of the monoclinic perovskite structure are occupied in a 1:1 ordered manner by Ni and a random ⅓Ni/⅔B‧ mixture. Electron microscopy demonstrated that this 1:1 ordering is maintained over microscopic distances, although diffuse scattering indicative of short-range ordering on the mixed site was observed. No magnetic Bragg scattering was observed in neutron diffraction patterns collected from La3Ni2B‧O9 (B‧ = Nb or Ta) at 5 K although in each case μSR identified the presence of static spins below 30 K. Magnetometry showed that La3Ni2NbO9 behaves as a spin glass below 29 K but significant short-range interactions are present in La3Ni2TaO9 below 85 K. The contrasting properties of these compounds are discussed in terms of their microstructure.

  11. Effects of cold-working on pinning behaviour and critical current densities in NbTi-based superconductors

    International Nuclear Information System (INIS)

    Yamada, Y.; Murase, S.; Wada, H.; Tachikawa, K.

    1985-01-01

    The effects of cold-working on high-field pinning behaviour at 1.8 K and 4.2 K have been studied for multifilamentary NbTi, NbTiHf and NbTiTa superconductors, which were subjected to cold-working, heat treatment and cold-working, in sequence. It is found that the cold-working, either before or after heat treatment, shifts the peak in pinning force density to a higher field, while the maximum pinning force value is first increased with increasing amount of cold-working, and then decreased. This result can not be predicted by existing pinning theories, and we conclude that for pinning behaviour induced by cold-working, not only the introduction of pinning centres but also their size and spacing must be taken into account. (author)

  12. Spectroscopic investigations of nanostructured LiNbO3 doped with Eu3+

    International Nuclear Information System (INIS)

    Hreniak, D.; Speghini, A.; Bettinelli, M.; Strek, W.

    2006-01-01

    Structural and optical properties of the sol-gel derived nanocrystalline lithium niobate (LiNbO 3 ) powders doped with Eu 3+ ions have been studied. In particular, the influence of the sizes of nanoparticles controlled by temperature on the structural and luminescence properties has been investigated. Emission bands corresponding to 5 D emission became more resolved with increasing nanocrystal size and changed to a typical Eu 3+ :LiNbO 3 single crystal spectrum for nanocrystals having an average size of more than 40 nm. Nonlinear optical properties of nanostructured LiNbO 3 have been confirmed by simple observation of second harmonic generation effect (SHG). The possibility of using nanostructured LiNbO 3 doped with rare-earth ions as self-doubling elements in integrated optoelectronic devices has been discussed

  13. Magnetic Parameters Of A NB3SN Superconducting Magnet For A 56 HGz ECR Ion Source

    International Nuclear Information System (INIS)

    Ferracin, P.; Caspi, S.; Felice, H.; Leitner, D.; Lyneis, C.M.; Prestemon, S.; Sabbi, G.L.; Todd, D.S.

    2009-01-01

    Third generation Electron Cyclotron Resonance (ECR) ion sources operate at microwave frequencies between 20 and 30 GHz and employ NbTi superconducting magnets with a conductor peak field of 6-7 T. A significant gain in performance can be achieved by replacing NbTi with Nb 3 Sn, allowing solenoids and sextupole coils to reach a field of 15 T in the windings. In this paper we describe the design of a Nb 3 Sn superconducting magnet for a fourth generation ECR source operating at a microwave frequency of 56 GHz. The magnet design features a configuration with an internal sextupole magnet surrounded by three solenoids. A finite element magnetic model has been used to investigate conductor peak fields and the operational margins. Results of the numerical analysis are presented and discussed.

  14. Anodic oxidation of Ta/Fe alloys

    International Nuclear Information System (INIS)

    Mato, S.; Alcala, G.; Thompson, G.E.; Skeldon, P.; Shimizu, K.; Habazaki, H.; Quance, T.; Graham, M.J.; Masheder, D.

    2003-01-01

    The behaviour of iron during anodizing of sputter-deposited Ta/Fe alloys in ammonium pentaborate electrolyte has been examined by transmission electron microscopy, Rutherford backscattering spectroscopy, glow discharge optical emission spectroscopy and X-ray photoelectron spectroscopy. Anodic films on Ta/1.5 at.% Fe, Ta/3 at.% Fe and Ta/7 at.% Fe alloys are amorphous and featureless and develop at high current efficiency with respective formation ratios of 1.67, 1.60 and 1.55 nm V -1 . Anodic oxidation of the alloys proceeds without significant enrichment of iron in the alloy in the vicinity of the alloy/film interface and without oxygen generation during film growth, unlike the behaviour of Al/Fe alloys containing similar concentrations of iron. The higher migration rate of iron species relative to that of tantalum ions leads to the formation of an outer iron-rich layer at the film surface

  15. Rational design of Nb-based alloys for hydrogen separation: A first principles study

    Directory of Open Access Journals (Sweden)

    Byungki Ryu

    2013-02-01

    Full Text Available We have investigated the effect of alloying metal elements on hydrogen solubility and mechanical integrity of Nb-based alloys, Nb15M1 (where M = Ca–Zn, Ge, using first principles-based calculations. In general, the chemical interaction between the interstitial H and metal is weakened as the alloying element is changed from an early to a late transition metal, leading to lower H solubility and higher resistance to H embrittlement. This effect becomes more pronounced when a smaller alloying element is used due to stronger elastic interaction between interstitial H and metal atoms. These finding may provide scientific basis for rational design of Nb-based hydrogen separation membranes with tailored H solubility to effectively suppress H embrittlement while maintaining excellent hydrogen permeation rate.

  16. Electrochemical studies of the molten system K2NbF7-Na2O-Nb-(LiF-NaF-KF)(eut) at 700 degrees C

    DEFF Research Database (Denmark)

    Rosenkilde, C.; Vik, A.; Østvold, T.

    2000-01-01

    . A slow, spontaneous reduction of Nb(V)-fluoru complexes to Nb(IV)-fluoro, complexes was observed in the absence of Nb metal. With a stoichiometric amount of Nb metal, Nb(V) is reduced rapidly to Nb(IV) according to the reaction 4NbF(7)(2-) + Nb reversible arrow 5NbF(x)((x-4)-). The solubilities of Nb2O5...

  17. Ta-based amorphous metal thin films

    Energy Technology Data Exchange (ETDEWEB)

    McGlone, John M., E-mail: mcglone@eecs.oregonstate.edu [School of Electrical Engineering and Computer Science, Oregon State University, Corvallis, OR 97331-5501 (United States); Olsen, Kristopher R. [Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003 (United States); Stickle, William F.; Abbott, James E.; Pugliese, Roberto A.; Long, Greg S. [Hewlett-Packard Company, Corvallis, OR, 97333 (United States); Keszler, Douglas A. [Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003 (United States); Wager, John F. [School of Electrical Engineering and Computer Science, Oregon State University, Corvallis, OR 97331-5501 (United States)

    2015-11-25

    With their lack of grains and grain boundaries, amorphous metals are known to possess advantageous mechanical properties and enhanced chemical stability relative to crystalline metals. Commonly, however, they exhibit poor high-temperature stability because of their metastable nature. Here, we describe two new Ta-based ternary metal thin films that retain thermal stability to 600 °C and above. The new thin-film compositions, Ta{sub 2}Ni{sub 2}Si{sub 1} and Ta{sub 2}Mo{sub 2}Si{sub 1}, are amorphous, exhibiting ultra-smooth surfaces (<0.4 nm) and resistivities typical of amorphous metals (224 and 177 μΩ cm, respectively). - Highlights: • New Ta-based amorphous metals were sputter deposited from individual targets. • As-deposited amorphous structure was confirmed through diffraction techniques. • Electrical and surface properties were characterized and possess smooth surfaces. • No evidence of crystallization up to 600 °C (TaNiSi) and 800 °C (TaMoSi). • Ultra-smooth surfaces remained unchanged up to crystallization temperature.

  18. Characterization of Rh films on Ta(110)

    International Nuclear Information System (INIS)

    Jiang, L.Q.; Ruckman, M.W.; Strongin, M.

    1989-01-01

    The surface and electronic structure of Rh films on Ta(110) up to several monolayers thick on Ta(110) are characterized by photoemission, Auger emission, low energy electron diffraction and low energy ion scattering. From the variation of the Rh Auger peak-to-peak intensity as a function of evaporation time, Rh/Ta(110) appears to grow in the Stranski-Krastanov mode at room temperature. However, the LEIS data show that the Rh adatoms begin to cluster on Ta(110) before growth of the monolayer is completed. Diffuse LEED scattering suggests that the Rh films are disordered. Photoemission shows that Rh chemisorption on Ta(110) generates two peaks located at 1.2 and 2. 5 eV binding energy during the initial phase of thin film growth (0 3.7 ML). Photoemission data for CO covered surfaces show that CO dissociates on the Rh/Ta(110) surface for Rh coverages less than 2.5 ML and also show that the Rh clusters develop at least one site capable of molecular CO adsorption above 0.3 ML Rh coverage. 38 refs., 5 figs

  19. Resonances in odd-odd 182Ta

    Science.gov (United States)

    Brits, C. P.; Wiedeking, M.; Bello Garrote, F. L.; Bleuel, D. L.; Giacoppo, F.; Görgen, A.; Guttormsen, M.; Hadynska-Klek, K.; Hagen, T. W.; Ingeberg, V. W.; Kheswa, B. V.; Klintefjord, M.; Larsen, A. C.; Malatji, K. L.; Nyhus, H. T.; Papka, P.; Renstrøm, T.; Rose, S.; Sahin, E.; Siem, S.; Tveten, G. M.; Zeiser, F.

    2017-09-01

    Enhanced γ-decay on the tail of the giant electric dipole resonance, such as the scissors or pygmy resonances, can have significant impact on (n,γ) reaction rates. These rates are important input for modeling processes that take place in astrophysical environments and nuclear reactors. Recent results from the University of Oslo indicate the existence of a significant enhancement in the photon strength function for nuclei in the actinide region due to the scissors resonance. Further, the M1 strength distribution of the scissors resonances in rare earth nuclei has been studied extensively over the years. To investigate the evolution and persistence of the scissor resonance in other mass regions, an experiment was performed utilizing the NaI(Tl) γ-ray detector array (CACTUS) and silicon particle telescopes (SiRi) at the University of Oslo Cyclotron laboratory. Particle-γ coincidences from the 181Ta(d,p)182Ta and 181Ta(d,d')181Ta reactions were used to measure the nuclear level density and photon strength function of the well-deformed 181Ta and 182Ta systems, to investigate the existence of resonances below the neutron separation energy. Note to the reader: the title of this article has been corrected on September 19, 2017.

  20. Resonances in odd-odd 182Ta

    Directory of Open Access Journals (Sweden)

    Brits C.P.

    2017-01-01

    Full Text Available Enhanced γ-decay on the tail of the giant electric dipole resonance, such as the scissors or pygmy resonances, can have significant impact on (n,γ reaction rates. These rates are important input for modeling processes that take place in astrophysical environments and nuclear reactors. Recent results from the University of Oslo indicate the existence of a significant enhancement in the photon strength function for nuclei in the actinide region due to the scissors resonance. Further, the M1 strength distribution of the scissors resonances in rare earth nuclei has been studied extensively over the years. To investigate the evolution and persistence of the scissor resonance in other mass regions, an experiment was performed utilizing the NaI(Tl γ-ray detector array (CACTUS and silicon particle telescopes (SiRi at the University of Oslo Cyclotron laboratory. Particle-γ coincidences from the 181Ta(d,p182Ta and 181Ta(d,d'181Ta reactions were used to measure the nuclear level density and photon strength function of the well-deformed 181Ta and 182Ta systems, to investigate the existence of resonances below the neutron separation energy.

  1. Concentrations of radionuclides and selected stable elements in fruits and vegetables

    International Nuclear Information System (INIS)

    Oakes, T.W.; Shank, K.E.

    1977-01-01

    Twenty-two types of fruits and vegetables collected from two commercial supermarkets have been analyzed for their radionuclidic and stable-element composition. A specific gamma-emitting isotope analysis was performed on each sample for 40 K, 60 Co, 95 Zr-Nb, 106 Ru, 137 Cs, 226 Ra, and 232 Th. The concentration of the stable elements in each sample were determined using multi-element neutron-activation analysis (Al, Ag, Au, As, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Cu, Eu, Fe, Hf, I, K, La, Mn, Mo, Mg, Na, Rb, Sb, Sc, Se, Sr, Ta, Te, Th, Ti, Zn, Zr) and atomic absorption (Cd, Ni, Pb). Information on the composition of a typical diet is used to estimate the radiological dose to man subsequent to ingestion of these fruits and vegetables. The stable-elemental compositions of the foodstuffs analyzed were compared with estimated values assuming foliar deposition and long-term buildup of effluents from a large modern coal-fired steam plant. It is tentatively concluded that for the general case of a precipitator-equipped, coal-fired steam plant, no toxic levels of trace elements in foodstuffs are expected as a result of the plant operation

  2. Concentrations of radionuclides and selected stable elements in fruits and vegetables

    Energy Technology Data Exchange (ETDEWEB)

    Oakes, T W; Shank, K E

    1977-01-01

    Twenty-two types of fruits and vegetables collected from two commercial supermarkets have been analyzed for their radionuclidic and stable-element composition. A specific gamma-emitting isotope analysis was performed on each sample for /sup 40/K, /sup 60/Co, /sup 95/Zr-Nb, /sup 106/Ru, /sup 137/Cs, /sup 226/Ra, and /sup 232/Th. The concentration of the stable elements in each sample were determined using multi-element neutron-activation analysis (Al, Ag, Au, As, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Cu, Eu, Fe, Hf, I, K, La, Mn, Mo, Mg, Na, Rb, Sb, Sc, Se, Sr, Ta, Te, Th, Ti, Zn, Zr) and atomic absorption (Cd, Ni, Pb). Information on the composition of a typical diet is used to estimate the radiological dose to man subsequent to ingestion of these fruits and vegetables. The stable-elemental compositions of the foodstuffs analyzed were compared with estimated values assuming foliar deposition and long-term buildup of effluents from a large modern coal-fired steam plant. It is tentatively concluded that for the general case of a precipitator-equipped, coal-fired steam plant, no toxic levels of trace elements in foodstuffs are expected as a result of the plant operation.

  3. Electron diffraction and resistivity measurements on the one-dimensional orthorhombic and monoclinic structures of TaS3

    International Nuclear Information System (INIS)

    Roucau, C.; Ayroles, R.; Monceau, P.

    1980-01-01

    Electron diffraction patterns are obtained of the orthorhombic and monoclinic structures of TaS 3 . For the orthorhombic structure one set of superlattice spots is observed at (l+-0.5)a*, (m+-0.125)b*, (n+-0.25)c* below 210 K. For the monoclinic structure two sets of superlattice spots are observed, the first one at la*, (m+-0.253)b*, nc* below 240 K, the second one at (l+-0.5)a*, (m+-0.245)b*, (n+-0.5)c* below 160 K. Diffuse scattering lines are present for the two structures. Resistivity measurements are performed on crystals with the two structures which show strong increase of the resistivity indicating metal-semiconducting transitions at the same temperatures where the superlattice spots appear. These transitions are interpreted as successive Peierls transitions on the different types of chains of TaS 3 . Also electron diffraction patterns are shown of NbSe 3 at very low temperatures where the two charge density waves that occur at 145 and 59 K are formed. A comparison is given between TaS 3 and NbSe 3 . (author)

  4. Direct electrochemical preparation of Nb-10Hf-1Ti alloy

    International Nuclear Information System (INIS)

    Abdelkader, Amr M.; Fray, Derek J.

    2010-01-01

    The preparation of 89Nb-10Hf-1Ti alloy by the electro-deoxidation of a porous precursor cathode made from a mixture of oxides containing the alloying elements has been investigated. The results confirmed the formation of the alloy, saturated with oxygen, after 4 h of the reduction. The X-ray diffraction (XRD) and microstructural analysis suggested that the reduction starts with the formation of niobium suboxides and calcium niobates. The calcium niobate slows down the reaction until some nonstoichiometric calcium niobate (Ca 3 Nb 2 O x-8 ) starts to form. Hafnium was also observed to be reduced through the formation of calcium hafnate without any side reactions with the other alloy constituents. Alloy with the target stoichiometry containing 390 ppm oxygen was obtained after 24 h of electro-deoxidation.

  5. Characteristics and Preparation Technologies of Nb/Nb5Si3 Microlaminate

    Directory of Open Access Journals (Sweden)

    MU Rende

    2016-06-01

    Full Text Available Nb/Nb5Si3 superalloy has the most potential in the application of future high temperature structures. Realization of microstructure lamination for this material is a new material design and preparation method. Characteristics and prevailing preparation technologies of Nb/Nb5Si3 microlaminate, including hot pressing, plasma spaying, magnetic sputtering and electron beam physical vapor deposition (EB-PVD are reviewed. It is pointed out that EB-PVD is a promising technology for producing Nb/Nb5Si3 microlaminate from the engineering application point of view. Structure and function compound, nano-laminating and toughening are the developing directions in the future electron beam physical vapor deposited Nb/Nb5Si3 microlaminate field.

  6. Characterization of Nb/AlOx-Al/Nb Josephson junctions by anodization profiles

    International Nuclear Information System (INIS)

    Imamura, T.; Hasuo, S.

    1989-01-01

    The thin tunneling barrier in a Nb/AlO x -Al/Nb Josephson junction was characterized by anodization profiles. Our studies focused on Nb/AlO x and Al/Nb interfaces in Nb/AlO x -Al/Nb junctions made by varying certain process parameters. The interface quality was checked by the anodization profiles and was greatly affected by film thickness, layer sequence, annealing treatment, and the existence of a thin oxide. By comparing the profiles with the junction characteristics measured at 4.2 K, we confirmed that the interface sharpness in the profiles is related to the junction quality. The anodization profile is a useful tool to diagnose the tunneling barrier interfaces in Nb/AlO x -Al/Nb Josephson junctions, especially at room temperature during fabrication

  7. Structural characterization of niobium oxide thin films grown on SrTiO3 (111) and (La,Sr)(Al,Ta)O3 (111) substrates

    Science.gov (United States)

    Dhamdhere, Ajit R.; Hadamek, Tobias; Posadas, Agham B.; Demkov, Alexander A.; Smith, David J.

    2016-12-01

    Niobium oxide thin films have been grown by molecular beam epitaxy on SrTiO3 (STO) (111) and (La0.18Sr0.82)(Al0.59Ta0.41)O3 (LSAT) (111) substrates. Transmission electron microscopy (TEM) confirmed the formation of high quality films with coherent interfaces. Films grown with higher oxygen pressure on STO (111) resulted in a (110)-oriented NbO2 phase with a distorted rutile structure, which can be described as body-centered tetragonal. The a lattice parameter of NbO2 was determined to be ˜13.8 Å in good agreement with neutron diffraction results published in the literature. Films grown on LSAT (111) at lower oxygen pressure produced the NbO phase with a defective rock salt cubic structure. The NbO lattice parameter was determined to be a ≈ 4.26 Å. The film phase/structure identification from TEM was in good agreement with in situ x-ray photoelectron spectroscopy measurements that confirmed the dioxide and monoxide phases, respectively. The atomic structure of the NbO2/STO and NbO/LSAT interfaces was determined based on comparisons between high-resolution electron micrographs and image simulations.

  8. Chemical Concentrations in Field Mice from Open-Detonation Firing Sites TA-36 Minie and TA-39 Point 6 at Los Alamos National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Fresquez, Philip R. [Los Alamos National Laboratory

    2011-01-01

    Field mice (mostly Peromyscus spp.) were collected at two open-detonation (high explosive) firing sites - Minie at Technical Area (TA) 36 and Point 6 at TA-39 - at Los Alamos National Laboratory in August of 2010 and in February of 2011 for chemical analysis. Samples of whole body field mice from both sites were analyzed for target analyte list elements (mostly metals), dioxin/furans, polychlorinated biphenyl congeners, high explosives, and perchlorate. In addition, uranium isotopes were analyzed in a composite sample collected from TA-36 Minie. In general, all constituents, with the exception of lead at TA-39 Point 6, in whole body field mice samples collected from these two open-detonation firing sites were either not detected or they were detected below regional statistical reference levels (99% confidence level), biota dose screening levels, and/or soil ecological chemical screening levels. The amount of lead in field mice tissue collected from TA-39 Point 6 was higher than regional background, and some lead levels in the soil were higher than the ecological screening level for the field mouse; however, these levels are not expected to affect the viability of the populations over the site as a whole.

  9. Liquidus projection of the Nb-Cr-Al system near the Al3(Nb,Cr) + Cr(Al,Nb) eutectic region

    International Nuclear Information System (INIS)

    Souza, S.A.; Ferrandini, P.L.; Nunes, C.A.; Coelho, A.A.; Caram, R.

    2006-01-01

    The system Nb-Cr-Al was investigated in the region near the Al 3 (Nb,Cr) + Cr(Al,Nb) eutectic and the liquidus projection of that region was determined based on the microstructural characterization of arc melted alloys. The characterization utilized scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential thermal analysis (DTA) and X-ray diffraction (XRD). The results allowed one to determine three primary solidification liquidus surfaces ((Cr,Al) 2 Nb, Cr(Al,Nb) and Al 3 (Nb,Cr)), that are originated from the binary systems Cr-Nb, Cr-Al and Al-Nb. It is proposed the occurrence of the invariant reaction L + (Cr,Al) 2 Nb ↔ Al 3 (Nb,Cr) + Cr(Al,Nb) and of a point of minimum, which involves a three phase reaction, L ↔ Al 3 (Nb,Cr) + Cr(Al,Nb). All alloys studied showed formation of the Al 3 (Nb,Cr) + Cr(Al,Nb) eutectic as the last solidification step with Al(Nb)Cr 2 precipitating from Cr(Al,Nb)

  10. Studies of the transition temperature and normal state resistivity of Nb3Ge and Nb films

    International Nuclear Information System (INIS)

    Lutz, H.; Weismann, H.; Gurvitch, M.; Goland, A.N.; Kammerer, O.F.; Strongin, M.

    1976-01-01

    Correlations between T/sub c/ and specific features of the normal state resistance vs temperature curves are discussed for both Nb 3 Ge and ion damaged Nb films. Of particular interest is the correlation between T/sub c/ and rho 0 in Nb 3 Ge films

  11. Continuous, flexible, and high-strength superconducting Nb3Ge and Nb3Sn filaments

    International Nuclear Information System (INIS)

    Ahmad, I.; Heffernan, W.J.

    1976-01-01

    Fabrication of continuous, flexible, and high-strength (1600 MN/m 2 ) composite filaments of Nb 3 Ge (T/subc/ 18 0 K) and Nb 3 Sn is reported, involving chemical vapor deposition of these compounds on Nb-coated high-strength W--1% ThO 2 filaments

  12. Tribological properties of self-lubricating Ta-Cu films

    Science.gov (United States)

    Qin, Wen; Fu, Licai; Zhu, Jiajun; Yang, Wulin; Li, Deyi; Zhou, Lingping

    2018-03-01

    In this paper, Ta and TaCu films were deposited by using magnetron sputtering, and the tribological properties of the films against Si3N4 balls were investigated under the loads of 2 N and 5 N. The average grain sizes of both films are below 25 nm. Ta and TaCu films have approximate hardness. While the wear rate of TaCu film is much smaller than that of Ta film. Post-wear testing XRD, Raman and XPS revealed the formation of tantalum oxide on the worn surface of both Ta and TaCu films. Tantalum oxidation is effectively lubricating to reduce friction coefficient. So the friction coefficient of both Ta and TaCu film is about 0.45 under different applied loads. Meanwhile, the addition of Cu could increase the toughness of the film, and avoid the generation of wear debris, resulting in a significant increase in wear resistance.

  13. Contributions to the crystal growth and characterization of the ferroelectric tetragonal tungsten bronze potassium-lithium niobate (K3Li2Nb5O15-KLN)

    International Nuclear Information System (INIS)

    Podlojenov, S.

    2003-01-01

    Undoped and Mg-doped KLN single crystals of optical quality were grown by the Czochralski technique. For decreasing temperature gradients in a growing single crystal an inductive afterheater was applied. The applicability for the frequency doubling of the KLN crystals was examined by using of powder SHG-tests. There was a clear correlation between the crystal composition (Nb-content) and the intensity of the second harmonic radiation. The niobium concentration of 49 mole % in the liquid phase can be appropriated as the boundary between the crystallization of paraelectric and ferroelectric KLN phase. All the grown KLTN crystals were paraelectric. The composition of the grown crystals was determined by X-ray fluorescence analysis and the atomic absorption analysis. The axial and radial concentration profiles of K and Nb over single crystals were determined by means of electron microprobe analysis. The segregation of elements is negligibly small in the investigated KLN single crystals. But in the KLTN single crystals the segregation of Ta was estimated to be in the order of 1 mole % / 1 cm crystal length. The ferroelectric phase transition in KLN was investigated with several techniques. The ferroelectric phase transition was estimated to lie within the range of 470-480 C. The second-order phase transition was detected by temperature-dependent measurements of the dielectric constant and the birefringence. But the DTA measurements indicated small thermal effect at the same temperature region, what refers to a first-order phase transition. The refractive indices of the paraelectric and the ferroelectric KLN phase were measured with an accuracy of 4 x 10 -5 over the wavelength region of 404-1083 nm. The data indicate that second harmonic generation in ferroelectric KLN crystals is possible at the primary wavelength 910 nm with non-critical phase matching (type I). (orig.)

  14. Sintering behavior and mechanical properties of a metal injection molded Ti–Nb binary alloy as biomaterial

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Dapeng, E-mail: dpzhao@hotmail.com [College of Biology, Hunan University, 410082 Changsha (China); Helmholtz-Zentrum Geesthacht, Institute of Materials Research, D-21502 Geesthacht (Germany); Chang, Keke [RWTH Aachen University, Materials Chemistry, D-52056 Aachen (Germany); Ebel, Thomas [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, D-21502 Geesthacht (Germany); Nie, Hemin [College of Biology, Hunan University, 410082 Changsha (China); Willumeit, Regine; Pyczak, Florian [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, D-21502 Geesthacht (Germany)

    2015-08-15

    Highlights: • The sintering of the MIM Ti–Nb alloy consists of three steps. • The Nb particles act as diffusion barriers during sintering. • The TiC{sub x} only precipitate in the cooling step during sintering. • The TiC{sub x} hardly influence the sintering process of MIM Ti–Nb alloy. • The MIM Ti–Nb alloy exhibits high strength, low Young’s modulus but poor ductility. - Abstract: Sintering behavior, microstructure and mechanical properties of a Ti–16Nb alloy processed by metal injection molding (MIM) technology using elemental powders were investigated in this work by optical microscopy, X-ray diffraction (XRD), dilatometer, scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). It was found that from 700 °C to 1500 °C the homogenization and densification process of MIM Ti–16Nb alloy consisted of three steps, i.e., Ti-diffusion-controlled step, Ti–Nb-diffusion step and matrix-diffusion step. Titanium carbide formation was observed in the samples sintered at 1300 °C and 1500 °C, but not in the ones sintered at 900 °C and 1100 °C. The MIM Ti–16Nb specimens sintered at 1500 °C exhibited a good combination of high tensile strength and low Young’s modulus. However, the titanium carbide particles led to poor ductility.

  15. Trace element characteristics of mafic and ultramafic meta-igneous rocks from the 3.5 Ga. Warrawoona group: evidence for plume-lithosphere interaction beneath Archaean continental crust

    International Nuclear Information System (INIS)

    Bolhar, R.; Hergt, J.; Woodhead, J.

    1999-01-01

    Full text: Magnesian- to Fe-rich tholeiitic basalts represent the dominant lithology in the Marble Bar Greenstone Belt, E-Pilbara Craton, and are locally associated with komatiitic basalts and rare komatiitic cumulates. Based on trace element characteristics, the extrusive and intrusive rocks from all three major stratigraphic units can be subdivided into LREE enriched and unfractionated to weakly LREE depleted groups. The former group is characterized by La/Sm pm = 1.7-4.6, Gd/Yb pm = 1.23.2 and Nb/Th pm 0.1-0.5, while the latter rocks possess ratios of La/Sm pm = 0.5-1.7, Gd/Yb pm = 0.8-1.9 and Nb/Th pm = 0.4-1.3. Nb/La -Nb/Th relationships in the LREE enriched samples indicate 7-28% contamination by crustal material similar in composition to Pilbara granitoids. LREE enrichment and strong negative HFSE anomalies, along with MgO = 2.2-22.0 wt% and SiO 2 = 39.2-63.5 wt%, have been observed in numerous Archaean greenstone belts, and can be successfully modeled in this study by AFC processes. In contrast, strong HFSE depletion combined with unfractionated to slightly depleted LREE in rocks of the latter group require different processes. Melting of mantle material previously depleted by melt extraction, enrichment of LILE and LREE relative to the HFSE in an arc-like environment and HFSE fractionation as a result of garnet retention in the melting source cannot account for negative Nb, Ta, Ti, P and strong positive Pb anomalies. Introduction of small amounts of crustal material into a depleted or primitive mantle, as possibly indicated by Nb/Ta ratios between 12 and 18, also fails to reproduce the trace element abundances of the second group of rocks. Recycling of oceanic crust previously processed through a subduction zone (low Th/Nb, La/Nb) and sub-arc lithospheric mantle (high Th/Nb, La/Nb), and subsequent mixing into the Archaean mantle has been recently invoked by several workers (e.g. Kerrich et al., EPSL, 168, 101-115; 1999) to explain the origin of

  16. Study of radionuclides created by 181Ta(γ,xn yp) reactions for bremsstrahlung photons produced by 150-MeV electrons

    International Nuclear Information System (INIS)

    Miller, M.A.; Dickens, J.K.

    1991-12-01

    Ten radionuclides, including isomers, from 172 Ta to 180 Ta and 180m Hf were produced by photon interactions with a sample of elemental tantalum and measured by counting photons using a high-resolution detection system. Relative yields of these radionuclides were obtained. In addition, precision half lives were obtained for 175,176,180 Ta and 180m Hf. Those obtained for the three Ta isotopes agree with previously reported values. For 180m Hf, the present measurements resulted in a half life determination of 6.05±0.06 hr, or about 10% longer than the currently adopted value for this half life

  17. Mineralogy, Geochemistry and Mass Changes at the Mombi Bauxite Deposit, (SW Iran): Using Geochemical Characteristics of the Immobile Elements

    Science.gov (United States)

    Ahmadnejad, Farhad; Vahabzadeh, Bahman; Zamanian, Hassan; Sameti, Mona; Asadi Haroni, Hooshang

    2016-04-01

    The Mombi bauxite deposit is located 160Km northwest of Dehdasht in the Zagros fold belt of Iran. The bauxite horizons are mineralogically homogeneous, and contains high amount of boehmite, diaspore, hematite, kaolinite, and anatase. Total geochemical analysis of the bauxite shows that Al2O3, SiO2, Fe2O3 and TiO2 are the main components. The immobile elements of Al, Ti, Nb, Zr, Hf, Cr, Ta, Y and Th are enriched while Rb, Ba, K, Sr, and P are depleted during bauxitization process. Chondrite-normalized REE pattern in the bauxite ore indicates REE enrichment (ΣREE=162.8-755.28ppm, ave. ~ 399.36 ppm) relative to the argillized limestone (ΣREE=76.26-84.03 ppm, ave. ~ 80.145 ppm). These patterns also reflect enrichment in LREE relative to HREE. Both positive and negative Ce anomalies (0.48-2.0) are observed in the Mombi bauxite horizons. These anomalies are related to the oxidation state of Ce (from Ce3+ to Ce4+), ionic potential, and complication of Ce4+ with carbonate compounds in the studied horizon. The present study uses the geochemistry of immobile elements to calculate the mass changes occurred during weathering and bauxitization. The results reveal that elements such as Si, Fe, Mg, P, K, Ba, Sr and Zn are depleted, while Al, Zr, V, Cr, Ni, Ga, Y and LREEs indicate positive mass changes during the weathering and bauxitization. In addition, Nb, Hf, Ta, Bi, Rb, Cs, U and HRRE exhibit little changes, suggesting relatively immobile features. Inter-elemental relationship analyses of the bauxite by using R-mode factor analysis method suggest that the elemental behaviors of trace elements and REEs during bauxite mineralization are mainly controlled by the mineral compositions and chemical properties of the elements. R-mode factor analysis reveals a number of key findings: (i) some of the low solubility elements were concentrated in detrital zircon (Zr), in anatase (Ti), and possibly in boehmite and hematite during the later stages of bauxitisation; (ii) Fe was

  18. Antimutagenic assay of carotenoids from green algae Chlorococcum humicola using Salmonella typhimurium TA98, TA100 and TA102

    Directory of Open Access Journals (Sweden)

    Bhagavathy S

    2011-12-01

    Full Text Available Objective: To evaluate the nonmutagenic and antimutagenic properties of the different carotenoids from the selected green algae Chlorococcum humicola (C. humicola using Ames mutagenicity assay. Methods: Antimutagenicity of fresh water green algae C. humicola was tested using its carotenoid extract. From the crude carotenoid extract, the different carotenoids were fractionated by column chromatography and further identified by high performance liquid chromatography (HPLC. In the in vitro antimutagenicity assay the total and individual carotenoids were used to check the nonmutagenicity and antimutagenicity effect using the strains of Salmonella typhimurium (S. typhimurium TA98, TA100 and TA102 with and without metabolic activation. The in vivo antimutagenic studies were carried out using animal model. Results: The results showed that the selected green algae were rich in carotenoids. In the crude carotenoid extract, astaxanthin, lutein and 毬 -carotene were found to be the major concentration. 毩 -carotene, zeaxanthin and violaxanthin were also found to be present. In the in vitro antimutagenic assay, the total carotenoids showed the maximum inhibition (P<0.001 against all three selected strains of S. typhimurium with and without metabolic activation. In the separated carotenoids, astaxanthin, lutein and 毬 -carotene showed significant mutational inhibition and exhibited good antitumor activity in the presence of S9 fraction. For direct acting mutagens sodium azide, ethidium bromide and hydroxyl amine with the specified concentration, the total carotenoids gave 63%, 60%, 66% inhibition for TA98, TA100 and TA102, respectively. In vivo antimutagenic assay was also confirmed the effective antimutagenic activity of total and separated carotenoids. The results also confirmed that the total and individual carotenoids had no mutagenic activity. Conclusions: The overall findings of the present study conclude that the green algae C. humicola possess

  19. Characterization of Rh films on Ta(110)

    International Nuclear Information System (INIS)

    Jiang, L.Q.; Ruckman, M.W.; Strongin, M.

    1990-01-01

    The surface and electronic structure of Rh films on Ta(110) up to several monolayers thick on Ta(110) are characterized by photoemission, Auger emission, low-energy electron diffraction (LEED) and low-energy ion scattering (LEIS). From the variation of the Rh Auger peak-to-peak intensity as a function of evaporation time, Rh appears to grow in the Stranski--Krastanov mode at room temperature. However, the LEIS data show that the Rh adatoms begin to cluster on Ta(110) before growth of the monolayer is completed. Diffuse LEED scattering suggests that the Rh films are disordered. Photoemission shows that Rh chemisorption on Ta(110) generates two peaks located at -1.5 and -2.5 eV binding energy during the initial phase of thin-film growth (0 3.7 ML). CO dissociates on the Rh/Ta(110) surface for Rh coverages<2.5 ML and the surface develops a site capable of molecular CO adsorption above 0.3-ML Rh coverage

  20. The Effect of Solute Nb on the Austenite-to-Ferrite Transformation

    Science.gov (United States)

    Jia, Tao; Militzer, Matthias

    2015-02-01

    Niobium is a widely used micro-alloying element in steels that can retard the austenite-to-ferrite transformation primarily by solute drag when Nb remains in solution. It is critical to develop quantitative models to predict the effect of Nb on the transformation kinetics. In the present work, dedicated continuous cooling transformation (CCT) studies were performed for a low-carbon steel microalloyed with 0.047 wt pct Nb starting from fully recrystallized austenite states with the same grain size but different amounts of Nb in solution. The austenite-to-ferrite transformation kinetics is described from a fundamental perspective by assuming a mixed-mode reaction including solute drag of Nb. Using the solute drag model of Fazeli and Militzer, the intrinsic interface mobility, trans-interface diffusivity of Nb, and its binding energy to the interface have been determined from the CCT data. The interfacial parameters are critically analyzed and compared with independent measurements of diffusion and grain boundary segregation.

  1. Corrosion Characteristics of Ti-29Nb-xHf Ternary Alloy for Biomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Pak, Sun Young; Choi, Han Chul [Chosun Univ., Kwangju (Korea, Republic of)

    2015-12-15

    The Cp-Ti and Ti-6Al-4V alloys were widely used for dental materials due to their mechanical properties and good corrosion resistance. However, Cp-Ti was known as bio-inert materials, Ti-6Al-4V alloy has a problem such as high Young modulus, potential loss of the surrounding bone, and to the release of potentially toxic ions from the alloy. To overcome this problem, Ti alloys containing Nb and Hf elements have been used for biomaterials due to low toxicity and high corrosion resistance. Especially, alloying element of Nb was known as β phase stabilizer. The β phase alloy was widely used to replace currently used implant materials. The corrosion resistances of Ti-29Nb-xHf ternary alloys were dependent on Hf content in oral environment solution.

  2. Comparing the thermal stability of NbTi and Nb3Sn wires

    International Nuclear Information System (INIS)

    Breschi, M; Trevisani, L; Bottura, L; Devred, A; Trillaud, F

    2009-01-01

    The investigation of quenching in low temperature superconducting wires is of great relevance for a proper design of superconductive cables and magnets. This paper reports the experimental results of a vast measurement campaign of quench induced by laser pulses on NbTi and Nb 3 Sn wires in pool boiling helium I. A comparison of the quench behavior of two typical NbTi and Nb 3 Sn wires is shown from different standpoints. Different qualitative behaviors of the voltage traces recorded during quenches and recoveries on NbTi and Nb 3 Sn wires are reported and analyzed. It is shown that the Nb 3 Sn wire exhibits a quench or no-quench behavior, whereas quenches and recoveries are exhibited by the NbTi wire. The two wires are also compared by considering the behaviors of the two main parameters describing quench, i.e. quench energies and quench velocities, with respect to operating current, pulse duration, and magnetic field. It is shown that the Nb 3 Sn wire exhibits a 'kink' of the quench energy versus current curve that makes the quench energy of Nb 3 Sn lower than that of NbTi at some intermediate current levels. Both the qualitative differences of the voltage traces and the different behaviors of quench energies and velocities are interpreted through a coupled electromagnetic-thermal model, with special emphasis on the detailed description of heat exchange with liquid helium.

  3. Studying superconducting Nb$_{3}$Sn wire

    CERN Multimedia

    AUTHOR|(CDS)2099575

    2015-01-01

    Studying superconducting Nb$_{3}$Sn wire. From the current experience from LHC and HL-LHC we know that the performance requirements for Nb$_{3}$Sn conductor for future circular collider are challenging and should exceed that of present state-of-the-art materials.

  4. Studying superconducting Nb3Sn wire

    CERN Multimedia

    AUTHOR|(CDS)2099575

    2015-01-01

    Studying superconducting Nb3Sn wire. From the current experience from LHC and HL-LHC we know that the performance requirements for Nb3Sn conductor for future circular collider are challenging and should exceed that of present state-of-the-art materials.

  5. Conditions for Ta(IV)-Ta(IV) bonding in trirutile Li(x)MTa2O6.

    Science.gov (United States)

    Gupta, Asha; Singh, Preetam; Celio, Hugo; Mullins, C Buddie; Goodenough, John B

    2015-02-16

    Stabilization of Ta-Ta bonding in an oxide across a shared octahedral-site edge of a Ta2 dimer is not known. Investigation of Li insertion into the trirutile structure of MTa2O6 with M = Mg, Cr, Fe, Co, and Ni indicates that Ta-Ta bonding across the shared octahedral-site edge of the dimer can be stabilized by a reversible electrochemical reduction of Ta(V) to Ta(IV) for M = Cr, Fe, Co, and Ni but not for M = Mg. Chemical reduction of MTa2O6 by n-butyl lithium only reduced NiTa2O6 to any significant extent. With M = Fe, Co, or Ni, electrochemical formation of the Ta-Ta bonds is accompanied by a partial reduction of the Fe(II), Co(II), or Ni(II) to Fe(0), Co(0), or Ni(0). For M = Cr, two Li per formula unit can be inserted reversibly with no displacement of Cr(0). For M = Mg, no Mg(II) are displaced by Li insertion, but a solid-electrolyte interphase (SEI) layer is formed on the oxide with no evidence of Ta-Ta bonding. Stabilization of Ta-Ta bonding across a shared octahedral-site edge in a dimer appears to require significant hybridization of the Ta(V) 5d(0) and M 4s(0) states.

  6. Nanostructured Ta{sub x}C interlayer synthesized via double glow plasma surface alloying process for diamond deposition on cemented carbide

    Energy Technology Data Exchange (ETDEWEB)

    Rong, Wolong; Hei, Hongjun; Zhong, Qiang; Shen, Yanyan; Liu, Xiaoping; Wang, Xin; Zhou, Bing; He, Zhiyong, E-mail: hezhiyong@tyut.edu.cn; Yu, Shengwang, E-mail: yushengwang@tyut.edu.cn

    2015-12-30

    Graphical abstract: - Highlights: • Ta{sub x}C interlayer was creatively obtained on WC–Co by DG-PSA for diamond deposition. • The interlayer with a flower-shaped surface consisted of Ta{sub 2}C and TaC nanocrystal. • Ta{sub x}C interlayer had a superior adherence because of gradual element distributions. • The samples’ surface microhardness is increased caused by nanostructured interlayer. • Ta{sub x}C interlayer improved diamond adhesion on WC–Co by suppressing Co diffusion. - Abstract: The aim in this work was to improve the adhesion of diamond coating with pre-deposition of a Ta{sub x}C interlayer on cemented carbide (WC–Co) substrate by double glow plasma surface alloying technique. The following deposition of diamond coating on the interlayer was performed in a microwave plasma chemical vapor deposition (MPCVD) reactor. Ta{sub x}C interlayer with an inner diffusion layer and an outer deposition layer was composed of Ta{sub 2}C and TaC nanocrystalline, and it exhibited a special compact surface morphology formed of flower-shaped pits. As the gradual element distributions existed in the diffusion layer, the interlayer displayed a superior adherence to the substrate with significantly enhanced surface microhardness to the original substrate. After CVD process, the preferred orientation of TaC changed from (2 2 2) to (2 0 0) plane, and a uniform and tense diamond coating with adhesion referred to class HF 2 at least (Verein Deutscher Ingenieure 3198 norm) was obtained on the interlayered substrate. It indicated that the diffusion of Co was effectively inhibited by the formation of Ta{sub x}C diffusion–deposition interlayer. The Ta{sub x}C interlayer is most likely to improve the performance of diamond coatings used in cutting tools.

  7. The effects of alloying elements on strength, hardenability, and ...

    African Journals Online (AJOL)

    Tensile and hardenability tests were carried out. Results showed that alloying elements in steel increased strength in the dual phase steels by amounts ranging from 150 Mpa for Nb-V steel to 226 MPa for Nb steel. Strain hardening exponent, n, was also increased from ~0.22 for annealed to 0.35 in the dual phase steels.

  8. Critical role of the semiconductor-electrolyte interface in photocatalytic performance for water-splitting reactions using Ta3N5 particles

    KAUST Repository

    Nurlaela, Ela

    2014-08-26

    Distinct photocatalytic performance was observed when Ta3N 5 was synthesized from commercially available Ta2O 5 or from Ta2O5 prepared from TaCl5 via the sol-gel route. With respect to photocatalytic O2 evolution with Ag+ as a sacrificial reagent, the Ta3N5 produced from commercial Ta2O5 exhibited higher activity than the Ta3N5 produced via the sol-gel route. When the Ta3N5 photocatalysts were decorated with Pt nanoparticles in a similar manner, the Ta3N5 from the sol-gel route exhibited higher photocatalytic hydrogen evolution activity from a 10% aqueous methanol solution than Ta3N5 prepared from commercial Ta2O5 where no hydrogen can be detected. Detailed surface and bulk characterizations were conducted to obtain fundamental insight into the resulting photocatalytic activities. The characterization techniques, including XRD, elemental analysis, Raman spectroscopy, UV-vis spectroscopy, and surface-area measurements, revealed only negligible differences between these two photocatalysts. Our thorough characterization of the surface properties demonstrated that the very thin outermost layer of Ta3N5, with a thickness of a few nanometers, consists of either the reduced state of tantalum (TaN) or an amorphous phase. The extent of this surface layer was likely dependent on the nature of precursor oxide surfaces. DFT calculations based on partially oxidized Ta3N4.83O0.17 and N deficient Ta3N4.83 consisting of reduced Ta species well described the optoelectrochemical properties obtained from the experiments. Electrochemical and Mott-Schottky analyses demonstrated that the surface layer drastically affects the energetic picture at the semiconductor-electrolyte interface, which can consequently affect the photocatalytic performance. Chemical etching of the surface of Ta3N5 particles to remove this surface layer unites the photocatalytic properties with the photocatalytic performance of these two materials. Mott-Schottky plots of these chemically etched Ta3N5 materials

  9. Microstructure and oxidation behaviour of TiAl(Nb)/Ti2AlC ...

    Indian Academy of Sciences (India)

    was found that after milling for 25 h, a Ti(Al) solid solution was formed; also with increase in the milling time to. 50 h, an ... solid solution after milling for 75 h, implying that the Al and Nb elements were dissolved in the Ti lattice in a non- equilibrium state. Annealing .... croscopy (SEM, VEGA Tescan machine) equipped with an.

  10. COST action TD1407: network on technology-critical elements (NOTICE)--from environmental processes to human health threats.

    Science.gov (United States)

    Cobelo-García, A; Filella, M; Croot, P; Frazzoli, C; Du Laing, G; Ospina-Alvarez, N; Rauch, S; Salaun, P; Schäfer, J; Zimmermann, S

    2015-10-01

    The current socio-economic, environmental and public health challenges that countries are facing clearly need common-defined strategies to inform and support our transition to a sustainable economy. Here, the technology-critical elements (which includes Ga, Ge, In, Te, Nb, Ta, Tl, the Platinum Group Elements and most of the rare-earth elements) are of great relevance in the development of emerging key technologies-including renewable energy, energy efficiency, electronics or the aerospace industry. In this context, the increasing use of technology-critical elements (TCEs) and associated environmental impacts (from mining to end-of-life waste products) is not restricted to a national level but covers most likely a global scale. Accordingly, the European COST Action TD1407: Network on Technology-Critical Elements (NOTICE)-from environmental processes to human health threats, has an overall objective for creating a network of scientists and practitioners interested in TCEs, from the evaluation of their environmental processes to understanding potential human health threats, with the aim of defining the current state of knowledge and gaps, proposing priority research lines/activities and acting as a platform for new collaborations and joint research projects. The Action is focused on three major scientific areas: (i) analytical chemistry, (ii) environmental biogeochemistry and (iii) human exposure and (eco)-toxicology.

  11. Elemental analysis of granite by instrumental neutron activation analysis (INAA) and X-ray fluorescence analysis (XRF).

    Science.gov (United States)

    El-Taher, A

    2012-01-01

    The instrumental neutron activation analysis technique (INAA) was used for qualitative and quantitative analysis of granite samples collected from four locations in the Aswan area in South Egypt. The samples were prepared together with their standards and simultaneously irradiated in a neutron flux of 7×10(11)n/cm(2)s in the TRIGA Mainz research reactor. Gamma-ray spectra from an hyper-pure germanium detector were analyzed. The present study provides the basic data of elemental concentrations of granite rocks. The following elements have been determined Na, Mg, K, Fe, Mn, Sc, Cr, Ti, Co, Zn, Ga, Rb, Zr, Nb, Sn, Ba, Cs, La, Ce, Nd, Sm, Eu, Yb, Lu, Hf, Ta, Th and U. The X-ray fluorescence (XRF) was used for comparison and to detect elements, which can be detected only by XRF such as F, S, Cl, Co, Cu, Mo, Ni, Pb, Se and V. The data presented here are our contribution to understanding the elemental composition of the granite rocks. Because there are no existing databases for the elemental analysis of granite, our results are a start to establishing a database for the Egyptian granite. It is hoped that the data presented here will be useful to those dealing with geochemistry, granite chemistry and related fields. Copyright © 2011 Elsevier Ltd. All rights reserved.

  12. Direct Ink Writing of Three-Dimensional (K, NaNbO3-Based Piezoelectric Ceramics

    Directory of Open Access Journals (Sweden)

    Yayun Li

    2015-04-01

    Full Text Available A kind of piezoelectric ink was prepared with Li, Ta, Sb co-doped (K, NaNbO3 (KNN powders. Piezoelectric scaffolds with diameters at micrometer scale were constructed from this ink by using direct ink writing method. According to the micro-morphology and density test, the samples sintered at 1100 °C for 2 h have formed ceramics completely with a high relative density of 98%. X-ray diffraction (XRD test shows that the main phase of sintered samples is orthogonal (Na0.52K0.4425Li0.0375(Nb0.87Sb0.07Ta0.06O3. The piezoelectric constant d33 of 280 pC/N, dielectric constant ε of 1775, remanent polarization Pr of 18.8 μC/cm2 and coercive field Ec of 8.5 kV/cm prove that the sintered samples exhibit good electrical properties. The direct ink writing method allows one to design and rapidly fabricate piezoelectric structures in complex three-dimensional (3D shapes without the need for any dies or lithographic masks, which will simplify the process of material preparation and offer new ideas for the design and application of piezoelectric devices.

  13. Direct Ink Writing of Three-Dimensional (K, Na)NbO₃-Based Piezoelectric Ceramics.

    Science.gov (United States)

    Li, Yayun; Li, Longtu; Li, Bo

    2015-04-14

    A kind of piezoelectric ink was prepared with Li, Ta, Sb co-doped (K, Na)NbO₃ (KNN) powders. Piezoelectric scaffolds with diameters at micrometer scale were constructed from this ink by using direct ink writing method. According to the micro-morphology and density test, the samples sintered at 1100 °C for 2 h have formed ceramics completely with a high relative density of 98%. X-ray diffraction (XRD) test shows that the main phase of sintered samples is orthogonal (Na 0.52 K 0.4425 Li 0.0375 )(Nb 0.87 Sb 0.07 Ta 0.06 )O₃. The piezoelectric constant d 33 of 280 pC/N, dielectric constant ε of 1775, remanent polarization P r of 18.8 μC/cm² and coercive field E c of 8.5 kV/cm prove that the sintered samples exhibit good electrical properties. The direct ink writing method allows one to design and rapidly fabricate piezoelectric structures in complex three-dimensional (3D) shapes without the need for any dies or lithographic masks, which will simplify the process of material preparation and offer new ideas for the design and application of piezoelectric devices.

  14. Effect of Nb content on deformation behavior and shape memory properties of Ti–Nb alloys

    International Nuclear Information System (INIS)

    Tobe, H.; Kim, H.Y.; Inamura, T.; Hosoda, H.; Nam, T.H.; Miyazaki, S.

    2013-01-01

    Highlights: ► Reorientation of martensite variants occurred by the deformation of the {1 1 1} type I and 〈2 1 1〉 type II twins. ► Magnitude of twinning shear in Ti–20Nb is larger than that in Ti–23Nb. ► Ti–20Nb exhibited a higher stress for the reorientation of martensite variants when compared with Ti–23Nb. -- Abstract: Deformation behavior and shape memory properties of Ti–(20, 23) at.% Nb alloys in a single α″ martensite state were investigated. The Ti–20Nb alloy exhibited a higher stress for the reorientation of martensite variants when compared with the Ti–23Nb alloy. The recovery strain due to the shape memory effect in the Ti–20Nb alloy was smaller than that in the Ti–23Nb alloy. Transmission electron microscope (TEM) observation revealed that the reorientation of martensite variants occurred by the deformation of {1 1 1} type I and 〈2 1 1〉 type II twins. The Nb content dependence of the deformation behavior and shape memory properties was discussed considering the magnitude of twinning shear of the twins

  15. LCD plus NB-UVB reduces time to improvement of psoriasis vs. NB-UVB alone.

    Science.gov (United States)

    Bagel, Jerry

    2009-04-01

    Use of coal tar with narrowband (NB) ultraviolet B (UVB) light (the Goeckerman regimen) is an effective treatment for plaque psoriasis that has become impractical in outpatient care mainly due to the inconvenience and aesthetic concerns of coal tar. This study evaluated the safety, efficacy, and convenience of adding a novel LCD (coal tar) solution to standard NB-UVB phototherapy in adults with chronic plaque psoriasis. Patients applied LCD solution to half-body twice daily at home and received outpatient full-body NB-UVB light therapy 3 times a week for up to 12 weeks. A blinded investigator graded psoriasis severity of body halves and bilateral target lesions and monitored adverse reactions. Patients rated their psoriasis symptoms and LCD solution aesthetics. NB-UVB + LCD therapy reduced the median time to clearance or minimal disease in at least 50% of the population by 3 weeks (4 weeks with NB-UVB + LCD versus 7 weeks with NB-UVB alone). A statistically superior clinical response was observed by the end of week 4 with NB-UVB + LCD versus NB-UVB alone (P LCD solution into outpatient NB-UVB light therapy is safe, convenient, effective, and can improve psoriasis more quickly than NB-UVB light therapy alone.

  16. Phase Evolution in and Creep Properties of Nb-Rich Nb-Si-Cr Eutectics

    Science.gov (United States)

    Gang, Florian; Kauffmann, Alexander; Heilmaier, Martin

    2018-03-01

    In this work, the Nb-rich ternary eutectic in the Nb-Si-Cr system has been experimentally determined to be Nb-10.9Si-28.4Cr (in at. pct). The eutectic is composed of three main phases: Nb solid solution (Nbss), β-Cr2Nb, and Nb9(Si,Cr)5. The ternary eutectic microstructure remains stable for several hundred hours at a temperature up to 1473 K (1200 °C). At 1573 K (1300 °C) and above, the silicide phase Nb9(Si,Cr)5 decomposes into α-Nb5Si3, Nbss, and β-Cr2Nb. Under creep conditions at 1473 K (1200 °C), the alloy deforms by dislocation creep while the major creep resistance is provided by the silicide matrix. If the silicide phase is fragmented and, thus, its matrix character is destroyed by prior heat treatment [ e.g., at 1773 K (1500 °C) for 100 hours], creep is mainly controlled by the Laves phase β-Cr2Nb, resulting in increased minimum strain rates. Compared to state of the art Ni-based superalloys, the creep resistance of this three-phase eutectic alloy is significantly higher.

  17. Measurements of tunneling barrier thicknesses for Nb/Al–AlOx/Nb tunnel junctions

    International Nuclear Information System (INIS)

    Kang, Xinjie; Ying, Liliang; Wang, Hai; Zhang, Guofeng; Peng, Wei; Kong, Xiangyan; Xie, Xiaoming; Wang, Zhen

    2014-01-01

    Highlights: • We estimate the average barrier height (Φ) of Nb/Al–AlO x /Nb tunnel junctions. • Dependence of the AlOx thickness (dAlOx) on O 2 exposure was described. • The thicknesses of AlOx barriers were measured using transmission electron microscopy (TEM). • X-ray Reflection (XRR) measurements and simulations were used to verify the AlOx thickness. - Abstract: The tunnel barrier thicknesses of Nb/Al–AlO x /Nb tunnel junctions were measured using transmission electron microscopy (TEM) and X-ray Reflection (XRR). By investigating the barrier thickness dependence of current density J c , the barrier height for Nb/Al–AlO x /Nb junctions was calculated. Nb/Al–AlO x /Nb junctions with different J c were fabricated by controlling the O 2 exposure in Al oxidation. The junctions show good tunneling properties with subgap leakage factor V m larger than 30 mV in the range of J c from tens of A/cm 2 to several kA/cm 2 . TEM images showed clear interface and indicated the AlO x thicknesses ranging from 0.8 nm to 1.9 nm, and the average barrier height was estimated to be 0.17 eV for Nb/Al–AlO x /Nb tunnel junctions

  18. Suppression of superconductivity in Nb by IrMn in IrMn/Nb bilayers

    KAUST Repository

    Wu, B. L.

    2013-10-10

    Effect of antiferromagnet on superconductivity has been investigated in IrMn/Nb bilayers. Significant suppression of both transition temperature (Tc) and lower critical field (Hc1) of Nb is found in IrMn/Nb bilayers as compared to a single layer Nb of same thickness; the suppression effect is even stronger than that of a ferromagnet in NiFe/Nb bilayers. The addition of an insulating MgO layer at the IrMn-Nb interface nearly restores Tc to that of the single layer Nb, but Hc1 still remains suppressed. These results suggest that, in addition to proximity effect and magnetic impurity scattering, magnetostatic interaction also plays a role in suppressing superconductivity of Nb in IrMn/Nb bilayers. In addition to reduced Tc and Hc1, the IrMn layer also induces broadening in the transition temperature of Nb, which can be accounted for by a finite distribution of stray field from IrMn.

  19. MeTA: Mediated Touch and Affect

    NARCIS (Netherlands)

    Huisman, Gijs; Bianchi-Berthouze, N.; Heylen, Dirk K.J.

    The main aim of this first workshop on Mediated Touch and Affect (MeTA) is to bring together researchers from diverse communities, such as affective computing, hap tics, augmented reality, communication, design, psychology, human-robot interaction, and telepresence. The goal is to discuss the

  20. Memory window engineering of Ta2O5-x oxide-based resistive switches via incorporation of various insulating frames

    Science.gov (United States)

    Lee, Ah Rahm; Baek, Gwang Ho; Kim, Tae Yoon; Ko, Won Bae; Yang, Seung Mo; Kim, Jongmin; Im, Hyun Sik; Hong, Jin Pyo

    2016-07-01

    Three-dimensional (3D) stackable memory frames, including nano-scaled crossbar arrays, are one of the most reliable building blocks to meet the demand of high-density non-volatile memory electronics. However, their utilization has the disadvantage of introducing issues related to sneak paths, which can negatively impact device performance. We address the enhancement of complementary resistive switching (CRS) features via the incorporation of insulating frames as a generic approach to extend their use; here, a Pt/Ta2O5-x/Ta/Ta2O5-x/Pt frame is chosen as the basic CRS cell. The incorporation of Ta/Ta2O5-x/Ta or Pt/amorphous TaN/Pt insulting frames into the basic CRS cell ensures the appreciably advanced memory features of CRS cells including higher on/off ratios, improved read margins, and increased selectivity without reliability degradation. Experimental observations identified that a suitable insulating frame is crucial for adjusting the abrupt reset events of the switching element, thereby facilitating the enhanced electrical characteristics of CRS cells that are suitable for practical applications.

  1. Effects of alloying elements and thermomechanical treatment on 9Cr Reduced Activation Ferritic–Martensitic (RAFM) steels

    International Nuclear Information System (INIS)

    Tan, L.; Yang, Y.; Busby, J.T.

    2013-01-01

    RAFM steels are one of the candidate structural materials for fusion reactors, in which tantalum (Ta) and tungsten (W) are alloyed to replace niobium (Nb) and molybdenum (Mo) in conventional FM steels, respectively. This paper, using three RAFM heats, presents the effects of Ta and the primary austenite stabilizer carbon (C) on microstructure and strength. Thermomechanical treatment (TMT) was also applied to the heats, leading to significant increases in strength, attributable to the TMT-refined sub-grains and precipitates. The Ta-alloying favored the formation of (V, Ta)(N, C) and (Ta, V)C and exhibited greater strength. Fractographs also revealed the beneficial effects of TMT and Ta-alloying. However, extra C content, favoring a larger amount of M 23 C 6 precipitates, did not show strengthening effect

  2. High-throughput exploration of thermoelectric and mechanical properties of amorphous NbO2 with transition metal additions

    International Nuclear Information System (INIS)

    Music, Denis; Geyer, Richard W.; Hans, Marcus

    2016-01-01

    To increase the thermoelectric efficiency and reduce the thermal fatigue upon cyclic heat loading, alloying of amorphous NbO 2 with all 3d and 5d transition metals has systematically been investigated using density functional theory. It was found that Ta fulfills the key design criteria, namely, enhancement of the Seebeck coefficient and positive Cauchy pressure (ductility gauge). These quantum mechanical predictions were validated by assessing the thermoelectric and elastic properties on combinatorial thin films, which is a high-throughput approach. The maximum power factor is 2813 μW m −1  K −2 for the Ta/Nb ratio of 0.25, which is a hundredfold increment compared to pure NbO 2 and exceeds many oxide thermoelectrics. Based on the elasticity measurements, the consistency between theory and experiment for the Cauchy pressure was attained within 2%. On the basis of the electronic structure analysis, these configurations can be perceived as metallic, which is consistent with low electrical resistivity and ductile behavior. Furthermore, a pronounced quantum confinement effect occurs, which is identified as the physical origin for the Seebeck coefficient enhancement.

  3. High-throughput exploration of thermoelectric and mechanical properties of amorphous NbO2 with transition metal additions

    Science.gov (United States)

    Music, Denis; Geyer, Richard W.; Hans, Marcus

    2016-07-01

    To increase the thermoelectric efficiency and reduce the thermal fatigue upon cyclic heat loading, alloying of amorphous NbO2 with all 3d and 5d transition metals has systematically been investigated using density functional theory. It was found that Ta fulfills the key design criteria, namely, enhancement of the Seebeck coefficient and positive Cauchy pressure (ductility gauge). These quantum mechanical predictions were validated by assessing the thermoelectric and elastic properties on combinatorial thin films, which is a high-throughput approach. The maximum power factor is 2813 μW m-1 K-2 for the Ta/Nb ratio of 0.25, which is a hundredfold increment compared to pure NbO2 and exceeds many oxide thermoelectrics. Based on the elasticity measurements, the consistency between theory and experiment for the Cauchy pressure was attained within 2%. On the basis of the electronic structure analysis, these configurations can be perceived as metallic, which is consistent with low electrical resistivity and ductile behavior. Furthermore, a pronounced quantum confinement effect occurs, which is identified as the physical origin for the Seebeck coefficient enhancement.

  4. High-throughput exploration of thermoelectric and mechanical properties of amorphous NbO{sub 2} with transition metal additions

    Energy Technology Data Exchange (ETDEWEB)

    Music, Denis, E-mail: music@mch.rwth-aachen.de; Geyer, Richard W.; Hans, Marcus [Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen (Germany)

    2016-07-28

    To increase the thermoelectric efficiency and reduce the thermal fatigue upon cyclic heat loading, alloying of amorphous NbO{sub 2} with all 3d and 5d transition metals has systematically been investigated using density functional theory. It was found that Ta fulfills the key design criteria, namely, enhancement of the Seebeck coefficient and positive Cauchy pressure (ductility gauge). These quantum mechanical predictions were validated by assessing the thermoelectric and elastic properties on combinatorial thin films, which is a high-throughput approach. The maximum power factor is 2813 μW m{sup −1} K{sup −2} for the Ta/Nb ratio of 0.25, which is a hundredfold increment compared to pure NbO{sub 2} and exceeds many oxide thermoelectrics. Based on the elasticity measurements, the consistency between theory and experiment for the Cauchy pressure was attained within 2%. On the basis of the electronic structure analysis, these configurations can be perceived as metallic, which is consistent with low electrical resistivity and ductile behavior. Furthermore, a pronounced quantum confinement effect occurs, which is identified as the physical origin for the Seebeck coefficient enhancement.

  5. Electric-field gradients at Ta donor impurities in Cr2O3(Ta) semiconductor

    International Nuclear Information System (INIS)

    Darriba, G.N.; Errico, L.A.; Munoz, E.L; Richard, D.; Eversheim, P.D.; Renteria, M.

    2009-01-01

    We report perturbed-angular-correlation (PAC) experiments on 181 Hf(→ 181 Ta)-implanted corundum Cr 2 O 3 powder samples in order to determine the magnitude and symmetry of the electric-field gradient (EFG) tensor at Ta donor impurity sites of this semiconductor. These results are analyzed in the framework of ab initio full-potential augmented-plane wave plus local orbitals (FP-APW+lo) calculations. The results are also compared with EFG results coming from PAC experiments in isomorphous α-Al 2 O 3 and α-Fe 2 O 3 doped with 111 In→ 111 Cd and 181 Hf→ 181 Ta tracers. This combined analysis enables us to quantify the magnitude of the lattice relaxations induced by the presence of the impurity and to determine the charge state of the impurity donor level introduced by Ta in the band gap of the semiconductor.

  6. Thermophysical properties of NbCsub(x)

    International Nuclear Information System (INIS)

    Korolev, L.A.; Taubin, M.L.

    1977-01-01

    The thermal conduction, specific heat, temperature conductivity and electric resistance of the NbCsub(X) compound (C/Nb=0.77; 0.82; 0.94) were measured in the range of temperatures between 20 and 900 deg C. The Lorenz number and the phonon component of the thermal conduction were analyzed and calculated. It was suggested that the phonon component of the thermal conduction is independent of the temperature, while the electron component increases and governs the temperature dependence of thermal conduction of the NbCsub(x) compound above the Debye temperature

  7. Solidification processing of intermetallic Nb-Al alloys

    Science.gov (United States)

    Smith, Preston P.; Oliver, Ben F.; Noebe, Ronald D.

    1992-01-01

    Several Nb-Al alloys, including single-phase NbAl3 and the eutectic of Nb2Al and NbAl3, were prepared either by nonconsumable arc melting in Ar or by zone processing in He following initial induction melting and rod casting, and the effect of the solidification route on the microstructure and room-temperature mechanical properties of these alloys was investigated. Automated control procedures and melt conditions for directional solidification of NbAl3 and the Nb2Al/Nb3Al eutectic were developed; high purity and stoichiometry were obtained. The effects of ternary additions of Ti and Ni are described.

  8. Cross-sectional TEM observation of Nb/AlOx-Al/Nb junction structures

    International Nuclear Information System (INIS)

    Imamura, T.; Hasuo, S.

    1991-01-01

    This paper reports on a study of microstructure of Nb/AlO x ---Al/Nb Josephson junctions by cross-sectional transmission electron microscopy (TEM) which yielded much information regarding the unction barrier region. Both thick Nb and several-nm Al form polycrystalline films with columnar structures. Nb is oriented to the (110) plane, and Al is (111). The 200-nm lower Nb has a wavy surface with ∼5 nm smoothness, but its surface is planarized by several-nm Al deposited on it. Thus AlO x with a smoothness under 1 nm can be formed on Al. The upper Nb has a good crystalline structure even just above the AlO x barrier

  9. Cross-sectional transmission electron microscopy observation of Nb/AlOx-Al/Nb Josephson junctions

    International Nuclear Information System (INIS)

    Imamura, T.; Hasuo, S.

    1991-01-01

    A study of microstructure of Nb/AlO x -Al/Nb Josephson junctions by cross-sectional transmission electron microscopy yielded much information regarding the junction barrier region. Both thick Nb and several-nanometer Al form polycrystalline films with columnar structures. Nb is oriented to the (110) plane, and Al is (111). The 200 nm lower Nb has a wavy surface with ∼5 nm smoothness, but its surface is planarized by several nanometers Al deposited on it. Thus AlO x with a smoothness under 1 nm can be formed on Al. The upper Nb has a good crystalline structure even just above the AlO x barrier

  10. The Geography of the ta-ra-si-ja

    DEFF Research Database (Denmark)

    Nosch, Marie-Louise Bech

    2000-01-01

    Thies paper demonstrates how ta-ra-si-ja is connected to a fixed series of toponyms in Crete, and concludes that ta-ra-si-ja is a duty limited to certain places......Thies paper demonstrates how ta-ra-si-ja is connected to a fixed series of toponyms in Crete, and concludes that ta-ra-si-ja is a duty limited to certain places...

  11. Modulation of the penetration depth of Nb and NbN films by quasiparticle injection

    International Nuclear Information System (INIS)

    Track, E.K.; Radparvar, M.; Faris, S.M.

    1989-01-01

    A novel approach to modulating the inductance of a superconducting microstrip is described. This approach could be the basis for numerous practical applications, such as phase shifters and high frequency tuning elements. The physical mechanisms involved are quasiparticle injection, gap suppression, and penetration depth modulation. In this current, the authors have investigated the modulation of the penetration depth of niobium and niobium nitride films by excess quasiparticle injection. To this effect, all-niobium and all-niobium-nitride SQUID circuits are designed and fabricated. These circuits allow quasiparticle injection into the inductive element of the SQUID. This injection is achieved by 1. optical irradiation through an opening in a Nb reflective layer which partially masks the rest of the circuit, and 2. electronic current injection through a tunnel junction overlaid on the microstrip inductance. Penetration depth modulation is achieved with both methods. The magnitude of the effect varies from 10% to over 200% change in inductance. These results and their dependence on temperature and on the parameters of the control mechanism (light intensity, amount of current injection, etc.) are presented and discussed

  12. Detailed uranium hydrogeochemical and stream sediment reconnaissance data release for the eastern portion of the Montrose NTMS Quadrangle, Colorado, including concentrations of forty-five additional elements

    International Nuclear Information System (INIS)

    Maassen, L.W.

    1981-01-01

    In September and October 1979, the Los Alamos Scientific Laboratory (LASL) conducted a detailed geochemical survey for uranium primarily in the Sawatch Range in the eastern part of the Montrose National Topographic Map Series (NTMS) quadrangle, Colorado, as part of the National Hydrogeochemical and Stream Sediment Reconnaissance (HSSR). Totals of 1034 water and 2087 sediment samples were collected from streams and springs from 2088 locations within a 5420-km 2 area. Statistical data for uranium concentrations in water and sediment samples are presented. Elemental concentration, field measurement, weather, geologic, and geographic data for each sample location are listed for waters and for sediments in appendices. Uranium/thorium ratios for sediment samples are also included. This report contains uranium analyses for water samples and multielement analyses for sediment samples. Sediments were analyzed for uranium and thorium as well as Al, Sb, As, Ba, Be, Bi, Cd, Ca, Ce, Cs, Cl, Cr, Co, Cu, Dy, Eu, Au, Hf, Fe, La, Pb, Li, Lu, Mg, Mn, Ni, Nb, K, Rb, Sm, Sc, Se, Ag, Na, Sr, Ta, Tb, Sn, Ti, W, V, Yb, Zn, and Zr. All elemental analyses were performed at the LASL. Water samples were analyzed for uranium by fluorometry. Sediments were analyzed for uranium by delayed neutron counting. Other elemental concentrations in sediments were determined by neutron activation analysis for 31 elements, by x-ray fluorescence for 12 elements, and by arc-source emission spectrography for 2 elements. Descriptions of procedures as analytical precisions and detection limits are given in the appendix

  13. On friction of Nb-Nb pair in He1 and He2

    International Nuclear Information System (INIS)

    Zinenko, S.A.; Karapetyan, S.S.; Silin, A.A.

    1990-01-01

    Peculiarities of manifestation of the effect of anomalous friction of superconductors (AFS) in He1 and He2 are studied. Helium thermodynamic state effect on the character of friction interaction of Nb-Nb pair velocity and reduction ratio for friction coefficient is studied. The intensity of heat removal released from friction contact region is estimated, the necessary and sufficient conditions for AFC effect manifestation are ascertained using characteristic relaxation time concept. Dependences for Nb-Nb pair friction coefficient in a superconducting state on the time of friction interaction in gaseous helium, He1, He2 are presented

  14. AC loss time constant measurements on Nb3Al and NbTi multifilamentary superconductors

    International Nuclear Information System (INIS)

    Painter, T.A.

    1988-03-01

    The AC loss time constant is a previously univestigated property of Nb 3 Al, a superconductor which, with recent technological developments, shows some advantages over the more commonly used superconductors, NbTi and Nb 3 Sn. Four Nb 3 Al samples with varying twist pitches and one NbTi sample are inductively measured for their AC loss time constants. The measured time constants are compared to the theoretical time constant limits imposed by the limits of the transverse resistivity found by Carr [5] and to the theoretical time constants found using the Bean Model as well as to each other. The measured time constants of the Nb 3 Al samples fall approximately halfway between the theoretical time constant limits, and the measured time constants of the NbTi sample is close to the theoretical lower time constant limit. The Bean Model adequately accounts for the variance of the permeability of the Nb 3 Al superconductor in a background magnetic field. Finally, the measured time constant values of the Nb 3 Al samples vary approximately according to the square of their twist pitch. (author)

  15. Effect of Al alloying on the martensitic temperature in Ti-Ta shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, Alberto; Rogal, Jutta; Drautz, Ralf [Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universitaet Bochum (Germany)

    2017-07-01

    Ti-Ta-based alloys are promising candidates as high temperature shape memory alloys (HTSMAs) for actuators and superelastic applications. The shape memory mechanism involves a martensitic transformation between the low-temperature α'' phase (orthorhombic) and the high-temperature β phase (body-centered cubic). In order to prevent the degradation of the shape memory effect, Ti-Ta needs to be alloyed with further elements. However, this often reduces the martensitic temperature M{sub s}, which is usually strongly composition dependent. The aim of this work is to analyze how the addition of a third element to Ti-Ta alloys affects M{sub s} by means of electronic structure calculations. In particular, it will be investigated how alloying Al to Ti-Ta alters the relative stability of the α'' and β phases. This understanding will help to identify new alloy compositions featuring both a stable shape memory effect and elevated transformation temperatures.

  16. Power trip : stumbling toward a policy for NB power

    International Nuclear Information System (INIS)

    Tucker, T.L.; Norris, B.A.

    2003-10-01

    New Brunswick Power has one of the highest debt burdens of any crown utility along with one of the highest operating costs of any publicly owned electric utility in Canada. NB Power has borrowed heavily to invest in capital projects such as the expansion of its aging Point Lepreau nuclear plant. The current assets will not generate sufficient revenues to recover the investment. Kyoto requirements to reduce emissions have placed additional financial strain on the utility. It must also ensure funds for the eventual decommissioning of its nuclear facility. The utility's high operating costs are due to the high cost of coal used in its thermal generating plants. Since the utility relies on nuclear energy for 40 per cent of its output, it must maintain a high and costly reserve capacity in case the nuclear facility shuts down. In 2002, the government of New Brunswick announced plans to reorganize NB Power by creating a parent holding company with separate business units responsible for power generation, nuclear generation, power transmission, power distribution and customer service. A system operator will supervise access to the transmission system. The author argued that the restructuring will not address the problem of excessive costs and high debt. The NB Electric Finance Corporation will be created to service and retire the province's portion of the utility's debt. Instead of taxes and dividends on its equity position, NB Power will make payments to achieve the debt repayment. The restructured utility will still have to generate sufficient revenues to meet expenses. The following recommendations were presented: the government should privatize NB Power to cap taxpayers' debt liability; the government should assume an appropriate protion of the stranded debt liabilities to attract private investors to purchase the utility; electricity rates should be allowed to rise over time to reflect the real cost of operating the system; and, the government should open both the

  17. Surface Treatments of Nb by Buffered Electropolishing

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Andy T. [JLAB; Rimmer, Robert A. [JLAB; Ciovati, Gianluigi [JLAB; Manus, Robert L. [JLAb; Reece, Charles E. [JLAB; Williams, J. S. [JLAB; Eozénou, F. [CEA, Gif-sur-Yvette; Jin, S. [PKU/IHIP, Beijing; Lin, L. [PKU/IHIP, Beijing; Lu, X.Y. [PKU/IHIP, Beijing; Mammosser, John D. [JLAB; Wang, E. [BNL

    2009-11-01

    Buffered electropolishing (BEP) is a Nb surface treatment technique developed at Jefferson Lab1. Experimental results obtained from flat Nb samples show2-4 that BEP can produce a surface finish much smoother than that produced by the conventional electropolishing (EP), while Nb removal rate can be as high as 4.67 μm/min. This new technique has been applied to the treatments of Nb SRF single cell cavity employing a vertical polishing system5 constructed at JLab as well as a horizontal polishing system at CEA Saclay. Preliminary results show that the accelerating gradient can reach 32 MV/m for a large grain cavity and 26.7 MV/m for a regular grain cavity. In this presentation, the latest progresses from the international collaboration between Peking University, CEA Saclay, and JLab on BEP will be summarized.

  18. Trace-Element Evidence for an Aqueous Atmospheric Origin of Desert Varnish: implications for the aqueous atmospheric input flux into the ocean

    Science.gov (United States)

    Thiagarajan, N.; Lee, C.

    2003-12-01

    Desert varnish is a slow-growing dark patina commonly found on rock surfaces in arid environments. Varnishes consist of about 30% Mn and Fe oxides accompanied by oxides of Si, Al, Mg, K and Ca, which occur primarily in the form of clays. Although it is generally agreed that varnishes have an atmospheric origin, their exact formation mechanism remains highly debated. Two endmember hypotheses are gradual accumulation of wind-blown dust followed by diagenesis, and direct chemical precipitation of dissolved elements from atmospheric aerosols. To rule out one of these hypotheses, we investigated the trace-element systematics of varnishes, in particular, focusing on those elements that have contrasting solubilities in aqueous environments. If our trace element analyses are consistent with the varnishes being derived from dissolved atmospheric constituents then the data can be used to quantify the paleofluxes of the soluble fraction of atmospheric aerosols to various depositional environments. For example, this will have implications for the transport of metals to the ocean that are immediately biologically available. We collected varnishes deposited on smooth basaltic lava flow surfaces in the Cima Volcanic Field (Mojave Desert) and in Death Valley, California. The chosen lava flows retain original flow surface structure and are topographical highs; the effects of erosion are hence minimal. Varnishes were scraped off with a quartz rod to minimize trace element contamination and the trace element compositions were then determined by ICP-MS using an external synthetic standard for calibration. Our analyses show that the rare-earth elements (REEs), Co, Ni, and Pb are enriched 1.5 to 10 times relative to the upper continental crust (UCC) and that Nb, Ti, Ta, Hf, Th, Rb and Cs are depleted to varying degrees relative to UCC and the REEs. These fractionations can be explained by their differing chemical behaviors in aqueous environments. The extreme depletion in Rb and Cs

  19. Oxidation behavior of U-2wt%Nb, Ti, and Ni alloys in air

    International Nuclear Information System (INIS)

    Ju, J. S.; Yoo, K. S.; Jo, I. J.; Gug, D. H.; Su, H. S.; Lee, E. P.; Bang, K. S.; Kim, H. D.

    2003-01-01

    For the long term storage safety study of the metallic spent fuel, U-Nb, U-Ti, U-Ni, U-Zr, and U-Hf simulated metallic uranium alloys, known as corrosion resistant alloys, were fabricated and oxidized in oxygen gas at 200 .deg. C-300 .deg. C. Simulated metallic uranium alloys were more corrosion resistant than pure uranium metal, and corrosion resistance increases Nb, Ni, Ti in that order. The oxidation rates of uranium alloys determined and activation energy was calculated for each alloy. The matrix microstructure of the test specimens were analyzed using OM, SEM, and EPMA. It was concluded that Nb was the best acceptable alloying elements for reducing corrosion of uranium metal considered to suitable as candidate

  20. Smooth Nb surfaces fabricated by buffered electropolishing

    International Nuclear Information System (INIS)

    Wu, Andy T.; Mammosser, John; Phillips, Larry; Delayen, Jean; Reece, Charles; Wilkerson, Amy; Smith, David; Ike, Robert

    2007-01-01

    It was demonstrated that smooth Nb surfaces could be obtained through buffered electropolishing (BEP) employing an electrolyte consisting of lactic, sulfuric, and hydrofluoric acids. Parameters that control the polishing process were optimized to achieve a smooth surface finish. The polishing rate of BEP was determined to be 0.646 μm/min which was much higher than 0.381 μm/min achieved by the conventional electropolishing (EP) process widely used in the superconducting radio frequency (SRF) community. Root mean square measurements using a 3D profilometer revealed that Nb surfaces treated by BEP were an order of magnitude smoother than those treated by the optimized EP process. The chemical composition of the Nb surfaces after BEP was analyzed by static and dynamic secondary ion mass spectrometry (SIMS) systems. SIMS results implied that the surface oxide structure of Nb might be more complicated than what usually believed and could be inhomogeneous. Preliminary results of BEP on Nb SRF single cell cavities and half-cells were reported. It was shown that smooth and bright surfaces could be obtained in 1800 s when the electric field inside a SRF cavity was uniform during a BEP process. This study showed that BEP is a promising technique for surface treatment on Nb SRF cavities to be used in particle accelerators

  1. Characterization and modification of the interface of superconducting Nb/Cu cavities by ion beams

    International Nuclear Information System (INIS)

    El Bouanani, M.

    1990-05-01

    Radiofrequency superconducting Nb/Cu cavities for electron beam acceleration are studied in a collaboration between CEA and IN2P3 (CNRS). The quality of superconducting cavity is closely related to the purity of the surface material. In such an aim, carbon and oxygen contaminations at the surface and at the interface of the Nb/Cu device has been measured. Since the niobium film is deposited on copper by magnetron sputtering under argon atmosphere, argon analysis is performed using the resonance in the nuclear reaction Ar 40 (p,γ) 41 K at the proton energy of 1102 keV. In order to simulate the energy deposition occurring during particle acceleration, Nb/Cu samples have been irradiated with a 600 keV argon beam. The element distribution evolution is then followed by RBS and NBS. Ion beam mixing effect in the case of samples with oxygen interface contamination (Nb/Nb + Ox + Cu/Cu) is shown to be enhanced [fr

  2. Synthesis and structure changes during mechanical alloying of Nb22Ti15Al alloy

    International Nuclear Information System (INIS)

    Rozmus, M.; Blicharski, M.; Dymek, S.

    2004-01-01

    The main aim of this work was an attempt to employ mechanical allowing to synthesise an intermetallic-based Nb22Ti15Al alloy which would exhibited better mechanical properties than its counterparts produced by other methods and to investigate structure changes during mechanical alloying and during annealing and consolidation. The material investigated in this study was produced by mechanical alloying of pure elemental powders of Nb, Ti, and Al. The morphology and structure changes during milling, annealing and consolidation were examined using a scanning electron microscope and the X-ray diffractometer with CoK α radiation. The power was also characterized by microhardness measurements. The mechanical alloying resulted in the formation of Nb solid solution. Intermetallic phases appeared during annealing and consolidation of powder. Influence of consolidation temperature on the phase content was established. The increase in consolidation temperature resulted in the nucleation of the brittle Nb 2 Al phase. It has been shown that mechanical alloying followed by hot pressing is a viable processing route for intermetallics Nb-Ti-Al. (author)

  3. Corrosion behavior of Zr-x(Nb, Sn and Cu) binary alloys

    International Nuclear Information System (INIS)

    Kim, M. H.; Lee, M. H.; Park, S. Y.; Jung, Y. H.; We, M. Y.

    1999-01-01

    For the development of advanced zirconium alloys for nuclear fuel cladding, the corrosion behaviors of zirconium binary alloys were studied on the Zr-xNb, Zr-xSn, and Zr-xCu alloys. The corrosion test were performed in water at 360 deg C, steam at 400 deg C and LiOH at 360 deg C for 45 days. The corrosion behaviors of Zr-xNb was similar to that of Zr-xCu alloys. However, the corrosion behavior of Zr-xSn was different from Zr-xNb and Zr-xCu. The weight gain of Zr-xNb and Zr-xCu was increased with addition of alloying elements. When Sn is added to Zr matrix in range below the solubility limit, the corrosion resistance decrease with increasing Sn-content, while in the range over solubility limit, Sn has an adverse effect on the corrosion resistance. Especially, Zr-xSn alloys showed higher corrosion resistance than Zr-xNb and Zr-xCu alloys in LiOH solution

  4. Use of INAA and ICP-MS for the assessment of trace element mass fractions in adult and geriatric prostate

    International Nuclear Information System (INIS)

    Vladimir Zaichick; Sofia Zaichick; Northwestern University, Chicago, IL

    2014-01-01

    The variation with age of the mass fraction of 54 trace elements (Ag, Al, As, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cs, Dy, Er, Eu, Fe, Ga, Gd, Hf, Hg, Ho, Ir, La, Li, Lu, Mn, Mo, Nb, Nd, Ni, Pb, Pd, Pr, Pt, Rb, Re, Sb, Sc, Se, Sm, Sn, Ta, Tb, Te, Th, Ti, Tl, Tm, U, Y, Yb, Zn, and Zr) in intact nonhyperplastic prostate of 65 healthy 21-87 year old males was investigated by instrumental neutron activation analysis with high resolution spectrometry of long-lived radionuclides and inductively coupled plasma mass spectrometry. This work revealed that there is a significant tendency for an increase in Bi, Cd, Co, Fe, Hg, Sc, Sn, Th, U, and Zn (p < 0.0014) mass fraction in normal prostate from age 21 years to the sixth decade. In the sixth to ninth decades the mass fractions of almost all chemical elements investigated in nonhyperplastic prostates were maintained at approximately stable levels. Our finding of correlation between pairs of prostatic chemical element mass fractions indicates that there is a great disturbance of prostatic chemical element relationships with increasing age. (author)

  5. Diffusivities of Redox-Sensitive Elements in Basalt vs. Oxygen Fugacity Determined by LA-ICP-MS

    Science.gov (United States)

    Szumila, Ian; Danielson, Lisa; Trail, Dustin

    2017-01-01

    Several diffusion experiments were conducted in a piston cylinder device across a range of oxygen fugacities (FMQ-3 FMQ-1.2, FMQ+6) at 1 GPa and 1300 C. This was done to explore the effects of oxygen fugacity (fO2) on diffusivity of redox sensitive trace elements. This allows investigation of how these elements diffuse across the fO2 range encountered in different reservoirs on planets and moons in our solar system. The University of Rochester LA-ICP-MS system was used for analysis of samples. Analyses were conducted using an Agilent 7900 quadrupole mass spectrometer connected to a Photon Machines 193 nm G2 laser ablation (LA) system equipped with a HelEx 2-volume sample chamber. Spots used were 35 micrometers circles spaced at 65 micrometers intervals. Laser fluence was 7.81 J/cm^2 with a rep rate of 10 Hz. The iolite software package was used to reduce data collected from laser ablation analysis of experiments with Si-29 used as the internal standard isotope. Iolite's global fit module was used to simultaneously fit elements' diffusivities in each experiment while keeping the Matano interface constant. Elements analysed include V, Nb, W, Mo, La, Ce, Pr, Sm, Eu, Gd, Ta, and W. Figures

  6. Three types of element fluxes from metabasite into peridotite in analogue experiments: Insights into subduction-zone processes

    Science.gov (United States)

    Perchuk, A. L.; Yapaskurt, V. O.; Griffin, W. L.; Shur, M. Yu.; Gain, S. E. M.

    2018-03-01

    Piston-cylinder experiments with natural rocks and mineral separates were carried out at 750-900 °C and 2.9 GPa, conditions relevant to hot subduction zones, to study the mechanisms of metasomatic alteration of mantle-wedge rocks such as dunite and lherzolite, and the transfer of trace elements released from a carbonate-bearing amphibolite during its eclogitization. Element transfer from the slab to the mantle lithologies occurred in porous-, focused- and diffusive-flow regimes that remove melt and carbon, and partially water, from the metabasite layer. Porous flow is recorded by dissolution of clinopyroxene and growth of orthopyroxene ± garnet ± magnesite ± chlorite along grain boundaries in the peridotite layers, but is invisible in the metabasite layers. Porous flow of the same fluids/melts produces harzburgite mineralogy in both dunite and lherzolite. The transformation of lherzolite to harzburgite reflects breakdown of clinopyroxene in the lherzolite and diffusion of the liberated calcium into the metabasite layer, i.e. against the direction of major fluid/melt flow. Focused flow develops along the side walls of the capsules, producing a melt-free omphacite ± phengite ± quartz paragenesis in the metabasite, and melt segregations, separated from the host peridotite layers by newly-formed omphacite ± garnet ± phlogopite + orthopyroxene + magnesite. Diffusive flow leads to the formation of orthopyroxene ± magnesite ± garnet reaction zones at the metabasite-peridotite interface and some melt-peridotite interfaces. Melt segregations in the peridotite layers at 850-900 °C are rich in LREE and LILE, strongly depleted in Y and HREE, and have higher Sr/Y and La/Yb ratios than island arc andesites, dacites and rhyolites. These features, and negative anomalies in Nb-Ta and low Nb/Ta, resemble those of high-silica adakites and TTGs, but K2O is high compared to TTGs. Metasomatism in the dunite layer changes the REE patterns of dunite, recording chromatographic

  7. Growth and surface characterization of TiNbZr thin films deposited by magnetron sputtering for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Tallarico, D.A. [Federal University of Sao Carlos, Materials Science and Engineering Graduation Program, Via Washington Luis km 235, CEP 13565-905 Sao Carlos, SP (Brazil); Gobbi, A.L. [Brazilian Nanotechnology National Laboratory, Rua Giuseppe Máximo Scolfaro 10.000, CEP 13083-100 Campinas, SP (Brazil); Paulin Filho, P.I. [Federal University of Sao Carlos, Department of Materials Engineering, Via Washington Luis km 235, CEP 13565-905 Sao Carlos, SP (Brazil); Maia da Costa, M.E.H. [Pontifical Catholic University of Rio de Janeiro, Department of Physics, CEP 22451-900 Rio de Janeiro, RJ (Brazil); Nascente, P.A.P., E-mail: nascente@ufscar.br [Federal University of Sao Carlos, Department of Materials Engineering, Via Washington Luis km 235, CEP 13565-905 Sao Carlos, SP (Brazil)

    2014-10-01

    Low modulus of elasticity and the presence of non-toxic elements are important criteria for the development of materials for implant applications. Low modulus Ti alloys can be developed by designing β-Ti alloys containing non-toxic alloying elements such as Nb and Zr. Actually, most of the metallic implants are produced with stainless steel (SS) because it has adequate bulk properties to be used as biomaterials for orthopedic or dental implants and is less expensive than Ti and its alloys, but it is less biocompatible than them. The coating of this SS implants with Ti alloy thin films may be one alternative to improve the biomaterial properties at a relatively low cost. Sputtering is a physical deposition technique that allows the formation of nanostructured thin films. Nanostructured surfaces are interesting when it comes to the bone/implant interface due to the fact that both the surface and the bone have nanoscale particle sizes and similar mechanical properties. TiNbZr thin films were deposited on both Si(111) and stainless steel (SS) substrates. The TiNbZr/Si(111) film was used as a model system, while the TiNbZr/SS film might improve the biocompatibility and extend the life time of stainless steel implants. The morphology, chemical composition, Young's modulus, and hardness of the films were analyzed by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), and nanoindentation. - Highlights: • TiNbZr thin films were deposited on Si(111) and stainless steel (SS). • Their Young's modulus differences are within 5.3% and hardness 1.7%. • TiNbZr/SS film chemical composition remained almost constant with depth. • TiNbZr films presented nanostructured grains and low roughness for substrates. • TiNbZr/SS film hardness was about 100% greater than the SS substrate hardness.

  8. Growth and surface characterization of TiNbZr thin films deposited by magnetron sputtering for biomedical applications

    International Nuclear Information System (INIS)

    Tallarico, D.A.; Gobbi, A.L.; Paulin Filho, P.I.; Maia da Costa, M.E.H.; Nascente, P.A.P.

    2014-01-01

    Low modulus of elasticity and the presence of non-toxic elements are important criteria for the development of materials for implant applications. Low modulus Ti alloys can be developed by designing β-Ti alloys containing non-toxic alloying elements such as Nb and Zr. Actually, most of the metallic implants are produced with stainless steel (SS) because it has adequate bulk properties to be used as biomaterials for orthopedic or dental implants and is less expensive than Ti and its alloys, but it is less biocompatible than them. The coating of this SS implants with Ti alloy thin films may be one alternative to improve the biomaterial properties at a relatively low cost. Sputtering is a physical deposition technique that allows the formation of nanostructured thin films. Nanostructured surfaces are interesting when it comes to the bone/implant interface due to the fact that both the surface and the bone have nanoscale particle sizes and similar mechanical properties. TiNbZr thin films were deposited on both Si(111) and stainless steel (SS) substrates. The TiNbZr/Si(111) film was used as a model system, while the TiNbZr/SS film might improve the biocompatibility and extend the life time of stainless steel implants. The morphology, chemical composition, Young's modulus, and hardness of the films were analyzed by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), and nanoindentation. - Highlights: • TiNbZr thin films were deposited on Si(111) and stainless steel (SS). • Their Young's modulus differences are within 5.3% and hardness 1.7%. • TiNbZr/SS film chemical composition remained almost constant with depth. • TiNbZr films presented nanostructured grains and low roughness for substrates. • TiNbZr/SS film hardness was about 100% greater than the SS substrate hardness

  9. Direct Electrolytic Reduction of Solid Ta2O5 to Ta with SOM Process

    Science.gov (United States)

    Chen, Chaoyi; Yang, Xiaqiong; Li, Junqi; Lu, Xionggang; Yang, Shufeng

    2016-06-01

    A process that uses the solid-oxide-oxygen-ion conducting membrane has been investigated to produce tantalum directly from solid Ta2O5 in molten CaCl2 or a molten mixture of 55.5MgF2-44.5CaF2 (in wt pct). The sintered porous Ta2O5 pellet was employed as the cathode, while the liquid copper alloy, saturated with graphite powder and encased in a one-end-closed yttria-stabilized-zirconia (YSZ) tube, acted as the anode. The electrolysis potential in this method is higher than that of the Fray-Farthing-Chen Cambridge process because the YSZ membrane tube blocks the melts to electrolyze, and only Ta2O5 is will be electrolyzed. The microstructures of reduced pellets and a cyclic voltammogram of solid Ta2O5 in molten CaCl2 were analyzed. In addition, the influence of particle size and porosity of the cathode pellets on metal-oxide-electrolyte, three-phase interlines was also discussed. The results demonstrate that the sintering temperature of cathode pellets and electrolytic temperature play important roles in the electrochemical process. Furthermore, this process can be used to produce Ta metal efficiently without the expensive cost of pre-electrolysis and generation of harmful by-products.

  10. High-qualitative face Josephson transitions Nb-Sisup(ast)-Nb

    International Nuclear Information System (INIS)

    Gudkov, A.L.; Likharev, K.K.; Makhov, V.I.

    1985-01-01

    Preliminary results of investigation into characteristics of face transitions on the basis of refractory materials (niobium and polycrystalline silicon) are reported. Measured values of characteristic voltage and normal resistance are given; typical current-voltage characteristics of Josephson transitions Nb-Sisub(*)-Nb are presented too

  11. Proximity effect Nb/Al,AlOxide, Al/Nb Josephson tunnel junctions

    NARCIS (Netherlands)

    Houwman, Evert Pieter; Gijsbertsen, J.G.; Gijsbertsen, Hans; Flokstra, Jakob; Rogalla, Horst; Le grand, J.B.; de Korte, P.A.J.; Golubov, Alexandre Avraamovitch

    1993-01-01

    Regions with reduced energy gap induced by the proximity effect give rise to quasi-particle loss in Josephson-junction X-ray detectors, but may also be used advantageously for quasi-particle collection. The influence of the thickness of the Al proximity layers in Nb/Al1 , AlOx, Al2/Nb Josephson

  12. Deposition and characterization of TaAIN thin films by reactive magnetron sputtering; Deposicao e caracterizacao de filmes finos de TaAIN depositados por magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, G.B.; Fernandez, D.R.; Fontes Junior, A.S.; Felix, L.C.; Tentardini, E.K. [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Departamento de Ciencia e Engenharia de Materiais; Hubler, R. [Pontificia Universidade Catolica do Rio Grande do Sul (PUC-RS), RS (Brazil); Silva Junior, A.H. da, E-mail: brito-g@hotmail.com [Universidade Federal do Rio Grande do Sul (UFRGS), RS (Brazil)

    2016-07-01

    Phase stability, oxidation resistance and great mechanical properties are the main objectives when synthesizing protective coatings. The tantalum nitride (TaN) has aroused interest because of its high temperature stability, chemical inertness and thermal conductivity. However, it has a low hardness value when compared to other coatings. Researches has shown that one way to improvements in the properties of a thin film is by adding other elements in the deposition process. Therefore, the objective of this study was to deposit thin films of TaAlN by magnetron sputtering, changing the aluminum concentration of 2, 5, 7, to 14%. Then the coatings were characterized by EDS, RBS, GIXRD and nanohardness. In this study was found that the aluminum deposited did not change the oxidation resistance of the coating, and the highest value of hardness was 28 GPa for the sample with 14 at.%. (author)

  13. Nanometer-scale separation of d(10) Zn(2+)-layers and twin-shift competition in Ba8ZnNb6O24-based 8-layered hexagonal perovskites.

    Science.gov (United States)

    Lu, Fengqi; Wang, Xiaoming; Pan, Zhengwei; Pan, Fengjuan; Chai, Shiqiang; Liang, Chaolun; Wang, Quanchao; Wang, Jing; Fang, Liang; Kuang, Xiaojun; Jing, Xiping

    2015-08-07

    The 8-layered shifted hexagonal perovskite compound Ba8ZnNb6O24 was isolated via controlling the ZnO volatilization, which features long-range B-cation ordering with nanometer-scale separation by ∼1.9 nm of octahedral d(10) cationic (Zn(2+)) layers within the purely corner-sharing octahedral d(0) cationic (Nb(5+)) host. The long-range ordering of the B-site vacancy and out-of-center distortion of the highly-charged d(0) Nb(5+) that is assisted by the second-order Jahn-Teller effect contribute to this unusual B-cation ordering in Ba8ZnNb6O24. A small amount (∼15%) of d(10) Sb(5+) substitution for Nb(5+) in Ba8ZnNb6-xSbxO24 dramatically transformed the shifted structure to a twinned structure, in contrast with the Ba8ZnNb6-xTaxO24 case requiring 50% d(0) Ta(5+) substitution for Nb(5+) for such a shift-to-twin transformation. Multiple factors including B-cationic sizes, electrostatic repulsion forces, long-range ordering of B-site vacancies, and bonding preferences arising from a covalent contribution to the B-O bonding that includes out-of-center octahedral distortion and the B-O-B bonding angle could subtly contribute to the twin-shift phase competition of B-site deficient 8-layered hexagonal perovskites Ba8B7O24. The ceramics of new shifted Ba8ZnNb6O24 and twinned Ba8ZnNb5.1Sb0.9O24 compounds exhibited good microwave dielectric properties (εr ∼ 35, Qf ∼ 36 200-43 400 GHz and τf ∼ 38-44 ppm/°C).

  14. Ferroelectric properties of lead-free polycrystalline CaBi2Nb2O9 thin films on glass substrates

    Science.gov (United States)

    Ahn, Yoonho; Jang, Joonkyung; Son, Jong Yeog

    2016-03-01

    CaBi2Nb2O9 (CBNO) thin film, a lead-free ferroelectric material, was prepared on a Pt/Ta/glass substrate via pulsed laser deposition. The Ta film was deposited on the glass substrate for a buffer layer. A (115) preferred orientation of the polycrystalline CBNO thin film was verified via X-ray diffraction measurements. The CBNO thin film on a glass substrate exhibited good ferroelectric properties with a remnant polarization of 4.8 μC/cm2 (2Pr ˜9.6 μC/cm2), although it had lower polarization than the epitaxially c-oriented CBNO thin film reported previously. A mosaic-like ferroelectric domain structure was observed via piezoresponse force microscopy. Significantly, the polycrystalline CBNO thin film showed much faster switching behavior within about 100 ns than that of the epitaxially c-oriented CBNO thin film.

  15. Processing and structure/property relations in Ba(Zn sub 1 sub / sub 3 Ta sub 2 sub / sub 3)O sub 3 microwave ceramics

    CERN Document Server

    Qazi, I

    2001-01-01

    Microwave filters utilize extensively, complex perovskite barium zinc tantalate ceramics, due to their superior selectivity and near zero temperature coefficient. A study of Ba sub 1 sub - sub x Sr sub x [Zn sub 1 sub / sub 3 (Ta sub 1 sub - sub y Nb sub y) sub 2 sub / sub 3]O sub 3 (BSZNT) synthesised by a mixed oxide route was conducted to understand the relationship between structure/microstructure and dielectric properties. Densities >95% and 97Vo were achieved in undoped (x=0 y=0) and Sr sup + sup 2 and or Nb sup + sup 5 doped Ba(Zn sub 1 sub / sub 3 Ta sub 2 sub / sub 3)O sub 3 (BZT) respectively. The investigation found a reversible order-disorder phase transition in pure barium zinc tantalate at approx 1600 degC. X-ray diffraction (XRD) showed a disordered cubic phase above, and an ordered trigonal-phase below, 1600 degC. Thermogravimetric analysis detected weight loss due to zinc oxide evaporation beginning at approximately 1200 degC. Thus, non-perovskite phases such BaTa sub 2 O sub 6 , observed as ...

  16. NbN/MgO/NbN SIS tunnel junctions for submm wave mixers

    Science.gov (United States)

    Stern, J. A.; Hunt, B. D.; Leduc, H. G.; Judas, A.; Mcgrath, W. R.; Cypher, S. R.; Khanna, S. K.

    1989-01-01

    The authors report on the fabrication and testing of all-refractory NbN/MgO/NbN SIS (superconductor-insulator-superconductor) tunnel junctions for use as high-frequency mixers. Progress in the development of techniques for the fabrication of submicron-area tunnel junctions is described. Junction structures which have been investigated include mesa, crossline, and edge geometries. Using reactive sputtering techniques, NbN tunnel junctions with critical currents in excess of 104 A/sq cm have been fabricated with Vm values as high as 65 mV and areas down to 0.1 sq micron. Specific capacitance measurements on NbN/MgO/NbN mesa-type tunnel junctions give values in the range 60-90 fF/sq micron. These SIS tunnel junctions have been integrated with antennas and coupling structures for mixer tests in a waveguide receiver at 207 GHz. Preliminary mixer results are reported.

  17. 3-D MnNb2O6 nanogears from 1-D Nb2O5 nanorods

    International Nuclear Information System (INIS)

    Hu Weibing; Cui Zhicai; Mi Yuanzhu

    2012-01-01

    Graphical abstract: The geometry morphology of Nb-based nanomaterial evolved from long Nb 2 O 5 nanorods to a mixture of short Nb 2 O 5 nanorods and MnNb 2 O 6 6-teeth nanogears, and eventually to fully developed pure 3-D nanogears. Highlights: ► MnNb 2 O 6 nanogears have been generated by a simple solvothermal process when the Mn: Nb ratio was 1:1. ► MnNb 2 O 6 6-teeth nanogears accompanied with MnNb 2 O 6 5-teeth nanogears are got when the Mn:Nb ratio reached 1:2. ► The nanomaterial consists of nanorods and 6-teeth nanogears at low Mn:Nb molar ratio(1:4). ► Pure long Nb 2 O 5 nanorods are achieved by only using NbCl 5 - Abstract: MnNb 2 O 6 nanogears have been generated by using mixed NbCl 5 and MnCl 2 at an optimized ratio of 1:1 in a cyclohexanol solvent in a simple solvothermal process. It has shown that the Mn:Nb ratio determines the shape of the products. Detailed characterization by electron microscopy has shown that increasing the Mn +2 concentration during the solvo-thermal synthesis promotes a morphological evolution from relatively long Nb 2 O 5 nanorods to a mixture of short Nb 2 O 5 nanorods and MnNb 2 O 6 6-teeth nanogears, then to a mixture of short Nb 2 O 5 nanorods and more MnNb 2 O 6 6-teeth nanogears, then to more and more MnNb 2 O 6 6-teeth nanogears that are occasionally accompanied with under-developed MnNb 2 O 6 5-teeth nanogears, and eventually to fully developed pure 3-D nanogears. The driving force for such interesting geometry transformations is attributed to the inclusion of Mn 2+ into the Nb 2 O 5 template at low Mn 2+ concentrations, which introduces internal stresses to the Nb 2 O 5 nanorods. At high Mn 2+ concentrations, close to the stoichiometric composition of MnNb 2 O 6 , the formation of the gears is triggered by the intrinsic sixfold symmetry of crystalline columbite, via a combination of initial nanorod nucleation and the competing self-assembly of neighboring parallel nanorods.

  18. Separation and Recycling for Rare Earth Elements by Homogeneous Liquid-Liquid Extraction (HoLLE Using a pH-Responsive Fluorine-Based Surfactant

    Directory of Open Access Journals (Sweden)

    Shotaro Saito

    2015-08-01

    Full Text Available A selective separation and recycling system for metal ions was developed by homogeneous liquid-liquid extraction (HoLLE using a fluorosurfactant. Sixty-two different elemental ions (e.g., Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, In, Ir, La, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Os, P, Pb, Pd, Pr, Pt, Re, Rh, Ru, Sb, Sc, Se, Si, Sm, Sn, Sr, Ta, Tb, Te, Ti, Tl, Tm, V, W, Y, Yb, Zn, and Zr were examined. By changing pH from a neutral or alkaline solution (pH ≥ 6.5 to that of an acidic solution (pH < 4.0, gallium, zirconium, palladium, silver, platinum, and rare earth elements were extracted at >90% efficiency into a sedimented Zonyl FSA® (CF3(CF2n(CH22S(CH22COOH, n = 6–8 liquid phase. Moreover, all rare earth elements were obtained with superior extraction and stripping percentages. In the recycling of rare earth elements, the sedimented phase was maintained using a filter along with a mixed solution of THF and 1 M sodium hydroxide aqueous solution. The Zonyl FSA® was filtrated and the rare earth elements were recovered on the filter as a hydroxide. Furthermore, the filtrated Zonyl FSA was reusable by conditioning the subject pH.

  19. Uranium hydrogeochemical and stream sediment reconnaissance data release for the Lewistown NTMS Quadrangle, Montana, including concentrations of forty-two additional elements

    International Nuclear Information System (INIS)

    Shannon, S.S. Jr.

    1980-08-01

    Totals of 758 water and 1170 sediment samples were collected from 1649 locations in the Levistown quadrangle. Water samples were collected at streams, springs, wells, ponds, and marshes; sediment samples were obtained from streams, springs, and ponds. Histograms and statistical data for uranium concentrations in water and sediment samples and thorium concentrations in sediment samples are given. All samples were collected at the nominal reconnaissance density of one sample location per 10 km 2 . Elemental concentration, field measurement, weather, geologic, and geographic data for each sample location are listed for waters and for sediments. Uranium to thorium (U/Th) ratios for sediment samples are included. Water samples were initially analyzed for uranium by fluorometry. All water samples containing more than 40 ppB U were reanalyzed by delayed-neutron counting. Sediments were analyzed for U and Th as well as Al, Sb, Ba, Be, Bi, Cd, Ca, Ce, Cs, Cl, Cr, Co, Cu, Dy, Eu, Au, Hf, Fe, La, Pb, Li, Lu, Mg, Mn, Ni, Nb, K, Rb, Sa, Sc, Ag, Na, Sr, Ta, Tb, Sn, Ti, W, V, Yb, and Zn. All sediments were analyzed for U by delayed neutron counting. Other elemental concentrations in sediments were determined by neutron activation analysis for 31 elements, by x-ray fluorescence for 9 elements, and by arc-source emission spectrography for 2 elements. Analytical results are reported as parts per million. Descriptions of procedures used for analysis of water and sediments samples as well as analytical precisions and detection limits are given

  20. Measurements of quadrupolar interaction by perturbed angular correltion method on intercalated 2H-TaS sub(2)

    International Nuclear Information System (INIS)

    Saitovitch, H.

    1979-01-01

    This work is based on our quadrupolar interaction (QI) measurements on intercalated 2H-TaS sub(2) coumponds. As intercalating elements we used the alcalines - Li, Na, K, Cs -as well as the NH sub(3) (ammonia) and C sub(6) H sub(5) N (pyridine) molecules. The (QI) measurements were performed via the differential perturbed angular correlation (DPAC) technique, using Ta sup(181) as the probe isotope, on the hydrated and anhidrous phases of the intercalated systems. Our results happened to be in better agreement with the ionic model, one of the accepted models used to describe the intercalation process, as well as the transfered charges quantities and its distribution in the intercalated systems. And by its side the measured quantities, quadrupole interaction frequencies (QIF) and their distributions δ, contributed to support and to improve the ionic model. A strong charge dynamics between the 2H-TaS sub(2) sandwiches was observed and a relation between the (QIF) changes and amount of transfered charge (e sup(-)/Ta) was established. The attempt to specify the numerical contributions to the (QI) changes arriving from the different components of the 2H-TaS sub(2) intercalated systems put in evidence the probable orbitals involved in the systems bonds. Finally the kinetics of the intercalation process to form the 2H-TaS sub(2) (Li) sub(x) system was followed continuously by the (DPAC) measurements. (author)

  1. A highly uniform ZnO/NaTaO3 nanocomposite: Enhanced self-sensitized degradation of colored pollutants under visible light

    International Nuclear Information System (INIS)

    Xing, Guanjie; Tang, Changhe; Zhang, Bo; Zhao, Lanxiao; Su, Yiguo; Wang, Xiaojing

    2015-01-01

    In this study, a highly uniform ZnO/NaTaO 3 composite was prepared via simple hydrothermal synthesis. XRD confirmed the composite was constructed by pure cubic phase of NaTaO 3 and hexagonal phase of ZnO. SEM analysis showed that as-prepared ZnO/NaTaO 3 shaped as an irregular ginger with an obviously smaller size than that of pure ZnO without obvious agglomeration. EDS mapping demonstrated that the four elements (Na, Ta, O, Zn) in the composite were very uniformly distributed. The photocatalytic behaviors of as-prepared composites were studied in the degradation of methylene blue both under UV and visible irradiation. The bare ZnO showed the highest activity with 99.8% methylene blue (MB) photodegraded in 70 min under UV light irradiation whereas 94% photodegraded rate was achieved for ZnO/NaTaO 3 . More importantly, the uniform composite of ZnO/NaTaO 3 exhibited effective degradation of methylene blue under visible light which can be attributed to the well dyes adsorption abilities and the high efficiency of electron separation, induced by the synergistic effect between ZnO and NaTaO 3 . It is confirmed the dye rather than a semiconductor is excited under visible light irradiation and a self-sensitized photocatalytic mechanism was then proposed based on the experimental results. - Graphical abstract: Visible light photocatalytic activity of ZnO/NaTaO 3 and proposed schematic of self-sensitization directed photogradation of MB. - Highlights: • Highly uniform ZnO/NaTaO 3 photocatalysts were fabricated by hydrothermal method. • ZnO/NaTaO 3 composite exhibited effective degradation of MB under visible light. • ZnO/NaTaO 3 composite effectively promoted dye adsorption and electrons separation. • A self-sensitized photocatalytic mechanism was proposed for the degradation of dye

  2. Paleoclimate from Tree Rings of Picea morrisonicola in Ta-Ta-Chia Area of Central Taiwan

    Science.gov (United States)

    Chen, T.; Wright, W. E.; Wei, K.; Cook, E. R.

    2009-12-01

    Almost no dendrochronology has been reported internationally from Taiwan, despite the existence of many dendrochronologically appropriate tree species. In this study, we reconstruct the regional paleoclimate using a multi-century tree ring-width chronology developed from Picea morrisonicola ( the endemic Taiwan Spruce), a subtropical species growing in the Ta-Ta-Chia subalpine mountain areas of central Taiwan. Picea morrisonicola in Taiwan is the only member of the Picea genus whose distribution crosses the Tropic of Cancer. Statistical analysis of the climate signal demonstrates that both the temperature and precipitation have significant effects on tree growth.

  3. Washability and Distribution Behaviors of Trace Elements of a High-Sulfur Coal, SW Guizhou, China

    Directory of Open Access Journals (Sweden)

    Wei Cheng

    2018-02-01

    Full Text Available The float-sink test is a commonly used technology for the study of coal washability, which determines optimal separation density for coal washing based on the desired sulfur and ash yield of the cleaned coal. In this study, the float-sink test is adopted for a high-sulfur Late Permian coal from Hongfa coalmine (No.26, southwestern Guizhou, China, to investigate its washability, and to analyze the organic affinities and distribution behaviors of some toxic and valuable trace elements. Results show that the coal is difficult to separate in terms of desulfurization. A cleaned coal could theoretically be obtained with a yield of 75.50%, sulfur 2.50%, and ash yield 11.33% when the separation density is 1.57 g/cm3. Trace elements’ distribution behaviors during the gravity separation were evaluated by correlation analysis and calculation. It was found that Cs, Ga, Ta, Th, Rb, Sb, Nb, Hf, Ba, Pb, In, Cu, and Zr are of significant inorganic affinity; while Sn, Co, Re, U, Mo, V, Cr, Ni, and Be are of relatively strong organic affinity. LREE (Light rare earth elements, however, seem to have weaker organic affinity than HREE (Heavy rare earth elements, which can probably be attributed to lanthanide contraction. When the separation density is 1.60 g/cm3, a large proportion of Sn, Be, Cr, U, V, Mo, Ni, Cd, Pb, and Cu migrate to the cleaned coal, but most of Mn, Sb and Th stay in the gangue. Coal preparation provides alternativity for either toxic elements removal or valuable elements preconcentration in addition to desulfurization and deashing. The enrichment of trace elements in the cleaned coal depends on the predetermined separation density which will influence the yields and ash yields of the cleaned coal.

  4. Overexpression of the Wheat Expansin Gene TaEXPA2 Improved Seed Production and Drought Tolerance in Transgenic Tobacco Plants.

    Science.gov (United States)

    Chen, Yanhui; Han, Yangyang; Zhang, Meng; Zhou, Shan; Kong, Xiangzhu; Wang, Wei

    2016-01-01

    Expansins are cell wall proteins that are grouped into two main families, α-expansins and β-expansins, and they are implicated in the control of cell extension via the disruption of hydrogen bonds between cellulose and matrix glucans. TaEXPA2 is an α-expansin gene identified in wheat. Based on putative cis-regulatory elements in the TaEXPA2 promoter sequence and the expression pattern induced when polyethylene glycol (PEG) is used to mimic water stress, we hypothesized that TaEXPA2 is involved in plant drought tolerance and plant development. Through transient expression of 35S::TaEXPA2-GFP in onion epidermal cells, TaEXPA2 was localized to the cell wall. Constitutive expression of TaEXPA2 in tobacco improved seed production by increasing capsule number, not seed size, without having any effect on plant growth patterns. The transgenic tobacco exhibited a significantly greater tolerance to water-deficiency stress than did wild-type (WT) plants. We found that under drought stress, the transgenic plants maintained a better water status. The accumulated content of osmotic adjustment substances, such as proline, in TaEXPA2 transgenic plants was greater than that in WT plants. Transgenic plants also displayed greater antioxidative competence as indicated by their lower malondialdehyde (MDA) content, relative electrical conductivity, and reactive oxygen species (ROS) accumulation than did WT plants. This result suggests that the transgenic plants suffer less damage from ROS under drought conditions. The activities of some antioxidant enzymes as well as expression levels of several genes encoding key antioxidant enzymes were higher in the transgenic plants than in the WT plants under drought stress. Collectively, our results suggest that ectopic expression of the wheat expansin gene TaEXPA2 improves seed production and drought tolerance in transgenic tobacco plants.

  5. Limited Range Sesame EOS for Ta

    Energy Technology Data Exchange (ETDEWEB)

    Greeff, Carl William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Crockett, Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Rudin, Sven Peter [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Burakovsky, Leonid [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-30

    A new Sesame EOS table for Ta has been released for testing. It is a limited range table covering T ≤ 26, 000 K and ρ ≤ 37.53 g/cc. The EOS is based on earlier analysis using DFT phonon calculations to infer the cold pressure from the Hugoniot. The cold curve has been extended into compression using new DFT calculations. The present EOS covers expansion into the gas phase. It is a multi-phase EOS with distinct liquid and solid phases. A cold shear modulus table (431) is included. This is based on an analytic interpolation of DFT calculations.

  6. The Effects of Al and Ti Additions on the Structural Stability, Mechanical and Electronic Properties of D8m-Structured Ta5Si3

    Directory of Open Access Journals (Sweden)

    Linlin Liu

    2016-05-01

    Full Text Available In the present study, the influence of substitutional elements (Ti and Al on the structural stability, mechanical properties, electronic properties and Debye temperature of Ta5Si3 with a D8m structure were investigated by first principle calculations. The Ta5Si3 alloyed with Ti and Al shows negative values of formation enthalpies, indicating that these compounds are energetically stable. Based on the values of formation enthalpies, Ti exhibits a preferential occupying the Ta4b site and Al has a strong site preference for the Si8h site. From the values of the bulk modulus (B, shear modulus (G and Young’s modulus (E, we determined that both Ti and Al additions decrease both the shear deformation resistance and the elastic stiffness of D8m structured Ta5Si3. Using the shear modulus/bulk modulus ratio (G/B, Poisson’s ratio (υ and Cauchy’s pressure, the effect of Ti and Al additions on the ductility of D8m-structured Ta5Si3 are explored. The results show that Ti and Al additions reduce the hardness, resulting in solid solution softening, but improve the ductility of D8m-structured Ta5Si3. The electronic calculations reveal that Ti and Al additions change hybridization between Ta-Si and Si-Si atoms for the binary D8m-structured Ta5Si3. The new Ta-Al bond is weaker than the Ta-Si covalent bonds, reducing the covalent property of bonding in D8m-structured Ta5Si3, while the new strong Ti4b-Ti4b anti-bonding enhances the metallic behavior of the binary D8m-structured Ta5Si3. The change in the nature of bonding can well explain the improved ductility of D8m-structured Ta5Si3 doped by Ti and Al. Moreover, the Debye temperatures, ΘD, of D8m-structured Ta5Si3 alloying with Ti and Al are decreased as compared to the binary Ta5Si3.

  7. A comparative study of the sensitivities of Salmonella typhimurium strains TA 98, TA 100 and TA 102 to hospital waste waters.

    Science.gov (United States)

    Gupta, Preeti; Mathur, P; Mathur, N; Aarya, B

    2014-07-01

    Hospitals are a release source of many chemical compounds in their wastewaters. In the present study Salmonella typhimurium strains TA 98, TA 100 and TA 102 were analyzed for their sensitivity to hospital waste waters. The results of the study showed that hospital waste waters consists of mutagens causing frame shift mutations and base pair substitutions and amongst the three strains used in this study, TA 102 was most effective which along with TA 98 can be used for quick assessment of genotoxicity of hospital waste waters prior to its discharge. Genotoxic potential of hospital waste waters from five major hospitals located in Jaipur and Delhi was studied. Such waste waters should be treated prior to their discharge. The results of this study call for further detailed study in this area of research.

  8. Microstructure and mechanical properties of Nb15Al10Ti alloy produced by mechanical alloying and high temperature processing.

    Science.gov (United States)

    Rozmus, M; Blicharski, M; Dymek, S

    2010-03-01

    In this work, an Nb15Al10Ti alloy produced by mechanical alloying was investigated. The milling of elemental powders of Nb, Al as well as TiAl intermetallic phase resulted in the formation of homogenous niobium solid solution, Nb(ss), and refinement of powder particles. Powder after milling was consolidated by conventional hot pressing at 1300 degrees C under pressure of 25 MPa as well as by hot isostatic pressing at 1200 degrees C under pressure of 1 GPa. Microstructure of consolidated material was examined by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. Materials after consolidation were composed of three phases: niobium solid solution Nb(ss), Nb(3)Al intermetallic phase and titanium oxide dispersoid TiO. The analysis of the mechanical properties indicated that both refinement of microstructure as well as introduction of ductile Nb(ss) into the microstructure contributed to very high yield strength and fracture toughness satisfactory for this strength.

  9. Optically induced inductance modulation of a Nb coil

    International Nuclear Information System (INIS)

    Nam, S.W.; Park, G.S.; Cabrera, B.; Huber, M.E.

    1994-01-01

    The authors have designed and tested an optically driven inductance modulator, for use as part of a 1/f noise reduction scheme for SQUID magnetometers. The modulated element is a Nb coil photolithographically patterned on a 6x6 nm silicon chip. The coil is covered by three concentric superconducting washers, patterned from a layer of PbInAu deposited above the Nb. Leads from the washers extend to a meander region directly below an optical fiber, which is coupled to a diode laser. With the laser off, the superconducting washer loops diamagnetically shield the coil, and the coil has a low effective inductance. With the laser on, the meander is driven normal and the superconducting washer loops are open, greatly reducing the shielding. The coil then has a high effective inductance. The inductance is measured using a SQUID connected to the coil. Using this method, they have modulated the coil inductance from 2 μH to nearly 20 μH. By using four of these inductance modulators, they plan to fabricate a low-noise chopping network at the input of a SQUID, which can be used to reduce the 1/f noise in SQUID measurements

  10. Aqueous corrosion behaviour of Zr-1 Nb and Zr-20 Nb with different heat treatments

    International Nuclear Information System (INIS)

    Jaime Solis, F.; Bordoni, Roberto; Olmedo, Ana M.; Villegas, Marina; Miyagusuku, Marcela

    2003-01-01

    The corrosion behaviour of Zr-1 Nb and Zr-20 Nb coupons annealed at 850 C degrees during 1 hour and afterwards aged at different temperatures and time periods was studied. The Zr-1 Nb samples were aged at 400 and 500 C degrees and the Zr-20 Nb samples at 265 and 550 C degrees. The results have shown that ageing increases the corrosion resistance because the aged microstructure is somewhat closer to the equilibrium one. This was not the case of Zr-1 Nb aged 72 hs at 400 C degrees. The presence of the ω-phase does not have a deleterious effect in the corrosion behaviour of Zr-20 Nb. Also, an ageing of 2200 h at 265 C degrees induced a relevant decrease in the corrosion rate of Zr-20 Nb indicating a decomposition of the β- Zr phase. This effect was observed at the inlet of pressure tubes in CANDU reactors. The results obtained will be used to establish the relative importance of the α-Zr and β-Zr phases in the corrosion behaviour of pressure tubes. (author)

  11. Paramagnetic Meissner effect in conventional Nb superconductors

    International Nuclear Information System (INIS)

    Thompson, D.J.; Wenger, L.E.; Chen, J.T.

    1996-01-01

    The paramagnetic Meissner effect (PME), in which the field-cooled-magnetization (FCM) of superconducting samples is positive below the superconducting transition temperature T c , has been observed in certain ceramic and single-crystal samples of the high-T c cuprate superconductors and more recently in disk-shaped Nb samples. Through systematic investigations of the conditions for observing the PME in Nb disks, various surface treatments to the Nb disks were found to change both the zero-field-cooled-magnetization (ZFCM) and the FCM, including the appearance of a positive FCM in samples previously not exhibiting the PME as well as the elimination of the PME through surface abrasion. These results suggest that the PME arises from the field distributions created by the flux pinning associated with microstructural defects on the surface layer of the disk

  12. An experimental study of the partitioning of trace elements between rutile and silicate melt as a function of oxygen fugacity.

    Science.gov (United States)

    Mallmann, Guilherme; Fonseca, Raúl O C; Silva, Adolfo B

    2014-12-01

    Subduction zone or arc magmas are known to display a characteristic depletion of High Field Strength Elements (HFSE) relative to other similarly incompatible elements, which can be attributed to the presence of the accessory mineral rutile (TiO2) in the residual slab. Here we show that the partitioning behavior of vanadium between rutile and silicate melt varies from incompatible (∼0.1) to compatible (∼18) as a function of oxygen fugacity. We also confirm that the HFSE are compatible in rutile, with D(Ta)> D(Nb)> (D(Hf)>/∼ D(Zr), but that the level of compatibility is strongly dependent on melt composition, with partition coefficients increasing about one order of magnitude with increasing melt polymerization (or decreasing basicity). Our partitioning results also indicate that residual rutile may fractionate U from Th due to the contrasting (over 2 orders of magnitude) partitioning between these two elements. We confirm that, in addition to the HFSE, Cr, Cu, Zn and W are compatible in rutile at all oxygen fugacity conditions.

  13. An experimental study of the partitioning of trace elements between rutile and silicate melt as a function of oxygen fugacity

    Directory of Open Access Journals (Sweden)

    GUILHERME MALLMANN

    2014-12-01

    Full Text Available Subduction zone or arc magmas are known to display a characteristic depletion of High Field Strength Elements (HFSE relative to other similarly incompatible elements, which can be attributed to the presence of the accessory mineral rutile (TiO2 in the residual slab. Here we show that the partitioning behavior of vanadium between rutile and silicate melt varies from incompatible (∼0.1 to compatible (∼18 as a function of oxygen fugacity. We also confirm that the HFSE are compatible in rutile, with D(Ta> D(Nb>> (D(Hf>/∼ D(Zr, but that the level of compatibility is strongly dependent on melt composition, with partition coefficients increasing about one order of magnitude with increasing melt polymerization (or decreasing basicity. Our partitioning results also indicate that residual rutile may fractionate U from Th due to the contrasting (over 2 orders of magnitude partitioning between these two elements. We confirm that, in addition to the HFSE, Cr, Cu, Zn and W are compatible in rutile at all oxygen fugacity conditions.

  14. Accident selection methodology for TA-55 FSAR

    International Nuclear Information System (INIS)

    Letellier, B.C.; Pan, P.Y.; Sasser, M.K.

    1995-01-01

    In the past, the selection of representative accidents for refined analysis from the numerous scenarios identified in hazards analyses (HAs) has involved significant judgment and has been difficult to defend. As part of upgrading the Final Safety Analysis Report (FSAR) for the TA-55 plutonium facility at the Los Alamos National Laboratory, an accident selection process was developed that is mostly mechanical and reproducible in nature and fulfills the requirements of the Department of Energy (DOE) Standard 3009 and DOE Order 5480.23. Among the objectives specified by this guidance are the requirements that accident screening (1) consider accidents during normal and abnormal operating conditions, (2) consider both design basis and beyond design basis accidents, (3) characterize accidents by category (operational, natural phenomena, etc.) and by type (spill, explosion, fire, etc.), and (4) identify accidents that bound all foreseeable accident types. The accident selection process described here in the context of the TA-55 FSAR is applicable to all types of DOE facilities

  15. Creep behavior of Zr-Nb alloys

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Yong Chan; Kim, Young Suk; Cheong, Yong Mu; Kwon, Sang Chul; Kim, Sung Soo; Choo, Ki Nam [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2000-01-01

    The creep characteristics of Zirconium alloy is affected by several parameters. Out-reactor creep increases both with an increasing amount of Nb, Sn and S contained in alpha-Zr and decreases with the increasing volume of alpha-Zr. Especially, the creep of Zr-2.5Nb alloy depends on the solubility of Nb in alpha-Zr, which is associated with the decomposition of beta-Zr. Since Zr of the hcp structure is strongly anisotropic, it shows the characteristics of texture and results in the anisotropy of creep. Due to the circumferential texture of Zr-2.5%Nb alloy (CANDU Pressure tube), the longitudinal slip is easier than the circumferential one, resulting in the high creep rate. The irradiation creep also increases with increasing neutron fluence. The neutron irradiation increases the strength of the zirconium alloys but decreases their creep strength. In contrast to the out-reactor creep, the irradiation creep is little sensitive to temperature, resulting in the lower activation energy. The most important factor to affect the in-reactor and out-reactor creep of niobium containing alloys seems to be the solution hardening by Nb or Sn which is soluble in alpha-zirconium and the texture as well. Irradiation growth is the mechanism which is caused only by the irradiation. It becomes saturated at lower fluence than the critical fluence but beyond it, shows the break-away growth. The onset of accelerated irradiation growth corresponds with the c-dislocation loop formation, though its mechanism needs better understanding. Generally, the irradiation growth of Zr-Nb alloys increases with an increase in fluence, cold working, dislocation, density and temperature, and with a decrease in the grain size. 141 refs., 59 figs., 10 tabs. (Author)

  16. Expression and functional analysis of TaASY1 during meiosis of bread wheat (Triticum aestivum

    Directory of Open Access Journals (Sweden)

    Langridge Peter

    2007-08-01

    Full Text Available Abstract Background Pairing and synapsis of homologous chromosomes is required for normal chromosome segregation and the exchange of genetic material via recombination during meiosis. Synapsis is complete at pachytene following the formation of a tri-partite proteinaceous structure known as the synaptonemal complex (SC. In yeast, HOP1 is essential for formation of the SC, and localises along chromosome axes during prophase I. Homologues in Arabidopsis (AtASY1, Brassica (BoASY1 and rice (OsPAIR2 have been isolated through analysis of mutants that display decreased fertility due to severely reduced synapsis of homologous chromosomes. Analysis of these genes has indicated that they play a similar role to HOP1 in pairing and formation of the SC through localisation to axial/lateral elements of the SC. Results The full length wheat cDNA and genomic clone, TaASY1, has been isolated, sequenced and characterised. TaASY1 is located on chromosome Group 5 and the open reading frame displays significant nucleotide sequence identity to OsPAIR2 (84% and AtASY1 (63%. Transcript and protein analysis showed that expression is largely restricted to meiotic tissue, with elevated levels during the stages of prophase I when pairing and synapsis of homologous chromosomes occur. Immunolocalisation using transmission electron microscopy showed TaASY1 interacts with chromatin that is associated with both axial elements before SC formation as well as lateral elements of formed SCs. Conclusion TaASY1 is a homologue of ScHOP1, AtASY1 and OsPAIR2 and is the first gene to be isolated from bread wheat that is involved in pairing and synapsis of homologous chromosomes.

  17. Low-field Instabilities in Nb$_{3}$Sn Multifilamentary Wires the Possible Role of Unreacted Nb

    CERN Document Server

    Devred, A; Celentano, G; Fabbricatore, P; Ferdeghini, C; Greco, M; Gambardella, U

    2007-01-01

    We report an experimental study aiming to demonstrate the not negligible role of unreacted Nb on the magnetic instabilities in superconducting Nb$_{3}$Sn multifilamentary wires, observable through partial flux jumps at magnetic field values below 0.5 T. The analysed wires were recently developed for use as dipoles required in future high-energy proton accelerators and are based on powder-in-tube technology. We studied both unreacted (only involving Nb filaments) and reacted wires, finding flux jump instabilities in both cases when performing magnetic measurements. The results can be interpreted on the basis of the critical state model and are coherent with the intrinsic stability criterion.

  18. Tunneling spectroscopy in NbN based Josephson junctions

    International Nuclear Information System (INIS)

    Chicault, R.; Villegier, J.C.

    1984-08-01

    Tunneling spectroscopy in high quality NbN-oxide-Pb(In) diodes offers a direct observation of various NbN and Pb phonon frequences as other vibrating modes existing near the tunnel barrier. The large number of peaks attribuated to dips in the transverses and longitudinal acoustic branches of NbN dispersion curves are found to confirm the previous theory developing the contribution of these modes to the strong coupling and high Tc behavior of NbN

  19. Aluminum-stabilized NB3SN superconductor

    Science.gov (United States)

    Scanlan, Ronald M.

    1988-01-01

    An aluminum-stabilized Nb.sub.3 Sn superconductor and process for producing same, utilizing ultrapure aluminum. Ductile components are co-drawn with aluminum to produce a conductor suitable for winding magnets. After winding, the conductor is heated to convert it to the brittle Nb.sub.3 Sn superconductor phase, using a temperature high enough to perform the transformation but still below the melting point of the aluminum. This results in reaction of substantially all of the niobium, while providing stabilization and react-in-place features which are beneficial in the fabrication of magnets utilizing superconducting materials.

  20. Aluminium stabilized Nb$-3$/Sn superconductors

    International Nuclear Information System (INIS)

    Thoener, M.; Krauth, H.; Rudolph, J.; Szulczyk, A.

    1988-01-01

    Composite superconductors made of reacted Nb 3 Sn stabilized with high purity Al were produced. Two methods were tested. The first involved soft soldering a Cu clad aluminum tape to the Nb 3 Sn conductor. In the second method the conductor, cable or monolith, was coextruded with the aluminum. Results obtained from using both methods indicated that mechanically reinforcing materials can be easily introduced into superconductors. Tests were conducted to determine magnetoresistance, electric contact resistance, yield strength, Young modulus, critical current, and other properties of the composites. Strengthening with Duratherm during coextrusion was also evaluated

  1. Mechanical Properties of Ingot Nb Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi; Dhakal, Pashupati; Kneisel, Peter; Mammosser, John; Matalevich, Joseph; Rao Myneni, Ganapati

    2014-07-01

    This contribution presents the results of measurements of the resonant frequency and of strain along the contour of a single-cell cavity made of ingot Nb subjected to increasing uniform differential pressure, up to 6 atm. The data were used to infer mechanical properties of this material after cavity fabrication, by comparison with the results from simulation calculations done with ANSYS. The objective is to provide useful information about the mechanical properties of ingot Nb cavities which can be used in the design phase of SRF cavities intended to be built with this material.

  2. Thin TaC layer produced by ion mixing

    DEFF Research Database (Denmark)

    Barna, Árpád; Kotis, László; Pécz, Béla

    2012-01-01

    Ion-beam mixing in C/Ta layered systems was investigated. C 8nm/Ta 12nm and C 20nm/Ta 19nm/C 20nm layer systems were irradiated by Ga+ ions of energy in the range of 2–30keV. In case of the 8nm and 20nm thick C cover layers applying 5–8keV and 20–30keV Ga+ ion energy, respectively resulted...... in strongly asymmetric ion mixing; the carbon was readily transported to the Ta layer, while the reverse process was much weaker. Because of the asymmetrical transport the C/TaC interface remained sharp independently from the applied fluence. The carbon transported to the Ta layer formed Ta......Cx. The stoichiometry of the carbide produced varied along the depth. The TaCx layer contained implanted Ga, the concentration of which decreased with increasing depth. The thickness of the TaCx layer could be tailored by the ion fluence and energy making possible to produce coating layer of desired thickness....

  3. Record high-nuclearity polyoxoniobates. Discrete nanoclusters {Nb_1_1_4}, {Nb_8_1}, and {Nb_5_2}, and extended frameworks based on {Cu_3Nb_7_8} and {Cu_4Nb_7_8}

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Lu; Zhu, Zeng-Kui; Wu, Yan-Lan; Qi, Yan-Jie; Li, Xin-Xiong; Zheng, Shou-Tian [State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fujian (China)

    2017-12-18

    A series containing the highest nuclearity polyoxoniobate (PONb) nanoclusters, ranging from dimers to tetramers, has been obtained. They include one 114-nuclear {Li_8 is contained in Nb_1_1_4O_3_1_6}, one 81-nuclear {Li_3K is contained in Nb_8_1O_2_2_5}, and one 52-nuclear {H_4Nb_5_2O_1_5_0}. The Nb nuclearity of these PONbs is remarkably larger than those of all known high-nuclearity PONbs (≤32). Furthermore, the introduction of 3d Cu{sup 2+} ions can lead to the generation of extended inorganic-organic hybrid frameworks built from novel, high-nuclearity, nanoscale heterometallic PONb building blocks {H_3Cu_3Nb_7_8O_2_2_2} or {H_3Cu_4(en)Nb_7_8O_2_2_2}. These building blocks also contain the largest number of Nb centers of any heterometallic PONbs reported to date. The synthesis of new-type PONbs has long been a challenging subject in PONb chemistry. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. The elemental abundances (with uncertainties) of the most Earth-like planet

    Science.gov (United States)

    Wang, Haiyang S.; Lineweaver, Charles H.; Ireland, Trevor R.

    2018-01-01

    To first order, the Earth as well as other rocky planets in the Solar System and rocky exoplanets orbiting other stars, are refractory pieces of the stellar nebula out of which they formed. To estimate the chemical composition of rocky exoplanets based on their stellar hosts' elemental abundances, we need a better understanding of the devolatilization that produced the Earth. To quantify the chemical relationships between the Earth, the Sun and other bodies in the Solar System, the elemental abundances of the bulk Earth are required. The key to comparing Earth's composition with those of other objects is to have a determination of the bulk composition with an appropriate estimate of uncertainties. Here we present concordance estimates (with uncertainties) of the elemental abundances of the bulk Earth, which can be used in such studies. First we compile, combine and renormalize a large set of heterogeneous literature values of the primitive mantle (PM) and of the core. We then integrate standard radial density profiles of the Earth and renormalize them to the current best estimate for the mass of the Earth. Using estimates of the uncertainties in i) the density profiles, ii) the core-mantle boundary and iii) the inner core boundary, we employ standard error propagation to obtain a core mass fraction of 32.5 ± 0.3 wt%. Our bulk Earth abundances are the weighted sum of our concordance core abundances and concordance PM abundances. Unlike previous efforts, the uncertainty on the core mass fraction is propagated to the uncertainties on the bulk Earth elemental abundances. Our concordance estimates for the abundances of Mg, Sn, Br, B, Cd and Be are significantly lower than previous estimates of the bulk Earth. Our concordance estimates for the abundances of Na, K, Cl, Zn, Sr, F, Ga, Rb, Nb, Gd, Ta, He, Ar, and Kr are significantly higher. The uncertainties on our elemental abundances usefully calibrate the unresolved discrepancies between standard Earth models under

  5. The structure of the NiTi surface layers after the ion-plasma alloying of Ta

    Energy Technology Data Exchange (ETDEWEB)

    Poletika, T. M., E-mail: poletm@ispms.tsc.ru; Girsova, S. L., E-mail: girs@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Meisner, L. L., E-mail: lm@ispms.tsc.ru; Meisner, S. N., E-mail: msn@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Schmidt, E. Yu., E-mail: shmidt.rin@yandex.ru [National Research Tomsk State University, Tomsk, 634050 (Russian Federation)

    2015-10-27

    The effect of the Ta-ion beam implantation on the micro- and nanostructures of the surface layers of NiTi alloy was investigated using transmission electron microscopy and Auger spectroscopy. It is found that the elements are distributed non-uniformly with depth, so that the sublayers differ significantly in structure. The modified surface layer was found to consist of two sublayers, i.e. the upper oxide layer and the lower-lying amorphous layer that contains a maximum of Ta atoms.

  6. Synthesis of New RE3+ Doped Li1+xTa1−xTixO3 (RE: Eu, Sm, Er, Tm, and Dy Phosphors with Various Emission Colors

    Directory of Open Access Journals (Sweden)

    Hiroyuki Hayashi

    2013-07-01

    Full Text Available New phosphors with various emission colors for RE3+ doped Li1+xTa1−xTixO3 (LTT (RE: Eu, Sm, Er, Tm, and Dy were synthesized by electric furnace at 1423 K for 15 h. The microstructure of the host material and the photoluminescence (PL property were determined and compared to those of RE3+ doped Li1+xNb1−xTixO3 (LNT. In the LTT phosphor, the highest PL intensity was achieved for the mixture composition Li1.11Ta0.89Ti0.11O3 with a LiTaO3 structure, although it has an M-phase superstructure. In the LTT host material, the effective activators were Eu3+ and Sm3+ ions, in contrast to the LNT host material. Here, we discuss the relationship between PL property and the host material’s structure.

  7. Diffusion of Redox-Sensitive Elements in Basalt at Different Oxygen Fugacities

    Science.gov (United States)

    Szumila, I.; Trail, D.; Danielson, L. R.

    2017-01-01

    The terrestrial planets and moons of our solar system have differentiated over a range of oxygen fugacity conditions. Basalts formed from magmas on the Earth cover a range of more oxidized states (from approximately IW (iron wustite) plus 2 to approximately FMQ (fayalite-magnetite-quartz) plus 3) than crustal rocks from Mars (IW to approximately IW plus 3), and basalts from the Moon are more reduced than both, ranging from IW to IW minus 2. The small body Vesta differentiated around IW minus 4. Characterization of redox sensitive elements' diffusivities will offer insight into behavior of these elements as a function of f (fugacity of) O2 for these planetary bodies. Here, we report a systematic study of the diffusion of redox-sensitive elements in basaltic melts with varying oxygen fugacities (fO2) for trace elements, V, Nb, W, Mo, La, Ce, Pr, Sm, Eu, Gd, Ta, and W. Since fO2 is an intensive variable that is different for the reservoirs of various planets and moons in our solar system, it is important to characterize how changes in redox states will affect diffusion. We conducted experiments in a piston cylinder device at 1300 degrees Centigrade and 1 gigapascal, at the University of Rochester and NASA Johnson Space Center. We buffered some experiments at Ru-RuO2 (FMQ plus 6.00), and conducted other experiments within either a graphite or Mo capsule, which corresponds to fO2s of either FMQ minus1.2, or FMQ minus 3.00, respectively. Characterizing the diffusivities of redox sensitive elements at different fO2s is important because some elements, like Eu, have varying valence states, such as Eu (sup 2 plus) and Eu (sup 3 plus). Differences in charge and ion radii may lead to differences in diffusivities within silicate melts. This could, lead to formation of a Eu anomaly by diffusion, the magnitude of which may be controlled by the fO2. Characterization of trace element diffusion is also important in understanding trace element fractionation. We found, during the

  8. Fabrication of electrocatalytic Ta nanoparticles by reactive sputtering and ion soft landing

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Grant E.; Moser, Trevor; Engelhard, Mark; Browning, Nigel D.; Laskin, Julia

    2016-11-07

    About 40 years ago, it was shown that tungsten carbide exhibits similar catalytic behavior to Pt for certain commercially relevant reactions, thereby suggesting the possibility of cheaper and earth-abundant substitutes for costly and rare precious metal catalysts. In this work, reactive magnetron sputtering of Ta in the presence of three model hydrocarbons (2-butanol, heptane, and m-xylene) combined with gas aggregation and ion soft landing was employed to prepare organic-inorganic hybrid nanoparticles (NPs) on surfaces for evaluation of catalytic activity and durability. The electro-catalytic behavior of the NPs supported on glassy carbon was evaluated in acidic aqueous solution by cyclic voltammetry. The Ta-heptane and Ta-xylene NPs were revealed to be active and robust toward promotion of the oxygen reduction reaction, an important process occurring at the cathode in fuel cells. In comparison, pure Ta and Ta-butanol NPs were essentially unreactive. Characterization techniques including atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were applied to probe how different sputtering conditions such as the flow rates of gases, sputtering current, and aggregation length affect the properties of the NPs. AFM images reveal the focused size of the NPs as well as their preferential binding along the step edges of graphite surfaces. In comparison, TEM images of the same NPs on carbon grids show that they bind randomly to the surface with some agglomeration but little coalescence. The TEM images also reveal morphologies with crystalline cores surrounded by amorphous regions for NPs formed in the presence of 2-butanol and heptane. In contrast, NPs formed in the presence of m-xylene are amorphous throughout. XPS spectra indicate that while the percentage of Ta, C, and O in the NPs varies depending on the sputtering conditions and hydrocarbon employed, the electron binding energies of the elements are similar

  9. Microstructure and oxidation behaviour of TiAl(Nb)/Ti2AlC ...

    Indian Academy of Sciences (India)

    Ti2AlC phases that showed the carbon that originates from hexane, participated in the reaction to form Ti2AlC during heating. Consolidation of ... Only the presence of γ-TiAl and Ti2AlC was detected and no secondary phases were observed on the base of Nb. ..... [32] Cullity B D 1969 Elements of X-ray diffraction (Reading,.

  10. Role of Nb in glass formation of Fe–Cr–Mo–C–B–Nb BMGs

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, Fuqiang, E-mail: fuqiangzhai@gmail.com [Departament Física Aplicada, EETAC, Universitat Politècnica Catalunya-BarcelonaTech, Esteve Terradas 5, 08860 Castelldefels (Spain); Pineda, Eloi [Departament Física i Enginyeria Nuclear, ESAB, Universitat Politècnica Catalunya- BarcelonaTech, Esteve Terradas 8, 08860 Castelldefels (Spain); Duarte, M. Jazmín [Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf (Germany); Crespo, Daniel [Departament Física Aplicada, EETAC, Universitat Politècnica Catalunya-BarcelonaTech, Esteve Terradas 5, 08860 Castelldefels (Spain)

    2014-08-01

    Highlights: • The Fe{sub 46}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Nb{sub 4} BMG of 3 mm Ø was produced for the first time. • The compressive strength of Fe–Cr–Mo–C–B–Nb BMG is reported. • The fragility parameter of Fe–Cr–Mo–C–B–Nb BMG was studied. • The microscopic mechanism is explained by E{sub g}, E{sub x}, E{sub p} and m parameters. - Abstract: A new Fe-based bulk metallic glass with superior glass-forming ability (GFA), Fe{sub 46}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Nb{sub 4}, was developed based on the Fe–Cr–Mo–C–B alloy system by minor addition of Nb. The effects of Nb addition on glass formation of the Fe{sub 50−x}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Nb{sub x} (x = 0, 2, 4 and 6 at.%) alloys were investigated. The optimum addition content of Nb was determined as 4 at.% by X-ray diffraction and differential scanning calorimeter analysis. A fully amorphous rod sample with 3 mm in diameter was produced by using commercial-grade raw materials and a copper mold casting technique. This alloy shows an ultimate compressive strength of 1920 MPa and Vicker’s hardness 1360 H{sub V}, which is two to three times that of conventional high strength steel and suggests a promising potential for applications combining outstanding corrosion and wear resistance properties. The crystallization kinetics studies found that the activation energies for glass transition, onset of crystallization and crystallization peak were higher than those of other reported Fe-based bulk metallic glasses. The value of the fragility parameter m for the Fe{sub 46}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Nb{sub 4} alloy was calculated to be 34, indicating that the Fe–Cr–Mo–C–B–Nb alloy system is a strong glass former according to the Angell’s classification scheme. It is inferred that the more sequential change in the atomic size, the generation of new atomic pairs with large negative heats of mixing and the amount of oxygen in the molten liquid

  11. 75 FR 43556 - TA-W-73,381, MT Rail Link, Inc., Missoula, MT; TA-W-73,381A, Billings, MT; TA-W-73,381B, Laurel...

    Science.gov (United States)

    2010-07-26

    ...., Missoula, MT; TA-W-73,381A, Billings, MT; TA-W-73,381B, Laurel, MT; TA-W-73,381C, Livingston, MT; TA-W-73... in Missoula, Montana and operations facilities (yards) in Billings, Laurel, Livingston, Helena and Missoula, Montana. The Billings, Laurel, Livingston, and Helena facilities operate in conjunction with the...

  12. On Mossbauer dynamics in Nb3Sn

    Indian Academy of Sciences (India)

    2015-11-27

    Nov 27, 2015 ... We compare the anharmonic Lamb Mossbauer factor and the -Lamb Mossbauer factor by studying the anharmonicity observed in the -factor data of Nb3Sn. We also show that this anharmonicity does not arise due to the presence of potential.

  13. Closely spaced fine filament multifilamentary NbTi strands

    International Nuclear Information System (INIS)

    Gregory, E.; Liu, H.; Seuntjens, J.M.

    1994-01-01

    A series of papers showing the advantages of close spacing and matrix alloying for the development of high J c , fine filament, NbTi materials which have low electrical coupling have appeared in the last seven years. In order to achieve the highest J c 's, it has been shown that close spacing has many advantages. This, however, leads to proximity coupling which has to be overcome by the addition of alloying elements to the matrix between the filaments. Of the three alloying materials normally used for this purpose, Ni, Si, and Mn, the most effective is Mn, which operates by a spin flip scattering mechanism whereas Ni and Si produce decoupling by less effective resistive scattering. Ni and Si, however, harden the matrix more than does the small amount of Mn, [0.5wt%], which has been used in most of the past work on the reduction of proximity coupling. This hardening allows the filaments to be separated to a greater extent than is possible in the case of a pure copper matrix without a significant increase in filament sausaging and a resultant J c decrease. Silicon also has one additional advantage over the other alloying elements in that it reduces the formation of compounds on the surface of the filaments, thus it may obviate the necessity for a Nb barrier layer and thus allow an even greater increase in J c . In this paper the authors explore further some of the effects of the addition of manganese and/or silicon to the matrix between the filaments in an effort to optimize properties at the smaller filament sizes

  14. Electroexcitation of giant resonances in 181Ta

    International Nuclear Information System (INIS)

    Hicks, R.S.; Auer, I.P.; Bergstrom, J.C.; Caplan, H.S.

    1977-01-01

    The giant resonance region of 181 Ta has been investigated by means of inelastic electron scattering with primary electron energies of 79.1 to 118.3 MeV. A peak-fitting procedure was employed to separate the measured spectrum into nine different resonance components. Multipolarity and strength assignments were deduced using DWBA analysis with the Goldhaber-Teller and Steinwedel-Jensen models. In addition to the well-known giant dipole structure, other resonances were identified at 23.2+-0.3 MeV (E2), 9.5+-0.2 and 11.5+-0.2 MeV (E2 or E0), 19.5+-0.8 MeV (E3), 3.70+-0.14 MeV (E3 or E4), and 5.40+-0.15 MeV (E4 or E5). The model dependence of the analysis is discussed. (Auth.)

  15. LRAD surface monitoring results at TA-21

    International Nuclear Information System (INIS)

    Bounds, J.A.

    1995-01-01

    In August/September 1994, NIS-6 personnel used LRAD soil surface monitor technology to characterize the extent of alpha contamination on the surface of a parking lot adjacent to TA-21, LANL, known as Material Disposal Area B. This report documents that monitoring. Based on this survey, there is no reason for concern about significant contamination in the parking area as a whole, although unexpected small hot spots could exist between the grid points where monitoring was performed. However, the grouping of high readings on the east side of the parking area does point to possible contamination at the level of 100 dpm/100 cm 2 or less (above background). Further monitoring or remediation of this area seems appropriate. In addition, because this was an alpha survey, one cannot rule out contamination under the asphalt or possibly between layers if it was paved more than once

  16. Local Variability of the Peierls Barrier of Screw Dislocations in Ta-10W.

    Energy Technology Data Exchange (ETDEWEB)

    Foiles, Stephen M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-10-01

    It is well know that the addition of substitutional elements changes the mechanical behavior of metals, a effect referred to solid solution hardening. For body-centered-cubic (BCC) metals, screw dislocation play a key role in the mechanical properties. Here the detailed modification of the Peierls barrier for screw dislocation motion in Ta with W substitutional atoms is computing using density functional theory (DFT). A reduced order model (ROM) of the influence of W substitution on the Peierls barrier is developed. The mean field change in the Peierls barrier for a Ta10W alloy is determined and shown to be larger than anticipated based on simple elasticity considerations. The ROM could be used in future calculations to determine the local variability of the Peierls barrier and the resultant influence on the motion of screw dislocation in this alloy.

  17. Low temperature properties of spin filter NbN/GdN/NbN Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Massarotti, D., E-mail: dmassarotti@na.infn.it [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy); Caruso, R. [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy); Pal, A. [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS (United Kingdom); Rotoli, G. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); Longobardi, L. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); American Physical Society, 1 Research Road, Ridge, New York 11961 (United States); Pepe, G.P. [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy); Blamire, M.G. [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS (United Kingdom); Tafuri, F. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy)

    2017-02-15

    Highlights: • We study the phase dynamics of ferromagnetic NbN/GdN/NbN Josephson junctions. • The ferromagnetic insulator GdN barrier generates spin-filtering properties. • Spin filter junctions fall in the underdamped regime. • MQT occurs with the same phenomenology as in conventional Josephson junctions. • Dissipation is studied in a wide range of critical current density values. - Abstract: A ferromagnetic Josephson junction (JJ) represents a special class of hybrid system where different ordered phases meet and generate novel physics. In this work we report on the transport measurements of underdamped ferromagnetic NbN/GdN/NbN JJs at low temperatures. In these junctions the ferromagnetic insulator gadolinium nitride barrier generates spin-filtering properties and a dominant second harmonic component in the current-phase relation. These features make spin filter junctions quite interesting also in terms of fundamental studies on phase dynamics and dissipation. We discuss the fingerprints of spin filter JJs, through complementary transport measurements, and their implications on the phase dynamics, through standard measurements of switching current distributions. NbN/GdN/NbN JJs, where spin filter properties can be controllably tuned along with the critical current density (J{sub c}), turn to be a very relevant term of reference to understand phase dynamics and dissipation in an enlarged class of JJs, not necessarily falling in the standard tunnel limit characterized by low J{sub c} values.

  18. AC magnetic and magnetoimpedance properties of CoFe(NbMnNi)BSi amorphous ribbons

    Science.gov (United States)

    Manna, Subhendu Kumar; Srinivas, V.

    2018-03-01

    We report magnetic and magnetoimpedance (MI) properties of cobalt-rich amorphous alloys to investigate the role of small quantities of 3d or 4d transition-metal elements in Co-rich alloys. The microstructure, thermal stability, AC soft magnetic properties and magnetoimpedance of the ribbons are investigated by substituting Nb in place of Ni and Mn. Present study shows an improvement in glass forming ability and reduction in electrical conductivity of the ribbon with Nb substitution. Higher Nb containing alloy shows minimum core loss compared to other compositions over a range of frequencies. Ribbon with higher core loss exhibited higher MI ratio (∼100% at 3 MHz), but decreased rapidly at higher frequencies due to its larger electrical conductivity. The ribbon with lower electrical conductivity showed a steady MI ratio and field sensitivity with frequency. These results indicate that MI and core losses at medium range of frequencies can be tuned by adding Nb that provides most favourable electrical conductivity and magnetic permeability values, which result in optimum skin depth and MI. The effect of electrical conductivity on MI is also validated through numerical simulations using standard electrodynamics models.

  19. Investigation of 63Ni diffusion along stationary and moving grain boundaries in Nb

    International Nuclear Information System (INIS)

    Razumovskii, I.M.; Mishin, Yu.; Herzig, C.

    1996-01-01

    Grain boundary diffusion of 63 Ni in high purity polycrystalline niobium has been studied in the temperature range 973-1258 K by the radiotracer serial sectioning technique. Since the grain size in the material could not be completely stabilized by pre-diffusion heat treatment, some part of the grain boundaries could migrate during the diffusion anneals. The tracer penetration profiles were treated using the model of diffusion in polycrystals containing both stationary and moving grain boundaries developed in our previous work. Along with the grain boundary diffusivity, also the average velocity of moving grain boundaries and the activation energy of boundary migration in Nb were determined from the effect of boundary motion on the profile shape. Grain boundary diffusion of Ni in Nb is anomalously fast and exhibits an activation energy of 155.2 kJ mol -1 . This behaviour is well consistent with that of Co diffusion in Nb studied previously and implies that diffusion of both elements in Nb is governed by a combined atomic mechanism involving both vacancies and interstitials. (orig.)

  20. Dielectric properties of Li doped Li-Nb-O thin films

    Energy Technology Data Exchange (ETDEWEB)

    Perentzis, G.; Horopanitis, E.E.; Papadimitriou, L. [Aristotle University of Thessaloniki, Department of Physics, 54124 Thessaloniki (Greece); Durman, V.; Saly, V.; Packa, J. [Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, Ilkovicova 3, 81219 Bratislava (Slovakia)

    2007-03-15

    Lithium niobate LiNbO{sub 3} was prepared as a thin film layered structure deposited on stainless steel substrate using e-gun evaporation. The Li doping was provided for by the formation of Li-Nb-O/Li/LiNb-O sandwich structure and annealing at about 250 C. AC impedance spectroscopy measurements were performed on the samples at temperatures from the interval between 28 and 165 C and in a frequency range of 10{sup -3} to 10{sup 6} Hz. Using the values Z' and Z'' at different frequencies, the dielectric parameters - parts of the complex permittivity {epsilon}' and {epsilon}'' and loss tangent tan {delta} were calculated. The results prove validity of the proposed equivalent circuit containing parallel RC elements connected in series where the first RC element represents the bulk of material and the second RC element belongs to the double layer at the metal interface. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Microstructure, Surface Characterization, and Electrochemical Behavior of New Ti-Zr-Ta-Ag Alloy in Simulated Human Electrolyte

    Science.gov (United States)

    Vasilescu, Cora; Drob, Silviu Iulian; Osiceanu, Petre; Moreno, Jose Maria Calderon; Prodana, Mariana; Ionita, Daniela; Demetrescu, Ioana; Marcu, Maria; Popovici, Ion Alexandru; Vasilescu, Ecaterina

    2017-01-01

    A new Ti-20Zr-5Ta-2Ag alloy was elaborated and characterized regarding its microstructure, its native passive film composition and thickness, its surface wettability, its electrochemical behavior in Ringer solution of different pH values, and its ion release. The new alloy has a bi-phase, α + β, acicular, homogeneous microstructure (scanning electron microscopy (SEM)). Its native passive film (12-nm thicknesses) consists of the protective TiO2, ZrO2, and Ta2O5 oxides, Ti and Ta suboxides, and metallic Ag (X-ray photoelectron spectroscopy (XPS) data). The alloy possesses high hydrophilic properties. The main electrochemical parameters of the new alloy are superior to those of Ti as a result of the beneficial influence of Zr, Ta, and Ag alloying elements, which reinforce its native passive film. Electrochemical impedance spectroscopy (EIS) spectra in Ringer solutions for the new alloy displayed better values of impedances and phase angles, proving a more insulate passive film than that on the Ti surface. The main corrosion parameters for the new Ti-20Zr-5Ta-2Ag alloy are more favorable by about 25 to 38 times than those of Ti, confirming extremely resistant passive film. The new Ti-20Zr-5Ta-2Ag alloy releases into Ringer solution low quantities of Ti4+, Zr4+ metallic ions (inductively coupled plasma-mass spectroscopy (ICP-MS)). The Ag+ ions are released in low quantity, conferring to this alloy's low antibacterial activity. All experimental results show that the new Ti-20Zr-5Ta-2Ag alloy fulfills the requirements for biocompatibility, corrosion resistance, and antibacterial protection.

  2. Energetic condensation growth of Nb thin films

    Directory of Open Access Journals (Sweden)

    M. Krishnan

    2012-03-01

    Full Text Available This paper describes energetic condensation growth of Nb films using a cathodic arc plasma, whose 60–120 eV ions penetrate a few monolayers into the substrate and enable sufficient surface mobility to ensure that the lowest energy state (crystalline structure with minimal defects is accessible to the film. Heteroepitaxial films of Nb were grown on a-plane sapphire and MgO crystals with good superconducting properties and crystal size (10  mm×20  mm limited only by substrate size. The substrates were heated to temperatures of up to 700°C and coated at 125°C, 300°C, 500°C, and 700°C. Film thickness was varied from ∼0.25  μm to >3  μm. Residual resistivity ratio (⟨RRR⟩ values (up to a record ⟨RRR⟩=587 on MgO and ⟨RRR⟩=328 on a-sapphire depend strongly on substrate annealing and deposition temperatures. X-ray diffraction spectra and pole figures reveal that RRR increases as the crystal structure of the Nb film becomes more ordered, consistent with fewer defects and, hence, longer electron mean-free path. A transition from Nb(110 to Nb(100 orientation on the MgO(100 lattice occurs at higher temperatures. This transition is discussed in light of substrate heating and energetic condensation physics. Electron backscattered diffraction and scanning electron microscope images complement the XRD data.

  3. Preparation and characterization of sputtered Cu films containing insoluble Nb

    International Nuclear Information System (INIS)

    Mahalingam, T.; Lin, C.H.; Wang, L.T.; Chu, J.P.

    2006-01-01

    Copper films containing various amounts of insoluble Nb (up to 24.7 at.%) were prepared by r.f. magnetron sputtering. The crystallography and microstructure of the films were investigated for as-deposited and annealed Cu(Nb) thin films. Cu(Nb) thin films are found to consist of non-equilibrium supersaturated solid solution of Nb in Cu with a nanocrystalline microstructure. X-ray diffraction and scanning electron microscope analyses revealed a reduction in the grain sizes of the films with increasing Nb content in the films leading to a grain refinement. The electrical resistivity of as-deposited and annealed Cu(Nb) thin films is found to be low for an Nb content 2.7 at.%. Significant drops in the resistivity were observed for the high Nb contents after annealing at 530 deg. C which may be due to grain growth and formation of Nb-bearing phase in the film. Microhardness of the films was found to increase with the Nb concentration due to the combined effects of grain refinement and the solute strengthening of Nb

  4. Signature splitting in two quasiparticle rotational bands of Ta

    Indian Academy of Sciences (India)

    2016-06-20

    Jun 20, 2016 ... ... of 182Ta are analysed within the framework of two-quasiparticle rotor model. The phase as well as magni- tude of the experimentally observed signature splitting in Kπ = 1+ band of 180Ta, which could not be explained in earlier calculations, is successfully reproduced. The conflict regarding placement of ...

  5. (procolobus verus) dans le Parc National de Taï

    African Journals Online (AJOL)

    HP_Administrateur

    Mots clés : Colobe Vert, vocalisation, cri unitaire, contexte social, communication, Parc National de Taï, Côte d'Ivoire. Abstract. Repertoire and ... Key words : Olive Colobus, vocalization, unit call, social context, communication, Taï National Park, Ivory Coast. 1. Introduction. L'étude ..... Auditory communication among vervet ...

  6. The TaSST: Tactile sleeve for social touch

    NARCIS (Netherlands)

    Huisman, Gijs; Darriba Frederiks, Aduén; van Dijk, Elisabeth M.A.G.; Heylen, Dirk K.J.; Krose, Ben

    In this paper we outline the design process of the TaSST (Tactile Sleeve for Social Touch), a touch-sensitive vibrotactile arm sleeve. The TaSST was designed to enable two people to communicate different types of touch over a distance. The touch-sensitive surface of the sleeve consists of a grid of

  7. Lecture Discourse of a Foreign TA: A Preliminary Needs Assessment.

    Science.gov (United States)

    Gillette, Susan

    1982-01-01

    A study of the communication skill needs of the foreign teaching associate (TA) in American universities focused on two questions: (1) What does a foreign TA do to communicate information in an American classroom in terms of comunication strategies and devices for cohesion and coherence of discourse? and (2) How does this compare with the way an…

  8. 76 FR 50739 - Hung Ta Fan: Debarment Order

    Science.gov (United States)

    2011-08-16

    ...] Hung Ta Fan: Debarment Order AGENCY: Food and Drug Administration, HHS. ACTION: Notice. SUMMARY: The... (the FD&C Act) debarring Hung Ta Fan for a period of 5 years from importing articles of food or.... Fan was convicted of a felony under Federal law for conduct relating to the importation into the...

  9. The TaSST: Tactile Sleeve for Social Touch

    NARCIS (Netherlands)

    Huisman, G.; Darriba Frederiks, A.; van Dijk, B.; Heylen, D.; Kröse, B.

    2013-01-01

    In this paper we outline the design process of the TaSST (Tactile Sleeve for Social Touch), a touch-sensitive vibrotactile arm sleeve. The TaSST was designed to enable two people to communicate different types of touch over a distance. The touch-sensitive surface of the sleeve consists of a grid of

  10. The TaSST - Tactile Sleeve for Social Touch

    NARCIS (Netherlands)

    Huisman, Gijs; Darriba Frederiks, Aduén; Van Dijk, Betsy; Heylen, Dirk

    2013-01-01

    In this paper we outline the design process of TaSST (Tactile Sleeve for Social Touch), a touch-sensitive vibrotactile arm sleeve. The TaSST was designed to enable two people to communicate different types of touches over a distance. The touch-sensitive surface of the sleeve consists of a grid of

  11. An investigation of the ternary system Nb-Ti-Al

    International Nuclear Information System (INIS)

    Kaltenbach, K.; Gama, S.

    1984-01-01

    The binary systems Nb-Ti, Nb-Al and Al-Ti as well the ternary system Nb-Ti-Al were studied by the aid of arc-beam melted alloys. The as-cast alloys and samples heat treated at 1200 0 C were examined and the liquidus surface projection, an isothermal section at 1200 0 C and the reaction scheme of the system Nb-Ti-Al were constructed. The phase relations of the binary systems Nb-Ti and Nb-Al were confirmed, in the system Al-Ti still some examinations are necessary to resolve the existing uncertainties. The melting process of Nb-Ti alloys in the electron-beam furnace has been studied. (Author) [pt

  12. X-ray investigation of Nb/O interfaces

    International Nuclear Information System (INIS)

    Delheusy, Melissa

    2008-01-01

    X-ray free electron lasers and the future International Linear Collider project are based on the performance of niobium superconducting rf cavities for efficient particle acceleration. A remarkable increase of the rf accelerating field is usually achieved by low-temperature annealing of the cavities (T 2 O 5 , NbO 2 and NbO, from the surface to the interface. It reduces progressively upon heating from Nb 2 O 5 to NbO 2 at low temperatures, and to NbO at 300 C. The Nb(110)/NbO(111) interface presents a Nishiyama-Wassermann epitaxial orientation relationship. The depth-distribution of interstitial oxygen has been established indicating that most of the oxygen is located in the direct vicinity of the oxide/niobium interface. No evidence of oxygen depletion below the oxide layer has been observed for the low temperature thermal treatments and surface preparations investigated in this study. (orig.)

  13. Radioactivity of Nb$_{3}$Sn/Cu wires after proton irradiation

    CERN Document Server

    Otto, Th; Catherall, R; Glaser, M; Militaru, O; Flükiger, R; Ballarino, A; Bottura, L

    2013-01-01

    Superconducting magnets based on Nb3Sn technology are being developed for the LHC high luminosity upgrade. In this context irradiation induced changes of the superconducting properties of state-of-the-art Ti and Ta doped Nb3Sn wires are presently studied. During irradiation tests with protons of 65 MeV at the cyclotron of Université Catholique de Louvain (UCL), 1.4 GeV at the CERN ISOLDE facility, and 24 GeV at the CERN IRRAD1 facility, the superconductor samples become radioactive and their handling must follow the legal specifications for radioactive materials. We have estimated the activation and the resulting ambient dose equivalent rate up to a fluence of 1017 p/cm2 with the Monte-Carlo Code FLUKA. The estimates were verified with experimental activation spectra. Samples for magnetization measurements with a mass of approximately 20 mg have to be considered as radioactive, but they do not have the potential to harm the operators handling them at radiation levels below 1 uSv/h. Larger samples (longer wi...

  14. Controlled Dissolution of Surface Layers for Elemental Analysis by Inductively Coupled Plasma-Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Lorge, Susan Elizabeth [Iowa State Univ., Ames, IA (United States)

    2007-01-01

    Determining the composition of thin layers is increasingly important for a variety of industrial materials such as adhesives, coatings and microelectronics. Secondary ion mass spectrometry (SIMS), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), glow discharge optical emission spectroscopy (GDOES), glow discharge mass spectrometry (GDMS), and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) are some of the techniques that are currently employed for the direct analysis of the sample surface. Although these techniques do not suffer from the contamination problems that often plague sample dissolution studies, they do require matrix matched standards for quantification. Often, these standards are not readily available. Despite the costs of clean hoods, Teflon pipette tips and bottles, and pure acids, partial sample dissolution is the primary method used in the semiconductor industry to quantify surface impurities. Specifically, vapor phase decomposition (VPD) coupled to ICP-MS or total reflection x-ray fluorescence (TXRF) provides elemental information from the top most surface layers at detection sensitivities in the 107-1010atoms/cm2 range. The ability to quantify with standard solutions is a main advantage of these techniques. Li and Houk applied a VPD-like technique to steel. The signal ratio of trace element to matrix element was used for quantification. Although controlled dissolution concentrations determined for some of the dissolved elements agreed with the certified values, concentrations determined for refractory elements (Ti, Nb and Ta) were too low. LA-ICP-MS and scanning electron microscopy (SEM) measurements indicated that carbide grains distributed throughout the matrix were high in these refractory elements. These elements dissolved at a slower rate than the matrix element, Fe. If the analyte element is not removed at a rate similar to the matrix element a true

  15. Variable substrate temperature deposition of CoFeB film on Ta for manipulating the perpendicular coercive forces

    Science.gov (United States)

    Lakshmanan, Saravanan; Rao, Subha Krishna; Muthuvel, Manivel Raja; Chandrasekaran, Gopalakrishnan; Therese, Helen Annal

    2017-08-01

    Magnetization of Ta/CoFeB/Ta trilayer films with thick layer of CoFeB deposited under different substrate temperatures (Ts) via ultra-high vacuum DC sputtering technique has been measured with the applied magnetic field parallel and perpendicular to the plane of the film respectively to study the perpendicular coercive forces of the film. The samples were further analyzed for its structural, topological, morphological, and electrical transport properties. The core chemical states for the elements present in the CoFeB thin film were analyzed by XPS studies. Magnetization studies reveal the existence of perpendicular coercive forces in CoFeB films deposited only at certain temperatures such as RT, 450 °C, 475 °C and 500 °C. CoFeB film deposited at 475 °C exhibited a maximum coercivity of 315 Oe and a very low saturation magnetization (Ms) of 169 emu/cc in perpendicular direction. This pronounced effect in perpendicular coercive forces observed for CoFeB475 could be attributed to the effect of temperature in enhancing the crystallization of the film at the Ta/CoFeB interfaces. However at temperatures higher than 475 °C the destruction of the Ta/CoFeB interface due to intermixing of Ta and CoFeB results in the disappearance of magnetic anisotropy.

  16. Microstructure and mechanical properties of Pt-added and Pd-added Zr-20Nb alloys and their metal release in 1 mass% lactic acid solution

    Energy Technology Data Exchange (ETDEWEB)

    Kondo, R.; Suyalatu,; Tsutsumi, Y. [Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Chiyoda-ku, Tokyo 101-0062 (Japan); Doi, H., E-mail: doi.met@tmd.ac.jp [Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Chiyoda-ku, Tokyo 101-0062 (Japan); Nomura, N. [Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Chiyoda-ku, Tokyo 101-0062 (Japan); Hanawa, T. [Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Chiyoda-ku, Tokyo 101-0062 (Japan); Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-8650 (Japan)

    2011-07-20

    The effects of Pt and Pd addition to a Zr-20Nb alloy on its microstructure and mechanical property, as well as the elution of metals from the alloys in lactic acid solution, were investigated. The microstructure was characterized with an X-ray diffractometer (XRD), an optical microscope (OM), and a transmission electron microscope (TEM). The mechanical properties were evaluated by a tensile test. The {beta} phase is dominantly observed in the Zr-20Nb as well as in the Pt-added and Pd-added Zr-20Nb alloys. Needle-like microstructures are observed in equiaxed grains in all alloys. Pd addition to the Zr-20Nb alloy suppresses {omega} phase formation more than Pt addition does. The 0.2% offset yield strength and the ultimate tensile strength of the Pt-added and Pd-added Zr-20Nb alloys increase with the Pt and Pd concentrations. XRD analysis revealed that the lattice parameter of {beta}-Zr in the Pt-added and Pd-added Zr-20Nb alloys decreases with the Pt and Pd concentrations. Pt and Pd solute in {beta}-Zr as a substitutional element and contribute to the increase in the strength by solid solution hardening. The addition of 2Pt and 2Pd to the Zr-20Nb alloy also improves metal elution from the alloys in lactic acid solution.

  17. Estudio de la estabilidad térmica de polvo de hierro nanoestructurado en función del tipo de refuerzo (Nb, NbC y de su contenido

    Directory of Open Access Journals (Sweden)

    Fuentes-Pacheco, L.

    2011-10-01

    Full Text Available In structural steels, an effective strategy to succeed in increasing both strength and toughness is the grain refining, like in microalloyed steels. To delay or even inhibit the grain growth there are two basic mechanisms: particle pinning and solute drag. The effect of the presence of small particles of NbC to inhibit the austenitic grain growth is well known. However, it is not so clear which mechanism will be more effective to delay ferritic grain growth. In order to confirm it, nanostructured iron powders reinforced with Nb and NbC have been prepared by mechanical alloying. The main objective of this work is, therefore, to study the thermal stability of the nanostructured powder as a function of the reinforce type (elemental Nb or NbC and its content.

    En los aceros estructurales, una estrategia efectiva para incrementar tanto la resistencia como la tenacidad es disminuir el tamaño de grano, tal y como ponen de manifiesto los aceros microaleados. Para retrasar e incluso inhibir el crecimiento de grano existen dos mecanismos básicos: la presencia de partículas de una segunda fase (“particle pinning” y la presencia de elementos en solución sólida substitucional (“solute drag”. El efecto de la presencia de NbC para inhibir el crecimiento del grano asutenítico está más que demostrado. Sin embargo, no está claro cuál de los dos mecanismos (particle pinning o solute drag es el más efectivo para retener el grano ferrítico. Para comprobarlo se han preparado polvos de hierro nanoestructurado mediante aleación mecánica, reforzados bien con niobio, bien con NbC. El presente trabajo tiene como objetivo estudiar la estabilidad térmica de la ferrita de dichos polvos en función del tipo de refuerzo (Nb en forma elemental o NbC y de su contenido.

  18. Effects of alloying element and temperature on the stacking fault energies of dilute Ni-base superalloys.

    Science.gov (United States)

    Shang, S L; Zacherl, C L; Fang, H Z; Wang, Y; Du, Y; Liu, Z K

    2012-12-19

    A systematic study of stacking fault energy (γ(SF)) resulting from induced alias shear deformation has been performed by means of first-principles calculations for dilute Ni-base superalloys (Ni(23)X and Ni(71)X) for various alloying elements (X) as a function of temperature. Twenty-six alloying elements are considered, i.e., Al, Co, Cr, Cu, Fe, Hf, Ir, Mn, Mo, Nb, Os, Pd, Pt, Re, Rh, Ru, Sc, Si, Ta, Tc, Ti, V, W, Y, Zn, and Zr. The temperature dependence of γ(SF) is computed using the proposed quasistatic approach based on a predicted γ(SF)-volume-temperature relationship. Besides γ(SF), equilibrium volume and the normalized stacking fault energy (Γ(SF) = γ(SF)/Gb, with G the shear modulus and b the Burgers vector) are also studied as a function of temperature for the 26 alloying elements. The following conclusions are obtained: all alloying elements X studied herein decrease the γ(SF) of fcc Ni, approximately the further the alloying element X is from Ni on the periodic table, the larger the decrease of γ(SF) for the dilute Ni-X alloy, and roughly the γ(SF) of Ni-X decreases with increasing equilibrium volume. In addition, the values of γ(SF) for all Ni-X systems decrease with increasing temperature (except for Ni-Cr at higher Cr content), and the largest decrease is observed for pure Ni. Similar to the case of the shear modulus, the variation of γ(SF) for Ni-X systems due to various alloying elements is traceable from the distribution of (magnetization) charge density: the spherical distribution of charge density around a Ni atom, especially a smaller sphere, results in a lower value of γ(SF) due to the facility of redistribution of charges. Computed stacking fault energies and the related properties are in favorable accord with available experimental and theoretical data.

  19. Optical analysis of adsorption sensitivity of titanium, Ti-6Al-4V, and Ti-35Nb-6Ta

    Czech Academy of Sciences Publication Activity Database

    Penttinen, N.; Hasoň, Stanislav; Vaněk, J.; Silvennoien, R.

    2012-01-01

    Roč. 51, č. 10 (2012), C32-C37 ISSN 1559-128X R&D Projects: GA ČR(CZ) GAP205/10/2378 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Institutional support: RVO:68081707 Keywords : PROTEIN ADSORPTION * FORCE MICROSCOPY * ELLIPSOMETRY Subject RIV: BO - Biophysics Impact factor: 1.689, year: 2012

  20. Electric properties of textured (K0. 44Na0. 52Li0. 04)(Nb0. 86Ta0 ...

    Indian Academy of Sciences (India)

    Author Affiliations. FANG FU1 JIWEI ZHAI2 ZHENGKUI XU3. Luoyang Institute of Science and Technology, Luoyang 471023, China; Functional Materials Research Laboratory, Tongji University, Shanghai 200092, China; Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong, Hong ...

  1. Newly developed Ti-Nb-Zr-Ta-Si-Fe biomedical beta titanium alloys with increased strength and enhanced biocompatibility\

    Czech Academy of Sciences Publication Activity Database

    Kopová, Ivana; Stráský, J.; Harcuba, P.; Landa, Michal; Janeček, M.; Bačáková, Lucie

    2016-01-01

    Roč. 60, Mar 1 (2016), s. 230-238 ISSN 0928-4931 R&D Projects: GA ČR(CZ) GAP107/12/1025 Institutional support: RVO:67985823 ; RVO:61388998 Keywords : elastic modulus * alloy hardening * cell growth * osteogenic cell differentiation * bone implants Subject RIV: EI - Biotechnology ; Bionics; BI - Acoustics (UT-L) Impact factor: 4.164, year: 2016

  2. Oxidation Behavior of a Refractory NbCrMo0.5Ta0.5TiZr Alloy

    Science.gov (United States)

    2014-04-01

    plotted in the logarithmic coordinates , two distinct behaviors can clearly be seen (Fig. 15). During the first 1500 s (*25 min), oxidation is fast and n...Chang S Y (2004) Adv Eng Mater 6(5):299 303 12. Yeh J W (2006) Annales de Chimie : Science des Materiaux 31:633 648 13. Yeh J W, Chen Y L, Lin S J

  3. Crystal chemistry and structure of the orthorhombic (Fe,Mn)(Ta,Nb) sub 2 O sub 6 family of compounds

    CERN Document Server

    Santos, C A D; Kinast, E J; Antonietti, V; Cunha, J B M D

    2001-01-01

    In this paper we review the crystal chemistry and structure data from the literature and our results reported in the last decade for natural and synthetic samples of the tantalite-columbite series. Order-disorder transitions and oxidation reactions on the ixiolite-columbite-wodginite system are reported for one Brazilian sample. It is shown that reports on these subjects are sometimes dubious and incomplete. In addition to the reaction atmosphere (air or vacuum), order-disorder and oxidation are strongly dependent on the physical state of the samples (powdered or crystal). Structure and chemical composition have been investigated in our laboratory using X-ray diffraction, electron probe microanalysis and Moessbauer spectroscopy.

  4. Atomic resolution imaging of precipitate transformation from cubic TaN to tetragonal CrTaN

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson; Hald, John; Somers, Marcel A. J.

    2012-01-01

    in the matrix. Using atomic resolution transmission electron microscopy, the current work demonstrates that metastable cubic TaN precipitates in a complex steel gradually transform compositionally and crystallographically into stable tetragonal CrTaN precipitates under the influence of Cr indiffusion from...

  5. Identification and Expression Analysis of Wheat TaGF14 Genes

    Directory of Open Access Journals (Sweden)

    Jun Guo

    2018-01-01

    Full Text Available The 14-3-3 gene family members play key roles in various cellular processes. However, little is known about the numbers and roles of 14-3-3 genes in wheat. The aims of this study were to identify TaGF14 numbers in wheat by searching its whole genome through blast, to study the phylogenetic relationships with other plant species and to discuss the functions of TaGF14s. The results showed that common wheat harbored 20 TaGF14 genes, located on wheat chromosome groups 2, 3, 4, and 7. Out of them, eighteen TaGF14s are non-ε proteins, and two wheat TaGF14 genes, TaGF14i and TaGF14f, are ε proteins. Phylogenetic analysis indicated that these genes were divided into six clusters: cluster 1 (TaGF14d, TaGF14g, TaGF14j, TaGF14h, TaGF14c, and TaGF14n; cluster 2 (TaGF14k; cluster 3 (TaGF14b, TaGF14l, TaGF14m, and TaGF14s; cluster 4 (TaGF14a, TaGF14e, and TaGF14r; cluster 5 (TaGF14i and TaGF14f; and cluster 6 (TaGF14o, TaGF14p, TaGF14q, and TaGF14t. Tissue-specific gene expressions suggested that all TaGF14s were likely constitutively expressed, except two genes, i.e., TaGF14p and TaGF14f. And the highest amount of TaGF14 transcripts were observed in developing grains at 20 days post anthesis (DPA, especially for TaGF14j and TaGF14l. After drought stress, five genes, i.e., TaGF14c, TaGF14d, TaGF14g, TaGF14h, and TaGF14j, were up-regulated expression under drought stress for both 1 and 6 h, suggesting these genes played vital role in combating against drought stress. However, all the TaGF14s were down-regulated expression under heat stress for both 1 and 6 h, indicating TaGF14s may be negatively associated with heat stress by reducing the expression to combat heat stress or through other pathways. These results suggested that cluster 1, e.g., TaGF14j, may participate in the whole wheat developing stages, e.g., grain-filling (starch biosynthesis and may also participate in combating against drought stress. Subsequently, a homolog of TaGF14j, TaGF14-JM22, were

  6. Blood levels of toxic metals and rare earth elements commonly found in e-waste may exert subtle effects on hemoglobin concentration in sub-Saharan immigrants.

    Science.gov (United States)

    Henríquez-Hernández, Luis Alberto; Boada, Luis D; Carranza, Cristina; Pérez-Arellano, José Luis; González-Antuña, Ana; Camacho, María; Almeida-González, Maira; Zumbado, Manuel; Luzardo, Octavio P

    2017-12-01

    Pollution by heavy metals and more recently by rare earth elements (REE) and other minor elements (ME) has increased due in part to their high use in technological and electronic devices. This contamination can become very relevant in those sites where e-waste is improperly processed, as it is the case in many countries of the African continent. Exposure to some toxic elements has been associated to certain hematological disorders, specifically anemia. In this study, the concentrations of 48 elements (including REE and other ME) were determined by ICP-MS in whole blood samples of sub-Saharan immigrants with anemia (n=63) and without anemia (n=78). We found that the levels of Fe, Cr, Cu, Mn, Mo, and Se were significantly higher in the control group than in the anemia group, suggesting that anemia was mainly due to nutritional deficiencies. However, since other authors have suggested that in addition to nutritional deficiency, exposure to some elements may influence hemoglobin levels, we wanted to explore the role of a broad panel of toxic and "emerging" elements in hemoglobin deficiency. We found that the levels of Ag, As, Ba, Bi, Ce, Eu, Er, Ga, La, Nb, Nd, Pb, Pr, Sm, Sn, Ta, Th, Tl, U and V were higher in anemic participants than in controls. For most of these elements an inverse correlation with hemoglobin concentration was found. Some of them also correlated inversely with blood iron levels, pointing to the possibility that a higher rate of intestinal uptake of these could exist in relation to a nutritional deficiency of iron. However, the higher levels of Pb, and the group of REE and other ME in anemic participants were independent of iron levels, pointing to the possibility that these elements could play a role in the development of anemia. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Critical element ratio maps of granitic terrains for exploration of atomic minerals

    International Nuclear Information System (INIS)

    Viswanathan, S.; Singh, Yamuna

    2010-01-01

    The paper proposes a new type of geochemical map, named the 'Critical Element Ratio Map', involving K/Rb, Ba/Rb, and Rb/Sr ratios, to aid exploration programmes for atomic minerals in granitic terrains. Granitic rocks formed from highly evolved melts are favourable for hosting ore deposits of U, Th, Li, Be, Nb, Ta, Y, the rare-earth elements (REEs), Sn, W, and Cs. The characteristic geochemical features of this type of granite are low K/Rb and Ba/Rb ratios and high Rb/Sr ratios. The average K/Rb, Ba/Rb, and Rb/Sr ratios of high-calcium granitic rocks (tonalites, granodiorites, and leucogranodiorites) are 229, 8.18, and 0.25, and those for low-calcium granitic rocks (adamellites, granites, leucogranites, and alaskites) are 247, 2.35, and 1.70, respectively. In sharp contrast, the K/Rb, Ba/Rb, and Rb/Sr ratios of granitic rocks formed from highly evolved melts will be less than 100, less than 0.25, and more than 5, respectively. The paper also describes a simple, accurate, precise, rapid, and non-destructive method for determining K, Rb, Sr, and in granitic rocks by wavelength-dispersive X-ray fluorescence spectrometry (WDXRFS) and outlines the methodology for preparing 'Critical Element Ratio Maps' of granitic terrains. granite-hosted 'Rossing-Type' of uranium ore deposits are to be discovered in India, it will be possible only by launching an intensive programme for preparing 'Critical Element Ratio Maps' to identify granitic bodies characterized anomalously low K/Rb and Ba/Rb ratios and high Rb/Sr ratios within the large granitic terrains of Peninsular and Extra-Peninsular India. (author)

  8. Plasma-assisted MOCVD growth of superconducting NbN thin films using Nb dialkylamide and Nb alkylimide precursors

    International Nuclear Information System (INIS)

    Liu Xiang; Ott, A.W.; Chang, R.P.H.; Babcok, J.R.; Belot, J.A.; Metz, M.V.; Marks, T.J.; Lane, M.A.; Kannewurf, C.R.

    2001-01-01

    The first example of the use of metal-organic precursors for depositing NbN superconducting thin films is described. The study, which employed niobium(IV) and niobium(V) pulsed source precursors and hydrazine plasma as the nitrogen source, indicates that T c is highly dependent on the lattice parameters and level of oxygen impurities, which are in turn governed by growth and post-deposition annealing temperatures. (orig.)

  9. Evolution of Si-2N2Nb island configuration on NbN (0 0 1) surface: A first-principles calculation

    International Nuclear Information System (INIS)

    Ren, Yuan; Xia, Qing; Zhang, Chao; Liu, Xuejie; Li, Zhi; Zhang, Fucheng

    2015-01-01

    Graphical abstract: - Highlights: • We investigate the separation and gathering of Nb, Si and N atom around come to NbN grain. • The adsorption and diffusion of single atom around 2N2Nb island were calculated by DFT. • The adsorption behavior of Si-2N2Nb island on NbN (0 0 1) surface were investigated. • The evolution of Si-2N2Nb island on NbN (0 0 1) were calculated by nudged elastic band. - Abstract: The separation and aggregation of Nb, Si, and N atoms around the NbN grain during the deposition of the Nb–Si–N nanocomposite film were discussed. The evolution behavior of the 2N2Nb island and the adsorption and diffusion energy of Nb, Si, and N atoms around the island on the NbN (0 0 1) surface were investigated using the first-principles method based on density functional theory. Results indicated that the most stable configuration of the Nb–Si–N island was the combination of Nb and N atoms to form the island and the possible aggregation of the Si atom to diagonal Nb atom outside the island. Substitution solid solution was eventually formed, in which the Nb atom of the 2N2Nb island was replaced by the Si atom during deposition. However, the Si atom was easily replaced by the Nb atom at the site with abundant Nb atoms. The diffusion energy of the evolution from Nb-2N1Nb1Si to Si-2N2Nb was 1.58 eV, and the total energy of the configuration decreased. Moreover, the interface of Si and NbN grains tended to separate. The highest energy adsorption sites for Nb, Si, N atoms adsorbed on the NbN (0 0 1) surface around the 2N2Nb island were P3, P1, and P2, respectively. The adsorption energies of Nb, Si, and N atoms on the NbN (0 0 1) surface around the 2N2Nb island were 7.3067, 5.3521, and 6.7113 eV, respectively, and their diffusion energies around the 2N2Nb island were 2.62, 1.35, and 5.094 eV, respectively. The low adsorption and diffusion energies of active Si atoms promoted the distribution of Nb and N atoms during deposition. Furthermore, the Nb

  10. Structure and properties of CaNb2O6:Sm3+ thin films by pulsed laser deposition

    International Nuclear Information System (INIS)

    Wang, Yinzhen; Zhang, Liaolin; Cao, Renping; Qiu, Jianrong; Miao, Qing

    2014-01-01

    CaNb 2 O 6 :Sm 3+ films were prepared on quartz glass and α-Al 2 O 3 (001) substrates by pulsed laser deposition. The structural, morphological, and optical properties of the CaNb 2 O 6 :Sm 3+ films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), emission-scan electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL) measurements. The results show that the structure and properties of CaNb 2 O 6 :Sm 3+ films were dependent on substrates. The CaNb 2 O 6 :Sm 3+ films on Al 2 O 3 (0001) substrate have better crystallinity. The full-width at half-maximum (FWHM) of (131) peak are 0.45 and 0.32 for the CaNb 2 O 6 :Sm 3+ film on glass and Al 2 O 3 (001), respectively. The crystallite size of CaNb 2 O 6 :Sm 3+ films grown on glass and Al 2 O 3 (001) was about 8.22 and 9.98 nm, respectively. The oxidation state of the Sm element on the films was Sm 3+ state. The photoluminescence (PL) spectra were measured at room temperature, the CaNb 2 O 6 :Sm 3+ films on Al 2 O 3 (001) substrate have a better PL intensity, the identified emission bands were by the intra 4f transitions of Sm 3+ from the excited level to the lower levels at 567 nm for 4 G 5/2 → 6 H 5/2 transition, at 609 nm for 4 G 5/2 → 6 H 7/2 transition, and at 657 nm for 4 G 5/2 → 6 H 9/2 transition. (orig.)

  11. Integrated design of Nb-based superalloys: Ab initio calculations, computational thermodynamics and kinetics, and experimental results

    International Nuclear Information System (INIS)

    Ghosh, G.; Olson, G.B.

    2007-01-01

    An optimal integration of modern computational tools and efficient experimentation is presented for the accelerated design of Nb-based superalloys. Integrated within a systems engineering framework, we have used ab initio methods along with alloy theory tools to predict phase stability of solid solutions and intermetallics to accelerate assessment of thermodynamic and kinetic databases enabling comprehensive predictive design of multicomponent multiphase microstructures as dynamic systems. Such an approach is also applicable for the accelerated design and development of other high performance materials. Based on established principles underlying Ni-based superalloys, the central microstructural concept is a precipitation strengthened system in which coherent cubic aluminide phase(s) provide both creep strengthening and a source of Al for Al 2 O 3 passivation enabled by a Nb-based alloy matrix with required ductile-to-brittle transition temperature, atomic transport kinetics and oxygen solubility behaviors. Ultrasoft and PAW pseudopotentials, as implemented in VASP, are used to calculate total energy, density of states and bonding charge densities of aluminides with B2 and L2 1 structures relevant to this research. Characterization of prototype alloys by transmission and analytical electron microscopy demonstrates the precipitation of B2 or L2 1 aluminide in a (Nb) matrix. Employing Thermo-Calc and DICTRA software systems, thermodynamic and kinetic databases are developed for substitutional alloying elements and interstitial oxygen to enhance the diffusivity ratio of Al to O for promotion of Al 2 O 3 passivation. However, the oxidation study of a Nb-Hf-Al alloy, with enhanced solubility of Al in (Nb) than in binary Nb-Al alloys, at 1300 deg. C shows the presence of a mixed oxide layer of NbAlO 4 and HfO 2 exhibiting parabolic growth

  12. Finite Element Study on Performance of Piezoelectric Bimorph Cantilevers Using Porous/Ceramic 0-3 Polymer Composites

    Science.gov (United States)

    Kiran, Raj; Kumar, Anuruddh; Chauhan, Vishal S.; Kumar, Rajeev; Vaish, Rahul

    2018-01-01

    Finite element analysis of 0-3 composites made of piezoceramic particles and pores embedded in polyvinylidene difluoride (PVDF) has been carried out. The representative volume element (RVE) approach was used to calculate the effective elastic and piezoelectric properties of the periodic isotropic 0-3 piezoelectric composites. It was observed that the elastic and piezoelectric properties increased with the volume fraction of {K}_{0.475} {Na}_{0.475} {Li}_{0.05} ( {{Nb}_{0.92} {Ta}_{0.05} {Sb}_{0.03} } ){O}3 (KNLNTS) particles but decreased for the porous composites. These effective properties were further used to analyze the potential use of such bimorph cantilever beams in sensing and energy harvesting applications. Sensing voltage continuously increased for KNLNTS filled composites while for porous materials it increased up to 15% volume fraction porosity and then decreased. The same trend was also observed for the power produced by the harvester. However, the sensing voltage and power produced by harvesters made of porous composites were lower than for harvesters made of pure PVDF.

  13. Forensic identification of trunk mat by trace element analysis of single fiber with laser ablation ICP-MS

    International Nuclear Information System (INIS)

    Hiroma, Yuki; Nakai, Izumi; Hokura, Akiko

    2010-01-01

    The application of LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) to the chemical characterization of single trunk mat fibers made of PET was investigated in order to establish a forensic analytical method for the discrimination of samples of different origins. The analytical conditions of LA-ICP-MS equipped with a 213 nm Nd : YAG laser were optimized to analyze trace elements, such as Cu, Sb, and Ba at ppm levels. A total of 31 samples produced by 7 car manufactures in Japan were used for analysis. The concentrations of Li, Mg, Al, P, Ca, Ti, Co, Cu, Ge, Nb, Sb, Ta, and Pb were successfully measured from a single fiber sample with a diameter of ca. 20 μm. It was possible to discriminate all 31 samples based on the analytical results of a single fiber by LA-ICP-MS combined with those of FT-IR and SEM-EDS. LA-ICP-MS has good analytical sensitivity, and requires a much shorter preparation time and a smaller sample size than any other conventional element analysis methods. This paper demonstrates for the first time that this method is practically useful as a powerful tool for the forensic identification of a single trunk mat fiber. (author)

  14. Multi-elemental contamination and historic record in sediments from the Santos-Cubatao Estuarine System, Brazil

    International Nuclear Information System (INIS)

    Luiz-Silva, Wanilson; Machado, Wilson; Matos, Rosa H.R.

    2008-01-01

    This paper records for the first time the contamination history and identifies the sources of 38 elements in sediments from the Santos-Cubatao Estuarine System (SE Brazil), at one of the most industrialized areas in Latin America. The compositions of samples from a 260 cm long sediment core collected in the Morrao River estuary were determined by ICP-MS. Enrichment factors, principal component analysis, correlation matrixes, and the characterization of geochemical signatures permitted a consistent data evaluation. Contaminant elements such as Cr, Mn, Ni, Zn, Ga, Ag, Cd, Sn, Sb, Pb, and Bi were associated with steel plant-derived Fe concentrations, while Be, Ca, Sc, Co, Cu, Sr, Y, Zr, Nb, Hf, Ta, Th, and U were associated with fertilizer industry-derived P concentrations. An overlap of sedimentary Fe distribution and local steel plant production indicated that Fe is a reliable marker of the contamination history, allowing the estimation of sedimentation rates over a period of 45 years of industrial activities. (author)

  15. Microstructure and mechanical behavior of metal injection molded Ti-Nb binary alloys as biomedical material.

    Science.gov (United States)

    Zhao, Dapeng; Chang, Keke; Ebel, Thomas; Qian, Ma; Willumeit, Regine; Yan, Ming; Pyczak, Florian

    2013-12-01

    The application of titanium (Ti) based biomedical materials which are widely used at present, such as commercially pure titanium (CP-Ti) and Ti-6Al-4V, are limited by the mismatch of Young's modulus between the implant and the bones, the high costs of products, and the difficulty of producing complex shapes of materials by conventional methods. Niobium (Nb) is a non-toxic element with strong β stabilizing effect in Ti alloys, which makes Ti-Nb based alloys attractive for implant application. Metal injection molding (MIM) is a cost-efficient near-net shape process. Thus, it attracts growing interest for the processing of Ti and Ti alloys as biomaterial. In this investigation, metal injection molding was applied to the fabrication of a series of Ti-Nb binary alloys with niobium content ranging from 10wt% to 22wt%, and CP-Ti for comparison. Specimens were characterized by melt extraction, optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). Titanium carbide formation was observed in all the as-sintered Ti-Nb binary alloys but not in the as-sintered CP-Ti. Selected area electron diffraction (SAED) patterns revealed that the carbides are Ti2C. It was found that with increasing niobium content from 0% to 22%, the porosity increased from about 1.6% to 5.8%, and the carbide area fraction increased from 0% to about 1.8% in the as-sintered samples. The effects of niobium content, porosity and titanium carbides on mechanical properties have been discussed. The as-sintered Ti-Nb specimens exhibited an excellent combination of high tensile strength and low Young's modulus, but relatively low ductility. © 2013 Elsevier Ltd. All rights reserved.

  16. Ni ion damage in Cu and Nb

    International Nuclear Information System (INIS)

    Roberto, J.B.; Narayan, J.

    1975-01-01

    Ni ion damage in Cu was studied using x-ray diffuse scattering and transmission electron microscopy, and in Nb using x-ray diffuse scattering. Single crystals of Cu and Nb were irradiated at room temperature to a fluence of 1.2 x 10 13 /cm 2 at 60 MeV, and Cu was also irradiated to 5 x 10 12 /cm 2 at 4 MeV. The x-ray diffuse scattering from loop-type defect clusters in the crystals was measured near several Bragg reflections in order to probe the depth distributions of the damage. In Cu, cluster size distributions derived from the x-ray measurements agreed well with TEM results. Comparison with fission reactor irradiations using the damage energy concept suggests similarities in retained damage between the neutron and Ni ion irradiations

  17. Corrosion and Serration Behaviors of TiZr0.5NbCr0.5VxMoy High Entropy Alloys in Aqueous Environments

    Directory of Open Access Journals (Sweden)

    Jiemin Li

    2014-12-01

    Full Text Available The corrosion and serration behaviors of TiZr0.5NbCr0.5, TiZr0.5NbCr0.5V and TiZr0.5NbCr0.5Mo high entropy alloys (HEAs in NaCl and H2SO4 solutions were studied by potentiodynamic polarizations (PP and immersion tests. The results show that all the alloys display excellent corrosion resistance no matter in NaCl solution or in H2SO4 solution. The additions of V and Mo increase the pitting corrosion resistance for the three alloys in NaCl solution slightly and greatly improve the corrosion resistance in H2SO4 solution. The corrosion behaviors of TiZr0.5NbCr0.5 and TiZr0.5NbCr0.5Mo alloys are more sensitive to temperature than that of TiZr0.5NbCr0.5V alloy. After immersion, the surface of TiZr0.5NbCr0.5 alloy appears some pitting holes, this may be related to the electrochemical noise and serration behavior on PP curves; localized corrosion initiates mainly on the boundaries of the BCC and Cr2Zr Laves phase for TiZr0.5NbCr0.5V alloy; while for the TiZr0.5NbCr0.5Mo alloy, the dendrites with Mo element rich region exhibit poor corrosion resistance.

  18. A Low Noise NbTiN-Based 850 GHz SIS Receiver for the Caltech Submillimeter Observatory

    Science.gov (United States)

    Kooi, J. W.; Kawamura, J.; Chen, J.; Chattopadhyay, G.; Pardo, J. R.; Zmuidzinas, J.; Phillips, T. G.; Bumble, B.; Stern, J.; LeDuc, H. G.

    2000-01-01

    We have developed a niobium titanium nitride (NbTiN) based superconductor- insulator-superconductor (SIS) receiver to cover the 350 micron atmospheric window. This frequency band lies entirely above the energy gap of niobium (700 GHz), a commonly used SIS superconductor. The instrument uses an open structure twin-slot SIS mixer that consists of two Nb/AlN/NbTiN tunnel junctions, NbTiN thin-film microstrip tuning elements, and a NbTiN ground plane. The optical configuration is very similar to the 850 GHz waveguide receiver that was installed at the Caltech Submillimeter Observatory (CSO) in 1997. To minimize front-end loss, we employed reflecting optics and a cooled beamsplitter at 4 K. The instrument has an uncorrected receiver noise temperature of 205K DSB at 800 GHz and 410K DSB at 900 GHz. The degradation in receiver sensitivity with frequency is primarily due to an increase in the mixer conversion loss, which is attributed to the mismatch between the SIS junction and the twin-slot antenna impedance. The overall system performance has been confirmed through its use at the telescope to detect a wealth of new spectroscopic lines.

  19. Highly dispersed TaOx nanoparticles prepared by electrodeposition as oxygen reduction electrocatalysts for polymer electrolyte fuel cells

    KAUST Repository

    Seo, Jeongsuk

    2013-06-06

    Based on the chemical stability of group IV and V elements in acidic solutions, TaOx nanoparticles prepared by electrodeposition in an ethanol-based Ta plating bath at room temperature were investigated as novel nonplatinum electrocatalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs). Electrodeposition conditions of Ta complexes and subsequent various heat treatments for the deposited TaOx were examined for the best performance of the ORR. TaOx particles on carbon black (CB), electrodeposited at a constant potential of -0.5 V Ag/AgCl for 10 s and then heat-treated by pure H2 flow at 523 K for 1 h, showed excellent catalytic activity with an onset potential of 0.93 VRHE (for 2 μA cm-2) for the ORR. Surface characterizations of the catalysts were performed by scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The loading amounts of the electrodeposited material on the CB were determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). All the physical results suggested that high dispersion of TaOx particles on the CB surface with 2-3 nm size was critical and key for high activity. The chemical identity and modified surface structure for the deposited TaOx catalysts before and after H 2 heat treatment were analyzed by X-ray photoelectron spectroscopy (XPS). The formation of more exposed active sites on the electrode surface and enhanced electroconductivity of the tantalum oxide promoted from the H 2 treatment greatly improved the ORR performance of the electrodeposited TaOx nanoparticles on CB. Finally, the highly retained ORR activity after an accelerated durability test in an acidic solution confirmed and proved the chemical stability of the oxide nanoparticles. The high utilization of the electrodeposited TaOx nanoparticles uniformly dispersed on CB for the ORR was comparable to that of commercial Pt/CB catalysts

  20. Finite Element Study on Acoustic Energy Harvesting Using Lead-Free Piezoelectric Ceramics

    Science.gov (United States)

    Kumar, Anuruddh; Sharma, Anshul; Kumar, Rajeev; Vaish, Rahul

    2018-02-01

    In this article, a numerical investigation is performed for ambient acoustic energy harvesting at a low-frequency acoustic signal. A model of a quarter-wavelength resonator with a rectangular cross section is constructed, and piezoelectric-laminated bimorph plates are placed inside the system. Finite element modeling is implemented to numerically formulate the piezoelectric energy harvester. With the application of acoustic pressure at the open end of the resonator, amplified acoustic pressure inside the tube vibrates the piezolaminated bimorphs inside the tube, thus generating electric potential on the piezoelectric layers. To generate higher voltage and power in the acoustic harvester, multiple piezolaminated plates are positioned inside the resonator. The lead-free piezoelectric material K0.475Na0.475Li0.05 (Nb0.92Ta0.05Sb0.03)O3 (KNLNTS) is laminated on the host structure as a layer of piezoelectric material for the acoustic energy harvester. With the application of an acoustic sound pressure of 1 dB at the opening of the tube, a maximum output voltage of 16.3 V is measured at the first natural frequency, while the maximum power calculated is 0.033 mW. Maximum voltage is obtained when five piezoelectric bimorphs are place inside the resonator. At the second natural frequency, the maximum voltage measured is 8.40 V, obtained when eight piezoelectric bimorphs are placed inside the resonator, and the maximum power calculated is 0.020 mW.

  1. Mechanical, In Vitro Corrosion Resistance and Biological Compatibility of Cast and Annealed Ti25Nb10Zr Alloy

    Directory of Open Access Journals (Sweden)

    Cosmin M. Cotrut

    2017-03-01

    Full Text Available Compared to other alloys, Ti6Al4V is the most used in medicine. In recent years, concerns regarding the toxicity of Al and V elements found in the composition of Ti6Al4V have drawn the attention of the scientific community, due to the release of Al or V ions after long term exposure to human body fluids which can lead to a negative response of the human host. Based on this, the aim of the paper was to manufacture a Ti25Nb10Zr alloy consisting of biocompatible elements which can replace Ti6Al4V usage in medical applications. In order to prove that this alloy possessed improved properties, the mechanical, wear and corrosion resistance, wettability, and cell viability were performed in comparison with those of the Ti6Al4V alloy. The corrosion behavior of this new alloy in simulated body fluid (SBF and Hank solutions is superior to that of Ti6Al4V. The cast Ti25Nb10Zr alloy has a good tribological performance in SBF, while annealed Ti25Nb10Zr alloy is better in Hank solution. Cell viability and proliferation assay after five days indicated that Ti25Nb10Zr presented a good viability and proliferation with values of approximately 7% and 10% higher, respectively, than the ones registered for pure Ti. When compared with Ti6Al4V, the obtained results for Ti25Nb10Zr indicated smaller values with 20% in the case of both tests. Overall, it can be concluded that cell proliferation and viability tests indicated that the biocompatibility of the Ti25Nb10Zr alloy is as good as pure Ti and Ti6Al4V alloy.

  2. Monolithic Cu-Cr-Nb Alloys for High Temperature, High Heat Flux Applications

    Science.gov (United States)

    Ellis, David L.; Locci, Ivan E.; Michal, Gary M.; Humphrey, Derek M.

    1999-01-01

    Work during the prior four years of this grant has resulted in significant advances in the development of Cu-8 Cr4 Nb and related Cu-Cr-Nb alloys. The alloys are nearing commercial use in the Reusable Launch Vehicle (RLV) where they are candidate materials for the thrust cell liners of the aerospike engines being developed by Rocketdyne. During the fifth and final year of the grant, it is proposed to complete development of the design level database of mechanical and thermophysical properties and transfer it to NASA Glenn Research Center and Rocketdyne. The database development work will be divided into three main areas: Thermophysical Database Augmentation, Mechanical Testing and Metallography and Fractography. In addition to the database development, work will continue that is focussed on the production of alternatives to the powder metallurgy alloys currently used. Exploration of alternative alloys will be aimed at both the development of lower cost materials and higher performance materials. A key element of this effort will be the use of Thermo-Calc software to survey the solubility behavior of a wide range of alloying elements in a copper matrix. The ultimate goals would be to define suitable alloy compositions and processing routes to produce thin sheets of the material at either a lower cost, or, with improved mechanical and thermal properties compared to the current Cu-Cr-Nb powder metallurgy alloys.

  3. Novel TaPO{sub 5-x}N{sub 2x/3} oxynitrides

    Energy Technology Data Exchange (ETDEWEB)

    Ray, Erwan [UMR CNRS 6226 ' Sciences Chimiques de Rennes' , equipe ' Verres et Ceramiques' , Universite de Rennes 1, F-35042 Rennes Cedex (France); Tessier, Franck, E-mail: Franck.Tessier@univ-rennes1.fr [UMR CNRS 6226 ' Sciences Chimiques de Rennes' , equipe ' Verres et Ceramiques' , Universite de Rennes 1, F-35042 Rennes Cedex (France); Chevire, Francois; Herbert, Nathalie; Lebullenger, Ronan; Roiland, Claire; Bureau, Bruno [UMR CNRS 6226 ' Sciences Chimiques de Rennes' , equipe ' Verres et Ceramiques' , Universite de Rennes 1, F-35042 Rennes Cedex (France)

    2012-02-05

    Graphical abstract: Tantalum-based nitridophosphate powders TaPO{sub 5-x}N{sub 2x/3} containing 9.1 (yellow) and 12.8 (orange) nitrogen wt.%, respectively. Highlights: Black-Right-Pointing-Pointer Synthesis of novel tantalum-based nitridophosphates. Black-Right-Pointing-Pointer Amorphous oxide and oxynitride powders. Black-Right-Pointing-Pointer Colored oxynitride phases. Black-Right-Pointing-Pointer High specific surface area powders. - Abstract: A series of novel nitrided tantalophosphates has been prepared by nitridation of X-ray amorphous TaPO{sub 5} precursors under ammonia flow. By varying the nitridation temperature, amorphous TaPO{sub 5-x}N{sub 2x/3} (1.6 < x < 4.1) oxynitrides were obtained with different nitrogen contents (N wt.% = 5-15). The most relevant features of this oxynitride series are as follow: (i) specific surface areas higher than 150 m{sup 2} g{sup -1}, (ii) yellow to orange colors depending on nitrogen contents and (iii) formation of a solid solution with variable nitrogen and oxygen contents. The precursors and corresponding oxynitrides have been characterized by several techniques including X-ray diffraction, oxygen/nitrogen elemental analyses, BET analysis, UV-vis spectrophotometry, thermal analysis, SEM, DRIFT and NMR analyses.

  4. ADHESION OF BIOCOMPATIBLE TiNb COATING

    Directory of Open Access Journals (Sweden)

    Tomas Kolegar

    2017-06-01

    Full Text Available Preparation of a coating with a high quality requires good adhesion of the film to the substrate. The paper deals with the adhesion of biocompatible TiNb coating with different base materials. Several materials such as titanium CP grade 2, titanium alloys Ti6Al4V and stainless steel AISI 316L were measured. Testing samples were made in the shape of small discs. Those samples were coated with a TiNb layer by using the PVD method (magnetron sputtering. Onto the measured layer of TiNb an assistant cylinder was stuck using a high strength epoxy adhesive E1100S. The sample with the assistant cylinder was fixed into a special fixture and the whole assembly underwent pull-off testing for adhesion. The main result of this experiment was determining the strength needed to peel the layer and morphology and size of the breakaway. As a result, we will be able to determine the best base material and conditions where the coating will be remain intact with the base material.

  5. Niobium and tantalum

    International Nuclear Information System (INIS)

    Polupanova, L.I.; Volkova, G.A.

    1983-01-01

    General mineralogical-geochemical and analytical characteristics of niobium and tantalum are presented. Potentialities of any analytical methods for determining these elements in various geologic samples are estimated. The following specific techniques are described: neutron + activation determination of Ta, fluorescence X-radiometric determination of Nb and Ta, fluorescence X-ray spectral determination of Nb and Ta, spectrographic determination of Nb and Ta, gravimetric determination of Nb and Ta, their extraction-photometric determination with various reagents (crystal violet, rhodamine 6 Y, butylrhodamine B)

  6. Degradation of superconducting Nb/NbN films by atmospheric oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Henry, Michael David; Wolfley, Steven L.; Young, Travis Ryan; Monson, Todd; Pearce, Charles Joseph; Lewis, Rupert M.; Clark, Blythe; Brunke, Lyle Brent; Missert, Nancy A.

    2017-03-01

    Niobium and niobium nitride thin films are transitioning from fundamental research toward wafer scale manufacturing with technology drivers that include superconducting circuits and electronics, optical single photon detectors, logic, and memory. Successful microfabrication requires precise control over the properties of sputtered superconducting films, including oxidation. Previous work has demonstrated the mechanism in oxidation of Nb and how film structure could have deleterious effects upon the superconducting properties. This study provides an examination of atmospheric oxidation of NbN films. By examination of the room temperature sheet resistance of NbN bulk oxidation was identified and confirmed by secondary ion mass spectrometry. As a result, Meissner magnetic measurements confirmed the bulk oxidation not observed with simple cryogenic resistivity measurements.

  7. Electronic signature of the vacancy ordering in NbO (Nb3O3)

    Science.gov (United States)

    Efimenko, A. K.; Hollmann, N.; Hoefer, K.; Weinen, J.; Takegami, D.; Wolff, K. K.; Altendorf, S. G.; Hu, Z.; Rata, A. D.; Komarek, A. C.; Nugroho, A. A.; Liao, Y. F.; Tsuei, K.-D.; Hsieh, H. H.; Lin, H.-J.; Chen, C. T.; Tjeng, L. H.; Kasinathan, D.

    2017-11-01

    We investigated the electronic structure of the vacancy-ordered 4 d -transition-metal monoxide NbO (Nb3O3) using angle-integrated soft- and hard-x-ray photoelectron spectroscopies as well as ultraviolet angle-resolved photoelectron spectroscopy. We found that density-functional-based band-structure calculations can describe the spectral features accurately provided that self-interaction effects are taken into account. In the angle-resolved spectra we were able to identify the so-called `vacancy' band that characterizes the ordering of the vacancies. This together with the band-structure results indicate the important role of the very large inter-Nb-4 d hybridization for the formation of the ordered vacancies and the high thermal stability of the ordered structure of niobium monoxide.

  8. Surface characterization of Nb samples electropolished with real superconducting rf accelerator cavities

    Directory of Open Access Journals (Sweden)

    Xin Zhao

    2010-12-01

    Full Text Available We report the results of surface characterizations of niobium (Nb samples electropolished together with a single cell superconducting radio-frequency accelerator cavity. These witness samples were located in three regions of the cavity, namely at the equator, the iris, and the beam pipe. Auger electron spectroscopy was utilized to probe the chemical composition of the topmost four atomic layers. Scanning electron microscopy with energy dispersive x ray for elemental analysis was used to observe the surface topography and chemical composition at the micrometer scale. A few atomic layers of sulfur (S were found covering the samples nonuniformly. Niobium oxide granules with a sharp geometry were observed on every sample. Some Nb-O granules appeared to also contain sulfur.

  9. Manufacture and evaluation of Nb3Sn conductors fabricated by the MJR method

    International Nuclear Information System (INIS)

    McDonald, W.K.; Curtis, C.W.; Scanlan, R.M.; Larbalestier, D.C.; Marken, K.; Smathers, D.B.

    1982-01-01

    The bronze matrix/niobium filament process has become established as a commercially viable method for producing multifilamentary Nb 3 Sn superconductors. This paper describes a new method, the Modified Jelly-Roll (MJR) approach, which can produce a structure similar to that in a conventionally fabricated multifilamentary Nb 3 Sn conductor. This approach utilizes alternate sheets of niobium expanded metal and bronze, which are rolled into a jelly-roll configuration and then extruded. During extrusion and subsequent drawing, the junctures in the niobium are elongated and the material develops a filamentary structure. This method may offer significant advantages in terms of reduced fabrication time and cost over the conventional approach. Results of a manufacturing development program will be presented in which two lengths of conductor were made to High-Field Test Facility conductor specifications. In addition, critical current and transition temperature measurements of the sub-elements used to construct the HFTF-type lengths will be reported

  10. Tunneling spectroscopy on superconducting Nb3Sn with artioficial barriers

    International Nuclear Information System (INIS)

    Schneider, U.

    1984-03-01

    Tunneling diodes on Nb 3 Sn were prepared by magnetron sputtering. The superconducting transition temperatures of the Nb 3 Sn films were in the range of 5 to 18 K. An energetically low-lying structure in the tunneling density of states has been localized by detailed studies of the second derivative of the current-voltage characteristics of the diodes. This structure was found near 5.5 meV for stoichiometric Nb 3 Sn (Tsub(c) approx.= 18 K) and at 6.7 meV for understoichiometric Nb 3 Sn (Tsub(c) approx.= 5 K). The minimum in the conductance at zero energy found in the normal state could be identified to be mainly due to inelastic phonon processes of barrier phonons and Nb 3 Sn phonons. Deformations were found in the tunneling density of states of stoichiometric Nb 3 Sn diodes which lead to contradiction when explained by proximity effects. (orig./GSCH)

  11. Amorphous-crystalline transition in thermoelectric NbO2

    International Nuclear Information System (INIS)

    Music, Denis; Chen, Yen-Ting; Bliem, Pascal; Geyer, Richard W

    2015-01-01

    Density functional theory was employed to design enhanced amorphous NbO 2 thermoelectrics. The covalent-ionic nature of Nb–O bonding is identical in amorphous NbO 2 and its crystalline counterpart. However, the Anderson localisation occurs in amorphous NbO 2 , which may affect the transport properties. We calculate a multifold increase in the absolute Seebeck coefficient for the amorphous state. These predictions were critically appraised by measuring the Seebeck coefficient of sputtered amorphous and crystalline NbO 2 thin films with the identical short-range order. The first-order phase transition occurs at approximately 550 °C, but amorphous NbO 2 possesses enhanced transport properties at all temperatures. Amorphous NbO 2 , reaching  −173 μV K −1 , exhibits up to a 29% larger absolute Seebeck coefficient value, thereby validating the predictions. (paper)

  12. Multi-component solid solution alloys having high mixing entropy

    Science.gov (United States)

    Bei, Hongbin

    2015-10-06

    A multi-component high-entropy alloy includes a composition selected from the following group: VNbTaTiMoWRe, VNbTaTiMoW, VNbTaTiMoRe, VNbTaTiWRe, VNbTaMoWRe, VNbTiMoWRe, VTaTiMoWRe, NbTaTiMoWRe, VNbTaTiMo, VNbTaTiW, VNbTaMoW, VNbTiMoW, VTaTiMoW, NbTaTiMoW, VNbTaTiRe, VNbTaMoRe, VNbTiMoRe, VTaTiMoRe, NbTaTiMoRe, VNbTaWRe, VNbTiWRe, VTaTiWRe, NbTaTiWRe, VNbMoWRe, VTaMoWRe, NbTaMoWRe, VTiMoWRe, NbTiMoWRe, TaTiMoWRe, wherein relative amounts of each element vary by no more than .+-.15 atomic %.

  13. Refractive Indices in Undoped and MgO-Doped Near-Stoichiometric LiTaO3 Crystals

    Science.gov (United States)

    Nakamura, Masaru; Higuchi, Shinji; Takekawa, Shunji; Terabe, Kazuya; Furukawa, Yasunori; Kitamura, Kenji

    2002-04-01

    Undoped and MgO (0.5 and 1.0-mol%)-doped near-stoichiometric LiTaO3 (SLT) crystals were grown from off-congruent Li-rich solutions (Li˜ 60 mol%) by the double-crucible Czochralski method using a continuous SLT ceramic grain charging system. Curie temperatures of the undoped and MgO (0.5 and 1.0-mol%)-doped SLT crystals are 688, 694 and 695°C, respectively. The ordinary and extraordinary refractive indices (no, ne) of these crystals were measured by the prism coupling technique in the wavelength range from 0.440 to 1.050 μm at room temperature, and the temperature-independent Sellmeier equations for each crystal were derived from the measured refractive index data. no of the SLT crystal was almost the same as that of a congruent-melt LiTaO3 (CLT) crystal, while ne of the SLT crystal was lower than that of the CLT crystal. ne was lower than no for the SLT crystal, similar to as in the case of the LiNbO3 crystal. The refractive indices of the SLT crystal, no and ne, were found to be almost independent of MgO concentration at the doping level of 0.5 and 1.0 mol%.

  14. Obtaining and Mechanical Properties of Ti-Mo-Zr-Ta Alloys

    Science.gov (United States)

    Bălţatu, M. S.; Vizureanu, P.; Geantă, V.; Nejneru, C.; Țugui, C. A.; Focşăneanu, S. C.

    2017-06-01

    Ti-based alloys are successfully used in the area of orthopedic biomaterials for their enhanced biocompatibility, good corrosion and mechanical properties. The most suitable metals as an alloying element for orthopedic biomaterials are zirconium, molybdenum and tantalum because are non toxic and have good properties. The paper purpose development of two alloys of Ti-Mo-Zr-Ta (TMZT) prepared by arc-melting with several mechanical properties determined by microindentation. The mechanical properties analyzed was Vickers hardness and dynamic elasticity modulus. The investigated alloys presents a low Young’s modulus, an important condition of biomaterials for preventing stress shielding phenomenon.

  15. The system Fe-Nb-S and its geological implications

    Czech Academy of Sciences Publication Activity Database

    Drábek, M.; Hybler, Jiří; Rieder, M.; Böhmová, Vlasta

    2010-01-01

    Roč. 48, č. 5 (2010), s. 1059-1068 ISSN 0008-4476 R&D Projects: GA ČR GA205/08/0122 Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z30130516 Keywords : phase relations * edgarite * Fe x Nb y S 2 solid solution * Nb sulfides * system Fe-Nb-S * crystal-structure refinements Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.289, year: 2010

  16. Radiation detection with Nb/Al-AlOx/Al/Nb superconducting tunnel junctions

    International Nuclear Information System (INIS)

    Matsumura, Atsuki; Takahashi, Toru; Kurakado, Masahiko

    1992-01-01

    Superconductor radiation detectors have the possibility of 20-30 times better energy resolution than that of a high resolution Si detector. We fabricated Nb/Al-AlOx/Al/Nb superconducting tunnel junctions with low leakage current. X rays were detected with large area junctions of 178x178 μm 2 . High energy resolution of 160 eV for 5.9 keV was obtained. We also fabricated series connected junctions which covers a rather large area of 4x4 mm 2 . α particles injected into the rear substrate were detected using nonthermal phonons induced by the radiations in the substrate. (author)

  17. NbC precipitates EELS spectra in a very low carbon microalloyed steel

    Directory of Open Access Journals (Sweden)

    Mancilla, J. E.

    2004-06-01

    Full Text Available In this paper a characterization study by transmission electron microscopy (TEM and electron energy loss spectroscopy (EELS of NbC precipitates in microalloyed steel is presented. The steel was hot rolled in a laboratory scale two-high reversing mill. The shape, size, location, and number of particles per unit area in the steel microstructure are reported. The particles were semi quantitatively analyzed for the heavier alloying elements using EDS, while EELS was used for the lighter elements, e. g. carbon and nitrogen. The EELS study of the precipitates reveals that the carbon is present as a compound (NbC without nitrogen.

    En este trabajo se presenta un estudio de caracterización por espectroscopia de pérdida de energía de electrones (EPEE realizado en un microscopio electrónico de transmisión de los precipitados de NbC en un acero microaleado. El acero se laminó en caliente en un laminador dúo reversible escala laboratorio. Las partículas de precipitados se caracterizaron en tamaños, formas y distribución y se analizaron semicuantitativamente para los elementos de aleación del acero más pesados, empleando un detector por dispersión de energías de rayos X, mientras que la EPEE se empleó para los elementos más ligeros, es decir, el carbono y el nitrógeno. El estudio por EPEE de los precipitados muestra que el carbono está presente como un compuesto (NbC sin que se haya encontrado nitrógeno en los mismos.

  18. Mechanical and electrochemical characterisation of new Ti-Mo-Nb-Zr alloys for biomedical applications.

    Science.gov (United States)

    Nnamchi, Paul S; Obayi, C S; Todd, Iain; Rainforth, M W

    2016-07-01

    The development and characterisation of new metallic biomaterials that contain non-toxic and non-allergic elements but possess low elastic modulus and low biodegradation rates, has become a topic of serious investigation in orthopaedic implant application. The lowering of elastic modulus and improving of corrosion resistance can be achieved by specific chemical alloying and super-elasticity effects, associated with a stress-induced phase transformation from the BCC metastable beta phase to the orthorhombic α″ martensite. Using this framework, this paper focuses on the effect of Nb and/or Zr micro-additions on the elastic modulus/yield strength balance and discusses microstructure, and the mechanical and electrochemical behaviour of four new β-Ti-8Mo-xNb-xZr (x=2-5) alloys, using tensile tests, X-ray diffraction, SEM characterisation, ultrasound technique and potentiodynamic polarisation methods. The results reveal that the alloys exhibit a pronounced microstructural sensitivity response, with alloying elements and excellent agreement between β-stability and high mechanical strength, with increasing Nb additions. Although all the alloys possess excellent corrosion resistance and low Young׳s modulus, Ti-8Mo-4Nb-2Zr alloy, which consists of β+α'' phases, exhibits a low Young modulus of 35GPa, which is lower than those of the commercial alloys already used in biomedical implantation. The significant corrosion resistance, nontoxicity and better mechanical compatibility are properties pertinent to preventing stress shielding and bone resorption in orthopaedic implant applications. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  19. Selective oxidation-induced strengthening of Zr/Nb nanoscale multilayers

    International Nuclear Information System (INIS)

    Monclús, M.A.; Callisti, M.; Polcar, T.; Yang, L.W.; Llorca, J.; Molina-Aldareguía, J.M.

    2017-01-01

    The paper presents a new approach, based on controlled oxidation of nanoscale metallic multilayers, to produce strong and hard oxide/metal nanocomposite coatings with high strength and good thermal stability. The approach is demonstrated by performing long term annealing on sputtered Zr/Nb nanoscale metallic multilayers and investigating the evolution of their microstructure and mechanical properties by combining analytical transmission electron microscopy, nano-mechanical tests and finite element models. As-deposited multilayers were annealed at 350 °C in air for times ranging between 1 and 336 h. The elastic modulus increased by ∼20% and the hardness by ∼42% after 15 h of annealing. Longer annealing times did not lead to changes in hardness, although the elastic modulus increased up to 35% after 336 h. The hcp Zr layers were rapidly transformed into monoclinic ZrO 2 (in the first 15 h), while the Nb layers were progressively oxidised, from top surface down towards the substrate, to form an amorphous oxide phase at a much lower rate. The sequential oxidation of Zr and Nb layers was key for the oxidation to take place without rupture of the multi-layered structure and without coating spallation, as the plastic deformation of the metallic Nb layers allowed for the partial relieve of the residual stresses developed as a result of the volumetric expansion of the Zr layers upon oxidation. Moreover, the development of residual stresses induced further changes in mechanical properties in relation to the annealing time, as revealed by finite element simulations.

  20. Evaluation of adsorbents for the Ta-178 generator

    International Nuclear Information System (INIS)

    Neirinckx, R.D.; Johnson, P.C.; Leblanc, A.; Trumper, J.

    1984-01-01

    The currently used Ta-178 generator is based on a radiation sensitive adsorbent and can be eluted about 50 times before W-178 breakthrough becomes unacceptable. The authors evaluated a series of inorganic and organic adsorbents as support for this generator. Hydrated inorganic materials adsorb tantalum very strongly from most aqueous solutions and none was found useful for the W-178/Ta-178 generator. Tantalum complexing agents are not able to desorb tantalum without dissolving the adsorbents to an appreciable extent. Chelating resins with a high affinity for W were investigated because they could reduce the W-178 breakthrough. They also adsorb tantalum too strongly to be suitable as substrates for the Ta-178 generator. The Bio-Rad AG1x8 system was found to be superior to the other tested systems. The effects of autoclaving, complexant additives and prolonged elution on the Ta-178 yield were measured and the chemical breakdown products quantitated