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Sample records for nb ta ha

  1. Solution chemistry of element 105. Pt. 1. Hydrolysis of group 5 cations: Nb, Ta, Ha and Pa

    Energy Technology Data Exchange (ETDEWEB)

    Pershina, V.

    1998-01-01

    Relativistic molecular orbital calculations of the electronic structure of hydrated and hydrolyzed complexes have been performed for group 5 elements Nb, Ta, Ha and their pseudohomology, Pa. On their basis, relative values of the free energy changes and constants of hydrolysis reactions were defined. These results show that hydrolysis decreases in the order Nb>Ta>Ha>>Pa, which for Nb, Ta and Pa is in agreement with experiment. A decisive factor in the process turned out to be a predominant electrostatic metal-ligand interaction. (orig.)

  2. Rutile is holding Nb and Ta in the mantle, negligible Nb and Ta in the core

    Science.gov (United States)

    McDonough, W. F.; Rudnick, R. L.

    2008-12-01

    Continental Crust has a significant depletion in Nb and Ta relative to La that has been attributed to convergent margin (arc) magmatism and greater retention of Nb and Ta in the mantle source. This depleted pattern is a consequence of the plotting order of elements, which has been established by the relative partitioning behavior of elements during MORB-OIB genesis. It is our hypothesis that rutile in subducting slabs or delaminated lower continental crust is the important phase causing Nb(Ta)-depletion in the continental crust, as well as lowering its Nb/Ta. Experimental studies reveal a range of Nb/Ta fractionation responses in residual rutile depending on temperature and phase relations(melting vs dehydration). Examples of rutile-bearing, refractory eclogites have been identified that serve as analog materials for residues of the continental crust. These rutiles have radiogenic Hf isotopes (Vervoort, unpubl. data), and thus are not recent precipitates from metasomatic melts, as has been recently suggested. What remains is to understand the total silicate Earth's mass balance. In this regard, it is worth noting that early Archean Barbarton komatiites possess chondritic La/Nb ratios, and Nb/Ta ~15, a value comparable to Allende CV3 chondrite. This observation is not consistent with the storage of Nb (or Ta) in the core and suggests that the silicate Earth controls the planetary budget of Nb and Ta. Constraints on the amount of Nb in the core must be evaluated by multi-element approaches, using ratios of refractory lithophile elements. Chondritic ratios for La/Nb and Nb/Ta are not defined simply as a single value with a restricted range and are not always constant, with examples of both negligible and distinct differences between groups of chondrites. The database for chondrites is still small for Nb and Ta.

  3. Nb/Ta variations of mafic volcanics on the Archean-Proterozoic boundary: Implications for the Nb/Ta imbalance

    Institute of Scientific and Technical Information of China (English)

    LIU Yongsheng; GAO Shan; WANG Xuance; HU Shenghong; WANG Jianqi

    2005-01-01

    The HFSE and REE of the Precambrian mafic volcanics from the North China craton demonstrate obvious A(Archean)-P(Proterozoic) boundary. The Neoarchean mafic vol-canics show weak correlation between HFSE and TiO2. Their superchondritic Nb/Ta ratio (18.8(1.2) could be attributed to partial melting of mantle peridotite in the presence of garnet. Compared with Neoarchean mafic volcanics, the Paleoproterozoic ones have higher HFSE contents and lower Nb/Ta ratio (15.6(2.9). The significantly elevated HFSE and REE contents of Paleoproterozoic mafic volcanics imply metasomatic enrichment of mantle source, in which Ti-rich silicates could be present as suggested by significant positive correlations between TiO2 and HFSE. The global database of Precambrian mafic volcanics shows a similar A-P boundary. 23 Archean mafic volcanic suites yield an average Nb/Ta ratio of 17.8(1.9 higher than or close to the PM value; Proterozoic mafic volcanics from 28 suites yield an average Nb/Ta ratio of 14.7(4.1 deficit could be mainly formed in post-Archean time. Archean mafic volcanics could be one of the geochemical reservoirs complementing the low Nb/Ta of the post-Archean continental crust and DM.

  4. 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.

  5. Ordering Effects in NbC and TaC

    Science.gov (United States)

    Venables, J. D.; Meyerhoff, M. H.

    1972-01-01

    By means of transmission electron microscopy and electron diffraction, evidence has been obtained for the existence of long range carbon atom ordering in single-crystal niobium carbide that has a carbon-to-metal ratio close to the integral composition Nb6C5. The ordering, which gives rise to superlattice and domain structures similar to those observed in V6C5, appears, however, only in samples that have been cooled slowly through the order-disorder temperature of 1025 C. In TaC of similar composition, the ordering, although present, remains very imperfect even after the crystals are subjected to the same thermal treatment. The results are interpreted in terms of the electronic structure of the transition metal carbides as it is currently understood, and their relevance to the mechanical properties of NbC and TaC are discussed.

  6. Partitioning and Hydrolysis of Nb and Ta and Their Implications with Regard to Mineralization

    Institute of Scientific and Technical Information of China (English)

    王玉荣; 顾复; 等

    1993-01-01

    K2NbOF5·H2O and K2TaF7 were prepared through melting Nb2O5 and Ta2O5 respectively with FHF2·2H2O, followed by recrystallizing .The hydrolysis properties of K2NbOF5 and K2TaF7 were determined again by using a rapidly quench vessel.As temperature (from 250 to 550℃) and pressure (from 500 to 1500 bars) increase, the degree of hydrolysis of both K2NbOF5 and K2TaF7 will increase.Nb- and Ta-fluorine complex compounds are instable in supercritical aqueous fluids.The degree of hydrolysis of both K2NbOF5 and K2TaF7 decreases with increasing concentra-tion of HF, independent of the concentration of NaF .The partition coefficients of Nb and Ta between granitic melt and fluid phase are less than 0.15,ie., most of Nb and Ta are left in granitic melt.The partition coefficient of Ta is more dependent on the concentration of HF than that of Nb.The significance of hydrolysis in Nb-ans Ta mineralization is also discussed in the present paper.

  7. 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.

  8. Experimental investigation of phase equilibria in the Nb-Si-Ta ternary system

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jian; Wang, Cuiping; Yao, Jun; Yang, Shuiyuan; Zhan Shi; Liu, Xingjun [Xiamen Univ. (China). Dept. of Materials Science and Engineering; Xiamen Univ. (China). Fujian Provincial Key Laboratory of Materials Genome; Kang, Yongwang [Beijing Institute of Aeronautical Materials (China). Science and Technology on Advanced High Temperature Structural Materials Lab.

    2016-12-15

    The phase equilibria in the Nb-Si-Ta ternary system at 1 373 K, 1 473 K and 1 573 K were investigated by means of back-scattered electron imaging, electron probe microanalysis and X-ray diffraction. The isothermal sections at 1 373 K, 1 473 K and 1 573 K consist of two three-phase regions and seven two-phase regions, without any ternary compounds. The compounds of NbSi{sub 2} and TaSi{sub 2}, αNb{sub 5}Si{sub 3} and αTa{sub 5}Si{sub 3} form continuous solid solutions, respectively. The solubilities of Nb in Ta{sub 3}Si and Ta{sub 2}Si phases are extremely large, whereas the solubility of Si in the β(Nb, Ta) phase is relatively small.

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

    Indian Academy of Sciences (India)

    Pramod Kumar Yadawa

    2011-04-01

    The ultrasonic properties of the hexagonal closed packed structured Ni3Mo, Ni3Nb and Ni3Ta compounds were studied at room temperature for their characterization. For the investigations of ultrasonic properties, the second-order elastic constants using Lennard–Jones potential were computed. 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 sound velocities of these compounds increase with the angle and has maximum at 55° with the unique axis at room temperature. Hence, when a sound wave travels at 55° with the unique axis of these materials, the average sound velocity is found to be maximum. The results achieved are discussed and compared with the available experimental and theoretical results.

  10. 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.

  11. Evolution of planetary cores and the Earth-Moon system from Nb/Ta systematics.

    Science.gov (United States)

    Münker, Carsten; Pfänder, Jörg A; Weyer, Stefan; Büchl, Anette; Kleine, Thorsten; Mezger, Klaus

    2003-07-04

    It has been assumed that Nb and Ta are not fractionated during differentiation processes on terrestrial planets and that both elements are lithophile. High-precision measurements of Nb/Ta and Zr/Hf reveal that Nb is moderately siderophile at high pressures. Nb/Ta values in the bulk silicate Earth (14.0 +/- 0.3) and the Moon (17.0 +/- 0.8) are below the chondritic ratio of 19.9 +/- 0.6, in contrast to Mars and asteroids. The lunar Nb/Ta constrains the mass fraction of impactor material in the Moon to less than 65%. Moreover, the Moon-forming impact can be linked in time with the final core-mantle equilibration on Earth 4.533 billion years ago.

  12. Structural studies of the metal-rich region in the ternary Ta-Nb-S system

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Xiaoqiang.

    1991-10-07

    Six new solid solution type compounds have been prepared using high temperature techniques and characterized by means of single crystal x-ray techniques during a study of the metal-rich region of the ternary Ta-Nb-S system. The structures of Nb{sub x}Ta{sub 11-x}S{sub 4} are reminiscent of niobium-rich sulfides, rather than of tantalum-rich sulfides. The coordinations of sulfur are capped trigonal prismatic while the metal coordinations are capped distorted cubic prismatic for Nb{sub x}Ta{sub 11-x}S{sub 4}, and capped distorted cubic prismatic and pentagonal prismatic for Nb{sub 12-x}Ta{sub x}S{sub 4}. The structures of Nb{sub x}Ta{sub 5-x}S{sub 2} contain homoatomic layers sequenced S-M3-M2-M1-M2-M3-S (M is mixed Nb, Ta) generating six-layer sheets, respectively. Weak S-S interactions at 3.26 and 3.19{Angstrom} between sheets contrast with the M-M binding within and between the sheets in these two novel layered compounds. The former are presumably responsible for the observed graphitic slippage of the samples. Nb{sub 21-x}Ta{sub x}S{sub 8} and Nb{sub x}Ta{sub 2-x}S are isostructural with Nb{sub 21}S{sub 8} and Ta{sub 2}S, respectively. Extended Hueckel band calculations were carried out for two layered compounds, Nb{sub x}Ta{sub 5-x}S{sub 2} (x {approx} 1.72) and Nb{sub x}ta{sub 2-x}S (x {approx} 0.95). Based upon band calculations metallic properties can be expected for these two layered compounds. The relative preference of the metal sites for the two metal elements (Ta, Nb) in two layered compounds is explained by the results of the band calculations. 17 figs., 31 tabs., 80 refs.

  13. Mechanical Properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 Refractory High Entropy Alloys (Postprint)

    Science.gov (United States)

    2011-05-01

    temper ature from 548 MPa at 1000 C to 405 MPa at 1600 C (Table 2).ublic release; distribution unlimited. Table 4 Composition (in wt.%) of Inconel 718 ...values of the refractory HEAs are much higher than those of Haynes 230 at all studied temperatures and higher than those of Inconel 718 at...than twice (for the Nb25Mo25 Ta25W25 alloy) or four times (for the V20Nb20Mo20Ta20W20 alloy) higher than for Inconel 718 or Haynes 230 at 1000 C. The

  14. Biocompatibility of new Ti-Nb-Ta base alloys.

    Science.gov (United States)

    Hussein, Abdelrahman H; Gepreel, Mohamed A-H; Gouda, Mohamed K; Hefnawy, Ahmad M; Kandil, Sherif H

    2016-04-01

    β-type titanium alloys are promising materials in the field of medical implants. The effect of β-phase stability on the mechanical properties, corrosion resistance and cytotoxicity of a newly designed β-type (Ti77Nb17Ta6) biocompatible alloys are studied. The β-phase stability was controlled by the addition of small quantities of Fe and O. X-ray diffraction and microstructural analysis showed that the addition of O and Fe stabilized the β-phase in the treated solution condition. The strength and hardness have increased with the increase in β-phase stability while ductility and Young's modulus have decreased. The potentio-dynamic polarization tests showed that the corrosion resistance of the new alloys is better than Ti-6Al-4V alloy by at least ten times. Neutral red uptake assay cytotoxicity test showed cell viability of at least 95%. The new alloys are promising candidates for biomedical applications due to their high mechanical properties, corrosion resistance, and reduced cytotoxicity.

  15. Laser-deposited Ti-Nb-Zr-Ta orthopedic alloys.

    Science.gov (United States)

    Banerjee, R; Nag, S; Samuel, S; Fraser, H L

    2006-08-01

    The complex quaternary Ti-35Nb-7Zr-5Ta orthopedic alloy has been successfully deposited from a powder feedstock consisting of a blend of elemental titanium, niobium, zirconium, and tantalum powders, using the laser engineered net-shaping (LENStrade mark) process. In the as laser-deposited form, these alloys exhibit a substantially higher tensile strength as compared with more conventionally processed counterparts of similar composition, while maintaining excellent ductility and a low modulus. Furthermore, the as-deposited alloys appear to exhibit a texture, with a substantially large number of grains of the beta phase aligning one of their axes nearly normal to the substrate or parallel to the growth direction. The microstructure of the as-deposited as well as tensile-tested alloys have been characterized in detail using scanning electron microscopy (SEM), orientation microscopy (OM), and transmission electron microscopy (TEM). Formation of a high density of shear bands, possibly arising from slip localization due to precipitates of the omega phase in the beta matrix, is clearly evident in the tensile-tested sample. The enhanced tensile strength and low modulus in these laser-deposited alloys coupled with the ability to form near-net shape components makes LENS an attractive processing technology for orthopedic implants.

  16. Microstructure and Elevated Temperature Properties of a Refractory TaNbHfZrTi Alloy

    Science.gov (United States)

    2012-01-24

    alloy was prepared by vacuum arc melting of the equimolar mixtures of the corresponding elements. Titanium, zirconium, and hafnium were in the form of...AND ELEVATED TEMPERATURE PROPERTIES OF A REFRACTORY TaNbHfZrTi ALLOY (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM...6260-2. 14. ABSTRACT Compression properties of a refractory multicomponent alloy , Ta20Nb20Hf20Zr20Ti20, were determined in the temperature range

  17. Low Dimensional K(Nb, Ta)O3 Thin Film Structures

    Science.gov (United States)

    2007-11-02

    solid state synthesis . The starting materials were K2CO3, Ta2O5, Nb2O5, and TiO2. The powders were reacted in air at 900˚C for 4 hrs, reground...KTa0.63Nb0.37O3 targets were made by solid state synthesis . The starting materials were K2CO3, Ta2O5, and Nb2O5. The powders were reacted in air at 900˚C

  18. A new RHQT Nb3Al superconducting wire with a Ta/Cu/Ta three-layer filament-barrier structure

    Science.gov (United States)

    Takeuchi, Takao; Tsuchiya, Kiyosumi; Nakagawa, Kazuhiko; Nimori, Shigeki; Banno, Nobuya; Iijima, Yasuo; Kikuchi, Akihiro; Nakamoto, Tatsushi

    2012-06-01

    To suppress the low-magnetic-field instability (flux jumps in low magnetic fields) of a rapid-heating, quenching and transformation (RHQT) processed Nb3Al superconductor, we had previously modified the cross-sectional design of an RHQT Nb3Al by adopting a Ta filament-barrier structure. Unlike Nb barriers, Ta barriers are not superconducting in magnetic fields at 4.2 K so that they electromagnetically decouple filaments. However, small flux jumps still occurred at 1.8 K, which is a typical operating temperature for the magnets used in high-energy particle accelerators. Furthermore, poor bonding at the Ta/Ta interface between neighboring Ta-coated jelly-roll (JR) filaments frequently caused precursor wires to break during drawing. To overcome these problems, we fabricated a new RHQT Nb3Al wire with a Ta/Cu/Ta three-layer filament-barrier structure for which an internal stabilization technique (Cu rods encased in Ta are dispersed in the wire cross section) was extended. Removing the Ta/Ta interface in the interfilamentary barrier (JR filament/Ta/Cu/Ta/JR filament) allowed precursor wires to be drawn without breaking. Furthermore, the Cu filament barrier electromagnetically decoupled filaments to suppress flux jumps at 1.8 K. The ductile Cu layer also improved the bending strain tolerance of RHQT Nb3Al.

  19. Ionic and electronic conductivity in the LaNbO4 - LaTaO4 system

    OpenAIRE

    Ertzeid, Odd-Arne

    2009-01-01

    Defect chemical investigations on the LaNbO4-LaTaO4 system are, except for investigations on the parent phases, LaNbO4 and LaTaO4, non-existent. Research on this system is required to understand the impact of tantalum-doping on the conductivity of LaNbO4. If Ta-doping is found to increase the conductivity of LaNbO4, it could, in turn, open interesting, new avenues relating to doping and solid solubility in solid oxide fuel cell materials research. In the work presented in this thesis, def...

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

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, A. E-mail: agupta@iucindore.ernet.inkane_sn@yahoo.com; Kane, S.N.; Bhagat, N.; Kulik, T

    2003-01-01

    The effect of successive additions of Cu, Nb and Ta in amorphous Fe{sub 77.5}Si{sub 13.5}B{sub 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{sub 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.

  1. Proposed long-range empirical potential to study the metallic glasses in the Ni-Nb-Ta system.

    Science.gov (United States)

    Dai, Y; Li, J H; Che, X L; Liu, B X

    2009-05-21

    An n-body potential is constructed for the Ni-Nb-Ta ternary metal system in the newly proposed form of long-range empirical potential. The constructed Ni-Nb-Ta potential can well reproduce the lattice constants, cohesive energies, and elastic modulus of the metals and some compounds as well as the equations of state of the system. Applying the constructed Ni-Nb-Ta potential, molecular dynamics simulations and Voronoi tessellations are carried out to study the issues related to the Ni-Nb-Ta metallic glasses. It is found that increasing the Ni content can obviously improve the glass-forming ability of the binary Nb-Ta system, which features a isomorphous phase diagram unfavoring for forming glass, indicating that the Ni solute plays a decisive role in forming the Nb-based or Ta-based Ni-Nb-Ta metallic glasses. Concerning the atomic structure, the Voronoi cell volume and coordination number (CN) of Ta are generally larger than those of Ni in the binary Ni-Ta metallic glasses. With increasing the Ni concentration, the fraction of icosidihedron (CN=13) increases, while the fractions of icosihexahedron (CN=15) and icosioctahedron (CN=16) decrease. Meanwhile, with increasing the Ni concentration, the dominating coordination numbers of Ta atoms increase. Interestingly, similar feature in the atomic structure with variation of Ni concentration is also observed in the Ni-Nb metallic glasses. For the ternary Ni-Nb-Ta alloys, it is observed from the CN distributions that the structure of the metallic glasses is mostly affected by the Ni concentration.

  2. Fabrication of tunnel junctions on thick X-ray absorbing substrates of Nb and Ta

    NARCIS (Netherlands)

    Hamster, A.W.; Ferrari, E.; Adelerhof, D.J.; Brons, G.C.S.; Schoofs, I.J.E.; Flokstra, J.; Rogalla, H.; Bruijn, M.P.; Kiewiet, F.; Luiten, O.J.; Korte, de P.A.J.

    1996-01-01

    X-ray detectors based on absorber-junction combinations can combine a large detector area with position resolution and good energy resolution. We plan to use a thick, single crystal Nb or Ta absorber with readout tunnel junctions integrated on top as our next generation X-ray detector. The thickness

  3. Interaction of interstitial atoms and configurational contribution to their thermodynamic activity in V, Nb, and Ta

    Science.gov (United States)

    Blanter, M. S.; Dmitriev, V. V.; Mogutnov, B. M.; Ruban, A. V.

    2017-02-01

    The pairwise interaction energies of O-O and N-N in bcc metals of group VB, which were calculated earlier using first-principles methods, have been employed to analyze the effect of the interatomic interactions on the configurational contribution to the thermodynamic activity. The strong effect of interstitial- interstitial interaction has been shown. The configurational contribution grows in the row (Nb-N) → (V-N) → (Ta-N) → (Nb-O) → (V-O) → (Ta-O), which is caused by a weakening of the mutual attraction of interstitial atoms in these solid solutions. The strong repulsion that characterizes the majority of coordination shells only weakly affects the thermodynamic activity. The character of the temperature dependence of the configurational contribution is defined by the strength of the mutual attraction of the interstitial atoms, i.e., upon strong attraction, the contribution increases with increasing temperature (Nb-N, V-N, Ta-N, and Nb-O) and, upon weak attraction, it decreases (V-O and Ta-O).

  4. 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.

  5. MRI-compatible Nb-60Ta-2Zr alloy used for vascular stents: haemocompatibility and its correlation with protein adsorption.

    Science.gov (United States)

    Li, Xiu-Mei; Li, Hui-Zhe; Wang, Shao-Ping; Huang, Hsun-Miao; Huang, Her-Hsiung; Ai, Hong-Jun; Xu, Jian

    2014-09-01

    Nb-60Ta-2Zr is a newly developed MRI-compatible alloy used for vascular stents. In this work, its haemocompatibility was investigated, including platelet adhesion (lactate dehydrogenase activity), platelet activation (P-selectin expression), coagulation and haemolysis. For comparison, parallel assessments for these factors were performed for the niobium, tantalum, 316L stainless steel (316L SS) and L605 Co-Cr alloy (L605). In addition, albumin and fibrinogen were selected to examine the correlation of protein adsorption with platelet adhesion and metal surface properties. The propensity for platelet adhesion and activation on the Nb-60Ta-2Zr alloy was at nearly the same level as that for Nb and Ta but was slightly less than those of 316L SS and L605. The mitigated platelet adhesion and activation of the Nb-60Ta-2Zr alloy is associated with its decreased adsorption of fibrinogen. The Nb-60Ta-2Zr alloy has a longer clotting time and exhibits significantly superior thromboresistance than 316L SS and L605. Moreover, the haemolysis rate of the Nb-60Ta-2Zr alloy satisfies the bio-safety requirement of the ISO 10993-4 standard. The favourable haemocompatiblity of the Nb-60Ta-2Zr alloy provides evidence of its good biocompatibility and of its suitability as a candidate stent material.

  6. Development of high performance multifilamentary Nb-Ti-Ta superconductor for LHC insertion quadrupoles

    CERN Document Server

    Lee, P J; Larbalestier, D C; Naus, M T; Squitieri, A A; Starch, W L; Werner, J; Limon, P J; Sabbi, G L; Zlobin, A V; Gregory, E

    1999-01-01

    A preliminary investigation of a new Nb-Ti-Ta (39 wt.Nb, 44 wt.Ti, 17 wt.Ta) alloy has been investigated as a possible material for application at 1.9 K and 10.5 T in the insertion quadrupoles of LHC, 1550 A/mm/sup 2/, the highest $9 yet reported critical current density at 10.5 T (1.9 K), was achieved in a monofilament of this material. The initial multifilamentary production strand produced a lower 10.5 T (1.9 K) critical current density of 1370 A/mm/sup 2/. $9 Large variations in precipitate size were produced in the microstructures, which have yet to be fully optimized. Quantitative analysis of the microstructures in a Nb-44 wt.Ti-15 wt.Ta alloy reveals a linear relationship between $9 volume 554330f alpha -Ti precipitate and critical current density at 5 T and 8 T (4.2 K). The increase in critical current with precipitate volume is less than for Nb-47 wt.Ti. High resolution FESEM electron backscatter images $9 suggest a high atomic number region adjacent to the grain boundaries after heat treatment. (18 ...

  7. Microstructure Transformation of WC-(Ti,W)C-(Ta,Nb)C-Co Sample during Sintering Process%WC-(Ti,W)C-(Ta,Nb)C-Co试样烧结过程中组织结构的变化

    Institute of Scientific and Technical Information of China (English)

    高跃红; 颜练武; 林江华; 左锐

    2014-01-01

    将成分为WC-5%(Ti,W)C-5%(Ta,Nb)C-6%Co的混合料在1 150、1 200、1 250、1 300、1 350、1 400、1 450℃不同的温度下烧结,保温30 min制备成烧结体.利用X射线衍射仪、扫描电镜及能谱仪研究各温度下烧结体的相成分和组织结构变化.研究结果表明:当烧结温度为1 150℃时,烧结体中存在四种物相:白色的WC,浅灰色的(Ta,Nb)C,深灰色棱角分明的(Ti,W)C和深灰色的Co相.当烧结温度升高到1 200℃时,(Ti,W)C和(Ta,Nb)C发生轻微的固溶反应形成(W,Ti,Ta,Nb)C相,WC向(Ti,W)C中扩散形成W含量更多的(Ti,W)C相.当温度升高到1 250℃时,(Ti,W)C相几乎消失,(Ta,Nb)C相进一步减少,形成大量的成分不均匀的(W,Ti,Ta,Nb)C相.当温度升高到1 300℃时,(W,Ti,Ta,Nb)C相的成分均匀化过程基本完成.当温度升高到1 350~1 450℃时,WC晶粒进一步长粗,烧结体中存在三个稳定的相:WC、(W,Ti,Ta,Nb)C、γ.

  8. A coprecipitation technique to prepare NaNbO3 and NaTaO3

    Indian Academy of Sciences (India)

    V Samuel; A B Gaikwad; V Ravi

    2006-04-01

    A simple coprecipitation technique has been used successfully for the preparation of pure, ultrafine, single phases of NaNbO3 (NN) and NaTaO3 (NT). An alcoholic solution of ammonium carbonate and ammonium hydroxide was used to precipitate Na+ and Nb5+ (or Ta5+) cations under basic conditions as carbonate and hydroxide, respectively. On heating at 700°C, these precursors produce respective products. For comparison, both NN and NT powders were also prepared by the traditional solid state method. The phase purity and lattice parameters were studied by powder X-ray diffraction (XRD). The particle size and morphology were studied by scanning electron microscopy (SEM).

  9. Senary Refractory High-Entropy Alloy HfNbTaTiVZr

    Science.gov (United States)

    Gao, M. C.; Zhang, B.; Yang, S.; Guo, S. M.

    2016-07-01

    Discovery of new single-phase high-entropy alloys (HEAs) is important to understand HEA formation mechanisms. The present study reports computational design and experimental validation of a senary HEA, HfNbTaTiVZr, in a body-centered cubic structure. The phase diagrams and thermodynamic properties of this senary system were modeled using the CALPHAD method. Its atomic structure and diffusion constants were studied using ab initio molecular dynamics simulations. The microstructure of the as-cast HfNbTaTiVZr alloy was studied using X-ray diffraction and scanning electron microscopy, and the microsegregation in the as-cast state was found to qualitatively agree with the solidification predictions from CALPHAD. Supported by both simulation and experimental results, the HEA formation rules are discussed.

  10. Assessment of relative Ti, Ta, and Nb (TITAN) enrichments in ocean island basalts

    Science.gov (United States)

    Peters, Bradley J.; Day, James M. D.

    2014-11-01

    sensitivity of trace element concentrations to processes governing solid-melt interactions has made them valuable tools for tracing the effects of partial melting, fractional crystallization, metasomatism, and similar processes on the composition of a parental melt. Recent studies of ocean island basalts (OIB) have sought to correlate Ti, Ta, and Nb (TITAN) anomalies to isotopic tracers, such as 3He/4He and 187Os/188Os ratios, which may trace primordial deep mantle sources. A new compilation of global OIB trace element abundance data indicates that positive TITAN anomalies, though statistically pervasive features of OIB, may not be compositional features of their mantle sources. OIB show a range of Ti (Ti/Ti* = 0.28-2.35), Ta (Ta/Ta* = 0.11-93.4), and Nb (Nb/Nb* = 0.13-17.8) anomalies that show negligible correlations with 3He/4He ratios, indicating that TITAN anomalies are not derived from the less-degassed mantle source traced by high-3He/4He. Positive TITAN anomalies can be modeled using variable degrees (0.1-10%) of nonmodal batch partial melting of garnet-spinel lherzolite at temperatures and pressures considered typical for OIB petrogenesis, and subjecting this partial melt to fractional crystallization and assimilation of mid-ocean ridge basalt-like crust (AFC). Correlations of TITAN anomalies with modal abundances of olivine and clinopyroxene in porphyritic Canary Islands lavas provide empirical support for this process and indicate that high abundances of these phases in OIB may create misleading trace element anomalies on primitive mantle-normalized spider diagrams. Because partial melting and AFC are common to all mantle-derived magmas, caution should be used when attributing TITAN anomalies to direct sampling of recycled or deep mantle sources by hotspots.

  11. Superconductivity in Y6Tr4Al43 (Tr = Nb, Mo, Ta) with Peanut-Shaped Cage Structure

    Science.gov (United States)

    Kase, Naoki; Satoh, Ryoh; Nakano, Tomohito; Takeda, Naoya

    2016-10-01

    Superconductivity is discovered in Y6Tr4Al43 (Tr = Nb, Mo, Ta) with a peanut-shaped cage structure at Tc = 0.86, 0.75, and 0.68 K, respectively. The superconducting state is revealed by performing electrical resistivity and specific heat measurements. The upper critical field is obtained to be 0.22 (Nb), 0.175 (Mo), and 0.15 T (Ta). A specific heat jump provides evidence of bulk superconductivity in these compounds.

  12. Direct Metal Deposition of Refractory High Entropy Alloy MoNbTaW

    Science.gov (United States)

    Dobbelstein, Henrik; Thiele, Magnus; Gurevich, Evgeny L.; George, Easo P.; Ostendorf, Andreas

    Alloying of refractory high entropy alloys (HEAs) such as MoNbTaW is usually done by vacuum arc melting (VAM) or powder metallurgy (PM) due to the high melting points of the elements. Machining to produce the final shape of parts is often needed after the PM process. Casting processes, which are often used for aerospace components (turbine blades, vanes), are not possible. Direct metal deposition (DMD) is an additive manufacturing technique used for the refurbishment of superalloy components, but generating these components from the bottom up is also of current research interest. MoNbTaW possesses high yield strength at high temperatures and could be an alternative to state-of-the-art materials. In this study, DMD of an equimolar mixture of elemental powders was performed with a pulsed Nd:YAG laser. Single wall structures were built, deposition strategies developed and the microstructure of MoNbTaW was analyzed by back scattered electrons (BSE) and energy dispersive X-ray (EDX) spectroscopy in a scanning electron microscope. DMD enables the generation of composition gradients by using dynamic powder mixing instead of pre-alloyed powders. However, the simultaneous handling of several elemental or pre-alloyed powders brings new challenges to the deposition process. The influence of thermal properties, melting point and vapor pressure on the deposition process and chemical composition will be discussed.

  13. Resistivity plateau and extremely large magnetoresistance in NbAs2 and TaAs2

    Science.gov (United States)

    Wang, Yi-Yan; Yu, Qiao-He; Guo, Peng-Jie; Liu, Kai; Xia, Tian-Long

    2016-07-01

    In topological insulators (TIs), metallic surface conductance saturates the insulating bulk resistance with decreasing temperature, resulting in resistivity plateau at low temperatures as a transport signature originating from metallic surface modes protected by time reversal symmetry (TRS). Such a characteristic has been found in several materials including Bi2Te2Se , SmB6 etc. Recently, similar behavior has been observed in metallic compound LaSb, accompanying an extremely large magnetoresistance (XMR). Shubnikov-de Hass (SdH) oscillation at low temperatures further confirms the metallic behavior of the plateau region under magnetic fields. LaSb [Tafti et al., Nat. Phys. 12, 272 (2015), 10.1038/nphys3581] has been proposed by the authors as a possible topological semimetal (TSM), while negative magnetoresistance is absent at this moment. Here, high quality single crystals of NbAs2/TaAs2 with inversion symmetry have been grown, and the resistivity under magnetic field is systematically investigated. Both of them exhibit metallic behavior under zero magnetic field, and a metal-to-insulator transition occurs when a nonzero magnetic field is applied, resulting in XMR (1.0 ×105% for NbAs2 and 7.3 ×105% for TaAs2 at 2.5 K and 14 T). With temperature decreased, a resistivity plateau emerges after the insulatorlike regime, and SdH oscillation has also been observed in NbAs2 and TaAs2.

  14. Upper critical fields of periodic and quasiperiodic Nb-Ta superlattices

    Science.gov (United States)

    Cohn, J. L.; Lin, J. J.; Lamelas, F. J.; He, H.; Clarke, R.; Uher, C.

    1988-08-01

    Upper critical fields have been studied for two series of Nb-Ta superlattices grown by molecular-beam epitaxy with both periodic and quasiperiodic (Fibonacci sequence) layering. X-ray results are presented to characterize the nature and quality of the layering. Positive curvature in the perpendicular upper critical field (Hc2⊥), pronounced negative curvature near Tc in the parallel upper critical field (Hc2), and dimensional crossover are observed in both types of samples. For quasiperiodic samples two upturns are observed in Hc2 with decreasing temperature. These are shown to be associated with dimensional crossover occurring twice as the superconducting coherence length in the growth direction, ξ⊥, samples the two length scales, 2dNb and dNb, that are present in these structures.

  15. Synthesis, crystal structures and magnetic properties of fluorite-related compounds Ce3MO7 (M = Nb, Ta)

    Science.gov (United States)

    Inabayashi, Masaki; Doi, Yoshihiro; Wakeshima, Makoto; Hinatsu, Yukio

    2017-10-01

    Ternary oxides Ce3NbO7 and Ce3TaO7 were successfully synthesized by the solid state reaction under flowing hydrogen atmosphere. The structures were determined by the powder X-ray diffraction. Both the compounds were crystallized in the orthorhombic space groups Pnma (for Ce3NbO7) and Cmcm (for Ce3TaO7). Both the structures have similar features: two kinds of infinite chains formed by corner-sharing NbO6 (TaO6) octahedra and edge-sharing Ce(1)O8 cubes, the slabs consisting of alternate chains, and 7-coordinated Ce(2) ions existing between the slabs. In the structure of Ce3NbO7, the NbO6 octahedra running along the a-axis are titled towards the 0 0 1 direction, while in the Ce3TaO7 structure, the TaO6 octahedra running along the c-axis are titled towards the 0 1 0 direction. Magnetic susceptibility measurements for Ce3NbO7 and Ce3TaO7 show that both compounds are paramagnetic down to 1.8 K, and confirm that the Ce ion is in the trivalent state. From specific heat (Cp) measurements, a rapid increase of Cp/T has been observed below 3 K for both the compounds, indicating the onset of magnetic ordering between Ce3+ ions at further lower temperatures.

  16. 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.

  17. 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.

  18. Large magnetoresistance in compensated semimetals TaAs2 and NbAs2

    Science.gov (United States)

    Yuan, Zhujun; Lu, Hong; Liu, Yongjie; Wang, Junfeng; Jia, Shuang

    2016-05-01

    We report large magnetoresistance (MR) at low temperatures in single-crystalline nonmagnetic compounds TaAs2 and NbAs2. Both compounds exhibit parabolic-field-dependent MR larger than 5 ×103 in a magnetic field of 9 Tesla at 2 K. The MR starts to deviate from parabolic dependence above 10 T and intends to be saturated in 45 T for TaAs2 at 4.2 K. The Hall resistance measurements and band structure calculations reveal their compensated semimetal characteristics. Their large MR at low temperatures is ascribed to an effect for compensation of electrons and holes with large mobilities. After discussing the MR for different samples of TaAs2 and other semimetals, we found that the magnitudes of MR are strongly dependent on the samples' quality for different compounds.

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

    Science.gov (United States)

    Izquierdo, Javier; Bolat, Georgiana; Cimpoesu, Nicanor; Trinca, Lucia Carmen; Mareci, Daniel; Souto, Ricardo Manuel

    2016-11-01

    A new titanium base Ti-21Nb-15Ta-6Zr alloy covered with hydroxyapatite-zirconia (HA-ZrO2) 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-ZrO2 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-ZrO2 coated Ti-21Nb-15Ta-6Zr alloy will have negligible effect upon biochemical and cellular events at the bone-implant interface and could facilitate osseointegration.

  20. Microstructure and Properties of a Refractory NbCrMo0.5Ta0.5ZrTi Alloy (Preprint)

    Science.gov (United States)

    2011-10-01

    FCC phase was highly enriched with Cr and it was identified as a Laves C15 phase , (Zr,Ta)(Cr,Mo,Nb)2, with the lattice parameter a = 733.38 ± 0.18 pm...enriched with Cr and it was identified as a Laves C15 phase , (Zr,Ta)(Cr,Mo,Nb)2, with the lattice parameter a = 733.38 ± 0.18 pm. The volume...amounts of Mo, Nb, Ta and Ti. This Laves phase can be described by a formula (Zr,Ta)(Cr, Mo, Nb)2, with Ti equally substituting both larger and

  1. Existence of topological nontrivial surface states in strained transition metals: W, Ta, Mo, and Nb

    Science.gov (United States)

    Thonig, Danny; Rauch, Tomáš; Mirhosseini, Hossein; Henk, Jürgen; Mertig, Ingrid; Wortelen, Henry; Engelkamp, Bernd; Schmidt, Anke B.; Donath, Markus

    2016-10-01

    We show that a series of transition metals with strained body-centered cubic lattice—W, Ta, Nb, and Mo—hosts surface states that are topologically protected by mirror symmetry and, thus, exhibits nonzero topological invariants. These findings extend the class of topologically nontrivial systems by topological crystalline transition metals. The investigation is based on calculations of the electronic structures and of topological invariants. The signatures of a Dirac-type surface state in W(110), e.g., the linear dispersion and the spin texture, are verified. To further support our prediction, we investigate Ta(110) both theoretically and experimentally by spin-resolved inverse photoemission: unoccupied topologically nontrivial surface states are observed.

  2. [Research and Application of the ICP-MS Detection Technology for the Content of Nb and Ta in Geochemical Sample].

    Science.gov (United States)

    Li, Zi-qiang; Li, Xiao-ying; Zhu, Kun; Xu, Xiao-xia; Yan, Zhi-yuan

    2015-08-01

    In order to provide the test analysis technology to support the exploration and development of niobium and tantalum resource, based on the special chemical properties of Nb and Ta in geochemical sample, we studied the detection methods for the content of Nb and Ta in geochemical sample by using inductively coupled plasma mass spectrometry (ICP-MS). The results show that the sample dissolution and instrumental parameter of ICP-MS, especially the former have significant influence? on detection results. Therefore, optimizing important parameters of sample dissolution is the key of the detection technology. The optimal parameters are that the weight of sample is 50 mg; the dosage of HF acid is 15 mL; the concentration of nitric acid and tartaric acid in the sample solution is 2% and 1.5%, respectively; the validity period of detection for sample solution ≤1 d. The detection method has been validated by the national geochemistry standard reference material. The precise and exaction of method meet the required of industry standards. The detection limits of method for Nb and Ta are 1.05 and 0.13 μg · g(-1), respectively. The experiment proved that the ICP-MS detection methods, which using certain preparation process of sample solutions, is suitable for accurate and rapid determination of Nb and Ta in geochemical sample, especially geochemical survey samples which with a large amount and low content of Nb and Ta.

  3. 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

  4. Structural evolution in Ni-Nb and Ni-Nb-Ta liquids and glasses - A measure of liquid fragility?

    Energy Technology Data Exchange (ETDEWEB)

    Mauro, N. A.; Johnson, M. L.; Bendert, J. C.; Kelton, K. F. [WU

    2013-01-07

    The structures of Ni59.5Nb40.5, Ni62Nb38, and Ni60Nb30Ta10 liquids and glasses were studied using synchrotron high-energy X-ray diffraction. To avoid reactions between the liquids and their containers and to deeply supercool them below their equilibrium liquidus temperatures, the liquids were processed without a container using the beamline electrostatic levitation (BESL) technique. The total static structure factor, S(q), and the total pair-correlation function, g(r), were obtained for all liquid compositions over a temperature range of approximately 250 °C; S(q) and g(r) were measured for the corresponding glasses at room temperature. All of the S(q)s have a shoulder on the high-q side of the second peak; this becomes more pronounced as the liquid is supercooled, and is most prominent in the glass. Based on a Honeycutt–Andersen analysis of the atomic configurations obtained from Reverse Monte Carlo fits to the total structure factors obtained from the scattering data, icosahedral short-range order (ISRO) is dominant in all liquids and becomes particularly pronounced in the glasses. No correlation is noted, however, between the amount of ISRO and easy glass formability. Structural features show evidence for an acceleration of ordering in the supercooled liquid above the glass transition temperature, consistent with the behavior expected for fragile liquids. This suggests that scattering data can provide a new method to assess liquid fragility, which is typically obtained from the temperature behavior of the viscosity near the glass transition temperature.

  5. Electronic Structure and Optical Properties of SrBi2A2O9(A=Nb,Ta)

    Institute of Scientific and Technical Information of China (English)

    ZHAO Na; WANG Yue-Hua; ZHAO Xin-Yin; ZHANG Min; GONG Sai

    2011-01-01

    The first-principles calculation is performed to investigate the energy band structures,density of states (DOS) and optical properties of SrBi2A2O9 (A =Nb,Ta),by using density functional theory (DFT) with the generalized gradient approximation (GGA).The results show that the band-gap of SrBi2Nb2O9 is smaller than that of SrBi2Ta2O9,and that there are strong hybridizations of A-O bands,which play very important roles in the electronic properties and optical responses of SrBi2A2O9. SrBi2 Ta2O9 stimulates much higher photocatalytic activity than SrBi2Nb2O9,which is due to its suitable crystal structure.

  6. Effect of annealing on atomic ordering of amorphous ZrTaTiNbSi alloy

    Science.gov (United States)

    Yang, Tsung-Han; Huang, Rong-Tang; Wu, Cheng-An; Chen, Fu-Rong; Gan, Jon-Yiew; Yeh, Jien-Wei; Narayan, Jagdish

    2009-12-01

    In this letter, we have reported on initial stages of atomic ordering in ZrTaTiNbSi amorphous films during annealing. The atomic ordering and structure evolution were studied in Zr17Ta16Ti19Nb22Si26 amorphous films as a function of annealing temperature in the temperature range from 473 to 1173 K. Up to annealing temperature of 1173 K, the films retained amorphous structure, but the degree of disorder is increased with the increase in temperature. The formation of Si-M covalent bonds, which contributed to the local atomic arrangement, occurred in the initial stages of ordering. The bonding reactions between Si and other metal species explain the anomalous structural changes which were observed in x-ray diffraction and transmission electron microscopy. We discuss the stages of phase transformation for amorphous films as a function of annealing temperature. From these results, we propose that annealing leads to formation of random Si-M4 tetrahedron, and two observed rings, a first and second in the electron diffraction patterns compared to M-M and Si-M bond length, respectively.

  7. Broadband microwave response of superconducting NbN and TaN thin films

    Energy Technology Data Exchange (ETDEWEB)

    Felger, M. Maximilian; Pracht, Uwe S.; Dressel, Martin; Scheffler, Marc [1. Physikalisches Institut, Universitaet Stuttgart, D-70669 Stuttgart (Germany); Ilin, Konstantin; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme, Karlsruher Institut fuer Technologie, D-76187 Karlsruhe (Germany)

    2015-07-01

    Ultrathin NbN and TaN films with their peculiar superconducting behavior are of interest both for fundamental physics (e.g. concerning the superconductor-insulator transition) and novel applications (e.g. for single-photon detectors). Here microwave spectroscopy is a powerful tool to characterize essential superconducting properties and to investigate the charge dynamics (Cooper pairs and quasiparticles). We have prepared by sputtering thin films of NbN (thickness between 3 nm and 20 nm; T{sub c} between 5 K and 13 K) and TaN (thickness 5 nm; T{sub c} between 8.5 K and 9.5 K) on sapphire substrates. We performed broadband microwave spectroscopy on these samples using a Corbino spectrometer at temperatures down to 1.1 K and at frequencies up to 50 GHz. From these data we determine the superconducting penetration depth and we evaluate the frequency-dependent conductivity. While many of the observed features can be described within expectations of conventional BCS theory, we also find deviations that are caused by fluctuations near the superconducting transition.

  8. Laser deposition and deformation behavior of Ti-Nb-Zr-Ta alloys for orthopedic implants.

    Science.gov (United States)

    Nag, S; Banerjee, R

    2012-12-01

    Microstructure and mechanical properties of laser deposited complex quaternary Ti-34Nb-7Zr-7Ta (all wt%), an orthopedic load-bearing implant alloy, has been investigated in detail in both as-deposited as well as heat-treated (β-solutionized and quenched) conditions. The difference in stress-strain behavior of this alloy in the above conditions has been characterized using scanning electron microscopy (SEM), orientation imaging microscopy (OIM™) and transmission electron microscopy (TEM). Compared to the sample in heat-treated condition, the as-deposited sample showed evidence of strong growth related texture. Again in the as-deposited post tensile-tested condition formation of a high density of shear bands, possibly arising from slip localization due to shearing of ω precipitates in the β matrix is observed. TEM investigations also show the presence of lenticular shaped deformation induced ω phase within the shear bands. In contrast, in case of the β-solutionized sample, twinning and the formation of stress-induced plates appears to be the primary mode of deformation. The change in deformation mechanism and thus the tensile property of this alloy could be attributed to the crystallographic texture along the growth direction as well as diffusion mediated isothermal ω precipitates, that cause an enrichment of Nb and Ta in the β matrix, during the laser-deposition process. This is no longer present after the solutionizing treatment. Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. Development of (Nb,Ta3Sn multifilamentary superconductor wire for high current applications

    Directory of Open Access Journals (Sweden)

    Rodrigues Jr. Durval

    2000-01-01

    Full Text Available The optimization of the energy generated by a MagnetoHydroDynamic (MHD channel using a superconducting magnet demands the optimization of the magnetic field of the system and of the critical points on the magnet winding. This work must include the development of a high performance superconductor wire suitable for this system. Aiming to the construction of improved performance MHD channel, it was developed a low cost superconductor wire, with the required characteristics. The wire was made using a technology compatible with the assembling steps and heat treatment conditions of the MHD superconducting magnets fabrication. It was used the internal Sn method in Nb-7.5wt%Ta tube to fabricate a 271-filament wire with a diameter of 0.81 mm and a Cu/nonCu ratio of 2.3. The wire was heat treated at 200 °C to diffuse the Sn into the Cu shell, producing bronze, followed by the final reaction at temperatures ranging from 670 °C to 730 °C during 25 to 150 h, to produce (Nb,Ta3Sn. The superconducting wire characterization was made measuring the critical current Ic versus the applied magnetic field in the range of 5 to 20 T, the critical temperature Tc and the residual resistivity ratio (RRR. The wire transported critical currents above those available in commercial superconducting wires. These values of Ic are higher than the expected values for the optimization of the MHD channel.

  10. Electronic band structures of AV(2) (A = Ta, Ti, Hf and Nb) Laves phase compounds.

    Science.gov (United States)

    Charifi, Z; Reshak, Ali Hussain; Baaziz, H

    2009-01-14

    First-principles density functional calculations, using the all-electron full potential linearized augmented plane wave method, have been performed in order to investigate the structural and electronic properties for Laves phase AV(2) (A = Ta, Ti, Hf and Nb) compounds. The generalized gradient approximation and the Engel-Vosko-generalized gradient approximation were used. Our calculations show that these compounds are metallic with more bands cutting the Fermi energy (E(F)) as we move from Nb to Ta, Hf and Ti, consistent with the increase in the values of the density of states at the Fermi level N(E(F)). N(E(F)) is controlled by the overlapping of V-p/d, A-d and A-p states around the Fermi energy. The ground state properties of these compounds, such as equilibrium lattice constant, are calculated and compared with the available literature. There is a strong/weak hybridization between the states, V-s states are strongly hybridized with A-s states below and above E(F). Around the Fermi energy we notice that V-p shows strong hybridization with A-p states.

  11. High Nb, Ta, and Al creep- and oxidation-resistant austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Brady, Michael P [Oak Ridge, TN; Santella, Michael L [Knoxville, TN; Yamamoto, Yukinori [Oak Ridge, TN; Liu, Chain-tsuan [Oak Ridge, TN

    2010-07-13

    An austenitic stainless steel HTUPS alloy includes, in weight percent: 15 to 30 Ni; 10 to 15 Cr; 2 to 5 Al; 0.6 to 5 total of at least one of Nb and Ta; no more than 0.3 of combined Ti+V; up to 3 Mo; up to 3 Co; up to 1 W; up to 0.5 Cu; up to 4 Mn; up to 1 Si; 0.05 to 0.15 C; up to 0.15 B; up to 0.05 P; up to 1 total of at least one of Y, La, Ce, Hf, and Zr; less than 0.05 N; and base Fe, wherein the weight percent Fe is greater than the weight percent Ni wherein said alloy forms an external continuous scale comprising alumina, nanometer scale sized particles distributed throughout the microstructure, said particles comprising at least one composition selected from the group consisting of NbC and TaC, and a stable essentially single phase fcc austenitic matrix microstructure, said austenitic matrix being essentially delta-ferrite-free and essentially BCC-phase-free.

  12. High Nb, Ta, and Al creep- and oxidation-resistant austenitic stainless steel

    Science.gov (United States)

    Brady, Michael P [Oak Ridge, TN; Santella, Michael L [Knoxville, TN; Yamamoto, Yukinori [Oak Ridge, TN; Liu, Chain-tsuan [Oak Ridge, TN

    2010-07-13

    An austenitic stainless steel HTUPS alloy includes, in weight percent: 15 to 30 Ni; 10 to 15 Cr; 2 to 5 Al; 0.6 to 5 total of at least one of Nb and Ta; no more than 0.3 of combined Ti+V; up to 3 Mo; up to 3 Co; up to 1 W; up to 0.5 Cu; up to 4 Mn; up to 1 Si; 0.05 to 0.15 C; up to 0.15 B; up to 0.05 P; up to 1 total of at least one of Y, La, Ce, Hf, and Zr; less than 0.05 N; and base Fe, wherein the weight percent Fe is greater than the weight percent Ni wherein said alloy forms an external continuous scale comprising alumina, nanometer scale sized particles distributed throughout the microstructure, said particles comprising at least one composition selected from the group consisting of NbC and TaC, and a stable essentially single phase fcc austenitic matrix microstructure, said austenitic matrix being essentially delta-ferrite-free and essentially BCC-phase-free.

  13. Texture Evolution in a Ti-Ta-Nb Alloy Processed by Severe Plastic Deformation

    Science.gov (United States)

    Cojocaru, Vasile-Danut; Raducanu, Doina; Gloriant, Thierry; Cinca, Ion

    2012-05-01

    Titanium alloys are extensively used in a variety of applications because of their good mechanical properties, high biocompatibility, and corrosion resistance. Recently, β-type Ti alloys containing Ta and Nb have received much attention because they feature not only high specific strength but also biocorrosion resistance, no allergic problems, and biocompatibility. A Ti-25Ta-25Nb β-type titanium alloy was subjected to severe plastic deformation (SPD) processing by accumulative roll bonding and investigated with the aim to observe the texture developed during SPD processing. Texture data expressed by pole figures, inverse pole figures, and orientation distribution functions for the (110), (200), and (211) β-Ti peaks were obtained by XRD investigations. The results showed that it is possible to obtain high-intensity share texture modes ({001}) and well-developed α and γ-fibers; the most important fiber is the α-fiber ({001} to {114} to {112} ). High-intensity texture along certain crystallographic directions represents a way to obtain materials with high anisotropic properties.

  14. Facile Route to Prepare TaC,NbC and WC Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    DU Yinxiao; LEI Ming; YANG Hui; WANG Xuefei

    2008-01-01

    By a novel solid-state reaction process using amorphous C3N4 (a-C3N4) and transition metal oxides as starting reagents,cubic TaC,NbC and hexagonal WC nanoparticles were successfully synthesized at 1150 ℃.The products were characterized by power X-ray diffraction (XRD),field-emission scanning electron microscope (FE-SEM),energy-dispersive X-ray spectroscopy (EDX),transmission electron microscopy (TEM) and high-resolution TEM (HRTEM).The experimental resuits show that a-C3N4 obtained by the reaction between C3N3Cl3 and Li3N is a highly efficient carburation reagent and the transition metal oxides are completely transformed into the corresponding metal carbide nanoparticles at 1150 ℃,respectively,which is significantly lower than that reported for the traditional preparation of carbides,typically> 1600 ℃.The TaC,NbC and WC nanoparticles are found to have an average particle size of 10 nm,15 nm and 8 nm by TEM observation,respectively.

  15. Temperature independent Seebeck coefficient through quantum confinement modulation in amorphous Nb-O/Ni-Ta-O multilayers

    Science.gov (United States)

    Music, Denis; Hunold, Oliver; Coultas, Sarah; Roberts, Adam

    2017-05-01

    Employing a correlative experimental and theoretical methodology, we have investigated amorphous monoxide Nb-O/Ni-Ta-O multilayers. It is feasible to obtain a temperature independent Seebeck coefficient up to 500 °C for these metallic-like conductors, attaining -25 μV K-1. While Nb and Ta strongly interact with O, Ni experiences the metallic and monoxide-like bonding. We observe a 3 eV wide region below the Fermi level convoluted through several first nearest neighbor Ni - Ni and second nearest neighbor Nb - Nb interactions resulting in many confined states. It can be proposed that by increasing temperature these modulated quantum states gradually become thermally accessible eradicating the temperature dependence of the Seebeck coefficient.

  16. Photoelectrochemical properties of titanium niobate (TiNb2O7) and titanium tantalate (TiTa2O7)

    NARCIS (Netherlands)

    Haart, L.G.J. de; Boessenkool, H.J.; Blasse, G.

    1985-01-01

    The diffuse reflection spectra and the photoelectrochemlcal properties of TiNb2O7 and TiTa2O7 are reported. Both compounds show an optical absorption edge near 3.0 eV. TiNb2O7 can be used as photoanode In a photoelectrochemlcal cell. The onset potential of the photocurrent is about −0.9 V SCE In 1M

  17. 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.

  18. On yield loci of HY80, HY100 steels and Ti-6Al-2Nb-1Ta-0. 8Mo

    Energy Technology Data Exchange (ETDEWEB)

    Chan, K.S.; Lindholm, U.S.; Wise, J.

    1984-11-01

    This paper extends other findings by examining the biaxial yield behavior of Ti-6A1-1Nb-1Ta-0.8Mo and HY 100 steel. The results of the study are compared with previous findings of HY80 steel to assess the effect of crystallography on the shape of the yield surface.

  19. Oxidation characteristics of Ti-33Al-6Nb-1.4Ta

    Science.gov (United States)

    Wallace, T. A.; Clark, R. K.; Sankaran, S. N.; Wiedemann, K. E.

    1991-01-01

    Static oxidation kinetics of the gamma titanium-aluminide alloy Ti-33Al-6Nb-1.4Ta (wt pct) have been investigated in air from 700 to 1000 C and in oxygen from 800 to 1000 C using thermogravimetric analysis. The oxidation kinetics were controlled by the presence of alumina for all oxygen exposures and in air below 800 C, while the kinetics in air above 800 C were more complex. Oxidation products were identified using X-ray diffraction techniques. Oxide scale morphology was examined by SEM and TEM of the surfaces and across sections of oxidized specimens. The oxidation products formed depended on the exposure: Al2O3 and TiO2 were identified on all specimens exposed in and air and oxygen; the nitride phases TiN and Ti2AlN were also found on specimens exposed in air.

  20. Oxidation characteristics of Ti-33Al-6Nb-1.4Ta

    Science.gov (United States)

    Wallace, T. A.; Clark, R. K.; Sankaran, S. N.; Wiedemann, K. E.

    1991-01-01

    Static oxidation kinetics of the gamma titanium-aluminide alloy Ti-33Al-6Nb-1.4Ta (wt pct) have been investigated in air from 700 to 1000 C and in oxygen from 800 to 1000 C using thermogravimetric analysis. The oxidation kinetics were controlled by the presence of alumina for all oxygen exposures and in air below 800 C, while the kinetics in air above 800 C were more complex. Oxidation products were identified using X-ray diffraction techniques. Oxide scale morphology was examined by SEM and TEM of the surfaces and across sections of oxidized specimens. The oxidation products formed depended on the exposure: Al2O3 and TiO2 were identified on all specimens exposed in and air and oxygen; the nitride phases TiN and Ti2AlN were also found on specimens exposed in air.

  1. Analytic bond-order potentials for the bcc refractory metals Nb, Ta, Mo and W.

    Science.gov (United States)

    Čák, M; Hammerschmidt, T; Rogal, J; Vitek, V; Drautz, R

    2014-05-14

    Bond-order potentials (BOPs) are based on the tight-binding approximation for determining the energy of a system of interacting atoms. The bond energy and forces are computed analytically within the formalism of the analytic BOPs. Here we present parametrizations of the analytic BOPs for the bcc refractory metals Nb, Ta, Mo and W. The parametrizations are optimized for the equilibrium bcc structure and tested for atomic environments far from equilibrium that had not been included in the fitting procedure. These tests include structural energy differences for competing crystal structures; tetragonal, trigonal, hexagonal and orthorhombic deformation paths; formation energies of point defects as well as phonon dispersion relations. Our tests show good agreement with available experimental and theoretical data. In practice, we obtain the energetic ordering of vacancy, [1 1 1], [1 1 0], and [1 0 0] self-interstitial atom in agreement with density functional theory calculations.

  2. Hemispherical emissivity of V, Nb, Ta, Mo, and W from 300 to 1000 K

    Science.gov (United States)

    Cheng, S. X.; Hanssen, L. M.; Riffe, D. M.; Sievers, A. J.; Cebe, P.

    1987-01-01

    The hemispherical emissivities of five transition elements, V, Nb, Ta, Mo, and W, have been measured from 300 to 1000 K, complementing earlier higher-temperature results. These low-temperature data, which are similar, are fitted to a Drude model in which the room-temperature parameters have been obtained from optical measurements and the temperature dependence of the dc resistivity is used as input to calculate the temperature dependence of the emissivity. A frequency-dependent free-carrier relaxation rate is found to have a similar magnitude for all these elements. For temperatures larger than 1200 K the calculated emissivity is always greater than the measured value, indicating that the high-temperature interband features of transition elements are much weaker than those determined from room-temperature measurements.

  3. 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.

  4. Search for high entropy alloys in the X-NbTaTiZr systems (X = Al, Cr, V, Sn)

    Energy Technology Data Exchange (ETDEWEB)

    Poletti, Marco Gabriele, E-mail: marcogabriele.poletti@unito.it [Dipartimento di Chimica, Università di Torino, Via P. Giuria 7, 10125 Torino (Italy); Fiore, Gianluca [Dipartimento di Chimica, Università di Torino, Via P. Giuria 7, 10125 Torino (Italy); Szost, Blanka A. [Strategic and Emerging Technologies Team (TEC-TS), European Space Agency, ESTEC, 1 Keplerlaan, 2201 AZ Noordwijk (Netherlands); Battezzati, Livio [Dipartimento di Chimica, Università di Torino, Via P. Giuria 7, 10125 Torino (Italy)

    2015-01-25

    Highlights: • Composition of refractory high entropy alloys predicted. • Solid solutions found in VNbTaTiZr and AlNbTaTiZr. • Alloys containing Cr and Sn are multi-phased. - Abstract: High entropy alloys, i.e. solid solution phases, are sought in the X-NbTaTiZr equiatomic system where the X element was chosen as Al, Cr, V and Sn by applying recent criteria based on size and electronegativity mismatch of alloy components, number of itinerant and total valence electrons, and the temperature at which the free energy of mixing changes at the alloy composition. The alloys containing V and Al are mostly constituted by solid solutions in good agreement with prediction.

  5. 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)

  6. Quantifying protein adsorption on combinatorially sputtered Al-, Nb-, Ta- and Ti-containing films with electron microprobe and spectroscopic ellipsometry

    Science.gov (United States)

    Byrne, T. M.; Lohstreter, L.; Filiaggi, M. J.; Bai, Zhijun; Dahn, J. R.

    2009-04-01

    Although metallic biomaterials are widely used, systematic studies of protein adsorption onto such materials are generally lacking. Combinatorial binary libraries of Al 1-xNb x, Al 1-xTa x, Al 1-xTi x, Nb 1-xTa x, Nb 1-xTi x, and Ta 1-xTi x (0 ⩽ x ⩽ 1) and a ternary library of Al 1-xTi xTa y (0 ⩽ x ⩽ 1 and 0 ⩽ y ⩽ 0.7), along with their corresponding pure element films were sputtered onto glass substrates using a unique magnetron sputtering technique. Films were characterized with wavelength-dispersive spectroscopy (WDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Fibrinogen and albumin adsorption amounts were measured by wavelength-dispersive spectroscopy (WDS) and spectroscopic ellipsometry (SE) equipment, both high throughput techniques with automated motion stage capabilities. Protein adsorption onto these films was found to be closely correlated to the alumina surface fraction, with high alumina content at the surface leading to low amounts of adsorbed fibrinogen and albumin. Protein adsorption amounts obtained with WDS and SE were in good agreement for all films.

  7. Electronic structure of the superconducting layered ternary nitrides CaTaN2 and CaNbN2

    Science.gov (United States)

    Oliva, Josep M.; Weht, Ruben; Ordejón, Pablo; Canadell, Enric

    2000-07-01

    The electronic structure of the layered ternary nitrides CaMN2 (M= Ta, Nb) has been studied and the results are compared with those for the related LiMoN2 phase. It is shown that the former are two-dimensional metals, with a Fermi surface very similar to that of the 1T-TaX2 (X= S, Se) dichalcogenides, whereas the latter is a three-dimensional metal. The three phases show strong covalent bonding within the layers but ionic bonding with the alkali atom sheets.

  8. Growth and study of SrBi 2 (Ta, Nb) 2 O 9 thin films by pulsed excimer laser ablation

    Science.gov (United States)

    Bhattacharyya, S.; Bharadwaja, S. S. N.; Krupanidhi, S. B.

    2000-05-01

    Thin films of SrBi 2(Ta,Nb) 2O 9 (SBTN) were grown using pulsed-laser ablation and were ex situ crystallized. Ferroelectric properties were achieved by low temperature deposition. A polycrystalline structure was achieved, with a Ta- to Nb-ratio nearly 1:1. The smaller thickness of the film allowed the switching voltage to be low enough (1.5 V), without affecting the insulating nature of the films. The hysteresis results showed an excellent square shaped loop with a remnant polarization ( Pr) of 7.6 μC/cm 2 and a coercive field ( Ec) of 75 kV/cm. This ferroelectric material composition is having a very high Curie temperature with higher stability and can be used in non-volatile random access memory (NVRAM) devices.

  9. In Vitro Cytotoxicity of a Ti-35Nb-7Zr-5Ta Alloy Doped with Different Oxygen Contents

    Directory of Open Access Journals (Sweden)

    Tatiani Ayako Goto Donato

    2014-03-01

    Full Text Available Cp-Ti is the most common material used for dental implants, but its elastic modulus is around five times higher than that of bone. Recently, promising alloys that add Nb, Ta, Zr and Mo to Ti have been developed. The mechanical properties of these alloys are directly related to its microstructure and the presence of interstitial elements, such as oxygen, carbon, nitrogen and hydrogen. In this study, the in vitro cytotoxicity of Ti-35Nb-7Zr-5Ta (TNZT alloys was analyzed in the as-received condition and after being doped with several small quantities of oxygen on a cultured osteogenic cell. The cell’s morphology was also examined by scanning electron microscopy (SEM. The TNZT alloy presented no cytotoxic effects on osteoblastic cells in the studied conditions.

  10. Are lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) ferroelectrics bioactive?

    Science.gov (United States)

    Vilarinho, Paula Maria; 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 LiNbO3 and LiTaO3 is reported. The formation of apatite-like structures on the surface of LiNbO3 and LiTaO3 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.

  11. Calibration graphs for Ti, Ta and Nb in sintered tungsten carbide by infrared laser ablation inductively coupled plasma atomic emission spectrometry.

    Science.gov (United States)

    Kanický, V; Otruba, V; Mermet, J M

    2001-12-01

    Infrared laser ablation (IR-LA) has been studied as a sample introduction technique for the analysis of sintered cobalt-cemented tungsten carbide materials by inductively coupled plasma atomic emission spectrometry (ICP-AES). Fractionation of cobalt was observed. Linearity of calibration plots was verified at least up to 15% Ti, 8% Ta, and 3% Nb. Above 1% (m/m) Ti, Ta, and Nb, the repeatability of results was better than 3% R.S.D. The relative uncertainty at the centroid of the calibration line was in the range from +/- 3% to +/- 4% for Ti, Ta, and Nb with internal standardization by tungsten and up to +/- 5% without internal standardization. The limits of detection were 0.004% Ti, 0.001% Ta, and 0.004% Nb. Elimination of the cemented hardmetal dissolution procedure is the main advantage of this method.

  12. Photoelectron spectra of the late rare-earth misfit layer compounds (LnS)(1+x)TS2 (Ln=Tb, Dy, Ho; T=Nb, Ta)

    NARCIS (Netherlands)

    Fang, CM; Wiegers, GA; Haas, C

    1997-01-01

    Photoemission spectra (XPS and UPS) are presented for the valence band of misfit layer compounds (LnS)(1+x)TS2 with Ln = Dy, Ho or Tb; T = Nb or Ta. The Nb 4d(x)2 (or Ta 5d(x)2) conduction band is almost filled, which indicates a charge transfer of slightly less than one electron per T from the LnS

  13. New insights into the structural and dynamical features of lithium hexaoxometalates Li7MO6 (M = Nb, Ta, Sb, Bi).

    Science.gov (United States)

    Mühle, Claus; Dinnebier, Robert E; van Wüllen, Leo; Schwering, Georg; Jansen, Martin

    2004-02-09

    We present a (re)investigation of the hexaoxometalates Li(8)MO(6) (M = Sn, Pb, Zr, Hf) and Li(7)MO(6) (M = Nb, Ta, Sb, Bi). Lithium motion and ionic conductivity in the hexaoxometalates were studied using impedance spectroscopy (for Li(7)MO(6), M = Sb, Bi, Ta) and (6)Li and (7)Li solid-state nuclear magnetic resonance (for Li(7)TaO(6)). The NMR data indicate a considerable exchange of Li among the tetrahedral and octahedral voids even at ambient temperature. In an investigation of the crystal structures using laboratory and synchrotron X-ray powder diffraction techniques, the structures of Li(7)TaO(6), Li(7)NbO(6), and Li(7)SbO(6) could be solved and refined. All three reveal a triclinic metric (Li(7)SbO(6), triclinic, P1, a = 5.38503(6) A, b = 5.89164(7) A, c = 5.43074(6) A, alpha = 117.2210(6) degrees, beta = 119.6311(6) degrees, gamma = 63.2520(7) degrees, V = 127.454(3) A(3), Z = 1; Li(7)NbO(6), triclinic, P1, a = 5.37932(9) A, b = 5.91942(11) A, c = 5.37922(9) A, alpha = 117.0033(9) degrees, beta = 119.6023(7) degrees, gamma = 63.2570(9) degrees, V = 126.938(4) A(3), Z = 1; Li(7)TaO(6), triclinic, P1, a = 5.38486(2) A, b = 5.92014(3) A, c = 5.38551(2) A, alpha = 117.0108(2) degrees, beta = 119.6132(2) degrees, gamma = 63.2492(2) degrees, V = 127.208(1) A(3), Z = 1.

  14. Characterization of the Ti-10Nb-10Zr-5Ta Alloy for Biomedical Applications. Part 2: Wettability, Tribological Performance and Biocompatibility

    Science.gov (United States)

    Braic, V.; Balaceanu, M.; Braic, M.; Vitelaru, C.; Titorencu, I.; Pruna, V.; Parau, A. C.; Fanara, C.; Vladescu, A.

    2014-01-01

    The Ti-10Nb-10Zr-5Ta alloy, prepared in a levitation melting furnace, was investigated as a possible candidate for replacing Ti6Al4V alloy in medical applications. The sessile drop method, pin-on-disc and in vitro tests were used to analyze wettability, wear resistance, and biocompatibility of the new alloy. The characteristics of the Ti-10Nb-10Zr-5Ta alloy were assessed in comparison to those of the Ti6Al4V alloy. The Ti-10Nb-10Zr-5Ta system was found to have hydrophilic characteristics with similar contact angle as the Ti6Al4V alloy. In all environments (deionized water, simulated body fluid and Fusayama Meyer artificial saliva), the friction coefficient showed a stable evolution versus sliding distance, being similar for both alloys. On overall, the wear resistance of Ti-10Nb-10Zr-5Ta alloy was lower than that of Ti6Al4V for all testing environments. The Ti-10Nb-10Zr-5Ta alloy exhibited good biocompatibility characteristics at in vitro test compared to Ti6Al4V alloy. The cell viability on Ti-10Nb-10Zr-5Ta surfaces was higher than the one observed on Ti6Al4V samples, regardless the number of days spent in osteoblast-like cells culture. A high degree of cell attachment and spreading was observed on both alloys.

  15. Surface phenomena of HA/TiN coatings on the nanotubular-structured beta Ti-29Nb-5Zr alloy for biomaterials

    Science.gov (United States)

    Kim, Eun-Ju; Jeong, Yong-Hoon; Choe, Han-Cheol; Brantley, William A.

    2012-01-01

    Surface phenomena of HA/TiN coatings on the nanotubular-structured beta Ti-29Nb-5Zr alloy for biomaterials have been investigated by several experimental methods. The nanotubular structure was formed by anodizing the Ti-29Nb-5Zr alloy in 1 M H3PO4 electrolytes with 1.0 wt.% NaF at room temperature. Hydroxyapatite (HA)/titanium nitride (TiN) films were deposited on Ti-29Nb-5Zr alloy specimens using a magnetron sputtering system. The HA target was made of human tooth-ash by sintering at 1300 °C for 1 h, and the HA target had an average Ca/P ratio of 1.9. The HA/TiN depositions were performed, using the pure HA target, on Ti-29Nb-5Zr alloy following the initial deposition of a TiN buffer layer coating. Microstructures and nanotubular morphology of the coated alloy specimens were examined by FE-SEM, EDX, XRD, and XPS. The Ti-29Nb-5Zr alloy substrate had small grain size and preferred orientation along the drawing direction. The HA/TiN coating was stable with a uniform morphology at the tips of the nanotubes.

  16. Comparative study on structural, elastic, dynamical, and thermodynamic properties of Weyl semimetals MX (M = Ta or Nb; X = As or P)

    Science.gov (United States)

    Liu, Lei; Wang, Zhao-Qi; Hu, Cui-E.; Cheng, Yan; Ji, Guang-Fu

    2017-09-01

    We present a comparative investigation on structural, elastic, dynamical and thermodynamic properties of Weyl semimetals MX (M = Ta or Nb; X = As or P) using density functional theory (DFT) within the generalized gradient approximation. The elastic properties of NbAs, TaP and NbP are obtained for the first time, then we compared them with each other and with some well-studied materials. Among four Weyl semimetals, TaP and NbAs possess the largest and smallest bulk modulus B, shear modulus G, and Young's modulus E, respectively, while NbP and TaAs own the maximum and minimum elastic Debye temperature. Through the analysis of three dimensional (3D) representations and two dimensional (2D) projections of Young's modulus, MX series exhibit distinct elastic anisotropy, especially for TaAs and NbAs. The calculated phonon dispersions of four Weyl semimetals show no imaginary frequency throughout the Brillouin zone, indicating they are dynamically stable. In addition, compared with other theoretical results, our calculated Brillouin-zone-center frequencies of MX series are more in line with experimental data. Furthermore, Phonon velocities are obtained using phonon spectra, and anisotropic phonon group velocities are responsible for their anisotropic lattice thermal conductivity. Additionally, thermodynamic properties are also predicted using the calculated phonon density of states. The results are in good agreement with available experimental values. We expect our work can provide more information for further experimental studies.

  17. 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.

  18. Electrophoretic deposition and characterization of HA/chitosan nanocomposite coatings on Ti6Al7Nb alloy

    Science.gov (United States)

    Moskalewicz, Tomasz; Kot, Marcin; Seuss, Sigrid; Kędzierska, Aleksandra; Czyrska-Filemonowicz, Aleksandra; Boccaccini, Aldo R.

    2015-01-01

    Nano-hydroxyapatite/chitosan (nc-HA/chitosan) composite coatings were produced on two phase (α+β) Ti6Al7Nb titanium alloy substrates by electrophoretic deposition (EPD). The microstructure of the coatings was examined by scanning- and transmission electron microscopy methods as well as by X-ray diffractometry. The coatings, 770 nm-800 nm thick, were uniform, without any cracks or presence of large voids and they exhibited good adhesion to the titanium alloy substrate. The microstructure of the coatings consisted of nc-HA needle-like particles homogeneously embedded in a chitosan matrix. The deposited coatings exhibited good adhesion to the substrate. The best adhesion to the titanium alloy was determined for the coating deposited from suspensions containing 4 g/L of HA at 10 V during 240 s. The results confirm EPD as a convenient method to develop uniform and crack-free nanoscale organic-inorganic composite coatings on two phase titanium alloy substrates with potential application in orthopedic and dental implants.

  19. 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.

  20. Microstructure and Room Temperature Properties of a High-Entropy TaNbHfZrTi Alloy (Postprint)

    Science.gov (United States)

    2014-04-01

    Vickers microhardness are  = 9.94 g/cm3 and Hv = 3826 MPa. The alloy has high compression yield strength (0 2 = 929 MPa) and ductility (ε > 50%). The...the BCC crystal structure, density, , Vickers microhardness, Hv, and yield strength, 0.2, of the pure metals and the studied alloy. Metal Ta Nb Hf...agreement with the random (disordered) distribution of the alloying elements in the BCC lattice of the alloy. The RT yield strength and Vickers microhardness

  1. Quantum and superconducting fluctuations effects in disordered Nb 1- xTa x thin films above Tc

    Science.gov (United States)

    Giannouri, M.; Papastaikoudis, C.

    1999-05-01

    Disordered Nb 1- xTa x thin films are prepared with e-gun coevaporation. The influence of the β-phase of tantalum in the critical temperature Tc is observed as a function of the substrate temperature. The measurements of transverse magnetoresistance at various isothermals are interpreted in terms of weak-localization and superconducting fluctuations. From the fitting procedure, the phase breaking rate τφ-1 and the Larkin parameter βL are estimated as a function of temperature. Conclusions about the dominant inelastic scattering mechanisms at various temperature regions as well as for the dominant mechanism of superconducting fluctuations near the transition temperature are extracted.

  2. Fibroblast Adhesion and Proliferation on a New β Type Ti-39Nb-13Ta-4.6Zr Alloy for Biomedical Application

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Cell attachment and spreading on Ti-based alloy surfaces is a major parameter in implant technology. Ti39Nb-13Ta-4.6Zr alloy is a new β type Ti alloy developed for biomedical application. This alloy has low modulus and high strength, which indicates that it can be used for medical purposes such as surgical implants.To evaluate the biocompatibility and effects of the surface morphology of Ti-39Nb-13Ta-4.6Zr on the cellular behaviour, the adhesion and proliferation of rat gingival fibroblasts were studied with substrates having different surface roughness and the results were also compared with commercial pure titanium and Ti-6Al-4V. The results indicate that fibroblast shows similar adhesion and proliferation on the smooth surfaces of commercial pure titanium (Cp Ti), Ti-39Nb-13Ta-4.6Zr, and Ti-6Al-4V, suggesting that Ti-39Nb-13Ta-4.6Zr has similar biocompatibility to Cp Ti and Ti-6Al-4V. The fibroblast adhesion and spreading was lower on rough surfaces of Cp Ti, Ti-39Nb-13Ta-4.6Zr and Ti-6Al-4V than on smooth ones. Surface roughness appeared to be a dominant factor that determines the fibroblast adhesion and proliferation.

  3. Ta/Ti O 2 -and Nb/Ti O 2 -Mixed Oxides as Efficient Solar Photocatalysts: Preparation, Characterization, and Photocatalytic Activity

    OpenAIRE

    Znad, Hussein; Ang, Ming H.; Tade, Moses O

    2012-01-01

    Ta/TiO2- and Nb/TiO2-mixed oxides photocatalysts were prepared by simple impregnation method at different TiO2 : Nb or Ta mass ratios of 1 : 0.1, 1 : 0.5, and 1 : 1, followed by calcination at 500∘C. The prepared powders have been characterized by XRD, XPS, UV-Vis spectra, and SEM. The photocatalytic activity was evaluated under natural solar light for decolorization and mineralization of azo dye Orange II solution. The results showed that Nb/TiO2- and Ta/TiO2-mixed oxides have higher activit...

  4. Ta/TiO2-and Nb/TiO2-Mixed Oxides as Efficient Solar Photocatalysts: Preparation, Characterization, and Photocatalytic Activity

    OpenAIRE

    Hussein Znad; Ming H. Ang; Moses O. Tade

    2012-01-01

    Ta/TiO2- and Nb/TiO2-mixed oxides photocatalysts were prepared by simple impregnation method at different TiO2 : Nb or Ta mass ratios of 1 : 0.1, 1 : 0.5, and 1 : 1, followed by calcination at 500∘C. The prepared powders have been characterized by XRD, XPS, UV-Vis spectra, and SEM. The photocatalytic activity was evaluated under natural solar light for decolorization and mineralization of azo dye Orange II solution. The results showed that Nb/TiO2- and Ta/TiO2-mixed oxides have higher activit...

  5. Quasi-optical THz spectroscopy on ultra-thin superconducting films of NbN and TaN

    Energy Technology Data Exchange (ETDEWEB)

    Pracht, Uwe Santiago; Heintze, Eric; Scheffler, Marc; Dressel, Martin [1. Physikalisches Institut, University of Stuttgart (Germany); Il' in, Konstantin; Henrich, Dagmar; Guo, Qiao; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme (IMS), Karlsruher Institut fuer Technologie (KIT) (Germany)

    2013-07-01

    Ultra-thin films of the conventional superconductors niobium nitride (NbN) and tantalum nitride (TaN) have recently attracted attention for devices such as single-photon detectors. Quasi-optical THz spectroscopy is a particularly suited tool with direct access to superconducting properties, such as the superconducting energy gap, which are necessary for a proper understanding of device performance and for future improvements. With our THz-spectroscopy approach we measure amplitude and phaseshift of coherent radiation (0.09-1.2 THz) passing through thin-film systems. We present the performance and possibilities of our experimental set-up, and we apply it to ultra-thin superconducting films of NbN and TaN. We fit the experimental data to weak-coupling BCS theory, and we obtain frequency- and temperature-dependent superconducting properties such as the complex optical conductivity, the complex dielectric function, the energy gap, the penetration depth, and the superfluid density.

  6. Newly developed Ti-Nb-Zr-Ta-Si-Fe biomedical beta titanium alloys with increased strength and enhanced biocompatibility.

    Science.gov (United States)

    Kopova, Ivana; Stráský, Josef; Harcuba, Petr; Landa, Michal; Janeček, Miloš; Bačákova, Lucie

    2016-03-01

    Beta titanium alloys are promising materials for load-bearing orthopaedic implants due to their excellent corrosion resistance and biocompatibility, low elastic modulus and moderate strength. Metastable beta-Ti alloys can be hardened via precipitation of the alpha phase; however, this has an adverse effect on the elastic modulus. Small amounts of Fe (0-2 wt.%) and Si (0-1 wt.%) were added to Ti-35Nb-7Zr-6Ta (TNZT) biocompatible alloy to increase its strength in beta solution treated condition. Fe and Si additions were shown to cause a significant increase in tensile strength and also in the elastic modulus (from 65 GPa to 85 GPa). However, the elastic modulus of TNZT alloy with Fe and Si additions is still much lower than that of widely used Ti-6Al-4V alloy (115 GPa), and thus closer to that of the bone (10-30 GPa). Si decreases the elongation to failure, whereas Fe increases the uniform elongation thanks to increased work hardening. Primary human osteoblasts cultivated for 21 days on TNZT with 0.5Si+2Fe (wt.%) reached a significantly higher cell population density and significantly higher collagen I production than cells cultured on the standard Ti-6Al-4V alloy. In conclusion, the Ti-35Nb-7Zr-6Ta-2Fe-0.5Si alloy proves to be the best combination of elastic modulus, strength and also biological properties, which makes it a viable candidate for use in load-bearing implants.

  7. 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.

  8. Electronic band structures of AV{sub 2} (A = Ta, Ti, Hf and Nb) Laves phase compounds

    Energy Technology Data Exchange (ETDEWEB)

    Charifi, Z; Baaziz, H [Physics Department, Faculty of Science and Engineering, University of M' sila, 28000 M' sila (Algeria); Reshak, Ali Hussain [Institute of Physical Biology, South Bohemia University, Nove Hrady 37333 (Czech Republic)], E-mail: maalidph@yahoo.co.uk

    2009-01-14

    First-principles density functional calculations, using the all-electron full potential linearized augmented plane wave method, have been performed in order to investigate the structural and electronic properties for Laves phase AV{sub 2} (A = Ta, Ti, Hf and Nb) compounds. The generalized gradient approximation and the Engel-Vosko-generalized gradient approximation were used. Our calculations show that these compounds are metallic with more bands cutting the Fermi energy (E{sub F}) as we move from Nb to Ta, Hf and Ti, consistent with the increase in the values of the density of states at the Fermi level N(E{sub F}). N(E{sub F}) is controlled by the overlapping of V-p/d, A-d and A-p states around the Fermi energy. The ground state properties of these compounds, such as equilibrium lattice constant, are calculated and compared with the available literature. There is a strong/weak hybridization between the states, V-s states are strongly hybridized with A-s states below and above E{sub F}. Around the Fermi energy we notice that V-p shows strong hybridization with A-p states.

  9. 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.

  10. Modelling potential photovoltaic absorbers Cu3MCh4(M = V, Nb, Ta; Ch = S, Se, Te) using density functional theory.

    Science.gov (United States)

    Kehoe, Aoife B; Scanlon, David O; Watson, Graeme W

    2016-05-05

    The geometric and electronic properties of a series of potential photovoltaic materials, the sulvanite structured Cu3MCh4(M = V, Nb, Ta; Ch = S, Se, Te), have been computationally examined using both PBEsol+U and HSE06 methods to assess the materials' suitability for solar cell application and to compare the predictions of the two theoretical approaches. The lattice parameters, electronic density of states, and band gaps of the compounds have been calculated to ascertain the experimental agreement obtained by each method and to determine if any of the systems have an optical band gap appropriate for photovoltaic absorber materials. The PBEsol+U results are shown to achieve better agreement with experiment than HSE06 in terms of both lattice constants and band gaps, demonstrating that higher level theoretical methods do not automatically result in a greater level of accuracy than their computationally less expensive counterparts. The PBEsol+U calculated optical band gaps of five materials suggest potential suitability as photovoltaic absorbers, with values of 1.72 eV, 1.49 eV, 1.19 eV, 1.46 eV, and 1.69 eV for Cu3VS4, Cu3VSe4, Cu3VTe4, Cu3NbTe4, and Cu3TaTe4, respectively, although it should be noted that all fundamental band gaps are indirect in nature, which could lower the open-circuit voltage and hence the efficiency of prospective devices.

  11. Sulvanite Compounds Cu3TMS4 (TM= V, Nb and Ta): Elastic, Electronic, Optical and Thermal Properties using First-principles Method

    OpenAIRE

    2015-01-01

    We present a systematic first-principles study of the structural, elastic, electronic, optical and thermodynamics properties of the sulvanite compounds Cu3TMS4 (TM = V, Nb and Ta). The structural, elastic and electronic properties are in fact revisited using a different calculation code than that used by other workers and the results are compared. The band gaps are found to be 1.041, 1.667 and 1.815 eV for Cu3VS4, Cu3NbS4 and Cu3TaS4, respectively which are comparable to other available calcu...

  12. Phase transformations and correlations between microstructure and properties of biocompabile alloys of the Ti-Nb and Ti-Nb-Ta systems

    OpenAIRE

    Sandra Andreia Stwart de Araujo Souza

    2008-01-01

    Resumo: Freqüentemente, os implantes femorais falham devido à transferência insuficiente de carregamento a partir da haste metálica para o osso adjacente. Este problema está relacionado à diferença de rigidez entre osso e prótese, que depende em parte de seus módulos de elasticidade. Dessa forma, ligas com módulos de elasticidade menores são desejáveis, a fim de melhorar a distribuição de tensões nos tecidos ósseos adjacentes. Adições de Nb e Ta ao titânio propiciam a redução do módulo de ela...

  13. Signatures of Fermi Arcs in the Quasiparticle Interferences of the Weyl Semimetals TaAs and NbP.

    Science.gov (United States)

    Chang, Guoqing; Xu, Su-Yang; Zheng, Hao; Lee, Chi-Cheng; Huang, Shin-Ming; Belopolski, Ilya; Sanchez, Daniel S; Bian, Guang; Alidoust, Nasser; Chang, Tay-Rong; Hsu, Chuang-Han; Jeng, Horng-Tay; Bansil, Arun; Lin, Hsin; Hasan, M Zahid

    2016-02-12

    The recent discovery of the first Weyl semimetal in TaAs provides the first observation of a Weyl fermion in nature. Such a topological semimetal features a novel type of anomalous surface state, the Fermi arc, which connects a pair of Weyl nodes through the boundary of the crystal. Here, we present theoretical calculations of the quasiparticle interference (QPI) patterns that arise from the surface states including the topological Fermi arcs in the Weyl semimetals TaAs and NbP. Most importantly, we discover that the QPI exhibits termination points that are fingerprints of the Weyl nodes in the interference pattern. Our results, for the first time, propose a universal interference signature of the topological Fermi arcs in TaAs, which is fundamental for scanning tunneling microscope (STM) measurements on this prototypical Weyl semimetal compound. More generally, our work provides critical guideline and methodology for STM studies on new Weyl semimetals. Further, the scattering channels revealed by our QPIs are broadly relevant to surface transport and device applications based on Weyl semimetals.

  14. Determination of Nb and Ta in Nb-Ta Ore by Inductively Coupled Plasma-Optical Emission Spectrometry with a Combined Microwave Digestion Hydrofluoric Acid-resistant System%微波消解-耐氢氟酸系统电感耦合等离子体发射光谱法测定铌钽矿中的铌和钽

    Institute of Scientific and Technical Information of China (English)

    马生凤; 温宏利; 李冰; 王蕾; 朱云

    2016-01-01

    Niobium and tantalum in hydrofluoric acid can form a stable solution,and thus the Nb and Ta content of Nb-Ta ore can be determined accurately by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) with a hydrofluoric acid resistant system.The determination method described in this paper for Nb and Ta in Nb-Ta ore,uses the microwave digestion mode of modular small tank and multiple digestion tank assembly (70 tank /group),and hydrofluoric acid resistant system of ICP-OES.This method shortens the dissolution time from 48 h to 1 h.By using a hydrofluoric acid medium the hydrolysis of high-level Nb and Ta in low acid concentration media is avoided.The detection limits of this method are 5.58 μg/g for Nb and 5.87 μg/g for Ta.The result of Nb-Ta concentrate with 19% Nb2 O5 and 27% Ta2 O5 is consistent with that acquired by the alkali fusion method and can be used to determine both high-grade and low-grade Nb-Ta ore with 42 μg/g -19% of Nb2 O5 and 86 μg/g -27%of Ta2 O5 .The main advantage of this method is to accurately determine Nb and Ta in high-grade Nb-Ta ore.%铌、钽在氢氟酸介质中能够形成稳定的溶液,使用耐氢氟酸进样系统的电感耦合等离子体发射光谱(ICP -OES)有利于提高分析的准确性。本文采用模块化的小罐型、多罐体组合(70罐/组)酸溶罐体的微波消解溶样模式,结合 ICP -OES 仪器的耐氢氟酸进样系统,建立了测定铌钽矿中铌、钽的分析方法。本方法加快了酸溶的溶样速度,溶样时间从原来的48 h 减少至1 h,且在氢氟酸介质中测定避免了高含量铌、钽在低酸度介质中容易水解的影响。方法检出限为铌5.58μg/g,钽5.87μg/g。本方法应用于测定铌钽精矿(19%Nb2 O5,27%Ta2 O5)的分析结果与碱熔方法一致,能够测定 Nb2 O5含量在42μg/g ~19%和 Ta2 O5含量在86μg/g ~27%高低品位的铌钽矿,尤其对于铌、钽在百分含量以上的铌钽矿具有优势。

  15. Properties of atomic-vapor and atomic-layer deposited Sr, Ti, and Nb doped Ta{sub 2}O{sub 5} Metal-Insulator-Metal capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Lukosius, M., E-mail: lukosius@ihp-microelectronics.com [IHP, Im Technologiepark 25, 15236 Frankfurt Oder (Germany); Kaynak, C. Baristiran; Kubotsch, S. [IHP, Im Technologiepark 25, 15236 Frankfurt Oder (Germany); Blomberg, T. [ASM Microchemistry Ltd., Vaeinoe Auerin katu 12 A, 00560 Helsinki (Finland); Ruhl, G. [Infineon Technologies AG, Wernerwerkstr. 2, 93049 Regensburg (Germany); Wenger, Ch. [IHP, Im Technologiepark 25, 15236 Frankfurt Oder (Germany)

    2012-05-01

    Atomic Vapor Deposition and Atomic Layer Deposition techniques were applied for the depositions of Ta{sub 2}O{sub 5}, Ti-Ta-O, Sr-Ta-O and Nb-Ta-O oxide films for Metal-Insulator-Metal (MIM) capacitors used in back-end of line for Radio Frequency applications. Structural and electrical properties were studied. Films, deposited on the TiN bottom electrodes, in the temperature range of 225-400 Degree-Sign C, were amorphous, whereas the post deposition annealing at 600 Degree-Sign C resulted in the crystallization of Nb-Ta-O films. Electrical properties of MIM structures, investigated after sputtering Au top electrodes, revealed that the main characteristics were different for each oxide. On one hand, Ti-Ta-O based MIM capacitors possessed the highest dielectric constant (50), but the leakages currents were also the highest ({approx} 10{sup -5} A/cm{sup 2} at - 2 V). On the other hand, Sr-Ta-O showed the lowest leakage current densities ({approx} 10{sup -9} A/cm{sup 2} at - 2 V) as well as the smallest capacitance-voltage nonlinearity coefficients (40 ppm/V{sup 2}), but the dielectric constant was the smallest (20). The highest nonlinearity coefficients (290 ppm/V{sup 2}) were observed for Nb-Ta-O based MIM capacitors, although relatively high dielectric constant (40) and low leakage currents ({approx} 10{sup -7} A/cm{sup 2} at - 2 V) were measured. Temperature dependent leakage-voltage measurements revealed that only Sr-Ta-O showed no dependence of leakage current as a function of the measurement temperature.

  16. Synthesis and structure of two new quaternary nitrides: Li{sub 3}Sr{sub 2}MN{sub 4} (M = Nb, Ta)

    Energy Technology Data Exchange (ETDEWEB)

    Chen, X.Z.; Eick, H.A. [Michigan State Univ., East Lansing, MI (United States)

    1997-04-01

    Two new quaternary nitrides, Li{sub 3}Sr{sub 2}MN{sub 4} (M = Nb, Ta) have been synthesized from Li, Sr, and Nb or Ta metals under a flowing Ar-NH{sub 3} atmosphere at 800{degrees}C under ambient pressure. The structures, determined by single crystal X-ray diffraction, are orthorhombic, space group Pnnm (No. 58) with Z=4, and have lattice parameters a = 8.713(6) {angstrom}, b=9.007(4) {angstrom}, c=7.006(5) {angstrom} and a=8.700(6) {angstrom}, b=9.004(4) {angstrom}, c=7.000(3) {angstrom} for M = Nb and Ta, respectively. Refinement based upon F yielded R=0.033 and R{sub w} = 0.036 for M = Nb and R=0.035 and R{sub w}=0.045 for M = Ta. The structures are isotypic with Na{sub 2}Li{sub 3}MO{sub 4}, M = Fe, Ga. The M and two independent Li atoms are tetrahedrally coordinated by N atoms. Each MN{sub 4} tetrahedron connects three Li(2)N{sub 4} tetrahedra, one by edge-sharing and two by corner-sharing, to form a two-dimensional layer in the bc plane. These layers are linked together by Li(1) atoms to form the three-dimensional structure. The two Sr atoms occupy channels formed by N atoms along the c direction. Crystalline Li{sub 3}Sr{sub 2}NbN{sub 4} was synthesized by heating a Li{sub 3}N-Sr{sub 2}NbN{sub 3} mixture at 750{degrees}C under an Ar atmosphere. Magnetic susceptibility data for Li{sub 3}Sr{sub 2}NbN{sub 4} between 4 and 300 K exhibit temperature independent paramagnetism.

  17. 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. .

  18. Effect of Al addition on mechanical properties and microstructure of refractory Al{sub x}HfNbTaTiZr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chun-Ming, E-mail: clin112@asu.edu; Juan, Chien-Chang; Chang, Chia-Hsiu; Tsai, Che-Wei; Yeh, Jien-Wei, E-mail: jwyeh@mx.nthu.edu.tw

    2015-03-05

    Highlights: • The study developed a series of refractory Al{sub x}HfNbTaTiZr HEAs. • The aim to improve strength, and reduce density of the very ductile base alloy. • These HEAs mainly consist of a simple BCC solid solution. • The addition of Al significantly improved the strength characteristics. • Solution hardening led to a decrease in ductility. - Abstract: This study developed a series of refractory Al{sub x}HfNbTaTiZr high-entropy alloys (HEAs) with an aim to improve strength, and reduce density of the very ductile base alloy HfNbTaTiZr. Despite the diversity of crystal structures among the constituent elements, all the HEAs are single solid solution phase with body-centered cubic (BCC) structure. The addition of Al significantly improves the strength but reduces the ductility due to large solution hardening. The linear relation between yield strength and atomic percentage of Al suggests that the strengthening effect of a certain element in a single-phase HEA alloy can be explained based on quasi-binary alloy concept. Crack formations in deformed AlHfNbTaTiZr alloy with the lowest fracture strain are mainly along the boundaries between dendrite and interdendrite. This agrees with its large deviation of Al content and thus strength between dendrite and interdendrite.

  19. Phonon and thermal expansion properties in Weyl semimetals MX (M = Nb, Ta; X = P, As): ab initio studies.

    Science.gov (United States)

    Chang, Dahu; Liu, Yaming; Rao, Fengfei; Wang, Fei; Sun, Qiang; Jia, Yu

    2016-06-07

    Weyl semimetal (WSM) is a new type of topological quantum material for future spintronic devices. Using the first-principles density functional theory, we systematically investigated the thermal expansion properties, and the temperature dependence of isovolume heat capacity and bulk modulus in WSMs MX (M = Nb, Ta; X = P, As). We also presented the phonon dispersion curves and its variation under stress in MX and the anisotropic thermal expansion properties due to the anisotropic crystal structure in WSMs have been predicted in our calculations. Intriguing, we found that the heat capacities increase more rapidly with increasing temperature in the low temperature region for all MX. Furthermore, our results showed that the thermal expansion properties are determined mainly by the isovolume heat capacity at low temperatures, while the bulk modulus has the major effect at high temperatures. These results are useful for applications of WSMs in electronic and spintronic devices.

  20. The electrical properties and relaxation behavior of AgNb1/2Ta1/2O3 ceramic

    Science.gov (United States)

    Prasad, K. Ganga; Niranjan, Manish K.; Asthana, Saket

    2017-02-01

    Polycrystalline AgNb1/2Ta1/2O3 powder was prepared by solid state reaction method. Preliminary x-ray diffractogram analysis of some aspects of crystal structure showed that a single phase compound formed exhibiting a monoclinic system. Impedance spectroscopy showed the presence of both bulk and grain boundary effects in the material. The relaxation behavior was studied by fitting electric modulus with Bergman function confirms us the existence of non-Debye type of relaxation the material. The ac conductivity spectrum obeyed Funke's double power law and fitting in results, the hopping parameters n1,n2 were indicating the existence of small and large range polaron hopping in the material. The band gap of the material 3.02 eV measured by using UV visible spectroscopy.

  1. Theoretical study of B2 type technetium AB (A=Tc, B=Ti, V, Nb and Ta) intermetallic compounds

    Science.gov (United States)

    Acharya, Nikita; Fatima, Bushra; Sanyal, Sankar P.

    2016-12-01

    The structural, electronic, elastic and thermal properties of the cubic AB type (A=Tc, B=Ti, V, Nb and Ta) technetium intermetallic compounds have been studied using the full potential linearized augmented plane wave (FP-LAPW) method within the generalized gradient approximation (GGA) and local density approximation (LDA) used for the exchange-correlation potential. The calculated lattice parameters agree well with the experimental results. The calculated electronic properties reveal that these compounds are metallic in nature with partial ionic bonding. The elastic constants obey the stability criteria for cubic system. Ductility for these compounds has been analyzed using the Pugh's rule and Cauchy's pressure revealing ductile in nature of all the compounds. Bonding nature is discussed using Fermi surface, band structure and charge density difference plots.

  2. The oxidation of TaBe sub 12 and NbBe sub 12 coatings on niobium

    Energy Technology Data Exchange (ETDEWEB)

    Courtright, E.L.

    1990-01-01

    The oxidation behavior of tantalum and niobium beryllide coatings on niobium were evaluated. Intermetallic bond layers consisting of Ir{sub 3}Ta and Ir{sub 3}Nb were used to butter the large thermal expansion mismatch between the beryllide coatings and underlying niobium substrate. All coatings were applied by Triode Sputtering except for a final environmental protection layer of stabilized zirconia deposited by RF Diode using a ceramic target. Severe delamination and spalling occurred during cyclic oxidation exposure, even at temperatures as low as 925{degrees}C, indicating that the bond layer did not prevent the differential expansion stresses from reaching the delamination failure threshold, particularly at the edges and corners. Hot pressed samples of the two beryllide compounds were also exposed to a similar cyclic oxidation history, but, in contrast to the coatings, exhibited excellent oxidation resistance to temperatures as high as 1370{degrees}C. 9 refs., 8 figs., 1 tab.

  3. 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

    2016-11-01

    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.

  4. A new mineral species rossovskyite, (Fe3+,Ta)(Nb,Ti)O4: crystal chemistry and physical properties

    Science.gov (United States)

    Konovalenko, Sergey I.; Ananyev, Sergey A.; Chukanov, Nikita V.; Rastsvetaeva, Ramiza K.; Aksenov, Sergey M.; Baeva, Anna A.; Gainov, Ramil R.; Vagizov, Farit G.; Lopatin, Oleg N.; Nebera, Tatiana S.

    2015-11-01

    A new mineral rossovskyite named after L.N. Rossovsky was discovered in granite pegmatites of the Bulgut occurrence, Altai Mts., Western Mongolia. Associated minerals are microcline, muscovite, quartz, albite, garnet of the almandine-spessartine series, beryl, apatite, triplite, zircon, pyrite, yttrobetafite-(Y) and schorl. Rossovskyite forms flattened anhedral grains up to 6 × 6 × 2 cm. The color of the mineral is black, and the streak is black as well. The luster is semi-metallic, dull. Mohs hardness is 6. No cleavage or parting is observed. Rossovskyite is brittle, with uneven fracture. The density measured by the hydrostatic weighing method is 6.06 g/cm2, and the density calculated from the empirical formula is 6.302 g/cm3. Rossovskyite is biaxial, and the color in reflection is gray to dark gray. The IR spectrum contains strong band at 567 cm-1 (with shoulders at 500 and 600 cm-1) corresponding to cation-oxygen stretching vibrations and weak bands at 1093 and 1185 cm-1 assigned as overtones. The reflection spectrum in visible range is obtained. According to the Mössbauer spectrum, the ratio Fe2+:Fe3+ is 35.6:64.4. The chemical composition is as follows (electron microprobe, Fe apportioned between FeO and Fe2O3 based on Mössbauer data, wt%): MnO 1.68, FeO 5.92, Fe2O3 14.66, TiO2 7.69, Nb2O5 26.59, Ta2O5 37.51, WO3 5.61, total 99.66. The empirical formula calculated on four O atoms is: {{Mn}}_{0.06}^{2 + } {{Fe}}_{0.21}^{2 + } {{Fe}}_{0.47}^{3 + } Ti0.25Nb0.51Ta0.43W0.06O4. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is monoclinic, space group P2/ c, a = 4.668(1), b = 5.659(1), c = 5.061(1) Å, β = 90.21(1)º; V = 133.70(4) Å3, Z = 2. Topologically, the structure of rossovskyite is analogous to that of wolframite-group minerals. The crystal-chemical formula of rossovskyite is [(Fe3+, Fe2+, Mn)0.57Ta0.32Nb0.11][Nb0.40Ti0.25Fe0.18Ta0.11W0.06]O4. The strongest lines of the powder X-ray diffraction pattern

  5. First-principles investigations of metal (V, Nb, Ta)-doped monolayer MoS2: Structural stability, electronic properties and adsorption of gas molecules

    Science.gov (United States)

    Zhu, Jia; Zhang, Hui; Tong, Yawen; Zhao, Ling; Zhang, Yongfan; Qiu, Yuzhi; Lin, Xianning

    2017-10-01

    Two-dimensional (2D) layered materials are at the forefront of research because of their unique structures and promising catalytic abilities. Here, the structural stability, electronic properties and gas adsorption of metal (V, Nb, Ta)-doped monolayer MoS2 have been investigated by density functional theory calculations. Our results show that the metal (V, Nb, Ta)-doped monolayer MoS2 is a stable catalyst under room temperature, due to the strong interaction between the doped metals (V, Nb, Ta) and S vacancy of monolayer MoS2. Compared with the gas adsorption (CO, NO2, H2O, NH3) on pristine monolayer MoS2, doped metal (V, Nb, Ta) can significantly improve the adsorption properties, chemical activity and the sensitivity of that of adsorbed gas molecules. This effect occurs due to the strong overlap between the metal nd orbitals and gas molecule orbitals, result in activation of the adsorbed gas molecules. Analysis of Bader charge shows that, more charge transfer (-0.66 e to -0.72 e) occur from metal (V, Nb, Ta)-doped monolayer MoS2 to the oxidizing gas molecules (NO2) acting as acceptors. While for the adsorption of CO molecules, the relative less electrons (about -0.24 e - -0.35 e) transfer occuring from substrate to the adsorbed gases. Whereas the direction of charge transfers is reversed for the adsorption of the reducing gas (H2O and NH3) behaving as donors, in which small electrons (0.04 e -0.09 e) transfer from adsorbed gas to metal (V, Nb, Ta)-doped monolayer MoS2. Our results suggested that metal (V, Nb, Ta)-doped monolayer MoS2 might be a good candidate for low-cost, highly active, and stable catalysts and gas sensors, providing an avenue to facilitate the design of high active MoS2-based two dimensional catalysts and gas sensors.

  6. Thermal Stability and Humidity Resistance of ScTaO_4 Modified(K_(0.5)Na_(0.5))NbO_3 Ceramics

    Institute of Scientific and Technical Information of China (English)

    ZHENG Li-Mei; WANG Jin-Feng; WANG Chun-Ming; WU Qing-Zao; ZANG Guo-Zhong

    2009-01-01

    Lead-free(Na_(0.5)K_(0.5))NbO_3-xmol% ScTaO_4(x = 0-1.5)ceramics are prepared using the conventional solid-state reaction method and their properties are investigated in detail.The results indicate that the piezoelectric properties and density are improved by the introduction of ScTaO_4.Due to the high orthorhombic-tetragonal phase transition temperature T_(O-T)(around 200℃),stable piezoelectric properties against temperature are obtained.In a wide temperature range of 15-160° C,k_p of the(Na_(0.5)K_(0.5))NbO_3-0.5 mol% ScTaO_4 ceramic remains almost unchanged and d_(31) increases slightly from 59pC/N to 71pC/N.The deliquescent problem is effectively solved by the addition of ScTaO_4.The piezoelectric properties of ScTaO_4 modified(Na_(0.5)K_(0.5))NbO_3 ceramics show no obvious reduction and dielectric loss increases slightly after 120 h of immersion.From the analysis,it is suggested that the density is an important factor that improves the humidity resistance of the specimens.

  7. Ta/TiO2-and Nb/TiO2-Mixed Oxides as Efficient Solar Photocatalysts: Preparation, Characterization, and Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    Hussein Znad

    2012-01-01

    Full Text Available Ta/TiO2- and Nb/TiO2-mixed oxides photocatalysts were prepared by simple impregnation method at different TiO2 : Nb or Ta mass ratios of 1 : 0.1, 1 : 0.5, and 1 : 1, followed by calcination at 500∘C. The prepared powders have been characterized by XRD, XPS, UV-Vis spectra, and SEM. The photocatalytic activity was evaluated under natural solar light for decolorization and mineralization of azo dye Orange II solution. The results showed that Nb/TiO2- and Ta/TiO2-mixed oxides have higher activity than the untreated TiO2 under natural solar light. The maximum activity was observed for Nb/TiO2 sample (at mass ratio of 1 : 0.1, which is characterized by the smallest crystalline size (17.79 nm. Comparing with the untreated TiO2, the solar decolorization and mineralization rates improved by about 140% and 237%, respectively, and the band gap reduced to 2.80 eV. The results suggest that the crystal lattices of TiO2 powder are locally distorted by incorporating Nb5+ species into TiO2, forming a new band energy structure, which is responsible for the absorption in the visible region. Unlike Ta/TiO2, the Nb/TiO2-mixed oxides can prevent the grain size growth of the treated TiO2, which is important to achieve high solar photoactivity.

  8. Micro-nanocomposites Al{sub 2}O{sub 3}/ NbC/ WC and Al{sub 2}O{sub 3}/ NbC/ TaC; Micro-nanocompositos de Al{sub 2}O{sub 3}/ NbC/ WC e Al{sub 2}O{sub 3}/ NbC/ TaC

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Thais da Silva

    2014-07-01

    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{sub 2}O{sub 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)

  9. Evidence of Nb-Ta mobility in high temperature F-rich fluids evidenced by the La Bosse quartz-Nb-ferberite stockwork (Echassières, French Massif Central).

    Science.gov (United States)

    Marignac, C.; Cuney, M.

    2012-04-01

    In the Echassières district (northern French Massif Central), the 310 Ma Beauvoir granite (a P-rich peraluminous RMG) overprints a quartz-ferberite stockwork. The 900 m-deep GPF1 scientific hole shows that the stockwork is split into two parts by the gently dipping Beauvoir intrusion: the upper section (~ 100m thick) occurs in the La Bosse quarry, , and the lower section (≥ 60 m thick) below the granite floor. The root of the stockwork (hypothetic La Bosse granite) has not been reached. The stockwork comprises flat-lying quartz veins (≤ 0.6 m thick) concordant to the regional schistosity of surrounding micaschists, and steep N10-N50°E quartz veins (≤ 0.2 m thick). The two sets result from hydraulic fracturing, and consistently display crack seal features. A family of aplites and aplo-pegmatites dikes follow the same set of fractures, being either later (with partial dissolution of pre-existing quartz veins) or earlier, than the quartz veins. There is no alteration, nor associated mineral other than ferberite, at the La Bosse quarry, whereas micaceous selvages are observed in the lower section. Ferberite display a trend of ferberite enrichment with increasing depth (0.71 to 0.95 Fb mole%). In the La Bosse quarry, three ferberite habitus are present: acicular, lanceolate and prismatic. Acicular crystals are typically nicely zoned, with alternating Nb-rich (4.95±0.94 % Nb2O5) and Nb-poor (1.57±0.38 % Nb2O5) growth bands. Ta (up to 0.30 Ta2O5), Ti and Sn are also enriched in the Nb-rich bands. Nb and Ta incorporation into the ferberite is in the form of columbite, as either true solid solution or nanoinclusions. Lanceolate crystals have a similarly zoned acicular core and a Nb-poor rim (1.08±0.66 % Nb2O5). Prismatic crystals are unzoned and Nb-poor (0.67±0.20 % Nb2O5). In the lower part of the stockwork, the Nb contents are lower (2.17 % Nb2O5 in the Nb-rich bands, 1.36 % in the Nb-poor bands, 0.08 % in the unzoned cortex, 0.15 % in the unzoned prisms

  10. Processing, physical metallurgy and creep of NiAl + Ta and NiAl + Nb alloys. Ph.D. Thesis. Final Contractor Report

    Science.gov (United States)

    Pathare, Viren M.

    1988-01-01

    Powder processed NiAl + Ta alloys containing 1, 2, and 4.5 at percent tantalum and NiAl + Nb alloys containing 1 and 2 at percent niobium were developed for improved creep properties. In addition, a cast alloy with 5 at percent tantalum was also studied. Hot extrusion parameters for processing alloys with 1 and 2 at percent of tantalum or niobium were designed. The NiAl + 4.5 at percent Ta alloy could be vacuum hot pressed successfully, even though it could not be extruded. All the phases in the multiphase alloys were identified and the phase transformations studied. The Ni2AlTa in NiAl + 4.5 at percent Ta alloy transforms into a liquid phase above 1700 K. Solutionizing and annealing below this temperature gives rise to a uniform distribution of fine second phase precipitates. Compressive creep properties were evaluated at 1300 K using constant load and constant velocity tests. In the higher strain rate region single phase NiAl + 1 at percent Ta and NiAl + 1 at percent Nb alloys exhibit a stress exponent of 5 characteristic of climb controlled dislocation creep. In slower strain rate regime diffusional creep becomes important. The two phase alloys containing 2 to 5 at percent Ta and 2 at percent Nb show considerable improvement over binary NiAl and single phase alloys. Loose dislocation networks and tangles stabilized by the precipitates were found in the as crept microstructure. The cast alloy which has larger grains and a distribution of fine precipitates shows the maximum improvement over binary NiAl.

  11. Phase analysis and dielectric properties of oxides obtained in the MgO-(1-)Nb2O5-()Ta2O5 system

    Indian Academy of Sciences (India)

    M Thirumal; A K Ganguli

    2001-10-01

    MgNb2-TaO6 (0 ≤ ≤ 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 = 1.75 and the tetragonal trirutile structure for MgTa2O6 ( = 2.0). For all the compositions there exist secondary phases like Nb2O5 or Ta2O5 in addition to the major AB2O6 phase. Sintered disks (1200°C) show dielectric constants varying between 14.8 and 16.0 for the entire range of composition at a frequency of 500 kHz. The dielectric loss is nearly constant around 0.025 to 0.03 between 0 ≤ ≤ 1 but increases to 0.17 for the MgTa2O6 phase ( = 2.0). Scanning electron micrographs reveal a gradual decrease in grain size with increase in Ta concentration with a size of 3 micron for the = 0 composition (sintered at 1200°C) while the = 2 phase shows a grain size of approximately 0.5 microns. The microwave dielectric constant at ∼14 GHz is found to be 20.9 for the = 0 composition and 17.7 for the = 2 composition.

  12. Ferroelectric and Piezoelectric Characterization of Porous (K,Na,Li)(Nb,Ta,Sb)O{sub 3}; Respuesta Ferro-Piezoelectrica de (K,Na,Li)(Nb,Ta,Sb)O{sub 3} Poroso

    Energy Technology Data Exchange (ETDEWEB)

    Barolin, S. A.; Rubia, M. A. de la; Terny, S.; Rubio-Marcos, F.; Sanctis, O. de; Alonso, R. E.; Fernandez Lozano, J. F.; Frutos, J. de

    2014-02-01

    KNL-NTS powder with (K{sub 0}.44Na{sub 0}.52Li{sub 0}.04)(Nb{sub 0}.86Ta{sub 0}.10Sb{sub 0}.04)O{sub 3} stoichiometry was prepared following the conventional ceramic method of mixing carbonates and oxides. KNL-NTS powder synthesis is carried out in solid state at 700 degree centigrade for 3h. To obtain ceramic samples with different porosity the sintering of pellets is carried out in air at different temperatures between 1088 and 1125 degree centigrade for 2h. Structural and microstructural characterizations are performed by XRD and SEM and the degree and type of porosity is determined by mercury intrusion porosimetry. The influence of sintering temperature on the porosity and its consequence on both the ferroelectric hysteresis loops and the piezoelectric response was evaluated. The maximum densification is achieved at 1125 degree centigrade and the best ferroelectric response is achieved in sintered pellets at 1125 degree centigrade. Meanwhile, it was observed that pellets sintered in a lower temperature range (1094-1100 degree centigrade) where porosity reaches values up to 15 % have good ferroelectric piezoelectric response, similar to that found in the sintered pellets to 1125 degree centigrade. (Author)

  13. Microstructures and Mechanical Property of MoSi2/TSi2(T=Cr,V,Nb,Ta,Ti)Two-Phase Alloys

    Institute of Scientific and Technical Information of China (English)

    Fu-Gao Wei; Yoshisato Kimura; Yoshinao Mishima

    2000-01-01

    In order to improve the low temperature ductility and high temperature strength ofMoSi2 while keeping its superior high temperature oxidation resistance, the present work attempts to combine MoSi2with the C40 type disilicides of transition metals including Cr, V, Nb, Ta and Ti. The possibility of producing a thermally compatible composite of MoSi2 and the C40 disilicides is discussed by critical assessment of MoSi2-TSi2(T=Cr, V,Nb,Ta, Ti) pseudo-binary phase diagrams. Relative phase stability between the CIIb MoSi2 and the C40 TSi2 is investigated and lamellar MoSi2/TSi2 two-phase microstructures are obtained by appropriate choice of composition and heat-treament. Preliminary result on the microhardness of MoSi2/TSi2two-phase alloys is also discussed.

  14. Transition from Mott insulator to superconductor in GaNb4Se8 and GaTa4Se8 under high pressure.

    Science.gov (United States)

    Abd-Elmeguid, M M; Ni, B; Khomskii, D I; Pocha, R; Johrendt, D; Wang, X; Syassen, K

    2004-09-17

    Electronic conduction in GaM4Se8 (M=Nb,Ta) compounds with the fcc GaMo4S8-type structure originates from hopping of localized unpaired electrons (S=1 / 2) among widely separated tetrahedral M4 metal clusters. We show that under pressure these systems transform from Mott insulators to a metallic and superconducting state with T(C)=2.9 and 5.8 K at 13 and 11.5 GPa for GaNb4Se8 and GaTa4Se8, respectively. The occurrence of superconductivity is shown to be connected with a pressure-induced decrease of the MSe6 octahedral distortion and simultaneous softening of the phonon associated with M-Se bonds.

  15. Li6La3SnMO12 (M = Sb, Nb, Ta), a Family of Lithium Garnets with High Li-Ion Conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Bridges, Craig A [ORNL; Goodenough, J. B. [University of Texas, Austin; Gupta, Dr Asha [University of Texas, Austin; Nakanishi, Masahiro [ORNL; Paranthaman, Mariappan Parans [ORNL; Sokolov, Alexei P [ORNL; Bi, Zhonghe [ORNL; Li, Yutao [University of Texas, Austin; Han, Jiantao [University of Texas, Austin; Dong, Youzhong [South China University of Technology, Guangzhou, PR China; Wang, Long [University of Texas, Austin; Xu, Maowen [University of Texas, Austin

    2012-01-01

    In order to investigate the influence of covalent bonding within the garnet framework on the conductivity of Li+ in the interstitial space, the Li+ conductivities in the family of Sn-based compounds Li6La3 SnMO12 (M = Sb, Nb, Ta) have been obtained and are compared with those of Li6La3ZrMO12. Refinement of the neutron diffraction pattern of Li6La3 SnNbO12shows that the interstitial tetrahedral sites (24d ) are about half-occupied and most of the Li in the interstitial bridging octahedral sites are displaced from the center position (48g ). The Sb-based compound has the largest lattice parameter while the Ta-based compound has the highest Li+-ion conductivity of 0.42 10 4 Scm 1.

  16. Comparative Studies on the Laser Damage Resistance of Ta2O5 and Nb2O5 Films Performed under Different Electron Beam Currents

    Institute of Scientific and Technical Information of China (English)

    XV Cheng; XU Lin-Min; ZHANG Han-Zhuo; QIANG Ying-Huai; ZHU Ya-Bo; LIU Jiong-Tian; SHAO Jian-Da

    2011-01-01

    @@ TaO and NbO films are deposited by conventional e-beam method under different electron beam currents.The optical transmittance, chemical composition, absorption, scattering, surface topography and laser-induced damage threshoM (LIDT) of the films are comparatively studied.It is shown that the increase of electron beam current results in a decrease of the optical transmittance and stoichiometry, whereas it increases the absorption, scattering and rms roughness for both TaO and NbO films.However, the LIDT increases first and then decreases with the increase of electron beam current.In addition, the annealing improves the optical transmittance, stoichiometry and LIDT for the two kinds of films.Both the effects of electron beam current and annealing on the LIDT can be mainly attributed to three factors: substoichiometric defects, structural defects and adhesive force.Furthermore, the comparative results indicate that the laser damage resistance of TaO is lower than that of NbO.%Ta2O5 and Nb2Os Rims are deposited by conventional e-beam method under different electron beam currents. The optical transmittance, chemical composition, absorption, scattering, surface topography and laser-induced damage threshold (LIDT) of the dims are comparatively studied. It is shown that the increase of electron beam current results in a decrease of the optical transmittance and stoichiometry, whereas it increases the absorption, scattering and rms roughness for both Ta2O5, and Ni2O5 Sims. However, the LIDT increases first and then decreases with the increase of electron beam current. In addition, the annealing improves the optical transmittance, stoichiometry and LIDT for the two kinds of Sims. Both the effects of electron beam current and annealing on the LIDT can be mainly attributed to three factors: substoichiometric defects, structural defects and adhesive force. Furthermore, the comparative results indicate that the laser damage resistance of Ta2O5 is lower than that ofNb2O5.

  17. Crystal structure and band structure calculations of Pb1/3TaS2 and Sn1/3NbS2

    NARCIS (Netherlands)

    Fang, C.M; Wiegers, G.A; Meetsma, A.; de Groot, R.A.; Haas, C

    The crystal structures of Pb1/3TaS2 and Sn1/3NbS2 were determined using single-crystal X-ray diffraction. The space group is P6(3)22 and the unit cell dimensions are: a = 5.759(1), c = 14.813(1)Angstrom and a = 5.778(1), c = 14.394(1)Angstrom, for the Pb and Sn compounds, respectively. The

  18. 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...

  19. 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.

  20. 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

  1. 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.

  2. Electrochemical stability of Li6.5La3Zr2M0.5O12 (M = Nb or Ta against metallic lithium

    Directory of Open Access Journals (Sweden)

    Yunsung eKim

    2016-05-01

    Full Text Available The electrochemical stability of Li6.5La3Zr1.5Nb0.5O12 (LLZNO and Li6.5La3Zr1.5Ta0.5O12 (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/cm2 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 Nb5+ to Nb4+. The negligible change in interfacial resistance and no color change in LLZTO suggest that Ta5+ may be more stable against reduction than Nb5+ in cubic garnet versus Li during cycling.

  3. Fluid-mediated alteration of (Y,REE,U,Th)-(Nb,Ta,Ti) oxide minerals in granitic pegmatite from the Evje-Iveland district, southern Norway

    Science.gov (United States)

    Duran, Charley J.; Seydoux-Guillaume, Anne-Magali; Bingen, Bernard; Gouy, Sophie; de Parseval, Philippe; Ingrin, Jannick; Guillaume, Damien

    2016-10-01

    We document the textural relations and chemical composition of (Y,REE,U,Th)-(Nb,Ta,Ti) oxide minerals in a granitic pegmatite from the Evje-Iveland district, southern Norway, using a combination of scanning and transmission electron microscopy, electron probe micro-analysis and infrared absorption spectroscopy. The (Y,REE,U,Th)-(Nb,Ta,Ti) oxide mineral is euxenite, which is strongly radiation damaged and surrounded by radial fractures. Within euxenite grains, three domains of distinct composition comprising unaltered, intermediate and altered euxenite, have been identified. In most cases pyrochlore occurs as corroded grain boundaries around euxenite and within relict fractures. Intermediate and altered euxenite are depleted in U, Pb, Ti, Nb, and Y, but enriched in Si and Ca relative to unaltered euxenite. Pyrochlore is also enriched in Fe, Pb, Zr and LREE relative to all euxenite phases. Altered domains of euxenite have deficient analytical totals and contain O-H. These domains are metamict and contain nanopores and nanodomains enriched in U and Ca. We suggest that as radiation damage accumulated in euxenite, radial fractures developed around the euxenite grains, thus allowing fluid infiltration. In the presence of fluid, euxenite was replaced by secondary euxenite then pyrochlore, owing to dissolution-precipitation and diffusion reactions. During alteration, U and the strategic metals Nb, Ti, and REE were mobilized at both the nanoscale and the scale of the pegmatite.

  4. Microstructure characteristics and mechanical properties of laser-TIG hybrid welded dissimilar joints of Ti-22Al-27Nb and TA15

    Science.gov (United States)

    Zhang, Kezhao; Lei, Zhenglong; Chen, Yanbin; Liu, Ming; Liu, Yang

    2015-10-01

    Laser-TIG-hybrid-welding (TIG - tungsten inert gas) process was successfully applied to investigate the microstructure and tensile properties of Ti-22Al-27Nb/TA15 dissimilar joints. The HAZ of the arc zone in Ti-22Al-27Nb was characterized by three different regions: single B2, B2+α2 and B2+α2+O, while the single B2 phase region was absent in the HAZ of the laser zone. As for the HAZ in TA15 alloy, the microstructure mainly contained acicular α‧ martensites near the fusion line and partially remained the lamellar structure near the base metal. The fusion zone consisted of B2 phase due to the relatively high content of β phase stabilizing elements and fast cooling rate during the welding process. The tensile strength of the welds was higher than that of TA15 alloy because of the fully B2 microstructure in the fusion zone, and the fracture preferentially occurred on the base metal of TA15 alloy during the tensile tests at room temperature and 650 °C.

  5. Light-Induced Cytotoxicity and Genotoxicity of a Sunscreen Agent, 2-Phenylbenzimidazole in Salmonella typhimurium TA 102 and HaCaT Keratinocytes

    Directory of Open Access Journals (Sweden)

    Hongtao Yu

    2007-06-01

    Full Text Available 2-Phenylbenzimidazole (PBI is an ingredient found in sunscreen agents. PBI can absorb the UV portion of the solar light and undergo a series of light-induced reactions to cause adverse effects in humans. Therefore, chemical and photochemical toxicity of PBI were investigated in the bacteria Salmonella typhimurium TA 102 and human skin keratinocyte cells. There is no appreciable bacteria death due to the exposure to PBI alone, indicating that PBI is not chemically toxic to the bacteria at a dose as high as 625μM. However, exposure to PBI and a solar simulator light (300-W Xe/Hg lamp, 30 min, 18.6 J/cm2, equivalent to 30 min outdoor sunlight causes significant bacteria death: 35% at 25μM and 55% at 625μM PBI. Exposure of the bacteria to light and PBI at doses 5-25μM causes the bacteria to revert, an indication of mutation. In the presence of PBI but without light irradiation, the number of revertant bacteria colonies is around 200 due to spontaneous mutation. Combination of light irradiation and PBI causes the number of revertant TA 102 colonies to increase in a dose dependent manner, reaching a maximum of around 1700 revertant colonies at 25 μM PBI. At higher PBI concentrations, the number of revertant colonies remains constant. This result clearly indicates that PBI is photomutagenic in TA 102. Exposure of the human skin HaCaT keratinocytes in aqueous solution in the presence of PBI causes the cell to lose its viability with or without light irradiation. There is no significant difference in cell viability for the light irradiated or non-irradiated groups, indication PBI is not photocytotoxic. However, exposure of the cells to both PBI and light irradiation causes cellular DNA damage, while exposure to PBI alone does not cause DNA damage.

  6. Effect of Zr, V, Nb, Mo, and Ta substitutions on magnetic properties and microstructure of melt-spun SmCo5 magnets.

    Science.gov (United States)

    Fukuzaki, Tomokazu; Iwane, Hiroaki; Abe, Kazutomo; Doi, Toshihiro; Tamura, Ryuji; Oikawa, Tadaaki

    2014-05-07

    We have investigated effects of metal substitutions on the magnetic properties and microstructure of melt-spun Sm-Co-Cu-Fe-M (M = Zr, V, Nb, Mo, Ta) magnets. We prepared melt-spun ribbons with compositions of Sm(Co1-x Cu x )5Fe0.54-y M y (x = 0.1-0.5, y = 0-0.43, M = Zr, V, Nb, Mo, Ta). For compositions of Sm(Co1-x Cu x )5Fe0.54 (x = 0.1-0.5), coercivity increased with increasing of annealing temperature, and a high coercivity of 17.6 kOe was obtained at a Cu content of x = 0.3. The coercivity was found to increase with increasing melting point of the substitution element. A high coercivity of 24.5 kOe was obtained for a composition of Sm(Co0.7Cu0.3)5Fe0.34Ta0.2.

  7. Extreme High Field Strength Element Depletion and Chondritic Nb/Ta in Central Andean Adakite-like Lavas (~27° S, ~68° W)

    Science.gov (United States)

    Goss, A. R.; Kay, S. M.

    2005-12-01

    We present new high precision ICP-MS HFSE data on ~30 samples from the adakite-like Pircas Negras (SiO2 =57-62 %; La/Yb= 20-60; Sr = 600-900 ppm, Cr to 200 ppm) and Dos Hermanos (SiO2 =56-59 %; La/Yb= 57-61; Sr = 1200-1500 ppm, Cr to 60 ppm) andesites from the southernmost Andean Central Volcanic Zone (CVZ). These andesites erupted in a broadened arc as the volcanic front was displaced about 50 km to the east between 8 and 3 Ma and likely reflect melting of a garnet bearing crustal source. Our data reveal a discrete change from chondritic Nb/Ta ratios (19-21) and low Zr/Sm (25-30) in older 8-7 Ma Dos Hermanos lavas to dominantly subchondritic Nb/Ta ratios (11-18) and higher Zr/Sm (30-45) in Hermanos (La/Ta= 90-100) lavas are best explained as hydrous and oxidizing conditions within the mantle wedge initially stabilized Ti-oxides (i.e. rutile) as the arc front migrated. These steeper REE patterns and high La/Ta are a transient feature measured in lavas erupting during the peak of arc migration, as mafic <2 Ma CVZ lavas to the north (~26° S) have lower La/Yb (< 20) and La/Ta (< 40). The observed temporal shift in Nb/Ta coupled with a general increase in Zr/Sm suggests a change from residual rutile to low-Mg amphibole within an eclogitic/granulitic crustal residue during the course of arc migration. A potential factor in explaining these data is that a transient period of increased subduction erosion associated with the migration of the frontal arc transported forearc crustal material into the progressively dehydrating mantle wedge. Partial melting of this eclogitized forearc material contributed to the transient adakite-like nature of the magmas erupted along the margin.

  8. 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.

  9. Photocatalytic properties of CoOx-loaded nano-crystalline perovskite oxynitrides ABO2N (A = Ca, Sr, Ba, La; B = Nb, Ta)

    Science.gov (United States)

    Oehler, Florian; Ebbinghaus, Stefan G.

    2016-04-01

    Highly crystalline niobium- and tantalum-based oxynitride perovskite nanoparticles were obtained from hydrothermally synthesized oxide precursors by thermal ammonolysis at different temperatures. The samples were studied with respect to their morphological, optical and thermal properties as well as their photocatalytic activity in the decomposition of methyl orange. Phase pure oxynitrides were obtained at rather low ammonolysis temperatures between 740 °C (CaNbO2N) and 1000 °C (BaTaO2N). Particle sizes were found to be in the range 27 nm-146 nm and large specific surface areas up to 37 m2 g-1 were observed. High photocatalytic activities were found for CaNbO2N and SrNbO2N prepared at low ammonolysis temperatures. CoOx as co-catalyst was loaded on the oxynitride particles resulting in a strong increase of the photocatalytic activities up to 30% methyl orange degradation within 3 h for SrNbO2N:CoOx.

  10. The formation of the Yichun Ta-Nb deposit, South China, through fractional crystallization of magma indicated by fluid and silicate melt inclusions

    Science.gov (United States)

    Li, Shenghu; Li, Jiankang; Chou, I.-Ming; Jiang, Lei; Ding, Xin

    2017-04-01

    The Yichun Ta-Nb deposit, which is located in Jiangxi Province, South China, can be divided into four lithological zones (from bottom upward): two-mica granite, muscovite granite, albite granite, and lepidolite-albite granite zones. It remains controversial whether these distinct vertical zones were formed through late magmatic-hydrothermal metasomatic alteration or fractional crystallization of magma. To investigate the evolution mechanism of rock- and ore-forming fluid in this deposit, we studied fluid and melt inclusions in quartz and lepidolite in these four granite zones. These fluid inclusions are mainly composed of H2O-NaCl, and have homogenization temperatures ranging from 160 °C to 240 °C, with densities between 0.86 and 0.94 g/cm3 and salinities between 0.5 and 6.5 wt% NaCl equivalent. Raman spectroscopic analyses showed that the daughter minerals contained in silicate melt inclusions are mainly quartz, lepidolite, albite, muscovite, microcline, topaz, and sassolite. From the lower to upper granite zones, the albite contents in silicate melt inclusions increase, while the muscovite contents decrease gradually until muscovite is substituted by lepidolite in the lepidolite-albite granite zone. Additionally, the calculated densities of the silicate melt inclusions exhibit decreasing trends from bottom upward. The total homogenization temperatures of silicate melt inclusions, which were observed under external pressures created in the sample chamber of a hydrothermal diamond-anvil cell, decreased from 860 °C in the lower lithological zone to 776 °C in the upper lithological zone, and the initial melting temperatures of solid phases were 570-710 °C. The calculated initial H2O contents of granitic magma showed an increasing trend from the lower (∼2 wt% in the two-mica granite zone) to the upper granitic zones (∼3 wt% in the albite granite zone). All of these features illustrate that the vertical granite zones in the Yichun Ta-Nb deposit formed through

  11. Lattice structure transformation and change in surface hardness of Ni{sub 3}Nb and Ni{sub 3}Ta intermetallic compounds induced by energetic ion beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Kojima, H., E-mail: sv110021@edu.osakafu-u.ac.jp [Department of Materials Science, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan); Yoshizaki, H.; Kaneno, Y. [Department of Materials Science, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan); Semboshi, S. [Materials Research Institute (Kansai Center), Tohoku University, Sakai, Osaka 599-8531 (Japan); Hori, F. [Department of Materials Science, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan); Saitoh, Y. [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, Takasaki, Gunma 370-1292 (Japan); Okamoto, Y. [Quantum Beam Science Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Iwase, A. [Department of Materials Science, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan)

    2016-04-01

    Ni{sub 3}Nb and Ni{sub 3}Ta intermetallic compounds, which show the complicated lattice structures were irradiated with 16 MeV Au{sup 5+} ions at room temperature. The X-ray diffraction measurement revealed that the lattice structure of these intermetallic compounds changed from the ordered structures to the amorphous state by the ion irradiation. The irradiation-induced amorphization caused the increase in Vickers hardness. The result was compared with our previous results for Ni{sub 3}Al and Ni{sub 3}V, and was discussed in terms of the intrinsic lattice structures of the samples.

  12. Synthesis, Characterization and Properties of Ca5A2TiO12 (A=Nb, Ta) Ceramic Dielectric Materials for Applications in Microwave Telecommunication Systems

    Science.gov (United States)

    Bijumon, Pazhoor Varghese; Mohanan, Pezholil; Sebastian, Mailadil Thomas

    2002-06-01

    Microwave ceramic dielectric materials Ca5Nb2TiO12 and Ca5Ta2TiO12 have been prepared by a conventional solid-state ceramic process. The structure was studied by X-ray diffraction and the dielectric properties were characterized at microwave frequencies. The ceramics posses a relatively high dielectric constant, very low dielectric loss (Qu× f> 30000 GHz) and small temperature variation of resonant frequency. These materials are potential candidates for dielectric resonator applications in microwave integrated circuits.

  13. Control of the Crystalline Structure and Piezoelectric Properties of (K,Na,Li)(Nb,Ta,Sb)O3 Ceramics through Transition Metal Oxide Doping

    Science.gov (United States)

    Rubio-Marcos, Fernando; José Romero, Juan; Francisco Fernández, José; Marchet, Pascal

    2011-10-01

    Divalent transition metal oxide doping of lead-free (K,Na,Li)(Nb,Ta,Sb)O3 piezoceramics is studied. Two different behaviors were observed independently of the doping metal: at low concentrations, the tetragonal structure is preserved, while at a high doping level, the material becomes orthorhombic. For any given doping level, a linear dependence was found between the pseudo-tetragonal lattice distortion and the ionic radii of doping ions. The ferroelectric and piezoelectric properties of the material are reduced by the doping, whereas the mechanical quality factor increases. Thus, the piezoelectric and ferroelectric properties of these lead-free piezoceramics can be easily controlled through metal oxide doping.

  14. Oxidation Behavior of a Refractory NbCrMo0.5Ta0.5TiZr Alloy (Preprint)

    Science.gov (United States)

    2012-03-01

    smaller than the atomic radii of other elements in the fourth alloy, causes additional formation of a minor FCC Laves phase [10]. Due to strongly...pattern of the HIPd NbCrMo0.5Ta0.5TiZr alloy. A major BCC1 phase and two minor phases , BCC2 and FCC ( Laves ), were identified [10]. The lattice parameters...parallel to the sample surface develop in the regions of former BCC2 and Laves phases (between former BCC1 particles). The cracks are also extended

  15. Ternary borides Nb7Fe3B8 and Ta7Fe3B8 with Kagome-type iron framework.

    Science.gov (United States)

    Zheng, Qiang; Gumeniuk, Roman; Borrmann, Horst; Schnelle, Walter; Tsirlin, Alexander A; Rosner, Helge; Burkhardt, Ulrich; Reissner, Michael; Grin, Yuri; Leithe-Jasper, Andreas

    2016-06-21

    Two new ternary borides TM7Fe3B8 (TM = Nb, Ta) were synthesized by high-temperature thermal treatment of samples obtained by arc-melting. This new type of structure with space group P6/mmm, comprises TM slabs containing isolated planar hexagonal [B6] rings and iron centered TM columns in a Kagome type of arrangement. Chemical bonding analysis in Nb7Fe3B8 by means of the electron localizability approach reveals two-center interactions forming the Kagome net of Fe and embedded B, while weaker multicenter bonding present between this net and Nb atoms. Magnetic susceptibility measurements reveal antiferromagnetic order below TN = 240 K for Nb7Fe3B8 and TN = 265 K for Ta7Fe3B8. Small remnant magnetization below 0.01μB per f.u. is observed in the antiferromagnetic state. The bulk nature of the magnetic transistions was confirmed by the hyperfine splitting of the Mössbauer spectra, the sizable anomalies in the specific heat capacity, and the kinks in the resistivity curves. The high-field paramagnetic susceptibilities fitted by the Curie-Weiss law show effective paramagnetic moments μeff≈ 3.1μB/Fe in both compounds. The temperature dependence of the electrical resistivity also reveals metallic character of both compounds. Density functional calculations corroborate the metallic behaviour of both compounds and demonstrate the formation of a sizable local magnetic moment on the Fe-sites. They indicate the presence of both antiferro- and ferrromagnetic interactions.

  16. Growth of doped and pure monocrystalline fibers and gradient crystals of REMO{sub 4} compounds (RE = rare earths and M = Nb and Ta); Crescimento de fibras monocristalinas puras e dopadas, e cristais gradientes de compostos REMO{sub 4} (RE= terras raras e M = Nb e Ta)

    Energy Technology Data Exchange (ETDEWEB)

    Octaviano, E.S.; Levada, C.L.; Missiato, O., E-mail: esoctaviano@if.sc.usp.br [Academia da Forca Aerea, Campo Fontenelle, Pirassununga , SP (Brazil). Div. de Ensino; Semenzato, M.J.; Silva, R.A.; Andreeta, J.P. [Universidade de Sao Paulo (USP), Sao Carlos, SP (Brazil). Instituto de Fisica

    2009-07-01

    A desirable alternative for a faster development, characterization and application of material of technological interest has been the growth of single crystal fibers by LHPG - Laser Heated Pedestal Growth. In this work it was reported the growth of pure, doped and gradient single crystal fibers of the chemical formulation REMO{sub 4} (M = Nb e Ta, e RE= Rare Earth), characterized through primary techniques such as X-Ray and optical spectroscopy. (author)

  17. 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

  18. Mg diffusion in K(Ta{sub 0.65}Nb{sub 0.35})O{sub 3} thin films grown on MgO evidenced by Auger electron spectroscopy investigation

    Energy Technology Data Exchange (ETDEWEB)

    Simon, Q.; Bouquet, V.; Demange, V.; Deputier, S. [Sciences Chimiques de Rennes, UMR 6226 CNRS/Universite de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France); Universite Europeenne de Bretagne (France); Wyczisk, F.; Garry, G.; Ziaie, A. [Thales Research and Technology, rd. 128, 91767 Palaiseau Cedex (France); Guilloux-Viry, M., E-mail: maryline.guilloux-viry@univ-rennes1.fr [Sciences Chimiques de Rennes, UMR 6226 CNRS/Universite de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France); Universite Europeenne de Bretagne (France)

    2011-09-01

    The diffusion of Mg in pulsed laser deposited K(Ta{sub 0.65}Nb{sub 0.35})O{sub 3} thin films epitaxially grown on (1 0 0) MgO single crystal substrate were investigated by Auger electron spectroscopy (AES). A diffusion of Mg from the substrate into the whole thickness (400 nm) of the as-deposited K(Ta{sub 0.65}Nb{sub 0.35})O{sub 3} films was observed with an accumulation of Mg at the surface. Ex situ post-annealing (750 deg. C/2 h) has led to a homogeneous distribution of Mg in all the ferroelectric coating. This strong reaction between film and substrate promotes a doping effect, responsible for the reduction of K(Ta{sub 0.65}Nb{sub 0.35})O{sub 3} dielectric losses in comparison with films grown on other substrates.

  19. Photocatalytic activity of R3MO7 and R2Ti2O7 (R=Y, Gd, La; M=Nb, Ta) for water splitting into H2 and O2.

    Science.gov (United States)

    Abe, Ryu; Higashi, Masanobu; Sayama, Kazuhiro; Abe, Yoshimoto; Sugihara, Hideki

    2006-02-01

    The photocatalytic activities of R3MO7 and R2Ti2O7 (R=Y, Gd, La; M=Nb, Ta) strongly depended on the crystal structure. Overall, photocatalytic water splitting into H2 and O2 proceeded over La3TaO7 and La3NbO7, which have an orthorhombic weberite structure, Y2Ti2O7 and Gd2Ti2O7, which have a cubic pyrochlore structure, and La2Ti2O7, which has a monoclinic perovskite structure. All of these materials are composed of a network of corner-shared octahedral units of metal cations (TaO6, NbO6, or TiO6); materials without such a network were inactive. The octahedral network certainly increased the mobility of electrons and holes, thereby enhancing photocatalytic activity.

  20. First principle study on electronic structure, structural phase stability, optical and vibrational properties of Ba2ScMO6 (M = Nb, Ta)

    Science.gov (United States)

    Rameshe, Balasubramaniam; Murugan, Ramaswamy; Palanivel, Balan

    2016-12-01

    First principle calculations are performed to investigate the electronic structure, structural phase stability, optical and vibrational properties of double perovskite oxide semiconductors namely Ba2ScMO6 (M = Nb, Ta) in the cubic symmetry using WIEN2k. In order to study the ground state properties of these compounds, the total energies are calculated as a function of reduced volumes and fitted with Brich Murnaghan equation. The estimated ground state parameters are comparable with the available experimental data. Calculations of electronic band structure on these compounds reveal that both Ba2ScNbO6 and Ba2ScTaO6 exhibit a semiconducting behavior with a direct energy gap of 2.78 and 3.15 eV, respectively. To explore the optical transitions in these compounds, the real and imaginary parts of the dielectric function, refractive index, extinction coefficient, reflectivity, optical absorption coefficient, real part of optical conductivity and the energy-loss function are calculated at ambient pressure and analyzed. The collective Raman active modes of the atoms of these materials are also calculated in order to understand the structural stability of these compounds.

  1. 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.

  2. Structures and luminescence properties of Yb3+ in the double perovskites Ba2YB'O6 (B'=Ta5+, Nb5+)phosphors

    Institute of Scientific and Technical Information of China (English)

    Zhou Wen-Long; Zhang Qing-Li; Gao Jin-Yun; Liu Wen-Peng; Ding Li-Hua; Yin Shao-Tang

    2011-01-01

    The Yb3+ doped Ba2YB'O6 (B'= Ta5+, Nh5+) were prepared by high temperature solid-state reaction method,their structures were determined by x-ray diffraction and refined by Rietveld method. The diffuse reflection absorption,the excitation of ultraviolet light, these phosphors exhibit broad charge transfer band emissions of TaO6 or NbO6centre with large Stokes shift. The Yb3+ doped into these hosts are situated at y3+ sites of cubic symmetry (Oh).The experimental energy levels of Yb3+ in Ba2YTaO6 and Ba2YNbO6 were determined by photoluminescence and diffuse reflection absorption spectra. Their wavefunctions and theoretical energy levels were obtained by diagonalising the Hamiltonian matrix. The experimental energy levels were fitted by Levenberg-Marquardt iteration algorithm to Nb5+) from (2F5/2)T-8 to the low-energy states were calculated.

  3. Synthesis and characterisation of the uranium pyrochlore betafite [(Ca,U){sub 2}(Ti,Nb,Ta){sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    McMaster, Scott A.; Ram, Rahul; Charalambous, Fiona [Centre for Advanced Materials and Industrial Chemistry, School of Applied Sciences RMIT University, GPO Box 2476, Melbourne, Vic 3001 (Australia); Pownceby, Mark I. [CSIRO Process Science and Engineering, Bayview Avenue Clayton, Victoria 3168 (Australia); Tardio, James [Centre for Advanced Materials and Industrial Chemistry, School of Applied Sciences RMIT University, GPO Box 2476, Melbourne, Vic 3001 (Australia); Bhargava, Suresh K., E-mail: suresh.bhargava@rmit.edu.au [Centre for Advanced Materials and Industrial Chemistry, School of Applied Sciences RMIT University, GPO Box 2476, Melbourne, Vic 3001 (Australia)

    2014-09-15

    Highlights: • First published method for preparation of a synthetic form of betafite. • X-ray photoelectron spectroscopy data on uranium oxidation state(s) in synthetic betafite. • Detailed microscopy based characterisation of synthetic betafite. - Abstract: Betafite of composition [(Ca,U){sub 2}(Ti,Nb,Ta){sub 2}O{sub 7}] was prepared via a solid state synthesis route. The synthesis was shown to be sensitive to initial reactant ratios, the atmosphere used (oxidising, neutral, reducing) and time. The optimum conditions for the synthesis of betafite were found to be heating the reactants required at 1150 °C for 48 h under an inert gas atmosphere. XRD characterisation revealed that the synthesised betafite contained minor impurities. EPMA analysis of a sectioned surface showed very small regions of Ca-free betafite on grain boundaries as well as minor rutile impurities. Some heterogeneity between the Nb:Ta ratio was observed by quantitative EPMA but was generally within the nomenclature requirements stated for betafite. SEM analysis revealed the synthesised betafite was comprised mostly of hexaoctohedral crystals of ∼3 μm in diameter. XPS analysis of the sample showed that the uranium in the synthesised betafite was predominately present in the U{sup 5+} oxidation state. A minor amount of U{sup 6+} was also detected which was possibly due to surface oxidation.

  4. Electronic, thermal, and superconducting properties of metal nitrides (MN) and metal carbides (MC) (M=V, Nb, Ta) compounds by first principles studies

    Energy Technology Data Exchange (ETDEWEB)

    Subhashree, G.; Sankar, S.; Krithiga, R. [Anna Univ., Chennai, Tamil Nadu (India). Condensed Matter Lab.

    2015-07-01

    Structural, electronic, and superconducting properties of carbides and nitrides of vanadium (V), niobium (Nb), and tantalum (Ta) (group V transition elements) have been studied by computing their electronic band structure characteristics. The electronic band structure calculations have been carried out based on the density functional theory (DFT) within the local density approximation (LDA) by using the tight binding linear muffin tin orbital method. The NaCl-type cubic structures of MN and MC (M=V, Nb, Ta) compounds have been confirmed from the electronic total energy minimum of these compounds. The ground state properties, such as equilibrium lattice constant (a{sub 0}), bulk modulus (B), and Wigner-Seitz radius (S{sub 0}) are determined and compared with available data. The electronic density of states reveals the metallic nature of the chosen materials. The electronic specific heat coefficient, Debye temperature, and superconducting transition temperature obtained from the band structure results are found to agree well with the earlier reported literature.

  5. 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)

  6. Striking Doping Effects on Thermal Methane Activation Mediated by the Heteronuclear Metal Oxides [XAlO4 ](.+) (X=V, Nb, and Ta).

    Science.gov (United States)

    Wu, Xiao-Nan; Li, Jilai; Schlangen, Maria; Zhou, Shaodong; González-Navarrete, Patricio; Schwarz, Helmut

    2017-01-18

    The thermal reactivity of the heteronuclear metal-oxide cluster cations [XAlO4 ](.+) (X=V, Nb, and Ta) towards methane has been studied by using mass spectrometry in conjunction with quantum mechanical calculations. Experimentally, a hydrogen-atom transfer (HAT) from methane is mediated by all the three oxide clusters at ambient conditions. However, [VAlO4 ](.+) is unique in that this cluster directly transforms methane into formaldehyde. The absence of this reaction for the Nb and Ta analogues demonstrates a striking doping effect on the chemoselectivity in the conversion of methane. Mechanistic aspects of the two reactions have been elucidated by quantum-chemical calculations. The HAT reactivity can be attributed to the significant spin density localized at the terminal oxygen atom (Ot(.-) ) of the cluster ions, while the ionic/covalent character of the Lewis acid-base unit [X-Ob ] plays a crucial role for the generation of formaldehyde. The mechanistic insight derived from this combined experimental/computational investigation may provide guidance for a more rational design of catalysts. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Development of 0.1C-11Cr-3W-3Co-V-Nb-Ta-Nd-N ferritic steel for USC boilers

    Energy Technology Data Exchange (ETDEWEB)

    Igarashi, M.; Sawaragi, Y. [Sumitomo Metal Industries, Ltd., Amagasaki (Japan). Corporate Research and Development

    1997-12-31

    A high Cr ferritic steel: O.1C-11Cr-3W-3Co-V-Nb-Ta-Nd-N has been developed for main steam pipe and header materials in ultra super critical (USC) boilers in fossil fired power plants. This steel has a higher creep rupture strength at elevated temperatures of up to 630{degree}C than conventional steels such as 9Cr-1Mo-V-Nb steel (ASME SA335 P91). High creep rupture strength is mainly achieved with a hard martensitic phase matrix and longer term phase stability of finely dispersed precipitates. The martensitic phase matrix has been found to be strengthened by the addition of Co to a great extent, although Co has only been recognized to suppress {delta}-ferrite in these steels. Finely dispersed MX type carbonitrides such as Nb(C,N) and V(C,N) are also essential to delay recovery of the martensitic phase. {mu}-phase (Fe{sub 7}W{sub 6} type) precipitation is found to be most effective for higher creep rupture strength at high temperatures of over 600{degree}C. W is the most important element for stabilizing the {mu}-phase and also M{sub 23}C{sub 6} type carbide and to delay coarsening of these precipitates, resulting in higher creep rupture strength at high temperatures. Co promotes the {mu}-phase precipitation, but not M{sub 23}C{sub 6} type carbide at high temperatures. Nd and Ta are found to be effective for increasing creep rupture strength of the weld joints of the steel. This is considered to be achieved by NdN and TaN type nitrides which are more stable than Nb(C,N) and V(C,N) at elevated temperatures of up to 1200{degree}C. It is thus concluded that the developed steel can be used for main steam pipe and header materials in ultra super critical boilers up to 630{degree}C. 8 refs., 10 figs., 1 tab.

  8. A pseudo-tetragonal tungsten bronze superstructure: a combined solution of the crystal structure of K6.4(Nb,Ta)(36.3)O94 with advanced transmission electron microscopy and neutron diffraction.

    Science.gov (United States)

    Paria Sena, Robert; Babaryk, Artem A; Khainakov, Sergiy; Garcia-Granda, Santiago; Slobodyanik, Nikolay S; Van Tendeloo, Gustaaf; Abakumov, Artem M; Hadermann, Joke

    2016-01-21

    The crystal structure of the K6.4Nb28.2Ta8.1O94 pseudo-tetragonal tungsten bronze-type oxide was determined using a combination of X-ray powder diffraction, neutron diffraction and transmission electron microscopy techniques, including electron diffraction, high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), annular bright field STEM (ABF-STEM) and energy-dispersive X-ray compositional mapping (STEM-EDX). The compound crystallizes in the space group Pbam with unit cell parameters a = 37.468(9) Å, b = 12.493(3) Å, c = 3.95333(15) Å. The structure consists of corner sharing (Nb,Ta)O6 octahedra forming trigonal, tetragonal and pentagonal tunnels. All tetragonal tunnels are occupied by K(+) ions, while 1/3 of the pentagonal tunnels are preferentially occupied by Nb(5+)/Ta(5+) and 2/3 are occupied by K(+) in a regular pattern. A fractional substitution of K(+) in the pentagonal tunnels by Nb(5+)/Ta(5+) is suggested by the analysis of the HAADF-STEM images. In contrast to similar structures, such as K2Nb8O21, also parts of the trigonal tunnels are fractionally occupied by K(+) cations.

  9. Investigation of magnetic phase transitions in B-site disordered PbBxB'1-xO3 (B = Fe, Co and B' = Nb, Ta)

    Science.gov (United States)

    Chillal, Shravani; Popova, Elena; Eulf, Erik; Gvasaliya, Severian; Shaplygina, Tatiana; Lushnikov, Sergey; Zheludev, Andrey

    2012-02-01

    Materials such as PbFe0.5Nb0.5O3 (PFN-0.5)/ PbFe0.5Ta0.5O3 (PFT-0.5) and PbCo0.33Nb0.67O3 (PCN-0.33) are relaxor ferroelectrics. PbFe0.5Nb0.5O3 (PFN-0.5) also shows anti-ferromagnetic order below ˜ 143 K. Though multiferroicity is an important property of PFN-0.5, its uniqueness stems from coexisting anti-ferromagnetic and spinglass phases below ˜ 12 K. Presently, it is the only known such case in a Heisenberg 3D spin system. We report a first systematic study of the H-T phase diagram of PFN-0.5 and discuss the results in the context of existing theories. In addition, we study the magnetic properties of PFT-0.5 and PCN-0.33. While PFN-0.5 and PFT-0.5 demonstrate similar behavior, PCN-0.33 does not show any anomalies that could signify magnetic ordering. We propose that the observed dramatic differences may result from partial B-site ordering.

  10. Microstructure and Mechanical Properties of Laser-Welded Joints of Ti-22Al-25Nb/TA15 Dissimilar Titanium Alloys

    Science.gov (United States)

    Li, Dalong; Hu, Shengsun; Shen, Junqi; Zhang, Hao; Bu, Xianzheng

    2016-05-01

    Laser beam welding (LBW) was applied to join 1-mm-thick dissimilar titanium alloys, Ti-22Al-25Nb (at.%) and TA15, and the microstructure and mechanical properties of the welded joints were systematically analyzed. Defect-free joints were obtained, and the fusion zone mainly consisted of B2 and martensitic α' phases because of the uneven distribution of the β phase stabilizer and rapid cooling rate of LBW. The phase compositions of the heat-affected zone varied with the different thermal cycles during the welding process. The different microstructures of the dissimilar titanium alloys led to an unsymmetrical hardness profile, with the welded seam exhibiting the lowest value of 271 HV. In room-temperature tensile tests, the fractures all occurred preferentially in the fusion zone. The strengths of the joints were close to those of the base metal but with prominently decreasing ductility. In tensile tests performed at 550 °C, all the joints fractured in the TA15 base metal, and the strength and plasticity of the welds were equivalent to those of the TA15 base metal.

  11. Ab initio study of Fermi surface and dynamical properties of Ni{sub 2}XAl (X = Ti, V, Zr, Nb, Hf and Ta)

    Energy Technology Data Exchange (ETDEWEB)

    Sreenivasa Reddy, P.V.; Kanchana, V., E-mail: kanchana@iith.ac.in

    2014-12-15

    Highlights: • Electronic structure properties studied at ambient as well as under compression. • Mechanical properties are predicted for the first time. • Vibrational properties are studied at ambient as well as under compression. • Ni{sub 2}TiAl is found to have the lowest C{sub v}, S, and higher U, F{sub vib} and linear thermal expansion coefficient. • T{sub c} of Ni{sub 2}NbAl is calculated and a non-monotonic variation in the T{sub c} is observed under compression. - Abstract: A detailed study on the pressure and temperature effects on ternary Ni-based inter-metallic compounds Ni{sub 2}XAl (X = Ti, V, Zr, Nb, Hf and Ta) have been carried out using density functional theory. The calculated ground state properties are in good agreement with experiments for all the investigated compounds. The band structures and Fermi surface topology is found to be quite similar for all the compounds except for Ni{sub 2}NbAl, where we find an extra band to cross the Fermi level under compression resulting in a new electron pocket at X-point. Ni{sub 2}NbAl is found to be a superconductor with superconducting transition temperature of 3.1 K which agrees quite well with the experimental value and the calculated T{sub c} is found to vary non-monotonically under pressure. From the calculated phonon dispersion relation, we find all the investigated Ni-based Heusler compounds to be dynamically stable, until high pressure. The ductile nature of these compounds is confirmed from the calculated Cauchy’s pressure, Pugh’s ratio and Poisson’s ratio. In addition, the thermodynamic properties show Ni{sub 2}TiAl to have lower specific heat and entropy but higher internal energy and free energy among all the investigated compounds.

  12. The contrasting effect of the Ta/Nb ratio in (111)-layered B-site deficient hexagonal perovskite Ba5Nb4-xTaxO15 crystals on visible-light-induced photocatalytic water oxidation activity of their oxynitride derivatives.

    Science.gov (United States)

    Hojamberdiev, Mirabbos; Bekheet, Maged F; Zahedi, Ehsan; Wagata, Hajime; Vequizo, Junie Jhon M; Yamakata, Akira; Yubuta, Kunio; Gurlo, Aleksander; Domen, Kazunari; Teshima, Katsuya

    2016-08-02

    The effect of the Ta/Nb ratio in the (111)-layered B-site deficient hexagonal perovskite Ba5Nb4-xTaxO15 (0 ≤ x ≤ 4) crystals grown by a KCl flux method on visible-light-induced photocatalytic water oxidation activity of their oxynitride derivatives BaNb1-xTaxO2N (0 ≤ x ≤ 1) was investigated. The Rietveld refinement of X-ray data revealed that all Ba5Nb4-xTaxO15 samples were well crystallized in the space group P3[combining macron]m1 (no. 164). Phase-pure BaNb1-xTaxO2N (0 ≤ x ≤ 1) porous structures were obtained by nitridation of the flux-grown oxide crystals at 950 °C for 20, 25, 30, 35, and 40 h, respectively. The absorption edge of BaNb1-xTaxO2N (0 ≤ x ≤ 1) was slightly shifted from 720 to 690 nm with the increasing Ta/Nb ratio. The O2 evolution rate gradually progressed and reached the highest value (127.24 μmol in the first 2 h) with the Ta content up to 50 mol% but decreased at 75 and 100 mol% presumably due to the reduced specific surface area and high density of structural defects, such as grain boundaries acting as recombination centers, originated from high-temperature nitridation for prolonged periods. Transient absorption spectroscopy provided evidence for the effect of the Ta/Nb ratio on the behavior and energy states of photogenerated charge carriers, indicating a direct correlation with photocatalytic water oxidation activity of BaNb1-xTaxO2N.

  13. Crystal Structure, Electronic Structure, and Photocatalytic Activity of Oxysulfides: La2Ta2ZrS2O8, La2Ta2TiS2O8, and La2Nb2TiS2O8.

    Science.gov (United States)

    Goto, Yosuke; Seo, Jeongsuk; Kumamoto, Kazunori; Hisatomi, Takashi; Mizuguchi, Yoshikazu; Kamihara, Yoichi; Katayama, Masao; Minegishi, Tsutomu; Domen, Kazunari

    2016-04-01

    The novel oxysulfides La2Ta2ZrS2O8 (LTZSO), La2Ta2TiS2O8 (LTTSO), and La2Nb2TiS2O8 (LNTSO) were synthesized, and their crystal structures, electronic structures, and photocatalytic activities for water splitting under visible light were investigated. Density functional theory calculations showed that these compounds are direct-band-gap semiconductors. Close to the conduction band minimum, the main contribution to the band structure comes from the d orbitals of Zr or Ti ions, while the region near the valence band maximum is associated with the 3p orbitals of S ions. The absorption-edge wavelength was determined to be 540 nm for LTZSO and 700 nm for LTTSO and LNTSO. An analysis of the crystal structure using synchrotron X-ray diffraction revealed that these compounds contained antisite defects at transition metal ion sites, and these were considered to be the origin of the broad absorption at wavelengths longer than that corresponding to band-gap excitation. LTZSO was revealed to be active in the oxygen evolution reaction from aqueous solution containing a sacrificial electron acceptor under visible-light illumination. This result was supported by the band alignment and flat-band potential determined by photoelectron spectroscopy and Mott-Schottky plots.

  14. Effect of Alloying Element (Nb, Ta, Fe and Zr) on Microstructure and Mechanical Properties of Biomedical Titanium Alloy%合金元素Nb、Ta、Fe、Zr对钛合金组织和性能的影响

    Institute of Scientific and Technical Information of China (English)

    廉才浩; 杨胜; 周慧; 唐仁波; 李丹

    2013-01-01

    综述了Nb、Ta、Fe、Zr四种元素对β钛合金组织和力学性能的影响,以期对合金的设计起到指导作用.%The effects of beta alloying element (Nb,Ta,Fe,Zr) on the microstructure and mechanical properties of biomedical titanium alloys were reviewed.

  15. Microwave dielectric properties of (A2+(1/3)B5+(2/3))0.5Ti0(0.5)O2 (A2+ = Zn, Mg, B5+ = Nb, Ta) ceramics.

    Science.gov (United States)

    Kim, E S; Kang, D H

    2008-05-01

    Dielectric properties of (A(2+)(1/3)B(5+)(2/3))(0.5)Ti0(0.5)O(2) (A(2+) = Zn, Mg, B(5+) = Nb, Ta) ceramics were investigated at microwave frequencies. A single phase with tetragonal rutile structure was obtained through the entire compositions. Dielectric properties were strongly dependent on the structural characteristics. The specimens with B(5+) = Nb showed a larger dielectric constant than those with B(5+) = Ta due to the decrease of bond valence. Quality factors (Qf) of the specimens with B(5+) = Ta were larger than those with B(5+) = Nb. Temperature coefficient of the resonant frequencies (TCF) of (Zn(1/3)Nb(2/3) )0(0.5)Ti0(0.5)O(2) was larger than that of (Mg(1/3)Ta(2/3))0(0.5)Ti0(0.5)O(2). These results could be attributed to the changes of the temperature coefficient of dielectric constant and the degree of oxygen octahedral distortion.

  16. The behaviour of the extended HFSE group (Nb, Ta, Zr, Hf, W, Mo) during the petrogenesis of mafic K-rich lavas: The Eastern Mediterranean case

    Science.gov (United States)

    Kirchenbaur, M.; Münker, C.

    2015-09-01

    In arc lavas, elements of the extended high field strength element group (HFSE; Nb, Ta, Zr, Hf, W, and Mo) are valuable tracers to unravel magma source processes. These elements can also help to identify residual mineral assemblages in subducting slabs and in the mantle. Most high-precision studies on HFSE behaviour to date only focused on intra-oceanic arc suites and data for mafic lavas of the K-rich series (medium-K, high-K and shoshonitic) are scarce. Arguably, K-rich series are the most incompatible element-rich end-members of subduction zone magmatism, and they often record sediment recycling into the mantle. Understanding HFSE fractionation in K-rich lavas can therefore provide important insight into the global HFSE budget. Here we present a comprehensive extended HFSE dataset obtained by isotope dilution on well-characterised K-rich lavas from the Eastern Mediterranean, also including subducting sediment samples drilled during DSDP Leg 13 and ODP Leg 160 South and West of Crete. The volcanic samples include mafic calc-alkaline lavas from the active Aegean Island arc (Santorini) and post-collisional Tertiary lavas from SE Bulgaria. The Santorini lavas record a hydrous sediment melt-mediated source overprint of a depleted mantle source by components from the subducting African plate. The Bulgarian lavas tap lithospheric mantle sources that were overprinted by fluid- and melt-like subduction components during Eocene subduction of the African Plate. The sediments in this study comprise silts/sands, marl oozes, limestones and clay-rich debris flows and approximate the bulk sediment subducted beneath the Hellenic arc. The marked enrichment of all HFSE in the lavas is controlled by the composition of the subducted sediments as shown by low 176Lu/177Hf (0.008630-0.02433) and Zr/Nb (11.3-29.4), combined with variable εHf (-3 to +11) and elevated W contents (up to 2.45 ppm) in the lavas. Nevertheless, the lavas display unfractionated ratios of Nb/Ta and Zr/Hf of 12

  17. The electrical properties and relaxation behavior of AgNb{sub 1/2}Ta{sub 1/2}O{sub 3} ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, K.Ganga, E-mail: kotagirigangaprasad@gmail.com; Niranjan, Manish K.; Asthana, Saket

    2017-02-01

    Polycrystalline AgNb{sub 1/2}Ta{sub 1/2}O{sub 3} powder was prepared by solid state reaction method. Preliminary x-ray diffractogram analysis of some aspects of crystal structure showed that a single phase compound formed exhibiting a monoclinic system. Impedance spectroscopy showed the presence of both bulk and grain boundary effects in the material. The relaxation behavior was studied by fitting electric modulus with Bergman function confirms us the existence of non-Debye type of relaxation the material. The ac conductivity spectrum obeyed Funke's double power law and fitting in results, the hopping parameters n{sub 1},n{sub 2} were indicating the existence of small and large range polaron hopping in the material. The band gap of the material 3.02 eV measured by using UV visible spectroscopy.

  18. Chemical Coupling SERS Properties of Pyridine on Silver-Caged Metal Clusters M@Ag12 (M = V-, Nb-, Ta-, Cr, Mo, W, Mn+, Tc+, Re+)

    Science.gov (United States)

    Chen, Lei; Wang, Zhigang; Li, Zhengqiang; Zhang, Rui-Qin

    2017-07-01

    Using density functional theory, this work presents a comprehensive analysis of nonresonant surface-enhanced Raman scattering enhancement of pyridine on M@Ag12 (M = V-, Nb-, Ta-, Cr, Mo, W, Mn+, Tc+, Re+). Computational results indicate that the chemical enhancement of pyridine on M@Ag12 is closely associated with the charge properties of silver-caged clusters. Pyridine on negative clusters exhibits the strongest chemical enhancement with a factor of about 103, while the chemical enhancement is only about 102 for pyridine on neutral clusters and 10 for pyridine on positive clusters. The polarizability analyses elucidate the nature of the chemical enhancement that delocalized electrons of negative adsorption systems occupy higher molecular orbitals than those of neutral and positive adsorption systems, which can lead to stronger nonresonant chemical enhancement.

  19. Crystal structure of triple oxides HO/sub 2/ScNbO/sub 7/ and Sm/sub 2/ScTaO/sub 7/

    Energy Technology Data Exchange (ETDEWEB)

    Filip' ev, V.S.; Cherner, Ya.E.; Bunina, O.A.; Seregin, V.F.

    The structure of new Ho/sub 2/Sc NbO/sub 7/ and Sm/sub 2/ScTaO/sub 7/ compounds synthesized by the three-stage roasting at 1100-1350 deg C was investigated. Powdergrams of the synthesized compounds indicated to be like the cubic structure of pyrochlore type. Periods of unit cells were determined by Bragg reflex angles. The dependence of unreliability factor on values of the position parameter of oxygen x atoms was calculated. Data were obtained that indirectly indicated a substantial disorder in the disposition of Ho and Sc atoms over A and B positions. Values of bond lengths and valence angles were presented.

  20. Electronic structure of the LiAA‧O6 (A = Nb, Ta, and A‧ = W, Mo) ceramics by modified Becke-Johnson potential

    Science.gov (United States)

    Ali, Zahid; Khan, Imad; Rahman, Mazhar; Ahmad, Rashid; Ahmad, Iftikhar

    2016-08-01

    DFT is used to study various transition metal based ceramics LiAA‧O6 (A = Nb, Ta, and A‧ = W, Mo) in tetragonal phase with space group 421 m (No. 113). The calculated structural and geometrical parameters are found in closed agreement with the experiments. Electronic clouds explain the chemical bonding and reveal that Li atom occupy central position and form ionic bond. Other bonds in these compounds are significantly covalent due to the sharing of electrons between O and A/A‧. The electronic properties demonstrate that these compounds are wide bandgap semiconductors in the energy range of 2.18-2.60 eV. These bandgap energies confirm the suitability of these oxides in optoelectronic devices operating in the visible range of the electromagnetic spectrum.

  1. Temperature dependence of dielectric and electromechanical properties of (K,Na)(Nb,Ta)O3 single crystal and corresponding domain structure evolution.

    Science.gov (United States)

    Zheng, Limei; Wang, Junjun; Huo, Xiaoqing; Wang, Rui; Sang, Shijing; Li, Shiyang; Zheng, Peng; Cao, Wenwu

    2014-07-28

    Domain structures and their evolution with temperature in the [001] C oriented (K,Na)(Nb,Ta)O3 (KNNT) single crystal have been studied before and after poling by polarizing light microscopy. The results indicate that the KNNT crystal is difficult to be completely poled by the room temperature poling process. The domain structure is rather stable in the orthorhombic phase, but exhibits substantial changes near the phase transition temperatures TO-T and TC. Narrower stripe domains are formed during both the orthorhombic-tetragonal and tetragonal-cubic phase transition processes, no intermediate phases were found during the phase transitions. The temperature dependence of the dielectric and piezoelectric properties were measured, and the influence of domain structures on the dielectric and electromechanical properties were quantified.

  2. Atomic defects and dopants in ternary Z-phase transition-metal nitrides Cr M N with M =V , Nb, Ta investigated with density functional theory

    Science.gov (United States)

    Urban, Daniel F.; Elsässer, Christian

    2017-09-01

    A density functional theory study of atomic defects and dopants in ternary Z-phase transition-metal nitrides Cr M N with M =V , Nb, or Ta is presented. Various defect formation energies of native point defects and of substitutional atoms of other metal elements which are abundant in the steel as well are evaluated. The dependence thereof on the thermodynamic environment, i.e., the chemical conditions of a growing Z-phase precipitate, is studied, and different growth scenarios are compared. The results obtained may help to relate results of experimental atomic-scale analysis by atom probe tomography or transmission electron microscopy to the theoretical modeling of the formation process of the Z phase from binary transition-metal nitrides.

  3. Chemical Coupling SERS Properties of Pyridine on Silver-Caged Metal Clusters M@Ag12 (M = V-, Nb-, Ta-, Cr, Mo, W, Mn+, Tc+, Re+)

    Science.gov (United States)

    Chen, Lei; Wang, Zhigang; Li, Zhengqiang; Zhang, Rui-Qin

    2016-10-01

    Using density functional theory, this work presents a comprehensive analysis of nonresonant surface-enhanced Raman scattering enhancement of pyridine on M@Ag12 (M = V-, Nb-, Ta-, Cr, Mo, W, Mn+, Tc+, Re+). Computational results indicate that the chemical enhancement of pyridine on M@Ag12 is closely associated with the charge properties of silver-caged clusters. Pyridine on negative clusters exhibits the strongest chemical enhancement with a factor of about 103, while the chemical enhancement is only about 102 for pyridine on neutral clusters and 10 for pyridine on positive clusters. The polarizability analyses elucidate the nature of the chemical enhancement that delocalized electrons of negative adsorption systems occupy higher molecular orbitals than those of neutral and positive adsorption systems, which can lead to stronger nonresonant chemical enhancement.

  4. 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.

  5. Calculated structural, electronic and elastic properties of M{sub 2}GeC (M=Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W)

    Energy Technology Data Exchange (ETDEWEB)

    Bouhemadou, A. [University of Setif, Laboratory for Developing New Materials and Their Characterization, Department of Physics, Faculty of Science, Setif (Algeria)

    2009-09-15

    Using ab initio calculations, we have studied the structural, electronic and elastic properties of M{sub 2}GeC, with M=Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W. Geometrical optimizations of the unit cell are in agreement with the available experimental data. The band structures show that all studied materials are electrical conductors. The analysis of the site and momentum projected densities shows that bonding is due to M d-C p and M d-Ge p hybridizations. The elastic constants are calculated using the static finite strain technique. The shear modulus C{sub 44}, which is directly related to the hardness, reaches its maximum when the valence electron concentration is in the range 8.41-8.50. We derived the bulk and shear moduli, Young's moduli and Poisson's ratio for ideal polycrystalline M{sub 2}GeC aggregates. We estimated the Debye temperature of M{sub 2}GeC from the average sound velocity. This is the first quantitative theoretical prediction of the elastic constants of Ti{sub 2}GeC, V{sub 2}GeC, Cr{sub 2}GeC, Zr{sub 2}GeC, Nb{sub 2}GeC, Mo{sub 2}GeC, Hf{sub 2}GeC, Ta{sub 2}GeC and W{sub 2}GeC compounds, and it still awaits experimental confirmation. (orig.)

  6. Modelling potential photovoltaic absorbers Cu3 MCh 4 (M  =  V, Nb, Ta; Ch  =  S, Se, Te) using density functional theory

    Science.gov (United States)

    Kehoe, Aoife B.; Scanlon, David O.; Watson, Graeme W.

    2016-05-01

    The geometric and electronic properties of a series of potential photovoltaic materials, the sulvanite structured \\text{C}{{\\text{u}}3}MC{{h}4} (M  =  V, Nb, Ta; Ch  =  S, Se, Te), have been computationally examined using both PBEsol+U and HSE06 methods to assess the materials’ suitability for solar cell application and to compare the predictions of the two theoretical approaches. The lattice parameters, electronic density of states, and band gaps of the compounds have been calculated to ascertain the experimental agreement obtained by each method and to determine if any of the systems have an optical band gap appropriate for photovoltaic absorber materials. The PBEsol+U results are shown to achieve better agreement with experiment than HSE06 in terms of both lattice constants and band gaps, demonstrating that higher level theoretical methods do not automatically result in a greater level of accuracy than their computationally less expensive counterparts. The PBEsol+U calculated optical band gaps of five materials suggest potential suitability as photovoltaic absorbers, with values of 1.72 eV, 1.49 eV, 1.19 eV, 1.46 eV, and 1.69 eV for Cu3VS4, Cu3VSe4, Cu3VTe4, Cu3NbTe4, and Cu3TaTe4, respectively, although it should be noted that all fundamental band gaps are indirect in nature, which could lower the open-circuit voltage and hence the efficiency of prospective devices.

  7. 钨青铜结构Ba6Zn0.67M9.33O30(M=Nb,Ta)的合成与介电特性%Synthesis and Dielectric Properties of Tungsten Bronze Structure Compounds Ba6Zn0.67M9.33O30 (M=Nb,Ta)

    Institute of Scientific and Technical Information of China (English)

    方亮; 杨俊峰; 黄涛华; 张辉; 刘韩星

    2004-01-01

    @@ 为满足现代通信技术的小型化、集成化与高可靠性的迫切要求,探索具有高介电常数、低介电损耗与低温度系数的微波介电材料引起了材料科学、化学、物理、电子学等领域科学工作者的广泛关注,其中BaO-ZnO-Ta2O5体系中以钙钛矿结构Ba(Zn1/3Ta2/3)O3为主晶相的微波介电陶瓷是目前使用频率和品质因数最高,温度系数最稳定的微波介电材料系统[1-3].考虑到复合钙钛矿结构和钨青铜结构的相似性,均由氧八面体共顶连接;而且近来Pani-grahi,Sebastian,陈湘明等报道了一些钨青铜结构铌、钽酸盐陶瓷具有较好的介电性能[4~8],因此我们期望在BaO-ZnO-Ta2O8/Nb2O5体系合成钨青铜结构铌、钽酸盐Ba6Zn0.67Nb9.33O30和BaZn0.67Ta9.33O30,测试其陶瓷体的介电性能以探索新型介电功能材料.

  8. Microstructural evaluation of Ti-35Nb-7,5 T alloy deformed by cold rolling and annealed; Avaliacao microestrutural da liga Ti-35Nb-7,5Ta deformada por laminacao a frio e recozida

    Energy Technology Data Exchange (ETDEWEB)

    Giudice, M.L.C.; Hayama, A.O.F.; Button, S.T.; Caram, R., E-mail: mlcgiudice@fem.unicamp.b [Universidade Estadual de Campinas (DEMA/FEM/UNICAMP), SP (Brazil). Faculdade de Engenharia Mecanica. Dept. de Engenharia de Materiais

    2010-07-01

    This work presents the main results of microstructural characterization of Ti- 35Nb-7.5Ta (% in weight) deformed by cold rolling and annealed. Samples were obtained by electric arc melting, heat treated at 1000 deg C for 8 hours and water quenched. Samples were deformed by cold rolling in multiple passes up to a maximum reduction of 84%. Deformed samples were encapsulated in quartz under vacuum and annealed at 600, 700 e 800 deg C, in variable times and water quenched. Characterization was carried out using light optical microscopy, X-ray diffraction, Vickers hardness test and acoustic emission measurements to determine the Young's modulus. The results show the orientation occurrence of the martensitic phase in relation to the cold rolling direction in deformed samples. In samples annealed at 600 deg C recovery is predominant and samples annealed at 800 deg C for 60 min are fully recrystallized. (author)

  9. 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.

  10. Computational study on the molecular structures and photoelectron spectra of bimetallic oxide clusters MW2O9(-/0) (M=V, Nb, Ta).

    Science.gov (United States)

    Chen, Wen-Jie; Zhang, Chang-Fu; Zhang, Xian-Hui; Zhang, Yong-Fan; Huang, Xin

    2013-05-15

    Density functional theory (DFT) and coupled cluster theory (CCSD(T)) calculations are carried out to investigate the electronic and structural properties of a series of bimetallic oxide clusters MW2O9(-/0) (M=V, Nb, Ta). Generalized Koopmans' theorem is applied to predict the vertical detachment energies (VDEs) and simulate the photoelectron spectra (PES). Theoretical calculations at the B3LYP level yield singlet and doublet ground states for the bimetallic anionic and neutral clusters, respectively. All the clusters present the six-membered ring structures with different symmetries, except that the TaW2O9(-) cluster shows a chained style with a penta-coordinated tantalum atom. Spin density analyses reveal oxygen radical species in all neutral clusters, consistent with their structural characteristics. Moreover, additional calculations are performed to study the oxidation reaction of CO molecule with the W3O9(+) cation and the isoelectronic VW2O9 cluster, and results indicate that the introduction of vanadium at tungsten site can efficiently improve the oxidation reactivity. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Computational study on the molecular structures and photoelectron spectra of bimetallic oxide clusters MWO9-/0 (M = V, Nb, Ta)

    Science.gov (United States)

    Chen, Wen-Jie; Zhang, Chang-Fu; Zhang, Xian-Hui; Zhang, Yong-Fan; Huang, Xin

    2013-05-01

    Density functional theory (DFT) and coupled cluster theory (CCSD(T)) calculations are carried out to investigate the electronic and structural properties of a series of bimetallic oxide clusters MWO9-/0 (M = V, Nb, Ta). Generalized Koopmans' theorem is applied to predict the vertical detachment energies (VDEs) and simulate the photoelectron spectra (PES). Theoretical calculations at the B3LYP level yield singlet and doublet ground states for the bimetallic anionic and neutral clusters, respectively. All the clusters present the six-membered ring structures with different symmetries, except that the TaWO9- cluster shows a chained style with a penta-coordinated tantalum atom. Spin density analyses reveal oxygen radical species in all neutral clusters, consistent with their structural characteristics. Moreover, additional calculations are performed to study the oxidation reaction of CO molecule with the WO9+ cation and the isoelectronic VW2O9 cluster, and results indicate that the introduction of vanadium at tungsten site can efficiently improve the oxidation reactivity.

  12. Influence of Bi2O3 on the Structure and Dielectric Properties of Ag(Nb0.8Ta0.2)O3 Ceramics%Bi2O3掺杂对Ag(Nb0.8Ta0.2)O3陶瓷结构和介电性能的影响

    Institute of Scientific and Technical Information of China (English)

    肖谧; 杨朝; 钟小蓉; 席芳芳

    2014-01-01

    本文研究了Bi2O3掺杂对Ag(Nb0.8Ta0.2)O3陶瓷的结构和介电性能的影响.X射线衍射(XRD)结果表明,Bi2O3的掺杂可以使陶瓷中Ag+被还原并析出,且银析出的量随Bi2O3掺杂量的增加而不断增加,这可能源自于Bi3+对Ag+的取代.在一定范围内增大Bi2O3掺杂量可提高Ag(Nb0.8Ta0.2)O3陶瓷的室温介电常数,降低介电损耗,并使温度系数向负值方向移动.当Bi2O3的掺杂量约为3.5wt%时,样品具有较大的介电常数(ε=672)和较小的介电损耗(tarδ=7.3×10-4).

  13. Crystallographic and dielectric properties of flux grown PbB1/2'B1/2″O (B'B″: InNb, InTa, YbNb, YbTa and MgW) single crystals

    Science.gov (United States)

    Kania, Antoni

    2008-05-01

    Single crystals of PbIn 1/2Nb 1/2O 3 (PIN), PbIn 1/2Ta 1/2O 3 (PIT), PbYb 1/2Nb 1/2O 3 (PYN), PbYb 1/2Ta 1/2O 3 (PYT) and PbMg 1/2W 1/2O 3 (PMW) have been grown by the flux method. The PbO-based solvents were used. Transparent, light yellow and arrow like shaped PIN and PIT crystals of the perovskite structure were obtained. Small amounts of red and of octahedron habit PIN and PIT crystals of the pyrochlore type were simultaneously grown. In the case of PYN, PYT and PMW only the crystals of the perovskite structure have been grown. The transparent and brown PYN and PYT crystals of octahedron habit were obtained. The transparent, light yellow and of octahedron or truncated octahedron shape PMW crystals were grown. The crystals were characterised by X-ray and dielectric studies. They showed that as-grown PIN crystals are nearly disordered, exhibit the rhombohedral distortion of the pseudo-perovskite unit cell and reveal relaxor behaviour. The partially ordered PIT crystals show monoclinic distortion and undergo antiferroelectric-paraelectric phase transition. The PYN, PYT and PMW single crystals, characterised by chemical order in the B'/B″ ion sublattice, exhibit orthorhombic symmetry and undergo the first-order antiferroelectric-paraelectric phase transitions.

  14. Investigation of the nanodomain structure formation by piezoelectric force microscopy and Raman confocal microscopy in LiNbO{sub 3} and LiTaO{sub 3} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Shur, V. Ya.; Zelenovskiy, P. S.; Nebogatikov, M. S.; Alikin, D. O.; Sarmanova, M. F.; Ievlev, A. V.; Mingaliev, E. A.; Kuznetsov, D. K. [Ferroelectric Laboratory, Institute of Physics and Applied Mathematics, Ural State University, 620083 Ekaterinburg (Russian Federation)

    2011-09-01

    Piezoelectric force microscopy (PFM) and Raman confocal microscopy have been used for studying the nanodomain structures in congruent LiNbO{sub 3} and LiTaO{sub 3} crystals. The high-resolution nanodomain images at the surface were observed via PFM. Raman confocal microscopy has been used for the visualization of the nanodomain structures in the bulk via layer-by-layer scanning at various depths. It has been shown experimentally that the nanodomain images obtained at different depths correspond to domain images at the polar surface obtained at different moments: the deeper the nanodomain, the earlier the moment. Such a correlation was applied for the reconstruction of the evolution of the domain structures with charged domain walls. The studied domain structures were obtained in highly non-equilibrium switching conditions realized in LiNbO{sub 3} and LiTaO{sub 3} via pulse laser irradiation and the electric field poling of LiNbO{sub 3}, with the surface layer modified by ion implantation. The revealed main stages of the domain structure evolution allow the authors to demonstrate that all geometrically different nanodomain structures observed in LiNbO{sub 3} and LiTaO{sub 3} appeared as a result of discrete switching.

  15. 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.

  16. 新型β钛合金Ti-25Nb-10Ta-1Zr-0.2Fe的固溶时效行为%Aging Response of Ti-25Nb-10Ta-1Zr-0.2Fe Alloys for Biomedical Application

    Institute of Scientific and Technical Information of China (English)

    廉才浩; 易丹青; 刘会群; 杨伏良; 田亮

    2011-01-01

    A new metastable β titanium alloy, Ti-25Nb-10Ta-lZr-0.2Fe, was designed for biomedical applications. The alloy ingot was prepared by vacuum consumable electrode arc melting. The solid-solution aging behavior of the alloy was investigated. The phase composition and the microstructure were studied by XRD, TEM and SEM. The tensile strength after aging and the hardness for different aging time were tested. Results show that only the a" phase is found after solid solution treatment at 800 °C for 1 h. The ω phase and fi phase are observed when the alloy is subjected to aging treatment at 400 °C for 0.5 h. The ω phase, as a brittle phase, keeps a high volume fraction during the aging treatment, which leads to a sharp increase of the Vicker hardness. In this case, the tensile strength of the alloy decreases dramatically to only about 400 Mpa, which is much smaller than that of the specimen in the cold-rolled condition (about 750 Mpa). Hence, a large mount of ω phase decreases the tensile property of the newly designed alloy Ti-25Nb-10Ta-lZr-0.2Fe.%设计一种新型生物医用亚稳定β钦合金,合金成分为Ti-25Nb-10Ta- 1Zr-0.2Fe(质量分数),采用真空自耗电弧熔炼制备合金锭坯,研究合金的固溶时效行为.通过X射线衍射(XRD)仪,透射电子显微镜(TEM),扫描电子显微镜(SEM)研究合金的相组成及微观组织.测量合金时效后的抗拉强度和不同时效时间的硬度.结果表明:800℃,1 h固溶后合金得到马氏体a″相,400℃下时效,短时间即得到ω相和β相.ω相为脆性相,大量ω相的产生使合金的硬度值提高很多,但是强度值相比较冷轧态下降明显,使得材料断裂方式变为脆性断裂.合金在72 h时效后ω相仍然保持较多量.

  17. The effect of boron addition on microstructure and mechanical properties of biomedical Ti35Nb6Ta alloy

    Energy Technology Data Exchange (ETDEWEB)

    Málek, Jaroslav, E-mail: malek@ujp.cz [UJP PRAHA a.s., Nad Kamínkou 1345, 156 10 Prague, Zbraslav (Czech Republic); CTU in Prague, Faculty of Mechanical Engineering, Department of Materials Engineering, Karlovo Namesti 13, 121 35 Praha 2 (Czech Republic); Hnilica, František, E-mail: hnilica@ujp.cz [UJP PRAHA a.s., Nad Kamínkou 1345, 156 10 Prague, Zbraslav (Czech Republic); Veselý, Jaroslav, E-mail: vesely@ujp.cz [UJP PRAHA a.s., Nad Kamínkou 1345, 156 10 Prague, Zbraslav (Czech Republic); Smola, Bohumil, E-mail: smola@met.mff.cuni.cz [Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5, 121 16 Prague 2 (Czech Republic); Březina, Vítězslav, E-mail: brezinavita@gmail.com [Masaryk University, Faculty of Medicine, Department of Stomathology, Komenského Náměstí 220/2, 662 43 Brno (Czech Republic); Kolařík, Kamil, E-mail: kamil.kolarik@email.cz [Faculty of Mechanical Engineering, University of West Bohemia, Univerzitní 22, 306 14 Plzeň (Czech Republic)

    2014-10-15

    The beta-titanium alloys are promising materials for bioapplications but their processing via melting is difficult. Coarse grains have been observed in as-cast specimens. Subsequent thermo-mechanical processing seems to be necessary in order to obtain fine-grained microstructure with better mechanical properties. The grain size can be decreased significantly by addition of small boron amount. In this work Ti–35Nb–6Ta alloy with various B additions (0, 0.05, 0.1, 0.3 and 0.5 wt.%) has been studied. Even the smallest amount of B leads to significant grain refinement in Ti–35Nb–6Ta alloy (from 1300 to about 350 μm). Slight grain refinement has been observed also after hot forging and solution treatment. TiB particles emerged in specimens due to B addition. These particles contribute to changes in mechanical properties not only in hot forged and solution treated specimens (hardness increase from 140 to 180 HV10), but also in cold swaged specimens (hardness from 230 to 250 HV10, tensile strength from 800 to 920 MPa). The hardness values can be increased up to 370 HV10 during aging at 400 °C (specimen with 0.5 wt.% B). It has been observed that specimens with low boron addition 0.05 wt.% possess no cytotoxicity. On the other hand in specimens with 0.1 wt.% B or more slight adverse effect on cytotoxicity has been observed. - Highlights: • The influence of boron on microstructure and mechanical properties has been studied. • Beta-transus temperature has been determined. • Cytotoxicity depending on boron content has been evaluated. • Possibility of final heat treatment has been determined.

  18. Cross sections of X-ray production induced by C and Si ions with energies up to 1 MeV/u on Ti, Fe, Zn, Nb, Ru and Ta

    Science.gov (United States)

    Prieto, José Emilio; Zucchiatti, Alessandro; Galán, Patricia; Prieto, Pilar

    2017-09-01

    X-ray production differential cross sections induced by C and Si ions with energies from 1 MeV/u down to 0.25 MeV/u, produced by the CMAM 5 MV tandem accelerator, have been measured for thin targets of Ti, Fe, Zn, Nb, Ru and Ta in a direct way. X-rays have been detected by a fully characterized silicon drift diode and beam currents have been measured by a system of two Faraday cups. Measured cross sections agree in general with previously published results. The ECPSSR theory with the united atoms correction gives absolute values close to the experimental ones for all the studied elements excited by C ions and for Ta, Nb and Ru excited by Si ions. For Ti, Fe and Zn excited by Si, the matching with theory is poor since even the ionization cross section is below the measured data.

  19. Cross sections of X-ray production induced by C and Si ions with energies up to 1 MeV/u on Ti, Fe, Zn, Nb, Ru and Ta

    CERN Document Server

    Prieto, J E; Galán, P; Prieto, P

    2016-01-01

    X-ray production differential cross sections induced by C and Si ions with energies from 1 MeV/u down to 0.25 MeV/u, produced by the CMAM 5 MV tandem accelerator, have been measured for thin targets of Ti, Fe, Zn, Nb, Ru and Ta in a direct way. X-rays have been detected by a fully characterized silicon drift diode and beam currents have been measured by a system of two Faraday cups. Measured cross sections agree in general with previously published results. The ECPSSR theory with the united atoms correction gives absolute values close to the experimental ones for all the studied elements excited by C ions and for Ta, Nb and Ru excited by Si ions. For Ti, Fe and Zn excited by Si, the basic ECPSSR theory gives better agreement, although on absolute values the gap for Ti is still large.

  20. Effect of B-site substitution on the stability of La0.2Sr0.8Fe0.8B0.2O3−, B=Al, Ga, Cr, Ti, Ta, Nb

    NARCIS (Netherlands)

    Lohne, O.F.; Gurauskis, J.; Phung, T.N.; Einarsrud, M.-A.; Grande, T.; Bouwmeester, H.J.M.; Wiik, K.

    2012-01-01

    Single phase, cubic perovskites of composition La0.2Sr0.8Fe0.8B0.2O3 − δ, B = Al, Ga, Cr, Ti, Ta and Nb, were prepared by spray pyrolysis from aqueous precursor solutions. The effect of B-site substitution on the stability in a H2 containing atmosphere was investigated using temperature programmed r

  1. Electronic structures and properties of eight-coordinate metal-polyarsenic complexes MAs8n- (M = V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re).

    Science.gov (United States)

    Li, J; Wu, K

    2000-04-03

    The eight-coordinate early transition metal polyarsenic complexes, MAs(8)3- (M = V, Nb, Ta), MAs(8)2- (M = Cr, Mo, W), and MAs8- (M = Mn, Tc, Re), have been studied using density functional theory (DFT). The geometry optimizations of these complexes indicate that in the most stable structures the transition metal atoms are trapped in a crownlike cavity consisting of a zigzag eight-membered ring of As8 cluster. The scalar-relativistic effects and spin-orbit coupling effects on the electronic structures and energy levels were taken into account. The stabilities of gas-phase MAs8n- ions and bonding between the As8 ring and early transition metals are discussed on the basis of population analysis, atomization energies, and decomposition reaction energies. All these complex ions are found to be diamagnetic with notable HOMO-LUMO energy gaps. The vibrational frequencies and infrared absorption intensities of the MAs8n- series are predicted theoretically. Brief theoretical calculations of the similar MoA(8)2- pnictide ions indicate that the analogous P, Sb, and even Bi complexes are likely to be stable, whereas the crownlike MoN(8)2- is not a stable complex.

  2. Microstructures and wear properties of surface treated Ti-36Nb-2Ta-3Zr-0.35O alloy by electron beam melting (EBM)

    Science.gov (United States)

    Chen, Zijin; Liu, Yong; Wu, Hong; Zhang, Weidong; Guo, Wei; Tang, Huiping; Liu, Nan

    2015-12-01

    Ti-36Nb-2Ta-3Zr-0.35O (wt.%) (TNTZO, also called gum metal) alloy was surface treated by electron beam melting (EBM), in order to improve wear properties. The microstructures and phase constitutions of the treated surface were characterized by optical microscopy (OM), scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GIXD) and electron backscattered diffraction (EBSD). The results showed that the martensitic phase and dendrites were formed from the β phase alloy after the EBM treatment, and microstructures in the surface changed with the processing parameters. Compared with the untreated TNTZO alloy, the surface modified TNTZO alloys exhibited higher nano-hardness, 8.0 GPa, and the wear loss was also decreased apparently. The samples treated at a scanning speed of 0.5 m/s exhibited the highest wear resistance due to the fast cooling rate and the precipitation of acicular α″ phase. The relationship between the wear property and the surface microstructure of TNTZO alloy was discussed.

  3. 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.

  4. Motif of misfit layer compounds (SnS) xTS 2 (T=Ti, V, Nb, Ta) in the matrix of SnS 2

    Science.gov (United States)

    Abramov, S. P.

    1999-09-01

    The possibility of T (T=Ti, V, Nb, Ta) insertion in the layer matrix of SnS 2 (when T≪Sn) presents a special case of intercalation for the specific interactions that are inherent in the misfit layer compounds (SnS) xTS 2 ( x≈1). FT Raman spectra of T xSnS 2 (T=Ti, V) with x≪1 testify to the SnS 2 matrix that is invariable with respect to a charge transfer from T to SnS 2 layers as compared with the pristine SnS 2. At the same time the T xSnS 2 structure ( x≪1) taken as a whole has substantial features in the UV-IR spectra as compared with the pristine SnS 2 but is still a semiconductor at least in the case of T=Ti. This points out in the cluster manner of TS 2 insertion in the matrix of SnS 2 with the interactions that are typical of the misfit layer compounds (SnS) xTS 2 in which metallic conductivity occurs in the TS 2 layers.

  5. Comparison of single-beam and dual-beam laser welding of Ti-22Al-25Nb/TA15 dissimilar titanium alloys

    Science.gov (United States)

    Shen, Junqi; Li, Bo; Hu, Shengsun; Zhang, Hao; Bu, Xianzheng

    2017-08-01

    Laser beam welding (LBW) was used to join Ti-22Al-25Nb/TA15 dissimilar titanium alloys. The microstructure and mechanical properties of the welded joints under single and dual beam welding were analyzed and compared. In the mode of single laser beam, the fusion zone only consisted of B2 phase because of existence of β-phase stabilizer and rapid cooling rate of LBW. However, O phase was formed in the fusion zone while applying dual-beam laser welding due to decrease of the cooling rate. The microhardness distribution of the welded joint in dual-beam welding mode was consistent with that in single mode, but the hardness of the weld under dual laser beam was higher than that of single laser beam. In room-temperature tensile tests, the fractures all occurred in the weld, but the morphology exhibited a quasi-cleavage feature in single mode while the morphology was dimple fracture in the mode of dual laser beam. The tensile strength and elongation were both increased under dual-beam laser welding compared with those under single-beam laser welding.

  6. Piezoelectric and dielectric properties of Lix(K0.46Na0.54)1-xNb0.86Ta0.1Sb0.04O3 lead-free ceramics

    Institute of Scientific and Technical Information of China (English)

    CHEN Zhi-wu; HU Jian-qiang

    2008-01-01

    Lead-free piezoelectric ceramics Lix(K0.46Na0.54)1-xNb0.86Ta0.1Sb0.04O3 (with x ranging from 0 to 0.1) were synthesized by conventional solid state sintering method.The effect of cationic substitution of Li for K and Na in the A sites of perovskite lattice on the structure,phase transition behavior and electrical properties were investigated.Morphotropic phase boundaries (MPB) between orthorhombic and tetragonal phase are found in the composition range of 0.06≤x≤0.08.Analogous to Pb (Zr,Ti) O3,the dielectric and piezoelectric properties are enhanced for the composition near the morphotropic phase boundary.The Li0.06 (K0.46Na0.54)0.94-Nb0 86Ta0.1Sb0.04O3 ceramics show excellent electrical properties,that is,piezoelectric constant,d33=215 pC/N,planar electromechanical coupling factor kp=41%,dielectric constant εT33/ε0=1303,and dielectric loss tanδ=2.45%.The results indicate that Lix (K0.46Na0.54)1-xNb0.86Ta0.1Sb0.04O3 ceramic is a promising lead-free piezoelectric material.

  7. Laser damage comparisons of broad-bandwidth, high-reflection optical coatings containing TiO2, Nb2O5, or Ta2O5 high-index layers

    Science.gov (United States)

    Field, Ella S.; Bellum, John C.; Kletecka, Damon E.

    2017-01-01

    Broad bandwidth coatings allow angle of incidence flexibility and accommodate spectral shifts due to aging and water absorption. Higher refractive index materials in optical coatings, such as TiO2, Nb2O5, and Ta2O5, can be used to achieve broader bandwidths compared to coatings that contain HfO2 high index layers. We have identified the deposition settings that lead to the highest index, lowest absorption layers of TiO2, Nb2O5, and Ta2O5, via e-beam evaporation using ion-assisted deposition. We paired these high index materials with SiO2 as the low index material to create broad bandwidth high reflection coatings centered at 1054 nm for 45 deg angle of incidence and P polarization. High reflection bandwidths as large as 231 nm were realized. Laser damage tests of these coatings using the ISO 11254 and NIF-MEL protocols are presented, which revealed that the Ta2O5/SiO2 coating exhibits the highest resistance to laser damage, at the expense of lower bandwidth compared to the TiO2/SiO2 and Nb2O5/SiO2 coatings.

  8. 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.

  9. STRUCTURE AND ELECTRICAL PROPERTIES OF CuO-DOPED (K0.5Na0.5)Nb0.9Ta0.1O3 LEAD- FREE PIEZOELECTRIC CERAMICS%STRUCTURE AND ELECTRICAL PROPERTIES OF CuO-DOPED (K0.5Na0.5)Nb0.9Ta0.1O3 LEAD- FREE PIEZOELECTRIC CERAMICS

    Institute of Scientific and Technical Information of China (English)

    LI Ming-ling; ZHAI Ji-wei

    2012-01-01

    CuO-doped (K0.5Na0.5)Nb0.9Ta0.1O3 lead-free piezoelectric ceramics have been prepared by conventional sintering technique and the effects of CuO on the phase structure and piezoelectric properties of the ceramics have been studied. The results show that a small amount of CuO can improve the densification of the ceramics, consequently, the electric properties are improved. Good piezoelectric and dielectric properties of d33=125 pC/N, Kp=0.38,er=700, Qm= 248, and Tc=370℃ were obtained for the K0.5Na0.5 Nb0.9Ta0.1O3 ceramics doped with 0.5mol% CuO sintered at 1000℃ for 2h.

  10. Enhanced 77 K vortex-pinning in Y Ba2Cu3O7−x films with Ba2Y TaO6 and mixed Ba2Y TaO6 + Ba2Y NbO6 nano-columnar inclusions with irreversibility field to 11 T

    Directory of Open Access Journals (Sweden)

    F. Rizzo

    2016-06-01

    Full Text Available Pulsed laser deposited thin Y Ba2Cu3O7−x (YBCO films with pinning additions of 5 at. % Ba2Y TaO6 (BYTO were compared to films with 2.5 at. % Ba2Y TaO6 + 2.5 at. % Ba2Y NbO6 (BYNTO additions. Excellent magnetic flux-pinning at 77 K was obtained with remarkably high irreversibility fields greater than 10 T (YBCO-BYTO and 11 T (YBCO-BYNTO, representing the highest ever achieved values in YBCO films.

  11. Enhanced 77 K vortex-pinning in Y Ba2Cu3O7-x films with Ba2Y TaO6 and mixed Ba2Y TaO6 + Ba2Y NbO6 nano-columnar inclusions with irreversibility field to 11 T

    Science.gov (United States)

    Rizzo, F.; Augieri, A.; Angrisani Armenio, A.; Galluzzi, V.; Mancini, A.; Pinto, V.; Rufoloni, A.; Vannozzi, A.; Bianchetti, M.; Kursumovic, A.; MacManus-Driscoll, J. L.; Meledin, A.; Van Tendeloo, G.; Celentano, G.

    2016-06-01

    Pulsed laser deposited thin Y Ba2Cu3O7-x (YBCO) films with pinning additions of 5 at. % Ba2Y TaO6 (BYTO) were compared to films with 2.5 at. % Ba2Y TaO6 + 2.5 at. % Ba2Y NbO6 (BYNTO) additions. Excellent magnetic flux-pinning at 77 K was obtained with remarkably high irreversibility fields greater than 10 T (YBCO-BYTO) and 11 T (YBCO-BYNTO), representing the highest ever achieved values in YBCO films.

  12. Simultaneous Determination of Nb and Ta in Geochemical Samples by Inductively Coupled Plasma Mass Spectrometry%ICP- MS同时测定地球化学样品中的铌钽

    Institute of Scientific and Technical Information of China (English)

    赵朝辉; 雷勇; 易建春

    2011-01-01

    建立了测定地球化学样品中铌、钽元素的ICP - MS方法.试样加入硝酸、氢氟酸、高氯酸,于电热板上加热消解样品,再以新配置王水提取,使铌、钽完全进入溶液,以内标法校正干扰,电感耦合等离子体质谱仪( ICP -MS)测定样品消解液中铌、钽元素.其中铌采用铑元素作为内标,以93质量数分析;钽采用铼元素作为内标,以181质量数分析.方法的检出限为Nb0.02 μg/g,Ta0.01μg/g精密度优于5%.整个方法检出限低、简单、快速和准确.经过国家一级地球化学标准物质的分析验证,结果与标准值吻合,方法已应用于国土资源调查的试样分析.%An analytical method for the determination of niobium ( Nb) and tantalum (Ta) in geochemical samples by inductively coupled plasma mass spectrometry (ICP-MS) was developed. The samples were digested on electrical hot plate by mixed acid consisted of nitric acid, hydrofluoric acid and perchloric acid. After digestion newly -prepared aqua regia was added to ensure the complete dissolution of Nb and Ta. Internal standards were adopted for the interference correction of ICP-MS analysis,among which Rh93 and Re181 were selected as internal standarc elements of Nb and Ta respectively. The limits of detection for Nb and Ta were 0.02 ug · g-1 and 0.01 ug · -1respectively with the relative standard deviation (RSD) better than 5%. The method was validated by the analysis of primary geochemical reference materials,with all of its results consistent with standard values, which was then applied to analyze land and resource survey samples,and was proved to be simple,sensitive and accurate.

  13. Geology and genesis of the Toongi rare metal (Zr, Hf, Nb, Ta, Y and REE) deposit, NSW, Australia, and implications for rare metal mineralization in peralkaline igneous rocks

    Science.gov (United States)

    Spandler, Carl; Morris, Caitlin

    2016-12-01

    The Toongi Deposit, located in central NSW, Australia, hosts significant resources of Zr, Hf, Nb, Ta, Y and REE within a small (ca. 0.3 km2), rapidly cooled trachyte laccolith. Toongi is part of regional Late Triassic to Jurassic alkaline magmatic field, but is distinguished from the other igneous bodies by its peralkaline composition and economically significant rare metal content that is homogenously distributed throughout the trachyte body. The primary ore minerals are evenly dispersed throughout the rock and include lueshite/natroniobite and complex Na-Fe-Zr-Nb-Y-REE silicate minerals dominated by a eudialyte group mineral (EGM). The EGM occurs in a unique textural setting in the rock, commonly forming spheroidal or irregular-shaped globules, herein called "snowballs", within the rock matrix. The snowballs are often protruded by aegirine and feldspar phenocrysts and contain swarms of fine aegirine and feldspar grains that often form spiral or swirling patterns within the snowball. Secondary ore minerals include REE carbonates, Y milarite, catapleiite and gaidonnayite that fill fractures and vesicles in the rock. Based on bulk-rock geochemical and Nd isotope data, and thermodynamic modelling of magma fractionation, the alkaline rocks of the region are interpreted to represent extrusive to hyperbyssal products of mantle-derived magma that ponded at mid-crustal levels (ca. 0.3 GPa) and underwent extensive fractionation under low-oxygen fugacity conditions. The high Na2O, peralkaline nature of the Toongi Deposit trachyte developed via extensive fractionation of an alkali olivine basalt parental magma initially in the mid-crust and subsequently at shallow levels (ca. 0.1 GPa). This extended fractionation under low fO2 and relatively low H2O-activity conditions limited volatile release and allowed build-up of rare metal contents to ore grades. We speculate that the ore minerals may have originally formed from rare metal-rich sodic-silicate melt that formed immiscible

  14. Assessing the performance and longevity of Nb, Pt, Ta, Ti, Zr, and ZrO₂-sputtered Havar foils for the high-power production of reactive [18F]F by proton irradiation of [18O]H2O.

    Science.gov (United States)

    Gagnon, K; Wilson, J S; Sant, E; Backhouse, C J; McQuarrie, S A

    2011-10-01

    As water-soluble ionic contaminants, which arise following proton irradiation of [18O]H2O have been associated with decreased [18F]FDG yields, the minimization of these contaminants is an asset in improving the [18F]F reactivity. To this end, we have previously demonstrated that the use of Nb-sputtered Havar foils results in decreased radionuclidic and chemical impurities in proton irradiated [18O]H2O, improved [18F]FDG yields, and improved [18F]FDG yield consistency when compared with non-sputtered Havar. Resulting from the highly reactive chemical microenvironment within the target however, this niobium layer is observed to degrade over time. To find a material that displays increased longevity with regards to maintaining high [18F]F reactivity, this project extensively investigated and compared Havar foils sputtered with Nb, Pt, Ta, Ti, Zr and ZrO₂. Of the materials investigated, the results of this study suggest that Ta-sputtered Havar foil is the preferred choice. For similar integrated currents (~1,000,000 μA min), when comparing the Ta-sputtered Havar with Nb-sputtered Havar we observed: (i) greater than an order of magnitude decrease in radionuclidic impurities, (ii) a 6.4 percent increase (p=0.0025) in the average TracerLab MX [18F]FDG yield, and (iii) an overall improvement in the FDG yield consistency. Excellent performance of the Ta-sputtered foil was maintained throughout its ~1,500,000 μA min lifetime.

  15. Abnormal Deformation Behavior of Oxygen-Modified β-Type Ti-29Nb-13Ta-4.6Zr Alloys for Biomedical Applications

    Science.gov (United States)

    Liu, Huihong; Niinomi, Mitsuo; Nakai, Masaaki; Cong, Xin; Cho, Ken; Boehlert, Carl J.; Khademi, Vahid

    2017-01-01

    Oxygen was added to the biomedical β-type Ti-29Nb-13Ta-4.6Zr alloy (TNTZ, mass pct) in order to improve its strength, while keeping its Young's modulus low. Conventionally, with an increase in the oxygen content, an alloy's tensile strength increases, while its tensile elongation-to-failure decreases. However, an abnormal deformation behavior has been reported in the case of oxygen-modified TNTZ alloys in that their strength increases monotonically while their elongation-to-failure initially decreases and then increases with the increase in the oxygen content. In this study, this abnormal tensile deformation behavior of oxygen-modified TNTZ alloys was investigated systematically. A series of TNTZ-(0.1, 0.3, and 0.7 mass pct)O alloy samples was prepared, treated thermomechanically, and finally solution treated; these samples are denoted as 0.1ST, 0.3ST, and 0.7ST, respectively. The main tensile deformation mechanisms in 0.1ST are a deformation-induced α″-martensitic transformation and {332} mechanical twinning. The large elongation-to-failure of 0.1ST is attributable to multiple deformation mechanisms, including the deformation-induced martensitic transformation and mechanical twinning as well as dislocation glide. In both 0.3ST and 0.7ST, dislocation glide is the predominant deformation mode. 0.7ST shows more homogeneous and extensive dislocation glide along with multiple slip systems and a higher frequency of cross slip. As a result, it exhibits a higher work-hardening rate and greater resistance to local stress concentration, both of which contribute to its elongation-to-failure being greater than that of 0.3ST.

  16. Wear transition of solid-solution-strengthened Ti-29Nb-13Ta-4.6Zr alloys by interstitial oxygen for biomedical applications.

    Science.gov (United States)

    Lee, Yoon-Seok; Niinomi, Mitsuo; Nakai, Masaaki; Narita, Kengo; Cho, Ken; Liu, Huihong

    2015-11-01

    In previous studies, it has been concluded that volume losses (V loss) of the Ti-29Nb-13Ta-4.6Zr (TNTZ) discs and balls are larger than those of the respective Ti-6Al-4V extra-low interstitial (Ti64) discs and balls, both in air and Ringer's solution. These results are related to severe subsurface deformation of TNTZ, which is caused by the lower resistance to plastic shearing of TNTZ than that of Ti64. Therefore, it is necessary to further increase the wear resistance of TNTZ to satisfy the requirements as a biomedical implant. From this viewpoint, interstitial oxygen was added to TNTZ to improve the plastic shear resistance via solid-solution strengthening. Thus, the wear behaviors of combinations comprised of a new titanium alloy, TNTZ with high oxygen content of 0.89 mass% (89O) and a conventional titanium alloy, Ti64 were investigated in air and Ringer's solution for biomedical implant applications. The worn surfaces, wear debris, and subsurface damage were analyzed using a scanning electron microscopy and an electron probe microanalysis. V loss of the 89O discs and balls are smaller than those of the respective TNTZ discs and balls in both air and Ringer's solution. It can be concluded that the solid-solution strengthening by oxygen effectively improves the wear resistance for TNTZ materials. However, the 89O disc/ball combination still exhibits higher V loss than the Ti64 disc/ball combination in both air and Ringer's solution. Moreover, V loss of the disc for the 89O disc/Ti64 ball combination significantly decreases in Ringer's solution compared to that in air. This decrease for the 89O disc/Ti64 ball combination in Ringer's solution can be explained by the transition in the wear mechanism from severe delamination wear to abrasive wear.

  17. 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

  18. 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.

  19. Electric properties of textured (K$_{0.44}$Na$_{0.52}$Li$_{0.04}$)(Nb$_{0.86}Ta$_{0.10}$Sb$_{0.04}$)O$_3$ thick film prepared by screen printing method

    Indian Academy of Sciences (India)

    FANG FU; JIWEI ZHAI; ZHENGKUI XU

    2016-08-01

    Textured (K$_{0.44}$Na$_{0.52}$Li$_{0.04}$) (Nb$_{0.86}$Ta$_{0.10}$Sb$_{0.04}$)O$_3$ thick film was fabricated by the screen printing method with plate-like NaNbO3 particles as template. Thick film with 75% grain orientation was prepared. Remnant polarization and coercive field observed from the P–E loops of textured thick film were 3.6 $\\mu$C cm$^{−2}$ and 21 kV cm$^{−1}$, respectively. Textured (K$_{0.44}$Na$_{0.52}$Li$_{0.04}$) (Nb$_{0.86}$Ta$_{0.10}$Sb$_{0.04}$)O$_{3}$ thick film exhibited diffusion behaviour by analysing the temperature dependence of permittivity and loss tangent. The result of leakage current density showed a conduction mechanism of Schottky emission. Piezoelectric (PZT) properties of the thick film were characterized by the relationship of unipolar strain and applied electric field and the PZT constant $d^∗_{33}$ of textured thick film reached to 150 pm V$^{−1}$. Nonlinear PZT property of the thick film was investigated by Rayleigh law.

  20. Extreme high field strength element (HFSE) depletion and near-chondritic Nb/Ta ratios in Central Andean adakite-like lavas (~ 28°S, ~ 68°W)

    Science.gov (United States)

    Goss, A. R.; Kay, S. M.

    2009-03-01

    The eruption of andesites with steep REE patterns and high Sr concentrations (adakite-like) in the northernmost Chilean flatslab region of the Central Andes spatially and temporally corresponds with the appearance of a marked HFSE (high field strength element) depletion in these lavas (La/Ta up to 95). Known as the Dos Hermanos and Pircas Negras andesites, these lavas erupted at the beginning (˜ 8 Ma), during (7-3 Ma), and immediately following (3-2 Ma) a period of tectonic instability characterized by eastward migration of the frontal volcanic arc. ICP-MS analyses of the HFSE reveal a range of chondritic (20-18) to subchondritic (18-11) Nb/Ta ratios in these lavas. Evident temporal trace element trends support a change from a rutile-bearing to an amphibole-bearing eclogitic residual assemblage in equilibrium with the mafic precursor magmas of these andesites. This change in residual mineralogy is contemporaneous with the onset of frontal arc migration in the region. Potential eclogitic sources for the Dos Hermanos and Pircas Negras adakitic andesites include mafic Andean lower crust and an additional flux of forearc crust transported to the sub-arc mantle via subduction erosion during the height of arc migration and Pircas Negras magmatism. Batch melting models of rutile- or amphibole-bearing eclogitic arc basalt in tandem with magma mixing calculations generate the observed adakitic signatures and near-chondritic Nb/Ta ratios of these Central Andean andesites.

  1. 生物医用Ti-Nb-Ta-Zr-Fe合金在林格溶液中的腐蚀行为%Corrosion behavior of Ti-Nb-Ta-Zr-Fe alloy for biomedical applications in Ringer’s solution

    Institute of Scientific and Technical Information of China (English)

    许艳飞; 肖逸锋; 易丹青; 刘会群; 吴靓; 文璟

    2015-01-01

    采用动电位极化方法研究Ti−25Nb−10Ta−1Zr−0.2Fe (质量分数,%)(TNTZF)合金37°C下在林格溶液中的抗腐蚀性能,并在同样的条件下用Ti−6Al−4V ELI(低间隙)合金做对比实验。结果表明:TNTZF比Ti−6Al−4V ELI合金表现出更高的腐蚀电位,更低的腐蚀电流密度,更加稳定的钝化电流密度和更宽的钝化区间,因此具有更加优越的抗腐蚀性能。除此之外,在Ti−6Al−4V ELI合金的表面钝化膜上观察到了点蚀现象,但是在TNTZF合金表面没有发现点蚀现象。XPS 分析结果表明:TNTZF 合金表面钝化膜由 TiO2基体以及 Nb2O5、NbO2、Ta2O5、ZrO2、TiO和Ti2O3等氧化物共同组成,从而使得钝化膜更加稳定且保护作用更强,因此TNTZF合金比Ti−6Al−4V ELI合金表现出更加优越的抗腐蚀性能。%The corrosion resistance of Ti−25Nb−10Ta−1Zr−0.2Fe (mass fraction, %) (TNTZF) alloy in Ringer’s solution at 37 °C was investigated by potentiodynamic polarization measurement. Ti−6Al−4V ELI (Extra low interstitial) alloy was also investigated to make a comparison. The results show that TNTZF alloy has higher corrosion potential, lower corrosion current density, more stable passive current density and wider passive region compared with Ti–6Al–4V ELI alloy, which indicates that TNTZF alloy has better corrosion resistance. In addition, pitting corrosion is observed on the surface passive film of Ti–6Al–4V ELI alloy but is not found on that of TNTZF alloy. The XPS analysis results reveal that the passive film formed on TNTZF alloy is composed of Nb2O5, NbO2, Ta2O5, ZrO2, TiO and Ti2O3oxides in the matrix of TiO2, which makes the passive film more stable and protective than that formed on Ti−6Al−4V ELI alloy and contributes much to its superior corrosion resistance.

  2. 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.

  3. 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.

  4. Influence of the B-site ordering on the magnetic properties of the new La{sub 3}Co{sub 2}MO{sub 9} double perovskites with M = Nb or Ta

    Energy Technology Data Exchange (ETDEWEB)

    Fuertes, V.C.; Blanco, M.C.; Franco, D.G. [INFIQC (CONICET), Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, X5000HUA Cordoba (Argentina); De Paoli, J.M.; Sanchez, R.D. [Centro Atomico Bariloche, CNEA and Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400 Rio Negro (Argentina); Carbonio, R.E., E-mail: carbonio@mail.fcq.unc.edu.ar [INFIQC (CONICET), Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, X5000HUA Cordoba (Argentina)

    2011-01-15

    Double perovskites La{sub 3}Co{sub 2}NbO{sub 9} and La{sub 3}Co{sub 2}TaO{sub 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{sub 1}/n), with different degrees of ordering of B' and B'' cations, with octahedra tilted according to the Glazer notation a{sup -}b{sup -}c{sup +}. 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{sub C} of 62 K for Nb and 72 K for Ta. On the other hand, materials prepared by sol-gel have T{sub 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{sup 2+} ions disorder on the B site of the double perovskite structure. This disorder affects the ratio between the antiferromagnetic Co{sup 2+}-O-Co{sup 2+} and the ferromagnetic Co{sup 2+}-O-M{sup 5+}-O-Co{sup 2+} couplings proposed for the system.

  5. 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.

  6. Relaxor Behaviour and Ferroelectric Properties of (Li0.12Na0.88)(Nb0.9-xTa0.10Sbx)O3 Lead-Free Ceramics

    Institute of Scientific and Technical Information of China (English)

    WANG Ying; LI Yong-Xiang; YI Zhi-Guo; WANG Dong; YIN Qing-Rui

    2006-01-01

    @@ New lead-free ceramics (Li0.12Na0.88)(Nb0.9-x Ta0.10 Sbx) O3 (0.01×0.06) are synthesized by solid-state reaction method. The dielectric, piezoelectric and ferroelectric properties of the ceramics are studied. The dielectric constant dependence with temperature and frequency of the ceramic specimen with x = 0.04 shows typical characteristics of relaxor ferroelectrics, and the Vogel-Fulcher relationship is fulfilled. The dielectric behaviour and its relation to the phase transition phenomena are discussed. The polarization hysteresis loops at room temperature are also measured.

  7. 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.

  8. Preparation and Characterization of Lead-Free (K0.5Na0.5NbO3-LiNbO3 and (K0.5Na0.5NbO3-LiTaO3 Ferroelectric Single Crystals

    Directory of Open Access Journals (Sweden)

    Tao Chu

    2014-07-01

    Full Text Available Lead-free (K0.5Na0.5NbO3-LiNbO3 (KNN-LN and (K0.5Na0.5NbO3-LiTaO3 (KNN-LT ferroelectric single crystals, with the dimensions of 11 ´ 11 ´ 5 mm3 and 5 ´ 5 ´ 3 mm3, were grown successfully using the top-seeded solution growth (TSSG method, respectively. The crystal structures were analyzed by means of X-ray diffraction, showing orthorhombic symmetry for KNN-LN single crystals and coexistence of orthorhombic and tetragonal symmetry for KNN-LT single crystals at room temperature. The orthorhombic-tetragonal (TO-T and tetragonal-cubic (TC phase transition temperatures are 195 °C and 420 °C for the KNN-LN single crystals, and 130 °C and 280 °C for KNN-LT single crystals, respectively. The remnant polarization (Pr is 27.8 μC/cm2 with a coercive field (Ec of 17 kV/cm for KNN-LT single crystals. The two single crystals showed 90° domains with layers in (parallel straight lines, while KNN-LT single crystals have a larger domain region. The actual stoichiometry deviates easily from the original composition in the process of crystal growth, thus, an appropriate nominal composition and optimized crystal growth method is desired to get high-quality crystals in the future.

  9. First Principles Investigation of the Elastic, Optoelectronic and Thermal Properties of XRuSb: (X = V, Nb, Ta) Semi-Heusler Compounds Using the mBJ Exchange Potential

    Science.gov (United States)

    Bencherif, K.; Yakoubi, A.; Della, N.; Miloud Abid, O.; Khachai, H.; Ahmed, R.; Khenata, R.; Bin Omran, S.; Gupta, S. K.; Murtaza, G.

    2016-07-01

    Semi-Heusler materials are intensively investigated due to their potential use in diverse applications, such as in spintronics and green energy applications. In this work, we employ the density functional theory to calculate the structural, electronic, elastic, thermal and optical properties of the VRuSb, NbRuSb and TaRuSb semi-Heusler compounds. The calculated results for the lattice constants, bulk moduli and their corresponding pressure derivative values are in fairly good agreement with previous works. In addition, besides the local density approximation, the modified Becke-Johnson exchange potential is also used to improve the value of the band gaps. The bonding nature reveals a mixture of covalent and ionic bonding character of the VRuSb, NbRuSb and TaRuSb compounds. Furthermore, the elastic constants ( C ij) and the related elastic moduli confirm their stability in the cubic phase and demonstrate their ductile nature. We also analyze the influence of the pressure and temperature on the primitive cell volume, heat capacity, volume expansion coefficient, and Debye temperature of the semi-Heusler compounds. Additionally, we investigate the optical properties, such as the complex dielectric function, refractive index, reflectivity, and the energy loss function.

  10. Shapes of isolated domains and field induced evolution of regular and random 2D domain structures in LiNbO{sub 3} and LiTaO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Chernykh, A. [Ferroelectric Laboratory, Ural State University, 51 Lenin Ave., 620083 Ekaterinburg (Russian Federation); Shur, V. [Ferroelectric Laboratory, Ural State University, 51 Lenin Ave., 620083 Ekaterinburg (Russian Federation)]. E-mail: vladimir.shur@usu.ru; Nikolaeva, E. [Ferroelectric Laboratory, Ural State University, 51 Lenin Ave., 620083 Ekaterinburg (Russian Federation); Shishkin, E. [Ferroelectric Laboratory, Ural State University, 51 Lenin Ave., 620083 Ekaterinburg (Russian Federation); Shur, A. [Ferroelectric Laboratory, Ural State University, 51 Lenin Ave., 620083 Ekaterinburg (Russian Federation); Terabe, K. [Advanced Material Laboratory, National Institute for Materials Science, 305-0044 Tsukuba (Japan); Kurimura, S. [Advanced Material Laboratory, National Institute for Materials Science, 305-0044 Tsukuba (Japan); Kitamura, K. [Advanced Material Laboratory, National Institute for Materials Science, 305-0044 Tsukuba (Japan); Gallo, K. [Optical Research Center, University of Southampton, Highfield, Mountbatten Bldg., SO17 1BJ Southampton (United Kingdom)

    2005-07-15

    The variety of the shapes of isolated domains, revealed in congruent and stoichiometric LiTaO{sub 3} and LiNbO{sub 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{sub 3} by 2D electrode pattern produced by photolithography. The polarization reversal in congruent LiTaO{sub 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.

  11. Investigation on transition behavior and electrical properties of (K0.5Na0.51-xLixNb0.84Ta0.1Sb0.06O3 around polymorphic phase transition region

    Directory of Open Access Journals (Sweden)

    Chen Zhu

    2014-01-01

    Full Text Available (K0.5Na0.51-xLixNb0.84Ta0.1Sb0.06O3 (KNLNTS lead free ceramics with different Li concentration were fabricated by conventional solid-state reaction method. By increasing Li ions in KNLNTS, the grains grow up and the crystal structure changes from orthorhombic to tetragonal. When 0.03 ≤ x ≤ 0.05, the ceramics structure lays in PPT region. Polarization versus electric field (P-E hysteresis loops at room temperature show good ferroelectric properties and the remnant polarization decreases by increasing Li content while coercive electric keeps almost unchanged. In PPT region, taking x = 0.04 as an example, the sample shows excellent dielectric properties: the dielectric constant is 1159 and loss tangent is 0.04, while the piezoelectric constant d33 is 245 pC/N and kp is 0.44 at room temperature, it is promising for (K0.5Na0.51-xLixNb0.84Ta0.1Sb0.06O3 with 4 at. % Li to substitute PZT.

  12. Effect of isovalent substitution on microstructure and phase transition of LaNb{sub 1−x}M{sub x}O{sub 4} (M=Sb, V or Ta; x=0.05–0.3)

    Energy Technology Data Exchange (ETDEWEB)

    Wachowski, S., E-mail: swachowski@mif.pg.gda.pl [Faculty of Applied Physics and Mathematics, Department of Solid State Physics, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk (Poland); Mielewczyk-Gryn, A. [Faculty of Applied Physics and Mathematics, Department of Solid State Physics, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk (Poland); Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California, Davis, CA 95616 (United States); Gazda, M. [Faculty of Applied Physics and Mathematics, Department of Solid State Physics, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk (Poland)

    2014-11-15

    LaNb{sub 1−x}M{sub x}O{sub 4} oxides with pentavalent elements of different ionic sizes (M=Sb, Ta and V, x=0.05–0.3) were synthesized by the solid state reaction method. Special interest was devoted to the antimony substituted lanthanum niobate which is a new material in this group. Rietveld analysis of the X-ray diffraction patterns was used to determine the influence of the material composition on unit cell parameters. On the basis of dilatometric measurements phase transition temperatures and thermal expansion coefficients of the studied materials were determined. It was shown that with increasing concentration of Sb the phase transition temperature decreases. Thermal expansion coefficient of the antimony substituted samples above the transition temperature is in the range from 8.1 to 9.1×10{sup −6} 1/K, whereas below the transition temperature the TEC value is between 14 and 17.3×10{sup −6} 1/K. Influence of Ta, V and Sb substitutions on the microstructure and grain size was studied. - Graphical abstract: Substitution of niobium by other pentavalent elements in LaNbO{sub 4} leads to change in phase transition temperature. In case of Sb substituent a shift of phase transition into the lower temperature region is observed. LaNb{sub 0.7}Sb{sub 0.3}O{sub 4} substitution allows to achieve material with tetragonal crystal structure at room temperature and no phase transition up to 1000 °C. - Highlights: • Antimony doped lanthanum niobate was successfully synthesized by solid state synthesis method. • The structural properties have been investigated by XRD and SEM. • The influence of doping on phase transition temperature has been studied.

  13. 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

    2015-09-01

    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

  14. 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

  15. MORB mantle hosts the missing Eu (Sr, Nb, Ta and Ti) in the continental crust: New perspectives on crustal growth, crust-mantle differentiation and chemical structure of oceanic upper mantle

    Science.gov (United States)

    Niu, Yaoling; O'Hara, Michael J.

    2009-09-01

    We have examined the high quality data of 306 mid-ocean ridge basalt (MORB) glass samples from the East Pacific Rise (EPR), near-EPR seamounts, Pacific Antarctic Ridge (PAR), near-PAR seamounts, Mid-Atlantic Ridge (MAR), and near-MAR seamounts. The data show a correlated variation between Eu/Eu* and Sr/Sr*, and both decrease with decreasing MgO, pointing to the effect of plagioclase crystallization. The observation that samples with MgO > 9.5 wt.% (before plagioclase on the liquidus) show Eu/Eu* > 1 and Sr/Sr* > 1 and that none of the major phases (i.e., olivine, orthopyroxene, clinopyroxene, spinel and garnet) in the sub-ridge mantle melting region can effectively fractionate Eu and Sr from otherwise similarly incompatible elements indicates that the depleted MORB mantle (DMM) possesses excess Sr and Eu, i.e., [Sr/Sr*]DMM > 1 and [Eu/Eu*]DMM > 1. Furthermore, the well-established observation that DNb ≈ DTh, DTa ≈ DU and DTi ≈ DSm during MORB mantle melting, yet primitive MORB melts all have [Nb/Th]PMMORB > 1, [Ta/U]PMMORB > 1 and [Ti/Sm]PMMORB > 1 (where PM indicates primitive mantle normalized), also points to the presence of excess Nb, Ta and Ti in the DMM, i.e., [Nb/Th]PMDMM > 1, [Ta/U]PMDMM > 1 and [Ti/Sm]PMDMM > 1. The excesses of Eu, Sr, Nb, Ta and Ti in the DMM complement the well-known deficiencies of these elements in the bulk continental crust (BCC). These new observations, which support the notion that the DMM and BCC are complementary in terms of the overall abundances of incompatible elements, offer new insights into the crust-mantle differentiation. These observations are best explained by partial melting of amphibolite of MORB protolith during continental collision, which produces andesitic melts with a remarkable compositional (major and trace element abundances as well as key elemental ratios) similarity to the BCC, as revealed by andesites in southern Tibet produced during the India-Asia continental collision. An average amphibolite of MORB

  16. A SUPERSPACE APPROACH TO THE MODULATED STRUCTURES OF MA(X)TE(2) (M=NB,TA A=SI,GE 1/3-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-1/2), EXEMPLIFIED BY NBGE3/7TE2

    NARCIS (Netherlands)

    VANDERLEE, A; EVAIN, M; MONCONDUIT, L; BREC, R; VANSMAALEN, S

    1994-01-01

    MA(x)Te(2) (M = Ta, Nb and A = Si, Ge) compounds show a great variety of commensurately and incommensurately modulated structures depending on the value for x. It is shown that the theory of superspace groups can be used to standardize the structures and to predict the 3D symmetry of the commensurat

  17. 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

  18. K_4CuNb_8O_(23)掺杂对K_(0.44)Na_(0.52)Li_(0.04)Nb_(0.86)Ta_(0.10)Sb_(0.04)O_3压电陶瓷性能的影响%Effect of K_4CuNb_8O_(23) Doped on the Properties of K_(0.44)Na_(0.52)Li_(0.04)Nb_(0.86)Ta_(0.10)Sb_(0.04)O_3 Piezoelectric Ceramics

    Institute of Scientific and Technical Information of China (English)

    陈燕; 江向平; 涂娜; 冯子义; 陈超; 李月明

    2009-01-01

    采用固相反应法制备了K_(0.44)Na_(0.52)Li_(0.04)Nb_(0.86)Ta_(0.10)Sb_(0.04)O_3+x mol %K_4CuNb_8O_(23)(0≤x≤2)(简称LF4-KCN)无铅压电陶瓷,使用XRD、SEM、 Agilent 4294A精密阻抗分析仪等对该体系的相组成、显微结构、压电及介电等性能进行表征.XRD分析表明,随着KCN含量的增加,室温时样品由四方相向正交相转变,且当x≥1时,出现K_6Li_4Nb_(10)O_(30)杂相.SEM分析表明,掺入KCN后,样品晶粒尺寸减小,晶粒轮廓清晰.随着KCN含量的增加,在100 ℃附近的介电常数温度曲线上出现第二介电常数极大值,即正交→四方铁电相变温度T_(O-T),同时居里温度TC向低温方向移动.KCN掺杂量对LF4的电性能有很大影响,表现为"硬性"掺杂,其压电常数d_(33),平面机电耦合系数k_p,1kHz频率下的介电损耗tanδ和介电常数ε_r均随着 KCN含量的增加而降低,而机械品质因素Q_m整体提高,样品的密度也显著增大.%The K_(0.44)Na_(0.52)Li_(0.04)Nb_(0.86)Ta_(0.10)Sb_(0.04)O_3+x mol%K_4CuNb_8O_(23)(0≤x≤2)(abbreviated as LF4-KCN) lead-free piezoelectric ceramics were fabricated by solid state reaction. The phase, microstructure, electric properties of the samples were characterized by XRD, SEM and Agilent 4294A impedance analyzer. XRD result shows that the phase of the sample transforms from tetragonal into orthorhombic with the increasing of KCN content. When x≥1, the trace amount of second phase K_6Li_4Nb_(10)O_(30) can be detected. SEM shows that the grain size of those materials decreases as the KCN content increasing, and the figure of the grain becomes clearly. There is another dielectric constant maximum value around 100 ℃, which is the phase transition from orthorhombic to tetragonal (T_(O-T)), while the curie temperature (TC) shifts to higher temperature. The KCN-doping has great influence on the electrical properties, the ceramic becomes "hardened", the piezoelectric constant (d_(33)), electromechanical planar

  19. Structural and microstructural characterization of SrBi{sub 2}(Ta{sub 0.5}Nb{sub 0.48}W{sub 0.02}){sub 2}O{sub 9} powders

    Energy Technology Data Exchange (ETDEWEB)

    Junior, N.L. Amsei [Instituto de Quimica, UNESP-Universiade Estadual Paulista, C.P. 355, 14801-970 Araraquara, SP (Brazil); Simoes, A.Z. [Instituto de Quimica, UNESP-Universiade Estadual Paulista, C.P. 355, 14801-970 Araraquara, SP (Brazil)], E-mail: alezipo@yahoo.com; Cavalheiro, A.A. [Instituto de Biociencia, UNESP-Universidade Estadual Paulista, Distrito de Rubiao Junior, s/n, 18618-000 Botucatu, SP (Brazil); Zanetti, S.M. [Instituto Nacional de Pesquisas Espaciais, INPE-Pc Marechal Eduardo Gomes, 50, Vila das Acacias, 12228-900 Sao Jose dos Campos, SP (Brazil); Longo, E.; Varela, J.A. [Instituto de Quimica, UNESP-Universiade Estadual Paulista, C.P. 355, 14801-970 Araraquara, SP (Brazil)

    2008-04-24

    SrBi{sub 2}(Ta{sub 0.5}Nb{sub 0.48}W{sub 0.02}){sub 2}O{sub 9} powders (SBTN-W) were prepared by the polymeric precursor method. The influence of annealing temperature on the phase formation and specific surface area was evaluated. TG/DTA associated with X-ray diffraction (XRD) analyses showed the formation of perovskite phase at around 500-600 deg. C. An orthorhombic structure with A21am space group was identified by Rietveld refinement. BET analysis revealed that the specific surface area reduces with increasing thermal annealing. SEM micrographies showed grains in an almost-spherical morphology with the presence of agglomerates.

  20. Synthesis, magnetic properties and Moessbauer spectroscopy for the pyrochlore family Bi{sub 2}BB Prime O{sub 7} with B=Cr and Fe and B Prime =Nb, Ta and Sb

    Energy Technology Data Exchange (ETDEWEB)

    Blanco, Maria C. [INFIQC (CONICET), Dpto. de Fisicoquimica, Fac. de Ciencias Quimicas, U.N.C., Cordoba (X5000HUA) (Argentina); Franco, Diego G. [INFIQC (CONICET), Dpto. de Fisicoquimica, Fac. de Ciencias Quimicas, U.N.C., Cordoba (X5000HUA) (Argentina); Centro Atomico Bariloche - CNEA, Av. E. Bustillo 9500, S.C. de Bariloche (8500), R.N. (Argentina); Jalit, Yamile; Pannunzio Miner, Elisa V. [INFIQC (CONICET), Dpto. de Fisicoquimica, Fac. de Ciencias Quimicas, U.N.C., Cordoba (X5000HUA) (Argentina); Berndt, Graciele; Paesano, Andrea [Departamento de Fisica, Universidade Estadual de Maringa, Parana (Brazil); Nieva, Gladys [Centro Atomico Bariloche - CNEA, Av. E. Bustillo 9500, S.C. de Bariloche (8500), R.N. (Argentina); Carbonio, Raul E., E-mail: carbonio@mail.fcq.unc.edu.ar [INFIQC (CONICET), Dpto. de Fisicoquimica, Fac. de Ciencias Quimicas, U.N.C., Cordoba (X5000HUA) (Argentina)

    2012-08-15

    The samples Bi{sub 2}BB Prime O{sub 7}, with B=Cr and Fe and B Prime =Nb, Ta and Sb were prepared by solid state method. The crystallographic structure was investigated on the basis of X-ray powder diffraction data. Rietveld refinements show that the crystal structure is cubic, space group Fd-3m. The Bi{sup 3+} cation on the eight-coordinate pyrochlore A-site shows displacive disorder, as a consequence of its lone pair electron configuration. There is also a considerable A-site disorder shown by Rietveld Analysis and confirmed in the case of the iron containing samples with Moessbauer spectroscopy. The magnetic measurements show paramagnetic behavior at all temperatures for the Cr oxides. The Fe pyrochlores show antiferromagnetic order around 10 K.

  1. Shape-controlled crystal growth of Sr3NbGa3Si2O14 and Sr3TaGa3Si2O14 piezoelectric crystals by the micro-pulling-down method.

    Science.gov (United States)

    Yokota, Yuui; Sato, Masato; Futami, Yoshisuke; Tota, Kazushige; Onodera, Ko; Yanagida, Takayuki; Yoshikawa, Akira

    2012-09-01

    We grew column-shaped Sr(3)NbGa(3)Si(2)O(14) (SNGS) and Sr(3)TaGa(3)Si(2)O(14) (STGS) langasite-type piezoelectric single crystals by the micro-pulling-down (μ-PD) method. 3-mm-diameter SNGS and STGS crystals were grown using a Pt-Rh crucible with a 3-mm-diameter columnar die. According to X-ray rocking curve measurements, the grown crystals had crystallinity equivalent to that of crystals grown by the Czochralski (Cz) method. The crystals were single-phase materials with langasite-type crystal structure. The lattice parameters of the grown crystals were almost consistent with those of crystals grown by the Cz method.

  2. Superconductivity of Ta{sub 34}Nb{sub 33}Hf{sub 8}Zr{sub 14}Ti{sub 11} high entropy alloy from first principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Jasiewicz, K.; Wiendlocha, B.; Korben, P.; Kaprzyk, S.; Tobola, J. [AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Al. Mickiewicza 30, 30-059, Krakow (Poland)

    2016-05-15

    The Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA) is applied to study the first superconducting high entropy alloy (HEA) Ta{sub 34}Nb{sub 33}Hf{sub 8}Zr{sub 14}Ti{sub 11} (discovered in 2014 with T{sub c}=7.3 K), focusing on estimations of the electron-phonon coupling constant λ. The electronic part of λ has been calculated using the rigid muffin-tin approximation (RMTA), while the phonon part has been approximated using average atomic mass and experimental Debye temperature. The estimated λ=1.16 is close to the value determined from specific heat measurements, λ=0.98, and suggests rather strong electron-phonon coupling in this material. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Structure, bonding and stability of semi-carbides M{sub 2}C and sub-carbides M{sub 4}C (M=V, Cr, Nb, Mo, Ta, W): A first principles investigation

    Energy Technology Data Exchange (ETDEWEB)

    Abderrahim, F.Z., E-mail: sara_ais@yahoo.fr [Unite de Recherche Materiaux et Energie Renouvelables, URMER, Universite de Tlemcen (Algeria); Faraoun, H.I. [Unite de Recherche Materiaux et Energie Renouvelables, URMER, Universite de Tlemcen (Algeria); Ouahrani, T. [Laboratoire de Physique Theorique, Universite de Tlemcen B.P. 230, 13000 Tlemcen (Algeria); Ecole Preparatoire en Sciences et Techniques, B.P. 230, 13000 Tlemcen (Algeria)

    2012-09-15

    Density functional theory within the generalized gradient approximation (GGA) is used to investigate the electronic structure and formation energies of semi-carbides M{sub 2}C and sub-carbides M{sub 4}C (where M=V, Cr, Nb, Mo, Ta and W). Our results show that M{sub 2}C carbides are more stable than M{sub 4}C. Total and partial densities of states were obtained and analyzed systematically for these phases. Moreover, the bonding nature of M{sub 2}C polymorphs is studied from the point of view of the Quantum Theory of Atoms in Molecules (QTAIM). It is found that inter-atomic interactions in these carbides are of mixed type including ionic, covalent and metallic components.

  4. Dielectric, ferroelectrics properties and impedance spectroscopy analysis of the [(Na0.535K0.480)0.966Li0.058](Nb0.90Ta0.10)O3-based lead-free ceramics

    Science.gov (United States)

    Saidi, M.; Chaouchi, A.; D'Astorg, S.; Rguiti, M.; Courtois, C.

    2015-04-01

    Polycrystalline of [(Na0.535K0.480)0.966Li0.058](Nb0.90Ta0.10)O3 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.

  5. Spectroscopic features of erbium-doped CaM{sub 2}O{sub 6} (M=Nb, Ta) single crystal fibers grown by the laser-heated pedestal growth technique

    Energy Technology Data Exchange (ETDEWEB)

    Camargo, A.S.S. de [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo (USP), C.P. 369, CEP 13560-970, Sao Carlos, SP (Brazil)], E-mail: andreasc@if.sc.usp.br; Ferrari, C.R.; Silva, R.A.; Nunes, L.A.O.; Hernandes, A.C.; Andreeta, J.P. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo (USP), C.P. 369, CEP 13560-970, Sao Carlos, SP (Brazil)

    2008-02-15

    Erbium-doped single crystal fibers, with low phonon energy and fairly high absorption and emission cross sections are interesting laser active media, for compact, near-infrared and/or upconversion lasers. In this work, high optical quality Er{sup 3+}-doped CaNb{sub 2}O{sub 6} and CaTa{sub 2}O{sub 6} single crystal fibers were successfully grown by the versatile laser-heated pedestal growth technique, and characterized from the structural and spectroscopic points of view. The results indicate that these crystal fiber compositions, which had not been explored so far, offer potential applications, not only as laser active media, but also in other optical devices.

  6. Theoretical study of interface structure and energetics in semicoherent Fe(001)/MX(001) systems ( M=Sc , Ti, V, Cr, Zr, Nb, Hf, Ta; X=C or N)

    Science.gov (United States)

    Fors, Dan H. R.; Wahnström, Göran

    2010-11-01

    We perform a systematic ab initio study of the electronic and atomic structure of semicoherent interfaces between bcc Fe and NaCl MX ( M=Sc , Ti, V, Cr, Zr, Nb, Hf, Ta; X=C or N). The interface energetics is accessed by using a Peierls-Nabarro framework, in which ab initio data for the chemical interactions across the interface are combined with a continuum description to account for the elastic distortions. The key factors to the trends in the interface energy are identified and discussed with respect to the size of the misfit and the electronic structure of the MX phase. Our approach shows that the inclusion of lattice misfit can have a significant contribution to the interface energy (up to 1.5J/m2 ) and must therefore be thoroughly accounted for in the interface description. The results will have important bearings on our ability to understand and describe precipitate stability in steels.

  7. 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.

  8. 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.

  9. 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.

  10. Improved Piezoelectricity in (K0.44Na0.52Li0.04) (Nb0.91Ta0.05Sb0.04)O3- xBi0.25Na0.25NbO3 Lead-Free Piezoelectric Ceramics

    Science.gov (United States)

    Zhao, Yan; Xu, Zhijun; Li, Huaiyong; Hao, Jigong; Du, Juan; Chu, Ruiqing; Wei, Dongdong; Li, Guorong

    2017-01-01

    (1 - x)[(K0.44Na0.52Li0.04)(Nb0.91Ta0.05Sb0.04)O3]- xBi0.25Na0.25NbO3 (KNLNTS- xBNN) lead-free piezoelectric ceramics have been prepared using a conventional solid-state reaction method and the effects of BNN on their phase structure, microstructure, and electrical properties systematically studied. X-ray diffraction analysis suggested that BNN substitution into KNLNTS induced coexistence of orthorhombic-tetragonal mixed phase and thus improved the ferroelectric and piezoelectric properties. The surface morphologies indicated that different amounts of BNN had two different effects on grain growth. Good electrical properties ( d 33 = 256 pC N-1, T c = 354.27°C, k p = 43.43%, P r = 26.85 μC cm-2, E c = 24.47 kV cm-1) were simultaneously obtained at x = 0.0025, suggesting that our research could benefit development of (K,Na)NbO3-based ceramics and widen their application range.

  11. Electrically tunable microwave properties in NiFeTa/[Pb(Mg1/3Nb2/3)O3]0.68-[PbTiO3]0.32(011) magnetoelectric heterostructures

    Science.gov (United States)

    Phuoc, Nguyen N.; Ong, C. K.

    2015-02-01

    The studied magnetoelectric heterostructure consisting of a NiFeTa thin film grown onto a [Pb(Mg1/3Nb2/3)O3]0.68-[PbTiO3]0.32(011) (PMN-PT) substrate was prepared by using gradient-composition sputtering technique. A shorted micro-strip transmission-line perturbation method using a vector network analyzer was employed to study the electrical field modulation of microwave properties of the NiFeTa/PMN-PT heterostructure. It was found that the resonance frequency of the sample can be tuned from 1.72 GHz to 2.05 GHz when the applied electrical field is varied from -6 kV/cm to 6 kV/cm. Moreover, we experimentally observed a quasi-linear relationship between the resonance frequency and the electrical field in a wide range of electrical field from 0 kV/cm to 6 kV/cm in the heterostructure, which is suggested to be useful for applications. All the results are discussed taking into account the reverse magnetostrictive effect and the reverse piezoelectric effect.

  12. ICP-AES 法同时测定钛合金中钽、铌、钨元素含量%Research on Determination of Ta, Nb, W in Titanium Alloy by ICP-AES

    Institute of Scientific and Technical Information of China (English)

    刘婷; 黄永红; 白焕焕

    2013-01-01

    The method of determination Ta , Nb, W elements in titanium alloy by ICP-AES was introduced .The best apparatus working parameters were selected firstly , exciting power was 1 300 W, atomizer flow was 0.7 L· min -1 and the times for integral was twice .The optimum analytical lines of Ta , Nb, W were found out by the analysis , and they were 240.063, 269.706, 207.912 nm, respectively.Besides, The internal correction method was used to check the testing results of the samples which the content of Nb exceed 3%.The recovery and precision tests were also per-formed, the determination recovery could reach 99%~102% and relative standard deviation ( RSD) was less than 2.3%, so this method could meet the requirements of daily testing .%介绍了采用ICP-AES法同时测定钛合金中Ta、 Nb、 W元素含量的方法。首先确定了仪器部分工作参数的最佳值,其中激发功率1300 W、雾化器流量0.7 L· min-1、积分次数2次。然后通过对基体、合金元素以及测定元素光谱间的干扰分析研究,确定了Ta、 Nb、 W元素最佳分析谱线的位置,依次为240.063、269.706、207.912 nm。此外,采用内标法对Nb质量分数大于3%的样品的测试结果进行了校正。试样加标回收试验及精密度试验表明采用上述方法可使回收率在99%~102%之间,相对标准偏差小于2.3%,能够满足日常生产的检测要求。

  13. 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 9–12% Cr creep-resistant steels Cr(V,Nb,Ta)N Z-phase is known to replace metastable (V,Nb,Ta)N MN precipitates at high temperatures. The precipitation process of Z-phase does not follow the classical nucleation theory, where dissolving MN particles provide constituents for Z-phase nucleation...

  14. Synthesis of Nanosized Ag0.9 Na0.1 (Nb0. 6 Ta0.4)O3 Ceramic Powder and Investigation on its Property%Ag0.9 Na0.1(Nb0.6 Ta0.4)O3纳米粉体的制备及介电性能研究

    Institute of Scientific and Technical Information of China (English)

    严玉清; 温玉刚; 孙春峰

    2014-01-01

    In this paper,Ag0.9 Na0.1 (Nb0.6 Ta0.4 )O3 (ANNT)mixed oxide nanosized powder was synthesized by citric acid gel method. XRD、TEM、electron diffraction and SEM analysis were used.The result showed that the reaction temperature was 800℃,the calcining time was three hours,and the product was pure ANNT in well-dispersed grain structure (40nm in average).The product was calcined to be dense ceramic between 1040℃ to 1060℃ and dielectric capability was better than that of solid method,such as the bigger dielectric constant and the smaller dielectric loss.%采用柠檬酸凝胶法合成(Ag0.9 Na0.1)(Nb0.6 Ta0.4)O3复合氧化物纳米粉体,应用x射线衍射(XRD)、透射电镜(TEM)和电子衍射方法对该纳米瓷粉进行了表征,并对该瓷粉烧结的陶瓷进行了SEM分析和介电性能研究;研究结果表明:该系列纳米瓷粉的合成温度为800℃,灼烧时间为3小时,瓷粉平均粒径大约为40nm,无严重的团聚现象;系统在1040℃~1060℃的范围内可烧结成致密的陶瓷,介电性能方面较固相法制备产品有明显改善,其具体表现在介电常数增大,介电损耗减小。

  15. Raman scattering and far infrared reflectivity of Ba{sub 5}Ta{sub 4}O{sub 15} and Ba{sub 5}Nb{sub 4}O{sub 15{minus}x} (0.0{le}x{le}0.56)

    Energy Technology Data Exchange (ETDEWEB)

    Massa, N.E. [Univ. Nacional de La Plata (Argentina); Pagola, S.; Carbonio, R.E. [Univ. Nacional de Cordoba (Argentina). Dept. de Fisicoquimica; Alonso, J.A.; Rasines, I. [Consejo Superior de Investigaciones Cientificas, Madrid (Spain). Inst. de Ciencia de Materiales; Polla, G.; Leyva, G. [Division Fisica del Solido, Buenos Aires (Argentina)

    1996-12-31

    Quite often the literature cites superconductors with high critical temperature as having an anharmonic lattice close to a structural phase transition. It is of interest then to find materials, with distorted perovskite structure, that reveal bare phonon behavior expected for such environment. Here the authors discuss layered Ba{sub 5}Nb{sub 4}O{sub 15} and Ba{sub 5}Ta{sub 4}O{sub 15{minus}x} (0.0{le}x{le}0.56) that have four Nb/Ta ions per formula unit. This implies that there is an empty octahedra that in the lattice avoids direct face sharing of the (Nb/Ta)O{sub 6} sublattice. As consequence, one expect strong anharmonicities that translate into several subtle anomalous shapes and wide phonon band profiles in the low temperature Raman and infrared spectra. They will see that while a centrosymmetric D{sub 3d}{sup 3}-P3m1 space group is deduced for both compounds from neutron diffraction measurements, narrow splits of a symmetric stretching Raman mode hint small local departures of that symmetry in Ba{sub 5}Nb{sub 4}O{sub 15}. Weaker structure on the band lower frequency side suggest that in their understanding one has to consider arguments that indicate that the anharmonic contributions to the lattice potential energy are so large that they cannot treated only by perturbation theory, i.e., there is a lifting of the degeneracy of phonon transitions in the harmonic approximation. Defect induced modes, that are Raman active in Ba{sub 5}Nb{sub 4}O{sub 15}, are understood as local modes due to unrelaxed portions of the lattice that may be related to changes the phonon damping in infrared reflectivity spectra. It is also noteworthy to point that the replacement Nb by Ta induces a hardening of most phonons. This is reflected in an increase of frequencies in spite of a heavier Ta ion.

  16. Piezoelectric properties and diffusion phase transition around PPT of La-doped (Na0.52K0.44Li0.04) Nb0.8Ta0.2O3 lead-free piezoelectric ceramics

    Science.gov (United States)

    Yang, Wenlong; Wang, Li; Li, Haidong; Han, Junsheng; Xiu, Hanjiang; Zhou, Zhongxiang

    2016-10-01

    Lead-free ceramics (Na0.52K0.44Li0.04)1-3xLaxNb0.8Ta0.2O3 (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 La3+ 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 d33=215pC/N, kp=42.8%and Qm=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 La3+-doped KNLTN.

  17. Structures and solid solution mechanisms of pyrochlore phases in the systems Bi{sub 2}O{sub 3}-ZnO-(Nb, Ta){sub 2}O{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Tan, K.B., E-mail: tankb@science.upm.edu.m [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Khaw, C.C. [Department of Engineering, Universiti Tunku Abdul Rahman, 53300 Setapak, Kuala Lumpur (Malaysia); Lee, C.K. [Academic Science Malaysia, 902-4 Jalan Tun Ismail, 50480 Kuala Lumpur (Malaysia); Zainal, Z. [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Miles, G.C. [Department of Engineering Materials, The University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom)

    2010-10-22

    Research highlights: {yields} Combined XRD and ND Rietveld structural refinement of pyrochlores. {yields} Structures and solid solution mechanisms of Bi-pyrochlores. {yields} Bi and Zn displaced off-centre to different 96g A-site positions. {yields} 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{sub 1.5} ZnTa{sub 1.5}O{sub 7} and non-stoichiometric Bi{sub 1.56}Zn{sub 0.92}Nb{sub 1.44}O{sub 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.

  18. Bending springback behavior related to deformation-induced phase transformations in Ti-12Cr and Ti-29Nb-13Ta-4.6Zr alloys for spinal fixation applications.

    Science.gov (United States)

    Liu, Huihong; Niinomi, Mitsuo; Nakai, Masaaki; Hieda, Junko; Cho, Ken

    2014-06-01

    The springback behavior of Ti-12Cr and Ti-29Nb-13Ta-4.6Zr (TNTZ) during deformation by bending was investigated; and the microstructures of the non-deformed and deformed parts of both alloys were systematically examined to clarify the relationship between microstructure and springback behavior. For the deformed Ti-12Cr alloy, deformation-induced ω-phase transformation occurs in both the areas of compression and tension within the deformed part, which increases the Young׳s modulus. With the deformed TNTZ alloy, deformation-induced ω-phase transformation is observed in the area of compression within the deformed part; while a deformation-induced α″ martensite transformation occurs in the area under tension, which is likely to be associated with the pseudoelasticity of TNTZ. Among these two alloys, Ti-12Cr exhibits a smaller springback and a much greater bending strength when compared with TNTZ; making Ti-12Cr the more advantageous for spinal fixation applications.

  19. Effect of sintering temperature on the piezoelectric and ferroelectric characteristics of CuO doped 0.95(Na{sub 0.5}K{sub 0.5})NbO{sub 3}-0.05LiTaO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Yang, M.-R. [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Hong, C.-S. [Department of Electronic Engineering, National Kaohsiung Normal University, Kaohsiung 811, Taiwan (China); Tsai, C.-C. [Department of Electronics Engineering and Computer Science, Tung-Fang Institute of Technology, Kaohsiung 829, Taiwan (China); Chu, S.-Y., E-mail: chusy@mail.ncku.edu.t [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China)

    2009-11-20

    In this paper, lead-free (Na{sub 0.5}K{sub 0.5})NbO{sub 3} ceramics doped with 5 mol% LiTaO{sub 3} and 2 mol% CuO were prepared using the conventional mixed-oxide method. The samples were characterized by X-ray diffraction analysis, scanning electron microscopy, and atomic force microscopy measurements. The effect of sintering temperature on the bulk density, piezoelectric and ferroelectric properties was investigated. The results show that an increase of CuO very effectively lowers the sintering temperature and improves the electric properties of (Na{sub 0.5}K{sub 0.5})NbO{sub 3}-LiTaO{sub 3} ceramics. High piezoelectric properties of k{sub p} = 37.8%, k{sub t} = 50.7%, and k{sub 33} = 58.9% and ferroelectric properties E{sub c} = 34.6 kV/cm and P{sub r} = 22.6 were obtained for the specimen containing 2 mol% CuO sintered at a suitable temperature. Cu{sup 2+} ions acted as a hardener, which increased the E{sub c}, P{sub r}, and Q{sub m} values of (Na{sub 0.5}K{sub 0.5})NbO{sub 3}-LiTaO{sub 3} ceramics.

  20. Invalidation manner and mechanism of new type NbO electrolytic capacitor anode

    Institute of Scientific and Technical Information of China (English)

    LI Jian; YI Dan-qing; WEN Jun-jie; LIU Hui-qun; ZHONG Hui

    2005-01-01

    Niobium suboxide powder was pressed and sintered in vacuum into NbO electrolytic capacitor sintered anode..High voltage and constant current formation experiment was performed on NbO electrolytic capacitor anode,during which electrolyte was 0.01 % Ha PO4 solution, temperature was 90 C and current was 50 mA per gram sample. Through the relationship between anode voltage and time and scanning electron microscopy(SEM) images of invalidated anode and normal forming anode, invalidation manner and mechanism of NbO electrolytic capacitor anode were discussed. The results show that, the main invalidation manner of NbO electrolytic capacitor anode is not short circuit but open circuit, which is different to that of traditional Ta electrolytic capacitor anode. The reason of invalidation is that anode oxide film whose thickness increases gradually penetrates the "connection neck" among anode powder particles, which leads to the open circuit invalidation of anode. Compared with Ta electrolytic capacitor,NbO electrolytic capacitor has better security.

  1. Assessing the performance and longevity of Nb, Pt, Ta, Ti, Zr, and ZrO{sub 2}-sputtered Havar foils for the high-power production of reactive [{sup 18}F]F{sup -} by proton irradiation of [{sup 18}O]H{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Gagnon, K., E-mail: kgagnon1@ualberta.ca [Department of Physics, University of Alberta, Edmonton, AB, T6G 2G7 (Canada); Edmonton PET Centre, Cross Cancer Institute, Edmonton, AB, T6G 1Z2 (Canada); Wilson, J.S. [Edmonton PET Centre, Cross Cancer Institute, Edmonton, AB, T6G 1Z2 (Canada); Department of Oncology, University of Alberta, Edmonton, AB, Canada T6G 1Z2 (Canada); Sant, E.; Backhouse, C.J. [Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB, T6G 2V4 (Canada); McQuarrie, S.A. [Edmonton PET Centre, Cross Cancer Institute, Edmonton, AB, T6G 1Z2 (Canada); Department of Oncology, University of Alberta, Edmonton, AB, T6G 1Z2 (Canada)

    2011-10-15

    As water-soluble ionic contaminants, which arise following proton irradiation of [{sup 18}O]H{sub 2}O have been associated with decreased [{sup 18}F]FDG yields, the minimization of these contaminants is an asset in improving the [{sup 18}F]F{sup -} reactivity. To this end, we have previously demonstrated that the use of Nb-sputtered Havar foils results in decreased radionuclidic and chemical impurities in proton irradiated [{sup 18}O]H{sub 2}O, improved [{sup 18}F]FDG yields, and improved [{sup 18}F]FDG yield consistency when compared with non-sputtered Havar. Resulting from the highly reactive chemical microenvironment within the target however, this niobium layer is observed to degrade over time. To find a material that displays increased longevity with regards to maintaining high [{sup 18}F]F{sup -} reactivity, this project extensively investigated and compared Havar foils sputtered with Nb, Pt, Ta, Ti, Zr and ZrO{sub 2}. Of the materials investigated, the results of this study suggest that Ta-sputtered Havar foil is the preferred choice. For similar integrated currents ({approx}1,000,000 {mu}A min), when comparing the Ta-sputtered Havar with Nb-sputtered Havar we observed: (i) greater than an order of magnitude decrease in radionuclidic impurities, (ii) a 6.4 percent increase (p=0.0025) in the average TracerLab MX [{sup 18}F]FDG yield, and (iii) an overall improvement in the FDG yield consistency. Excellent performance of the Ta-sputtered foil was maintained throughout its {approx}1,500,000 {mu}A min lifetime.

  2. Structural state of relaxor ferroelectrics PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3 at high pressures up to 30 GPa

    Science.gov (United States)

    Maier, B. J.; Waeselmann, N.; Mihailova, B.; Angel, R. J.; Ederer, C.; Paulmann, C.; Gospodinov, M.; Friedrich, A.; Bismayer, U.

    2011-11-01

    The pressure-induced structural changes in perovskite-type (ABO3) Pb-based relaxor ferroelectrics are studied on the basis of in situ single-crystal synchrotron x-ray diffraction and Raman scattering experiments on PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3 conducted under hydrostatic conditions up to 30 GPa. Complementary density functional theory calculations have been performed to compare the stability of various atomic configurations for both compounds at high pressures. By combining the experimental and theoretical results, the following sequence of structural transformations is proposed. At a characteristic pressure p1 the mesoscopic polar order is violated and a local antipolar order of Pb atoms as well as quasidynamical long-range order of antiphase octahedral tilts is developed. These structural changes facilitate the occurrence of a continuous phase transition at pc1>p1 from cubic to a nonpolar rhombohedral structure comprising antiphase octahedral tilts of equal magnitude (a-a-a-). At a characteristic pressure p2>pc1 the octahedral tilts around the cubic [100], [010], and [001] directions become different from each other on the mesoscopic scale. The latter precedes a second phase transition at pc2, which involves long-range order of Pb antipolar displacements along cubic [uv0] directions and a compatible mixed tilt system (a+b-b-) or long-range ordered antiphase tilts with unequal magnitudes (a0b-b-) without Pb displacement ordering. The phase-transition pattern at pc2 depends on the fine-scale degree of chemical B-site order in the structure.

  3. 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.

  4. β-Nb9VO25

    Directory of Open Access Journals (Sweden)

    Rawia Nasri

    2014-05-01

    Full Text Available The title compound, nonaniobium vanadium pentacosaoxide, was prepared by a solid-state reaction at 1198 K. It is isotypic with Nb9AsO25, Nb9PO25 and Ta9VO25. The structure consists of NbO6 octahedra (one with 4/m.. and two with m.. symmetry and VO4 tetrahedra (-4.. symmetry sharing corners and edges to form a three-dimensional framework. This framework can be considered as a junction between ribbons made up from NbO6 octahedra and chains of NbO6 octahedra and chains of VO4 tetrahedra. The V site shows half-occupancy, hence one half of the VO4 tetrahedra is unoccupied. The structural differences with α-Nb9VO25, VOSO4, SbOPO4 and NbOPO4 oxides are discussed.

  5. Atomic displacements in dilute alloys of Cr, Nb and Mo

    CERN Document Server

    Sharma, H

    2002-01-01

    Kanzaki lattice static method is used to calculate the atomic displacements due to substitutional impurities in 3d (Cr) and 4d (Nb, Mo) metals. Wills and Harrison interatomic potential is used to calculate dynamical matrix and the impurity-induced forces up to second nearest neighbors. The calculated atomic displacements for 3d, 4d and 5d impurities in Cr (V, Mn, Fe, Ni, Nb, Mo, Ta and W), Nb (V, Cr, Mn, Fe, Zr, Mo, Ta and W) and Mo (V, Cr, Mn, Fe, Zr, Nb, Ta and W) are tabulated up to 10 NN's. The strain field due to 3d impurities is least in Cr metal while it is larger in Nb and Mo metals. For 4d and 5d impurities the strain is larger in Cr metal than in Nb and Mo hosts. Similar trend is found for relaxation energies also. (author)

  6. Atomic displacements in dilute alloys of Cr, Nb and Mo

    Indian Academy of Sciences (India)

    Hitesh Sharma; S Prakash

    2002-09-01

    Kanzaki lattice static method is used to calculate the atomic displacements due to substitutional impurities in 3d (Cr) and 4d (Nb, Mo) metals. Wills and Harrison interatomic potential is used to calculate dynamical matrix and the impurity-induced forces up to second nearest neighbors. The calculated atomic displacements for 3d, 4d and 5d impurities in Cr (V, Mn, Fe, Ni, Nb, Mo, Ta and W), Nb (V, Cr, Mn, Fe, Zr, Mo, Ta and W) and Mo (V, Cr, Mn, Fe, Zr, Nb, Ta and W) are tabulated up to 10 NN’s. The strain field due to 3d impurities is least in Cr metal while it is larger in Nb and Mo metals. For 4d and 5d impurities the strain is larger in Cr metal than in Nb and Mo hosts. Similar trend is found for relaxation energies also.

  7. "ta surnud sõbrad..." : [luuletused] / Caspar Tops

    Index Scriptorium Estoniae

    Tops, Caspar

    2002-01-01

    Autorist lk 133. Sisu: "ta surnud sõbrad..." ; "ta kummaline hüüd..." ; "nii salakaval oli üks naine..." ; "ta tõmbas..." ; "mul meeles üks..." ; "rohi saab lahti iga päev üha..." ; "aeg riietab end lahti..." ; "ta kunagi..." ; "me riietume..." ; "ma tean armastuse põsepuna..." ; "kunas see suudlus..." ; "sina mu mälestuste tydruk..." ; "su õde mind armastas..." ; "hingata valutult..." ; "need juuksed pesemata..." ; "ah saab olema..." ; "siit natuke maad edasi..."

  8. "ta surnud sõbrad..." : [luuletused] / Caspar Tops

    Index Scriptorium Estoniae

    Tops, Caspar

    2002-01-01

    Autorist lk 133. Sisu: "ta surnud sõbrad..." ; "ta kummaline hüüd..." ; "nii salakaval oli üks naine..." ; "ta tõmbas..." ; "mul meeles üks..." ; "rohi saab lahti iga päev üha..." ; "aeg riietab end lahti..." ; "ta kunagi..." ; "me riietume..." ; "ma tean armastuse põsepuna..." ; "kunas see suudlus..." ; "sina mu mälestuste tydruk..." ; "su õde mind armastas..." ; "hingata valutult..." ; "need juuksed pesemata..." ; "ah saab olema..." ; "siit natuke maad edasi..."

  9. Influence of BiFeTaO{sub 3} addition on the electrical properties of Na{sub 0.4725}K{sub 0.4725}Li{sub 0.055}NbO{sub 3} ceramics system using impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kumari, Poonam [School of Physics, Shoolini University, Solan, HP (India); Rai, Radheshyam, E-mail: rshyam1273@gmail.com [School of Physics, Shoolini University, Solan, HP (India); Kholkin, A.L. [Department of Glass and Ceramics, Aveiro University, Aveiro (Portugal)

    2015-07-15

    Highlights: • (1 − x)(Na{sub 0.4725}K{sub 0.4725}Li{sub 0.055}NbO{sub 3}) − x(BiFe{sub 0.5}Ta{sub 0.5}O{sub 3}) ceramic samples have monoclinic phase. • Ferroelectric transition temperature (T{sub c}) of this system was 400–405 °C. • Dielectric properties were observed in (1 − x)(Na{sub 0.4725}K{sub 0.4725}Li{sub 0.055}NbO{sub 3}) − x(BiFe{sub 0.5}Ta{sub 0.5}O{sub 3}) system. • Activation energy increases with for concentration ratio. - Abstract: Polycrystalline samples of (1 − x)(Na{sub 0.4725}K{sub 0.4725}Li{sub 0.055}NbO{sub 3}) − x(BiFe{sub 0.5}Ta{sub 0.5}O{sub 3}) (where x = 0.005 and 0.007 were prepared by using a solid state reaction technique. The XRD patterns of the samples at room temperature shows perovskite phase with monoclinic structure. The dielectric constant for x = 0.007 is maximum. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100 Hz–1 MHz) and temperatures (RT–500 °C) shows that dielectric properties were strongly temperature and frequency dependent. Dielectric and electrical properties of samples, indicate that the Curie temperature shifted to higher temperature side with the increase in frequency. The AC conductivity also increases with increase in frequency. The low value of activation energy obtained for the ceramic samples could be attributed to the influence of electronic contribution to the conductivity. The plots of Z″ and M″ vs frequency at various temperatures shows peaks in the higher temperature range (>320 °C). The compounds show dielectric relaxation, which is found to be of non-Debye type and the relaxation frequency shifted to higher side with increase in temperature. The Nyquist plot and conductivity studies showed the NTCR character of samples.

  10. The contribution of amphibole from deep arc crust to the silicate Earth's Nb budget

    Science.gov (United States)

    Tiepolo, Massimo; Vannucci, Riccardo

    2014-11-01

    The continental crust (CC) and the depleted mantle (DM) are generally assumed to be complementary reservoirs within the Earth. However, the mixture between CC and upper mantle does not generate the Nb/Ta and Nb/La ratios of chondrites. A reservoir with superchondritic ratios for Nb/Ta and Nb/La is thus required in the Earth's system. The occurrence of a hidden amphibole reservoir in the lower arc crust has been recently proposed. This, coupled with the capability of calcic amphibole to give rise to a superchondritic Nb/Ta and Nb/La reservoir, led us to determine to what extent amphibole-rich ultramafic rocks can account for the Nb (and Nb/Ta, Nb/La as well) imbalance on Earth. We have considered lower crust mafic and ultramafic amphibole-rich intrusive rocks from collisional settings worldwide. Because CC is considered to have primarily formed in collisional setting these rocks are important for its genetic model. We modeled Nb, Ta and La contents of the hidden Nb reservoir by mass balance calculations between continental crust, depleted mantle and primitive mantle. Modeling shows that amphibole-rich mafic lower crust can solve the so-called Nb paradox if large volumes of materials are supposed to be returned into the mantle during the Earth's history. A possible mechanism is recycling, particularly in Precambrian times, of eclogites that underwent pre-eclogitic melting in the amphibolite facies field and then recrystallized under eclogite-facies conditions.

  11. 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.

  12. 镁粉还原-仲辛醇萃取法从钽铌矿分解液中除Sb的实验研究%Experimental Study on Sb Removal from Ta-Nb Ore Decomposition Solution by Reduction with Magnesium Powder and Extraction with 2-Octanol

    Institute of Scientific and Technical Information of China (English)

    胡根火; 郭永忠; 宋金华

    2014-01-01

    从Sb的价态着手,研究了仲辛醇对Sb(Ⅲ)和Sb(Ⅴ)萃取性能的差异,证实在相同的萃取条件下,Sb(Ⅴ)更容易被仲辛醇萃取.在此基础上,采用一定量的镁粉还原钽铌矿分解液中Sb,使高价态Sb转化成低价态Sb,以达到Sb与Ta/Nb分离的目的.实验结果表明,为使Nb2O5产品中Sb含量低于20×10-6,还原条件应采用镁粉用量10g/L、反应5h.

  13. Zn-B玻璃掺杂的(K0.5Na0.44Li0.06)(Nb0.84Ta0.1Sb0.06)O3陶瓷相变及电学性能研究%Phase Transition and Electrical Properties of (K0.5Na0.44Li0.06 )( Nb0.84Ta0.1Sb0.06)O3 Ceramics with Zn-B Glass Sintering Aid

    Institute of Scientific and Technical Information of China (English)

    范桂芬; 吕文中; 王允祺; 汪小红; 梁飞

    2011-01-01

    研究了Zn-B玻璃掺杂的(K0.5Na0.44Li0.06)(Nb0.84Ta0.1Sb0.06)O3(KNLNTS)陶瓷的制备、相变及电学性能.研究发现,Zn-B玻璃能够有效地促进铌酸钾钠基无铅压电陶瓷的烧结特性.XRD结果显示Zn-B玻璃掺杂的KNLNTS陶瓷为正交-四方共存结构,随掺杂量的增加正交结构相的含量逐渐增加;并且降低烧结温度能够有效地抑制第二相的产生.介电温谱测试结果显示Zn-B玻璃掺杂的KNLNTS陶瓷其居里温度先降后增在x=0.1时达到最小值.在1050℃保温5 h条件下烧结可以获得最佳的压电性能:d33=197 pC/N,kp=0.37,εr=975,tanδ=0.028.%The preparation, phase transition and electrical properties of (K0. 5 Na0. 44 Li0. 06 ) ( Nb0. 84 Ta0. 1 Sb0.06 )O3 (KNLNTS) lead-free piezoelectric ceramics with Zn-B glass sintering aid were studied in this paper. It was fount that the addition of Zn-B glass could greatly enhance the sintering properties of KNLNTS ceramics. The XRD results showed that Zn-B doped KNLNTS ceramics had the coexistence structure of the orthorhombic and tetragonal phase, and the orthorhombic phase increased gradually with the amount of Zn-B doping increasing. Lowering the sintering temperature could inhibit the production of the second phase. The dielectric spectrum test results showed that the Curie temperature of the Zn-B-doped KNLNTS ceramics first decreases and then increases, it reaches the minimum at x=0.1. At the sintering temperature of 1 050 ℃ with the soaking time of 5 h, the Zn-B doped KNLNTS-x ceramics obtained the optimum piezoelectric properties of d33 = 197 pC/N, kp =0.37, εr = 975 and tan δ=0.028.

  14. Discovery of Liangyuan Nb-Ta-Rb-W-polymetallic deposit in Shixing county,Guangdong Province and its significance%广东始兴良源铌钽铷钨多金属矿床的发现及其意义

    Institute of Scientific and Technical Information of China (English)

    肖惠良; 陈乐柱; 鲍晓明; 范飞鹏; 周延; 吴涵宇; 姚正红; 武玲; 滕龙

    2012-01-01

    The Liangyuan Nb-Ta-Rb-W polymetallic deposit in Shixing county,Guangdong Province,a deposit with a prospect of large scale,was found during the new-round investigation of tungsten polymetallic ores in the eastern Nanling mineralization zones deployed by China Geological Survey(CGS)in recent years.The new results show that five mineralized types can be recognized in the deposit,namely,greisen-type niobium-tantalum-rubidium-tungsten polymetallic ore,muscovitization albite granite-type niobium-tantalum-tungsten polymetallic ore,quartz vein-type tungsten ore,fractured belt alterated rock-type tungsten tin polymetallic ore and skarn-type scheelite,among them,muscovitization albite granite-type niobium-tantalum-tungsten polymetallic deposit shows the most prospective potential of exploration in this area.From the top level downwards to the deeper of the ore-bearing granite,the following differentiation evolution series are successively observed: porphyritic granite,medium-fine grained biotite granite,medium-fine grained two-mica albite granite,medium-fine grained muscovitization albite granite and greisen.In addition,alteration zoning,including muscovitization,chloritization and potassic alteration,is evidently observed in the ore-bearing granite.The ore bodies mainly occur in greisens,and fine grained muscovitization albite granites,and secondarily in quartz veins.The major ore minerals are scheelite,cassiterite,wolframite,molybdenite,bismuth,stibnite,fergusonite,fluorine-tantalum minerals,columbotantalite,galena,sphalerite,chalcopyrite and pyrite.A preliminary study indicates that the Nb-Ta-Rb-W-polymetallic ore bodies might be originated from the differentiation of deep-seated ore-bearing magma.The Liangyuan Nb-Ta-Rb-W-polymetallic deposit is characteristic of stable-grade, large scale and complex ore-forming elements with a Nb-Ta-Rb-W-Mo-Sn-Bi assemblage,enriched in Be、REE、Ag.The discovery of Liangyuan deposit is not only a breakthrough of prospecting in the

  15. Tensile Properties of the Individual Phases in Unreacted Multifilament Nb3Sn Wires

    CERN Document Server

    Scheuerlein, C; Fedelich, B; Finn, M; Griepentrog, M; El-Kallassi, P; Lecouturier, F; Oberli, L; Rehmer, B; Sgobba, Stefano; Thilly, L; Vidal, V

    2007-01-01

    The room temperature elastic and plastic properties under uniaxial tensile loading of the different phases of an un-reacted, internal-tin process, Nb3Sn wire have been determined by tensile tests of whole wires and of extracted Ta, Nb and Nb alloy filaments, as well as by indentation hardness measurements in metallographic wire cross sections.

  16. HA-Coated Implant

    DEFF Research Database (Denmark)

    Daugaard, Henrik; Søballe, Kjeld; Bechtold, Joan E

    2014-01-01

    The goal of osseointegration of orthopedic and dental implants is the rapid achievement of a mechanically stable and long lasting fixation between living bone and the implant surface. In total joint replacements of cementless designs, coatings of calcium phosphates were introduced as a means...... of improving the fixation of implants. Of these, hydroxyapatite (HA) is the most widely used and most extensively investigated. HA is highly osseoconductive, and the positive effect is well documented in both basic and long-term clinical research [1–6]. This chapter describes experimental and clinical studies...... evaluating bone-implant fixation with HA coatings....

  17. Haïti

    Directory of Open Access Journals (Sweden)

    Marc Pabois

    2012-04-01

    Full Text Available Figure 1Carte schématique de Haïti. Atelier de photogrammétrie de l’Inventaire généralMichel MaumontTrois missions ont eu lieu à Haïti, la première en 1997, les deux autres en 1998. Le Directeur du patrimoine à Haïti et le Directeur de la division du patrimoine culturel à l’Unesco ont ainsi fait appel au Ministère de la Culture afin de faire bénéficier Haïti de l’expérience acquise par la France dans le domaine de l’Inventaire. L’objectif de la première mission était d’analyser avec les respo...

  18. Determination Systems of Nb and Ta in Geochemical Samples and Rare Earth ores by ICP-MS and ICP-AES%ICP-MS和 ICP -AES 测定地球化学勘查样品及稀土矿石中铌钽方法体系的建立

    Institute of Scientific and Technical Information of China (English)

    高会艳

    2014-01-01

    A method to deal with the conditions of incomplete digestion of geological samples,and the complexity of the analysis for present technologies,along with the routine methods of wet digestion on constant temperature electric heating plate with mixed acids and Na2 O2 fusion pre-treatment method and to ease the hydrolysis of Nb and Ta are describe in this paper. Both Inductively Coupled Plasma-Mass Spectrometry( ICP-MS ) and Inductively Coupled Plasma-Atomic Emission Spectrometry( ICP-AES)were applied to establish two sets of analysis methods which can be used to detect the contents of Nb and Ta in geochemical exploration samples and rare earth ores. Wet digestion on constant temperature electric heating plate is suitable for low content and easy decomposition of samples with nitric acid-hydrofluoric acid-sulfuric acid by ICP-MS. Na2 O2 fusion pre-treatment method is suitable for high content and insoluble samples by using ICP-AES. Through the analysis of a series of national certified reference samples of soil,stream sediments,rocks and rare earth ores,the results show that mixed acid pre-treatment coupled with ICP-MS had a linear range of 0-200 ng/mL and detection limits of Nb and Ta were 0 . 01 μg/g and 0. 05 μg/g,respectively. The relative error was less than 10%,and the relative standard deviation( RSD)was less than 6%. The Na2 O2 fusion pre-treatment coupled with ICP-AES had a linear range of 0 -30 μg/mL, detection limits of Nb and Ta were 0. 2 μg/g and 2. 5 μg/g,respectively. The relative error was less than 10%, and the precision( RSD)was less than 7%. The two sets of analysis method satisfy the demand of analysis of Nb and Ta in samples with a complex matrix,a large range of content and large quantities of samples.%针对目前铌钽分析中出现的样品溶解不完全、元素易水解及现有分析技术流程复杂的情况,本文对常用的混合酸恒温电热板溶解和过氧化钠碱熔两种样品前处理方式

  19. Effect of BaZrO3 Depant on the Structure and Electric Properties of (K0.49Na0.51)0.98Li0.02(Nb0.77Ta0.18Sb0.05)O3 Lead-free Piezoceramics%BaZrO3掺杂对(K0.49Na0.51)0.98Li0.02(Nb0.77Ta0.18Sb0.05)O3无铅压电陶瓷的结构与电性能的影响

    Institute of Scientific and Technical Information of China (English)

    李月明; 肖祖贵; 沈宗洋; 王竹梅; 洪燕; 潘铁政; 吴芬

    2013-01-01

    采用固相反应法制备了(K0.49Na0.5 1)0.98Li0.02(Nb0.77Ta0.18Sb0.05)O3-xBaZrO3 (NKNLST-xBZ,x=0~0.020 mol)无铅压电陶瓷,系统研究了BaZrO3的掺杂量对陶瓷的压电、介电、机电和铁电性能的影响.结果表明:随着BaZrO3掺杂量x的增加,陶瓷的晶体结构由正交相向四方相转变,在x=0.005~0.008区间出现正交相与四方相两相共存的区域,在此区域内陶瓷的晶粒变得细小且均匀,介电损耗tanδ大幅降低,压电常数d33和平面机电耦合系数kp增加.该体系陶瓷的介电常数ε33(T) /ε0则随着BaZrO3的增加持续增加,相变温度则向低温方向移动.当x=0.005时,该组成陶瓷具有最佳的综合性能:压电常数d33=372 pC/N,平面机电耦合系数kp=47.2%,介电损耗tanδ=3.1%,以及较高的介电常数ε33(T)/ε0=1470和居里温度Tc=208℃.%(K0.45Na0.55)0.98Li0.020Nb0.77Ta0.18Sb0.05)O3-xBaZrO3 (NKNLST-xBZ,x =0-0.020 mol) lead-free piezoelectric ceramics were prepared by solid state reaction method.The effect of BaZrO3 doping amount on the piezoelectric,dielectric,electromechanical and ferroelectric properties were investigated systematically.The results revealed that the crystal structures transformed from orthorhombic phase to tetragonal phase with BaZrO3 doping amount increasing,and the coexistence of orthorhombic-tetragonal phases were observed in the x range from 0.005 to 0.008.Under the condition of two phases co-existence,the ceramic grain became small and uniform and dielectric loss tanδ significantly decreased,while the piezoelectric constant d33 and planar electro-mechanical coupling factor kp increased.The dielectric constant ε33(T)/ε0 of this system ceramics increased continuously with the increase of the BaZrO3 doping amount and the phase transition temperatures shifted to lower temperature.The optimized piezoelectric properties could be obtained at the x =0.005 composition ceramic as follows:the mized piezoelectric properties could be obtained at

  20. Microstructural and weldability evaluation of 310TaN

    Energy Technology Data Exchange (ETDEWEB)

    Lundin, C.D.; Qiao, C.Y.P. [Univ. of Tennessee, Knoxville, TN (United States); Swindeman, R.W. [Oak Ridge National Lab., TN (United States)

    1996-08-01

    Excellent weldability and good microstructural stability of 310TaN, in terms of the formation and growth of secondary phases at elevated temperature, was revealed in this investigation. The interganular stress corrosion resistance of 310TaN is superior to modified 800H and 310HCbN evaluated previously due to the fact that TaC, TaN and Ta(C,N) particles are more stable compared to Nb-rich or Ti-rich carbides, nitrides and carbonitrides presented in the other advanced alloys. Using resistance spot welding technique for which extremely fast cooling is a characteristic, it was found that a very minor amount of gain boundary liquation takes place during welding thermal cycling. The limited grain boundary liquation is of the eutectic type i.e., a low tendency to weld HAZ hot cracking.

  1. 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...

  2. 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...

  3. Estudio de materiales cerámicos basados en el sistema (K,Na,Li)(Nb,Ta,Sb)O3: relación entre la estructura y las propiedades eléctricas

    OpenAIRE

    Rubio Marcos, Fernando

    2009-01-01

    Las cerámicas piezoeléctricas nacieron en los años 1940 con el descubrimiento del fenómeno de la ferroelectricidad como la fuente de la inusual constante dieléctrica de los condensadores cerámicos de Titanato de Bario [i]. Desde entonces han sido el motor de una industria que ha permitido el desarrollo de numerosas aplicaciones prácticas como los transductores piezoeléctricos, los PTC, ó las válvulas electro-óptica. Dos son los sistemas composicionales que han dominado los materiales...

  4. Mishima jo ha kyu

    Directory of Open Access Journals (Sweden)

    Matteo Casari

    2012-01-01

    Full Text Available Abstract – IT La grandezza artistica di Mishima si è espressa attraverso una eterogenea gamma di linguaggi tra i quali il teatro – nella drammaturgia ma anche nella saggistica, regia, recitazione e direzione di compagnia – ha avuto un ruolo di primo piano. Al pari di un uomo di scena Mishima inaugura, a partire dagli anni ’50, un processo di attenzione al proprio corpo come possibile, anzi necessario, veicolo di estrinsecazione etico-estetica tanto da poter istituire l’equazione corpo-teatro quale snodo profondo del suo processo creativo. Il corpo sognato e ottenuto da Mishima attraverso l’addestramento nel kendo, in altre arti marziali e nel body building si conformava ad un ideale estetico di matrice greco-classica assai lontano dal corpo teatrale nipponico. Il corpo come luogo di elaborazione e strumento di espressione autentica da realizzare con impegno, però, lo legano profondamente alle esperienze nascenti – tra gli anni ’50 e ’60 – delle avanguardie teatrali giapponesi. La metafora teatrale è spesso usata nella lettura critica del Mishima uomo e artista con accezione deteriore: un personaggio che dà spettacolo di sé con ripetute provocazioni tra le quali il suicidio del 25 novembre 1970 non sarebbe che l’esempio ultimo e più estremo. La costruzione di sé come personaggio, invece, sembrerebbe corrispondere ad una ben più profonda e meditata necessità di comporre la propria vita in una sapiente messa in scena di classica perfezione: i principi della scansione ritmico formale del jo ha kyu, pilastro teorico del teatro no codificato da Zeami tra XIV e XV secolo, offrono un valido modello di riferimento. Abstract – EN Mishima’s artistic greatness has been expressed through a diverse range of languages among wich theater – in dramaturgy as well as in written essays, as a director, performer and in company direction – played a central role. As a true front-man, Mishima – starting from the 50’s

  5. Growth and Holographic Storage Properties of Fe:LiTaO3 Crystal

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Using Si-Mo bar as heater and doping Fe2O3 in LiTaO3, Fe∶LiTaO3 crystal was grown by Czochralski method. The curie temperature of the crystal was measured by thermal analyze method. The lattice constants of the crystal were calculated by measuring of X-ray spectra. The response time, exponential gain coefficient and diffraction efficiency of Fe:LiTaO3 were obtained by two wave coupled technique. Compared with Fe∶LiNbO3, the response time of Fe:LiTaO3 is six times shorter, the storage time of Fe:LiTaO3 is ten times longer and the photo scattering resistance ability of Fe:LiTaO3 is four times higher. Fe:LiTaO3 is an excellent holographic storage material.

  6. 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.

  7. Large coupled magnetoresponses in EuNbO2N

    NARCIS (Netherlands)

    Jorge, A. Belen; Oro-Sole, Judith; Bea, Ana M.; Mufti, Nandang; Palstra, Thomas T. M.; Rodgers, Jennifer A.; Attfield, J. Paul; Fuertes, Amparo

    2008-01-01

    We have explored a new strategy to discover materials with large resistive or capacitive responses to magnetic fields by synthesizing EuMO2N (M = Nb, Ta) perovskites that combine ferromagnetic order of S = 7/2 Eu2+ spins with possible offcenter distortions of the d(0) M5+ cations enhanced by covalen

  8. 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.

  9. Fast ultradense GdTa1-xNbxO4 scintillator crystals

    Science.gov (United States)

    Voloshyna, Olesia; Gerasymov, Iaroslav; Sidletskiy, Oleg; Kurtsev, Daniil; Gorbacheva, Tatyana; Hubenko, Kateryna; Boiaryntseva, Ianina; Ivanov, Alexey; Spassky, Dmitry; Omelkov, Sergey; Belsky, Andrei

    2017-04-01

    Single crystals of GdTaO4 and GdTa0.8Nb0.2O4 were grown by the Czochralski technique, and their luminescent and scintillation properties were studied. Both crystals demonstrate fast emission with decay time around 10-8 s. Meanwhile, in GdTaO4 the fast decay is accompanied by a huge build-up with the decay time around 1 μs, while in the mixed crystal the contribution of slow components is negligible. UV- and X-ray excited luminescence, curves of thermostimulated luminescence and absolute light yields of crystals are presented as well. GdTa0.8Nb0.2O4 crystal is shown to be an ultradense (8.37 g/cm3) and fast (shortest component decay time 17 ns) scintillator with a high stopping power.

  10. Síndrome HaNDL / HaNDL Syndrome / Síndrome HaNDL

    Directory of Open Access Journals (Sweden)

    Camilo Ernesto Barros-Gutiérrez, MD., Esp.

    2015-03-01

    Full Text Available Introducción: El Síndrome HaNDL (Headache and neurologic deficits with cerebroespinal fluid lymphocytosis por sus siglas en inglés, es una patología que cursa con cefalea, focalización neurológica y linfocitosis en el líquido cefalorraquídeo. Objetivo: este artículo busca presentar un caso de Síndrome de HaNDL, puesto que esta condición nosológica implica un reto diagnóstico. Resultados y conclusiones: Se presenta el caso de un paciente con diagnóstico de síndrome de HaNDL los hallazgos al examen físico y del líquido cefalorraquídeo. [Barros-Gutiérrez CE, Silva-Monsalve E, Gualtero-Trujillo S. Síndrome HaNDL. MedUNAB 2015; 17(3: xx-xx]. Introduction: The syndrome of transient Headache and Neurological Deficits with cerebrospinal fluid Lymphocytosis, is a pathology that presents cephalalgia, neurological focalization and lymphocytes in the cerebrospinal fluid. Objective: This article presents a HaNDL Syndrome case, since this nosological condition implies a diagnostic challenge. Results and conclusions: A case of a patient with HaNDL syndrome diagnosis, physical examination findings and cerebrospinal fluid are presented. [Barros-Gutiérrez CE, Silva-Monsalve E, Gualtero-Trujillo S. HaNDL Syndrome. MedUNAB 2015; 17(3: xx-xx]. Introdução: A síndrome de HaNDL (Headache and neurologic déficits with cerebrospinal fluid lymphocytosis por sua sigla em inglês é uma doença que causa dor de cabeça, foco neurológico e linfocitose no líquido cefalorraquidiano. Objetivo: Este artigo tem como objetivo apresentar um caso de Síndrome de HaNDL, uma vez que esta condição nosológica envolve um desafio diagnóstico. Resultados e conclusões: Apresenta-se o caso de um paciente diagnosticado com a síndrome de HaNDL, o encontrado no exame físico e o líquido cefalorraquidiano. [Barros-Gutiérrez CE, Silva-Monsalve E, Gualtero-Trujillo S. Síndrome HaNDL. MedUNAB 2015; 17(3: xx-xx].

  11. Interface Roughness in Copper-Tantalum Wire and NB3SN Superconductor Composites

    Science.gov (United States)

    Hartwig, K. T.; Balachandran, S.; Mathaudhu, S. N.; Barber, R. E.; Pyon, T.; Griffin, R. B.

    2008-03-01

    Poor deformation behavior of tantalum (Ta) sheet used for tin diffusion barriers in Nb3Sn composite superconductors can lead to Ta layer rupture and even strand fracture during wire drawing. These problems arise because the Ta layer deforms nonuniformly as it is reduced in thickness. The origin of the problem resides in the microstructure of the Ta and the co-deformation mechanics of relatively strong body centered cubic Ta with surrounding weaker and more ductile face centered cubic Cu. In an attempt to remedy this problem, 25 mm square bars of Ta were processed by multi-axis severe plastic deformation (SPD) via equal channel angular extrusion (ECAE), then rolled to sheet and recrystallized. The SPD processing was done to refine the microstructure and reduce nonuniformities in grain size and texture. Measurements of the Cu-Ta interface roughness in experimental Cu-Ta composite wires were made and compared with the interface roughness seen in commercial Ta diffusion barrier layers. Results show that Ta sheet made from SPD processed bulk Ta co-deforms well with Cu and leads to less interface roughening than is developed in commercial Ta sheet material fabricated into superconductor wire.

  12. Cs0.49NbPS6

    Directory of Open Access Journals (Sweden)

    Hoseop Yun

    2011-01-01

    Full Text Available The quaternary thiophosphate, Cs0.49NbPS6, caesium hexathioniobiophosphate(V, has been synthesized by the reactive halide flux method. The title compound is isotypic with Rb0.46TaPS6 and is made up of a bicapped trigonal–biprismatic [Nb2S12] unit and a tetrahedral [PS4] group. The [Nb2S12] units linked by the [PS4] tetrahedra form infinite chains, yielding a three-dimensional network with rather large van der Waals gaps along the c axis in which the disordered Cs+ ions reside. The electrons released by the Cs atoms are transferred to the pairwise niobium metal site and there are substantial intermetallic Nb—Nb bonding interactions. This leads to a significant decrease of the intermetallic distance in the title compound compared to that in TaPS6. The classical charge balance of the title compound may be represented as [Cs+]0.49[Nb4.51+][P5+][S2−]4[S22−].

  13. Trinh T. Minh-ha

    DEFF Research Database (Denmark)

    Nelund, Sidsel; Trinh T, Minh-ha

    2012-01-01

    Born in Vietnam, Trinh T. Minh-ha is known as a filmmaker, composer and writer. Contributing generously to these art forms, she was also a pioneer in the 1980’s theoretical conceptualisation of the Other, verbalising especially the position of women in developing countries. 
 Currently, Trinh T. ...

  14. 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.

  15. Trinh T. Minh-ha

    DEFF Research Database (Denmark)

    Nelund, Sidsel; Trinh T, Minh-ha

    2012-01-01

    Born in Vietnam, Trinh T. Minh-ha is known as a filmmaker, composer and writer. Contributing generously to these art forms, she was also a pioneer in the 1980’s theoretical conceptualisation of the Other, verbalising especially the position of women in developing countries. 
 Currently, Trinh T....... Minh-ha holds the post of Professor of Gender and Women's Studies, and of Rhetoric at the University of California, Berkeley. She has lived, among other places, in Vietnam, USA, France, Senegal, and Japan and this geographic diversity is reflected in her work, in which several countries have been...... for marginalised groups. However, she also moves in circles of documentary, cinema, feminist studies, postcolonial theory, contemporary visual art, literature, and music composition. This interview consists of 4 parts concerning positioning, research, and media, finally coming back to positioning again....

  16. Investigation of TaC–TaB2 ceramic composites

    Indian Academy of Sciences (India)

    Behzad Mehdikhani; Gholam Hossein Borhani; Saeed Reza Bakhshi; Hamid Reza Baharvandi

    2016-02-01

    The TaC–TaB2 composition was sintered by spark plasma (SPS) at 1900–2100°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 TaC–TaB2 composition could be SPS to 97% of theoretical density in 10 min at 2100°C. Addition of B4C leads to an increase in the density sample from 76 to 97%. B4C nano-powder resists grain growth even at high temperature 2100°C. The formation of TaB2/carbon at TaC grain boundaries helps in pinning the grain boundary and inhibiting grain growth. The phase formation was associated with carbon and boron diffusion from the starting particles B4C to form TaB2 phases. TaC grain sizes decreased with increase in B4C concentration. Samples with 2.0 wt% B4C composition had highest flexure strength up to 520 MPa. The effect of B4C addition on hardness measured by microhardness has been studied. Hardness of samples containing 3.0 wt% B4C was 16.99 GPa.

  17. Core-Shell Structure of Intermediate Precipitates in a Nb-Based Z-Phase Strengthened 12% Cr Steel.

    Science.gov (United States)

    Rashidi, Masoud; Andrén, Hans-Olof; Liu, Fang

    2017-04-01

    In creep resistant Z-phase strengthened 12% Cr steels, MX (M=Nb, Ta, or V, and X=C and/or N) to Z-phase (CrMN, M=Ta, Nb, or V) transformation plays an important role in achieving a fine distribution of Z-phase precipitates for creep strengthening. Atom probe tomography was employed to investigate the phase transformation in a Nb-based Z-phase strengthened trial steel. Using iso-concentration surfaces with different concentration values, and subtracting the matrix contribution enabled us to reveal the core-shell structure of the transient precipitates between MX and Z-phase. It was shown that Z-phase forms by diffusion of Cr into NbN upon ageing, and Z-phase has a composition corresponding to Cr1+x Nb1-x N with x=0.08.

  18. Lo que se ha hecho

    OpenAIRE

    Alvarado A. Víctor Hernando

    1992-01-01

    Después de transcurrido el primer módulo e iniciado el segundo, en el Curso de Postgrado en DERECHO ADMINISTRATIVO, resulta conveniente, formular algunas reflexiones sobre el avance del programa en su etapa inicial. El programa aprobado por el Instituto Colombiano para el Fomento de la Educación Superior -ICFES-, a desarrollarse en cuatro (4) MODULOS semestrales cada uno, requiriéndose dos (2) años para su cumplimiento, nos ha permitido ver que reúne las exigencias que la Universidad pretend...

  19. Lo que se ha hecho

    OpenAIRE

    1992-01-01

    Después de transcurrido el primer módulo e iniciado el segundo, en el Curso de Postgrado en DERECHO ADMINISTRATIVO, resulta conveniente, formular algunas reflexiones sobre el avance del programa en su etapa inicial. El programa aprobado por el Instituto Colombiano para el Fomento de la Educación Superior -ICFES-, a desarrollarse en cuatro (4) MODULOS semestrales cada uno, requiriéndose dos (2) años para su cumplimiento, nos ha permitido ver que reúne las exigencias que la Universidad pretend...

  20. Landau-Ginzburg description of anomalous properties of novel room temperature multiferroics Pb(Fe{sub 1/2}Ta{sub 1/2}){sub x}(Zr{sub 0.53}Ti{sub 0.47}){sub 1-x}O{sub 3} and Pb(Fe{sub 1/2}Nb{sub 1/2}){sub x}(Zr{sub 0.53}Ti{sub 0.47}){sub 1−x}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Glinchuk, Maya D.; Eliseev, Eugene A. [Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Krjijanovskogo 3, 03142 Kyiv (Ukraine); Morozovska, Anna N., E-mail: anna.n.morozovska@gmail.com [Institute of Physics, National Academy of Sciences of Ukraine, 46, pr. Nauky, 03028 Kyiv (Ukraine)

    2016-01-14

    Landau-Ginzburg thermodynamic formalism is used for the description of the anomalous ferroelectric, ferromagnetic, and magnetoelectric properties of Pb(Fe{sub 1/2}Ta{sub 1/2}){sub x}(Zr{sub 0.53}Ti{sub 0.47}){sub 1−x}O{sub 3} and Pb(Fe{sub 1/2}Nb{sub 1/2}){sub x}(Zr{sub 0.53}Ti{sub 0.47}){sub 1−x}O{sub 3} micro-ceramics. We calculated temperature, composition, and external field dependences of ferroelectric, ferromagnetic, and antiferromagnetic phases transition temperatures, remanent polarization, magnetization, hysteresis loops, dielectric permittivity, and magnetoelectric coupling. Special attention was paid to the comparison of developed theory with experiments. It appeared possible to describe adequately main experimental results including a reasonable agreement between the shape of calculated and measured hysteresis loops and remnant polarization. Since Landau-Ginzburg thermodynamic formalism appertains to single domain properties of a ferroic, we did not aim to describe quantitatively the coercive field under the presence of realistic poly-domain switching. Information about linear and nonlinear magnetoelectric coupling coefficients was extracted from the experimental data. From the fitting of experimental data with theoretical formula, we obtained the composition dependence of Curie-Weiss constant that is known to be inversely proportional to harmonic (linear) dielectric stiffness, as well as the strong nonlinear dependence of anharmonic parameters in free energy. Keeping in mind the essential influence of these parameters on multiferroic properties, the obtained results open the way to govern practically all the material properties with the help of suitable composition choice. A forecast of the strong enough influence of antiferrodistortive order parameter on the transition temperatures and so on the phase diagrams and properties of multiferroics are made on the basis of the developed theory.

  1. Thermodynamic description of the systems Co–Nb, Al–Nb and Co–Al–Nb

    Energy Technology Data Exchange (ETDEWEB)

    He, Cuiyun, E-mail: he-cy@gxu.edu.cn [College of Materials Science and Engineering, Guangxi University (China); Stein, Frank; Palm, Martin [Max-Planck-Institut für Eisenforschung GmbH, Postfach 140444, D-40074 Düsseldorf (Germany)

    2015-07-15

    Highlights: • The Co–Nb and Al–Nb were updated to get a reasonable description of Co–Al–Nb system. • A consistent thermodynamic description of Co–Al–Nb system is obtained basing on rich experimental data. • Alkemade theorem could not decide the saddle point of two congruently melting phase. - Abstract: The Co–Al–Nb ternary system and its two binary subsystems Co–Nb and Al–Nb were thermodynamically modeled by the Calphad method based on own experimental results and critically assessed literature data. A characteristic of the Co–Nb and Co–Al–Nb system is the coexistence of three polytypes of Laves phases: hexagonal C14 and C36 as well as cubic C15. Two-sublattice models were used for the three Laves phases to enable a realistic description of their homogeneity ranges in the Co–Nb and Co–Al–Nb system. A re-assessment was needed for the Al–Nb system to obtain a better description of the homogeneity range of Nb{sub 2}Al and the liquidus projection of the Co–Al–Nb system. The comparison between calculated and experimental values shows that the optimized set of thermodynamic parameters gives a very good description of most of the experimental data resulting in a complete, consistent thermodynamic description of the three systems Co–Nb, Al–Nb and Co–Al–Nb.

  2. Effect of the adhesive antibiotic TA on adhesion and initial growth of E-coli on silicone rubber

    NARCIS (Netherlands)

    Simhi, E; van der Mei, HC; Ron, EZ; Rosenberg, E; Busscher, HJ

    2000-01-01

    Catheter-associated urinary tract infection is the most common nosocomial infection, and contributes to patient morbidity and mortality. We investigated the effect that the TA adhesive antibiotic had on adhesion and initial growth in urine of Escherichia coli on silicone rubber. The TA antibiotic ha

  3. 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.

  4. History-dependent thermal expansion in NbO{sub 2}F

    Energy Technology Data Exchange (ETDEWEB)

    Wilkinson, Angus P., E-mail: angus.wilkinson@chemistry.gatech.edu [School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (United States); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 (United States); Josefsberg, Ryan E.; Gallington, Leighanne C.; Morelock, Cody R.; Monaco, Christopher M. [School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (United States)

    2014-05-01

    Materials with cubic ReO{sub 3}-type structures are of interest for their low or negative thermal expansion characteristics. TaO{sub 2}F is known to display almost zero thermal expansion over a wide temperature range. On heating NbO{sub 2}F, its volume coefficient of thermal expansion decreases from ∼+45 ppm K{sup −1} at 100 K to almost zero at 400 K. NbO{sub 2}F is cubic between 100 and 500 K. Samples of “NbO{sub 2}F” prepared by the digestion of Nb{sub 2}O{sub 5} in aqueous HF followed by mild drying contain hydroxyl defects and metal vacancies. On heating, they can undergo irreversible chemical changes while maintaining a cubic ReO{sub 3}-type structure. The possibility of hydroxyl defect incorporation should be considered when preparing oxyfluorides for evaluation as battery materials. - Graphical abstract: “NbO{sub 2}F” prepared by the digestion of Nb{sub 2}O{sub 5} in HF contains cation vacancies and hydroxyl groups. It undergoes irreversible changes on heating to low temperatures, unlike NbO{sub 2}F prepared by the solid state reaction of Nb{sub 2}O{sub 5} and NbF{sub 5}. - Highlights: • The digestion of Nb{sub 2}O{sub 5} in aqueous HF followed by mild drying does not produce NbO{sub 2}F. • The ReO{sub 3}-type product from the HF digestion of Nb{sub 2}O{sub 5} contains metal vacancies and hydroxyl. • The thermal expansion coefficient of NbO{sub 2}F decreases on heating and approaches zero at ∼400 K.

  5. Due testimonianze di Josip Vaništa

    Directory of Open Access Journals (Sweden)

    Radmila Iva Janković

    2013-12-01

    Full Text Available Radmila Iva Janković ha intervistato nel luglio 2013 Josip Vaništa, artista che aveva partecipato al gruppo Gorgona e preso parte alla residenza d'artista a Brunnenburg nel 1991, organizzata da Francesco Conz con l'obiettivo di includere il gruppo di artisti nel progetto La Livre, una monumentale edizione d'artista dedicata a Ezra Pound.

  6. 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

  7. 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.

  8. 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.

  9. Catalytic efficiency of Nb and Nb oxides for hydrogen dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Isobe, Shigehito, E-mail: isobe@eng.hokudai.ac.jp [Graduate School of Engineering, Hokkaido University, N-13, W-8, Sapporo 060-0813 (Japan); Creative Research Institution, Hokkaido University, N-20, W-10, Sapporo 001-0021 (Japan); Kudoh, Katsuhiro; Hino, Satoshi; Hashimoto, Naoyuki; Ohnuki, Somei [Graduate School of Engineering, Hokkaido University, N-13, W-8, Sapporo 060-0813 (Japan); Hara, Kenji [Catalysis Research Center, Hokkaido University, N-20, W-10, Sapporo 001-0021 (Japan)

    2015-08-24

    In this letter, catalytic efficiency of Nb, NbO, Nb{sub 2}O{sub 3}, NbO{sub 2}, and Nb{sub 2}O{sub 5} for dissociation and recombination of hydrogen were experimentally investigated. On the surface of Nb and Nb oxides in a gas mixture of H{sub 2} and D{sub 2}, H{sub 2} and D{sub 2} molecules can be dissociated to H and D atoms; then, H{sub 2}, D{sub 2}, and HD molecules can be produced according to the law of probability. With increase of frequency of the dissociation and recombination, HD ratio increases. The ratio of H{sub 2} and HD gas was analyzed by quadrupole mass spectrometry. As a result, NbO showed the highest catalytic activity towards hydrogen dissociation and recombination.

  10. Mg-doped congruent LiTaO3 crystal for large-aperture quasi-phase matching device.

    Science.gov (United States)

    Ishizuki, Hideki; Taira, Takunori

    2008-10-13

    Mg-doped congruent composition LiTaO(3) (MgLT) crystal, which can be grown by a conventional Czochralski method, has improved properties such as transparent range, thermal conductivity, and coercive field compared to conventional undoped congruent LiTaO(3). In this paper, various properties of MgLT including Mg-doping dependence are characterized, and also compared to that of undoped congruent LiTaO(3), LiNbO(3), and Mg-doped congruent LiNbO(3), as a material of high power quasi-phase matching (QPM) device. Up to 3-mm-thick periodically poled MgLT crystal is shown to demonstrate the possibility of large-aperture QPM-MgLT devices. Subsequently, optical parametric oscillation experiments by using periodically poled MgLT are demonstrated to discuss an efficient QPM condition.

  11. PLLA-HA composites: Synthesis and characterization

    Science.gov (United States)

    Gonzalez, Gema; Albano, Carmen; Palacios, Jordana

    2012-07-01

    A composite based on PLLA -HA was prepared by the solvent casting technique and characterized. An interaction between the polymer matrix and HA through the carbonyl and phosphate groups was obtained by FTIR . The several thermal transitions of PLLA were evaluated by DSC: the glass transition, crystallization, cold crystallization, melt-recrystallization and melting. The addition of HA to PLLA matrix increases its glass transition temperature and no major changes on the melting temperature and crystallinity were observed. The PLLA-HA composite showed better thermal stability than the neat polymer. The introduction of the nano-HA particles increased the decomposition temperature and the activation energy retarding the decomposition process.

  12. Co-sputtered amorphous Nb–Ta, Nb–Zr and Ta–Zr coatings for corrosion protection of cyclotron targets for [{sup 18}F] production

    Energy Technology Data Exchange (ETDEWEB)

    Skliarova, Hanna, E-mail: Hanna.Skliarova@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell’Università, 2, 35020 Legnaro, Padua (Italy); University of Ferrara, Ferrara (Italy); Azzolini, Oscar, E-mail: Oscar.Azzolini@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell’Università, 2, 35020 Legnaro, Padua (Italy); Johnson, Richard R., E-mail: richard.johnson@teambest.com [BEST Cyclotron Systems Inc., 8765 Ash Street Unit 7, Vancouver, BC V6P 6T3 (Canada); Palmieri, Vincenzo, E-mail: Vincenzo.Palmieri@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell’Università, 2, 35020 Legnaro, Padua (Italy); University of Padua, Padua (Italy)

    2015-08-05

    Highlights: • Nb–Ta, Nb–Zr and Ta–Zr alloy films were deposited by co-sputtering. • Co-sputtered Nb–Zr and Nb–Ta alloy coatings had crystalline microstructures. • Diffusion barrier efficiency of Nb–Zr and Nb–Ta decreased with the increase of Nb %. • Co-sputtered Ta–Zr films with 30–73 at.% Ta were amorphous. • Sputtered amorphous Ta–Zr films showed superior diffusion barrier efficiency. - Abstract: Protective corrosion resistant coatings serve for decreasing the amount of ionic contaminants from Havar® entrance foils of the targets for [{sup 18}F] production. The corrosion damage of coated entrance foils is caused mainly by the diffusion of highly reactive products of water radiolysis through the protective film toward Havar® substrate. Since amorphous metal alloys (metallic glasses) are well-known to perform a high corrosion resistance, the glass forming ability, microstructure and diffusion barrier efficiency of binary alloys containing chemically inert Nb, Ta, Zr were investigated. Nb–Ta, Nb–Zr and Ta–Zr films of different alloy composition and ∼1.5 μm thickness were co-deposited by magnetron sputtering. Diffusion barrier efficiency tests used reactive aluminum underlayer and protons of acid solution and gallium atoms at elevated temperature as diffusing particles. Though co-sputtered Nb–Ta and Nb–Zr alloy films of different contents were crystalline, Ta–Zr alloy was found to form dense amorphous microstructures in a range of composition with 30–73% atomic Ta. The diffusion barrier efficiency of Nb–Zr and Nb–Ta alloy coatings decreased with increase of Nb content. The diffusion barrier efficiency of sputtered Ta–Zr alloy coatings increased with the transition from nanocrystalline columnar microstructure to amorphous for coatings with 30–73 at.% Ta.

  13. Phase relations and crystal structures in the system Ta-V-Ge.

    Science.gov (United States)

    Khan, Atta U; Bursik, J; Rogl, P

    2012-05-28

    Phase equilibria have been derived for the isothermal section of the Ta-V-Ge system at 1500 °C (for concentrations phases have been identified within the isothermal section, out of which three were characterized by Rietveld refinement of X-ray powder diffraction data. τ(1)-(Ta(1-x)V(x))(5)Ge(3) (0.21 ≤ x ≤ 0.63) adopts the Mn(5)Si(3)-type and τ(2)-Ta(Ta(x)V(1-x-y)Ge(y))(2), x = 0.02, y = 0.12 was found to be a MgZn(2)-type Laves phase. Detailed transmission electron microscopy (TEM) in several crystallographic directions confirmed lattice parameters and crystal symmetry of this phase and rejected the presence of any superstructure. τ(3)-Ta(9-x+y)V(4+x-y-z)Ge(1+z), x = 0.32, y = 0.51, z = 0.98 crystallizes with the Nb(9)Co(4)Ge-type, whereas the structure of τ(4) is not yet known. Although a MgCu(2)-type cubic Laves phase is not present in the Ta-V binary at this temperature, additions of Ge stabilize this phase in the ternary system: C15-Ta(Ta(x)V(1-x-y)Ge(y))(2), x = 0.04, y = 0.05. V(11)Ge(8) (Cr(11)Ge(8) type) shows a large solubility up to (Ta(x)V(1-x))(11)Ge(8), x = 0.64 at 1500 °C.

  14. Dead Layer in a Ta/Ni81Fe19/Ta Structure

    Institute of Scientific and Technical Information of China (English)

    于广华; 任婷婷; 李明华; 朱逢吾; 姜宏伟; 赖武彦

    2002-01-01

    The effect of Ta seed layers and Ta cap layers on the effective magnetic thickness of ultrathin permalloy (Ni81 Fe19)was experimentally investigated for magnetic random access memory applications. The films were deposited by magnetron sputtering. For a Ta/Ni81Fe19/Ta fundamental structure, the Ta seed and Ta cap layers resulted in a loss of moment equivalent to a magnetically dead layer of thickness 1.6 ± 0.2 nm. In order to find the mechanism, the composition and chemical states at the interface regions of Ta/Ni81 Fe19 and Ni81 Fe19/Ta were studied using x-ray photoelectron spectroscopy and the peak decomposition technique. The results show that there are thermodynamically favourable reactions at the Ta/Ni81 Fe19 and Ni81Fe19/Ta interfaces: 2Ta + Ni = NiTa2.

  15. Structure and physical properties of EuTa2O6 tungsten bronze polymorph

    Science.gov (United States)

    Kolodiazhnyi, T.; Sakurai, H.; Vasylkiv, O.; Borodianska, H.; Forbes, S.; Mozharivskyj, Y.

    2014-08-01

    A tetragonal tungsten bronze (TTB) polymorph of EuTa2O6 was prepared and analyzed. EuTa2O6 crystallizes in the centrosymmetric Pnam space group (with unit cell: a = 12.3693, b = 12.4254, and c = 7.7228 Å) isomorphous with orthorhombic β-SrTa2O6. In contrast to early reports, we see no evidence of deviation from paramagnetic Curie-Weiss behavior among the Eu2+ 4f7spins in EuTa2O6 down to 2 K. Dielectric constant shows a broad peak at ca. 50 K with dielectric dispersion resembling diffuse phase transition. The relaxation time, however, follows a simple (non-freezing) thermally activated process with an activation energy of 92 meV and an attempt frequency of f0 = 5.79 × 1012 Hz. A thermal conductivity of EuTa2O6 shows a low-temperature (T ≈ 30 K) "plateau" region reminiscent of a glass-like behaviour in Nb-based TTB compounds. This behaviour can be attributed to the loosely bound Eu2+ ions occupying large tricapped trigonal prismatic sites in the EuTa2O6 structure.

  16. Observation of 186mTa

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Unreported tantalum isomer 18mTa has been produced through the reaction 186W(n,p) by irradiation of natW with 14 MeV neutrons. The activity of 186Ta and 186Ta was measured using HPGe detectors and several X-γ as well as γ-γ coincidence arrangements. The 186mTa has been identified by means of measuring known γ rays from 186Ta p-decay. The half-life of 186mTa has been determined to be (1.5±0.1) min.

  17. Laser treatment of plasma sprayed HA coatings

    NARCIS (Netherlands)

    Khor, KA; Vreeling, A; Dong, ZL; Cheang, P

    1999-01-01

    Laser treatment was conducted on plasma sprayed hydroxyapatite (HA) coatings using a Nd-YAG pulse laser. Various laser parameters were investigated. The results showed that the HA surface melted when an energy level of greater than or equal to 2 J and a spot size of 2 mm was employed during continuo

  18. ha õhtu seltskonnalaud / Kaire Nurk

    Index Scriptorium Estoniae

    Nurk, Kaire, 1960-

    2005-01-01

    ha õhtusöömaaja teemast kunstis. Saksa kunstiajaloolase Horst Schwebeli poolt Leonardo da Vinci "Püha õhtusöömaaja" XX sajandi "töötlustes" välja toodud poliitilise agitatsiooni ja ühisest probleemist haaratud seltskonna kujutiste suunast. Laua kujutisest kunstis

  19. ha õhtu seltskonnalaud / Kaire Nurk

    Index Scriptorium Estoniae

    Nurk, Kaire, 1960-

    2005-01-01

    ha õhtusöömaaja teemast kunstis. Saksa kunstiajaloolase Horst Schwebeli poolt Leonardo da Vinci "Püha õhtusöömaaja" XX sajandi "töötlustes" välja toodud poliitilise agitatsiooni ja ühisest probleemist haaratud seltskonna kujutiste suunast. Laua kujutisest kunstis

  20. Laser treatment of plasma sprayed HA coatings

    NARCIS (Netherlands)

    Khor, KA; Vreeling, A; Dong, ZL; Cheang, P

    1999-01-01

    Laser treatment was conducted on plasma sprayed hydroxyapatite (HA) coatings using a Nd-YAG pulse laser. Various laser parameters were investigated. The results showed that the HA surface melted when an energy level of greater than or equal to 2 J and a spot size of 2 mm was employed during continuo

  1. Evaluation of Excitation Function for 182Ta

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>Present work concerns the evaluated neutron induced excitation function data for 182Ta, and mainly on (n, γ) reaction channel. The related experimental data were collected, analyzed and corrected for 182Ta

  2. Fission from Fe and Nb reactions with heavy targets at 50--100 MeV/nucleon

    Energy Technology Data Exchange (ETDEWEB)

    Begemann-Blaich, M.; Blaich, T.; Fowler, M.M.; Wilhelmy, J.B. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)); Britt, H.C.; Fields, D.J.; Hansen, L.F.; Lanier, R.G.; Massoletti, D.J.; Namboodiri, M.N.; Remington, B.A.; Sangster, T.C.; Struble, G.L.; Webb, M.L. (Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)); Chan, Y.D.; Dacal, A.; Harmon, A.; Pouliot, J.; Stokstad, R.G. (Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States)); Kaufman, S.; Videbaek, F. (Argonne National Laboratory, Argonne, Illinois 60439 (United States)); Fraenkel, Z. (Weizmann Institute of Science, 76100 Rehovot (Israel))

    1992-02-01

    Cross sections, parallel and perpendicular momentum transfers, charge loss, and velocity systematics are presented for fission following reactions of Fe and Nb projectiles at 50--100 MeV/nucleon on targets of Ta, Au, and Th. Data are compared to simple models for peripheral heavy ion collisions.

  3. Main: 1TA3 [RPSD[Archive

    Lifescience Database Archive (English)

    Full Text Available 1TA3 小麦 Bread Wheat Triticum aestivum Xylanase Inhibitor Protein I Precursor. Name=...479.1; -.|PDB; 1OM0; X-ray; A=31-304.|PDB; 1TA3; X-ray; A=-.|PDB; 1TE1; X-ray; A=...CGYPPAAHVGRALATGIFERAHVRTYESDKWCNQNLGWEGSWDKWTAAYPATRFYVGLTADDKSHQWVHPKNVYYGVAPVAQKKDNYGGIMLWDRYFDKQTNYSSLIKYYA wheat_1TA3.jpg ...

  4. Study and control of the conductivity of Nb-doped Bi4Ti3O12 for high temperature piezoelectric applications

    Directory of Open Access Journals (Sweden)

    Damjanovic, D.

    1999-12-01

    Full Text Available Bismuth-based layered compounds have been considered during the last years as interesting materials for high temperature piezoelectric applications, due to their stability and wide thermal range of the ferroelectric activity. The high electrical conductivity present at high temperatures has been a disadvantage for the potential applications of these compounds. On Bi4Ti3O12 (BIT, different doping, such as Nb5+ and W6+ were used to increase resistivity. It has been shown that Nb5+ doping modifies piezoelectric response, passing from relatively high hysteretic to linear and almost completely non-hysteretic. In the present work, the effect of Nb5+ doping related to the conduction response is investigated. Studies of the I-V curves as a function of the temperature allows us, for the first time, to measure the conductivity of these compounds at room temperature (RT and to discuss which are the microstructural elements that control the conductivity of the material using a serial electrical model. It is shown that at temperatures between RT and 125ºC the grain boundary conductivity limits the total conductivity. At higher temperatures, the material conducts mainly through the bulk of grains. Conduction type, conductivity thermal regimes and chemical composition may explain the change in the piezoelectric behaviour.Compuestos laminares de bismuto han sido considerados en los últimos años materiales interesantes como piezoeléctricos en aplicaciones de alta temperatura, debido a su estabilidad y amplio rango térmico de existencia de actividad ferroeléctrica. Sin embargo, la elevada conductividad presente a altas temperaturas ha sido una desventaja para las potenciales aplicaciones de estos compuestos. En el caso de Bi4Ti3O12 (BIT, diferentes dopantes como Nb5+ o W6+ han sido empleados para aumentar la resistencia eléctrica del material. Es conocido que el dopado con Nb5+ modifica la respuesta piezoeléctrica del material pasando de presentar una

  5. Atomic resolution investigations of phase transformation from TaN to CrTaN in a steel matrix

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson; Hald, John

    2012-01-01

    , thus preserving long-term creep strength. This can be done by alloying with Ta instead of Nb and V. Recent investigations have indicated a direct transformation of MN into CrMN to take place, not the traditional nucleation/dissolution process. In this paper atomic resolution microscopy shows how Cr......In development of 12%Cr high temperature steels used for fossil fired power plants, the precipitation of large Z-phase particles, CrMN, has been identified as a major problem since they replace small and finely distributed MN particles. This causes a premature breakdown in the longterm creep...... strength of the steel. The Cr content promotes Z-phase precipitation, making MN strengthening of these materials unfeasible, since 12%Cr is necessary for oxidation resistance. The authors have suggested an acceleration of Z-phase precipitation to obtain a fine and stable distribution of CrMN instead of MN...

  6. 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)

  7. Mediating states in 180Ta

    OpenAIRE

    Alexa, Petr

    2002-01-01

    Possible theoretical electromagnetic paths between the ground state and the isomeric state at 75.3 keV in 180Ta are discussed in the framework of the two-quasiparticle-plus-phonon model and the standard axially-symmetric rotor model including Coriolis mixing. Experimental transition rates from the isomeric state to the ground state via observed mediating states are compared to the theoretical ones.

  8. Theoretical study of the electronic states of Nb4, Nb5 clusters and their anions (Nb4?, Nb5?)

    Energy Technology Data Exchange (ETDEWEB)

    Balasubramanian, K; Majumdar, D

    2004-05-06

    Geometries and energy separations of the various low-lying electronic states of Nb{sub n} and Nb{sub n}{sup -} (n = 4, 5) clusters with various structural arrangements have been investigated. The complete active space multi-configuration self-consistent field (CASMCSCF) method followed by multi-reference singles and doubles configuration interaction (MRSDCI) calculations that included up to 52 million configuration spin functions have been used to compute several electronic states of these clusters. The ground states of both Nb{sub 4} ({sup 1}A', pyramidal) and Nb{sub 4}{sup -} ({sup 2}B{sub 3g}, rhombus) are low-spin states at the MRSDCI level. The ground state of Nb{sub 5} cluster is a doublet with a distorted trigonal bipyramid (DTB) structure. The anionic cluster of Nb{sub 5} has two competitive ground states with singlet and triplet multiplicities (DTB). The low-lying electronic states of these clusters have been found to be distorted due to Jahn-Teller effect. On the basis of the energy separations of our computed electronic states of Nb{sub 4} and Nb{sub 5}, we have assigned the observed photoelectron spectrum of Nb{sub n}{sup -}(n = 4, 5) clusters. We have also compared our MRSDCI results with density functional calculations. The electron affinity, ionization potential, dissociation and atomization energies of Nb{sub 4} and Nb{sub 5} have been calculated and the results have been found to be in excellent agreement with the experiment.

  9. Magnetic property and interface structure of Ta/NiO/NiFe/Ta

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ta/NiO/NiFe/Ta multilayers, utilizing Ta as buffer layer, were prepared by rf reactive and dc magnetron sputtering. The exchange coupling field between NiO and NiFe reached a maximum value of 9.6×103 A/m at a NiO film thickness of 50 nm. The composition and chemical states at interface region of Ta/NiO/Ta were studied by using the X-ray photoelectron spectroscopy (XPS) and peak decomp- osition technique. The results show that there is an "inter- mixing layer" at the Ta/NiO (and NiO/Ta) interface due to a thermodynamically favorable reaction 2Ta + 5NiO = 5Ni + Ta2O5. This interface reaction has a great effect on exchange coupling. The thickness of Ni+NiO estimated by XPS depth- profiles is about 8-10 nm.

  10. Morphological Effects of HA on the Cell Compatibility of Electrospun HA/PLGA Composite Nanofiber Scaffolds

    Directory of Open Access Journals (Sweden)

    Adnan Haider

    2014-01-01

    Full Text Available Tissue engineering is faced with an uphill challenge to design a platform with appropriate topography and suitable surface chemistry, which could encourage desired cellular activities and guide bone tissue regeneration. To develop such scaffolds, composite nanofiber scaffolds of nHA and sHA with PLGA were fabricated using electrospinning technique. nHA was synthesized using precipitation method, whereas sHA was purchased. The nHA and sHA were suspended in PLGA solution separately and electrospun at optimized electrospinning parameters. The composite nanofiber scaffolds were characterized by FE-SEM, EDX analysis, TEM, XRD analysis, FTIR, and X-ray photoelectron. The potential of the HA/PLGA composite nanofiber as bone scaffolds in terms of their bioactivity and biocompatibility was assessed by culturing the osteoblastic cells onto the composite nanofiber scaffolds. The results from in vitro studies revealed that the nHA/PLGA composite nanofiber scaffolds showed higher cellular adhesion, proliferation, and enhanced osteogenesis performance, along with increased Ca+2 ions release compared to the sHA/PLGA composite nanofiber scaffolds and pristine PLGA nanofiber scaffold. The results show that the structural dependent property of HA might affect its potential as bone scaffold and implantable materials in regenerative medicine and clinical tissue engineering.

  11. Mechanical Properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 Refractory High-Entropy Alloys (Preprint)

    Science.gov (United States)

    2011-07-01

    yield stress (YS) of the studied HEAs and two high-temperature Ni-based superalloys, Inconel 718 [9] and Haynes 230 [10 Figure 3 ]. Inconel 718 is a...YS of Inconel 718 rapidly decreases to 138 MPa with a further increase in temperature to 982°C, while melting occurs at ~1210°C. Inconel 718 is...that of Haynes 230 at all studied temperatures and higher than that of Inconel 718 at temperatures above 800°C (see Figure 3). Moreover, the

  12. Superconductivity in the niobium-rich compound Nb{sub 5}Se{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Klimczuk, T., E-mail: tomasz.klimczuk@pg.gda.pl [Faculty of Applied Physics and Mathematics, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk (Poland); Baroudi, K.; Krizan, J.W. [Department of Chemistry, Princeton University, Princeton NJ 08544 (United States); Kozub, A.L. [Faculty of Applied Physics and Mathematics, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk (Poland); Cava, R.J. [Department of Chemistry, Princeton University, Princeton NJ 08544 (United States)

    2015-11-15

    The niobium rich selenide compound Nb{sub 5}Se{sub 4} was synthesized at ambient pressure by high-temperature solid–state reaction in a sealed Ta tube. Resistivity and heat capacity measurements reveal that this compound is superconducting, with a T{sub c} = 1.85 K. The electronic contribution to the specific heat γ and the Debye temperature are found to be 18.1 mJmol{sup −1}K{sup −2} and 298 K respectively. The calculated electron-phonon coupling constant λ{sub ep} = 0.5 and the ΔC{sub p}/γT{sub c} = 1.42 ratio imply that Nb{sub 5}Se{sub 4} is a weak coupling BCS superconductor. The upper critical field and coherence length are found to be 1.44 T and 15.1 nm, respectively. - Highlights: • High purity Nb{sub 5}Se{sub 4} is synthesized at high temperature in a sealed metal tube. • The superconductivity of Nb{sub 5}Se{sub 4} is reported for the first time. • The superconducting properties of Nb{sub 5}Se{sub 4} are compared to other Nb-chalcogenides.

  13. Diffusion of Hf and Nb in Zr-19%Nb

    Energy Technology Data Exchange (ETDEWEB)

    Zou, H. [Atomic Energy of Canada Ltd., Chalk River, ON (Canada). Chalk River Nuclear Labs.; Hood, G.M. [Atomic Energy of Canada Ltd., Chalk River, ON (Canada). Chalk River Nuclear Labs.; Schultz, R.J. [Atomic Energy of Canada Ltd., Chalk River, ON (Canada). Chalk River Nuclear Labs.; Matsuura, N. [Atomic Energy of Canada Ltd., Chalk River, ON (Canada). Chalk River Nuclear Labs.; Roy, J.A. [Atomic Energy of Canada Ltd., Chalk River, ON (Canada). Chalk River Nuclear Labs.; Jackman, J.A. [CANMET, Ottawa, Ont. (Canada). Met. Sci. and Technol.

    1996-05-01

    Diffusion of Hf and Nb in large-grained bcc Zr-19%Nb has been studied. Diffusion coefficients of Hf, D(Hf), were measured in the range 620-1173 K and D(Nb) was measured at 920 and 1167 K. The Hf diffusion profiles were determined by SIMS and the Nb profiles by microtome sectioning and radio-tracer counting. The Hf data show a smooth, temperature-dependent behaviour through the monotectoid temperature, 875 K, and may be characterised by D{approx}10{sup -9}.exp-1.4 (eV/kT) m{sup 2}/s. D(Nb) tends to be lower than the corresponding values for D(Hf). Overall, diffusion of Hf and Nb are characteristic of diffusion in bcc Zr. Surface hold-up (oxide film) at low temperatures was overcome by using ion-implanted Hf diffusion sources. The results are compared with earlier work and discussed in terms of diffusion mechanisms and the {beta}-phase transformation of commercial Zr-2.5Nb. (orig.).

  14. Site occupancy of transition elements in C15 NbCr2 laves phase: A first-principles study

    Directory of Open Access Journals (Sweden)

    Long Q.

    2017-01-01

    Full Text Available Using first-principles calculations, site occupancy behaviors of transition elements in C15 NbCr2 Laves phase are systematically investigated. Elements Y, Sc, Zr, Hf, Cd, Ta, Ti and Ag prefer to occupy the Nb site, and elements Zn, Pt, Re, Tc, Ir, V, Os, Rh, Ru, Ni, Co, Mn, Fe and Cu favor to occupy the Cr site; whereas elements Mo, W, Pd and Au have weak site preference for Cr or Nb site. The present calculations agree well with the available experimental and previously calculated results. It was found that the site occupancy behavior of transition elements in NbCr2 is mainly affected by the radii of transition elements. The present calculations also propose the correlation between the site preference energy and radii of transition elements.

  15. Elastic properties of Nb-based alloys by using the density functional theory

    Institute of Scientific and Technical Information of China (English)

    Liu Zeng-Hui; Shang Jia-Xiang

    2012-01-01

    A first-principles density functional approach is used to study the electronic and the elastic properties of Nb15X (X =Ti,Zr,Hf,V,Ta,Cr,Mo,and W) alloys.The elastic constants c11 and c12,the shear modulus C′,and the elastic modulus E〈100〉 are found to exhibit similar tendencies,each as a function of valence electron number per atom (EPA),while c44 seems unclear.Both c11 and c12 of Nb15X alloys increase monotonically with the increase of EPA.The C′ and E〈100〉 also show similar tendencies.The elastic constants (except c44) increase slightly when alloying with neighbours of a higher d-transition series.Our results are supported by the bonding density distribution.When solute atoms change from Ti(Zr,Hf) to V(Ta) then to Cr(Mo,W),the bonding electron density between the central solute atom and its first neighbouring Nb atoms is increased and becomes more anisotropic,which indicates the strong interaction and thus enhances the elastic properties of Nb-Cr(Mo,W) alloys.Under uniaxial (100) tensile loading,alloyed elements with less (more) valence electrons decrease (increase) the ideal tensile strength.

  16. 78 FR 28627 - TA-W-80,340; TA-W-80,340A; TA-W-80,340B

    Science.gov (United States)

    2013-05-15

    ... Employment and Training Administration TA-W-80,340; TA-W-80,340A; TA-W-80,340B] Bush Industries, Inc., Mason... (TA-W-80,340) and Bush Industries, Inc., Allen Street Facility, Jamestown, New York (TA-W- 80,340A... the subject firm's Erie, Pennsylvania facility. The amended notice applicable to TA-W-80,340 is...

  17. Fabrication of fine-grain tantalum diffusion barrier tube for Nb{sub 3}Sn conductors

    Energy Technology Data Exchange (ETDEWEB)

    Hartwig, K. T.; Balachandran, S.; Mezyenski, R.; Seymour, N. [Department of Mechanical Engineering, Texas A and M University, TX 77843 (United States); Robinson, J.; Barber, R. E. [Shear Form Inc, 207 Dellwood St, Bryan 77801 (United States)

    2014-01-27

    Diffusion barriers used in Nb{sub 3}Sn wire are often fabricated by wrapping Ta sheet into a tube with an overlap seam. A common result of such practice is non-uniform deformation in the Ta sheet as it thins by wire drawing because of non-uniform grain size and texture in the original Ta sheet. Seamless Ta tube with a fine-grain and uniform microstructure would be much better for the diffusion barrier application, but such material is expensive and difficult to manufacture. This report presents results on a new fabrication strategy for Ta tube that shows promise for manufacture of less costly tube with an improved microstructure. The fabrication method begins with seam-welded tube but gives a fine-grain uniform microstructure with little difference between the longitudinal seam weld region and the parent metal after post-weld processing. Severe plastic deformation processing (SPD) applied by area reduction extrusion and tube equal channel angular extrusion (tECAE) are used to refine and homogenize the microstructure. Microstructure and mechanical property results are presented for Ta tubes fabricated by this new processing strategy.

  18. Fabrication of fine-grain tantalum diffusion barrier tube for Nb3Sn conductors

    Science.gov (United States)

    Hartwig, K. T.; Balachandran, S.; Mezyenski, R.; Seymour, N.; Robinson, J.; Barber, R. E.

    2014-01-01

    Diffusion barriers used in Nb3Sn wire are often fabricated by wrapping Ta sheet into a tube with an overlap seam. A common result of such practice is non-uniform deformation in the Ta sheet as it thins by wire drawing because of non-uniform grain size and texture in the original Ta sheet. Seamless Ta tube with a fine-grain and uniform microstructure would be much better for the diffusion barrier application, but such material is expensive and difficult to manufacture. This report presents results on a new fabrication strategy for Ta tube that shows promise for manufacture of less costly tube with an improved microstructure. The fabrication method begins with seam-welded tube but gives a fine-grain uniform microstructure with little difference between the longitudinal seam weld region and the parent metal after post-weld processing. Severe plastic deformation processing (SPD) applied by area reduction extrusion and tube equal channel angular extrusion (tECAE) are used to refine and homogenize the microstructure. Microstructure and mechanical property results are presented for Ta tubes fabricated by this new processing strategy.

  19. Preparation of silicon-substituted hydroxyapatite coatings on Ti–30Nb–xTa alloys using cyclic electrochemical deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eun-Sil [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, School of Dentistry, Chosun University (Korea, Republic of); Jeong, Yong-Hoon [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, Research Center of Nano-Interface Activation for Biomaterials, School of Dentistry, Chosun University (Korea, Republic of); Brantley, William A. [Division of Restorative Science and Prosthodontics, College of Dentistry, The Ohio State University, Columbus, OH (United States)

    2014-12-01

    Silicon-substituted hydroxyapatite coatings on Ti–30Nb–xTa alloys, prepared using a cyclic electrochemical deposition method, have been investigated using a variety of surface analytical experimental methods. The silicon-substituted hydroxyapatite (Si-HA) coatings were prepared by electrolytic deposition in electrolytes containing Ca{sup 2+}, PO{sub 4}{sup 3−} and SiO{sub 3}{sup 2−} ions. The deposited layers were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and a wettability test. Phase transformation from (α″ + β) to largely β occurred with increasing Ta content in the Ti –30Nb–xTa alloys, yielding larger grain size. The morphology of the Si-HA coatings was changed by increasing the number of deposition cycles, with the initial plate-like structures changing to mixed rod-like and plate-like shapes, and finally to a rod-like structure. From the ATR-FTIR spectra, Si existed in the form of SiO{sub 4}{sup 4−} groups in Si-HA coating layer. The lowest aqueous contact angles and best wettability were found for the Si-HA coatings prepared with 30 deposition cycles. - Highlights: • Electrochemically deposited Si-HA coatings on Ti –30Nb–xTa alloys were investigated. • The Si-HA coatings were initially precipitated along the martensitic structure. • The morphology of the Si-HA coating changed with the deposition cycles. • Si existed in the form of SiO{sub 4}{sup 4−} groups in the Si-HA coating.

  20. Breakdown of the Hume-Rothery Rules in Sub-Nanometer-Sized Ta-Containing Bimetallic Small Clusters

    Science.gov (United States)

    Miyajima, Ken; Fukushima, Naoya; Himeno, Hidenori; Yamada, Akira; Mafuné, Fumitaka

    2009-11-01

    The Hume-Rothery rules are empirical rules to predict the solid solubility of metals. We examined whether the rules hold for sub-nanometer-sized small particles. We prepared bimetallic cluster ions in the gas phase by a double laser ablation technique. Taking advantage of the magic compositions of the bimetallic cluster ions relating to the distinguished stabilities, the coalescence or the segregation of Ta and another element in the sub-nanometer-sized clusters was discussed. It was found that W, Nb, and Mo readily coalesce with Ta, while Ag, Al, Au, Co, Cu, Fe, Hf, Ni, Pt, Ti, and V are segregated from Ta. On the basis of these results, we concluded that the Hume-Rothery rules do not hold for sub-nanometer-sized particles.

  1. 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.

  2. Morphology of hydroxyapatite coated nanotube surface of Ti-35Nb-xHf alloys for implant materials

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae-Un [Functional Coatings Group, Materials Processing Division, Korea Institute of Materials Science (KIMS), Changwon, Kyungnam (Korea, Republic of); Jeong, Yong-Hoon [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials and Research Center for Oral Disease Regulation of the Aged, Chosun University, Gwangju (Korea, Republic of); Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, 305 W. 12th Ave. Columbus, OH (United States); Choe, Han-Cheol, E-mail: hcchoe@chosun.ac.kr [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials and Research Center for Oral Disease Regulation of the Aged, Chosun University, Gwangju (Korea, Republic of)

    2011-11-01

    The purpose of this research is to study the morphology of hydroxyapatite coated nanotube surface of Ti-35Nb-xHf for implant materials using various experiments. For this study, Ti-35Nb-xHf (x = 0, 3, 7 and 15 wt.%) alloys were prepared by arc melting and heat treated for 12 h at 1000 Degree-Sign C in an argon atmosphere and then water quenching. Nanotube formation on the Ti-35Nb-xHf alloys was achieved by anodizing in H{sub 3}PO{sub 4} electrolytes containing 0.8 wt.% NaF at room temperature. Anodization was carried out using an electrochemical method and all experiments were conducted at room temperature. Hydroxyapatite (HA) was deposited on the nanotubular Ti-35Nb-xHf alloys surface for the biomaterials by radio-frequency (RF) magnetron sputtering method. The morphologies of nanotubular and HA coated surface were characterized by X-ray diffractometer (XRD), optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM). The wettability of HA coated surface was measured by contact angle goniometer. The microstructure of Ti-35Nb-xHf alloys was transformed needle-like to equiaxed structure with Hf content and {alpha} Double-Prime phase decreased, whereas {beta} phase increased as Hf content increased. HA coating surface was affected by microstructure of bulk and morphology of nanotube formation. In case of low Hf content, tip of nanotube formed at {beta} phase was coated with HA film, whereas {alpha} Double-Prime phase was not coated with HA film. In case of high Hf content, nanotube surface was coated uniformly with HA film. The wettability of HA coated nanotubular surface was higher than that of non coated samples.

  3. Resistance to He{sup 2+} irradiation damage in metallic glass Ta{sub 38}Ni{sub 62}

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Wenjing [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024 (China); Mei, Xianxiu, E-mail: xxmei@dlut.edu.cn [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024 (China); Zhang, Xiaonan; Wang, Yingmin; Qiang, Jianbing [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024 (China); Sun, Jianrong [Institute of Modern Physics, The Chinese Academy of Sciences, Lanzhou 730000 (China); Wang, Younian [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024 (China)

    2016-10-15

    Highlights: • Metallic glass Ta{sub 38}Ni{sub 62} irradiated by different fluence of He{sup 2+} remained amorphous. • The helium bubble layer appeared at the end of ion range 1.01 μm away from surface. • Helium bubbles were larger in the layer center and reduced to top and bottom sides. • No significant damage appeared in the surface of metallic glass Ta{sub 38}Ni{sub 62}. • Ta{sub 38}Ni{sub 62} better resisted to He{sup 2+} irradiation than W and V{sub 87.5}Cr{sub 4.17}Ti{sub 4.17}Nb{sub 4.17}. - Abstract: Metallic glass Ta{sub 38}Ni{sub 62} strips, metallic W, and V{sub 87.5}Cr{sub 4.17}Ti{sub 4.17}Nb{sub 4.17} alloy were irradiated using a 500 keV He{sup 2+} ion beam at different fluence to compare the metallic glass resistance to irradiation. Metallic glass Ta{sub 38}Ni{sub 62} remained amorphous at different He{sup 2+} irradiation fluence. Transmission electron microscopy analysis revealed the presence of helium bubbles at the end of the range of helium ions in the metallic glass. No significant damage resulted in the metallic glass surface, and the root mean square roughness increased nonlinearly with the increase in fluence. At 1 × 10{sup 18} ions/cm{sup 2}, metallic W appeared in larger sunken areas on the surface and V{sub 87.5}Cr{sub 4.17}Ti{sub 4.17}Nb{sub 4.17} alloy experienced multi-layer flaking. The metallic glass Ta{sub 38}Ni{sub 62} resistance to He{sup 2+} ion beam irradiation was better than that of metallic W, and that of the V{sub 87.5}Cr{sub 4.17}Ti{sub 4.17}Nb{sub 4.17} alloy was the poorest.

  4. 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.

  5. Electrochemical and surface behavior of hydyroxyapatite/Ti film on nanotubular Ti-35Nb-xZr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Yong-Hoon [Division of Restorative and Prosthetic Dentistry, College of Dentistry, Ohio State University, 305 W. 12th Ave., Columbus, OH (United States); Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, and Research Center for Oral Disease Regulation of the Aged School of Dentistry, Chosun University, Gwangju (Korea, Republic of); Choe, Han-Cheol, E-mail: hcchoe@chosun.ac.kr [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, and Research Center for Oral Disease Regulation of the Aged School of Dentistry, Chosun University, Gwangju (Korea, Republic of); Brantley, William A. [Division of Restorative and Prosthetic Dentistry, College of Dentistry, Ohio State University, 305 W. 12th Ave., Columbus, OH (United States)

    2012-01-01

    In this paper, we investigated the electrochemical and surface behavior of hydroxyapatite (HA)/Ti films on the nanotubular Ti-35Nb-xZr alloy. The Ti-35Nb-xZr ternary alloys with 3-10 wt.% Zr content were made by an arc melting method. The nanotubular oxide layers were developed on the Ti-35Nb-xZr alloys by an anodic oxidation method in 1 M H{sub 3}PO{sub 4} electrolyte containing 0.8 wt% NaF at room temperature. The HA/Ti composite films on the nanotubular oxide surfaces were deposited by a magnetron sputtering method. Their surface characteristics were analyzed by field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS) and an X-ray diffractometer (XRD). The corrosion behavior of the specimens was examined through potentiodynamic and AC impedance tests in 0.9% NaCl solution. From the results, the Ti-35Nb-xZr alloys showed a solely {beta} phase microstructure that resulted from the addition of Zr. The nanotubular structure formed with a diameter of about 200 nm, and the HA/Ti thin film was deposited on the nanotubular structure. The HA/Ti thin film-coated nanotubular Ti-35Nb-xZr alloys showed good corrosion resistance in 0.9% NaCl solution.

  6. NB Power Transmission system

    Energy Technology Data Exchange (ETDEWEB)

    Williamson, J. [NB Power Transmission, Fredericton, NB (Canada)

    2006-07-01

    The NB Power Transmission System operates 6700 km of transmission lines having voltages of 69 kV, 138 kV, 230 kV, and 345 kV. The history of lightning protection on this transmission system was presented. Lightning protection with shield wires has been applied selectively on the 69 kV and 138 kV lines and has been applied to all lines in the 230 kV and 345 kV range. Beginning in 2000, line arresters were installed on selected 69 kV and 138 kV lines. It was noted that although overhead shield wires are commonly installed to capture lightning strikes and shield the conductors, problems can occur if the electrical flashover of insulators result in a line to ground fault. Good grounding is needed to ensure that lightning enters the ground from the tower. The new approach is to install line arresters on structures without overhead shield wires. Line arresters are surge arresters applied in parallel with the insulator string. This new line arrester technology was tested by installing nearly 1200 arresters in the Saint John area. This paper described the reasons for choosing line arresters over shield wires and presented the methods of installation. The problems and failure rates of the installed line arresters were presented along with solutions, including solutions to protect lines against lightning in areas with heavy icing. Recommendations for future research into the use, application and development of line arresters were also presented. tabs., figs.

  7. Anomalous behaviour of the transverse acoustic phonons in KTa[sub 1-x]Nb[sub x]O[sub 3

    Energy Technology Data Exchange (ETDEWEB)

    Fontana, M.D. (Groupe Materiaux Optiques a Proprietes Specifiques, CLOES, Univ. de Metz et Supelec, 57 Metz (France)); Kugel, G.E. (Groupe Materiaux Optiques a Proprietes Specifiques, CLOES, Univ. de Metz et Supelec, 57 Metz (France)); Foussadier, L. (Groupe Materiaux Optiques a Proprietes Specifiques, CLOES, Univ. de Metz et Supelec, 57 Metz (France)); Kress, W. (Max-Planck Inst., Stuttgart (Germany)); Rytz, D. (Centre de Recherche en Optoelectronique Sandoz S. A., 68 Huningue (France))

    1993-08-20

    In addition to the already known softening of the lowest transverse optic mode (TO) in KTa[sub 1-x]Nb[sub x]O[sub 3] a pronounced temperature dependence of the transverse acoustic (TA) mode in the [100] direction of the Brillouin zone has been observed by inelastic-neutron-scattering measurements for Nb concentrations of x = 0.008 and 0.012. In the vicinity of the phase transition the dispersion curve of the TA branch exhibits peculiarities at small wave vectors. The observed anomalies are attributed to hybridization effects of modes belonging to the same representation and to an exchange of eigenvectors between TO and TA modes. (orig.).

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

    Energy Technology Data Exchange (ETDEWEB)

    McFadden, L.D. [Geoprofile, Inc., Albuquerque, NM (United States)

    1995-03-01

    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.

  9. Structural, elastic, electronic and optical properties of a new layered-ternary Ta{sub 4}SiC{sub 3} compound

    Energy Technology Data Exchange (ETDEWEB)

    Islam, M.S. [Department of Physics, Rajshahi University, Rajshahi 6205 (Bangladesh); Islam, A.K.M.A., E-mail: azi46@ru.ac.b [Department of Physics, Rajshahi University, Rajshahi 6205 (Bangladesh)

    2011-01-15

    We propose a new layered-ternary Ta{sub 4}SiC{sub 3} with two different stacking sequences ({alpha}- and {beta}-phases) of the metal atoms along c axis and study their structural stability. The mechanical, electronic and optical properties are then calculated and compared with those of other compounds M{sub 4}AX{sub 3} (M=V, Nb, Ta; A=Al, Si and X=C). The predicted compound in the {alpha}-phase is found to possess higher bulk modulus than these compounds. The independent elastic constants of the two phases are also evaluated and the results discussed. The electronic band structures for {alpha}- and {beta}-Ta{sub 4}SiC{sub 3} show metallic conductivity. Ta 5d electrons are mainly contributing to the total density of states (DOS). We see that the hybridization peak of Ta 5d and C 2p lies lower in energy and the Ta 5d-C 2p bond is stronger than Ta 5d-Si 3p bond. Further an analysis of the different optical properties shows the compound to possess improved behavior compared to similar types of compounds.

  10. Effect of Nb Solute and NbC Precipitates on Dynamic or Static Recrystallization in Nb Steels

    Institute of Scientific and Technical Information of China (English)

    XIAO Fu-ren; CAO Ya-bin; QIAO Gui-ying; ZHANG Xiao-bing; LIAO Bo

    2012-01-01

    Nb is often considered to be a powerful alloying element for controlling the recrystaUization process in mi- croalloyed high strength steels. However, Nb can be presented either as solute in solution, where it is thought to ex- hibit a strong solute drag effect, or as NbC precipitates, which are thought to be effective at pinning grain bounda- ries. Therefore, it is very important to quantitatively measure Nb in solution or in NbC precipitates. A quantitative analysis method of Nb in solution and in precipitates was proposed. The test procedure involved chemical dissolution, filtration and inductively coupled plasma atomic emission spectroscopic (ICP-AES) analysis. The amount of Nb in solution in Nb-microallyed steels under different treatment conditions was evaluated. The results show that the niobium and carbon contents in steels have a great effect on niobium dissolution kinetics. The solute Nb is more effective to retard dynamic recrystallization, while the NbC precipitates are more effective to inhibit static recrystaltization. The results may help to comprehend effect of Nb in steels, and provide some guides in the design of new high strength Nb-bearing steels.

  11. Intermonomer Interactions in Hemagglutinin Subunits HA1 and HA2 Affecting Hemagglutinin Stability and Influenza Virus Infectivity

    Science.gov (United States)

    DeFeo, Christopher J.; Alvarado-Facundo, Esmeralda; Vassell, Russell

    2015-01-01

    ABSTRACT Influenza virus hemagglutinin (HA) mediates virus entry by binding to cell surface receptors and fusing the viral and endosomal membranes following uptake by endocytosis. The acidic environment of endosomes triggers a large-scale conformational change in the transmembrane subunit of HA (HA2) involving a loop (B loop)-to-helix transition, which releases the fusion peptide at the HA2 N terminus from an interior pocket within the HA trimer. Subsequent insertion of the fusion peptide into the endosomal membrane initiates fusion. The acid stability of HA is influenced by residues in the fusion peptide, fusion peptide pocket, coiled-coil regions of HA2, and interactions between the surface (HA1) and HA2 subunits, but details are not fully understood and vary among strains. Current evidence suggests that the HA from the circulating pandemic 2009 H1N1 influenza A virus [A(H1N1)pdm09] is less stable than the HAs from other seasonal influenza virus strains. Here we show that residue 205 in HA1 and residue 399 in the B loop of HA2 (residue 72, HA2 numbering) in different monomers of the trimeric A(H1N1)pdm09 HA are involved in functionally important intermolecular interactions and that a conserved histidine in this pair helps regulate HA stability. An arginine-lysine pair at this location destabilizes HA at acidic pH and mediates fusion at a higher pH, while a glutamate-lysine pair enhances HA stability and requires a lower pH to induce fusion. Our findings identify key residues in HA1 and HA2 that interact to help regulate H1N1 HA stability and virus infectivity. IMPORTANCE Influenza virus hemagglutinin (HA) is the principal antigen in inactivated influenza vaccines and the target of protective antibodies. However, the influenza A virus HA is highly variable, necessitating frequent vaccine changes to match circulating strains. Sequence changes in HA affect not only antigenicity but also HA stability, which has important implications for vaccine production, as well

  12. [Hypoallergenic milks (HA formulas) in infant nutrition].

    Science.gov (United States)

    Zoppi, G

    1993-01-01

    According to the definition of the European Scientific Committee for Food, hypoallergenic or hypoantigenic formulas (HA-formulas) are those which contain hydrolysed protein derived both from casein or whey. Soy-based formulas are not comprised in this definition since it has been demonstrated from several years that soy-protein, in several circumstances, may be highly allergenic. Hypoallergenic formulas contain besides hydrolysed protein, carbohydrate and lipid in amount and proportion similar to those indicated by ESPGAN recommendations on adapted formulas. As far as it concerns composition in lipid, recently great attention has been given to optimal supply and ratio of omega 3 and omega 6 fatty acids. Hypoallergenic formulas are therefore suitable for balanced nutrition of suckling infants. Specific indications on prevention of atopic diseases are not treated.

  13. Biocompatibility of new Ti–Nb–Ta base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hussein, Abdelrahman H. [Department of Materials Science, Institute of Graduate Studies and Research, Alexandria University, Alexandria (Egypt); Gepreel, Mohamed A.-H.; Gouda, Mohamed K. [Department of Materials Science and Engineering, Egypt–Japan University of Science and Technology, Alexandria (Egypt); Hefnawy, Ahmad M.; Kandil, Sherif H. [Department of Materials Science, Institute of Graduate Studies and Research, Alexandria University, Alexandria (Egypt)

    2016-04-01

    β-type titanium alloys are promising materials in the field of medical implants. The effect of β-phase stability on the mechanical properties, corrosion resistance and cytotoxicity of a newly designed β-type (Ti{sub 77}Nb{sub 17}Ta{sub 6}) biocompatible alloys are studied. The β-phase stability was controlled by the addition of small quantities of Fe and O. X-ray diffraction and microstructural analysis showed that the addition of O and Fe stabilized the β-phase in the treated solution condition. The strength and hardness have increased with the increase in β-phase stability while ductility and Young's modulus have decreased. The potentio-dynamic polarization tests showed that the corrosion resistance of the new alloys is better than Ti–6Al–4V alloy by at least ten times. Neutral red uptake assay cytotoxicity test showed cell viability of at least 95%. The new alloys are promising candidates for biomedical applications due to their high mechanical properties, corrosion resistance, and reduced cytotoxicity. - Highlights: • The properties and biocompatibility of new titanium alloys for biomedical applications were investigated. • Biocompatibility is excellent compared to Ti-6Al-4V in terms of a lower young's modulus and better corrosion resistance. • The newly designed alloys have good strength and lower Young's modulus combined with excellent corrosion resistance. • The new alloys have a strong potential for biomedical applications.

  14. Anisotropic properties of TaS2

    Institute of Scientific and Technical Information of China (English)

    Qiao Yan-Bin; Li Yan-Ling; Zhong Guo-Hua; Zeng Zhi; Qin Xiao-Ying

    2007-01-01

    The anisotropic properties of 1T- and 2H-TaS2 are investigated by the density functional theory within the framework of full-potential linearized augmented plane wave method. The band structures of 1T- and 2H-TaS2 exhibit anisotropic properties and the calculated electronic specific-heat coefficient γ of 2H-TaS2 accords well with the existing experimental value. The anisotropic frequency-dependent dielectric functions including the effect of the Drude term are analysed, where the εxx(ω) spectra corresponding to the electric field E perpendicular to the z axis show excellent agreement with the measured results except for the ε1xx(ω) of 1T-TaS2 below the energy level of 2.6 eV which is due to the lack of the enough CDW information for reference in our calculation. Furthermore, based on the values of optical effective mass ratio P of 1T and 2H phases it is found that the anisotropy in 2H-TaS2 is stronger than that in 1T-TaS2.

  15. HA/Ti composite for biomedical application by mechanical milling

    Institute of Scientific and Technical Information of China (English)

    刘咏; 刘芳; 周科朝; 黄伯云

    2003-01-01

    In order to overcome the poor mechanical properties of HA and the low bioactivity of Ti, HA/Ti com-posites with various compositions were prepared by mechanical milling. The effects of milling condition and the com-position on the microstructure, the density and the hardness of the composites were studied. The results show thatduring the ball milling process, Ti particles are refined and the homogeneity of the HA/Ti mixtures is improved;HA will partially decompose due to the existence of Ti and high sintering temperature. The microstructure of HA/Ti composites is highly dependent on the milling condition and the composition. In the microstructure, Ti phase con-nects to be a continuous network, and HA/Ti mixtures disperse in the network. The longer the milling time, the fi-ner the network will be. The density of HA/Ti composites decreases with the content of HA increasing and themilling time prolonging, because HA deteriorates the sinterability of Ti. The hardness of HA/Ti composites increa-ses firstly with the content of HA increasing, and then drops when the content of HA exceeds 30%. Addition ofHA will strengthen the HA/Ti composite but will decrease the density of the composite, which accounts for theeffect of HA on the hardness of the composites.

  16. Oxidation induced ionization and reactions of metal carbide clusters (Nb, Zr, V, Ta)

    Science.gov (United States)

    Deng, H. T.; Kerns, K. P.; Bell, R. C.; Castleman, A. W.

    1997-11-01

    Following our recent report of the oxidation induced formation of Ti8C12+ (H.T. Deng, K.P. Kerns, and A.W. Castleman, Jr., J. Chem. Phys. 104 (1996) 4862), the oxidation induced ionization of niobium and zirconium carbide clusters are studied using a triple quadrupole mass spectrometer coupled with a laser induced plasma reaction source. It was found that reactions of both of these neutral carbide clusters with dioxygen leads to formation of carbide ions. The ion product distributions show that zirconium carbide clusters mainly take the form of Met--Car cations, but niobium carbide clusters favor a cubic-like crystalline pattern. Furthermore, reactions of mass-selected NbxCy+ with dioxygen result in a sequential loss of C2 units from NbxCy+, and leads to formation of Nbx+ and NbxC+ depending on y being an even or odd number. However, NbxCy+ shows comparably low reactivity towards nitrous oxide through a single oxygen abstraction mechanism. In comparison with the reaction products of VxCy+ with dioxygen, the complementary information obtained in the present study suggests that the C2 unit is a basic building block for formation of small early transition metal carbide clusters. The oxidation induced ionization mechanisms are also discussed in relation with the stability, ionization potentials, and structures of the clusters.

  17. Nb K- and L3-edges XAFS study on the structure of supported Nb carbide catalyst

    Science.gov (United States)

    Ichikuni, N.; Yanagase, F.; Mitsuhara, K.; Hara, T.; Shimazu, S.

    2016-05-01

    Mesoporous silica SBA-15 supported NbC catalysts were prepared under reduced pressure of CH4-H2 gas in a closed circulating system. Nb K- and L 3-edges XAFS measurements revealed that small NbC cluster formed on SBA-15 support and gradual carburization process by lengthening the carburization temperature-maintaining period. Carburization degree of Nb species was clearly explained by using threshold energy shift of Nb L 3-edge XANES profile.

  18. Enhanced Interfacial Adhesion in HDPE/HA Composites by Surface Modification of HA Particles via in situ Polymerization and Copolymerization

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Hydroxyapatite ( HA )-reinforced high density polyethylene (HDPE) was developed as a bone replacement material. In order to enhance the interfacial bondiag between HA and polyethylene and improve the mechanical properties of HDPE/ HA composites, the surface of the micron-sized HA particles was modified by in situ polymerization of butyl acrylate ( BA ) and in situ copolynerization of vinyl triethoxyl silane (VTES) and BA ,then the modified HA particles were compounded with HDPE. The effects of the surface modification of HA on morphology and mechanical properties of HDPE/ HA composites were investigated. The experimental results show that the presence of HA particles does not inhibit the polymerization of BA . The poly( butyl acrylate) ( PBA ) segments on the HA surface enhance the compatibility between HA and HDPE, improve the dispersion of HA particles in HDPE matrix, and enhance the interfacial ndhesion between HA and matrix. Surface modifications, especially by in situ copolymerization of VTES and BA , significantly increase notch impact strengths and marginal stiffness and tensile strengths of HDPE/ HA composites. And it is found that there is a critical thickness of PBA coating on HA particles for optimum mechanical properties of HDPE / HA composites.

  19. Giant semiclassical magnetoresistance in high mobility TaAs{sub 2} semimetal

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Desheng [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Department of Physics, Center for Optoelectronics Materials and Devices, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Liao, Jian; Yi, Wei; Wang, Xia; Weng, Hongming, E-mail: ygshi@iphy.ac.cn, E-mail: hmweng@iphy.ac.cn; Shi, Youguo, E-mail: ygshi@iphy.ac.cn, E-mail: hmweng@iphy.ac.cn; Li, Yongqing; Dai, Xi; Fang, Zhong [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Li, Peigang [Department of Physics, Center for Optoelectronics Materials and Devices, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Luo, Jianlin [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)

    2016-01-25

    We report the observation of colossal positive magnetoresistance (MR) in single crystalline, high mobility TaAs{sub 2} semimetal. The excellent fit of MR by a single quadratic function of the magnetic field B over a wide temperature range (T = 2–300 K) suggests the semiclassical nature of the MR. The measurements of Hall effect and Shubnikov-de Haas oscillations, as well as band structure calculations, suggest that the giant MR originates from the nearly perfectly compensated electrons and holes in TaAs{sub 2}. The quadratic MR can even exceed 1 200 000% at B = 9 T and T = 2 K, which is one of the largest values among those of all known semi-metallic compounds, including the very recently discovered WTe{sub 2} and NbSb{sub 2}. The giant positive magnetoresistance in TaAs{sub 2} not only has a fundamentally different origin from the negative colossal MR observed in magnetic systems but also provides a nice complemental system that will be beneficial for applications in magnetoelectronic devices.

  20. Structural and Dielectric Properties of Ba5RNiNb9O30(R=La, Nd and Sm) ceramics

    Institute of Scientific and Technical Information of China (English)

    XU Man; HU Changzheng; ZHANG Hui; WU Bolin

    2006-01-01

    Three novel Ba5RNiNb9O30 (R= La, Nd and Sm) ceramics were prepared and characterized in the BaO-R2O3-NiO-Nb2O5 system. All three compounds are paraelectric phases adopting the filled tetragonal tungsten bronze (TB) structure at room temperature. At 1MHz, Ba5RNiNb9O30 ceramics have a high dielectric constants in the range 193-245.3, a low dielectric loss in range 0.0059-0.0087, and the temperature coefficients of the dielectric constant (τε) in the range -1 140--1 310×10-6·℃-1.Their temperature coefficientsof the dielectric constant are significantly reduced compared to those of Ba 5RTi 3Ta 7O 30(R=La, Nd, Sm) ceramics.

  1. 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.

  2. The 181Ta Nuclear Quadrupole Interaction in the Charge Density Wave Phases of 1T-TaS2

    Science.gov (United States)

    Ganal, P.; Butz, T.; Lerf, A.; Naito, M.; Nishihara, H.

    1990-04-01

    With a high resolution time differential perturbed angular correlation spectrometer we investigated the nuclear quadrupole interaction of Ta in 1T-TaS2 . The results obtained for the commensurate charge density wave phase lead to a revised assignment of the previously observed 181Ta NQR resonances. Differences in the intracluster architecture of the 13-atom Star of David cluster between 1T-TaS2 and 1T-TaSe2 could be responsible for the metal to semiconductor transition which occurs in lT-TaS2 but not in lT-TaSe2 .

  3. Ta thickness-dependent perpendicular magnetic anisotropy features in Ta/CoFeB/MgO/W free layer stacks

    Energy Technology Data Exchange (ETDEWEB)

    Yang, SeungMo; Lee, JaBin; An, GwangGuk [Novel Functional Materials and Devices Lab, The Research Institute for Natural Science, Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Kim, JaeHong [Division of Nano-Scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Chung, WooSeong [Nano Quantum Electronics Lab, Department of Electronics and Computer Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Hong, JinPyo, E-mail: jphong@hanyang.ac.kr [Novel Functional Materials and Devices Lab, The Research Institute for Natural Science, Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Division of Nano-Scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2015-07-31

    We describe Ta underlayer thickness influence on thermal stability of perpendicular magnetic anisotropy in Ta/CoFeB/MgO/W stacks. It is believed that thermal stability based on Ta underlay is associated with thermally-activated Ta atom diffusion during annealing. The difference in Ta thickness-dependent diffusion behaviors was confirmed with X-ray photoelectron spectroscopy analysis. Along with a feasible Ta thickness model, our observations suggest that an appropriate seed layer choice is needed for high temperature annealing stability, a critical issue in the memory industry. - Highlights: • We observed changes in the diffusion behavior with regard to Ta seed layer thickness. • It was observed that a thinner Ta seed layer induced more annealing-stable features. • However, ultra-thin (0.75 nm) Ta shows unstable characteristics about the annealing process. • It was possibly due to a rugged interface of the Ta layer by the island growth process.

  4. Spin polarization effect for molecule Ta2

    Institute of Scientific and Technical Information of China (English)

    Xie An-Dong

    2006-01-01

    Density functional theory (DFT) (B3p86) has been used to optimize the structure of the molecule Taa- The result shows that the ground state of molecule Ta,2 is a 7- multiple state and its electronic configuration is 7∑+u which shows the spin polarization effect for molecule Ta2 of transition metal elements for the first time. Meanwhile, spin pollution has not been found because the wavefunction of the ground state does not mix with those of higher states. So, the fact that the ground state of molecule Ta2 is a 7-multiple state indicates a spin polarization effect of molecule Ta2 of the transition metal elements, i.e. there exist 6 parallel spin electrons and the non-conjugated electrons are greatest in number. These electrons occupy different space orbitals so that the energy of molecule Ta2 is minimized. It can be concluded that the effect of parallel spin of the molecule Ta2 is larger than the effect of the conjugated molecule, which is obviously related to the effect of d-electron delocalization. In addition, the Murrell-Sorbie potential functions with parameters for the ground state 7∑+u and other states of the molecule Ta2 are derived. The dissociation energy De, equilibrium bond length Re and vibration frequency ωe for the ground state of molecule Ta2 are 4.5513eV, 0.2433nm and 173.06cm-1, respectively. Its force constants f2,f3 and f4 are 1.5965×l02aJ·nm-2,-6.4722×l03aJ·nm-3 and 29.4851×04aJ·nm-4, respectively. Other spectroscopic data ωe χe, Be and αe for the ground state of Ta2 are 0.2078cm-1, 0.0315cm-1 and 0.7858×104 cm-1, respectively.

  5. Reconstruction of HaSNPV with helicoverpa hormone receptor 3

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In order to develop a more efficient virus for controlling the cotton bollworm Helicoverpa armigera,Helicoverpa hormone receptor 3 (HHR3), which is involved in the ecdysteroid regulatory pathway, was used to genetically modify wild HaSNPV. HaSNPV-HHR3 budded virus and occlusion body virus were constructed in three steps: preparation of pFastBacHaPhpP10-HHR3 donor plasmid, transposition of HHR3 into the HaBacHZ8 bacmid, and transfection of HzAM1 cells to get HaSNPV-HHR3 virus. HHR3was proved to be expressed in the HaSNPV-HHR3 virus infected HzAM1 cells by immunoblotting. Results of bioassay indicated that the body weight of the HaSNPV-HHR3 infected larvae was lower than the larvae infected with wild virus and uninfected normal larvae, which suggests that HaSNPV-HHR3 delayed larval growth.

  6. Wet ammonia Synthesis of Semiconducting N:Ta2O5, Ta3N5 and β-TaON Films for Photoanode Applications

    NARCIS (Netherlands)

    Dabirian, A.; Van 't Spijker, H.; Van der Krol, R.

    2012-01-01

    Tantalum oxynitride (β-TaON) is a promising photoanode material for photoelectrochemical water splitting. However, the synthesis of phase-pure β-TaON films is a challenging task. This paper describes a novel approach to achieve this by the controlled nitridation of Ta2O5 films under a flow of ammoni

  7. Large enhanced perpendicular magnetic anisotropy in CoFeB/MgO system with the typical Ta buffer replaced by an Hf layer

    Directory of Open Access Journals (Sweden)

    T. Liu

    2012-09-01

    Full Text Available By systematically comparing the magnetic properties of the Ta/CoFeB/Ta and MgO/CoFeB/MgO structures with and without a submonolayer of MgO, Ta, V, Nb, Hf and W inserted in the middle of the CoFeB layer, we have proved that the observed perpendicular magnetic anisotropy (PMA in Ta/CoFeB/MgO sandwiches is solely originated from the CoFeB/MgO interface with the Ta buffer acting to enhance the CoFeB/MgO interface anisotropy significantly. Moreover, replacing Ta with Hf causes the CoFeB/MgO interfacial PMA further enhanced by 35%, and the CoFeB layer with perpendicular magnetization has a much larger critical thickness accordingly, leaving a wider thickness margin for the CoFeB/MgO-based perpendicular magnetic tunnel junction optimization. Also the sputter deposited thin Hf films are amorphous with low surface roughness. These results will ensure the Hf/CoFeB/MgO more promising material system for PMA device development.

  8. Thermally stable perpendicular magnetic anisotropy features of Ta/TaO{sub x}/Ta/CoFeB/MgO/W stacks via TaO{sub x} underlayer insertion

    Energy Technology Data Exchange (ETDEWEB)

    Yang, SeungMo; Lee, JaBin; An, GwangGuk [Novel Functional Materials and Devices Laboratory, Research Institute for Natural Science, Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Kim, JaeHong [Division of Nano-Scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Chung, WooSeong [Nano Quantum Electronics Lab, Department of Electronics and Computer Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Hong, JinPyo, E-mail: jphong@hanyang.ac.kr [Novel Functional Materials and Devices Laboratory, Research Institute for Natural Science, Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Division of Nano-Scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2014-09-21

    We report that a TaO{sub x} underlayer enhances the stability of perpendicular magnetic anisotropy (PMA) in TaO{sub x}/Ta/CoFeB/MgO stacks during annealing; control of oxygen content in the TaO{sub x} layer is critical. X-ray photoelectron spectroscopy observations revealed clear suppression of Ta atom diffusion towards the CoFeB/MgO interface or MgO regions. The TaO{sub x} underlayer possibly served as a diffusion sponge, permitting some thermally activated Ta atoms to impregnate the TaO{sub x} underlayer via a diffusion path, such as grain boundaries. We propose a possible mechanism for enhanced PMA stability based on diffusion of thermally activated Ta atoms.

  9. Intrabeam Scattering Studies at CesrTA

    CERN Document Server

    Fermilab; Peterson, DP; Rider, NT; Rubin, DL; Holtzapple, R; Campbell, R; Shanks, JP; Strohman, CR; Wang, S; Papaphilippou, Y

    2012-01-01

    Intrabeam scattering (IBS) dilutes the emittance of low energy, low emittance rings. Because CesrTA can be operated at low energies with low transverse emittances and high bunch intensity, it is well-suited for the study of IBS. Furthermore, CesrTA is instrumented for accurate beam size measurements in all three dimensions, providing the possibility of a complete determination of the intensity dependence of emittances. Measurements from dedicated IBS machine studies at different emittances, intensities, and species are presented. A model based on analytic IBS theories is developed and compared to the data.

  10. Structure and physical properties of EuTa{sub 2}O{sub 6} tungsten bronze polymorph

    Energy Technology Data Exchange (ETDEWEB)

    Kolodiazhnyi, T., E-mail: kolodiazhnyi.taras@nims.go.jp; Sakurai, H.; Vasylkiv, O.; Borodianska, H. [National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Forbes, S.; Mozharivskyj, Y. [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S4M1 (Canada)

    2014-08-11

    A tetragonal tungsten bronze (TTB) polymorph of EuTa{sub 2}O{sub 6} was prepared and analyzed. EuTa{sub 2}O{sub 6} crystallizes in the centrosymmetric Pnam space group (with unit cell: a = 12.3693, b = 12.4254, and c = 7.7228 Å) isomorphous with orthorhombic β-SrTa{sub 2}O{sub 6}. In contrast to early reports, we see no evidence of deviation from paramagnetic Curie-Weiss behavior among the Eu{sup 2+} 4f{sup 7}spins in EuTa{sub 2}O{sub 6} down to 2 K. Dielectric constant shows a broad peak at ca. 50 K with dielectric dispersion resembling diffuse phase transition. The relaxation time, however, follows a simple (non-freezing) thermally activated process with an activation energy of 92 meV and an attempt frequency of f{sub 0} = 5.79 × 10{sup 12 }Hz. A thermal conductivity of EuTa{sub 2}O{sub 6} shows a low-temperature (T ≈ 30 K) “plateau” region reminiscent of a glass-like behaviour in Nb-based TTB compounds. This behaviour can be attributed to the loosely bound Eu{sup 2+} ions occupying large tricapped trigonal prismatic sites in the EuTa{sub 2}O{sub 6} structure.

  11. Preparation of c-Axis Oriented LiNb1-xTaxO3 Films on Si(111) Substrates by a Modified Sol-gel Process

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In this work, we succeeded in the preparation of LiNb1-xTaxO3 films on Si(111) substrates by means of sol-gel process, and the usual sol-gel process for the preparation of LiNbO3 and LiTaO3 films on Si substrates was improved by adding a 33% aqueous solution of CH3CH2OH to the mixed sols of LiNb(OCH2CH3)6 and LiTa(OCH2CH3)6. The crystallization behavior of LiNb1-xTaxO3 films on Si(111) substrates has been studied. Highly c-axis oriented LiNb1-xTaxO3 films have been obtained within the tantalum composition range of 0

  12. Antitumor activities of a new indolocarbazole substance, NB-506, and establishment of NB-506-resistant cell lines, SBC-3/NB.

    Science.gov (United States)

    Kanzawa, F; Nishio, K; Kubota, N; Saijo, N

    1995-07-01

    The novel anticancer glucosyl derivative of indolo-carbazole (NB-506), an inhibitor of DNA topoisomerase I, exhibited strong in vitro cytotoxicity against various human cancer cell lines. In order to elucidate its cytotoxic mechanisms, we established nine NB-506-resistant sublines with different resistance ratios from human small cell lung cancer cells (SBC-3/P) by stepwise and brief exposure (24 h) to NB-506. Among them, SBC-3/NB#9 was 454 times more resistant to NB-506 than the parent cell line. The SBC-3/NB#9 cells showed cross-resistance only to topoisomerase I inhibitors, such as 11,7-ethyl-10-[4-(1-piperidino)-1-piperidino] carbonyloxycamptothecia and 7-ethyl-10-hydroxy-camptothecin, and not to other anticancer drugs, such as vincristine, vinblastine, Adriamycin, etoposide, and teniposide. These results indicate that the difference on the effect of topoisomerase I was considered to be related to a resistance mechanism. The topoisomerase I activities of nuclear extracts eluted from SBC-3/NB#9 cells was only one-tenth of the parent cell activity. A Western blotting study indicated that this lower activity was due to a lower amount of DNA topoisomerase I. Furthermore, we found correlations between topoisomerase I activity and sensitivity to NB-506 in sublines with different degrees of resistance. Accumulation of 3H-labeled NB-506 by SBC-3/NB#9 cells was only one-fifth of that by the parent cells, whereas intracellular accumulation of 3H-labeled camptothecin by both cell lines did not differ. The reduction of accumulation was specific to NB-506, and this result may explain why the resistance ratio for NB-506 was higher than those for 11,7-ethyl-10-[4-(1-piperidino)-1-piperidino] carbonyloxycamptothecin and 7-ethyl-10-hydroxy-camptothecin.

  13. 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.

  14. X-Cut LiNbO3 Optical Modulators Using Gap-Embedded Patch-Antennas for Wireless-Over-Fiber Systems

    Directory of Open Access Journals (Sweden)

    Yusuf Nur Wijayanto

    2012-01-01

    Full Text Available We propose an x-cut LiNbO3 optical modulator using gap-embedded patch-antennas for wireless-over-fiber systems. The proposed device is composed of an array of narrow-gap-embedded patch-antennas and an optical waveguide located at the center of the gap without a buffer layer. The modulation efficiency of the proposed x-cut LiNbO3 optical modulators was enhanced by 6 dB compared to the z-cut LiTaO3-based devices.

  15. Engineering Mathematics Assessment Using "MapleTA"

    Science.gov (United States)

    Jones, Ian S.

    2008-01-01

    The assessment of degree level engineering mathematics students using the computer-aided assessment package MapleTA is discussed. Experience of academic and practical issues for both online coursework and examination assessments is presented, hopefully benefiting other academics in this novel area of activity. (Contains 6 figures and 1 table.)

  16. Miks ta nii teeb? / Kristiina Voolaid

    Index Scriptorium Estoniae

    Voolaid, Kristiina

    1999-01-01

    Kuidas mõtleb ruumikujundaja, kui ta valib vorme, värve, materjale ja esemeid? Sisearhitekt Kristiina Voolaid seletab oma mõtteid Kawe Plaza hoones asuvate Hüvitusfondi ja Werol Tehased kontorite ning noorele perekonnale sisustatud vanalinnakorteri näitel

  17. Miks ta nii teeb? / Kristiina Voolaid

    Index Scriptorium Estoniae

    Voolaid, Kristiina

    1999-01-01

    Kuidas mõtleb ruumikujundaja, kui ta valib vorme, värve, materjale ja esemeid? Sisearhitekt Kristiina Voolaid seletab oma mõtteid Kawe Plaza hoones asuvate Hüvitusfondi ja Werol Tehased kontorite ning noorele perekonnale sisustatud vanalinnakorteri näitel

  18. En busca del taíno, historia de una pelea cubana contra el normativismo

    Directory of Open Access Journals (Sweden)

    Daniel Torres Etayo

    2008-11-01

    Full Text Available Durante mucho tiempo la Arqueología caribeña ha usado ampliamente el término“Taíno” para identificar a las sociedades tribales más desarrolladas encontradas por los europeos en el momento de la conquista. Sin embargo, cuando penetramos en el profuso mundo de las investigaciones realizadas descubrimos que “lo taíno” se refiere a fenómenos distintos, dependiendo del autor, las evidencias manejadas y el país. Hasta el día de hoy, el concepto de “Cultura Taína” ha buscado, salvo raras excepciones, presentar un artificial panorama homogéneo atribuible a todos estos grupos aborígenes que poblaban las Grandes Antillas. En Cuba el caso no es diferente y el dilatado camino recorrido para encontrar una definición para la cultura o las culturas agroceramistas que ocuparon el suelo cubano, aun no ha llegado a su fin. En el trabajo se presentan las diferentes posiciones se han presentado a lo largo del tiempo, y se destacan las dos grandes líneas teóricas: la etnográfica y la particularista. También se realiza un análisis crítico de la tendencia marxista generalizadora en la Arqueología cubana y la sugerencia de algunos problemas teóricos-metodológicos a resolver desde el propio marxismo para lograr la definición, si es que existe, de la llamada cultura taina en Cuba.

  19. Roles of TaON and Ta(3)N(5) in the visible-Fenton-like degradation of atrazine.

    Science.gov (United States)

    Du, Yingxun; Zhao, Lu; Zhang, Yuanyuan

    2014-02-28

    In this study, the roles of TaON and Ta3N5 in the degradation of atrazine by the visible-Fenton-like system were examined in detail. The TaON and Ta3N5 samples prepared by the nitridation of Ta2O5 and characterized by XRD, DRS, BET and PL analyses. The results showed that the TaON sample had weaker absorption in the visible region but higher specific surface area than the Ta3N5 sample. The degradation rate of atrazine in visible-TaON-Fenton-like system was 2.64 times than that in visible-Ta3N5-Fenton-like system. Both Fe(2+) and H2O2 could be reduced by eCB (electrons in the conduction band) in TaON or Ta3N5, while atrazine could not be oxidized by hVB (holes in the valance band). OH is the active species for the degradation of atrazine in visible-TaON/Ta3N5-Fenton-like systems. Majority of OH originated from Fenton reaction. After Fe(3+) was reduced by eCB to Fe(2+), Fe(2+) reacted quickly with H2O2 to generate OH. In addition, by capturing eCB, a little of H2O2 was reduced to yield OH, which contributed a small fraction of atrazine degradation. Based on the experimental results, the roles of TaON and Ta3N5 in the visible-Fenton-like system were proposed. And the higher photocatalytic activity of TaON than Ta3N5 was suggested to be due to the higher separation efficiency of electrons and holes, which may be related to the larger specific surface area.

  20. 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...

  1. HA/UHMWPE Nanocomposite Produced by Twin-screw Extrusion

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The HA/UHMWPE nanocomposite is compounded by twin-screw extrusion of the HA and UHMWPE powder mixture in paraffin oil and then compression molded to a sheet form. TGA measurement shows the HA weight loss after processing is about 1%-2% . FTIR spectra indicate the paraffin oil residue is trivial and UHMWPE is not oxidized. SEM reveals the HA nano particles are homogeneously dispersed by twin- screw extrusion and the inter-particle spaces are penetrated with UHMWPE fibrils by swelling treatment. HRTEM image indicates the HA particles and UHMWPE are intimately contacted by mechanical interlocking. Compared with the unfilled UHMWPE, stiffness of the composite with the HA volume fraction 0.23 was significantly enhanced to 9 times without detriment of the yield strength and the ductility.

  2. In vitro cytotoxicity and hemocompatibility studies of Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf biomedical shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wang, B L; Li, L; Zheng, Y F, E-mail: blwang@hrbeu.edu.c, E-mail: lili_heu@hrbeu.edu.c, E-mail: yfzheng@pku.edu.c [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China)

    2010-08-01

    The in vitro cytotoxicity and hemocompatibility of the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf biomedical shape memory alloys (SMAs) were investigated by cell culture (L-929 fibroblast cell), hemolytic test and platelet adhesion test, with CP Ti as a reference material. The cytotoxicity test indicates that all the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf SMAs show over 94% cell viability for different incubation times (2, 4 and 7 days) in comparison with a negative control and CP Ti. The cell morphology observation shows good polygon-like adherent growth and proliferation of L-929 in the extracts of all the test samples and CP Ti. These results suggest excellent cytocompatibility for the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf SMAs. The hemolytic test reveals that the hemolysis ratios of the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf alloys are far less than 5%, so they cannot give rise to acute hemolysis. The platelet morphology observation shows almost the same adhered platelet morphology and activation ratio for the test samples in comparison with CP Ti, except the Ti-22Nb-6Hf alloy, which shows a lower activation ratio of platelets, indicating excellent blood compatibility. Therefore, it is proposed that the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf SMAs will be candidates to replace Ti-Ni for biomedical applications.

  3. In vitro cytotoxicity and hemocompatibility studies of Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf biomedical shape memory alloys.

    Science.gov (United States)

    Wang, B L; Li, L; Zheng, Y F

    2010-08-01

    The in vitro cytotoxicity and hemocompatibility of the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf biomedical shape memory alloys (SMAs) were investigated by cell culture (L-929 fibroblast cell), hemolytic test and platelet adhesion test, with CP Ti as a reference material. The cytotoxicity test indicates that all the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf SMAs show over 94% cell viability for different incubation times (2, 4 and 7 days) in comparison with a negative control and CP Ti. The cell morphology observation shows good polygon-like adherent growth and proliferation of L-929 in the extracts of all the test samples and CP Ti. These results suggest excellent cytocompatibility for the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf SMAs. The hemolytic test reveals that the hemolysis ratios of the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf alloys are far less than 5%, so they cannot give rise to acute hemolysis. The platelet morphology observation shows almost the same adhered platelet morphology and activation ratio for the test samples in comparison with CP Ti, except the Ti-22Nb-6Hf alloy, which shows a lower activation ratio of platelets, indicating excellent blood compatibility. Therefore, it is proposed that the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf SMAs will be candidates to replace Ti-Ni for biomedical applications.

  4. Sequence analysis for the complete proviral genome of reticuloendotheliosis virus Chinese strain HA9901

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The genomic DNA extracted from chicken embryo fibroblast (CEF) infected with a Chinese field isolate HA9901 of reticuloendotheliosis virus (REV) was used as the template to amplify the REV proviral genomic cDNA by PCR with 6 pairs of primers according to published sequences. Six overlapping fragments were amplified, cloned into the TA vector and sequenced, including a fragment which was amplified from the circular proviral cDNA and covering both 5'- and 3'-ends. The complete sequence of the whole genome was established and analyzed with a DNAstar software. Comparisons of the sequence with two other strains demonstrated that the genomes of REV were relatively conservative, the homogenecity for all genes or LTR fragments of the 3 strains was over 92%, no matter whether they were isolated from different species and regions in different years. But, the homology of Chinese strain HA9901 to a fowl pox virus-associated strain from Chickens was higher than that to strain SNV isolated from ducks.

  5. Distribution of Nb atom in the TiAl+Nb system

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Based on MEAM (the modified embedded atom method) potential and an average atom model similar to B-W (Bragg-Williams) method, the distribution of Nb atoms in TiAl+Nb compounds with various composition was calculated. The calculation results showed that Nb atoms prefer to occupy the Ti sublattice of L10 structure for all compounds in question. With increasing atomic fraction of Nb and Al, Nb atoms exhibited a trend of ordered distribution on the Ti sublattice and result in a new L10 derivative superlattice structure.

  6. Enhancement of the superconducting critical temperature in Nb/Py/Nb trilayers

    Energy Technology Data Exchange (ETDEWEB)

    Ilyina, E.A., E-mail: i.katerina@sa.infn.it [CNR-SPIN Salerno, Dipartimento di Fisica ' E.R. Caianiello' , Universita degli Studi di Salerno, Via Ponte don Melillo, Fisciano I-84084 (Italy); Hernandez, J.M.; Garcia-Santiago, A. [Departament de Fisica Fonamental, Facultat de Fisica, Universitat de Barcelona, Avinguda Diagonal 645, ES-08028 Barcelona (Spain); Institut de Nanociencia i Nanotecnologia IN2UB, Universitat de Barcelona, c. Marti i Franques 1, ES-08028 Barcelona (Spain); Cirillo, C.; Attanasio, C. [CNR-SPIN Salerno, Dipartimento di Fisica ' E.R. Caianiello' , Universita degli Studi di Salerno, Via Ponte don Melillo, Fisciano I-84084 (Italy)

    2012-09-15

    Superconducting critical temperature, T{sub c}, have been measured in a series of Nb/Py/Nb (here Py = Ni{sub 80}Fe{sub 20}) trilayers having constant Py thickness, d{sub Py} = 432 nm, and variable Nb thickness, d{sub Nb}, in the range 20-30 nm. We have observed that, for d{sub Nb} between 23 and 27 nm, resistive transitions shift towards higher temperature if stripe domains are present in the Py layer. We relate those observations to the non-homogeneous magnetization in the Py layer due to the presence of stripe domain structures.

  7. Oxygen Atom Adsorption on and Diffusion into Nb(110) and Nb(100) from First Principles

    Energy Technology Data Exchange (ETDEWEB)

    Tafen, De Nyago; Gao, Michael C

    2013-11-01

    In order to understand the dynamics of oxidation of Nb, we examine the adsorption, absorption, and diffusion of an oxygen atom on, in, and into Nb(110) and Nb(100) surfaces, respectively, using density functional theory. Our calculations predict that the oxygen atom adsorbs on the threefold site on Nb(110) and the fourfold hollow site on Nb(100), and the adsorption energy is -5.08 and -5.18 eV respectively. We find the long and short bridge sites to be transition states for O diffusion on Nb(110), while the on top site is a rank-2 saddle point. In the subsurface region, the oxygen atom prefers the octahedral site, as in bulk niobium. Our results also show that the O atom is more stable on Nb(110) subsurface than on Nb(100) subsurface. The diffusion of oxygen atoms into niobium surfaces passes through transition states where the oxygen atom is coordinated to four niobium atoms. The diffusion barriers of the oxygen atom into Nb(110) and Nb(100) are 1.81 and 2.05 eV, respectively. Analysis of the electronic density of states reveals the emergence of well localized electronic states below the lowest states of clean Nb surfaces due to d-p orbital hybridization.

  8. Oxygen Atom Adsorption on and Diffusion into Nb(110) and Nb(100) from First Principles

    Energy Technology Data Exchange (ETDEWEB)

    Tafen, De Nyago; Gao, Michael C

    2013-11-01

    In order to understand the dynamics of oxidation of Nb, we examine the adsorption, absorption, and diffusion of an oxygen atom on, in, and into Nb(110) and Nb(100) surfaces, respectively, using density functional theory. Our calculations predict that the oxygen atom adsorbs on the threefold site on Nb(110) and the fourfold hollow site on Nb(100), and the adsorption energy is -5.08 and -5.18 eV respectively. We find the long and short bridge sites to be transition states for O diffusion on Nb(110), while the on top site is a rank-2 saddle point. In the subsurface region, the oxygen atom prefers the octahedral site, as in bulk niobium. Our results also show that the O atom is more stable on Nb(110) subsurface than on Nb(100) subsurface. The diffusion of oxygen atoms into niobium surfaces passes through transition states where the oxygen atom is coordinated to four niobium atoms. The diffusion barriers of the oxygen atom into Nb(110) and Nb(100) are 1.81 and 2.05 eV, respectively. Analysis of the electronic density of states reveals the emergence of well localized electronic states below the lowest states of clean Nb surfaces due to d-p orbital hybridization.

  9. 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.

  10. TeleEducation NB. Report 1994.

    Science.gov (United States)

    TeleEducation NB, Fredericton (New Brunswick).

    This is the first report of TeleEducation NB, the bilingual education network of New Brunswick, Canada. The mission of TeleEducation NB is to provide residents of New Brunswick and other regions cost-effective, equitable access to a range of training, information, and educational services in both official languages, English and French. The network…

  11. 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.

  12. Atomically engineering Cu/Ta interfaces.

    Energy Technology Data Exchange (ETDEWEB)

    Webb, Edmund Blackburn, III (, Sandia National Laboratories, Albuquerque, NM); Zhou, Xiao Wang

    2007-09-01

    This report summarizes the major research and development accomplishments for the late start LDRD project (investment area: Enable Predictive Simulation) entitled 'Atomically Engineering Cu/Ta Interfaces'. Two ultimate goals of the project are: (a) use atomistic simulation to explore important atomistic assembly mechanisms during growth of Cu/Ta multilayers; and (b) develop a non-continuum model that has sufficient fidelity and computational efficiency for use as a design tool. Chapters 2 and 3 are essentially two papers that address respectively these two goals. In chapter 2, molecular dynamics simulations were used to study the growth of Cu films on (010) bcc Ta and Cu{sub x}Ta{sub 1-x} alloy films on (111) fcc Cu. The results indicated that fcc crystalline Cu films with a (111) texture are always formed when Cu is grown on Ta. The Cu films are always polycrystalline even when the Ta substrate is single crystalline. These polycrystalline films are composed of grains with only two different orientations, which are separated by either orientational grain boundaries or misfit dislocations. Periodic misfit dislocations and stacking fault bands are observed. The Cu film surface roughness was found to decrease with increasing adatom energy. Due to a Cu surface segregation effect, the Cu{sub x}Ta{sub 1-x} films deposited on Cu always have a higher Cu composition than that used in the vapor mixture. When Cu and Ta compositions in the films are comparable, amorphous structures may form. The fundamental origins for all these phenomena have been studied in terms of crystallography and interatomic interactions. In chapter 3, a simplified computational method, diffusional Monte Carlo (dMC) method, was developed to address long time kinetic processes of materials. Long time kinetic processes usually involve material transport by diffusion. The corresponding microstructural evolution of materials can be analyzed by kinetic Monte Carlo simulation methods, which

  13. Deformation Twinning During Nanoindentation of Nanocrystalline Ta

    OpenAIRE

    Wang, Y. M.; Hodge, A. M.; Biener, J.; Hamza, A.V.; Barnes, D E; Liu, Kai; Nieh, T. G.

    2005-01-01

    The deformation mechanism of body-centered cubic (bcc) nanocrystalline tantalum with grain sizes of 10–30 nm is investigated by nanoindentation, scanning electron microscopy and high-resolution transmission electron microscopy. In a deviation from molecular dynamics simulations and existing experimental observations on other bcc nanocrystalline metals, the plastic deformation of nanocrystalline Ta during nanoindentation is controlled by deformation twinning. The observation of multiple twin i...

  14. Isolation and identiifcation of Serratia marcescens Ha1 and herbicidal activity of Ha1‘pesta’ granular formulation

    Institute of Scientific and Technical Information of China (English)

    YANG Juan; WANG Wei; YANG Peng; TAO Bu; YANG Zheng; ZHANG Li-hui; DONG Jin-gao

    2015-01-01

    A total of 479 bacterial strains were isolated from brine (Bohai, Qinhuangdao City, Hebei Province, China). Bioassay results indicated that 4 strains named Ha1, Ha17, Ha38, and Ha384 had herbicidal activity. And strain Ha1 had the highest effective herbicidal activity. As a result, this study aims to identify strain Ha1, characterize its physiological and biological activities, evaluate the herbicidal activity of its metabolites, and develop a‘pesta’ formulation and assess its effectiveness on Digitaria sanguinalis. Ha1 was identiifed as Serratia marcescens based on 16S rDNA sequencing. This strain has a lfagel um, a diameter of 0.5 to 0.8μm, and a length of 0.9 to 2.0μm. The indole test shows positive results, and the catalase enzyme exhibits strong positive reactions. Results further showed that the inhibitory concentration (IC50) of the crude extracts to D. sanguinalis radicula and coleoptile were 3.332 and 2.828 mg mL–1, respectively. Both the suppression of D. sanguinalis and the cel viability of the Ha1 formulation in‘pesta’ were higher when stored at 4°C than at (25±2)°C. These results indi-cated that S. marcescens Ha1 can potential y be used as a biocontrol agent against D. sanguinalis.

  15. 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.

  16. 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.

  17. Syntheses and Properties of Homoleptic Carbonyl and Trifluorophosphane Niobates: [Nb(CO)(6)](-), [Nb(PF(3))(6)](-) and [Nb(CO)(5)](3)(-) (,)(1).

    Science.gov (United States)

    Barybin, Mikhail V.; Ellis, John E.; Pomije, Marie K.; Tinkham, Mary L.; Warnock, Garry F.

    1998-12-14

    Reductive carbonylations of NbCl(4)(THF)(2), THF = tetrahydrofuran, mediated by sodium naphthalene in 1,2-dimethoxyethane, DME, or sodium anthracene in THF, provide [Nb(CO)(6)](-) as the tetraethylammonium salt in 60% or 70% isolated yields, respectively, the highest known for atmospheric pressure syntheses of this metal carbonyl. Corresponding reductions involving PF(3) give about 40% yields of [Et(4)N][Nb(PF(3))(6)], which in the past was only accessible by a photochemical route. Electrochemical data for [Nb(CO)(6)](-) and [Nb(PF(3))(6)](-) are compared and show that the PF(3) complex is almost 1 V more difficult to oxidize than the CO analogue. Protonation of [Nb(PF(3))(6)](-) by concentrated sulfuric acid yields a volatile, thermally unstable species, which has been shown by (1)H NMR and mass spectral studies to be the new niobium hydride, Nb(PF(3))(6)H. Previously unpublished (93)Nb and (13)C NMR studies corroborate prior claims that the sodium metal reduction of [Nb(CO)(6)](-) in liquid ammonia affords [Nb(CO)(5)](3)(-), the only known Nb(III-) species. The first details of this synthesis and those of [Nb(CO)(5)H](2)(-), [Nb(CO)(5)SnPh(3)](2)(-), [Nb(CO)(5)NH(3)](-), and [Nb(CO)(5)(CNtBu)](-) are presented.

  18. Võidupüha 8. mail? / Leonti Kährik

    Index Scriptorium Estoniae

    Kährik, Leonti

    2005-01-01

    Eesti peaks väärikalt tähistama võidupüha kui euroopalike demokraatlike väärtuste võitu natsismi ja fašismi üle. Lähtudes 1940. a. juunini Eestis kehtinud vööndiajast, võiks võidupüha tähistada 8. mail

  19. Võidupüha 8. mail? / Leonti Kährik

    Index Scriptorium Estoniae

    Kährik, Leonti

    2005-01-01

    Eesti peaks väärikalt tähistama võidupüha kui euroopalike demokraatlike väärtuste võitu natsismi ja fašismi üle. Lähtudes 1940. a. juunini Eestis kehtinud vööndiajast, võiks võidupüha tähistada 8. mail

  20. ha Platoni ordeni sai kaks saarlast / Isa Andreas

    Index Scriptorium Estoniae

    Andreas, Isa

    2009-01-01

    ha Platoni päeval päeval jagas metropoliit Stefanus püha Platoni ordeneid aktiivsetele kirikutegelastele ning pühitseti Tartu piiskopiks arhimandriit Eelija(Ojaperv) ja Pärnu ja Saare piiskopiks arhimandriit Aleksander (Hopjorski)

  1. ha Platoni ordeni sai kaks saarlast / Isa Andreas

    Index Scriptorium Estoniae

    Andreas, Isa

    2009-01-01

    ha Platoni päeval päeval jagas metropoliit Stefanus püha Platoni ordeneid aktiivsetele kirikutegelastele ning pühitseti Tartu piiskopiks arhimandriit Eelija(Ojaperv) ja Pärnu ja Saare piiskopiks arhimandriit Aleksander (Hopjorski)

  2. Nanoindentation and Adhesion Properties of Ta Thin Films

    Directory of Open Access Journals (Sweden)

    Yuan-Tsung Chen

    2013-01-01

    Full Text Available Ta films were sputtered onto a glass substrate with thicknesses from 500 Å to 1500 Å under the following conditions: (a as-deposited films were maintained at room temperature (RT, (b films were postannealed at TA=150°C for 1 h, and (c films were postannealed at TA=250°C for 1 h. X-ray diffraction (XRD results revealed that the Ta films had a body-centered cubic (BCC structure. Postannealing conditions and thicker Ta films exhibited a stronger Ta (110 crystallization than as-deposited and thinner films. The nanoindention results revealed that Ta thin films are sensitive to mean grain size, including a valuable hardness (H and Young’s modulus (E. High nanomechanical properties of as-deposited and thinner films can be investigated by grain refinement, which is consistent with the Hall-Petch effect. The surface energy of as-deposited Ta films was higher than that in postannealing treatments. The adhesion of as-deposited Ta films was stronger than postannealing treatments because of crystalline degree effect. The maximal H and E and the optimal adhesion of an as-deposited 500-Å-thick Ta film were 15.6 GPa, 180 GPa, and 51.56 mJ/mm2, respectively, suggesting that a 500-Å-thick Ta thin film can be used in seed and protective layer applications.

  3. Defect-inhibited incommensurate distortion in Ta2NiSe7

    Science.gov (United States)

    Fleming, R. M.; Sunshine, S. A.; Chen, C. H.; Schneemeyer, L. F.; Waszczak, J. V.

    1990-09-01

    We have observed evidence of an incommensurate structural distortion in the ternary chalcogenide Ta2NiSe7. The structure of Ta2NiSe7 is similar to FeNb3Se10 with one tantalum-centered trigonal prismatic chain and two inequivalent chains with octahedral coordination. Anomalies are observed in the resistance and magnetic susceptibility near 52.5 K. X-ray- and electron-diffraction data show the presence of an incommensurate modulation at temperatures below 52.5 K and strong diffuse scattering above 52.5 K. Hysteresis in the resistance and x-ray order parameter suggest that true long-range order of the lattice modulation is never achieved. We interpret the diffuse scattering as resulting from an inhibition of the phase transition caused by strong interactions between the lattice distortion and impurities or defects. Based on the transport data, we interpret the incommensurate structural distortion as being electronic in origin, a charge-density wave.

  4. The Optical Properties of Nanostructured Ta2O5 Films

    Institute of Scientific and Technical Information of China (English)

    Minmin Zhu; Wei Miao; Zhengjun Zhang

    2006-01-01

    Amorphous Ta2O5 films were prepared on Si (100) substrates by thermal oxidization. The film consisted of amorphous Ta2O5 nanostructure that grew vertically and compactly at a large range. It was found that Ta2O5 films became crystalline when annealed at or above 650℃ and remained amorphous below 650℃. The effects of annealing on the optical properties of Ta2O5 film were also discussed. It is estimated that the refraction indexes and the optical energy gaps of both amorphous Ta2O5 film and crystal one are stable. The optical energy gap of as-deposited Ta2O5 film is about 4.81 eV. The above results indicate that Ta2O5 films have a promising application in the optical devices.

  5. Preparation of bioactive porous HA/PCL composite scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, J.; Guo, L.Y.; Yang, X.B. [Key Laboratory of Advanced Technologies of Materials (Ministry of Education), School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Weng, J. [Key Laboratory of Advanced Technologies of Materials (Ministry of Education), School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China)], E-mail: jweng@swjtu.cn

    2008-12-30

    Porous hydroxyapatite (HA) bioceramic scaffold has been widely attracted the attention to act as a three-dimensional (3D) template for cell adhesion, proliferation, differentiation and thus promoting bone and cartilage regeneration because of its osteoinduction. However, the porous bioceramic scaffold is fragile so that it is not suitable to be applied in clinic for bone repair or replacement. Therefore, it is significant to improve the mechanical property of porous HA bioceramics while the interconnected structure is maintained for tissue ingrowth in vivo. In the present research, a porous composite scaffold composed of HA scaffold and polycaprolactone (PCL) lining was fabricated by the method of polymer impregnating to produce HA scaffold coated with PCL lining. Subsequently, the composite scaffolds were deposited with biomimetic coating for improving the bioactivity. The HA/PCL composite scaffolds with improved mechanical property and bioactivity is expected to be a promising bone substitute in tissue engineering applications.

  6. Preparation of bioactive porous HA/PCL composite scaffolds

    Science.gov (United States)

    Zhao, J.; Guo, L. Y.; Yang, X. B.; Weng, J.

    2008-12-01

    Porous hydroxyapatite (HA) bioceramic scaffold has been widely attracted the attention to act as a three-dimensional (3D) template for cell adhesion, proliferation, differentiation and thus promoting bone and cartilage regeneration because of its osteoinduction. However, the porous bioceramic scaffold is fragile so that it is not suitable to be applied in clinic for bone repair or replacement. Therefore, it is significant to improve the mechanical property of porous HA bioceramics while the interconnected structure is maintained for tissue ingrowth in vivo. In the present research, a porous composite scaffold composed of HA scaffold and polycaprolactone (PCL) lining was fabricated by the method of polymer impregnating to produce HA scaffold coated with PCL lining. Subsequently, the composite scaffolds were deposited with biomimetic coating for improving the bioactivity. The HA/PCL composite scaffolds with improved mechanical property and bioactivity is expected to be a promising bone substitute in tissue engineering applications.

  7. 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.

  8. Effect of Nb content on deformation behavior and shape memory properties of Ti–Nb alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tobe, H. [Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Kim, H.Y., E-mail: heeykim@ims.tsukuba.ac.jp [Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Inamura, T.; Hosoda, H. [Precision and Intelligence Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Nam, T.H. [School of Materials Science and Engineering and ERI, Gyeongsang National University, 900 Gazwadong, Jinju, Gyeongnam 660-701 (Korea, Republic of); Miyazaki, S., E-mail: miyazaki@ims.tsukuba.ac.jp [Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); School of Materials Science and Engineering and ERI, Gyeongsang National University, 900 Gazwadong, Jinju, Gyeongnam 660-701 (Korea, Republic of); Center of Excellence for Advanced Materials Research, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia)

    2013-11-15

    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.

  9. 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.

  10. Registration of two confection sunflower germplasm Lines, HA-R10 and HA-R11, Resistant to sunflower rust

    Science.gov (United States)

    Two confection sunflower (Helianthus annuus L.) germplasm lines, HA-R10 (Reg. No.xxx, PI670043) and HA-R11 (Reg. No.xxx, PI670044) were developed by the USDA-ARS Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station and released December, 20...

  11. Registration of two double rust resistant germplasms, HA-R12 and HA-R13 for confection sunflower

    Science.gov (United States)

    The confection sunflower (Helianthus annuus L.) germplasms HA-R12 (Reg. No. ______, PI 673104) and HA-R13 (Reg. No. ______, PI 673105) were developed by the USDA-ARS, Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station, and released in Jul...

  12. Powder-in-tube (PIT) $Nb_{3}Sn$ conductors for high-field magnets

    CERN Document Server

    Lindenhovius, J L H; den Ouden, A; Wessel, W A J; ten Kate, H H J

    2000-01-01

    New Nb/sub 3/Sn conductors, based on the powder-in-tube (PIT) process, have been developed for application in accelerator magnets and high-field solenoids. For application in accelerator magnets, SMI has developed a binary 504 filament PIT conductor by optimizing the manufacturing process and adjustment of the conductor lay-out. It uniquely combines a non-copper current density of 2680 A/mm/sup 2/@10 T with an effective filament diameter of about 20 mu m. This binary conductor may be used in a 10 T, wide bore model separator dipole magnet for the LHC, which is being developed by a collaboration of the University of Twente and CERN. A ternary (Nb/7.5wt%Ta)/sub 3/Sn conductor containing 37 filaments is particularly suited for application in extremely high-field superconducting solenoids. This wire features a copper content of 43%, a non-copper current density of 217 A/mm/sup 2/@20 T and a B/sub c2/ of 25.6 T. The main issues and the experimental results of the development program of PIT Nb/sub 3/Sn conductors a...

  13. $Nb_{3}Sn macrostructure, microstructure, and property comparisons for bronze and internal Sn process strands

    CERN Document Server

    Lee, P J; Larbalestier, D C

    2000-01-01

    The variation in irreversibility field, B*(T), with temperature has been measured for Nb/sub 3/Sn superconducting strands manufactured for ITER using vibrating sample and SQUID magnetometers. The high performance strands were developed for both high transport critical current density, J/sub c/, and low hysteresis loss. Despite a wide variety of designs and components, the strands could be split into two distinctive groups, based on the extrapolated irreversibility fields, which lie about 10% lower than the upper critical field. "Bronze-process" strands exhibited consistently higher B*(T) (28 T to 31 T) compared with "internal Sn" process (24 T to 26 T) conductors. The intrinsic critical current density of the superconductor, J/sub c (sc)/, and the specific pinning force of the grain boundaries, Q/sub gb/, were evaluated using the measured J/sub c/, and image analysis of the macro- and micro-structures. A bronze-processed Nb(-Ta)/sub 3 /Sn was found to have a higher J/sub c(sc)/ but lower Q/sub gb/ than Nb/sub...

  14. 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

    with late‐stage magmatic, presumably Na‐ and F‐ rich aqueous fluids. The alteration effectively fractionates the major components into the secondary minerals, producing separate Zr‐, Nb and REE‐ phases, leading to an increased complexity of the mineralisation and potential ore recovery.......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......‐group minerals are easily extracted from the host rock through magnetic separation, and contain 12 wt% ZrO2, 2 % TRE2O3 and 1% Nb2O5 on average. Petrographic investigations show that a large fraction of eudialyte at Ilímaussaq is replaced by complex aggregates of secondary minerals as a result of interaction...

  15. 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

    ... Employment and Training Administration TA-W-73,381, MT Rail Link, Inc., Missoula, MT; TA-W-73,381A, Billings, MT; TA-W-73,381B, Laurel, MT; TA-W-73,381C, Livingston, MT; TA-W-73,381D, Helena, MT; Amended... applicable to TA-W-73,381 is hereby issued as follows: All workers of Montana Rail Link, Inc.,...

  16. 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 ...

  17. Formation of a solar Ha filament from orphan penumbrae

    CERN Document Server

    Buehler, D; van Noort, M; Solanki, S K

    2016-01-01

    The formation of an Ha filament in active region (AR) 10953 is described. Observations from the Solar Optical Telescope (SOT) aboard the Hinode satellite starting on 27th April 2007 until 1st May 2007 were analysed. 20 scans of the 6302A Fe I line pair recorded by SOT/SP were inverted using the SPINOR code. The inversions were analysed together with SOT/BFI G-band and Ca II H and SOT/NFI Ha observations. Following the disappearance of an initial Ha filament aligned along the polarity inversion line (PIL) of the AR, a new Ha filament formed in its place some 20 hours later, which remained stable for at least 1.5 days. The creation of the new Ha filament was driven by the ascent of horizontal magnetic fields from the photosphere into the chromosphere at three separate locations along the PIL. The magnetic fields at two of these locations were situated directly underneath the initial Ha filament and formed orphan penumbrae already aligned along the Ha filament channel. The 700 G orphan penumbrae were stable and ...

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Structural and superconducting properties of ion beam sputtered Nb thin films and Nb/Cu bilayers

    Science.gov (United States)

    Nath, S. K.; Dhawan, R.; Rai, S.; Lodha, G. S.; Sokhey, K. J. S.

    2012-01-01

    We present the results of a study of structural and superconducting properties of polycrystalline Nb thin films (200 Å, 300 Å, 400 Å, 700 Å and 1000 Å) and Nb/Cu bilayers (300 Å/300 Å and 400 Å/300 Å) prepared on Si substrates by ion beam sputtering at room temperature. The thicknesses, roughnesses at the surfaces and interfaces were determined by X-ray reflectivity whereas the grain sizes were determined from grazing incidence X-ray diffraction and transmission electron microscopic studies. The superconducting transition temperature ( T C) of Nb thin films are smaller than T C of bulk Nb. The Nb-200 Å sample does not show T C down to 2.3 K. The average size of the grains varies from 42 Å for Nb-200 Å sample to 69 Å for Nb-1000 Å sample. Our results show that the T C in these polycrystalline films is not only limited by its thickness but also by the size of the grains. The Nb films deposited in situ on the Cu layer (Nb/Cu) show a marginal increase in average sizes of the grains as compare to their respective values in Nb films of same thicknesses. As a result a marginal increase in T C of these films is also observed. The maximum decrease in T C due to oxygen intake during deposition should be about 0.5 K from its bulk value (9.28 K). We have attributed the large decrease in T C in our case on the basis of decrease in the Debye temperature and density of states at the Fermi level for Nb thin films as compared to their respective values for bulk Nb.

  3. Electrochemical Properties of HA Coated Titanium Dioxide Nanotubes.

    Science.gov (United States)

    Kang, Kyungho; Zakiyuddin, Ahmad; Lee, Kwangmin

    2016-02-01

    CP Grade II titanium was first anodized in order to form TiO2 nanotubes, and then the TiO2 nano- tubes were coated with hydroxyapatite using the sol-gel method. The electrochemical properties of pure Ti, anodized TiO2 nanotubes, and HA-coated TiO2 nanotubes were investigated using poten- tiodynamic polarization and impedance tests. The sol-gel-coated HA nanoparticles were observed to sufficiently penetrate into the TiO2 nanotubes, and the polarization resistance of the HA-coated titanium nanotubes was higher than that of those that had just been anodized. In conclusion, the HA coating on the TiO2 nanotubes provides improved electrochemical properties and can be effective in overcoming the negative influence of passive TiO2 films.

  4. Haïti et l'anthropologie

    OpenAIRE

    2008-01-01

    Le premier numéro de la nouvelle série de GRADHIVA est consacré à l’anthropologie en Haïti : ses origines, son rôle, ses évolutions récentes, son devenir. Ce numéro double de 272 pages, illustré de nombreux clichés, évoque les rapports étroits entre l’anthropologie et la culture multiforme d’Haïti, à travers l’oeuvre de peintres, d’historiens, d’écrivains, ou d’ethnologues haïtiens. Le dossier analyse le développement d’une anthropologie haïtienne nécessairement liée à la question raciale et ...

  5. A-Ha. Drum'n'bassi supernimi FABIO

    Index Scriptorium Estoniae

    2002-01-01

    7.sept. annab norra menukaim popansambel A-Ha Tallinnas Lauluväljakul kontserdi, kus presenteerib ka oma viimast albumit "Lifelines". 14. sept.tuleb drum'n'bassi spetsialist Fabio Tallinna üritusele Circulation

  6. Electromechanical constants and their anisotropy in LiNbO sub 3 -type crystals having 180 deg. inclined domain walls

    CERN Document Server

    Topolov, V Y

    1998-01-01

    The paper is devoted to the determination of effective electromechanical constants d sub i sub j sup p , e sub i sub j sup p , epsilon sub k sub l supsigma sup , sup p and s sub f sub g sup E sup , sup p of polydomain LiNbO sub 3 and LiNb sub 0 sub . sub 1 Ta sub 0 sub . sub 9 O sub 3 crystals at room temperature. 180 deg domain structures considered here contain inclined plane walls providing a significant anisotropy of piezoelectric constants e sub i sub j sup p. The effect of such domain structures is established for the first time and discussed. (author)

  7. Adhesive strength of hydroxyl apatite(HA coating and biomechanics behavior of HA-coated prosthesis:an experimental study

    Directory of Open Access Journals (Sweden)

    Tian-yang ZHANG

    2011-05-01

    Full Text Available Objective To explore the influence of adhesive strength of hydroxyapatite(HA coating on the post-implantation stability of HA-coated prosthesis.Methods The adhesive strength and biomechanics behavior of HA coating were studied by histopathological observation,material parameters and biomechanical testing,the titanium(Ti-coated prosthesis was employed as control.Results Scratch test showed that the adhesive strength of HA coating was significantly lower than that of Ti coating(P < 0.01.Histopathological examination and bone morphometry showed that,at the early stage of prosthesis implantation,the bony growth around HA-coated prosthesis was significantly higher than that around Ti-coated prosthesis(P < 0.01,but the ultimate shear strength of HA-coated prosthesis was much lower than that of Ti-coated prosthesis(P < 0.01.After the push-out test with prosthesis,histopathological observation showed that there were accumulations of clump-and strip-like granular residues on the surface of bones that newly grew around the HA-coated prosthesis,and surface energy-dispersive X-ray spectroscopy(EDX analysis also confirmed that the shear stress induced HA decohesion from the substrate of prosthesis.Conclusions Although HA coating showed a satisfactory effect on early bone formation and prosthetic stability,due to the deficiencies of adhesive strength,the early stability of prosthesis may be gradually destroyed by the shear loads of human body and coating degradation.

  8. Magnetic study of the Fe-Co-Nb {mu} and Nb{sub ss} phases

    Energy Technology Data Exchange (ETDEWEB)

    Raposo, M.T. E-mail: mtraposo@funrei.br; Ardisson, J.D.; Persiano, A.I.C

    2004-05-01

    The phases {mu} (Fe{sub 1-x}Co{sub x})Nb and Nb{sub ss} (Nb dissolving a little amount of Fe{sub 1-x}Co{sub x}) were found in (Fe{sub 1-x}Co{sub x}){sub 1-y}Nb{sub y} alloys, with x=0.0; 0.25; 0.50; 0.75; 1.0 and y=0.50; 0.67. The magnetic features were determined by using Moessbauer and VSM analyses. The magnetic behavior of {mu} was related to the Co atomic sites occupation.

  9. Magnetron Sputtered NbN Films with Nb Interlayer on Mild Steel

    Directory of Open Access Journals (Sweden)

    Kulwant Singh

    2011-01-01

    Full Text Available The aim of the study is to extend the NbN coating on MS with Nb interlayer to explore the benefits of hard nitride coatings on low-cost structural material and to compare the coating with NbN monolithic coating on SS. NbN on MS and SS was deposited by reactive d.c. magnetron sputtering at various N2/Ar flow ratios and substrate bias. Deposition rate decreased from 20 to 10 nm/min (without biasing and from 16 to 8 nm/min (−50 V biasing when N2/Ar ratio was varied from zero to 70%. Deposition rate decreased with the increase in bias voltage. Coatings showed hexagonal β Nb2N, cubic δ NbN, and hexagonal δ′ NbN as major phases with the increasing N2 flow. Surface hardness reached a maximum of 2040 HK25 at a N2/Ar of 20%. Critical loads, for cohesive and adhesive failure for coating on MS, were between 6–8 N and 9–12 N respectively; for coating on SS, the values were between 7–15 N and 12–25 N respectively. Duplex coatings were studied for hardness by Knoop microindentation, adhesion by scratch tester, and corrosion by potentiodynamic polarization technique. Hardness, adhesion, and corrosion resistance all improved when NbN coating was incorporated with Nb interlayer on MS.

  10. Reactive ion etching of Nb thin films for Nb/Al-AlO[sub x]/Nb Josephson tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Popova, K. (Dept. of Physics and Applied Physics, Univ. of Strathclyde, Glasgow (United Kingdom)); Lea, W.F. (Dept. of Physics and Applied Physics, Univ. of Strathclyde, Glasgow (United Kingdom)); Hutson, D. (Dept. of Physics and Applied Physics, Univ. of Strathclyde, Glasgow (United Kingdom)); Sydow, J.P. (Dept. of Physics and Applied Physics, Univ. of Strathclyde, Glasgow (United Kingdom)); Pegrum, C.M. (Dept. of Physics and Applied Physics, Univ. of Strathclyde, Glasgow (United Kingdom))

    1994-03-01

    Reactive ion etching of both Nb and Nb/Al-AlO[sub x]/Nb trilayer has been optimised for the fabrication of Josephson tunnel junctions. Niobium thin films deposited by magnetron sputtering on silicon wafers have been patterned by a process using CF[sub 4] + O[sub 2]. The effect of main process parameters on photoresist mask etch anisotropy has been demonstrated by scanning electron microscopy (SEM) observations, and the influence of gas composition, total pressure and discharge power on etch rates has been evaluated by response surface methodology. A face-centred cubed experimental design with 17 trials has been performed and the data processed using multiple regression analysis. Second-order polynomial expressions (response surfaces) for Nb and Si etch rates as functions of process parameters have been obtained. A reliable and repeatable Nb etch process has been defined in the range 100-270 mTorr total pressure, 50-70 W input power and 0-10% by flow of O[sub 2] added to the CF[sub 4]. Maximum Nb and Si etch rates were obtained with 7% O[sub 2] in the gas mixture, and SEM showed that vertical etch profiles were produced at 50 mTorr CF[sub 4] + 5%O[sub 2]. (orig.)

  11. 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...

  12. On Mossbauer dynamics in Nb3Sn

    Indian Academy of Sciences (India)

    Ashok Razdan

    2000-06-01

    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. Nanoscale decomposition of Nb-Ru-O

    Science.gov (United States)

    Music, Denis; Geyer, Richard W.; Chen, Yen-Ting

    2016-11-01

    A correlative theoretical and experimental methodology has been employed to explore the decomposition of amorphous Nb-Ru-O at elevated temperatures. Density functional theory based molecular dynamics simulations reveal that amorphous Nb-Ru-O is structurally modified within 10 ps at 800 K giving rise to an increase in the planar metal - oxygen and metal - metal population and hence formation of large clusters, which signifies atomic segregation. The driving force for this atomic segregation process is 0.5 eV/atom. This is validated by diffraction experiments and transmission electron microscopy of sputter-synthesized Nb-Ru-O thin films. Room temperature samples are amorphous, while at 800 K nanoscale rutile RuO2 grains, self-organized in an amorphous Nb-O matrix, are observed, which is consistent with our theoretical predictions. This amorphous/crystalline interplay may be of importance for next generation of thermoelectric devices.

  14. 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.

  15. Advances in $Nb_{3}Sn$ performance

    CERN Document Server

    Godeke, A

    2009-01-01

    Nb3Sn wires with non-Cu critical current densities (Jc) that surpass 3 kAmm−2 at 12 T and 4.2 K are commercially available in piece lengths longer than 10 km. Acceleratortype magnets that utilize these conductors have achieved record magnetic fields. This article summarizes key developments in the last decade that have led to these significant improvements in the performance of Nb3Sn wires.

  16. Advances in Nb3Sn Performance

    Energy Technology Data Exchange (ETDEWEB)

    Godeke, Arno

    2008-05-19

    Nb{sub 3}Sn wires with non-Cu critical current densities (J{sub c}) that surpass 3 kAmm{sup -2} at 12 T and 4.2 K are commercially available in piece lengths longer than 10 km. Accelerator-type magnets that utilize these conductors have achieved record magnetic fields. This article summarizes key developments in the last decade that have led to these significant improvements in the performance of Nb{sub 3}Sn wires.

  17. 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....

  18. Generation of the regulatory protein rtTA transgenic mice

    Institute of Scientific and Technical Information of China (English)

    Kang Xu; Xin-Yan Deng; Ying Yue; Zhong-Min Guo; Bing Huang; Xun Hong; Dong Xiao; Xi-Gu Chen

    2005-01-01

    AIM: To translate Tet-on system into a conditional mouse model, in which hepatitis B or C virus (HBV or HCV) gene could be spatiotemporally expressed to overcome "immune tolerance" formed during the embryonic development and "immune escape" against hepatitis virus antigen(s), an effector mouse, carrying the reverse tetracycline-responsive transcriptional activator (rtTA) gene under the tight control of liver-specific human apoE promoter, is required to be generated. METHODS: To address this end, rtTA fragment amplified by PCR was effectively inserted into the vector of pLiv.7 containing apoE promoter to create the rtTA expressing vector, I.e., pApoE-rtTA. ApoE-rtTA transgenic fragment (-6.9 kb) released from pApoE-rtTA was transferred into mice by pronucleus injection, followed by obtaining one transgene (+) founder animal from microinjection through PCR and Southern blot analysis.RESULTS: rtTA transgene which could be transmitted to subsequent generation (F1) derived from founder was expressed in a liver-specific fashion. CONCLUSION: Taken together, these findings demonstrate that rtTA transgenic mice, in which rtTA expression is appropriately targeted to the murine liver, are successfully produced, which lays a solid foundation to 'off-on-off' regulate expression of target gene (s) (e.g., HBV and/or HCV) in transgenic mice mediated by Tet-on system.

  19. Thermodynamic assessment of the Nb-Ge system

    Energy Technology Data Exchange (ETDEWEB)

    Geng Tai [School of Materials Science and Engineering, University of Science and Technology Beijing, Xueyuan Road, 30, Haidian District, Beijing 100083 (China); Li Changrong, E-mail: crli@mater.ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Xueyuan Road, 30, Haidian District, Beijing 100083 (China); Du Zhenmin; Guo Cuiping [School of Materials Science and Engineering, University of Science and Technology Beijing, Xueyuan Road, 30, Haidian District, Beijing 100083 (China); Zhao Xinqing; Xu Huibin [School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China)

    2011-02-10

    Research highlights: > For the phases Nb{sub 3}Ge{sub 2} and Nb{sub 3}Ge, the reasonable sublattice models were constructed. > A set of thermodynamic parameters for the Nb-Ge system was obtained. > The optimized result can interpreter the vaporization of Ge during preparation. - Abstract: The Nb-Ge binary system has been thermodynamically assessed using the CALPHAD (Calculation of Phase Diagrams) approach on the basis of the experimental data of both the phase equilibria and the thermochemical properties. The reasonable models were constructed for all the phases of the system. The liquid and the terminal solid solution phases, Bcc-(Nb) and Diamond-(Ge), were described as the substitutional solutions with Redlich-Kister polynomials for the expressions of the excess Gibbs free energies. The intermediate phases (Nb{sub 3}Ge), (Nb{sub 5}Ge{sub 3}), (Nb{sub 3}Ge{sub 2}) and (NbGe{sub 2}) with homogeneity ranges were treated as the sublattice models Nb{sub 0.75}(Ge,Nb,Va){sub 0.25}, Nb{sub 0.5}(Nb,Ge){sub 0.125}(Ge,Va){sub 0.375}, (Nb,Ge){sub 0.222}(Nb,Ge){sub 0.333}Nb{sub 0.333}(Ge,Va){sub 0.111} and (Nb,Ge){sub 0.333}(Nb,Ge){sub 0.667} respectively based on their structure features of atom arrangements. A set of self-consistent thermodynamic parameters for the Nb-Ge system was obtained. Using the present thermodynamic data, the calculation results can reproduce the experimental data well.

  20. Osteoblast interaction with laser cladded HA and SiO{sub 2}-HA coatings on Ti-6Al-4V

    Energy Technology Data Exchange (ETDEWEB)

    Yang Yuling [Department of Physics, Northeastern University, Shenyang 110004 (China); Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Serpersu, Kaan [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); He Wei, E-mail: whe5@utk.edu [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Department of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Paital, Sameer R. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Dahotre, Narendra B. [Department of Materials Science and Engineering, University of North Texas, Denton, TX 76207 (United States)

    2011-12-01

    In order to improve the bioactivity and biocompatibility of titanium endosseous implants, the morphology and composition of the surfaces were modified. Polished Ti-6Al-4V substrates were coated by a laser cladding process with different precursors: 100 wt.% HA and 25 wt.% SiO{sub 2}-HA. X-ray diffraction of the laser processed samples showed the presence of CaTiO{sub 3}, Ca{sub 3}(PO{sub 4}){sub 2}, and Ca{sub 2}SiO{sub 4} phases within the coatings. From in vitro studies, it was observed that compared to the unmodified substrate all laser cladded samples presented improved cellular interactions and bioactivity. The samples processed with 25 wt.% SiO{sub 2}-HA precursor showed a significantly higher HA precipitation after immersion in simulated body fluid than 100 wt.% HA precursor and titanium substrates. The in vitro biocompatibility of the laser cladded coatings and titanium substrate was investigated by culturing of mouse MC3T3-E1 pre-osteoblast cell line and analyzing the cell viability, cell proliferation, and cell morphology. A significantly higher cell attachment and proliferation rate were observed for both laser cladded 100 wt.% HA and 25 wt.% SiO{sub 2}-HA samples. Compared to 100 wt.% HA sample, 25 wt.% SiO{sub 2}-HA samples presented a slightly improved cellular interaction due to the addition of SiO{sub 2}. The staining of the actin filaments showed that the laser cladded samples induced a normal cytoskeleton and well-developed focal adhesion contacts. Scanning electron microscopic image of the cell cultured samples revealed better cell attachment and spreading for 25 wt.% SiO{sub 2}-HA and 100 wt.% HA coatings than titanium substrate. These results suggest that the laser cladding process improves the bioactivity and biocompatibility of titanium. The observed biological improvements are mainly due to the coating induced changes in surface chemistry and surface morphology. Highlights: {yields} Laser cladding of Ti alloys with bioceramics creates new

  1. Wet ammonia Synthesis of Semiconducting N:Ta2O5, Ta3N5 and β-TaON Films for Photoanode Applications

    OpenAIRE

    Dabirian, A.; Van't Spijker, H; Van de Krol, R.

    2012-01-01

    Tantalum oxynitride (β-TaON) is a promising photoanode material for photoelectrochemical water splitting. However, the synthesis of phase-pure β-TaON films is a challenging task. This paper describes a novel approach to achieve this by the controlled nitridation of Ta2O5 films under a flow of ammonia gas (ammonolysis), which was obtained by bubbling argon through an aqueous ammonium hydroxide solution followed by a 5 Å molecular sieve to remove the water. Depending on the nitridation conditio...

  2. Prospects of HA-Based Universal Influenza Vaccine

    Directory of Open Access Journals (Sweden)

    Anwar M. Hashem

    2015-01-01

    Full Text Available Current influenza vaccines afford substantial protection in humans by inducing strain-specific neutralizing antibodies (Abs. Most of these Abs target highly variable immunodominant epitopes in the globular domain of the viral hemagglutinin (HA. Therefore, current vaccines may not be able to induce heterosubtypic immunity against the divergent influenza subtypes. The identification of broadly neutralizing Abs (BnAbs against influenza HA using recent technological advancements in antibody libraries, hybridoma, and isolation of single Ab-secreting plasma cells has increased the interest in developing a universal influenza vaccine as it could provide life-long protection. While these BnAbs can serve as a source for passive immunotherapy, their identification represents an important step towards the design of such a universal vaccine. This review describes the recent advances and approaches used in the development of universal influenza vaccine based on highly conserved HA regions identified by BnAbs.

  3. CILogon-HA. Higher Assurance Federated Identities for DOE Science

    Energy Technology Data Exchange (ETDEWEB)

    Basney, James [Univ. of Illinois, Urbana-Champaign, IL (United States)

    2015-08-01

    The CILogon-HA project extended the existing open source CILogon service (initially developed with funding from the National Science Foundation) to provide credentials at multiple levels of assurance to users of DOE facilities for collaborative science. CILogon translates mechanism and policy across higher education and grid trust federations, bridging from the InCommon identity federation (which federates university and DOE lab identities) to the Interoperable Global Trust Federation (which defines standards across the Worldwide LHC Computing Grid, the Open Science Grid, and other cyberinfrastructure). The CILogon-HA project expanded the CILogon service to support over 160 identity providers (including 6 DOE facilities) and 3 internationally accredited certification authorities. To provide continuity of operations upon the end of the CILogon-HA project period, project staff transitioned the CILogon service to operation by XSEDE.

  4. Fabrication of high-quality submicron Nb/Al-AlOx/Nb tunnel junctions

    Institute of Scientific and Technical Information of China (English)

    Yu Hai-Feng; Cao Wen-Hui; Zhu Xiao-Bo; Yang Hai-Fang; Yu Hong-Wei; Ren Yu-Feng; Gu Chang-Zhi; Chen Geng-Hua; Zhao Shi-Ping

    2008-01-01

    Nb/Al-AlOx/Nb tunnel junctions are often used in the studies of macroscopic quantum phenomena and supercon-ducting qubit applications of the Josepheon devices. In this work, we describe a convenient and reliable process using electron beam lithography for the fabrication of high-quality, submicron-sized Nb/Al-AlOx/Nb Josephson junctions.The technique follows the well-known selective Nb etching process and produces high-quality junctions with Vm=100 mV at 2.3 K for the typical critical current density of 2.2 kA/cm2, which can be adjusted by controlling the oxygen pressure and oxidation time during the formation of the tunnelling barrier. We present the results of the temperature depen-dence of the sub-gap current and in-plane magnetic-field dependence of the critical current, and compare them with the theoretical predictions.

  5. 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.

  6. 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.

  7. Intrabeam Scattering Studies at CesrTA

    CERN Document Server

    Ehrlichman, M P; Heltsley, B; Peterson, D P; Rider, N; Rubin, D; Sagan, D; Shanks, J; Wang, S T; Campbell, R; Holtzapple, R

    2013-01-01

    Intrabeam scattering (IBS) limits the emittance and single-bunch current that can be achieved in electron or positron storage ring colliders, damping rings, and light sources. Much theoretical work on IBS exists, and while the theories have been validated in hadron and ion machines, the presence of strong damping makes IBS in lepton machines a different phenomenon. We present the results of measurements at CesrTA of IBS dominated beams, and compare the data with theory. The beams we study have parameters typical of those specified for the next generation of wiggler dominated storage rings: low emittance, small bunch length, and few GeV energy. Our measurements are in good agreement with IBS theory, provided a tail-cut procedure is applied.

  8. Characterization and Modeling of Nonfilamentary Ta/TaOx/TiO2/Ti Analog Synaptic Device.

    Science.gov (United States)

    Wang, Yu-Fen; Lin, Yen-Chuan; Wang, I-Ting; Lin, Tzu-Ping; Hou, Tuo-Hung

    2015-05-08

    A two-terminal analog synaptic device that precisely emulates biological synaptic features is expected to be a critical component for future hardware-based neuromorphic computing. Typical synaptic devices based on filamentary resistive switching face severe limitations on the implementation of concurrent inhibitory and excitatory synapses with low conductance and state fluctuation. For overcoming these limitations, we propose a Ta/TaOx/TiO2/Ti device with superior analog synaptic features. A physical simulation based on the homogeneous (nonfilamentary) barrier modulation induced by oxygen ion migration accurately reproduces various DC and AC evolutions of synaptic states, including the spike-timing-dependent plasticity and paired-pulse facilitation. Furthermore, a physics-based compact model for facilitating circuit-level design is proposed on the basis of the general definition of memristor devices. This comprehensive experimental and theoretical study of the promising electronic synapse can facilitate realizing large-scale neuromorphic systems.

  9. Effect of Water-Glass Coating on HA and HA-TCP Samples for MSCs Adhesion, Proliferation, and Differentiation

    Directory of Open Access Journals (Sweden)

    Indu Bajpai

    2016-01-01

    Full Text Available Ca-P and silicon based materials have become very popular as bone tissue engineering materials. In this study, water-glass (also known as sodium silicate glass was coated on sintered hydroxyapatite (HA and HA-TCP (TCP stands for tricalcium phosphate samples and subsequently heat-treated at 600°C for 2 hrs. X-rays diffraction showed the presence of β- and α-TCP phases along with HA in the HA-TCP samples. Samples without coating, with water-glass coating, and heat-treated after water-glass coating were used to observe the adhesion and proliferation response of bone marrow derived-mesenchymal stem cells (MSCs. Cell culture was carried out for 4 hrs, 1 day, and 7 days. Interestingly, all samples showed similar response for cell adhesion and proliferation up to 7-day culture but fibronectin, E-cadherin, and osteogenic differentiation related genes (osteocalcin and osteopontin were significantly induced in heat-treated water-glass coated HA-TCP samples. A water-glass coating on Ca-P samples was not found to influence the cell proliferation response significantly but activated some extracellular matrix genes and induced osteogenic differentiation in the MSCs.

  10. Cs10Ta29.27O78

    Directory of Open Access Journals (Sweden)

    Wolfgang Schnick

    2009-02-01

    Full Text Available Single crystals of caesium tantalate(V, Cs10Ta29.27O78, were obtained as a serendipitous product in a welded tantalum ampoule by a blank reaction of CsBr and bismuth subnitrate [Bi5O(OH9(NO34] with the container material. The crystal structure of the title compound is made up of a three-dimensional framework constituted by two types of layers, viz. (Ta6O15n and (Ta3O9n, parallel to (001, which are linked together by TaO6 octahedra (3m. symmetry along [001]. This framework has cavities where three independent Cs+ ions (3m. and overline{6}m2 symmetry, respectively are located. The compound reveals a Ta deficiency at one trigonal prismatic coordinated site (overline{6}m2 symmetry. The composition of the title compound was verified by energy-dispersive X-ray analysis of single crystals.

  11. Diffusion behavior of Nb element in high Nb containing TiAl Alloys by reactive hot pressing

    Institute of Scientific and Technical Information of China (English)

    WANG Yanhang; LIN Junpin; HE Yuehui; WANG Yanli; CHEN Guoliang

    2006-01-01

    Diffusion behavior of Nb in elemental powder metallurgy high Nb containing TiAl alloys was investigated. The results show that Nb element dissolves into the matrix by diffusion. Pore nests are formed in situ after Nb diffusion. With the increase in hot pressing temperature, the diffusion of Nb will be more sufficient, and the microstructure is more homogeneous. Nb element diffuses completely at 1400℃. Meanwhile, compression deformation and agglomeration phenomena of pores are observed in some pore nests. Hot isostatic pressing (HIP) treatment can only efficiently decrease but not eliminate porosity completely.

  12. Characterization of a TaJ Gene from Wheat

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A novel J-domain protein gene was cloned from wheat (Triticum aestivum L.) using RT-PCR technology and named as TaJ. The J-domain protein is defined by the presence of a J-domain. The cDNA of T. aestivum gene, TaJ (GenBank accession number: DQ789026), was 1 263 bp and contained a complete open reading frame (ORF) encoding a J-domain protein of 420 amino acid residues. The predicted amino acid sequence of TaJ possesses three functionally essential domains: the N-terminal J-domain which includes the highly conserved HPD tripeptide, an adjacent domain that is rich in glycine and phenylalanine residues (G/F) and a Cysteine-rich zinc-finger domain with four repeats of CxxCxGxG that is important for protein interactions. The C-terminal of TaJ was -CAQQ, a farnesylation motif. The full-length deduced amino acid sequence of TaJ is highly homologous to J-domain proteins from various plant species. Southern blot analysis indicated that a single copy of TaJ existed in wheat genome. The expression pattern of TaJ performed by real-time PCR demonstrated that heat shock (HS) at 37℃ induced the expression of TaJ rapidly and strongly, but the response of the TaJ gene to cold stress was much slower than that to HS. Tissue-specific expression analysis showed that the expression level of TaJ gene was much higher in leaves than that in roots.

  13. Cu-Nb reinforced (Nb, Ti){sub 3}Sn superconducting wire; Cu-Nb hokyo anteika (Nb, Ti){sub 3}Sn chodendo sen

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, H.; Endo, S.; Kimura, A.; Wada, K.; Meguro, S. [The Furukawa Electric Co., Ltd., Tokyo (Japan); Watanabe, K.; Awaji, S. [Tohoku Univ., Sendai (Japan)

    2000-05-29

    The development of Nb{sub 3}Sn super-conducting wire material by combining in-Situ Cu-Nb alloy as a reinforced stabilization material in the wire inside has been carried out until now. Since the reinforced stabilization wire materials are used for cryogenic magnet of large diameter refrigerating machine, manufacture of long wire is vital. In this report, the results of investigating characteristics of Cu-Nb reinforced stabilization wire materials produced in different manufacturing scale are reported. The Cu-20wt%-Nb alloy is adopted as the reinforced stabilization material of the bronze process Nb{sub 3}Sn super-conducting wire. The produced wire is heat-treated at 650 degrees C and 864ks for 240 hrs and its characteristics are investigated. The non-copper part Jc of the reinforced stabilization wire material is 551A/mm {sup 2} at 12T, 184A/mm{sup 2} at 16T, and 76A/mm{sup 2} at 18T, and rates to the non-copper part Jc of the comparison wire materials in the same magnetic field are 0.87, 0.75 and 0.61 respectively. (NEDO)

  14. Läkaköha - aktuaalne uurimisteema / Marje Oona

    Index Scriptorium Estoniae

    Oona, Marje, 1963-

    2012-01-01

    TÜ peremeditsiini õppetooli töötajate poolt algatatud uurimistööst, mille eesmärgiks on uurida Bordetella spp. infektsioonide epidemioloogiat, molekulaargeneetikat ja kliinilisi eripärasid ning selgitada läkaköha sagedasema diagnsimise põhjusi Eestis

  15. Läkaköha - aktuaalne uurimisteema / Marje Oona

    Index Scriptorium Estoniae

    Oona, Marje, 1963-

    2012-01-01

    TÜ peremeditsiini õppetooli töötajate poolt algatatud uurimistööst, mille eesmärgiks on uurida Bordetella spp. infektsioonide epidemioloogiat, molekulaargeneetikat ja kliinilisi eripärasid ning selgitada läkaköha sagedasema diagnsimise põhjusi Eestis

  16. Microstructures evolution and physical properties of laser induced NbC modified nanocrystalline composites

    Science.gov (United States)

    Li, Jianing; Liu, Kegao; Yuan, Xingdong; Shan, Feihu; Zhang, Bolun; Wang, Zhe; Xu, Wenzhuo; Zhang, Zheng; An, Xiangchen

    2017-10-01

    The nanoscale quasicrystals (NQs), amorphous and ultrafine nanocrystals (UNs) modified hard composites are produced by laser cladding (LC) of the Ni60A-TiC-NbC-Sb mixed powders on the additive manufacturing (AM) TA1 titanium alloy. The LC technique is favorable to formations of icosahedral quasicrystals (I-phase) with five-fold symmetry due to its rapid cooling and solidification characteristics. The formation mechanism of this I-phase is explained here. Under the actions of NQs, amorphous and UNs, such LC composites exhibited an extremely high micro-hardness. UNs may also intertwin with amorphous, forming yarn-shape materials. This research provides essential theoretical basis to improve the quality of laser-treated composites.

  17. Thermodynamics of formation reactions of intermetallides Ni/sub 3/Ta and Ni/sub 2/Ta

    Energy Technology Data Exchange (ETDEWEB)

    Lyakishev, N.P.; Snitko, Yu.P.; Alekseev, V.I.; Levshin, G.A. (Tsentral' nyj Nauchno-Issledovatel' skij Inst. Chernoj Metallurgii, Moscow (USSR))

    1981-01-01

    Thermodynamical functions of the formation of Ni/sub 3/Ta and Ni/sub 2/Ta intermetallides are studied when investigating the electromotive force of the cell MoVertical BarTa/sub 2/O/sub 5/, Nisub(x)Tasub(y)Vertical Bar0.99ThOsub(2)i0.01 CaOVertical Bar Fe, Fesub(0.95)OVertical BarMo in the temperature range of 1173-1323 K. Thermodynamical functions of Ni/sub 3/Ta and Ni/sub 2/Ta formation are equal to: ..delta..Gsub(f)sup(0) (1273 K) 31.70 and 28.86; ..delta..Hsub(f)sup(0) (1173-1323 K) 27.88, 07.9 kcal/mol; ..delta..Ssub(f)sup(0) (1173-1323 K) 3,U and 0.75 cal/molxdegree, respectively.

  18. Chemically mediated quantum criticality in NbFe2.

    Science.gov (United States)

    Alam, Aftab; Johnson, D D

    2011-11-11

    Laves-phase Nb(1+c)Fe(2-c) is a rare itinerant intermetallic compound exhibiting magnetic quantum criticality at c(cr)∼1.5%Nb excess; its origin, and how alloying mediates it, remains an enigma. For NbFe(2), we show that an unconventional band critical point above the Fermi level E(F) explains most observations and that chemical alloying mediates access to this unconventional band critical point by an increase in E(F) with decreasing electrons (increasing %Nb), counter to rigid-band concepts. We calculate that E(F) enters the unconventional band critical point region for c(cr) > 1.5%Nb and by 1.74%Nb there is no Nb site-occupation preference between symmetry-distinct Fe sites, i.e., no electron-hopping disorder, making resistivity near constant as observed. At larger Nb (Fe) excess, the ferromagnetic Stoner criterion is satisfied.

  19. Transition probabilities of astrophysical interest in the niobium ions Nb+ and Nb2+

    Science.gov (United States)

    Nilsson, H.; Hartman, H.; Engström, L.; Lundberg, H.; Sneden, C.; Fivet, V.; Palmeri, P.; Quinet, P.; Biémont, É.

    2010-02-01

    Aims: We attempt to derive accurate transition probabilities for astrophysically interesting spectral lines of ion{Nb}{ii} and ion{Nb}{iii} and determine the niobium abundance in the Sun and metal-poor stars rich in neutron-capture elements. Methods: We used the time-resolved laser-induced fluorescence technique to measure radiative lifetimes in ion{Nb}{ii}. Branching fractions were measured from spectra recorded using Fourier transform spectroscopy. The radiative lifetimes and the branching fractions were combined yielding transition probabilities. In addition, we calculated lifetimes and transition probablities in ion{Nb}{ii} and ion{Nb}{iii} using a relativistic Hartree-Fock method that includes core polarization. Abundances of the sun and five metal-poor stars were derived using synthetic spectra calculated with the MOOG code, including hyperfine broadening of the lines. Results: We present laboratory measurements of 17 radiative lifetimes in ion{Nb}{ii}. By combining these lifetimes with branching fractions for lines depopulating the levels, we derive the transition probabilities of 107 ion{Nb}{ii} lines from 4d35p configuration in the wavelength region 2240-4700 Å. For the first time, we present theoretical transition probabilities of 76 Nb III transitions with wavelengths in the range 1430-3140 Å. The derived solar photospheric niobium abundance log ɛ_⊙ = 1.44 ± 0.06 is in agreement with the meteoritic value. The stellar Nb/Eu abundance ratio determined for five metal-poor stars confirms that the r-process is a dominant production method for the n-capture elements in these stars.

  20. 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)

  1. Low-field Instabilities in Nb3Sn 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 Nb3Sn 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.

  2. 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.

  3. 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.

  4. Critical current density of Nb3Sn wires after irradiation with 65MeV and 24GeV protons

    Science.gov (United States)

    Spina, T.; Scheuerlein, C.; Richter, D.; Bottura, L.; Ballarino, A.; Flükiger, R.

    2014-05-01

    Industrial Nb3Sn wires with Ti and Ta additives (RRP process) and with Ta additives (PIT process) with a diameter of 1 mm have been irradiated at room temperature with protons of 65 MeV and of 24 GeV at various fluences up to 1×1021 p/m2. A steady increase of Jc vs. fluence was observed for all the wires up to the highest fluence. The observed increase of Jc at 4.2K in all wires was quite similar in spite of the very different proton energies. With increasing fluence. the radiation induced pinning force was found to increase. the enhancement Jc/Jco after 5.04×1020 p/m2 reaching 1.4 for Ta and 1.8 for Ti alloyed wires at 10T. The present results were quantitatively analysed by assuming a radiation induced point pinning mechanism in addition to grain boundary pinning. The results are compared with those of an ongoing neutron irradiation study undertaken on the same Nb3Sn wires in collaboration with the Atominstitut Vienna. Proton irradiation was found to produce considerably higher damage than neutron irradiation.

  5. First-principles study of the charge transfer and evolution of Si doping 2N2Ta islands adsorption on TaN (001) surfaces

    Science.gov (United States)

    Ren, Yuan; Zhang, Honglv; Zhang, Chao; Zeng, Haiqing; Liu, Xuejie

    2017-01-01

    The separation and aggregation of Si atoms around TaN grains during deposition of Ta-Si-N nanocomposite films were studied, and the adsorption energies, charge transfer and atomic partial density of state of Si-2N2Ta islands on the TaN (001) surface and diffusion energy of the islands during their evolution were evaluated using the first-principles method based on density functional theory (DFT). In the lowest total energy stable configuration, N and Ta atoms tended to combine to form 2N2Ta islands, whereas Si atoms tended to stay at a position diagonal to the Ta atom outside of the island. Si atoms entered the position of the missing N atom of the TaN island and formed a substitute solid solution during Ta-Si-N growth. The Si atoms of the solid solution in the island could be easily extruded by Ta- or N-rich island during the deposition process. The process of Si atom extrusion by a N atom which was the configuration of N-by-2Ta1N1Si island evolved into Si-by-2N2Ta island in rich N-atom. The process of Si atom was extruded by the Ta atom which was the configuration of Ta-by-2N1Ta1Si island evolved into Si-of-2Ta2N island, that reduced the total energy of island. The diffusion energies of these evolutions were 0.974 and 1.712 eV, respectively. The Si atoms and TaN grain phase tended to separate during the deposition process. Si atoms could give way to Ta and N atoms during the Ta-Si-N nanocomposite film deposition process.

  6. Magnetism of Ta dichalcogenide monolayers tuned by strain and hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Manchanda, Priyanka; Sellmyer, D. J.; Skomski, Ralph [Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588 (United States); Sharma, Vinit [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Yu, Hongbin [School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287 (United States)

    2015-07-20

    The effects of strain and hydrogenation on the electronic, magnetic, and optical properties of monolayers of Ta based dichalcogenides (TaX{sub 2}; X = S, Se, and Te) are investigated using density-functional theory. We predict a complex scenario of strain-dependent magnetic phase transitions involving paramagnetic, ferromagnetic, and modulated antiferromagnetic states. Covering one of the two chalcogenide surfaces with hydrogen switches the antiferromagnetic/nonmagnetic TaX{sub 2} monolayers to a semiconductor, and the optical behavior strongly depends on strain and hydrogenation. Our research opens pathways towards the manipulation of magnetic as well as optical properties for future spintronics and optoelectronics applications.

  7. El griot no ha muerto, viva el hip-hop

    Directory of Open Access Journals (Sweden)

    Fco. Javier González García-Mamely

    2015-11-01

    Full Text Available La oratura en África ha jugado un papel vital a lo largo de los milenios como un (único medio de preservar y transmitir la historia, la cultura y el imaginario de cada comunidad. El griot es un claro modelo de las artes orales, pero ha sufrido cambios drásticos en su modo de vida y en los recursos narrativos de los que dispone. Tras el mecenazgo de los grandes reyes y las sucesivas llegadas del islam, el colonialismo y los procesos de modernización y occidentalización, los griots se han tenido que adaptar a nuevos patrones, audiencias y medios de comunicación, convirtiéndose en políticos o en figuras del espectáculo. La aparición del rap y el hip-hop reclamando ser los “modernos griots” ha ocasionado una respuesta crítica y una atracción viral hacia el nuevo fenómeno, sea éste un nuevo género o una reinvención de la oratura del antiguo griot.

  8. 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.

  9. NbN/MgO/NbN edge-geometry tunnel junctions

    Science.gov (United States)

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

    1989-01-01

    The fabrication and low-frequency testing of the first edge-geometry NbN/MgO/NbN superconducting tunnel junctions are reported. The use of an edge geometry allows very small junction areas to be obtained, while the all-NbN electrodes permit operation at 8-10 K with a potential maximum operating frequency above 1 THz. Edge definition in the base NbN film was accomplished utilizing Ar ion milling with an Al2O3 milling mask, followed by a lower energy ion cleaning step. This process has produced all-refractory-material tunnel junctions with areas as small as 0.1 sq micron, resistance-area products less than 21 ohm sq micron, and subgap to normal state resistance ratios larger than 18.

  10. MEAM Simulation of Distribution of Nb Atoms in TiAl+Nb System

    Institute of Scientific and Technical Information of China (English)

    Xiaodong NI; Guoliang CHEN; Xitao WANG; Xudong HUI

    2001-01-01

    An accurate MEAM (modified embedded atom method) potential including angular dependence for TiAl compound has been developed. The properties of TiAl compound can be reproduced well. With this potential, the distribution of Nb atoms in L10 type TiAl compound with various composition are calculated by using an average-atom model similar to B-W (Bragg-Williams)method. The results of calculation showed that Nb atoms prefer to occupy the Ti sublattice of L10 structure, and with increasing atomic percent of Nb and Al, Nb atoms exhibited a trend of ordered distribution in Ti sublattice, and result in the formation of L10 derivative superlattice structure.

  11. Metastability of NbN in the ordered vacancy NbO phase

    CERN Document Server

    Ethridge, E C; Pickett, W E

    1995-01-01

    A metastable phase of NbN with superconducting Tc=16.4 K was reported recently by Treece and collaborators. The reported structure of the thin film sample deviates from the rocksalt (B1) NbN structure with 25% ordered vacancies on each sublattice (space group Pm3m) and a lattice constant of 4.442 Angstroms. Using full potential electronic structure methods, we contrast the electronic structure with that of B1 NbN. The calculated energy, 1.00 eV/molecule higher than B1 NbN, and calculated lattice constant of 4.214 Angstroms indicate that the new phase must be something other than the ordered stoichiometric Pm3m phase.

  12. Characterization of NbC and (Nb, Ti)N nanoprecipitates in TRIP assisted multiphase steels

    NARCIS (Netherlands)

    Tirumalasetty, G.K.; Van Huis, M.A.; Fang, C.M.; Xu, Q.; Tichelaar, F.D.; Hanlon, D.N.; Sietsma, J.; Zandbergen, H.W.

    2011-01-01

    Multiphase steels utilising composite strengthening may be further strengthened via grain refinement or precipitation by the addition of microalloying elements. In this study a Nb microalloyed steel comprising martensite, bainite and retained austenite has been studied. By means of transmission

  13. 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

  14. Anomalous Proximity Effect in the Nb-BiSb-Nb Junctions

    Energy Technology Data Exchange (ETDEWEB)

    Kasumov, A.Y.; Kononenko, O.V.; Matveev, V.N.; Borsenko, T.B.; Tulin, V.A.; Vdovin, E.E.; Khodos, I.I. [Institute of Microelectronics Technology and High Purity Materials, RAS, 142432 Chernogolovka, Moscow Region (Russia)

    1996-09-01

    An anomalous proximity effect was observed in coplanar Nb-BiSb-Nb junctions. The effect consists of a considerable increase of the critical current with an increase in the distance between the superconducting electrodes. The effect is explained by the quantum character of Cooper pair transport through the normal region. Some advantages of the application of such junctions are discussed. {copyright} {ital 1996 The American Physical Society.}

  15. The Effect of Microstructure on the Creep behavior of Ti-6Al-2Nb-1Ta-0.8Mo.

    Science.gov (United States)

    1985-09-01

    J. Gittus , "Creep, Viscoelasticity and Creep Fracture in Solids"* Applied Science Publishers LTD, London, England, 1975. 36. S. M. L. Sastry, P. S...Induced by Load Cycling in a C-Mn Steel ", Acta. Met., Vol. No. 24, 511 (1976). 75. C. E. Feltner, Trans. AIME, Vol. No. 227, 798 (1963). 76. E, W. Lee...34The Effect of Strain-Rate on the Cyclic Deformation Properties ofza- Iron Single Crystals", Acta. Met., Vol. No. 24, 659 (1976). 79. H. G. Paris, B. G

  16. Oxidation Behavior of a Refractory NbCrMo0.5Ta0.5TiZr Alloy

    Science.gov (United States)

    2014-04-01

    Laves ), were identified [10]. The lattice parameters of these phases were deter- mined to be a = 324.76 ± 0.16, 341 ± 1, and 740.0 ± 0.5 pm...Table 5. Locations of former BCC1 (regions 1 and 2 in Fig. 12), BCC2 (regions 3 and 4), and Laves phases (region 5) are clearly distinguished. During...the Laves phase (gray particles, similar to region 5 in Fig. 12) leads to formation of sharp, almost linear cracks, some of which are parallel to each

  17. Isoelectronic Substitutions and Aluminium Alloying in the Ta-Nb-Hf-Zr-Ti High-Entropy Alloy Superconductor

    OpenAIRE

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

    2017-01-01

    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 i...

  18. Nb2O5 nanofiber memristor

    Science.gov (United States)

    Grishin, A. M.; Velichko, A. A.; Jalalian, A.

    2013-07-01

    Non-woven bead-free 100 μm long and 80-200 nm in diameter highly crystalline orthorhombic T-Nb2O5 nanofibers were sintered by sol-gel assisted electrospinning technique. Electrical and dielectric spectroscopy tests of individual fibers clamped onto Pt coated Si substrate were performed using a spreading resistance mode of atomic force microscope. Reproducible resistive switching with ON-OFF resistance ratio as high as 2 × 104 has a bipolar character, starts with a threshold voltage of 0.8-1.7 V, and follows by continuous growth of conductivity. Resistive memory effect is associated with a voltage-driven accumulation/depletion of oxygen vacancies at Nb2O5/Pt cathode interface. Poole-Frenkel emission from the electronic states trapped at reduced NbOx complexes determines a shape of Nb2O5/Pt diode I-V characteristics. Simple thermodynamic model explains a threshold character of switching, relates experimentally observed characteristics in low and high resistive states, and gives a reasonable estimate of the concentration of oxygen vacancies.

  19. Diffusion of $^{6}$Li in Ta and W

    CERN Document Server

    Vacik, J

    2006-01-01

    The objective of this work was the study of 6Li diffusion in the Ta and W refractory metals. The samples were prepared by ion implantation of 380 keV 6Li+ ions into W and Ta thin foils (up to the fluence of 1016 ions/cm2) and annealed up to the temperature 1940 °C. The depth profiles of 6Li were determined using the Thermal Neutron Depth Profiling (TNDP) technique. The results showed that diffusion of 6Li in both W and Ta foils is very complex and cannot be described by simple Fick’s laws. Trapping centers (in the subsurface layers of both W and Ta metals) were supposed in a trial to explain the 6Li diffusion behaviour. However, the 6Li depth profiles were only partly explained. Other aspects are necessary to take into account for more proper quantification; such as spatially dependent diffusion coefficients, etc.

  20. 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.

  1. Stereo-dynamics of the exchange reaction Ha+LiHb→LiHa+Hb and its isotopic variants

    Institute of Scientific and Technical Information of China (English)

    Zhai Hong-Sheng; Yin Shu-Hui

    2012-01-01

    The quasi-classical trajectory (QCT) method is used to calculate the stereo-dynamics of the exchange reaction Ha+LiHb→LiHa+Hb and its isotopic variants based on an accurate potential energy surface reported by Prudente et al.[Prudente F V,Marques J M C and Maniero A M 2009 Chem.Phys.Lett.474 18].The reactive probability of the title reaction is computed.The vector correlations and four polarization-dependent generalized differential cross sections (PDDCSs) at different collision energies are presented.The influences of the collision energy and the reagent rotation on the product polarization are studied in the present work.The results indicate that the product rotational angular momentum j' is not only aligned,but also oriented along the direction perpendicular to the scattering plane.The product polarization distributions of the title reaction and its isotopic variants exhibit distinct differences which may arise from different mass combinations.

  2. Ultrasensitive Anomalous Hall Effect in Ta/CoFe/Oxide/Ta Multilayers

    Directory of Open Access Journals (Sweden)

    Guang Yang

    2016-01-01

    Full Text Available Ultrahigh anomalous Hall sensitivity has been demonstrated in Ta/CoFe/Oxide/Ta multilayers. By changing oxides (MgO and HfO2 and annealing temperature, different annealing dependence of sensitivity was found in MgO-sample and HfO2-sample. For the MgO-sample, the anomalous Hall sensitivity reaches 18792 Ω/T in the as-deposited state and significantly reduces as annealing temperature increases. On the contrary, the sensitivity of the as-deposited HfO2-sample is only 765 Ω/T, while it remarkably increases with annealing temperature increasing, finally reaching 14741 Ω/T at 240°C. The opposite variation of anomalous sensitivity in two samples originates from the different change of magnetic anisotropy and anomalous Hall resistance during the annealing process. Our study provides a new perspective that both the choice of oxide material and the optimization of annealing treatment are important to the anomalous Hall sensitivity.

  3. Characterization of phases in the Fe-Nb system

    Science.gov (United States)

    Raposo, M. T.; Ardisson, J. D.; Persiano, A. I. C.; Mansur, R. A.

    1994-12-01

    The Fe-Nb system was investigated by means of X-ray diffraction and Mössbauer spectroscopy (at 300 and 77 K), in the range from 1 to 66.7 at%. We have found that the limit of solubility of Fe in Nb at 1100°C is between 3 and 4 at% Fe, and observed the coexistence of the Nb solid solution (Nbss) phase and Fe21Nb19 in the range from 4 to 40 at% Fe. The Mössbauer parameters of all the single phases are reported. The lattice parameters of Nbss phase present no significant variation with the Nb content. The X-ray pattern for the Fe21Nb19 phase could not be solved. The Laves phase Fe2Nb presents Mössbauer and X-ray parameters that agree with the literature.

  4. Single-crystalline nanoporous Nb2O5 nanotubes

    Directory of Open Access Journals (Sweden)

    Liu Jun

    2011-01-01

    Full Text Available Abstract Single-crystalline nanoporous Nb2O5 nanotubes were fabricated by a two-step solution route, the growth of uniform single-crystalline Nb2O5 nanorods and the following ion-assisted selective dissolution along the [001] direction. Nb2O5 tubular structure was created by preferentially etching (001 crystallographic planes, which has a nearly homogeneous diameter and length. Dense nanopores with the diameters of several nanometers were created on the shell of Nb2O5 tubular structures, which can also retain the crystallographic orientation of Nb2O5 precursor nanorods. The present chemical etching strategy is versatile and can be extended to different-sized nanorod precursors. Furthermore, these as-obtained nanorod precursors and nanotube products can also be used as template for the fabrication of 1 D nanostructured niobates, such as LiNbO3, NaNbO3, and KNbO3.

  5. Thermodynamic assessment of the Si-Ta system

    Energy Technology Data Exchange (ETDEWEB)

    Drouelle, I., E-mail: coletteservant@orange.fr [Laboratoire de Physicochimie de l' Etat Solide, ICMMO, Universite de Paris-Sud, 91405 Orsay Cedex (France); Servant, C. [Laboratoire de Physicochimie de l' Etat Solide, ICMMO, Universite de Paris-Sud, 91405 Orsay Cedex (France)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer The thermodynamic modelling of the Si-Ta system is made with the CALPHAD method. Black-Right-Pointing-Pointer The liquid and bcc phases are treated with a solution model and compounds as stoichiometric. Black-Right-Pointing-Pointer The excess Gibbs energy of the solution phases is assessed with the T dependence by Kaptay. Black-Right-Pointing-Pointer The calculations based on the thermodynamic optimisation agree well with the experiments. - Abstract: The thermodynamic modeling of the silicon-tantalum binary system was carried out with the help of the CALPHAD (CALculation of PHAse Diagram) method. A solution model was used for the description of the liquid and bcc phases while the Si{sub 2}Ta, Si{sub 3}Ta{sub 5L}T, Si{sub 3}Ta{sub 5H}T SiTa{sub 2} and SiTa{sub 3} compounds are treated as stoichiometric. The excess Gibbs energy function of the solution phases was assessed with the recent exponential temperature dependence of the interaction parameters by Kaptay [1-3] and compared with the Redlich-Kister [4] polynomial equation results. The calculations based on the thermodynamic modeling are in good agreement with the phase diagram data and experimental thermodynamic values available in literature.

  6. Modelling the mechanical behaviour of heterogeneous Ta/TA6V welded joints: behaviour and failure criteria; Modelisation du comportement mecanique des liaisons soudees heterogenes Ta/TA6V: comportement et critere de rupture

    Energy Technology Data Exchange (ETDEWEB)

    Paris, Th

    2008-12-15

    As laser welding of two different materials (heterogeneous welding) leads to a joint having a characteristic size close to the millimetre, i.e. much smaller than that of a structure, and as such a junction displays completely different mechanical properties because of the metallurgical transformations induced by intense thermal loading, the aim of this research thesis is to develop a behaviour model, flexible and robust enough, to represent all together the mechanical behaviours of the Ta, the TA6V and the melted zone. This model must be able to take plasticity and visco-plasticity into account, and also to provide a failure criterion through damage mechanics and its coupling with the behaviour. The author first reports the experimental characterization of the base materials (Ta and TA6V) by using tensile tests under different strain rates and different directions, relaxation tests and fatigue shear tests. He also characterizes the melted zone by describing the influence of a thermal treatment (induced by welding) on the formation of the melted zone, and by using different tests: four point bending on notched specimens, nano-indentation test, and longitudinal tensile test. In a second part, the author develops the model within the framework of continuum thermodynamics, and explores the numerical issues. The last part deals with the validation of the model for the concerned materials (Ta and TA6V) and melted zone.

  7. The HaDREB2 transcription factor enhances basal thermotolerance and longevity of seeds through functional interaction with HaHSFA9

    Directory of Open Access Journals (Sweden)

    Carranco Raúl

    2009-06-01

    Full Text Available Abstract Background Transcription factor HaDREB2 was identified in sunflower (Helianthus annuus L. as a drought-responsive element-binding factor 2 (DREB2 with unique properties. HaDREB2 and the sunflower Heat Shock Factor A9 (HaHSFA9 co-activated the Hahsp17.6G1 promoter in sunflower embryos. Both factors could be involved in transcriptional co-activation of additional small heat stress protein (sHSP promoters, and thus contribute to the HaHSFA9-mediated enhancement of longevity and basal thermotolerance of seeds. Results We found that overexpression of HaDREB2 in seeds did not enhance longevity. This was deduced from assays of basal thermotolerance and controlled seed-deterioration, which were performed with transgenic tobacco. Furthermore, the constitutive overexpression of HaDREB2 did not increase thermotolerance in seedlings or result in the accumulation of HSPs at normal growth temperatures. In contrast, when HaDREB2 and HaHSFA9 were conjointly overexpressed in seeds, we observed positive effects on seed longevity, beyond those observed with overexpression of HaHSFA9 alone. Such additional effects are accompanied by a subtle enhancement of the accumulation of subsets of sHSPs belonging to the CI and CII cytosolic classes. Conclusion Our results reveal the functional interdependency of HaDREB2 and HaHSFA9 in seeds. HaDREB2 differs from other previously characterized DREB2 factors in plants in terms of its unique functional interaction with the seed-specific HaHSFA9 factor. No functional interaction between HaDREB2 and HaHSFA9 was observed when both factors were conjointly overexpressed in vegetative tissues. We therefore suggest that additional, seed-specific factors, or protein modifications, could be required for the functional interaction between HaDREB2 and HaHSFA9.

  8. Effect of Ta concentration on the refractive index of TiO2:Ta studied by spectroscopic ellipsometry

    Science.gov (United States)

    Nurfani, Eka; Kurniawan, Robi; Muhammady, Shibghatullah; Marlina, Resti; Sutjahja, Inge M.; Winata, Toto; Rusydi, Andrivo; Darma, Yudi

    2016-04-01

    We have investigated optical properties of Ta-doped TiO2 thin film on LaAlO3 (LAO) substrate using Spectroscopic Ellipsometry (SE) at room temperature. Amplitude ratio Ψ and phase difference L1 between p- and s- polarized light waves are obtained by multiple incident angles measurement (60°, 70°, and 80°) at energy range of 0.5 - 6.5 eV. In order to obtain optical properties for every Ta concentrations (0.01, 0.4, and 5 at. %), multilayer modelling was performed simultaneously by using Drude-Lorentz model. Refractive index and optical dispersion parameters were determined by Wemple-DiDomenico relation. In general, refractive index at zero photon energy n(0) increases by increasing Ta concentration. Furthermore, optical band gap shows a significant increasing due to presence of Ta dopant. In addition, other optical constants are discussed as well.

  9. Pre-Test Analysis Predictions for the Shell Buckling Knockdown Factor Checkout Tests - TA01 and TA02

    Science.gov (United States)

    Thornburgh, Robert P.; Hilburger, Mark W.

    2011-01-01

    This report summarizes the pre-test analysis predictions for the SBKF-P2-CYL-TA01 and SBKF-P2-CYL-TA02 shell buckling tests conducted at the Marshall Space Flight Center (MSFC) in support of the Shell Buckling Knockdown Factor (SBKF) Project, NASA Engineering and Safety Center (NESC) Assessment. The test article (TA) is an 8-foot-diameter aluminum-lithium (Al-Li) orthogrid cylindrical shell with similar design features as that of the proposed Ares-I and Ares-V barrel structures. In support of the testing effort, detailed structural analyses were conducted and the results were used to monitor the behavior of the TA during the testing. A summary of predicted results for each of the five load sequences is presented herein.

  10. CRED Shallow CTD Profiles; Ta'u, American Samoa; Cruise: HA1201_LEGII&III, Data Date Range: 20120422-20120423 (NODC Accession 0107470)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — CRED shallow Conductivity-Temperature-Depth (CTD) casts are vertical profiles (max 30 meter depth, downcast only) of temperature, conductivity and pressure. Data...

  11. Mineralogy and geochemistry of REE-Zr-Nb mineralised nepheline syenites in the peralkaline Ilímaussaq complex, South Greenland

    DEFF Research Database (Denmark)

    Borst, Anouk Margaretha

    -related Gardar province and comprises a series of highly unusual magmatic rocks described as agpaitic nepheline syenites. Agpaitic rocks are characterised by the presence of complex Na-Zr-Ti-silicates such as eudialyte and rinkite instead of common accessory Zr and Ti minerals like zircon and titanite....... The present study focusses on the lower part of the magmatic sequence in the southern part of the complex (Kringlerne), comprising a c. 250 m thick sequence of spectacularly layered syenites called kakortokites. The kakortokites are of particular interest for their enrichment in Zr, Nb, Ta and REE, largely...... potential of these rocks. It is shown that widespread hydrothermal alteration of primary magmatic eudialyte has led to the formation of fine-grained intergrowths of secondary Zr, Nb and REE phases. The alteration was not associated with significant loss or gain of the valuable metals, although the increased...

  12. Episodic magmatism at 105 Ma in the Kinki district, SW Japan: Petrogenesis of Nb-rich lamprophyres and adakites, and geodynamic implications

    Science.gov (United States)

    Imaoka, T.; Nakashima, K.; Kamei, A.; Itaya, T.; Ohira, T.; Nagashima, M.; Kono, N.; Kiji, M.

    2014-01-01

    Cretaceous episodic magmatism produced Nb-rich lamprophyres and adakitic granitoids in the Kinki district of SW Japan. K-Ar dating of minerals from the lamprophyres, adakites, and hornblende peridotite xenoliths yielded ages of 109-99 Ma, indicating a short-lived episodic magmatism. The lamprophyres generally display primitive high-Mg basaltic to basaltic andesite compositions with high Mg# and high Cr and Ni contents that preclude substantial differentiation. Some high-Nb basalt (HNB) and Nb-enriched basalt (NEB) compositions also occur. The lamprophyres have high large-ion lithophile element (LILE) and high field-strength element (HFSE) contents and variable (La/Yb)n ratios, and can be divided into high-(La/Yb)n (12.5-22.1) and low-(La/Yb)n (3.6-6.1) groups. The former contains nepheline-normative rocks with positive initial ɛNd(T) values, whereas the latter contains hypersthene-normative subalkaline rocks with negative initial ɛNd(T) values. The adakitic granitoids have relatively high TiO2, Nb, and Ta contents compared to more typical high-silica adakites elsewhere, indicating that they were produced by high temperatures (ca. 920 to 970 °C) during slab melting.

  13. Combined experimental and theoretical assessments of the lattice dynamics and optoelectronics of TaON and Ta3N5

    KAUST Repository

    Nurlaela, Ela

    2015-06-15

    Presented herein is a detailed discussion of the properties of the lattice dynamic and optoelectronic properties of tantalum(V) oxynitride (TaON) and tantalum(V) nitride (Ta3N5), from experimental and theoretical standpoint. The active Raman and infra red (IR) frequencies of TaON and Ta3N5 were measured using confocal Raman and Fourier Transform Infrared spectroscopies (FTIR) and calculated using the linear response method within the density functional perturbation theory (DFPT). The detailed study leads to an exhaustive description of the spectra, including the symmetry of the vibrational modes. Electronic structures of these materials were computed using DFT within the range-separated hybrid HSE06 exchange–correlation formalism. Electronic and ionic contributions to the dielectric constant tensors of these materials were obtained from DFPT within the linear response method using the PBE functional. Furthermore, effective mass of photogenerated holes and electrons at the band edges of these compounds were computed from the electronic band structure obtained at the DFT/HSE06 level of theory. The results suggest that anisotropic nature in TaON and Ta3N5 is present in terms of dielectric constant and effective masses.

  14. Combined experimental and theoretical assessments of the lattice dynamics and optoelectronics of TaON and Ta3N5

    Science.gov (United States)

    Nurlaela, Ela; Harb, Moussab; del Gobbo, Silvano; Vashishta, Manish; Takanabe, Kazuhiro

    2015-09-01

    Presented herein is a detailed discussion of the properties of the lattice dynamic and optoelectronic properties of tantalum(V) oxynitride (TaON) and tantalum(V) nitride (Ta3N5), from experimental and theoretical standpoint. The active Raman and infra red (IR) frequencies of TaON and Ta3N5 were measured using confocal Raman and Fourier Transform Infrared spectroscopies (FTIR) and calculated using the linear response method within the density functional perturbation theory (DFPT). The detailed study leads to an exhaustive description of the spectra, including the symmetry of the vibrational modes. Electronic structures of these materials were computed using DFT within the range-separated hybrid HSE06 exchange-correlation formalism. Electronic and ionic contributions to the dielectric constant tensors of these materials were obtained from DFPT within the linear response method using the PBE functional. Furthermore, effective mass of photogenerated holes and electrons at the band edges of these compounds were computed from the electronic band structure obtained at the DFT/HSE06 level of theory. The results suggest that anisotropic nature in TaON and Ta3N5 is present in terms of dielectric constant and effective masses.

  15. Prediction of new high pressure phase of TaB{sub 3}: First-principles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaozheng [College of Science, Inner Mongolia University of Technology, Hohhot 010051 (China); State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zhao, Erjun, E-mail: ejzhao@yahoo.com [College of Science, Inner Mongolia University of Technology, Hohhot 010051 (China); Wu, Zhijian, E-mail: zjwu@ciac.ac.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

    2015-05-25

    Highlights: • Crystal structure of TaB{sub 3} is predicted using the evolutionary algorithm USPEX code. • The structural and mechanical properties of tantalum borides are investigated by DFT. • The stable phases are found by enthalpy-pressure relationship and convex hull. • oC16–TaB{sub 3} has a estimated hardness (41.2 GPa) and indentation strength (22.8 GPa). • High pressure is advantageous to syntheses of ruthenium Triborides oC16–TaB{sub 3}. - Abstract: The phase stability, elastic, mechanical, dynamical and electronic properties of tantalum borides, i.e., Ta{sub 2}B, TaB, Ta{sub 3}B{sub 4}, Ta{sub 5}B{sub 6}, TaB{sub 2} and TaB{sub 3}, have been investigated by first-principles. The calculated convex hull indicates that at ambient conditions, the ground state phases are tI12–Ta{sub 2}B, oC8–TaB, oC22–Ta{sub 5}B{sub 6}, oI14–Ta{sub 3}B{sub 4}, and hP3–TaB{sub 2}; while at 75 GPa, they are tI12–Ta{sub 2}B, oC8–TaB, oC22–Ta{sub 5}B{sub 6}, oI14–Ta{sub 3}B{sub 4}, hP3–TaB{sub 2} and oC16–TaB{sub 3}; oC8–TaB, oC22–Ta{sub 5}B{sub 6}, oI14–Ta{sub 3}B{sub 4}, oC16–TaB{sub 3} are the most stable phases at 120 GPa. The enthalpy-pressure relationship reveals that the hP3–TaB{sub 2} is the most stable below 75 GPa, while the predicted oC16–TaB{sub 3} becomes the most stable above 75 GPa. Combining the estimated hardness (41.2 GPa) and indentation strength (22.8 GPa) for oC16–TaB{sub 3}, it is suggested that oC16–TaB{sub 3} is hard or potential superhard. Since it is not available experimentally, further experimental synthesis could be rewarding.

  16. Construction of Eukaryotic Expressing Plasmids Encoding HA and HA1 of Influenza A Virus and Their Transient Expression in HEK293 Cells

    Institute of Scientific and Technical Information of China (English)

    ZHANG Weidong; LI Mingyuan; CAO Kang; YANG Jing; SHI Qiaofa; WANG Baoning; JIANG Zhonghua; LI Hong

    2006-01-01

    In order to explore the feasibility and protective efficiency of influenza DNA vaccine, we constructed eukaryotic expressing plasmids encoding HA and HA1 of influenza A virus (A/PR/8/34) and studied their expression in HEK293 cells. HA and HA1 genes were amplified by RT-PCR and cloned into pcDNA3. 1 (+) to generate pcDNA3. 1 (+)/HA and pcDNA3.1 (+)/HA1, respectively. After verification of the cloning fidelity by restriction endonuclease digestion, PCR, and sequencing, pcDNA3.1 (+)/HA and pcDNA3.1 (+)/HA1 were transfected into HEK293 cells using PolyFect Transfection Reagent. Immunofluorescence assay was used to detect the transient expressing cells. Fluorescence microscopy revealed strong expression of target gene in HEK293 cells transiently transfected with either pcDNA3. 1 (+)/HA or pcDNA3. 1 (+)/HA1. Therefore, the results confirm the successful construction of eukaryotic expressing plasmids capable of driving the eukaryotic expression of influenza virus antigen HA and HA1, which is likely to provide a basis for both further investigation of the mechanism of influenza viral infection and the development of influenza DNA vaccine.

  17. L'oggetto del desiderio ha il colore del vuoto

    Directory of Open Access Journals (Sweden)

    Giovanni Bottiroli

    2011-07-01

    Full Text Available L’oggetto del desiderio non è semplicemente un oggetto empirico; su ciò, con qualche esitazione, potrebbe esistere un consenso generale. Resta la difficoltà di indicare le caratteristiche dell’oggetto del desiderio: che non sono banalmente delle proprietà, e neanche solo delle parti (in senso empirico, come si potrebbe nominarle da un punto di vista mereologico. L’oggetto del desiderio ha uno statuto modale: è un oggetto modalmente diviso, nei registri e nei regimi. Nella dimensione del desiderio, tanto il soggetto quanto l’oggetto sono abitati dal conflitto tra il diviso e l’indiviso. La spinta verso l’indiviso corrisponde a ciò che Freud ha introdotto con la nozione enigmatica di «pulsione di morte». In termini lacaniani, è l’attrazione verso la Cosa (das Ding. E la Cosa vuole coincidere con se stessa, abolendo ogni distinzione. L’oggetto del desiderio non è un dato o una forma empirica, per attraente che sia: l’attrazione che esercita proviene dal caos. Alla pericolosa coincidenza del «vuoto-pieno» (das Ding il desiderio oppone il vuoto logico della non-coincidenza. Una teoria del desiderio non può fare a meno di una riflessione sui differenti significati del vuoto.

  18. Biomedical potential of chitosan/HA and chitosan/β-1,3-glucan/HA biomaterials as scaffolds for bone regeneration — A comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Przekora, Agata, E-mail: agata.przekora@umlub.pl [Department of Biochemistry and Biotechnology, Medical University of Lublin, Chodzki 1, 20-093 Lublin (Poland); Palka, Krzysztof [Department of Materials Engineering, Lublin University of Technology, Nadbystrzycka 36, 20-618 Lublin (Poland); Ginalska, Grazyna [Department of Biochemistry and Biotechnology, Medical University of Lublin, Chodzki 1, 20-093 Lublin (Poland)

    2016-01-01

    The aim of this work was to compare biomedical potential of chitosan/hydroxyapatite (chit/HA) and novel chitosan/β-1,3-glucan/hydroxyapatite (chit/glu/HA) materials as scaffolds for bone regeneration via characterization of their biocompatibility, porosity, mechanical properties, and water uptake behaviour. Biocompatibility of the scaffolds was assessed in direct-contact with the materials using normal human foetal osteoblast cell line. Cytotoxicity and osteoblast proliferation rate were evaluated. Porosity was assessed using computed microtomography analysis and mechanical properties were determined by compression testing. Obtained results demonstrated that chit/HA scaffold possessed significantly better mechanical properties (compressive strength: 1.23 MPa, Young's modulus: 0.46 MPa) than chit/glu/HA material (compressive strength: 0.26 MPa, Young's modulus: 0.25 MPa). However, addition of bacterial β-1,3-glucan to the chit/HA scaffold improved its flexibility and porosity. Moreover, chit/glu/HA scaffold revealed significantly higher water uptake capability (52.6% after 24 h of soaking) compared to the chit/HA (30.7%) and thus can serve as a very good drug delivery carrier. Chit/glu/HA scaffold was also more favourable to osteoblast survival (near 100% viability after 24-h culture), proliferation, and spreading compared to the chit/HA (63% viability). The chit/glu/HA possesses better biomedical potential than chit/HA scaffold. Nevertheless, poor mechanical properties of the chit/glu/HA limit its application to non-load bearing implantation area. - Highlights: • Chitosan/HA and chit/β-1,3-glucan/HA scaffolds for bone regeneration were compared. • Chit/HA significantly reduced osteoblast viability to 63% compared to chit/glu/HA. • Unlike chit/HA, chit/glu/HA favoured cell adhesion, spreading, and proliferation. • Chit/HA had better compressive strength and Young's modulus than chit/glu/HA. • Chit/glu/HA revealed significantly higher

  19. TA/TA list planning principles of TD-LTE system%TD-LTE系统TA及TA list规划原则

    Institute of Scientific and Technical Information of China (English)

    吕邦国; 于涛

    2013-01-01

      Firstly the TD-LTE system location area management mechanism is introduced in this paper. Secondly this paper analyzes the network paging mechanism, paging capacity according to the TD-LTE system capabilities and the current TD-LTE device performance. Lastly, by predicting the number of users as well as LTE cell single-user paging model, the TA/TA list planning principles and recommendations are given in this paper.%  本文首先介绍了TD-LTE系统位置区的管理机制,其次从TD-LTE系统能力以及目前TD-LTE设备性能等角度,分析了TD-LTE网络的寻呼机制和寻呼容量,最后通过预测LTE小区的用户数目以及单用户寻呼模型,给出了TA/TA list的规划原则和建议。

  20. Enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers by inhibiting Ta diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xu-Jing; Jiang, Shao-Long; Zhang, Jing-Yan; Liu, Qian-Qian; Liu, Yi-Wei; Zhao, Jian-Cheng [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Wu, Zheng-Long [Analytical and Testing Center, Beijing Normal University, Beijing 100875 (China); Feng, Chun, E-mail: fengchun@ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Li, Ming-Hua [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yu, Guang-Hua, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2016-03-01

    Graphical abstract: To reveal the underlying mechanism of Mg influence on the enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers, the X-ray photoelectron spectroscopy analysis have been performed. It is found that a certain amount of Mg interlayer at the CoFeB/MgO interface could prevent the Ta oxidation to some extent due to the oxygen deficit MgO{sub x} (x < 1), and consequently lower the diffusion motivation of Ta from the bottom layer to the CoFeB/MgO interfaces to some extent during the annealing process. The prevention of Ta diffusion realizes the effective hybridization of Fe and O at the CoFeB/MgO interface and maintains interfacial magnetic anisotropy (K{sub CoFeB/MgO}). As a result, the perpendicular magnetic anisotropy at high annealing temperatures was maintained. - Highlights: • High annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers was realized. • X-ray photoelectron spectroscopy analysis has been performed to explore the reasons. • The prevention of Ta diffusion was realized by introducing Mg at the CoFeB/MgO interface. - Abstracts: To reveal the underlying mechanism of Mg influence on the enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers, the X-ray photoelectron spectroscopy analysis has been performed. It is found that a certain amount of Mg interlayer at the CoFeB/MgO interface could prevent the Ta oxidation, and consequently lower the diffusion motivation of Ta from the bottom layer to the CoFeB/MgO interfaces to some extent in the annealing process. The prevention of Ta diffusion realizes the effective hybridization of Fe and O at the CoFeB/MgO interface and maintains interfacial magnetic anisotropy (KCoFeB/MgO). As a result, the perpendicular magnetic anisotropy at high annealing temperatures is maintained.

  1. 77 FR 47671 - TA-W-81,520, T-Mobile USA, Inc., Call Center, Allentown, PA; TA-W-81,520G, T-Mobile USA, Inc...

    Science.gov (United States)

    2012-08-09

    ... Employment and Training Administration TA-W-81,520, T-Mobile USA, Inc., Call Center, Allentown, PA; TA- W-81..., Inc., Call Center, Allentown, Pennsylvania (TA-W-81,520), Fort Lauderdale, Florida (TA-W-81,520A), Frisco, Texas (TA-W-81,520B), Brownsville, Texas (TA-W- 81,520C), Lenexa, Kansas (TA-W-81,520D),...

  2. The Spectral Properties of Zn doped LiNbO3 Crystals%掺锌LiNbO3晶体的光谱性质

    Institute of Scientific and Technical Information of China (English)

    赵业权; 徐悟生; 朱质彬; 张玥; 徐蔚青; 王继扬

    2000-01-01

    在LiNbO3中掺进2 mol%,4 mol%,6 mol%,8 mol%的ZnO,生长Zn(2 mol%):LiNbO3,Zn(4 mol%):LiNbO3,Zn(6 mol%):LiNbO3和Zn(8 mol%):LiNbO3晶体,测试LiNbO3和掺锌LiNbO3晶体的透射光谱.LiNbO3和掺锌LiNbO3晶体在350-900 nm的范围内都是透明的.Zn:LiNbO3晶体的吸收边发生紫移.对Zn:LiNbO3晶体吸收边紫移的机理进行探讨.

  3. LARP Long Nb3Sn Quadrupole Design.

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio,G.; Andreev, N.; Anerella, M.; Barzi, E.; Bossert, R.; Caspi, S.; Chlachidize, G.; Dietderich, D.; Feher, S.; Felice, H.; Ferracin, P.; Ghosh, A.; Hafalia, A.R.; Hannaford, C.R.; Kashikhin, V.V.; Kerby, J.; Lamm, M.; Lietzke, A.; McInturff, A.; Muratore, J.; Nobrega, F.; Novitsky, I.; Sabbi, G.L.; Schmalzle, J.; Tartaglia, M.; Turrioni, D.; Wanderer, P.; Whitson, G.; Zlobin, A.V.

    2007-08-27

    A major milestone for the LHC Accelerator Research Program (LARP) is the test, by the end of 2009, of two 4m-long quadrupole magnets (LQ) wound with Nb{sub 3}Sn conductor. The goal of these magnets is to be a proof of principle that Nb{sub 3}Sn is a viable technology for a possible LHC luminosity upgrade. The design of the LQ is based on the design of the LARP Technological Quadrupoles, presently under development at FNAL and LBNL, with 90-mm aperture and gradient higher than 200 T/m. The design of the first LQ model will be completed by the end of 2007 with the selection of a mechanical design. In this paper we present the coil design addressing some fabrication technology issues, the quench protection study, and three designs of the support structure.

  4. AlNb-Based Titanium Aluminide

    Science.gov (United States)

    Zhang, Kezhao; Liu, Ming; Lei, Zhenglong; Chen, Yanbin

    2014-10-01

    The microstructure of laser-tungsten inert gas hybrid welded Ti2AlNb-based joints and their tensile properties at room temperature were investigated in this paper. The results showed that good-quality joints could be obtained by hybrid welding process. The microstructure evolution was identified by means of optical microscopy, scanning electron microscopy, x-ray diffraction, and transmission electron microscopy. The fusion zone mainly consisted of B2 phase due to the rapid cooling rate, as well as high Nb content. The phase compositions of the heat-affected zone were varied with different thermal cycles during the welding process. Tensile tests at room temperature showed that fracture tended to occur in the fusion zone, and the tensile strength and elongation were 950 MPa and 4.3%, respectively. The fracture mode was quasi-cleavage based on the observation of the fracture morphology.

  5. Bør leger ha reservasjonsrett ved assistert befruktning?

    Directory of Open Access Journals (Sweden)

    Morten Magelssen

    2011-10-01

    Full Text Available Omfanget av helsepersonells reservasjonsrett har nylig vært gjenstand for debatt i Norge. Vi spør om leger bør ha reservasjonsrett ved utførelse og henvisning til assistert befruktning, og drøfter argumenter for og imot ved hjelp av et rammeverk med sju kriterier for vurdering av reservasjon. Reservasjonsrettens grunnleggende dilemma er hvordan to viktige hensyn, henholdsvis pasientens rett til behandling og hensynet til helsepersonellets moralske integritet, best kan ivaretas. Det argumenteres for at leger bør ha rett til å reservere seg mot å utføre, assistere ved og henvise til assistert befruktning generelt hvis begrunnelsen er hensynet til befruktede eggs moralske verdi. Videre finner vi at leger også kan ha en moralsk rett til reservasjon mot å utføre, assistere ved og henvise til assistert befruktning for likekjønnede, men da på nærmere spesifiserte vilkår.Nøkkelord: reservasjonsrett, assistert befruktning, samvittighet, moralsk integritetEnglish summary: Should physicians have the right to conscientiously object to assisted reproduction?The extent of the healthcare worker's right to conscientious objection has recently been debated in Norway. This article asks whether physicians should have a right to conscientious objection to the performance of, and referral for, assisted reproduction, and discusses arguments for and against the same, utilizing a framework of seven criteria for the evaluation of conscientious objection. The fundamental dilemma of conscientious objection is how two important considerations can be reconciled: the patient's right to treatment, and the protection of the healthcare worker's moral integrity. It is argued that physicians should have the right to object to performing, assisting with, and referring for assisted reproduction generally when the objection is grounded in the moral value of the embryo. Furthermore, physicians may also have a moral right to object to performing, assisting with, and

  6. Transport properties of nanoperforated Nb thin films

    Energy Technology Data Exchange (ETDEWEB)

    Trezza, M., E-mail: trezza@sa.infn.i [Laboratorio Regionale SuperMat, CNR-INFM Salerno and Dipartimento di Fisica ' E. R. Caianiello' , Universita degli Studi di Salerno, Baronissi I-84081 (Italy); Cirillo, C. [Laboratorio Regionale SuperMat, CNR-INFM Salerno and Dipartimento di Fisica ' E. R. Caianiello' , Universita degli Studi di Salerno, Baronissi (Saudi Arabia) I-84081 (Italy); Prischepa, S.L. [State University of Informatics and RadioElectronics, P. Brovka Street 6, Minsk 220013 (Belarus); Attanasio, C. [Laboratorio Regionale SuperMat, CNR-INFM Salerno and Dipartimento di Fisica ' E. R. Caianiello' , Universita degli Studi di Salerno, Baronissi I-84081 (Italy)

    2010-10-01

    Porous silicon, obtained by electrochemical etching, has been used as a substrate for the growth of nanoperforated Nb thin films. The films, deposited by UHV magnetron sputtering, inherited from the Si substrates their structure, made of holes of 10 nm diameter and of 20 and 40 nm spacing, which provide an artificial pinning lattice. Commensurability effects between the Abrikosov vortex lattice and the artificial array of holes were investigated by transport measurements.

  7. 75 FR 43564 - TA-W-71,483, Continental Airlines, Inc., Reservations Division, Houston, TX; TA-W-71,483A...

    Science.gov (United States)

    2010-07-26

    ... Employment and Training Administration TA-W-71,483, Continental Airlines, Inc., Reservations Division, Houston, TX; TA-W-71,483A, Continental Airlines, Inc., Reservations Division, Tampa, FL; TA-W-71,483B, Continental Airlines, Inc., Reservations Division, Salt Lake City, UT; Notice of Negative Determination...

  8. Pd/Ta2O5/SiC Schottky-diode hydrogen sensors formed by using rapid thermal oxidation of Ta thin films

    Science.gov (United States)

    Joo, Sung-Jae; Choi, Je Hoon; Kim, Seong Jeen; Kim, Sang-Cheol

    2013-11-01

    Pd/Ta2O5/SiC Schottky-diode hydrogen sensors were fabricated, and their hydrogen gas sensing performance was investigated at 573 K and 773 K. Interfacial Ta2O5 films of 120 nm in thickness were formed by using rapid thermal oxidation (RTO) of the sputtered Ta films on SiC. The crystallinity of the Ta and the Ta2O5 films were characterized by using X-ray diffraction (XRD). As-sputtered Ta films on 4H-SiC are composed of α-Ta (body-centered-cubic) and β-Ta (tetragonal), and α-Ta (110) is the dominant orientation. After RTO at 573 K, the Ta films are converted to β-Ta2O5 (orthorhombic). The diode sensors show high sensitivity to H2 even at the low H2 concentration of 500 ppm, and the voltage change of the sensor upon H2 exposure is proportional to the H2 concentration in the range of 500 ˜ 2000 ppm at 573 K. The response voltage ΔV is shown to arise mostly from the change in the series resistance component of the sensor upon H2 exposure; the main origin of that change is believed to be the Ta2O5 interfacial layer. The response time t90 of the sensor at 573 K was estimated to be approximately 8 s.

  9. Effects of contents of Nb and C on hot deformation behaviors of high Nb X80 pipeline steels

    Institute of Scientific and Technical Information of China (English)

    QIAO Gui-ying; XIAO Fu-ren; ZHANG Xiao-bing; CAO Ya-bin; LIAO Bo

    2009-01-01

    The behavior of the flow deformation and the effects of contents of Nb and C on deformation behaviors of high Nb X80 pipeline steels during hot compression deformation were studied by thermal simulation test.The content of solid solution Nb was quantificationally studied during the reheating and hot deformation process,and the effects of change of solid solution Nb in steels on hot deformation behaviors were discussed.The results show that the contents of Nb and C have great effects on the flow stress behaviors of high Nb X80 pipeline steels.When the C content in steels is constant,the recrystallization activation energy increases from 387 to 481 kJ/mol with increasing the Nb from 0.082% to 0.13% (mass fraction).However,the effect of Nb is correlative to the C content,I.e.w(Nb)/w(C).When w(Nb)/w(C) decreases from 3.61 to 2.18,the recrystallization activation energy decreases from 481 to 434 kJ/mol.

  10. Optical waveguides in LiNbO3 and stoichiometric LiNbO3 crystals by proton exchange

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The formation of optical planar waveguides in LiNbO3 and stoichiometric LiNbO3 crystals by proton exchange was reported. The prism-coupling method was used to characterize the dark-line spectroscopy at the wavelength of 633 and 1539 nm, re-spectively. The mode optical near-field outputs from proton-exchanged LiNbO3 and SLN waveguides at 633 nm were presented. The mode field from stoichiometric LiNbO3 (SLN) waveguide is lighter and more uniform than that from LiNbO3 waveguide, which means the quality of the waveguide in SLN crystal is better than that of the LiNbO3 waveguide. For proton-exchanged LiNbO3 waveguides, the evo-lution of the refractive index profile with annealing was presented. The disorder profiles of Nb atoms in proton-exchanged LiNbO3 waveguides were obtained by Rutherford backscattering/channeling technique. It is shown that the longer the exchange time, the larger the displacement of Nb atoms.

  11. Immunomodulatory Effects of Hemagglutinin- (HA- Modified A20 B-Cell Lymphoma Expanded as a Brain Tumor on Adoptively Transferred HA-Specific CD4+ T Cells

    Directory of Open Access Journals (Sweden)

    Valentin P. Shichkin

    2014-01-01

    Full Text Available Previously, the mouse A20 B-cell lymphoma engineered to express hemagglutinin (HA antigen (A20HA was used as a systemic tumor model. In this work, we used the A20HA cells as a brain tumor. HA-specific CD4+ T cells were transferred intravenously in a tail vein 5 days after A20HA intracranial inoculation and analyzed on days 2, 9, and 16 after the adoptive transfer by different methods. The transferred cells demonstrated state of activation as early as day 2 after the adoptive transfer and most the of viable HA-specific cells became anergic on day 16. Additionally, symptoms of systemic immunosuppression were observed in mice with massive brain tumors at a late stage of the brain tumor progression (days 20–24 after the A20HA inoculation. Despite that, a deal of HA-specific CD4+ T cells kept the functional activity even at the late stage of A20HA tumor growth. The activated HA-specific CD4+ T cells were found also in the brain of brain-tumor-bearing mice. These cells were still responding to reactivation with HA-peptide in vitro. Our data support an idea about sufficient role of both the tumor-specific and -nonspecific mechanisms inducing immunosuppression in cancer patients.

  12. Glycosylation of Residue 141 of Subtype H7 Influenza A Hemagglutinin (HA) Affects HA-Pseudovirus Infectivity and Sensitivity to Site A Neutralizing Antibodies

    Science.gov (United States)

    Alvarado-Facundo, Esmeralda; Vassell, Russell; Schmeisser, Falko; Weir, Jerry P.; Weiss, Carol D.; Wang, Wei

    2016-01-01

    Human infections with H7 subtype influenza virus have been reported, including an H7N7 outbreak in Netherlands in 2003 and H7N9 infections in China in 2013. Previously, we reported murine monoclonal antibodies (mAbs) that recognize the antigenic site A of H7 hemagglutinin (HA). To better understand protective immunity of H7 vaccines and vaccine candidate selection, we used these mAbs to assess the antigenic relatedness among two H7 HA isolated from past human infections and determine residues that affect susceptibility to neutralization. We found that these mAbs neutralize pseudoviruses bearing HA of A/Shanghai/02/2013(H7N9), but not A/Netherlands/219/2003(H7N7). Glycosylation of the asparagine residue at position 141 (N141) (N133, H3 HA numbering) in the HA of A/Netherlands/219/2003 HA is responsible for this resistance, and it affects the infectivity of HA-pseudoviruses. The presence of threonine at position 143 (T135, H3 HA numbering) in the HA of A/Netherlands/219/2003, rather than an alanine found in the HA of A/Shanghai/02/2013(H7N9), accounts for these differences. These results demonstrate a key role for glycosylation of residue N141 in affecting H7 influenza HA-mediated entry and sensitivity to neutralizing antibodies, which have implications for candidate vaccine design. PMID:26862918

  13. Initiation of student-TA interactions in tutorials

    Directory of Open Access Journals (Sweden)

    Raymond A. Hodges

    2006-12-01

    Full Text Available At the University of Maryland we videotaped several semesters of tutorials as part of a large research project. A particular research task required us to locate examples of students calling the teaching assistants (TAs over for assistance with a physics question. To our surprise, examples of this kind of interaction were difficult to find. We undertook a systematic study of TA-student interactions in tutorial: In particular, how are the interactions initiated? Do the students call the TA over for help with a particular issue, does the TA stop by spontaneously, or does the worksheet require a discussion with the TA at that point? The initiation of the interaction is of particular interest because it provides evidence of the motivation for and purpose of the interaction. This paper presents the results of that systematic investigation. We discovered that the majority of student-TA interactions in tutorial are initiated by teaching assistants, confirmed our initial observation that relatively few interactions are initiated by students, and found, further, that even fewer interactions are worksheet initiated. Perhaps most importantly, we found that our sense of who initiates tutorial interactions—based on extensive but informal observations—is not necessarily accurate. We need systematic investigations to uncover the reality of our classroom experiences.

  14. Fibroblast functionality on novel Ti-30Ta nanotube array

    Energy Technology Data Exchange (ETDEWEB)

    Capellato, Patricia, E-mail: pat_capellato@yahoo.com.br [Department of Materials, Faculty of Engineering Guaratingueta, Sao Paulo State University-UNESP, Av. Ariberto Pereira da Cunha, 333, Pedregulho, CEP 12516-410, Guaratingueta, SP (Brazil); Smith, Barbara S. [School of Biomedical Engineering, Colorado State University, Fort Collins CO 80523 (United States); Popat, Ketul C. [School of Biomedical Engineering, Colorado State University, Fort Collins CO 80523 (United States); Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523 (United States); Claro, Ana P.R. Alves [Department of Materials, Faculty of Engineering Guaratingueta, Sao Paulo State University-UNESP, Av. Ariberto Pereira da Cunha, 333, Pedregulho, CEP 12516-410, Guaratingueta, SP (Brazil)

    2012-10-01

    In this study, the mechanical substrate and topographical surface properties of anodized Ti-30Ta alloy were investigated using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and contact angle measurement. The anodization process was performed in an electrolyte solution containing HF (48%) and H{sub 2}SO{sub 4} (98%) in the volumetric ratios 1:9 with the addition of 5% dimethyl sulfoxide (DMSO) at 15 V, 25 V and 35 V for 20 and 40 min, producing a nanotube architecture when anodized at 35 V for 40 min. Human dermal fibroblasts (HDF, neonatal) were utilized to evaluate the biocompatibility of Ti-30Ta nanotubes and Ti-30Ta alloy after 1 and 3 days of culture. Cellular adhesion, proliferation, viability, cytoskeletal organization and morphology were investigated using fluorescence microscope imaging, biochemical assay and SEM imaging respectively. The results presented identify altered material properties and improved cellular interaction on Ti-30Ta nanotubes as compared to Ti-30 Ta alloy. - Highlights: Black-Right-Pointing-Pointer The surface was modified by anodization, biomimetic treatment and ion bean etching. Black-Right-Pointing-Pointer SEM, EDS and contact angle measurements were used to characterize the surface. Black-Right-Pointing-Pointer Group 5 the most hydrophobic. Black-Right-Pointing-Pointer Group 4 the most hydrophilic. Black-Right-Pointing-Pointer Group 3 and 4 are the more indicated for biomedical application.

  15. 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.

  16. "Fine grain Nb tube for SRF cavities"

    Energy Technology Data Exchange (ETDEWEB)

    Robert E. Barber

    2012-07-08

    Superconducting radio frequency (SRF) cavities used in charged particle linear accelerators, are currently fabricated by deep drawing niobium sheets and welding the drawn dishes together. The Nb sheet has a non-uniform microstructure, which leads to unpredictable cavity shape and surface roughness, and inconsistent "spring-back" during forming. In addition, weld zones cause hot spots during cavity operation. These factors limit linear accelerator performance and increase cavity manufacturing cost. Equal channel angular extrusion (ECAE) can be used to refine and homogenize the microstructure of Nb tube for subsequent hydroforming into SRF cavities. Careful selection of deformation and heat treatment conditions during the processing steps can give a uniform and consistent microstructure in the tube, leading to improved deformability and lower manufacturing costs. Favorable microstructures were achieved in short test samples of RRR Nb tube, which may be particularly suitable for hydroforming into SRF cavity strings. The approach demonstrated could be applicable to microstructure engineering of other tube materials including tantalum, titanium, and zirconium.

  17. Review of oxidation of Nb-1Zr

    Energy Technology Data Exchange (ETDEWEB)

    DiStefano, J.R.

    1989-04-01

    A major objective of the SP-100 Program Nuclear Assembly Test is to demonstrate the performance of a full-scale nuclear subsystem of a 100-kWe space nuclear power supply. The test will be run in a large vacuum chamber to protect the Nb-1Zr components from oxidation during operation. Much information about the oxidation of niobium and Nb-1Zr alloy already exists, and previous work in this area is reviewed. Oxidation of Nb-1Zr can proceed by solution, internal oxidation, and/or film formation. At temperatures up to about 650 K (377/degree/C), oxidation generally follows a parabolic rate law because of the formation of protective oxide(s). At higher temperatures, oxidation becomes linear, but results are extremely sensitive to pressure and other system variables. Results obtained by several investigators could not be predicted using empirical equations developed by one investigator relating the increase in oxygen concentration to pressure, temperature, time, and specimen thickness. Additional data are required to provide more reliable guidelines for system operation that will protect against catastrophic effects. 20 refs., 12 figs., 7 tabs.

  18. 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.

  19. Nb3Sn Superconductor Loss Study

    Science.gov (United States)

    1988-01-08

    Bean model Q(-) is proportionalo 3 to HA For the case where HA is large compared with the penetration field, the loss is directly proportional to j...the time rate of change of flux density B is equal to the time rate of change of the applied field HA in a Bean model for the current densities. From...cor- rected for the field of neighboring turns in the sample. With the use of the expression for I’ estimated from a Bean model it follows that 0.4 d

  20. Low temperature spark plasma sintering of TC4/HA composites

    Institute of Scientific and Technical Information of China (English)

    Huiliang Shao; Lei Cao; Daqian Sun; Zhankui Zhao

    2016-01-01

    Ti6Al4V/hydroxyapatite composites (TC4/HA) have been prepared by high energy ball milling and low temperature spark plasma sintering at 600 °C, 550 °C, 500 °C and 450 °C, respectively. The sintering temperature of the composites was sharply decreased as the result of the activation and surficial modification effects induced from high energy ball milling. The decomposition and reaction of hydro-xyapatite was successfully avoided, which offers the composites superior biocompatibility. The hydro-xyapatite in the composites was distributed in gap uniformly, and formed an ideal network structure. The lowest hardness, compressive strength and Young's modulus of the composites satisfy the requirements of human bone.