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Sample records for shock-recovered tantalum single

  1. Simulations of X-ray diffraction of shock-compressed single-crystal tantalum with synchrotron undulator sources.

    Science.gov (United States)

    Tang, M X; Zhang, Y Y; E, J C; Luo, S N

    2018-05-01

    Polychromatic synchrotron undulator X-ray sources are useful for ultrafast single-crystal diffraction under shock compression. Here, simulations of X-ray diffraction of shock-compressed single-crystal tantalum with realistic undulator sources are reported, based on large-scale molecular dynamics simulations. Purely elastic deformation, elastic-plastic two-wave structure, and severe plastic deformation under different impact velocities are explored, as well as an edge release case. Transmission-mode diffraction simulations consider crystallographic orientation, loading direction, incident beam direction, X-ray spectrum bandwidth and realistic detector size. Diffraction patterns and reciprocal space nodes are obtained from atomic configurations for different loading (elastic and plastic) and detection conditions, and interpretation of the diffraction patterns is discussed.

  2. Simulations of X-ray diffraction of shock-compressed single-crystal tantalum with synchrotron undulator sources

    Energy Technology Data Exchange (ETDEWEB)

    Tang, M. X.; Zhang, Y. Y.; E, J. C.; Luo, S. N.

    2018-04-24

    Polychromatic synchrotron undulator X-ray sources are useful for ultrafast single-crystal diffraction under shock compression. Here, simulations of X-ray diffraction of shock-compressed single-crystal tantalum with realistic undulator sources are reported, based on large-scale molecular dynamics simulations. Purely elastic deformation, elastic–plastic two-wave structure, and severe plastic deformation under different impact velocities are explored, as well as an edge release case. Transmission-mode diffraction simulations consider crystallographic orientation, loading direction, incident beam direction, X-ray spectrum bandwidth and realistic detector size. Diffraction patterns and reciprocal space nodes are obtained from atomic configurations for different loading (elastic and plastic) and detection conditions, and interpretation of the diffraction patterns is discussed.

  3. Strength of shock-loaded single-crystal tantalum [100] determined using in situ broadband x-ray Laue diffraction.

    Science.gov (United States)

    Comley, A J; Maddox, B R; Rudd, R E; Prisbrey, S T; Hawreliak, J A; Orlikowski, D A; Peterson, S C; Satcher, J H; Elsholz, A J; Park, H-S; Remington, B A; Bazin, N; Foster, J M; Graham, P; Park, N; Rosen, P A; Rothman, S R; Higginbotham, A; Suggit, M; Wark, J S

    2013-03-15

    The strength of shock-loaded single crystal tantalum [100] has been experimentally determined using in situ broadband x-ray Laue diffraction to measure the strain state of the compressed crystal, and elastic constants calculated from first principles. The inferred strength reaches 35 GPa at a shock pressure of 181 GPa and is in excellent agreement with a multiscale strength model [N. R. Barton et al., J. Appl. Phys. 109, 073501 (2011)], which employs a hierarchy of simulation methods over a range of length scales to calculate strength from first principles.

  4. Shock compression and quasielastic release in tantalum

    International Nuclear Information System (INIS)

    Johnson, J.N.; Hixson, R.S.; Tonks, D.L.; Gray, G.T. III

    1994-01-01

    Previous studies of quasielastic release in shock-loaded FCC metals have shown a strong influence of the defect state on the leading edge, or first observable arrival, of the release wave. This is due to the large density of pinned dislocation segments behind the shock front, their relatively large pinning separation, and a very short response time as determined by the drag coefficient in the shock-compressed state. This effect is entirely equivalent to problems associated with elastic moduli determination using ultrasonic methods. This is particularly true for FCC metals, which have an especially low Peierls stress, or inherent lattice resistance, that has little influence in pinning dislocation segments and inhibiting anelastic deformation. BCC metals, on the other hand, have a large Peierls stress that essentially holds dislocation segments in place at low net applied shear stresses and thus allows fully elastic deformation to occur in the complete absence of anelastic behavior. Shock-compression and release experiments have been performed on tantalum (BCC), with the observation that the leading release disturbance is indeed elastic. This conclusion is established by examination of experimental VISAR records taken at the tantalum/sapphire (window) interface in a symmetric-impact experiment which subjects the sample to a peak longitudinal stress of approximately 7.3 GPa, in comparison with characteristic code calculations. copyright 1994 American Institute of Physics

  5. Hydrocode analysis of lateral stress gauges in shocked tantalum

    International Nuclear Information System (INIS)

    Harris, E. J.; Winter, R. E.

    2007-01-01

    Experiments published by other workers, on the resistance change of manganin stress gauges embedded in a lateral orientation in tantalum targets shocked to a range of stresses, have been analysed using an adaptive mesh refinement hydrocode. It was found that for all of the four experiments the shape of the time profile of the computed lateral stress in the mounting layer closely matched the shape of the experimental lateral stress profiles. However, the calculated lateral stresses at the gauge location in the mounting layer are significantly less than the lateral stresses that would have been produced in the target if no gauge had been present. The perturbation caused by the gauge increased as the strength of the applied shock increased. When the perturbations are taken into account values of flow stress that are significantly smaller than those reported in the original research paper are derived. The work shows that the lateral gauge technique can give valuable information on strength provided high resolution simulation is used to compensate for the perturbations caused by the gauges

  6. Niobium and tantalum

    Science.gov (United States)

    Schulz, Klaus J.; Piatak, Nadine M.; Papp, John F.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

    2017-12-19

    mineral tantalite ((Fe,Mn)(Ta,Nb)2O6), which is found as an accessory mineral in rare-metal granites and pegmatites that are also enriched in lithium and cesium (termed lithium-cesium-tantalum (LCT)-type pegmatites).Brazil and Canada are the leading nations that produce niobium mineral concentrates, but Brazil is by far the leading producer, accounting for about 90 percent of production, which comes mostly from weathered material derived from carbonatites. Brazil and Canada also have the largest identified niobium resources; additional resources, although they are less well reported, occur in Angola, Australia, China, Greenland, Malawi, Russia, and South Africa. Australia and Brazil have been the leading producers of tantalum mineral concentrates, although recently Ethiopia and Mozambique have also been significant suppliers of tantalum. Artisanal mining of columbite-tantalite (also called coltan) is practiced in many countries, particularly Burundi, the Democratic Republic of the Congo (Congo [Kinshasa]), Nigeria, Rwanda, and Uganda. Brazil has about 40 percent of the identified tantalum resources; other countries and regions with identified tantalum resources include, in decreasing order of resources, Australia, Asia, Russia and the Middle East, Africa, North America, and Europe. Identified niobium and tantalum resources in the United States are small, low grade, and difficult to recover and process, and are thus not commercially recoverable at current prices. Consequently, the United States meets its current and expected future needs for niobium and tantalum through imports of primary mineral concentrates and alloys and through recovery from foreign and domestic alloy scrap that contain the metals.Environmentally, the main issues related to niobium and tantalum mining are land disruptions, the volume of waste materials and their disposal, and the radioactivity of some tailings and waste materials that contain thorium and uranium. Because of the relative biological

  7. Sound velocity of tantalum under shock compression in the 18–142 GPa range

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Feng, E-mail: xifeng@caep.cn; Jin, Ke; Cai, Lingcang, E-mail: cai-lingcang@aliyun.com; Geng, Huayun; Tan, Ye; Li, Jun [National Key Laboratory of Shock Waves and Detonation Physics, Institute of Fluid Physics, CAEP, P.O. Box 919-102 Mianyang, Sichuan 621999 (China)

    2015-05-14

    Dynamic compression experiments of tantalum (Ta) within a shock pressure range from 18–142 GPa were conducted driven by explosive, a two-stage light gas gun, and a powder gun, respectively. The time-resolved Ta/LiF (lithium fluoride) interface velocity profiles were recorded with a displacement interferometer system for any reflector. Sound velocities of Ta were obtained from the peak state time duration measurements with the step-sample technique and the direct-reverse impact technique. The uncertainty of measured sound velocities were analyzed carefully, which suggests that the symmetrical impact method with step-samples is more accurate for sound velocity measurement, and the most important parameter in this type experiment is the accurate sample/window particle velocity profile, especially the accurate peak state time duration. From these carefully analyzed sound velocity data, no evidence of a phase transition was found up to the shock melting pressure of Ta.

  8. Fabrication of a tantalum-clad tungsten target for KENS

    International Nuclear Information System (INIS)

    Kawai, Masayoshi; Kikuchi, Kenji; Kurishita, Hiroaki; Li, J.-F.; Furusaka, Michihiro

    2001-01-01

    Since the cold neutron source intensity of KENS (the spallation neutron source at High Energy Accelerator Research Organization) was decreased into about a third of the designed value because a cadmium liner at the cold neutron source deformed and obstructed the neutron beam line, the target-moderator-and-reflector assembly (TMRA) has been replaced by a new one aimed at improving the neutron performance and recovering the cold neutron source. The tantalum target has also been replaced by a tantalum-clad tungsten one. In order to bond the tantalum-clad with the tungsten block, a hot isostatic press (HIP) process was applied and optimized. It was found that gaseous interstitial impurity elements severely attacked tantalum and embrittled, and that the getter materials such as zirconium and tantalum were effective to reduce the embrittlement

  9. Dislocation-drag contribution to high-rate plastic deformation in shock-loaded tantalum

    International Nuclear Information System (INIS)

    Tonks, D.L.; Hixson, R.S.; Johnson, J.N.; Gray, G.T. III

    1994-01-01

    Time-resolved plastic waves in plate-impact experiments give information on the relationship between applied shear stress and plastic strain rate at low plastic strain. This information is essentially different from that obtained at intermediate strain rates using Hopkins on bar techniques, because in the former case the material deformation state is driven briefly into the regime dominated by dislocation drag rather than thermal activation. Two VISAR records of the particle velocity at the tantalum/sapphire (window) interface are obtained for symmetric impact producing peak in situ longitudinal stresses of approximately 75 kbar and 111 kbar. The risetimes of the plastic waves are about 100 ns and 60 ns, respectively, with peak strain rates of about 2x10 5 /s and 1x10 6 /s, respectively, as determined by weak-shock analysis [Wallace, Phys. Rev. B 22, 1487 (1980), and Tonks, Los Alamos DataShoP Report LA-12068-MS (1991)]. These data show a much stronger dependence of plastic strain rate on applied shear stress than previously predicted by linear viscous drag models in combination with thermal activation through a large Peierls barrier. The data also show complex evolution of the mobile dislocation density during early stages of high-rate plastic flow. This measurement and analysis aid significantly in establishing the fundamental picture of dynamic deformation of BCC metals and the evolution of the internal material state at early times following shock compression. copyright 1994 American Institute of Physics

  10. Recovery of metal values and hydrofluoric acid from tantalum and columbium waste sludge

    International Nuclear Information System (INIS)

    Bielecki, E.; Romberger, K.; Bakke, B.; Hobin, M.A.; Clark, C.

    1992-01-01

    A metallurgical processing system for economically recovering metal values, such as columbium, tantalum, thorium, and uranium from dilute source solids, such as digestion sludges, by a series of steps including: (1) slurrying the source solids with dilute hydrofluoric acid to produce a solid phase and a liquid phase containing dissolved tantalum and columbium, then extracting tantalum and/or columbium from the liquid phase by means of a liquid ion-exchange process and then, additionally; (2) roasting the solid phase with sulfuric acid to recover and recycle hydrofluoric acid, leaching the roasted solids with dilute sulfuric acid to produce a disposable solid phase and a liquid phase containing thorium and uranium, and extracting thorium and uranium from the liquid phase by means of a liquid-liquid amine extraction process

  11. Tantalum strength model incorporating temperature, strain rate and pressure

    Science.gov (United States)

    Lim, Hojun; Battaile, Corbett; Brown, Justin; Lane, Matt

    Tantalum is a body-centered-cubic (BCC) refractory metal that is widely used in many applications in high temperature, strain rate and pressure environments. In this work, we propose a physically-based strength model for tantalum that incorporates effects of temperature, strain rate and pressure. A constitutive model for single crystal tantalum is developed based on dislocation kink-pair theory, and calibrated to measurements on single crystal specimens. The model is then used to predict deformations of single- and polycrystalline tantalum. In addition, the proposed strength model is implemented into Sandia's ALEGRA solid dynamics code to predict plastic deformations of tantalum in engineering-scale applications at extreme conditions, e.g. Taylor impact tests and Z machine's high pressure ramp compression tests, and the results are compared with available experimental data. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  12. Tantalum and niobium carbides obtention by carbothermic reduction of columbotantalite ores

    International Nuclear Information System (INIS)

    Gordo, E.; Garcia-Carcedo, F.; Torralba, J.M.

    1998-01-01

    Tantalum and niobium carbides are characterized by its high hardness and chemical corrosion resistance. Both carbides, but mainly TaC, are used in hard metals (sintered carbides), together with their carbides, to manufacture cutting tools and dies in special machining applications involving mechanical shock at high temperature. Its use as reinforcement of wear resistant materials through powder metallurgy techniques are being investigated. However, the use of TaC is usually limited because of its high cost. Therefore tantalum carbide with niobium content, which is cheaper, is used. In this work the obtention of complex tantalum and niobium carbides from a Spanish columbotantalite ore is studied through relatively cheap and simple process as it is carbothermic reduction. Concentration of the ore, its reduction and the characterization of products are described. (Author) 11 refs

  13. Material removal mechanisms in electrochemical-mechanical polishing of tantalum

    International Nuclear Information System (INIS)

    Gao, F.; Liang, H.

    2009-01-01

    Material removal mechanisms in tantalum chemical-mechanical polishing (CMP) and electrochemical-mechanical polishing (ECMP) were investigated using the single frequency electrochemical impedance spectroscopy (EIS). Through measuring the impedance of the tantalum surface, the single frequency EIS scan made it possible to observe the CMP and ECMP processes in situ. The impedance results presented competing mechanisms of removal and formation of a surface oxide layer of tantalum. Analysis indicated that the thickness of the oxide layer formed during polishing was related to the mechanical power correlated to the friction force and the rotating speed. Furthermore, the rate of growth and removal of the oxide film was a function of the mechanical power. This understanding is beneficial for optimization of CMP and ECMP processes.

  14. Vapor deposition of tantalum and tantalum compounds

    International Nuclear Information System (INIS)

    Trkula, M.

    1996-01-01

    Tantalum, and many of its compounds, can be deposited as coatings with techniques ranging from pure, thermal chemical vapor deposition to pure physical vapor deposition. This review concentrates on chemical vapor deposition techniques. The paper takes a historical approach. The authors review classical, metal halide-based techniques and current techniques for tantalum chemical vapor deposition. The advantages and limitations of the techniques will be compared. The need for new lower temperature processes and hence new precursor chemicals will be examined and explained. In the last section, they add some speculation as to possible new, low-temperature precursors for tantalum chemical vapor deposition

  15. Efficacy of Tantalum Tungsten Alloys for Diffusion Barrier Applications

    Science.gov (United States)

    Smathers, D. B.; Aimone, P. R.

    2017-12-01

    Traditionally either Niobium, Tantalum or a combination of both have been used as diffusion barriers in Nb3Sn Multi-filament wire. Vanadium has also been used successfully but the ultimate RRR of the copper is limited unless an external shell of Niobium is included. Niobium is preferred over Tantalum when alternating current losses are not an issue as the Niobium will react to form Nb3Sn. Pure Tantalum tends to deform irregularly requiring extra starting thickness to ensure good barrier qualities. Our evaluations showed Tantalum lightly alloyed with 3 wt% Tungsten is compatible with the wire drawing process while deforming as well as or better than pure Niobium. Ta3wt%W has been processed as a single barrier and as a distributed barrier to fine dimensions. In addition, the higher modulus and strength of the Tantalum Tungsten alloy improves the overall tensile properties of the wire.

  16. Multi-scale Modeling of Plasticity in Tantalum.

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Hojun [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Battaile, Corbett Chandler. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Carroll, Jay [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Buchheit, Thomas E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Boyce, Brad [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Weinberger, Christopher [Drexel Univ., Philadelphia, PA (United States)

    2015-12-01

    In this report, we present a multi-scale computational model to simulate plastic deformation of tantalum and validating experiments. In atomistic/ dislocation level, dislocation kink- pair theory is used to formulate temperature and strain rate dependent constitutive equations. The kink-pair theory is calibrated to available data from single crystal experiments to produce accurate and convenient constitutive laws. The model is then implemented into a BCC crystal plasticity finite element method (CP-FEM) model to predict temperature and strain rate dependent yield stresses of single and polycrystalline tantalum and compared with existing experimental data from the literature. Furthermore, classical continuum constitutive models describing temperature and strain rate dependent flow behaviors are fit to the yield stresses obtained from the CP-FEM polycrystal predictions. The model is then used to conduct hydro- dynamic simulations of Taylor cylinder impact test and compared with experiments. In order to validate the proposed tantalum CP-FEM model with experiments, we introduce a method for quantitative comparison of CP-FEM models with various experimental techniques. To mitigate the effects of unknown subsurface microstructure, tantalum tensile specimens with a pseudo-two-dimensional grain structure and grain sizes on the order of millimeters are used. A technique combining an electron back scatter diffraction (EBSD) and high resolution digital image correlation (HR-DIC) is used to measure the texture and sub-grain strain fields upon uniaxial tensile loading at various applied strains. Deformed specimens are also analyzed with optical profilometry measurements to obtain out-of- plane strain fields. These high resolution measurements are directly compared with large-scale CP-FEM predictions. This computational method directly links fundamental dislocation physics to plastic deformations in the grain-scale and to the engineering-scale applications. Furthermore, direct

  17. Recovery of hafnium radioisotopes from a proton irradiated tantalum target

    International Nuclear Information System (INIS)

    Taylor, W.A.; Garcia, J.G.; Hamilton, V.T.; Heaton, R.C.; Jamriska, D.J.; Ott, M.A.; Philips, D.R.; Radzinski, S.D.

    1998-01-01

    The 178m2 Hf nucleus, with its long half-life (31 y) and high-spin isomeric state (16 + ) is desired for new and exotic nuclear physics studies. The Los Alamos Radioisotope Program irradiated a kilogram of natural tantalum at the Los Alamos Meson Physics Facility in early 1981. After fifteen years of decay, this target was ideal for the recovery of 178m2 Hf. There was more than a millicurie of 178m2 Hf produced during this irradiation and there has been a sufficient period of time for most of the other hafnium radioisotopes to decayed away. Traditionally, separation techniques for recovering hafnium isotopes from tantalum targets employ solvent extractions with reagents that are considered hazardous. These techniques are no longer condoned because they generate a mixed-waste (radioactive and hazardous components) that can not be treated for disposal. In this paper we describe a new and unique procedure for the recovery of hafnium radioisotopes from a highly radioactive, proton irradiated, tantalum target using reagents that do not contribute a hazardous waste component. (author)

  18. Effect of strain rate and dislocation density on the twinning behavior in tantalum

    Energy Technology Data Exchange (ETDEWEB)

    Florando, Jeffrey N., E-mail: florando1@llnl.gov; Swift, Damian C.; Barton, Nathan R.; McNaney, James M.; Kumar, Mukul [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States); El-Dasher, Bassem S. [TerraPower LLC, Bellevue, WA 98005 (United States); Chen, Changqiang [Materials Research Laboratory, University of Illinois at Urbana Champaign, Urbana, IL 61801 (United States); Ramesh, K. T.; Hemker, Kevin J. [Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218 (United States)

    2016-04-15

    The conditions which affect twinning in tantalum have been investigated across a range of strain rates and initial dislocation densities. Tantalum samples were subjected to a range of strain rates, from 10{sup −4}/s to 10{sup 3}/s under uniaxial stress conditions, and under laser-induced shock-loading conditions. In this study, twinning was observed at 77 K at strain rates from 1/s to 10{sup 3}/s, and during laser-induced shock experiments. The effect of the initial dislocation density, which was imparted by deforming the material to different amounts of pre-strain, was also studied, and it was shown that twinning is suppressed after a given amount of pre-strain, even as the global stress continues to increase. These results indicate that the conditions for twinning cannot be represented solely by a critical global stress value, but are also dependent on the evolution of the dislocation density. In addition, the analysis shows that if twinning is initiated, the nucleated twins may continue to grow as a function of strain, even as the dislocation density continues to increase.

  19. The dislocation-internal friction peak γ in tantalum

    International Nuclear Information System (INIS)

    Baur, J.; Benoit, W.; Schultz, H.

    1989-01-01

    Torsion-pendulum measurements were carried out on high-purity single crystal specimens of tantalum, having extremely low oxygen contents ( 2 peak, which appears close to γ is small traces of oxygen are presents. The γ 2 peak was formerly explained as a ''dislocation-enhanced Snoek peak''. The γ peak recovers at the peak temperature, whereas the γ 2 peak is more stable. On the basis of their results, and making use of earlier investigations of Rodrian and Schultz, the authors suggest that γ 2 is modified γ relaxation, related to screw-dislocation segments, stabilized by oxygen-decorated kinks. The stability of the γ 2 peak allows an accurate determination of the activation energy, found to be 1.00 +- 0.03 eV. This value is distinctly lower than the activation energy of the oxygen Snoek effect (1.10 eV) and is related here to the mechanism of ''kink-pair formation'' in screw dislocations, as the original γ peak. The numerical value is compatible with recent values derived from flow-stress measurements. The peak γ 2 shows increasing stability with increasing oxygen content. This is explained by single- and multi-decorated kinks

  20. Photo field emission spectroscopy of the tantalum band structure

    International Nuclear Information System (INIS)

    Kleint, Ch.; Radon, T.

    1978-01-01

    Photo field emission (PFE) currents of clean and barium covered tantalum tips have been measured with single lines of the mercury arc spectrum and phase-sensitive detection. Field strength and work function were determined from Fowler-Nordheim plots of the FE currents. Shoulders in the PFE current-voltage characteristics could be correlated to transitions in the band structure of tantalum according to a recently proposed two-step PFE model. A comparison with the relativistic calculations of Mattheiss and the nonrelativistic bands of Petroff and Viswanathan shows that Mattheiss' bands are more appropriate. Beside direct transitions several nondirect transitions from the different features composing the upper two density of states maxima below the Fermi edge of tantalum have been found. (Auth.)

  1. Thermal shock cracking of GSO single crystal

    International Nuclear Information System (INIS)

    Miyazaki, Noriyuki; Yamamoto, Kazunari; Tamura, Takaharu; Kurashige, Kazuhisa; Ishibashi, Hiroyuki; Susa, Kenzo

    1998-01-01

    The quantitative estimation of the failure stress of a gadolinium orthosilicate (Gd 2 SiO 5 , hereafter abbreviated as GSO) single crystal due to thermal shock was investigated. A cylindrical test specimen was heated in a silicone oil bath, then subjected to thermal shock by pouring room temperature silicone oil. Cracking occurred during cooling. The heat conduction analysis was performed to obtain temperature distribution in a GSO single crystal at cracking, using the surface temperatures measured in the thermal shock cracking test. Then the thermal stress was calculated using temperature profile of the test specimen obtained from the heat conduction analysis. It is found from the results of the thermal stress analysis and the observation of the cracking in test specimens that the thermal shock cracking occurs in a cleavage plane due to the stress normal to the plane. Three-point bending tests were also performed to examine the relationship between the critical stress for thermal shock cracking and the three-point bending strength obtained from small-sized test specimens. (author)

  2. Electromigration of hydrogen and deuterium in vanadium, niobium, and tantalum

    International Nuclear Information System (INIS)

    Jensen, C.L.

    1977-10-01

    The electric mobility and effective valence of hydrogen and deuterium in vanadium, niobium, tantalum and three niobium-tantalum alloys were measured. A resistance technique was used to directly determine the electric mobility of hydrogen and deuterium at 30 0 C while a steady-state method was used to measure the effective valence. The use of mass spectrographic techniques on a single specimen which contained both hydrogen and deuterium greatly increased the precision with which the isotope effect in the effective valence could be measured

  3. Electrorecovery of tantalum in molten fluorides

    International Nuclear Information System (INIS)

    Espinola, A.; Dutra, A.J.B.; Silva, F.T. da

    1988-01-01

    Considering the privileged situation of Brazil as a productor of tantaliferous minerals, the authors have in view the development of a technology for production of metallic tantalum via molten salts electrolysis; this has the advantage of improving the aggregate value of exportation products, additionally to tantalum oxide and tantalum concentrates. Having in view the preliminary determintion of better conditions of temperature, electrolyte composition and current density for this process, electrolysis were conducted with a solvent composed of an eutetic mixture of lithium, sodium and potassium fluoride for dipotassium fluotantalate and occasionally for tantalum oxide. Current efficiencies as high as 83% were obtained in favoured conditions. (author) [pt

  4. Tantalum-based semiconductors for solar water splitting.

    Science.gov (United States)

    Zhang, Peng; Zhang, Jijie; Gong, Jinlong

    2014-07-07

    Solar energy utilization is one of the most promising solutions for the energy crises. Among all the possible means to make use of solar energy, solar water splitting is remarkable since it can accomplish the conversion of solar energy into chemical energy. The produced hydrogen is clean and sustainable which could be used in various areas. For the past decades, numerous efforts have been put into this research area with many important achievements. Improving the overall efficiency and stability of semiconductor photocatalysts are the research focuses for the solar water splitting. Tantalum-based semiconductors, including tantalum oxide, tantalate and tantalum (oxy)nitride, are among the most important photocatalysts. Tantalum oxide has the band gap energy that is suitable for the overall solar water splitting. The more negative conduction band minimum of tantalum oxide provides photogenerated electrons with higher potential for the hydrogen generation reaction. Tantalates, with tunable compositions, show high activities owning to their layered perovskite structure. (Oxy)nitrides, especially TaON and Ta3N5, have small band gaps to respond to visible-light, whereas they can still realize overall solar water splitting with the proper positions of conduction band minimum and valence band maximum. This review describes recent progress regarding the improvement of photocatalytic activities of tantalum-based semiconductors. Basic concepts and principles of solar water splitting will be discussed in the introduction section, followed by the three main categories regarding to the different types of tantalum-based semiconductors. In each category, synthetic methodologies, influencing factors on the photocatalytic activities, strategies to enhance the efficiencies of photocatalysts and morphology control of tantalum-based materials will be discussed in detail. Future directions to further explore the research area of tantalum-based semiconductors for solar water splitting

  5. Process for the production of a tantalum and niobium bearing concentrate from a tantalum and niobium bearing ferro-alloy

    International Nuclear Information System (INIS)

    Deweck, J.; Van, H.

    1980-01-01

    In a process for the production of a tantalum and niobium bearing concentrate from a tantalum and niobium bearing ferro-alloy containing tantalum and niobium as carbide, by treating the ferro-alloy in molten state with a controlled amount of an oxidizing agent in order to slag at least most of the tantalum and at least part of the niobium and by separting the so obtained slag phase from the metal phase, the improvement which comprises using air, oxygen enriched air or oxygen as oxidizing agent and adjusting the iron content to the ferro-alloy by adding at least 70% by weight of iron prior to the step of forming the slag so that at least most of the tantalum carbide is dissolved in the molten ferro-alloy

  6. Tantalum: A strategic metal; Tantalo: Un metal estrategico

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Lopez, G.; Lopez-Lopez, J.; Garcia-Yagues, M. R.

    2009-07-01

    In nature, the main source of tantalum is an isomorphous series of minerals containing oxides of tantalum, niobium, iron and manganese, which are collectively known as columbine-tantalite (coltan). Upgraded Ta{sub 2}O{sub 5}-containing tin slags are also used as a secondary source of tantalum. Coltan, either naturally occurring or synthetically produced as concentrates from tin slags, are digested with hydrofluoric and sulphuric acid at an elevated temperature. the aqueous solution of ta-Nb in hydrofluoric acid is extracted in several continuously operating mixer-settler systems or extraction columns with an organic solvent like methyl isobutyl ketone. The organic phase is then scrubbed with 6-15 N H{sub 2}SO{sub 4} to separate the niobium from the tantalum by selective stripping. The tantalum salt is extracted from the organic phase with water or diluted aqueous ammonium fluoride solution, the demands of the solid tantalum capacitor industry for high quality, high surface area tantalum powders have driven improvements in the sodium reduction of K{sub 2}TaF{sub 7}. The much-improved chemistry reflects the many modifications to the process put in place after 1990 and the subsequent improvements in the electrical quality as measured by the performance of tantalum capacitors. (Author) 5 refs.

  7. Formation of nickel-tantalum compounds in tantalum fluoride halide melts

    International Nuclear Information System (INIS)

    Matychenko, Eh.S.; Zalkind, O.A.; Kuznetsov, B.Ya.; Orlov, V.M.; Sukhorzhevskaya, S.L.

    2001-01-01

    Interaction of nickel with NaCl-K 2 TaF 7 melt (14 mol.%) at 750 deg C was studied, the composition of intermetallic compounds formed in Ni-Ta system being analyzed, using the methods of chemical and X-ray phase analyses, IR spectroscopy. It was ascertained that composition of intermetallic compounds (Ni 3 Ta, Ni 2 Ta) depends on K 2 TaF 7 concentration in the melt, metallic tantalum additions, nickel substrate thickness and experiment duration. The mechanism of currentless deposition of tantalum on nickel was considered and the assumption was made that disproportionation reaction lies in the basis of the process [ru

  8. Oxidized Metal Powders for Mechanical Shock and Crush Safety Enhancers; TOPICAL

    International Nuclear Information System (INIS)

    GARINO, TERRY J.

    2002-01-01

    The use of oxidized metal powders in mechanical shock or crush safety enhancers in nuclear weapons has been investigated. The functioning of these devices is based on the remarkable electrical behavior of compacts of certain oxidized metal powders when subjected to compressive stress. For example, the low voltage resistivity of a compact of oxidized tantalum powder was found to decrease by over six orders of magnitude during compaction between 1 MPa, where the thin, insulating oxide coatings on the particles are intact, to 10 MPa, where the oxide coatings have broken down along a chain of particles spanning the electrodes. In this work, the behavior of tantalum and aluminum powders was investigated. The low voltage resistivity during compaction of powders oxidized under various conditions was measured and compared. In addition, the resistivity at higher voltages and the dielectric breakdown strength during compaction were also measured. A key finding was that significant changes in the electrical properties persist after the removal of the stress so that a mechanical shock enhancer is feasible. This was verified by preliminary shock experiments. Finally, conceptual designs for both types of enhancers are presented

  9. Hydride Olefin complexes of tantalum and niobium

    NARCIS (Netherlands)

    Klazinga, Aan Hendrik

    1979-01-01

    This thesis describes investigations on low-valent tantalum and niobium hydride and alkyl complexes, particularly the dicyclopentadienyl tantalum hydride olefin complexes Cp2Ta(H)L (L=olefin). ... Zie: Summary

  10. Human bone ingrowth into a porous tantalum acetabular cup

    Directory of Open Access Journals (Sweden)

    Gregory N. Haidemenopoulos

    2017-11-01

    Full Text Available Porous Tantalum is increasingly used as a structural scaffold in orthopaedic applications. Information on the mechanisms of human bone ingrowth into trabecular metal implants is rather limited. In this work we have studied, qualitatively, human bone ingrowth into a retrieved porous tantalum monoblock acetabular cup using optical microscopy, scanning electron microscopy and energy dispersive X-ray analysis. According to the results and taking into account the short operational life (4 years of the implant, bone ingrowth on the acetabular cup took place in the first two-rows of porous tantalum cells to an estimated depth of 1.5 to 2 mm. The bone material, grown inside the first raw of cells, had almost identical composition with the attached bone on the cup surface, as verified by the same Ca:P ratio. Bone ingrowth has been a gradual process starting with Ca deposition on the tantalum struts, followed by bone formation into the tantalum cells, with gradual densification of the bone tissue into hydroxyapatite. A critical step in this process has been the attachment of bone material to the tantalum struts following the topology of the porous tantalum scaffold. These results provide insight to the human bone ingrowth process into porous tantalum implants.

  11. Preparation of potassium-reduced tantalum powders

    International Nuclear Information System (INIS)

    Kolosov, V.N.; Miroshnichenko, M.N.; Orlov, V.M.; Prokhorova, T.Yu.

    2005-01-01

    Characteristics of tantalum powders prepared by reduction of molten potassium heptafluorotantalate with liquid potassium are studied in a temperature range of 750 - 850 deg C using potassium chloride as a flux at a ratio of K 2 TaF 7 : KCl = 1, 2, and 3. The use of potassium as a reducing agent facilitates washing of tantalum powders for impurity salt removal, reduces sodium content and leakage currents in the anodes. As compared to sodium process, the potassium reduction results in a high yield of sponge material, a decrease in the specific surface area and yield of tantalum powder suitable for manufacture of capacitor anodes [ru

  12. Early stage of deformation in tungsten, tantalum, and nickel single crystals

    International Nuclear Information System (INIS)

    Pinatti, D.G.

    1977-01-01

    High purity Tantalum, Tungsten and Nickel single crystals were tested in simple tension between 77 and 300 K. The Ta and W was oriented for maximum resolved shear stress on the [111] (101) system. Simultaneously microstrain and ultrasonic propagation measurements (attenuation and modulus defect) were performed at various stress bias in order to test details of theories concerning the preyield region and the flow stress in body-centered cubic refractory metals. The experimental retical predictions for the kink chain model over the string model for dislocation. It appears that double kink nucleation in non-screw dislocations has negligible effect in this domains. The results for annealed Ta exhibited no stress bias effect on the ultrasonic propagation measurements, which suggest that the strong influence of impurities mask our ability to discern this fine structure for dislocation motion. For prestrained W and Ta, it was found that double-kink nucleation on nonscrew dislocation plays an important role and revealed interesting results with respect to our understanding of the intrinsic dislocation structure in bcc metals. These results support the kink chain model for dislocation unambiguously. The experiments on the prestrained samples also exhibited experimental results which are qualitatively but not quantitatively in agreement with the theoretical predictions of Seeger and Sectak. The Ni single crystals were prestrained between 10 and 23 percent in stage II, and the microstrain damping loops have been studied as a function of stress amplitude, temperature and magnetic field. The predominant hysteretic contribution to the observed decrement was analyzed according to the model of Roberts (Al. 14, Al. 15), and good agreement between theory and experiment was found

  13. The bactericidal effect of shock waves

    Science.gov (United States)

    Leighs, J. A.; Appleby-Thomas, G. J.; Wood, D. C.; Goff, M. J.; Hameed, A.; Hazell, P. J.

    2014-05-01

    There are a variety of theories relating to the origins of life on our home planet, some of which discuss the possibility that life may have been spread via inter-planetary bodies. There have been a number of investigations into the ability of life to withstand the likely conditions generated by asteroid impact (both contained in the impactor and buried beneath the planet surface). Previously published data regarding the ability of bacteria to survive such applied shockwaves has produced conflicting conclusions. The work presented here used an established and published technique in combination with a single stage gas gun, to shock and subsequently recover Escherichia coli populations suspended in a phosphate buffered saline solution. Peak pressure across the sample region was calculated via numerical modelling. Survival data against peak sample pressure for recovered samples is presented alongside control tests. SEM micrographs of shocked samples are presented alongside control sets to highlight key differences between cells in each case.

  14. The bactericidal effect of shock waves

    International Nuclear Information System (INIS)

    Leighs, J A; Appleby-Thomas, G J; Wood, D C; Goff, M J; Hameed, A; Hazell, P J

    2014-01-01

    There are a variety of theories relating to the origins of life on our home planet, some of which discuss the possibility that life may have been spread via inter-planetary bodies. There have been a number of investigations into the ability of life to withstand the likely conditions generated by asteroid impact (both contained in the impactor and buried beneath the planet surface). Previously published data regarding the ability of bacteria to survive such applied shockwaves has produced conflicting conclusions. The work presented here used an established and published technique in combination with a single stage gas gun, to shock and subsequently recover Escherichia coli populations suspended in a phosphate buffered saline solution. Peak pressure across the sample region was calculated via numerical modelling. Survival data against peak sample pressure for recovered samples is presented alongside control tests. SEM micrographs of shocked samples are presented alongside control sets to highlight key differences between cells in each case

  15. Electrosynthesis of tantalum borides in oxygen-free and oxygen-containing fluoride melts

    DEFF Research Database (Denmark)

    Polyakova, L.P.; Polyakov, E.G.; Makarova, O.V.

    2001-01-01

    Results of electrosynthesis of tantalum borides in fluoride and oxyfluoride melts are compared. It is shown that the single-phase X-ray-amorphous micro-layered coatings form only in the latter case. Linear and square-wave voltammetry, complemented by X-ray diffraction analysis, IR spectroscopy...

  16. 21 CFR 886.3100 - Ophthalmic tantalum clip.

    Science.gov (United States)

    2010-04-01

    ... blood vessels in the eye. (b) Classification. Class II (special controls). The device is exempt from the...) MEDICAL DEVICES OPHTHALMIC DEVICES Prosthetic Devices § 886.3100 Ophthalmic tantalum clip. (a) Identification. An ophthalmic tantalum clip is a malleable metallic device intended to be implanted permanently...

  17. Valence electronic structure of tantalum carbide and nitride

    Institute of Scientific and Technical Information of China (English)

    FAN; ChangZeng

    2007-01-01

    The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent, metallic and ionic characters. For a quantitative analysis of the relative strength of these components, their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN, which coincides to that deduced from the first-principles method.……

  18. Valence electronic structure of tantalum carbide and nitride

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent, metallic and ionic characters. For a quantitative analysis of the relative strength of these components, their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN, which coincides to that deduced from the first-principles method.

  19. Uptake and retention of insufflated tantalum by lymph nodes

    International Nuclear Information System (INIS)

    Kilpper, R.W.; Bianco, A.; Gibb, F.R.; Landman, S.; Morrow, P.E.

    1976-01-01

    A nonsacrifice, radiographic technique is presented for evaluating the lymph node uptake of radiographically dense materials from the lungs of beagle dogs into which the material was insufflated. With tantalum as the contrast agent, lymph nodes sometimes become visible within 2 days after exposure when the insufflation resulted in radiographic ''alveolarization'' of some of the tantalum. Localization of the material within the nodes was observed in subsequent radiographs as well as persistent retention after as much as 1 year. Through the use of preinsufflation control films and tantalum foils of varying thickness, densitometric methods for determining the amount of tantalum within the lymph nodes are being investigated. Tantalum-182 is being used to follow the lung retention of the material as well as to verify estimates of burdens in harvested nodes. Preliminary lymphokinetic data are presented from experiments utilizing powders of 1 and 5 μm (mean) particle sizes

  20. Extraction of Tantalum from locally sourced Tantalite using ...

    African Journals Online (AJOL)

    acer

    Extraction of Tantalum from locally sourced Tantalite using ... ABSTRACT: The ability of polyethylene glycol solution to extract tantalum from locally .... metal ion in question by the particular extractant. ... Loparite, a rare-earth ore (Ce, Na,.

  1. Tantalum high-temperature oxidation kinetics

    International Nuclear Information System (INIS)

    Grigor'ev, Yu.M.; Sarkisyan, A.A.; Merzhanov, A.G.

    1981-01-01

    Kinetics of heat release and scale growth during tantalum oxidation within 650-1300 deg C temperature range in oxygen-containing media is investigated. Kinetic equations and temperature and pressure dependences of constants are ound Applicability of the kinetic Lorie mechanism for the description of the tantalum oxidation kinetics applicably to rapid-passing processes is shown. It is stated that the process rate (reaction ability) is determined by adsorption desorption factors on the external surface of the ''protective'' oxide for the ''linear'' oxidation stage [ru

  2. Modeling the mechanical behavior of tantalum

    International Nuclear Information System (INIS)

    Lee, B.J.; Ahzi, S.

    1997-01-01

    A crystal plasticity model is proposed to simulate the large plastic deformation and texture evolution in tantalum over a wide range of strain rates. In the model, a modification of the viscoplastic power law for slip and a Taylor interaction law for polycrystals are employed, which account for the effects of strain hardening, strain-rate hardening, and thermal softening. A series of uniaxial compression tests in tantalum at strain rates ranging from 10 -3 to 10 4 s -1 were conducted and used to verify the model's simulated stress-strain response. Initial and evolved deformation textures were also measured for comparison with predicted textures from the model. Applications of this crystal plasticity model are made to examine the effect of different initial crystallographic textures in tantalum subjected to uniaxial compression deformation or biaxial tensile deformation

  3. Reaction of tantalum-alkyne complexes with isocyanates or acyl cyanides

    International Nuclear Information System (INIS)

    Kataoka, Yasutaka; Oguchi, Yoshiyuki; Yoshizumi, Kazuyuki; Miwatashi, Seiji; Takai, Kazuhiko; Utimoto, Kiitiro

    1992-01-01

    Treatment of alkynes with low-valent tantalum derived from TiCl 5 and zinc produces tantalum-alkyne complexes (not isolated), which react in situ with phenyl isocyanate (or butyl isocyanate) to give (E)-α, β-unsaturated amides stereoselectively. The tantalum-alkyne complexes also react with acyl cyanides in the presence of BF 3 ·OEt 2 to give α-cyanohydrins. In both reactions, filtration of the reaction mixture containing the tantalum-alkyne complexes before addition of isocyanates (or acyl cyanides) is indispensable to obtain good yields. (author)

  4. Study of electrochemical behaviour of tantalum in molten alkali metal chlorides

    International Nuclear Information System (INIS)

    Bajmakov, A.N.; Ezrokhina, A.M.; Sashinina, O.A.; Shkol'nikov, S.N.

    1985-01-01

    Equilibrium potentials of metallic tantalum in the melt TaCl 5 +KCl-NaCl are studied. Are average degree of tantalum ion oxidation, which are in equilibrium with metallic tantalum, is determined. Anodic behaviour of tantalum in equimolar mixture of potassium and sodium chlorides with Ta and F ion additions is considered. An average degree of oxidation of Ta ions, which transfer into the melt, depending on current density, is determined. It is established that tantalum is dissolved in the regime of diffusional kinetics. It is shown that tantalum corrodes in equimolar mixture of potassium and sodiUm chlorides, at that, corrosion rate increases with introdUction of Ta and F ions into solution. The corrosion is of electrochemical nature and it proceeds in the regime of diffusional kinetics

  5. Tantalum oxide thin films as protective coatings for sensors

    DEFF Research Database (Denmark)

    Christensen, Carsten; Reus, Roger De; Bouwstra, Siebe

    1999-01-01

    Reactively sputtered tantalum oxide thin films have been investigated as protective coatings for aggressive media exposed sensors. Tantalum oxide is shown to be chemically very robust. The etch rate in aqueous potassium hydroxide with pH 11 at 140°C is lower than 0.008 Å h-l. Etching in liquids...... with pH values in the range from pH 2 to 11 have generally given etch rates below 0.04 Å h-l. On the other hand patterning is possible in hydrofluoric acid. Further, the passivation behaviour of amorphous tantalum oxide and polycrystalline Ta2O5 is different in buffered hydrofluoric acid. By ex situ...... annealing O2 in the residual thin-film stress can be altered from compressive to tensile and annealing at 450°C for 30 minutes gives a stress-free film. The step coverage of the sputter deposited amorphous tantalum oxide is reasonable, but metallization lines are hard to cover. Sputtered tantalum oxide...

  6. Tantalum oxide thin films as protective coatings for sensors

    DEFF Research Database (Denmark)

    Christensen, Carsten; Reus, Roger De; Bouwstra, Siebe

    1999-01-01

    Reactively sputtered tantalum oxide thin-films have been investigated as protective coating for aggressive media exposed sensors. Tantalum oxide is shown to be chemically very robust. The etch rate in aqueous potassium hydroxide with pH 11 at 140°C is lower than 0.008 Å/h. Etching in liquids with p......H values in the range from pH 2-11 have generally given etch rates below 0.04 Å/h. On the other hand patterning is possible in hydrofluoric acid. Further, the passivation behaviour of amorphous tantalum oxide and polycrystalline Ta2O5 is different in buffered hydrofluoric acid. By ex-situ annealing in O2...... the residual thin-film stress can be altered from compressive to tensile and annealing at 450°C for 30 minutes gives a stress-free film. The step coverage of the sputter deposited amorphous tantalum oxide is reasonable, but metallisation lines are hard to cover. Sputtered tantalum oxide exhibits high...

  7. Diffusion coefficient of hydrogen in niobium and tantalum

    International Nuclear Information System (INIS)

    Vargas, P.; Miranda, L.; Lagos, M.

    1988-08-01

    We show that the current data on hydrogen diffusion in Tantalum between 15K and 550K and in Niobium between 135K and 400K can be quantitatively explained by the small polaron theory. The experimental data can be understood assuming ground-state to ground-state tunneling between interstitial sites with tetrahedral symmetry plus an activated contribution due to tunneling between excited states having octahedral symmetry. The break of the diffusivity curve at T approx. = 250K follows naturally. It evidences the transition between the tetrahedral and octahedral hopping. For Ta the second break of the diffusivity curve at T approx. = 20K indicated the recovering of the ground-state hopping with tetrahedral symmetry. Below T approx. = 10K for Ta and T approx. = 7K for Nb the diffusion coefficient becomes independent of T. (author). 17 refs, 3 figs, 1 tab

  8. Phenomenological effets of tantalum incorporation into diamond films: Experimental and first principle studies

    Energy Technology Data Exchange (ETDEWEB)

    Ullah, Mahtab, E-mail: mahtabullah@bzu.edu.pk [Department of Physics, Bahauddin Zakariya University Multan (Pakistan); Rana, Anwar Manzoor; Ahmad, E. [Department of Physics, Bahauddin Zakariya University Multan (Pakistan); Raza, Rizwan [Department of Physics, COMSATS Institute of Information Technology, Lahore-54000 (Pakistan); Hussain, Fayyaz [Department of Physics, Bahauddin Zakariya University Multan (Pakistan); Hussain, Akhtar; Iqbal, Muhammad [Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)

    2016-09-01

    Graphical abstract: - Highlights: • Fabrication of tantalum incorporated diamonds films using HFCVD technique. • Decrease in resistivity by increasing tantalum content in diamond thin films. • Electronic structure calculations of tantalum incorporated diamonds films through VASP code. • A rise of bond length and bond angles by addition of tantalum in the diamond lattice. • Confirmation of decrease of resistivity by adding tantalum due to creation of impurity states in the bandgap. - Abstract: Tantalum (Ta) incorporated diamond films are synthesized on silicon substrate by chemical vapor deposition under gas mixture of CH{sub 4} + H{sub 2}. Characterizations of the resulting films indicate that morphology and resistivity of as-grown diamond films are significantly influenced by the process parameters and the amount of tantalum incorporated in the diamond films. XRD plots reveal that diamond films are composed of TaC along with diamond for higher concentration of tantalum and Ta{sub 2}C phases for lower concentration of tantalum. EDS spectra confirms the existence of tantalum in the diamond films. Resistivity measurements illustrate a sudden fall of about two orders of magnitude by the addition of tantalum in the diamond films. Band structure of Ta-incorporated diamond has been investigated based on density functional theory (DFT) using VASP code. Band structure calculations lead to the semiconducting behavior of Ta-incorporated diamond films because of the creation of defects states inside the band gap extending towards conduction band minimum. Present DFT results support experimental trend of resistivity that with the incorporation of tantalum into diamond lattice causes a decrease in the resistivity of diamond films so that tantalum-incorporated diamond films behave like a good semiconductor.

  9. The global tantalum industry and Sons of Gwalia Ltd

    International Nuclear Information System (INIS)

    Paull, D.

    2002-01-01

    Sons of Gwalia Ltd., in Perth Australia is a long-term supplier of tantalum (Ta), a valuable rare metal with adequate supply. Tantalum is soft and ductile with high melting and boiling points and a low co-efficient of thermal expansion. It has excellent capacity to store and release electrical charge and offers exceptional resistance to corrosion. Its' main use is in consumer electronics such as mobile phones, laptop computers, DVD players, personal video recorders and MP-3 players. For automotive electronics, tantalum is used for air-bags, audio systems, navigation systems, anti-lock break systems and under the hood vehicle management systems. The super alloy is also in demand by the aerospace industry and for turbine blades for power stations. The total demand of Tantalum in 2000 was 5 million lbs. Demand growth has increased steadily since 1993 with perhaps a slight increase in the past 5 years. Resources are estimated at a 125 year supply based on year 2000 production rates. 41 per cent of the world supply of tantalum is obtained from Australia, 13 per cent from Africa, 16 per cent from America, 22 per cent from Asia. The Greenbushes mine in Australia is the world's largest tantalum mine with 80 million lbs Ta, followed by Australia's Wodgina Mine with 50 million lbs Ta. Both mines are expected to be operational for the next 25 years. 12 figs

  10. PREPARATION OF TANTALUM CARBIDE FROM AN ORGANOMETALLIC PRECURSOR

    Directory of Open Access Journals (Sweden)

    C. P. SOUZA

    1999-03-01

    Full Text Available In this work we have synthesized an organometallic oxalic precursor from tantalum oxide. This oxide was solubilized by heating with potassium hydrogen sulfate. In order to precipitate Ta2O5.nH2O, the fused mass obtained was dissolved in a sulfuric acid solution and neutralized with ammonia. The hydrated tantalum oxide precipitated was dissolved in an equimolar solution of oxalic acid/ammonium oxalate. The synthesis and the characterization of the tantalum oxalic precursor are described. Pyrolysis of the complex in a mixture of hydrogen and methane at atmospheric pressure was studied. The gas-solid reaction made it possible to obtain tantalum carbide, TaC, in the powder form at 1000oC. The natural sintering of TaC powder in an inert atmosphere at 1400°C during 10 hours, under inert atmosphere made it possible to densify the carbide to 96% of the theoretical value.

  11. Force-dominated non-equilibrium oxidation kinetics of tantalum

    International Nuclear Information System (INIS)

    Kar, Prasenjit; Wang, Ke; Liang, Hong

    2008-01-01

    Using a combined electrochemical and mechanical manipulation technique, we compared the equilibrium and non-equilibrium oxidation processes and states of tantalum. Experimentally, a setup was developed with an electrochemical system attached to a sliding mechanical configuration capable of friction force measurement. The surface chemistry of a sliding surface, i.e., tantalum, was modified through the electrolyte. The mechanically applied force was fixed and the dynamics of the surface was monitored in situ through a force sensor. The formation of non-equilibrium oxidation states of tantalum was found in oxidation limiting environment of acetic acid. An oxidative environment of deionized water saturated with KCl was used as comparison. We proposed a modified Arrhenius-Eyring equation in which the mechanical factor was considered. We found that the mechanical energy induced the non-stable-state reactions leading to metastable oxidation states of tantalum. This equation can be used to predict mechanochemical reactions that are important in many industrial applications

  12. Shock wave response of ammonium perchlorate single crystals to 6 GPa

    International Nuclear Information System (INIS)

    Yuan, G.; Feng, R.; Gupta, Y. M.; Zimmerman, K.

    2000-01-01

    Plane shock wave experiments were carried out on ammonium perchlorate single crystals compressed along [210] and [001] orientations to peak stresses ranging from 1.2 to 6.2 GPa. Quartz gauge and velocity interferometer techniques were used to measure the elastic and plastic shock wave velocities, and stress and particle velocity histories in the shocked samples. The measured Hugoniot elastic limit (HEL) was 0.48±0.09 GPa. Above the HEL and up to about 6 GPa, the data show a clear two-wave structure, indicating an elastic-plastic response. Time-dependent elastic precursor decay and plastic wave ramping are discernable and orientation dependent in the low stress data. However, the orientation dependence of the peak state response is small. Hence, data for both orientations were summarized into a single isotropic, elastic-plastic-stress relaxation model. Reasonable agreement was obtained between the numerical simulations using this model and the measured wave profiles. At a shock stress of about 6 GPa and for the time duration and crystal orientations examined, we did not observe any features that may be identified as a sustained chemical reaction or a phase transformation. (c) 2000 American Institute of Physics

  13. Electronic structure and charge transport in nonstoichiometric tantalum oxide

    Science.gov (United States)

    Perevalov, T. V.; Gritsenko, V. A.; Gismatulin, A. A.; Voronkovskii, V. A.; Gerasimova, A. K.; Aliev, V. Sh; Prosvirin, I. A.

    2018-06-01

    The atomic and electronic structure of nonstoichiometric oxygen-deficient tantalum oxide TaO x<2.5 grown by ion beam sputtering deposition was studied. The TaO x film content was analyzed by x-ray photoelectron spectroscopy and by quantum-chemistry simulation. TaO x is composed of Ta2O5, metallic tantalum clusters and tantalum suboxides. A method for evaluating the stoichiometry parameter of TaO x from the comparison of experimental and theoretical photoelectron valence band spectra is proposed. The charge transport properties of TaO x were experimentally studied and the transport mechanism was quantitatively analyzed with four theoretical dielectric conductivity models. It was found that the charge transport in almost stoichiometric and nonstoichiometric tantalum oxide can be consistently described by the phonon-assisted tunneling between traps.

  14. Titrimetric determination of tungsten in its alloys with tantalum

    International Nuclear Information System (INIS)

    Elinson, S.V.; Nezhnova, T.I.

    1982-01-01

    Titrimetric method of tungsten determination in tantalum base alloys has been developed. The method permits to determine 5-10% tungsten in the alloys with relative standard deviation of 0.013. The conditions are created by application of precipitation from homogeieous solutions or by the method of appearing reagents at pH values, which condition gradual hydrolytic precipitation of tantalum, and sodium tungstate remains in the solution and is not sorbed on tantalum hydroxide. After separation of tantalum oxide tungsten is precipitated in the form of lead tungstate by the excess of ti trated solution of lead salt during boiling and then at the background of lead tungstate precipitate without its separation lead excess is titrated by EDTA in the presence of mixed indicator-4-(2-pyridylazo)resocinol and xylenole orange in acetate buffer solution

  15. Optical properties of single doped Cr3+ and co-doped Cr3+-Nd3+ aluminum tantalum tellurite glasses

    International Nuclear Information System (INIS)

    Rodriguez-Mendoza, U.R.; Speghini, A.; Jaque, D.; Zambelli, M.; Bettinelli, M.

    2004-01-01

    The optical properties for single doped Cr 3+ and co-doped Cr 3+ -Nd 3+ aluminum tantalum tellurite glasses have been studied as a function of temperature. For the single doped glass, the existence of two bands in the emission spectra at low temperature indicates the presence of two different sites for the Cr 3+ ions, labelled as usual as low- and high-field sites. The broad band centred in the Near Infrared region, corresponds to low-field sites transition 4 T 2 → 4 A 2 , and the narrow band centred at approximately 715 nm to the high-field sites transition 2 E→ 4 A 2 . The emission intensity for both high- and low-field sites shows a strong decrease with increasing temperature, with the emission for the former sites vanishing at RT. In both cases the quenching observed with the increase of temperature can be ascribed to the presence of non-radiative relaxation mechanisms. Experimental observations for the co-doped glass show that both radiative and non-radiative energy transfer processes from Cr 3+ to Nd 3+ are present

  16. Preparation of tantalum targets of known thicknesses

    International Nuclear Information System (INIS)

    Alexander, J.R.; Wirth, H.L.

    1985-01-01

    A series of carbon-backed tantalum targets were produced in a heavy ion sputtering system with a Penning ion source. The target thicknesses were then measured using the alpha-ray energy loss method. The resulting tabulated measurements were reproducible and make possible the production of carbon-backed tantalum targets with pre-determined thicknesses ranging from 20 μg/cm 2 to 1 mg/cm 2 . (orig.)

  17. Producing tantalum or columbium powder

    International Nuclear Information System (INIS)

    Rerat, C.F.

    1979-01-01

    A process is described for the production of tantalum or columbium powder with a high yield within a desired range of particle sizes. A molten salt bath of a double salt comprising either an alkali metal tantalum fluoride or an alkali metal columbium fluoride and a relatively large amount of alkali metal halide diluent salt to act as a heat sink is initially maintained at a temperature a little above the liquidus temperature of the salt mixture. A liquid alkali metal at a comparatively low temperature is added to the continuously stirred bath at a high mass flow rate, and reduces the double salt, producing tantalum or columbium. The reaction is exothermic and causes the temperature to rise rapidly to a desired final reaction temperature within the range 760 to 1000 0 . The liquid alkali metal is thereafter fed at a high mass flow rate to complete the reaction quickly at the final reaction temperature. Forced cooling at a heat extraction rate not less than 42 kilojoules/min./kg. of double salt is used during at least a portion of the reaction cycle at a rate sufficient to maintain the final reaction temperature within a desired range. (author)

  18. Bacterial adherence to tantalum versus commonly used orthopedic metallic implant materials.

    Science.gov (United States)

    Schildhauer, Thomas A; Robie, Bruce; Muhr, Gert; Köller, Manfred

    2006-07-01

    Evaluation of bacterial adhesion to pure tantalum and tantalum-coated stainless steel versus commercially pure titanium, titanium alloy (Ti-6Al-4V), and grit-blasted and polished stainless steel. Experimental in vitro cell culture study using Staphylococcus aureus and Staphylococcus epidermidis to evaluate qualitatively and quantitatively bacterial adherence to metallic implants. A bacterial adhesion assay was performed by culturing S. aureus (ATCC 6538) and S. epidermidis (clinical isolate) for one hour with tantalum, tantalum-coated stainless steel, titanium, titanium alloy, grit-blasted and polished stainless steel metallic implant discs. Adhered living and dead bacteria were stained using a 2-color fluorescence assay. Adherence was then quantitatively evaluated by fluorescence microscopy and digital image processing. Qualitative adherence of the bacteria was analyzed with a scanning electron microscope. The quantitative data were related to the implant surface roughness (Pa-value) as measured by confocal laser scanning microscopy. Bacterial adherence of S. aureus varied significantly (p = 0.0035) with the type of metallic implant. Pure tantalum presented with significantly (p titanium alloy, polished stainless steel, and tantalum-coated stainless steel. Furthermore, pure tantalum had a lower, though not significantly, adhesion than commercially pure titanium and grit-blasted stainless steel. Additionally, there was a significantly higher S. aureus adherence to titanium alloy than to commercially pure titanium (p = 0.014). S. epidermidis adherence was not significantly different among the tested materials. There was no statistically significant correlation between bacterial adherence and surface roughness of the tested implants. Pure tantalum presents with a lower or similar S. aureus and S. epidermidis adhesion when compared with commonly used materials in orthopedic implants. Because bacterial adhesion is an important predisposing factor in the development of

  19. Shock compression experiments on Lithium Deuteride single crystals.

    Energy Technology Data Exchange (ETDEWEB)

    Knudson, Marcus D.; Desjarlais, Michael Paul; Lemke, Raymond W.

    2014-10-01

    S hock compression exper iments in the few hundred GPa (multi - Mabr) regime were performed on Lithium Deuteride (LiD) single crystals . This study utilized the high velocity flyer plate capability of the Sandia Z Machine to perform impact experiments at flyer plate velocities in the range of 17 - 32 km/s. Measurements included pressure, density, and temperature between %7E200 - 600 GPa along the Principal Hugoniot - the locus of end states achievable through compression by large amplitude shock waves - as well as pressure and density of re - shock states up to %7E900 GPa . The experimental measurements are compared with recent density functional theory calculations as well as a new tabular equation of state developed at Los Alamos National Labs.

  20. Tantalum markers in radiography

    International Nuclear Information System (INIS)

    Aronson, A.S.; Jonsson, N.; Alberius, P.

    1985-01-01

    The biocompatibility of two types of radiopaque tantalum markers was evaluated histologically. Reactions to pin markers (99.9% purity) and spherical markers (95.2% purity) were investigated after 3-6 weeks in rabbits and 5-48 weeks in children with abnormal growth. Both marker types were firmly attached to bone trabeculae; this was most pronounced in rabbit bone, and no adverse macroscopic reactions were observed. Microscopically, no reactions or only slight fibrosis of bone tissue were detected, while soft tissues only demonstrated a minor inflammatory reaction. Nevertheless, the need for careful preparation and execution of marker implantations is stressed, and particularly avoidance iof the use of emery in sharpening of cannulae. The bioinertness of tantalum was reconfirmed as was its suitability for use as skeletal and soft tissue radiographic markers. (orig.)

  1. Dynamic material properties of refractory metals: tantalum and tantalum/tungsten alloys

    International Nuclear Information System (INIS)

    Furnish, M.D.; Lassila, D.H.; Chhabildas, L.C.; Steinberg, D.J.

    1996-01-01

    We have made a careful set of impact wave-profile measurements (16 profiles) on tantalum and tantalum-tungsten alloys at relatively low stresses (to 15 GPa). Alloys used were Ta 96.5 W 3.5 and Ta 86.5 W 13.5 (wt%) with oxygen contents of 30 endash 70 ppm. Information available from these experiments includes Hugoniot, elastic limits, loading rates, spall strength, unloading paths, reshock structure and specimen thickness effects. Hugoniot and spall properties are illustrated, and are consistent with expectations from earlier work. Modeling the tests with the Steinberg-Guinan-Lund rate-dependent material model provides for an excellent match of the shape of the plastic loading wave. The release wave is not well modeled due to the absence of the dynamic Bauschinger effect. There is also a discrepancy between experiments and calculations regarding the relative timing of the elastic and plastic waves that may be due to texture effects. copyright 1996 American Institute of Physics

  2. Structural changes in the human vas deferens after tantalum clip occlusion and conventional vasectomy.

    Science.gov (United States)

    Kothari, L K; Gupta, A S

    1978-02-01

    In 15 human subjects, the vasa deferentia were occluded by applying two tantalum clips on one side and by conventional vasectomy with silk ligatures on the other. After 2 weeks, the occluded segments were recovered for histopathologic examination of serial sections. Obstructing the seminal tract did not, as such, produce any significant change in the vas: the distal and proximal segments appeared to be essentially similar and normal. At the actual site of occlusion, however, tantalum clips produced marked flattening of the tube, complete loss of lining epithelium, distortion of the muscular lamellae, and areas of hemorrhage. The lumen was converted into a narrow slit. Under the ligatures, the damage was largely confined to denudation of the mucosal epithelium. The mucosa of the intersegment left unexcised between two clips showed hyalinization, invasion by macrophages, and degeneration of the epithelium. The changes under the clips suggest that, although clip occlusion may offer several advantages, sterility cannot be reversed merely by removing the clips. The mechanisms of these changes, different in the case of clips and ligatures, are discussed and some possible long-term consequences are considered.

  3. Fabrication of a Tantalum-Based Josephson Junction for an X-Ray Detector

    Science.gov (United States)

    Morohashi, Shin'ichi; Gotoh, Kohtaroh; Yokoyama, Naoki

    2000-06-01

    We have fabricated a tantalum-based Josephson junction for an X-ray detector. The tantalum layer was selected for the junction electrode because of its long quasiparticle lifetime, large X-ray absorption efficiency and stability against thermal cycling. We have developed a buffer layer to fabricate the tantalum layer with a body-centered cubic structure. Based on careful consideration of their superconductivity, we have selected a niobium thin layer as the buffer layer for fabricating the tantalum base electrode, and a tungsten thin layer for the tantalum counter electrode. Fabricated Nb/AlOx-Al/Ta/Nb and Nb/Ta/W/AlOx-Al/Ta/Nb Josephson junctions exhibited current-voltage characteristics with a low subgap leakage current.

  4. Work hardening and plastic equation of state of tantalum

    International Nuclear Information System (INIS)

    Gypen, L.A.; Aernoudt, E.; Deruyttere, A.

    1983-01-01

    The influence of cold deformation on the thermal and athermal components of the flow stress of tantalum was investigated. Up to high deformation levels the strain hardening is due only to the development of internal stress fields; the effective stress remains almost constant. The athermal strain hardening of tantalum is parabolic at low deformation levels (epsilon < 0.5) and linear at high deformation levels, as for other bcc metals. Hart's plastic equation of state is shown to be valid for tantalum at room temperature in the whole deformation range investigated (from epsilon = 0.005 to epsilon = 2.8). (author)

  5. Shock compression experiments on Lithium Deuteride (LiD) single crystals

    Science.gov (United States)

    Knudson, M. D.; Desjarlais, M. P.; Lemke, R. W.

    2016-12-01

    Shock compression experiments in the few hundred GPa (multi-Mbar) regime were performed on Lithium Deuteride single crystals. This study utilized the high velocity flyer plate capability of the Sandia Z Machine to perform impact experiments at flyer plate velocities in the range of 17-32 km/s. Measurements included pressure, density, and temperature between ˜190 and 570 GPa along the Principal Hugoniot—the locus of end states achievable through compression by large amplitude shock waves—as well as pressure and density of reshock states up to ˜920 GPa. The experimental measurements are compared with density functional theory calculations, tabular equation of state models, and legacy nuclear driven results that have been reanalyzed using modern equations of state for the shock wave standards used in the experiments.

  6. Experimental investigation of shock wave diffraction over a single- or double-sphere model

    Science.gov (United States)

    Zhang, L. T.; Wang, T. H.; Hao, L. N.; Huang, B. Q.; Chen, W. J.; Shi, H. H.

    2017-01-01

    In this study, the unsteady drag produced by the interaction of a shock wave with a single- and a double-sphere model is measured using imbedded accelerometers. The shock wave is generated in a horizontal circular shock tube with an inner diameter of 200 mm. The effect of the shock Mach number and the dimensionless distance between spheres is investigated. The time-history of the drag coefficient is obtained based on Fast Fourier Transformation (FFT) band-block filtering and polynomial fitting of the measured acceleration. The measured peak values of the drag coefficient, with the associated uncertainty, are reported.

  7. Advances in the chemical vapor deposition (CVD) of Tantalum

    DEFF Research Database (Denmark)

    Mugabi, James Atwoki; Eriksen, Søren; Christensen, Erik

    2014-01-01

    The chemical stability of tantalum in hot acidic media has made it a key material in the protection of industrial equipment from corrosion under such conditions. The Chemical Vapor Deposition of tantalum to achieve such thin corrosion resistant coatings is one of the most widely mentioned examples...

  8. Fracture of an uncemented tantalum patellar component

    Directory of Open Access Journals (Sweden)

    Nathan L. Grimm, MD

    2016-06-01

    Full Text Available A 62-year-old man presented with the acute, atraumatic onset of pain 3 years after uncemented right total knee arthroplasty. He complained of new mechanical locking with the knee held in extension on examination and unable to flex the knee. On the plain radiographs, the patellar component peg was fractured and the plate was dislocated. The knee was immobilized, and revision to a cemented 3-peg component was performed. Fracture of a single-peg, tantalum-backed uncemented patellar component has not been described. Clinical suspicion for this should be given in the setting of acute locking. We recommend revision with a cemented polyethylene component.

  9. The relationship between elastic constants and structure of shock waves in a zinc single crystal

    Science.gov (United States)

    Krivosheina, M. N.; Kobenko, S. V.; Tuch, E. V.

    2017-12-01

    The paper provides a 3D finite element simulation of shock-loaded anisotropic single crystals on the example of a Zn plate under impact using a mathematical model, which allows for anisotropy in hydrostatic stress and wave velocities in elastic and plastic ranges. The simulation results agree with experimental data, showing the absence of shock wave splitting into an elastic precursor and a plastic wave in Zn single crystals impacted in the [0001] direction. It is assumed that the absence of an elastic precursor under impact loading of a zinc single crystal along the [0001] direction is determined by the anomalously large ratio of the c/a-axes and close values of the propagation velocities of longitudinal and bulk elastic waves. It is shown that an increase in only one elastic constant along the [0001] direction results in shock wave splitting into an elastic precursor and a shock wave of "plastic" compression.

  10. The influence of cobalt, tantalum, and tungsten on the elevated temperature mechanical properties of single crystal nickel-base superalloys

    Science.gov (United States)

    Nathal, M. V.; Ebert, L. J.

    1985-01-01

    The influence of composition on the tensile and creep strength of 001-line oriented nickel-base superalloy single crystals at temperatures near 1000 C was investigated. Cobalt, tantalum, and tungsten concentrations were varied according to a matrix of compositions based on the single crystal version of MAR-M247. For alloys with the baseline refractory metal level of 3 wt pct Ta and 10 wt pct W, decreases in Co level from 10 to 0 wt pct resulted in increased tensile and creep strength. Substitution of 2 wt pct W for 3 wt pct Ta resulted in decreased creep life at high stresses, but improved life at low stresses. Substitution of Ni for Ta caused large reductions in tensile strength and creep resistance, and corresponding increases in ductility. For these alloys with low Ta-plus-W totals, strength was independent of Co level. The effects of composition on properties were related to the microstructural features of the alloys. In general, high creep strength was associated with high levels of gamma-prime volume fraction, gamma-gamma-prime lattice mismatch, and solid solution hardening.

  11. Assessment of In Situ Time Resolved Shock Experiments at Synchrotron Light Sources*

    Science.gov (United States)

    Belak, J.; Ilavsky, J.; Hessler, J. P.

    2005-07-01

    Prior to fielding in situ time resolved experiments of shock wave loading at the Advanced Photon Source, we have performed feasibility experiments assessing a single photon bunch. Using single and poly-crystal Al, Ti, V and Cu shock to incipient spallation on the gas gun, samples were prepared from slices normal to the spall plane of thickness 100-500 microns. In addition, single crystal Al of thickness 500 microns was shocked to incipient spallation and soft recovered using the LLNL e-gun mini-flyer system. The e-gun mini-flyer impacts the sample target producing a 10's ns flat-top shock transient. Here, we present results for imaging, small-angle scattering (SAS), and diffraction. In particular, there is little SAS away from the spall plane and significant SAS at the spall plane, demonstrating the presence of sub-micron voids. * Use of the Advanced Photon Source was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. W-31-109-Eng-38 and work performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

  12. Use of sulfoxides for extraction-gravimetric determination of niobium and tantalum

    International Nuclear Information System (INIS)

    Nikolaev, A.I.; Babkin, A.G.; Tkachenko, V.G.

    1977-01-01

    An extraction-gravimetrical technique has been developed for determination of niobium and tantalum. The technique permits simultaneous extraction of tantalum and its concentrating in the aqueous phase; the range of Ta concentrations determined is essentially wider than in case of the routine gravimetric methods. The technique is based upon the fact, that tantalum is extracted by sulfoxides from fluorine-sulphate solutions at lower concentration of Hf and at lower ratios between the volumes of organic and aqueous phases than niobium. Two subsequent extractions by 1M sulfoxide solutions provide for practically complete transfer of tantalum into the organic phase, whereas extraction of niobium is only 3-20%. Sufficient recovery of Ta and Nb from organic phases is provided by re-extraction by NH 4 F solution. The technique is suitable for niobium and tantalum determination at the ratios of their pentoxides from 1:100 to 100:1. The disturbing influence of Fe(3) is suppressed by reductions to Fe(2)

  13. Spectrographic determination of impurities in high-purity tantalum oxide and niobium oxide

    International Nuclear Information System (INIS)

    Anderson, S.T.G.; Russell, G.M.

    1990-01-01

    The development of spectrographic methods by direct current arc excitation and carrier distillation for the determination of impurities in tantalum and niobium oxides are described. Iron, silicon, aluminium, titanium, calcium, silver, tin, magnesium, and manganese can be determined in tantalum oxide and niobium oxide in concentrations ranging from 3 to 300 p.p.m. Niobium can be determined in tantalum oxide in concentrations ranging from 10 to 300 p.p.m. Tantalum cannot be determined in niobium oxide, and tungsten cannot be determined in either matrix as a result of the absence of sensitive lines in the spectra of these elements. Relative standard deviations of analyte element concentrations are in the region of 0,18 for tantalum oxide samples, and 0,13 for niobium oxide samples. A detailed laboratory method is included. 4 figs., 4 tabs., 3 refs

  14. Separation of niobium and tantalum by paper chromatography and their following spectrographic determination

    International Nuclear Information System (INIS)

    Moroshkina, T.M.; Peres Sanfiel', F.

    1975-01-01

    The paper presents the results of an investigation into the use of water-saturated furfural to separate niobium and tantalum in a 1:1 ratio by means of ascending paper chromatography. The influence of sulphuric acid, ammonium fluoride and hydrofluoric acid concentrations on the completeness of the niobium and tantalum separation was investigated, the extent of the separation being checked by a spectral method. The results indicate that the use of furfural creates favourable conditions for niobium and tantalum separation. The purest tantalum is obtained at concentrations of sulphuric acid 600 k/l, hydrofluoric acid 4.6% and ammonium fluoride 30 g/l. To obtain pure niobium the acid concentrations remain the same but the quantity of ammonium fluoride is doubled. The fluoride ion concentration has a significant effect on the completeness of niobium and tantalum separation. The variation coefficient for the niobium determination is 14%, for the tantalum determination 1O% (author)

  15. Effect of target-fixture geometry on shock-wave compacted copper powders

    Science.gov (United States)

    Kim, Wooyeol; Ahn, Dong-Hyun; Yoon, Jae Ik; Park, Lee Ju; Kim, Hyoung Seop

    2018-01-01

    In shock compaction with a single gas gun system, a target fixture is used to safely recover a powder compact processed by shock-wave dynamic impact. However, no standard fixture geometry exists, and its effect on the processed compact is not well studied. In this study, two types of fixture are used for the dynamic compaction of hydrogen-reduced copper powders, and the mechanical properties and microstructures are investigated using the Vickers microhardness test and electron backscatter diffraction, respectively. With the assistance of finite element method simulations, we analyze several shock parameters that are experimentally hard to control. The results of the simulations indicate that the target geometry clearly affects the characteristics of incident and reflected shock waves. The hardness distribution and the microstructure of the compacts also show their dependence on the geometry. With the results of the simulations and the experiment, it is concluded that the target geometry affects the shock wave propagation and wave interaction in the specimen.

  16. HIP (hot isostatic pressing) sintering of Tantalum (Ta) and tantalum carbide (TaC) powder mixture: relations between microstructure and properties

    International Nuclear Information System (INIS)

    Valin, F.; Schnedecker, M.

    1994-01-01

    HIP sintering at 1630 C and 195 MPa, during 2 hours, can be used for complete densification of mixtures of commercial tantalum carbide and tantalum powders. HIPed material properties are depending upon initial compositions. For C/Ta ratios inferior to 80%, the monocarbide structure is preserved. A partial ordering of the carbon vacancies will result, for TaC(0.80), in microhardness maximization. The microstructurally homogenous TaC(0.45) shows an excellent toughness. 2 figs., 2 refs

  17. Preparation of potassium tantalum fluoride from tantalum hydroxide

    International Nuclear Information System (INIS)

    Silva, F.T. da; Espinola, A.; Dutra, A.J.B.

    1987-01-01

    Potassium tantalum fluoride (K 2 TaF 7 ) is an intermediary product in the processing of tantaliferous materials; it is the basic raw material for both reduction processes in use presently: reduction by metallic sodium and electrolysis in molten halides. It is normally obtained from a fluorotantalic acid solution to which potassium ions are added the precipitation of white acicular crystals of K 2 TaF 7 . The conditions for precipitation and recrystallization were studied, and crystal characterization were done by scanning electron microscopy, X-ray diffraction and thermogravimetric and thermodifferential analyses. (Author) [pt

  18. Mineral-deposit model for lithium-cesium-tantalum pegmatites

    Science.gov (United States)

    Bradley, Dwight C.; McCauley, Andrew D.; Stillings, Lisa L.

    2017-06-20

    Lithium-cesium-tantalum (LCT) pegmatites comprise a compositionally defined subset of granitic pegmatites. The major minerals are quartz, potassium feldspar, albite, and muscovite; typical accessory minerals include biotite, garnet, tourmaline, and apatite. The principal lithium ore minerals are spodumene, petalite, and lepidolite; cesium mostly comes from pollucite; and tantalum mostly comes from columbite-tantalite. Tin ore as cassiterite and beryllium ore as beryl also occur in LCT pegmatites, as do a number of gemstones and high-value museum specimens of rare minerals. Individual crystals in LCT pegmatites can be enormous: the largest spodumene was 14 meters long, the largest beryl was 18 meters long, and the largest potassium feldspar was 49 meters long.Lithium-cesium-tantalum pegmatites account for about one-fourth of the world’s lithium production, most of the tantalum production, and all of the cesium production. Giant deposits include Tanco in Canada, Greenbushes in Australia, and Bikita in Zimbabwe. The largest lithium pegmatite in the United States, at King’s Mountain, North Carolina, is no longer being mined although large reserves of lithium remain. Depending on size and attitude of the pegmatite, a variety of mining techniques are used, including artisanal surface mining, open-pit surface mining, small underground workings, and large underground operations using room-and-pillar design. In favorable circumstances, what would otherwise be gangue minerals (quartz, potassium feldspar, albite, and muscovite) can be mined along with lithium and (or) tantalum as coproducts.Most LCT pegmatites are hosted in metamorphosed supracrustal rocks in the upper greenschist to lower amphibolite facies. Lithium-cesium-tantalum pegmatite intrusions generally are emplaced late during orogeny, with emplacement being controlled by pre-existing structures. Typically, they crop out near evolved, peraluminous granites and leucogranites from which they are inferred to be

  19. AN EXTERNAL SHOCK ORIGIN OF GRB 141028A

    Energy Technology Data Exchange (ETDEWEB)

    Burgess, J. Michael; Bégué, Damien; Ryde, Felix [The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, SE-106 91 Stockholm (Sweden); Omodei, Nicola [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Pe’er, Asaf [Physics Department, University College Cork, Cork (Ireland); Racusin, J. L.; Cucchiara, A., E-mail: jamesb@kth.se, E-mail: damienb@kth.se [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2016-05-10

    The prompt emission of the long, smooth, and single-pulsed gamma-ray burst, GRB 141028A, is analyzed under the guise of an external shock model. First, we fit the γ -ray spectrum with a two-component photon model, namely, synchrotron+blackbody, and then fit the recovered evolution of the synchrotron νF{sub ν} peak to an analytic model derived considering the emission of a relativistic blast wave expanding into an external medium. The prediction of the model for the νF{sub ν} peak evolution matches well with the observations. We observe the blast wave transitioning into the deceleration phase. Furthermore, we assume the expansion of the blast wave to be nearly adiabatic, motivated by the low magnetic field deduced from the observations. This allows us to recover within an order of magnitude the flux density at the νF{sub ν} peak, which is remarkable considering the simplicity of the analytic model. Under this scenario we argue that the distinction between prompt and afterglow emission is superfluous as both early-time emission and late-time emission emanate from the same source. While the external shock model is clearly not a universal solution, this analysis opens the possibility that at least some fraction of GRBs can be explained with an external shock origin of their prompt phase.

  20. Bronchography by tantalum aerosols, an experimental investigation of lung clearance and retention

    International Nuclear Information System (INIS)

    Causse, Andre.

    1974-01-01

    Lung clearance of tantalum used as contrast medium has been studied in three animal species: rat, monkey and cat. In rats and monkeys, 80 to 90 percent of the inhaled tantalum was removed with a half life of 10 to 30 hr, but the residual fraction was removed with a half life longer than 100 days; consequently persistent roentgenographic pictures could be observed. These results were in accordance with those obtained by other authors studying dogs and men (accidental inhalation of radioactive tantalum). In cats, about 98 percent was removed with a half life of 15 hr and the remaining fraction with a half life of 18 days. In the three species, the physiological lung clearance mechanisms did not seem disturbed. Microscopic examination showed the peribronchiolar localisation of remaining tantalum in rats and monkeys, with proliferation of granulomes and fibrotic reaction. These results must induce to the greatest care when using tantalum in man in order to outline peripheral airways [fr

  1. Development of technology of high-purity compounds of tantalum and niobium with octanol use

    International Nuclear Information System (INIS)

    Majorov, V.G.; Nikolaev, A.I.; Kopkov, V.K.; Baklanova, I.V.; Safonova, L.A.

    2001-01-01

    Effect of composition of solutions and extractant expenditure on tantalum and niobium distribution during extraction by octanol and purification of tantalum and niobium extracts from impurities was studied. Scheme was developed according to which samples of high-pure tantalum and niobium pentaoxides were prepared [ru

  2. The Chemical Vapour Deposition of Tantalum - in long narrow channels

    DEFF Research Database (Denmark)

    Mugabi, James Atwoki

    protective layers of tantalum because of the process’ ability to coat complex geometries and its relative ease to control. This work focuses on studying the CVD of tantalum in long narrow channels with the view that the knowledge gained during the project can be used to optimise the commercial coating...... and that there is a major change in morphology between 850 – 900 °C. The effects of system pressure and precursor partial pressure are also studied, and were found to have relevance to the tantalum distribution along the substrates but little effect on the structural morphology of the deposited layer. In the implemented...

  3. Synthesis and characterization of tantalum organometallic complexes. Catalytic activity for olefins

    International Nuclear Information System (INIS)

    Baley, A.S.

    1990-11-01

    Synthesis of monoaryloxy (alcoxy) neopentyl compounds is investigated. The tantalum-oxygen bond is formed by two parallel ways from TaCl 5 or TaR 2 Cl 3 with R = neopentyl and the tantalum carbon bond from a neopentyl derivative of the main series. Some compounds were isolated and characterized by NMR, elemental analysis and sometimes X-ray structure, some others are characterized in solution only. Catalytic effect is tested by ethylene dimerization and olefin polymerization. Reactivity of tantalum aryloxy neopentyl in respect to complexing and chelating ligands is studied for preparation of neopentylidene complexes

  4. Additively manufactured porous tantalum implants

    NARCIS (Netherlands)

    Wauthle, Ruben; Van Der Stok, Johan; Yavari, Saber Amin; Van Humbeeck, Jan; Kruth, Jean Pierre; Zadpoor, Amir Abbas; Weinans, Harrie; Mulier, Michiel; Schrooten, Jan

    2015-01-01

    The medical device industry's interest in open porous, metallic biomaterials has increased in response to additive manufacturing techniques enabling the production of complex shapes that cannot be produced with conventional techniques. Tantalum is an important metal for medical devices because of

  5. Strength and deformation of shocked diamond single crystals: Orientation dependence

    Science.gov (United States)

    Lang, J. M.; Winey, J. M.; Gupta, Y. M.

    2018-03-01

    Understanding and quantifying the strength or elastic limit of diamond single crystals is of considerable scientific and technological importance, and has been a subject of long standing theoretical and experimental interest. To examine the effect of crystalline anisotropy on strength and deformation of shocked diamond single crystals, plate impact experiments were conducted to measure wave profiles at various elastic impact stresses up to ˜120 GPa along [110] and [111] crystal orientations. Using laser interferometry, particle velocity histories and shock velocities in the diamond samples were measured and were compared with similar measurements published previously for shock compression along the [100] direction. Wave profiles for all three orientations showed large elastic wave amplitudes followed by time-dependent inelastic deformation. From the measured wave profiles, the elastic limits were determined under well characterized uniaxial strain loading conditions. The measured elastic wave amplitudes for the [110] and [111] orientations were lower for higher elastic impact stress (stress attained for an elastic diamond response), consistent with the result reported previously for [100] diamond. The maximum resolved shear stress (MRSS) on the {111}⟨110⟩ slip systems was determined for each orientation, revealing significant orientation dependence. The MRSS values for the [100] and [110] orientations (˜33 GPa) are 25%-30% of theoretical estimates; the MRSS value for the [111] orientation is significantly lower (˜23 GPa). Our results demonstrate that the MRSS depends strongly on the stress component normal to the {111} planes or the resolved normal stress (RNS), suggesting that the RNS plays a key role in inhibiting the onset of inelastic deformation. Lower elastic wave amplitudes at higher peak stress and the effect of the RNS are inconsistent with typical dislocation slip mechanisms of inelastic deformation, suggesting instead an inelastic response

  6. Laser driven single shock compression of fluid deuterium from 45 to 220 GPa

    Energy Technology Data Exchange (ETDEWEB)

    Hicks, D; Boehly, T; Celliers, P; Eggert, J; Moon, S; Meyerhofer, D; Collins, G

    2008-03-23

    The compression {eta} of liquid deuterium between 45 and 220 GPa under laser-driven shock loading has been measured using impedance matching to an aluminum (Al) standard. An Al impedance match model derived from a best fit to absolute Hugoniot data has been used to quantify and minimize the systematic errors caused by uncertainties in the high-pressure Al equation of state. In deuterium below 100 GPa results show that {eta} {approx_equal} 4.2, in agreement with previous impedance match data from magnetically-driven flyer and convergent-explosive shock wave experiments; between 100 and 220 GPa {eta} reaches a maximum of {approx}5.0, less than the 6-fold compression observed on the earliest laser-shock experiments but greater than expected from simple extrapolations of lower pressure data. Previous laser-driven double-shock results are found to be in good agreement with these single-shock measurements over the entire range under study. Both sets of laser-shock data indicate that deuterium undergoes an abrupt increase in compression at around 110 GPa.

  7. Tribological performance of polycrystalline tantalum-carbide-incorporated diamond films on silicon substrates

    Science.gov (United States)

    Ullah, Mahtab; Rana, Anwar Manzoor; Ahmed, E.; Malik, Abdul Sattar; Shah, Z. A.; Ahmad, Naseeb; Mehtab, Ujala; Raza, Rizwan

    2018-05-01

    Polycrystalline tantalum-carbide-incorporated diamond coatings have been made on unpolished side of Si (100) wafer by hot filament chemical vapor deposition process. Morphology of the coatings has been found to vary from (111) triangular-facetted to predominantly (111) square-faceted by increasing the concentration of tantalum carbide. The results have been compared to those of a diamond reference coating with no tantalum content. An increase in roughness has been observed with the increase of tantalum carbide (TaC) due to change in morphology of the diamond films. It is noticed that roughness of the coatings increases as grains become more square-faceted. It is found that diamond coatings involving tantalum carbide are not as resistant as diamond films with no TaC content and the coefficient of friction for such coatings with microcrystalline grains can be manipulated to 0·33 under high vacuum of 10-7 Torr. Such a low friction coefficient value enhances tribological behavior of unpolished Si substrates and can possibly be used in sliding applications.

  8. Kinetic Study of the Chemical Vapor Deposition of Tantalum in Long Narrow Channels

    DEFF Research Database (Denmark)

    Mugabi, James Atwoki; Eriksen, Søren; Petrushina, Irina

    2016-01-01

    A kinetic study of the chemical vapor deposition of tantalum in long narrow channels is done to optimize the industrial process for the manufacture of tantalum coated plate heat exchangers. The developed model fits well at temperatures between 750 and 850 °C, and in the pressure range of25–990 mbar....... According to the model, the predominant tantalum growth species is TaCl3. The temperature is shown to have a pronounced effect onthe morphology and rate of deposition of the tantalum and an apparent change in deposition mechanism occurs between 850–900 °C, resulting in the deposition rate at 900 °C being...

  9. An investigation of tantalum and niobium contents by nuclear technique

    International Nuclear Information System (INIS)

    Patmasiriwat, N.

    1981-01-01

    The objective of this experimental study was to find suitable nuclear techniques to determine the quantities of niobium and tantalum in columbite. The study has been performed by using radioisotope X-ray fluorescent technique (X RF) and neutron activation analysis (NAA). The results showed a good agreement between these two techniques. Nevertheless, with NAA, if there is uranium in the sample, the spectrum of niobium will be interfered. So practically, on the basis of accuracy and speed of determination, X-ray fluorescence is more suitable than NAA to determine the quantity of niobium while tantalum is preferable to use NAA. The detection limit of niobium and tantalum using the above techniques are 0.661% and 0.1 mg respectively

  10. RNA-Seq-based analysis of cold shock response in Thermoanaerobacter tengcongensis, a bacterium harboring a single cold shock protein encoding gene.

    Directory of Open Access Journals (Sweden)

    Bo Liu

    Full Text Available BACKGROUND: Although cold shock responses and the roles of cold shock proteins in microorganisms containing multiple cold shock protein genes have been well characterized, related studies on bacteria possessing a single cold shock protein gene have not been reported. Thermoanaerobacter tengcongensis MB4, a thermophile harboring only one known cold shock protein gene (TtescpC, can survive from 50° to 80 °C, but has poor natural competence under cold shock at 50 °C. We therefore examined cold shock responses and their effect on natural competence in this bacterium. RESULTS: The transcriptomes of T. tengcongensis before and after cold shock were analyzed by RNA-seq and over 1200 differentially expressed genes were successfully identified. These genes were involved in a wide range of biological processes, including modulation of DNA replication, recombination, and repair; energy metabolism; production of cold shock protein; synthesis of branched amino acids and branched-chain fatty acids; and sporulation. RNA-seq analysis also suggested that T. tengcongensis initiates cell wall and membrane remodeling processes, flagellar assembly, and sporulation in response to low temperature. Expression profiles of TtecspC and failed attempts to produce a TtecspC knockout strain confirmed the essential role of TteCspC in the cold shock response, and also suggested a role of this protein in survival at optimum growth temperature. Repression of genes encoding ComEA and ComEC and low energy metabolism levels in cold-shocked cells are the likely basis of poor natural competence at low temperature. CONCLUSION: Our study demonstrated changes in global gene expression under cold shock and identified several candidate genes related to cold shock in T. tengcongensis. At the same time, the relationship between cold shock response and poor natural competence at low temperature was preliminarily elucidated. These findings provide a foundation for future studies on genetic

  11. Hydrogen adsorption on skeletal rhodium-tantalum electrodes-catalysts

    International Nuclear Information System (INIS)

    Tsinstevich, V.M.; Krejnina, N.M.

    1975-01-01

    Skeleton rhodium-tantalic catalyst electrodes with a tantalum mass percentage of 0 to 100 have been obtained by the methodology of Crupp and others. The hydrogen adsorption is studied through the method of removing the galvano-static and potentiodynamic curves of charging in sulfuric acid and potassium hydroxide. It has been discovered that the maximum adsorption ability relatively to the hydrogen can be observed in an alloy with a 5% tantalum contents. The energetic characteristics of the alloys are higher in alkali than in acid

  12. Standard specification for tantalum and tantalum alloy plate, sheet, and strip. ASTM standard

    International Nuclear Information System (INIS)

    1998-09-01

    This specification is under the jurisdiction of ASTM Committee B-10 on Reactive and Refractory Metals and Alloys and is the direct responsibility of Subcommittee B10.03 on Niobium and Tantalum. Current edition approved May 10, 1998 and published September 1998. Originally published as B 708-82. Last previous edition was B 708-92

  13. Effect of sputtering parameters and substrate composition on the structure of tantalum thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hallmann, Lubica, E-mail: lubica.hallmann@zzm.uzh.c [Clinic of Fixed and Removable Prosthodontics and Dental Material Science, Center of Dental Medicine, University of Zürich (Switzerland); Ulmer, Peter [Institute of Geochemistry and Petrology, ETH Zürich (Switzerland)

    2013-10-01

    The crystallographic properties of tantalum films deposited as a bioactive coating on Co–Cr–Mo and Ti–Al–Nb alloys have been investigated. The desired tough and ductile alpha phase of tantalum has been obtained by DC magnetron sputtering on Co–Cr–Mo and Ti–Al–Nb substrates. The thickness of the tantalum layer was between 20 and 600 nm. The crystallographic structure of tantalum thin film was dependent on the sputtering parameters such as DC power, bias voltage and gas impurities. Oxygen is an important factor for the stabilization of the tantalum alpha phase on Co–Cr–Mo substrate. The crystallographic structure and texture of tantalum thin films was found to be additionally dependent on the substrate composition. For Ti–Al–Nb substrate, oxygen content was not an important factor for the stabilization of the alpha phase. The observed shift of X-ray diffraction peaks to lower 2(θ) is an indication of stress evolving during the sputtering process and was dependent on bias voltage and oxygen content of the carrier gas.

  14. Experimental lumbar spine fusion with novel tantalum-coated carbon fiber implant

    DEFF Research Database (Denmark)

    Li, Haisheng; Zou, Xuenong; Woo, Charlotte

    2007-01-01

    the possibility of coating a biocompatible metal layer on top of the carbon fiber material, to improve its biological performance. Tantalum was chosen because of its bone compatibility, based on our previous studies. A novel spinal fusion cage was fabricated by applying a thin tantalum coating on the surface...

  15. Tantalum(V) impurity extraction by octanol from niobium(V) fluoride solutions

    International Nuclear Information System (INIS)

    Majorov, V.G.; Nikolaev, A.I.; Kopkov, V.K.

    2002-01-01

    The conditions of the niobium and tantalum extraction separation by octanol in the fluoride solutions, depending on the metals and free hydrofluoric acid concentration as well as on the organic and water phases voluminous relation, are studied for the purpose of developing the technology of niobium deep purification from the tantalum impurities. The technological scheme of the niobium solutions(V) extraction purification from the tantalum impurities(V), which provides for obtaining the niobium oxide(V), containing less than 0.005 mass % Ta 2 O 5 , is proposed on the basis of the established optimal separation conditions. The possibility of using the developed technology by the pyrochlore reprocessing is indicated [ru

  16. Behaviour of tantalum- and ceramics implants in the organism

    International Nuclear Information System (INIS)

    Reich, M.

    1987-01-01

    Studies of human and animal tissues after the use of orthopaedic implants were carried out by means of instrumental neutron activation analysis (INAA), as well as studies on the corrosion behaviour of tantalum by means of tracer techniques. After the use of an Al 2 O 3 -ceramic-metal compound prosthesis of the hip joint samples from the joint capsule and the Fascia Lata of 9 patients were studied. The measured Al amounts in the capsule tissues were greater than the normal values by up to 3 orders of magnitude. The corrosion experiment with tantalum was carried out in Ringer's solution as a model of body fluids. Local and systemic changes because of tantalum implants in animal experiments showed massive local stress of the contact tissue as a result of corrosion. Along with this, increased values of Ta were found in the spleen and the liver. (orig./RB) [de

  17. Temperature and Pressure Dependences of the Elastic Properties of Tantalum Single Crystals Under Tensile Loading: A Molecular Dynamics Study

    Science.gov (United States)

    Li, Wei-bing; Li, Kang; Fan, Kan-qi; Zhang, Da-xing; Wang, Wei-dong

    2018-04-01

    Atomistic simulations are capable of providing insights into physical mechanisms responsible for mechanical properties of the transition metal of Tantalum (Ta). By using molecular dynamics (MD) method, temperature and pressure dependences of the elastic properties of Ta single crystals are investigated through tensile loading. First of all, a comparative study between two types of embedded-atom method (EAM) potentials is made in term of the elastic properties of Ta single crystals. The results show that Ravelo-EAM (Physical Review B, 2013, 88: 134101) potential behaves well at different hydrostatic pressures. Then, the MD simulation results based on the Ravelo-EAM potential show that Ta will experience a body-centered-cubic (BCC) to face-centered-cubic (FCC) phase transition before fracture under tensile loading at 1 K temperature, and model size and strain rate have no obvious effects on tensile behaviors of Ta. Next, from the simulation results at the system temperature from 1 to 1500 K, it can be derived that the elastic modulus of E 100 linearly decrease with the increasing temperature, while the yielding stress decrease with conforming a quadratic polynomial formula. Finally, the pressure dependence of the elastic properties is performed from 0 to 140 GPa and the observations show that the elastic modulus increases with the increasing pressure overall.

  18. Carbon monoxide and carbon dioxide interaction with tantalum

    International Nuclear Information System (INIS)

    Belov, V.D.; Ustinov, Yu.K.; Komar, A.P.

    1978-01-01

    The adsorption of carbon monoxide and carbon dioxide on tantalum and the dissolution of these gases in the adsorbent at T >= 300 K have been studied. The flash-filament method (FFM) in a monopole mass-spectrometer and a field emission microscopy was used in the same apparatus. Carbon monoxide and carbon dioxide dissociate on the tantalum surface, carbon monoxide being desorbed in both cases during the flash. The desorption curves of CO reveal three different binding states: two of them (α and β' 1 ) for the adsorbed particles whereas the high temperature desorption state relates to the adsorbate dissolved in the metal. For the β' 1 state of CO the activation energy, the pre-exponential factor and the kinetic order in the kinetic equation of desorption have been estimated. They turned out to be E = 110 kcal/mol, C = 3 X 10 12 sec -1 , and γ = 1. The activation energy of diffusion for CO in tantalum and the energy of outgassing for the metal were found to be 9.4 and 49 kcal/mole, respectively. (Auth.)

  19. Carbon monoxide and carbon dioxide interaction with tantalum

    Energy Technology Data Exchange (ETDEWEB)

    Belov, V D; USTINOV, YU K; KOMAR, A P [AN SSSR, LENINGRAD. FIZIKO-TEKHNICHESKIJ INST.

    1978-03-01

    The adsorption of carbon monoxide and carbon dioxide on tantalum and the dissolution of these gases in the adsorbent at T >= 300 K have been studied. The flash-filament method (FFM) in a monopole mass-spectrometer and a field emission microscopy was used in the same apparatus. Carbon monoxide and carbon dioxide dissociate on the tantalum surface, carbon monoxide being desorbed in both cases during the flash. The desorption curves of CO reveal three different binding states: two of them (..cap alpha.. and ..beta..'/sub 1/) for the adsorbed particles whereas the high temperature desorption state relates to the adsorbate dissolved in the metal. For the ..beta..'/sub 1/ state of CO the activation energy, the pre-exponential factor and the kinetic order in the kinetic equation of desorption have been estimated. They turned out to be E = 110 kcal/mol, C = 3 X 10/sup 12/ sec/sup -1/, and ..gamma.. = 1. The activation energy of diffusion for CO in tantalum and the energy of outgassing for the metal were found to be 9.4 and 49 kcal/mole, respectively.

  20. Niobium and tantalum

    International Nuclear Information System (INIS)

    Polupanova, L.I.; Volkova, G.A.

    1983-01-01

    General mineralogical-geochemical and analytical characteristics of niobium and tantalum are presented. Potentialities of any analytical methods for determining these elements in various geologic samples are estimated. The following specific techniques are described: neutron + activation determination of Ta, fluorescence X-radiometric determination of Nb and Ta, fluorescence X-ray spectral determination of Nb and Ta, spectrographic determination of Nb and Ta, gravimetric determination of Nb and Ta, their extraction-photometric determination with various reagents (crystal violet, rhodamine 6 Y, butylrhodamine B)

  1. Short wave infrared hyperspectral imaging for recovered post-consumer single and mixed polymers characterization

    Science.gov (United States)

    Bonifazi, Giuseppe; Palmieri, Roberta; Serranti, Silvia

    2015-03-01

    Postconsumer plastics from packing and packaging represent about the 60% of the total plastic wastes (i.e. 23 million of tons) produced in Europe. The EU Directive (2014/12/EC) fixes as target that the 60%, by weight, of packaging waste has to be recovered, or thermally valorized. When recovered, the same directive established that packaging waste has to be recycled in a percentage ranging between 55% (minimum) and 60% (maximum). The non-respect of these rules can produce that large quantities of end-of-life plastic products, specifically those utilized for packaging, are disposed-off, with a strong environmental impact. The application of recycling strategies, finalized to polymer recovery, can represent an opportunity to reduce: i) not renewable raw materials (i.e. oil) utilization, ii) carbon dioxide emissions and iii) amount of plastic waste disposed-off. Aim of this work was to perform a full characterization of different end-of-life polymers based products, constituted not only by single polymers but also of mixtures, in order to realize their identification for quality control and/or certification assessment. The study was specifically addressed to characterize the different recovered products as resulting from a recycling plant where classical processing flow-sheets, based on milling, classification and separation, are applied. To reach this goal, an innovative sensing technique, based on the utilization of a HyperSpectral[b] I[/b]maging (HSI) device working in the SWIR region (1000-2500 nm), was investigated. Following this strategy, single polymers and/or mixed polymers recovered were correctly recognized. The main advantage of the proposed approach is linked to the possibility to perform "on-line" analyses, that is directly on the different material flow streams, as resulting from processing, without any physical sampling and classical laboratory "off-line" determination.

  2. Durability of adhesive bonds to uranium alloys, tungsten, tantalum, and thorium

    International Nuclear Information System (INIS)

    Childress, F.G.

    1975-01-01

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

  3. Microstructures and phase transformations in interstitial alloys of tantalum

    International Nuclear Information System (INIS)

    Dahmen, U.

    1979-01-01

    The analysis of microstructures, phases, and possible ordering of interstitial solute atoms is fundamental to an understanding of the properties of metal-interstitial alloys in general. As evidenced by the controversies on phase transformations in the particular system tantalum--carbon, our understanding of this class of alloys is inferior to our knowledge of substitutional metal alloys. An experimental clarification of these controversies in tantalum was made. Using advanced techniques of electron microscopy and ultrahigh vacuum techology, an understanding of the microstructures and phase transformations in dilute interstitial tantalum--carbon alloys is developed. Through a number of control experiments, the role and sources of interstitial contamination in the alloy preparation (and under operating conditions) are revealed. It is demonstrated that all previously published work on the dilute interstitially ordered phase Ta 64 C can be explained consistently in terms of ordering of the interstitial contaminants oxygen and hydrogen, leading to the formation of the phases Ta 12 O and Ta 2 H

  4. Structural characterisation of oxygen diffusion hardened alpha-tantalum PVD-coatings on titanium.

    Science.gov (United States)

    Hertl, C; Koll, L; Schmitz, T; Werner, E; Gbureck, U

    2014-08-01

    Titanium substrates were coated with tantalum layers of 5 μm thickness using physical vapour deposition (PVD). The tantalum layers showed a (110)-preferred orientation. The coated samples were hardened by oxygen diffusion. Using X-ray diffraction the crystallographic structure of the tantalum coatings was characterised, comparing untreated and diffusion hardened specimen conditions. Oxygen depth profiles were determined by glow discharge spectrometry. The hardening effect of the heat treatment was examined by Vickers microhardness testing. The increase of surface hardness caused by oxygen diffusion was at least 50%. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Interaction between shock wave and single inertial bubbles near an elastic boundary.

    Science.gov (United States)

    Sankin, G N; Zhong, P

    2006-10-01

    The interaction of laser-generated single inertial bubbles (collapse time = 121 mus) near a silicon rubber membrane with a shock wave (55 MPa in peak pressure and 1.7 mus in compressive pulse duration) is investigated. The interaction leads to directional, forced asymmetric collapse of the bubble with microjet formation toward the surface. Maximum jet penetration into the membrane is produced during the bubble collapse phase with optimal shock wave arrival time and stand-off distance. Such interaction may provide a unique acoustic means for in vivo microinjection, applicable to targeted delivery of macromolecules and gene vectors to biological tissues.

  6. Polymerized phase and amorphous diamond synthesized from C60 fullerene by shock compression

    International Nuclear Information System (INIS)

    Niwase, K.; Homae, T.; Nakamura, K.G.; Kondo, K.

    2006-01-01

    C 60 fullerene films were shock compressed to 23 and 52GPa. Both the recovered samples exhibit fracture into platelets and broad photoluminescence, and intensity of these increases with increasing pressure. At 23GPa, a characteristic single broad band appears at 1560-1570cm -1 , which is similar to the one found for three-dimensional (3D) polymerized C 60 fullerene under high-pressure-high-temperature treatment. At 52GPa, on the other hand, the single broad band has disappeared and a diamond peak sometimes appears, depending on platelets

  7. Biological Response of Human Bone Marrow-Derived Mesenchymal Stem Cells to Commercial Tantalum Coatings with Microscale and Nanoscale Surface Topographies

    Science.gov (United States)

    Skoog, Shelby A.; Kumar, Girish; Goering, Peter L.; Williams, Brian; Stiglich, Jack; Narayan, Roger J.

    2016-06-01

    Tantalum is a promising orthopaedic implant coating material due to its robust mechanical properties, corrosion resistance, and excellent biocompatibility. Previous studies have demonstrated improved biocompatibility and tissue integration of surface-treated tantalum coatings compared to untreated tantalum. Surface modification of tantalum coatings with biologically inspired microscale and nanoscale features may be used to evoke optimal tissue responses. The goal of this study was to evaluate commercial tantalum coatings with nanoscale, sub-microscale, and microscale surface topographies for orthopaedic and dental applications using human bone marrow-derived mesenchymal stem cells (hBMSCs). Tantalum coatings with different microscale and nanoscale surface topographies were fabricated using a diffusion process or chemical vapor deposition. Biological evaluation of the tantalum coatings using hBMSCs showed that tantalum coatings promote cellular adhesion and growth. Furthermore, hBMSC adhesion to the tantalum coatings was dependent on surface feature characteristics, with enhanced cell adhesion on sub-micrometer- and micrometer-sized surface topographies compared to hybrid nano-/microstructures. Nanostructured and microstructured tantalum coatings should be further evaluated to optimize the surface coating features to promote osteogenesis and enhance osseointegration of tantalum-based orthopaedic implants.

  8. Design of a high-pressure single pulse shock tube for chemical kinetic investigations

    International Nuclear Information System (INIS)

    Tranter, R. S.; Brezinsky, K.; Fulle, D.

    2001-01-01

    A single pulse shock tube has been designed and constructed in order to achieve extremely high pressures and temperatures to facilitate gas-phase chemical kinetic experiments. Postshock pressures of greater than 1000 atmospheres have been obtained. Temperatures greater than 1400 K have been achieved and, in principle, temperatures greater than 2000 K are easily attainable. These high temperatures and pressures permit the investigation of hydrocarbon species pyrolysis and oxidation reactions. Since these reactions occur on the time scale of 0.5--2 ms the shock tube has been constructed with an adjustable length driven section that permits variation of reaction viewing times. For any given reaction viewing time, samples can be withdrawn through a specially constructed automated sampling apparatus for subsequent species analysis with gas chromatography and mass spectrometry. The details of the design and construction that have permitted the successful generation of very high-pressure shocks in this unique apparatus are described. Additional information is provided concerning the diaphragms used in the high-pressure shock tube

  9. The evaluation of hydroxyapatite (HA) coated and uncoated porous tantalum for biomedical material applications

    International Nuclear Information System (INIS)

    Safuan, Nadia; Sukmana, Irza; Kadir, Mohammed Rafiq Abdul; Noviana, Deni

    2014-01-01

    Porous tantalum has been used as an orthopedic implant for bone defects as it has a good corrosion resistance and fatigue behaviour properties. However, there are some reports on the rejection of porous Ta after the implantation. Those clinical cases refer to the less bioactivity of metallic-based materials. This study aims to evaluate hydroxyapatite coated and uncoated porous Tantalum in order to improve the biocompatibility of porous tantalum implant and osseointegration. Porous tantalum was used as metallic-base substrate and hydroxyapatite coating has been done using plasma-spraying technique. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FESEM) techniques were utilizes to investigate the coating characteristics while Confocal Raman Microscopy to investigate the interface and image. The effect of coating to the corrosion behaviour was assessed by employing potentiodynamic polarization tests in simulated body fluid at 37±1 °C. Based on SEM and FESEM results, the morphologies as well the weight element consists in the uncoated and hydroxyapatite coated porous tantalum were revealed. The results indicated that the decrease in corrosion current density for HA coated porous Ta compared to the uncoated porous Ta. This study concluded that by coating porous tantalum with HA supports to decrease the corrosion rate of pure porous.

  10. The Evaluation of Hydroxyapatite (HA) Coated and Uncoated Porous Tantalum for Biomedical Material Applications

    Science.gov (United States)

    Safuan, Nadia; Sukmana, Irza; Kadir, Mohammed Rafiq Abdul; Noviana, Deni

    2014-04-01

    Porous tantalum has been used as an orthopedic implant for bone defects as it has a good corrosion resistance and fatigue behaviour properties. However, there are some reports on the rejection of porous Ta after the implantation. Those clinical cases refer to the less bioactivity of metallic-based materials. This study aims to evaluate hydroxyapatite coated and uncoated porous Tantalum in order to improve the biocompatibility of porous tantalum implant and osseointegration. Porous tantalum was used as metallic-base substrate and hydroxyapatite coating has been done using plasma-spraying technique. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FESEM) techniques were utilizes to investigate the coating characteristics while Confocal Raman Microscopy to investigate the interface and image. The effect of coating to the corrosion behaviour was assessed by employing potentiodynamic polarization tests in simulated body fluid at 37±1 °C. Based on SEM and FESEM results, the morphologies as well the weight element consists in the uncoated and hydroxyapatite coated porous tantalum were revealed. The results indicated that the decrease in corrosion current density for HA coated porous Ta compared to the uncoated porous Ta. This study concluded that by coating porous tantalum with HA supports to decrease the corrosion rate of pure porous.

  11. Fast, multiphase volume adaptation to hyperosmotic shock by Escherichia coli.

    Directory of Open Access Journals (Sweden)

    Teuta Pilizota

    Full Text Available All living cells employ an array of different mechanisms to help them survive changes in extra cellular osmotic pressure. The difference in the concentration of chemicals in a bacterium's cytoplasm and the external environment generates an osmotic pressure that inflates the cell. It is thought that the bacterium Escherichia coli use a number of interconnected systems to adapt to changes in external pressure, allowing them to maintain turgor and live in surroundings that range more than two-hundred-fold in external osmolality. Here, we use fluorescence imaging to make the first measurements of cell volume changes over time during hyperosmotic shock and subsequent adaptation on a single cell level in vivo with a time resolution on the order of seconds. We directly observe two previously unseen phases of the cytoplasmic water efflux upon hyperosmotic shock. Furthermore, we monitor cell volume changes during the post-shock recovery and observe a two-phase response that depends on the shock magnitude. The initial phase of recovery is fast, on the order of 15-20 min and shows little cell-to-cell variation. For large sucrose shocks, a secondary phase that lasts several hours adds to the recovery. We find that cells are able to recover fully from shocks as high as 1 Osmol/kg using existing systems, but that for larger shocks, protein synthesis is required for full recovery.

  12. Evaluation of residual stress in sputtered tantalum thin-film

    Energy Technology Data Exchange (ETDEWEB)

    Al-masha’al, Asa’ad, E-mail: asaad.al@ed.ac.uk; Bunting, Andrew; Cheung, Rebecca

    2016-05-15

    Highlights: • Tantalum thin-films have been deposited by DC magnetron sputtering system. • Thin-film stress is observed to be strongly influenced by sputtering pressure. • Transition towards the compressive stress is ascribed to the annealing at 300 °C. • Expose thin-film to air ambient or ion bombardment lead to a noticeable change in the residual stress. - Abstract: The influence of deposition conditions on the residual stress of sputtered tantalum thin-film has been evaluated in the present study. Films have been deposited by DC magnetron sputtering and curvature measurement method has been employed to calculate the residual stress of the films. Transitions of tantalum film stress from compressive to tensile state have been observed as the sputtering pressure increases. Also, the effect of annealing process at temperature range of 90–300 °C in oxygen ambient on the residual stress of the films has been studied. The results demonstrate that the residual stress of the films that have been deposited at lower sputtering pressure has become more compressive when annealed at 300 °C. Furthermore, the impact of exposure to atmospheric ambient on the tantalum film stress has been investigated by monitoring the variation of the residual stress of both annealed and unannealed films over time. The as-deposited films have been exposed to pure Argon energy bombardment and as result, a high compressive stress has been developed in the films.

  13. Examination of the damage and failure response of tantalum and copper under varied shock loading conditions

    Energy Technology Data Exchange (ETDEWEB)

    Bronkhorst, Curt A [Los Alamos National Laboratory; Dennis - Koller, Darcie [Los Alamos National Laboratory; Cerreta, Ellen K [Los Alamos National Laboratory; Gray Ill, George T [Los Alamos National Laboratory; Bourne, Neil [AWE-ALDERMASTON

    2010-12-16

    A number of plate impact experiments have been conducted on high purity polycrystalline tantalum and copper samples using graded flyer plate configurations to alter the loading profile. These experiments are designed in a way so that a broad range of damage regimes are probed. The results show that the nucleation of damage primarily occurs at the grain boundaries of the materials. This affords us the opportunity to propose a porosity damage nucleation criterion which begins to account for the length scales of the microstructure (grain size distribution) and the mechanical response of the grain boundary regions (failure stress distribution). This is done in the context of a G-T-N type model for the ductile damage and failure response of both the materials examined. The role of micro-inertial effects on the porosity growth process is also considered.

  14. Tantalum oxide-based compounds as new non-noble cathodes for polymer electrolyte fuel cell

    International Nuclear Information System (INIS)

    Ishihara, Akimitsu; Tamura, Motoko; Matsuzawa, Koichi; Mitsushima, Shigenori; Ota, Ken-ichiro

    2010-01-01

    Tantalum oxide-based compounds were examined as new non-noble cathodes for polymer electrolyte fuel cell. Tantalum carbonitride powder was partially oxidized under a trace amount of oxygen gas at 900 o C for 4 or 8 h. Onset potential for oxygen reduction reaction (ORR) of the specimen heat-treated for 8 h was 0.94 V vs. reversible hydrogen electrode in 0.1 mol dm -3 sulfuric acid at 30 o C. The partial oxidation of tantalum carboniride was effective to enhance the catalytic activity for the ORR. The partially oxidized specimen with highest catalytic activity had ca. 5.25 eV of ionization potential, indicating that there was most suitable strength of the interaction of oxygen and tantalum on the catalyst surface.

  15. The plastic response of Tantalum in Quasi-Isentropic Compression Ramp and Release

    Science.gov (United States)

    Moore, Alexander; Brown, Justin; Lim, Hojun; Lane, J. Matthew D.

    2017-06-01

    The mechanical response of various forms of tantalum under extreme pressures and strain rates is studied using dynamic quasi-isentropic compression loading conditions in atomistic simulations. Ramp compression in bcc metals under these conditions tend to show a significant strengthening effect with increasing pressure; however, due to limitations of experimental methods in such regimes, the underlying physics for this phenomenon is not well understood. Molecular dynamics simulations provide important information about the plasticity mechanisms and can be used to investigate this strengthening. MD simulations are performed on nanocrystalline Ta and single crystal defective Ta with dislocations and point defects to uncover how the material responds and the underlying plasticity mechanisms. The different systems of solid Ta are seen to plastically deform through different mechanisms. Fundamental understanding of tantalum plasticity in these high pressure and strain rate regimes is needed to model and fully understand experimental results. Sandia National Labs is a multi program laboratory managed and operated by Sandia Corp., a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  16. A study for an electrolytic reduction of tantalum oxide in a LiCl-Li2O molten salt

    International Nuclear Information System (INIS)

    Park, Sung Bin; Park, Byung Heung; Seo, Chung Seok; Kang, Dae Seung; Kwon, Seon Gil; Park, Seong Won

    2005-01-01

    Korea Atomic Energy Research Institute (KAERI) has developed the Advanced Spent Fuel Conditioning Process (ACP) to be an innovative technology for handling the PWR spent fuel. As part of ACP, the electrolytic reduction process (ER process) is the electrochemical reduction process of uranium oxide to uranium metal in a molten salt. The ER process has advantages in a technical stability, an economic potential and a good proliferation resistance. KAERI has reported on the good experimental results of an electrochemical reduction of the uranium oxide in a 20 kg HM/batch lab-scale. The ER process can be applicable to the reduction of other metal oxides. Metal tantalum powder has attracted attention for a variety of applications. A tantalum capacitor made from superfine and pliable tantalum powders is very small in size and it has a higher-capacitance part, therefore it is useful for microelectronic devices. By the ER process the metal tantalum can be obtained from tantalum pentoxide. In this work, a 40 g Ta 2 O 5 /batch electrochemical reactor was used for the synthesis of the metal tantalum. From the results of the cyclic voltammograms for the Ta 2 O 5 -LiCl-Li 2 O system, the mechanism of the tantalum reduction in a molten LiCl-Li 2 O salt system was investigated. Tantalum pentoxide is chemically reduced to tantalum metal by the lithium metal which is electrochemically deposited into an integrated cathode assembly in the LiCl-Li 2 O molten salt. The experiments for the tantalum reduction were performed with a chronopotentiometry in the reactor cell, the reduced products were analyzed from an analysis of the X-ray diffraction (XRD), scanning electron microscope and energy dispersive X-ray (SEM-EDX). From the results, the electrolytic reduction process is applicable to the synthesis of metal tantalum

  17. Recent advances in P/M-tantalum products

    International Nuclear Information System (INIS)

    Kumar, P.; Uhlenhut, H.

    2001-01-01

    The metallurgical grade tantalum powder is used for producing parts and mill products. Some of the key requirements include purity, physical characteristics (flow, fill density and compressibility) and interstitial contents. A process to produce 99.99 % pure tantalum powder with less than 150 ppm oxygen has been developed. This powder was consolidated into metallurgical products via conventional P/M processing; resulting products had high purity and low oxygen. It also retained fine grain-size and uniform properties inherent in P/M-derived products. In addition, the desired crystallographic texture was obtained by controlled thermo-mechanical processing (TMP) of the consolidated powder. Fully dense products of this powder were tested for various applications, such as deep drawing, sputtering, ballistics and capacitors. Critical functional requirements in these applications along with the results of evaluations are discussed. (author)

  18. Micro/Nano Structural Tantalum Coating for Enhanced Osteogenic Differentiation of Human Bone Marrow Stem Cells.

    Science.gov (United States)

    Ding, Ding; Xie, Youtao; Li, Kai; Huang, Liping; Zheng, Xuebin

    2018-04-03

    Recently, tantalum has been attracting much attention for its anticorrosion resistance and biocompatibility, and it has been widely used in surface modification for implant applications. To improve its osteogenic differentiation of human bone marrow stem cells (hBMSCs), a micro/nano structure has been fabricated on the tantalum coating surface through the combination of anodic oxidation and plasma spraying method. The morphology, composition, and microstructure of the modified coating were comprehensively studied by employing scanning electron microscopy (SEM), X-ray diffraction (XRD) as well as transmission electron microscopy (TEM). The effects of hierarchical structures as well as micro-porous structure of tantalum coating on the behavior for human bone marrow stem cells (hBMSCs) were evaluated and compared at both cellular and molecular levels in vitro. The experimental results show that a hierarchical micro/nano structure with Ta₂O₅ nanotubes spread onto a micro-scale tantalum coating has been fabricated successfully, which is confirmed to promote cell adhesion and spreading. Besides, the hierarchical micro/nano tantalum coating can provide 1.5~2.1 times improvement in gene expression, compared with the micro-porous tantalum coating. It demonstrates that it can effectively enhance the proliferation and differentiation of hBMSCs in vitro.

  19. Micro/Nano Structural Tantalum Coating for Enhanced Osteogenic Differentiation of Human Bone Marrow Stem Cells

    Directory of Open Access Journals (Sweden)

    Ding Ding

    2018-04-01

    Full Text Available Recently, tantalum has been attracting much attention for its anticorrosion resistance and biocompatibility, and it has been widely used in surface modification for implant applications. To improve its osteogenic differentiation of human bone marrow stem cells (hBMSCs, a micro/nano structure has been fabricated on the tantalum coating surface through the combination of anodic oxidation and plasma spraying method. The morphology, composition, and microstructure of the modified coating were comprehensively studied by employing scanning electron microscopy (SEM, X-ray diffraction (XRD as well as transmission electron microscopy (TEM. The effects of hierarchical structures as well as micro-porous structure of tantalum coating on the behavior for human bone marrow stem cells (hBMSCs were evaluated and compared at both cellular and molecular levels in vitro. The experimental results show that a hierarchical micro/nano structure with Ta2O5 nanotubes spread onto a micro-scale tantalum coating has been fabricated successfully, which is confirmed to promote cell adhesion and spreading. Besides, the hierarchical micro/nano tantalum coating can provide 1.5~2.1 times improvement in gene expression, compared with the micro-porous tantalum coating. It demonstrates that it can effectively enhance the proliferation and differentiation of hBMSCs in vitro.

  20. Shock wave compression of hexagonal-close-packed metal single crystals: Time-dependent, anisotropic elastic-plastic response of beryllium

    International Nuclear Information System (INIS)

    Winey, J. M.; Gupta, Y. M.

    2014-01-01

    Understanding and modeling the response of hcp metals to high stress impulsive loading is challenging because the lower crystal symmetry, compared to cubic metals, results in a significantly more complex material response. To gain insight into the inelastic deformation of hcp metals subjected to high dynamic stresses, shock wave compression of single crystals provides a useful approach because different inelastic deformation mechanisms can be examined selectively by shock compression along different crystal orientations. As a representative example, we report, here, on wave propagation simulations for beryllium (Be) single crystals shocked along the c-axis, a-axis, and several low-symmetry directions to peak stresses reaching 7 GPa. The simulations utilized a time-dependent, anisotropic material model that incorporated dislocation dynamics, deformation twinning, and shear cracking based descriptions of inelastic deformation. The simulation results showed good overall agreement with measured wave profiles for all the different crystal orientations examined [Pope and Johnson, J. Appl. Phys. 46, 720 (1975)], including features arising from wave mode coupling due to the highly anisotropic inelastic response of Be. This good agreement demonstrates that the measured profiles can be understood in terms of dislocation slip along basal, prismatic, and pyramidal planes, together with deformation twinning along (101 ¯ 2) planes. Our results show that the response of shocked Be single crystals involves the simultaneous operation of multiple, distinct inelastic deformation mechanisms for all orientations except the c-axis. For shocked c-axis Be, the measured wave profiles do not provide good discrimination between pyramidal slip and other inelastic deformation mechanisms, such as shear cracking. The findings presented here provide insight into the complex inelastic deformation response of shocked Be single crystals and are expected to be useful for other hcp crystals. More

  1. Condensed matter at high shock pressures

    International Nuclear Information System (INIS)

    Nellis, W.J.; Holmes, N.C.; Mitchell, A.C.; Radousky, H.B.; Hamilton, D.

    1985-01-01

    Experimental techniques are described for shock waves in liquids: Hugoniot equation-of-state, shock temperature and emission spectroscopy, electrical conductivity, and Raman spectroscopy. Experimental data are reviewed and presented in terms of phenomena that occur at high densities and temperatures in shocked He, Ar, N 2 , CO, SiO 2 -aerogel, H 2 O, and C 6 H 6 . The superconducting properties of Nb metal shocked to 100 GPa (1 Mbar) and recovered intact are discussed in terms of prospects for synthesizing novel, metastable materials. Ultrahigh pressure data for Cu is reviewed in the range 0.3 to 6TPa (3 to 60 Mbar). 56 refs., 9 figs., 1 tab

  2. Random Vibration Testing of Advanced Wet Tantalum Capacitors

    Science.gov (United States)

    Teverovsky, Alexander

    2015-01-01

    Advanced wet tantalum capacitors allow for improved performance of power supply systems along with substantial reduction of size and weight of the systems that is especially beneficial for space electronics. Due to launch-related stresses, acceptance testing of all space systems includes random vibration test (RVT). However, many types of advanced wet tantalum capacitors cannot pass consistently RVT at conditions specified in MIL-PRF-39006, which impedes their use in space projects. This requires a closer look at the existing requirements, modes and mechanisms of failures, specifics of test conditions, and acceptance criteria. In this work, different lots of advanced wet tantalum capacitors from four manufacturers have been tested at step stress random vibration conditions while their currents were monitored before, during, and after the testing. It has been shown that the robustness of the parts and their reliability are mostly due to effective self-healing processes and limited current spiking or minor scintillations caused by RVT do not increase the risk of failures during operation. A simple model for scintillations events has been used to simulate current spiking during RVT and optimize test conditions. The significance of scintillations and possible effects of gas generation have been discussed and test acceptance criteria for limited current spiking have been suggested.

  3. Superconducting properties and uniaxial strain characteristics of Nb3Sn fiber-reinforced superconductors with tantalum reinforcement fibers

    International Nuclear Information System (INIS)

    Arai, Kazuaki; Umeda, Masaichi; Agatsuma, Koh; Tateishi, Hiroshi

    1998-01-01

    We have been developing fiber-reinforced superconductors (FRS) for high-field and large-scale magnets. Tungsten fibers have been selected as the reinforcement fiber for FRS so far because tungsten has the highest elastic modulus of approximately 400 GPa which can minimize the strain from electromagnetic force. The preparation process of FRS consists of sputtering deposition and heat treatment because it may be difficult to apply drawing methods to materials of high-elastic modulus such as tungsten. Tantalum has high elastic modulus of 178 GPa and its thermal expansion coefficient that is closer to that of Nb 3 Sn than tungsten's, which means prestrain in Nb 3 Sn in FRS is reduced by adopting tantalum fibers. Tantalum has been used as barriers between bronze and copper in conventional Nb 3 Sn superconductors which are usually prepared with drawing process despite of the tantalum's high elastic modulus. That implies drawing process may be applied to prepare FRS with tantalum reinforcement fibers. In this paper, FRS using tantalum fibers prepared with sputtering process are described with making comparison with FRS of tungsten to clarify the basic properties of FRS using tantalum fibers. Depth profiles in Nb 3 Sn layer in FRS were measured to examine reaction between superconducting layers and reinforcement fibers. Superconducting properties including strain and stress characteristics were shown. Those data will contribute to design of FRS using tantalum reinforcement fibers with adopts the drawing processes. (author)

  4. Time-resolved diffraction of shock-released SiO2 and diaplectic glass formation

    International Nuclear Information System (INIS)

    Gleason, A. E.; Bolme, C. A.; Lee, H. J.; Nagler, B.

    2017-01-01

    Understanding how rock-forming minerals transform under shock loading is critical for modeling collisions between planetary bodies, interpreting the significance of shock features in minerals and for using them as diagnostic indicators of impact conditions, such as shock pressure. To date, our understanding of the formation processes experienced by shocked materials is based exclusively on ex situ analyses of recovered samples. Formation mechanisms and origins of commonly observed mesoscale material features, such as diaplectic (i.e., shocked) glass, remain therefore controversial and unresolvable. Here in this paper we show in situ pump-probe X-ray diffraction measurements on fused silica crystallizing to stishovite on shock compression and then converting to an amorphous phase on shock release in only 2.4 ns from 33.6 GPa. Recovered glass fragments suggest permanent densification. These observations of real-time diaplectic glass formation attest that it is a back-transformation product of stishovite with implications for revising traditional shock metamorphism stages.

  5. Interaction of single-pulse laser energy with bow shock in hypersonic flow

    Directory of Open Access Journals (Sweden)

    Hong Yanji

    2014-04-01

    Full Text Available Pressure sensing and schlieren imaging with high resolution and sensitivity are applied to the study of the interaction of single-pulse laser energy with bow shock at Mach 5. An Nd:YAG laser operated at 1.06 μm, 100 mJ pulse energy is used to break down the hypersonic flow in a shock tunnel. Three-dimensional Navier–Stokes equations are solved with an upwind scheme to simulate the interaction. The pressure at the stagnation point on the blunt body is measured and calculated to examine the pressure variation during the interaction. Schlieren imaging is used in conjunction with the calculated density gradients to examine the process of the interaction. The results show that the experimental pressure at the stagnation point on the blunt body and schlieren imaging fit well with the simulation. The pressure at the stagnation point on the blunt body will increase when the transmission shock approaches the blunt body and decrease with the formation of the rarefied wave. Bow shock is deformed during the interaction. Quasi-stationary waves are formed by high rate laser energy deposition to control the bow shock. The pressure and temperature at the stagnation point on the blunt body and the wave drag are reduced to 50%, 75% and 81% respectively according to the simulation. Schlieren imaging has provided important information for the investigation of the mechanism of the interaction.

  6. Comparison of the mechanical properties between tantalum and nickel-titanium foams implant materials for bone ingrowth applications

    International Nuclear Information System (INIS)

    Sevilla, P.; Aparicio, C.; Planell, J.A.; Gil, F.J.

    2007-01-01

    Metallic porous materials are designed to allow the ingrowth of living tissue inside the pores and to improve the mechanical anchorage of the implant. In the present work, tantalum and nickel-titanium porous materials have been characterized. The tantalum foams were produced by vapour chemical deposition (CVD/CVI) and the NiTi foams by self-propagating high temperature synthesis (SHS). The former exhibited an open porosity ranging between 65 and 73% and for the latter it ranged between 63 and 68%. The pore sizes were between 370 and 440 μm for tantalum and between 350 and 370 μm for nickel-titanium. The Young's modulus in compression of the foams studied, especially for tantalum, were very similar to those of cancellous bone. This similitude may be relevant in order to minimize the stress shielding effect in the load transfer from the implant to bone. The strength values for NiTi foam are higher than for tantalum, especially of the strain to fracture which is about 23% for NiTi and only 8% for tantalum. The fatigue endurance limit set at 10 8 cycles is about 7.5 MPa for NiTi and 13.2 MPa for tantalum. The failure mechanisms have been studied by scanning electron microscopy

  7. Spectrochemical determination of tantalum in plutonium metal using direct current plasma emission spectrometry

    International Nuclear Information System (INIS)

    Fadeff, S.K.; Morris, W.F.

    1983-01-01

    Tantalum is determined by direct current plasma spectrometry after separation of plutonium from solution as PuF 3 . After centrifugation of the PuF 3 precipitate, a low level of plutonium remains in solution in sufficient quantity to cause spectral interferences. It is necessary to determine the plutonium by dc plasma spectrometry and apply a correction to determine low tantalum concentrations with good accuracy and precision. Tantalum can be determined down to 0.4 ppM in solution with a relative standard deviation of 10 percent. Better precision can be achieved at higher concentrations. The procedure is simple and convenient for glovebox work. 5 references, 1 figure, 1 table

  8. Bone remodeling around cementless tantalum cups

    NARCIS (Netherlands)

    Grillo, J. -C.; Flecher, X.; Bouvenot, J.; Argenson, J. -N.

    2008-01-01

    Purpose of the study.-Most studies have reported a significant decrease in periacetabular bone stock one year after implantation of a cementless cup. The purpose of this work was to study the bone-implant interface of the tantalum cup using plain X-rays and dual-energy X-ray absorptiometry (DEXA).

  9. The recovery of tin, and the production of niobium pentoxide and potassium tantalum fluoride, from a tin slag

    International Nuclear Information System (INIS)

    Iorio, G.; Tyler, M.S.

    1987-01-01

    This report describes the results of testwork on the recovery of tin, niobium, and tantalum from a tin slag. The slag, which consisted mainly of amorphous silica, with varying amounts of calcuim, magnesium, manganese, iron, and aluminium, contained an average of 8,8 per cent niobium pentoxide and 6,2 per cent tantalum pentoxide. The metallic tin-ion phase was removed from the crushed slag by magnetic separation. The slag was then leached with hydrochloric acid to remove magnesium, calcium, aluminium, iron, manganese, and the remainder of the tin. Leaching with sodium hydroxide for the removal of silica and phosphorous was followed by a final leach with hydrochloric acid for the removal of sodium. The upgraded concentrate thus obtained was purified by leaching with hydrofluoric acid, solvent extraction of niobium and tantalum into tri-n-butyl phosphate and methyl isobutyl ketone, and selective stripping of niobium with sulphuric acid and tantalum with ammonium floride. Niobium pentoxide and potassium tantalum fluoride were then precipitated by the addition of ammonium hydroxide and potassium fluoride to the respective strip liquors. The overall recoveries in the upgraded concentrate were 98 per cent for tantalum and 92 per cent for niobium. Dissolutions and recoveries of over 99 per cent were obtained for both tantalum and niobium in the purification steps. The niobium pentoxide and potassium tantalum fluoride precipitates obtained were of high purity

  10. Temperature and strain-rate dependence of the flow stress of ultrapure tantalum single crystals

    International Nuclear Information System (INIS)

    Werner, M.

    1987-01-01

    Measurements of the temperature dependence of the cyclic flow stress of ultrapure tantalum single crystals (RRR >∼ 14000) are extended to lower temperatures. After cyclic deformation well into saturation at 400 K, the temperature dependence of the flow stress is measured between 80 and 450 K at five different plastic resolved shear-strain rates, ε pl , in the range 2 x 10 -5 to 6 x 10 -3 s -1 . Below a critical temperature T k the flow stress is dominantly controlled by the mobility of screw dislocations. A recent theory of Seeger describes the 'thermal' component, σ*, of the flow stress (resolved shear stress) in the temperature and stress regime where the strain rate is determined by the formation and migration of kink pairs. The analytical expressions are valid in well-defined ranges of stress and temperature. The evaluation of the experimental data yields a value for the formation enthalpy of two isolated kinks 2H k = 0.98 eV. From the low-stress (σ* k = 2.0 x 10 -6 m 2 s -1 . The product of the density of mobile screw dislocations and the distance between insurmountable obstacles is found to be 2 x 10 -5 m -1 . The stress dependence of the kink-pair formation enthalpy H kp follows the theoretically predicted curve in the elastic-interaction stress regime. At the transition to the line-tension approximation (near σ* ∼ 80 MPa) the activation volume increases rather abruptly. Moreover, the quantitative analysis involves kinks other than those of minimum height. The most likely candidates are kinks on {211} planes. (author)

  11. Comparison of the thermal shock performance of different tungsten grades and the influence of microstructure on the damage behaviour

    International Nuclear Information System (INIS)

    Wirtz, M; Linke, J; Pintsuk, G; Singheiser, L; Uytdenhouwen, I

    2011-01-01

    The thermal shock performances of two new tungsten grades with 1 and 5 wt% of tantalum were characterized with the electron beam facility JUDITH 1. As a reference material, ultra-high-purity tungsten (W-UHP) with a purity of 99.9999 wt% was used. The induced thermal shock crack networks and surface modifications were analysed by a scanning electron microscope, light microscopy and laser profilometry. Damage and cracking thresholds were defined for all materials as a function of absorbed power density and base temperature. The materials showed significantly different thermal shock behaviour, which is, among others, expressed by differences in cracking patterns, i.e. crack distance and depth. These results allow us to quantify the influence of the materials' mechanical and thermal properties on the thermal shock performance. Furthermore, the specific grain structure of the materials has a significant influence on crack propagation towards the bulk material.

  12. Laser welding of a beryllium/tantalum collimator

    International Nuclear Information System (INIS)

    Lingenfelter, A.C.; Anglin, C.D.

    1985-01-01

    This report describes the methods utilized in the fabrication of a collimator from 0.001 inch thick beryllium and tantalum foil. The laser welding process proved to be an acceptable method for joining the beryllium in a standing edge joint configuration

  13. Intercalated compounds of niobium and tantalum dicalcogenides

    International Nuclear Information System (INIS)

    Wypych, F.

    1988-01-01

    The synthesis of niobium and tantalum lamellar compounds and its intercalated derivatives is described. The intercalated compounds with lithium, with alkaline metal and with metals of the first-row transition are studied, characterized by X-ray diffraction. (C.G.C.) [pt

  14. A preliminary deposit model for lithium-cesium-tantalum (LCT) pegmatites

    Science.gov (United States)

    Bradley, Dwight; McCauley, Andrew

    2013-01-01

    This report is part of an effort by the U.S. Geological Survey to update existing mineral deposit models and to develop new ones. We emphasize practical aspects of pegmatite geology that might directly or indirectly help in exploration for lithium-cesium-tantalum (LCT) pegmatites, or for assessing regions for pegmatite-related mineral resource potential. These deposits are an important link in the world’s supply chain of rare and strategic elements, accounting for about one-third of world lithium production, most of the tantalum, and all of the cesium.

  15. Condensed matter at high shock pressures

    Energy Technology Data Exchange (ETDEWEB)

    Nellis, W.J.; Holmes, N.C.; Mitchell, A.C.; Radousky, H.B.; Hamilton, D.

    1985-07-12

    Experimental techniques are described for shock waves in liquids: Hugoniot equation-of-state, shock temperature and emission spectroscopy, electrical conductivity, and Raman spectroscopy. Experimental data are reviewed and presented in terms of phenomena that occur at high densities and temperatures in shocked He, Ar, N/sub 2/, CO, SiO/sub 2/-aerogel, H/sub 2/O, and C/sub 6/H/sub 6/. The superconducting properties of Nb metal shocked to 100 GPa (1 Mbar) and recovered intact are discussed in terms of prospects for synthesizing novel, metastable materials. Ultrahigh pressure data for Cu is reviewed in the range 0.3 to 6TPa (3 to 60 Mbar). 56 refs., 9 figs., 1 tab.

  16. Multiple spacecraft observations of interplanetary shocks Four spacecraft determination of shock normals

    Science.gov (United States)

    Russell, C. T.; Mellott, M. M.; Smith, E. J.; King, J. H.

    1983-01-01

    ISEE 1, 2, 3, IMP 8, and Prognoz 7 observations of interplanetary shocks in 1978 and 1979 provide five instances where a single shock is observed by four spacecraft. These observations are used to determine best-fit normals for these five shocks. In addition to providing well-documented shocks for future investigations these data allow the evaluation of the accuracy of several shock normal determination techniques. When the angle between upstream and downstream magnetic field is greater than 20 deg, magnetic coplanarity can be an accurate single spacecraft method. However, no technique based solely on the magnetic measurements at one or multiple sites was universally accurate. Thus, the use of overdetermined shock normal solutions, utilizing plasma measurements, separation vectors, and time delays together with magnetic constraints, is recommended whenever possible.

  17. Multiple spacecraft observations of interplanetary shocks: four spacecraft determination of shock normals

    International Nuclear Information System (INIS)

    Russell, C.T.; Mellott, M.M.; Smith, E.J.; King, J.H.

    1983-01-01

    ISEE 1,2,3 IMP8, and Prognoz 7 observations of interplanetary shocks in 1978 and 1979 provide five instances where a single shock is observed by four spacecraft. These observations are used to determine best-fit normals for these five shocks. In addition to providing well-documented shocks for furture techniques. When the angle between upstream and downstream magnetic field is greater than 20, magnetic coplanarity can be an accurate single spacecraft method. However, no technique based solely on the magnetic measurements at one or multiple sites was universally accurate. Thus, we recommend using overdetermined shock normal solutions whenever possible, utilizing plasma measurements, separation vectors, and time delays together with magnetic constraints

  18. Oxidation and Volatilization from Tantalum Alloy T-222 During Air Exposure

    Energy Technology Data Exchange (ETDEWEB)

    Smolik, Galen Richard; Petti, David Andrew; Sharpe, John Phillip; Schuetz, Stanley Thomas

    2000-10-01

    Tantalum alloys are one of the refractory metals with renewed consideration for high temperatures in fusion reactor applications. Tantalum alloys perform well in protective environments but oxidized readily in gases containing higher oxygen levels. In addition, the radioactive isotope Ta-182 would be produced in tantalum and could be a significant contributor to dose if mobilized. Other isotopes of importance are produced from tungsten and hafnium. Mobilization of activated products during an accident with air ingress is therefore a safety issue. In this study, we measured the extent of oxidation and mobilization from tantalum alloy T-222 oxidized in flowing air between 500 and 1200°C. This alloy nominally contains 10 wt% tungsten, 2.5 wt% hafnium and 0.01 wt% carbon. We found that the mobilization of Ta and Hf was closely linked to the occurrence of oxide spalling. These elements showed no migration from the test chamber. Some W was mobilized by volatilization as evidenced by transport from the chamber. Tungsten volatilization could occur primarily during initial stages of oxidation before an oxide scale forms and impedes the process. The mobilization of Ta and W are presented in terms of the mass flux (g/m 2 -h) as a function of test temperature. These measurements along with specific designs, activation calculations, and accident scenarios provide information useful for dose calculations of future fusion devices

  19. Oxidation and Volatilization from Tantalum Alloy T-222 During Air Exposure

    Energy Technology Data Exchange (ETDEWEB)

    Smolik, G.R.; Petti, D.A.; Sharpe, J.P.; Schuetz, S.T.

    2000-10-31

    Tantalum alloys are one of the refractory metals with renewed consideration for high temperatures in fusion reactor applications. Tantalum alloys perform well in protective environments but oxidized readily in gases containing higher oxygen levels. In addition, the radioactive isotope Ta-182 would be produced in tantalum and could be a significant contributor to dose if mobilized. Other isotopes of importance are produced from tungsten and hafnium. Mobilization of activated products during an accident with air ingress is therefore a safety issue. In this study, we measured the extent of oxidation and mobilization from tantalum alloy T-222 oxidized in flowing air between 500 and 1200 C. This alloy nominally contains 10 wt% tungsten, 2.5 wt% hafnium and 0.01 wt% carbon. We found that the mobilization of Ta and Hf was closely linked to the occurrence of oxide spalling. These elements showed no migration from the test chamber. Some W was mobilized by volatilization as evidenced by transport from the chamber. Tungsten volatilization could occur primarily during initial stages of oxidation before an oxide scale forms and impedes the process. The mobilization of Ta and W are presented in terms of the mass flux (g/m 2 -h) as a function of test temperature. These measurements along with specific designs, activation calculations, and accident scenarios provide information useful for dose calculations of future fusion devices.

  20. A Novel Method for Assessment of Polyethylene Liner Wear in Radiopaque Tantalum Acetabular Cups

    DEFF Research Database (Denmark)

    Troelsen, Anders; Greene, Meridith E; Ayers, David C

    2015-01-01

    Conventional radiostereometric analysis (RSA) for wear is not possible in patients with tantalum cups. We propose a novel method for wear analysis in tantalum cups. Wear was assessed by gold standard RSA and the novel method in total hip arthroplasty patients enrolled in a randomized controlled...

  1. Novel Single-Stranded DNA Virus Genomes Recovered from Chimpanzee Feces Sampled from the Mambilla Plateau in Nigeria

    Science.gov (United States)

    Walters, Matthew; Bawuro, Musa; Christopher, Alfred; Knight, Alexander; Kraberger, Simona; Stainton, Daisy; Chapman, Hazel

    2017-01-01

    ABSTRACT Metagenomic approaches are rapidly expanding our knowledge of the diversity of viruses. In the fecal matter of Nigerian chimpanzees we recovered three gokushovirus genomes, one circular replication-associated protein encoding single-stranded DNA virus (CRESS), and a CRESS DNA molecule. PMID:28254982

  2. Catalytic Hydroamination of Alkynes and Norbornene with Neutral and Cationic Tantalum Imido Complexes

    Science.gov (United States)

    Anderson, Laura L.; Arnold, John; Bergman, Robert G.

    2005-01-01

    Several tantalum imido complexes have been synthesized and shown to efficiently catalyze the hydroamination of internal and terminal alkynes. An unusual hydroamination/hydroarylation reaction of norbornene catalyzed by a highly electrophilic cationic tantalum imido complex is also reported. Factors affecting catalyst activity and selectivity are discussed along with mechanistic insights gained from stoichiometric reactions. PMID:15255680

  3. Swelling and tensile properties of EBR-II-irradiated tantalum alloys for space reactor applications

    International Nuclear Information System (INIS)

    Grossbeck, M.L.; Wiffen, F.W.

    1985-01-01

    The tantalum alloys T-111, ASTAR-811C, Ta-10 W, and unalloyed tantalum were examined following EBR-II irradiation to a fluence of 1.7 x 10 26 neutrons/m 2 (E > 0.1 MeV) at temperatures from 650 to 950 K. Swelling was found to be negligible for all alloys; only tantalum was found to exhibit swelling, 0.36%. Tensile testing revealed that irradiated T-111 and Ta-10 W are susceptible to plastic instability, but ASTAR-811C and tantalum were not. The tensile properties of ASTAR-811C appeared adequate for current SP-100 space nuclear reactor designs. Irradiated, oxygen-doped T-111 exhibited no plastic deformation, and the abrupt failure was intergranular in nature. The absence of plastic instability in ASTAR-811C is encouraging for alloys containing carbide precipitates. These fine precipitates might prevent dislocation channeling, which leads to plastic instability in many bcc metals after irradiation. 10 refs., 13 figs., 8 tabs

  4. The pretective effects of heat shock protein 70 on radiation injury of V79 cells

    International Nuclear Information System (INIS)

    Qin Yongchun; Zhang Baoguo; Hong Chengjiao

    2008-01-01

    Westem blot was used to detect the expression of heat shock protein 70 in V79 cells after heat shock pretreatment; V79 cells were irradiated using γ-ray after heat shock pretreatment, survival rate was observed using Colony formation assay. Our study shows that 1) the overexpression of heat shock protein 70 was observed in cells recovering for 1 hour after heat shock pretreatment, with peak expression in cells recovering for 4 hours, and could last for 24 hours; 2) heat shock pretreatment was able to elevate survival rate of V79 cells after irradiation by 60 Co γ ray (when the irradiation dose was less than 6 Gy). The results indicate that heat shock protein 70 has protective effect on radiation induced cell death of V79 cells (when the irradiation dose was less than 6 Gy). (authors)

  5. Sputter deposition of tantalum-nitride films on copper using an rf-plasma

    International Nuclear Information System (INIS)

    Walter, K.C.; Fetherston, R.P.; Sridharan, K.; Chen, A.; Shamim, M.M.; Conrad, J.R.

    1994-01-01

    A tantalum-nitride film was successfully deposited at ambient temperature on copper with a modified ion-assisted-deposition (IAD) technique. The process uses an argon and nitrogen plasma to sputter deposit from a tantalum rf-cathode and ion implant the deposited film simultaneously. Both argon and nitrogen ions are used for sputtering and ion implantation. Auger spectroscopy and x-ray diffraction were used to characterize the resulting film

  6. Review of tantalum and niobium alloy production

    International Nuclear Information System (INIS)

    Buckman, R.W. Jr.

    1984-01-01

    This paper concentrates on the current state of niobium- and tantalum-base alloy production. The materials requirements, alloy compositions of interest, and production status are discussed. Finally, a list of developments needed to support the SP-100 program will be identified. A bibliography is included

  7. Clindamycin-induced Anaphylactic Shock During General Anesthesia

    OpenAIRE

    Chiuan-Shiou Chiou; Su-Man Lin; Shih-Pin Lin; Wen-Guei Chang; Kwok-Hon Chan; Chien-Kun Ting

    2006-01-01

    Clindamycin-related anaphylactic reaction is rarely reported. We report a male patient with buccal cancer who was undergoing radical neck dissection when life-threatening anaphylactic shock developed soon after intravenous infusion of clin-damycin. Immediate cardiopulmonary resuscitation was performed, and the patient recovered uneventfully. Perioperative anaphylactic shock is a serious problem due to the difficulty of judgment and potentially disastrous outcome. Immediate diagnosis and halti...

  8. Design of a Facility for Studying Shock-Cell Noise on Single and Coaxial Jets

    Directory of Open Access Journals (Sweden)

    Daniel Guariglia

    2018-03-01

    Full Text Available Shock-cell noise occurs in aero-engines when the nozzle exhaust is supersonic and shock-cells are present in the jet. In commercial turbofan engines, at cruise, the secondary flow is often supersonic underexpanded, with the formation of annular shock-cells in the jet and consequent onset of shock-cell noise. This paper aims at describing the design process of the new facility FAST (Free jet AeroacouSTic laboratory at the von Karman Institute, aimed at the investigation of the shock-cell noise phenomenon on a dual stream jet. The rig consists of a coaxial open jet, with supersonic capability for both the primary and secondary flow. A coaxial silencer was designed to suppress the spurious noise coming from the feeding lines. Computational fluid dynamics (CFD simulations of the coaxial jet and acoustic simulations of the silencer have been carried out to support the design choices. Finally, the rig has been validated by performing experimental measurements on a supersonic single stream jet and comparing the results with the literature. Fine-scale PIV (Particle Image Velocimetry coupled with a microphone array in the far field have been used in this scope. Preliminary results of the dual stream jet are also shown.

  9. Change in lattice parameter of tantalum due to dissolved hydrogen

    Directory of Open Access Journals (Sweden)

    Gyanendra P. Tiwari

    2012-06-01

    Full Text Available The volume expansion of tantalum due to the dissolved hydrogen has been determined using Bragg equation. The hydrogen was dissolved in the pure tantalum metal at constant temperature (360 °C and constant pressure (132 mbar by varying the duration of hydrogen charging. The amount of dissolved hydrogen was within the solid solubility limit. The samples with different hydrogen concentration were analyzed by X-ray diffraction technique. Slight peak shifts as well as peak broadening were observed. The relative changes of lattice parameters plotted against the hydrogen concentration revealed that the lattice parameters varied linearly with the hydrogen concentration.

  10. [Short-term curative effects of Tantalum rod treatment in early avascular necrosis].

    Science.gov (United States)

    Ye, Fu-Sheng; Ni, Zhe-Ji; Chu, Xiao-Bing; He, Bang-Jian; Li, Ju; Tong, Pei-Jian

    2013-08-01

    To explore the recent clinical curative effect of Tantalum rod in treating the early avascular necrosis. From January 2008 to November 2008, the 25 patients (39 hips) with early avascular necrosis accepted tantalum rod placement and included 9 males (11 hips) and 16 females (28 hips) with an average age of 37 years old ranging from 18 to 74 years old. Four patients (6 hips) caused by Alcoholic, 6 patients (8 hips) by hormone, 2 cases (2 hips) by traumatic, 13 cases (23 hips) by idiopathic. Steinberg preoperative stage involved 7 hips in period I, 24 hips in period II, 8 hips in period III. Curative effect analysis included preoperative and postoperative Harris score, radiographic changes and hip replacement for follow-up to accept the end of the femoral head survival rate. All patients were followed up for 6 to 47 months (averaged 37.4 months). All 12 hips imaging appeard progress,including tantalum rod exit in 1 hip, hip hemiarthroplasty collapse in 3 hips, the area increased to avascular necrosis in 8 hips. Six hips accepted total hip replacement, including imaging progress in 5 hips (41.7%, 5/12), no imaging progress in 1 hip (3.7%,1/27). All hips' Kaplan-Meier survival curves showed 6-month survival rate was (97.4 +/- 2.5)% after tantalum stick insertion, 1-year survival rate was (94.7 +/- 3.6), and 2-year survival rate was (88.6 +/- 5.4)%, 3-year survival rate was (72.5 +/- 11.2). It is effective for treatment of avascular necrosis of femoral head in Steinberg I and II by Tantalum rod, and it can effectively relieve femoral head replacement time.

  11. The effects of argon ion bombardment on the corrosion resistance of tantalum

    Science.gov (United States)

    Ramezani, A. H.; Sari, A. H.; Shokouhy, A.

    2017-02-01

    Application of ion beam has been widely used as a surface modification method to improve surface properties. This paper investigates the effect of argon ion implantation on surface structure as well as resistance against tantalum corrosion. In this experiment, argon ions with energy of 30 keV and in doses of 1 × 1017-10 × 1017 ions/cm2 were used. The surface bombardment with inert gases mainly produces modified topography and morphology of the surface. Atomic Force Microscopy was also used to patterned the roughness variations prior to and after the implantation phase. Additionally, the corrosion investigation apparatus wear was applied to compare resistance against tantalum corrosion both before and after ion implantation. The results show that argon ion implantation has a substantial impact on increasing resistance against tantalum corrosion. After the corrosion test, scanning electron microscopy (SEM) analyzed the samples' surface morphologies. In addition, the elemental composition is characterized by energy-dispersive X-ray (EDX) analysis. The purpose of this paper was to obtain the perfect condition for the formation of tantalum corrosion resistance. In order to evaluate the effect of the ion implantation on the corrosion behavior, potentiodynamic tests were performed. The results show that the corrosion resistance of the samples strongly depends on the implantation doses.

  12. An exploration in mineral supply chain mapping using tantalum as an example

    Science.gov (United States)

    Soto-Viruet, Yadira; Menzie, W. David; Papp, John F.; Yager, Thomas R.

    2013-01-01

    This report uses the supply chain of tantalum (Ta) to investigate the complexity of mineral and metal supply chains in general and show how they can be mapped. A supply chain is made up of all the manufacturers, suppliers, information networks, and so forth, that provide the materials and parts that go into making up a final product. The mineral portion of the supply chain begins with mineral material in the ground (the ore deposit); extends through a series of processes that include mining, beneficiation, processing (smelting and refining), semimanufacture, and manufacture; and continues through transformation of the mineral ore into concentrates, refined mineral commodities, intermediate forms (such as metals and alloys), component parts, and, finally, complex products. This study analyses the supply chain of tantalum beginning with minerals in the ground to many of the final goods that contain tantalum.

  13. Assembly of tantalum porous films with graded oxidation profile from size-selected nanoparticles

    Science.gov (United States)

    Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Cassidy, Cathal; Benelmekki, Maria; Bohra, Murtaza; Hawash, Zafer; Baughman, Kenneth W.; Sowwan, Mukhles

    2014-05-01

    Functionally graded materials offer a way to improve the physical and chemical properties of thin films and coatings for different applications in the nanotechnology and biomedical fields. In this work, design and assembly of nanoporous tantalum films with a graded oxidation profile perpendicular to the substrate surface are reported. These nanoporous films are composed of size-selected, amorphous tantalum nanoparticles, deposited using a gas-aggregated magnetron sputtering system, and oxidized after coalescence, as samples evolve from mono- to multi-layered structures. Molecular dynamics computer simulations shed light on atomistic mechanisms of nanoparticle coalescence, which govern the films porosity. Aberration-corrected (S) TEM, GIXRD, AFM, SEM, and XPS were employed to study the morphology, phase and oxidation profiles of the tantalum nanoparticles, and the resultant films.

  14. Unrecoverable bi-products of drilling titanium alloy and tantalum metal implants: a pilot study.

    Science.gov (United States)

    Skowronek, Paweł; Olszewski, Paweł; Święszkowski, Wojciech; Synder, Marek; Sibiński, Marcin; Mazek, Jacek

    2018-05-01

    Trabecular metal implants with a porous architecture that allows for the incorporation of bone into the implant during healing are gaining popularity in alloplastic revision procedures. The bi-products of drilling titanium alloy (Ti) and tantalum (Ta) implants have not been previously assessed. Four holes were drilled in each of two spatially porous trabecular implants, one Ta and the other Ti alloy (Ti-6Al-7Nb), for this pilot in vitro study. The particles were flushed out with a continuous flow of saline. The particles' weight and the volume were then measured using a Radwag XA 110/2X (USA) laboratory balance. The total volume of the obtained metal fines was measured by titration using a 10 mm 3 measurement system. A cobalt carbide bit was used since the holes could not be made with a standard bone drill. Each Ti and Ta implant lost 1.26 g and 2.48 g of mass, respectively. The volume of free particles recovered after each stage was 280 mm 3 and 149 mm 3 , respectively. Approximately 0.6% of the total implant mass was not recovered after drilling (roughly 2% of the mass of the particles created by drilling), despite the use of 5 µm filters. It is technically difficult to drill holes in Ti and Ta implants using standard surgical tools. The drilling process creates a considerable amount of metal particles, which cannot be recovered despite intensive flushing. This may have an adverse influence on the bio-functionality (survival) of the endoprosthesis and present deleterious systemic consequences.

  15. Shock-induced devolatilization of calcite

    Science.gov (United States)

    Boslough, M. B.; Ahrens, T. J.; Vizgirda, J.; Becker, R. H.; Epstein, S.

    1982-01-01

    Experimental measurements of the release adiabats by Vizgirda (1981) indicate that substantial vaporization takes place upon release from shock pressures of 37 GPa for calcite and 14 GPa for aragonite. The present investigation includes the first controlled partial vaporization experiments on calcite. The experiments were conducted to test the predictions of the release adiabat experiments. The quantities of the gaseous species produced from shocked calcite and their carbon and oxygen isotopic compositions were determined, and the shock-induced effect on the Mn(2+) electron spin resonance spectrum in the shock-recovered calcite was observed. On the basis of the obtained results, it is concluded that shock stresses at the 17-18 GPa level give rise to volatilization of 0.03-0.3 (mole) percent of calcite to CO2 and CO. The devolatilization of calcite occurs at low pressure at significantly lower entropy densities than predicted on the basis of thermodynamic continuum models.

  16. A theoretical framework for understanding recovered memory experiences.

    Science.gov (United States)

    Brewin, Chris R

    2012-01-01

    If recovered memory experiences appear counter-intuitive, this is in part due to misconceptions about trauma and memory, and to a failure to adopt a comprehensive model of memory that distinguishes personal semantic memory, autobiographical event memory, and memory appraisal. Memory performance is generally superior when events, including traumas, are central to identity. Prolonged trauma in childhood, however, can produce severe identity disturbances that may interfere with the encoding and later retrieval of personal semantic and autobiographical event information. High levels of emotion either at encoding or recall can also interfere with the creation of coherent narrative memories. For example, high levels of shock and fear when memories are recovered unexpectedly may lead to the experience of vivid flashbacks. Memory appraisals may also influence the sense that an event has been forgotten for a long time. Recovered memories, although unusual, do not contradict what we know about how memory works.

  17. Orientation Dependence in Molecular Dynamics Simulations of Shocked Single Crystals

    International Nuclear Information System (INIS)

    Germann, Timothy C.; Holian, Brad Lee; Lomdahl, Peter S.; Ravelo, Ramon

    2000-01-01

    We use multimillion-atom molecular dynamics simulations to study shock wave propagation in fcc crystals. As shown recently, shock waves along the direction form intersecting stacking faults by slippage along {111} close-packed planes at sufficiently high shock strengths. We find even more interesting behavior of shocks propagating in other low-index directions: for the case, an elastic precursor separates the shock front from the slipped (plastic) region. Shock waves along the direction generate a leading solitary wave train, followed (at sufficiently high shock speeds) by an elastic precursor, and then a region of complex plastic deformation. (c) 2000 The American Physical Society

  18. New Sesame equation of state for tantalum

    International Nuclear Information System (INIS)

    Greeff, C. W.; Johnson, J. D.

    2000-01-01

    A new Sesame equation of state (EOS) table has been created for tantalum. This EOS incorporates new high pressure Hugoniot data and diamond anvil cell compression data. The new EOS gives better agreement with this data as well as with sound speeds and Hugoniot curves of porous samples

  19. Cast and hipped gamma titanium aluminum alloys modified by chromium, boron, and tantalum

    International Nuclear Information System (INIS)

    Huang, Shyhchin.

    1993-01-01

    A cast body is described of a chromium, boron, and tantalum modified titanium aluminum alloy, said alloy consisting essentially of titanium, aluminum, chromium, boron, and tantalum in the following approximate atomic ratio: Ti-Al 45-50 Cr 1-3 Ta 1-8 B 0.1-0.3 , and said alloy having been prepared by casting the alloy to form said cast body and by HIPping said body

  20. Tantalum-based multilayer coating on cobalt alloys in total hip and knee replacement

    Energy Technology Data Exchange (ETDEWEB)

    Balagna, C., E-mail: cristina.balagna@polito.it [Institute of Materials Engineering and Physics, Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24,10129 Torino (Italy); Faga, M.G. [Istituto di Scienza e Tecnologia dei Materiali Ceramici, Consiglio Nazionale delle Ricerche, Strada delle Cacce 73, 10135 Torino (Italy); Spriano, S. [Institute of Materials Engineering and Physics, Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24,10129 Torino (Italy)

    2012-05-01

    Cobalt-chromium-molybdenum (CoCrMo) alloys are widely used in total hip and knee joint replacement, due to high mechanical properties and resistance to wear and corrosion. They are able to form efficient artificial joints by means of coupling metal-on-polymer or metal-on-metal contacts. However, a high concentration of stress and direct friction between surfaces leads to the formation of polyethylene wear debris and the release of toxic metal ions into the human body, limiting, as a consequence, the lifetime of implants. The aim of this research is a surface modification of CoCrMo alloys in order to improve their biocompatibility and to decrease the release of metal ions and polyethylene debris. Thermal treatment in molten salts was the process employed for the deposition of tantalum-enriched coating. Tantalum and its compounds are considered biocompatible materials with low ion release and high corrosion resistance. Three different CoCrMo alloys were processed as substrates. An adherent coating of about 1 {mu}m of thickness, with a multilayer structure consisting of two tantalum carbides and metallic tantalum was deposited. The substrates and modified layers were characterized by means of structural, chemical and morphological analysis. Moreover nanoindentation, scratch and tribological tests were carried out in order to evaluate the mechanical behavior of the substrates and coating. The hardness of the coated samples increases more than double than the untreated alloys meanwhile the presence of the coating reduced the wear volume and rate of about one order of magnitude. - Highlights: Black-Right-Pointing-Pointer Thermal treatment in molten salts deposits a Ta-based coating on Co-based alloys. Black-Right-Pointing-Pointer Coating is composed by one or two tantalum carbides and/or metallic tantalum. Black-Right-Pointing-Pointer The coating structure depends on thermal temperature and substrates carbon content. Black-Right-Pointing-Pointer Coating is able to

  1. Poisoning Experiments Aimed at Discriminating Active and Less-Active Sites of Silica-Supported Tantalum Hydride for Alkane Metathesis

    KAUST Repository

    Saggio, Guillaume

    2010-10-04

    Only 50% of the silica-supported tantalum hydride sites are active in the metathesis of propane. Indeed, more than 45% of the tantalum hydride can be eliminated by a selective oxygen poisoning of inactive sites with no significant decrease in the global turnover. Conversely, cyclopentane induces no such selective poisoning. Hence, the active tantalum hydride sites that show greater resistance to oxygen poisoning correspond to the νTa-H bands of higher wavenumbers, particularly that at 1860cm-1. These active tantalum hydride sites should correspond to tris- or monohydride species relatively far from silica surface oxygen atoms. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Tantalum-containing Z-phase in 12%Cr martensitic steels

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson; Hald, John

    2009-01-01

    Z-phases in tantalum-containing 12%Cr steels have been investigated. In 12%Cr steel without any Nb or V, the formation of CrTaN Z-phases was observed. In 12%Cr steel which also contained V, the Ta entered Z-phase as a minor element, Cr(V,Ta)N. The crystal structure of Cr(V,Ta)N seems to be identi......Z-phases in tantalum-containing 12%Cr steels have been investigated. In 12%Cr steel without any Nb or V, the formation of CrTaN Z-phases was observed. In 12%Cr steel which also contained V, the Ta entered Z-phase as a minor element, Cr(V,Ta)N. The crystal structure of Cr(V,Ta)N seems...

  3. Evaluation of corrosion behaviour of tantalum coating obtained by low pressure chemical vapor deposition using electrochemical polarization

    Science.gov (United States)

    Levesque, A.; Bouteville, A.; de Baynast, H.; Laveissière, B.

    2002-06-01

    antalum coatings are elaborated on titanium substrates through Low Pressure Chemical Vapor Deposition from tantalum pentachloride-hydrogen gaseous phase at a deposition temperature of 800 °C and a total pressure of 3.3 mbar. The aim of this paper is to evaluate the effectiveness of this tantalum coating in corrosive solution. Optical Microscopy and Scanning Electron Microscopy observations reveal that deposits are of 1.7 μm in thickness and conformal. The corrosion resistance of tantalum coated titanium substrates is quantified through standard potentiodynamic polarization method. Even for tantalum coatings exhibiting some defects as pores, the corrosion current density is as low as 0.25 mA/cm^2.in very agressive solutions like kroll reagent (HN03/HF).

  4. Effect of Reverse Bias Stress on Leakage Currents and Breakdown Voltages of Solid Tantalum Capacitors

    Science.gov (United States)

    Teverovsky, Alexander A.

    2011-01-01

    The majority of solid tantalum capacitors are produced by high-temperature sintering of a fine tantalum powder around a tantalum wire followed by electrolytic anodization that forms a thin amorphous Ta2O5 dielectric layer and pyrolysis of manganese nitrite on the oxide to create a conductive manganese dioxide electrode. A contact to tantalum wire is used as anode terminal and to the manganese layer as a cathode terminal of the device. This process results in formation of an asymmetric Ta -- Ta2O5 -- MnO2 capacitor that has different characteristics at forward (positive bias applied to tantalum) and reverse (positive bias applied to manganese cathode) voltages. Reverse bias currents might be several orders of magnitude larger than forward leakage currents so I-V characteristics of tantalum capacitors resemble characteristics of semiconductor rectifiers. Asymmetric I-V characteristics of Ta -- anodic Ta2O5 systems have been observed at different top electrode materials including metals, electrolytes, conductive polymers, and manganese oxide thus indicating that this phenomenon is likely related to the specifics of the Ta -- Ta2O5 interface. There have been multiple attempts to explain rectifying characteristics of capacitors employing anodic tantalum pentoxide dielectrics. A brief review of works related to reverse bias (RB) behavior of tantalum capacitors shows that the mechanism of conduction in Ta -- Ta2O5 systems is still not clear and more testing and analysis is necessary to understand the processes involved. If tantalum capacitors behave just as rectifiers, then the assessment of the safe reverse bias operating conditions would be a relatively simple task. Unfortunately, these parts can degrade with time under reverse bias significantly, and this further complicates analysis of the I-V characteristics and establishing safe operating areas of the parts. On other hand, time dependence of reverse currents might provide additional information for investigation of

  5. Clustering of transmutation elements tantalum, rhenium and osmium in tungsten in a fusion environment

    Science.gov (United States)

    You, Yu-Wei; Kong, Xiang-Shan; Wu, Xuebang; Liu, C. S.; Fang, Q. F.; Chen, J. L.; Luo, G.-N.

    2017-08-01

    The formation of transmutation solute-rich precipitates has been reported to seriously degrade the mechanical properties of tungsten in a fusion environment. However, the underlying mechanisms controlling the formation of the precipitates are still unknown. In this study, first-principles calculations are therefore performed to systemically determine the stable structures and binding energies of solute clusters in tungsten consisting of tantalum, rhenium and osmium atoms as well as irradiation-induced vacancies. These clusters are known to act as precursors for the formation of precipitates. We find that osmium can easily segregate to form clusters even in defect-free tungsten alloys, whereas extremely high tantalum and rhenium concentrations are required for the formation of clusters. Vacancies greatly facilitate the clustering of rhenium and osmium, while tantalum is an exception. The binding energies of vacancy-osmium clusters are found to be much higher than those of vacancy-tantalum and vacancy-rhenium clusters. Osmium is observed to strongly promote the formation of vacancy-rhenium clusters, while tantalum can suppress the formation of vacancy-rhenium and vacancy-osmium clusters. The local strain and electronic structure are analyzed to reveal the underlying mechanisms governing the cluster formation. Employing the law of mass action, we predict the evolution of the relative concentration of vacancy-rhenium clusters. This work presents a microscopic picture describing the nucleation and growth of solute clusters in tungsten alloys in a fusion reactor environment, and thereby explains recent experimental phenomena.

  6. Silicon transport in sputter-deposited tantalum layers grown under ion bombardment

    International Nuclear Information System (INIS)

    Gallais, P.; Hantzpergue, J.J.; Remy, J.C.; Roptin, D.

    1988-01-01

    Tantalum was sputter deposited on (111) Si substrate under low-energy ion bombardment in order to study the effects of the ion energy on the silicon transport into the Ta layer. The Si substrate was heated up to 500 0 C during growth. For ion energies up to 180 eV silicon is not transported into tantalum and the growth temperature has no effect. An ion bombardment energy of 280 eV enhances the transport of silicon throughout the tantalum layer. Growth temperatures up to 300 0 C have no effect on the silicon transport which is mainly enhanced by the ion bombardment. For growth temperatures between 300 and 500 0 C, the silicon transport is also enhanced by the thermal diffusion. The experimental depth distribution of silicon is similar to the theoretical depth distribution calculated for the case of an interdiffusion. The ion-enhanced process of silicon transport is characterized by an activation energy of 0.4 eV. Silicon into the layers as-grown at 500 0 C is in both states, amorphous silicide and microcrystalline cubic silicon

  7. Clindamycin-induced anaphylactic shock during general anesthesia.

    Science.gov (United States)

    Chiou, Chiuan-Shiou; Lin, Su-Man; Lin, Shih-Pin; Chang, Wen-Guei; Chan, Kwok-Hon; Ting, Chien-Kun

    2006-11-01

    Clindamycin-related anaphylactic reaction is rarely reported. We report a male patient with buccal cancer who was undergoing radical neck dissection when life-threatening anaphylactic shock developed soon after intravenous infusion of clindamycin. Immediate cardiopulmonary resuscitation was performed, and the patient recovered uneventfully. Perioperative anaphylactic shock is a serious problem due to the difficulty of judgment and potentially disastrous outcome. Immediate diagnosis and halting of drug infusion should be the first actions taken.

  8. Obtainment of tantalum oxide from national ores

    International Nuclear Information System (INIS)

    Pinatti, D.G.; Ribeiro, S.; Martins, A.H.

    1988-01-01

    The experimental results of tantalum oxides (Ta 2 O 5 ) obtainment from Brazilian ores of tantalite and columbite are described. This study is a part of the technologic and scientific research design of refractory metals (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W) and correlate ceramics. (C.G.C.) [pt

  9. Tantalum coating of porous carbon scaffold supplemented with autologous bone marrow stromal stem cells for bone regeneration in vitro and in vivo.

    Science.gov (United States)

    Wei, Xiaowei; Zhao, Dewei; Wang, Benjie; Wang, Wei; Kang, Kai; Xie, Hui; Liu, Baoyi; Zhang, Xiuzhi; Zhang, Jinsong; Yang, Zhenming

    2016-03-01

    Porous tantalum metal with low elastic modulus is similar to cancellous bone. Reticulated vitreous carbon (RVC) can provide three-dimensional pore structure and serves as the ideal scaffold of tantalum coating. In this study, the biocompatibility of domestic porous tantalum was first successfully tested with bone marrow stromal stem cells (BMSCs) in vitro and for bone tissue repair in vivo. We evaluated cytotoxicity of RVC scaffold and tantalum coating using BMSCs. The morphology, adhesion, and proliferation of BMSCs were observed via laser scanning confocal microscope and scanning electron microscopy. In addition, porous tantalum rods with or without autologous BMSCs were implanted on hind legs in dogs, respectively. The osteogenic potential was observed by hard tissue slice examination. At three weeks and six weeks following implantation, new osteoblasts and new bone were observed at the tantalum-host bone interface and pores. At 12 weeks postporous tantalum with autologous BMSCs implantation, regenerated trabecular equivalent to mature bone was found in the pore of tantalum rods. Our results suggested that domestic porous tantalum had excellent biocompatibility and could promote new bone formation in vivo. Meanwhile, the osteogenesis of porous tantalum associated with autologous BMSCs was more excellent than only tantalum implantation. Future clinical studies are warranted to verify the clinical efficacy of combined implantation of this domestic porous tantalum associated with autologous BMSCs implantation and compare their efficacy with conventional autologous bone grafting carrying blood vessel in patients needing bone repairing. © 2016 by the Society for Experimental Biology and Medicine.

  10. The effect of hydrostatic vs. shock pressure treatment on plant seeds

    Science.gov (United States)

    Mustey, Adrian; Leighs, James; Appleby-Thomas, Gareth; Wood, David; Hazael, Rachael; McMillan, Paul; Hazell, Paul

    2013-06-01

    The hydrostatic pressure and shock response of plant seeds have both been previously investigated (primarily driven by an interest in reducing bacterial contamination of crops and the theory of panspermia respectively). However, comparisons have not previously been made between these two methods of applying pressure to plant seeds. Here such a comparison has been undertaken based on the premise that any correlations in such data may provide a route to inform understanding of damage mechanisms in the seeds under test. In this work two varieties of plant seeds were subjected to hydrostatic pressure via a non-end-loaded piston cylinder set-up and shock compression via employment of a 50-mm bore, single stage gas gun using the flyer-plate technique. Results from germination tests of recovered seed samples have been compared and contrasted, and initial conclusions made regarding causes of trends in the resultant data-set.

  11. Porous tantalum coatings prepared by vacuum plasma spraying enhance bmscs osteogenic differentiation and bone regeneration in vitro and in vivo.

    Directory of Open Access Journals (Sweden)

    Ze Tang

    Full Text Available Tantalum, as a potential metallic implant biomaterial, is attracting more and more attention because of its excellent anticorrosion and biocompatibility. However, its significantly high elastic modulus and large mechanical incompatibility with bone tissue make it unsuitable for load-bearing implants. In this study, porous tantalum coatings were first successfully fabricated on titanium substrates by vacuum plasma spraying (VPS, which would exert the excellent biocompatibility of tantalum and alleviate the elastic modulus of tantalum for bone tissue. We evaluated cytocompatibility and osteogenesis activity of the porous tantalum coatings using human bone marrow stromal cells (hBMSCs and its ability to repair rabbit femur bone defects. The morphology and actin cytoskeletons of hBMSCs were observed via electron microscopy and confocal, and the cell viability, proliferation and osteogenic differentiation potential of hBMSCs were examined quantitatively by PrestoBlue assay, Ki67 immunofluorescence assay, real-time PCR technology and ALP staining. For in vivo detection, the repaired femur were evaluated by histomorphology and double fluorescence labeling 3 months postoperation. Porous tantalum coating surfaces promoted hBMSCs adhesion, proliferation, osteogenesis activity and had better osseointegration and faster new bone formation rate than titanium coating control. Our observation suggested that the porous tantalum coatings had good biocompatibility and could enhance osseoinductivity in vitro and promote new bone formation in vivo. The porous tantalum coatings prepared by VPS is a promising strategy for bone regeneration.

  12. Shock compression of synthetic opal

    International Nuclear Information System (INIS)

    Inoue, A; Okuno, M; Okudera, H; Mashimo, T; Omurzak, E; Katayama, S; Koyano, M

    2010-01-01

    Structural change of synthetic opal by shock-wave compression up to 38.1 GPa has been investigated by using SEM, X-ray diffraction method (XRD), Infrared (IR) and Raman spectroscopies. Obtained information may indicate that the dehydration and polymerization of surface silanole due to high shock and residual temperature are very important factors in the structural evolution of synthetic opal by shock compression. Synthetic opal loses opalescence by 10.9 and 18.4 GPa of shock pressures. At 18.4 GPa, dehydration and polymerization of surface silanole and transformation of network structure may occur simultaneously. The 4-membered ring of TO 4 tetrahedrons in as synthetic opal may be relaxed to larger ring such as 6-membered ring by high residual temperature. Therefore, the residual temperature may be significantly high at even 18.4 GPa of shock compression. At 23.9 GPa, opal sample recovered the opalescence. Origin of this opalescence may be its layer structure by shock compression. Finally, sample fuse by very high residual temperature at 38.1 GPa and the structure closes to that of fused SiO 2 glass. However, internal silanole groups still remain even at 38.1 GPa.

  13. Shock compression of synthetic opal

    Science.gov (United States)

    Inoue, A.; Okuno, M.; Okudera, H.; Mashimo, T.; Omurzak, E.; Katayama, S.; Koyano, M.

    2010-03-01

    Structural change of synthetic opal by shock-wave compression up to 38.1 GPa has been investigated by using SEM, X-ray diffraction method (XRD), Infrared (IR) and Raman spectroscopies. Obtained information may indicate that the dehydration and polymerization of surface silanole due to high shock and residual temperature are very important factors in the structural evolution of synthetic opal by shock compression. Synthetic opal loses opalescence by 10.9 and 18.4 GPa of shock pressures. At 18.4 GPa, dehydration and polymerization of surface silanole and transformation of network structure may occur simultaneously. The 4-membered ring of TO4 tetrahedrons in as synthetic opal may be relaxed to larger ring such as 6-membered ring by high residual temperature. Therefore, the residual temperature may be significantly high at even 18.4 GPa of shock compression. At 23.9 GPa, opal sample recovered the opalescence. Origin of this opalescence may be its layer structure by shock compression. Finally, sample fuse by very high residual temperature at 38.1 GPa and the structure closes to that of fused SiO2 glass. However, internal silanole groups still remain even at 38.1 GPa.

  14. Shock compression of synthetic opal

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, A; Okuno, M; Okudera, H [Department of Earth Sciences, Kanazawa University Kanazawa, Ishikawa, 920-1192 (Japan); Mashimo, T; Omurzak, E [Shock Wave and Condensed Matter Research Center, Kumamoto University, Kumamoto, 860-8555 (Japan); Katayama, S; Koyano, M, E-mail: okuno@kenroku.kanazawa-u.ac.j [JAIST, Nomi, Ishikawa, 923-1297 (Japan)

    2010-03-01

    Structural change of synthetic opal by shock-wave compression up to 38.1 GPa has been investigated by using SEM, X-ray diffraction method (XRD), Infrared (IR) and Raman spectroscopies. Obtained information may indicate that the dehydration and polymerization of surface silanole due to high shock and residual temperature are very important factors in the structural evolution of synthetic opal by shock compression. Synthetic opal loses opalescence by 10.9 and 18.4 GPa of shock pressures. At 18.4 GPa, dehydration and polymerization of surface silanole and transformation of network structure may occur simultaneously. The 4-membered ring of TO{sub 4} tetrahedrons in as synthetic opal may be relaxed to larger ring such as 6-membered ring by high residual temperature. Therefore, the residual temperature may be significantly high at even 18.4 GPa of shock compression. At 23.9 GPa, opal sample recovered the opalescence. Origin of this opalescence may be its layer structure by shock compression. Finally, sample fuse by very high residual temperature at 38.1 GPa and the structure closes to that of fused SiO{sub 2} glass. However, internal silanole groups still remain even at 38.1 GPa.

  15. Antimicrobial activity of tantalum oxide coatings decorated with Ag nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Huiliang, E-mail: hlc@mail.sic.ac.cn; Meng, Fanhao; Liu, Xuanyong, E-mail: xyliu@mail.sic.ac.cn [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

    2016-07-15

    Silver plasma immersion ion implantation was used to decorate silver nanoparticles (Ag NPs) on tantalum oxide (TO) coatings. The coatings acted against bacterial cells (Staphylococcus epidermidis) in the dark by disrupting their integrity. The action was independent of silver release and likely driven by the electron storage capability of the Schottky barriers established at the interfaces between Ag NPs and the TO support. Moreover, no apparent side effect on the adhesion and differentiation of rat bone mesenchymal stem cells was detected when using Ag NPs-modified TO coatings. These results demonstrate that decoration of tantalum oxide using Ag NPs could be a promising procedure for improving the antibacterial properties for orthopedic and dental implants.

  16. Shock diffraction in alumina powder

    International Nuclear Information System (INIS)

    Venz, G.; Killen, P.D.; Page, N.W.

    1996-01-01

    In order to produce complex shaped components by dynamic compaction of ceramic powders detailed knowledge of their response under shock loading conditions is required. This work attempts to provide data on release effects and shock attenuation in 1 μm and 5 μm α-alumina powders which were compacted to between 85 % and 95 % of the solid phase density by the impact of high velocity steel projectiles. As in previous work, the powder was loaded into large cylindrical dies with horizontal marker layers of a contrasting coloured powder to provide a record of powder displacement in the recovered specimens. After recovery and infiltration with a thermosetting resin the specimens were sectioned and polished to reveal the structure formed by the passage of the projectile and shock wave. Results indicate that the shock pressures generated were of the order of 0.5 to 1.4 GPa and higher, with shock velocities and sound speeds in the ranges 650 to 800 m/s and 350 to 400 m/s respectively

  17. Radiography for a Shock-accelerated Liquid Layer

    International Nuclear Information System (INIS)

    P. Meekunnasombat J.G. Oakley/inst M.H. Anderson R. Bonazza

    2005-01-01

    This program supported the experimental study of the interaction of planar shock waves with both solid structures (a single cylinder or a bank of cylinders) and single and multiple liquid layers. Objectives of the study included: characterization of the shock refraction patterns; measurements of the impulsive loading of the solid structures; observation of the response of the liquid layers to shock acceleration; assessment of the shock-mitigation effects of single and multiple liquid layers. The uploaded paper is intended as a final report for the entire funding period. The poster described in the paper won the Best Poster Award at the 25 International Symposium on Shock Waves

  18. Clindamycin-induced Anaphylactic Shock During General Anesthesia

    Directory of Open Access Journals (Sweden)

    Chiuan-Shiou Chiou

    2006-11-01

    Full Text Available Clindamycin-related anaphylactic reaction is rarely reported. We report a male patient with buccal cancer who was undergoing radical neck dissection when life-threatening anaphylactic shock developed soon after intravenous infusion of clin-damycin. Immediate cardiopulmonary resuscitation was performed, and the patient recovered uneventfully. Perioperative anaphylactic shock is a serious problem due to the difficulty of judgment and potentially disastrous outcome. Immediate diagnosis and halting of drug infusion should be the first actions taken.

  19. Activation analysis of trace amounts of rare earth in high purity tantalum

    International Nuclear Information System (INIS)

    Ishibashi, Wataru; Saito, Shinichi; Hirayama, Tooru.

    1975-01-01

    It is necessary to separate rare earth from tantalum by rapid methods in order to remove effects of a strong radioactivity and a short half-life. Tantalum is extracted with 10%N-lauryl (trialkylmethyl) amino-benzene pre-equilibrated with a solution of 9 M hydrochloric and 0.15 M hydrofluoric acid. A non-radioactive rare earth element is added to this aqueous solution, a precipitate of trace amounts of radioactive rare earth in aqueous solution is formed by this addition of rare earth. Some factors in the determination are: 1) the effect of the irradiation position of the sample in the atomic reactor, 2) the effect on the extraction with 10%N-lauryl (trialkylmethyl) amino-benzene for the radioactive rare earth, 3) the effect of the concentration of hydrofluoric acid, ammonia water and nitric acid on co-precipitation. As a result of the investigation we obtained the following satisfactory results: 1) Rare earth was not effected by the extraction of tantalum with 10%N-lauryl (trialkylmethyl) amino-benzene. 2) The recovery of rare earth by co-precipitation increases when an ammonium ion coexists, and when the concentration of hydrofluoric acid decreases, but the recovery decreases with the increase of nitric acid concentration. 3) The time required for the extraction is 9 hours. In case of determination for dysprosium, tantalum extracted with 10%N-lauryl (trialkylmethyl) amino-benzene before activation and the time for separation is 2 hours. (auth.)

  20. Synthesis and characterization of polystyrene embolization particles doped with tantalum oxide nanoparticles for X-ray contrast.

    Science.gov (United States)

    Morrison, Rachel; Thompson, James; Bird, Luke; Hill, Mark A; Townley, Helen

    2015-08-01

    Radiopaque and fluorescent embolic particles have been synthesized and characterised to match the size of vasculature found in tumours to ensure effective occlusion of the vessels. A literature search showed that the majority of vessels surrounding a tumour were less than 50 µm and therefore polydispersed polystyrene particles with a peak size of 50 µm have been synthesised. The embolic particles contain 5-8 nm amorphous tantalum oxide nanoparticles which provide X-ray contrast. Embolic particles containing up to 9.4 wt% tantalum oxide were prepared and showed significant contrast compared to the undoped polystyrene particles. The X-ray contrast of the embolic particles was shown to be linear (R(2) = 0.9) with respect to the concentration of incorporated tantalum nanoparticles. A model was developed which showed that seventy-five 50 µm embolic particles containing 10% tantalum oxide could provide the same contrast as 5 cm of bone. Therefore, the synthesized particles would provide sufficient X-ray contrast to enable visualisation within a tumour.

  1. Potentiometric determination of the tungsten content of tantalum-tungsten alloys with chromium II

    International Nuclear Information System (INIS)

    Gavra, Z.; Ronen, S.; Levin, R.

    1977-05-01

    A method was developed for the potentiometric determination of the tungsten content of tantalum-tungsten alloys of different compositions. These were dissolved under conditions that enabled the tungsten content to be determined with chromium (II). Phosphoric acid was selected as a suitable complexing agent for the prevention of the precipitation of tungsten and tantalum compounds. The use of chromium (II) required an oxygen-tight system and therefore the work was carried out in suitable vessels for storage and tritation

  2. Niobium, tantalum and titanium extraction from natural and technogenic raw materials of the Kola Peninsula by liquid-liquid extraction methods

    International Nuclear Information System (INIS)

    Kassikova, N.I.; Kassikov, A.G.; Balabanov, Yu.I.; Petrov, V.B.; Kalinnikov, V.T.

    2003-01-01

    Such rare metals as niobium and tantalum are important strategic materials underlying many of the modern advanced technologies. Since the extraction and processing of rare metal concentrates from own deposits has diminished abruptly in recent years, it is essential to look into the possibility of extracting these elements from various production wastes. This work discusses liquid-liquid extraction and purification of niobium, tantalum and titanium from process solutions of loparite, perovskite and sphene concentrate decomposition with sulphuric and hydrochloric acids; niobium from lithium niobate production wastes decomposed by hydrochloric acid; and tantalum from tantalum capacitor and heat-resistant alloy wastes. (Original)

  3. Tantalum X-ray contrast media, by M.G. Zuev and L.P. Larionov (Ekaterinburg: UrO RAN, 2002. 155 p.)

    International Nuclear Information System (INIS)

    Zhuravleva, E.Yu.

    2004-01-01

    The monograph of M.G. Zuev and L.P. Larionov Tantalum X-ray contrast media (Solid state chemistry for medicine series) is discussed. The monograph includes information on physical and chemical properties of tantalum, rare earths, and their oxides, phase compositions and phase diagrams of M 2 O 3 -Ta 2 O 5 (M - rare earths) systems is performed. Data on preclinical tests of yttrium orthotantalate and lanthanum orthotantalate as X-ray contrast media are given. Procedures for the production of X-ray contrast media involving tantalum oxide, rare earth tantalate and tantalum powder are described [ru

  4. Reaction-time-resolved measurements of laser-induced fluorescence in a shock tube with a single laser pulse

    Science.gov (United States)

    Zabeti, S.; Fikri, M.; Schulz, C.

    2017-11-01

    Shock tubes allow for the study of ultra-fast gas-phase reactions on the microsecond time scale. Because the repetition rate of the experiments is low, it is crucial to gain as much information as possible from each individual measurement. While reaction-time-resolved species concentration and temperature measurements with fast absorption methods are established, conventional laser-induced fluorescence (LIF) measurements with pulsed lasers provide data only at a single reaction time. Therefore, fluorescence methods have rarely been used in shock-tube diagnostics. In this paper, a novel experimental concept is presented that allows reaction-time-resolved LIF measurements with one single laser pulse using a test section that is equipped with several optical ports. After the passage of the shock wave, the reactive mixture is excited along the center of the tube with a 266-nm laser beam directed through a window in the end wall of the shock tube. The emitted LIF signal is collected through elongated sidewall windows and focused onto the entrance slit of an imaging spectrometer coupled to an intensified CCD camera. The one-dimensional spatial resolution of the measurement translates into a reaction-time-resolved measurement while the species information can be gained from the spectral axis of the detected two-dimensional image. Anisole pyrolysis was selected as the benchmark reaction to demonstrate the new apparatus.

  5. The efficacy of extracorporeal shock wave lithotripsy on single dense calcified gallstones according to computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Takao (Mie Univ., Tsu (Japan). School of Medicine); Shimono, Kazuko; Moriyama, Shigeru; Masuda, Touru; Ikeda, Tetsuya; Umegae, Satoru; Nagata, Norikazu

    1993-05-01

    The efficacy and complications of extracorporeal shock wave lithotripsy (ESWL) for single gallstones were compared between 15 patients with a CT-lucent stone and 18 patients with a dense calcified stone. In all of five patients with a stone smaller than 10 mm in diameter, complete or sufficient clearance was observed, regardless of calcification. However, in 28 patients with a stone larger than 11 mm in diameter, the rates of complete or sufficient clearance were lower in those with a dense calcified stone (64%) than in those with a computed tomography (CT) lucent stone (93%). There was no difference in the rate of complications between patients with a CT-lucent stone and those with a dense calcified stone. These results thus suggest that extracorporeal shock wave lithotripsy may be safely employed for patients with a single calcified gallstone. (author).

  6. Preparation of tantalum carbide layers on carbon using the metalliding process

    Energy Technology Data Exchange (ETDEWEB)

    Massot, L. [Laboratoire de Genie Chimique UMR 5503, Departement Procedes Electrochimiques, Universite Paul Sabatier, 31062 Toulouse Cedex 9 (France)], E-mail: massot@chimie.ups-tlse.fr; Chamelot, P. [Laboratoire de Genie Chimique UMR 5503, Departement Procedes Electrochimiques, Universite Paul Sabatier, 31062 Toulouse Cedex 9 (France); Winterton, P. [UFR Langues vivantes, Universite Paul Sabatier, 31062 Toulouse Cedex 9 (France); Taxil, P. [Laboratoire de Genie Chimique UMR 5503, Departement Procedes Electrochimiques, Universite Paul Sabatier, 31062 Toulouse Cedex 9 (France)

    2009-03-05

    This work concerns the preparation of tantalum carbide films on carbon-based substrates using the metalliding process in LiF/NaF molten medium (60-40 mol%), containing tantalum heptafluorotantalate ions TaF{sub 7}{sup 2-}, in the 800-900 deg. C temperature range. The process uses a metalliding cell symbolised as: (+) C, TaC{sub x}/LiF-NaF-K{sub 2}TaF{sub 7}/Ta (-) involving the dissolution of Ta at the anode and the reduction of Ta ions in TaC{sub x} at the cathode. The experiments of this process were performed with different carbon substrates as cathodic material: graphite, glassy carbon and carbon braid. Samples analysis (SEM-EDS and XRD) after metalliding showed the formation of tantalum carbides (TaC and Ta{sub 2}C) at the surface of the substrate at a relatively low temperature. A kinetic study, based on the control of the cathodic reaction by the intermetallic diffusion, allowed the diffusion parameters, such as Ta/C diffusion coefficient, to be determined at several temperatures. Furthermore, the results are shown to be independent of the type of carbon substrate.

  7. Refractive indices of CaF2 single crystals under elastic shock loading

    Science.gov (United States)

    Li, Y.; Zhou, X. M.; Liu, C. L.; Luo, S. N.

    2017-07-01

    Refractive indices and Hugoniots of CaF2 single crystals are investigated by laser displacement interferometry under shock loading below 5 GPa. Birefringence is observed for the [110] loading. We obtain the Hugoniot equation of states for [100], [110] and [111], and refractive indices for these orientations with consideration of their polarization. The measured refractive indices are in reasonable agreement with predictions based on the piezo-optic theory, and are used to refine the elasto-optic coefficients.

  8. Conflict minerals from the Democratic Republic of the Congo: global tantalum processing plants, a critical part of the tantalum supply chain

    Science.gov (United States)

    Papp, John F.

    2014-01-01

    The U.S. Geological Survey (USGS) analyzes mineral and metal supply chains to identify and describe major components of mineral and metal material flows from ore extraction, through intermediate forms, to a final product. Supply chain analyses may be used (1) to identify risks to the United States associated with the supply of critical and strategic minerals and metals and (2) to provide greater supply chain transparency so that policymakers have the fact-based information needed to formulate public policy. This fact sheet focuses on the post-mining/pre-consumer-product part of the tantalum supply chain. The USGS National Minerals Information Center (NMIC) has been asked by governmental and non-governmental organizations to provide information about tantalum, tin, tungsten, and gold (collectively known as “3TG minerals”) processing facilities worldwide in response to U.S. legislation aimed at identifying and removing the supply chain links between the trade in these minerals and civil unrest in the Democratic Republic of the Congo and adjacent countries.

  9. Niobium Nb and tantalum Ta

    International Nuclear Information System (INIS)

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

    1978-01-01

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

  10. "Hydro-metathesis" of olefins: A catalytic reaction using a bifunctional single-site tantalum hydride catalyst supported on fibrous silica (KCC-1) nanospheres

    KAUST Repository

    Polshettiwar, Vivek

    2011-02-18

    Tantalizing hydrocarbons: Tantalum hydride supported on fibrous silica nanospheres (KCC-1) catalyzes, in the presence of hydrogen, the direct conversion of olefins into alkanes that have higher and lower numbers of carbon atoms (see scheme). This catalyst shows remarkable catalytic activity and stability, with excellent potential of regeneration. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. "Hydro-metathesis" of olefins: A catalytic reaction using a bifunctional single-site tantalum hydride catalyst supported on fibrous silica (KCC-1) nanospheres

    KAUST Repository

    Polshettiwar, Vivek; Thivolle-Cazat, Jean; Taoufik, Mostafa; Stoffelbach, Franç ois; Norsic, Sé bastien; Basset, Jean-Marie

    2011-01-01

    Tantalizing hydrocarbons: Tantalum hydride supported on fibrous silica nanospheres (KCC-1) catalyzes, in the presence of hydrogen, the direct conversion of olefins into alkanes that have higher and lower numbers of carbon atoms (see scheme). This catalyst shows remarkable catalytic activity and stability, with excellent potential of regeneration. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Case history of tantalum-weld cracking

    International Nuclear Information System (INIS)

    Knorovsky, G.A.

    1982-01-01

    Tantalum welding is normally a routine operation. Of course, the routine involves careful cleaning beforehand, and welding in an atmosphere which excludes reactive gases (O 2 , N 2 , H 2 ). Recently a weld cracking problem was encountered at SNLA despite the fact that normal precautions had been taken. This account reviews what happened, the analytical procedures followed to determine the unusual source of the problem, and the remedy which solved the problem

  13. A novel tantalum-based sol-gel packed microextraction syringe for highly specific enrichment of phosphopeptides in MALDI-MS applications.

    Science.gov (United States)

    Çelikbıçak, Ömür; Atakay, Mehmet; Güler, Ülkü; Salih, Bekir

    2013-08-07

    A new tantalum-based sol-gel material was synthesized using a unique sol-gel synthesis pathway by PEG incorporation into the sol-gel structure without performing a calcination step. This improved its chemical and physical properties for the high capacity and selective enrichment of phosphopeptides from protein digests in complex biological media. The specificity of the tantalum-based sol-gel material for phosphopeptides was evaluated and compared with tantalum(V) oxide (Ta2O5) in different phosphopeptide enrichment applications. The tantalum-based sol-gel and tantalum(V) oxide were characterized in detail using FT-IR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM), and also using a surface area and pore size analyzer. In the characterization studies, the surface morphology, pore volume, crystallinity of the materials and PEG incorporation into the sol-gel structure to produce a more hydrophilic material were successfully demonstrated. The X-ray diffractograms of the two different materials were compared and it was noted that the broad signals of the tantalum-based sol-gel clearly represented the amorphous structure of the sol-gel material, which was more likely to create enough surface area and to provide more accessible tantalum atoms for phosphopeptides to be easily adsorbed when compared with the neat and more crystalline structure of Ta2O5. Therefore, the phosphopeptide enrichment performance of the tantalum-based sol-gels was found to be remarkably higher than the more crystalline Ta2O5 in our studies. Phosphopeptides at femtomole levels could be selectively enriched using the tantalum-based sol-gel and detected with a higher signal-to-noise ratio by matrix-assisted laser desorption/ionization-mass spectrometer (MALDI-MS). Moreover, phosphopeptides in a tryptic digest of non-fat bovine milk as a complex real-world biological sample were retained with higher yield using a tantalum-based sol-gel. Additionally, the sol-gel material

  14. Hot pressing of nanocrystalline tantalum using high frequency induction heating and pulse plasma sintering

    Science.gov (United States)

    Jakubowicz, J.; Adamek, G.; Sopata, M.; Koper, J. K.; Siwak, P.

    2017-12-01

    The paper presents the results of nanocrystalline powder tantalum consolidation using hot pressing. The authors used two different heating techniques during hot pressing: high-frequency induction heating (HFIH) and pulse plasma sintering (PPS). A comparison of the structure, microstructure, mechanical properties and corrosion resistance of the bulk nanocrystalline tantalum obtained in both techniques was performed. The nanocrystalline powder was made to start from the microcrystalline one using the high-energy ball milling process. The nanocrystalline powder was hot-pressed at 1000 °C, whereas, for comparison, the microcrystalline powder was hot pressed up to 1500 °C for proper consolidation. The authors found that during hot pressing, the powder partially reacts with the graphite die covered by boron nitride, which facilitated punches and powder displacement in the die during densification. Tantalum carbide and boride in the nanocrystalline material was found, which can improve the mechanical properties. The hardness of the HFIH and PPS nanocrystalline tantalum was as high as 625 and 615 HV, respectively. The microstructure was more uniform in the PPS nanomaterial. The corrosion resistance in both cases deteriorated, in comparison to the microcrystalline material, while the PPS material corrosion resistance was slightly better than that of the HFIH one.

  15. TiO2 effect on break-down of low-grade tantalum-niobium concentrates in the process of sulphatization

    International Nuclear Information System (INIS)

    Petrova, N.V.; Popov, A.D.; Mulenko, V.N.

    1982-01-01

    The effect of TiO 2 additive or materials containing it on tantalum-niobate decomposition in the process of sulphatization is investigated. It is shown that favourable effect of titanium dioxide in the process of sulphatization is especially noticeable in reprocessing of hard-brokening down tantalum-niobium concentrates with low Nb:Ta ratio etc. Chemical composition and type of tantalum-niobium mineralization of enrichment products used in the given investigation is presented. It is stated that the degree of concentrate break-down under similar sulphatization conditions (t=230 deg C; tau=2 h) essentially depends on the quantity of the introduced titanium dioxide. It is shown that sulphatization in the presence of titanium dioxide additive or materials containing it permits to exercise practically complete break-down of lean tantalum-niobium raw material, to avoid application of complexers in leaching of sulphatization products

  16. Electron microprobe analysis of tantalum--nitride thin films

    International Nuclear Information System (INIS)

    Stoltz, D.L.; Starkey, J.P.

    1979-06-01

    Quantitative chemical analysis of 500- and 2000-angstrom tantalum--nitride films on glass substrates has been accomplished using an electron microprobe x-ray analyzer. In order to achieve this analysis, modifications to the microprobe were necessary. A description of the calibration procedure, the method of analysis, and the quantitative results are discussed

  17. Poisoning Experiments Aimed at Discriminating Active and Less-Active Sites of Silica-Supported Tantalum Hydride for Alkane Metathesis

    KAUST Repository

    Saggio, Guillaume; Taoufik, Mostafa; Basset, Jean-Marie; Thivolle-Cazat, Jean

    2010-01-01

    Only 50% of the silica-supported tantalum hydride sites are active in the metathesis of propane. Indeed, more than 45% of the tantalum hydride can be eliminated by a selective oxygen poisoning of inactive sites with no significant decrease

  18. Shock and Microstructural Characterization of the α-ω Phase Transition in Titanium Crystals

    Science.gov (United States)

    Morrow, Benjamin M.; Rigg, Paulo A.; Jones, David R.; Addessio, Francis L.; Trujillo, Carl P.; Saavedra, Ramon A.; Martinez, Daniel T.; Cerreta, Ellen K.

    2017-12-01

    A multicrystal comprised of a small number of large crystals of high-purity titanium and a [0001] oriented high-purity single crystal titanium sample were shock loaded using gas gun plate impact experiments. Tests were performed at stresses above the α {-}ω phase transition stress (for high-purity polycrystalline specimens) to observe the behavior of oriented crystals under similar conditions. Post-mortem characterization of the shocked microstructure was conducted on the single crystal sample to measure textures, and quantify phases and twinning. The apparent activation of plastic and transformation mechanisms was dependent upon crystal orientation. Specifically, the [0001] crystal showed a higher Hugoniot elastic limit than the [10\\bar{1}0] or [3\\bar{1}\\bar{4}4] orientations. The slope of velocity as a function of time was lower in the [0001] orientation than the other orientations during plastic deformation, indicating sluggish transformation kinetics for the α to ω phase transition for the [0001] oriented crystal. Microtexture measurements of a recovered [0001] oriented single crystal revealed the presence of retained ω phase after unloading, with orientations of the constituent phase fractions indicative of the forward α → ω transition, rather than the reverse ω → α transition, suggesting that the material never achieved a state of 100% ω phase.

  19. Corrosion resistance of high-performance materials titanium, tantalum, zirconium

    CERN Document Server

    2012-01-01

    Corrosion resistance is the property of a material to resist corrosion attack in a particular aggressive environment. Although titanium, tantalum and zirconium are not noble metals, they are the best choice whenever high corrosion resistance is required. The exceptionally good corrosion resistance of these high–performance metals and their alloys results from the formation of a very stable, dense, highly adherent, and self–healing protective oxide film on the metal surface. This naturally occurring oxide layer prevents chemical attack of the underlying metal surface. This behavior also means, however, that high corrosion resistance can be expected only under neutral or oxidizing conditions. Under reducing conditions, a lower resistance must be reckoned with. Only very few inorganic and organic substances are able to attack titanium, tantalum or zirconium at ambient temperature. As the extraordinary corrosion resistance is coupled with an excellent formability and weldability these materials are very valua...

  20. Electrodepositions on Tantalum in Alkali Halide Melts

    DEFF Research Database (Denmark)

    Barner, Jens H. Von; Jensen, Annemette Hindhede; Christensen, Erik

    2013-01-01

    Surface layers of tantalum metal were electrodeposited on steel from K2TaF7-LiF-NaF-KF melts. With careful control of the oxide contents dense and adherent deposits could be obtained by pulse plating. In NaCl-KCl-NaF-Na2CO3 and NaCl-KCl-Na2CO3 melts carbonate ions seems to be reduced to carbon in...

  1. Electrodepositions on Tantalum in alkali halide melts

    DEFF Research Database (Denmark)

    Barner, Jens H. Von; Jensen, Annemette Hindhede; Christensen, Erik

    2012-01-01

    Surface layers of tantalum metal were electrodeposited on steel from K 2TaF7-LiF-NaF-KF melts. With careful control of the oxide contents dense and adherent deposits could be obtained by pulse plating. In NaCl-KCl-NaF-Na2CO3 and NaCl-KCl-Na2CO 3 melts carbonate ions seems to be reduced to carbon ...

  2. Technological challenges in extractive metallurgy and refining of niobium, tantalum and preparation of their alloys

    International Nuclear Information System (INIS)

    Mirji, K.V.; Sheela; Saibaba, N.

    2016-01-01

    Manufacturing of refractory and reactive metals, their alloys and fabricated products has been always difficult due to their high affinity with atmospheric gases, stringent specifications and exhaustive quality requirements. In the field of development of these materials, Nuclear Fuel Complex (NFC), Hyderabad has been at the fore front in accepting the challenges for the advancement of technological growth. Extensive developments have been carried out during the last few decades in the field of niobium, tantalum, zirconium etc in the form of pure metal, their compounds and alloys. Over the period of time, efforts have been made for developing sophisticated facilities along with trained man power for manufacturing of critical items for which technical knowhow is not available either with private industries or any other organizations in the country. In the field of reactive metals, though general theory is well established, production is intriguing and requires expert handling on the field. At NFC, efforts were put towards industrial adoptability of the useful knowledge gained from lab scale to reliable production scale. Comprehensive study was conducted to systematically study the effects of various process parameters starting from ore to the metals and their alloys, equipment were modified for ease of operation with stress on recycling/reusing of the waste and handling of effluents. However scale of operation and therefore cost of production has been matter of concern in the field of tantalum and niobium. Electron beam refining is used for production of highly pure reactive and refractory metals like tantalum, niobium, zirconium etc. and their alloys under high vacuum. Special Materials Plant (SMP) at Nuclear Fuel Complex, Hyderabad has developed processes for production of niobium oxide, tantalum oxide, tantalum metal powder, tantalum anodes/capacitors, potassium tantalum fluoride, Nb thermit, Nb metal granules, RRR grade niobium, Nb base alloys such as Zr

  3. Use of a Tantalum Liner to Reduce Bore Erosion and Increase Muzzle Velocity in Two-Stage Light Gas Guns

    Science.gov (United States)

    Bogdanoff, David W.

    2015-01-01

    Muzzle velocities and gun erosion predicted by earlier numerical simulations of two stage light gas guns with steel gun tubes were in good agreement with experimental values. In a subsequent study, simulations of high performance shots were repeated with rhenium (Re) gun tubes. Large increases in muzzle velocity (2 - 4 km/sec) were predicted for Re tubes. In addition, the hydrogen-produced gun tube erosion was, in general, predicted to be zero with Re tubes. Tantalum (Ta) has some mechanical properties superior to those of Re. Tantalum has a lower modulus of elasticity than Re for better force transmission from the refractory metal liner to an underlying thick wall steel tube. Tantalum also has greater ductility than Re for better survivability during severe stress/strain cycles. Also, tantalum has been used as a coating or liner in military powder guns with encouraging results. Tantalum has, however, somewhat inferior thermal properties to those of rhenium, with a lower melting point and lower density and thermal conductivity. The present study was undertaken to see to what degree the muzzle velocity gains of rhenium gun tubes (over steel tubes) could be achieved with tantalum gun tubes. Nine high performance shots were modeled with a new version of our CFD gun code for steel, rhenium and tantalum gun tubes. For all except the highest velocity shot, the results with Ta tubes were nearly identical with those for Re tubes. Even for the highest velocity shot, the muzzle velocity gain over a steel tube using Ta was 82% of the gain obtained using Re. Thus, the somewhat inferior thermal properties of Ta (when compared to those of Re) translate into only very slightly poorer overall muzzle velocity performance. When this fact is combined with the superior mechanical properties of Ta and the encouraging performance of Ta liners/coatings in military powder guns, tantalum is to be preferred over Re as a liner/coating material for two stage light gas guns to increase muzzle

  4. Evaluation of Ferrite Chip Beads as Surge Current Limiters in Circuits with Tantalum Capacitors

    Science.gov (United States)

    Teverovsky, Alexander

    2014-01-01

    Limiting resistors are currently required to be connected in series with tantalum capacitors to reduce the risk of surge current failures. However, application of limiting resistors decreases substantially the efficiency of the power supply systems. An ideal surge current limiting device should have a negligible resistance for DC currents and high resistance at frequencies corresponding to transients in tantalum capacitors. This work evaluates the possibility of using chip ferrite beads (FB) as such devices. Twelve types of small size FBs from three manufacturers were used to evaluate their robustness under soldering stresses and at high surge current spikes associated with transients in tantalum capacitors. Results show that FBs are capable to withstand current pulses that are substantially greater than the specified current limits. However, due to a sharp decrease of impedance with current, FBs do not reduce surge currents to the required level that can be achieved with regular resistors.

  5. Do structural oil-market shocks affect stock prices?

    International Nuclear Information System (INIS)

    Apergis, Nicholas; Miller, Stephen M.

    2009-01-01

    This paper investigates how explicit structural shocks that characterize the endogenous character of oil price changes affect stock-market returns in a sample of eight countries - Australia, Canada, France, Germany, Italy, Japan, the United Kingdom, and the United States. For each country, the analysis proceeds in two steps. First, modifying the procedure of Kilian [Not All Oil Price Shocks are Alike: Disentangling Demand and Supply Shocks in the Crude Oil Market. American Economic Review.], we employ a vector error-correction or vector autoregressive model to decompose oil-price changes into three components: oil-supply shocks, global aggregate-demand shocks, and global oil-demand shocks. The last component relates to specific idiosyncratic features of the oil market, such as changes in the precautionary demand concerning the uncertainty about the availability of future oil supplies. Second, recovering the oil-supply shocks, global aggregate-demand shocks, and global oil-demand shocks from the first analysis, we then employ a vector autoregressive model to determine the effects of these structural shocks on the stock market returns in our sample of eight countries. We find that international stock market returns do not respond in a large way to oil market shocks. That is, the significant effects that exist prove small in magnitude. (author)

  6. Radiographic examination of tracheal strictures by means of powdered tantalum

    International Nuclear Information System (INIS)

    Scheel, W.; Dippmann, A.

    1979-01-01

    This report deals with the diagnostic value of a tracheobronchography with powdered tantalum in 5 patients who suffer from a severe stricture of the trachea. The own experiences with this method are described. (orig.) [de

  7. Tantalum Nitride Electron-Selective Contact for Crystalline Silicon Solar Cells

    KAUST Repository

    Yang, Xinbo; Aydin, Erkan; Xu, Hang; Kang, Jingxuan; Hedhili, Mohamed N.; Liu, Wenzhu; Wan, Yimao; Peng, Jun; Samundsett, Christian; Cuevas, Andres; De Wolf, Stefaan

    2018-01-01

    novel electron‐selective, passivating contact for c‐Si solar cells is presented. Tantalum nitride (TaN x ) thin films deposited by atomic layer deposition are demonstrated to provide excellent electron‐transporting and hole‐blocking properties

  8. Twinning anisotropy of tantalum during nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Goel, Saurav, E-mail: S.GOEL@qub.ac.uk [School of Mechanical and Aerospace Engineering, Queen' s University, Belfast, BT9 5AH (United Kingdom); Beake, Ben [Micro Materials Limited, Willow House, Yale Business Village, Ellice Way, Wrexham LL13 7YL (United Kingdom); Dalton Research Institute, Manchester Metropolitan University, Manchester, M15GD (United Kingdom); Chan, Chi-Wai [School of Mechanical and Aerospace Engineering, Queen' s University, Belfast, BT9 5AH (United Kingdom); Haque Faisal, Nadimul [School of Engineering, Robert Gordon University, Garthdee Road, Aberdeen AB10 7GJ (United Kingdom); Dunne, Nicholas [School of Mechanical and Aerospace Engineering, Queen' s University, Belfast, BT9 5AH (United Kingdom)

    2015-03-11

    Unlike other BCC metals, the plastic deformation of nanocrystalline Tantalum (Ta) during compression is regulated by deformation twinning. Whether or not this twinning exhibits anisotropy was investigated through simulation of displacement-controlled nanoindentation test using molecular dynamics (MD) simulation. MD data was found to correlate well with the experimental data in terms of surface topography and hardness measurements. The mechanism of the transport of material was identified due to the formation and motion of prismatic dislocations loops (edge dislocations) belonging to the 1/2〈111〉 type and 〈100〉 type Burgers vector family. Further analysis of crystal defects using a fully automated dislocation extraction algorithm (DXA) illuminated formation and migration of twin boundaries on the (110) and (111) orientation but not on the (010) orientation and most importantly after retraction all the dislocations disappeared on the (110) orientation suggesting twinning to dominate dislocation nucleation in driving plasticity in tantalum. A significant finding was that the maximum shear stress (critical Tresca stress) in the deformation zone exceeded the theoretical shear strength of Ta (Shear modulus/2π~10.03 GPa) on the (010) orientation but was lower than it on the (110) and the (111) orientations. In light of this, the conventional lore of assuming the maximum shear stress being 0.465 times the mean contact pressure was found to break down at atomic scale.

  9. The physicochemical/biological properties of porous tantalum and the potential surface modification techniques to improve its clinical application in dental implantology

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yindong [State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu (China); Bao, Chongyun, E-mail: cybao9933@scu.edu.cn [State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu (China); Wismeijer, Daniel [Department of Oral Implantology and Prosthetic Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), MOVE Research Institute Amsterdam, VU University Amsterdam and University of Amsterdam, Amsterdam (Netherlands); Wu, Gang, E-mail: g.wu@acta.nl [Department of Oral Implantology and Prosthetic Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), MOVE Research Institute Amsterdam, VU University Amsterdam and University of Amsterdam, Amsterdam (Netherlands)

    2015-04-01

    More rapid restoration and more rigid functionality have been pursued for decades in the field of dental implantology. Under such motivation, porous tantalum has been recently introduced to design a novel type of dental implant. Porous tantalum bears interconnected porous structure with pore size ranging from 300 to 600 μm and a porosity of 75–85%. Its elastic modulus (1.3–10 GPa) more closely approximates that of natural cortical (12–18 GPa) and cancellous bone (0.1–0.5 GPa) in comparison with the most commonly used dental materials, such as titanium and titanium alloy (106–115 GPa). Porous tantalum is highly corrosion-resistant and biocompatible. It can significantly enhance the proliferation and differentiation of primary osteoblasts derived from elderly people than titanium. Porous tantalum can allow bone ingrowth and establish not only osseointegration but also osseoincorporation, which will significantly enhance the secondary stability of implants in bone tissue. In this review, we summarize the physicochemical, mechanical and biological properties of porous tantalum. We further discuss the performance of current tantalum dental implants and present the methodologies of surface modifications in order to improve their biological performance.

  10. The physicochemical/biological properties of porous tantalum and the potential surface modification techniques to improve its clinical application in dental implantology

    International Nuclear Information System (INIS)

    Liu, Yindong; Bao, Chongyun; Wismeijer, Daniel; Wu, Gang

    2015-01-01

    More rapid restoration and more rigid functionality have been pursued for decades in the field of dental implantology. Under such motivation, porous tantalum has been recently introduced to design a novel type of dental implant. Porous tantalum bears interconnected porous structure with pore size ranging from 300 to 600 μm and a porosity of 75–85%. Its elastic modulus (1.3–10 GPa) more closely approximates that of natural cortical (12–18 GPa) and cancellous bone (0.1–0.5 GPa) in comparison with the most commonly used dental materials, such as titanium and titanium alloy (106–115 GPa). Porous tantalum is highly corrosion-resistant and biocompatible. It can significantly enhance the proliferation and differentiation of primary osteoblasts derived from elderly people than titanium. Porous tantalum can allow bone ingrowth and establish not only osseointegration but also osseoincorporation, which will significantly enhance the secondary stability of implants in bone tissue. In this review, we summarize the physicochemical, mechanical and biological properties of porous tantalum. We further discuss the performance of current tantalum dental implants and present the methodologies of surface modifications in order to improve their biological performance

  11. Micro/Nano Structural Tantalum Coating for Enhanced Osteogenic Differentiation of Human Bone Marrow Stem Cells

    OpenAIRE

    Ding Ding; Youtao Xie; Kai Li; Liping Huang; Xuebin Zheng

    2018-01-01

    Recently, tantalum has been attracting much attention for its anticorrosion resistance and biocompatibility, and it has been widely used in surface modification for implant applications. To improve its osteogenic differentiation of human bone marrow stem cells (hBMSCs), a micro/nano structure has been fabricated on the tantalum coating surface through the combination of anodic oxidation and plasma spraying method. The morphology, composition, and microstructure of the modified coating were co...

  12. Spark plasma sintering of tantalum carbide

    International Nuclear Information System (INIS)

    Khaleghi, Evan; Lin, Yen-Shan; Meyers, Marc A.; Olevsky, Eugene A.

    2010-01-01

    A tantalum carbide powder was consolidated by spark plasma sintering. The specimens were processed under various temperature and pressure conditions and characterized in terms of relative density, grain size, rupture strength and hardness. The results are compared to hot pressing conducted under similar settings. It is shown that high densification is accompanied by substantial grain growth. Carbon nanotubes were added to mitigate grain growth; however, while increasing specimens' rupture strength and final density, they had little effect on grain growth.

  13. Plasma-sprayed tantalum/alumina cermets

    International Nuclear Information System (INIS)

    Kramer, C.M.

    1977-12-01

    Cermets of tantalum and alumina were fabricated by plasma spraying, with the amount of alumina varied from 0 to 65 percent (by volume). Each of four compositions was then measured for tensile strength, elastic modulus, and coefficient of thermal expansion. In general, strength and strain to failure decreased with increasing alumina content: 62 MPa for 100 percent Ta to 19 MPa for 35 v percent Ta. A maximum of 0.1 percent strain was observed for the sprayed 100 percent Ta specimens. The coefficient of thermal expansion measured for the pure Ta was 6.2 (10 -6 )/K

  14. Partial molar volumes of hydrogen and deuterium in niobium, vanadium, and tantalum

    International Nuclear Information System (INIS)

    Peterson, D.T.; Herro, H.M.

    1983-01-01

    The partial molar volumes of hydrogen and deuterium were measured in vanadium, niobium, and tantalum by a differential pressure technique. One-half of an electrolytically charged sample plat was compressed between hardened steel blocks in a hydraulic press. The activity of hydrogen in the hig pressure region was raised and caused hydrogen to diffuse into the low pressure region. The partia molar volume was calculated from the ratio of the hydrogen concentrations in the high and low pressure regions of the sample. Small isotope effects were found in the partial molar volume. Hydrogen had the larger volume in niobium and tantalum, but the reverse was true in vanadium

  15. Tin(2) difluoride and antimony(3) trifluoride as fluorine donors in reactions with tantalum halides in various solvents

    International Nuclear Information System (INIS)

    Kokunov, Yu.V.; Ershova, M.M.; Razgonyaeva, G.A.; Buslaev, Yu.A.

    2001-01-01

    The reactions of SnF 2 , SbF 3 with TaF 5 and TaCl 5 in acetonitrile and dimethylsulfoxide were studied by means of 19 F and 119 Sn NMR. SnF 2 and SbF 3 were established to be donors of fluorine ions for the tantalum(5). It was found that the anion and cation tantalum fluorochloride complexes were formed in acetonitrile, and [TaF 6 ] - was dominated in dimethylsulfoxide. In the solution the tin(2) is present as fluorine-containing polymer cations. Dimethylsulfoxide, as distinct from acetonitrile, leads to disproportionation of tantalum fluorochlorides [ru

  16. Redox Chemisty of Tantalum Clusters on Silica Characterized by X-ray Absorption Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nemana,S.; Gates, B.

    2006-01-01

    SiO{sub 2}-supported clusters of tantalum were synthesized from adsorbed Ta(CH{sub 2}Ph){sub 5} by treatment in H{sub 2} at 523 K. The surface species were characterized by X-ray absorption spectroscopy (extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray absorption near edge spectroscopy (XANES)) and ultraviolet-visible spectroscopy. The EXAFS data show that SiOO{sub 2}-supported tantalum clusters were characterized by a Ta-Ta coordination number of approximately 2, consistent with the presence of tritantalum clusters, on average. When these were reduced in H{sub 2} and reoxidized in O{sub 2}, the cluster nuclearity remained essentially unchanged, although reduction and oxidation occurred, respectively, as shown by XANES and UV-vis spectra; in the reoxidation, the tantalum oxidation state change was approximately two electronic charges per tritantalum cluster. The data demonstrate an analogy between the chemistry of group 5 metals on the SiO{sub 2} support and their chemistry in solution, as determined by the group of Cotton.

  17. Structural changes and tribological behaviors of nitrogen ion-implanted tantalum

    International Nuclear Information System (INIS)

    Wang, W.J.; Wang, T.M.; Wang, X.J.

    1996-01-01

    Single-crystal tantalum sheets were implanted by 110 keV nitrogen ions to a dose of 5 x 10 17 ions/cm 2 at a temperature less than 100 C. The structural changes and the concentration depth profiles of the implanted layers were characterized by glancing-angle X-ray diffraction (GXRD), selected area diffraction (SAD) and Auger electron spectroscopy (AES), respectively. The microhardness, the friction coefficient and the wear rate of the specimens against hardened GCr15 steel balls were also determined before and after the implantation. Scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA) were used to analyze the wear tracks. The results showed that there exist deviations between the characterization results of AES and GXRD or SAD. The AES measurement suggests the formation of the tantalum nitrides with a maximum N/Ta ratio of 1/2, while the GXRD and SAD reveal the formation of bcc Ta(N), fcc TaN and a trace amount of hcp Ta 2 N. This can be explained by considering the inhomogeneous distribution of nitrogen atoms in micro-regions: the enrichment of nitrogen atoms in local micro-regions leads to the formation of fcc TaN; however, the unfavorable structural compatibility between bcc Ta and hcp Ta 2 N hinders the formation of hcp Ta 2 N in the regions where the N/Ta ratio reaches 1/2. The detected trace amount of the hcp Ta 2 N phase in the implanted layers can be considered as an after effect of nitrogen loss from the originally formed nitrides. The results also showed that the tribological properties of the Ta surfaces were improved due to the implantation. It is believed that the implantation-induced Ta(N), fcc TaN, and hcp Ta 2 N phases are responsible for this improvement. (orig.)

  18. Revisiting the thermal effect on shock wave propagation in weakly ionized plasmas

    International Nuclear Information System (INIS)

    Zhou, Qianhong; Dong, Zhiwei; Yang, Wei

    2016-01-01

    Many researchers have investigated shock propagation in weakly ionized plasmas and observed the following anomalous effects: shock acceleration, shock recovery, shock weakening, shock spreading, and splitting. It was generally accepted that the thermal effect can explain most of the experimental results. However, little attention was paid to the shock recovery. In this paper, the shock wave propagation in weakly ionized plasmas is studied by fluid simulation. It is found that the shock acceleration, weakening, and splitting appear after it enters the plasma (thermal) region. The shock splits into two parts right after it leaves the thermal region. The distance between the splitted shocks keeps decreasing until they recover to one. This paper can explain a whole set of features of the shock wave propagation in weakly ionized plasmas. It is also found that both the shock curvature and the splitting present the same photoacoustic deflection (PAD) signals, so they cannot be distinguished by the PAD experiments.

  19. Upgrading tantalum and niobium oxides content in Bangka tin slag with double leaching

    Science.gov (United States)

    Soedarsono, J. W.; Permana, S.; Hutauruk, J. K.; Adhyputra, R.; Rustandi, A.; Maksum, A.; Widana, K. S.; Trinopiawan, K.; Anggraini, M.

    2018-03-01

    Tantalum has become one of the 14 types of critical materials where the level of its availability is assumed as the midterm critical metal. Benefits of the element tantalum in the electronics field increased the deficit balance of supply / demand, as more variations of electronic products developed. The tantalum experts calculated the level of availability until 2020. Base on the previous studies, tin slag is a secondary source of tantalum and niobium. This study uses tin slag from Bangka, Indonesia, abbreviated, Bangka Tin Slag (BTS). BTS was roasted, water quenched and sieved, abbreviated BTS-RQS.BTS was roasted, water quenched and sieved, abbreviated BTS-RQS.BTS-RQS was roasted at a temperature 700□C given sample code BTS-R700QS, while roasted at 800°C given sample code BTS-R800QS.A variable leaching experiment on BTS-R700QS was solvent concentration variable and on BTS-R800QS was time variable. The entire residue was characterized by X-Ray Fluorescence (XRF), and the optimum results are on the BTS-R800QS leaching into 5 M NaOH for 20 min followed by 5M HCl for 50 min, with content of Ta2O5 and Nb2O51.56% and 1.11%, respectively. The result of XRF measurement showed was the increasing of TNO content due to the increasing solvent concentration and time of acid leaching. The discussion of thermodynamics this study used was HSC Chemistry 6 as a supporting data.

  20. Evaluation of Polymer Hermetically Sealed Tantalum Capacitors

    Science.gov (United States)

    Teverovsky, Alexander A.

    2014-01-01

    Polymer cathode tantalum capacitors have lower ESR (equivalent series resistance) compared to other types of tantalum capacitors and for this reason have gained popularity in the electronics design community. Their use allows improved performance of power supply systems along with substantial reduction of size and weight of the components used. However, these parts have poor thermal stability and can degrade in humid environments. Polymer hermetically sealed (PHS) capacitors avoid problems related to environmental degradation of molded case parts and can potentially replace current wet and solid hermetically sealed capacitors. In this work, PHS capacitors manufactured per DLA LAM DWG#13030 are evaluated for space applications. Several lots of capacitors manufactured over period from 2010 to 2014 were tested for the consistency of performance, electrical and thermal characteristics, highly accelerated life testing, and robustness under reverse bias and random vibration conditions. Special attention was given to analysis of leakage currents and the effect of long-term high temperature storage on capacitors in as is condition and after hermeticity loss. The results show that PHS capacitors might be especially effective for low-temperature applications or for system requiring a cold start-up. Additional screening and qualification testing have been recommended to assure the necessary quality of capacitors for space projects.

  1. The influence of peak shock stress on the high pressure phase transformation in Zr

    International Nuclear Information System (INIS)

    Cerreta, E K; Addessio, F L; Bronkhorst, C A; Brown, D W; Escobedo, J P; Fensin, S J; Gray, G T III; Lookman, T; Rigg, P A; Trujillo, C P

    2014-01-01

    At high pressures zirconium is known to undergo a phase transformation from the hexagonal close packed (HCP) alpha phase to the simple hexagonal omega phase. Under conditions of shock loading, a significant volume fraction of high-pressure omega phase is retained upon release. However, the hysteresis in this transformation is not well represented by equilibrium phase diagrams and the multi-phase plasticity under shock conditions is not well understood. For these reasons, the influence of peak shock stress and temperature on the retention of omega phase in Zr has been explored. VISAR and PDV measurements along with post-mortem metallographic and neutron diffraction characterization of soft recovered specimens have been utilized to quantify the volume fraction of retained omega phase and qualitatively understand the kinetics of this transformation. In turn, soft recovered specimens with varying volume fractions of retained omega phase have been utilized to understand the contribution of omega and alpha phases to strength in shock loaded Zr.

  2. Particle Acceleration in Two Converging Shocks

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xin; Wang, Na; Shan, Hao [Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011 (China); Giacalone, Joe [Lunar and Planetary Laboratory, University of Arizona, Tucson AZ 85721 (United States); Yan, Yihua [CAS Key Laboratory of Solar Activity, National Astronomical Observatories, Beijing 100012 (China); Ding, Mingde, E-mail: wangxin@xao.ac.cn [Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University) Ministry of Education, Nanjing 210093 (China)

    2017-06-20

    Observations by spacecraft such as ACE , STEREO , and others show that there are proton spectral “breaks” with energy E {sub br} at 1–10 MeV in some large CME-driven shocks. Generally, a single shock with the diffusive acceleration mechanism would not predict the “broken” energy spectrum. The present paper focuses on two converging shocks to identify this energy spectral feature. In this case, the converging shocks comprise one forward CME-driven shock on 2006 December 13 and another backward Earth bow shock. We simulate the detailed particle acceleration processes in the region of the converging shocks using the Monte Carlo method. As a result, we not only obtain an extended energy spectrum with an energy “tail” up to a few 10 MeV higher than that in previous single shock model, but also we find an energy spectral “break” occurring on ∼5.5 MeV. The predicted energy spectral shape is consistent with observations from multiple spacecraft. The spectral “break,” then, in this case is caused by the interaction between the CME shock and Earth’s bow shock, and otherwise would not be present if Earth were not in the path of the CME.

  3. Establishment of an analytical procedure for the determination of niobium and tantalum in minerals containing these elements using X-ray fluorescence technique

    International Nuclear Information System (INIS)

    Nguyen Xuan Chien

    2003-01-01

    The study of determination of niobium, tantalum in mineral and tin slags using X-ray fluorescence spectrometry was carried out. Analytical samples of powder and pellet were prepared. the interference of the major accompanied elements in sample with the determination of niobium and tantalum was also studied. The analysis of niobium and tantalum in mineral and in tin slags samples was given in this work. (author)

  4. Shock and Release Data on Forsterite (Mg2SiO4) Single Crystals

    Science.gov (United States)

    Root, S.; Townsend, J. P.; Shulenburger, L.; Davies, E.; Kraus, R. G.; Spaulding, D.; Stewart, S. T.; Jacobsen, S. B.; Mattsson, T. R.

    2016-12-01

    The Kepler mission has discovered numerous extra-solar rocky planets with sizes ranging from Earth-size to the super-Earths with masses 40 times larger than Earth. The solid solution series of (Mg, Fe)2SiO4 (olivine) is a major component in the mantle of Earth and likely these extra-solar rocky planets. However, understanding how the (Mg, Fe)2SiO4 system behaves at Earth like and super-Earth like pressures is still unknown. Using Sandia's Z machine facility, we shock compress single crystal forsterite, the Mg end-member of the olivine series. Solid aluminum flyers are accelerated up to 28 km/s to generate steady shock states up to 950 GPa. Release states from the Hugoniot are determined as well. In addition to experiments, we perform density functional theory (DFT) calculations to examine the potential phases along the Mg2SiO4 Hugoniot. We compare our results to other recent shock experiments on forsterite. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  5. Investigation of Shock-Induced Reactions in a Ni+Al Powder Mixture

    International Nuclear Information System (INIS)

    Eakins, D. E.; Thadhani, N. N.

    2006-01-01

    The shock-compression and reaction response of equi-volumetric micron-scale (∼50-60% dense) spherical nickel and aluminum powder mixtures is investigated in the range of the calculated crush-up pressure (P = 0.4 GPa) and up to 6 GPa. Time resolved stress measurements (using PVDF gauges) coupled with VISAR data is used to determine the shock states. Evidence of reaction or lack thereof is inferred by comparing the measured states with calculated Hugoniot state of reaction products based on the ballotechnic model proposed by Bennett and Horie, (Shock Waves 4:127-136). Post-impact micro-structural analysis of recovered material and comparison of calculated and measured product states is used to establish the criterion for reaction occurring in the shock or post-shock states

  6. Two-dimensional tantalum disulfide: controlling structure and properties via synthesis

    Science.gov (United States)

    Zhao, Rui; Grisafe, Benjamin; Krishna Ghosh, Ram; Holoviak, Stephen; Wang, Baoming; Wang, Ke; Briggs, Natalie; Haque, Aman; Datta, Suman; Robinson, Joshua

    2018-04-01

    Tantalum disulfide (TaS2) is a transition metal dichalcogenide (TMD) that exhibits phase transition induced electronic property modulation at low temperature. However, the appropriate phase must be grown to enable the semiconductor/metal transition that is of interest for next generation electronic applications. In this work, we demonstrate direct and controllable synthesis of ultra-thin 1T-TaS2 and 2H-TaS2 on a variety of substrates (sapphire, SiO2/Si, and graphene) via powder vapor deposition. The synthesis process leads to single crystal domains ranging from 20 to 200 nm thick and 1-10 µm on a side. The TaS2 phase (1T or 2H) is controlled by synthesis temperature, which subsequently is shown to control the electronic properties. Furthermore, this work constitutes the first demonstration of a metal-insulator phase transition in directly synthesized 1T-TaS2 films and domains by electronic means.

  7. Origins of Beta Tantalum in Sputtered Coatings

    National Research Council Canada - National Science Library

    Mulligan, C

    2001-01-01

    .... Some of the most recent work has attempted to relate the energetics (i.e., atom/ion energy) of the plasma to the alpha right arrow beta transition. It has been shown that the energetics of the plasma can relate to the most crucial sputtering parameters. The most significant feature of the use of plasma energy to explain the alpha right arrow beta transition is that it relates the formation of beta-tantalum to a quantifiable measure.

  8. Two-zone elastic-plastic single shock waves in solids.

    Science.gov (United States)

    Zhakhovsky, Vasily V; Budzevich, Mikalai M; Inogamov, Nail A; Oleynik, Ivan I; White, Carter T

    2011-09-23

    By decoupling time and length scales in moving window molecular dynamics shock-wave simulations, a new regime of shock-wave propagation is uncovered characterized by a two-zone elastic-plastic shock-wave structure consisting of a leading elastic front followed by a plastic front, both moving with the same average speed and having a fixed net thickness that can extend to microns. The material in the elastic zone is in a metastable state that supports a pressure that can substantially exceed the critical pressure characteristic of the onset of the well-known split-elastic-plastic, two-wave propagation. The two-zone elastic-plastic wave is a general phenomenon observed in simulations of a broad class of crystalline materials and is within the reach of current experimental techniques.

  9. 2014 NEPP Tasks Update for Ceramic and Tantalum Capacitors

    Science.gov (United States)

    Teverovsky, Alexander A.

    2014-01-01

    Presentation describes recent development in research on MnO2, wet, and polymer tantalum capacitors. Low-voltage failures in multilayer ceramic capacitors and techniques to reveal precious metal electrode (PME) and base metal electrode (BME) capacitors with cracks are discussed. A voltage breakdown technique is suggested to select high quality low-voltage BME ceramic capacitors.

  10. Synergistic helium and deuterium blistering in tungsten–tantalum composites

    International Nuclear Information System (INIS)

    Dias, M.; Mateus, R.; Catarino, N.; Franco, N.; Nunes, D.; Correia, J.B.; Carvalho, P.A.; Hanada, K.; Sârbu, C.

    2013-01-01

    Abstruct: Tungsten–tantalum composites with 10 and 20 at.% Ta were prepared by ball milling W powder with Ta fibers and by consolidating the milled materials with spark plasma sintering. The composites were implanted at room temperature with He + (30 keV with a fluence 5 × 10 21 at/m 2 ) and/or D + (15 keV with a fluence 5 × 10 21 at/m 2 ) ion beams. The materials were studied by scanning and high-resolution transmission electron microscopy, both coupled with energy dispersive X-ray spectroscopy, and by X-ray diffraction, Rutherford backscattering spectrometry and nuclear reaction analysis. The microstructure observations revealed that the milling operation resulted in severe fragmentation of the Ta fibers. Furthermore, during the consolidation process the Ta phase acted as oxygen getter and reduced the W oxide present in the original material. The surface of the tungsten–tantalum composites implanted with D + remained essentially unaltered, while the materials implanted with He + evidenced blisters on the Ta-rich regions. D retention in the composites increased with He + pre-implantation

  11. Sol–gel synthesis of tantalum oxide and phosphonic acid-modified carbon nanotubes composite coatings on titanium surfaces

    International Nuclear Information System (INIS)

    Maho, Anthony; Detriche, Simon; Delhalle, Joseph; Mekhalif, Zineb

    2013-01-01

    Carbon nanotubes used as fillers in composite materials are more and more appreciated for the outstanding range of accessible properties and functionalities they generate in numerous domains of nanotechnologies. In the framework of biological and medical sciences, and particularly for orthopedic applications and devices (prostheses, implants, surgical instruments, …), titanium substrates covered by tantalum oxide/carbon nanotube composite coatings have proved to constitute interesting and successful platforms for the conception of solid and biocompatible biomaterials inducing the osseous regeneration processes (hydroxyapatite growth, osteoblasts attachment). This paper describes an original strategy for the conception of resistant and homogeneous tantalum oxide/carbon nanotubes layers on titanium through the introduction of carbon nanotubes functionalized by phosphonic acid moieties (-P(=O)(OH) 2 ). Strong covalent C-P bonds are specifically inserted on their external sidewalls with a ratio of two phosphonic groups per anchoring point. Experimental results highlight the stronger “tantalum capture agent” effect of phosphonic-modified nanotubes during the sol–gel formation process of the deposits compared to nanotubes bearing oxidized functions (-OH, -C=O, -C(=O)OH). Particular attention is also paid to the relative impact of the rate of functionalization and the dispersion degree of the carbon nanotubes in the coatings, as well as their wrapping level by the tantalum oxide matrix material. The resulting effect on the in vitro growth of hydroxyapatite is also evaluated to confirm the primary osseous bioactivity of those materials. Chemical, structural and morphological features of the different composite deposits described herein are assessed by X-ray photoelectron spectroscopy (XPS), scanning (SEM) and transmission (TEM) electronic microscopies, energy dispersive X-rays analysis (EDX) and peeling tests. Highlights: ► Formation of tantalum/carbon nanotube

  12. Sol–gel synthesis of tantalum oxide and phosphonic acid-modified carbon nanotubes composite coatings on titanium surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Maho, Anthony [Laboratory of Chemistry and Electrochemistry of Surfaces, University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium); Fonds pour la Formation à la Recherche dans l' Industrie et dans l' Agriculture (FRIA), Rue d' Egmont 5, B-1000 Bruxelles (Belgium); Detriche, Simon; Delhalle, Joseph [Laboratory of Chemistry and Electrochemistry of Surfaces, University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium); Mekhalif, Zineb, E-mail: zineb.mekhalif@fundp.ac.be [Laboratory of Chemistry and Electrochemistry of Surfaces, University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium)

    2013-07-01

    Carbon nanotubes used as fillers in composite materials are more and more appreciated for the outstanding range of accessible properties and functionalities they generate in numerous domains of nanotechnologies. In the framework of biological and medical sciences, and particularly for orthopedic applications and devices (prostheses, implants, surgical instruments, …), titanium substrates covered by tantalum oxide/carbon nanotube composite coatings have proved to constitute interesting and successful platforms for the conception of solid and biocompatible biomaterials inducing the osseous regeneration processes (hydroxyapatite growth, osteoblasts attachment). This paper describes an original strategy for the conception of resistant and homogeneous tantalum oxide/carbon nanotubes layers on titanium through the introduction of carbon nanotubes functionalized by phosphonic acid moieties (-P(=O)(OH){sub 2}). Strong covalent C-P bonds are specifically inserted on their external sidewalls with a ratio of two phosphonic groups per anchoring point. Experimental results highlight the stronger “tantalum capture agent” effect of phosphonic-modified nanotubes during the sol–gel formation process of the deposits compared to nanotubes bearing oxidized functions (-OH, -C=O, -C(=O)OH). Particular attention is also paid to the relative impact of the rate of functionalization and the dispersion degree of the carbon nanotubes in the coatings, as well as their wrapping level by the tantalum oxide matrix material. The resulting effect on the in vitro growth of hydroxyapatite is also evaluated to confirm the primary osseous bioactivity of those materials. Chemical, structural and morphological features of the different composite deposits described herein are assessed by X-ray photoelectron spectroscopy (XPS), scanning (SEM) and transmission (TEM) electronic microscopies, energy dispersive X-rays analysis (EDX) and peeling tests. Highlights: ► Formation of tantalum

  13. Enhanced fear recall and emotional arousal in rats recovering from chronic variable stress.

    Science.gov (United States)

    McGuire, Jennifer; Herman, James P; Horn, Paul S; Sallee, Floyd R; Sah, Renu

    2010-11-02

    Emergence of posttraumatic-like behaviors following chronic trauma is of interest given the rising prevalence of combat-related posttraumatic stress disorder (PTSD). Stress associated with combat usually involves chronic traumatization, composed of multiple, single episode events occurring in an unpredictable fashion. In this study, we investigated whether rats recovering from repeated trauma in the form of chronic variable stress (CVS) express posttraumatic stress-like behaviors and dysregulated neuroendocrine responses. Cohorts of Long-Evans rats underwent a 7 day CVS paradigm followed by behavioral and neuroendocrine testing during early (16 h post CVS) and delayed (7 day) recovery time points. A fear conditioning-extinction-reminder shock paradigm revealed that CVS induces exaggerated fear recall to reminder shock, suggestive of potentiated fear memory. Rats with CVS experience also expressed a delayed expression of fearful arousal under aversive context, however, social anxiety was not affected during post-CVS recovery. Persistent sensitization of the hypothalamic-pituitary-adrenocorticotropic response to a novel acute stressor was observed in CVS exposed rats. Collectively, our data are consistent with the constellation of symptoms associated with posttraumatic stress syndrome, such as re-experiencing, and arousal to fearful contexts. The CVS-recovery paradigm may be useful to simulate trauma outcomes following chronic traumatization that is often associated with repeated combat stress. Copyright © 2010 Elsevier Inc. All rights reserved.

  14. Determination of tantalum in standard steels by INAA and absorption spectrophotometry

    Energy Technology Data Exchange (ETDEWEB)

    Obrusnik, I; Posta, S [Ustav Jaderneho Vyzkumu, Rez (Czechoslovakia)

    1978-02-14

    Two analytical methods, instrumental neutron activation analysis (INAA) and absorption spectrophotometry with malachite green, have been used for the determination of tantalum in standard steels produced by the Research Institute of CKD Prague - steels No. 167 and No. 169 with expected concentrations of Ta 0.01% and 0.03%, respectively. INAA method consisted of irradiation of steel samples (chips) in a nuclear reactor and Ge(Li) ..gamma..-ray spectrometry after a cooling period of one month. A spectrophotometric determination is based on the extraction of ionic associate of TaF/sub 6//sup -/ with malachite green into Oenzene from a solution of diluted sulphuric acid and hydrofluoric acid. The results obtained by the two methods are in a good agreement. However, INAA method is more sensitive and precise then spectrophotometry for the determination of tantalum in steels in the above-mentioned concentration ranges.

  15. Determination of tantalum in standard steels by INAA and absorption spectrophotometry

    International Nuclear Information System (INIS)

    Obrusnik, I.; Posta, S.

    1978-01-01

    Two analytical methods, instrumental neutron activation analysis (INAA) and absorption spectrophotometry with malachite green, have been used for the determination of tantalum in standard steels produced by the Research Institute of CKD Prague - steels No. 167 and No. 169 with expected concentrations of Ta 0.01% and 0.03%, respectively. INAA method consisted of irradiation of steel samples (chips) in a nuclear reactor and Ge(Li) γ-ray spectrometry after a cooling period of one month. A spectrophotometric determination is based on the extraction of ionic associate of TaF 6 - with malachite green into Oenzene from a solution of diluted sulphuric acid and hydrofluoric acid. The results obtained by the two methods are in a good agreement. However, INAA method is more sensitive and precise then spectrophotometry for the determination of tantalum in steels in the above-mentioned concentration ranges. (author)

  16. Coronal mass ejection shock fronts containing the two types of intermediate shocks

    International Nuclear Information System (INIS)

    Steinolfson, R.S.; Hundhausen, A.J.

    1990-01-01

    Numerical solutions of the time-dependent, magnetohydrodynamic (MHD) equations in two dimensions are used to demonstrate the formation of both types of intermediate shocks in a single shock front for physical conditions that are an idealization of those expected to occur in some observed coronal mass ejections. The key to producing such a shock configuration in the simulations is the use of an initial atmosphere containing a magnetic field representative of that in a coronal streamer with open field lines overlying a region of closed field lines. Previous attempts using just open field lines (perpendicular to the surface) produced shock configurations containing just one of the two intermediate shock types. A schematic of such a shock front containing both intermediate shock types has been constructed previously based solely on the known properties of MHD shocks from the Rankine-Hugoniot equations and specific requirements placed on the shock solution at points along the front where the shock normal and upstream magnetic field are aligned. The shock front also contains, at various locations along the front, a hydrodynamic (nonmagnetic) shock, a switch-on shock, and a fast shock in addition to the intermediate shocks. This particular configuration occurs when the shock front speed exceeds the upstream (preshock) intermediate wave speed but is less than a critical speed defined in the paper (equation 1) along at least some portion of the shock front. A distinctive feature of the front is that it is concave upward (away from the surface) near the region where the field in the preshock plasma is normal to the front of near the central portion of the shock front

  17. X-ray microtomography study of the spallation response in Ta-W

    International Nuclear Information System (INIS)

    McDonald, S A; Withers, P J; Cotton, M; Millett, J C F; Bourne, N K

    2014-01-01

    Measurement of the damage field resulting from spallation due to shock induced loading is an important aspect of understanding the mechanisms controlling the dynamic tensile failure process. Furthermore, the ability to observe in three-dimensions, and in a non-invasive manner, the physical damage present in a spalled sample post-impact can provide important data for predictive damage models. In the current study, the influence of peak shock stress and pulse duration on the spallation damage response in the tantalum alloy Ta-2.5% W is presented. Rear surface velocimetry (HetV) measurements from plate impact experiments have been combined with 3-D characterisation and quantification of the resulting damage evolution in the recovered targets using X-ray microtomography. Small differences in spall strength are observed - an increase in the pulse duration results in a decrease in spall strength, while spall strength increases with increase in peak shock stress. The level of damaged induced (void coalescence) is more significant for an increase in pulse duration, with a local damage volume fraction double that of the case for an increase in peak shock stress.

  18. Inferring Pre-shock Acoustic Field From Post-shock Pitot Pressure Measurement

    Science.gov (United States)

    Wang, Jian-Xun; Zhang, Chao; Duan, Lian; Xiao, Heng; Virginia Tech Team; Missouri Univ of Sci; Tech Team

    2017-11-01

    Linear interaction analysis (LIA) and iterative ensemble Kalman method are used to convert post-shock Pitot pressure fluctuations to static pressure fluctuations in front of the shock. The LIA is used as the forward model for the transfer function associated with a homogeneous field of acoustic waves passing through a nominally normal shock wave. The iterative ensemble Kalman method is then employed to infer the spectrum of upstream acoustic waves based on the post-shock Pitot pressure measured at a single point. Several test cases with synthetic and real measurement data are used to demonstrate the merits of the proposed inference scheme. The study provides the basis for measuring tunnel freestream noise with intrusive probes in noisy supersonic wind tunnels.

  19. Diffusion-Cooled Tantalum Hot-Electron Bolometer Mixers

    Science.gov (United States)

    Skalare, Anders; McGrath, William; Bumble, Bruce; LeDuc, Henry

    2004-01-01

    A batch of experimental diffusion-cooled hot-electron bolometers (HEBs), suitable for use as mixers having input frequencies in the terahertz range and output frequencies up to about a gigahertz, exploit the superconducting/normal-conducting transition in a thin strip of tantalum. The design and operation of these HEB mixers are based on mostly the same principles as those of a prior HEB mixer that exploited the superconducting/normal- conducting transition in a thin strip of niobium and that was described elsewhere.

  20. Tantalum acetabular augments in one-stage exchange of infected total hip arthroplasty: a case-control study.

    Science.gov (United States)

    Klatte, Till Orla; Kendoff, Daniel; Sabihi, Reza; Kamath, Atul F; Rueger, Johannes M; Gehrke, Thorsten

    2014-07-01

    During the one-stage exchange procedure for periprosthetic joint infection (PJI) after total hip arthroplasty (THA), acetabular defects challenge reconstructive options. Porous tantalum augments are an established tool for addressing acetabular destruction in aseptic cases, but their utility in septic exchange is unknown. This retrospective case-control study presents the initial results of tantalum augmentation during one-stage exchange for PJI. Primary endpoints were rates of re-infection and short-term complications associated with this technique. Study patients had no higher risk of re-infection with equivalent durability at early follow-up with a re-infection rate in both groups of 4%. In conclusion, tantalum augments are a viable option for addressing acetabular defects in one-stage exchange for septic THA. Further study is necessary to assess long-term durability when compared to traditional techniques for acetabular reconstruction. Copyright © 2014 Elsevier Inc. All rights reserved.

  1. Temperature measurements of shock-compressed deuterium

    International Nuclear Information System (INIS)

    Holmes, N.C.; Ross, M.; Nellis, W.J.

    1994-11-01

    The authors measured the temperatures of single and double-shocked D 2 and H 2 up to 85 GPa (0.85 Mbar) and 5,200 K. While single shock temperatures, at pressures to 23 GPa, agree well with previous models, the double shock temperatures are as much as 40% lower than predicted. This is believed to be caused by molecular dissociation, and a new model of the hydrogen EOS at extreme conditions has been developed which correctly predicts their observations. These data and model have important implications for programs which use condensed-phase hydrogen in implosion systems

  2. Grain destruction in interstellar shocks

    International Nuclear Information System (INIS)

    Seab, C.G.; Shull, J.M.

    1984-01-01

    One of the principal methods for removing grains from the Interstellar Medium is to destroy them in shock waves. Previous theoretical studies of shock destruction have generally assumed only a single size and type of grain; most do not account for the effect of the grain destruction on the structure of the shock. Earlier calculations have been improved in three ways: first, by using a ''complete'' grain model including a distribution of sizes and types of grains; second, by using a self-consistent shock structure that incorporates the changing elemental depletions as the grains are destroyed; and third, by calculating the shock-processed ultraviolet extinction curves for comparison with observations. (author)

  3. Rapid synthesis of tantalum oxide dielectric films by microwave microwave-assisted atmospheric chemical vapor deposition

    International Nuclear Information System (INIS)

    Ndiege, Nicholas; Subramanian, Vaidyanathan; Shannon, Mark A.; Masel, Richard I.

    2008-01-01

    Microwave-assisted chemical vapor deposition has been used to generate high quality, high-k dielectric films on silicon at high deposition rates with film thicknesses varying from 50 nm to 110 μm using inexpensive equipment. Characterization of the post deposition products was performed by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Auger electron spectroscopy and Raman spectroscopy. Film growth was determined to occur via rapid formation and accumulation of tantalum oxide clusters from tantalum (v) ethoxide (Ta(OC 2 H 5 ) 5 ) vapor on the deposition surface

  4. Effect of oxygen deficiency on electronic properties and local structure of amorphous tantalum oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Denny, Yus Rama [Department of Physics Education, University of Sultan Ageng Tirtayasa, Banten 42435 (Indonesia); Firmansyah, Teguh [Department of Electrical Engineering, University of Sultan Ageng Tirtayasa, Banten 42435 (Indonesia); Oh, Suhk Kun [Department of Physics, Chungbuk National University, Cheongju 28644 (Korea, Republic of); Kang, Hee Jae, E-mail: hjkang@cbu.ac.kr [Department of Physics, Chungbuk National University, Cheongju 28644 (Korea, Republic of); Yang, Dong-Seok [Department of Physics Education, Chungbuk National University, Cheongju 28644 (Korea, Republic of); Heo, Sung; Chung, JaeGwan; Lee, Jae Cheol [Analytical Engineering Center, Samsung Advanced Institute of Technology, Suwon 16678 (Korea, Republic of)

    2016-10-15

    Highlights: • The effect of oxygen flow rate on electronic properties and local structure of tantalum oxide thin films was studied. • The oxygen deficiency induced the nonstoichiometric state a-TaOx. • A small peak at 1.97 eV above the valence band side appeared on nonstoichiometric Ta{sub 2}O{sub 5} thin films. • The oxygen flow rate can change the local electronic structure of tantalum oxide thin films. - Abstract: The dependence of electronic properties and local structure of tantalum oxide thin film on oxygen deficiency have been investigated by means of X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results showed that the oxygen flow rate change results in the appearance of features in the Ta 4f at the binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV whose peaks are attributed to Ta{sup 1+}, Ta{sup 2+}, Ta{sup 3+}/Ta{sup 4+}, and Ta{sup 5+}, respectively. The presence of nonstoichiometric state from tantalum oxide (TaOx) thin films could be generated by the oxygen vacancies. In addition, XAS spectra manifested both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the decrease of oxygen deficiency.

  5. Hydroxyaromatic compounds of tantalum, tungsten, and the lighter actinides

    International Nuclear Information System (INIS)

    Gfaller, H.

    1980-01-01

    Some hydroxyaromatic compounds of the elements tantalum, tungsten, thorium and uranium were prepared as well as the basic materials for these synthesis processes, i.e. metal halides and metal alkoxides. The hydroxyaromatic compounds were studied by elemental analysis, IR spectroscopy, 1 H-NMR spectroscopy (if soluble in suitable solvents) and, in some cases, by X-ray fine structure analysis. (orig./EF) [de

  6. Mass transfer modeling on the separation of tantalum and niobium from dilute hydrofluoric media through a hollow fiber supported liquid membrane

    International Nuclear Information System (INIS)

    Buachuang, Duenphen; Ramakul, Prakorn; Leepipatpiboon, Natchanun; Pancharoen, Ura

    2011-01-01

    Highlights: → Simultaneous separation of tantalum and niobium from the mixture solution. → An extraction through a hollow fiber supported liquid membrane (HFSLM). → The effect on tantalum removal found from Aliquat 336. → The mathematical model focusing on the extraction side of the liquid membrane system was presented. → The mass transfer coefficients of the aqueous feed (k i ) and the organic membrane phase (k m ) for the system were estimated as 1.19 x 10 -5 and 1.39 x 10 -7 cm/s, respectively. → Experimental data and theoretical values were found to be in good agreement when the concentration of Aliquat336 in the membrane phase was below 4% (v/v). - Abstract: The separation of a mixture of tantalum and niobium in dilute hydrofluoric media via hollow fiber supported liquid membrane (HFSLM) was examined. Quaternary ammonium salt (Aliquat336) diluted in kerosene was used as a carrier. The various effects on the transport and separation of tantalum and niobium were studied: concentration of hydrofluoric acid in the feed solution, concentration of the carrier (Aliquat336) in the membrane phase, types of stripping solutions (NaClO 4 , thiourea and HCl) and their concentration. The extraction of tantalum in the membrane phase from 0.3 M hydrofluoric acid (HF) by 3% (v/v) Aliquat336 was achieved by leaving niobium in the feed solution. Quantitative recovery of tantalum was achieved by 0.2 M NaClO 4 . Furthermore, a mathematical model focusing on the extraction side of the liquid membrane system was presented in order to predict the concentration of tantalum at different times. The mass transfer coefficients of the aqueous feed (k i ) and the organic membrane phase (k m ) were estimated as 1.19 x 10 -5 and 1.39 x 10 -7 cm/s, respectively. Therefore, the mass transfer limiting step is the diffusion of tantalum-Aliquat336 through the liquid membrane. Moreover, mass transfer modeling was performed and the validity of the developed model evaluated. Experimental

  7. Mass transfer modeling on the separation of tantalum and niobium from dilute hydrofluoric media through a hollow fiber supported liquid membrane

    Energy Technology Data Exchange (ETDEWEB)

    Buachuang, Duenphen [Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330 (Thailand); Ramakul, Prakorn [Department of Chemical Engineering, Faculty of Engineering and Industrial Technology, Silpakorn University, Nakhon Pathom 73000 (Thailand); Leepipatpiboon, Natchanun [Chromatography and Separation Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Pancharoen, Ura, E-mail: ura.p.@chula.ac.th [Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330 (Thailand)

    2011-09-29

    Highlights: > Simultaneous separation of tantalum and niobium from the mixture solution. > An extraction through a hollow fiber supported liquid membrane (HFSLM). > The effect on tantalum removal found from Aliquat 336. > The mathematical model focusing on the extraction side of the liquid membrane system was presented. > The mass transfer coefficients of the aqueous feed (k{sub i}) and the organic membrane phase (k{sub m}) for the system were estimated as 1.19 x 10{sup -5} and 1.39 x 10{sup -7} cm/s, respectively. > Experimental data and theoretical values were found to be in good agreement when the concentration of Aliquat336 in the membrane phase was below 4% (v/v). - Abstract: The separation of a mixture of tantalum and niobium in dilute hydrofluoric media via hollow fiber supported liquid membrane (HFSLM) was examined. Quaternary ammonium salt (Aliquat336) diluted in kerosene was used as a carrier. The various effects on the transport and separation of tantalum and niobium were studied: concentration of hydrofluoric acid in the feed solution, concentration of the carrier (Aliquat336) in the membrane phase, types of stripping solutions (NaClO{sub 4}, thiourea and HCl) and their concentration. The extraction of tantalum in the membrane phase from 0.3 M hydrofluoric acid (HF) by 3% (v/v) Aliquat336 was achieved by leaving niobium in the feed solution. Quantitative recovery of tantalum was achieved by 0.2 M NaClO{sub 4}. Furthermore, a mathematical model focusing on the extraction side of the liquid membrane system was presented in order to predict the concentration of tantalum at different times. The mass transfer coefficients of the aqueous feed (k{sub i}) and the organic membrane phase (k{sub m}) were estimated as 1.19 x 10{sup -5} and 1.39 x 10{sup -7} cm/s, respectively. Therefore, the mass transfer limiting step is the diffusion of tantalum-Aliquat336 through the liquid membrane. Moreover, mass transfer modeling was performed and the validity of the

  8. [A patient with toxic shock syndrome following correction of the nasal septum].

    Science.gov (United States)

    Schweitzer, D H; Moffie, B G; van der Mey, A G; Thompson, J

    1990-11-03

    A male aged 30 suffered from toxic shock syndrome after septorhinoplasty with positioning of a tampon. Initial treatment consisted of removing the tampon and supportive care, as a result of which the patient recovered. The patient was a carrier of Staphylococcus aureus which produced toxic shock syndrome toxin-I (TSST-I). Anti-TSST-I antibodies were already found in the serum in the initial phase of the disease.

  9. Synergistic helium and deuterium blistering in tungsten–tantalum composites

    Energy Technology Data Exchange (ETDEWEB)

    Dias, M., E-mail: marta.dias@itn.pt [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Mateus, R.; Catarino, N.; Franco, N. [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Nunes, D. [CENIMAT-I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Correia, J.B. [LNEG, Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 1649-038 Lisboa (Portugal); Carvalho, P.A. [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); ICEMS, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Hanada, K. [AIST, National Institute of Advanced Industrial Science and Technology, 1-2-1 Namiki, Tsukuba, 305-8564 Ibaraki (Japan); Sârbu, C. [National Institute of Materials and Physics, 105bis Atomistilor street, 077125 Magurele-Ilfov (Romania); and others

    2013-11-15

    Abstruct: Tungsten–tantalum composites with 10 and 20 at.% Ta were prepared by ball milling W powder with Ta fibers and by consolidating the milled materials with spark plasma sintering. The composites were implanted at room temperature with He{sup +} (30 keV with a fluence 5 × 10{sup 21} at/m{sup 2}) and/or D{sup +} (15 keV with a fluence 5 × 10{sup 21} at/m{sup 2}) ion beams. The materials were studied by scanning and high-resolution transmission electron microscopy, both coupled with energy dispersive X-ray spectroscopy, and by X-ray diffraction, Rutherford backscattering spectrometry and nuclear reaction analysis. The microstructure observations revealed that the milling operation resulted in severe fragmentation of the Ta fibers. Furthermore, during the consolidation process the Ta phase acted as oxygen getter and reduced the W oxide present in the original material. The surface of the tungsten–tantalum composites implanted with D{sup +} remained essentially unaltered, while the materials implanted with He{sup +} evidenced blisters on the Ta-rich regions. D retention in the composites increased with He{sup +} pre-implantation.

  10. Application of on-line HPLC-ICP-MS for the determination of the nuclide abundances of lanthanides produced via spallation reactions in an irradiated tantalum target of a spallation neutron source

    International Nuclear Information System (INIS)

    Kerl, W.; Becker, J.S.; Dietze, H.J.

    1998-01-01

    An analytical procedure has been developed for the determination of spallation nuclides in an irradiated tantalum target using HPLC coupled on-line to ICP-MS after dissolution and separation of the tantalum matrix. Pieces of tantalum were taken from different locations of the irradiated tantalum target which had been used as the target material in a spallation neutron source. Tantalum was dissolved in a HNO 3 /HF mixture and the tantalum matrix was separated by liquid-liquid extraction so that only the spallation nuclides were left in the sample solutions. The major fraction of the spallation nuclides in the tantalum target are lanthanide metals in the μg g -1 concentration range determined in the present study. Additional reaction products are formed by the irradiation of trace impurities in the original tantalum target. The nuclide abundances of the lanthanide metals measured in the tantalum target differ significantly from the natural isotopic composition so that a lot of isobaric interferences of long-lived radionuclides and stable isotopes in the mass spectrum are to be expected. Therefore, all the lanthanide metals had to be separated chemically prior to their mass spectrometric determination. The separation of all rare earth elements was performed by ion chromatography on-line to ICP-MS. The nuclide abundances of each lanthanide were determined using a sensitive double-focusing sector field inductively coupled plasma mass spectrometer. The nuclide abundances of the lanthanides in the irradiated tantalum target calculated theoretically and the experimental results obtained by on-line HPLC-ICP-MS proved to be in good agreement. (orig.)

  11. Experimental investigation of shock wave - bubble interaction

    Energy Technology Data Exchange (ETDEWEB)

    Alizadeh, Mohsen

    2010-04-09

    In this work, the dynamics of laser-generated single cavitation bubbles exposed to lithotripter shock waves has been investigated experimentally. The energy of the impinging shock wave is varied in several steps. High-speed photography and pressure field measurements simultaneously with image acquisition provide the possibility of capturing the fast bubble dynamics under the effect of the shock wave impact. The pressure measurement is performed using a fiber optic probe hydrophone (FOPH) which operates based on optical diagnostics of the shock wave propagating medium. After a short introduction in chapter 1 an overview of the previous studies in chapter 2 is presented. The reported literatures include theoretical and experimental investigations of several configurations of physical problems in the field of bubble dynamics. In chapter 3 a theoretical description of propagation of a shock wave in a liquid like water has been discussed. Different kinds of reflection of a shock wave at an interface are taken into account. Undisturbed bubble dynamics as well as interaction between a planar shock wave and an initially spherical bubble are explored theoretically. Some physical parameters which are important in this issue such as the velocity of the shock-induced liquid jet, Kelvin impulse and kinetic energy are explained. The shock waves are generated in a water filled container by a focusing piezoelectric generator. The shock wave profile has a positive part with pulse duration of ∼1 μs followed by a longer tension tail (i.e. ∼3 μs). In chapter 4 high-speed images depict the propagation of a shock wave in the water filled tank. The maximum pressure is also derived for different intensity levels of the shock wave generator. The measurement is performed in the free field (i.e. in the absence of laser-generated single bubbles). In chapter 5 the interaction between lithotripter shock waves and laserinduced single cavitation bubbles is investigated experimentally. An

  12. Effect of arc suppression on the physical properties of low temperature dc magnetron sputtered tantalum thin films

    International Nuclear Information System (INIS)

    Subrahmanyam, A.; Valleti, Krishna; Joshi, Srikant V.; Sundararajan, G.

    2007-01-01

    Arcing is a common phenomenon in the sputtering process. Arcs and glow discharges emit electrons which may influence the physical properties of films. This article reports the properties of tantalum (Ta) thin films prepared by continuous dc magnetron sputtering in normal and arc-suppression modes. The substrate temperature was varied in the range of 300-673 K. The tantalum films were ∼1.8 μm thick and have good adherence to 316 stainless steel and single-crystal silicon substrates. The phase of the Ta thin film determines the electrical and tribological properties. The films deposited at 300 K using both methods were crystallized in a tetragonal structure (β phase) with a smooth surface (grain size of ∼10 nm) and exhibited an electrical resistivity of ∼194 μΩ cm and a hardness of ∼20 GPa. When the substrate temperature was 473 K and higher, the arc-suppression mode appears to influence the films to crystallize in the α phase with a grain size of ∼40 nm, whereas the normal power mode gave mixed phases β and α beyond 473 K, the arc-suppression mode yields larger grain sizes in the Ta thin films and the hardness decreases. These changes in the physical properties in arc-suppression mode are attributed to either the change in plasma characteristics or the energetic particle bombardment onto the substrate, or both

  13. Cation mobility in H+/Na+ ion exchange products of acid tantalum and zirconium phosphates

    International Nuclear Information System (INIS)

    Tarnopol'skij, V.A.; Yaroslavtsev, A.B.

    2000-01-01

    Ionic conductivity of Na + /H + exchange products on acid zirconium phosphate with different substitution degree and on acid tantalum phosphate, where ion exchange occurs via formation of a continuous series of solid solutions, was studied by the method of conductometry. It was ascertained that ionic conductivity decreases monotonously with growth in substitution degree of H + for Na + in acid tantalum phosphate. Anomalous increase in ionic conductivity of ion exchange products on acid zirconium phosphate with a low substitution degree has been detected for the first time. Formation of a double electric layer with a high concentration of cationic defects on the interface surface is the reason for increase in ionic conductivity [ru

  14. Characterization of a texture gradient in tantalum plate

    International Nuclear Information System (INIS)

    Wright, S.I.; Gray, G.T. III.

    1994-01-01

    Clark et al. have shown that significant texture gradients can be produced in rolled tantalum plate and that the strength of the gradient is dependent on the processing path. Texture gradients are often ignored because they are time consuming to characterize and add significant complexity to materials modeling. The variation in texture through the thickness of rolled materials is most commonly measured by sectioning samples to different depths through the thickness of the plate and then measuring the texture from these section planes by X-ray diffraction. A new technique based on automatic indexing of electron backscatter diffraction patterns in the scanning electron microscope enables spatially specific orientations to be measured in a practical manner. This technique allows spatial variations in texture to be measured directly enabling gradients in texture to be investigated in more detail than previously possible. This data can be used directly in coupled finite-element/polycrystal-plasticity models to simulate the effects of variations in texture on the plastic behavior of polycrystals. This work examines the variation in texture through the thickness of a tantalum plate and its resultant effect on the compressive deformation of samples prepared from the plate. The characterization of the texture gradient using the automatic point-by-point measurement technique mentioned above is described in detail. The effect of the gradient on the plastic response of through-thickness compression tests is also discussed

  15. Cracking and delamination of vapor-deposited tantalum films

    International Nuclear Information System (INIS)

    Fisher, R.M.; Duan, J.Z.; Liu, J.B.

    1990-01-01

    This paper reports on tantalum films which begin to crack and spall during vapor deposition on glass at a thickness of 180 nm. Islands and ribbons, 10 - 30 μm in size, delaminate by crack growth along the Ta/glass interface for several μm after which the crack penetrates into the glass to a depth of 0.5 - 1 μm and complete spalling occurs. X-ray diffraction showed that about 50% of the original bct, β-tantalum, phase had transformed to the bcc α-Ta phase. When Ta was deposited on glass that was first covered with 52 nm of copper, spalling was observed to begin at a thickness of 105 nm. In this case, the film first cracks and then peels along the Cu/glass interface and curls into scrolls indicating the presence of a small stress gradient. X-ray diffraction of the as-deposited film, and electron diffraction of ion-milled flakes, showed that the Ta films deposited on Cu-coated glass almost completely transform to bcc α-Ta. The critical thickness for delamination along the Cu/glass interface is about 1/2 that for cracking in the glass substrate when an intermediate layer of Cu is not present. All of the above findings are in good agreement with previous observations on Cr films

  16. Effect of silicon, tantalum, and tungsten doping and polarization on bioactivity of hydroxyapatite

    Science.gov (United States)

    Dhal, Jharana

    Hydroxyapatite (HAp) ceramics has important applications as bone graft because of the structural and compositional similarities with bone tissue. However, inferior osteogenic capacity to bone and poor mechanical properties have been identified to be major disadvantages of synthetic HAp compared to the living bone tissue. The objective of the current study is to evaluate the effect of doping with higher valent cations (Tungsten, tantalum, and silicon) and polarization or combination of both on change in property of doped HAp and subsequent impact its bioactivity. In vitro study with human osteoblast cells was used to investigate the influences of doping and polarization on bone cell-materials interactions. The bioactivity of doped HAp was compared with pure HAp. Effect of doping and polarization on the change in HAp was investigated by monitoring change in mineral phases, stored charge, and activation energy of HAp. Activation energy of depolarization was used to explain the possible mechanism of polarization in doped samples. Bioactivity of HAp increased when doped with tantalum and tungsten. Polarization further increased the bioactivity of tungsten- and tantalum-doped samples. Increase in bioactivity on polarized and doped samples was attributed to increase in surface energy and increase in surface wettability. Whereas, an increase in bioactivity on doped unpolarized surface was attributed to change in microstructure. Polarized charge calculated from TSDC indicates that polarized charge decreases on tantalum- and tungsten-doped HAp. The decrease in polarized charge was attributed to the presence of significant amount of different phases that may hinder the ionic motion in doped samples. However, for silicon-doped HAp, TSDC study showed no difference in the mechanism of polarization between doped and undoped samples. Increase in silicon doping decreased the grain size though mechanism is not affected by grain size. Total stored charge decreased with increase in

  17. Inter-diffusion study of rhodium and tantalum by RBS

    International Nuclear Information System (INIS)

    Nuttens, V.E.; Hubert, R.L.; Bodart, F.; Lucas, S.

    2005-01-01

    The inter-diffusion of rhodium and tantalum has been studied with the goal of synthesizing an alloy acting as a diffusion barrier for high temperature applications. Rh/Ta sandwiched samples were annealed in vacuum at temperature ranging from 800 to 900 deg. C and from 1000 to 1075 deg. C. The diffusion profiles were obtained by RBS. They suggest the formation of two clearly different phases in each temperature range considered

  18. Synthesis, Consolidation and Characterization of Sol-gel Derived Tantalum-Tungsten Oxide Thermite Composites

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes, O [Univ. of California, Davis, CA (United States)

    2010-06-01

    Energetic composite powders consisting of sol-gel (SG) derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition-tested and results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High Pressure Spark Plasma Sintering (HPSPS) technique, on the SG derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The SG derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO3) energetic composite was consolidated to a density of 9.17 g·cm-3 or 93% relative density. In addition, those samples were consolidated without significant pre-reaction of the constituents, thus retaining their stored chemical energy.

  19. Ion beam and dual ion beam sputter deposition of tantalum oxide films

    Science.gov (United States)

    Cevro, Mirza; Carter, George

    1994-11-01

    Ion beam sputter deposition (IBS) and dual ion beam sputter deposition (DIBS) of tantalum oxide films was investigated at room temperature and compared with similar films prepared by e-gun deposition. Optical properties ie refractive index and extinction coefficient of IBS films were determined in the 250 - 1100 nm range by transmission spectrophotometry and at (lambda) equals 632.8 nm by ellipsometry. They were found to be mainly sensitive to the partial pressure of oxygen used as a reactive gas in the deposition process. The maximum value of the refractive index of IBS deposited tantalum oxide films was n equals 2.15 at (lambda) equals 550 nm and the extinction coefficient of order k equals 2 X 10-4. Films deposited by e-gun deposition had refractive index n equals 2.06 at (lambda) equals 550 nm. Films deposited using DIBS ie deposition assisted by low energy Ar and O2 ions (Ea equals 0 - 300 eV) and low current density (Ji equals 0 - 40 (mu) A/cm2) showed no improvement in the optical properties of the films. Preferential sputtering occurred at Ea(Ar) equals 300 eV and Ji equals 20 (mu) A/cm2 and slightly oxygen deficient films were formed. Different bonding states in the tantalum-oxide films were determined by x-ray spectroscopy while composition of the film and contaminants were determined by Rutherford scattering spectroscopy. Tantalum oxide films formed by IBS contained relatively high Ar content (approximately equals 2.5%) originating from the reflected argon neutrals from the sputtering target while assisted deposition slightly increased the Ar content. Stress in the IBS deposited films was measured by the bending technique. IBS deposited films showed compressive stress with a typical value of s equals 3.2 X 109 dyn/cm2. Films deposited by concurrent ion bombardment showed an increase in the stress as a function of applied current density. The maximum was s approximately equals 5.6 X 109 dyn/cm2 for Ea equals 300 eV and Ji equals 35 (mu) A/cm2. All

  20. Ion-beam and dual-ion-beam sputter deposition of tantalum oxide films

    Science.gov (United States)

    Cevro, Mirza; Carter, George

    1995-02-01

    Ion-beam sputter deposition (IBS) and dual-ion-beam sputter deposition (DIBS) of tantalum oxide films was investigated at room temperature and compared with similar films prepared by e-gun deposition. The optical properties, i.e., refractive index and extinction coefficient, of IBS films were determined in the 250- to 1100-nm range by transmission spectrophotometry and at (lambda) equals 632.8 nm by ellipsometry. They were found to be mainly sensitive to the partial pressure of oxygen used as a reactive gas in the deposition process. The maximum value of the refractive index of IBS deposited tantalum oxide films was n equals 2.15 at (lambda) equals 550 nm and the extinction coefficient of order k equals 2 X 10-4. Films deposited by e-gun deposition had refractive index n 2.06 at (lambda) equals 550 nm. Films deposited using DIBS, i.e., deposition assisted by low energy Ar and O2 ions (Ea equals 0 to 300 eV) and low current density (Ji equals 0 to 40 (mu) A/cm2), showed no improvement in the optical properties of the films. Preferential sputtering occurred at Ea(Ar) equals 300 eV and Ji equals 20 (mu) A/cm2 and slightly oxygen deficient films were formed. Different bonding states in the tantalum-oxide films were determined by x-ray spectroscopy, whereas composition of the film and contaminants were determined by Rutherford backscattering spectroscopy (RBS). Tantalum oxide films formed by IBS contained relatively high Ar content (approximately equals 2.5%) originating from the reflected argon neutrals from the sputtering target whereas assisted deposition slightly increased the Ar content. Stress in the IBS-deposited films was measured by the bending technique. IBS-deposited films showed compressive stress with a typical value of s equals 3.2 X 109 dyn/cm2. Films deposited by concurrent ion bombardment showed an increase in the stress as a function of applied current density. The maximum was s approximately equals 5.6 X 109 dyn/cm2 for Ea equals 300 eV and Ji equals

  1. Converging shocks in elastic-plastic solids.

    Science.gov (United States)

    Ortega, A López; Lombardini, M; Hill, D J

    2011-11-01

    We present an approximate description of the behavior of an elastic-plastic material processed by a cylindrically or spherically symmetric converging shock, following Whitham's shock dynamics theory. Originally applied with success to various gas dynamics problems, this theory is presently derived for solid media, in both elastic and plastic regimes. The exact solutions of the shock dynamics equations obtained reproduce well the results obtained by high-resolution numerical simulations. The examined constitutive laws share a compressible neo-Hookean structure for the internal energy e=e(s)(I(1))+e(h)(ρ,ς), where e(s) accounts for shear through the first invariant of the Cauchy-Green tensor, and e(h) represents the hydrostatic contribution as a function of the density ρ and entropy ς. In the strong-shock limit, reached as the shock approaches the axis or origin r=0, we show that compression effects are dominant over shear deformations. For an isothermal constitutive law, i.e., e(h)=e(h)(ρ), with a power-law dependence e(h) is proportional to ρ(α), shock dynamics predicts that for a converging shock located at r=R(t) at time t, the Mach number increases as M is proportional to [log(1/R)](α), independently of the space index s, where s=2 in cylindrical geometry and 3 in spherical geometry. An alternative isothermal constitutive law with p(ρ) of the arctanh type, which enforces a finite density in the strong-shock limit, leads to M is proportional to R(-(s-1)) for strong shocks. A nonisothermal constitutive law, whose hydrostatic part e(h) is that of an ideal gas, is also tested, recovering the strong-shock limit M is proportional to R(-(s-1)/n(γ)) originally derived by Whitham for perfect gases, where γ is inherently related to the maximum compression ratio that the material can reach, (γ+1)/(γ-1). From these strong-shock limits, we also estimate analytically the density, radial velocity, pressure, and sound speed immediately behind the shock. While the

  2. Effect of tantalum on α-martensite crystal structure in Co-Ta alloy

    International Nuclear Information System (INIS)

    Skorodzievskij, V.S.; Ustinov, A.I.; Chuistov, K.V.

    1985-01-01

    Changes in the crystal structure of α-martensite, formed during Co-Ta alloy hardening from the region of a homogeneous solid solution, are investigated by X-ray analysis methods. In case of increasing tantalum content in the alloy, intensity redistribution of X-ray scattering along the direction of the reverse space of H-K not equal to 3N (N=0, +-1, +-2...) type is fixed, which appears, depending on concentration, in continuous displacement of maxima from positions being characteristic for the initial 2H structure, as well as in occurring additional maxima and in changing the ratio between them by ipteΣity. For limiting values of tantalum concentration, where β → α-transformations are still observed, the number of intepsity maxima and their positions an the period of α-martensite reverse lattice recurrence period is closer to the location of 15R 1 -structure reverse structure unit

  3. Oscillating nonlinear acoustic shock waves

    DEFF Research Database (Denmark)

    Gaididei, Yuri; Rasmussen, Anders Rønne; Christiansen, Peter Leth

    2016-01-01

    We investigate oscillating shock waves in a tube using a higher order weakly nonlinear acoustic model. The model includes thermoviscous effects and is non isentropic. The oscillating shock waves are generated at one end of the tube by a sinusoidal driver. Numerical simulations show that at resona......We investigate oscillating shock waves in a tube using a higher order weakly nonlinear acoustic model. The model includes thermoviscous effects and is non isentropic. The oscillating shock waves are generated at one end of the tube by a sinusoidal driver. Numerical simulations show...... polynomial in the space and time variables, we find analytical approximations to the observed single shock waves in an infinitely long tube. Using perturbation theory for the driven acoustic system approximative analytical solutions for the off resonant case are determined....

  4. Fast-neutrons incident on rotors: Tantalum

    International Nuclear Information System (INIS)

    Smith, Alan B.

    2005-01-01

    Mono-energetic neutrons are elastically and inelastically scattered from elemental tantalum at incident energies of ∼0.3-10.0 MeV. These experimental results are augmented with neutron total-cross-section and additional neutron-scattering data from the literature to form a composite experimental database. The latter is interpreted in the context of optical-statistical and coupled-channels models, including consideration of collective rotations, dispersion effects and other physical properties. The results are compared with those of similar processes in this region of collective nuclei. A regional model is proposed for the interpretation and prediction of such interactions. The model and the experimental results are compared with corresponding values given in ENDF/B-VI

  5. Properties of Coronal Shocks at the Origin of SEP events Observed by Only One Single Spacecraft

    Science.gov (United States)

    Lario, D.; Kwon, R.

    2017-12-01

    The simultaneous observation of solar energetic particle (SEP) events by multiple spacecraft distributed in the interplanetary medium depends not only on the spatial separation among the different spacecraft, but also on the properties of the particle sources and the characteristics of the SEP transport in interplanetary space. Among the SEP events observed by STEREO-A, STEREO-B and/or near-Earth spacecraft during solar cycle 24, we select SEP events observed by a single spacecraft (specifically, the SEP events observed only by near-Earth spacecraft on 2012 April 5, 2011 September 4, and 2013 August 17). We analyze whether the properties of the coronal shock associated with the origin of the events (as seen in extreme-ultraviolet and white-light coronal images) differ from those associated with SEP events observed by two or three spacecraft. For the selected events we find that the associated CMEs are, in general, narrower than those associated with SEP events observed by two or three spacecraft. The confined extension of the parent coronal shock and the absence of magnetic connection between distant spacecraft and the regions of the expanding coronal shock able to efficiently accelerate SEPs seem to be the conditions leading to intense SEP events observed only over narrow regions of interplanetary space by spacecraft magnetically connected to regions close to the parent eruption site. Weak and gradual intensity increases observed in extended regions of space might involve transport processes and/or later connections established with interplanetary shocks. Systematic analyses of a larger number of events are required before drawing firm conclusions.

  6. Equation of State and Viscosity of Tantalum and Iron from First Principles

    Science.gov (United States)

    Miljacic, Ljubomir; Demers, Steven; van de Walle, Axel

    2011-03-01

    To understand and model at continuum level the high-energy-density dynamic response in transition metals like Tantalum and Iron, as it arises in hypervelocity impact experiments, an accurate prediction of the underlying thermodynamic and kinetic properties for a range of temperatures and pressures is of critical importance. The relevant time scale of atomic motion in a dense gas, liquid, and solid is accessible with ab-initio Molecular Dynamics (MD) simulations. We calculate EoS for Ta and Fe via Thermodynamical Integration in 2D (V,T) phase space throughout different single and two-component phases. To reduce the ab-initio demand in selected regions of the space, we fit available gas-liquid data to the Peng-Robinson model and treat the solid phase within the Boxed-quasi-harmonic approximation. In the fluid part of the 2D phase space, we calculate shear viscosity via Green-Kubo relations, as time integration of the stress autocorrelation function.

  7. Electrochemical Properties of Transparent Conducting Films of Tantalum-Doped Titanium Dioxide

    Czech Academy of Sciences Publication Activity Database

    Krýsová, Hana; Mazzolini, P.; Casari, C. S.; Russo, V.; Li Bassi, A.; Kavan, Ladislav

    2017-01-01

    Roč. 232, APR 2017 (2017), s. 44-53 ISSN 0013-4686 R&D Projects: GA ČR GA13-07724S Institutional support: RVO:61388955 Keywords : titanium dioxide * tantalum doping * electrochemistry Subject RIV: CG - Electrochemistry OBOR OECD: Electrochemistry (dry cells, batteries, fuel cells, corrosion metals, electrolysis) Impact factor: 4.798, year: 2016

  8. Shear strength of shock-loaded polycrystalline tungsten

    International Nuclear Information System (INIS)

    Asay, J.R.; Chhabildas, L.C.; Dandekar, D.P.

    1980-01-01

    Previous experiments have suggested that tungsten undergoes a significant loss of shear strength when shock loaded to stresses greater than 7 GPa. In order to investigate this effect in more detail, a series of experiments was conducted in which polycrystalline tungsten was first shock loaded to approximately 10 GPa and then either unloaded or reloaded from the shocked state. Analysis of measured time-resolved wave profiles indicates that during initial compression to 9.7 GPa, the shear stress in polycrystalline tungsten increases to a maximum value of 1.1 GPA near a longitudinal stress of 5 GPa, but decreases to a final value of 0.8 GPa for stresses approaching 10 GPa. During reloading from a longitudinal stress of 9.7 GPa to a final value of approx.14 GPa, the shear stress increases to a peak value of 1.2 GPa and softens to 1.0 GPa in the final state. During unloading from the shocked state, the initial response is elastic with a strong Baushinger effect. Examination of a recovered sample shows evidence for both deformation slipping and twinning, which may be responsible for the observed softening

  9. Shock therapy: Gris Gun's shock absorber can take the punch

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    2000-04-01

    A newly developed shock impedance tool that isolates downhole tools that measure the effects of well stimulation techniques from being damaged by the violent shaking caused by various well stimulation techniques which combine perforating and propellant technology in a single tool, is discussed. The shock exerted by a perforating gun can exceed 25,000 G forces within 100 to 300 milliseconds, may damage or even destroy the sensitive electronics housed in the various recorders that record data about fracture gradients, permeability and temperature. The shock absorber developed by Tesco Gris Gun and Computalog, incorporates the mechanics of a piston style shock absorber in combination with a progressive spring stack and energy-dampening silicone oil chambers. The end results is an EUE 'slim line' assembly that is adaptable between the gun perforating string and the electronic equipment. It is typically attached below, reducing the shock load by as much as 90 per cent. The shock absorber is now available commercially through Gris Gun's exclusive distributorship. An improved version, currently under development, will be used for wireline perforating and tubing-conveyed perforating applications. 2 figs.

  10. Direct electroplating of copper on tantalum from ionic liquids in high vacuum: origin of the tantalum oxide layer.

    Science.gov (United States)

    Schaltin, Stijn; D'Urzo, Lucia; Zhao, Qiang; Vantomme, André; Plank, Harald; Kothleitner, Gerald; Gspan, Christian; Binnemans, Koen; Fransaer, Jan

    2012-10-21

    In this paper, it is shown that high vacuum conditions are not sufficient to completely remove water and oxygen from the ionic liquid 1-ethyl-3-methylimidazolium chloride. Complete removal of water demands heating above 150 °C under reduced pressure, as proven by Nuclear Reaction Analysis (NRA). Dissolved oxygen gas can only be removed by the use of an oxygen scavenger such as hydroquinone, despite the fact that calculations show that oxygen should be removed completely by the applied vacuum conditions. After applying a strict drying procedure and scavenging of molecular oxygen, it was possible to deposit copper directly on tantalum without the presence of an intervening oxide layer.

  11. Investigations on the density fluctuations of deuterium in niobium and tantalum by means of energy resolving neutron small-angle scattering

    International Nuclear Information System (INIS)

    Muenzing, W.

    1978-01-01

    Density fluctuations of solved deuterium were measured by means of small angle scattering ob subthermal neutrons at deuterated niobium and tantalum single crystals between temperatures of 340 and 640 K. The concentrations were varied at the NbD between c = 0.10 and c = 0.53 (atomic ratio D-atom / Nb-atom). The center point was at the critical concentration of c = 0.31. In TaD there was only one concentration c = 0.14 (D-atoms / Ta-atoms) measured. At the critical point of Tsub(c) approx. 455 K no diverging critical scattering intensity was observed. (orig./HSI) [de

  12. Effect of Preconditioning and Soldering on Failures of Chip Tantalum Capacitors

    Science.gov (United States)

    Teverovsky, Alexander A.

    2014-01-01

    Soldering of molded case tantalum capacitors can result in damage to Ta205 dielectric and first turn-on failures due to thermo-mechanical stresses caused by CTE mismatch between materials used in the capacitors. It is also known that presence of moisture might cause damage to plastic cases due to the pop-corning effect. However, there are only scarce literature data on the effect of moisture content on the probability of post-soldering electrical failures. In this work, that is based on a case history, different groups of similar types of CWR tantalum capacitors from two lots were prepared for soldering by bake, moisture saturation, and longterm storage at room conditions. Results of the testing showed that both factors: initial quality of the lot, and preconditioning affect the probability of failures. Baking before soldering was shown to be effective to prevent failures even in lots susceptible to pop-corning damage. Mechanism of failures is discussed and recommendations for pre-soldering bake are suggested based on analysis of moisture characteristics of materials used in the capacitors' design.

  13. NEPP Evaluation of Automotive Grade Tantalum Chip Capacitors

    Science.gov (United States)

    Sampson, Mike; Brusse, Jay

    2018-01-01

    Automotive grade tantalum (Ta) chip capacitors are available at lower cost with smaller physical size and higher volumetric efficiency compared to military/space grade capacitors. Designers of high reliability aerospace and military systems would like to take advantage of these attributes while maintaining the high standards for long-term reliable operation they are accustomed to when selecting military-qualified established reliability tantalum chip capacitors (e.g., MIL-PRF-55365). The objective for this evaluation was to assess the long-term performance of off-the-shelf automotive grade Ta chip capacitors (i.e., manufacturer self-qualified per AEC Q-200). Two (2) lots of case size D manganese dioxide (MnO2) cathode Ta chip capacitors from 1 manufacturer were evaluated. The evaluation consisted of construction analysis, basic electrical parameter characterization, extended long-term (2000 hours) life testing and some accelerated stress testing. Tests and acceptance criteria were based upon manufacturer datasheets and the Automotive Electronics Council's AEC Q-200 qualification specification for passive electronic components. As-received a few capacitors were marginally above the specified tolerance for capacitance and ESR. X-ray inspection found that the anodes for some devices may not be properly aligned within the molded encapsulation leaving less than 1 mil thickness of the encapsulation. This evaluation found that the long-term life performance of automotive grade Ta chip capacitors is generally within specification limits suggesting these capacitors may be suitable for some space applications.

  14. Antibacterial properties and cytocompatibility of tantalum oxide coatings with different silver content

    International Nuclear Information System (INIS)

    Huang, Heng-Li; Chang, Yin-Yu; Chen, Hung-Jui; Chou, Yu-Kai; Lai, Chih-Ho; Chen, Michael Y. C.

    2014-01-01

    Tantalum (Ta) oxides and their coatings have been proved to increase their applications in the biomedical fields by improving osseointegration and wear resistance. In this study, Ta oxide coatings containing different proportions of Ag are deposited on SS304 materials. A twin-gun magnetron sputtering system is used to deposit the tantalum oxide-Ag coating. In this study, Staphylococcus aureus, which exhibits physiological commensalism on the human skin, nares, and mucosal and oral areas, is chosen as the model for in vitro antibacterial analyses via a fluorescence staining method using Syto9. The cytocompatibility and adhesive morphology of human skin fibroblast cells (CCD-966SK) on the coatings are also determined by using the microculture tetrazolium assay. This study shows that Ta 2 O 5 and Ta 2 O 5 -Ag coatings with 12.5 at. % of Ag exhibit improved antibacterial effects against S. aureus and have good skin fibroblast cell cellular biocompatibility

  15. Antibacterial properties and cytocompatibility of tantalum oxide coatings with different silver content

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Heng-Li [School of Dentistry, China Medical University, Taichung 404, Taiwan (China); Chang, Yin-Yu, E-mail: yinyu@mail2000.com.tw; Chen, Hung-Jui; Chou, Yu-Kai [Department of Mechanical and Computer-Aided Engineering, National Formosa University, Yunlin 632, Taiwan (China); Lai, Chih-Ho [School of Medicine, China Medical University, Taichung 404, Taiwan (China); Chen, Michael Y. C. [Division of Oral and Maxillofacial Surgery, China Medical University Hospital, Taichung 404, Taiwan (China)

    2014-03-15

    Tantalum (Ta) oxides and their coatings have been proved to increase their applications in the biomedical fields by improving osseointegration and wear resistance. In this study, Ta oxide coatings containing different proportions of Ag are deposited on SS304 materials. A twin-gun magnetron sputtering system is used to deposit the tantalum oxide-Ag coating. In this study, Staphylococcus aureus, which exhibits physiological commensalism on the human skin, nares, and mucosal and oral areas, is chosen as the model for in vitro antibacterial analyses via a fluorescence staining method using Syto9. The cytocompatibility and adhesive morphology of human skin fibroblast cells (CCD-966SK) on the coatings are also determined by using the microculture tetrazolium assay. This study shows that Ta{sub 2}O{sub 5} and Ta{sub 2}O{sub 5}-Ag coatings with 12.5 at. % of Ag exhibit improved antibacterial effects against S. aureus and have good skin fibroblast cell cellular biocompatibility.

  16. Isentropic/shock compression and recovery methodology for materials using high-amplitude laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Maddox, B.R., E-mail: maddox3@llnl.gov [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Park, H.-S., E-mail: park1@llnl.gov [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Lu, C.-H., E-mail: chiahuilu@gmail.com [University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093 (United States); Remington, B.A., E-mail: remington2@llnl.gov [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Prisbrey, S., E-mail: prisbrey1@llnl.gov [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Kad, B., E-mail: bkad@ucsd.edu [University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093 (United States); Luo, R., E-mail: luorwga@gmail.com [General Atomics, 3483 Dunhill Street, San Diego, CA 92121-1200 (United States); Meyers, M.A., E-mail: mameyers@eng.ucsd.edu [University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093 (United States)

    2013-08-20

    Abstarct: A new method of subjecting samples to high-amplitude laser pulses with durations in the ns range and recovering them for characterization is presented. It is applied to tantalum monocrystals and nanocrystals that are subjected to controlled and prescribed ramp loading configurations, creating a quasi-isentropic loading in the front that is retained up to 40 μm into the specimen. This is enabled by the use of a reservoir into which six laser beams impinge simultaneously, thereby creating plasma in a reservoir, from which the pulse is launched into the metal. This technique enables, with proper wave trapping devices, the recovery of the specimens for subsequent characterization. Successful experiments conducted in the Laboratory for Laser Energetics, U. of Rochester, generated pressure pulses with initial amplitudes ranging from 15 to 110 GPa and initial durations of ∼3 ns. The quasi-isotropic loading minimizes thermal effects at the front surface. The compression history of the recovered samples is measured using velocity interferometry from an Al-coated LiF witness target on the same shot driven by a separate, but equivalent set of laser beams. These experimental measurements are compared with computations using a radiation hydrodynamics code. Recovered samples are investigated using optical, scanning, and transmission electron microscopy. The laser damage to the surface is characterized.

  17. Diffusive Shock Acceleration and Turbulent Reconnection

    Science.gov (United States)

    Garrel, Christian; Vlahos, Loukas; Isliker, Heinz; Pisokas, Theophilos

    2018-05-01

    Diffusive Shock Acceleration (DSA) cannot efficiently accelerate particles without the presence of self-consistently generated or pre-existing strong turbulence (δB/B ˜ 1) in the vicinity of the shock. The problem we address in this article is: if large amplitude magnetic disturbances are present upstream and downstream of a shock then Turbulent Reconnection (TR) will set in and will participate not only in the elastic scattering of particles but also in their heating and acceleration. We demonstrate that large amplitude magnetic disturbances and Unstable Current Sheets (UCS), spontaneously formed in the strong turbulence in the vicinity of a shock, can accelerate particles as efficiently as DSA in large scale systems and on long time scales. We start our analysis with "elastic" scatterers upstream and downstream and estimate the energy distribution of particles escaping from the shock, recovering the well known results from the DSA theory. Next we analyze the additional interaction of the particles with active scatterers (magnetic disturbances and UCS) upstream and downstream of the shock. We show that the asymptotic energy distribution of the particles accelerated by DSA/TR has very similar characteristics with the one due to DSA alone, but the synergy of DSA with TR is much more efficient: The acceleration time is an order of magnitude shorter and the maximum energy reached two orders of magnitude higher. We claim that DSA is the dominant acceleration mechanism in a short period before TR is established, and then strong turbulence will dominate the heating and acceleration of the particles. In other words, the shock serves as the mechanism to set up a strongly turbulent environment, in which the acceleration mechanism will ultimately be the synergy of DSA and TR.

  18. Yield strength of molybdenum, tantalum and tungsten at high strain rates and very high temperatures

    International Nuclear Information System (INIS)

    Škoro, G.P.; Bennett, J.R.J.; Edgecock, T.R.; Booth, C.N.

    2012-01-01

    Highlights: ► New experimental data on the yield strength of molybdenum, tantalum and tungsten. ► High strain rate effects at record high temperatures (up to 2700 K). ► Test of the consistency of the Zerilli–Armstrong model at very high temperatures. - Abstract: Recently reported results of the high strain rate, high temperature measurements of the yield strength of tantalum and tungsten have been analyzed along with new experimental results on the yield strength of molybdenum. Thin wires are subjected to high stress by passing a short, fast, high current pulse through a thin wire; the amplitude of the current governs the stress and the repetition rate of the pulses determines the temperature of the wire. The highest temperatures reached in the experiments were 2100 °C (for molybdenum), 2250 °C (for tantalum) and 2450 °C (for tungsten). The strain-rates in the tests were in the range from 500 to 1500 s −1 . The parameters for the constitutive equation developed by Zerilli and Armstrong have been determined from the experimental data and the results have been compared with the data obtained at lower temperatures. An exceptionally good fit is obtained for the deformation of tungsten.

  19. Optimum deposition, structure, and properties of tantalum oxide films

    International Nuclear Information System (INIS)

    Lin, Y.C.

    1985-01-01

    Amorphous, ductile, and uniform Ta 2 O 5 films that acted as diffusion barriers were developed by sputter depositing Ta metal on Al single crystals (99.99%) and subsequently anodizing these thin films. The morphology, microstructure, composition and properties were characterized by scanning and transmission electron microscopy, surface and Fourier transform infrared spectroscopy, X-ray diffraction, and fluorescence. Superior corrosion resistance in a water saturated Cl 2 atmosphere was provided by Ta 2 O 5 coating on Al single crystal substrates but not on Al alloys. The strong Ta-O bond, the non-porous nature of the film and good adhesion to the substrate are attributed to the outstanding corrosion resistance of these oxide coatings. Al alloy surfaces are not protected, since the anodic film formed over grain boundaries, processing lines and emergent precipitates is poorly adherent, thus providing loci for corrosion. These problems were eliminated by casting a 400 A layer of tantalum oxyhydroxide polymer from ethanol solution onto Al substrate and curing to a Ta 2 O 5 layer that effectively resisted attack by wet Cl 2 . The mechanical properties of Ta 2 O 5 films on Al alloys were studied at various pH's by in-situ fatigue loading coupled with electrochemical measurements of corrosion potential and corrosion current. These results indicate the fatigue resistance of this oxide film effectively protects the underlying metal from strong HCl solution attack. The very unusual ductility and high corrosion resistance of Ta 2 O 5 films could be related to the graphite-like structure that exists in the amorphous state of this oxide

  20. The development of fast tantalum foil targets for short-lived isotopes

    CERN Document Server

    Bennett, J R J; Drumm, P V; Ravn, H L

    2003-01-01

    The development of fast tantalum foil targets for short-lived isotopes was discussed. It was found that the effusion was faster but the diffusion out of the foils was a limiting factor. The performance of the targets at ISOLDE with beams of **1**1Li, **1**2Be and **1**4Be was also analyzed. (Edited abstract) 13 Refs.

  1. In situ production of tantalum carbide nanodispersoids in a copper matrix by reactive milling and hot extrusion

    Energy Technology Data Exchange (ETDEWEB)

    Manotas-Albor, Milton, E-mail: manotasm@uninorte.edu.co [Grupo de Investigación en Física Aplicada, Departamento de Física, Universidad del Norte, Km. 5 vía a Puerto Colombia, Barranquilla (Colombia); Departamento de Ingeniería Mecánica, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Beauchef 850, Santiago (Chile); Vargas-Uscategui, Alejandro [Laboratorio de Materiales a Nanoescala, Departamento de Ciencia de los Materiales, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Tupper Av. 2069, Santiago (Chile); Palma, Rodrigo [Departamento de Ingeniería Mecánica, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Beauchef 850, Santiago (Chile); Mosquera, Edgar [Laboratorio de Materiales a Nanoescala, Departamento de Ciencia de los Materiales, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Tupper Av. 2069, Santiago (Chile)

    2014-06-15

    Highlights: • Tantalum carbide nanodispersoids were obtained in a copper matrix. • Nanodispersoids were obtained by means of reactive milling followed by hot extrusion. • Hexane was used as the liquid medium for the reactive mechanical alloying process. • Hexane provides the carbon (C) needed for the process. • The reaction of tantalum carbide formation takes place in the hot extrusion. - Abstract: This paper presents a study of the in situ production of tantalum carbide nanodispersoids in a copper matrix. The copper matrix composites were produced by means of reactive milling in hexane (C{sub 6}H{sub 14}) followed by hot extrusion. The composite materials were characterized by means of optical emission spectroscopy (OES), X-ray fluorescence (XRF), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Vickers micro-hardness. The effect of milling time was analyzed in 10, 20 and 30 h in a composite with a nominal composition Cu–5 vol.% TaC. A systematic increase of the dislocations density and the carbon concentration were observed when the milling time was increased, whereas the crystallite size of the composite matrix decreased. The material milled for 30 h and hot-extruded showed a density of 9037 kg m{sup −3} (98.2% densification) and a softening resistance of 204 HV; however the latter value showed an abrupt drop after an annealing treatment at 923 K for 1 h. Finally, the TEM analysis showed the presence of tantalum carbide (Ta{sub 4}C{sub 3}) nanodispersoids.

  2. Elastic-plastic collapse of super-elastic shock waves in face-centered-cubic solids

    International Nuclear Information System (INIS)

    Zhakhovsky, Vasily V; Demaske, Brian J; Oleynik, Ivan I; Inogamov, Nail A; White, Carter T

    2014-01-01

    Shock waves in the [110] and [111] directions of single-crystal Al samples were studied using molecular dynamics (MD) simulations. Piston-driven simulations were performed to investigate the split shock-wave regime. At low piston velocities, the material is compressed initially to a metastable over-compressed elastic state leading to a super-elastic single shock wave. This metastable elastic state later collapses to a plastic state resulting in the formation of a two-wave structure consisting of an elastic precursor followed by a slower plastic wave. The single two-zone elastic-plastic shock-wave regime appearing at higher piston velocities was studied using moving window MD. The plastic wave attains the same average speed as the elastic precursor to form a single two-zone shock wave. In this case, repeated collapse of the highly over-compressed elastic state near the plastic shock front produces ultrashort triangle pulses that provide the pressure support for the leading elastic precursor.

  3. Environment sensitive embedding energies of impurities, and grain boundary stability in tantalum

    International Nuclear Information System (INIS)

    Krasko, G.L.

    1996-01-01

    Metalloid impurities have a very low solubility in tantalum, and therefore prefer to segregate at the grain boundaries (GBs). In order to analyze the energetics of the impurities on the tantalum GB, the LMTO calculations were performed on a simple 8-atom supercell emulating a typical (capped trigonal prism) GB environment. The so-called environment-sensitive embedding energies were calculated for hydrogen, boron, carbon, nitrogen, oxygen, phosphorus, and sulphur, as a function of the electron charge density due to the host atoms at the impurity site. The calculations showed that, at the electron density typical of a GB, carbon has the lowest energy (followed by Nitrogen and Boron) and thus would compete with the other impurities for the site on the GB, tending to displace them from the GB. The above energies were then used in a modified Finnis-Sinclair embedded atom approach for calculating the cohesive energies and the equilibrium interplanar distances in the vicinity of a (111) Σ3 tilt GB plane, both for the clean GB and that with an impurity. These distances were found to oscillate, returning to the value corresponding to the equilibrium spacing between (111) planes in bulk BCC tantalum by the 10th--12th plane off the GB. Carbon, nitrogen and boron somewhat dampen the deformation wave (making the oscillations less than in the clean GB), while oxygen, phosphorus and sulphur result in an increase of the oscillations. The cohesive energies follow the same trend, the GB with carbon being the most stable. Thus, carbon, nitrogen and boron may be thought of as being cohesion enhancers, while oxygen, phosphorus and sulphur result in decohesion effects

  4. Measurements of the Shock Release Of Quartz and Paralyene-N

    Science.gov (United States)

    Hawreliak, James; Karasik, Max; Oh, Jaechul; Aglitskiy, Yefim

    2017-06-01

    The shock and release properties of Quartz and hydrocarbons are important to high energy density (HED) research and inertial confinement fusion (ICF) science. The bulk of HED material research studies single shock or multiple shock conditions. The challenge with measuring release properties is unlike shocks which have a single interface from which to measure the properties, the release establishes gradients in the sample. The streaked x-ray imaging capability of the NIKE laser allow the interface between quartz and CH to be measured during the release, giving measurements of the interface velocity and CH density. Here, we present experimental results from the NIKE laser where quartz and parylene-N are shock compressed to high pressure and temperature and the release state is measured through x-ray imaging. The shock state is characterized by shock front velocity measurements using VISAR and the release state is characterized by using side-on streaked x-ray radiography Work supported by DOE/NNSA.

  5. Tantalum coating on TiO2 nanotubes induces superior rate of matrix mineralization and osteofunctionality in human osteoblasts

    International Nuclear Information System (INIS)

    Frandsen, Christine J.; Brammer, Karla S.; Noh, Kunbae; Johnston, Gary; Jin, Sungho

    2014-01-01

    Nanostructured surface geometries have been the focus of a multitude of recent biomaterial research, and exciting findings have been published. However, only a few publications have directly compared nanostructures of various surface chemistries. The work herein directly compares the response of human osteoblast cells to surfaces of identical nanotube geometries with two well-known orthopedic biomaterials: titanium oxide (TiO 2 ) and tantalum (Ta). The results reveal that the Ta surface chemistry on the nanotube architecture enhances alkaline phosphatase activity, and promotes a ∼ 30% faster rate of matrix mineralization and bone-nodule formation when compared to results on bare TiO 2 nanotubes. This study implies that unique combinations of surface chemistry and nanostructure may influence cell behavior due to distinctive physico-chemical properties. These findings are of paramount importance to the orthopedics field for understanding cell behavior in response to subtle alterations in nanostructure and surface chemistry, and will enable further insight into the complex manipulation of biomaterial surfaces. With increased focus in the field of orthopedic materials research on nanostructured surfaces, this study emphasizes the need for careful and systematic review of variations in surface chemistry in concurrence with nanotopographical changes. - Highlights: • A TiO 2 nanotube surface structure was coated with tantalum. • Osteoblast cell response was compared between the tantalum coated and as-formed TiO 2 nanotube surface. • We observed superior rates of bone matrix mineralization and osteoblast maturation on the tantalum coated nanotube surface

  6. Shock pressure estimation in basement rocks of the Chicxulub impact crater using cathodoluminescence spectroscopy of quartz

    Science.gov (United States)

    Tomioka, N.; Tani, R.; Kayama, M.; Chang, Y.; Nishido, H.; Kaushik, D.; Rae, A.; Ferrière, L.; Gulick, S. P. S.; Morgan, J. V.

    2017-12-01

    The Chicxulub impact structure, located in the northern Yucatan Peninsula, Mexico, was drilled by the joint IODP-ICDP Expedition 364 in April-May 2016. This expedition is the first attempt to obtain materials from the topographic peak ring within the crater previously identified by seismic imaging. A continuous core was successfully recovered from the peak ring at depths between 505.7 and 1334.7 mbsf. Uplifted, fractured, and shocked granitic basement rocks forming the peak ring were found below, in the impact breccia and impact melt rock unit (747.0-1334.7 mbsf; Morgan et al. 2016). In order to constrain impact crater formation, we investigated shock pressure distribution in the peak-ring basement rocks. Thin sections of the granitic rocks were prepared at intervals of 60 m. All the samples contains shocked minerals, with quartz grains frequently showing planar deformation features (PDFs). We determined shock pressures based on the cathodoluminescence (CL) spectroscopy of quartz. The strong advantage of the CL method is its applicability to shock pressure estimation for individual grains for both quartz and diaplectic SiO2 glass with high-spatial resolution ( 1 μm) (Chang et al. 2016). CL spectra of quartz shows a blue emission band caused by shock-induced defect centers, where its intensity increases with shock pressure. A total of 108 quartz grains in ten thin sections were analyzed using a scanning electron microscope with a CL spectrometer attached (an acceleration voltage of 15 kV and a beam current of 2 nA were used). Natural quartz single crystals, which were experimentally shocked at 0-30 GPa, were used for pressure calibration. CL spectra of all the quartz grains in the basement rocks showed broad blue emission band at the wavelength range of 300-500 nm and estimated shock pressures were in the range of 15-20 GPa. The result is consistent with values obtained from PDFs analysis in quartz using the universal stage (Ferrière et al. 2017; Rae et al. 2017

  7. Relative Shock Effects in Mixed Powders of Calcite, Gypsum, and Quartz: A Calibration Scheme from Shock Experiments

    Science.gov (United States)

    Bell, Mary S.

    2009-01-01

    The shock behavior of calcite and gypsum is important in understanding the Cretaceous/Tertiary event and other terrestrial impacts that contain evaporite sediments in their targets. Most interest focuses on issues of devolatilization to quantify the production of CO2 or SO2 to better understand their role in generating a temporary atmosphere and its effects on climate and biota [e.g., papers in 1,2,3,4]. Devolatilization of carbonate is also important because the dispersion and fragmentation of ejecta is strongly controlled by the expansion of large volumes of gas during the impact process as well [5,6]. Shock recovery experiments for calcite yield seemingly conflicting results: early experimental devolatilization studies [7,8,9] suggested that calcite was substantially outgassed at 30 GPa (> 50%). However, the recent petrographic work of [10,11,12] presented evidence that essentially intact calcite is recovered from 60 GPa experiments. [13] reported results of shock experiments on anhydrite, gypsum, and mixtures of those phases with silica. Their observations indicate little or no devolatilization of anhydrite shocked to 42 GPa and that the fraction of sulfur, by mass, that degassed is approx.10(exp -2) of theoretical prediction. In another (preliminary) report of shock experiments on calcite, anhydrite, and gypsum, [14] observe calcite recrystallization when shock loaded at 61 GPa, only intensive plastic deformation in anhydrite shock loaded at 63 GPa, and gypsum converted to anhydrite when shock loaded at 56 GPa. [15] shock loaded anhydrite and quartz to a peak pressure of 60 GPa. All of the quartz grains were trans-formed to glass and the platy anhydrite grains were completely pseudomorphed by small crystallized anhydrite grains. However, no evidence of interaction between the two phases could be observed and they suggest that recrystallization of anhydrite grains is the result of a solid state transformation. [16] reanalyzed the calcite and anhydrite shock

  8. Texture evolution in upset-forged P/M and wrought tantalum: Experimentation and modeling

    International Nuclear Information System (INIS)

    Bingert, J.F.; Desch, P.B.; Bingert, S.R.; Maudlin, P.J.; Tome, C.N.

    1997-11-01

    Preferred orientations in polycrystalline materials can significantly affect their physical and mechanical response through the retention of anisotropic properties inherent to the single crystal. In this study the texture evolution in upset-forged PIM and wrought tantalum was measured as a function of initial texture, compressive strain, and relative position in the pressing. A / duplex fiber texture parallel to the compression axis was generally observed, with varying degrees of a radial component evident in the wrought material. The development of deformation textures derives from restricted crystallographic slip conditions that generate lattice rotations, and these grain reorientations can be modeled as a function of the prescribed deformation gradient. Texture development was simulated for equivalent deformations using both a modified Taylor approach and a viscoplastic self-consistent (VPSC) model. A comparison between the predicted evolution and experimental results shows a good correlation with the texture components, but an overly sharp prediction at large strains from both the Taylor and VPSC models

  9. The effect of yttrium addition on oxidation of a sputtered nanocrystalline coating with moderate amount of tantalum in composition

    International Nuclear Information System (INIS)

    Wang, Jinlong; Chen, Minghui; Yang, Lanlan; Liu, Li; Zhu, Shenglong; Wang, Fuhui; Meng, Guozhe

    2016-01-01

    Graphical abstract: - Highlights: • Effect of Y addition on oxidation of nanocrystalline coating is studied. • Y addition delays transformation of q-Al_2O_3 to a-Al_2O_3 during oxidation. • Y addition prevents scale rumpling. • Y segregates at grain boundaries of the nanocrystalline coating. • Y retards the transportation of Ta thus reduces its oxidation. - Abstract: The effect of yttrium addition on isothermal oxidation at 1050 °C of a sputtered nanocrystalline coating with moderate amount of tantalum in composition was investigated. Results indicate that yttrium addition delays transformation of metastable θ-Al_2O_3 to equilibrium α-Al_2O_3 grown on the nanocrystalline coatings. It prevents scale rumpling and promotes the formation of oxide pegs at interface between the oxide scale and the underlying coating. Besides, yttrium prefers to segregate at grain boundaries of the nanocrystalline coating and retards the outward transportation of tantalum from coating to oxide scale, thus reducing the excessive oxidation of tantalum.

  10. Impulsive shock induced single drop steam explosion visualized by high-speed x-ray radiography and photography - metallic melt

    International Nuclear Information System (INIS)

    Park, H. S.; Hansson, R. C.; Sehgal, B. R.

    2003-01-01

    Experimental investigation of fine fragmentation process during vapor explosion was conducted in a small-scale single drop system employing continuous high-speed X-ray radiography and photography. A molten tin drop of about 0.7 g at approximately 1000 .deg. C was dropped into a water pool, at temperatures ranging from 20 to 90 .deg. C, and the explosion was triggered by an external shock pulse of about 1 MPa. X-ray radiographs show that finely fragmented melt particles accelerates to the vapor bubble boundary and forms a particle shell during the period of vapor bubble expansion due to vapor explosions. From the photographs, it was possible to observe a number of counter-jets on the vapor boundary. For tests with highly subcooled coolant, local explosion due to external impulsive shock trigger initiates the stratified mode of explosion along the entire melt surface. For tests with lower subcooled coolant local explosions were initiated by an external impulsive shock trigger and by collapse of vapor/gas pocket attached on the top of the melt drop. Transient spatial distribution map of melt fragments during vapor explosion was obtained by a series of image processing and calibration tests

  11. X-ray photoelectron spectroscopy and paramagnetic resonance evidence for shock-induced intramolecular bond breaking in some energetic solids

    Science.gov (United States)

    Owens, F. J.; Sharma, J.

    1980-03-01

    Solid samples of 1,3,5, trinitro 1,3,5, triazacyclohexane (RDX), trinitrotoluene (TNT), and ammonium nitrate were subjected to shock pulses of strength and duration less than the threshold to cause detonation. The recovered shocked samples were studied by x-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). The results of these measurements indicate that the shock pulse either broke or altered the internal bonds of the molecules of the solid. The results of the shock decomposition are compared with measurements of the uv and slow thermal decomposition of these materials using the same experimental techniques.

  12. [(≡SiO)TaV (=CH2)Cl2], the first tantalum methylidene species prepared and identified on the silica surface

    KAUST Repository

    Chen, Yin

    2013-11-01

    A novel surface tantalum methylidene [(≡SiO)TaV (=CH 2)Cl2] was obtained via thermal decomposition of the well-defined surface species [(≡SiO)TaVCl2Me 2]. This first surface tantalum methylidene ever synthesized has been fully characterized and the kinetics of the a-hydrogen abstraction reaction has also been investigated in the heterogeneous system. © 2013 Elsevier B.V. All rights reserved.

  13. [(≡SiO)TaV (=CH2)Cl2], the first tantalum methylidene species prepared and identified on the silica surface

    KAUST Repository

    Chen, Yin; Callens, Emmanuel; Abou-Hamad, Edy; Basset, Jean-Marie

    2013-01-01

    A novel surface tantalum methylidene [(≡SiO)TaV (=CH 2)Cl2] was obtained via thermal decomposition of the well-defined surface species [(≡SiO)TaVCl2Me 2]. This first surface tantalum methylidene ever synthesized has been fully characterized and the kinetics of the a-hydrogen abstraction reaction has also been investigated in the heterogeneous system. © 2013 Elsevier B.V. All rights reserved.

  14. A shock surface geometry: The February 15--16, 1967, event

    International Nuclear Information System (INIS)

    Lepping, R.P.; Chao, J.K.

    1976-01-01

    The flare-associated interplanetary (IP) shock of February 15--16, 1967, observed by Explorer 33 and Pioneer 7 is analyzed to yield an estimation of the ecliptic plane geometry of the shock surface near 1 AU. These spacecraft were separated by 23degree in heliocentric longitude, and Pioneer 7 was at a distance of 1.12 AU from the sun. There was an 18.9-hour delay between the two observations. The estimated shock normal, obtained by using a least squares shock parameter fitting procedure for the Explorer 33 data, is found to be theta/subS//subE/=-53degree and phi/subS//subE/=198degree. The error cone angle for the shock normal of the Explorer 33 observation was approximately 7degree. This severely inclined shock normal is not typical of IP shocks. The shock normal at the Pioneer 7 position is found to be theta/subn/=-14degree and phi/subn/=161degree. However, the uncertainty is large (approx. =25degree for a 1sigma cone angle). Although a data gap occurred at the apparent time of passage of the disturbance at Pioneer 6,the recovered data did not suggest such a passage. A consistent picture of the shock propagation is given. The average shock speed from the sun to each spacecraft and the local speed at Explorer 33 and their relations to the position of the initiating solar flare are obtained and discussed. In the region of space between the earth and Pioneer 7 the shock surface radius of curvature in the ecliptic plane appears to have been 0.4 AU or less

  15. On the Magnitude and Orientation of Stress during Shock Metamorphism: Understanding Peak Ring Formation by Combining Observations and Models.

    Science.gov (United States)

    Rae, A.; Poelchau, M.; Collins, G. S.; Timms, N.; Cavosie, A. J.; Lofi, J.; Salge, T.; Riller, U. P.; Ferrière, L.; Grieve, R. A. F.; Osinski, G.; Morgan, J. V.; Expedition 364 Science Party, I. I.

    2017-12-01

    Shock metamorphism occurs during the earliest moments after impact. The magnitude and orientation of shock leaves recordable signatures in rocks, which spatially vary across an impact structure. Consequently, observations of shock metamorphism can be used to understand deformation and its history within a shock wave, and to examine subsequent deformation during crater modification. IODP-ICDP Expedition 364 recovered nearly 600 m of shocked target rocks from the peak ring of the Chicxulub Crater. Samples from the expedition were used to measure the magnitude and orientation of shock in peak ring materials, and to determine the mechanism of peak-ring emplacement. Here, we present the results of petrographic analyses of the shocked granitic target rocks of the Chicxulub peak ring; using universal-stage optical microscopy, back-scattered electron images, and electron back-scatter diffraction. Deformation microstructures in quartz include planar deformation features (PDFs), feather features (FFs), which are unique to shock conditions, as well as planar fractures and crystal-plastic deformation bands. The assemblage of PDFs in quartz suggest that the peak-ring rocks experienced shock pressures of 15 GPa throughout the recovered drill core, and that the orientation of FFs are consistent with the present-day orientation of the maximum principal stress direction during shock is close to vertical. Numerical impact simulations of the impact event were run to determine the magnitude and orientation of principal stresses during shock and track those orientations throughout crater formation. Our results are remarkably consistent with the geological data, and accurately predict both the shock-pressure magnitudes, and the final near-vertical orientation of the direction of maximum principal stress in the shock wave. Furthermore, analysis of the state of stress throughout the impact event can be used to constrain the timing of fracture and fault orientations observed in the core

  16. Broadband Shock Noise in Internally-Mixed Dual-Stream Jets

    Science.gov (United States)

    Bridges, James E.

    2009-01-01

    Broadband shock noise (BBSN) has been studied in some detail in single-flow jets and recently in dual-stream jets with separate flow exhaust systems. Shock noise is of great concern in these latter cases because of the noise created for the aircraft cabin by the underexpanded nozzle flow at cruise. Another case where shock noise is of concern is in the case of future supersonic aircraft that are expected to have bypass ratios small enough to justify internally mixed exhaust systems, and whose mission will push cycles to the point of imperfectly expanded flows. Dual-stream jets with internally mixed plume have some simplifying aspects relative to the separate flow jets, having a single shock structure given by the common nozzle pressure. This is used to separate the contribution of the turbulent shear layer to the broadband shock noise. Shock structure is held constant while the geometry and strength of the inner and merged shear layers are varying by changing splitter area ratio and core stream temperature. Flow and noise measurements are presented which document the efforts at separating the contribution of the inner shear layer to the broadband shock noise.

  17. Low-temperature diffusion of hydrogen isotopes in tantalum

    International Nuclear Information System (INIS)

    Peichl, R.; Ziegler, P.; Weidinger, A.

    1987-01-01

    The mobility of hydrogen and deuterium in tantalum is investigated in the temperature range between 4.2 and 30 K. On the time scale of the present experiment (25 μs) we find that hydrogen begins to move above 15 K whereas deuterium remains immobile at least up to 30 K. Since the interpretation of the data depends critically on the exact hydrogen configurations a major part of the paper is devoted to this problem. We suggest that hydrogen can exist in fairly localized or more extended states depending on the local homogeneity of the crystal. (orig.)

  18. Synthesis of Monodispersed Tantalum(V) oxide Nanospheres by an Ethylene Glycol Mediated Route

    Science.gov (United States)

    Tantalum(V) oxide (Ta2O5) nanospheres have been synthesized by a very simple ethylene glycol mediated route. The two-step process involves the formation of glycolate nanoparticles and their subsequent hydrolysis and calcination to generate the final Ta2O5 nanospheres. The synthes...

  19. A multiple shock model for common cause failures using discrete Markov chain

    International Nuclear Information System (INIS)

    Chung, Dae Wook; Kang, Chang Soon

    1992-01-01

    The most widely used models in common cause analysis are (single) shock models such as the BFR, and the MFR. But, single shock model can not treat the individual common cause separately and has some irrational assumptions. Multiple shock model for common cause failures is developed using Markov chain theory. This model treats each common cause shock as separately and sequently occuring event to implicate the change in failure probability distribution due to each common cause shock. The final failure probability distribution is evaluated and compared with that from the BFR model. The results show that multiple shock model which minimizes the assumptions in the BFR model is more realistic and conservative than the BFR model. The further work for application is the estimations of parameters such as common cause shock rate and component failure probability given a shock,p, through the data analysis

  20. Characterization of anodic barrier films on tantalum and 1100 aluminum by ISS/SIMS

    International Nuclear Information System (INIS)

    McCune, R.C.

    1978-01-01

    Ion scattering spectrometry (ISS) and concurrent secondary ion mass spectrometry (SIMS) were used to determine the depth profiles of anodic barrier oxide films grown on tantalum and type 1100 aluminum. The sputter rate in each case was determined from the film thickness measured by the anodic overvoltage, and the penetration time determined by the decrease in intensity of the metal oxide fragment observed using SIMS. A mixture of helium and neon ions was used to sputter aluminum oxide films in order to observe ion scattering of helium by oxygen, while taking advantage of the higher sputtering rate available with neon. A comparison of sputter rates for helium and neon on tantalum oxide indicated that neon sputtered the film at a rate eight times that of helium. SIMS depth profiling of the residual boron in the anodic aluminum oxide indicated a mixing effect which did not permit adequate resolution of the interface between the oxide film and the underlying metal

  1. Optoheterodyne Doppler measurements of the ballistic expansion of the products of the shock wave-induced surface destruction: Experiment and theory

    International Nuclear Information System (INIS)

    Andriyash, A. V.; Astashkin, M. V.; Baranov, V. K.; Golubinskii, A. G.; Irinichev, D. A.; Kondrat’ev, A. N.; Kuratov, S. E.; Mazanov, V. A.; Rogozkin, D. B.; Stepushkin, S. N.; Khatunkin, V. Yu.

    2016-01-01

    The results of optoheterodyne Doppler measurements of the ballistic expansion of the products of surface destruction under shock-wave loading are presented. The possibility of determining the physical characteristics of a rapidly flying dust cloud, including the microparticle velocities, the microparticle sizes, and the areal density of the dust cloud, is shown. A compact stand for performing experiments on shock-wave loading of metallic samples is described. Shock-wave loading is performed by a 100-µm-thick tantalum flyer plate accelerated to a velocity of 2.8 km/s. As the samples, lead plates having various thicknesses and the same surface roughness are used. At a shock-wave pressure of 31.5 GPa, the destruction products are solid microparticles about 50 µm in size. At a pressure of 42 and 88 GPa, a liquid-drop dust cloud with a particle size of 10–15 µm is formed. To interpret the spectral data on the optoheterodyne Doppler measurements of the expansion of the surface destruction products (spalled fragments, dust microparticles), a transport equation for the function of mutual coherence of a multiply scattered field is used. The Doppler spectra of a backscattered signal are calculated with the model developed for the dust cloud that appears when a shock wave reaches the sample surface at the parameters that are typical of an experimental situation. Qualitative changes are found in the spectra, depending on the optical thickness of the dust cloud. The obtained theoretical results are in agreement with the experimental data.

  2. Optoheterodyne Doppler measurements of the ballistic expansion of the products of the shock wave-induced surface destruction: Experiment and theory

    Energy Technology Data Exchange (ETDEWEB)

    Andriyash, A. V. [All-Russia Research Institute of Automatics (Russian Federation); Astashkin, M. V.; Baranov, V. K.; Golubinskii, A. G.; Irinichev, D. A. [Russian Federal Nuclear Center, All-Russia Research Institute of Experimental Physics (VNIIEF) (Russian Federation); Kondrat’ev, A. N., E-mail: an.kondratev@physics.msu.ru; Kuratov, S. E. [All-Russia Research Institute of Automatics (Russian Federation); Mazanov, V. A. [Russian Federal Nuclear Center, All-Russia Research Institute of Experimental Physics (VNIIEF) (Russian Federation); Rogozkin, D. B. [All-Russia Research Institute of Automatics (Russian Federation); Stepushkin, S. N.; Khatunkin, V. Yu. [Russian Federal Nuclear Center, All-Russia Research Institute of Experimental Physics (VNIIEF) (Russian Federation)

    2016-06-15

    The results of optoheterodyne Doppler measurements of the ballistic expansion of the products of surface destruction under shock-wave loading are presented. The possibility of determining the physical characteristics of a rapidly flying dust cloud, including the microparticle velocities, the microparticle sizes, and the areal density of the dust cloud, is shown. A compact stand for performing experiments on shock-wave loading of metallic samples is described. Shock-wave loading is performed by a 100-µm-thick tantalum flyer plate accelerated to a velocity of 2.8 km/s. As the samples, lead plates having various thicknesses and the same surface roughness are used. At a shock-wave pressure of 31.5 GPa, the destruction products are solid microparticles about 50 µm in size. At a pressure of 42 and 88 GPa, a liquid-drop dust cloud with a particle size of 10–15 µm is formed. To interpret the spectral data on the optoheterodyne Doppler measurements of the expansion of the surface destruction products (spalled fragments, dust microparticles), a transport equation for the function of mutual coherence of a multiply scattered field is used. The Doppler spectra of a backscattered signal are calculated with the model developed for the dust cloud that appears when a shock wave reaches the sample surface at the parameters that are typical of an experimental situation. Qualitative changes are found in the spectra, depending on the optical thickness of the dust cloud. The obtained theoretical results are in agreement with the experimental data.

  3. Tantalum coating on TiO{sub 2} nanotubes induces superior rate of matrix mineralization and osteofunctionality in human osteoblasts

    Energy Technology Data Exchange (ETDEWEB)

    Frandsen, Christine J.; Brammer, Karla S. [Materials Science and Engineering, University of California at San Diego, La Jolla, CA 92093 (United States); Noh, Kunbae [Corporate Research Institute, Cheil Industries, Inc., Gocheon-Dong, Uiwang-Si, Gyeonggi-Do, 437-711 (Korea, Republic of); Johnston, Gary [Materials Science and Engineering, University of California at San Diego, La Jolla, CA 92093 (United States); Jin, Sungho, E-mail: jin@ucsd.edu [Materials Science and Engineering, University of California at San Diego, La Jolla, CA 92093 (United States); Mechanical and Aerospace Engineering, University of California at San Diego, La Jolla, CA 92093 (United States)

    2014-04-01

    Nanostructured surface geometries have been the focus of a multitude of recent biomaterial research, and exciting findings have been published. However, only a few publications have directly compared nanostructures of various surface chemistries. The work herein directly compares the response of human osteoblast cells to surfaces of identical nanotube geometries with two well-known orthopedic biomaterials: titanium oxide (TiO{sub 2}) and tantalum (Ta). The results reveal that the Ta surface chemistry on the nanotube architecture enhances alkaline phosphatase activity, and promotes a ∼ 30% faster rate of matrix mineralization and bone-nodule formation when compared to results on bare TiO{sub 2} nanotubes. This study implies that unique combinations of surface chemistry and nanostructure may influence cell behavior due to distinctive physico-chemical properties. These findings are of paramount importance to the orthopedics field for understanding cell behavior in response to subtle alterations in nanostructure and surface chemistry, and will enable further insight into the complex manipulation of biomaterial surfaces. With increased focus in the field of orthopedic materials research on nanostructured surfaces, this study emphasizes the need for careful and systematic review of variations in surface chemistry in concurrence with nanotopographical changes. - Highlights: • A TiO{sub 2} nanotube surface structure was coated with tantalum. • Osteoblast cell response was compared between the tantalum coated and as-formed TiO{sub 2} nanotube surface. • We observed superior rates of bone matrix mineralization and osteoblast maturation on the tantalum coated nanotube surface.

  4. Kinetics of the Thermal Decomposition of Tetramethylsilane behind the Reflected Shock Waves in a Single Pulse Shock Tube (SPST) and Modeling Study

    Science.gov (United States)

    Parandaman, A.; Sudhakar, G.; Rajakumar, B.

    Thermal reactions of Tetramethylsilane (TMS) diluted in argon were studied behind the reflected shock waves in a single-pulse shock tube (SPST) over the temperature range of 1085-1221 K and pressures varied between 10.6 and 22.8 atm. The stable products resulting from the decomposition of TMS were identified and quantified using gas chromatography and also verified with Fourier Transform Infrared (FTIR) spectrometer. The major reaction products are methane (CH4) and ethylene (C2H4). The minor reaction products are ethane (C2H6) and propylene (C3H6). The initiation of mechanism in the decomposition of TMS takes plays via the Si-C bond scission by ejecting the methyl radicals (CH3) and trimethylsilyl radicals ((CH3)3Si). The measured temperature dependent rate coefficient for the total decomposition of TMS was to be ktotal = 1.66 ×1015 exp (-64.46/RT) s-1 and for the formation of CH4 reaction channel was to be k = 2.20 × 1014 exp (-60.15/RT) s-1, where the activation energies are given in kcal mol-1. A kinetic scheme containing 17 species and 28 elementary reactions was used for the simulation using chemical kinetic simulator over the temperature range of 1085-1221 K. The agreement between the experimental and simulated results was satisfactory.

  5. Is shock index associated with outcome in children with sepsis/septic shock?*.

    Science.gov (United States)

    Yasaka, Yuki; Khemani, Robinder G; Markovitz, Barry P

    2013-10-01

    To investigate the association between PICU shock index (the ratio of heart rate to systolic blood pressure) and PICU mortality in children with sepsis/septic shock. To explore cutoff values for shock index for ICU mortality, how change in shock index over the first 6 hours of ICU admission is associated with outcome, and how the use of vasoactive therapy may affect shock index and its association with outcome. Retrospective cohort. Single-center tertiary PICU. Five hundred forty-four children with the diagnosis of sepsis/septic shock. None. From January 2003 to December 2009, 544 children met International Pediatric Sepsis Consensus Conference of 2005 criteria for sepsis/septic shock. Overall mortality was 23.7%. Among all patients, hourly shock index was associated with mortality: odds ratio of ICU mortality at 0 hour, 1.08, 95% CI (1.04-1.12); odds ratio at 1 hour, 1.09 (1.04-1.13); odds ratio at 2 hours, 1.09 (1.05-1.13); and odds ratio at 6 hours, 1.11 (1.06-1.15). When stratified by age, early shock index was associated with mortality only in children 1-3 and more than or equal to 12 years old. Area under the receiver operating characteristic curve in age 1-3 and more than or equal to 12 years old for shock index at admission was 0.69 (95% CI, 0.58-0.80) and 0.62 (95% CI, 0.52-0.72) respectively, indicating a fair predictive marker. Although higher shock index was associated with increased risk of mortality, there was no particular cutoff value with adequate positive or negative likelihood ratios to identify mortality in any age group of children. The improvement of shock index in the first 6 hours of ICU admission was not associated with outcome when analyzed in all patients. However, among patients whose shock index were above the 50th percentile at ICU admission for each age group, improvement of shock index was associated with lower ICU mortality in children between 1-3 and more than or equal to 12 years old (p = 0.02 and p = 0.03, respectively). When

  6. Development of India-specific RAFM steel through optimization of tungsten and tantalum contents for better combination of impact, tensile, low cycle fatigue and creep properties

    Energy Technology Data Exchange (ETDEWEB)

    Laha, K., E-mail: laha@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, TN (India); Saroja, S.; Moitra, A.; Sandhya, R.; Mathew, M.D.; Jayakumar, T. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, TN (India); Rajendra Kumar, E. [Institute for Plasma Research, Bhat, Gandhinagar 382 428, Gujarat (India)

    2013-08-15

    Effects of tungsten and tantalum contents on impact, tensile, low cycle fatigue and creep properties of Reduced Activation Ferritic–Martensitic (RAFM) steel were studied to develop India-specific RAFM steel. Four heats of the steel have been melted with tungsten and tantalum contents in the ranges 1–2 wt.% and 0.06–0.14 wt.% respectively. Increase in tungsten content increased the ductile-to-brittle transition temperature (DBTT), low cycle fatigue and creep strength of the steel, whereas the tensile strength was not changed significantly. Increase in tantalum content increased the DBTT and low cycle fatigue strength of the steel whereas the tensile and creep strength decreased. Detailed TEM investigations revealed enhanced microstructural stability of the steel against creep exposure on tungsten addition. The RAFM steel having 1.4 wt.% tungsten with 0.06 wt.% tantalum was found to possess optimum combination of impact, tensile, low cycle fatigue and creep properties and is considered for Indian-specific RAFM steel.

  7. Estimation of niobium, tantalum and zirconium in a carbonate rich ore

    International Nuclear Information System (INIS)

    Navale, A.S.; Venkatakrishnan, R.R.; Sreenivas, T.

    2013-01-01

    A simple method using ICP-OES for estimation of tantalum, niobium and zirconium in a carbonate rich matrix is described. The sample is boiled with 10% v/v hydrochloric acid for 15 min and filtered. The residue is fused with ammonium bifluoride-ammonium sulphate flux and the melt is leached with water. Nb, Ta and Zr are estimated in the water leach by ICP-OES. (author)

  8. Design of a facility for studying shock-cell noise on single and coaxial jets

    NARCIS (Netherlands)

    Guariglia, Daniel; Rubio Carpio, A.; Schram, Christophe

    2018-01-01

    Shock-cell noise occurs in aero-engines when the nozzle exhaust is supersonic and shock-cells are present in the jet. In commercial turbofan engines, at cruise, the secondary flow is often supersonic underexpanded, with the formation of annular shock-cells in the jet and consequent onset of

  9. Short-term heat shock affects the course of immune response in Galleria mellonella naturally infected with the entomopathogenic fungus Beauveria bassiana.

    Science.gov (United States)

    Vertyporokh, Lidiia; Taszłow, Paulina; Samorek-Pieróg, Małgorzata; Wojda, Iwona

    2015-09-01

    We aimed to investigate how exposition of infected insects to short-term heat shock affects the biochemical and molecular aspects of their immune response. Galleria mellonella larvae were exposed to 43°C for 15min, at the seventy second hour after natural infection with entomopathogenic fungus Beauveria bassiana. As a result, both qualitative and quantitative changes in hemolymph protein profiles, and among them infection-induced changes in the amount of apolipophorin III (apoLp-III), were observed. Heat shock differently affects the expression of the tested immune-related genes. It transiently inhibits expression of antifungal peptides gallerimycin and galiomicin in both the fat body and hemocytes of infected larvae. The same, although to a lesser extent, concerned apoLp-III gene expression and was observed directly after heat shock. Nevertheless, in larvae that had recovered from heat shock, apoLp-III expression was higher in comparison to unshocked larvae in the fat body but not in hemocytes, which was consistent with the higher amount of this protein detected in the hemolymph of the infected, shocked larvae. Furthermore, lysozyme-type activity was higher directly after heat shock, while antifungal activity was significantly higher also in larvae that had recovered from heat shock, in comparison to the respective values in their non-shocked, infected counterparts. These results show how changes in the external temperature modulate the immune response of G. mellonella suffering from infection with its natural pathogen B. bassiana. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. Chemical kinetics studies at high temperatures using shock tubes

    OpenAIRE

    Rajakumar, B; Anandraj, D; Reddy, KPJ; Arunan, E

    2002-01-01

    Shock tube is an unique facility to create temperature gradients exceeding million degrees Kelvin per second. We have established two shock tubes for measuring the kinetic reaction rates at high temperatures with two different but complementary detection techniques. The first one is a single pulse shock tube, in which the reflected shock is used to heat the molecules. The equilibrated products are analyzed by gas chromatograph and infrared spectrometer. The second one uses laser-schlieren sys...

  11. Extraction - spectrophotometric determination of tantalum (V) with 2-(2-thiazolylazo)-5-dimethylaminophenol and 1,3-diphenylguanidine

    International Nuclear Information System (INIS)

    Tsurumi, C.; Furuya, K.; Kamada, H.

    1981-01-01

    Tantalum(V)-2-(2-thiazolylazo)-5-dimethylaminophenol (TAM) chelate anion is extracted quantitatively into benzyl alcohol with 1,3-diphenylguanidine (DPG) to form a ternary complex. In the organic phase, the complex has an absorption maximum at 605 nm. The optimum pH range for the extraction is 4.1 to 4.9 and the ternary complex is stable for at least 50 min. Beer's law is obeyed over a concentration range of 2 to 18 μg of tantalum(V) in 10 ml of the organic phase. The molar absorptivity of the ternary complex is 4.1 x 10 4 l mol -1 at 605 nm. The composition of the ternary complex is considered to be (TaO 2 ) 2 (TAM) 3 (DPG + ). (author)

  12. Electron tunneling in tantalum surface layers on niobium

    International Nuclear Information System (INIS)

    Ruggiero, S.T.; Track, E.K.; Prober, D.E.; Arnold, G.B.; DeWeert, M.J.

    1986-01-01

    We have performed electron tunneling measurements on tantalum surface layers on niobium. The tunnel junctions comprise 2000-A-circle Nb base electrodes with 10--100-A-circle in situ--deposited Ta overlayers, an oxide barrier, and Ag, Pb, or Pb-Bi alloy counterelectrodes. The base electrodes were prepared by ion-beam sputter deposition. The characteristics of these junctions have been studied as a function of Ta-layer thickness. These include the critical current, bound-state energy, phonon structure, and oxide barrier shape. We have compared our results for the product I/sub c/R versus tantalum-layer thickness with an extended version of the Gallagher theory which accounts for both the finite mean free path in the Ta overlayers and suppression of the I/sub c/R product due to strong-coupling effects. Excellent fits to the data yield a value of the intrinsic scattering probability for electrons at the Ta/Nb interface of r 2 = 0.01. This is consistent with the value expected from simple scattering off the potential step created by the difference between the Fermi energies of Ta and Nb. We have found a universal empirical correlation in average barrier height phi-bar and width s in the form phi-bar = 6 eV/(s-10 A-circle) for measured junctions which holds both for our data and results for available data in the literature for oxide-barrier junctions. The latter are composed of a wide variety of base and counterelectrode materials. These results are discussed in the general context of oxide growth and compared with results for artificial tunnel barriers

  13. Multifunctional hybrid coating on titanium towards hydroxyapatite growth: Electrodeposition of tantalum and its molecular functionalization with organophosphonic acids films

    International Nuclear Information System (INIS)

    Arnould, Christelle; Delhalle, Joseph; Mekhalif, Zineb

    2008-01-01

    Titanium and its alloys are base materials used in the dental and orthopaedic fields owing to suitable intrinsic properties: good biocompatibility, high corrosion resistance and excellent mechanical properties. However, the bonding between titanium and bone tissue is not always strong enough and can become a critical problem. In this context, the two main objectives of this paper are the increase of the corrosion resistance and the improvement of the hydroxyapatite (HAp) growth. The surface modification considered here is achieved in three main steps and consists in the elaboration of different inorganic and organic coatings. The first step is the elaboration of electrodeposition of tantalum on the titanium oxide film of a titanium substrate. The second step is the modification of the tantalum oxide coating with organophosphonic acids. The last step is the nucleation and growth of HAP on the outermost layer of the system by immersion in a simulated body fluid. The hybrid coating tantalum oxide/organophosphonic acids/molecular layer is shown to be promising for orthopaedic implants

  14. Dissolution kinetics of small amounts of oxygen in tantalum alloy T-111 and internal oxide displacement reactions during annealing

    Science.gov (United States)

    Stecura, S.

    1976-01-01

    Oxygen was added to T-111 (Ta-8W-2Hf, wt. %) at 820 and 990 C at an oxygen pressure of about 0.0003 torr. The technique employed permitted predetermined and reproducible doping of T-111 up to 3.0 at. % oxygen. Based on the temperature dependence of the doping reaction, it is concluded that the initial rates of oxygen pickup are probably controlled by solution of oxygen into the T-111 lattice. Although hafnium oxides are more stable than those of tantalum or tungsten, analyses of extracted residues indicate that the latter oxides predominate in the as-doped specimens, presumably because of the higher concentrations of tantalum and tungsten in the alloy. However, high-temperature annealing promotes gettering of dissolved oxygen and of other oxides to form hafnium oxides. Small amounts of tantalum and tungsten oxides were still present after high-temperature annealing. Tungsten oxide (WO3) volatilizes slightly from the surface of T-111 at 990 C. The vaporization of WO3 has no apparent affect on the doping reaction.

  15. Shock compression of simulated adobe

    Science.gov (United States)

    Braithwaite, C. H.; Church, P. D.; Gould, P. J.; Stewart, B.; Jardine, A. P.

    2017-01-01

    A series of plate impact experiments were conducted to investigate the shock response of a simulant for adobe, a traditional form of building material widely used around the world. Air dried bricks were sourced from the London brick company, dry machined and impacted at a range of velocities in a single stage gas gun. The shock Hugoniot was determined (Us =2.26up+0.37) as well as release information. The material was found to behave in a manner which was similar to that of loose sand and considerably less stiff than a weak porous sandstone. The effect of any cementing of the grains was examined by shocking powdered samples contained within a cell arrangement.

  16. Analytical extension of curved shock theory

    Science.gov (United States)

    Emanuel, G.

    2018-03-01

    Curved shock theory (CST) is limited to shock waves in a steady, two-dimensional or axisymmetric (2-Ax) flow of a perfect gas. A unique feature of CST is its use of intrinsic coordinates that result in an elegant and useful formulation for flow properties just downstream of a shock. For instance, the downstream effect of upstream vorticity, shock wave curvature, and the upstream pressure gradient along a streamline is established. There have been several attempts to extend CST, as mentioned in the text. Removal of the steady, 2-Ax, and perfect gas limitations, singly or in combination, requires an appropriate formulation of the shock wave's jump relations and the intrinsic coordinate Euler equations. Issues discussed include flow plane versus osculating plane, unsteady flow, vorticity, an imperfect gas, etc. The extension of CST utilizes concepts from differential geometry, such as the osculating plane, streamline torsion, and the Serret-Frenet equations.

  17. Universal shocks in the Wishart random-matrix ensemble.

    Science.gov (United States)

    Blaizot, Jean-Paul; Nowak, Maciej A; Warchoł, Piotr

    2013-05-01

    We show that the derivative of the logarithm of the average characteristic polynomial of a diffusing Wishart matrix obeys an exact partial differential equation valid for an arbitrary value of N, the size of the matrix. In the large N limit, this equation generalizes the simple inviscid Burgers equation that has been obtained earlier for Hermitian or unitary matrices. The solution, through the method of characteristics, presents singularities that we relate to the precursors of shock formation in the Burgers equation. The finite N effects appear as a viscosity term in the Burgers equation. Using a scaling analysis of the complete equation for the characteristic polynomial, in the vicinity of the shocks, we recover in a simple way the universal Bessel oscillations (so-called hard-edge singularities) familiar in random-matrix theory.

  18. Synthesis and magnetic properties of highly dispersed tantalum carbide nanoparticles decorated on carbon spheres

    CSIR Research Space (South Africa)

    Bhattacharjee, K

    2016-01-01

    Full Text Available The decoration of carbon spheres (CS) by highly dispersed tantalum carbide nanoparticles (TaC NPs) was achieved, for the first time by a unique carbothermal reduction method at 1350 °C for 30 min under reduced oxygen partial pressure. TaC NPs...

  19. The extraction of trace amounts of tantalum(V) from different mineral acid solutions by 4-(5-nonyl) pyridine oxide and trioctylamine oxide

    International Nuclear Information System (INIS)

    Ejaz, M.; Carswell, D.J.

    1976-01-01

    Data are presented on the distribution of trace amounts of tantalum(V) between different mineral acid solutions and 0.1M solutions of N-oxides of 4-(5-nonyl) pyridine and trioctylamine. The optimal acidity is 0.01-0.5M, depending on the nature of the acid. Common anions have little effect on extraction. Possible mechanism of extraction are suggested making use of slope analysis data. Separation factors for a number of metal ions with respect to tantalum are reported for the 0.1M 4-(5-nonyl)pyridine oxide - 1M sulphuric acid extraction system. Separation from uranium(VI), thorium(IV) and a number of fission products is suggested. The conclusions are unique as follows: Amine oxides are as unique as oxygen-donor extractants in their extraction of tantalum(V) from weakly acid solutions; tantalum is almost completely extracted from weakly nitric, hydrochloric and sulphuric acid solutions by both of the amine oxides; the extraction in low acidity solutions is independent of the nature of the anion of the acids present, indicating the ability of amine oxides to extract the product of hydrolysis of hydrolysable elements. In this respect amine oxides are much better than tributyl phosphate. (T.G.)

  20. Ultrafast dynamic ellipsometry and spectroscopy of laser shocked materials

    Energy Technology Data Exchange (ETDEWEB)

    Mcgrane, Shawn David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bolme, Cindy B [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Whitley, Von H [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Moore, David S [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2010-01-01

    Shock waves create extreme states of matter with very high pressures, temperatures, and volumetric compressions, at an exceedingly rapid rate of change. We review how to use a beamsplitter and a note card to turn a typical chirp pulse amplified femtosecond laser system into an ultrafast shock dynamics machine. Open scientific questions that can be addressed with such an apparatus are described. We report on the development of several single shot time resolved diagnostics needed to answer these questions. These single shot diagnostics are expected to be broadly applicable to other types of laser ablation experiments. Experimental results measured from shocked material dynamics of several systems are detailed. Finally, we report on progress towards using transient absorption as a measure of electronic excitation and coherent Raman as a picosecond probe of temperature in shock compressed condensed matter.

  1. Elasticity of Tantalum to 105 Gpa using a stress and angle-resolved x-ray diffraction

    International Nuclear Information System (INIS)

    Cynn, H; Yoo, C S

    1999-01-01

    Determining the mechanical properties such as elastic constants of metals at Mbar pressures has been a difficult task in experiment. Following the development of anisotropic elastic theory by Singh et al.[l], Mao et a1.[2] have recently developed a novel experimental technique to determine the elastic constants of Fe by using the stress and energy-dispersive x-ray diffraction (SEX). In this paper, we present an improved complementary technique, stress and angle-resolved x-ray diffraction (SAX), which we have applied to determine the elastic constants of tantalum to 105 GPa. The extrapolation of the tantalum elastic data shows an excellent agreement with the low-pressure ultrasonic data[3]. We also discuss the improvement of this SAX method over the previous SEX.[elastic constant, anisotropic elastic theory, angle-dispersive synchrotron x-ray diffraction, mechanical properties

  2. Experimental analysis of shock wave effects in copper

    International Nuclear Information System (INIS)

    Llorca, Fabrice; Buy, Francois; Farre, Jose

    2002-01-01

    This paper proposes the analysis of shock wave effects for a high purity copper. The method developed is based on the analysis of the mechanical behavior of as received and shocked materials. Shock effect is generated through plates impact tests performed in the range 9 GPa to 12 GPa on a single stage light gas gun. Therefore, as-received and impacted materials are characterized on quasi static and Split Hopkinson apparatus. The difference between measured stresses between as received and shocked materials allows to understand shock effects in the low pressure range of study. A specific modeling approach is engaged in order to give indications about the evolution of the microstructure of the materials

  3. H2 profiles of C-type bow shocks

    International Nuclear Information System (INIS)

    Smith, M.D.; Brand, P.W.J.L.

    1990-01-01

    We present emission-line profiles of molecular hydrogen from curved C-shocks within molecular clouds. Shock configurations arising from the supersonic motion of jets and bullets within a dense cloud are chosen. Bow shock speeds in the range υ w = 40-200 km s -1 are investigated. Breakdown through dissociation and self-ionization restricts the C-shock section to the bow tail. We find that profiles are essentially single-peaked and narrow with full widths (at 10 per cent maximum intensity, deconvolved) of up to about 50, 40 and 30 km s -1 for cones, hemispherical caps and paraboloids, respectively. Exceptional field alignments can produce lines as wide as 75 km s -1 in the conical shock model. (author)

  4. Particle acceleration at shocks in the inner heliosphere

    Science.gov (United States)

    Parker, Linda Neergaard

    This dissertation describes a study of particle acceleration at shocks via the diffusive shock acceleration mechanism. Results for particle acceleration at both quasi-parallel and quasi-perpendicular shocks are presented to address the question of whether there are sufficient particles in the solar wind thermal core, modeled as either a Maxwellian or kappa- distribution, to account for the observed accelerated spectrum. Results of accelerating the theoretical upstream distribution are compared to energetic observations at 1 AU. It is shown that the particle distribution in the solar wind thermal core is sufficient to explain the accelerated particle spectrum downstream of the shock, although the shape of the downstream distribution in some cases does not follow completely the theory of diffusive shock acceleration, indicating possible additional processes at work in the shock for these cases. Results show good to excellent agreement between the theoretical and observed spectral index for one third to one half of both quasi-parallel and quasi-perpendicular shocks studied herein. Coronal mass ejections occurring during periods of high solar activity surrounding solar maximum can produce shocks in excess of 3-8 shocks per day. During solar minimum, diffusive shock acceleration at shocks can generally be understood on the basis of single independent shocks and no other shock necessarily influences the diffusive shock acceleration mechanism. In this sense, diffusive shock acceleration during solar minimum may be regarded as Markovian. By contrast, diffusive shock acceleration of particles at periods of high solar activity (e.g. solar maximum) see frequent, closely spaced shocks that include the effects of particle acceleration at preceding and following shocks. Therefore, diffusive shock acceleration of particles at solar maximum cannot be modeled on the basis of diffusive shock acceleration as a single, independent shock and the process is essentially non-Markovian. A

  5. The effect of hydrostatic vs. shock pressure treatment of plant seeds

    International Nuclear Information System (INIS)

    Mustey, A; Leighs, J A; Appleby, G J; Wood, D C; Hazael, R; McMillan, P F; Hazell, P J

    2014-01-01

    The hydrostatic pressure and shock response of plant seeds has been investigated antecedently, primarily driven by interest in reducing bacterial contamination of crops and the theory of panspermia, respectively. However, comparisons have not previously been made between these two methods ofapplying pressure to plant seeds. Here such a comparison has been undertaken based on the premise that any correlations in collected data may provide a route to inform understanding of damage mechanisms in the seeds under test. In this work two varieties of plant seeds were subjected to hydrostatic pressure via a non-end-loaded piston cylinder setup and shock compression via employment of a 50 mm bore, single stage gas gun using the flyer plate technique. Results from germination tests of recovered seed samples have been compared and contrasted, and initial conclusions made regarding causes of trends in the resultant data-set. Data collected has shown that cress seeds are extremely resilient to static loading, whereas the difference in the two forms of loading is negligible for lettuce seeds. Germination time has been seen to extend dramatically following static loading of cress seeds to greater than 0.4 GPa. In addition, the cut-off pressure previously seen to cause 0% germination in dynamic experiments performed on cress seeds has now also been seen in lettuce seeds.

  6. The effect of hydrostatic vs. shock pressure treatment of plant seeds

    Science.gov (United States)

    Mustey, A.; Leighs, J. A.; Appleby-Thomas, G. J.; Wood, D. C.; Hazael, R.; McMillan, P. F.; Hazell, P. J.

    2014-05-01

    The hydrostatic pressure and shock response of plant seeds has been investigated antecedently, primarily driven by interest in reducing bacterial contamination of crops and the theory of panspermia, respectively. However, comparisons have not previously been made between these two methods ofapplying pressure to plant seeds. Here such a comparison has been undertaken based on the premise that any correlations in collected data may provide a route to inform understanding of damage mechanisms in the seeds under test. In this work two varieties of plant seeds were subjected to hydrostatic pressure via a non-end-loaded piston cylinder setup and shock compression via employment of a 50 mm bore, single stage gas gun using the flyer plate technique. Results from germination tests of recovered seed samples have been compared and contrasted, and initial conclusions made regarding causes of trends in the resultant data-set. Data collected has shown that cress seeds are extremely resilient to static loading, whereas the difference in the two forms of loading is negligible for lettuce seeds. Germination time has been seen to extend dramatically following static loading of cress seeds to greater than 0.4 GPa. In addition, the cut-off pressure previously seen to cause 0% germination in dynamic experiments performed on cress seeds has now also been seen in lettuce seeds.

  7. Anterograde effects of a single electroconvulsive shock on inhibitory avoidance and on cued fear conditioning

    Directory of Open Access Journals (Sweden)

    Oliveira M.G.M.

    1998-01-01

    Full Text Available A single electroconvulsive shock (ECS or a sham ECS was administered to male 3-4-month-old Wistar rats 1, 2, and 4 h before training in an inhibitory avoidance test and in cued classical fear conditioning (measured by means of freezing time in a new environment. ECS impaired inhibitory avoidance at all times and, at 1 or 2 h before training, reduced freezing time before and after re-presentation of the ECS. These results are interpreted as a transient conditioned stimulus (CS-induced anxiolytic or analgesic effect lasting about 2 h after a single treatment, in addition to the known amnesic effect of the stimulus. This suggests that the effect of anterograde learning impairment is demonstrated unequivocally only when the analgesic/anxiolytic effect is over (about 4 h after ECS administration and that this impairment of learning is selective, affecting inhibitory avoidance but not classical fear conditioning to a discrete stimulus.

  8. Modification of mechanical properties of single crystal aluminum oxide by ion beam induced structural changes

    International Nuclear Information System (INIS)

    Ensinger, W.; Nowak, R.; Horino, Y.; Baba, K.

    1993-01-01

    The mechanical behaviour of ceramics is essentially determined by their surface qualities. As a surface modification technique, ion implantation provides the possibility to modify the mechanical properties of ceramics. Highly energetic ions are implanted into the near-surface region of a material and modify its composition and structure. Ions of aluminum, oxygen, nickel and tantalum were implanted into single-crystal α-aluminum oxide. Three-point bending tests showed that an increase in flexural strength of up to 30% could be obtained after implantation of aluminum and oxygen. Nickel and tantalum ion implantation increased the fracture toughness. Indentation tests with Knoop and Vickers diamonds and comparison of the lengths of the developed radial cracks showed that ion implantation leads to a reaction in cracking. The observed effects are assigned to radiation induced structural changes of the ceramic. Ion bombardment leads to radiation damage and formation of compressive stress. In case of tantalum implantation, the implanted near-surface zone becomes amorphous. These effects make the ceramic more resistant to fracture. (orig.)

  9. Measurement of the production of charged pions by protons on a tantalum target

    CERN Document Server

    Catanesi, M.G.; Edgecock, R.; Ellis, Malcolm; Robbins, S.; Soler, F.J.P.; Gossling, C.; Bunyatov, S.; Krasnoperov, A.; Popov, B.; Serdiouk, V.; Tereschenko, V.; Di Capua, E.; Vidal-Sitjed, G.; Artamonov, A.; Arce, P.; Giani, S.; Gilardoni, S.; Gorbunov, P.; Grant, A.; Grossheim, A.; Gruber, P.; Ivanchenko, V.; Kayis-Topaksu, A.; Panman, J.; Papadopoulos, I.; Pasternak, J.; Tcherniaev, E.; Tsukerman, I.; Veenhof, R.; Wiebusch, C.; Zucchelli, P.; Blondel, A.; Borghi, S.; Campanelli, M.; Morone, M.C.; Prior, G.; Schroeter, R.; Engel, R.; Meurer, C.; Kato, I.; Gastaldi, U.; Mills, G.B.; Graulich, J.S.; Gregoire, G.; Bonesini, M.; De Min, A.; Ferri, F.; Paganoni, M.; Paleari, F.; Kirsanov, M.; Bagulya, A.; Grichine, V.; Polukhina, N.; Palladino, V.; Coney, L.; Schmitz, D.; Barr, G.; De Santo, A.; Pattison, C.; Zuber, K.; Bobisut, F.; Gibin, D.; Guglielmi, A.; Mezzetto, M.; Dumarchez, J.; Vannucci, F.; Dore, U.; Orestano, D.; Pastore, F.; Tonazzo, A.; Tortora, L.; Booth, C.; Buttar, C.; Hodgson, P.; Howlett, L.; Bogomilov, M.; Chizhov, M.; Kolev, D.; Tsenov, R.; Apollonio, M.; Chimenti, P.; Giannini, G.; Santin, G.; Burguet-Castell, J.; Cervera-Villanueva, A.; Gomez-Cadenas, J.J.; Martin-Albo, J.; Novella, P.; Sorel, M.; Tornero, A.

    2007-01-01

    A measurement of the double-differential cross-section for the production of charged pions in proton--tantalum collisions emitted at large angles from the incoming beam direction is presented. The data were taken in 2002 with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 \\GeVc to 12 \\GeVc hitting a tantalum target with a thickness of 5% of a nuclear interaction length. The angular and momentum range covered by the experiment ($100 \\MeVc \\le p < 800 \\MeVc$ and $0.35 \\rad \\le \\theta <2.15 \\rad$) is of particular importance for the design of a neutrino factory. The produced particles were detected using a small-radius cylindrical time projection chamber (TPC) placed in a solenoidal magnet. Track recognition, momentum determination and particle identification were all performed based on the measurements made with the TPC. An elaborate system of detectors in the beam line ensured the identification of the incident particles. Results a...

  10. Hydrogen in niobium, tantalum, and vanadium: Structures, phase diagrams, and morphologies

    International Nuclear Information System (INIS)

    Schober, T.

    1978-07-01

    The paper discusses basic aspects of the reactions between the metals niobium, tantalum, vanadium, and hydrogen or deuterium. After an introduction to problems of preparation experimental technqiues for the investigation of hydrides are presented. The possible hydride structures are discussed. With vanadium, there are great differences between the structures of hydrides and deuterides. Detailed mention is also made of recent measurements of the NGH, TaH, VH, and VD phase diagrams. (orig./WBU) [de

  11. Effect of continuous hemofiltration on internal environment and survival rate of severe heatstroke dogs with shock

    Directory of Open Access Journals (Sweden)

    Guang-ming CHEN

    2011-08-01

    Full Text Available Objective To explore the effect of continuous hemofiltration(CHF on internal environment and survival rate of severe heatstroke dogs with shock.Methods Sixteen healthy male dogs were randomly divided into heatshock group(HS group,n=8 and continuous hemofiltration group(CHF group,n=8.Severe heatstroke model was established by applying high temperature to whole body,and then the animals were removed from the heating cabin as soon as they presented manifestations of shock.Dogs of HS group were put into an ordinary environment,while dogs of CHF group received CHF treatment.The core temperature(Tc,mean arterial pressure(MAP,blood gas analysis,serum electrolytes and survival rate of dogs in two groups were observed.Results The time from heat exposure to shock was 107.0±28.5min and 111.4±22.2min in HS group and CHF group respectively(t=-0.354,P=0.729.The Tc in CHF group declined to normal level 15 to 30 minitues after CHF treatment,while the Tc in HS group remained at a level higher than that before heat exposure at 90min after shock.The Tc of two groups showed significant difference at each time point after shock(P < 0.01.The MAP of both groups was obviously lowered than that before heatstroke.The MAP of CHF group raised gradually 30 min after treatment,while the MAP of HS group rose very slowly,and it was significantly lower than that of CHF group at each time point after 45min(P < 0.05,P < 0.01.All the dogs in both groups manifested hyperventilation and respiratory alkalosis when shock appeared.After shock,respiratory alkalosis in HS group gradually became metabolic acidosis,with some animals manifested combined metabolic and respiratory acidosis because of respiratory decompensation,while the blood gas levels in CHF group recovered to normal gradually.The blood gas levels of two groups showed significant difference at each time point after shock(P < 0.05,P < 0.01.Hypernatremia,hyperchloraemia and hyperpotassaemia were found in all animals of both

  12. Carbothermal shock synthesis of high-entropy-alloy nanoparticles

    Science.gov (United States)

    Yao, Yonggang; Huang, Zhennan; Xie, Pengfei; Lacey, Steven D.; Jacob, Rohit Jiji; Xie, Hua; Chen, Fengjuan; Nie, Anmin; Pu, Tiancheng; Rehwoldt, Miles; Yu, Daiwei; Zachariah, Michael R.; Wang, Chao; Shahbazian-Yassar, Reza; Li, Ju; Hu, Liangbing

    2018-03-01

    The controllable incorporation of multiple immiscible elements into a single nanoparticle merits untold scientific and technological potential, yet remains a challenge using conventional synthetic techniques. We present a general route for alloying up to eight dissimilar elements into single-phase solid-solution nanoparticles, referred to as high-entropy-alloy nanoparticles (HEA-NPs), by thermally shocking precursor metal salt mixtures loaded onto carbon supports [temperature ~2000 kelvin (K), 55-millisecond duration, rate of ~105 K per second]. We synthesized a wide range of multicomponent nanoparticles with a desired chemistry (composition), size, and phase (solid solution, phase-separated) by controlling the carbothermal shock (CTS) parameters (substrate, temperature, shock duration, and heating/cooling rate). To prove utility, we synthesized quinary HEA-NPs as ammonia oxidation catalysts with ~100% conversion and >99% nitrogen oxide selectivity over prolonged operations.

  13. Influence of process parameters on plasma electrolytic surface treatment of tantalum for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Sowa, Maciej, E-mail: maciej.sowa@polsl.pl [Faculty of Chemistry, Silesian University of Technology, B. Krzywoustego Street 6, 44-100 Gliwice (Poland); Woszczak, Maja; Kazek-Kęsik, Alicja [Faculty of Chemistry, Silesian University of Technology, B. Krzywoustego Street 6, 44-100 Gliwice (Poland); Dercz, Grzegorz [Institute of Materials Science, University of Silesia, 75 Pułku Piechoty Street 1A, 41-500 Chorzów (Poland); Korotin, Danila M. [M.N. Mikheev Institute of Metal Physics of the Ural Branch of Russian Academy of Sciences, S. Kovalevskoi Street 18, 620990 Yekaterinburg (Russian Federation); Institute of Physics and Technology, Ural Federal University, Mira Street 19, 620002 Yekaterinburg (Russian Federation); Zhidkov, Ivan S. [Institute of Physics and Technology, Ural Federal University, Mira Street 19, 620002 Yekaterinburg (Russian Federation); Kurmaev, Ernst Z. [M.N. Mikheev Institute of Metal Physics of the Ural Branch of Russian Academy of Sciences, S. Kovalevskoi Street 18, 620990 Yekaterinburg (Russian Federation); Institute of Physics and Technology, Ural Federal University, Mira Street 19, 620002 Yekaterinburg (Russian Federation); Cholakh, Seif O. [Institute of Physics and Technology, Ural Federal University, Mira Street 19, 620002 Yekaterinburg (Russian Federation); Basiaga, Marcin [Faculty of Biomedical Engineering, Silesian University of Technology, Gen. de Gaulle’a Street 66, 41-800 Zabrze (Poland); Simka, Wojciech, E-mail: wojciech.simka@polsl.pl [Faculty of Chemistry, Silesian University of Technology, B. Krzywoustego Street 6, 44-100 Gliwice (Poland)

    2017-06-15

    Highlights: • 2-step plasma electrolytic oxidation (PEO) of tantalum was investigated. • PEO coatings surface composition were reflected by the composition of anodizing baths. • Hydrophobic surfaces were obtained from acetate and formate containing baths. • Bioactive phases were identified. - Abstract: This work aims to quantify the effect of anodization voltage and electrolyte composition used during DC plasma electrolytic oxidation (PEO), operated as a 2-step process, on the surface properties of the resulting oxide coatings on tantalum. The first step consisted of galvanostatic anodization (150 mA cm{sup −2}) of the tantalum workpiece up to several limiting voltages (200, 300, 400 and 500 V). After attaining the limiting voltage, the process was switched to voltage control, which resulted in a gradual decrease of the anodic current density. The anodic treatment was realized in a 0.5 M Ca(H{sub 2}PO{sub 2}){sub 2} solution, which was then modified by the addition of 1.15 M Ca(HCOO){sub 2} as well as 1.15 M and 1.5 M Mg(CH{sub 3}COO){sub 2}. The increasing voltage of anodization led to the formation of thicker coatings, with larger pores and enriched with electrolytes species to a higher extent. The solutions containing HCOO{sup −} and CH{sub 3}COO{sup −} ions caused the formation of coatings which were slightly hydrophobic (high contact angle). In the case of the samples anodized up to 500 V, scattered crystalline deposits were observed. Bioactive phases, such as hydroxyapatite, were detected in the treated oxide coatings by XRD and XPS.

  14. From single-site tantalum complexes to nanoparticles of TaxNy and TaOxNy supported on silica: elucidation of synthesis chemistry by dynamic nuclear polarization surface enhanced NMR spectroscopy and X-ray absorption spectroscopy

    KAUST Repository

    Mohandas, Janet Chakkamadathil; Abou-Hamad, Edy; Callens, Emmanuel; Samantaray, Manoja; Gajan, David; Gurinov, Andrei; Ma, Tao; Ould-Chikh, Samy; Hoffman, Adam S.; Gates, Bruce C.; Basset, Jean-Marie

    2017-01-01

    Air-stable catalysts consisting of tantalum nitride nanoparticles represented as a mixture of TaxNy and TaOxNy with diameters in the range of 0.5 to 3 nm supported on highly dehydroxylated silica were synthesized from TaMe5 (Me = methyl) and dimeric

  15. The pressure, internal energy, and conductivity of tantalum plasma

    Energy Technology Data Exchange (ETDEWEB)

    Apfelbaum, E.M. [Russian Academy of Sciences, Joint Institute for High Temperatures, Department of Computational Physics, Moscow (Russian Federation)

    2017-11-15

    The pressure, internal energy, and conductivity of a tantalum plasma were calculated at the temperatures 10-100 kK and densities less than 3 g/cm{sup 3}. The plasma composition, pressure, and internal energy were obtained by means of the corresponding system of the coupled mass action law equations. We have considered atom ionization up to +3. The conductivity was calculated within the relaxation time approximation. Comparisons of our results with available measurements and calculation data show good agreement in the area of correct applicability of the present model. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Synthesis of a Bis(thiophenolate)pyridine Ligand and Its Titanium, Zirconium, and Tantalum Complexes

    KAUST Repository

    Lenton, Taylor N.; VanderVelde, David G.; Bercaw, John E.

    2012-01-01

    -membered chelate with longer metal-sulfur and carbon-sulfur bonds. Solid-state structures of tantalum complexes (SNS)Ta(NMe 2) 3 (5) and (SNS)TaCl(NEt 2) 2 (6) also display pronounced C 2 twisting of the SNS ligand. 1D and 2D NMR experiments show that 5

  17. XPS and GDOES Characterization of Porous Coating Enriched with Copper and Calcium Obtained on Tantalum via Plasma Electrolytic Oxidation

    Directory of Open Access Journals (Sweden)

    Krzysztof Rokosz

    2016-01-01

    Full Text Available XPS and GDOES characterizations of porous coatings on tantalum after Plasma Electrolytic Oxidation (PEO at 450 V for 3 minutes in electrolyte containing concentrated (85% phosphoric acid with calcium nitrate and copper (II nitrate are described. Based on the obtained data, it may be concluded that the PEO coating consists of tantalum (Ta5+, calcium (Ca2+, copper (Cu2+  and Cu+, and phosphates (PO43-. It has to be pointed out that copper and calcium are distributed throughout the volume. The authors also propose a new model of PEO, based on the derivative of GDOES signals with sputtering time.

  18. Emissive spectra of shock-heated argon

    International Nuclear Information System (INIS)

    Tang Jingyou; Gu Yan; Peng Qixian; Bai Yulin; Li Ping

    2003-01-01

    To study the radiant properties of argon under weak shock compression, an aluminum target filled with gaseous argon at ambient states was impacted by a tungsten alloy projectile which was launched from a two-stage light gun to 2.00 km/s. The radiant signals of single shock-compressed argon were recorded by a six-channel pyrometer and oscilloscopes, which varied with time linearly for the five channels from 405 nm to 700 nm and exponentially for the channel 800 nm, and the corresponding velocity of shock wave was determined to be 4.10 ± 0.09 km/s. By the present experiment, it has been shown that the absorbability of the shock-heated argon is low for visual light and the optical depths of argon gas turn from thin to thick as wavelengths gradually increase. The time-resolved spectra in the rising-front of the radiant signal in the re-shocked argon were recorded by means of an OMA, and strong emissive spectrum bands near 450 nm light-wave length but no linear spectrum were found. The emissive spectrum properties of shock-compression argon were qualitatively explained by the state parameters and ionization degree

  19. Effect of tungsten and tantalum on the low cycle fatigue behavior of reduced activation ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Shankar, Vani, E-mail: vani@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102 (India); Mariappan, K.; Nagesha, A.; Prasad Reddy, G.V.; Sandhya, R.; Mathew, M.D.; Jayakumar, T. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102 (India)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Effect of tungsten and tantalum on low cycle fatigue behavior of RAFM steels. Black-Right-Pointing-Pointer Both alloying elements W and Ta improved fatigue life. Black-Right-Pointing-Pointer Increase in Ta content improved fatigue life more than W. Black-Right-Pointing-Pointer Optimization of W content at 1.4 wt.%. Black-Right-Pointing-Pointer Softening behavior closely related to W and Ta content. - Abstract: Reduced activation ferritic/martensitic (RAFM) steels are candidate materials for the test blanket modules of International Thermonuclear Experimental Reactor (ITER). Several degradation mechanisms such as thermal fatigue, low cycle fatigue, creep fatigue interaction, creep, irradiation hardening, swelling and phase instability associated irradiation embrittlement must be understood in order to estimate the component lifetime and issues concerning the structural integrity of components. The current work focuses on the effect of tungsten and tantalum on the low cycle fatigue (LCF) behavior of RAFM steels. Both alloying elements tungsten and tantalum improved the fatigue life. Influence of Ta on increasing fatigue life was an order of magnitude higher than the influence of W on improving the fatigue life. Based on the present study, the W content was optimized at 1.4 wt.%. Softening behavior of RAFM steels showed a strong dependence on W and Ta content in RAFM steels.

  20. Studies of renal parenchymal impairments with extracorporeal shock wave lithotripsy (ESWL) by diagnostic imaging methods

    Energy Technology Data Exchange (ETDEWEB)

    Ohishi, Yukihiko; Machida, Toyohei; Tashiro, Kazuya; Wada, Tetsuro; Mochizuki, Atsushi; Torii, Shinichiro; Yoshigoe, Fukuo; Kawashima, Yoshio; Asano, Koji (Jikei Univ., Tokyo (Japan). School of Medicine)

    1989-05-01

    Renal parenchymal impairments with extracorporeal shock wave lithotripsy (ESWL) were studied by diagnostic imaging methods. The subjects were 25 patients with renal stones, and EDAP LT-01 (piezoelectric system) was used for the equipment of ESWL. The examination by MRI, X-ray CT and /sup 99m/Tc-DMSA scintigraphy using SPECT were performed before and after ESWL. To the 24 kidneys of 12 adult dogs, shock waves were fired in order to examine the experimental renal parenchymal impairments. After the treatment with ESWL, renal abnormal findings were obtained with MRI in 6 patients out of 11 (54.5%), with X-ray CT in 1 patient out of 12 (8.3%), and with the /sup 99m/Tc-DMSA renal scintigraphy in 4 patients out of 6 (66.7%). In the inspections with X-ray CT and renal scintigraphy conducted in 4 weeks, it was noted that the conditions of patients were recovered to the states before ESWL was performed. Using the therapeutic doses of shock wave for humans, the renal parenchymal impairments in the kidney in dogs were normalized in 7 days. Although it has been considered that the degree of renal parenchymal impairments with ESWL treatment may be influenced by the kind of the equipment, frequency of shock waves and their strength, the extent of impairments were rather mild, and it was presumed that the impairments might be recovered on the images in 3 to 4 weeks at the latest. (author).

  1. Studies of renal parenchymal impairments with extracorporeal shock wave lithotripsy (ESWL) by diagnostic imaging methods

    International Nuclear Information System (INIS)

    Ohishi, Yukihiko; Machida, Toyohei; Tashiro, Kazuya; Wada, Tetsuro; Mochizuki, Atsushi; Torii, Shinichiro; Yoshigoe, Fukuo; Kawashima, Yoshio; Asano, Koji

    1989-01-01

    Renal parenchymal impairments with extracorporeal shock wave lithotripsy (ESWL) were studied by diagnostic imaging methods. The subjects were 25 patients with renal stones, and EDAP LT-01 (piezoelectric system) was used for the equipment of ESWL. The examination by MRI, X-ray CT and 99m Tc-DMSA scintigraphy using SPECT were performed before and after ESWL. To the 24 kidneys of 12 adult dogs, shock waves were fired in order to examine the experimental renal parenchymal impairments. After the treatment with ESWL, renal abnormal findings were obtained with MRI in 6 patients out of 11 (54.5%), with X-ray CT in 1 patient out of 12 (8.3%), and with the 99m Tc-DMSA renal scintigraphy in 4 patients out of 6 (66.7%). In the inspections with X-ray CT and renal scintigraphy conducted in 4 weeks, it was noted that the conditions of patients were recovered to the states before ESWL was performed. Using the therapeutic doses of shock wave for humans, the renal parenchymal impairments in the kidney in dogs were normalized in 7 days. Although it has been considered that the degree of renal parenchymal impairments with ESWL treatment may be influenced by the kind of the equipment, frequency of shock waves and their strength, the extent of impairments were rather mild, and it was presumed that the impairments might be recovered on the images in 3 to 4 weeks at the latest. (author)

  2. Misfortunes never come singly: Structural change, multiple shocks and child malnutrition in rural Senegal.

    Science.gov (United States)

    Lazzaroni, Sara; Wagner, Natascha

    2016-12-01

    This study considers the two most pronounced shocks Senegalese subsistence farmers struggle with, namely increasing purchase prices and droughts. We assess the relationship of these self-reported shocks with child health in a multi-shock approach to account for concomitance of adverse events from the natural, biological, economic and health sphere. We employ a unique farming household panel dataset containing information on children living in poor, rural households in eight regions of Senegal in 2009 and 2011 and account for structural changes occurring between survey periods due to the large scale, national Nutrition Enhancement Program. By zooming in to the micro level we demonstrate that Senegal as a Sahelian country, mainly reliant on subsistence agriculture, is very vulnerable to climate variability and international price developments: According to our conservative estimates, the occurrence of a drought explains 25% of the pooled weight-for-age standard deviation, income losses 31%. Our multi-shock analysis reveals that the shocks are perceived as more severe in 2011 with droughts explaining up to 44% of the standard deviation of child health, increased prices up to 21%. Yet, the concomitance of droughts and increased prices after the structural change, i.e. the Nutrition Enhancement Program, indicates that the health of children experiencing both shocks in 2011 has improved. We argue that these results are driven by the increase in rural household income as theoretically outlined in the agricultural household model. Thus, adequate policy responses to shocks do not only depend on the nature but also on the concomitance of hazardous events. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Reshock and release response of aluminum single crystal

    International Nuclear Information System (INIS)

    Huang, H.; Asay, J. R.

    2007-01-01

    Reshock and release experiments were performed on single crystal aluminum along three orientations and on polycrystalline 1050 aluminum with 50 μm grain size at shock stresses of 13 and 21 GPa to investigate the mechanisms for previously observed quasielastic recompression behavior. Particle velocity profiles obtained during reshocking both single crystals and polycrystalline aluminum from initial shock stresses of 13-21 GPa show similar quasielastic recompression behavior. Quasielastic release response is also observed in all single crystals, but the magnitude of the effect is crystal orientation dependent, with [111] and [110] exhibiting more ideal elastic-plastic release for unloading from the shocked state than for the [100] orientation and polycrystalline aluminum. The quasielastic response of 1050 aluminum is intermediate to that of the [100] and [111] orientations. Comparison of the wave profiles obtained for both unloading and reloading of single crystals and polycrystalline 1050 aluminum from shocked states suggests that the observed quasielastic response of polycrystalline aluminum results from the averaging response of single crystals for shock propagation along different orientations, and that the response of 1050 aluminum with large grain boundaries is not significantly different from the results obtained on single crystal aluminum. The yield strength of the single crystals and 1050 aluminum is found to increase with shock stress, which is consistent with previous results [H. Huang and I. R. Asay, J. Appl. Phys. 98, 033524 (2005)

  4. The Advanced Composition Explorer Shock Database and Application to Particle Acceleration Theory

    Science.gov (United States)

    Parker, L. Neergaard; Zank, G. P.

    2015-01-01

    The theory of particle acceleration via diffusive shock acceleration (DSA) has been studied in depth by Gosling et al. (1981), van Nes et al. (1984), Mason (2000), Desai et al. (2003), Zank et al. (2006), among many others. Recently, Parker and Zank (2012, 2014) and Parker et al. (2014) using the Advanced Composition Explorer (ACE) shock database at 1 AU explored two questions: does the upstream distribution alone have enough particles to account for the accelerated downstream distribution and can the slope of the downstream accelerated spectrum be explained using DSA? As was shown in this research, diffusive shock acceleration can account for a large population of the shocks. However, Parker and Zank (2012, 2014) and Parker et al. (2014) used a subset of the larger ACE database. Recently, work has successfully been completed that allows for the entire ACE database to be considered in a larger statistical analysis. We explain DSA as it applies to single and multiple shocks and the shock criteria used in this statistical analysis. We calculate the expected injection energy via diffusive shock acceleration given upstream parameters defined from the ACE Solar Wind Electron, Proton, and Alpha Monitor (SWEPAM) data to construct the theoretical upstream distribution. We show the comparison of shock strength derived from diffusive shock acceleration theory to observations in the 50 keV to 5 MeV range from an instrument on ACE. Parameters such as shock velocity, shock obliquity, particle number, and time between shocks are considered. This study is further divided into single and multiple shock categories, with an additional emphasis on forward-forward multiple shock pairs. Finally with regard to forward-forward shock pairs, results comparing injection energies of the first shock, second shock, and second shock with previous energetic population will be given.

  5. A polycrystalline model for stress-strain behaviour of tantalum at 300 K

    International Nuclear Information System (INIS)

    Frenois, S.; Munier, E.; Pilvin, P.

    2001-01-01

    A polycrystalline model is proposed to model the large plastic deformation and texture evolutions in tantalum over a wide range of strain rates at room temperature. The mechanical behaviour is discussed in terms of back and effective stresses with the help of qualitative and quantitative TEM observations. Using these observations, an elasto-visco-plastic formulation for b.c.c. crystals is developed in the thermal activation framework. (orig.)

  6. Formation of oxide layers on aluminum, niobium, and tantalum in molten alkali metal carbonates

    Science.gov (United States)

    Nikitina, E. V.; Kazakovtseva, N. A.

    2013-08-01

    The electrochemical synthesis of niobium, tantalum, and aluminum oxide nanolayers is studied in the melt of lithium, sodium, and potassium carbonates with various additives to a salt phase in an oxidizing atmosphere at a temperature of 773 and 873 K. A scheme is proposed for high-temperature anion local activation of the process.

  7. Metal halide-phosphorus halide-alkyl halide complexes: reaction with niobium and tantalum pentachlorides

    International Nuclear Information System (INIS)

    Puri, D.M.; Saini, M.S.

    1978-01-01

    The reactions of niobium and tantalum pentachlorides with trichlorophosphine and phenyldichlorophosphine have been studied in presence of alkylating agents such as sec-butyl chloride, iso-butyl chloride, tert-butyl chloride, tert-anylchloride, cyclohexyl chloride and triphenylmethyl chloride. Solid products have been isolated and characterised by vibrational spectroscopy as ionic complexes of alkyl- and/or aryl-phosphonium cations with hexachloroniobate and hexachlorotantalate anions. (author)

  8. On-line separation of refractory hafnium and tantalum isotopes at the ISOCELE separator

    CERN Document Server

    Liang, C F; Obert, J; Paris, P; Putaux, J C

    1981-01-01

    By chemical evaporation technique, neutron deficient hafnium nuclei have been on-line separated at the ISOCELE facility, from the isobar rare-earth elements, in the metal-fluoride HfF/sub 3//sup +/ ion form. Half-lives of /sup 162-165/Hf have been measured. Similarly, tantalum has been selectively separated on the TaF/sub 4//sup +/ form. (4 refs) .

  9. Iron Damage and Spalling Behavior below and above Shock Induced α ε Phase Transition

    International Nuclear Information System (INIS)

    Voltz, Christophe; Buy, Francois; Roy, Gilles

    2006-01-01

    The study of dynamic damage and fracture of iron has been undertaken below and above phase transition by series of time resolved experiments using both light gas launcher and powder gun. Shock wave tests were conducted by symmetrical impacts of high purity iron. To reveal the material behavior we have done shock experiments where the target is covered with a window in order to limit release amplitude and to avoid specimen fragmentation. Metallurgical analysis of soft recovered samples yields information about damage and fracture processes related to thermo-mechanical loading paths. Tests conducted without window allow studying effects of both phase change and release transition. Optical and SEM characterizations lead us to observe several modes of damage: brittle, ductile diffuse with void growth and heavily localized smooth one. These figures are related with: rarefaction shock waves or interfaces between transformed and not transformed iron. Simulations are performed with the 1D to compare experimental data with numerical results. We explain post-mortem observations by the complex shock wave structure interactions: P1 and P2 shock fronts associated with some corresponding shock release during unloading stages

  10. Density Effects on Post-shock Turbulence Structure

    Science.gov (United States)

    Tian, Yifeng; Jaberi, Farhad; Livescu, Daniel; Li, Zhaorui; Michigan State University Collaboration; Los Alamos National Laboratory Collaboration; Texas A&M University-Corpus Christi Collaboration

    2017-11-01

    The effects of density variations due to mixture composition on post-shock turbulence structure are studied using turbulence-resolving shock-capturing simulations. This work extends the canonical Shock-Turbulence Interaction (STI) problem to involve significant variable density effects. The numerical method has been verified using a series of grid and LIA convergence tests, and is used to generate accurate post-shock turbulence data for a detailed flow study. Density effects on post-shock turbulent statistics are shown to be significant, leading to an increased amplification of turbulent kinetic energy (TKE). Eulerian and Lagrangian analyses show that the increase in the post-shock correlation between rotation and strain is weakened in the case with significant density variations (referred to as the ``multi-fluid'' case). Similar to previous single-fluid results and LIA predictions, the shock wave significantly changes the topology of the turbulent structures, exhibiting a symmetrization of the joint PDF of second and third invariant of the deviatoric part of velocity gradient tensor. In the multi-fluid case, this trend is more significant and mainly manifested in the heavy fluid regions. Lagrangian data are also used to study the evolution of turbulence structure away from the shock wave and assess the accuracy of Lagrangian dynamical models.

  11. Reactivity Control of Rhodium Cluster Ions by Alloying with Tantalum Atoms.

    Science.gov (United States)

    Mafuné, Fumitaka; Tawaraya, Yuki; Kudoh, Satoshi

    2016-02-18

    Gas phase, bielement rhodium and tantalum clusters, RhnTam(+) (n + m = 6), were prepared by the double laser ablation of Rh and Ta rods in He carrier gas. The clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He and were subjected to collisions with NO and He at room temperature. The product species were observed by mass spectrometry, demonstrating that the NO molecules were sequentially adsorbed on the RhnTam(+) clusters to form RhnTam(+)NxOx (x = 1, 2, 3, ...) species. In addition, oxide clusters, RhnTam(+)O2, were also observed, suggesting that the NO molecules were dissociatively adsorbed on the cluster, the N atoms migrated on the surface to form N2, and the N2 molecules were released from RhnTam(+)N2O2. The reactivity, leading to oxide formation, was composition dependent: oxide clusters were dominantly formed for the bielement clusters containing both Rh and Ta atoms, whereas such clusters were hardly formed for the single-element Rhn(+) and Tam(+) clusters. DFT calculations indicated that the Ta atoms induce dissociation of NO on the clusters by lowering the dissociation energy, whereas the Rh atoms enable release of N2 by lowering the binding energy of the N atoms on the clusters.

  12. Particle magnetic moment conservation and resonance in a pure magnetohydrodynamic shock and field inclination influence on diffusive shock acceleration

    International Nuclear Information System (INIS)

    Lieu, R.; Quenby, J.J.

    1990-01-01

    Computational and analytical methods have been used in a study of particle acceleration by MHD shocks. Numerical simulations of single-particle trajectories indicate that magnetic moment is conserved quite accurately for an encounter with a near-perpendicular shock, and for all pitch angles except the very small ones. Acceleration is most effective for particles which are reflected by the shock at small pitch angles. If future encounters with the shock are possible, large acceleration will be repeated only for relativistic plasma flow velocities. Results for the pure MHD shock are then considered within the context of a diffusion model (hence a diffusive MHD shock). The microscopic approach is employed whereby one follows the history of a test particle and explicitly takes into account the possibility of reflection by the shock. Exact analytical solutions are currently available to order V/c, where V is the plasma flow speed, and are found to be in complete agreement with diffusion theory. More specifically, the presence of electromagnetic effects leads to a shortening of acceleration time scale but does not change the steady state spectrum of energetic particles. 7 refs

  13. Electrochemical Capacitors Based on Aligned Carbon Nanotubes Directly Synthesized on Tantalum Substrates

    International Nuclear Information System (INIS)

    Kim, Byung Woo; Chung, Hae Geun; Kim, Woong; Min, Byoung Koun; Kim, Hong Gon

    2010-01-01

    We demonstrate that vertically aligned carbon nanotubes can be synthesized directly on tantalum substrate via waterassisted chemical vapor deposition and evaluate their properties as electrochemical capacitors. The mean diameter of the carbon nanotubes was 7.1 ± 1.5 nm, and 70% of them had double walls. The intensity ratio of G-band to D-band in Raman spectra was as high as 5, indicating good quality of the carbon nanotubes. Owing to the alignment and low equivalent series resistance, the carbon nanotube based supercapacitors showed good rate performance. Rectangular shape of cyclic voltammogram was maintained even at the scan rate of > 1 V/s in 1 M sulfuric acid aqueous solution. Specific capacitance was well-retained (∼94%) even when the discharging current density dramatically increased up to 145 A/g. Consequently, specific power as high as 60 kW/kg was obtained from as-grown carbon nanotubes in aqueous solution. Maximum specific energy of ∼20 Wh/kg was obtained when carbon nanotubes were electrochemically oxidized and operated in organic solution. Demonstration of direct synthesis of carbon nanotubes on tantalum current collectors and their applications as supercapacitors could be an invaluable basis for fabrication of high performance carbon nanotube supercapacitors

  14. M551 metals melting experiment. [space manufacturing of aluminum alloys, tantalum alloys, stainless steels

    Science.gov (United States)

    Li, C. H.; Busch, G.; Creter, C.

    1976-01-01

    The Metals Melting Skylab Experiment consisted of selectively melting, in sequence, three rotating discs made of aluminum alloy, stainless steel, and tantalum alloy. For comparison, three other discs of the same three materials were similarly melted or welded on the ground. The power source of the melting was an electron beam unit. Results are presented which support the concept that the major difference between ground base and Skylab samples (i.e., large elongated grains in ground base samples versus nearly equiaxed and equal sized grains in Skylab samples) can be explained on the basis of constitutional supercooling, and not on the basis of surface phenomena. Microstructural observations on the weld samples and present explanations for some of these observations are examined. In particular, ripples and their implications to weld solidification were studied. Evidence of pronounced copper segregation in the Skylab A1 weld samples, and the tantalum samples studied, indicates a weld microhardness (and hence strength) that is uniformly higher than the ground base results, which is in agreement with previous predictions. Photographs are shown of the microstructure of the various alloys.

  15. Absolute Hugoniot measurements from a spherically convergent shock using x-ray radiography

    Science.gov (United States)

    Swift, Damian C.; Kritcher, Andrea L.; Hawreliak, James A.; Lazicki, Amy; MacPhee, Andrew; Bachmann, Benjamin; Döppner, Tilo; Nilsen, Joseph; Collins, Gilbert W.; Glenzer, Siegfried; Rothman, Stephen D.; Kraus, Dominik; Falcone, Roger W.

    2018-05-01

    The canonical high pressure equation of state measurement is to induce a shock wave in the sample material and measure two mechanical properties of the shocked material or shock wave. For accurate measurements, the experiment is normally designed to generate a planar shock which is as steady as possible in space and time, and a single state is measured. A converging shock strengthens as it propagates, so a range of shock pressures is induced in a single experiment. However, equation of state measurements must then account for spatial and temporal gradients. We have used x-ray radiography of spherically converging shocks to determine states along the shock Hugoniot. The radius-time history of the shock, and thus its speed, was measured by radiographing the position of the shock front as a function of time using an x-ray streak camera. The density profile of the shock was then inferred from the x-ray transmission at each instant of time. Simultaneous measurement of the density at the shock front and the shock speed determines an absolute mechanical Hugoniot state. The density profile was reconstructed using the known, unshocked density which strongly constrains the density jump at the shock front. The radiographic configuration and streak camera behavior were treated in detail to reduce systematic errors. Measurements were performed on the Omega and National Ignition Facility lasers, using a hohlraum to induce a spatially uniform drive over the outside of a solid, spherical sample and a laser-heated thermal plasma as an x-ray source for radiography. Absolute shock Hugoniot measurements were demonstrated for carbon-containing samples of different composition and initial density, up to temperatures at which K-shell ionization reduced the opacity behind the shock. Here we present the experimental method using measurements of polystyrene as an example.

  16. Testing the Asymmetry of Shocks with Euro Area

    Directory of Open Access Journals (Sweden)

    Marius-Corneliu MARINAŞ

    2012-01-01

    Full Text Available The objective of this study is to identify the demand and supply shocks affecting 13 EU member states and to estimate their degree of correlation with the Euro area shocks. This research ensures identifying the asymmetry of shocks degree with the monetary union, depending on which it’s judging the desirability of adopting a single currency. The analysis is also useful for the economies outside the Euro area, because they are strongly commercial and financial integrated especially with the core economies from union. Applying the Blanchard and Quah methodology to estimate the shocks in the period from 1998:1- 2010:3, I have found a weak and negative correlation between demand shocks and a medium to high correlation of the supply shocks. The results obtained suggest the presence of a structural convergence process with the Euro area, in the context of domestic macroeconomic policies rather different, both inside and outside the monetary union.

  17. High-Gain Shock Ignition on the National Ignition Facility

    Science.gov (United States)

    Perkins, L. J.; Lafortune, K.; Bailey, D.; Lambert, M.; MacKinnon, A.; Blackfield, D.; Comley, A.; Schurtz, G.; Ribeyre, X.; Lebel, E.; Casner, A.; Craxton, R. S.; Betti, R.; McKenty, P.; Anderson, K.; Theobald, W.; Schmitt, A.; Atzeni, S.; Schiavi, A.

    2010-11-01

    Shock ignition offers the possibility for a near-term test of high-gain ICF on the NIF at less than 1MJ drive energy and with day-1 laser hardware. We will summarize the status of target performance simulations, delineate the critical issues and describe the R&D program to be performed in order to test the potential of a shock-ignited target on NIF. In shock ignition, compressed fuel is separately ignited by a late-time laser-driven shock and, because capsule implosion velocities are significantly lower than those required for conventional hotpot ignition, simulations indicate that fusion energy gains of 60 may be achievable at laser energies around 0.5MJ. Like fast ignition, shock ignition offers high gain but requires only a single laser with less demanding timing and focusing requirements. Conventional symmetry and stability constraints apply, thus a key immediate step towards attempting shock ignition on NIF is to demonstrate adequacy of low-mode uniformity and shock symmetry under polar drive

  18. Leakage Current Degradation Due to Ion Drift and Diffusion in Tantalum and Niobium Oxide Capacitors

    Directory of Open Access Journals (Sweden)

    Kuparowitz Martin

    2017-06-01

    Full Text Available High temperature and high electric field applications in tantalum and niobium capacitors are limited by the mechanism of ion migration and field crystallization in a tantalum or niobium pentoxide insulating layer. The study of leakage current (DCL variation in time as a result of increasing temperature and electric field might provide information about the physical mechanism of degradation. The experiments were performed on tantalum and niobium oxide capacitors at temperatures of about 125°C and applied voltages ranging up to rated voltages of 35 V and 16 V for tantalum and niobium oxide capacitors, respectively. Homogeneous distribution of oxygen vacancies acting as positive ions within the pentoxide layer was assumed before the experiments. DCL vs. time characteristics at a fixed temperature have several phases. At the beginning of ageing the DCL increases exponentially with time. In this period ions in the insulating layer are being moved in the electric field by drift only. Due to that the concentration of ions near the cathode increases producing a positively charged region near the cathode. The electric field near the cathode increases and the potential barrier between the cathode and insulating layer decreases which results in increasing DCL. However, redistribution of positive ions in the insulator layer leads to creation of a ion concentration gradient which results in a gradual increase of the ion diffusion current in the direction opposite to the ion drift current component. The equilibrium between the two for a given temperature and electric field results in saturation of the leakage current value. DCL vs. time characteristics are described by the exponential stretched law. We found that during the initial part of ageing an exponent n = 1 applies. That corresponds to the ion drift motion only. After long-time application of the electric field at a high temperature the DCL vs. time characteristics are described by the exponential

  19. Structural and photoluminescent properties of a composite tantalum oxide and silicon nanocrystals embedded in a silicon oxide film

    International Nuclear Information System (INIS)

    Díaz-Becerril, T.; Herrera, V.; Morales, C.; García-Salgado, G.; Rosendo, E.; Coyopol, A.; Galeazzi, R.; Romano, R.; Nieto-Caballero, F.G.; Sarmiento, J.

    2017-01-01

    Tantalum oxide crystals encrusted in a silicon oxide matrix were synthesized by using a hot filament chemical vapor deposition system (HFCVD). A solid source composed by a mixture in different percentages of Ta 2 O 5 and silicon (Si) powders were used as reactants. The films were grown at 800 °C and 1000 °C under hydrogen ambient. The deposited films were characterized by X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) at room temperature. From the XPS results it was confirmed the formation of a mixture of Tantalum oxide, silicon oxide and Si nanoparticles (Ta 2 O 5- SiO 2 -Si(nc)) as seen from the Si (2p) and Ta (4f) lines corresponding to Si + and Ta + states respectively. Ta 2 O 5 and Si nanocrystals (Si-NCs) embedded in the silicon oxide films were observed on HRTEM images which corroborate the XPS results. Finally the emission properties of the films exhibited a broad band from 400 to 850 nm caused by the independent PL properties of tantalum oxide and Si-NCs that compose the film. The intensity of the emissions was observed to be dependent on both temperature of deposition and the ratio Ta 2 O 5 /Si, used as initial reactants. Results from this work might supply useful data for the development of future light emitter devices.

  20. Activation of human leukocytes on tantalum trabecular metal in comparison to commonly used orthopedic metal implant materials.

    Science.gov (United States)

    Schildhauer, T A; Peter, E; Muhr, G; Köller, M

    2009-02-01

    We analyzed leukocyte functions and cytokine response of human leukocytes toward porous tantalum foam biomaterial (Trabecular Metaltrade mark, TM) in comparison to equally sized solid orthopedic metal implant materials (pure titanium, titanium alloy, stainless steel, pure tantalum, and tantalum coated stainless steel). Isolated peripheral blood mononuclear cells (PBMC) and polymorphonuclear neutrophil leukocytes (PMN) were cocultured with equally sized metallic test discs for 24 h. Supernatants were analyzed for cytokine content by enzyme-linked immunosorbent assay. Compared to the other used test materials there was a significant increase in the release of IL (interleukin)-1ra and IL-8 from PMN, and of IL-1ra, IL-6, and TNF-alpha from PBMC in response to the TM material. The cytokine release correlated with surface roughness of the materials. In contrast, the release of IL-2 was not induced showing that mainly myeloid leukocytes were activated. In addition, supernatants of these leukocyte/material interaction (conditioned media, CM) were subjected to whole blood cell function assays (phagocytosis, chemotaxis, bacterial killing). There was a significant increase in the phagocytotic capacity of leukocytes in the presence of TM-conditioned media. The chemotactic response of leukocytes toward TM-conditioned media was significantly higher compared to CM obtained from other test materials. Furthermore, the bactericidal capacity of whole blood was enhanced in the presence of TM-conditioned media. These results indicate that leukocyte activation at the surface of TM material induces a microenvironment, which may enhance local host defense mechanisms.

  1. Cobalt phosphate-modified barium-doped tantalum nitride nanorod photoanode with 1.5% solar energy conversion efficiency

    KAUST Repository

    Li, Yanbo

    2013-10-03

    Spurred by the decreased availability of fossil fuels and global warming, the idea of converting solar energy into clean fuels has been widely recognized. Hydrogen produced by photoelectrochemical water splitting using sunlight could provide a carbon dioxide lean fuel as an alternative to fossil fuels. A major challenge in photoelectrochemical water splitting is to develop an efficient photoanode that can stably oxidize water into oxygen. Here we report an efficient and stable photoanode that couples an active barium-doped tantalum nitride nanostructure with a stable cobalt phosphate co-catalyst. The effect of barium doping on the photoelectrochemical activity of the photoanode is investigated. The photoanode yields a maximum solar energy conversion efficiency of 1.5%, which is more than three times higher than that of state-of-the-art single-photon photoanodes. Further, stoichiometric oxygen and hydrogen are stably produced on the photoanode and the counter electrode with Faraday efficiency of almost unity for 100 min. © 2013 Macmillan Publishers Limited. All rights reserved.

  2. Revisiting the single cell protein application of Cupriavidus necator H16 and recovering bioplastic granules simultaneously.

    Directory of Open Access Journals (Sweden)

    Balakrishnan Kunasundari

    Full Text Available Cupriavidus necator H16 (formerly known as Hydrogenomonas eutropha was famous as a potential single cell protein (SCP in the 1970s. The drawback however was the undesirably efficient accumulation of non-nutritive polyhydroxybutyrate (PHB storage compound in the cytoplasm of this bacterium. Eventually, competition from soy-based protein resulted in SCP not receiving much attention. Nevertheless, C. necator H16 remained in the limelight as a producer of PHB, which is a material that resembles commodity plastics such as polypropylene. PHB is a 100% biobased and biodegradable polyester. Although tremendous achievements have been attained in the past 3 decades in the efficient production of PHB, this bioplastic is still costly. One of the main problems has been the recovery of PHB from the cell cytoplasm. In this study, we showed for the first time that kilogram quantities of PHB can be easily recovered in the laboratory without the use of any solvents and chemicals, just by using the cells as SCP. In addition, the present study also demonstrated the safety and tolerability of animal model used, Sprague Dawley given lyophilized cells of C. necator H16. The test animals readily produced fecal pellets that were whitish in color, as would be expected of PHB granules. The pellets were determined to contain about 82-97 wt% PHB and possessed molecular mass of around 930 kg/mol. The PHB granules recovered biologically possessed similar molecular mass compared to chloroform extracted PHB [950 kg/mol]. This method now allows the production and purification of substantial quantities of PHB for various experimental trials. The method reported here is easy, does not require expensive instrumentation, scalable and does not involve extensive use of solvents and strong chemicals.

  3. Morphology, proliferation, and osteogenic differentiation of mesenchymal stem cells cultured on titanium, tantalum, and chromium surfaces

    DEFF Research Database (Denmark)

    Stiehler, Maik; Lind, M.; Mygind, Tina

    2007-01-01

    the interactions between human mesenchymal stem cells (MSCs) and smooth surfaces of titanium (Ti), tantalum (Ta), and chromium (Cr). Mean cellular area was quantified using fluorescence microscopy (4 h). Cellular proliferation was assessed by (3)H-thymidine incorporation and methylene blue cell counting assays (4...

  4. Parametric study on the performance of automotive MR shock absorbers

    Science.gov (United States)

    Gołdasz, J.; Dzierżek, S.

    2016-09-01

    The paper contains the results of a parametric study to explore the influence of various quantities on the performance range of semi-active automotive shock absorbers using the magnetorheological (MR) fluid under steady-state and transient excitations. The analysis was performed with simulated data and using a standard single-tube shock absorber configuration with a single-gap MR valve. Additionally, the impact of material variables and valves geometry was examined as the parameters were varied and its dynamic range studied.

  5. Thermophysical properties of multi-shock compressed dense argon.

    Science.gov (United States)

    Chen, Q F; Zheng, J; Gu, Y J; Chen, Y L; Cai, L C; Shen, Z J

    2014-02-21

    In contrast to the single shock compression state that can be obtained directly via experimental measurements, the multi-shock compression states, however, have to be calculated with the aid of theoretical models. In order to determine experimentally the multiple shock states, a diagnostic approach with the Doppler pins system (DPS) and the pyrometer was used to probe multiple shocks in dense argon plasmas. Plasma was generated by a shock reverberation technique. The shock was produced using the flyer plate impact accelerated up to ∼6.1 km/s by a two-stage light gas gun and introduced into the plenum argon gas sample, which was pre-compressed from the environmental pressure to about 20 MPa. The time-resolved optical radiation histories were determined using a multi-wavelength channel optical transience radiance pyrometer. Simultaneously, the particle velocity profiles of the LiF window was measured with multi-DPS. The states of multi-shock compression argon plasma were determined from the measured shock velocities combining the particle velocity profiles. We performed the experiments on dense argon plasmas to determine the principal Hugonoit up to 21 GPa, the re-shock pressure up to 73 GPa, and the maximum measure pressure of the fourth shock up to 158 GPa. The results are used to validate the existing self-consistent variational theory model in the partial ionization region and create new theoretical models.

  6. Experimental Shock Transformation of Gypsum to Anhydrite: A New Low Pressure Regime Shock Indicator

    Science.gov (United States)

    Bell, Mary S.; Zolensky, Michael E.

    2011-01-01

    The shock behavior of gypsum is important in understanding the Cretaceous/Paleogene event and other terrestrial impacts that contain evaporite sediments in their targets (e.g., Mars Exploration Rover Spirit detected sulfate at Gusev crater, [1]). Most interest focuses on issues of devolatilization to quantify the production of SO2 to better understand its role in generating a temporary atmosphere and its effects on climate and biota [2,3]. Kondo and Ahrens [4] measured induced radiation emitted from single crystal gypsum shocked to 30 and 40 GPa. They observed greybody emission spectra corresponding to temperatures in the range of 3,000 to 4,000 K that are a factor of 2 to 10 times greater than calculated pressure-density energy equation of state temperatures (Hugoniot) and are high enough to melt gypsum. Chen et al. [5] reported results of shock experiments on anhydrite, gypsum, and mixtures of these phases with silica. Their observations indicated little or no devolatilization of anhydrite shocked to 42 GPa and that the fraction of sulfur, by mass, that degassed is approx.10(exp -2) of theoretical prediction. In another report of shock experiments on calcite, anhydrite, and gypsum, Badjukov et al. [6] observed only intensive plastic deformation in anhydrite shock loaded at 63 GPa, and gypsum converted to anhydrite when shock loaded at 56 GPa but have not experimentally shocked gypsum in a step-wise manner to constrain possible incipient transformation effects. Schmitt and Hornemann [7] shock loaded anhydrite and quartz to a peak pressure of 60 GPa and report the platy anhydrite grains were completely pseudomorphed by small crystallized anhydrite grains. However, no evidence of interaction between the two phases could be observed and they suggested that recrystallization of anhydrite grains is the result of a solid-state transformation. They concluded that significant decomposition of anhydrite requires shock pressures higher than 60 GPa. Gupta et al. [8

  7. X-ray diffraction measurements to determine longitudinal and transverse lattice deformation in shocked LiF

    International Nuclear Information System (INIS)

    Rigg, P.A.; Gupta, Y.M.

    2000-01-01

    Experimental methods using both single and multiple x-ray diffraction were developed to determine real time, lattice deformation in directions parallel and perpendicular to shock wave propagation in single crystals subjected to plate impact loading. Initial experiments used single diffraction to monitor the interplanar spacing change, parallel to the shock propagation direction, in LiF crystals shocked along the [111] and [100] directions. These measurements, in combination with the macroscopic volume compression, were used to determine the state of compression of the unit cell. Subsequent development of a multiple diffraction technique permitted simultaneous determination of both the longitudinal and transverse lattice deformations. The present results showed that shock compression, below 4 GPa, along the [111] orientation--which results in macroscopic elastic deformation - produced one-dimensional unit cell compression. In contrast, shock compression along the [100] orientation - which results in macroscopic elastic-plastic deformation--produced isotropic unit cell compression. The implications of the present results and the ability to make quantitative x-ray diffraction measurements under shock loading are discussed

  8. Evaluation of a recycling process for printed circuit board by physical separation and heat treatment

    International Nuclear Information System (INIS)

    Fujita, Toyohisa; Ono, Hiroyuki; Dodbiba, Gjergj; Yamaguchi, Kunihiko

    2014-01-01

    Highlights: • The parts mounted on printed circuit board (PCB) were liberated by underwater explosion and mechanical crushing. • The crushed PCB without surface-mounted parts was carbonized under inert atmosphere at 873 K to recover copper. • The multi-layered ceramic capacitors including nickel was carbonized at 873 K to recover nickel by the magnetic separation. • The tantalum powders were recovered from the molded resins by heat treatment at 723 and 823 K in air atmosphere and screening. • Energy and treatment cost of new process increased, however, the environmental burden decreased comparing conventional one. - Abstract: Printed circuit boards (PCBs) from discarded personal computer (PC) and hard disk drive were crushed by explosion in water or mechanical comminution in order to disintegrate the attached parts. More parts were stripped from PCB of PC, composed of epoxy resin; than from PCB of household appliance, composed of phenol resin. In an attempt to raise the copper grade of PCB by removing other components, a carbonization treatment was investigated. The crushed PCB without surface-mounted parts was carbonized under a nitrogen atmosphere at 873–1073 K. After screening, the char was classified by size into oversized pieces, undersized pieces and powder. The copper foil and glass fiber pieces were liberated and collected in undersized fraction. The copper foil was liberated easily from glass fiber by stamping treatment. As one of the mounted parts, the multi-layered ceramic capacitors (MLCCs), which contain nickel, were carbonized at 873 K. The magnetic separation is carried out at a lower magnetic field strength of 0.1 T and then at 0.8 T. In the +0.5 mm size fraction the nickel grade in magnetic product was increased from 0.16% to 6.7% and the nickel recovery is 74%. The other useful mounted parts are tantalum capacitors. The tantalum capacitors were collected from mounted parts. The tantalum-sintered bodies were separated from molded resins

  9. Surface flaw in a thermally shocked hollow cylinder

    International Nuclear Information System (INIS)

    Kobayashi, A.S.; Emery, A.F.; Polvanich, N.; Love, W.J.

    1975-01-01

    The objective of this paper is to illustrate a procedure for estimating the stress intensity factors of a semi-elliptical crack located in the inner or outer surface of a thermally shocked hollow cylinder. The first step in this procedure is to estimate the transient thermal elastic stresses induced by sudden cooling of an uncracked cylinder by numerically evaluating standard heat transfer and thermal stress formulae. The stresses at the location of the crack surface in the uncracked cylinder are eliminated by the method of superposition in order to obtain a stress free crack surface. The stress intensity factors are then determined by a judicious use of two sets of solutions, one set involving stress intensity factors for a semi-elliptical crack in a flat plate and subjected to a polynomial distribution of pressure loading, and another set involving single-edge notched plates with prescribed edge-displacements and single-edge internally or externally notched cylinders with thermal shock loading. The former solutions are determined by the alternating technique in three-dimensional fracture mechanics with a fourth order polynomial pressure distribution on the crack surface where both the front and back surface effects are accounted for. The latter solutions involve two-dimensional finite element solutions of single-edge notched plates with prescribed edge-displacements and single-edge notched cylinders with thermal shock loading. By comparing these two two-dimensional solutions, an estimate of the effect of the cylindrical curvature on an edge-cracked plate is obtained. The combination of these two sets of solutions thus yields an estimate of the stress intensity factor in an internal and external semi-elliptical crack in a thermally shocked cylinder

  10. Trace diffusion of different nuclear reactions products in polycrystalline tantalum

    International Nuclear Information System (INIS)

    Beyer, G.J.; Fromm, W.D.; Novgorodov, A.F.

    1976-07-01

    Measurements of the lattice diffusion coefficients for carrier free isotopes of Hf, Lu, Yb, Tm, Tb, Gd, Eu, Ba, Cs, Y, Sr, Rb and As in polycrystalline tantalum were made over the temperature range 1700 Fsub(As)>Fsub(lanthanides)>Fsub(Sr)>Fsub(Ba)>Fsub(Hf)>Fsub(Rb)>Fsub(Cs). The data indicate, that the Arrhenius relation was obeyed over the entire temperature range. Within the lanthanide-group no differences in the diffusion velocities could be detected, this fact points to a diffusion mechanism of Me 3+ -ions of lanthanides, Me 2+ -ions of earth alkaline elements and Me + -ions of alkaline elements. (author)

  11. Unusual behaviour of usual materials in shock waves

    International Nuclear Information System (INIS)

    Kanel, G I

    2014-01-01

    Exotic results of investigations of inelastic deformation and fracture under shock wave loading are presented and briefly discussed. Temperature effects on the flow stress at high strain rate may differ even in sign from those we observe at low and moderate strain rates. Investigations of the temperature-rate dependence of the yield stress at shock compression demonstrate intense multiplication of dislocations. At the highest strain rates, so-called ideal (ultimate) shear and tensile strength is reached in experiments with picosecond durations of shock loading. Although grain boundaries, in general, reduce resistance to fracture as compared to single crystals, the spall strength of ultra-fine-grained metals usually slightly exceeds that of coarse-grain samples. Failure wave phenomena have been observed in shock-compressed glasses.

  12. Evolution of elastic precursor and plastic shock wave in copper via molecular dynamics simulations

    International Nuclear Information System (INIS)

    Perriot, Romain; Zhakhovsky, Vasily V; Oleynik, Ivan I; Inogamov, Nail A

    2014-01-01

    Large-scale molecular dynamics (MD) simulations are performed to investigate shock propagation in single crystal copper. It is shown that the P-V plastic Hugoniot is unique regardless of the sample's orientation, its microstructure, or its length. However, the P-V pathway to the final state is not, and depends on many factors. Specifically, it is shown that the pressure in the elastic precursor (the Hugoniot elastic limit (HEL)) decreases as the shock wave propagates in a micron-sized sample. The attenuation of the HEL in sufficiently-long samples is the main source of disagreement between previous MD simulations and experiment: while single crystal experiments showed that the plastic shock speed is orientation-independent, the simulated plastic shock speed was observed to be orientation-dependent in relatively short single-crystal samples. Such orientation dependence gradually disappears for relatively long, micrometer-sized, samples for all three low-index crystallographic directions (100), (110), and (111), and the plastic shock velocities for all three directions approach the one measured in experiment. The MD simulations also demonstrate the existence of subsonic plastic shock waves generated by relatively weak supporting pressures.

  13. Effects of the [OC6F5] moiety upon structural geometry: crystal structures of half-sandwich tantalum(V) aryloxide complexes from reaction of Cp*Ta(N(t)Bu)(CH2R)2 with pentafluorophenol.

    Science.gov (United States)

    Cole, Jacqueline M; Chan, Michael C W; Gibson, Vernon C; Howard, Judith A K

    2011-10-01

    The synthesis, chemical and structural characterization of a series of pentamethylcyclopentadienyl (Cp*) tantalum imido complexes and aryloxide derivatives are presented. Specifically, the imido complexes Cp*Ta(N(t)Bu)(CH(2)R)(2), where R = Ph [dibenzyl(tert-butylamido) (η(5)-pentamethylcyclopentadienyl)tantalum(IV) (1)], Me(2)Ph [tert-butylamido)bis(2-methyl-2-phenylpropyl) (η(5)-pentamethylcyclopentadienyl)tantalum(IV) (2)], CMe(3) [(tert-butylamido)bis(2,2-dimethylpropyl) (η(5)-pentamethylcyclopentadienyl)tantalum(IV) (3)], are reported. The crystal structure of (3) reveals α-agostic interactions with the Ta atom. The resulting increase in the tantalum core coordination improves electronic stability. As such it does not react with pentafluorophenol, in contrast to the other two reported imido complexes [(1) and (2)]. Addition of C(6)F(5)OH to (1) yields a dimeric aryl-oxide derivative, [Cp*Ta(CH(2)Ph)(OC(6)H(5))(μ-O)](2) [di-μ-oxido-bis[benzyl(pentafluorophenolato) (η(5)-pentamethylcyclopentadienyl)tantalum(V)] (4)]. Its crystal structure reveals long Ta-O(C(6)H(5)) bonds but short oxo-bridging Ta-O bonds. This is explained by accounting for the fierce electronic competition for the vacant d(π) orbitals of the electrophilic Ta(V) centre. Steric congestion around each metal is alleviated by a large twist angle (77.1°) between the benzyl and pentafluorophenyl ligands and the ordering of each of these groups into stacked pairs. The imido complex (2) reacts with C(6)F(5)OH to produce a mixture of Cp*Ta(OC(6)F(5))(4) [tetrakis(pentafluorophenolato)(η(5)-pentamethylcyclopentadienyl)tantalum(V) (5)] and [Cp*Ta(OC(6)F(5))(2)(μ-O)](2) [di-μ-oxido-bis[bis(pentafluorophenolato)(η(5)-pentamethylcyclopentadienyl)tantalum(V)] (6)]. Steric congestion is offset in both cases by the twisting of its pentafluorophenyl ligands. Particularly strong electronic competition for the empty d(π) metal orbitals in (6) is reflected in its bond geometry, and owes itself to the

  14. Modified porous tantalum rod technique for the treatment of femoral head osteonecrosis.

    Science.gov (United States)

    Pakos, Emilios E; Megas, Panayiotis; Paschos, Nikolaos K; Syggelos, Spyridon A; Kouzelis, Antonios; Georgiadis, Georgios; Xenakis, Theodoros A

    2015-11-18

    To study a modified porous tantalum technique for the treatment of osteonecrosis of the femoral head. The porous tantalum rod was combined with endoscopy, curettage, autologous bone grafting and use of bone marrow aspirates from iliac crest aspiration in 49 patients (58 hips) with a mean age of 38 years. The majority of the patients had idiopathic osteonecrosis, followed by corticosteroid-induced osteonecrosis. Thirty-eight hips were of Steinberg stage II disease and 20 hips were of stage III disease. Patients were followed for 5 years and were evaluated clinically with the Merle D'Aubigne and Postel score and radiologically. The primary outcome of the study was survival based on the conversion to total hip arthroplasty (THA). Secondary outcomes included deterioration of the osteonecrosis to a higher disease stage at 5 years compared to the preoperative period and identification of factors that were associated with survival. The Kaplan-Meier survival analysis was performed to evaluate the survivorship of the prosthesis, and the Fisher exact test was performed to test associations between various parameters with survival. No patient developed any serious intraoperative or postoperative complication including implant loosening or migration and donor site morbidity. During the 5-year follow up, 1 patient died, 7 patients had disease progression and 4 hips were converted to THA. The 5-year survival based on conversion to THA was 93.1% and the respective rate based on disease progression was 87.9%. Stage II disease was associated with statistically significant better survival rates compared to stage III disease (P = 0.04). The comparison between idiopathic and non-idiopathic osteonecrosis and between steroid-induced and non-steroid-induced osteonecrosis did not showed any statistically significant difference in survival rates. The clinical evaluation revealed statistically significantly improved Merle d'Aubigne scores at 12 mo postoperatively compared to the

  15. Proposal for a method to estimate nutrient shock effects in bacteria

    Directory of Open Access Journals (Sweden)

    Azevedo Nuno F

    2012-08-01

    Full Text Available Abstract Background Plating methods are still the golden standard in microbiology; however, some studies have shown that these techniques can underestimate the microbial concentrations and diversity. A nutrient shock is one of the mechanisms proposed to explain this phenomenon. In this study, a tentative method to assess nutrient shock effects was tested. Findings To estimate the extent of nutrient shock effects, two strains isolated from tap water (Sphingomonas capsulata and Methylobacterium sp. and two culture collection strains (E. coli CECT 434 and Pseudomonas fluorescens ATCC 13525 were exposed both to low and high nutrient conditions for different times and then placed in low nutrient medium (R2A and rich nutrient medium (TSA. The average improvement (A.I. of recovery between R2A and TSA for the different times was calculated to more simply assess the difference obtained in culturability between each medium. As expected, A.I. was higher when cells were plated after the exposition to water than when they were recovered from high-nutrient medium showing the existence of a nutrient shock for the diverse bacteria used. S. capsulata was the species most affected by this phenomenon. Conclusions This work provides a method to consistently determine the extent of nutrient shock effects on different microorganisms and hence quantify the ability of each species to deal with sudden increases in substrate concentration.

  16. Comparison of structure, function and regulation of plant cold shock domain proteins to bacterial and animal cold shock domain proteins.

    Science.gov (United States)

    Chaikam, Vijay; Karlson, Dale T

    2010-01-01

    The cold shock domain (CSD) is among the most ancient and well conserved nucleic acid binding domains from bacteria to higher animals and plants. The CSD facilitates binding to RNA, ssDNA and dsDNA and most functions attributed to cold shock domain proteins are mediated by this nucleic acid binding activity. In prokaryotes, cold shock domain proteins only contain a single CSD and are termed cold shock proteins (Csps). In animal model systems, various auxiliary domains are present in addition to the CSD and are commonly named Y-box proteins. Similar to animal CSPs, plant CSPs contain auxiliary C-terminal domains in addition to their N-terminal CSD. Cold shock domain proteins have been shown to play important roles in development and stress adaptation in wide variety of organisms. In this review, the structure, function and regulation of plant CSPs are compared and contrasted to the characteristics of bacterial and animal CSPs. [BMB reports 2010; 43(1): 1-8].

  17. Tantalum films with well-controlled roughness grown by oblique incidence deposition

    Science.gov (United States)

    Rechendorff, K.; Hovgaard, M. B.; Chevallier, J.; Foss, M.; Besenbacher, F.

    2005-08-01

    We have investigated how tantalum films with well-controlled surface roughness can be grown by e-gun evaporation with oblique angle of incidence between the evaporation flux and the surface normal. Due to a more pronounced shadowing effect the root-mean-square roughness increases from about 2 to 33 nm as grazing incidence is approached. The exponent, characterizing the scaling of the root-mean-square roughness with length scale (α), varies from 0.75 to 0.93, and a clear correlation is found between the angle of incidence and root-mean-square roughness.

  18. Graphene-induced strengthening in spark plasma sintered tantalum carbide–nanotube composite

    International Nuclear Information System (INIS)

    Lahiri, Debrupa; Khaleghi, Evan; Bakshi, Srinivasa Rao; Li, Wei; Olevsky, Eugene A.; Agarwal, Arvind

    2013-01-01

    Transverse rupture strength of spark plasma sintered tantalum carbide (TaC) composites reinforced with long and short carbon nanotubes (CNTs) is reported. The rupture strength depends on the transformation behavior of the CNTs during spark plasma sintering, which is dependent on their length. The TaC composite with short nanotubes shows the highest specific rupture strength. Shorter CNTs transform into multi-layered graphene sheets between TaC grains, whereas long ones retain the tubular structure. Two-dimensionsal graphene platelets offer higher resistance to pull-out, resulting in delayed fracture and higher strength.

  19. Thermal and electrical conductivities of high purity tantalum

    International Nuclear Information System (INIS)

    Archer, S.L.

    1978-01-01

    The electrical resistivity and thermal conductivity of three high purity tantalum samples have been measured as functions of temperature over a temperature range of 5K to 65K. Sample purities ranged up to a resistivity ratio of 1714. The highest purity sample had a residual resistivity of .76 x 10 -10 OMEGA-m. The intrinsic resistivity varied as T 3 . 9 from 10K to 31K. The thermal conductivity of the purest sample had a maximum of 840 W/mK at 9.8K. The intrinsic thermal resistivity varied as T 2 . 4 from 10K to 35K. At low temperatures electrons were scattered primarily by impurities and by phonons with both interband and intraband transitions observed. The electrical and thermal resistivity is departed from Matthiessen's rule at low temperatures

  20. Geometrical shock dynamics for magnetohydrodynamic fast shocks

    KAUST Repository

    Mostert, W.; Pullin, D. I.; Samtaney, Ravi; Wheatley, V.

    2016-01-01

    We describe a formulation of two-dimensional geometrical shock dynamics (GSD) suitable for ideal magnetohydrodynamic (MHD) fast shocks under magnetic fields of general strength and orientation. The resulting area–Mach-number–shock-angle relation is then incorporated into a numerical method using pseudospectral differentiation. The MHD-GSD model is verified by comparison with results from nonlinear finite-volume solution of the complete ideal MHD equations applied to a shock implosion flow in the presence of an oblique and spatially varying magnetic field ahead of the shock. Results from application of the MHD-GSD equations to the stability of fast MHD shocks in two dimensions are presented. It is shown that the time to formation of triple points for both perturbed MHD and gas-dynamic shocks increases as (Formula presented.), where (Formula presented.) is a measure of the initial Mach-number perturbation. Symmetry breaking in the MHD case is demonstrated. In cylindrical converging geometry, in the presence of an azimuthal field produced by a line current, the MHD shock behaves in the mean as in Pullin et al. (Phys. Fluids, vol. 26, 2014, 097103), but suffers a greater relative pressure fluctuation along the shock than the gas-dynamic shock. © 2016 Cambridge University Press

  1. Geometrical shock dynamics for magnetohydrodynamic fast shocks

    KAUST Repository

    Mostert, W.

    2016-12-12

    We describe a formulation of two-dimensional geometrical shock dynamics (GSD) suitable for ideal magnetohydrodynamic (MHD) fast shocks under magnetic fields of general strength and orientation. The resulting area–Mach-number–shock-angle relation is then incorporated into a numerical method using pseudospectral differentiation. The MHD-GSD model is verified by comparison with results from nonlinear finite-volume solution of the complete ideal MHD equations applied to a shock implosion flow in the presence of an oblique and spatially varying magnetic field ahead of the shock. Results from application of the MHD-GSD equations to the stability of fast MHD shocks in two dimensions are presented. It is shown that the time to formation of triple points for both perturbed MHD and gas-dynamic shocks increases as (Formula presented.), where (Formula presented.) is a measure of the initial Mach-number perturbation. Symmetry breaking in the MHD case is demonstrated. In cylindrical converging geometry, in the presence of an azimuthal field produced by a line current, the MHD shock behaves in the mean as in Pullin et al. (Phys. Fluids, vol. 26, 2014, 097103), but suffers a greater relative pressure fluctuation along the shock than the gas-dynamic shock. © 2016 Cambridge University Press

  2. Contact Resistance of Tantalum Coatings in Fuel Cells and Electrolyzers using Acidic Electrolytes at Elevated Temperatures

    DEFF Research Database (Denmark)

    Jensen, Annemette Hindhede; Christensen, Erik; Barner, Jens H. Von

    2014-01-01

    stainless steel were found to be far below the US Department of Energy target value of 10mcm2. The good contact resistance of tantalum was demonstrated by simulating high temperature polymer electrolyte membrane electrolysis conditions by anodization performed in 85% phosphoric acid at 130◦C, followed...

  3. Extended charge banking model of dual path shocks for implantable cardioverter defibrillators.

    Science.gov (United States)

    Dosdall, Derek J; Sweeney, James D

    2008-08-01

    Single path defibrillation shock methods have been improved through the use of the Charge Banking Model of defibrillation, which predicts the response of the heart to shocks as a simple resistor-capacitor (RC) circuit. While dual path defibrillation configurations have significantly reduced defibrillation thresholds, improvements to dual path defibrillation techniques have been limited to experimental observations without a practical model to aid in improving dual path defibrillation techniques. The Charge Banking Model has been extended into a new Extended Charge Banking Model of defibrillation that represents small sections of the heart as separate RC circuits, uses a weighting factor based on published defibrillation shock field gradient measures, and implements a critical mass criteria to predict the relative efficacy of single and dual path defibrillation shocks. The new model reproduced the results from several published experimental protocols that demonstrated the relative efficacy of dual path defibrillation shocks. The model predicts that time between phases or pulses of dual path defibrillation shock configurations should be minimized to maximize shock efficacy. Through this approach the Extended Charge Banking Model predictions may be used to improve dual path and multi-pulse defibrillation techniques, which have been shown experimentally to lower defibrillation thresholds substantially. The new model may be a useful tool to help in further improving dual path and multiple pulse defibrillation techniques by predicting optimal pulse durations and shock timing parameters.

  4. Investigation of the dynamic behavior in materials submitted to sub-picosecond laser driven shock

    International Nuclear Information System (INIS)

    Cuq-Lelandais, Jean-Paul

    2010-01-01

    Laser driven shocks allow to investigate materials behavior at high strain rate and present a great interest for research and industrial applications. The latest laser technologies evolutions provide an access to shorter regimes in duration, below the picosecond. This work, which results from a collaboration between the P' institute, the PIMM laboratory and the CEA-DAM, is dedicated to the characterization of the metallic material behavior in this ultra-short mode (aluminium, tantalum), leading to extreme dynamic solicitation in the target (>10 7 s -1 ). The study includes the validation of experimental results obtained on the LULI 100 TW facility by comparison with numerical model. First, the study is orientated to the femtosecond (fs) laser-matter interaction, which is different from what happens in nanosecond regime. Indeed, the characteristic duration scale is comparable to several molecular phenomena like non-equilibrium electrons-ions states. The aim is to determine the equivalent pressure loading induced by the laser pulse on the target. Then, the shock wave propagation within the target has been studied and particularly its pressure decay, notably strong in this regime. In this configuration, the spalls observed are thin, a few μm order, and show a planar rupture morphology. The results obtained by post-mortem observation show that the spall thickness is thinner if the target thickness is reduced. The spalls are characterized by the VISAR measurement. Within the framework of dynamic damage modeling and rupture criteria dimensioning, particularly those which have been validated in the ns regime as Kanel, shots with different thicknesses have been carried out to determine the damage properties in function of strain rate and validate the parameters by prolongation to the ultra-shorts modes. Then, the study has been generalized to the 2D propagation waves, which can explain the spall diameter evolutions. Meanwhile, microscopic simulations of ultra-short laser

  5. Influence of laser alloyed layer of carbon steel with tantalum on the structure and surface layer properties

    International Nuclear Information System (INIS)

    Woldan, A.; Kusinski, J.; Kac, S.

    1999-01-01

    The paper describes the microstructure and properties (chemical composition and microhardness) of the surface laser alloyed layer with tantalum. The surface alloyed zones varied in microstructure, zones depth and width, as well as Ta content according to the thickness of the coated layer, bonding paint type and process parameters (power and scanning velocity). The electron microprobe analysis of melts showed that higher tantalum content in the melted zone resulted from the thicker original Ta coating as well as slower scanning velocity. Scanning electron microscopy examinations show that dendritic structure of the melted zone becomes evident when carbon was used as one of the components of the binder, while structure is typically martensitic when silicon containing binder was used for powder deposition. Samples covered with Ta and carbon containing binder showed after laser alloying higher hardness than in case of using silicon containing binder. (author)

  6. Structural and photoluminescent properties of a composite tantalum oxide and silicon nanocrystals embedded in a silicon oxide film

    Energy Technology Data Exchange (ETDEWEB)

    Díaz-Becerril, T., E-mail: tomas.diaz.be@gmail.com; Herrera, V.; Morales, C.; García-Salgado, G.; Rosendo, E.; Coyopol, A., E-mail: acoyopol@gmail.com; Galeazzi, R.; Romano, R.; Nieto-Caballero, F.G.; Sarmiento, J.

    2017-04-15

    Tantalum oxide crystals encrusted in a silicon oxide matrix were synthesized by using a hot filament chemical vapor deposition system (HFCVD). A solid source composed by a mixture in different percentages of Ta{sub 2}O{sub 5} and silicon (Si) powders were used as reactants. The films were grown at 800 °C and 1000 °C under hydrogen ambient. The deposited films were characterized by X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) at room temperature. From the XPS results it was confirmed the formation of a mixture of Tantalum oxide, silicon oxide and Si nanoparticles (Ta{sub 2}O{sub 5-}SiO{sub 2}-Si(nc)) as seen from the Si (2p) and Ta (4f) lines corresponding to Si{sup +} and Ta{sup +} states respectively. Ta{sub 2}O{sub 5} and Si nanocrystals (Si-NCs) embedded in the silicon oxide films were observed on HRTEM images which corroborate the XPS results. Finally the emission properties of the films exhibited a broad band from 400 to 850 nm caused by the independent PL properties of tantalum oxide and Si-NCs that compose the film. The intensity of the emissions was observed to be dependent on both temperature of deposition and the ratio Ta{sub 2}O{sub 5}/Si, used as initial reactants. Results from this work might supply useful data for the development of future light emitter devices.

  7. Analysis of cobalt, tantalum, titanium, vanadium and chromium in tungsten carbide by inductively coupled plasma-optical emission spectrometry

    CSIR Research Space (South Africa)

    Archer, M

    2003-12-01

    Full Text Available Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to measure the concentrations of cobalt, tantalum, titanium, vanadium and chromium in solutions of tungsten carbide. The main advantage of the method described here lies...

  8. Noninvasive optoacoustic system for rapid diagnosis and management of circulatory shock

    Science.gov (United States)

    Petrov, Irene Y.; Kinsky, Michael; Petrov, Yuriy; Petrov, Andrey; Henkel, S. N.; Seeton, Roger; Esenaliev, Rinat O.; Prough, Donald S.

    2013-03-01

    Circulatory shock can lead to death or severe complications, if not promptly diagnosed and effectively treated. Typically, diagnosis and management of circulatory shock are guided by blood pressure and heart rate. However, these variables have poor specificity, sensitivity, and predictive value. Early goal-directed therapy in septic shock patients, using central venous catheterization (CVC), reduced mortality from 46.5% to 30%. However, CVC is invasive and complication-prone. We proposed to use an optoacoustic technique for noninvasive, rapid assessment of peripheral and central venous oxygenation. In this work we used a medical grade optoacoustic system for noninvasive, ultrasound image-guided measurement of central and peripheral venous oxygenation. Venous oxygenation during shock declines more rapidly in the periphery than centrally. Ultrasound imaging of the axillary [peripheral] and internal jugular vein [central] was performed using the Vivid e (GE Healthcare). We built an optoacoustic interface incorporating an optoacoustic transducer and a standard ultrasound imaging probe. Central and peripheral venous oxygenations were measured continuously in healthy volunteers. To simulate shock-induced changes in central and peripheral oxygenation, we induced peripheral vasoconstriction in the upper extremity by using a cooling blanket. Central and peripheral venous oxygenations were measured before (baseline) and after cooling and after rewarming. During the entire experiment, central venous oxygenation was relatively stable, while peripheral venous oxygenation decreased by 5-10% due to cooling and recovered after rewarming. The obtained data indicate that noninvasive, optoacoustic measurements of central and peripheral venous oxygenation may be used for diagnosis and management of circulatory shock with high sensitivity and specificity.

  9. Interaction of rippled shock wave with flat fast-slow interface

    Science.gov (United States)

    Zhai, Zhigang; Liang, Yu; Liu, Lili; Ding, Juchun; Luo, Xisheng; Zou, Liyong

    2018-04-01

    The evolution of a flat air/sulfur-hexafluoride interface subjected to a rippled shock wave is investigated. Experimentally, the rippled shock wave is produced by diffracting a planar shock wave around solid cylinder(s), and the effects of the cylinder number and the spacing between cylinders on the interface evolution are considered. The flat interface is created by a soap film technique. The postshock flow and the evolution of the shocked interface are captured by a schlieren technique combined with a high-speed video camera. Numerical simulations are performed to provide more details of flows. The wave patterns of a planar shock wave diffracting around one cylinder or two cylinders are studied. The shock stability problem is analytically discussed, and the effects of the spacing between cylinders on shock stability are highlighted. The relationship between the amplitudes of the rippled shock wave and the shocked interface is determined in the single cylinder case. Subsequently, the interface morphologies and growth rates under different cases are obtained. The results show that the shock-shock interactions caused by multiple cylinders have significant influence on the interface evolution. Finally, a modified impulsive theory is proposed to predict the perturbation growth when multiple solid cylinders are present.

  10. Shock-induced modification of the structure of yttria stabilised zirconia powder

    International Nuclear Information System (INIS)

    Frazer, B.G.; Killen, P.D.; Page, N.W.; Charleson, S.W.

    1999-01-01

    Full text: Powder samples of 3 mol% yttria stabilised zirconia were shock compacted in Russia using the explosive flyer plate compaction technique in which a flyer plate is driven by an explosive charge to impact on the surface of a target fixture containing the powder. In these experiments the impact velocity of the flyer plate was approximately 2130 m.s -1 . Initial precompaction densities of 30% and 60% of solid phase densities were used in the shock compaction process. The precompaction densities were responsible for the different values of the shock strength transmitted to the sample. These pressures were 5 GPa and 16 GPa (for the 30% and 60% dense samples respectively). Fragments of all shock compacted samples were obtained for analysis with the only exception being one of the 5 GPa samples which remained intact and was encased in a resin. X-Ray diffraction scans of the recovered samples were analysed using the Rietveld refinement program GSAS. Results show significant changes in crystallite size and strain and an alteration to the shape of the monoclinic lattice as well as the pressure induced phase change from cubic to tetragonal described in another paper. Copyright (1999) Australian X-ray Analytical Association Inc

  11. EVALUATION OF SERUM LACTATE LEVELS AS A PROGNOSTIC INDICATOR IN VARIOUS TYPES OF SHOCK

    Directory of Open Access Journals (Sweden)

    Siddaraj Wali

    2017-08-01

    Full Text Available BACKGROUND Sepsis is a lethal disease that has a complex pathophysiology including a dysregulated inflammatory response, endothelial injury, microvascular thrombosis, vasoplegia and myocardial depression leading to multiorgan failure. Prompt recognition of sepsis, early initiation of antibiotics, source control, optimal fluid and vasopressor therapy are of utmost importance. Early diagnosis of sepsis is very critical for the timely and efficient use of treatment modalities, however, there are no reliable, specific biomarkers that can guide the diagnosis of sepsis. Cardiopulmonary failure, sepsis, trauma, oncologic pathology and so can lead to lactic acidosis. The aim of the study is to evaluate the serum lactic acid levels as a prognostic marker in various type of shock. MATERIALS AND METHODS It is a prospective clinical study with 50 patients studied for 1 year. To study the values of serum lactate levels in shock patients. Statistical analysis- Chi-square test 2. Student’s t-test (two tailed, independent. RESULTS Out of the 50 patients included in the study, the incidence of shock was found to be high in the 21-30 years age group, 13 (26%. This study of ours revealed the most common focus of sepsis as respiratory tract (60%, followed by urinary tract (25%, skin and soft tissue (15%. Out of the 18 patients who died, it was noted that mortality rates were highest 10 (55.5% in patients with initial (0 hours high positive serum lactate levels (>4 mmol/L. Out of the 32 patients who recovered, majority 21 (65.6% had low positive serum lactate levels (0-2.5 mmol/L on admission (0 hours. Serum lactate level is significantly reduced in recovered patients. CONCLUSION Approximately, 30% to 45% of patients with septic shock and 60% to 90% of patients with cardiogenic shock die within 1 month of presentation. Lactate was chosen because it is used as a prognostic marker of global hypoxia. Serial lactate values followed over a period of time can be used to

  12. Compact all-fiber interferometer system for shock acceleration measurement

    Science.gov (United States)

    Zhao, Jiang; Pi, Shaohua; Hong, Guangwei; Zhao, Dong; Jia, Bo

    2013-08-01

    Acceleration measurement plays an important role in a variety of fields in science and engineering. In particular, the accurate, continuous and non-contact recording of the shock acceleration profiles of the free target surfaces is considered as a critical technique in shock physics. Various kinds of optical interferometers have been developed to monitor the motion of the surfaces of shocked targets since the 1960s, for instance, the velocity interferometer system for any reflector, the fiber optic accelerometer, the photonic Doppler velocimetry system and the displacement interferometer. However, most of such systems rely on the coherent quasi-monochromatic illumination and discrete optic elements, which are costly in setting-up and maintenance. In 1996, L. Levin et al reported an interferometric fiber-optic Doppler velocimeter with high-dynamic range, in which fiber-coupled components were used to replace the discrete optic elements. However, the fringe visibility of the Levin's system is low because of the coupled components, which greatly limits the reliability and accuracy in the shock measurement. In this paper, a compact all-fiber interferometer system for measuring the shock acceleration is developed and tested. The advantage of the system is that not only removes the non-interfering light and enhances the fringe visibility, but also reduces polarization induced signal fading and the polarization induced phase shift. Moreover, it also does not require a source of long coherence length. The system bases entirely on single-mode fiber optics and mainly consists of a polarization beam splitter, a faraday rotator, a depolarizer and a 3×3 single-mode fiber coupler which work at 1310 nm wavelength. The optical systems of the interferometer are described and the experimental results compared with a shock acceleration calibration system with a pneumatic exciter (PneuShockTM Model 9525C by The Modal Shop) are reported. In the shock acceleration test, the

  13. Dielectric properties of tantalum powder with broccoli-like morphology

    Energy Technology Data Exchange (ETDEWEB)

    Baba, Masahiko [Department of Energy Science and Technology, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501 (Japan); Suzuki, Ryosuke O [Department of Energy Science and Technology, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)

    2005-04-19

    Metallic tantalum powder with broccoli-like morphology, consisting of spherical fine particles and of long rods or thin plates, was prepared in a hundred gram scale by calcium reduction of Ta{sub 2}O{sub 5} in molten CaCl{sub 2}. The properties as electrolytic capacitor were evaluated in comparison with commercial powder obtained by Na reduction and with powder consisting of only fine particles obtained by Ca reduction. The capacitance was larger than that of conventional powder with the same surface area, because the broccoli-like powder showed a strong resistance against shrinkage during high temperature annealing due to the framework of branches. The powder with new broccoli-like morphology can circumvent the conventional treatments for grain size control and gas removal.

  14. Dielectric properties of tantalum powder with broccoli-like morphology

    International Nuclear Information System (INIS)

    Baba, Masahiko; Suzuki, Ryosuke O.

    2005-01-01

    Metallic tantalum powder with broccoli-like morphology, consisting of spherical fine particles and of long rods or thin plates, was prepared in a hundred gram scale by calcium reduction of Ta 2 O 5 in molten CaCl 2 . The properties as electrolytic capacitor were evaluated in comparison with commercial powder obtained by Na reduction and with powder consisting of only fine particles obtained by Ca reduction. The capacitance was larger than that of conventional powder with the same surface area, because the broccoli-like powder showed a strong resistance against shrinkage during high temperature annealing due to the framework of branches. The powder with new broccoli-like morphology can circumvent the conventional treatments for grain size control and gas removal

  15. Split-Hopkinson pressure bar tests on pure tantalum

    International Nuclear Information System (INIS)

    Dick, Richard D.; Armstrong, Ronald W.; Williams, John D.

    1998-01-01

    Pure tantalum (Ta) was loaded in compression by a split-Hopkinson pressure bar (SHPB) to strain rates from 450 to 6350 s -1 . The results are compared with SHPB data for commercial Ta and with predictions from the constitutive model for Ta developed by Zerilli and Armstrong (Z-A). The main conclusions are: (1) the flow stress versus log strain rate agree with the Z-A constitutive model and other reported data, (2) uniform strain exponents computed on a true stress-strain basis for pure Ta are somewhat greater than those determined from SHPB data for commercial Ta, and (3) in both cases the uniform strain exponents versus log strain rate are in good agreement with predictions from the Z-A constitutive model for strain rates above 1500 s -1 without a clear indication of dislocation generation

  16. Energy-harvesting shock absorber with a mechanical motion rectifier

    Science.gov (United States)

    Li, Zhongjie; Zuo, Lei; Kuang, Jian; Luhrs, George

    2013-02-01

    Energy-harvesting shock absorbers are able to recover the energy otherwise dissipated in the suspension vibration while simultaneously suppressing the vibration induced by road roughness. They can work as a controllable damper as well as an energy generator. An innovative design of regenerative shock absorbers is proposed in this paper, with the advantage of significantly improving the energy harvesting efficiency and reducing the impact forces caused by oscillation. The key component is a unique motion mechanism, which we called ‘mechanical motion rectifier (MMR)’, to convert the oscillatory vibration into unidirectional rotation of the generator. An implementation of a MMR-based harvester with high compactness is introduced and prototyped. A dynamic model is created to analyze the general properties of the motion rectifier by making an analogy between mechanical systems and electrical circuits. The model is capable of analyzing electrical and mechanical components at the same time. Both simulation and experiments are carried out to verify the modeling and the advantages. The prototype achieved over 60% efficiency at high frequency, much better than conventional regenerative shock absorbers in oscillatory motion. Furthermore, road tests are done to demonstrate the feasibility of the MMR shock absorber, in which more than 15 Watts of electricity is harvested while driving at 15 mph on a smooth paved road. The MMR-based design can also be used for other applications of vibration energy harvesting, such as from tall buildings or long bridges.

  17. Energy-harvesting shock absorber with a mechanical motion rectifier

    International Nuclear Information System (INIS)

    Li, Zhongjie; Zuo, Lei; Kuang, Jian; Luhrs, George

    2013-01-01

    Energy-harvesting shock absorbers are able to recover the energy otherwise dissipated in the suspension vibration while simultaneously suppressing the vibration induced by road roughness. They can work as a controllable damper as well as an energy generator. An innovative design of regenerative shock absorbers is proposed in this paper, with the advantage of significantly improving the energy harvesting efficiency and reducing the impact forces caused by oscillation. The key component is a unique motion mechanism, which we called ‘mechanical motion rectifier (MMR)’, to convert the oscillatory vibration into unidirectional rotation of the generator. An implementation of a MMR-based harvester with high compactness is introduced and prototyped. A dynamic model is created to analyze the general properties of the motion rectifier by making an analogy between mechanical systems and electrical circuits. The model is capable of analyzing electrical and mechanical components at the same time. Both simulation and experiments are carried out to verify the modeling and the advantages. The prototype achieved over 60% efficiency at high frequency, much better than conventional regenerative shock absorbers in oscillatory motion. Furthermore, road tests are done to demonstrate the feasibility of the MMR shock absorber, in which more than 15 Watts of electricity is harvested while driving at 15 mph on a smooth paved road. The MMR-based design can also be used for other applications of vibration energy harvesting, such as from tall buildings or long bridges. (paper)

  18. Graphite furnace atomic absorption spectrometry with a tantalum boat for the determination of yttrium, samarium, and dysprosium in a mish metal

    International Nuclear Information System (INIS)

    Daidoji, Hidehiro; Tamura, Shohei

    1982-01-01

    The determination of yttrium, samarium, and dysprodium by means of graphite-furnace atomic absorption spectrometry (AAS) was studied by a tantalum boat inserted into a graphite tube atomizer. These elements could not be determined by the use of a commercial graphite tube, In the atomization from a tantalum boat, better analytical sensitivities and negligible memory effects for these rare earths are obtained. The analytical sensitivities of yttrium, samarium, and dysprodium with the tantalum boat were 0.60 ng, 0.86 ng, and 0.17 ng respectively. This method was applied for the determination of yttrium, samarium, and dysprosium in a mish metal. The measurements were performed with slightly acidified solutions (0.01 mol dm 3 HCI or HNO 3 ). The sensitivities and the precisions for these elements decreased with increasing acid concentration. An enhancement in the sensitivities of yttrium and dysprosium upon the addition of a large excess of lanthanum, neodymium, and praseodymium salts were observed. The yttrium, samarium, and dysprosium in a mish metal were determined with both analytical curves of standard solutions containing an excess of lanthanum, cerium, and neodymium ions and of the standard addition. The precisions for this work were in the 3 - 9.3% range. (author)

  19. Observation of the shock wave propagation induced by a high-power laser irradiation into an epoxy material

    International Nuclear Information System (INIS)

    Ecault, Romain; Boustie, Michel; Touchard, Fabienne; Berthe, Laurent; Lescoute, Emilien; Sollier, Arnaud; Mercier, Patrick; Benier, Jacky

    2013-01-01

    The propagation of laser-induced shock waves in a transparent epoxy sample is investigated by optical shadowgraphy. The shock waves are generated by a focused laser (3 ns pulse duration—1.2 to 3.4 TW cm −2 ) producing pressure from 44 to 98.9 GPa. It is observed that the shock wave and the release wave created by the shock reverberation at the rear face are both followed by a dark zone in the pictures. This corresponds to the creation of a tensile zone resulting from the crossing on the loading axis of the release waves coming from the edge of the impact area (2D effects). After the laser shock experiment, the residual stresses in the targets are identified and quantified through a photoelasticimetry analysis of the recovered samples. This work results in a new set of original data which can be directly used to validate numerical models implemented to reproduce the behaviour of epoxy under extreme strain rate loading. The residual stresses observed prove that the high-pressure shocks can modify the pure epoxy properties, which could have an influence on the use made of these materials. (paper)

  20. Back-pressure Effect on Shock-Train Location in a Scramjet Engine Isolator

    Science.gov (United States)

    2010-03-01

    breathing single-stage-to-orbit ( SSTO ) reusable spacecraft, X-30. It made a great contribution towards developing a rectangular, airframe-integrated...scramjet. This program was cancelled without conducting a flight test. The goal of this program was to build a full scale operational SSTO vehicle...bomber, SSTO , or hypersonic transportation. Shock system A shock-train is a system of series of oblique or normal shocks, which is a very complex flow

  1. Physics of Collisionless Shocks Space Plasma Shock Waves

    CERN Document Server

    Balogh, André

    2013-01-01

    The present book provides a contemporary systematic treatment of shock waves in high-temperature collisionless plasmas as are encountered in near Earth space and in Astrophysics. It consists of two parts. Part I develops the complete theory of shocks in dilute hot plasmas under the assumption of absence of collisions among the charged particles when the interaction is mediated solely by the self-consistent electromagnetic fields. Such shocks are naturally magnetised implying that the magnetic field plays an important role in their evolution and dynamics. This part treats both subcritical shocks, which dissipate flow energy by generating anomalous resistance or viscosity, and supercritical shocks. The main emphasis is, however, on super-critical shocks where the anomalous dissipation is insufficient to retard the upstream flow. These shocks, depending on the direction of the upstream magnetic field, are distinguished as quasi-perpendicular and quasi-parallel shocks which exhibit different behaviours, reflecti...

  2. Modeling Shock Induced Plasticity in Copper Single Crystal: Numerical and Strain Localization Issues

    International Nuclear Information System (INIS)

    Shehadeh, M

    2011-01-01

    Multiscale dislocation dynamics plasticity (MDDP) simulations are carried out to address the following issues in modeling shock-induced plasticity: 1- the effect of finite element (FE) boundary conditions on shock wave characteristics and wave-dislocation interaction, 2- the effect of the evolution of the dislocation microstructure on lattice rotation and strain localization. While uniaxial strain is achieved with high accuracy using confined boundary condition, periodic boundary condition yields a disturbed wave profile due the edge effect. Including lattice rotation in the analysis leads to higher dislocation density and more localized plastic strain. (author)

  3. Phase transition in cadmium sulfide single crystals shocked along the c axis

    International Nuclear Information System (INIS)

    Tang, Z.P.; Gupta, Y.M.

    1997-01-01

    Cadmium sulfide crystals were shocked along the crystal c axis to peak stresses ranging between 18 and 75 kbar. Stress-time profiles were measured both at the impact surface and after transmission through 1 to 2-mm-thick samples. Detailed analysis of the present data in combination with published static results makes a persuasive case for the completion of the wurtzite to rocksalt phase change in less than 0.2 μs under shock loading. The main findings are: the transition stress is measured to be 32.5±1kbar; transformation to the final state is a two step process with the first step being too rapid (less than 10 ns) to be observed in our experiments and the second step occurring in 0.1 to 0.2 μs; the transition occurs directly from the elastic state prior to any plastic deformation. The calculated mean stress for the transition is 22.9 kbar in good agreement with the 23 kbar pressure reported in static high pressure studies; the presence of large shear stress has no effect on the transition pressure. Our results suggest that the onset of the phase transition results in plastic deformation and, subsequently, the phase transition and plasticity are coupled under shock loading. copyright 1997 American Institute of Physics

  4. Bubbles with shock waves and ultrasound: a review.

    Science.gov (United States)

    Ohl, Siew-Wan; Klaseboer, Evert; Khoo, Boo Cheong

    2015-10-06

    The study of the interaction of bubbles with shock waves and ultrasound is sometimes termed 'acoustic cavitation'. It is of importance in many biomedical applications where sound waves are applied. The use of shock waves and ultrasound in medical treatments is appealing because of their non-invasiveness. In this review, we present a variety of acoustics-bubble interactions, with a focus on shock wave-bubble interaction and bubble cloud phenomena. The dynamics of a single spherically oscillating bubble is rather well understood. However, when there is a nearby surface, the bubble often collapses non-spherically with a high-speed jet. The direction of the jet depends on the 'resistance' of the boundary: the bubble jets towards a rigid boundary, splits up near an elastic boundary, and jets away from a free surface. The presence of a shock wave complicates the bubble dynamics further. We shall discuss both experimental studies using high-speed photography and numerical simulations involving shock wave-bubble interaction. In biomedical applications, instead of a single bubble, often clouds of bubbles appear (consisting of many individual bubbles). The dynamics of such a bubble cloud is even more complex. We shall show some of the phenomena observed in a high-intensity focused ultrasound (HIFU) field. The nonlinear nature of the sound field and the complex inter-bubble interaction in a cloud present challenges to a comprehensive understanding of the physics of the bubble cloud in HIFU. We conclude the article with some comments on the challenges ahead.

  5. Synthesis of tantalum carbide and nitride nanoparticles using a reactive mesoporous template for electrochemical hydrogen evolution

    KAUST Repository

    Alhajri, Nawal Saad; Yoshida, Hiroshi; Anjum, Dalaver H.; Garcia Esparza, Angel T.; Kubota, Jun; Domen, Kazunari; Takanabe, Kazuhiro

    2013-01-01

    Tantalum carbide and nitride nanocrystals were prepared through the reaction of a tantalum precursor with mesoporous graphitic (mpg)-C 3N4. The effects of the reaction temperature, the ratio of the Ta precursor to the reactive template (mpg-C3N4), and the selection of the carrier gas (Ar, N2 and NH3) on the resultant crystal phases and structures were investigated. The produced samples were characterized using powder X-ray diffraction (XRD), CHN elemental analyses, thermogravimetric analyses (TGA), nitrogen sorption, a temperature-programmed reaction with mass spectroscopy (MS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results indicate that the different tantalum phases with cubic structure, TaN, Ta2CN, and TaC, can be formed under a flow of nitrogen when formed at different temperatures. The Ta3N5 phase with a Ta5+ oxidation state was solely obtained at 1023 K under a flow of ammonia, which gasified the C 3N4 template and was confirmed by detecting the decomposed gaseous products via MS. Significantly, the formation of TaC, Ta2CN, and TaN can be controlled by altering the weight ratio of the C 3N4 template relative to the Ta precursor at 1573 K under a flow of nitrogen. The high C3N4/Ta precursor ratio generally resulted in high carbide content rather than a nitride one, consistent with the role of mpg-C3N4 as a carbon source. Electrochemical measurements revealed that the synthesized nanomaterials were consistently able to produce hydrogen under acidic conditions (pH 1). The obtained Tafel slope indicates that the rate-determining step is the Volmer discharge step, which is consistent with adsorbed hydrogen being weakly bound to the surface during electrocatalysis. © 2013 The Royal Society of Chemistry.

  6. Determination of niobium, tantalum, and uranium in tantalite-columbite ores by X-ray fluorescence spectrometry; Application de la spectrometrie de fluorescence de rayos X a la determination de niobium, tantale et uranium dans niobiotantalites

    Energy Technology Data Exchange (ETDEWEB)

    Latorre, O; Bermudez Polonio, J

    1964-07-01

    A simple and quick procedure is carried out to determine niobium, tantalum and uranium employing the internal standard technique; zinc as internal standard for tantalum and molybdenum for niobium and uranium were selected. Some inter element effects were studied and the ratios. (Author)

  7. Shock loading influence on mechanical behavior of high purity iron

    International Nuclear Information System (INIS)

    Buy, Francois; Voltz, Christophe

    2004-01-01

    This paper proposes the analysis of shock wave effects for high purity iron. The method developed is based on the characterization of the mechanical behavior of as received and shocked material. Shock effect is generated through plate impact tests performed in the range of 4 GPa to 39 GPa on a single stage light gas gun or a powder gun. Therefore, as-received and impacted materials are characterized. A formalism proposed by J.R.Klepaczko and based on physical relations has been adopted to describe stress strain curves

  8. Synthesis and crystal structure of triammine pentafluorido tantalum(V) [TaF{sub 5}(NH{sub 3}){sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Baer, Sebastian A.; Kraus, Florian [Department Chemie, Technische Universitaet Muenchen, Lichtenbergstrasse 4, 85747 Garching (Germany); Lozinsek, Matic [Department of Inorganic Chemistry and Technology, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia)

    2013-07-01

    [Sr(HF){sub 3}(TaF{sub 6}){sub 2}] reacts with liquid ammonia under the formation of colorless crystals of triammine pentafluorido tantalum(V) [TaF{sub 5}(NH{sub 3}){sub 3}] (1). The structure was elucidated by low-temperature X-ray structure analysis. Compound 1 crystallizes in the monoclinic space group P2{sub 1}/c with a = 5.1525(6), b = 11.736(1), c = 10.171(1) Aa, β = 94.843(9) , V = 612.8(1) Aa{sup 3} at 123 K with Z = 4. Its structure displays discrete TaF{sub 5}(NH{sub 3}){sub 3} molecules, which are interconnected by N-H..F hydrogen bonds to form a complex three-dimensional network. The title compound is a rare example of a neutral, molecular, eight-coordinate tantalum species. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Dynamical efficiency of collisionless magnetized shocks in relativistic jets

    Science.gov (United States)

    Aloy, Miguel A.; Mimica, Petar

    2011-09-01

    The so-called internal shock model aims to explain the light-curves and spectra produced by non-thermal processes originated in the flow of blazars and gamma-ray bursts. A long standing question is whether the tenuous collisionless shocks, driven inside a relativistic flow, are efficient enough to explain the amount of energy observed as compared with the expected kinetic power of the outflow. In this work we study the dynamic efficiency of conversion of kinetic-to-thermal/magnetic energy of internal shocks in relativistic magnetized outflows. We find that the collision between shells with a non-zero relative velocity can yield either two oppositely moving shocks (in the frame where the contact surface is at rest), or a reverse shock and a forward rarefaction. For moderately magnetized shocks (magnetization σ ~= 0.1), the dynamic efficiency in a single two-shell interaction can be as large as 40%. Hence, the dynamic efficiency of moderately magnetized shocks is larger than in the corresponding unmagnetized two-shell interaction. We find that the efficiency is only weakly dependent on the Lorentz factor of the shells and, thus internal shocks in the magnetized flow of blazars and gamma-ray bursts are approximately equally efficient.

  10. Shocks and finite-time singularities in Hele-Shaw flow

    Energy Technology Data Exchange (ETDEWEB)

    Teodorescu, Razvan [Los Alamos National Laboratory; Wiegmann, P [UNIV OF MONTREAL; Lee, S-y [UNIV OF CHICAGO

    2008-01-01

    Hele-Shaw flow at vanishing surface tension is ill-defined. In finite time, the flow develops cusplike singularities. We show that the ill-defined problem admits a weak dispersive solution when singularities give rise to a graph of shock waves propagating in the viscous fluid. The graph of shocks grows and branches. Velocity and pressure jump across the shock. We formulate a few simple physical principles which single out the dispersive solution and interpret shocks as lines of decompressed fluid. We also formulate the dispersive solution in algebro-geometrical terms as an evolution of Krichever-Boutroux complex curve. We study in details the most generic (2,3) cusp singularity which gives rise to an elementary branching event. This solution is self-similar and expressed in terms of elliptic functions.

  11. In situ STM and EQCM studies of tantalum electrodeposition from TaF5 in the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide

    International Nuclear Information System (INIS)

    Borisenko, N.; Ispas, A.; Zschippang, E.; Liu, Q.; Zein El Abedin, S.; Bund, A.; Endres, F.

    2009-01-01

    The electroreduction of 0.5 M TaF 5 on Au(1 1 1) and on polycrystalline gold substrates was investigated at room temperature in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide, [Py 1,4 ]TFSA, by cyclic voltammetry, in situ scanning tunneling microscopy (STM) and electrochemical quartz crystal microbalance (EQCM). The electrochemical reduction of TaF 5 in the employed ionic liquid occurs in several steps. The first redox process is attributed to the reduction of TaF 5 to TaF 3 , which likely occurs in the solution, as EQCM indicates no mass change. The electrodeposition of tantalum occurs only in a very narrow potential window and is preceded by the formation of various non-stoichiometric tantalum subhalides. Attempts to deposit micrometer thick tantalum layers at room temperature fail, presumably because of kinetic reasons

  12. ICP-MS determination of rare earth elements, yttrium, uranium and thorium in niobium-tantalum rich samples

    International Nuclear Information System (INIS)

    Sunilkumar, Beena; Padmasubashini, V.

    2013-01-01

    ICP-MS is a powerful and extremely sensitive technique which has been applied successfully for the determination of REEs in diverse geological samples. In the present work, ICP-MS has been applied for the rapid determination of REEs, yttrium as well as uranium and thorium in niobium and tantalum rich samples, using a fluoride fusion method for sample dissolution

  13. Shock compression of a recrystallized anorthositic rock from Apollo 15

    Science.gov (United States)

    Ahrens, T. J.; Gibbons, R. V.; O'Keefe, J. D.

    1973-01-01

    Hugoniot measurements on 15,418, a recrystallized and brecciated gabbroic anorthosite, yield a value of the Hugoniot elastic limit (HEL) varying from 45 to 70 kbar as the final shock pressure is varied from 70 to 280 kbar. Above the HEL and to 150 kbar, the pressure-density Hugoniot is closely described by a hydrostatic equation of state constructed from ultrasonic data for single-crystal plagioclase and pyroxene. Above 150 kbar, the Hugoniot states indicate that a series of one or more shock-induced phase changes are occurring in the plagioclase and pyroxene. From Hugoniot data for both the single-crystal minerals and the Frederick diabase, we infer that the shock-induced high-pressure phases in 15,418 probably consists of a 3.71 g/cu cm density, high-pressure structure for plagioclase and a 4.70 g/cu cm perovskite-type structure for pyroxene.

  14. Tantalum powder consolidation, modeling and properties

    International Nuclear Information System (INIS)

    Bingert, S.R.; Vargas, V.D.; Sheinberg, H.C.

    1996-01-01

    A systematic approach was taken to investigate the consolidation of tantalum powders. The effects of sinter time, temperature and ramp rate; hot isostatic pressing (HIP) temperature and time; and powder oxygen content on consolidation density, kinetics, microstructure, crystallographic texture, and mechanical properties have been evaluated. In general, higher temperatures and longer hold times resulted in higher density compacts with larger grain sizes for both sintering and HIP'ing. HIP'ed compacts were consistently higher in density than sintered products. The higher oxygen content powders resulted in finer grained, higher density HIP'ed products than the low oxygen powders. Texture analysis showed that the isostatically processed powder products demonstrated a near random texture. This resulted in isotropic properties in the final product. Mechanical testing results showed that the HIP'ed powder products had consistently higher flow stresses than conventionally produced plates, and the sintered compacts were comparable to the plate material. A micromechanics model (Ashby HIP model) has been employed to predict the mechanisms active in the consolidation processes of cold isostatic pressing (CIP), HIP and sintering. This model also predicts the density of the end product and whether grain growth should be expected under the applied processing conditions

  15. Disintegration of Dust Aggregates in Interstellar Shocks and the Lifetime of Dust Grains in the ISM

    Science.gov (United States)

    Dominik, C.; Jones, A. P.; Tielens, A. G. G. M.; Cuzzi, Jeff (Technical Monitor)

    1994-01-01

    Interstellar grains are destroyed by shock waves moving through the ISM. In fact, the destruction of grains may be so effective that it is difficult to explain the observed abundance of dust in the ISM as a steady state between input of grains from stellar sources and destruction of grains in shocks. This is especially a problem for the larger grains. Therefore, the dust grains must be protected in some way. Jones et al. have already considered coatings and the increased post-shock drag effects for low density grains. In molecular clouds and dense clouds, coagulation of grains is an important process, and the largest interstellar grains may indeed be aggregates of smaller grains rather than homogeneous particles. This may provide a means to protect the larger grains, in that, in moderate velocity grain-grain collisions in a shock the aggregates may disintegrate rather than be vaporized. The released small particles are more resilient to shock destruction (except in fast shocks) and may reform larger grains later, recovering the observed size distribution. We have developed a model for the binding forces in grain aggregates and apply this model to the collisions between an aggregate and fast small grains. We discuss the results in the light of statistical collision probabilities and grain life times.

  16. Simulations of Converging Shock Collisions for Shock Ignition

    Science.gov (United States)

    Sauppe, Joshua; Dodd, Evan; Loomis, Eric

    2016-10-01

    Shock ignition (SI) has been proposed as an alternative to achieving high gain in inertial confinement fusion (ICF) targets. A central hot spot below the ignition threshold is created by an initial compression pulse, and a second laser pulse drives a strong converging shock into the fuel. The collision between the rebounding shock from the compression pulse and the converging shock results in amplification of the converging shock and increases the hot spot pressure above the ignition threshold. We investigate shock collision in SI drive schemes for cylindrical targets with a polystyrene foam interior using radiation-hydrodynamics simulations with the RAGE code. The configuration is similar to previous targets fielded on the Omega laser. The CH interior results in a lower convergence ratio and the cylindrical geometry facilitates visualization of the shock transit using an axial X-ray backlighter, both of which are important for comparison to potential experimental measurements. One-dimensional simulations are used to determine shock timing, and the effects of low mode asymmetries in 2D computations are also quantified. LA-UR-16-24773.

  17. Electron velocity distributions near the earth's bow shock

    International Nuclear Information System (INIS)

    Feldman, W.C.; Anderson, R.C.; Bame, S.J.; Gary, S.P.; Gosling, J.T.; McComas, D.J.; Thomsen, M.F.; Paschmann, G.; Hoppe, M.M.

    1983-01-01

    A survey of two-dimensional electron velocity distributions, f(V), measured near the earth's bow shock using Los Alamos/Garching plasma instrumentation aboard ISEE 2 is presented. This survey provides clues to the mechanisms of electron thermalization within the shock and the relaxation of both the upsteam and downstream velocity distributions. First, near the foreshock boundary, fluxes of electrons having a power law shape at high energies backstream from the shock. Second, within the shock, cuts through f(V) along B. f(V), often show single maxima offset toward the magnetosheath by speeds comparable to, but larger than, the upstream thermal speed.Third, magnetosheath distributions generally have flat tops out to an energy, E 0 , with maxima substantially lower than that in the solar wind. Occasionally, cuts through f(V) along B show one and sometimes two small peaks at the edge of the flat tops making them appear concave upward. The electron distributions characteristic of these three regions are interpreted as arising from the effects of macroscopic (scale size comparable to or larger than the shock width) electric and magnetic fields and the subsequent effects of microscopic (scale size small in comparison with the shock width) fields. In particular, our results suggest that field-aligned instabilities are likely to be present in the earth's bow shock

  18. Response of Seven Crystallographic Orientations of Sapphire Crystals to Shock Stresses of 16 to 86 GPa

    OpenAIRE

    Kanel, G. I.; Nellis, W. J.; Savinykh, A. S.; Razorenov, S. V.; Rajendran, A. M.

    2009-01-01

    Shock-wave profiles of sapphire (single-crystal Al2O3) with seven crystallographic orientations were measured with time-resolved VISAR interferometry at shock stresses in the range 16 to 86 GPa. Shock propagation was normal to the surface of each cut. The angle between the c-axis of the hexagonal crystal structure and the direction of shock propagation varied from 0 for c-cut up to 90 degrees for m-cut in the basal plane. Based on published shock-induced transparencies, shock-induced optical ...

  19. A genetic algorithm approach for evaluation of optical functions of very thin tantalum pentoxide films on Si substrate

    International Nuclear Information System (INIS)

    Sharlandjiev, P S; Nazarova, D I

    2013-01-01

    The optical characteristics of tantalum pentoxide films, deposited on Si(100) substrate by reactive sputtering, are studied. These films are investigated as high-kappa materials for the needs of nano-electronics, i.e. design of dynamic random access memories, etc. One problem in their implementation is that metal oxides are thermodynamically unstable with Si and an interfacial layer is formed between the oxide film and the silicon substrate during the deposition process. Herein, the center of attention is on the optical properties of that interfacial layer, which is studied by spectral photometric measurements. The evaluation of the optical parameters of the structure is fulfilled with the genetic algorithm approach. The spectral range of evaluation covers deep UV to NIR. The equivalent physical thickness (2.5 nm) and the equivalent refractive index of the interfacial layer are estimated from 236 to 750 nm as well as the thickness of the tantalum pentoxide film (9.5 nm). (paper)

  20. Conflict minerals in the compute sector: estimating extent of tin, tantalum, tungsten, and gold use in ICT products.

    Science.gov (United States)

    Fitzpatrick, Colin; Olivetti, Elsa; Miller, Reed; Roth, Richard; Kirchain, Randolph

    2015-01-20

    Recent legislation has focused attention on the supply chains of tin, tungsten, tantalum, and gold (3TG), specifically those originating from the eastern part of the Democratic Republic of Congo. The unique properties of these so-called “conflict minerals” lead to their use in many products, ranging from medical devices to industrial cutting tools. This paper calculates per product use of 3TG in several information, communication, and technology (ICT) products such as desktops, servers, laptops, smart phones, and tablets. By scaling up individual product estimates to global shipment figures, this work estimates the influence of the ICT sector on 3TG mining in covered countries. The model estimates the upper bound of tin, tungsten, tantalum, and gold use within ICT products to be 2%, 0.1%, 15%, and 3% of the 2013 market share, respectively. This result is projected into the future (2018) based on the anticipated increase in ICT device production.

  1. Study of the formation process and the characteristics of tantalum layers electrodeposited on Nitinol plates in the 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid

    International Nuclear Information System (INIS)

    Maho, A.; Delhalle, J.; Mekhalif, Z.

    2013-01-01

    Highlights: ► Tantalum electrodeposition on Nitinol plates in the [BMP]Tf 2 N ionic liquid at room temperature. ► Generation of intrinsically nanostructured porous tantalum layers in “soft” cathodic current conditions. ► Important impact of substrate nature, working solution composition and electrodeposition duration. ► Primary assessment of surface corrosion resistance and bioactivity. -- Abstract: Thanks to excellent mechanical and biochemical properties, the nickel–titanium shape memory alloy (Nitinol) constitutes an increasingly praised platform material in dental, cardiovascular and orthopedic biomedical devices. In order to strengthen their protective abilities toward corrosion, to reinforce their biocompatibility and to confer them specific osseointegrative capacities, Nitinol plates are covered with a thin tantalum layer by electrodeposition in the 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid. XPS and SEM/EDX analyses highlight the chemical and morphological characteristics of the deposits: notably, these present an intrinsic dimpled nanometric structuration which is particularly remarkable considering the “soft” experimental conditions and very interesting for fundamental and applied bioactive perspectives. The present study investigates the specific and synergic effects of the Ni occurrence on the surface of the Nitinol substrates, the presence of fluorine species in the working bath, and the electrodeposition duration on the resulting formation process, morphology and chemical composition of the tantalum coating. Finally, samples are submitted to electrochemical characterizations and in vitro hydroxyapatite growth tests for a primary assessment of their corrosion resistance and osseoinductive features

  2. On the failure of NiAl bicrystals during laser-induced shock compression

    International Nuclear Information System (INIS)

    Loomis, Eric; Swift, Damian; Peralta, Pedro; McClellan, Ken

    2005-01-01

    Thin NiAl bicrystals 5 mm in diameter and 150-350 μm thick were tested under laser-induced shock compression to evaluate the material behavior and the effect of localized strain at the grain boundary on the failure of these specimens. Circular NiAl bicrystal samples with random misorientation were grown using a modified Czochralski technique and samples were prepared for shock compression at moderate pressures (<10 GPa). The observed crack patterns on the drive surface as well as the free surface were examined using optical microscopy. Transmission electron microscopy (TEM) of the drive surface as well as in the bulk of one grain was performed on recovered specimens following shock compression. This revealed that a nanocrystalline region with a grain size of 15-20 nm formed on a thin layer at the drive surface following the plasma expansion phase of the laser-induced shock. TEM in the bulk of one grain showed that plastic deformation occurred in a periodic fashion through propagation of dislocation clusters. Cracking on the free surface of the samples revealed a clear grain boundary affected zone (GBAZ) due to scattering of the shock wave and variations in wave speed across the inclined boundary. Damage tended to accumulate in the grain into which the elastic wave refracted. This damage accumulation corresponds well to the regions in which the transmitted waves impinged on the free surface as predicted by elastic scattering models

  3. Evaluation of XHVRB for Capturing Explosive Shock Desensitization

    Science.gov (United States)

    Tuttle, Leah; Schmitt, Robert; Kittell, Dave; Harstad, Eric

    2017-06-01

    Explosive shock desensitization phenomena have been recognized for some time. It has been demonstrated that pressure-based reactive flow models do not adequately capture the basic nature of the explosive behavior. Historically, replacing the local pressure with a shock captured pressure has dramatically improved the numerical modeling approaches. Models based upon shock pressure or functions of entropy have recently been developed. A pseudo-entropy based formulation using the History Variable Reactive Burn model, as proposed by Starkenberg, was implemented into the Eulerian shock physics code CTH. Improvements in the shock capturing algorithm were made. The model is demonstrated to reproduce single shock behavior consistent with published pop plot data. It is also demonstrated to capture a desensitization effect based on available literature data, and to qualitatively capture dead zones from desensitization in 2D corner turning experiments. This models shows promise for use in modeling and simulation problems that are relevant to the desensitization phenomena. Issues are identified with the current implementation and future work is proposed for improving and expanding model capabilities. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  4. Toxic shock syndrome following inguinal hernia repair: a rare condition

    Directory of Open Access Journals (Sweden)

    Rohit Prasad Yadav

    2014-01-01

    Full Text Available A 25-year-old man developed fulminant multisystem failure 28 hours after elective repair of an inguinal hernia. Toxic shock syndrome (TSS was diagnosed. The patient recovered fully with supportive care in ICU, antibiotics, and IV human immunoglobin . To the best of our knowledge, only one case of TSS following inguinal hernia repair have ever been previously published. Journal of College of Medical Sciences-Nepal, 2013, Vol-9, No-2, 57-59 DOI: http://dx.doi.org/10.3126/jcmsn.v9i2.9689

  5. Shock Dynamics in Stellar Outbursts. I. Shock Formation

    Energy Technology Data Exchange (ETDEWEB)

    Ro, Stephen; Matzner, Christopher D., E-mail: ro@astro.utoronto.ca [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada)

    2017-05-20

    Wave-driven outflows and non-disruptive explosions have been implicated in pre-supernova outbursts, supernova impostors, luminous blue variable eruptions, and some narrow-line and superluminous supernovae. To model these events, we investigate the dynamics of stars set in motion by strong acoustic pulses and wave trains, focusing on nonlinear wave propagation, shock formation, and an early phase of the development of a weak shock. We identify the shock formation radius, showing that a heuristic estimate based on crossing characteristics matches an exact expansion around the wave front and verifying both with numerical experiments. Our general analytical condition for shock formation applies to one-dimensional motions within any static environment, including both eruptions and implosions. We also consider the early phase of shock energy dissipation. We find that waves of super-Eddington acoustic luminosity always create shocks, rather than damping by radiative diffusion. Therefore, shock formation is integral to super-Eddington outbursts.

  6. Streak-photographic investigation of shock wave emission after laser-induced plasma formation in water

    Science.gov (United States)

    Noack, Joachim; Vogel, Alfred

    1995-05-01

    The shock wave emission after dielectric breakdown in water was investigated to assess potential shock wave effects in plasma mediated tissue ablation and intraocular photodisruption. Of particular interest was the dependence of shock wave pressure as a function of distance from the plasma for different laser pulse energies. We have generated plasmas in water with a Nd:YAG laser system delivering pulses of 6 ns duration. The pulses, with energies between 0.4 and 36 mJ (approximately equals 180 times threshold), were focused into a cuvette containing distilled water. The shock wave was visualized with streak photography combined with a schlieren technique. An important advantage of this technique is that the shock position as a function of time can directly be obtained from a single streak and hence a single event. Other methods (e.g. flash photography or passage time measurements between fixed locations) in contrast rely on reproducible events. Using the shock wave speed obtained from the streak images, shock wave peak pressures were calculated providing detailed information on the propagation of the shock. The shock peak pressure as a function of distance r from the optical axis was found to decrease faster than 1/r2 in regions up to distances of 100-150 micrometers . For larger distances it was found to be roughly proportional to 1/r. The scaling law for maximum shock pressure p, at a given distance was found to be proportional to the square root of the laser pulse energy E for distances of 50-200 micrometers from the optical axis.

  7. Shock fabrics in fine-grained micrometeorites

    Science.gov (United States)

    Suttle, M. D.; Genge, M. J.; Russell, S. S.

    2017-10-01

    The orientations of dehydration cracks and fracture networks in fine-grained, unmelted micrometeorites were analyzed using rose diagrams and entropy calculations. As cracks exploit pre-existing anisotropies, analysis of their orientation provides a mechanism with which to study the subtle petrofabrics preserved within fine-grained and amorphous materials. Both uniaxial and biaxial fabrics are discovered, often with a relatively wide spread in orientations (40°-60°). Brittle deformation cataclasis and rotated olivine grains are reported from a single micrometeorite. This paper provides the first evidence for impact-induced shock deformation in fine-grained micrometeorites. The presence of pervasive, low-grade shock features in CM chondrites and CM-like dust, anomalously low-density measurements for C-type asteroids, and impact experiments which suggest CM chondrites are highly prone to disruption all imply that CM parent bodies are unlikely to have remained intact and instead exist as a collection of loosely aggregated rubble-pile asteroids, composed of primitive shocked clasts.

  8. The structure of steady shock waves in porous metals

    Science.gov (United States)

    Czarnota, Christophe; Molinari, Alain; Mercier, Sébastien

    2017-10-01

    The paper aims at developing an understanding of steady shock wave propagation in a ductile metallic material containing voids. Porosity is assumed to be less than 0.3 and voids are not connected (foams are not considered). As the shock wave is traveling in the porous medium, the voids are facing a rapid collapse. During this dynamic compaction process, material particles are subjected to very high acceleration in the vicinity of voids, thus generating acceleration forces at the microscale that influence the overall response of the porous material. Analyzing how stationary shocks are influenced by these micro-inertia effects is the main goal of this work. The focus is essentially on the shock structure, ignoring oscillatory motion of pores prevailing at the tail of the shock wave. Following the constitutive framework developed by Molinari and Ravichandran (2004) for the analysis of steady shock waves in dense metals, an analytical approach of steady state propagation of plastic shocks in porous metals is proposed. The initial void size appears as a characteristic internal length that scales the overall dynamic response, thereby contributing to the structuring of the shock front. This key feature is not captured by standard damage models where the porosity stands for the single damage parameter with no contribution of the void size. The results obtained in this work provide a new insight in the fundamental understanding of shock waves in porous media. In particular, a new scaling law relating the shock width to the initial void radius is obtained when micro-inertia effects are significant.

  9. Analysis of internal stress and anelasticity in the shock-compressed state from unloading wave data

    International Nuclear Information System (INIS)

    Johnson, J.N.; Lomdahl, P.S.; Wills, J.M.

    1991-01-01

    This paper reports on time resolved shock-wave measurements have often been used to infer microstructural behavior in crystalline solids. The authors apply this approach to an interpretation of the release-wave response of an aluminum alloy (6061-T6) as it is dynamically unloaded from a shock-compressed state of 20.7 GPa. The anelastic behavior in the initial portion of the unloading wave is attributed to the accumulation of internal stresses created by the shock process. Specific internal-stress models which are investigated are the double pile-up, the single pile-up, and single dislocation loops between pinning points. It is found that the essential characteristics of double and single pile-ups can be represented by a single dislocation between two pinned dislocations of like sing. Calculations of anelastic wave speeds at constant unloading strain rate are then compared with experimental data. The results suggest that the residual internal stress is due to pinned loops of density 10 15 M - 2 , and the viscous drag coefficient in the shock-compressed state is on the order of 10 - 7 MPa s (approximately two orders of magnitude greater than expected under ambient conditions)

  10. Titanium modified with layer-by-layer sol-gel tantalum oxide and an organodiphosphonic acid: a coating for hydroxyapatite growth.

    Science.gov (United States)

    Arnould, C; Volcke, C; Lamarque, C; Thiry, P A; Delhalle, J; Mekhalif, Z

    2009-08-15

    Titanium and its alloys are widely used in surgical implants due to their appropriate properties like corrosion resistance, biocompatibility, and load bearing. Unfortunately when metals are used for orthopedic and dental implants there is the possibility of loosening over a long period of time. Surface modification is a good way to counter this problem. A thin tantalum oxide layer obtained by layer-by-layer (LBL) sol-gel deposition on top of a titanium surface is expected to improve biocorrosion resistance in the body fluid, biocompatibility, and radio-opacity. This elaboration step is followed by a modification of the tantalum oxide surface with an organodiphosphonic acid self-assembled monolayer, capable of chemically binding to the oxide surface, and also improving hydroxyapatite growth. The different steps of this proposed process are characterized by surfaces techniques like contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM).

  11. On high-pressure melting of tantalum

    Science.gov (United States)

    Luo, Sheng-Nian; Swift, Damian C.

    2007-01-01

    The issues related to high-pressure melting of Ta are discussed within the context of diamond-anvil cell (DAC) and shock wave experiments, theoretical calculations and common melting models. The discrepancies between the extrapolations of the DAC melting curve and the melting point inferred from shock wave experiments, cannot be reconciled either by superheating or solid-solid phase transition. The failure to reproduce low-pressure DAC melting curve by melting models such as dislocation-mediated melting and the Lindemann law, and molecular dynamics and quantum mechanics-based calculations, undermines their predictions at moderate and high pressures. Despite claims to the contrary, the melting curve of Ta (as well as Mo and W) remains inconclusive at high pressures.

  12. Induction of heat-shock proteins and phagocytic function of chicken macrophage following in vitro heat exposure

    International Nuclear Information System (INIS)

    Miller, L.; Qureshi, M.A.

    1992-01-01

    The protein profiles and phagocytic ability of Sephadex-elicited chicken peritoneal macrophages were examined following heat-shock exposure. Macrophage cultures were exposed to various temperatures, time exposures and recovery periods. Densitometric analysis of SDS-PAGE autoradiographs revealed that heat-induced macrophages synthesized three major (23, 70 and 90 kD) heat-shock proteins (HSPs). The optimal temperature and time for induction of these HSPs was 45-46 degrees C for 1 h, with a variable recovery period for each HSP. Macrophages exposed to 45 degrees C for 30 and 60 min were significantly depressed in phagocytosis of uncoated sheep erythrocytes (SE) under 45 degrees C incubation conditions. However, phagocytosis of antibody-coated SE was not affected when compared to 41 degrees C control cultures. Macrophages allowed to recover at 41 degrees C following heat-shock exhibited no alterations in their phagocytic ability for either antibody-coated or uncoated SE. This study suggests that heat shock induces three major HSPs in chicken peritoneal macrophages in addition to maintaining their Fc-mediated phagocytic function while significantly depressing their nonspecific phagocytosis

  13. Vibrational spectroscopy of shock-compressed fluid N2 and O2

    International Nuclear Information System (INIS)

    Schmidt, S.C.; Moore, D.S.; Shaw, M.S.; Johnson, J.D.

    1987-01-01

    Single-pulse multiplex coherent anti-Stokes Raman scattering (CARS) was used to observe the vibrational spectra of liquid N 2 shock-compressed to several pressures and temperatures up to 41 GPa and 5200 K and liquid O 2 shock-compressed to several pressures and temperatures up to 10 GPa and 1000 K. For N 2 , the experimental spectra were compared to synthetic spectra calculated using a semiclassical model for CARS intensities and estimated vibrational frequencies, peak Raman susceptibilities, and Raman line widths. The question of excited state populations in the shock-compressed state is addressed

  14. Uranium material removing and recovering device

    International Nuclear Information System (INIS)

    Takita, Shin-ichi.

    1997-01-01

    A uranium material removing and recovering device for use in removing surplus uranium heavy metal (UO 2 ) generated in a uranium handling facility comprises a uranium material removing device and a uranium material recovering device. The uranium material removing device comprises an adsorbing portion filled with a uranium adsorbent, a control portion for controlling the uranium adsorbent of the uranium adsorbing portion by a controlling agent, a uranium adsorbing device connected thereto and a jetting device for jetting the adsorbing liquid to equipments deposited with uranium. The recovering device comprises a recovering apparatus for recovering uranium materials deposited with the adsorbent liquid removed by the jetting device and a recovering tank for storing the recovered uranium materials. The device of the present invention can remove surplus uranium simply and safely, mitigate body's load upon removing and recovering operations, facilitate the processing for the exchange of the adsorbent and reduces the radioactive wastes. (T.M.)

  15. Tantalum coating on porous Ti6Al4V scaffold using chemical vapor deposition and preliminary biological evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiang, E-mail: xiangliwj@sjtu.edu.cn [School of Mechanical Engineering, Shanghai Jiao Tong University, State Key Laboratory of Mechanical System and Vibration, Shanghai, 200240 (China); Wang, Lin [Institute of Orthopaedics, Xijing Hospital, The Fourth Military Medical University, Xi' an, 710032 (China); Yu, Xiaoming [The Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016 (China); Feng, Yafei [Institute of Orthopaedics, Xijing Hospital, The Fourth Military Medical University, Xi' an, 710032 (China); Wang, Chengtao [School of Mechanical Engineering, Shanghai Jiao Tong University, State Key Laboratory of Mechanical System and Vibration, Shanghai, 200240 (China); Yang, Ke [The Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016 (China); Su, Daniel [School of Mechanical Engineering, Shanghai Jiao Tong University, State Key Laboratory of Mechanical System and Vibration, Shanghai, 200240 (China)

    2013-07-01

    Porous tantalum (Ta), produced via chemical vapor deposition (CVD) of commercially pure Ta onto a vitreous carbon, is currently available for use in orthopedic applications. However, the relatively high manufacturing cost and the incapability to produce customized implant using medical image data have limited its application to gain widespread acceptance. In this study, Ta film was deposited on porous Ti6Al4V scaffolds using CVD technique. Digital microscopy and scanning electron microscopy indicated that the Ta coating evenly covered the entire scaffold structure. X-ray diffraction analysis showed that the coating consisted of α and β phases of Ta. Goat mesenchymal stem cells were seeded and cultured on the Ti6Al4V scaffolds with and without coating. The tetrazolium-based colorimetric assay exhibited better cell adhesion and proliferation on Ta-coated scaffolds compared with uncoated scaffolds. The porous scaffolds were subsequently implanted in goats for 12 weeks. Histological analysis revealed similar bone formation around the periphery of the coated and uncoated implants, but bone ingrowth is better within the Ta-coated scaffolds. To demonstrate the ability of producing custom implant for clinical applications via this technology, we designed and fabricated a porous Ti6Al4V scaffold with segmental mandibular shape derived from patient computerized tomography data. - Highlights: • Ta film was coated on porous Ti6Al4V scaffold using chemical vapor deposition. • Tantalum coating allowed for higher levels of cell adhesion and proliferation. • Better new bone formation occurred inside the tantalum-coated scaffolds. • Clinical image data was integrated with EBM to fabricate customized scaffold.

  16. Tantalum coating on porous Ti6Al4V scaffold using chemical vapor deposition and preliminary biological evaluation

    International Nuclear Information System (INIS)

    Li, Xiang; Wang, Lin; Yu, Xiaoming; Feng, Yafei; Wang, Chengtao; Yang, Ke; Su, Daniel

    2013-01-01

    Porous tantalum (Ta), produced via chemical vapor deposition (CVD) of commercially pure Ta onto a vitreous carbon, is currently available for use in orthopedic applications. However, the relatively high manufacturing cost and the incapability to produce customized implant using medical image data have limited its application to gain widespread acceptance. In this study, Ta film was deposited on porous Ti6Al4V scaffolds using CVD technique. Digital microscopy and scanning electron microscopy indicated that the Ta coating evenly covered the entire scaffold structure. X-ray diffraction analysis showed that the coating consisted of α and β phases of Ta. Goat mesenchymal stem cells were seeded and cultured on the Ti6Al4V scaffolds with and without coating. The tetrazolium-based colorimetric assay exhibited better cell adhesion and proliferation on Ta-coated scaffolds compared with uncoated scaffolds. The porous scaffolds were subsequently implanted in goats for 12 weeks. Histological analysis revealed similar bone formation around the periphery of the coated and uncoated implants, but bone ingrowth is better within the Ta-coated scaffolds. To demonstrate the ability of producing custom implant for clinical applications via this technology, we designed and fabricated a porous Ti6Al4V scaffold with segmental mandibular shape derived from patient computerized tomography data. - Highlights: • Ta film was coated on porous Ti6Al4V scaffold using chemical vapor deposition. • Tantalum coating allowed for higher levels of cell adhesion and proliferation. • Better new bone formation occurred inside the tantalum-coated scaffolds. • Clinical image data was integrated with EBM to fabricate customized scaffold

  17. Influence of strain-rate on the flow stress and ductility of copper and tantalum

    International Nuclear Information System (INIS)

    Regazzoni, G.; Montheillet, F.; Dormeval, R.; Stelly, M.

    1981-09-01

    Tensile experiments were carried out at strain-rates in a range from epsilon = 6.10 -5 to 3.10 3 s -1 at 293 K and 673 K or 773 K. Two types of copper (FCC) and pure tantalum (BCC) were tested. The variations of ductility have been investigated in relation with the σ - epsilon equations of the materials and the examinations of fracture surfaces. They can be explained in terms of stability and intrinsic ductility

  18. Complete equation of state for shocked liquid nitrogen: Analytical developments

    International Nuclear Information System (INIS)

    Winey, J. M.; Gupta, Y. M.

    2016-01-01

    The thermodynamic response of liquid nitrogen has been studied extensively, in part, due to the long-standing interest in the high pressure and high temperature dissociation of shocked molecular nitrogen. Previous equation of state (EOS) developments regarding shocked liquid nitrogen have focused mainly on the use of intermolecular pair potentials in atomistic calculations. Here, we present EOS developments for liquid nitrogen, incorporating analytical models, for use in continuum calculations of the shock compression response. The analytical models, together with available Hugoniot data, were used to extrapolate a low pressure reference EOS for molecular nitrogen [Span, et al., J. Phys. Chem. Ref. Data 29, 1361 (2000)] to high pressures and high temperatures. Using the EOS presented here, the calculated pressures and temperatures for single shock, double shock, and multiple shock compression of liquid nitrogen provide a good match to the measured results over a broad range of P-T space. Our calculations provide the first comparison of EOS developments with recently-measured P-T states under multiple shock compression. The present EOS developments are general and are expected to be useful for other liquids that have low pressure reference EOS information available.

  19. Ion species stratification within strong shocks in two-ion plasmas

    Science.gov (United States)

    Keenan, Brett D.; Simakov, Andrei N.; Taitano, William T.; Chacón, Luis

    2018-03-01

    Strong collisional shocks in multi-ion plasmas are featured in many environments, with Inertial Confinement Fusion (ICF) experiments being one prominent example. Recent work [Keenan et al., Phys. Rev. E 96, 053203 (2017)] answered in detail a number of outstanding questions concerning the kinetic structure of steady-state, planar plasma shocks, e.g., the shock width scaling by the Mach number, M. However, it did not discuss shock-driven ion-species stratification (e.g., relative concentration modification and temperature separation). These are important effects since many recent ICF experiments have evaded explanation by standard, single-fluid, radiation-hydrodynamic (rad-hydro) numerical simulations, and shock-driven fuel stratification likely contributes to this discrepancy. Employing the state-of-the-art Vlasov-Fokker-Planck code, iFP, along with multi-ion hydro simulations and semi-analytics, we quantify the ion stratification by planar shocks with the arbitrary Mach number and the relative species concentration for two-ion plasmas in terms of ion mass and charge ratios. In particular, for strong shocks, we find that the structure of the ion temperature separation has a nearly universal character across ion mass and charge ratios. Additionally, we find that the shock fronts are enriched with the lighter ion species and the enrichment scales as M4 for M ≫ 1.

  20. Experimental determination of electron shock excitation cross sections for a singly charged gadolinium ion

    International Nuclear Information System (INIS)

    Smirnov, Yu.M.

    1995-01-01

    The trends observed in the processes of excitation with simultaneous ionization have received little study. This is particularly so for rare-earth elements having electron shells of complex structure and optical spectra very rich in lines. Among the basic factors responsible for such a situation, we should mention two: the difficulty presented by theoretical analysis of the processes discussed and the absence of factual information about the excitation cross sections with simultaneous ionization for the majority of rare-earth elements. The aim of the present work is to investigate the excitation of a singly charged gadolinium ion in the collisions of monokinetic electrons with gadolinium atoms. Up to the present time, only the excitation cross sections of a gadolinium atom have been measured, where investigation of the electron shock excitation of gadolinium atoms in their free state is associated with overcoming large experimental difficulties. About 160 crosss sections for the excitation of a singly charged gadolinium ion were measured and for a third of the cross sections; the energy dependences were recorded for the change in energy of the elecrons from the excitation threshold up to 200 eV. Included are tables of the wavelength, transistion, internal quantum number, the energy of the lowere and upper levels, and the values of cross sections for the charged gadolinium ion. Diagrams of the transistion energy states of Gd (II) and spectroscopy are presented and explained

  1. Raman spectra of ruthenium and tantalum trimers in argon matrices

    Science.gov (United States)

    Fang, Li; Shen, Xiaole; Chen, Xiaoyu; Lombardi, John R.

    2000-12-01

    The resonance Raman spectra of ruthenium trimers (Ru 3) in argon matrices have been obtained. Three resonance Raman transitions were observed between 570 and 590 nm. Two of them (303.4 and 603.7 cm -1) are assigned to the totally symmetric vibrational progression, giving k e=1.86 mdyne/ Å. The line at 581.5 cm-1 is assigned as the origin of a low-lying electronic state. We also report on the observation of a resonance Raman spectrum of tantalum trimers (Ta 3). Observed lines include 251.2 and 501.9 cm-1 which we assign to the fundamental and the first overtone of the symmetric stretch in Ta 3. This gives k e=2.25 mdyne/ Å.

  2. Molten fuel/coolant interaction studies: some results obtained with the Windscale small shock tube rig

    International Nuclear Information System (INIS)

    Higham, E.J.; Vaughan, G.J.

    1978-02-01

    Experiments are described in which water has been brought into contact with various molten metals in a shock tube, thus simulating the fall of coolant into molten uranium dioxide in a postulated reactor accident. Impact velocities of the water on to the molten material were in the range 5 to 7 m/s. Shock-pulse pressures in the water column after impact and particle size distributions of the dispersed resolidified material that was recovered were measured. The proportion of dispersed material and the size of the shock pulse (by comparison with that expected from water hammer alone) have been used as criteria for the occurrence of a molten fuel/coolant interaction and such interactions of varying degrees of violence have been found for water/aluminium, water/bismuth, water/tin, over a range of temperatures from 350 0 C to 950 0 C, for water/boric oxide, but not for water/magnesium. (author)

  3. Numerical studies of cavitation erosion on an elastic-plastic material caused by shock-induced bubble collapse

    Science.gov (United States)

    Turangan, C. K.; Ball, G. J.; Jamaluddin, A. R.; Leighton, T. G.

    2017-09-01

    We present a study of shock-induced collapse of single bubbles near/attached to an elastic-plastic solid using the free-Lagrange method, which forms the latest part of our shock-induced collapse studies. We simulated the collapse of 40 μm radius single bubbles near/attached to rigid and aluminium walls by a 60 MPa lithotripter shock for various scenarios based on bubble-wall separations, and the collapse of a 255 μm radius bubble attached to aluminium foil with a 65 MPa lithotripter shock. The coupling of the multi-phases, compressibility, axisymmetric geometry and elastic-plastic material model within a single solver has enabled us to examine the impingement of high-speed liquid jets from the shock-induced collapsing bubbles, which imposes an extreme compression in the aluminium that leads to pitting and plastic deformation. For certain scenarios, instead of the high-speed jet, a radially inwards flow along the aluminium surface contracts the bubble to produce a `mushroom shape'. This work provides methods for quantifying which parameters (e.g. bubble sizes and separations from the solid) might promote or inhibit erosion on solid surfaces.

  4. First order and second order fermi acceleration of energetic charged particles by shock waves

    International Nuclear Information System (INIS)

    Webb, G.M.

    1983-01-01

    Steady state solutions of the cosmic ray transport equation describing first order Fermi acceleration of energetic charged particles at a plane shock (without losses) and second order Fermi acceleration in the downstream region of the shock are derived. The solutions for the isotropic part of the phase space distribution function are expressible as eigenfunction expansions, being superpositions of series of power law momentum spectra, with the power law indices being the roots of an eigenvalue equation. The above exact analytic solutions are for the case where the spatial diffusion coefficient kappa is independent of momentum. The solutions in general depend on the shock compression ratio, the modulation parameters V 1 L/kappa 1 , V 2 L/kappa 2 (V is the plasma velocity, kappa is the energetic particle diffusion coefficient, and L a characteristic length over which second order Fermi acceleration is effective) in the upstream and downstream regions of the shock, respectively, and also on a further dimensionless parameter, zeta, characterizing second order Fermi acceleration. In the limit as zeta→0 (no second order Fermi acceleration) the power law momentum spectrum characteristic of first order Fermi acceleration (depending only on the shock compression ratio) obtained previously is recovered. Perturbation solutions for the case where second order Fermi effects are small, and for realistic diffusion coefficients (kappainfinityp/sup a/, a>0, p = particle momentum), applicable at high momenta, are also obtained

  5. Mechanical analysis of a heat-shock induced developmental defect

    Science.gov (United States)

    Crews, Sarah M.; McCleery, W. Tyler; Hutson, M. Shane

    2014-03-01

    Embryonic development in Drosophila is a complex process involving coordinated movements of mechanically interacting tissues. Perturbing this system with a transient heat shock can result in a number of developmental defects. In particular, a heat shock applied during the earliest morphogenetic movements of gastrulation can lead to apparent recovery, but then subsequent morphogenetic failure 5-6 hours later during germ band retraction. The process of germ band retraction requires an intact amnioserosa - a single layered extra-embryonic epithelial tissue - and heat shock at gastrulation can induce the later opening of holes in the amnioserosa. These holes are highly correlated with failures of germ band retraction. These holes could be caused by a combination of mechanical weakness in the amnioserosa or local increases in mechanical stress. Here, we assess the role of mechanical stress using confocal imaging to compare cell and tissue morphology in the amnioserosa of normal and heat-shocked embryos and laser hole drilling to map the stress field around the times and locations at which heat-shock induced holes open.

  6. Slow shocks and their transition to fast shocks in the inner solar wind

    International Nuclear Information System (INIS)

    Wang, Y.C.

    1987-01-01

    The jump conditions of MHD shocks may be directly calculated as functions of three upstream conditions: the shock Alfven number based on the normal component of the relative shock speed, the shock angle, and the plasma β value. The shock Alfven number is less than 1 for a slow shock and greater than 1 for a fast shock. A traveling, forward shock can be a slow shock in coronal space, where the Alfven speed is of the order of 1000 km/s. The surface of a forward slow shock has a bow-shaped geometry with its nose facing toward the sun. The decrease in the Alfven speed at increasing heliocentric distance causes the shock Alfven number of a forward slow shock to become greater than 1, and the shock eventually evolves from a slow shock into a fast shock. During the transition the shock system consists of a slow shock, a fast shock, and a rotational discontinuity. They intersect along a closed transition line. As the system moves outward from the sun, the area enclosed by the transition line expands, the fast shock grows stronger, and the slow shock becomes weaker. Eventually, the slow shock diminishes, and the entire shock system evolves into a forward fast shock. copyrightAmerican Geophysical Union 1987

  7. In situ STM and EQCM studies of tantalum electrodeposition from TaF{sub 5} in the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide

    Energy Technology Data Exchange (ETDEWEB)

    Borisenko, N. [Chair of Interface Processes, Institute of Particle Technology, Clausthal University of Technology, 38678 Clausthal-Zellerfeld (Germany); Ispas, A.; Zschippang, E. [Lehrstuhl fuer Physikalische Chemie und Elektrochemie, Technische Universitaet Dresden, 01062 Dresden (Germany); Liu, Q.; Zein El Abedin, S. [Chair of Interface Processes, Institute of Particle Technology, Clausthal University of Technology, 38678 Clausthal-Zellerfeld (Germany); Bund, A. [Lehrstuhl fuer Physikalische Chemie und Elektrochemie, Technische Universitaet Dresden, 01062 Dresden (Germany)], E-mail: andreas.bund@chemie.tu-dresden.de; Endres, F. [Chair of Interface Processes, Institute of Particle Technology, Clausthal University of Technology, 38678 Clausthal-Zellerfeld (Germany)], E-mail: frank.endres@tu-clausthal.de

    2009-02-01

    The electroreduction of 0.5 M TaF{sub 5} on Au(1 1 1) and on polycrystalline gold substrates was investigated at room temperature in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide, [Py{sub 1,4}]TFSA, by cyclic voltammetry, in situ scanning tunneling microscopy (STM) and electrochemical quartz crystal microbalance (EQCM). The electrochemical reduction of TaF{sub 5} in the employed ionic liquid occurs in several steps. The first redox process is attributed to the reduction of TaF{sub 5} to TaF{sub 3}, which likely occurs in the solution, as EQCM indicates no mass change. The electrodeposition of tantalum occurs only in a very narrow potential window and is preceded by the formation of various non-stoichiometric tantalum subhalides. Attempts to deposit micrometer thick tantalum layers at room temperature fail, presumably because of kinetic reasons.

  8. Contribution of forensic anthropology to identification process in Croatia: examples of victims recovered in wells.

    Science.gov (United States)

    Slaus, Mario; Strinović, Davor; Petrovecki, Vedrana; Vyroubal, Vlasta

    2007-08-01

    To describe the contribution of forensic anthropology to the recovery, analysis, and identification of victims from the 1991-1995 war in Croatia recovered in wells. From 1996 to the present, human remains of a total of 61 individuals have been recovered from 13 wells. Six wells contained the remains of a single individual, one well contained the remains of 2 individuals, and 6 wells contained the remains 3 or more individuals. The majority of wells, containing 90.2% (55/61) of recovered individuals, were located within a 4 km radius of the Croatian-Serbian border. Forensic anthropologists re-individualized 26/61 (42.6%) individuals out of skeletonized and commingled remains, provided basic biological data on sex, age-at-death, and stature in all identifications (n=37), as well as established positive identification by recognizing unique skeletal features (antemortem fractures and skeletal evidence of antemortem surgical interventions) in 3/37 (8.1%) cases. Trauma analyses carried out by forensic anthropologists contributed to the determination of the cause of death in 38/61 (62.3%) individuals and to the probable cause of death in an additional 18/61 (29.5%) individuals. The most frequent (27/38, 71.0%) type of trauma causing death in individuals recovered from wells was a single gunshot wound. Forensic anthropologists, collaborating closely with forensic pathologists, forensic odontologists, forensic radiologists, criminologists, and molecular biologists contributed significantly to trauma analysis and identification of war victims recovered from wells.

  9. Effect of concentrated light on morphology and vibrational properties of boron and tantalum mixtures

    Directory of Open Access Journals (Sweden)

    Lina Sartinska

    2018-03-01

    Full Text Available Heating a mixture of boron (impurities: carbon ∼ B50C2, boric acid – H3BO3 and tantalum (Ta powders in nitrogen flow in a xenon high-flux optical furnace was performed. As-received powder composed of h-BN, H3BO3, TaB2, B9H11 and a number of other phases including β-rhombohedral boron, apparently, heavily doped with Ta. FT–IR examination of any sample of the material reveals the complicated vibration spectrum containing, in particular, an absorption band near 2260 cm−1. The shapes of these bands are different for samples because powders were synthesized at different temperatures. Known, that in β-rhombohedral boron lattice, there are nano-sized voids of different types, which allow an accommodation of single atoms or small groups of atoms. Theoretical calculations performed by the method of quasi-classical type yields the same value, 2260 cm−1, for the vibrations frequency of Ta atoms in D-type crystallographic voids in β-rhombohedral boron lattice. Since, Ta atoms are known to prefer accommodation just in D-voids the experimentally detected bands can be identified with localized vibrations of Ta atoms. Keywords: Condensed matter physics, Materials science, Nanotechnology

  10. Insight into magnetorheological shock absorbers

    CERN Document Server

    Gołdasz, Janusz

    2015-01-01

    This book deals with magnetorheological fluid theory, modeling and applications of automotive magnetorheological dampers. On the theoretical side a review of MR fluid compositions and key factors affecting the characteristics of these fluids is followed by a description of existing applications in the area of vibration isolation and flow-mode shock absorbers in particular. As a majority of existing magnetorheological devices operates in a so-called flow mode a critical review is carried out in that regard. Specifically, the authors highlight common configurations of flow-mode magnetorheological shock absorbers, or so-called MR dampers that have been considered by the automotive industry for controlled chassis applications. The authors focus on single-tube dampers utilizing a piston assembly with one coil or multiple coils and at least one annular flow channel in the piston.

  11. Reduction of a dimeric tantalum(III) compound in acetonitrile solution by pulse radiolysis

    International Nuclear Information System (INIS)

    Koulkes-Pujo, A.-M.; Le Motais, B.; Hubert-Pfalzgraf, L.G.

    1986-01-01

    The reduction of the compound [Ta 2 Cl 6 (4Me-py) 4 ] (4Me-py 4-methylpyridine), having a metal-metal double bond, has been achieved by pulse radiolysis in dry oxygen-free acetonitrile. The reduction occurs by CH 3 CN - which leads to a transient species assigned to a tantalum dimer in a 2.5 oxidation state. The spectrum of this species has been established. It decays by a first-order process to give a new transient species which in turn decays more slowly by a second-order reaction. (author)

  12. Pre-equilibrium decay process in alpha particle induced reactions on thulium and tantalum

    International Nuclear Information System (INIS)

    Mohan, Rao, A.V.; Chintalapudi, S.N.

    1994-01-01

    Alpha particle induced reactions on the target elements Thulium and Tantalum were investigated upto 60 MeV using stacked foil activation technique and Ge(Li) gamma ray spectroscopy method. Excitation functions for six reactions of 169 Tm(α,xn); x=1-4 and 181 Ta(α,xn); x=2,4 were studied. The experimental results were compared with the updated version of Hybrid model (ALICE/90) using initial exciton configuration n 0 =4(4pOh). A general agreement was found for all the reactions with this option. (author)

  13. Pre-equilibrium decay process in alpha particle induced reactions on thulium and tantalum

    Energy Technology Data Exchange (ETDEWEB)

    Mohan, Rao, A.V.; Chintalapudi, S.N. (Inter Univ. Consortium for Dept. of atomic Energy Facilities, Calcutta (India))

    1994-01-01

    Alpha particle induced reactions on the target elements Thulium and Tantalum were investigated upto 60 MeV using stacked foil activation technique and Ge(Li) gamma ray spectroscopy method. Excitation functions for six reactions of [sup 169]Tm([alpha],xn); x=1-4 and [sup 181]Ta([alpha],xn); x=2,4 were studied. The experimental results were compared with the updated version of Hybrid model (ALICE/90) using initial exciton configuration n[sub 0]=4(4pOh). A general agreement was found for all the reactions with this option. (author).

  14. Linkage of molecular units in the chemistry of niobium and tantalum cluster halides

    International Nuclear Information System (INIS)

    Perrin, C.; Sergent, M.

    1991-01-01

    In low valency niobium and tantalum halides, interunit linkages are observed between the (Me 6 X 12 )X 6 units. They are insulators and interesting magnetic properties are observed, due to the intrinsic potential magnetism of the Me 6 cluster and depending on the inserted cations, for instance rare earths in MM'Nb 6 Cl 18 (M = monovalent cation, M' = rare earth). Of special interest are the niobium iodides which exhibit (Me 6 X 8 )X 6 units, an exception in the niobium chemistry; interesting properties have been reported for some of these iodides

  15. Behavioral changes induced by single and multiple electron beam pulses

    International Nuclear Information System (INIS)

    Pease, V.P.; McNulty, P.J.

    1985-01-01

    The effects of single, and low-dose, high-dose-rate and multiple electron beam pulses on passive avoidance behavior in mice were studied. Passive avoidance was measured by recording the time that an animal took to enter a chamber from a narrow platform. There were four conditions in the experiment: (1) no shock no radiation-control, (2) radiation only, (3) shock only, and (4) radiation plus shock. Forty animals were run for each data point. Dose rate was held constant at 9 x 10/sup 7/ rads/sec. Average doses for the two single pulses were 7.18 and 8.72 rads. The average total dose for a 25 pulse per second condition was 324.0 rads. The differences between the single versus multiple pulse radiation-only conditions were significant with longer avoidance latencies in the multiple pulse condition. Avoidance latencies were also significantly longer in the shock plus radiation condition for the multiple beam pulse than the single pulse. It is concluded that single and multiple electron beam pulses significantly effect behavior, in this case producing avoidance

  16. Analysis of a cylindrical imploding shock wave

    International Nuclear Information System (INIS)

    Mishkin, E.A.; Fujimoto, Y.

    1978-01-01

    the self-similar solution of the gasdynamic equations of a strong cylindrical shock wave moving through an ideal gas, with γ = csub(p)/csub(v), is considered. These equations are greatly simplified following the transformation of the reduced velocity U 1 (xi) → U 1 = 1/2(γ + 1 ) (U + xi). The requirement of a single maximum pressure, dsub(xi)P = 0, leads to an analytical determination of the self-similarity exponent α(γ). For gases with γ = 2 + 3sup(1/2), this maximum ensues right at the shock front and the pressure distribution then decreases monotonically. The postulate of analyticity by Gelfand and Butler is shown to concur with the requirement dsub(xi)P 0. The saturated density of the gas left in the wake of the shock is computed and - U is shown to be the reduced velocity of sound at P = P sub(m). (author)

  17. Measure the Propagation of a Halo CME and Its Driven Shock with the Observations from a Single Perspective at Earth

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Lei; Feng, Li; Liu, Siming [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, 210008 Nanjing (China); Inhester, Bernd [Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Zhao, Xinhua, E-mail: lfeng@pmo.ac.cn, E-mail: inhester@mps.mpg.de [State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190 (China)

    2017-02-01

    We present a detailed study of an Earth-directed coronal mass ejection (full-halo CME) event that happened on 2011 February 15, making use of white-light observations by three coronagraphs and radio observations by Wind /WAVES. We applied three different methods to reconstruct the propagation direction and traveling distance of the CME and its driven shock. We measured the kinematics of the CME leading edge from white-light images observed by Solar Terrestrial Relations Observatory ( STEREO ) A and B , tracked the CME-driven shock using the frequency drift observed by Wind /WAVES together with an interplanetary density model, and obtained the equivalent scattering centers of the CME by the polarization ratio (PR) method. For the first time, we applied the PR method to different features distinguished from LASCO/C2 polarimetric observations and calculated their projections onto white-light images observed by STEREO-A and STEREO-B . By combining the graduated cylindrical shell (GCS) forward modeling with the PR method, we proposed a new GCS-PR method to derive 3D parameters of a CME observed from a single perspective at Earth. Comparisons between different methods show a good degree of consistence in the derived 3D results.

  18. Tantalum induced butterfly-like clusters on Si (111)-7 x 7 surface: STM/STS study at low coverage

    Czech Academy of Sciences Publication Activity Database

    Shukrynau, Pavel; Mutombo, Pingo; Švec, Martin; Hietschold, M.; Cháb, Vladimír

    2012-01-01

    Roč. 606, 3-4 (2012), s. 356-361 ISSN 0039-6028 R&D Projects: GA AV ČR IAA1010413 Institutional research plan: CEZ:AV0Z10100521 Keywords : tantalum * silicon * chemisorption * scanning tunneling microscopy * scanning tunneling spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.838, year: 2012

  19. Estimation of niobium, tantalum and zirconium in a carbonate rich ore

    International Nuclear Information System (INIS)

    Navale, A.S.; Venkatakrishnan, R.R.; Sreenivas, T.

    2013-01-01

    Tantalum, niobium and zirconium form refractory compounds and therefore pose problems in estimation by methods like spectrophotometry, AAS etc. Their estimation is best carried out with ICP-OES as the plasma is capable of breaking the refractory compounds and releases these elements in the form of excited atoms. But another major problem is bringing these elements in solution as they require very strong reagents and tend to hydrolyze easily in solution. Complexing agents need to be added to maintain these elements in dissolved condition. The commonly employed dissolution techniques for these elements are fusion with potassium pyrosulfate (for Nb and Ta), sodium hydroxide or peroxide (for zirconium). Digestion with mineral acids in combination with hydrofluoric acid is also employed

  20. Toxic shock syndrome

    Science.gov (United States)

    Staphylococcal toxic shock syndrome; Toxic shock-like syndrome; TSLS ... Toxic shock syndrome is caused by a toxin produced by some types of staphylococcus bacteria. A similar problem, called toxic shock- ...

  1. A Proposed Computed Tomography Contrast Agent Using Carboxybetaine Zwitterionic Tantalum Oxide Nanoparticles: Imaging, Biological, and Physicochemical Performance.

    Science.gov (United States)

    FitzGerald, Paul F; Butts, Matthew D; Roberts, Jeannette C; Colborn, Robert E; Torres, Andrew S; Lee, Brian D; Yeh, Benjamin M; Bonitatibus, Peter J

    2016-12-01

    The aim of this study was to produce and evaluate a proposed computed tomography (CT) contrast agent based on carboxybetaine zwitterionic (CZ)-coated soluble tantalum oxide (TaO) nanoparticles (NPs). We chose tantalum to provide superior imaging performance compared with current iodine-based clinical CT contrast agents. We developed the CZ coating to provide biological and physical performance similar to that of current iodinated contrast agents. In addition, the aim of this study was to evaluate the imaging, biological, and physicochemical performance of this proposed contrast agent compared with clinically used iodinated agents. We evaluated CT imaging performance of our CZ-TaO NPs compared with that of an iodinated agent in live rats, imaged centrally located within a tissue-equivalent plastic phantom that simulated a large patient. To evaluate vascular contrast enhancement, we scanned the rats' great vessels at high temporal resolution during and after contrast agent injection. We performed several in vivo CZ-TaO NP studies in healthy rats to evaluate tolerability. These studies included injecting the agent at the anticipated clinical dose (ACD) and at 3 times and 6 times the ACD, followed by longitudinal hematology to assess impact to blood cells and organ function (from 4 hours to 1 week). Kidney histological analysis was performed 48 hours after injection at 3 times the ACD. We measured the elimination half-life of CZ-TaO NPs from blood, and we monitored acute kidney injury biomarkers with a kidney injury assay using urine collected from 4 hours to 1 week. We measured tantalum retention in individual organs and in the whole carcass 48 hours after injection at ACD. Carboxybetaine zwitterionic TaO NPs were synthesized and analyzed in detail. We used multidimensional nuclear magnetic resonance to determine surface functionality of the NPs. We measured NP size and solution properties (osmolality and viscosity) of the agent over a range of tantalum concentrations

  2. A Multi-wavelength Study of an Isolated MSP Bow Shock

    Science.gov (United States)

    Romani, Roger W.; Slane, Patrick; Green, Andrew

    2017-08-01

    PSR J2124-3358 is the only single MSP known to sport an Halpha bow shock. This shock, now also seen in the UV, encloses an unusual X-ray pulsar wind nebula (PWN) with a long off-axis trail. Combining the X-ray and UV images with AAT/KOALA integral field spectroscopy of the Halpha emission, we have an unusually complete picture of the pulsar's (101 km/s transverse) motion and the latitudinal distribution of its wind flux. These images reveal the 3-D orientation of a hard-spectrum PWN jet and a softer equatorial outflow. Within the context of a thin shock model, we can constrain the total energy output of the pulsar and the neutron star moment of inertia. The IFU spectra show extreme Balmer dominance, which also constrains the nature of the UV shock emission.

  3. A study on the effect of tantalum-impurity content on the superconducting properties of niobium materials used for making superconducting radio frequency cavities

    Science.gov (United States)

    Roy, S. B.; Sharath Chandra, L. S.; Chattopadhyay, M. K.; Tiwari, M. K.; Lodha, G. S.; Myneni, G. R.

    2012-11-01

    Niobium materials in highly pure form are used in the fabrication of superconducting radio frequency cavities. We present here a study of the superconducting properties of such niobium materials that have been used in the fabrication of high accelerating gradient superconducting radio frequency cavities after determining their tantalum-impurity contents using a synchrotron-based x-ray fluorescence spectroscopy technique. Our results show that there is a small change in superconducting parameters such as TC,HC1 and HC2 when the tantalum-impurity content varies from ≈150 to ≈1300 ppm. In contrast, a buffered chemical polishing of the same niobium samples changes all these superconducting parameters more significantly. The implications of these results on the performance of niobium superconducting radio frequency cavities are discussed.

  4. Alkane metathesis with the tantalum methylidene [(≡SiO)Ta(=CH2)Me2]/[(≡SiO)2Ta(=CH2)Me] generated from well-defined surface organometallic complex [(≡SiO)TaVMe4

    KAUST Repository

    Chen, Yin; Abou-Hamad, Edy; Hamieh, Ali Imad Ali; Hamzaoui, Bilel; Emsley, Lyndon; Basset, Jean-Marie

    2015-01-01

    By grafting TaMe5 on Aerosil700, a stable, well-defined, silica-supported tetramethyl tantalum(V) complex, [(≡SiO)TaMe4], is obtained on the silica surface. After thermal treatment at 150 °C, the complex is transformed into two surface tantalum methylidenes, [(≡SiO)2Ta(=CH2)Me] and [(≡SiO)Ta(=CH2)Me2], which are active in alkane metathesis and comparable to the previously reported [(≡SiO)2TaHx]. Here we present the first experimental study to isolate and identify a surface tantalum carbene as the intermediate in alkane metathesis. A systematic experimental study reveals a new reasonable pathway for this reaction.

  5. Alkane metathesis with the tantalum methylidene [(≡SiO)Ta(=CH2)Me2]/[(≡SiO)2Ta(=CH2)Me] generated from well-defined surface organometallic complex [(≡SiO)TaVMe4

    KAUST Repository

    Chen, Yin

    2015-01-21

    By grafting TaMe5 on Aerosil700, a stable, well-defined, silica-supported tetramethyl tantalum(V) complex, [(≡SiO)TaMe4], is obtained on the silica surface. After thermal treatment at 150 °C, the complex is transformed into two surface tantalum methylidenes, [(≡SiO)2Ta(=CH2)Me] and [(≡SiO)Ta(=CH2)Me2], which are active in alkane metathesis and comparable to the previously reported [(≡SiO)2TaHx]. Here we present the first experimental study to isolate and identify a surface tantalum carbene as the intermediate in alkane metathesis. A systematic experimental study reveals a new reasonable pathway for this reaction.

  6. Synthesis of chemical vapor deposition graphene on tantalum wire for supercapacitor applications

    International Nuclear Information System (INIS)

    Li, Mingji; Guo, Wenlong; Li, Hongji; Xu, Sheng; Qu, Changqing; Yang, Baohe

    2014-01-01

    Highlights: • The capacitance of graphene/tantalum (Ta) wire electrodes is firstly reported. • Graphene was grown on the Ta surface by hot-filament chemical vapor deposition. • Graphene/Ta wire structure is favorable for fast ion and electron transfer. • The graphene/Ta wire electrode shows high capacitive properties. - Abstract: This paper studies the synthesis and electrochemical characterization of graphene/tantalum (Ta) wires as high-performance electrode material for supercapacitors. Graphene on Ta wires is prepared by the thermal decomposition of methane under various conditions. The graphene nanosheets on the Ta wire surface have an average thickness of 1.3–3.4 nm and consist typically of a few graphene monolayers, and TaC buffer layers form between the graphene and Ta wire. A capacitor structure is fabricated using graphene/Ta wire with a length of 10 mm and a diameter of 0.6 mm as the anode and Pt wire of the same size as the cathode. The electrochemical behavior of the graphene/Ta wires as supercapacitor electrodes is characterized by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy in 1 M Na 2 SO 4 aqueous electrolyte. The as-prepared graphene/Ta electrode has highest capacitance of 345.5 F g −1 at current density of 0.5 A g −1 . The capacitance remains at about 84% after 1000 cycles at 10 A g −1 . The good electrochemical performance of the graphene/Ta wire electrode is attributed to the unique nanostructural configuration, high electrical conductivity, and large specific surface area of the graphene layer. This suggests that graphene/Ta wire electrode materials have potential applications in high-performance energy storage devices

  7. The shock and spall response of AA 7010-T7651

    Science.gov (United States)

    Hazell, Paul; Appleby-Thomas, Gareth; Wood, David; Painter, Jonathan

    2013-06-01

    Aluminium alloys are used extensively in armour. Their use as armour materials is primarily due to their relatively low densities and their high strength characteristics. The aerospace-grade 7000-series alloy Al7010-T7651 is one possible contender for armour. In this study a series of plate-impact experiments were undertaken to investigate the behaviour of this alloy under shock. Manganin stress gauges and a heterodyne velocimeter system were used to interrogate both strength and dynamic tensile failure (spall) respectively; with microscopic analysis of recovered samples providing insight into the development of failure in the material.

  8. Intracellular formation of α-synuclein oligomers and the effect of heat shock protein 70 characterized by confocal single particle spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Levin, Johannes [Department of Neurology, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich (Germany); German Center for Neurodegenerative Diseases – DZNE, Site Munich, Feodor-Lynen-Str. 17, 81377 Munich (Germany); Hillmer, Andreas S. [Center for Neuropathology and Prion Research, Ludwig-Maximilians-University, Feodor-Lynen-Str. 23, 81377 Munich (Germany); Högen, Tobias [Department of Neurology, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich (Germany); McLean, Pamela J. [Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224 (United States); Giese, Armin, E-mail: armin.giese@med.uni-muenchen.de [Center for Neuropathology and Prion Research, Ludwig-Maximilians-University, Feodor-Lynen-Str. 23, 81377 Munich (Germany)

    2016-08-12

    Synucleinopathies such as dementia with Lewy bodies or Parkinson’s disease are characterized by intracellular deposition of pathologically aggregated α-synuclein. The details of the molecular pathogenesis of PD and especially the conditions that lead to intracellular aggregation of α-synuclein and the role of these aggregates in cell death remain unknown. In cell free in vitro systems considerable knowledge about the aggregation processes has been gathered. In comparison, the knowledge about these aggregation processes in cells is far behind. In cells α-synuclein aggregates can be toxic. However, the crucial particle species responsible for decisive steps in pathogenesis such as seeding a continuing aggregation process and triggering cell death remain to be identified. In order to understand the complex nature of intracellular α-synuclein aggregate formation, we analyzed fluorescent particles formed by venus and α-synuclein-venus fusion proteins and α-synuclein-hemi-venus fusion proteins derived from gently lyzed cells. With these techniques we were able to identify and characterize α-synuclein oligomers formed in cells. Especially the use of α-synuclein-hemi-venus fusion proteins enabled us to identify very small α-synuclein oligomers with high sensitivity. Furthermore, we were able to study the molecular effect of heat shock protein 70, which is known to inhibit α-synuclein aggregation in cells. Heat shock protein 70 does not only influence the size of α-synuclein oligomers, but also their quantity. In summary, this approach based on fluorescence single particle spectroscopy, that is suited for high throughput measurements, can be used to detect and characterize intracellularly formed α-synuclein aggregates and characterize the effect of molecules that interfere with α-synuclein aggregate formation. - Highlights: • Single particle spectroscopy detects intracellular formed α-synuclein aggregates. • Fusion proteins allow detection of protein

  9. EMU and macroeconomic shocks: some evidence on Spanish regions

    OpenAIRE

    Maza, Adolfo; Sanchez-Robles, Blanca

    2002-01-01

    According to the Theory of Optimal Currency Areas, one of the main costs that EMU may entail for countries and regions belonging in it is the loss of monetary autonomy at the country level. In fact, the scenario brought about by the single currency does not allow for domestic policy adjustments (i.e a change in the exchange rate or a specific monetary measure) in response to shocks. The importance of this cost, in turn, is related to the nature of shocks impinging over the different countries...

  10. Shock-induced spall in copper: the effects of anisotropy, temperature, loading pulse and defect

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Shengnian [Los Alamos National Laboratory; Germann, Timothy C [Los Alamos National Laboratory; An, Qi [Los Alamos National Laboratory; Han, Li - Bo [USTC

    2009-07-28

    Shock-induced spall in Cu is investigated with molecular dynamics simulations. We examine spallation in initially perfect crystals and defective solids with grain boundaries (columnar bicrystals), stacking faults or vacancies, as well as the effect of temperature and loading pulses. Spall in single crystal Cu is anisotropic, and defects and high temperature may reduce the spall strength. Taylor-wave (triangular shock-release wave) loading is explored in comparison with square wave shock loading.

  11. Anomalous elastic response of silicon to uniaxial shock compression on nanosecond time scales.

    Science.gov (United States)

    Loveridge-Smith, A; Allen, A; Belak, J; Boehly, T; Hauer, A; Holian, B; Kalantar, D; Kyrala, G; Lee, R W; Lomdahl, P; Meyers, M A; Paisley, D; Pollaine, S; Remington, B; Swift, D C; Weber, S; Wark, J S

    2001-03-12

    We have used x-ray diffraction with subnanosecond temporal resolution to measure the lattice parameters of orthogonal planes in shock compressed single crystals of silicon (Si) and copper (Cu). Despite uniaxial compression along the (400) direction of Si reducing the lattice spacing by nearly 11%, no observable changes occur in planes with normals orthogonal to the shock propagation direction. In contrast, shocked Cu shows prompt hydrostaticlike compression. These results are consistent with simple estimates of plastic strain rates based on dislocation velocity data.

  12. KAJIAN SIFAT OPTIK FILM TIPIS BST DIDADAH NIOBIUM DAN TANTALUM

    Directory of Open Access Journals (Sweden)

    Farida Huriawati

    2016-11-01

    Full Text Available In this research thin films of Barium Strontium Titanate (BST has been synthesis with different compositions Ba0,5Sr0,5TiO3 and Ba0,25Sr0,75TiO3 which doped by Nb2O5 (Niobium and Ta2O5 (Tantalum on Si (100 type-p substrate. Thin films were produced by chemical solution deposition technique (CSD and spin coating technique with annealing temperature at 850oC, 900oC dan 950oC. Rotation velocity at 3000 rpm and time of rotation is 30 seconds. Characterization of Films is optic Characterization (absorbance ana reflectance. From the Characterizations were obtained BNST thin film with 5% doping and anneling temperature at 8500C as photodiode light sensor which applied in electronic circuit.

  13.  Celery – cause of severe anaphylactic shock

    Directory of Open Access Journals (Sweden)

    Krzysztof Pałgan

    2012-03-01

    Full Text Available  Background:We present a case of anaphylactic shock induced by celery ingestion in a 28-year old woman with pollinosis during allergen (50�0birch, 50�0grass immunotherapy.Case Report:A female patient, aged 28 was admitted to the clinic due to a serious anaphylactic reaction. The event took place 15 min after ingesting fresh celery. She recovered after routine treatment with adrenaline, corticosteroids and antazoline.Conclusions:Our case shows the possibility of simultaneous occurrence of hypersensitivity to inhaled allergens and food. In such cases, it is considered part of cross-reactivity We discuss the importance of cross- reactivity associated with sensitization to pollen and vegetable foods.

  14. Shock wave compression and metallization of simple molecules

    International Nuclear Information System (INIS)

    Ross, M.; Radousky, H.B.

    1988-03-01

    In this paper we combine shock wave studies and metallization of simple molecules in a single overview. The unifying features are provided by the high shock temperatures which lead to a metallic-like state in the rare gases and to dissociation of diatomic molecules. In the case of the rare gases, electronic excitation into the conduction band leads to a metallic-like inert gas state at lower than metallic densities and provides information regarding the closing of the band gap. Diatomic dissociation caused by thermal excitation also leads to a final metallic-like or monatomic state. Ina ddition, shock wave data can provide information concerning the short range intermolecular force of the insulator that can be useful for calculating the metallic phase transition as for example in the case of hydrogen. 69 refs., 36 figs., 2 tabs

  15. Atomistic simulation of orientation dependence in shock-induced initiation of pentaerythritol tetranitrate.

    Science.gov (United States)

    Shan, Tzu-Ray; Wixom, Ryan R; Mattsson, Ann E; Thompson, Aidan P

    2013-01-24

    The dependence of the reaction initiation mechanism of pentaerythritol tetranitrate (PETN) on shock orientation and shock strength is investigated with molecular dynamics simulations using a reactive force field and the multiscale shock technique. In the simulations, a single crystal of PETN is shocked along the [110], [001], and [100] orientations with shock velocities in the range 3-10 km/s. Reactions occur with shock velocities of 6 km/s or stronger, and reactions initiate through the dissociation of nitro and nitrate groups from the PETN molecules. The most sensitive orientation is [110], while [100] is the most insensitive. For the [001] orientation, PETN decomposition via nitro group dissociation is the dominant reaction initiation mechanism, while for the [110] and [100] orientations the decomposition is via mixed nitro and nitrate group dissociation. For shock along the [001] orientation, we find that CO-NO(2) bonds initially acquire more kinetic energy, facilitating nitro dissociation. For the other two orientations, C-ONO(2) bonds acquire more kinetic energy, facilitating nitrate group dissociation.

  16. A transport equation for the evolution of shock amplitudes along rays

    Directory of Open Access Journals (Sweden)

    Giovanni Russo

    1991-05-01

    Full Text Available A new asymptotic method is derived for the study of the evolution of weak shocks in several dimension. The method is based on the Generalized Wavefront Expansion derived in [1]. In that paper the propagation of a shock into a known background was studied under the assumption that shock is weak, i.e. Mach Number =1+O(ε, ε ≪ 1, and that the perturbation of the field varies over a length scale O(ε. To the lowest order, the shock surface evolves along the rays associated with the unperturbed state. An infinite system of compatibility relations was derived for the jump in the field and its normal derivatives along the shock, but no valid criterion was found for a truncation of the system. Here we show that the infinite hierarchy is equivalent to a single equation that describes the evolution of the shock along the rays. We show that this method gives equivalent results to those obtained by Weakly Nonlinear Geometrical Optics [2].

  17. Experimental investigation of thermophysical properties of eutectic Mo–C, graphite and tantalum at high temperatures

    International Nuclear Information System (INIS)

    Senchenko, V N; Belikov, R S; Popov, V S

    2016-01-01

    An experimental technique based on fast electrical heating for investigation of thermophysical properties of refractory materials under high pressures and at high temperatures is considered. A set of thermophysical properties of refractory materials such as specific enthalpy, specific heat capacity, specific resistivity, melting heat of eutectic Mo-C and thermal expansion of graphite and tantalum were determined. The obtained temperature of eutectic melting of MoC 0.82 shows close agreement with equilibrium Mo-C phase diagram. (paper)

  18. Diffusion of intracerebrally injected [1-14C]arachidonic acid and [2-3H]glycerol in the mouse brain. Effects of ischemia and electroconvulsive shock

    International Nuclear Information System (INIS)

    Pediconi, M.F.; Rodriguez de Turco, E.B.; Bazan, N.G.

    1982-01-01

    [2- 3 H]Glycerol and [1- 14 C]arachidonic acid were injected into the region of the frontal horn of the left ventricle of mice and were distributed rapidly throughout the brain. After 10 sec, most of the radioactive fatty acid was found in the hemisphere near the injection site; after 10 min, it was recovered in similar proportions in the cerebellum and brain stem. [2- 3 H]Glycerol showed a heterogeneous distribution, with most of the label remaining in the left hemisphere even after 10 min. On a fresh weight basis, cerebrum, cerebellum, and brain stem were found to contain similar amounts of labeled glycerol. However, the amount of [1- 14 C]arachidonate in cerebrum was only 50% of that recovered from cerebellum or brain stem. Brain ischemia or a single electroconvulsive shock reduced the spread of the label, producing an accumulation of radioactivity in the injected hemisphere, except for an increase in [2- 3 H]glycerol in the brain stem during ischemia. Despite the significant decrease in available precursor in the cerebellum and brain stem after electroshock, the amount of label incorporated into lipids was not altered in these areas and only slightly diminished in the cerebrum

  19. High temperature thermodynamics of solutions of oxygen in vanadium, niobium and tantalum

    International Nuclear Information System (INIS)

    Boureau, G.; Gerdanian, P.

    1981-01-01

    The Tian-Calvet microcalorimetric method has been applied to the determination at 1323 K of ΔH(O 2 ), the partial molar enthalpy of mixing of oxygen in vanadium, niobium and tantalum. The present results are in good agreement with earlier studies using e.m.f. techniques. Nevertheless in the first two solutions, ΔH(O 2 ) has been found somewhat more negative than previously reported. The partial molar entropies of mixing have been recalculated. The low values of the excess entropies are explained by a strong increase of the Debye temperature and a decrease of the electronic density of states at the Fermi level as the oxygen content increases. (author)

  20. Some organoperoxo complexes of antimony, niobium and tantalum and their oxidation properties

    International Nuclear Information System (INIS)

    Tarafder, M.T.H.

    1999-05-01

    Several novel organoperoxo complexes of Nb(V), Ta(V) and Sb(V) have been synthesized and characterized. The complexes have the compositions [M(O 2 ) 2 L Cl] and [M(O 2 ) 2 L'] [L = monodentate and bidentate, neutral ligand; L' = bidentate, uninegative ligand]. These complexes are very reactive to both organic and inorganic substrates. Niobium and tantalum complexes were found to oxidize phosphines and arsines to their oxides. These also oxidize olefins to epoxides under stoichiometric conditions while under catalytic conditions, ring opening of the epoxides occur producing α-hydroxyketone when the substrate is trans-stilbene. The antimony complexes are decidedly inert towards oxidation. (author)

  1. demystifying the shock of shocking

    African Journals Online (AJOL)

    (with a pulse), atrial fibrillation and atrial flutter. The energy dose in cardioversion is less (0.5. - 2 J/kg) than in defibrillation (2 - 4 J/kg). In cardioversion the shock is discharged synchronously with the native R wave of the patient. Without synchronisation,. VF can be induced if a shock is delivered during the refractory period ...

  2. OBSERVATIONAL SIGNATURES OF SUB-PHOTOSPHERIC RADIATION-MEDIATED SHOCKS IN THE PROMPT PHASE OF GAMMA-RAY BURSTS

    International Nuclear Information System (INIS)

    Levinson, Amir

    2012-01-01

    A shock that forms below the photosphere of a gamma-ray burst (GRB) outflow is mediated by Compton scattering of radiation advected into the shock by the upstream fluid. The characteristic scale of such a shock, a few Thomson depths, is larger than any kinetic scale involved by several orders of magnitude. Hence, unlike collisionless shocks, radiation-mediated shocks cannot accelerate particles to nonthermal energies. The spectrum emitted by a shock that emerges from the photosphere of a GRB jet reflects the temperature profile downstream of the shock, with a possible contribution at the highest energies from the shock transition layer itself. We study the properties of radiation-mediated shocks that form during the prompt phase of GRBs and compute the time-integrated spectrum emitted by the shocked fluid following shock breakout. We show that the time-integrated emission from a single shock exhibits a prominent thermal peak, with the location of the peak depending on the shock velocity profile. We also point out that multiple shock emission can produce a spectrum that mimics a Band spectrum.

  3. Carbochlorination kinetics of tantalum and niobium pentoxides

    International Nuclear Information System (INIS)

    Allain, E.; Gaballah, I.; Garcia, F.; Ferreira, S.; Ayala, J. N.; Hernandez, A.

    1999-01-01

    The carbochlorination kinetics of pure Nb 2 O 5 and Ta 2 O 5 by gas mixture (CL 2 +CO+N 2 ) between 380 and 1,000 degree centigree is studied. A calculation of the standard free energy of the carbochlorination reactions is made. A diagram of the phases stability is drawn. The influence of the gas flow, temperature and the partial pressure of Cl 2 and Co at temperatures below 650 degree centigree on the reaction rate is studied. The apparent activation energy is approximately 75 and 110 kJ/mol for Nb 2 O 5 and Ta 2 O 5 , respectively. At temperatures above 650 degree centigree the Arrhenius diagram presents and anomaly which may be attributed to the decomposition of the COCL 2 formed in situ. The apparent reaction order of the carbochlorination of these oxides against Cl 2 +CO is approximately 2. The carbochlorination rates of these oxides are much greater than those of chlorination by Cl 2 +N 2 . The carbochlorination kinetics of tin furnace slag leaching concentrates containing tantalum and niobium compounds are also studied and compared with the carbochlorination kinetics of the pure oxides. (Author) 14 refs

  4. Shock absorbing structure

    International Nuclear Information System (INIS)

    Kojima, Naoki; Matsushita, Kazuo.

    1992-01-01

    Small pieces of shock absorbers are filled in a space of a shock absorbing vessel which is divided into a plurality of sections by partitioning members. These sections function to prevent excess deformation or replacement of the fillers upon occurrence of falling accident. Since the shock absorbing small pieces in the shock absorbing vessel are filled irregularly, shock absorbing characteristics such as compression strength is not varied depending on the direction, but they exhibit excellent shock absorbing performance. They surely absorb shocks exerted on a transportation vessel upon falling or the like. If existing artificial fillers such as pole rings made of metal or ceramic and cut pieces such as alumium extrusion molding products are used as the shock absorbing pieces, they have excellent fire-proofness and cold resistance since the small pieces are inflammable and do not contain water. (T.M.)

  5. Development of tantalum oxynitride thin films produced by PVD: Study of structural stability

    Energy Technology Data Exchange (ETDEWEB)

    Cristea, D. [Centro de Física, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Department of Materials Science, Transylvania University, 500036 Brasov (Romania); Crisan, A. [Department of Materials Science, Transylvania University, 500036 Brasov (Romania); Barradas, N.P.; Alves, E. [Instituto Superior Técnico, Universidade Técnica de Lisboa Estrada Nacional 10, ao km 139,7 2695-066, Bobadela LRS (Portugal); Moura, C.; Vaz, F. [Centro de Física, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Cunha, L., E-mail: lcunha@fisica.uminho.pt [Centro de Física, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal)

    2013-11-15

    The purpose of this work is to study the evolution of the structure and of the thermal stability of a group of tantalum oxynitride thin films, prepared by magnetron sputtering, under the influence of vacuum annealing, up to a temperature of 800 °C. When varying the partial pressure of the reactive gases (P{sub O{sub 2+N{sub 2}}}), during the deposition process, the films change from a structure with a combination of poorly developed crystallites of the tetragonal β-Ta and of the face centred cubic (fcc) Ta(O,N) phases, for the films deposited with low P{sub O2+N2}, to a quasi-amorphous structure, for the films deposited with highest pressures. For intermediate pressures, the films reveal the presence of the fcc-Ta(O,N) structure. This structure corresponds to O atoms substituting some of the N atoms on the fcc-TaN structure and/or N atoms substituting O atoms of the fcc-γ-TaO structure. When subjected to the thermal annealing at 700 °C or higher, the film produced with lowest partial pressure revealed a remarkable structural change. New diffraction peaks appear and can only be attributed to a sub-stoichiometric hexagonal tantalum nitride structure. The film did not reveal any signs of delamination or cracks after all annealing temperatures. The two films produced with highest partial pressure proved to be the most stable. Structurally, they maintain the amorphous structure after all the annealing treatments and, in addition, no cracks or delamination were detected.

  6. Influence of edge conditions on material ejection from periodic grooves in laser shock-loaded tin

    Energy Technology Data Exchange (ETDEWEB)

    Rességuier, T. de; Roland, C. [Institut PPRIME, UPR 3346, CNRS, ENSMA, Université de Poitiers, 1 ave. Clément Ader, 86961 Futuroscope Cedex (France); Prudhomme, G.; Lescoute, E.; Mercier, P. [CEA, DAM, DIF, 91297 Arpajon (France); Loison, D. [Institut de Physique de Rennes, CNRS, Université de Rennes 1, 35042 Rennes (France)

    2016-05-14

    In a material subjected to high dynamic compression, the breakout of a shock wave at a rough free surface can lead to the ejection of high velocity debris. Anticipating the ballistic properties of such debris is a key safety issue in many applications involving shock loading, including pyrotechnics and inertial confinement fusion experiments. In this paper, we use laser driven shocks to investigate particle ejection from calibrated grooves of micrometric dimensions and approximately sinusoidal profile in tin samples, with various boundary conditions at the groove edges, including single groove and periodic patterns. Fast transverse shadowgraphy provides ejection velocities after shock breakout. They are found to depend not only on the groove depth and wavelength, as predicted theoretically and already observed in the past, but also, unexpectedly, on the edge conditions, with a jet tip velocity significantly lower in the case of a single groove than behind a periodic pattern.

  7. Fractionated Repetitive Extracorporeal Shock Wave Therapy: A New Standard in Shock Wave Therapy?

    Directory of Open Access Journals (Sweden)

    Tobias Kisch

    2015-01-01

    Full Text Available Background. ESWT has proven clinical benefit in dermatology and plastic surgery. It promotes wound healing and improves tissue regeneration, connective tissue disorders, and inflammatory skin diseases. However, a single treatment session or long intervals between sessions may reduce the therapeutic effect. The present study investigated the effects of fractionated repetitive treatment in skin microcirculation. Methods. 32 rats were randomly assigned to two groups and received either fractionated repetitive high-energy ESWT every ten minutes or placebo shock wave treatment, applied to the dorsal lower leg. Microcirculatory effects were continuously assessed by combined laser Doppler imaging and photospectrometry. Results. In experimental group, cutaneous tissue oxygen saturation was increased 1 minute after the first application and until the end of the measuring period at 80 minutes after the second treatment (P<0.05. The third ESWT application boosted the effect to its highest extent. Cutaneous capillary blood flow showed a significant increase after the second application which was sustained for 20 minutes after the third application (P<0.05. Placebo group showed no statistically significant differences. Conclusions. Fractionated repetitive extracorporeal shock wave therapy (frESWT boosts and prolongs the effects on cutaneous hemodynamics. The results indicate that frESWT may provide greater benefits in the treatment of distinct soft tissue disorders compared with single-session ESWT.

  8. Nitro Stretch Probing of a Single Molecular Layer to Monitor Shock Compression with Picosecond Time-Resolution

    Science.gov (United States)

    Berg, Christopher; Lagutchev, Alexei; Fu, Yuanxi; Dlott, Dana

    2011-06-01

    To obtain maximum possible temporal resolution, laser-driven shock compression of a molecular monolayer was studied using vibrational spectroscopy. The stretching transitions of nitro groups bound to aromatic rings was monitored using a nonlinear coherent infrared spectroscopy termed sum-frequency generation, which produced high-quality signals from this very thin layer. To overcome the shock opacity problem, a novel polymer overcoat method allowed us to make the observation window (witness plate) a few micrometers thick. The high signal-to-noise ratios (>100:1) obtained via this spectroscopy allowed us to study detailed behavior of the shocked molecules. To help interpret these vibrational spectra, additional spectra were obtained under conditions of static pressures up to 10 GPa and static temperatures up to 1000 C. Consequently, this experiment represents a significant step in resolving molecular dynamics during shock compression and unloading with both high spatial and temporal resolution. Supported by the Stewardship Sciences Academic Alliance Program from the Carnegie-DOE Alliance Center under grant number DOE CIW 4-3253-13 and the US Air Force Office of Scientific Research under award number FAA9550-09-1-0163.

  9. Investigation of magnetic flux transport and shock formation in a staged Z-pinch

    Science.gov (United States)

    Narkis, J.; Rahman, H. U.; Wessel, F. J.; Beg, F. N.

    2017-10-01

    Target preheating is an integral component of magnetized inertial fusion in reducing convergence ratio. In the staged Z-pinch concept, it is achieved via one or more shocks. Previous work [Narkis et al., Phys. Plasmas 23, 122706 (2016)] found that shock formation in the target occurred earlier in higher-Z liners due to faster flux transport to the target/liner interface. However, a corresponding increase in magnitude of magnetic pressure was not observed, and target implosion velocity (and therefore shock strength) remained unchanged. To investigate other means of increasing the magnitude of transported flux, a Korteweg-de Vries-Burgers equation from the 1-D single-fluid, resistive magnetohydrodynamic equations is obtained. Solutions to the nondispersive (i.e., Burgers) equation depend on nondimensional coefficients, whose dependence on liner density, temperature, etc., suggests an increase in target implosion velocity, and therefore shock strength, can be obtained by tailoring the mass of a single-liner gas puff to a double-liner configuration. In the selected test cases of 1-D simulated implosions of krypton on deuterium, the peak Mach number increased from ˜ 5 to ˜ 8 . While a notable increase was seen, Mach numbers exceeding 10 (implosion velocities exceeding ˜25 cm/μs) are necessary for adequate shock preheating.

  10. Study on Reflected Shock Wave/Boundary Layer Interaction in a Shock Tube

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong Wook; Kim, Tae Ho; Kim, Heuy Dong [Andong Nat’l Univ., Andong (Korea, Republic of)

    2017-07-15

    The interaction between a shock wave and a boundary layer causes boundary layer separation, shock train, and in some cases, strong unsteadiness in the flow field. Such a situation is also observed in a shock tube, where the reflected shock wave interacts with the unsteady boundary layer. However, only a few studies have been conducted to investigate the shock train phenomenon in a shock tube. In the present study, numerical studies were conducted using the two-dimensional axisymmetric domain of a shock tube, and compressible Navier-Stokes equations were solved to clarify the flow characteristics of shock train phenomenon inside a shock tube. A detailed wave diagram was developed based on the present computational results, which were validated with existing experimental data.

  11. Biological characteristics of the MG-63 human osteosarcoma cells on composite tantalum carbide/amorphous carbon films.

    Directory of Open Access Journals (Sweden)

    Yin-Yu Chang

    Full Text Available Tantalum (Ta is a promising metal for biomedical implants or implant coating for orthopedic and dental applications because of its excellent corrosion resistance, fracture toughness, and biocompatibility. This study synthesizes biocompatible tantalum carbide (TaC and TaC/amorphous carbon (a-C coatings with different carbon contents by using a twin-gun magnetron sputtering system to improve their biological properties and explore potential surgical implant or device applications. The carbon content in the deposited coatings was regulated by controlling the magnetron power ratio of the pure graphite and Ta cathodes. The deposited TaC and TaC/a-C coatings exhibited better cell viability of human osteosarcoma cell line MG-63 than the uncoated Ti and Ta-coated samples. Inverted optical and confocal imaging was used to demonstrate the cell adhesion, distribution, and proliferation of each sample at different time points during the whole culture period. The results show that the TaC/a-C coating, which contained two metastable phases (TaC and a-C, was more biocompatible with MG-63 cells compared to the pure Ta coating. This suggests that the TaC/a-C coatings exhibit a better biocompatible performance for MG-63 cells, and they may improve implant osseointegration in clinics.

  12. Fabrication of Nano-Crossbar Resistive Switching Memory Based on the Copper-Tantalum Pentoxide-Platinum Device Structure

    Science.gov (United States)

    Olga Gneri, Paula; Jardim, Marcos

    Resistive switching memory has been of interest lately not only for its simple metal-insulator-metal (MIM) structure but also for its promising ease of scalability an integration into current CMOS technologies like the Field Programmable Gate Arrays and other non-volatile memory applications. There are several resistive switching MIM combinations but under this scope of research, attention will be paid to the bipolar resistive switching characteristics and fabrication of Tantalum Pentaoxide sandwiched between platinum and copper. By changing the polarity of the voltage bias, this metal-insulator-metal (MIM) device can be switched between a high resistive state (OFF) and low resistive state (ON). The change in states is induced by an electrochemical metallization process, which causes a formation or dissolution of Cu metal filamentary paths in the Tantalum Pentaoxide insulator. There is very little thorough experimental information about the Cu-Ta 2O5-Pt switching characteristics when scaled to nanometer dimensions. In this light, the MIM structure was fabricated in a two-dimensional crossbar format. Also, with the limited available resources, a multi-spacer technique was formulated to localize the active device area in this MIM configuration to less than 20nm. This step is important in understanding the switching characteristics and reliability of this structure when scaled to nanometer dimensions.

  13. Mid-term results of total knee arthroplasty with a porous tantalum monoblock tibial component.

    Science.gov (United States)

    Hayakawa, Kazue; Date, Hideki; Tsujimura, Shunzo; Nojiri, Sho; Yamada, Harumoto; Nakagawa, Kenji

    2014-01-01

    The objectives of the present study were to assess the mid-term results of cementless total knee arthroplasty (TKA) with the porous tantalum monoblock tibial component and to examine the time course of bone changes on plain radiographs. The subjects were 32 patients, 29 patients were available for follow-up. We investigated the mid-term results of TKA after a mean follow-up period of 7 years and 8 months. We also examined changes of the bone over time on plain radiographs. The Knee Society Clinical Rating scores showed significant improvement. Bone changes around the tibial component were as follows: new bone formation and longitudinal trabecular thickening in 41.4% (Type A), only longitudinal trabecular thickening in 41.4% (Type B), and no changes in 17.2% (Type C). Type A and B changes were more frequent in patients with osteoarthritis, whereas Type C was only seen in patients with rheumatoid arthritis. Three knees had an initial gap, but this disappeared in all cases, and no new radiolucent lines were detected. Stress shielding was observed in seven knees (21.9%), but there was no implant loosening related to it. When we examined the relationship between the mechanical axis and the locations of the tips of the tibial pegs in patients with or without stress shielding, no significant differences were found. The results of mid-term follow-up have demonstrated favorable bone ingrowth, suggesting that porous tantalum is a promising material for cementless TKA. © 2013.

  14. The size effects upon shock plastic compression of nanocrystals

    Science.gov (United States)

    Malygin, G. A.; Klyavin, O. V.

    2017-10-01

    For the first time a theoretical analysis of scale effects upon the shock plastic compression of nanocrystals is implemented in the context of a dislocation kinetic approach based on the equations and relationships of dislocation kinetics. The yield point of crystals τy is established as a quantitative function of their cross-section size D and the rate of shock deformation as τy ɛ2/3 D. This dependence is valid in the case of elastic stress relaxation on account of emission of dislocations from single-pole Frank-Read sources near the crystal surface.

  15. Influence of tantalum underlayer on magnetization dynamics in Ni81Fe19 films

    International Nuclear Information System (INIS)

    Kwon, Jae Hyun; Deorani, Praveen; Yoon, Jungbum; Yang, Hyunsoo; Hayashi, Masamitsu

    2015-01-01

    The effect of tantalum (Ta) underlayer is investigated in Ni 81 Fe 19 thin films for magnetization dynamics. The damping parameters extracted from spin wave measurements increase systematically with increasing Ta thickness, whereas the damping parameters from ferromagnetic resonance measurements are found to be weakly dependent on the Ta thickness. The difference is attributed to propagating properties of spin wave and short spin diffusion length in Ta. The group velocity of spin waves is found to be constant for different Ta thicknesses, and nonreciprocity of spin waves is not affected by the Ta thickness. The experimental observations are supported by micromagnetic simulations

  16. Successive heterolytic cleavages of H2 achieve N2 splitting on silica-supported tantalum hydrides: A DFT proposed mechanism

    KAUST Repository

    Solá ns, Xavier Luis; Chow, Catherine; Gouré , Eric; Kaya, Yasemin; Basset, Jean-Marie; Taoufik, Mostafa; Quadrelli, Elsje Alessandra; Eisenstein, Odile

    2012-01-01

    DFT(B3PW91) calculations have been carried out to propose a pathway for the N2 cleavage by H2 in the presence of silica-supported tantalum hydride complexes [(≡ SiO)2TaHx] that forms [(≡SiO)2Ta(NH)(NH2)] (Science2007, 317, 1056). The calculations

  17. Validating a pragmatic definition of shock in adult patients presenting to the ED.

    Science.gov (United States)

    Li, Yan-ling; Chan, Cangel Pui-yee; Sin, King-keung; Chan, Stewart S W; Lin, Pei-yi; Chen, Xiao-hui; Smith, Brendan E; Joynt, Gavin M; Graham, Colin A; Rainer, Timothy H

    2014-11-01

    The importance of the early recognition of shock in patients presenting to emergency departments is well recognized, but at present, there is no agreed practical definition for undifferentiated shock. The main aim of this study was to validate an a priori clinical definition of shock against 28-day mortality. This prospective, observational, cross-sectional, single-center study was conducted in Hong Kong, China. Data were collected between July 1, 2012, and January 31, 2013. An a priori definition of shock was designed, whereby patients admitted to the resuscitation room or high dependency area of the emergency department were divided into 1 of 3 groups-no shock, possible shock, and shock. The primary outcome was 28-day mortality. Secondary outcomes were in-hospital mortality or admission to the intensive or coronary care unit. A total of 111 patients (mean age, 67.2 ± 17.1 years; male = 69 [62%]) were recruited, of which 22 were classified as no shock, 54 as possible shock, and 35 as shock. Systolic blood pressure, mean arterial pressure, lactate, and base deficit correlated well with shock classifications (P definition of undifferentiated shock has been proposed and validated in a group of patients presenting to an emergency department in Hong Kong. This definition needs further validation in a larger population and other settings. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Collisionless electrostatic shocks

    DEFF Research Database (Denmark)

    Andersen, H.K.; Andersen, S.A.; Jensen, Vagn Orla

    1970-01-01

    An attempt was made in the laboratory to observe the standing collisionless electrostatic shocks in connection with the bow shock of the earth......An attempt was made in the laboratory to observe the standing collisionless electrostatic shocks in connection with the bow shock of the earth...

  19. Multistate Memristive Tantalum Oxide Devices for Ternary Arithmetic

    Science.gov (United States)

    Kim, Wonjoo; Chattopadhyay, Anupam; Siemon, Anne; Linn, Eike; Waser, Rainer; Rana, Vikas

    2016-11-01

    Redox-based resistive switching random access memory (ReRAM) offers excellent properties to implement future non-volatile memory arrays. Recently, the capability of two-state ReRAMs to implement Boolean logic functionality gained wide interest. Here, we report on seven-states Tantalum Oxide Devices, which enable the realization of an intrinsic modular arithmetic using a ternary number system. Modular arithmetic, a fundamental system for operating on numbers within the limit of a modulus, is known to mathematicians since the days of Euclid and finds applications in diverse areas ranging from e-commerce to musical notations. We demonstrate that multistate devices not only reduce the storage area consumption drastically, but also enable novel in-memory operations, such as computing using high-radix number systems, which could not be implemented using two-state devices. The use of high radix number system reduces the computational complexity by reducing the number of needed digits. Thus the number of calculation operations in an addition and the number of logic devices can be reduced.

  20. Metal derivatives of organo-phosphorous compounds. Part II : niobium(V) and tantalum(V) derivatives

    International Nuclear Information System (INIS)

    Puri, D.M.; Singh, Soran

    1981-01-01

    Reactions between niobium(V) chloride, tantalum(V) chloride and dialkyl/diaryl (Et-, Prsup(i)-, Busup(n)- and Ph-) phosphites have been studied in different molar ratios and under different conditions of temperature and solvent systems. The isolated complex compounds have been characterised on the basis of infrared spectral measurements, elemental analyses and magnetic susceptibility data. The polymeric nature of the products has been indicated by their molecular weights. The coordination of phosphite units to metal atom of the other molecule through phosphoryl oxygen gave rise to O-P-O-bridges. (author)