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Sample records for metallic powders hyperfine

  1. Hyperfine structure studies of transition metals

    SciTech Connect

    Young, L.; Kurtz, C.; Hasegawa, S.

    1995-08-01

    This past year our studies of hyperfine structure (hfs) in metastable states of transition metals concentrated on the analysis of hfs in the four-valence electron system, Nb II. Earlier, we measured hfs intervals using the laser-rf double resonance and laser-induced fluorescence methods in a fast-ion beam of Nb{sup +}. The resulting experimental magnetic dipole and electric quadrupole interaction constants are compared to those calculated by a relativistic configuration interaction approach. These are the first hfs data on this refractory element. Theoretically, it is found that the most important contributions to the energy are the pair excitations, valence single excitations and core polarization from the shallow core. However, the inner core polarization is found to be crucial for hfs, albeit unimportant for energy. For the J=2 level at 12805 cm{sup -1}, 4d{sup 4} {sup 3}F. the theoretical relativistic configuration A-value is in agreement with the experimental result to an accuracy of 4%. Other calculated A-values are expected to be of the same accuracy. A paper describing these results was accepted for publication. Experimental studies of the four-valence electron system V{sup +} in the (4s+3d){sup 4} manifold are complete. The theoretical difficulties for the 3d manifold, noted earlier for the three-valence electron Ti{sup +}, as compared to the 4d manifold appear to be repeated in the case of the four-valence electron systems (Nb{sup +} and V{sup +}). Relativistic configuration interaction calculations are underway, after which a paper will be published.

  2. Magnetic Properties and Hyperfine Interactions in Iron Containing Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Unruh, Karl Marlin

    Amorphous samples of Fe(,x)B(,100-x) (30 (LESSTHEQ) x (LESSTHEQ) 90), Fe(,x)Ag(,100-x) (40 (LESSTHEQ) x (LESSTHEQ) 50), and Fe(,x)Zr(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 93) have been prepared, and their magnetic properties and hyperfine interactions studied by ('57)Fe Mossbauer spectroscopy. Each system is representative of either Fe-metalloid (Fe-B), Fe-noble metal (Fe-Ag), or Fe-early transition metal (Fe -Zr) amorphous alloys. Therefore, by studying these three amorphous solids an overview is obtained, not only of the properties of the individual alloys, but also of the wider class of alloys of which they are representative. The amorphous Fe-B and Fe-Zr systems have been successfully fabricated over very wide ranges in composition, allowing the evolution of the magnetic properties and hyperfine interactions to be systematically studied. As a result it has been possible to determine the critical concentration for magnetic order (x(,c)). It has been shown that the loss of magnetic order below x(,c) is the result of the reduction and eventual disappearance of the Fe moment. The isomer shifts (IS) and quadrupole splittings (QS) have also been determined over wide composition ranges. This has led to the observation of a maximum in IS with decreasing Fe concentration in amorphous alloys of Fe and B. On the other hand, IS in the amorphous Fe-Zr alloys has been found to decrease monotonically over the same concentration range. In the paramagnetic region all the samples display quadrupole split doublets characteristic of site symmetries lower than cubic. It has been found that the observed asymmetry in the quadrupole spectra can be correlated with the relative changes in IS and QS as a function of composition. Amorphous alloys of Fe and Ag have been prepared for the first time and have been found to be stable at room temperature. The somewhat unusual magnetic properties of these alloys suggests that they may be simpler magnetically than previously studied magnetic

  3. Calculation of radiative corrections to hyperfine splittings in the neutral alkali metals

    SciTech Connect

    Sapirstein, J.; Cheng, K.T.

    2003-02-01

    The radiative correction to hyperfine splitting in hydrogen is dominated by the Schwinger term, {alpha}/2{pi} E{sub F}, where E{sub F} is the lowest-order hyperfine splitting. Binding corrections to this term, which enter as powers and logarithms of Z{alpha}, can be expected to be increasingly important in atoms with higher nuclear charge Z. Methods that include all orders of Z{alpha}, developed first to study highly charged ions, are adapted to the study of the neutral alkali metals, lithium through francium. It is shown that the use of the Schwinger term alone to account for radiative corrections to hyperfine splittings becomes qualitatively incorrect for the heavier alkali metals.0.

  4. Yield behavior of metal powder assemblages

    NASA Astrophysics Data System (ADS)

    Brown, Stuart; Abou-Chedid, Georges

    1994-03-01

    W E PRESENT EXPERIMENTAL data on the compaction of powder metals using two powder systems with different powder particle morphologies. The data have been collected using biaxial and triaxial compaction systems that load powders radially in deformation space. Our results indicate that several current models proposed for powder metal compaction do not represent actual constitutive behavior. Additionally, the powders tested demonstrate a strong dependence on powder morphology and a possible associated dependence on interparticle cohesion. This dependence on cohesion may necessitate the use of an additional state variable beyond those of relative density and particle hardening ordinarily used to represent powder yield behavior.

  5. Powder metal technologies and applications

    SciTech Connect

    Eisen, W.B.; Ferguson, B.L.; German, R.M.; Iacocca, R.; Lee, P.W.; Madan, D.; Moyer, K.; Sanderow, H.; Trudel, Y.

    1998-12-31

    This volume is: (1) a completely updated and expanded edition in all areas of powder production, sampling, characterization, shaping, consolidation, sintering, quality control, machining, heat treating, and P/M applications; (2) single source for practical engineering information on sintering practices, tool design, P/M metallography, dimensional control, part design, powders, binders, lubricants, and the processing, properties, and performance of P/M materials in different production technologies and applications; (3) comprehensive coverage of P/M technologies and applications including warm compaction, injection molding, rapid prototyping, thermal spray forming, reactive sintering, and P/M gears, bearings, high-performance parts, composites, machine parts, electric contacts, magnetic materials, metallic foams, hardfacing powders, automotive parts, and more.

  6. Polymer quenched prealloyed metal powder

    DOEpatents

    Hajaligol, Mohammad R.; Fleischhauer, Grier; German, Randall M.

    2001-01-01

    A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3 % Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

  7. Preparation of metal diboride powders

    DOEpatents

    Brynestad, J.; Bamberger, C.E.

    Finely-divided titanium diboride or zirconium diboride powders are formed by reacting gaseous boron trichloride with a material selected from the group of consisting of titanium powder, zirconium powder, titanium dichloride powder, titanium trichloride powder, and gaseous titanium trichloride.

  8. Hyperfine frequency shift and Zeeman relaxation in alkali-metal-vapor cells with antirelaxation alkene coating

    NASA Astrophysics Data System (ADS)

    Corsini, Eric P.; Karaulanov, Todor; Balabas, Mikhail; Budker, Dmitry

    2013-02-01

    An alkene-based antirelaxation coating for alkali-metal vapor cells exhibiting Zeeman relaxation times up to 77 s was recently identified by Balabas The long relaxation times, two orders of magnitude longer than in paraffin- (alkane-) coated cells, motivate revisiting the question of what the mechanism is underlying wall-collision-induced relaxation and renew interest in applications of alkali-metal vapor cells to secondary frequency standards. We measure the width and frequency shift of the ground-state hyperfine mF=0→mF'=0 transition (clock resonance) in vapor cells with 85Rb and 87Rb atoms, with an alkene antirelaxation coating. We find that the frequency shift is slightly larger than for paraffin-coated cells and that the Zeeman linewidth scales linearly with the hyperfine frequency shift.

  9. Plated Metal Powders for Electrode Pastes

    NASA Technical Reports Server (NTRS)

    Bickler, D. B.

    1984-01-01

    Metal grains to be sintered precoated with frit metal. Coated metal powders used to make ink-like electrode pastes for printing and sintering electrode-fabrication process. Grains of base metal coated with lowmelting-point--, lead or tin-- by electroless deposition.

  10. Plated Metal Powders for Electrode Pastes

    NASA Technical Reports Server (NTRS)

    Bickler, D. B.

    1984-01-01

    Metal grains to be sintered precoated with frit metal. Coated metal powders used to make ink-like electrode pastes for printing and sintering electrode-fabrication process. Grains of base metal coated with lowmelting-point--, lead or tin-- by electroless deposition.

  11. Metal powder absorptivity: Modeling and experiment

    SciTech Connect

    Boley, C. D.; Mitchell, S. C.; Rubenchik, A. M.; Wu, S. S. Q.

    2016-08-10

    Here, we present results of numerical modeling and direct calorimetric measurements of the powder absorptivity for a number of metals. The modeling results generally correlate well with experiment. We show that the powder absorptivity is determined, to a great extent, by the absorptivity of a flat surface at normal incidence. Our results allow the prediction of the powder absorptivity from normal flat-surface absorptivity measurements.

  12. Metal powder absorptivity: Modeling and experiment

    SciTech Connect

    Boley, C. D.; Mitchell, S. C.; Rubenchik, A. M.; Wu, S. S. Q.

    2016-08-10

    Here, we present results of numerical modeling and direct calorimetric measurements of the powder absorptivity for a number of metals. The modeling results generally correlate well with experiment. We show that the powder absorptivity is determined, to a great extent, by the absorptivity of a flat surface at normal incidence. Our results allow the prediction of the powder absorptivity from normal flat-surface absorptivity measurements.

  13. Method for preparing metal powder, device for preparing metal powder, method for processing spent nuclear fuel

    DOEpatents

    Park, Jong-Hee [Clarendon Hills, IL

    2011-11-29

    A method for producing metal powder is provided the comprising supplying a molten bath containing a reducing agent, contacting a metal oxide with the molten bath for a time and at a temperature sufficient to reduce the metal in the metal oxide to elemental metal and produce free oxygen; and isolating the elemental metal from the molten bath.

  14. Metal powder reactions in ball milling

    NASA Technical Reports Server (NTRS)

    Arias, A.

    1976-01-01

    On milling chromium powder in three metal chlorides and either chromium or nickel powders in ten organic liquids representative of nine different functional groups, the powders always reacted with the liquids and became contaminated with elements from them. The milled powders had specific surface areas ranging from 0.14 to 37 sq m/g, and the total contamination with elements from the milling liquid ranged from 0.01 to 56 wt%. In most milling runs, compounds resulting from substitution, addition, or elimination reactions formed in or from the milling liquid, and in most runs with organic liquids H2, CH4, and CO2 were generated.

  15. Metal ion oxidation state assignment based on coordinating ligand hyperfine interaction.

    PubMed

    Oyala, Paul H; Stich, Troy A; Britt, R David

    2015-04-01

    In exchange-coupled mixed-valence spin systems, the magnitude and sign of the effective ligand hyperfine interaction (HFI) can be useful in determining the formal oxidation state of the coordinating metal ion, as well as provide information about the coordination geometry. This is due to the fact that the observed ligand HFI is a function of the projection factor (Clebsch-Gordon coefficient) that maps the site spin value S i of the local paramagnetic center onto the total spin of the exchange-coupled system, S T. Recently, this relationship has been successfully exploited in identifying the oxidation state of the Mn ion coordinated by the sole nitrogenous ligand to the oxygen-evolving complex in certain states of photosystem II. The origin and evolution of these efforts is described.

  16. Relativistic many-body investigation of hyperfine interactions in excited S states of alkali metals: Francium and potassium

    SciTech Connect

    Owusu, A.; Dougherty, R.W.; Gowri, G.; Das, T.P.; Andriessen, J.

    1997-07-01

    To enhance the current understanding of mechanisms contributing to magnetic hyperfine interactions in excited states of atomic systems, in particular, alkali-metal atom systems, the hyperfine fields in the excited 5{sup 2}S{sub 1/2}{endash}8{sup 2}S{sub 1/2} states of potassium and 8{sup 2}S{sub 1/2}{endash}12{sup 2}S{sub 1/2} states of francium atoms have been studied using the relativistic linked-cluster many-body perturbation procedure. The net theoretical values of the hyperfine fields for the excited states studied are in excellent agreement with available experimental data for both atoms. There is a significant decrease in importance of the correlation contribution in going from the ground state to the excited states, the correlation contributions as ratios of the direct contribution decreasing rapidly as one moves to the higher excited states. However, the contribution from the exchange core polarization (ECP) effect is nearly a constant fraction of the direct effect for all the excited states considered. Physical explanations are offered for the observed trends in the contributions from the different mechanisms. A comparison is made of the different contributing effects to the hyperfine fields in potassium and francium to those in the related system, rubidium, studied earlier. Extrapolating from our results to the highly excited states of alkali-metal atoms, referred to as the Rydberg states, it is concluded that in addition to the direct contribution from the excited valence electron to the hyperfine fields, a significant contribution is expected from the ECP effect arising from the influence of exchange interactions between electrons in the valence and core states. {copyright} {ital 1997} {ital The American Physical Society}

  17. Progress in Titanium Metal Powder Injection Molding

    PubMed Central

    German, Randall M.

    2013-01-01

    Metal powder injection molding is a shaping technology that has achieved solid scientific underpinnings. It is from this science base that recent progress has occurred in titanium powder injection molding. Much of the progress awaited development of the required particles with specific characteristics of particle size, particle shape, and purity. The production of titanium components by injection molding is stabilized by a good understanding of how each process variable impacts density and impurity level. As summarized here, recent research has isolated the four critical success factors in titanium metal powder injection molding (Ti-MIM) that must be simultaneously satisfied—density, purity, alloying, and microstructure. The critical role of density and impurities, and the inability to remove impurities with sintering, compels attention to starting Ti-MIM with high quality alloy powders. This article addresses the four critical success factors to rationalize Ti-MIM processing conditions to the requirements for demanding applications in aerospace and medical fields. Based on extensive research, a baseline process is identified and reported here with attention to linking mechanical properties to the four critical success factors. PMID:28811458

  18. From powders to bulk metallic glass composites.

    PubMed

    Krämer, Lisa; Champion, Yannick; Pippan, Reinhard

    2017-07-27

    One way to adjust the properties of materials is by changing its microstructure. This concept is not easily applicable on bulk metallic glasses (BMGs), because they do not consist of grains or different phases and so their microstructure is very homogeneous. One obvious way to integrate inhomogeneities is to produce bulk metallic glass composites (BMGCs). Here we show how to generate BMGCs via high-pressure torsion (HPT) starting from powders (amorphous Zr-MG and crystalline Cu). Using this approach, the composition can be varied and by changing the applied shear strains, the refinement of the microstructure is adjustable. This process permits to produce amorphous/crystalline composites where the scale of the phases can be varied from the micro- to the nanometer regime. Even mixing of the two phases and the generation of new metallic glasses can be achieved. The refinement of microstructure increases the hardness and a hardness higher than the initial BMG can be obtained.

  19. Rotation of hyperfine fields at the V site in the multiband metal K2V8O6

    NASA Astrophysics Data System (ADS)

    Shimizu, Yasuhiro; Okai, Katsunori; Itoh, Masayuki; Isobe, Masahiro; Yamaura, Jun-ichi; Ueda, Yutaka

    2010-01-01

    51V nuclear magnetic resonance measurements are conducted on a single crystal of the mixed valence compound K2V8016 with 1.25 3d electrons per one V site. We determine the 51V Knight shift tensor, 51K, in the metallic state. 51K has the small anisotropy despite the conduction electrons in the anisotropic 3d orbitals. The principal axis of 51K rotates continuously on cooling temperature in the metallic state without breaking the lattice symmetry, I4/m. Taking into account the isotropic spin susceptibility, the thermal variation is attributed to a change in the hyperfine field tensor reflecting the 3d orbital shape.

  20. Joining of parts via magnetic heating of metal aluminum powders

    SciTech Connect

    Baker, Ian

    2013-05-21

    A method of joining at least two parts includes steps of dispersing a joining material comprising a multi-phase magnetic metal-aluminum powder at an interface between the at least two parts to be joined and applying an alternating magnetic field (AMF). The AMF has a magnetic field strength and frequency suitable for inducing magnetic hysteresis losses in the metal-aluminum powder and is applied for a period that raises temperature of the metal-aluminum powder to an exothermic transformation temperature. At the exothermic transformation temperature, the metal-aluminum powder melts and resolidifies as a metal aluminide solid having a non-magnetic configuration.

  1. First principles density functional calculation of magnetic moment and hyperfine fields of dilute transition metal impurities in Gd host

    NASA Astrophysics Data System (ADS)

    Mohanta, S. K.; Mishra, S. N.; Srivastava, S. K.

    2014-04-01

    We present first principles calculations of electronic structure and magnetic properties of dilute transition metal (3d, 4d and 5d) impurities in a Gd host. The calculations have been performed within the density functional theory using the full potential linearized augmented plane wave technique and the GGA+U method. The spin and orbital contributions to the magnetic moment and the hyperfine fields have been computed. We find large magnetic moments for 3d (Ti-Co), 4d (Nb-Ru) and 5d (Ta-Os) impurities with magnitudes significantly different from the values estimated from earlier mean field calculation [J. Magn. Magn. Mater. 320 (2008) e446-e449]. The exchange interaction between the impurity and host Gd moments is found to be positive for early 3d elements (Sc-V) while in all other cases an anti-ferromagnetic coupling is observed. The trends for the magnetic moment and hyperfine field of d-impurities in Gd show qualitative difference with respect to their behavior in Fe, Co and Ni. The calculated total hyperfine field, in most cases, shows excellent agreement with the experimental results. A detailed analysis of the Fermi contact hyperfine field has been made, revealing striking differences for impurities having less or more than half filled d-shell. The impurity induced perturbations in host moments and the change in the global magnetization of the unit cell have also been computed. The variation within each of the d-series is found to correlate with the d-d hybridization strength between the impurity and host atoms.

  2. PREPARATION OF METAL POWDER COMPACTS PRIOR TO PRESSING

    DOEpatents

    Mansfield, H.

    1958-08-26

    A method of fabricating uranium by a powder metallurgical technique is described. It consists in introducing powdered uranium hydride into a receptacle shaped to coincide with the coatour of the die cavity and heating the hydride so that it decomposes to uranium metal. The metal particles cohere in the shapw of the receptacle and thereafter the prefurmed metal powder is pressed and sintered to obtain a dense compact.

  3. Calculation of laser absorption by metal powders in additive manufacturing.

    PubMed

    Boley, C D; Khairallah, S A; Rubenchik, A M

    2015-03-20

    We have calculated the absorption of laser light by a powder of metal spheres, typical of the powder employed in laser powder-bed fusion additive manufacturing. Using ray-trace simulations, we show that the absorption is significantly larger than its value for normal incidence on a flat surface, due to multiple scattering. We investigate the dependence of absorption on powder content (material, size distribution, and geometry) and on beam size.

  4. Generation of metal, metal oxide and metal-metal oxide powders by spray pyrolysis for microelectronic thick film applications

    NASA Astrophysics Data System (ADS)

    Majumdar, Diptarka

    Materials in powdered form have wide ranging applications. In thick film microelectronics, powders are dispersed in organic liquids to form pastes which are screen printed on ceramic substrates and fired to fabricate active and passive electronic devices. The functional phase is a metal powder in conductive pastes, a metal or conductive metal oxide powder in resistive pastes and a ceramic powder in dielectric pastes. Particulate additives such as glasses and metal oxides in pastes promote adhesion of conductor lines to the substrate, minimize shrinkage mismatch during cofiring of conductors and dielectrics and facilitate densification of the functional phase during firing. This dissertation focuses on the generation of metal, metal oxide and metal-metal oxide powders by spray pyrolysis for microelectronic applications. The important results of this work are outlined below. (1) This work has demonstrated the ability to synthesize phase-pure, micron-sized, spherical, unagglomerated metal (gold) and metal oxide (copper (I) oxide) particles by spray pyrolysis. (2) It has extended the versatility of spray pyrolysis as a powdermaking technique to include the synthesis of metal-metal oxide composite particles. Such particles have been generated for both wetting (silver-copper (II) oxide) and poorly wetting (silver-silica) metal-metal oxide pairs. (3) The sintering of thick films of the metal-metal oxide particles has indicated the possibility of retarding the sintering kinetics of silver by using composite particles of the metal with relatively refractory metal oxides.

  5. Printed circuit board metal powder filters for low electron temperatures.

    PubMed

    Mueller, Filipp; Schouten, Raymond N; Brauns, Matthias; Gang, Tian; Lim, Wee Han; Lai, Nai Shyan; Dzurak, Andrew S; van der Wiel, Wilfred G; Zwanenburg, Floris A

    2013-04-01

    We report the characterisation of printed circuit boards (PCB) metal powder filters and their influence on the effective electron temperature which is as low as 22 mK for a quantum dot in a silicon MOSFET structure in a dilution refrigerator. We investigate the attenuation behaviour (10 MHz-20 GHz) of filter made of four metal powders with a grain size below 50 μm. The room-temperature attenuation of a stainless steel powder filter is more than 80 dB at frequencies above 1.5 GHz. In all metal powder filters, the attenuation increases with temperature. Compared to classical powder filters, the design presented here is much less laborious to fabricate and specifically the copper powder PCB-filters deliver an equal or even better performance than their classical counterparts.

  6. Hyperfine interactions in nanocrystallized NANOPERM-type metallic glass containing Mo

    NASA Astrophysics Data System (ADS)

    Cesnek, M.; Kubániová, D.; Kohout, J.; Křišťan, P.; Štěpánková, H.; Závěta, K.; Lančok, A.; Štefánik, M.; Miglierini, M.

    2016-12-01

    NANOPERM-type alloy with chemical composition Fe76Mo8CuB15 was studied by combination of 57Fe Mössbauer spectroscopy and 57Fe(10B, 11B) nuclear magnetic resonance in order to determine distribution of hyperfine magnetic fields and evolution of relative concentration of Fe-containing crystalline phases within the surface layer and the volume of the nanocrystallized ribbons with annealing temperature. Differential scanning calorimetry revealed two crystallization stages at T x1 ˜ 510 ∘C and T x2 ˜ 640 ∘C, connected to precipitation of α-Fe and Fe(Mo,B) nanocrystals, respectively. The amorphous and partially crystalline state was obtained by annealing at several temperatures in the range 510-650 ∘C. The combination of conversion electron (CEMS) and transmission Mössbauer spectrometry (TMS) showed that annealing induces crystallization starting from both surfaces of the ribbons. For the as-quenched sample, scanning electron microscopy (SEM) and CEMS revealed significant differences in the "air" and "wheel" sides of the ribbons, crystallites were preferentially formed at the latter. While SEM micrographs of annealed samples showed various mean diameters of the crystals at opposite sides of the ribbons, the amounts of crystalline volume derived from the CEMS spectra approximately equaled. Mössbauer spectra of annealed samples contained narrow sextet ascribed to crystalline α-Fe phase, three sextets with distribution of hyperfine field assigned to the interface regions of the nanocrystals and the contribution of the amorphous phases. In-field TMS performed at 4.2 K with magnetic moments aligned by external magnetic field enabled to properly determine in particular the contribution of the amorphous phases in the samples. Resulting distributions of the hyperfine fields were compared with 57Fe(10B, 11B) nuclear magnetic resonance (NMR) spectra.

  7. The effect of oxygen vacancies on the hyperfine properties of metal-doped SnO2

    NASA Astrophysics Data System (ADS)

    Aragón, F. H.; Villegas-Lelovsky, L.; Martins, J. B. L.; Coaquira, J. A. H.; Cohen, R.; Nagamine, L. C. C. M.; Morais, P. C.

    2017-03-01

    We have performed a Mössbauer investigation of oxygen-vacancy formation on a doped substitutional solution of Sn1‑y M y O2 (M  =  Al, Fe, Ce and Er) nanoparticles. Experimental results were assessed from Mössbauer spectroscopy data, which suggest the rise of the oxygen-vacancy population while increasing the content of dopant ions (M). Likewise, we have analyzed the dependence of the structural, electronic and hyperfine properties on the oxygen-vacancy concentration through first-principles calculations of the SnO2‑x (where x varies from 0 to 0.25) system. The results obtained from the isomer shift and quadrupole splitting indicate a significant dependence of the hyperfine properties on the number of oxygen vacancies. Moreover, after structural optimization of the Sn16O32-Vo supercell (where Vo is the number of oxygen vacancies) we found an increase of the unit-cell volume with the increase of Vo, while the bulk modulus showed a linear decrease with Vo. Indeed, our results corroborate the experimental findings for pure and transition-metal-doped SnO2 systems for which the presence of the oxygen vacancy plays a key role.

  8. Substantiating powder metal life methodologies for engines

    NASA Astrophysics Data System (ADS)

    Domas, P. A.

    1993-04-01

    The application of powder metal (PM) superalloys in aircraft turbine engine rotating components is prompted by performance driven high strength and creep resistance requirements. Fine grain, precipitation strengthened nickel-base alloys such as IN100, Rene'95, and Rene'88DT meet these requirements up to operating temperatures in the 1200-1300F (649-704C) range. In addition to burst and deformation limits, design constraints include durability (fatigue) and damage tolerance (crack growth resistance) capability to insure reliability and safety. Fatigue life for these alloys can be influenced by inhomogeneities (inclusions) intrinsic to the microstructure as the result of processing, and by perturbations of the surface integrity during component manufacture and subsequent usage. Understanding of PM fatigue behavior and substantiation of life assessment methodology must appropriately recognize these potential influences. New testing, modeling, and analysis schemes are necessitated in engineering development programs addressing generation and validation of life prediction techniques for these materials. This paper outlines one approach to substantiating PM fatigue life prediction that attempts to recognize homogeneous fatigue initiation by incorporating probabilistic models and development testing methods that address material volume and component feature effects. Complications and limitations being addressed in ongoing work are discussed.

  9. Method and apparatus for the production of metal oxide powder

    DOEpatents

    Harris, Michael T.; Scott, Timothy C.; Byers, Charles H.

    1992-01-01

    The present invention provides a method for preparing metal oxide powder. A first solution, which is substantially organic, is prepared. A second solution, which is an aqueous solution substantially immiscible in the first solution, is prepared and delivered as drops to the first solution. The drops of the second solution are atomized by a pulsed electric field forming micro-drops of the second solution. Reagents in the first solution diffuse into and react with reactants in the micro-drops of the second solution forming metal hydroxide or oxalate particles. The metal hydroxide or metal oxalate particles are then recovered and dried to produce the metal oxide powder. An apparatus for preparing a metal oxide powder is also disclosed.

  10. Method and apparatus for the production of metal oxide powder

    DOEpatents

    Harris, Michael T.; Scott, Timothy C.; Byers, Charles H.

    1993-01-01

    The present invention provides a method for preparing metal oxide powder. A first solution, which is substantially organic, is prepared. A second solution, which is an aqueous solution substantially immiscible in the first solution, is prepared and delivered as drops to the first solution. The drops of the second solution are atomized by a pulsed electric field forming micro-drops of the second solution. Reagents in the first solution diffuse into and react with reactants in the micro-drops of the second solution forming metal hydroxide or oxalate particles. The metal hydroxide or metal oxalate particles are then recovered and dried to produce the metal oxide powder. An apparatus for preparing a metal oxide powder is also disclosed.

  11. Method and apparatus for the production of metal oxide powder

    DOEpatents

    Harris, M.T.; Scott, T.C.; Byers, C.H.

    1992-06-16

    The present invention provides a method for preparing metal oxide powder. A first solution, which is substantially organic, is prepared. A second solution, which is an aqueous solution substantially immiscible in the first solution, is prepared and delivered as drops to the first solution. The drops of the second solution are atomized by a pulsed electric field forming micro-drops of the second solution. Reagents in the first solution diffuse into and react with reactants in the micro-drops of the second solution forming metal hydroxide or oxalate particles. The metal hydroxide or metal oxalate particles are then recovered and dried to produce the metal oxide powder. An apparatus for preparing a metal oxide powder is also disclosed. 2 figs.

  12. Metal powder production by gas atomization

    NASA Technical Reports Server (NTRS)

    Ting, E. Y.; Grant, N. J.

    1986-01-01

    The confined liquid, gas-atomization process was investigated. Results from a two-dimensional water model showed the importance of atomization pressure, as well as delivery tube and atomizer design. The atomization process at the tip of the delivery tube was photographed. Results from the atomization of a modified 7075 aluminum alloy yielded up to 60 wt pct. powders that were finer than 45 microns in diameter. Two different atomizer designs were evaluated. The amount of fine powders produced was correlated to a calculated gas-power term. An optimal gas-power value existed for maximized fine powder production. Atomization at gas-power greater than or less than this optimal value produced coarser powders.

  13. 40 CFR 471.100 - Applicability; description of the powder metals subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... powder metals subcategory. 471.100 Section 471.100 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS NONFERROUS METALS FORMING AND METAL POWDERS POINT SOURCE CATEGORY Metals Powders Subcategory § 471.100 Applicability; description of the powder...

  14. 40 CFR 471.100 - Applicability; description of the powder metals subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... powder metals subcategory. 471.100 Section 471.100 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS NONFERROUS METALS FORMING AND METAL POWDERS POINT SOURCE CATEGORY Metals Powders Subcategory § 471.100 Applicability; description of the powder...

  15. Fluidized reduction of oxides on fine metal powders without sintering

    NASA Technical Reports Server (NTRS)

    Hayashi, T.

    1985-01-01

    In the process of reducing extremely fine metal particles (av. particle size or = 1000 angstroms) covered with an oxide layer, the metal particles are fluidized by a gas flow contg. H, heated, and reduced. The method uniformly and easily reduces surface oxide layers of the extremely fine metal particles without causing sintering. The metal particles are useful for magnetic recording materials, conductive paste, powder metallurgy materials, chem. reagents, and catalysts.

  16. Characterization of Metal Powders Used for Additive Manufacturing.

    PubMed

    Slotwinski, J A; Garboczi, E J; Stutzman, P E; Ferraris, C F; Watson, S S; Peltz, M A

    2014-01-01

    Additive manufacturing (AM) techniques can produce complex, high-value metal parts, with potential applications as critical parts, such as those found in aerospace components. The production of AM parts with consistent and predictable properties requires input materials (e.g., metal powders) with known and repeatable characteristics, which in turn requires standardized measurement methods for powder properties. First, based on our previous work, we assess the applicability of current standardized methods for powder characterization for metal AM powders. Then we present the results of systematic studies carried out on two different powder materials used for additive manufacturing: stainless steel and cobalt-chrome. The characterization of these powders is important in NIST efforts to develop appropriate measurements and standards for additive materials and to document the property of powders used in a NIST-led additive manufacturing material round robin. An extensive array of characterization techniques was applied to these two powders, in both virgin and recycled states. The physical techniques included laser diffraction particle size analysis, X-ray computed tomography for size and shape analysis, and optical and scanning electron microscopy. Techniques sensitive to structure and chemistry, including X-ray diffraction, energy dispersive analytical X-ray analysis using the X-rays generated during scanning electron microscopy, and X-Ray photoelectron spectroscopy were also employed. The results of these analyses show how virgin powder changes after being exposed to and recycled from one or more Direct Metal Laser Sintering (DMLS) additive manufacturing build cycles. In addition, these findings can give insight into the actual additive manufacturing process.

  17. Characterization of Metal Powders Used for Additive Manufacturing

    PubMed Central

    Slotwinski, JA; Garboczi, EJ; Stutzman, PE; Ferraris, CF; Watson, SS; Peltz, MA

    2014-01-01

    Additive manufacturing (AM) techniques1 can produce complex, high-value metal parts, with potential applications as critical parts, such as those found in aerospace components. The production of AM parts with consistent and predictable properties requires input materials (e.g., metal powders) with known and repeatable characteristics, which in turn requires standardized measurement methods for powder properties. First, based on our previous work, we assess the applicability of current standardized methods for powder characterization for metal AM powders. Then we present the results of systematic studies carried out on two different powder materials used for additive manufacturing: stainless steel and cobalt-chrome. The characterization of these powders is important in NIST efforts to develop appropriate measurements and standards for additive materials and to document the property of powders used in a NIST-led additive manufacturing material round robin. An extensive array of characterization techniques was applied to these two powders, in both virgin and recycled states. The physical techniques included laser diffraction particle size analysis, X-ray computed tomography for size and shape analysis, and optical and scanning electron microscopy. Techniques sensitive to structure and chemistry, including X-ray diffraction, energy dispersive analytical X-ray analysis using the X-rays generated during scanning electron microscopy, and X-Ray photoelectron spectroscopy were also employed. The results of these analyses show how virgin powder changes after being exposed to and recycled from one or more Direct Metal Laser Sintering (DMLS) additive manufacturing build cycles. In addition, these findings can give insight into the actual additive manufacturing process. PMID:26601040

  18. Advanced NDE Technologies for Powder Metal Components

    SciTech Connect

    Martin, P; Haskins, J; Thomas, G; Dolan, K

    2003-05-01

    Nondestructive evaluation encompasses numerous technologies that assess materials and determine important properties. This paper demonstrates the applicability of several of these technologies to the field of powder metallurgy. The usual application of nondestructive evaluation is to detect and quantify defects in fully sintered product. But probably its most appealing role is to sense problems earlier in the manufacturing process to avoid making defects at all. Also nondestructive evaluation can be incorporated into the manufacturing processes to monitor important parameters and control the processes to produce defect free product. Nondestructive evaluation can characterize powders, evaluate components in the green state, monitor the sintering process, and inspect the final component.

  19. Calculation of the magnetic hyperfine structure constant of alkali metals and alkaline-earth-metal ions using the relativistic coupled-cluster method

    NASA Astrophysics Data System (ADS)

    Sasmal, Sudip

    2017-07-01

    The Z -vector method in the relativistic coupled-cluster framework is used to calculate the magnetic hyperfine structure constant (AJ) of alkali metals and singly charged alkaline earth metals in their ground state electronic configuration. The Z -vector results are in very good agreement with the experiment. The AJ values of Li, Na, K, Rb, Cs, Be+, Mg+, Ca+, and Sr+ obtained in the Z -vector method are compared with the extended coupled-cluster results taken from Phys. Rev. A 91, 022512 (2015), 10.1103/PhysRevA.91.022512. The same basis and cutoff are used for the comparison purpose. The comparison shows that the Z -vector method with the single and double approximation can produce a more precise wave function in the nuclear region than the ECC method.

  20. Denudation of metal powder layers in laser powder bed fusion processes

    DOE PAGES

    Matthews, Manyalibo J.; Guss, Gabe; Khairallah, Saad A.; ...

    2016-05-20

    Understanding laser interaction with metal powder beds is critical in predicting optimum processing regimes in laser powder bed fusion additive manufacturing of metals. In this work, we study the denudation of metal powders that is observed near the laser scan path as a function of laser parameters and ambient gas pressure. We show that the observed depletion of metal powder particles in the zone immediately surrounding the solidified track is due to a competition between outward metal vapor flux directed away from the laser spot and entrainment of powder particles in a shear flow of gas driven by a metalmore » vapor jet at the melt track. Between atmospheric pressure and ~10 Torr of Ar gas, the denuded zone width increases with decreasing ambient gas pressure and is dominated by entrainment from inward gas flow. The denuded zone then decreases from 10 to 2.2 Torr reaching a minimum before increasing again from 2.2 to 0.5 Torr where metal vapor flux and expansion from the melt pool dominates. In addition, the dynamics of the denudation process were captured using high-speed imaging, revealing that the particle movement is a complex interplay among melt pool geometry, metal vapor flow, and ambient gas pressure. The experimental results are rationalized through finite element simulations of the melt track formation and resulting vapor flow patterns. The results presented here represent new insights to denudation and melt track formation that can be important for the prediction and minimization of void defects and surface roughness in additively manufactured metal components.« less

  1. Fundamental Models of Selective Laser Sintering of Metal Powders

    DTIC Science & Technology

    2006-12-01

    melting points is investigated analytically [J6, C I]. Shrinkage induced by melting is taken into account in the physical model. The effects of porosity...indicate that the thicknesses of the loose metal powder layer, the moving heat source intensity and the scanning velocity have significant effects on the...laser beam is much smaller than the sizes of the powder bed in the horizontal direction, and the effect of laser heating is limited in the region very

  2. Atomizing apparatus for making polymer and metal powders and whiskers

    DOEpatents

    Otaigbe, Joshua U.; McAvoy, Jon M.; Anderson, Iver E.; Ting, Jason; Mi, Jia; Terpstra, Robert

    2003-03-18

    Method for making polymer particulates, such as spherical powder and whiskers, by melting a polymer material under conditions to avoid thermal degradation of the polymer material, atomizing the melt using gas jet means in a manner to form atomized droplets, and cooling the droplets to form polymer particulates, which are collected for further processing. Atomization parameters can be controlled to produce polymer particulates with controlled particle shape, particle size, and particle size distribution. For example, atomization parameters can be controlled to produce spherical polymer powders, polymer whiskers, and combinations of spherical powders and whiskers. Atomizing apparatus also is provided for atoomizing polymer and metallic materials.

  3. Method for Making Metal Coated Powders

    DTIC Science & Technology

    2001-01-19

    of cobalt, copper , nickel, lead and silver using the polyol method . These particles consisted of single elements. Depending upon the... Copper -coated alumina powders formed by this method . Two grams of alpha-form alumina, -325 mesh, as added to a stirred solution of ethylene glycol...can be controlled by the selection of the proper synthesis conditions to favor either nucleation or growth, respectively. Figure 1 is a LaMer

  4. Metal matrix composites from dynamic consolidation of powder mixtures

    SciTech Connect

    Korth, G.E.; Williamson, R.L.; Rabin, B.H.

    1989-01-01

    Mixtures of 2124 aluminum alloy and silicon carbide powders were dynamically consolidated using explosives. This process results in a fully dense product and has the potential of becoming an economical method of producing metal matrix composites, especially where undesirable reactions would normally occur between the metal and ceramic reinforcement. With the correct processing parameters, the aluminum powder plastically deforms to form a continuous matrix with minimum interaction with SiC. Microstructure and mechanical properties of the composite are presented. Numerical simulations were performed to better understand the consolidation process and determine test parameters difficult to obtain by experimentation. 7 refs., 3 figs., 2 tabs.

  5. Spectrum, radial wave functions, and hyperfine splittings of the Rydberg states in heavy alkali-metal atoms

    NASA Astrophysics Data System (ADS)

    Sanayei, Ali; Schopohl, Nils

    2016-07-01

    We present numerically accurate calculations of the bound-state spectrum of the highly excited valence electron in the heavy alkali-metal atoms solving the radial Schrödinger eigenvalue problem with a modern spectral collocation method that applies also for a large principal quantum number n ≫1 . As an effective single-particle potential we favor the reputable potential of Marinescu et al. [Phys. Rev. A 49, 982 (1994)], 10.1103/PhysRevA.49.982. Recent quasiclassical calculations of the quantum defect of the valence electron agree for orbital angular momentum l =0 ,1 ,2 ,... overall remarkably well with the results of the numerical calculations, but for the Rydberg states of rubidium and also cesium with l =3 this agreement is less fair. The reason for this anomaly is that in rubidium and cesium the potential acquires for l =3 deep inside the ionic core a second classical region, thus invalidating a standard Wentzel-Kramers-Brillouin (WKB) calculation with two widely spaced turning points. Comparing then our numerical solutions of the radial Schrödinger eigenvalue problem with the uniform analytic WKB approximation of Langer constructed around the remote turning point rn,j ,l (" close=")n -δ0)">+ we observe everywhere a remarkable agreement, apart from a tiny region around the inner turning point rn,j ,l (-). For s states the centrifugal barrier is absent and no inner turning point exists: rn,j ,0 (-)=0 . With the help of an ansatz proposed by Fock we obtain for the s states a second uniform analytic approximation to the radial wave function complementary to the WKB approximation of Langer, which is exact for r →0+ . From the patching condition, that is, for l =0 the Langer and Fock solutions should agree in the intermediate region 0

  6. Nuclear magnetic and quadrupole resonance in metallic powders in the presence of strong quadrupole interaction: Rhenium metal

    SciTech Connect

    Dimitropoulos, C.; Maglione, M.; Borsa, F.

    1988-03-01

    The nuclear-magnetic-resonance and nuclear-quadrupole-resonance (NQR-NMR) spectra of /sup 187/Re and /sup 185/Re in a powder of rhenium metal were measured in the temperature range 5--10 K both in zero field and with an external magnetic field. The zero-field NQR spectrum is severely broadened by a nonuniform distribution of quadrupole interactions. The average quadrupole coupling frequencies measured at 5 K are, for the two isotopes, ..nu../sub Q/ = 39 +- 0.2 MHz (/sup 187/Re) and ..nu../sub Q/ = 40.8 +- 0.3 MHz (/sup 185/Re). The spectra obtained in the presence of an external magnetic field can be interpreted satisfactorily in terms of transitions among the eigenstates of the full Hamiltonian (Zeeman plus quadrupolar). Measurements of relaxation rates yield T/sub 1/T = 0.03 sK, indicating a relaxation mechanism driven by the hyperfine interaction with the conduction electrons. The feasibility of NQR-NMR studies in small metal particles in the presence of strong inhomogeneous quadrupole interactions is assessed

  7. Powder and particulate production of metallic alloys

    NASA Technical Reports Server (NTRS)

    Grant, N. J.

    1982-01-01

    Developments of particulate metallurgy of alloyed materials where the final products is a fully dense body are discussed. Particulates are defined as powders, flakes, foils, silvers, ribbons and strip. Because rapid solidification is an important factor in particulate metallurgy, all of the particulates must have at least one dimension which is very fine, sometimes as fine as 10 to 50 microns, but move typically up to several hundred microns, provided that the dimension permits a minimum solidification rate of at least 100 K/s.

  8. Gelled liquid oxygen/metal powder monopropellants

    NASA Technical Reports Server (NTRS)

    Wickman, John H.; James, Eric

    1992-01-01

    Al, Al-80/Mg-20 wt pct, Si, and Fe powders were mixed with LOX and gelled with 2-3 wt pct Cab-o-Sil to viscosities of 100 to 900 cps, at shear rates of up to 300/sec. These monopropellants were burned in a cylinder that was submerged in a liquid nitrogen bath. Ambient pressure data have shown that the monopropellants were extinguished when the flame front reached regions that had been submerged under the liquid nitrogen. Burning occurred in a pulsed fashion, and was most nearly steady in the case of the Al-Mg mixture. No sparking or energetic burning occurred in any of the cases tested.

  9. 40 CFR 471.100 - Applicability; description of the powder metals subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... powder metals subcategory. 471.100 Section 471.100 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) NONFERROUS METALS FORMING AND METAL POWDERS POINT SOURCE CATEGORY Metals Powders Subcategory § 471.100 Applicability; description of...

  10. 40 CFR 471.100 - Applicability; description of the powder metals subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... powder metals subcategory. 471.100 Section 471.100 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) NONFERROUS METALS FORMING AND METAL POWDERS POINT SOURCE CATEGORY Metals Powders Subcategory § 471.100 Applicability; description of...

  11. 40 CFR 471.100 - Applicability; description of the powder metals subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... powder metals subcategory. 471.100 Section 471.100 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) NONFERROUS METALS FORMING AND METAL POWDERS POINT SOURCE CATEGORY Metals Powders Subcategory § 471.100 Applicability; description of...

  12. Titanium Metal Powder Production by the Plasma Quench Process

    SciTech Connect

    R. A. Cordes; A. Donaldson

    2000-09-01

    The goals of this project included the scale-up of the titanium hydride production process to a production rate of 50 kg/hr at a purity level of 99+%. This goal was to be achieved by incrementally increasing the production capability of a series of reactor systems. This methodic approach was designed to allow Idaho Titanium Technologies to systematically address the engineering issues associated with plasma system performance, and powder collection system design and performance. With quality powder available, actual fabrication with the titanium hydride was to be pursued. Finally, with a successful titanium production system in place, the production of titanium aluminide was to be pursued by the simultaneously injection of titanium and aluminum precursors into the reactor system. Some significant accomplishments of the project are: A unique and revolutionary torch/reactor capable of withstanding temperatures up to 5000 C with high thermal efficiency has been operated. The dissociation of titanium tetrachloride into titanium powder and HC1 has been demonstrated, and a one-megawatt reactor potentially capable of producing 100 pounds per hour has been built, but not yet operated at the powder level. The removal of residual subchlorides and adsorbed HC1 and the sintering of powder to form solid bodies have been demonstrated. The production system has been operated at production rates up to 40 pounds per hour. Subsequent to the end of the project, Idaho Titanium Technologies demonstrated that titanium hydride powder can indeed be sintered into solid titanium metal at 1500 C without sintering aids.

  13. Process for preparing fine-grain metal carbide powder

    DOEpatents

    Kennedy, C.R.; Jeffers, F.P.

    Fine-grain metal carbide powder suitable for use in the fabrication of heat resistant products is prepared by coating bituminous pitch on SiO/sub 2/ or Ta/sub 2/O/sub 5/ particles, heating the coated particles to convert the bituminous pitch to coke, and then heating the particles to a higher temperature to convert the particles to a carbide by reaction of said coke therewith.

  14. Rapid prototyping with lasers using metal powder jets

    NASA Astrophysics Data System (ADS)

    Liedl, Gerhard; Schuoecker, D.; Kny, E.

    2003-09-01

    Rapid Prototyping is an important part of modern development sequences, where a variety of solutions is available nowadays, ranging from ultrafast machining via casting technologies, laminated objects manufacturing, also with lasers, to stereolithography and laser sintering. Most of these processes suffer from certain restrictions, either in terms of raw material, geometry or quality of the finished workpiece. In particular, laser sintering leads to structures with a low density that reduces the strength of the part considerably. Since the individual powder particles are only molten at their surface and adhere thus to each other, only in small regions of the surface leaving the majority of the grain mass unmolten and resulting in a faint lattice that must be filled with an additional material to reach the necessary strength. A different solution offers the Blown Powder Process, where a jet of e.g. metal powder is directed towards the surface of the workpiece in the focus of a laser beam, thus melting each metal particle totally and producing practically molten droplets that settle on the momentary surface of the workpiece, thus being welded to the latter. Since all the material delivered to the workpiece is perfectly molten and resolidified, very dense structures with a high strength comparable to the strength of the initial unpowderized material are obtained, as experiments carried out by the authors with differed powderized materials have shown. It has also been demonstrated that the latter process can be used to generate nearly arbitrary 3D geometry. A lot of effort has been invested by the authors to avoid the influence of the direction of the necessary relative motion between laser, powder jet and workpiece and also to reduce the roughness of the surface generated by the actual process. Further experimental investigations will be devoted to the clarification of the range of materials, where the actual process can be applied and to the generation of practical

  15. Mechanical Properties of a Metal Powder-Loaded Polyurethane Foam

    SciTech Connect

    C. L. Neuschwanger; L. L. Whinnery; S. H. Goods

    1999-04-01

    Quasi-static compression tests have been performed on polyurethane foam specimens. The modulus of the foam exhibited a power-law dependence with respect to density of the form: E* {proportional_to} {rho}*{sup n}, where n = 1.7. The modulus data is well described by a simple geometric model (attributed to the work of Gibson and Ashby) for closed-cell foam in which the stiffness of the foam is governed by the flexure of the cell struts and cell walls. The compressive strength of the foam is also found to follow a power-law behavior with respect to foam density. In this instance, Euler buckling is used to rationalize the density dependence. The modulus of the polyurethane foam was modified by addition of a gas atomized, spherical aluminum powder. Additions of 30 and 50 weight percent of the powder significantly increased the foam modulus. However, there were only slight increases in modulus with 5 and 10 weight percent additions of the metal powder. Strength was also slightly increased at high loading fractions of powder. This increase in modulus and strength could be predicted by combining the above geometric model with a well-known model describing the effect on modulus of a rigid dispersoid in a compliant matrix.

  16. The combustion synthesis of iron group metal fine powders

    NASA Astrophysics Data System (ADS)

    Lee, J. H.; Nersisyan, H. H.; Won, C. W.

    2004-01-01

    The new approach has been developed for the synthesis of nickel (Ni), cobalt (Co) and iron (Fe) powders from the appropriate oxides by the solid combustion method. The reduction was made by sodium azide (NaN 3) at the presence of carbon in the argon atmosphere. The variation of combustion temperature and velocity was performed by using alkali metal salt as an inert diluent. The values of combustion parameters were measured and also the temperature distribution in a combustion wave are obtained. The geometric sizes of reactionary zones and the activation energy of the process were estimated. The optimum conditions for single-phase metal powder synthesis were found. Powders fabricated in this way had cubic structure and particles size about 0.5-2.0 μm for Ni, Co and 1-3 μm for Fe. In a number of cases the formation of spherical particles with the average size about 5-15 μm were observed.

  17. Simulation of powder metal fabrication with high pressure gas atomization

    SciTech Connect

    Kuntz, D.W.; Payne, J.L.

    1994-12-31

    A computational/analytical technique has been developed which models the physics of high pressure gas atomization. The technique uses an uncoupled approach, such that the gas flowfield is initially calculated with a commercially-available Navier-Stokes code. The liquid metal droplet breakup, dynamics, and thermodynamics, are then calculated using the pre-computed flowfield by a separate computer program written by the authors. The atomization code models the primary breakup of the liquid metal stream, tracks the droplets resulting from primary breakup through the flowfield until they undergo secondary breakup, and then tracks the subdroplets until they breakup, solidify, or leave the flowfield region of interest. The statistical properties of the metal powder produced are then computed from the characteristics of these droplets. Comparisons between experimental measurements and computations indicate that the Navier-Stokes code is predicting the gas flowfield well, and that the atomization code is properly modeling the physics of the droplet dynamics and breakup.

  18. Selective Laser Melting of Metal Powder Of Steel 3161

    NASA Astrophysics Data System (ADS)

    Smelov, V. G.; Sotov, A. V.; Agapovichev, A. V.; Tomilina, T. M.

    2016-08-01

    In this article the results of experimental study of the structure and mechanical properties of materials obtained by selective laser melting (SLM), metal powder steel 316L was carried out. Before the process of cultivation of samples as the input control, the morphology of the surface of the powder particles was studied and particle size analysis was carried out. Also, 3D X-ray quality control of the grown samples was carried out in order to detect hidden defects, their qualitative and quantitative assessment. To determine the strength characteristics of the samples synthesized by the SLM method, static tensile tests were conducted. To determine the stress X-ray diffraction analysis was carried out in the material samples.

  19. Anomalous oxidative diffusion in titanium pyrotechnic powders [Anomalous oxidative diffusion in metal pyrotechnic powders

    DOE PAGES

    Erikson, William W.; Coker, Eric N.

    2016-11-10

    It has long been observed that oxidation processes in metals tend to follow a parabolic rate law associated with the growth of a surface oxide layer. Here we observe that for certain titanium powders, the expected parabolic law (∝t1/2) is recovered, yet for others, the exponent differs significantly. One explanation for this non-parabolic, anomalous diffusion arises from fractal geometry. Theoretical considerations indicate that the time response of diffusion-limited processes in an object closely follow a power-law in time (tn) with n=(E–D)/2, where E is the object's Euclidean dimension and D is its boundary's Hausdorff dimension. Non-integer, (fractal) values of Dmore » will result in n≠1/2. Finite element simulations of several canonical fractal objects were performed to verify the application of this theory; the results matched the theory well. Two different types of titanium powder were tested in isothermal thermogravimetric tests under dilute oxygen. Time-dependent mass uptake data were fit with power-law forms and the associated exponents were used to determine an equivalent fractal dimension. One Ti powder type has an implied surface dimension of ca. 2.3 to 2.5, suggesting fractal geometry may be operative. Finally, the other has a dimension near 2.0, indicating it behaves like traditional material.« less

  20. Pulsed high energy synthesis of fine metal powders

    NASA Technical Reports Server (NTRS)

    Witherspoon, F. Douglas (Inventor); Massey, Dennis W. (Inventor)

    1999-01-01

    Repetitively pulsed plasma jets generated by a capillary arc discharge at high stagnation pressure (>15,000 psi) and high temperature (>10,000 K) are utilized to produce 0.1-10 .mu.m sized metal powders and decrease cost of production. The plasma jets impact and atomize melt materials to form the fine powders. The melt can originate from a conventional melt stream or from a pulsed arc between two electrodes. Gas streams used in conventional gas atomization are replaced with much higher momentum flux plasma jets. Delivering strong incident shocks aids in primary disintegration of the molten material. A series of short duration, high pressure plasma pulses fragment the molten material. The pulses introduce sharp velocity gradients in the molten material which disintegrates into fine particles. The plasma pulses have peak pressures of approximately one kilobar. The high pressures improve the efficiency of disintegration. High gas flow velocities and pressures are achieved without reduction in gas density. Repetitively pulsed plasma jets will produce powders with lower mean size and narrower size distribution than conventional atomization techniques.

  1. Flow characteristics of metallic powder grains for additive manufacturing

    NASA Astrophysics Data System (ADS)

    Peters, Bernhard; Pozzetti, Gabriele

    2017-06-01

    Directed energy deposition technologies for additive manufacturing such as laser selective melting (SLM) or electron beam melting (EBM) is a fast growing technique mainly due to its flexibility in product design. However, the process is a complex interaction of multi-physics on multiple length scales that are still not entirely understood. A particular challenging task are the flow characteristics of metallic powder ejected as jets from a nozzle and shielded by an inert turbulent gas flow. Therefore, the objective is to describe numerically the complex interaction between turbulent flow and powder grains. In order to include both several physical processes and length scales an Euler-Lagrange technology is applied. Within this framework powder is treated by the Discrete-Element-Method, while gas flow is described by Euler approaches as found in classical Computational Fluid Dynamics (CFD). The described method succeeded in delivering more accuracy and consistency than a standard approach based on the volume averaging technique and therefore, is suited for the solution of problems within an engineering framework.

  2. Green nanochemistry: metal oxide nanoparticles and porous thin films from bare metal powders.

    PubMed

    Redel, Engelbert; Petrov, Srebri; Dag, Omer; Moir, Jonathon; Huai, Chen; Mirtchev, Peter; Ozin, Geoffrey A

    2012-01-09

    A universal, simple, robust, widely applicable and cost-effective aqueous process is described for a controlled oxidative dissolution process of micrometer-sized metal powders to form high-purity aqueous dispersions of colloidally stable 3-8 nm metal oxide nanoparticles. Their utilization for making single and multilayer optically transparent high-surface-area nanoporous films is demonstrated. This facile synthesis is anticipated to find numerous applications in materials science, engineering, and nanomedicine.

  3. Thermochemical Processing of Radioactive Waste Using Powder Metal Fuels

    SciTech Connect

    Ojovan, M. I.; Sobolev, I. A.; Dmitriev, S. A.; Panteleev, V. I.; Karlina, O. K.; Klimov. V. L.

    2003-02-25

    Problematic radioactive wastes were generated during various activities of both industrial facilities and research institutions usually in relative small amounts. These can be spent ion exchange resins, inorganic absorbents, wastes from research nuclear reactors, irradiated graphite, mixed, organic or chlorine-containing radioactive waste, contaminated soils, un-burnable heavily surface-contaminated materials, etc. Conventional treatment methods encounter serious problems concerning processing efficiency of such waste, e.g. complete destruction of organic molecules and avoiding of possible emissions of radionuclides, heavy metals and chemically hazardous species. Some contaminations cannot be removed from surface using common decontamination methods. Conditioning of ash residues obtained after treatment of solid radioactive waste including ashes received from treating problematic wastes also is a complicated task. Moreover due to relative small volume of specific type radioactive waste the development of target treatment procedures and facilities to conduct technological processes and their deployment could be economically unexpedient and ecologically no justified. Thermochemical processing technologies are used for treating and conditioning problematic radioactive wastes. The thermochemical processing uses powdered metal fuels (PMF) that are specifically formulated for the waste composition and react chemically with the waste components. The composition of the PMF is designed in such a way as to minimize the release of hazardous components and radionuclides in the off gas and to confine the contaminants in the ash residue. The thermochemical procedures allow decomposition of organic matter and capturing hazardous radionuclides and chemical species simultaneously. A significant advantage of thermochemical processing is its autonomy. Thermochemical treatment technologies use the energy of exothermic reactions in the mixture of radioactive or hazardous waste with PMF

  4. Thallium hyperfine anomaly

    NASA Astrophysics Data System (ADS)

    Gustavsson, Martin G. H.; Forssén, Christian; Mårtensson Pendrill, Ann Marie

    2000-08-01

    Measurements of the hyperfine structure in the highly charged hydrogen like systems 203Tl80+ and 205Tl80+ are underway at the Super EBIT at LLNL. This work considers the effects of the nuclear magnetization distribution on the hyperfine structure. The difference in energy splitting due to hyperfine structure for 203Tl and 205Tl, respectively, is found to be 0.031 04(1) eV, which corresponds to a transition wavelength difference of 3.640(1) nm.

  5. Powder-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2016-05-03

    A powder-based adsorbent and a related method of manufacture are provided. The powder-based adsorbent includes polymer powder with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the powder-based adsorbent includes irradiating polymer powder, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Powder-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  6. Ultrasonic characterization of microstructure in powder metal alloy

    NASA Technical Reports Server (NTRS)

    Tittmann, B. R.; Ahlberg, L. A.; Fertig, K.

    1986-01-01

    The ultrasonic wave propagation characteristics were measured for IN-100, a powder metallurgy alloy used for aircraft engine components. This material was as a model system for testing the feasibility of characterizing the microstructure of a variety of inhomogeneous media including powder metals, ceramics, castings and components. The data were obtained for a frequency range from about 2 to 20 MHz and were statistically averaged over numerous volume elements of the samples. Micrographical examination provided size and number distributions for grain and pore structure. The results showed that the predominant source for the ultrasonic attenuation and backscatter was a dense (approx. 100/cubic mm) distribution of small micropores (approx. 10 micron radius). Two samples with different micropore densities were studied in detail to test the feasibility of calculating from observed microstructural parameters the frequency dependence of the microstructural backscatter in the regime for which the wavelength is much larger than the size of the individual scattering centers. Excellent agreement was found between predicted and observed values so as to demonstrate the feasibility of solving the forward problem. The results suggest a way towards the nondestructive detection and characterization of anomalous distributions of micropores when conventional ultrasonic imaging is difficult. The findings are potentially significant toward the application of the early detection of porosity during the materials fabrication process and after manufacturing of potential sites for stress induced void coalescence leading to crack initiation and subsequent failure.

  7. Ultrasonic study of the vibrational modes of sintered metal powders

    NASA Astrophysics Data System (ADS)

    Maliepaard, M. C.; Page, J. H.; Harrison, J. P.; Stubbs, R. J.

    1985-11-01

    The propagation of (1-20)-MHz ultrasound in sintered metal powder discs with powder diameter d~1, 10, and 300 μm and occupied volume fractions 0.3>d, the sound propagates with a velocity that agrees well with that expected for continuous medium phonons in a percolation system above threshold. The elasticity exponent τ~3.6+/-0.5 is in agreement with the recent Kantor-Webman limit τ>3.55. By increasing the frequency, it was shown that a band edge exists, at λ~10d, beyond which sound does not propagate. This edge is associated with a transition from propagating to localized modes of the sinter and is analogous with the fracton edge discussed by Derrida, Orbach, and Yu for a percolation system.

  8. Reducing metal alloy powder costs for use in powder bed fusion additive manufacturing: Improving the economics for production

    NASA Astrophysics Data System (ADS)

    Medina, Fransisco

    AM. Alternative powders can be made by blending or re-spheroidizing HDH and CPTi powders. Machine modifications were performed to allow the testing and manufacturing with these low cost alternative powders. A comparison was made between alternative powders and gas atomized powders. Powders were compared in terms of morphology and at the microstructural level. Flowability of different powder blends was also measured. Finally, a comparison of parts fabricated from the multiple powder blends and gas atomized powder was made. It has been demonstrated that powder blending can produce fully dense parts in the Arcam system by utilizing the double melt technique or HIPing the built pars. The double melt technique increased the density of the sample part and modified the microstructure into finer martensitic grains. The HIP process can make a part fully dense regardless of what percentage of HDH powder blending is used. The HIP process yielded the same microstructure, regardless of the grain structure it started with. This research allows for the reduction of costs using titanium powders in the EBM system, but can also be implemented with more costly elements and alloys using other metal AM technologies. This includes niobium, tantalum, and nickel-based superalloys for use in various industries.

  9. Numerical simulation of metallic powder flow in a coaxial nozzle in laser direct metal deposition

    NASA Astrophysics Data System (ADS)

    Zhu, Gangxian; Li, Dichen; Zhang, Anfeng; Tang, Yiping

    2011-02-01

    To investigate the influencing rule of deposited layer's shape on coaxial powder feeding flow field in the metal forming process, gas-solid two-phase flow theory is used to analyze effect of deposited layers on powder concentration distribution and variation of focus distance from nozzle outlet to convergence point (the center of the convergent zone). Different height and width parameters of deposited layers were chosen to calculate the powder concentration distribution, consequently, and also their effect on additive height of single-trace cladding layer was studied by experimental investigations. The numerical results are in good agreement with experimental observations. The results indicated that additive height of cladding layer was non-uniform under uneven wall thickness of parts fabrication condition. Consequently, the surface of deposited layers with uneven thickness is not smooth, and hence affects surface forming quality.

  10. Inhalation carcinogenicity study with nickel metal powder in Wistar rats

    SciTech Connect

    Oller, Adriana R. Kirkpatrick, Daniel T.; Radovsky, Ann; Bates, Hudson K.

    2008-12-01

    Epidemiological studies of nickel refinery workers have demonstrated an association between increased respiratory cancer risk and exposure to certain nickel compounds (later confirmed in animal studies). However, the lack of an association found in epidemiological analyses for nickel metal remained unconfirmed for lack of robust animal inhalation studies. In the present study, Wistar rats were exposed by whole-body inhalation to 0, 0.1, 0.4, and 1.0 mg Ni/m{sup 3} nickel metal powder (MMAD = 1.8 {mu}m, GSD = 2.4 {mu}m) for 6 h/day, 5 days/week for up to 24 months. A subsequent six-month period without exposures preceded the final euthanasia. High mortality among rats exposed to 1.0 mg Ni/m{sup 3} nickel metal resulted in the earlier termination of exposures in this group. The exposure level of 0.4 mg Ni/m{sup 3} was established as the MTD for the study. Lung alterations associated with nickel metal exposure included alveolar proteinosis, alveolar histiocytosis, chronic inflammation, and bronchiolar-alveolar hyperplasia. No increased incidence of neoplasm of the respiratory tract was observed. Adrenal gland pheochromocytomas (benign and malignant) in males and combined cortical adenomas/carcinomas in females were induced in a dose-dependent manner by the nickel metal exposure. The incidence of pheochromocytomas was statistically increased in the 0.4 mg Ni/m{sup 3} male group. Pheochromocytomas appear to be secondary to the lung toxicity associated with the exposure rather than being related to a direct nickel effect on the adrenal glands. The incidence of cortical tumors among 0.4 mg Ni/m{sup 3} females, although statistically higher compared to the concurrent controls, falls within the historical control range; therefore, in the present study, this tumor is of uncertain relationship to nickel metal exposure. The lack of respiratory tumors in the present animal study is consistent with the findings of the epidemiological studies.

  11. Improved retort for cleaning metal powders with hydrogen

    NASA Technical Reports Server (NTRS)

    Arias, A.

    1969-01-01

    Improved cleaning retort produces uniform temperature distribution in the heated zone and minimizes hydrogen channeling through the powder bed. Retort can be used for nonmetallic powders, sintering in a reducing atmosphere, and for cleaning powders in reduction atmospheres other than hydrogen.

  12. METHOD OF PRODUCING SHAPED BODIES FROM POWDERED METALS

    DOEpatents

    Blainey, A.

    1960-05-31

    A method is given for enclosing a body of uranium in a sheath of compacted beryllium or zirconium powder and comprises enveloping the body with uncompacted powder and pressing at a temperature above the beta - gamma transition point of uranium, thereby causing the uranium to flow and isotropically compress the powder.

  13. Star-like copolymer stabilized noble-metal nanoparticle powders

    NASA Astrophysics Data System (ADS)

    Cao, Peng-Fei; Yan, Yun-Hui; Mangadlao, Joey Dacula; Rong, Li-Han; Advincula, Rigoberto

    2016-03-01

    The amphiphilic star-like copolymer polyethylenimine-block-poly(ε-caprolactone) (PEI-b-PCL) was utilized to transfer the pre-synthesized citrate-capped noble metal nanoparticles (NMNPs) from an aqueous layer to an organic layer without any additional reagents. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) were utilized to study the assembly of the polymers coated on the surface of the citrate-capped NMNPs. After removing the organic solvent, the polymer-coated NMNPs in powder form (PCP-NMNPs) were obtained. The excellent solubility of the PEI-b-PCL allows the PCP-NMNPs to be easily dispersed in most of the organic solvents without any significant aggregation. Moreover, the good thermal stability and long-term stability make PCP-NMNPs an excellent NMNP-containing hybrid system for different specific applications, such as surface coating, catalysis and thermoplastic processing of nanocomposite materials.The amphiphilic star-like copolymer polyethylenimine-block-poly(ε-caprolactone) (PEI-b-PCL) was utilized to transfer the pre-synthesized citrate-capped noble metal nanoparticles (NMNPs) from an aqueous layer to an organic layer without any additional reagents. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) were utilized to study the assembly of the polymers coated on the surface of the citrate-capped NMNPs. After removing the organic solvent, the polymer-coated NMNPs in powder form (PCP-NMNPs) were obtained. The excellent solubility of the PEI-b-PCL allows the PCP-NMNPs to be easily dispersed in most of the organic solvents without any significant aggregation. Moreover, the good thermal stability and long-term stability make PCP-NMNPs an excellent NMNP-containing hybrid system for different specific applications, such as surface coating, catalysis and thermoplastic processing of nanocomposite materials. Electronic supplementary information (ESI) available: Synthesis scheme and the 1H NMR spectrum of PEI

  14. Modeling the hot consolidation of ceramic and metal powders

    SciTech Connect

    Dutton, R.E.; Shamasundar, S.; Semiatin, S.L.

    1995-08-01

    Modeling of the consolidation of ceramic and metal powders by sintering, hot pressing, and hot-isostatic pressing (HIP) was conducted using a continuum yield function and associated-flow rule modified to incorporate microstructure effects such as grain growth, pore size, and pore geometry. It was shown that consolidation behavior can be described over the entire range of densities through two parameters, the stress intensification factor and Poisson`s ratio, which are readily measured using uniaxial upset tests. Both parameters are functions of relative density, whose exact dependence varies from one material to another. Furthermore, it was demonstrated that in sinter forging of ceramics, an apparent Poisson`s ratio depending on stress level (relative to the sintering stress) gives a quantitative measure of the competition between sintering and creep deformation. The accuracy of the microstructure-sensitive yield function was established through finite-element modeling (FEM) simulations of the isothermal sintering of a soda-lime glass, sinter forging of alumina, and die pressing of an alpha-two titanium aluminide alloy.

  15. Problems of Development and Application of Metal Matrix Composite Powders for Additive Technologies

    NASA Astrophysics Data System (ADS)

    Korosteleva, Elena N.; Pribytkov, Gennadii A.; Krinitcyn, Maxim G.; Baranovskii, Anton V.; Korzhova, Victoria V.

    2016-07-01

    The paper considers the problem of structure formation in composites with carbide phase and a metal binder under self-propagating high-temperature synthesis (SHS) of powder mixtures. The relation between metal binder content and their structure and wear resistance of coatings was studied. It has been shown that dispersion of the carbide phase and volume content of metal binder in the composite powders structure could be regulated purposefully for all of studied composites. It was found that the structure of surfaced coating was fully inherited of composite powders. Modification or coarsening of the structure at the expense of recrystallization or coagulation carbide phase during deposition and sputtering does not occur.

  16. Research of the possibility of using an electrical discharge machining metal powder in selective laser melting

    NASA Astrophysics Data System (ADS)

    Golubeva, A. A.; Sotov, A. V.; Agapovichev, A. V.; Smelov, V. G.; Dmitriev, V. N.

    2017-02-01

    In this paper the research of a Ni-20Cr-10Fe-3Ti (heat-resistant) alloy metal powder conducted for use in a selective laser melting technology. This metal powder is the slime after electric discharge machining. The technology of cleaning and melting the powder discussed in this article. As a control input of the powder, immediately before 3D printing, dimensional analysis, surface morphology and the internal structure of the powder particles after the treatment were examined using optical and electron microscopes. The powder granules are round, oval, of different diameters with non-metallic inclusions. The internal structure of the particles is solid with no apparent defects. The content of the required diameter of the total volume of test powder granules was 15%. X-ray fluorescence analysis of the powder materials carried out. The possibility of powder melting was investigated in the selective laser melting machine ‘SLM 280HL’. A selection of the melting modes based on the physical properties of the Ni-20Cr-10Fe-3Ti alloy, data obtained from similar studies and a mathematical model of the process. Conclusions on the further investigation of the possibility of using electric discharge machining slime were made.

  17. IMPROVED V II log(gf) VALUES, HYPERFINE STRUCTURE CONSTANTS, AND ABUNDANCE DETERMINATIONS IN THE PHOTOSPHERES OF THE SUN AND METAL-POOR STAR HD 84937

    SciTech Connect

    Wood, M. P.; Lawler, J. E.; Den Hartog, E. A.; Sneden, C.; Cowan, J. J. E-mail: jelawler@wisc.edu E-mail: chris@verdi.as.utexas.edu

    2014-10-01

    New experimental absolute atomic transition probabilities are reported for 203 lines of V II. Branching fractions are measured from spectra recorded using a Fourier transform spectrometer and an echelle spectrometer. The branching fractions are normalized with radiative lifetime measurements to determine the new transition probabilities. Generally good agreement is found between this work and previously reported V II transition probabilities. Two spectrometers, independent radiometric calibration methods, and independent data analysis routines enable a reduction in systematic uncertainties, in particular those due to optical depth errors. In addition, new hyperfine structure constants are measured for selected levels by least squares fitting line profiles in the FTS spectra. The new V II data are applied to high resolution visible and UV spectra of the Sun and metal-poor star HD 84937 to determine new, more accurate V abundances. Lines covering a range of wavelength and excitation potential are used to search for non-LTE effects. Very good agreement is found between our new solar photospheric V abundance, log ε(V) = 3.95 from 15 V II lines, and the solar-system meteoritic value. In HD 84937, we derive [V/H] = –2.08 from 68 lines, leading to a value of [V/Fe] = 0.24.

  18. Brazeability of powder aluminum brazing filler metals with non-corrosive flux

    SciTech Connect

    Takemoto, T.; Matsunawa, A.; Ujie, T.

    1994-12-31

    Various brazed aluminum products, mainly heat exchangers, have been widely used especially in automobiles and electric power industries. They have been produced by using brazing sheet; however, recently the demand to braze the complicated shape is increasing, leading to the necessity for setting brazing filler metal at braze parts instead of using brazing sheet. Therefore, the present work aimed to investigated the brazeability of aluminum powder filler metal in nitrogen gas atmosphere using KAIF{sub 4}-K{sub 3}AIF{sub 6} system noncorrosive brazing flux. By considering the applicability of filler metal, brazing pastes were made of powder filler metal, flux and organic binder. AI-Si powder brazing filler metals were made by automization. T-type specimen was made by A3003 base metal with thickness of 2 mm. in the present experiment, fillet formabiltity, the percentage of the length of formed fillet against the length of vertical member wall at each side, was adopted to evaluate brazeability. The shape of the atomized powder depended on atomize atmosphere and atomizing gas. Sound fillet formation was achieved on the full length of both sides of the vertical member under the condition of appropriate surface treatment and sufficient flux content. Decrease in flux content gave partial fillet formation at the opposite side of the paste set side. Further decrease brought the partial fillet formation at the paste set side also. The paste made of air-atomized powder required more flux content to achieve 100% fillet formation at the opposite side. On the other hand, argon-atomized powders formed fillet in full length using paste with less flux content. powders sorted to remove fine particles and powders with low oxygen content were found to be suitable for brazing filler metal powders, because they required less flux content to obtain 100% fillet formation under the same amount of paste.

  19. Bonding bases coated with porous metal powder: a comparison with foil mesh.

    PubMed

    Hanson, G H; Gibbon, W M; Shimizu, H

    1983-01-01

    This study was undertaken to test the theory that a special porous metal powder coating can provide better mechanical keying than mesh by virtue of its greater surface area and intricate microscopic void network. Identical brackets were laser-welded to an equal number of conventional foil-mesh and powder-coated bases of identical shape and peripheral dimensions. The experimental base material was found to provide significantly greater tensile bond strength at the metal/adhesive interface.

  20. Microstructure and mechanical properties of hip-consolidated Rene 95 powders. [hot-isostatic pressed nickel-based powder metal

    NASA Technical Reports Server (NTRS)

    Shimanuki, Y.; Nishino, Y.; Masui, M.; Doi, H.

    1980-01-01

    The effects of heat-treatments on the microstructure of P/M Rene 95 (a nickel-based powder metal), consolidated by the hot-isostatic pressing (HIP), were examined. The microstructure of as-HIP'd specimen was characterized by highly serrated grain boundaries. Mechanical tests and microstructural observations reveal that the serrated grain boundaries improved ductility at both room and elevated temperatures by retarding crack propagation along grain boundaries.

  1. Physical and chemical characterization techniques for metallic powders

    SciTech Connect

    Slotwinski, J. A.; Stutzman, P. E.; Ferraris, C. F.; Watson, S. S.; Peltz, M. A.; Garboczi, E. J.

    2014-02-18

    Systematic studies have been carried out on two different powder materials used for additive manufacturing: stainless steel and cobalt-chrome. An extensive array of characterization techniques were applied to these two powders. The physical techniques included laser-diffraction particle-size analysis, X-ray computed tomography for size and shape analysis, and optical and scanning electron microscopy. Techniques sensitive to chemistry included X-ray diffraction and energy-dispersive analytical X-ray analysis. The background of these techniques will be summarized and some typical findings comparing different samples of virgin additive manufacturing powders, taken from the same lot, will be given. The techniques were used to confirm that different samples of powder from the same lot were essentially identical, within the uncertainty of the measurements.

  2. Mechanofused metal-carbide-oxide cermet powders for thermal spraying

    SciTech Connect

    Bernard, D.; Yokota, O.; Grimaud, A.; Fauchais, P.; Usmani, S.; Chen, Z.J.; Berndt, C.C.; Herman, H.

    1994-12-31

    By generating a mechano-chemical reaction between two or more materials, the mechanofusion process enables the production of novel powdered materials having different mechanical properties. In this study, different varieties of starting materials have been combined with the aim of manufacturing powders for thermal spraying, the objective being to produce a coating having good wear resistance in severe environments (e.g., high temperatures). Sets of NiCrAlY-TiC-ZrO{sub 2} and NiAl-TiC-ZrO{sub 2} powders with different levels of ceramic have been sprayed and the resultant coatings evaluated for microstructure, microhardness, wear and thermal shock resistance. The principal objective of the present study was to evaluate mechanofusion for the production of thermal spray cermet powders.

  3. Effects of Metal Powder Addition in Ni-Sheathed PIT MgB2 Tapes

    NASA Astrophysics Data System (ADS)

    Tachikawa, K.; Yamada, Y.; Katagiri, K.; Kumakura, H.; Iwamoto, A.; Watanabe, K.

    2004-06-01

    The effect of different metal powder additions on the transport current and stress/strain performance of ex-situ processed MgB2 tapes with Ni sheath has been studied. The metal powder added to the core exhibits elongated morphology after the fabrication. The addition of low melting point metal powder, e.g. In and Sn, produces an appreciable increase in the Jc of MgB2 core. An addition of 10 vol% In enhances Jc by a factor of 6 to 7 after the combination of rolling and annealing at 200 °C, up to the order of 105 A/cm2 at 0.5 T and 4.2 K. An addition of 10 vol% Sn enhances Jc by a factor of ˜ 3. The In and Sn additions also appreciably increase the n-value of the current-voltage transition. Both In and Sn metals infiltrate into gaps between MgB2 grains, improving the linkage of the grains. Current may transfer through the impregnated metal by the proximity effect. Furthermore, the metal powder addition appreciably improves the strain tolerance in MgB2 tapes. The low melting point metal powder addition is a relatively simple and easy approach to yield better transport current and stress/strain performance in ex-situ MgB2 tapes.

  4. Thermal analysis and evolution of shape loss phenomena during polymer burnout in powder metal processing

    NASA Astrophysics Data System (ADS)

    Enneti, Ravi Kumar

    2005-07-01

    Powder metallurgy technology involves manufacturing of net shape or near net shape components starting from metal powders. Polymers are used to provide lubrication during shaping and handling strength to the shaped component. After shaping, the polymers are removed from the shaped components by providing thermal energy to burnout the polymers. Polymer burnout is one of the most critical step in powder metal processing. Improper design of the polymer burnout cycle will result in formation of defects, shape loss, or carbon contamination of the components. The effect of metal particles on polymer burnout and shape loss were addressed in the present research. The study addressing the effect of metal powders on polymer burnout was based on the hypothesis that metal powders act to catalyze polymer burnout. Thermogravimetric analysis (TGA) on pure polymer, ethylene vinyl acetate (EVA), and on admixed powders of 316L stainless steel and 1 wt. % EVA were carried out to verify the hypothesis. The effect of metal powders additions was studied by monitoring the onset temperature for polymer degradation and the temperature at which maximum rate of weight loss occurred from the TGA data. The catalytic behavior of the powders was verified by varying the particle size and shape of the 316L stainless powder. The addition of metal particles lowered the polymer burnout temperatures. The onset temperature for burnout was found to be sensitive to the surface area of the metal particle as well as the polymer distribution. Powders with low surface area and uniform distribution of polymer showed a lower burnout temperature. The evolution of shape loss during polymer burnout was based on the hypothesis that shape loss occurs during the softening of the polymer and depends on the sequence of chemical bonding in the polymer during burnout. In situ observation of shape loss was carried out on thin beams compacted from admixed powders of 316L stainless steel and 1 wt. % ethylene vinyl acetate

  5. Application of physical and chemical characterization techniques to metallic powders

    SciTech Connect

    Slotwinski, J. A.; Watson, S. S.; Stutzman, P. E.; Ferraris, C. F.; Peltz, M. A.; Garboczi, E. J.

    2014-02-18

    Systematic studies have been carried out on two different powder materials used for additive manufacturing: stainless steel and cobalt-chrome. The characterization of these powders is important in NIST efforts to develop appropriate measurements and standards for additive materials and to document the property of powders used in a NIST-led additive manufacturing material round robin. An extensive array of characterization techniques was applied to these two powders, in both virgin and recycled states. The physical techniques included laser diffraction particle size analysis, X-ray computed tomography for size and shape analysis, and optical and scanning electron microscopy. Techniques sensitive to chemistry, including X-ray diffraction and energy dispersive analytical X-ray analysis using the X-rays generated during scanning electron microscopy, were also employed. Results of these analyses will be used to shed light on the question: how does virgin powder change after being exposed to and recycled from one or more additive manufacturing build cycles? In addition, these findings can give insight into the actual additive manufacturing process.

  6. Foamed lightweight materials made from mixed scrap metal waste powder and sewage sludge ash.

    PubMed

    Wang, Kuen-Sheng; Chiou, Ing-Jia

    2004-10-01

    The porous properties and pozzolanic effects of sewage sludge ash (SSA) make it possible to produce lightweight materials. This study explored the effects of different metallic foaming agents, made from waste aluminium products, on the foaming behaviours and engineering characteristics, as well as the microstructure of sewage sludge ash foamed lightweight materials. The results indicated that aluminium powder and mixed scrap metal waste powder possessed similar chemical compositions. After proper pre-treatment, waste aluminium products proved to be ideal substitutes for metallic foaming agents. Increasing the amount of mixed scrap metal waste by 10-15% compared with aluminium powder would produce a similar foaming ratio and compressive strength. The reaction of the metallic foaming agents mainly produced pores larger than 10 microm, different from the hydration reaction of cement that produced pores smaller than 1 microm mostly. To meet the requirements of the lightweight materials characteristics and the compressive strength, the amount of SSA could be up to 60-80% of the total solids. An adequate amount of aluminium powder is 0.5-0.9% of the total solids. Increasing the fineness of the mixed scrap metal waste powder could effectively reduce the amount required and improve the foaming ratio.

  7. Method of making metal oxide ceramic powders by using a combustible amino acid compound

    DOEpatents

    Pederson, Larry R.; Chick, Lawrence A.; Exarhos, Gregory J.

    1992-01-01

    This invention is directed to the formation of homogeneous, aqueous precursor mixtures of at least one substantially soluble metal salt and a substantially soluble, combustible co-reactant compound, typically an amino acid. This produces, upon evaporation, a substantially homogeneous intermediate material having a total solids level which would support combustion. The homogeneous intermediate material essentially comprises highly dispersed or solvated metal constituents and the co-reactant compound. The intermediate material is quite flammable. A metal oxide powder results on ignition of the intermediate product which combusts same to produce the product powder.

  8. Method of making metal oxide ceramic powders by using a combustible amino acid compound

    DOEpatents

    Pederson, L.R.; Chick, L.A.; Exarhos, G.J.

    1992-05-19

    This invention is directed to the formation of homogeneous, aqueous precursor mixtures of at least one substantially soluble metal salt and a substantially soluble, combustible co-reactant compound, typically an amino acid. This produces, upon evaporation, a substantially homogeneous intermediate material having a total solids level which would support combustion. The homogeneous intermediate material essentially comprises highly dispersed or solvated metal constituents and the co-reactant compound. The intermediate material is quite flammable. A metal oxide powder results on ignition of the intermediate product which combusts same to produce the product powder.

  9. Excellent capability in degrading azo dyes by MgZn-based metallic glass powders.

    PubMed

    Wang, Jun-Qiang; Liu, Yan-Hui; Chen, Ming-Wei; Louzguine-Luzgin, Dmitri V; Inoue, Akihisa; Perepezko, John H

    2012-01-01

    The lack of new functional applications for metallic glasses hampers further development of these fascinating materials. In this letter, we report for the first time that the MgZn-based metallic glass powders have excellent functional ability in degrading azo dyes which are typical organic water pollutants. Their azo dye degradation efficiency is about 1000 times higher than that of commercial crystalline Fe powders, and 20 times higher than the Mg-Zn alloy crystalline counterparts. The high Zn content in the amorphous Mg-based alloy enables a greater corrosion resistance in water and higher reaction efficiency with azo dye compared to crystalline Mg. Even under complex environmental conditions, the MgZn-based metallic glass powders retain high reaction efficiency. Our work opens up a new opportunity for functional applications of metallic glasses.

  10. Excellent capability in degrading azo dyes by MgZn-based metallic glass powders

    PubMed Central

    Wang, Jun-Qiang; Liu, Yan-Hui; Chen, Ming-Wei; Louzguine-Luzgin, Dmitri V.; Inoue, Akihisa; Perepezko, John H.

    2012-01-01

    The lack of new functional applications for metallic glasses hampers further development of these fascinating materials. In this letter, we report for the first time that the MgZn-based metallic glass powders have excellent functional ability in degrading azo dyes which are typical organic water pollutants. Their azo dye degradation efficiency is about 1000 times higher than that of commercial crystalline Fe powders, and 20 times higher than the Mg-Zn alloy crystalline counterparts. The high Zn content in the amorphous Mg-based alloy enables a greater corrosion resistance in water and higher reaction efficiency with azo dye compared to crystalline Mg. Even under complex environmental conditions, the MgZn-based metallic glass powders retain high reaction efficiency. Our work opens up a new opportunity for functional applications of metallic glasses. PMID:22639726

  11. Influence of Powder Characteristics in Laser Direct Metal Deposition of SS316L for Metallic Parts Manufacturing

    NASA Astrophysics Data System (ADS)

    Boisselier, Didier; Sankaré, Simon

    Laser direct metal deposition (LDMD) is a rapid manufacturing technique, dedicated to new part construction or worn part repairing. The process depends on a various range of parameters and the powder characteristics are one of the main crucial parameters. The powder (size,…) has then a direct impact on an optimized process behavior and the mechanical properties of the manufactured component. This paper focuses on powder investigation, for a better understanding of its influence. The work was performed with different batches of stainless steel AISI316 that have been analyzed and characterized before processing. This paper discusses the results derived from the manufactured samples, highlights the influence of the main powders characteristics and demonstrates the flexibility of the process when the powders meet the specifications.

  12. Fluidized Bed Sputtering for Particle and Powder Metallization

    DTIC Science & Technology

    2013-04-01

    used microwave and radio frequency (RF) plasma coupled with a gas-fluidized bed to produce thin titania coatings on glass powders. Chen et al. (16...2000, 35 (6), 1439–1444. 8. Park, J.; Bae, D. H.; Lee, S. Y.; Kwak, J.; Park, H. W.; Lim, J. Large-Scale Production of Titania Nano-Coated Silica

  13. Elasticity, fracture and yielding of cold compacted metal powders

    NASA Astrophysics Data System (ADS)

    Martin, C. L.

    2004-08-01

    The behaviour of powder compacts is modelled by explicitly introducing the possibility of plastic loading, elastic unloading and decohesion at contacts. The study is limited to cold compaction and to perfectly plastic materials for which the analysis of Mesarovic and Johnson (J. Mech. Phys. 48 (2000) 2009) is used. We model the compact behaviour both with an analytical approach based upon a mean field assumption and with the discrete element method (DEM) that allows force equilibrium to be treated in a realistic manner. Using these two approaches, we are able to predict the effective elastic properties of a powder compact at the onset of unloading. The knowledge of the conditions that lead to decohesion at the contact scale is used to model the fracture of the powder compact (green strength). It is shown that, in first approximation, green strength is inversely proportional to the size of the powder particles. The two methods are used to generate failure and yield surfaces for axisymmetric conditions. Both isostatic and close die conditions are studied.

  14. Novel Route to Transition Metal Isothiocyanate Complexes Using Metal Powders and Thiourea

    NASA Technical Reports Server (NTRS)

    Harris, Jerry D.; Eckles, William E.; Hepp, Aloysius F.; Duraj, Stan A.; Hehemann, David G.; Fanwick, Phillip E.; Richardson, John

    2003-01-01

    A new synthetic route to isothiocyanate-containing materials is presented. Eight isothiocyanate- 4-methylpyridine (y-picoline) compounds were prepared by refluxing metal powders (Mn, Fe, Co, Ni, and Cu) with thiourea in y-picoline. With the exception of compound 5,prepared with Co, the isothiocyanate ligand was generated in situ by the isomerization of thiourea to NH4+SCN- at reflux temperatures. The complexes were characterized by x-ray crystallography. Compounds 1,2, and 8 are the first isothiocyanate- 4-methylpyridine anionic compounds ever prepared and structurally characterized. Compounds 1 and 2 are isostructural with four equatorially bound isothiocyanate ligands and two axially bound y-picoline molecules. Compound 8 is a five-coordinate copper(II) molecule with a distorted square-pyramidal geometry. Coordinated picoline and two isothiocyanates form the basal plane and the remaining isothiocyanate is bound at the apex. Structural data are presented for all compounds.

  15. The Potential of Aluminium Metal Powder as a Fuel for Space Propulsion Systems

    NASA Astrophysics Data System (ADS)

    Ismail, A. M.; Osborne, B.; Welch, C. S.

    Metal powder propulsion systems have been addressed intermittently since the Second World War, initially in the field of underwater propulsion where research in the application of propelling torpedoes continues until this day. During the post war era, researchers attempted to utilise metal powders as a fuel for ram jet applications in missiles. The 1960's and 1970's saw additional interest in the use of `pure powder' propellants, i.e. fluidised metal fuel and oxidiser, both in solid particulate form. Again the application was for employment in space-constrained missiles where the idea was to maximise the performance of high energy density powder propellants in order to enhance the missile's flight duration. Metal powder as possible fuel was investigated for in-situ resource utilisation propulsion systems post-1980's where the emphasis was on the use of gaseous oxygen or liquid oxygen combined with aluminium metal powder for use as a ``lunar soil propellant'' or carbon dioxide and magnesium metal powder as a ``Martian propellant''.Albeit aluminium metal powder propellants are lower in performance than cryogenic and Earth storable propellants, the former does have an advantage inasmuch that the propulsion system is generic, i.e. it can be powered with chemicals mined and processed on Earth, the Moon and Mars. Thus, due to the potential refuelling capability, the lower performing aluminium metal powder propellant would effectively possess a much higher change in velocity (V) for multiple missions than the cryogenic or Earth storable propellant which is only suitable for one planet or one mission scenario, respectively.One of the principal limitations of long duration human spaceflight beyond cis-lunar orbit is the lack of refuelling capabilities on distant planets resulting in the reliance on con- ventional non-cryogenic, propellants produced on Earth. If one could develop a reliable propulsion system operating on pro- pellants derived entirely of ingredients found on

  16. Chemical reactions of metal powders with organic and inorganic liquids during ball milling

    NASA Technical Reports Server (NTRS)

    Arias, A.

    1975-01-01

    Chromium and/or nickel powders were milled in metal chlorides and in organic liquids representative of various functional groups. The powders always reacted with the liquid and became contaminated with elements from them. The milled powders had specific surface areas ranging from 0.14 to 37 sq m/g, and the total contamination with elements from the milling liquid ranged from 0.01 to 56 weight percent. Compounds resulting from substitution, addition, or elimination reactions formed in or from the milling liquid.

  17. Metal vapor micro-jet controls material redistribution in laser powder bed fusion additive manufacturing.

    PubMed

    Ly, Sonny; Rubenchik, Alexander M; Khairallah, Saad A; Guss, Gabe; Matthews, Manyalibo J

    2017-06-22

    The results of detailed experiments and finite element modeling of metal micro-droplet motion associated with metal additive manufacturing (AM) processes are presented. Ultra high speed imaging of melt pool dynamics reveals that the dominant mechanism leading to micro-droplet ejection in a laser powder bed fusion AM is not from laser induced recoil pressure as is widely believed and found in laser welding processes, but rather from vapor driven entrainment of micro-particles by an ambient gas flow. The physics of droplet ejection under strong evaporative flow is described using simulations of the laser powder bed interactions to elucidate the experimental results. Hydrodynamic drag analysis is used to augment the single phase flow model and explain the entrainment phenomenon for 316 L stainless steel and Ti-6Al-4V powder layers. The relevance of vapor driven entrainment of metal micro-particles to similar fluid dynamic studies in other fields of science will be discussed.

  18. Effect of metal powder packing on the conductivity of nanometal ink.

    PubMed

    Kim, Nam-Soo; Amert, Anthony K; Woessner, Stephen M; Decker, Shawn; Kang, Sun-Mee; Han, Kenneth N

    2007-11-01

    The power of nanotechnology is realized in its application in numerous areas. One such area is undoubtedly the use of metallic nanoparticles as a direct write application. An effort in this area has resulted in a conductive ink whose conductivity approaches 60-70% that of the bulk copper. Such an ink has been developed by reducing silver, gold, and copper nano-sized powders by a wet method and followed by a heat treatment at less than 400 degrees C. The conductivity of the resulting ink product was found to be very much affected by how various sizes of metal powders are packed when particles were dried and packed on various substrates. The effect of packing and various kinds of metal powders on the eventual conductivity of the final product of the ink has been described and discussed in this paper.

  19. Measurement of electromagnetic properties of powder and solid metal materials for additive manufacturing

    NASA Astrophysics Data System (ADS)

    Todorov, Evgueni Iordanov

    2017-04-01

    The lack of validated nondestructive evaluation (NDE) techniques for examination during and after additive manufacturing (AM) component fabrication is one of the obstacles in the way of broadening use of AM for critical applications. Knowledge of electromagnetic properties of powder (e.g. feedstock) and solid AM metal components is necessary to evaluate and deploy electromagnetic NDE modalities for examination of AM components. The objective of this research study was to develop and implement techniques for measurement of powder and solid metal electromagnetic properties. Three materials were selected - Inconel 625, duplex stainless steel 2205, and carbon steel 4140. The powder properties were measured with alternate current (AC) model based eddy current technique and direct current (DC) resistivity measurements. The solid metal properties were measured with DC resistivity measurements, DC magnetic techniques, and AC model based eddy current technique. Initial magnetic permeability and electrical conductivity were acquired for both powder and solid metal. Additional magnetic properties such as maximum permeability, coercivity, retentivity, and others were acquired for 2205 and 4140. Two groups of specimens were tested along the build length and width respectively to investigate for possible anisotropy. There was no significant difference or anisotropy when comparing measurements acquired along build length to those along the width. A trend in AC measurements might be associated with build geometry. Powder electrical conductivity was very low and difficult to estimate reliably with techniques used in the study. The agreement between various techniques was very good where adequate comparison was possible.

  20. In vitro absorption of metal powders through intact and damaged human skin.

    PubMed

    Filon, Francesca Larese; D'Agostin, Flavia; Crosera, Matteo; Adami, Gianpiero; Bovenzi, Massimo; Maina, Giovanni

    2009-06-01

    The bioavailability of metals, which are known as important contact allergens, is decisive for the development and the maintenance of contact dermatitis. The aim of this study was to evaluate the percutaneous penetration of metal powders of cobalt (Co), nickel (Ni) and chromium (Cr) and the effect of skin lesions on skin absorption. In vitro permeation experiments were performed using the Franz diffusion cells with intact and damaged human skin. Physiological solution was used as receiving phase and metal powders (Co, Ni and Cr) dispersed in synthetic sweat at pH 4.5 were applied as donor phase to the outer surface of the skin for 24h. The amount of each metal permeating the skin was analysed by electro-thermal atomic absorption spectroscopy (ETAAS). Donor solution analysis demonstrated that metals were present as ions. Measurements of metals skin content were also exploited. Median Co and Ni concentrations found in the receiving phase were significantly higher when Co and Ni powders were applied on the abraded skin than after application on the intact skin (3566 and 2631ngcm(-2) vs. 8.4 and 31ngcm(-2), respectively). No significant difference was found in Cr permeation through intact and damaged skin. The measurement of metals skin content showed that Co, Ni and Cr concentrations were significantly higher in the damaged skin than in the intact skin. Co and Ni ions concentrations increased significantly when the donor solutions were applied on the damaged skin, while Cr ions concentrations did not increase. This study demonstrated that Co and Ni powders can permeate through damaged skin more easily than Cr powder, which has probably a stronger skin proteins binding capacity. Therefore, our results suggest that is necessary to prevent skin contamination when using toxic substances because a small injury to the skin barrier can significantly increase skin absorption.

  1. Microstructure engineering from metallic powder blends for enhanced mechanical properties

    NASA Astrophysics Data System (ADS)

    Langlois, P.; Fagnon, N.; Dirras, G.

    2010-07-01

    The present work focuses on the transformation of high-purity Ni powder blends of controlled volume fractions (40 and 60 %) of nanometre-sized (100 nm) and micrometre-sized (544 nm) particles into bulk samples as part of a strategy for producing ultrafine-grained materials usefully exhibiting both strength and ductility. The process involved cold isostatic pressing at 1.5 GPa and sintering. The resulting bulk samples had relative densities near 95 %, were texture-free, and exhibited two different grain size distributions with an average value of 600 ± 30 nm. The mechanical properties were investigated by compression and microhardness tests, both at room temperature, and compared to the behaviour of a sample processed from micrometre-sized powder only. Samples prepared from the blends exhibited high yield stresses of 440 and 550 MPa after compression, and they did sustain work hardening. Tests conducted before and after compression up to 50 % deformation showed the same relative amount of hardness increase around 20 %, which was three times lower than that of the monolithic sample for which a decrease of the average grain size close to 26 % was measured.

  2. On the development of constitutive relations for metallic powders

    NASA Technical Reports Server (NTRS)

    Watson, T. J.; Wert, J. A.

    1993-01-01

    This article describes the development of elastic and plastic constitutive relations as functions of relative density for partially consolidated -100 mesh aluminum powder. First, measurements of yield stress as a function of stress state and relative density are described. Measurements of the plastic strain increments associated with yielding in unconstrained compression tests and elastic properties, both as functions of relative density, are also described. The experimental results are combined with the associated flow rule to show that the yield surface is asymmetric with respect to hydrostatic tension and compression. Second, it is shown that the yield stress results can be represented by a two-part (capped Drucker-Prager) yield surface. The consolidation yield surface moves along the hydrostatic stress axis during densification, while the shear yield surface approaches the Mises yield surface. For the Al powder used in the present investigation, superposition of shear stress on a hydrostatic stress state aids the densification process. However, the hydrostatic stress requirement was found to be reduced by only about 20 pct for relative densities below 0.98.

  3. Cold Sprayability of Mixed Commercial Purity Ti Plus Ti6Al4V Metal Powders

    NASA Astrophysics Data System (ADS)

    Aydin, Huseyin; Alomair, Mashael; Wong, Wilson; Vo, Phuong; Yue, Stephen

    2017-02-01

    In the present work, metallic composite coatings of commercial purity Ti plus Ti6Al4V were produced by cold spraying to explore the effect of mixing on porosity and mechanical properties of the coatings. The coatings were deposited using N2 gas at 800 °C and 4 MPa pressure on 1020 steel substrate. Coating characteristics were studied by examining porosity percentages and Vickers's hardness. The microstructure was examined using optical and electron microscopy techniques. It was observed that mixing metal powders can lead to improvements in cold sprayability, specifically decreases in the porosity of the `matrix' powder. It is shown that a critical addition can significantly influence porosity, but above this critical level, there is a little change in porosity. Hardness differences between the two powders are considered to be the first-order influence, but differences in particle sizes and morphology may also be contributing factors.

  4. USE OF COMBUSTION SYNTHESIS IN PREPARING CERAMIC-MATRIX AND METAL-MATRIX COMPOSITE POWDERS

    SciTech Connect

    Weil, K. Scott; Hardy, John S.

    2005-03-01

    A standard combustion-based approach typically used to synthesize nanosize oxide powders has been modified to prepare composite oxide-metal powders for subsequent densification via sintering or hot-pressing into ceramic- or metal-matrix composites. Copper and cerium nitrate salts were dissolved in the appropriate ratio in water and combined with glycine, then heated to cause autoignition. The ratio of glycine-to-total nitrate concentration was found to have the largest effect on the composition, agglomerate size, crystallite size, and dispersivity of phases in the powder product. After consolidation and sintering under reducing conditions, the resulting composite compact consists of a well-dispersed mixture of sub-micron size reinforcement particles in a fine-grained matrix.

  5. Method for continuous synthesis of metal oxide powders

    DOEpatents

    Berry, David A.; Haynes, Daniel J.; Shekhawat, Dushyant; Smith, Mark W.

    2015-09-08

    A method for the rapid and continuous production of crystalline mixed-metal oxides from a precursor solution comprised of a polymerizing agent, chelated metal ions, and a solvent. The method discharges solution droplets of less than 500 .mu.m diameter using an atomizing or spray-type process into a reactor having multiple temperature zones. Rapid evaporation occurs in a first zone, followed by mixed-metal organic foam formation in a second zone, followed by amorphous and partially crystalline oxide precursor formation in a third zone, followed by formation of the substantially crystalline mixed-metal oxide in a fourth zone. The method operates in a continuous rather than batch manner and the use of small droplets as the starting material for the temperature-based process allows relatively high temperature processing. In a particular embodiment, the first zone operates at 100-300.degree. C., the second zone operates at 300-700.degree. C., and the third operates at 700-1000.degree. C., and fourth zone operates at at least 700.degree. C. The resulting crystalline mixed-metal oxides display a high degree of crystallinity and sphericity with typical diameters on the order of 50 .mu.m or less.

  6. Effect of layered manufacturing techniques, alloy powders, and layer thickness on metal-ceramic bond strength.

    PubMed

    Ekren, Orhun; Ozkomur, Ahmet; Ucar, Yurdanur

    2017-07-06

    Direct metal laser sintering (DMLS) and direct metal laser melting (DMLM) have become popular for fabricating the metal frameworks of metal-ceramic restorations. How the type of layered manufacturing device, layer thickness, and alloy powder may affect the bond strength of ceramic to metal substructure is unclear. The purpose of this in vitro study was to evaluate the bond strength of dental porcelain to metal frameworks fabricated using different layered manufacturing techniques (DMLS and DMLM), Co-Cr alloy powders, and layer thicknesses and to evaluate whether a correlation exists between the bond strength and the number of ceramic remnants on the metal surface. A total of 75 bar-shaped metal specimens (n=15) were fabricated using either DMLS or DMLM. The powder alloys used were Keramit NP-S and EOS-Cobalt-Chrome SP-2 with layer thicknesses of 20 μm and 30 μm. After ceramic application, the metal-ceramic bond strength was evaluated with a 3-point-bend test. Three-way ANOVA followed by the Tukey honest significance difference test were used for statistical analysis (α=.05). De-bonding surface microstructure was observed with scanning electron microscopy. Energy dispersive spectroscopy analysis was conducted to evaluate the correlation between ceramic remnants on the metal surface and bond strength values. The mean bond strength value of DMLS was significantly higher than that of DMLM. While no statistically significant difference was found between layer thicknesses, alloy powders closely affected bond strength. Statistical comparisons revealed that the highest bond strength could be achieved with DMLS-Cobalt-Chrome SP2-20μm, and the lowest bond strength was observed in DMLS-Keramit NP-S-20μm (P≤.05). No correlation was found between porcelain remnants on the metal surface and bond strength values. The layered manufacturing device and the alloy powders evaluated in the current study closely affected the bond strength of dental porcelain to a metal framework

  7. Aluminium alloys with transition metals prepared by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Kucera, V.; Prusa, F.; Vojtech, D.

    2017-02-01

    Powder metallurgy represented by mechanical alloying and spark plasma sintering was used for preparation of the AlFe16 and the AlSi20Fe16 alloys. Microstructure of the both alloys consisted of very fine intermetallic phases homogenously dispersed in the matrix of α-Al solid solution. Fine nature of microstructure led to promising results of compressive stress-strain tests performed at laboratory and elevated temperature of 400 °C. The compressive strengths of the AlSi20Fe16 and the AlFe16 alloys at laboratory temperature were 780 MPa and 508 MPa, respectively. Elevated temperature resulted in drop of the compressive strengths to 480 MPa and 211 MPa, respectively. However, the results of investigated alloys outperformed the thermally stable AlSi12Cu1Mg1Ni1 (wt. %) used as reference material.

  8. A highly efficient degradation mechanism of methyl orange using Fe-based metallic glass powders.

    PubMed

    Xie, Shenghui; Huang, Ping; Kruzic, Jamie J; Zeng, Xierong; Qian, Haixia

    2016-02-23

    A new Fe-based metallic glass with composition Fe76B12Si9Y3 (at. %) is found to have extraordinary degradation efficiency towards methyl orange (MO, C14H14N3SO3) in strong acidic and near neutral environments compared to crystalline zero-valent iron (ZVI) powders and other Fe-based metallic glasses. The influence of temperature (294-328 K) on the degradation reaction rate was measured using ball-milled metallic glass powders revealing a low thermal activation energy barrier of 22.6 kJ/mol. The excellent properties are mainly attributed to the heterogeneous structure consisting of local Fe-rich and Fe-poor atomic clusters, rather than the large specific surface and strong residual stress in the powders. The metallic glass powders can sustain almost unchanged degradation efficiency after 13 cycles at room temperature, while a drop in degradation efficiency with further cycles is attributed to visible surface oxidation. Triple quadrupole mass spectrometry analysis conducted during the reaction was used to elucidate the underlying degradation mechanism. The present findings may provide a new, highly efficient and low cost commercial method for azo dye wastewater treatment.

  9. FINISHING FABRICATED METAL PRODUCTS WITH POWDER COATING. Project Summary (EPA/600/SR-96/152)

    EPA Science Inventory

    This report provides a technical and economic evaluation of a polyester powder coating system applied to the exterior and interior surfaces of metal boxes fabricated for the telephone and cable industries. This evaluation summarized many of the requirements and benefits of a clea...

  10. A highly efficient degradation mechanism of methyl orange using Fe-based metallic glass powders

    PubMed Central

    Xie, Shenghui; Huang, Ping; Kruzic, Jamie J.; Zeng, Xierong; Qian, Haixia

    2016-01-01

    A new Fe-based metallic glass with composition Fe76B12Si9Y3 (at. %) is found to have extraordinary degradation efficiency towards methyl orange (MO, C14H14N3SO3) in strong acidic and near neutral environments compared to crystalline zero-valent iron (ZVI) powders and other Fe-based metallic glasses. The influence of temperature (294–328 K) on the degradation reaction rate was measured using ball-milled metallic glass powders revealing a low thermal activation energy barrier of 22.6 kJ/mol. The excellent properties are mainly attributed to the heterogeneous structure consisting of local Fe-rich and Fe-poor atomic clusters, rather than the large specific surface and strong residual stress in the powders. The metallic glass powders can sustain almost unchanged degradation efficiency after 13 cycles at room temperature, while a drop in degradation efficiency with further cycles is attributed to visible surface oxidation. Triple quadrupole mass spectrometry analysis conducted during the reaction was used to elucidate the underlying degradation mechanism. The present findings may provide a new, highly efficient and low cost commercial method for azo dye wastewater treatment. PMID:26902824

  11. FINISHING FABRICATED METAL PRODUCTS WITH POWDER COATING. Project Summary (EPA/600/SR-96/152)

    EPA Science Inventory

    This report provides a technical and economic evaluation of a polyester powder coating system applied to the exterior and interior surfaces of metal boxes fabricated for the telephone and cable industries. This evaluation summarized many of the requirements and benefits of a clea...

  12. Needs Assessment for Curriculum Design and Development in the Powdered Metals Industry. Project Number One.

    ERIC Educational Resources Information Center

    Immel, Michael C.; Geroy, Gary D.

    This study, which investigated industry-wide needs for training development in the powdered metals industry, identified the following knowledge areas as those most needed by workers: (1) basic reading and communication skills; (2) basic and algebra mathematical skills; (3) blueprint reading; (4) statistical process control; (5) standard and…

  13. A highly efficient degradation mechanism of methyl orange using Fe-based metallic glass powders

    NASA Astrophysics Data System (ADS)

    Xie, Shenghui; Huang, Ping; Kruzic, Jamie J.; Zeng, Xierong; Qian, Haixia

    2016-02-01

    A new Fe-based metallic glass with composition Fe76B12Si9Y3 (at. %) is found to have extraordinary degradation efficiency towards methyl orange (MO, C14H14N3SO3) in strong acidic and near neutral environments compared to crystalline zero-valent iron (ZVI) powders and other Fe-based metallic glasses. The influence of temperature (294–328 K) on the degradation reaction rate was measured using ball-milled metallic glass powders revealing a low thermal activation energy barrier of 22.6 kJ/mol. The excellent properties are mainly attributed to the heterogeneous structure consisting of local Fe-rich and Fe-poor atomic clusters, rather than the large specific surface and strong residual stress in the powders. The metallic glass powders can sustain almost unchanged degradation efficiency after 13 cycles at room temperature, while a drop in degradation efficiency with further cycles is attributed to visible surface oxidation. Triple quadrupole mass spectrometry analysis conducted during the reaction was used to elucidate the underlying degradation mechanism. The present findings may provide a new, highly efficient and low cost commercial method for azo dye wastewater treatment.

  14. One-step synthesis of dithiocarbamates from metal powders

    NASA Technical Reports Server (NTRS)

    Hepp, Aloysius F.; Hehemann, David G.; Duraj, Stan A.; Clark, Eric B.; Eckles, William E.; Fanwick, Phillip E.

    1994-01-01

    Neutral metal dithiocarbamate complexes (M(NR2CS2)X) are well-known precursors to metal sulfides, a class of materials with numerous technological applications. We are involved in a research effort to prepare new precursors to metal sulfides using simple, reproducible synthetic procedures. We describe the results of our synthetic and characterization studies for M = Fe, Co, Ni, Cu. and In. For example, treatment of metallic indium with tetramethylthiuram disulfide (tmtd) in 4-methylpyridine (4-Mepy) at 25 deg C produces a new homoleptic indium (III) dithiocarbamate, In(N(CH3)2CS2)3(I), in yields of over 60 percent. The indium (III) dithiocarbamate was characterized by X-ray crystallography; (I) exists in the solid state as discrete distorted-octahedral molecules. Compound (I) crystallizes in the P1bar (No. 2) space group with lattice parameters: a = 9.282(1) A, b = 10.081(1) A, c = 12.502 A, alpha = 73.91(1) deg, beta = 70.21(1) deg, gamma = 85.8(1)deg, and Z = 2. X-ray diffraction and mass spectral data were used to characterize the products of the analogous reactions with Fe, Co, Ni, and Cu. We discuss both use of dithiocarbamates as precursors and our approach to their preparation.

  15. Sonochemical water splitting in the presence of powdered metal oxides.

    PubMed

    Morosini, Vincent; Chave, Tony; Virot, Matthieu; Moisy, Philippe; Nikitenko, Sergey I

    2016-03-01

    Kinetics of hydrogen formation was explored as a new chemical dosimeter allowing probing the sonochemical activity of argon-saturated water in the presence of micro- and nano-sized metal oxide particles exhibiting catalytic properties (ThO2, ZrO2, and TiO2). It was shown that the conventional sonochemical dosimeter based on H2O2 formation is hardly applicable in such systems due to catalytic degradation of H2O2 at oxide surface. The study of H2 generation revealed that at low-frequency ultrasound (20 kHz) the sonochemical water splitting is greatly improved for all studied metal oxides. The highest efficiency is observed for relatively large micrometric particles of ThO2 which is assigned to ultrasonically-driven particle fragmentation accompanied by mechanochemical water molecule splitting. The nanosized metal oxides do not exhibit particle size reduction under ultrasonic treatment but nevertheless yield higher quantities of H2. The enhancement of sonochemical water splitting in this case is most probably resulting from better bubble nucleation in heterogeneous systems. At high-frequency ultrasound (362 kHz), the effect of metal oxide particles results in a combination of nucleation and ultrasound attenuation. In contrast to 20 kHz, micrometric particles slowdown the sonolysis of water at 362 kHz due to stronger attenuation of ultrasonic waves while smaller particles show a relatively weak and various directional effects. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. MODELING MOLECULAR HYPERFINE LINE EMISSION

    SciTech Connect

    Keto, Eric; Rybicki, George

    2010-06-20

    In this paper, we discuss two approximate methods previously suggested for modeling hyperfine spectral line emission for molecules whose collisional transition rates between hyperfine levels are unknown. Hyperfine structure is seen in the rotational spectra of many commonly observed molecules such as HCN, HNC, NH{sub 3}, N{sub 2}H{sup +}, and C{sup 17}O. The intensities of these spectral lines can be modeled by numerical techniques such as {Lambda}-iteration that alternately solve the equations of statistical equilibrium and the equation of radiative transfer. However, these calculations require knowledge of both the radiative and collisional rates for all transitions. For most commonly observed radio frequency spectral lines, only the net collisional rates between rotational levels are known. For such cases, two approximate methods have been suggested. The first method, hyperfine statistical equilibrium, distributes the hyperfine level populations according to their statistical weight, but allows the population of the rotational states to depart from local thermal equilibrium (LTE). The second method, the proportional method, approximates the collision rates between the hyperfine levels as fractions of the net rotational rates apportioned according to the statistical degeneracy of the final hyperfine levels. The second method is able to model non-LTE hyperfine emission. We compare simulations of N{sub 2}H{sup +} hyperfine lines made with approximate and more exact rates and find that satisfactory results are obtained.

  17. PVC-based composite material containing recycled non-metallic printed circuit board (PCB) powders.

    PubMed

    Wang, Xinjie; Guo, Yuwen; Liu, Jingyang; Qiao, Qi; Liang, Jijun

    2010-12-01

    The study is directed to the use of non-metallic powders obtained from comminuted recycled paper-based printed circuit boards (PCBs) as an additive to polyvinyl chloride (PVC) substrate. The physical properties of the non-metallic PCB (NMPCB) powders were measured, and the morphological, mechanical and thermal properties of the NMPCB/PVC composite material were investigated. The results show that recycled NMPCB powders, when added below a threshold, tended to increase the tensile strength and bending strength of PVC. When 20 wt% NMPCB powders (relative to the substrate PVC) of an average diameter of 0.08 mm were added, the composite tensile strength and bending strength reached 22.6 MPa and 39.83 MPa, respectively, representing 107.2% and 123.1% improvement over pure PVC. The elongation at break of the composite material reached 151.94% of that of pure PVC, while the Vicat softening temperature of the composite material did not increase significantly compared to the pure PVC. The above results suggest that paper-based NMPCB powders, when used at appropriate amounts, can be effective for toughening PVC. Thus, this study suggests a new route for reusing paper-based NMPCB, which may have a significant beneficial environmental impact.

  18. Metal-Assisted Laser-Induced Gas Plasma for the Direct Analysis of Powder Using Pulse CO2 Laser

    NASA Astrophysics Data System (ADS)

    Khumaeni, A.; Lie, Z. S.; Kurniawan, K. H.; Kagawa, K.

    2017-01-01

    Analysis of powder samples available in small quantities has been carried out using metal-assisted gas plasma by utilizing a transversely excited atmospheric (TEA) CO2 laser. The powder was homogeneously mixed with Si grease, and the mixed powder was painted on a metal subtarget. When a TEA CO2 laser was directly focused on the metal subtarget at atmospheric pressure of He gas, a high-temperature He gas plasma was induced. It is assumed that the powder particles were vaporized to be effectively atomized and excited in the gas plasma region. This method has been employed in the rapid analyses of elements in organic and inorganic powder samples present in small quantities. Detection of trace elements of Cr and Pb has been successfully made by using the supplement powder and loam soil, respectively. The detection limits of Pb in loam soil were approximately 20 mg/kg.

  19. Study on the fabrication of low-pass metal powder filters for use at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Lee, Sung Hoon; Lee, Soon-Gul

    2016-08-01

    We fabricated compact low-pass stainless-steel powder filters for use in low-noise measurements at cryogenic temperatures and investigated their attenuation characteristics for different wire lengths, filter shapes, and preparation methods at frequencies up to 20 GHz. We used nominally 30- μm-sized SUS 304L powder and mixed it with Stycast 2850FT (Emerson and Cumming) with catalyst 23LV. A 0.1-mm insulated copper wire was wound on preformed powder-mixture spools in the shape of a right-circular cylinder, a flattened elliptic cylinder and a toroid, and the coils were encapsulated in metal tubes or boxes filled with the powder mixture. All the fabricated powder filters showed a large attenuation at high frequencies with a cut-off frequency near 1 GHz. However, the toroidal filter showed prominent ripples corresponding to resonance modes in the 0.5-m-long coil wire. A filter with a 2:1 powder/epoxy mixture mass ratio and a wire length of 1.53 m showed an attenuation of -93 dB at 4 GHz, and the attenuation was linearly proportional to the wire's length. As the powder-to-epoxy ratio was increased, the high-frequency attenuation increased. An equally-spaced single-layer coil structure was found to be more efficient in attenuation than a double-layer coil. The geometry of the metal filter's case affected the noise ripples, with the least noise being found for a circular tube.

  20. Soft magnetic composites manufactured by warm co-extrusion of bulk metallic glass and steel powders

    SciTech Connect

    Johnson, Francis; Raber, Thomas R.; Zabala, Robert J.; Buresh, Steve J.; Tanico, Brian

    2013-05-07

    Soft magnetic composites of Fe-based bulk metallic glass and low-alloy steel have been manufactured by warm co-extrusion of precursor powders at temperatures within the supercooled liquid region of the glass. Composites were manufactured with amorphous volume fractions of 75%, 67%, and 100%. Full consolidation of the constituent powders was observed with the bulk metallic glass remaining substantially amorphous. The composite electrical resistivity was observed to be anisotropic with a resistivity of 79 {mu}{Omega} cm measured transverse to the extrusion axis in a sample with 75% amorphous volume fraction. A 0-3 connectivity pattern with the low-resistivity steel phase embedded in a 3-dimensionally connected high-resistivity bulk metallic glass phase was observed with scanning electron microscopy. This confirms that the flow characteristics of the bulk metallic glass and the steel powders were comparable during extrusion at these temperatures. The saturation magnetization of 1.3 T was consistent with the volume weighted average of the saturation magnetization of the two phases. A relatively high quasistatic coercivity of 8 Oe was measured and is likely due to slight crystallization of the bulk metallic glass as well as domain wall pinning at prior particle boundaries. Careful control of the thermal environment during the extrusion process is required to minimize glass crystallization and achieve the desired balance of magnetic and electrical properties.

  1. Soft magnetic composites manufactured by warm co-extrusion of bulk metallic glass and steel powders

    NASA Astrophysics Data System (ADS)

    Johnson, Francis; Raber, Thomas R.; Zabala, Robert J.; Buresh, Steve J.; Tanico, Brian

    2013-05-01

    Soft magnetic composites of Fe-based bulk metallic glass and low-alloy steel have been manufactured by warm co-extrusion of precursor powders at temperatures within the supercooled liquid region of the glass. Composites were manufactured with amorphous volume fractions of 75%, 67%, and 100%. Full consolidation of the constituent powders was observed with the bulk metallic glass remaining substantially amorphous. The composite electrical resistivity was observed to be anisotropic with a resistivity of 79 μΩ cm measured transverse to the extrusion axis in a sample with 75% amorphous volume fraction. A 0-3 connectivity pattern with the low-resistivity steel phase embedded in a 3-dimensionally connected high-resistivity bulk metallic glass phase was observed with scanning electron microscopy. This confirms that the flow characteristics of the bulk metallic glass and the steel powders were comparable during extrusion at these temperatures. The saturation magnetization of 1.3 T was consistent with the volume weighted average of the saturation magnetization of the two phases. A relatively high quasistatic coercivity of 8 Oe was measured and is likely due to slight crystallization of the bulk metallic glass as well as domain wall pinning at prior particle boundaries. Careful control of the thermal environment during the extrusion process is required to minimize glass crystallization and achieve the desired balance of magnetic and electrical properties.

  2. Insertion and confinement of hydrophobic metallic powder in water: The bubble-marble effect

    NASA Astrophysics Data System (ADS)

    Meir, Yehuda; Jerby, Eli

    2014-09-01

    Metallic powders such as thermite are known as efficient fuels also applicable in oxygen-free environments. However, due to their hydrophobicity, they hardly penetrate into water. This paper presents an effect that enables the insertion and confinement of hydrophobic metallic powders in water, based on encapsulating an air bubble surrounded by a hydrophobic metallic shell. This effect, regarded as an inverse of the known liquid-marble effect, is named here "bubble marble" (BM). The sole BM is demonstrated experimentally as a stable, maneuverable, and controllable soft-solid-like structure, in a slightly deformed hollow spherical shape of ˜1-cm diameter. In addition to experimental and theoretical BM aspects, this paper also demonstrates its potential for underwater applications, such as transportation of solid objects within BM and underwater combustion of thermite BM by localized microwaves. Hence, the BM phenomena may open new possibilities for heat and thrust generation, as well as material processing and mass transfer underwater.

  3. Insertion and confinement of hydrophobic metallic powder in water: the bubble-marble effect.

    PubMed

    Meir, Yehuda; Jerby, Eli

    2014-09-01

    Metallic powders such as thermite are known as efficient fuels also applicable in oxygen-free environments. However, due to their hydrophobicity, they hardly penetrate into water. This paper presents an effect that enables the insertion and confinement of hydrophobic metallic powders in water, based on encapsulating an air bubble surrounded by a hydrophobic metallic shell. This effect, regarded as an inverse of the known liquid-marble effect, is named here "bubble marble" (BM). The sole BM is demonstrated experimentally as a stable, maneuverable, and controllable soft-solid-like structure, in a slightly deformed hollow spherical shape of ∼1-cm diameter. In addition to experimental and theoretical BM aspects, this paper also demonstrates its potential for underwater applications, such as transportation of solid objects within BM and underwater combustion of thermite BM by localized microwaves. Hence, the BM phenomena may open new possibilities for heat and thrust generation, as well as material processing and mass transfer underwater.

  4. Nuclear Rocket Ceramic Metal Fuel Fabrication Using Tungsten Powder Coating and Spark Plasma Sintering

    NASA Technical Reports Server (NTRS)

    Barnes, M. W.; Tucker, D. S.; Hone, L.; Cook, S.

    2017-01-01

    Nuclear thermal propulsion is an enabling technology for crewed Mars missions. An investigation was conducted to evaluate spark plasma sintering (SPS) as a method to produce tungsten-depleted uranium dioxide (W-dUO2) fuel material when employing fuel particles that were tungsten powder coated. Ceramic metal fuel wafers were produced from a blend of W-60vol% dUO2 powder that was sintered via SPS. The maximum sintering temperatures were varied from 1,600 to 1,850 C while applying a 50-MPa axial load. Wafers exhibited high density (>95% of theoretical) and a uniform microstructure (fuel particles uniformly dispersed throughout tungsten matrix).

  5. Progressive Powder Coating: New Infrared Curing Oven at Metal Finishing Plant Increases Production by 50%

    SciTech Connect

    2003-05-01

    Progressive Powder Coating in Mentor, Ohio, is a metal finishing plant that uses a convection oven in its manufacturing process. In an effort to save energy and improve production, the company installed an infrared oven in between the powder coating booth and the convection oven on its production line. This installation allowed the plant to increase its conveyor line speed and increase production by 50 percent. In addition, the plant reduced its natural gas consumption, yielding annual energy savings of approximately $54,000. With a total project cost of $136,000, the simple payback is 2.5 years.

  6. Progressive Powder Coating: New Infrared Curing Oven at Metal Finishing Plant Increases Production by 50%

    SciTech Connect

    Not Available

    2003-05-01

    Progressive Powder Coating in Mentor, Ohio, is a metal finishing plant that uses a convection oven in its manufacturing process. In an effort to save energy and improve production, the company installed an infrared oven in between the powder coating booth and the convection oven on its production line. This installation allowed the plant to increase its conveyor line speed and increase production by 50 percent. In addition, the plant reduced its natural gas consumption, yielding annual energy savings of approximately$54,000. With a total project cost of$136,000, the simple payback is 2.5 years.

  7. Preparation of mixed metal thin films by a PVD method using several kinds of powder targets

    NASA Astrophysics Data System (ADS)

    Suda, Yoshiaki; Kawasaki, Hiroharu; Ohshima, Tamiko; Yagyu, Yoshihito; Ihara, Takeshi; Yamauchi, Makiko; Plasma process; application Team

    2015-09-01

    Bismuth iron garnet (Bi3Fe5O12) and aluminum doped zinc oxide (AZO) thin films were prepared by a physical vapor deposition method using mixed metal powder targets. The X-ray powder diffraction and X-ray photoelectron spectroscopy results suggest that crystalline thin films can be prepared using powder targets with quality similar to that of the films prepared using bulk targets. Bi3Fe5O12 films prepared using the pulsed laser deposition method were Bi rich, which may be due to the lower melting temperature of Bi (544 K) compared with that of Fe (1811 K). The mean transparency and resistivity of the AZO films prepared by the sputtering method were approximately 79%-84% and 0.5 - 1.4 ohm/cm, respectively.

  8. Hyperfine interaction in hydrogenated graphene

    NASA Astrophysics Data System (ADS)

    Garcia, Noel; Melle, Manuel; Fernandez-Rossier, Joaquin

    We study the hyperfine interaction of Hydrogen chemisorbed in graphene nanostructures with a gap in their spectrum, such as islands and ribbons. Chemisorption of Hydrogen on graphene results in a bound in-gap state that hosts a single electron localized around the adatom. Using both density functional theory and a four-orbital tight-binding model we study the hyperfine interaction between the hydrogen nuclear spin and the conduction electrons in graphene. We find that the strength of the hyperfine interaction decreases for larger nanostructures for which the energy gap is smaller. We then compare the results of the hyperfine interaction for large nanostructures with those of graphene 2D crystal with a periodic arrangement of chemisorbed Hydrogen atoms, obtaining very similar results. The magnitude of the hyperfine interaction is about 150 MHz, in line with that of Si:P. We acknowledge financial support by Marie-Curie-ITN 607904-SPINOGRAPH.

  9. Improvement on ball-milling composite process of metal matrix micro-nanometer powder using nanosuspension as the precursor

    NASA Astrophysics Data System (ADS)

    Wang, Hongyu; Zhou, Jianzhong; Li, Xiangfeng; Shen, Qing; Cheng, Man

    2014-12-01

    The wet ball-milling preparation of metal matrix micro-nanometer powder using nanosuspension as the precursor can well solve the agglomeration of nanoscale component, but the micro-nanometer powder prepared by the method can hardly meet the requirement of powder feeding in laser cladding process and its composite effect is still not desirable enough. Aiming at the problem, the ball-milling composite process of metal matrix micro-nanometer powder using nanosuspension as the precursor was analyzed. It has been found that the morphological diversity of original micron powder is the main influencing factor of the deliverability and the composite effect of micro-nanometer powder. In addition, the deposition of the compounding powder in the bottom of ball-milling tank also has some negative influences on the composite effect. Accordingly, two improving measures namely the micron powder pretreatment with Ball Mill Reshaping + Screening and the additional stirring during ball-milling process are proposed and experimented. Results show that the micron powder pretreatment could significantly improve the composite effect and the deliverability of micro-nanometer powder, and the additional stirring could further improve the composite effect of micro-nanometer powder.

  10. Metal Matrix Composites Deposition in Twin Wire Arc Spraying Utilizing an External Powder Injection Composition

    NASA Astrophysics Data System (ADS)

    Tillmann, W.; Abdulgader, M.; Hagen, L.; Nellesen, J.

    2014-01-01

    The powder injection parameters, the location of the injection port, as well as the metal matrix composites are important features, which determine the deposition efficiency and embedding behavior of hard materials in the surrounding matrix of the twin wire arc-spraying process. This study investigates the applicability of external powder injection and aims to determine whether the powder injection parameters, the location, and the material combination (composition of the matrix as well as hard material) need to be specifically tailored. Therefore, the position of the injection port in relation to the arc zone was altered along the spraying axis and perpendicular to the arc. The axial position of the injection port determines the thermal activation of the injected powder. An injection behind the arc, close to the nozzle outlet, seems to enhance the thermal activation. The optimal injection positions of different hard materials in combination with zinc-, nickel- and iron-based matrices were found to be closer to the arc zone utilizing a high-speed camera system. The powder size, the mass of the particle, the carrier gas flow, and the electric insulation of the hard material affect the perpendicular position of the radial injection port. These findings show that the local powder injection, the wetting behavior of particles in the realm of the molten pool as well as the atomization behavior of the molten pool all affect the embedding behavior of the hard material in the surrounded metallic matrix. Hardness measurement by means of nanoindentation and EDX analysis along transition zones were utilized to estimate the bonding strength. The observation of a diffusion zone indicates a strong metallurgical bonding for boron carbides embedded in steel matrix.

  11. Experimental Study on Tensile Properties of a Novel Porous Metal Fiber/Powder Sintered Composite Sheet

    PubMed Central

    Zou, Shuiping; Wan, Zhenping; Lu, Longsheng; Tang, Yong

    2016-01-01

    A novel porous metal fiber/powder sintered composite sheet (PMFPSCS) is developed by sintering a mixture of a porous metal fiber sintered sheet (PMFSS) and copper powders with particles of a spherical shape. The characteristics of the PMFPSCS including its microstructure, sintering density and porosity are investigated. A uniaxial tensile test is carried out to study the tensile behaviors of the PMFPSCS. The deformation and failure mechanisms of the PMFSCS are discussed. Experimental results show that the PMFPSCS successively experiences an elastic stage, hardening stage, and fracture stage under tension. The tensile strength of the PMFPSCS is determined by a reticulated skeleton of fibers and reinforcement of copper powders. With the porosity of the PMFSS increasing, the tensile strength of the PMFPSCS decreases, whereas the reinforcement of copper powders increases. At the elastic stage, the structural elastic deformation is dominant, and at the hardening stage, the plastic deformation is composed of the structural deformation and the copper fibers’ plastic deformation. The fracture of the PMFPSCS is mainly caused by the breaking of sintering joints. PMID:28773833

  12. Metal solubilization from powdered printed circuit boards by microbial consortium from bauxite and pyrite ores.

    PubMed

    Adhapure, N N; Waghmare, S S; Hamde, V S; Deshmukh, A M

    2013-01-01

    With the current rapid developments in technology, there is an increasing accumulation of outdated electronic equipment. The primary reason for this increase is the low rate of recycling due to the complex nature of such waste. Bioleaching offers a promising solution for this problem. Study was conducted on the solubilization of heavy metals from electronic waste (e-waste). For this purpose, a microbial consortium from bauxite and pyrite ore samples was obtained using a simple "top down" approach. Essentially, printed circuit boards (PCB) were obtained and used as representative samples of e-waste. Various concentrations (1-5%) of PCB powder were subjected to bioleaching, and the effects on metal solubilization, changes in pH and concentration of ferrous iron produced were assessed. It was observed that a maximum of 96.93% Cu and 93.33% Zn was solubilized by microbial consortium from 10 g/l of PCB powder, whereas only 10.26% Ni was solubilized from 30 g/l of PCB powder. For lead, only 0.58% solubilization was achieved from 20 g/l of PCB powder. An analysis of the precipitate formed during bioleaching using scanning electron microscopy with energy dispersive x-ray analysis revealed the presence of Tin (59.96%), Cu (23.97%), Pb (9.30%) and Fe (5.92%).

  13. Mechanical properties of metals for biomedical applications using powder metallurgy process: A review

    NASA Astrophysics Data System (ADS)

    Dewidar, Montasser Marasy; Yoon, Ho-Chel; Lim, Jae Kyoo

    2006-06-01

    The uses of biomaterials have been revolutionizing the biomedical field in deployment as implants for humans. During the past five decades, many implant materials made of metals have been put into practical use. Powder metallurgy techniques have been used to produce controlled porous structures, such as porous coatings applied for dental and orthopedic surgical implants, which allow bony tissue ingrowth within the implant surface, thereby improving fixation. This paper examines various important metals using powder metallurgy technology to produce elements of a total hip replacement. These alloys are 316L stainless steel alloy, Co-Cr-Mo alloy, and Ti-6Al-4V alloy. Also, this paper examines current information on the mechanical properties. Mechanical properties are discussed as a function of type of materials and process of fabrication. This article addresses the engineering aspects concerning the advantages and disadvantages of each type of material.

  14. Assembled camshaft for I. C. engines with forged powder metal cams

    SciTech Connect

    Lugosi, R.; Brauer, M.; Cook, J.

    1987-01-01

    A key element in the Automotive Industry's efforts to improve fuel economy and engine performance is the introduction of roller tappets to reduce friction in valve trains. As a result, contact stresses in excess of 200,000 psi may be experienced at the roller and cam (shaft) interface. Conventional cast iron camshafts cannot effectively carry this stress level. After studying several alternatives, the authors have developed a camshaft which promises to be a viable solution to the problem, both technically and economically. The purpose of this work was to demonstrate the acceptable wear performance of an assembled camshaft containing forged powder metal lobes in a series of motored engine tests with roller hydraulic valve train. In this study, a camshaft consisting of a carbon steel tube and forged powder metal lobes (4660 composition) joined by brazing was tested at low speed and at high speed in a motored engine at approximately 250,000 psi maximum contact stress.

  15. Crystal structure and magnetic properties of Nd2Fe14B powder prepared by using high energy milling from elements metal Nd,Fe,B powders

    NASA Astrophysics Data System (ADS)

    Ramlan; Muljadi; Sardjono, P.; Gulo, F.; Setiabudidaya, D.

    2016-11-01

    The Nd2Fe14B powder has been made by using High Energy Milling (HEM) from mixed metal powders Iron (Fe), Neodymium (Nd) and Boron (B). The Nd, Fe and B powders were mixed according stoichiometric composition (atomic ratio Nd:Fe:B = 2: 14: 1) and milled and milling time was varied in 10, 20, and 40 hours by using HEM. Toluene liquid was used as milling media to protect of metal powders from oxygen. The measurement result of x- ray diffraction show that the optimum Nd2Fe14B phase already formed about 69,46% after milling 40 hours with crystallite size about 25.64 nm. The magnetic properties of milled powders were measured by using VSM at room temperature. The highest value of magnetic properties are obtained at powder milled in 40 hours, at this condition, it is obtained Ms = 122 emu/g, Mr = 81 emu/g, Hc = 5.54 kOe and BHmax = 11.01 MGOe.

  16. Metal vapor micro-jet controls material redistribution in laser powder bed fusion additive manufacturing

    DOE PAGES

    Ly, Sonny; Rubenchik, Alexander M.; Khairallah, Saad A.; ...

    2017-06-22

    The results of detailed experiments and finite element modeling of metal micro-droplet motion associated with metal additive manufacturing (AM) processes are presented. Ultra high speed imaging of melt pool dynamics reveals that the dominant mechanism leading to micro-droplet ejection in a laser powder bed fusion AM is not from laser induced recoil pressure as is widely believed and found in laser welding processes, but rather from vapor driven entrainment of micro-particles by an ambient gas flow. The physics of droplet ejection under strong evaporative flow is described using simulations of the laser powder bed interactions to elucidate the experimental results.more » Hydrodynamic drag analysis is used to augment the single phase flow model and explain the entrainment phenomenon for 316 L stainless steel and Ti-6Al-4V powder layers. The relevance of vapor driven entrainment of metal micro-particles to similar fluid dynamic studies in other fields of science will be discussed.« less

  17. Preparation of micro-foils for TEM/STEM analysis from metallic powders.

    PubMed

    Dawson, Karl; Tatlock, Gordon J

    2015-07-01

    A technique has been developed which facilitates the preparation of electro-polished micro-foil transmission electron microscopy (TEM) specimens, which have previously been machined out of ≈100 μm diameter metallic powder particles using a Focussed Ion Beam (FIB) instrument. The technique can be used to create small volume TEM specimens from most metallic powder particles and bulk metal samples. This is especially useful when the matrices are ferritic steels, which are often difficult to image in the electron microscope, since the necessary aberration corrections change as the sample is tilted in the magnetic field of the objective lens. Small samples, such as powder particles, were attached to gold support grids using deposited platinum and were then ion milled to approximately 2 μm thickness in a focussed ion beam (FIB) instrument. Subsequently, the specimen assemblies were electropolished for short durations under standard conditions, to produce large (5 μm×5 μm) electron transparent regions of material. The specimens produced by this technique were free from FIB related artefacts and facilitated atomic resolution scanning-TEM (STEM) imaging of ferritic and nickel matrices containing, for example, yttrium rich oxide nano-dispersoids. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Application of Freeze-Dried Powders of Genetically Engineered Microbial Strains as Adsorbents for Rare Earth Metal Ions.

    PubMed

    Moriwaki, Hiroshi; Masuda, Reiko; Yamazaki, Yuki; Horiuchi, Kaoru; Miyashita, Mari; Kasahara, Jun; Tanaka, Tatsuhito; Yamamoto, Hiroki

    2016-10-12

    The adsorption behaviors of the rare earth metal ions onto freeze-dried powders of genetically engineered microbial strains were compared. Cell powders obtained from four kinds of strains, Bacillus subtilis 168 wild type (WT), lipoteichoic acid-defective (ΔLTA), wall teichoic acid-defective (ΔWTA), and cell wall hydrolases-defective (EFKYOJLp) strains, were used as an adsorbent of the rare earth metal ions at pH 3. The adsorption ability of the rare earth metal ions was in the order of EFKYOJLp > WT > ΔLTA > ΔWTA. The order was the same as the order of the phosphorus quantity of the strains. This result indicates that the main adsorption sites for the ions are the phosphate groups and the teichoic acids, LTA and WTA, that contribute to the adsorption of the rare earth metal ions onto the cell walls. The contribution of WTA was clearly greater than that of LTA. Each microbial powder was added to a solution containing 16 kinds of rare earth metal ions, and the removals (%) of each rare earth metal ion were obtained. The scandium ion showed the highest removal (%), while that of the lanthanum ion was the lowest for all the microbial powders. Differences in the distribution coefficients between the kinds of lanthanide ions by the EFKYOJLp and ΔWTA powders were greater than those of the other strains. Therefore, the EFKYOJLp and ΔWTA powders could be applicable for the selective extraction of the lanthanide ions. The ΔLTA powder coagulated by mixing with a rare earth metal ion, although no sedimentation of the WT or ΔWTA powder with a rare earth metal ion was observed under the same conditions. The EFKYOJLp powder was also coagulated, but its flocculating activity was lower than that of ΔLTA. The ΔLTA and EFKYOJLp powders have a long shape compared to those of the WT or ΔWTA strain. The shapes of the cells will play an important role in the sedimentation of the microbial powders with rare earth metal ions. As the results, three kinds of the genetically

  19. Alumina coating on dense tungsten powder by fluidized bed metal organic chemical vapour deposition.

    PubMed

    Rodriguez, Philippe; Caussat, Brigitte; Ablitzer, Carine; Iltis, Xavière; Brothier, Meryl

    2011-09-01

    In order to study the feasibility of coating very dense powders by alumina using Fluidized Bed Metal Organic Chemical Vapour Deposition (FB-MOCVD), experiments were performed on a commercial tungsten powder, 75 microm in median volume diameter and 19,300 kg/m3 in grain density. The first part of the work was dedicated to the experimental study of the tungsten powder fluidization using argon as carrier gas at room temperature and at 400 degrees C. Due to the very high density of the tungsten powder, leading to low initial fixed bed heights and low bed expansions, different weights of powder were tested in order to reach satisfactory temperature profiles along the fluidized bed. Then, using argon as a fluidized bed former and aluminium acetylacetonate Al(C5O2H7)3 as a single source precursor, alumina thin films were deposited on tungsten particles at a low temperature range (e.g., 370-420 degrees C) by FB-MOCVD. The influence of the weight of powder, bed temperature and run duration was studied. Characterizations of the obtained samples were performed by various techniques including scanning electron microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS) analyses, Field Emission Gun SEM (FEG-SEM) and Fourier Transform InfraRed (FT-IR) spectroscopy. The different analyses indicated that tungsten particles were uniformly coated by a continuous alumina thin film. The thickness of the film ranged between 25 and 80 nm, depending on the coating conditions. The alumina thin films were amorphous and contained carbon contamination. This latter may correspond to the adsorption of species resulting from incomplete decomposition of the precursor at so low deposition temperature.

  20. Revisiting formic acid decomposition on metallic powder catalysts: Exploding the HCOOH decomposition volcano curve

    NASA Astrophysics Data System (ADS)

    Tang, Yadan; Roberts, Charles A.; Perkins, Ryan T.; Wachs, Israel E.

    2016-08-01

    This study revisits the classic volcano curve for HCOOH decomposition by metal catalysts by taking a modern catalysis approach. The metal catalysts (Au, Ag, Cu, Pt, Pd, Ni, Rh, Co and Fe) were prepared by H2 reduction of the corresponding metal oxides. The number of surface active sites (Ns) was determined by formic acid chemisorption. In situ IR indicated that both monodentate and bidentate/bridged surface HCOO* were present on the metals. Heats of adsorption (ΔHads) for surface HCOO* values on metals were taken from recently reported DFT calculations. Kinetics for surface HCOO* decomposition (krds) were determined with TPD spectroscopy. Steady-state specific activity (TOF = activity/Ns) for HCOOH decomposition over the metals was calculated from steady-state activity (μmol/g-s) and Ns (μmol/g). Steady-state TOFs for HCOOH decomposition weakly correlated with surface HCOO* decomposition kinetics (krds) and ΔHads of surface HCOO* intermediates. The plot of TOF vs. ΔHads for HCOOH decomposition on metal catalysts does not reproduce the classic volcano curve, but shows that TOF depends on both ΔHads and decomposition kinetics (krds) of surface HCOO* intermediates. This is the first time that the classic catalysis study of HCOOH decomposition on metallic powder catalysts has been repeated since its original publication.

  1. Adsorption of heavy metal from aqueous solution by dehydrated root powder of long-root Eichhornia crassipes.

    PubMed

    Li, Qiang; Chen, Bo; Lin, Peng; Zhou, Jiali; Zhan, Juhong; Shen, Qiuying; Pan, Xuejun

    2016-01-01

    The root powder of long-root Eichhornia crassipes, as a new kind of biodegradable adsorbent, has been tested for aqueous adsorption of Pb, Zn, Cu, and Cd. From FT-IR, we found that the absorption peaks of phosphorous compounds, carbonyl, and nitrogenous compounds displayed obvious changes before and after adsorption which illustrated that plant characteristics may play a role in binding with metals. Surface properties and morphology of the root powders have been characterized by means of SEM and BET. Energy spectrum analysis showed that the metals were adsorbed on root powders after adsorption. Then, optimum quantity of powder, pH values, and metal ion concentrations in single-system and multi-system were detected to discuss the characteristics and mechanisms of metal adsorption. Freundlich model and the second-order kinetics equation could well describe the adsorption of heavy metals in single-metal system. The adsorption of Pb, Zn, and Cd in the multi-metal system decreased with the concentration increased. At last, competitive adsorption of every two metals on root powder proved that Cu and Pb had suppressed the adsorption performance of Cd and Zn.

  2. Fabrication of metal matrix composite by semi-solid powder processing

    SciTech Connect

    Wu, Yufeng

    2011-01-01

    Various metal matrix composites (MMCs) are widely used in the automotive, aerospace and electrical industries due to their capability and flexibility in improving the mechanical, thermal and electrical properties of a component. However, current manufacturing technologies may suffer from insufficient process stability and reliability and inadequate economic efficiency and may not be able to satisfy the increasing demands placed on MMCs. Semi-solid powder processing (SPP), a technology that combines traditional powder metallurgy and semi-solid forming methods, has potential to produce MMCs with low cost and high efficiency. In this work, the analytical study and experimental investigation of SPP on the fabrication of MMCs were explored. An analytical model was developed to understand the deformation mechanism of the powder compact in the semi-solid state. The densification behavior of the Al6061 and SiC powder mixtures was investigated with different liquid fractions and SiC volume fractions. The limits of SPP were analyzed in terms of reinforcement phase loading and its impact on the composite microstructure. To explore adoption of new materials, carbon nanotube (CNT) was investigated as a reinforcing material in aluminum matrix using SPP. The process was successfully modeled for the mono-phase powder (Al6061) compaction and the density and density distribution were predicted. The deformation mechanism at low and high liquid fractions was discussed. In addition, the compaction behavior of the ceramic-metal powder mixture was understood, and the SiC loading limit was identified by parametric study. For the fabrication of CNT reinforced Al6061 composite, the mechanical alloying of Al6061-CNT powders was first investigated. A mathematical model was developed to predict the CNT length change during the mechanical alloying process. The effects of mechanical alloying time and processing temperature during SPP were studied on the mechanical, microstructural and

  3. Numerical modeling of sintering of two-component metal powders with laser beams

    NASA Astrophysics Data System (ADS)

    Niziev, V. G.; Koldoba, A. V.; Mirzade, F. Kh.; Panchenko, V. Ya.; Poveschenko, Yu. A.; Popov, M. V.

    2010-09-01

    Direct laser sintering of a mixture of two metal powders with significantly different melting points is investigated by numerical simulation. The model is based on self-consistent non-linear continuity equations for volume fractions of components and on energy transfer equations for the powder mixture. It includes the movement of the solid particles due to shrinkage because of the density change of the powder mixture and the liquid flow driven by the capillary and gravity forces. The liquid flow is determined by Darcy's law. The effect of surface settlement of the powder is obtained. The width increasing rate of the melting zone depend both on the parameters of the laser radiation (on the power of the beam) and on the physical parameters of the particle's material, and it increases with the increasing of the penetrability or the increasing of the phase-transition heat. The increasing of the laser power under other factors being equal results in the acceleration of the melting front propagation.

  4. Numerical modeling of sintering of two-component metal powders with laser beams

    NASA Astrophysics Data System (ADS)

    Niziev, V. G.; Koldoba, A. V.; Mirzade, F. Kh.; Panchenko, V. Ya.; Poveschenko, Yu. A.; Popov, M. V.

    2011-02-01

    Direct laser sintering of a mixture of two metal powders with significantly different melting points is investigated by numerical simulation. The model is based on self-consistent non-linear continuity equations for volume fractions of components and on energy transfer equations for the powder mixture. It includes the movement of the solid particles due to shrinkage because of the density change of the powder mixture and the liquid flow driven by the capillary and gravity forces. The liquid flow is determined by Darcy's law. The effect of surface settlement of the powder is obtained. The width increasing rate of the melting zone depend both on the parameters of the laser radiation (on the power of the beam) and on the physical parameters of the particle's material, and it increases with the increasing of the penetrability or the increasing of the phase-transition heat. The increasing of the laser power under other factors being equal results in the acceleration of the melting front propagation.

  5. Fluctuating hyperfine interactions: computational implementation

    NASA Astrophysics Data System (ADS)

    Zacate, M. O.; Evenson, W. E.

    2010-04-01

    A library of computational routines has been created to assist in the analysis of stochastic models of hyperfine interactions. We call this library the stochastic hyperfine interactions modeling library (SHIML). It provides routines written in the C programming language that (1) read a text description of a model for fluctuating hyperfine fields, (2) set up the Blume matrix, upon which the evolution operator of the system depends, and (3) find the eigenvalues and eigenvectors of the Blume matrix so that theoretical spectra of experimental hyperfine interaction measurements can be calculated. Example model calculations are included in the SHIML package to illustrate its use and to generate perturbed angular correlation spectra for the special case of polycrystalline samples when anisotropy terms of higher order than A22 can be neglected.

  6. Displacement method and apparatus for reducing passivated metal powders and metal oxides

    DOEpatents

    Morrell; Jonathan S. , Ripley; Edward B.

    2009-05-05

    A method of reducing target metal oxides and passivated metals to their metallic state. A reduction reaction is used, often combined with a flux agent to enhance separation of the reaction products. Thermal energy in the form of conventional furnace, infrared, or microwave heating may be applied in combination with the reduction reaction.

  7. Numerical modeling of heat transfer and fluid flow in laser metal deposition by powder injection

    NASA Astrophysics Data System (ADS)

    Fan, Zhiqiang

    Laser metal deposition is an additive manufacturing technique which allows quick fabrication of fully-dense metallic components directly from Computer Aided Design (CAD) solid models. A self-consistent three-dimensional model was developed for the laser metal deposition process by powder injection, which simulates heat transfer, phase changes, and fluid flow in the melt pool. The governing equations for solid, liquid and gas phases in the calculation domain have been formulated using the continuum model. The free surface in the melt pool has been tracked by the Volume of Fluid (VOF) method, while the VOF transport equation was solved using the Piecewise Linear Interface Calculation (PLIC) method. Surface tension was modeled by taking the Continuum Surface Force (CSF) model combined with a force-balance flow algorithm. Laser-powder interaction was modeled to account for the effects of laser power attenuation and powder temperature rise during the laser metal deposition process. The governing equations were discretized in the physical space using the finite volume method. The advection terms were approximated using the MUSCL flux limiter scheme. The fluid flow and energy equations were solved in a coupled manner. The incompressible flow equations were solved using a two-step projection method, which requires a solution of a Poisson equation for the pressure field. The discretized pressure Poisson equation was solved using the ICCG (Incomplete Cholesky Conjugate Gradient) solution technique. The energy equation was solved by an enthalpy-based method. Temperature-dependent thermal-physical material properties were considered in the numerical implementation. The numerical model was validated by comparing simulations with experimental measurements.

  8. Surface characterization of Ti and Ti (6 percent, Al-4 percent, V) metal powders and interaction with primer solutions

    NASA Technical Reports Server (NTRS)

    Siriwardane, R. V.; Wightman, J. P.

    1983-01-01

    The interaction of Ti and Ti 6-4 powders with water and primer solutions was investigated experimentally by measuring the heats of immersion. Similar comparative studies were made on anatase and rutile TiO2 powders. The surface oxide layers of Ti and Ti 6-4 cracked on heating in vacuum between 300 and 400 C as evidenced by high heats of immersion in both water and primer solutions. Polyimide and polyphenylquinoxaline interacted preferentially, compared with the solvents with both metal powders after outgassing at room temperature. The heats of immersion of Ti 6-4 in water, solvents, and primer solutions increased significantly after pretreatment of the powder by an alkaline etch and a phosphate-fluoride process. The TiO2 powders were not satisfactory models for the surface oxide layer on either Ti or Ti 6-4 powder.

  9. Facile synthesis of Curcuma longa tuber powder engineered metal nanoparticles for bioimaging applications

    NASA Astrophysics Data System (ADS)

    Sankar, Renu; Rahman, Pattanathu K. S. M.; Varunkumar, Krishnamoorthy; Anusha, Chidambaram; Kalaiarasi, Arunachalam; Shivashangari, Kanchi Subramanian; Ravikumar, Vilwanathan

    2017-02-01

    Nanomaterials based fluorescent agents are rapidly becoming significant and promising transformative tools for improving medical diagnostics for extensive in vivo imaging modalities. Compared with conventional fluorescent agents, nano-fluorescence has capabilities to improve the in vivo detection and enriched targeting efficiencies. In our laboratory we synthesized fluorescent metal nanoparticles of silver, copper and iron using Curcuma longa tuber powder by simple reduction. The physicochemical properties of the synthesized metal nanoparticles were attained using UV-visible spectrophotometry, scanning electron microscopy with EDAX spectroscopy, dynamic light scattering, Fourier-transform infrared spectroscopy and X-ray diffraction. The Curcuma longa tuber powder has one of the bioactive compound Curcumin might act as a capping agent during the synthesis of nanoparticles. The synthesized metal nanoparticles fluorescence property was confirmed by spectrofluorometry. When compared with copper and iron nanoparticles the silver nanoparticles showed high fluorescence intensity under spectrofluorometry. Moreover, in vitro cell images of the silver nanoparticles in A549 cell lines also correlated with the results of spectrofluorometry. These silver nanoparticles show inspiring cell-imaging applications. They enter into cells without any further modifications, and the fluorescence property can be utilized for fluorescence-based cell imaging applications.

  10. Selective extraction and recovery of rare earth metals from phosphor powders in waste fluorescent lamps using an ionic liquid system.

    PubMed

    Yang, Fan; Kubota, Fukiko; Baba, Yuzo; Kamiya, Noriho; Goto, Masahiro

    2013-06-15

    The recycling of rare earth metals from phosphor powders in waste fluorescent lamps by solvent extraction using ionic liquids was studied. Acid leaching of rare earth metals from the waste phosphor powder was examined first. Yttrium (Y) and europium (Eu) dissolved readily in the acid solution; however, the leaching of other rare earth metals required substantial energy input. Ionization of target rare earth metals from the waste phosphor powders into the leach solution was critical for their successful recovery. As a high temperature was required for the complete leaching of all rare earth metals, ionic liquids, for which vapor pressure is negligible, were used as an alternative extracting phase to the conventional organic diluent. An extractant, N, N-dioctyldiglycol amic acid (DODGAA), which was recently developed, showed a high affinity for rare earth metal ions in liquid-liquid extraction although a conventional commercial phosphonic extractant did not. An effective recovery of the rare earth metals, Y, Eu, La and Ce, from the metal impurities, Fe, Al and Zn, was achieved from the acidic leach solution of phosphor powders using an ionic liquid containing DODGAA as novel extractant system. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Copper Benzenetricarboxylate Metal-Organic Framework Nucleation Mechanisms on Metal Oxide Powders and Thin Films formed by Atomic Layer Deposition.

    PubMed

    Lemaire, Paul C; Zhao, Junjie; Williams, Philip S; Walls, Howard J; Shepherd, Sarah D; Losego, Mark D; Peterson, Gregory W; Parsons, Gregory N

    2016-04-13

    Chemically functional microporous metal-organic framework (MOF) crystals are attractive for filtration and gas storage applications, and recent results show that they can be immobilized on high surface area substrates, such as fiber mats. However, fundamental knowledge is still lacking regarding initial key reaction steps in thin film MOF nucleation and growth. We find that thin inorganic nucleation layers formed by atomic layer deposition (ALD) can promote solvothermal growth of copper benzenetricarboxylate MOF (Cu-BTC) on various substrate surfaces. The nature of the ALD material affects the MOF nucleation time, crystal size and morphology, and the resulting MOF surface area per unit mass. To understand MOF nucleation mechanisms, we investigate detailed Cu-BTC MOF nucleation behavior on metal oxide powders and Al2O3, ZnO, and TiO2 layers formed by ALD on polypropylene substrates. Studying both combined and sequential MOF reactant exposure conditions, we find that during solvothermal synthesis ALD metal oxides can react with the MOF metal precursor to form double hydroxy salts that can further convert to Cu-BTC MOF. The acidic organic linker can also etch or react with the surface to form MOF from an oxide metal source, which can also function as a nucleation agent for Cu-BTC in the mixed solvothermal solution. We discuss the implications of these results for better controlled thin film MOF nucleation and growth.

  12. Biological responses of isolated macrophages to cobalt metal and tungsten carbide-cobalt powders.

    PubMed

    Lison, D; Lauwerys, R

    1991-10-01

    A previous study from this laboratory, using morphological and biochemical (LDH release) parameters, has shown that tungsten carbide-cobalt dust exhibits a greater cytotoxicity toward isolated macrophages than cobalt metal powder alone. The present study extends this comparison by examining additional biological parameters. Glucose uptake and superoxide anion production by isolated macrophages were significantly more depressed by the tungsten carbide-cobalt mixture (WC-Co) than by cobalt alone (Co) while pure tungsten carbide (WC) had no effect or even stimulated the cells. For glucose-6-phosphate dehydrogenase and cell-associated plasminogen activator (PA) activities, no difference between Co and WC-Co dusts was observed. These observations add further evidence to our previous findings regarding the different biological reactivity of cobalt metal alone or mixed with tungsten carbide.

  13. Atomic-layer electroless deposition: a scalable approach to surface-modified metal powders.

    PubMed

    Cappillino, Patrick J; Sugar, Joshua D; El Gabaly, Farid; Cai, Trevor Y; Liu, Zhi; Stickney, John L; Robinson, David B

    2014-04-29

    Palladium has a number of important applications in energy and catalysis in which there is evidence that surface modification leads to enhanced properties. A strategy for preparing such materials is needed that combines the properties of (i) scalability (especially on high-surface-area substrates, e.g. powders); (ii) uniform deposition, even on substrates with complex, three-dimensional features; and (iii) low-temperature processing conditions that preserve nanopores and other nanostructures. Presented herein is a method that exhibits these properties and makes use of benign reagents without the use of specialized equipment. By exposing Pd powder to dilute hydrogen in nitrogen gas, sacrificial surface PdH is formed along with a controlled amount of dilute interstitial hydride. The lattice expansion that occurs in Pd under higher H2 partial pressures is avoided. Once the flow of reagent gas is terminated, addition of metal salts facilitates controlled, electroless deposition of an overlayer of subnanometer thickness. This process can be cycled to create thicker layers. The approach is carried out under ambient processing conditions, which is an advantage over some forms of atomic layer deposition. The hydride-mediated reaction is electroless in that it has no need for connection to an external source of electrical current and is thus amenable to deposition on high-surface-area substrates having rich, nanoscale topography as well as on insulator-supported catalyst particles. STEM-EDS measurements show that conformal Rh and Pt surface layers can be formed on Pd powder with this method. A growth model based on energy-resolved XPS depth profiling of Rh-modified Pd powder is in general agreement. After two cycles, deposits are consistent with 70-80% coverage and a surface layer with a thickness from 4 to 8 Å.

  14. Stochastic hyperfine interactions modeling library

    NASA Astrophysics Data System (ADS)

    Zacate, Matthew O.; Evenson, William E.

    2011-04-01

    The stochastic hyperfine interactions modeling library (SHIML) provides a set of routines to assist in the development and application of stochastic models of hyperfine interactions. The library provides routines written in the C programming language that (1) read a text description of a model for fluctuating hyperfine fields, (2) set up the Blume matrix, upon which the evolution operator of the system depends, and (3) find the eigenvalues and eigenvectors of the Blume matrix so that theoretical spectra of experimental techniques that measure hyperfine interactions can be calculated. The optimized vector and matrix operations of the BLAS and LAPACK libraries are utilized; however, there was a need to develop supplementary code to find an orthonormal set of (left and right) eigenvectors of complex, non-Hermitian matrices. In addition, example code is provided to illustrate the use of SHIML to generate perturbed angular correlation spectra for the special case of polycrystalline samples when anisotropy terms of higher order than A can be neglected. Program summaryProgram title: SHIML Catalogue identifier: AEIF_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEIF_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU GPL 3 No. of lines in distributed program, including test data, etc.: 8224 No. of bytes in distributed program, including test data, etc.: 312 348 Distribution format: tar.gz Programming language: C Computer: Any Operating system: LINUX, OS X RAM: Varies Classification: 7.4 External routines: TAPP [1], BLAS [2], a C-interface to BLAS [3], and LAPACK [4] Nature of problem: In condensed matter systems, hyperfine methods such as nuclear magnetic resonance (NMR), Mössbauer effect (ME), muon spin rotation (μSR), and perturbed angular correlation spectroscopy (PAC) measure electronic and magnetic structure within Angstroms of nuclear probes through the hyperfine interaction. When

  15. Four Decades of Hyperfine Anomalies

    NASA Astrophysics Data System (ADS)

    Gustavsson, Martin G. H.; Mårtensson-Pendrill, Ann-Marie

    Isotopic differences in the distribution of nuclear charge and magnetization give rise to "hyperfine structure anomalies" which were observed already in the 1950s. More recently, the distribution of nuclear magnetization has been found to complicate the interpretation of the measured hyperfine splittings in highly charged hydrogen-like ions. In this paper, results of numerical calculations for a few hydrogen-like systems (133Cs, 165Ho, 185,187Re and 209Bi) of current experimental interest are presented in terms of moments of the nuclear charge and magnetization distribution, thereby displaying directly the sensitivity and emphasizing the need for a better understanding of nuclear wavefunctions. In addition, we also present results of many-body perturbation theory calculations for Cs hyperfine anomalies, in connection with experiments planned at ISOLDE.

  16. A brief survey of sensing for metal-based powder bed fusion additive manufacturing

    NASA Astrophysics Data System (ADS)

    Foster, Bryant K.; Reutzel, Edward W.; Nassar, Abdalla R.; Dickman, Corey J.; Hall, Benjamin T.

    2015-05-01

    Purpose - Powder bed fusion additive manufacturing (PBFAM) of metal components has attracted much attention, but the inability to quickly and easily ensure quality has limited its industrial use. Since the technology is currently being investigated for critical engineered components and is largely considered unsuitable for high volume production, traditional statistical quality control methods cannot be readily applied. An alternative strategy for quality control is to monitor the build in real time with a variety of sensing methods and, when possible, to correct any defects as they occur. This article reviews the cause of common defects in powder bed additive manufacturing, briefly surveys process monitoring strategies in the literature, and summarizes recently-developed strategies to monitor part quality during the build process. Design/methodology/approach - Factors that affect part quality in powder bed additive manufacturing are categorized as those influenced by machine variables and those affected by other build attributes. Within each category, multiple process monitoring methods are presented. Findings - A multitude of factors contribute to the overall quality of a part built using PBFAM. Rather than limiting processing to a pre-defined build recipe and assuming complete repeatability, part quality will be ensured by monitoring the process as it occurs and, when possible, altering the process conditions or build plan in real-time. Recent work shows promise in this area and brings us closer to the goal of wide-spread adoption of additive manufacturing technology. Originality/value - This work serves to introduce and define the possible sources of defects and errors in metal-based PBFAM, and surveys sensing and control methods which have recently been investigated to increase overall part quality. Emphasis has been placed on novel developments in the field and their contribution to the understanding of the additive manufacturing process.

  17. Fabrication of Ni-Nb-Sn metallic glassy alloy powder and its microwave-induced sintering behavior.

    PubMed

    Xie, Guoqiang; Li, Song; Louzguine-Luzgin, D V; Cao, Ziping; Yoshikawa, Noboru; Sato, Motoyasu; Inoue, Akihisa

    2009-01-01

    In the present study, we prepared Ni59.35Nb34.45Sn6.2 metallic glassy alloy powder by an argon gas atomization process. Microwave (MW)-induced heating and sintering was carried out by a single-mode 2.45 GHz MW applicator in the separated magnetic field or electric field using the obtained glassy powders. The structure and thermal stability of the sintered glassy alloy specimens were investigated.

  18. Bioaccessibility of micron-sized powder particles of molybdenum metal, iron metal, molybdenum oxides and ferromolybdenum--Importance of surface oxides.

    PubMed

    Mörsdorf, Alexander; Odnevall Wallinder, Inger; Hedberg, Yolanda

    2015-08-01

    The European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, that are manufactured, imported or used in different products (substances or articles) are identified and proven safe for humans and the environment. Metals and alloys need hence to be investigated on their extent of released metals (bioaccessibility) in biologically relevant environments. Read-across from available studies may be used for similar materials. This study investigates the release of molybdenum and iron from powder particles of molybdenum metal (Mo), a ferromolybdenum alloy (FeMo), an iron metal powder (Fe), MoO2, and MoO3 in different synthetic body fluids of pH ranging from 1.5 to 7.4 and of different composition. Spectroscopic tools and cyclic voltammetry have been employed to characterize surface oxides, microscopy, light scattering and nitrogen absorption for particle characterization, and atomic absorption spectroscopy to quantify released amounts of metals. The release of molybdenum from the Mo powder generally increased with pH and was influenced by the fluid composition. The mixed iron and molybdenum surface oxide of the FeMo powder acted as a barrier both at acidic and weakly alkaline conditions. These findings underline the importance of the surface oxide characteristics for the bioaccessibility of metal alloys.

  19. Variation of the shape and morphological properties of silica and metal oxide powders by electro homogeneous precipitation

    DOEpatents

    Harris, Michael T.; Basaran, Osman A.; Sisson, Warren G.; Brunson, Ronald R.

    1997-01-01

    The present invention provides a method for preparing irreversible linear aggregates (fibrils) of metal oxide powders by utilizing static or pulsed DC electrical fields across a relatively non-conducting liquid solvent in which organometal compounds or silicon alkoxides have been dissolved. The electric field is applied to the relatively non-conducting solution throughout the particle formation and growth process promoting the formation of either linear aggregates (fibrils) or spherical shaped particles as desired. Thus the present invention provides a physical method for altering the size, shape and porosity of precursor hydrous metal oxide or hydrous silicon oxide powders for the development of advanced ceramics with improved strength and insulating capacity.

  20. High-Temperature Solid Lubricant Coating by Plasma Spraying Using Metal-Metal Clad Powders

    NASA Astrophysics Data System (ADS)

    Zhang, Tiantian; Lan, Hao; Yu, Shouquan; Huang, Chuanbing; Du, Lingzhong; Zhang, Weigang

    2017-08-01

    NiCr/Ag-Mo composite coating was fabricated by atmospheric plasma spray technology using clad powders as the feedstock. Its tribological properties at variable temperature were evaluated using a ball-on-disk high-temperature tribometer in air. The results showed that compared with NiCr, the NiCr/Ag-Mo composite coating exhibited better lubrication effect and higher wear resistance at all test temperatures, especially above 600 °C. At 800 °C, NiCr/Ag-Mo composite coating showed the lowest friction coefficient of about 0.2 and its corresponding wear rate reached 2.5 × 10-5 mm3/Nm. Characterizations of NiCr/Ag-Mo composite coating revealed that at temperatures below 400 °C, Ag was smeared and spread onto the wear surface, reducing the friction and wear. At temperature above 500 °C, the Ag2MoO4 lubrication film formed by tribo-oxidation significantly improved the coating's lubrication effect and wear resistance.

  1. High-Temperature Solid Lubricant Coating by Plasma Spraying Using Metal-Metal Clad Powders

    NASA Astrophysics Data System (ADS)

    Zhang, Tiantian; Lan, Hao; Yu, Shouquan; Huang, Chuanbing; Du, Lingzhong; Zhang, Weigang

    2017-07-01

    NiCr/Ag-Mo composite coating was fabricated by atmospheric plasma spray technology using clad powders as the feedstock. Its tribological properties at variable temperature were evaluated using a ball-on-disk high-temperature tribometer in air. The results showed that compared with NiCr, the NiCr/Ag-Mo composite coating exhibited better lubrication effect and higher wear resistance at all test temperatures, especially above 600 °C. At 800 °C, NiCr/Ag-Mo composite coating showed the lowest friction coefficient of about 0.2 and its corresponding wear rate reached 2.5 × 10-5 mm3/Nm. Characterizations of NiCr/Ag-Mo composite coating revealed that at temperatures below 400 °C, Ag was smeared and spread onto the wear surface, reducing the friction and wear. At temperature above 500 °C, the Ag2MoO4 lubrication film formed by tribo-oxidation significantly improved the coating's lubrication effect and wear resistance.

  2. Adsorption properties of ultradispersed powders of aluminum alloys with rare-earth metals, before and after water treatment

    NASA Astrophysics Data System (ADS)

    Ryabina, A. V.; Shevchenko, V. G.; Eselevich, D. A.

    2014-10-01

    Adsorption of nitrogen on Al-3% La, Al-1.5% Sc, and Al-3% Ce powders before and after processing with water in the relative pressure range p/p s = 10˜3 to 0.999 is experimentally studied at a temperature of 78 K. It is shown that the interaction between ultradispersed powder and water depends on the properties of the original powder, including the original content and composition of the oxide-hydroxide phases in the surface layers of metal particles, and the length and conditions of storage. Results confirming that processing powders containing rare-earth metals with water at room temperature leads to the formation of new phases and affects their morphology are presented. It is shown that the nanopores formed between crystallites on the surface of the particles during oxidation with water and subsequent thermal dehydration play an important role in the properties of powders processed with water. The specific surface and the porosity of powders are calculated.

  3. Influence of phosphorus element on direct laser sintering of multicomponent Cu-based metal powder

    NASA Astrophysics Data System (ADS)

    Gu, D. D.; Shen, Y. F.

    2006-12-01

    This article presents a detailed investigation on the influence of the phosphorus element upon the laser sintering of a multicomponent Cu-based metal powder system consisting of Cu, Cu-10Sn, and Cu-8.4P. Powder systems containing 0, 10, 15, and 20 wt pct CuP were sintered in atmosphere at room temperature using the following optimal processing parameters: laser power of 350 W, scan speed of 0.04 m/s, scan line spacing of 0.15 mm, and layer thickness of 0.25 mm. It was found that the relative density of the sintered sample with 15 wt pct CuP increased by 24,4 pct as compared with the sample without phosphorus addition. A further increase in the CuP content (≥20 wt pct), however, resulted in a poor densification with a serious delamination. The exact metallurgical roles of the phosphorus element in the laser sintering process were addressed as follows. First, the phosphorus could prevent the sintering system from oxidation by forming CuPO3, thereby improving the wetting characteristics and the sintering kinetics. Second, the phosphorus could decrease the surface tension of molten materials, leading to a successive transition from highly discontinuous sintered tracks to fairly coherent ones with increasing the phosphorus content. Third, the phosphorus could lower the melt viscosity, thereby improving the microstructural homogeneity of the laser-sintered samples.

  4. Laser powder bed fusion additive manufacturing of metals; physics, computational, and materials challenges

    SciTech Connect

    King, W. E.; Anderson, A. T.; Ferencz, R. M.; Hodge, N. E.; Kamath, C.; Khairallah, S. A.; Rubencik, A. M.

    2015-12-29

    The production of metal parts via laser powder bed fusion additive manufacturing is growing exponentially. However, the transition of this technology from production of prototypes to production of critical parts is hindered by a lack of confidence in the quality of the part. Confidence can be established via a fundamental understanding of the physics of the process. It is generally accepted that this understanding will be increasingly achieved through modeling and simulation. However, there are significant physics, computational, and materials challenges stemming from the broad range of length and time scales and temperature ranges associated with the process. In this study, we review the current state of the art and describe the challenges that need to be met to achieve the desired fundamental understanding of the physics of the process.

  5. Laser powder bed fusion additive manufacturing of metals; physics, computational, and materials challenges

    DOE PAGES

    King, W. E.; Anderson, A. T.; Ferencz, R. M.; ...

    2015-12-29

    The production of metal parts via laser powder bed fusion additive manufacturing is growing exponentially. However, the transition of this technology from production of prototypes to production of critical parts is hindered by a lack of confidence in the quality of the part. Confidence can be established via a fundamental understanding of the physics of the process. It is generally accepted that this understanding will be increasingly achieved through modeling and simulation. However, there are significant physics, computational, and materials challenges stemming from the broad range of length and time scales and temperature ranges associated with the process. In thismore » study, we review the current state of the art and describe the challenges that need to be met to achieve the desired fundamental understanding of the physics of the process.« less

  6. Laser powder bed fusion additive manufacturing of metals; physics, computational, and materials challenges

    NASA Astrophysics Data System (ADS)

    King, W. E.; Anderson, A. T.; Ferencz, R. M.; Hodge, N. E.; Kamath, C.; Khairallah, S. A.; Rubenchik, A. M.

    2015-12-01

    The production of metal parts via laser powder bed fusion additive manufacturing is growing exponentially. However, the transition of this technology from production of prototypes to production of critical parts is hindered by a lack of confidence in the quality of the part. Confidence can be established via a fundamental understanding of the physics of the process. It is generally accepted that this understanding will be increasingly achieved through modeling and simulation. However, there are significant physics, computational, and materials challenges stemming from the broad range of length and time scales and temperature ranges associated with the process. In this paper, we review the current state of the art and describe the challenges that need to be met to achieve the desired fundamental understanding of the physics of the process.

  7. Synchrotron hard X-ray imaging of shock-compressed metal powders

    NASA Astrophysics Data System (ADS)

    Rutherford, Michael E.; Chapman, David J.; Collinson, Mark A.; Jones, David R.; Music, Jasmina; Stafford, Samuel J. P.; Tear, Gareth R.; White, Thomas G.; Winters, John B. R.; Drakopoulos, Michael; Eakins, Daniel E.

    2015-06-01

    This poster will present the application of a new, high-energy (50 to 250 keV) synchrotron X-ray radiography technique to the study of shock-compressed granular materials. Following plate-impact loading, transmission radiography was used to quantitatively observe the compaction and release processes in a range of high-Z metal powders (e.g. Fe, Ni, Cu). By comparing the predictions of 3D numerical models initialized from X-ray tomograms-captured prior to loading-with experimental results, this research represents a new approach to refining mesoscopic compaction models. The authors gratefully acknowledge the ongoing support of Imperial College London, EPSRC, STFC and the Diamond Light Source, and AWE Plc.

  8. Laser powder bed fusion additive manufacturing of metals; physics, computational, and materials challenges

    SciTech Connect

    King, W. E.; Anderson, A. T.; Ferencz, R. M.; Hodge, N. E.; Khairallah, S. A.; Kamath, C.; Rubenchik, A. M.

    2015-12-15

    The production of metal parts via laser powder bed fusion additive manufacturing is growing exponentially. However, the transition of this technology from production of prototypes to production of critical parts is hindered by a lack of confidence in the quality of the part. Confidence can be established via a fundamental understanding of the physics of the process. It is generally accepted that this understanding will be increasingly achieved through modeling and simulation. However, there are significant physics, computational, and materials challenges stemming from the broad range of length and time scales and temperature ranges associated with the process. In this paper, we review the current state of the art and describe the challenges that need to be met to achieve the desired fundamental understanding of the physics of the process.

  9. Scalable process for application of stabilized lithium metal powder in Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Ai, Guo; Wang, Zhihui; Zhao, Hui; Mao, Wenfeng; Fu, Yanbao; Yi, Ran; Gao, Yue; Battaglia, Vincent; Wang, Donghai; Lopatin, Sergey; Liu, Gao

    2016-03-01

    A simple solution processing method is developed to achieve a uniform and scalable stabilized lithium metal powder (SLMP) coating on a Li-ion negative electrode. A solvent and binder system for the SLMP coating is developed, including the selection of solvent, polymer binder, and optimization of polymer concentration. The optimized binder solution is a 1% concentration of polymer binder in xylene; a mixture of poly(styrene-co-butadiene) rubber (SBR) and polystyrene (PS) is chosen as the polymer binder. Results show that long-sustained, uniformly dispersed SLMP suspension can be achieved with the optimized binder solution. The uniform SLMP coating can be achieved using a simple "doctor blade" coating method, and the resulting SLMP coating can be firmly glued on the anode surface. By using SLMP to prelithiate the negative electrode, improvements in electrochemical performances are demonstrated in both graphite/NMC and SiO/NMC full cells.

  10. Characterization of the whiskerlike products formed by hydriding magnesium metal powders

    NASA Astrophysics Data System (ADS)

    Herley, Patrick J.; Jones, William; Vigeholm, Bjorn

    1985-07-01

    The structure of filamentary crystals produced during the hydriding of magnesium powder has been studied in detail. The needles of small dimensions (typically 0.5 μm in diameter) have been identified by electron analytical techniques to be oriented microcrystals of metallic magnesium. Their formation has been ascribed to the melting of localized aluminum impurities within the bulk magnesium to form a liquid eutectic. In the presence of sublimed magnesium vapor and hydrogen (as a carrier gas) a vapor-liquid-solid mechanism operates to produce a rapid unidirectional extension followed by a slower, two-dimensional growth. As a consequence the needle becomes broader at the tip. In addition, the tip is surmounted by a small Mg-Al eutectic aggregate.

  11. Mechanically strong nanocrystalline Fe-Si-B-P-Cu soft magnetic powder cores utilizing magnetic metallic glass as a binder

    NASA Astrophysics Data System (ADS)

    Luan, Jian; Sharma, Parmanand; Yodoshi, Noriharu; Zhang, Yan; Makino, Akihiro

    2016-05-01

    We report on the fabrication and properties of soft magnetic powder cores with superior mechanical strength as well as low core loss (W). Development of such cores is important for applications in automobiles/devices operating in motion. High saturation magnetic flux density (Bs) Fe-Si-B-P-Cu powder was sintered with Fe55C10B5P10Ni15Mo5 metallic glass (MG) powder in its supercooled liquid state by spark plasma sintering. The sintered cores are made from the nanocrystalline powder particles of Fe-Si-B-P-Cu alloy, which are separated through a magnetic Fe55C10B5P10Ni15Mo5 MG alloy. Low W of ˜ 2.2 W/kg (at 1T and 50 Hz), and high fracture strength (yielding stress ˜500 MPa), which is an order of magnitude higher than the conventional powder cores, were obtained. Stronger metal-metal bonding and magnetic nature of MG binder (which is very different than the conventional polymer based binders) are responsible for the superior mechanical and magnetic properties. The MG binder not only helps in improving the mechanical properties but it also enhances the overall Bs of the core.

  12. Conical shaped charge pressed powder, metal liner jet characterization and penetration in aluminum

    SciTech Connect

    Vigil, M.G.

    1997-05-01

    This work was conducted as part of a Near-wellbore Mechanics program at Sandia National Laboratories. An understanding of the interaction of the perforator jet from an explosive shaped charge with the fluid filled porous sandstone media is of basic importance to the completion of oil wells. Tests were conducted using the five-head Flash X-ray Test Site to measure the jet tip velocities and jet geometry for the OMNI and CAPSULE Conical Shaped Charge (CSC) oil well perforator jets fired into air. These tests were conducted to generate jet velocity and geometry information to be used in validating the CTH hydrocode modeling/simulation development of pressed powder, metal liner jets in air. Ten tests were conducted to determine the CSC jet penetration into 6061-T6 aluminum targets. Five tests were conducted with the OMNI CSC at 0.25, 6.0, and 19 inch standoffs from the target. Five tests were conducted with the CAPSULE CSC at 0.60, 5.0, 10.0, and 19 inch standoffs from the target. These tests were conducted to generate jet penetration into homogeneous target information for use in validating the CTH code modeling/simulation of pressed powder, metal liner jets penetrating aluminum targets. The Flash X-ray radiographs, jet velocities, jet diameters, and jet lengths data for jets fired into air are presented in this report. The jet penetration into aluminum and penetration hole profile data are also presented for the OMNI and CAPSULE perforators. Least Squares fits are presented for the measured jet velocity and jet penetration data.

  13. Consolidation of nanostructured metal powders by rapid forging: Processing, modeling, and subsequent mechanical behavior

    NASA Astrophysics Data System (ADS)

    Shaik, G. R.; Milligan, W. W.

    1997-03-01

    Fe-10Cu powders containing 20-nm grains were produced by attritor milling of elemental powders in argon. A rapid powder forging technique was developed to consolidate the powders into fully dense compacts while maintaining nanoscale grain sizes. Grain growth during the consolidation was controlled by reducing the time of exposure at elevated temperature to a few minutes or less, a technique which is applicable to all materials and does not necessitate the addition of dispersoids. This was achieved by heating green compacts quickly using an induction heater, and then forging and rapidly cooling them back to room temperature. Forging was conducted in a protective argon atmosphere to limit contamination. Fully dense compacts were produced at relatively low temperatures, mainly due to the accelerated creep rates exhibited by the nanostructures. Transmission electron microscopy and X-ray diffraction analysis found an average grain size of 45 nm in the fully dense samples forged at 530°C. Indications are that finer grain sizes should be attainable by using slightly lower temperatures and higher pressures. The success of the technique (compared to hot-isostatic pressing (“hipping”)) is due to both reducing time at elevated temperatures and applying relatively high pressures. Microhardness tests revealed a significant strengthening effect due to grain size refinement, following a Hall-Petch relation. Compression testing at room temperature showed no strain hardening during plastic deformation, which occurred by shear banding. High strengths, up to 1800 MPa, were obtained at room temperature. Compression testing at 575°C revealed a significant strain rate dependence of mechanical behavior and also the possibility of superplastic behavior. Power-law creep was observed at 575°C, with very high steady-state creep rates on the order of 50 pct/s at 230 MPa. The consolidation process was successfully modeled by slightly modifying and applying the Arzt, Ashby, and

  14. Modified Sol-Gel Technique as a Cost-Effective Method of Ultradispersed Metal Oxide Powders Production

    NASA Astrophysics Data System (ADS)

    Vokhmintcev, K. V.; Konstantinov, O. V.; Belousov, V. V.

    2013-05-01

    A modified sol-gel technique was developed for fabrication of ultradispersed metal oxides powders of Bi2O3, CeO2, Cr2O3, Y2O3, ZnO2 and ZrO2. Hexamethylenetetramine, monoethanolamine and acetylacetone were used for the sol formation and gel stabilization.

  15. Development of protective coatings using fly ash premixed with metal powder on aluminium substrates.

    PubMed

    Satapathy, Alok; Sahu, Suvendu Prasad; Mishra, Debadutta

    2010-07-01

    Fly ash is a solid waste generated in huge quantities from coal-fired thermal power stations during the combustion of coal. Rich in metal oxides, it has tremendous potential as a coating material on structural and engineering components. This work aims at developing and characterizing a new class of such coatings made of fly ash by a novel technique - plasma spraying. Plasma spray technology has the advantage of being able to process various low-grade ore minerals to obtain value-added products and also to deposit ceramics, metals and a combination of these, generating near-homogeneous coatings with the desired microstructure on a range of substrates. In the present investigation, coatings are developed on aluminium substrates using fly ash premixed with aluminium powder in different weight proportions at various plasma torch input power levels ranging from 9- 18 kW DC. The coatings are characterized in terms of interface adhesion strength and deposition efficiency. Maximum adhesion strength of about 35 MPa is recorded with coatings deposited at 12 kW power level. It was noticed that the quality and properties are significantly affected by the operating power level of the plasma sprayer. This work identifies fly ash as a potential coating material, suitable for possible tribological applications.

  16. Edetate calcium disodium nanoparticle dry powder inhalation: a novel approach against heavy metal decorporation.

    PubMed

    Kumar, Neeraj; Soni, Sandeep; Jaimini, Abhinav; Ahmad, Farhan Jalees; Bhatnagar, Aseem; Mittal, Gaurav

    2011-09-15

    Objective was to develop and characterize nano-edetate calcium disodium (Ca-Na(2)EDTA) dry powder inhaler (DPI), and assess its in vitro and in vivo deposition using pharmacoscintigraphy techniques. Factors influencing nanoparticle formation including concentration of drug, polymer solution and stirring rate were determined. Optimized formulation was characterized with the help of SEM, TEM and Malvern Zetasizer studies. Any change in physical characteristics after nanosizing was determined by FT-IR, XRD and DSC studies. Anderson cascade impaction showed that nano Ca-Na(2)EDTA exhibited significantly higher respirable fraction of 67.35±2.27% and 66.40±2.87% by scintigraphic and spectroscopic analysis respectively, as compared to 10.08±1.17% and 9.36±1.02% respectively for micronized form. Ventilation lung scintigraphy done in 12 volunteers showed significant increase in drug delivery till alveolar region with nano Ca-Na(2)EDTA. The developed formulation may have a role in neutralizing heavy metal toxicity through inhalation route, including radio-metal contamination. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Process defects and in situ monitoring methods in metal powder bed fusion: a review

    NASA Astrophysics Data System (ADS)

    Grasso, Marco; Colosimo, Bianca Maria

    2017-04-01

    Despite continuous technological enhancements of metal Additive Manufacturing (AM) systems, the lack of process repeatability and stability still represents a barrier for the industrial breakthrough. The most relevant metal AM applications currently involve industrial sectors (e.g. aerospace and bio-medical) where defects avoidance is fundamental. Because of this, there is the need to develop novel in situ monitoring tools able to keep under control the stability of the process on a layer-by-layer basis, and to detect the onset of defects as soon as possible. On the one hand, AM systems must be equipped with in situ sensing devices able to measure relevant quantities during the process, a.k.a. process signatures. On the other hand, in-process data analytics and statistical monitoring techniques are required to detect and localize the defects in an automated way. This paper reviews the literature and the commercial tools for in situ monitoring of powder bed fusion (PBF) processes. It explores the different categories of defects and their main causes, the most relevant process signatures and the in situ sensing approaches proposed so far. Particular attention is devoted to the development of automated defect detection rules and the study of process control strategies, which represent two critical fields for the development of future smart PBF systems.

  18. Development of Metal/Polymer Mixtures for Micro Powder Injection Moulding

    SciTech Connect

    Quinard, C.; Barriere, T.; Gelin, J. C.

    2007-04-07

    Important research tasks at ENSMM/LMA are concerned for the development of mixtures of Fine powders associated to polymer binders dedicated to the powder injection moulding (PIM) and to the powder injection micro-moulding ({mu}PIM) in accordance with many works already carried out with different feedstock suppliers dedicated to the macro-components.

  19. Development of Metal/Polymer Mixtures for Micro Powder Injection Moulding

    NASA Astrophysics Data System (ADS)

    Quinard, C.; Barriere, T.; Gelin, J. C.

    2007-04-01

    Important research tasks at ENSMM/LMA are concerned for the development of mixtures of Fine powders associated to polymer binders dedicated to the powder injection moulding (PIM) and to the powder injection micro-moulding (μPIM) in accordance with many works already carried out with different feedstock suppliers dedicated to the macro-components.

  20. Enhanced degradation of azo dye by nanoporous-copper-decorated Mg-Cu-Y metallic glass powder through dealloying pretreatment

    NASA Astrophysics Data System (ADS)

    Luo, Xuekun; Li, Ran; Zong, Jingzhen; Zhang, Ying; Li, Haifei; Zhang, Tao

    2014-06-01

    A controllable uniform nanoporous copper (NPC) layer was synthesized on the surface of the ball-milled powder of Mg65Cu25Y10 metallic glass by dealloying. The morphology, the elemental surface composition and the phase structure of the powders were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffractometry, respectively. The composite powder with a core-shell structure shows higher degradation efficiency of the azo dye of Direct Blue 6 than the untreated powder and the pure NPC. The improved performance can be attributed to the strong synergistic effect between the NPC layer and the metallic glass matrix, because the nanoporous structure provides large surface area for the adsorption of the dye molecules and three-dimensional diffusion channels of reaction masses, as well as the dissolution acceleration of the active atoms through local galvanic cell reaction. This tunable pretreatment is a promising surface activation method for novel chemical applications of metallic glasses.

  1. Hyperfine magnetic fields in substituted Finemet alloys

    NASA Astrophysics Data System (ADS)

    Brzózka, K.; Sovák, P.; Szumiata, T.; Gawroński, M.; Górka, B.

    2016-12-01

    Transmission Mössbauer spectroscopy was used to determine the hyperfine fields of Finemet-type alloys in form of ribbons, substituted alternatively by Mn, Ni, Co, Al, Zn, V or Ge of various concentration. The comparative analysis of magnetic hyperfine fields was carried out which enabled to understand the role of added elements in as-quenched as well as annealed samples. Moreover, the influence of the substitution on the mean direction of the local hyperfine magnetic field was examined.

  2. Metal release from stainless steel powders and massive sheets--comparison and implication for risk assessment of alloys.

    PubMed

    Hedberg, Yolanda; Mazinanian, Neda; Odnevall Wallinder, Inger

    2013-02-01

    Industries that place metal and alloy products on the market are required to demonstrate that they are safe for all intended uses, and that any risks to humans, animals or the environment are adequately controlled. This requires reliable and robust in vitro test procedures. The aim of this study is to compare the release of alloy constituents from stainless steel powders of different grades (focus on AISI 316L) and production routes into synthetic body fluids with the release of the same metals from massive sheets in relation to material and surface characteristics. The comparison is justified by the fact that the difference between massive surfaces and powders from a metal release/dissolution and surface perspective is not clearly elucidated within current legislations. Powders and abraded and aged (24 h) massive sheets were exposed to synthetic solutions of relevance for biological settings and human exposure routes, for periods of up to one week. Concentrations of released iron, chromium, nickel, and manganese in solution were measured, and the effect of solution pH, acidity, complexation capacity, and proteins elucidated in relation to surface oxide composition and its properties. Implications for risk assessments based on in vitro metal release data from alloys are elucidated.

  3. From Powders to Dense Metal Parts: Characterization of a Commercial AlSiMg Alloy Processed through Direct Metal Laser Sintering.

    PubMed

    Manfredi, Diego; Calignano, Flaviana; Krishnan, Manickavasagam; Canali, Riccardo; Ambrosio, Elisa Paola; Atzeni, Eleonora

    2013-03-06

    In this paper, a characterization of an AlSiMg alloy processed by direct metal laser sintering (DMLS) is presented, from the analysis of the starting powders, in terms of size, morphology and chemical composition, through to the evaluation of mechanical and microstructural properties of specimens built along different orientations parallel and perpendicular to the powder deposition plane. With respect to a similar aluminum alloy as-fabricated, a higher yield strength of about 40% due to the very fine microstructure, closely related to the mechanisms involved in this additive process is observed.

  4. From Powders to Dense Metal Parts: Characterization of a Commercial AlSiMg Alloy Processed through Direct Metal Laser Sintering

    PubMed Central

    Manfredi, Diego; Calignano, Flaviana; Krishnan, Manickavasagam; Canali, Riccardo; Ambrosio, Elisa Paola; Atzeni, Eleonora

    2013-01-01

    In this paper, a characterization of an AlSiMg alloy processed by direct metal laser sintering (DMLS) is presented, from the analysis of the starting powders, in terms of size, morphology and chemical composition, through to the evaluation of mechanical and microstructural properties of specimens built along different orientations parallel and perpendicular to the powder deposition plane. With respect to a similar aluminum alloy as-fabricated, a higher yield strength of about 40% due to the very fine microstructure, closely related to the mechanisms involved in this additive process is observed. PMID:28809344

  5. Fabrication and Characterization of Graded Impedance Gas Gun Impactors from Tape Cast Metal Powders

    SciTech Connect

    Martin, L P; Nguyen, J H

    2005-11-21

    Fabrication of compositionally graded structures for use as light-gas gun impactors has been demonstrated using a tape casting technique. Mixtures of metal powders in the Mg-Cu system were cast into a series of tapes with uniform compositions ranging from 100% Mg to 100% Cu. The individual compositions were fabricated into monolithic pellets for characterization by laminating multiple layers together, thermally removing the organics, and hot-pressing to near-full density. The pellets were characterized by optical and scanning electron microscopy, X-ray diffraction, and measurement of density and sound wave velocity. The density and acoustic impedance were observed to vary monotonically (and nearly linearly) with composition. Graded structures were fabricated by stacking layers of different compositions in a sequence calculated to yield a desired acoustic impedance profile. The measured physical properties of the graded structures compare favorably with those predicted from the monolithic-pellet characteristics. Fabrication of graded impactors by this technique is of significant interest for providing improved control of the pressure profile in gas gun experiments.

  6. Comparison of gamma-gamma Phase Coarsening Responses of Three Powder Metal Disk Superalloys

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Gayda, J.; Johnson, D. F.; MacKay, R. A.; Rogers, R. B.; Sudbrack, C. K.; Garg, A.; Locci, I. E.; Semiatin, S. L.; Kang, E.

    2016-01-01

    The phase microstructures of several powder metal (PM) disk superalloys were quantitatively evaluated. Contents, chemistries, and lattice parameters of gamma and gamma strengthening phase were determined for conventionally heat treated Alloy 10, LSHR, and ME3 superalloys, after electrolytic phase extractions. Several of long term heat treatments were then performed, to allow quantification of the precipitation, content, and size distribution of gamma at a long time interval to approximate equilibrium conditions. Additional coarsening heat treatments were performed at multiple temperatures and shorter time intervals, to allow quantification of the precipitation, contents and size distributions of gamma at conditions diverging from equilibrium. Modest differences in gamma and gamma lattice parameters and their mismatch were observed among the alloys, which varied with heat treatment. Yet, gamma coarsening rates were very similar for all three alloys in the heat treatment conditions examined. Alloy 10 had higher gamma dissolution and formation temperatures than LSHR and ME3, but a lower lattice mismatch, which was slightly positive for all three alloys at room temperature. The gamma precipitates of Alloy 10 appeared to remain coherent at higher temperatures than for LSHR and ME3. Higher coarsening rates were observed for gamma precipitates residing along grain boundaries than for those within grains in all three alloys, during slow-moderate quenching from supersolvus solution heat treatments, and during aging at temperatures of 843 C and higher.

  7. Laser-beam modulation to improve efficiency of selecting laser melting for metal powders

    NASA Astrophysics Data System (ADS)

    Okunkova, A.; Peretyagin, P.; Vladimirov, Yuri; Volosova, M.; Torrecillas, R.; Fedorov, S. V.

    2014-05-01

    Nowadays additive manufacturing becomes more and more popular. It depends on the results of last achievements in developing of the new constructions for modern machine tools. One of the most developed AM technology is SLM or SLS. About twenty years ago the technology of rapid prototyping started to grow up from building prototypes and developed to real functional item production. Especially this becomes more important in producing medical implants in the full accordance with individual digital 3D-model from metallic powder as Ti6Al4V or CoCr. The additive technology gives the possibility to reduce additional steps in implants production process as work preparation process, forwarding a work piece from one shop to another one, post treatment etc. This approach is very topical to production of tooth, knee and coxal implants. This idea is realized in the commercial SLM machines as EOS M280, SLM Solutions 125HL (Germany), Phenix systems PXS/PXM Dental (France) (fig. 1).

  8. Variation of the shape and morphological properties of silica and metal oxide powders by electro homogeneous precipitation

    DOEpatents

    Harris, M.T.; Basaran, O.A.; Sisson, W.G.; Brunson, R.R.

    1997-02-18

    The present invention provides a method for preparing irreversible linear aggregates (fibrils) of metal oxide powders by utilizing static or pulsed DC electrical fields across a relatively non-conducting liquid solvent in which organometal compounds or silicon alkoxides have been dissolved. The electric field is applied to the relatively non-conducting solution throughout the particle formation and growth process promoting the formation of either linear aggregates (fibrils) or spherical shaped particles as desired. Thus the present invention provides a physical method for altering the size, shape and porosity of precursor hydrous metal oxide or hydrous silicon oxide powders for the development of advanced ceramics with improved strength and insulating capacity. 3 figs.

  9. Metal oxide superconducting powder comprised of flake-like single crystal particles

    DOEpatents

    Capone, D.W.; Dusek, J.

    1994-10-18

    Powder of a ceramic superconducting material is synthesized such that each particle of the powder is a single crystal having a flake-like, nonsymmetric morphology such that the c-axis is aligned parallel to the short dimension of the flake. Nonflake powder is synthesized by the normal methods and is pressed into pellets or other shapes and fired for excessive times to produce a coarse grained structure. The fired products are then crushed and ground producing the flake-like powder particles which exhibit superconducting characteristics when aligned with the crystal lattice. 3 figs.

  10. Metal oxide superconducting powder comprised of flake-like single crystal particles

    DOEpatents

    Capone, Donald W.; Dusek, Joseph

    1994-01-01

    Powder of a ceramic superconducting material is synthesized such that each particle of the powder is a single crystal having a flake-like, nonsymmetric morphology such that the c-axis is aligned parallel to the short dimension of the flake. Nonflake powder is synthesized by the normal methods and is pressed into pellets or other shapes and fired for excessive times to produce a coarse grained structure. The fired products are then crushed and ground producing the flake-like powder particles which exhibit superconducting characteristics when aligned with the crystal lattice.

  11. Hyperfine structure parametrisation in Maple

    NASA Astrophysics Data System (ADS)

    Gaigalas, G.; Scharf, O.; Fritzsche, S.

    2006-02-01

    In hyperfine structure examinations, routine high resolution spectroscopy methods have to be combined with exact fine structure calculations. The so-called magnetic A and electric B factor of the fine structure levels allow to check for a correct fine structure analysis, to find errors in the level designation, to find new levels and to probe the electron wavefunctions and its mixing coefficients. This is done by parametrisation of these factors into different contributions of the subshell electrons, which are split further into their radial and spin-angular part. Due to the routine with which hyperfine structure measurements are done, a tool for keeping the necessary information together, performing checks online with the experiment and deriving standard quantities is of great help. MAPLE [Maple is a registered trademark of Waterloo Maple Inc.] is a highly-developed symbolic programming language, often referred to as the pocket calculator of the future. Packages for theoretical atomic calculation exist ( RACAH and JUCYS) and the language meets all the requirements to keep and present information accessible for the user in a fast and practical way. We slightly extended the RACAH package [S. Fritzsche, Comput. Phys. Comm. 103 (1997) 51] and set up an environment for experimental hyperfine structure calculations, the HFS package. Supplying the fine structure and nuclear data, one is in the position to obtain information about the hyperfine spectrum, the different contributions to the splitting and to perform a least square fit of the radial parameters based on the semiempirical method. Experimentalist as well as theoretical physicist can do a complete hyperfine structure analysis using MAPLE. Program summaryTitle of program: H FS Catalogue number: ADXD Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXD Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: none Computers for which the program is designed

  12. Hydrogen molecule binding to unsaturated metal sites in metal-organic frameworks studied by neutron powder diffraction and inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Liu, Yun; Brown, Craig; Neumann, Dan; Dinca, Mircea; Long, Jeffrey; Peterson, Vanessa; Kepert, Cameron

    2007-03-01

    Metal organic framework (MOF) materials have shown considerable potential for hydrogen storage arising from very large surface areas. However, the low binding energy of hydrogen molecules limits its storage capability to very low temperatures (< 77 K), which is impractical for industrial applications. Using neutron powder diffraction (NPD), we have characterized the hydrogen adsorption sites in a selected series of MOF materials with exposed unsaturated metal ions. Direct binding between the unsaturated metal ions and hydrogen molecules is observed and responsible for the enhanced initial hydrogen adsorption enthalpy. The different metals centers in these MOFs show different binding strength and interaction distances between the hydrogen molecule and metal ions. The organic linker also affects the overall H2 binding strength. Inelastic neutron scattering spectra of H2 in these MOFs are also discussed.

  13. Dry sliding wear behavior of ceramic-metal composite coatings prepared by plasma spraying of self-reacting powders

    NASA Astrophysics Data System (ADS)

    Dong, Yanchun; Yan, Dianran; He, Jining; Li, Xiangzhi; Zhang, Jianxin

    2006-09-01

    Ceramic-metal composite (CMC) coatings were deposited on the surface of Fe-0.14 0.22 wt.% C steel by plasma spraying of self-reacting Fe2O3-Al composite powders. The dry sliding friction and wear character of the CMC coatings are investigated in this paper. The wear resistance of the CMC coatings was significantly better than that of Al2O3 coatings under the same sliding wear conditions. The tough metal, which is dispersed in the ceramic matrix, obviously improved the toughness of the CMC coatings. Wear mechanisms of the CMC coatings were identified as a combination of abrasive and adhesive wear.

  14. Using optical diagnostics to determine the melt temperature field in layer-by-layer laser alloying of metal powder

    NASA Astrophysics Data System (ADS)

    Zavalov, Yu. N.; Dubrov, A. V.; Mirzade, F. Kh.; Dubrovin, N. G.; Makarova, E. S.; Dubrov, V. D.

    2017-07-01

    The results of application of optical diagnostics in the estimation of the temperature field at the melt surface in layer-by-layer laser alloying of metal powder are presented. It is demonstrated that surface concavity induced by the thermocapillary effect upon nonuniform heating may distort pyrometry data considerably. The use of external illumination provides an opportunity to determine the shape of the melt surface. The obtained minimum estimate of the temperature gradient in the metal region affected by laser radiation is 2.8 × 104 K/cm.

  15. Effect of particle size distribution on the structure, hyperfine, and magnetic properties of Ni0.5Zn0.5Fe2O4 nanopowders

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Kaustav; Pati, Satya P.; Das, G. C.; Das, D.; Chattopadhyay, K. K.

    2014-12-01

    Ni0.5Zn0.5Fe2O4 nano powders were synthesized by an auto combustion method and then heat treated at different temperatures in air for a fixed time. As a consequence, a distribution in particle size and strain was incorporated within the specimens, as estimated from the Rietveld refinement analysis of the powder x-ray diffraction data. The changes in the microstructure and crystal structure parameters were carefully extracted through the refinement analysis. Thermal annealing causes increment in the dispersion and mean of the size distribution. Reallocation of cations in the lattice sites occur as a consequence of the heat treatment which was manifested in their altered unit cell length (a), r.m.s. strain (⟨ɛ2⟩1/2), oxygen positional parameter (u), metal-oxygen bond lengths ( RO A and RO B ), and the band positions (ν1and ν2) in the vibrational spectroscopy. We also investigate the hyperfine and magnetic properties of the samples using different instrumental techniques (with different operating time scales) like Mössbauer spectroscopy, electron paramagnetic resonance spectroscopy, and superconducting quantum interference device magnetometry. Results show that the effect of particle size distribution was manifested in their hyperfine field distribution profile, paramagnetic resonance spectra, and magnetic anisotropy energy distribution profile. Co-existence of superparamagnetic and ferrimagnetic phase was recorded at room temperature in the samples when annealed at lower temperature. However, with increase in annealing temperature, the nature of the size distribution changes and ferrimagnetic ordering predominates for the larger size nanoparticles. Thus, the effect of particle size distribution on the structural, hyperfine, and magnetic properties of various Ni0.5Zn0.5Fe2O4 nanoparticles was investigated herein which hitherto has not been discussed in the literature.

  16. Hyperfine-field spectrum of epitaxially grown bcc cobalt

    NASA Astrophysics Data System (ADS)

    Riedi, P. C.; Dumelow, T.; Rubinstein, M.; Prinz, G. A.; Qadri, S. B.

    1987-09-01

    The hyperfine-field spectrum of the bcc phase of a 357-romanÅ-thick metallic cobalt film, epitaxially grown on a GaAs substrate, has been determined by spin-echo nuclear magnetic resonance. The peak of the distribution of hyperfine fields in bcc Co occurs at 167 MHz, much lower than the value found for fcc Co (217 MHz), suggesting that the moment in the bcc phase is lower than that of the fcc phase, in agreement with the measurements of Prinz, but in disagreement with recent theoretical calculations (assuming that no significant structural differences exist between theory and experiment). The full width of the distribution is 75 MHz, seven times greater than that found in thin fcc Co films. X-ray rocking-curve measurements yield a linewidth of 118 arc seconds, implying too low a dislocation density to explain the observed NMR line broadening.

  17. Modeling flux noise in SQUIDs due to hyperfine interactions.

    PubMed

    Wu, Jiansheng; Yu, Clare C

    2012-06-15

    Recent experiments implicate spins on the surface of metals as the source of flux noise in superconducting quantum interference devices and indicate that these spins are able to relax without conserving total magnetization. We present a model of 1/f flux noise in which electron spins on the surface of metals can relax via hyperfine interactions. Our results indicate that flux noise would be significantly reduced in superconducting materials where the most abundant isotopes do not have nuclear moments, such as zinc and lead.

  18. Powder treatment process

    DOEpatents

    Weyand, John D.

    1988-01-01

    (1) A process comprising spray drying a powder-containing slurry, the slurry containing a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, while reducing the tendency for oxidation of the constituent by including as a liquid constituent of the slurry an organic liquid; (2) a process comprising spray drying a powder-containing slurry, the powder having been pretreated to reduce content of a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, the pretreating comprising heating the powder to react the constituent; and (3) a process comprising reacting ceramic powder, grinding the reacted powder, slurrying the ground powder, spray drying the slurried powder, and blending the dried powder with metal powder.

  19. Powder treatment process

    DOEpatents

    Weyand, J.D.

    1988-02-09

    Disclosed are: (1) a process comprising spray drying a powder-containing slurry, the slurry containing a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, while reducing the tendency for oxidation of the constituent by including as a liquid constituent of the slurry an organic liquid; (2) a process comprising spray drying a powder-containing slurry, the powder having been pretreated to reduce content of a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, the pretreating comprising heating the powder to react the constituent; and (3) a process comprising reacting ceramic powder, grinding the reacted powder, slurrying the ground powder, spray drying the slurried powder, and blending the dried powder with metal powder. 2 figs.

  20. Analysis of powdered tungsten carbide hard-metal precursors and cemented compact tungsten carbides using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Novotný, K.; Staňková, A.; Häkkänen, H.; Korppi-Tommola, J.; Otruba, V.; Kanický, V.

    2007-12-01

    Laser-induced breakdown spectroscopy (LIBS) has been applied to the direct analysis of powdered tungsten carbide hard-metal precursors and cemented tungsten carbides. The aim of this work was to examine the possibility of quantitative determination of the niobium, titanium, tantalum and cobalt. The investigated samples were in the form of pellets, pressed with and without binder (powdered silver) and in the form of cemented tungsten carbides. The pellets were prepared by pressing the powdered material in a hydraulic press. Cemented tungsten carbides were embedded in resin for easier manipulation. Several lasers and detection systems were utilized. The Nd:YAG laser working at a basic wavelength of 1064 nm and fourth-harmonic frequency of 266 nm with a gated photomultiplier or ICCD detector HORIBA JY was used for the determination of niobium which was chosen as a model element. Different types of surrounding gases (air, He, Ar) were investigated for analysis. The ICCD detector DICAM PRO with Mechelle 7500 spectrometer with ArF laser (193 nm) and KrF laser (248 nm) were employed for the determination of niobium, titanium, tantalum and cobalt in samples under air atmosphere. Good calibration curves were obtained for Nb, Ti, and Ta (coefficients of determination r2 > 0.96). Acceptable calibration curves were acquired for the determination of cobalt (coefficient of determination r2 = 0.7994) but only for the cemented samples. In the case of powdered carbide precursors, the calibration for cobalt was found to be problematic.

  1. Microstructure and Properties of W-Cu Composite/Fe-Based Powder Alloy Vacuum Brazed Joint with Different Filler Metals

    NASA Astrophysics Data System (ADS)

    Xia, C. Z.; Yang, J.; Xu, X. P.; Zou, J. S.

    2017-05-01

    W-Cu composite and Fe-based powder alloy were brazed with filler metals of Ag-Cu and Cu-Mn-Co alloys in a vacuum furnace. Both of filler metals can join W-Cu composite with Fe-based powder alloy directly in the experiment process. Microstructure, distribution of elements and fracture morphology were observed and analyzed using scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) methods, and phase composition of bonding area was analyzed by X-ray diffraction (XRD). The obtained results indicated that the smooth faying surface and dense microstructure of brazed joint were formed and the primary microstructure of brazing seam were, respectively, Ag(Cu) solid solution and Cu(Mn) solid solution, which ensured forming the stable connection of brazed joint. The bending strength of Ag-based and Cu-based brazed joint can, respectively, reach to 317 and 704 MPa, where fracture showed a typical ductile fracture characteristic. The fracture of Cu-based brazed joint located at brazing seam area, and the fracture of Ag-based brazed joint occurred in Fe-based powder alloy side.

  2. Preparation of bismuth substituted yttrium iron garnet powder and thin film by the metal-organic decomposition method

    NASA Astrophysics Data System (ADS)

    Lee, Hanju; Yoon, Youngwoon; Kim, Songhui; Yoo, Hyung Keun; Melikyan, Harutyun; Danielyan, Emma; Babajanyan, Arsen; Ishibashi, Takayuki; Friedman, Barry; Lee, Kiejin

    2011-08-01

    The crystallization of bismuth substituted yttrium iron garnet (Bi-YIG) powder and thin film prepared by the metal-organic decomposition method (MOD) have been studied. In the powder analysis, it was observed that the pyrolysis of metal-organic compounds begins at 250 °C and completed at 450 °C from the thermo-gravimetric-differential thermal analysis experiment. The crystallization temperature of Bi-YIG powder was 900 °C, and at lower temperature, secondary YFeO 3, γ-Fe 2O 3, α-Fe 2O 3, and BiFeO 3 phases were observed by X-ray diffraction and Fourier transform infrared spectroscope. This crystallization temperature is higher than other chemical solution decomposition methods, so we suggest that the formation of BiFeO 3 in the MOD method increases the crystallization temperature. In the thin film analysis, the crystallization temperature for Bi-YIG is 750 °C, and at lower temperature, secondary phases are observed by X-ray diffraction. It is observed that high pre-annealing temperature promotes the crystallization of secondary phases. From the magneto-optical measurement, it was observed that the secondary phases strongly degrade the magneto-optical properties of the Bi-YIG thin film.

  3. Plasticity in Ni59Zr20Ti16Si2Sn3 metallic glass matrix composites containing brass fibers synthesized by warm extrusion of powders

    NASA Astrophysics Data System (ADS)

    Bae, D. H.; Lee, M. H.; Kim, D. H.; Sordelet, D. J.

    2003-09-01

    Deformation behavior of centimeter-scale Ni-based metallic glass matrix composites reinforced by brass fibers, synthesized by warm extrusion of gas atomized powders, has been investigated under the uniaxial compression condition at room temperature. Throughout the extrusion process, all blended spherical powders are elongated along the extrusion direction. The brass fibers are well distributed in the metallic glass matrix for the metallic glass matrix composites containing the brass up to 0.4 in volume fraction and no pores are visible. With increasing the brass content, elastic modulus and strength decrease due to the softness of the brass, but enhanced macroscopic plasticity is observed due to the formation of multiple shear bands, initiated from the interface between brass fiber and metallic glass matrix, as well as their confinement between the brass fibers. These behaviors are not observed in the sample synthesized by warm extrusion of only metallic glass powders.

  4. Combined synchrotron X-ray tomography and X-ray powder diffraction using a fluorescing metal foil.

    PubMed

    Kappen, P; Arhatari, B D; Luu, M B; Balaur, E; Caradoc-Davies, T

    2013-06-01

    This study realizes the concept of simultaneous micro-X-ray computed tomography and X-ray powder diffraction using a synchrotron beamline. A thin zinc metal foil was placed in the primary, monochromatic synchrotron beam to generate a divergent wave to propagate through the samples of interest onto a CCD detector for tomographic imaging, thus removing the need for large beam illumination and high spatial resolution detection. Both low density materials (kapton tubing and a piece of plant) and higher density materials (Egyptian faience) were investigated, and elemental contrast was explored for the example of Cu and Ni meshes. The viability of parallel powder diffraction using the direct beam transmitted through the foil was demonstrated. The outcomes of this study enable further development of the technique towards in situ tomography∕diffraction studies combining micrometer and crystallographic length scales, and towards elemental contrast imaging and reconstruction methods using well defined fluorescence outputs from combinations of known fluorescence targets (elements).

  5. Combined synchrotron X-ray tomography and X-ray powder diffraction using a fluorescing metal foil

    NASA Astrophysics Data System (ADS)

    Kappen, P.; Arhatari, B. D.; Luu, M. B.; Balaur, E.; Caradoc-Davies, T.

    2013-06-01

    This study realizes the concept of simultaneous micro-X-ray computed tomography and X-ray powder diffraction using a synchrotron beamline. A thin zinc metal foil was placed in the primary, monochromatic synchrotron beam to generate a divergent wave to propagate through the samples of interest onto a CCD detector for tomographic imaging, thus removing the need for large beam illumination and high spatial resolution detection. Both low density materials (kapton tubing and a piece of plant) and higher density materials (Egyptian faience) were investigated, and elemental contrast was explored for the example of Cu and Ni meshes. The viability of parallel powder diffraction using the direct beam transmitted through the foil was demonstrated. The outcomes of this study enable further development of the technique towards in situ tomography/diffraction studies combining micrometer and crystallographic length scales, and towards elemental contrast imaging and reconstruction methods using well defined fluorescence outputs from combinations of known fluorescence targets (elements).

  6. Laser metal deposition with spatial variable orientation based on hollow-laser beam with internal powder feeding technology

    NASA Astrophysics Data System (ADS)

    Shi, Tuo; Lu, Bingheng; Shi, Shihong; Meng, Weidong; Fu, Geyan

    2017-02-01

    In this study, a hollow-laser beam with internal powder feeding (HLB-IPF) head is applied to achieve non-horizontal cladding and deposition of overhanging structure. With the features of this head such as uniform scan energy distribution, thin and straight spraying of the powder beam, the deposition in spatial variable orientation is conducted using a 6-axis robot. During the deposition process the head keeps tangential to the growth direction of the part. In the experiment, a "vase" shaped metal part with overhanging structure is successfully deposited, and the largest overhanging angle achieves 80° to the vertical direction. The "step effect" between cladding layers is completely eliminated with the best surface roughness of Ra=3.864 μm. Cross section of cladding layers with unequal height are deposited for angle change. Test results indicate that the formed part has uniform wall thickness, fine microstructure and high microhardness.

  7. HfS, Hyperfine Structure Fitting Tool

    NASA Astrophysics Data System (ADS)

    Estalella, Robert

    2017-02-01

    Hyperfine Structure Fitting (HfS) is a tool to fit the hyperfine structure of spectral lines with multiple velocity components. The HfS_nh3 procedures included in HfS simultaneously fit the hyperfine structure of the NH3 (J, K) = (1, 1) and (2, 2) transitions, and perform a standard analysis to derive {T}{ex}, NH3 column density, {T}{rot}, and {T}{{k}}. HfS uses a Monte Carlo approach for fitting the line parameters. Special attention is paid to the derivation of the parameter uncertainties. HfS includes procedures that make use of parallel computing for fitting spectra from a data cube.

  8. The influence of SWCNT-metallic nanoparticle mixtures on the desorption properties of milled MgH2 powders.

    PubMed

    Amirkhiz, Babak Shalchi; Danaie, Mohsen; Mitlin, David

    2009-05-20

    We have examined the effect of single-walled carbon nanotube (SWCNT)-metallic nanoparticle additions on the hydrogen desorption behavior of MgH(2) after high-energy co-milling. The metallic nanoparticles were the catalysts used for the SWCNT growth. The co-milling consisted of high-energy planetary milling in an inert argon environment of the hydride powder mixed with the SWCNTs. Identically milled pure MgH(2) powders were used as a baseline. The composites were tested using a combined differential scanning calorimeter and thermogravimetric analyzer, while the microstructures were examined using a variety of techniques including x-ray diffraction and transmission electron microscopy (TEM). We found that the SWCNT-nanoparticle additions do have an influence on the desorption kinetics. However, the degree to which they are effective depends on the composite's final state. The optimum microstructure for sorption, obtained after 1 h of co-milling, consists of highly defective SWCNTs in intimate contact with metallic nanoparticles and with the hydride. This microstructure is optimum, presumably because of the dense and uniform coverage of the defective SWCNTs on the MgH(2) surface. Prolonged co-milling of 7 h destroys the SWCNT structure and reduces the enhancement. Even after 72 h of co-milling, when the SWCNTs are completely destroyed, the metallic nanoparticles remain dispersed on the hydride surfaces. This indicates that the metallic nanoparticles alone are not responsible for the enhanced sorption and that there is indeed something catalytically unique about a defective SWCNT-metal combination. Cryo-stage TEM analysis of the hydride powders revealed that they are nanocrystalline and in some cases multiply twinned. To our knowledge this is the first study where the structure of milled alpha- MgH(2) has been directly imaged. Since defects are an integral component of hydride-to-metal phase transformations, such analysis sheds new insight regarding the fundamental

  9. Energetic powder

    DOEpatents

    Jorgensen, Betty S.; Danen, Wayne C.

    2003-12-23

    Fluoroalkylsilane-coated metal particles. The particles have a central metal core, a buffer layer surrounding the core, and a fluoroalkylsilane layer attached to the buffer layer. The particles may be prepared by combining a chemically reactive fluoroalkylsilane compound with an oxide coated metal particle having a hydroxylated surface. The resulting fluoroalkylsilane layer that coats the particles provides them with excellent resistance to aging. The particles can be blended with oxidant particles to form energetic powder that releases chemical energy when the buffer layer is physically disrupted so that the reductant metal core can react with the oxidant.

  10. Catalytic behavior of Sn/Bi metal powder in anhydride-based epoxy curing.

    PubMed

    Jang, Keon-Soo; Eom, Yong-Sung; Moon, Jong-Tae; Oh, Yong-Soo; Nam, Jae-Do

    2009-12-01

    In this paper, we report the catalytic activity of the Sn/Bi alloy beads and its acceleration of the exothermic epoxy curing reactions in various thermal conditions and bead compositions. As being used as low-melting solder balls in electronic interconnection processes with various epoxy systems, it was found that the Sn/Bi beads substantially lowered the exothermic peak temperature of the diglycidyl ether of bisphenol A (DGEBA)/anhydride systems in up to ca. 140 degrees C depending on different types of anhydride curing agents. The catalytic activation of Sn/Bi powder was initiated with a small amount of Sn/Bi powder, for example, lowering ca. 50 degrees C of the exothermic peak temperature by adding only 0.1 vol% of Sn/Bi powder. The catalytic capability of the powder was increased by using smaller sized beads corresponding to larger catalytic surface area at the same volume fraction. Exhibiting a latent catalytic effect, the catalytic activity of Sn/Bi powder was remained latent at temperatures lower than 100 degrees C in isothermal conditions.

  11. Effective Hyperfine-structure Functions of Ammonia

    NASA Astrophysics Data System (ADS)

    Augustovičová, L.; Soldán, P.; Špirko, V.

    2016-06-01

    The hyperfine structure of the rotation-inversion (v 2 = 0+, 0-, 1+, 1-) states of the 14NH3 and 15NH3 ammonia isotopomers is rationalized in terms of effective (ro-inversional) hyperfine-structure (hfs) functions. These are determined by fitting to available experimental data using the Hougen’s effective hyperfine-structure Hamiltonian within the framework of the non-rigid inverter theory. Involving only a moderate number of mass independent fitting parameters, the fitted hfs functions provide a fairly close reproduction of a large majority of available experimental data, thus evidencing adequacy of these functions for reliable prediction. In future experiments, this may help us derive spectroscopic constants of observed inversion and rotation-inversion transitions deperturbed from hyperfine effects. The deperturbed band centers of ammonia come to the forefront of fundamental physics especially as the probes of a variable proton-to-electron mass ratio.

  12. Hyperfine interaction and magnetoresistance in organic semiconductors

    NASA Astrophysics Data System (ADS)

    Sheng, Y.; Nguyen, T. D.; Veeraraghavan, G.; Mermer, Ö.; Wohlgenannt, M.; Qiu, S.; Scherf, U.

    2006-07-01

    We explore the possibility that hyperfine interaction causes the recently discovered organic magnetoresistance (OMAR) effect. We deduce a simple fitting formula from the hyperfine Hamiltonian that relates the saturation field of the OMAR traces to the hyperfine coupling constant. We compare the fitting results to literature values for this parameter. Furthermore, we apply an excitonic pair mechanism model based on hyperfine interaction, previously suggested by others to explain various magnetic-field effects in organics, to the OMAR data. Whereas this model can explain a few key aspects of the experimental data, we uncover several fundamental contradictions as well. By varying the injection efficiency for minority carriers in the devices, we show experimentally that OMAR is only weakly dependent on the ratio between excitons formed and carriers injected, likely excluding any excitonic effect as the origin of OMAR.

  13. Molecular hyperfine fields in organic magnetoresistance devices

    NASA Astrophysics Data System (ADS)

    Giro, Ronaldo; Rosselli, Flávia P.; dos Santos Carvalho, Rafael; Capaz, Rodrigo B.; Cremona, Marco; Achete, Carlos A.

    2013-03-01

    We calculate molecular hyperfine fields in organic magnetoresistance (OMAR) devices using ab initio calculations. To do so, we establish a protocol for the accurate determination of the average hyperfine field Bhf and apply it to selected molecular ions: NPB, TPD, and Alq3. Then, we make devices with precisely the same molecules and perform measurements of the OMAR effect, in order to address the role of hole-transport layer in the characteristic magnetic field B0 of OMAR. Contrary to common belief, we find that molecular hyperfine fields are not only caused by hydrogen nuclei. We also find that dipolar contributions to the hyperfine fields can be comparable to the Fermi contact contributions. However, such contributions are restricted to nuclei located in the same molecular ion as the charge carrier (intramolecular), as extramolecular contributions are negligible.

  14. The Contents of Heavy Metals (Cd, Cr, As, Pb, Ni, and Sn) in the Selected Commercial Yam Powder Products in South Korea

    PubMed Central

    Shin, Mee-Young; Cho, Young-Eun; Park, Chana; Sohn, Ho-Yong; Lim, Jae-Hwan; Kwun, In-Sook

    2013-01-01

    Yam (Dioscorea) has long been used as foods and folk medicine with the approved positive effects for health promotion. Although consumption of yam products is increasing for health promotion, reports for the metal contamination in commercial yam powder products to protect the consumers are lacking. In this study, we aimed to assess whether the commercial yam powder products were heavy metal contaminated or not using the yam products from six commercial products from various places in South Korea. The contents of heavy metals (Cd, Cr, As, Pb, Ni, and Sn) in yam powder products were measured and compared to national and international food standard levels. Also, the metal contamination was monitored during the food manufacturing steps. The study results showed that the contents of heavy metals (Cd, Cr, As, and Pb) in yam powder products are similar to those in national ‘roots and tubers’ as well as in various crops. In comparison to three international standard levels (EU, Codex and Korea), Cd content in yam powder products was lower but Pb content was 5 times higher. Also, Pb, Ni, and Sn may have the potential to be contaminated during food manufacturing steps. In conclusion, the level of heavy metals (Cd, Cr, As, Ni, and Sn) except Pb is considered relatively safe on comparison to national and international food standard levels. PMID:24551826

  15. Additive Manufacturing/Diagnostics via the High Frequency Induction Heating of Metal Powders: The Determination of the Power Transfer Factor for Fine Metallic Spheres

    SciTech Connect

    Rios, Orlando; Radhakrishnan, Balasubramaniam; Caravias, George; Holcomb, Matthew

    2015-03-11

    Grid Logic Inc. is developing a method for sintering and melting fine metallic powders for additive manufacturing using spatially-compact, high-frequency magnetic fields called Micro-Induction Sintering (MIS). One of the challenges in advancing MIS technology for additive manufacturing is in understanding the power transfer to the particles in a powder bed. This knowledge is important to achieving efficient power transfer, control, and selective particle heating during the MIS process needed for commercialization of the technology. The project s work provided a rigorous physics-based model for induction heating of fine spherical particles as a function of frequency and particle size. This simulation improved upon Grid Logic s earlier models and provides guidance that will make the MIS technology more effective. The project model will be incorporated into Grid Logic s power control circuit of the MIS 3D printer product and its diagnostics technology to optimize the sintering process for part quality and energy efficiency.

  16. Study of the rare-earth metals magnetic powders filling influence on the basic properties of elastomeric materials

    NASA Astrophysics Data System (ADS)

    Zhansakova, K. S.; Mitryaeva, N. S.; Russkikh, G. S.

    2017-08-01

    The work deals with the studying of technological, vulcanization and physical-mechanical properties of magnetic elastomeric compositions. Powders of rare-earth metals with different morphology of particles and different magnetic characteristics were used as fillers. Based on the results of the work performed, it was revealed that the applied technology of manufacturing magnetic elastomeric compositions based on synthetic rubber is optimal. The rationale for this is the balanced technological and physical-mechanical properties of vulcanizates. Morphology and magnetic characteristics of fillers also do not significantly change the vulcanization properties.

  17. Prelithiation of silicon-carbon nanotube anodes for lithium ion batteries by stabilized lithium metal powder (SLMP).

    PubMed

    Forney, Michael W; Ganter, Matthew J; Staub, Jason W; Ridgley, Richard D; Landi, Brian J

    2013-09-11

    Stabilized lithium metal powder (SLMP) has been applied during battery assembly to effectively prelithiate high capacity (1500-2500 mAh/g) silicon-carbon nanotube (Si-CNT) anodes, eliminating the 20-40% first cycle irreversible capacity loss. Pressure-activation of SLMP is shown to enhance prelithiation and enable capacity matching between Si-CNT anodes and lithium nickel cobalt aluminum oxide (NCA) cathodes in full batteries with minimal added mass. The prelithiation approach enables high energy density NCA/Si-CNT batteries achieving >1000 cycles at 20% depth-of-discharge.

  18. Bio-ecological consequences of crop seeds treatment with metal nano-powders

    NASA Astrophysics Data System (ADS)

    Churilov, G.

    2015-11-01

    As a result of our investigations we have determined the optimal concentrations of ferrum, cobalt and cuprum nano-powders recommended to be used as micro-fertilizers increasing the yield and feed value of crops at the expense of accumulating biologically active combinations by 25-35%. In unfavorable climate conditions, for example in a case of excess moisture or heat and drought, the plants development and ripening suffer. Our investigations have shown that the stimulating effect of nano-powders has lowered the effect of stress situations on plants development and simultaneously increased the rape seeds yield and quality. Treating the seeds with the drugs being studied has provided the high crop protection. If consider that the maximum efficiency of protectants Chinuk, SK (20 kg/t of seeds) and Cruiser, KS (10 kg/t of seeds) then for the same effect one needs nano-powders 0.1 g per hectare norm of seeds planting.

  19. Analysis of Hazards Associated with a Process Involving Uranium Metal and Uranium Hydride Powders

    SciTech Connect

    Bullock, J.S.

    2000-05-01

    An analysis of the reaction chemistry and operational factors associated with processing uranium and uranium hydride powders is presented, focusing on a specific operation in the Development Division which was subjected to the Job Hazard Analysis (JHA) process. Primary emphasis is on the thermodynamic factors leading to pyrophoricity in common atmospheres. The discussion covers feed powders, cold-pressed and hot-pressed materials, and stray material resulting from the operations. The sensitivity of the various forms of material to pyrophoricity in common atmospheres is discussed. Operational recommendations for performing the work described are given.

  20. Adsorption of oils, heavy metals and dyes by recovered carbon powder from spent pot liner of aluminum smelter plant.

    PubMed

    Mazumder, B; Devi, Sasmita Rani

    2008-07-01

    Aluminum smelter plants employ Hall-Heroult electrolysis cells for electrolysis of molten cryolite to recover aluminum metal by electrolysis. These cells use carbon cathode blocks as a lining material inside. At the end of service life of the cells, pot lines are discarded and new carbon blocks are laid for fresh charging. These used carbon cathode blocks, known as spent pot liners, are heavily infested with toxic elements such as fluoride, cyanide, alkali, etc. Therefore, their disposal in open field poses great environmental risk. A simple process has been developed for decontamination of these spent pot liners and to recover its carbon value. The experiments indicated that this carbon, in the form of fine powder (around 20 micron in size) can absorb toxic elements like heavy metals, dyes, oils, etc. to a great extent and thus can be used for mitigating environmental pollution occuring due to various toxic wastes.

  1. Cluster model of amorphized particles formation by plasma spraying of metallic powder

    NASA Astrophysics Data System (ADS)

    Barakhtin, Boris K.; Nesterova, E. V.

    1999-05-01

    Multifunctional coatings from materials with amorphized microcrystalline or nano-phase structure cause a considerable scientific and practical interest. With their help it is to manufacture heat resistant neutralizers of harmful ejections, to produce ecologically clean sources of electric current, to design electromagnetic protective shields and to fabricate a lot of other technical products. The variety of application and a unique complex of operating characteristics (ductility, strength, magnetic and chemical properties) are governed by the basic peculiarity of material in amorphized state - its thermodynamic instability. In comparison with traditional thermodynamically equilibrium metallic alloys, the kinetics of structure changes in amorphous materials is quite different. Thus, it is suggested, that they have peculiar defects (phasonics) which are not typical of materials in crystalline state, they have no translational symmetry and elementary cells. In the process of coatings forming with non-equilibrium structure states can be realized in them, which are characterized by a fluctuation type of origin, entropy export, appearance of space or temporary symmetry uncertainty of the transition direction 'order $ARLR disorder' in bifurcation points. The aforesaid explains a great scientific (not only practical) interest in the structure study of disordered medium. Functional coatings with amorphized, nano- and microcrystalline structure components formed on copper substrate by plasma spraying of dispersed (to 50 mcm) Ni-Al powder. According to the constitutional diagram it was expected to obtain a mixture from equilibrium intermetallide phases NiAl3 + Ni2Al3. The experimental results and investigations performed by X-ray structure, X-ray spectrum and electron microscopy techniques have shown it is possible to obtain phases of variable composition (Ni)m(Al)n with Ni content from 25 to 75 vol.%, including NiAl. It turned out that in the process of spraying the

  2. A retrospective cohort mortality study among workers occupationally exposed to metallic nickel powder at the Oak Ridge Gaseous Diffusion Plant.

    PubMed

    Cragle, D L; Hollis, D R; Newport, T H; Shy, C M

    1984-01-01

    The Oak Ridge Gaseous Diffusion Plant (ORGDP) employed over 800 white male workers between 1 January 1948, and 31 December 1953, in the manufacture of "barrier" material that required metallic nickel powder in its production. A retrospective cohort study was conducted to determine whether persons working with metallic nickel powder have a higher mortality from cancers of the respiratory tract than non-nickel workers. A comparison group was defined as all white males employed at ORGDP sometime between 1 January 1948, and 31 December 1953, who had no indications of occupational involvement in barrier production. This group comprised over 7 500 workers. Vital status determination has been completed up to 31 December 1977, allowing at least 24 years of follow-up for all persons in the study. Death certificates were available for 97% of the deaths among the nickel workers and non-nickel worker groups. End-points of interest were selected site-specific cancers and the general overall pattern of disease-specific mortality. Mortality rates in the nickel workers and non-nickel worker groups were compared with those for the white male population of the United States and with each other. There was no evidence of increased mortality due to lung cancers or nasal sinus cancers in nickel workers. Increases (not statistically significant) in mortality due to cancers of the buccal cavity and pharynx, and of the digestive system were observed in the nickel worker group, compared with the non-nickel worker group.

  3. Effect of mechanical milling on Ni-TiH{sub 2} powder alloy filler metal for brazing TiAl intermetallic alloy: The microstructure and joint's properties

    SciTech Connect

    He Peng Liu Duo; Shang Erjing; Wang Ming

    2009-01-15

    A TiH{sub 2}-50 wt.% Ni powder alloy was mechanically milled in an argon gas atmosphere using milling times up to 480 min. A TiAl intermetallic alloy was joined by vacuum furnace brazing using the TiH{sub 2}-50 wt.% Ni powder alloy as the filler metal. The effect of mechanical milling on the microstructure and shear strength of the brazed joints was investigated. The results showed that the grains of TiH{sub 2}-50 wt.% Ni powder alloy were refined and the fusion temperature decreased after milling. A sound brazing seam was obtained when the sample was brazed at 1140 deg. C for 15 min using filler metal powder milled for 120 min. The interfacial zones of the specimens brazed with the milled filler powder were thinner and the shear strength of the joint was increased compared to specimens brazed with non-milled filler powder. A sample brazed at 1180 deg. C for 15 min using TiH{sub 2}-50 wt.% Ni powder alloy milled for 120 min exhibited the highest shear strength at both room and elevated temperatures.

  4. Removal of selected metals from drinking water using modified powdered block carbon

    NASA Astrophysics Data System (ADS)

    Campos, V.; Sayeg, I. J.; Buchler, P. M.

    2008-09-01

    This paper presents the possible alternative removal options for the development of safe drinking water supply in the trace elements affected areas. Arsenic and chromium are two of the most toxic pollutants, introduced into natural waters from a variety of sources and causes various adverse effects on living bodies. Performance of three filter bed method was evaluated in the laboratory. Experiments have been conducted to investigate the sorption of arsenic and chromium on carbon steel and removal of trace elements from drinking water with a household filtration process. The affinity of the arsenic and chromium species for Fe/Fe3C (iron/iron carbide) sites is the key factor controlling the removal of the elements. The method is based on the use of powdered block carbon (PBC), powder carbon steel and ball ceramic in the ion-sorption columns as a cleaning process. The PBC modified is a satisfactory and practical sorbent for trace elements (arsenite and chromate) dissolved in water.

  5. Processing and properties of Ag/BSCCO PIT tapes containing different proportions of silver metal powder

    NASA Astrophysics Data System (ADS)

    dos Santos, Dayse I.; Rodrigues, Durval; Rubo, Elisabete Ap. A.; Cursino, Eliana

    2004-08-01

    Monofilamentary tapes (150 μm thickness) were prepared by swaging and rolling silver tubes containing the Bi:2212 ceramic (granulation below 20 μm) and the silver powder (about 0.8 μm). The study has been made, among other samples, on tapes with nominal proportions of 0, 10 and 20 wt.% of silver. The samples were characterized by SEM, and by electrical measurements under varying applied magnetic field. The measurements of Jc showed that the addition of 10 wt.% silver powder is very beneficent to this property, doubling the obtained values at 60 K, while the 20 wt.% tape presented very low Jc. The tape with no silver content showed to have a Jc as high as 2.2 × 10 5 A/cm 2, at 4.2 K, zero applied magnetic field.

  6. Influence of Heavy Metal Powders on Rheological Properties of Poly(Lactic Acid)

    NASA Astrophysics Data System (ADS)

    Lebedev, S. M.; Gefle, O. S.; Amitov, E. T.; Berchuk, D. Yu.; Zhuravlev, D. V.

    2017-08-01

    Main properties of poly(lactic acid) (PLA) and composite materials on its basis filled with tungsten and lead powders are investigated. An anomalous decrease of the viscosity of melts of poly(lactic acid)/tungsten and poly(lactic acid)/lead composites is detected. The methods of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and IR spectroscopy are used for investigation. It is shown that the temperature at which the composites filled with tungsten and lead begin to melt decreases by more than 8 and 3°C in comparison with neat PLA. Our investigations show impossibility of preparing radiation resistant polymer composites based on PLA filled with tungsten and lead powders.

  7. Mechanistic Models for Ignition and Combustion of Metallic Powders in Different Environments

    DTIC Science & Technology

    2010-09-17

    describing thermally activated ignition of aluminum powders. A new experimental technique is developed to investigate combustion dynamics of individual...aluminum particles in varied environments. 3. Characterize combustion dynamics and burn rates of single aluminum particles and aerosolized aluminum...is structurally similar to the  polymorph—may be stabilized by the adsorption of H2O on its surface, resulting in the preferred formation of fresh

  8. Facile synthesis of multi-shell structured binary metal oxide powders with a Ni/Co mole ratio of 1:2 for Li-Ion batteries

    NASA Astrophysics Data System (ADS)

    Choi, Seung Ho; Park, Sun Kyu; Lee, Jung-Kul; Kang, Yun Chan

    2015-06-01

    Multi-shell structured binary transition metal oxide powders with a Ni/Co mole ratio of 1:2 are prepared by a simple spray drying process. Precursor powder particles prepared by spray drying from a spray solution of citric acid and ethylene glycol have completely spherical shape, fine size, and a narrow size distribution. The precursor powders turn into multi-shell powders after a post heat-treatment at temperatures between 250 and 800 °C. The multi-shell structured powders are formed by repeated combustion and contraction processes. The multi-shell powders have mixed crystal structures of Ni1-xCo2O4-x and NiO phases regardless of the post-treatment temperature. The reversible capacities of the powders post-treated at 250, 400, 600, and 800 °C after 100 cycles are 584, 913, 808, and 481 mA h g-1, respectively. The low charge transfer resistance and high lithium ion diffusion rate of the multi-shell powders post-treated at 400 °C with optimum grain size result in superior electrochemical properties even at high current densities.

  9. Thin-film preparation by back-surface irradiation pulsed laser deposition using metal powder targets

    NASA Astrophysics Data System (ADS)

    Kawasaki, Hiroharu; Ohshima, Tamiko; Yagyu, Yoshihito; Ihara, Takeshi; Yamauchi, Makiko; Suda, Yoshiaki

    2017-01-01

    Several kinds of functional thin films were deposited using a new thin-film preparation method named the back-surface irradiation pulsed laser deposition (BIPLD) method. In this BIPLD method, powder targets were used as the film source placed on a transparent target holder, and then a visible-wavelength pulsed laser was irradiated from the holder side to the substrate. Using this new method, titanium oxide and boron nitride thin films were deposited on the silicon substrate. Surface scanning electron microscopy (SEM) images suggest that all of the thin films were deposited on the substrate with some large droplets irrespective of the kind of target used. The deposition rate of the films prepared by using this method was calculated from film thickness and deposition time to be much lower than that of the films prepared by conventional PLD. X-ray diffraction (XRD) measurement results suggest that rutile and anatase TiO2 crystal peaks were formed for the films prepared using the TiO2 rutile powder target. Crystal peaks of hexagonal boron nitride were observed for the films prepared using the boron nitride powder target. The crystallinity of the prepared films was changed by annealing after deposition.

  10. Powder-XRD and (14) N magic angle-spinning solid-state NMR spectroscopy of some metal nitrides.

    PubMed

    Kempgens, Pierre; Britton, Jonathan

    2016-05-01

    Some metal nitrides (TiN, ZrN, InN, GaN, Ca3 N2 , Mg3 N2 , and Ge3 N4 ) have been studied by powder X-ray diffraction (XRD) and (14) N magic angle-spinning (MAS) solid-state NMR spectroscopy. For Ca3 N2 , Mg3 N2 , and Ge3 N4 , no (14) N NMR signal was observed. Low speed (νr  = 2 kHz for TiN, ZrN, and GaN; νr  = 1 kHz for InN) and 'high speed' (νr  = 15 kHz for TiN; νr  = 5 kHz for ZrN; νr  = 10 kHz for InN and GaN) MAS NMR experiments were performed. For TiN, ZrN, InN, and GaN, powder-XRD was used to identify the phases present in each sample. The number of peaks observed for each sample in their (14) N MAS solid-state NMR spectrum matches perfectly well with the number of nitrogen-containing phases identified by powder-XRD. The (14) N MAS solid-state NMR spectra are symmetric and dominated by the quadrupolar interaction. The envelopes of the spinning sidebands manifold are Lorentzian, and it is concluded that there is a distribution of the quadrupolar coupling constants Qcc 's arising from structural defects in the compounds studied.

  11. Dense and Homogeneous Compaction of Fine Ceramic and Metallic Powders: High-Speed Centrifugal Compaction Process

    SciTech Connect

    Suzuki, Hiroyuki Y.

    2008-02-15

    High-Speed Centrifugal Compaction Process (HCP) is a variation of colloidal compacting method, in which the powders sediment under huge centrifugal force. Compacting mechanism of HCP differs from conventional colloidal process such as slip casting. The unique compacting mechanism of HCP leads to a number of characteristics such as a higher compacting speed, wide applicability for net shape formation, flawless microstructure of the green compacts, etc. However, HCP also has several deteriorative characteristics that must be overcome to fully realize this process' full potential.

  12. Applications of high-temperature powder metal aluminum alloys to small gas turbines

    NASA Technical Reports Server (NTRS)

    Millan, P. P., Jr.

    1982-01-01

    A program aimed at the development of advanced powder-metallurgy (PM) aluminum alloys for high-temperature applications up to 650 F using the concepts of rapid solidification and mechanical alloying is discussed. In particular, application of rapidly solidified PM aluminum alloys to centrifugal compressor impellers, currently used in auxiliary power units for both military and commercial aircraft and potentially for advanced automotive gas turbine engines, is examined. It is shown that substitution of high-temperature aluminum for titanium alloy impellers operating in the 360-650 F range provides significant savings in material and machining costs and results in reduced component weight, and consequently, reduced rotating group inertia requirements.

  13. Quadrupolar contact terms and hyperfine structure

    SciTech Connect

    Karl, G.; Novikov, V. A.

    2006-08-15

    In the interaction of two electric quadrupoles, there is at short range a contact term proportional to the second derivative of a {delta} function. This contact term contributes to the hyperfine splitting of bound states of two particles with spin one or higher -- for example, the bound state of {omega}{sup -} and a nucleus with spin one. The contact hyperfine splitting occurs in states with orbital angular momentum unity (P wave), in contrast to the Fermi contact interaction, which is in S states. We find that these contact splittings will be observable with {omega}{sup -} atoms and help measure the quadrupole moment and charge radius of the hyperon.

  14. Understanding heme proteins with hyperfine spectroscopy

    NASA Astrophysics Data System (ADS)

    Van Doorslaer, Sabine

    2017-07-01

    Heme proteins are versatile proteins that are involved in a large number of biological processes. Many spectroscopic methods are used to gain insight into the different mechanistic processes governing heme-protein functions. Since many (intermediate) states of heme proteins are paramagnetic, electron paramagnetic resonance (EPR) methods, such as hyperfine spectroscopy, offer unique tools for these investigations. This perspective gives an overview of the use of state-of-the-art hyperfine spectroscopy in heme research, focusing on the advantages, limits and challenges of the different techniques.

  15. Evaluation of the safety and efficiency of novel metallic implant scaler tips manufactured by the powder injection molding technique.

    PubMed

    Chun, Kyung A; Kum, Kee-Yeon; Lee, Woo-Cheol; Baek, Seung-Ho; Choi, Hae-Won; Shon, Won-Jun

    2017-07-11

    Although many studies have compared the properties of ultrasonic scaling instruments, it remains controversial as to which is most suitable for implant scaling. This study evaluated the safety and efficiency of novel metallic ultrasonic scaler tips made by the powder injection molding (PIM) technique on titanium surfaces. Mechanical instrumentation was carried out using four types of metal scaler tips consisting of copper (CU), bronze (BR), 316 L stainless steel (316 L), and conventional stainless steel (SS) tips. The instrumented surface alteration image of samples was viewed with scanning electron microscope (SEM) and surface profile of the each sample was investigated with confocal laser scanning microscopy (CLSM). Arithmetic mean roughness (Ra) and maximum height roughness (Rmax) of titanium samples were measured and dissipated power of the scaler tip was estimated for scaling efficiency. The average Ra values caused by the 316 L and SS tip were about two times higher than those of the CU and BR tips (p < 0.05). The Rmax value showed similar results. The efficiency of the SS tip was about 3 times higher than that of CU tip, the 316 L tip is about 2.7 times higher than that of CU tip, and the BR tip is about 1.2 times higher than that of CU tip. Novel metallic bronze alloy ultrasonic scaler tip minimally damages titanium surfaces, similar to copper alloy tip. Therefore, this bronze alloy scaler tip may be promising instrument for implant maintenance therapy.

  16. 3D online submicron scale observation of mixed metal powder's microstructure evolution in high temperature and microwave compound fields.

    PubMed

    Kang, Dan; Xu, Feng; Hu, Xiao-fang; Dong, Bo; Xiao, Yu; Xiao, Ti-qiao

    2014-01-01

    In order to study the influence on the mechanical properties caused by microstructure evolution of metal powder in extreme environment, 3D real-time observation of the microstructure evolution of Al-Ti mixed powder in high temperature and microwave compound fields was realized by using synchrotron radiation computerized topography (SR-CT) technique; the spatial resolution was enhanced to 0.37  μm/pixel through the designed equipment and the introduction of excellent reconstruction method for the first time. The process of microstructure evolution during sintering was clearly distinguished from 2D and 3D reconstructed images. Typical sintering parameters such as sintering neck size, porosity, and particle size of the sample were presented for quantitative analysis of the influence on the mechanical properties and the sintering kinetics during microwave sintering. The neck size-time curve was obtained and the neck growth exponent was 7.3, which indicated that surface diffusion was the main diffusion mechanism; the reason was the eddy current loss induced by the external microwave fields providing an additional driving force for mass diffusion on the particle surface. From the reconstructed images and the curve of porosity and average particle size versus temperature, it was believed that the presence of liquid phase aluminum accelerated the densification and particle growth.

  17. 3D Online Submicron Scale Observation of Mixed Metal Powder's Microstructure Evolution in High Temperature and Microwave Compound Fields

    PubMed Central

    Xu, Feng; Hu, Xiao-fang; Xiao, Yu; Xiao, Ti-qiao

    2014-01-01

    In order to study the influence on the mechanical properties caused by microstructure evolution of metal powder in extreme environment, 3D real-time observation of the microstructure evolution of Al-Ti mixed powder in high temperature and microwave compound fields was realized by using synchrotron radiation computerized topography (SR-CT) technique; the spatial resolution was enhanced to 0.37 μm/pixel through the designed equipment and the introduction of excellent reconstruction method for the first time. The process of microstructure evolution during sintering was clearly distinguished from 2D and 3D reconstructed images. Typical sintering parameters such as sintering neck size, porosity, and particle size of the sample were presented for quantitative analysis of the influence on the mechanical properties and the sintering kinetics during microwave sintering. The neck size-time curve was obtained and the neck growth exponent was 7.3, which indicated that surface diffusion was the main diffusion mechanism; the reason was the eddy current loss induced by the external microwave fields providing an additional driving force for mass diffusion on the particle surface. From the reconstructed images and the curve of porosity and average particle size versus temperature, it was believed that the presence of liquid phase aluminum accelerated the densification and particle growth. PMID:24737986

  18. Effects of mold geometry on fiber orientation of powder injection molded metal matrix composites

    SciTech Connect

    Ahmad, Faiz Aslam, Muhammad Altaf, Khurram Shirazi, Irfan

    2015-07-22

    Fiber orientations in metal matrix composites have significant effect on improving tensile properties. Control of fiber orientations in metal injection molded metal composites is a difficult task. In this study, two mold cavities of dimensions 6x6x90 mm and 10x20x180 mm were used for comparison of fiber orientation in injection molded metal composites test parts. In both mold cavities, convergent and divergent flows were developed by modifying the sprue dimensions. Scanning electron microscope (SEM) was used to examine the fiber orientations within the test samples. The results showed highly aligned fiber in injection molded test bars developed from the convergent melt flow. Random orientation of fibers was noted in the composites test bars produced from divergent melt flow.

  19. Sintering Behavior of Metal Powders Involving Microwave-Enhanced Chemical Reaction

    NASA Astrophysics Data System (ADS)

    Takayama, Sadatsugu; Saito, Yasushi; Sato, Motoyasu; Nagasaka, Takuya; Muroga, Takeo; Ninomiya, Yoshihiko

    2006-03-01

    Copper powder compacts were sintered by microwave radiation in air. In this procedure, the samples were sintered by microwave in air without using any special atmosphere, only by protecting them in a container filled with ceramic powder. The enhancement of the deoxidation reaction by the microwave was observed. The samples were analyzed by using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis. The samples were deoxidized on the surface and were well sintered to the edge from the inside throughout the entire cross section. The tensile strength of the copper samples sintered by the microwave in air was higher than that found in conventional sintering in N2 gas. No other differences were noticed between the samples sintered by the microwave under the air-rich conditions and in the conventional furnace in H2+N2 gas. The microwave-sintered copper samples were of good quality; for example, the tensile strength measured throughout the cross section was the same as that for the samples sintered in H2+N2 gas by the conventional method.

  20. Improved electrochemical performance of micro-sized SiO-based composite anode by prelithiation of stabilized lithium metal powder

    NASA Astrophysics Data System (ADS)

    Pan, Qingrui; Zuo, Pengjian; Mu, Tiansheng; Du, Chunyu; Cheng, Xinqun; Ma, Yulin; Gao, Yunzhi; Yin, Geping

    2017-04-01

    The micro-sized SiO-based composite anode material (d-SiO/G/C) for lithium-ion batteries (LIBs) is achieved via the disproportionation reaction of SiO followed by a pitch pyrolysis reaction. The d-SiO/G/C composite exhibits an initial reversible capacity of 905 mAh g-1 and excellent cycling stability. The initial Coulombic efficiency of the d-SiO/G/C composite can be significantly improved from 68.1% to 98.5% by the prelithiation of the composite anode using stabilized lithium metal powders (SLMP), which counteracts the irreversible capacity loss caused by the solid electrolyte interphase (SEI) formation and irreversible conversion reaction during the first lithiation. The micro-sized d-SiO/G/C composite anode with SLMP prelithiation maintains an excellent cycling stability, suggesting its great potential in practical application for high specific energy lithium ion batteries.

  1. Effect of particle size distribution on the structure, hyperfine, and magnetic properties of Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} nanopowders

    SciTech Connect

    Bhattacharjee, Kaustav; Das, G. C.; Pati, Satya P.; Das, D.

    2014-12-21

    Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} nano powders were synthesized by an auto combustion method and then heat treated at different temperatures in air for a fixed time. As a consequence, a distribution in particle size and strain was incorporated within the specimens, as estimated from the Rietveld refinement analysis of the powder x-ray diffraction data. The changes in the microstructure and crystal structure parameters were carefully extracted through the refinement analysis. Thermal annealing causes increment in the dispersion and mean of the size distribution. Reallocation of cations in the lattice sites occur as a consequence of the heat treatment which was manifested in their altered unit cell length (a), r.m.s. strain (〈ε{sup 2}〉{sup 1/2}), oxygen positional parameter (u), metal-oxygen bond lengths (R{sub OA} and R{sub OB}), and the band positions (ν{sub 1}and ν{sub 2}) in the vibrational spectroscopy. We also investigate the hyperfine and magnetic properties of the samples using different instrumental techniques (with different operating time scales) like Mössbauer spectroscopy, electron paramagnetic resonance spectroscopy, and superconducting quantum interference device magnetometry. Results show that the effect of particle size distribution was manifested in their hyperfine field distribution profile, paramagnetic resonance spectra, and magnetic anisotropy energy distribution profile. Co-existence of superparamagnetic and ferrimagnetic phase was recorded at room temperature in the samples when annealed at lower temperature. However, with increase in annealing temperature, the nature of the size distribution changes and ferrimagnetic ordering predominates for the larger size nanoparticles. Thus, the effect of particle size distribution on the structural, hyperfine, and magnetic properties of various Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} nanoparticles was investigated herein which hitherto has not been discussed in the literature.

  2. Four-Component Relativistic Density Functional Theory Calculations of EPR g- and Hyperfine-Coupling Tensors Using Hybrid Functionals: Validation on Transition-Metal Complexes with Large Tensor Anisotropies and Higher-Order Spin-Orbit Effects.

    PubMed

    Gohr, Sebastian; Hrobárik, Peter; Repiský, Michal; Komorovský, Stanislav; Ruud, Kenneth; Kaupp, Martin

    2015-12-24

    The four-component matrix Dirac-Kohn-Sham (mDKS) implementation of EPR g- and hyperfine A-tensor calculations within a restricted kinetic balance framework in the ReSpect code has been extended to hybrid functionals. The methodology is validated for an extended set of small 4d(1) and 5d(1) [MEXn](q) systems, and for a series of larger Ir(II) and Pt(III) d(7) complexes (S = 1/2) with particularly large g-tensor anisotropies. Different density functionals (PBE, BP86, B3LYP-xHF, PBE0-xHF) with variable exact-exchange admixture x (ranging from 0% to 50%) have been evaluated, and the influence of structure and basis set has been examined. Notably, hybrid functionals with an exact-exchange admixture of about 40% provide the best agreement with experiment and clearly outperform the generalized-gradient approximation (GGA) functionals, in particular for the hyperfine couplings. Comparison with computations at the one-component second-order perturbational level within the Douglas-Kroll-Hess framework (1c-DKH), and a scaling of the speed of light at the four-component mDKS level, provide insight into the importance of higher-order relativistic effects for both properties. In the more extreme cases of some iridium(II) and platinum(III) complexes, the widely used leading-order perturbational treatment of SO effects in EPR calculations fails to reproduce not only the magnitude but also the sign of certain g-shift components (with the contribution of higher-order SO effects amounting to several hundreds of ppt in 5d complexes). The four-component hybrid mDKS calculations perform very well, giving overall good agreement with the experimental data.

  3. Metals for bone implants. Part 1. Powder metallurgy and implant rendering.

    PubMed

    Andani, Mohsen Taheri; Shayesteh Moghaddam, Narges; Haberland, Christoph; Dean, David; Miller, Michael J; Elahinia, Mohammad

    2014-10-01

    New metal alloys and metal fabrication strategies are likely to benefit future skeletal implant strategies. These metals and fabrication strategies were looked at from the point of view of standard-of-care implants for the mandible. These implants are used as part of the treatment for segmental resection due to oropharyngeal cancer, injury or correction of deformity due to pathology or congenital defect. The focus of this two-part review is the issues associated with the failure of existing mandibular implants that are due to mismatched material properties. Potential directions for future research are also studied. To mitigate these issues, the use of low-stiffness metallic alloys has been highlighted. To this end, the development, processing and biocompatibility of superelastic NiTi as well as resorbable magnesium-based alloys are discussed. Additionally, engineered porosity is reviewed as it can be an effective way of matching the stiffness of an implant with the surrounding tissue. These porosities and the overall geometry of the implant can be optimized for strain transduction and with a tailored stiffness profile. Rendering patient-specific, site-specific, morphology-specific and function-specific implants can now be achieved using these and other metals with bone-like material properties by additive manufacturing. The biocompatibility of implants prepared from superelastic and resorbable alloys is also reviewed.

  4. Retention of Compressive Residual Stresses Introduced by Shot Peening in a Powder Metal Disk Superalloy

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Danetti, Andrew; Draper, Susan L.; Locci, Ivan E.; Telesman, Jack

    2016-01-01

    The fatigue lives of disk superalloys can be increased by shot peening their surfaces, to induce compressive residual stresses near the surface that impede cracking there. As disk application temperatures increase for improved efficiency, the persistence of these beneficial stresses could be impaired, especially with continued fatigue cycling. The objective of this work was to study the retention of residual stresses introduced by shot peening, when subjected to fatigue and high temperatures. Fatigue specimens of powder metallurgy processed nickel-base disk superalloy ME3 were prepared with consistent processing and heat treatment. They were then shot peened using varied conditions. Strain-controlled fatigue cycles were run at room temperature and 704 C, to allow re-assessment of residual stresses.

  5. Fluctuating hyperfine interactions: an updated computational implementation

    NASA Astrophysics Data System (ADS)

    Zacate, M. O.; Evenson, W. E.

    2015-04-01

    The stochastic hyperfine interactions modeling library (SHIML) is a set of routines written in the C programming language designed to assist in the analysis of stochastic models of hyperfine interactions. The routines read a text-file description of the model, set up the Blume matrix, upon which the evolution operator of the quantum mechanical system depends, and calculate the eigenvalues and eigenvectors of the Blume matrix, from which theoretical spectra of experimental techniques can be calculated. The original version of SHIML constructs Blume matrices applicable for methods that measure hyperfine interactions with only a single nuclear spin state. In this paper, we report an extension of the library to provide support for methods such as Mössbauer spectroscopy and nuclear resonant scattering of synchrotron radiation, which are sensitive to interactions with two nuclear spin states. Examples will be presented that illustrate the use of this extension of SHIML to generate Mössbauer spectra for polycrystalline samples under a number of fluctuating hyperfine field models.

  6. Applying Massively Parallel Kinetic Monte Carlo Methods to Simulate Grain Growth and Sintering in Powdered Metals

    DTIC Science & Technology

    2011-09-01

    into the Earth’s atmosphere, linings for friction brakes, turbine disks, and metallic glasses for high-strength films and ribbons to name a few...vacancies for describing the phenomenon of pore elimination. Vacancies and atoms can move by surface diffusion, evaporation -condensation, grain...particles, which does not occur during surface transport mechanisms [19]. Category Mechanisms Involved Surface Transport Evaporation -Condensation

  7. Compressed Air System Overhaul Improves Production at a Powdered Metal Manufacturing Plant (GKN Sinter Metals in Salem, IN)

    SciTech Connect

    2000-11-01

    In 1998, GKN Sinter Metals completed a successful compressed air system improvement project at its Salem, Indiana manufacturing facility. The project was performed after GKN undertook a survey of its system in order to solve air quality problems and to evaluate whether the capacity of their compressed air system would meet their anticipated plant expansion. Once the project was implemented, the plant was able to increase production by 31% without having to add any additional compressor capacity.

  8. Preliminary survey report: control technology for manual transfer of chemical powders at Porcelain Metals Corporation, Louisville, Kentucky

    SciTech Connect

    Godbey, F.W.

    1984-08-01

    Health hazard control methods, work processes, and existing control technologies used in the manual transfer of chemical powders were evaluated at Porcelain Metals Corporation, Louisville, Kentucky in May, 1984. The company employed 97 workers involved in the manufacture of porcelain and metal stampings. The major dry ingredients were frit, silica, and clays. Raw materials were received in bags that were opened as needed and dumped directly into a hopper. The material was discharged into a mill, and various amounts were dispensed by scoop into a pan for weighing. The pan contents were then dumped into the hopper, the mill head was attached, and water was added. After milling, the slurry was pumped to a storage tank for later use. General exhaust ventilation was used, and hearing protectors, safety glasses, hard hats, and dust masks were provided. Workers were encouraged to use good work practices, and were given pre-employment physicals and annual hearing tests. Periodic atmospheric dust sampling was performed, and monthly inspections were conducted. The author does not recommend an in depth study of control technologies at this company since no unique control methods are used.

  9. 2D TRIPLE in orientationally disordered samples—a means to resolve and determine relative orientation of hyperfine tensors

    NASA Astrophysics Data System (ADS)

    Goldfarb, D.; Epel, B.; Zimmermann, H.; Jeschke, G.

    2004-05-01

    The two-dimensional (2D) TRIPLE experiment provides correlations between electron-nuclear double resonance (ENDOR) frequencies that belong to the same electron-spin manifold, MS, and therefore allows to assign ENDOR lines to their specific paramagnetic centers and MS manifolds. This, in turn, also provides the relative signs of the hyperfine couplings. So far this experiment has been applied only to single crystals, where the cross-peaks in the 2D spectrum are well resolved with regular shapes. Here we introduce the application of the 2D TRIPLE experiment to orientationally disordered systems, where it can resolve overlapping powder patterns. Moreover, analysis of the shape of the cross-peaks shows that it is highly dependent on the relative orientation of the hyperfine tensors of the two nuclei contributing to this particular peak. This is done initially through a series of simulations and then demonstrated experimentally at a high field (W-band, 95 GHz). The first example concerned the 1H hyperfine tensors of the stable radical α,γ-bisdiphenylene-β-phenylallyl (BDPA) immobilized in a polystyrene matrix. Then, the experiment was applied to a more complex system, a frozen solution of Cu(II)-bis(2,2 ':6 ',2″ terpyridine) complex. There, the 2D TRIPLE experiment was combined with the variable mixing time (VMT) ENDOR experiment, which determined the absolute sign of the hyperfine couplings involved, and orientation selective ENDOR experiments. Analysis of the three experiments gave the hyperfine tensors of a few coupled protons.

  10. Dendrite Suppression by Synergistic Combination of Solid Polymer Electrolyte Crosslinked with Natural Terpenes and Lithium Powder Anode for Lithium Metal Batteries.

    PubMed

    Shim, Jimin; Lee, Jae Won; Bae, Ki Yoon; Kim, Hee Joong; Yoon, Woo Young; Lee, Jong-Chan

    2017-04-03

    Lithium metal anode has fundamental problems concerning formation and growth of lithium dendrites which prevents practical applications of next generation of high-capacity lithium metal batteries. The synergistic combination of solid polymer electrolyte (SPE) crosslinked with naturally occurring terpenes and lithium powder anode is promising solution to resolve the dendrite issues by substituting conventional liquid electrolyte/separator and lithium foil anode system. A series of SPEs based on polysiloxane crosslinked with natural terpenes are prepared by facile thiol-ene click reaction under mild condition and structural effect of terpene crosslinkers on electrochemical properties is studied. Lithium powder with large surface area is prepared by droplet emulsion technique (DET) and used as anode materials. The effect of physical state of electrolyte (solid/liquid) and morphology of lithium metal anode (powder/foil) on dendrite growth behavior is systematically studied. The synergistic combination of SPE and lithium powder anode suggests effective solution to suppress the dendrite growth due to formation of stable solid electrolyte interphase (SEI) layer and delocalized current density.

  11. Effect of chlorine in clay-mineral specimens prepared on silver metal-membrane mounts for X-ray powder diffraction analysis

    USGS Publications Warehouse

    Poppe, L.J.; Commeau, J.A.; Pense, G.M.

    1989-01-01

    Silver metal-membrane filters are commonly used as substrates in the preparation of oriented clay-mineral specimens for X-ray powder diffraction (XRD). The silver metal-membrane filters, however, present some problems after heat treatment if either the filters or the samples contain significant amounts of chlorine. At elevated temperature, the chloride ions react with the silver substrate to form crystalline compounds. These compounds change the mass-absorption coefficient of the sample, reducing peak intensities and areas and, therefore, complicating the semiquantitative estimation of clay minerals. A simple procedure that eliminates most of the chloride from a sample and the silver metal-membrane substrate is presented here.

  12. Hyperfine interactions in magnetoelectric hexaferrite system

    NASA Astrophysics Data System (ADS)

    Kouřil, Karel; Chlan, Vojtěch; Štěpánková, Helena; Novák, Pavel; Knížek, Karel; Hybler, Jiří; Kimura, Tsuyoshi; Hiraoka, Yuji; Buršík, Josef

    2010-05-01

    Nuclear magnetic resonance (NMR) in Y-hexaferrite system (Ba 1-xSr x) 2Zn 2Fe 12O 22 was measured on both monocrystalline and polycrystalline samples at liquid helium temperature. Corresponding ab-initio calculation of the hyperfine parameters was also performed. The signal from 57Fe was detected in the frequency interval 65-76 MHz, while NMR spectrum of 67Zn nuclei occurs between 15 and 30 MHz. Due to the disorder in two tetrahedral sublattices occupied partly by Zn and partly by Fe, the NMR lines are broad and the spectra are poorly resolved. Comparison between the experimentally observed 67Zn spectra and the spectra modelled using the calculated hyperfine parameters was made. It indicates that the spectra of 67Zn can be used to determine the distribution of Zn and Fe between the two tetrahedral sublattices.

  13. Tribochemical peculiarities of lubricant composition with surface-modified metal powder

    NASA Astrophysics Data System (ADS)

    Syrkov, A. G.; Silivanov, M. O.; Kushchenko, A. N.

    2016-07-01

    The influence of different factors (adhesion, surface hydrophobicity, etc.) on antifrictional properties of lubricant with modified metal additives was discussed. The measurings of friction coefficient (f) and friction force (F fr) were carried out for the heterogeneous systems as oil I-20 with Al-additives modified by triamon (T), alkamon (A) and ethylhydridesiloxane according to various programs. It was established that as a number of T-underlayers, included in Al-additives with chemisorpted external layer of ethylhydridsiloxane reduces from 3 to 1 the force of friction and coefficient of friction reduce. It was discovered that the value of summand which stands for the amount of intermolecular forces in the boundary friction equation can be regulated in Al-additives by using low-molecular T-underlayer.

  14. Magneto-structural properties of PbFe 12O 19 hexaferrite powders prepared by decomposition of hydroxide-carbonate and metal-organic precipitates

    NASA Astrophysics Data System (ADS)

    Díaz-Castañón, S.; Sánchez Ll, J. L.; Estevez-Rams, E.; Leccabue, F.; Watts, B. E.

    1998-06-01

    PbFe 12O 19 powders were obtained by thermal decomposition of hydroxide-carbonate coprecipitated salts and metal-organic precursors at 920°C. Significant microstructural differences have been found between both specimens. The MOD powder comprised submicronic particles of remarkably high coercivity (5 kOe), and the magnetization mechanism was dominated by coherent rotation. In contrast, the coercivity for chemically coprecipitated powders was very poor (1.6 kOe), when compared with Ba- and Sr-compounds prepared following the same method, a behavior associated with excessive grain growth. Cell parameters, microstructure, Curie temperature, hysteretic properties, anisotropy field and the saturation magnetization as a function of the temperature in the interval 77-300 K are reported.

  15. Hyperfine Structure measurements of 45Sc

    NASA Astrophysics Data System (ADS)

    Jones, K. D.; Rossi, D. M.; Minamisono, K.; Miller, A. J.; Asberry, H.; Mantica, P. F.

    2015-10-01

    A chain of charge radii shows discontinuity at nucleon magic numbers. This signature of the shell closure, however, is missing at the neutron magic number N = 20 for Ar, Ca and K isotopes. A collinear laser spectroscopy experiment on the stable 45Sc isotope, which is one proton added to Ca, was performed as a prerequisite of radioactive beam experiments on Sc across N = 20 to further investigate the abnormal behavior. The experiment was performed at BEam COoling and LAser spectroscopy (BECOLA) facility at NSCL and a hyperfine spectrum was measured for the electronic transition of 3 d 4 s 3D1 --> 3 d 4 p 3F2 at λ = 364 . 3 nm in 45ScII. The magnetic dipole and electric quadrupole hyperfine coupling constants A and B of both the lower and upper states were obtained from the hyperfine structure by fitting a pseudo-Voigt profile. The results obtained from these data are in good agreement with previous values and have smaller statistical errors. The detail of experiment and analysis will be discussed. This work was supported in part by NSF Grant No. PHY-11-02511.

  16. Fabrication and Characterization of High Strength Al-Cu Alloys Processed Using Laser Beam Melting in Metal Powder Bed

    NASA Astrophysics Data System (ADS)

    Ahuja, Bhrigu; Karg, Michael; Nagulin, Konstantin Yu.; Schmidt, Michael

    The proposed paper illustrates fabrication and characterization of high strength Aluminium Copper alloys processed using Laser Beam Melting process. Al-Cu alloys EN AW-2219 and EN AW-2618 are classified as wrought alloys and 2618 is typically considered difficult to weld. Laser Beam Melting (LBM) process from the family of Additive Manufacturing processes, has the unique ability to form fully dense complex 3D geometries using micro sized metallic powder in a layer by layer fabrication methodology. LBM process can most closely be associated to the conventional laser welding process, but has significant differences in terms of the typical laser intensities and scan speeds used. Due to the use of high intensities and fast scan speeds, the process induces extremely high heating and cooling rates. This property gives it a unique physical attribute and therefore its ability to process high strength Al-Cu alloys needs to be investigated. Experiments conducted during the investigations associate the induced energy density controlled by varying process parameters to the achieved relative densities of the fabricated 3D structures.

  17. Relativistic spin-orbit effects on hyperfine coupling tensors by density-functional theory

    NASA Astrophysics Data System (ADS)

    Arbuznikov, Alexei V.; Vaara, Juha; Kaupp, Martin

    2004-02-01

    A second-order perturbation theory treatment of spin-orbit corrections to hyperfine coupling tensors has been implemented within a density-functional framework. The method uses the all-electron atomic mean-field approximation and/or spin-orbit pseudopotentials in incorporating one- and two-electron spin-orbit interaction within a first-principles framework. Validation of the approach on a set of main-group radicals and transition metal complexes indicates good agreement between all-electron and pseudopotential results for hyperfine coupling constants of the lighter nuclei in the system, except for cases in which scalar relativistic effects become important. The nonrelativistic Fermi contact part of the isotropic hyperfine coupling constants is not always accurately reproduced by the exchange-correlation functionals employed, particularly for the triplet and π-type doublet radicals in the present work. For this reason, ab initio coupled-cluster singles and doubles with perturbative triples results for the first-order contributions have been combined in the validation calculations with the density-functional results for the second-order spin-orbit contributions. In the cases where spin-orbit corrections are of significant magnitude relative to the nonrelativistic first-order terms, they improve the agreement with experiment. Antisymmetric contributions to the hyperfine tensor arise from the spin-orbit contributions and are discussed for the IO2 radical, whereas rovibrational effects have been evaluated for RhC, NBr, and NI.

  18. Development of Metal/Polymer Mixtures Dedicated to Macro and Micro powder Injection Moulding : Experiments and Simulations

    SciTech Connect

    Quinard, C.; Barriere, T.; Gelin, J. C.; Song, J. P.; Cheng, Z. Q.; Liu, B. S.

    2007-05-17

    Important research tasks at ENSMM/LMA are concerned for the development of mixtures of fine powders associated to polymer binders dedicated to the powder injection moulding (PIM) and to the powder injection micro-moulding ({mu}PIM) in accordance with many works already carried out with different feedstock suppliers dedicated to the macro-components. These research tasks are completed with the simulations of injection and sintering for solid state diffusion for to validate the mumerical models.

  19. Preparation of superconductor precursor powders

    DOEpatents

    Bhattacharya, Raghunath

    1998-01-01

    A process for the preparation of a precursor metallic powder composition for use in the subsequent formation of a superconductor. The process comprises the steps of providing an electrodeposition bath comprising an electrolyte medium and a cathode substrate electrode, and providing to the bath one or more soluble salts of one or more respective metals which are capable of exhibiting superconductor properties upon subsequent appropriate treatment. The bath is continually energized to cause the metallic and/or reduced particles formed at the electrode to drop as a powder from the electrode into the bath, and this powder, which is a precursor powder for superconductor production, is recovered from the bath for subsequent treatment. The process permits direct inclusion of all metals in the preparation of the precursor powder, and yields an amorphous product mixed on an atomic scale to thereby impart inherent high reactivity. Superconductors which can be formed from the precursor powder include pellet and powder-in-tube products.

  20. Toxicology and occupational hazards of new materials and processes in metal surface treatment, powder metallurgy, technical ceramics, and fiber-reinforced plastics.

    PubMed

    Midtgård, U; Jelnes, J E

    1991-12-01

    Many new materials and processes are about to find their way from the research laboratory into industry. The present paper describes some of these processes and provides an overview of possible occupational hazards and a list of chemicals used or produced in the processes. The technological areas that are considered are metal surface treatment (ion implantation, physical and chemical vapor deposition, plasma spraying), powder metallurgy, advanced technical ceramics, and fiber-reinforced plastics.

  1. Co-evaporation of transition metal salt and SiO powder toward copper(or nickel)/silicon-contained composite nanostructures

    SciTech Connect

    Zhou, Gang; Cao, Yang; He, Junhui

    2013-01-15

    Graphical abstract: Copper(or nickel)/silicon-contained composite nanostructures were successfully synthesized by co-evaporating SiO powder and corresponding transition metal salts (nickel formate and copper sulfate). Display Omitted Highlights: ► Novel nanostructures were synthesized by co-evaporating SiO and metal salts. ► A pre-sintering process was used in the synthesis of copper/silicon nanocomposites. ► A Ni{sub 31}Si{sub 12}/Si/SiO{sub 2} nanocomposite was obtained. ► Peapod-like copper/silicon-contained nanocomposites were obtained. ► On the basis of experimental results, the formation mechanism was discussed. -- Abstract: We demonstrate that several novel copper(or nickel)/silicon-contained composite nanostructures were successfully synthesized by co-evaporating SiO powder and corresponding transition metal salts (transition metal organic salt and transition metal inorganic salt), including nickel formate, cobalt acetate, and copper sulfate. The morphologies, compositions, and crystal structures of products were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The results indicate that the morphology and composition of formed copper(or nickel)/silicon-contained composite nanostructures are dramatically influenced by the distance between SiO powder and transition metal salts, or by the pre-sintering temperature of the reactants. The possible formation mechanisms of these composite nanostructures were discussed on the basis of experimental observations.

  2. 2 D-Hyperfine sublevel correlation spectroscopy of tyrosyl radicals

    NASA Astrophysics Data System (ADS)

    Deligiannakis, Y.; Ivancich, A.; Rutherord, A. W.

    2002-04-01

    Hyperfine sublevel correlation (HYSCORE) spectroscopy has been used to study the tyrosyl radicals in Photosystem II and bovine liver catalase. The HYSCORE data allow a complete resolution of all the 1H hyperfine tensors of these radicals. The present work shows that the proper analysis of the HYSCORE data allows the complete assignment of the 1H-hyperfine tensors in tyrosine radicals and this offers an alternative experimental tool relative to ENDOR.

  3. Role of HSAB concept in understanding biosorptive behaviour of various metal ions employing green biosorbent - Dry Cow Dung Powder

    NASA Astrophysics Data System (ADS)

    Bagla, Hemlata; Khilnani, Roshan

    2016-04-01

    Hard & Soft Acid Base concept, HSAB theory given by Pearson, elucidates the crucial role of HSAB characteristics of both pollutants as well as the aqueous milieu. This theory can also explain the biosorptive behaviour of Dry Cow dung Powder, which helps in governing the success of process. The various metal ionic species exhibit a preference for the ligand binding on the biomass based on its chemical coordination characteristics. A comparative batch equilibration biosorptive assay has been carried out employing radiotracer technique for uptake of Cr(III), Cr(VI), Cd(II), Hg(II), Sr(II), Cs(I) and Co(II) at optimum biosorption parameters. To study the effect of interference of different salts on the percentage biosorption of metal ions on DCP, different organic as well as inorganic salts with varying proportion of 10 mg, 25 mg, 50 mg and 100 mg have been studied. The dynamics of the biosorption in terms of the order of the rate constant was studied applying different kinetic models. The best fitting model was Lagergren pseudo second order model. DCP, an eco-friendly humiresin, enriched with minerals, carbohydrates, fats, proteins, bile pigments, aliphatic - aromatic species such as 'Humic acid', Fulvic acid and many naturally present functional group such as carboxyl, phenols, quinols, amide etc. of both hard and soft nature, making it 'combo' in nature sorbs both concerned metal ions as well as ligands present in the system. Thus the ligands which were masking the biosorption process of heavy metal ions in this study were treated by mere increase in the dose of DCP, which successfully solves the problem without affecting efficiency of the process. This is exemplified by three very basic interactions happening in multicomponent system i.e. Synergism: Mutual enhancement; Antagonism: Mutual decrement; Non-interaction: Neutral effect. Thus DCP has a great potential in the field of water decontamination, industrial water treatment and in abatement of water pollution. So

  4. Observation of the hyperfine spectrum of antihydrogen

    NASA Astrophysics Data System (ADS)

    Ahmadi, M.; Alves, B. X. R.; Baker, C. J.; Bertsche, W.; Butler, E.; Capra, A.; Carruth, C.; Cesar, C. L.; Charlton, M.; Cohen, S.; Collister, R.; Eriksson, S.; Evans, A.; Evetts, N.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Gutierrez, A.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Isaac, C. A.; Ishida, A.; Johnson, M. A.; Jones, S. A.; Jonsell, S.; Kurchaninov, L.; Madsen, N.; Mathers, M.; Maxwell, D.; McKenna, J. T. K.; Menary, S.; Michan, J. M.; Momose, T.; Munich, J. J.; Nolan, P.; Olchanski, K.; Olin, A.; Pusa, P.; Rasmussen, C. Ø.; Robicheaux, F.; Sacramento, R. L.; Sameed, M.; Sarid, E.; Silveira, D. M.; Stracka, S.; Stutter, G.; So, C.; Tharp, T. D.; Thompson, J. E.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.

    2017-08-01

    The observation of hyperfine structure in atomic hydrogen by Rabi and co-workers and the measurement of the zero-field ground-state splitting at the level of seven parts in 1013 are important achievements of mid-twentieth-century physics. The work that led to these achievements also provided the first evidence for the anomalous magnetic moment of the electron, inspired Schwinger’s relativistic theory of quantum electrodynamics and gave rise to the hydrogen maser, which is a critical component of modern navigation, geo-positioning and very-long-baseline interferometry systems. Research at the Antiproton Decelerator at CERN by the ALPHA collaboration extends these enquiries into the antimatter sector. Recently, tools have been developed that enable studies of the hyperfine structure of antihydrogen—the antimatter counterpart of hydrogen. The goal of such studies is to search for any differences that might exist between this archetypal pair of atoms, and thereby to test the fundamental principles on which quantum field theory is constructed. Magnetic trapping of antihydrogen atoms provides a means of studying them by combining electromagnetic interaction with detection techniques that are unique to antimatter. Here we report the results of a microwave spectroscopy experiment in which we probe the response of antihydrogen over a controlled range of frequencies. The data reveal clear and distinct signatures of two allowed transitions, from which we obtain a direct, magnetic-field-independent measurement of the hyperfine splitting. From a set of trials involving 194 detected atoms, we determine a splitting of 1,420.4 ± 0.5 megahertz, consistent with expectations for atomic hydrogen at the level of four parts in 104. This observation of the detailed behaviour of a quantum transition in an atom of antihydrogen exemplifies tests of fundamental symmetries such as charge-parity-time in antimatter, and the techniques developed here will enable more-precise such tests.

  5. Nagaoka's atomic model and hyperfine interactions.

    PubMed

    Inamura, Takashi T

    2016-01-01

    The prevailing view of Nagaoka's "Saturnian" atom is so misleading that today many people have an erroneous picture of Nagaoka's vision. They believe it to be a system involving a 'giant core' with electrons circulating just outside. Actually, though, in view of the Coulomb potential related to the atomic nucleus, Nagaoka's model is exactly the same as Rutherford's. This is true of the Bohr atom, too. To give proper credit, Nagaoka should be remembered together with Rutherford and Bohr in the history of the atomic model. It is also pointed out that Nagaoka was a pioneer of understanding hyperfine interactions in order to study nuclear structure.

  6. Hyperfine structure of hydrogenlike thallium isotopes

    NASA Astrophysics Data System (ADS)

    Beiersdorfer, Peter; Utter, Steven B.; Wong, Keith L.; Crespo López-Urrutia, José R.; Britten, Jerry A.; Chen, Hui; Harris, Clifford L.; Thoe, Robert S.; Thorn, Daniel B.; Träbert, Elmar; Gustavsson, Martin G. H.; Forssén, Christian; Mårtensson-Pendrill, Ann-Marie

    2001-09-01

    The hyperfine splitting of the 1s ground state of hydrogenlike Tl has been measured for the two stable isotopes using emission spectroscopy in the SuperEBIT electron-beam ion trap, giving 3858.22+/-0.30 Å for 203Tl80+ and 3821.84+/-0.34 Å for 205Tl80+ with a wavelength difference Δλ=36.38+/-0.35 Å. This difference is consistent with estimates based on hyperfine anomaly data for neutral Tl only if finite size effects are included in the calculation. By using previously determined nuclear magnetic moments, and applying appropriate corrections for the nuclear charge distribution and radiative effects, the experimental splittings can be interpreted in terms of nuclear magnetization radii 1/2=5.83(14) fm for 203Tl and 1/2=5.89(14) fm for 205Tl. These values are 10% larger than derived from single-particle nuclear magnetization models, and are slightly larger than the corresponding charge distributions.

  7. A new apparatus for non-destructive evaluation of green-state powder metal compacts using the electrical-resistivity method

    NASA Astrophysics Data System (ADS)

    Bogdanov, Gene; Ludwig, Reinhold; Michalson, William R.

    2000-02-01

    This paper presents a new apparatus developed for non-destructive evaluation (NDE) of green-state powder metal compacts. A green-state compact is an intermediate step in the powder metallurgy (PM) manufacturing process, which is produced when a metal powder-lubricant mixture is compacted in a press. This compact is subsequently sintered in a furnace to produce the finished product. Non-destructive material testing is most cost effective in the green state because early flaw detection permits early intervention in the manufacturing cycle and thus avoids scrapping large numbers of parts. Unfortunately, traditional NDE methods have largely been unsuccessful when applied to green-state PM compacts. A new instrumentation approach has been developed, whereby direct currents are injected into the green-state compact and an array of spring-loaded needle contacts records the voltage distributions on the surface. The voltage distribution is processed to identify potentially dangerous surface and sub-surface flaws. This paper presents the custom-designed hardware and software developed for current injection, voltage acquisition, pre-amplification and flaw detection. In addition, the testing algorithm and measurement results are discussed. The success of flaw detection using the apparatus is established by using controlled samples, which are PM compacts with dielectric inclusions inserted.

  8. Method for synthesizing powder materials

    DOEpatents

    Buss, R.J.; Ho, P.

    1988-01-21

    A method for synthesizing ultrafine powder materials, for example, ceramic and metal powders, comprises admitting gaseous reactants from which the powder material is to be formed into a vacuum reaction chamber maintained at a pressure less than atmospheric and at a temperature less than about 400/degree/K (127/degree/C). The gaseous reactants are directed through a glow discharge provided in the vacuum reaction chamber to form the ultrafine powder material. 1 fig.

  9. Explosibility of Metal Powders

    DTIC Science & Technology

    1964-01-01

    040 60 74 7,500 3.6 Calcium silicide ................ 267 540 540 .060 150 73 13,000 2.0 Iron, carbonyl .................. 126 320 310 .105 20 41...308 - -600 - - 39 200 << .1 Beryllium .......................... 95 910 540 - - - - << .1 Copper ............................ 110 700...1 None Aluminum-bronze alloy ........... 234 - 990 - - - Beryllium -copper alloy .......... .259 - - - - Manganese-bronze alloy .......... 285

  10. Method for Production of Powders

    NASA Technical Reports Server (NTRS)

    Stoltzfus, Joel M. (Inventor); Sircar, Subhasish (Inventor)

    1997-01-01

    Apparatus and method are disclosed for producing oxides of metals and of metal alloys. The metal or alloy is placed in an oxygen atmosphere in a combustion chamber and ignited. Products of the combustion include one or more oxides of the metal or alloy in powdered form. In one embodiment of the invention a feeder is provided whereby material to be oxidized by combustion can be achieved into a combustion chamber continuously. A product remover receives the powder product of the combustion.

  11. Hyperfine transitions of 13CN from pre-protostellar sources

    NASA Astrophysics Data System (ADS)

    Flower, D. R.; Hily-Blant, P.

    2015-09-01

    Recent quantum mechanical calculations of rate coefficients for collisional transfer of population between the hyperfine states of 13CN enable their population densities to be determined. We have computed the relative populations of the hyperfine states of the N = 0, 1, 2 rotational states for kinetic temperatures 5 ≤ T ≤ 20 K and molecular hydrogen densities 1 ≤ n(H2) ≤1010 cm-3. Spontaneous and induced radiative transitions were taken into account. Our calculations show that, if the lines are optically thin, the populations of the hyperfine states, F, within a given rotational manifold are proportional to their statistical weights, (2F + 1) - i.e. in local thermodynamic equilibrium - over the entire range of densities. We have re-analysed IRAM 30 m telescope observations of 13CN hyperfine transitions (N = 1 → 0) in four starless cores. A comparison of these observations with our calculations confirms that the hyperfine states are statistically populated in these sources.

  12. Negative muon spin precession measurement of the hyperfine states of muonic sodium

    NASA Astrophysics Data System (ADS)

    Brewer, J. H.; Ghandi, K.; Froese, A. M.; Fryer, B. A.

    2005-05-01

    Both hyperfine states of muonic 23Na and the rate R of conversion between them have been observed directly in a high field negative muon spin precession experiment using a backward muon beam with transverse spin polarization. The result in metallic sodium, R=13.7±2.2μs-1, is consistent with Winston's prediction in 1963 based on Auger emission of core electrons, and with the measurements of Gorringe et al. in Na metal, but not with their smaller result in NaF. In NaOH we find R=23.5±8μs-1, leaving medium-dependent effects ambiguous.

  13. Potential applications of cold sprayed Cu50Ti20Ni30 metallic glassy alloy powders for antibacterial protective coating in medical and food sectors.

    PubMed

    El-Eskandrany, M Sherif; Al-Azmi, Ahmed

    2016-03-01

    Mechanical alloying was utilized for synthesizing of metallic glassy Cu50Ti20Ni30 alloy powders, using a low energy ball milling technique. The metallic glassy powders obtained after 100 h of ball milling had an average particle size of 1.7 mm in diameter and possessed excellent thermal stability, indexed by a relatively high glass transition temperature (358.3 °C) with a wide supercooled liquid region (61 °C). This amorphous phase crystallized into Ti2Cu and CuTiNi2 ordered phases through two overlapped crystallization temperatures at 419.3 °C and 447.5 °C, respectively. The total enthalpy change of crystallization was -4.8 kJ/mol. The glassy powders were employed as feedstock materials to double-face coating the surface of SUS 304 substrate, using cold spraying process under helium gas pressure at 400 °C. This coating material had an extraordinary high nanohardness value of 3.1 GPa. Moreover, it showed a high resistance to wear with a low value of the coefficient of friction ranging from 0.45 to 0.45. Biofilms were grown on 20-mm(2) SUS304 sheets coated coupons inoculated with 1.5 × 10(8) CFU ml(-1)E. coli. Significant biofilm inhibition (p The inhibition of biofilm formation by nanocrystalline powders of Cu-based provides a practical approach to achieve the inhibition of biofilms formation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Predictive modeling, simulation, and optimization of laser processing techniques: UV nanosecond-pulsed laser micromachining of polymers and selective laser melting of powder metals

    NASA Astrophysics Data System (ADS)

    Criales Escobar, Luis Ernesto

    One of the most frequently evolving areas of research is the utilization of lasers for micro-manufacturing and additive manufacturing purposes. The use of laser beam as a tool for manufacturing arises from the need for flexible and rapid manufacturing at a low-to-mid cost. Laser micro-machining provides an advantage over mechanical micro-machining due to the faster production times of large batch sizes and the high costs associated with specific tools. Laser based additive manufacturing enables processing of powder metals for direct and rapid fabrication of products. Therefore, laser processing can be viewed as a fast, flexible, and cost-effective approach compared to traditional manufacturing processes. Two types of laser processing techniques are studied: laser ablation of polymers for micro-channel fabrication and selective laser melting of metal powders. Initially, a feasibility study for laser-based micro-channel fabrication of poly(dimethylsiloxane) (PDMS) via experimentation is presented. In particular, the effectiveness of utilizing a nanosecond-pulsed laser as the energy source for laser ablation is studied. The results are analyzed statistically and a relationship between process parameters and micro-channel dimensions is established. Additionally, a process model is introduced for predicting channel depth. Model outputs are compared and analyzed to experimental results. The second part of this research focuses on a physics-based FEM approach for predicting the temperature profile and melt pool geometry in selective laser melting (SLM) of metal powders. Temperature profiles are calculated for a moving laser heat source to understand the temperature rise due to heating during SLM. Based on the predicted temperature distributions, melt pool geometry, i.e. the locations at which melting of the powder material occurs, is determined. Simulation results are compared against data obtained from experimental Inconel 625 test coupons fabricated at the National

  15. 21 CFR 73.1647 - Copper powder.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Copper powder. 73.1647 Section 73.1647 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1647 Copper powder. (a) Identity. (1) The color additive copper powder is a very fine free-flowing metallic powder prepared from virgin electrolytic copper....

  16. 21 CFR 73.1647 - Copper powder.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Copper powder. 73.1647 Section 73.1647 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1647 Copper powder. (a) Identity. (1) The color additive copper powder is a very fine free-flowing metallic powder prepared from virgin electrolytic copper....

  17. 21 CFR 73.1647 - Copper powder.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Copper powder. 73.1647 Section 73.1647 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1647 Copper powder. (a) Identity. (1) The color additive copper powder is a very fine free-flowing metallic powder prepared from virgin electrolytic copper....

  18. Surface geophysical investigation of the areal and vertical extent of metallic waste at the former Tyson Valley Powder Farm near Eureka, Missouri, Spring 2004

    USGS Publications Warehouse

    Ball, Lyndsay B.; Kress, Wade H.; Anderson, Eric D.; Teeple, Andrew; Ferguson, James W.; Colbert, Charles R.

    2004-01-01

    The former Tyson Valley Powder Farm near Eureka, Missouri, was used primarily as a storage facility for the production of small arms ammunition during 1941?47 and 1951?61. A secondary use of the site was for munitions testing and disposal. Surface exposures of small arms waste, characterized by brass shell casings and fragments, as well as other miscellaneous scrap metal are remnants of disposal practices that took place during U.S. Army operation and can be found throughout the site. Little historical information exists describing disposal practices, and more debris is believed to be buried in the subsurface. The U.S. Army Corps of Engineers has identified several areas of concern throughout the former Tyson Valley Powder Farm. A surface-geophysical investigation was performed by the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, to evaluate the areal and vertical extent of metallic debris in the subsurface within three of these areas of concern. Electromagnetic and magnetic methods were used to locate anomalies indicating relatively large concentrations of buried metallic debris within the selected areas of concern. Maps were created identifying twelve anomalous zones in the three areas of concern, and three of these zones were selected for further investigation. The extent and depth of the anomalies within these zones were explored using two-dimensional direct-current resistivity methods. Resistivity and time-domain induced polarization data were compared to the anomalous locations of the electromagnetic and magnetic surveys. The geophysical methods selected for this study were useful in determining the areal and vertical extent of metallic waste within the former Tyson Valley Powder Farm. However, electromagnetic and magnetic methods were not able to differentiate magnetic scrap metal from non-magnetic metallic small arms waste, most likely due to the small size and scattered distribution of the small arms waste, in addition to

  19. Electroelastic hyperfine tuning of phosphorus donors in silicon.

    PubMed

    Dreher, L; Hilker, T A; Brandlmaier, A; Goennenwein, S T B; Huebl, H; Stutzmann, M; Brandt, M S

    2011-01-21

    We demonstrate an electroelastic control of the hyperfine interaction between nuclear and electronic spins opening an alternative way to address and couple spin-based qubits. The hyperfine interaction is measured by electrically detected magnetic resonance in phosphorus-doped silicon epitaxial layers employing a hybrid structure consisting of a silicon-germanium virtual substrate and a piezoelectric actuator. By applying a voltage to the actuator, the hyperfine interaction is changed by up to 0.9 MHz, which would be enough to shift the phosphorus donor electron spin out of resonance by more than one linewidth in isotopically purified 28Si.

  20. Hyperfine structure of S-states of muonic tritium

    NASA Astrophysics Data System (ADS)

    Martynenko, F. A.; Faustov, R. N.; Martynenko, A. P.

    2016-12-01

    On the basis of quasipotential method in quantum electrodynamics we carry out a precise calculation of hyperfine splitting of S-states in muonic tritium. The one-loop and two-loop vacuum polarization corrections, relativistic effects, nuclear structure corrections in first and second orders of perturbation theory are taken into account. The contributions to hyperfine structure are obtained in integral form and calculated analytically and numerically. Obtained results for hyperfine splitting can be used for a comparison with future experimental data of CREMA collaboration.

  1. Calculation of radiative corrections to hyperfine splitting in p{sub 1/2} states

    SciTech Connect

    Sapirstein, J.; Cheng, K. T.

    2006-10-15

    Techniques to calculate one-loop radiative corrections to hyperfine splitting including binding corrections to all orders have been developed in the last decade for s states of atoms and ions. In this paper these methods are extended to p{sub 1/2} states for three cases. In the first case, the point-Coulomb 2p{sub 1/2} hyperfine splitting is treated for the hydrogen isoelectonic sequence, and the lowest order result ({alpha}/4{pi})E{sub F}, is shown to have large binding corrections at high Z. In the second case, neutral alkali-metal atoms are considered. In the third case, hyperfine splitting of the 2p{sub 1/2} state of lithiumlike bismuth is treated. In the latter two cases, correlation corrections are included and, in addition, the point is stressed that uncertainties associated with nuclear structure, which complicate comparison with experiment for s states, are considerably reduced because of the smaller overlap with the nucleus.

  2. ESTABLISHING SUSTAINABLE US HEV/PHEV MANUFACTURING BASE: STABILIZED LITHIUM METAL POWDER, ENABLING MATERIAL AND REVOLUTIONARY TECHNOLOGY FOR HIGH ENERGY LI-ION BATTERIES

    SciTech Connect

    Yakovleva, Marina

    2012-12-31

    FMC Lithium Division has successfully completed the project “Establishing Sustainable US PHEV/EV Manufacturing Base: Stabilized Lithium Metal Powder, Enabling Material and Revolutionary Technology for High Energy Li-ion Batteries”. The project included design, acquisition and process development for the production scale units to 1) produce stabilized lithium dispersions in oil medium, 2) to produce dry stabilized lithium metal powders, 3) to evaluate, design and acquire pilot-scale unit for alternative production technology to further decrease the cost, and 4) to demonstrate concepts for integrating SLMP technology into the Li- ion batteries to increase energy density. It is very difficult to satisfy safety, cost and performance requirements for the PHEV and EV applications. As the initial step in SLMP Technology introduction, industry can use commercially available LiMn2O4 or LiFePO4, for example, that are the only proven safer and cheaper lithium providing cathodes available on the market. Unfortunately, these cathodes alone are inferior to the energy density of the conventional LiCoO2 cathode and, even when paired with the advanced anode materials, such as silicon composite material, the resulting cell will still not meet the energy density requirements. We have demonstrated, however, if SLMP Technology is used to compensate for the irreversible capacity in the anode, the efficiency of the cathode utilization will be improved and the cost of the cell, based on the materials, will decrease.

  3. Formation of Bi2Sr2CaCu2O x /Ag multifilamentary metallic precursor powder-in-tube wires

    NASA Astrophysics Data System (ADS)

    Zhang, Yun; Koch, Carl C.; Schwartz, Justin

    2016-12-01

    Previously, a metallic precursor (MP) approach to synthesizing Bi2Sr2CaCu2O x (Bi2212), with a homogeneous mixture of Bi, Sr, Ca, Cu and Ag was produced by mechanical alloying. Here, Bi2212/Ag round multifilamentary wire is manufactured using a metallic precursor powder-in-tube (MPIT) process. The MP powders were packed into a pure Ag tube in an Ar atmosphere and then sealed. After deformation, multifilamentary round wires and rolled tapes were heat treated in flowing oxygen through three stages: oxidation, conversion and partial-melt processing (PMP). Processing-microstructure-property relationships on 20-50 mm long multifilamentary round wires and rolled tapes were studied extensively. It is shown that conventional wire deformation processes, optimized for oxide-powder-in-tube wires, are not effective for deforming MPIT wires, and that as with prior studies of MPIT Bi2Sr2Ca2Cu3O y conductors, hot extrusion is required for obtaining a multifilamentary structure with fine filaments. As a result, the Bi2212 MPIT wires reported here have low engineering critical current density. Nonetheless, by focusing on sections of wires that remain intact after deformation, it is also shown that the first heat treatment stage, the oxidation stage, plays a crucial role in chemical homogeneity, phase transformation, and microstructural evolution and three reaction pathways for MP oxidation are presented. Furthermore, it is found the Bi2212 grain alignment within an MPIT filament is significantly different from that found in OPIT filaments after PMP, indicating the formation of highly dense filaments containing Bi2212 fine grains and Ag particles before PMP aids the formation of large, c-axis textured Bi2212 filaments during PMP. These results show that, with improved wire deformation, high critical current density may be obtained via a MPIT process.

  4. Proton-structure corrections to hyperfine splitting in muonic hydrogen

    SciTech Connect

    Carlson, Carl E.; Nazaryan, Vahagn; Griffioen, Keith

    2011-04-15

    We present the derivation of the formulas for the proton structure-dependent terms in the hyperfine splitting of muonic hydrogen. We use compatible conventions throughout the calculations to derive a consistent set of formulas that reconcile differences between our results and some specific terms in earlier work. Convention conversion corrections are explicitly presented, which reduce the calculated hyperfine splitting by about 46 ppm. We also note that using only modern fits to the proton elastic form factors gives a smaller than historical spread of Zemach radii and leads to a reduced uncertainty in the hyperfine splitting. Additionally, hyperfine splittings have an impact on the muonic hydrogen Lamb shift and proton radius measurement, however the correction we advocate has a small effect there.

  5. Spin-torsion effects in the hyperfine structure of methanol

    NASA Astrophysics Data System (ADS)

    Coudert, L. H.; Gutlé, C.; Huet, T. R.; Grabow, J.-U.; Levshakov, S. A.

    2015-07-01

    The magnetic hyperfine structure of the non-rigid methanol molecule is investigated experimentally and theoretically. 12 hyperfine patterns are recorded using molecular beam microwave spectrometers. These patterns, along with previously recorded ones, are analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling due to the large amplitude internal rotation of the methyl group [J. E. M. Heuvel and A. Dymanus, J. Mol. Spectrosc. 47, 363 (1973)]. The theoretical approach setup to analyze the observed data accounts for this spin-torsion in addition to the familiar magnetic spin-rotation and spin-spin interactions. The theoretical approach relies on symmetry considerations to build a hyperfine coupling Hamiltonian and spin-rotation-torsion wavefunctions compatible with the Pauli exclusion principle. Although all experimental hyperfine patterns are not fully resolved, the line position analysis yields values for several parameters including one describing the spin-torsion coupling.

  6. Spin-torsion effects in the hyperfine structure of methanol

    SciTech Connect

    Coudert, L. H. Gutlé, C.; Huet, T. R.; Grabow, J.-U.; Levshakov, S. A.

    2015-07-28

    The magnetic hyperfine structure of the non-rigid methanol molecule is investigated experimentally and theoretically. 12 hyperfine patterns are recorded using molecular beam microwave spectrometers. These patterns, along with previously recorded ones, are analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling due to the large amplitude internal rotation of the methyl group [J. E. M. Heuvel and A. Dymanus, J. Mol. Spectrosc. 47, 363 (1973)]. The theoretical approach setup to analyze the observed data accounts for this spin-torsion in addition to the familiar magnetic spin-rotation and spin-spin interactions. The theoretical approach relies on symmetry considerations to build a hyperfine coupling Hamiltonian and spin-rotation-torsion wavefunctions compatible with the Pauli exclusion principle. Although all experimental hyperfine patterns are not fully resolved, the line position analysis yields values for several parameters including one describing the spin-torsion coupling.

  7. Quantum Theory of Hyperfine Structure Transitions in Diatomic Molecules.

    ERIC Educational Resources Information Center

    Klempt, E.; And Others

    1979-01-01

    Described is an advanced undergraduate laboratory experiment in which radio-frequency transitions between molecular hyperfine structure states may be observed. Aspects of the quantum theory applied to the analysis of this physical system, are discussed. (Authors/BT)

  8. Quantum Theory of Hyperfine Structure Transitions in Diatomic Molecules.

    ERIC Educational Resources Information Center

    Klempt, E.; And Others

    1979-01-01

    Described is an advanced undergraduate laboratory experiment in which radio-frequency transitions between molecular hyperfine structure states may be observed. Aspects of the quantum theory applied to the analysis of this physical system, are discussed. (Authors/BT)

  9. Hyperfine selectivity using multiquantum electron-nuclear-electron triple resonance

    NASA Astrophysics Data System (ADS)

    Christidis, T. C.; Mchaourab, Hassane S.; Hyde, James S.

    1996-06-01

    Hyperfine selectivity is demonstrated in a continuous wave electron-nuclear double resonance (ENDOR) experiment. A multiquantum electron-electron double resonance (ELDOR) signal is monitored as a function of the nuclear radio frequency. The signs and relative intensities of the ENDOR lines permit separating the case where both ELDOR and ENDOR frequencies match hyperfine couplings from the cases where this condition is not satisfied.

  10. Polarization operator contributions to the Lamb shift and hyperfine splitting

    SciTech Connect

    Eides, Michael I.; Shelyuto, Valery A.

    2003-10-01

    We calculate radiative corrections to the Lamb shift of order {alpha}{sup 3}(Z{alpha}){sup 5}m and radiative corrections to hyperfine splitting of order {alpha}{sup 3}(Z{alpha})E{sub F} generated by the diagrams with insertions of radiative photons and electron polarization loops in the graphs with two external photons. We also obtain the radiative-recoil correction to hyperfine splitting in muonium generated by the diagrams with the {tau} polarization loop.

  11. The hyperfine structure in the rotational spectrum of CF+

    NASA Astrophysics Data System (ADS)

    Guzmán, V.; Roueff, E.; Gauss, J.; Pety, J.; Gratier, P.; Goicoechea, J. R.; Gerin, M.; Teyssier, D.

    2012-12-01

    Context. CF+ has recently been detected in the Horsehead and Orion Bar photo-dissociation regions. The J = 1-0 line in the Horsehead is double-peaked in contrast to other millimeter lines. The origin of this double-peak profile may be kinematic or spectroscopic. Aims: We investigate the effect of hyperfine interactions due to the fluorine nucleus in CF+ on the rotational transitions. Methods: We compute the fluorine spin rotation constant of CF+ using high-level quantum chemical methods and determine the relative positions and intensities of each hyperfine component. This information is used to fit the theoretical hyperfine components to the observed CF+ line profiles, thereby employing the hyperfine fitting method in GILDAS. Results: The fluorine spin rotation constant of CF+ is 229.2 kHz. This way, the double-peaked CF+ line profiles are well fitted by the hyperfine components predicted by the calculations. The unusually large hyperfine splitting of the CF+ line therefore explains the shape of the lines detected in the Horsehead nebula, without invoking intricate kinematics in the UV-illuminated gas.

  12. Theory of hyperfine anomalies in muonic atoms

    SciTech Connect

    Freeman, A.J.; Mallow, J.V.; Desclaux, J.P.; Weinert, M.

    1983-01-01

    Negative muon spin precession experiments by Yamazaki, et al. have found giant hyperfine anomalies in muonic atoms ranging from a few percent up to 36%. In order to understand their results, we present Breit interaction calculations based on atomic self-consistent unrestricted Dirac-Fock solutions which explicitly include all electrons and the negative muon. The Breit interaction results (including the relativistic correction for the bound muon g-factor), vary from near zero for ..mu../sup -/ O/N to -5% for ..mu../sup -/Pd/Rh; this latter is much larger than the calculated muonic or nuclear Bohr-Weisskopf anomalies and much smaller than the 36% measured value. For ..mu../sup -/Ni/Co we find a calculated range of results (depending on assumed electronic configurations) of -2.3 to -2.7% in excellent agreement with recent measurements of the Yamazaki group. This excellent agreement in ..mu../sup -/Ni/Co provides strong support for the earlier suggestions that the discrepancy in the case of ..mu../sup -/Pd/Rh is due to experimental factors.

  13. Niobium hyperfine structure in crystal calcium tungstate

    NASA Technical Reports Server (NTRS)

    Tseng, D. L.; Kikuchi, C.

    1972-01-01

    A study of the niobium hyperfine structure in single crystal calcium tungstate was made by the combination of the technique of electron paramagnetic resonance and electron nuclear double resonance (EPR/ENDOR). The microwave frequency was about 9.4 GHz and the radio frequency from 20MHz to 70 MHz. The rare earth ions Nd(3+), U(3+), or Tm(3+) were added as the charge compensator for Nb(5+). To create niobium paramagnetic centers, the sample was irradiated at 77 deg K with a 10 thousand curie Co-60 gamma source for 1 to 2 hours at a dose rate of 200 K rads per hour and then transferred quickly into the cavity. In a general direction of magnetic field, the spectra showed 4 sets of 10 main lines corresponding to 4 nonequivalent sites of niobium with I = 9/2. These 4 sets of lines coalesced into 2 sets of 10 in the ab-plane and into a single set of 10 along the c-axis. This symmetry suggested that the tungsten ions are substituted by the niobium ions in the crystal.

  14. Laser alloying and cladding of glass-ceramic surfaces using nano-scaled metal-oxide powders

    NASA Astrophysics Data System (ADS)

    Rohde, Magnus; Schreck, Sabine; Sachse, Sophia

    2008-02-01

    Laser supported processes can be used to modify the properties of ceramic substrates locally. These processes are characterised by a strong thermal interaction between the laser beam and the ceramic surface which leads to localised melting. During the dynamic melting process second phase particles are introduced into the melt pool in order to modify the physical properties. LTCC (Low Temperature Co-fired Ceramics)-substrates were laser alloyed and coated by laser cladding using nanoscaled powders of WO 3 and CuO. Depending on the process parameters and the powders used modified areas with different geometries could be fabricated with a complex multiphase microstructure. Particle agglomerates, small crystals as well as grains covered with reaction phase could be found inside the microstructure, in parts with typical length scales in the submicron range. The properties of the laser modified tracks differ significantly from that of the substrate. In particular the thermal and electrical properties were changed. An enhanced thermal conductivity could be detected in laser tracks alloyed with the nano-scaled CuO- and WO 3-powders. The electrical resistivity showed a semiconducting behaviour with a negative temperature coefficient, i.e. it decreases with increasing temperature.

  15. Advanced powder processing

    SciTech Connect

    Janney, M.A.

    1997-04-01

    Gelcasting is an advanced powder forming process. It is most commonly used to form ceramic or metal powders into complex, near-net shapes. Turbine rotors, gears, nozzles, and crucibles have been successfully gelcast in silicon nitride, alumina, nickel-based superalloy, and several steels. Gelcasting can also be used to make blanks that can be green machined to near-net shape and then high fired. Green machining has been successfully applied to both ceramic and metal gelcast blanks. Recently, the authors have used gelcasting to make tooling for metal casting applications. Most of the work has centered on H13 tool steel. They have demonstrated an ability to gelcast and sinter H13 to near net shape for metal casting tooling. Also, blanks of H13 have been cast, green machined into complex shape, and fired. Issues associated with forming, binder burnout, and sintering are addressed.

  16. Self-interaction correction and relativistic exchange on the core states and core hyperfine fields in Fe, Co, and Ni

    NASA Astrophysics Data System (ADS)

    Severin, L.; Richter, M.; Steinbeck, L.

    1997-04-01

    Local density calculations with self-interaction-corrected core states are reported for the transition-metal ferromagnets Fe, Co, and Ni. The hyperfine field matrix elements have been computed. Good agreement with measurements is obtained for Co, whereas for Fe and Ni the discrepancy between local density theory and experiment remains also in the self-interaction-corrected calculation. Possible changes in the core states due to relativistic exchange corrections are also discussed and found to be of minor importance.

  17. Enhanced microwave dielectric properties of Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} ceramics doping by metal Fe powders

    SciTech Connect

    Zhang Qiwei; Zhai Jiwei; Yao Xi; Ben Qianqian; Yu Xian

    2012-11-15

    Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} ceramics by adding mental Fe powders have been fabricated via the solid-state reaction method. The microstructures and optical properties of samples are systematically studied in order to establish the effects of Fe powder additives on microwave dielectric properties of Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} ceramics by x-ray diffraction, x-ray photoelectron spectroscopy, and optical reflective spectrum. The results show the coexistence of Fe{sup 2+} and Fe{sup 3+} in Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} ceramics, the decrease of O vacancy concentrations, and their incorporation into the B-site (Ti) of the Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} host lattice give rise to excellent microwave dielectric properties. All samples have a higher Q value above 290 while maintaining relatively high tunability above 16.6%. In particular, the sample with the composition of x = 0.035 mol has the dielectric constant of 889, Q Multiplication-Sign f value of 826 (at 1.370 GHz), and tunability of 24%, which are very promising for high power tunable devices. In comparison, Fe{sub 2}O{sub 3} oxide doped Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} ceramics with the same molar ratios of Fe exhibit inferior microwave properties. It indicates that additives of the metal Fe powders can more effectively improve dielectric properties of Ba{sub x}Sr{sub 1-x}TiO{sub 3} system than Fe{sub 2}O{sub 3} oxide.

  18. Enhanced microwave dielectric properties of Ba0.4Sr0.6TiO3 ceramics doping by metal Fe powders

    NASA Astrophysics Data System (ADS)

    Zhang, Qiwei; Zhai, Jiwei; Ben, Qianqian; Yu, Xian; Yao, Xi

    2012-11-01

    Ba0.4Sr0.6TiO3 ceramics by adding mental Fe powders have been fabricated via the solid-state reaction method. The microstructures and optical properties of samples are systematically studied in order to establish the effects of Fe powder additives on microwave dielectric properties of Ba0.4Sr0.6TiO3 ceramics by x-ray diffraction, x-ray photoelectron spectroscopy, and optical reflective spectrum. The results show the coexistence of Fe2+ and Fe3+ in Ba0.4Sr0.6TiO3 ceramics, the decrease of O vacancy concentrations, and their incorporation into the B-site (Ti) of the Ba0.4Sr0.6TiO3 host lattice give rise to excellent microwave dielectric properties. All samples have a higher Q value above 290 while maintaining relatively high tunability above 16.6%. In particular, the sample with the composition of x = 0.035 mol has the dielectric constant of 889, Q × f value of 826 (at 1.370 GHz), and tunability of 24%, which are very promising for high power tunable devices. In comparison, Fe2O3 oxide doped Ba0.4Sr0.6TiO3 ceramics with the same molar ratios of Fe exhibit inferior microwave properties. It indicates that additives of the metal Fe powders can more effectively improve dielectric properties of BaxSr1-xTiO3 system than Fe2O3 oxide.

  19. Formation of silicon nanowire packed films from metallurgical-grade silicon powder using a two-step metal-assisted chemical etching method.

    PubMed

    Ouertani, Rachid; Hamdi, Abderrahmen; Amri, Chohdi; Khalifa, Marouan; Ezzaouia, Hatem

    2014-01-01

    In this work, we use a two-step metal-assisted chemical etching method to produce films of silicon nanowires shaped in micrograins from metallurgical-grade polycrystalline silicon powder. The first step is an electroless plating process where the powder was dipped for few minutes in an aqueous solution of silver nitrite and hydrofluoric acid to permit Ag plating of the Si micrograins. During the second step, corresponding to silicon dissolution, we add a small quantity of hydrogen peroxide to the plating solution and we leave the samples to be etched for three various duration (30, 60, and 90 min). We try elucidating the mechanisms leading to the formation of silver clusters and silicon nanowires obtained at the end of the silver plating step and the silver-assisted silicon dissolution step, respectively. Scanning electron microscopy (SEM) micrographs revealed that the processed Si micrograins were covered with densely packed films of self-organized silicon nanowires. Some of these nanowires stand vertically, and some others tilt to the silicon micrograin facets. The thickness of the nanowire films increases from 0.2 to 10 μm with increasing etching time. Based on SEM characterizations, laser scattering estimations, X-ray diffraction (XRD) patterns, and Raman spectroscopy, we present a correlative study dealing with the effect of the silver-assisted etching process on the morphological and structural properties of the processed silicon nanowire films.

  20. Coupling in-situ X-ray micro- and nano-tomography and discrete element method for investigating high temperature sintering of metal and ceramic powders

    NASA Astrophysics Data System (ADS)

    Yan, Zilin; Martin, Christophe L.; Bouvard, Didier; Jauffrès, David; Lhuissier, Pierre; Salvo, Luc; Olmos, Luis; Villanova, Julie; Guillon, Olivier

    2017-06-01

    The behaviour of various powder systems during high temperature sintering has been investigated by coupling X-ray microtomography and discrete element method (DEM). Both methods are particularly relevant to analyse particle interactions and porosity changes occurring during sintering. Two examples are presented. The first one deals with a copper powder including artificially created pores which sintering has been observed in situ at the European synchrotron and simulated by DEM. 3D images with a resolution of 1.5 μm have been taken at various times of the sintering cycle. The comparison of the real displacement of particle centers with the displacement derived from the mean field assumption demonstrates significant particle rearrangement in some regions of the sample. Although DEM simulation showed less rearrangement, it has been able to accurately predict the densification kinetics. The second example concerns multilayer ceramic capacitors (MLCCs) composed of hundreds of alternated metal electrode and ceramic dielectric layers. The observation of Ni-based MLCCs by synchrotron nanotomography at Argon National Laboratory with a spatial resolution between 10 and 50 nm allowed understanding the origin of heterogeneities formed in Ni layers during sintering. DEM simulations confirmed this analysis and provided clues for reducing these defects.

  1. Formation of silicon nanowire packed films from metallurgical-grade silicon powder using a two-step metal-assisted chemical etching method

    PubMed Central

    2014-01-01

    In this work, we use a two-step metal-assisted chemical etching method to produce films of silicon nanowires shaped in micrograins from metallurgical-grade polycrystalline silicon powder. The first step is an electroless plating process where the powder was dipped for few minutes in an aqueous solution of silver nitrite and hydrofluoric acid to permit Ag plating of the Si micrograins. During the second step, corresponding to silicon dissolution, we add a small quantity of hydrogen peroxide to the plating solution and we leave the samples to be etched for three various duration (30, 60, and 90 min). We try elucidating the mechanisms leading to the formation of silver clusters and silicon nanowires obtained at the end of the silver plating step and the silver-assisted silicon dissolution step, respectively. Scanning electron microscopy (SEM) micrographs revealed that the processed Si micrograins were covered with densely packed films of self-organized silicon nanowires. Some of these nanowires stand vertically, and some others tilt to the silicon micrograin facets. The thickness of the nanowire films increases from 0.2 to 10 μm with increasing etching time. Based on SEM characterizations, laser scattering estimations, X-ray diffraction (XRD) patterns, and Raman spectroscopy, we present a correlative study dealing with the effect of the silver-assisted etching process on the morphological and structural properties of the processed silicon nanowire films. PMID:25349554

  2. Formation of silicon nanowire packed films from metallurgical-grade silicon powder using a two-step metal-assisted chemical etching method

    NASA Astrophysics Data System (ADS)

    Ouertani, Rachid; Hamdi, Abderrahmen; Amri, Chohdi; Khalifa, Marouan; Ezzaouia, Hatem

    2014-10-01

    In this work, we use a two-step metal-assisted chemical etching method to produce films of silicon nanowires shaped in micrograins from metallurgical-grade polycrystalline silicon powder. The first step is an electroless plating process where the powder was dipped for few minutes in an aqueous solution of silver nitrite and hydrofluoric acid to permit Ag plating of the Si micrograins. During the second step, corresponding to silicon dissolution, we add a small quantity of hydrogen peroxide to the plating solution and we leave the samples to be etched for three various duration (30, 60, and 90 min). We try elucidating the mechanisms leading to the formation of silver clusters and silicon nanowires obtained at the end of the silver plating step and the silver-assisted silicon dissolution step, respectively. Scanning electron microscopy (SEM) micrographs revealed that the processed Si micrograins were covered with densely packed films of self-organized silicon nanowires. Some of these nanowires stand vertically, and some others tilt to the silicon micrograin facets. The thickness of the nanowire films increases from 0.2 to 10 μm with increasing etching time. Based on SEM characterizations, laser scattering estimations, X-ray diffraction (XRD) patterns, and Raman spectroscopy, we present a correlative study dealing with the effect of the silver-assisted etching process on the morphological and structural properties of the processed silicon nanowire films.

  3. Influence of Metal-Coated Graphite Powders on Microstructure and Properties of the Bronze-Matrix/Graphite Composites

    NASA Astrophysics Data System (ADS)

    Zhao, Jian-hua; Li, Pu; Tang, Qi; Zhang, Yan-qing; He, Jian-sheng; He, Ke

    2017-01-01

    In this study, the bronze-matrix/x-graphite (x = 0, 1, 3 and 5%) composites were fabricated by powder metallurgy route by using Cu-coated graphite, Ni-coated graphite and pure graphite, respectively. The microstructure, mechanical properties and corrosive behaviors of bronze/Cu-coated-graphite (BCG), bronze/Ni-coated-graphite (BNG) and bronze/pure-graphite (BPG) were characterized and investigated. Results show that the Cu-coated and Ni-coated graphite could definitely increase the bonding quality between the bronze matrix and graphite. In general, with the increase in graphite content in bronze-matrix/graphite composites, the friction coefficients, ultimate density and wear rates of BPG, BCG and BNG composites all went down. However, the Vickers microhardness of the BNG composite would increase as the graphite content increased, which was contrary to the BPG and BCG composites. When the graphite content was 3%, the friction coefficient of BNG composite was more stable than that of BCG and BPG composites, indicating that BNG composite had a better tribological performance than the others. Under all the values of applied loads (10, 20, 40 and 60N), the BCG and BNG composites exhibited a lower wear rate than BPG composite. What is more, the existence of nickel in graphite powders could effectively improve the corrosion resistance of the BNG composite.

  4. Influence of Metal-Coated Graphite Powders on Microstructure and Properties of the Bronze-Matrix/Graphite Composites

    NASA Astrophysics Data System (ADS)

    Zhao, Jian-hua; Li, Pu; Tang, Qi; Zhang, Yan-qing; He, Jian-sheng; He, Ke

    2017-02-01

    In this study, the bronze-matrix/x-graphite (x = 0, 1, 3 and 5%) composites were fabricated by powder metallurgy route by using Cu-coated graphite, Ni-coated graphite and pure graphite, respectively. The microstructure, mechanical properties and corrosive behaviors of bronze/Cu-coated-graphite (BCG), bronze/Ni-coated-graphite (BNG) and bronze/pure-graphite (BPG) were characterized and investigated. Results show that the Cu-coated and Ni-coated graphite could definitely increase the bonding quality between the bronze matrix and graphite. In general, with the increase in graphite content in bronze-matrix/graphite composites, the friction coefficients, ultimate density and wear rates of BPG, BCG and BNG composites all went down. However, the Vickers microhardness of the BNG composite would increase as the graphite content increased, which was contrary to the BPG and BCG composites. When the graphite content was 3%, the friction coefficient of BNG composite was more stable than that of BCG and BPG composites, indicating that BNG composite had a better tribological performance than the others. Under all the values of applied loads (10, 20, 40 and 60N), the BCG and BNG composites exhibited a lower wear rate than BPG composite. What is more, the existence of nickel in graphite powders could effectively improve the corrosion resistance of the BNG composite.

  5. Synthesis and luminescence properties of ZnS and metal (Mn, Cu)-doped-ZnS ceramic powder

    NASA Astrophysics Data System (ADS)

    Ummartyotin, S.; Bunnak, N.; Juntaro, J.; Sain, M.; Manuspiya, H.

    2012-03-01

    ZnS and metal (Mn, Cu)-doped-ZnS were successfully prepared by wet chemical synthetic route. The understanding of substituted metal ions (Mn, Cu) into ZnS leads to transfer the luminescent centre by small amount of metal dopant (Mn, Cu). Fourier transform infrared and X-ray diffraction were used to determine chemical bonding and crystal structure, respectively. It showed that small amount of metal (Mn, Cu) can be completely substituted into ZnS lattice. X-ray fluorescence was used to confirm the existence of metal-doped ZnS. Scanning electron microscope revealed that their particles exhibits blocky particle with irregular sharp. Laser confocal microscope and photoluminescence spectroscopy showed that ZnS and metal-doped-ZnS exhibited intense, stable, and tunable emission covering the blue to red end of the visible spectrum. ZnS, Mn-doped-ZnS and Cu-doped-ZnS generated blue, yellow and green color, respectively.

  6. Surface fatigue and failure characteristics of hot forged powder metal AISI 4620, AISI 4640, and machined AISI 4340 steel spur gears

    NASA Technical Reports Server (NTRS)

    Townsend, D. P.

    1986-01-01

    Spur gear surface fatigue endurance tests were conducted to investigate hot forged powder metal AISI 4620 and 4640 steel for use as a gear material, to determine endurance characteristics and to compare the results with machined AISI 4340 and 9310 steel gear materials. The as-forged and unground SISI 4620 gear exhibited a 10 percent fatigue life that was approximately one-fourth of that for AISI 9310 and less than one-half that for the AISI 4340 gears. The forged and finish ground AISI 4620 gears exhibited a 10 percent life, approximately 70 percent that of AISI 9310 and slightly better than that of AISI 4340. The AISI 4640 hot forged gears had less fracture toughness and slightly less fatigue life than the AISI 4620 test gears.

  7. Surface fatigue and failure characteristics of hot-forged powder metal AISI 4620, AISI 4640, and machined AISI 4340 steel spur gears

    NASA Technical Reports Server (NTRS)

    Townsend, Dennis P.

    1987-01-01

    Spur gear surface fatigue endurance tests were conducted to investigate hot forged powder metal AISI 4620 and 4640 steel for use as a gear material, to determine endurance characteristics and to compare the results with machined AISI 4340 and 9310 steel gear materials. The as-forged and unground AISI 4620 gear exhibited a 10 percent fatigue life that was approximately one-fourth of that for AISI 9310 and less than one-half that for the AISI 4340 gears. The forged and finish ground AISI 4620 gears exhibited a 10 percent life, approximately 70 percent that of AISI 9310 and slightly better than that of AISI 4340. The AISI 4640 hot forged gears had less fracture toughness and slightly less fatigue life than the AISI 4620 test gears.

  8. Surface fatigue and failure characteristics of hot-forged powder metal AISI 4620, AISI 4640, and machined AISI 4340 steel spur gears

    NASA Technical Reports Server (NTRS)

    Townsend, Dennis P.

    1987-01-01

    Spur gear surface fatigue endurance tests were conducted to investigate hot forged powder metal AISI 4620 and 4640 steel for use as a gear material, to determine endurance characteristics and to compare the results with machined AISI 4340 and 9310 steel gear materials. The as-forged and unground AISI 4620 gear exhibited a 10 percent fatigue life that was approximately one-fourth of that for AISI 9310 and less than one-half that for the AISI 4340 gears. The forged and finish ground AISI 4620 gears exhibited a 10 percent life, approximately 70 percent that of AISI 9310 and slightly better than that of AISI 4340. The AISI 4640 hot forged gears had less fracture toughness and slightly less fatigue life than the AISI 4620 test gears.

  9. Stochastic hyperfine interactions modeling library-Version 2

    NASA Astrophysics Data System (ADS)

    Zacate, Matthew O.; Evenson, William E.

    2016-02-01

    The stochastic hyperfine interactions modeling library (SHIML) provides a set of routines to assist in the development and application of stochastic models of hyperfine interactions. The library provides routines written in the C programming language that (1) read a text description of a model for fluctuating hyperfine fields, (2) set up the Blume matrix, upon which the evolution operator of the system depends, and (3) find the eigenvalues and eigenvectors of the Blume matrix so that theoretical spectra of experimental techniques that measure hyperfine interactions can be calculated. The optimized vector and matrix operations of the BLAS and LAPACK libraries are utilized. The original version of SHIML constructed and solved Blume matrices for methods that measure hyperfine interactions of nuclear probes in a single spin state. Version 2 provides additional support for methods that measure interactions on two different spin states such as Mössbauer spectroscopy and nuclear resonant scattering of synchrotron radiation. Example codes are provided to illustrate the use of SHIML to (1) generate perturbed angular correlation spectra for the special case of polycrystalline samples when anisotropy terms of higher order than A22 can be neglected and (2) generate Mössbauer spectra for polycrystalline samples for pure dipole or pure quadrupole transitions.

  10. Anomalous hyperfine coupling and nuclear magnetic relaxation in Weyl semimetals

    NASA Astrophysics Data System (ADS)

    Okvátovity, Zoltán; Simon, Ferenc; Dóra, Balázs

    2016-12-01

    The electron-nuclear hyperfine interaction shows up in a variety of phenomena including, e.g., NMR studies of correlated states and spin decoherence effects in quantum dots. Here we focus on the hyperfine coupling and the NMR spin relaxation time T1 in Weyl semimetals. Since the density of states in Weyl semimetals varies with the square of the energy around the Weyl point, a naive power counting predicts a 1 /T1T ˜E4 scaling, with E the maximum of temperature (T ) and chemical potential. By carefully investigating the hyperfine interaction between nuclear spins and Weyl fermions, we find that while its spin part behaves conventionally, its orbital part diverges unusually, with the inverse of the energy around the Weyl point. Consequently, the nuclear spin relaxation rate scales in a graphenelike manner as 1 /T1T ˜E2ln(E /ω0) , with ω0 the nuclear Larmor frequency. This allows us to identify an effective hyperfine coupling constant, which is tunable by gating or doping. This is relevant for the decoherence effect in spintronics devices and double quantum dots, where hyperfine coupling is the dominant source of spin-blockade lifting.

  11. Possibilities of the Technology of Additive Production for Making Complex-Shape Parts and Depositing Functional Coatings from Metallic Powders

    NASA Astrophysics Data System (ADS)

    Grigor'ev, S. N.; Tarasova, T. V.

    2016-01-01

    The aspects of terminology, definitions and classification in the technology of additive production are considered. The principal possibility of fabrication of complex-shape parts from a refractory cobalt alloy by the method of selective laser melting and deposition of hard and wear-resistant coatings from Ti and SiC powders by coaxial laser surfacing is shown. The technological possibility of microlaser surfacing with lateral resolution about 100 μm in the production of parts from aluminum alloys is considered. The mechanisms of formation of structure in the studied alloys typical for selective laser melting, laser surfacing and microlaser surfacing are determined. The physical and mechanical properties of the alloys are investigated.

  12. Photon Doppler Velocimeter to Measure Entrained Additive Manufactured Bulk Metal Powders in Hot Subsonic and Supersonic Oxygen Gas

    NASA Technical Reports Server (NTRS)

    Tylka, Jonathan

    2016-01-01

    Parts produced by additive manufacturing, particularly selective laser melting (SLM), have been shown to silt metal particulate even after undergoing stringent precision aerospace cleaning processes (Lowrey 2016). As printed parts are used in oxygen systems with increased pressures, temperatures, and gas velocity, the risk of ignition by particle impact, the most common direct ignition source of metals in oxygen, substantially increases. The White Sands Test Facility (WSTF), in collaboration with Marshall Space Flight Center (MSFC), desires to test the ignitability of SLM metals by particle impact in heated oxygen. The existing test systems rely on gas velocity calculations to infer particle velocity in both subsonic and supersonic particle impact systems. Until now, it was not possible to directly measure particle velocity. To increase the fidelity of planned SLM ignition studies, it is necessary to validate that the Photon Doppler Velocimetry(PDV) test system can accurately measure particle velocity.

  13. Preparation, spectral, X-ray powder diffraction and computational studies and genotoxic properties of new azo-azomethine metal chelates

    NASA Astrophysics Data System (ADS)

    Bitmez, Şirin; Sayin, Koray; Avar, Bariş; Köse, Muhammet; Kayraldız, Ahmet; Kurtoğlu, Mükerrem

    2014-11-01

    A new tridentate azo-azomethine ligand, N‧-[{2-hydroxy-5-[(4-nitrophenyl)diazenyl]phenyl}methylidene]benzohydrazidemonohydrate, (sbH·H2O) (1), is prepared by condensation of benzohydrazide and 2-hydroxy-5-[(4-nitrophenyl)diazenyl]benzaldehyde (a) with treatment of a solution of diazonium salt of p-nitroaniline and 2-hydroxybenzaldehyde in EtOH. The five coordination compounds, [Co(sb)2]·4H2O (2), [Ni(sb)2]·H2O (3), [Cu(sb)2]·4H2O (4), [Zn(sb)2]·H2O (5) and [Cd(sb)2]·H2O (6) are prepared by reacting the Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) ions with the ligand. The structures of the compounds are elucidated from the elemental analyses data and spectroscopic studies. It is found the ligand acts as a tridentate bending through phenolic and carbonyl oxygens and nitrogen atom of the Cdbnd Nsbnd group similar to the most of salicylaldimines. Comparison of the infrared spectra of the ligand and its metal complexes confirm that azo-Schiff base behaves as a monobasic tridentate ligand towards the central metal ion with an ONO donor sequence. Upon complexation with the ligand, the Cd(II), and Zn(II) ions form monoclinic structures, while Co(II), Cu(II) and Ni(II) ions form orthorhombic structures. Quantum chemical calculations are performed on tautomers and its metal chelates by using DFT/B3LYP method. Most stable tautomer is determined as tautomer (1a). The geometrical parameters of its metal chelates are obtained as theoretically. The NLO properties of tautomer (1a) and its metal complexes are investigated. Finally, the ligand and its metal complexes are assessed for their genotoxicity.

  14. Hyperfine-mediated static polarizabilities of monovalent atoms and ions

    SciTech Connect

    Dzuba, V. A.; Flambaum, V. V.; Beloy, K.; Derevianko, A.

    2010-12-15

    We apply relativistic many-body methods to compute static differential polarizabilities for transitions inside the ground-state hyperfine manifolds of monovalent atoms and ions. Knowledge of this transition polarizability is required in a number of high-precision experiments, such as microwave atomic clocks and searches for CP-violating permanent electric dipole moments. While the traditional polarizability arises in the second order of interaction with the externally applied electric field, the differential polarizability involves an additional contribution from the hyperfine interaction of atomic electrons with nuclear moments. We derive formulas for the scalar and tensor polarizabilities including contributions from magnetic dipole and electric quadrupole hyperfine interactions. Numerical results are presented for Al, Rb, Cs, Yb{sup +}, Hg{sup +}, and Fr.

  15. Preparation of superconductor precursor powders

    DOEpatents

    Bhattacharya, R.

    1998-08-04

    A process for the preparation of a precursor metallic powder composition for use in the subsequent formation of a superconductor. The process comprises the steps of providing an electrodeposition bath comprising an electrolyte medium and a cathode substrate electrode, and providing to the bath one or more soluble salts of one or more respective metals which are capable of exhibiting superconductor properties upon subsequent appropriate treatment. The bath is continually energized to cause the metallic and/or reduced particles formed at the electrode to drop as a powder from the electrode into the bath, and this powder, which is a precursor powder for superconductor production, is recovered from the bath for subsequent treatment. The process permits direct inclusion of all metals in the preparation of the precursor powder, and yields an amorphous product mixed on an atomic scale to thereby impart inherent high reactivity. Superconductors which can be formed from the precursor powder include pellet and powder-in-tube products. 7 figs.

  16. Iowa Powder Atomization Technologies

    SciTech Connect

    2012-01-01

    The same atomization effect seen in a fuel injector is being applied to titanium metal resulting in fine titanium powders that are less than half the width of a human hair. Titanium melts above 3,000°F and is highly corrosive therefore requiring specialized containers. The liquid titanium is poured through an Ames Laboratory - USDOE patented tube which is intended to increase the energy efficiency of the atomization process, which has the ability to dramatically decrease the cost of fine titanium powders. This novel process could open markets for green manufacturing of titanium components from jet engines to biomedical implants.

  17. Iowa Powder Atomization Technologies

    ScienceCinema

    None

    2016-07-12

    The same atomization effect seen in a fuel injector is being applied to titanium metal resulting in fine titanium powders that are less than half the width of a human hair. Titanium melts above 3,000°F and is highly corrosive therefore requiring specialized containers. The liquid titanium is poured through an Ames Laboratory - USDOE patented tube which is intended to increase the energy efficiency of the atomization process, which has the ability to dramatically decrease the cost of fine titanium powders. This novel process could open markets for green manufacturing of titanium components from jet engines to biomedical implants.

  18. Adsorptive separation and photocatalytic degradation of methylene blue dye on titanate nanotube powders prepared by hydrothermal process using metal Ti particles as a precursor.

    PubMed

    Hu, Keshui; Xiao, Xin; Cao, Xiufang; Hao, Rong; Zuo, Xiaoxi; Zhang, Xiaojing; Nan, Junmin

    2011-08-30

    Titanate nanotube powders (TNTPs) with the twofold removal ability, i.e. adsorptive separation and photocatalytic degradation, are synthesized under hydrothermal conditions using metal Ti particles as a precursor in the concentrated alkaline solution, and their morphology, structure, adsorptive and photocatalytic properties are investigated. Under hydrothermal conditions, the titanate nanotubes (TNTs) with pore diameter of 3-4nm are produced on the surface of metal Ti particles, and stacked together to form three-dimensional (3D) network with porous structure. The TNTPs synthesized in the autoclave at 130°C for 24h exhibits a maximum adsorption capability of about 197mg g(-1) in the neutral methylene blue (MB) solution (40mg L(-1)) within 90min, the adsorption process can be described by pseudo second-order kinetics model. Especially, in comparison with the adsorptive and the photocatalytic processes are performed in turn, about 50min can be saved through synchronously utilizing the double removal ability of TNTPs when the removal ratio of MB approaches 95% in MB solution (40mg L(-1)) at a solid-liquid (S/L) ratio of 1:8 under ultraviolet (UV) light irradiation. These 3D TNTPs with the twofold removal properties and easier separation ability for recycling use show promising prospect for the treatment of dye pollutants from wastewaters in future industrial application.

  19. The NH2D hyperfine structure revealed by astrophysical observations

    NASA Astrophysics Data System (ADS)

    Daniel, F.; Coudert, L. H.; Punanova, A.; Harju, J.; Faure, A.; Roueff, E.; Sipilä, O.; Caselli, P.; Güsten, R.; Pon, A.; Pineda, J. E.

    2016-02-01

    Context. The 111-101 lines of ortho- and para-NH2D (o/p-NH2D) at 86 and 110 GHz, respectively, are commonly observed to provide constraints on the deuterium fractionation in the interstellar medium. In cold regions, the hyperfine structure that is due to the nitrogen (14N) nucleus is resolved. To date, this splitting is the only one that is taken into account in the NH2D column density estimates. Aims: We investigate how including the hyperfine splitting caused by the deuterium (D) nucleus affects the analysis of the rotational lines of NH2D. Methods: We present 30 m IRAM observations of the above mentioned lines and APEX o/p-NH2D observations of the 101-000 lines at 333 GHz. The hyperfine patterns of the observed lines were calculated taking into account the splitting induced by the D nucleus. The analysis then relies on line lists that either neglect or include the splitting induced by the D nucleus. Results: The hyperfine spectra are first analyzed with a line list that only includes the hyperfine splitting that is due to the 14N nucleus. We find inconsistencies between the line widths of the 101-000 and 111-101 lines, the latter being larger by a factor of ~1.6 ± 0.3. Such a large difference is unexpected because the two sets of lines probably originate from the same region. We next employed a newly computed line list for the o/p-NH2D transitions where the hyperfine structure induced by both nitrogen and deuterium nuclei was included. With this new line list, the analysis of the previous spectra leads to compatible line widths. Conclusions: Neglecting the hyperfine structure caused by D leads to overestimating the line widths of the o/p-NH2D lines at 3 mm. The error for a cold molecular core is about 50%. This error propagates directly to the column density estimate. We therefore recommend to take the hyperfine splittings caused by both the 14N and D nuclei into account in any analysis that relies on these lines. Based on observations carried out with the IRAM

  20. On the hyperfine structures in the m-type hexaferrite

    NASA Astrophysics Data System (ADS)

    Bahgat, A. A.; Fayek, M. K.

    1980-04-01

    Mössbauer measurements have been made on polycrystalline barium and strontium hexaferrite samples. The subspectra corresponding to the iron ion in the bypyramid lattice site in the temperature range 4.2 to 293 K with and without externally applied magnetic field up to 25 kG have been considered particularly. The quadrupole shift is vanishing, and the five magnetic hyperfine fields related to the magnetic sites are equal at low temperature. Values of the hyperfine fields for the pentahedral site are discussed.

  1. A computer program for analyzing unresolved Mossbauer hyperfine spectra

    NASA Technical Reports Server (NTRS)

    Schiess, J. R.; Singh, J. J.

    1978-01-01

    The program for analyzing unresolved Mossbauer hyperfine spectra was written in FORTRAN 4 language for the Control Data CYBER 170 series digital computer system with network operating system 1.1. With the present dimensions, the program requires approximately 36,000 octal locations of core storage. A typical case involving two innermost coordination shells in which the amplitudes and the peak positions of all three components were estimated in 25 iterations requires 30 seconds on CYBER 173. The program was applied to determine the effects of various near neighbor impurity shells on hyperfine fields in dilute FeAl alloys.

  2. Hyperfine structure constants of atomic bromine (Br I)

    NASA Astrophysics Data System (ADS)

    Ni, Xue; Deng, Lunhua; Wang, Hailing

    2017-07-01

    The absorption spectrum of the neutral bromine (Br I), lying in the region from 11,300 cm-1 to 12,600 cm-1 has been investigated using concentration modulation absorption spectroscopy with a tunable Ti:Sapphire laser. The bromine atoms were excited by discharging the mixture of Helium and bromine vapour in a hollow discharge glass tube. The hyperfine structure spectra of 45 lines were analyzed. Hyperfine structure constants A and B were derived for 20 even and 27 odd levels amongst which constants for 12 even and 21 odd levels were newly reported.

  3. All-orders Binding Corrections to Muonium Hyperfine Splitting

    NASA Astrophysics Data System (ADS)

    Sapirstein, Jonathan

    1997-04-01

    The use of exact Dirac-Coulomb propagators allows the evaluation of binding corrections to the Schwinger correction in ground state muonium hyperfine splitting to all orders (S.A. Blundell, K.T. Cheng, and J. Sapirstein, to appear in March issue of Physical Review A). The calculational method is described and used to verify recent perturbative calculations of higher order binding corrections and to estimate the residual terms of even higher order. Implications for the theory of muonium hyperfine splitting will be discussed.

  4. Magnetic blackbody shift of hyperfine transitions for atomic clocks

    SciTech Connect

    Berengut, J. C.; Flambaum, V. V.; King-Lacroix, J.

    2009-12-15

    We derive an expression for the magnetic blackbody shift of hyperfine transitions such as the cesium primary reference transition which defines the second. The shift is found to be a complicated function of temperature, and has a T{sup 2} dependence only in the high-temperature limit. We also calculate the shift of ground-state p{sub 1/2} hyperfine transitions which have been proposed as new atomic clock transitions. In this case interaction with the p{sub 3/2} fine-structure multiplet may be the dominant effect.

  5. Doubly Magic Optical Trapping for Cs Atom Hyperfine Clock Transitions

    NASA Astrophysics Data System (ADS)

    Carr, A. W.; Saffman, M.

    2016-10-01

    We analyze doubly magic trapping of Cs hyperfine transitions including previously neglected contributions from the ground state hyperpolarizability and the interaction of the laser light and a static magnetic field. Extensive numerical searches do not reveal any doubly magic trapping conditions for any pair of hyperfine states. However, including the hyperpolarizability reveals light intensity insensitive traps for a wide range of wavelengths at specific intensities. We then investigate the use of bichromatic trapping light fields. Deploying a bichromatic scheme, we demonstrate doubly magic red and blue detuned traps for pairs of states separated by one or two single photon transitions.

  6. Hyperfine Coherence in the Presence of Spontaneous Photon Scattering

    NASA Astrophysics Data System (ADS)

    Ozeri, R.; Langer, C.; Jost, J. D.; Demarco, B.; Ben-Kish, A.; Blakestad, B. R.; Britton, J.; Chiaverini, J.; Itano, W. M.; Hume, D. B.; Leibfried, D.; Rosenband, T.; Schmidt, P. O.; Wineland, D. J.

    2005-07-01

    The coherence of a hyperfine-state superposition of a trapped 9Be+ ion in the presence of off-resonant light is studied experimentally. It is shown that Rayleigh elastic scattering of photons that does not change state populations also does not affect coherence. We observe coherence times that exceed the average scattering time of 19 photons which is determined from measured Stark shifts. This result implies that, with sufficient control over its parameters, laser light can be used to manipulate hyperfine-state superpositions with very little decoherence.

  7. 7P1/2 hyperfine splitting in 206 , 207 , 209 , 213Fr and the hyperfine anomaly

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Orozco, L. A.; Collister, R.; Gwinner, G.; Tandecki, M.; Behr, J. A.; Pearson, M. R.; Gomez, E.; Aubin, S.

    2013-05-01

    We perform precision measurements on francium, the heaviest alkali with no stable isotopes, at the recently commissioned Francium Trapping Facility at TRIUMF. A combination of RF and optical spectroscopy allows better than 10 ppm (statistical) measurements of the 7P1 / 2 state hyperfine splitting for the isotopes 206 , 207 , 209 , 213Fr, in preparation for weak interaction studies. Together with previous measurements of the ground state hyperfine structure, it is possible to extract the hyperfine anomaly. This is a correction to the point interaction of the nuclear magnetic moment and the electron wavefunction, known as the Bohr Weisskopf effect. Our measurements extend previous measurements to the neutron closed shell isotope (213) as well as further in the neutron deficient isotopes (206, 207). Work supported by NSERC and NRC from Canada, NSF and DOE from USA, CONYACT from Mexico.

  8. A new strategy for pressed powder eye shadow analysis: allergenic metal ion content and particle size distribution.

    PubMed

    Contado, Catia; Pagnoni, Antonella

    2012-08-15

    Nine cheap eye shadow products were analyzed through graphite furnace atomic absorption spectrometry (GF-AAS) to quantify their Cr, Co and Ni contents, all known to be skin sensitizers. In many cases, the concentrations were higher than 1 or 5 ppm (μg/g), i.e. the limits recommended in the scientific literature to minimize the risk of reaction in particularly sensitive subjects. In most cases, the concentration of Cr was higher than that of Ni and Co, up to a limit case of 150 mg/g. In this particular sample, the potential amount of Cr that could be released in ionic form was determined in sweat simulating solutions by GF-AAS and confirmed through a specific spectrofluorimetric method; the results indicated the presence of approximately 80-90 ppb (ng/g) of Cr(3+). The water dispersible particles were isolated from the eye shadow powders through a simple solvent extraction procedure. The aqueous suspensions were then sorted through sedimentation field flow fractionation (SdFFF) and the particles sizes were calculated from experimental fractograms using theory. For the most part, the computed sizes were in the micron range, as confirmed by some SEM photographs taken on fractions collected during the separations. The SdFFF coupled off-line with the GFAAS enabled elemental characterization of pigment particles as a function of size. This finding reduces the concern that the ingredients of such makeup formulations may contain nanoparticles. Copyright © 2012 Elsevier B.V. All rights reserved.

  9. Relativistic extended-coupled-cluster method for the magnetic hyperfine structure constant

    NASA Astrophysics Data System (ADS)

    Sasmal, Sudip; Pathak, Himadri; Nayak, Malaya K.; Vaval, Nayana; Pal, Sourav

    2015-02-01

    The article deals with the general implementation of the four-component spinor relativistic extended-coupled-cluster (ECC) method to calculate first-order property of atoms and molecules in their open-shell ground-state configuration. The implemented relativistic ECC is employed to calculate hyperfine structure constants of alkali metals (Li, Na, K, Rb, and Cs), singly charged alkaline-earth-metal atoms (Be+ ,Mg+,Ca+, and Sr+), and molecules (BeH, MgF, and CaH). We have compared our ECC results with the calculations based on the restricted active space configuration interaction (RAS-CI) method. Our results are in better agreement with the available experimental values than those of the RAS-CI values.

  10. Method for synthesizing ultrafine powder materials

    DOEpatents

    Buss, Richard J.; Ho, Pauline

    1988-01-01

    A method for synthesizing ultrafine powder materials, for example, ceramic and metal powders, comprises admitting gaseous reactants from which the powder material is to be formed into a vacuum reaction chamber maintained at a pressure less than atmospheric and at a temperature less than about 400.degree. K. (127.degree.C.). The gaseous reactants are directed through a glow discharge provided in the vacuum reaction chamber to form the ultrafine powder material.

  11. Method and apparatus for production of powders

    NASA Technical Reports Server (NTRS)

    Stolzfus, Joel M. (Inventor); Sircar, Subhasish (Inventor)

    1995-01-01

    Apparatus and method are disclosed for producing oxides of metals and of metal alloys. The metal or alloy is placed in an oxygen atmosphere in a combustion chamber and ignited. Products of the combustion include one or more oxides of the metal or alloy in powdered form. In one embodiment of the invention a feeder is provided whereby material to be oxidized by combustion can be advanced into a combustion chamber continuously. A product remover receives the powder product of the combustion.

  12. Method and Apparatus for Production of Powders

    NASA Technical Reports Server (NTRS)

    Storltzfus, Joel M. (Inventor); Sircar, Subhasish (Inventor)

    1998-01-01

    Apparatus and method are disclosed for producing oxides of metals and of metal alloys. The metal or alloy is placed in an oxygen atmosphere in a combustion chamber and ignited. Products of the combustion include one or more oxides of the metal or alloy in powdered form. In one embodiment of the invention a feeder is provided whereby material to be oxidized by combustion can be advanced into a combustion chamber continuously. A product remover receives the powder product of the combustion.

  13. The effect of alkaline earth metal ion dopants on photocatalytic water splitting by NaTaO(3) powder.

    PubMed

    Iwase, Akihide; Kato, Hideki; Kudo, Akihiko

    2009-01-01

    Alkaline earth metal ions (Ca, Sr, and Ba) are doped into a NaTaO(3) photocatalyst, yielding fine particles and surface structures with nanometer-scale "steps." The formation of the surface nanostep structure depends on the amount of doped Sr and Ba. The photocatalytic water splitting over NaTaO(3) is enhanced: NaTaO(3) doped with 0.5 and 1.0 mol % of Sr shows high activities for photocatalytic water splitting without loading of a co-catalyst, and the photocatalytic activity is further improved by loading with a NiO co-catalyst.

  14. Hyperfine and nuclear quadrupole coupling in chlorine and fluorine dioxides

    NASA Astrophysics Data System (ADS)

    Fernández, Berta; Christiansen, Ove; Jørgensen, Poul; Byberg, Jørgen; Gauss, Jürgen; Ruud, Kenneth

    1997-02-01

    The hyperfine and nuclear quadrupole coupling tensors have been calculated for the two chlorine dioxide isomers OClO and ClOO and for fluorine dioxide FOO. The coupled-cluster singles and doubles (CCSD) approach with a perturbative treatment of triple excitations [CCSD(T)] has been used and basis saturation has been investigated. For the symmetric isomer OClO close agreement is obtained with the accurate and detailed experimental data. For FOO a geometry optimization as well as a comparison of calculated and experimental hyperfine coupling tensors suggest a shorter F-O bond length than that obtained experimentally. For the isomer ClOO, calculations have been carried out at the theoretical equilibrium geometry determined by Peterson and Werner and at the geometry proposed by Byberg for the matrix isolated molecule. The hyperfine coupling tensors obtained at these two geometries are substantially different, but the estimated accuracy of the calculations is not high enough to allow a determination of the geometry of ClOO from the hyperfine data.

  15. Hyperfine Interactions for Hole Spins in Quantum Dots

    NASA Astrophysics Data System (ADS)

    Philippoppoulos, Pericles; Chesi, Sefano; Coish, William

    2014-03-01

    Due to the anisotropic nature of the hyperfine coupling for hole spins in semiconductor quantum dots, these systems may show significantly longer coherence times than electron spins given the correct quantum-dot geometry and magnetic field orientation. This advantage of hole spins relies on the hyperfine tensor taking-on an Ising-like form. This form of the hyperfine coupling has been recently called into question with experiments that have been interpreted to indicate a strong hybridization of p-like and d-like components in the valence band of III-V semiconductors. However, this interpretation relies on two assumptions: (1) That spin-orbit coupling is weak in these systems compared to the anisotropic crystal field, and (2) that higher-angular-momentum contributions are negligible. Assumption (1) may break down in light of the fact that the spin-orbit energy is even larger than the principle gap in InAs, and assumption (2) is difficult to justify in any crystal that breaks pure rotational symmetry. Using a generalization of the group-theoretic analysis in, we show here that relaxing either of these assumptions can restore the Ising-like nature of the hyperfine tensor, albeit for a particular choice of coupling constants.

  16. On the Observability of Optically Thin Coronal Hyperfine Structure Lines

    NASA Astrophysics Data System (ADS)

    Chatzikos, M.; Ferland, G. J.; Williams, R. J. R.; Fabian, A. C.

    2014-06-01

    We present CLOUDY calculations for the intensity of coronal hyperfine lines in various environments. We model indirect collisional and radiative transitions, and quantify the collisionally excited line emissivity in the density-temperature phase space. As an observational aid, we also express the emissivity in units of that in the 0.4-0.7 keV band. For most hyperfine lines, knowledge of the X-ray surface brightness and the plasma temperature is sufficient for rough estimates. We find that the radiation fields of both Perseus A and Virgo A can enhance the populations of highly ionized species within 1 kpc. They can also enhance line emissivity within the cluster core. This could have implications for the interpretation of spectra around bright active galactic nuclei. We find the intensity of the 57Fe XXIV λ3.068 mm line to be about two orders of magnitude fainter than previously thought, at ~20 μK. Comparably bright lines may be found in the infrared. Finally, we find the intensity of hyperfine lines in the Extended Orion Nebula to be low, due to the shallow sightline. Observations of coronal hyperfine lines will likely be feasible with the next generation of radio and submillimeter telescopes.

  17. On the observability of optically thin coronal hyperfine structure lines

    SciTech Connect

    Chatzikos, M.; Ferland, G. J.; Williams, R. J. R.; Fabian, A. C.

    2014-06-01

    We present CLOUDY calculations for the intensity of coronal hyperfine lines in various environments. We model indirect collisional and radiative transitions, and quantify the collisionally excited line emissivity in the density-temperature phase space. As an observational aid, we also express the emissivity in units of that in the 0.4-0.7 keV band. For most hyperfine lines, knowledge of the X-ray surface brightness and the plasma temperature is sufficient for rough estimates. We find that the radiation fields of both Perseus A and Virgo A can enhance the populations of highly ionized species within 1 kpc. They can also enhance line emissivity within the cluster core. This could have implications for the interpretation of spectra around bright active galactic nuclei. We find the intensity of the {sup 57}Fe XXIV λ3.068 mm line to be about two orders of magnitude fainter than previously thought, at ∼20 μK. Comparably bright lines may be found in the infrared. Finally, we find the intensity of hyperfine lines in the Extended Orion Nebula to be low, due to the shallow sightline. Observations of coronal hyperfine lines will likely be feasible with the next generation of radio and submillimeter telescopes.

  18. Preparation of superconductor precursor powders

    DOEpatents

    Bhattacharya, Raghunath; Blaugher, Richard D.

    1995-01-01

    A process for the preparation of a precursor metallic powder composition for use in the subsequent formation of a superconductor. The process comprises the steps of providing an electrodeposition bath comprising an electrolyte medium and a cathode substrate electrode, and providing to the bath one or more soluble salts of one or more respective metals, such as nitrate salts of thallium, barium, calcium, and copper, which are capable of exhibiting superconductor properties upon subsequent appropriate treatment. The bath is continually energized to cause the metallic particles formed at the electrode to drop as a powder from the electrode into the bath, and this powder, which is a precursor powder for superconductor production, is recovered from the bath for subsequent treatment. The process permits direct inclusion of thallium in the preparation of the precursor powder, and yields an amorphous product mixed on an atomic scale to thereby impart inherent high reactivity. Superconductors which can be formed from the precursor powder include pellet and powder-in-tube products.

  19. Synthesis of nanoparticles from malleable and ductile metals using powder-free, reactant-assisted mechanical attrition.

    PubMed

    McMahon, Brandon W; Perez, Jesus Paulo L; Yu, Jiang; Boatz, Jerry A; Anderson, Scott L

    2014-11-26

    A reactant-assisted mechanochemical method was used to produce copious nanoparticles from malleable/ductile metals, demonstrated here for aluminum, iron, and copper. The milling media is intentionally degraded via a reactant-accelerated wear process, where the reactant aids particle production by binding to the metal surfaces, enhancing particle production, and reducing the tendency toward mechanochemical (cold) welding. The mechanism is explored by comparing the effects of different types of solvents and solvent mixtures on the amount and type of particles produced. Particles were functionalized with oleic acid to aid in particle size separation, enhance dispersion in hydrocarbon solvents, and protect the particles from oxidation. For aluminum and iron, the result is air-stable particles, but for copper, the suspended particles are found to dissolve when exposed to air. Characterization was performed using electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, solid state nuclear magnetic resonance, and X-ray photoelectron spectroscopy. Density functional theory was used to examine the nature of carboxylic acid binding to the aluminum surface, confirming the dominance of bridging bidentate binding.

  20. Laser and electron-beam powder-bed additive manufacturing of metallic implants: A review on processes, materials and designs.

    PubMed

    Sing, Swee Leong; An, Jia; Yeong, Wai Yee; Wiria, Florencia Edith

    2016-03-01

    Additive manufacturing (AM), also commonly known as 3D printing, allows the direct fabrication of functional parts with complex shapes from digital models. In this review, the current progress of two AM processes suitable for metallic orthopaedic implant applications, namely selective laser melting (SLM) and electron beam melting (EBM) are presented. Several critical design factors such as the need for data acquisition for patient-specific design, design dependent porosity for osteo-inductive implants, surface topology of the implants and design for reduction of stress-shielding in implants are discussed. Additive manufactured biomaterials such as 316L stainless steel, titanium-6aluminium-4vanadium (Ti6Al4V) and cobalt-chromium (CoCr) are highlighted. Limitations and future potential of such technologies are also explored. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  1. Polymer powder prepregging: Scoping study

    NASA Technical Reports Server (NTRS)

    Throne, James L.

    1988-01-01

    Early on, it was found that NEAT LARC-TPI thermoplastic polyimide powder behaved elastoplastically at pressures to 20 ksi and temperatures to 260 degrees celcius (below MP). At high resin assay, resin powder could be continuously cold-flowed around individual carbon fibers in a metal rolling mill. At low resin assay (2:1, C:TPI), fiber breakage was prohibitive. Thus, although processing of TPI below MP would be quite unique, it appears that the polymer must be melted and flowed to produce low resin assay prepreg. Fiber tow was spread to 75 mm using a venturi slot tunnel. This allowed intimate powder/fiber interaction. Two techniques were examined for getting room temperature powder onto the room temperature fiber surface. Electrostatic powder coating allows the charged powder to cling tenaciously to the fiber, even while heated with a hot air gun to above its melt temperature. A variant of the wet slurry coating process was also explored. The carbon fibers are first wetted with water. Then dry powder is sprinkled onto the wet tow and doctor-rolled between the fibers. The wet structure is then taken onto a heated roll, with hot air guns drying and sinter-melting the powder onto the fiber surfaces. In both cases SEM shows individual fibers coated with powder particles that have melted in place and flowed along the fiber surface via surface tension.

  2. Mechanochemical processing for metals and metal alloys

    DOEpatents

    Froes, Francis H.; Eranezhuth, Baburaj G.; Prisbrey, Keith

    2001-01-01

    A set of processes for preparing metal powders, including metal alloy powders, by ambient temperature reduction of a reducible metal compound by a reactive metal or metal hydride through mechanochemical processing. The reduction process includes milling reactants to induce and complete the reduction reaction. The preferred reducing agents include magnesium and calcium hydride powders. A process of pre-milling magnesium as a reducing agent to increase the activity of the magnesium has been established as one part of the invention.

  3. Metallic glassy Zr70Ni20Pd10 powders for improving the hydrogenation/dehydrogenation behavior of MgH2.

    PubMed

    El-Eskandarany, M Sherif

    2016-05-25

    Because of its low density, storage of hydrogen in the gaseous and liquids states possess technical and economic challenges. One practical solution for utilizing hydrogen in vehicles with proton-exchange fuel cells membranes is storing hydrogen in metal hydrides. Magnesium hydride (MgH2) remains the best hydrogen storage material due to its high hydrogen capacity and low cost of production. Due to its high activation energy and poor hydrogen sorption/desorption kinetics at moderate temperatures, the pure form of MgH2 is usually mechanically treated by high-energy ball mills and catalyzed with different types of catalysts. These steps are necessary for destabilizing MgH2 to enhance its kinetics behaviors. In the present work, we used a small mole fractions (5 wt.%) of metallic glassy of Zr70Ni20Pd10 powders as a new enhancement agent to improve its hydrogenation/dehydrogenation behaviors of MgH2. This short-range ordered material led to lower the decomposition temperature of MgH2 and its activation energy by about 121 °C and 51 kJ/mol, respectively. Complete hydrogenation/dehydrogenation processes were successfully achieved to charge/discharge about 6 wt.%H2 at 100 °C/200 °C within 1.18 min/3.8 min, respectively. In addition, this new nanocomposite system shows high performance of achieving continuous 100 hydrogen charging/discharging cycles without degradation.

  4. Metallic glassy Zr70Ni20Pd10 powders for improving the hydrogenation/dehydrogenation behavior of MgH2

    PubMed Central

    El-Eskandarany, M. Sherif

    2016-01-01

    Because of its low density, storage of hydrogen in the gaseous and liquids states possess technical and economic challenges. One practical solution for utilizing hydrogen in vehicles with proton-exchange fuel cells membranes is storing hydrogen in metal hydrides. Magnesium hydride (MgH2) remains the best hydrogen storage material due to its high hydrogen capacity and low cost of production. Due to its high activation energy and poor hydrogen sorption/desorption kinetics at moderate temperatures, the pure form of MgH2 is usually mechanically treated by high-energy ball mills and catalyzed with different types of catalysts. These steps are necessary for destabilizing MgH2 to enhance its kinetics behaviors. In the present work, we used a small mole fractions (5 wt.%) of metallic glassy of Zr70Ni20Pd10 powders as a new enhancement agent to improve its hydrogenation/dehydrogenation behaviors of MgH2. This short-range ordered material led to lower the decomposition temperature of MgH2 and its activation energy by about 121 °C and 51 kJ/mol, respectively. Complete hydrogenation/dehydrogenation processes were successfully achieved to charge/discharge about 6 wt.%H2 at 100 °C/200 °C within 1.18 min/3.8 min, respectively. In addition, this new nanocomposite system shows high performance of achieving continuous 100 hydrogen charging/discharging cycles without degradation. PMID:27220994

  5. Study of metallic powder behavior in very low pressure plasma spraying (VLPPS) — Application to the manufacturing of titanium–aluminum coatings

    SciTech Connect

    Vautherin, B.; Planche, M.-P.; Montavon, G.; Lapostolle, F.; Quet, A.; Bianchi, L.

    2015-08-28

    In this study, metallic materials made of aluminum and titanium were manufactured implementing very low pressure plasma spraying (VLPPS). Aluminum was selected at first as a demonstrative material due to its rather low vaporization enthalpy (i.e., 381.9 kJ·mol⁻¹). Developments were then carried out with titanium which exhibits a higher vaporization enthalpy (i.e., 563.6 kJ·mol⁻¹). Optical emission spectroscopy (OES) was implemented to analyze the behavior of each solid precursor (metallic powders) when it is injected into the plasma jet under very low pressure (i.e., in the 150 Pa range). Besides, aluminum, titanium and titanium–aluminum coatings were deposited in the same conditions implementing a stick-cathode plasma torch operated at 50 kW, maximum power. Coating phase compositions were identified by X-Ray Diffraction (XRD). Coating elementary compositions were quantified by Glow Discharge Optical Emission Spectroscopy (GDOES) and Energy Dispersive Spectroscopy (EDS) analyses. The coating structures were observed by Scanning Electron Microscopy (SEM). The coating void content was determined by Ultra-Small Angle X-ray Scattering (USAXS). The coatings exhibit a two-scale structure corresponding to condensed vapors (smaller scale) and solidified areas (larger scale). Titanium–aluminum sprayed coatings, with various Ti/Al atomic ratios, are constituted of three phases: metastable α-Ti, Al and metastable α₂-Ti₃Al. This latter is formed at elevated temperature in the plasma flow, before being condensed. Its rather small fraction, impeded by the rather small amount of vaporized Ti, does not allow modifying however the coating hardness.

  6. Metallic glassy Zr70Ni20Pd10 powders for improving the hydrogenation/dehydrogenation behavior of MgH2

    NASA Astrophysics Data System (ADS)

    El-Eskandarany, M. Sherif

    2016-05-01

    Because of its low density, storage of hydrogen in the gaseous and liquids states possess technical and economic challenges. One practical solution for utilizing hydrogen in vehicles with proton-exchange fuel cells membranes is storing hydrogen in metal hydrides. Magnesium hydride (MgH2) remains the best hydrogen storage material due to its high hydrogen capacity and low cost of production. Due to its high activation energy and poor hydrogen sorption/desorption kinetics at moderate temperatures, the pure form of MgH2 is usually mechanically treated by high-energy ball mills and catalyzed with different types of catalysts. These steps are necessary for destabilizing MgH2 to enhance its kinetics behaviors. In the present work, we used a small mole fractions (5 wt.%) of metallic glassy of Zr70Ni20Pd10 powders as a new enhancement agent to improve its hydrogenation/dehydrogenation behaviors of MgH2. This short-range ordered material led to lower the decomposition temperature of MgH2 and its activation energy by about 121 °C and 51 kJ/mol, respectively. Complete hydrogenation/dehydrogenation processes were successfully achieved to charge/discharge about 6 wt.%H2 at 100 °C/200 °C within 1.18 min/3.8 min, respectively. In addition, this new nanocomposite system shows high performance of achieving continuous 100 hydrogen charging/discharging cycles without degradation.

  7. Method for molding ceramic powders

    DOEpatents

    Janney, M.A.

    1990-01-16

    A method for molding ceramic powders comprises forming a slurry mixture including ceramic powder, a dispersant for the metal-containing powder, and a monomer solution. The monomer solution includes at least one multifunctional monomer, a free-radical initiator, and an organic solvent. The slurry mixture is transferred to a mold, and the mold containing the slurry mixture is heated to polymerize and crosslink the monomer and form a firm polymer-solvent gel matrix. The solid product may be removed from the mold and heated to first remove the solvent and subsequently remove the polymer, where after the product may be sintered.

  8. Method for molding ceramic powders

    DOEpatents

    Janney, Mark A.

    1990-01-01

    A method for molding ceramic powders comprises forming a slurry mixture including ceramic powder, a dispersant for the metal-containing powder, and a monomer solution. The monomer solution includes at least one multifunctional monomer, a free-radical initiator, and an organic solvent. The slurry mixture is transferred to a mold, and the mold containing the slurry mixture is heated to polymerize and crosslink the monomer and form a firm polymer-solvent gel matrix. The solid product may be removed from the mold and heated to first remove the solvent and subsequently remove the polymer, whereafter the product may be sintered.

  9. Determination of hyperfine field distributions in amorphous magnets.

    PubMed

    Bentley, P M; Kilcoyne, S H

    2006-08-16

    We present an overview of two leading methods of determining probability distributions from Mössbauer spectra, using the model amorphous magnet Fe(80)B(20). A comparison is made between the maximum-entropy method, which permits analysis using truly arbitrary parameter probability distributions, and a Voigtian-based analysis, which uses a sum of Gaussian components to create parameter distributions of pseudo-arbitrary shape. Our results indicate that, in Fe(80)B(20), a Gaussian distribution of magnetic hyperfine fields is a very good approximation, although small deviations from a Gaussian shape are evident. We find that the apparent existence of correlations between the isomer shift and magnetic hyperfine field parameters, as found using Voigt-based analyses, may be an artefact of imposing a Gaussian shape on the parameter distributions. We conclude that maximum entropy and Voigtian analyses together provide a very powerful means of characterizing magnetic materials with Mössbauer spectroscopy.

  10. Tuning hyperfine fields in conjugated polymers for coherent organic spintronics.

    PubMed

    Lee, Sang-Yun; Paik, Seo-Young; McCamey, Dane R; Yu, Justin; Burn, Paul L; Lupton, John M; Boehme, Christoph

    2011-02-23

    An appealing avenue for organic spintronics lies in direct coherent control of the spin population by means of pulsed electron spin resonance techniques. Whereas previous work has focused on the electrical detection of coherent spin dynamics, we demonstrate here the equivalence of an all-optical approach, allowing us to explore the influence of materials chemistry on the spin dynamics. We show that deuteration of the conjugated polymer side groups weakens the local hyperfine fields experienced by electron-hole pairs, thereby lowering the threshold for the resonant radiation intensity at which coherent coupling and spin beating occur. The technique is exquisitively sensitive to previously obscured material properties and offers a route to quantifying and tuning hyperfine fields in organic semiconductors.

  11. Hadronic light-by-light scattering in muonium hyperfine splitting

    SciTech Connect

    Karshenboim, S. G.; Shelyuto, V. A.; Vainshtein, A. I.

    2008-09-15

    We consider an impact of hadronic light-by-light scattering on the muonium hyperfine structure. A shift of the hyperfine interval {delta}{nu}(Mu){sub HLBL} is calculated with the light-by-light scattering approximated by the exchange of pseudoscalar and pseudovector mesons. Constraints from the operator product expansion in QCD are used to fix parameters of the model similar to the one used earlier for the hadronic light-by-light scattering in calculations of the muon anomalous magnetic moment. The pseudovector exchange is dominant in the resulting shift, {delta}{nu}(Mu){sub HLBL}=-0.0065(10) Hz. Although the effect is tiny it is useful in understanding the level of hadronic uncertainties.

  12. Measurement of hyperfine structure and isotope shifts in Gd II

    NASA Astrophysics Data System (ADS)

    Del Papa, Dylan F.; Rose, Christopher D. M.; Rosner, S. David; Holt, Richard A.

    2017-07-01

    We have applied fast-ion-beam laser-fluorescence spectroscopy to measure the isotope shifts of 73 optical transitions in the wavelength range 421.5-455.8 nm and the hyperfine structures of 35 even parity and 33 odd parity levels in Gd II. Many of the isotope shifts and hyperfine structure measurements are the first for these transitions and levels. These atomic data can be used to correct for saturation and blending in the analysis of stellar spectra to determine chemical abundances. As a result, they have an important impact on studies of the history of nucleosynthesis in the Universe and on the use of photospheric abundance anomalies in Chemically Peculiar stars to infer indirect information about stellar interiors.

  13. Chiral Extrapolation of Lattice Data for Heavy Meson Hyperfine Splittings

    SciTech Connect

    X.-H. Guo; P.C. Tandy; A.W. Thomas

    2006-03-01

    We investigate the chiral extrapolation of the lattice data for the light-heavy meson hyperfine splittings D*-D and B*-B to the physical region for the light quark mass. The chiral loop corrections providing non-analytic behavior in m{sub {pi}} are consistent with chiral perturbation theory for heavy mesons. Since chiral loop corrections tend to decrease the already too low splittings obtained from linear extrapolation, we investigate two models to guide the form of the analytic background behavior: the constituent quark potential model, and the covariant model of QCD based on the ladder-rainbow truncation of the Dyson-Schwinger equations. The extrapolated hyperfine splittings remain clearly below the experimental values even allowing for the model dependence in the description of the analytic background.

  14. Laminated composite of magnetic alloy powder and ceramic powder and process for making same

    SciTech Connect

    Moorhead, A.J.; Kim, H.

    1999-08-10

    A laminated composite structure of alternating metal powder layers, and layers formed of an inorganic bonding media powder, and a method for manufacturing same are disclosed. The method includes the steps of assembling in a cavity alternating layers of a metal powder and an inorganic bonding media of a ceramic, glass, and glass-ceramic. Heat, with or without pressure, is applied to the alternating layers until the particles of the metal powder are sintered together and bonded into the laminated composite structure by the layers of sintered inorganic bonding media to form a strong composite structure. The method finds particular application in the manufacture of high performance magnets wherein the metal powder is a magnetic alloy powder. 9 figs.

  15. Laminated composite of magnetic alloy powder and ceramic powder and process for making same

    DOEpatents

    Moorhead, Arthur J.; Kim, Hyoun-Ee

    1999-01-01

    A laminated composite structure of alternating metal powder layers, and layers formed of an inorganic bonding media powder, and a method for manufacturing same are discosed. The method includes the steps of assembling in a cavity alternating layers of a metal powder and an inorganic bonding media of a ceramic, glass, and glass-ceramic. Heat, with or without pressure, is applied to the alternating layers until the particles of the metal powder are sintered together and bonded into the laminated composite structure by the layers of sintered inorganic bonding media to form a strong composite structure. The method finds particular application in the manufacture of high performance magnets wherein the metal powder is a magnetic alloy powder.

  16. Laminated composite of magnetic alloy powder and ceramic powder and process for making same

    DOEpatents

    Moorhead, A.J.; Kim, H.

    1999-08-10

    A laminated composite structure of alternating metal powder layers, and layers formed of an inorganic bonding media powder, and a method for manufacturing same are disclosed. The method includes the steps of assembling in a cavity alternating layers of a metal powder and an inorganic bonding media of a ceramic, glass, and glass-ceramic. Heat, with or without pressure, is applied to the alternating layers until the particles of the metal powder are sintered together and bonded into the laminated composite structure by the layers of sintered inorganic bonding media to form a strong composite structure. The method finds particular application in the manufacture of high performance magnets wherein the metal powder is a magnetic alloy powder. 9 figs.

  17. Hadronic deuteron polarizability contribution the hyperfine structure in muonic deuterium

    NASA Astrophysics Data System (ADS)

    Eskin, A. V.; Martynenko, A. P.; Elekina, E. N.

    2016-12-01

    The calculation of the contribution to the polarizability of the nucleus to hyperfine structure of muonic hydrogen is carried out within the unitary isobar model and on the basis of experimental data on the structure functions of deep inelastic lepton-proton and lepton-deuteron scattering. The calculation of virtual absorption cross sections of transversely and longitudinally polarized photons by nucleons in the resonance region is performed in the framework of the program MAID.

  18. Hadronic deuteron polarizability contribution the hyperfine structure in muonic deuterium

    NASA Astrophysics Data System (ADS)

    Eskin, A. V.; Martynenko, A. P.; Elekina, E. N.

    2017-01-01

    The calculation of the contribution to the polarizability of the nucleus to hyperfine structure of muonic hydrogen is carried out within the unitary isobar model and on the basis of experimental data on the structure functions of deep inelastic lepton-proton and lepton-deuteron scattering. The calculation of virtual absorption cross sections of transversely and longitudinally polarized photons by nucleons in the resonance region is performed in the framework of the program MAID.

  19. Weak-interaction contributions to hyperfine splitting and Lamb shift

    SciTech Connect

    Eides, M.I.

    1996-05-01

    Weak-interaction contributions to hyperfine splitting and the Lamb shift in hydrogen and muonium are discussed. The problem of sign of the weak-interaction contribution to HFS is clarified, and simple physical arguments that make this sign evident are presented. It is shown that weak-interaction contributions to HFS in hydrogen and muonium have opposite signs. A weak-interaction contribution to the Lamb shift is obtained. {copyright} {ital 1996 The American Physical Society.}

  20. Deuterium hyperfine structure in interstellar C3HD

    NASA Technical Reports Server (NTRS)

    Bell, M. B.; Watson, J. K.; Feldman, P. A.; Matthews, H. E.; Madden, S. C.; Irvine, W. M.

    1987-01-01

    The deuterium nuclear quadrupole hyperfine structure of the transition 1(10)-1(01) of the ring molecule cyclopropenylidene-d1 (C3HD) has been observed in emission from interstellar molecular clouds. The narrowest linewidths (approximately 7 kHz) so far observed are in the cloud L1498. The derived D coupling constants Xzz = 186.9(1.4) kHz, eta=0.063(18) agree well with correlations based on other molecules.

  1. The hyperfine properties of iron-gallium alloys

    NASA Astrophysics Data System (ADS)

    Elzain, M.; Gismelseed, A.; Al-Rawas, A.; Yousif, A.; Widatallah, H.; Al-Azri, Maya; Al-Barwani, M.

    2016-12-01

    The hyperfine properties at Fe site in iron-gallium alloy are calculated using the full-potential linear-augmented-plane-waves method. We have calculated the Fermi contact field (Bhf) and isomer shift ( δ) at the Fe site versus the number of neighbouring Ga atoms. We found that Bhf decrease whereas δ increases with increasing number of neighbouring G atom. In addition we have calculated the hyperfine properties of FeGa system with DO3 structure, where various distributions of 4 the Ga atoms in the conventional unit cell are considered (including the regular DO3 structure). We found that the DO3 structure has the lowest energy as compared to the other configurations. The two distinct A and D sites of the ordered DO3 conventional unit cell have two distinct values for Bhf and δ. On changing the atomic arrangement of the Ga atoms within the conventional unit cell, the configuration of the A site is maintained whereas that of the D site becomes imperfect. The contact magnetic hyperfine fields of the D-like sites in the imperfect structures are lower than that of the DO3D site.

  2. Mapping the magnetic hyperfine field in GdCo5

    NASA Astrophysics Data System (ADS)

    Krylov, V. I.; Bosch-Santos, B.; Cabrera-Pasca, G. A.; Delyagin, N. N.; Carbonari, A. W.

    2016-05-01

    The magnetic hyperfine field (Bhf) in ferrimagnetic GdCo5 compound has been investigated as a function of temperature by Mössbauer effect (ME) spectroscopy and perturbed angular correlation (PAC) spectroscopy using 119Sn and 111Cd probe nuclei, respectively. Results show that the non-magnetic probe atoms 119Sn and 111Cd substitute all three non-equivalent positions in GdCo5: Gd, CoI, and CoII. For 119Sn and 111Cd probes at Gd sites, the saturation magnetic hyperfine fields are very different with values of Bhf1 = 57.0(1) T and Bhf1= 20.7(1) T, respectively. For 119Sn and 111Cd atoms localized at CoI and CoII sites the magnetic hyperfine fields are practically identical and, in saturation, reach the values of Bhf2 = 11.6(1) T and Bhf2 = 11.1(2) T, and Bhf3 = 14.8(1) T and Bhf3 = 14.4(2) T, respectively.

  3. First Optical Hyperfine Structure Measurement in an Atomic Anion

    SciTech Connect

    Fischer, A.; Canali, C.; Warring, U.; Kellerbauer, A.; Fritzsche, S.

    2010-02-19

    We have investigated the hyperfine structure of the transition between the 5d{sup 7}6s{sup 2} {sup 4}F{sub 9/2}{sup e} ground state and the 5d{sup 6}6s{sup 2}6p {sup 6}D{sub J}{sup o} excited state in the negative osmium ion by high-resolution collinear laser spectroscopy. This transition is unique because it is the only known electric-dipole transition in atomic anions and might be amenable to laser cooling. From the observed hyperfine structure in {sup 187}Os{sup -} and {sup 189}Os{sup -} the yet unknown total angular momentum of the bound excited state was found to be J=9/2. The hyperfine structure constants of the {sup 4}F{sub 9/2}{sup e} ground state and the {sup 6}D{sub 9/2}{sup o} excited state were determined experimentally and compared to multiconfiguration Dirac-Fock calculations. Using the knowledge of the ground and excited state angular momenta, the full energy level diagram of {sup 192}Os{sup -} in an external magnetic field was calculated, revealing possible laser cooling transitions.

  4. PLUTONIUM-HYDROGEN REACTION PRODUCT, METHOD OF PREPARING SAME AND PLUTONIUM POWDER THEREFROM

    DOEpatents

    Fried, S.; Baumbach, H.L.

    1959-12-01

    A process is described for forming plutonlum hydride powder by reacting hydrogen with massive plutonium metal at room temperature and the product obtained. The plutonium hydride powder can be converted to plutonium powder by heating to above 200 deg C.

  5. Method of producing homogeneous mixed metal oxides and metal-metal oxide mixtures

    DOEpatents

    Quinby, Thomas C.

    1978-01-01

    Metal powders, metal oxide powders, and mixtures thereof of controlled particle size are provided by reacting an aqueous solution containing dissolved metal values with excess urea. Upon heating, urea reacts with water from the solution leaving a molten urea solution containing the metal values. The molten urea solution is heated to above about 180.degree. C. whereupon metal values precipitate homogeneously as a powder. The powder is reduced to metal or calcined to form oxide particles. One or more metal oxides in a mixture can be selectively reduced to produce metal particles or a mixture of metal and metal oxide particles.

  6. Powder Extinguishants for Jet-Fuel Fires

    NASA Technical Reports Server (NTRS)

    Altman, R. L.; Mayer, L. A.; Ling, A. C.

    1986-01-01

    Mixtures of alkali metal dawsonite and metal halide show superior performance. In tests of new dry powder fire extinguishants, mixtures of potassium dawsonite with either stannous iodide or potassium iodide found effective for extinguishing jet-fuel fires on hot metal surfaces (up to 900 degrees C). Mixtures performed more effectively than either compound alone.

  7. Ceramic Powders

    NASA Technical Reports Server (NTRS)

    1984-01-01

    In developing its product line of specialty ceramic powders and related products for government and industrial customers, including companies in the oil, automotive, electronics and nuclear industries, Advanced Refractory Technologies sought technical assistance from NERAC, Inc. in specific areas of ceramic materials and silicon technology, and for assistance in identifying possible applications of these materials in government programs and in the automotive and electronics industry. NERAC conducted a computerized search of several data bases and provided extensive information in the subject areas requested. NERAC's assistance resulted in transfer of technologies that helped ART staff develop a unique method for manufacture of ceramic materials to precise customer specifications.

  8. Hyperfine magnetic field in Au2MnIn

    SciTech Connect

    Saleh, N.S.; Jha, S.; Julian, G.M.

    1985-01-01

    The hyperfine magnetic field (hmf) at nonmagnetic impurity Cd in the Heusler alloy Au2MnIn has been measured by the Time Differential Perturbed Angular Correlation (TDPAC) technique. The measurement utilized the 84-nsec 247 kev state in Cd-111 populated in the decay of 2.8-d In-111. The alloy was prepared by heating together in argon atmoshpere stoichiometric amounts of the constituents. The hmf at the Cd site was measured as 155 plus or minus 3 kG at 77 K. 5 references.

  9. Determination of hyperfine fields orientation in nuclear probe techniques

    NASA Astrophysics Data System (ADS)

    Szymański, K.; Olszewski, W.; Satuła, D.; Gawryluk, D. J.; Krzton-Maziopa, A.; Kalska-Szostko, B.

    2017-02-01

    One of the most popular nuclear probes, 57Fe is used for the investigation of orientations of hyperfine fields and also for the determination of other important properties. In particular, the orientation of iron magnetic moments can be unambiguously determined, including its signs. Experiments with polarized radiation are presented with regard to selected systems. Orientation of electric field gradient is used for acquiring information about the shape of the texture-free spectra. Applications on the analysis of iron-based superconductors are presented.

  10. A search for the tritium hyperfine line from nearby stars

    NASA Astrophysics Data System (ADS)

    Valdes, F.; Freitas, R. A., Jr.

    1986-01-01

    A search for the tritium hyperfine line at 1516 MHz from 108 assorted astronomical objects, with emphasis on 53 nearby stars, was conducted in June 1983. All stars within 20 light-years visible from the 26-m telescope at Hat Creek Radio Observatory were examined using 256 4883-Hz channels. Twelve stars were also examined using 1024 76-Hz channels. The wideband- and narrow-band-channel observations achieved sensitivities of 5 - 14×10-24W/m2/channel and 0.7 - 2×10-24W/m2/channel, respectively. No detections were made. The tritium frequency is highly attractive for SETI work.

  11. Determination of hyperfine fields orientation in nuclear probe techniques.

    PubMed

    Szymański, K; Olszewski, W; Satuła, D; Gawryluk, D J; Krzton-Maziopa, A; Kalska-Szostko, B

    2017-02-15

    One of the most popular nuclear probes, (57)Fe is used for the investigation of orientations of hyperfine fields and also for the determination of other important properties. In particular, the orientation of iron magnetic moments can be unambiguously determined, including its signs. Experiments with polarized radiation are presented with regard to selected systems. Orientation of electric field gradient is used for acquiring information about the shape of the texture-free spectra. Applications on the analysis of iron-based superconductors are presented.

  12. Effect of hyperfine splitting on light-induced drift

    NASA Astrophysics Data System (ADS)

    Parkhomenko, A. I.; Shalagin, A. M.

    1986-09-01

    The influence of the hyperfine structure (hfs) of the levels upon the light-induced drift (LID) effect is investigated. It is shown that hfs considerably affects the dependence of the LID velocity upon the radiation frequency. It is concluded that for decreasing separation between the hfs components the LID effect can both increase and decrease depending upon the relationship of the system parameters (collision frequencies in different levels, the pressure of a buffer gas, etc.). A considerable decrease of the effect however is highly unlikely. It is shown that a change in the buffer gas pressure can lead to reversal of the LID velocity direction.

  13. Reduction Expansion Synthesis for Magnetic Alloy Powders

    DTIC Science & Technology

    2015-12-01

    21 1. Preparation of Precursors ...19 Magnetic Agglomeration of AlNiCo Alloys..............................................20 Figure 9. Metal Powder Precursors in Mortar...Prior to Mixing .................................22 Figure 10. Precursor Slurry in Alumina Boat for Heating ..........................................23

  14. Additive Technologies Based on Composite Powder Nanomaterials

    NASA Astrophysics Data System (ADS)

    Gorynin, I. V.; Oryshchenko, A. S.; Malyshevskii, V. A.; Farmakovskii, B. V.; Kuznetsov, P. A.

    2015-01-01

    The possibilities of application of promising adaptive technologies of bulk laser deposition and selective laser sintering in machine building with the aim of creation of complex-configuration parts and reconditioning of worn components of various-purpose articles from metallic powder materials are considered. The possibilities of the production chain from making of metallic powders to creation of ready coatings and articles on the base of a single unit are described.

  15. Hyperfine coupling of the hydrogen atom in high temperature water.

    PubMed

    Nuzhdin, Kirill; Bartels, David M

    2013-03-28

    The hyperfine coupling constant of the hydrogen atom has been measured in pressurized liquid water up to 300 °C. The reduced constant A(water)∕A(vacuum) is 0.9939 at room temperature, and decreases to a minimum of 0.9918 at 240 °C. The reduced constant then increases at higher temperature. The g-factor is 2.002244(10) at room temperature and decreases to 2.00221(1) at 240 °C. The change in g-factor is proportional to the change in hyperfine coupling. The behavior below 110 °C is in excellent agreement with a previously proposed model in which the H atom is confined to a harmonic solvent cage, and vibrations within the cage mix "p-type" character into the wavefunction, resulting inA(water)∕A(vacuum) < 1. The harmonic model breaks down above 130 °C. We demonstrate that a classical binary collision model using approximate partial molar volume information can recover the observed minima near 240 °C.

  16. Hyperfine meson splittings: chiral symmetry versus transverse gluon exchange

    SciTech Connect

    Felipe J. Llanes-Estrada; Stephen R. Cotanch; Adam P. Szczepaniak; Eric S. Swanson

    2004-02-01

    Meson spin splittings are examined within an effective Coulomb gauge QCD Hamiltonian incorporating chiral symmetry and a transverse hyperfine interaction necessary for heavy quarks. For light and heavy quarkonium systems the pseudoscalar-vector meson spectrum is generated by approximate BCS-RPA diagonalizations. This relativistic formulation includes both S and D waves for the vector mesons which generates a set of coupled integral equations. A smooth transition from the heavy to the light quark regime is found with chiral symmetry dominating the /pi-/rho mass difference. A good, consistent description of the observed meson spin splittings and chiral quantities, such as the quark condensate and the /pi mass, is obtained. Similar comparisons with TDA diagonalizations, which violate chiral symmetry, are deficient for light pseudoscalar mesons indicating the need to simultaneously include both chiral symmetry and a hyperfine interaction. The /eta{sub b} mass is predicted to be around 9400 MeV consistent with other theoretical expectations and above the unconfirmed 9300 MeV candidate. Finally, for comparison with lattice results, the J reliability parameter is also evaluated.

  17. Spectra of charmed and bottom baryons with hyperfine interaction

    NASA Astrophysics Data System (ADS)

    Wang, Zhen-Yang; Qi, Jing-Juan; Guo, Xin-Heng; Wei, Ke-Wei

    2017-09-01

    Up to now, the excited charmed and bottom baryon states have still not been well studied experimentally or theoretically. In this paper, we predict the mass of , the only L = 0 baryon state which has not been observed, to be 6069.2 MeV. The spectra of charmed and bottom baryons with the orbital angular momentum L = 1 are studied in two popular constituent quark models, the Goldstone boson exchange (GBE) model and the one gluon exchange (OGE) hyperfine interaction model. Inserting the latest experimental data from the “Review of Particle Physics", we find that in the GBE model, there exist some multiplets (Σc(b), and Ωc(b)) in which the total spin of the three quarks in their lowest energy states is 3/2, but in the OGE model there is no such phenomenon. This is the most important difference between the GBE and OGE models. These results can be tested in the near future. We suggest more efforts to study the excited charmed and bottom baryons both theoretically and experimentally, not only for the abundance of baryon spectra, but also for determining which hyperfine interaction model best describes nature. Supported by National Natural Science Foundation of China (11175020, 11575023, U1204115)

  18. Hyperfine interactions at nitrogen interstitial defects in diamond.

    PubMed

    Atumi, M K; Goss, J P; Briddon, P R; Shrif, F E; Rayson, M J

    2013-02-13

    Diamond has many extreme physical properties and it can be used in a wide range of applications. In particular it is a highly effective particle detection material, where radiation damage is an important consideration. The WAR9 and WAR10 are electron paramagnetic resonance centres seen in irradiated, nitrogen-containing diamond. These S = 1/2 defects have C(2v) and C(1h) symmetry, respectively, and the experimental spectra have been interpreted as arising from nitrogen split-interstitial centres. Based upon the experimental and theoretical understanding of interstitial nitrogen defect structures, the AIMPRO density functional code has been used to assess the assignments for the structures of WAR9 and WAR10. Although the calculated hyperfine interaction tensors are consistent with the measured values for WAR9, the thermal stability renders the assignment problematic. The model for the WAR10 centre yields principal directions of the hyperfine tensor at variance with observation. Alternative models for both centres are discussed in this paper, but no convincing structures have been found.

  19. Zeeman effects in the hyperfine structure of atomic iodine photodissociation laser emission.

    NASA Technical Reports Server (NTRS)

    Hwang, W. C.; Kasper, J. V. V.

    1972-01-01

    Observation of hyperfine structure in laser emission from CF3I and C2F5I photodissociation lasers. Constant magnetic fields affect the time behavior of the emission by changing the relative gains of the hyperfine transitions. Time-varying fields usually present in photodissociation lasers further complicate the emission.

  20. Zeeman effects in the hyperfine structure of atomic iodine photodissociation laser emission.

    NASA Technical Reports Server (NTRS)

    Hwang, W. C.; Kasper, J. V. V.

    1972-01-01

    Observation of hyperfine structure in laser emission from CF3I and C2F5I photodissociation lasers. Constant magnetic fields affect the time behavior of the emission by changing the relative gains of the hyperfine transitions. Time-varying fields usually present in photodissociation lasers further complicate the emission.

  1. Analytical calculation of radiative-recoil corrections to muonium hyperfine splitting: Muon-line contribution

    SciTech Connect

    Eides, M.I.; Karshenboim, S.G.; Shelyuto, V.A. )

    1991-02-01

    Analytic expression for radiative-recoil corrections to muonium ground-state hyperfine splitting induced by muon-line radiative insertions is obtained. This result completes the program of analytic calculation of all radiative-recoil corrections. The perspectives of further muonium hyperfine splitting investigations are also discussed.

  2. O(alpha{sup 3} ln(alpha)) Corrections to Muonium and Positronium Hyperfine Splitting

    SciTech Connect

    Melnikov, Kirill

    2001-07-25

    We compute O({alpha}{sup 3} ln {alpha}) relative corrections to the ground state hyperfine splitting of a QED two body bound state with different masses of constituents. The general result is then applied to muonium and positronium. In particular, a new value of the muon to electron mass ratio is derived from the muonium ground state hyperfine splitting.

  3. Muon loop light-by-light contribution to hyperfine splitting in muonium.

    PubMed

    Eides, Michael I; Shelyuto, Valery A

    2014-05-02

    Three-loop corrections to hyperfine splitting in muonium, generated by the gauge-invariant sets of diagrams with muon and tauon loop light-by-light scattering blocks, are calculated. These results complete calculations of all light-by-light scattering contributions to hyperfine splitting in muonium.

  4. New technology for separating resin powder and fiberglass powder from fiberglass-resin powder of waste printed circuit boards.

    PubMed

    Li, Jia; Gao, Bei; Xu, Zhenming

    2014-05-06

    New recycling technologies have been developed lately to enhance the value of the fiberglass powder-resin powder fraction (FRP) from waste printed circuit boards. The definite aim of the present paper is to present some novel methods that use the image forces for the separation of the resin powder and fiberglass powder generated from FRP during the corona electrostatic separating process. The particle shape charactization and particle trajectory simulation were performed on samples of mixed non-metallic particles. The simulation results pointed out that particles of resin powder and particles of fiberglass powder had different detach trajectories at the conditions of the same size and certain device parameters. An experiment carried out using a corona electrostatic separator validated the possibility of sorting these particles based on the differences in their shape characteristics. The differences in the physical properties of the different types of particles provided the technical basis for the development of electrostatic separation technologies for the recycling industry.

  5. Anti-Corrosive Powder Particles

    NASA Technical Reports Server (NTRS)

    Parker, Donald; MacDowell, Louis, III

    2005-01-01

    The National Aeronautics and Space Administration (NASA) seeks partners for a new approach in protecting embedded steel surfaces from corrosion. Corrosion of reinforced steel in concrete structures is a significant problem for NASA structures at Kennedy Space Center (KSC) because of the close proximity of the structures to salt spray from the nearby Atlantic Ocean. In an effort to minimize the damage to such structures, coatings were developed that could be applied as liquids to the external surfaces of a substrate in which the metal structures were embedded. The Metallic Pigment Powder Particle technology was developed by NASA at KSC. This technology combines the metallic materials into a uniform particle. The resultant powder can be sprayed simultaneously with a liquid binder onto the surface of concrete structures with a uniform distribution of the metallic pigment for optimum cathodic protection of the underlying steel in the concrete. Metallic Pigment Powder Particle technology improves upon the performance of an earlier NASA technology Liquid Galvanic Coating (U.S. Patent No. 6,627,065).

  6. Three-Loop Radiative-Recoil Corrections to Hyperfine Splitting in Muonium: Diagrams with Polarization Loops

    SciTech Connect

    Eides, Michael I.; Shelyuto, Valery A.

    2009-09-25

    We consider three-loop radiative-recoil corrections to hyperfine splitting in muonium generated by the diagrams with electron and muon vacuum polarizations. We calculate single-logarithmic and nonlogarithmic contributions of order alpha{sup 3}(m/M)E{sub F} generated by gauge invariant sets of diagrams with electron and muon polarization insertions in the electron and muon factors. Combining these corrections with the older results, we obtain total contribution to hyperfine splitting generated by all diagrams with electron and muon polarization loops. The calculation of this contribution completes an important stage in the implementation of the program of reduction of the theoretical uncertainty of hyperfine splitting below 10 Hz. The new results improve the theory of hyperfine splitting and affect the value of the electron-muon mass ratio extracted from experimental data on muonium hyperfine splitting.

  7. Magnetic hyperfine coupling of a methyl group undergoing internal rotation: a case study of methyl formate.

    PubMed

    Tudorie, M; Coudert, L H; Huet, T R; Jegouso, D; Sedes, G

    2011-02-21

    The hyperfine structure of methyl formate was recorded in the 2-20 GHz range. A molecular beam coupled to a Fourier transform microwave spectrometer having an instrumental resolution of 0.46 kHz and limited by a Doppler width of a few kHz was used. A-type lines were found split by the magnetic hyperfine coupling while no splittings were observed for E-type lines. Symmetry considerations were used to account for the internal rotation of the methyl top and to derive effective hyperfine coupling Hamiltonians. Neglecting the spin-rotation magnetic coupling, the vanishing splittings of the E-type lines could be understood and analyses of the hyperfine patterns of the A-type lines were performed. The results are consistent with a hyperfine structure dominated by the magnetic spin-spin coupling due to the three hydrogen atoms of the methyl group.

  8. First-principles hyperfine tensors for electrons and holes in silicon and GaAs

    NASA Astrophysics Data System (ADS)

    Philippopoulos, Pericles; Chesi, Stefano; Coish, William

    Knowing (and controlling) hyperfine interactions in silicon and III-V semiconductor nanostructures is important for quantum information processing with electron and nuclear spin states. We have performed density-functional theory (DFT) calculations that fully account for spin structure of the Bloch states (in contast with approaches that rely on the density alone). Using this method, we confirm the known value for the contact hyperfine coupling in the conduction band of silicon, but find a significant deviation in the value for the conduction band of GaAs relative to the accepted value, estimated in ref.. Moreover, this method can be used to calculate the full hyperfine tensor for the valence band, where spin-orbit effects may be strong, precluding methods that determine hyperfine couplings from the density alone. This general method can be applied to a broad class of materials with strong combined spin-orbit and hyperfine interactions.

  9. First-principles hyperfine tensors for electrons and holes in silicon and GaAs

    NASA Astrophysics Data System (ADS)

    Philippopoulos, Pericles; Chesi, Stefano; Coish, William

    Knowing (and controlling) hyperfine interactions in silicon and III-V semiconductor nanostructures is important for quantum information processing with electron and nuclear spin states. We have performed density-functional theory (DFT) calculations that fully account for spin structure of the Bloch states (in contast with approaches that rely on the density alone). Using this method, we confirm the known value for the contact hyperfine coupling in the conduction band of silicon, but find a significant deviation in the value for the conduction band of GaAs relative to the accepted value, estimated in ref.. Moreover, this method can be used to calculate the full hyperfine tensor for the valence band, where spin-orbit effects may be strong, precluding methods that determine hyperfine couplings from the density alone. This general method can be applied to a broad class of materials with strong combined spin-orbit and hyperfine interactions

  10. Stepwise effects of the BCR sequential chemical extraction procedure on dissolution and metal release from common ferromagnesian clay minerals: a combined solution chemistry and X-ray powder diffraction study.

    PubMed

    Ryan, P C; Hillier, S; Wall, A J

    2008-12-15

    Sequential extraction procedures (SEPs) are commonly used to determine speciation of trace metals in soils and sediments. However, the non-selectivity of reagents for targeted phases has remained a lingering concern. Furthermore, potentially reactive phases such as phyllosilicate clay minerals often contain trace metals in structural sites, and their reactivity has not been quantified. Accordingly, the objective of this study is to analyze the behavior of trace metal-bearing clay minerals exposed to the revised BCR 3-step plus aqua regia SEP. Mineral quantification based on stoichiometric analysis and quantitative powder X-ray diffraction (XRD) documents progressive dissolution of chlorite (CCa-2 ripidolite) and two varieties of smectite (SapCa-2 saponite and SWa-1 nontronite) during steps 1-3 of the BCR procedure. In total, 8 (+/-1) % of ripidolite, 19 (+/-1) % of saponite, and 19 (+/-3) % of nontronite (% mineral mass) dissolved during extractions assumed by many researchers to release trace metals from exchange sites, carbonates, hydroxides, sulfides and organic matter. For all three reference clays, release of Ni into solution is correlated with clay dissolution. Hydrolysis of relatively weak Mg-O bonds (362 kJ/mol) during all stages, reduction of Fe(III) during hydroxylamine hydrochloride extraction and oxidation of Fe(II) during hydrogen peroxide extraction are the main reasons for clay mineral dissolution. These findings underscore the need for precise mineral quantification when using SEPs to understand the origin/partitioning of trace metals with solid phases.

  11. Oxygen-17 hyperfine structures in the pure rotational spectra of SrO, SnO, BaO, HfO and ThO.

    PubMed

    Dewberry, Christopher T; Etchison, Kerry C; Grubbs Ii, Garry S; Powoski, Robert A; Serafin, Michal M; Peebles, Sean A; Cooke, Stephen A

    2007-11-28

    Hyperfine structures arising from the couplings of the nuclear spin angular momentum of (17)O (I = 5/2) with the end over end rotation of several metal-containing diatomic monoxides have been observed using a Fourier transform microwave spectrometer. The molecules have been produced by reacting (17)O(2) with laser ablated metal atoms. The oxygen-17 nuclear quadrupole coupling constants have been determined for the title molecules and are interpreted in terms of a simple Townes-Dailey model. Also, the oxygen-17 nuclear spin-rotation constants have been determined and used to calculate the oxygen-17 shieldings for each molecule.

  12. Charge distribution and hyperfine interactions in the vicinity of impurity sites in In2O3 doped with Fe, Co, and Ni

    NASA Astrophysics Data System (ADS)

    Sena, C.; Costa, M. S.; Muñoz, E. L.; Cabrera-Pasca, G. A.; Pereira, L. F. D.; Mestnik-Filho, J.; Carbonari, A. W.; Coaquira, J. A. H.

    2015-08-01

    In this paper, first-principles calculations based on density functional theory (DFT) were used to determine TM (TM=Fe, Ni, Co) and Cd impurity locations in the In2O3 host structure, their charge states, the electronic and structural relaxations induced in the host lattice as well as to interpret previous and supplementary experimental results of hyperfine interactions. Different techniques were carried out to characterize TM-doped In2O3 bulk samples prepared by the sol-gel method starting from very pure metals. Perturbed angular correlation (PAC) spectroscopy, a sensitive nuclear technique capable of measuring interactions from electronic charge and spins within an atomic distance, was used to experimentally determine hyperfine interactions at cation sites of In2O3 doped with Co and Ni using 111In →111Cd as probe nuclei. Room temperature results of magnetization measurements in In2O3 doped with Fe, Co and Ni show ferromagnetic ordering coexisting with a paramagnetic behavior for all samples. Results of PAC spectroscopy and DFT calculations show that TM atoms locate as second nearest neighbors of Cd probes preferentially occupy symmetric sites of the doped In2O3 crystal structure with lattice parameters slightly different from that of pure In2O3. Moreover, while a major population of 111Cd probes observes almost the same hyperfine interactions measured for pure In2O3, a small population detects magnetic dipole interactions with magnetic hyperfine field at Cd probes of 2.6 T, 3.1 T, and 4.6 T, respectively for Ni, Co, and Fe doping presenting an almost linear dependence on the number of unpaired 3d electrons of the transition metal impurity.

  13. Synchrotron Mossbauer spectroscopy of powder samples

    NASA Astrophysics Data System (ADS)

    Alp, E. E.; Sturhahn, W.; Toellner, T.

    1995-05-01

    Synchrotron Mossbauer spectroscopy, SMS, is an emerging technique that allows fast and accurate determination of hyperfine field parameters similar to conventional Mossbauer spectroscopy with radioactive sources. This new technique, however, is qualitatively different from Mossbauer spectroscopy in terms of equipment, methodology, and analysis to warrant a new name. In this paper, we report on isomer shift and quadrupole splitting measurements of Mohr's salt, Fe(NH4)2 (SO4)2 · 6H2O for demonstration purposes. Theoretical calculations were performed and compared to experiments both in energy and time domain to demonstrate the influence of thickness distribution and preferential alignment of powder samples. Such measurements may prove to be useful when the data collection times are reduced to few seconds in the third generation, undulator based synchrotron radiation sources.

  14. An application of powder metallurgy to dentistry.

    PubMed

    Oda, Y; Ueno, S; Kudoh, Y

    1995-11-01

    Generally, the dental casting method is used to fabricate dental prostheses made with metal. The method of fabricating dental prostheses from sintered titanium alloy has certain advantages: the elimination of casting defects, a sintering temperature that is lower than the melting point, and a shorter processing time. By examining (1) the properties of green, sintered compacts of titanium powder, (2) the effects of adding aluminum powder on the properties of green, sintered compacts of Ti-Al compound, and (3) the effects of adding copper powder on the properties of green, sintered compacts of Ti-Al-Cu compound, the authors developed a sintered titanium alloy on a trial basis. Because the properties satisfied the requirements of dental restorations, a powder metallurgical method of making dental restorations from this sintered titanium alloy was devised. Applications of such sintered titanium alloys for the metal coping of metal-ceramic crowns and denture base plates were discussed.

  15. Nagaoka’s atomic model and hyperfine interactions

    PubMed Central

    INAMURA, Takashi T.

    2016-01-01

    The prevailing view of Nagaoka’s “Saturnian” atom is so misleading that today many people have an erroneous picture of Nagaoka’s vision. They believe it to be a system involving a ‘giant core’ with electrons circulating just outside. Actually, though, in view of the Coulomb potential related to the atomic nucleus, Nagaoka’s model is exactly the same as Rutherford’s. This is true of the Bohr atom, too. To give proper credit, Nagaoka should be remembered together with Rutherford and Bohr in the history of the atomic model. It is also pointed out that Nagaoka was a pioneer of understanding hyperfine interactions in order to study nuclear structure. PMID:27063182

  16. Isotope shift and hyperfine structure measurements in titanium I

    NASA Astrophysics Data System (ADS)

    Luc, P.; Vetter, R.; Bauche-Arnoult, C.; Bauche, J.

    1994-09-01

    High accuracy measurements of hyperfine structure due to47Ti and49Ti in the 3 d 2 4 s 2 a 3 F 2-3 d 2 4 s4 p z 5 D 1 absorption line at σ=18482.772 cm-1 have been performed by use of a Doppler-free experiment, where a beam of titanium atoms is crossed by a CW single mode tunable dye laser. They have allowed for the determination of isotope shifts between46Ti,47Ti,48Ti,49Ti and50Ti. By use of accurate values of mean square nuclear charge radii for the even isotopes, it has been possible to separate mass shifts from field shifts and to determine accurate values for the mean square nuclear charge radii of47Ti and49Ti. The field shift presents a marked odd-even staggering.

  17. Theoretical study of the hyperfine parameters of OH

    NASA Technical Reports Server (NTRS)

    Chong, Delano P.; Langhoff, Stephen R.; Bauschlicher, Charles W., Jr.

    1991-01-01

    In the present study of the hyperfine parameters of O-17H as a function of the one- and n-particle spaces, all of the parameters except oxygen's spin density, b sub F(O), are sufficiently easily tractable to allow concentration on the computational requirements for accurate determination of b sub F(O). Full configuration-interaction (FCI) calculations in six Gaussian basis sets yield unambiguous results for (1) the effect of uncontracting the O s and p basis sets; (2) that of adding diffuse s and p functions; and (3) that of adding polarization functions to O. The size-extensive modified coupled-pair functional method yields b sub F values which are in fair agreement with FCI results.

  18. Opto-Electronic Oscillator Stabilized By A Hyperfine Atomic Transition

    NASA Technical Reports Server (NTRS)

    Strekalov, Dmitry; Aveline, David; Matsko, Andrey B.; Thompson, Robert; Yu, Nan

    2004-01-01

    Opto-electronic oscillator (OEO) is a closed-loop system with part of the loop is implemented by an optical beam, and the rest by RF circuitry. The technological advantage of this approach over traditional all-RF loops in the gigahertz range comes from the that frequency filtering can be done far more efficiently in the optical range with compact, low power, and have superior stability. In this work, we report our preliminary results on using the phenomenon of coherent population trapping in (87) Rb vapor as an optical filter. Such a filter allows us to stabilize the OEO at the hyperfine splitting frequency of rubidium, thus implementing a novel type of frequency standard.

  19. Coulomb artifacts and bottomonium hyperfine splitting in lattice NRQCD

    NASA Astrophysics Data System (ADS)

    Liu, T.; Penin, A. A.; Rayyan, A.

    2017-02-01

    We study the role of the lattice artifacts associated with the Coulomb binding effects in the analysis of the heavy quarkonium within lattice NRQCD. We find that a "na¨ıve" perturbative matching generates spurious linear Coulomb artifacts, which result in a large systematic error in the lattice predictions for the heavy quarkonium spectrum. This effect is responsible, in particular, for the discrepancy between the recent determinations of the bottomonium hyperfine splitting in the radiatively improved lattice NRQCD [1, 2]. We show that the correct matching procedure which provides full control over discretization errors is based on the asymptotic expansion of the lattice theory about the continuum limit, which gives M Y(1 S) - M ηb (1 S) = 52.9 ± 5.5 MeV [1].

  20. Systematics of Mössbauer hyperfine parameters in Np intermetallics

    NASA Astrophysics Data System (ADS)

    Kalvius, G. M.; Gal, J.; Asch, L.; Potzel, W.

    1992-05-01

    Data for intermetallic compounds of neptunium obtained with the 60 keV Mössbauer resonance of237Np are reviewed. Measurements of temperature, pressure and field dependencies are available. The main questions addressed are: (a) the degree of delocalization of 5f-electrons, (b) the formal charge state of Np, and (c) the influence of the ligand on the neptunium electronic structure. For this purpose, we present an evaluation of systematic behavior concerning mainly the hyperfine field and isomer shift in the cubic Laves phase materials NpX2, the NaCl-type monochalcogenides and monopnictides, and intermetallics with AuCu3 and ThCr2Si2 structures. Analogies to corresponding rare-earth compounds will be pointed out.

  1. Theoretical study of the hyperfine parameters of OH

    NASA Technical Reports Server (NTRS)

    Chong, Delano P.; Langhoff, Stephen R.; Bauschlicher, Charles W., Jr.

    1991-01-01

    In the present study of the hyperfine parameters of O-17H as a function of the one- and n-particle spaces, all of the parameters except oxygen's spin density, b sub F(O), are sufficiently easily tractable to allow concentration on the computational requirements for accurate determination of b sub F(O). Full configuration-interaction (FCI) calculations in six Gaussian basis sets yield unambiguous results for (1) the effect of uncontracting the O s and p basis sets; (2) that of adding diffuse s and p functions; and (3) that of adding polarization functions to O. The size-extensive modified coupled-pair functional method yields b sub F values which are in fair agreement with FCI results.

  2. HCN hyperfine ratio analysis of massive molecular clumps

    NASA Astrophysics Data System (ADS)

    Schap, W. J.; Barnes, P. J.; Ordoñez, A.; Ginsburg, A.; Yonekura, Y.; Fukui, Y.

    2017-03-01

    We report a new analysis protocol for HCN hyperfine data, based on the PYSPECKIT package, and results of using this new protocol to analyse a sample area of seven massive molecular clumps from the Census of High- and Medium-mass Protostars (CHaMP) survey, in order to derive maps of column density for this species. There is a strong correlation between the HCN integrated intensity, IHCN, and previously reported I_HCO+ in the clumps, but I_N_{2H+} is not well correlated with either of these other two 'dense gas tracers'. The four fitted parameters from PYSPECKIT in this region fall in the range of VLSR = 8-10 km s-1, σV = 1.2-2.2 km s-1, Tex = 4-15 K, and τ = 0.2-2.5. These parameters allow us to derive a column density map of these clouds, without limiting assumptions about the excitation or opacity. A more traditional (linear) method of converting IHCN to total mass column gives much lower clump masses than our results based on the hyperfine analysis. This is primarily due to areas in the sample region of low I, low Tex, and high τ. We conclude that there may be more dense gas in these massive clumps not engaged in massive star formation than previously recognized. If this result holds for other clouds in the CHaMP sample, it would have dramatic consequences for the calibration of the Kennicutt-Schmidt star formation laws, including a large increase in the gas depletion time-scale in such regions.

  3. Hyperfine interactions at dangling bonds in amorphous germanium

    NASA Astrophysics Data System (ADS)

    Graf, T.; Ishikawa, T.; Itoh, K. M.; Haller, E. E.; Stutzmann, M.; Brandt, M. S.

    2003-11-01

    Isotope-engineered amorphous germanium (a-Ge) films with 73Ge concentrations in the range of 0.1 to 95.6 % have been investigated by electron spin resonance (ESR) and electrically detected magnetic resonance (EDMR) at microwave frequencies between 0.434 and 9.35 GHz. The hyperfine interactions of dangling bond (DB) defects with many 73Ge nuclei and their spin localization radius have been extracted from the broadening of the EDMR signals in isotope enriched samples at different 73Ge concentrations. Linewidths as low as ΔBexppp=2.6 G have been observed at 0.434 GHz in a sample without 73Ge nuclear spins. At low 73Ge concentrations, the frequency-dependent linewidth BSOpp/ν=4.4 G/GHz is determined by g-factor anisotropy and disorder. A frequency-independent linewidth contribution of about 1 G is attributed to dipolar broadening between the DB electronic spins. Over a large range of intermediate concentrations, the statistically distributed nuclear spins of 73Ge atoms on sites close to the DB defect atom are responsible for the overall linewidth. The large linewidth ΔBexppp=300 G of samples with 73Ge concentrations of 95.6% requires a model wave function with a Fermi contact interaction of Aiso=29 G×gμB at the defect atom, indicating that a fraction of 3.4% of the DB wave function originates from s-like orbitals there. The decay of the rest of the DB wave function can be described with a spin localization radius of 3.5 Å by a numerical model for the statistical hyperfine broadening. The delocalization of the DB spin is much smaller than that of the DB charge density determined in transport measurements.

  4. Full hyperfine structure analysis of singly ionized molybdenum

    NASA Astrophysics Data System (ADS)

    Bouazza, Safa

    2017-03-01

    For a first time a parametric study of hyperfine structure of Mo II configuration levels is presented. The newly measured A and B hyperfine structure (hfs) constants values of Mo II 4d5, 4d45s and 4d35s2 configuration levels, for both 95 and 97 isotopes, using Fast-ion-beam laser-induced fluorescence spectroscopy [1] are gathered with other few data available in literature. A fitting procedure of an isolated set of these three lowest even-parity configuration levels has been performed by taking into account second-order of perturbation theory including the effects of closed shell-open shell excitations. Moreover the same study was done for Mo II odd-parity levels; for both parities two sets of fine structure parameters as well as the leading eigenvector percentages of levels and Landé-factor gJ, relevant for this paper are given. We present also predicted singlet, triplet and quintet positions of missing experimental levels up to 85000 cm-1. The single-electron hfs parameter values were extracted in their entirety for 97Mo II and for 95Mo II: for instance for 95Mo II, a4d01 =-133.37 MHz and a5p01 =-160.25 MHz for 4d45p; a4d01 =-140.84 MHz, a5p01 =-170.18 MHz and a5s10 =-2898 MHz for 4d35s5p; a5s10 =-2529 (2) MHz and a4d01 =-135.17 (0.44) MHz for the 4d45s. These parameter values were analysed and compared with diverse ab-initio calculations. We closed this work with giving predicted values of magnetic dipole and electric quadrupole hfs constants of all known levels, whose splitting are not yet measured.

  5. Investigation of hyperfine interactions in RMO3 (R =La, Nd; M =Cr, Fe) antiferromagnetic perovskite oxides using PAC spectroscopy

    NASA Astrophysics Data System (ADS)

    Carbonari, A. W.; Cavalcante, F. H. M.; Junqueira, A. C.; Leite, D. M. T.; Saxena, R. N.; Mestnik-Filho, J.

    The local magnetic interaction at the transition metal sites in RMO3 (R=La, Nd; M=Cr, Fe) compounds has been investigated by perturbed angular correlation (PAC) technique using 181Hf→181Ta probe nuclei. The present measurements cover a temperature range from 10 K to 1000 K. Above the respective Neel temperature, each compound shows a unique quadrupolar frequency that decreases linearly with temperature. These interactions were assigned to the radioactive probe substituting Cr or Fe sites. Below TN, a combined electric plus magnetic hyperfine interaction was observed. The magnetic interaction revealed that the super transferred hyperfine fields on 181Ta at the Cr sites in (La,Nd)CrO3 extrapolated to 0 K, are much smaller than the corresponding values at Fe sites in (La,Nd)FeO3. This difference was attributed to different distribution of d electrons in Cr3+ (3d3) and Fe3+ (3d5) ions in each compound. As the fields for Nd compounds are smaller than those for La compounds, the role of rare-earth ions in the magnetism of these oxides is also discussed.

  6. Investigation of hyperfine interactions in RMO 3 (R = La, Nd; M = Cr, Fe) antiferromagnetic perovskite oxides using PAC spectroscopy

    NASA Astrophysics Data System (ADS)

    Carbonari, A. W.; Cavalcante, F. H. M.; Junqueira, A. C.; Leite, D. M. T.; Saxena, R. N.; Mestnik-Filho, J.

    2007-07-01

    The local magnetic interaction at the transition metal sites in RMO3 (R = La, Nd; M = Cr, Fe) compounds has been investigated by perturbed angular correlation (PAC) technique using 181Hf→181Ta probe nuclei. The present measurements cover a temperature range from 10 K to 1000 K. Above the respective Néel temperature, each compound shows a unique quadrupolar frequency that decreases linearly with temperature. These interactions were assigned to the radioactive probe substituting Cr or Fe sites. Below T N , a combined electric plus magnetic hyperfine interaction was observed. The magnetic interaction revealed that the super transferred hyperfine fields on 181Ta at the Cr sites in (La,Nd)CrO3 extrapolated to 0 K, are much smaller than the corresponding values at Fe sites in (La,Nd)FeO3. This difference was attributed to different distribution of d electrons in Cr3 + (3d3) and Fe3 + (3d5) ions in each compound. As the fields for Nd compounds are smaller than those for La compounds, the role of rare-earth ions in the magnetism of these oxides is also discussed.

  7. Spheroidization of glass powders for glass ionomer cements.

    PubMed

    Gu, Y W; Yap, A U J; Cheang, P; Kumar, R

    2004-08-01

    Commercial angular glass powders were spheroidized using both the flame spraying and inductively coupled radio frequency plasma spraying techniques. Spherical powders with different particle size distributions were obtained after spheroidization. The effects of spherical glass powders on the mechanical properties of glass ionomer cements (GICs) were investigated. Results showed that the particle size distribution of the glass powders had a significant influence on the mechanical properties of GICs. Powders with a bimodal particle size distribution ensured a high packing density of glass ionomer cements, giving relatively high mechanical properties of GICs. GICs prepared by flame-spheroidized powders showed low strength values due to the loss of fine particles during flame spraying, leading to a low packing density and few metal ions reacting with polyacrylic acid to form cross-linking. GICs prepared by the nano-sized powders showed low strength because of the low bulk density of the nano-sized powders and hence low powder/liquid ratio of GICs.

  8. Multispectral plasmon-induced transparency in hyperfine terahertz meta-molecules

    NASA Astrophysics Data System (ADS)

    Yang, Shengyan; Xia, Xiaoxiang; Liu, Zhe; Yiwen, E.; Wang, Yujin; Tang, Chengchun; Li, Wuxia; Li, Junjie; Wang, Li; Gu, Changzhi

    2016-11-01

    We experimentally and theoretically demonstrated an approach to achieve multispectral plasmon-induced transparency (PIT) by utilizing meta-molecules that consist of hyperfine terahertz meta-atoms. The feature size of such hyperfine meta-atoms is 400 nm, which is one order smaller than that of normal terahertz metamaterials. The hyperfine meta-atoms with close eigenfrequencies and narrow resonant responses introduce different metastable energy levels, which makes the multispectral PIT possible. In the triple PIT system, the slow light effect is further confirmed as the effective group delay at three transmission windows can reach 7.3 ps, 7.4 ps and 4.5 ps, respectively. Precisely controllable manipulation of the PIT peaks in such hyperfine meta-molecules was also proven. The new hyperfine planar design is not only suitable for high-integration applications, but also exhibits significant slow light effect, which has great potential in advanced multichannel optical information processing. Moreover, it reveals the possibility to construct hyperfine N-level energy systems by artificial hyperfine plasmonic structures, which brings a significant prospect for applications on miniaturized plasmonic devices.

  9. Graft polymerization of acrylic acid and methacrylic acid onto poly(vinylidene fluoride) powder in presence of metallic salt and sulfuric acid

    NASA Astrophysics Data System (ADS)

    Deng, Bo; Yu, Yang; Zhang, Bowu; Yang, Xuanxuan; Li, Linfan; Yu, Ming; Li, Jingye

    2011-02-01

    Poly(vinylidene fluoride) (PVDF) powder was grafted with acrylic acid (AAc) or methacrylic acid (MAA) by the pre-irradiation induced graft polymerization technique. The presence of graft chains was proven by FT-IR spectroscopy. The degree of grafting (DG) was calculated by the acid-base back titration method. The synergistic effect of acid and Mohr's salt on the grafting kinetics was examined. The results indicated that adding sulfuric acid and Mohr's salt simultaneously in AAc or MAA solutions led to a strong enhancement in the degree of grafting. The grafted PVDF powder was cast into microfiltration (MF) membranes using the phase inversion method and some properties of the obtained MF membranes were characterized.

  10. Hyperfine Structure in Rotational Spectra of Deuterated Molecules: the Hds and ND_3 Case Studies

    NASA Astrophysics Data System (ADS)

    Cazzoli, Gabriele; Puzzarini, Cristina

    2016-06-01

    The determination of hyperfine parameters (quadrupole-coupling, spin-spin coupling, and spin-rotation constants) is one of the aims of high-resolution rotational spectroscopy. These parameters are relevant not only from a spectroscopic point of view, but also from a physical and/or chemical viewpoint, as they might provide detailed information on the chemical bond, structure, etc. In addition, the hyperfine structure of rotational spectra is so characteristic that its analysis may help in assigning the spectra of unknown species. In astronomical observations, hyperfine structures of rotational spectra would allow us to gain information on column densities and kinematics, and the omission of taking them into account can lead to a misinterpretation of the line width of the molecular emission lines. Nevertheless, the experimental determination of hyperfine constants can be a challenge not only for actual problems in resolving hyperfine structures themselves, but also due to the lack of reliable estimates or the complexity of the hyperfine structure itself. It is thus important to be able to rely on good predictions for such parameters, which can nowadays be provided by quantum-chemical calculations. In fact, the fruitful interplay of experiment and theory will be demonstrated by means of two study cases: the hypefine structure of the rotational spectra of HDS and ND_3. From an experimental point of view, the Lamb-dip technique has been employed to improve the resolving power in themillimeter- and submillimeterwave frequency range by at least one order of magnitude, thus making it possible to perform sub-Doppler measurements as well as to resolve narrow hyperfine structures. Concerning theory, it will be demonstrated that high-level calculations can provide quantitative estimates for hyperfine parameters (quadrupole coupling constants, spin-rotation tensors, spin-spin couplings, etc.) and shown how theoretical predictions are often essential for a detailed analysis of

  11. Nonaqueous solution synthesis process for preparing oxide powders of lead zirconate titanate and related materials

    DOEpatents

    Voigt, J.A.; Sipola, D.L.; Tuttle, B.A.; Anderson, M.T.

    1999-06-01

    A process is disclosed for producing powders of perovskite-type compounds which comprises mixing a metal alkoxide solution with a lead acetate solution to form a homogeneous, clear metal solution, adding an oxalic acid/n-propanol solution to this metal solution to form an easily filterable, free-flowing precursor powder and then calcining this powder. This process provides fine perovskite-phase powders with ferroelectric properties which are particularly useful in a variety of electronic applications. 4 figs.

  12. Nonaqueous solution synthesis process for preparing oxide powders of lead zirconate titanate and related materials

    DOEpatents

    Voigt, James A.; Sipola, Diana L.; Tuttle, Bruce A.; Anderson, Mark T.

    1999-01-01

    A process for producing powders of perovskite-type compounds which comprises mixing a metal alkoxide solution with a lead acetate solution to form a homogeneous, clear metal solution, adding an oxalic acid/n-propanol solution to this metal solution to form an easily filterable, free-flowing precursor powder and then calcining this powder. This process provides fine perovskite-phase powders with ferroelectric properties which are particularly useful in a variety of electronic applications.

  13. Hyperfine structure in the configuration 4 f 136 s7 s of Tm I

    NASA Astrophysics Data System (ADS)

    Kronfeldt, H.-D.; Kröger, S.

    1995-12-01

    Doppler-free saturation absorption spectroscopy was applied on an atomic thulium vapour in a see-through hollow cathode for the determination of precise values for the magnetic dipole hyperfine structure constants A of 6 levels of the configuration 4 f 13 6 s7 s. A parametric analysis of the hyperfine structure has been performed, using wave-functions from a fine structure calculation, which leads to one-electron hyperfine structure parameters a {4/f 01}=-500(6) MHz, a {6/s 10}=-5058(47) MHz, and a {7/s 10}=-1012 MHz.

  14. VizieR Online Data Catalog: Spectroscopy of N2D+ hyperfine structur

    NASA Astrophysics Data System (ADS)

    Dore, L.; Caselli, P.; Beninati, S.; Bourke, T.; Myers, P. C.; Cazzoli, G.

    2003-11-01

    The analysis of the fully resolved Nitrogen hyperfine structure of N2D+ (1-0) observed toward L183, together with laboratory measurements of the same molecular transition, allowed an accurate determination of the hyperfine constants of both outer and inner Nitrogen. In addition, accurate rotational and centrifugal distortion constants were derived from submillimeter-wave laboratory measurements. The Tables list calculated hyperfine frequencies of J+1<--J transitions, with J in the range 1-11, which occur in the millimeter- and submillimeter-wave region. (5 data files).

  15. High-precision optical measurement of the 2S hyperfine interval in atomic hydrogen.

    PubMed

    Kolachevsky, N; Fischer, M; Karshenboim, S G; Hänsch, T W

    2004-01-23

    We have applied an optical method to the measurement of the 2S hyperfine interval in atomic hydrogen. The interval has been measured by means of two-photon spectroscopy of the 1S-2S transition on a hydrogen atomic beam shielded from external magnetic fields. The measured value of the 2S hyperfine interval is equal to 177 556 860(16) Hz and represents the most precise measurement of this interval to date. The theoretical evaluation of the specific combination of 1S and 2S hyperfine intervals D21 is in fair agreement (within 1.4 sigma) with the value for D21 deduced from our measurement.

  16. Resin-Powder Dispenser

    NASA Technical Reports Server (NTRS)

    Standfield, Clarence E.

    1994-01-01

    Resin-powder dispenser used at NASA's Langley Research Center for processing of composite-material prepregs. Dispenser evenly distributes powder (resin polymer and other matrix materials in powder form) onto wet uncured prepregs. Provides versatility in distribution of solid resin in prepreg operation. Used wherever there is requirement for even, continuous distribution of small amount of powder.

  17. Preparation of titanium diboride powder

    DOEpatents

    Brynestad, Jorulf; Bamberger, Carlos E.

    1985-01-01

    Finely-divided titanium diboride or zirconium diboride powders are formed by reacting gaseous boron trichloride with a material selected from the group consisting of titanium powder, zirconium powder, titanium dichloride powder, titanium trichloride powder, and gaseous titanium trichloride.

  18. Low temperature behavior of hyperfine fields in amorphous and nanocrystalline FeMoCuB

    SciTech Connect

    Kohout, Jaroslav; Křišt'an, Petr; Kubániová, Denisa; Kmječ, Tomáš; Závěta, Karel; Štepánková, Helena; Lančok, Adriana; Sklenka, L'ubomír; Matúš, Peter; and others

    2015-05-07

    Low temperature (4.2 K) magnetic behavior of Fe{sub 76}Mo{sub 8}Cu{sub 1}B{sub 15} metallic glass was studied by {sup 57}Fe Mössbauer spectrometry (MS) and {sup 57}Fe NMR. Distributions of hyperfine magnetic fields P(B) were determined for as-quenched and annealed (nanocrystalline) samples with relative fraction of the grains about 43%. P(B) distributions were derived for both the amorphous matrix and nanocrystalline grains. NMR of alloys with natural and {sup 57}Fe enriched Fe enabled to assess the contribution of {sup 11}B to the total NMR signal. P(B) distribution of the as-quenched alloy derived from MS matches reasonably well the one from NMR of the enriched sample. NMR signal from the sample with natural Fe exhibits contributions from {sup 11}B nuclei. The principal NMR lines of the annealed alloys at 47 MHz correspond to bcc Fe nanocrystals. Small asymmetry of the lines towards higher frequencies might be an indication of possible impurity atoms in the bcc structure. The observed differences between natural and enriched samples are attributed to higher sensitivity in the latter. Positions of the lines attributed to bcc Fe nanocrystals obtained from MS and NMR are in perfect agreement.

  19. Single-crystal and humidity-controlled powder diffraction study of the breathing effect in a metal-organic framework upon water adsorption/desorption.

    PubMed

    Aríñez-Soriano, Javier; Albalad, Jorge; Vila-Parrondo, Christian; Pérez-Carvajal, Javier; Rodríguez-Hermida, Sabina; Cabeza, Aurelio; Juanhuix, Jordi; Imaz, Inhar; Maspoch, Daniel

    2016-05-26

    Herein we report a study on water adsorption/desorption-triggered single-crystal to single-crystal transformations in a MOF, by single-crystal and humidity-controlled powder X-ray diffraction and water-sorption measurements. We identified a gate-opening effect at a relative humidity of 85% upon water adsorption, and a gate-closure effect at a relative humidity of 55 to 77% upon water desorption. This reversible breathing effect between the "open" and the "closed" structures of the MOF involves the cleavage and formation of several coordination bonds.

  20. Synthesis and ab initio X-ray powder diffraction structure of the new alkali and alkali earth metal borate NaCa(BO3).

    PubMed

    Wu, L; Chen, X L; Li, X Z; Dai, L; Xu, Y P; Zhao, M

    2005-03-01

    A sodium calcium borate, NaCaBO3, has been synthesized by the solid-state reaction method and the structure solved from X-ray powder diffraction data. The compound crystallizes in space group Pmmn and has a desired structure type containing isolated planar BO3(3-) anions. Mixed occupancy is found to exist in the Ca site, with partial replacement by Na. One Ca/Na mixed atom and one Na atom are at sites with mm2 symmetry, and a second Ca/Na mixed atom, an Na atom, two B and two O atoms are on mirror planes.

  1. Polarized 3He− ion source with hyperfine state selection

    SciTech Connect

    Dudnikov, V.; Morozov, Vasiliy; Dudnikov, A.

    2015-04-01

    High beam polarization is essential to the scientific productivity of a collider. Polarized 3He ions are an essential part of the nuclear physics programs at existing and future ion-ion and electron-ion colliders such as BNL's RHIC and eRHIC and JLab's ELIC. Ion sources with performance exceeding that achieved today are a key requirement for the development of these next generation high-luminosity high-polarization colliders. The development of high-intensity high-brightness arc-discharge ion sources at the Budker Institute of Nuclear Physics (BINP) has opened up an opportunity for realization of a new type of a polarized 3He− ion source. This report discusses a polarized 3He− ion source based on the large difference of extra-electron auto-detachment lifetimes of the different 3He− ion hyperfine states. The highest momentum state of 5/2 has the largest lifetime of τ ∼ 350 µs while the lower momentum states have lifetimes of τ ~ 10 µs. By producing 3He− ion beam composed of only the |5/2, ±5/2> hyperfine states and then quenching one of the states by an RF resonant field, 3He− beam polarization of 90% can be achieved. Such a method of polarized 3He− production has been considered before; however, due to low intensities of the He+ ion sources existing at that time, it was not possible to produce any interesting intensity of polarized 3He− ions. The high-brightness arc-discharge ion source developed at BINP can produce a high-brightness 3He+ beam with an intensity of up to 2 A allowing for selection of up to ∼1-4 mA of 3He− ions with ∼90% polarization. The high gas efficiency of an arc-discharge source is important due to the high cost of 3He gas. Some features of such a PIS as well as prototype designs are considered. An integrated 3He− ion source design providing high beam polarization could be prepared using existing BNL equipment with incorporation of new designs of the 1) arc discharge plasma generator, 2) extraction system, 3) charge

  2. Role of zero-point vibrational corrections to carbon hyperfine coupling constants in organic π radicals

    NASA Astrophysics Data System (ADS)

    Chen, X.; Rinkevicius, Z.; Ruud, K.; Ågren, H.

    2013-02-01

    By analyzing a set of organic π radicals, we demonstrate that zero-point vibrational corrections give significant contributions to carbon hyperfine coupling constants, in one case even inducing a sign reversal for the coupling constant. We discuss the implications of these findings for the computational analysis of electron paramagnetic spectra based on hyperfine coupling constants evaluated at the equilibrium geometry of radicals. In particular, we note that a dynamical description that involves the nuclear motion is in many cases necessary in order to achieve a semi-quantitatively predictive theory for carbon hyperfine coupling constants. In addition, we discuss the implications of the strong dependence of the carbon hyperfine coupling constants on the zero-point vibrational corrections for the selection of exchange-correlation functionals in density functional theory studies of these constants.

  3. Theory of the hyperfine structure of the S states of muonic tritium

    NASA Astrophysics Data System (ADS)

    Martynenko, A. P.; Martynenko, F. A.; Faustov, R. N.

    2017-06-01

    The hyperfine structure of the energy spectrum of the S levels of muonic tritium has been calculated using the quasi-potential method in quantum electrodynamics (QED). The α5- and α6-order effects on the polarization of vacuum, the structure and recoil of the nucleus, and relativistic corrections have been taken into account. The obtained numerical values of hyperfine splittings of 239.819 meV (1S state) and 29.965 meV (2 S state) can be treated as reliable estimates for comparing with future experimental data of the CREMA collaboration, and hyperfine structure interval Δ12 = 8Δ E hfs (2 S)-Δ E hfs (1 S) =-0.100 meV can be used for verifying the QED predictions. The resultant precision values of hyperfine splitting are also important for calculating the rates of formation of (μ dt) mesomolecules in muonic catalysis reactions.

  4. Hyperfine contribution to spin-exchange frequency shifts in the hydrogen maser

    SciTech Connect

    Verhaar, B.J.; Koelman, J.M.V.A.; Stoof, H.T.C.; Luiten, O.J.; Crampton, S.B.

    1987-05-01

    We have rigorously included hyperfine interactions during electron-spin-exchange collisions between ground-state hydrogen atoms and find additional frequency shifts which are significant for low-temperature atomic hydrogen maser oscillators.

  5. Relativistic Calculating the Spectral Lines Hyperfine Structure Parameters for Heavy Ions

    SciTech Connect

    Khetselius, O. Yu.

    2008-10-22

    The energies and constants of the hyperfine structure, derivatives of the one-electron characteristics on nuclear radius, nuclear electric quadrupole, magnetic dipole moments for some Li-like multicharged ions are calculated.

  6. Nonequilibrium nuclear polarization and induced hyperfine and dipolar magnetic fields in semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Ţifrea, Ionel; Flatté, Michael E.

    2011-10-01

    We investigate the dynamic nuclear polarization (DNP) caused by hyperfine coupling between nonequilibrium electronic spins and nuclear spins in semiconductor nanostructures. We derive the time and position dependence of the resulting hyperfine and dipolar magnetic fields. In GaAs quantum wells the induced nuclear spin polarization greatly exceeds the polarization of the electronic system that causes the DNP. The induced magnetic fields vary between tens of tesla for the electronic hyperfine field acting on nuclei, to hundreds of gauss for the nuclear hyperfine field acting on electrons, to a few gauss for the induced nuclear dipolar fields that act on both nuclei and electrons. The field strengths should be measurable via optically induced nuclear magnetic resonance or time-resolved Faraday rotation experiments. We discuss the implications of our calculations for low-dimensional semiconductor nanostructures.

  7. Hyperfine-changing collisions in an optically trapped gas of ultracold cesium and lithium

    NASA Astrophysics Data System (ADS)

    Mudrich, Marcel; Kraft, Stephan; Lange, Jörg; Mosk, Allard; Weidemüller, Matthias; Tiesinga, Eite

    2004-12-01

    We present measurements of the rate of hyperfine-state-changing collisions of unpolarized cesium (Cs133) and lithium (Li7) atoms confined in an optical dipole trap in the temperature range between 30 and 130μK . To infer rate coefficients from trap-loss data, we derive a simple thermodynamic model describing relaxation heating as a consequence of atom loss in a conservative potential. For hyperfine-changing Cs-Cs collisions, the experimental results are compared with theoretical predictions and excellent agreement is found. Hyperfine-state-changing collisions in a mixture of lithium and cesium atoms are observed and rate coefficients are inferred for all combinations of hyperfine ground-state asymptotes.

  8. Relativistically corrected hyperfine structure constants calculated with the regular approximation applied to correlation corrected ab initio theory

    NASA Astrophysics Data System (ADS)

    Filatov, Michael; Cremer, Dieter

    2004-09-01

    The infinite-order regular approximation (IORA) and IORA with modified metric (IORAmm) is used to develop an algorithm for calculating relativistically corrected isotropic hyperfine structure (HFS) constants. The new method is applied to the calculation of alkali atoms Li-Fr, coinage metal atoms Cu, Ag, and Au, the Hg+ radical ion, and the mercury containing radicals HgH, HgCH3, HgCN, and HgF. By stepwise improvement of the level of theory from Hartree-Fock to second-order Møller-Plesset theory and to quadratic configuration interaction theory with single and double excitations, isotropic HFS constants of high accuracy were obtained for atoms and for molecular radicals. The importance of relativistic corrections is demonstrated.

  9. Direct measurement of excited-state dipole matrix elements using electromagnetically induced transparency in the hyperfine Paschen-Back regime

    NASA Astrophysics Data System (ADS)

    Whiting, Daniel J.; Keaveney, James; Adams, Charles S.; Hughes, Ifan G.

    2016-04-01

    Applying large magnetic fields to gain access to the hyperfine Paschen-Back regime can isolate three-level systems in a hot alkali metal vapors, thereby simplifying usually complex atom-light interactions. We use this method to make the first direct measurement of the |<5 P ||e r ||5 D >| matrix element in 87Rb. An analytic model with only three levels accurately models the experimental electromagnetically induced transparency spectra and extracted Rabi frequencies are used to determine the dipole matrix element. We measure |<5 P3 /2||e r ||5 D5 /2>| =(2.290 ±0 .002stat±0 .04syst) e a0 , which is in excellent agreement with the theoretical calculations of Safronova, Williams, and Clark [Phys. Rev. A 69, 022509 (2004), 10.1103/PhysRevA.69.022509].

  10. Metallic powder-bed based 3D printing of cellular scaffolds for orthopaedic implants: A state-of-the-art review on manufacturing, topological design, mechanical properties and biocompatibility.

    PubMed

    Tan, X P; Tan, Y J; Chow, C S L; Tor, S B; Yeong, W Y

    2017-07-01

    Metallic cellular scaffold is one of the best choices for orthopaedic implants as a replacement of human body parts, which could improve life quality and increase longevity for the people needed. Unlike conventional methods of making cellular scaffolds, three-dimensional (3D) printing or additive manufacturing opens up new possibilities to fabricate those customisable intricate designs with highly interconnected pores. In the past decade, metallic powder-bed based 3D printing methods emerged and the techniques are becoming increasingly mature recently, where selective laser melting (SLM) and selective electron beam melting (SEBM) are the two representatives. Due to the advantages of good dimensional accuracy, high build resolution, clean build environment, saving materials, high customisability, etc., SLM and SEBM show huge potential in direct customisable manufacturing of metallic cellular scaffolds for orthopaedic implants. Ti-6Al-4V to date is still considered to be the optimal materials for producing orthopaedic implants due to its best combination of biocompatibility, corrosion resistance and mechanical properties. This paper presents a state-of-the-art overview mainly on manufacturing, topological design, mechanical properties and biocompatibility of cellular Ti-6Al-4V scaffolds via SLM and SEBM methods. Current manufacturing limitations, topological shortcomings, uncertainty of biocompatible test were sufficiently discussed herein. Future perspectives and recommendations were given at the end. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Hyperfine interactions in titanates: Study of orbital ordering and local magnetic properties

    SciTech Connect

    Agzamova, P. A. Leskova, Yu. V.; Nikiforov, A. E.

    2013-05-15

    Hyperfine magnetic fields induced on the nuclei of nonmagnetic ions {sup 139}La and {sup 89}Y in LaTiO{sub 3} and YTiO{sub 3}, respectively, have been microscopically calculated. The dependence of the hyperfine fields on the orbital and magnetic structures of the compounds under study has been analyzed. The comparative analysis of the calculated and known experimental data confirms the existence of the static orbital structure in lanthanum and yttrium titanates.

  12. Calculation of the hyperfine structure of the superheavy elements Z=119 and Z=120{sup +}

    SciTech Connect

    Dinh, T. H.; Dzuba, V. A.; Flambaum, V. V.

    2009-10-15

    The hyperfine-structure constants of the lowest s and p{sub 1/2} states of superheavy elements Z=119 and Z=120{sup +} are calculated using ab initio approach. Core polarization and dominating correlation effects are included to all orders. Breit and quantum electrodynamic effects are also considered. Similar calculations for Cs, Fr, Ba{sup +}, and Ra{sup +} are used to control the accuracy. The dependence of the hyperfine-structure constants on the nuclear radius is discussed.

  13. Hyperfine structure of the S- and P-wave states of muonic deuterium

    SciTech Connect

    Martynenko, A. P. Martynenko, G. A.; Sorokin, V. V.; Faustov, R. N.

    2016-03-15

    Corrections of order α{sup 5} and α{sup 6} to the hyperfine structure of the S- and P-wave states of muonic deuteriumwere calculated on the basis of the quasipotential approach in quantum electrodynamics. Relativistic corrections, vacuum-polarization and deuteron-structure effects, and recoil corrections were taken into account in this calculation. The resulting hyperfine-splitting values can be used in a comparison with experimental data obtained by the CREMA Collaboration.

  14. Molecular environment and temperature dependence of hyperfine interactions in sugar crystal radicals from first principles.

    PubMed

    Declerck, R; Pauwels, E; Speybroeck, V Van; Waroquier, M

    2008-02-07

    The effect of the molecular environment and the temperature dependence of hyperfine parameters in first principles calculations in alpha-d-glucose and beta-d-fructose crystal radicals have been investigated. More specifically, we show how static (0 K) cluster in vacuo hyperfine calculations, commonly used today, deviate from more advanced molecular dynamics calculations at the experimental temperature using periodic boundary conditions. From the latter approach, more useful information can be extracted, allowing us to ascertain the validity of proposed molecular models.

  15. Powder metallurgy in aerospace research: A survey

    NASA Technical Reports Server (NTRS)

    Blakeslee, H. W.

    1971-01-01

    The various techniques by which powders can be produced, as pure metals or as alloys, are discussed; the methods by which these powders can be formed into the final parts are explained as well as further processing that may be necessary to meet specific requirements. The NASA developments are detailed, and references are provided for those who wish to obtain further information characteristic of any methodology.

  16. Dynamic consolidation of metastable nanocrystalline powders

    SciTech Connect

    Korth, G.E.; Williamson, R.L.

    1995-10-01

    Nanocrystalline metal powders synthesized by mechanical alloying in a ball mill resulted in micron-sized powder particles with a nanosized (5 to 25 nm) substructure. Conventional consolidation methods resulted in considerable coarsening of the metastable nanometer crystallites, but dynamic consolidation of these powders using explosive techniques produced fully dense monoliths while retaining the 5- to 25-nm substructure. Numerical modeling used to guide the experimental phase, revealed that the compression wave necessary for suitable consolidation was of order of 10 GPa for a few tenths of a microsecond. The consolidation process is described, and the retention of the metastable nanostructure is illustrated.

  17. Magnetic hyperfine interactions on Cd sites of the rare-earth cadmium compounds R Cd (R =Ce , Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er)

    NASA Astrophysics Data System (ADS)

    Cavalcante, F. H. M.; Leite Neto, O. F. L. S.; Saitovitch, H.; Cavalcante, J. T. P. D.; Carbonari, A. W.; Saxena, R. N.; Bosch-Santos, B.; Pereira, L. F. D.; Mestnik-Filho, J.; Forker, M.

    2016-08-01

    This paper reports the investigation of the magnetic hyperfine field Bh f in a series of rare-earth (R ) cadmium intermetallic compounds R Cd and GdCd2 measured by perturbed angular correlation (PAC) spectroscopy using 111In/111Cd as probe nuclei at Cd sites as well as first-principles calculations of Bh f at Cd sites in the studied compounds. Vapor-solid state reaction of R metals with Cd vapor and the 111In radioisotope was found to be an appropriate route of doping rare-earth cadmium compounds with the PAC probe 111In/111Cd. The observation that the hyperfine parameters depend on details of the sample preparation provides information on the phase preference of diffusing 111In in the rare-earth cadmium phase system. The 111Cd hyperfine field has been determined in the compounds R Cd for the R constituents Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er, in several cases as a function of temperature. For most R constituents, the temperature dependence Bh f(T ) of 111Cd:R Cd is consistent with ferromagnetic order of the compound. DyCd, however, presents a remarkable anomaly: a finite magnetic hyperfine field is observed only in the temperature interval 35 K ≤ T ≤ 80 K which indicates a transition from ferromagnetic order to a spin arrangement where all 4 f -induced contributions to the magnetic hyperfine field at the Cd site cancel. First-principles calculation results for DyCd show that the (π , π , 0) antiferromagnetic configuration is energetically more favorable than the ferromagnetic. The approach used in the calculations to simulate the R Cd system successfully reproduces the experimental values of Bh f at Cd sites and shows that the main contribution to Bh f comes from the valence electron polarization. The de Gennes plot of the hyperfine field Bh f of 111Cd:R Cd vs the 4 f -spin projection (g -1 )J reflects a decrease of the strength of indirect 4 f -4 f exchange across the R series. Possible mechanisms are discussed and the experimental results indicate that

  18. New Precise Measurement of the Hyperfine Splitting of Positronium

    SciTech Connect

    Ishida, A.

    2015-09-15

    Positronium (Ps) is an ideal system for precision test of bound state quantum electrodynamics. The hyperfine splitting (HFS) of the ground state of Ps, which is one of the most precisely tested quantity, has a large discrepancy of 16 ppm (4.5 σ) between previous experiments and theoretical calculation up to O(α{sup 3}lnα{sup −1}) and part of O(α{sup 3}) corrections. A new experiment which reduces possible systematic uncertainties of Ps thermalization effect and nonuniformity of magnetic field was performed. It revealed that the Ps thermalization effect was as large as 10 ± 2 ppm. Treating the thermalization effect correctly, a new result of 203.3942 ± 0.0016(stat., 8.0 ppm) ± 0.0013(sys., 6.4 ppm) GHz was obtained. This result is consistent with theory within 1.1 σ, whereas it disfavors the previous experimental result by 2.6 σ. It shows that the Ps thermalization effect is crucial for precision measurement of HFS. Future prospects for improved precision are briefly discussed.

  19. ISOTROPIC INELASTIC COLLISIONS IN A MULTITERM ATOM WITH HYPERFINE STRUCTURE

    SciTech Connect

    Belluzzi, Luca; Landi Degl’Innocenti, Egidio; Bueno, Javier Trujillo

    2015-10-10

    A correct modeling of the scattering polarization profiles observed in some spectral lines of diagnostic interest, the sodium doublet being one of the most important examples, requires taking hyperfine structure (HFS) and quantum interference between different J-levels into account. An atomic model suitable for taking these physical ingredients into account is the so-called multiterm atom with HFS. In this work, we introduce and study the transfer and relaxation rates due to isotropic inelastic collisions with electrons, which enter the statistical equilibrium equations (SEE) for the atomic density matrix of this atomic model. Under the hypothesis that the electron–atom interaction is described by a dipolar operator, we provide useful relations between the rates describing the transfer and relaxation of quantum interference between different levels (whose numerical values are in most cases unknown) and the usual rates for the atomic level populations, for which experimental data and/or approximate theoretical expressions are generally available. For the particular case of a two-term atom with HFS, we present an analytical solution of the SEE for the spherical statistical tensors of the upper term, including both radiative and collisional processes, and we derive the expression of the emission coefficient in the four Stokes parameters. Finally, an illustrative application to the Na i D{sub 1} and D{sub 2} lines is presented.

  20. Hyperfine anomalies of HCN in cold dark clouds

    SciTech Connect

    Walmsley, C.M.; Churchwell, E.; Nash, A.; Fitzpatrick, E.

    1982-07-15

    We report observations of the J = 1..-->..0 line of HCN measured toward six positions in nearby low-temperature dark clouds. The measured relative intensities of the hyperfine components of the J = 1..-->..0 line are anomalous in that the F = 0..-->..1 transition is stronger than would be expected if all three components (F = 2..-->..1, F = 1..-->..1, F = 0..-->..1) had equal excitation temperatures. Differences of approximately 20% in the populations per sublevel of J = 1 could account for the observations. The results are in contrast to the situation observed in warmer molecular clouds associated with H II regions where the F = 1..-->..1 line is anomalously weak. The apparent overpopulation of J = 1, F = 0 in dark clouds may be related to the phenomenon observed in the J = 1..-->..0 transitions of HCO/sup +/ and HNC in the same objects where /sup 13/C substituted version of these species is found to be stronger than the /sup 12/C species.

  1. Theoretical study of the nitrogen atom hyperfine coupling constant

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    The nitrogen-atom isotropic hyperfine coupling constant A(iso) is studied as a function of improvements in both the one-particle and n-particle basis sets. The study underscores the importance of diffuse basis functions. For example, the (9s 5p) primitive set of Huzinaga (1965) augmented with an even-tempered diffuse s function yields values for A(iso) that are virtually identical to an energy-optimized (23s 12p) even-tempered set. The A(iso) constant is found to converge relatively quickly with increasing l quantum numbers: d, f, and g functions are estimated to contribute 2.5 + or - 0.2, 0.4 + or - 0.1, and 0.05 + or - 0.05 MHz, respectively. Full CI calibration calculations indicate that very high levels of correlation treatment are required for quantitative results. In addition, a strong coupling is observed between the one-particle and n-particle requirements. The best result, 10.4 MHz, is in excellent agreement with the accurate experimental value of 10.4509 MHz.

  2. Isotropic Inelastic Collisions in a Multiterm Atom with Hyperfine Structure

    NASA Astrophysics Data System (ADS)

    Belluzzi, Luca; Landi Degl'Innocenti, Egidio; Trujillo Bueno, Javier

    2015-10-01

    A correct modeling of the scattering polarization profiles observed in some spectral lines of diagnostic interest, the sodium doublet being one of the most important examples, requires taking hyperfine structure (HFS) and quantum interference between different J-levels into account. An atomic model suitable for taking these physical ingredients into account is the so-called multiterm atom with HFS. In this work, we introduce and study the transfer and relaxation rates due to isotropic inelastic collisions with electrons, which enter the statistical equilibrium equations (SEE) for the atomic density matrix of this atomic model. Under the hypothesis that the electron-atom interaction is described by a dipolar operator, we provide useful relations between the rates describing the transfer and relaxation of quantum interference between different levels (whose numerical values are in most cases unknown) and the usual rates for the atomic level populations, for which experimental data and/or approximate theoretical expressions are generally available. For the particular case of a two-term atom with HFS, we present an analytical solution of the SEE for the spherical statistical tensors of the upper term, including both radiative and collisional processes, and we derive the expression of the emission coefficient in the four Stokes parameters. Finally, an illustrative application to the Na i D1 and D2 lines is presented.

  3. Characterization and Control of Powder Properties for Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Strondl, A.; Lyckfeldt, O.; Brodin, H.; Ackelid, U.

    2015-03-01

    Powder characterization and handling in powder metallurgy are important issues and the required powder properties will vary between different component manufacturing processes. By understanding and controlling these, the final material properties for different applications can be improved and become more reliable. In this study, the metal powders used in additive manufacturing (AM) in terms of electron beam melting and selective laser melting have been investigated regarding particle size and shape using dynamic image analysis. In parallel, powder flow characteristics have been evaluated with a powder rheometer. Correlations within the results have been found between particle shape and powder flow characteristics that could explain certain effects of the powder processing in the AM processes. The impact, however, in the processing performance as well as in ultimate material properties was found to be limited.

  4. Fuel powder production from ductile uranium alloys.

    SciTech Connect

    Clark, C. R.

    1998-10-23

    Metallic uranium alloys are candidate materials for use as the fuel phase in very-high-density LEU dispersion fuels. These ductile alloys cannot be converted to powder form by the processes routinely used for oxides or intermetallics. Three methods of powder production from uranium alloys have been investigated within the US-RERTR program. These processes are grinding, cryogenic milling, and hydride-dehydride. In addition, a gas atomization process was investigated using gold as a surrogate for uranium. Grinding was found to be inefficient and introduced impurities into the fuel. Cryogenic milling of machine chips in a steel vial was found to have similar shortcomings. The hydride-dehydride process has historically been used to produce very fine powder that may not be suitable for fuel fabrication. Uranium is made to form its hydride by heating in a hydrogen atmosphere. Subsequent heating under vacuum drives off hydrogen gas and returns the hydride to a metallic state. The volume change on hydride formation results in a fine powder upon dehydriding. The effects of alloying elements, partial hydriding, and subsequent milling treatments on particle size distribution are being explored. Inert gas atomization is used on an industrial scale to produce metal powder. Current designs are not suitable for use with uranium. A system was specifically designed for uranium atomization. A prototype was built and tested using gold as a surrogate for uranium. The system operates efficiently and can produce powder in a variety of size ranges by changing the atomization nozzle.

  5. Low-Flow-Rate Dry-Powder Feeder

    NASA Technical Reports Server (NTRS)

    Ramsey, Keith E.

    1994-01-01

    Apparatus feeds small, precise flow of dry powder through laser beam of optical analyzer measuring patterns of light created by forward scattering (Fraunhofer diffraction) of laser beam from powder particles. From this optical measurement, statistical distribution of sizes of powder particles computed. Rates of flow optimized for measurement of particle-size distributions. Developed for analyzing particle-size distributions of solid-propellant powders. Also adapted to pharmaceutical industry, in manufacture of metal powder, and in other applications where particle-size distributions of materials used to control rates of chemical reactions and/or physical characteristics of processes.

  6. Low-Flow-Rate Dry-Powder Feeder

    NASA Technical Reports Server (NTRS)

    Ramsey, Keith E.

    1994-01-01

    Apparatus feeds small, precise flow of dry powder through laser beam of optical analyzer, measuring patterns of light created by forward scattering (Fraunhofer diffraction) of laser beam from powder particles. From measurement, statistical distribution of sizes of powder particles computed. Developed for analyzing particle-size distributions of solid-propellant powders. Also adapted to use in pharmaceutical industry, in manufacture of metal powder, and in other applications in which particle-size distributions of materials used to control rates of chemical reactions and/or physical characteristics of processes.

  7. Low-Flow-Rate Dry-Powder Feeder

    NASA Technical Reports Server (NTRS)

    Ramsey, Keith E.

    1994-01-01

    Apparatus feeds small, precise flow of dry powder through laser beam of optical analyzer measuring patterns of light created by forward scattering (Fraunhofer diffraction) of laser beam from powder particles. From this optical measurement, statistical distribution of sizes of powder particles computed. Rates of flow optimized for measurement of particle-size distributions. Developed for analyzing particle-size distributions of solid-propellant powders. Also adapted to pharmaceutical industry, in manufacture of metal powder, and in other applications where particle-size distributions of materials used to control rates of chemical reactions and/or physical characteristics of processes.

  8. Low-Flow-Rate Dry-Powder Feeder

    NASA Technical Reports Server (NTRS)

    Ramsey, Keith E.

    1994-01-01

    Apparatus feeds small, precise flow of dry powder through laser beam of optical analyzer, measuring patterns of light created by forward scattering (Fraunhofer diffraction) of laser beam from powder particles. From measurement, statistical distribution of sizes of powder particles computed. Developed for analyzing particle-size distributions of solid-propellant powders. Also adapted to use in pharmaceutical industry, in manufacture of metal powder, and in other applications in which particle-size distributions of materials used to control rates of chemical reactions and/or physical characteristics of processes.

  9. Structure–Reactivity Studies, Characterization, and Transformation of Intermediates by Lithium Chloride in the Direct Insertion of Alkyl and Aryl Iodides to Metallic Zinc Powder

    DOE PAGES

    Feng, Chao; Easter, Quinn T.; Blum, Suzanne A.

    2017-02-03

    Employment of fluorophore-tagged alkyl and aryl iodides permitted detection of persistent surface intermediates during their direct insertion to commercially available zinc powder. The sensitivity of this subensemble microscopy technique enabled structure–reactivity studies in the formation of intermediates that are present in quantities sufficiently low as to have been undetected previously by traditional ensemble analytical techniques. In these surface intermediates we transformed them using lithium chloride, which lead to the assignment of the mechanistic role of lithium chloride as changing the rate-determining step in the reaction by lowering the barrier for solubilization of these otherwise persistent surface organometallic intermediates. The temperaturemore » dependence/qualitative barrier of the direct insertion step was determined independently from the solubilization step and from the barrier for the overall reaction. Detection of these zinc surface intermediates at the single-molecule level, i.e., of individual surface organometallic species, has been achieved for the first time. Energy dispersive X-ray spectroscopy (EDS) measurements of the elemental composition of the surface of the zinc powder determined that lithium chloride does not clean the surface of the oxides; instead, pretreatment of the surface with TMSCl effects partial removal of surface oxides after the 2 h pretreatment time previously reported in the empirically optimized synthetic procedure. The current limitations of this microscopy approach are also determined and discussed with respect to the addition of solid reagents during in operando imaging. Characterization of the resulting soluble fluorophore-tagged organozinc/LiCl complex by 1H NMR spectroscopy, mass spectrometry, and fluorescence spectroscopy provided insight into its solution dynamics and chemical exchange processes.« less

  10. Co-administration of monoisoamyl dimercaptosuccinic acid and Moringa oleifera seed powder protects arsenic-induced oxidative stress and metal distribution in mice.

    PubMed

    Mishra, Deepshikha; Gupta, Richa; Pant, S C; Kushwah, Pramod; Satish, H T; Flora, S J S

    2009-02-01

    Arsenic contamination of groundwater in the West Bengal basin in India is unfolding as one of the worst natural geo-environmental disasters to date. Chelation therapy with chelating agents is considered to be the best known treatment against arsenic poisoning; however, they are compromised with certain serious drawbacks/side-effects. Efficacy of combined administration of Moringa oleifera (M. oleifera) (English: Drumstick tree) seed powder, a herbal extract, with a thiol chelator monoisoamyl DMSA (MiADMSA) post-arsenic exposure in mice was studied. Mice were exposed to 100 ppm arsenic in drinking water for 6 months, followed by 10-days treatment with M. oleifera seed powder (500 mg/kg, orally through gastric gavage, once daily), MiADMSA (50 mg/kg, intraperitoneally, once daily) either individually or in combination. Arsenic exposure caused significant decrease in blood glutathione, delta-aminolevulinic acid dehydratase (ALAD), accompanied by increased production of reactive oxygen species in blood and soft tissues. Significant inhibition of superoxide dismutase, catalase, and glutathione peroxidase activities in tissues (liver in particular) along with significant increase in thiobarbituric acid reactive substances and metallothionein levels in arsenic intoxicated mice was also noted. Combined administration of MiADMSA with M. oleifera proved better than all other treatments in the recovery of most of the above parameters accompanied by more pronounced depletion of arsenic. The results suggest that concomitant administration of M. oleifera during chelation treatment with MiADMSA might be a better treatment option than monotherapy with the thiol chelator in chronic arsenic toxicity.

  11. 29Si-NMR study of magnetic anisotropy and hyperfine interactions in the uranium-bsed ferromagnet UNiSi2

    SciTech Connect

    Sakai, Hironori; Baek, Seung H; Bauer, Eric D; Ronning, Filip; Thompson, J D

    2009-01-01

    UNiSi{sub 2} orders ferromagnetically below T{sub Curie} = 95 K. This material crystallizes in the orthorhombic CeNiSi{sub 2}-type structure. The uranium atoms form double-layers, which are stacked along the crystallographic b axis (the longest axis). From magnetization measurement the easy (hard) magnetization axis is found to be the c axis (b axis). {sup 29}Si-NMR measurements have been performed in the paramagnetic state. In UNiSi{sub 2}, two crystallographic Si sites exist with orthorhombic local symmetry. The Knight shifts on each Si site have been estimated from the spectra of random and oriented powders. The transferred hyperfine couplings have been also derived. It is found that the transferred hyperfine coupling constants on each Si site are nearly isotropic, and that their Knight shift anisotropy comes from that of the bulk susceptibility. The nuclear-spin lattice relaxation rate 1/T{sub 1} shows temperature-independent behavior, which indicates the existence of localized 5f electron.

  12. On the basis size problem in ultracold molecular scattering: Approximate hyperfine cross sections from hyperfine-free calculations

    NASA Astrophysics Data System (ADS)

    Gonzalez-Martinez, Maykel Leonardo

    2014-05-01

    Understanding (ultra)cold collisions is crucial to assess both the prospects of cooling techniques that rely on thermalization and trapping lifetimes. However, brute-force application of the coupled-channel method to many low-temperature scattering problems finds two main obstacles: (1) the need for large basis sets that are computationally intractable, and (2) the need to explore a multidimensional parametric space in order to tackle questions concerning real experimental conditions. The basis size problem arises because many interactions that are negligible at thermal temperatures become comparable to, or larger than, the collision energies involved. Taking all such terms into account significantly increases the size of the basis needed for convergence, with dramatic effects on the computing effort. Here, I discuss an approximate method to account for the effect of hyperfine interactions in ultracold molecular scattering. The method naturally resolves the effects discussed by Gonzalez-Martinez and Hutson in calculations on Mg+NH, and may be combined with those by Tscherbul et al. and Croft et al. to tackle problems which are computationally intractable to date. Depending on the system, the proposed method may lead to one to four orders-of-magnitude savings in computing times. This work was partially supported by EPSRC, and by FP7/2007-2013 under grant No. 330623.

  13. Precision powder feeder

    DOEpatents

    Schlienger, M. Eric; Schmale, David T.; Oliver, Michael S.

    2001-07-10

    A new class of precision powder feeders is disclosed. These feeders provide a precision flow of a wide range of powdered materials, while remaining robust against jamming or damage. These feeders can be precisely controlled by feedback mechanisms.

  14. Composite powder particles

    NASA Technical Reports Server (NTRS)

    Parker, Donald S. (Inventor); MacDowell, Louis G. (Inventor)

    2009-01-01

    A liquid coating composition including a coating vehicle and composite powder particles disposed within the coating vehicle. Each composite powder particle may include a magnesium component, a zinc component, and an indium component.

  15. Aluminum powder metallurgy processing

    SciTech Connect

    Flumerfelt, J.F.

    1999-02-12

    The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization, commercial inert gas atomization, and gas atomization reaction synthesis (GARS). A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a conventional consolidation process for fabricating aerospace components with aluminum powder and a proposed alternative. The consolidation procedures were compared by evaluating the consolidated microstructures and the corresponding mechanical properties. A low temperature solid state sintering experiment demonstrated that tap densified GARS aluminum powders can form sintering necks between contacting powder particles, unlike the total resistance to sintering of commercial air atomization aluminum powder.

  16. Measurement of hyperfine splitting and determination of hyperfine structure constant of cesium 8S1/2 state by using of ladder-type EIT

    NASA Astrophysics Data System (ADS)

    Wang, Jie; Wang, Junmin; Liu, Huifeng; Yang, Baodong; He, Jun

    2013-05-01

    The narrow electromagnetically-induced transparency (EIT) resonance peaks are observed with two low-power counter-propagating diode lasers in cesium (Cs) 6S1/2 - 6P1/2 - 8S1/2 ladder-type atomic system. To precisely determine the centers of resonance peaks, multiple background-free EIT signals are achieved using a novel scanning scheme in which the coupling laser driving Cs 6P1/2 - 8S1/2 transition is scanned and the probe laser driving Cs 6S1/2 - 6P1/2 is frequency locked. A temperature-stabilized fiber-pigtailed waveguide-type phase electro-optical modulator (EOM) and a stable confocal Fabry-Perot cavity are used as a precise frequency marker to measure the hyperfine splitting of Cs 8S1/2 state. The impact of the external magnetic field on the measurement is also investigated. Furthermore, the hyperfine structure constant (here it is the hyperfine magnetic dipole constant, A) of Cs 8S1/2 state is determined to be A = 219.06 MHz +/- 0.12 MHz based on the measured hyperfine splitting (Δhfs = 876.24 MHz +/- 0.50 MHz).

  17. Hydrothermal Synthesis and Characterization of a Metal-Organic Framework by Thermogravimetric Analysis, Powder X-Ray Diffraction, and Infrared Spectroscopy: An Integrative Inorganic Chemistry Experiment

    ERIC Educational Resources Information Center

    Crane, Johanna L.; Anderson, Kelly E.; Conway, Samantha G.

    2015-01-01

    This advanced undergraduate laboratory experiment involves the synthesis and characterization of a metal-organic framework with microporous channels that are held intact via hydrogen bonding of the coordinated water molecules. The hydrothermal synthesis of Co[subscript 3](BTC)[subscript 2]·12H[subscript 2]O (BTC = 1,3,5-benzene tricarboxylic acid)…

  18. Hydrothermal Synthesis and Characterization of a Metal-Organic Framework by Thermogravimetric Analysis, Powder X-Ray Diffraction, and Infrared Spectroscopy: An Integrative Inorganic Chemistry Experiment

    ERIC Educational Resources Information Center

    Crane, Johanna L.; Anderson, Kelly E.; Conway, Samantha G.

    2015-01-01

    This advanced undergraduate laboratory experiment involves the synthesis and characterization of a metal-organic framework with microporous channels that are held intact via hydrogen bonding of the coordinated water molecules. The hydrothermal synthesis of Co[subscript 3](BTC)[subscript 2]·12H[subscript 2]O (BTC = 1,3,5-benzene tricarboxylic acid)…

  19. Hyperfine Splittings in the Near-Infrared Spectrum of 14NH_3

    NASA Astrophysics Data System (ADS)

    Twagirayezu, Sylvestre; Sears, Trevor; Hall, Gregory

    2016-06-01

    Sub-Doppler, saturation dip, measurements of transitions in the ν_1 + ν_3 band of 14NH_3 have been made by frequency comb-referenced diode laser absorption spectroscopy. The observed spectra exhibit either resolved or partially-resolved hyperfine splittings that are primarily determined by the 14N quadrupole coupling in the molecule. Modeling of the line shapes based on the known hyperfine level structure of the ground state of the molecule shows that, in nearly all cases, the upper state level has splittings similar to that of the same rotational level in the ground state. The data provide accurate frequencies for the line positions and the observed hyperfine splittings can be used to make or confirm rotational assignments. Of all the measurements, one transition, pP(5,4)_a at 195 994.73457 GHz, exhibits hyperfine structure which does not conform to that expected based on extrapolation from the known lower state hyperfine splittings. Examination of the known vibration-rotation level structure near the upper state energy shows that there exists a near degeneracy between this level and one in the ν_1 + 2ν_4 manifold which is of the appropriate symmetry to be mixed by magnetic hyperfine terms that couple ortho- and para- modifications of the molecule. It is possible that the unusual hyperfine splittings are a consequence of ortho-paro mixing, which has been predicted, but not previously seen in ammonia and further experimental measurements to investigate this possibility are ongoing. Acknowledgments: Work at Brookhaven National Laboratory was carried out under Contract No. DE-SC0012704 with the U.S. Department of Energy, Office of Science, and supported by its Division of Chemical Sciences, Geosciences and Biosciences within the Office of Basic Energy Sciences.

  20. Semi-empirical predictions of even atomic energy levels and their hyperfine structure for the scandium atom

    SciTech Connect

    Dembczynski, J. . E-mail: Jerzy.Dembczynski@put.poznan.pl; Elantkowska, M.; Ruczkowski, J.; Stefanska, D.

    2007-01-15

    We report fine and hyperfine structure analysis of the system of even configurations of the Sc atom in a large multi-configuration basis. The complete energy scheme in the energy region up to about 50,000 cm{sup -1} has been established with the predicted values of the hyperfine cture constants A. The effects of the configuration interaction in the fine and hyperfine structure are discussed.

  1. Static and Dynamical Structural Investigations of Metal-Oxide Nanocrystals by Powder X-ray Diffraction: Colloidal Tungsten Oxide as a Case Study

    SciTech Connect

    Caliandro, Rocco; Sibillano, Teresa; Belviso, B. Danilo; Scarfiello, Riccardo; Dooryhee, Eric; Manca, Michele; Cozzoli, P. Davide

    2016-02-02

    In this study, we have developed a general X-ray powder diffraction (XPD) methodology for the simultaneous structural and compositional characterization of inorganic nanomaterials. The approach is validated on colloidal tungsten oxide nanocrystals (WO3-x NCs), as a model polymorphic nanoscale material system. Rod-shaped WO3-x NCs with different crystal structure and stoichiometry are comparatively investigated under an inert atmosphere and after prolonged air exposure. An initial structural model for the as-synthesized NCs is preliminarily identified by means of Rietveld analysis against several reference crystal phases, followed by atomic pair distribution function (PDF) refinement of the best-matching candidates (static analysis). Subtle stoichiometry deviations from the corresponding bulk standards are revealed. NCs exposed to air at room temperature are monitored by XPD measurements at scheduled time intervals. The static PDF analysis is complemented with an investigation into the evolution of the WO3-x NC structure, performed by applying the modulation enhanced diffraction technique to the whole time series of XPD profiles (dynamical analysis). Prolonged contact with ambient air is found to cause an appreciable increase in the static disorder of the O atoms in the WO3-x NC lattice, rather than a variation in stoichiometry. Finally, the time behavior of such structural change is identified on the basis of multivariate analysis.

  2. Static and Dynamical Structural Investigations of Metal-Oxide Nanocrystals by Powder X-ray Diffraction: Colloidal Tungsten Oxide as a Case Study

    DOE PAGES

    Caliandro, Rocco; Sibillano, Teresa; Belviso, B. Danilo; ...

    2016-02-02

    In this study, we have developed a general X-ray powder diffraction (XPD) methodology for the simultaneous structural and compositional characterization of inorganic nanomaterials. The approach is validated on colloidal tungsten oxide nanocrystals (WO3-x NCs), as a model polymorphic nanoscale material system. Rod-shaped WO3-x NCs with different crystal structure and stoichiometry are comparatively investigated under an inert atmosphere and after prolonged air exposure. An initial structural model for the as-synthesized NCs is preliminarily identified by means of Rietveld analysis against several reference crystal phases, followed by atomic pair distribution function (PDF) refinement of the best-matching candidates (static analysis). Subtle stoichiometry deviationsmore » from the corresponding bulk standards are revealed. NCs exposed to air at room temperature are monitored by XPD measurements at scheduled time intervals. The static PDF analysis is complemented with an investigation into the evolution of the WO3-x NC structure, performed by applying the modulation enhanced diffraction technique to the whole time series of XPD profiles (dynamical analysis). Prolonged contact with ambient air is found to cause an appreciable increase in the static disorder of the O atoms in the WO3-x NC lattice, rather than a variation in stoichiometry. Finally, the time behavior of such structural change is identified on the basis of multivariate analysis.« less

  3. Static and Dynamical Structural Investigations of Metal-Oxide Nanocrystals by Powder X-ray Diffraction: Colloidal Tungsten Oxide as a Case Study.

    PubMed

    Caliandro, Rocco; Sibillano, Teresa; Belviso, B Danilo; Scarfiello, Riccardo; Hanson, Jonathan C; Dooryhee, Eric; Manca, Michele; Cozzoli, P Davide; Giannini, Cinzia

    2016-03-03

    We have developed a general X-ray powder diffraction (XPD) methodology for the simultaneous structural and compositional characterization of inorganic nanomaterials. The approach is validated on colloidal tungsten oxide nanocrystals (WO3-x NCs), as a model polymorphic nanoscale material system. Rod-shaped WO3-x NCs with different crystal structure and stoichiometry are comparatively investigated under an inert atmosphere and after prolonged air exposure. An initial structural model for the as-synthesized NCs is preliminarily identified by means of Rietveld analysis against several reference crystal phases, followed by atomic pair distribution function (PDF) refinement of the best-matching candidates (static analysis). Subtle stoichiometry deviations from the corresponding bulk standards are revealed. NCs exposed to air at room temperature are monitored by XPD measurements at scheduled time intervals. The static PDF analysis is complemented with an investigation into the evolution of the WO3-x NC structure, performed by applying the modulation enhanced diffraction technique to the whole time series of XPD profiles (dynamical analysis). Prolonged contact with ambient air is found to cause an appreciable increase in the static disorder of the O atoms in the WO3-x NC lattice, rather than a variation in stoichiometry. The time behavior of such structural change is identified on the basis of multivariate analysis.

  4. Oxide-dispersion strengthening of porous powder metalurgy parts

    DOEpatents

    Judkins, Roddie R.

    2002-01-01

    Oxide dispersion strengthening of porous metal articles includes the incorporation of dispersoids of metallic oxides in elemental metal powder particles. Porous metal articles, such as filters, are fabricated using conventional techniques (extrusion, casting, isostatic pressing, etc.) of forming followed by sintering and heat treatments that induce recrystallization and grain growth within powder grains and across the sintered grain contact points. The result is so-called "oxide dispersion strengthening" which imparts, especially, large increases in creep (deformation under constant load) strength to the metal articles.

  5. Hyperfine structure of the hydroxyl free radical (OH) in electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Maeda, Kenji; Wall, Michael L.; Carr, Lincoln D.

    2015-05-01

    We investigate single-particle energy spectra of the hydroxyl free radical (OH) in the lowest electronic and rovibrational level under combined static electric and magnetic fields, as an example of heteronuclear polar diatomic molecules. In addition to the fine-structure interactions, the hyperfine interactions and centrifugal distortion effects are taken into account to yield the zero-field spectrum of the lowest 2Π3 / 2 manifold to an accuracy of less than 2kHz. We also examine level crossings and repulsions in the hyperfine structure induced by applied electric and magnetic fields. Compared to previous work, we found more than 10 percent reduction of the magnetic fields at level repulsions in the Zeeman spectrum subjected to a perpendicular electric field. In addition, we find new level repulsions, which we call Stark-induced hyperfine level repulsions, that require both an electric field and hyperfine structure. It is important to take into account hyperfine structure when we investigate physics of OH molecules at micro-Kelvin temperatures and below. This research was supported in part by AFOSR Grant No.FA9550-11-1-0224 and by the NSF under Grants PHY-1207881 and NSF PHY-1125915. We appreciate the Aspen Center for Physics, supported in part by the NSF Grant No.1066293, for hospitality.

  6. Powder Size and Distribution in Ultrasonic Gas Atomization

    NASA Astrophysics Data System (ADS)

    Rai, G.; Lavernia, E.; Grant, N. J.

    1985-08-01

    Ultrasonic gas atomization (USGA) produces powder sizes dependent on the ratio of the nozzle jet diameter to the distance of spread dt/R, Powder size distribution is attributed to the spread of atomizing gas jets during travel from the nozzle exit to the metal stream. The spread diminishes at higher gas atomization pressures. In this paper, calculated powder sizes and distribution are compared with experimentally determined values.

  7. Electrochemical cell with powdered electrically insulative material as a separator

    DOEpatents

    Mathers, James P.; Olszanski, Theodore W.; Boquist, Carl W.

    1978-01-01

    A secondary electrochemical cell includes electrodes separated by a layer of electrically insulative powder. The powder includes refractory materials selected from the oxides and nitrides of metals and metaloids. The powdered refractory material, blended with electrolyte particles, can be compacted in layers with electrode materials to form an integral electrode structure or separately assembled into the cell. The assembled cell is heated to operating temperature leaving porous layers of electrically insulative, refractory particles, containing molten electrolyte between the electrodes.

  8. Copper dynamics in doped metal-bis(histidine) complexes.

    PubMed

    Colaneri, Michael J; Vitali, Jacqueline

    2014-07-03

    Electron paramagnetic resonance (EPR) temperature-dependent measurements were undertaken on three Cu(II)-doped metal-histidine complexes to assess copper site dynamic behavior. Previous single-crystal EPR analysis on two of these, zinc d,l-histidine pentahydrate (ZnDLH) and bis(l-histidinato)cadmium dihydrate (CdLH), found that doped Cu(2+) can be modeled as hopping between two neighboring conformational states, with a temperature-dependent rate becoming large enough at room temperature to produce an "averaged" spectrum. By comparing spectra from their powdered form, we show that Cu(2+) doped into a third system, Cd(2+)-d,l-histidine (CdDLH), also exhibits temperature-dependent EPR with features indicating a similar motional-averaging process. In addition, the change of g and copper hyperfine parameters from low to high temperature for CdDLH resembles that in ZnDLH, whereas the change in these parameters for CdLH is like that found in a fourth copper-doped system, zinc l-histidine dihydrate (ZnLH). Taken together, these results suggest that averaging motion between neighboring copper sites is common in metal-bis(histidine) compounds. More detailed studies on biological models are thus warranted, especially because they reveal unique relationships between structure, dynamic processes, and stability and can lead to a better understanding of the role played by site flexibility in copper proteins.

  9. Fabrication of metallic glass structures

    DOEpatents

    Cline, Carl F.

    1986-01-01

    Amorphous metal powders or ribbons are fabricated into solid shapes of appreciable thickness by the application of compaction energy. The temperature regime wherein the amorphous metal deforms by viscous flow is measured. The metal powders or ribbons are compacted within the temperature range.

  10. Fabrication of metallic glass structures

    DOEpatents

    Cline, C.F.

    1983-10-20

    Amorphous metal powders or ribbons are fabricated into solid shapes of appreciable thickness by the application of compaction energy. The temperature regime wherein the amorphous metal deforms by viscous flow is measured. The metal powders or ribbons are compacted within the temperature regime.

  11. Solid state ¹³C-NMR, infrared, X-ray powder diffraction and differential thermal studies of the homologous series of some mono-valent metal (Li, Na, K, Ag) n-alkanoates: a comparative study.

    PubMed

    Nelson, Peter N; Ellis, Henry A; White, Nicole A S

    2015-06-15

    A comparative study of the molecular packing, lattice structures and phase behaviors of the homologous series of some mono-valent metal carboxylates (Li, Na, K and Ag) is carried out via solid state FT-infrared and (13)C-NMR spectroscopes, X-rays powder diffraction, density measurements, differential scanning calorimetry, polarizing light microscopy and variable temperature infrared spectroscopy. It is proposed that, for lithium, sodium and potassium carboxylates, metal-carboxyl coordination is via asymmetric chelating bidentate bonding with extensive intermolecular interactions to form tetrahedral metal centers, irrespective of chain length. However, for silver n-alkanoates, carboxyl moieties are bound to silver ions via syn-syn type bridging bidentate coordination to form dimeric units held together by extensive head group inter-molecular interactions. Furthermore, the fully extended hydrocarbon chains which are crystallized in the all-trans conformation are tilted at ca. 30°, 27°, 15° and 31° with respect to a normal to the metal plane, for lithium, sodium, silver and potassium carboxylates, respectively. All compounds are packed as lamellar bilayer structures, however, lithium compounds are crystallized in a triclinic crystal system whilst silver, sodium and potassium n-alkanoates are all monoclinic with possible P1 bravais lattice. Odd-even alternation observed in various physical features is associated with different inter-planar spacing between closely packed layers in the bilayer which are not in the same plane; a phenomenon controlled by lattice packing symmetry requirements. All compounds, except silver carboxylates, show partially reversibly first order pre-melting transitions; the number of which increases with increasing chain length. These transitions are associated, for the most part, with lamellar collapse followed by increased gauche-trans isomerism in the methylene group assembly, irrespective of chain length. It is proposed that the absence

  12. Solid state 13C-NMR, infrared, X-ray powder diffraction and differential thermal studies of the homologous series of some mono-valent metal (Li, Na, K, Ag) n-alkanoates: A comparative study

    NASA Astrophysics Data System (ADS)

    Nelson, Peter N.; Ellis, Henry A.; White, Nicole A. S.

    2015-06-01

    A comparative study of the molecular packing, lattice structures and phase behaviors of the homologous series of some mono-valent metal carboxylates (Li, Na, K and Ag) is carried out via solid state FT-infrared and 13C-NMR spectroscopes, X-rays powder diffraction, density measurements, differential scanning calorimetry, polarizing light microscopy and variable temperature infrared spectroscopy. It is proposed that, for lithium, sodium and potassium carboxylates, metal-carboxyl coordination is via asymmetric chelating bidentate bonding with extensive intermolecular interactions to form tetrahedral metal centers, irrespective of chain length. However, for silver n-alkanoates, carboxyl moieties are bound to silver ions via syn-syn type bridging bidentate coordination to form dimeric units held together by extensive head group inter-molecular interactions. Furthermore, the fully extended hydrocarbon chains which are crystallized in the all-trans conformation are tilted at ca. 30°, 27°, 15° and 31° with respect to a normal to the metal plane, for lithium, sodium, silver and potassium carboxylates, respectively. All compounds are packed as lamellar bilayer structures, however, lithium compounds are crystallized in a triclinic crystal system whilst silver, sodium and potassium n-alkanoates are all monoclinic with possible P1 bravais lattice. Odd-even alternation observed in various physical features is associated with different inter-planar spacing between closely packed layers in the bilayer which are not in the same plane; a phenomenon controlled by lattice packing symmetry requirements. All compounds, except silver carboxylates, show partially reversibly first order pre-melting transitions; the number of which increases with increasing chain length. These transitions are associated, for the most part, with lamellar collapse followed by increased gauche-trans isomerism in the methylene group assembly, irrespective of chain length. It is proposed that the absence of

  13. Nitridation of chromium powder in ammonia atmosphere

    NASA Astrophysics Data System (ADS)

    Li, Ling; Zhen, Qiang; Li, Rong

    2015-03-01

    CrN powder was synthesized by nitriding Cr metal in ammonia gas flow, and its chemical reaction mechanism and nitridation process were studied. Through thermodynamic calculations, the Cr-N-O predominance diagrams were constructed for different temperatures. Chromium nitride formed at 7002-1200°C under relatively higher nitrogen and lower oxygen partial pressures. Phases in the products were then investigated using X-ray diffraction (XRD), and the Cr2N content varied with reaction temperature and holding time. The results indicate that the Cr metal powder nitridation process can be explained by a diffusion model. Further, Cr2N formed as an intermediate product because of an incomplete reaction, which was observed by high-resolution transmission electron microscopy (HRTEM). After nitriding at 1000°C for 20 h, CrN powder with an average grain size of 63 nm was obtained, and the obtained sample was analyzed by using a scanning electron microscope (SEM).

  14. Densification of powder metallurgy billets by a roll consolidation technique

    NASA Technical Reports Server (NTRS)

    Sellman, W. H.; Weinberger, W. R.

    1973-01-01

    Container design is used to convert partially densified powder metallurgy compacts into fully densified slabs in one processing step. Technique improves product yield, lowers costs and yields great flexibility in process scale-up. Technique is applicable to all types of fabricable metallic materials that are produced from powder metallurgy process.

  15. Observation of molecular hyperfine structure in the extreme ultraviolet: The HF C-X spectrum.

    PubMed

    Philippson, Jeffrey N; Shiell, Ralph C; Reinhold, Elmar; Ubachs, Wim

    2008-11-07

    Clearly resolved hyperfine structure has been observed in the extreme ultraviolet (XUV) spectra of the C (1)Pi, v=0-X (1)Sigma(+), v=0 transition of H(19)F obtained through 1 XUV+1 UV resonance enhanced multiphoton ionization spectroscopy. The hyperfine splitting within the R-branch lines shows significant perturbations, which we attribute to mixing with the rotational levels of the nearby v=29 level of the B (1)Sigma(+) ion-pair state. A deperturbation analysis quantitatively explains the apparent variation of the fluorine magnetic hyperfine parameter a(F), for which a value of 4034(83) MHz was obtained by averaging over the values derived from the R(0)-R(4) lines, after correcting for the effects of the perturbations.

  16. Appraising nuclear-octupole-moment contributions to the hyperfine structures in 211Fr

    NASA Astrophysics Data System (ADS)

    Sahoo, B. K.

    2015-11-01

    Hyperfine structures of 211Fr due to the interactions of magnetic dipole (μ ), electric quadrupole (Q ), and magnetic octupole (Ω ) moments with the electrons are investigated using the relativistic coupled-cluster theory with the single, double, and important valence triple excitations approximations. The validity of our calculations is substantiated by comparing these values with the available experimental results. Its Q value has also been elevated by combining the measured hyper-fine-structure constant of the 7 p 2P3 /2 state with our improved calculation. Considering the preliminary value of Ω from the nuclear shell model, its contributions to the hyperfine structures up to the 7 d 2D5 /2 low-lying states in 211Fr are estimated. Hyperfine energy-level splittings of many states have been assessed to find the suitability for carrying out their precise measurements so that Ω of 211Fr can be inferred from them unambiguously.

  17. 2s Hyperfine splitting in light hydrogen-like atoms: Theory and experiment

    SciTech Connect

    Karshenboim, S. G. Kolachevsky, N. N.; Ivanov, V. G.; Fischer, M.; Fendel, P.; Haensch, T. W.

    2006-03-15

    Since the combination D{sub 21} = 8f{sub HFS}(2s)-f{sub HFS}(1s) of hyperfine intervals in hydrogen and light two-body hydrogen-like atomic systems weakly depends on the nuclear structure, comparison between theory and experiment can be sensitive to high order QED corrections. New theoretical and experimental results are presented. Calculations have been performed for the hydrogen and deuterium atoms and for the helium-3 ion. Experiments on the 2s hyperfine splitting (responsible for the dominant contribution to the error in D{sub 21}) have been conducted for hydrogen and deuterium. The theory and experiment are in good agreement, and their accuracy is comparable to that attained in verifying the QED theory of the hyperfine splitting in leptonic atoms (muonium and positronium)

  18. Powder-Metallurgy Process And Product

    NASA Technical Reports Server (NTRS)

    Paris, Henry G.

    1988-01-01

    Rapid-solidification processing yields alloys with improved properties. Study undertaken to extend favorable property combinations of I/M 2XXX alloys through recently developed technique of rapid-solidification processing using powder metallurgy(P/M). Rapid-solidification processing involves impingement of molten metal stream onto rapidly-spinning chill block or through gas medium using gas atomization technique.

  19. Multiple feed powder splitter

    DOEpatents

    Lewis, Gary K.; Less, Richard M.

    2001-01-01

    A device for providing uniform powder flow to the nozzles when creating solid structures using a solid fabrication system such as the directed light fabrication (DLF) process. In the DLF process, gas entrained powders are passed through the focal point of a moving high-power laser light which fuses the particles in the powder to a surface being built up in layers. The invention is a device providing uniform flow of gas entrained powders to the nozzles of the DLF system. The device comprises a series of modular splitters which are slidably interconnected and contain an integral flow control mechanism. The device can take the gas entrained powder from between one to four hoppers and split the flow into eight tubular lines which feed the powder delivery nozzles of the DLF system.

  20. Multiple feed powder splitter

    DOEpatents

    Lewis, Gary K.; Less, Richard M.

    2002-01-01

    A device for providing uniform powder flow to the nozzles when creating solid structures using a solid fabrication system such as the directed light fabrication (DLF) process. In the DLF process, gas entrained powders are passed through the focal point of a moving high-power laser light which fuses the particles in the powder to a surface being built up in layers. The invention is a device providing uniform flow of gas entrained powders to the nozzles of the DLF system. The device comprises a series of modular splitters which are slidably interconnected and contain an integral flow control mechanism. The device can take the gas entrained powder from between one to four hoppers and split the flow into eight tubular lines which feed the powder delivery nozzles of the DLF system.

  1. Granulation of fine powder

    DOEpatents

    Chen, Ching-Fong

    2016-08-09

    A mixture of fine powder including thorium oxide was converted to granulated powder by forming a first-green-body and heat treating the first-green-body at a high temperature to strengthen the first-green-body followed by granulation by crushing or milling the heat-treated first-green-body. The granulated powder was achieved by screening through a combination of sieves to achieve the desired granule size distribution. The granulated powder relies on the thermal bonding to maintain its shape and structure. The granulated powder contains no organic binder and can be stored in a radioactive or other extreme environment. The granulated powder was pressed and sintered to form a dense compact with a higher density and more uniform pore size distribution.

  2. The effect of TiB II powder on microstructure and mechanical behavior of Al-TiB II metal matrix composites

    NASA Astrophysics Data System (ADS)

    Ehsani, N.; Abdi, F.; Abdizadeh, H.; Baharvandi, H. R.

    2007-07-01

    Cast metal matrix composites produced by stir casting method have cost advantages over the composites made by other techniques. In this study, the influence of TiB II volume fraction on microstructure and mechanical properties of Al-TiB II composites has been investigated. Three different volume fractions (5, 10, and 15) of particulate TiB II were used in production of aluminum matrix composite at 750°C. Microstructure of the composites was studied by Scanning Electron Microscopy (SEM). Composition of the samples was analyzed by X-ray diffraction (XRD). The mechanical properties of the specimens (hardness and tensile strength) were also measured. Experimental results show that the microstructure is remarkably affected by TiB II addition level. The mechanical properties were considerably improved by addition of TiB II particles.

  3. Effect of Rare Earth Oxide Content on Nanograined Base Metal Electrode Multilayer Ceramic Capacitor Powder Prepared by Aqueous Chemical Coating Method

    NASA Astrophysics Data System (ADS)

    Zhang, Yichi; Wang, Xiaohui; Kim, Jinyong; Li, Longtu

    2013-02-01

    The aqueous chemical coating route is highly effective in preparing BaTiO3 nanoparticles uniformly coated with additives. Such nanoparticles can be used to produce nano-grained temperature stable BaTiO3 ceramics with core-shell structure, fulfilling the need of next-generation ultrathin layer base metal electrode (BME) multilayer ceramic capacitors (MLCCs). Rare earth oxides are an important class of additives owing to their ability to fulfill both donor and acceptor roles. In this paper, the effects of Y2O3 and Ho2O3 co-dopant content on dielectric and microstructural properties were investigated. By applying chemical coating, BaTiO3-based high performance temperature stabilized ceramics with the average grain size of about 130 nm, which met the requirement of next generation BME MLCCs, were obtained.

  4. Theoretical and experimental investigation of magnetic resonance on the Cs hyperfine structure

    NASA Astrophysics Data System (ADS)

    Ding, Zhichao; Yuan, Jie; Wang, Guochen; Luo, Hui; Long, Xingwu

    2017-08-01

    When the influence of hyperfine structure is ignored for atomic magnetometers, it will lead to considerable measuring errors in some cases. Considering the Cs hyperfine structure, an analytical form of magnetic resonance spectrum of the exciting-field frequency response is obtained through theoretical derivation, which is verified by the experiment. Based on the results of the experimental scheme, the optimal frequency and intensity of pump light for a Cs atomic magnetometer with well-resolved magnetic resonance spectrum are found. Additional applications in minimizing the measuring error of atomic magnetometers and the study of optical pumping are explored.

  5. Hyperfine structure of the ground state in muonic-lithium ions

    SciTech Connect

    Martynenko, A. P. Ulybin, A. A.

    2016-03-15

    Small intervals of the hyperfine structure of the ground state in the muonic-lithium ions (μe{sub 3}{sup 6,7}Li){sup +} were calculated by perturbation theory in the fine-structure constant and in the electronto- muon mass ratio. Vacuum-polarization, recoil, and nuclear-structure effects and electron vertex corrections were taken into account. The values obtained for the small hyperfine-splitting intervals can be used in a comparison with future experimental data and in tests of quantum electrodynamics.

  6. Hyperfine field of einsteinium in iron and nuclear magnetic moment of {sup 254}Es

    SciTech Connect

    Severijns, N.; Kraev, I. S.; Phalet, T.; Tandecki, M.; Traykov, E.; Gorp, S. Van; Wauters, F.; Belyaev, A. A.; Lukhanin, A. A.; Noga, V. I.; Erzinkyan, A. L.; Parfenova, V. P.; Eversheim, P.-D.; Herzog, P.; Tramm, C.; Filimonov, V. T.; Toporov, Yu. G.; Zotov, E.; Golovko, V. V.; Gurevich, G. M.

    2009-06-15

    The angular distributions of {gamma} rays and {alpha} particles from oriented {sup 250}Bk, {sup 253,254}Es, and {sup 255}Fm nuclei were investigated to extract hyperfine interaction information for these actinide impurities in an iron host lattice. The hyperfine field of einsteinium in iron was found to be |B{sub hf}(EsFe{sub lowbar|})=396(32) T. With this value the magnetic moment of {sup 254}Es was then determined as |{mu}|=4.35(41) {mu}{sub N}.

  7. Hyperfine structure constants for singly ionized manganese (Mn II) using Fourier transform spectroscopy

    NASA Astrophysics Data System (ADS)

    Townley-Smith, Keeley; Nave, Gillian; Pickering, Juliet C.; Blackwell-Whitehead, Richard J.

    2016-09-01

    We expand on the comprehensive study of hyperfine structure (HFS) in Mn II conducted by Holt et al. (1999) by verifying hyperfine magnetic dipole constants (A) for 20 levels previously measured by Holt et al. (1999) and deriving A constants for 47 previously unstudied levels. The HFS patterns were measured in archival spectra from Fourier transform (FT) spectrometers at Imperial College London and the National Institute of Standards and Technology. Analysis of the FT spectra was carried out in XGREMLIN. Our A constant for the ground level has a lower uncertainty by a factor of 6 than that of Blackwell-Whitehead et al.

  8. Study of coupled-cluster correlations on electromagnetic transitions and hyperfine structure constants of W VI

    NASA Astrophysics Data System (ADS)

    Bhowmik, Anal; Roy, Sourav; Nath Dutta, Narendra; Majumder, Sonjoy

    2017-06-01

    This work presents precise calculations of important electromagnetic transition amplitudes along with details of their many-body correlations using the relativistic coupled-cluster method. Studies of hyperfine interaction constants, useful for plasma diagnostics, with this correlation exhaustive many-body approach, are another important area of this work. The calculated oscillator strengths of allowed transitions, amplitudes of forbidden transitions and lifetimes are compared with the other theoretical results wherever available and they show a good agreement. Hyperfine constants of different isotopes of W VI, presented in this paper, will be helpful in gaining an accurate picture of the abundances of this element in different astronomical bodies.

  9. Theory of Electric-Field Effects on Electron-Spin-Resonance Hyperfine Couplings

    SciTech Connect

    Karna, S.P.

    1997-07-01

    A quantum mechanical theory of the effects of a uniform electric field on electron-spin-resonance hyperfine couplings is presented. The electric-field effects are described in terms of perturbation coefficients which can be used to probe the local symmetry as well as the strength of the electric field at paramagnetic sites in a solid. Results are presented for the first-order perturbation coefficients describing the Bloembergen effect (linear electric-field effect on hyperfine coupling tensor) for the O atom and the OH radical. {copyright} {ital 1997} {ital The American Physical Society}

  10. Suppression of ultracold ground-state hyperfine-changing collisions with laser light

    SciTech Connect

    Sanchez-Villicana, V.; Gensemer, S.D.; Tan, K.Y.N.; Kumarakrishnan, A.; Dinneen, T.P.; Sueptitz, W.; Gould, P.L.

    1995-06-05

    Using laser light tuned to a repulsive molecular potential, we have been able to suppress inelastic ground-state hyperfine-changing collisions between ultracold {sup 87}Rb atoms. Adiabatic excitation to the repulsive curve alters the atomic trajectories and prevents the atoms from approaching close enough for the hyperfine change to occur. Experimental results show suppressions up to {similar_to}50% and are in reasonable agreement with a simple Landau-Zener model. Our ability to control collisional trap loss processes may have important implications for the achievement of high densities in laser cooled samples.

  11. Dustiness of Fine and Nanoscale Powders

    PubMed Central

    Evans, Douglas E.; Baron, Paul A.

    2013-01-01

    Dustiness may be defined as the propensity of a powder to form airborne dust by a prescribed mechanical stimulus; dustiness testing is typically intended to replicate mechanisms of dust generation encountered in workplaces. A novel dustiness testing device, developed for pharmaceutical application, was evaluated in the dustiness investigation of 27 fine and nanoscale powders. The device efficiently dispersed small (mg) quantities of a wide variety of fine and nanoscale powders, into a small sampling chamber. Measurements consisted of gravimetrically determined total and respirable dustiness. The following materials were studied: single and multiwalled carbon nanotubes, carbon nanofibers, and carbon blacks; fumed oxides of titanium, aluminum, silicon, and cerium; metallic nanoparticles (nickel, cobalt, manganese, and silver) silicon carbide, Arizona road dust; nanoclays; and lithium titanate. Both the total and respirable dustiness spanned two orders of magnitude (0.3–37.9% and 0.1–31.8% of the predispersed test powders, respectively). For many powders, a significant respirable dustiness was observed. For most powders studied, the respirable dustiness accounted for approximately one-third of the total dustiness. It is believed that this relationship holds for many fine and nanoscale test powders (i.e. those primarily selected for this study), but may not hold for coarse powders. Neither total nor respirable dustiness was found to be correlated with BET surface area, therefore dustiness is not determined by primary particle size. For a subset of test powders, aerodynamic particle size distributions by number were measured (with an electrical low-pressure impactor and an aerodynamic particle sizer). Particle size modes ranged from approximately 300nm to several micrometers, but no modes below 100nm, were observed. It is therefore unlikely that these materials would exhibit a substantial sub-100nm particle contribution in a workplace. PMID:23065675

  12. Hyperfine magnetic field on Cd-111 in Heusler alloys Co2MnZ (Z = Si, Ga, Ge, Sn)

    NASA Technical Reports Server (NTRS)

    Jha, S.; Mitros, C.; Lahamer, Amer; Yehia, Sherif; Julian, Glenn M.

    1989-01-01

    The time differential perturbed angular correlation method has been used to measure, as a function of temperature, the hyperfine magnetic field at Cd sites in the Heusler alloys Co2MnZ (Z = Si, Ga, Ge, Sn). The hyperfine fields, normalized to the total magnetic moment per formula unit, show an approximately linear trend toward more positive values with increasing lattice parameter.

  13. Cow dung powder poisoning.

    PubMed

    Sherfudeen, Khaja Mohideen; Kaliannan, Senthil Kumar; Dammalapati, Pavan Kumar

    2015-11-01

    Cow dung, which has germicidal property, was used in ancient days to clean living premises in South India. Nowadays, people are using commercially available synthetic cow dung powder. It is locally known as "saani powder" in Tamil Nadu. It is freely available in homes and is sometimes accidentally consumed by children. It is available in two colors - yellow and green. Cow dung powder poisoning is common in districts of Tamil Nadu such as Coimbatore, Tirupur, and Erode. We report two cases of yellow cow dung powder poisoning from our hospital.

  14. Binding of molybdate to uteroferrin. Hyperfine interactions of the binuclear center with /sup 95/Mo, /sup 1/H, and /sup 2/H

    SciTech Connect

    Doi, K.; McCracken, J.; Peisach, J.; Aisen, P.

    1988-04-25

    Uteroferrin, an acid phosphatase with a spin-coupled and redox-active binuclear iron center, is paramagnetic in its pink, enzymatically active, mixed-valence (S = 1/2) state. Phosphate, a product and inhibitor of the enzymatic activity of uteroferrin, converts the pink, EPR-active form of the protein to a purple, EPR-silent species. In contrast, molybdate, a tetrahedral oxyanion analog of phosphate, transforms the EPR spectrum of uteroferrin from a rhombic to an axial form. With both electron spin echo envelope modulation (ESEEM) and electron nuclear double resonance (ENDOR) spectroscopies, we observe a hyperfine interaction of (95Mo)molybdate with the S = 1/2, Fe(II)-Fe(III) center of the protein. A pair of 95Mo resonances centered at the 95Mo Larmor frequency at the applied magnetic field and separated by a hyperfine coupling constant of 1.2 MHz is evident. Therefore, a single monomeric species of molybdate is close to, and likely a ligand of, the binuclear cluster. 1H ENDOR studies on uteroferrin reveal at least six sets of lines mirrored about the 1H Larmor frequency. Two pairs of these lines become reduced in intensity when the protein is exchanged against D2O. Moreover, ESEEM and 2H ENDOR spectra display resonances at the 2H Larmor frequency. Therefore, the metal-binding region of the protein is accessible to solvent. Additional deuterium lines observable by ESEEM spectroscopy provide evidence for a population of strongly coupled, readily exchangeable protons associated with the binuclear center. The measured hyperfine coupling constants for these deuterons are orientation-dependent with splittings of nearly 4 MHz at g3 = 1.59 and less than 1 MHz at g1 = 1.94. In the presence of molybdate, ESEEM spectra of D2O-exchanged samples reveal a resonance at the 2H Larmor frequency, with no evidence of spectral components due to strongly coupled deuterons.

  15. Magnetic hyperfine field at diluted {sup 57}Fe in vapor-quenched heavy-rare-earth films

    SciTech Connect

    Passamani, E.C.; Baggio-Saitovitch, E.; Micklitz, H.

    1997-05-01

    In this work, we combine vapor-quenching technique at low temperature (20 K) and {ital in situ} {sup 57}Fe M{umlt o}ssbauer spectroscopy at different temperatures (7{endash}300 K) to study out-of-equilibrium solubility and magnetic properties of {sup 57}Fe(5at.{percent}) in some magnetic heavy-rare-earth (RE) metals (RE=Dy, Ho, Er, and Tm). The spectra were fitted using the full Hamiltonian including electric quadrupole and magnetic interactions. Two magnetic components are observed in the 7 K M{umlt o}ssbauer spectra: one with a magnetic hyperfine field (B{sub hf}) varying between 5.3(2) and 1.9(2) T, which has been attributed to Fe at a substitutional site, and the other one, with a smaller field ({lt}2.1T), which is assumed to be due to Fe at an interstitial site. The behavior of B{sub hf} for Fe at the substitutional site in the different RE metals scales with the de Gennes factor. {copyright} {ital 1997} {ital The American Physical Society}

  16. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-05

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of ternary mixtures consisting of: Ni powder, Cu powder, and Al powder, Ni powder, Cr powder, and Al powder; Ni powder, W powder and Al powder; Ni powder, V powder, and Al powder; Ni powder, Mo powder, and Al powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  17. Theoretical and electron paramagnetic resonance studies of hyperfine interaction in nitrogen doped 4H and 6H SiC

    SciTech Connect

    Szász, K.; Gali, A.

    2014-02-21

    Motivated by recent experimental findings on the hyperfine signal of nitrogen donor (N{sub C}) in 4 H and 6 H SiC, we calculate the hyperfine tensors within the framework of density functional theory. We find that there is negligible hyperfine coupling with {sup 29}Si isotopes when N{sub C} resides at h site both in 4 H and 6 H SiC. We observe measurable hyperfine coupling to a single {sup 29}Si at k site in 4 H SiC and k{sub 1} site in 6 H SiC. Our calculations unravel that such {sup 29}Si hyperfine coupling does not occur at k{sub 2} site in 6 H SiC. Our findings are well corroborated by our new electron paramagnetic resonance studies in nitrogen doped 6 H SiC.

  18. Preparation and characterization of Miocene clay powders in the region of Taza (Morocco) after doping with metal oxides Al2O3

    NASA Astrophysics Data System (ADS)

    Mesrar, L.; Lakrim, M.; Akdim, M.; Benmar, A.; –Sbai, N. ES; Jabrane, R.

    2017-03-01

    The marl’s minerals are abundant untreated material in several areas worldwide. They are often under-valued for human use. However, due to demands of the society in terms of sustainability and energy saving, the valuation of these resources to develop new materials, most environmentally friendly has become a concern both scientific and industrial aims. Ceramics are the growing research to obtain materials with good chemical stability and good hot properties [1]. The balance between these properties and industrial requirements allowed clay materials uses at craft departure (pottery, tile), to progress towards high-tech applications such as electrical and thermal insulation, electric candle, sound insulation [2]. The behavior of the doping (Al2O3), which has more scientific research interest, has been a renewed interest since 1980 [3] with the emergence of alumina very high purity. Miocene marl is one of the widespread geological substrates in Fez-Taza vicinity (Central Morocco). In this study we proceed by a physicochemical characterization of the marl after doping with metal oxides, by various analytical techniques, namely the X-ray fluorescence, the mineralogical analysis and geotechnical test. The doping of these marl was conducted by solid oxides of Al2O3 at different percentages (5%, 10% and 15%). The results of chemical analysis showed the Al2O3 increase during doping. So, the mineralogical analysis of doped clays shows peaks’ increases for kaolin. The marl doped acquired the property of their good plasticity and good mechanical resistance compared to crass marl.

  19. The reactive surface of Castor leaf [Ricinus communis L.] powder as a green adsorbent for the removal of heavy metals from natural river water

    NASA Astrophysics Data System (ADS)

    Martins, Amanda E.; Pereira, Milene S.; Jorgetto, Alexandre O.; Martines, Marco A. U.; Silva, Rafael I. V.; Saeki, Margarida J.; Castro, Gustavo R.

    2013-07-01

    In this study, a green adsorbent was successfully applied to remove toxic metals from aqueous solutions. Dried minced castor leaves were fractionated into 63-μm particles to perform characterization and extraction experiments. Absorption bands in FTIR (Fourier Transform Infrared Spectroscopy) spectra at 1544, 1232 and 1350 cm-1 were assigned to nitrogen-containing groups. Elemental analysis showed high nitrogen and sulfur content: 5.76 and 1.93%, respectively. The adsorption kinetics for Cd(II) and Pb(II) followed a pseudo-second-order model, and no difference between the experimental and calculated Nf values (0.094 and 0.05 mmol g-1 for Cd(II) and Pb(II), respectively) was observed. The Ns values calculated using the modified Langmuir equation, 0.340 and 0.327 mmol g-1 for Cd(II) and Pb(II), respectively, were superior to the results obtained for several materials in the literature. The method proposed in this study was applied to pre-concentrate (45-fold enrichment factor) and used to measure Cd(II) and Pb(II) in freshwater samples from the Paraná River. The method was validated through a comparative analysis with a standard reference material (1643e).

  20. Core-Shell Metal-Organic Frameworks/Molecularly Imprinted Nanoparticles as Absorbents for the Detection of Pyrraline in Milk and Milk Powder.

    PubMed

    Liu, Huilin; Mu, Lin; Chen, Xiaomo; Wang, Jing; Wang, Shuo; Sun, Baoguo

    2017-02-01

    A novel core-shell metal-organic framework coated with a dummy template molecularly imprinted polymer (MOF@DMIP) was synthesized by one-pot bulk polymerization for the detection of pyrraline in food samples. The pyrraline analogue pyrrolidine-3-carboxylic acid was used as the template because of its lower cost, and MIL-101 was used as the MOF core owing to its numerous inherent advantages, including high chemical and hydrothermal stabilities. MIL-101@DMIP was used to detect trace pyrraline in foods by solid-phase extraction combined with high-performance liquid chromatography. It exhibited the advantages of faster mass transport, excellent sensitivity, and selectivity. Under optimum conditions, the detection limit of this system was 40.7 μg L(-1), and a linear range was from 5 × 10(-7) to 2 × 10(-3) mol L(-1), within relative standard deviations of 4.46-6.87%. The recoveries ranged from 92.23 to 103.87%, indicating the excellent ability of the prepared MIL-101@DMIP to recognize pyrraline in complex food matrices and its potential for application in pyrraline detection.